US20140374428A1

US20140374428A1 - Container and cap

Info

Publication number: US20140374428A1
Application number: US14/356,508
Authority: US
Inventors: Martin John Watson; Alejandro Graner Solana
Original assignee: Crown Packaging Technology Inc
Current assignee: Crown Packaging Technology Inc
Priority date: 2011-11-08
Filing date: 2012-10-31
Publication date: 2014-12-25
Also published as: CN103987628A; CN103987628B; RU2623925C2; EP2592011A1; EP2776329A1; MX2014005585A; RU2014121072A; CA2865172A1; AU2012334251A1; WO2013068292A1; JP2015501762A

Abstract

A container (100) comprising: a substantially circular opening (406); and a radially projecting curled lip (408) extending around the opening for securing a substantially circular cap over the opening by way of a snap-fit, wherein the radial dimension of the curled lip varies around the opening.

Description

TECHNICAL FIELD

The invention relates to a container comprising an opening to which a cap may be snap-fitted. The invention also relates to a cap for snap-fitting to a container opening. The invention also relates to a container and a cap, the cap being configured to snap-fit to an opening of a container.

BACKGROUND

Containers for storing material may have openings from which the material stored therein may be dispensed. It may be desirable to fit a cap to such openings to prevent any unplanned exit of material from the container and also to seal the opening and prevent degradation of the material.
A particular type of container is used to store liquids and comprises a circular opening and a curled lip formed around the circumference of the opening. A cap may be snap-fitted to the opening about the curled lip and thereby retained in position.
The force required to snap-fit a cap to an opening comprising a curled lip may be large, in the region of 400 N. This may result in caps being incorrectly or only partially fitted. This may be because the machine used in fitting the cap may not administer the requisite force to securely fit the cap to the opening of the container. Alternatively, if the force required to fit a cap to a container is too large then the curled lip may bend away from the cap during fitting and prevent a snap-fit from occurring. An incorrectly or only partially fitted cap may result in the cap detaching from the container allowing the material stored therein to exit the container. In addition, an incorrectly or only partially fitted cap may result in an insufficient seal between the cap and the opening allowing the material stored therein to degrade.

