Patent GB-970881-A (GB)
Title: Self-engaging synchronous clutch
IPC: F16D23/10
Filed: 1961-11-29
Abstract: 970,881. Clutch control. MAAG GEAR WHEEL & MACHINE CO. Ltd. Nov. 29, 1961 [Dec. 5, 1960], No. 42751/61. Headings F2C and F2L. Initial engagement of a clutch is obtained by a screwing motion of one clutch part relative to the other clutch part, final engagement being produced by hydraulic pressure means. Provision is made for manual engagement of the clutch in the event of failure of the hydraulic pressure. The clutch may connect a gas turbine to a shaft which is being driven by a steam turbine and comprises a clutch sleeve 3 having internal teeth permanently engaging a gear 1 on the shaft of the gas turbine, and internal clutch teeth 4 engageable with clutch teeth 6 fast with a gear 7 driven by the steam turbine. The sleeve 3 has an internal wall 11 fast with a pawlcarrying sleeve 22, the pawls 26 of which cooperate with teeth 36 of a ratchet member 35 which is provided with internal helical teeth 37 engaging helical teeth 60 on a sleeve 38 having a pin and helical slot 43 connection with the gear 7. A piston 14 is mounted in a stationary cylinder 17 and its piston-rod 12 has a flange so engaged between the wall 11 and a flange 13 as to move axially with the clutch sleeve 3 but not to rotate therewith. As shown, the clutch is disengaged, the piston 14 is held in its left-hand position by medium-pressure liquid supplied through a duct 45 in a distributing member 20 to a duct 55 in the piston leading to the righthand side of the piston, and also leading through a passage in the piston-rod to the pawl-carrying sleeve 22 to urge annular pistons 31, 32 towards each other whereby conical surfaces 33, 34 of the pistons engage the pawls 26 and hold them out of contact with the ratchet teeth 36. The lefthand side of the piston 14 is subject to lowpressure which is permanently supplied to a duct 48 leading to a groove 56 registering with a groove 54 in the piston leading to the left-hand chamber. Low-pressure liquid is also supplied to a duct 47 leading to a groove 49 which is sealed off in this position of the piston. To bring the clutch to a stand-by condition for automatic engagement on synchronization, a control valve (not shown) is actuated to supply medium-pressure liquid to the duct 47 and lowpressure liquid to the duct 45. Low-pressure liquid is now supplied to both sides of the piston 14 which is held in its left-hand position due to its differential areas, and the pistons 31, 32 are subject to low pressure only and release the pawls 26. The gas turbine is brought into operation during or after the changeover of the control valve, so that the coupling sleeve 3 and pawl-carrying sleeve 22 are rotated by the gear 1. At a predetermined speed parts 51 of the pawls are thrust outwardly by centrifugal force so that parts 52 engage the ratchet teeth 36. When the speed of the sleeve 22 exceeds that of the gear 7 one of the pawls abuts a tooth 36 and entrains the ratchet member 35. The ratchet member 35, together with the sleeve 22 and the clutch sleeve 3, screws along the sleeve 38 to a position producing initial engagement between bevelled parts 41, 42 of the clutch teeth 4, 6, and in this position the piston 14, which is shifted axially together with the clutch sleeve 3, is in a position such that the groove 54 ceases to register with the groove 56 and registers with the groove 49 which is supplied with mediumpressure liquid. The left-hand side of the piston is thus subjected to medium-pressure and the piston is moved to the right, shifting the clutch sleeve 3 to the right to fully engage the clutch teeth 4, 6. The sleeve 38 is also shifted by the piston 14, and due to the pin and helical slot 43 connection with the gear 7, the sleeve 38 and ratchet member 35 are rotated slightly relatively to the pawls 26 to separate the pawls from the teeth 36 to ensure that torque is transmitted wholly through the clutch teeth 4, 6. The clutch is disengaged by returning the control valve to its initial position so that medium-pressure liquid acts on the righthand side of the piston 14 to shift it to the left together with the clutch sleeve 3. Means may be provided for moving the piston 14 manually so that should the oil pressure fail the clutch can be engaged manually when stationary.