Make and break head valve assembly

摘要

A pneumatically operated fastener driving device is provided including an inlet head valve structure mounted within a housing for movement between (1) a closed position sealing a piston chamber from communication with a main air pressure reservoir and (2) an open position enabling the main air pressure reservoir to communicate with the piston chamber, and an outlet head valve structure mounted within the housing for movement separate from the inlet head valve structure between (1) a closed position sealing the piston chamber from communication with an exhaust opening and (2) an open position enabling the piston chamber to communicate with the exhaust opening. The inlet and outlet head valve structures include first and second reservoir pressure responsive surfaces respectively. The inlet and outlet head valve structures include first and second pilot pressure responsive surfaces disposed in opposing relation to the reservoir pressure responsive surfaces respectively and in continuous communicating relation to the pressure within a pilot pressure chamber so as to bias the inlet head valve structure to move in an opposite direction toward its closed position and the outlet head valve structure to move in the same opposite direction toward its open position. A spring is provided to bias the inlet head valve structure so it (1) moves to its open position after movement of the outlet valve to its closed position in one direction and (2) moves to its closed position prior to movement of the outlet valve structure to its open position in an opposite direction.