WO2002021898A1

WO2002021898A1 - Lifting device for tractor for coupling and uncoupling a weight without manual control

Info

Publication number: WO2002021898A1
Application number: PCT/FR2001/002607
Authority: WO
Inventors: Hubert Defrancq
Original assignee: Hubert Defrancq
Priority date: 2000-09-15
Filing date: 2001-08-13
Publication date: 2002-03-21
Also published as: FR2814038B1; FR2814038A1

Abstract

The invention concerns a lifting device (1) for a tractor, in particular for an agricultural tractor, for coupling a weight in at least two lateral points, and for uncoupling, comprising: a lower frame (3) articulated on a transverse axis (A); means for lifting the frame (R); and two forearms (7a, 7b) articulated on the frame, one on each side, each forearm including a coupling hand (10) with a housing (11) at its end furthest from the frame. The housing (11) of each coupling hand (10) is open along a longitudinal direction of the forearm (7a, 7b) so that, for a range of suitable orientations of the forearms, a weight coupling bolt can penetrate into the housing (11) of the hand, or exit therefrom, by a relative forward or backward movement, and means (C) for controlling in rotation the forearms are designed to rotate said forearms (7a, 7b) upwards relative to the frame (3) in response to a movement lifting the frame, and downwards in response to a movement lowering the frame

Description

LIFT DEVICE FOR A TRACTOR FOR ATTACHING AND DETECTING A MASS WITHOUT MANUAL INTERVENTION.

The invention relates to a lifting device for a tractor, in particular an agricultural tractor, making it possible to couple a mass at at least two lateral points, and to uncouple it, comprising:

- a frame, in the lower part, articulated on a transverse axis;

- means for lifting the frame; - And two forearms articulated on the frame, one on each side, each forearm comprising a coupling hand with a housing at its end remote from the frame.

A device of this type is known, for example from patents FR 2,688,378, or FR 2,769,789, in the name of the same applicant. Such a device makes it possible to add weights to the tractor in order to obtain the traction force necessary during heavy work, or to compensate for the weight of increasingly heavy tools which are coupled to the back.

New technologies (for example electronic injection regulation) and new materials lead, for a given power, to reduce the mass of the tractor. It is thus possible to produce relatively light tractors which compact the soil less. However, the reduction in the mass of the tractor reduces its traction capacity, hence the need to add weights under certain working conditions.

The addition of weights is not without drawbacks when the tractor no longer performs the specific work requiring these weights. In particular, tractors being more and more equipped with suspensions making it possible to safely increase their movement on the road at relatively high speed, the presence of ballast weights is penalizing for such movements.

It is therefore desirable to be able to quickly add and remove the ballast weights either at the front or at the rear of the tractor. The mounting of linkages at the front of tractors is more and more widespread to allow the use of tools at the front to combine operations, or to distribute the tools between the front and the rear to balance the tractor. The front lifting devices also make it easier to hitch and unhitch the masses before weighing down.

However, coupling or uncoupling of masses currently requires the driver to dismount from the tractor. This results in a waste of time. In addition, since tractors are now fitted with comfortable cabins, most often air-conditioned and soundproofed, drivers are more and more sensitive to the comfort of their environment and seek to avoid leaving their cab during work.

The object of the invention is, above all, to allow the coupling and uncoupling of a ballast mass, in particular at the front of the tractor, without the driver having to leave the tractor cabin. It is also desirable that the lifting device, in particular front lifting, make it possible to retain the functionalities of a conventional lifting.

The invention also aims to offer a simple, reliable, inexpensive device whose operation does not cause confusion for the operator. The device must also make it possible to easily switch from the mass carrier mode to the conventional coupling mode of the tools without having to modify the coupling triangle of the tools.

It is also important that the hitched mass, especially at the front, is securely locked to avoid accidental stalling. According to the invention, a lifting device of the kind defined above allowing coupling and uncoupling of a mass, is characterized in that:

each coupling hand is open in the longitudinal direction of the forearm, so that for a suitable range of orientations of the forearms, a mass coupling pin can enter the housing of the hand, or leave it, by a relative displacement of advance or retreat,

- And that a means for controlling the rotation of the forearms is provided to rotate these forearms upward relative to the frame in response to the lifting movement of the frame, and downward in response to the downward movement of the frame .

The range of orientations of the forearm allowing entry and the exit of the piton preferably goes from the horizontal to an inclination of 45 ° on the horizontal. The range of orientations results in coupling hands whose housings are oriented vertically when the forearms are folded up. The mass cannot then come out of its housing because it is driven downwards by its own weight.

