Counterbalance valve

A counterbalance valve assembly for directing hydraulic fluid flow in a first direction for raising a load, and for directing hydraulic fluid flow in a reverse direction for lowering the load, said counterbalance valve assembly providing gradual and continuous lowering of the load comprising:

• a valve body having a first port, a pilot port adapted for fluid connection to pilot fluid pressure, a third port adapted for connection to a fluid source, and a valve bore in fluid communication with said first, pilot, and third ports;
• and a counterbalance valve disposed within said valve bore and including an outer barrel and an inner barrel, said outer barrel having a predetermined inner diameter dimension and an inner valve seat, said inner barrel having pressure responsive valve means for establishing fluid flow in said forward direction between said first and third ports for raising the load, said inner barrel being disposed within said outer barrel and having a reduced diameter portion forming an annular channel providing fluid connection between said first and third ports for fluid flow in said reverse direction, an outer relief valve surface formed on said inner barrel and arranged to engage said valve seat within said annular channel, an outer barrel chamber, and an annular flange of lesser dimension than said outer barrel inner diameter dimension forming an annular space therewith in fluid communication with said annular channel and said outer barrel chamber, said annular space being the sole means of communication with said outer barrel chamber, said inner barrel being movable in a first direction into said outer barrel chamber for separating said valve seat and said relief valve surface and biased by biasing means in a second direction for engagement of said valve seat and said relief valve surface, said inner barrel further including a piston surface in fluid communication with said pilot port for moving said barrel in said first direction responsive to fluid pressure received through said pilot port during lowering of the load to provide said fluid flow in said reverse direction from said first port to said third port through said annular channel for lowering the load, said relief valve surface being tapered to provide gradual variations in the rate of fluid flow in said reverse direction as said inner barrel moves, and said annular space between said outer barrel inner dimension and said inner barrel flange and said outer barrel chamber forming a dashpot means for resisting abrupt movement of said inner barrel in both said first and second directions, said tapered relief valve surface and said annular space thereby providing gradual and continuous fluid flow in said reverse direction from said first port to said third port through said annular channel to provide gradual and continuous lowering of the load.

A counterbalance valve assembly for directing a hydraulic fluid flow in a forward direction to move a load in one direction, and for directing fluid flow in a reverse direction to move the load in the opposite direction, said counterbalance valve assembly providing gradually controlled fluid flow in the reverse direction to provide gradual and continuous movement of the load, said counterbalance valve comprising:

• a valve body including a first valve port, a second valve port adapted for fluid communication with a source of fluid, a third valve port adapted for connection to a pilot fluid pressure, and a valve bore in fluid communication with said first, second, and third valve ports and comprising a first chamber portion having a predetermined inner diameter dimension and a second chamber portion, inner barrel means disposed within said second chamber portion, said inner barrel means including pressure responsive valve means for providing fluid flow in said forward direction from said third port to said first port for moving the load in said one direction and said inner barrel means being arranged for moving in first and second linear directions and including a circumferential section separating said first and second chambers, said circumferential section being of lesser dimension than said first chamber inner dimension forming an annular space therebetween, said annular space being the sole means of communication with said first chamber, said inner barrel means also including a piston surface in fluid communication with said second port and relief valve means between said first and third valve port, resilient means connected with and urging said inner barrel means in said second linear direction for normally closing said relief valve means, said inner barrel means being movable in said first linear direction responsive to pilot fluid pressure against said piston surface into said first chamber for providing controlled fluid flow in said reverse direction from the first port, past said relief valve, and to said third port to exhaust the fluid back to the fluid source for moving the load in said opposite direction and said annular space between said inner barrel means circumferential section and said inner dimension and said first chamber forming a dashpot to provide dampened controlled movement of said inner barrel means for movement in both said first and second linear directions to promote smooth fluid flow in said reverse direction and continuous movement of the load.