EP0889000A1 - Fork lift truck - Google Patents

Abstract

Each branch (7A,7B) of the fork lift (1) is supported on the raised support surface by two support points (8,9). One of these (8) is a roller enabling a transfer of load from the second wheel (6) to it, in order to retract this second wheel and enable a first translation phase on the surface, bringing the other fork support point onto the surface. This other support point (9) enables unballasting the first wheel (5) from the ground and raising it as far as the fork support points to ensure movement of the whole device to any point of the surface.

Description

The present invention relates to a forklift, in especially for loading and unloading of a load on a receiving surface in elevation, such as a load floor of a vehicle so-called light transport, a platform receiving surface, etc.

It relates more particularly to elevators fork of the type comprising at least one device for fork lift and lower control minus a first wheel arranged directly above the device for controlling the fork and at least one second wheel, distant from the first, and can be placed at the right of fork and under load. Such forklifts of the aforementioned type are well known to those versed in this art.

For many years, we have sought to design forklifts capable of being transported by the transport vehicle receiving loads to be loaded and unloaded by said forklift, this transport to be carried out in such a way that the forklift is out of contact with the surface of the road.

Examples of embodiment of such fork lifts are particularly described in patents FR-A-2,215,380, US-A-4,061,237 and US-A-5,174,415. These forklifts fork are all made on the same principle and therefore have all the same disadvantages. In indeed, in all of the forklifts described, the fork tines are brought into sockets or integrated stirrups or other generally elongated members in the transport vehicle. Thanks to this positioning fork tines in the elongated sockets carried by said transport vehicle, it is subsequently possible to apply fork power in a downward direction so that the rest of the vehicle forklift is lifted to allow it to be transported by the transport vehicle. This transport is carried out with the forklift out of contact with the road surface. To allow a such introduction of the fork teeth in these elongated elements such as stirrups, sockets, sheaths of the transport vehicle it is necessary that the wheels before the forklift can tilt, generally around an axis of rotation, a position forward relative to the forklift at one position rear compared to the rest of the forklift. This tilting generates a pivoting torque on the teeth of the fork, which requires immobilization of the teeth the fork relative to the transport vehicle, like this has been described above. This results in two disadvantages major of such a forklift. First of all, the transport of such a forklift cannot be carried out only by means of a dedicated transport vehicle and fitted with such sockets or stirrups or other fixing suitable for receiving the teeth of the fork and for immobilize in transport position. In addition, the cart forklift in transport position exceeds usually from the back of the truck. This results in a significant overall size.

Other forklifts not requiring the specific layout of a vehicle are described in WO-83.04226 and FR-A-1,506,606.

The fork vehicle described in patent WO-83.04226 is equipped with at least two wheels corresponding respectively to the first wheel and to the second elevator wheel at fork described in this patent application. This forklift still has a fulcrum roller placed under the fork and a fulcrum additional arranged at the end of a telescopic arm at the back of the frame. The rolling fulcrum of the fork allows load transfer from the second wheel to the rolling support point to retract this second wheel and authorize a first phase of displacement generally in translation on the receiving surface in elevation. For allow shedding of the first wheel it is necessary to ensure the exit of a telescopic arm, carrying the rolling fulcrum at its free end additional. This additional rolling support point allows the lifting of the forklift chassis to a position beyond the surface in elevation. Once the first wheel is placed directly above the fork control device resting on the receiving surface in elevation, the telescopic arm is retracted until brought into a position corresponding to its initial position. In this position, on the surface in elevation, the forklift rests on the one hand on the rolling support placed under the fork, on the other hand on the first wheel placed vertically above the fork raising and lowering control.

Document FR-A-1.506.606 describes a forklift based on the same principle as that described in the WO-83.04226 cited above. Indeed, again in this forklift, we use a foot located at the back of the chassis which constitutes a telescopic stand and serves additional support point when lifting the frame. This forklift therefore again comprises a first wheel disposed directly above the device fork control and a second wheel located at the fork right and under load. Each branch of the fork has a rolling support. The forklift also has an additional support point constituted by a wheel so that the points additional support for the fork and wheel are arranged on one side and the other of the first and second forklift wheels. Again, in this case, the rolling support point under the fork is used for a load transfer from the second wheel to this rolling support and thus allow the elevation of this second wheel then a displacement of the assembly on the receiving surface in elevation, while the point additional support placed at the rear of the chassis allows the first and second wheels to rise up to the surface in elevation, to be brought to bear on this last so that, once in the support position, the additional support point placed at the rear of the chassis can be unloaded.