It is thus possible for the tractor operator to couple and unhitch a mass either at the front or at the rear of the tractor without manual intervention requiring exit and descent from the cabin.

The means for controlling the rotation of the forearms relative to the frame may comprise at least one control jack provided between a point of articulation on the frame and a pivot linked to the forearms, but offset radially relative to the axis of rotation of the forearms.

The pivot is advantageously located lower than the axis of rotation of the forearms.

Preferably the forearms are fixed on a transverse beam articulated on the frame. The pivot is supported by extensions integral with the beam.

The forearm control cylinder is advantageously synchronized with the lifting of the frame so that the forearms are folded when the frame is raised. In particular, when the lifting means of the frame comprise at least one jack, synchronization is ensured by hydraulic connection of the chamber (s) on the rod side / bottom side of the lifting cylinder with the chamber on the bottom side / rod side of the control cylinder. A tap is advantageously provided to cut or open at will the connection between the chambers.

According to another possibility, the means for controlling the rotation of the forearms relative to the frame comprises a connecting rod disposed between a point of articulation on the frame and a pivot linked to the forearms, in particular provided on a beam when the forearms arms are integral with such a beam, this pivot being offset radially relative to the axis of rotation of the forearms.

The device preferably comprises a tab linked in rotation to the forearms and placed so as to cover a bar fixed to a mass, when the forearms are raised relative to the frame, to retain the mass against a vertical movement ascending.

The device may also include a retaining member mass against a horizontal movement, this member being pivotally mounted relative to the forearms and bearing at one end against the frame so as to hang the bar fixed to the mass when the forearms are raised. Each forearm may comprise a base part fixed to an articulation beam and an end part pivotally mounted on the base part, with a removable locking means allowing either to block the end part on the part of base, or to leave the end part pivoting, in particular to allow the floating of a tool.

The opening of the latching hand may include, at its bottom, a recess below the entry in order to ensure better retention of a latching bolt during lifting.

This attachment hand may include holes for the passage of a retaining pin in order to couple a tool.

The device can be installed at the front or rear of the tractor.

The invention consists, apart from the arrangements set out above, of a certain number of other arrangements which will be more explicitly discussed below in connection with embodiments described with reference to the attached drawings, but which are in no way limiting.

Figure 1 of these drawings is a schematic perspective view, from the front, of a front lifting device for tractor 1 according to the invention.

Figure 2 is a schematic view along line II-II of Fig.4, with parts in section, parts outside and parts cut away, the forearms being in the low position.

Figure 3 shows, similarly to Figure 2 but without the hydraulic circuit, the device in the lifting position with the forearms raised.

Figure 4 is a schematic plan view of the device of Figs. 2 and 3.

Figure 5 is an enlarged side view of an alternative embodiment of the coupling hand.

Figure 6 is a partial perspective view of an alternative embodiment of a forearm. Figure 7 is a side view of a weight mass with a mass carrier.

Figure 8 is a left view, with respect to Fig.7, of the mass carrier. Figure 9 is an enlarged side view of part of the device in the raised position with a coupled mass.

Figure 10 is a simplified side view of a variant with connecting rod, in the lower position of the forearms.

Figure 11 shows the device of Fig. 10 in the raised position.

Figure 12, finally, is a schematic view of a rear lifting device according to the invention.

Referring to the drawings in particular in Figs. 1 to 4, we can see a front lifting device 1 for agricultural tractor comprising a frame 2 having two sides 2a, 2b to frame the chassis of the tractor (not shown) and be fixed in front of the tractor. The sides 2a, 2b are connected in the upper part by a cross member 2c formed by an angle iron in Fig.l and by a tube in Figs.2 and 3. The framework 2 is equipped in the lower part with a frame 3. The frame 3 comprises two lateral members 3a, 3b welded to a rear cross member 3c articulated on a transverse axis A carried by the frame 2.

Lifting means R are provided between the frame 3 and the frame 2. These lifting means R comprise, on each side, a jack 4a, 4b connecting the frame 2 to the frame 3. In the example shown, the cylinder of each cylinder is oriented so that the cylinder rod comes down. The bottom of the cylinder, located in the upper part, is provided with an ear articulated on an axis 5a, 5b supported by bearings of the frame 2. The lower end of the rods of the jacks 4a, 4b is provided with a yoke articulated on an axis 6a, 6b mounted in a bearing of the frame 3. The jacks 4a, 4b ensure the pivoting of the frame 3 around the axis A. The raised position of the frame 3 is obtained by entry of the jack rods into their cylinder respective.

