FR2729816A1 - Towing device for agricultural tractor - Google Patents

Abstract

The tow bar consists of two separable parts (1, 3), an upper part (3) designed to be fixed to the rear end of the chassis (C) of the tractor and the lower part (1), carrying the towing hook (2). The lower part is suspended below the upper part by means of a system of linked connecting rods (4, 5), with mutual bolts (6,18) ensuring that the lower part is retained in a high position. The towing hook is fixed permanently to the lower part and the device is constructed with a removable beam (8), which is fitted at its rear extremity with a towing strap (800), forming an opening (83), which is suitable to engage the said hook (2). In this position the beam is made solid with the lower part by means of the fixing devices (13, 21 & 23).

Description

HITCHING DEVICE FOR AGRICULTURAL TRACTOR
The present invention relates to a coupling device for an agricultural tractor and more specifically a device of the type comprising two separable parts, namely an upper part intended to be fixed to the rear end of the tractor chassis, and a lower part carrying a tow hook, the lower part being suspended from the upper part by means of a system of articulated links, mutual locking means ensuring the retention of the lower part in the high position (working position).

A device of this kind is described in particular in the document
FR-A-2 513360.

 In this known device, the lower part has the shape of a sheath receiving the tow hook, and the link system is designed so that the lifting movement of the lower part combines rotation with forward translation; thanks to these kinematics, when the lower part is in the low position, the hook is moved back and lowered while respecting an inclination favorable to the attachment of the towed device, and is fully visible from the tractor driving position, which facilitates the operation ; on the other hand, in the locked position, the lower part is completely retracted under the upper part, the assembly forming a compact device which does not protrude, or protrudes little, downwards or rearwards relative to the chassis.

 The trailer, the agricultural machine, or the implement to be towed by the device is generally hitched directly to the hook carried by the movable lower part of the coupling device; this hook is positioned in the vicinity of the rear edge of this part.

 However, for the correct towing of certain vehicles, it can happen that the attachment point must be at a certain distance behind the coupling device; for this, a tow bar - or drawbar - is used, the front end of which is fixed to the coupling device and the rear end of which carries a yoke receiving the attachment ring of the machine.

Advantageously, the angular position of this drawbar is also adjustable laterally.
In the embodiment which is the subject of document FR-A-2 sound 360, the hook and the yoke are provided at the two ends of a single bar, which can play the role of drawbar.

 The bar is reversible inside the sheath which forms the lower part of the coupling device. In a first position, it is retracted inside the sheath, leaving beyond the rear of the latter that the hook end in another position, it emerges from the rear of the sheath over a certain length, making protrude from the end of the yoke.

 Similar systems, with reversible bars, are also known from documents FR-A-2 463 689, FR-A-2 602721 and GB-A-1 470 941.

 In these known devices, the drawbar is therefore carried permanently by the coupling device, which significantly increases the cost price, and often the size.

 This is very disadvantageous for the farmer, or other user of the device, insofar as the drawbar is generally used only very occasionally, or never by certain users.

 This is why, the main objective of the invention is to propose a coupling device of the general type mentioned above, which does not have this drawback, the device being able to be fitted with a drawbar with drawbar only when the user considers it necessary.

 Another objective of the invention is to propose an extremely compact coupling device, in particular of reduced thickness which, in the working position, protrudes little below and at the rear of the tractor chassis.

 Another objective of the invention is to provide a device whose main functional elements are protected from the outside environment, and are thus protected from wear, dirt, and shocks, which cause malfunctions.

 These objectives are achieved, in accordance with the invention, thanks to the fact that the towing hook is permanently fixed to the movable lower part of the device, and that the latter comprises a removable drawbar equipped at its rear end with a towing yoke and having an opening capable of engaging on the hook, fixing means making it possible to secure this drawbar of the lower part while it is engaged on the hook by its opening.

 Thus, when the user has - as is most often the case - to use only the towing hook, there is no need for him to obtain the drawbar. If he has to make use of this drawbar on certain occasions, he obtains it, but leaves it in a storage place during periods of non-use.

 When use is made of the drawbar, it fits easily and naturally into the interior of the device, by covering the coupling hook through its opening.

