Abstract:
A continuous, fully automated and highly productive system for the production of open core elements utilizes a fluting method and related apparatus effective for providing large pitch flutes for the input webs used in forming the core elements. A wide variety of core elements can be produced for uses ranging from large light weight building panels to small light weight packing elements.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This is a continuation-in-part of application Ser. No. 11/769,879 filed Jun. 28, 2007, which is a continuation-in-part of application Ser. No. 11/476,474, filed Jun. 28, 2006. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention pertains light weight open core materials having a honeycomb-like structure useful in a number of applications where light weight core elements are desirable or necessary.  
         [0003]     It has long been known to utilize honeycomb core materials in the manufacture of structural members such as doors, wall panels and floor panels. The honeycomb core material may be made from paper, metal or even plastic web material. Conventional honeycomb construction may utilize paper strips laid together in a stack and connected to one another with intermittent lengths of adhesive, and then expanded or opened to form a hexagonal honeycomb core element. It is also known to use corrugated paper or metal webs either with or without smooth facing webs which are stacked and glued together, again resulting in an open core structure.  
         [0004]     Although honeycomb-type core elements have long been proposed for use in structural panels, one reason for the lack of significant development of this use is the absence of a high speed process for making and assembling multi-layer honeycomb core elements. Also, when open core elements are made with conventional corrugated paper webs, conventional corrugating techniques and machinery are typically limited to flute sizes that are unnecessarily small for making open core elements for use in structural members. The inability to control thickness as well as the width of the expanded core material has been a problem.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention comprises a fully automated and highly productive method and apparatus for the continuous manufacture of open core elements using fluted web material of various kinds and with or without intermediate smooth web materials.  
         [0006]     In accordance with one embodiment of the present invention, an apparatus for forming large pitch fluted web uses a rigid fluted rotary roll that has flute teeth defined by adjacent tips and gullets and spaced circumferentially at the desired flute pitch. A counterroll uses parallel fluting bars that are circumferentially spaced at the flute pitch and have fluting tips that extend into the gullets of the fluting roll teeth for fluting engagement with the fluting roll. The counterroll has a rigid cylindrical core and an outer elastomer sleeve in which the fluting bars are embedded and held to permit individual fluting tips to move in response to cyclically varying force as a result of fluting tip contact with the teeth of the fluting roll. The fluting roll teeth are generally V-shaped in cross section and the tooth gullets and tips have a circular cross section and are interconnected by flat tooth flanks. The fluting tips of the counterroll fluting bars have a radius slightly less than the radius of fluting roll tooth gullets and, preferably, the radius of the fluting tips is less than the radius of the tooth gullets by an amount approximately equal to the thickness of the web being processed.  
         [0007]     With the narrow construction of the fluting bars, contact with the fully formed web flutes occurs only in the flute gullets of the fluting roll. Correspondingly, there is no contact between the fluting roll flute tips and the flute flanks of the counterroll teeth.  
         [0008]     The fluting roll, which is typically larger in diameter than the counterroll, has a cylindrical tubular body in which is formed a series of circumferentially spaced axial bores which may be used to supply vacuum and/or heat to the roll. The vacuum system helps bring the fluted web into full contact with the fluting roll tooth gullets and hold the fluted web in contact with the corrugating roll for continued processing. The heat which is preferably derived from steam assists in web conditioning, flute formation and setting and drying of the adhesive.  
         [0009]     In a preferred embodiment of the present invention, the method and apparatus for forming a large pitch fluted web, as described herein, is applied to the formation of a composite double medium, single liner fluted web using two pairs of a fluting roll and counterroll operated in tandem and with the fluted rolls in register. In accordance with the method of this embodiment, formation of the composite web includes the steps of (1) positioning a pair of fluted rolls, each of which has axially extending teeth that are defined by adjacent tips and gullets spaced circumferentially at a given pitch, with the rolls in counter-rotating closely spaced relation and the teeth in register to form a nip between the fluted rolls, (2) for each fluted roll, positioning a counterroll that has axially extending fluting bars spaced at the flute pitch, the bars having tips that extend into counter-rotating engagement with the gullets of the fluted roll to form a fluting nip, (3) directing a web into each fluting nip to form a fluted medium web, (4) retaining the fluted mediums on their respective fluted rolls, (5) applying an adhesive to the tips of each fluted medium web while the web is retained on the fluted rolls, (6) bringing a liner web into contact with one of the fluted medium webs on its fluted roll, and (7) bringing the liner web into contact with the other fluted medium web in the nip formed by the fluted rolls to form the composite double medium, single liner fluted web.  
         [0010]     The foregoing method may be advantageously applied to form small light weight packing elements by performing the additional steps of (1) using paper for the webs, (2) slitting the composite paper web in the direction of web travel into narrow parallel strips, and (3) cutting the strips into short length pieces on lateral cut lines in the gullets of the medium webs. Preferably, the cutting step comprises die cutting.  
         [0011]     The method of forming a composite double medium, single liner fluted web, described above, may also include the steps of (1) heating the fluted rolls, and (2) applying a vacuum to the gullets of the fluted rolls along circumferential portions of said rolls on which the fluted medium webs are carried. The method may also include the step of embedding the ends of the fluting bars opposite the tips in an elastomer layer that is formed on the outer surface of the counterroll. The method may further include the step of retaining the composite web on one of the fluted rolls downstream of the nip.  
