EP1647721B1 - Fluid cylinder, preferably double-acting, with end position damping - Google Patents

Abstract

The cylinder has a piston (3) with a stopper (10) whose hollow body delimits a channel (14) and has a conical generator to create a passage with variable opening between the body and a housing (13). The passage communicating with the channel links the piston`s pressure chamber (8) with a fluid evacuation conduit (6). The stopper is applied against its seat to limit speed of displacement of the piston at piston`s end of course.

Description

The present invention relates to a cylinder, preferably double-acting, with end-of-stroke damper.

Many cylinders, in particular hydraulic cylinders, are equipped today with a device which makes it possible to slow down the speed of movement of the piston of the cylinder to, or in the vicinity of, its end-of-travel position and this up to its position of limit switch. Such end-of-stroke dampers equip cylinders of the type comprising a cylinder body housing an actuating piston of a cylinder rod. The cylinder body is provided with at least one fluid discharge conduit. This fluid discharge conduit is generally disposed in a cylinder head closing one of the chambers, said pressure chamber or large chamber of the cylinder body. The cylinder head is generally equipped with a nozzle deposited at the outlet of the fluid discharge duct. This nozzle is usually screwed to the end of the fluid discharge conduit opening into the pressure chamber. The piston body is in turn equipped with a housing for capping the nozzle as the piston moves in the direction of the cylinder head. When the nozzle is housed at least partially in the piston housing, the fluid discharge is effected through the body of the nozzle after the flow of fluid within a passage defined between the piston body and the body of the nozzle. nozzle.

Such a solution poses different problems. Firstly, as soon as a misalignment occurs between the piston and the cylinder body, the piston housing does not come to cap the nozzle in such a way that the nozzle is centered inside said housing and a risk jamming of the piston occurs. In addition, during the fluid supply of the pressure chamber that takes place by the discharge conduit, the fluid must necessarily pass through the body of the nozzle and then through the passage that extends between body and housing. Due to the low level of fluid supply that results, there are problems of cavitation. As a result, this solution has so far been abandoned.

It is also known a cylinder incorporating a limit damper in the form of a shutter equipping the piston of the cylinder. This shutter is applied in the vicinity of the end of stroke of the cylinder against a seat opening into a first fluid discharge duct. This shutter is slidably mounted in the piston body with the interposition of a compression spring allowing the total stroke of the piston in the cylinder body. In the closed state, the emptying of the pressure chamber is effected by means of a second exhaust duct calibrated so as to slow the speed of movement of the piston to its end position. This second duct is formed in parallel with the first fluid discharge duct at the cylinder head and opens into the pressure chamber. This solution has various disadvantages. It can be seen first of all clogging of the second fluid discharge duct due to the small dimensions of this duct. This solution is described in DE-A-2,254,495 . In Figure 4 of this document, this second path is deleted. In this case, the shutter, which is slidably mounted inside the cylinder rod, and is guided in displacement via an oblong slot and an axis, is provided, at its head , an axial bore and a radial bore which allow emptying of the pressure chamber in the end position of the shutter. No progressive damping of the end-of-race race is planned.

The document US 4,706,781 discloses a double-acting cylinder comprising a cylinder body 1 housing a piston 5 for actuating a rod 7. This cylinder body is provided with a conduit 3 for supplying and discharging the fluid (in the figures). The duct is disposed in the head of the cylinder 2 closing one of the chambers, said pressure chamber 4A. The piston is equipped side cylinder head, a shutter. The body of the shutter is hollow. Thus, the shutter comprises a channel 10, channel putting in communication the piston pressure chamber and the discharge channel. In addition, the shutter has orifices 14 (FIG. 2) placed radially at the shutter, the diameter of which increases from the head of the jack towards the cylinder rod. The fluid is thus transmitted from the pressure chamber to the cylinder head via its orifices and the channel.

The production of radial apertures of progressive diameter from the free end of the shutter towards its bearing end inside a housing formed in the jack piston allows a gradual damping of the stroke of the jack by variation of the leak rate. However, the solution adopted for obtaining such a progressive damping is a complex solution to be implemented which weakens the shutter due to the multiplication of the orifices. In addition, for holes of smaller diameter, a risk of clogging can not be excluded.

