Apparatus for braking webs of photographic material or the like

Claim 1

Apparatus for repeated rapid acceleration and controlled braking of a web which is provided with a series of markers, such as notches, or perforations, comprising means for moving the web lengthwise along a predetermined path, including a variable-speed motor; a light source adjacent to said path; a succession of photosensitive transducers positioned to receive light seriatim from said source in response to movement of a marker past said source and to effect transmission of different first signals which are indicative of decreasing permissible speeds of said motor while such marker occupies those portions of said path in which it brings about illumination of successive transducers, said transducers including a first transducer and a last transducer; means for changing the speed of said motor in response to said first signals, including means for furnishing a second signal which is indicative of the actual speed of said motor and means for comparing said second signal with first signals whose transmission is effected by successive transducers and for changing the speed of said motor in response to transmission of successive first signals thereto so that the speed of said motor decreases from the speed indicated by said second signal to the speed indicated by a first signal not later than when the next-following transducer of said succession effects the transmission of a first signal, the first signal whose transmission is effected by said last transducer being indicative of zero speed; and a chain of series-connected resistors in circuit with said transducers, one for each of said transducers said chain having a terminal for transmission of first signals to said signal comparing means.