Furthermore, according to a certain number of additional, non-limiting characteristics of the invention:
- The lower part comprises a plate - or bottom - on which the towing hook is fixed, the latter projecting in overhang at one rear of the plate;
- The lower part includes a pair of superimposed transverse plates located above the plate, between which is inserted the front end of the drawbar when it is engaged on the hook, the mutual spacing of said plates corresponding to the interlocking game near, to the thickness of said end;
- These transverse plates are pierced with at least one pair of holes adapted to receive an axis intended to pass through a hole provided in the drawbar to ensure its attachment to the lower part;
- These plates are pierced with several pairs of holes offset transversely with respect to each other and can be used selectively to secure the drawbar to the lower part in different directions angularly offset laterally;
- The lower part is provided at its rear end with a pair of lateral locking nozzles capable of cooperating with retaining levers provided on the upper part, and the hook is secured to a base plate extending between these two spouts and having a flat upper face serving as support for the drawbar;
- The hook has a convex wall, and the drawbar has a recess with an oblique face (in the form of a bevel) capable of coming to bear against the rear zone of this wall when the drawbar is fixed to the lower part;
- The device comprises a removable stop adapted to be fixed to said lower part when the drawbar is not used, said stop having a bearing surface capable of limiting the movement of the towing eye forwards, when this is in place on the hook
Other characteristics and advantages of the invention will emerge from the description and the appended drawings which represent a simple, non-limiting example, a preferred embodiment.

In these drawings:
- Figure 1 is a general schematic view in perspective of the lower part of the device, the lifting links are shown partially cut;
- Figure 2 is a perspective view of the removable stop fitted to the device;
- Figures 3 and 4 are schematic side views of the device, it being shown respectively in the open position (lower part lowered) and in the closed position (lower part raised and locked relative to the upper part);
- Figure 5 is a perspective view of the removable drawbar capable of equipping the device of Figures 1,3 and 4;
- Figures 6 and 7 are schematic side views which illustrate how the drawbar is placed on the lower part of the device;
- Figure 8 is a similar view, on a larger scale, of the rear portion of the lower part of the device, the latter being devoid of the drawbar, but provided with the stop illustrated in Figure 2;
- Figure 9 is a top view of Figure 8;
- Figure 10 is a schematic top view illustrating the possibility of lateral angular adjustment of the drawbar relative to the device.

 The device represented in FIG. 1 and in FIGS. 3 and 4 comprises two separable metal parts, namely an upper part 3 and a lower part 1.

 The upper part 3 comprises a square base formed by a horizontal plate 30 and a vertical plate 31 which are fixed to a chassis element of an agricultural tractor; this chassis element is symbolized in broken dashed lines and referenced C in Figures 3 and 4. The fixing is ensured for example using screws of which only the axis lines, referenced 300 and 310, have been shown.

 The base is fixed to the rear of the tractor, the front of which is located to the right of Figures 3 and 4, as symbolized by the front arrow.

 The plate 30 is extended towards the rear (to the left of the figures) by a plate 34 forming a stop for raising the part 1.

 On the underside of the plate 30 and on the rear of the plate 31 are fixed mounting pieces 32, respectively 33 which receive transverse horizontal articulation axes, respectively 50 and 40, for a link 5 and, respectively, a pair of rods 4 to which the movable lower part 1 is suspended.

 As can be seen more particularly in FIG. 1, at the front end of part 1 is articulated, on a pin 17 of transverse axis ZZ ′, the central link 5.

 In the central zone of part 1 is mounted a transverse shaft 16, of axis YY ′, the ends of which protrude laterally from each side of part 1 forming articulation journals for the pair of rods 4.

 The lower part 1 has the general shape of a half-casing, open upwards, and provided with a plate 10, constituting a flat bottom which has a recess 100 at its front part, and two vertical side walls - or flanks - 11. In top view, this box has a generally rectangular shape, symmetrical with respect to a median longitudinal axis, but the lateral edges of which converge symmetrically towards the front part up to axis 17.

 At the rear end and inside the half-housing are provided two spouts 18 which extend the sides 1 1 of the housing by projecting upwards; they are bent forward and downward.

 At the level of these nozzles 18, outside the sides 11, extend two pins 15 of transverse axis XX '.