SUMMARY OF THE INVENTION

According to a first aspect of the invention a container comprises a substantially circular opening; and a radially projecting curled lip extending around the opening for securing a substantially circular cap over the opening by way of a snap-fit, wherein the radial dimension of the curled lip varies around the opening.
The varying radial dimension of the curled lip allows a cap to deform out-of-round during snap-fitting to the opening. Regions of the perimeter of the cap may deform radially outward to fit over the regions of the curled lip having greater radial dimension while other regions of the cap may deform radially inwardly. The force required to produce deformation out-of-round is less than the force required to deform the entire perimeter of the cap radially outward. Therefore, the amount of force required to fit the cap to the opening is reduced without significantly affecting the security of the fit of the cap to the opening. A reduction in required fitting force may lead to a higher proportion of caps being securely and fully fitted to containers.
As used herein, the term “deform out-of-round” encompasses the distortion of a shape such that the geometry of the perimeter of the shape changes. The deformation of a shape out-of-round may result in the length of the perimeter of the shape remaining substantially constant. However, some increase in the length of the perimeter may be experienced. By way of example, a circle may deform out-of-round to form an ellipse having a circumference substantially equal to that of the circle.
Additionally, by varying the radial dimension of the curled lip, the container may be used in conjunction with existing caps.
Optionally, the curled lip projects radially outward.
For the avoidance of doubt, the term “radially projecting” encompasses inward radial extension and outward radial extension.
Optionally, the varying radial dimension provides the curled lip with two or more radially projecting wings.
The wings may provide the regions of the curled lip around which the perimeter of a cap may deform outwardly. The regions between the wings may provide areas between the curled lip and a wall of the cap into which the wall of the cap may deform inwardly. Therefore, the wings and regions between the wings allow for a cap to deform out-of-round during snap-fitting to the opening.
Optionally, the curled lip comprises two wings around the circumference of the opening.
The use of two wings may allow for a large deformation out-of-round of the cap and, therefore, a large reduction in the force required to snap-fit a cap to the opening.
Optionally, the curled lip comprises four wings around the circumference of the opening.
The use of four wings allows for a secure fit of a cap to the opening as the curled lip may retain the cap at four places around the circumference of the cap.
Optionally, the radial dimension of the curled lip varies between a minimum dimension in the range 0 mm to 1.5 mm and a maximum dimension in the range 1.6 mm to 2.5 mm.
Optionally, the radial dimension of the curled lip varies between a minimum dimension in the range 0.5 mm to 1 mm and a maximum dimension in the range 1.8 mm to 2 mm.
Optionally, the radial dimension of the curled lip varies between a minimum dimension and a maximum dimension, wherein the minimum dimension is in the range from 0% to 75% of maximum dimension.
Optionally, the minimum dimension is in the range from 20% to 55% of the maximum dimension.
Optionally, the varying radial dimension of the curled lip is arranged to require a maximum force of 300 N to snap-fit a cap about the curled lip.
Optionally, the required maximum force may be 200 N.
Optionally, the required maximum force may be 140 N
Optionally, the required force in the range from 100 N to 150 N.
According to a second aspect of the invention a substantially circular cap for snap-fitting to a substantially circular opening of a container comprises: a resiliently deformable wall; and a radially projecting lip extending around the wall for securing the cap over a curled lip extending around the opening, wherein the radial dimension of the lip varies around the wall.
By varying the radial dimension of the lip of the cap the cap is allowed to deform out-of-round when snap-fitting to a container opening. That is, regions of the lip deform to occupy the space between the curled lip of a container and the radially thinner regions of the lip. As discussed above with respect to the invention in a first aspect, this allows a reduction in the force required to fit the cap.
In addition, by varying the radial dimension of the lip, the cap may be used in conjunction with existing containers comprising curled lips formed about an opening.
Optionally, the varying radial dimension of the lip provides the lip with two or more radially projecting wings.
Optionally, the cap further comprises a substantially circular inner plug configured to mate within a substantially circular opening of a container, wherein an annular cavity is defined between the inner plug and the resiliently deformable wall to accommodate a curled lip formed around the opening.
Optionally, the curled lip forms a continuous arc.
Optionally, a first section of the curled lip extends radially inwardly and a second section of the curled lip extends radially outwardly.
Optionally, the maximum radially projecting wings, the second section of the curled lip continues until the curled lip extends vertically downward.
Optionally, the curled lip forms a rounded inner edge of the substantially circular opening.
Optionally, at the radially projecting wings, the curled lip forms a rounded outer edged of the substantially circular opening.
According to a third aspect of the invention a container and a cap are provided, the cap being configured to snap-fit to a substantially circular opening of the container, wherein the container comprises a radially projecting curled lip extending around the opening, and the cap comprises a resiliently deformable wall and a radially projecting lip extending around the wall, and wherein a radial dimension of the curled lip varies around the opening or a radial dimension of the lip varies around the wall.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 a is a perspective view of a known container;

FIG. 1 b is a section through a top plate of a known container during manufacture;

FIG. 1 c is a section through a top plate of a known container;

FIG. 2 is a section through a known cap;

FIG. 3 is a perspective view of a known cap fitted to a known container;

FIG. 4 a is a plan view of the top of a first container according to the invention;

FIG. 4 b is a first section through a top plate of a container according to the invention;

FIG. 4 c is a second section through a top plate of a container according to the invention;

FIG. 5 is a partial section through a cap fitted to a container;

FIG. 6 is a plan view of the top of a second container according to the invention; and

FIG. 7 is a plan view of the base of a cap according to the invention.

