Container And Closure Therefor

Abstract

A container with a closure retention groove is provided with a rigid stacking ring structure of reduced height, comprising a vertical wall section extending upwardly from the outer periphery of a horizontal lower stacking shoulder to the inner periphery of a horizontal annular rim. A compressional camming wall section extends inwardly and downwardly from the inner periphery of the lower stacking shoulder to the upper extent of the closure retention groove. A closure for the container can be formed so that the portion of the closure between the closure rim and the retention bead grips the portion of the container between the retention groove and the container rim, to secure the closure to 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 a 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, a significant degree of compressibility of the stacking ring section of the containers can promote jamming of the containers, depending upon the type of thermoplastic material, the wall thickness, the size of the container and the overall container design, the configuration of the closure, and the handling procedures to which the package is to be subjected. The seal between the container and closure can be improved or adversely affected by such resiliency in the portions of the container and closure involved in the closure retention function.

While the stacking structure of the container can be separated from the closure retention structure of the container by placing the stacking structure below the closure retention portion of the container, this increases the height of the configurated portion of the sidewall of the container, which can adversely affect the esthetic values of the container design as well as reducing the area of the sidewall available for printing.

In accordance with the present invention it has been discovered that the stacking ring section and the closure retention section of the container can be combined while providing different degrees of resilience for the stacking function and the closure retention function.

Accordingly, it is an object of the invention to provide a new and improved container. It is another 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, and the thus gripped portion of the container is contoured for increased resilience. 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 reduce the effects 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 and closure constructed in accordance with the present invention;

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 non-venting 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;

FIG. 6 is a fragmentary cross-sectional view of a stack 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, an upstanding sidewall 14, a closure retention groove wall section 15, a compressional camming wall section 16, a stacking shoulder 17, a stacking spacing ring wall section 18, and a rim 19. The sidewall 14 is a circumferentially continuous frustoconically contoured wall section which extends generally upwardly and outwardly from the outer periphery of bottom wall 13. Closure retention groove wall section 15 is contoured to provide a circumferentially continuous, outwardly directed, inwardly opening, annular groove, extending generally upwardly from the periphery of the upper extent of sidewall 14. Compressional camming wall section 16 is a circumferentially continuous frustoconically contoured wall section extending upwardly and outwardly from the periphery of the upper extent of closure retention groove wall section 15. Stacking shoulder 17 is a circumferentially continuous annular ring extending substantially horizontally outwardly from the periphery of the upper extent of compressional camming wall section 16. Stacking or spacing ring 18 extends at least substantially vertically upwardly from the outer extent of stacking shoulder 17 and is a circumferentially continuous substantially cylindrical wall section. Rim 19 comprises a flat annular ring portion 20 which extends outwardly substantially horizontally from the upper extent of spacer wall section 18, the ring portion 20 being joined to the spacer section 18 at a substantially 90.degree. angle. A second portion 21 of rim 19 extends outwardly and downwardly from the outer periphery of the annular ring portion 20. The rim 19 can be in the form of an inverted U or in the form of a rolled rim, as illustrated. In either case the vertical height of the rim 19 is less than the vertical height of spacer wall section 18. The outer diameter of the closure retention groove wall section 15 is less than the inner diameter of the upper extent of the stacking ring section 18 to permit the insertion of the closure retention stacking groove wall section 15 of an upper container within the area bounded by the spacer ring section 18 of the next lower container in the operation of providing a nested stack of identical containers. The outer diameter of stacking shoulder ring 17 is greater than the inner diameter of rim 19, preferably at least by twice the thickness of spacer wall section 18 at its upper extent. As illustrated in FIG. 6, this configuration permits the nesting of identical containers in a vertical stack with at least the outer portion of the annular stacking shoulder 17 of an upper container resting upon the inner portion of annular ring section 20 of rim 19 of the next lower container in the stack. The alignment of spacer wall sections 18 in a straight vertical line, with each shoulder 17 resting on the ring portion 20 of the next lower container in the nested stack provides the maximum stacking rigidity for a given wall thickness and a given thermoplastic material.

Referring now to FIG. 2, 3, 4, and 5, closure 12 is a one piece, thermoformed structure having substantially horizontal 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 or skirt 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. 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 thereof 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 upper extent of sidewall 14. Wall 24 of closure 12 is spaced inwardly from the wall formed by wall section 16, stacking shoulder 17, and wall 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 wall 14 of container 11 below disc 22.

Stacking lugs 31 are provided at circumferentially spaced positions in side wall 24. The stacking lugs 31 are inwardly directed, outwardly opening embossments. Each lug 31 has a substantially vertical or upwardly and slightly inwardly inclined back wall 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 identical closures. The circumferential discontinuity of 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. 3, upon insertion of closure 12 into container 11, bend 23 is initially centered on and cammed inwardly by compressional camming wall section 16, and then snaps outwardly into closure retention groove 15. 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 during the capping operation.