An object of the present invention is therefore to provide a cylinder with end-of-stroke damper of the aforementioned type whose design allows an ease of adjustment of the speed of movement of the piston in the vicinity of its end-of-travel position and a progressive damping of the stroke end of the cylinder, without having to change the parts of the cylinder.

Another object of the present invention is to provide an integrated end-of-stroke damper cylinder whose design makes it possible to limit or even eliminate the risks of jamming of the piston during the reciprocating movement of the latter without increasing the pressure of the piston. overall size.

Another object of the present invention is to provide an integrated end-of-stroke damper cylinder whose design makes it possible to eliminate the risk of clogging or clogging of the fluid evacuation duct while eliminating the cavitation problems during operation. supply of fluid to the pressure chamber.

For this purpose, the subject of the invention is a jack, of the type comprising a jack body housing a piston for actuating a jack rod, this jack body being provided with at least one feed pipe and at least one fluid discharge duct, said fluid discharge duct being disposed in a cylinder head closing off one of the chambers, called the pressure chamber, of the cylinder body, the piston of the cylinder being equipped, on the cylinder head side, with a shutter which is applied, in the vicinity of the end of stroke of the cylinder , against a seat opening into the fluid discharge duct, this shutter being slidably mounted in a housing of the piston body with the interposition of a compression spring allowing the total stroke of said piston in the cylinder body and the passage of the fluid in a calibrated passage slowing the speed of movement of the piston to its end position, characterized in that the body of the shutter is a hollow body delimiting a channel, this hollow body having a conical generatrix so as to create a variable opening passage between the body of the shutter and its housing in the piston, said passage communicating with the channel for communicating the pressure chamber of the piston with the pipe t evacuation of the cylinder head, in the applied state of the shutter on its seat, so as to limit the speed of movement of the piston, in particular in the vicinity of its end of stroke.

Thanks to the fact that the shutter is embedded on the piston body and that this shutter is designed as a hollow body capable of delimiting a channel which cooperates with the delimitation of the calibrated passage with adjustable opening, putting in communication, the chamber of pressure of the piston with the exhaust duct of the cylinder head, in the applied state of the shutter on its seat, it becomes easy to reduce, in an adjustable manner, the speed of movement of the piston, particularly in the vicinity end of stroke without increasing the bulk of the assembly, the design of the shutter for easy change of the latter to allow an adjustment of the speed of movement of the piston according to the wishes of the user. The realization of the body of the shutter in the form of a body with a conical generator makes it possible to obtain, at low cost, a gradual damping of the end of stroke of the jack. This results in a braking action which increases as the piston approaches its end position.

• la figure 1 représente une vue partielle en coupe d'un vérin conforme à l'invention au cours de la rétraction de la tige de vérin en position non appliquée de l'obturateur contre un siège débouchant dans le conduit d'évacuation de fluide ;
• la figure 2 représente une vue partielle en coupe d'un vérin, conforme à l'invention, en position d'application de l'obturateur, au voisinage de la fin de course du vérin, contre un siège débouchant dans le conduit d'évacuation du fluide ;
• la figure 3 représente une vue partielle en coupe d'un vérin conforme à l'invention en position de fin de course du vérin, à l'état appliqué de l'obturateur sur son siège ;
• la figure 4 représente une vue partielle en coupe du vérin, dans une position voisine de sa position de fin de course, lors du début de l'alimentation en fluide de la chambre de pression pour permettre la sortie de la tige du vérin et
• la figure 5 représente une vue partielle en coupe du vérin conforme à l'invention.

The invention will be better understood on reading the following description of exemplary embodiments, with reference to the appended drawings in which:

• Figure 1 shows a partial sectional view of a cylinder according to the invention during the retraction of the cylinder rod in the unapplied position of the shutter against a seat opening into the fluid discharge conduit;
• FIG. 2 represents a partial sectional view of a jack, according to the invention, in the position of application of the shutter, in the vicinity of the end of stroke of the jack, against a seat opening into the evacuation duct; fluid;
• 3 shows a partial sectional view of a cylinder according to the invention in end position of the cylinder, in the applied state of the shutter on its seat;
• FIG. 4 represents a partial sectional view of the jack, in a position close to its end-of-stroke position, at the beginning of the supply of fluid to the pressure chamber to allow the cylinder rod to exit and
• Figure 5 shows a partial sectional view of the cylinder according to the invention.

