Rubber blanket with register cut-outs, and method of aligning a rubber blanket

Information

  • Patent Grant
  • 6827019
  • Patent Number
    6,827,019
  • Date Filed
    Monday, October 23, 2000
    23 years ago
  • Date Issued
    Tuesday, December 7, 2004
    19 years ago
Abstract
A method of aligning a rubber blanket formed with register cut-outs, relative to a clamping device having register pins, for clamping the rubber blanket onto a cylinder, includes bringing the register cut-outs formed in the rubber cylinder into contact with the register pins of the clamping device when the clamping device has been applied to the cylinder.
Description




BACKGROUND OF THE INVENTION




FIELD OF THE INVENTION




The invention relates to a rubber blanket with register cut-outs, and a method of aligning a rubber blanket, more particularly, formed with register cut-outs, relative to a clamping device having register pins, for clamping the rubber blanket onto a cylinder.




Such a method is described in the published German Patent Document DE 35 45 172 A1, corresponding to U.S. Pat. No. 4,707,902, wherein, initially, the ends of a rubber blanket formed with register cut-outs are inserted between clamping bars in a clamping device outside of a printing machine until the register cutouts come into contact with register pins belonging to the clamping devices. The clamping bars of the clamping devices are then connected by clamping screws, The clamping devices with the rubber blanket are then applied to a cylinder in the printing machine.




This method is unsuitable for printing or varnishing machines having clamping devices which are permanently arranged on the cylinder and which serve to fasten a printing plate to the cylinder. Because of the high flexural rigidity of printing plates, they are required to be rolled onto the cylinder, as described, for example, in the published German Patent Document DE 42 14 207 C1, for which purpose clamping devices applied permanently to the cylinder are used.




A rubber blanket corresponding to the rubber blanket generally described in the introduction hereto and in greater detail in the aforementioned published German Patent Document DE 35 45 172 A1 does indeed permit the alignment thereof in-register for cut-out in-line varnishing, but is unfavorable from several points of view because the register cut-outs are introduced directly into the soft blanket material.




On the one hand, the dimensional stability of the register cut-outs is very low. For example, distortion of the register cut-outs cannot be ruled out during frequently repeated fastening of the rubber blanket or because of swelling of the rubber. In addition, the risk exists that cracks will form at the register cut-outs as a result of careless handling of the rubber blanket.




On the other hand, the easily deformable register cut-outs require that the delicate ends of the blanket be aligned and firmly clamped very carefully outside the machine.




In addition, the published German Utility-Model Document DE 94 16 007 U1 describes a rubber blanket having a clamping bar which, in a construction as a flat profile, is vulcanized together with the rubber blanket only on the upper side of the blanket, so that the clamping bar ends flush with an edge of the rubber blanket. The design of the rubber blanket is unfavorable from various points of view.




On the one hand, the rubber blanket is unsuitable for cut-out in-line varnishing because this requires the top rubber layer of the rubber blanket to be cut out in locations corresponding to the varnishing cut-outs, as is extensively described in the aforementioned published German Patent Document DE 35 45 172 A1. Because the rubber blanket does not have any register cut-outs, cutting out the cut-outs in-register is possible only within the printing machine, which is very awkward to do.




On the other hand, the rubber blanket having the clamping bar formed as a flat profile assumes the presence of a clamping device having a maximum opening width, between a clamping pad and a clamping jaw, that is greater than the thickness of the blanket material together with the thickness of the clamping bar connected to the blanket material. Clamping devices which can be closed by rotating a slightly eccentric shaft do not always have such a large opening width, however.




SUMMARY OF THE INVENTION




It is accordingly an object of the invention to provide an improved method of aligning a rubber blanket having register cut-outs, and to provide such a rubber blanket which is particularly well suited for performing the method.




