Patent ID: 7201456
Filing Date: 2007-04-10
Classification: B60T

Abstract:
1. A pneumatic brake booster for a motor vehicle, comprising a piston ( 22 ) mounted between a control rod 20 ( 24 ) and a push rod ( 34 ), the control rod being terminated by a distributor plunger ( 28 ) guided translationally in a housing ( 48 ) of the piston, and a three-way valve ( 30 ) mounted in the piston ( 22 ) around the control, rod ( 24 ) and comprising a shutter ( 56 ) engaging with a seat of the piston ( 22 ) and with a seat ( 70 ) of the distributor plunger ( 28 ), a cylindrical sleeve ( 46 ) mounted in an axially sliding manner in said housing ( 48 ) around the distributor plunger ( 28 ), and means ( 52 ) which permanently urge the sleeve ( 46 ) elastically toward the shutter ( 56 ) of the three-way valve in order to move said shutter away, from the seat ( 70 ) on the distributor plunger ( 28 ) and to increase the supply of atmospheric air to a working, chamber ( 16 ) of the booster means ( 58 , 58 ′) for axially locking the sleeve ( 46 ) when the shutter ( 56 ) is in a moved-away position, and means ( 66 ) for unlocking the sleeve which are sensitive to the speed of movement of the control rod ( 24 ) and of the distributor plunger ( 28 ) in the direction of braking and which unlock the sleeve ( 46 ) when this speed is at least equal to a predetermined value, characterized in that the means for axially locking the sleeve ( 46 ) are arranged in the housing ( 48 ) of the piston between the distributor plunger ( 28 ) and the piston ( 22 ) and comprise an elastically deformable element ( 58 , 58 ′) for retaining the sleeve ( 46 ), said deformable element ( 58 , 58 ′) being mounted in an annular groove or slot in the body ( 42 ) of the piston ( 22 ), said deformable element ( 58 , 58 ′) bears on a ramp or oblique surface ( 66 ) of the distributor plunger ( 28 ) so that it can be moved away from said plunger and release the sleeve ( 46 ) when the distributor plunger ( 28 ) is moved axially toward the push rod ( 34 ) with respect to the piston ( 22 ), said deformable element ( 58 , 58 ′) being formed by a spring steel wire stirrup comprising at least one kink housed in said groove in the housing ( 48 ) of the piston and at least one kink ( 62 ) housed in a notch or slot in the sleeve ( 46 ), said deformable element ( 58 , 58 ′) comprises at least two opposed kinks ( 62 ) housed in opposing notches or slots in the sleeve ( 46 ).