Abstract:
A roller for moving one of ink and water through a printing press is disclosed as an elastomeric covering on a solid journal. The elastomeric covering includes spiral lands and valleys adjacent the lands having depths ranging from 0.002 to 0.004 inch for ducting water, and ranging from 0.002 to 0.015 inch for ducting ink. At valley depths of greater than 0.015, ink is carried solely on the lands for the purpose of lubricating the ductor system. One embodiment includes reversed spiral land and valley end segments that direct ink inwardly from the ends of the rollers to prevent ink buildup at those positions on a ductor roller.

Description:
This is a continuation of copending application Ser. No. 07/558,774, filed on Jul. 26, 1990, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates generally to improvements in rollers used in off-set printing presses, and, more particularly, to improvements in the outer surface of soft elastomeric rollers for water dampening systems and ink train rollers providing improved direction and flow control for ink and water through their respective fluid feeding systems in offset printing presses. 
     Offset printing presses generally have separate product feeding systems for moving water, ink and paper to and through the printing press. Typically, these systems consist of a plurality of rollers which transfer and advance the necessary water, ink, and paper webs through the printing press. Ink train systems and water dampening systems move those respective fluids by passing same from one roller to an adjacent roller and so forth, with an initial roller picking up ink or water from a pan or fountain and passing same on to an adjacent roller. Typically, the ink or water feed system for a printing press includes alternating hard or metal rollers with soft or elastomeric material rollers positioned in between and in pinching communication with the adjacent metal rollers. In the case of water and ink feed systems, the respective fluid also helps to keep the series of rollers lubricated. Relevant patents to prior art inking rollers include U.S. Pat. Nos. 1,079,339; 905,182; and 4,601,242. Patents relating to elastomeric covered rollers for use in printing rolls include U.S. Pat. Nos. 3,750,250; 4,143,092; and 4,492,012. 
     An elastomeric covered rigid core roller for cross stretching printing webs is disclosed in U.S. Pat. No. 4,566,162. 
     While these patents disclose elastomeric covered rollers for use in printing presses, and disclose certain textured surfaces for such rollers for various purposes, a need has developed for an elastomeric covered rigid core roller for use in ink and water feeding systems of printing presses having lands and grooves of specified depths, widths and spiral directions capable of improving the direction and control of fluids travelling along such ink and water feed systems, respectively. Also, a need exists for rollers which aid in milling the ink in its travels along the ink train. Such a need exists especially in present day ink feed systems wherein adjustable fountain keys positioned adjacent the fountain rollers utilize a wiping action to control direction of ink flow across cylindrically surfaced rollers in the ink train. For example, the disclosure in old prior patent 905,182 at lines 30-37 indicates that the press in which that roller is to be used does not have adjustable fountain keys. 
     It is therefore an object of the present invention to provide improved elastomeric covered rollers for use in offset printing presses having multi-directional spiral lands and valleys positioned thereon for providing improved flow of water and ink through their respective water and ink feed systems. 
     SUMMARY OF THE INVENTION 
     The invention resides in a roller for use in a printing press fluid feeding system. The roller includes a journal centrally positioned on the roller and extending axially along its length, a generally elastomeric covering surrounding and secured on the journal, an outer surface of the elastomeric covering includes at least one spiral land extending generally circumferentially around the covering and extending axially outwardly of a central portion of the covering with a spiral valley being positioned adjacent the spiral land and extending therealong, the depth of the spiral valleys from the spiral lands being between about 0.002 inch and 0.004 inch for carrying ink in the valleys, and from about 0.002 to about 0.015 for carrying water in the valleys. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. This invention, together with further objects and advantages thereof, may best be understood by reference to the following detailed description taken in conjunction with the accompanying sheets of drawings, in the several figures of which like reference numerals identify like elements, and in which: 
     FIG. 1 is a perspective view of an elastomeric coated roller having an outer generally cylindrical surface having lands and valleys configured thereon in accordance with the present invention. 
     FIG. 2 is a front elevational view of the elastomeric covered roller shown in FIG. 1. 
     FIG. 3 is a fragmentary cross-sectional view taken substantially along line 3--3 of FIG. 2. 
