CA1041457A - Sealing gaskets for container closures - Google Patents
Sealing gaskets for container closuresInfo
- Publication number
- CA1041457A CA1041457A CA227,839A CA227839A CA1041457A CA 1041457 A CA1041457 A CA 1041457A CA 227839 A CA227839 A CA 227839A CA 1041457 A CA1041457 A CA 1041457A
- Authority
- CA
- Canada
- Prior art keywords
- radial length
- peripheral portion
- central panel
- container
- plane
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B67—OPENING, CLOSING OR CLEANING BOTTLES, JARS OR SIMILAR CONTAINERS; LIQUID HANDLING
- B67B—APPLYING CLOSURE MEMBERS TO BOTTLES JARS, OR SIMILAR CONTAINERS; OPENING CLOSED CONTAINERS
- B67B3/00—Closing bottles, jars or similar containers by applying caps
- B67B3/02—Closing bottles, jars or similar containers by applying caps by applying flanged caps, e.g. crown caps, and securing by deformation of flanges
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D41/00—Caps, e.g. crown caps or crown seals, i.e. members having parts arranged for engagement with the external periphery of a neck or wall defining a pouring opening or discharge aperture; Protective cap-like covers for closure members, e.g. decorative covers of metal foil or paper
- B65D41/02—Caps or cap-like covers without lines of weakness, tearing strips, tags, or like opening or removal devices
- B65D41/04—Threaded or like caps or cap-like covers secured by rotation
- B65D41/0435—Threaded or like caps or cap-like covers secured by rotation with separate sealing elements
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D41/00—Caps, e.g. crown caps or crown seals, i.e. members having parts arranged for engagement with the external periphery of a neck or wall defining a pouring opening or discharge aperture; Protective cap-like covers for closure members, e.g. decorative covers of metal foil or paper
- B65D41/02—Caps or cap-like covers without lines of weakness, tearing strips, tags, or like opening or removal devices
- B65D41/10—Caps or cap-like covers adapted to be secured in position by permanent deformation of the wall-engaging parts
- B65D41/14—Caps or cap-like covers adapted to be secured in position by permanent deformation of the wall-engaging parts made of metallic foil or like thin flexible material
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Closures For Containers (AREA)
- Sealing Of Jars (AREA)
Abstract
A B S T R A C T
In known sealing gaskets for container closures, and, in par-ticular, for threaded closures, a spin-line process is used which does not allow the gasket profile to be varied or a molded gasket is used with a pro-file which is disadvantageous for "reform" sealing techniques. This invention relate? to gaskets of a molded material which allows the peripheral portion adjoining the central panel of the gasket to take a particular profile which provides improved sealing characteristics and overcomes the difficulties heretofore associated with the "reform" operations.
In known sealing gaskets for container closures, and, in par-ticular, for threaded closures, a spin-line process is used which does not allow the gasket profile to be varied or a molded gasket is used with a pro-file which is disadvantageous for "reform" sealing techniques. This invention relate? to gaskets of a molded material which allows the peripheral portion adjoining the central panel of the gasket to take a particular profile which provides improved sealing characteristics and overcomes the difficulties heretofore associated with the "reform" operations.
Description
4S~ :
This invention relates to sealing gaskets for container closures, in particular to the configuration ~profile) of gaskets for threaded closures.
Container closures are provided with gaskets primarily in order to prevent air from entering the container and/or loss of contents of the container to the outside. They are especially important in closures for containers which hold food or drink since conta~ination of the food or drink within a container by the entry of air before consumption can be a serious health hazard. A major area of use of gasketted closures is for the closing of bottles.
In order to enable a customer to re-close the container after it has been opened it is desirable to provide a threaded closure which can be removed by unscrewing. Gne general type of threaded closure which has found wldespread commercial acceptance is the in situ-threaded type: threads are formed during or after the operation of closing the closure onto the container.
Generally, a closure which is initially unthreadcd is closed by pressure onto -the neck of a threaded container. Further, lateral, pressure is then applied to impart threads to the closure while it is on the container, the threads formed in the closure corresponding to those on the neck of the container.
For example the threads may be formed with the aid of a roller. Closure caps ~, 20 having threads formed in this way are termed "roll-on" caps and are usually used on bottles.
; Gaskets for closures of the above type have hitherto been produc-ed by the so-called spin-line process. In the spin-line process a pre- -determined quantity of a plastisol of polyvinyl chloride is metered into a closure; the closure is spun rapidly about an axis through the center of *he flat top of the closure so as to distribute the plastisol by the action of centrlfugal ~orce, and the plastisol in the closure is then fluxed. The ;plastisol is a viscous dispersion of polyvinyl chloride in a plasticiser. It ~ -is fluxed by heating it to a temperature at which the plasticiser is absorbed 30~ b~ the polyuinyl chlorlde to form a homogeneous mass, which upon cooling gives ~, ~L0~57 a rubbery solid.
The spin-line process, although commercially successful~ has limitations. One limitation is that the profile of gasket cannot be satis-factorily varied. It is desirable to be able to vary the profile of a gasket according to the particular size of cap and dimensions of bottle employed.
Because in the spin-line process the shaping is effected by centrifugal force the gaskets produced will inevitably gradually increase in thickness from the centre of the closure to its periphery. Thus, if for a particular closure one wants to increase the thickness of the gasket near the periphery, it is necessary to increase the total charge of plastisol metered into the closure . ' or to increase the centrifugal force applied. The former is disadvantageous because it results in a gasket which is also thicker near the centre of the closure; this extra thickness at the centre is not required and thus there is a waste of the valuable plastiso]. The latter is disadvantageous because the whole profile of the gasket is changed and plastisol may be thrown a ....
considerable distance away from the top of the closure along the skirt, a posi- ~;
tion where it is not required. Thus the relatively "fixed" profile of the gaskets produced by the spin-line process is disadvantageous because of the difficulty or lack of economy in making minor variations to the profile.
A second problem of the spin-line gaskets is that for at least ,:,:~ ~
certain closures of the above-described type a relatively large amount of gasket is required to give an effective sealing performance.
Another problem of the spin-line process is that in large produc-tion~runs it is difficult to introduce the gasket-forming plastisol sy~metri-j~ ~ cally into the region of the centre of the closurej with the result that when the closure is spun the sealing portion is not ~ormed consistently in the shape desired.
~ Yet another problem is that the choice of materials used for the gasket is limi~ed to those which can be formulated as a viscous liquid for .: :
spinning~ such as a polyvinyl chloride plastisol.
This invention relates to sealing gaskets for container closures, in particular to the configuration ~profile) of gaskets for threaded closures.
Container closures are provided with gaskets primarily in order to prevent air from entering the container and/or loss of contents of the container to the outside. They are especially important in closures for containers which hold food or drink since conta~ination of the food or drink within a container by the entry of air before consumption can be a serious health hazard. A major area of use of gasketted closures is for the closing of bottles.
In order to enable a customer to re-close the container after it has been opened it is desirable to provide a threaded closure which can be removed by unscrewing. Gne general type of threaded closure which has found wldespread commercial acceptance is the in situ-threaded type: threads are formed during or after the operation of closing the closure onto the container.
Generally, a closure which is initially unthreadcd is closed by pressure onto -the neck of a threaded container. Further, lateral, pressure is then applied to impart threads to the closure while it is on the container, the threads formed in the closure corresponding to those on the neck of the container.
For example the threads may be formed with the aid of a roller. Closure caps ~, 20 having threads formed in this way are termed "roll-on" caps and are usually used on bottles.
; Gaskets for closures of the above type have hitherto been produc-ed by the so-called spin-line process. In the spin-line process a pre- -determined quantity of a plastisol of polyvinyl chloride is metered into a closure; the closure is spun rapidly about an axis through the center of *he flat top of the closure so as to distribute the plastisol by the action of centrlfugal ~orce, and the plastisol in the closure is then fluxed. The ;plastisol is a viscous dispersion of polyvinyl chloride in a plasticiser. It ~ -is fluxed by heating it to a temperature at which the plasticiser is absorbed 30~ b~ the polyuinyl chlorlde to form a homogeneous mass, which upon cooling gives ~, ~L0~57 a rubbery solid.
The spin-line process, although commercially successful~ has limitations. One limitation is that the profile of gasket cannot be satis-factorily varied. It is desirable to be able to vary the profile of a gasket according to the particular size of cap and dimensions of bottle employed.
Because in the spin-line process the shaping is effected by centrifugal force the gaskets produced will inevitably gradually increase in thickness from the centre of the closure to its periphery. Thus, if for a particular closure one wants to increase the thickness of the gasket near the periphery, it is necessary to increase the total charge of plastisol metered into the closure . ' or to increase the centrifugal force applied. The former is disadvantageous because it results in a gasket which is also thicker near the centre of the closure; this extra thickness at the centre is not required and thus there is a waste of the valuable plastiso]. The latter is disadvantageous because the whole profile of the gasket is changed and plastisol may be thrown a ....
considerable distance away from the top of the closure along the skirt, a posi- ~;
tion where it is not required. Thus the relatively "fixed" profile of the gaskets produced by the spin-line process is disadvantageous because of the difficulty or lack of economy in making minor variations to the profile.
A second problem of the spin-line gaskets is that for at least ,:,:~ ~
certain closures of the above-described type a relatively large amount of gasket is required to give an effective sealing performance.
Another problem of the spin-line process is that in large produc-tion~runs it is difficult to introduce the gasket-forming plastisol sy~metri-j~ ~ cally into the region of the centre of the closurej with the result that when the closure is spun the sealing portion is not ~ormed consistently in the shape desired.
~ Yet another problem is that the choice of materials used for the gasket is limi~ed to those which can be formulated as a viscous liquid for .: :
spinning~ such as a polyvinyl chloride plastisol.
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f ~:
In our United States Patent Specification No. 3,883,025~ issued May 13, 19759 we have proposed certain gaskets of a different pro~ile from those produced by the spin-line process. These gaskets are useful in the in situ threaded container closure in general, and may be made by moulding. Considered in their undeformed configuration, i.e. before the closure is closed onto the container, these gaskets comprise a substantially flat central panel and an ad-joining peripheral portion, the thickness of which is at all points greater than the thickness of the central panel and which increases continuously and/or stepwise radially outwards to the skirt of the closure.
