CA1100442A

CA1100442A - Closure cap

Info

Publication number: CA1100442A
Application number: CA290,545A
Authority: CA
Inventors: Ralph W. Birch
Original assignee: U M P PLASTICS Ltd
Current assignee: U M P PLASTICS Ltd
Priority date: 1976-11-25
Filing date: 1977-11-09
Publication date: 1981-05-05
Also published as: US4125201A; GB1544854A; JPS5369780A

Abstract

ABSTRACT

A closure cap adapted to seal the neck of a container, the closure cap having a top portion and an annular skirt which extends from the periphery of the top portion, the skirt being provided internally with a skirt thread which is adapted to cooperate with an external neck thread on the neck of the container, the skirt also being provided internally with a radially extending resilient annular thread flange which is disposed immediately adjacent to and on the same helix as the skirt thread and is disposed on the side of the skirt thread facing the open end of the skirt, the thread flange, when undeformed, extending substantially radially inwardly of the skirt thread with a gap therebetween, the thread flange, when the closure cap is fully screwed onto the neck resiliently engaging the outer wall of the neck to effect centralisation and resist loosening of the closure cap, the thread flange being forced by the neck towards the skirt thread so as to reduce said gap.

Description

~ 4~ FP/6271001 This invention concerns both a con-tainer whose neck is sealed by a closure cap, and a closure cap therefor.
An attempt has been made in the past to devise a closure cap for a container which requires considera~le torque to remove it from the container, so as to ensure that the closure cap does not become loose during storage or txansit. Such an attempt, however, has involved pro~iding interference hetween threads on the closure cap and container, and this has ill turn : :
produced radial bulging of the closure cap which may, in certain circumstances, detract from sealing effectiveness and .
is unsightly.
According to the present invention, there is provided a closure cap adapted to seal the neck of a container, the closure cap having a top poxtion and an annular skirt which extends from the periphery of the top portion, the skirt .......................................................................................... ..... ~
being provided internally with a skirt thread which is adapted to cooperate with an external neck thread on the neck of the container, the skixt also being provided internally with a radially extending resilient annular thread flange which is disposed immediately adjacent to and on the same helix as the skirt thread and is disposed on the side of the skirt thread facing the open end of the skirt, the thread flange, when undeformed, extending substantially radia~ly inwardly of the skirt $hread with a gap therebetween, and the arrangement being such that when the closure cap is fully screwed onto the neck, the thread flange resilientIy engages the outer wall of the neck to effec~ .
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centralisation and resist loosening of the closure cap, the thread flange being forced by the neck towards the skir-t thread so as to reduce or eliminate said yap.
According to another aspec-t of the present invention, to which also the invention is in no way restricted~ there is provided a container having a neck provided externally with a neck thread, and a closure cap which is screwed onto the neck and which has a top portion and an annular skirt which extends from the periphery of the top portion, the skirt being provided internally with a skirt thread which cooperates with ~ the neck thread, the skirt also being provided internally with a radially exkending resilient annular thread flange which is disposed immediately adjacent to and on the same helix as the skirt thread and is disposed on the side of the skirt thread facing the open end of the skirt, the thread flange resiliently engaging the.o~ter wall of the neck to effect centralisation and resist loosening of the closure cap, and the thread flange having been forced : by the neck from an undeformed position, in which it extends substantially radially inwardly of the skirt thread with a gap therebe-tween, towards the skirt thread so as to reduce or eliminate said gap.
The closure cap may also be provided with a sealing fIange which seals against khe neck of the container.
The sealing 1ange is preferably a radially extending annular sealing flange which seals against the rim of the neck of the container, the seàling flange being disposed between the skirt thread and the said top portion, and the sealing flange extending radially inwardly of the skirt thread.
~he sealing flange and rim preferably have corresponding

