Nesting container

Abstract

A plastic container that has a plurality of sides and a bottom with a frustro-pyramidal portion projecting upwardly to a flat surface.

Parent Case Text

This is a continuation of application Ser. No. 76,395 filed Sept. 29, 1970, now abandoned.

Description

BACKGROUND

This invention relates to plastic containers such as might be used, for example, as berry containers. Prior art plastic containers are subject to such defects as flimsiness and weak bottoms. Thus, the bottoms tend to oil can and the container generally tends to split readily. The oil canning caused when the container is filled tends to create splits in the bottom edges where the sides and bottoms join. The bottom corners are also particularly weak because an insufficient amount of plastic flows to those corners when the containers are molded. The top edge or top rim of such containers is another weak area at which splitting tends to occur. This is particularly true at the top corners which are subjected to forces of twisting when the container is used.

Further, because the containers are so flimsy, they are difficult to use. If one attempts to pick up a filled container with one hand, it tends to bend, twist and bow and the material of the container tends to split. Their flimsiness also makes them undesirable for merchandising berries since the berries become crushed when the flimsy containers are handled. This can be overcome by increasing the amount of plastic of which the container is made. However, this increases the expense of the container and makes it uneconomical for many applications.

In the present invention, the bottom of such a molded plastic container comprises a generally cone-shaped portion extending upwardly so as to resist oil canning. In order to resist bottom edge splitting, the juncture between the sides of the container and its bottom are beveled. Similarly, the corners formed by the sides and bottom of the container are beveled. Finally, top splitting is avoided by the provision of a rim including two generally vertical surfaces joined by a horizontal surface.

Thus, this invention provides a plastic container which has far more utility than those which are currently available. Undesirable oil canning, split edges and ruptured corners are minimized. Increased strength is achieved without increasing the amount of plastic used in the container.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of the invention will be seen by reference to the specification and appended drawings wherein:

FIG. 1 is a plan view of the plastic container;

FIG. 2 is a cross section taken along II--II of FIG. 1;

FIG. 3 is a cross section taken along III--III of FIG. 1; and

FIG. 4 is an enlarged view of a top corner of the container.

PREFERRED EMBODIMENT

The container 1 of this invention is preferably formed of biaxially oriented polystyrene, although other plastics could be acceptable. The bottom of the container comprises an upwardly extending cone-shaped portion 30 and a generally flat portion 20. Sides 10 and bottom 20 are joined along beveled edges 60 (FIG. 2) and at beveled corners 50 (FIG. 3). A step-shaped rim 40 (FIGS. 1, 2 and 3) is provided at the top edge of the container.

Cone-shaped portion 30 is preferably frustro-pyramidal in shape, comprising a plurality of flat segments 31 extending upwardly to a generally flat top 32. The segments 31 preferably extend upwardly in a linear fashion rather than extend upwardly along an arc of curvature. The fact that this protrusion is generally cone-shaped provides this construction with considerable resistance to oil canning since the cone tends to resist inversion. The provision of flat segments 31 lends further resistance to oil canning. Because segments 31 are flat, the lateral cross sections of the cone 30 are rectilinear in shape. Thus, an angle is formed between different segments 31 of the cone 30. In order to "oil can" the bottom, one would not only have to invert the angle of the cone, one would have to invert the angles between the flat sides 31. Finally, it is important that the cone-shaped portion 30 comes either to a point or to a generally flat upper surface 32. If upper surface 32 were radiused, it would tend itself to oil can and defeat the purpose of cone-shaped portion 30. Of course, if cone-shaped portion 30 were brought to a point, the point could have a slight radius thereon since this would not provide any substantial surface area which could oil can.

Cone 30 also resists oil canning because it is thicker generally than flat bottom 20. Additionally, cone 30 becomes progressively thicker as it proceeds upwardly, and its thickest portion is top 32. As an example, one of these containers was formed of a 30 mil sheet of plastic draw such that bottom portion 20 had a thickness of seven mils while top portion 32 had a thickness of 12 mils. The thickness of cone 30 approximately half-way up was about 8 mils. This added thickness in the center of the bottom of the container adds considerable strength thereto.

A step or shoulder portion 33 joins cone-shaped portion 30 to flat bottom portion 20 and further tends to minimize oil canning (FIGS. 2 and 3). Shoulder 33 extends upwardly from flat surface 20 and intersects cone 30 at an angle thereto. Preferably, it extends generally vertically upwardly from flat bottom 20. When a downwardly acting force is applied to cone 30, much of it is transmitted to the point of intersection between cone 30 and flat bottom 20. This acts to force cone-shaped portion 30 down through the bottom of the container which the presence of shoulder 33 tends to resist.

