Film processing machine

Claim 1

In a film processing unit having a row of film processing tanks, carriage means including a track supported horizontally over said row of tanks and a carriage mounted on said track, said carriage having means for holding film, and an electric motor drivingly coupled to said carriage and operable to move said carriage along said track to lower said film successively into said tanks, to raise said film therefrom, and to transport said film therebetween, electrical control means for controlling operation of said motor comprising: a timer, an operating circuit for said motor connected between said timer and said motor, said operating circuit including first and second switching means, each separately operable to be closed to complete said operating circuit for operatIng said motor, said first switching means normally being closed for operating said motor, said first switching means including a switching element for each of said tanks distributed along said track, engageable by said carriage, and operable in response to engagement by said carriage to open said first switching means, each of said switching elements being positioned to be engaged by said carriage in response to said carriage being moved over a respective one of said tanks, said timer supplying signals at different intervals dependent upon the amount of time film is to be immersed in each of said tanks, said second switching means being closed for a predetermined interval in response to application of signals from said timer to start operation of said motor for moving said carriage, and a successive one of said switching elements being operable in response to its engagement by said carriage to stop operation of said motor for stopping movement of said carriage said track being a plurality of parallel conductive wires including first and second wires, said carriage being conductive and being slidingly mounted to said first wire, said first switching means including a first switching contact means extending from said carriage to press on said second wire, and said switching elements comprising insulating material applied to the surface of said second wire at each of the points where said first switching contact means presses on said second wire when said carriage is positioned over any of said successive ones of said tanks.