         [0012]     Another embodiment of the present invention comprises an alternate method for the manufacture of open core elements. The method comprises the steps of (1) forming two composite web halves, each comprising a smooth web and a fluted web, (2) orienting the composite web halves with the exposed fluted web flutes facing up, (3) applying an adhesive to the exposed flute tips of one web half, (4) adhering the other web half by its smooth web to the glued flute tips of said one web half to form an open face double wall web, (5) slitting the open face double wall web longitudinally to form a plurality of adjacent equal width open face double wall strips, (6) applying an adhesive to the exposed flute tips of said open face double wall strips, (7) cutting the strips transversely to a common selected length, (8) separating the strips in a lateral direction, (9) conveying each strip in the lateral direction individually and serially into a vertical stacker, (10) dropping each strip vertically in the stacker such that each strip, after the lead strip, is deposited on the glued flute tips of the preceding strip to form an intermediate open core block of strips, (11) upending the intermediate block onto a lateral block edge to orient the exposed glued flute tips of the last deposited strip to face in the lateral downstream direction, and (12) conveying the intermediate block in the lateral downstream direction to bring the exposed glued flute tips into bonding contact with the exposed smooth web face of a preceding intermediate block to form the open core element.  
         [0013]     The foregoing method preferably includes, prior to the step of adhering one web half to the other web half, the step of aligning the flute tips of the web halves tip-to-tip. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is a perspective view of a system for the continuous manufacture of open core elements utilizing one embodiment of the method of the present invention.  
         [0015]      FIG. 2  is a top plan view of the system shown in  FIG. 1 .  
         [0016]      FIG. 3  is a perspective view of an upstream portion of the  FIG. 1  system showing one embodiment of an apparatus for forming the composite web.  
         [0017]      FIG. 4  is a perspective view of an intermediate downstream portion of the system showing the incremental formation of core elements.  
         [0018]      FIG. 5  is a perspective view of the downstream portion of the system shown in  FIG. 1 .  
         [0019]      FIG. 6  is a perspective view of an apparatus for forming an all-fluted composite web.  
         [0020]      FIG. 7  is a side elevation detail of an alternate flute forming apparatus of a presently preferred construction.  
         [0021]      FIG. 8  is a perspective view of an alternate system for the manufacture of open core elements.  
         [0022]      FIG. 9  is a perspective detail of a portion of the system shown in  FIG. 8 .  
         [0023]      FIG. 10  is a further perspective detail of the system shown in  FIG. 8 .  
         [0024]      FIG. 11  is a side elevation detail of a preferred embodiment of an upender used in the method of the present invention.  
         [0025]      FIGS. 12-14  are cross sectional details of the progressive formation of an open core element from its component webs.  
         [0026]      FIG. 15  is an end view of the web fluting apparatus of a presently preferred embodiment.  
         [0027]      FIG. 16  is an enlarged view of a portion of  FIG. 15 .  
         [0028]      FIG. 17  is a view similar to  FIG. 16  showing the fluting progression of the interacting fluting rolls.  
         [0029]      FIG. 18  is a perspective view of a glue machine for applying a liquid adhesive to a fluted web.  
         [0030]      FIG. 19  is a schematic top plan view of the glue machine of  FIG. 18 .  
         [0031]      FIG. 20  is an end view of the web fluting apparatus shown in  FIG. 15  used to form a single face fluted web.  
         [0032]      FIG. 21  is an end view of an apparatus using two pairs of the web fluting apparatus of  FIG. 20  to form a composite double medium, single liner fluted web.  
         [0033]      FIG. 22  is a perspective view of a small packing piece cut from the composite double medium, single liner fluted web shown in  FIG. 21 .  
         [0034]      FIG. 23  is a perspective view of a modified apparatus for making open core elements.  
         [0035]      FIG. 24  is a plan view showing the application of the core elements made in the  FIG. 23  apparatus to make an open core panel.  
         [0036]      FIG. 25  is a top plan view of a modified system for making open core elements.  
         [0037]      FIGS. 26 and 27  show operation of the  FIG. 25  system in the respective formation and transfer modes for intermediate open core elements. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0038]     Referring initially to  FIGS. 1 and 3 , a core element lay up system  10  utilizes core element components made from a composite web  11  which is converted to form strip like elements (28) which are, in turn, joined to form a core element  13 . In the embodiment of the invention shown, a double width composite web  11  is formed by joining a smooth web  14  and a fluted web  15  utilizing any of a number of prior art techniques. For example, the webs  14  and  15  could be formed and glued together in a single facer  16  in a manner well known in the corrugating industry. A smooth web from a supply roll  17  is fluted under heat and pressure in the single facer  16 , glue is applied to the flute tips on one side of the fluted web  15 , and the fluted web is then joined to the smooth web  14  from the supply roll  18 .  
         [0039]     The composite web  11  is formed (or reoriented after forming) with the fluted web component  15  facing upwardly. As the composite web  11  exits the single facer  16 , it is slit longitudinally on its centerline by a slitting blade  20  to form two web halves  21  and  22 . A suitable glue or adhesive is applied to the flute tips of the lower web half  21  by a glue roll  23 . The other web half  21  is directed onto an angled turning bar  24  around which it is wrapped and displaced laterally to bring it into contact with the glued web half  21  where the smooth web face of the web half  22  is laid onto the glued flute tips of the other web half  21  to form an open face double wall web  25 . The double wall web  25  is directed over a heating plate  26  or other heating device to cure the adhesive and permanently join the two web halves  21  and  22 . As will be described in greater detail below with respect to the presently preferred embodiment, the flutes of the two component webs forming the open face double wall web  25  are brought together and joined so that the flutes of the two component webs are in flute tip-to-flue tip alignment.  
