Patent GB-837051-A (GB)
Title: Improvements relating to gear change apparatus for change-speed gears
IPC: F16H63/30
Filed: 1957-11-25
Abstract: 837,051. Change-speed controls. DAIMLERBENZ A.G. Nov. 25, 1957 [Nov. 24, 1956; Dec. 18, 1956], No. 36706/57. Class 80 (2). [Also in Group XXXI] Change-speed control mechanism for a motorcar comprises a selector disc 14, Fig. 2, having cam slots 15 engaged by pins 16 actuating gear striker forks, a lever 20 pivoting on the axis of the cam disc carrying a double pawl 25 engaging with notches 17, 19 on the disc when solenoids 22, 23 are energized for down and up ratio shifts, respectively. The lever 20 is biased to the central position shown by springs 21 and is fast with a shaft 45. Ratio shifts are effected by a steering-column-mounted shifter lever 10, Fig. 1, moved repeatedly to two positions 10<SP>1</SP>, 10<SP>11</SP> to effect up and down shifts by closing switches 10<SP>1</SP>, 10<SP>11</SP>, Fig. 2, thereby Connecting a battery 28 to the solenoids 22, 23, which accordingly attract an armature 24 carried by the lever 20. The transmission includes an automatic clutch 29 (not further described) with which are associated electric devices 30, 32 energized by closure of the switches 10<SP>1</SP>, 10<SP>11</SP> to disengage the clutch and adjust the throttle setting of the car engine 3 during a ratio shift. An engine-driven governor 33 controls switches 37, 38, 41, 43 which, together with switches 39, 42, 44 controlled by a cam 40 turned on depressing the accelerator pedal 36, prohibit or initiate changes of ratio under certain circumstances. The switch 37 is in series with the down-shift switch 10<SP>11</SP> and is opened by the governor 33 at a relatively high engine speed to prohibit down-shifts causing excessive engine racing. The switch 38 is also in parallel with the downshift switch 10<SP>11</SP>, and is closed at a relatively low engine speed. If, at low engine speed, the accelerator pedal 36 is depressed through approximately three-quarters of its travel, the switch 39, which is in series with the switch 38, is closed, and the down-shift solenoid 22 is energized to produce a downward ratio shift so that the engine does not labour. The switch 41 is closed over a moderately high range of engine revolutions, and is in series with the switch 42 which is closed when the accelerator pedal 36 has been depressed through approximately onehalf of its travel. Under these conditions, the up-shift switch 10<SP>1</SP> is by-passed, and a ratio upshift is effected by energization of the solenoid 23. The switch 43 is closed by the engine-driven governor 33 when the engine reaches its maximum speed. In series with this switch 43 is the switch 44 which is closed when the accelerator pedal 36 is fully depressed, or " kicked down." Accordingly energization of the solenoid 23 results for an up-shift in ratio. When the lever 20 reaches either of its extreme positions at the end of a ratio establishing movement, a snap switch 27 breaks the connection of the associate solenoid 22, 23 to earth and the solenoid is accordingly de-energized. Switches 48, 52 are provided in the earth line leading from the down-shift solenoid 22 and are opened by cams 46, 50 fast on the lever shaft 45 in such a way that down shifts to neutral and reverse by operation of the steering-column-mounted shift lever 10 are prohibited. When the change-ratio gearing is in first gear, the cam 46 opens the switch 48, and the down-shift solenoid 22 accordingly cannot be energized. To obtain neutral a separate press-button N is operated to close the switch 48 mechanically and simultaneously connect the down-shift solenoid 22 to the battery 28. Accordingly the cam disc 14 is stepped in the appropriate direction. When neutral has thus been reached, the cam 50 of the shaft lever 45 opens the switch 52, which similarly prohibits energization of the downshift solenoid 22. To obtain reverse, a second press-button R is operated which cuts through links 53 to close both switches 48, 52 and connect the down shift solenoid 22 to earth, simultaneously connecting the battery 28 to the solenoid 22 again to step the cam disc 14 in the appropriate direction. Engine braking is obtained by full depression of the car service brake pedal 54 to turn a cam 55 and close a switch 56 completing a circuit to the downshift solenoid 22, which accordingly establishes a lower ratio. An electrical device 13, Fig. 1 (not further described), indicates the ratio established in the gearing at any time. The gearing controlled by the device may be arranged to be locked solidly within itself by establishing two or more ratios at a time. In one form, the gearing comprises coaxial input and output shafts, Fig. 3 (not shown), a countershaft, constant-mesh gears and ratio selecting positive clutches. In a modified control system for obtaining internal locking of the gear, the cam disc 14, Fig. 4, is operated substantially as described above, but a switch 152 is provided which can be closed by movement of a link 151, operable only when the driven shaft of the gear is stationary, to withdraw a catch 149 from a projection 148 on the cam disc, which can then be rotated by the down-shift solenoid 22 beyond the reverse position to a position establishing two &c. ratios at once, locking the gear solid. The gearing can be unlocked by opening the switch 152 and simultaneously closing a switch 153, so that the up-shift switch 10<SP>1</SP> can be closed to energize the up-shift solenoid 23. The locking switch 152 may be a press-button switch located on the instrument panel of the car, or it may be operated automatically, for example by a door lock when the doors of the vehicle are closed.