GB827585A - Improvements relating to power transmission systems - Google Patents

Abstract

827,585. Reverse gear; ratchet clutches. SINCLAIR, H. March 6, 1956 [March 14, 1955], No. 7408/55. Class 80 (2). Reverse gear, for driving a marine propeller shaft 10 from the shaft 5 of a non-reversing Diesel engine or gas turbine, comprises scooptube controlled fluid couplings 3, 4 in respective forward and reverse gear paths 8, 9 and 11, 12, 14, together with a mechanical clutch 15 for disconnecting the drive between the output shaft 10 and the turbine of the reverse coupling 4 during normal forward running using the coupling 3. In Fig. 1, the mechanical clutch 15 is arranged between the output shaft 10 and the final wheel 14 of the reverse train, and is of the synchro-self-shifting type, comprising an intermediate member 16 helix-mounted on the output shaft 10 and moved helically therealong to engage synchronously clutch teeth 17 with teeth 15 on the reverse wheel 14 by action of subsidiary pawls 20, when the reverse wheel 14 is caused to rotate in the forward sense (i.e. opposite to its normal drive direction) faster than the forwardly rotating output shaft 10, such overtaking being produced by a synchronizing clutch 21 as follows. If, when operating in forward drive through the coupling 3 and gear-train 8, 9, reverse is required, the forward coupling 3 is emptied and the output shaft 10 coasts under propeller action. The synchronizing clutch 21 is then engaged to drive the reverse wheel 14 from the output shaft 10 through wheels 23, 12 at a slightly greater forward speed than that of the shaft 10, causing the subsidiary pawls 20 to wind the helixmounted intermediate member 16 into clutch engagement 17, 15 with the reverse wheel 14, whereupon a sleeve 19 is moved to the right to lock the member 16 to the shaft for reverse torque transmission. The synchronizing clutch 21 is then released and the reverse coupling 4 filled for reverse drive. Fig. 2 (not shown) has only a single output wheel such as 9, Fig. 1, which the reverse coupling drives through an idler countershaft having a wheel at each end meshing respectively the wheel 9 and a wheel such as 11, Fig. 1. That wheel meshing the wheel 11 is connected to its countershaft by a helix clutch as above, synchronized by a clutch connecting the countershaft to the wheel 11 through an overtaking gear train. Fig. 3 (not shown) modifies the arrangement of Fig. 2 (not shown) by providing an additional helix clutch between the two first-motion wheels such as 8, 11, Fig. 1, to be engaged in forward drive after disengagement of the reverse train release clutch 15, thereby permitting both the forward and reverse couplings 3, 4 to be filled to share the forward drive load. In a gas-turbine drive, Fig. 4 (not shown) the forward and reverse fluid couplings are arranged at opposite ends of an input shaft, with the gearing therebetween. The synchronizing clutch is a countershaftmounted fillable fluid coupling and there is an additional mechanical clutch for connecting the input shaft directly to the forward pinion for a mechanical forward drive by passing the fluid coupling. This additional clutch is of the helixoperated type, as above, but is biased into engagement by a spring or by magnetic means as in Specification 773,545, and is held in engagement by oil pressure acting on pistons connected to a flange on the intermediate member. The auxiliary synchronizing drive may receive power from a separate source such as an electric motor, or fluid-pressure turbine or positive displacement motor supplied with fluid pressure by the prime mover. Specifications 629,725 and 655,476 also are referred to.