U.S. patent number 3,759,206 [Application Number 05/180,785] was granted by the patent office on 1973-09-18 for push-in easy-opening closures.
This patent grant is currently assigned to The Broken Hill Proprietary Company Limited. Invention is credited to Alan George Dalli, Michael Debenham, Ralph Edward Schackleford.
United States Patent |
3,759,206 |
Dalli , et al. |
September 18, 1973 |
PUSH-IN EASY-OPENING CLOSURES
Abstract
This specification dislcoses an easy-opening closure for a can
end which comprises an opening formed by partially severing a
portion from the can end to leave the portion attached thereto by
an integral neck, and a closure member formed from said severed
portion and which is larger than said opening. The sheet metal
adjacent the free edge of the opening is downwardly turned while
the sheet metal adjacent the free edge of the closure member is
upwardly turned, said free edges being in contact with or in close
proximity to each other. A sealant is applied at least in the
region of the free edges if required by the purpose for which the
can end is to be used. The specification also discloses a method of
forming such a closure comprising the steps of: forming an upwardly
directed bulge in the sheet metal, thus stretching the sheet;
partially severing a central portion of said bulge, to define an
opening and said severed portion defining a closure member for said
opening, and displacing the closure member downwardly so that its
free edge is below the free edge of the opening; partially
flattening the thus truncated bulge of sheet metal around said
opening to reduce its size, and turning downwardly said free edge
defining said opening; partially flattening the closure member to
increase its size, and turning upwardly said free edge of the
closure member, the free edge portion of said closure member being
in contact with or in close proximity to said free edge defining
said opening, and applying a sealant at least in the region of the
free edges of the opening and the closure member to seal the
closure if required by the purpose for which said container member
is to be used.
Inventors: |
Dalli; Alan George (Warrandyte,
Victoria, AU), Debenham; Michael (Frankston,
Victoria, AU), Schackleford; Ralph Edward (Ferntree
Gully, Victoria, AU) |
Assignee: |
The Broken Hill Proprietary Company
Limited (Melbourne, AU)
|
Family
ID: |
3764703 |
Appl.
No.: |
05/180,785 |
Filed: |
September 15, 1971 |
Foreign Application Priority Data
Current U.S.
Class: |
413/13; 413/17;
220/268; 413/19 |
Current CPC
Class: |
B21D
51/383 (20130101); B65D 17/401 (20180101); B65D
2205/00 (20130101) |
Current International
Class: |
B21D
51/38 (20060101); B21d 051/00 () |
Field of
Search: |
;220/27,48,53,54
;113/121R,121A,121C,116BB,116CC |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lanham; Charles W.
Assistant Examiner: Keenan; M. J.
Claims
We claim:
1. A method of forming an easy-opening closure in a sheet metal
container member, said method comprising
forming a bulge in an area of the sheet metal container member,
at least partially severing a portion of the sheet metal in said
area to provide a free edge
wherein at least a portion of said bulge lies substantially outside
of said portion,
the free edge of the sheet metal from which said portion is at
least partially severed defining an opening, and said severed
portion defining a closure member for said opening,
thereafter reducing the size of said opening by at least partly
flattening said bulge
to place at least a part of the free edge portion of said closure
member and the free edge defining said opening or the interior
surface of the sheet metal adjacent said opening in overlapping
contact or in overlapping close proximity,
whereby said container member having said easy-opening closure is
suitable for use in forming a container for liquids.
2. Method as claimed in claim 1, wherein said portion of the sheet
metal is only partially severed with at least one unsevered area
connecting said closure member to the remainder of said sheet metal
and serving as a hinge during the closure opening operation.
3. Method as claimed in claim 2, wherein said bulge includes an
approximately flat area of sheet metal that is generally parallel
to the plane of the sheet metal surrounding said bulge, said
severing being carried out substantially within said flat area.
4. Method as claimed in claim 3, wherein said sheet metal is
steel.
