Method of forming an article support

Information

  • Patent Grant
  • 6773651
  • Patent Number
    6,773,651
  • Date Filed
    Thursday, March 9, 2000
    24 years ago
  • Date Issued
    Tuesday, August 10, 2004
    20 years ago
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




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.



Claims
  • 1. 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, and a rear member said front member and said rear 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, said rear member comprising a slot, providing a passage way to said grooves; b. allowing said frame to partially cool and sufficiently harden to withstand insertion into said grooves of a planar sheet having a top surface and a thickness less than that of said grooves; c. sliding said generally planar sheet through said slot 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; and e. covering said slot with a cover after said sheet has been inserted into said frame.
  • 2. The method of claim 1 wherein step a. comprises injection moulding said frame.
  • 3. The method of claim 1 wherein said frame is moulded at temperatures between approximately 370° F. and 400° F.
  • 4. The method of claim 1 wherein said moulding is preformed in a mould and wherein said method further comprises removing said frame from said mould prior to step c.
  • 5. 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 and a rear member, said front member and said rear 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, said rear member comprising a slot; b. allowing said frame to partially cool and sufficiently harden to withstand insertion into said grooves of a planar sheet having a top surface and a thickness less than that of said grooves; c. sliding said generally planar sheet through said slot 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, thereby forming a liquid-impermeable interface between said frame and said top surface of said planar sheet.
  • 6. The method of claim 5 wherein step a. comprises injection moulding said frame.
  • 7. The method of claim 5 further comprising covering said slot with a cover after said sheet has been inserted into said frame.
  • 8. The method of claim 5 wherein said frame is moulded at temperatures between approximately 370° F. and 400° F.
  • 9. The method of claim 5 wherein said moulding is preformed in a mould and wherein said method further comprises removing said frame from said mould prior to step c.
  • 10. The method of claim 5 wherein said planar sheet comprises a glass sheet.
  • 11. The method of claim 5 wherein said frame contracts linearly in all directions by a factor of approximately between 0.013 to 0.016 per inch as said frame cools.
Parent Case Info

This application is a division of Ser. No. 09/016,486 filed Jan. 30, 1998, now U.S. Pat. No. 6,045,101.

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6210618 Bird et al. Apr 2001 B1
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Number Date Country
0 613 766 Sep 1994 EP