Shovel loader comprising two hinged frames.

Abstract

 The invention relates to a vehicle, in particular a shovel loader, comprising a first frame (1) with a first set of wheels (2,3) and a second frame (4) with a second set of wheels (5,6), whereby the first frame (1) is connected to the second frame (4) by means of a hinged joint (13), such that the first frame can move in relation to the second frame, whereby means (28,29,23) are provided to dampen the movement of the first frame (1) in relation to the second frame (4).

Description

[0001] The invention concerns a vehicle, in particular a shovel loader, comprising a first frame with a first set of wheels and a second frame with a second set of wheels, whereby the first frame is connected to the second frame by means of a hinged joint, such that the first frame can move in relation to the second frame, whereby means are provided to dampen the movement of the first frame in relation to the second frame.

[0002] Such vehicles are thus provided with a buckling control, whereby a first frame, which for example forms the front part of the vehicle, is hinge-mounted and/or mounted in a pivoting manner to a second frame which then forms the rear part of the vehicle. These vehicles usually comprise four wheels whereby the front and the rear part of the vehicle are each carried by wheels. Said rear part usually has a large mass so as to keep the vehicle stable, and it is usually provided with a seat for the driver.

[0003] On the front side, said vehicles are usually provided with a lifting arm on which can be mounted detachable elements such as for example a loading shovel. These vehicles are particularly advantageous in that they are very manoeuvrable and compact, but it turns out that they are very unstable and that, when used on rough ground, a lot of accidents happen due to the vehicle tipping when riding over a bump or along a slope at reasonable speed. The latter is all the more so when the loading bucket of the vehicle is loaded with earth, for example, and the lifting arm is directed upward.

[0004] Moreover, said problem arises in particular with smaller vehicles having no cabin, which implies a real risk of serious injuries for the driver should the vehicle tip.

[0005] Document FR 2 663 590 describes a vehicle comprising two frames which are connected by means of a hinged joint. When using the hinged joint which is applied in said vehicle, the risk of the vehicle tipping is practically negligible. However, such a hinged joint is only applied in very large vehicles, whereby it is observed that when said vehicle moves without a load, both frames will oscillate in relation to one another. Said document FR 2 663 590 describes a system which makes it possible to dampen oscillations of both frames in relation to one another on the one hand, and to stabilize both frames in relation to one another when the vehicle is being worked with on the other hand. However, no solution is offered to stabilize a vehicle moving with a load in the loading bucket over rough ground.

[0006] The invention aims to remedy the above-mentioned disadvantages and to provide a vehicle with buckling control which proves to be extremely stable, even when moving at high speed with a loaded loading bucket over rough ground.

[0007] To this aim, said means to dampen the movement of the first frame in relation to the second frame comprise two liquid reservoirs containing a hydraulic liquid which are connected via a throttle valve whereby, during the movement of said first frame in relation to the second frame, said liquid is displaced between both reservoirs via said throttle valve.

[0008] Practically, said hinged joint has a hinge pin around which the first frame can rotate in relation to the second frame, whereby this hinge pin can also pivot and said liquid reservoirs co-operate with the hinged joint such that, when the hinge pin moves in a direction crosswise to the longitudinal axis of the second frame, liquid will be displaced between both reservoirs via said throttle valve.

[0009] Advantageously, said hinged joint has a hinge pin which is determined by a point of rotation on the one hand around which the hinge pin can pivot, and which has a fixed position in relation to both frames, and a hinge point situated almost vertically above said point of rotation on the other hand which is fixed in relation to the first frame and hinge-mounted to the first far end of a rod, whereas the second far end of the rod is hinge-mounted to the second frame in a point which is preferably situated in a vertical plane of symmetry of the latter frame extending in the longitudinal direction, whereby said means dampen the movement of said hinge point according to an arc with said second far end of said rod as a centre.

[0010] According to a preferred embodiment of the vehicle according to the invention, said hinge point forms the centre of a ball joint which connects said first frame to said rod, whereby each of the two liquid reservoirs is further provided with a corresponding hydraulic cylinder, whereby the axis of each of these cylinders extends such that it practically or almost touches said arc on either side of the ball joint between the latter and a supporting point on said second frame, such that these cylinders can exert a pressure force between the supporting point concerned and said ball joint.

[0011] The invention also concerns a method for dampening the buckling movement of a vehicle with a first and a second frame which are hinge-mounted in relation to one another, whereby the movement of a hinge pin is dampened in a direction which is practically crosswise to the longitudinal direction of the vehicle by displacing a hydraulic liquid via a throttle valve between two liquid reservoirs, in particular between two hydraulic cylinders.