SPECIFIC DESCRIPTION

The inventors have appreciated that a reduction in the force required to fit a cap to an opening of a container without significantly reducing the security of the fit may be desirable. The reduced force required to fit the cap may lead to a greater proportion of caps being fitted correctly and fully. The inventors have further appreciated that deforming a substantially circular shaped cap out-of-round requires less force than deforming a substantially circular shaped cap to be a larger (i.e. greater diameter) substantially circular shaped cap.
In view of the above, the inventors have invented a container and a cap that result in a reduced force required to fit a cap to a container.
FIG. 1 a shows a perspective view of a container 100 known in the prior art. The container 100 may be for storing fruit syrup and comprises a top plate 102, a body 104 and a base (not shown). An opening 106 is formed in the top plate 102. The opening 106 has formed around it a radially projecting curled lip 108.
FIGS. 1 b and 1 c show two sections through the top plate 102 of the known container 100 at different stages of manufacture.
To manufacture the opening 106 and the curled lip 108 in a top plate 102 for a container 100 a piercing tool is passed through the top plate 102. FIG. 1 b shows a section through a top plate 102 after the piercing tool has been passed through it. The top plate 102 of FIG. 1 b comprises a chimney 110, which defines an aperture 112. The aperture 112 will form the opening 106 of the container 100. The wall of the chimney 110 is formed by the area of the top plate 102 that has been forced out by the piercing tool when it is passed through the top plate 102 to define the aperture 112. A crimped region 114 is formed around the periphery of the top plate 102 and is used in conjunction with a complimentary crimped region on the body 104 to create a double seam to attach the top plate 102 to the body 104.
After the top plate 102 has been pierced to define the chimney 110, the wall of the chimney 110 may be curled down using a curling tool to define a curled lip 108. FIG. 1 c shows a section through a top plate 102 after the wall of the chimney 110 has been curled down. FIG. 1 c therefore shows the opening 106 and the curled lip 108. The curled lip has a radial dimension 109. The radial dimension is defined from the circumference of the opening to radial limit of the curled lip 108.
Further detail of the manufacture of containers of the type discussed above is disclosed in European Patent number EP 0521637.
FIG. 2 shows a section through a known circular cap 200. The cap 200 comprises a resiliently deformable wall 202. The cap 200 further comprises an inner plug 204. The resiliently deformable wall 202 is manufactured to have a diameter greater than or equal to the outer diameter of the curled lip 108 of the container 100 to which the cap 200 is to be fitted. A lip 208 extends around the resiliently deformable wall 202. In FIG. 2, the lip 208 is shown to be integral to the wall 202. However, in other embodiments, the lip 208 may be formed separately and attached to the wall 202. The lip 208 has a radial dimension 206. The radial dimension 206 is configured to define an internal diameter 209 of the cap 200 that is less than the outer diameter of the curled lip 108 of the container 100 to which the cap 200 is to be fitted. The lip 208 is configured to be retained by the curled lip 108 of the container 100 when the cap 200 is fitted to the container 100.
The cap 200 is snap-fitted to the container 100 by applying a force to the cap to stretch the resiliently deformable wall 202 of the cap 200 over the curled lip 108 of the container 100. As the internal diameter 209 of the cap 200 is less than the outer diameter of the curled lip 108, the wall 202 is forced radially outward by the force applied to the cap. The resiliently deformable wall 202 of the cap 200 is stretched to increase its diameter such that the lip 208 of the cap 200 is able to pass over the curled lip 108 of the container 100. Once the lip 208 has passed over the end of the curled lip 108, the resiliently deformable wall 202 returns to its original diameter. The lip 208 is thereby retained by the end of the curled lip 108 preventing the cap 200 from being removed from the container 100.
FIG. 3 shows a perspective view of a known cap 200 fitted to a known container 100.
FIG. 4 a shows a plan view of a container 400 according to an embodiment of the invention. The container 400 comprises a top plate 402 and a substantially circular opening 406. A radially projecting curled lip 408 extends around the opening 406. The curled lip 408 projects radially outward from the centre of the opening 406 as shown in greater detail in FIGS. 4 b and 4 c. In alternative embodiments the radially projecting curled lip 408 may project inwardly toward the centre of the opening 406. For the avoidance of doubt it is noted here that radial extension can be one of outward from the centre of the opening 406 or inward toward the centre of the opening 406.
The curled lip 408 may be formed using the method described above in relation to FIG. 1 but sections may be cut from the chimney before it is curled down to form a curled lip 408 having a varying radial extension. Alternatively, the curled lip 408 may be curled down and then sections may be removed to form a curled lip 408 having a varying radial extension.
The radial dimension of the radially projecting curled lip 408 varies around the circumference of the opening 406. Specifically, the curled lip 408 comprises two radially projecting wings 408 a, 408 b. Two regions 408 c, 408 d between the wings 408 a, 408 b are thereby defined. The radial dimension of the wings 408 a, 408 c is greater than the radial dimension of the regions between the wings 408 c, 408 d.
