Inking cylinder used in a printing apparatus and method for producing the inking cylinder

Abstract: An inking cylinder adapted for a keyless inking system of a printing apparatus comprises a cylindrical base mumber, and an ink receiving layer covered over the surface of the cylindrical base member. The ink receiving layer is composed of a flexible substrate and many fine spherical members (and hard material powder) uniformly dispersed in the flexible substrate. External shell of each the fine spherical members is partially ruptured by grinding force and its hollow interior is opened. The ink on the cylinder surface is caught by this opened hollow interior of each the fine spherical members. A method for producing the above inking cylinder comprises a a first step for uniformly dispersing fine spherical members (and hard material powder) in a substrate, a second step for covering the substrate dispersed with the fine spherical members on a surface of a cylindrical base member to form an ink receiving layer on the base member, and a third step for grinding the surface of the ink receiving layer so that the fine spherical members in the surface region are partially grinded and their shells are ruptured to open the hollow interior of the fine spherical members.

Description: The present invention relates to an inking cylinder used in a printing apparatus. More particularly, the present invention relates to an inking cylinder adapted for a keyless inking system which removes excess ink from the inking cylinder and supplies essentially constant amount of ink onto a printing surface of a plate cylinder. Further, the present invention relates to method for producing the inking cylinder. In an offset printing system which has been broadly employed for printing newspaper, ink is precisely supplied to a plate cylinder by a cooperation between a metering roller and a doctor blade. The surface of the metering roller is formed with a plurality of cells configured in an essentially identical size and arranged in a regular formation. A constant amount of ink fluid is remained in each of the cells owing to the removing function of the doctor blade. This ink supplying system is called "keyless inking". Some prior arts have provided the especially designed metering roller adapted for such keyless inking. For example, Japanese Patent Laid-Open Publication No. 58-42463 entitled "metering Roller For Offset Printing system", Japanese Patent Laid-Open Publication No. 58-56856 entitled "Metering Roller For Offset Printing System" and Japanese Patent Laid-Open Publication No. 61-181645 entitled "Ink Measuring Roller Used For Planography" have taught that the surface layer, including the cells, of these metering rollers are partially or wholly made of lipophilic material such as copper or copper alloy to prevent dampening fluid from entering into the inking system. Further, other designed metering rollers whose surfaces are made of mixture of inorganic (metal) powders and resin have been provided by Japanese Patent Publication No. 59-42119 entitled "Press Roller And Producing Method Thereof" (referred to 1st. prior art), Japanese Patent Laid-Open Publication No. 61-696 entitled "Press Roller" (referred to 3rd. prior art), Japanese Patent Laid-Open Publication No. 61-14997 entitled "Inking Cylinder For An Offset Printing" (referred to 3rd. prior art), Japanese Patent Laid-Open Publication No. 62-71649 entitled "Dampening Device Used In An Offset Printing Apparatus" (referred to 4th. prior art), and Japanese Patent (Utility Model) Laid-Open Publication No. 63-33970 entitled "Form Roller Used In An Offset Printing Apparatus" (referred to 5th. prior art). The 1st. prior art discloses an press roller whose surface is made of non-porous hard polyurethane including stone powder to be in possession of Shore D hardness of 70 or more. The 2nd. prior art discloses another press roller whose surface is made of thermosetting resin including inorganic powders to be in possession of Shore D hardness of 70 or more. These press roller are provided with advantages that (a) their mechanical strength are extremely great, (b) they are easily separated from paper, and (c) their surfaces can be kept smooth because the contained powderly particles are hardly lost. The 3rd. prior art discloses an inking cylinder used for an offset printing system whose surface is made of urethane resin including metal powder such as aluminium, brass or the like. The inking cylinder is in possession of advantages that (a) it is free from deterioration due to the ink solvent, (b) it can easily receive and release printing ink, and (c) ink particles are prevented from dispersing due to fine uneven surface caused by included powder. The 4th. prior art discloses an dampening roller used in an offset printing apparatus. The surface of the dampening roller is covered with a layer made of liquid resin including hydrophilic powder. This dampening roller is in possession of advantages that (a) it can supply dampening fluid at a constant rate, (b) its life period is elongated, (c) its surface has superior water holding capacity owing to fine uneven configuration of the hydrophilic inorganic power included in the surface layer, and (d) its surface can be easily repaired. The 5th. prior art discloses a form roller used in an offset printing apparatus. The surface of the roller is made of flexible urethane synthetic resin including at least one kind of oxidized ceramic powders. This roller is in possession of advantages that (a) lipophilic property of the roller surface is gradually changed to hydrophilic property in accordance with the kind and amount of the included powder, and (b) ink amount transferred to the form roller can be reduced owing to the hydrophilic property without addition of ink distributing roller. The above described metering roller is provided on its surface with a plurality of cells each of which is formed in precise and essentially identical configuration. The cells are