US3467741A - Method of making a shelf front - Google Patents

Description

K. K. KEsLlNG METHOD OF MAKING A SHELF FRONT Filed NOV. 17. 1967 5f 40 fz LQ z/t sept. 16,1969

/ /ia/A T'TOR/VEY United States Patent O 3,467,741 METHOD F MAKING A SHELF FRONT Keith K. Kesling, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Nov. 17, 1967, Ser. No. 684,049 Int. Cl. B29c 17/04 U.S. Cl. 264-92 2 Claims ABSTRACT 0F THE DISCLOSURE In the preferred process, a suitable plastic sheet is positioned over a vacuum forming mold Ihaving projections for `forming shelves and forming bars, around which a shelf front is formed, which are Iremovable from the mold. The sheet is heated and lwhile being heated is drawn onto the mold and around the forming bars. When the plastic sheet is removed from the mold, the forming bars remain enveloped in the plastic sheet as reinforcing bars in the shelf front.

This invention relates to a method of forming insulated doors having plastic sheet inner walls provided with door shelves.

It is customary to make refrigerator doors with plastic inner walls. Shelves have been added in various ways such as are shown in the Saunders Patent No. 2,837,816 issued June 10, 1958. It is not unusually difficult to provide integral shelves but the shelf fronts have been in the form of attached pieces.

It is an object of this invention to provide a simple, inexpensive process for vacuum forming an integral sheet plastic shelf and shelf front in the inner wall of a door.

It is another object of this invention to provide a simple, inexpensive process for vacuum forming an integral sheet plastic shelf and shelf front in which a forming bar is removable from the mold and remains enveloped in the shelf front and serves as a reinforcement.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

FIGURE 1 is a vertical sectional view illustrating the first step in vacuum forming the inner wall of a door with integral shelves and shelf fronts embodying one form of my invention;

FIGURE 2 is a vertical sectional view similar to FIG- URE 1 showing the completion of the vacuum forming process;

FIGURE 3 is an enlarged sectional view showing the completed form of the shelf front;

FIGURE 4 is a fragmentary perspective view showing one of the integral completed lshelves with an integral shelf front; and

FIGURE 5 is a vertical sectional view through the completed door.

Referring now to FIGURE 1, there is shown a plastic sheet which is to be formed into the inner wall of an insulated door. The sheet 20 may be of ABS copolymer or polypropylene, for example. A vacuum forming door mold 22 rests upon the support 24. This vacuum forming mold includes a relatively thick perimeter portion 26 which extends around a thin Wall portion 28 provided with substantially uniform perforations 30. The upper face of the mold 22 is provided with two shelf forming projections 30 and 32 which extend between the wide portions 34, 36 of the side perimeter 26. The portions 34 and 36 of the perimeter portions 26 which extend to the left of the prolCC jections 30 and 32 are made of a width or height equal to the height or protrusion of the shelf forming projections 30 and 32.

According to my invention, each of these portions 34 and 36 are provided with notches 38 and 40 which receive and normally removably hold the rectangular wooden sticks 42 and 44. The sheet 20 is clamped at its edges between the turned down peripheral portion 46 of the rectangular holder 48 and an open rectangular member 50 which is clamped to the upper portion of the holder 48. The sheet holding member 48 may be provided with a plurality of infrared lamps 52 which are energized to heat the sheet 20 of plastic causing the plastic to be stretchable and formable. As the plastic 20 is heated, a valve 54 is opened to apply a vacuum to the space or chamber 56 located lbetween the support 24 and the perforated wall 28 of the mold 22. A pipe 58 forms a connection between the valve 54 and the chamber 56. The valve 54 connects to a vacuum pipe 60.