As mentioned above, the cylinder 1, object of the invention, comprises a cylinder body 2 housing a piston 3 for actuating a rod 4 cylinder. This cylinder body 2 is provided with at least one supply duct 5 and at least one duct 6 for discharging fluid. In the examples shown, the fluid evacuation duct 6 is disposed in a cylinder head 9 closing one of the chambers 7, 8, called the pressure chamber 8, of the cylinder body 2. This pressure chamber 8 may also be called the piston chamber of the cylinder piston. The fluid supply of this chamber 8 controls the output of the cylinder rod. Conversely, the emptying of this chamber causes a retraction of the cylinder rod. For double-acting cylinders, the piston is used to define two chambers, respectively called large and small chambers, each chamber being provided with a fluid supply duct and a fluid discharge duct. One can also imagine a solution in which the cylinder is a single-acting jack, the pressure chamber being adapted to be fed and to be drained fluid, a spring being positioned in the other chamber, this spring tending to recall the piston in an end position corresponding to a retraction position of the cylinder rod 4. It is also possible to imagine a spring-free solution, the retraction of the rod being obtained by the weight of the load, particularly in the case of a lifting cylinder.

The piston 3 of the jack is in turn equipped, on the head 9 of the jack, with a shutter 10 which, in the vicinity of the end of the stroke of the jack 1, bears against a seat 11 opening into the pipe 6 for the evacuation of fluid. This shutter 10 is slidably mounted in the body of the piston 3 and in particular in the body of the cylinder rod when the rod passes through the piston 3 and constitutes part of the piston 3. In the examples shown, the shutter 10 is slidably mounted. in a housing 13 of the piston body 3. This shutter 10 is loaded by spring 12 and is positioned axially inside the cylinder body to be in axial disposition with the cylinder rod 4. The spring 12 is compressed inside the housing 13 formed in the piston body, as the piston 3 moves towards its end position, in the applied state of the shutter against the seat of the conduit 6 of fluid evacuation. In the applied state of the shutter against the seat 11 of the fluid evacuation duct 6, during the displacement of the piston 3 to its end-of-travel position corresponding to its position of application against the cylinder head 9 , the fluid can no longer flow directly from the pressure chamber 8 to the conduit 6 for discharging fluid. It then borrows a calibrated passage 19 which extends between the body of the shutter 10 and its housing 13 in the piston before entering the body of the shutter 10, part of which is constituted by a channel 14 delimited by the body of the shutter 10. The body of the shutter is indeed in the form of a hollow body which delimits the channel 14. This channel 14 thus allows, in cooperation with the passage 19, the implementation communication of the piston pressure chamber 8 with the conduit 6 for discharging the cylinder head 9 in the applied state of the shutter 10 on its seat 11. To reach this channel 14, the fluid takes a passage 19 formed between the body of the shutter and its housing in the piston.

This passage 19 defines a variable opening between the body of the shutter and the housing 13 of the jack slidably receiving said shutter. This variable opening is obtained thanks to the fact that the body of the shutter has a generally conical shape, in this case frustoconical, the large base of the cone being formed by the free end of the shutter while the small base of the trunk cone or the top of the cone is closed by the support end of the shutter within the housing 13 formed in the piston of the cylinder. The opening of the passage 19 thus tends to be reduced as and when the introduction of the shutter in its housing generating a progressive damping of the end of stroke of the cylinder. This results in a braking action which increases as the piston approaches its end position. As this limitation of the speed occurs in the vicinity of the end of stroke of the piston, one thus avoids any damage of the piston which would come, in the absence of damper, to hit brutally the face of the head 9 of the jack arranged opposite the thrust face of the piston. Such progressive damping can be obtained without weakening the body of the shutter or make it more difficult to manufacture. The passage 19, as described above, constitutes a calibrated passage section and thus allows the supply of fluid from the chamber 8 into the channel 14. The channel 14 communicates with the conduit 6 for discharging fluid and allows , by evacuation of the fluid, the emptying of the chamber 8. The channel 14 is of smaller dimension, in particular of passage section below the conduit 6 of discharge of the fluid.

