Pneumatically operated servo-booster

摘要

A pneumatically operated servo-booster has a housing divided by a movable diaphragm assembly into chambers (A, B), and a hub connected to the diaphragm and forming a vacuum valve seat for co-operation with a spring-loaded valve member. A valve element movable relative to the hub forms an atmospheric valve seat for co-operation with the valve member. A sleeve co-axial with but separate from the hub carries an abutment member which forms a fixed abutment for the valve seat when the sleeve is in abutment with the shoulder of the housing. When the seat abuts the member, co-operation of the vacuum valve seat with the valve member under the action of pressure in one of the chambers maintains the atmospheric valve in a position of readiness for activation of the booster. This arrangement contributes to increased sensitivity of operation.