3 cur~ed surfaces so that, when the closurs cap is scrswsd onto the nsck, ~ ~ ~
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4~ P/627~001*
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an initial line contact occurs therebetween.
Prefexably the skirt thread at its root extends through an axial dist~nce exceeding that through ~thich the thread flange ex-tends at its root. The gap may extend radially throughout the greater part of the distance be-tween the root and crest of the skirt thread.
Alternatively the gap may extend radially throughout the radially innermost portion only oE the skirt thread.
The skirt thread preferably has a straight sided profile in cross section. Moreover, the skirt thread may have leading and trailing flanks which are substantially at right angles to each other.
The thread flange may have a stra~ght sided trailing flank in cross section.
The trailing flanks of the skirt thread and thread flange may be substantially parallel to each other.
The thread flange, when undeformed and axially aligned with but spaced from the container, may extend radially inwardly of the outer wall of the neck by between 0.15 mm and 0.45 mm.
The skirt thread at its root may extend through an axial distance o between 1.5 mm and 2.05 mm.
The thread flange at its root may extend through an axial distance of between 0~63 mm and 0.76 mm.
Preferably, there ls one complete turn only of the thread flange The invention is illustrated, merely by way of an example, in the accompanylng drawings, in whlch:-Figure l is a broken-away cross-sectional view of a container and a closure cap therefor, the closure cap being shown in the position immedlately before it is screwed on-to the container, Figure 2 is a broken-away cross-sectional view showing the closure cap o~ Figure l screwed fully onto a container having minimum acceptable external dimensions, _ ~ _ ~ 42 P/6271001*
Figure 3 is a broken-away cross-sectional view showing the closure cap of Figure 1 screwed fully onto a container having n~aximum accepta~le external dimensions, Figure 4 is a broken--away cross-sectional view oE another em~odiment of a closure cap accordi.ng to the present invention, Figure 5 is a broken-away cross-sectional view showing a part of the closure cap of Figure 4 screweci fully onto a container ~aving minimum acceptable external dimensions, Figure 6 is a broken away cross-sectional view showing the closure cap of Figure 4 screwed onto a container having maximum acceptable external dimensions, Figures 7, 8 and 9 are broken-away cross-sectional views of further embodiments of closure caps according to the present invention.

In Figure 1 there is shown a container 10, of glass or other material, having a neck 11 provided externally with a thread 12 o~ conventional rounded profile. The neck 11 is adapted to be sealea by a closure cap 13. The closure cap 13 is adapted to be screwed onto the neck 11 as shown in Figure 2, 20.
but is shown in Figure 1 as being spaced froln the neck 11 but a~ially aligned therewith.
The closure cap 13 is an integral injection moulding of an elastomeric material such, for example, as polypropylene.
~5 The closure cap 13 has a top portion 14 having a flat internal surface 15 and an annular skirt 16 which extends rom the periphery o the top portion 14.
The skirt 16 is provided internally with a thread 17 which cooperates with the thread 12 of the neck 11 to retain the closure rap 13 on the container 10. The thread 17 has a straight sided profile in cross-section having, in cross-section, a flat axially extending crest 20 and :Elat leading and trailing -- 5 -- .
, ~ 4~ P/6271001*

