| 摘要 |
1,196,737. Hydraulic steering systems for vehicles. PLESSEY CO. Ltd. 4 Aug., 1967 [10 Aug., 1966], No. 35880/66. Heading B7H. An hydraulic steering system for vehicles comprises a rotary-vane master pump A e.g. as described in Specification 1,190,768, connected to a slave cylinder L (whose piston is connected to steering linkage) via a control valve comprising a bored piston M, which is spring- urged to a central position, wherein a fixeddisplacement power-assistance pump X freely supplies liquid via ports R, Q, Q 1 and line T to the tank J, but which is moved (thus closing ports Q or Q 1 ) by the pressure created by the pump A in chamber C or E so as to deliver the pressure liquid from the pump X via port R, bore Z, non-return valves CC or EE and chamber C or E to the lower pressure side of the master pump A to assist the torque applied thereto by the steering wheel B (or its equivalent) and 80 as to disconnect the lower pressure side of the slave cylinder L from the pump A (by blocking bore D 1 or F 1 ) and connect it via ports D or F and Q or Q 1 to the tank J. Thus the pressure difference in the slave cylinder L is equal to the sum of the manually produced pressure in master pump A and the pressure supplied by the pump X to the lower-pressure side of the master pump A. The vehicle steers itself when being towed. Failure of the pump X or its delivery line does not interfere with manual operation of the system. In Fig. 2, a single pre-loaded spring N 2 urges the piston M to a central position, and each vane A 1 of the master pump A is urged by a spring A 2 against its housing. |