With the foregoing and other objects in view, there is consequently provided, in accordance with one aspect of the invention, a method of aligning a rubber blanket formed with register cut-outs, relative to a clamping device having register pins, for clamping the rubber blanket onto a cylinder, which comprises bringing the register cut-outs formed in the rubber cylinder into contact with the register pins of the clamping device when the clamping device has been applied to the cylinder.




In accordance with another aspect of the invention, there is provided a rubber blanket having register cut-outs and being formed of blanket material, comprising a clamping bar of the rubber blanket, the cut-outs being formed in the clamping bar.




In accordance with a further feature of the invention, the clamping bar is disposed only on an underside of the blanket material.




In accordance with an added feature of the invention, the clamping bar projects beyond an edge of the blanket material.




In accordance with an additional feature of the invention, the edge is a leading edge of the blanket material.




In accordance with yet another feature of the invention, the register cut-outs are formed only in the clamping bar.




In accordance with yet a further feature of the invention, the rubber blanket includes a sealing substance provided in at least one corner angle between the blanket material and the clamping bar.




In accordance with yet an added feature of the invention, the rubber blanket includes a clamping device, only the clamping bar being grippable by the clamping device for fastening the rubber blanket to a cylinder.




In accordance with a third aspect of the invention, there is provided a rubber blanket comprising structures defining register cut-outs, the register cut-outs being arranged in the rubber blanket so as to correspond to register cut-outs formed in a printing plate.




In accordance with a fourth and a fifth aspect of the invention, there are provided a printing machine and a varnishing machine, respectively, having a rubber blanket with register cut-outs and being formed of blanket material, the rubber blanket comprising a clamping bar, and the cut-outs being formed in the clamping bar.




Thus, the method according to the invention calls for bringing the register cut-outs in contact with the register pins when the clamping device is applied or fitted to a cylinder.




This method is extremely well suited for printing or by varnishing machines having clamping devices permanently arranged on the cylinder, the clamping devices hating been originally provided only for fastening a printing plate, and being now also selectively used for fastening the rubber blanket. In the method according to the invention, the actions of aligning the register cut-outs in relation to the register pins, and firmly clamping the rubber blanket are performed within the printing or varnishing machine.




The rubber blanket according to the invention is distinguished by the fact that the register cut-outs are introduced into a clamping bar belonging to the rubber blanket.




In this rubber blanket, high dimensional stability of the register cut-outs is assured, which means that multiple in-register clamping of the rubber blanket is possible over a long service life. The clamping bar can be formed as a hard metal strip or plastic strip. For example, in a construction as an aluminum strip, the clamping bar is eminently practical. In order to align the rubber blanket, the register cut-outs introduced into the clamping bar can be brought into engagement with register pins of a clamping device applied or fitted to a cylinder.




In an embodiment which is advantageous with regard to the register cut-outs striking the register pin without tilting, the clamping bar or strip is arranged on the rear side of the blanket material of the rubber blanket, i.e., that side thereof which faces the cylinder and is formed, for example, of a fabric. When the clamping bar or strip is clamped into the clamping device, it therefore rests directly on a clamping pad belonging to the clamping device.




In an embodiment which is advantageous with regard to a clamping device having a small opening width, the clamping bar or strip projects beyond an end of the rubber-covered blanket material which is preferably located at the start of the print. When the rubber blanket is fastened to the cylinder by a clamping device, it is therefore merely necessary for the clamping bar or strip, and not the blanket material, to be inserted into the clamping device and firmly clamped by the latter. The thickness of the clamping bar or strip, which is about 0.3 mm, is several times less than the thickness of the blanket material which is about 2 mm. Because of this fact, the rubber blanket can even be clamped firmly in clamping devices having an opening width which is smaller than the thickness of the rubber blanket.




In an embodiment which is advantageous with regard to the economic production of the clamping bar or strip, only the clamping bar or strip and not the rubber-covered blanket material is provided with the register cut-outs. Although it is also conceivable to stamp the register cut-outs only through the clamping bar or strip or through both the clamping bar or strip and the blanket in the case of a clamping bar or strip that is already permanently connected to the blanket material, it is more beneficial to stamp the register cut-outs into the clamping bar or strip before the clamping bar or strip is connected to the flexible blanket material.




