Load control and holding valve

Claim 2

A valve assembly comprising a body having a stepped bore terminating at its small end in a valve seat and a valve port for connection to a directional control valve, said body having a motor port and a pilot port leading to different diameter portions of said bore and adapted to be connected to the respective ports of a double acting fluid motor; a counterbalance valve member movable in said bore into and out of engagement with said seat and defining with said bore first and second annular areas which are exposed to fluid pressure in said motor and pilot ports respectively; spring means biasing said valve member into engagement with said seat to prevent flow of fluid from said motor port to said valve port except when fluid pressure in said motor port due to thermal expansion of the fluid or to motor load inertia or shock is of magnitude sufficient to overcome the bias of said spring means thus to move said valve member out of engagement with said seat for relief of excess pressure through said motor and valve ports and except when fluid pressure in said pilot port from the pressure side of the fluid motor is of magnitude sufficient to overcome the bias of said spring means thus to permit return flow of fluid from the motor through said motor and valve ports; and a check valve member movable in said counterbalance valve member to permit flow of fluid in the opposite direction from said valve port to said motor port.

Claim 3

The valve assembly of claim 1 wherein said counterbalance valve member is moved out of engagement with said seat by the conjoint effect of motor load pressure and pilot pressure respectively acting on said first and second annular areas.

Claim 4

The valve assembly of claim 1 wherein said second annular area is larger than said first annular area.

Claim 5

The valve assembly of claim 1 wherein said counterbalance valve member is tubular at its small end and has an internal seat for said check valve member and a passage through the wall thereof for communicating said valve and motor ports with each other when said check valve member is moved away from said internal seat.

Claim 6

A valve assembly comprising a body having a bore terminating at one end in a valve seat and a valve port for connection to a directional control valve, said body having a motor port and a pilot port leading to axially spaced-apart portions of said bore and adapted to be connected to the respective ports of a double acting fluid motor; a counterbalance valve member movable in said bore into and out of engagement with said seat and defining with said bore first and second annular areas which are exposed to fluid pressure in said motor and pilot ports respectively; spring means biasing said valve member in engagement with said seat to prevent flow of fluid from said motor port to said valve port except when fluid pressure in said motor port due to thermal expansion of the fluid or to motor load inertia or shock is of magnitude sufficient to overcome the bias of said spring means thus to move said valve member out of engagement with said seat for relief of excess pressure through said motor and valve ports and except when fluid pressure in said pilot port from the pressure side of the fluid motor is of magnitude sufficient to overcome the bias of said spring means thus to permit return flow of fluid from the motor through said motor and valve ports; and a check valve member movable in said counterbalance valve member to permit flow of fluid in the opposite direction from said valve port to said motor port.

Claim 7

A valve assembly comprising a body having a bore terminating at one end in a valve seat and a valve port for connection to a directional control valve, said body having a motor port and a pilot port leading to axially spaced-apart portions of said bore and adapted to be connected to the respective ports of a double acting fluid motor; a counterbalance valve member movable in said bore into and out of engagement with said seat and defining with said bore first and second annular areas which are exposed to fluid pressure in said motor and pilot ports respectively; spring means biasing said valve member in engagement with said seat to prevent flow of fluid from said motor port to said valve port except when fluid pressure in said motor port due to thermal expansion of the fluid or to motor load inertia or shock is of magnitude sufficient to overcome the bias of said spring means thus to move said valve member out of engagement with said seat for relief of excess pressure through said motor and valve ports and except when fluid pressure in said pilot port from the pressure side of the fluid motor is of magnitude sufficient to overcome the bias of said spring means thus to permit return flow of fluid from the motor through said motor and valve ports; and a check valve member movable in said counterbalance valve member to permit flow of fluid in the opposite direction from said valve port to said motor port.

Claim 8

The valve assembly of claim 5 wherein said body has cap means closing the other end of said bore; and wherein said cap means has adjusting screw means bearing on said spring means to vary the overload pressure in said motor port and the pilot pressure in said pilot port at which said counterbalance valve member is moved out of engagement with said seat.