     FIG. 4 is a front elevational view of a second embodiment of the present invention having right and left hand spiral surfaces and two distinct reverse spiral surface segments, one at each end of the roller. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, an elastomeric roller 10, constructed generally in accordance with the present invention, and suitable for use in both an ink train system and a water dampening system, includes a metal central shaft or core 11, an enlarged raised cylindrical journal portion 12 which is not as long as shaft 11, and a generally cylindrical raised outer elastomeric covering, generally indicated at 13, which is not as long as journal 12. A preferred material for outer covering 13 is polyurethane, which may be cast and later machined to the proper contours. As is shown most clearly in FIG. 2, the outer surface of covering 13, in this embodiment includes a plurality of central annular lands 14--14 separated by a plurality of annular valleys 15--15 in alternating relation so as to define a central segment A of the outer surface of elastomeric coating 13. The outer covering 13 is shown is made of polyurethane, although rubber and other elastomeric materials, to a hardness equivalent of a material sold under the trademark NYLON may be utilized. Typical durometer hardness readings for preferred materials range from approximately 35-62, on the Shore A hardness test. 
     To the left of the annular lands of Segment A, is an elongate Segment B consisting of a left-handed spiral land 16 which spirals from the outer edge 15a of Segment A to the end of covering 13, and a left handed spiral valley 17 positioned immediately there adjacent also extending from the left edge 15a of Segment A to the end surface 13a of the covering 13. To the right side of Segment A is a right handed spiral Segment C consisting of a right handed spiral land 18 extending from the right edge 15b of Segment A to the right end surface 13b of covering 13, and a right handed spiral valley 20 positioned immediately thereadjacent and also extending from the right edge 15b of Segment A to the right end surface 13b of covering 13. On a typical roller having a central raised portion 13 approximating eighteen inches in length, and two inches in diameter, a preferred size for the width of annular rings 14--14, left hand land 16 and right hand land 18 approximates 0.125 inch. A preferred width for the annular valleys 15--15, and left hand valley 17 and right hand valley 20 also approximates 0.125 inches. 
     It should be noted that the depth of the grooves may also be considered an effective depth at the line of contact between rollers in the feed system. A softer roller having a greater installed pressure against an adjacent roller may have an effective groove depth of less than its actual unmounted groove depth. A roller having a relatively harder elastomeric covering would not have much change of effective groove depth when in mounted position on a printing press. 
     Referring to FIGS. 1, 2, 3, a preferred depth for the valleys on a roller for carrying water would be very shallow, approximating 0.002 inch, 0.003 inch or 0.004 inch. A preferred depth of the valleys on a roller for carrying ink in a portion of the valleys where the ink is to be transferred to another roller for eventual placement on a printing plate cylinder, would range from 0.002 inch to approximately 0.010 inch, with a most preferred range being from 0.003 inch to 0.007 inch. From valleys having a depth of about 0.007 inch to approximately 0.015 inch, ink may be carried, but the final image at the printing plate produced when ink train rollers with such depth valleys are used turns out to be somewhat degraded. At a roller valley depth of greater than 0.015 inch, ink mass in the valleys becomes large enough to be spit or thrown from the roller by centrifugal force. However, the use of valleys having a depth greater than 0.015 inch may be desirable on surface portions of a roller where it is desired that ink not be transferred down the ink feed system in sufficient quantities other than to lubricate the train of rollers, i.e., in portions of the roller where adjacent portions of a printing plate cylinder is not to have ink transferred thereto, as will be discussed in more detail below. 
     The spiral lands and valleys also help to direct the flow of ink sideways to desired positions on printing plate cylinders (not shown) and act to mill the ink for greater product uniformity. For example, with the roller 10 of FIG. 2 rolling in a direction with the lands and valleys moving spirally inwardly of the roller, the formation of the spirals as shown in FIG. 2 would keep the ink transferred on the roller from piling up on the ends of the roller, as is quite common in heretofore known ink train rollers. The addition of the annular lands 14 and valleys 15, providing that the valleys 15 were greater than 0.015 inches in depth and that fountain keys (not shown) at a similar axial position on an adjacent fountain roller were closed down would also keep ink from piling up in the center of the roller. 
     Further, when the spiral lands and valleys move the ink sideways on a roller, the grinding mill action enhances the uniformity of the ink being applied in the press and, therefore, produces a better quality product. While vibrating or oscillating rollers in the ink train normally move ink sideways in the ink train, the use of spiral lands and valleys increases the grinding or milling effect on ink pigment over that normally found on prior art cylindrical oscillating rollers. Radial lands 14 and valleys 15 have a zero deviation from 90° to the cylindrical axis X--X as shown in FIG. 2. 
     Spiral lands and valleys having an angle of from about 15° to about 45° from perpendicular to the X--X axis have a preferred combination of increased control of ink movement and increased milling of the ink. The lesser the angle the greater the control of the ink, and the greater the angle, the more the milling of the ink. 
     Additionally, if an offset printing press is set up to print material having two separate printed images positioned across the web with a blank space therebetween, the roller of FIG. 2 may be reversed in its mounting, so that ink is directed outwardly from the central portion of the roller where no printing is to take place on that axial position of an adjacent printing plate cylinder. 
