Patent ID: 7267040
Filing Date: 2007-09-11
Classification: B60T

Abstract:
1. A pneumatic brake booster comprising a casing ( 2 ) of longitudinal axis (X) formed by first and second shells connected by their radially external ends, in which said casing is an assembly made up of a skirt ( 6 ) and a pneumatic piston ( 12 ) of longitudinal axis (X) is slideably mounted in a sealed manner, said assembly ( 6 , 12 ) dividing the inner space ( 4 ) of the casing ( 2 ) into a low-pressure chamber ( 8 ) and into a variable-pressure chamber ( 10 ), a return spring which returns the skirt/pneumatic piston assembly ( 6 , 12 ) into the rest position being mounted in the low-pressure chamber ( 8 ) between the first shell and a face of the pneumatic piston ( 12 ), a three-way valve arrangement ( 26 ) actuated by a control rod ( 28 ) being mounted in a longitudinal passage ( 34 ) bored in the pneumatic piston ( 12 ), said control rod ( 28 ) being connected by a first longitudinal end to a brake pedal and a second end of said control rod ( 28 ) being received in a reception cavity made in a first longitudinal end of a plunger distributor ( 32 ), said control rod being returned into a rest position by a return spring ( 112 ), said plunger distributor ( 32 ) comprising, at a second longitudinal end, a feeler which applies the force of the control rod ( 28 ) to a hydraulic piston ( 122 ) of a master cylinder by way of a reaction device (DH), said skirt/piston assembly ( 6 , 12 ) transmitting a pneumatic boost force to the hydraulic piston ( 122 ) of the master cylinder via a central face ( 127 ) of the pneumatic piston, said three-way valve arrangement ( 26 ) comprising first ( 48 ) and second ( 50 ) valve seats and a valve ( 46 ) applied to at least one of the first and second valve seats ( 48 , 50 ) by a valve spring ( 106 ), said second valve seat ( 50 ) being borne by a first longitudinal end ( 44 ) of the plunger distributor ( 32 ), characterized in that the first valve seat is borne by a first longitudinal end of a bushing ( 54 ) slideably mounted in a sealed manner in the pneumatic piston ( 12 ) over a first defined travel (C), and in that it comprises a securing means for connecting said bushing ( 54 ) axially to the pneumatic piston ( 12 ) when said pneumatic piston has completed the defined travel (C), further characterized in that it comprises an elastic means ( 58 ) maintaining the bushing immobile with respect to the casing ( 2 ) of the booster until such time as said defined travel (C) has been achieved, said elastic means being mounted in compression axially between an annular bearing surface ( 60 , 172 ) made in a wall of an axial passage of the pneumatic piston and a shoulder ( 64 , 170 ) of the bushing ( 54 ).