Abstract:
A leg attachment mechanism for an article of furniture including a bracket attached to the article of furniture and an expandable post attached to the bracket. The leg includes a receptacle of sufficient dimension to receive the post. The leg is attached to the post by fitting the receptacle over the post and then expanding the post to forcefully engage the walls of the leg defining the receptacle. The post preferably includes a flexible wall that is movable outwardly by rotation of a threaded element, such as a set screw. A foam overmold is preferably formed over the edge of the article of furniture and the bracket. The overmold prferably includes an undercut boot that closely receives upper end of the leg. The present invention also provides a method of manufacturing an article of furniture incorporating the leg attachment mechanism.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to furniture and, more specifically, to furniture leg attachment mechanisms and related components.  
           [0002]    Many pieces of furniture have rigidly attached legs. Pieces of furniture with long legs, such as tables, are often delivered to the end consumer without the legs attached. The furniture takes up less space and is easier to transport without the legs already attached. The furniture suppler or the end consumer must then attach the legs to the furniture.  
           [0003]    Typically legs are attached to furniture using brackets and screws. Several problems result from this type of leg attachment. One problem is that it can be complicated to assemble the legs to the furniture. With bracket and screw assemblies, it is necessary to work with several small parts. It is often difficult for an end consumer to figure out where each part needs to be connected, and there is a danger of losing some of the parts, especially smaller parts like screws. Another problem is the ability of the furniture to withstand force. If the bracket and screw assembly is not robust enough or the legs are not properly attached to the furniture, the furniture may buckle or collapse under heavier loads. Yet another problem with bracket and screw assemblies is that they are aesthetically unpleasing. Often, these assemblies are plainly visible after the legs are assembled, for example, from the side.  
         SUMMARY OF THE INVENTION  
         [0004]    The aforementioned problems are overcome by the present invention wherein an attachment assembly is provided with a post that is affixed to the undersurface of an article of furniture. The post is generally wedge-shaped and is configured to be fitted within an opening in the upper end of the leg. The post is expandable to bind against the inner surfaces of the leg, creating a secure connection.  
           [0005]    In a preferred embodiment, the post is generally triangular in cross section and includes an expansion wall that is capable of outward movement to increase the cross-sectional size of the post. The post is preferably a one-piece component with the expansion wall being an integral portion of the post. The post preferably includes a set screw that is threaded through the expansion wall and engages a fixed portion of the post. Movement of the set screw causes the expansion wall to swing inwardly and outwardly with respect to the remainder of the post. This causes all three walls of the post to bind against the corresponding inner surfaces of the leg creating a secure connection. The leg preferably defines an opening permitting access to the set screw.  
           [0006]    In a more preferred embodiment, the leg attachment mechanism includes a mounting bracket that is separate from the post. The bracket defines a series of mounting holes for securing the bracket to the undersurface of the article of furniture using conventional fasteners. The bracket defines a post hole for securing the post to the bracket. The post hole is positioned so that the post is disposed over the corner fastener.  
           [0007]    In an even more preferred embodiment, the leg attachment mechanism includes a foam overmold that covers the bracket and forms a boot for the upper end of the leg. The foam overmold is preferably configured to hide the entire leg attachment mechanism once assembled. The overmold also preferably provides a foam edge for at least a portion of the article of furniture.  
           [0008]    In a second aspect, the present invention provides a method for manufacturing the leg attachment mechanism including the steps of (a) attaching a bracket to the article of furniture; (b) overmolding the bracket with foam using a plug in the mold to define a void for the post wherein the foam forms a boot on the underside of the article of furniture; (c) attaching the post to the bracket; (d) inserting a hollow part of a leg around the post; and (e) expanding the post to force the post to bind against the inner walls of the leg, thereby firmly connecting the leg to the article of furniture. In a preferred embodiment, the plug is manufactured from a flexible and resilient material. As the mold is closed, the plug is compressed causing it to bulge outwardly forming a somewhat undercut boot. When the mold is opened, the plug returns to its original shape, permitting it to be withdrawn through the narrowing opening of the molded boot foam.  
