Self-cleaning photographic transparency processing and projection system

Claim 1

A self-cleaning photographic transparency processing and projection system, comprising a first opaque housing, means forming a film gate in said first housing, film transport means in said first housing, a strip of film having takeup and supply ends connected to said film transport means and extending between said ends over a path through said film gate, said film transport means being operable to move said film in opposite directions over said path, film processing means in said first housing adjacent said path and operable to coat said film with processing composition while said film is moved in a predetermined direction over said path from a first extreme position toward a second extreme position, said film processing means exerting a first drag force on said film during its operation, film engaging means for terminating the operation of said film processing means and simultaneously terminating the first movement of said film in said predetermined direction in a third position intermediate said extreme positions, said film engaging means being moved upon engagement with said film to a position in which it becomes permanently disengaged from said film upon movement of said film from said third position toward said first extreme position to allow subsequent movement of said film from said first extreme position to said second extreme position, said first housing comprising means forming an optical path through the portion of said film in said film gate for transmitting light through that portion, a second opaque housing, means forming a receptacle in said second housing to receive said first housing, means forming an entrance aperture in said receptacle for admitting light to said optical path, an aperture plate mounted in said receptacle in position to register with said film gate, means forming an aperture in said aperture plate to define the bounds of light transmitted along said optical path, and a cleaning pad mounted on saiD film adjacent said takeup end in a position that will not pass through said film gate when said film moves between said first position and said third position but which will pass through said film when said film gate moves between said third position and said second position for engaging and cleaning said aperture plate as said film is moved between said third position and said second extreme position along said path said cleaning pad exerting a second drag force on said film during said engagement and cleaning, whereby said first and second drag forces are not both exerted at the same time.