Patent GB-500311-A (GB)
Title: Improvements in or relating to change speed gears
IPC: F16H61/02
Filed: 1937-12-02
Abstract: 500,311. Change-speed gearing. AUTO UNION AKT.-GES. Dec. 2, 1937, No. 33417. Convention date, Dec. 2, 1936. [Class 80 (ii)] Fluid-pressure controlled main-clutches 4, 5 selectively couple a driving shaft 1 to either of two elements, e.g. a planet-carrier 55 and a loose sun-wheel 61, of an epicyclic train, whilst that one of the said elements not being clutched is locked by a uni-directional mechanical lock operated automatically in dependence on its direction of rotation, such lock being rendered bi-directional by additional means controlled by the same fluid-pressure which controls the main-clutches 4, 6. A final sun-wheel 62 is fast to the driven shaft 63. The main-clutches 4, 5 comprise plates connected alternately to a common driving casing 2 and to driven members 8, 13 fast on concentric shafts 7, 14 secured respectively to the carrier 56 and sun-wheel 61. Selective clutch-engagement is effected by pressure-oil acting on groups of pistons 24, 25 through chambers 26, 27, passages (not shown) leading to collector-rings 22, 22a, pipes 20, 21, and a distributing-valve 19, connected through a pips 18 to a gear-pump 15, constantly driven by the driving casing 2. on is also supplied through ports, not shown, to the plates 4 or 5 of the clutch in engagement. Engagement of the clutch 5 yields low-speed, of the clutch 4, second-speed, whilst engagement of both together gives direct-drive. Selective locking of the carrier 55 or sun-wheel 61 is effected by pivoted pawls 70, which, under a control described below, engage ratchet-teeth 57, 65, respectively on the carrier 55 and on a disc 64, fast to the shaft 14 of the sun-wheel 61. Each pawl 70 is selectively moved into or out of engagement with the ratchet-teeth in accordance with the direction of rotation by means of a brake-band 67, Fig. 2, arranged adjacent the ratchet-teeth and having its ends connected to arms 72, 73 integral with the pawl 70, and carried on the pivot 32. Thus, clockwise rotation of the carrier 55, Fig. 2, will cause the brake-band to drag on the pawl-arm 73 and lift the pawl 70 clear of the ratchet-teeth 57, whilst anticlockwise rotation will cause the brake-band to pull the other arm 73, moving the pawl 70 into engagement with the ratchetteeth 57, so as positively to prevent anticlockwise rotation of the carrier 55. In order to lock the pawl 70 in engagement with the ratchet-teeth 57, thus locking the carrier 55 (or disc 64) against rotation in either direction, a tension-spring 82 pulls downwardly on one arm 78 of a bell-crank lever 78, the other arm of which carries balls 76 which ride up a camsurface behind the pawl 70, thereby holding the latter against the ratchet-teeth 57. In order to release the pawl from this constraint, oil-pressure is applied to a piston 79 which lifts the arm 78 of the bell-crank lever against the force of the spring 82, such oil-pressure being applied simultaneously with the energizing of the corresponding clutch 4 or 5, through pipes 80 or 81, branched respectively to the clutch supply-pipes 20, 21. In order to provide for starting the engine of a vehicle by towing the vehicle, no oil-pressure being present under such conditions, the arm 78 of the bell-crank lever controlling the pawl 70 of the carrier 55 only, can be lifted by a lover 83 connected to a manual push-button. At the same time, a clutch 84, effective in one direction only, is engaged to connect the driving shaft 1 and the carrier-shaft 7. Under such conditions, the carrier 55 is released for forward rotation whibt the sun-wheel 61 remains locked in both directions, so that a back-drive in second-speed results. The distributer-valve arrangement 19 comprises two separate valves 30, 31 controlled by a pair of rotary cams 34, 35, having peripheral notches 49, 50 &c., Fig. 3, which when brought opposite rollers 53 on the valves allow springs to push the valves inwardly and open the pressure-line 18 to the selected clutch-engaging and lock. releasing line 20 and/or 21. The notches 49 in the cam 34 are selectively positioned and the cam is fast on a shaft 36 connected to a selector lever 42, whilst the cam 35 is loose on the shaft 36 and is linked to pedal 45, which may be used as a main clutch-pedal, depression of which moves the notches 50 of the cam 36 out of registry with the valve-rollers 53, thereby lifting the valves and venting both clutchlines 20, 21. The cam 35 and pedal 45 may be omitted.