To express this profile in another way, consider the closure in its inverted or up~turned position, meaning the opposite way up to which it is seen when closed onto a bottle. The peripheral portion of the gaskets of our aore-said United States Patent Specification No. 3,883,025 extends to a point on the skirt of the closure which is overall upwards from the central panel of the gas-ket. Considered in the direction of increasing radius from the centre of the closure ~the radially outward direction), the height of the peripheral portion . .
above the central panel starts by increasing and thereafter either continues to increase or remains the same.
The gaskets of our aforesaid United States Patent Specification No.
za 3,883,025 having the above-defined profile enable the above-described problems ;
; to be overcome, at least to a considerable extent. They do not require such large amounts of gasket material. Since they are made by moulding, their pro-file can be varied. It is easy ~o introduce the gasket-forming material into .
and form it centrally in the closure and a wide variety of different materials ` may be employed. However, caps utilising these gaskets often become cocked out of their correct alignment when the closing head is brought to bear on them~
with the result that the cap is not closed at all or is closed in an off-centre ; ~ manner, thereby often ~ailing to give a satisactory seal.
The present invention is concerned specifically ~ith gaskets for in 3Q s _ threaded caps~ especially roll-on caps~ which are to be closed onto , .-: .. :.
~3 ,:
.''~, ' ': :' , the container by a "reform" operation. In this operation force is exerted during the closing of the cap not only downwardly but also laterally of the ` skirt of the cap, so as to pinch the top of the skirt inwards. In other words, ~ -- the diameter of the skirt of the cap is reduced so as to compress ~he gasket between the top of the skirt of the cap and the side of the neck of the con-. tainer. A "reform" operation of this type is described in British Patent `I Specification No. 975,739.
:, Among the general class of gasket profiles described in our afore-'~'' .9~ ' ~-/fJi ~,d~ s~fes A said ~ s~ Patent Specification No.3,8~3,~a~ certain profiles are described as giving a good sealing performance when the cap is subjected to a reform .?~ operation. We have now found certain other profiles within this general class which not only give a good sealing performance in this operation, but possess another advantage not enjoyed by the general class or by the profiles speci-' fically disclosed for use in the reform operation.
:~ The present invention provides a container having a threaded neck, i~ a flat-topped rim adjacent said neck, a metal cap blank with a gasket therein mounted over the threaded neck of the container in a pressing relationship thereto, with cap blank having a reduced and deformed skirt diameter to com- :
press the gasket between the top of said skirt and the side of said container ~1 20 neck and to form threads in said skirt mating w.ith said container neck threads, said gasket in said cap blank comprising a flat central panel occupying from 50 to 9~% of the internal radius of said cap blank and an adjoining peripheral portion occupying the remaining 6 to 50% of the radius, the configuration of said~peripheral portion when considering the cap blank in an up-turned posi-l ~
tion relative to that which the cap occupies on the container with the peri-pheral portion extending in a radially outward direction comprising:
~ ~ ~i) a first~part of relatively steep gradient upwards from the edge J~ of the central panel making an angle with the plane of the central panel of from 25 to 90 and having a radial length of from 5 to 30% of the radial length of the whole peripheral portion;
.; .
~L0~ 7 (ii) an adjoining relatively flat step part o:E constant gradient making an angle with the plane of the central panel of from 0 to 25 and having ~ a radial length of from 10 to 70% of the radial length of the whole peripheral portion; .:
. ~iii) an adjoining corner part sloping upwardly, the height above the plane of the step part being from 20 to 65% of ~he height of the top of the corner part above the plane of the central panel, and ~ .
~iv) an adjoining final marginal part extending to the skirt . , either as flat step or upwardly and having a radial length of from 2 to 15% of the radial length of the whole peripheral portion; said peripheral portion having at least part of said flat-topped rim pressed against at least part of .: -.~ the flat step part.
; A further aspect of the invention is the method of closing a con-tainer having a neck which is threaded and a flat-topped rim, comprising plac-ing a gasketted metal cap blank over the threaded neck of the container, pres- ...
' sing the cap blank down against the neck of the container, and whilst holding :~ it so pressed~ reducing the diameter of the skirt of the cap blank, so as to .
~ compress the gasket between the top of the skirt of the cap blank and the I side of the neck of the container, de.forming the skir~ of the cap blank so as .
to form threads therein which mate with threads on the neck of the container, wherein said gasket in the cap blank comprises a flat central panel occup~ing from 50 to 9~% of the internal radius o~ the cap blank and an adjoining peri-.
: pheral pOTtiOn occupying the remaining 6 to 50% of the radius, the configura-tion of the peripheral portionJ when considering the cap blank in an up-turned position relative to that which the cap occupies on the container and when ~ considering the peripheral por~ion in a radially outward direction comprising ; ~; consecutively: ~ ;
.:, ) a firs~ part of relatively steep gradient upwards from the edge ~ ~ of the central panel which makes an angle with the plane of the central panel .' 30 : of from 25 to 90 and which has a radial length of from 5 to 30~ of the radial .. , ~ . .
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i7 length of the whole peripheral portion;
~ii) an adjoining relatively flat step part of constant gradient .
which makes an angle with the plane of the central panel of from 0 to 25 and :~`
which has a radial length of from 10 to 70% of the radial length of the whole .
peripheral portion;
Ciii) an adjoining corner part sloping upwardly, the height of which ...
above the plane of the step part is from 20 to 65% of the height of the top . :
of the corner part above the plane o the central panel, and ~iv) an adjoining final marginal part which extends to the skirt either as flat step or upwardly and which has a radial length of from 2 to 15% o the radial length of the whole peripheral portion; and the closing of the cap blank onto the neck of the container is effected so that at least part .. ~ :
~ of the flat area of the rim of the neck is pressed against at least part of f the flat step part. ~ .
Preerred embodiments o the invention will now be described with reference to the accompanying drawings, in which: ~
Figure 1 is a sectional view of a gasketted cap blank of the .. ~ ;
~ invention taken through a diameter, the cap being in an up-turned position . .
. rela$ive to its position on a container;
Figure 2 is an enlarged sectional view of part of a gasketted . cap blank showing the configuration of the peripheral portion of the gasket; :. .
.. Figure 3 is an enlarged sectional view of a second configura- .
tion o the peripheral portion~ .~ ;: :
Figure 4 is an enlarged sectional view of yet another con- .`
figur~ation o~ the peripheral portion, Figure S is a side view of the top portlons of a bottle neck onto which gasketted cap blanks of the invention may be closed, and Figure 6 is a side view of another configuration of a bottle ~; neck. ...
~ 3~ ~eferring now to Figure 1, a cap blank 1 shown has not yet i - 6 -been closed onto a container. It is made of thin aluminium, typically 0.008 to 0.012 inch (200 to 300 microns) thick, and will normally be lacquered on -the inside and outside. (However, the presence of a lacquer or its nature is not critical to the present invention). It has a flat top 3 from which depends a skirt 5 bent over at its other end into a bead 6 clefining a mouth 7. The gasket, having a configuration in accordance with the present invention, con-sists of a peripheral portion 2 beginning at a radial distance x from the ~;
centre of the flat top 3 of the cap blank and adjoining a central panel 4.
The distance d marked is the maximum internal diameter of the cap blank. For a cap blank having an external diameter of 28 mm., d is 1.092 inch ~27.7 mm.~. -The diameter of the cap blank is not critical and the invention is applicable to cap blanks having a variety of different diameters, including the commonly employed bottle cap blanks of external diameters 26, 28 and 31.5 mm.
Some cap blanks have a knurled band stamped therein just above :1 :,, .
the level of the gasket. A main purpose of this band is to stop the gasket-ting material from being flung too far along the skirt in the spin-line process.
, .. .
This band is not needed in the present invention and so is not shown in Figure 1, but it could of course be provided if desired. ~ -Figures 2 and 3 show the peripheral portions 2 of two gaskets in accordance with a first embodiment of the invention. These Figures have been . , labelled geometrically to show distances and angles. We refer first to the geometric labelling of Figures 2 and 3 to explain the invention generally.
~; The peripheral portion 2 of the gasket has an upper surface defined by the Iine ABCDE.~ The first part AB has a relatîvely steep gradient upwards from the edge A where the peripheral portion 2 joins the eentral panel 4. It may have :~ ~ ` a planar or convex s~lope, preferably convex for ease of moulding. The angle .
is between 25 and 90. The radial length of the portion AB is from 5 to 30%, more usually 5 to 20%, of the radial length AW of the whole peripheral portlon AE. In principle the radial distance AB could be greater, thereby pro- -30~ ~ ducing a less steep gradient for any given height of B above the central panel, , - 7 -': , ~:, - ` :
but since part of the aim of the invention is to take advantage of every reasonable economy which can be made in gasket material without adversely affecting the quality of the seal, a length of more than 30% on the above `. ` i ' !:
basis is of little practical interest. Because the gasket can be moulded it ``
is possible to make the gradient AB fairly steep and thereby economise on gasket material. ~ `
The second step portion BC may be flat or have a slight upward slope so that the angle ~ may be from 0 to 25 usually 0 to 15'~ and preferably ;
5-10. The radial length of the step portion BC will generally be ,~rom 30 to ~;
70, preferably 40 to 60 percent of A~. The optimum height XY of the step portion above the level of the central panel 4 will depend on the resilience ~ ;
and toughness of the gasket material employed ,~ld may also depend on the nature of the neck of the bottle. This will be discussed further with reference to Figures 5 and 6.
The "corner part" CD will normally have a concave slope when viewed as in Figures 2 and 3, but a planar or slightly convex slope might be `
appropriate for some purposes. The height of CD will vary according to pre cisely how much gasket material it is desirable to have pressed into the corner of the cap when the cap ~lan~ is closed onto the bottle. In general the dis- !','.:~'".. '~"
tance DX ~ill be fro~l 20 to 65% of the total height DY of point D above the central panel.
The distance of point D radially from the centre of the cap cor-responds to the radius of the moulding member employed to mould the gaskets.
Th~ls~the remainder of the peripheral portion, represented by DE is the radial tolerance of the moulding operation. The dimensions of the portion DE *here- ~ :
fore have no great significance in themselves but DE will generally slope up-,~ . .
~ wards e.g., as in Figure 2j or be flat as in Figure 3. The radial length of !
