Electrohydraulic propeller governor

#The present application claims priority under 35 U.S.C. 119 to German Patent Application No. 10 2008 004 196.3, filed Jan. 11, 2008, which is hereby incorporated by reference.

#The invention relates to a hydraulically controlled variable pitch propeller system for air, land or water craft having the features as set forth in the preamble of claim 1.

#One such propeller system is known in practice to comprise an engine for powering a propeller having at least two variable pitch propeller blades. This is done by means of fixed controller consequently forming a propeller governor as a hydraulic means with which the pitch of the propeller blades can be adapted to the operating mode in each case. Existing propeller governors comprise an arm acting on a governor spring for positioning a control spool, the spring being supported by the spool. The position of the control spool dictates the pressure acting on a servo piston for varying the pitch of the propeller blades. The adjusting arm of the propeller governor is mechanically connected to a control lever in the cockpit of the aircraft for manual control by the pilot. This means that the pilot has the task of defining propeller RPM. Existing propeller governors thus work mechanically and hydraulically in combination, their activating control being mechanical.

#An example aspect of a hydraulically controlled variable pitch propeller system in accordance with the invention will now be detained with reference to its simplified illustration in the drawing in which:

#FIG. 1 is a longitudinal section through a propeller hub portion;

#FIG. 2 is a first side view of a propeller governor for varying propeller pitch;

#Referring now to FIG. 1 there is illustrated a hydraulically controlled variable pitch propeller assembly comprising a propeller hub 12 and at least two propeller blades 16 each assigned bearings 14. Provided at each propeller blades 16 is a flyweight 18 which together with springs 17 feathers the corresponding propeller blades 16. For powered rotation of the propeller 10, the propeller hub 12 is connected to an engine of an aircraft or other vehicle.

#Provided furthermore in the propeller hub 12 is a servo piston 20 by means of which the pitch of the propeller blades 16 can be varied. Displacement of the servo piston 20 occurs hydraulically. For this purpose a cylinder space in which the servo piston 20 is guided and hydraulically connected to a propeller governor 30 serving as a control shown in detail in FIGS. 2 to 4.

#The propeller governor 30 comprises a governor body 32 made of metal and a governor head 34 with a head housing 36. The governor body 32 contains a gear pump 34 which uses hydraulic fluid, pumped from the engine, to increase the servo pressure between 18 and 42 bar. To vary the pitch of the propeller blades 16 the servo piston 20 is moved by this servo pressure.