           [0009]    The present invention provides several advantages over prior leg attachment mechanisms. First, the leg is easily attached to the article of furniture because a minimum number of parts are involved. In the preferred embodiment, only a single set screw is tightened to attached each leg. Also, it is difficult to incorrectly install the leg. In a preferred embodiment, the leg defines an opening permitting access to the set screw. The set screw will be accessible only when the leg is properly installed. Second, the connection between the leg and the post is highly secure. Because the post is wedge shaped, there is a high degree of engagement between the post and the inner surfaces of the leg. As the post expands, all three walls of the post are driven more forcefully against the corresponding surfaces of the leg. Third, because the bracket and post are separate pieces, the bracket can be secured to the article of furniture by a fastener located immediately beneath the leg. This reduces any “fulcrum” effect that might be caused by an offset fastener. Fourth, the use of a separate post permits the bracketed to be overmolded before the post is attached. This eliminates the concern that the mold will be damaged by the post. Further, the flexible plug permits an undercut void to be formed to receive the leg. This eliminates the need for a conventional draft angle in the mold and ultimately provides a tighter fit of the overmold around the leg. Fifth, the assembly is aesthetically pleasing because the leg attachment mechanism is hidden beneath foam.  
           [0010]    These and other objects, advantages, and features of the invention will be more readily understood and appreciated by reference to the detailed description of the preferred embodiment and the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a perspective view of a table including the leg attachment mechanism of the present invention;  
         [0012]    [0012]FIG. 2 is a top view of the table;  
         [0013]    [0013]FIG. 3 is a sectional view of the leg attachment mechanism taken along the line C-C in FIG. 2;  
         [0014]    [0014]FIG. 4 is a sectional view of the leg attachment mechanism taken along the line D-D in FIG. 2;  
         [0015]    [0015]FIG. 5 is a top view of the bracket;  
         [0016]    [0016]FIG. 6 is a perspective exploded view of the leg attachment mechanism;  
         [0017]    [0017]FIG. 7 is a top view of the post with the leg attached;  
         [0018]    [0018]FIG. 8 is a rear view of the post;  
         [0019]    [0019]FIG. 9 is a sectional view of the leg attachment mechanism showing the plug insert in an unclamped mold.  
         [0020]    [0020]FIG. 10 is a sectional view of the leg attachment mechanism in the clamped mold. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0021]    A table  20  incorporating a leg attachment mechanism  10  in accordance with a preferred embodiment of the present invention is shown in FIG. 1. The leg attachment mechanism  10  is intended to be used with an article of furniture to allow for the easy attachment of legs to the article of furniture. FIG. 1 shows the leg attachment mechanism  10  connected to a table  20 , with one leg attachment mechanism  10  located in each corner of the table  20 . The leg attachment mechanism  10  is, however, well suited for use in attaching legs to a wide variety of articles of furniture. As shown in FIGS.  2 - 4 , the leg attachment mechanism  10  generally includes a bracket  30 , screws  44  for attaching the bracket  30  to the table  20 , a post  50 , and a bolt  98  for attaching the post to the bracket. The leg attachment mechanism  10  may optionally have foam  84  surrounding part of the table  20 , the bracket  30 , and part of the post  50 . In use, the post  50  is fitted within the leg  94  and expanded by set screw  80  to bind against the inner surfaces of the leg  94 .  
         [0022]    I. Construction  
         [0023]    As noted above, the leg attachment mechanism  10  includes a bracket that is mounted to the undersurface of the table  20 . The table  20  preferably includes four brackets  30 , one located in each corner of the table  20 . In the illustrated embodiment, the brackets  30  provide for attachment of a separate leg  94  in each corner of table  20 , but it will be readily apparent to those skilled in the art that the location of the brackets may vary from application to application depending on the desired location of the legs. The bracket  30  is generally triangular and preferably is manufactured (e.g. cast) of aluminum. As shown in FIG. 5., the bracket  30  preferably defines five holes  32 ,  34 ,  36 ,  38 ,  40  to secure the bracket  30  to the table  20 , for example, using conventional fasteners such as screws. Hole  36  is preferably placed near the tip of the bracket  30 , where it will lie beneath the installed post  50 . This positioning greatly reduces any fulcrum effect that might be created by an offset fastener and, accordingly, reduces the likelihood that the bracket  30  might peel away from the table  20  under heavy loads. The bracket  30  also has a tapped or threaded hole  42  to bolt the post  50  to the bracket  30 . Alternatively, the bracket  30  could contain a different number of screw holes, and the screw holes  32 ,  34 ,  36 ,  38 , and  40  and the bolt hole  42  could be placed in different locations. As another alternative, the bracket  30  may be designed to accommodate other mechanisms for attaching it to the table  20  as apparent to those skilled in the furniture art. The bracket  30  also preferably defines relieved portions  31  to reduce the weight and amount of material required to form the bracket  30 . The size, location and arrangement of relieved portions will vary from application to application depending in large part on the strength required by the bracket and the positioning of the screw holes or other mounting devices.  
