Abstract:
The present invention discloses a connector used to join two or more panels having a foam core and having a cavity defined in a edge thereof. The connector includes a connector body having at least two attachment heads which are dimensioned to fit snugly within the corresponding cavities bounded by internal sidewalls defined in the foam core. Barbs provided on each attachment head are configured to pierce the internal sidewalls of the panels and inhibit withdrawal of the attachment head from the cavity defined in the foam core.

Description:
FIELD OF THE INVENTION 
     The present invention relates to foam core panels in general, and more particularly to a method and devices used to connect the edges of two or more panels. The method and devices of the present invention are particularly useful in constructing point of purchase displays. 
     BACKGROUND 
     The use of foam core panels in the construction of point of purchase displays or the like has become increasingly popular because such panels are light, rigid, relatively inexpensive, and easy to use. Such panels typically consist of an extruded polystyrene, polyethylene or polyurethane foam core laminated on both sides with bleached white clay coated Kraft paper liners. 
     Foam core panels are popular in part because they are great for printing, easily accept most glues and are easy to cut. However, one long felt but unmet need relates the connection together of foam core panels and their use to construct three-dimensional displays. It is often desirable to join two or more panels edge-to-edge to form a smooth continuous surface. However, conventional methods for joining foam core panels are not sufficiently sturdy or easy to use. 
     One conventional method for connecting foam core panels is through the use of glue. However, the use of glue is not desirable in many applications. Moreover, the use of glue may not be practical depending on the size and weight of the panels being connected. Moreover, the use of glue requires time for the glue to set. 
     Another conventional method for connecting foam core panels uses screws and grommets. The use of grommets and screws is particularly suited to connecting high density boards but is not suitable in applications in which the panels must be rigidly connected to form a continuous surface. Further, conventional panel connection hardware remains visible in the end of the product. One Objective in creating multi-panel point of purchase displays is to present “clean” surfaces which are free of straps, tape, rivets and like visually distracting artifacts of connection. 
     Accordingly, what is needed is an inexpensive and easy to use connector for rigidly connecting foam core panels, without the use of adhesives, screws, or other visible hardware. 
     SUMMARY OF THE INVENTION 
     The present invention provides a connector used to join two or more panels, each having a foam core and having a cavity, bounded by internal sidewalls, defined in an edge thereof. The connector includes a body having at least two attachment heads dimensioned to fit snugly within corresponding cavities defined in edges of the foam core panel. Plural barbs provided on each attachment head are configured to enter respective cavities, pierce the internal sidewalls and inhibit withdrawal of the attachment head from the cavity. 
     According to one aspect of the invention, the foam core has a density D foam  and the internal sidewalls bounding the cavity have a density D skin  wherein D foam &lt;D skin . 
     According to one embodiment of the present invention the barbs are configured to facilitate easy insertion into the cavity and subsequently resist withdrawal of the barbs from the foam core. 
     According to another embodiment, the body of the connector includes a spacer portion which inhibits insertion of the body into the cavity beyond a predetermined depth such that the spacer portion provides predetermined spacing between adjacent panels. 
     The connector of the present invention may be used to construct a point of purchase display including a support member having at least one hole defined therethrough and at least two foam core panels. Each panel has a foam core having a cavity, bounded by internal sidewalls, formed to extend inwardly from an edge of the panel. A connector having a body portion is provided having at least two attachment heads dimensioned to fit snugly within corresponding cavities defined in the foam core panels. Plural barbs provided on each attachment head are configured to pierce the internal sidewalls and inhibit withdrawal of the attachment head from the cavity. In operation, the connector is inserted into the hole defined in the support member and connects foam core panels on opposite sides of the support member. 
     The support member may optionally be formed of a flexible transparent or translucent material such as plastic, and may optionally be curved with the curved member being contoured to conform to the edges of the foam core panels and provide additional rigidity to the member. 
