Hydraulic anti-locking brake unit

A hydraulic antilock brake unit comprising:

• at least one hydraulically actuated wheel brake;
• a brake pedal operated master cylinder;
• said master cylinder and wheel brake interconnected to enable pressurization of said wheel brake by said master cylinder;
• pump means having an inlet for drawing in hydraulic fluid and an outlet for discharging pressurized hydraulic fluid, said pump means connected to enable evacuation and pressurization of said wheel brake upon activation of said pump means;
• said outlet of said pump means connected with said wheel brake to enable pressurization of said wheel brake by said pump means;
• inlet valve means enabling control of communication of said master cylinder and said outlet of said pump means with said wheel brake;
• outlet valve means enabling control of communication between said inlet of said pump means and said wheel brake;
• high pressure accumulator means to initially receive flow from said outlet of said pump means and create a stored volume of pressurized hydraulic fluid, said high pressure accumulator means comprising a housing having a bore formed therein, an accumulator piston have one and an other end, said piston mounted in said housing bore for slidable movement therein in one or an other direction along said bore, one end of said piston defining in part an accumulator chamber in said housing, said accumulator chamber increasing or decreasing in volume respectively with movement of said accumulator piston in said one or the other direction to cause charging or discharging of said high pressure accumulator means, and spring means acting on said another end of said accumulator piston to resist accumulator piston movement in said one direction increasing the volume of said accumulator chamber;
• a counter pressure chamber in said housing defined in part by said other end of said accumulator piston;
• a direct fluid connection between said wheel brake and said counterpressure chamber to enable establishing pressure in said accumulator chamber as a function of wheel brake pressure and said spring force by shifting of said accumulator piston;
• relief valve means connecting said pump means outlet to a low pressure region in said brake unit upon development of a predetermined pressure difference between said accumulator chamber and said wheel brake;
• isolator valve means separate from said relief valve means acting to positively cut off communication between said master cylinder and said wheel brake when said accumulator piston undergoes a predetermined extent of said travel in said one direction.