Patent GB-788750-A (GB)
Abstract: 788,750. Change-speed control. EATON MANUFACTURING CO. June 3, 1955 [June 16, 1954], No. 15953/55. Class SO (2). In a motor car, a main clutch in series with a planetary gear is partly disengaged while a brake is in the process of being applied to the planetary gear reaction element to change the ratio, in order that drive may be taken up smoothly. In one form, the solenoid 16 of an electromagnetically-operated clutch 10 is energized to couple a driving-shaft 12 to a shaft 20 and a planet gear carrier 24. Planet gears 28 thereon mesh an internally toothed annulus 38 fast with a driven shaft 40, and a reaction sun gear 30 which can be held stationary by a band brake 34. A free-wheel 22 connects the shafts 20, 40 for direct drive. A centrifugal governor 46, controlling the engagement of the clutch 10 and brake 34, is driven by the shaft 40. The governor actuates a switch 52, Fig. 4, in an electric circuit feeding a solenoid 54, controlling a valve V, Fig. 2, normally spring- biased to connect the engine inlet manifold through a conduit 68 and vacuum tank 66, with a conduit 70 and two servomotors 72, 74. The servomotor 74 controls a rod 92 actuating the brake 34, and, when it is not connected to the Inlet manifold, is spring-biased to engage the brake. The servomotor 72 moves axially a rod 78, carrying two cam lobes 80, 82 either of which can close a switch 88, and is spring-biased when it is not connected to the inlet manifold to a position in which the cam lobe 80 closes the switch. The switch 88, Fig. 3, short-circuits a resistor 97 and is in a circuit feeding the solenoid 16 of the clutch 10. When the gear gives direct drive through the free-wheel .22, the governor 46 is not rotated quickly enough to close the switch 52, so that the solenoid 54 is not energized and the valve V therefore connects the servo-motors 72, 74 to the engine inlet manifold through the vacuum tank 66 &c. Thus the brake 34 is not applied, and the cam lobe 82 closes the switch 88 to short-circuit the resistor 97 so that the clutch 10 is fully engaged. As the speed of the car increases, the governor 46 closes the switch 52 and energizes the solenoid 54 of the valve V, which is therefore conditioned so that it no longer connects the servo-motors 72, 74 to the vacuum tank 66, &c., but to the atmosphere. Accordingly, the rod 78 is moved to the right of Fig. 2 and the cam lobe 82 no longer closes the switch 88. The circuit feeding the coil 16 of the clutch 10 now includes the resistor 97, which reduces the flow of current so that the clutch is only partly engaged. Simultaneously, the spring-biased servomotor 74 is applying the brake 34 to station the reaction sun gear 24. Any shock thus produced is absorbed by slipping in the clutch 10. As the engagement of the brake 34 is completed, the continuing movement of the rod 78 carries it on to the position in which the cam lobe 80 closes the switch 88, and the full flow of current to the solenoid 16 re-engages the clutch 10. In a modification, the valve V and the vacuum servomotors 72, 74 are replaced by a reversible electric motor 100, Fig. 5, controlled by the governor-actuated switch 52 to drive a screwed shaft 106 and a nut 102 simultaneously applying the brake 34 and moving a tongue 104 to engage either of the contacts of the switch 88 in the circuit feeding the solenoid 16 of the main clutch, the torque not engaging either contact while the brake is in the process of being applied.