As the vacuum is drawn, the holder 48 is gradually lowered and the sheet of plastic is drawn into the large space between the shelves 30 and 32 by the vacuum drawing air through the perforations 30. The plastic is heated and drawn by the differential in pressure thereon until the plastic sheet 20 envelopes the shelf forming projections 30 and 32 and is also completely around the sticks comprising the reinforcing members 42 and 44 which form separate folds in the plastic sheet 20. These sticks 42 and 44 are completely surrounded in the adjacent folds by the plastic sheet 20 and between each of the sticks 42 and 44 and the adjacent shelf projections 30 and 32 the plastic sheet 20 comes into substantial flat contact 66. This forms a pleasing shelf front as is shown in FIG- URE 4. The plastic also envelops both sides of the shelf forming projections 30 and 32.

Before the completion of the vacuum forming operation, the infrared lamps 52 are extinguished and the sheet plastic 20 forming'the inner wall is removed from the mold 22 along with the sticks or reinforcing members 42 and 44 which are enveloped in the folds forming the shelf fronts. The completed shelf structure is illustrated in FIG- URE 4. The completed door is illustrated in FIGURE 5 in which the inner wall is designated by the reference character 70.

The periphery of this inner wall membe-r 70 is fitted within a notch extending longitudinally in the bottom 72 of the magnetic door seal 74. The outer sheet metal wall 76 has a peripheral edge 78 provided with an inturned flange 80 extending within the interior and fitting against the bottom of the magnetic door seal 74 to hold it in place. The space between the formed inner wall 70 and the outer wall 76 is preferably filled with polyurethane foam insulation 82 preferably containing an insulating gas. This foam insulation fills the hollow space formed by the shelf projections 30 and 32 to form the reinforced shelves 84 and 86. The foam insulation adheres to the outer metal wall 76 and the inner plastic wall 70 and is rigid enough to substantially reinforce the shelves. These shelves are furt-her reinforced by the integral shelf fronts 66 immediately above wherein the two sheets of plastic are directly in Contact. These shelves 84 and 86 are also reinforced by the reinforcing members 42 and 44 in the form of the sticks which are enveloped by the folds of the plastic sheet 20. By forming the shelf fronts 66 by enveloping the reinforcing sticks 42 and 44 which are -removable from the mold 22, two integral shelf fronts are provided which are formed each by a fold of the sheet of plastic 20, as an integral part thereof. By this integral arrangement, the hollow shelf portions 84 and 86 are reinforced by the shelf fronts 66 and the reinforcing bars or sticks 42 and 44. The polyurethane foam 82 is relatively stili and strong even though it is of light weight. It has suicient adhesiveness to prevent the separation of the inner and outer Walls.

While the embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.

I claim:

1. The method of forming a shelf and shelf front into a plastic sheet which includes providing a mold having a projection forming member over which the shelf is to be formed, supporting a removable reinforcing member in a selected location relative to said projection forming member and a cavity of the mold, placing a plastic sheet over said projection forming member and reinforcing member, heating the plastic sheet and during said heating of the plastic sheet applying a difference in pressure to opposite sides of the sheet to cause the sheet to envelope the reinforcing member and conform to said cavity and projection forming member to form a shelf and shelf front, and removing the plastic sheet with the enveloped reinforcing member therein from said projection forming member.

2. The method of forming an inner door panel with an integral shelf and shelf front which includes providing a door shaping form having a plurality of shelf forming projections and also having supports for reinforcing members ,4 located in a desired relationship to said shelf forming projections, placing reinforcing members onto said supports, placing a plastic sheet substantially against said door shaping form and substantially against said shelf forming pro jections and said reinforcing members, heating the plastic sheet and during said heating applying a difference in pressure to opposite sides of the sheet to cause the sheet to form folds enveloping said reinforcing members and conforming to said shelf forming projections to form an inner door panel with integral shelves and shelf fronts, and removing the plastic sheet with the enveloped reinforcing member therein from said form.

References Cited UNITED STATES PATENTS 6/1956` Jewell et al 264-90 X 2/ 1967 Scott.

U.S. Cl. X.R.

l8-l9, 35; 264-275; S12- 138, 214

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