Patent GB-598618-A (GB)
Title: Improvements in and relating to multi-ratio gearing
IPC: F16H61/02
Filed: 1945-09-05
Abstract: 598,618. Controlling change-speed gearing. SINCLAIR, H. Sept. 5, 1945, No. 22906. [Class 80(ii)] In a variable-speed gear having a highspeed power path including a slipable clutch and a low-speed power path including a clutch adapted to disengage on reversal of torque and having means rendering it capable of transmitting overrunning torque, torque-discriminating means prevent the engagement of the slipable clutch while there is an overrunning torque on the driven shaft. The runner shaft 13 of a turbocoupling 12 is connected to a two-speed countershaft gear 15 through a torquediscriminating coupling 14 and a slipable clutch 32. The shaft 13 carries splined thereto a collar 16 which is secured to a collar 19 having right-hand helical splines mating with splines on a bush 20 secured to a shaft 21. A yoke lever 30 co-operates with a groove 29 in the collar 16. The slipable clutch 32 has a driving body 33 rigid with the shaft 21 and a coverplate 34 splined to the front end of a hollow shaft 37 carrying a gear 55. The driven disc 39 of the clutch is splined to the output shaft 38. Forward movement of a striking ring 48 causes levers 45 to cooperate with pins 42 to move a pressure plate 41 against the action of springs 44 and engage the clutch. The gear 55 drives, through countershaft gears 56, 58, a gear 59 freely mounted on the output shaft 38 and adapted to be connected thereto by a freewheel or synchro-coupling such as described in Specifications 376,468, 410,083 or 486,589. As shown in Fig. 1, the shaft 38 has right-hand helical splines 63 mating with splines in a nut 62 having dog teeth 64 engageable with teeth 61 on the gear 59. Axial movement of the nut is restricted by snap rings 65, 66. When the nut is in its forward position the teeth 61 are engaged by pawls 67 mounted on the tooth flange 64. In its rearward position the nut can be locked to a ring 70 by sliding a sleeve 68 operated by the striking fork and lever 72. The lever 72 is operated from the selector rod 74 through a preloaded spring coupling 79 'capable of yielding in both. directions. The front end of the rod 74 is connected to lever 81 by a preloaded extensible spring link 82, and has a cam 87 capable of raising a detent 86 on a lever 85. A second detent lever 89 is connected to a preloaded compressible spring link 92 on the lever 30. In the condition shown in which the direction of rotation is shown by the arrow on the shaft 13, low gear is engaged and an overrunning torque is acting on shaft 38. Disengagement of the lowspeed clutch is prevented by the locking sleeve 68, movement of which is prevented by spline friction, which causes the spring 79 to yield when the rod 74 is moved. As the torque-discriminating coupling 14 is fully forward by virtue of the overrunning torque conditions, the detent lever 89 prevents movement of the lever 48 and, therefore, engagement of the slipable clutch 32. With driving torque throughout the system, the coupling 14 will be to the rear and there will be no load on the splines of the locking sleeve 68, consequently movement of the rod 74 causes the low-speed clutch to be moved forward until the pawl 67 engages the teeth 61 to continue the drive until the clutch 32 is engaged by further movement of the rod 74. The change from high to low speed is effected by moving the rod 74 forward to disengage the clutch 32 and bias the sleeve 68 towards the engaged position. Acceleration of the gear 59 causes the pawl 67 to engage the teeth 61 and thus screw the nut 62 rearwards until the teeth 61 and 64 mesh, and the sleeve 68 locks on the ring 70. In a modification, the torque-discriminating coupling 14 is incorporated in the highspeed clutch 32 and use is made of different spline widths to provide balking means. A further modification shows the low-speed clutch and torque-discriminating coupling combined by the use of axially moving helical gears in the countershaft gear. Specification 513,974 also is referred to.