Abstract:
A web pleating apparatus comprising a first series of converging elongate spaced protuberances and a second series of elongate spaced protuberances converging in the machine direction. The first series of protuberances and said second series of protuberances interleave in the Z-direction. The interleaved protuberances are capable of folding a pleatable web into a generally pleated pattern of machine direction pleats upon contact with said first and second series of protuberances.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an in-line apparatus for pleating a web. The pleated web may be useful for the manufacture of pleated filter elements.  
         BACKGROUND OF THE INVENTION  
         [0002]    Glass micro fiber media consisting of a laminate of micro glass paper and polyester nonwoven can filter contaminants such as microbiological cysts and asbestos from drinking water. This material can be formed into a pleated structure to increase useful surface area for filtration. However, forming pleats quickly and reliably in glass micro fiber media challenges existing pleating equipment. Glass micro fiber media material tends to have memory and is highly elastic in bending and resists plastic deformation. Material that bends elastically will generally not take a set when folded and can spring back to its original shape if not controlled properly. Glass micro fiber media can also be delicate to handle and can be damaged if strained excessively. A filter requiring a small pleat height, for example, less than 0.25 inches (0.64 centimeter), creates further challenges for manufacturing due to geometrical and physical constraints.  
           [0003]    In a pleating process, forces can act upon a web in primarily three directions. The direction of travel of the web is generally known in the art as the machine direction (MD). The direction orthogonal and coplanar to web motion is generally known as the cross-machine direction (CD). The direction orthogonal to both the MD and CD is generally known as the Z-direction.  
           [0004]    Two commercial approaches for creating pleats in glass micro fiber media webs are commonly used. The approaches are the pusher bar and rotary score pleaters. Both pusher bar and rotary score pleaters create pleats parallel to the CD of a web.  
           [0005]    The pusher bar, also known in the art as a blade pleater, uses a reciprocating blade to produce a CD fold as the web travels in the MD. This method of forming pleats is relatively slow and requires multiple machines or CD lanes to achieve high throughput.  
           [0006]    A rotary score pleater applies evenly spaced CD scores. The CD scored web is driven by nips on a slow MD conveyor that bends the web about the scores forming CD folds. A rotary score pleater can produce pleats faster than the pusher bar pleater, however, the individual folds are not controlled during the pleating process. In addition, webs that bend elastically run with low reliability due to the inability to positively control Z-direction movement of the pleated web.  
           [0007]    In addition to conventional CD pleating, MD pleating methods are described in the art. Generally these MD processes were intended for more plastic materials that take a set when folded, tolerate higher strain, and have larger pleat heights.  
           [0008]    An example of an MD pleater is described in Rosenburg, U.S. Pat. No. 4,252,591. This method constrains the web between converging “V”-shaped guides and chains, where the chains pull the web though the guides. These chains ride inside the “V” and the web is sandwiched between the chains and the guides. This method is not well suited for small pleat heights due to the relatively large chain cross-section required to generate sufficient force to drive the web. Secondly, this method produces poor pleats in a web that bends elastically because the weight of the chains must hold the web into the guides. A web that bends elastically can lift the chains out of the guides and prevent folding. Lastly, the web scoring process disclosed employs male rings that press the web into female grooves. This method of scoring produces excessive strain on the web and can lead to catastrophic failure. Moll, German Patent DE 583,894, attempts to minimize strain in a web during the formation of longitudinal corrugations by employing soft rollers. Moll does not address control of a web that bends elastically. Practically, soft rollers cannot fully press the longitudinal corrugations of a web that bends elastically into the grooves of a forming plate unless the longitudinal corrugations are very shallow. Also the pleats are not controlled in the Z-direction between successive rollers.  
           [0009]    MacFarland, U.S. Pat. No. 1,313,712, Rowe, U.S. Pat. No. 2,335,313, and Jackson, Great Britain Patent No. GB 376,846, disclose methods for folding pleats in a web between converging belts. These methods are not practical for small pleats because this requires the use of an impractically small belt. Also, these methods cannot control a web that bends elastically because the belts are not able to resist the Z-direction spring force of the compressed pleated web.  