[0012] Other particularities and advantages of the invention will become clear from the following description of a few special embodiments of the vehicle and the method according to the invention; this description is given as an example only and does not limit the scope of the claimed protection in any way; the figures of reference used hereafter refer to the accompanying drawings.

Figure 1 is a schematic side elevation of a vehicle with a lifting arm and a loading bucket provided with a buckling control according to the present state of the art.

Figure 2 is a schematic view from above of the vehicle from figure 1, whereby the lifting arm and the loading bucket have been omitted for clarity's sake.

Figure 3 is a schematic view from above of a vehicle according to an interesting embodiment of the vehicle according to the invention.

Figure 4 is a highly schematic section of the hinged joint from figure 3 according to line IV-IV in a neutral position.

Figure 5 is the schematic section of the hinged joint from figure 4 whereby both frames of the vehicle according to the invention are rotated in relation to one another round an axis extending in the longitudinal direction of the vehicle.

Figure 6 is a schematic view from above of a vehicle according to a variant embodiment of the vehicle according to the invention

Figure 7 is a schematic view from above of a vehicle according to another embodiment of the vehicle according to the invention

[0013] In the different drawings, the same reference figures refer to identical or analogous elements.

[0014] Figures 1 and 2 schematically represent a shovel loader according to the present state of the art. This shovel loader has a first frame 1 which is provided with a set of wheels with two wheels 2 and 3 and a second frame 4 with a set of wheels including wheels 5 and 6.

[0015] The first frame 1 forms the front part of the vehicle and is provided with a hydraulically operated lifting arm 7 on which is mounted a loading bucket 8. The rear part of the vehicle is formed by said second frame 4 and has a steering wheel 9 and a seat 10 for the driver of the vehicle. Said rear part is further equipped with a hydraulic system, not represented in the drawings, which provides among others for the drive of the lifting arm 7, the loading bucket 8 and the steerage. Said steerage comprises a hydraulic cylinder 11 which can move the first frame 1 in relation to the second frame 4 round a hinge pin 12. When the vehicle is situated on a flat horizontal surface, said hinge pin 12 will extend vertically and will be situated in a vertical plane of symmetry 14 extending in the longitudinal direction of the second frame 4. In this position, the hinge pin 12 is situated in what is called a neutral position.

[0016] The first frame 1 is connected to the second frame 4 by means of a hinged joint 13. The latter makes it possible, among others, for the first frame 1 to move in relation to the second frame 4. In particular, the first frame 1 can be subjected to a rotation round the hinge pin 12 in relation to the second frame 4. In addition to this, the hinge pin 12 can also pivot round a point of rotation 15 which forms the centre of a ball joint 16. This ball joint 16 connects the first frame 1 to the second frame 2, whereby the point of rotation 15 thus has a fixed position in relation to both frames.

[0017] In said neutral position, a hinge point 17 is situated practically vertically above the point of rotation 15, which hinge point 17 is fixed in relation to the first frame 1 and is hinge-mounted to a rod 18. The hinge point 17 as well as the point of rotation 15 are situated on said hinge pin 12. The rod 18 may be somewhat elastically deformable in its longitudinal direction.

[0018] The hinge point 17 is situated in the centre of a second ball joint 19 which forms a first far end of said rod 18. The other far end of this rod 18 is hinge-mounted to the second frame 4 in a point which is preferably situated in the vertical plane of symmetry of the latter, extending in the longitudinal direction. In particular, this other far end of the rod 18 is preferably also formed of a ball joint 20.

[0019] When the vehicle moves over rough ground, the first frame 1 can thus undergo a rotation in relation to the second frame 4 round an axis of rotation 21 situated in said plane of symmetry 14 and going through said point of rotation 15. The hinge pin 12 is thereby subjected to a pivoting movement round said point of rotation 15, and the hinge point 17 describes an arc having said ball joint 20 as a centre.

[0020] If this vehicle rides over a bumpiness with one of the front wheels 2 or 3, for example, with the lifting arm 7 directed upward and with the loading bucket 8 being loaded, the first frame will be subjected to a sudden acceleration round said axis of rotation 21, and it will move at a relatively high speed in relation to the second frame 4 until a maximum rotation of the first frame 1 in relation to the second frame 2 is reached, determined among others by said rod 18. Consequently, the mass of this second frame cannot immediately stabilise the vehicle. As soon as the maximum rotation round the axis of rotation 21 is reached, both frames form a rigid whole in said direction of rotation. Due to the inertia of the moving, filled loading bucket, the mass of the second frame will not suffice, however, to maintain the vehicle in a stable position, and consequently it will tip.

