Anti-skid control apparatus

In a hydraulic braking system for an engine-driven vehicle having front and rear wheel brakes, brake energization means including a master cylinder interconnected with said front and rear wheel brakes and operable to effect pressurization thereof, and a cut-off valve between said master cylinder and said rear wheel brakes and operable to interrupt pressurization of said rear wheel brakes in response to a signal indicating a skid condition;

• the improvement which comprises pressure responsive means operably engaging said cut-off valve and acted upon by fluid pressure from said master cylinder, an engine driven fluid pressure source acting on said pressure responsive means in opposition to said master cylinder pressure and normally operable to hold said cut-off valve open, pressure control means between said fluid pressure source and said pressure responsive means and including means developing a predetermined minimum pressure in said fluid pressure source, said pressure control means including a housing having a bore, a control piston slidably disposed in said bore, means interconnecting said pressure control means and said brake energization means to vary the pressure from said fluid pressure source to said pressure responsive means in response to change in pressure developed by said brake energization means, said interconnecting means including a second piston slidable in a second bore and aligned with said control piston, said second piston being movable toward said control piston by pressure developed by said brake energization means, a compression spring caged between said control piston and said second piston, a control valve operable in response to a signal indicating a skid condition at said rear wheels to lower the pressure from said fluid pressure source to said pressure responsive means to close said cut-off valve and interrupt pressurization of said rear wheel brakes, and a safety valve between said cut-off valve and said rear wheel brakes and operable by pressure from said fluid pressure source to communicate said master cylinder to said rear wheel brakes through the normally open cut-off valve, said safety valve being operable upon failure of pressure from fluid pressure source to communicate the master cylinder to said rear wheel brakes through the cut-off valve.

In a hydraulic braking system for an engine-driven vehicle having front and rear wheel brakes, brake energization means including a master cylinder interconnected with said front and rear wheel brakes and operable to effect pressurization thereof, and a cut-off valve between said master cylinder and said rear wheel brakes and operable to interrupt pressurization of said rear wheel brakes in response to a signal indicating a skid condition;

• the improvement which comprises pressure responsive means operably engaging said cut-off valve and acted upon by fluid pressure from said master cylinder, an engine-driven fluid pressure source acting on said pressure responsive means in opposition to said master cylinder pressure and operable to hold said cut-off valve open, pressure control means between said fluid pressure source and said pressure responsive means and including means developing a predetermined minimum pressure in said fluid pressure source, said pressure control means further including a housing having a bore, a control piston slidably disposed in said bore, an inlet port in said housing communicating said fluid pressure source and said bore, a discharge port in said housing communicating said pressure responsive means and said bore, said control piston being movable in response to change in pressure developed by said brake energization means to balance the opposing forces on said pressure responsive means, means interconnecting said pressure control means and said brake energization means to vary the pressure from said fluid pressure source to said pressure responsive means in response to change in pressure developed by said brake energization means, said pressure control means further including opposing piston means slidably disposed in a second bore formed in said housing and generally aligned with said first mentioned bore, a compression spring caged between said opposing piston means and said control piston and operable to position said control piston to develop said predetermined minimum pressure in said fluid pressure source, said opposing piston means being acted upon by pressure from said brake energization means to bias said opposing piston means toward said control piston, a control valve operable in response to a signal indicating a skid condition at said rear wheels to lower the pressure from said fluid pressure source to said pressure responsive means to close said cut-off valve and interrupt pressurization of said rear wheel brakes.