 In known manner, are articulated on the pins 15 a pair of tie rods not shown, which are used for controlling the raising or lowering of the lower part 1; this lifting is symbolized by the arrow T in FIG. 3.

 Part 1 is secured to a tow hook 2; the latter has the general shape of a ball presenting a rounded point directed upwards. It has a convex curved wall, the rear zone of which is referenced 200.

 This hook 2 forms an integral part of a base plate 20 which is fixed, for example by welding, on the upper face of the plate 10.

 As seen in particular in Figure 3, the bottom 10 is inclined downward and backward in the rear portion of the part 1; the base 20 has an increasing thickness from front to rear, by a corresponding angle.

 Thus, the base plate 20 has a substantially constant flexural resistance over its entire length, and its upper face is parallel to the bottom 10.

 As an indication, the diameter of the spherical portion of the hook 2 is of the order of 50 mm, while the base plate 20 has a length of the order of 150 to 200 mm and a width close to the diameter of the hook ( 50 mm).

 This plate 20 has an elongated shape, extending axially inside the housing-shaped part 1; its width is appreciably narrower than the mutual spacing of the spouts 18. It is connected, on the front side, to a transverse plate 21 whose upper face is in the same plane as that of the plate 20. The transfer plate 21 is for example welded to the plate 20 and to the bottom 10.

 Above the plate 21 is disposed a similar transverse plate 13, the lateral ends of which are welded to the edges of the sides 11.

 The plates 13, 21 are each pierced with a series of circular holes 14, respectively 22. Each hole 14 is plumb with a hole 22. Similarly, opposite each hole 22 a hole is drilled in plate 10.

 In the embodiment shown in FIG. 1, three series of holes 14, 22 are provided; the axis of the central holes lies in the median longitudinal plane of symmetry of part 1; the two other series of holes are offset laterally on either side of this plane; the axes of the three series of holes are at the same distance Rdel'axeducrochet2.

 The stop 7 shown in FIG. 2 comprises a main part 70 in the form of a rectangular parallelepiped whose height corresponds, apart from the interlocking clearance, to the spacing of the plates 13, 21. In its front end zone, this part 70 is pierced with a vertical hole 72 of the same diameter as the holes 14 and 22. At its rear part, it is provided with two fins forming a dihedral 71 of very open angle, the edge of which is directed towards the front .

 The stop 7 is dimensioned in such a way that the front end of the part 70 can be inserted in the central zone of the space between the two plates 13, 21 and be fixed by means of an axis passing through the central holes 14 , 22 and the hole 72. This axis, referenced 23 in Figures 8 and 9, is provided with a head 230 and immobilized by an easily removable pin 231. The part 70 rests on the base 20 while the fins 71 are positioned between the spouts 18, just in front of the hook 2.

 The dihedral-shaped rear face of the stopper 7 then forms a bearing surface limiting the forward movement of a coupling ring 9 surrounding the hook 2 (see FIGS. 3,4,8 and 9).

 Note that there is provided on the top of the part 70 a lining of flexible and elastic material 73, of conical or domed shape. This lining - or pad - constitutes the deformable head of a threaded rod screwed inside the part 70.

 A similar packing 51 is provided on the front face of the link 5 (see FIG. 3).

 In known manner, the upper part 3 is provided with a pair of locking levers 6 which are articulated around a transverse axis 60 carried by the mounting piece 33. The levers 6 comprise hooking spouts 61 able to cooperate each with a spout 18 of the movable part 1.

 The two levers 6 are integral with one another in rotation, a tension spring 62 tending to cause them to pivot constantly in their locked position, this pivoting being limited by an appropriate stop 63.

 The observation of FIGS. 3 and 4 makes it possible to understand the kinematics of lifting and blocking of part 1 relative to part 3, which is the same as that of the device which is the subject of document FR-A-2 ton 360 already cited.

 Part 1 being in the low position, the operator grasps by means of the hook 2 The towing ring 9 fitted to the trailer or any other vehicle to be towed. By actuation of the lifting rods, symbolized by the arrow T, it then raises part 1; the trajectories in the form of arcs of a circle have been symbolized by the arrows F1 and F2 the axes 16 and 17 of the rods 4, respectively 5, trajectories which combine an upward and forward movement, according to the principle of the deformable quadrilateral .

