Abstract:
An apparatus for stretching a cylinder blanket on a sheet transfer cylinder of a sheet-fed printing press includes a tiltable member mounted on the cylinder. A first end of the blanket is first attached to the cylinder in a cylinder groove, the blanket is wrapped around the cylinder, and the second end of the blanket is attached to the tiltable member, while the tiltable member is in an open position. The tiltable member is then closed to stretch the blanket about the cylinder, and locked into the closed position to maintain the blanket about the cylinder.

Description:
BACKGROUND OF THE INVENTION 
     A. Field of the Invention: 
     This invention relates to an apparatus for stretching a cylinder blanket on a sheet transfer cylinder of a sheet-fed rotary printing press. A first end of the blanket is maintained in a cylinder groove, and the other end of the blanket is fastened to a tiltable segment. The blanket is attached to the tiltable segment when the tiltable segment is in an open position, and the blanket is then stretched by closing the tiltable segment. 
     B. Background Information: 
     One example of a tiltable cylinder segment that could be used for stretching a cylinder blanket can be found in U.S. Pat. No. 1,858,305. However, the disclosed device is a printing plate stretching device on a plate cylinder, and it is not possible to stretch a blanket on a transfer cylinder in the same manner that a blanket can be stretched on a plate cylinder. 
     Another stretching apparatus for a blanket can be found in German Patent No. 75 22 036. However, the German patent does not provide a simple and easy manner in which to stretch the blanket. 
     OBJECT OF THE INVENTION 
     The object of this invention is therefore to create a stretching apparatus for a blanket on a transfer cylinder for a sheet-fed printing press, on which cylinder it is easily possible to stretch and change the blanket, even inside the press, without having to remove the entire cylinder from the press. 
     SUMMARY OF THE INVENTION 
     This object is achieved by the present invention with a blanket that is stretched around the transfer cylinder by a tilting mechanism. On the outer edge of the end-of-printing end of the blanket, there are preferably several bolts or bottom means located in proximity to one another across the width of the blanket. These bolts are for being suspended in recesses of a leaf spring that is fastened into a groove of the cylinder and extends over the length of the cylinder. In the peripheral region on the other end of the blanket, or the start-of-printing end, the blanket preferably has a spring rod which extends across the width of the blanket. This spring rod is for being suspended by several bolts in proximity to one another, installed across the length of the tilting segment. The tilting segment is openable to allow for fastening of the blanket to the tilting segment, and by closing the tilting segment with the blanket attached thereto, the blanket is essentially stretched around the cylinder. The tilting segment can be locked into the closed position by fastening with locking means, such as locking screws. 
     By means of the solution according to the present invention, it becomes possible to easily insert or replace a blanket on the cylinder, which insertion or replacement of a blanket is possible even in the printing press, without having to remove the entire cylinder from the press. The solution of the present invention also essentially simultaneously guarantees that when the blanket is stretched, it will essentially always have precisely the required tension. Also, because there may be variance in the blankets due to manufacturing tolerances, the solution according to the present invention essentially provides compensation for any manufacturing tolerances which may be present. 
     Several additional advantageous configurations of the invention preferably include providing the tilting segment with adjusting means, such as adjusting screws or set screws, so that the position of the tilting segment can be adjusted on the cylinder, securing the ends of the blanket by leaf springs, and providing a liner sheet, or mat, under the blanket, to cover the surface of the cylinder. 
     In place of the blanket, which is typically used to prevent smearing and thus damage to the printed image on freshly printed sheets, a metal film which has an ink repellant surface can also be used. In a modification of the solution disclosed above, one advantageous configuration of the invention provides the ability for using the present invention to secure the metal film to the cylinder. In this embodiment, the metal film can be bent back at the start-of-printing end, suspended on the tilting segment and secured by leaf springs. Just as for stretching a blanket, the tilting segment can be closed and fastened in place by the locking means, such as the locking screws. In this manner, a precise tension can also be applied to the metal film. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is schematically illustrated in the accompanying drawings, in which: 
     FIG. 1 shows a partial cross section through a transfer cylinder with a blanket stretched therearound; 
     FIG. 2 shows a partial cross section through a transfer cylinder with the tilting segment in an open position; 
     FIG. 3 shows a detail of the leaf spring at the end-of-printing end of the sheet; 
     FIG. 4 shows a partial cross section through the leaf spring of FIG. 3, with suspended blanket attached thereto; and 
     FIG. 5 shows a suspended metal film disposed over a liner sheet. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     On the transfer cylinder 1, the sheets 2, to be transported, can be held by means of a gripper system 3 and a gripper bar 4, and from the transfer cylinder, are transferred to the next transfer cylinder or printing cylinder. The gripper system 3 is preferably fastened about a gripper shaft 5, and can be controlled by cams (not shown). Since such transfer cylinders are typically used to transport freshly printed sheets, there is a danger that the fresh printing will smear on the convex surface of the transfer cylinder, and thus damage the printed image. To prevent smearing, cylinder blankets are often used. Such blankets can be made of textile material, and are typically designed so that they do not absorb any ink, thereby preventing damage to the printed image. The blankets preferably cover the entire convex surface of the transfer cylinder to which cylinder the blankets are preferably fastened under tension. 
