Sealing surfaces for container end panels

Abstract

A tubular container is provided with an angled sealing surface extending outwardly and downwardly around the upper periphery of the container. A flexible end panel, such as plastic film, metal foil, or thin plastic, or coated paper stock is heat or adhesively sealed to the angled surface of the container. This combination of container and end panel is particularly effective for food products and the like that are subjected to heat treatment, such as in a retort, following a filling operation of the container and sealing of the end panel thereto. The angled sealing surface retains the end panel in shear, rather than in peel, as the end panel bulges upwardly because of increased internal pressure. The integrity of the seal, at the interface of the container and the overlying end panel, is greatly enhanced.

Description

FIELD OF THE INVENTION

The invention relates to containers of the type used for packaging food products and the like and, more particularly, to the shape of sealing surfaces on or at the ends of containers for accommodating the application of closures in the form of end panels for sealing the containers.

BACKGROUND OF THE INVENTION

End closures, or end panels, or lids, for containers expand or bulge axially outwardly from a container during a retort operation wherein fluids contained therein expand and create internal pressure. Particularly with flexible end panels, i.e., usually films, foils, or thin plastic closures and the like, and more particularly with such closures that are heat-sealed or adhesively secured to the peripheral rim of the container, increased pressure and the resultant outward bulging of the end closure is likely to cause leaks or ruptures in the seal. Any such leaks, ruptures, discontinuities, and the like are highly undesirable because they will very likely result in contamination and spoilage of the products.

SUMMARY OF THE INVENTION

An important feature of the invention relates to its use for preventing damage to the container seal with containers formed of molded or extruded plastic, of the type referred to as tubs or bowls, which are subjected to being heated to treat the container contents, such as in a retort.

The present invention provides very substantial improvements in the securing of end panels to containers and reduces potential damage to heat-seals or adhesive seals during and after retort operations. Instead of a rounded, or beaded, or horizontally disposed sealing surface at the upper end of a container of the type known in the prior art, the invention provides a substantial, peripheral sealing area, and more particularly one wherein the sealing surface extends radially outwardly and downwardly at an inclined angle for placing the end panel and sealing surface of the container in shear, rather than in peel, during a retort operation thereby minimizing or precluding development of pin hole leaks or tears in the seal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a prior art example of a container having an end panel secured to the top end thereof.

FIG. 2 is an enlarged, fragmentary, sectional view taken on line 2-2 of FIG. 1.

FIG. 3 is a perspective view of a container having an end panel secured at the top thereof in accord with the present invention.

FIG. 4 is an enlarged, fragmentary, sectional view taken on line 4-4 of FIG. 3.

FIG. 5 is a fragmentary sectional view wherein the container flange, as is shown in FIG. 4, has an upper surface that is partially inclined and also partially horizontal, and the underside of the flange includes a horizontal portion, the container flange and end panel portion being shown disposed between operating surfaces of a sealing tool that has complementary faces to correspond to the contour of the container flange.

FIG. 6 shows the container and end panel portions separately from the tool of FIG. 5, the end panel and container being shown lightly spaced for clarity.

FIG. 7 is a fragmentary, sectional view showing an angled flange of a container topped by an end panel and disposed between two operating faces of a sealing tool.

FIG. 8 shows the container and end panel portions separately from the tool shown in FIG. 7, the end panel and container being shown slightly spaced for clarity.

FIG. 9 is a fragmentary sectional view of a container flange and end panel wherein the angled flange/sealing area is located inwardly from the outer edge of the flange portion.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides for improved sealing of container bodies and end panels to overcome the deficiencies in prior art devices of the type shown in FIGS. 1 and 2 wherein a known type of plastic container, generally indicated by the numeral 10, includes a tubular side wall 12 having an outwardly extending flange 14 with a horizontal upper sealing surface 16 having an end panel 18 sealed thereto for closing the container and protecting the container contents (not shown.)

As is best shown in FIG. 2, when container 10 is subjected to a retort operation, pressure builds within the container and causes end panel 18 to bulge or expand upwardly thereby creating the possibility that the end panel 18 will peel from the flange 14 resulting in a defective product.

