Valve assembly

In a master cylinder having a fluid reservoir, a master cylinder body with a bore formed therein, a mating piston received in said bore and actuatably cooperating therewith in apply and release modes, said bore and said piston defining a low pressure high volume displacing pressurizing first chamber and a high pressure low volume displacing pressurizing second chamber, and wall means forming a valve chamber communicating with the bore in said master cylinder body through first and second compensation ports and opening into said reservoir, said first compensation port being continually connected only with said first chamber of said bore and said second compensation port being connected only with said second chamber of said bore when said piston is in the fully released position of said release mode, an improved compensation control and blow-off unit valve assembly operable during the apply mode of said piston to selectively vent said first chamber and comprising:

• a check valve and a valve body insertable into said valve chamber to form therewith a chamber portion communicating with said compensation ports, said valve body defining a valve seat for said check valve and having a lip type compensating seal extending about the outer periphery thereof between said valve seat and said chamber portion and in sealing contact with said valve chamber wall means to permit fluid flow between said valve body and said wall means in one direction only;
• said valve body having a passage including said valve seat extending therethrough for connecting said reservoir and said chamber portion, said check valve being normally closed with respect to said valve seat and said passage to prevent unrestricted flow from said reservoir through said passage to said compensation ports when said piston is in the release mode;
• and unitary means for retaining said valve assembly in said valve chamber and for supporting said check valve, said unitary means comprising an annular valve body retainer having a check valve spring portion extending radially inwardly in cantilever fashion to said check valve for supporting same for movement with respect to said valve seat, said annular valve body retainer further including an annular retainer ring portion operatively engaging said valve body and said wall means to hold said valve body in a fixed position in said valve chamber;
• and means forming a continuously open restricted flow passage bypassing said check valve when said check valve is closed to provide a controlled leak between said reservoir and said first chamber, thereby accommodating a delayed pressure equalization between said reservoir and said first chamber under static pressure conditions;
• said check valve opening in response to a predetermined blow-off pressure generated in said first chamber during pressure generating actuation of said piston in said apply mode to vent said first chamber to said reservoir after said second compensation port is no longer in communication with said second pressurizing chamber.

In a master cylinder having a fluid reservoir, a stepped bore, and a mating stepped piston reciprocably received in said bore, said piston and said bore defining a large diameter low pressure high volume displacing first pressurizing chamber and a smaller diameter high pressure low volume displacing second pressurizing chamber, a valve chamber having an upper end in open fluid communication with said reservoir and a lower end having a first port opening into said first pressurizing chamber and a second port opening into said second pressurizing chamber, a valve body mounted in said valve chamber and having an upper end continuously exposed to fluid in said reservoir, a lower end continuously exposed to said first and second ports, and first and second valve passage means extending between and through said valve body upper and lower ends, and a fluid flow sensitive first valve permitting fluid flow therepast from said reservoir to said first chamber through said first valve passage means and preventing fluid flow therepast in the reverse direction, the improvement comprising:

• a unitary valve and valve body retainer formed to provide an annular retainer ring portion and a resiliently yieldable cantilever spring tongue portion extending radially inwardly from said ring and a valve member portion formed on the free end of said tongue portion;
• said retainer ring portion fitting within said valve chamber in axially fixed relation and acting on said valve body to hold said valve body against axial movement in said valve chamber, said valve portion overlying the end of said second valve passage means and cooperating therewith to define a second valve with said yieldable spring tongue portion continuously urging said second valve closed, and a continuously open restricted flow passage formed through said valve portion bypassing said second valve between said reservoir and said first chamber and providing a controlled leak accommodating a delayed pressure equalization between said reservoir and said first chamber under a static pressure condition, said second valve having one side exposed to fluid in said reservoir and another side continuously exposed to fluid in said first chamber of said bore and selectively exposed to fluid in said second chamber of said bore;
• said second valve being opened only at a predetermined pressure in the fluid at said valve body lower end and acting on said second valve against the urging of said yieldable spring tongue portion;
• said second valve including an area exposed to fluid in said first chamber and responsive to a predetermined pressure differential between a higher fluid pressure generated in said first chamber during master cylinder actuation and the lower fluid pressure of said reservoir to open said second valve against the urging of said yieldable spring tongue portion to relieve pressure in said first chamber;
• pressure generated in said first chamber during master cylinder actuation therefore being limited so that the master cylinder actuating force is not required to continuously overcome a continuously increasing pressure generated in said first chamber during full master cylinder actuation.