Pneumatic operating-mechanism construction

An improved pneumatic operating mechanism comprising, in combination:

• means defining a stationary operating cylinder and a movable main driving piston reciprocally operable therewithin;
• pneumatic valve means operable to admit a pneumatic operating fluid to a first driving side of said reciprocally-operable main driving piston;
• said pneumatic valve means comprising a stationary valve-body housing-member having a stationary valve-piston bore provided therein;
• a movable valve piston reciprocally operable within said stationary valve-piston bore;
• a movable valve-sealing member attached to said first driving side of said main driving piston and carried by said main driving piston;
• said movable valve sealing member being positioned within said stationary valve piston bore of the stationary valve body housing member in the non-driving condition of the pneumatic operating mechanism;
• means for admitting high-pressure pneumatic operating fluid to the driving side of said movable valve piston during a driving operation of the operating mechanism to thereby force it into abutting sealing engagement with said movable valve sealing member during the first portion of the operation;
• means defining an exhaust port means pneumatically communicating to the region interposed between the movable valve piston and said valve sealing member within the stationary valve piston bore;
• whereby during the final portion of the driving operation of the pneumatic operating mechanism the movable valve piston halts and blocks off the exhaust-port means whereas the main movable driving piston continues in its reciprocal driving motion within the operating cylinder to its final end driving position.