In an embodiment which is advantageous with regard to reducing the risk of the clamping bar or strip loosening or separating from the blanket material, vulcanizing or bonding gaps between the clamping bar or strip and the blanket material are sealed on the outside, for which purpose use can be made again of an adhesive which is already used for the large-area bonding of the clamping bar or strip to the blanket material, or a different adhesive provided specifically for the sealing. The adhesive is applied into the corner angle formed by the blanket material and the clamping bar or strip together, so that the corner angles are partially filled with a wedge of adhesive, and peeling of the soft blanket material off the clamping bar or strip is prevented absolutely reliably, even after a relatively long service time of the rubber blanket.




Sealing is advantageous not only in the case of the clamping bar or strip being connected to the blanket material by adhesive bonding but also in the case of a connection being made by vulcanizing the blanket material onto the clamping bar or strip. In addition to an adhesive or vulcanization bond between the clamping bar or strip and the blanket material, the formlocking connection thereof, for example by rivets, is also conceivable. In this regard, it is noted that a formlocking connection is one which connects two elements together due to the shape of the elements themselves, as opposed to a forcelocking connection, which locks the elements together by force external to the elements.




In an embodiment which is advantageous with regard to clamping the rubber blanket into a clamping device in an unyielding and therefore secure manner, only the clamping bar or strip, but not the soft blanket material, is clamped into the clamping device. Because only the flat sides of the clamping bar or strip and either the very soft rubber surface (upper side) nor the fabric surface (underside) of the blanket material are provided as areas for the action of a force or contact areas for the clamping device, there is o danger that there will be any clamping traces pressed persistently into the blanket material, which could have adverse effects upon renewed clamping, even after frequent clamping and unclamping. In addition, it has been shown that a highly permanent bonding of the clamping bar or strip to the blanket material is surprisingly able to withstand the shear loading resulting from the clamping force required to tension or tauten the rubber blanket.




In an embodiment which is advantageous with regard to the variable use of a printing or varnishing-machine cylinder comprising a clamping device with register pins, both the register cut-outs in the rubber blanket and the register cut-outs of a printing plate can be clamped onto the cylinder as a replacement for the rubber blanket and can be pushed in-register onto one and the same register pins belonging to the clamping device. The register cut-outs in the rubber blanket essentially correspond in terms of the shape thereof to the register cut-outs in the printing plate. For example, the center spacing of the register pins is exactly the same as the center spacing of the register cut-outs in the rubber blanket, and exactly the same as the center spacing of the register cut-outs in the printing plate. In the case of a printing plate which, if required, is clamped in register onto the cylinder and, for example, is formed as a flexographic printing plate, the latter can be used for very fine spot varnishing, for example contoured so as to correspond to a line of text. In the case of a rubber blanket, clamped in register onto the cylinder as required, this can be used for varnishing with simply contoured and, for example, rectangular varnishing cut-outs, for which purpose the uppermost rubber layer of the blanket material is cut out so as to coincide with the varnishing cut-outs. Of course, when a blanket is clamped on in the delivered state without making any subsequent cut-outs, the cylinder can also be used for full-surface varnishing and coating.




It is also noted that, in some cases, the register cut-outs in the rubber blanket arranged so as to correspond to the register cut-outs in the printing plate can be introduced into the soft blanket material of a rubber blanket which does not have a clamping bar or strip.




Other features which are considered as characteristic for the invention are set forth in the appended claims.




Although the invention is illustrated and described herein as embodied in a rubber blanket with register cut-outs, and a method of aligning a rubber blanket, 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 best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein:











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a fragmentary diagrammatic cross-sectional view of an offset printing unit of a rotary printing machine including a cylinder with a rubber blanket thereon;





FIG. 1



a


is a fragmentary view of

FIG. 1

showing part of the rubber blanket and of a printing plate clamped thereon; and





FIG. 2

is a top plan view of the rubber blanket after it has been removed from the cylinder.











