Printing cylinder

Abstract: Disclosed is a printing cylinder which makes it possible to remove the ink adhered to the side surfaces of the printing cylinder after the printing has been finished without the need of moving the printing cylinder.

Description: BACKGROUND OF THE INVENTION A printing method has been put into practice according to which a printing ink is fed onto the printing face constituted by the outer surface of a printing cylinder of a cylindrical shape, hereinafter simply referred to as printing cylinder, the printing cylinder is set to a printing press and is rotated in order to print the papers, as is done, for example, in the gravure printing. In the above-mentioned printing method using the printing cylinder, the ink adhered to the printing face of the printing cylinder is wiped off after the printing is finished. The ink layer adhered to the side surfaces of the printing cylinder usually becomes as thick as ten and several millimeters at a moment when the printing is finished. The ink adhered to the side surfaces of the printing cylinder cannot be automatically removed because of the reasons that the printing cylinder is heavy and that the ink is not adhered uniformly. If the ink that is adhered is not wiped off but is left to stay, then it mixes into the ink used in the printing of the next time causing the ink to lose its color tone. Furthermore, the ink that is coagulated peels off at the time of printing and adheres to the surface of the printing cylinder causing the doctor blade to be damaged and hindering the printing. In order to solve the problem caused by the ink that is adhered to the side surfaces of the printing cylinder, a method has been disclosed in Japanese Laid-Open Patent Publication No. 91281/1987 according to which the printing cylinder is removed from the printing press and the side surfaces thereof are cleaned. That is, the printing cylinder having ink adhered to the side surfaces thereof is removed from the printing press, and the water of a very high pressure is blown against the printing cylinder. According to the above method, however, it is necessary to clean the side surfaces of the printing cylinder in addition to the operation for wiping the ink off the printing face of the printing cylinder that is removed from the printing press; i.e., a great deal of labor is required to move the very heavy printing cylinder to the cleaning device which uses the water of a very high pressure. Moreover, there is a likelihood of giving damage to the printing face of the printing cylinder while it is being moved or during the operation for washing out the ink. Japanese Utility Model Laid-Open Publication No. 93236/1986 proposes a printing cylinder which prevents the ink from adhering onto the side surfaces by providing the side surfaces of the printing cylinder with a layer of a fluorine-contained resin such as polytetrafluoroethylene. This method makes it possible to considerably reduce the amount of ink adhered to the side surfaces of the printing cylinder making, however, it necessary to remove the ink adhered to the side surfaces in addition to the operation for wiping the ink off the printing face of the printing cylinder. Like the above-mentioned method, therefore, it is necessary to clean the side surfaces of the printing cylinder leaving such problems as the introduction of a cleaning step and likelihood of damaging the printing cylinder while it is being moved for the purpose of being cleaned. OBJECTS OF THE INVENTION The object of the present invention is to provide a printing cylinder which makes it possible to remove the ink adhered to the side surfaces of the printing cylinder after the printing has been finished without the need of moving the printing cylinder. Another object of the present invention is to provide a printing cylinder which makes it possible to efficiently clean the side surfaces thereof even under the condition where the printing cylinder is being mounted on the printing press. CONSTITUTION OF THE INVENTION The above objects of the present invention are accomplished by the constitution in which annular side plates are detachably attached to the side surfaces of the body of the printing cylinder utilizing the magnetic force, the annular side plates having a circumference close to the circumference of the side surfaces of the body of the printing cylinder. The present invention will now be described in further detail in conjunction with the drawings that illustrate preferred embodiments of the printing cylinder constituted according to the invention. Figs. 1 to 4 are perspective views illustrating the printing cylinder according to a representative embodiment of the present invention. Fig. 5 is a sectional view illustrating the internal structure of the annular side plate provided on the side surfaces of the printing cylinder according to a representative embodiment of the present invention. Fig. 6 is a perspective view illustrating the condition where the printing cylinder of the present invention is mounted on a printing press. The structure of the body of the printing cylinder of the present invention will now be described in conjunction with Fig. 1. In the present invention, a widely known structure comprising a cylindrical drum constituting the printing face and members constituting side surfaces 3, is employed as a body 1 of the printing cylinder without any particular limitation. There is no particular limitation with regard to the materials, either. Widely known materials are generally used such as a steel, an aluminum alloy, etc. The cylindrical drum and the side surfaces of the body of the printing cylinder may be made of the same material or different materials. Representative examples may be the one in which the whole printing