Patent ID: 6988778

Claim:
A pneumatic brake booster for use in a motor vehicle having an axial piston ( 20 ) interposed between an output push rod ( 24 ) and a plunger ( 32 ) connected to the end of a control rod ( 22 ) to define a plunger-feeler assembly and emergency brake assist means comprising a feeler ( 42 ) connected to the plunger ( 32 ) and moved by axial sliding with respect to the plunger ( 32 ) and means for axially immobilizing the feeler ( 42 ) by blocking the movement of the feeler ( 42 ) with respect to the plunger ( 32 ) at rest and during a brake application when a rate of travel of the control rod ( 22 ) and of the plunger ( 32 ) is below a limit value, and to allow the plunger ( 32 ) to slide with respect to the feeler ( 42 ) in a direction to reduce an axial length of the plunger-feeler assembly during an emergency brake application when the rate of travel of the control rod and of the plunger is above said limit value, said feeler ( 42 ′) comprising means ( 52 ) collaborating with the piston ( 20 ) to define a position of rest of the feeler, characterizing a pin ( 52 ) mounted in a transverse orifice of the feeler ( 42 ) with first and second ends that are respectively located in first and second oblong slots ( 56 ) of a cylindrical part of the piston ( 20 ) to delimit a maximum axial travel of the feeler ( 42 ) with respect to the piston ( 20 ).