[0021] This situation is remedied thanks to the application of an interesting embodiment of the present invention as illustrated in figures 3 to 5. In particular, figure 3 shows the vehicle from figures 1 and 2, whereby means are provided to dampen the movement of the first frame 1 in relation to the second frame 4.

[0022] In particular, these means comprise two liquid reservoirs which are filled with a hydraulic liquid and which are connected via a hydraulic line 22 in which has been provided a throttle valve 23. During the movement of said first frame 1 in relation to the second frame 4 round the axis of rotation 21, said liquid is displaced between both reservoirs via the throttle valve 23.

[0023] Each of these liquid reservoirs is situated in a corresponding hydraulic cylinder 24 and 25 with a cylinder housing and a piston rod. These cylinders 24 and 25 are connected to respective supports 26 and 27 with their cylinder housing, which supports are fixed to said second frame 4. The corresponding far ends of the respective piston rods of these cylinders 24 and 25 rest freely against the ball joint 19 on either side of the above-mentioned plane of symmetry 14. The axis of each of said cylinders 24 and 25 hereby extends such that it almost touches the above-mentioned arc on either side of the ball joint 19, such that said cylinders can exert a pressure force on the ball joint 19.

[0024] When the first frame 1 is subjected to a rotation round the axis of rotation 15 in relation to the second frame 4, as represented in figure 5, the ball joint 19 will push against the piston rod of the hydraulic cylinder 24. This makes sure that the liquid reservoir 28 in the cylinder housing of the cylinder 24 is moved via the line 22 and the throttle valve 23 to the reservoir 29 of the opposite hydraulic cylinder 25.

[0025] Thus, the piston rod of the cylinder 24 will exert a pressure force on the ball joint 19 which makes sure that the movement of the hinge pin 12 round the point of rotation 15, and thus also the movement of the first frame in relation to the second frame, is slowed down.

[0026] In particular, the throttling of the flow of the hydraulic liquid through the throttle valve is adjusted such that, under normal working conditions, the dampening due to the displacement of the liquid is negligible, whereas in case of a quick and sudden movement of both frames in relation to one another round the axis of rotation 15, said throttling will make sure that the movement is slowed down and that both frames form a practically rigid whole, at least approximately, such that the mass of the second frame 4 provides for stabilisation and prevents the vehicle from tipping.

[0027] The influence of the throttle valve 23 is particularly negligible when the shovel loader is in a stable position. In such a case, while driving the vehicle, the force exerted by the cylinders 24 and 25 will be negligible compared to the force that must be exerted by the steerage, in particular by the hydraulic cylinder 11 of the latter.

[0028] It is clear that the dimensions of the piston rod and the cylinder housing of the hydraulic cylinders 24 and 25 are selected as a function of the loads to be expected and the size of the vehicle. Usually, a pressure in the order of magnitude of 200 bar is used as an operating pressure for the hydraulic liquid. The diameter of the hydraulic line 22 is normally selected in the order of magnitude of 3 to 4 mm, as is usually applied as standard in hydraulic systems.

[0029] When the hydraulic cylinder has a piston with a diameter (D) in the order of magnitude of 30 mm, it is found that an appropriate throttling in the throttle valve 23 is obtained when the latter has a passage for the hydraulic liquid with a diameter (d) of about 0.6 mm. In the case of a hydraulic cylinder with a piston having a diameter (D) of 40 mm, the diameter (d) of the passage of the throttle valve 23 will be preferably 0.8 mm.

[0030] More generally it can be said that, according to the invention, the D/d ratio of the diameter (D) of the piston in relation to the diameter (d) of the passage of the throttle valve 23 is situated between 35 and 65. Preferably, this D/d ratio is in the order of magnitude of 50.

[0031] The diameter (d) of the passage of the throttle valve 23 is preferably selected as a function of the allowed speed of movement of the hinge pin 12 in relation to the second frame 4, taking into account the diameter (D) of the piston of the hydraulic cylinders 24 and 25.

[0032] The length of stroke of the piston rods is preferably in the order of magnitude of 9 cm, but it may deviate as a function of the allowed movement of the first frame 1 in relation to the second frame 4. When the length of stroke amounts to 9 cm and the piston is moved over this length, a quantity of hydraulic liquid of some 63 cc will be displaced when the diameter of the piston amounts to 30 mm, and of some 113 cc when said diameter amounts to 40 mm.

[0033] It is indicated for the piston rods of both hydraulic cylinders 24 and 25 to maintain contact with said ball joint 19, possibly save for a little play. This is obtained as the reservoirs of both hydraulic cylinders are connected such that when one of the piston rods is being compressed over a certain distance, the other piston rod will be automatically moved over the same distance. Thus, the distance between both piston rods remains practically constant and is about equal to the diameter of the ball joint 19 concerned.