     In the embodiment illustrated in FIG. 1, a blanket 6 is stretched around the convex surface of the transfer cylinder 1. A first end of the blanket, which typically is disposed adjacent a starting edge of a printed sheet when a printed sheet is disposed about the cylinder, is sometimes called the start-of-printing end, while the other end of the blanket, disposed at the opposite edge of a printed sheet when a printed sheet is disposed about the cylinder is sometimes called the end-of-printing end. In the peripheral region at the start-of-printing end, there is preferably a resilient means, such as a spring rod 7, which preferably extends along the entire width of the blanket. The spring rod 7 can be suspended from the tilting segment 8 by means of several bolts 9 which are installed across the length of a tilting segment 8. For accommodating the spring rod 7, the bolts 9 can have recesses 9a which preferably have a configuration to match the configuration of the rod 7, for example a concave surface to match the convex surface of the rod. In the peripheral edge of the blanket, there can preferably be openings (not shown) which fit over the bolts 9 so that the bolts can essentially be disposed through the end of the blanket. 
     In FIG. 2, the tilting segment 8 is shown in the opened position, in which position the blanket 6 is essentially not stretched. To prevent the spring rod 7 from unhooking from the bolts 9, there can preferably be retaining springs 10 which are fastened by means of the bolts 9. The tilting segment 8 can preferably be supported, on both sides of the cylinder, on a pivot 11, which pivot 11 can be fastened by means of bearings 12 to the transfer cylinder 1. 
     When the tilting segment 8 is tilted to its base position to stretch the blanket, the segment 8 can be fastened on both sides by a locking device, such as locking screws 13. 
     A bar 14 can preferably be fastened in the vicinity of the outer edge of the end-of-printing end of the blanket 6. Bolts, or pins, 15 can be located next to one another along this bar, and are for being suspended in recesses 16 of a leaf spring 17. The leaf spring 17 preferably extends over the entire length of the cylinder and can be fastened by means of screws 18 and a bar 19 into the cylinder groove 20 of the transfer cylinder 1. 
     In FIG. 3, the leaf spring 17 is shown with the recesses 16 into which the bolts 15 can be hooked. The bolts 15, along with the recesses 16 are preferably distributed uniformly at intervals over the length of the cylinder to provide fastening of the blanket 6 substantially evenly along the length of the cylinder. The recesses 16 can preferably have a first dimension larger than a dimension of the bolts 15 so that the bolts 15 can easily be passed through the recesses. In addition, the recesses can also have a portion 16a which has a dimension smaller than a dimension of the bolts 15 to maintain the bolts within the recesses once the bolts have been inserted therein. To prevent the bolts 15 from slipping out of the recesses 16, when the blanket 6 is stretched, there can be a resilient member, such as a spring rod 21, for forcing the bolt 15 into the smaller dimension portion 16a of the recess 16. Such a spring rod 21 can preferably be fastened in a mounting 22, which mounting 22 can, in turn, be screwed to the leaf spring 17 by means of screws 23. In this regard, FIG. 4 shows a side view, whereby a grasping device, such as a hook 24 can be fastened to the bolts 15. Such a grasping device preferably provides means by which the bolts 15 can be easily unhooked from the recesses 16 by allowing the bolts 15 to be moved against the force of the spring rod and therefore out of engagement with the small dimension portion 16a of the recess 16. 
     In view of the above description, a method for stretching the cylinder blanket onto the transfer cylinder could possibly involve the following steps: 
     1) fastening the end-of-printing end of the blanket 6 into the cylinder groove 20 by pushing the bolts 15 into corresponding recesses of the leaf spring 17, so that the retaining rods 21 hold the bolts 15 in the recesses; 
     2) wrapping the cylinder blanket about the cylinder; 
     3) opening the tilting member 8; 
     4) engaging the start-of-printing end of the blanket 6 onto the tilting member 8 by pushing the blanket over the bolts 9 so that the bolts 9 are disposed through openings (not shown) in the blanket and so that the spring rod 7 engages the bolts 9 in the recess 9a; 
     5) stretching the blanket by pivoting the tilting member 8 into its closed position; and 
     6) locking the tilting member 8 in the closed position by means of the locking screws 13. 
