Abstract:
An article support such as a shelf or a table top has a frame that, in its heated state, slidably receives a glass or plastic planar sheet into grooves along two opposing edges of the frame, until an end of the sheet abuts a third edge of the frame that joins the two opposing edges. The edges of the frame have lips that rest on a portion of the top surface of the sheet. When cooled, the frame contracts such that the edges of the sheet are tightly engaged within the grooves of the frame and the lips tightly abut the top surface of the sheet, thereby creating an article support that resists spills around its periphery. The frame may be reheated to expand the material of the frame, permitting removal of the sheet from the frame. Thus, the frame and the sheet may be recycled.

Description:
This application is a division of Ser. No. 09/016,486 filed Jan. 30, 1998, now U.S. Pat. No. 6,045,101. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to article supports, such as shelves and table tops, and more particularly, to an article support that is generally spill-resistant and to a method for producing such an article support. 
     BACKGROUND OF THE INVENTION 
     Article supports include shelves and table tops which may be used to support a variety of items. Conventionally, cabinets and appliances, such as hospital cabinets, kitchen cabinets and refrigerators, have multiple shelves for storing items, including liquids such as medicines, food, and beverages, vertically upright. Typically, such shelves extend between two interior upstanding appliance or cabinet walls, and are generally level. Tables, such as kitchen tables, have a table top which is a horizontal surface that can support a variety of items, including liquids such as food and beverages. Typically, such table tops are supported by three or more vertical legs to maintain them in a horizontal position, a suitable distance from the floor. 
     Article supports may be made of a tempered glass sheet surrounded by a plastic or metal frame. Items are placed on the top surface of the sheet portion of such article supports. When liquid spills on one of the article supports, it may not be confined to that article support and may overflow from the article support at its edges. The frame surrounding the sheet is often designed to limit this overflow, so that small spills can be trapped at the frame. However, even with small spills, liquid often leaks through the junctures between the sheet and the frame and spills to the shelf or floor below it. It is therefore desirable to prevent leaking of liquid from the top surface of such shelves at the juncture between the sheet and the frame, providing a shelf with improved spill resistance. 
     Framed article supports are typically manufactured either by pre-manufacturing a frame and dropping the glass in the frame (the “drop in glass method”) or by moulding a frame directly about a glass sheet (the “encapsulation method”). 
     In the “drop in glass method”, the front, rear and side portions of a metal or plastic frame are first individually extruded from metal or plastic. These frame portions are then attached to form a frame, and a tempered glass sheet is slid freely into the frame to create the article support. As there is no chemical or mechanical bond between the top surface of the sheet and the frame, article supports made by this method are not very spill-resistant. Also, such frames lack integrity and often come apart, as the frame portions are attached together. 
     In the “encapsulation method”, a tempered glass sheet is secured in a plastic injection mould. A hot melt of resin is then moulded around the edge of the glass and is permitted to cool to create the framed article support. As will be appreciated, the resin forms a tight bond with the glass sheet near its edges, by adhering to the glass. Although this may produce an article support that has increased spill-resistance, it does not permit easy removal of the glass from the frame to permit recycling of the frame and the glass, should the sheet or frame break. Moreover, this method requires an injection mould particularly suited to seat a glass sheet. Additionally, this method results in significant glass breakage, of up to approximately 30%, during the manufacturing process. As will be understood, this waste increases the overall production costs of such article supports, causes an occupational hazard, and raises environmental concerns. Finally, as the glass sheet is superheated at its perimeter and placed under extreme pressure during the injection moulding process, the resulting article support may be weak and prone to break, in use. 
     The present invention attempts to overcome some of the disadvantages associated with known article supports, and methods for producing such article supports. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an improved spill-resistant article support and method for producing such an article support. 
     In accordance with one aspect of the present invention there is provided a spill-resistant article support comprising a generally planar sheet having a flat top surface; a frame receiving said sheet, said frame comprising: first and second opposing side members each defining a lengthwise extending groove; said grooves receiving opposing edges of said planar sheet; said first and second side members each comprising a side lip; each said side lip covering a portion of said top surface; a front member, extending between said side members and in abutment with an end of said sheet; said front member comprising a front lip; said front lip covering a portion of said top surface; said side lips meeting said front lip such that said lips extend continuously along a periphery of said sheet; said frame comprised of heat sensitive material; said material adapted to expand at a first temperature so that said sheet is freely slidable within said grooves for easy removal of said sheet from said frame; said material further adapted to contract at a second temperature so that said edges of said sheet are tightly engaged within said grooves and said side and front lips tightly abut said top surface to inhibit spillage of liquids from said top surface at said periphery. 