Claim 9

A valve assembly comprising a body having a stepped bore terminating at its small end iN a valve seat and a valve port for connection to a directional control valve, said body having a motor port and a pilot port leading to different diameter portions of said bore and adapted to be connected to the respective ports of a double acting fluid motor and having closure means at the large end of said bore; a counterbalance valve member movable in said bore into and out of engagement with said seat and defining with said bore first and second annular areas which are exposed to fluid pressure in said motor and pilot ports respectively, and defining with the large end of said bore and closure means a chamber which is in fluid communication with said valve port; spring means in said chamber biasing said valve member into engagement with said seat to prevent flow of fluid from said motor port to said valve port except when fluid pressure in said motor port due to thermal expansion of the fluid or to motor load inertia or shock is of magnitude sufficient to overcome the bias of said spring means thus to move said valve member out of engagement with said seat for relief of excess pressure through said motor and valve ports and except when the fluid pressure in said pilot port from the pressure side of the fluid motor is of magnitude sufficient to overcome the bias of said spring means thus to permit return flow of fluid from the motor through said motor and valve ports; and a check valve member movable in said counterbalance valve member to permit flow of fluid in the opposite direction from said valve port to said motor port.

Claim 10

A valve assembly comprising a body having a stepped bore terminating at its small end iN a valve seat and a valve port for connection to a directional control valve, said body having a motor port and a pilot port leading to different diameter portions of said bore and adapted to be connected to the respective ports of a double acting fluid motor and having closure means at the large end of said bore; a counterbalance valve member movable in said bore into and out of engagement with said seat and defining with said bore first and second annular areas which are exposed to fluid pressure in said motor and pilot ports respectively, and defining with the large end of said bore and closure means a chamber which is in fluid communication with said valve port; spring means in said chamber biasing said valve member into engagement with said seat to prevent flow of fluid from said motor port to said valve port except when fluid pressure in said motor port due to thermal expansion of the fluid or to motor load inertia or shock is of magnitude sufficient to overcome the bias of said spring means thus to move said valve member out of engagement with said seat for relief of excess pressure through said motor and valve ports and except when the fluid pressure in said pilot port from the pressure side of the fluid motor is of magnitude sufficient to overcome the bias of said spring means thus to permit return flow of fluid from the motor through said motor and valve ports; and a check valve member movable in said counterbalance valve member to permit flow of fluid in the opposite direction from said valve port to said motor port.

Claim 11

The valve assembly of claim 7 wherein said counterbalance valve member has tubular end portions with partition means therebetween; said check valve member being located in the small end of said counterbalance valve member to engage an internal seat therein; and wherein another spring means between said check valve member and said partition means biases the former into engagement with said internal seat.

Claim 12

The valve assembly of claim 8 wherein said spring means for biasing said counterbalance valve member extends into the large tubular end portion to bear on said counterbalance valve member; and wherein said closure means has adjusting screw means bearing on said spring means for varying the degree of biasing of said counterbalance valve member.

Claim 13

A valve assembly comprising a body having a stepped bore terminating at its small end in a valve seat and a valve port for connection to a directional control valve, said body having a motor port and a pilot port leading to different diameter portions of said bore and adapted to be connected to the respective ports of a double acting fluid motor; a stepped counterbalance valve member in said bore spring biased into engagement with said seat to prevent return flow of fluid from said motor port to said valve port; said valve member having a first relatively small annular area defined between said valve seat and a first enlargement of said bore which is exposed to fluid pressure in said motor port, whereby fluid pressure of relatively large magnitude due to thermal expansion of the fluid or to motor load inertia or shock will overcome the spring bias to move said valve member away from said seat for relief of excess pressure through said motor and valve ports, and a second relatively large annular area defined between said first enlargement of said bore and a second enlargement thereof which is exposed to fluid pressure in said pilot port whereby fluid pressure in said pilot port of relatively low magnitude will overcome the spring bias to move said valve member as aforesaid for return flow of fluid from the motor through said motor and valve ports; and a check valve member movable in said counterbalance valve member to permit flow of fluid in the opposite direction from said valve port to said motor port.

Claim 14

A valve assembly comprising a body having a stepped bore terminating at its small end in a valve seat and a valve port for connection to a directional control valve, said body having a motor port and a pilot port leading to different diameter portions of said bore and adapted to be connected to the respective ports of a double acting fluid motor; a stepped counterbalance valve member in said bore spring biased into engagement with said seat to prevent return flow of fluid from said motor port to said valve port; said valve member having a first relatively small annular area defined between said valve seat and a first enlargement of said bore which is exposed to fluid pressure in said motor port, whereby fluid pressure of relatively large magnitude due to thermal expansion of the fluid or to motor load inertia or shock will overcome the spring bias to move said valve member away from said seat for relief of excess pressure through said motor and valve ports, and a second relatively large annular area defined between said first enlargement of said bore and a second enlargement thereof which is exposed to fluid pressure in said pilot port whereby fluid pressure in said pilot port of relatively low magnitude will overcome the spring bias to move said valve member as aforesaid for return flow of fluid from the motor through said motor and valve ports; and a check valve member movable in said counterbalance valve member to permit flow of fluid in the opposite direction from said valve port to said motor port.