5. Method as claimed in claim 4, wherein after said bulge is
flattened, a sealant is applied to at least the region of the free
edges of said opening and said closure member.
6. Method as claimed in claim 4, wherein the container contents are
below atmospheric pressure.
7. Method as claimed in claim 4, wherein the container contents are
above atmospheric pressure.
8. Method as claimed in claim 2, wherein said bulge is formed
before said portion is severed.
9. Method as claimed in claim 8, wherein the size of said closure
member is increased prior to the application of said sealant.
10. Method as claimed in claim 9, wherein said closure member is
bulged when severed, and thereafter the bulged closure member is
flattened to increase the size thereof.
11. Method as claimed in claim 2, wherein said free-edge portion of
said closure member has a plurality of segments, at least one of
said segments overlying a surface of the sheet metal adjacent said
opening, and at least one other of said segments overlying the
opposite surface of the sheet metal adjacent said opening.
12. Method as claimed in claim 2, wherein said unsevered area is
located in the bulged area of the sheet metal container member.
13. A method of forming an easy-opening closure in a container
member of sheet metal comprising the following steps:
1. forming a bulge in the sheet metal, thus stretching the
sheet;
2. partially or wholly severing a central portion of said bulge to
provide a free edge, the free edge of said sheet metal from which
said portion is severed defining an opening and said severed
portion defining a closure member for said opening;
3. displacing the closure member in the opposite direction from
said bulge so that its free edge is in a different plane than the
free edge of the opening;
4. at least partially flattening the bulge of sheet metal around
said opening to reduce its size and to place at least a part of the
free edge portion of said closure member and said free edge
defining said opening or the surface of the sheet metal adjacent
said opening in overlapping contact or in overlapping close
proximity, and
5. applying a sealant at least in the region of the free edges of
the opening and the closure member to seal the closure if required
by the purpose for which said container member is to be used,
whereby said container member having said easy-opening closure is
suitable for use in forming a container for liquids.
14. Process as claimed in claim 13, wherein the free edge defining
said opening is displaced in the direction of the closure member
displacement.
15. Method as claimed in claim 13, wherein steps (1) and (2) are in
a single operation.
16. Method as claimed in claim 13, wherein said bulge includes an
approximately flat area of sheet metal that is generally parallel
to the plane of the sheet metal surrounding said bulge, said
severing being carried out substantially within said flat area.
17. Method as claimed in claim 16, wherein said portion of the
sheet metal is only partially severed with at least one unsevered
area connecting said closure member to the remainder of said sheet
metal and serving as a hinge during the closure opening
operation.
18. Method as claimed in claim 17, wherein said sheet metal is
steel.
19. Method as claimed in claim 13, wherein the closure member is
bulged when severed and thereafter the bulged closure member is at
least partially flattened to increase its size.
20. A method of forming an easy-opening closure in a sheet metal
container member, the steps comprising:
forming a bulge in an area of the member to displace metal in said
area generally normally of the sheet;
at least partially severing a portion of the displaced sheet metal
inwardly of the periphery thereof to provide a free edge of
displaced metal outwardly of the severed portion at least partially
defining an opening, with said severed portion defining a closure
member for said opening;
and reducing the size of said opening by at least partly flattening
the said displaced metal defining said opening to move the marginal
portion of the free edge and the marginal edge portion of the
closure member into overlapping relationship.
21. Method as claimed in claim 2, wherein the free edge defining
said opening is displaced towards the free edge portion of the
closure member, whereby the easy-opening closure presents a smooth
opening periphery to an opener's finger.
Description
This invention relates to easy-opening closures for containers made
at least partly from sheet metal, such as metal cans for beverages
of all kinds, other liquids, and pourable products.
The most widely marketed easy-opening closures for beverage cans
are formed in can ends made from aluminium or an aluminium alloy,
the closure member being defined by a score line that weakens the
metal and having attached to it a pull ring for tearing the closure
member from the can end. In another type of closure, a tinplate can
end has an insert of aluminium that incorporates a closure member
defined by a score line. Again, a pull ring is attached to the
closure member to enable it to be torn from the can end.
