Abstract:
An insulating roll comprising: a metal conduit having an outer peripheral portion; a plurality of discs having outer peripheries and preferably fabricated from an inorganic material positioned axially on and around the metal conduit; a tubular shell having an inner surface about and spaced apart from said outer peripheries; metallic foils extending between each or a plurality of said discs from said outer peripheral portion to and beyond said outer peripheries to the inner surface of said tubular shell, said metallic foils being in interference or frictional contact with said inner surface. A novel method for attaching the tubular shell to the conduit to simplify removal and replacement thereof is also described.

Description:
FIELD OF THE INVENTION 
     The present invention relates to idler or transfer rolls of the type used in, for example, annealing ovens and more particularly to such rolls that, because of their structure allow for reduced thermal fatigue and consequently extended roll life over those of the prior art. 
     BACKGROUND OF THE INVENTION 
     The provision of transfer or idler rolls for the transport of material, for example, steel through annealing ovens and the like has been the subject of development for a number of years. At one point such rolls comprised steel that extracted heat at an unacceptable rate. Subsequently, rolls that utilized compacted particulate inorganic materials as a back-up to a steel surface sleeve were designed and used. While these rolls provided some improvement over the steel variety, the compacted inorganic material proved to be too “soft” and over time resulted in the surface of the roll sagging in the area filled with the inorganic material thus resulting in failure of the roll. 
     In 1999, Hart et al in U.S. Pat. No. 5,989,170 described a roll structure that comprised a plurality of annular discs of a highly compacted ceramic fiber about a central cooling water conduit. Again, while this structure provided an apparent improvement in roll capability by limiting the amount of heat extracted by the roll and providing extended roll life, it was not entirely satisfactory for a number of reasons that are pointed out in U.S. Pat. No. 6,196,957 to Hiraguri et al issued Mar. 6, 2001. 
     Hiraguri et al describe an insulating roll that is constructed with a roll body formed of a plurality of inorganic material derived discs laminated with each other and positioned axially of and around a metal conduit, and a heat resistant metal tube or shell disposed integrally over an outer periphery of the roll body. The roll described in Haraguri et al is claimed to have low thermal conductivity, and high impact strength without involving reduction of the surface temperature of a material being heat treated in a furnace or reducing the ambient temperature in the furnace during heat treatment. It is to be noted that the claims of this patent were ultimately limited to a structure for retaining the tubular shell on the roll structure. Again, while this revised structure apparently provided some benefits as claimed, the roll demonstrated an inability to operate at very high temperatures, above about 2000° F., due to the presence of welds used to attach a variety of the members to a hollow core. It is also to be specifically noted that in the roll of Hiraguri et al, the axially oriented inorganic material discs are in direct contact with the overlying steel shell at their outer peripheries. 
     Subsequent to the development described in Hiraguri et al, various apparently unpatented attempts were made to alter the heat transfer characteristics of Hiraguri et al&#39;s roll. Among these were the insertion of so-called “foils”, i.e. thin strips of stainless steel located between adjacent inorganic material discs or sets of discs that extended partially through the thickness dimension of the array of discs from the outer periphery of the interior water cooling channel outward toward the steel shell. The presence of such “foils” apparently increase the heat exchange capability of the roll of Hiraguri et al a small amount. Again, while this appears to have provided a step in the right direction, it was not enough to adequately extend roll surface shell life. 
     Accordingly, there remains the need for improvement in the structure of these so-called “insulating rolls” to extend the useful operating life of the steel shell while minimizing heat extraction from the heat treatment process. 
     OBJECT OF THE INVENTION 
     It is therefore an object of the present invention to provide a roll structure that provides minimal heat extraction from the heat treatment process while providing sufficient heat extraction from the roll surface to optimize the life of the operating life of the roll surface shell. 
     It is another object of the present invention to provide a novel method for the attachment of a tubular shell to a water cooled roll. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided, an insulating roll comprising: a metal conduit having an outer peripheral portion; a plurality of discs having outer peripheries and fabricated from an inorganic material positioned axially on and around the metal conduit; a tubular shell having an inner surface about and spaced apart from said outer peripheries; metallic foils extending between each or a plurality of said discs from said outer peripheral portion to and beyond said outer peripheries to the inner surface of the tubular shell, said metallic foils being in interference or frictional contact with said inner surface. A novel method for attaching the tubular shell to the conduit to simplify removal and replacement thereof is also described. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cutaway cross-sectional view of one embodiment of the roll of the present invention. 
     FIG. 2 is partially cross-sectional and partially plan view of one embodiment of the roll of the present invention. 
     FIG. 3 is a detailed cross-sectional view of one embodiment of the key area of one embodiment of the roll of the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIG. 2, the roll  10  of the present invention comprises a roll core  12  consisting of a tubular member  18 , a conduit  16  for the passage of a cooling fluid such as water, and journals  14  for mounting in a bearing structure (not shown). While such an arrangement simplifies fabrication of roll  10 , it will be obvious to the skilled artisan that roll core  12  could be machined or otherwise fabricated. Affixed either permanently by welding or removably by a threaded type of connection to the outer periphery of tubular member  18  are annular flanged spacers  22  and  24  (best seen in FIG. 1) that serve to contain further elements described more fully below. Annular flanges  26  and  28  may be separate from spacers  22  and  24 , described below, or form individual portions of a single integral part. 