~ ~DE may constitute between 2 and 15% of the radial length AW of the whole peri-.
~ pheral portion. If the portions CD and DE both slope upwards so tha~ i~ is . , impossible to discern a point D, the radial length DE may be assumed to be ~ ' ` ' :, :-.
~0~ 7 the tolerance of the moulding member within the cap.
All the corners at points A, B and C are preferably rounded slight-ly, for ease of moulding, but in principle they could be sharply defined.
Table 1 gives the dimensions applicable to some particular gasket~
ted cap blanks in accordance with Figures 2 and 3:
Table 1 ;
Figure 2 Figure 3 "~ :
inches (mm.) inches (mm.) External diameter of closure1.102 f~28-00~n0~ 1.102 (28.000) Internal diameter of closure d1.092 (27.737) 1.092 ~27.737) Distance x 0.425 ~10.795) 0.400 (10.160) atio x/d 0.39 0.37 . .. _.___ ' ~adial lengths ~f AB 0.0223 (0.566) 0.0203 ~0.516) _ f BC 0.0521 fl.323) 0.0791 f2.009) , _ ~ , . .~
f CD 0.0331 (0.841~ 0.0331 (0.841) ~ -__ ~ _ - __ ____ . . ..
~f DE O.0135 ~0.343) O.0135 (0-34_}
, ~f AE (=AW) 0.121 ~3.073) 0.1460 ~3.708) ~eights YZ (central panel) 0.006 (0.152~ 0.006 ~0.152) ~ 20 - -0.0416 CI-0s7~ - -- 0.0341 ~0.866) _ 1 DX = 0.0336 C0.853~ 0.0336 ~0.853) Radii of curva~ure ~t A (conc~ve) _ None 0.10 ~2.54) ~t B (convex) _ _ 0.27* (6.86) 0.015* ~0.38~ :M
; )f CD (concave) _ _ 0.040 (1.016) 0.040 f~l.076) ~ -; ~ngles (degrees) -~
;~ o~ 10 . 10 :~ '. .' ,~ ~ ~ - ~ _ _ 50 _ 36 _ ;~
'~ ~ Gasket Material: Mixture of equal par~s by weight of polyethylene and . ~ butyl rubber __ _ ; ~ * The whole po~tion AB ~except for the concave radius at A in Figure 3) has , .
a convex slope of this radius of curvature.
g_ , , :' ~L~4~4S7 In principle, any gasketting ~aterial may be employed in the .:, ,.
present invention. A preferred material is a mixture comprising polyethylene, ;
butyl rubber, and optionally an ethylene/vinyl acetate copolymer. Poly-ethylene/butyl rubber mixtures containing e.g., 40-70% by weight of poly- ;~
ethylene and 60-30% by weight of butyl rubber, are generally suitable. Gaskets are preferably formed from these mixtures by cold-moulding as described, e.g., in our British Patent Specification No. 1,112,023, Australian Patent Specifica-tion No. 420,653 and German Auslegeschrift 1,544,989. Other usable gasket-ting materials include plasticised polyvinyl chloride and other vinyl chloride !
; 10 polymers known in the gasket-making art, other materials described in our i British Patent Specification Nos. 1,112,024, and 1,112,025 and thermoplastic ~ -,. ..
copolymers o butadiene with styrene, optionally in admixture with other materials such as polyethylene. This class of materials is described in our ~, British Patent Specification Nos. 1,196,125 and 1,196,127. The gasketting material is conveniently, but need not be, introduced into the cap in the . ~ ~ . ..
form of a solid. It may be a plastisol of a vlnyl chloride polymer. Such a ~ plastisol can be moulded by the process described in our British Patent `' ~ Specification No. 1,?39,927.
;`J~ The gasketting materials may of coursa contain any of the usual additives such as a stabiliser, plasticiser, pigment, dye, filler, slip agent or lubricant.
.,~ ~ , , .
~1 Al~hough, as explained above, a wide choice of gasketting mater- ~
~ !. - :~ -~ ials~is available, certain practical considerations influence the choice of -1 ~ : - ;
mat~erlals. To provlde a good gasket for an in sit~ threaded closure regard must be paid~both to sealing performance and to the need to be able to un-screw the closure easily from the container. In general terms a gasket made !~,, of~a soft, relatively resilient, material will give an excellcnt seal but will cause~the closure to be difficult to unscrew. Conversely9 a gasket made of a hard, relatiYely unresilient materîal will not gi.ve a very good seal, but 1 ~30 ~ will allow the closure to be unscre~éd easily. It is necessary to strike a ' ~ , .
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balance between the two requirements.
We have now found that this balance can more easily be struckif the dimensions of the peripheral portion of the gasket, in particular of the flat part (ii) and the corner part (iii) J are modified from those recom-mended in the above-described first embodiment of ~he invention. In general ; terms~ the nature of the modification is to enlarge the corner part (iii) both in the radial direction and in the direction parallel to the skirt of the ~ ;
cap. To do this it is necessary to reduce the radial length of the step part (ii) somewhat. Too severe a reduction of the step part would reduce the -; 10 resistance of the cap to cocking during the closing operation. The second embodiment of the invention is therefore concerned with a delicate selection , of dimensions which alters the balance between sealing performance of the ~; i`-gasket and unscrewability of the cap so as to permit relatively hard gasket ~~ .
r, materials to be used with better results, yet still mitigates or overcomes ;i problems of cocking during the closing operation.
;~j The second embodiment will be better unders~ood by reference to :'!
~- ~ Figure 4 of the accompanying drawings which shows in section, taken through -;~ part of the radius, the peripheral portion of a gasket of the invention within ~
; ~ . :
a cap blank.
Figure 4 has been labelled geometrically with the same reference letters and numerals as for Pigures 2 and 3. Referring to the peripheral portion 2 of the gasket, the first part AB is as described with reference ;'~ to Figures 2 and 3,~except that its preferred radial length is 15 to 30 per-
`. ', '' ' ' ,.
~: .. '.: ' , .
f ~:
In our United States Patent Specification No. 3,883,025~ issued May 13, 19759 we have proposed certain gaskets of a different pro~ile from those produced by the spin-line process. These gaskets are useful in the in situ threaded container closure in general, and may be made by moulding. Considered in their undeformed configuration, i.e. before the closure is closed onto the container, these gaskets comprise a substantially flat central panel and an ad-joining peripheral portion, the thickness of which is at all points greater than the thickness of the central panel and which increases continuously and/or stepwise radially outwards to the skirt of the closure.
To express this profile in another way, consider the closure in its inverted or up~turned position, meaning the opposite way up to which it is seen when closed onto a bottle. The peripheral portion of the gaskets of our aore-said United States Patent Specification No. 3,883,025 extends to a point on the skirt of the closure which is overall upwards from the central panel of the gas-ket. Considered in the direction of increasing radius from the centre of the closure ~the radially outward direction), the height of the peripheral portion . .
above the central panel starts by increasing and thereafter either continues to increase or remains the same.
The gaskets of our aforesaid United States Patent Specification No.
za 3,883,025 having the above-defined profile enable the above-described problems ;
; to be overcome, at least to a considerable extent. They do not require such large amounts of gasket material. Since they are made by moulding, their pro-file can be varied. It is easy ~o introduce the gasket-forming material into .
and form it centrally in the closure and a wide variety of different materials ` may be employed. However, caps utilising these gaskets often become cocked out of their correct alignment when the closing head is brought to bear on them~
with the result that the cap is not closed at all or is closed in an off-centre ; ~ manner, thereby often ~ailing to give a satisactory seal.
The present invention is concerned specifically ~ith gaskets for in 3Q s _ threaded caps~ especially roll-on caps~ which are to be closed onto , .-: .. :.
~3 ,:
.''~, ' ': :' , the container by a "reform" operation. In this operation force is exerted during the closing of the cap not only downwardly but also laterally of the ` skirt of the cap, so as to pinch the top of the skirt inwards. In other words, ~ -- the diameter of the skirt of the cap is reduced so as to compress ~he gasket between the top of the skirt of the cap and the side of the neck of the con-. tainer. A "reform" operation of this type is described in British Patent `I Specification No. 975,739.
:, Among the general class of gasket profiles described in our afore-'~'' .9~ ' ~-/fJi ~,d~ s~fes A said ~ s~ Patent Specification No.3,8~3,~a~ certain profiles are described as giving a good sealing performance when the cap is subjected to a reform .?~ operation. We have now found certain other profiles within this general class which not only give a good sealing performance in this operation, but possess another advantage not enjoyed by the general class or by the profiles speci-' fically disclosed for use in the reform operation.
:~ The present invention provides a container having a threaded neck, i~ a flat-topped rim adjacent said neck, a metal cap blank with a gasket therein mounted over the threaded neck of the container in a pressing relationship thereto, with cap blank having a reduced and deformed skirt diameter to com- :
press the gasket between the top of said skirt and the side of said container ~1 20 neck and to form threads in said skirt mating w.ith said container neck threads, said gasket in said cap blank comprising a flat central panel occupying from 50 to 9~% of the internal radius of said cap blank and an adjoining peripheral portion occupying the remaining 6 to 50% of the radius, the configuration of said~peripheral portion when considering the cap blank in an up-turned posi-l ~
tion relative to that which the cap occupies on the container with the peri-pheral portion extending in a radially outward direction comprising:
~ ~ ~i) a first~part of relatively steep gradient upwards from the edge J~ of the central panel making an angle with the plane of the central panel of from 25 to 90 and having a radial length of from 5 to 30% of the radial length of the whole peripheral portion;
.; .
~L0~ 7 (ii) an adjoining relatively flat step part o:E constant gradient making an angle with the plane of the central panel of from 0 to 25 and having ~ a radial length of from 10 to 70% of the radial length of the whole peripheral portion; .:
. ~iii) an adjoining corner part sloping upwardly, the height above the plane of the step part being from 20 to 65% of ~he height of the top of the corner part above the plane of the central panel, and ~ .
~iv) an adjoining final marginal part extending to the skirt . , either as flat step or upwardly and having a radial length of from 2 to 15% of the radial length of the whole peripheral portion; said peripheral portion having at least part of said flat-topped rim pressed against at least part of .: -.~ the flat step part.
; A further aspect of the invention is the method of closing a con-tainer having a neck which is threaded and a flat-topped rim, comprising plac-ing a gasketted metal cap blank over the threaded neck of the container, pres- ...
