Patent GB-748076-A (GB)
Title: Control systems for variable pitch marine screw propellers
Inventor: DANVERS ELLIS
IPC: B63H3/10
Filed: 1952-06-06
Abstract: 748,076. Variable - pitch propellers. ROTOL, Ltd. May 29, 1953 [June 6, 1952], No. 14385/52. Class 114. A control system for a hydraulic variable-pitch marine screw propeller having a hydraulic pitch change motor, comprises a single manual control member which, over a first range of control movement, is arranged to control the supply of hydraulic fluid to the pitch change motor through a follow-up system responsive to the pitch of the propeller so that each setting of said manual control member within said one range corresponds to a particular pitch of the propeller from maximum reverse pitch through zero pitch to a predetermined forward pitch substantially within the forward pitch range, and which, over a successive range of control movement, is arranged to control the supply of hydraulic fluid to the pitch change motor through a follow-up system responsive to the speed of rotation of the propeller so that each setting of said manual control member within said successive range corresponds to a particular propeller speed, the arrangement being such that when the manual control member is moved in one direction through its entire range of control movement, the pitch of the propeller first changes from maximum reverse pitch through zero pitch to a predetermined forward pitch substantially within the forward pitch range at which predetermined forward pitch the propeller is rotating at a predetermined speed, and then the speed of the propeller increases, and when the manual control member is moved in its other direction through its entire range of control movement the speed of the propeller first decreases to said predetermined speed at which speed the propeller assumes said predetermined forward pitch substantially within the forward pitch range, and then the pitch of the propeller changes through zero pitch to maximum reverse pitch. A pitch motor comprising a cylinder 6 and piston 8 varies the pitch of the propeller blades 2 through a crosshead 10 mounted on the piston rod 9. A main pump 60 actuates the motor by delivering hydraulic fluid past a non- return valve 63, into the delivery passage 49 of a make-up pump 61 and thence to the regulating valve 43 of a constant-speed unit 41. As shown, the regulating valve is in a neutral position; lowering it connects the pump to a conduit 19 leading to a passage 16 in an extension 12 of the cylinder 6, the passage being in communication with the front of the piston 8 through passages 141, 142; raising the valve opens a passage 18 leading to a passage 15 in the cylinder extension 12 and thence through a passage 143 and valve 25 to the back of the piston 8. In the neutral position shown, the piston is locked in position by fluid in conduits 67, 17 a lock valve 52, 53 and an annular chamber 139 between the extension 12 and a sleeve 20. Excess pressure in either of the conduits 18, 19 opens an unloading valve 65 which by-passes the pumps 60, 61. If hydraulic pressure fails, a spring 22 moves sleeve 20 to the right closing off the passage 15 and the piston 6 remains locked. Speed regulator controls.-The regulating valve 43 by its stem 155 and a flange 154 thereon engages the end of a lever 93 adjustable by a hand lever 90. This hand lever, through a resilient connection 95 and a dashpot 96 rocks a cam-shaft 94 rotating a speed cam 97 which through a rod and lever system 100-102 turns a pinion 46 engaging a rack 45 movable on the stem 155. This rack forms an abutment for a speed governor spring 44 opposing the flyweights 42 of a speed governor. Movement of the cam-shaft 94 by the hand lever 90 also rotates a pitch selection cam 98 connected to a differential follow-up device 108 ; the movement rotates a sun wheel 107 causing a planetpinion carrier 113 to turn since the remaining sun wheel 109 is held stationary being linked to the piston 8 of the pitch motor. The planet carrier 113 rotates a cam 114 itself controlling a cam 56 by which the hydraulic lock valve 52, 53 is operated; the cam 56 also rocks the lever 123 to actuate the regulator valve-43. The movement of the planet carrier 113 thus first causes release of the lock valve 52, 53 and the displacement of the regulator valve 43, the pressure fluid then actuating the pitch motor 6, 8 movement of which actuates a lever 33 connected by a rod 112 to a lever arm 110 on the planet carrier 113 restoring it to its original position and thereby re-setting the valve 43 and the lock 52, 53. As propeller speed increases, the speed governor takes over control, the flyweights 42 raising the valve 43 against the action of the governor spring 44, the tension of which however, is adjusted by the setting of the hand lever 90 which thus sets an adjustable limit to the control range of the speed governor. Within this range when the flyweights have raised or permitted the lowering of the regulator valve, the variation in the pitch setting restores the propeller speed and the flyweights and valve 43 return to their neutral setting. A separate hand lever 91 acting through a transmission 92 and lever 93 is adapted to raise the flange 154 and valve 43 for feathering.