Two forearms 7a, 7b are articulated on an axis 8 engaged in bearings provided at the ends of the lateral members 3a, 3b, distant from the cross member 3c. The axis 8 is parallel to the axis A. Preferably, each forearm 7a, 7b is located inside the frames of the frame 3 and is secured to a transverse beam 9, by example formed by a cylindrical tube.

Each forearm 7a, 7b has at its end remote from the frame 3 a coupling hand 10 provided with a housing 11 open substantially in the longitudinal direction of the forearm. The arrangement of the opening of the housing 11 is such that a bolt P of mass coupling can enter the housing 11, and leave it, by a relative movement of advance or retreat of the device 1 relative to a mass placed on the floor, for a range of suitable forearm orientations. For such engagement to take place, it is not essential that the frame 3, and the forearms 7a, 7b are horizontal. The housing 11 open in the longitudinal direction of the forearm is provided to allow engagement of the pin P for an inclination of the forearm on the horizontal up to 45 °. Preferably, however, in the low position of the frame 3 the forearms 7a, 7b are substantially horizontal.

A means C for controlling the rotation of the forearms 7a, 7b is provided for rotating these forearms upward relative to the frame 3 in response to the lifting movement of the frame 3 relative to the frame 2, and towards the low in response to the downward movement of this frame.

According to the embodiment of Figs. 1 to 4, the control means C comprises a control cylinder 12, provided at mid-width of the frame 3. The bottom of the cylinder 12 is articulated on an axis 13 supported by cheeks 13a, 13b, fixed on the rear crossmember 3c of the frame. The end of the rod of the jack 12 is articulated on a pivot 14 sohdaire of the beam 9, but offset radially, lower than the axis of rotation 8 of the forearms. The pivot 14 is supported by radial extensions 15 fixed, for example welded, to the beam 9 and directed downwards.

The assembly is provided so that the forearms 7a, 7b extend substantially in the extension of the side members 3a, 3b of the frame 3 when the rod of the jack 12 is in the retracted position as illustrated in FIG. 2. In this configuration, the assembly of the forearms and of the frame 3 constitutes a lower stretcher as encountered on a standard front linkage for an agricultural tractor. According to the embodiment of Fig.2, the jacks 4a, 4b are connected in parallel with each other and with the jack 12 by means of hydraulic lines 16, 17. Line 16 is connected to the chamber bottom side of the cylinders 4a, 4b and, by a branch 16a, to the chamber on the rod side of the cylinder 12. The pipe 17 is connected to the chamber on the rod side of the cylinders 4a, 4b and, by a branch 17a provided with a tap 18 , to the chamber on the bottom side of the jack 12. With this connection, the jacks 4a, 4b are shortened when the jack 12 is extended.

Alternatively, an arrangement could be provided in which the upward rotation movement of the forearms 7a, 7b relative to the frame 3 would be controlled by retraction of the rod of the jack 12, the pivot 14 then being located above the axis of rotation 8 of the forearms. In this case, the positioning of the control cylinder similar to the cylinder 12 would however be more problematic because of the risk of interference with a PTO drive shaft (not shown) whose location varies from one tractor to another. . The tap 18 is in the open position when the device is used for coupling a mass. This tap 18 is placed in the closed position with the forearms 7a, 7b in the extension of the frame 3 when it is desired to use the device as a conventional lifting.

A tab 19 is welded to the transverse beam 9, in the middle region. This tab 19 is constituted by a sheet metal plate, the front part of which is semi-cylindrical with its concavity turned downwards; the rear part is flat, welded along a horizontal generatrix of the beam 9. Gussets (not shown) for reinforcing the fixing can be provided. The tab 19 is placed so as to cover a bar 20 fixed to a weight M when the latter is coupled to the forearms and when these have been raised relative to the frame 3 (Fig. 3 and 9) . The tab 19 allows, when the forearms 7a, 7b, are raised, to retain the mass M against an upward vertical movement, for example due to a rebound.

