Packaging Container And Closure Therefor

Abstract

A container having a closure retention shoulder is combined with a closure having a retention bead. The closure is formed so that the portion thereof between the closure rim and the retention bead grips the portion of the container between the retention shoulder and the container rim to secure the closure to the container. The container wall section between the points of the rim and retention shoulder is substantially straight and at least approximately parallel to and positioned at least closely adjacent to a line through the points of contact at the retention shoulder and rim. This container wall section and a substantially parallel second wall section below the retention shoulder can serve as upper and lower stacking shoulders for the container.

Description

This invention relates to improvements in packaging containers and closures therefor.

Variations in the outer diameter of the retention bead on a closure and variations in the maximum inner diameter of the closure retention groove in the container have caused numerous problems with such packages. If the retention bead is too large for the retention groove, the closure can be distorted with unsightly buckling and the closure can be difficult to remove from the container. If the retention bead is too small, the closure fits loosely in the container and can be inadvertently dislodged from the container, exposing the contents of the package. With some products, it is desirable that the package be provided with a reclosable venting means. Numerous closures have been designed utilizing venting grooves in the closure retention bead which open into the packaging space of the container only when a pressure buildup causes a distortion of the closure. If the closure retention bead fits too tightly in the retention groove of the container, the venting action may be impaired or even prevented. If the closure fits loosely in the container, the venting grooves may be open continuously, eliminating any sanitary seal.

While the problem of dimensional accuracy is acute with paper containers and closures, it is also serious with thermoplastic containers and closures, particularly of the thermoformed type. The retention groove in thermoformed containers and the retention bead of thermoformed closures are customarily formed in an undercut in a female mold wall, which causes localized variations in the reduction in thickness of the thermoplastic sheet in these particular areas during the thermoforming operation. The location of these areas a significant distance below the rim of the mold also results in the sheet thickness being reduced to a substantially greater extent than in the rim portions of the container or closure.

In addition, many of the containers have been designed to provide resiliency in the upper wall portion thereof for stacking purposes. However, with some container designs a significant degree of compressibility of the stacking ring section of the containers can promote jamming of the containers when a nested stack of the containers is subjected to axial compression. In some packages, this compressibility can also reduce the effectiveness of the seal between the container and closure.

In accordance with the invention it has been discovered that a container can be provided with satisfactory stacking shoulders while also having greater rigidity in the stacking portion of the container, thereby permitting a more effective seal with the closure. This can be accomplished by the container and closure structure described more fully hereinafter.

Accordingly, it is an object of the invention to provide a new and improved container. It is an object of the invention to provide an improved stacking structure for a container. Another object of the invention is to provide an improved package comprising a container and a closure therefor wherein the closure is formed as a C-clamp to grip the container. Another object of the invention is to provide an improved reclosable venting structure for a combined container and closure. A further object of the invention is to provide a more effective, sanitary seal for a combined container and closure. Yet another object of the invention is to minimize the effect of dimensional variations on the fit of a closure and container .

Other objects, aspects and advantages of the invention will be apparent from a study of the specification, the drawings and the appended claims to the invention.

In the drawings:

FIG. 1 is a side elevational view of a container having a closure thereon;

FIG. 2 is a top plan view of the container and closure of FIG. 1;

FIG. 3 is a fragmentary cross-sectional view taken along line 3--3 in FIG. 2 when the package is in a static or nonventing condition;

FIG. 4 is a fragmentary cross-sectional view taken along line 4--4 in FIG. 2;

FIG. 5 is a fragmentary cross-sectional view taken along line 3--3 in FIG. 2 when the package is in a venting condition; and

FIG. 6 is a fragmentary cross-sectional view in elevation of a nested stack of a plurality of the containers of FIG. 1.

Referring now to the drawings in detail, and to FIGS. 1, 3, 4 and 6 in particular, the package 10 comprises a container or cup 11 and a closure 12. The container 11 is a one-piece integral structure, and can be fabricated by thermoforming a sheet of thermoplastic material. Container 11 comprises a bottom wall 13 of a suitable configuration, preferably having an annular, downwardly directed groove 14, formed therein. A first circumferentially continuous frustoconical sidewall section 15 extends generally upwardly and outwardly from the periphery of bottom wall 13 at a first acute angle with respect to the vertical. A second circumferentially continuous, substantially straight, frustoconical sidewall section 16 extends generally upwardly and outwardly from the periphery of the upper extent of sidewall section 15 at a second acute angle to the vertical, the second acute angle being greater than the first acute angle. A third circumferentially continuous sidewall section 17 curves upwardly and inwardly from the upper extent of section 16 and serves as a closure retention shoulder. A circumferentially continuous, substantially straight, frustoconical fourth side wall section 18 extends upwardly and outwardly from the periphery of the inner extent of sidewall section 17 at a third acute angle with respect to the vertical. The third acute angle is approximately equal to the second acute angle for section 16.