         [0024]    A post  50  is secured to the bracket  30  to removably receive the leg  94 . The post  50  is preferably extruded from aluminum or other materials of sufficient strength to withstand the forces applied to the leg. The post  50  can alternatively be machined or otherwise fabricated using conventional techniques and apparatus. The post  50  is generally triangular in cross section, having somewhat convex sides  60 ,  62  and  64  and beveled corners  72 ,  74 , and  76 . As shown in FIGS.  6 - 7 , the post  50  defines a central hole  52  that receives a bolt  98  to secure the post  50  to the bracket  30 . The post  50  also defines an elongated slot  54  and a channel  66  that cooperate to define a movable wall  75 . As shown in FIG. 8, a set screw  80  is threadedly fitted through the movable wall  75 . The set screw  80  extends through and abuts the inner wall  55  of the groove  54 . As described in more detail below, the movable wall  75  can be flexed outwardly to expand the post  50  by tightening the set screw  80 . The post  50  also defines two voids  56 ,  58  that reduce the weight and material required to form the post  50 . The size, number and location of voids can vary from application to application depending in part on the material used and the strength required. Sides  62 ,  64  of the post  30  each have a channel  68 ,  70  providing a fixturing surface for machining purposes. As another alternative, the post may be integrally formed with the bracket or may be attached to the bracket using other conventional techniques as will be readily apparent to those skilled in the art.  
         [0025]    In a preferred embodiment, a urethane foam  84  covers the brackets  30  and the edge of the table  20  (See FIG. 1). As perhaps best shown in FIG. 3, the foam  84  forms a boot  86  on the underside of the table  20 . The foam  84  preferably extends from the top surface of the table  20  over the edge of the table and about halfway down the length of the post  50 . This provides the table  20  with a “soft” edge and hides the leg attachment mechanism  10  once the legs  94  are attached. The foam  84  also is located on the underside of the table  20  covering the bracket  30  and extending about halfway down the length of the post  50 . The described foam placement is merely exemplary. The configuration of the foam may vary from application to application as desired. Although the foam  84  is preferably a urethane material, it can alternatively be other resilient materials that are capable of being overmolded onto the table  20  and bracket  30 .  
         [0026]    As noted above, the table  20  includes four legs  94 , one supporting each corner of the table  20 . The leg  94  is to a large degree conventional, however, it includes a hollow upper end that is shaped to be fitted over the post  50 . The leg  94  preferably includes a cross section that corresponds to the cross section of the post  50 . More specifically, the leg  94  is preferably somewhat triangular in cross section having convex sides. Unlike the post  50 , the corners of the leg  94  are preferably pointed, rather than beveled. One of the sides of the leg  94  defines a hole  96  to allow access to the set screw  80  within the post  50 . The leg  94  is preferably includes an upper portion  95  that is extruded from aluminum and a lower portion  97  that is secured to the upper portion  95 . The lower portion  97  is preferably adjustable in length to permit separate adjustment of the height of each leg  94 .  
         [0027]    II. Manufacture  
         [0028]    In a preferred embodiment, the brackets  30  are attached on the underside of the table  20  with screws  44 . FIG. 5 shows the location of the five screw holes  32 ,  34 ,  36 ,  38  and  40 . As noted above, the screw hole  36  is preferably disposed near the tip of the bracket  30  where it will lie beneath the post  50 . A metal bolt insert  102  may be preferably installed within the table  20  in alignment with screw hole  36  to enhance the strength of the connection between the bracket  30  and the table  20 . The insert  102  is not, however, necessary. Similar metal inserts may be installed in the table  20  to receive the other screws, if desired. Although the position will vary from application to application, four brackets  30  are attached in the four corner of the table  20  so the legs  94  will support the four corners of the table  20 . The brackets  30  are preferably casting from aluminum using conventional techniques and apparatus. The bolt hole  42  is preferably tapped after casting. If additional strength is required, an insert (not shown) can be fitted into the bracket  30  about bolt hole  42 . The insert can be manufactured from steel or other materials of sufficient strength to bear the load of bolt  98 .  
