Pneumatically powered actuator with hydraulic latching

A bistable pneumatically powered actuator mechanism comprising

• a working piston reciprocable in opposed first and second directions toward respective first and second stable positions,
• pneumatic means for causing translation of said piston in said opposed first and second directions, and
• hydraulic latching means for latching said piston in said first stable position against an opposing force provided by said pneumatic means, and for latching said piston in said second stable position against an opposing force provided by said pneumatic means,
• a make-up reservoir for supplying hydraulic fluid to said hydraulic latching means, and
• means for pressurizing said make-up reservoir by air pressure from said pneumatic means.

A bistable pneumatically powered actuator mechanism comprising

• a working piston reciprocable in opposed first and second directions toward respective first and second stable positions,
• pneumatic means for causing translation of said piston in said opposed first and second directions,
• first working chamber means for compressing air as said piston translates in said second direction, thereby providing damping as said piston approaches said second stable position,
• second working chamber means for compressing air as said piston translates in said first direction, thereby providing damping as said piston approaches said first stable position,
• an engine valve coupled to said working piston and movable relative to said working piston during operation of the actuator, said engine valve being closed when said working piston is in said first stable position, and
• means urging said engine valve in said first direction relative to said working piston when said working piston is in said first stable position, thereby providing positive seating for said engine valve.