           [0010]    U.S. Pat. Nos. 654,884; 813,593; 1,402,548; 1,759,844; 2,084,362; 2,164,702; 2,196,006; 2,314,757; 2,494,431; 2,986,076; 3,038,718; 3,205,791; 3,348,458, European Patent No. WO 99/47347, and British Patent No. GB 541,015 disclose systems that pull a web though a converging set of blades or guides. None of these teach driving a web during folding with blades. The friction created by pulling a web through the process can create excessive strain and damage web fibers. U.S. Pat. Nos. 136,267; 775,495; and 5,185,052 are representative of systems that form pleats or corrugations by running a material between progressive rollers. These systems have difficulty controlling the folds of a web that bends elastically between successive sets of rolls.  
           [0011]    The present invention provides an improved apparatus for producing pleats in the MD direction, at high speed, in a delicate web that bends elastically. This process is likewise able to produce pleats in materials that easily take a set when folded or are insensitive to strain.  
         SUMMARY OF THE INVENTION  
         [0012]    The present invention relates to a web pleating apparatus having a mutually orthogonal machine direction, a cross machine direction and a Z-direction. The apparatus comprises a first series of elongate spaced protuberances converging in the machine direction, and a second series of elongate spaced protuberances converging in the machine direction. The first series of protuberances and the second series of protuberances interleave in the Z-direction. Additionally, the first series and the second series of interleaved protuberances are capable of folding a pleatable web into a generally pleated pattern of machine direction pleats upon contact with the first and second series of protuberances.  
           [0013]    The present invention also relates to a method for forming a pleatable web comprising the steps of providing a pleatable web, scoring the pleatable web in the machine direction, transporting the scored web relative to a first series and second series of machine direction converging elongate spaced protuberances interleaved and spaced in the Z-direction, and, folding the scored web with the interleaved first series and second series of converging protuberances. The interleaved converging protuberances pleat the pleatable web in the machine direction.  
           [0014]    The present invention also relates to a filter which comprises a pleated web formed by providing a pleatable web, scoring the pleatable web, transporting the scored web relative to a first and second series of interleaved converging elongate spaced protuberances, and, folding the scored web with the interleaved first and second series of converging protuberances wherein the interleaved converging protuberances pleat the pleatable web. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    While the specification concludes with claims which particularly point out and distinctly claim the present invention, it is believed that the present invention will be better understood from the following description of preferred embodiments, taken in conjunction with the accompanying drawings wherein:  
         [0016]    [0016]FIG. 1 is an elevational view of a preferred embodiment of the web pleating apparatus in accordance with the present invention;  
         [0017]    [0017]FIG. 2 is a plan view of a preferred embodiment of the web pleating apparatus;  
         [0018]    [0018]FIG. 3 is a cross-sectional view of the scoring rolls taken along line  3 - 3  of FIG. 2;  
         [0019]    [0019]FIG. 3 a  is an expanded view of the region labeled  3   a  of FIG. 3;  
         [0020]    [0020]FIG. 4 is a cross-sectional view of a driven pleat forming board taken along line  44  of FIG. 2;  
         [0021]    [0021]FIG. 5 is a cross-sectional view of a driven pleat forming board driven from above and taken along line  5 - 5  of FIG. 2;  
         [0022]    [0022]FIG. 6 is a cross-sectional view of a driven pleat forming board driven from below and taken along line  6 - 6  of FIG. 2;  
         [0023]    [0023]FIG. 7 is a cross-sectional view of a convergence board taken along line  7 - 7  of FIG. 2;  
         [0024]    [0024]FIG. 8 is a cross-sectional view of a convergence board driven from above taken along line  8 - 8  of FIG. 2;  
         [0025]    [0025]FIG. 9 is a cross-sectional view of a convergence tunnel taken along line  9 - 9  of FIG. 2;  
         [0026]    [0026]FIG. 10 is a cross-sectional view of a heated tunnel taken along line  10 - 10  of FIG. 2;  
         [0027]    FIGS.  11 - 13  are successive cross-sectional views of a cylindrical forming tunnel taken along lines  11 - 11 ,  12 - 12 , and  13 - 13  of FIG. 2 respectively; and,  