         [0040]     The open face double wall web  25  is then slit longitudinally with a multi-blade slitter  27  to form a plurality of equal width open face double wall strips  28 . The open face double wall web  25  has an upper exposed fluted face and, therefore, the strips  28  also have laterally extending flutes. The strips then pass beneath a second glue roll  30  which applies a suitable adhesive to the exposed flute tips. When the plurality of strips  28  reaches a selected length in the machine direction, a cut-off knife  31  downstream of the glue roll cuts the strips  28  to a common length. The strips are preferably cut at the bottom of the next flute which will provide a core element just slightly larger than the desired length. The plurality of glued and cut strips  32  is accelerated on a transport conveyor  33  to form a gap between the strips and the next-following uncut strips.  
         [0041]     The plurality of glued and cut strips  32  is then cross-transferred out of the machine direction path of the next following plurality of strips and onto a lateral feed conveyor  34  to a strip upender  35 . As is best seen in  FIG. 4 , an upender roll  36  has a series of circumferentially spaced vacuum headers  37  that serially capture each glued and cut strip to reorient the strip from a horizontal to a vertical position such that succeeding strips are deposited on common lateral strip edges and in face to face relation with each strip that precedes it. In this orientation, the glued flutes of each strip face the smooth web face of the preceding strip and, when deposited on the element forming conveyor  38 , are brought into adhesive contact. As can be seen in  FIG. 4 , the flutes on the strips extend vertically and together comprise a core element  13 . To facilitate removal of each strip  28  from the vacuum header  37  on the upender roll  36 , each vacuum header includes a series of laterally spaced vacuum ports between which the tines of a discharge fork  40  extend. The fork is operable to engage the unglued smooth face of each strip and push it into contact with the preceding strip on the element forming conveyor as the vacuum is released. The discharge fork is then returned to its discharge position for the next following strip.  
         [0042]     In this embodiment, as the core element  13  is being formed, a set of conveyor belts  41 , positioned over the top of the core element, applies a normal force to assist in compacting the core element and press the glued flute tips of each strip to the smooth face of the preceding strip by running slightly faster than the advancing core block which is held back by downstream holding rolls.  
         [0043]     When a core element  13  comprising a desired number of strips has been formed, the core element  13  is accelerated into a trim and cut station where it can be cut into any number of smaller core elements. In the example shown in  FIG. 5 , the large formed core element  13  is trimmed longitudinally (in the longitudinal direction of the strips  28 ) with a trim blade  42  to a selected edge dimension. The trimmed element  13  is then moved to a cutting position where a series of cutting blades  43 , including an edge trim blade, cuts the long core element into final element sizes. For example, if the final core elements are to be used in the manufacture of hollow-core doors, the strips  28  could be cut to lengths of 240″, upended and stacked to a core width of 30″ and finally trimmed and cut to provide three door pieces each 80″×30″.  
         [0044]     The height or thickness of the core element  13  depends on the width to which the strips  28  are slit. The length of the core element  13  can be varied as desired. Thus, the system has the capability of continuously and rapidly forming core elements of widely varying dimensions.  
         [0045]     Composite fluted webs, useful in forming core elements, can be made in a number of different ways, can utilize different kinds of web materials, and the fluted web can be formed in various ways. As indicated above, it is preferable to utilize a flute size for the fluted web that is larger than flutes commonly made on a typical single facer. A larger flute size will provide adequate strength for the core element, but utilize significantly less paper or other web material in the formation of the fluted web.  
         [0046]     Referring to  FIG. 6 , an alternate apparatus utilizing an alternate flute forming method is shown. In the embodiment shown, a composite web is made by simultaneously fluting two incoming webs which may be made of the same or different materials. If, for example, two paper webs are utilized, an upper web  44  has a layer of glue, such as a starch adhesive, applied to its lower face upstream of a fluting nip  45 . A lower web  46  is also fed with the glued upper web  44  into the nip  45  formed at the upper and lower tail sprockets  47  and  48  carrying a pair of intermeshing fluting conveyors  50  and  51 . Each of the fluting conveyors  50  or  51  includes a continuous series of fluting bars  52  made, for example, from aluminum extrusions and extending the full width of the incoming webs  44  and  46  (e.g. 96″ or about 2440 mm). The fluting bars may be carried on a series of laterally spaced ¾″ pitch roller chains with the fluting bars  52  attached thereto with conventional K-1 attachments. The roller chains may, for example, be laterally spaced 16″ or about 406 mm apart. Each fluting bar has an exposed flute forming tip  53  that is shaped to form a flute one ½″ (about 13 mm) deep and with a pitch of ¾″ (about 19 mm) corresponding to the pitch of the carrying roller chains.  
         [0047]     As the webs  44  and  46  come into the fluting nip  45 , they are simultaneously fluted, one flute at a time, and joined by the adhesive previously applied to the contacting face of one of the webs. The joined webs are held together in a straight fluting run  54  of the fluting conveyors  50  and  51  to which heat is applied by upper and lower heating elements  50  and  51  to bond and cure the adhesive. Each of the fluting conveyors  50  and  51  may include flute pre-heaters  57  to help maintain the temperature of the fluting bars  52 . A composite fluted web  58  exits the fluting conveyors  50  and  51  at their head ends where, preferably, the conveyor flights are separated gradually on a much larger radius arc than that of the tail sprockets  47  and  48 . The resulting composite fluted web  58  is substantially cured and rigid enough for further processing with or without the addition of a smooth facing web.  