The present invention overcomes the shortcomings of the prior art discussed above and shown in FIGS. 1 and 2.

As is shown in FIGS. 3 and 4, a plastic container, generally indicated by the numeral 20, includes a tubular side wall 22 terminating at its upper periphery in an outwardly extending flange 24 which is somewhat trapezoidal in shape and includes a horizontal lower surface 25. Flange 24 further includes an outwardly and downwardly extending sealing surface 26 and an uppermost top sealing surface 28. An end panel 30, which may be a film, or foil, or thin plastic lid or the like, has a peripheral portion 32 heat-sealed, or adhesively sealed, etc., to the downwardly angled surface 26 and top sealing surface 28 of flange 24.

As is shown in FIG. 5, container flange 24 and the peripheral portion 32 of end panel 33 are acted upon by jaws 40 and 42 of a sealing tool, generally indicated by the numeral 44, to either heat-seal, or adhesively seal, peripheral portion 32 to the sealing surfaces 26 and 28 of flange 24.

As best shown in FIG. 6, end panel 30 is caused to expand or bulge upwardly to the dotted line position as the result of increased internal pressure. It is a feature of the invention that the outermost peripheral portion 32, of end panel 30, remains adhered to the angled sealing surface 26 of flange 24 because the surfaces are in shear, rather than in peel, as shown in the prior art embodiment of FIG. 2. As a result, containers utilizing the present invention are not likely to develop leaks at the interface between the end panel 30 and the container flange 24.

FIGS. 7 and 8 show a further embodiment of the invention wherein a container wall 122 includes a flange portion 124 that is sealed by sealing jaws 140 and 142 of a sealing tool 144. This embodiment differs from that of FIGS. 5 and 6 in that an undersurface 125 of flange 124 is conventionally angled upwardly rather than horizontal as surface 25 of container 20. Accordingly, the faces of jaws 140 and 142 need to be shaped at corresponding angles to assure proper sealing, FIG. 8 shows the end panel 130, in the dotted line position, has its peripheral portion 132 disposed in shear with the angled surface 126 of flange 124. Here again, as in FIG. 6, the end panel 132 and flange 124 are in shear, rather than in peel, and therefore less likely to develop leaks as in the prior art shown in FIG. 2

FIG. 9 is a further embodiment differing from FIGS. 6 and 8, in that the interface of sealing surface 226 and peripheral portion 232 of end panel 230 are located inwardly from the outermost edge 240 of container wall 222. It is clear that with the end panel 230 in the expanded or bulged position, as indicated by the dotted line showing of end panel 230, the peripheral portion 230 and the inclined sealing surface 226 are in shear rather than in peel, thereby minimizing the possibility of developing leaks during a retort operation.

It is to be understood that the foregoing description illustrates the invention for those skilled in the art and various changes may be made without departing from the spirit and scope of the invention and the described embodiments thereof.

Claims

1. A container, said container comprising a tubular side wall terminating at an upper periphery thereof, an outwardly extending flange extending about said periphery and including a sealing surface thereon, said sealing surface being adapted for providing sealing engagement with a container end panel, characterized in that said sealing surface on said container extends radially outwardly and downwardly about said periphery for maintaining an interface of said end panel and said sealing surface in shear rather than peel.

2. A container as defined in claim 1 wherein said container is constructed of thermoplastic material.

3. A container as defined in claim 2 wherein said flange extends outwardly from said tubular side wall and includes a lower surface for being engaged by a sealing tool.

4. A container as defined in claim 1 wherein said flange includes an uppermost, horizontal sealing surface extending radially outwardly and joining with said outwardly and downwardly sealing surface.

5. A container as defined in claim 3 wherein said flange includes an uppermost, horizontal sealing surface extending radially outwardly and joining with said outwardly and downwardly sealing surface.

6. A container as defined in claim 3 wherein said lower surface (25) extends horizontally outwardly from said tubular side wall of said container.

7. A container as defined in claim 3 wherein said lower surface (125) extends downwardly and outwardly from said tubular side wall essentially parallel with said sealing surface.

8. A container as defined in claim 1 wherein said sealing surface and a peripheral portion of said end panel are located inwardly of an outermost edge (240) of said container side wall.