In embodiments the container 400 may be manufactured from metal. In particular embodiments, the container 400 may be manufactured from steel. The thickness of the steel off the top plate 402 may be in the range from 0.2 mm to 0.3 mm. In particular embodiments, the thickness of the steel may be 0.24 mm.
FIG. 4 b shows a section 4 b-4 b through the top plate 402 of the container 400. Referring to FIG. 4 c there is shown a section 4 c-4 c through the top plate 402 of the container 400. In FIG. 4 b, the regions 408 c, 408 d of the curled lip 408 between the wings 408 a, 408 b have a radial dimension 409. In FIG. 4 c, the wings 408 a, 408 b have a radial dimension 410. The radial dimensions 409, 410 are defined from the circumference of the opening 406 to the outer radial dimension of the curled lip 408. Therefore, the radial dimension of the curled lip 408 may vary between a minimum radial dimension 409 and a maximum radial dimension 410.
As can be seen in FIGS. 4 b and 4 c, the opening 406 is formed in the centre of a circular top plate 402 configured to fit on top of sidewalls of a container 400. A crimped region is used to secure the circular top plate 402 to the sidewalls. As can be seen from FIGS. 4 a-4 c, the diameter of the opening 406 is less than the diameter of the top plate 402.
The curled lip 408 may extend to form a continuous arc from a surface of the top plate 402 to an end of the curled lip 408. The continuous arc may extend radially inwardly before arcing outwards to extend radially outwardly. In exemplary containers, the regions 408 c, 408 d of the curled lip 408 between the wings 408 a, 408 b may extend in an arc until the curled lip 408 is horizontal (or parallel to the top plate 402). In exemplary containers, the wings 408 a, 408 b of the curled lip 408 may curve round in a continuous arc from until the curled lip 408 is pointing vertically down (or parallel to the sidewalls). The curled lip 408 therefore forms a continuous curve to the end of the curled lip 408. In specific embodiments, a section through the curled lip 408 follows a circular path to the end of the curled lip 408.
In exemplary containers 400, the sides of the opening 406 may comprise a circular chamfered region angled upwards and radially inwards toward the curled lip 408. The chamfered region elevates the curled lip away from an upper surface of the top plate 402 to allow room for a cap to be fitted. The curled lip 408 may extend from the inner edge of the chamfered region and curve around in an arc to extend radially outward.
The curled lip 408 provides a rounded surface on the inner edge of the curled lip that defines the opening 406. This helps an inner plug 204 of a cap to be easily located in the opening 406, as any misalignment will be corrected by the curved inner surface of the curled lip 408. At the wings 408 a, 408 b, the curled lip 408 provides a rounded outer surface. This reduces the amount of force required to fit a cap by snap-fit. Additionally, at the wings 408 a, 408 b, the end curled lip faces downwards. This makes a more secure fit of a cap than other lip arrangement, such as horizontal lips, as the stiffness of the curled lip is increased.
The minimum radial dimension 409 may be in the range from 0 mm to 1.5 mm. The maximum radial dimension 410 may be in the range from 1.6 mm to 2.5 mm. In other embodiments, the minimum radial dimension 409 may be in the range from 0.5 mm to 1 mm. The maximum radial dimension 410 may be in the range from 1.8 mm to 2 mm. In a specific embodiment, the maximum radial dimension may be 1.975 mm.
In other embodiments, the minimum radial dimension 409 may be in the range from 0% to 75% of the maximum radial dimension 410. More specifically, the minimum radial dimension 409 may be in the range from 20% to 55% of the maximum radial dimension 410.
A cap 200 may be configured to snap fit to the opening 406 of the container 400. A wall 202 of the cap 200 may be configured to have a diameter greater than or equal to the outer diameter of the curled lip 408 defined by the wings 408 a, 408 b (or the maximum dimension 410). A lip 208 extends around the internal face of the wall 202. The lip 208 defines an internal diameter 209 that is less than the outer diameter of the curled lip 408 defined by the wings 408 a, 408 b (or the maximum dimension 410), but greater than the diameter of the curled lip 408 defined by the regions 408 c, 408 d between the wings 408 a, 408 b (or the minimum dimension 409). The wall 202 of the cap 200 may be formed from a resiliently deformable material such as a plastics material.
When fitting the cap 200 to the opening 406, the cap 200 may be rested on the wings 408 a, 408 b and a force applied to the cap 200 to snap-fit it to the opening 406.
When the force is applied to the cap 200, the resiliently deformable wall 202 is deformed radially outwardly at the regions of the wall 202 where the lip 208 is required to pass over the wings 408 a, 408 b. At the regions of the wall 202 where the lip 208 is required to pass over the regions 408 c, 408 d between the wings 408 a, 408 b, the wall 202 is deformed radially inward. The circumference of the wall 202 may remain substantially the same before and after deformation. In practical embodiments there may be some extension of the circumference of the wall 202. However, the extension of the circumference will be decreased with respect to the known caps and containers discussed above.
