US 5,179,835 AGranted

Brake valve for use in load sensing hydraulic system

AssigneeEaton Corporation

InventorsTodd A. Casey, Alan D. Jackson

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Abstract

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.

Claims10

Dependent claims

A brake valve for use in a hydraulic system of the type including a source of pressurized fluid, and means operable to very the fluid output of the source in response to a system load signal;

a priority hydraulic circuit connected to receive pressurized fluid from the source, in parallel with said brake valve, the priority hydraulic circuit including means operable to generate a priority load signal representative of the demand for fluid by the priority hydraulic circuit;
and brake valve being of the type including housing means defining a fluid inlet port adapted to be connected to the source of pressurized fluid, a work port adapted to be connected to a fluid pressure operated brake actuator, a return port adapted to be connected to a system reservoir, and a valve bore interconnecting said fluid inlet port, said work port, and said return port;
a valve spool reciprocable in said valve bore and having an end extending outside said housing means for forcible, manual reciprocation of said valve spool;
said valve spool having a neutral position blocking fluid communication from said fluid inlet port to said work port, a power brake position permitting fluid communication from said inlet port to said workport, and a manual brake position in which a piston assembly is operable to generate fluid pressure at said work port, in response to movement of said valve spool, and in the absence of pressurized fluid at said fluid port;
characterized by:
(a) said housing means defines a brake load signal chamber adapted to be connected to the system load signal;
(b) said valve spool, in said neutral position, blocks fluid communication between said work port and said brake load signal chamber, and permits fluid communication between said brake load signal chamber and said return port;
(c) said valve spool, in said power brake position, blocks fluid communication between said brake load signal chamber and said return port, and permits fluid communication between said work port and said brake load signal chamber;
and
(d) said valve spool, in said manual brake position, blocks fluid communication between said work port and said brake load signal chamber.

7 more elements

A brake valve for use in a hydraulic system of the type including a source of pressurized fluid;

said brake valve being of the type including housing means defining a fluid inlet port adapted to be connected to the source of pressurized fluid, a work port adapted to be connected to a fluid pressure operated brake actuator, a return port adapted to be connected to a system reservoir, and a valve bore interconnecting said fluid inlet port, said work port, and said return port;
a valve spool reciprocable in said valve bore and having an end extending outside said housing means for forcible, manual reciprocation of said valve spool;
said valve spool having a neutral position blocking fluid communication from said fluid inlet port to said work port, a power brake position permitting fluid communication from said inlet port to said work port, and a manual brake position in which a first piston member axially movable in a first piston bore is operable to generate fluid pressure at said work port, in response to movement of said valve spool, and in the absence of pressurized fluid at said fluid inlet port;
characterized by:
(a) said housing means defining a second relatively larger piston bore in fluid communication with said first piston bore when said valve spool is in said neutral position;
(b) a second, relatively larger piston member being axially movable in said second piston bore;
(c) means operably associated with said valve spool to cause movement of said second piston member, in response to movement of said valve spool toward said manual brake position, thereby displacing fluid from said second piston bore to said first piston bore.

4 more elements

Dependencies are inferred from the claim text.