Patent GB-719490-A (GB)
Title: Improvements in or relating to centering and damping and like apparatus for rotatable members, such as steerable wheel mountings
IPC: B64C25/50
Filed: 1952-04-16
Abstract: 719,490. Steering vehicles. SOC. D'INVENTIONS AERONAUTIQUES ET MECANIQUES S.I.A.M. April 16, 1952 [April 17, 1951]. No. 9611/52. Class 79(5) [Also in Group XXXIII] Apparatus for controlling the movements of a rotatable member such as a steerable wheel mounting, of the type comprising a pin or the like on the rotatable member engaging a slot adapted to transmit a restoring force when the rotatable member is positioned within a predetermined arc and disengaged when the member moves out of said arc, has the slot incorporated in a linkage backed up by resilient means and automatically displaceable and deformable to receive the pin when the member moves back within the predetermined are. As shown in Fig. 7, the pin takes the form of a roller G revolving with the member O fast with the castoring axis of a wheel. The slot is formed between two members E<SP>1</SP> and E<SP>2</SP> pivoted together at S and coupled to damping and restoring pistons P<SP>1</SP> and <SP>p2</SP>. When roller G returns to the central position after dis-engagement from the slot, member E (say) is displaced by a cam face 26 to allow the roller to regain the slot, as can be seen in Fig. 9. The construction of the restoring and damping mechanism is shown in Fig. 3. The piston P<SP>1</SP> slides in the hollow cylinder H<SP>1</SP> fitted with a stop ring t<SP>1</SP>. H<SP>1</SP> itself slides in the hollow member L<SP>1</SP> under the action of a spring R<SP>1</SP>. When the wheel is turned, as shown in Fig. 7, piston P<SP>2</SP> is pushed in and P<SP>1</SP> pulled out. Illustrating both these actions from Fig. 3, the second damping and restoring device being similar, having references with subscript 2, the pulling out of piston P<SP>1</SP> draws oil in through port 11, annular passage 18, non-return valve C\ and apertures in the diaphragm 20, to the chamber 17. Return of the piston to neutral position is damped by the throttling orifice e<SP>1</SP>. Pushing piston P<SP>1</SP> in is similarly damped, and spring R<SP>1</SP> is also compressed, storing energy for a return to the neutral position. Thus shiming is damped, and a self-centering action is set up. When the wheel member is sufficiently rotated to disengage the roller from the slot, spring R<SP>1</SP> or R<SP>2</SP> moves members E<SP>1</SP> and E<SP>2</SP> to a symmetrical position, and urges them towards the centre of member 0. For this reason the pivot S is given a rotatable cylindrical sleeve to facilitate further rotation of member 0. Re-engagement ot roller G in the slot involves displacement of E<SP>1</SP> or E<SP>2</SP>, the movement being damped by piston P<SP>1</SP> or P<SP>2</SP>. Relief valves D<SP>1</SP> and D<SP>2</SP> are provided in case pressure due e.g., to violent shiming, in chamber 17 should become dangerously high. Ports V<SP>1</SP> and V<SP>2</SP> are provided so that in the event of a failure, the wheel can be centered by admitting high pressure fluid between cylinders H<SP>1</SP> and L<SP>1</SP>, and H<SP>2</SP> and L<SP>2</SP>. By trapping this fluid, the wheel can be locked in central position.