EP0176381B1 - High-pressure hydraulic directional control valve with a pilot pressure generator - Google Patents

Description

The present invention relates to a high pressure hydraulic distributor.

More specifically, it relates to a hydraulic distributor of the type comprising at least one inlet conduit capable of being connected to a source of hydraulic fluid under high pressure, at least one main outlet conduit capable of being connected to user means of hydraulic fluid under high pressure, at least one return duct capable of being connected to a reservoir of hydraulic fluid under a low pressure, and distributor means capable of occupying several states in which they establish or interrupt hydraulic connections between some of said conduits, and in particular at least one passive state in which the distributor means establish a hydraulic connection between the inlet conduit and the return conduit by interrupting any hydraulic connection between the inlet conduit and the main outlet conduit, and at least one active state in which the distributor means establish a hydraulic connection in be the inlet duct and the main outlet duct by interrupting any hydraulic connection between the inlet duct and the return duct (GB-A-2 073 821).

Such hydraulic distributors are very often used as systems for controlling different motor functions on mobile machines, and we will generally understand by “high pressures” pressures of the order of magnitude of those which are brought into play by example when the user means are constituted by hydraulic cylinders fulfilling the functions of handling loads or moving organs on mobile mechanical handling machines or on agricultural machines, and by "low pressures" pressures of the order of significantly smaller magnitude, for example of the order of magnitude of atmospheric pressure.

In such applications, several hydraulic distributors are generally juxtaposed in a composite central distributor, each of which constitutes a section, assigned to a specific function.

In such applications, it is very often asked to be able to independently control the flow rates of high pressure hydraulic fluid supplying the different sections; for example, in the case of a forklift, a distribution section of which is assigned to a load lifting cylinder and other sections, respectively, to mast tilt, mast advance, d '' fork spacing, these examples should be considered non-limiting, the section controlling the lifting of the load requires a comparatively large flow, due to the large displacement of the lifting cylinder, while the other sections require comparatively low flows .

Compliance with these different requirements, in terms of flow rates, depending on whether a function or another is used by an appropriate actuation of the respectively corresponding distribution section, is difficult to reconcile with the supply of the distributor from a source. single hydraulic fluid, in practice a pump actuated by a motor of the machine and drawing from a reservoir of hydraulic fluid which the various distribution sections convey at will either towards the organs fulfilling the functions to which these sections are respectively assigned, or in return towards the reservoir; in the current state of the art, it is ensured that a sufficient flow rate can be provided to fulfill all of the functions, possibly simultaneously, by continuously operating the pump at its maximum flow rate, which leads to recycling directly to the tank, almost permanently, a flow which can be significant; in other words, this leads to a waste of energy since the more the pump provides a large flow, the more energy it consumes.

However, any excess energy consumption is to be avoided, especially in the case of mobile, autonomous machines, that is to say carrying their own source of energy such as, for example, storage batteries, insofar as where any waste of energy leads in this case to a reduction in autonomy.

To remedy this drawback, it has been envisaged to supply each distribution section with a clean source of hydraulic fluid, providing a flow rate suited to the needs of the member associated with this section; such a supply from several sources would however prove to be costly in material.

The object of the present invention is to allow the use of a single source of hydraulic fluid for the supply of a compound distributor, without, however, wasting energy.

To this end, the present invention provides a hydraulic distributor which is capable of constituting one of the distribution sections of a compound distributor, and which makes it possible to control the speed of the pump at all times, so that its flow is at each instant adapted to the needs, that is to say at each instant to limit the consumption of the motor ensuring the drive of the pump; naturally, as soon as the compound distributor issues a control signal representative of the flow requirements, this signal can also be used for other purposes and for example to supply means for displaying these requirements.

The hydraulic distributor according to the present invention, of the type comprising at least one inlet duct capable of being connected to a source of hydraulic fluid under high pressure, at least one main outlet duct capable of being connected to user means of hydraulic fluid under high pressure, at least one return duct capable of being connected to a reservoir of hydraulic fluid under low pressure, and distributor means capable of occupying several states in which they establish or interrupt hydraulic connections between some of said conduits, and in particular at least one passive state in which the distributor means establish a hydraulic connection between the inlet conduit and the return conduit by interrupting any hydraulic connection between the inlet conduit and the main outlet conduit, and at least one active state in which

• . un conduit de sortie auxiliaire,
• . des moyens réducteurs de pression, sensibles à la pression hydraulique dans le conduit d'entrée, pour établir une liaison hydraulique entre le conduit d'entrée et le conduit de sortie auxiliaire:
  • - lorsque la valeur de la pression hydraulique dans le conduit d'entrée dépasse un seuil prédéterminé, et provoquer alors l'apparition, dans le conduit de sortie auxiliaire, d'une pression hydraulique de pilotage de valeur réduite par rapport à la valeur de la pression hydraulique dans le conduit d'entrée,
  • - lorsque la valeur de la pression hydraulique dans le conduit d'entrée est inférieure audit seuil, et transmettre cette pression à la sortie auxiliaire,
    • ledit seuil étant d'une part supérieur à une valeur maximale de pression hydraulique dans le conduit d'entrée lorsque les moyens distributeurs occupent ledit état passif et que le conduit d'entrée et le conduit de retour sont raccordés respectivement à la source et au réservoir, et d'autre part inférieur à une valeur minimale de pression hydraulique dans le conduit d'entrée lorsque les moyens distributeurs occupent ledit état actif et que le conduit d'entrée et le conduit de sortie principale sont raccordés respectivement à la source et aux moyens utilisateurs,
    • . des moyens de modulation, couplés auy moyens distributeurs, pour moduler la valeur de la pression hydraulique de pilotage de façon prédéterminée, en fonction de l'état des moyens distributeurs.

the distributor means establish a hydraulic connection between the inlet duct and the main outlet duct by interrupting any hydraulic connection between the inlet duct and the return duct, is characterized in that it further comprises:

• . an auxiliary outlet duct,
• . pressure reducing means, sensitive to the hydraulic pressure in the inlet pipe, for establishing a hydraulic connection between the inlet pipe and the auxiliary outlet pipe:
  • - when the value of the hydraulic pressure in the inlet pipe exceeds a predetermined threshold, and then cause the appearance, in the auxiliary outlet pipe, of a hydraulic control pressure of reduced value compared to the value of the hydraulic pressure in the inlet pipe,
  • - when the value of the hydraulic pressure in the inlet pipe is less than said threshold, and transmit this pressure to the auxiliary outlet,
    • said threshold being on the one hand greater than a maximum value of hydraulic pressure in the inlet pipe when the distributor means occupy said passive state and when the inlet pipe and the return pipe are connected respectively to the source and to the reservoir , and on the other hand less than a minimum value of hydraulic pressure in the inlet pipe when the distributor means occupy said active state and the inlet pipe and the main outlet pipe are connected respectively to the source and to the means users,
    • . modulation means, coupled to the distributor means, for modulating the value of the hydraulic control pressure in a predetermined manner, as a function of the state of the distributor means.

According to one embodiment of the invention, the modulation means are suitable for assigning to the hydraulic pilot pressure a first predetermined value when the distributor means occupy the passive state, and at least a second predetermined value, different from the first and for example greater than this, when the dispensing means occupy the active state.

• . un alésage présentant una face périphérique intérieure définissant une direction longitudinale, une première extrémité transversale, une deuxième extrémité transversale,
• . des moyens de liaison hydraulique de ladite première extrémité avec le conduit de sortie auxiliaire,
• . des moyens de liaison hydraulique de la deuxième extrémité avec le conduit de retour,
• . au moins deux orifices aménagés dans ladite face périphérique intérieure, à raison d'un premier orifice comparativement plus proche de ladite première extrémité et d'un deuxième orifice comparativement plus éloigné de ladite première extrémité,
• . un piston monté au coulissement longitudinal à l'intérieur de l'alésage et présentant une face périphérique extérieure en contact glissant et étanche avec la face périphérique intérieure de l'alésage, une face de première extrémité transversale en regard de la première extrémité de l'alésage, et une deuxième extrémité transversale en regarde de la deuxième extrémité de l'alésage,
• . un ressort de compression agissant entre lesdites deuxièmes extrémités pour solliciter élastiquement le piston, dans l'alésage, vers la première extrémité de ce dernier,
• . un passage, aménagé dans le piston, débouchant d'une part dans la face de première extrémité transversale du piston et d'autre part dans la face périphérique extérieure du piston, en regarde desdits orifices de la face périphérique intérieure de l'alésage,
• . des moyens distributeurs auxiliaires, couplés aux moyens distributeurs principaux, pour établir une liaison hydraulique entre le conduit d'entrée et, alternativement, le premier orifice ou le deuxième orifice selon que, respectivement, les moyens distributeurs cités en premier occupent l'état passif ou l'état actif.

