GB845784A - Improvements in pneumatically assisted steering arrangements - Google Patents

Abstract

845,784. Vehicle power steering. WESTING. HOUSE BRAKE & SIGNAL CO. Ltd. Dec. 3, 1957 [Dec. 3, 1956], No. 37595/57. Class 79(5). A cylindrical control valve 4, Fig. 1 for a pneumatic powered steering cylinder 15 and adapted for use as a drag link to transmit steering movement between the drop arm 7 and wheel lever 8 comprises pairs of slidable inlet and exhaust valves in resiliently urged seated engagement and displaceable after limited lost motion of the actuating rod 35, Fig. 3 to close an equalising passage 43 between the valve pairs. The valve has a cylindrical casing 4<SP>1</SP> coupled at one end through an end plate 38<SP>1</SP> and ball joint 6 to the steering system, the actuating rod 35 being connected by a ball joint 5 to the drop arm 7. Ports 27, 28 in the valve body 4<SP>1</SP> are connected by a flexible pipe 3 to the compressed air supply 1 and ports 19, 20 are connected through flexible pipes 21, 22 to the steering cylinder 15. Passages 44, 45, 46 in the actuating rod are exhausted to atmosphere through a vent 53 in the end plate 38<SP>1</SP>. Inlet valve closure members 33, 34 are slidable on the actuating rod 35 and are yieldingly held in engagement with seats 38, 39 of the valve body by springs 36, 37. Exhaust closure members 40, 41 are also slidable on the actuating rod 35 with lost motion which is limited by abutments 47 in slots 49 and are normally urged to seat on the inlet closure members 33, 34 by springs 49<SP>1</SP>, 50<SP>1</SP>. The actuating rod 35 further has a piston 42 fixed thereto which is influenced by the pressures on its opposite faces to provide feel and contains the equalising passage 43. Shoulders 51<SP>1</SP>, 52<SP>1</SP> on the valve casing 4<SP>1</SP> are engaged by the piston 42 in event of failure of the pneumatic system to permit mechanical operation. In normal steering initial movement of the actuating rod 35 first closes the gap between the piston 42 and valve member 40 or 41 to close the equalising passage 43 and then opens the valve member 33 or 34 against springs 36 or 37 so that the pressure supply passes to the ports 19 or 20. At the same time, the valve member 40 or 41 moves to connect the port 19 or 20 to exhaust through the passage 46.