Electromagnetic actuator for providing a hard stop for moving blade aperture systems

A hard stop for use with an aperture mechanism that is comprised of at least one blade moveable along a path between a closed position and at least one open position, and at least one hard stop piston that is moveable between a first position, out of the blade path, and a second position, in the blade path, to position the blade in the open position when an edge of the blade contacts the hard stop piston, wherein said improved hard stop is comprised of:

• a magnetic piston;
• electromagnet means including a coil proximate to said magnetic piston and a ferromagnetic ring arranged such that when current is applied in one direction through the coil it causes the magnetic piston to move to the first position in a first direction and held in such position by the attraction of the magnetic piston to the ferromagnetic ring and causes said magnetic piston to move to the second position when current is applied in an opposite direction to the coil and said magnetic piston is held in such position by the attraction of the magnetic piston to the ferromagnetic ring.