GB422189A - Improvements in transmission mechanism - Google Patents

Abstract

422,189. Change-speed gearing. BENDIX AVIATION CORPORATION, 105, West Adams Street, Chicago, U.S.A. April 29, 1933, No. 12532. Convention date, June 17, 1932. [Class 80 (ii)] In automatic change-speed gearing having high, intermediate, and low gears, the intermediate and low gears including each an overrunning clutch, the overrunning clutch of the intermediate gear is positively held in operative position when the lower gear is operative and is urged towards operative position by means responsive to the driven shaft speed. There is a direct-driving plate clutch 12, Fig. 1, and intermediate and low speed countershaft-driven gears 13, 14. A positive clutch 17 connects a driven shaft 11 to a propeller shaft 16 for forward automatic drives. Centrifugal weights 27, 28 carried by the shaft 11 have heels which act on a spring presser ring 33 of the plate clutch and toes which act on a washer 40, as shown also in Fig. 12. The toes of the weights 27 act also on the end of a control nut 53. The washer 40 is fast upon a sleeve 61 which is splined on the shaft 11 and externally screw threaded to engage the threaded extension 57 of the hub 41 of the middle-speed gear 13. Beyond the middle-speed splined sleeve 61 is a low-speed splined sleeve 62 upon which is screw threaded the hub 63 of the low-speed gear 14. The lowspeed one-way clutch is illustrated in Fig. 7, not shown. It acts conventionally. Grip rollers 71, Fig. 1, are spring-pressed by blocks with medial guide pins 74. The middle-speed one-way clutch is shown in Fig. 5. This comprises grip rollers 30 with spring-pressed blocks and guide pins 44 in a cage 32 with a sleeve extension screw threaded on the control nut 53. The nut 53 is in turn threaded on the extension 57 of the hub 41. At high speed of the shaft 11, the weights 27, 28 engage the plate clutch 12 for direct drive. Increased load causes the clutch 12 to slip so that the splined sleeve 61 is screwed left to the position of Fig. 12, collapsing the weights and opening the plate clutch. The drive is then on middle speed through the gear 13, rollers 30, hub 41 and extension 57 and sleeve 61 to the shaft 11. The nut 53 which has been thrust right by the weights 27 remains there because the clutch rollers 30 are jammed. If the load further increases and it is desired to engage low speed, the torque is released by closing the throttle momentarily whereupon the rollers 30 are freed and a spring 54 thrusts the control nut 53 left so as to turn the cage 32 and disable the middlespeed one-way clutch. The low-speed one-way clutch 71 picks up automatically and the splined sleeve 62 is screwed left to the position of Fig. 11. The middle-speed one-way clutch is then positively held inoperative by pins 84 carried by the sleeve 62 which contact with the end of the nut 53 and hold it at left with the cage 32 holding that clutch out. The middlespeed clutch is thus disengaged and held so by the low-speed device. Decreases in load change up from the position of Fig. 11 by increasing the speed and expanding the weights. These first bring the nut 53 to the position at right shown in Fig. 12 which allows the middle-speed clutch to pick up. Further expansion of the weights sufficient to thrust the sleeve 61 right engages the plate clutch for high speed. In rest position illustrated in Fig. 10, (not shown), the nut 53 is thrust to the extreme left by the spring 54 so that the middle-speed clutch is held inoperative whenever the transmission stops. A vehicle with this gearing will therefore start in low speed. To prevent violent pick-up in the change to middle from low, the external teeth 86, Fig. 13, of the nut 53 are provided with shoulders 87 which engage over the ends of the internal threads 52 of the cage 32. The change into middle can take place only after throttle closing and consequent speed reduction. To bring in a positive low speed specially useful in braking by the engine, the clutch member 17 is slid so as to bring teeth 92 into engagement with teeth 93 on a wheel 94 loose on the shaft 16 and driven from a countershaft pinion 97. The teeth 92 are in segments adapted to pass through windows 114, Fig. 20, in a synchronizing cone 101 splined like the member 17 on the shaft 16. The cone 101 is engaged momentarily with a cone 102 on the gear 94 by a selector bar 103 which carries a fork 104, Fig. 1, moving the member 17. A cam 106 on the bar 103 strikes a yielding roller 107, Fig. 20, on a pivoted yoke 108 so that the cone 101 is engaged to synchronize whereafter the roller 107 slips and the segments of teeth 92 slip through the windows 114 into positive engagement. Reverse driving is effected by sliding a pinion 121, Fig. 1, into mesh with an idler. The reverse pinion 121 is controlled from a selector bar parallel to the bar 103 and means are described with reference to Figs. 15 to 19, (not shown), for operating these bars by admitting vacuum to one end or the other of two cylinders under the control of sliding valves operated by Bowden wires. Means are also described with reference to Figs. 23 to 25, (not shown), for modifying the action of the weights 27, 28 and hence the capacity of the plate clutch in accordance with throttle opening. As the accelerator pedal is depressed beyond a point defined by a slot connection, a valve is opened to evacuate a servo cylinder which moves a muff over the centrifugal weights, depressing them, so that lower speeds are brought in than would otherwise be the case in view of a relatively small load as in city driving.