A retaining member 21 is pivotally mounted relative to the forearms 7a, 7b and to the beam 9. This member 21 (Fig.4 and 9) is formed by a rod bent at right angles. A branch 21a of the rod is located in a plane perpendicular to the beam 9, above this beam. The branch 21a is articulated on a transverse axis 22, supported by plates 23 welded to the beam 9. The front end of the branch 21a is bent downward to form a hook 24. The branch 21b of the rod 21 is bent outward so as to bear against the frame 3a of the frame 3. The weight of the part of the member 21 located on the side of the axis 22 opposite the hook 24 is greater than that of the part located on the other side of the axis 22, so that the gravity recalls the branch 21b against the frame 3a. The retaining member 21 is provided for retaining the bar 20 and the mass M against a horizontal movement, for example due to braking, when the forearms 7a, 7b are raised relative to the frame 3.

Fig.5 shows an alternative embodiment 11a of the housing of the coupling hand 10. The housing 11a is always open in the longitudinal direction of the forearm, but the mean direction of this housing is inclined downwards, the entrance to the bottom. The angle of inclination on the horizontal can reach 45 °. In addition, the bottom of this housing has a lower recess lld located below the entrance to the housing for receiving a bolt P for coupling the mass M. The safety of holding the bolt P during the lifting of the 'forearm 7a, 7b is improved with this arrangement.

With a view to using the lifting device not only for coupling a mass M, but also as a conventional lifting allowing the attachment of working tools, provision is advantageously made in the spouts 10a, 10b of the hand d hitch 10, delimiting the housing 11 or 11a, two coaxial holes 25a, 25b for the installation of a pin G making it possible to retain, in the hitching hand 10, the hooking stud of a tool (not represented). For this use, the jack 12 is locked in the position where the forearms 7a, 7b are in the extension of the frame 3.

Of course, when the lifting device is used for coupling a weight mass, no pin G is placed on the coupling hands 10. FIG. 6 shows an alternative embodiment of a forearm 7a 'intended to allow the floating of a tool attached to the lifting device and a transverse monitoring of the relief of the ground. The forearm 7a 'comprises a base portion 26 formed by two rectangular parallel plates 26a, 26b vertical, spaced apart in the transverse direction, and welded to the beam 9. Towards their front end, the plates 26a, 26b each have a hole serving as a bearing for an axis 27 on which is pivotally mounted, between the plates 26a, 26b, an end portion 28. Behind the axis 27 the two plates 26a, 26b have a hole 29 to which corresponds a hole (not visible) in the part 28. A removable pin 30 can be engaged in the holes 29 of the plates 26a, 26b and pass through the hole corresponding to the end part 28. In this case, the end part 28 is locked in rotation relative to the base part 26 and extends the plates 26a, 26b.

When the pin 30 is withdrawn from the holes 29, the end part 28 can oscillate relative to the base part 26 which allows floating and transverse tracking of the relief by a tool. Means not shown may be provided to limit the angular movement of the end part 28 relative to the base part 26.

Fig.7 shows a weighting mass M which is generally composed of several elements ml, m2 ... (Fig.4) juxtaposed in a direction perpendicular to the plane of Fig.7. The weighting mass M can reach relatively high values, for example of the order of 1500 kg. The elements of the mass M have a recess at the rear, with curved edges. These elements are engaged, by sliding in a direction perpendicular to the plane of Fig.7, on a substantially prismatic core 29 having a vertical flat rear face provided with holes for fixing a mass-carrying device 30 shown in Fig.8. This mass carrier 30 comprises a steel plate 31 pierced with holes 32 for the passage of fixing screws 33 (symbolically represented in FIG. 7) on the core 29 of the mass M. The coupling pins P are integral with the plate 31 and protrude laterally on either side. In the lower middle part of the plate 31 are provided, integral with this plate, two vertical extensions 34, 35 directed downwards between which the bar 20 is fixed. The mass-carrying device 30 makes it possible to use a standard mass M of the tractor agricultural.

Alternatively, the mass M can be made specially for the coupling device in which case the coupling pins P and the crossbar 20 are provided directly on this mass. Fig. 9 shows on a larger scale the mass coupled and lifted by the forearms 7a, 7b raised substantially vertically. Fig.10 shows an alternative embodiment according to which the means C for controlling the rotation of the forearms 7a, 7b relative to the frame comprises a connecting rod 36 articulated on an axis 37 secured to the frame 2 and on a pivot 14a carried by radial extensions 15a integral with the beam 9, and directed downwards. For normal use of the lift according to this variant, it is necessary to dismantle the connecting rod 36 and lock the forearms 7a, 7b, relative to the frame. For this purpose, a removable locking pin (not shown) is provided between each forearm 7a, 7b, and the frame 3. Fig.11 shows the device of Fig.10 in the raised position.

