Receptacles – End wall structure – One-piece side and end wall
Patent
1994-11-30
1996-02-20
Moy, Joseph M.
Receptacles
End wall structure
One-piece side and end wall
B65D 634
Patent
active
054922453
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a container of thermoplastic material for containing liquids. The container is designed so as to resist bulging.
BACKGROUND OF THE INVENTION
It is well known in the art to use thermoplastic materials to manufacture containers for liquids. Some of the liquids to be contained by such containers, for instance bleach-containing compositions, create internal pressure which builds up with time. In such cases, the containers are progressively subjected to deformation due to the internal pressure build-up, especially at their base. This phenomenon is often referred to as "bulging". This phenomenon is especially acute in warm countries where the containers may be exposed to particularly elevated temperatures. In some instances, bulging can be so severe so as to induce a base deformation which is such that the container can no longer stay in upright position. For instance in supermarkets, the containers may fall of the shelves.
Anti-bulging containers have been disclosed in the art, for instance in DE 16 07 895, DE 21 11 534, EP 0 002 082 and our co-pending European Application EP 91202524. These references disclose containers having a central dome, where the dome is connected to the side walls of the container by pieces of thermoplastic material of various shapes. It is therefore an object of the present invention to provide a container of thermoplastic material for containing liquids with improved resistance to bulging.
It is also an object of the present invention to provide a solution to bulging which is particularly applicable to containers of smaller size.
The problem of bulging can to some extent be addressed by increasing the quantity of thermoplastic material used, so as to manufacture a container with thick walls. However, this solution is quite objectionable from an environmental point of view as well as from an ease of manufacturing viewpoint. It is therefore an another object of the present invention to provide an anti-bulging container of thermoplastic material having walls of minimum thickness.
SUMMARY OF THE INVENTION
The present invention is a container (1) of thermoplastic material comprising a side wall (2) and a base (3), said base comprising, in a cross section in a plane comprising the container's vertical axis (A), a concave inwards curved section (4) connected to the side wall (2), at least two successive stairs, each stair consisting of a straight part (5,5') forming an angle (.alpha.1, .alpha.2) with a plane (B) perpendicular to said axis (A), followed by a sharp concave outwards curve (6,6'), and a dome (8) consisting of a smooth concave outwards curve. The base (3) of the container (1) is symmetrical about said axis (A).
DETAILED DESCRIPTION OF THE INVENTION
The container according to the invention is made of a thermoplastic material. Such materials have been extensively described in the art and include vinyl chloride based resins, polymers and copolymers derived from olefins, acrylic polymers and copolymers, polyethylene, polypropylene, polystyrene, polyethylene terephthalate, polyethylene terephthalate glycol, or mixtures thereof. The container can be made by single or multi layer extrusion of such materials. It can also be made out of recycled thermoplastic materials. A preferred thermoplastic material for use herein is polyethylene.
The cross section of the container according to the present invention, and/or its base, in a plane perpendicular to the container's vertical axis (A), can be square or rectangular, ovoid or circular. Furthermore, the base (3) of the container according to the present invention is symmetrical about said axis (A). In a preferred embodiment of the invention, said cross section is circular. The present invention is particularly suitable for containers of rather small size, i.e. where the container's largest dimension in said cross section is less than 10 cm.
The following description refers to FIG. 1 which represents the lower part of the container in a cross section in a plane comprising the co
REFERENCES:
patent: 3409167 (1968-11-01), Blanchard
patent: 4120419 (1978-10-01), Saunders
patent: 4147271 (1979-04-01), Yamaguchi
patent: 4177746 (1979-12-01), Lee, Jr. et al.
patent: 4408698 (1983-10-01), Ballester
patent: 4542029 (1985-09-01), Caner et al.
Kock Ronald W.
Moy Joseph M.
Reed T. David
The Procter & Gamble & Company
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