For example, for this purpose, the pressure reducing means and the modulation means coupled to the dispensing means can advantageously be constituted in that the dispenser comprises:

• . a bore having an inner peripheral face defining a longitudinal direction, a first transverse end, a second transverse end,
• . means of hydraulic connection of said first end with the auxiliary outlet conduit,
• . means of hydraulic connection of the second end with the return duct,
• . at least two orifices arranged in said inner peripheral face, on the basis of a first orifice comparatively closer to said first end and a second orifice comparatively further from said first end,
• . a piston mounted for longitudinal sliding inside the bore and having an outer peripheral face in sliding and sealed contact with the inner peripheral face of the bore, a face of first transverse end opposite the first end of the bore, and a second transverse end facing the second end of the bore,
• . a compression spring acting between said second ends to elastically urge the piston, in the bore, towards the first end of the latter,
• . a passage, arranged in the piston, opening on the one hand into the face of the first transverse end of the piston and on the other hand into the external peripheral face of the piston, facing said orifices of the internal peripheral face of the bore,
• . auxiliary distributor means, coupled to the main distributor means, to establish a hydraulic connection between the inlet duct and, alternatively, the first orifice or the second orifice depending on whether, respectively, the distributor means cited first occupy the passive state or the active state.

Advantageously, the auxiliary dispensing means and the dispensing means mentioned first can be constituted by the same drawer, in which said bore can advantageously be located, which leads to a particularly simple and compact structure.

According to a particularly advantageous embodiment of the invention, when the dispensing means are capable of occupying a plurality of active states in which they establish a hydraulic connection between the inlet pipe and the main outlet pipe by authorizing respective flow rates different from the inlet duct to the main outlet duct, and by interrupting any hydraulic connection between the inlet duct and the return duct, the modulation means are produced in such a way that they are suitable for assigning at the hydraulic control pressure a first predetermined value when the distributor means occupy the passive state, and a plurality of respective second predetermined values, different from the first and different from each other, when the distributor means occupy the different active states; then, advantageously, said second values are greater than the first value, and increase or decrease, respectively, when the flow authorized by the dispensing means increases or decreases; in a particularly simple manner, the calibration means can assign said second values in stages, even when the different active states are accessible in continuous succession, by authorizing flow rates varying continuously.

In the case of the practical embodiment of the pressure reducing means and of the modulation means mentioned above, this result can advantageously be obtained in that the inner peripheral face of the bore has a plurality of second orifices differently distant from the first end of the bore, and in that the auxiliary distributor means coupled to the main distributor means are capable of establishing a hydraulic connection between the inlet duct and, selectively, a respective one of said second orifices when the main distributor means occupy said active states, said respective second orifice being all the more distant from the first end of the bore that the active state occupied by the distributor means corresponds to a higher authorized flow rate.

It may be observed that, in the case where the hydraulic control signal is used to control the speed of a pump constituting the source of hydraulic fluid, the variation in stages of the value of this control signal also leads to a variation by stages of the pump speed, that is to say not to a strict adaptation of the flow rate of the latter and of the consumption of its drive motor in energy to the real flow needs, but to an approximate adaptation, necessarily by excess; however, such an approximation constitutes an excellent compromise in view of the great simplicity of practical realization with which it is accompanied.

• . établir automatiquement une liaison entre le conduit de sortie auxiliaire et le conduit de retour si la valeur de la pression hydraulique dans le conduit de sortie auxiliaire dépasse un seuil prédéterminé supé- reiur auxdites valeurs de la pression de pilotage,
• . interrompre automatiquement toute liaison entre le conduit de sortie auxiliaire et le conduit de retour si la valeur de la pression hydraulique dans le conduit de sortie auxiliaire est inférieure à cet autre seuil prédéterminé.

Advantageously, the hydraulic distributor according to the invention may include safety means, for:

• . automatically establishing a connection between the auxiliary outlet pipe and the return pipe if the value of the hydraulic pressure in the auxiliary outlet pipe exceeds a predetermined threshold greater than said values of the pilot pressure,
• . automatically interrupt any connection between the auxiliary outlet pipe and the return pipe if the value of the hydraulic pressure in the auxiliary outlet pipe is lower than this other predetermined threshold.

To this end, advantageously, in the case of the practical embodiment of the pressure reducing means and of the modulation means mentioned above, these safety means can be constituted by means for automatically establishing a hydraulic connection between the passage of the piston and the second end of the bore if the hydraulic pressure at the first end of the bore exceeds a predetermined threshold, or to automatically interrupt any hydraulic connection between the passage of the piston and the second end of the bore if the hydraulic pressure at the first end of the bore is less than this predetermined threshold.

Thus, the possible appearance of a back pressure in the auxiliary outlet conduit, which can occur for example when the pilot pressure is used to control a speed adjustment cylinder of a thermal engine driving the source. of hydraulic fluid, cannot cause damage to the distributor insofar as the possible back pressure is automatically evacuated towards the tank as soon as it exceeds a predetermined threshold.

Other characteristics and advantages of the present invention will emerge from the description below, relating to a non-limiting mode of implementation, as well as from the appended drawings which form an integral part of this description.

FIG. 1 shows, by way of example of a machine implementing the present invention in a particularly advantageous manner, a forklift, propelled by thermal engine, of which only the elements essential for understanding the description have been schematized. go follow.

• La figure 3 montre une coupe de distributeur selon l'invention dans une telle position neutre.
• La figure 4 montre une coupe de ce distributeur dans une position intermédiaire entre la position neutre et une position correspondant à un état actif tel qu'un tel état a été défini plus haut.
• Les figures 5 et 6 montrent des coupes du distributeur dans deux états actifs, correspondant à des débits autorisés, du conduit d'entrée vers le conduit de sortie principale, de valeurs respectivement moyenne et maximale.
• La figure 7 montre une coupe du distributeur dans un état passif différant de celui qui est illustré à la figure 3.
• La figure 8 montre une coupe du distributeur à l'état neutre, lorsqu'une contre-pression excessive apparaît dans le conduit de sortie auxiliaire.
• La figure 9 montre une coupe du distributeur en position neutre, alors qu'un distributeur d'une autre section de distribution se trouve à l'état actif tel qu'on l'a défini plus haut à propos du distributeur selon l'invention.
• La figure 10 montre un diagramme représentatif de la pression de pilotage en fonction du déplacement du distributeur de la première ou des sections supérieures de distribution dans le cas d'un distributeur intégré selon l'invention.

FIG. 2 shows a diagram of integration of a distributor according to the invention as a first distribution section, in a central compound distributor integrated into the hydraulic circuit of the carriage illustrated in FIG. 1, the distributor being in neutral position, corresponding to a passive state if one refers to the definition of such a state which was given above.

• Figure 3 shows a dispenser section according to the invention in such a neutral position.
• Figure 4 shows a section of this dispenser in an intermediate position between the neutral position and a position corresponding to an active state such that such a state has been defined above.
• Figures 5 and 6 show sections of the distributor in two active states, corresponding to authorized flow rates, from the inlet duct to the main outlet duct, of average and maximum values respectively.
• FIG. 7 shows a section of the distributor in a passive state different from that which is illustrated in FIG. 3.
• FIG. 8 shows a section of the distributor in the neutral state, when an excessive back pressure appears in the auxiliary outlet conduit.
• Figure 9 shows a section of the distributor in the neutral position, while a distributor of another distribution section is in the active state as defined above with respect to the distributor according to the invention.
• FIG. 10 shows a diagram representing the pilot pressure as a function of the displacement of the distributor of the first or upper distribution sections in the case of an integrated distributor according to the invention.

In FIG. 1, a forklift truck 1 has been shown diagrammatically comprising a heat engine 3 for driving a pump 4 the function of which is to pump hydraulic fluid into a reservoir 5 at low pressure, with a flow rate controlled by the engine speed 3 itself controlled by a hydraulic booster 2, for supplying such a fluid under high pressure to a number of cylinders, and for example a double-acting cylinder not shown intended to cause at will a tilting movement 6 d a mast 7 carrying the fork 8, around a horizontal axis 9 linked to the carriage 1, and a single-acting cylinder 10 intended to act positively on the fork 8 in the direction of a rise along the mast 7, and to allow the fork 8 to passively descend along the mast 7, at the will of an operator expressed by action on a control lever 11 of a distributor according to the invention 12.

This distributor, which will now be described with reference to FIGS. 2 to 9, has for this purpose connection means with a pipe 13 for connection with the pump 4, for receiving from the latter hydraulic fluid under pressure when it is in service, with a main outlet pipe 14 ensuring the connection of this distributor with the chamber (not shown) of the jack 10 to introduce hydraulic fluid therein and making this jack active, with a return pipe 15 linking the distributor 12 to the reservoir 5 to ensure, together with the pipe 14, the return of fluid to this reservoir 5 when the jack 10 operates in the passive state, and, in accordance with the present invention, with an auxiliary output line 16 suitable for transmitting to the hydraulic servomotor 2 a pressure for controlling the speed of the motor 3, that is to say the flow rate of the pump 4.

In Figure 2, there is shown schematically the distributor 12 integrated as the first distribution section in a distributor bench, or compound central distributor, supplied in parallel.

This FIG. 2 shows the pipes 13, 14, 15, 16, as well as the pump 4, the reservoir 5, the single-acting cylinder 10, and the hydraulic booster 2.

