FR2828532A1 - Trailer with steerable rear wheels linked hydraulically to towing vehicle has cylinder with sliding sleeve and ring of locking balls - Google Patents

Abstract

The trailer, having a set of steerable wheels controlled by a hydraulic circuit with a transmitting cylinder close to the towing vehicle connector and a receiving cylinder linked to the wheel steering mechanism, has one end of the transmitting cylinder mounted on a coupling (24) on the towing vehicle. The transmitting cylinder has an outer sleeve (36) able to slide over its end joint, and a ring of locking balls (39) that are able to pass through holes in the sleeve and are actuated by a stepped bush (40) with springs (49) and an inner collar (42) with a sloping surface.

Description

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 The invention relates to a trailer comprising a steerable train of wheels and more particularly a rear wheel train capable of being oriented to accompany a change of orientation resulting in a momentary misalignment between the towing vehicle and the trailer. The invention relates more particularly to an improvement facilitating the connection to the towing vehicle of the end of a transmitter jack carried by the trailer and forming part of a hydraulic control circuit of the orientation mechanism of said steerable train of wheels.

 In a trailer of relatively long length, hinged in an articulated manner to the rear of a towing vehicle, it is advantageous for at least one of the wheel sets of the trailer, preferably the wheel set located furthest from the 'rear, is adjustable by a variable angle which depends on that which is formed, during the change of direction, between the towing vehicle and said trailer. This change of orientation of the rear wheels facilitates maneuvering, reinforces the stability of the towed assembly and reduces the wear of the tires. To do this, it is known to associate with said train of wheels an orientation mechanism moved by a hydraulic control circuit comprising a transmitting cylinder mounted in the vicinity of the stowage point of the trailer to said towing vehicle and a receiving cylinder coupled to said wheel orientation mechanism. These two jacks can be double-acting hydraulic jacks whose chambers are connected two by two by conduits of said hydraulic control circuit. The emitter cylinder is mounted articulated between the front of the trailer and a hooking element carried by the towing vehicle. Consequently, the elongation of the jack is representative of the angle of misalignment between the towing vehicle and the trailer.

 When the trailer is hooked to the rear of the towing vehicle, it is difficult to connect the emitter cylinder to the hooking element. Indeed, in the case of a hydraulic circuit, the rod of the jack cannot be moved manually. It is therefore necessary to orient the towing vehicle relative to the trailer in order to connect the end of the jack to the hooking element. This

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 delicate maneuvering requires the presence of two people, one to connect the jack and the other to maneuver the tractor.

 The invention relates firstly to an improvement making it possible to facilitate this operation. More particularly, the invention therefore relates to a trailer comprising a steerable train of wheels controlled by a hydraulic control circuit comprising a transmitting cylinder mounted in the vicinity of the point of securing of said trailer to a towing vehicle and a receiving cylinder coupled to a mechanism orientation of the wheels of said train of wheels, one end of said emitter cylinder being connected to a hooking element carried by such a towing vehicle, characterized in that said end of said emitter cylinder is connected to said hooking element by a connection comprising a sheath dimensioned for slidingly accommodating said end of said jack, in that this sheath comprises a ring of locking elements capable of projecting inside said sheath, mounted in housings of the wall of said sheath and displaceable radially under the control of a sleeve having internally two sections of different diameters, said sleeve being slidably mounted outside of said sheath and in that said end of said jack is provided with a groove with which said locking elements cooperate.

 When the section of smaller internal diameter of the sleeve is opposite the ring of locking elements, these protrude inside the sheath and are inserted in the groove formed at the end of the jack. In practice, the locking elements are balls respectively housed in holes in the sleeve. Each hole has a narrowing in the vicinity of the inner orifice of the sleeve so that the balls are held captive in their respective holes while being held externally by the sleeve.

 Advantageously, the groove is located at the end of the rod of the jack or of a cylindrical extension fixed to the end of this rod.

 The sleeve and the sleeve have opposite longitudinal hollows defining two by two of the housings housing the springs. These springs are compressed to request a relative movement between the sleeve and the sleeve, tending to push said locking elements towards

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 the inside of the sleeve by cooperation of these with the section of smaller diameter of said sleeve. The springs therefore act to position the section of smaller diameter around the ring of locking elements.

