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CROSS REFERENCE RELATED APPLICATION 
       [0001]    This application is a continuation application, which is based on and claims priority to co-pending U.S. Utility patent application Ser. No. 11/414,474, filed on Apr. 28, 2006, which claims priority to Provisional Patent Application Ser. No. 60/675,912, filed Apr. 29, 2005, which is entirely incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to a novel hinge system for connecting a pair of panel members so as to allow them to be stacked closely together but readily separated to a selected, fixed perpendicular spacing. 
       BACKGROUND OF THE INVENTION 
       [0003]    The hinge system of the invention is useful in the manufacture of easy to assemble and erect structures having two or more vertical or horizontal shelving units, for example, chests, bookshelves, closet organizers, tables and seating. A shelving unit or other structure incorporating the hinge system of the invention can be produced relatively simply and inexpensively by the manufacturer and requires no tools for assembly by the ultimate purchaser and user of the unit. 
         [0004]    To achieve these advantages, a hinged panel assembly according to the invention comprises a first panel crossed by an elongate channel having a narrow entranceway; a second panel; a hinge having a first portion located in the channel of the first panel and protruding through the entranceway and a second portion which attaches to the second panel. The first and second portions of the hinge are pivotally connected together by axial flexion means, which can be a conventional hinge pin assembly or a “living” hinge. 
         [0005]    The hinge unit connecting the panels itself comprises a dowel or other elongate locking member adapted to be received within a specially routed slotted channel in the surface of a first panel. A leaf member extends away from the elongate member along axial flexion means. The leaf member connects to one surface of a rigid cross piece so as to allow rotational motion of the cross piece in one angular direction, from an extended position perpendicular to the first panel to a folded position substantially parallel to and contiguous with the first panel. 
         [0006]    When a second, corresponding hinge unit is installed on the facing surface of a second panel, with the leaf member of that second hinge unit connected to the opposite surface of the cross piece, then translation of the first and second panels in opposite directions results in the folding over of the cross piece and its sandwiching between the first and second panels as they come together. 
         [0007]    A particular aspect of the invention is a new and simple method for hingedly connecting a pair of panels. A recess for receiving the dowel portion of the hinge unit is formed in the first panel by routing a narrow rectangular passage into the first panel, then routing a channel into the first panel in open communication with the narrow rectangular passage. The channel receives the dowel portion of the hinge unit, both the channel and the dowel portion having a cross-sectional shape which prevents rotation of the dowel within the channel. Novel router bits are provided for the purpose of forming a channel with narrow entranceway in the first panel or workpiece to receive the first portion of the hinge unit, which may be used with conventional routing tools. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0008]    Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0009]      FIGS. 1A and 1B  are respectively disassembled and assembled schematic views of the hinge system of the invention according to a first embodiment (“pin edge”). 
           [0010]      FIGS. 2A to 2C  illustrate the erection or folding up of a two-shelf unit employing four of the hinge systems of  FIG. 1 . 
           [0011]      FIG. 3  is a schematic view of a second embodiment (“flex hinge”) of hinge system according to the present invention. 
           [0012]      FIG. 4A  is a schematic view of a further example of a hinge system according to the second embodiment of the invention. 
           [0013]      FIG. 4B  is a different perspective view of the hinge system of  FIG. 4A . 
           [0014]      FIG. 5  illustrates a panel adapted to receive three hinge units according to the invention having elongate locking members of differing cross-sectional contour. 
           [0015]      FIGS. 6A and 6B  are schematic views of a third embodiment of hinge system according to the present invention, respectively showing the hinge partly and completely removed from the locking channel. 
           [0016]      FIGS. 6C and 6D  are two views of the hinge system of  FIGS. 6A and 6B , fully assembled, with the panel and cross piece shown at two different angular spacings. 
           [0017]      FIG. 7  is a perspective view of three examples of router bits for use in forming channels in panel members to receive hinge units according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    In the drawings,  10  indicates a portion of a panel member, such as a shelf, which has been prepared for installation of a hinge unit according to the invention by routing therealong a channel  12  open to the surface along slot  13 . An elongate locking member  14  of the hinge unit is configured to slide into channel  12  leaving axial flexion means projecting outwardly through slot  13  and connecting. In the drawings, for different embodiments of the hinge system, analogous components will be identified by the same numerals, but differing alphabetic subscripts. 
         [0019]    In the embodiment of hinge unit illustrated in  FIGS. 1A to 2C  (the “pin edge” arrangement) elongate locking member  14  is in the form of a circular dowel but, as will be noted below, other cross sections are possible and useful for particular applications. 