In many applications it is desirable that the first acute angle of side wall section 15 be as small as possible to minimize the cross-sectional area required for a given volume, while permitting stacking. Although stacking of identical containers can often be accomplished with only one or two degrees of taper for the sidewall, serious difficulties are encountered in denesting such containers where the area of contact between adjacent superimposed containers occurs on a sidewall section having less than about 15.degree. inclination to the vertical. In order to achieve minimum required cross-sectional area for readily denestable containers, the acute angle of sidewall section 15 can be less than the minimum angle required to prevent jamming of parallel surfaces while the acute angles for sidewall sections 16 and 18 are greater than such minimum angle. A rim 19 extends generally outwardly and downwardly from the periphery of the upper extent of sidewall section 18. The rim 19 can have a generally inverted U-shaped configuration, but the rolled rim having at least 270.degree. of curvature is presently preferred.

As shown in FIG. 6, the inner diameter of the upper extent of sidewall section 18 is sufficiently greater than the outer diameter of the lower extent of sidewall section 16 to permit at least a partial insertion of sidewall section 16 of an upper container within the sidewall section 18 of the next lower container in the stacking of identical containers 11. The inner diameter of the lower extent of sidewall section 18 is sufficiently less than the outer diameter of the upper extent of sidewall section 16 to permit at least a portion of the sidewall section 16 of the upper container to rest upon the sidewall section 18 of the next lower container in the stack.

Referring now to FIGS. 2, 3, 4 and 5, closure 12 is a one-piece thermoformed structure having substantially circular cross sections and comprises a circular closure disc or diaphragm 22, a retention bead 23, upwardly and outwardly sloping wall section 24, rim 25 and depending flange 26. Disc 22 is illustrated as being planar, but can be bowed upwardly or dished downwardly and/or provided with an annular expansion groove if desired. The retention bead 23 is an inwardly opening, outwardly directed, concavely shaped groove section extending generally upwardly between the periphery of disc 22 and the lower extent of wall section 24. The outer diameter of bead 23 is greater than the diameter of the inner extent of retention shoulder 17, is less than the inner diameter of the upper extent of straight sidewall section 18 and is less than the inner diameter of the upper extent of sidewall section 16. Thus, upon application of closure 12 to container 11, the retention bead 23 is inserted downwardly into the container beyond retention shoulder 17 and then snaps outwardly under retention shoulder 17. In a presently preferred package, the retention shoulder 17 is curved upwardly and inwardly from the upper extent of sidewall section 16 in an upwardly directed, downwardly opening arcuate contour conforming generally to the contour of the upper portion of retention bead 23 to increase the area of contact therebetween. Retention bead 23 is interrupted at circumferentially spaced locations by a plurality of inwardly directed, outwardly opening notches or venting grooves 27. Each notch 27 will generally be disposed with the elongated axis thereon in a substantially vertical plane. The innermost wall portion of each notch 27 extends downwardly and inwardly from wall section 24 to a point on disc 22 which has a significantly smaller diameter than the inner diameter of the laterally adjacent portion of sidewall section 16. Wall 24 of closure 12 is spaced inwardly from the wall formed by straight sidewall section 18 of container 11 to form a continuous annular space 28. The upper portion of each notch 27 opens into the annular space 28. This provides continuous fluid access between the annular space 28 and the packaging space 29 within walls 15 and 16 of container 11 below disc 22.

Stacking lugs 31 are provided at circumferentially spaced positions in sidewall 24. The stacking lugs 31 are inwardly directed, outwardly opening embossments. Each lug 31 has a substantially vertical or upwardly and slightly inwardly inclined backwall 32, a generally horizontal shoulder 33 and substantially vertical sidewalls 34. Shoulder 33 extends outwardly in a generally horizontal direction from the upper extent of back or inner wall 32 to wall 24. Shoulder 33 can be curved outwardly and upwardly in conformance with the contour of the lower portion of bead 23. The outer diameter of shoulder 33 is at least equal to the outer diameter of the corresponding portion of bead 23 so that the bead 23 of one closure rests upon the shoulder 33 of the next lower closure in a nested stack of superimposed closures. The circumferential discontinuity of the stacking shoulders 33 readily permits air to flow out of or into the space between superimposed closures during stacking or denesting operations.

