Supply passage for brake booster of positive pressure type

Abstract

A brake booster of positive pressure type includes a valve mechanism to which a positive pressure such as compressed air from a source located externally of a shell is fed for switching a flow path, through a conduit disposed within a constant pressure chamber disposed forwardly of a power piston and a supply passage which is formed in a valve body. The supply passage according to the invention comprised a radial passage which extends radially outward through the valve body from a shank portion thereof, and an axial passage which communicates with the radial passage, which an opening of the radial passage into the peripheral surface of the valve body being closed by a seal member which may be formed of an elastic material such as rubber. The seal member is covered by part of the power piston. This construction permits the supply passage to be formed in an inexpensive manner as compared with a formation of a supply passage which extends obliquely through the valve body. The power piston reliably prevents the withdrawal of the seal member from the radial passage.