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to show as clearly as possible the arrangement and manner of working. The scraper—not shown in the illustration—works on the tympan O. A, carriage or bed of the press, carrying the printing plate. B, a slide of light wood. This prevents the frame D and the printing paper M coming in contact with the plate before the impression is actually being taken by the scraper. The wooden slide bridges over the plate, and may be 15 to 25 millimetres higher than the plate itself. When the rolling up or inking of the plate has taken place the slide is pushed so far forwards as to allow only just sufficient room for the scraper to rest upon the plate. The action of the scraper during the taking of the impression causes the slide to work out, and allows the paper to come in contact with the print layer. E E are adjustable buttons to regulate the traverse of the carriage when printing. D is a second frame necessary to carry the strips of thin zinc, Ef Ef, Eg Eg, which entirely protect the edges of the paper to be printed upon, and so produce an impression with a white margin. These strips may be almost instantly adjusted to give any required size. The frame D must be so much smaller than the frame L as to be easily covered by the latter, allowing for the projecting screws and nuts of the clamps f. The zinc strips should be reduced to a feather edge on the sides next the picture, and should have secured to them strips of fine paper (foreign letter-paper), which should extend over the edges about three millimetres, to prevent damage to the gelatine layer. f f are clamps for the zinc strips Ef. They are put through the slots, and the tension adjusted by the nuts. The zinc strips are perforated by two holes at each end, and secured to the clamps by means of screws. Eg are also zinc strips; g clamps provided with two holes, in each of which a hook is inserted. Corresponding with these a second pair of hooks are inserted in holes in the frame I, the hooks being connected together by the strong indiarubber bands h. This gives to the strips Eg a certain amount of elastic tension. The clamps K are also adjustable in slots, and similar to f; L, frame for the reception of the tympan; M, large clamp for stretching the elastic sheet O; N, zinc tympan, greased to facilitate its movement under the scraper, it also prevents grease penetrating the sheet O; P, a bracket on bed A, against which the tympan frame rests when raised and thrown back. The arrangement is used as follows: When the plate has been satisfactorily inked or rolled in, the slide or bridge B is adjusted over the plate, leaving a strip of about three
mm. uncovered to allow of adjustment of the scraper. Lower the frame D in which the zinc strips have been adjusted to the size of picture; the printing paper is placed over this slide, and covered with a few sheets of paper backing. The tympan frame L, together with the sheeting and greased zinc plate, are lowered upon the work, the scraper adjusted, and an impression taken.
Fig. 7.
