Manufacturing container or tube from paper; or other manufacturi – Bending – Folding
Reexamination Certificate
2001-02-20
2002-09-24
Sipos, John (Department: 3721)
Manufacturing container or tube from paper; or other manufacturi
Bending
Folding
C493S363000
Reexamination Certificate
active
06454692
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a method of folding printed materials lying above one another in a crossfold, in particular for folding paper webs used for producing printed products, cutting devices being used to perform the method.
During longitudinal folding and crossfolding, i.e., the crosswise folding of printed materials lying above one another, tensile forces act upon the outside of the printed material, while compressive forces act upon the inside thereof. As a result, in the vicinity of the cutting point of the folds which are produced in succession and run transversely with respect to one another, creases are formed, and a displacement of the pages of the signature produced by the folding operation occurs.
In the printing industry, various folders are known wherein paper webs lying one above another are folded. Web-fed rotary printing machines generally include a folder which has at least one folding unit wherein the printed material is folded longitudinally, and a folding unit wherein the printed material is folded transversely, i.e., at right angles to the first fold. The printed materials to be folded may be either material webs or web strands which have previously been cut from the web in the longitudinal direction. During the production of folded sheets or signatures, the use of such folders inevitably leads to the formation of creases at the cut point of the folds, by which the printed image is impaired, in that under certain circumstances individual letters become hidden and, because of the waviness, the perception of the printed image is changed. In addition, displacement of the individual pages in the interior of the signature occurs, and also, subsequently, displacement of the position of the pages as a whole, on account of the increase in volume. The points at which the creases occur are consequently thicker than the rest of the signature, which leads to problems when a large number of signatures are to be separated again for subsequent further processing. Deformation of the separating device even occurs often during the separating operation. In addition, this thickening of the signatures has the effect of thickening the finished printed product, which includes a large number of signatures.
The detrimental effect of these creases is all the greater the more pages there are in a signature and the thicker the paper that is used. Accordingly, it is hardly possible to produce signatures with 32, 48 or more pages from relatively thick paper, so that the page count of such signatures has to be restricted to 24, 16 or even 8 pages. The creases produced in the crossfold during folding therefore have visible, practical and financial consequences. By avoiding the creases, the visual effect of the printed products is improved, which leads to greater satisfaction among customers and readers. In addition, further processing is made easier, because the geometric position of the signatures, and therefore also of the finished product, is improved. In addition, increased economy of the production process of printed products can be achieved because signatures with a high page count can be produced even with relatively thick paper, without having to reduce the production printing speed or the further processing speed.
U.S. Pat. No. 3,228,710 is concerned with the perforation of a section of paper sheets which have been folded longitudinally and transversely. The perforations run halfway over the width of the sheets, inclined at a first angle and, in addition, the perforation can extend over the width of the sheets on both sides of a line of symmetry, the inclinations of the perforation slits being opposed to one another. The perforating knives for making the perforation are fitted to a cylinder which cooperates with a grooved-bar cylinder serving as a counter-cylinder.
U.S. Pat. No. 4,951,967 discloses a perforating knife which is inserted into a sprung mounting in a grooved cylinder. According to the disclosure, the perforating knife is provided with teeth which are fitted with lateral flat pieces which, in an alternating sequence, are alternatingly oriented upwardly or downwardly. The perforating knife is clamped between two clamping bars which, in turn, are inserted in a sprung manner into a common housing in the perforating cylinder.
U.S. Pat. No. 5,524,930 likewise relates to a perforating knife and a signature perforated by this perforating knife. The knife, having mutually inclined teeth, is accommodated in a mounting in the cylinder and has both rounded parts and angular perforating sections. With the aid of the angular and the rounded perforating sections, both curved and slightly curved perforation slits, and also perforations running in a straight line, are produced in the signature.
Attempts have already often been made to avoid creases and to eliminate their consequences, for example, by having the fold, which is subsequently crossed by a further fold, perforated or cut into in a complicated manner over the entire length thereof or only partially. These methods require, to some extent, the use of comprehensive and costly devices and, although they reduce the creases and/or displace them to a different point on the folded printed product, they are not able to solve the problem in a satisfactory manner. In addition, creases are formed, and the position of the pages is displaced.
SUMMARY OF THE INVENTION
In view of the foregoing prior art, it is accordingly an object of the invention to provide an improvement in the folding accuracy of multi-layer folded signatures by previous sectional perforation of the signatures.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a method of producing folds on signatures separated from a material web stream, including a multilayer material web stream, which comprises the method steps of disposing two cutting and perforating devices, respectively, in a web travel direction; cutting the material web stream in the region of a first longitudinal fold by a first cutting device assigned to the fold; perforating/cutting the material web stream in the region of a crossfold forming material bridges; and providing that at least one of the cutting or perforating tools is adjustable in relation to the material web stream.
In accordance with another mode, the method of the invention includes providing that one of the perforating/cutting devices be adjustable in terms of angle of attack in relation to the material web stream.
In accordance with a further mode, the method of the invention includes providing that one of the perforating/cutting devices be adjustable in terms of penetration depth in relation to the material web stream.
In accordance with an added mode, the method of the invention includes providing that one of the perforating/cutting devices be displaceable in vertical direction in relation to the material web stream.
In accordance with an additional mode, the method of the invention includes providing that a second perforating/cutting device begin a delayed cutting and perforation operation, respectively, in relation to a first cutting device.
In accordance with yet another mode, the method of the invention includes providing that a delayed perforation and cutting operation, respectively, be completed by a further perforating/cutting device by generating the first crossfold.
In accordance with yet a further mode, the method of the invention includes detaching established material bridges in the region of the first crossfold during the completion of the folding operation.
In accordance with yet an added mode, the method of the invention includes detaching the material bridges by thrust forces occurring in the interior of the material web stream.
In accordance with yet an additional mode, the method of the invention includes providing that the material bridges constitute intended rupture points having a thickness determined by the configuration of the perforating/cutting tool.
In accordance with still another mode, the metho
Ganneval Bernard
Hoynant Pierre
Desai Hemant M.
Greenberg Laurence A.
Heidelberger Druckmaschinen AG
Locher Ralph E.
Sipos John
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