Patent GB-480771-A (GB)
Title: Improvements in or relating to gear change transmission mechanism
IPC: F16H61/02
Filed: 1936-05-26
Abstract: 480,771. Controlling change - speed gearing. GOULDBOURN, J. May 26, 1936, No. 14806. [Class 80 (ii)] [Also in Group XXIX] Comprises the combination with the engine and changespeed gearing upon a vehicle of a control for the engine and an automatic gearchanging device for effecting gear changes accompanied by disengagement and re-engagement of the drive, at certain engine speeds, which device includes means for effecting at each change, a temporary adjustment of said control, and means for ensuring that re-engagement of the drive, or engagement of the members in the changespeed gearing giving the new ratio, is dependent upon a change in free engine speed subsequent to drive disengagement. The apparatus comprises a device 14, Fig. 1, responsive to changes in engine speed, an " up-ordown " selector for determining whether the change is to be up or down, a ratio selector, and means for effecting the gear change. Figs. 1 2 and 3 show an adaptation to the Cotal gearbox described in Specifications 332,789, [Class 80 (ii)], and 444,899. Figs. 4, 5 and 6 show the application to the Wilson gearbox described in Specifications 402,794 and 427,385. Figs. 4 and 7 show the application to the De Normanville gearbox described in Specification 372,382. The Cotal gearbox is epicyclic with brakes and clutches controlled by four electromagnetic coils A, B, C, D, Fig. 2, excited from terminals 45-51, there being a main terminal 53 by which the drive is disengaged and re-engaged. The engine is in a casing 10, Fig. 1, and there may be a centrifugal or a fluid-flywheel main clutch. The device 14 responsive to engine speed may be a fluid pump and is shown as a centrifugal governor which moves a pivoted finger 21 which carries a contact strip 23 over a change-up contact 25 and over a changedown contact 26 on a " contactor " lever 27, Fig. 2, which is pivoted on the same arbor 28 as the governor finger 21. The change-up contact 25 is connected electrically to a " valving " solenoid 30 and to a change-up solenoid 35. The change-down contact 26 is connected to valving and change-down solenoids 32, 34. The changing solenoids 34, 35 deflect a core lever 36 pivoted at 38 which carries with it a pin 39 fast on the contactor lever 27, this apparatus constituting the " up-or-down '' selector. Pivoted on the same arbor 28 is a ratchet lever 37 of the ratio selector, which has two groups of ratchet teeth 40a, 40b adapted to be engaged and displaced alternatively by two pawls 41a, 41b pivoted on the contactor lever 27. The lever 37 carries a spring strip 43 which is connected by a wire to the master contact 53 and is adapted to connect the contacts 45, 46 to the contacts 48, 49. 50, 51. Displacement of the ratchet lever 37 selects a new ratio and movement of the contactor lever 27 controls energization of the clutches and brakes of the gearbox by means of the master contact 53, and therefore controls disengagement of the drive. The valving solenoids 30, 32 both act to open a valve 33, which admits engine suction by a conduit 66 both upwards by a conduit 69 to a valve-chest 56 and downwards through a conduit 67 and a conduit 78, Fig. 1, to a cylinder 77. In the valve-chest 56 is a piston valve 55 connected to pin 39 on the lever 27 which is biassed to central position by a two-way acting spring 58. The valve 55 in its normal position shown admits suction through a throttle-closing conduit 63, but when moved right it admits the suction to a throttle-opening conduit 64. A throttle 70, Fig. 3 may be opened by depressing a pedal (not shown) which thrusts an accelerator rod 71, Fig. 1, right and turns a bell-crank 72 and so pulls down a cylinder 80 relatively to its piston 81 and so, by a lever 185, Fig. 3, opens the throttle 70. Suction is admitted to the cylinder 77, Fig. 1, during the automatic speed change and this causes a dog 75 to engage and lock a rack 74 and so prevent the accelerator being depressed by the driver during such change. In the normal position of the valve 55, Fig. 2, suction is admitted by conduits 63, 83 under the piston 81 to raise the cylinder 80 and close the throttle. During change-up, the valve 55 moves left and the suction remains under the piston, and the; throttle remains partially closed to facilitate speed changing. During change-down, the throttle is at first partially closed, but after the valve 55 has moved right, the suction passes by conduits 64, 82 to above the piston 81, and the cylinder 80 moves down to open the throttle. A rod 184 is separate from the piston 81 and pinjointed to the bell-crank 72, and there is a spring 85 connected to the cylinder 80 and to a collar on the rod 184, so that accelerator depression pulls the cylinder downwards through the spring. Upward displacement of the piston 81 and its rod 84 is limited by a stop 86, Fig. 3, on a rod 87, Fig. 1, biassed upwards by a spring 88 but pushed downwards