Flow control valve

Claim 1

In a fluid circuit comprising: a. a pressurized fluid source, b. actuating means including a fluid pressure load responsive expansible chamber, c. selector control valve means operatively connectable to said source, and d. expansible chamber flow control means operatively connected to said valve means and said chamber including: 1. surge damping means including a housing containing a first annular chamber, a spool positioned in said housing, a single set of radial ports in said spool communicating fluid between said valve means, said first annular chamber, and a first interior chamber of said spool, spring means positioning said spool in said housing in normally open communication through said ports, axial port means in said spool communicating normally unrestricted fluid flow between said first spool interior chamber and a second spool interior chamber, and surge damping flow restricting baffle means formed on said spool and defining said axial port and between said first and second spool chambers, said surge damping means automatically decreasing the flow rate of fluid returned from said actuating means to said pressurized fluid source through said valve means in direct proportion to an increase in the magnitude of loads imposed on said actuating means and a resulting increase in the fluid pressure level present in the expansible chamber thereof, and provides substantially constant speed of the motion of said actuating means, and 2. counterbalance pressure control means between said second spool chamber and said actuating means including a piston positioned in a chamber formed by a counterbalance housing, a second annular chamber formed by said piston and said counterbalance housing, and fluid back pressure maintaining spring means between said piston and said counterbalance housing, said counterbalance means maintaining said fluid back pressure in the chamber of said actuating means when fluid flow from said pressurized fluid source to said actuating means is prevented.