cylinder is made of a steel and the one in which the drum of the printing cylinder is made of an aluminum alloy and the side surfaces are made of a steel. Further, the body of the printing cylinder has a mechanism at the center of both side surfaces thereof that couples to the rotary shaft of a printing press. For instance, the rotary shaft of the printing press may be secured to the centers of side surfaces of the body of the printing cylinder as a unitary structure or bores for fixing the rotary shaft may be formed at the centers of the side surfaces, without any particular limitation. The embodiment shown in Fig. 1 deals with the structure in which bores are formed to fix the rotary shaft. In this case, it is desired to provide the bore with a cylindrical cone 9 which spreads outwardly to facilitate the mounting of the rotary shaft on the printing press. When the side surfaces are not constituted by a ferromagnetic substance such as a steel, the side surfaces are provided with a layer of a ferromagnetic substance or with a layer of a permanent magnet using a fixing means such as screws or the like. Depending upon the mode of printing, furthermore, there is formed a metal-plated layer or a rubber layer for forming a printing plate on the drum of the body of the printing cylinder. According to the present invention, annular side plates 2 are detachably attached to both side surfaces of the printing cylinder utilizing the magnetic force to cover the side surfaces. There is no particular limitation to the size of the annular side plates 2 provided they have an outer diameter D2 which is close to the outer diameter D1 of the body 1 of the printing cylinder. In general, the outer diameter D2 of the annular side plates should desirably lie over a range from the outer diameter D1 of side surfaces of the body of the printing cylinder to a diameter which is smaller by 20 mm than the outer diameter D1. In the case of the structure in which the rotary shaft is fixed to the printing cylinder, the bore diameter D3 of the annular side plates should be smaller than the outer diameter D2 of the side plates but should be greater than the outer diameter of the rotary shaft. In the case of the structure where bores are provided to insert the rotary shaft in the printing cylinder as shown in Fig. 1, the bore diameter D3 should be smaller than the outer diameter of the side plates. When the bore is provided with the cone 9 to receive the rotary shaft, furthermore, the bore diameter D3 of the annular side plates should be determined to be greater than the outer diameter of the cone 9. The annular side plates should desirably be so designed as to partly cover the outer circumferential portion of the side surfaces as shown in Fig. 1 from the standpoint of facilitating the operation for attaching and detaching the annular side plates, reducing the weight, and enhancing the effect of preventing the ink from adhering onto the side surfaces of the body of the printing cylinder despite an increase in the areas that are covered. In this case, the annular side plates 2 should desirably be so designed that the difference between the outer diameter D2 thereof and the bore diameter D3 thereof is from 10 to 60% with respect to the outer diameter D1 of the printing cylinder. It is further desired that the annular side plates have a small thickness to reduce the weight thereof. However, too small thickness is accompanied by the reduction in the mechanical strength which may result in the breakage when the annular side plates are being attached to or detached from the side surfaces of the body of the printing cylinder. Therefore, a suitable thickness should be determined by taking the reduction in weight and the mechanical strength into consideration. Usually, the thickness ranges from 0.5 to 10 mm. As shown in Fig. 1-A, the annular side plates 2 may have a tapered outer surface whose thickness increases from the outer circumference toward the inner circumference. There is no particular limitation in the embodiment of detachably attaching the annular side plates to the side surfaces of the printing cylinder by utilizing the magnetic force provided the side plates can be held on the side surfaces of the printing cylinder by the magnetic force. In general, the side surfaces of the body of the printing cylinder are constituted by a ferromagnetic substance and the annular side plates are partly or entirely constituted by a permanent magnet, or the side surfaces of the body of the printing cylinder are constituted by the permanent magnet and the annular side plates are partly or entirely constituted by the ferromagnetic substance. Any widely known material can be used as the ferromagnetic material without any particular limitation provided it is magnetized and is attracted by the magnetic field of a permanent magnet. Examples include such metals as iron, cobalt, nickel, etc. Moreover, any permanent magnet may be used without any particular limitation. Examples include carbon steel, tungsten steel, KS-steel, Alnico, etc. The above ferromagnetic substance and permanent magnet may be used in their own form or may be used in the form of a so-called "plastic magnet" by pulverizing them and mixing them in a matrix of a resin or a rubber. The side plates which are held on the side surfaces of the printing cylinder by the magnetic force may begin to be deviated from the side surfaces if they are too heavy due to the centrifugal force produced during the printing operation by the rotation of the printing cylinder. According to the present invention, therefore, though the annular side plates can entirely be constituted by the permanent magnet (including plastic magnet) or the ferromagnetic substance, it is desired to partly use the permanent magnet or the