         [0028]    [0028]FIG. 14 is a cross-sectional view of a seamed cylindrical product in a cooling tube and taken along line  14 - 14  of FIG. 2. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]    The present invention is related to an in-line pleating process to manufacture pleated webs for filter elements useful for water filtration products. The pleated elements can be a component of a disposable replacement filter cartridge. The pleated element can be responsible for the removal of microbiological cysts, such as giardia and cryptosporidium, as well as suspended solids, etc. Other non-limiting uses for pleated webs include oil and air filtration and structural corrugation. Exemplary, but non-liming, materials that can be supplied in continuous web or discontinuous sheet form and pleated in the machine direction by the present invention include wet or dry laid papers (i.e. glass, cellulose, quartz, asbestos, carbon, metal, and synthetic polymer fibers), woven natural fabrics (i.e. cotton, silk, and wool), polymeric wovens (multifilament or monofilament) and melt blown, spunbonded, and flash spun nonwovens (i.e. polyamide, polyaramid, polyester, polyethylene, polypropylene, polytetrafluoroethylene, and polyvinyl chloride), felts, needle felts, perforated metals and plastics, metal or plastic screens and meshes, metal or plastic sheets or foils, and combinations thereof. Loose filter media such as granules, powders, or fibers can also be combined to a web substrate and pleated. Exemplary, but non-limiting, loose media that can be combined with a web are carbon granules, diatomite, expanded pearlite, sand, glass, carbon, molecular sieves, and cellulose fibers. However, the web can generally consist of any material that can be folded into the desired pleated shape without failure due to exceeding the ultimate strength of the material during bending.  
         [0030]    Referring to FIGS. 1 and 2, a flat web  20  can be supplied in continuous web form by unwinding the flat web  20  from roll  21 . A tension control device  22 , such as a dancer that controls torque by a braking action, can be used to maintain constant tension from the roll  21 . Alternatively flat web sheets  20   a  can be inserted as individual sheets that move in the MD in a discontinuous manner.  
         [0031]    The flat web  20  is fed into scoring rolls  23 . The scoring rolls  23  comprise an upper roll  24  and a lower roll  25  that form a nip therebetween. The flat web  20  is inserted between rolls  24  and  25 . Upper roll  24  and lower roll  25  are driven so that the surface speeds of scoring rolls  23  equals the speed of flat web  20 . Tensioning device  26  can be used to provide feedback to the drive of the scoring rolls  23  to provide a constant tension in web  20  between scoring rolls  23  and driven pleat forming board  28 . Entrance idler  27  preferably is inserted to transport web  20  to the entrance of driven pleat forming board  28 . Entrance idler  27  can generally have a convex, or crowned, surface to prevent wrinkling of web  20  due to potential unequal path lengths in the MD of web  20  as it enters driven pleat forming board  28 .  
         [0032]    [0032]FIG. 3 shows a cross-sectional view of upper roll  24  and lower roll  25 . As a non-limiting example, upper roll  24  can be loaded against lower roll  25  by force from a pneumatic cylinder or other method of supplying force as would be known to one skilled in the art. The distance between the axis of upper roll  24  and lower roll  25  is preferably constrained to maintain a fixed gap between adjacent surfaces of upper roll  24  and lower roll  25 . This gap is preferably less than the thickness of the flat web  20 .  
         [0033]    [0033]FIG. 3 a  shows an enlarged detail of the working surface of scoring rolls  23 . Flat web  20  is compressed between alternating radiused teeth  24   a ,  25   a  and flats  24   b ,  25   b  that circumscribe the face of rolls  24 ,  25 . Teeth  24   a ,  25   a  can have any surface that provides an effective score line on the web. For example, teeth  24   a ,  25   a  can be paralellpiped, tapered, semi-cylindrical, or pyramidal. Flats  24   b ,  25   b  provide a mating surface for teeth  24   a ,  25   a  located on the opposite roll. Tooth  24   a  compresses web  20  against the center of flat  25   b  and tooth  25   a  compresses web  20  against the center of flat  24   b . This results in web  20  having a score line with an inner apex pressed in the upper surface corresponding to  24   a  and  25   b  and a score line with an inner apex pressed in the lower surface corresponding to  25   a  and  24   b . Mating radiused teeth  24   a ,  25   a  and flats  24   b ,  25   b  are preferably equally spaced and alternate orientation across the face of rolls  24 ,  25  resulting in a plurality of continuous and equally spaced parallel alternating upper and lower score lines across the width of web  20 . Alternating upper and lower score lines predispose the web to fold with less effort upwards and downwards respectively. As a result, the scored flat web  20  is predisposed to be alternately folded to form pleats. However, it would be known to one skilled in the art that scoring is not required for every type of web material. It would be also known to those of skill in the art that teeth  24   a ,  25   a  and flats  24   b ,  25   b  can be unequally spaced, discontinuous, and may be aggregated in any combination on either roll  24 ,  25 .  
