Anti-lock vehicle brake system with variable decay rate

Claim 1

An anti-lock vehicle brake system for an associated vehicle having a plurality of wheels comprising: a source of fluid pressure, a wheel brake cooperating with at least one of said wheels, a first fluid conduit interconnecting said source of fluid pressure and said brake, an anti-lock control valve coupled to said first fluid conduit to relieve brake pressure when opened, sensing and control means connected to said control valve for detecting when one of said associated wheels tends to lock, said control valve opening responsive to said sensing and control means to allow fluid flow from said brake to relieve braking pressure therein, restricting means in said first fluid conduit for selectively restricting fluid flow to said brake from said source of fluid pressure, a second fluid conduit coupling said control valve to said restricting means, said restricting means being responsive to fluid flow from said brake through said control valve for restricting fluid flow from said source of fluid pressure to said brake to reduce fluid pressure delivered to said brake, and means connected in series with said control valve between said brake and said restricting means for controlling fluid flow through said control valve to said restricting means to a limited rate after an initial surge of fluid flow at a rate higher than said limited rate only during pressure values in said brake greater than a predetermined value to limit the rate of change of pressure in said brake, said means connected in series comprising a piston member, flow restricting means actuated by said piston member, spring means normally urging said piston member to a non-restricting position and pressure balancing means for balancing the fluid pressure on opposite sides of said piston.