Improvements in or relating to fluid pressure systems, more particularly for the control of variable pitch propellers

摘要

665,894. Gear pumps. BENDIX AVIATION CORPORATION. July 4, 1947 [July 18, 1946], No. 17760/47. Class 110(ii). [Also in Group XXIX] A gear pump in a fluid-pressure servomotor control system for feathering or unfeathering the blades of a variable pitch aircraft propeller is maintained ready for immediate operation by the circulation of warm oil through a control valve associated therewith and located in or adjacent to the pump casing. As shown, a pump 16 driven by a reversible electric motor 18 and having a control valve 20 located adjacent the pump, supplies high pressure oil to urge the plunger 64 of the valve 20 to the right against its spring 70 to open communication between ports 44, 56 and pass the oil to the left of the plunger 30 of a valve 14 to urge it to the right against its spring 34 and the pressure of a lowpressure, engine-driven gear pump 12 receiving warm oil from the engine lubricating system to operate the servomotor 10 to feather or unfeather the blades of the propeller. When the pump 16 is inoperative and the pump 12 is supplying the servomotor 10 to normally adjust the blade pitch in accordance with aircraft speed, oil from the latter pump passes through an orifice 32 in the plunger 30 and thence through the plunger 64 to the inlet of the pump 16 to warm the valve 20 and the pump 16.