A first vacuum valve seat 17 is formed on a valve body 3, and a second vacuum valve seat 18 is formed on a tubular member 21 which is slidably mounted on the valve body 3. A lever member 41 is provided between the tubular member 21 and a valve plunger 14, ...

When a booster is inoperative, a first atmosphere valve (S1) and a second atmosphere valve (S2) are both closed to block a communication of an orifice passage (36) with a variable pressure chamber (B); at the commencement of operation of the booster, the f...

During a normal brake operation, a brake reaction from a reaction disc (12) is transmitted to a valve plunger (15) through an outer plunger (17) and an inner plunger (18); during an emergency brake operation, as a valve plunger (15) is driven forward throu...

At rest the rubber sealing element (15,16) is not in contact with the piston seating (26) and the low pressure zone (8) is connected to the rear (9) of the piston (4,7). The plunger seating (20) is in contact with the sealing element and prevents atmospher...

A negative pressure type booster, comprising a valve seat member (40), a spring (47) energizing the valve seat member (40), and a holding member (52) having an engaging part (52b) disposed on a power piston (22) movably only in radial direction and engaged...