' sing the cap blank down against the neck of the container, and whilst holding :~ it so pressed~ reducing the diameter of the skirt of the cap blank, so as to .
~ compress the gasket between the top of the skirt of the cap blank and the I side of the neck of the container, de.forming the skir~ of the cap blank so as .
to form threads therein which mate with threads on the neck of the container, wherein said gasket in the cap blank comprises a flat central panel occup~ing from 50 to 9~% of the internal radius o~ the cap blank and an adjoining peri-.
: pheral pOTtiOn occupying the remaining 6 to 50% of the radius, the configura-tion of the peripheral portionJ when considering the cap blank in an up-turned position relative to that which the cap occupies on the container and when ~ considering the peripheral por~ion in a radially outward direction comprising ; ~; consecutively: ~ ;
.:, ) a firs~ part of relatively steep gradient upwards from the edge ~ ~ of the central panel which makes an angle with the plane of the central panel .' 30 : of from 25 to 90 and which has a radial length of from 5 to 30~ of the radial .. , ~ . .
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i7 length of the whole peripheral portion;
~ii) an adjoining relatively flat step part of constant gradient .
which makes an angle with the plane of the central panel of from 0 to 25 and :~`
which has a radial length of from 10 to 70% of the radial length of the whole .
peripheral portion;
Ciii) an adjoining corner part sloping upwardly, the height of which ...
above the plane of the step part is from 20 to 65% of the height of the top . :
of the corner part above the plane o the central panel, and ~iv) an adjoining final marginal part which extends to the skirt either as flat step or upwardly and which has a radial length of from 2 to 15% o the radial length of the whole peripheral portion; and the closing of the cap blank onto the neck of the container is effected so that at least part .. ~ :
~ of the flat area of the rim of the neck is pressed against at least part of f the flat step part. ~ .
Preerred embodiments o the invention will now be described with reference to the accompanying drawings, in which: ~
Figure 1 is a sectional view of a gasketted cap blank of the .. ~ ;
~ invention taken through a diameter, the cap being in an up-turned position . .
. rela$ive to its position on a container;
Figure 2 is an enlarged sectional view of part of a gasketted . cap blank showing the configuration of the peripheral portion of the gasket; :. .
.. Figure 3 is an enlarged sectional view of a second configura- .
tion o the peripheral portion~ .~ ;: :
Figure 4 is an enlarged sectional view of yet another con- .`
figur~ation o~ the peripheral portion, Figure S is a side view of the top portlons of a bottle neck onto which gasketted cap blanks of the invention may be closed, and Figure 6 is a side view of another configuration of a bottle ~; neck. ...
~ 3~ ~eferring now to Figure 1, a cap blank 1 shown has not yet i - 6 -been closed onto a container. It is made of thin aluminium, typically 0.008 to 0.012 inch (200 to 300 microns) thick, and will normally be lacquered on -the inside and outside. (However, the presence of a lacquer or its nature is not critical to the present invention). It has a flat top 3 from which depends a skirt 5 bent over at its other end into a bead 6 clefining a mouth 7. The gasket, having a configuration in accordance with the present invention, con-sists of a peripheral portion 2 beginning at a radial distance x from the ~;
centre of the flat top 3 of the cap blank and adjoining a central panel 4.
The distance d marked is the maximum internal diameter of the cap blank. For a cap blank having an external diameter of 28 mm., d is 1.092 inch ~27.7 mm.~. -The diameter of the cap blank is not critical and the invention is applicable to cap blanks having a variety of different diameters, including the commonly employed bottle cap blanks of external diameters 26, 28 and 31.5 mm.
Some cap blanks have a knurled band stamped therein just above :1 :,, .
the level of the gasket. A main purpose of this band is to stop the gasket-ting material from being flung too far along the skirt in the spin-line process.
, .. .
This band is not needed in the present invention and so is not shown in Figure 1, but it could of course be provided if desired. ~ -Figures 2 and 3 show the peripheral portions 2 of two gaskets in accordance with a first embodiment of the invention. These Figures have been . , labelled geometrically to show distances and angles. We refer first to the geometric labelling of Figures 2 and 3 to explain the invention generally.
~; The peripheral portion 2 of the gasket has an upper surface defined by the Iine ABCDE.~ The first part AB has a relatîvely steep gradient upwards from the edge A where the peripheral portion 2 joins the eentral panel 4. It may have :~ ~ ` a planar or convex s~lope, preferably convex for ease of moulding. The angle .
is between 25 and 90. The radial length of the portion AB is from 5 to 30%, more usually 5 to 20%, of the radial length AW of the whole peripheral portlon AE. In principle the radial distance AB could be greater, thereby pro- -30~ ~ ducing a less steep gradient for any given height of B above the central panel, , - 7 -': , ~:, - ` :
but since part of the aim of the invention is to take advantage of every reasonable economy which can be made in gasket material without adversely affecting the quality of the seal, a length of more than 30% on the above `. ` i ' !:
basis is of little practical interest. Because the gasket can be moulded it ``
is possible to make the gradient AB fairly steep and thereby economise on gasket material. ~ `
The second step portion BC may be flat or have a slight upward slope so that the angle ~ may be from 0 to 25 usually 0 to 15'~ and preferably ;
5-10. The radial length of the step portion BC will generally be ,~rom 30 to ~;
70, preferably 40 to 60 percent of A~. The optimum height XY of the step portion above the level of the central panel 4 will depend on the resilience ~ ;
and toughness of the gasket material employed ,~ld may also depend on the nature of the neck of the bottle. This will be discussed further with reference to Figures 5 and 6.
The "corner part" CD will normally have a concave slope when viewed as in Figures 2 and 3, but a planar or slightly convex slope might be `
appropriate for some purposes. The height of CD will vary according to pre cisely how much gasket material it is desirable to have pressed into the corner of the cap when the cap ~lan~ is closed onto the bottle. In general the dis- !','.:~'".. '~"
tance DX ~ill be fro~l 20 to 65% of the total height DY of point D above the central panel.
The distance of point D radially from the centre of the cap cor-responds to the radius of the moulding member employed to mould the gaskets.
Th~ls~the remainder of the peripheral portion, represented by DE is the radial tolerance of the moulding operation. The dimensions of the portion DE *here- ~ :
fore have no great significance in themselves but DE will generally slope up-,~ . .
~ wards e.g., as in Figure 2j or be flat as in Figure 3. The radial length of !
~ ~DE may constitute between 2 and 15% of the radial length AW of the whole peri-.
~ pheral portion. If the portions CD and DE both slope upwards so tha~ i~ is . , impossible to discern a point D, the radial length DE may be assumed to be ~ ' ` ' :, :-.
~0~ 7 the tolerance of the moulding member within the cap.
All the corners at points A, B and C are preferably rounded slight-ly, for ease of moulding, but in principle they could be sharply defined.
Table 1 gives the dimensions applicable to some particular gasket~
ted cap blanks in accordance with Figures 2 and 3:
Table 1 ;
Figure 2 Figure 3 "~ :
inches (mm.) inches (mm.) External diameter of closure1.102 f~28-00~n0~ 1.102 (28.000) Internal diameter of closure d1.092 (27.737) 1.092 ~27.737) Distance x 0.425 ~10.795) 0.400 (10.160) atio x/d 0.39 0.37 . .. _.___ ' ~adial lengths ~f AB 0.0223 (0.566) 0.0203 ~0.516) _ f BC 0.0521 fl.323) 0.0791 f2.009) , _ ~ , . .~
f CD 0.0331 (0.841~ 0.0331 (0.841) ~ -__ ~ _ - __ ____ . . ..
~f DE O.0135 ~0.343) O.0135 (0-34_}
, ~f AE (=AW) 0.121 ~3.073) 0.1460 ~3.708) ~eights YZ (central panel) 0.006 (0.152~ 0.006 ~0.152) ~ 20 - -0.0416 CI-0s7~ - -- 0.0341 ~0.866) _ 1 DX = 0.0336 C0.853~ 0.0336 ~0.853) Radii of curva~ure ~t A (conc~ve) _ None 0.10 ~2.54) ~t B (convex) _ _ 0.27* (6.86) 0.015* ~0.38~ :M
; )f CD (concave) _ _ 0.040 (1.016) 0.040 f~l.076) ~ -; ~ngles (degrees) -~
;~ o~ 10 . 10 :~ '. .' ,~ ~ ~ - ~ _ _ 50 _ 36 _ ;~
'~ ~ Gasket Material: Mixture of equal par~s by weight of polyethylene and . ~ butyl rubber __ _ ; ~ * The whole po~tion AB ~except for the concave radius at A in Figure 3) has , .
a convex slope of this radius of curvature.
g_ , , :' ~L~4~4S7 In principle, any gasketting ~aterial may be employed in the .:, ,.
present invention. A preferred material is a mixture comprising polyethylene, ;
butyl rubber, and optionally an ethylene/vinyl acetate copolymer. Poly-ethylene/butyl rubber mixtures containing e.g., 40-70% by weight of poly- ;~
ethylene and 60-30% by weight of butyl rubber, are generally suitable. Gaskets are preferably formed from these mixtures by cold-moulding as described, e.g., in our British Patent Specification No. 1,112,023, Australian Patent Specifica-tion No. 420,653 and German Auslegeschrift 1,544,989. Other usable gasket-ting materials include plasticised polyvinyl chloride and other vinyl chloride !
; 10 polymers known in the gasket-making art, other materials described in our i British Patent Specification Nos. 1,112,024, and 1,112,025 and thermoplastic ~ -,. ..
copolymers o butadiene with styrene, optionally in admixture with other materials such as polyethylene. This class of materials is described in our ~, British Patent Specification Nos. 1,196,125 and 1,196,127. The gasketting material is conveniently, but need not be, introduced into the cap in the . ~ ~ . ..
form of a solid. It may be a plastisol of a vlnyl chloride polymer. Such a ~ plastisol can be moulded by the process described in our British Patent `' ~ Specification No. 1,?39,927.
;`J~ The gasketting materials may of coursa contain any of the usual additives such as a stabiliser, plasticiser, pigment, dye, filler, slip agent or lubricant.
.,~ ~ , , .