Referring now to FIG. 4, upon insertion of closure 12 into container 11, bead 23 cams inwardly on the upper shoulder 18 and then snaps under closure retention shoulder 17. The notches 27 permit continuous outflow of air from the interior of the package during the insertion of closure 12 into container 11, thereby preventing a buildup of excessive pressure in the package 10 during the capping operation. The upper surface of bead 23 contacts the inner surface of the upper portion of retention shoulder 17 at point 35. The underside of rim 25 contacts the top of rim 19 at point 36. This results from the formation of closure 12 in such a manner that the distance between points 35 and 36 in the unstressed closure is less than the distance between points 35 and 36 on the uncapped container. Thus, the upper portion of bead 23, wall 24 and rim 25 act as a C-clamp to grip the mating surfaces of container 11 to thereby removably secure the closure 12 to the container 11. The contact of closure rim 25 and container rim 19 is circumferentially continuous and serves as a seal for the capped container. In contrast to containers which provide a sealing surface at the top or bottom of the closure retention bead, the present configuration provides a seal at the top of the container rim to insure sanitary conditions for the entire interior of the container.

Closure 12 is provided with a plurality of circumferentially spaced venting cams 37, bridging rim 25 and depending flange 26. Cams 37 project inwardly from flange 26 and downwardly from rim 25 to form a camming surface which is inclined downwardly at an acute angle to the horizontal reference. The cams 37 are positioned at least closely adjacent the outwardly and downwardly curving portion of rim 19, and camming contact therebetween occurs during venting of the package. Preferably this contact is made in the first 45.degree. of curvature of rim 19 outwardly and downwardly from the horizontal. When the pressure in packaging space 29 and annular space 28 is not excessive, the relationship of the closure 12 and the container 11 is illustrated in FIG. 3. Upon the occurrence of excessive pressure in packaging space 29 and annular space 28, the upstanding wall 24 of closure 12 is forced inwardly, causing the cams 37 to contact and slide on the upper half of the upper and outer quadrant of rim 19. The camming action causes rim 25 of the closure 12 to move upwardly from rim 19 to the position shown in FIG. 5, thereby providing a continuous passageway to the atmosphere from packaging space 29 through annular space 28 and through the space between rim 19 and rim 25 and depending flange 26. The inner diameter of depending flange 26 is sufficiently greater than the outer diameter of rim 19 to provide a clearance therebetween even when the closure is contorted to the venting condition. Upon the release of the excessive pressure, the closure and container return to the relationship shown in FIG. 3.

Thermoformed containers and thermoformed closures are customarily formed in female molds. This has the advantage that the outside dimensions of the container are substantially constant; however, the wall thickness varies within each container. The retention bead 23 of closure 12 is relatively thin because of the double-stretching to which the thermoplastic sheet material is subjected. The sheet is initially stretched as it is drawn downwardly into the main mold cavity, and then a portion thereof is additionally stretched as that portion is drawn into the mold groove which forms bead 23. A similar double-stretching action occurs in the formation of closure retention shoulder 17 in container 11. The increased resiliency of the thinner wall of bead 23 assists in the insertion of the closure 12 into container 11 as the bead 23 will flex inwardly to pass the section 18 of container 11 and then snap outwardly under shoulder 17. However, the thinner wall of bead 23 is more subject to a stress fold than rim 25, which could prevent a normally closed venting groove from being opened or which could result in the formation of an undesired continuously open venting passageway.

The rim 25 and depending skirt 26 will normally have the greatest thicknesses of any part of a thermoformed closure 12. Similarly, the rim 19 will normally have the greatest thickness of any part of a thermoformed container 11. These greater thicknesses also normally result in the greatest rigidity and dimensional accuracy for any portion of the container or closure. This results in a more effective seal where the seal is between the container rim and the closure rim than where the seal is between the retention bead and the retention groove. The location of the venting cams at the junction of the rim 25 and skirt 26 also takes advantage of the greater rigidity and dimensional accuracy to provide a more effective reclosable venting action than would be obtained with reclosable vents in the retention bead or in the retention groove. However, in some applications it is desirable that the rigidity of the portion of container 11 within the C-clamp of closure 12 be enhanced. While this could be accomplished by increasing the thickness of the container walls, it would also substantially increase the cost of the container. In accordance with one aspect of the invention it has been discovered that the desired greater rigidity can be achieved without any increase in cost of the container. As shown in FIGS. 3 and 4, straight sidewall section 18 of the container 11 is formed at least approximately parallel to and at least closely adjacent to an imaginary line through contact points 35 and 36. The smaller the angle of divergence between the line of sidewall 18 and the line between points 35 and 36 and the smaller the mean distance between the two lines, the greater the rigidity of the portion of container 11 gripped by the C-clamp portion of closure 12. The length of the curved portion of rim 19 between the upper extent of section 18 and point 36 can be reduced by decreasing the radius of curvature thereof. However, this distance is so short in container 11, as illustrated, that it does not provide any significant leverage for a bending action and can be disregarded. The effectiveness of the C-clamp can be further enhanced by forming closure sidewall 24 substantially parallel to sidewall section 18 and spaced therefrom a minimum distance to provide sufficient radial thickness of annular space 28.

