Patent GB-498697-A (GB)
Title: Improvements in control devices for mechanisms operated by fluid pressure
IPC: F16H61/02
Filed: 1937-08-26
Abstract: 498,697. Fluid - actuated valves. MAYBACH - MOTORENBAU GES. Aug. 26, 1937, No. 23439. Convention date, Aug. 28, 1936. [Class 135] [Also in Group XXIV] A control device for mechanisms, such as change-speed gears, operated by fluid-pressure or vacuum, comprises a valve 21, operatively connected through slipping friction means 7 to an operating lever 1, such as a clutch, accelerator or other pedal on a'motor vehicle, the frictionally actuated part 8 having its range of movement limited by collars 9, 10 adapted to engage a fixed abutment 11, so that forward or backward movement of the lever, at any part of its range, immediately actuates the valve 21, whereafter the frictional connection slips and the lever continues its travel. The valve 21 controls the supply of fluid-pressure for operating a fluid-actuated valve 32, which closes in both end positions. The frictional connection may comprise a split bushing 7 of material having a high frictional coefficient, which bushing may be tightened by a clamping device or, in Fig. 2 (not shown), split externally conical bushings are pressed apart by a spring into engagement with an internally conical housing to cause them to contract and grip the rod 8. In the vacuum-operated change-speed control shown in Fig. 1, speeds are pre-selected by a driveroperated rotary distributing-valve 48, controlling pipes 51, leading to speed-changing cylinders, such as 116, 117, Fig. 3. The supply of suction from a pipe 30 to the inletport 46 of the distributing-valve is controlled by the valve 32, which closes in both end positions and is actuated by a piston 42 energized through a pipe 18 leading through the frictionally-actuated valve 21 to a suction inlet 17. In operation, after the driver has moved the distributing-valve 48, he presses the pedal 1, sending suction to the piston 42 which moves to the left into the position shown, compressing a spring 41 which moves the double-ended valve 32 into an intermediate open position, as shown, thereby energizing the preselected speed-changing cylinders. The valve 32 is retained against further leftward movement by a stop 67, engaging a reduced part 38 of its stem, and being carried by a spring-loaded piston 64, the underside of which is subjected to pressure in a chamber 62, communicating through a constriction 61 with the duct 46 supplying the distributing-valve. At a predetermined time after the double-ended valve 32 has opened the duct 46 to suction, the suction builds up in the chamber 62 sufficient to retract the stop 67, permitting the spring 41 to complete the leftward movement of the valve 32 which cuts off the suction from the distributing-valve 48 and chamber 62. Leakage around the piston 64 soon dissipates the suction in the chamber 62. At the commencement of the release movement of the pedal 1, a spring 22 closes the valve 21 and opens the pipe 18 to atmosphere at 16. Springs 35 and 41 thereupon move the double-ended valve 32 and piston 42 to the right, the former being arrested by the stop 67 in an intermediate position in which suction is again supplied to the distributing-valve 48 and chamber 62, to effect another speed-change if the distributing-valve has been altered. After a predetermined interval, the stop 67 is again withdrawn and the valve 32 completes its rightward movement, cutting off the suction. In Fig. 3, the main-clutch is operated by a vacuum-motor 121, the supply-pipe 122 of which either leads directly to the doubleended valve 118, corresponding to the valve 32, Fig. 1, or as shown, is connected to the speed-changing distributing-valve 48 so that the clutch-motor 121 is rendered inoperative in one or more positions of the distributing- valve. The manual clutch-pedal 1, which is connected with lost-motion 123 to the clutchmotor 121, actuates the executive valve 21 through a slipping frictional connection 75, but is rendered ineffective for opening the valve 21, unless the accelerator pedal 106 has first been released. For this purpose the frictionally moved rod 8 actuates the valve 21 through a rockshaft 86 and a spring-loaded lever 101, which is retracted away from the valve 21 during the time the acceleratorpedal is depressed. A suction-reservoir 114 is provided.