The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 27, 1978
Filed:
Sep. 20, 1976
W Benjamin Harlamert, Piqua, OH (US);
Hartzell Propeller, Inc., Piqua, OH (US);
Abstract
A propeller hub supports a plurality of angularly disposed propeller blades which are movable by a hydraulic cylinder between a high pitch position and a reverse position through a low pitch position. Hydraulic fluid is supplied to the cylinder from a governor unit driven by the aircraft engine, and a fluid pressure responsive relief valve controls the pressure of the hydraulic fluid. The pressure responsive relief valve is manually adjustable by the aircraft pilot to change the fluid pressure at which the valve responds in order to change the pitch of the propeller blades. The fluid pressure must be increased above a predetermined normal operating limit for actuating the cylinder against the bias of a spring within the propeller to move the blades to their reverse pitch position. In addition, a centrifugally actuated lock unit prevents actuation of the cylinder and movement of the blades to their reverse pitch position until the speed of the propeller is reduced to a slow idle. The pressure responsive relief valve also incorporated hydraulic means to assure that the valve responds immediately to the pilot's command.