Tandem master cylinder with central valves
View Patent ↗A tandem master cylinder ( 1 ) with central valves has ball-shaped valve members ( 25, 40 ) with leaf springs ( 26, 41 ) serving as valve springs. The ball-shaped valve members ( 25, 40 ) can be manufactured of a plastic material, coated with an elastomer. The size of the balls is preferably adjusted to the size of the pistons ( 4, 5 ) to allow a maximum flow while ensuring at the same time that the piston walls retain a thickness. The leaf springs ( 26, 41 ) have a bowl-shaped body ( 61 ), which is shaped like a partial sphere. To avoid an entrapment of brake fluid or a vacuum between the balls ( 25, 40 ) and the leaf springs ( 26, 41 ), respectively, a central hole ( 62 ) has been provided in the bowl-shaped body ( 61 ). The leaf springs ( 26, 41 ) are equipped with a plurality of tongue-shaped extremities ( 63 ) extending radially outward with end portions ( 64 ) bent toward the axial side on which the valve members ( 25, 40 ) are located.
1. A tandem master cylinder ( 1 ) for an automotive hydraulic brake system including a housing ( 2 ) having a bore ( 3 ), a first and a second piston ( 4 , 5 ) slidably arranged in the bore ( 3 ) to define a first pressure chamber ( 29 ) between the first and second pistons ( 4 , 5 ) and a second pressure chamber ( 35 ) between the second piston ( 5 ) and one end ( 38 ) of the bore ( 3 ), first and second stops ( 32 , 37 ) in the housing ( 2 ) respectively engageable with the first and second pistons ( 4 , 5 ) to define respective rest positions, first and second valves ( 25 , 26 , 27 ; 40 , 41 , 42 ) located respectively inside the first and second pistons ( 4 , 5 ) for hydraulically connecting the first and second pressure chambers ( 29 , 35 ) to an unpressurized supply chamber ( 8 , 9 ) when the first and second pistons ( 4 , 5 ) are engaged with their respective first and second stops ( 32 , 37 ) and movable to respective closed positions sealing the first and second pressure chambers ( 29 , 35 ) upon movement of the first and second pistons ( 4 , 5 ) out of engagement with the first and second stops ( 32 , 37 ),
wherein at least one of the first and second valves ( 25 , 26 , 27 ; 40 , 41 , 42 ) comprises a ball-shaped valve member ( 25 , 40 ) which contacts one of the stops ( 32 , 37 ) when the piston ( 4 , 5 ) accommodating the valve member ( 25 , 40 ) is resting on its respective stop ( 32 , 37 ).
2. The tandem master cylinder according to claim 1 , wherein the ball shaped valve member ( 25 , 40 ) is biased toward the stop ( 32 , 37 ) by means of a leaf spring ( 26 , 41 ).
3. The tandem master cylinder according to claim 2 , wherein the leaf spring ( 26 , 41 ) has a bowl-shaped body ( 61 ) and is equipped with a plurality of tongue-shaped extremities ( 63 ) extending radially outward.
4. The tandem master cylinder according to claim 2 , wherein the leaf spring ( 26 , 41 ) has a central hole ( 62 ).
5. The tandem master cylinder according to claim 1 , wherein the valve member ( 25 , 40 ) is accommodated in a recess ( 24 , 42 ) inside one of the pistons ( 4 , 5 ) and wherein the recess ( 24 , 42 ) has a partially spherical shape.
6. The tandem master cylinder according to claim 1 , wherein the valve member ( 25 , 40 ) is made of a plastic material with an elastomeric coating.
7. The tandem master cylinder according to claim 1 , wherein the valve member ( 25 , 40 ) has a diameter exceeding one third of the diameter of the bore ( 3 ).