Fig.12 shows a variant of the lifting device of the invention installed at the rear of a tractor T. The frame 3 'is articulated at the rear of the tractor, and extends towards the rear. The lifting means R of the frame 3 ′ comprises an arm 38 located in the upper rear part of the tractor controlled in rotation about a transverse horizontal axis 39 by motor means not shown. The end of the arm 38 remote from the axis 39 is connected by an articulation to one end of a candle 40 whose lower end is articulated on the frame 3 '. A rotation of the arm 38 anti-clockwise according to Fig.12 ensures the lifting of the frame 3 '. The forearms such as 7b extend rearward from the frame 3 '. The control means C of the rotation of the forearms relative to the frame 3 ′ comprises a connecting rod 36a articulated, at one end, at a point 37a of the chassis of the tractor and, at its other end, at a point 14b fixed relative to forearms. The. frame 3 'can be constituted by the conventional rear linkage of a tractor. The set of forearms 7a, 7b is then mounted in the rear lifting hooks.

That said, the coupling and uncoupling of a weight M is carried out as follows. We first consider the case where the lifting device is mounted at the front of the tractor as illustrated in Figs.l to 4 and 9. The valve 18 (Fig.2) is open.

The mass M rests on the ground. The frame 3 of the lifting device is in the low position (Fig. 2) and the forearms 7a, 7b are in the extension of this frame.

The driver advances the tractor equipped with the lifting device and adjusts the height of the frame 3 so that the pins P of the mass M engage respectively in the housings 11 of the forearms 7a, 7b which frame the mass M. The engagement of the pegs P in the housings 11 can take place even if the frame is inclined up to 45 ° on the horizontal . When this engagement operation is carried out, the driver commands, or extends the command to raise the frame 3, The pressurized oil arrives via the line 17. The jacks which require the least oil pressure move first; in principle these are lifting cylinders 4a, 4b due to the kinematics of the lifting. When these jacks are fully retracted, the jack 12 begins its extension.

When the ground is raised, the mass M starts to rotate relative to the forearms. The shape of the housings 11, in particular according to FIG. 5, is designed so that the rotation of the mass M cannot cause it to escape from the housings 11. The forearms 7a, 7b rotate upwards relative to the frame 3 for reach a position close to the vertical as illustrated in Fig. 3.

The housings 11 are oriented upwards and the pins P of the mass cannot escape therefrom normally. The mass M having its center of gravity offset forward relative to the housings 11, this mass naturally approaches all of the forearms 7a, 7b when they are folded upwards.

The tab 19 comes to cover the bar 20 located at the bottom at the rear of the mass M and prevents an upward vertical movement of this mass, risking causing it to stall, for example in the event of a rebound during the passage of a large obstacle.

The hook 24 (Fig. 9) also covers the bar 20 and retains, by its lower front end, the mass M against a horizontal displacement. The hook locking control 24 is obtained by pressing part 21b on the side member 3a or 3b, during the folding of the forearms 7a, 7b relative to the frame 3. The bar 20 is locked when all of the forearm 7a, 7b is fully raised. There is thus holding in position, in a secure manner, of the mass M. In addition, the mass M is naturally brought closer to the tractor, which reduces the longitudinal bulk. The uncoupling of the mass M is carried out by controlling the descent of the frame 3 by placing the cover of the hydraulic line 17. The hook 24 releases the bar 20 as soon as the forearms 7a, 7b begin to rotate relative to the frame 3 Taking into account the position offset towards the front of the center of gravity of mass M, the latter will touch the ground by its lower front corner.

It suffices for the driver to make the tractor back slightly while continuing to control the descent of the frame 3 in order to make the pins P out of the housings 11 from the coupling hands.

The coupling and uncoupling operations could be carried out with the driver in the tractor cabin.

For the use of the lifting device 1 as a conventional lifting with attachment of an agricultural implement, it suffices to remove the hydraulic connection between the jacks 4a, 4b and the jack 12 by closing the isolation valve 18 when the assembly forearms 7a, 7b extends in the extension of the frame 3. The locking of the agricultural tool is obtained by using the retaining pins G (Fig.5) at the coupling hands 10 and adding an upper connecting bar (not shown), called the third point, between a central support S (Fig.l) of the frame and the upper attachment point of the tool.

