US Patent 7582372 Pressure regulator for fuel cell

When a stepping motor is de-energized, a valve shaft is turned in a direction to open a valve body under the resilient forces stored in a fully opening spring through a receptacle and a driven plate. At this time, a drive plate is turned in unison with the driven plate. When the valve body reaches a fully open position, a positioning finger on the drive plate abuts against a stopper pin, thus stopping the turning movement of the drive plate.