Another forklift described in the application international WO-96.26153 is of even more design complex. This elevator requires the presence of at least four forks, the forks for elevation and the lowering of the load being equipped with only one fulcrum.

The purpose of the present invention is therefore to overcome the disadvantages mentioned above by proposing a forklift whose design makes it possible to avoid, for transport to means of a transport vehicle, to have a specific equipment for said vehicle transport.

Another object of the present invention is to provide a forklift which can, in the transport position, be move to any point on the receiving surface in elevation so as not to exceed the rear of the transport vehicle in the transport position.

Another object of the present invention is to provide a particularly simple design forklift free of additional support point at the rear of the said elevator so that the whole elevator is small footprint.

To this end, the invention relates to an elevator fork, especially for loading and unloading operations unloading of a load placed on a pallet on a receiving surface in elevation, such as a floor load of a transport vehicle, of the type comprising at minus an elevation control device and lowering the fork, at least one first wheel positioned directly above the fork control device and at least one second wheel, distant from the first, and can be placed in front of the fork and under the load, characterized in that each branch of the fork is supported on the receiving surface in elevation by at least two support points, at least one of which is rolling, the rolling support point allowing a transfer load from the second wheel to said rolling support for retract this second wheel and authorize a first displacement phase, generally in translation, on the receiving surface in elevation until bringing the other fork support point also on the surface of reception in elevation, this other support point allowing to unload the first support wheel on the ground and to raise it preferably at least up to the level of the support points of the fork to ensure a possible displacement of the entire device at any point in the receiving surface in elevation.

Thanks to this design, we see that no couple of tipping is only exerted on the fork legs when the transition from a low position to a high position followed a generally translational displacement of said fork branches. This results in the possibility of get rid of fasteners that would have on the transport vehicle to ensure immobilization of said branches of the fork. Finally, the design of this forklift allows its displacement at any point on the surface of reception in elevation. Furthermore, the deletion of additional support points at the rear of the elevator allows the realization of a low lift size.

According to a preferred embodiment of the invention, the support points of the same fork leg are rolling supports.

la figure 1 représente de manière schématique les étapes A à F de chargement d'un élévateur à fourche, objet de l'invention, sur une surface de réception en élévation, telle qu'une plate-forme d'un véhicule de transport ;

la figure 2 représente une vue en perspective d'un élévateur à fourche, la fourche étant représentée en position haute avant positionnement de la fourche sur la surface de réception en élévation ;

la figure 3 représente une vue en perspective d'un élévateur à fourche, la fourche étant représentée en position basse d'appui sur une surface de réception en élévation non représentée.

The invention will be clearly understood on reading the following description of an exemplary embodiment, with reference to the accompanying drawings in which:

FIG. 1 schematically represents the steps A to F of loading a forklift, object of the invention, on a receiving surface in elevation, such as a platform of a transport vehicle;

2 shows a perspective view of a forklift, the fork being shown in the high position before positioning the fork on the receiving surface in elevation;

3 shows a perspective view of a forklift, the fork being shown in the low position of support on a receiving surface in elevation not shown.

The forklift, object of the invention, is shown in the figures under the general reference 1. This forklift is able to change working level on his own without the help of an incline or another lifting device. This forklift is more particularly used for operations of loading and unloading of load from a surface in elevation preferably located at most 80 cm from the ground, this elevated surface can for example be formed by the floor of a light commercial vehicle. This forklift comprises, in a manner known per se, a lifting and lowering control device of a fork, this device being represented under the general reference 4. This control device comprises at at least one chassis made up of at least two elements of chassis 11, 12 animated by a relative movement one by relative to each other by means of a cylinder 13 controlled by operated by suitable control devices which will be described below.

The first frame element 11 of the device 4 of movement control of the fork 7 affects the shape of a U whose core is arranged to conform a bearing allowing the housing of at least one wheel 5 called by the following first wheel of the forklift, this first wheel 5 being disposed directly above the device 4 control. Note that in the examples shown, this first wheel 5 is actually constituted by a pair of wheels, these wheels being able to be possibly directional to facilitate moving the entire elevator.

The body of the actuator 13 extends in turn substantially parallel to the branches of the U or, in other words, parallel to the uprights of the first frame member 11. This cylinder body 13 is disposed between said uprights of the first frame element 11 and rests at one of its ends on the core of the U constituting the first element of chassis 11. The cylinder body 13 is held in this vertical position by means of a spacer 14 disposed at the near the upper end of the cylinder body 13, this spacer 14 being fixed to each of its ends to the uprights of the first chassis element 11.