 At its other end, the sheath is extended by a coupling end piece to a said hooking element carried by a tractor vehicle. This attachment element advantageously consists of a ball joint with a spherical end. Consequently, the coupling end piece has an open cavity with a substantially spherical bottom capable of coming to cover this ball joint. The patella is provided with a cylindrical neck of diameter smaller than that of said spherical end. This configuration is used to effectively lock the coupling end piece on the ball joint. More specifically, the sheath houses two parallel rods sliding longitudinally in housings opening into said cavity. The rods are arranged so as to be able to engage on either side of the neck of the patella when the latter is in position in the cavity.

 The movement of the sleeve along the sheath is controlled by a lever forming an operating handle which is articulated to the sheath and connected to the sleeve by articulated links. This same lever forming an operating handle controls the movement of the rods. The kinematics of the lever is such that a pre-locking of the spherical ball joint is obtained before the locking of the crown of locking elements.

 With this system, the mounting of the transmitter cylinder and more particularly its connection to the attachment element carried by the towing vehicle is greatly facilitated. The user, by operating the lever releases the crown of balls and can freely engage in the sheath the end of the jack, of a variable length depending on the distance which separates the anchoring point of the jack to the ball and trailer carried by the towing vehicle. It then suffices for it to engage the spherical bottom cavity on the ball of the fastening element carried by the towing vehicle and to release the lever. The engagement of the balls in the groove of the jack takes place automatically when the tractor vehicle is reoriented.

 Of course, the invention also covers the technically equivalent variant consisting in connecting one end of the jack to an element

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 above attachment (for example in the form of a ball joint) located at the front of the trailer and no longer at the rear of the towing vehicle.

 According to another aspect of the invention, the hydraulic control circuit comprises a damping device making it possible to absorb the overpressures caused by shocks affecting the orientation of the wheels of the wheel train. This damping circuit includes a double hydroelastic cylinder with a common piston.

This piston moves in a body and defines with it two annular hydraulic chambers, respectively connected to a chamber of the sending cylinder and to a chamber of the receiving cylinder. The hydroelastic cylinder is advantageously of the hydropneumatic type. In this case, the common piston is hollow and defines with said body a pneumatic chamber maintained under air pressure.

 The invention will be better understood and other advantages thereof will appear more clearly in the light of the following description of a trailer equipped in accordance with the invention, given solely by way of example and made with reference to attached drawings in which: - Figure 1 shows schematically, top view, a trailer coupled to a tractor vehicle, during a straight line movement; - Figure 2 is a view similar to Figure 1 when the tractor vehicle describes a curve; - Figure 3 is an elevational view of a connection device according to the invention; - Figure 4 is a view along arrow IV of Figure 3; - Figure 5 is a schematic view, partially broken away, illustrating the attachment of the end of the transmitter cylinder to a fastening element carried by a towing vehicle by means of a connection device according to the invention; - Figure 6 is a section 6-6 of Figure 3; - Figure 7 is a schematic view of the entire hydraulic control circuit fitted to the trailer; - Figure 8 is a detail view on a larger scale of the double hydroelastic cylinder fitted to the hydraulic control circuit of Figure 7; and

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 - Figure 9 is a detail view illustrating the coupling between the end of the emitting cylinder and the connection device.

 In the drawings, there is shown a trailer 11 of relatively great length, comprising at the front a coupling arm 12 by which it is hitched in an articulated manner to the rear of a tractor vehicle 13, in this case here an agricultural tractor. In a manner known per se, the trailer 11 comprises, at the rear, at least one steerable train of wheels 15, that is to say equipped with an orientation mechanism 17 of the wheels of the train of wheels 15 forming by example a kind of deformable parallelogram as illustrated in Figure 7. This mechanism is controlled by a hydraulic control circuit 20 which includes in particular two hydraulically interconnected cylinders. A transmitting cylinder 22 is normally connected articulated between a point located on the axis of the coupling arm and a fastening element 24 carried by the towing vehicle 13 and located behind it, slightly on the side by relative to the point of articulation 25 between the towing vehicle and the front end of the coupling arm. Furthermore, a receiving cylinder 26 is coupled to said orientation mechanism 17 of the wheels of the rear wheel train.