~1 Al~hough, as explained above, a wide choice of gasketting mater- ~
~ !. - :~ -~ ials~is available, certain practical considerations influence the choice of -1 ~ : - ;
mat~erlals. To provlde a good gasket for an in sit~ threaded closure regard must be paid~both to sealing performance and to the need to be able to un-screw the closure easily from the container. In general terms a gasket made !~,, of~a soft, relatively resilient, material will give an excellcnt seal but will cause~the closure to be difficult to unscrew. Conversely9 a gasket made of a hard, relatiYely unresilient materîal will not gi.ve a very good seal, but 1 ~30 ~ will allow the closure to be unscre~éd easily. It is necessary to strike a ' ~ , .
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balance between the two requirements.
We have now found that this balance can more easily be struckif the dimensions of the peripheral portion of the gasket, in particular of the flat part (ii) and the corner part (iii) J are modified from those recom-mended in the above-described first embodiment of ~he invention. In general ; terms~ the nature of the modification is to enlarge the corner part (iii) both in the radial direction and in the direction parallel to the skirt of the ~ ;
cap. To do this it is necessary to reduce the radial length of the step part (ii) somewhat. Too severe a reduction of the step part would reduce the -; 10 resistance of the cap to cocking during the closing operation. The second embodiment of the invention is therefore concerned with a delicate selection , of dimensions which alters the balance between sealing performance of the ~; i`-gasket and unscrewability of the cap so as to permit relatively hard gasket ~~ .
r, materials to be used with better results, yet still mitigates or overcomes ;i problems of cocking during the closing operation.
;~j The second embodiment will be better unders~ood by reference to :'!
~- ~ Figure 4 of the accompanying drawings which shows in section, taken through -;~ part of the radius, the peripheral portion of a gasket of the invention within ~
; ~ . :
a cap blank.
Figure 4 has been labelled geometrically with the same reference letters and numerals as for Pigures 2 and 3. Referring to the peripheral portion 2 of the gasket, the first part AB is as described with reference ;'~ to Figures 2 and 3,~except that its preferred radial length is 15 to 30 per-
3~ ~ cent o the radial length AW of the whole peripheral portion AE.
The second step portion BC may be flat or have a slight upwa~d slope so ~hat the angle ~ may be from 0 to 25 usually 0 to 15 and preferably - ;
;~ S~to 10. The radial length of the step portion BC will generally be at least ~ -lO but less than 30~percent of the radial length A~ of the whole peripheral - ~-~ pQrtion AE~ pxe~e~ably 15-25%. This is distinguished from the range o 30-70%
; ~ 30 recommended for the first embodiment. The optimum height XY of the step ~ ~
:' : . .
:
; ~ ' ' ,'' portion above the level of the central panel 4 will depend on the resilience and toughness of the gasket material employed and may also depend on the nature of the neck of the bottle, as discussed furt,her with reference to Figures 5 and 6.
The "corner part" CD will normally have a concave slope when view-ed as in the drawing, but a planar or slightly convex slope might be approp-riate for some purposes. The radial length of corner part CD should be from 25 to 48% of AW. In a closure of internal diameter about 1 inch ~25-30 mm.), corner part CD is preferably concave with a radius of about 0.045 to 0.06 inch (1.1 to 1.5 mm.). The height of corner part CD will vary according to ; precisely how much gasket material it is desirable to have pressed into the corner of the cap when the cap is closed onto the bottle. In general the ; distance DX will be from 55 to 65% of the total height DY of point D above the central panel ~compared with 20 to 60% in the first embodiment).
The ratio of the radial length of corner portion CD to the step ~;
portion BC should be at least about 0.8:1. It could be made as high as, say, ~-, 4.7:1 depending on the precise combination of sealing, unscrewability and anti-cocklng properties required. Towards the higher end of this range cocking , problems may begin to re-appear, and the preferred range is about 0.8:1 to 1.7:1. Of course, if a soter gasket material were used the ratio could be as low as 0.6:1, e.g. in a cap o internal diameter about one inch C25-30 mm.) in which corner part CD is concave with a radius of about 0.04 inch (1.02 mm.). ;
However, the removal torque may then become rather high.
The portion DE is as described with reference to Figures 2 and 3.
~ All the corners at points A, B and C are preferably rounded !
i ~ slightly, for ease of moulding, but in principle they could be sharply ;
defined.
The above-given dimensions ha~e been found particularly suitable for gaskets made of mixtures of polyethylen~ and butyl rubber containing more than 50% and up to 70% polyethylene, by weight; such gaskets being defined : ' - -' '~' - 12 - ;~
.' ;" " ~, , in our British Patent Specification No. 1,112,025. They are also suitable for gaskets made of mixtures of polyethylene with a thermoplastic copolymer of styrene and butadiene as defined in our British Patent Specification No.
1,196,125. These mixtures are harder than 50% polyethylene/50% butyl rubber compositions and impart a lower removal torque to the cap. For example gasket No. 1 of the Table below has a removal torque, measured after 3 days, of about 20 inch-lb. (23.0 kg. cm.) when the gasketting material is 50% poly-ethylene/50% butyl rubber and about 12 inch-lb. (13.8 kg. cm.) when the gasket-ting material is 7~% polyethylene/30% butyl rubber.
It is possible to reduce removal torque by including a slip additive in the gasket composition typically in a proportion of up to 1.5 weight percent based on the weight of the gasketting polymer. However such an additive is often difficult to mix with the gasketting polymer, especially if more than about 1 weight percent has to be added. An advantage of the second embodiment of the present invention is that satisfactory removal tor- -ques can be obtained ~ithout recourse to adding large amounts of slip additive.
Table 2 gives the dimensions of one particular gasketted cap blank in accordance ~ith Figure ~ and, repeats for comparison the dimensions set out in Tablé 1 for a gasketted cap blank in accordance with Figure 2.
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..... ,..... .. , . : ..... . , ,,,, ,,, , , .: ~.
Table 2 Figure 2 Figure 4 inches (mm.) inches (mm.) External diameter of closure 1.102 ~28.000) 1.102 ~28.000 . ~ . ~ ,_ Internal diameter of closure d 1.092 (27.737) 1.092 (27.737?_ Distance x 0.425 (10.795) 0.415 ~10.541) _ _ ~ .
Ratio x/d 0 39 0 38 .:
Radial len ths g ~f AB 0.0223 (0.566) 0.0323 (0.820) ~f BC 0.0521 ~1.323) 0.0315 (0.800) ... . : . .
` 10 ~f CD 0.0331 (0.841) 0.0537 (1-364) ~f DE 0.0135 rO.3431 O.OI35 tO.343) _ ~ . . ~
Df AE t=AW)_ 0.121 ~3.073) 0.131 ~3.327) Ratio of radial lengths of CD/BC _ 64 1.70 Heights YX ~central panel) 0.006 ~0.152) 0.006 ~0.152) ~Y -0.0416 ~1.057~ 0.0416 rl.OS7) . . . .: . .
.....
j DX 0.0336 ~0.853) 0.0545 tl.384~
'.i _ . . ~ , ~ Radii of Curvature i ~t A ~concavel None 0.10 r2.54) , . . _ . ~ , ~t B (Sconvex) 0.027* ~6.86)0.027* ~6.86) ~f CD ~concave 0.040 ~1-0~L____0.065 tl.651) - ~ngles (degrees) ,., ' '' 10 _ 10 '' ' ':, ~ ~ 50 36 ~
, ~ . _ _ , . . .
* The whole portion AB (except for the concave radius at A in Figure 4) has a convex slope of this radius of curvature.
~ Considerable variation is possible from the dimensions given in .~ ~ Tables I and 2 but in general the overall weight of gasket material ~"film ~ weight") ~ill be less than the 450 mg. frequently needed for spun-lined . . ~ .
gaske*s in this type of cap. A film weight as low as about 250 mg. can be attained by the present invention.
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The method of closing the cap blank onto a container comprises placing the gasketted metal cap blank (which is of course made of thin metal, e.g., aluminium of thickness 0.008 to 0.012 inch [200-300 microns]) over the threaded neck of the contalner, pressing the cap blank down against the neck of the container, and whilst holding it so pressed, reducing the diameter of ^
the skirt of the cap blank at a position above the threads on the neck of the container, so as to compress the gasket material between the top of the skirt of the cap blank and the side of the neck of the container, and forming threads in the skirt of the closure by deforming it at a position and in a configura-` 10 tion corresponding to the threads on the neck of the container. The reduction -; of diameter of the skirt may be effected by use of a closure head of suitable shape, as described in British Patent Specification No. 975,739. This operation will normally precede the operation of forming the threads.
The closures of the invention may be closed onto a variety of ;
:~ :
~ containers, but it is envisaged that the invention will be of use mainly for ~
::
caps closable onto glass bottles. The glass bottles may have necks of various ~ ;
types. One type common in the U.K. is shown in Figure 5. The neck has a re-inforcing rîng 11 located below khe threads 12. If the peripheral portion of the gasket is too thin the cap will be pressed too far onto the bottle, caus-ing the head of the cap to hît the locking ring. This collision with the locking ring will damage the cap and the seal. If the cap is pressed onto the bottle slightly out of the correct vertical alignment, i.e., i there is cock-ing, the lower end of the cap may strike the reinforcing ring. The flat step part of the peripheral portion helps to prevent this from happening. The . ~ .
invention is therefore of particular use in relation to containers having on the neck a ring located immediately ~elow the threads which is of larger diameter than the internal diameter of the mouth of the cap blank.
Figure 6 shows a "pilferproof" neck, the so-called "MCA finish"~
widely used in Germany, Belgium, Netherlands and l.uxembourg. The reinforcing 30 ~ ring in Figure 6 ta~es the form of a locking band 11 located below threads !. ' ': ~ 'i"' ' ..1 ~ :
12 is thicker, butofsmaller diameter than the ring 11 in Figure 5. A cap with a long skirt is employed, so that the skirt is closed over the locking band 11 and into the area 13 of narrower diameter below it. The cap is then pressed into the container neck in the area 13. A n~rrow band which is easily fracturable is provided in the skirt of the cap in the region corresponding to the locking band 11. It is then impossible to ~mscrew the cap from the neck without causing fracture at the said narrow band.
