Patent GB-766253-A (GB)
Title: Improvements in or relating to power transmission systems
Inventor: FLETCHER ARTHUR HOLMES
IPC: B63H23/00
Filed: 1953-09-01
Abstract: 766,253. Elastic fluid turbines. ROLLS-ROYCE, Ltd. Nov. 26, 1954 [Sept. 1, 1953], No. 24121/53. Addition to 742,173, [Group XXIV]. Class 110 (3). [Also in Group XXIV] Relates to the combination of a gas &c. turbine (not shown) and a boat propeller 10, Fig. 1, connected through gearing of the type in which an input shaft 11 drives an output shaft 21 through a first gear &c. train 13, 16 for forward motion and through a second gear &c. train 12, 22-26, 16 for reverse, the gear trains including clutches 14, 25 engaged alternatively to select the direction of motion, and in which an output shaft brake 17, 18 is applied to bring the turbine &c. substantially to rest before change of engagement of the forward-reverse clutches. Such an arrangement is described in the parent Specification. According to the present invention, the control mechanism for reversing the direction of drive is so arranged that the output shaft brake 17, 18 is applied only after reduction of the fuel supply to the turbine and the clutches 14, 25 are engaged/disengaged only after the application of the brake. The clutches 14, 25, Fig. 2, are constituted by sleeves 28, mounted on helical splines 29 on the two gear parts 13, 24, formed with bell-mouthed extensions 28a having dogs 30 which can be engaged by spring-biased pivoted pawls 34, or dogs 31 on radial flanges 32 fast on the shafts 11, 23. Sleeves 35 are slidable axially by a pivoted lever 27 to engage cam surfaces 36 inside the sleeves with cams 37 connected to the pawls 34 to rock the pawls out of engagement with the dogs 30. A manuallyoperated forward-reverse control wheel 40, Fig. 1, is connected to a shaft 40a formed with cams 42-45 controlling valves in fluid pipe lines 46-49. The pipe 46 supplies fluid to a motor 50 which applies the brake 17, 18, the pipe 47 supplies fluid to a valve 51 controlled by a lever 41 and a direction control motor 52 operating the pivoted lever 27 selecting which clutch 14, 25 is to be engaged &c., the pipe 48 supplies fluid to the normally free casing of a vane-type motor 55 and the pipe 49 supplies fluid to the motor 55 to reverse the direction of rotation of the input shaft 11. A manually operated throttle wheel 39 controls the supply of fuel to the turbine, and is connected to the forwardreverse control wheel 40 by an interlock 53 which operates in such a way that the wheel 40 cannot be turned until the throttle wheel 39 has been turned to reduce the fuel supply. The interlock may comprise coaxially arranged discs rotating with the wheels 39, 40 and connected by a rocking pawl unlocking in the throttled down position, or may comprise screw-threaded means. The throttle wheel 39 also operates means 54 controlling blow-off valves for the turbine compressor to allow rapid deceleration of the turbine, and is connected by a further interlock 57 to the lever 41 of the direction control valve 51 to prevent operation of the latter until the turbine has been throttled down. The cams 42-45 are so arranged on the shaft 40a that the correct sequence of events is obtained in changing from, e.g. ahead to reverse. Having closed the throttle 39, and thus released the interlocks 53, 57, the direction control lever 41 is moved from the ahead to the astern position and the forward-reverse control wheel 40 is turned. This causes the output shaft brake 17, 18 to be applied and then pivots the lever 27 to move the sleeves 35, Fig. 2, in opposite senses. The sleeve 35 and cam 36 of the clutch 25, hitherto disengaged, moves clear of the cams 37 on the pawls 34, which latter are accordingly spring-biased to engage the dogs 30 on the sleeve 28. While this happens, the dogs 30, 31 of the ahead clutch 14 remain engaged so that both clutches are engaged and no part of the mechanism can " run away." On further movement of the sliding sleeves 35, the cam surface 36 on the sleeve 35 of the ahead clutch 14 engages the cams 37 on the pawls 34 which are thereby turned to the disengaged position. Further turning of the forward-reverse wheel 40 then renders operative the vane-type motor 55 to rotate the power-turbine and shaft 11 backwards. As the output shaft brake 17, 18 is engaged, this causes the sleeve 28 of the engaged ahead clutch 14 to be screwed along its helical splines 29 to the disengaged position. The dogs 30 on the sleeve 28 are then in the plane of the pawls 34 which, however, are held in the disengaged position by the cam surface 36 on the sleeve 35 engaging the cams 37. Further rotation of the forward-reverse wheel 40 cause the vane-type motor 55 to be rendered inoperative so that the power-turbine can rotate. The shafts 11, 23 then begin to turn, but, as the output shaft brake 17, 18 is still applied and the pawls 34 of the reverse clutch 25 engage the dogs 30, the sleeve 28 of this clutch is screwed along its helical splines 29 to engage the dogs 30, 31. The output shaft brake 17, 18 is then released and the drive in reverse is taken up. In a modification, Fig. 3, two gas turbine engines are coupled through trains of gears and control systems similar to the above to drive a single boat propeller 10. The two turbines &c. have a common forward-reverse control wheel 140 and individual throttle wheels 39 and blow-off controls 54. Interlocks 53 prevent rotation of the forward-reverse wheel 140 until the turbines have been throttled down. A common direction control lever 141 and valve 151 effects the operation of the rocking levers 27. The valves operated by the cams 42-45 control simultaneously the supply of fluid under pressure to both gear trains, so that on turning the forwardreverse wheel 140, both brakes 18 are applied, and both reverse torque motors 55 operated in the correct sequence. The control system is arranged to allow one train to be put into neutral while the other is driving, but to prevent a train from being put into neutral unless the corresponding throttle is closed and to prevent a turbine from being started with its train in neutral. To this end, the forked rocking levers 27 of each train are operated by parallel arms 27a interconnected by links and springs 60, 61 to the operating piston 152a of the fluid motor 152 actuated by the direction control lever 141. The fulcrum 63 of each of the rocking levers 27 is carried on a slide 65 displaceable through a linkage 64 by a manually-operated lever (not shown) having a first position corresponding to neutral and a second position in which one or other of the forward-reverse clutches 14, 25 is engaged. When the lever is moved to the neutral position, the slide moves to the right, as seen in Fig. 3, and both clutches 14, 25 are disengaged. The ends of each pivoted lever 27 are also connected by links 66 to sun-wheels 67 of a differential mechanism. The pairs of sunwheels 67 each mesh a common planet gear 68 in a carrier 69, and the carrier is connected by an interlock to a fuel shut-off cock 70 in the fuel supply system of the associated turbine in such a way as to prevent movement of the linkage 64 to the neutral position unless the shut-off cock has been closed. The interlock may comprise a pin moved by the planet carrier 69 into a bore in a movable part of the shut-off cock 70, the bore being exposed only when the shut-off cock is closed. With the linkage 64 in the position corresponding to engagement of one or other of the clutches 14, 25, no movement of the carrier 69 is caused by clutch operation.