TRACTION DEVICE

Abstract: This invention relates to a draw device, intended to be arranged at the fore portion of a draw bar of a trailer, towed by a vehicle, and comprising a socket hitch which is intended to be fastened on the tow hook of the vehicle, the draw device being intended to act upon the brakes of the trailer. According to the invention to draw device is characterized by the combination of the following features: the socket hitch (9; 27) is fastened to the fore portion of the draw device by means of a hinge (8; 29) in that way that the socket hitch (9; 27) can be pivoted essentially in a vertical plane backwards in relation to the draw device, the movement backwards of the socket hitch (9; 27) creating a force which is transmitted to the brakes of the trailer for retardation of the same; the socket hitch (9; 27) is arranged above the hinge (8; 29), whereby the draw device allows a presetting of the force by which the brakes of the trailer are influenced.

Description: TRACTION DEVICE. This invention relates to a draw device intended to be arranged at the fore part of the draw bar of a trailer, towed by a vehicle, and comprising a socket hitch which is intended to be fastened on the tow hook of the vehicle, the draw device being intended to act upon the brakes of the trailer. According to known technique trailers for non-heavy vehicles are provided with a braking device which is intended to be influenced by means of a draw bar of the trailer. In that connection the draw bar is. so arranged that its fore part is displacebly journalled in relation to the remaining part of the draw bar essentially in the longitudinal direction of this one. The fore part of the draw bar acts upon the brakes of trailer either in a hydraulic way or in a mechanical way.' Due to the weight of the trailer, the draw bar rests against the tow hook of the vehicle with a certain force. This force can vary in dependence upon the load of the trailer. In case of heavy load on the trailer, the draw bar may have such a strong contact with the tow hook of the vehicle that the bar is bent. Due to that fact the relative movement between the parts of the draw bar is deterioated during the retardation of the vehicle. If the vehicle is retarded strongly, this fact may lead to that at first nothing happens regarding the retardation of the trailer due to the difficulties for the mutual movement of the parts of the draw bar. Then there is a violent retardation of the trailer due to the fact that the parts of the draw bar suddenly overcome the resistance against the relative movement between the parts so that the fore part of the draw bar suddenly with full force acts upon the brakes of the trailer. This retardation of the trailer can be so strong that the trailer begins to skid och causes a critical situation for the driver of the vehicle. By the American patent No. 2 720 309 is previously known a draw device comprising a socket hitch which is fastened to the fore part of a draw bar. The socket hitch is pivotably arranged in relation to the draw bar, the socket hitch being intended to act on the hydraulic braking system of the trailer. An essential draw back with this known device is the fact that the socket hitch is positioned under the pivoting pin. When retarding, this means that the socket hitch will move downwards and backwards. However, this movement will be counteracted by the fact that the rear portion of the draw vehicle with the tow hook gets a movement which is directed upwards when retarding. Due to that fact the function of the draw device will not be satisfac¬ tory. Furthermore, there is no possibility to pre-set the force by which the braking system is influenced by the known device. This invention intends to remove the problems with known technique and offer a draw device for trailers which gives a soft and effective transmission of the retardation force of the vehicle to the brakes of the trailer. This has been made possible by a draw device of the kind mentioned by way of introduction which is characterized by the combination of the following features: - The socket hitch is fastened to the fore part of the draw device by means of a hinge so that the socket hitch can be pivoted essentially in a vertical plane backwards in relation the draw bar, the movement backwards of the socket hitch creating a force which is transmitted to the brakes of the trailer for retardation of the same; The socket hitch is arranged above the hinge, whereby the draw device allows a pre-setting of the force by which the brakes of the trailer are influenced. The constructive design of the new draw device means that that part of the socket hitch being in engagement with the tow hook of the draw vehicle in an active position will place itself essentially straight above the hinge. Thus, if the socket hitch is made longer or is moved forwards in .the device, which means that the socket hitch in an inactive position is displaced in front of the hinge, the force on the brakes will be strengthened. On the other hand, if the socket