In the examples shown, this channel 14 of the shutter is constituted by a through axial nozzle 14a and radial nozzles 14b of the shutter body 10.

To avoid cavitation phenomena, it is found that the duct 6 fluid evacuation of the pressure chamber 8, formed in the cylinder head 9, further constitutes the conduit 5 for supplying fluid to said pressure chamber 8. Thus, when the cylinder pressure chamber 8 is supplied with fluid, as illustrated in FIG. 4, the portion of the shutter intended to be applied on the seat 11 of the evacuation duct 6 deviates from the latter under the effect of pressure and thus directly allows the passage of fluid duct 5 in the pressure chamber 8, without passage through the shutter 10, to drive the piston in a direction corresponding to the output of the rod of the cylinder. Thus, no cavitation phenomenon is observed.

In order to eliminate the risks of jamming during the reciprocating movements of the piston 3, the telescopic shutter 10 is mounted floating inside its housing 13 in the body of the piston 3. This floating assembly allows on the one hand to delimit the calibrated passage 19 communicating with the channel 14 and allowing the braking speed of movement of the piston, on the other hand to correct the misalignment that may be exerted between the shutter 10 and the piston body 3 In the example shown, the floating assembly of the shutter 10 in its housing 13 is formed by a ring 15 mounted with radial and axial clearances in the housing 13 of the piston 3. This ring 15 is held axially in said housing 13 of the piston 3 by a ring 16.

In a more detailed embodiment of the invention, the body of the shutter 10 is provided at one of its ends with a radial protrusion 17 intended to constitute the application seat of the compression spring 12. This protrusion 17 forms, by pressing on one of the faces of the ring 15, an end stop of the shutter 10 marking the extreme position of its outlet 13 of said shutter 10. The ring 15 is in turn housed inside a shoulder portion 18 of the seat piston piston 3 of said ring 15. A groove 21 is formed in this shoulder portion 18 to accommodate the ring 16. This ring may be further provided with a keying preventing its assembly upside down. The body of the shutter 10 with its conical generatrix, inside the housing 13 of the piston, in the presence of said ring 15, a passage 19 with variable opening between the body shutter 10 and the guide ring 15. The portion of the shutter 10 intended to be applied on the seat 11 of the fluid evacuation duct 6 is in the form of a protuberance 20 of spherical shape to apply to sealing contact against a ridge formed in the seat 11 of the duct 6 evacuation. Again, this configuration of the part of the shutter 10 intended to be applied on the seat 11 of the duct 6 evacuation ensures a seal of the assembly, including misalignment between shutter and body piston. This protrusion 20 gives the obturator a general form of mushroom whose stem would constitute the body of the mushroom and the protrusion 20, the head of the mushroom.

The operation of such a jack is as follows. When the pressure chamber 8 of the cylinder is filled with fluid, the cylinder rod is output. To allow the return of this rod, the emptying of the chamber is controlled. For this purpose, the conduit 6 for discharging fluid from the pressure chamber 8 is open or placed in the exhaust. The rod / piston assembly can then move towards the cylinder head 9 closing said chamber 8. This assembly moves until the head of the shutter 10 comes to bear against the seat of the duct 6. fluid evacuation. The fluid is then forced to flow from the pressure chamber 8 between the ring and the body of the shutter through the calibrated passage with variable opening to reach the radial nozzles 14b and the axial nozzle 14a formed in the body of the shutter 10 and disposed in the extension of the conduit 6 for discharging fluid. The nozzles 14a and 14b are calibrated to create a leakage flow. The fluid then flows through the conduit 6 of fluid discharge allowing movement of the piston as the emptying of the chamber. In the end position of the piston, in which the latter is applied against the head 9 of the jack, the body of the shutter is housed essentially inside the housing 13 formed in the piston body and the spring is compressed.

When it is desired, conversely, to control an output movement of the cylinder rod, it feeds the conduit 6 for discharging fluid which then becomes a conduit 5 for supplying fluid to the pressure chamber 8. This supply automatically causes a detachment of the head of the shutter 10 of the seat 11 equipping the conduit outlet 6 fluid discharge. The fluid then flows directly from the fluid supply conduit 5 to the pressure chamber 8 to cause the piston to move in the direction of an outlet of the cylinder rod.