         [0034]    Referring to FIGS. 1 and 2, the scored web  20  next enters the driven pleat forming board  28  where the pleat folds are gradually formed in the machine direction. A plurality of pleat forming blades  29 ,  30  guide the inner apex of each pleat fold from above and below. As shown in FIG. 2, pleat forming blades  29 ,  30  are preferably continuous singular linear blades, collectively elongate and span the length of the driven pleat forming board  28 . However, it would be known to one skilled in the art to use collinear or non-collinear, collectively elongate or non-collectively elongate surfaces to form pleats. Pleat forming blades  29 ,  30  initially engage web  20  at a spacing equal to the desired pleat height corresponding to the spacing of the score lines. Blades  29 ,  30  generally converge down stream toward the MD centerline of web  20 . The point where overlap and interleaving of blades  29 ,  30  begins is generally known as the inlet. The last occurrence of contact of web  20  with blades  29 ,  30  is generally known as the outlet.  
         [0035]    Pleat forming blades  29 ,  30  alternate above and below the web  20  across the width of the web  20  corresponding to the alternating upper and lower score lines. Upper blades  29  correspond to score lines created by upper teeth  24   a  and lower blades  30  correspond to score lines created by lower teeth  25   a . Web  20  is controlled and constrained into a pleated shape when traveling in the MD by upper pleat forming blades  29  and lower pleat forming blades  30 . Lower pleat forming blades  30  preferably remain level over their entire span. The upper pleat forming blades  29  are in a plane that declines in the Z-direction as the blades  29  extend downstream in the MD. The intersection of the declined plane of the upper blades  30  and the level plane of the lower blades  30  is a CD line. Each of the lower blades  30  converges to a downstream point located on the web MD centerline. Likewise each of the upper blades  29  converges to another downstream point on the web MD centerline. This point is located on the line orthogonal to the horizontal plane that intersects the lower blade convergence point. The angle between each successive pair of lower blades  30  is bisected by the horizontal projection of the upper blades  29 . At the inlet of the board there is a clearance in the Z-direction between the edge of the lower blades  30  and upper blades  29 . As the upper blades  29  follow the declining plane downstream, the upper blades  29  gradually interleave in the Z-direction with the lower blades  30 .  
         [0036]    At the entrance of the driven pleat forming board  28 , the vertical clearance of upper blades  29  and lower blades  30  is approximately equal to the web thickness and provides sufficient clearance so web  20  can be threaded between blades  29 ,  30 . At the exit of driven pleat forming board  28 , the upper blades  29  interfere with the lower blades in the Z-direction to constrain the pleats of web  20  between blades. Clearance in the Z-direction is provided to allow for the thickness of the web  20  and additional clearance is provided to minimize friction between blades  29 ,  30  and web  20 . The paths of blades  29 ,  30  maintain a nearly constant distance between upper and lower blade endpoints at cross-sections perpendicular to the web  20 . The outer pleat forming blades  29 ,  30  of the board are generally longer than the center pleat forming blades  29 ,  30 . Hence, the length of driven pleat forming board  28  should be sized so web  20  behaves elastically when strained in the MD due to the unequal path length. The MD strain on outer fibers is generally larger in a short MD pleat forming board  28  than in a long MD driven pleat forming board  28  because the path lengths are more nearly equal on the longer driven pleat forming board  28 . If driven pleat forming board  28  is not long enough in the MD, the stress on the outer fibers of web  20  can exceed the yield stress, causing the web to plastically deform. If the ultimate web strength is exceeded, web  20  can fail.  
         [0037]    [0037]FIG. 4 shows a cross-section of driven pleat forming board  28 . Upper pleat forming blades  29  are supported by upper plate  33  and the lower pleat forming blades  30  are supported by lower plate  34 . Preferably, each lower pleat forming blade  30  lines up with a corresponding lower score line in the web  20  and each upper pleat forming blade  29  lines up with the corresponding upper score line of web  20 . Web  20  is constrained between the edges of pleat forming blades  29 ,  30  and shallow alternating folds have begun to form.  