     In accordance with another aspect of the present invention there is provided a method for producing a spill-resistant article support comprising the steps of: a. moulding a frame using heated plastic, said frame comprising first and second opposing side members each defining a lengthwise extending groove; said first and second members each comprising a side lip; said frame further comprising a front member, extending between said side members; said front member comprising a front lip; said side lips meeting said front lip such that said lips extend continuously along a perimeter of said frame; b. allowing said frame to partially cool and sufficiently harden to withstand insertion into said grooves of a planar sheet having a thickness less than that of said grooves; c. sliding said generally planar sheet into said grooves until an end of said sheet abuts said front member such that said frame receives edges of said planar sheet and said side and front lips cover a portion of said top surface; d. cooling said frame and said sheet, thereby permitting said frame to contract so that said edges of said sheet are tightly engaged within said grooves and said side and front lips tightly abut said top surface of said planar sheet. 
     In accordance with yet another aspect of the present invention there is provided a method of disassembling an article support, said article support comprising: a generally planar sheet; a frame receiving said sheet; said frame comprising first and second opposing members each defining a lengthwise extending groove; said grooves receiving opposing edges of said planar sheet; said edges of said sheet tightly engaged within said grooves of said frame; said frame made of a heat sensitive material and having a slot, comprising the steps of: a. heating said article support, so that said heat sensitive material expands so that said sheet is freely slidable within said grooves of said frame; b. removing said sheet from said frame through said slot. 
     The present invention provides a spill-resistant article support and a method for producing such an article support. As the method does not require superheating of the sheet and subjecting the sheet to high pressure, glass breakage may be minimized. The resulting article support maintains its integrity in the finished product. Also, should either the frame or sheet portion of the article support break, recycling of either element is permitted, as the sheet may be easily removed by warming the frame. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING: 
     In figures which illustrate preferred embodiments of the invention, 
     FIG. 1 is a perspective view of a shelf from above; 
     FIG. 2 is a further perspective view of the shelf of FIG. 1, from below; 
     FIG. 3 is a cross-sectional view taken along line III—III of FIG. 1; 
     FIG. 4 is a cross-sectional view taken along IV—IV of FIG. 1; 
     FIG. 5 is a cross-sectional view taken along V—V of FIG. 1; 
     FIG. 6 is an enlarged perspective view of a portion of the shelf of FIG. 1; 
     FIG. 7 is a cross sectional view taken along VII—VII of FIG. 1; and 
     FIG. 8 is a further view of FIG.  7 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 and 2 illustrate a shelf  20  exemplary of an article support in accordance with the invention. Shelf  20  comprises a rectangular sheet  22 , enclosed around its periphery by a frame  21 . Sheet  22  is planar, made of tempered glass, and has a generally flat top surface  18  and a generally flat bottom surface  19 . 
     Frame  21  comprises a front frame member  23 , side frame members  25   a ,  25   b , and a rear frame member  27 . Front frame member  23  and rear frame member  27  are of equal length. The side members  25   a  and  25   b  are also of equal length, and extend at right angles from the ends of front and rear frame members  23  and  27 . The front member  23  and rear member  27  are longer than the side members  25   a  and  25   b , making frame  21  generally rectangular in shape, complementary to sheet  22 . 
     Side frame member  25   a  has a generally backward S-shaped cross-section, proximate rear frame member  27 , as best illustrated in FIG.  3 . The upper leg of the backward S-shaped cross-section terminates in a lip  28   a . The top half of the backward S-shaped outline defines a groove  50  in side frame member  25   a  which receives a side edge of sheet  22 . The bottom portion of the generally backward S-shaped outline defines a mounting channel  54 . Thus channel  54  is directly below groove  50 . As described below, channel  54  permits mounting of shelf  20  within a cabinet or appliance. 
     As illustrated in FIG. 2, channel  54  only extends partway from rear frame member  27  toward front frame member  23 , along side member  25   a  Thus, in cross-section, side member  25   a  is generally C-shaped proximate front member  23 , as illustrated in FIG.  4 . As seen in FIGS. 1,  3  and  4 , lip  28   a  extends continuously along side frame member  25   a  from rear frame member  27  to front frame member  23 . Side frame member  25   b  is a mirror image of side frame member  25   a.    
