GB623818A - Control of variable pitch airscrews for aircraft - Google Patents

Abstract

623,818. Variable-pitch propellers. MARTIN, J., and MARTIN-BAKER AIRCRAFT CO., Ltd. Oct. 2, 1946, Nos. 29353/46 and 22620/47. [Class 114] In a variable-pitch airscrew additional means for setting the blades to a feathered position comprise an auxiliary cylinder 32 located on the end flange 33 of the cylinder 13 of the main pitch changing piston 14, containing a piston 35 having a recess 36 in the head. Located in the recess 36 and secured to the flange 33 is a sealed pressure reservoir 37 containing compressed gas and having an end plate 38 provided with a diaphragm 40 and a pointed pin 41 which may be actuated to perforate the diaphragm 40 by a cam lever 48 operated by a cable 50 controlled automatically or by hand, whereon gas passes from the reservoir 37 through the diaphragm 40 and a passage 42 to the cylinder 32 to operate the piston 35 which contacts a further piston 16 which in turn contacts the piston 14 to feather the blades. The piston 16 has a hollow shaft 20 sealed at one end by a diaphragm 23 and passing over a hollow tube 22 through which liquid is supplied to either side of the piston 14. A pointed striker 43 on the piston 35 perforates the diaphragm 23 to allow liquid behind the piston 14 to pass to the top of the piston 16. In a modification the reservoir 37 is replaced by a device containing an explosive cartridge which is fired by the operating cable 50 to create the pressure necessary to operate the piston 35. A ring 45 on the piston 35 passes out of the cylinder 32 in the fully feathered position and expands to lock the blades in that position. The cable 50 is connected to a spring-pressed plunger in a cylinder held in position by a sear connected to a lever. A cam plate, adjacent the rotating hub is moved into the path of the lever which withdraws the sear whereon the spring actuates the cable 50. Specification 601,718 is referred to.