GB730893A - Improvements in power steering mechanisms for land vehicles - Google Patents

Abstract

730,893. Fluid-pressure servomotor control systems. BENDIX AVIATION CORPORATION. Oct. 10, 1952 [Oct. 20, 1951], No. 25501/52. Class 135. A power steering mechanism for a land vehicle comprises a hollow worm 16 mounted on a coaxial steering shaft 14 and rotatable in bearings 20 which prevent axial movement of the worm relative to its housing 10, the shaft engaging the interior of the worm by screw threads 18 whereby relative rotation between the worm and shaft results in axial movement of the shaft which actuates a valve 44 controlling a fluid-pressure motor 38 connected by a rack 32 to a gear sector member 24 in mesh with the worm. Member 24 is mounted on a shaft 26 operatively connected to the steerable wheels. The valve comprises a sleeve 54 fixed between bearings 56 on shaft 14 and slidable in a housing 50 to connect pressure fluid inlet 61 to either end of the motor cylinder via lines 40, 42, the end not so connected being exhausted through appropriate groove 46 and an exhaust port (not shown). Circulation of pressure fluid from the inlet to both ends of the cylinder and to exhaust occurs in the central position of the sleeve. The valve sleeve is centred in the housing by at least two precompressed springs 64 urging plungers 62 against the bearings 56 and shoulders 66, and relative rotation between the worm and shaft will not occur until the force of these springs is overcome. Movement of the motor piston 36 recentres the valve by rotating the worm and thus causing axial movement of the shaft 14. If the power fails, the steering can be effected manually by engagement of a shoulder 70 or a nut 72 with the ends of the worm. The pitch of the threads 18 is subsequently greater than that of the exterior threads on the worm.