In a slide projector having:
- an optical system including an optical axis, a slide-projection station along said axis in a plane substantially perpendicular to the axis, and a condensing lens along said axis closely adjacent to one side thereof, for directing light from a light source through a slide positioned in said station,
- means supporting a series of slides in said projector for movement along an endless, closed-loop path including two substantially straight side sections and two arcuate connecting sections at the opposite ends of said side sections, one of said end sections being located alongside said slide-projection station for swinging of slides along an arcuate path into and out of the slide-projection station, through arcs of approximately ninety degrees and generally about an axis defined by said one arcuate section, said lens having an inner side adjacent said one arcuate section, an outer side remote from said one arcuate section, and upper and lower sides,
- and actuating means for feeding slides along said path and into and out of the slide-projection station,
- the improvement comprising:
- means movably supporting said condensing lens on said projector including:
- first and second tracks associated, respectively, with the outer and inner sides of said lens, said first track extending outwardly from said outer side substantially parallel to said plane, and said second track extending outwardly from said inner side substantially radially of said arcuate path and being inclined relative to said first track,
- and follower means on said frame for riding on said tracks and guiding the lens for movement thereon to swing the lens about said outer side as the lens moves along said tracks;
- lens-moving means for shifting the lens back and forth along said tracks in timed relation with the feeding of slides along said track by said actuating means, between the normal position in which said lens is closely adjacent the slide-projection station and a retracted position spaced outwardly from said normal position away from said one arcuate section and out of the slide path, including:
- a rotary crank mechanism having a lateral throw of preselected length during each revolution,
- a connecting rod connected at one end to said crank mechanism and at the other end to said lens, adjacent said outer side, to shift said outer side back and forth along said first track between said positions during each revolution,
- a spring-loaded lost-motion connection between said crank mechanism and said lens,
- and means for stopping outward movement of said lens at said retracted position before the lateral throw of the crank mechanism is complete, thereby to hold the lens stationary in the retracted position during a portion of each revolution,
- and means driving said crank mechanism with said actuating means to produce one revolution of the crank mechanism during each slide change.