     The connector of the present invention may further be used to construct a point of purchase display including a plurality of panels, each having a foam core having a first cavity defined in a vertical edge portion thereof and a second cavity defined in a horizontal side edge portion thereof. Each cavity being bounded by internal sidewalls. A plurality of connectors are provided, each having a body portion and at least two attachment heads dimensioned to fit snugly within corresponding ones of the cavities. Barbs provided on each attachment head are configured to pierce the internal sidewalls and inhibit withdrawal of the attachment head from the cavity. The plurality of panels are connected in a series of rows and columns with connectors connecting adjacent ones of the plurality of panels. 
     These and other aspects of the invention will be better explained in the detailed description of the preferred embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1A-1L show several different configurations of a connector according to the present invention; 
     FIG. 2A shows an exploded view of a conventional foam core panel; 
     FIG. 2B shows an enlarged sectional detail view of the foam core panel of FIG. 2A; 
     FIG. 3 shows a cavity-forming tool according to the present invention; 
     FIGS. 4A and 4B show how the cavity-forming tool of FIGS. 3A and 3B is used to form a cavity in the foam core; 
     FIGS. 5A and 5B shows an enlarged view of a connector attachment head piercing the foam core of a panel according to the present invention; 
     FIG. 5C is a sectional view showing the connector of the present invention connecting two foam core panels;. 
     FIGS. 6A and 6B show an enlarged view of an attachment head according to the present invention; 
     FIGS. 7A and 7B show a first configuration of a display constructed using a connector having a spacer portion according to the present invention; 
     FIGS. 8A and 8B show a second configuration of a display constructed using a connector according to the present invention; 
     FIGS. 9A and 9B show a third configuration of a display constructed using a connector according to the present invention; and 
     FIG. 10 shows a fourth configuration of a display constructed using a connector according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1A-1L illustrate several alternative configurations of a connector  10  according to the present invention. In its simplest form the connector  10  has a body  12  with at least one attachment head  14  and plural barbs projecting away from the attachment head  14 . However, the connector  10  may have any number of attachment heads  14  at varying angles relative to the connector body  12 . 
     In the configuration shown in FIG. 1A the connector  10  has two attachment heads  14 , each head  14  having plural barbs  16 . Indentations  13  may be used to form a hinge line H where the connected panels are not to be coplanar. 
     In the configuration shown in FIG. 1B the connector  10  has two attachment heads on a first side of the connector body  12 , and two additional attachment heads on a second side of the connector body  12 . 
     In the configuration shown in FIG. 1C the connector body  12  is generally circular and includes plural attachment heads  14  radially projecting from a central disk. 
     In the configuration shown in FIG. 1D the connector body  12  includes a spacer portion  18  which will be described herein below. 
     In the configuration shown in FIG. 1E the connector body  12  is stepped such that two attachment heads  14 A are on a different plane than another opposed attachment head  14 B. 
     In the configurations shown in FIGS. 1F and 1G the connector  10  includes three attachment heads  14 , two on one side of the connector body  12  and one on the other side. In FIG. 1F, the attachment heads on one side are parallel to each other, while in FIG. 1G the attachment heads  14  on one side of the spacer  18  project at an angle to each other. 
     In the configuration shown in FIG. 1H the connector  10  includes four attachment heads  14 , two on each side of the connector body  12 . 
     In the configuration shown in FIG. 11 the connector  10  includes six attachment heads  14 , three on each side of the connector body  12  and projecting outwardly at different angles. 
     In the configuration shown in FIGS. 1J-L the connector  10  has a single attachment head  14 . More particularly, the connector  10  in FIGS. 1J and 1K includes an attachment head  14  at one end and a mounting hole  15  at another end. The mounting hole  15  may be connected, for example, to a support (not shown) such as a hook, or a string or wire suspended from a ceiling. The body  12  in FIG. 1J is generally in the same plane with the attachment head  14 , whereas in FIG. 1K the connector body  12  is in a different plane than the attachment head  14 . 
     The connector  10  shown in FIG. 1L includes an attachment head  14  at one end and a support portion  17  at another end. The support portion  17  may be used, for example, to support a display item (shown in dashed lines in FIG. 10) such as a shoe, a shelf or the like. 
