A relief printing method and apparatus for its implementation

Abstract: A relief printing technique wherein the material (2) to be printed on is placed between an inked relief (1) and a supporting assembly comprising a dressing web (5) and a second relief (3) reproducing the pattern of the printing relief (1).

Description: The present invention relates to the field of printing techniques and in particular to a novel method of relief or "book" printing. The invention relates also to an apparatus adapted to implement the method. The art of relief printing is known since centuries. A stereotype plate or block has a relief reproducing the pattern to be printed, and the protruding areas thereof are ink-loaded and pressed against a material to be printed on, e.g. a web of paper whereby the ink is transferred from the relief to the material. During this printing operation, the material web is supported by a somewhat resilient support which frequently is designated a "dressing web"; this designation indicates that the printer has to manipulate or "dress" the support so as to adapt it to the particular pattern to be printed. Such manipulation comprises placing of paper bits or trims beneath the dressing web at appropriate locations to be determined by a trial and error process. The reason necessitating such dressing is that the pattern to be printed exhibits inked areas of different size, and the protruding relief portions usually taper from a normally rigid carrier portion of the stereotype towards the inked areas. In resuit, the contact pressure is not uniform, and without proper dressing, smaller areas will usually transfer more ink to the paper web than larger areas. Document US-A-3,245,345 discloses a printing apparratus and printing methods wherein rotating rigid drums or rollers form a support carrying a rubber layer of a particular design comparable to the dressing web of the present invention. Two such rollers transfer ink to a print pattern roller comparable to the stereotype block of the present invention. A paper web, the material to be printed on, is passed through a nip between the print pattern roller and a counter drum. The two ink transfer rollers and the counter drum each have the rubber coating adapted to make the ink transfer more uniform than hitherto possible. The inventors have discovered that manipulation of the dressing web can become superfluous if the present invention is applied. In substance, the dressing web (this designation is adhered to despite the fact that no dressing in the sense of the word will be necessary any more) is replaced with a composite support including a resilient web (the "dressing web") plus a duplicate of the stereotype relief of the printing block. In one embodiment, the duplicate stereotype is identical with the printing or inked stereotype and is placed between the material web to be printed on and the dressing web, both the printing and the supporting reliefs facing towards the dressing web. Means are provided to properly align the two reliefs or to position them "in register". In a second embodiment, the duplicate stereotype relief mirrors that of the printing stereotype and is placed beneath the dressing web, the two reliefs facing one another and being properly aligned as in the first embodiment. The attached drawings illustrate schematically the two alternatives of the present invention. Fig. 1 is a partial section view of an apparatus of the first embodiment, Fig. 2 is a similar view relating to the second embodiment. Referring first to Fig. 1, a printing block 9 carries a stereotype member 1 having a relief in accordance with the pattern to be reproduced or printed on a web of material, for example, a sheet of paper 2. Block 9 with its stereotype member is reciprocable towards and away with respect to a rigid support 10. Support 10 supports a dressing web 5 consisting e.g of rubber of a suitable hardness. A second stereotype member 3 is disposed upon the dressing web with its relief facing towards the latter. It is to be noted that the position of stereotype 3 relative to support 10 is accurately determined by means of posts 8 engaging into respective holes 7 of stereotype member 3. Similarly, printing stereotype 9 has holes 6 which engage over posts 8 when the printing block approaches support 10. In this manner congruence of the relief patterns of both the stereotype members is assured. It will be understood that other means may be provided to effect registration of the two reliefs but such means will not be further discussed as they are readily available to a person skilled in the art of printing. It is to be noted that the printing stereotype member has a rather rigid carrier of the relief. In contrast thereto, the carrier portion 4 of the supporting stereotype block 3 is rather resilient such that the individual "islands" of the relief are displaceable relative to one another in reciprocation direction of the printing block so that they may uniformly distribute the contact pressure towards the underlying dressing web. Referring to Fig. 2, similar or equivalent members to those of the first embodiment have been marked with the same reference sign plus an index '. Printing block 9' is drum-shaped and may roll along the dressing web 5'. Of course, the printing stereotype block 1' is curved so that its shape is adapted to the circumference of block 9'. The rigid support 10' supports the second stereotype member 3' with its relief facing the relief of the printing stereotype member 1'. It will be seen that the relief of member 3' duplicates that of member 1' in a mirrored fashion so that the individual "islands" of the reliefs are again congruent provided that the members 1' and 3' are in proper alignment or registration; means similar to those illustrated in Fig. 1 may be provided for this purpose. The dressing web 5' is comprised of a rubber web similar to that of Fig. 1 plus a thin, very resilient layer 4' which is the equivalent of the carrier 4 in Fig. 1. In this manner, the individual pairs of facing islands will perform their printing action independent of adjacent other pairs of islands.

Claims: A relief printing method wherein a first stereotype block (1) having an ink-carrying relief is pressed against a material (2) to be printed on and wherein said material is supported by a resilient dressing web (5) which, in turn, rests on a rigid support (10), the method comprising the steps of providing a second stereotype block (3) having a relief identical with the relief of said first stereotype block, and placing said second stereotype block between said material and said dressing web with the reliefs of said first and second stereotype blocks being in register and facing towards said rigid support. An apparatus for implementing the method set forth in claim 1 and comprising: a rigid support (10), a printing block (9) displaceable towards and away from said rigid support, a dressing web (5) disposed on said rigid support, an first stereotype block (1) mounted on said printing block and having an ink-carrying relief facing towards said dressing web, a second stereotype block (3) having a relief identical with the relief of said first stereotype block and disposed on top of said dressing web, with its relief facing towards said dressing web, said second stereotype block having a rear face adapted to support material to be printed on, means (6, 8) for positioning said first and second stereotype blocks in register with one another when said printing block is displaced towards said rigid support so as to transfer printing ink to material supported by said second stereotype block. The apparatus of claim 2 wherein said first stereotype block (1) includes a rigid relief carrier and wherein said second stereotype block includes a resilient relief carrier (4). A relief printing method wherein a first stereotype block (1') having an ink-carrying relief is pressed against a material (2') to be printed on and wherein said material is supported by a resilient dressing web (5') which, in turn, is supported by rigid means, (10', 3'), the method comprising the steps of providing a second stereotype block (3') having a relief which mirrors the relief of said first stereotype block, and use of said second stereotype block as a part of said rigid supporting means, the reliefs of said first and second stereotype blocks being disposed in register with one another and facing one another. An apparatus for implementing the method set forth in claim 4 and comprising: a rigid support (10'), a printing block (9') displaceable towards and away from said rigid support, a dressing web (5') supported by said rigid support and adapted to support a material (2') to be printed on, a first stereotype block (1') mounted on said printing block and having an ink-carrying relief facing towards said dressing web, a second stereotype block (3') having a relief which mirrors the relief of said first stereotype block, said second stereotype block being disposed between said dressing web and said rigid support with the relief of said second stereotype block facing said dressing web, means for positioning said first and second stereotype blocks in register with one another when said printing block is displaced towards said rigid support so as to transfer printing ink to material supported by said dressing web.

Inventors: MELZER RAINER, MELZER ROLAND, MELZER, RAINER,, MELZER, ROLAND
Applicants: MELZER MASCHINENBAU GMBH
Application year: 1993
Main classification: B41F5
IPC codes: B41M1, B41M3, B41M9, B41F5