Elal~s 21, 22 which extend at e~ual obtuse angles, e.g. of 120 , to the crest 20. The thread 17 at i~s root 18 ex~ends through an axial distance between 1.5 mm and 2.05 mm. The crest 20 of the thread 17 has a diame-ter between 0.05 mm and 0.1 mm greater than that of the outer wall 19 of the neck 11 to provide the necessary clearance to enable the closure cap 13 to be screwed onto the neck 11.
The skirt 16 is also provided internally with a radially extending resilient annular thread flange 23 which is disposed immediately adjacent to the thread 17, is on the same helix as the thread 17, and is disposed on the side of the thread 17 facing the open end of the skirt 16. The thread flange 23 has a straight sided trailing flank 24 in cross section which, in the undeformed position of the thread flange 23 shown in Figure 1, extends parallel to the internal surface 15 of the top portion 14. The thread flange 23 also has a leading flank 25 which is curved in cross section. The thread flange 23, when undeformed and axlally aligned with but spaced from the container 11 as shown in Figure 1, extends radially inwardly of the outer wall 19 of the neck 11 by between 0.15 mm and 0.~5 mm. Thus, when so undeformed, the thread flange 23 extends radially inwardly of the crest 20 of the thread 17 to a substantial extent so that, as the closure cap 13 is screwed down onto the neck 11, the thread 1ange resiliently engages the outer wall 19 so as to centralise the closure cap 13 on the neck 11, while when the closure cap 13 is screwed fully onto the neck 11, the resilient engagement of the thread flange 23 with the outer wall 19 resists loosening of thè closure cap 13.
The thread flange 23, at its root 27, extends through an axial distance of between 0.63 mm and 0.76 mm, so that the thread .
~ 6 ~ 4~ P/6271001*
17 a-t its root 18 extends through an axial distance exceeding that through which the thread flange 23 extends at its root 27. For this reason, and because, when undeformed t the thread flange 23 extends radially inwardly of the crest 20 to a substantial extent, the thread Elange 23 is resilient whereas the thread 17 is substantially non-resilient, so that the thread 17 remains substantially undeEormed even when the thread flange 23 is deformed.
The thread flange 23, when undeformed, is spaced from the thread 17 by a gap 26 which extends radially throughout the greater part of the radial distance between the root 18 and crest 20 of the thread 17.
There is preferably one complete turn only of the thread flange 23 since if further turns are provided it can be very difficult to screw the closure cap 13 d~wn onto the neck 11.
' The closure cap 13 is also provided with an annular sealing flange 28 which extends radially inwardly from the skirt 16 and is disposed between the thread 17 and the top portion 1~. The sealing flange 28, which extends radially inwardly of the thread 17, has a flat surface 28a which extends parallel to and is spaced from the internal surface 15 of the top portion 14, a surface 28b which faces the open end of the skirt 16 and which exterids radially inwardly from the skirt 16 so as to slope towards the internal surface 15, and a curved or arcuate surface 28c which joins the surfaces 28a, 28b. The curved surface 28c of the sealing flange 28, as describea in greater detail in United States Patent No.3,784,0~1, lS adapted when the closure cap 13 is screwed onto the neck 11, to make an initial circular line contact with a curved surface 29 at the rim of the neck 11 so that a primary seal is effected therebetween.
The closure cap 13 is designed for use with a container 10 whose external dimensions may vary by -~ 0.33 mm due to manufacturing tolerances. In Figure 2 the closure cap 13 is shown as ~eing screwed fully onto the neck 11 of a container 10 having the ~ .
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P/6271001**
minimum acceptahle external dimensions. As the closure cap .
13 is screwed do~m, the curved surEaces 2~c, 29 are brought into an initial line contact to effect an initial or primary seal and then, as the closure cap 13 is screwed further down the sealing flange 28 is orced into contact with a greatly lncreased area of the neck 11, such area incl.uding part of the flat radially extending surface 30 at the top of the neck 11, whereby to make a secondary seal therewith. By reason, however, of the fact that the primary seal occurs along a circular line only high sealing effectiveness is produced.
As will be appreciated, however, the best possible sealing effectiveness will only be realised if the closure cap 13 is accurately centralised coaxially in relation to the container neck 11 since otherwise an uneven distribution of the available sealing pressure will occur being greater on one side of the neck 11 than on the other. The need to allow clearance between a closure cap and a container neck, due to manufacturing tolerances, invariably permits some sideways movement of the closure when tightened with.
consequent failure to achieve accurate co-axial centralisation. :
It is in this respect that the thread flange 23 is very important ..
since once the closure cap 13 has been screwed down sufficiently to engage the outer wall 19 of the neck 11, the engagement therebetween centralises the closure cap 13 with respect to the neck 11 and thus aligns them in such a way that the best possible seal is achieved, whereby to ensure that there is even sealing pressure all round.
: As the closure cap 13 is screwed down onto the neck 11, moreover, the neck 11 has forced the thread flange 23 towards the thread 17 so as ~ substantially to eliminate the gap 26, the radially innermost part 30 of the thread flange 23 resiliently engaging the outer wall 19 and : .

