Patent GB-937259-A (GB)
Title: Synchronous self-shifting clutch
Inventor: CLEMENTS HERBERT ARTHUR
IPC: F16D23/10
Filed: 1961-05-12
Abstract: 937,259. Ratchet clutches. S.S.S. GEARS Ltd. May 7, 1962 [May 12, 1961], No. 17449/61. Class 80 (2). In a synchronous self-shifting clutch having an intermediate member having toothed clutch engagement with a first clutch member and helically movable on a second clutch member, some of the parts of the clutch can be assembled in alternative dispositions such that the clutch is capable of transmitting torque in one direction of rotation only or in the other direction only according to the selected disposition of the parts. As shown in the upper half of Fig. 1, an intermediate member 6, which is helically splined on a shaft 4, is in its disengaged position limited by a stop 9 on the shaft 4 and has pawls 8 engaging clutch teeth 3 formed on a first clutch member 1. For one direction of relative rotation of the clutch part 1 and shaft 4, the clutch teeth 3 engage pawls 8 and shift the intermediate member 6 helically along the shaft 4 to engage clutch teeth 7 with the clutch teeth 3. When it is desired to re-arrange the clutch so that it engages when the part 1 rotates in the opposite direction relative to the shaft 4, the stop 9 is removed from the shaft 4, the intermediate member 6 is removed, axially reversed and replaced, and the collar 9 is replaced and secured to the shaft 4 as shown in the lower half of Fig. 1, so that the pawls 8 point in the opposite direction and engage the clutch teeth 3 in the disengaged position of the intermediate member which is limited by a stop 10 on the shaft 4. In a modification (not shown) the first clutch member 1 carries two rings of ratchet teeth arranged on either side of the teeth 3, and the pawls 8 co-operate with one or other ring of ratchet teeth according to the disposition of the intermediate member 6. In a further modification, the intermediate member can be axially reversed and carries ratchet teeth, and the first clutch member carries pawls which can be selectively arranged in one or other of two grooves in this member so that the pawls can co-operate with the ratchet teeth of the intermediate member in either of its dispositions. In the embodiment of Fig. 2, the first clutch member comprises a part 21 drivably connected to the shaft 22 by a sleeve 23 having teeth 24, 24<SP>1</SP> engaged with teeth 25, 25<SP>1</SP> on the part 21 and shaft 22. The second clutch member 26 is journalled in the first clutch member 21 by bearings 28, 28<SP>1</SP> and has helical spline engagement with an intermediate clutch sleeve 31 which is formed with clutch teeth 33 engageable with clutch teeth 29 on the part 21. The clutch sleeve 31 is formed with ratchet teeth 30<SP>1</SP> which in the disengaged condition of the clutch are engaged by pawls 34 carried by the part 21. The pawls 34 are spring-biased into engagement with the ratchet teeth 30<SP>1</SP> and are released by centrifugal force above a predetermined speed of the part 21. The sleeve 31 carries secondary pawls 34<SP>1</SP> urged outwardly centrifugally into engagement with ratchet teeth 30 on the part 21. Assuming that the shaft 22 is rotating in the direction of arrow A and that the second clutch member 26 is stationary, the clutch sleeve 31 is in its disengaged position limited by a stop ring 41, and below predetermined speed of the member 21 the pawls 34 ratchet over the teeth 30<SP>1</SP>. Above this speed the pawls 34 are disengaged centrifugally. If the second clutch member 26 is accelerated in the direction of arrow A the clutch sleeve 31 rotates and the pawls 34<SP>1</SP> are urged centrifugally into ratcheting relationship with the teeth 30. When the second clutch member 26 tends to overrun the first clutch member 21, the pawls 34<SP>1</SP> engage the teeth 30 and the clutch sleeve 31 is shifted helically along the clutch member 26 to engage the clutch teeth 33 with the clutch teeth 29, so that the clutch member 26 drives the shaft 22. If the shaft 22 is initially at rest, the shaft can be driven by accelerating the part 26, in which case the pawls 34 co-operate with the ratchet teeth 30<SP>1</SP> to move the clutch sleeve 31 into toothed engagement with the part 21. In order for the clutch to transmit torque in the opposite direction both the clutch sleeve 31 and the clutch part 21 are reversed. In the embodiment of Fig. 6, the first clutch member 51 has bolted thereto a ring 52 carrying a plurality of horseshoe magnets 55, and the second clutch member is a shaft 57 having helical splined engagement with a clutch sleeve 61 having clutch teeth 62 engageable with teeth 53 on the ring 52. The clutch sleeve 61 is formed with a flange 64 of ferromagnetic material in which is inset a ring 65 of non- magnetic material such as brass. With the shaft 57 rotating in the direction of arrow B relative to the first clutch member 51 the clutch sleeve 61 tends to move to the right from the disengaged position shown in the upper half of the Figure due to the axial magnetic force of the magnets 55 on the armature formed by the portion 66 of the flange 64. However, so long as there is appreciable relative rotation between the first and second clutch members eddy currents induced in the ring 65 produce a drag force opposing the axial magnetic force sufficient to keep the intermediate member 61 in its disengaged position. As the clutch member 51 is accelerated in the direction of the arrow B the eddy current effects fall off progressively until the magnetic force draws the clutch sleeve 61 to the right to bring the clutch teeth 62 into nuzzling contact with the teeth 53. When the first clutch member 51 moves through synchronism with the second clutch member the clutch sleeve 61 is drawn into initial toothed engagement with the teeth 53, clutch engagement being completed by the interaction of the clutch teeth 53, 62 to move the sleeve 61 against a stop collar 58. When it is desired to transmit torque in the opposite direction the clutch is re-arranged as shown in the lower half of Fig. 6. In a modification of this arrangement instead of two parts 52, 54 being movable and reversible, the magnets 55 alone can be fixed selectively in alternative positions on either side of the clutch teeth 53. In the embodiment of Fig. 7, the intermediate clutch sleeve 79 is helically splined on a second clutch member 77, and has an auxiliary member 82 helically splined thereon. The member 82 carries pawls 84 co-operating with ratchet teeth 75 formed on a ring 73 bolted to the first clutch member 71. With the second clutch member 77 rotating relative to the first clutch member in the direction of arrow C, the pawls 84 ratchet past the ratchet teeth 75. If the first clutch member 71 is accelerated in the direction of arrow C, on passage through synchronism the teeth 75 engage the pawls 84 and move the auxiliary member 82 helically to the right to bring teeth 83 on the auxiliary member into engagement with clutch teeth 74 carried by ring 72 bolted to the first clutch member 71. The interaction between the teeth 83, 74 shifts the auxiliary member 83 further to the right until it abuts a stop 86 on the intermediate member 79 whereupon the intermediate member 79 is shifted helically to the right to initiate toothed engagement of clutch teeth 80 of the intermediate member 79 with the clutch teeth 74. The ring 73 is formed with an oil-retaining lip 76 such that excessive movement of the pawls 84 is prevented by a ring of oil during operation of the clutch. The clutch is re-arranged as shown in the lower half of Fig. 7 for the transmission of torque in the opposite direction. Reference has been directed by the Comptroller to Specifications 773,545 and 839,638.