Brake valve for use in load sensing hydraulic system

• Main Authors: JACKSON; ALAN D, CASEY; TODD A
• Format: Patent
• Language: English
• Published: 19.01.1993
• Subjects: ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS; MOTOR VEHICLES; PERFORMING OPERATIONS; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OFVEHICLES; TRAILERS; TRANSPORTING; VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES; VEHICLES IN GENERAL

A brake valve (45) is disclosed of the type which permits communication from a source (11) of pressurized fluid to a brake actuator (47) in response to manual movement of a valve spool (57) from a neutral position (FIG. 2) to a power brake position (FIG. 5). In the power brake position, the valve spool permits fluid communication between a work port (53), which communicates with a brake actuator, and a brake load signal chamber (87), the brake load signal controlling the fluid output of the source. As the valve spool moves toward a manual brake position (FIG. 6) communication between the work port and the brake load signal chamber is blocked. In the manual brake position, movement of the valve spool causes a large piston (63) to displace fluid from its piston bore (73) into a piston bore (75) in which is disposed a small piston (61), the small piston being operable in response to movement of the valve spool to build brake pressure in the work port (53). A relief valve arrangement (137,139,141) relieves fluid pressure in the larger piston bore (73) to limit the manual force required to move the valve spool and the pistons.