Patent Application
20070113747
This application is a division of copending application Ser. No. 09/658,712, filed Sep. 11, 2000; this application also claims the priority, under 35 U.S.C. § 119, of German patent application No. 199 43 028.4, filed Sep. 9, 1999; the earlier applications are herewith incorporated by reference in their entirety.
1. Field of the Invention
The invention relates to a roller for printing machines and, more particularly, to such a roller having a circumferential surface provided with a surface structure and being formed of a nonmetallic material.
Such a roller is described in the published Japanese Patent Document JP-A2 H3-221453 (1991). The roller described in that document is a metering roller which carries water and has a circumferential surface formed of rubber and having axially parallel grooves.
Further prior art includes a roller which is described in U.S. Pat. No. 4,033,262 and has a surface structure formed of rhomboidal bulges or humps, or a helical web. The roller described therein rotates at a circumferential speed which differs from the circumferential speed of an adjacent engaging roller, and is consequently a so-called slip roller. The patent specification does not contain any statements which relate to the material forming the circumferential surface of the roller.
In addition, the prior art also includes a roller described in the published German Non-prosecuted Patent Application (DE-OS) 26 59 557 and referred to therein as a distributor cylinder. The distributor cylinder rotates with slip and is provided with a profiled surface. No more specific statements as to the material of which the surface is formed are made in the published specification.
The prior art further likewise includes a vibrator-type inking unit described in the published German Document DE 298 19 744 U1 and having slip rollers, but no statements relating to the surface condition thereof are made in the described utility model.
Reference ought also be made to U.S. Pat. No. 4,949,637 and U.S. Pat. No. 5,540,145, wherein emulsion-film dampening units are described. These publications are mentioned at this point, because the roller according to the invention, which is described hereinbelow, is particularly suitable for use in such an emulsion-film dampening unit.
It is accordingly an object of the invention to provide at least another improved roller for printing machines.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a rotatable body for a printing machine having a plurality of rollers, the rotatable body comprising:
In accordance with another feature of the invention, the roller serves for carrying ink or emulsion.
In accordance with a further feature of the invention, during printing, the roller is in permanent engagement with two other rollers.
In accordance with an added feature of the invention, the surface structure is a groove running helically in the circumferential surface.
In accordance with an additional feature of the invention, the nonmetallic material is selected from the group of materials consisting of hard rubber and hard plastic material.
In accordance with yet another feature of the invention, the surface structure is made up of a multiplicity of dimples formed in the circumferential surface.
In accordance with yet a further feature of the invention, the surface structure is formed of slats.
In accordance with yet an added feature of the invention, average roughness of the surface structure, determined by the slats, is at least 12 microns.
In accordance with yet an additional feature of the invention, the nonmetallic material is selected from the group of materials consisting of soft rubber and soft plastic material.
In accordance with a concomitant aspect of the invention, there is provided a printing machine comprising at least one roller with a circumferential surface provided with a surface structure and formed of a nonmetallic material, the roller being selected from the group of rollers consisting of a slip roller and a vibrator roller.
Thus, the invention is based upon the concept that, by transferring the surface construction heretofore known for a metering roller to a slip roller and to a vibrator roller, specific advantages result for the last-mentioned rollers. The advantages could not be foreseen, nor could such a transfer be suggested in any way, because the intended use of a slip roller and the intended use of a vibrator roller is in each case quite different from that of a metering roller.
The slip roller rotates with rolling slip relative to a roller resting thereon and, together with the slip roller, forms a slip gap or nip. A liquid film transported through the slip gap or nip is not only split therein but is also sheared. As a result of the shear, shear forces become effective and are particularly great if the liquid is viscid and, for example, is an offset printing ink or a printing-ink/dampening-solution emulsion. With regard to the slip rollers disclosed by the prior art, the shear forces depend to a very great extent upon the set pressure in the slip gap or nip.
Due to the filigree machined structure of the slip-roller surface in the case of the slip roller according to the invention, and due to the properties of the material selected for the surface thereof, the shear forces that act upon the slip roller are advantageously reduced or compensated for and are virtually independent of the pressure. Consequently, the stability requirements for the mounting of the slip roller, and the sensitivity thereof to adjustment, are reduced.