         [0048]     A composite fluted web  58  of the foregoing type could, for example, be glued to a smooth web and the web processed to form core elements in the manner previously described. However, the composite fluted web  58  also has utility for other applications, such as a substitute for the ubiquitous styrofoam peanuts used as packaging filler and cushioning material.  
         [0049]     An alternate apparatus for forming a fluted web is shown schematically in  FIG. 7 . In this embodiment, a lower fluting conveyor  75  is similar to the fluting conveyor  51  of the  FIG. 6  embodiment. The flute bars  76  are heated and, in addition, are provided with a vacuum system enabling the formed flutes to be drawn into the valleys between the flute bars. In lieu of an upper fluting conveyor, a spoked fluting roll  77  is used. The fluting roll is provided with a plurality of circumferentially spaced spokes  78  which press the incoming web one flute at a time into the fluting conveyor  75  where the applied vacuum holds the web in position. If two webs of paper or other materials are joined as described with respect to the  FIG. 6  embodiment, the vacuum and heat applied to the web downstream of the fluting roll  77  will cure the composite web resulting in a composite fluted web cured and rigid enough for further processing. the exposed flutes of the upper web may have an adhesive applied by a downstream glue roll  80  for the addition of a smooth facing web.  
         [0050]     Although a single wall composite web, having one fluted web and one smooth web, can be utilized in the overall process of the present invention, it is preferable to use an open face double wall web such as web  25  used in the process described with respect to  FIGS. 1-5 . In that process, a full width single face web is slit on its center line and one of the slit halves is turned and moved laterally on a turning bar to be joined with the other web half. However, an open face double wall web may also be formed by joining two full width single face webs each formed on a separate single facer, as will be described in the following preferred embodiment. Regardless of how an open face double wall web is formed, it is important in order to maximize the strength of the core elements to be formed to align the flutes in the joined single face webs so that they are in alignment flute tip-to-flute tip in the double wall web. On the other hand, if a more springy cushioning effect is desired in a core element, the flutes in the two component single face webs may be aligned one half pitch from flute-to-flute alignment or such that the flutes of one composite single face web align with the valleys of the other composite single face web.  
         [0051]     Another embodiment of a system for carrying out the process for the continuous manufacture of open core elements is shown in  FIGS. 8-11 . The incoming web  60  from the upstream single facer or single facers  59  and  61  may be open face single wall or open face double wall, the later being either full width or half width. Preferably, however, for the reasons stated above, the incoming web  60  is an open face double wall web. A pair of single facers  59  and  61  (or fluted web forming apparatus of  FIG. 6  or  7 ) provide an upper fluted single face web  81  (see the  FIG. 12  detail) with its smooth web on the bottom and is joined to a lower fluted single face web  82  ( FIG. 12  detail) to the exposed flute tips of which an adhesive has been applied with a glue roll  83 . The resulting composite open face double wall web  60  (see the  FIG. 13  detail) is heated and cured and brought into the lay-up portion of the system for further processing.  
         [0052]     The web  60  is slit in a multi-blade slitting knife  62  into open face double wall strips  63  with the flutes oriented upwardly. As with the previously described process and methods, the width of the strips  63  determines the height or thickness of the finished open core elements. The strips  63  move from the slitting knife under a glue roll  64  where glue is applied to the exposed flute tips. However, in this embodiment one strip is left unglued. The unglued strip  65  may be provided in a number of ways, such as using a laterally movable scraper blade operatively engaging the glue roll to prevent glue from being applied to the unglued strip  65 . Successive unglued strips  65  are placed among the strips exiting the glue roll to space between them a selected number of glued strips  63  desired in the finally formed core element. Thus, the unglued strips  65  may not always be in the same lateral position on the strips exiting the glue roll  64  because the desired core element may utilize more or less than the total number strips  63  slit from the incoming web  60 .  
         [0053]     Each group of strips  63  exiting the glue roll is accelerated on a speed-up conveyor  66  to separate the strips from the next incoming group of strips. The strip group  68  is then cross-transferred onto a lateral feed conveyor  67  where each of the strips now extends laterally across the feed conveyor  67 . At the downstream end of the lateral feed conveyor  67 , a strip upender  35  identical to the one described with respect to the preceding embodiment, operates to sequentially reorient each strip  63  from a horizontal to a vertical position. Each reoriented strip is positioned with its glued flute tips extending vertically and facing in the downstream direction and is brought into contact with the smooth web on the back of the preceding strip  63 .  
         [0054]     Referring to  FIGS. 8-11 , each unglued strip  65  forms the lead strip of a hollow core element  70  (see the  FIG. 14  detail) of a desired size. The unglued lead strip  65 , after it is upended, is brought into contact with a toothed gate  71  operating between the strip upender  35  and the upstream end of an element forming conveyor  72 . When a hollow core element  70  is formed, the toothed gate  71  is retracted and the element  72  moves into contact with a downstream compactor plate  73  on the element forming conveyor  72 . As the elements  72  move downstream, an upstream compactor plate  74  moves into contact with the smooth web face of the upstream most stream  63  in the formed element  70 . Because the downstream compactor plate  73  engages an unglued strip  65  and the upstream compactor plate  74  engages the smooth web face of the last strip which carries no glue, the problem of a strip adhering to the toothed gate  71  or one of the compactor plates  73  or  74  is minimized.  