The distributor bench illustrated in FIG. 2 has an inlet section 17, to which the first distribution section defined by the distributor 12 is directly juxtaposed, to which a second distribution section constituted by a distributor 18 is juxtaposed. of the traditional type intended for example for supplying the double-acting cylinder (not shown) implementing the tilting 6 of the mast 7, with the section 18 being juxtaposed an end section 19; naturally, the distributor constituting the second section 18 could be different from that which has been illustrated, and several distribution sections could be interposed in place of the second section 18 between the first section 12 and the end section 19; the latter could also be juxtaposed directly with the first section 12.

The inlet section 17 defines a first conduit 20 for supplying hydraulic fluid, which has a first end 21 having means of connection to the line 13 and a second end 22 having means of connection with a first end 23 of a first inlet conduit 24 of the body 25 of the distributor 12; between the ends 21 and 22 of the fluid conduit 20 derive from the latter, inside the inlet section 17, on the one hand a second fluid supply conduit 26, moreover having an end 27 provided with connection means at one end 28 of a second inlet conduit 29 arranged in the body 25 of the distributor 12, and on the other hand a conduit 30 returning to the reservoir 15, which conduit 30 has inside the block inlet 17 a pressure relief valve 31 and branches so as to also have two ends, at the rate of one end 91 having means for connection to the pipe 15 and one end 32 provided with means for connection to a end 33 of a return duct 34 arranged in the body 25 of the distributor 12; in a manner known per se, the conduits 24, 29, 34 are connected, by their respective ends 23, 28, 33, to the ends 22, 27, 32 of the conduits 20, 26, 30 of the inlet section 17 due to 'A simple juxtaposition of the body 25 of the distributor 12 to the inlet section 17 during assembly, the connection means being constituted by the means for assembling the body 25 and the inlet section 17 and by seals sealing around the various conduits to be connected together; analog means are used to ensure all the connections of a duct of one section to a duct of another section which will be described later.

The conduit 29 passes through the body 25 of the distributor 12 right through, to present a second end 35 provided with connection means at one end 36 of a similar conduit 37 of a body 195 of the distributor constituting the section 18, this conduit 37 continuing itself through this distributor body to an end 38 provided with connection means at one end 39 of a conduit 40 arranged in the end section 19, in which this conduit 40 has a closed end 41.

Between the ends 28 and 35 of the conduit 29 derives from the latter, inside the body 25 of the distributor 12, a conduit 42 opening, through one end 43, into a bore 44 passing through the body 25 right through, according a rectilinear axis 45 defining a longitudinal direction and perpendicular to the direction in which the conduit 29 passes through the body 25 (see FIGS. 3 to 9 as regards references 44 and 45, which do not appear in FIG. 2); between its connection with the duct 29 and its end 43, the duct 42 comprises a non-return valve 116 allowing a passage of fluid from the duct 29 to the end 43 and preventing a passage of fluid from the end 43 to the duct 29 .

The duct 24 has a second end 46 through which it also opens the bore 44, in the form of an annular groove of revolution around the axis 45 like the end 43 of the duct 42.

The conduit 34 passes through the body 25 right through, like the conduit 29, to present a second end 47 provided with connection means at a first end 48 of a conduit 49 of the body 195 of the distributor constituting the second section 18, this conduit 49 continuing through this body 195 to a second end 150 to which it has connection means with a first end 51 of a conduit 52 arranged in the end section 19, this conduit 52 opening out also outside this section 19 by a second end 53 provided with connection means at a first end 54 of a conduit 55 which is arranged in the body 195 of the distributors constituting the second section 18 and which also has inside of this body 195 a second end 56 which a drawer 57 of the distributor constituting the second section 18 makes it possible to connect to one end 58 of another conduit 59 of the body of this distributor, which conduit 59 has another end 60 provided with means for connection to a first end 61 of a conduit 62 of the body 25 of the distributor 12; this conduit 62 also has a second end 63 through which it opens into the bore 44, in the form of an annular groove of revolution around the axis 45.

In addition, from the duct 34 derives, inside the body 25, a duct 64 opening through one end 65, in the form of an annular groove of revolution around the axis 45, in the bore 44.

Finally, in the body 25 are dug two other conduits 87, 88 of which the first opens on the one hand into the bore 44 for a groove 66, annular of revolution around the axis 45, and on the other hand to the outside of the body 25 by an end 89 provided means 90 for connection to the pipe 14 for connection with the jack 10, and the second of which opens on the one hand into the bore 44 for an annular groove 96 of revolution around the axis 45, and on the other hand to the outside of the body by an end 191 provided with means 92 for connection to the auxiliary outlet pipe 16; the connection means 90 and 92 are for example constituted by an internal thread of the conduits 87 and 88 at their ends 89 and 191, respectively.

If we now refer to FIGS. 3 to 9, we see that the duct 34, cutting the bore 44, and the grooves 96, 46, 63, 43, 66, 65, annular of revolution around the axis 45, follow each other in this order from left to right along axis 45; the intersection of the conduit 34 with the bore 44 and the different grooves 96, 46, 63, 43, 66, 65 are in the form of enlargements, transversely with respect to the axis 45, of the bore 44 moreover cylindrical of revolution around this axis 45 with a constant diameter D, to define on either side of the intersection of the bore 44 with the conduit 34 and on either side of each of the abovementioned grooves of the narrowing, with which a slide 67, mounted to slide along the axis 45 in the bore 44, makes it possible to establish a sealed contact.

The slide 67 passes through the body 12 right through along an axis 45, via the bore 44, and has respectively on either side of the body 12 an end 68 of articulation on the control lever 11 around a axis 71 perpendicular to axis 45 and parallel to an axis 72 of articulation of the lever 11 on the body 25, and one end 69 of functional connection with a return spring 70.

In the example illustrated, where the end 68 of articulation on the lever 11 as well as the latter are located to the right of the body 25 while the end 69 is located to the left of the latter, the spring 70 is placed to the left of an extreme left face 73 of the body 25, and is in the form of a helical spring of axis 45, working under compression between two cups 74 and 78, both also axis 45 and mounted to slide parallel to this axis, on the slide 67, between an end head 75 of this slide 67 and a shoulder 77 that the latter presents towards this end head 75; the cup 78, located to the right of the cup 74 in Figures 3 to 9, thus has a radially inner peripheral zone, with reference to the axis 45, directly opposite the shoulder 77, turned to the left and towards the head 75, and a radially outer zone placed directly opposite the end face 73 of the body 25 of the distributor 12, and more precisely facing a zone of this plane face 73, perpendicular to the axis 45, surrounding the bore 44 at its intersection with face 73; the cup 74, for its part, thus has a radially inner peripheral zone, with reference to the axis 45, interposed between the internal peripheral zone of the cup 77 and the head 75, and a radially external peripheral zone, with reference to the axis 45, interposed between the outer peripheral zone of the cup 78 and a face of the stop 82, flat, annular of revolution around the axis 45, that a casing 76 carried integrally by the face 73 of the body 12 for close the bore 44 at its end corresponding to this face 73 present towards the latter; the dimensions of the cups 74 and 78 in particular parallel to the axis 45, the distance separating the head 75 from the shoulder 77 parallel to this axis, and the distance separating the abutment face 82 of the casing 76 from the area of the face 73 surrounding the outlet of the bore 44 in the latter, parallel to the axis 45, are chosen such that, when the slide 67 occupies a neutral position illustrated in FIG. 3 and which will be described later, the cups 74 and 78 are in contact respectively with the face 82 of the casing 76 and with the face 73 by their external peripheral zones, and in contact respectively with the end head 75 and with the shoulder 77 by their internal peripheral zones, the spring 70 being in compression, so that this neutral position illustrated in FIG. 3 constitutes a stable position towards which the slide 67 tends to return automatically in the event of displacement relative to this position, by sliding inside the bore 44 along axis 45; the above-mentioned dimensions are further such that, from this neutral position and by acting on the lever 11, the slide 67 can be displaced by sliding along the axis 45 inside the bore 44, in one way or the other, that is to say either to the right until the inner peripheral zone of the cup 74, abutting to the left against the end head 75 of the drawer 67, comes abut to the right against the inner peripheral zone of the cup 78 itself in abutment to the right against the face 73 by its outer peripheral zone, the contacts respectively between the inner peripheral zone of the cup 78 and the shoulder 77 of the drawer 67 and between the outer peripheral zone of the cup 74 and the face 82 of the casing 76 then being broken, either to the left to a limit position in which the inner peripheral zone of the cup 78, pressing to the right against the shoulder 77 of drawer 67, comes b uter to the left against the inner peripheral zone of the cup 74 itself resting, by its outer peripheral zone, against the annular face 82 of the housing 76, the contact between the inner peripheral zone of the cup 74 and the head end 75 and the contact between the outer peripheral zone of the cup 78 and the face 73 then being interrupted; whether this movement from the neutral position is accomplished to the right or to the left, it is accompanied by additional compression of the spring 70, which, as said above, tends to bring the drawer 67 in the neutral position; naturally, these displacements to the right or to the left are understood with reference to the representation of FIGS. 3 to 9, as well as to that of FIG. 2, and are indicated without any limiting intention, for the sole purpose of to facilitate the understanding of the relative positions of different elements of the dispenser according to the invention described by way of nonlimiting example; the neutral position of the drawer 67 is illustrated in Figures 3, 8, 9; the limit position of this slide 67 in sliding to the right with respect to the body 25 is illustrated in FIG. 6, intermediate positions being illustrated in FIGS. 4 and 5, and its extreme position

sliding to the left is shown in Figure 7.