[0034] Consequently, the hydraulic cylinders 24 and 25 will dampen the movement of said hinge point 17 according to an arc which has said second far end 20 of said rod 18 as a centre.

[0035] Although in the preceding embodiment, the piston rods rest freely on said ball joint 19, it is of course possible for said piston rods to be either fixed to the latter or directly to the first frame 1 in the vicinity of said hinge pin 12, the hinge point 17 or the ball joint 19 concerned.

[0036] Further, it is clear that the axis of said hydraulic cylinders must not necessarily touch the arc being described by the hinge point 17, but that these cylinders should only be able to exert a force component according to a tangent to said arc.

[0037] The above-mentioned hydraulic line 22 may further be provided with a stop valve 30 which can prevent the displacement of liquid between said reservoirs of the hydraulic cylinders 24 and 25 concerned.

[0038] Further, said hydraulic line is preferably connected to a hydraulic system via a non-return valve 31 in order to bring the liquid in said reservoirs to a certain pressure, whereby the hydraulic liquid cannot flow back from said liquid reservoirs to the hydraulic system.

[0039] The hydraulic cylinders which are represented in figures 3 to 5 may consist of single-acting hydraulic cylinders and are preferably formed of a piston cylinder.

[0040] According to an alternative embodiment of the vehicle according to the invention, said reservoirs are part of one and the same double-acting hydraulic cylinder which connects said first frame to a supporting point which has a practically fixed position in relation to said second frame in the vicinity of said hinge pin.

[0041] Yet another embodiment of the vehicle according to the invention is represented in figure 6. In this embodiment is provided only one hydraulic cylinder 32 to dampen the movement of the first frame 1 in relation to the second frame 4. This hydraulic cylinder 32 is formed of a double-acting cylinder which thus contains two liquid reservoirs 28 and 29 in the cylinder housing which are separated by means of a piston 33. Said reservoirs 28 and 29 are connected via a hydraulic line containing a throttle valve 23.

[0042] The piston 33 of this double-acting cylinder 32 is fixed to a piston rod 34 of which one far end is connected to said hinge point 17 or thus to the corresponding ball joint 19. Thus, this far end of the piston rod 34 is hinge-mounted to a flange 35 which is fixed to said ball joint 19.

[0043] The cylinder housing of the hydraulic cylinder 32 is connected to said second frame 4 in a hinge point 36.

[0044] When the first frame 1 moves in relation to the second frame 4, this movement will be dampened by the displacement of hydraulic liquid via the hydraulic line 22 and the corresponding throttle valve 23 between said liquid reservoirs 28 and 29.

[0045] In a variant of this embodiment of the vehicle according to the invention, a piston rod 34 of a double-acting cylinder 32 is fixed to said second frame 4 via supports 26 and 27, as represented in figure 7. A piston 33 is fixed to this piston rod 34 and divides the cylinder housing of the cylinder 32 in two liquid reservoirs 28 and 29. The cylinder housing of the cylinder 32 thereby has two flanges 37 and 38 extending laterally on either side of said ball joint 19 or said hinge point 17, and practically joining the latter. When the first frame 1 with the ball joint 19 is thus moved in relation to the second frame 4, said ball joint 19 will push against one of the flanges 37 or 38, such that the cylinder housing of the cylinder 32 moves along the piston rod 34. Hydraulic liquid is thereby displaced between the liquid reservoirs 28 and 29 via a hydraulic line 22 and a throttle valve 23, such that the movement of the first frame 1 in relation to the second frame 4 is dampened.

[0046] Naturally, with the double-acting hydraulic cylinders from figures 6 and 7, it is possible to integrate a throttle valve in the cylinder itself, for example in the piston 33.

Claims

1. Vehicle, in particular a shovel loader, comprising a first frame (1) with a first set of wheels (2,3) and a second frame (4) with a second set of wheels (5,6), whereby the first frame (1) is connected to the second frame (4) by means of a hinged joint, such that the first frame (1) can move in relation to the second frame (4), whereby means are provided to dampen the movement of the first frame (1) in relation to the second frame (4), characterised in that said means comprise two liquid reservoirs (28,29) with a hydraulic liquid which are connected via a throttle valve (23), whereby during the movement of said first frame (1) in relation to the second frame (4) said liquid is displaced between both reservoirs (28,29) via said throttle valve (23).

2. Vehicle according to claim 1, whereby said hinged joint has a hinge pin (12) around which the first frame (1) can rotate in relation to the second frame (4), whereby this hinge pin (12) can also pivot and said liquid reservoirs co-operate with this hinged joint, such that when the hinge pin (12) is moved in a direction crosswise to the longitudinal axis of the second frame (4), liquid is displaced between both reservoirs (28,29) via said throttle valve (23).

