Patent GB-447590-A (GB)
Title: Improvements in automatic change speed devices
IPC: B60K17/08
Filed: 1935-09-09
Abstract: 447,590. Change-speed gearing; overload - release clutches. ATHIMON, A., 10, Rue Auguste Chabrieres, Paris. Sept. 9, 1935, No. 25028. Convention date, Sept. 12, 1934. [Class 80 (ii)] Three or four speed countershaft gearing, especially for a motor vehicle, comprising clutches such as 17, 75, automatically released in succession by the torque, preferably opposed by centrifugal speed-responsive means 30 ; and oneway clutches 27, 36 which allow lower speeds to overrun when higher speeds drive, is characterized by automatic clutches the parts of which are provided with co-operating inclined surfaces which are independent of each other in the disengaged position. An intermediate sleeve 19, splined to the driven shaft 3 of the direct-drive clutch, carries conical clutching rollers 17 urged by a spring 21 into driving engagement with curved, inclined teeth 16 in the face of the driving member 8, the rollers being adapted to ride out over the teeth 16 at a predetermined load. Mounted with limited rotary play in the driving member 8 is a toothed baulking-ring 32, which is turned by the release movement, into a position, shown dotted in Fig. 7, in which its projecting teeth 31 are radially aligned with the gaps between the driving teeth 16, so as to form a smooth and continuous raceway for the rollers 17, thus preventing re-engagement of the latter for an upward change until the sense of relative rotation is reversed by closing the engine throttle, which is performed manually or automatically by means described below. The baulking-ring 32 is spring- pressed outwardly to a limited extent, and is turned by engagement of its teeth 31 with bevelled teeth 35, projecting from the driven sleeve 19. Pegs 33 on the driving member 8 limit the relative rotary movement of the baulking-ring 32. When the direct-drive clutch 17 disengages and the free-wheel secondspeed pinion 14 picks up the drive, the torque passes through a screw-threaded connection 183 between the pinion 14 and the driven sleeve 19, whereby the sleeve 19 is fully withdrawn away from the driving member 8. By suitably proportioning the pitch of the thread 183 to the inclination of the teeth 16, the clutch can be arranged to engage at the same, or a different torque from that at which it disengages. The loading of the clutchspring 21 is determined by centrifugal masses 30 pivotally carried by the nut-member 24 on the sleeve 19. In a modification the masses slide radially and have inclined tails for loading the spring 21. The second-speed automatic clutch 75 on the countershaft differs from the direct-drive clutch 17 in that the ends of its driving teeth and those of the baulking-ring 32 are inclined so as to form together, in the disengaged position, a ratchetlike face, which engages the projecting teeth 174 on the driven sleeve 38 and assists them in turning the baulking-ring into position for clutch re-engagement, which action is desirable in view of the fact that, unlike the case of the direct-drive clutch, only the momentum of the parts is available for this purpose. In the three-speed gear shown, the speeds are obtained as follows. Direct-drive passes from a driving shaft 1, through a pinion 8, automatic clutch 17, internal shaft 3 and clutch-teeth 6 to the driven shaft 4, the pinions 11, 14 then free-wheeling. Excessive load releases the automatic clutch 17, whereupon the free-wheel clutch 27 picks up a second-speed drive through the fast pinion 8, automatically-clutched pinion 10, fast pinion 13 and free-wheel pinion 14. Further increase in load releases the automatic clutch 75, whereupon the low-speed free-wheel pinion 11 picks up the drive from a fast pinion 9. To provide a bidirectional second-speed, for engine-braking, a splined pinion 5 is slid along the driven shaft to clutch the pinion 14 at 46. The pinion 5 also provides reverse. In Fig. 2 (not shown), all the pinions are at rest in direct-drive, the wheel 8 being clutched to the driving shaft 1 by a spring- loaded ratchet-toothed dog-clutch, disengaged by a lever-connection with an axially moving part of the automatic clutch 75. The mainshaft wheels 8, 14 are similarly declutched by a direct connection with the automatic clutch 17. To facilitate opening the dogclutches, the automatic clutches first close the engine-throttle before opening the dogclutches. In a four-speed construction, Fig. 3 (not shown), the countershaft carries an additional automatically clutched pinion. In all forms, the operation of the automatic clutches is accompanied by an axial sliding of flanges 22, 47, which, for synchronizing an upward change, momentarily close the enginethrottle 73, Fig. 12, through trigger-mechanism comprising levers 51, 61, Fig. 1, having forked connections, such as 55, with the clutch-flanges 22 and 47. The levers 51, 61 engage a spring- mounted pawl 54, which yields idly during a downward change, and is carried by a spring- loaded bellcrank lever 57, 60, which forms the floating fulcrum 66a, Fig. 12, of a lever 65, connected positively with an accelerator-pedal 66, and with lost-motion 72 to the enginethrottle 73. When the automatic clutch fully engages, the lever 51 passes over and releases the pawl 54, and the consequent reopening of the throttle may be retarded by a dashpot. In Fig. 13 (not shown), the bellcrank lever 60 is positively and directly linked to the engine-throttle, the accelerator-pedal being coimected thereto with spring-absorbed lost-motion. Downward changes can be made at any time by suddenly opening the enginethrottle ; or by braking the vehicle to increase the load; or by declutching and allowing the engine to race. In order to provide the driver with a better control of the gear, the latter part of the downward movement of the accelerator-pedal may be resisted by an additional return-spring, which does not act during the first part of the movement. The Specification as open to inspection under Sect. 91 states that the automatic clutches may be screw-operated claw or friction clutches. This statement does not appear in the Specification as accepted.