The second chassis element 12 carries meanwhile branches or arms 7A, 7B of the fork 7. These branches or arms 7A, 7B of the fork 7 extend substantially horizontally. These branches or arms of the fork are integral in displacement with the second chassis element 12 and always move parallel to themselves from so as to avoid any reversal of the load 2.

The second frame element 12 is driven by a movement back and forth vertical with respect to said first element chassis 11 under the action of the jack 13. To do this, this second frame element 12 is connected so as to preferably detachable, at the free end of the rod of the jack 13 and further comprises, in a location any rollers or rolling elements capable of move inside of slideway arranged in amounts of the first frame element 11. Thus, in the example shown in Figures 2 and 3, these rollers are carried by arms extending perpendicular to the uprights of the first frame element 11. This mounting to sliding of the second chassis element 12 relative to to the first frame element 11 and the connection by the rod cylinder 13 between the first and second elements of chassis of the control device 4 make it possible to obtain this displacement in a vertical plane following a movement in back and forth of the second chassis element 12. It results a movement up and down of the branches 7A, 7B of the fork 7, said branches 7A, 7B moving always parallel to themselves.

The extension and retraction of the jack 13 can be ordered in different ways, this command can be hydraulic, manual or other. In the examples shown in Figures 2 and 3, the control of the output of the rod of the jack 13 is carried out manually by actuation of a drawbar 15 according to the arrow shown in Figure 2, and in a manner known per se. Back to school the rod of the jack 13 is controlled by means a pedal disposed on said first chassis element 11 of the control device 4 and possibly of a controller. This control device 4 is further provided a pressure accumulator which builds up pressure particularly during the extension of the cylinder rod 13. This pressure will then be used again when retraction of the jack as will be described below.

In addition to this device 4 for controlling the elevation and lowering the fork known per se, the elevator fork further comprises, between the plane of the fork 7 and the ground support plane, at least one pair 10 of arms 10A, 10B arranged in scissors. In this case, in the example shown, each branch 7A, 7B of the fork is equipped of such a pair of scissor arms. Said arms are articulated together at a substantially central point of each arm, this articulation being represented at 16 to Figure 2.

One of the arms, in this case the arm 10A in the examples shown, carries, at its free end, a second ground support wheel 6 and, at its other end, an axis of articulation or pivot to the fork. This axis is not shown. The second wheel 6 is away from the first wheel 5 and is usually placed substantially at the fork and under the load 2.

The other arm 10B of this pair of arms is mounted respectively sliding at each of its ends, on the one hand on the chassis of the control device 4, on the other hand on the corresponding branch 7A or 7B of the fork 7. The end of the arm 10B mounted to slide on the chassis of the elevation control device 4 and lowering fork 7 is immobilized in position on said chassis by means of a locking member unlockable. This locking member, not shown in the figures, is generally constituted by a lever swivel whose free end takes the form of a hook so as to allow, in the active position of said lever, the immobilization on the move of one of the ends of the arm 10B. This concerned end of the arm 10B is that slidingly mounted on the first element chassis 11 in the example shown in FIGS. 2 and 3. This moving immobilization of the arm 10B is particularly important when the forklift occupies the position shown in Figure 2 because it ensures, for a given position of the fork 7, a stationary position of the arms 10A, 10B.

Each branch 7A, 7B of the fork 7 also comprises, preferably near its free end, at least a wheel 8 constituting a first rolling fulcrum. This first rolling support point 8 allows a transfer of load from the second wheel 6 to said rolling support 8, as will be described below so that retract this second wheel 6. It should be noted that this rolling support point of branch 7A, 7B of fork 7 also consists of a retractable wheel 8, retraction being effected by pivoting around an axis 17 substantially orthogonal to the longitudinal axis of the branch of the fork 7. The role of this retraction will also described below when describing diagrams A to F shown in Figure 1.

Each branch 7A, 7B of the fork 7 also has a second support 9, preferably rolling. It is to highlight that each fulcrum of a fork leg can be common to that of the other fork leg. In that case this fulcrum is generally placed in space free between the branches of the fork below these past. In the examples shown in Figures 1 to 3, this second support is a rolling support produced by means of a wheel 9, also retractable by pivoting around a axis 18 substantially orthogonal to the longitudinal axis of each branch of the fork. This retraction allows shift the wheel 9 from an active position to a position inactive. This other fulcrum 9 of the branch of the fork makes it possible to unload the first support wheel 5 at the soil and preferably raise it to the level of the points support 8, 9 of the fork on a receiving surface 3 in elevation. This fulcrum 9 of the branch of the fork is preferably arranged in the interval between the first and second wheels 5, 6 of the elevator. In summary, the points of support of the same branch of the fork 7 are constituted respectively by a wheel 8, 9 retractable by pivoting about an axis 17, 18 substantially orthogonal to the longitudinal axis of each fork branch. Wheel retraction is controlled by means of a single control member arranged on the elevation control frame and lowering the fork. This control member can be a manual member, such as a lever, or a jack hydraulic or any other suitable device.

