Patent GB-644455-A (GB)
Title: An improved hydraulic steering mechanism for trailers
IPC: B62D13/04
Filed: 1947-11-24
Abstract: 644,455. Trailer steering arrangement. HARDING. H. A., and BUTLER, M. R. Nov. 24, 1947, No. 31129. [Classes 79 (iii) and 79 (v)] In a hydraulic steering mechanism for trailers having a piston and cylinder assembly associated with a track rod for steering the wheels of the trailer there is provided means actuated by the towing vehicle to control the flow of fluid in the assembly in accordance with relative disposition of the vehicle and trailer and locking means responsive to the direction of rotation of a wheel of the trailer serving to rock the track rod when the trailer is being towed but to release the rod allowing steering deflection of the trailer wheels when the trailer is being pushed by the vehicle. In the embodiment shown when the vehicle 1 is pushing the trailer rearwardly, the wheels 8 of the trailer are steered by lateral displacement of the track rod 14 to conform with deflections of the vehicle by the piston and cylinder assembly. When the vehicle is pulling the trailer, the track rod 14 is locked against transverse movements and the wheels 8 are not deflected. Movement of the track rod is dependent on a clutch operated by one of the wheels. A draw plate 2 is pivoted to the vehicle ana pivoted on a pin 4 to a draw bar 5 of the chassis frame 6 of the trailer. Connected by brackets 27a on the draw bar 5 is a fluid reservoir 27 containing cylinders 28, 28a, the piston rods of which are connected by a cross-bar 30 carried by a spindle 30a journalled in the top and bottom of the reservoir 27. A lever 31 is connected to one end of the spindle 30a and has a sliding and pivotal connection with an arm 32 integral with the plate 2 so that on variation of the angle between the plate 2 and the bar 5 the bar 30 is turned and the pistons in the cylinders 28, 28a moved forcing fluid along one and withdrawing it from the other of pipes 11, 11a. The pipes 11, 11a are connected by flexible pipes to cylinders 12, 13. The pistons 12a, 13a of the cylinders 12, 13 are connected to the track rod 14 by studs 13b. The track rod 14 is connected by links 14b to steering arms of the stub axles 7a of the wheels 8, and is also connected by a pin 16 to a slot in a plate 16a and connected to a two-armed lever 17b pivoted on a pin 18a on an extension 15 of the trailer axle 7. The other arm of the lever 17b is connected to a plate 17a with which the cylinder 12 is connected by a pin 17 and slot. Integral with the pin 18a is a block 18 to which is pivoted an arm 9. An arm 9a has at one end a sliding connection with the arm 9 and at the other a pivotal connection 9c with an annular member 10 forming a part of the clutch, Figs. 11 and 12. The hub 10a of one wheel 8 is secured to a ring plate 19 on which the member 10 is rotatable. Retained in position by a recessed part of the member 10 and by a ring plate 20 is a rotatable ring plate 20a. On the inner periphery of the member 10 is a recess 21 having a narrow middle portion and at the ends spring pressed rollers 24, 24a. Projecting into the recess 21 is a tongue 23 on the plate 20 which has on its other side pins 25, 25a, either of which is adapted to engage a stop piece 26 on the stub axle 7a. When the vehicle and trailer is reversed in direction, the rotation of the wheel causes the ring plate 19 to frictionally draw one of the rollers into the narrower part of the recess 21 and the annular member 10 is rotated. This rotation is arrested by the engagement of one of the pins 25, 25a with the stop 26 which causes the tongue 23 to engage the roller and push it back to its end of the recess thus interrupting the drive from the hub to the annular member 10. The limited movement of the member 10 rotates the arm 9 and the two-armed lever 17b about the pivot 18. Rotation of the lever 17b in one direction moves the plate 17a rearwardly and engages it with dowel pins 17c on the extension 15 thus preventing lateral movement of the cylinders 12, 13 relative to the axle 7, whilst the other plate 16a is forced forwardly freeing it from its dowel pins 16c and allowing the track rod to move parallel to the axle. Rotation of the lever 176 in the opposite direction releases the plate 17a from its pins 17c and moves the plate 16a into engagement with the pins 16c thus preventing lateral movement of the track rod 14 relative to the axle and permitting lateral movement of the cylinders 12, 13. The arrangement is such that for rearward rotation of the wheels 8 the cylinders 12, 13 are restrained from lateral movement and the track rod 14 is free to move laterally so that deflection of the towing vehicle to one side will charge one of the pipes 11, 11a for example, the pipe 11, causing the pistons 12a, 13a and the track rod 14 to move to the left in Fig. 6 relative to the cylinders and causing the requisite deflection of the wheels 8. When however the vehicle and trailer are moving forward, the arrangement is such that the track rod is restrained from and the cylinders permitted to move parallel to the axle. If during forward travel the tractor is deflected with corresponding charging of one of the pipes 11, 11a, the cylinder will move relative to the pistons and the track rod, and thus the wheels 8 will not be deflected for steering.