         [0055]     Instead of utilizing an unglued strip  65 , it is also possible to insert an unglued sheet of paper  84  which adheres to the glued flute tips of the facing strip and becomes part of the core element  70 . Alternately, the face of the downstream compactor plate  73 , in the previously described embodiment, may be coated with a non-stick material.  
         [0056]     In an alternate method for compacting the formed core elements  70 , the element forming conveyor  72  may be angled downwardly to utilize the force of gravity to help press the strips  63  together. In addition, a weighted plate may be inserted against the smooth web face of the rearmost strip of the core element  70 .  
         [0057]     In a presently preferred apparatus for forming flutes in a continuous web, reference is made to  FIGS. 15-17 . The apparatus includes an upper rotary fluting roll  85  made of a rigid tubular cylindrical shell  86 . The fluted outer surface is defined by circumferentially spaced flute teeth  87  having adjacent tips  88  and gullets  90 . The teeth  87  are spaced at a common flute pitch which, for example, for a large fluting apparatus, may be ¾″ (about 19 mm). The flute tooth depth vertically from tip  88  to gullet  90  may be ½″ (about 13 mm). As indicated previously, the flutes are substantially larger than typically formed in the corrugating industry for the manufacture of corrugated paperboard and the like. The fluting roll  85  may have a nominal diameter of 16″ (about 406 mm).  
         [0058]     A lower rotary counterroll  91  is mounted and positioned for counterrotational engagement with the fluting roll  85 . Typically, the upper fluting roll  85  is the driving roll and the counterroll  91  is the driven roll. The nominal diameter of the counterroll  91  may be 8″ (about 203 mm). The counterroll  91  also has a rigid cylindrical interior shell  92 , but it is covered on its exterior with an elastomer sleeve  93 , preferably made of a relatively hard rubber, such as conventional die rubber. Imbedded in the elastomer sleeve  93  are a plurality of circumferentially spaced fluting bars  94  having round outer tips  95  circumferentially spaced at the pitch of the fluting roll  85 . As may be seen in the drawings, the fluting bars  94  have a sort of tear drop cross sectional shape and are preferably made from hollow aluminum extrusions. The fluting bars  94  and the flute teeth  87  of the fluting roll  85  extend axially together and parallel to one another the full width of the rolls  85  and  91 , which conveniently may be 96″ (about 245 cm). However, axial roll length is not critical and the rolls may be made with any length suited to the web material on which they operate.  
         [0059]     The flute teeth  87  of the fluting roll  85  are generally V-shaped in cross section with the gullets  90  having a circular cross section. The tips  88  also have a circular cross section. The flute teeth  87  have flat flanks  96  between the tips and gullets. It is significant in the formation of large pitch flutes in a web  97 , as shown in  FIGS. 16 and 17 , that the fluting bars make contact with the formed web flutes  98  only in the gullets  90  of the fluting roll  85 . In addition, there is no contact between the fluting roll flute tips  88  and the flanks  100  of the counterroll fluting bars  94 . Thus, as may best be seen in  FIG. 17 , the tips  95  of the fluting bars  94  progressively engage and push the web material  97  into the gullets  90  of the fluting roll  85  with operative contact between the fluting bar tips  95  and the teeth  87  of the fluting roll only at the points of full web flute formation.  
         [0060]     Preferably, the tips  95  of the fluting bars  94  have a radius slightly less than the radius of the flute teeth gullets  90  of the fluting roll  85 . Typically, for a web  97  of a given thickness, radius of the fluting tips  95  is less than the radius of the flute teeth gullets  90  by an amount approximately equal to the web thickness, e.g. 0.009″ (0.23 mm). Instead of circular cross section tips  88  and  95  on the fluting roll teeth  85  and fluting bars  94 , respectively, a compound radius may be used.  
         [0061]     The rubber sleeve  93  in which the fluting bars  94  are embedded serves two important functions, in addition to providing firm support for the bars. First, if the lower counterroll  91  were made with the fluting bars  94  rigidly attached to the steel shell  92 , the vertical radial distance between the two roll centers, as the paper web  97  passes through the fluting nip, is forced to change. Without the cushioning effect provided by the rubber sleeve  93 , the rigid steel rolls would be forced to deflect, resulting in high vibration and noise and, quite possibly, damage to the web. For example, using a 16″ diameter fluting roll  85  and an 8″ diameter counterroll  91 , referring to  FIGS. 16 and 17 , as the fluting bar  101  that is just upstream from the top dead center position of the rolls and has the web fully engaged with the gullet  90 , moves to the top dead center position (from  FIG. 16  to  FIG. 17 ), the gullet  90  and the bar tip  95  move relatively more closely together by 0.027″ (0.7 mm). However, the deflection that would otherwise have to be taken up by rigid steel rolls is absorbed by the rubber sleeve  93 , thereby minimizing vibration and noise, as well as possible damage to the web  97 .  
         [0062]     In addition, after the fluting bar  94  passes the top dead center position (moving from  FIG. 17  to  FIG. 16 ), the resilience of the rubber sleeve  93  pushes the tip  95  of the fluting bar radially outwardly so that it maintains contact with the fluted web in the gullet  90  until the following fluting bar makes full contact in the tooth gullet  90  with which it is associated. This provides a smooth transition from flute bar to flute bar without loss of intimate fluting contact between the fluting bar tips  95  and the fluting roll gullets  90 .  