ferromagnetic substance depending upon the intensity of magnetic force of the permanent magnet and constitute other portion using a light material such as a thermoplastic resin, e.g., polyolefin resin, polyvinyl chloride resin or the like resin, in order to reduce the weight of the side plates yet covering the side surfaces of the printing cylinder. Fig. 5 is a sectional view illustrating the internal structure of the annular side plate which partly employs the permanent magnet according to a representative embodiment. In Fig. 5, the side plate is formed in an annular shape and has a thermoplastic resin film 8 laminated on one surface of the permanent magnet (inclusive of a plastic magnet) and a thermoplastic resin 7 molded on the other surface thereof. According to this embodiment, the thermoplastic resin film having a small thickness is formed on one side of the permanent magnet. Therefore, if this side is faced to the side surface of the printing cylinder, the magnetic force of the side plate is not lost with respect to the above side. The present invention also provides a printing cylinder employing the above-mentioned annular side plates that are constituted to be capable of being opened and that can be attached to or detached from the body of the printing cylinder under the condition where the body of the printing cylinder is being mounted on the printing press. That is, the annular side plate shown in Fig. 1 is continuous throughout the whole circumference and must be attached thereto or detached therefrom by removing the printing cylinder from the printing press. On the other hand, the annular side plate that is constituted to be capable of being opened can be attached to and detached from the printing cylinder by opening it under the condition where the printing cylinder is being mounted on the printing press, making it possible to carry out the operation more efficiently. The annular side plate can be formed in a manner to be split or cut only one portion so that it can be opened. As shown in Figs. 4, 4-A and 4-B, the annular side plate 2 can be split into two or more segments. As shown in Figs. 4-C and 4-D, furthermore, the annular side plate 2 can be opened by cutting only one portion thereof only provided it has flexibility. In order to prevent the ink adhered to the side surfaces of the body 1 of the printing cylinder from moving in the direction of the rotary shaft according to the present invention as shown in Fig. 2, it is desired to provide a continuous protrusion 4 along the inner circumference on the surface of the annular side plate 2 opposite to the surface that comes in contact with the side surface of the printing cylinder. Though there is no particular limitation, the protrusion usually has a height of about 2 to 50 mm. According to the present invention as shown in Fig. 3 or 4, furthermore, it is desired to provide a flange 5 along the outer circumference of the protrusion 4 in order to further increase the effect of the protrusion 4 that is shown in Fig. 2. The flange usually has a width of from 1 mm to several mm. According to the embodiment in which the protrusion is provided along the inner circumference of the side plate as shown in Figs. 2 to 4, it is allowed to decrease the width of the annular side plate and to reduce the weight thereof. According to the present invention, it is desired that the annular side plate has at least the surface thereof composed of a material on which the ink adheres sparingly. Examples of such a material include polyamide, polypropylene, polyethylene, fluorine-contained resin, silicone resin, and like resins. The printing cylinder of the present invention is mounted on the printing press by a known method without any particular limitation. For instance, the body of the printing cylinder having a rotary shaft fixed thereto is used with its rotary shaft being held by the bearings of the rotary device of the printing press. The body of the printing cylinder having bores for fixing the rotary shaft thereto is used with its rotary shaft fixed to the bores and held by the bearings of the rotary device of the printing press. Or, the printing cylinder is used by pressing the rotary shaft interlocked to the rotary device to the cones 9 fitted to the bores on both sides of the printing cylinder. Fig. 6 is a perspective view illustrating the major structure of the printing unit of a gravure printing press under the condition where a rotary shaft 10 interlocked to the rotary device is pressed by a fastening device 11 onto the cones 9 fitted to the bores on both sides of the printing cylinder 1 of the embodiment shown in Fig. 1 thereby to fix the printing cylinder. In Fig. 6, reference numeral 12 denotes an ink pan, 13 denotes an applicator, 14 denotes a doctor blade, 15 denotes a back-up roller, 16 denotes an ink tank, 17 denotes an ink feeding pump, and reference numeral 18 denotes an ink feeding pipe. According to the present invention, usually, the printing cylinder is removed from the printing press after the printing is finished, and the annular side plates are replaced by the new ones after the ink is wiped off the printing face or prior to wiping the ink off. Or, the annular side plates of the structure capable of being opened can be replaced by the new ones without the need of removing the printing cylinder from the printing press. The used side plates may be discarded away but are usually cleaned and used again for the printing cylinder. The above side plates can be easily cleaned compared with the case of directly cleaning the side surfaces of the printing cylinder because there is no need of moving the printing cylinder. Furthermore, difficulty is involved if it is attempted to automatically clean the side surfaces of the printing cylinder. However, the