The diameter t of the threads in Figure 5 is typically 1.063 or 1.088 inches ~26.00 or 26.65 mm.), the diameter e of the rim correspondingly 1.000 or 0.975 inch (25.4 or 24.8 mm.) and the height h ~rom the rim of the ~-neck to the top of the reinforcing ring about 0.58 inch C14.7 mm.). Typical dimensions for Figure 6 are: t = 27.65 mm., e 2~.92 mm. and h = 9.65 mm.
\ The rim of the neck has a flat top 14 which at its circumference curves downwardly to meet side wall 15. The radially outermost edge of the flat top (flat area) of the rim is marked by F. When the rim contacts the gasket initially in the closing operation, places beyond F on the rim in the radially outward direction should not contact the gaske~ at places radially ~;
in~ard of B within the cap blank.
The gaskets may be formed within the caps by moulding them, using a punch. A quantity of gasketting material is deposited within the up-turned cap which, when appropriate, may be pre-heated. It will normally be necessary to h0at the gasketting material to soften it. It is then moulded with the punch, which may optionally itself be heated. The methods of moulding well known to those skilled in the art of gasketting "crown" bottle caps have ; general applicability. Although moulding is very advantageous, the invention ;
lies primarily in the configuration of the gasket. Therefore any method of producing this configuration is in principle acceptable, and the invention is not to be construed as limited by the process of making ~he gaskets.
The invention includes containers, especially bottles filled with ~; 30 beverages for human consumption, closed by caps of the invention. In the ':~ ' ' `
- 16 - ` ;
, .. . " .~' ,'~.
following examples tests are reported showing the excellent seals which can be obtained. Percentages are by weight. ~' EXAMPLE 1 ', A cap blank of Figure 2 containing a polyethylene/butyl rubber gasket and having the cap blank and gasket dimensions given in Table 1 and a '~ ' gasket film weight of 259 mg. was closed by a reform operation onto glass ;
bottles having the standard "continuous thread" finish shown in Figure 4. The force of the closing head was 320 lb. ~145 kg.) and the side-roller force on the skirt of the cap blank was 40 lb. (18.1 kg.). For comparison caps lined ~' with 470 mg. of a spun-line polyvinyl chloride gasket were closed onto the `' '~
same type of glass bottles under the same conditions.
No problems of "cocking" occurred. ~ :
,~ Venting pressure tests showed that caps having both kinds of i' ' ~, gasket had excellent resistance to the internal pressure of gases, such as i , , .i :: ,,.
are present in carbonated beverages, there being little difference between the '' ' , two sets of results Csee Table 3). Venting pressures were determined as ' follows. The caps were closed onto glass bottles with a hole cut in the - ~''',~
bottom. The necks of the bottles were immersed in a water bath so that the ,,' , ,' cap was under water. The bottles were pressurised with compressed air intro- ' ' !
~, 20 duced through the hole in the bottom at a rate of 10 p.s.i. ~0.7 kg./sq. cm.) :`'''"~''~' per 10 seconds, until bubbles appeared in the water indicating failure of the ,~
' seal or the pressure reached 120 p.s.i. C8.4 kg./sq. cm.). Attainment of this '~'"'"'~'"' '~ pressure indicates a satisfactory seal.
''Table'3'-'venting'pressures (six sàmples~
Gap~of present invention: >120, 110, >120, >120 ~ ~120, >I20 p.s.i. '~ - '' '~ Cap containing spun-line >l?Q, ~120, 115, 115~ ',, ' ' '~ ' gasket: >120, >120 p.s.i.
(110 p.s~i~ = 7.7 kg./sq. cm, 115 p.s.i. = 8.1 kg./sq. cm; 120 p.s.i. = 8.4 ,' ~ kg./sq. cm.~
'~ 30 ~ T~is example shows that a far lo~er film weight is possible in ''' :
~ 17 -'~ ' . '. ~ '. ' ;, , .;
. ''' ' ':
~o~457 :~ ~
the present invention than that used in a cap gasketted with a spun-line gaske~. Part of the 45% decrease in film weight is attributable to the use of a material which is less dense than polyvinyl chloride, the specific gravity of the polyethylene/butyl rubber gasket being 0.9 compared with 1.2 for the polyvinyl chloride one. However, polyethylene/butyl rubber mixture is not usable in the spin-line process and it is a particular advantage of the inven-tion that by providing a sui~able configuration for a gasket which can be moulded, it is possible to use polyethylene/butyl rubber. Moreover, the de-crease in film weight attributable to difference in density of the gasket materials is only 25% out of a total decrease of 45%.
:.
Pellets of gasketting material were moulded into gaskets in a 28 mm. roll-on bottle cap blank of thin aluminium. Three different main types of gaskets were moulded, details as follows: ;
~ Designation Composition of gasketting material Configuration of gasket - in weight % ;
A 70% polyethylene/30% butyl rubber Figure 2/Table 2 B 70% polyethylene/30% butyl rubber Figure 4/Table 2 .~ .
C 50% polyethylene/50% thermoplastic Figure 4/Table 2 styrenebutadiene copolymer -"Cariflex TR 1102" -D Polyvinyl chloride plastisol Spun-line ~i.e. accord-ing to prior art ~ormed by spinning the closure about an axis through its centre) ; Gaskets were moulded from compositions A~ B and C containing no slip additive and various proportions of an oleamlde slip additive. `~
Removal torques were de~ermined after allowing the gaskets to age for one day. Some samples were subjected to venting pressure tests to deter-mine the strength of the seal. The results show that all the gaskets impart- ;
ed satisfactory removaI torques, i.e. good unscrewability, to the caps, but gaskets A according to ~igure 2 did not give a satisfactory seal because of the hardness of the material chosen. On the other hand, an excellent seal and low removal torque were obtained from the gaskets B and C. ~It will be -18 ~
. ' ~ ', ' ,';
understood that the Figure 2 gasket would have given a good seal if a softer material had been used for the gasket. A slip additive would then be useful to decrease the removal torque).
Results are shown in Table 4 below. The removal torqueSwere ob-tained as an average of 10 samples, except in the instances otherwise noted.
Table 4 Removal torques after 1 day in i~ch lb.
(kg. cm.}
% slip ?~
ad~itive A B C D
O 10.5 C12.1)12.1 C13.9)10.5 C12.1) 9.2t C10.6) 10 0.1 7.9 ( 9.1)8.4 ( 9.7j7.~ ( 8.3) 0.2 7.9 ( 9-1)8.3 ( 9.6) 5.8 ( 6-7) 0.4 6.8 ( 7.8)7.4 ( 8.5)6.0 ( 6.9~ -0.7 5.4 ( 6.2)7.3 ( 8.4) 4.9 ~5.6) 1.0 7.6 ( 8.8)8.~7 Cl~) 5.1 C 5~9) ~
1.5 4.4* C5.1)4.1 C 4~7 * average of 9 samples ~ average of 6 samples Venting pressures of 2 samples of A Ccontaining 0.1 and 1.5% slip :, :
' additive) were only 25 and 35 p.s.i. Cl.75 and 2.45 kg./sq. cm.) respectively, ~ `
Venting pressures were determined on 25 samples of B and C. Two samples of B
and one of C containing no slip agent withstood pressures of 110, 112, and 120 ; p.s.i. (7.7, 7.8 and 8.4 kg./cm.2) respectively and the other 22 withstood ~ pressures of over 120 p.s.i. Cover 8.4 kg./cm.2).
~:....... :.
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The second step portion BC may be flat or have a slight upwa~d slope so ~hat the angle ~ may be from 0 to 25 usually 0 to 15 and preferably - ;
;~ S~to 10. The radial length of the step portion BC will generally be at least ~ -lO but less than 30~percent of the radial length A~ of the whole peripheral - ~-~ pQrtion AE~ pxe~e~ably 15-25%. This is distinguished from the range o 30-70%
; ~ 30 recommended for the first embodiment. The optimum height XY of the step ~ ~
:' : . .
:
; ~ ' ' ,'' portion above the level of the central panel 4 will depend on the resilience and toughness of the gasket material employed and may also depend on the nature of the neck of the bottle, as discussed furt,her with reference to Figures 5 and 6.
The "corner part" CD will normally have a concave slope when view-ed as in the drawing, but a planar or slightly convex slope might be approp-riate for some purposes. The radial length of corner part CD should be from 25 to 48% of AW. In a closure of internal diameter about 1 inch ~25-30 mm.), corner part CD is preferably concave with a radius of about 0.045 to 0.06 inch (1.1 to 1.5 mm.). The height of corner part CD will vary according to ; precisely how much gasket material it is desirable to have pressed into the corner of the cap when the cap is closed onto the bottle. In general the ; distance DX will be from 55 to 65% of the total height DY of point D above the central panel ~compared with 20 to 60% in the first embodiment).
The ratio of the radial length of corner portion CD to the step ~;
portion BC should be at least about 0.8:1. It could be made as high as, say, ~-, 4.7:1 depending on the precise combination of sealing, unscrewability and anti-cocklng properties required. Towards the higher end of this range cocking , problems may begin to re-appear, and the preferred range is about 0.8:1 to 1.7:1. Of course, if a soter gasket material were used the ratio could be as low as 0.6:1, e.g. in a cap o internal diameter about one inch C25-30 mm.) in which corner part CD is concave with a radius of about 0.04 inch (1.02 mm.). ;
However, the removal torque may then become rather high.
The portion DE is as described with reference to Figures 2 and 3.
~ All the corners at points A, B and C are preferably rounded !
i ~ slightly, for ease of moulding, but in principle they could be sharply ;
defined.
The above-given dimensions ha~e been found particularly suitable for gaskets made of mixtures of polyethylen~ and butyl rubber containing more than 50% and up to 70% polyethylene, by weight; such gaskets being defined : ' - -' '~' - 12 - ;~
.' ;" " ~, , in our British Patent Specification No. 1,112,025. They are also suitable for gaskets made of mixtures of polyethylene with a thermoplastic copolymer of styrene and butadiene as defined in our British Patent Specification No.
1,196,125. These mixtures are harder than 50% polyethylene/50% butyl rubber compositions and impart a lower removal torque to the cap. For example gasket No. 1 of the Table below has a removal torque, measured after 3 days, of about 20 inch-lb. (23.0 kg. cm.) when the gasketting material is 50% poly-ethylene/50% butyl rubber and about 12 inch-lb. (13.8 kg. cm.) when the gasket-ting material is 7~% polyethylene/30% butyl rubber.
