Patent ID: 6899010
Filing Date: 2005-05-31
Classification: B60T

Abstract:
1. A pneumatic booster in which a housing is divided into a constant pressure chamber and a variable pressure chamber by a power piston, the power piston being connected to a valve body, and a plunger provided inside the valve body is movable by an input rod, to thereby open a valve means to introduce a working fluid into the variable pressure chamber, thus generating a pressure differential between the constant pressure chamber and the variable pressure chamber, wherein a thrust force generated in the power piston due to the pressure differential is applied through a reaction member to an output rod, and a reaction force of the output rod applied to the reaction member is partly transmitted to the input rod, wherein a contractible brake assisting mechanism is provided between the plunger and the reaction member and comprises: a sleeve slidably guided in the valve body; a plunger rod inserted in the sleeve and connected to the plunger; a reaction rod provided to face the reaction member and in axial alignment with the plunger rod so that associated ends of the reaction rod and the plunger rod face each other; and balls provided between the plunger rod and the reaction rod inside the sleeve, wherein when the speed or the amount of movement of the plunger relative to the valve body reaches a predetermined level, due to relative movement between the sleeve and the plunger rod, the balls shift from a position between the reaction rod and the plunger rod in a radial direction of the plunger rod, to thereby allow said ends of the reaction rod and the plunger rod to abut against each other to shorten the combination of the reaction rod and the plunger rod.