Counterbalance valve

Claim 2

A counterbalance holding valve assembly comprising: passage means defining a fluid flow path, a check valve member in said passage means for blocking flow in one direction therein, pilot-operated means for opening said valve member, valve means in said passage means for maintaining the pressure drop across the valve member substantially constant, and means responsive to the pressure drop across the valve member for controlling said valve means.

Claim 3

A counterbalance holding valve assembly comprising: passage means defining a fluid flow path, a check valve member in said passage means for blocking flow in one direction therein, pilot-operated means for opening said valve member, and throttling valve means for maintaining the flow across said valve member substantially constant, said throttling valve being responsive to the pressure drop across the valve member.

Claim 4

A counterbalance holding valve assembly comprising: passage means defining a fluid flow path, a check valve member in said passage means for blocking flow in one direction therein, pilot-operated means for opening said valve member, and throttling valve means for maintaining the flow across said valve member substantially constant, said throttling valve being responsive to the pressure drop across the valve member.

Claim 5

A counterbalance holding valve comprising: passage means defining a fluid flow path, a pilot-operated check valve in said passage means for selectively blocking flow in one direction through said passage means, said valve defining a fixed orifice when the valve is open, and means for controlling the pressure drop across the valve including a throttling valve in said passage means upstream of said pilot-operated valve, said throttling valve being responsive to the pressure drop across the orifice and providing an increased restriction to flow in said passage means in response to an increase in flow in said passage means to maintain a constant flow across said orifice valve.

Claim 6

A counterbalance holding valve comprising: passage means defining a fluid flow path, a pilot-operated check valve in said passage means for selectively blocking flow in one direction through said passage means, said valve defining a fixed orifice when the valve is open, and means for controlling the pressure drop across the valve including a throttling valve in said passage means upstream of said pilot-operated valve, said throttling valve being responsive to the pressure drop across the orifice and providing an increased restriction to flow in said passage means in response to an increase in flow in said passage means to maintain a constant flow across said orifice valve.

Claim 7

A counterbalance holding valve according to claim 3, wherein said throttling valve maintains a substantially constant pressure drop across said orifice.

Claim 8

A counterbalance holding valve according to claim 3, wherein said pilot-operated valve includes a pilot piston and a fluid chamber for moving said piston when pressurized, second passage means for selectively delivering fluid under pressure, said pilot chamber being connected to be pressurized by fluid in said second passage means.

Claim 9

A counterbalance holding valve comprising: passage means defining a fluid flow path, a pilot-operated valve in said passage means for selectively blocking fluid flow through said passage means, said valve defining a fixed orifice when the valve is open, a throttling valve in said passage means upstream of said pilot-operated valve, said throttling valve being responsive to the pressure drop across the orifice and providing an increased restriction to flow in said passage means in response to an increase in pressure drop across the orifice, said throttling valve including a generally cylindrical piston having a first fluid chamber on one side thereof and a second fluid chamber on the other side thereof, means communicating the first fluid chamber with one side of said orifice, and said second fluid chamber with the other side of said orifice.

Claim 10

A counterbalance holding valve comprising: passage means defining a fluid flow path, a pilot-operated valve in said passage means for selectively blocking fluid flow through said passage means, said valve defining a fixed orifice when the valve is open, a throttling valve in said passage means upstream of said pilot-operated valve, said throttling valve being responsive to the pressure drop across the orifice and providing an increased restriction to flow in said passage means in response to an increase in pressure drop across the orifice, said throttling valve including a generally cylindrical piston having a first fluid chamber on one side thereof and a second fluid chamber on the other side thereof, means communicating the first fluid chamber with one side of said orifice, and said second fluid chamber with the other side of said orifice.

Claim 11

A counterbalance holding valve according to claim 6 including a spring in said first chamber biasing said cylindrical piston to a position of minimum restriction.