DESCRIPTION OF THE PREFERRED EMBODIMENTS




Referring now to the drawings and, first, particularly to

FIG. 1

thereof, there is shown therein one of a umber of offset printing units which may be included in a rotary printing machine. In

FIG. 1

, there is shown a varnishing unit arranged downline of the offset printing unit in the transport direction of the printing material, the varnishing unit including an impression cylinder


2


for transporting a sheet of printing material


3


, and a cylinder


4


with a rubber blanket


5


, which is fastened to the cylinder


4


by clamping devices


6


and


7


.




The rubber blanket


5


includes an upper-side rubber layer


8


(note

FIG. 3

) which carries the varnish and from which at least one recess


9


for the cut-out in-line varnishing of the printing material


3


has been cut, and an underside fabric layer


10


and clamping bars


11


and


12


, which are bonded to the fabric layer


10


. Intermediate layers may also be disposed between the layers


8


and


10


. The sheet-like composite material formed of at least the layers


8


and


10


are referred to hereinbelow as the blanket material


13


.




The corner angles formed by the upper sides of the clamping bars


11


and


12


together with the arrow sides of the blanket material


13


, and those formed by the arrow sides of the clamping bars


11


and


12


together with the underside of the blanket material


13


, are provided, over the entire width of the rubber blanket


4


with applied seals


14


for which an adhesive different from that used for bonding the clamping bars


11


and


12


to the blanket material


13


has been used.




The overall width of each clamping bar


11


,


12


disposed on one side of the blanket material


13


is 2 to 3 cm and, as shown in

FIG. 2

, is subdivided into an overlap width


15


corresponding approximately to half the total width, by which each clamping bar


11


,


12


projects beyond a corresponding edge


16


of the blanket material


13


, and a remaining covering width over which each clamping bar


11


,


12


is (nondestructively) inseparably connected to the blanket material


13


.




Each of the clamping devices


6


and


7


belonging to a tensioning device for tensioning the rubber blanket


5


includes a respective clamping pad


17


,


18


and a respective clamping jaw


19


,


20


which is adjustable relative to the respective clamping pad


17


,


18


in order to clamp only the respective clamping bar


11


,


12


firmly between the respective clamping pad


17


,


18


and the respective clamping jaw


19


,


20


, while the blanket material


13


is located completely outside the clamping devices


6


and


7


. In other words, when the clamping bars


11


and


12


are firmly clamped, the blanket material


13


is located either between the clamping pad


17


and the clamping jaw


19


or between the clamping pad


18


and the clamping jaw


20


.




Only the clamping device


6


assigned to the start of the print includes two cylindrical register pins


21


and


22


, which engage, through register cut-outs


23


and


24


, with the clamping bar


11


clamped in and projecting beyond a supporting surface for the clamping bar


11


on the clamping pad


17


. The register pin


21


rests on the approximately semicircular register cut-out


23


, along the inner edge of the latter, and the register pin


22


, which is formed like the register pin


21


, contacts the inner wall of the rectangular register cut-out


24


only at a tangential point, as can be seen in FIG.


2


. In order to achieve such a contact, the width of the cut-out


24


is somewhat greater than the diameter of the cut-out


23


, and the diameter of the pin


22


can also be somewhat smaller than the diameter of the pin


21


.




The rubber blanket


5


is clamped onto the cylinder


4


in the following manner:




Initially, the rubber blanket


5


is inserted into the machine


1


, the clamping bar


11


being placed with one flat side thereof onto the clamping pad


17


disposed on the cylinder


4


, and being displaced on the pad


17


until the register pins


21


and


22


make contact in the register cut-outs


23


and


24


. The clamping jaw


19


is then pressed onto the other flat side of the clamping bar


11


by an otherwise on-illustrated eccentric shaft so that the clamping bar


11


is firmly held, and the in-register position of the leading end of the rubber blanket


5


is fixed.




