Abstract:
A heat resistant roll is useful for supporting and conveying articles for transport at high temperature. The roll has a mandrel core and a sleeve. The sleeve is enlarged over the core to define a radial clearance therebetween. The mandrel and the sleeve have differing coefficients of thermal expansion. Interposed between the mandrel and the sleeve is a brush roll. The brush roll maintains engagement with both the mandrel and the sleeve during thermal expansion.

Description:
FIELD OF THE INVENTION  
         [0001]    A heat resistant roll is useful for supporting and conveying articles such as glass in plate form. The roll has a mandrel core and an outer sleeve, each with different coefficients of thermal expansion. The present invention relates generally to accommodating these differences.  
         BACKGROUND OF THE INVENTION  
         [0002]    High temperature transport rollers find service such as in sheet glass production. A sheet of glass can be transported by rollers through a cooling passage for further processing. In this exemplary utilization of heat resistant conveying rolls, each roller is typically attached at each end to an end assembly. It may be necessary to secure the roller to the end assemblies in a manner taking into consideration thermally induced, axial displacement between the end assembly and the roller.  
           [0003]    In one exemplary embodiment of transport rollers that are discussed for use in the float glass process, the central roller can be arranged between end trunnions. As disclosed in U.S. Pat. No. 4,925,014, there is proposed that at least one end trunnion not be completely rigidly attached to the roller. For example, where star-shaped end supports are used between the trunnions and the central roller, one such support at one end may be secured, such as by welding, only to the roller. The patent teaches that by such an arrangement differential thermal expansions can be accommodated.  
           [0004]    A different approach to this problem has been taught in U.S. Pat. No. 5,370,596. Therein, it is taught to support a ceramic roll by metal ferrules, or end caps. At the ends of the ceramic roll, which ends are typically necked down to fit within the end caps, there is space provided between the roll and the end caps. In this space, thermodeformable bimetallic elements are wedged between the end caps and the ceramic roll. These elements will expand at elevated temperature to accommodate the greater thermal expansion of the ferrule relative to the roll.  
           [0005]    In applications that do not ostensibly lend themselves to the above-discussed high temperature applications, there can nevertheless be assemblies of an outer ceramic roll and an inner metal shaft. Such assemblies need to be resistant to sliding occasioned by torque pressures received from loads on the outer cylindrical element. One such approach for coupling cylinders to metal shafts has been shown in U.S. Pat. No. 3,847,260. Therein, it is disclosed to utilize tubular elements, or sleeves, for the coupling. Such sleeves which are made, for example, of hard rubber or plastic, have ribs that deform in assembly. The ribs deflect when slidingly coupling the shaft to the ceramic cylinder.  
           [0006]    The foregoing assembly was apparently somewhat unreliable, as has been mentioned in U.S. Pat. No. 4,385,683. Therein, it is disclosed that an ostensibly more reliable, easier to install device could be made for a similar purpose. The patent teaches the use of a sleeve for coupling an outer ceramic disk to an inner cylindrical shaft. The sleeve is made of a rigid plastic. By providing the plastic with a void content to permit compression of the sleeve, such is advocated as providing a very reliable assembly.  
           [0007]    There is nevertheless, a need for providing an assembly that would be operable at elevated temperatures beyond those tolerable for elastomeric or plastic materials. It would also be desirable for such a system to readily provide full contact, such as for support, along at least substantially the complete axial length of an outer, typically ceramic, member and an inner, usually metal, member. Such assembly members would still maintain desirable inter-member engagement, even for roll operations at varying temperatures during utilization of the roll.  
         SUMMARY OF THE INVENTION  
         [0008]    There is now provided an improved roll adapted for elevated operating temperature applications. The roll has a sleeve, or cover, over a mandrel, or core, with the sleeve fitted over the mandrel in a manner defining a radial clearance therebetween. Yet each are in secure engagement by interposing a brush roll in the radial clearance. Furthermore, the improved roll can offer extended operation at elevated temperature, including operation at varying high temperatures during utilization of the roll. Such extended operation can be achieved even where the mandrel has a coefficient of thermal expansion that is greater than the coefficient of thermal expansion for the sleeve.  
           [0009]    In one respect, the invention is directed to a high temperature roll for supporting and conveying material for transport, such roll comprising a mandrel, a sleeve fitted thereover to define a radial clearance therebetween and a brush roll interposed between the mandrel and sleeve within such radial clearance and engaging both the mandrel and the sleeve.  
