Patent ID: 6067891
Filing Date: 2000-05-30
Classification: B60T

Abstract:
A pneumatic booster for braking assistance, comprising:an envelope having an axis of symmetry;at least one movable partition structure for sealingly separating said envelope into a first chamber connected permanently to a source of low pressure and a second chamber; andthree way valve means actuated by a control rod for selectively connecting said second chamber to said first chamber or to a source of high pressure, said control rod being capable of bearing, through the intermediary of a front face of a plunger on the rear face of a thrust rod, said thrust rod being solid with a reaction disc, said plunger sliding in a bore in the movable partition, said three way valve further including a valve member disposed in a tubular rear part of said movable partition and co-operating through an annular front face with a first valve seat formed on said plunger and with a second valve seat formed on said movable partition, said tubular part having a space between said first and second valve seats and communicating with at least one radial passage formed in said movable partition which opens out into said second chamber, said tubular part having at least one axial passage which opens into said first chamber, said the annular front face of said valve member being urged in the direction of said first and second valve seats by a valve spring, said second valve seat being characterised by a surface formed on the movable partition by bringing together at least two circular arcs which are concentric, coplanar and of different radii.