The body 27 of the receiving cylinder is mounted articulated on the chassis of the trailer while the rod 28 of this cylinder is mounted articulated to one of the bars of the wheel orientation mechanism. The two cylinders 22, 26 are double-acting cylinders, that is to say comprising two hydraulic chambers on either side of the piston. The chambers 22a, 22b of the sending cylinder 22 and the chambers 26a, 26b of the receiving cylinder 26 are connected hydraulically in pairs, respectively, by conduits of the hydraulic control circuit 20. The chambers and the conduits are filled with oil. The assembly is such that a difference in alignment (FIG. 2) between the towing vehicle 13 and the trailer 11, occurring during a turn, results in a variation in length between the two articulation points of the emitting cylinder. 22 and therefore by a displacement of the piston inside of it. The assembly is such that the displacement of the liquid in the circuit results in a displacement of the piston of the receiving cylinder 26 and consequently by a modification of the orientation of the wheels of the wheel set 15. Thus, as shown in FIG. 2, a left turn initiated by the towing vehicle results in a slight

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 right of the rear wheels of the trailer, favorable to the behavior of the assembly during the curve.

 Furthermore, the hydraulic control circuit 20 comprises a damping device 30 making it possible to absorb the overpressures caused by shocks affecting the orientation of the wheels of the rear wheel train. This damping device therefore makes it possible to prevent momentary overpressures from having repercussions on the emitting cylinder 22. The adjustment of this damping device is carried out by means of a manually actuated pump 32 making it possible to inject oil into the two branches of the hydraulic circuit, as will be seen below.

 It is known that, when the coupling arm is mounted articulated at the rear of the tractor vehicle, it is quite difficult to connect the front end 34 of the emitter cylinder 22 to the rear of the tractor vehicle 13 because it does not It is not possible to move the cylinder rod by hand to come and connect it to the hooking element 24 located at the rear on the side of said towing vehicle.

 According to an important characteristic of the invention, one end of the emitter jack is capable of being connected to the hooking element located at the rear of the tractor vehicle by a connection device 35 comprising a sheath 36 with an internal cavity dimensioned for slidingly accommodate said end of said cylinder. In the example, said end 34 is constituted by a cylindrical element fixed to the rod 37 of the jack in the axial extension of the latter. In addition, the sleeve 36 comprises a crown 38 of locking elements 39 capable of projecting inside the cavity of said sleeve. These elements are mounted in housings of the wall of said sleeve and are radially displaceable under the control of a sleeve 40 having internally two sections 42, 43 of different diameters. The sleeve 40 is slidably mounted outside the sheath 36, on the latter. The two sections of said sleeve are separated by an annular ramp 44. In the example described, said locking elements 39 are balls respectively housed in holes in the sleeve. Each bore comprises, in the vicinity of its internal orifice opening into the cylindrical cavity of the sleeve, a narrowing forming a shoulder which prevents the ball from escaping into the cavity of the sleeve. As also the sleeve 40 slides around the

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 sleeve 34 by surrounding the crown 38 of the locking elements 39 (the balls) these remain trapped in their respective housings formed in the wall of the sleeve. When the section 42 of smaller diameter of the sleeve 40 is opposite the ring of locking elements, it pushes them towards the inside of the sheath. In other words, the balls protrude inside the sheath cavity. On the other hand, when the section 43 of larger diameter of the sleeve 40 is opposite the crown of locking elements, these can move radially outward and disengage the interior of the sheath. In this position, it is therefore possible to engage said end 34 of the jack 32 inside the sheath.

 Furthermore, said end of the jack (in this case the cylindrical element here) is provided with a groove 46 with which said locking elements cooperate. It is clear from the above description that, when said end of the jack is engaged in the sheath, when the locking elements 39 are engaged in the groove 46 and when the section 42 of smaller diameter of the sleeve 40 covers the crown of the elements for locking, the end of the jack 35 is fixed to the sheath 36.

 Furthermore, the sleeve 40 and the sheath 36 have opposite longitudinal hollows defining two by two of the housings housing helical springs 49. These springs are mounted with initial compression and so as to request a relative displacement between the sheath 36 and the sleeve 40, tending to push the section 42 of small diameter of the sleeve above the crown 38 of the locking elements and therefore to push the latter towards the inside of the sheath. In other words, in the absence of intervention on said connection device 35, the latter is arranged to push the locking elements towards the inside of the sleeve in order to hook the end of the jack engaged in said scabbard.

