Patent GB-533075-A (GB)
Title: Improvements in or relating to electrical devices for clutches and associated change-speed gears
IPC: F16H63/42
Filed: 1939-05-05
Abstract: 533,075. Variable speed gearing; dashpots. DERUNGS, E. A. May 5, 1939, No. 13456. Convention date, May 7, 1938. [Class 80 (ii)] [Also in Group XXXII] In a change speed gear wherein actuation of the clutch and change of gear is effected by electromagnetic means controlled by a selector switch having a contact member adapted to be moved to different positions, corresponding to the different speeds, to complete the exciting circuits of the electromagnetic means for the time required to effect gear change, damping means are operatively connected to the clutch actuation mechanism to retard engagement of the clutch following a gear change, the damping effect being made dependent on the position of the contact member and consequently upon the engaged gear. The manual selector switch, Figs. 1 and 2, is adapted to energize a relay 23 controlling a speed-changing and clutch-controlling circuit 21, which is broken at the end of the change by abutment of an element 33 of the speed-changing members against the relay armature 23. The switch may control the electromagnetic system described in Specification 497,478, in which completion of a common circuit 30 energizes an electromagnet effecting a stroke for disengaging the main-clutch and simultaneously moving an executive member to establish a gear selected by a number of individual circuits R, N, I, II, III, corresponding to reverse, neutral and the three forward speeds respectively. The switch comprises an insulated drum 1, secured to a shaft 2 which is turned into the selected speed positions, in which a non-rotary radial conducting-arm 16 connects contacts 14, leading to the common clutch- and executive-circuit 30, with contacts 13 leading to the relay-contact 21. In the speedpositions R, I, II, III, the same arm 16 also bridges contacts 14<1> leading to the selector circuits of the respective speeds. In positions intermediate the speed positions, i.e. during a change, the arm 16 bridges contact-studs 5, 9 &c. completing the circuit of the relay 23 which thereupon closes the relay-contact 21, connecting the inner contact-studs 13 to the current-source, so that the executive- and selector-circuits 30, I, II &c. are complete when the arm 16 overlies their studs 13, 14, 14<1> &c. The non-rotary contactarm 16 is slidable axially on a stationary support 4 and by engagement of balls 28 with facial teeth 27 on the rotary drum 1, is periodically lifted axially out of engagement with each co-operating group of studs, e.g. 5, 9 or 13, 14, 14<1> &c. during the transition from one group to the next, against the force of a spring 18. A lamp 47 in the executive-circuit indicates that a speed change is in progress, the lamp being extinguished by the breaking of the relay-contacts 21 by the element 33 at the end of the change. During the change, the admission of fuel to the driving engine is automatically controlled by a spring-centralized rocker 37, which, by means of teeth 36 on the selector-shaft 2, is tilted in one direction or the other for momentarily closing contacts 40 or 41 energizing electromagnets (not shown), respectively for increasing the admission of fuel during a downward change and reducing it during an upward change, independently of the usual accelerator pedal. The stroke of the clutch-controlling and gear-establishing electromagnet (not shown) is retarded by an air dashpot, Fig. 5, the piston 66 of which reciprocates in a cylinder 51 which is itself axially movable to a small extent in a support 49, having adjustable throttling escape openings 61, 62 communicating with opposite ends of the cylinder through openings 59, 60. The cylinder 51 is connected for rotation, by a belt 54, with a pulley 3 on the selector-shaft 2. The angular position of the hole 59 differs slightly from the angular positions R, N, I. II, III so that the retardation of the clutch engagement varies in accordance with the gear engaged, e.g. so that clutch engagement at first speed is more gradual than at second or third speed. The small axial movement of the cylinder 51 allows the cylinder to be moved in the same direction as the piston to apply its face against the support 49 in the direction of movement, whereby only the opening 59 or 60 in front of the piston is effective for retarding its movement. By this means the retardation can be arranged to be different in each direction, i.e. clutch engagement can be more gradual than clutch disengagement. In addition, the pressure of the cylinder 51 against the support applies a frictional resistance to the turning of the manual selector-switch which informs the operator that the change is in progress. Fig. 4 shows an automatic selector control which also serves as an indicator to show the operator which speed he should be employing if he is using the manual control. An arm 68 is pivoted about an axis 73 by movement of the accelerator-pedal 74, and serves as an indicating pointer which tracks a quadrant scale 72 which is pivotally moved about the same axis 73 by a control which operates in response to changes in vehicle-speed. For use as an automatic control, the arm 68 carries a contact which moves over studs on sectors 71, 71<1> 71<11> formed on the quadrant 72 such studs leading to the appropriate selector and executive circuits. A main reversing switch (not shown) connects the current supply either to the manual selectorswitch. Figs. 1 and 2. or to the automatic selector-switch, Fig. 4. as desired.