Between its two ends 68 and 69, and more precisely between its articulation zone on the lever 11 1 around the axis 71 and between the shoulder 77, the drawer 67 has the shape of a cylindrical rod of revolution around axis 45, with a diameter substantially identical to diameter D, in which annular grooves of revolution have been dug around this axis 45, respectively 79, 80, 81, succeeding each other in this order, from left to right, according to the direction of axis 45.

• . une zone 83 cylindrique de révolution autour de l'axe 45 avec un diamètre sensiblement égal au diamètre D, cette zone 83 étant en contact prériphéri- que étanche avec l'alésage 44 entre la face 73 et le conduit 34, entre le conduit 34 et la gorge 96, entre le gorge 96 et la gorge 46 quelle que soit celle des positions que le tiroir 67 occupe, par coulissement dans l'alésage 45, entre sa position extrême gauche et sa position extrême droite définies plus haut, de même que lorsqu'il occupe l'une ou l'autre de ces positions extrêmes; cette zone 83 est également en contact d'étanchéité avec l'alésage 44 entre les gorges 46 et 63, en chevauchant la gorge 46 et éventuellement une partie de la gorge 63 dès lors que, en agissant sur le levier 11, on déplace le tiroir 67 vers la droite dans l'alésage 44, c'est-à-dire dans la position extrême droite du tiroir 67 ainsi que dans les positions intermédiaires, à l'exception des positions intermédiaires immédiatement voisines de la position neutre; lorsque le tiroir 67 occupe sa position extrême gauche, ainsi que dans toute position du tiroir 67 intermédiaire entre cette position et la position neutre, la partie 83 du tiroir 67 conserve un contact d'étanchéité avec l'alésage 44 entre le conduit 34 et la gorge 96 de même qu'entre les gorges 96 et 46;
• . la gorge 79, chevauchant des gorges 46 et 63 dans la position neutre illustrée aux figures 2 et 3 de même que dans la position extrême gauche du tiroir 67 et que dans toutes les positions intermédiaires entre cette position extrême gauche et la position neutre, de même que dans les positions du tiroir 67 les plus voisines de la position neutre lorsque le tiroir 67 est déplacé vers la droite; par contre, cette gorge 79 chevauche exclusivement la gorge 63, ainsi qu'une partie de l'alésage 44 entre cette gorge 63 et la gorge 43, dans toutes les autres positions intermédiaires du tiroir 67 vers sa position extrême droite, et dans cette position extrême droite;
• . une zone 84 cylindrique de révolution autour de l'axe 45 avec le diamètre D, en contact d'étanchéité avec l'alésage 44 entre les gorges 63 et 43 quelle que soit la position du tiroir 67 dans l'alésage 44, de la position extrême droite à la position extrême gauche;
• . la gorge 80, chevauchant la gorge 43 dans la position neutre illustrée à la figure 3, et chevauchant les gorges 43 et 66 dans la position extrême droite illustré à la figure 6 ainsi que dans les positions in-
• termédiaires les plus proches de cette position extrême droite; la gorge 80 est placée en regarde de l'alésage 44 entre les gorges 43 et 63 en position extrême gauche du tiroir 67 ainsi que dans les positions intermédiaires les plus proches de cette position extrême;
• . une zone 85 cylindrique de révolution autour de l'axe 45 avec le diamètre D, cette zone 85 étant en contact d'étanchéité avec l'alésage 44 entre la gorge 66 et la gorge 43, d'une part, et entre la gorge 66 et la gorge 81, d'autre part, lorsque le tiroir 67 occupe la position neutre illustrée à la figure 3, en chevauchant la gorge 66; cette zone 85 reste en contact d'étanchéité avec l'alésage 44 entre les gorges 65 et 66 pour toute position du tiroir 67 décalée vers la droite par rapport à la position neutre, et en contact d'étanchéité avec l'alésage 44 entre les gorges 43 et 66 pour toute position du tiroir 67 décalée vers la gauche par rapport à la position neutre;
• . la gorge 81, placée en regarde de la gorge 65 en position neutre du tiroir, cette gorge 65 étant placée en regard des gorges 65 et 66 en chevauchant la zone de l'alésage 44 intermédiaire entre des deux gorges 65 et 66 lorsque le tiroir occupe sa position extrême gauche ainsi que dans les positions intermédiaires entre la position neutre et cette position extrême gauche les plus proches de cette dernière;
• . une zone 86 cylindrique de révolution autour de l'axe 45 avec le diamètre D, cette zone 86 étant en contact d'étanchéité avec l'alésage 44 entre la gorge 81 et la limite extrême droite du corps 25 quelle que soit la position du tiroir 67 par rapport à ce dernier, de la position extrême droite à la position extrême gauche.

If we refer to the neutral position illustrated in FIG. 3, the slide 67 thus has from left to right, from the shoulder 77 of its end 69 to the articulation zone of its end 68 on the lever 11 around the 'axis 71:

• . a cylindrical zone 83 of revolution around the axis 45 with a diameter substantially equal to the diameter D, this zone 83 being in sealed peripheral contact with the bore 44 between the face 73 and the conduit 34, between the conduit 34 and the groove 96, between the groove 96 and the groove 46 whatever that of the positions that the slide 67 occupies, by sliding in the bore 45, between its extreme left position and its extreme right position defined above, as well as when 'he occupies one or other of these extreme positions; this zone 83 is also in sealing contact with the bore 44 between the grooves 46 and 63, overlapping the groove 46 and possibly a part of the groove 63 when, by acting on the lever 11, the drawer is moved 67 to the right in the bore 44, that is to say in the extreme right position of the slide 67 as well as in the intermediate positions, with the exception of the intermediate positions immediately adjacent to the neutral position; when the drawer 67 occupies its extreme left position, as well as in any position of the drawer 67 intermediate between this position and the neutral position, the part 83 of the drawer 67 maintains a sealing contact with the bore 44 between the duct 34 and the groove 96 as well as between grooves 96 and 46;
• . the groove 79, overlapping grooves 46 and 63 in the neutral position illustrated in FIGS. 2 and 3 as well as in the extreme left position of the drawer 67 and that in all the intermediate positions between this extreme left position and the neutral position, likewise that in the positions of the drawer 67 closest to the neutral position when the drawer 67 is moved to the right; on the other hand, this groove 79 exclusively overlaps the groove 63, as well as part of the bore 44 between this groove 63 and the groove 43, in all the other intermediate positions of the slide 67 towards its extreme right position, and in this position far right;
• . a cylindrical area 84 of revolution around the axis 45 with the diameter D, in sealing contact with the bore 44 between the grooves 63 and 43 whatever the position of the slide 67 in the bore 44, from the position extreme right at the extreme left position;
• . the groove 80, overlapping the groove 43 in the neutral position illustrated in FIG. 3, and overlapping the grooves 43 and 66 in the extreme right position illustrated in FIG. 6 as well as in the positions
• closest to this extreme right position; the groove 80 is placed opposite the bore 44 between the grooves 43 and 63 in the extreme left position of the slide 67 as well as in the intermediate positions closest to this extreme position;
• . a cylindrical zone 85 of revolution around the axis 45 with the diameter D, this zone 85 being in sealing contact with the bore 44 between the groove 66 and the groove 43, on the one hand, and between the groove 66 and the groove 81, on the other hand, when the drawer 67 occupies the neutral position illustrated in FIG. 3, overlapping the groove 66; this zone 85 remains in sealing contact with the bore 44 between the grooves 65 and 66 for any position of the slide 67 offset to the right relative to the neutral position, and in sealing contact with the bore 44 between the grooves 43 and 66 for any position of the drawer 67 shifted to the left relative to the neutral position;
• . the groove 81, placed facing the groove 65 in the neutral position of the drawer, this groove 65 being placed opposite the grooves 65 and 66 overlapping the zone of the bore 44 intermediate between two grooves 65 and 66 when the drawer occupies its extreme left position as well as in the intermediate positions between the neutral position and this extreme left position closest to the latter;
• . a cylindrical zone 86 of revolution around the axis 45 with the diameter D, this zone 86 being in sealing contact with the bore 44 between the groove 81 and the extreme right limit of the body 25 whatever the position of the drawer 67 relative to the latter, from the extreme right position to the extreme left position.

In addition, in zone 85 are hollowed out, at the junction thereof with grooves 80 and 81, progressive grooves such as 93 and 94, respectively, placed opposite bore 44, which closes them, respectively. between the groove 66 and the groove 43 and between the groove 66 and the groove 81 when the drawer 67 occupies the neutral position illustrated in FIG. 3, the progressiveness grooves 93 progressively coming towards the groove 66 as and when the drawer 67 is moved to the right from the neutral position, to gradually put the grooves 80 and 66 into communication, while the progressiveness grooves 94 come gradually opposite the groove 66 when the drawer is moved 67 to the left from the neutral position, to gradually connect the grooves 81 and 66; such grooves of progressiveness are known in themselves to those skilled in the art, and therefore do not seem to require further description thereof.