 A lever 51 forming an operating handle is articulated to said sheath. It comprises two parallel arms 52 spaced by a distance corresponding to the outside diameter of the sheath. These two arms are mounted articulated with pins 53 extending along a diameter of the sheath. The lever is connected to the sleeve by rods 55. Each rod is articulated between an arm 52 of the lever and a point on said sleeve 40. The mounting is suitable for

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 causing the displacement of the sleeve 40 (when the lever is maneuvered in a direction tending to move it away from the sheath) in a direction releasing the locking elements 39 (the balls) from the section 42 of the sleeve having the smallest internal diameter. In other words, when the lever is actuated manually, the sleeve is moved so that the section 43 of the sleeve having the largest internal diameter is momentarily opposite the crown 38 of said locking elements.

 At the opposite end of its entry, said sheath is extended by a coupling end 57 allowing its connection to an abovementioned hooking element 24 carried by the towing vehicle. In the example, the hooking element 24 comprises a ball joint 59 with a spherical end. This ball joint is provided with a cylindrical neck 60 of diameter smaller than that of said spherical end. The base of the cylindrical neck is fixed to the towing vehicle. Consequently, the coupling end piece 57 comprises an open cavity 64 with a substantially spherical bottom, in which said ball joint 59 can be housed. In addition, the sleeve 36 houses two parallel rods 66 sliding longitudinally in housings opening into said cavity. The rods are arranged so as to be able to engage on either side of the neck 60 of the ball when the latter is in position in the cavity 64. In addition, the rods are articulated to the two lateral arms 52 of said lever forming a handle. maneuver and can retract at the same time as the springs 49 are compressed, in a direction such that the sleeve moves to release the balls. The articulated attachment points between the lever and the rods, on the one hand, and between this same lever and the rods 55, on the other hand, are determined so that, when the lever 51 is released, a pre is obtained locking of the ball joint 59 in the cavity 64 before an effective and final locking of the ring of balls. The connection of the end of the emitter cylinder to the rear of the towing vehicle is therefore carried out very simply in the following manner.

 The operator first connects the coupling arm 12 to the rear of the towing vehicle. A certain angle is temporarily maintained between the tractor and the trailer. In this situation, the operator engages the free end of the jack 22 (also mounted articulated on the coupling arm) in the sleeve 36 after having raised the lever 51 as shown in FIG. 5. In this position,

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 the end of the emitting cylinder is engaged in the sheath so that the groove 46 exceeds the position of the crown 38 of locking elements. Then, the operator engages the open cavity 64 of the coupling end 57 on the ball joint carried by the towing vehicle and releases the handle. Under the effect of the springs, it automatically folds down along the body of the sheath 36 and the two rods 66 slide and protrude into the cavity 64 on either side of the neck, which has the effect of coupling the sleeve 36 to the ball 59 forming said attachment element. By straightening the towing vehicle 13 relative to the trailer 11, the end of the jack 22 tends to be released from the sheath 36 but when the groove 46 passes opposite the balls, they engage in said groove, being acted upon by the ramp 38 defined between the two sections of different diameters and, under the effect of the springs 49, the lever returns to its position illustrated in FIG. 3. This last pivoting movement of the lever causes the balls, covered by the smaller diameter portion of the sleeve. Consequently, the emitter cylinder 22 is definitively connected to the rear of the tractor vehicle 13.

 Returning to the hydraulic control circuit 20, we will now describe in more detail the damping device 30 which is inserted therein. It should be noted that, in normal operation, this damper does not affect the movement of the receiving cylinder 26 controlled by the transmitting cylinder 22. On the other hand, when an impact or any disturbance comes to temporarily deflect the inclination of the wheels beyond what it should be, in one direction or the other, the resulting displacement of oil in the receiving cylinder 26 is absorbed by the damping device 30 and does not generate a reaction harmful on the emitting cylinder 22. The damping device 30 essentially consists of a double hydroelastic cylinder defined in a hollow cylindrical body 66 constituted by the screwed assembly of two hollow cylinders 67,68 of different diameters. The larger diameter cylinder 68 is closed at one end by a welded disc 69 while the common piston 70 projects from the other end of the smaller diameter hollow cylinder 67. Furthermore, said common piston 70 also has two adjacent parts 71,72 coaxial with different diameters defining with the two cylinders 67,68 of said body two annular hydraulic chambers 74,75, each being