     Referring to FIG. 1A, the attachment heads  14  generally have a width W head  and a thickness T head  which is varied depending on the density and thickness of the foam core and the required fastening force and the resiliency of the material from which the barbs are made. The barbs  16  generally have length L barb  which is also varied depending on the density and thickness of the foam core and the required fastening force. The width W head  is generally much greater than the thickness T head  (W head &gt;&gt;T head ), such that the connector  10  may be used with relatively thin panels  20 , be made of a material such as plastic yet possess the strength required to perform its fastening function. 
     The width W may be dictated by the strength of the material used to form the connector. Moreover, a wide connector  10  acts against torsion of the panels around the connector axis, and thus is useful in constructing a more rigid connection. 
     The barbs  16  are preferably resilient or springy, and should be elongated so that they will yield to a cantilever force placed on them more easily than to a column force applied in alignment with their lengths. 
     According to a preferred embodiment, the head  14  has a thickness T head  is selected in relation to the thickness of the foam core T foam  into which of the head is being inserted. According to a preferred embodiment, the ratio of T head  to T foam  is generally 1:3. In other words, the thickness of the head  14  is generally ⅓ of the thickness of the foam core  22 . 
     The connector  10  is suitable for use in conjunction with a wide variety of low-density foam products, and provides between 5.5 and 12 pounds of fastening force depending on the density of the foam core, the size and number of attachments heads, and the size and number of barbs  16 . 
     The connector  10  may be formed from any of a number of different materials such as plastic, metal, or the like. According to a presently preferred embodiment, the connector  10  is integrally formed from injection molded plastic. 
     Preferably, the attachment heads  14 , connector body  12 , and barbs  16  are integrally formed as a single piece. However, the attachment heads  14  and barbs may be formed separately from the connector body  12 , such that the attachment head is later joined with the connector body by thermo-bonding or the like. 
     The dimensions of the connector  10  may be adjusted depending on the size and thickness of panels to be connected, and the amount of fastening force required. According to a presently preferred embodiment, the head  14  has a thickness generally falling in the range {fraction (1/16)} inch≦T head ≦{fraction (3/16)} which generally corresponds to a foam core thickness in the range {fraction (3/16)} inch≦T foam ≦½ inch. However, it should be appreciated that the invention is not limited to any particular dimensions. 
     FIG. 2A shows an exploded view of a conventional foam core panel  20  which includes a foam core  22  formed of a thermoplastic, foamed polymer such as polystyrene, polyethylene or polyurethane laminated on both sides with bleached white clay coated Kraft paper liners  24 . FIG. 2B shows an enlarged sectional view showing that the foam core  22  is composed of plural foam cells  26 . 
     Use of the connector  10  of the present invention is not limited to any particular composition of foam core panel, and will work with commercially available foam core boards. However, the density of the foam core must be sufficiently low to allow the barbs to pierce a heat-collapsed skin made from the foam core. Preferably, the density of the foam core is between 0.02 and 0.15 grams per cubic centimeter. 
     FIG. 3 shows a cavity-forming tool  40  according to the present invention, and FIGS. 4A and 4B show how the tool  40  is used to form a cavity  28  in the foam core  22 . As best r seen in FIG. 4B heat generated by the heating element  42  of the tool  40  causes the foam cells  26  to collapse upon insertion of the element  42  into the foam core layer  22 , creating a cavity  28 . More particularly, the foam has a melting point of approximately 375 to 425 degrees Fahrenheit. As the cells collapse due to the heat they form a skin  30  of collapsed material which is denser than the foamed material. Notably, the foamed material has a density between 0.02 and 0.15 grams per cubic centimeter, whereas the collapsed or unfoamed material has a density between 0.9 and 1.25 grams per cubic centimeter. Specifically, unfoamed polystyrene has a density of approximately 1.04 to 1.09 grams per cubic centimeter, unfoamed polyethylene has a density of approximately 0.91 to 0.965 grams per cubic centimeter, and unfoamed polyurethane has a density of approximately 1.05 to 1.25 grams per cubic centimeter. 
     The cavity  28  is dimensioned to snugly accommodate one of the attachment heads  14 . Care must be exercised to ensure that the cavity  28  is slightly narrower than the combined width W combined  of the attachment head  14  and barb  16  connector, and is of generally the same thickness as the thickness T of the attachment head  14  of the connector  10 . See FIG.  5 B. 
