Film cassette drive mechanism in dental radiographic apparatus for photographing entire jaws

A dental radiographic apparatus for photographing the entire jaw providing an X-ray source and a film holder incorporating a platelike X-ray film cassette therein respectively at one end of a rotary arm and at the other end thereof in an opposed relation with each other and maintaining the same constantly in a mutually opposed relation by bringing the linear travelling speed of the film cassette into synchronism with the travelling speed of the X-ray source following the rotational movement of said arm so as to irradiate X-ray beams convergent from said X-ray source onto said film cassette in a state of the beams intersecting at right angles with said cassette, characterised by a film cassette drive mechanism including said platelike film cassette fixed to said film holder, a slide bar provided in the direction of travel of said cassette, a roller in rolling contact with said slide bar, and a variable motor for driving said roller, whereby said film holder together with said film cassette are enabled to move linearly along the direction of rotation of said arm through the rolling friction between said roller and said slide bar.