It is possible to reduce removal torque by including a slip additive in the gasket composition typically in a proportion of up to 1.5 weight percent based on the weight of the gasketting polymer. However such an additive is often difficult to mix with the gasketting polymer, especially if more than about 1 weight percent has to be added. An advantage of the second embodiment of the present invention is that satisfactory removal tor- -ques can be obtained ~ithout recourse to adding large amounts of slip additive.
Table 2 gives the dimensions of one particular gasketted cap blank in accordance ~ith Figure ~ and, repeats for comparison the dimensions set out in Tablé 1 for a gasketted cap blank in accordance with Figure 2.
. ...
. :`. , ~ ' ' ' ; '' : ~: ' ': ~ '- ' . . ~. -.,, , ~ .
. ` , .
..... ,..... .. , . : ..... . , ,,,, ,,, , , .: ~.
Table 2 Figure 2 Figure 4 inches (mm.) inches (mm.) External diameter of closure 1.102 ~28.000) 1.102 ~28.000 . ~ . ~ ,_ Internal diameter of closure d 1.092 (27.737) 1.092 (27.737?_ Distance x 0.425 (10.795) 0.415 ~10.541) _ _ ~ .
Ratio x/d 0 39 0 38 .:
Radial len ths g ~f AB 0.0223 (0.566) 0.0323 (0.820) ~f BC 0.0521 ~1.323) 0.0315 (0.800) ... . : . .
` 10 ~f CD 0.0331 (0.841) 0.0537 (1-364) ~f DE 0.0135 rO.3431 O.OI35 tO.343) _ ~ . . ~
Df AE t=AW)_ 0.121 ~3.073) 0.131 ~3.327) Ratio of radial lengths of CD/BC _ 64 1.70 Heights YX ~central panel) 0.006 ~0.152) 0.006 ~0.152) ~Y -0.0416 ~1.057~ 0.0416 rl.OS7) . . . .: . .
.....
j DX 0.0336 ~0.853) 0.0545 tl.384~
'.i _ . . ~ , ~ Radii of Curvature i ~t A ~concavel None 0.10 r2.54) , . . _ . ~ , ~t B (Sconvex) 0.027* ~6.86)0.027* ~6.86) ~f CD ~concave 0.040 ~1-0~L____0.065 tl.651) - ~ngles (degrees) ,., ' '' 10 _ 10 '' ' ':, ~ ~ 50 36 ~
, ~ . _ _ , . . .
* The whole portion AB (except for the concave radius at A in Figure 4) has a convex slope of this radius of curvature.
~ Considerable variation is possible from the dimensions given in .~ ~ Tables I and 2 but in general the overall weight of gasket material ~"film ~ weight") ~ill be less than the 450 mg. frequently needed for spun-lined . . ~ .
gaske*s in this type of cap. A film weight as low as about 250 mg. can be attained by the present invention.
' , !, ` .
45~7 :
The method of closing the cap blank onto a container comprises placing the gasketted metal cap blank (which is of course made of thin metal, e.g., aluminium of thickness 0.008 to 0.012 inch [200-300 microns]) over the threaded neck of the contalner, pressing the cap blank down against the neck of the container, and whilst holding it so pressed, reducing the diameter of ^
the skirt of the cap blank at a position above the threads on the neck of the container, so as to compress the gasket material between the top of the skirt of the cap blank and the side of the neck of the container, and forming threads in the skirt of the closure by deforming it at a position and in a configura-` 10 tion corresponding to the threads on the neck of the container. The reduction -; of diameter of the skirt may be effected by use of a closure head of suitable shape, as described in British Patent Specification No. 975,739. This operation will normally precede the operation of forming the threads.
The closures of the invention may be closed onto a variety of ;
:~ :
~ containers, but it is envisaged that the invention will be of use mainly for ~
::
caps closable onto glass bottles. The glass bottles may have necks of various ~ ;
types. One type common in the U.K. is shown in Figure 5. The neck has a re-inforcing rîng 11 located below khe threads 12. If the peripheral portion of the gasket is too thin the cap will be pressed too far onto the bottle, caus-ing the head of the cap to hît the locking ring. This collision with the locking ring will damage the cap and the seal. If the cap is pressed onto the bottle slightly out of the correct vertical alignment, i.e., i there is cock-ing, the lower end of the cap may strike the reinforcing ring. The flat step part of the peripheral portion helps to prevent this from happening. The . ~ .
invention is therefore of particular use in relation to containers having on the neck a ring located immediately ~elow the threads which is of larger diameter than the internal diameter of the mouth of the cap blank.
Figure 6 shows a "pilferproof" neck, the so-called "MCA finish"~
widely used in Germany, Belgium, Netherlands and l.uxembourg. The reinforcing 30 ~ ring in Figure 6 ta~es the form of a locking band 11 located below threads !. ' ': ~ 'i"' ' ..1 ~ :
12 is thicker, butofsmaller diameter than the ring 11 in Figure 5. A cap with a long skirt is employed, so that the skirt is closed over the locking band 11 and into the area 13 of narrower diameter below it. The cap is then pressed into the container neck in the area 13. A n~rrow band which is easily fracturable is provided in the skirt of the cap in the region corresponding to the locking band 11. It is then impossible to ~mscrew the cap from the neck without causing fracture at the said narrow band.
The diameter t of the threads in Figure 5 is typically 1.063 or 1.088 inches ~26.00 or 26.65 mm.), the diameter e of the rim correspondingly 1.000 or 0.975 inch (25.4 or 24.8 mm.) and the height h ~rom the rim of the ~-neck to the top of the reinforcing ring about 0.58 inch C14.7 mm.). Typical dimensions for Figure 6 are: t = 27.65 mm., e 2~.92 mm. and h = 9.65 mm.
\ The rim of the neck has a flat top 14 which at its circumference curves downwardly to meet side wall 15. The radially outermost edge of the flat top (flat area) of the rim is marked by F. When the rim contacts the gasket initially in the closing operation, places beyond F on the rim in the radially outward direction should not contact the gaske~ at places radially ~;
in~ard of B within the cap blank.
The gaskets may be formed within the caps by moulding them, using a punch. A quantity of gasketting material is deposited within the up-turned cap which, when appropriate, may be pre-heated. It will normally be necessary to h0at the gasketting material to soften it. It is then moulded with the punch, which may optionally itself be heated. The methods of moulding well known to those skilled in the art of gasketting "crown" bottle caps have ; general applicability. Although moulding is very advantageous, the invention ;
lies primarily in the configuration of the gasket. Therefore any method of producing this configuration is in principle acceptable, and the invention is not to be construed as limited by the process of making ~he gaskets.
The invention includes containers, especially bottles filled with ~; 30 beverages for human consumption, closed by caps of the invention. In the ':~ ' ' `
- 16 - ` ;
, .. . " .~' ,'~.
following examples tests are reported showing the excellent seals which can be obtained. Percentages are by weight. ~' EXAMPLE 1 ', A cap blank of Figure 2 containing a polyethylene/butyl rubber gasket and having the cap blank and gasket dimensions given in Table 1 and a '~ ' gasket film weight of 259 mg. was closed by a reform operation onto glass ;
bottles having the standard "continuous thread" finish shown in Figure 4. The force of the closing head was 320 lb. ~145 kg.) and the side-roller force on the skirt of the cap blank was 40 lb. (18.1 kg.). For comparison caps lined ~' with 470 mg. of a spun-line polyvinyl chloride gasket were closed onto the `' '~
same type of glass bottles under the same conditions.
No problems of "cocking" occurred. ~ :
,~ Venting pressure tests showed that caps having both kinds of i' ' ~, gasket had excellent resistance to the internal pressure of gases, such as i , , .i :: ,,.
are present in carbonated beverages, there being little difference between the '' ' , two sets of results Csee Table 3). Venting pressures were determined as ' follows. The caps were closed onto glass bottles with a hole cut in the - ~''',~
bottom. The necks of the bottles were immersed in a water bath so that the ,,' , ,' cap was under water. The bottles were pressurised with compressed air intro- ' ' !
~, 20 duced through the hole in the bottom at a rate of 10 p.s.i. ~0.7 kg./sq. cm.) :`'''"~''~' per 10 seconds, until bubbles appeared in the water indicating failure of the ,~
' seal or the pressure reached 120 p.s.i. C8.4 kg./sq. cm.). Attainment of this '~'"'"'~'"' '~ pressure indicates a satisfactory seal.
''Table'3'-'venting'pressures (six sàmples~
Gap~of present invention: >120, 110, >120, >120 ~ ~120, >I20 p.s.i. '~ - '' '~ Cap containing spun-line >l?Q, ~120, 115, 115~ ',, ' ' '~ ' gasket: >120, >120 p.s.i.
(110 p.s~i~ = 7.7 kg./sq. cm, 115 p.s.i. = 8.1 kg./sq. cm; 120 p.s.i. = 8.4 ,' ~ kg./sq. cm.~
'~ 30 ~ T~is example shows that a far lo~er film weight is possible in ''' :
~ 17 -'~ ' . '. ~ '. ' ;, , .;
. ''' ' ':
~o~457 :~ ~
the present invention than that used in a cap gasketted with a spun-line gaske~. Part of the 45% decrease in film weight is attributable to the use of a material which is less dense than polyvinyl chloride, the specific gravity of the polyethylene/butyl rubber gasket being 0.9 compared with 1.2 for the polyvinyl chloride one. However, polyethylene/butyl rubber mixture is not usable in the spin-line process and it is a particular advantage of the inven-tion that by providing a sui~able configuration for a gasket which can be moulded, it is possible to use polyethylene/butyl rubber. Moreover, the de-crease in film weight attributable to difference in density of the gasket materials is only 25% out of a total decrease of 45%.
:.
Pellets of gasketting material were moulded into gaskets in a 28 mm. roll-on bottle cap blank of thin aluminium. Three different main types of gaskets were moulded, details as follows: ;
~ Designation Composition of gasketting material Configuration of gasket - in weight % ;
A 70% polyethylene/30% butyl rubber Figure 2/Table 2 B 70% polyethylene/30% butyl rubber Figure 4/Table 2 .~ .