     The attachment head  14  is forcedly inserted into the cavity  28  such that the barbs  16  pierce the denser skin  30  and are retained therein. See FIGS. 5A and 5B. 
     FIG. 5C is a sectional view showing the connector  10  inserted into corresponding cavities  28  of the foam core panels  20 , and providing a substantially smooth planar connection therebetween. 
     According to an alternative embodiment, the cavity  28  may be formed by mechanically removing the foam using, for example, a knife or the like rather than by the heating tool  40 . However, the use of heating tool  40  is preferred because it creates the denser skin  30  which is believed to more effectively retain the barbs  16  of the connector  10 . 
     As shown in FIGS. 1D and 1E, the connector body  12  may be provided with a spacer portion  18  which provides spacing between adjacent panels  20 . The spacer portion  18  is configured to prevent more than a predetermined length of the connector  10  from being inserted into the cavity  28 . When the connector  10  is formed of a clear plastic, an effect may be achieved whereby a panel looks as if it is suspended in mid-air without any support. 
     In the embodiment depicted in FIG. 1D, the spacer portion  18  has a width W spacer  which is larger than the combined width W combined  of the attachment head  14  and the barb  16 . In the embodiment depicted in FIG. 1E, the spacer portion  18  is stepped such that attachment head  14 A is in a different plane from attachment head  14 B. Moreover, the spacer portion  18  may be mutually perpendicular to both attachment heads  14 A and  14 B. 
     According to one aspect of the present invention, the connector  10  is configured such that when a cantilever loading is imposed on the barbs  16  they are generally more resilient and yielding in an insertion direction (FIG. 6) than they are in a withdrawal direction. 
     More particularly, and referring to FIG. 5B, when an insertion force is applied to urge the connector  10  into the cavity  28 , the peripheral wall of the foam core  22  contacts the barbs  16  and imposes a compressive force F cantilever  at a significant angle to axis A of the barbs  16 , urging the barbs inwardly toward the body  12 . Correspondingly, when a withdrawal force is applied to withdraw the connector  10  from the cavity  28 , the peripheral wall of the foam core  22  interferes with the barbs  16  and imposes a column loading force F column  that is at an acute angle to axis A of the barbs, pulling the barbs  16  away from the body  12 . Importantly, F column  is significantly greater than F cantilever  such that a greater force is required to withdraw the connector from the cavity  28  than the force required to insert the connector into the cavity  28 . Stated in another way, the elongate, resilient barbs  16  are more yielding to forces at a substantial angle to the direction of the length of the connector body than they are to an extraction force in substantial alignment with that direction. The barbs  16  elastically deform toward the center of the attachment head  14  when the attachment head is inserted into the cavity  28 , but resist deformation when an attempt is made to withdraw the attachment head  14  from cavity  28 . 
     The simplest use of the connector  10  is the edge-to-edge assembly of two or more panels  20  into a single contiguous display. The form of connector  10  shown in FIG. 2A is used for this kind of construction. Such a multipanel display may be chosen to reside substantially in the same plane, or may be hinged such that the panels are at angles to each other. One important technical advantage of the present invention is that in use, the form of connector  10  shown in FIG. 2A is invisible to an observer of the display, providing a neater and less cluttered appearance. 
     The connector  10  of the present invention facilitates the construction of several other novel displays, which for example may be point of purchase displays. By way of illustration, FIGS. 7A and 7B show a display  70  constructed using the connector  10  having a spacer portion  18  (FIGS.  1 D and  1 E). The display  70  is composed of plural foam core panels  20  which are connected in vertically in columns, which vertical columns are connected horizontally to adjacent columns. For example, panels  20 A- 20 C, panels  20 D- 20 F and panels  20 H- 20 J, respectively, are connected in a vertically spaced relationship using a connector  10  having a spacer portion  18  such depicted in FIG.  1 D. The spacer portion  18  ensures that the panels  20 A- 20 C and  20 D- 20 F are uniformly spaced a predetermined distance from one another. 
