| 摘要 |
734,904. Fluid-pressure servomotor-control systems. CARRIER CORPORATION. July 29, 1953 [Sept. 30, 1952], No. 21081/53. Class 135. [Also in Groups XIII and XXVIII] The cold storage compartment 12, e.g. of a vehicle is cooled by the evaporator 6 of a refrigerating system including a continuouslyrunning compressor 2, and when the temperature of the compartment reaches a predetermined minimum a thermal bulb 16 closes a solenoid-actuated valve 14 in the liquid line 7, the low evaporator pressure is transmitted to the line 7 through a restricted by-pass 40 round the expansion valve 8 and this decrease in pressure is utilized to unload the compressor 2. As shown, the compressor has a plurality of cylinders each having an unloading device 20 normally held out of action by oil pressure transmitted from an oil pump (not shown) through a restriction 24 and a pipe 23. When unloading is required, the oil is bled from the unloading devices 20 through a pipe 25 and a valve 27 to the compressor crankcase. Valve 27 is normally held closed by the high pressure in line 7 being transmitted through a pipe 32 to the underside of diaphragm 29, but when valve 14 closes, the reduction in pressure in line 7 allows a spring to open valve 27. Each compressor cylinder 40 has a piston 41, an annular discharge valve 44 which is spring- loaded and an annular suction valve 35 loaded by springs 43 and disposed above a suction port 42. A sleeve 36, beneath which is disposed a stop 39, is slidable on the cylinder 40 and abuts spring-loaded rods 37, the springs 38 of which keep the rods and the sleeve in lowered position as long as the end 53 of a lever 51 is lowered. This position of lever 51 is normally maintained by oil pressure supplied through pipe 23 to the space beneath a piston 49 attached to the outer end of lever 51. When unloading is required, the oil pressure in pipe 23 is relieved, a spring 54 forces down piston 49, then end 53 of lever 51 is thus raised, the sleeve 36 is raised and the rods 37 are raised to hold the suction valve 35 in open position. |
