GB1366898A - Control valves for controlling the hydraulic brake of a trailer vehicle - Google Patents

Abstract

1366898 Tractor/trailer control valves; valves DEERE & CO 2 Sept 1971 [2 Sept 1970] 40979/71 Headings F2F and F2V An hydraulic control valve for trailer brakes, actuated by a tractor system, comprises a spool with a throttle duct therethrough, movable in a bore towards a main return duct at one bore end, allowing fluid to flow from a port connected to a pressure source to a trailer brake part, a pressure acting on the spool due to the movement to bias it toward the other bore end, at which the spool either allows communication through its throttle duct between the brake port and the main return duct, or allows communication between the brake port and a further return duct. Fig. 3 indicates a valve having a tractor brake inlet 25, a port 26 communicating with hydraulic load devices, e.g. lift motors, on the tractor, the trailer brake part 27 and the main return duct 32 to a reservoir. Upon tractor brake actuation, the spool 22, 23 moves leftwardly against spring washers and allows flow from the port 26 through the throttle duct 28 in the spool to the trailer port 27. A bleed passage 30, 31 leads from the port 27 to the reservoir for brake release. Fig. 4 shows a construction wherein when the tractor brakes are not applied, fluid flows freely from the power inlet 40 to the further return duct 41 leading to load devices. Upon tractor brake application the spool 35, 36 moves upwardly and reduces this flow by a face 42, thus increasing fluid pressure to the trailer brake part 43. A bleed passage system comprising the throttle duct 46, 36 in the spool and throttle passages 54, 55, 52, 53 which are adjustable, lead to a reservoir through the main return duct. The hydraulic tractor system is fed by a pump in both embodiments and the trailer brakes are applied by a pedal operated actuator.