The different zones of the drawer 67 which have just been described have also been shown diagrammatically in FIG. 2.

In addition to this alternation of zones of diameter D and of grooves, the slide 67 has internally a longitudinal bore 95, of revolution around the axis 45.

When, as illustrated, the drawer 67 is formed by integral assembly of two parts, namely a rod 97 extending from its end 68 of articulation on the lever 11 around the axis 71 to the shoulder 77 and a bolt 98 screwed along axis 45 in the rod 97, to define the second end 69 of the drawer and, at this end 69, the end head 75 and the area of the drawer 67 which is located between this head 75 and the shoulder 77 to allow relative sliding of the cups 74 and 78, the bore 95 advantageously extends to the left if reference is made to FIGS. 3 to 9, from a transverse level, with reference to the axis 45, corresponding to that of the shoulder 77 inside which it opens out of the rod 97, to a level, transverse to the axis 45, corresponding to that of the groove 79 and to which it is closed by a transverse end face 99, for example conical of revolution around axis 45; from this transverse end face 99 at its mouth inside the shoulder 77, the bore 95 is delimited by an inner peripheral face of the rod 97, which the inner peripheral face has a first cylindrical section 100 of revolution around the axis 45 with a diameter less than the minimum diameter of the groove 79, from the face 99 to a level, transversely with respect to the axis 45, intermediate between the respective levels of the grooves 96 and 34 with reference to this axis when the slide 67 occupies the neutral position illustrated in FIG. 3 whereas this limit level of the first section 100 of the external peripheral face of the bore 95 corresponds with that of the groove 96 in the extreme right position illustrated in FIG. 6, and with that of the groove 34 in the extreme left position illustrated in FIG. 7; beyond this limit level of the first section 100 in the direction of a distance from the face 99, along the axis 45, the inner peripheral face of the bore 95 is defined by a second section 101 also cylindrical of revolution around the axis 45, with a diameter intermediate between that of the section 100 and the maximum diameter D of the slide 67 (of the rod 97); the two sections 100 and 101 are connected to each other by an annular shoulder 102, plane, of revolution about the axis 45 to which it is perpendicular and which thus defines both the extreme left limit of the first section 100 and the extreme right limit the second section 101; the latter continues until the mouth of the bore 95 outside the rod 97, at the shoulder 77 transversely to the axis 45, and has near this mouth a threaded zone 103 in which is screwed, by means of a seal provided by any means known to a person skilled in the art, the bolt 98 and more precisely a threaded rod 104 thereof; this rod 104 is connected, by an annular shoulder 105, plane, perpendicular to the axis 45 and bearing against the shoulder 77 at the junction of the latter with the mouth of the bore 95, to a cylindrical face 106 of revolution around the axis 45 and turned in the direction of a radial distance from it, with a diameter intermediate between the maximum diameter of the tapped zone 103 and the diameter D, this face 106 defining the sliding zone cups 74 and 78 on the drawer 67; in the direction of a distance from the shoulder 105, this face 106 is itself delimited by junction with an annular shoulder 107, plane, of revolution about the axis 45 to which it is perpendicular, this shoulder 107 being defined by the head 75 and turned towards the shoulder 77 to constitute for the cup 74 the stop to the left, relative to the drawer 67, described above.

Inside the bore 95, the threaded rod 104 of the bolt 98 is delimited by a flat annular face 108, of revolution about the axis 45 to which it is perpendicular, and by a stud 109 forming with respect to this face 108 a projection, along the axis 45, inside the bore 95; the face 108 and the central stud 109 thereof define by convention the left transverse end of the bore 95, the face 99 of which defines the right transverse end, if we refer to the positions illustrated in the figures.

Between the shoulder 102 of the inner peripheral face of the bore 95 and the transverse end of the latter defined by the face 108 and the stud 109, a level corresponding to that of the intersection of the bore 44 with the conduit 34 whatever that of the positions that the slide 67 can occupy from the extreme right position to the extreme left position, opens into the section 101 of the inner peripheral face of the bore 95 a passage 110 arranged radially, with reference to the axis 45, in the rod 97 and also opening into the section 83 of the drawer 67.

Similarly, in the section 100 of the inner peripheral face of the bore 95 open through respective orifices four passages 111, 112, 113, 114 arranged radially, with reference to the axis 45, in the rod 97 and also opening by respective orifices in the section 83 of the rod 67; of these passages 111, 112, 113, 114, the passage 114 is that which opens closest to the end face 99 of the bore 95 in the section 100 of the inner peripheral face of this bore, being however spaced opposite the end face 99; with reference to the axis 45, it is arranged at a transverse level corresponding to that of the groove 46 when the drawer occupies the neutral position illustrated in FIG. 3 as well as in the extreme left position of the drawer illustrated in FIG. 7 and that in all intermediate positions between the neutral position and the extreme left position; in the extreme right position of the drawer, illustrated in FIG. 6, as well as in the intermediate positions of its passage from the neutral position to the extreme right position which are closest to this extreme right position, this passage 114 is located at a level corresponding to that of the zone of the bore 44 separating the grooves 46 to 63, so that it is closed by the bore 44.

The passages 111, 112, 113 are in turn located at respective levels following each other in this order, along the axis 45, from the level of the passage 114 to that of the shoulder 102 connecting between the sections 100 and 101 of the inner peripheral face of the bore 95; in the neutral position of the drawer illustrated in Figure 3, their respective levels correspond with it that of the groove 96; in the extreme right position of the slide, illustrated in FIG. 6, the levels of the passages 111, 112, 113 coincide respectively with that of the groove 46, that of the zone of the bore 44 intermediate between the grooves 46 and 96, and that of the throat 96; in the extreme left position of the drawer, illustrated in FIG. 7, the levels of the passages 111, 112, 113 coincide respectively with that of the groove 96, that of the zone of the bore 44 intermediate between the groove 96 and the intersection of the bore 44 with the conduit 34, and that of this intersection of the bore 44 with the conduit 34.

Inside the bore 95 is mounted, when sliding along the axis 45 relative to the slide 67, a piston 115 having an outer peripheral face 116 cylindrical of revolution around the axis 45 with a diameter substantially coinciding with that the first section 100 of the inner peripheral face of the bore 95, so as to establish a sliding and sealed mutual contact between the faces 100 and 116; towards the end face 99 of the bore 95, the face 116 is delimited by junction with a face 117 of transverse end of the piston 115, which face 117 is planar and perpendicular to the axis 45; in the direction of a distance from the end face 99 of the bore 95 along the axis 45, that is to say towards the face 108 and its stud 109, the face 116 is delimited by junction with a planar annular face 118, of revolution about the axis 45 to which it is perpendicular, this face 118 having a stud 119 projecting along the axis 45 towards the stud 109, of which this stud 119 constitutes a specular image with respect to a virtual plane, not shown, perpendicular to the axis 45; the distance separating the faces 117 and 118 of the piston 115 parallel to the axis 45 is intermediate between the distances separating respectively from the annular shoulder 102 of the inner peripheral face of the bore 95, the end face 99 of it ci and the passage 114, in the mouth area of the latter in the bore 95 closest to the face 99 of the latter, so that the piston 115 can in particular occupy, inside the bore 95 , a position which is illustrated in FIG. 3 and in which its face 118 is coplanar with the shoulder 102 and its face 117 placed facing the face 99 but at a distance therefrom, along the axis 45, to delimit with this face 99, as well as with a part of the first section 100 of the inner peripheral face of the bore 95, a sealed chamber 219; this position of the drawer 115 inside the bore 95 constitutes a stable, rest position, from which the drawer can move to the left, that is to say in the direction of a distance from its face 117 opposite the face 99 of the bore 95, by means of compression of a helical spring 220, of axis 45, interposed between the face 108, around the stud 109, and an intermediate washer 221 bearing on the face 118, around the stud 119; during such displacement of the piston, the spring 220 tends to return it to the initial position illustrated in FIG. 3; in this initial position, the washer 221 for supporting the spring 220 on the face 118 of the piston 115 also bears against the shoulder 102, which then interrupts the biasing of the piston 115 towards the face 99 of the bore 95 under the action of the spring 220, a continuation of the movement of the piston 115 towards the face 99 being excluded, when the distributor is in service, by the presence of pressurized fluid in the chamber 219 as will appear below.

In its outer peripheral face 116, the piston 115 has in the illustrated example two grooves 120 and 121, annular of revolution around the axis 45 and disposed respectively closer to the face 117 and closer to the face 118, and in each of these grooves 120 and 121 opens a passage 122 arranged inside the piston 115, essentially along the axis 45, and also opening into the face 117 of the piston 115, that is to say in the chamber 219 with which it thus puts the two grooves 120 and 121 into communication.

If one refers to the initial position of the piston 115 illustrated in Figure 3, the grooves 120 and 121 are arranged so that the groove 120 is placed opposite the passage 114 in this initial position, and that the groove 121 either placed opposite passages 111 and 112; in this initial position of the piston 115 as also in all the positions of the latter which will be discussed below, the passage 10 opens freely, that is to say without being closed by the piston 115, inside the second section 101 of the inner peripheral face of the bore 95 whose end corresponding to the face 108 and to the stud 109 thus remains permanently open towards the conduit 34.