     More particularly, the panels  20  are connected using the above described method in which a cavity  28  is formed in the foam core  22  using a cavity-forming heating tool, resulting in the formation of a cavity skin  30  which aids in retaining the barbs  16 . 
     The column of panels  20 A- 20 C is horizontally connected to the column of panels  20 D-F and  20 H-J using a connector  10  having a spacer portion  18  such as depicted in FIG.  1 E. Importantly, the spacer portion  18  (FIG. 1E) is stepped such that attachment head  14 A is in a different plane from attachment head  14 B. Consequently, the connector  10  shown in FIG. 1E will position the column of panels  20 A- 20 C in a fixed, spaced relationship in a different plane from the columns of panels  20 D-F and  20 H-J. 
     FIGS. 8A and 8B illustrate a second point of purchase display  80  which may be constructed using the connector  10  of the present invention. The display  80  includes a panel  82  and two foam core panels (leg members)  20 . For visual design reasons, the panel  82  may be formed of transparent plastic; however, the panel  82  may be formed of practically any material, and need not be formed of foam core, and may as easily be translucent or opaque. While the constructions illustrated herein are built around thin intervening panels, the present invention can also be used with central or intermediate through-connected members having greater thicknesses. 
     As best see in FIG. 8B, one or more holes  86  are defined in panel  82  to facilitate connector  10  to interconnect panels  20 . The attachment head  14 A of connector  10 A is inserted through the hole  86  into the cavity  28 A formed in a side edge portion of the foam core  22 A, and attachment head  14 B is inserted through the hole  86  into the cavity  28 B formed in a side edge portion of the foam core  22 B. It should be noted that the panels  20  provide additional support or rigidity for the panel  82 . 
     The panels  20  are connected using the above described method in which a cavity  28  is formed in the foam core  22  using a cavity-forming heating tool, resulting in the formation of a cavity skin  30  which aids in retaining the barbs  16 . 
     FIGS. 9A and 9B illustrate yet another point of purchase display  90  which may be constructed using the connector  10  of the present invention. The display  90  includes a support member  92  and two or more foam core panels  20 . For aesthetic reasons, the support member  92  is preferably formed of transparent plastic; however, the support member  92  may be formed of practically any material and need not be formed of foam core. As shown in FIG. 9A the support member  92  does not have to be planar (flat). In particular, the support member  92  may be curved in any number of shapes. The foam core panels  20  are contoured to match the surface profile of the support member  92 , and provide additional support or rigidity to the support member  92 . The panels  20  may be used as shelves to support samples of goods for sale. 
     As best seen in FIG. 9B, one or more holes  96  are defined in the support member  92  to facilitate connector  10  to interconnect corresponding panels  20 . The attachment head  14 A of connector  10 A is inserted through the hole  96  into the cavity  28 A formed in a side edge portion of the foam core  22 A, and attachment head  14 B is inserted through the hole  96  into the cavity  28 B formed in a side edge portion of the foam core  22 B. 
     The panels  20  are connected using the above described method in which a cavity  28  is formed in the foam core  22  using a cavity-forming heating tool, resulting in the formation of a skin  30  which aids in retaining the barbs  16 . 
     FIG. 10 illustrates yet another point of purchase display  1000  which may be constructed using the connector  10  of the present invention. The display  1000  includes a foam core panel  20  and at least one connector  10 A. The connector  10  of the type shown in FIG. 1J or FIG. 1K is inserted in an edge portion, with the mounting hole  15  exposed. The mounting hole  15  enables the display  1000  to be removably attached to a hook, or a vertical support such as a wire or the like. 
     More particularly, the display  1000  may be constructed as any of the displays  70 ,  80 , or  90  shown in FIGS. 7A-9B, and further including the connector  10  of the type shown in FIG. 1J or FIG.  1 K. 
     Still further any of the displays  70 ,  80 ,  90  or  1000  may further be provided with a connector  10  of the type shown in FIG. 1L having a support portion  17 . In this manner, a display capable of supporting display items may be constructed. 
     While the preferred embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made therein without departing from the spirit of the invention, the scope of which is defined by the appended claims.