         [0038]    [0038]FIG. 5 shows a cross-section of the driven pleat forming board taken at the center of an upper drive roll  31 . The driven elements need not be limited to rollers, for example, drive belts or feet in traction with the web can be used. Upper roller  31  has equally, or unequally, spaced clearance grooves  52  around the periphery of roller  31 . A clearance groove  52  allows upper roll  31  to extend beyond upper blade  29  and contact the upper surface of web  20 . Web  20  is driven due to a differential friction between roll  31  and blade  29 . Blades  29 ,  30  are preferably made from a smooth material with a low coefficient of friction. The surface of roll  31  is preferably a compliant material with a high coefficient of friction against the web, for example, rubber or urethane. The axis of roll  31  can be held horizontal and the drive roll  31  loaded by a normal force against web  20  to insure that roll  31  remains in traction with web  20 . Alternatively, or additionally, as shown in the cross-sectional view of FIG. 6, lower drive roll  32  may engage the lower surface of the web  20 . Drive rolls  31 ,  32  are driven at a surface speed to match the surface speed of the transported web. Drive rolls  31 ,  32  provide energy to the web  20  to drive it through folding board  28 .  
         [0039]    Alternatively, web  20  may be pulled through driven pleat forming board  28  without drive rolls  31 ,  32 . However, pulling web  20  imparts a high frictional force to web  20  resisting motion. This frictional force can create high stress in web  20 , and may lead to plastic deformation or failure. Thus, drive rolls  31 ,  32  are preferably distributed along the length of driven pleat forming board  28  at sufficient spacing to keep strain in the web due to frictional forces at an acceptably low level.  
         [0040]    The critical control angle (CCA) is the maximum angle at which the pleated web  20  will tolerate a MD discontinuity in one set of blades and not come out of the remaining blades. If the pleat angle is above the CCA, the pleat may not remain controlled by a single set of blades and one side of the forming pleats may slide off due to lateral compressive forces in the media. For exemplary purposes only, the CCA has been found to range from approximately 100 to 150 degrees for several glass micro fiber media. However, this angle depends upon the material properties of the selected web. Generally, when web  20  has a fold angle greater than the CCA, the upper and lower blades  29 ,  30  should maintain continuous contact with the web  20  to retain control of the pleats and correctly form the final pleated web product. After the fold angle becomes less than the CCA, it is possible to use discontinuous upper and lower blades  29 ,  30 . This can allow for overall design simplification, for instance, no longer requiring grooves on the rolls, and allowing all rolls to be loaded from one side and turn the same direction. Of course, driven pleat forming board  28  can be continued for the full MD length of the system.  
         [0041]    [0041]FIG. 2 shows the convergence driven folding board  35  that continues the gradual pleating process initiated by the driven pleat forming board  28 . FIG. 7 shows a cross-sectional view of the convergence driven folding board  35  taken at an upper plate  38 . Convergence driven folding board lower blades  37  are preferably collinear to each of the lower blades  30 . These can be continuous extensions of lower blades  30  or there can be a gap between convergence driven folding board lower blades  37  and lower blades  30 . Preferably, convergence driven folding board lower blades  37  are continuous in the MD for the entire length of convergence driven folding board  35 . Convergence driven folding board lower blades  37  can be made discontinuous to provide access for lower drive rolls. The partially pleated web  20  is constrained between convergence driven folding board lower blades  37  and convergence driven folding board upper blades  36 . Convergence driven folding board upper blades  36  are preferably collinear to upper blades  29 . Convergence driven folding board upper blades  36  are preferably discontinuous to allow clearance for upper drive rolls  40 . Convergence driven folding board upper blades  36  can alternatively be made continuous for the length of board  35 . Web  20  is controlled from below by convergence driven folding board lower blades  37  and from above by convergence driven folding board upper blades  36 . Convergence driven folding board lower blades  37  are supported by lower plate  39 . Convergence driven folding board upper blades  36  are supported by upper plate  38 . The height of the upper plate  38  above the lower plate  39  is preferably set by spacers. The upper plate  38  generally follows a decline as with upper plate  33 . Upper plates  38  can be supported only by web  20 , however, this can create additional friction. Drive rolls  40  are preferably used to overcome the friction between web  20  and convergence driven folding board upper and lower blades  36 ,  37  to drive web  20  through convergence driven folding board  35 .  