• . la gorge 120 est placée pour l'essentiel en regarde du premier tronçon 100 de la face périphérique intérieure de l'alésage 95 entre les niveaux respectifs du passage 114 et du passage 111, et pour une moindre part en regarde du passage 114 (position intermédiaire illustré à la figure 4) puis intégralement en regarde du premier tronçon 100 de la face périphérique intérieure de l'alésage 95 entre les niveau respectifs des passages 114 et 111 (position non illustrée), alors que la gorge 121 continue à être placée en regarde des passages 111 et 112,
• . la gorge 120 est placée en regarde du premier tronçon 100 de la face périphérique intérieure de l'alésage 95 entre les niveaux respectifs des passages 114 et 1 1 alors que la gorge 121 est placée en regard des passages 112 et 113, et, pour une moindre part, en regard du passage 111 (position illustrée à la figure 5 et à la figure 6),
• . la gorge 120 est placée en regarde du premier tronçon 100 de la face périphérique intérieure de l'alésage 95 entre les niveaux respectifs des passages 114 et 111, et ta gorge 121 est placée en regarde des passages 112 et 113 ainsi qu'en regard du deuxième tronçon 101 de la face périphérique intérieure de l'alésage 95, en chevauchant l'épaulement 102 de celle-ci (position de sécurité, ou position extrême gauche du piston 115 à l'intérieur de l'alésage 95, illustrée à la figure 8).

If, from the initial position illustrated in FIG. 3, the piston 115 gradually moves to the left to an extreme left position, relative to the bore 95, or safety position illustrated in FIG. 8, it passes successively through intermediate positions in which, respectively:

• . the groove 120 is essentially placed facing the first section 100 of the inner peripheral face of the bore 95 between the respective levels of the passage 114 and the passage 111, and to a lesser extent facing the passage 114 (intermediate position illustrated in FIG. 4) then integrally looking at the first section 100 of the inner peripheral face of the bore 95 between the respective levels of the passages 114 and 111 (position not shown), while the groove 121 continues to be placed facing passages 111 and 112,
• . the groove 120 is placed facing the first section 100 of the inner peripheral face of the bore 95 between the respective levels of the passages 114 and 1 1 while the groove 121 is placed opposite the passages 112 and 113, and, for a lesser part, opposite passage 111 (position illustrated in FIG. 5 and in FIG. 6),
• . the groove 120 is placed facing the first section 100 of the inner peripheral face of the bore 95 between the respective levels of the passages 114 and 111, and your groove 121 is placed facing the passages 112 and 113 as well as opposite the second section 101 of the inner peripheral face of the bore 95, overlapping the shoulder 102 thereof (safety position, or extreme left position of the piston 115 inside the bore 95, illustrated in FIG. 8).

The arrangements which have just been described lead to the following operation of the distributor 12, assumed to be integrated as the first distribution section in a compound distributor of the type illustrated in FIG. 2 where the piston 15 has been shown in the form of a distributor drawer, the spring 220, as well as the passages 111, 112, 113, 114 in their different functions which will appear at present; each of these passages fulfill different functions depending on the state of the dispenser, the corresponding references appear several times in FIG. 2.

The distributor 12 being connected in the manner described with reference to FIG. 2, in particular indirectly to the lines 13 and 15, and directly to the lines 14 and 16 as well as to the lines 37, 59, 49 of the second distribution section 18 and, by means of the latter, to the conduits 52 and 40 of the end section 19, the initial state illustrated in FIG. 3 will be considered, in which the drawer 67 occupies its neutral position inside the bore 44, under the action of spring 70, and piston 115 occupies its initial position described above inside bore 95.

Then, the groove 79 of the drawer ensures communication between the grooves 46 and 63, which makes it possible to ensure, through the distributor 12, the supply of the second distribution section 18 on the one hand via the conduits 24 and 62 and on the other hand via conduit 29; on the other hand, the section 85 of the slide 67 isolates the groove 66 both from the groove 43 and from the groove 65, and the jack 10 can neither receive hydraulic fluid from the pump 4, nor flow out towards the reservoir 5 so that it is stationary in a position determined by a previous actuation of the dispenser; the drawer 57 of the second distribution section 18 also occupying a neutral position, that is to say corresponding to an immobility of the jack controlling the tilting 6 of the mast by ensuring a connection between the conduits 59 and 55 and, through them , with the conduits 52, 49, 34, 30, 15 back to the tank 5, the pump 4 is not stressed, and can be stopped or simply used at a speed of circulation of the hydraulic fluid coming from the tank 5 and back to this tank 5, substantially at the low pressure of this tank; this low pressure also prevails in the chamber 219, in communication with the groove 46 in the passage 114 of the drawer 67, the groove 120 of the piston 115 and the passage 122 thereof, and this low pressure also prevails in the groove 96 and the conduit 88 leading to the conduit 16 for connection with the booster 2, due to the connection provided by the passage 122 between the chamber 219 and the groove 121, itself placed opposite the passages 111 and 112 then terminating in the groove 96; the actuator 2 therefore receives a pressure signal of a value corresponding substantially to the pressure of the reservoir 5.

If the slide 67 is moved from the neutral position, corresponding to this initial state, to the right, in order to put the grooves 43 and 66 into communication via the groove 80, that is to say supply the jack 10 in hydraulic fluid coming from the duct 29 and, by the latter, from the pump 4, the section 83 of the slide 67 gradually closes the connection between the grooves 63 and 46, which results in a rise in pressure in the ducts 24 and 29, that is to say in the gorges 43 and 46; this increase in pressure in the groove 46 results, via the passage 114, the groove 120, the passage 122, by an increase in pressure in the chamber 219, which creates a force tending to push the piston 115 to the left at the inside the bore 95 of the drawer 67, that is to say to close the connection between the groove 120 and the conduit 114, while the spring 220 is opposed to such closure; this results in a position illustrated in FIG. 4, in which the connection between the grooves 63 and 46 is closed while the connection between the grooves 43 and 66 is not yet open, and in which the piston 115 occupies at the inside the bore 95 of the slide 67 an equilibrium position, in which the fluid passage section of the passage 114 towards the groove 120 is sufficiently reduced to cause a reduction in pressure from the groove 46 to the chamber 219, and thus establishing in the latter a pressure, reduced compared to that which prevails in the groove 46, and producing on the piston 115 a force balancing that opposed to it by the return spring 220.

Appropriate calibration of the spring 220 makes it possible to adjust the pressure threshold, in the chamber 46, leading to the passage of the piston 115 at such an equilibrium position, to a value greater than a maximum value of hydraulic pressure in the grooves 46 and 43 , that is to say in the conduits 24 and 29, when the slide 67 occupies the neutral position and the conduits 24 and 29 are connected to the source 4 while the conduit 34 and the conduit 62 (via of the second distribution section 18 and of the end section 19) are connected to the reservoir 5, this threshold also being chosen to be less than a minimum value of hydraulic pressure in conduits 24 and 29, that is to say in the grooves 46 and 43, when the slide 67 occupies an active state of communication of the grooves 43 and 66 by the groove 80, as will be described later, while the conduits 24 and 29 on the one hand, the conduit 87 on the other hand are connected respectively to the source 4 and to the jack 10.

The pressure thus appearing in the chamber 219 is transmitted, via the passage 122, the groove 121, and the passages 111 and 112, to the groove 96 and beyond to the conduit 88, that is to say to the servomotor 2 which then acts on the heat engine 3 to adjust the flow rate of the pump 4 to a minimum level, greater than the possible flow rate corresponding to the initial state described with reference to FIG. 3.

The hydraulic pressure value thus obtained in line 88 represents a first level of this piloting pressure of the hydraulic booster 2.

FIG. 9 shows that this first level of pilot pressure in the conduit 88 is also obtained when the drawer 67 occupies its neutral position, illustrated in FIG. 3 and described with reference to it, but that the drawer 67 of the distributor 18 constituting the second distribution section is placed in a position of interruption of the connection between the conduits 59 and 55, that is to say of interruption of the connection between the conduit 62 (groove 63) of the distributor 12 and the tank 5; such an interruption in fact causes in the grooves 43 and 46 an increase in pressure entirely similar to that which has been described with reference to FIG. 4, and, the chamber 219 then being connected respectively to the grooves 46 and 96 of the same so that in the case described with reference to FIG. 4, the slide 115 is placed in an equilibrium position identical to that which has been described with reference to this FIG. 4, inside the bore 95 of the slide 67 .

