Shutter opening and closing mechanism for an electrographic apparatus

Claim 1

In a shutter opening and closing mechanism for an electrographic apparatus comprising a reciprocating exposing and scanning means for producing a manuscript image on a photosensitive screen so as to produce a first electrostatic latent image corresponding to the manuscript image thereon, means for modulating a flow of corona ions by the first electrostatic latent image so as to produce a second electrostatic latent image on a record sheet, a dark box for surrounding said photosensitive screen and intercepting exterior light, an opening being provided in said dark box for passage of light flux reflected from said manuscript image therethrough onto said photosensitive screen, and a shutter for closing said opening and operatively interlocked with said reciprocating exposing and scanning means so as to open said opening when said first electrostatic latent image is to be produced on said photosensitive screen and to close said opening at intervals of time other than said time of producing said first electrostatic latent image on said photosensitive screen, the improvement comprising a rotary shaft for rotatably supporting said shutter so as to effect opening and closing movements thereof, a first lever secured to one end of said rotary shaft and biassed in a direction of opening said shutter, an adjustable member engaged with said first lever and limiting an inclined angle of said shutter in its open position to a value selected in response to the concentration of said manuscript image, a second lever freely mounted on said rotary shaft and biassed in a direction to be urged against said first lever, and a third lever freely mounted on said rotary shaft and biassed in a direction to be urged against said second lever, the forward movement of said exposing and scanning means for producing said first electrostatic latent image causing said exposing and scanning means to be engaged with said third lever so as to rotate the third lever in one direction and through said second lever rotating said first lever by an angle defined by said adjustable member, thereby opening said shutter through said rotary shaft by a given angle, said shutter being operative thereby as an exposure controlling diaphragm, the backward movement of said exposing and scanning means causing it to be engaged with said third lever and rotating said third lever only in an opposite direction, thereby maintaining the closed position of said shutter.