The operating principle of such a forklift is the following, as shown in diagrams A to F of the figure 1. To allow obtaining a position of the forklift as shown in Figure 1 diagram A, it is necessary to assume that the arms 10A, 10B in scissors arranged under each branch 7A, 7B of the fork 7 have been folded, that the branches 7A, 7B of the fork 7 were placed in the low position by actuation of the jack 13 to allow the loading of a load 2 on said branches 7A, 7B of the fork 7. This load 2 is generally carried by a pallet, not shown in the figures. The branches 7A, 7B of the fork 7 then enter between the surface of the pallet receiving the load and the ground surface of this palette. In this pallet loading position and of the load 2 on the branches 7A, 7B of the fork 7, the wheels 8, 9 of each branch 7A, 7B of the fork 7 are in retracted position so as not to hinder such loading. At during the loading of load 2 and the pallet on the branches 7A, 7B of the fork 7, the forklift is moved by rolling on its first wheel 5 and its second wheel 6 until the arms 7A, 7B of the fork are positioned under the pallet between the surface of reception of the load by the pallet and the bearing surface on the floor of this palette. Once the branches of the fork 7 correctly positioned, load 2 can be moved either in the lower position of the fork legs 7, either in the up position of the latter or in any intermediate position between these two positions like this can be done with a lift classic fork. Regardless of the position of the branches 7A, 7B of the fork 7, the arm 10B of each pair of forklift arms is locked to one of its ends by means of the lock described above so that the second wheel 6 carried by the other arm 10A of the pair of arm provides effective ground support.

When the forklift is brought in the vicinity of a receiving surface 3 in elevation, this surface possibly be formed by the platform of a vehicle or by any other receiving surface in elevation, the branches 7A, 7B of the fork 7 are raised to bring the latter to a level of preference slightly higher than that of the receiving surface 3 in elevation. Such a position is represented in diagram A of figure 1. In this case, the chisel, whose arm 10B is still locked, occupies a deployed position and the rolling supports 8 and 9 of each fork leg are still in position retracted. The forklift is then moved to a position in which the free end of each branch 7A, 7B of the fork 7 comes to bear on the receiving surface 3 in elevation through the wheel 8 disposed in the vicinity of the free end of each branch of the fork. Such a position of the forklift is particularly represented in the diagram B of figure 1. Obviously, in this position, the wheel 8 is in the active position corresponding to a non-retracted position of said wheel. The passage of the inactive position at the active wheel position 8 generally takes place simultaneously with that of wheel 9, this passage being controlled manually by means of a member single control, such as a joystick, arranged on the elevation control frame and lowering the fork. In fact, generally wheels 8 and 9 are mechanically coupled to allow this simultaneous displacement.

As the free end of the forks is resting on the receiving platform 3 in elevation, the wheel 6 of the arm 10A of the pair of arms no longer supports any load. he then becomes possible to unlock the arm 10B by actuation of its locking member, such as a lever, to allow folding (diagram C) of the pair arm 10A, 10B under the fork leg. As he has been clarified above, each branch of the fork is equipped with a pair of arms. Unlocking takes place so for each pair of arms from each branch of the fork. The final folding position of the pair of scissor arm is shown in diagram D in Figure 1. once the pair of arms arranged in scissors brought in folded position under the fork legs, it is then possible to continue moving generally by translation of the forklift until bringing a second support point 9 of the fork legs in pressing on said receiving surface 3 in elevation as this is represented in diagram E of figure 1. In this case, the second support is again constituted by a support rolling, in this case the wheel 9 which is in position active. In this position, the branches of the fork have at least two support points 8, 9 on the surface 3 reception in elevation. The result is perfect stability of the fork legs which cannot be subject to no tilting torque. The result also the possibility of reassembling the rest of the device 4 for raising and lowering the fork 7 and raise it at least to the level of points of support of the fork legs on the surface of reception in elevation. To do this, we use again the jack 13 of the device 4 for controlling the movement of fork branches. Indeed, during the support of the second fulcrum 9 of the branches of the fork on the receiving surface 3 in elevation, we offload the first support wheel on the ground 5 of the forklift, raising the control device 4 can therefore be carried out without problem, the wheel 5 no longer fulfilling any role. A Once the control device 4 has been brought to level, it is possible, by moving the elevator again to fork on the receiving surface in elevation, to bring in support the first support wheel on the ground 5 of the elevator fork on the receiving surface in elevation, like the shows the diagram F of figure 1. This then results three rolling support points of this forklift on the receiving surface 3 in elevation. Therefore, it there is no longer any difficulty in moving the whole of the forklift on the receiving surface 3 in elevation. In the event that it is necessary to deposit load 2 on this receiving surface in elevation to allow the loading of another load, it suffices then to raise, by means of the control device 4, the branches 7A, 7B of the fork 7 to a position in which the arms 10A, 10B arranged in scissors can be deployed again, the arm 10B being locked in this deployed position. The wheel 6 is then pressed again on the receiving surface in elevation. This results in a possibility of retracting the wheels 8 and 9. Once these wheels 8 and 9 retracted, it is then possible to lower to new branches 7A, 7B of the fork 7 of the elevator fork to deposit load 2 on the ground.

