Patent GB-384710-A (GB)
Title: Roller clutches and variable speed gear mechanisms
IPC: B60K17/08
Filed: 1931-08-18
Abstract: 384,710. Variable - speed gearing ; clutches. BLACKSTOCK, G., 52, Warren Road, Toronto, Canada. Aug. 18, 1931, No. 23295. [Class 80 (ii).] A roller clutch, applicable to motor-vehicle variable-speed gearing, which is disengaged by overload and may, according to a modification in design, allow free-wheeling in one construction, or a bi-directional drive only in another, comprises a drum 11 driving through cylindrical, spherical or conical rollers 17, a floating wedgesurfaced drive-transmitting member 16 having a lost-motion connection with a plate 42 rigidly attached to a driven shaft 2. Releasable detent means are provided for retaining the floating member at one end, the driving end, of its path, such means being unlocked to allow the floating member to be carried to the other end, an idle position, by the relative movement, a part of the shift of the floating member being performed without transmission of load. There is also means operating in consequence of the shift to disengage the rollers from the driving surfaces. The lost-motion connection and detent between the floating member 16 and driven plate 42 comprises three outwardly spring- . and centrifugally-pressed arms 34 each pivoted at 31 to an arm on an integral part 33 of the floating member, and having a wheel 37 at its free end engaging the plate 42 in a cam-shaped recess 44 including a circular pocket 44o, corresponding to a driving position, Fig. 2, communicating with a shallower circular pocket 45o, for the idle position. The retaining side 44x of the pocket 45o is cut away concentric with the axis of the coupling so that the wheel 37 is less securely retained in the idle, than in the driving pocket. The floating member 16 is provided with two wedge surfaces, a'driving surface 17o and a " catch " surface 16o and there are two balls 17, 18, or a single ball, the two balls being pressed apart by springs 27 carried by a flange attached to the floating member 16. A flange 24 attached to the driven shaft 2 carries strikers 25 which push the rollers 17, 18 from their wedge surfaces at the appropriate instant. Assuming that the drum 11 is driving in the direction of the arrow, Fig. 2, and a sudden overload occurs, the relative retardation of the driven member 42 will be sufficient to cause the wheel 37 to ride out of the driving pocket 44o into the idle pocket 45o, as shown in Fig. 4. The consequent relative movement of the floating member 16 causes the striker 25 carried by the driven member to push the driving roller 17 away from its wedge surface, the movement of the roller taking place whilst it is unloaded. The last part of the movement of the floating member, after the striking off of the roller 17, is performed under the influence of its own inertia. The driving member is now overrunning the driven member, the coupling remaining in the idle disengaged position, Fig. 4, until the driving member is retarded to below the synchronous speed whereafter the " catch" roller 18, which has been rolling idly during the overrun period, grips and turns the floating member 16 backwards relative to the driven member, the wheel 37 re-entering the driving pocket 44o. The " catch roller 18 is simultaneously pushed off its wedging surface and the driving roller 17 released by the strikers 25, the driving roller rolling idly for free-wheeling until the driver is once more accelerated to take up the drive. As shown, free-wheeling or overrun of the driven shaft is permitted but if the striker 25 holding off the " catch " roller 18 in Fig. 2 were disposed far enough to the left the " catch" roller would not leave its wedging surface and the drive would be bidirectional only. In the single-roller form, one roller performs both " catch and drive functions, and the springs 27 are omitted being replaced by spring plungers on the strikers 25. The clutch may be applied to constant-mesh helically-toothed motor vehicle variable-speed gear, or to the three-speed and reverse sliding gear shown in Fig. 1, the clutch being permanently connected between the driving shaft 1 and the driven shaft 2 and giving automatic change between second and high speeds. A roller free-wheel 67 of normal construction is arranged on the second speed pinion 69 and the layshaft driving pinion 74 is rigidly connected to the driving shaft by arms 77. The automatic clutch can be looked in the directdrive position by a dog clutch between the pinions 74 and 69, but if the bidirectional form of the clutch is used the dog clutch may be omitted and leftward movement of the pinion 69 used to engage an intermediate gear. To facilitate pushing the car and starting its engine a latch is provided to lock out the main clutch. To change down, the free-wheel second speed being in mesh, the throttle is opened up suddenly the resulting overload disengaging the automatic clutch and allowing the engine to race and the drive to pass through the lower ratio. To change up from second to high the engine is throttled, the free-wheel clutch 67 free-wheels and the automatic clutch goes to driving condition when it free-wheels until the throttle is reopened to take up the drive in high. An additional automatic clutch may be used in an intermediate train giving automatic change amongst three speeds instead of two as above.