Can ends made from steel or tinplate and incorporating a score line
defining an easy-opening closure adapted for removal by a pull ring
are also known. However, the disadvantage with such closures is
that the scoring operation causes work hardening of the steel, thus
making more difficult the easy removal of the closure by the usual
tearing operation. The difficulty is accentuated when the edge of
the scoring tool becomes rounded in use. Then the strength of the
deformed metal can reach levels where the forces necessary to tear
the score are higher than those necessary to tear the adjacent
sheet. As a result, the tear does not follow the score line and the
can becomes difficult to open and dangerous in use.
A major disadvantage of such "tear-out" closures is that they are
relatively complicated and costly to manufacture. Another
disadvantage is that the closure member, after being torn from the
container, is usually thrown away thus producing a serious litter
problem.
Easy-opening closures which are not torn out of the container have
been proposed. Such closures are opened by displacing the closure
member into the container. One such proposal is disclosed in Klein
and Harper U.S. Pat. No. 3,334,775 which describes a closure formed
by drawing and shaping the sheet metal so that it is underfolded in
two superimposed 180.degree. folds, the pushin closure member or
gate panel being defined by a score cut near the lower of these
folds. Since access to the sheet metal is available only from he
underside, a conventional shearing operation is not possible and
the score cut must be made by forcing a knife into the sheet metal.
This constitutes a major disadvantage because the service life of
such a knife is likely to be short when the closure is made from
steel or tinplate especially when these are of high temper. Another
disadvantage is that the formation of the superimposed 180.degree.
folds involves severe deformation of the sheet metal and this can
cause stress cracking especially if the formation is attempted at
high speed.
The primary object of the invention is therefore to provide an
easy-opening closure that can be readily and economically formed
from steel or tinplate and that avoids the abovementioned
disadvantages. Another object of the invention is to provide an
easy-opening closure that can be economically formed from aluminium
or aluminium alloy and that has a closure member which is not
removed from the confines of the container when the closure is
opened thus reducing the litter problem.
In accordance with the invention, therefore, there is provided in a
container member formed from sheet metal, an easy-opening closure
comprising an opening formed by partially or wholly severing a
portion of the sheet metal of said container member, the free edge
of said sheet metal from which said portion is severed defining
said opening, and a closure member formed from or comprising said
severed portion and which is larger than said opening, said closure
member having part of a free edge portion thereof in contact with
or in close proximity to said free edge defining said opening, or
the interior surface of the sheet metal adjacent said opening, said
closure member having a sealant at least in the region of the free
edges of said opening and closure member if required by the purpose
for which said container member is to be used and being adapted to
be pushed away from said interior surface to open the closure.
The closure member is larger than the opening in order that any
internal pressure arising from the contents, e.g., carbonated
beverages, of the container is resisted by the overlap.
Preferably, said portion is only partially severed from said
container member to leave an integral neck that serves as a hinge
during the opening operation and ensures that the closure member
remains connected to the container member. Alternatively, a hinge
may be formed separately, such as by a strong adhesive
material.
In the present specification, the term "container member" is
intended to include any integral part of a container, such as part
of the container body, a container end or an insert adapted to form
part of a container body or end. The term "sheet metal" includes
steel, tinplate, aluminium and its alloys, other metals suitable
for container manufacture, and laminates of these metals with
relatively thin plastic films. The term "severing" means an
incision extending through the full thickness of the sheet metal
from one surface to the other. Thus "partially severing portion of
the sheet metal" means that such portion remains attached to the
parent metal only by one or more necks of unincised metal between
the two ends of the incision or incisions. The term "free edge"
means the metal surface created by the incision and includes the
corners defining said surface. The term "free edge portion"
includes the free edge as defined as well as the sheet metal
adjacent to the corners of the free edge. The term "in close
proximity" includes spacings such that a seal effective for the
purpose for which the container member is to be used is obtained by
the use of a suitable conventional sealant. In the case of
constructions not requiring sealant, say for powders, the term
includes spacings such that the contents of the container can not
escape.