           [0010]    Another aspect of the invention is the combination comprising a heating means capable of attaining elevated operational temperatures, and means for conveying material for transport at said elevated operational temperatures, such means for conveying comprising a plurality of rolls, and at least one roll comprising a mandrel, a sleeve fitted thereover to define a radial clearance therebetween, and a brush roll interposed between such mandrel and sleeve within the radial clearance and engaging both the mandrel and the sleeve.  
           [0011]    Yet a further aspect of the invention includes the method of securing a sleeve to a mandrel for preparing a high temperature roll for supporting and conveying material for transport, wherein the mandrel has a first coefficient of thermal expansion and the sleeve has a second coefficient of thermal expansion, which method comprises providing a mandrel having an outer peripheral surface, providing a sleeve having an inner peripheral surface defining a radial clearance from the outer peripheral surface of the mandrel, establishing a brush roll of a tubular portion having a outer peripheral surface containing a multitude of radially extending projections; and interposing the brush roll into the radial clearance, with the brush roll engaging the outer peripheral surface of the mandrel as well as the inner peripheral surface of the sleeve.  
           [0012]    Another aspect of the invention is an assembly adapted for engaging a mandrel to provide a high temperature roll for supporting and conveying material for transport, which assembly comprises a brush roll comprising a tubular portion having a peripheral surface, together with a multitude of projections extending radially from the peripheral surface and a sleeve fitted over the brush roll in interference fit therewith. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is an exploded view, partly in section, of a portion only of an elevated temperature roll of the invention having a mandrel and sleeve with a brush roll interposed in between.  
         [0014]    [0014]FIG. 2 is a perspective view, partly in section, of a roll of substantial axial length having a mandrel with a brush roll thereover.  
         [0015]    [0015]FIG. 3 is an isometric showing of a portion only of a roll embodying the invention with parts broken away to show construction of the roll.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    For the roll, the core of the roll will generally be referred to herein as the mandrel. However, the use of other terms such as ‘core’ or ‘shaft’ may also be used herein. The mandrel may be solid, but a non-solid configuration may also be useful. Such a configuration can include tubular mandrels having an open core through which a cooling fluid may circulate. A typical mandrel will have an axial length larger than its diameter, although it will be understood that such should not be a limitation on the mandrel structure.  
         [0017]    The typical mandrel will have an elongated, cylindrical shape. The outer surface of the mandrel, usually referred to herein as the ‘outer peripheral surface’ will generally have a seamless surface. The material for the mandrel is advantageously a metal material. Usually this will be steel such as mild steel or stainless steel. Other steel mandrels can include cast alloy. Moreover, metal mandrels of other metal alloys may also be utilized, such as nickel-chrome alloy. It is contemplated that in some instances the mandrel could also be of a material other than metal, and such materials can include ceramics such as silicon carbide. The mandrel will have a coefficient of thermal expansion that will most often be referred to herein as a ‘first coefficient of thermal expansion.’ This will be discussed again, hereinbelow in relation to the sleeve.  
         [0018]    The sleeve is sized so that it fits over the mandrel to provide a radial clearance between the mandrel and the sleeve. This clearance will be between the outer peripheral surface of the mandrel and the inner peripheral surface of the sleeve. The radial clearance between the mandrel and the sleeve must be maintained to provide some of this clearance at the elevated temperatures under which the roll may be operating. The sleeve is generally sized in an axial direction to be as long as, or if shorter, usually at least substantially as long as, the axial length of the mandrel. Therefore, the sleeve typically has an axial length larger than its diameter, although it will be understood such need not be the case. The sleeve will generally be a tubular and elongated, open-ended sleeve of cylindrical shape. For such a sleeve, it need not be retained in open-ended characteristic after the roll has been assembled.  
         [0019]    The sleeve will most always have a seamless outer peripheral surface, which surface may also be referred to herein as the working surface for the roll. It will be understood that the roll will most always be cylindrical, although other shapes such as for non-turning rolls, are contemplated. It will be understood that particularly where the working surface of the roll need not be lengthy, the axial length of the sleeve may be substantially shorter than such length of the mandrel.  
         [0020]    The sleeve will have a coefficient of thermal expansion that will usually be referred to herein as a ‘second coefficient of thermal expansion’. This second coefficient will generally be smaller than the coefficient for the mandrel. Thus as temperature increases, such as from typically room temperature for the assembly of the roll to an elevated operational temperature, the radial clearance between mandrel and sleeve can shrink. However, as noted hereinabove, some clearance should be retained.  