         [0020]    Hinge leaf  16  is pivotably connected to member  14  by axial flexion means  18  which, in the embodiment illustrated, comprise aligned interfitting hinge eyes  19  for removably receiving a hinge pin  20  which holds the leaf  16  to the locking member  14 , and allows the leaf to swing smoothly and freely relative to the facing surface of panel member  10 . Leaf  16  may be provided with apertures  17  through which screws or other fastening means can be inserted to interconnect a pair of panel members. The locking member  14 , hinge pin  20 , hinge eyes  19  and the leaf  16  may be made of any machinable metal or alloy such as brass or steel. 
         [0021]    A two-panel hinged interconnection according to the invention is illustrated in  FIGS. 2A to 2C . Parallel panel members  10   a  and lob are provided with opposed pairs of routed channels ( 12   a ,  12   b ) and ( 12   c ,  12   d ). Hinge units as described in connection with  FIGS. 1A and 1B  are fitted into the routed channels in the facing panel members. Extending between opposed pairs of hinge units are cross pieces  22   a  and  22   b , to which the leaves  16   a  and  16   b  of opposed hinges are attached to opposite surfaces of the cross piece. Translation of parallel panels  10   a  and l o b in the opposite directions indicated by arrows A and B then collapses the four-member structure (two panels/shelves and two cross pieces) into the flat, stackable arrangement of  FIG. 2C . 
         [0022]    The pin edge arrangement, employing metallic hinge components, is intended for heavy duty use. For smaller shelf or storage space installations, a light plastic living hinge structure is useful. A hinge unit of that kind is illustrated in  FIG. 3 . 
         [0023]    The embodiment of hinge unit illustrated in  FIGS. 3A and 38  is an integral hinge formed of an engineering plastic, in which flexion is afforded by a thinned portion or notch line  17  in the plastic material connecting leaf  16   a  to a narrow ledge extension  20  extending diametrically away from the locking member portion  14   a  and through the slot portion  13  of routed channel  12  in a panel member  10 . 
         [0024]    Suitable materials for manufacturing this “flex hinge” version of the hinge unit of the invention include engineering grades of polyvinyl chloride (PVC) copolymers of polystyrene [e.g. ABS], polyethylene, polypropylene and polyamides (nylon). With suitable materials, the entire hinge unit can be made in a single injection molding step. 
         [0025]    The flex hinge of  FIG. 3  can be used to form a collapsing shelf structure as in  FIGS. 2A to 2C , just as with the pin edge metallic hinge unit of  FIG. 1 . For added locking stability, the flex hinge can be made with locking dowels  24  integral with and perpendicular to leaf  16   a , for fitting into corresponding holes formed in the cross pieces of the structure (not shown in  FIG. 3 ). 
         [0026]      FIGS. 4 ,  4 A and  48  show a flex hinge unit like that of  FIG. 3 , but with the elongate locking member indicated by  14   b  having a different, part-triangular cross-sectional shape. A mating slotted channel  12   b  is shown routed into the surface of a panel  10  to be hingedly joined to cross piece  22 . Flexion at the hinge is about notch line  17   a.    
         [0027]    Again, leaf portion  16   a  is provided with locking dowels  24  which fit within mating recesses  25  in cross piece  22 . 
         [0028]      FIG. 5  shows a panel member  10  in which three different routed channel configurations  12   e ,  12   f  and  129  have been formed, respectively square, triangular and circular and adapted to connect with hinge units  30   e ,  30   f  and  309 . 
         [0029]    A second, reverse-side view is given of hinge unit  30   f  to show the provision on these units of integral projections  31  which, in fully assembled  5  configurations of the storage unit, fit into and engage corresponding recesses  32  on the panel (shelf) members for added stability of the erected structure. 
         [0030]    Particular ease of manufacture of hinges according to the present invention is illustrated by the “dovetail” version of hinge unit indicated by  30  in  FIGS. 6A and 68 . The hinge  30  may be made in indefinite lengths by extrusion molding and cutting to fully formed hinges of the desired length. The hinge contour comprises two elongate locking members  14   c  and  14   d  at opposite sides of axial flexion means. These locking members respectively engage with corresponding routed channels  12   c  which has been formed in the main panel member  10  and the cross pieces  22 , respectively. The fully connected panel member  10  and row piece  22  are illustrated in  FIG. 68 , at two different angular spacings. 
         [0031]      FIG. 7  illustrates three forms of router bit which have been developed to form slotted channels of different configurations. Thus, routers of shapes A, B and C have the configurations  12   b  in  FIGS. 4 and 12   a  in  FIG. 3 , respectively. 
         [0032]    While specific embodiments of the invention have been described, it will be appreciated by those skilled in the art that various modifications and alternatives could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full benefit of all the claims appended and any and all equivalents.

Summary:
A hinge unit useful in the manufacture of readily assembled and erect shelving and storage units and furniture comprises an elongate locking member adapted to be received within a slotted channel in the surface of a first panel, means extending away from the elongate member for attaching the hinge to a second panel and integral axial flexion means between the two portions of the hinge. The cross-sectional shape of the elongate locking member and the channel are selected to prevent rotation of the locking member within the channel.