         [0029]    Once the brackets are affixed to the table  20 , the edge of the table  20  and the brackets  30  are overmolded with the urethane foam  84 . The foam overmold is produced using a relatively large mold  92  capable of closing around the periphery of the table  20 . The mold  92  is used to shape the foam into a boot  86  on the underside of the table  20 . FIG. 9 and FIG. 10 are cross sectional views of a portion of the mold  92 . The mold  92  includes a flexible, resilient plug  90  that is inserted into the mold cavity  93  to define a void where the post  50  will be inserted. The plug  90  is preferably carried on a moving mold part  106  that automates insertion and removal of the plug  92  from the mold cavity  93 . The plug  90  is made of silicone that is capable of deforming under pressure. FIG. 10 shows the mold part  106  and the plug  90  in the closed position in phantom lines. As illustrated, in the closed position, the plug  90  is compressed between the mold part  106  and the bracket  30 . This causes the sides of the plug  90  to bulge outwardly. The urethane foam is injected into the mold  92  while the plug  90  is maintained in a bulged shape. Because the plug  90  bulges out in the mold  92 , an undercut  108  is created in the foam  84 . When the foam is sufficiently cured, the plug  90  is removed from the mold cavity  93 . As the mold part  106  moves away from the mold  92 , the pressure on the plug  90  is removed and it returns to it original, non-bulged shape. This permits the plug  90  to be withdrawn through the opening in the boot. The undercut  108  reduces the amount of force required to insert a leg  94  into the leg attachment mechanism  10  because it reduces the amount of surface to surface contact between the leg  94  and the boot  86 . Also, because of the undercut, a draft angle is not needed in the foam  84  and the fit between the leg  94  and the boot  86  is improved. Although the overmold is preferably a conventional urethane foam, other similar materials capable of overmolding can be used in the alternative.  
         [0030]    The post  50  is preferably manufactured using conventional extrusion techniques and apparatus. The post extrusion is cut to the desired length and the set screw hole is drilled and tapped in the movable wall  75 . The post  50  is then ready to be attached to a bracket  30 .  
         [0031]    The posts  50  are attached to the brackets  30  after the overmolding process is complete. Each post  50  is preferably attached to the corresponding bracket  30  using a bolt  98  or other conventional fastener. The bolt  98  is inserted into the post  52  through the bolt hole  52 , and then threaded into the bolt hole  42  in the bracket  30 . In the preferred embodiment, the foam boot  86  surrounds approximately the top half of the post  50 . However, the size and configuration of the boot  86  may vary from application to application as desired. For example, the boot may alternatively be of sufficient size to cover the set screw access opening in the leg. In this alternative embodiment (not shown), the boot will also include a set screw access opening. Because of the flexible nature of the foam, the set screw access opening can be stretched when access to the set screw is desired. Accordingly, the smaller set screw opening can be smaller than would be necessary with rigid materials.  
         [0032]    The legs  94  are preferably attached to the table  20  after the product has been delivered to the point of use. To attach a leg  94 , he hollow, upper end of the leg  94  is fitted around the post  50 . The leg  94  is positioned so that the leg hole  96  is aligned with the set screw  80  in the post  50 . The set screw  80  is then turned causing the movable wall  75  to flex outwardly from the remainder of the post  50  in increasingly forceful engagement with the inner surface of the leg  94 . This force causes the walls of the leg  94  to wrap tightly around the somewhat convex walls of the post  50  in a wedge-like action. The high level of force and high degree of contact between the post  50  and the leg  94  securely attaches the leg  94  to the table  20 . The upper end of the leg  94  is preferably fitted within foam boot  86 .  
         [0033]    The present invention is adapted for attachment of legs to various articles of furniture, such as tables. The leg attachment mechanism may come is various sizes and include brackets of different shapes to fit different types of furniture.  
         [0034]    The above description is that of a preferred embodiment of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents. Any reference to claim elements in the singular, for example, using the articles “a,” “an,” “the” or “said,” is not to be construed as limiting the element to the singular.