In the case of a distributor comprising several distribution sections, as already mentioned in relation to the description of FIG. 2, the second level of pilot pressure Pp2 can, also as shown in FIG. 10, be obtained by actuation of the one and / or the other of the drawers 67 of the distributors constituting the upper sections of a distributor bench as shown in FIG. 2, the first distributor, or first distribution section having its drawer 67 maintained in the neutral position. In FIG. 10, it appears that the pressure level Pp2 is constant, reference curve 2, as a function of the position d of the drawers of the upper distribution sections. In the case of simultaneous action of one or more of the drawers of the upper distribution sections and of drawer 67 of the first distribution section, the pressure level obtained for the pilot pressure in the conduit 88 is that of the only first section distribution whose action is predominant, curve reference 1. Thus, it is also possible to obtain, from the modulation means 111, 112, 113, 114 suitable for assigning to the hydraulic pilot pressure said first value Pp 1 predetermined when the distributor means or drawers 67 occupy the passive state, said second predetermined Pp2 value different from the first when one or more drawers 67 of the upper distribution sections are actuated, the drawer of the first distribution section being in position neutral.

If, from the state illustrated in FIG. 4, the slide 67 is continued to move to the right inside the bore 44, the reduced pressure, relative to that which prevails in the groove 46, prevails in the chamber 219 and in the conduit 88 remains constant, the slide 115 remaining stationary relative to the slide 67 inside the bore 95, while the progressive grooves 93, then the groove 80, gradually establish communication between the grooves 43 and 66 for supplying the jack 10 with hydraulic fluid coming from the source 4; however, since, during this movement of the slide 67, the passage 111 is facing the groove 46, which allows the introduction into the chamber 219, by this passage 111, by the groove 121 and by the passage 122 of the piston 115, of fluid coming from the groove 46, and which upsets the balance of the drawer 115 between the force which it receives from the pressure prevailing in the chamber 219 and that which receives it from the spring 220, the piston 115 moves again to the left, inside the bore 95 of the slide 67, to tend to close the connection thus created between the comparatively high pressure in the passage 111 and the comparatively low pressure prevailing in the chamber 219 , and to gain a new equilibrium position, illustrated in FIG. 5, which is reached when the pressure prevailing in the chamber 219, reduced compared to the pressure prevailing in the groove 46, applies to the piston 115 an equal and opposite force the force applied to the piston 115 by the spring 220; insofar as, in this position, the spring 220 is compressed more than before, that is to say that in the state illustrated in FIG. 4, the pressure then prevailing in the chamber 219 has a value greater than the one it had in the equilibrium position described with reference to FIG. 4 and this pressure is transmitted,

via the passage 122 and the groove 121 of the piston 115, and via the conduits 112 and 113 at the groove 96, that is to say at the conduit 88 in which a pilot pressure of a second level thus appears.

This pilot pressure of a second level, supplied to the servomotor via line 16, is used to increase the speed of the motor 3 driving the pump 4 to increase the flow rate of the latter.

In the position illustrated in Figure 5, a connection is already established by the groove 80 between the grooves 43 and 66, while any connection remains interrupted between the grooves 63 and 46, on the one hand, 63 and 43, on the other part, and between gorges 66 and 81.

FIG. 6 illustrates the extreme right position of the slide 67 in the bore 44 and shows that, from the intermediate position illustrated in FIG. 5 to this extreme position illustrated in FIG. 6, the conditions for supplying the chamber 219 with fluid from the groove 46 remain unchanged while a communication remains established between the chamber 219 and the groove 96 through the passage 113, so that the drawer 115 retains, inside the bore 95 of the drawer 67, the position balance described in Figure 6 and that the distributor emits at the conduit 88 a hydraulic pressure of the aforementioned second level.

It will be noted that one could provide between the respective levels of passage 111 and passage 112, along the axis 45, other passages arranged radially, with reference to the axis 45, in the drawer 67 to connect the section 83 of the latter to section 100 of its bore 95; the successive appearance, when looking at the groove 46, of holes corresponding to these additional passages respectively more and more distant from the passage 1 1 to the left, during the progression of the slide 67 from the position illustrated in FIG. 5 to the position illustrated in FIG. 6, would cause successive passages of the piston 115, inside the bore 95, at successive equilibrium positions respectively more and more distant from the face 99 by the process described with reference to passages 114 and 111, which would result in the emission, in the conduit 88, of piloting pressures having respective values lower than the pressure prevailing in the groove 46, but respectively larger and larger, in stages, as and as the groove 80 would allow the passage of an increasing flow, varying meanwhile continuously, from the groove 43 to the groove 66; a determined pressure level would be kept, as this slide 67 moves to the right, until a pilot pressure of the immediately higher level is emitted.

By way of nonlimiting example, there has thus been made appear between the passages 111 and 112 an additional passage 123, offset with respect to the passage 111 not only to the left but also angularly with reference to the axis 45, such additional passages can be multiplied at will to cause any desired number of pilot pressure levels (see Figure 3); in general, the difference in value between two pressure levels appearing successively, when the slide 67 moves to the right, would then be a function of the difference, along axis 45, between the two passages such as 111 and 123 appearing successively opposite the groove 46 during such a movement in the case of passages associated with the same groove 121 of the piston 115; in the case of passages such as passages 111 and 114, associated with two different grooves 120 and 121 of the piston 115, the difference between the pilot pressure levels respectively associated with these two passages is a function of both their relative spacing the along the axis 45, and the relative spacing as well as the dimensions of the grooves 120 and 121; the determination of the most appropriate dimensions is within the domain of the normal aptitudes of a person skilled in the art, as is the choice of a solution using a single groove on the piston 115 or a solution using several grooves on this piston.

The states of the distributor 12 illustrated in FIGS. 5 and 6 correspond to active states insofar as the distributor 12 then routes fluid, coming from the source 4, to the jack 10.

These active states require that the source 4 provide a sufficient flow of fluid, taking into account the volume of the chamber (not shown) of the jack 10.

In addition to these active states and the passive state constituted by the neutral position illustrated in FIG. 3, the distributor 12 can also occupy several other passive states corresponding to a displacement of the slide 67 to the left inside the bore 45, until the drawer 67 reaches an extreme left position illustrated in FIG. 7.

In this extreme left position, as in any intermediate position between the latter and the neutral position, the passage 114 remains placed opposite the groove 46, so that the piston 115 occupies its initial position illustrated in FIG. 3 if the second section distribution 18, or the various sections replacing it, allows free passage from the conduit 62 to the conduit 52, or the position illustrated in FIG. 9 if the distribution section 18 or one of the sections replacing it interrupts this connection.

Whatever the position occupied by the slide valve 67, and in particular when the pilot pressure appearing in the pipe 88 is used to control, as the servomotor 2, a cylinder for adjusting the speed of the heat engine 3, it is possible that back pressures increase the pressure in the passage 88, and consequently in the chamber 219, due to effects external to the system constituted by the distributor 12 as just described; whatever the equilibrium position then occupied by the piston 115, the increase in the pressure in the chamber 219 pushes the piston 115 to the left inside the bore 95, which could lead to damage to the device , or even prove to be dangerous.

Consequently, in the example of implementation of the device according to the invention which has been described and shown, provision has been made for a security system in the form of a possibility of intercommunication between the line 88 and the intersection of the conduit 34 with bore 44, when the piston 115 reaches, by sliding to the left inside the bore 95, a position further away from the face 99 of the bore 95 than its positions corresponding to the different levels pilot pressure.

To this end, if the pressure in the duct drops a predetermined threshold, greater than these pressure levels, this pressure transmitted to the chamber 219 by at least one of the passages 111, 112, 113, placed opposite the groove 96 depending on the position of the slide 67 in the bore 44, causes a displacement of the piston 115 to the left inside the bore 95 until the groove 121, overlapping the shoulder 102 of the peripheral face inside the bore 95, connects at least the passage 113, and also the passage 112 in the example illustrated in FIG. 8, with the space then existing between the external peripheral face 116 of the piston 115 and the section 101 , of larger diameter, of the bore 95, that is to say with the whole of the end zone thereof communicating via the passage 110 with the intersection of the conduit 34 and the bore 44; the back pressure thus appeared in the conduit 88, exceeding a predetermined threshold by the level of compression of the spring 220 when the groove 121 begins to overlap the shoulder 102 of the inner peripheral face of the bore 95, is thus evacuated towards the reservoir 5 and the piston 115 can return to its normal equilibrium position, exclusively dictated by the position of the slide 67 and the pressure level in the groove 46, when the back pressure ceases.

