Reaction structure of booster

Claim 1

In a brake booster including: a cylinder housing, a power piston with a center hub of synthetic resin axially movable within the housing and including a cylindrical hollow shaft rearwardly extending from the center hub, a control valve mechanism arranged in the cylindrical hollow shaft and including first and second valve elements coaxially aligned, the second valve element being operatively connected at its rear end with a manually operable push rod and the front end thereof being slidably disposed in a small bore in the hub of said power piston, a power output rod with its rear end axially slidably disposed in a large bore in the hub of said power piston, said large bore having a peripheral wall of synthetic resin perpendicular to a rear end wall of synthetic resin and being coaxial with and open at its rear end to the front opening of said small bore, a peripheral wall of said small bore intersecting the rear end wall of said large bore at a right angle and the intersection of the peripheral wall and rear end wall of said large bore defining an annular corner at the rear end of said large bore, and an elastic reaction disc being disposed in the large bore and abutting the rear end of the power output rod, said reaction disc in an uncompressed state having a peripheral wall of a diameter substantially equal to and being parallel to the peripheral wall of said large bore and having a rear end wall parallel to the rear end wall of said large bore, the intersection of the peripheral and rear end walls of said reaction disc defining an annular corner, said reaction disc being received in said large bore so as to be compressed upon booster operation between the rear end of the power output rod and the front end of the second valve element and the rear end wall of said large bore, the improvement comprising the annular corners of said large bore and said reaction disc in an uncompressed state each being rounded at the same predetermined radius and the rear end wall and annular corner of said reaction disc directly contacting and cooperating with the rear end wall and annular corner of said large bore to permit precise determination of the time and distance of compression of the rear end wall of said reaction disc into said small bore to contact the front end of said second valve element thereby providing a definite jumping value without indefinite delay of output power rise.