Dual external pin reservoir valves for tandem master cylinder assembly

A tandem master cylinder for hydraulic brake systems, said cylinder comprising:

• a housing adapted for attachment to a booster housing of a brake power booster and having a closed end longitudinal bore and first and second valve bores extending parallel to said longitudinal bore;
• a primary plunger piston within said longitudinal bore and movable along said longitudinal bore;
• a secondary plunger piston within said longitudinal bore and movable along said longitudinal bore, the space between said primary plunger piston and said secondary plunger piston defining a primary pressure chamber and the space between said secondary plunger piston and the closed end of said longitudinal bore defining a secondary pressure chamber;
• means for coupling said primary and said secondary plunger pistons together;
• a return spring urging said primary plunger piston away from said housing;
• a cylindrical bushing within said longitudinal bore and radially outward of said primary and said secondary plunger pistons;
• a first sealing cup sealing said primary pressure chamber from the atmosphere;
• second and third sealing cups fitted between said cylindrical bushing and said secondary plunger piston sealing said primary pressure chamber from said secondary pressure chamber;
• first and second fluid passage means extending through said housing for conducting hydraulic fluid to said primary and said secondary pressure chambers, respectively;
• means for connecting said first and said second fluid passage means to a hydraulic fluid supply tank;
• and first and second valves respectively positioned within said first and said second fluid passage means and within said first and second valve bores of said housing and responsive independently of each other to movement of said primary plunger piston to control flow of hydraulic fluid to said primary and said secondary pressure chambers.

A tandem master cylinder for hydraulic brake systems, said cylinder comprising:

• a housing having a closed end longitudinal bore and adapted for attachment to a booster housing of a brake power booster;
• a primary plunger piston within said longitudinal bore and movable along said longitudinal bore;
• a secondary plunger piston within said longitudinal bore and movable along said longitudinal bore, the space between said primary plunger piston and said secondary plunger piston defining a primary pressure chamber and the space between said secondary plunger piston and the closed end of said longitudinal bore defining a secondary pressure chamber;
• means for coupling said primary and said secondary plunger pistons together;
• a return spring urging said primary plunger piston away from said housing;
• a cylindrical bushing within said longitudinal bore and radially outward of said primary and said secondary plunger pistons, said cylindrical bushing:
• (a) screwed into said housing and
• (b) having:
• (i) a circumferential recess adapted to receive an axial collar of said brake power booster housing, and
• (ii) a radial annular flange adapted to engage said booster housing in an axial direction on one side and supporting said return spring on a second side;
• a first sealing cup sealing said primary pressure chamber from the atmosphere;
• second and third sealing cups fitted between said cylindrical bushing and said secondary plunger piston sealing said primary pressure chamber from said secondary pressure chamber;
• first and second fluid passage means extending through said housing for conducting hydraulic fluid to said primary and said secondary pressure chambers, respectively;
• means for connecting said first and said second fluid passage means to a hydraulic fluid supply tank;
• and first and second valves respectively positioned within said first and said second fluid passage means and within said first and second valve bores of said housing and responsive independently of each other to movement of said primary plunger piston to control flow of hydraulic fluid to said primary and said secondary pressure chambers.

A tandem master cylinder for hydraulic brake systems, said cylinder comprising:

• a housing having a closed end longitudinal bore with an axial stop, said housing adapted for attachment to a booster housing of a brake power booster;
• a primary plunger piston within said longitudinal bore and movable along said longitudinal bore;
• a secondary plunger piston within said longitudinal bore and movable along said longitudinal bore, the space between said primary plunger piston and said secondary plunger piston defining a primary pressure chamber and the space between said secondary plunger piston and the closed end of said longitudinal bore defining a secondary pressure chamber;
• means for coupling said primary and said secondary plunger pistons together;
• a return spring urging said primary plunger piston away from said housing;
• a cylindrical bushing within said longitudinal bore abutting said axial stop of said longitudinal bore and radially outward of said primary and said secondary plunger pistons, said cylindrical bushing screwed into said housing;
• a first sealing cup sealing said primary pressure chamber from the atmosphere;
• second and third sealing cups fitted between said cylindrical bushing and said secondary plunger piston sealing said primary pressure chamber from said secondary pressure chamber;
• first and second fluid passage means extending through said housing for conducting hydraulic fluid to said primary and said secondary pressure chambers, respectively;
• means for connecting said first and said second fluid passage means to a hydraulic fluid supply tank;
• and first and second valves respectively positioned within said first and said second fluid passage means and within said first and second valve bores of said housing and responsive independently of each other to movement of said primary plunger piston to control flow of hydraulic fluid to said primary and said secondary pressure chambers.