GB887123A - Improvements relating to combined feathering and pitch lock systems for variable pitch propellers - Google Patents

Abstract

887,123. Variable pitch propellers. UNITED AIRCRAFT CORPORATION. Nov. 13, 1959 [Nov. 14, 1958], No. 38572/59. Class 114. A combined feathering and pitch lock system for a propeller having blades 12 supported by a hub 14 and a pitch lock 44 comprising sliding toothed ring 52 urged by spring 284 into engagement with fixed toothed ring 50, the teeth then acting ratchet fashion to permit increase in blade pitch angle but to prevent decrease in pitch, the ring 52 normally being disengaged by hydraulic fluid in the chamber 54; includes a hydraulic motor 24 comprising a piston 26 in said hub connected to a rotatable sleeve 36 having a gear 34 engaging a gear 40 on each blade so that reciprocation of the piston rotates the blades to vary the pitch thereof, a main pump 72 supplying hydraulic fluid through a distributer valve 144 positioned by propeller speed control unit 250, a manually operated pitch lock arming valve 120 and a propeller overspeed topping governor cylinder 130 to said chamber 54 to disarm the pitch lock, the distributer valve 144, the manually operated valve 120 and the topping governor cylinder being hydraulically connected so that actuation of any one will bleed chamber 54 and arm said pitch lock. The pump 72 supplies fluid through line 76, filter 78 and line 92 to emergency feathering valve 100, thence through line 102 into pressure reducing and sequencing valve unit 104, whence after passing through metering port 105, lines 108, 110, annuli 114, 116, line 118, manual pitch lock solenoid unit 120, line 122 and, topping governor cylinder 130 it flows via line 60 into chamber 54 to disarm the lock 44. When piston 96 of feathering valve 100 is moved leftward by lever 202 or panic lever 230, main pump line 92 is connected to high pitch line 30 leading to high pitch side 162 of pitch change motor 24 directly without passing through distributer valve 144, the valve 100 also connecting standby pump 232 via line 236 to line 30. Propeller speed control unit 250 acts through gear system 252 to position distributer valve piston 140 to cause the propeller to rotate at constant speed. Rotation of gear 296 via gear train 292 and hub gear 294 causing movement of distributer valve piston 140 to the right connects line 118 to sump via passage 302 and hence drains chamber 54, thereby arming the pitch lock. Pilot operated unit 120 is actuable to move piston 290 to the right so that line 122 is connected to atmosphere, thereby draining line 60 and chamber 54. Movement of piston 126 of cylinder 130 connects line 60 to drain line 282 and hence arms the pitch lock. Low pitch stops 200 normally prevent motor piston 26 moving sufficiently far left to rotate blades 12 to reverse pitch. When lever 202 is moved to reverse pitch, piston 204 of reversing valve 206 is moved to block line 208 of low pitch pressure regulating valve 210 and hence pressure builds up in line 32, thence in servo valve 214 and line 218 to allow stops 200 to pivot inwardly, and also in chamber 160 to move the piston 26 to the desired reverse pitch position. Overspeed topping governor 90 and cylinder 130 cause engagement of pitch lock unit 44 during periods of propeller malfunction. When flyweights 270 are thrown outwardly due to propeller overspeed, valve 88 is moved to the left permitting main pump fluid from line 84 to enter line 274, pass through valve 206 to line 278 theme to cylinder 130 where it moves piston 126 to the right, thereby placing line 60 and hence pitch lock chamber 54 into communication with drain 282. A negative torque condition causes a negative torque control 306 to move piston 96 of valve 100 to the left to feather the propeller. Leftward movement of piston 96 actuates a link 308 to move piston 126 to the right, thus connecting line 60 to drain 282 and disarming chamber 54. Specifications 514,725, 696,658, 724,284, 754,095, 777,572 and 821,415 are referred to.