3. Vehicle according to claim 1 or 2, whereby said reservoirs (28,29) are part of at least one hydraulic cylinder (24,25,32) connecting said first frame (1) to a supporting point (26,27) which has a practically fixed position in relation to said second frame (4) in the vicinity of said hinge pin (12).

4. Vehicle according to claim 3, whereby said hydraulic cylinder (24,25,32) has a piston with a diameter (D), whereas said throttle valve (23) has a passage for said liquid with a diameter (d), whereby the (D/d) ratio of the diameter (D) of the piston in relation to the diameter (d) of the passage of the throttle valve (23) is situated between about 35 and about 65 and is in particular in the order of magnitude of about 50.

5. Vehicle according to any one of claims 1 to 4, whereby said hinged joint has a hinge pin (12) which is determined by a point of rotation (15) on the one hand around which this hinge pin (12) can pivot and which has a fixed position in relation to both frames (1,4), and a hinge point (17) situated practically vertically above this point of rotation (15) on the other hand, which is fixed in relation to the first frame (1) and which is hinge-mounted to the first far end of a rod (18), whereas the second far end of this rod (18) is hinge-mounted to the second frame (4) in a point which is preferably situated in a plane of symmetry (14) of the latter extending vertically in the longitudinal direction, whereby said means dampen the movement of said hinge point (17) according to an arc having said second far end of the rod (18) as a centre.

6. Vehicle according to claim 5, whereby said hinge point (17) forms the centre of a ball joint (19) which connects said first frame (1) to said rod (18), whereby each of the two liquid reservoirs (28,29) is further provided in a corresponding hydraulic cylinder (24,25,32), whereby the axis of each of these cylinders extends on either side of the ball joint (19), almost touching said arc, between the latter and a supporting point (26,27) on said second frame (4), such that these cylinders (24,25,32) can exert a pressure force between the supporting point (26,27) concerned and said ball joint (19).

7. Vehicle according to any one of claims 1 to 6, whereby said reservoirs (26,27) are connected via a hydraulic line (22) in which said throttle valve (23) is provided and which further contains a stop valve (30) to prevent any displacement of liquid between said reservoirs (26,27).

8. Vehicle according to any one of claims 1 to 6, whereby said liquid reservoirs (28,29) are connected to a hydraulic system in order to bring the liquid in said reservoirs (28,29) to a certain pressure, via a non-return valve (31), such that hydraulic liquid cannot flow back from said liquid reservoirs (28,29) to the hydraulic system.

9. Method for stabilising a vehicle, in particular a shovel loader, comprising a first frame (1) with a first set of wheels (2,3) and a second frame (4) with a second set of wheels (5,6), whereby the first frame (1) is connected to the second frame (4) by means of a hinged joint,
whereby this hinged joint has a hinge pin (12) which is determined by a point of rotation (15) on the one hand around which this hinge pin (12) can pivot and having a fixed position in relation to both frames (1,4), and a hinge point (17) situated above this point of rotation (15) on the other hand which is fixed in relation to the first frame (1) and hinge-mounted to the first far end of a rod (18), whereas the second far end of this rod (18) is hinge-mounted to the second frame (4) in a point which is preferably situated in a vertical plane of symmetry (14) of the latter extending in the longitudinal direction,
characterised in that the movement of said hinge pin (12) in relation to the second frame (4) is dampened.

10. Method according to claim 9, whereby the movement of said hinge pin (12) is dampened by displacing a hydraulic liquid through a throttle valve (23).

11. Method according to claim 10, whereby a diameter for the passage of said throttle valve (23) is selected such that the dampening of the movement of the hinge pin (12) through the throttle valve (23) is practically negligible when the speed of movement of said hinge pin (12) is lower than a preset value, whereby this movement of the hinge pin (12) is dampened when said predetermined value is exceeded.

12. Method according to claim 10 or 11, whereby said hinge pin (12) co-operates with two liquid reservoirs (28,29) containing a hydraulic liquid, such that hydraulic liquid is displaced via said throttle valve (12) between both reservoirs (28,29) when said hinge pin (12) is moved.

13. Method according to claim 12, whereby said reservoirs (28,29) are part of at least one hydraulic cylinder (24,25,32) connecting said first frame (1) to a supporting point (26,27) which has a practically fixed position in relation to said second frame (4) in the vicinity of said hinge pin (12), whereby said cylinder (24,25,32) is operated by the movement of the hinge pin (12).

Drawing