Therefore, the wall 202 of the cap is deformed out-of-round to form a lobed shape or, put another way, a “flattened” circle. Such deformation of the wall 202 out-of-round requires less force than the radial expansion of the entire wall 202 to define a greater diameter. Therefore, the container 400 requires a reduced force to be applied to a cap 200 in order to fit it to the opening 406 of the container 400.
Once the lip 208 of the cap 200 has passed the ends of the curled lip 408 at the wings 408 a, 408 b then the wall 202 may return to its original substantially circular shape and the lip 208 thereby retains the cap 200 on the container 400 as described previously.
FIG. 5 shows a section through a cap 200 fitted to an opening 406. The lip 208 is shown below the end of the wing 408 a, 408 b of the curled lip 408. As such, the cap 200 cannot be lifted from the container 400 without application of a significant force. A seal is provided by interference fit between the inner plug 204 of the cap and the curled lip 408 a, 408 b. That is, the inner plug of the cap may be made larger in diameter than the opening 406 such that the curled lip 408 a, 408 b is forced against the wall of the inner plug 204 to form a seal.
In embodiments, the varying radial dimension of the curled lip 408 of the container 400 may be arranged such that the maximum force required to fit the cap 200 to the opening 406 is 300 N. In other embodiments, the maximum required force may be 200 N. In other embodiments, the maximum required force may be 140 N. In other embodiments, the force required to snap-fit the cap 200 about the curled lip 408 a, 408 b may be in the range from 100 N to 140 N.
The manufacture of the cap 200 may affect the force required to fit the cap 200 to the opening 406. Therefore, the varying radial dimension of the curled lip 408 may be arranged in dependence on the manufacture of the cap 200.
FIG. 6 shows a plan view of a container 600 of a further embodiment in which there are four wings 608 a-608 d and four regions 608 e-608 h between the wings 608 a-608 d. The remaining features of the container 600 are the same as those for the embodiment of FIG. 4 a and are therefore not repeated here.
When fitting a cap 200 to the opening 606 of the container 600, the wall 202 of the cap will again be deformed out-of-round. The regions of the lip 208 required to pass over the wings 608 a-608 d deform radially outwardly, and the regions of the lip 208 required to pass over the regions 608 e-608 h between the protrusions 608 a-608 d deform radially inwardly. The circumference of the wall 202 before and after deformation remains substantially the same. As discussed above, in practical embodiments there may be some extension of the circumference of the wall 202.
The invention is not limited to embodiments of the container comprising two or four wings. In other embodiments the curled lip may comprise three, five, six, seven or eight wings.
FIG. 7 shows a plan view of the base a cap 700 according to an embodiment of the invention.
The cap 700 is substantially circular and comprises a resiliently deformable wall 702. A lip 708 extends around the circumference of the wall 702. The resiliently deformable wall 702 and the lip 708 are configured to snap-fit about and be retained by a curled lip 108 formed around an opening 106 of a container 100. The radial dimension 706 of the lip 708 varies around the circumference of the wall 702. This variation of radial dimension 706 allows the wall 702 to deform out-of-round during snap-fitting about the curled lip 108.
For clarity, the cap 700 of FIG. 7 includes only those features required to describe the operation of the invention. The skilled person will appreciate that other features of such caps known in the art may be added within the scope of the invention.
The cap 700 further comprises an inner plug 704 that fits within the opening 106 of the container 100. The inner plug 704 is, in certain embodiments, configured to be a tight fit within the opening 106 and to mate therewith. An annular cavity 705 is defined between the wall 702 and the inner plug 704 to accommodate the curled lip 108 when the cap 700 is fitted to the container 100.
The lip 708 comprises two wings 708 a, 708 b and two regions 708 c, 708 d between the wings 708 a, 708 b. The wings 708 a, 708 b project radially inwards toward the centre of the cap 700. The radial dimension of the wings 708 a, 708 b is greater than the radial dimension of the regions 708 c, 708 d between the wings 708 a, 708 b.
As explained above in relation to the container, the invention is not limited to embodiments of the cap comprising two wings. In other embodiments the lip may comprise three, four, five, six, seven or eight wings.
The inner diameter of the wall 702 is greater than or equal to the outer diameter of defined by the curled lip 108 of the container 100. An inner diameter 709 of the lip 708 defined by the wings 708 a, 708 b is less than the outer diameter of the curled lip 108 of the container 100. An inner diameter 710 of the lip 708 defined by the regions 708 c, 708 d is greater than the outer diameter of the curled lip 108 of the container 100. Therefore, when a force is applied to snap-fit the cap 700 to the opening 106 of the container 100, the wall 702 will deform radially outwardly at the wings 708 a, 708 b and the wall will deform radially inwardly at the regions 708 c, 708 d between the wings 708 a, 708 b. Therefore, the cap 700 is configured to deform out-of-round when fitted to a container 100.
The skilled person will be able to envisage additional embodiments of the invention within the scope of the appended claims.

