Patent GB-964147-A (GB)
Title: Fluid pressure motor mechanism
IPC: B60T13/14
Filed: 1962-12-10
Abstract: 964,147. Fluid-pressure brakes. KELSEYHAYES CO. Dec. 10, 1962 [Dec. 8, 1961; Dec. 26, 1961], No. 46458/62. Headings F2E and F2F. A fluid pressure servomotor, e.g. for applying a brake, comprises a pressure-responsive unit which is moved by fluid pressure under control of a valve structure, and a pedal lever assembly which is connectible both with a valve element of the valve structure and through lostmotion linkage with a manual operating member acting directly on the pressure-responsive unit, and means is provided which is automatically operative upon failure in the fluid supply to move the pedal lever from its normal inoperative position to a different inoperative position in which it is movable to operate the manual operating member without moving the valve element. As shown, a brake master cylinder 14 contains a piston 15 which is operated via a sleeve portion 40 by a diaphragm unit consisting of rolling diaphragm 30 and piston member 28 arranged in a two-part housing 11, 25, whenever compressed air is fed to chamber 55 from a source 67 by way of the valve structure. The valve structure comprises a housing part 60 integral with housing part 25 of the servomotor, a housing part 80 secured to the former, a plug 61 in the part 60 providing a seat for an inlet valve 63 normally closed by a spring 77, an operating member 85 carrying a seat member 86 co-operating with an exhaust valve 76 which is secured to the inlet valve, the valve 76 being normally open to communicate with the atmosphere by passage 75 and hole 78, and a diaphragm 82 engaged by a presser member 87 urged by a spring 88, the member 87 being normally spaced from a cushioned abutment shoulder on the member 85 so that " feel " is transmitted back to member 85 in two stages as pressure builds up in the outlet chamber 71 of the valve, which is connected via port 70 with chamber 55. The operating member 85 extends through an opening in a fire wall 95 of a vehicle, to which the housing part 25 is bolted, and is positioned for abutment by a resilient buffer 120 carried by a slide structure 108 which surrounds and is guided for longitudinal sliding on a pedal lever 100 pivoted at 101 to a bracket 103 secured to wall 95. Slots 127 are provided on opposite sides of the structure 108 to guide, with some free transverse play, a pin 136 passed through the slots 127 and through a slot 126 in the pedal lever, and arranged between the forked ends of a link 45 which is connected at 44 to a plunger 36 slidable in the housing part 25 and acting via a cushion 38 directly on the piston 28 of the pressure-responsive unit. A torsion spring 114 has one arm 115 acting against bracket 103 and the other arm 116 acting on the structure 108 to bias it downwardly. The action of the spring is opposed by a piston in a cylinder 140 secured to the pedal lever 100 and connected directly to the source 67. As a result the buffer 120 is normally positioned opposite the end of the operating member 85 and pin 136 is located at the bottoms of the slots 127. In this position the pedal 105, Fig. 2, is set in the chain-line position near the toe board of the vehicle, i.e. about the same height as the accelerator pedal for ease of operation, and movement of the pedal operates the valve structure in known manner, the valves being self-lapping to regulate the pressure in chamber 55. The free play of pin 136 in slots 127 prevent the small movements of the pedal being transmitted to the plunger 36. Should pressure at the source 67 fail, spring 114, together with another spring (Fig. 3, not shown) within the cylinder 140, urges the structure 108 downwardly until a limit position is reached in which buffer 120 is below the level of operating member 85, this movement causing a cam action of the slots 127 on the pin 136 so that lever 100 is swung away from the firewall 95 to the full-line position of Fig. 2 and pin 136 is lodged in part 129 of the slots 127. Pedal travel and mechanical advantage between the pedal and link 45 are thus increased and braking is effected manually by action of link 45 to urge plunger 36 against cushion 38 of piston 28.