Differential pressure holding valve

Claim 2

A holding valve for controlling flow relative to a hydraulic load, comprising; housing means, discharge passage means in said housing means adapted to receive fluid from said hydraulic load, holding valve means in said discharge passage means for selectively preventing discharge flow from said hydraulic load, and means for biasing said holding valve means to a closed position, including means biasing said holding valve means to a closed position in opposition to fluid pressure in the discharge passage means and the hydraulic load, fluid pressure in said discharge passage means tends to open the holding valve, said means biasing said holding valve means to a closed position including means responsive to fluid pressure in said discharge passage means on the hydraulic load side of said holding valve means, and bypass valve means for supplying fluid to the hydraulic load.

Claim 3

A holding valve for controlling flow relative to a hydraulic load, comprising; housing means, first discharge passage in said housing means for receiving fluid from the hydraulic load, second discharge passage means in said housing means for conveying fluid from the housing means, holding valve means selectively blocking flow from said first discharge passage means to said second discharge means, fluid pressure in said first discharge passage means tends to open said holding valve means, said holding valve means being constructed to close in opposition to the force of fluid in the first discharge passage means, means biasing said holding valve means to a blocking position including means responsive to fluid pressure in said first discharge passage means, and means for selectively opening said holding valve means to provide communication between said first discharge passage means and said second discharge passage means.

Claim 4

A holding valve for controlling flow relative to a hydraulic load, comprising; housing means, first discharge passage in said housing means for receiving fluid from the hydraulic load, second discharge passage means in said housing means for conveying fluid from the housing means, holding valve means selectively blocking flow from said first discharge passage means to said second discharge means, fluid pressure in said first discharge passage means tends to open said holding valve means, said holding valve means being constructed to close in opposition to the force of fluid in the first discharge passage means, means biasing said holding valve means to a blocking position including means responsive to fluid pressure in said first discharge passage means, and means for selectively opening said holding valve means to provide communication between said first discharge passage means and said second discharge passage means.

Claim 5

A counterbalance holding valve for Controlling flow relative to a hydraulic load, comprising; housing means, first discharge passage in said housing means for recovering fluid from the hydraulic load, second discharge passage means in said housing means for conveying fluid from the housing means, counterbalance holding valve means selectively blocking flow from said first discharge passage means to said second discharge passage means, fluid pressure in said first discharge passage means tends to open said holding valve means, said holding valve being positioned to close in opposition to the force of fluid in the first discharge passage means, means biasing said counterbalance holding valve means to a blocking position including means responsive to fluid pressure in said first discharge passage means, and means for selectively opening said counterbalance holding valve means to provide communication between said first discharge passage means and said second discharge passage means.

Claim 6

A counterbalance holding valve for Controlling flow relative to a hydraulic load, comprising; housing means, first discharge passage in said housing means for recovering fluid from the hydraulic load, second discharge passage means in said housing means for conveying fluid from the housing means, counterbalance holding valve means selectively blocking flow from said first discharge passage means to said second discharge passage means, fluid pressure in said first discharge passage means tends to open said holding valve means, said holding valve being positioned to close in opposition to the force of fluid in the first discharge passage means, means biasing said counterbalance holding valve means to a blocking position including means responsive to fluid pressure in said first discharge passage means, and means for selectively opening said counterbalance holding valve means to provide communication between said first discharge passage means and said second discharge passage means.

Claim 7

A counterbalance holding valve as defined in claim 3 including spring means biasing said counterbalance holding valve means to a closed position in opposition to the force of fluid pressure in said first discharge passage means.

Claim 8

A counterbalance holding valve as defined in claim 3 including a bypass valve in said housing means coaxial with said counterbalance holding valve means for permitting flow from said second discharge passage to said first discharge passage means to pressurize the hydraulic load.

Claim 9

A holding valve as defined in claim 2 wherein said means for biasing said holding valve means to a closed position including piston means associated with said holding valve and positioned when pressurized to tend to close said holding valve means, and fluid passage means communicating said piston means with said first passage means.

Claim 10

A holding valve as defined in claim 2, including a bypass valve associated coaxially with respect to said holding valve means to permit flow from said second discharge passage means to said first discharge passage means, said bypass valve means having seat means in said housing means and a stem portion slidable in said counterbalance holding valve means.