Claim 12

A counterbalance holding valve comprising: passage means defining a fluid flow path, a pilot-operated valve in said passage means for selectively blocking fluid flow through said passage means, said valve defining a fixed orifice when the valve is open, a throttling valve in said passage means upstream of said pilot-operated valve, said throttling valve being responsive to the pressure drop across the orifice and providing an increased restriction to flow in said passage means in response to an increased restriction to flow in said passage means in response to an increase in pressure drop across the orifice, said throttling valve including a generally cylindrical piston having a first fluid chamber on one side thereof and a second fluid chamber on the other side thereof, means communicating the first fluid chamber with one side of said orifice, and said second fluid chamber with the other side of said orifice, said means communicating said first chamber with said one side of said orifice including a passage, a second pilot-operated check valve in said passage for blocking flow from said first chamber when the first pilot-operated valve in said passage means is blocking flow through said passage means.

Claim 13

A counterbalance holding valve comprising: passage means defining a fluid flow path, a pilot-operated valve in said passage means for selectively blocking fluid flow through said passage means, said valve defining a fixed orifice when the valve is open, a throttling valve in said passage means upstream of said pilot-operated valve, said throttling valve being responsive to the pressure drop across the orifice and providing an increased restriction to flow in said passage means in response to an increased restriction to flow in said passage means in response to an increase in pressure drop across the orifice, said throttling valve including a generally cylindrical piston having a first fluid chamber on one side thereof and a second fluid chamber on the other side thereof, means communicating the first fluid chamber with one side of said orifice, and said second fluid chamber with the other side of said orifice, said means communicating said first chamber with said one side of said orifice including a passage, a second pilot-operated check valve in said passage for blocking flow from said first chamber when the first pilot-operated valve in said passage means is blocking flow through said passage means.

Claim 14

A counterbalance holding valve according to claim 8, including second passage means for delivering hydraulic fluid, said first and second pilot-operated check valves being connected to be actuated by fluid pressure in said second passage means.

Claim 15

A counterbalance holding valve assembly comprising: first passage means defining a first hydraulic fluid flow path, second passage means defining a second hydraulic fluid flow path, a pilot-operated check valve in said first passage means, said pilot-operated check valve opening in response to fluid under pressure in the first passage means, said pilot-operated check valve opening in response to fluid under pressure in said second passage means and defining a fixed orifice, said check valve closing blocking flow when fluid is not delivered to either said first and second passage means, a compensator valve in said passage means axially aligned with said check valve for throttling flow through said orifice, said compensator valve being responsive to the pressure drop across said orifice to throttle flow through said first passage means and maintaining a constant flow through said orifice, spring means biasing said compensator valve in a direction providing minimum restriction to flow in said first passage means, said compensator valve including a cylindrical piston having first and second actuating chambers on the opposite sides thereof, said first chamber communicating with the downstream return side of said orifice, a second pilot-operated check valve in said first passage means, said second check valve being pilot-operated to an open position in response to fluid pressure delivered through said second passage means, said second pilot-operated check valve closing and preventing flow from said second actuating chamber when neither of said first or second passage means are delivering fluid, said second check valve opening when the first passage means is delivering fluid and thereby pressurizing said second actuating chamber and placing the compensator valve in a position of minimum restriction.

Claim 16

A counterbalance holding valve assembly comprising: first passage means defining a first hydraulic fluid flow path, second passage means defining a second hydraulic fluid flow path, a pilot-operated check valve in said first passage means, said pilot-operated check valve opening in response to fluid under pressure in the first passage means, said pilot-operated check valve opening in response to fluid under pressure in said second passage means and defining a fixed orifice, said check valve closing blocking flow when fluid is not delivered to either said first and second passage means, a compensator valve in said passage means axially aligned with said check valve for throttling flow through said orifice, said compensator valve being responsive to the pressure drop across said orifice to throttle flow through said first passage means and maintaining a constant flow through said orifice, spring means biasing said compensator valve in a direction providing minimum restriction to flow in said first passage means, said compensator valve including a cylindrical piston having first and second actuating chambers on the opposite sides thereof, said first chamber communicating with the downstream return side of said orifice, a second pilot-operated check valve in said first passage means, said second check valve being pilot-operated to an open position in response to fluid pressure delivered through said second passage means, said second pilot-operated check valve closing and preventing flow from said second actuating chamber when neither of said first or second passage means are delivering fluid, said second check valve opening when the first passage means is delivering fluid and thereby pressurizing said second actuating chamber and placing the compensator valve in a position of minimum restriction.