The operation of the variant embodiment of FIG. 10 is deduced from the foregoing explanations. The connecting rod 36, during the lifting of the frame 3, causes the forearms 7a, 7b to rotate substantially vertically. The connecting rod 36 can be offset laterally to clear the space necessary for the passage of a transmission shaft for animated agricultural tools. For use in normal front lift mode, the connecting rod 36 is removed and a locking pin between the forearms 7a, 7b and the frame 3 is put in place. The operation of the lifting device placed at the rear of the tractor according to Fig. 12 is similar to that described for mounting at the front. The engagement of the pins P in the housings 11 is ensured by a backward movement of the tractor.

The use of this lifting device at the rear of the tractor makes it possible to hitch weights at the rear, which is advantageous when using trailed implements, or to provide a counterweight when the use of a front loader.

Claims

1. Lifting device for a tractor, in particular for an agricultural tractor, making it possible to couple a mass at at least two lateral points, and to uncouple it, comprising:

- a frame (3,3 '), in the lower part, articulated on a transverse axis (A);

- lifting means (R) of the frame;

- And two forearms (7a, 7b) articulated on the frame, one on each side, each forearm comprising a coupling hand (10) with a housing (11) at its end remote from the frame, characterized by the make that :

- The housing (11) of each coupling hand (10) is open in the longitudinal direction of the forearm (7a, 7b) so that, for a range of suitable orientations of the forearms, a piton mass hitch (P) can enter or exit the housing (11) by hand, by a relative movement forward or backward,

- And that a means (C) for controlling the rotation of the forearms is provided for rotating these forearms (7a, 7b) upward relative to the frame (3,3 ') in response to the lifting movement of the frame, and down in response to the downward movement of the frame.

2. Device according to claim 1, characterized in that the range of orientations of the forearms (7a, 7b) allowing the entry and exit of the peg in the housing (11) goes from horizontal to an inclination 45 ° on the horizontal.

3. Device according to claim 1 or 2, characterized in that the means (C) for controlling the rotation of the forearms relative to the frame comprises at least one control cylinder (12) provided between a point of articulation (13 ) linked to the frame (3) and a pivot (14) linked to the forearms, but offset radially relative to the axis of rotation (8) of the forearms.

4. Device according to claim 3, characterized in that the pivot (14) is offset radially downward relative to the axis of rotation (8) of the forearms.

5. Device according to claim 3 or 4, characterized in that the forearms (7a, 7b) are fixed on a transverse beam (9) articulated on the frame (3), and that the pivot (14) is supported by cheeks (13a, 13b) integral with the beam (9).

6. Device according to claim 3, characterized in that the control cylinder (12) of the forearms is synchronized with the lifting (R; 4a, 4b) of the frame (3).

7. Device according to claim 6, characterized in that synchronization is ensured by a hydraulic connection (17a / 16a) between the chamber or chambers on the rod side / bottom side of the lifting cylinders (4a, 4b) to the chamber on the bottom side / rod side of the control cylinder (12).

8. Device according to claim 7, characterized in that a tap (18) is provided to cut or open at will the connection between the chambers.

9. Device according to claim 1 or 2, characterized in that the means (C) for controlling the rotation of the forearms relative to the frame comprises a connecting rod (36, 36a) disposed between a point of articulation (37,37a ) on the frame and a pivot (14a, 14b) linked to the forearms and offset radially relative to the axis of rotation (8) of the forearms.

10. Device according to one of the preceding claims, characterized in that it comprises a tab (19) linked in rotation to the forearms (7a, 7b) and placed so as to come and cover a bar (20) fixed to a mass (M) when the forearms are raised relative to the frame, to retain the mass (M) against an upward vertical movement.

11. Device according to one of the preceding claims, characterized in that it comprises a member (21) for retaining the mass (M) against a horizontal movement, this member (21) being pivotally mounted relative to the forearms (7a, 7b) and pressing at one end against the frame (3) so as to hang a bar (20) fixed to the mass when the forearms are raised.

12. Device according to one of the preceding claims, characterized in that each forearm has a base part (26) fixed to a hinge beam (9) and an end part (28) pivotally mounted on the base part, with a removable locking means (30) allowing either to block the end part (28) on the base part (26), or to leave the end part pivoting.

13. Device according to one of the preceding claims, characterized in that the attachment hand has holes (25a, 25b) for the passage of a retaining pin (G) in order to couple a tool.

14. Device according to one of the preceding claims, characterized in that it is intended to be installed at the front of a tractor.