A pressure roller


25


is then set against or into engagement with the blanket material


11


, and the cylinder


4


is set into rotation, so that the pressure roller


25


rolls on the blanket material


13


from the start of the print in a direction towards the tail end of the print and, as a result, tautens the blanket material


13


and places it smoothly from the start to the tail end thereof onto the cylinder


4


.




After the pressure roller


25


has reached the tail end of the print, the clamping bar


12


is placed on the clamping pad


18


disposed on the cylinder


4


in the alignment resulting from the rubber blanket


5


being pulled onto the cylinder


4


, and this alignment is fixed by closing the clamping device


7


The clamping device


7


, which otherwise corresponds in the construction thereof to the clamping device


6


, does not have any register pins, and the clamping bar


12


is formed without register cut-outs, which are required only for the leading end and not for the tail end of the rubber blanket


5


. The clamping devices


6


and


7


are then adjusted towards one another, thereby tautening the rubber blanket


5


. In this regard, the force flow of the tensioning or tautening force flows from the clamping device


7


, over the clamping bar


12


, further over a flat bond


26


, further over the blanket material


13


, further over a further bond


27


and ultimately over the clamping bar


11


to the clamping device


6


. It has been shown that adhesive bonds


26


and


27


produced with a suitable adhesive, for example No. 588 from 3 M, i.e., the Minnesota Mining and Manufacturing Co., exhibit a sufficiently high shear strength of ≧4 Newtons per square millimeter and withstand loadings of this type over a long service life, even without the bonded parts


11


,


13


and


12


,


13


, respectively, being pressed together, which is conceivable as distinguished from the exemplary embodiment shown under the loading by the clamping devices


6


and


7


.




A printing plate


28


forming a register system together with the rubber blanket and the cylinder


4


can be clamped onto the cylinder


4


as required, alternating with the rubber blanket


5


. Positioning the printing plate


28


by the register pins


21


and


22


, pulling on the printing plate


28


by the pressure roller


25


, and firmly clamping the ends of the printing plate in the clamping devices


6


and


7


are performed in the manner already explained hereinbefore with regard to clamping the rubber blanket


5


.




For this purpose, the leading end of the printing plate


28


is provided with register cut-outs


30


and


31


(register cut-out


30


hides the register cut-out


31


located behind it in

FIG. 1

) which, in terms of the shape thereof, correspond to the register cut-outs


23


and


24


, the center spacing of the cut-outs


30


and


31


, in exactly the same way as that of the register cut-outs


23


and


24


, corresponding to a center spacing


29


of the register pins


21


and


22


.




In order for the ends of the printing plate


28


to be insertable into clamping devices


6


and


7


which open only slightly, the ends of the printing plate


28


are tapered over a width corresponding approximately to the overlap width


15


to a thickness corresponding approximately to the thickness of the clamping bars


11


and


12


. The printing plate


28


is a flexographic printing plate having a printing relief layer


32


bearing the printed image and being tapered in the region of the ends of the plate during the development process of the printing image. If the relief layer


32


is a photo polymer layer, the development of the printing image and the tapering of the ends of the plate can be performed by a washing process. If the printing plate


28


is additionally a multilayer plate, the relief layer


32


is removable completely down to a stable carrier layer


33


. The register cut-outs


30


and


31


, before the use thereof for the in-register positioning of the printing plate


28


in the clamping device


6


, have already been used for the in-register positioning of the printing plate


21


during the imaging or image-setting process preceding the washing process and producing the printed image, which was latent only before the washing process.