The upper surface of bead 23 contacts the inner surface of the upper portion of retention groove 15 at point 35. The underside of rim 25 contacts the top of rim 20 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 surface of container 11 to thereby removably secure the closure 12 to the container 11. The contact of closure rim 25 and the container rim section 20 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 rim to insure sanitary conditions for the entire interior of the container. The incorporation of the flat annular ring 20 in the rim 19 provides for contact between the rim 19 and rim 25 of the closure 12 along an annular band rather than merely a line contact. This increased width of contact area increases the effectiveness of the seal. The angle between camming wall section 16 and spacer wall section 18 and the presence of the shoulder 17 permits the desired degree of resiliency of the portion of the container within the C-clamp.

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 to the initially outwardly and downwardly curving portion of rim 21, and camming contact therebetween occurs during venting of the package. Preferably this contact is made in the first 45.degree. of curvature of rim section 21 outwardly and downwardly from the annular ring section 20. 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 the 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 the space between rim 19 and rim 25 and depending flange 26. The inner diameter of the flange 26 is sufficiently greater than the outer diameter of the container 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 obviously 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 groove wall section 15 in container 11. Increased resiliency of the thinner wall of bead 23 assists in the insertion of closure 12 into container 11 as the bead 23 will flex inwardly to pass the compressional camming wall section 16 of container 11 and then snap outwardly into the groove of wall section 15. 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 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 vent in the retention bead or in the retention groove.

Reasonable variations and modifications are possible within the scope of the foregoing disclosure, the drawings and the appended claims to the invention.

Claims

We claim:

1. A container comprising a bottom wall, an upstanding wall extending generally upwardly and outwardly from the periphery of said bottom wall, an inwardly opening outwardly directed closure retention groove wall section extending generally upwardly from the periphery of the upper extent of said upstanding wall, a compressional camming wall section extending generally upwardly and outwardly from the periphery of the upper extent of said closure retention groove wall section, a circumferentially continuous annular ring stacking shoulder extending at least substantially horizontally outwardly from the upper extent of said compressional camming wall section, a stacking ring wall section extending at least substantially vertically upwardly from the outer extent of said stacking shoulder, a rim having a flat annular ring portion extending horizontally outwardly from the periphery of the upper extent of said stacking ring wall section, said flat annular ring being joined to the upper extent of said stacking ring wall section at a substantially 90.degree. angle, the outer diameter of said closure retention groove wall section being less than the inner diameter of the upper extent of said stacking ring wall section, the outer diameter of said stacking shoulder being greater than the inner diameter of said rim so that the stacking shoulder of an upper container rests upon the rim of the next lower container in a stack of superimposed identical containers, with the at least substantially vertical configuration of the stacking ring wall section providing at least substantially maximum stacking rigidity.

2. A container in accordance with claim 1 wherein said upstanding wall and said compressional camming wall section are circumferentially continuous frustoconically contoured wall sections.

3. A container in accordance with claim 1 wherein the outer diameter of said stacking shoulder exceeds the inner diameter of said rim by at least twice the thickness of the upper extent of said stacking ring wall section.

4. A container in accordance with claim 1 wherein said rim further comprises a second portion extending outwardly and downwardly from the outer periphery of said annular ring portion, the vertical height of said rim being less than the vertical height of said stacking ring wall section.

5. A container in accordance with claim 4 wherein said upstanding wall and said compressional camming wall section are circumferentially continuous frustoconically contoured wall sections, and wherein the outer diameter of said stacking shoulder exceeds the inner diameter of said rim by approximately twice the thickness of the upper extent of said stacking ring wall section.

6. A container in accordance with claim 1 wherein said container is a one piece, integral thermoformed structure with the thickness of said stacking ring wall section decreasing from the upper extent thereof to the lower extent thereof.

7. A container in accordance with claim 1 further comprising a closure applied to said container and having a diaphragm, a sidewall, an outwardly directed, inwardly opening retention bead extending generally upwardly from the periphery of said diaphragm to the lower extent of said sidewall, and a rim extending outwardly from the upper extent of said sidewall; said retention bead being dimensioned to snap into said closure retention groove wall section of said container; said rim of said closure extending outwardly over said rim of said container and in contact therewith; the distance between the point of contact of the container rim and the closure rim and the point of contact of the retention bead and the closure retention groove wall section 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; each of said stacking shoulder and said spacer wall section being inclined at an acute angle to an imaginary line through said points of contact to increase the resilience of the portion of said container between said points of contact.

8. A container and closure in accordance with claim 7 wherein said retention bead is interrupted at circumferentially spaced locations by a plurality of venting grooves which extend to a point on said diaphragm which is spaced inwardly a significant distance from the inner edge of said closure retention groove wall section to provide continuously open fluid communication between the packaging space within the container below said diaphragm and the annular space between said sidewall of said closure and the laterally adjacent portion of said container; wherein said rim of said container curves outwardly and downwardly; and further comprising a skirt depending from the outer periphery of the rim of said closure, and inwardly directed camming grooves formed at the junction of said rim of said closure and said depending skirt, said camming grooves contacting said outwardly and downwardly curved portion of said rim of said container to effect a lifting of the closure rim from the container rim upon the occurrence of excessive pressure in said packaging space to thereby vent said packaging space.