' P/6271001*

being forced into a space 32 between the crest 20 and the outer wall 19. The provlsion of the thread flange 23 very substantially increases frictional resistance to the loosening of the clos~e cap 13 after it has been screwed onto the container 10, without causing any signiEicant bulging of the skirt 16 as a result.
In Figure 3 the closure cap 13 is shown as being screwed fully onto the neck 11 of a container 10 having maximum acceptable external dimensions. As will be seen from Figure 3, the disposition of the parts is very similar to that shown in Figure 2 except that, since the space 32 is in this case at a minumum, the thread flange 23 does not necessarily enter the space 32 but assumes a more bulbous configurationthan in the Figure 2 arrangement. Elere again, however, the thread flange 23 extends somewhat radially inwardly of the crest 20, so that it resiliently engages the outer wall 19 to resist loosening of the closure cap 13 and to effect centralisation of the closure cap 13 with respect to the neck 11.
As will be seen, when the parts are disposed as shown in Figure 2 or in Figure 3, the thread 17 and thread flange 23 engage each other so as to form, in effect, a single thread.
In Figure 4 there is shown part of a modified closure cap 33 having a thread 34 and a thread flange 350 The closure cap 33 may also have a sealing flange corresponding to the sealing flange 28 but thls is omitted from the drawings so as to simplify them. The thread 34 is spaced from the thread flange 35 by a gap 36 which extends radially throughout the radially innermost portion only of the thread 34.
The thread 34 has a straight sided profile in cross ~ section having leading and trailing flanks 40, 41 which are substan-tially at right angles to each other. The thread flange 35 .

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2 P/627l00l has leading and trailing flanks 42, 43 which are flat in cross-section and joined together by a radiused crest 44. rrhe leading flank 42 extends perEectly radially, whereas the trailing flank 43 is substantially parallel to the trailing flank 41.
Figure 5 shows theclosure cap 33 screwed fully onto a container 10 having the minimum acceptable ex-ternal dimensions As will be seen, the ef~ect is substantially the same as in Fi~ure 2 except that the gap 36, although substantially reduced in SiZ2 by comparison with its size in Figure 4, is not eliminated.
Figure 6 shows the closure cap 33 screwed fully GntO
a container 10 having the maximu~ acceptable external dimensions.
As will be seen, the eEfect is substar.tially the same as in Figure 3, but in this case the gap 36 virtually disappears so that the threacl 34 and thread flanye 35 become in effect one single thread.
In Figures 7, 8 and 9 there are respectively shown broken-away cross-sectional views of closure caps 45, 46, 47 according to the present invention. The portions of the closure caps 45, 46,47 sho~m in the ~rawings do not include a sealing flange corresponding to the sealing flange 28, but it should he clearly understood that each of the closure caps 4S, 46, 47 may, if desired, incorporate such a sealing flange.
'rhe closure caps 4S, 46 of Figures 7 and 8 are generally similar to the closure cap 33 of Figure 4, while the - closure cap 45 of Figure 9 is generally similar to the closure cap 13 of Figure 1, and for this reason the closure caps 45, 46, 47 will not be described in detail, like references indica-ting like parts.
In the case of the cIosure cap 45, however, the thread flange 35 has a radially extending trailing flank 50 which is at right .