When the contents of the container are at or below atmospheric
pressure, the invention provides an easy-opening closure as
hereinbefore described and in which a segment or segments of the
free edge portion of the closure member are formed to extend over
the exterior surface of the sheet metal adjacent to the opening.
The extent to which this overlap occurs is designed to resist
opening of the closure by atmospheric pressure or accidental
contact but to allow opening of the closure by finger pressure.
The invention also provides a method of forming an easy-opening
closure in a container member formed from sheet metal comprising
partially or wholly severing a portion of the sheet metal, the free
edge of said sheet metal from which said portion is severed
defining an opening and said severed portion defining a closure
member for said opening, and then reducing the size of said opening
and/or increasing the size of said closure member, a part of a free
edge portion of said closure member being in contact with or in
close proximity to said free edge defining said opening or the
interior surface of the sheet metal adjacent said opening and
applying a sealant at least in the region of the free edges of the
opening and closure member if required by the purpose for which
said container member is to be used.
In order that the invention may be more clearly understood, typical
preferred forms thereof are hereinafter more fully described with
reference to the accompanying drawings in which:
FIG. 1 is a plan view of one form of a can end embodying the
invention;
FIG. 2 is a sectional elevation view taken along the line 2--2 of
FIG. 1;
FIG. 3 is an enlarged plan view of one closure of the can end of
FIG. 1;
FIG. 4 is a plan view of a form of can end suitable for containers
having contents at or below atmospheric pressure;
FIG. 5 is a plan view of a modified form of can end suitable for
containers with contents at or below atmospheric pressure;
FIG. 6 is a sectional elevation view taken along the line 9--9 of
FIG. 3 and shows the first stage in the formation of a closure in
the can end shown in the preceding figures;
FIGS. 7, 8 and 9 are sectional elevation views taken along line
9--9 of FIG. 3, showing successive stages in the formation of the
said closure;
FIG. 10 is a sectional elevation view taken along the line 10--10
of FIG. 3;
FIG. 11 is a sectional elevation view taken along the line 11--11
of FIG. 4, and
FIG. 12 is a sectional elevation view taken along the line 12--12
of FIG. 5 .
For clarity the Figures show the configurations of the metal
defining the closure during the various stages of formation in a
somewhat exaggerated and idealized form. The actual configurations
may therefore depart from those shown.
The can end 10 shown in the drawings comprises a circular disc of
tinplate, the rim of which is preformed (FIG. 2) in the usual way
for subsequent attachment by a seaming operation to the upper end
of a can body.
The can end 10 is provided with a diametrically opposed pair of
easy-opening closures each including an integral push-in closure
member 12 which has been severed from the disc and each of which
remains connected thereto by a narrow neck 14 which is best shown
in FIGS. 3 and 10, each suck neck being arranged centrally at the
outer end of the respective closure member 12 and serving as a
hinge during the closure opening operation.
The particular location of the neck or hinge 14 with respect to
closure member 12 has been chosen to strengthen the can end in
resisting internal pressure created by the contents of the can.
However, other locations can be used providing the can end can
resist the maximum internal pressure for the particular
application.
The formation of each closure member 12 in the can end 10 provides
a corresponding opening 16 defined by the free edge 17 of the can
end 10 which is created by the severing of closure member 12 from
the can end 10 but each such opening is completely covered and
sealed by the respective closure member 12 until the latter is
subsequently pressed downwardly, as shown in broken lines in FIG.
10, to open the closure. It will be appreciated that only one such
closure member 12 need be formed in the end 10 and that the closure
or closures may assume any desired shape or configuration. The
shape shown in the drawings has been chosen both for its pouring
characteristics and its aesthetic appeal.
