Patent GB-841983-A (GB)
Title: Control apparatus for variable ratio power transmission means
Inventor: HODKIN RICHARD KEITH
IPC: F16H61/00
Filed: 1956-07-20
Abstract: 841,983. Controlling change-speed gearing. ENGINEERING RESEARCH & APPLICATION Ltd. July 9, 1957 [July 20, 1956], No. 22528/56. Class 80 (2). In change-speed gear control means in which a servo means actuates the gear shift member in one line of motion and a control means actuates the shift member in another line of motion transverse to the first line, the servo and control means are controlled through-an electric circuit comprising a first switch means to control the supply to the servo and control means, second and third switch means energizing the first switch means when the input shaft speed falls below a first, or exceeds a second, predetermined speed, a fourth switch means operated in accordance with the position of the shift member to control the supply to the second switch means according to whether up or down shifts are to be permitted, and fifth switch means for passing current to the servo for actuating the latter in different directions. A sliding gear change speed gear is controlled by a shift member G carried by a bar 47 movable axially by a servo electric motor SM acting through screw and nut mechanism, and is rotated to provide transverse movement of the shift member by solenoid CS acting against a spring 42. The shift member G engages with selector forks 44, 45, 46 to engage four speeds and reverse in a known manner. The rod 47 carries brackets 70, 76 having cam projections to operate switches 60, 61, 62 and 63 respectively. The servomotor SM and the solenoid are controlled by the electric circuit, shown in Fig. 1, which also controls the current to the winding CL of a magnetic powder clutch between the engine and the change-speed gear. The lead B is connected to the vehicle battery through the ignition switch lead IS and the lead A is earthed at E. A lead CB is connected to the engine contact breaker and can be connected through any of three switches RD3, GSN3 or RL3 to the lead IC of the ignition coil; these switches provide ignition cut-off during upward changes only and also provide for no ignition cut-off when the gear-box input speed is less than 1000 R.P.M. as sensed by a governor switch GVI. A lead DY is connected to the engine dynamo and can be connected by switches RL1, GSN1 and manual switch 30 to the clutch coil CL such that the dynamo is connected to the dynamo below predetermined speeds and to the battery above that speed, the clutch being energized either directly through RH1 or through a resistance R3 when an inertia switch GS opens RH1, on downward changes, to provide decreased torque capacity. The manual switch 30 is ganged to switch 31 to provide in position 35, 35A the starting of the engine, from this position the switches are spring loaded to 34, 34A which is the non-driving position. Position 33, 33A is the normal driving position to which the switches are also spring-loaded from a position 32, 32A which connects the clutch coil CL to B to hold in any existing gear ratio in spite of other controls. Leads FD and FR are connected to the dynamo field and dynamo regulator respectively, a resistance R1 and a choke switch CS being connected across them. With the choke in operation the resistance R6 is inserted in the circuit and below a predetermined input shaft speed the resistance R1 is inserted. The switch RL2 earths the field through a switch TS, which is closed when the throttle is closed to prevent clutch energization. RL2 can also be earthed through switch TR on the hand brake lever to prevent clutch engagement with the brake on; this switch has a manual override for uphill starts. The clutch CL is normally energized through RH1 or R3 but during changes GSN1 and GSN2 are operated by the shift control solenoid GSN/3 to reverse the clutch current and remove magnetic remanence. A manual selector lever is connected to three ganged switches 10, 11 and 11A having contacts M, A, L, R for manual, automatic, low gear and reverse. Low gear and reverse are manually engaged when required and 2nd, 3rd and top gears may be engaged or held when the switches are in the M position, though overrides prevent changes into a ratio which would be incorrect with respect to conditions of engine speed or gear ratio engaged. In the A position of the switches, automatic change is provided between the top three ratios in relation to the gear-box input shaft speeds as sensed by governors GV1, GV2, GV3 and GV4 which may be of the type described in Specification 815,244. Specification 841,985 also is referred to.