Patent attributes
In a vacuum type booster device, when the advance of an input member causes an atmosphere valve seat to be separated from an atmosphere valve to advance a power piston, the position of a vacuum valve seat is moved backward relative to the power piston by a distance to which the advance amount of the power piston relative to a housing is decreased at a predetermined ratio. Thus, when a slight advance of the input member causes the atmosphere valve seat to be separated from the atmosphere valve to advance the power piston relative to the housing, the vacuum valve seat is retracted relative to the power piston and is advanced by a distance which is obtained by subtracting a retraction amount of the atmosphere valve seat from the advance amount of the power piston relative to the housing, whereby a valve mechanism of the construction as aforementioned can be closed again with the advance of the power piston.