 The upward and forward movement of the part 1 is stopped when the elastic pads 73 and 51 come to bear respectively against a plate 34 provided at the rear of the base 30, 31 and against the plate 30.

 At the same time that a compression of these flexible linings is obtained, the automatic locking of the spouts 18 takes place in the complementary attachment spouts 61 of the levers 6. In known manner, these spouts have ramps ensuring the automacity of their mutual attachment.

 The two parts 1,3 then form a sort of practically closed casing, which occupies a space requirement of small thickness under the chassis element C.

 The ring 9 is trapped in the longitudinal direction between the hook 2 and the stop 7. It also cannot escape upwards due to the presence at this level of the elements of the mounting part 33.

 The locking members 6, 18 being located inside the casing 1, 3, the device is protected from untimely unlocking, all the more since the compression of the flexible linings 73 and 51 dampens the transmission of vibrations of the tractor to the device, and guarantees a locking under preload of the two parts 1 and 3.

 To unlock the system, it suffices to apply pressure on the levers 6 in the direction of their opening, as symbolized by the arrow P in FIG. 4; the levers are thus pivoted against the spring 62, which has the effect of releasing the spouts 18, allowing the descent of the part 1.

 In known manner, the triggering P can be achieved by means of a linkage which can be operated remotely by the operator, from the tractor cabin.

 An essential element of the invention is the drawbar 8, which is illustrated in FIG. 5.

 it is formed by two metal bars 80, 86, which have identical rectangular cross sections, and are fixed to each other, for example by welding.

 This cross section is identical to that of part 70 of the stop 7.

 As an indication, the drawbar has a total length L of the order of 0.6 meters to 0.7 meters, while the section of each bar 80, 86 has a width I of the order of 50 mm and a height h of the order of 35 mm.

 The width of the drawbar is substantially the same as that of the base plate 20, on which it is intended to come to bear by the lower face of the front bar 80.

The rear bar 86 is located in the longitudinal extension of the front bar 80, but it is located at a lower level, because it is fixed (at its front end) by its upper face against the lower face of the rear end of the front bar 80
The front edge 860 of the bar 86 is inclined downward and forward, thus forming a bevel-shaped recess.

 The front part 80 of the drawbar has, from front to rear, a cylindrical bore 81 similar to the bore 72 of the stop 7, an elastic buffer 85 similar to the buffer 73 of this same stop, and a through opening 83, in form of elongated light, the major axis of which coincides with that of the drawbar.

 This opening 83 has a sufficient width to allow its engagement, apart from the interlocking clearance, on the hook 2.

 The distance between the opening 83 and the hole 81 is such that, when the drawbar is placed on the rear end of the part 1, the hole 81 comes into alignment with the holes 14, 22 when the opening 83 came to cover the hook 2, and that its rear edge is substantially in abutment against the rear wall of the hook, as illustrated in FIG. 7.

 This distance therefore corresponds to the dimension R of FIG. 1.

 At the periphery of the opening 83, the bar 80 has a zone 82 of greater width, intended to compensate for the weakening of the mechanical resistance of the bar at this level, due to the presence of this opening.

 On the top of the rear bar 86 is fixed, for example by means of screws 88, a double-angled fitting 87 which forms, with the rear portion of the bar, a yoke 800 which receives an axis 89; that it is provided, in a well known manner, with an operating handle 890, and with ad hoc locking means.

 Figures 6 and 7 provide a good understanding of how the establishment and fixing of the drawbar in the device takes place.

 The operator begins by engaging the front end of the drawbar between the transverse plates 13 and 21, the drawbar being inclined downward and forward, but coaxial, in the longitudinal direction, relative to the part 1.

 A chamfer 84 provided in the front area of the underside of the bar 80 facilitates this engagement.

 This implementation can be done from a remote position thanks to the fact that the opening 83 has the form of an elongated lumen.

 The operator, while lowering the drawbar, pushes it forward (arrow J, Figure 6), until the hole 81 comes in alignment with a pair of holes 14, 22.

At this moment, the opening 83 completely surrounds the hook 2, and the bevelled face 860 bears against the curve 200 of the hook.

