GB575313A - Improvements in or relating to means for controlling clutch and brake mechanism of road and like vehicles - Google Patents

Abstract

575,313. Valves. CLAYTON DEWAN DRE CO., Ltd., and EDGE, S. H. Nov. 18, 1940, No. 16613. [Class 135] [Also in Group XXXI] A pneumatic or vacuum control system comprises a reaction valve or valves operated by a single lever or pedal, pressure fluid or vacuum being utilised to react against the applied effort, and serve cylinders adapted respectively to control the clutch and brakes, the clutch being disengaged before the application of the brakes. To steer endless-track vehicles, two hand levers are provided each controlling a clutch and brake at the corresponding side of the vehicle. In the arrangement shown in Fig. 1, a lever 1 actuates a reaction valve 3 adapted to connect a brake cylinder 18 and a clutch cylinder 19 either to the atmosphere at 21 or to a compressed air pipe 14. In the position shown both cylinders are connected to the atmosphere through a valve seat 8 and a port 21, the clutch being engaged and the brakes free. When the lever 1 is actuated, it moves piston 4 to compress spring 5 and move piston 6 to the right to compress spring 7 ; movement of piston 6 closes valve seat 8 on valve 9 and thereafter moves the double valves 9 and 11 to the right to admit pressure air from pipe 14 through pipes 15 to the cylinders. A moderate air pressure in cylinder 19 disengages the clutch but the brake cylinder contains a strong spring 20 and so its action is delayed until after the clutch has been disengaged and the air pressure in cylinder 18 has increased beyond that necessary to disengage the clutch. When the lever 1 is released the brakes are completely released before the clutch is engaged. In a modification, separate reaction valves are provided for the brake and the clutch cylinder and the lever 1 acts on the brake valve through a lostmotion or delay device. In the arrangement shown in Fig. 5, the clutch is engaged by air pressure controlled by a valve 23 and the brake is controlled by a separate reaction valve 22. The valve 23 is directly connected to the operating lever 37 by a link 38, but the brake valve 22 is actuated by an arm 26 only after the clutch has been disengaged. In the normal position shown air passes from the pressure pipe 30 past valve 32 to pipe 34 and the clutch cylinder (not shown) to engage the clutch ; valve 11 is shut so that the brakes are " off." When lever 37 is rotated clockwise valve plunger 39 is moved to the left first allowing valve 32 to close to shut off the air supply to the clutch cylinder and then the plunger 39 leaves valve seat 74 to allow air to escape from the clutch cylinder to the atmosphere through pipe 34, valve 74 and port 69, thus causing the clutch to disengage. Arm 26 now acts on plunger 4 of brake valve 22 and opens valve 11 to admit air to the pipe 33 and brake cylinder (not shown) to apply the brakes. Plunger 4 acts through spring 5 on piston 6 which controls the double valve 9, 11. In the arrangement shown in Fig. 4 the hand lever 42 operates a reaction valve 43 controlling the clutch cylinder 53 and the brake cylinder 46. In the normal position shown, the brakes are released, the brake cylinder being connected to the atmosphere through the valve 43, but the clutch is engaged by air admitted from the pressure pipe 48 through pipe 49, valve 50 and pipe 52. When hand lever 42 is rotated clockwise valve 44 is opened and pressure air is admitted to pipe 45 and through pipe 51 to the space above a spring- loaded piston 57 thus depressing the latter. As the piston descends a rod 77 thereon allows a piston 56 to be depressed by its spring 76 ; this again allows a piston 55 to be depressed by its spring 85 so that (1) valve 54 is closed by its spiing 84 to shut off the air supply to pipe 52 and clutch cylinder 53, and (2) valve seat 83 on piston 55 leaves valve 82, thus connecting clutch cylinder 53 and pipe 52 to the atmosphere through ports 86, 80 to allow the clutch to be disengaged by its spring 60. Although air pressure now exists in the brake pipe 45 a strong spring 47 in brake cylinder 46 ensures that the brakes are not applied until after the clutch has been disengaged. Specification 575,314 is referred to.