Claims
  • 1. A method of aligning a rubber blanket configuration relative to a clamping device having register pins, for clamping the rubber blanket configuration onto a cylinder, which comprises:providing the rubber blanket configuration with a blanket material and a clamping bar having substantially u-shaped register cut-outs formed therein; inseparably connecting the clamping bar to the blanket material; and bringing the substantially u-shaped register cut-outs formed in the clamping bar into contact with the register pins of the clamping device when the clamping device has been applied to the cylinder.
  • 2. A rubber blanket configuration, comprising:a rubber blanket having a blanket material and a clamping bar with substantially u-shaped register cut-outs formed therein; said blanket material having an upperside layer and an underside layer; and said clamping bar being disposed only on said underside layer.
  • 3. The rubber blanket configuration according to claim 2, wherein said clamping bar is disposed only on an underside of said underside layer.
  • 4. The rubber blanket configuration according to claim 2, wherein said clamping bar projects beyond an edge of the blanket material.
  • 5. The rubber blanket configuration according to claim 4, wherein said edge is a leading edge of the blanket material.
  • 6. The rubber blanket configuration according to claim 2, wherein the register cut-outs are formed only in said clamping bar.
  • 7. The rubber blanket configuration according to claim 2, including a sealing substance provided in at least one corner angle between the blanket material and said clamping bar.
  • 8. An assembly, comprising:a rubber blanket configuration having a blanket material; said rubber blanket configuration having a clamping bar with substantially u-shaped register cut-outs formed therein; and a clamping device fastening said rubber blanket configuration to a cylinder, said clamping device gripping only said clamping bar.
  • 9. A register system, comprising:a cylinder having register pins; a flexographic printing plate with substantially u-shaped register cut-outs formed therein; and a rubber blanket configuration having structures defining further substantially u-shaped register cut-outs disposed in the rubber blanket configuration and corresponding to said substantially u-shaped register cut-outs of said printing plate; said substantially u-shaped register cut-outs and said further substantially u-shaped resister cut-outs both corresponding to said register pins of said cylinder.
  • 10. A printing machine, comprising;a rubber blanket configuration including a blanket material and a clamping bar having substantially u-shaped register cut-outs formed therein; said blanket material having an upperside layer and an underside layer; and said clamping bar being disposed only on said underside layer.
  • 11. A varnishing machine, comprising:a rubber blanket configuration including a blanket material and a clamping bar having substantially u-shaped register cut-outs formed therein; said blanket material having an upperside layer and an underside layer; and said clamping bar being disposed only on said underside layer.
  • 12. An assembly, comprising:a rubber blanket configuration having a blanket material; said rubber blanket configuration having a clamping bar with substantially u-shaped register cut-outs formed only in said clamping bar and said clamping bar projecting beyond an edge of said blanket material; and a clamping device fastening said rubber blanket configuration to a cylinder, said clamping device gripping only said clamping bar.
  • 13. A method of aligning a rubber blanket configuration relative to a clamping device having register pins, for clamping the rubber blanket configuration onto a cylinder, which comprises:providing a blanket material; providing at least one clamping bar; forming substantially u-shaped register cut-outs in the at least one clamping bar; and producing the blanket configuration by inseparably connecting the at least one clamping bar to the blanket material, for later installation of the blanket configuration onto the cylinder by bringing the substantially u-shaped register cut-outs formed in the at least one clamping bar into contact with the register pins of the clamping device when the clamping device has been applied to the cylinder.
  • 14. A method of aligning a rubber blanket configuration relative to a clamping device having register pins, for clamping the rubber blanket configuration onto a cylinder, which comprises:obtaining the rubber blanket configuration including at least one clamping bar with substantially u-shaped register cut-outs formed therein and a blanket material inseparably connected to the at least one clamping bar; and installing the blanket configuration onto the cylinder by bringing the substantially u-shaped register cut-outs formed in the at least one clamping bar into contact with the register pins of the clamping device when the clamping device has been applied to the cylinder.
Priority Claims (1)
Number Date Country Kind
199 50 605 Oct 1999 DE
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