annular side plates taken out from the side surfaces of the printing cylinder can be cleaned in the cleaning tank easily and automatically. The printing cylinder of the present invention can be adapted not only to the gravure printing press but also to any other widely known printing presses that use the printing cylinder. EFFECTS OF THE INVENTION According to the printing cylinder of the present invention, the annular side plates are detachably attached to the body of the printing cylinder utilizing the magnetic force. Therefore, the side plates can be easily attached utilizing the magnetic force prior to the printing operation and can be easily detached after the printing operation is finished while the ink is being wiped off the printing face. Moreover, the side surfaces of the printing cylinder have been covered with the annular side plates during the printing operation and need not be cleaned after the side plates are taken out; i.e., attaching the new annular side plates is all that takes to constitute the printing cylinder of the present invention again for use in the printing operation. Therefore, no operation is required for moving the printing cylinder to other processing step for removing the ink adhered on the side surfaces, and there arises no problem of giving damage to the printing cylinder. Moreover, the time for removing the ink adhered on the side surfaces can be shortened by more than 90% compared with the conventional method of removing the ink adhered on the side surfaces by cleaning after the ink has been wiped off the printing cylinder. In particular, the annular side plates capable of being opened, i.e., the annular side plates split into a plurality of segments or having flexibility and cut at one portion, can be replaced without the need of removing the printing cylinder from the printing press to further enhance the above-mentioned effects. The annular side plates detached from the side surfaces of the printing cylinder can be cleaned for being used repetitively, i.e., can be cleaned in a step separate from the printing step. A known automatic cleaning system can be employed for the step of cleaning to greatly improve the efficiency. EMBODIMENTS Embodiment 1. The printing cylinder shown in Fig. 3 was constituted. That is, the annular side plates 2 made of a plastic magnet having an outer diameter D2 of 290 mm, a bore diameter D3 of 190 mm, a protrusion 4 with a height of 30 mm, and a flange 5 with a width of 20 mm and a thickness of 3 mm, where magnetically attached to both side surfaces of a body 1 of the printing cylinder made of a steel having an outer diameter D1 of 290 mm. The printing cylinder was mounted on a gravure printing press shown in Fig. 6, and the printing was carried out under the following conditions. Line speed 200 mm/min. Number of revolutions of the printing cylinder 219.6 rpm Printing time 30 min. Type of ink rubber-type ink for gravure printing The annular side plates did not almost deviate from the body of the printing cylinder during the printing operation. After the printing operation, the printing cylinder was removed from the printing press, and the annular side plates 2 were detached from the body of the printing press, and the annular side plates 2 were detached from the body of the printing cylinder with ease. The ink did not at all adhere to the side surfaces of the main body of the printing cylinder or to the rotary shaft. The ink was wiped off the printing face, and the new annular side plates were attached to the side surfaces of the body of the printing cylinder which was then mounted on the printing press in order to carry out the printing in the same manner as described above. The annular side plates detached from the printing cylinder were dipped in methylene chloride. The adhered ink was completely removed, and the annular side plates could be used again. The aforementioned attachment of the annular side plates to the body of the printing cylinder, printing operation, wiping of the ink, detachment of the annular side plates, and cleaning operation, were repeated 50 times by changing the ink color each time. However, there was no reduction in the magnetic force of the annular side plates and no discoloration, either, due to inks used before and after the printing. Embodiment 2. The annular side plates were attached to the body of the printing cylinder, the printing was carried out, the ink was wiped off, the annular side plates were detached, and the cleaning operation was carried out all repetitively in the same manner as in the embodiment 1 with the exception of using the annular side plates 2 having an outer diameter D2 of 290 mm, a bore diameter D3 of 190 mm and a thickness of 3.3 mm. The side plates possessed the internal structure shown in Fig. 5. That is, the plastic magnet having a width of 35 mm and a thickness of 2.1 mm was held between a polypropylene film 8 having a thickness of 100 µm and a polypropylene resin mold. The annular side plates did not almost deviate from the body of the printing cylinder during the printing operation. After the printing operation, the printing cylinder was removed from the printing press, and the annular side plates 2 were detached from the body 1 of the printing cylinder with ease. The ink did not at all adhere to the side surfaces of the main body of the printing cylinder or to the rotary shaft. The annular side plates detached from the printing cylinder were dipped in methylene chloride. The adhered ink was completely removed, and the annular side plates could be used again. Even after the experiment, there was no reduction in the magnetic force of the annular side plates and no discoloration, either, due to inks used before and after the printing. Embodiment 3. The printing was carried out using