         [0021]    Most always the sleeve will be an incompressible outer roll member. However, the sleeve need not be completely rigid and incompressible if such is not desired. The sleeve may also provide heat insulation for the roll. This would be insulation for the components of the roll within the sleeve, including the mandrel. The sleeve can be made of a material such as fused silica, include sintered materials such as silicon carbide, silicon nitride, alumina and zirconia, or ceramic composites such as sialon, and cermets such as silicon-silicon carbide, as well as refractory materials such as titanium diboride and boron nitride. Other contemplated materials for the sleeve include graphitic composites. Although the sleeve will generally be a solid sleeve between its inner and outer peripheral surfaces, such need not be so. Hence, porous sleeves are contemplated, although the sleeve will most always have a non-porous working surface.  
         [0022]    The brush roll in a most typical form can be a wire brush having a cylindrical hollow shaft member. This shaft member may have, at its radially outer peripheral surface, wires projecting, radially outwardly therefrom. Such shaft member, or ‘tube’ or ‘tubular portion’ as such will sometimes be referred to herein for the brush roll, can be an elongated, open-ended tube of cylindrical shape. The tube will most always have an axial length longer than its diameter. It will preferably extend for the full axial length of the sleeve, although it will be understood that it may be longer than, or only substantially as long as, the sleeve. Its axial length along the mandrel can vary, e.g., it may not be nearly as long as the mandrel and so might be only substantially as long as the mandrel.  
         [0023]    It is also contemplated that the brush roll may be discontinuous. For example, it might be provided by a series of brush roll ‘sections’ or ‘tires’ that are placed along the mandrel. In a most usual form as described hereinabove, each tire can be a tube having outwardly projecting wire at its peripheral surface. In a typical case, each tire may have a short axial length, e.g., an axial length that approximates its diameter. Each tire may be sized so as to be slid onto the mandrel. Spacing may be maintained between tires, e.g., adjacent brush roll tires can be spaced apart from each other along the mandrel, or they can be slid together to form a continuous brush roll. Where they are spaced apart, the brush roll wires can then be axially discontinuous along the length of the brush roll. It is also contemplated that the wires may be circumferentially discontinuous around each tire or even for a brush roll of full axial length. Thus, for example, the wires may be present in rows on the brush roll and there can be spacing between the rows.  
         [0024]    Where the most typical form brush roll is slid over the mandrel, it is preferred that the inner peripheral surface of the tube be sized so as to provide for a firm fit with the outer peripheral surface of the mandrel. This can be achieved, for example, where there is an interference fit, e.g., as by frictional engagement of the brush roll and mandrel surfaces, which fit should be retained at the elevated operational temperatures of the roll. However, any means for securing the brush roll to the mandrel, e.g., by metallurgical means such as soldering or welding or brazing, or by other means including adhesive means and mechanical means, may be suitable. It is also contemplated that the brush roll may initially be in loose fit over the mandrel, but have at least a tube with a smaller coefficient of thermal expansion than for the mandrel. On heating, the thermal expansion of the mandrel firmly engages the brush roll to supply some to all of the secure engagement for the brush roll with the mandrel. Such secure engagement may then be readily retained at the elevated operational temperatures of the roll.  
         [0025]    It will be understood that the tube of the brush roll can be so integrally engaged with the mandrel so as to form a single unit. For such an article, the tube of the brush roll may be indistinguishable from the mandrel, and the wires of the brush roll might have the appearance of projecting directly from the mandrel. This structure is generally to be included within the use of the term ‘brush roll’ herein even where separate mention may be made of the mandrel. Furthermore, it is also contemplated that the brush roll may be inverted, wherein the tube of the roll engages the sleeve and the wires of the roll project radially inwardly to engage the mandrel. In this configuration, it will be understood that the tube of the brush roll may be integrally engaged with the sleeve so as to form a single unit. Such an integrally engaged structure is generally to be included within the use of the term ‘brush roll’ herein when used in reference to this configuration, even where separate mention may be made of the sleeve.  