hitch is made shorter or is moved backwards in the device, which means that the socket hitch in an inactive position is displaced inside the hinge, the force on the brakes will be weakened. A further advantage with the new draw device is the fact that when retarding a trailer provided with a draw device according to the invention, the movement directed downwards of the draw device, arising during the retardation, creates a force which strengthens the braking force by which the braking system of the trailer is influenced. Two preferred embodiments of the invention shall be de¬ scribed more closely below with reference to the accompanying drawings, in which Fig. 1 shows a side view of a first embodiment of the draw device according to the invention, this one being shown fastened on the fore part of a draw bar of a trailer, Fig. 2 . shows a view of the device according to Fig. 1, seen from the front, Fig. 3 shows a view of the device according to Fig. 1, seen from above, and Fig. 4 schematically shows a second embodi¬ ment of the draw device according to the invention. Referring to the Figs. 1-3 is shown there the first embo¬ diment of the invention which is intended for trailers with a hydraulic braking system. The embodiment comprises two essential- ly vertical, parallel side walls 1, 2, which are positioned at a certain distance from each other so that a lateral space is created between these ones. When mounting the side walls 1, 2 on the draw bar of the trailer, these ones have a direction which is essentially the same as the longitudinal direction of the trailer. From respective side wall 1, 2 a portion 3, 4 projects straight forwards in such a way that between these two parts 3, 4 is also created a space, the lateral size of which essentially corresponds to the lateral size of the space between the side walls l, 2. With the lateral size of a space is meant the width of the space in a direction which is essentially perpendicular to the longitudinal direction of the draw device. In these spaces between the portions 3, 4 and the side walls 1,- 2 there is an angle bar-like means 5 (yoke) intended to be pivotably suspended. This means comprises an essentially straight and horizontal part 6 which is directed forwards and an essentially straight and vertical part 7 which is directed upwards. In this connection the fore portion of the horizontal part 6 is pivotably fastened on an essentially horizontal shaft 8 which is arranged at the project¬ ing portions 3, 4 of the draw device. In the upper portion of the vertical part 7 the rear part of a socket hitch 9 is fastened. This socket hitch which in normal position has essentially a horizontal extension, is accordingly directed forwards, that part 10 of the socket hitch which is intended to be in engagement with the tow hook of the vehicle, is arranged essentially straight above the shaft 8, forming the hinge of the means 5 of the socket hitch 9, and at a vertical distance A from this one. This dis¬ tance A shall be so large that the tow hook and possibly the base of this one shall be able to be freely applied between the pro¬ jecting portions 3, 4 of the tow hook and the socket hitch. As appears from the drawing the socket hitch 9 and the means 5 shall be able to be pivoted backwards a number of degrees and back to the original position, pivoting being made about the shaft 8. This pivoting is limited according to this embodiment by the piston stroke of a hydraulic piston cylinder 11, the one end 12 of which is articulatedly fastened to the vertical part 7 of the means 5, whereas the other end 13 of the piston cylinder is articulatedly fastened to an essentially horizontal shaft 14 which is arranged between the side walls l, 2 in a rear part of the draw device. The piston cylinder is so arranged that in rest¬ ing position it is directed obliquely upwards, seen from behind and forwards. This means that when the means 5 has been pivoted a number of degrees in a clockwise direction, seen in Fig. 1, the angle between the part 7 of the means 5 and the longitudinal direction of the hydraulic cylinder will be about 90°. During the continued pivoting of the means 5, the pivoting movement of this means, seen a the point 12 of the front attachment means of the piston cylinder, will have a direction which approximately corre- sponds to the longitudinal direction of the piston cylinder. This fact leads to a very effective transmission of the force from the socket hitch 9 and the means 5 to the piston cylinder 11. The device functions in the following way: A trailer provided with a new draw device is coupled to a vehicle, the socket hitch 9 being fastened on the tow hook of the vehicle. When retarding the vehicle, the socket hitch is forced backwards. This fact leads to an immediate reaction of the means 5 which begins to pivot in the clockwise direction about the shaft 8. Due to that fact the hydraulic piston 11 is pressed together, whereby hydraulic oil is forced out into the braking pipes leading oil to the brakes of the trailer. Due to the design of the