C 50% polyethylene/50% thermoplastic Figure 4/Table 2 styrenebutadiene copolymer -"Cariflex TR 1102" -D Polyvinyl chloride plastisol Spun-line ~i.e. accord-ing to prior art ~ormed by spinning the closure about an axis through its centre) ; Gaskets were moulded from compositions A~ B and C containing no slip additive and various proportions of an oleamlde slip additive. `~
Removal torques were de~ermined after allowing the gaskets to age for one day. Some samples were subjected to venting pressure tests to deter-mine the strength of the seal. The results show that all the gaskets impart- ;
ed satisfactory removaI torques, i.e. good unscrewability, to the caps, but gaskets A according to ~igure 2 did not give a satisfactory seal because of the hardness of the material chosen. On the other hand, an excellent seal and low removal torque were obtained from the gaskets B and C. ~It will be -18 ~
. ' ~ ', ' ,';
understood that the Figure 2 gasket would have given a good seal if a softer material had been used for the gasket. A slip additive would then be useful to decrease the removal torque).
Results are shown in Table 4 below. The removal torqueSwere ob-tained as an average of 10 samples, except in the instances otherwise noted.
Table 4 Removal torques after 1 day in i~ch lb.
(kg. cm.}
% slip ?~
ad~itive A B C D
O 10.5 C12.1)12.1 C13.9)10.5 C12.1) 9.2t C10.6) 10 0.1 7.9 ( 9.1)8.4 ( 9.7j7.~ ( 8.3) 0.2 7.9 ( 9-1)8.3 ( 9.6) 5.8 ( 6-7) 0.4 6.8 ( 7.8)7.4 ( 8.5)6.0 ( 6.9~ -0.7 5.4 ( 6.2)7.3 ( 8.4) 4.9 ~5.6) 1.0 7.6 ( 8.8)8.~7 Cl~) 5.1 C 5~9) ~
1.5 4.4* C5.1)4.1 C 4~7 * average of 9 samples ~ average of 6 samples Venting pressures of 2 samples of A Ccontaining 0.1 and 1.5% slip :, :
' additive) were only 25 and 35 p.s.i. Cl.75 and 2.45 kg./sq. cm.) respectively, ~ `
Venting pressures were determined on 25 samples of B and C. Two samples of B
and one of C containing no slip agent withstood pressures of 110, 112, and 120 ; p.s.i. (7.7, 7.8 and 8.4 kg./cm.2) respectively and the other 22 withstood ~ pressures of over 120 p.s.i. Cover 8.4 kg./cm.2).
~:....... :.
`~: .:'' . ':
:. ' ' :, .:, .:
, .. .
' '. ~
;:` ~ : ;''. '
Claims (12)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of closing a container having a neck which is threaded and a flat-topped rim, comprising placing a gasketted metal cap blank over the threaded neck of the container, pressing the cap blank down against the neck of the container, and whilst holding it so pressed, reducing the diameter of the skirt of the cap blank, so as to compress the gasket between the top of the skirt of the cap blank and the side of the neck of the container, deforming the skirt of the cap blank so as to form threads therein which mate with threads on the neck of the container, wherein said gasket in the cap blank comprises a flat central panel occupying from 50 to 94% of the internal radius of the cap blank and an adjoining peripheral portion occupying the remaining 6 to 50% of the radius, the configuration of the peripheral portion, when considering the cap blank in an up-turned position relative to that which the cap occupies on the container and when considering the peripheral portion in a radially outward direction comprising consecutively:
(i) a first part of relatively steep gradient upwards from the edge of the central panel which makes an angle with the plane of the central panel of from 25 to 90° and which has a radial length of from 5 to 30% of the radial length of the whole peripheral portion;
(ii) an adjoining relatively flat step part of constant gradient which makes an angle with the plane of the central panel of from 0 to 25° and which has a radial length of from 10 to 70% of the radial length of the whole peripheral portion;
(iii) an adjoining corner part sloping upwardly, the height of which above the plane of the step part is from 20 to 65% of the height of the top of the corner part above the plane of the central panel, and (iv) an adjoining final marginal part which extends to the skirt either as flat step or upwardly and which has a radial length of from 2 to 15%
of the radial length of the whole peripheral portion, and the closing of the cap blank onto the neck of the container is effected so that at least part of the flat area of the rim of the neck is pressed against at least part of the flat step part.
(i) a first part of relatively steep gradient upwards from the edge of the central panel which makes an angle with the plane of the central panel of from 25 to 90° and which has a radial length of from 5 to 30% of the radial length of the whole peripheral portion;
(ii) an adjoining relatively flat step part of constant gradient which makes an angle with the plane of the central panel of from 0 to 25° and which has a radial length of from 10 to 70% of the radial length of the whole peripheral portion;
(iii) an adjoining corner part sloping upwardly, the height of which above the plane of the step part is from 20 to 65% of the height of the top of the corner part above the plane of the central panel, and (iv) an adjoining final marginal part which extends to the skirt either as flat step or upwardly and which has a radial length of from 2 to 15%
of the radial length of the whole peripheral portion, and the closing of the cap blank onto the neck of the container is effected so that at least part of the flat area of the rim of the neck is pressed against at least part of the flat step part.
2. A method according to claim 1 wherein the corner part has a con-cave upward slope.
3. A method according to claim 1 wherein the angle between the plane of the central panel and the adjoining step part is from 5 to 10°.
4. A method according to claim 1, 2 or 3 wherein the first part has a convex slope, the angle between the first part and the plane of the central panel being the angle which a planar slope from bottom to top of the first part would make with the central panel.
5. A method according to claim 1, 2 or 3 wherein the cap blank is a bottle cap blank having an internal diameter of from 25 to 32 mm.
6. A method according to claim 1, 2 or 3 wherein the neck of the con-tainer has a ring thereon located immediately below the threads and having a larger diameter than the internal diameter of the mouth of the cap blank.
7. A method according to claim 1 wherein the radial length of the step part is at least 10 but less than 30% of the radial length of the whole peripheral portion, the ratio of the radial length of the corner part to the step part is from 0.8:1 to 1.7:1, and the height of the corner part above the plane of the step part is from 55 to 65% of the height of the top of the corner part above the plane of the central panel.
8. A method according to claim 7 wherein the radial length of the step part is 15 to 25% of the radial length.
9. A container having a threaded neck, a flat-topped rim adjacent said neck, a metal cap blank with a gasket therein mounted over the threaded neck of the container in a pressing relationship thereto, with cap blank having a reduced and deformed skirt diameter to compress the gasket between the top of said skirt and the side of said container neck and to form threads in said skirt mating with said container neck threads, said gasket in said cap blank comprising a flat central panel occupying from 50 to 94% of the internal radius of said cap blank and an adjoining peripheral portion occupy-ing the remaining 6 to 50% of the radius, the configuration of said peripheral portion when considering the cap blank in an up-turned position relative to that which the cap occupies on the container with the peripheral portion ex-tending in a radially outward direction comprising:
(i) a first part of relatively steep gradient upwards from the edge of the central panel making an angle with the plane of the central panel of from 25 to 90° and having a radial length of from 5 to 30% of the radial length of the whole peripheral portion;
(ii) an adjoining relatively flat step part of constant gradient mak-ing an angle with the plane of the central panel of from 0 to 25° and having a radial length of from 10 to 70% of the radial length of the whole peripheral portion;
(iii) an adjoining corner part sloping upwardly, the height above the plane of the step part being from 20 to 65% of the height of the top of the corner part above the plane of the central panel, and (iv) an adjoining final marginal part extending to the skirt either as flat step or upwardly and having a radial length of from 2 to 15% of the radial length of the whole peripheral portion; said peripheral portion having at least part of said flat-topped rim pressed against at least part of the flat step part.
(i) a first part of relatively steep gradient upwards from the edge of the central panel making an angle with the plane of the central panel of from 25 to 90° and having a radial length of from 5 to 30% of the radial length of the whole peripheral portion;
(ii) an adjoining relatively flat step part of constant gradient mak-ing an angle with the plane of the central panel of from 0 to 25° and having a radial length of from 10 to 70% of the radial length of the whole peripheral portion;
(iii) an adjoining corner part sloping upwardly, the height above the plane of the step part being from 20 to 65% of the height of the top of the corner part above the plane of the central panel, and (iv) an adjoining final marginal part extending to the skirt either as flat step or upwardly and having a radial length of from 2 to 15% of the radial length of the whole peripheral portion; said peripheral portion having at least part of said flat-topped rim pressed against at least part of the flat step part.
10. A container as claimed in claim 9 wherein the radial length of the step part of said peripheral portion of said gasket is at least 10 but less than 30% of the radial length of the whole peripheral portion, the ratio of the radial length of the corner part to the step part is from 0.8:1 to 1.7:1, and the height of the corner part above the plane of the step part is from 55 to 65% of the height of the top of the corner part above the plane of the central panel.
11. A method according to claim 1 wherein the radial length of the step part is 30 to 70% of the radial length of the whole peripheral portion, and the height of the corner part above the plane of the step part is from 20 to 60% of the height of the top of the corner part above the plane of the central panel.
12. A method according to claim 11 wherein the radial length of the step part is 40 to 60% of the radial length of the whole peripheral portion.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB2361174A GB1475604A (en) | 1974-05-28 | 1974-05-28 | Method of closing a container with a closure provided with a sealing gasket |
| GB2929774 | 1974-07-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1041457A true CA1041457A (en) | 1978-10-31 |
Family
ID=26256620
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA227,839A Expired CA1041457A (en) | 1974-05-28 | 1975-05-27 | Sealing gaskets for container closures |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS587541B2 (en) |
| AU (1) | AU525925B2 (en) |
| CA (1) | CA1041457A (en) |
| DE (1) | DE7516519U (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS58138356U (en) * | 1982-03-11 | 1983-09-17 | 中部電力株式会社 | solar power generation device |
-
1975
- 1975-05-24 DE DE19757516519 patent/DE7516519U/en not_active Expired
- 1975-05-26 AU AU81534/75A patent/AU525925B2/en not_active Expired
- 1975-05-26 JP JP50062049A patent/JPS587541B2/en not_active Expired
- 1975-05-27 CA CA227,839A patent/CA1041457A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE7516519U (en) | 1975-10-30 |
| AU8153475A (en) | 1976-12-02 |
| JPS587541B2 (en) | 1983-02-10 |
| JPS512581A (en) | 1976-01-10 |
| AU525925B2 (en) | 1982-12-09 |
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