     The cross-section of front frame member  23  along the majority of its length is illustrated in FIG.  5 . As shown, the outer frontmost portion  24  of front frame member  23  is bevelled and downwardly sloped the entire length of front frame member  23  (see FIG.  1 ), such that the front portion  24  of front member  23  has a smooth, rather than a sharp, edge to prevent injury when placing items onto or removing items from shelf  20 . A lip  30  extends rearwardly from front portion  24 . An abutting wall  32  extends vertically downward at the intersection of lip  30  and front portion  24  of front frame member  23 , to abut a front edge of sheet  22  at a right angle. A bottom ledge  34 , extends from wall  32  below, and in a direction parallel to, lip  30  so that sheet  22  is received between lip  30  and ledge  34  and is in abutment with wall  32  such that sheet  22  is supported at its front edge by ledge  34 . As illustrated in FIG. 2, ledge  34  is discontinuous near the mid-point of front frame member  23 . 
     As illustrated in FIGS. 7 and 8, rear frame member  27  is comprised of a lower portion  40  and an upper portion having a rear lip  36  and a back  44  extending upwardly therefrom. Lower portion  40  has a flat top surface. The bottom of lower portion  40  has a lengthwise extending groove  61  proximate the rear edge of lower portion  40 , which will be further described below. The width of lower portion  40  (the distance between the rear edge and the inner edge) approximates that of lip  36 . Lower portion  40  and the upper portion extend between side members  25   a  and  25   b  and are spaced to define a slot  46 . Slot  46  has a height approximately equal to the thickness of sheet  22 . Back  44  creates a rear bumper for shelf  20 , which is eventually pushed into abutment with a rear cabinet or appliance wall (not shown). Back  44  may prevent scratching of the rear wall, acts as a stop, and prevents spillage onto the rear wall of the cabinet or appliance. 
     As best illustrated in FIG. 1, lip  30  of front frame member  23 , lips  28   a  and  28   b  of side frame members  25   a  and  25   b , and lip  36  of rear frame member  27  extend continuously along the entire periphery of sheet  22 . Lips  28   a ,  28   b ,  30 , and  36  extend from the outer edge of front, side, and rear frame members  23 ,  25   a ,  25   b , and  27  towards the centre of the sheet  22 . The width of the lips  28   a ,  28   b ,  30  and  36  is approximately five and one-half times the thickness of sheet  22 . Lips  28   a ,  28   b ,  30 , and  36  extend lengthwise substantially the entire length of the side members  25   a  and  25   b , front member  23 , and rear member  27 , respectively. The top face of lips  28   a ,  28   b ,  30 , and  36  slope downwards as these lips extend away from the edges of sheet  22  toward the centre of the sheet  22 , thus inhibiting spill over the lips. 
     Additionally, as illustrated in FIGS. 1,  2  and  6 , a centre rail  48  extends at a right angle from approximately the mid-point of front member  23  to rear member  27 . Rail  48  is in contact with bottom surface  19  of sheet  22 , and provides support for a load placed on top surface  18 . The width of rail  48  approximates the width of side members  25   a  and  25   b.    
     As shown in FIGS. 6-8, a cover  56  is pivotally attached to the outside portion of the upwardly extending back  44  of rear frame member  27 . Cover  56  extends along the entire length of rear member  27 , to cover slot  46  in closed, forwardly pivoted position (FIG.  8 ). In a raised position, as best illustrated in FIGS. 6 and 7, cover  56  exposes slot  46  in rear member  27 , for insertion and removal of sheet  22 , as described below. Cover  56  may be pivoted in the direction “A” (FIG. 7) through an arc of approximately 110° to open and close cover  56 . Cover  56  is integrally formed with back  44  of rear member  27 . The pivotal movement of cover  56  is achieved by decreasing the thickness of the plastic at the juncture between the cover  56  and back  44  of rear member  27 , allowing the material (typically plastic) at this juncture to be flexible, and thus forming a hinge. At its free end, away from back  44 , cover  56  has a hooked edge  60  which extends along its entire length. The lower flat portion  40  of rear member  27  has a complementary groove  61  which extends the entire length of rear member  27 , and engages hooked edge  60 , when cover  56  is in its closed position (FIG.  8 ). Cover  56  is latched in place by snapping hooked edge  60  into corresponding groove  61 . 
     Frame  21  is integrally formed of a heat sensitive injection-moulded material. The material is preferably plastic with a specific gravity of approximately 1.04. The plastic may be a copolymer polypropylene with an approximately ten percent talc additive and may be recycled. 
