Patent GB-836458-A (GB)
Title: Improvements relating to marine forward-reverse gear propulsion systems
IPC: F16H3/00
Filed: 1957-07-08
Abstract: 836,458. Reverse gear control; friction clutches. SINCLAIR, H. July 3, 1958 [July 8, 1957], No. 21617/57. Class 80 (2). [Also in Group XXXIV] A marine propulsion system comprising forward and reverse gearing with positive clutches for driving a ship's propeller in the ahead or astern sense, has a brake operable to bring the propeller shaft to rest, means being provided to control the brake application pressure in accordance with the speed of the propeller shaft, over at least a part of the speed range of the propeller, in such a way that the brake application pressure is higher at a higher propeller shaft speed than at a lower propeller shaft speed. Gearing.-A steam or gas turbine (not shown) drives a shaft 1 fast on which is a gear 2 meshing a gear 3 which can be connected through an ahead drive clutch C1 to a shaft 4 carrying a gear 5 meshing a final output gear 9 on a propeller shaft 10, the gear 3 also meshing a gear 6 which can be connected by a reverse drive clutch C2 to a shaft 7 carrying a gear 8 also meshing the output gear 9. As shown, the clutches C1, C2 are positive claw clutches having toothed sleeves 12, 12<SP>1</SP> axially slidable upon their shafts 4, 7 by spring links A, B under the control of a hand-operated selector lever 27, but alternatively Legge clutches may be used. The input shaft 1 of the gear can be rotated backwardly, when the driving turbine is not operative, by a barring motor 59 driving through a worm and worm wheel 61, 62 and a friction disc clutch C3. A brake disc 98 is mounted upon the propeller shaft 10. Control.-To effect a change from, e.g. astern drive, as shown, with the clutch C2 engaged, the speed control lever 52 of the driving turbine is moved to the idling position, shown dotted, and a switch 49 thereby closed to energize the barring motor 59. The forward-reverse selector handle 27 is then moved to its neutral position II, biasing the spring link B to tend to disengage the astern drive clutch. Transmission of torque through the astern drive clutch C2, caused by movement of the ship through the water, prevents such clutch disengagement. Moving the forwardreverse selector handle 27 to its neutral position opens a valve 40 to admit compressedair through a pipe 100 to a pipe 101. A branch pipe 102 connected to the pipe 101 leads compressed-air to a pneumatic interlock 58 which ejects a plunger 54 to engage a notch 57 and hold the turbine speed control lever 52 in its idling position. Compressed-air in the pipe 101 passes a restriction 99 and is fed through pipes 103, 105 to two valves V2, V3. The valve V3, Fig. 2, comprises a piston 87 acted upon by the pressure of oil supplied from a propeller shaft driven pump 74 through pipes 75, 83, 85 against the bias of a spring 91 to close ports connecting the pipe 105 to a pipe 92. The pipe 92 leads to a pressure intensifier 17 which, when operative, supplies liquid under pressure through pipes 95 to engage the disc brake 98. While the speed of the ship through the water is considerable, the pressure of the oil supplied by the shaft-driven pump 74 prevents movement of the valve V3 and engagement of the brake. As the momentum of the ship decreases, the speed of rotation of the propeller shaft 10 falls, and simultaneously the oil pressure supplied from the pump 74 through the pipes 75, 83, 85 falls, so that the piston 87 of the valve V3 is gradually moved leftwards by the spring 91 until, ultimately, compressed-air from the pipes 103, 105 is admitted to the pipe 92. The air pressure therein acts upon a large diameter piston 16 of the pressure intensifier 17, which is accordingly biased downwardly so that a small diameter piston 18 forces liquid under pressure to engage the disc brake 98, &c. As the speed of the ship further decreases, the oil pressure in the pipe 75 also decreases, and this pressure, which is transmitted through a pipe 81 to one side of a diaphragm 14 in the valve V2, is no longer sufficient to keep a port 13, connected to the compressed-air supply pipe 103, closed. When the port 13 begins to open, compressed-air leaks passed and escapes to atmosphere, and, due to the restriction 99 in the pipe 101, the pressure of air in the pipes 103, 105 begins to fall. Since this is the pressure supplied to the pressure intensifier 17, the liquid pressure engaging the disc brake 98, &c. begins to fall. The oil pressure in the pipe 75 has also been supplied through the pipe 83 and the pipe 84, to act upon a large diameter piston 65 of a valve V1 against the bias of a spring 70. When the ship has come almost to rest, the pressure of the oil supplied from the propeller shaft driven pump 74 to the pipe 75 approaches zero, and the spring 70 moves the piston 65 to connect a pipe 104, leading from the pipe 103, to a pipe 104<SP>1</SP> which feeds compressed-air into the clutch C3, which is engaged, so that the already rotating barring motor 59 is connected to the input gear shaft 1. The input gear shaft 1 is accordingly turned backwards, and the bias of the spring link B is able to effect disengagement of the astern clutch C2. The forward-reverse selector handle 27 can then be moved to its ahead position I, thereby throwing-in the ahead drive clutch C1 and shutting off the supply of compressed-air through the valve 40 to the pipe 101, which is instead connected to exhaust. The fall in pressure in the pipe 102 releases the pneumatic interlock 58, so that the turbine speed control lever 52 can be moved away from the idling position, breaking the circuit through the switch 49 to stop the barring motor 59, and start the main turbine in operation. As a modification, the compressed-air pressure control valve V2 of Fig. 1 may be replaced by a valve V4, Fig. 4, which gives a stepped reduction in brake applying pressure, instead of a continuous reduction with falling propeller shaft speed. The valve V4 comprises a piston 106 moved leftwards by oil pressure supplied through a pipe 81 from the propeller shaft driven pump 74 against the bias of a spring 108, gradual rightwards movement of the valve piston 106 with falling oil pressure and decreasing propeller shaft speed keeping ports 109, 110 separated until a substantial speed reduction has been effected, when compressed-air from the pipe 103, &c. suddenly passes therethrough to a restriction 111 in a pipe 112 leading to exhaust. When the ports 109, 110 are put into communication, compressed-air pressure in the pipes 103, &c. is maintained substantially constant at a reduced proportion of its original value, and the brake engaging pressure is similarly maintained at a reduced value. Friction clutches.-The barring drive clutch C3, Fig. 3, comprises a worm wheel 62 driving a casing 114 within which is a driven disc 118 fast with the input gear shaft 1. Compressedair fed in through the pipe 104<SP>1</SP> passes through a passage 115 and a pipe 121 to an inflatable bag 120 which expands and slides a presserplate 119 leftwards to engage the driven disc 118. Specification 762,901 is referred to.