While the invention has been illustrated with a container and closure having circular horizontal cross sections, other configurations can be utilized, for example oval, rectangular with at least the corners being rounded and more preferably with the sides being bowed outwardly, and the like. Other reasonable variations and modifications are possible within the scope of the foregoing disclosure, the drawings and the appended claims to the invention.

Claims

I claim:

1. A package comprising a container and a closure therefor;

said container comprising a bottom wall, a container sidewall extending generally upwardly and outwardly from the periphery of said bottom wall, a closure retention shoulder extending generally inwardly from the periphery of the upper extent of said container sidewall, a straight frustoconical wall section extending upwardly and outwardly from the periphery of the inner extent of said retention shoulder, and a container rim extending generally outwardly from the upper extent of said straight frustoconical wall section;

said closure comprising a diaphragm, an at least substantially frustoconical closure sidewall extending upwardly and outwardly, an outwardly directed, inwardly opening retention bead extending upwardly from the periphery of said diaphragm to the lower extent of said closure sidewall, and a closure rim extending outwardly from the upper extent of said closure sidewall;

the outer diameter of said retention bead being greater than the diameter of the inner extent of said retention shoulder and less than the inner diameter of the upper extent of said container sidewall so that upon application of said closure to said container the retention bead is inserted downwardly into the container beyond said retention shoulder and then snaps outwardly under said retention shoulder, said container sidewall extending downwardly and inwardly from said retention shoulder in a substantially straight line to at least a point substantially below said diaphragm to reduce the area of contact of the lower portion of said retention bead with said container sidewall;

said closure rim extending outwardly over said container rim and in contact therewith, the distance between the point of contact of said container rim and said closure rim and the point of contact of said retention shoulder and said retention bead being greater than the distance between the same points in the unstressed closure before the unstressed closure is applied to said container so that the portion of said closure between said points of contact serves as a C-clamp to grip the mating portion of said container to thereby secure said closure to said container, said straight frustoconical wall section of said container being closely adjacent to and at least substantially parallel to an imaginary line through said points of contact to increase the rigidity of said mating portion, and said closure sidewall being at least substantially parallel to said straight frustoconical wall section of said container to increase the rigidity of said C-clamp.

2. A package in accordance with claim 1, wherein said closure side wall is spaced inwardly from said straight frustoconical wall section of said container to form an annular space therebetween, said retention bead is interrupted by at least one venting groove which extends to a point on said diaphragm which is spaced inwardly a significant distance from the inner surface of said container sidewall to provide a continuously open fluid communication between the packaging space within said container below said diaphragm and said annular space,

said container rim has an outwardly and downwardly curving peripheral portion, and said closure rim has camming means formed therein to contact said outwardly and downwardly curving portion of said container rim to effect a lifting of said closure rim from said container rim upon the occurrence of excessive pressure in said packaging space to thereby vent said annular space and said packaging space.

3. A package in accordance with claim 2, wherein said retention bead is an outwardly directed, inwardly opening concavely contoured wall section, and wherein said retention shoulder is curved upwardly and inwardly from the upper extent of said container sidewall in an upwardly directed, downwardly opening arcuate contour conforming generally to the contour of the upper portion of said retention bead.

4. A package in accordance with claim 2, wherein said container and closure have substantially circular horizontal cross sections, wherein said container is a one-piece integral thermoformed structure, and wherein said closure is a one-piece integral thermoformed structure.

5. A package in accordance with claim 2 wherein said container sidewall comprises a first frustoconical sidewall section extending generally upwardly and outwardly from the periphery of said bottom wall to said point substantially below said diaphragm at a first acute angle, and a second frustoconical sidewall section extending upwardly and outwardly from the periphery of the upper extent of said first frustoconical sidewall section to the lower outer extent of said retention shoulder at a second acute angle, said second acute angle being significantly greater than said first acute angle, said second frustoconical sidewall section and said straight frustoconical wall section being substantially parallel to each other.