device, according to the invention, there is a very soft transmission of the retardation movement of the vehicle to the trailer and its braking device. This soft transmission of the force is made independently of the weight of the load of the trailer. Due to that fact the risk is removed that troublesome situations shall arise for the driver of the vehicle. The described draw device is, as has previously been mentioned, intended to be placed at the fore part of the draw bar 15 of the trailer. This draw bar 15 suitably comprises two parts 16, 17, which diverge in relation to each other in the direction backwards. For fastening the parts 16, 17 of the draw bar the draw device is provided with two essentially horizontal side flanges 18, 19, one side flange projecting out essentially perpendicularly from the upper portion of respective side wall l, 2. Of course it would be possible to modify the device so that the side flange instead projects out from the lower portion of respective side wall. In order to be adapted to the diverging parts 16, 17 of the draw bar, the width measure of each flange 18, 19 increases in the direction backwards. The draw bar is suitably fastened by means of bolts 20, 23 on the parts 16, 17 of the draw bar. The described embodiment according to Figs. 1-3 is intended to be used in trailers provided with a hydraulic braking system. In Fig. 4, however, is shown an embodiment of the invention which is intended to be used in trailers provided with mechanically in¬ fluenced brakes, i.e. brakes which are influenced for instance by tightening a steel wire or the like. The draw device for trailers with mechanical brakes has the same principle design as the draw device for trailers with hydraulic brakes. The difference is that the angle bar-like means (yoke) 24 in Fig. 4 is intended to in¬ fluence a mechanical, pivoting means 25, whereas the angle bar- like means in the embodiment according to Figs. 1-3 is intended to influence a hydraulic cylinder. The angle bar-like means 24 in Fig. 4 comprises two parts, one essentially straight, vertical part 26 which at the top is connected with the schematically shown socket hitch 27, and a straight, almost horizontal lower part 28, the fore portion of which is pivotably fastened on an essentially horizonal shaft 29. The transition area between the vertical part 26 and the essen¬ tially horizontal lower part 28 forms a corner-formed portion 30. This portion 30 is intended to cooperate with the pivoting means 25, which is pivotably fastened on an essentially horizontal shaft 31 and has a portion 32, 33 on each side of the shaft 31. In that connection the one portion 32 is elongated and pointed and is intended to be in contact with the corner-formed portion 30 of the anglebar-like means 24 (yoke) . The portion 33 of the means 25 on the other side of the shaft 31 is also elongated and lias a hole 34 in which the means for the mechanical influence of the brakes of the trailer can be fastened. By changing the form of the corner-formed portion 30 of the means 24 and of the portions 32, 33 of the means 25 the gear be¬ tween the means 24 and 25 can be changed. When retarding a trailer provided with a draw device according to Fig. 4, the socket hitch 27 is removed backwards, whereby the angle bar-like means 24 is pivoted in the counter¬ clockwise direction about the shaft 29 constituting the hinge. In that connection the corner-formed portion 30 of the means 24 in¬ fluences the portion 32 of the pivoting means 25 so that this means pivots in the clockwise direction about the shaft 31 constituting the hinge. Due to that fact a wire or the like, Which is connected with upper portion 33 of the pivoting means 25 is tightened. This has the consequence that the brakes are en¬ gaged mechanically on the trailer. An extremely essential advantage with the draw device according to the invention is the possibility of presetting the force by which the braking system of the trailer can be influen¬ ced. This has been made possible by the constructive design of the new draw device meaning that the fastening point of the socket hitch is above the pivoting point of the yoke. Due to that fact in an active drawing position always a centering of the fastening point is made in relation to the pivoting point so that the former one becomes positioned straight above the later one " which is indicated by a dotted, vertical line L in Fig. 1. The invention is of course not limited to the embodiments which have been.described here but can be modified within the scope of the following claims. Thus, if the traffic legislation of any country should require that, the device could be provided with a shock absorbing means in order that the force from the vehicle to the trailer shall be transmitted still softer. A suitable placing of such a shock absorbing means would be to arrange its one end in the upper portion of the vertical part 7; 26 of the angle bar-like means 5; 24 and the other end of theshock ab-sorbing means on a shaft which is positioned between the side walls 1, 2.

