Photographic printing apparatus

Claim 1

In combination with photographic projection printing apparatus, a printing mask assembly permitting rapid conversion to a plurality of mask arrangements, said mask assembly comprising: a. a frame having longitudinal and lateral inner edges defining a rectangular opening, and b. a plurality of mask members adapted for selective assembly with said frame and producing variations in the borders of said rectangular opening, c. a flat ledge extending into said frame from said inner edges and having longitudinal and lateral vertical walls spaced outwardly respectively from said longitudinal and lateral inner edges and generally surrounding said opening, d. said mask members engaging said ledge during assembly with said frame, e. a plurality of ledge protuberances recessing through said longitudinal vertical walls into said frame and forming spaced locating notches in the plane of said ledge, f. said mask members respectively having a body with opposed ends, the length between said body ends being slightly less than the dimension between said longitudinal vertical walls but greater than the dimension between said longitudinal inner edges, g. said body ends each having at least one ear projecting therefrom for receipt into at least one of said locating notches upon positioning the mask member body between said longitudinal vertical walls, and h. said ears and locating notches being positioned to permit limited predetermined interchange-ability between the location of selected mask members to produce desired variations in the borders of said rectangular opening.