disposed in an regular arrangement. After excess ink is removed by scraping motion of a doctor blade, ink amount remained in each the cells is substantially equivalent. However, special works are required to form the cells on the metering roller surface. Further, the metering roller formed with the cells is subjected to abrasion by the doctor blade under its working condition. Thus the metering roller surface is gradually abraded as it works, so that the capacity of each the cells is too decreased to supply the ink with enough amount for accomplishing the printing work. On the other hand, the rollers taught by the 1st. to 5th. prior arts are in possession of relatively high hardness because their surfaces are made of the combination of inorganic powder and synthetic resin. Although these hard surfaces have good abrasion resistance, they are not adapted to be used as a metering roller which should be brought in contact with a doctor blade to remove the excess ink from the metering roller for supplying essentially constant amount. DE-A 28 56 088 representing the closest prior art discloses an inking cylinder made of foamed plastics having foam pores. The foam pores located at the circumference of the inking cylinder are open towards the outside and are able to receive ink to be transferred to transfer rollers. DE-B 1 135 950 discloses an inking cylinder made of thermoplastic material, a powder of metal particles being admixed thereto for increasing the resistance of the material to the attack by the ink to which it is exposed. EP-A 0 343 250 representing prior art according to Article 54(3) EPC, as far as the Contracting States DE, FR, GB and IT are concerned, describes an ink transfer roller having a core and a matrix layer formed on the periphery of the core roller. Within said matrix layer are embedded a number of hollow microballoons which are opened at the surface of the matrix layer by a grinding process. The surface region of the matrix layer may contain copper powder, copper alloy made of brass powder or bronze powder. It is therefore an object of the present invention to provide an inking cylinder used in a printing apparatus without any cells conventionally formed in an ink receiving layer. Another object of the present invention is to provide an inking cylinder adapted for a keyless inking system which removes excess ink from the inking cylinder by a doctor blade brought in contact with the surface of the inking cylinder and supplies essentially constant amount of ink onto a printing surface of a plate cylinder. A further object of the present invention is to provide an inking cylinder whose surface has an abrasion resistance against the doctor blade. A still further object of the present invention is to provide a method for producing the inking cylinder. To accomplish these objects the inking cylinder according to claim 1 is provided. According to another aspect of the present invention, a method for producing the inking cylinder according to the independent method claim is provided. This method can easily provide the inking cylinder covered with the ink receiving layer including many dimple shape recesses which inking cylinder is in possession of superior metering and abrasion resistance properties. Preferred embodiments of the present inventions are defined in the subclaims. Other objects and advantages of the present invenion will become apparent during the following discussion of the accompanying drawings. Fig. 1 is a schematic illustration showing the overall view of the inking cylinder according to preferred embodiment of the present invention; Fig. 2 is partially enlarged illustration of the ink receiving layer of the inking cylinder shown in Fig. 1; and Fig. 3 is partially enlarged illustration of the ink receiving layer which is a modification of Fig. 2. One preferred embodiment of an inking cylinder according to the present invention will be discussed in conjunction with the drawings. Through the drawings the same numerals denote the same parts or corresponding elements, so that the same explanation will not be repeated. In Fig. 1, the reference numeral 1 denotes an inking cylinder whose base member 6 formed in a cylindrical shape is made of steel or the like. The base member 6 is covered with an ink receiving layer 2. As shown in Fig. 2, the ink receiving layer 2 comprises a substrate 4 and a plurality of fine spherical members 3 uniformly dispersed in the substrate 4. Alternatively, the ink receiving layer 2 further includes hard material powder 5 in addition to the substrate 4 and fine spherical members 3 as shown in Fig. 3. The substrate 4 is made of a flexible material such as synthetic resin, natural resin, rubber or the like. In the embodiment, the substrate 4 is made of urethane resin. The interior of each of the fine spherical members 3 is hollow. The shell of the fine spherical member 3 is easily ruptured by grinding force so that the hollow interior is opened. The opened hollow space can catch the ink on the cylinder surface as same as conventional metering rollers formed with many cells. The spherical member 3 per se has been well known as various names of micro-balloon, micro-sphere, hollow balloon, and syntactic foam. For example, carbon balloon, glass balloon, silica balloon, shirasu balloon, phenol balloon, vinylidene chloride balloon, alumina balloon, and zirconia balloon have broadly been used as the fine spherical members. Typically, as commercial products "Carbo Spheres" (trade name) manufactured by VERSA Manufacturing Inc. in U.S.A. and "Fillite" (trade name) manufactured by Fillite Co., Ltd. in England have been commonly known. The former belongs to a carbon balloon and has bulk density of 0.15g/cm³ and shell thickness of 1 to 2 µm. The company has supplied four types depending on particle size. A first type has particle diameter range of 50 to 150 µm (average particle diameter; 50 µm ), a second type has particle diameter range of 5 to 100 µm (average particle diameter; 