Top rim 40 comprises a first generally vertical surface 41 and a second generally vertical surface 43 of smaller circumference with these two surfaces being joined by a horizontal surface 42 (FIGS. 2 and 3). Second vertical surface 43 is then joined to the sides 10 of container 1 by a second generally horizontal surface 44. This step-like construction provides the top edge of the container with considerable resistance to fraying and splitting. It also gives rigidity to the sides 10 of the container and prevents them from bowing laterally outwardly.

The sides 10, first vertical surface 41 and second vertical surface 43 are all radiused i.e., given an arcuate curvature at the corner of the container 1 as is shown in FIG. 4. In order to further strengthen rim 40 at these corners, the radii of first curved surface 41, second curved surface 43 and the curve between sides 10, represented by the letters a, b, and c respectively, are slightly different. Thus, radius of curvature a of first vertical surface 41 is the shortest, while radius of curvature c of sides 10 is the greatest. This minimizes the tendency of the container to bow inwardly or outwardly at its corners and provides resistance to the forces of twisting which would otherwise tear container 1 at these corners.

The sides 10 and bottom 20 are joined at the bottom corners of container 1 at beveled corner 50. Because these corners are beveled, the plastic does not have as far to flow when the container is molded and thus, beveled corners 50 are thicker than are conventional corners. This in itself adds strength to these bottom corners. Further, the bevel provides resistance to twisting forces and thereby further strengthens the bottom corners of the container.

Each separate side 10 is also joined to container 20 along a beveled bottom edge 60. Bevel 60 need not be nearly as pronounced as bevels 50. This provides the bottom edges with resistance against twisting and thereby prevents bottom edge tearing which so frequently occurs in current prior art devices.

Thus, it can be seen that this invention provides a plastic container which is considerably more rigid than prior art containers and yet which can be made with the same amount of plastic. It is resistant to oil canning at its bottom. It is resistant to bulging at its sides. Tearing along the top edges is minimized by a unique stepped rim construction 40. Tearing at the top corners is minimized by providing each step with a different radius. The bottom corners 50 are beveled to provide added thickness and strength to the container. Finally, the bottom edges 60 are beveled to provide resistance to twisting and splitting.

It is understood that the above is merely a preferred embodiment of the invention and that many changes and alterations can be made thereof without departing from its spirit and broader aspects. Further, the theoretical explanations of the manner in which the features of this invention strengthen the container are not meant to be exhaustive and it may well be that these features provide added strength for reasons other than those outlined above.

Claims

What is claimed is:

1. A polygonal, polymeric container having a plurality of sides and a bottom forming a polyhedron, the improvement in said container comprising: a stepped rim at the top thereof formed by first and second generally vertical surfaces joined by a first generally horizontal surface, and a third generally vertical surface joined to said second generally vertical surface by a second generally horizontal surface; said first surface being the outermost, said third surface being innermost and said second surface being intermediate, relative to said container; said first, second and third generally vertical surfaces being curved at the corners of said container, with the radius of curvature for each surface being different whereby collapsing of the container at these corners is resisted.

2. The container of claim 1 in which said first surface has the shortest radius of curvature at each corner and said third surface has the longest radius of curvature at each corner.

3. A polygonal polymeric container having sides and a bottom, said container comprising: said bottom comprising a generally flat portion, a many sided frustro-pyramidal portion projecting upwardly from said generally flat portion, and a generally vertical, upstanding annular shoulder wall joining said flat bottom portion and the sides of said many sided frustro-pyramidal portion; the sides of said frustro-pyramidal portion being flat side segments, the number of which exceeds the number of sides for said container; said shoulder wall being disposed at a definite angle to the sides of said frustro-pyramidal portion and to said flat bottom portion, the angle between said flat side segments of said frustro-pyramidal portion and said shoulder wall being less than 180.degree. on the interior of said frustro-pyramidal portion, whereby the combination of said generally vertical shoulder wall and said frustro-pyramidal portion resists inversion of the container bottom with filling of the container.

4. The polymeric container of claim 3 in which the top perimeter of the container comprises a stepped rim formed by first and second generally vertical surfaces joined by a generally horizontal surface and the sides of said container being joined to said second vertical surface by another generally horizontal surface; said first and second vertical surfaces and the juncture of said sides being curved, with the radius of curvature for each of said first, second and side juncture surfaces being different; said first surface having the shortest radius of curvature and said side surface juncture having the longest radius of curvature.

5. The polymeric container of claim 4 which comprises a polyhedron, the corners formed by the intersection of adjacent ones of said sides and said bottom of said container being beveled.