| 摘要 |
1,190,423. Fluid-pressure servomotor systems. WEATHERHEAD CO. Sept.25, 1967 [Feb. 2, 1967], No. 43435/67. Heading G3P. A variable displacement pump 10 supplies a motor 23 through control valve 17, and the higher of the two pressures in chambers 27, 28 is admitted via check valve 82 or 83 to line 81 to move piston 74 to the left to increase the load exerted by spring 62 on spool 42. The latter is responsive to pump outlet pressure via line 41 and controls the stroke-varying piston via line 53. The pump outlet pressure thus rises to a level determined by the load exerted by spring 62 which in turn is a function of the magnitude of load 26. Bore 73 is somewhat larger than bore 39 and a balance spring 77 may be fitted to ensure a fixed differential between lines 41, 81 which is a function of the ratio of the areas of bores 39, 73 and is independent of pump outlet pressure. When shoulder 75 prevents further leftward movement of piston 74, spool 42 prevents any further increase in pump outlet pressure by reducing displacement. In the modification of Fig. 2 (not shown), the pump supplies two motors (114, 128) through respective control valves (108, 122) and the motor pressures connect with the spacer between floating pistons (164, 166, 168) and plunger (159) so that the highest of these pressures controls the loading on spring (147) biasing spool (137) controlling the displacement-varying piston. In Fig.3, (not shown), pump (180) supplies single-acting motor (192) through valve (187) and the motor pressure acts via line (194) and passages 232, 233 of reducing valve (235) on spool land (207) to bias the latter against the pump outlet pressure. As valve (235) moves to the left at cut-off, piston (213) uncovers bleed outlet (236) and the ports (233) are obturated to equalise the flows to and from chamber (208). This arrangement provides abrupt cut-off. In Fig. 4, (not shown), reducing valve (296) controls the bias pressure in chamber (275) in response to the highest of four motor pressures, and relief valve (316) controls the maximum bias pressure. In Fig. 5 (not shown), the motor pressure is only communicated to chamber (371) to modify the spring-loading on spool (345) when the motor control valve is positioned to supply the motor. |