45 µm), a third type has particle diameter range of 5 to 50 µm (average particle diameter; 30 µm), and a fourth type has particle diameter range of 50 to 150 µm (average particle diameter; 60 µm). Further, these particles may be coated with various metals such as nickle, iron, copper, gold or the like. Such metal coated particles are also effectively used. "Fillite" belongs to a silica balloon and has bulk density of 0.4 g/cm³ and particle diameter range of 30 to 300 µm. The fine spherical members 3 of this invention are preferably selected from the particle diameter range of 5 to 300 µm. The hard material powder 5 is preferably selected from ceramics powder, metal powder, alloy powder, or combination thereof. The hard material powder 5 has preferably particle diameter range of 1 to 100 µm. Next, a method for producing the above constituted inking cylinders according to the preferred embodiment and modification will be described. The inking cylinder according to the preferred embodiment is produced by a method comprising a first step for dispersing the fine spherical members 3 in the substrate 4, a second step for covering the substrate 4 on the surface of the cylindrical base member 6 to form the ink receiving layer 2, and a third step for grinding the surface of the ink receiving layer 2. The fine spherical members 3 dispersed in the vicinity of the surface are subjected to the grinding work and thus their shells are partially ruptured. The hollow interior of the fine spherical members 3 are partially opened in the surface of the ink receiving layer 2 as shown in Fig. 2. At the first step also the hand material powder 5 may be dispersed in the substrate 4. At the first step the fine spherical members 3 (and the hard material powder 5) are uniformly dispersed in the substrate 4 by well known mixing or kneading means in response to the properties and shape of the substrate 4. At the second step, the substrate 4 dispersed with the fine spherical members 3 (and the hard material powder 5) is coated on the surface of the cylindrical base member 6 by well known casting, winding, or coating manner. At the third step, the surface of the ink receiving layer 2 is ground by a grinding machine or subjected to the grinding function by a doctor blade after the inking cylinder 1 has been assembled on a printing apparatus. By this grinding step, each the shell of the fine spherical members 3 dispersed in the vicinity of the surface of the ink receiving layer 2 is partially ruptured and removed so that the hollow interior of each the fine spherical member 3 is opened in the surface of the inking cylinder 1. Also the hard material powder 5 dispersed in the vicinity of the surface of the ink receiving layer 2 is appeared by this grinding step. Operation of the inking cylinder according to the present invention will be described. When the inking cylinder 1 shown in Fig. 2 is assembled on commonly used printing apparatus not shown and ink is supplied to the inking cylinder 1, the supplied ink is stuck on the ink receiving layer 2 of the inking cylinder 1 and caught by the hollow space of the fine spherical members 3. Then a doctor blade, not shown, is brought in contact with the surface of the ink receiving layer 2 to remove the excess ink from the surface. The ink partially enters into the hollow space of the fine spherical members 3. Each the hollow space functions as well as cells formed in the inking cylinder as disclosed in prior arts. So that the ink remained on the ink receiving layer 2 can be always controlled within substantially equivalent amount. The inking cylinder 1 shown in Fig. 3 is operated in the same manner as the above and ensures the same function of the former. This inking cylinder 1 further provides abrasion resistance function against the doctor blade. The surface of the ink receiving layer 2 includes some hard material powder 5 which mainly suffers the abrasion force caused by the doctor blade. Accordingly the ink receiving layer 2 can be free from remarkable abrading and thus its life can be elongated. The ink receiving layer 2 includes many fine spherical members 3 (and hard material powder 5) uniformly mixed in the substrate 4. Even if the ink receiving layer 2 will be gradually abraded, new fine spherical members 3 (and the hard material powder 5) will be apparent on the surface of the ink receiving layer 2. Then such newly appeared fine spherical members 3 will be subjected to abrasion work, so that the hollow interior of the fine spherical member 3 will be also opened. Accordingly, the external surface of the inking cylinder 1 will be always kept in its primary state that a plurality of hollow space like as cell can catch ink therein to ensure the ink metering function with equivalent level. This ink metering function of the inking cylinder 1 will be maintained for a long period until immediately before the ink receiving layer 2 disappears. The inking cylinder 1 provided by the present invention is especially optimum for use as a metering cylinder in a keyless inking system because the inking cylinder 1 can always supply ink at essentially equivalent rate without fluctuation of ink-metering which has been caused in conventional metering roller formed with mesh-shape recesses. Such mesh-shape recesses will become shallow by abrasion, and thus ink-metering amount will be fluctuated or decreased. Further, the method for producing the inking cylinder 1 does not need complicated working steps such as cell forming work or special coating work required in conventional arts, thereby providing the inking cylinder with low costs in comparison with a flexible material so that the ink receiving layer 2 is softer than conventional cylinder surface. Thus the doctor blade brought in contact with the inking cylinder 1 is free from remarkable abrasion owing to scraping work against the inking cylinder 1 to remove the excess ink therefrom. Such constituted inking cylinder 1 can ensure long life span of the doctor blade.

