Patent ID: 6119578
Filing Date: 2000-09-19
Classification: B60T

Abstract:
A pneumatic brake booster comprising: a rigid casing; a moving partition delimiting, in leaktight fashion, a front chamber and a rear chamber inside said casing, said front chamber in operation being connected to a first pressure source delivering a first pressure; a pneumatic piston moving with said moving partition and ending in a hub mounted to slide in an opening in said casing; a three-way valve housed in said hub and capable selectively of adopting a state of rest and an actuating state, said the rear chamber in said state of rest being connected to said first pressure source and in said actuation state to a second pressure source which delivers a second pressure higher than said first pressure; an operating rod mounted to slide in said hub in a first axial direction between first and second extreme positions in which said valve is respectively in said state of rest and said actuating state, said operating rod being subjected to an elastic force acting in a second axial direction the opposite of said first axial direction; and an annular purification filter located between said second pressure source and said rear chamber and housed in said hub around said operating rod, characterized in that said filler is made of a compressible material having a first face attached to an annular support secured to said hub to retain said first face in a stationary position with respect to said hub and a second face which is kinematically connected to said operating rod and displaced with respect to said hub, said filter having a volume that varies with the displacement of said second face of with respect to said hub, said filter having a minimum volume upon being compressed as said operating rod moves to said first extreme position and a maximum volume upon being relaxed as said operating rod moves to said second extreme position.