GB1196691A - Improvements in or relating to Gear Change Mechanisms. - Google Patents

Abstract

1,196,691. Change-speed gear control. CLAYTON DEWANDRE CO. Ltd. 23 Jan., 1969 [26 Jan., 1968], No. 4175/68. Heading F2D. In a pneumatic shift mechanism for a motor vehicle change-speed gear (not shown) affording five forward speeds and reverse, comprising a universally mounted shift-lever 12 guided in a slotted gate 13 of a remote valve housing 11 (Fig. 1, not shown) to actuate a series of pneumatic ratio shift control valves A to O (Figs. 2 and 3), wherein a shifter arm 80 is turned angularly by a double-acting pneumatic servomotor C, D (Fig. 6) to engage one of three shift rods and is moved bodily by a similar motor A, B (Fig. 5) arranged at right-angles to the motor C, D, both motors being in a common.housing (60) (Fig. 4, not shown) secured to the gear-box, to move the engaged rod to establish the selected gear, the whole system is pressurized when the lever 12 is in the central neutral gear position (Fig. 1) from a pneumatic source, such that movement of the shift lever 12 to a gear selecting position exhausts one or other side of the servomotors C, D and A, B whereby the pressure remaining in the other sides of the servomotors first selects then establishes the appropriate gear and maintains the shift lever in the selected gear position. Each of the four control valves, formed in opposed pairs A, B and C, D and arranged at right angles (Fig. 1), is spring biased inwardly into contact with ends 21, 58 of the universally movable shift-lever 12 and is formed in two parts 23, 25 (Fig. 2) spring loaded at 26 to close its integral valve seat 27 such that in neutral the servomotors A to D are pressurized via ducts 31, 32 adjacent the appropriate valves A to D in the valve housing 11, and fluid lines (not shown) connected to the appropriate ports 64 &c of the servomotors. Movement of the shift lever for gear selection of first and reverse, or, fourth and fifth, moves one or other valves 41, 56 (Fig. 3) outwardly to initially seat at 59 the inner valve member 49 to close the pressure source, further movement of the outer valve member 41 opening the valve seat 46 whereby the circuit pressure of servomotor C or D is exhausted via valve ports 54 and ducts 55 to atmosphere and the pressurised servomotor D or C appropriately moves the selector 80 via arms 90, 89. Gear establishment is then similarly effected by corresponding movement of the lever 12 at right angles to operate the similar valves 23, 37 in the valve housing A, B (Fig. 2) directly connected in similar fashion to the servomotors A, B (Fig. 5). The servomotors (Figs. 6 and 5) are constructed with one of each pair of pistons, for example 91 (Fig. 6), formed with a differential land permanently connected via a duct 99 to the pressure source, each pair of pistons 91, 85 having a sliding pin and bush 79, 89 lost motion connection. When first gear is selected and the servomotor C exhausted, servomotor D moves, i.e. rocks the selector to the right as shown. Selection of second and third gear through neutral is effected by centering the shift lever 12 to re-pressurize servo C to centrally return the selector by the additional differential pressure at 99 in servo D, the piston 85 in servo C seating on the casing. For selection of fourth and fifth gear, the servo D is exhausted, the piston 91 being moved leftwards solely by the differential pressure at 99, moving the selector 80 via the connected arms 90, 89 the latter of which slides via the lost motion connection on the spindle 79 of the piston 85 retained against its seating in the servo cylinder C. The gear establishing servomotors A, B (Fig. 5) are of the same construction and are similarly operated for forward and backward movement of the shift rods. A clutch interlock 101 prevents gear engagement until the vehicle's clutch pedal is depressed, and a reverse gear safety catch is released by lifting a sleeve 6 surrounding the lever 12 clear of a gate boss 7.