     In a modification of the invention, a metal film 25, instead of a blanket, can be stretched over the convex surface of the transfer cylinder 1 as shown in FIG. 5. The metal film 25 should preferably have an ink-repellant outer surface to prevent damage to the printed image. To adjust the metal film 25 to the diameter of the cylinder, the metal film 25 can be underlaid with a liner sheet, or mat 26, of a required thickness to compensate for any diameter difference. Such a liner sheet could also be used with a blanket, if desired or if necessitated by a diameter difference. By means of a bent portion 27, the metal film can be suspended at the start-of-printing end on the tilting segment 8, and prevented from sliding out by means of a leaf spring 28. The fastening on the end-of-printing end is essentially designed like that for the blanket, as discussed above. 
     In FIG. 5, the tilting segment 8 can be pivoted inward and fastened by means of the locking screws 13. The locking screws 13 can then be screwed into a rotating abutment 29, which is preferably pivotable so that the screws 13 can be pivoted into a rest position, as shown in FIG. 2, by means of a resilient member, such as a torsion spring 30. 
     In addition, the tilting member 8 can also have set screws 31 for adjusting the tilting segment. Such an adjustment can be used to compensate for any variances in stretch between the blankets used, or to compensate for wear of the blankets which would, over time, typically increase the length of the blankets. 
     In summary, one aspect of the invention resides broadly in an apparatus for stretching a blanket on transfer cylinders of sheet-fed printing presses, in which the blanket is held on one end in a cylinder groove, and the other end is fastened to a tilting segment, whereby the blanket is stretched by closing the tilting segment, characterized by the fact that the blanket 6 on the end-of-printing end has several bolts 15 located next to one another across the width on the outer edge, which bolts are suspended in recesses 16 on a leaf spring 17 which extends over the length of the cylinder, whereby the leaf spring 17 is fastened in the cylinder groove 20, that the blanket 6 on the start-of-printing end has a spring rod 7, which extends over the width of the blanket in the peripheral region and is suspended in several bolts 9 located next to one another across the width on the tilting segment 8, and that the tilting segment 8 is fastened by locking screws 13 when closed. 
     Another aspect of the invention resides broadly in an apparatus characterized by the fact that the tilting segment 8 can be adjusted by means of set screws 31. 
     A further aspect of the invention resides broadly in an apparatus characterized by the fact that the ends of the blanket 6 are secured by springs 7, 21. 
     Still another aspect of the invention resides broadly in an apparatus characterized by the fact that a liner sheet 26 which covers the convex surface of the cylinder is stretched under the blanket 6. 
     A yet another feature of the invention resides broadly in an apparatus for stretching a metal film on transfer cylinders of sheet fed printing presses, characterized by the fact that the metal film 25 is bent back 27 on the start-of-printing end, suspended on the tilting segment 8 and secured by leaf springs 28. 
     Some examples of printing press cylinders onto which blankets are stretched, and the means for stretching the blankets onto the cylinder are disclosed in the following U.S. Pat. No. 4,854,237 to Theilacker, entitled &#34;Printing Machine Cylinder Underlay Holding Arrangement&#34;; U.S. Pat. No. 4,648,318 to Fischer, entitled &#34;Rubber Blanket Attachment Arrangement for an Offset Rotary Printing Machine&#34;; U.S. Pat. No. 4,584,942 to Sauer, entitled &#34;Device for Fastening One Extremity of a Soft and Folding-Proof Blanket on a Cylinder of a Rotary Printing Machine&#34;; U.S. Pat. No. 4,403,549 to Matuschke, entitled &#34;Printing Plate Attachment Arrangement&#34;; U.S. Pat. No. 4,263,849 to Spac and Kunkel, entitled &#34;Stretching and Fastening Device for Blankets and the like on Printing Press Cylinders&#34;; and U.S. Pat. No.: 4,006,686 to Ackerman, entitled &#34;Blanket Fastening Means for a Cylinder Blanket&#34;. 
     All, or substantially all, of the components and methods of the various embodiments may be used with at least one embodiment or all of the embodiments, if any, described herein. 
     All of the patents, patent applications and publications recited herein, if any, are hereby incorporated by reference as if set forth in their entirety herein. 
     The details in the patents, patent applications and publications may be considered to be incorporable, at applicant&#39;s option, into the claims during prosecution as further limitations in the claims to patentably distinguish any amended claims from any applied prior art. 
     The appended drawings, in their entirety, including all dimensions, proportions and/or shapes in at least one embodiment of the invention, are, if applicable, accurate and to scale and are hereby incorporated by reference into this specification. 
     The invention as described hereinabove in the context of the preferred embodiments is not to be taken as limited to all of the provided details thereof, since modifications and variations thereof may be made without departing from the spirit and scope of the invention.