         [0042]    [0042]FIG. 8 shows a cross-section of convergence driven folding board  35  taken at the axis of one of the drive rolls  40 . Pleated web  20  is supported and controlled by convergence driven folding board lower blades  37 . Upper drive roll  40  has traction with the top of web  20 . Discontinuous convergence driven folding board upper blades  36  are not present near drive roll  40 , allowing a flat face (no groove) roll design to engage web  20 . The face of drive roll  40  has a higher coefficient of friction with web  20  than convergence driven folding board lower blades  37 . Drive roll  40  is preferably driven to match the surface speed of web  20  and drive web  20  through folding board  28  due to the differential friction present. Drive rolls  40  are preferably spaced sufficiently close together to maintain the strain in web  20 , caused by friction with the blades, at an acceptably low level.  
         [0043]    Because outer convergence driven folding board lower blades  37  are skewed in the CD and are not perpendicular with the drive roll  40 , the shear component of the roll traction can tend to pull web  20  out of the outer convergence driven folding board lower blades  37 . An alternative to the full width drive roll  40  is to drive the web  20  with a narrow roll that does not cover the outer four or so pleats on each side. The convergence driven folding board upper blades  36  can be continued along these outer pleats adjacent to the drive rolls  40 . It is also possible with materials that bend more plastically to replace the convergence driven folding board upper blades  36  with floating dead plates that hold the pleats into the convergence driven folding board lower blades  37 .  
         [0044]    As would be known to one of skill in the art that boards  28 ,  35  can have many alternative configurations. Driven rolls  31 ,  32 ,  40  can be located on either side of web  20 . Blades  29 ,  30 , and convergence driven folding board blades  36 ,  37  can be continuous or discontinuous on either side of web  20  as desired for the web material chosen. It is also possible for convergence driven folding board  35  to be used for the full length of pleating without the need for board  28  if web  20  is not highly elastic in bending. Likewise, board  28  can extend the full length of pleating. Optionally, board  35  can precede board  28  in the process, if desired.  
         [0045]    [0045]FIG. 9 shows a cross-section of web  20  in convergence tunnel  41  located down stream of convergence driven folding board  35 . The convergence tunnel  41  is a smooth walled tunnel that constrains the pleated material from four sides so that the pleats cannot pop out or loose their form. During convergence, the clearance between the sidewalls of tunnel  41  decreases and the clearance between the upper and lower walls increases as web  20  moves downstream. Once web  20  reaches the desired width, tunnel  41  generally maintains a constant width. Since the final filter product is generally cylindrical, the convergence width of the pleated web  20  is approximately equal to the outer diameter circumference of the final cylindrical product. Drive rolls  42  in the constant width section of the tunnel  41  impart energy to the pleated web  20  to pull it though the tunnel  41 . Drive rolls  42  push web  20  against the respective upper and lower tunnel walls. Convergence driven folding board upper blades  36  can extend out of convergence driven folding board  35  and into tunnel  41  and preferably extend the length of convergence tunnel  41  ending prior to drive roll  42 . Convergence driven folding board upper blades  36  preferably continue at a constant convergence angle in the CD and then straighten out and run parallel at the constant width portion of tunnel  41 . Optionally, convergence driven folding board lower blades  37 , or a combination of convergence driven folding board upper blades  36  and convergence driven folding board lower blades  37 , can extend into convergence tunnel  41 .  
         [0046]    Depending on the web material, once the width of the pleated web  20  is converged, the web  20  is optionally, but preferably, heated to soften the web  20  folds so they will take a set when cooled to hold the web  20  in a pleated shape. Heat can be transferred to the web by convection, radiation, including infra red radiation, or conduction. Preferably, heating is done by convection using hot air. Referring to FIG. 10, the converged web  20  is preferably constrained on four sides by heat tunnel  43 . The width of the pleated web  20  is controlled so that the pleats have a slight spacing between folds. Such spacing can provide an even heat transfer to the pleats and prevents adjacent edges from melting together. Heating can also occur at any point in folding driven pleat forming board  28 , convergence driven folding board  35 , and convergence tunnel  41  or at any point in the pleating process described supra. Additionally, blades can be present within heat tunnel  43 .  
