Abstract:
A continuous, fully automated and highly productive system for the production of open core elements utilizes various formations of fluted input webs which are cut into strips, glued, cross-transferred, and serially upended for placement against preceding strips to build up an open core element. The open core elements are useful in the manufacture of structural members such as doors, floor panels and all panels.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    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. 
         [0002]    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. 
         [0003]    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 
       [0004]    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. 
         [0005]    In one embodiment, the method of the present invention includes 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 of the web halves, (4) adhering the other web half by its smooth web to the glued flute tips of the 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 the strips, (7) cutting the strips transversely to a selected common length, and (8) upending the strips onto common lateral strip edges and adhering the adhesively glued flutes of each strip to the smooth web of the next adjacent strip to form the open core element. 
         [0006]    The foregoing method preferably includes, prior to the step of adhering the two web halves, the step aligning the flute tips of the web halves tip-to-tip. The method may also include, after the step of adhering the two web halves, the step of heating the open face double wall web to cure the adhesive. Preferably, the method includes, prior to the upending step, the steps of (1) accelerating the strips to form a gap between said strips and the next following plurality of strips, and (2) cross-transferring the strips out of the path of the next following plurality of strips. The method also preferably includes the additional step of applying a normal force to the upended and adhered strips. 
         [0007]    The method may also include the step of cutting the completed open core element to a selected size. The cutting comprises one or both of the steps of (1) cutting one edge of the core element in the longitudinal direction of the strips, and (2) cutting one end of the core element in a direction transverse to the strips. 
         [0008]    In one embodiment of the method of the present invention each of the composite web halves is formed separately. In this embodiment, the webs are formed with the fluted web flutes facing downwardly and the webs are reoriented before applying the adhesive to position the flutes to face upwardly. In a variation of the basic method the composite web halves are formed by (1) forming a double width composite web, and (2) slitting the double width web to form the two composite web halves. 
         [0009]    A somewhat more basic method of the present invention includes the steps of (1) forming a composite web from at least one smooth web and a fluted web, (2) orienting the composite web with the flutes facing up, (3) slitting the web longitudinally to form a plurality of adjacent equal width strips, (4) applying an adhesive to the exposed flute tips of the strips, (5) cutting the strips transversely to a common selected length, and (6) upending the strips onto common lateral edges and adhering the adhesively glued flutes of each strip to the smooth web of the next adjacent strip to form the open core element. 
         [0010]    In a variation of the foregoing method, there are performed the steps of (1) eliminating the application of adhesive to a lead strip for a strip group of a selected number of strips, (2) supporting the upended lead strip on its unglued face, and (3) pressing the subsequent upended strips of the group against the lead strip. The method may also include the step of orienting the upended strips to form a downwardly directed core element. The method may also include the step of inserting a weighted strip on the upper end strip of each core element. Prior to the upending step, method may include the step of aligning the flute tips on adjacent strips tip-to-tip. 
         [0011]    The forming step may comprise forming two composite webs, and joining said webs to form an open face double wall web. In this variation, the method includes the preliminary steps of (1) forming a double width composite web, and (2) slitting the double width web to form the two composite webs. Alternately, said composite webs may be formed separately. When formed separately, the webs are formed with the fluted web flutes facing downwardly, and the method includes the step of reorienting the webs before joining to position the flutes to face upwardly. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      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. 
           [0013]      FIG. 2  is a top plan view of the system shown in  FIG. 1 . 
           [0014]      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. 
           [0015]      FIG. 4  is a perspective view of an intermediate downstream portion of the system showing the incremental formation of core elements. 
           [0016]      FIG. 5  is a perspective view of the downstream portion of the system shown in  FIG. 1 . 
           [0017]      FIG. 6  is a perspective view of an apparatus for forming an all-fluted composite web. 
           [0018]      FIG. 7  is a side elevation detail of an alternate flute forming apparatus of a presently preferred construction. 
           [0019]      FIG. 8  is a perspective view of an alternate system for the manufacture of open core elements. 
           [0020]      FIG. 9  is a perspective detail of a portion of the system shown in  FIG. 8 . 
           [0021]      FIG. 10  is a further perspective detail of the system shown in  FIG. 8 . 
           [0022]      FIG. 11  is a side elevation detail of a preferred embodiment of an upender used in the method of the present invention. 
           [0023]      FIGS. 12-14  are cross sectional details of the progressive formation of an open core element from its component webs. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]    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 . 
         [0025]    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. 
         [0026]    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. 
         [0027]    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. 
         [0028]    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. 
         [0029]    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″. 
         [0030]    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. 
         [0031]    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. 
         [0032]    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. 
         [0033]    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. 
         [0034]    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. 
         [0035]    An alternate and presently preferred 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. 
         [0036]    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. 
         [0037]    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. 
         [0038]    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 . 
         [0039]    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 . 
         [0040]    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. 
         [0041]    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. 
         [0042]    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 .