Patent GB-496055-A (GB)
Title: Improvements in gear shifting mechanisms for motor vehicles
IPC: F16H61/30
Filed: 1937-05-27
Abstract: 496,055. Variable-speed gearing. AUTOMATIC SHIFTERS, Inc. May 27, 1937, No. 14775. Convention date, July 30, 1936. [Class 80 (ii)] In a gear-shifting mechanism for a motor vehicle having a synchronizing transmission and motor devices for operating the gear shifts therein, an automatic device is provided for checking the speed of the motor device, said checking device being inoperative just prior to the stage in which gear synchronization takes place and being automatically rendered operative by the gear synchronizing means of the transmission. The invention is an improvement in the gear-shifting mechanism described in U.S.A. Specification 2,030,838, the general mode of operation of which is followed in the mechanisms described in Specifications 494,699 and 494,756. The gear enclosed in a casing 11, Fig. 1, is of the synchronizing type and has shift forks 16, 17 carried by shift rods 18, 19. A shaft 21 has a crank 22 carrying a socket 23 engaging a ball 24 at the lower end of a lever 14, and a projection 20 therefrom enters a slot 41 in a valve-controlling slide 40. A crank 25 is splined on the shaft 21 and is connected by a rod 29 to the piston 28 of a cylinder 27. The shaft 21 is adapted to be moved axially by a cross-shift motor 45 to determine which of the rods 18, 19 is to be actuated, and actuation of these rods is effected by the rotation of the shaft 21 by the piston 28, adapted to be actuated by engine manifold suction transmitted through a pipe 32 to a valve mechanism 31. A selector valve mechanism comprising a casing 53, valve 54, shaft 55 with handle 56 working in an H-slot, is connected by pipes 36 ... 38 and 42, 43, 47, 48 to the valve devices 31, 39 and cross-shift motor 45. In the pipes 33, 34 connecting the valve device 31 with the ends of the cylinder 27 is inserted the valve mechanism 35 for controlling the speed of the piston 28 according to the invention. This mechanism, Fig. 2, comprises a cylindrical casing 60 for a valve 61, and an enlarged portion 84 divided by a diaphragm 89 into chambers 85, 88. The diaphragm is loaded on both sides by springs 92, 93 and is connected to the valve 61, stops being provided at 95, 97. The casing 60 has ports 67, 68, 70, 71 with which communicate the pipes 33, 34 from valve mechanism 31, Fig. 1, and pipes 73, 74 leading to ports 81, 82 at the ends of the cylinder 27. The valve 61 has reduced portions 62, 63 adjacent which are bevelled portions 65, 66. The diaphragm chambers 85, 88 are connected by pipes 101, 103 with the pipes 73, 74 provided with flexible rubber portions 77, 78 to allow for the swinging movement of the cylinder 27. To engage low gear, the handle 56 is moved to the left and rearwardly, which opens pipe 38 to atmosphere causing the motor 45 to slide the shaft 21 to the right. At the same time, pipe 48 is opened, and pipe 47 closed, to atmosphere. Also, the valve 31 connects pipe 34 to atmosphere and pipe 33 to suction. Valve 61 being in normal position, the right-hand end of cylinder 27 is connected to suction and the other end to atmosphere and piston 27 moves to the right to bring in low gear. Initial movement of piston 28 is relatively rapid and the slight pressure difference of its two sides is communicated to the diaphragm 89 to move valve 61 to the left but not sufficiently to reduce communication between pipes 33, 73 and 34, 74. During synchronizing of the gears, the movement of piston 28 is resisted and the pressure in the forward end of the cylinder will be reduced and the increased difference of pressure is transmitted to the diaphragm 89 to move the valve 61 to the left, and the communications with pipes 33, 34 will be restricted by the bevelled portions of the valve. This will cause the speed of piston 28 to be reduced while synchronizing takes place, thus simulating manual change. After synchronization, the piston speed increases, the pressure difference on opposite sides of the diaphragm 89 is reduced and the valve 61 is restored to normal position. The valve mechanism 44, Fig. 1, permits of pre-selection but the mechanism 35 acts, as described, independently of this. After clutch release, the handle 56 is moved forwardly to neutral and then transversely and forwardly into second gear. When neutral is reached, the motor 45 transfers the shift to the high gear side. The valve mechanism 31 now reverses the previously described operation. The valve mechanism 35 is independent of the form of the valve device 31, and functions for all gear positions in which synchronization has to take place prior to meshing of the gears.