Abstract:
An anilox roller base comprised of a carbon fiber composite cylinder over which a metal sleeve is fitted. Metal journals, journal headers, or end caps are installed in the anilox roller base ends. A ceramic coating is added to the metal sleeve external surface and subsequently machined to the precise dimensions required of an anilox roller.

Description:
RELATED U.S. APPLICATION DATA 
     This application claims the benefit of Provisional Application No. 60/306,089, filed Jul. 17, 2001. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to fluid metering rolls, and in particular, to anilox rollers used in printing processes. 
     Anilox rollers are fluid metering rollers and are used in printing presses and have the function of precisely metering the amount of ink that is deposited onto a printing plate printing roller, or the like. The anilox roller has an exterior surface formed with outward opening metering cells. The anilox roller picks up liquid ink from an ink source and deposits the ink on a printing plate, printing roller, or the like, in discrete increments, the quantity deposited by each cell being controlled within precise tolerances across the entire surface of the printing plate, printing roller, or the like. This result is affected by the anilox roller having a multiplicity of closely-spaced, i.e., up to 1,000 or more, cells per lineal inch, the cells having virtually identical volumetric capacities. 
     Anilox rollers have been in use for many years. A typical anilox roller is comprised of a cylindrical metal body (usually steel) and rigidly fixed journals (typically, welded or shrink fit construction) through which the roller is mounted on bearings or a drive system. The surface of the metal roller is then modified to contain many (millions) of very small cells in which ink can be retained. The cells are typically made by either mechanically engraving the roller or by coating the metal roller with ceramic and engraving the cells with a laser. Metal rollers have many characteristics which are undesirable. These characteristics include heavy weight and high rotating inertia. They also exhibit poor vibration attenuation. 
     As an alternative to metal anilox rollers, some companies have manufactured anilox rollers using a carbon fiber reinforced composite material rather than metal as the roller body. Examples of this may be seen in U.S. Pat. Nos. 6,240,639 and 5,857,950. An anilox roller made out of a carbon fiber reinforced composite typically weighs substantially less (up to 50% less) and has a lower rotating inertia (up to 80% less) than its metal equivalent. A carbon fiber anilox roller is typically made by coating a carbon fiber roller body with ceramic and subsequently laser engraving the surface. 
     Although typical carbon fiber anilox rollers provide rollers that weigh considerably less than and have a considerably lower rotating inertia than their metal counterparts, they do have their own significant disadvantages. Carbon fiber anilox rollers typically do not last as long as their steel counterparts. The bond between the ceramic coating and the composite roller body is generally not as strong as that between a ceramic coating and a metal body. Consequently, the ceramic coating on a carbon fiber anilox base is known to prematurely flake off. Carbon fiber anilox rollers also cost two to three times as much as metal anilox rollers. Both metal and carbon fiber anilox rollers can only be refinished (reground and recoated) a limited number of times, typically two to five times. 
     Due to the corrosive nature of chemicals that are employed in the printing process and the anilox roller cleaning process, anilox rollers generally require refurbishing after extended period of use. Refurbishment of a metal anilox roller generally involves grinding off the ceramic coating or engraving surface and a small amount of metal below the coating in order to obtain a new, clean surface. Refurbishment of a prior art carbon fiber anilox roller involves stripping of the ceramic coating by various means and removal of a small layer of carbon fiber composite in order to obtain a new, clean surface. Metal anilox rollers can generally be refurbished about three times before they must be discarded. Carbon fiber anilox rollers can, in general, be refurbished more times than metal anilox rollers, but the number of times they can be refurbished is still very limited. 
     SUMMARY OF THE INVENTION 
     The present invention addresses the problem of prior art anilox rollers by providing a metal-sleeved carbon fiber anilox roller base which is a hybrid between the prior art metal anilox roller base and the prior art carbon fiber anilox roller base. The present invention is an improvement over both technologies. The present invention is comprised of a carbon fiber composite cylinder over which a metal sleeve is fitted. Metal journals, journal headers, or end caps are installed into the invention ends. A ceramic coating is then typically added to the metal sleeve external surface. The sleeve is subsequently machined to the precise dimensions required of an anilox roller. 
     The metal-sleeved carbon fiber anilox roller combines the light weight and low inertia characteristics of the carbon fiber anilox roller base with the durability and ease of processing of the metal anilox roller base. The metal-sleeved carbon fiber anilox roller can be made into an anilox roller by any of the dozens of companies that manufacture metal anilox rollers from metal anilox roller bases. No change in processing is required. The ceramic coating adheres as well to the metal-sleeved roller base as it does to a standard metal anilox roller base. The present invention allows any company that manufactures metal anilox rollers to now participate in the lightweight, low inertia anilox roller market, and provides a unique solution to the problem of poor adherence between carbon fiber composites and ceramic coatings. 
