Patent GB-427735-A (GB)
Title: Improvements in or relating to gear changing mechanism for motor vehicles
Filed: 1933-10-20
Abstract: 427,735. Controlling variable-speed gears and clutches. DICKER, S. G. S., 20, Holborn, London.-(Clerk, R. C. ; 60, King Street, Kingston, Jamaica, British West Indies) Oct. 20, 1933, No. 29088. [Class 80 (ii)] [See also Group XXXI] The operation of the clutch and change-speed gear of a motor vehicle is effected by fluidpressure means comprising multiple series valves selectively controlled by the combined movements of the accelerator and either or both of the gear-changing means and the brakecontrolling means. The fluid-pressure means may be vacuum, or compressed air or liquid operated. In the construction shown in Figs. 1, 2 and 4 applied to a vehicle driven by an engine 10 through a clutch 11 and pre-selector gear-box 12, the gears are selected by means of a control lever 17<a> mounted on the steering hand wheel 18 and the gear selected is put into operation by a vacuum servo-motor 20 controlled by a valve 50 adapted to connect the servo-motor either with the engine induction pipe 28 or with the atmosphere. The servomotor 20 actuates an arm 19<a> which operates the gear and the clutch, or that which serves as a clutch in this kind of gear-box. If a clutch has to be operated separately from the gear change the arm 19<a> disengages the clutch before the gear is changed. The valve body 50 is formed with vacuum passages 51, 52 connected together by a cross-passage 54 and by a port 59 with the induction pipe, and air or relief passages 55, 56 offset from the passages 51, 52 but connected at one end to the same crosspassage 54 and at the other end to the atmosphere. The cross-passage 54 is connected by a port 60 and pipe 29 to the servo-motor 20. The valve is controlled by two ported slides 57, 58, having forks 57<a>, 58a controlling the vacuum passages 51, 52 and forks 57b, 58b controlling the relief passages 55, 56. The slide 57 is actuated by the accelerator pedal 13 through the throttle rod 14, bell-crank 40 and link 31, and the slide 58 is controlled jointly by the pre-selector mechanism and the servomotor 20. The pre-selector crank 15<a> is connected by linkage 35 to a rod 67 slidable in but normally moving with a bar 63 sliding in guides 66, the rod and bar being connected together by centring springs 68, 69 so that the bar moves with the rod unless the resistance of one or other of the springs is overcome. The bar is formed with evenly-spaced teeth 63<a>-63<e>, the space between each pair of teeth corresponding to the various gear changes. A pawl 72 pivoted at 71 to the slide 58 has a tooth 73 normally pressed into engagement with the teeth on the bar 63 by means of a bell-crank 76 controlled by a spring 80. Springs 82, 83 tend to return the slide 58 to the central position shown in Fig. 1. These springs may act directly or through a lever 85, Fig. 2. Fig. 1 shows the apparatus in the position in which the selector gear is in the first forward speed, the pawl 73 being between teeth 63b and 63<c>. The spaces below 63<c> are for the other forward gears, that between 63<a> and 63b is the neutral position, and the reverse is engaged when the pawl is above the top tooth 63<a>. To change from the first gear to the second the selector lever 17<a> is moved to the indicated position and the rod 67 and bar 63 are raised through a distance equal to the pitch of the teeth on the bar. The slide 58 is thus raised to the position shown in Fig. 2 in which a port 85 in fork 58<a> opens on to passage 52. If the throttle is now allowed to close, the slide 57 is moved to the position shown in Fig. 2 in which a port 84 in fork 57<a> also opens on to passage 52. The servo-motor 20 is thus energized through the passage 52 and ports 84, 85, the connection to the atmosphere being cut off by forks 57<a>, 58<a> and the clutch and first gear are disengaged. As the servo-motor is operated it acts through linkage 22, 81 on the bell-crank 76 and disengages the tooth 73 from the bar 63, so that the tension spring 83 returns the slide 58 to its central position shown in Fig. 1 and cuts off the servo-motor from the induction pipe. At the same time a bleed port 90 in fork 58b opens on to relief passage 55 which is open to the atmosphere through port 87 in fork 57<b> while the throttle is closed, so that the servo-motor is slowly. de-energized and second gear is engaged. Further upward changes of gear are obtained in the same manner. In changing " down " from a high gear to a lower gear the selector lever 17<a> moves the bar 63 down one tooth and this lowers the slide 58 to the position shown in Fig. 4 in which a port 86 in 58<a> is open to vacuum passage 51 ; if the accelerator pedal is now depressed and the slide 57 is also raised as shown, the port 84 in 57<a> is also open to the passage 51 and the servo-motor is energized to disengage the clutch and gear. The servomotor simultaneously acts on the bell-crank 76 and disengages the tooth 73 from the bar 63 so