When a new adjustment of the speed of movement of the piston in the vicinity of its end-of-stroke position is desired, it is sufficient to replace the shutter fitted to the piston with a new shutter whose outer dimensions have been modified according to the wish of the user. It thus becomes extremely easy to adjust the speed of movement of the piston in the vicinity of its end position. In addition, since the shutter is mounted floating inside its housing, the risk of damage to such a shutter is reduced.

Claims (9)

1. Jack (1), of the type comprising a jack body (2) which accommodates a piston (3) for activation of a jack rod (4), this jack body (2) being provided with at least one supply pipe (5) and at least one fluid discharge pipe (6), the said fluid discharge pipe (6) being disposed in a jack head (9) which shuts one (8) of the chambers (7, 8), known as the pressure chamber (8) of the jack body (2), the piston (3) of the jack being equipped, on the jack head side (9), with a shutter (10) which is applied in the vicinity of the end of travel of the jack (1), against a seat (11) which opens into the fluid discharge pipe (6), this shutter (10) being fitted such as to slide in a receptacle (13) in the body of the piston (3) with interposition of a compression spring (12) which allows the said piston (3) to complete its full travel in the body (2) of the jack, and permits passage of the fluid into a calibrated passage which brakes the speed of displacement of the piston (3) as far as its end-of-travel position, characterised in that the body of the shutter (10) is a hollow body which delimits a channel (14), this hollow body having a conical generatrix such as to create a passage (19) with variable opening between the body of the shutter and its receptacle (13) in the piston, the said passage (19) communicating with the channel (14) in order to put the pressure chamber (8) of the piston (3) into communication with the discharge duct (6) of the head (9) of the jack, in the state in which the shutter (10) is applied on its seat (11), such as to limit the speed of displacement of the piston (3), in particular in the vicinity of its end of travel.
2. Jack (1) according to claim 1, characterised in that the channel (14) is constituted by an axial through nozzle (14a) and radial nozzles (14b) of the shutter body (10).
3. Jack (1) according to one of claims 1 and 2, characterised in that the telescopic shutter (10) is fitted such as to float inside its receptacle (13) in the body of the piston (3), in order to delimit a calibrated passage (19) which communicates with the channel (14) of the shutter, this floating fitting making it possible to rectify faults of alignment which could occur between the shutter (10) and the piston body (3), and thus eliminate the risks of jamming during to-and-fro manoeuvres of the piston (3).
4. Jack (1) according to claim 3, characterised in that the floating fitting of the shutter (10) in its receptacle (13) is carried out by means of a ring (15) which is fitted with radial and axial play in the receptacle (13), this ring (15) being retained axially in the said receptacle (13) by a retainer ring (16).
5. Jack (1) according to claim 4, characterised in that the body of the shutter (10) is provided at one of its ends with a radial protuberance (17) which is designed to constitute the seat of application of the spring (12), this protuberance (17), by being supported on one of the surfaces of the ring (15), forming an end-of-travel stop for the shutter (10) which demarcates the extreme output position of the said shutter (10), from its receptacle (13).
6. Jack (1) according to one of claims 4 and 5, characterised in that the ring (15) is accommodated inside a shouldered portion (18) of the piston (3) of the jack, which forms a seat for the said ring (15), a groove (21) being provided in this shouldered portion (18) for accommodation of the retainer ring (16).
7. Jack (1) according any one of claims 4 to 6, characterised in that the body of the shutter (10) has a conical generatrix such as to create a passage (19) with a variable opening between the shutter body (10) and the guide ring (15).
8. Jack (1) according to any one of claims 1 to 7, characterised in that the part of the shutter (10) which is designed to be applied to the seat (11) of the fluid discharge pipe (6) is in the form of a protuberance (20) with a spherical shape, in order to be applied in sealed contact against a ridge provided in the seat (11) of the discharge pipe (6).
9. Jack (1) according to any one of claims 1 to 8, characterised in that the pipe (6) for discharge of fluid from the pressure chamber (8), which pipe is provided in the head (9) of the jack, additionally comprises the pipe (5) for supply of fluid to the pressure chamber (8).

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