GB691755A - Improvements in or relating to variable-pitch propellers - Google Patents

Abstract

691,755. Variable-pitch propellers. ROTOL, Ltd. Sept. 12, 1951. [Sept. 29, 1950] No. 23937/50. Class 114. A variable-pitch propeller has its blades adjustable, by a hydraulic jack, into a normal pitch range controllable by a speed governor, a first extended range, and a second extended range, e.g. reverse pitch, movement from one range to the other being limited by first and second stops 28, 27 respectively which are withdrawn in succession, restraint means being provided to prevent the second stop from being withdrawn until it has been engaged by the moving member of the hydraulic jack. The stops are carried by spring fingers 26, 25 respectively and are held in an outer position by an abutment 31 on a hydraulic piston 30 loaded by springs 33, 43. The normal pitch range is limited by engagement of the end 23 of the jack piston S, which is linked to the blades, with the stops 28. The latter are withdrawn by supplying hydraulic fluid to the piston 30 which moves to the right thus releasing the stops 28 whilst keeping the stops 27 operative. The jack piston may then move further to the left until it is again stopped by engagement of a shoulder 24 with the second stops 27. Movement of the piston 30 for releasing the second stops is prevented by engagement of a sleeve 42, carried by the piston, with stops 39 carried by spring fingers 40. The latter are held inwardly by a ring 38, biased by the spring 33, carried by the fingers 25 of the second stops 27. When the hydraulic pressure on the jack piston 8, which is then in engagement with the second stops, is increased beyond a given value by the direct action of the pilot, the stops 27 and the ring 38 move to the left against the spring 33 thereby releasing the stops 39. The piston 30 may then be moved by hydraulic fluid further to the right to release the second stops 27. Specifiation 672,953 is referred to in the Provisional Specification.