     Refurbishment of a metal-sleeved anilox roller is carried out via the same means used for a metal anilox roller. After several refurbishments, the remaining sleeve material becomes too thin to grind effectively. When the sleeve material becomes too thin to regrind, the sleeve is removed and a new sleeve is installed saving considerable cost over a replacement roller, be it metal or carbon fiber composite. The resulting refurbished roller is generally indistinguishable from the original anilox roller. Replacement of the metal sleeve thereby permits an unlimited number of refurbishments of a metal-sleeved carbon fiber anilox roller. This provides an additional advantage of the present invention over prior art anilox rollers because the cost of resleeving is less than the cost of a new metal roller base or a carbon fiber anilox roller base. 
     These together with other objects of the invention, along with various features of novelty which characterize the invention, are pointed out with particularity in this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated a preferred embodiment of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side, cross-sectional view of the invention. 
     FIG. 2 is an end view thereof. 
     FIG. 3 is a close up side sectional view with a journal. 
     FIG. 4 is a close up sectional view of one end of the invention. 
     FIG. 5 is a close up view of the thermal expansion joint at ambient temperatures. 
     FIG. 6 is a close up view of the thermal expansion joint at elevated temperatures. 
    
    
     DETAILED DESCRIPTION OF INVENTION 
     Referring to the drawings in detail wherein like elements are indicated by like numerals, there is shown an anilox roller  1  constructed according to the invention. The invention  1  is comprised of a hollow carbon fiber tube  10  over which a metal sleeve  20  is joined. The metal sleeve has an external surface  21  and an interior surface  22 . The metal sleeve exterior surface  21  is adapted for anilox machining or to being coated with a ceramic  2  adapted for anilox machining. While the metal sleeve  20  can be virtually any thickness, a thickness in the range of 0.05 inches to 0.20 inches works best, with a preferred thickness of between 0.10 and 0.14 inches. The metal sleeve  20  is preferably made from steel or aluminum, but may also be made from stainless steel or titanium. 
     The joining of the metal sleeve  20  to the carbon fiber tube  10  must be done carefully to avoid slippage between the metal sleeve and the carbon fiber tube. Joining may be done mechanically, by shrink fitting, or by adhesive bonding. Mechanical joining is the least expensive but provides the poorest operating characteristics. Shrink fitting the metal sleeve to the carbon fiber tube provides the best operating characteristics, but is the most expensive process. Adhesive bonding of the metal sleeve to the carbon fiber tube is a compromise between mechanical and shrink fitting joining and provides a middle ground between cost and operating characteristics. 
     In general, the ceramic coating  2  process used on newer anilox rollers is a thermal process and causes the temperature of the roller base  1  to increase considerably during coating. The temperature of the roller base  1  may reach 150° F. or greater. In general, the thermal expansion coefficient of carbon fiber composite as implemented in a roller base is considerably less than that of most metals. The preferred embodiment of this invention contains a feature that accommodates this differential thermal expansion by incorporating an expansion joint  3  as depicted in FIGS. 4-6. 
     Referring more particularly to FIGS. 4-6, there is shown an anilox roller end  4  comprised of a carbon fiber tube end  13  and metal sleeve end  23 . As may be best seen in FIG. 4, the metal sleeve interior surface  22  is joined to a carbon fiber tube exterior surface  11 . The carbon fiber tube end  13  terminates before the metal sleeve end  23 . The metal sleeve interior surface portion  24  not engaged by said carbon fiber tube exterior surface  11  is chamfered for engagement by a metal journal/header/end cap  5  inserted into the roller end  4  engaging a portion of the carbon fiber tube interior surface  12 , the carbon fiber tube end  13 , and the portion  24  of the metal sleeve interior surface  22  not engaged by said carbon fiber tube exterior surface  11 . The metal journal/header/end cap  5  is glued to the carbon fiber tube  10 . The metal journal/header/end cap  5  may also be mechanically fastened or shrunk fit to the carbon fiber tube  10 . The metal journal/header/end cap  5  is generally shaped to conform to the shape of the roller end  4 . An expansion joint  3  is formed by notching about the circumferential perimeter  6  of the metal journal/header/end cap  5  where the metal journal/header meets the carbon fiber tube end  13  and beginning of the metal sleeve interior surface chamfer  25 . The thermal expansion joint  3  permits unrestrained expansion of the metal sleeve  20  during the coating process, leaving the metal journals, journal headers, or end caps unaffected. See FIG.  6 . Upon cooling, the sleeve reverts to its original length. See FIG.  5 . Omission of a thermal expansion joint causes the metal sleeve  20  to unseat the journal/header/end cap  5  from its position in the roller end  4 . In such case, upon cooling, the journal/header/end cap  5  would remain removed from the roller body end  4  rendering the assembly useless. 
     It is understood that the above-described embodiment is merely illustrative of the application. Other embodiments may be readily devised by those skilled in the art which will embody the principles of the invention and fall within the spirit and scope thereof.