| 摘要 |
An improved hard stop for use with an aperture mechanism 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 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 a hard stop piston. The improved hard stop is comprised of a magnetic piston, an electromagnet that is positioned proximate the magnetic piston for causing the magnetic piston to move to the first position when current is applied to the electromagnet in a first direction and for causing the magnetic piston to move to the second position when current is applied to the electromagnet in a second direction. A first ferromagnet is positioned at the first position to maintain the magnetic piston at the first position when current ceases to be applied to the electromagnet in the first direction. A second ferromagnetic is positioned at the second position to maintain the magnetic piston at the second position when current ceases to be applied to the electromagnet in the second direction.
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