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hydrauliques annulaires 74, 75, entre la chambre annulaire 74 et l'extérieur et 9 entre la chambre annulaire 75 et la chambre pneumatique 78 sous pression. Des valves de purge 85 permettent d'ajuster les quantités de liquide injecté dans chaque chambre annulaire et par conséquent dans chaque branche du circuit de commande hydraulique 20. Ainsi, la chambre annulaire 74 se trouve connectée entre les chambres 22a et 26a tandis que la chambre annulaire 75 se trouve connectée entre les chambres 22b et 26b. Les surfaces utiles sur lesquelles s'exerce la pression dans les deux chambres sont calculées en fonction des surfaces utiles correspondantes dans les chambres 22a, 22b, 26a et 26b. Il ressort clairement de la description qui précède et des dessins que les deux chambres hydrauliques 74,75 sont conformées pour qu'une augmentation de pression dans l'une ou l'autre se traduise par une sollicitation tendant à déplacer le piston dans un sens, tandis que la chambre pneumatique 78 est agencée pour qu'une augmentation de pression dans celle-ci se traduise par une sollicitation tendant à déplacer le piston dans l'autre sens. Au moment de l'attelage de la remorque, les quantités de fluide hydraulique dans les deux branches du circuit 20 et la pression d'air dans la chambre 78 sont ajustées pour que ledit piston commun occupe une position prédéterminée à l'intérieur du corps. Cette position est repérée par un index 89 solidaire du piston, se déplaçant en regard d'un repère gradué 90 solidaire du corps. Le fonctionnement est le suivant. Si un choc sur le train de roues arrière se traduit par une accentuation momentanée de l'inclinaison des roues arrière, il en résulte un déplacement de la tige de vérin 28 du vérin récepteur 26 qui engendre un déplacement du piston à l'intérieur du vérin récepteur 26. Le fluide est refoulé dans la chambre hydraulique annulaire correspondante, ce qui entraîne un déplacement dudit piston commun 70 respectively connected to a chamber of the sending cylinder and to a chamber of the receiving cylinder. An elastic means biases the common piston 70 towards the outside of said body. In the example shown, the double jack is of the hydropneumatic type in the sense that the hollow common piston 70, defines with the body a pneumatic pressure chamber 78. This chamber is pressurized during an initial adjustment, by means of 'A valve 79 provided in the front wall 80 of the piston which projects beyond said body 66. Different annular seals 80, 81, 82 ensure the seal between the two chambers

hydraulic annular 74, 75, between the annular chamber 74 and the outside and 9 between the annular chamber 75 and the pneumatic chamber 78 under pressure. Purge valves 85 make it possible to adjust the quantities of liquid injected into each annular chamber and consequently into each branch of the hydraulic control circuit 20. Thus, the annular chamber 74 is connected between the chambers 22a and 26a while the chamber annular 75 is connected between the chambers 22b and 26b. The useful surfaces on which the pressure is exerted in the two chambers are calculated as a function of the corresponding useful surfaces in the chambers 22a, 22b, 26a and 26b. It is clear from the above description and from the drawings that the two hydraulic chambers 74,75 are shaped so that an increase in pressure in one or the other results in a stress tending to move the piston in one direction, while the pneumatic chamber 78 is arranged so that an increase in pressure therein results in a stress tending to move the piston in the other direction. At the time of coupling of the trailer, the quantities of hydraulic fluid in the two branches of the circuit 20 and the air pressure in the chamber 78 are adjusted so that said common piston occupies a predetermined position inside the body. This position is identified by an index 89 secured to the piston, moving opposite a graduated mark 90 secured to the body. The operation is as follows. If a shock on the rear wheel assembly results in a momentary increase in the inclination of the rear wheels, this results in a displacement of the jack rod 28 of the receiving jack 26 which generates a movement of the piston inside the jack receiver 26. The fluid is discharged into the corresponding annular hydraulic chamber, which causes a displacement of said common piston 70

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 tending to increase the volume of this chamber. This movement is only slightly slowed down by the vacuum which is created in the neighboring annular hydraulic chamber whose volume also increases. Consequently, the absorption of the displacement of the hydraulic fluid by the damping device prevents the pressure spike generated by the disturbance on the train of wheels from propagating up to the emitting cylinder whose operation is not affected. When the disturbance has ceased to affect the wheel assembly 15, the air pressure in said pneumatic chamber 78 rapidly returns said common piston to its equilibrium position.

