Patent GB-554973-A (GB)
Title: Improvements in or relating to power transmission mechanism for vehicles
Filed: 1941-10-21
Abstract: 554,973. Fluid-pressure servomotor-control systems. BENDIX AVIATION CORPORATION. Oct. 21, 1941, No. 13545. Convention date, Feb. 24, 1941. Addition to 549.573. [Class 135] [Also in Groups XXIV and XXXVII] In control mechanism for automobiles having a change speed transmission and an ignition system, the latter is momentarily disabled when the vehicle accelerator is completely depressed or if the vehicle speed falls below a predetermined minimum. The invention is described in connection with control mechanism of a two-speed gear, such disablement of the ignition occurring when the gear is being changed from high to low gear ratio to enable the meshing gears to synchronize. The system includes a fluid pressure servomotor 12, Fig. 1, an accelerator-operated switch 22, a speed responsive switch 24, an interrupter switch 18, a relay switch 20, cut-out switch 25, a battery 37, ignition switch 30, primary winding 27 of an ignition coil 28, a distributer 32, a breaker switch 35 and condenser 33. The piston of the servomotor 12 is connected to the control arm 247 of a two-speed gear 10. The servomotor 12, Fig. 4, has a piston 46 on a rod 58 slidable on a pin 60 fixed to a core 62 of an electromagnet 26. The core 62 carries a winding 66 and is secured within an iron cylinder 68 fixed in the motor casing 36 by brass rings 64, 70. An iron. ring 72 on the core 62 is separated from the cylinder 68 by a small air gap. Mounted on a rod 108 slidable in the pin 60 is a hub 80 carrying a steel disc 84 and a valve 82, the latter controlling ports 88, 90 connected to the engine intake manifold and the atmosphere respectively. A contact ring 102 of the cut-out switch 25 is slidable on the rod 108 and is urged towards contacts 96, 97 by a spring 112 and away from the contacts by a weaker spring 114. The chambers 238, 245 of the servomotor cylinder are connected respectively to the valve chamber 240 and to atmosphere. A steel plate 252 is fixed to the piston 46. The interrupter switch 18, Fig. 6, has a solenoid 122 the winding of which is grounded at 126 and wired to a terminal 128 connected to the contact 130 of the relay switch 20. An armature 132 has a disc 134 slidable in a cup 136 which is connected to a flexible switch member 140 by a pin 138. The base of the cup 136 has air holes 256 controlled by a disc valve 257 slidable on the pin 138. One end of the switch member 140 is grounded at 142 and the other end carries a contact 144 cooperating with a contact 152 wired' to the contact 97 of the switch 25. When the solenoid' is energized the armature 132 moves upwardly and sucks the cup 136 with it to close the switch 18. Immediately air leaks through the holes 256 to destroy the suction between the disc 134 and the cup 136 and the switch 18 opens: In a modification, the disc 134 and cup 136 are replaced by a pair of flexible diaphragms, one secured to the pin 138 and the other to the solenoid 132. The centrifugal switch 24, Fig. 8, includes pivoted weights 224 carried by a spindle 214 rotated according to the speed of the vehicle so that above a predetermined vehicle speed the weights 224 move outwardly and slide a sleeve 230 upwardly to open the switch. The relay switch 20, Fig. 2, has a switch member 202 pivoted at 204' and carrying a contact 208 which engages a contact 130 when the solenoid 200 is energized, and a contact 210 when solenoid 200 is de-energized, the latter movement being effected by a tension spring 209. Operation.-When the vehicle is stationary with the engine idling the parts are in the position shown in Fig. 1, the gear-box being in low gear setting and the switch 18 open, the motor piston 46 being in the left-hand position with the actuating spring 244 expanded, the valve 82 being in its right-hand position, as the electromagnet 26 is de-energized. As the car starts up the accelerator is depressed and when the car speed reaches say 5 m.p.h. the switch 24 opens to de-energize the solenoid 200 and complete the circuit through the electromagnet 26 whereupon the valve 82 moves to connect the motor compartment 238 to the engine manifold. When the car reaches the desired speed the accelerator is partly released; this increases the vacuum in the engine manifold and causes movement' of the piston 46 to the right so that the change speed lever 247 under the action of a spring 250 moves to introduce the high speed ratio. The action of the electromagnet 26 on the steel plate 252 maintains the parts in th& high gear position even should the vacuum decrease slightly. Change into low gear occurs when either the speed responsive switch 24 of the accelerator switch 22 is closed whereupon the relay switch 20 causes de-energization of the electromagnet 26, the spring 85 moves valve 82 to open the motor compartment 238 to atmosphere and the piston 46 moves to the left, Fig. 4. At the same time the interrupter switch 18 is actuated to momentarily disable the ignition and the switch 25 is opened. There is a slight lag between the actuation of the relay switch 20 and closure of the interrupter switch 18, such lag being sufficient to enable the slack to be taken tip in the transmission mechanism before the ignition system is disabled. The two-speed gear 10 may be used in combination with a manually-operated speed gear with a fluid clutch and a friction clutch. ! Reference has been directed by the Comptroller to Specification 655,637, [Group XXIV].