| 摘要 |
<p>1,201,787. Fluid - pressure servomotors. CATERPILLAR TRACTOR CO. Nov.2, 1967 [Dec.21, 1966] No.49888/67. Heading G3P. [Also in Division F2] A duel relief valve has a spring-loaded dump spool 43 controlling the relief of a passage 14 to reservoir via passage 45, and port 44. Fluid passes through a bore 50 in the spool into chamber 47 to assist the spring-loading and is relieved to reservoir via passages 51, 52 and 53 when the spring-loaded poppet valve 54 is overcome. Fluid pressure in chamber 47 is also communicated to the rear of piston 60 via passages 64, 65 and restriction 63 to assist the spring-loading of poppet valve 53. The communication is controlled by a shuttle valve 66 which acts to connect the passage 65 to either passage 51 or to reservoir via passage 71. The shuttle valve 66 is moved from the position shown wherein due to the increased loading of valve 54 the relief valve operates at a high pressure to one wherein the relief valve operates at a low pressure due to passage 65 being connected to reservoir when fluid pressure acts in passage 70 on moving the shuttle valve 16 to connect to passage 14 to the port 30. Ports 48 in the dump spool graduate the pressure release to port 44. The valve 16 controls the lighting and lowering of earth moving equipment wherein a higher relief pressure is required on lifting to that on lowering.</p> |
