| 摘要 |
A mask mechanism which allows the dimensional adjustment of at least one of the exposure apertures associated with a photographic printer. The mask mechanism includes a substantially planar plate member that has a rectangular opening therethrough. A pair of movable gates are disposed on opposite sides of the rectangular opening and at least one pneumatic cylinder operates to move these gates between a first open position and a second restricted position. The gates include a substantially linear outer edges oriented parallel to one another to maintain the rectangular nature of the exposure aperture. Typically, the mask mechanism would take the form of a negative cropping riser block or a photographic paper mask assembly. In this manner, either, or both, the exposure aperture associated with the negative or the exposure aperture associated with the photographic paper as it relates to the overall photographic printer can be controlled, respectively. The gates are adapted to positively move between a plurality of positions using a plurality of pneumatic cylinders to move each of the moveable gates between a plurality of positions. At least one spring member operates to bias the pair of movable gates disposed on opposite sides of the rectangular opening toward the widest open positions, and at least one shaft operates to maintain the alignment of the pair of movable gates as the gates move between various positions.
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