Patent GB-436714-A (GB)
Title: Variable speed gear
IPC: F16H61/02
Filed: 1934-03-16
Abstract: 436,714. Controlling change-speed gearing. DEMOCRATIS, A., 38, St. Augustine's Road, Camden Square, and ROSTON, J., 24, High Holborn, both in London. March 16, 1934, Nos. 23361/35, 23362/35, and 23363/35. Divided out of 436,652. [Class 80 (ii)] Relates to variable-speed gearing of the type comprising spur gear trains adapted to be put into operation by the engagement of dog clutch and like toothed parts, and provides automatically acting control means which, during speed changes, first depresses suddenly the speed of the engine in such a way as to relieve of torque the formerlyengaged train and to render possible the disengagement of the corresponding dog members, and subsequently accelerates the engine gradually, so producing a reversal of the relative rotation of the dog members about to be coupled, and provides also a synchronism detector adapted automatically to effect engagement of the new train by servo means at the moment when the said reversal occurs. In the change-speed gearing for vehicles shown in Fig. 1, a spider 3 fast on a driving-shaft 1 carries stepped planets meshing with a sun 11 fast on a driven shaft 10 and with suns rigid with loose sleeves 13, 14, 15, 16. A solid high-speed drive is effected by engaging a dog clutch 20, 21, which clutches the sleeve 13 to the shaft 10. Reduced speeds are effected by sliding a non-rotary dog member 17 left and right to engage dog members 131, 141 on the sleeves 13, 14, respectively. Low speed and reverse are effected by applying brakes to drums 18, 19 on the sleeves 15, 16. In Specification 436,652, there is described automatic speed and torque responsive and alternative manual means for acting on a lever 124, Fig. 6, and so rocking a selector cam shaft 51. This has cams 74, 741, 74<2> for the three dog members, and cams 87, 87<1> for the two brakes. As the shaft 51 is tilted to effect a speed change, a cam 67, Fig. 9, tilts a beam 65 so as to turn a lever 60 from a stop 62 to a stop 61 and so tilt the spindle 59 of a valve 58, Fig. 7, to admit pressure oil into a cylinder 56 and so tilt a beam 52 of an executive control shaft 50, Fig. 6, to the gear disengaged position. An electric contact 161 then completes a circuit from a battery 160 which circuit by a solenoid 149 decelerates the engine suddenly and speeds it up again slowly by means shown in Fig. 20. At C is shown a differential clutch described with reference to Figs. 13 to 16 of the specification referred to, by means of which a middle disc 144 is displaced by whichever of two side discs 142, 140 is displaced the farther. Thus a rod 143 leading to the engine throttle can be operated from the solenoid 149 independently of the accelerator pedal 141. When at the beginning of a speed change, the solenoid 149 is energized, the lever 142 is pulled sharply to the right so that the rod 143 is also pulled rightwardly towards closed position and the engine slowed down suddenly. Thus pressure between the teeth of the clutch 20, 21, Fig. 1, or between either of the dogs 13<1>, 14<1> and the dog member 17 is relieved, and it is readily possible to disengage these parts. But the return of the throttle rod 143, Fig. 20, leftwardly to the open position is delayed because on the operative stroke of the solenoid armature 148, an arm 153 thereon had struck an arm 152 on a slider 150 so as to break the circuit at 154 and introduce a resistance 155. This weakens the pull of the solenoid 149, which however resists a spring 146 in returning the throttle to the open position and so delays the opening operation, like a dashpot. During the gradual acceleration of the engine, a gear train will be engaged. This is done by the same current passing through a solenoid 64, Fig. 6, which turns the lever 60, Fig. 9, back against the stop 62 thereby admitting oil to another cylinder 55, Fig. 7, and throwing the executive shaft 50, Fig. 6, back to the gear engaged position, and so breaking the current at 161 and neutralizing the solenoid 149. As the engine is accelerating, the relative rotations of the various pairs of dog members reverse in turn as the pairs synchronize in turn. Detector mechanism for the brake dogs is shown in Fig. 13. When the dog member 13<1> has been selected for engagement, a cam 92 on the selector shaft 51 strikes up a pad 90 against the said member which rotates relatively to the fixed member 17. The rotation is in the direction of the arrow 98 so that the pad 90 moves right relatively to fixed pins 93 to the position shown, and there is no contact at 96. On reversal occurring, the pad 90 is slid to the left, and electric contact at 96 is closed, which, as shown in Fig. 6, effects an earth and enables the executive shaft 50 to be rocked to the gear engaged position. The selector shaft 51 had previously engaged a latch such as 72, Fig. 11, with a helical slot 761 in the shaft 50 so that the rocking of the shaft 50 to the engaged position, through a fork 701, Fig. 1, slides the dog member 17 into engagement with the dog member 13<1>, bringing in the new speed. Detector mechanism for the clutch dogs 20, 21, both of which are rotary, is shown in Fig. 15. Upon the reversal taking place, there is a like reversal between the other more handy parts 14<1>, 18, Fig. 1, of the changespeed gearing. Discs 101, 102, Fig. 15, are fixed to the said parts 14<1>, 18. When the clutch 20, 21 is to be engaged, the engine is slowed, and, as it speeds up, the selector means rocks a shaft 109, Fig. 15, which presses a pad 103 on the disc 101 against the disc 102. At the reversal, the pad 103 turns relatively to its disc 101 and makes contact at 108 with a slip-ring 105 connected to earth at 106 whereby the circuit is completed to rock the executive shaft 50 to gear engaging position. This by means of a helix 76, and a latch 72, Fig. 11, slides a fork 70, Fig. 1, to engage the clutch 21. Fig. 12 shows means for applying a brake 81 to the drum 18, the brake for the drum 19 being similar. The selector shaft 51 by its cam 87 depresses a latch 85 into a straight slot 86 in the shaft 50 thereby clutching a loose arm 80 to the executive shaft 50 a rocking of which is therefore communicated through a lever 83 to apply the brake 81. The latch 85 makes contact at 88 to complete the electric circuit of Fig. 6.