Patent GB-517979-A (GB)
Title: Improvements in or relating to gear shifting mechanism
IPC: F16H61/30
Filed: 1938-08-12
Abstract: 517,979. Fluid-pressure servomotor-control systems. AUTOMATIC SHIFTERS, INC. Aug. 12, 1938, No. 23829. Convention date, Aug, 28, 1937. [Class 135] [Also in Group XXIV] Operator-controlled gear-shifting mechanism, particularly for motor-vehicles, comprises a gear-shifting lever, e.g., 30, Fig. f, movable in opposite directions from a neutral position into different gear-positions, under the influence of force applied thereto both by a manual control lever 13 and a fluid-pressure servomotor, 39, energized by displacement of a floating device, e.g., a lever 33, Fig. 1, relative to the lever 30, such relative displacement being instituted by the manual lever 13 in the direction to cause the gear-shifting lever 30 to follow-up the movement of the manual lever, the arrangement being such that a force proportional to that of the servomotor reacts back on the manual lever 13, whereby the operator will feel a resistance to movement of the lever substantially proportional to the gear-shift resistance encountered by the gear-shifting lever 30. Such " feel " is useful in synchromesh transmissions. The operator is thus always required to supply a force in a direct, and if desired, adjustable, proportion to the resistance, and in the event of failure of the fluid-pressure may supply the whole of the force necessary for the shift by exerting greater pressure on the manual lever 13. The motive fluid may be air or liquid under pressure, or engine-suction and the follow-up control may be effected by a floating lever or a valve with a movable seating. " Vacuum-suspension," explained below, is used in one form. In the form shown in Fig. 1, the gear-shifting lever 30, turning on a fixed pivot 31 on the gear-casing 10, is adapted to be connected to either of two shifter-rails 11, 12 by means of a link 16 having a depending pin 15 for engagement with notches in the shifter-rails when the link is swung transversely about the end of the lever 30. Such swinging is effected through a slotted rod 22, secured to the diaphragm 18 of a single-acting cross-shift motor 17, which has a permanent spring bias 19. Selection of the rails is effected by supplying engine-suction to the diaphragm 18 through a simple two-way valve 24, operated through a slotted lever 28 by the lateral movement of the ball-mounted manual lever 13. The follow-up gear includes the floating lever 33, pivoted on the outer end of the lever 30, and connected at one end to a gear-establishing piston, bellows or diaphragm motor 39, and at its other end, by a link 41 and lever 42, to a bar 43 which is moved longitudinally by the fore-and-aft movements of the manual lever 13. Initial movement of the lever 13 first turns the floating lever 33, which, through a bell-crank 61 actuates a valve 55, supplying suction from an inlet-pipe 26 to one side or other of the motor 39, which imparts a follow-up movement to the ]ever 30 and also turns the floating-lever 33 to close the valve 55. During this movement the servomotor 39 reacts back on the manual lever 13 through the floating-lever 33, in a proportion determined by the fulcrum-pivot 34 of the lever, such pivot being adjustable by the provision of a series of holes. The end of the link 41 has a yoke 68 so that direct manual operation of the lever 30 is possible if the power fails. To compensate for the lesser travel required by the shifter-rail 11 operating the synchromeshed speeds, the manual lever 13 is arranged to pick up the bar 43 at a point nearer its fulcrum 45 when operating one of the rails, for which purpose the bar terminates in two parts 43a, 43b, spaced along the lever 13, and having notches by which the lever communicates its movement to them after it has been moved laterally into engagement with one of them. In a central position the lever engages both notches at once and is positively locked thereby, so that the lever is compelled to move in the usual H-path. In the movable-seating type of follow-up control shown in Fig. 3, the link 41b, corresponding to 41 in Fig. 1, carries a valve-member 72b, cooperating with a seating-member 70b, pivoted to the transmission lever 30b, corresponding to 30 in Fig. 1. The servomotor 39b reacts back on the manual lever through an adjustable fulcrum 84 on a lever 82, mounted on a fixed pivot 83 and connected to lever 42b, corresponding to 42 in Fig. 1. A modification of this form replaces the lever 82 by a floating-lever similarly situated to the floating-lever 33. Fig. 1, its inner end being connected to the valvemember 72b, the seating-member 70b of which has a yoke passing round the transmission lever 30b. In both these forms the valve-member 72b carries collars 71b which transmit the operator's force mechanically to the seating-member if the power fails. In Fig. 4, the seating-member 107 of the follow-up valve is anchored to a fixed part 96 through rubber washers, the servomotor 95 being similarly anchored. The valve-member 105 is secured to a rod 103 hinged at 102 to a floating-lever 91, fulcrummed at 92 on a transmission lever 90. The lower end 93 of the floating-lever is hinged to the piston-rod 94 of the servomotor 95, and an adjustable intermediate point 115 of the floating-lever constitutes the connection to the manual linkage 114. The valve member carries collars 106 which abut against the seating and station the lever-end 102 to act as a fulcrum for direct mechanical actuation if the power fails. In this form the valve closure-elements 105 are spaced apart a slightly greater distance than the delivery ports 110 so that when not being actuated. the servopiston 101 is "vacuum-suspended" with enginesuction on both sides. When the motor is to be energized one port 110 is opened further to suction whilst the other is vented at 111. The relatively short path from the port 111 to the cylinder, through which the atmospheric air has to travel to energize the piston, makes for a more rapid response than if suction had to be supplied to one side of the cylinder through the relatively long inlet-pipe 112. The linkage shown in Fig. 4 is a compact form suitable for use with a marine reversing-gear, as well as for location in a confined space on a motor-vehicle. Specication 509,164 is referred to.