that the springs 82, 83 return the slide 58 to its central position to close the vacuum passage 51. The servo-motor is now connected to atmosphere, the throttle being still open, through relief passage 56, and one of the ports 87, 88, 89 in fork 57b, and a port 92 in 58b, so that the servo-motor is slowly de-energized and the clutch and lower gear are slowly engaged. A more rapid engagement of the lower gear may be obtained for braking by closing the throttle immediately after it has been opened, when the servo-motor will be de-energized through port 91 in 58<b> and port 87 in 57b. If the selector lever 17<a> is moved through more than one notch the bar 63 and slide 58 are prevented from moving more than one notch by means of a pin 75 on bell-crank 76 working in a slot 74 in the pawl 72, the extra movement of the selector lever 17<a> simply moving the rod 67 in the bar 63 against the resistance of the springs 68, 69. In the construction shown in Figs. 7 and 9 the gear-box 12 is of the pre-selector type in which a gear is selected by the arm 15<a> and is put into operation by the arm 19<a>, but there is no hand control of the pre-selector, and the gear is changed automatically step - by - step, up or down, by means controlled by the accelerator pedal 13 and the brake pedal 33. In this construction, which is suitable for racing cars, changing down is effected by applying the brake or while the brake is applied. The valve 50 in this construction has a single vacuum passage 51 and a single relief passage 55 both communicating at one end with the port 60 and the servo-motor 20. One ported valve slide 57 is connected by a link 31 to the accelerator pedal, and the other valve slide 58 is fixed to a slidable bar 62 having a cam 62<a> adapted to engage levers 93, 94 pivoted at 95, 96 respectively. A pair of levers 98, 99 mounted on a common pivot 97 carry pawls 100, 101 fixed to arms 100<a>, 101<a> which are pivoted to adjacent ends of the levers and are pressed towards the lever pivot by springs 100<b>, 101<b>. The pawls are adapted to engage teeth 102<a>-102<g> on a slidable bar 102 connected to the gear selecting arm 15a, but when the slide 58 and cam 62<a> are not in the central position, the cam acts on one of the levers 93, 94 and moves one of the pawls out of engaging position with the teeth of the bar. The levers 98, 99 are normally held together as shown in Fig. 7 by a spring 97<a>, but are opened out as shown in Fig. 9 when the servo-motor 20 is operated to change the gear, the levers being connected to the servo-motor by a cable 103. The slide 58 is normally kept in a central position by springs 105, 106 acting on one end of a lever 104, the other end of which passes between pins on the bar 62. The spring 105 is connected to a fixed point, but the spring 106 is connected by a cable 33a to the brake pedal 33 which serves as a normally-fixed point. In the position shown in Fig. 7 first gear is engaged, the pawls 100, 101 being between the teeth 102<c>, 102d, the two spaces above the pawls corresponding to neutral and reverse, while the spaces below the pawls correspond to the higher forward gears. The valve slide 57 is moved down as the throttle opens until at full open position of the throttle a stop 108 on the slide abuts the lever 104. To change up to second gear the accelerator pedal is momentarily depressed still further, and moves the slide 57 down so that the stop 108 rocks lever 104 counterclockwise and lowers the slide 58 and cam 62<a>. In the position now reached ports 115, 116 in the valve slides 57<a>, 58<a> open on to the vacuum passage 51 so that the servo-motor 20 is energized and the clutch and gear disengaged. As the servo-motor operates it pulls the cable 103 and opens the levers 98, 99 as shown in Fig. 9 so that pawl 100 is lowered and pawl 101 raised. The lowering of cam 62<a> has rocked lever 94 until it holds pawl 100 out of engagement with bar 102, so that only pawl 101 is operative, and this pawl engages tooth 102<c> and lifts the bar 102 through a space equal to the pitch of the teeth, the bar thus being moved sufficiently to select the second gear. The final opening movement of the levers 98, 99 acts through a pin-and-slot connection 110 on a link 111 to rock the lever 104 to the position shown in Fig. 9, in which the slide 58 is returned to its central position and the slide 57 to the position corresponding to full open throttle. This movement of the slides closes the vacuum passage 51 and opens the relief passage 55 through ports 130, 131 in the slides, the result being that the servo-motor is de-energized and the second gear is engaged. The change up to higher gear is effected by a repetition of the operations. To change down the brake is applied by the pedal 33 and the lever 104 is rocked in clockwise direction by the cable 33<a> so that the slide 58 and cam 62<a> are moved up from the central position, thus putting pawl 101 out of action. With the slide 57 in the open throttle position the vacuum passage 51 is open through the slide