Unloading empty or under load from the elevator fork of receiving surface 3 in elevation is carried out in reverse to the operations described above. In fact, initially, the control 4 is lowered so that wheel 5 comes resting on the ground as shown in diagram E of FIG. 1, then the forklift is again moved to the receiving surface in elevation to allow the deployment of the pair of scissor arms to a position in which the wheel 6 is brought to bear on the ground, arm 10B of the pair of arms being locked in this position. Support 8 then becomes unnecessary. It is therefore possible to move again, usually in backing up, the forklift to a position in which none of the rolling supports 8, 9 is supported on the receiving surface 3 in elevation. The operations are therefore operations strictly inverse to those which have have been described in Figure 1. Note that when the elevation of the control device 4 to bring the wheel 5 in support on the ground up to the level of the support points of the fork on the elevated platform we use for actuation of the actuator 13, in particular the retraction of the latter, the pressure accumulated in the accumulator of pressure described above.

Claims (7)

Fork lift (1), in particular for loading and unloading operations for a load (2) arranged on a pallet on a receiving surface (3) in elevation, such as a load floor of a vehicle transport, of the type comprising at least one device (4) for controlling the raising and lowering of the fork, at least one first wheel (5) disposed directly above the device (4) for controlling the fork and at at least a second wheel (6), distant from the first (5), and able to be placed in line with the fork (7) and under the load (2),
characterized in that each branch (7A, 7B) of the fork (7) is supported on the receiving surface (3) in elevation by at least two support points (8, 9), one of which (8) at less is rolling, the rolling support point (8) allowing a load transfer from the second wheel (6) to said rolling support (8) to retract this second wheel (6) and allow a first phase of movement generally in translation on the receiving surface in elevation until bringing the other fulcrum of the fork also on the receiving surface (3) in elevation, this other fulcrum (9) making it possible to unload the first wheel (5 ) support on the ground and preferably raise it at least to the level of the support points (8, 9) of the fork (7) to ensure possible displacement of the entire device at any point of the receiving surface (3) in elevation. Forklift according to claim 1,
characterized in that the support points (8, 9) of the same branch of the fork (7) are rolling supports. Fork lift according to claim 2,
characterized in that the bearing points of the same branch of the fork (7) consist respectively of a wheel (8, 9) retractable by pivoting around an axis (17, 18) substantially orthogonal to the axis longitudinal of each branch of the fork. Fork lift according to claim 3,
characterized in that the retraction of the wheels is controlled by means of a single control member arranged on the chassis of the device (4) for controlling the raising and lowering of the fork (1). Fork lift according to one of claims 1 to 4,
characterized in that it comprises, between the plane of the fork (7) and the ground support plane, at least one pair of arms (10) arranged in scissors, one (10A) of the arms (10) bearing, at its free end, the second wheel (6) for supporting the ground and, at its other end, a hinge pin to the fork (7), the other arm (10B) being mounted to slide respectively, at each of its ends, on the one hand on the chassis of the control device (4), on the other hand on the corresponding branch (7A, 7B) of the fork (7). Forklift according to claim 5,
characterized in that the end of the arm (10B) slidably mounted on the chassis of the device (4) for controlling the raising and lowering of the fork (7) is immobilized in position on said chassis by means of a unlockable locking member. Fork lift according to one of claims 1 to 6,
characterized in that the device (4) for raising and lowering the fork comprises at least one cylinder (13) and a pressure accumulator which accumulates pressure during an extension of the cylinder rod, the accumulated pressure used during a retraction of said cylinder.

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