GB611780A - Improved control mechanism for variable pitch propellers - Google Patents

Abstract

611,780. Fluid-pressure servomotor-control systems; valves. GENERAL MOTORS CORPORATION. May 8, 1946, No. 13897. Convention date, June 27, 1945. [Class 136] [Also in Groups XXVI and XXXIII] A control mechanism for a variable-pitch propeller comprises a governor valve for controlling negative and positive pitch within respective ranges, a switch-over valve for changing between the ranges, the governor valve being held in a pitch-increasing position when the switch over valve is operated, and being automatically released when the change has been effected. The governor valve 40 controls flow from the main pump 87 to the pitch change cylinder 15, adjustment of the governor setting being made by movement of the pivot 47. Change over to reverse pitch is initiated by the cam 151 moving valve 140 and operating cam 175 to lock governor valve 40. Cam surfaces 131, 132, 133 move the valve 122 when pitch alteration has been made so that the governor valve is released. Valve 50 adjusts the pressure available for pitchchanging in accordance with propeller speed. Big variations in speed operate valve 70 to bring into effective operation the auxiliary pump 82. If an engine fails, the blades are feathered by moving the part 118 to the position 1181 rendering the governor valve inoperative. The pumps 82, 87 will be operated initially by the windmilling of the propeller, but as the speed and hence the liquid pressure falls further movement is completed by pressure from the accumulator 119 through the valve 90. As applied to a particular construction, many units of the system are mounted on a plate 201 (Fig. 7) in which the passages 21 &c. are formed. The governor valve 42 has the fulcrum 47 of its lever adjusted by the collar 225 operated by the screw 224.