The Homer Lee Power Plate-printing Mackine.—A few years ago Mr. Homer Lee, an expert in the engraving and printing art, after a long series of experiments, finally introduced a plate-printing machine operated by steam power as in ordinary printing presses, in which the engraved plate was mechanically inked and wiped ready for the impression. This press, omitting the wiper cloths, resembles the well-known form of printing press termed •` stop cylinder." wherein after the impression takes place the impression cylinder conies to a, stop i during the feeding of the next sheet to its grippers, while the bed is traveling back idly to be inked preparatory to moving forward again. The frame of this press is extended upward so as to provide bearings over the travel of the bed for the rolls carrying the wiping cloths. These cloths extended from one roll down under what is termed a pad, and then upward to another roll; the rolls being intermittently moved, one to unroll a small portion of the cloth, and the other to roll up a like portion, thereby presenting a fresh wiping surface below the pad. There are a number of these pads extending transversely across the machine so as to hear the cloths upon the plate as the latter travels beneath them. These pads were given a constant transverse reciprocating motion, so that the cloths were rubbed over the surface of the inked plate as the bed moves forward into the plane of impression with the cylinder. The plate is kept constantly heated by gas jets burning below the bed ; and in sonic cases one or more of the wiping cloths is dampened by passing the cloth through a water trough, the amount of water absorbed thereby being regulated by a squeezing roll ; and finally the last pad, or the one nearest the impression cylinder, has or may have its cloth omitted and the chalk applied to its under surface so as to give the final polish to the plate just before printing ; the cloth also in some cases is employed with this pad, and in this case the cloth has chalk automatically applied to it instead of to the pad. The sheets to be printed are fed by a girl from the usual feed-board to the grippers of the impression cylinder, and after being printed upon are delivered in the usual manner.
This flat-bed plate-printing machine has met with great success in printing many difficult , _4_ plates entirely automatic, and has lately been used by the United States Government with great success for printing the cigar and beer internal revenue stamps, which are considered a very severe test on the automatic inking and wiping features of the machine.
The art of plate printing by machinery was still further improved by the introduction by Mr. Homer Lee of his rotary machine illustrated in Fig. 9. In this machine the plate is carried by one of the cylinders, over which the wiping-pads are arranged, the other cylinder being the impression cylinder, with grippers for carrying the sheet, ; and the smaller cylinder is the delivery cylinder, also having grippers which take the printed sheet from the impression cylinder, and thence by the tapes and fly frame is delivered onto the delivery table printed side uppermost. This machine embraces all the various adjustments of the parts necessary to obtain any variation in inking, wiping. impression, and heating of the plate the printer may desire. The pads, in some respects similar to the pads in the other machine, are also rendered adjustable, so that they may exert any degree of yielding pressure upon the plate, and any portion of the pad is equally capable of adjustment, so that the wiping of the plate is absolutely within the control of the pressman. Two of the pads reciprocate transversely across the plate as in the other machine, and the other two have an elliptical motion across the plate, this motion imitating the hand-wiping operation to perfection. The cloths are carried by the rolls arranged at the top of the machine, and are carried down beneath the wipers and back up to the winding-up rolls. In this machine the unwinding rolls are mounted loosely so as to revolve to unwind a portion of the cloth when it is drawn upon by the winding-up rolls, which are all moved in unison, step by step, but to different extents, if necessary, ny a reciprocating longitudinal bar that carries short, adjustable inclines, which move under their respective pawls, and thus rotate the connected ratchets and thence the winding-up rolls. This rotary machine has been used recently in printing postal notes for the United States Government, and has printed in one week as many as 70,000 sheets, size 18 x 18 in.. containing 8 postal notes with their stubs, which is considered by persons familiar with the difficulties of plate printing by power as a most credible showing.