GB1112404A - Fluid operable braking system - Google Patents

Abstract

1,112,404. Fluid-pressure brakes. COMPAGNIE DES FREINS ET SIGNAUX WEST INGHOUSE. 15 Sept., 1966 [16 Sept., 1965], No.41182/66. Heading F2F. In a compressed-air braking system for a road vehicle of the kind which includes locking rollers 12 which are engageable with piston-rod 15 of an actuator cylinder 6, under the action of spring 14, and are releasable by a piston 13 when compressed air is supplied to a chamber 1 11bis, an emergency/park control valve 8 is provided, operable manually by a handle 16 adapted to rotate a cover 41, Fig. 4A, about an axis 19 to control, through mating camming members 42, 47, the calibration of a spring 49 controlling a self-lapping valve assembly 48, 50 feeding air to emergency chamber 10bis and, in addition, to control, in the park position, beyond the range in which the calibration of spring 49 is varied, a further valve assembly 56, 57 so as to cut off the supply of air to the chamber 1 11bis, the arrangement being such that when the handle 16 is moved from the park position to the range in which air is supplied to the chamber 11bis to release the locking rollers and a controlled air pressure is supplied to the chamber 10bis, the pressure supplied to the chamber 10bis is initially higher than that which obtained at the time the locking rollers were engaged by movement of the handle 16 into the park position. For this purpose, the cam 42 has a special profile (Fig. 4c, not shown), such that the compression of the spring 49 controlling the self-lapping valve assembly 48, 50 reaches a maximum before the point at which handle 16 enters the park position and then falls to a lower value, causing a reduction of pressure in the chamber 10bis on reaching this point. The locking rollers 12 are thus applied to the piston-rod 15 when a pressure less than the maximum pressure is present in the chamber 10bis and, conversely, when the handle 16 is returned to the emergency braking range, the pressure in the chamber 10bis is temporarily increased to assist release of the locking rollers by re-application of pressure to the chamber 11bis. Handle 16 is slidable along a rod 43 against the action of a spring and must be thus pulled out to enable a flange 44 to clear the end of a guide 69 before movement to and from the park position can be effected. The valve 56, 57 is controlled via a plunger 65 by a cam surface 68 on the cover 41. It is also independently controllable by pressure in a service brake line 7 which is arranged to act on a piston 55 integral with valve member 56, in addition to its acting in a service chamber 4bis of the actuator cylinder 6. separated from the emergency chamber 10bis by one of two pistons (24, 26, Fig. 2, not shown) acting on the rod 15. A non-return valve 61 bypassed by a calibrated orifice 63 causes release of air from the chamber 10bis to be effected gradually when handle 16 is in the park position.