Claims

1. A container comprising:

a body;

a substantially circular opening; and

a radially projecting curled lip extending around the opening for securing a substantially circular cap over the opening by way of a snap-fit,

wherein the radial dimension of the curled lip varies around the opening for allowing regions of a perimeter of a cap to deform radially outward, while other regions of the perimeter of the cap deform radially inwards during snap-fitting.

2. A container according to claim 1, wherein the curled lip projects radially outward.

3. A container according to claim 1, wherein the varying radial dimension provides the curled lip with two or more radially projecting wings.

4. A container according to claim 3, wherein the curled lip comprises four wings around the circumference of the opening.

5. A container according to claim 3, wherein the radial dimension of the curled lip varies between a minimum dimension in the range 0 mm to 1.5 mm and a maximum dimension in the range 1.6 mm to 2.5 mm.

6. A container according to claim 5, wherein the radial dimension of the curled lip varies between a minimum dimension in the range 0.5 mm to 1 mm and a maximum dimension in the range 1.8 mm to 2 mm.

7. A container according to claim 3, wherein the radial dimension of the curled lip varies between a minimum dimension and a maximum dimension, wherein the minimum dimension is in the range from 0% to 75% of maximum dimension.

8. A container according to claim 7, wherein the minimum dimension is in the range from 20% to 55% of the maximum dimension.

9. A container according to claim 1, wherein the varying radial dimension of the curled lip is arranged to require a maximum force of 300 N to snap-fit a cap about the curled lip.

10. A container according to claim 9, wherein the maximum required force is 200 N.

11. A container according to claim 9, wherein the maximum required force is 140 N.

12. A container according to claim 9, wherein the force required to snap-fit a cap about the curled lip is in the range from 100 N to 150 N.

13. A container according to claim 1, wherein the curled lip forms a continuous arc.

14. A container according to claim 13, wherein a first section of the curled lip extends radially inwardly and a second section of the curled lip extends radially outwardly.

15. A container according to claim 14, wherein, at the maximum radially projecting wings, the second section of the curled lip continues until the curled lip extends vertically downward.

16. A container according to claim 1, wherein the curled lip forms a rounded inner edge of the substantially circular opening.

17. A container according to claim 3, wherein at the radially projecting wings, the curled lip forms a rounded outer edged of the substantially circular opening.

18. A cap for snap-fitting to a substantially circular opening of a container, the cap comprising:

a substantially cylindrical and resiliently deformable wall; and

a radially projecting lip extending around the wall for securing the cap over a curled lip extending around the opening,

wherein the radial dimension of the lip varies around the wall for allowing regions of a wall to deform radially outward, while other regions of the wall deform radially inwards during snap-fitting.

19. A cap according to claim 18, wherein the varying radial dimension of the lip provides the lip with two or more radially projecting wings.

20. A container and a cap combination comprising:

the container comprising a body, a substantially circular opening, and a radially projecting curled lip extending around the opening,

the cap comprising a resiliently deformable wall and a radially projecting lip extending around the wall, the cap being configured to snap-fit to the substantially circular opening of the container;

wherein a radial dimension of the curled lip varies around the opening for allowing regions of a perimeter of a cap to deform radially outward, while other regions of the perimeter of the cap deform radially inwards during snap-fitting or a radial dimension of the lip varies around the wall for allowing regions of a wall to deform radially outward, while other regions of the wall deform radially inwards during snap-fitting.