         [0026]    The wires of the brush roll will generally be of the same length, although such need not be the case. Where they are of the same length, at their outer projecting ends they can form a cylindrical outside diameter for the brush roll. For convenience, this outside diameter of the brush roll may be referred to herein as the outer peripheral surface of the brush roll. It will be understood that this is a discontinuous ‘surface’ made up of these ends of the multitude of wires. The wires may be short or long. However, for best accommodation of the difference in thermal expansion coefficients for the mandrel and sleeve, the wires will advantageously have a length that is very substantially longer than their diameter. The word ‘wire’ has been employed hereinabove and may be used hereinafter for convenience. However, it may be that the form which the ‘multitude of radial projections’, as such term is used herein, will take, can also be described as nails or spikes or the like, as well as wires. The wires may be hollow, like straws, or solid. In any case, the wires should advantageously not be rigid so that they can provide some radial flexibility at the elevated operational temperatures of the roll. Such flexibility most always allows for the difference between thermal expansions for the mandrel and the sleeve without occasioning any deleterious effect, e.g., an effect such as cracking of the sleeve, during elevated temperature operation of the roll. Such flexibility can also assist in the brush roll achieving a firm engagement, e.g., a frictional engagement, between the outer peripheral surface of the brush roll and the inner peripheral surface of the sleeve. This can be secure engagement across a broad temperature range, e.g., at the temperatures at which the roller is assembled, presumably room temperature, as well as the elevated operating temperatures of the roll.  
         [0027]    In construction, the brush roll will most always be completely a metal brush roll of metal tube and metal wires. The metal of the tube and wires can be the same or different. For example, a stainless steel tube can have mild steel wires. Other materials for the tube or for the wire include heat resistant metal alloys. It is also contemplated that, particularly if a ceramic mandrel is utilized, the tube of the brush roll may itself be ceramic and the wires be metal.  
         [0028]    Referring then to the Figures, FIG. 1 shows a roll ( 10 ), that is representative of the present invention. FIG. 1 is in exploded view and partly in section wherein a portion only of the elevated temperature roll ( 10 ) is depicted. The inner member of the roll ( 10 ) is supplied by a mandrel ( 2 ). The mandrel ( 2 ) has a peripheral outer surface ( 3 ). Proceeding outwardly for the roll ( 10 ) in the radial direction from the mandrel ( 3 ) is a brush roll ( 4 ). The brush roll ( 4 ) has a tubular portion, or tube, ( 6 ). This tube ( 6 ) has an outer peripheral surface ( 7 ) and an inner peripheral surface ( 8 ). Extending radially outwardly from the outer peripheral surface ( 7 ) are a multitude of extending wires ( 5 ) of the brush roll ( 4 ). The inner peripheral surface ( 8 ) of the brush roll is sized so as to provide a snug fit with the outer peripheral surface ( 3 ) of the mandrel ( 2 ).  
         [0029]    The last member extending radially outwardly from the mandrel ( 3 ) for the roll ( 10 ) of FIG. 1 is the sleeve ( 11 ). The sleeve ( 11 ) has an inner peripheral surface ( 12 ) as well as an outer peripheral surface ( 13 ). The inner peripheral surface ( 12 ) is sized so as to fit snugly over the outward ends of the multitude of extending wires ( 5 ) of the brush roll ( 4 ). The outer peripheral surface ( 13 ) of the sleeve ( 11 ) is the working surface of this representative roll ( 10 ).  
         [0030]    Referring then to FIG. 2, there is provided a perspective view of elements of a roll ( 10 ) that is of a more substantial axial length, which will be typical of the rolls of the present invention. The elements of the roll depicted in FIG. 2 do not show a sleeve ( 11 ) (FIG. 1). In FIG. 2 there is shown a mandrel ( 2 ). The mandrel ( 2 ) is a hollow and elongated cylindrical mandrel ( 2 ). The mandrel has an outer surface ( 3 ) (FIG. 1). On this outer surface ( 3 ), in snug fit, there is mounted a brush roll ( 4 ). The brush roll ( 4 ) has a tubular portion ( 6 ). From the outer peripheral surface ( 7 ) of this tubular portion ( 6 ) project a multitude of extending wires ( 5 ). The brush roll tube ( 6 ) is a hollow, cylindrical and open-ended tube ( 6 ). The snug fit of the brush roll ( 4 ) over the mandrel ( 2 ) is provided at the respective outer peripheral surface ( 3 ) (FIG. 1) of the mandrel and inner peripheral surface ( 8 )(FIG. 1) of the brush roll ( 4 ).  