Claims (15)

1. A hydraulic distributor (12) of the type comprising at least one inlet duct (24, 42) able to be connected to a source (4) of hydraulic fluid under high pressure, at least one principal outlet duct (87) able to be connected to utilisation means (10) of hydraulic fluid under high pressure, at least one return duct (34, 62) able to be connected to a reservoir (5) of hydraulic fluid under low pressure, and distributor means (67) able to occupy serveral conditions in which it establishes or interrupts hydraulic connections between certain of said ducts, and in particular at least one passive condition in which said distributor means (67) establishes a hydraulic connection between said inlet duct (24) and said return duct (62) interrupting any hydraulic connection between said inlet duct (42) and said principal outlet duct (87), and at least one active condition in which said distributor means (67) establishes a hydraulic connection between said inlet duct (42) and said principal outlet duct (87) interrupting any hydraulic connection between said inlet duct (24) and said return duct (62), characterized in that it further comprises:

. an auxiliary outlet duct ()88),

. pressure reducing means (95, 111, 112, 113, 114, 115, 220), sensitive to the hydraulic pressure in said inlet duct (24), for establishing a hydraulic connection between said inlet duct (24) and said auxiliary outlet duct (88): ^-

- when the value of the hydraulic pressure in said inlet duct (24) exceeds a predetermined threshold, and then for causing the appearance, in said auxiliary outlet duct (88), of a hydraulic pilot pressure of a reduced value with respectto the value of hadraulic pressure in said inled duct (24),

- when the value of the hydraulic pressure in said inlet duct (24) is below the said threshold, and for transmitting this pressure to said auxiliary outlet (88),
the said threshold being on the one hand greater than a maximum value of hydraulic pressure in said inlet duct (24) when said distributor means (67) occupies a passive condition and said inlet duct (24) and said return duct (62) are respectively connected to the source (4) and to the reservoir (5), and on the other hand lower than a minimum value of hydraulic pressure in said inlet duct (24) when said distributor means (67) occupies an active conditions and said inlet duct (24) and said principal outlet duct (87) are respectively connected to the source (4) and to the utilisation means (10),

. modulation means (111, 112, 113, 114), coupled to said distributor means (67), for modulating the value of the hydraulic pilot pressure in a predetermined manner, as a function of the condition of said distributor means (67).

2. A hydraulic distributor according to claim 1, characterized in that said modulation means (111, 112, 113, 114) are able to give the hydraulic pilot pressure a first predetermined value when said distributor means (67) occupies a passive condition, and at least a second predetermined value, different from the first, when said distributor means (67) occupies an active condition.

3. A hydraulic distributor according to claim 2, characterized in that the second value is greater than the first.

4. A hydraulic distributor according to claim 1, said distributor means (67) being able to occupy a plurality of active conditions in which it establishes a hydraulic connection between said inlet duct (42) and said principal outlet duct, permitting respective different flow rates from said inlet duct (42) towards said principal outlet duct (87), interrupting any hydraulic connection between said inlet duct (24) and said outlet duct (87), characterized in that said modulation means (111, 112, 113, 114) are able to give to the hydraulic pilot pressure a first predetermined value when said distributor means (67) occupies a passive condition, and a plurality of respective second predetermined values, different from the first and different fron each other, when said distributor means (67) occupies the different active conditions.

5..A hydraulic distributor according to claim 4, characterized in that the said second values are greater than the first value, and increase or decrease respectively, according to wheter the flow rate per- mittingby said distributor means (67) increases or decreases;

6. A hydraulic distributor according to anyone of claims 4 and 5, the said active conditions being accessible in continuous succession, permitting the flow rate to vary continuously, characterized in that said modulation means give the said second values progressively.

7. A hydraulic distributor according to anyone of the preceeding claims, characterized in that it comprises safety means (110), for:

- automatically establishing a connection between said auxiliary outlet duct (88) and said return duct (34) if the value of hydraulic pressure in said auxiliary outlet duct (88) exceeds another predetermined threshold greater than the said values of pilot pressure,

- interrupting automatically any connection between said auxiliary outlet duct (88) and said return duct (34) if the value of hydraulic pressure in said auxiliary outlet duct (88) is below that of this other predetermined threshold.

8. A hydraulic distributor of the type comprising at least one inlet duct (24, 42) able to be connected to a source (4) of hydraulic fluid under high pressure, at least one principal outlet duct (87) able to be connected to utilisation means (10) of hydraulic fluid under high pressure, at least one return duct (34, 62) able to be connected to a reservoir (5) of hydraulic fluid under low pressure, and principal distributor means (67) able to occupy several conditions in which it establishes or interrupts hydraulic connections between certain of said ducts, and in particular at least one passive condition in which said principal distributor means (67) establishes a hydraulic connection between said inlet duct (24) and said return duct (62) interrupting any hydraulic connection between said inlet duct (42) and said principal outlet duct (87), and at least one active condition in which said principal distributor means (67) establishes a hydraulic connection between said inlet duct (24) and said principal outlet duct (87) interrupting any hydraulic connection between said inlet duct (24) and said return duct (62), characterized in that it further comprises:

. an auxiliary outlet duct (88),

. a bore (95) having an internal peripheral surface (100, 101) defining a longitudinal direction, a first transverse end (99) and a second transverse end (108, 109),

. means (111, 112, 113, 114) for hydraulic connection of said first end (99) with said auxiliary outlet duct (88),

. means (110) for hydraulic connection of said second end (108, 109), with said return duct (34),

. at least two orifices (111, 114, 123) arranged in said internal peripheral surface (100), with a first said orifice (114) comparatively close to said first end (99) and at least one second saif orifice (111) co mparatively further from said first end (99),

. a piston (115) mounted for longitudinal sliding inside said bore (95) and having an external peripheral surface (116) in sliding and fluid-tight contact with said internal peripheral surface (100) of said bore (95), a transverse face (117) of a first transverse end opposite said first transverse end (99) of said bore (95), a second transverse end (118, 119) opposite said second end (108, 109) of said bore (95),

. a compression spring (220) acting between said second ends (108, 118) for resiliently urging said piston (115) in said bore (95), towards said first end (99) of this latter,

. a passage (122), arranged in said piston (115), opening on the one hand in said face (117) of said first transverse end of said piston (115) and on the other hand in said external peripheral surface (116) of said piston (115), opposite said orifices (111, 114, 123) of said internal peripheral surface (100) of said bore (95),

. auxiliary distributor means (67), coupled to said principal distributor means (67), for establishing a hydraulic connection between said inlet duct (24) and, alternatively, said first orifice (114) or said second orifice (111) accordind to, respectively, said principal distributor means (67) occupying the passive condition or the active condition.

9. A hydraulic distributor according to claim 8, said principal distributor means (67) being able top occupy a plurality of active conditions in which it establishes a hydraulic connection between said inlet duct (42) and said principal outlet duct (87) permitting respective different flow rates from said inlet duct (42) towards said principal outlet duct (87), interrupting any hydraulic connection between said inlet duct (42) and said return duct (62), characterized in that said internal peripheral face (100) of said bore (95) has a plurality of second orifices (111, 123) differently elongated from said first end (99) of said bore (95), and said auxiliary distributor means (67) coupled to said principal distributor means (67) are able to establish a hydraulic connection between said inlet duct (24) and, selectively, a respective one of said second orifices (111, 123) when said principal distributor means (67) occupies the said active conditions, said second respective orifice (111, 123) being itself as far from said first end (99) of said bore (95) as the active condition occupied by said principal distributor means (67) corresponds to a greather permitted flow rate.

10. A hydraulic distributor according to anyone of claims 8 and 9, characterized in that it comprises means (102, 110, 111, 112, 113, 115,119, 121, 122, 220) for establishing automatically a hydraulic connection between said auxiliary outlet duct (88) and said return duct (34) if the hydraulic pressure in said auxiliary outlet duct (88) exceeds another predetermined threshold, and for interrupting automatically any hydraulic connection between said auxiliary outlet duct (88) and said return duct (34) if the hydraulic pressure in said auxiliary outlet duct (88) is less than this other predetermined threshold.

11. A hydraulic distributor according to anyone of claims 8 and 9, characterized in that it comprises means (102, 110, 112, 113, 121, 220) for automatically establishing a hydraulic connection between said passage (122) of said piston (115) and said second end (108,109) of said bore (95) if the hydraulic pressure at said first end (99) of said bore (95) exceeds another predetermined threshold, or for interrupting automatically any hydraulic connection between said passage (122) of said piston (115) and said second end (108, 109) of said bore (95) if the hydraulic pressure at said first end (99) of said bore (95) is lower than this other predetermined threshold.

12. A hydraulic distributor according to anyone of claims 8 through 11, said principal distributor means (67) comprising a slide (67) movable inside a body (25) of said distributor having said ducts for inlet (24, 42), for principal outlet (87), for return (34, 62), for auxiliary outlet (88), and means (11) of actuation of said slide (67), characterized in that said auxiliary distributor means (67) are constituted by said slide (67).

13. A hydraulic distributor according to claim 12, characterized in that said bore (95) is situated inside said slide (67), and said auxiliary distributor means (67) for establishing a hydraulic connection between said inlet duct (24) and, alternatively, said first orifice (114) or said second orifice (111, 123), said means (111, 112, 113, 122) for hydraulic connection from said first end (99) of said bore (95) with said auxiliary outlet duct (88) and said means (110) for hydraulic connection from said second end (108,109) of said bore (95) with said return duct (34) comprise passages (110, 111, 112, 113, 114, 123) in said slide (67).

14. A hydraulic distributor according to anyone of claims 1 through 13, characterized in that it is combined with means (2), in hydraulic connection with said auxiliary outlet duct (28), for piloting the flow rate of the source (4) as a function of the value of the hydraulic pilot pressure.

15. An integrated hydraulic distributor, characterized in that it comprises a plurality of distribution sections of which the first at least is constituted by a hydraulic distributor according to anyone of the preceeding claims, in which the second predetermined value (Pp2) of pilot pressure differing from the first (Pp 1) is obtained when one or several slides (67) of higher distribution sections are actuated, the slide (67) of the first distribution section being in a neutral position.

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