GB778569A - Adjustable pitch propeller - Google Patents

Abstract

778,569. Variable pitch propellers. HARTZELL INDUSTRIES, Inc. Feb. 23, 1956, No. 5690/56. Addition to 773,065. Class 114. The invention of the parent Specification is adapted to provide for reversing the blades and for a minimum positive pitch during forward operation. A port 62 in the crank shaft 14 opens into an inner tube 52 having a port or ports 56 open during normal forward working to an elongated port 50 in a tube 44 sliding on the tube 52 and adjustably secured to the movable cylinder 40 actuating the pitch change. The port 50 opens into the tube 32. A port 64 in the crankshaft 14 opens into a short tube 58 out of which the tube 44 emerges completely when the minimum forward setting is reached putting the port 64 into communication with the interior of the tube 32, there being, however, a direct communication through a check valve 130. In operation, when the cylinder 40 has reached the minimum forward pitch position, the port 50 ceases to register with the port 56 and the fluid supply is cut off. Any further movement opens the gap between the tubes 44 and 58 opening the cylinder 40 to exhaust through the port 64. Pressure fluid for reversing is drawn from an accumulator 90 through a valve 96 when the valve is set to connect a conduit 92 from the accumulator 90 with a conduit 100 leading to the port 64 ; returning the valve to the position shown opens the cylinder 40 to exhaust and the spring 36 turns the blade to the forward pitch.