The vibrator roller comes periodically into rolling contact with another roller. At the instant of time at which the vibrator roller strikes the other roller, the latter roller rotates with the circumferential surface thereof at a speed greater than zero relative to that of the vibrator roller, as a result of which the latter experiences a so-called starting jolt. The starting jolt is particularly severe if the vibrator roller is rotating in the opposite direction to the other roller at the instant that it strikes the other roller and, as a result of being frictionally entrained by the other roller, experiences a change in the direction of rotation thereof, after which the rollers roll on one another synchronously. By synchronously it is meant that one roller rotates in clockwise direction and the other roller rotates counterclockwise or opposite thereto.
Due to the filigree machined structure of the vibrator roller surface, and due to the properties of the material selected for the surface, the starting jolt is advantageously reduced, so that it cannot be propagated into the drive gear train of the printing unit containing the vibrator roller, and therefore cannot lead to ghosting faults.
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 roller for printing machines, 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:
Referring now to the drawings and, first, particularly to
The third roller 14 is a dip roller and, together with the fourth roller 15, which is a metering roller, forms a press nip 20, wherein a dampening-solution film or, more precisely, an emulsion film, is produced. In the press nip 20, the printing-ink/dampening-solution emulsion on the fourth roller 15 is enriched with the dampening solution scooped out of the container 13 by the third roller 14.
The fifth roller 16 is advantageously a slip roller which, during printing, simultaneously rests permanently on the two rollers 15 and 17 in order to transfer emulsion from the roller 15 to the roller 17. For specific purposes, for example, in the event of interruptions in the printing or for the purpose of cleaning the dampening unit 8, a space can be produced between the rollers 16 and 17, by lifting the fifth roller 16 off or away from the sixth roller 17. The lifted-off position of the fifth roller 16 is illustrated in phantom in
The sixth roller 17 is an applicator roller, which rolls on the printing form 7, while a seventh roller 18, in addition to the fifth roller 16, engages with the sixth roller 17. As viewed in the direction of rotation of the sixth roller 17, the seventh roller 18 is disposed downline from a press nip 21 and upline from a contact location formed by the sixth roller 17 and the printing form 7. The seventh roller 18 is a distributor roller which oscillates in the axial direction thereof. This is advantageous from the standpoint of stabilizing the emulsion and smoothing or evening out the liquid film on the sixth roller 17.
In addition to the fifth roller 16, two further rollers, namely the seventh roller 18 and an eighth roller 19, preferably rest on the sixth roller 17. As viewed in the direction of rotation of the sixth roller 17, the eighth roller 19 is disposed downline from the contact location between the sixth roller 17 and the printing form 7, and upline from the press nip 21. The eighth roller 19 is a connecting roller, which permits a selective connection between the dampening unit 8 and the inking unit 9 by resting simultaneously on the sixth roller 17 and a ninth roller 22 which, during printing, belongs to the inking unit 9 as an applicator roller. This construction is advantageous with regard to the operation of the dampening unit 8 coupled to the inking unit 9, the inking unit 9 being supplied with the dampening solution, and the dampening unit 8 being supplied with the printing ink via the eighth roller 19.
The arrows representing rotation shown in
In the press nip 21, a surface slip is effective between the rollers 16 and 17, the film of emulsion transported through the press nip 21 not only being split in the radial direction of the rollers 16 and 17 in the press nip 21 but also being sheared in the tangential direction. A press nip 23 of this type, which is comparable with the press nip 21 and in which, because of the rolling slip, shearing of the liquid film likewise occurs, is advantageously also located between the rollers 15 and 16.
The sixth roller 17 is rotated by a first drive 24, which also rotatively drives the printing-form cylinder 6 and, consequently, the printing form 7. The sixth roller 17 is form-lockingly or positively rotated by the first drive 24 via a first gear transmission 25, for example, a toothed gear mechanism, which is diagrammatically represented in
The fifth roller 16 is rotatively driven by frictional entrainment with the fourth roller 15, so that a circumferential surface speed of the fifth roller 16 is established which lies between the circumferential surface speeds of the fourth roller 15 and the sixth roller 17.