lO -angles to an axially extending crest 51 of the thread 34, the thread flange 35 having a leading flank 52 which slopes radially inwardly towards the top portion (not shown) of the closure cap 45.
In the case of the closure cap 46, the construction is the same as that of the closure cap 33 of Figure 4 except that the thread flange 35 has a leading flank 53 which slopes radially i.nwardly towards the top portion (not shown) of the closure eap 46.
In the case of the closure cap 47~ the construction is the sc~e as that of the closure cap 13 of Figure 1 except that the thread flange 34 has a trailing flange 54 and a leading flange 55 whieh respeetively slope radially inwardly away from and towards the top portion (not shown) of the closuro eap 47.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:-

1. A closure cap adapted to seal the neck of a container, the closure cap having a top portion and an annular skirt which extends from the periphery of the top portion, the skirt being provided internally with a skirt thread which is adapted to cooperate with an external neck thread on the neck of the container, the skirt also being provided internally with a radially extending resilient annular thread flange which is disposed immediately adjacent to and on the same helix as the skirt thread and is disposed on the side of the skirt thread facing the open end of the skirt, the thread flange, when undeformed, extending substantially radially inwardly of the skirt thread with a gap therebetween, the thread flange, when the closure cap is fully screwed onto the neck resiliently engaging the outer wall of the neck to effect centralisation and resist loosening of the closure cap, the thread flange being forced by the neck towards the skirt thread so as to reduce said gap.

2. A container having a neck provided externally with a neck thread, and a closure cap which is screwed onto the neck and which has a top portion and an annular skirt which extends from the periphery of the top portion, the skirt being provided internally with a skirt thread which cooperates with the neck thread, the skirt also being provided internally with a radially extending resilient annular thread flange which is disposed immediately adjacent to and on the same helix as the skirt thread and is disposed on the side of the skirt thread facing the open end of the skirt, the thread flange resiliently engaging the outer wall of the neck thread to effect centralisation and resist loosening of the closure cap, and the thread flange having been forced by the neck from an undeformed position, in which it extends substantially radially inwardly of the skirt thread with a gap therebetween, towards the skirt thread so as to reduce or eliminate said gap.

3. A container as claimed in claim 2 in which the closure cap is also provided with a sealing flange which seals against the neck of the container.

4. A container as claimed in claim 3 in which the sealing flange is a radially extending annular sealing flange which seals against the rim of the neck of the container, the sealing flange being disposed between the skirt thread and the said top portion, and the sealing flange extending radially inwardly of the skirt thread.

5. A container as claimed in claim 4 in which the sealing flange and rim have corresponding curved surfaces, an initial line contact occurring therebetween when the closure cap is screwed onto the neck.

6. A container as claimed in claim 2 in which the skirt thread at its root extends through an axial distance exceeding that through which the thread flange extends at its root.

7. A container as claimed in claim 2 in which the gap extends radially throughout the greater part of the distance between the root and crest of the skirt thread.

8. A container as claimed in claim 2 in which the gap extends radially throughout the radially innermost portion only of the skirt thread.

9. A container as claimed in claim 2 in which the skirt thread has a straight sided profile in cross section.

10. A container as claimed in claim 9 in which the skirt thread has leading and trailing flanks which are substantially at right angles to each other.

11. A container as claimed in claim 2 in which the thread flange has a straight sided trailing flank in cross section.

12. A container as claimed in claim 11 in which the trailing flanks of the skirt thread and thread flange are substantially parallel to each other.

13. A container as claimed in claim 2 in which the thread flange, when undeformed and axially aligned with but spaced from the container, extends radially inwardly of the outer wall of the neck by between 0.15 mm and 0.45 mm.

14. A container as claimed in claim 2 in which the skirt thread at its root extends through an axial distance of between 1.5 mm and 2.05 mm.

15. A container as claimed in claim 2 in which the thread flange at its root extends through an axial distance of between 0.63 mm and 0.76 mm.

16. A container as claimed in claim 2 in which there is one complete turn only of the thread flange.