Hydraulic Variable Pitch Propeller

Abstract

Proposed is a redundant hydraulic variable pitch propeller for an air, land or water craft, comprising at least two propeller blades ( 14 ) mounted in the region of a propeller hub ( 12 ) with variable pitch control by means of a hydraulically powered piston assembly ( 18 ). In accordance with the invention the piston assembly ( 18 ) comprises two mechanically interconnected servo pistons ( 20, 22 ) each assigned to an independent hydraulic circuit. Each of the servo pistons is engineered as a double-acting piston.

1 . A hydraulic variable pitch propeller for an air, land or water craft, comprising:
 at least two propeller blades, each of said propeller blades having a variable pitch;   a propeller hub including a hydraulically powered piston assembly controlling the pitch of the propeller blades, said assembly having two mechanically interconnected double-acting servo pistons, each of said servo pistons being coupled to an independent hydraulic circuit.   
     
     
         2 . The hydraulic variable pitch propeller as set forth in  claim 1 , in which said two hydraulic circuits comprise a common valve assembly by means of which the two servo pistons are movable in synchronism with a desired servo pressure. 
     
     
         3 . The hydraulic variable pitch propeller as set forth in  claim 2 , in which said valve assembly and servo pistons are interconnected by a control tube comprising four control passageways each of which is assigned a pressure space two each of which define one of the two servo pistons. 
     
     
         4 . The hydraulic variable pitch propeller as set forth in  claim 3 , in which said control tube cooperates with two control spools of the valve assembly, each assigned to one of the hydraulic circuits. 
     
     
         5 . The hydraulic variable pitch propeller as set forth in  claim 4 , in which said control spools are connected to a common actuating rod. 
     
     
         6 . The hydraulic variable pitch propeller as set forth in  claim 1 , in which said valve assembly includes two independent hydraulic chambers supplied by two pressure sources and hydraulically connected via the control tube to the pressure spaces each coupled to one of the servo pistons. 
     
     
         7 . The hydraulic variable pitch propeller as set forth in  claim 1 , in which said two servo pistons are dimensioned so that varying the pitch of the propeller blades is assured under all operating conditions with just one of the servo pistons moved by the hydraulic fluid.