         [0047]    [0047]FIG. 10 shows a cross-section of converged web  20  inside of the heat tunnel  43 . Hot air can be supplied from above and below web  20 . The temperatures of the upper and lower hot air can be independently controlled, allowing the natural curl of the final cooled heat set pleated web  20  to be predetermined. Optionally, a cooling section is located downstream from heat tunnel  43 . Optionally the width of the web can be reduced to compress the pleats past heat tunnel  43 . However, web  20  should be generally constrained during cooling.  
         [0048]    The post-heating drive tunnel  44  uses drive rolls  45  to drive the pleated web  20  from heat tunnel  43  to cylinder former  46 . These additional drive rolls  45  are in traction with web  20  and can provide additional driving force to the web to counter the friction between web  20  and various stationary guides in contact with web  20 . To better counter friction, additional drive rolls can optionally be added to other areas of the process such as heat tunnel  43 , cylinder former  46 , and cooling tube  48 .  
         [0049]    Referring to FIGS.  10 - 14 , the pleated web  20  is preferably passed through cylinder forming tunnel  46  that gradually, or progressively, forms the flat web  20  into a cylindrical web  20 . The cross-section of the cylinder forming tunnel  46  is in the shape of an arc (arcuate) with constant arc length. Cylinder forming tunnel  46  constrains the periphery of the pleated web  20  to form an arcuate cross-section. The radius of the arc is gradually reduced from the entrance of the tunnel to the exit of the tunnel. In addition to cylindrical products, various other closed or open cross-sectional shapes can be obtained such as flat pleat panels, triangles, squares, higher order polygons, and various curved shapes. Web  20  can also be compressed or released in cylinder forming tunnel  46 . Blades may also be present in cylinder forming tunnel  46 .  
         [0050]    If a closed cross-section is desired, a continuous seam  49  can be made in cylindrical web  20  to join the edges together and create a closed cylindrical web  20  that is a continuous tube. A hot melt adhesive applicator  47  is preferably located downstream of the cylinder forming tunnel  46  to apply adhesive to mating outer edges of cylindrical web  20  to create seam  49 . Other non-limiting methods could be used to create continuous or discontinuous seams, such as, ultrasonic bonding, heat sealing, and mechanical methods such as crimping sewing, stapling, taping and clipping. Additionally, two or more cylinder forming tunnels can be combined to create more than one seam  49 . Such a combination can be useful for the production of large pleated products.  
         [0051]    [0051]FIG. 14 shows a cross-section of the cylindrical pleated web  20  with seam  49  traveling through cooling tube  48 . The cooling tube  48  preferably includes air jets  53  above seam  49  to cool seam  49  prior to cutting. Cooling tube  48  can support the formed cylinder and keep it at a controlled diameter. An inner core or vacuum canals can be included to prevent the cylindrical web from collapsing.  
         [0052]    Referring to FIGS. 1 and 2, a saw  50  can be used to cut cylindrical web  20  into discrete cylindrical products  51 . If cylindrical web  20  is in constant continuous motion, saw  50  should translate at a matched speed with web  20  during cutting. The preferred method of cutting is with circular saw blade, however a band saw or other cutting apparatus known to those skilled in the art can also be used. Sensors can measure the cut length obtained from the saw and this data can be used as feedback to adjust the speed of the drive rolls to maintain a constant product cut length. This can allow for compensation of gradual changes in roll pitch diameter due to wearing of the rollers.  
         [0053]    The raw material does not necessarily need to be in continuous web form. Discrete, discontinuous sheets can be used in the pleating process. Additionally, this process can also be used to produce corrugated structures. In the instance where the folds are gradually radiused such as corrugations with a sinusoidal cross section, the cross section of the blades can be adjusted to yield an appropriate shape.  
         [0054]    While particular embodiments of the present invention have been illustrated and described, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. One skilled in the art will also be able to recognize that the scope of the invention also encompasses interchanging various features of the embodiments illustrated and described above. Accordingly, the appended claims are intended to cover all such modifications that are within the scope of the invention.