     Annular flanged spacer  22  and press ring  40  serve to contain annular inorganic material discs  30 . According to a preferred embodiment for the securing of annular discs  30  shown in the various Figures, a compressed assembly of annular discs  30 , referred to hereinafter as a disc bundle, including foils  32 , as described more fully below, is inserted between flanged spacer  24  and press ring  40  and secured in place by snap ring  34  that engages a recess  36  in tubular member  18  and a recess  38  in retention member  40 , the latter serving to maintain the compression of discs  30  and foils  32  into the disc bundle. The area  35  that coincides with the axial extent of annular discs  30  is referred to herein and in the attached claims as the “working area”, i.e. that area of outer surface  37  of tubular shell  42  that can be expected to contact material passing over and in contact with roll  10  during operation. 
     Overlying but separated from the outer periphery of discs  30  is tubular shell  42 . Tubular shell  42  is maintained in position on roll assembly  10  through the action of second keys  44  that engage tubular shell  42  through longitudinally “oversized” apertures  43  in tubular shell  42  preferably located outside of the working area  35  of roll  10 , i.e. that area beyond the limits of compressed annular discs  30 , i.e. the disc bundle, and engages shoulders in annular flanged spacers  22  and  24 . The term longitudinally “oversized” means and refers to the fact that apertures  43  are longer in the longitudinal direction than keys  44  and of a size in the peripheral direction as to appropriately retain keys  44  in apertures  43 . In this fashion tubular shell  42  is restrained from rotational movement about tubular member  18  yet is permitted to “grow and “shrink” longitudinally as well as radially as it heats and cools during use. Keys  44  are held in position by at least one and preferably a pair of bolts such as socket head cap screws  46  whose base(s) are secured into annular flanged spacers  22  and  24  in the embodiment depicted in the attached Figures. Longitudinally “oversized” apertures  43  thus allow for the longitudinal and radial movement or growth of tubular shell  42  in expansion as tubular shell  42  is heated during operation. This attachment mechanism for tubular shell  42  to roll  10  is novel and forms part of the instant invention. As will be apparent to the skilled artisan, one can relatively easily envision a design where keys  44  engaged slots or other openings in the inner surface of tubular shell  42  within the working area of the roll, however, this is not generally preferred as such a design might affect the heat exchange/transfer capabilities of roll  10 . Additionally, the term “key” as used herein is meant to include attachment mechanisms that utilize alternatives to rectangular keys such as, for example, pins or other securing devices that attach to tubular member  18  and engage one or more “oversized” apertures in tubular shell  42  to allow for growth thereof while limiting rotation about conduit  16  and tubular member  18 . 
     As best seen in FIGS. 1 and 3, foils  32 , preferably of stainless steel, are laminated into the laminated or compressed assembly of discs  30 , the disc bundle, by the insertion of foils  32  between each of discs  30  or pairs or other numbers of discs  30  as may be desirable prior to compression. An important element toward achieving the heat removal capabilities of roll  10  of the present invention is that foils  32 , regardless of their number or spacing between discs  30 , extend from the outer annular surface  96  of tubular member  18  through and beyond the outer periphery  48  of compressed discs  30  such that they are in frictional or interference fit with inner peripheral surface  50  of tubular shell  42 . The presence of foils  32  in this configuration provides at least two distinct advantages. Firstly, they provide a direct path for the exchange of heat between tubular shell  42  and the outer surface  96  of tubular member  18  and, secondly, because of their interference fit they also serve to provide a certain amount of structural support to tubular shell  42  during operation. While this amount of support may seem relatively small it has been shown to be actual and to extend the operating life of roll  10  beyond that of similar prior art such devices. The increased heat exchange provided by the extended configuration of the foils also allows for the more efficient removal of heat from tubular shell  42  thereby reducing the degradation of tubular shell  42  due to exposure to high temperatures, thermal fatigue. With the configuration described: 1) the temperature of tubular shell  42  can be more carefully controlled without significantly increasing the cooling effects in, for example, an annealing oven that can result in the consumption of additional fuel to maintain an elevated temperature in such a device, or 2) the amount of water that must be circulated through conduit  16  to obtain appropriate cooling of tubular shell  42 . 
     Thus, when assembled by the insertion of roll core  12  or tubular member  18  having annular discs  30  attached thereto as described above, into a new or reworked tubular shell  42 , foils  32  enter into interference fit into the inner periphery  50  of tubular shell  42  providing the support and heat exchange advantages described above. 
     There has thus been described a novel insulating/sleeved transfer/idler roll system that provides a simplified and reliable method for the attachment of a replaceable tubular roll shell as well as a novel interior roll configuration that provides enhanced shell cooling control. The use of foils that extend from the outer surface of an interior conduit to and beyond the outer periphery of an annular laminated/compressed inorganic material disc bundle to frictionally/interferentially engage the inner surface of a tubular outer shell has also been described along with its apertenant benefits. 
     While the tubular shell described herein is currently fabricated from metal, it will be readily apparent to the skilled artisan that in view of the method of attachment described herein, tubular shell  42  could be fabricated from any number of alternative materials, for example, ceramics or cermets that can be fabricated into tubular shapes as described herein for tubular shell  42 . 
     As the invention has been described, it will be apparent to those skilled in the art to which this invention applies that the same may be varied in many ways without departing from the spirit and scope of the invention. Any such modifications are intended to be included within the scope of the appended claims.