Patent GB-422806-A (GB)
Title: Improvements in or relating to control mechanism for variable-speed transmission gearing suitable for motor vehicles
Filed: 1933-09-18
Abstract: 422,806. Controlling change-speed gearing and clutches. GENERAL MOTORS CORPORATION, Detroit, Michigan, U.S.A. Sept. 18, 1933, No. 25810. Convention date, Sept. 17, 1932. [Class 80 (ii)] A transmission upon a vehicle comprises in combination an engine 11, Fig. 1, a clutch 19, change-speed gearing 15 and a power cylinder 97 to release the clutch and sequentially to change the speed from low to second and thereafter from second to third, back to second, then to third, and so on each time the accelerator 29 is released and depressed. The power cylinder 97 may be rendered inoperative by mechanism 127 &c. responsive to the locking out of a freewheel tail clutch 173, Fig. 3. The low speed must be put in mechanically by a manual selector lever 219, Fig. 4, and when the power is inoperative all changes may be made by that lever. The change gearing shown comprises a synchronized double jaw clutch 201<1>, Fig. 3, shiftable to effect high and middle speeds by a fork 203, Fig. 4, and rail 205, and comprises also a gear 209, Fig. 3, shiftable over the jaw clutch sleeve 201<1> to effect low speed and reverse by a fork 207, Fig. 4, and rail 179. A lever 213 engages in grooves in the forks 203, 207 and pivots about each fork when anchored to shift the other fork. This alternative anchoring is effected by a bowed interlocking plate 215 which has a longitudinal slot 217 in which the heel of the hand lever 219 slides. The plate 215 constantly engages pins 221, 221<1> on the forks 203, 207, respectively, and is constrained to slide transversely only by two fixed pins 225, 227. In the neutral position shown, the plate 215 engages both pins 221, 221<1> and anchors both forks. Lateral displacement of the hand lever 219 frees one of these pins only so that the freed fork can be slid by a longitudinal displacement of the same lever 219 which acts to rock the lower lever 213 through a lever 239 which turns about a fixed pivot shaft 237 and is pivoted to the lever 213 intermediately at 245. This shifter rocking of the lever 213 can also be effected by rocking the shaft 237 by power. To this end, the shaft 237, Fig. 2, carries a lever 249 having a pin connection 295 with a rocker 291 which is rocked one way and the other by power to shift alternately between high and second speeds by the shifting of the fork 203 only. During each power stroke, the piston 100, Fig. 1, of the cylinder 97 is sucked upwards by vacuum admitted through a triple valve chest 57. In the open position of Fig. 9, the vacuum passes through annular ducts in all three similar plungers 53, 76, 71, this corresponding to the released position of the accelerator 29, Fig. 1, with the throttle 23 closed. In the depressed position of the pedal 29 shown in Fig. 1, the vacuum, which enters by a pipe 89 connected to the engine manifold 13, is cut off, and the cylinder 97 is vented through a pipe 95 and through a central bore valve duct 83, Fig. 9, and air vent 55. Thus release and depression of the accelerator 29 by momentarily connecting the cylinder 97 to vacuum effects a power stroke of the cylinder which effects a gear shift and also a prior engine clutch disengagement. The power stroke can be alternatively effected by the valve plunger 76 which is connected through a linkage 133 to a button 127, the power stroke being effected with the accelerator released by depressing and releasing the button 127 which also controls mechanically the freewheel lockout. At any time the power may be rendered inoperative so that changes may be effected manually by the clutch lever 21 and hand-shift lever 219 by releasing a button 65 which is kept down by the left foot of the driver as long as power operation is desired. This button 65 is connected to the lowest valve plunger 71 which vents the cylinder when pressed leftwardly of Fig. 9 by a return spring 67, Fig. 1. The power stroke raises and depresses a lever 103 which disengages the clutch and shifts the gear. The clutch 19 is disengaged through a vertical rock-shaft, not shown, which has an arm 113 pushed rightwardly by a link 111 as the lever 103 rises. The clutch pedal 21 is then not moved because the power stroke merely thrusts an auxiliary lever 115 idly away from the pedal 21, the lever 115 being pivoted thereto at 116. The pedal 21 can move the clutch-disengaging arm 113 independently of the power because then the lever 115 bears at 121 against the pedal 21, is moved by the pedal, and pulls the arm 113. The power stroke resiliently pulls leftwardly a link 125 which is connected through cam levers 271, 279, Fig. 2, to thrust a slider 283 upwardly of Fig. 2. The slider 283 carries twin pivoted pushers 313, 315 with their gapped operative ends held inwards by spring-separated rods 319. During low speed which is brought in by the hand lever 219, the rocker 291 is as shown in Fig. 7. The power means comprises means for throwing over the interlocking plate 215 in changing up. A rock-shaft 251, Fig. 3, has one arm 253 engaging a pin 255 on the plate 215 and another arm 257, Fig. 8, with a spring nose 261. When it is desired to bring in second speed from the low-speed position of Fig. 7, a power stroke is set in action. The pusher 315 engages the nearer pin 299 on the rocker 291 which is thus thrust towards the reversed position of Fig. 8. In passing middle travel, a cam 305 on the slider strikes the nose 261 so that the levers 257, 253 are rocked and the interlocking plate 215, Fig. 4, thrown over to release the fork 203 of the two higher speeds. That power stroke ends in the position of Fig. 8 and final depression of the accelerator vents the cylinder with the second speed in and the clutch engaged. Next release of the accelerator rocks the rocker back to the position of Fig. 7, but with high speed in instead of low, since the lever arm 257 is out of the path of the cam 305. Successive power strokes thereafter change back to second, again back to high, and so on. To return to low speed or reverse, manual operation of the lever 219 must be resorted to. In shifting into reverse, the freewheel tail clutch 173, Fig. 3, is necessarily locked out mechanically through a shoulder 181 on the low speed and reverse rail 179 engaging a fork 167 which carries parts 163, 171 rightwardly to engage a locking clutch 175. This mechanical engagement of reverse turns a lever 147, Fig. 2, which through a rod 145 and levers 143, 137, Fig. 1 pushes in the plunger 76, Fig. 9, and so leaves the cylinder 97 vented. The button 127 operates the freewheel lockout lever 147 mechanically through a further link connection 135, 129. The lockout lever 147 cannot be moved until a stop 187, Fig. 2, has been removed from its path on disengagement of the clutch through a rod 191. The Specification as open to inspection under Sect. 91 comprises an arrangement illustrated in a cancelled Fig. 10 in which the power operation is dispensed with and the rod 125, Fig. 2, instead of passing beyond the clutch pedal 21, Fig. 1, to the power means, is pivoted to the clutch pedal which thus controls both the clutch and the gear-changing mechanically, all in combination with the selector lever 219 as described above. This subject-matter does not appear in the Specification as accepted.