     As is shown most clearly in FIG. 3, depending upon the purpose to be used by the portion of the roller 30 of the invention, the valleys, whether they be circumferential valleys, or spiral valleys, may be varied in depth along the same roller in order to perform specific differing tasks. Elastomeric roller 30 in FIG. 3 has an adjacent metal roller surface 31 positioned in line or thin surface (1 mm wide) contact with roller 30 to transfer or not to transfer ink from roller 30 to roller 31, as shall be described in greater detail below. As with the first embodiment of the present invention, the outer surface of the roller 30 includes a continuous spiral land which in cross section is identified as lands 32a-32n, each segment thereof being separated by a continuous spiral valley, which for clarity is shown as Segment 33a-33o. 
     While the lands 32a-32n and valleys 33a-33o of the embodiment shown in FIG. 3 are similar in width to the lands and valleys shown in FIG. 2, the depth of the valleys shown on the roller of FIG. 3 vary along the length of the roller. The valleys shown as Segments 33a-33c and 33m-33o vary between 0.002 and 0.007 inch deep. The valleys shown as 33d-33l are between 0.007 and 0.015 inch deep. The valley shown as 33e is greater than 0.015 of an inch deep with ink in it, and valleys 33f-33k have a depth greater than 0.015 and have no ink in them because individually adjustable fountain keys (not shown) mounted on a similar axial position of an adjacent fountain roller (not shown) have been closed down. Valleys 33a-33d as well as the lands 32a-32d adjacent to those valley segments and valleys 33l-33o and lands 32k-32n carry ink from roller 30 to roller 31, and provide for positioning ink on rollers downstream on the ink train system for producing images at that axial position on a printing plate cylinder (not shown). Lands 32e-32j carry ink on them in a quantity only sufficient to lubricate the roller, but not to produce an image downstream on the printing plate cylinder. The quantity of ink on lands 32e-32j is governed by the movement of the fountain keys on the fountain roller. Typical individually adjustable fountain keys approximate 1/2 inch in width and can be loosened or tightened against the fountain roller as desired and may be adjusted for each printing operation carried out by the printing press. 
     In FIG. 3, ink has been shown positioned in valley 33e, which has a depth greater than 0.015 inch for illustrational purposes only. In operation, the mass of ink in valleys having a depth greater than 0.015 inch is sufficient for centrifugal force to cause spitting of the ink, which is intolerable in the printing process. Therefore, when in operation, the fountain key adjacent land 32c and valley 33e should be closed down so ink is not carried in valley 33e. 
     Referring to FIG. 4, a third embodiment of the present invention is shown and described as roller 40, and it includes a central core 41 and a journal 42 having an elastomeric covering 43 on the outside thereof. The outer surface of elastomeric covering 43 is divided in this embodiment, into four sections, namely, 43A, 43B, 43C and 43D. On roller 40, left handed spiral land 44 and left handed spiral valley 45 make up the segment defined as surface 43A extending outward leftwardly from the center of roller 40. Outwardly of Segment 43 A is a right handed spiral segment 43C which is made up of a right handed land 46 and a right handed valley 47. To the right of the center of roller 40 is a right handed spiral segment 43B made up of a right handed spiral land 50 and a right handed spiral valley 51. Outwardly adjacent segment 43B is surface segment 43D which is a left handed spiral segment made up of left handed spiral land 52 and left handed spiral valley 53. In between each of these respective right and left handed segments is a crescent shaped transition surface denoted in between right and left handed segments 43A-43B as crescent 55 and in between left hands segment 43A and 43C as crescent 56, and in between right hand surface segment 43A and 43C as crescent 56, and in between right hand surface segment 43B and left handed surface segment 43D as crescent 57. 
     In operation, the roller 40 of FIG. 4 is utilized in a printing press wherein two split images are printed on a single web of paper. Ink is positioned on the central portion of roller 40 and spreads there outwardly to the left and right handed segments 43A, 43B, respectively to print images in the location of those segments downstream from the roller 40. The reverse spiraling end segments of roller surface 43C and 43D are positioned at the ends of the roller to prevent buildup of ink on the ends of the roller, which buildup is a common practice in heretofore known prior art rollers. In use, if the valleys 47 and 53 of the end segments of roller 40 were made deeper than 0.015 of an inch, the lands 46 and 52 would have only sufficient ink thereon to provide for lubrication of rollers in the ink train system. 
     While three embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in it broader aspects. Therefore, the aim in the appended claims is to cover all such changes and modifications as far as within the true spirit and scope of the present invention.