         [0063]     To assist in formation of the flutes  98 , it is desirable to provide vacuum to the gullets  90  of the upper roll flute teeth  87 . Vacuum is supplied through a series of circumferentially spaced, axially extending vacuum bores  102  in the fluting roll shell  86 . With appropriate internal valving, the vacuum is preferably applied at the point of flute formation and to help retain the formed web in contact with the roll, as shown in  FIGS. 16 and 17 . After the fluted web  103  moves out of the fluting nip between the rolls  85  and  91 , a glue roll  109  may be used to apply an adhesive to the web which is subsequently joined downstream to a liner web, as shown in  FIGS. 20 and 21 .  
         [0064]     It may also be desirable to heat the fluting roll  85  by supplying steam to a circumferentially spaced, axially extending series of steam bores  104  formed in the fluting roll shell  86 . As shown, the steam bores  104  alternate circumferentially with the vacuum bores  102 . However, any convenient arrangement may be used. The heat applied to the roll  85  and the web  97  helps precondition the fluted web for downstream application of an adhesive, such as a starch-based glue, to the flute tips of the fluted web  103 , as will be described in more detail below. The heat also enhances the progress of the starch-based glue into the green bond stage, as is known in the art.  
         [0065]     Because in some applications it may be desirable to waterproof a paper web  97 , the heated fluting roll  85  may assist in drying a liquid adhesive applied to the web  97  before fluting. For example, if an A-phase phenolic resin is applied to the paper web, it is dried to a B-phase before fluting.  
         [0066]     In accordance with the overall system of the present invention for producing open core elements, fluted webs are joined with an adhesive to plain unfluted webs in various steps of the operation to progressively form the open core elements as shown schematically in  FIGS. 12-14 . In the system previously described, for example, glue rolls  23  ( FIG. 1 ),  80  ( FIG. 7 ),  30  ( FIG. 3 ),  64  ( FIG. 8 ) and  109  ( FIGS. 15 and 20 ) are used to apply a liquid adhesive to the flute tips of a fluted web.  FIGS. 18 and 19  show a glue machine which may include any of the glue rolls just identified.  
         [0067]     In  FIG. 18 , a glue machine  105  includes a pump  106  for supplying a liquid adhesive, such as an aqueous starch-based adhesive, and a glue roll assembly  107  for applying the adhesive to the flute tips of an incoming web  108 .  
         [0068]     A presently preferred pump  106  comprises a ganged array of positive displacement pumps commonly driven to provide laterally spaced beads of adhesive to the glue roll  110  of the glue roll assembly  107 . Preferably, the pump  106  comprises a ganged peristaltic pump which receives a supply of a liquid adhesive to the inlet ends  111  of laterally spaced flexible tubes  112  made of a suitable synthetic rubber, such as neoprene. The tubes extend through the pump  106  and terminate in outlet ends  113  evenly spaced laterally across the surface of the glue roll  110 . The pump  106  may, for example, have 24 supply tubes  112  and, if the adhesive is being applied to a 48″ web, the tubes  112  would be spaced at about 2″ intervals.  
         [0069]     The pump  106  includes a supporting frame  114  that has a semicylindrical backing surface  115  and a driven rotating roller assembly  116  that has an axis of rotation coincident with the axis of the backing surface  115 . In the embodiment shown, there are four laterally spaced roller assemblies, each of which carries three orbitally mounted rollers  117 . The adhesive supply tubes  112  extend from an upstream tube harness  118  downwardly between the backing surface  115  and the roller assembly  116  to the outlet ends  113  of the tubes adjacent the surface of the glue roll  110 . Rotation of the orbital rollers  117  brings individual rollers sequentially into contact with the tubes  112 , squeezing them against the backing surface  115  and pushing accurately metered amounts of liquid adhesive through the tubes to the outlet ends  113 . By carefully controlling the supply of liquid adhesive to the inlet ends  111  of the tubes  112 , the pre-calculated exact volume of adhesive desired to be applied to the web is delivered by the pump to the glue roll. In this manner, the pump supplies only the volume of adhesive needed and there is no need to recirculate unused adhesive which could be contaminated or otherwise unsatisfactory for reuse. Once the starch formula has been used to calculate the mix of starch and water (with other well known additives), the volume to be supplied to the pump and the transferred to the glue roll is calculated based on pump rotational speed, web speed and web width. One important benefit of utilizing a peristaltic pump apparatus is that none of the pump mechanism, except the tubes  112 , is contacted by the adhesive. This minimizes adhesive build up on internal parts and facilitates considerably the cleaning of the glue machine, as will be described.  
         [0070]     The outlet ends  113  of the adhesive supply tubes  112  are attached to a tube outlet support assembly  120  extending across the width of the glue machine  105  above the glue roll  110 . The glue roll assembly  107  includes a flexible adhesive spreading tongue  121  that has its upper edge attached to a tongue support  122  and a free downstream end  123  that is shaped to lie against and conform to the cylindrical surface of the glue applicator roll  110 . The beads of liquid adhesive supplied to the glue roll surface upstream of the shaped end  123  of the spreading tongue  121  are smoothed into a uniform layer on an engraved surface on the glue roll  110  from which it is applied to the flute tips of the incoming web  108  that makes tangent contact with the glue roll  110 .  
         [0071]     The outlet ends  113  of the adhesive supply tubes  112  are mounted on the support assembly  120  such that their positions can be selectively adjusted to a desired spacing in order to accommodate different width webs  108 . In the embodiment shown in  FIG. 19 , each tube end  113  is carried on a separate tube holder  124  and all of the tube holder are mounted on an elastic band  125  that is partially stretched to provide an initial closely spaced array. By stretching the band equally and in opposite directions, as with a lead screw arrangement  126 , the tube holders  124  and attached tube ends  113  may be moved to an increased spacing.  