the same printing press as that of the embodiment 3 but changing the annular side plates 2 into those having an outer diameter D2 of 290 mm, a bore diameter D3 of 190 mm and a thickness of 3.3 mm, and having a cut at one portion thereof as shown in Fig. 1. The side plates possessed the internal structure as shown in Fig. 5. That is, a plastic magnet having a width of 35 mm and a thickness of 2.1 mm was held between the polypropylene film 8 having a thickness of 100 µm and a polypropylene resin mold. The body of the printing cylinder was mounted on the gravure printing press shown in Fig. 6, and the annular side plates 2 were fitted through their cut portions to the rotary shaft and were magnetically attached to the side surfaces of the body of the printing cylinder. The annular side plates did not almost deviate from the body of the printing cylinder during the printing operation. After the printing operation, the annular side plates 2 could be detached from the body 1 of the printing cylinder without the need of removing the printing cylinder from the printing press. The ink did not at all adhere to the side surfaces of the body of the printing cylinder or to the rotary shaft. The ink could be wiped off the printing face and the new annular side plates could be attached under the condition where the body of the printing cylinder was being mounted on the printing press. The annular side plates detached from the printing cylinder were dipped in methylene chloride. The adhered ink was completely removed, and the annular side plates could be used again. The aforementioned attachment of the annular side plates to the body of the printing cylinder, printing operation, wiping of the ink, detachment of the annular side plates and cleaning operation, were repeated 50 times by changing the ink color each time. However, there was no reduction in the magnetic force of the annular side plates and no discoloration, either, due to inks used before and after the printing. Embodiment 4. The procedure was carried out in the same manner as in the embodiment 3 but using the annular side plates that are split into two as shown in Fig. 4 instead of the annular side plates used in the embodiment 1. The annular side plates did not almost deviate from the body of the printing cylinder during the printing operation. The annular side plates could be attached to and detached from the body of the printing cylinder without the need of removing the body of the printing cylinder from the printing press. The ink did not at all adhere to the side surfaces or the main body of the printing cylinder or to the rotary shaft. The annular side plates detached from the printing cylinder were dipped in methylene chloride. The adhered ink was completely removed, and the annular side plates could be used again. The aforementioned attachment of the annular side plates to the body of the printing cylinder, printing operation, wiping of the ink, detachment of the annular side plates and cleaning operation, were repeated 50 times by changing the ink color each time. However, there was no reduction in the magnetic force of the annular side plates and no discoloration, either, due to inks used before and after the printing.

Claims: A printing cylinder in which annular side plates are detachably attached to the side surfaces of the body of said printing cylinder of a cylindrical shape utilizing the magnetic force, said annular side plates having a circumference close to the circumference of the side surfaces of the body of said printing cylinder. A printing cylinder according to claim 1, wherein the side surfaces of the body of the printing cylinder are constituted by a ferromagnetic substance, and the annular side plates are constituted by a permanent magnet. A printing cylinder according to claim 1, wherein the side surfaces of the body of the printing cylinder are constituted by a permanent magnet, and the annular side plates are constituted by a ferromagnetic substance. A printing cylinder according to claim 1 to 3, wherein a protrusion is formed along the inner circumference of the annular side plates on the surfaces opposite to the surfaces that come in contact with the side surfaces of the body of the printing cylinder, said protrusion being formed continuously and perpendicularly to the side surfaces. A printing cylinder according to claims 1 to 3, wherein a protrusion is formed along the inner circumference of the annular side plates on the surfaces opposite to the surfaces that come in contact with the side surfaces of the body of the printing cylinder, said protrusion being formed continuously and perpendicularly to said surfaces, and a flange is formed along the circumference of said protrusion. A printing cylinder according to claims 1 to 5, wherein the annular side plates are constituted to be capable of being opened at least at one portion thereof. A printing cylinder according to claims 1 to 6, wherein the annular side plates comprise a molded article of a thermoplastic polymer and a permanent magnet buried in said molded article being deviated toward the side surfaces of the body of the printing cylinder. A printing cylinder according to claim 7, wherein the annular side plates comprise an annular member made of a permanent magnet, a layer of a thermoplastic resin film laminated on said annular member on the side of the side surfaces of the body of the printing cylinder, and a molded layer of a thermoplastic resin which covers the other surface of the annular member and which is formed integrally with the film layer.

Inventors: KAZUYUKI HADA C O TOKUYAMA SOD, KAZUYUKI, HADA, C/O TOKUYAMA SODA K. K.
Applicants: TOKUYAMA CORP, TOKUYAMA CORPORATION
Application year: 1992
Main classification: B41F13
IPC codes: B41F13, B41N1, B41F31, B41F35