         [0031]    Referring then to FIG. 3, there is shown an isometric view of a portion only of a roll embodying the present invention. As shown in FIG. 3, the roll ( 10 ) has as its inner member a mandrel ( 2 ). The mandrel ( 2 ) is a solid and elongated cylindrical mandrel ( 2 ). Surrounding this mandrel ( 2 ) is a brush roll ( 4 ). The brush roll ( 4 ) at its outer peripheral surface ( 7 ) has a multitude of extending wires ( 5 ). The wires ( 5 ) extend from the tubular portion ( 6 ) of the brush roll. This tubular portion ( 6 ) is an elongated, open-ended portion ( 6 ) of cylindrical shape. As can be seen in the Figure, whereas the mandrel ( 2 ) and brush roll tube ( 6 ) are in secure engagement, between the outer peripheral surface ( 7 ) of the brush roll ( 4 ) and the roll outer member, i.e., the sleeve ( 11 ), there is a radial clearance that is occupied by the multitude of extending wires ( 5 ). These wires ( 5 ) extend from the brush roll tube ( 6 ) to the inner peripheral surface ( 12 ) of the sleeve ( 11 ). The brush roll ( 4 ) thereby occupies the radial clearance between the sleeve ( 11 ) and the mandrel ( 2 ). The outer peripheral surface ( 13 ) of the sleeve ( 11 ) can be the working surface for this roll ( 10 ).  
         [0032]    In making the roll ( 10 ), any method for providing the final assembly of the roll ( 10 ) is contemplated. Advantageously for economy of manufacture, the tube ( 6 ) of the brush roll ( 4 ) is slid over the outer peripheral surface ( 3 ) of the mandrel ( 2 ). The tube ( 6 ) and mandrel ( 2 ) are advantageously sized so as to provide for a secure fit between the brush roll ( 4 ) and the mandrel ( 2 ). It is preferred that the brush roll ( 4 ) be positioned on the mandrel ( 2 ), such as by sliding the roll ( 4 ) over the mandrel ( 2 ), with the sliding providing frictional engagement between the tube ( 6 ) inner peripheral surface ( 8 ) and the outer peripheral surface ( 3 ) of the mandrel ( 2 ). Other means of securing the roll ( 4 ) to the mandrel ( 2 ), such as after the roll ( 4 ) has been slid over the mandrel ( 2 ), can include metallurgical means such as soldering and welding, adhesive means, mechanical means such as by peening or latching, or combinations of these means.  
         [0033]    Also, the mandrel ( 2 ) and the tube ( 6 ) may be configured so that the sliding of the tube ( 6 ) and mandrel ( 2 ) provides secure engagement even including locking of the tube ( 6 ) and mandrel ( 2 ). For example, the mandrel ( 2 ) can have axial slots or keyways along its length and the tube ( 6 ) have elements such as ridges that slip within the slots as the tube ( 6 ) is slid over the mandrel ( 2 ). It is also contemplated that the brush roll ( 4 ) may be loosely fit over the mandrel ( 2 ) as when the roll ( 10 ) is assembled at a moderate temperature, e.g., room temperature, and the tube ( 6 ) of the brush roll ( 4 ) has a smaller coefficient of thermal expansion than for the mandrel ( 2 ). Particularly in a situation such as when the brush roll ( 4 ) may be temporarily secured over the mandrel as by mechanical means, elevating the temperature of the tube ( 6 ) will then contribute to a firm interference fit between roll ( 4 ) and mandrel ( 2 ) during thermal expansion of the assembly. By use of the term ‘interference fit’ herein there is thus meant a fit between the brush roll ( 4 ) and the mandrel ( 2 ) as may, for example, be achieved by one or more of frictional engagement, sliding as described hereinabove that might include locking and the fit obtained by thermal expansion.  
         [0034]    In what is contemplated as the general manner of assembling the roll ( 10 ), the sleeve ( 11 ) is then typically slid over the brush roll ( 4 ) so as to have the inner peripheral surface ( 12 ) of the sleeve ( 11 ) engage the outer projecting tips of the multitude of extending wires ( 5 ) of the brush roll ( 4 ). This sliding of the sleeve ( 11 ) over the brush roll ( 4 ) may be accommodated merely by mechanical means. However, it is also contemplated that there may be utilized other means of assembly such as shrink fitting. Where the sleeve ( 11 ) and brush roll ( 4 ) are involved, the sleeve ( 11 ) may be heated to provide thermal expansion of the sleeve ( 11 ) while the brush roll ( 4 ) is retained at moderate, e.g., room, temperature. Then the thermally expanded sleeve ( 11 ) can be slid over the brush roll ( 4 ). Contact between the inner peripheral surface ( 12 ) of the sleeve ( 11 ) and the extending wires ( 5 ) of the brush roll ( 4 ) can be initiated, or enhanced, by contraction of the sleeve ( 11 ) during cooling to provide the desired interference fit. In any manner of assembly it will be understood that the wires ( 5 ) need not be straight. Thus, they may be bent or curved, e.g., in the form of an arc. Such wire forms might be utilized to assist in assembly, as well as to reduce stress that the wires ( 5 ) impart to the sleeve ( 11 ).  
