Locking mechanism for pneumatic differential engine for power-operated doors

An emergency door opening mechanism for use with a locking mechanism of a differential engine for a power-operated door, said differential engine including a pair of aligned cylinders and a pair of associated pistons having a rack and pinion assembly including a pinion gear, said rack and pinion assembly connected between and controlled by movement of said associated pistons for opening and closing of said door, said emergency door opening mechanism comprising:

• (a) a series of cams associated with said locking mechanism;
• (b) an emergency cable for applying a force to said series of cams causing said series of cams to rotate and cause said locking mechanism to be released;
• and
• (c) an air dump control lever associated with said series of cams and an air dump valve controlled by said air dump control lever for releasing air pressure from said pneumatic cylinders upon rotation of said series of cams wherein release of air pressure enables a manual opening of the doors wherein said locking mechanism includes a locking rod, a plunger associated with said locking rod for causing extension and retraction of said locking rod and a spring member associated with said plunger for maintaining said plunger and said locking rod in an extended position during a door closed position and for contacting and locking said gear during said door closed position.