If the angular speed of the sixth roller 17 is kept constant by the first drive 24, the slip that acts in the press nip 21 can be set finely in terms of the magnitude thereof by varying the angular speed of the fourth roller 15 and, therefore, of the fifth roller 16 by the second drive 26. By appropriate activation of the second drive 26, it is possible to set the speed differential by which the circumferential surface speed of the fifth roller 16 differs from that of the sixth roller 17, and is preferably lower than the circumferential surface speed of the sixth roller 17. By this advantageous speed control, it is, therefore, possible for the amount of liquid transferred from the fifth roller 16 to the sixth roller 17 for each revolution of the printing form 7 to be set precisely.
The circumferential surface 28 has a roughness, advantageously produced by removing material, with an average roughness which is 12 μm or more. The surface structure 29 produced by machining the circumferential surface 28 may be formed by using a suitable grinding disk with a sufficiently coarse grain during the cylindrical grinding of the circumferential surface 28, i.e., when regrinding the soft coating previously applied to the respective roller 12, 16. In a comparison with the production of conventional smooth rollers, no additional costs occur during the production of the structured rollers 12 and 16, respectively.
The surface structure 29 is illustrated in a very exaggerated manner in
A significant feature of the structure elements 30 is the elasticity thereof in the circumferential direction of the respective roller 12, 16. By the bending of the structure elements 30, the force 32 acting thereon in the tangential direction is advantageously compensated for. In other words, the structured circumferential surface 28 does not present any great resistance to small deformations taking place in the circumferential direction, and the circumferential surface 28 absorbs the force 32 resiliently. In the case of the vibrator roller 12, the force 32 is the force which causes the starting jolt when the vibrator roller 12 strikes the more rapidly rotating second roller 11. In the case of the slip roller 16 (fifth roller 16), the force 32 is the aforementioned shear force in the press nip 21.
In addition, from the surface structure 29, there results the beneficial effect that the printing ink or printing-ink/dampening-solution emulsion held from time to time between the elevated structure elements 30 has the effect of a partial thickening of the film layer in the resilient nip, referred to as the press nip 21, due to which the force 32, here the shear force 32, is not only compensated for but is also reduced. As a result of the partial thickening of the liquid film, the latter may be sheared more easily.
Due to the function thereof, the structure elements 30 can be referred to as slats 30a and, due to the shape thereof, as ridges or webs. The structure elements 30 are situated very close to one another. In
The structure elements 30, which are somewhat punctiform or point-like as seen in plan view, are dimples 30b and are introduced into the nonmetallic material by a material-removing machining method. The structure elements 30 can be introduced into the circumferential surface 28 formed of the nonmetallic material by a metal-removing process, for example, drilling, or by a chemical process, for example, etching, or by a thermal process, for example, by partial evaporation of the material with a laser beam.
The structure elements 30 can be arranged irregularly, for example, randomly distributed, or regularly, for example, in a grid pattern, in the circumferential surface 28. As was also the case in the first embodiment of
When the structure elements 30 pass through the press nip 21, the printing ink or printing-ink/dampening-solution emulsion that is accumulated in the structure elements 30 is pressed out of the structure elements 30. As a result, a reinforced lubricating film is advantageously provided in the press nip 21, this film having the effect of reducing the shear force or the starting jolt.
The structure elements 30 can also be bores or holes which pass completely through the soft coating, the inner openings of the bores or holes being closed by the roller core whereon the soft coating is located. This is also to be understood to be included under the term dimples used for the structure elements 30.
A depth t of the structure element 30, which can also be referred to as the groove depth, is less than 1 mm, preferably less than 0.3 mm and, for example, about 0.1 mm.
In some applications, it may be advantageous to provide the rollers 12 and 16, respectively, with a number of such structure elements 30. For example, the respective roller 12, 16 may be provided with two helical grooves having respective pitches running in mutually opposite directions, similar to those in a left-hand thread and a right-hand thread. In addition, instead of a helical groove, in some applications, a number of mutually spaced and respective self-contained annular grooves could also be introduced into the circumferential surface 28 as the structure elements 30.
The nonmetallic material of which the circumferential surface 28 of the respective roller 12, 16 shown in
In the third embodiment of the surface structure 29, which is shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 199 43 028.4 | Sep 1999 | DE | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 09658712 | Sep 2000 | US |
| Child | 11655411 | Jan 2007 | US |