         [0035]    Although the roll ( 10 ) is generally considered for use at elevated temperature, such as utilization as a glass conveying roll, a roll for a rolling mill, steel conveying roll, glass pulling roll, steel galvanizing roll or rolls in zones such preheat zones, it will be understood that the roll ( 10 ) could be used at moderate or even reduced temperature. As a glass conveying roll, the elevated operational temperature may be greater than 1500° F., e.g., on the order of 1700° F. And for a steel conveying roll, it can be expected to be greater than 2000° F., but not to exceed about 2500° F. Generally the brush roll ( 4 ) will extend at least substantially along the axial length of the mandrel ( 2 ) and the sleeve ( 11 ) will extend essentially along the complete axial length of the brush roll ( 4 ) although, in both instances, such need not be the case. Furthermore, usually the brush roll ( 4 ) and sleeve ( 11 ) will be continuous units such as to provide a seamless working surface for the outer peripheral surface ( 13 ) of the sleeve ( 11 ). However, it is also contemplated that the roll ( 10 ) could be formed of individual units, or ‘tires’. A representative complete ‘tire’ or ‘section’ of brush roll ( 4 ) plus sleeve ( 11 ) can take the form as generally shown by the roll portion in FIG. 3. These sections of brush roll ( 4 ) plus sleeve ( 11 ) can be slid along a mandrel ( 2 ) and axially pressed together to form a continuous roll ( 10 ). The sections of brush roll ( 4 ) and sleeve ( 11 ) might be pre-made, or could be formed on the mandrel by initially placing sections of brush roll ( 4 ) on the mandrel ( 2 ) and then covering each brush roll section with a section of sleeve ( 11 ).  
         [0036]    It is also contemplated that the roll ( 10 ) could be made with a radially reversed order for the brush roll tube ( 6 ) and wires ( 5 ). In this embodiment, the brush roll tube ( 6 ) would fit within the inner peripheral surface ( 12 ) of the sleeve ( 11 ). Then the wires ( 5 ) would extend radially inwardly to contact the outer peripheral surface ( 3 ) of the mandrel ( 2 ). It is further contemplated that in this reversal of the general embodiment of the invention, the sleeve ( 11 ) may be metallic and the mandrel ( 2 ) ceramic. Such might occur where the assembly is used in retrofitting an existing structure. For example, a fused silica roll in an existing structure might be in the form of a mandrel ( 2 ) which is maintained as a mandrel in the retrofitting.  
         [0037]    Although it will be usual to employ a metal mandrel, the mandrel may be a composite structure. Such composite structure might take the form of a mandrel having an inner ceramic portion and an outer metal layer. The outer metal layer might be obtained such as by spray coating. Compound structures which are typically layered structures such as a surface layer of a sintered ceramic over a metallic layer, are also contemplated for the tube ( 6 ) of the brush roll ( 4 ) as well as for the sleeve ( 11 ).  
         [0038]    Also, it is contemplated that insulation means can be used in the roll ( 1 ) where desired. For example, ceramic fibers, e.g., compressed ceramic fibers, or other fiber products such as moldable fiber material, might be present, such as in the form of a wrap around the mandrel ( 2 ). Then the tube ( 6 ) inner surface ( 8 ) can be slid over the insulation wrap. Or insulation such as ceramic fiber in disc form might be present between brush roll ( 4 ) sections that have a form such as shown by the roll portion in FIG. 3. This insulation could take the form of alternating a brush roll ( 4 ) with a ceramic fiber disk. Or insulation products could be forced into the wires ( 5 ), thereby occupying space such as between the brush roll outer peripheral surface ( 7 ) and the sleeve inner peripheral surface ( 12 ). Application of insulation as combinations of the foregoing is also contemplated.