Patent GB-691760-A (GB)
Title: Electrically operated gear shift and clutch control mechanism for transmissions
Filed: 1950-12-18
Abstract: 691,760. Control of D.C. motors; electromagnetic interrupters. NERACHER, C. A. Dec. 18, 1950 [Dec. 19, 1949], No. 30838/50. Classes 38 (iii) and 38 (v) [Also in Group XXIV] A reversible electric motor M, which is used to supply power for automatic gear shift with coincidental clutch-operation on a motor-vehicle (see Group XXIV) operates during a complete shift cycle in three equally-spaced phases, during the first and third of which it operates under continuous steady full-load current, (for clutch release and re-engagement) and during the second at reduced speed and intermittent current under the control of a vibratory interrupter magnet Ri, Figs. 7 and 9. Throughout all phases of the cycle the motor field winding 267 is fully and continuously energised. The variation for the three phases of operation is brought about by an interrupter switch Si operated by a cam 210 driven mechanically, by the motor through one complete revolution during the whole shift-cycle. Co-operating in the motor energisation to start the shift-cycle are a manual selector-switch Ss, a neutral switch Sn operated by the gear shift member 161, a vehicle-driven governor switch Sg; switch Sa operated by the accelerator-pedal 215; brake-operated switch Sb; upshift and downshift relay-magnets Ru, Rd (shown twice); motor field reversing switch Sr operated by a cam 199 turned mechanically by the motor near the end of a complete shift-cycle to reverse the field connections ready for the next shift back; and various one-way rectifiers 270, 271, 281, 314 for blocking passage of current in undesired directions. Upshift from second to high speed is obtained when the driver releases the accelerator-pedal 215 to close switch contacts #<SP>1</SP> at any vehicle-speed above that (10 m.p.h.) at which the governor Sg closes its contacts #<SP>1</SP>, as shown, which completes the following circuit from B+ through switches CB, Ss, Sn, contacts #<SP>1</SP> of the governor Sg, lead 25b, closed contacts #<SP>1</SP> of the accelerator-switch Sa, brake-switch Sb, contacts #<SP>1</SP> of the fieldreversing switch Sr, upshift relay-magnet Ru and negative battery lead 261. This energises the upshift relay-magnet Ru, which opens its contacts #<SP>1</SP> and closes #<SP>2</SP>, completing a branch-circuit from the selector-switch Ss through leads 262, 263, closed contacts #<SP>2</SP> of the upshift magnet Ru, leads 264, 265, 266, motor field-windings 267, lead 268, now-closed contacts #1 of the idle downshift relay-magnet Rd to the negative battery lead 261. At the same time a branch hold-on circuit for the upshift magnet Ru is established from the motor-field 267 through a rectifier 281, closed contacts #<SP>1</SP> of the reversing switch Sr, upshift magnet Ru, and negative battery lead 261, so that the upshift magnet remains energised independently of the neutral governor, accelerator and brake switches. Simultaneously a second branch circuit is established from the motor-field 267, through a lead 313, rectifier 270, interrupter magnet Ri, and closed contacts #<SP>1</SP> of the interrupter switch Si to the negative battery lead 261, the consequent energising of the interrupter magnet Ri closing contacts 250 for direct heavycurrent supply to the armature M of the shift-motor, which latter then rotates through the first third of its shift cycle under full and continuous current supply. At the end of this phase the motor-driven interrupter cam 210 opens the contacts #<SP>1</SP> of the interrupter switch Si and closes #<SP>2</SP>. This de-energises the interrupter magnet Ri, opening the heavy-current contacts 250 supplying the motor armature and substituting a greatly reduced current path from the closed contacts #<SP>2</SP> of the upshift magnet Ru, through lead 272, rectifier 271, interrupter magnet Ri, contacts #<SP>2</SP> of the interrupter-switch Si, a resistor R, the motor armature M and negative battery-lead 261. Since energisation of the field 267 is fully maintained, the motor M, in slowing down, acts as a generator producing a current opposing the line current in interrupter-magnet Ri, so that it is only after the motor has slowed down to a predetermined speed that the line current is able to overcome the counter current sufficiently to re-energise the interrupter magnet Ri for it again to close the contacts 250 to restore full armature current. Closure of the contacts 250 however now also completes a shuntcircuit around the interrupter magnet Ri through the now-closed contacts #<SP>2</SP> of the interrupter switch Si, so that the magnet Ri is again de-energised, opening .the main contacts 250. This sequence repeats, the contacts 250 of the interrupter magnet opening and closing in a continuous vibratory manner to regulate motor-speed, which, during this second third of the shift-cycle, is thus reduced to a value determined by the value of the resistor R. A construction of the interrupter magnet Ri and associated contacts is described below. At the end of the second third of the cycle, the motor-driven cam 210 allows the contacts #<SP>2</SP> of the interrupter switch S<SP>1</SP> to reopen and #<SP>1</SP> to close, restoring full armature current through the closed contacts 250 for the final third of the cycle. Towards the end of the cycle the cam 199 operates the reversing switch Sr, opening its contacts #<SP>1</SP> and closing #<SP>2</SP>, thus breaking the hold-on and associated circuits and reversing the connections to the field 267 ready for the next shift, which has a similar sequence, with the motor rotating in the opposite direction. Fig. 9 shows a construction of the interrupter magnet Ri and its associated main armature supply contacts 250 shown diagrammatically in Fig. 7. Energisation of a magnet-winding 292 draws down a plunger 292, carrying an insulated plate 296 which, at 250, contacts and bridges terminal-posts 297. The plunger moves the plate 296 first in opposition to a spring 294, and then alone continues its downward movement at reduced air-gap 301 against a stronger spring 300 which applies considerably increased contact-pressure to the plate 296. This action occurs during the first and third phases of the shift-cycle, when the magnet-winding is continuously energised for steady maximum motor current, but during the second phase of the shift-cycle, when the contacts 250 have vibratory continuous interruption for reduced motor-speed, the full compression of the upper spring 300 is not reached.