Patent GB-458693-A (GB)
Abstract: 458,693. Controlling change - speed gearing. MAYBACH - MOTORENBAU GES., Friedrichshafen, Bodensee, Germany. July 22, 1935, No. 20836. Convention date, Aug. 8, 1934. [Class 80 (ii)] Relates to servo-pneumatic controlling-means for change-speed gearing, especially of vehicles in which there is a selector distributer of pressure air such as 55, Fig. 1, and in which the executive stroke in the selected servo cylinder is effected by depressing or by releasing the accelerator 5, by one or the other indifferently according to whether the vehicle is at rest or in motion, as described in Specification 458,694. There is a two-position connector valve 19, Fig. 1, or 97, Fig. 2, which must be set by the selector before the accelerator stroke can have any speedchanging effect. There are a number of ducts 45, Fig. 1, leading to servo cylinders, not shown, and according to the selective operation by the selector 55 of one of a set of valves 42, pressure air (or suction) is admitted from a reservoir 1 eventually to the selected duct 45. In order that pressure air may reach the passage 43 of a valve 42 which has been selected and moved left, a master valve 37 has to be opened. This is done by a push rod 31 when pressure air is admitted at 28 to the left of a piston 30. The air reaches the passage 28 as a waist 17 in a poppet valve 16 passes over a passage 27 one way or the other indifferently as to whether it is caused by a depression or a release of the accelerator pedal 5. In order for the air to reach the waist 17 it must have reached a space 25 and it can reach the space 25 from a duct 3 only when the connector valve 19 has been moved to its position at left by a cam disc 51 on the same spindle 54 as the selector 55 and operated by a selector handle 53. The valve 19 is locked by a coned plunger 24 in either of its two end positions, and it must be in its position at left before the accelerator can effect a change. After a change, the two-position valve 19 is restored to its position at right in readiness for another change by pressure air percolating past a constriction 50 from a space 39 beyond the master valve 37 and through a duct 49 to a space 48 on the left of the valve 19. Air reaches the executive servo cylinder from a main duct 2 when the master valve 37 has been opened. The invention is applicable especially to change-speed gearing having claw clutches with repelling teeth as described in Specification 298,186, [Class 80 (ii)], with which a main or engine clutch is not required. In the arrangement of Fig. 2, the necessary setting of the two-position valve 97 is effected by pressure air admitted by a pipe 71 when a stop valve 69 is opened by the act of setting a preselector distributer valve 81 from a hand wheel 66. When the stop valve 69 is opened, air in a pipe 88 leading from a reservoir 1 is admitted under the two-position valve 97 which shoots to its upper locked position in which a through duct 98 connects a space 150 under the master valve 93 and connected to a pressure pipe 2 to a duct 115 leading to a waisted valve 112. Thus when the accelerator 109 is depressed, a stop valve 94 is opened so that air in a pipe 92 passes to above the waisted valve 112. As this valve 112 shoots down, when the waist 114 passes the pressure duct 115, air shoots across to a chamber 130 above a piston 110. The piston 110 descending opens the master valve 93 so that pressure air from the space 150 passes along a duct 131 and down a pipe 87 to a space 89 above distributer 81 which sends it selectively through pipes 82, 83, 84, 85 to the servo cylinders of the executive control. As long as the accelerator 109 is kept depressed with the throttle 125 open, the slide valve 112 is held depressed and the master valve 93 is not opened. But when the accelerator 109 is released, and provided the two-position valve 97 has been lifted in consequence of a preselector turning of the manual shaft 64, then the pin valve 106 falls, the stop valve 94 closes, the waisted valve 112 is shot upwards by its spring 134, and as the waist 114 passes the pressure duct 115, pressure air passes to the space 130, the piston 110 is depressed as before, and the master valve 93 opened admitting executive air through the pipe 87 to the selector distributing valve 81. Another slide valve 75 operated from the manual selector 64 controls the passage of air down a pipe 78 to disconnect the engine clutch. In the arrangement shown, there is a four-speed gear in a casing 123 with two pairs of clutches with repelling teeth. On making a speed change and as long as the repelling condition lasts, pressure air is admitted to a duct 122 and opens the throttle 125 to accelerate the driving-shaft of the gearing, as described in Specification 369,864, to facilitate the change. This pressure air in a pipe 121 raises a further waisted valve 118 so that air from the duct 131 passes by a duct 117 to the space 130 and so holds the master valve 93 open. Pressure air also passes down a pipe 77 and thrusts a valve 74 and the piston 75 left so that the manual control shaft 64 is locked against movement until the ratcheting of the clutch teeth has ended and the speed change has been completed. U.S.A. Specification 1,883,743 also is referred to.