Claims: CLAIMS 1. Draw device intended to be arranged at the fore part of a draw bar of a trailer, towed by a vehicle, and comprising a socket hitch which is intended to be fastened on the tow hook of the vehicle, the draw device being intended to act upon the brakes of the trailer, c h a r a c t e r i z e d by the combination of the following features: The socket hitch (9; 27) is fastened to the fore part of the draw device by means of a hinge (8; 29) in that way that the socket hitch (9; 27) can be pivoted essentially in a vertical plane backwards in relation to the draw device, the movement backwards of the socket hitch (9; 27) creating a force which is transmitted to the brakes of the trailer for retardation of the same; - The socket hitch (9; 27) is arranged above the hinge (8; 29) , whereby the draw device allows a presetting of the force by which the brakes of the trailer are influenced. 2. Draw device according to claim 1, c h a r a c t e r ¬ i z e d in that it comprises a means (5; 24) with an upper part (7; 26) and a lower part (6; 28), that the socket hitch (9; 27) is arranged in the upper part (7; 26) of the means (5; 24), whereas the lower part (6; 28) of the means (5; 24) is fastened to the fore portion of the draw device on an essentially hori¬ zontal shaft (8; 29) constituting the hinge of the socket hitch (9; 27) , and that the means (5; 24) has such a design that in an active traction position that part of the socket hitch (9; 27) which is in engagement with the tow hook of the vehicle is positioned essentielly straight above the shaft (8; 29). 3. Draw device according to claim 2, c h a r a c t e r - i z e d in that it comprises two essentially vertical, parallel side walls (1, 2) which are positioned at a distance from each other, seen in a direction which is essentially perpendicular to the longitudinal direction of the draw device, a part (3, 4) projeting essentially straight forwards from respective side wall (1, 2) , whereby there is created a space between the side walls (1, 2) and the parts (3, 4) , respectively, and that the means (5; 24) is arranged in the mentioned space. 4. Draw device according to claim 3, c h a r a c t e r - i z e d in that the means (5; 24) has an anglebar-like design with such an extention that its lower part (6; 28) extends for¬ wards in the draw device, the fore portion of the lower part (6; 28) being pivotably fastened on the shaft (8; 29) , which connects the projecting parts (3, 4). with each other, whereas the upper part (7; 26) of the anglebar-like means (5; 24) extends essenti¬ ally vertically, the socket hitch (9; 27) being arranged in the upper portion of the upper part (7; 26). 5. Draw device according to any one of the claims 2-4, the draw device being intended to be used in a trailer provided with hydraulic brakes, c h a r a c t e r i z e d in that the socket hitch (9) and by that the means (5) on which the socket hitch (9) is arranged, are intended to influence a hydraulic piston cylinder (11) which via brake pipes are in contact with the brakes of the trailer, the one end (12) of the piston cylinder (11) being articulatedly fastened to the vertical part (7) of the means (5) , whereas the other end (13) of the piston cylinder is articulatedly fastened on an essentially horizontal shaft (14) which is arranged between the side walls (1, 2) in a rear part of the draw device. 6. Draw device according to any one of the claims 2-4, the draw device being intended to be used in a trailer provided with mechanical brakes, c h a r a c t e r i z e d in that the socket hitch (27) and by that the means (24) , on which the socket hitch is arranged, are intended to influence a pivoting means (25) which in its turn is intended to be connected with a means for mechanical action upon the brakes of the trailer. 7. Draw device according to claim 6, c h a r a c t e r ¬ i z e d in that the pivoting means (25) is pivotably fastened on an essentially horizontal shaft (31) , arranged between the side walls (1, 2) , and that the means (25) on the one side of the shaft (31) has a lower elongated portion (32) which is intended to be in contact with a corner-formed portion (30) of the angle¬ bar-like means (24) between its upper (26) and lower part (28) , and an upwards projecting portion (33) on the other side of the shaft (32) , which portion (33) is intended to be connected with the means acting upon the brakes of the trailer. 8. Draw device according to claim 7, c h a r a c t e r - i z e d in that when retarding the draw vehicle, the anglebar- like means (24) is pivoted in a counter clockwise direction about the first shaft (29) and influences the pivoting means (25) to pivot in a clockwise direction about the second shaft (31) , the gear between the movements, of the two means (24, 25) being able to be changed by modification of the corner-formed portion (30) of the first means (24) and the projecting portions (32, 33) of the second means (25) . 9. Draw device according to any one of the preceding claims, the draw device being intended to be fastened on a draw bar (15) of a trailer, c h a r a c t e r i z e d in that the fastening is made by means of flanges (18, 19) and anchoring means (20-23) .

Inventors: FORSGREN STELLAN, SJOELUND ANDERS, FORSGREN, STELLAN, SJOELUND, ANDERS
Applicants: FORSGREN STELLAN, SJOELUND ANDERS, FORSGREN, STELLAN, SJOELUND, ANDERS
Application year: 1992
Main classification: B60T7
IPC codes: B60T7, B60T11