     Shelf  20  is manufactured by first plastic injection moulding frame  21 . Frame  21  is formed using a single mould made of P 20  tool steel and conventional injection moulding techniques. Molten plastic is forced under pressure into an injection mould having a cavity  20  adapted to form the above described frame  21 , at a temperature of approximately 370° F.-400° F. and a pressure of approximately 1600-1800 psi. The resin is then allowed to cool slightly ie. to approximately 120°, until frame  21  is sufficiently hard to withstand insertion into its grooves of a planar pre-cut sheet  22 . The thickness of the grooves is greater than that of sheet  22 . Frame  21  is then removed from the mould and placed onto a fixture. Sheet  22 , having dimensions suitable for frame  21 , is then slid into the frame  21  through slot  46  of rear member  27 , into the grooves  50  of the side member  25   a  (and a corresponding groove in side member  25   b ), until the front edge of sheet  22  rests in abutment with wall  32  of front member  23 . Cover  56  is then rotated as shown in FIG. 7 into its latched position with hooked edge  60  engaging slot  61  as shown in FIG. 8, closing the slot  46 . Shelf  20  is then placed on a cooling aid. Frame  21 , upon cooling, contracts such that the groove  50  in side frame member  25   a  and the corresponding groove in side frame member  25   b  shrink, causing the lips  28   a  and  28   b  to tightly abut the top surface  18  of sheet  22  around its periphery. Front frame member  23  contracts causing ledge  34  and lip  30  to tightly abut sheet  22 . Rear frame member  27  similarly contracts, narrowing slot  46 , pushing bottom portion  40  and lip  36  of rear frame member  27  into abutment with sheet  22 . Contraction ceases after approximately forty-eight hours. This results in a substantially spill-resistant shelf  20 . The heat sensitive material of which frame  21  is formed shrinks linearly in all directions by a factor of approximately 0.013 to 0.016 per inch, as frame  21  cools to room temperature. 
     In use, shelf  20  may be inserted in a cabinet or appliance (not shown). Tracks on the inner walls of the cabinet or appliance engage channels  54 , to support shelf  20  so that the top surface  18  of sheet  22  may support food, medicine, drink, etc. Shelf  20  is slid into the cabinet or appliance with rear frame member  27  leading, until the back  44  abuts the back wall of the interior of the cabinet or appliance. Centre rail  48  may be used to slide shelf  20  in and out of the cabinet or appliance along the support tracks. 
     In the event that a small amount of liquid is spilled on top surface  18  of shelf  20 , the liquid may spread toward front, side and rear edges of sheet  22 . However, because of the outwardly upward slope of lips  28   a ,  28   b ,  30  and  36 , small amounts of liquid are unlikely to spill over these lips. Additionally, as the entire frame  21  has contracted to tightly engage sheet  22 , the juncture between lips  28   a ,  28   b ,  30  and  36  and the corresponding portions of top surface  18  should be virtually impermeable to liquids. The spilt liquid is thus trapped on top surface  19 , by lips  28   a ,  28   b ,  30  and  36 . As such, spilt liquid may easily be cleaned from the shelf  20 . 
     If sheet  22  or frame  21  should break, the cover  56  may be snapped open thereby exposing slot  46 . Shelf  20  may then be re-heated to approximately 120° F. to 140° F. using the radiant heat of light bulbs or a hot air appliance, thereby expanding fame  21  linearly about sheet  22  so that groove  50 , the corresponding groove in side member  25   b , and the gap between lip  30  and ledge  34  widen. This, in turn permits easy removal of sheet  22  from frame  21  through slot  46 . The broken portion, sheet  21  or frame  22  as required, of shelf  20  may then be replaced and recycled. Depending on the working environment, frame  21  may need to be reheated several times in order to properly remove and replace sheet  21  or frame  22 . This warming step does not cause frame  21  to lose its shape or ability to grip sheet  22 , after replacement and cooling. 
     A person skilled in the art will recognize that numerous modifications to the above described embodiments are possible. For example, the material used to create the frame may be varied, provided it can expand upon heating and contract upon cooling, within an appropriate range of shrinkage. The dimensions and shape of sheet  22  may also be varied. Sheet  22  need not be rectangular, but may be oval or square. Cover  56  need not be pivotally attached to rear member  27 , but may be created independently of the frame  21  and suitably attached. Lip  34  of front member  23  is not necessary. Also, the elements of the frame need not be integrally formed, as long and the formed frame expands and contracts to engage sheet  22 . Centre rail  48  need not extend at a midpoint of front or rear member  23 ,  27 ; several or no support rails could be used. As well, back  44  could be eliminated. 
     A person skilled in the art will also appreciate that by eliminating channels  54 , centre rail  48 , and back  44  of the shelf described above, a table top in accordance with the invention may be created. 
     Numerous other modifications, variations, and adaptations may be made to the particular embodiments of the invention described above without departing from the spirit and scope of the invention, as defined by the claims.