Abstract: A tandem dual-head lithographic duplicator is equipped for operation in alternative modes, i.e., either for duplexing by printing on opposite faces of the copy sheets in sequence, or for simplexing. In the simplexing mode the printing of the copy sheets is carried out on one head simultaneously with the cleanup and preparation operations on the other head, with a sequence of printing jobs being performed alternately on one printing head and then on the other while, in each case, the non-printing head is being prepared. Accordingly, substantially continuous simplexing operation can be achieved except in the case of very short printing runs.

Abstract: A pressure roll assembly for applying pressure forces to sheet material articles being driven by a conveyor. A pressure roll is mounted for rotation about a central axis. A longitudinally extending leaf spring has a first portion which supports the pressure roll for rotation about its central axis, and a longitudinally spaced second portion which is fixedly connected with a support member so that the leaf spring supports the pressure roll in a cantilevered condition. An axially extending shaft is disposed normal to the longitudinal axis of the leaf spring and is fixed to the support member. Means are provided for guiding the shaft for axial movement and for restraining movement of the shaft transverse to its axis. Means are further provided for adjusting the axial position of the shaft for adjusting the pressure in the nip between the pressure roll and the conveyor surface.