by a cam-following link 90 according to the position of a housing 52 which swings about the arbor 28 and carries the valve-chest 56 and the valving and changing solenoids. The link 90 moves over a fixed cam 91 to depress a pin 92 on the rod 87. The stop 86 is lowered as the housing 52 swings clockwise and provides an abutment against which the piston rod 84 pushes, in the event of a change taking place on a small throttle opening, to cause a temporary farther opening. The lower the stop 86, the earlier and wider is this automatic throttle opening. This swinging of the housing 52 is effected from the accelerator by a lever 111, Fig. 1, engaging stops 112, 113 on the housing. Carried by the stop rod 87 is a cross-head 93 to which are pivoted two pendant links 94, 95, adapted to make electrical connections with contacts 99, 98 on the top of the cylinder 80. These pendant links are in the circuits to the two changing solenoids 34, 35, Fig. 2. At large throttle openings, the cylinder 80 is depressed so far below these links as to break circuit and render speed changing impossible until the cylinder has risen. That is, in the case of changes at full engine power, or with the accelerator well down, the pendant links ensure that the throttle is partially closed before the interruption of the drive by the release of a gear brake or clutch, thereby preventing overspeeding of the engine in neutral. Also when the throttle is wide open, the gear changes take place at higher speeds than they do at smaller throttle openings. If the pendant links are omitted, a greater time elapses between disengagement and re-engagement of the drive. In operation, an increase in engine speed brings the governor contact 23 over the change-up contact 25. The solenoid 30, Fig. 2, opens the needle valve 33 so that the accelerator is locked and the cylinder 80 caused to rise to close the throttle and engage the pendant links. As the engine slows the change-up solenoid 35 acts and the contact lever 27 moves left thereby effecting the ratio change through the pawl 41a and operating the valve 55 and also making the contacts 23, 25 overlap farther than before. This overlap which can be regulated by stops 102, 103 determines the distance that the contact 23 must move, and therefore the extent to which the engine speed must fall-subsequent to partial throttle closure and subsequent to drive disengagement-before these contacts, 23, 25 separate to cause re-engagement of drive on a higher gear ratio. On the separation of these contacts 23, 25 the spring 58 brings the lever 27 back to mid position, leaving the ratchet lever 37 in its displaced gear position, until the main electric circuit is made at contact 53 to energize the brakes and clutches in the gearbox. Change in the speed of the engine after it has been freed thus effects re-engagement of the drive. The closing of the valve 33 releases the rack 74 so that the accelerator pedal again commands the throttle. In the Wilson gearbox control of Figs. 4, 5 and 6, the invention is applied to supply the power for moving both the usual cam-shaft selector and the executive changer. The changes are made by depressing a busbar (not shown) geared to a shaft 133, Fig. 5, with a finger 134 which is raised to depress the bar and disconnect the drive by a piston 135 in a cylinder 136 to which oil from an accumulator is admitted by a conduit 137. The hydraulic cylinder is controlled by a valve 139 operated against a spring 150 by suction in a cylinder 140 which arrives by a conduit 128, Fig. 4. The speed-changing solenoids 34, 35 are connected directly to the changeup and change-down contacts 25, 26 on the contactor lever 227, these contacts being supplied with current from the contact 23 on the finger 21, Fig. 1, rocked by the engine governor. Rocking of the lever 227 slides a valve 225 which admits suction either to a change-up conduit 120 or to a change-down conduit 121. A valve 131 shown is operated from the selector cam shaft to prevent changes beyond the extremes, like a bluff 104, Fig. 2. The change-up conduit 120 leads by a conduit 122 to the cylinder 80 of Fig. 1, to close the throttle, also by a conduit 129, Fig. 4, to the cylinder 77, Fig. 1, to lock the accelerator, also by a conduit 124 to a cylinder 125, Fig. 6, and also by the conduit 128 to the cylinder 140, Fig. 5, to depress the bus-bar. The cylinder 125, Fig. 6, is the up-or-down selector which displaces a double bluff 126 left against a spring 130 so as to mask a ratchet 147 from a pawl 145 and allow a pawl 146 to act on a ratchet 148 fast on a shaft 149. These pawls correspond to the pawls 41a, 41b, of Fig. 2, but instead of the power to move them being supplied from the changing solenoids 34, 35, it is supplied from the hydraulic cylinder 136, Fig. 5. As the bus-bar is depressed, pawlcarrying levers 143, 144, Fig. 6, are opened out by links 141, 142, Fig. 5, from arms on the shaft 133 so that the pawl 146 turns the shaft 149 which is geared to the usual selector cam shaft (not shown)