Claims: Claims for the following Contracting States : DE, FR, GB, IT An inking cylinder for a printing apparatus comprising a base member (6) of cylinderical shape, and an ink receiving layer (2) covered on the base member (6), which ink receiving layer (2) comprises a substrate (4) in which a plurality of fine spherical members (3) having a shell and a hollow interior, and hard material powder (5) are finely and uniformly dispersed. The inking cylinder as set forth in Claim 1, wherein the substrate (4) is made of a flexible material such as synthetic resin, natural resin, rubber or the like. The inking cylinder as set forth in Claim 2, wherein the synthetic resin is urethane resin. The inking cylinder as set forth in Claim 1, wherein the fine spherical member (3) has particle diameter within a range of 5 to 300 µm. The inking cylinder as set forth in Claim 1, wherein the hard material powder (5) is selected from ceramics powder, metal powder, alloy powder, and the like, whose particle diameter is in a range of 1 to 100 µm. A method of producing an inking cylinder (1) comprising a first step of uniformly dispersing fine spherical members (3) having a shell and a hollow interior, and a hard material powder (5) in a substrate (4), a second step of covering the substrate (4) having said uniformly dispersed fine spherical members (3) and said hard material powder (5) on a surface of a cylindrical base member (6) to form an ink receiving layer (2) thereon, and a third step of grinding the surface of the ink receiving layer (2) so that the fine spherical members (3) in the surface region are partially grinded and their shells are ruptured to open the hollow interior, such that upon gradual abrasion new spherical members (3) and hard material powder (5) will appear on the surface of the ink receiving layer (2). The method as set forth in Claim 6, wherein the first step is carried out by mixing or kneading means. The method as set forth in Claim 6, wherein the second step is carried out by casting, winding or coating means. The method as set forth in Claim 6, wherein the third step is carried out by any grinding machine or abrading function caused by a doctor blade after the inking cylinder is assembled on a printing apparatus. Claims for the following Contracting States : AT, CH, LI An inking cylinder for a printing apparatus comprising a base member (6) of cylinderical shape, and an ink receiving layer (2) covered on said base member (6), which ink receiving layer (2) comprises a substrate (4), characterized in that said substrate (4) contains uniformly dispersed fine spherical members (3) having a shell and a hollow interior, said shells being partially ruptured in the surface region of the substrate (4) due to grinding forces applied to the ink receiving layer (2). The inking cylinder as set forth in Claim 1, wherein the ink receiving layer (2) further comprises hard material powder (5). The inking cylinder as set forth in Claim 2, wherein the hard material powder (5) is uniformly dispersed in the substrate (4). The inking cylinder as set forth in Claim 1, wherein the substrate (4) is made of a flexible material such as synthetic resin, natural resin, rubber or the like. The inking cylinder as set forth in Claim 4, wherein the synthetic resin is urethane resin. The inking cylinder as set forth in Claim 1, wherein the fine spherical member (3) has particle diameter within a range of 5 to 300 µm. The inking cylinder as set forth in Claim 2, wherein the hard material powder (5) is selected from ceramics powder, metal powder, alloy powder, and the like, whose particle diameter is in a range of 1 to 100 µm. A method for producing an inking cylinder, characterized by a first step of uniformly dispersing fine spherical members (3) having a shell and a hollow interior in a substrate (4), a second step of covering said substrate having the uniformly dispersed fine spherical members (3) on a surface of a cylindrical base member (6) to form an ink receiving layer (2) thereon, and a third step of grinding the surface of the ink receiving layer (2) so that the fine spherical members (3) in the surface region are partially grinded and their shells are ruptured to open the hollow interior of the fine spherical members (3). The method as set forth in Claim 8, wherein in said first step also a hard material powder (5) is uniformly dispersed in the substrate (4). The method as set forth in Claim 8 or 9, wherein the first step is carried out by mixing or kneading means. The method as set forth in Claim 8 or 9, wherein the second step is carried out by casting, winding or coating means. The method as set forth in Claim 8 or 9, wherein the third step is carried out by any grinding machine or abrading function caused by a doctor blade after the inking cylinder is assembled on a printing apparatus.

Inventors: OKAMURA YUICHI, SHIBA NORIYUKI, OKAMURA, YUICHI, SHIBA, NORIYUKI
Applicants: TOKYO KIKAI SEISAKUSHO LTD, KABUSHIKI KAISHA TOKYO KIKAI SEISAKUSHO
Application year: 1989
Main classification: B41N7
IPC codes: B41F31, B41N7