         [0072]     The glue machine  105  also includes a laterally adjustable adhesive width control assembly  127  that includes a pair of laterally adjustable doctor blades  128  which may be moved into contact with the glue roll surface to remove unneeded adhesive and to define the width of the glue layer to be applied to the incoming web  108 . The doctor blades  128  are slidably mounted on a lateral support member  130  and each doctor blade assembly includes a vacuum connection  131  to carry unused glue away. When the glue supply from the pump  106  is terminated, the inlet ends  111  of the glue supply tubes  112  are supplied with a cleaning fluid that travels through the tubes, onto the glue roll and mating face of the spreading tongue  121  and over the cleaning doctor blade  133 .  
         [0073]     It is also preferable to mount the adhesive supply tubes  112  so they can be adjusted axially in the tube harness to change their positions to present different areas to contact by the pump rollers  117 . In this manner, the points at which constant intermittent squeezing of the tubes occurs can be changed to present fresh unstressed tube portions to the rollers.  
         [0074]     In  FIG. 20 , there is shown the use of the large flute forming apparatus of  FIG. 15  to make a single face fluted web  134 . The fluted web  103  is retained on the fluting roll  85  where a liquid adhesive is applied by a glue roll  109  to the flute tips of the web  103 . Further downstream, a web delivery or generator roll  135  brings a liner web  136  into contact with the glued flute tips of the fluted web  103 .  
         [0075]     In  FIG. 21 , there is shown an adaptation of the large flute forming apparatus of  FIG. 15  for forming a composite double medium, single liner fluted web  140 . The apparatus includes a pair of fluted rolls  85  and  85 ′ that are mounted for counter rotation in closely spaced relation and with their teeth in register to form a nip  137 . A counterroll  91 ,  91 ′ is positioned diametrically opposite the nip  137  and in counter rotating engagement with the respective fluted roll  85 ,  85 ′.  
         [0076]     Each of the incoming medium webs  97  and  97 ′ is provided with the large flutes, as previously described, and exits the fluting nip in contact with the fluted roll  85  and  85 ′. An adhesive is applied to the flute tips of the respective fluted webs  103  and  103 ′ by glue rolls  109  and  109 ′, respectively. A web delivery roll  135  brings a liner web  136  into intimate contact with the glued flute tips of lower fluted web  103 . The resulting single face web  138  enters the nip  137  where it is joined with the glued flute tips of fluted web  103 ′ to form the composite double medium, single liner fluted web  140 . It may be advantageous to retain the composite web  140  on one or the other of the fluted rolls  85  and  85 ′ to take advantage of the heat to enhance the attainment of green bond strength for further processing.  
         [0077]     Downstream of the nip  137 , the web  140  may be slit longitudinally on slit lines  141  (see  FIG. 22 ) into a plurality of narrow strips  142  which may be, for example, ⅜″ wide. The large flutes themselves, as previously described, may have a flute pitch of ¾″ and a flute depth of ½″. The narrow strips  142  are then die cut in the lateral or cross machine direction at the base of the gullet  143 . The lateral die cuts  149  are made along the center of the glue line  144  so that the resulting small pieces  146  remain glued. In other words, where the gullets of the fluted webs  103  are joined to opposite sides of the liner web  136 , each adjacent laterally cut web piece will share one-half of the glue line  144 . If the lateral die cut slits  145  are made every other pitch length, as shown in  FIG. 22 , the resultant small web pieces  146  will have a sort of  FIG. 8  shape which shape is stabilized and fairly rigid by the intermediate glued liner web  136 .  
         [0078]     The small web pieces  146  may be used as a substitute for the ubiquitous styrofoam packaging and filter “peanuts” that are fraught with environmental and disposal problems. Small web pieces  146  have a very low material weight-to-volume ratio, possess the necessary rigidity, and are recyclable or at least biodegradable. Furthermore, the process and apparatus of the present invention can use medium web stock  108  and liner web stock  136  that, in the corrugating industry, are referred to as “trim rolls”. These are rolls of edge trim paper resulting from trimming a standard width (e.g. 96″) roll of paper. Trim rolls of about 1 foot in axial length or less are typically discarded or repulped. Even trim rolls as long as 4 feet are difficult to dispose of. However, trim rolls of this range in axial lengths are well suited for the process of the present invention.  
         [0079]     In  FIG. 23  there is shown a modified apparatus for making open core elements in accordance with the present invention. A single face web  147  is formed in a single facer  148  by joining a liner web  150  from roll  151  to a corrugated medium web  152  from a roll  153  in a known manner. The single face web  147  exiting the single facer may be heated to enhance curing by moving over a heating plate  154  after which the web is slit longitudinally in a slitting knife  155  into a plurality of adjacent single face web strips  156 . A glue roll  157  applies a suitable adhesive (e.g. starch) to the exposed flute tips of the medium web  152 . The glued strips  156  are then separated and wound with the liner web  150  on the outside to form circular spiral open core elements  158 . The elements may be wound to any desired diameter with the strips  156  cut in a cutoff knife  160  to establish the desired diameters. Other control of the slitting knife  155  and cutoff knife  160  may be employed to provide core elements  158  of different thicknesses and/or diameters.  
