Controllable pitch propeller

Claim 1

A controllable pitch propeller mechanism having a generally hollow hub having an axis, blades mounted in the hub, the hub being adapted to be secured to a tailshaft of a vessel the hub rotating with the tailshaft; in combination with the foregoing, a. a shaft within and co-axial of the hub, and adapted for axial movement relative to the hub; a piston and a crosshead mounted on the shaft moving therewith; the shaft having a bore, b. means, within the bore, slidably adapted for forward and aft movement within the bore and relative to the hub, the movement being responsive to difference between a force applied to the said means tending to move it forward, and a force applied to the said means tending to move it aft, the means aforesaid remaining in an initial balanced position stationary with respect to the hub and to the bore so long as the forces remain equal, the means including: b.1. a pilot spool within the shaft bore, a compression spring bearing against the forward end and a compression spring bearing against the aft end applying equal forces to each end of the spool and centering the spool in a balanced position within the bore, b.2. tHe spool having a recessed central portion forming lands at opposite ends of the spool, b.3. a passage extending from the bore to an aft cylinder space, a passage extending from the bore to a forward cylinder space, the passages being closed by the lands when the spool is in the balanced position, b.4. means selectively to supply and direct hydraulic fluid under pressure to either end of the spool so that there is a difference in force applied to each end of the spool effecting axial movement as aforesaid, which movement opens both of the passages, b.5. means admitting the hydraulic fluid under pressure to the recessed central portion of the spool so that, when both of the passages are opened as aforesaid by movement of the spool, the piston is urged to move, and with it the shaft and crosshead, altering the pitch of the blade, b.6. and means to scavenge fluid displaced by movement of the piston, the means being constructed and arranged so that, with closing of a valve of the means selectively supplying and directing the hydraulic fluid as aforesaid, there is no longer difference in force supplied to each end of the spool, and the spool resumes the balanced position at which both the passages opened as aforesaid are closed, effectively locking the blade in a changed pitch position, c. means responsive to the movement as aforesaid concurrently to cause the piston, and with it the shaft and the crosshead, to move axially relative to the hub through the particular distance, so that in the new balanced position, the pilot spool has the same position relative to the shaft bore as in the initial position, d. means responsive to the movement of the crosshead through the particular distance to change pitch of a blade, the means including: d.1. a propeller blade having a longitudinal axis, a root, a blade connecting plate at the root, the connecting plate having a boss, d.2. the hub having a mid portion with an opening, and means mounting the blade within the opening for rotation about the longitudinal axis and providing restraint from force on the blade as the hub rotates, d.3. the crosshead having a flat parallel to an inner face of the plate and perpendicular to the blade longitudinal axis, the flat having a groove at an angle to the shaft axis, adapted for the crosshead movement to rotate the blade about its longitudinal axis so altering the pitch.