Claim 11

A holding valve as defined in claim 2, including a bypass valve associated coaxially with respect to said holding valve means to permit flow from said second discharge pump means to said first discharge passage means, said bypass valve means having seat means in said counterbalance holding valve means.

Claim 12

A counterbalance holding valve as defined in claim 3, wherein said means biasing said holding valve means to a blocking position includes an annular peripheral piston portion on said counterbalance holding valve means, and passage means communicating with said piston portion and extending axially through said counterbalance holding valve means to said first discharge passage means.

Claim 13

A counterbalance holding valve as defined in claim 3, wherein said means biasing said holding valve means to a blocking position includes a central circular piston portion on said counterbalance holding valve means, and passage means communicating with said piston portion and extending axially through said counterbalance holding valve means to said first discharge passage means.

Claim 14

A counterbalance holding valve assembly, comprising: a housing, first passage means in said housing adapted to be connected selectively to a source of fluid under pressure or drain, second passage means in said housing adapted to be connected to one side of a fluid actuator, a valve seat in said housing communicating said first and second passage means, a valve bore in said housing coaxial with said valve seat, a counterbalance holding valve slidable in said valve bore and having a conical end portion directly engageable with said valve seat, fluid pressure in said second passage means tends to open said holding valve, said counterbalance holding valve being movable to a closed position in opposition to fluid pressure in said second passage means, piSton means on said counterbalance holding valve when pressurized tending to urge said valve to its seated position, axially extending passage means in said counterbalance holding valve communicating said piston means with said second passage means so that fluid in said second passage means tends to close the counterbalance holding valve, spring means in said valve bore urging said counterbalance valve means toward its closed position, pilot piston means on said counterbalance holding valve when pressurized opening said counterbalance holding valve against the force of fluid acting on said piston means, and bypass valve means in said valve bore permitting fluid flow from said first passage means to said second passage means to pressurize said one side of the hydraulic actuator.

Claim 15

A counterbalance holding valve assembly, comprising: a housing, first passage means in said housing adapted to be connected selectively to a source of fluid under pressure or drain, second passage means in said housing adapted to be connected to one side of a fluid actuator, a valve seat in said housing communicating said first and second passage means, a valve bore in said housing coaxial with said valve seat, a counterbalance holding valve slidable in said valve bore and having a conical end portion directly engageable with said valve seat, fluid pressure in said second passage means tends to open said holding valve, said counterbalance holding valve being movable to a closed position in opposition to fluid pressure in said second passage means, piSton means on said counterbalance holding valve when pressurized tending to urge said valve to its seated position, axially extending passage means in said counterbalance holding valve communicating said piston means with said second passage means so that fluid in said second passage means tends to close the counterbalance holding valve, spring means in said valve bore urging said counterbalance valve means toward its closed position, pilot piston means on said counterbalance holding valve when pressurized opening said counterbalance holding valve against the force of fluid acting on said piston means, and bypass valve means in said valve bore permitting fluid flow from said first passage means to said second passage means to pressurize said one side of the hydraulic actuator.

Claim 16

A holding valve for controlling flow relative to a hydraulic load, comprising; housing means, discharge passage means in said housing means adapted to receive fluid from said hydraulic load, holding valve means in said discharge passage means for selectively preventing discharge flow from said hydraulic load, and means for biasing said holding valve means to a closed position, including means biasing said holding valve means to a closed position in opposition to fluid pressure in the discharge passage means and the hydraulic load, fluid pressure in said discharge passage means tends to open the holding valve, said means biasing said holding valve means to a closed position including means responsive to fluid pressure in said discharge passage means on the hydraulic load side of said holding valve means.

Claim 17

A holding valve for controlling flow relative to a hydraulic load, comprising; housing means, discharge passage means in said housing means adapted to receive fluid from said hydraulic load, holding valve means in said discharge passage means for selectively preventing discharge flow from said hydraulic load, and means for biasing said holding valve means to a closed position, including means biasing said holding valve means to a closed position in opposition to fluid pressure in the discharge passage means and the hydraulic load, fluid pressure in said discharge passage means tends to open the holding valve, said means biasing said holding valve means to a closed position including means responsive to fluid pressure in said discharge passage means on the hydraulic load side of said holding valve means.