         [0080]     Whereas the open core elements  13  and  70  of the previously described embodiments are rectangular in shape and typically enclosed on both faces with rectangular skin sheets, circular core members  158  made in accordance with the  FIG. 23  embodiment may also be used to form rectangular panels utilizing rectangular skin sheets. As shown, for example, in  FIG. 24 , a rectangular panel having opposite skin sheets  161  of say 12′×24′ can utilize large 12′ diameter core elements  162  with the peripheral spaces filled by say 2′-3′ diameter small core elements  163 . It is believed that spirally formed core elements  158  possess better strength in certain applications. Also, the simplified process and apparatus of  FIG. 23  provides material handling advantages over the rectilinear processes of the previously described embodiments. A further and most important advantage in the manufacture of spirally wound circular open core elements is that very narrow strips  156 , as thin as, for example, ½″ may be processed. An attempt to handle such thin strips using the cross-transfer mechanism and methods of the previously described embodiments would likely not be successful.  
         [0081]     Referring now to  FIG. 25 , there is shown an improved apparatus for the lay-up of hollow core elements, particularly suitable for the manufacture of hollow core elements having a depth or thickness suitable for the manufacture of floor and roof panels for building construction. As shown in my co-pending patent application Ser. No. 11/485,823, a 16 in. panel thickness for roof construction is typically suitable.  
         [0082]     In the system of  FIGS. 25-27 , a composite double wall open face web  25  is formed to a width of 48 in., as described above with respect to the  FIG. 1  system. The web  25  is then slit longitudinally in a slitter to form three 16 in. wide open face double wall strips  165 . In a manner similar to that previously described, the strips  165  are oriented with the flutes on top and extending laterally. The strips are directed beneath a second glue roll which applies a suitable adhesive to the exposed flute tips of the strips  165 . When the group of three strips  165  reaches a selected length in the machine direction (e.g. 50 ft. for a roof panel), a cutoff knife cuts the strips to length. The three glued and cut strips  165  are accelerated on a transport conveyor to form a gap between the strips and the next-following uncut strips. The strips are then transferred laterally on a cross transfer conveyor  170  onto an accumulation conveyor  164  using a cross transfer pusher  166 . From the accumulation conveyor, a speed-up conveyor  167  accelerates the lead strip  165  and creates a gap between it and the next adjacent strip. The speed-up conveyor delivers the strips individually onto a higher speed stacker infeed conveyor  168  that engages the upstream (rear) edge of the strip and launches the strip into the bay of a downstacker  171 . The transfer of individual strips  165  into the downstacker  171  may be conveniently effected by engaging the upstream edge of the strip on the stacker infeed conveyor  168  with positive engagement dogs, or the like, using a servo drive for rapid acceleration.  
         [0083]     In the stacker  171 , the strips  165  are initially supported along both long edges with, for example, rotatable fingers positioned in spaced orientation along the strip edges. Both edges are released simultaneously and the strip drops vertically onto a supporting pan  169  out of the path of the next incoming strip. The strips  165  are preferably guided in their vertical descent on the pan  169  by engaging opposite narrow edges to assure that the strips are accurately aligned with one another in the stacker. Vertically moving arrays of guide belts  172  spaced along the strip edges are a presently preferred arrangement. The belts  172  are adjustable to vary the space between them for handling different width strips.  
         [0084]     Because the strips  165  have fresh adhesive glue on the flute tips, the second incoming strip  165  will drop onto the first strip in the stacker where the smooth web underside of the second strip will engage and adhere to the glued flute tips of the first strip. The third strip will follow in the same manner and the result will be the formation in the stacker of a three-ply stack of open face double wall strips comprising an intermediate open core block  173 .  
         [0085]     Each three-ply intermediate open core block  173  is removed from the stacker  171  by lifting the pan  169  to the top of the stacker bay, and rotating the stacker  171  90° in the counterclockwise direction to upend the open core block  173  (from the  FIG. 26  to the  FIG. 27  position). Thereafter, it is moved horizontally into face-to-face relation with each block that precedes it. Glued flutes of each block, facing in the downstream direction, contact the smooth web face of the preceding block and, when deposited on an element forming conveyor  176 , the blocks  173  are brought into adhesive contact. It may be desirable to apply vacuum to the block supporting pan  169  in the vertical upended position to hold the block until it is brought into contact with the preceding block.  
         [0086]     The large building stack  174  moves against a stacking pan  175  on a core panel building conveyor  176 . Because the lead face of the first block  173  has fresh adhesive applied upstream to the exposed flute tips, a face sheet must be inserted against the glued flute tips somewhere upstream of the  FIG. 25  system. This avoids contact between the glued flute tips and the backing pan  175 . As shown in  FIG. 14 , each intermediate open core block  173  will thus comprise a three-ply stack of open face double wall strips  60  (including an end element facing sheet  84 ).  
         [0087]     If a large open core panel is formed, such as might be used as a building floor or roof panel, each intermediate open core block  173  may have a thickness of 3 in., a width in vertical direction of 16 in. and a length, in the cross machine direction, of 50 ft. To form an open core roof or floor element having a width of 10 ft.,  40  intermediate blocks  173  would be assembled on the forming conveyor  176 . For this large an open core panel, strips  165  having a length of 50 ft. would be produced. However, the inherent stiffness of a three-ply double wall intermediate open core block  173  makes these intermediate blocks much easier to handle. After the formation of a large 50 ft.×10 ft.×16 in. deep roof or floor panel, the panel is moved out of the apparatus on a suitable panel discharge conveyor. Subsequently, a floor or roof panel is completed by affixing upper and lower skin sheets to the open core panel  174  in accordance with the teachings in my co-pending application Ser. Nos. 11/485,823, filed Jul. 13, 2006, and 11/777,002, filed Jul. 12, 2007.