This application claims the priority, under 35 U.S.C. ยง 119, of German Patent Application DE 10 2006 049 798.8, filed Oct. 23, 2006; the prior application is herewith incorporated by reference in its entirety.
1. Field of the Invention
The invention relates to a drum for conveying a sheet, including a drum body, at least one jacket or backing forming a circumferential surface, at least one device for fixing the jacket onto the drum body, grippers for holding the sheet on the circumferential surface, a device for actuating the grippers, journals for mounting the drum in a frame and a drive for rotating the drum about a longitudinal axis.
In printing press, drums or cylinders equipped with grippers are used to convey sheets. The grippers hold the leading edges of the sheets while the sheets rest on the circumferential surface of a drum. A drum is formed of a drum body with a gap of channel formed therein that accommodates a gripper system. The drum bodies of sheet-guiding impression cylinders are produced by casting. The circumferential surface of the drum is produced by machining in the form of chip removal. In general, the circumferential surface is protected against corrosion by a coating.
For reasons inherent to the printing process, the drum or cylinder may be provided with a jacket. The ends of the jacket are held in clamping devices. The jacket is tensioned or tautened about the cylindrical surface of the drum body in the circumferential direction.
German Published, Non-Prosecuted Patent Application DE102 49 731 A1 discloses a clamping and pulling for a cylinder jacket. The jacket is clamped and pulled tight through the use of a wedge transmission.
In a tensioning device, as it is disclosed in German Patent DE 197 41 092C2, insertion rails are provided at the ends of a jacket for a cylinder in a printing process. For tensioning purposes, the insertion rails are fixed in a tensioning rail. The tensioning rail is adjusted in the redial direction through the use of tensioning screws. Thus, the jacket is tautened on the surface of the cylinder.
German Patent DE 43 26 250 C2, corresponding to U.S. Pat. No. 5,503,072, discloses a device for tensioning a printing blanket on a transfer cylinder. In the device, a blocking device acts on one end of the printing blanket to exert pulling forces in the circumferential direction of the transfer cylinder.
The clamping and tensioning devices proposed by the prior art are costly and complex in terms of the required material. When a sheet is guided through a printing nip under pressure, the drum bodies are cohesive and bend-resistant.
It is accordingly an object of the invention to provide a drum for conveying a sheet, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which offers a cohesive sheet-guiding surface with little effort or cost.
With the foregoing and other objects in view there is provided, in accordance with the invention, a drum for conveying a sheet. The drum comprises a drum body, at least one jacket disposed above a gap and forming a circumferential surface, and at least one device for fixing said at least one jacket onto said drum body. The at least one device for fixing is radially adjustable and has at least one tensioning body acting on said at least one jacket in vicinity of said gap. Grippers hold the sheet on said circumferential surface and device actuates said grippers. Journals mount the drum in a frame and a drive rotates the drum about a longitudinal axis.
According to the invention, the gap or other type of hollow space is formed in the drum. The at least one jacket is placed over the gap. The tensioning body pulls the jacket, which is located above the gap, into the gap in the radial direction, thus tensioning or tautening the jacket. The tensioning gap for the jacket preferably extends parallel to the longitudinal axis of the drum and may be provided in addition to a gap that accommodates the grippers for the leading edge of a sheet.
In particular, when large-format sheets are to be conveyed, several backings or jackets may be disposed next to each other in the axial direction of the drum and may be pulled into the tensioning gap through the use of one or more tensioning bodies.
A jacket may have two ends that are fixed on the drum body before the tensioning bodies tension the jacket. The tensioning gap for the jacket is preferably located close to an end of the jacket.
A jacket may also be endless and sleeve-shaped. In this case, the jacket is pushed over the drum body having the tensioning gap before the jacket is tensioned, and the grippers for the sheet edge extend through openings in the jacket.
The tensioning body is preferably a tensioning a profile that rests against the jacket from outside in the region of the tensioning gap and is adjustable in a radially inward direction through the use of tensioning screws.
A particularly light-weight drum is created if ribs are formed on the drum body for the jacket to rest on after tensioning. The aforementioned tensioning gap for the jacket is formed by cut-outs in the ribs. In this embodiment, tensioning screws for pulling a tensioning profile inward in a radial direction are screwed into the ribs.
Other features which are considered as characteristics for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein ad embodied in a drum for conveying a sheet, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be understood from the following description of specific embodiments when read in connection with accompanying drawings.
Referring now to the figures of the drawings in detail and first, particularly, to
The printing unit 8 includes an inking unit 9, a dampening unit 10, a plate cylinder 11, a transfer cylinder 12, and an impression cylinder 13. The diameter of the impression cylinder 13 is twice the diameter of the plate cylinder 11 or the transfer cylinder 12. The impression cylinder 13 carries two gripper systems 14, 15.
Sheets 16 in the pile 2 are separated from the pile 2 and conveyed to the table 4 through the use of the suction head 3. The leading edge of a sheet 16 resting against the front guides or lays 5 is gripped by the oscillating grippers 6 and transferred to a gripper system 17 of the feed cylinder 7. The sheet 16 is held on the circumferential surface of the feed cylinder 7 and transferred to a gripper system 14, 15 of the impression cylinder 13. The sheet-fed printing press has a drive that rotates the cylinders 7 and 11 to 13 as indicated by arrows.
Number | Date | Country | Kind |
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10 2006 049 798 | Oct 2006 | DE | national |
Number | Name | Date | Kind |
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3926118 | Preuss | Dec 1975 | A |
5026045 | Wirz et al. | Jun 1991 | A |
5503072 | Schneider | Apr 1996 | A |
5673624 | Grundke | Oct 1997 | A |
5927198 | Tada | Jul 1999 | A |
7448625 | Forch et al. | Nov 2008 | B2 |
Number | Date | Country |
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4326250 | Feb 1995 | DE |
19741092 | Mar 1999 | DE |
10249731 | May 2003 | DE |
Number | Date | Country | |
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20080093790 A1 | Apr 2008 | US |