 The fixing pin 23 is then put in place through the holes 14, 81 and 22.

 The axis 23 is immobilized in translation by its head 230 and by a pin 231.

 Of course, the same axis 23 can be used for fixing the stop 7 or that of the drawbar 8.

 The lifting of part 1, equipped with its drawbar 8, and its locking against part 3 is done in the same manner as in the absence of drawbar, in the manner explained above with reference to FIGS. 3 and 4.

 The trailer or other agricultural machine is then towed via the yoke 89, at a remote attachment point of the chassis C.

 The drawbar is immobilized without play in the device, its lateral immobilization being ensured by the axis 23 and the hook 2; the upward forces are absorbed by the support of the recess 860 against the curved wall 200 of the hook 2.

 FIGS. 8 and 9 partially represent the device without drawbar, with the use of the stop 7, and direct attachment of the coupling ring 9 by the hook 2.

 Generally, the drawbar will be arranged along the longitudinal axis of the device, the fixing axis 23 passing through the central pair of holes 14,22.

 As illustrated in FIG. 10, it is however possible to orient the drawbar in a direction BB 'offset angularly, on one side or the other, by an angle a with respect to the longitudinal direction AA', by making use of a pair of side holes.

 This allows the towed machine to be offset laterally with respect to the tractor, which is sought after in certain applications.

 It goes without saying that the width of the drawbar part 80 which is inserted into part 1 of the device is chosen so that there is sufficient play to allow this angular movement. A series of holes greater than three could be provided.

 When the drawbar 8 is not used it can be left by the user in the garage, or stored on the tractor; thus it does not have to be handled or supported unnecessarily by the coupling device.

Claims (1)

CLAIMS 1. Coupling device for agricultural tractor, which comprises two separable parts (1,3), namely an upper part (3) intended to be fixed to the rear end of the chassis (C) of the tractor, and a part lower (1) carrying a tow hook (2), which is suspended from the upper part (3) by means of a system of articulated links (4, 5), mutual locking means (6, 18) ensuring the retention of the lower part (1) in the high position, characterized in that said towing hook (2) is permanently fixed to said lower part (1), and that the device comprises a removable drawbar (8) equipped at its rear end of a towing yoke (800) and having an opening (83) capable of engaging on said hook (2), fixing means (13, 21,  23) for securing this drawbar (8) of the lower part (1) while it is engaged on the hook (2) through its opening (83).  2. Device according to claim 1, characterized in that said lower part (1) comprises a plate (10) on which is fixed the towing hook (2), the latter projecting in overhang at the rear of the plate (10).  3. Device according to claim 2, characterized in that said lower part (1) comprises a pair of superimposed transverse plates (21, 13) located above the plate (10), between which is inserted the front end of the drawbar (8) when it is engaged on the hook (2), the mutual spacing of said plates corresponding to the thickness of said end.  4. Device according to claim 3, characterized in that said transverse plates (21, 13) are pierced with at least one pair of holes (14, 22) capable of receiving an axis (23) intended to pass through a hole ( 81) provided in the drawbar (8) to ensure its attachment to the lower part (1).  5. Device according to claim 4, characterized in that said plates (21, 13) are pierced with several pairs of holes (14,22) offset transversely with respect to each other and selectively usable for securing the drawbar ( 8) to the lower part (1) in different directions (A-A ', B-B') angularly offset laterally 6.A device according to one of claims 2 to 5, characterized in that said lower part (1) is provided at its rear end with a pair of lateral locking spouts (18) able to cooperate with retaining levers (6) provided on the upper part (3), and that said hook (2) is integral with a base plate (20) extending between said spouts (18) and having a flat upper face serving as support for the drawbar (8).  7. Device according to claim 6, characterized in that said hook (2) has a convex wall, and that the drawbar (8) has a recess with an oblique face (860) capable of coming to bear against the rear area (200 ) of this wall when the drawbar (8) is fixed to the lower part (1).  8. Device according to one of claims 1 to 7, characterized in that it comprises a removable stop (7) adapted to be fixed to said lower part (1) when the drawbar (8) is not used, said stop (7) having a bearing surface (71) capable of limiting the displacement of the towing eye (9) forwards, when the latter is in place on the hook (2).