Claims (14)

1. Trailer comprising a steerable train of wheels controlled by a hydraulic control circuit comprising a transmitting cylinder (22) mounted in the vicinity of the point of securing of said trailer to a towing vehicle and a receiving cylinder (26) coupled to a mechanism orientation of the wheels of said wheel set, one end of said emitter cylinder being connected to a hooking element (24) carried by such a towing vehicle, characterized in that said end of said emitting cylinder is connected to said hooking element by a connection device (35) comprising a sheath (36) dimensioned for slidingly accommodating said end of said jack, in that this sheath comprises a ring (38) of locking elements capable of projecting inside said sheath, mounted in housings of the wall of said sheath and radially displaceable under the control of a sleeve (40) having internally two sections d e different diameters, said sleeve being slidably mounted outside of said sheath and in that said end of said jack is provided with a groove (46) with which said locking elements cooperate.  2. Trailer according to claim 1, characterized in that said two sections of said sleeve are separated by an annular ramp (44).  3. Trailer according to claim 1 or 2, characterized in that said locking elements are balls (39) respectively housed in bores of said sheath.  4. Trailer according to one of claims 1 to 3, characterized in that said end of said jack provided with a groove is the rod of this jack or integral with it and in that said jack is of hydraulic double type effect whose two chambers (22a, 22b) are respectively connected to the two chambers (26a, 26b) of another double-acting hydraulic cylinder constituting the aforementioned receiving cylinder (26).  5. Trailer according to one of the preceding claims, characterized in that said sleeve and said sheath have longitudinal recesses defining two by two of the housings housing springs (46) to request a relative movement between said sheath and said sleeve, tending to repel <Desc / Clms Page number 13>  said locking elements towards the inside of said sleeve by cooperation of these with the section of smaller diameter (42) of said sleeve (40).  6. Trailer according to claim 5, characterized in that a lever (51) forming an operating handle is articulated to said sheath and connected to said sleeve by articulated links (55), the assembly being adapted to cause the displacement of said sleeve in a direction releasing said locking elements of said section of the sleeve having the smallest internal diameter.  7. Trailer according to one of the preceding claims, characterized in that said sheath is extended by a coupling end piece (57) to an above-mentioned hooking element (24) carried by a tractor vehicle.  8. Trailer according to claim 7, characterized in that, said coupling element comprises a ball joint (59) with a spherical end, said coupling end piece comprises an open cavity with a substantially spherical bottom in which said ball joint can be accommodated.  9. Trailer according to claim 8, characterized in that such a ball joint being provided with a cylindrical neck (60) of diameter smaller than that of said spherical end, said sheath houses two parallel rods (66) sliding longitudinally in housings opening into said cavity, said rods being arranged so as to be able to engage on either side of an abovementioned neck when such a ball joint is in position in said cavity.  10. Trailer according to all of claims 6 and 8, characterized in that said rods (66) are articulated to said lever forming an operating handle to retract at the same time as said springs are compressed.  11. Trailer according to one of the preceding claims, characterized in that said hydraulic control circuit comprises a damping device (30) making it possible to absorb the overpressures caused by shocks affecting the orientation of the wheels of said train of wheels.  12. Trailer according to claim 11, characterized in that said damping device comprises a double hydroelastic cylinder with common piston (70), moving in a body and defining with it two annular hydraulic chambers (74,75), each being respectively connected to a chamber of the sending cylinder and to a chamber of the receiving cylinder. <Desc / Clms Page number 14>  13. trailer according to claim 12, characterized in that said common piston is hollow and defines with said body a pneumatic chamber (78) under pressure.  14. Trailer according to claim 13, characterized in that the two hydraulic chambers (74,75) are shaped so that an increase in pressure in one or the other results in a stress tending to move the piston in a direction, while said pneumatic chamber (78) is arranged so that an increase in pressure therein results in a stress tending to move the piston in the other direction.