As best seen in FIGS. 9 and 10, the free edge 18 of the free edge
portion 19 of the closure member 12 is in contact with or in close
proximity to the free edge 17 of the opening 16. The closure member
12 is most desirably formed so as to be resiliently biased towards
the opening 16 so that contact with the free edge 17 of the opening
occurs at least around some of its periphery. Clearly, since the
closure member 12 has part of its free edge 18 beyond or outside
the free edge 17 of the opening 16, the area of the closure member
12 is larger than that of the opening 16. The amount of overlap
between the closure member 12 and the opening 16 is indicated by
the distance x in the various Figures. Hence, the closure member
will be positively restrained from being displaced upwardly by
internal pressure in a can to which the end 10 is applied. The
application of a suitable sealant S to seal any gap between the
free edge 18 of the closure member 12 and the free edge 17 opening
16 results in the closure providing an hermetically sealed can
after filling and completion. To gain access to the contents, the
closure member may be readily pushed downwardly as shown in FIG. 10
and when so displaced remains attached by neck 14 to the can end
10.
The sealants may be any suitable polymer, either natural or
synthetic. Typical sealants that may be used are those based on
polyvinyl chloride, polyvinyl dichloride, polyethylene or its
copolymers, polyamides, and the like. Conceivably, soft solder
could also be used. The coating of lacquer commonly applied to the
interior surfaces of metal containers may serve to seal the
closure.
If a relatively viscous sealant is applied to the interior of the
closure, unsightly penetration of sealant to the exterior does not
take place even if the closure member is not in a close proximity
to the opening as would have to be the case when a relatively fluid
sealant is used. In both cases, the objective is to prevent
unsightly penetration of sealant to the exterior surface of the
closure, and to obtain an effective seal after the sealant has been
subjected to the normal curing process. We have found that when
using a coventional polyvinyl chloride resin with a plastisol, for
example a commercial product made by W.R. Grace Australia Ltd. and
known as Darex cap compound no. 6385-A4, the proximity of the
closure member to the opening is not critical, and a gap of a few
thousandths of an inch (a few 0.025 mm) can be tolerated without
difficulty.
The general method of forming each closure 12 is illustrated in
successive stages in FIGS. 6, 7, 8 and 9 though it will be apparent
to those skilled in the art that the required result is not
dependent upon using the particular shapes which are illustrated
and that the number of forming operations could be reduced or
increased.
Referring to FIG. 6, an upward bulge 20 is formed initially in can
end 10, either before, after or during formation of its rim, thus
stretching the sheet metal within the region of the bulge 20. The
bulge 20 has a shoulder 22 where the metal is generally parallel to
the plane of the undeformed sheet metal around the bulge 20.
In the succeeding operation shown in FIG. 7, a generally central
portion 24 of the bulge 20 is partially severed approximately
centrally of the shoulder 22, thus defining the portion which will
be formed into the closure member 12 and also defining the opening
16. The portion 24 which remains connected to the can end by the
unincised neck 14 of sheet metal not visible in FIGS. 6 to 9, is
also displaced downwardly so that its free edge 18 is below the
free edge 17 defining the opening 16. As FIG. 7 clearly shows, the
portion 24 and the opening 16 are surrounded by flat rims, formerly
parts of the shoulder 22.
In the next operation shown in FIG. 8, the truncated portion of
bulge 20 around the opening 16 including the flat rim is partially
flattened, thus reducing the size of the opening 16 by forcing its
free edge 17 inwardly. The free edge 17 is also turned downwardly,
which has the important result of presenting a smooth periphery to
the opener's fingers or lips should he drink from the can.
In the final operation shown in FIG. 9, the closure member 12 is
partially flattened, thus increasing its size by forcing its free
edge 18 outwardly. The free edge 18 is also turned upwardly so that
it is in contact with or at least in close proximity to the free
edge 17 of the opening 16. The upward turning of the free edge of
the closure member has the advantage that any fin F of raw and
ragged metal produced by the shearing operation at the lower corner
of the free edge 18 of the closure member 12 is located more
definitely in the region of application of sealant S around the
gap. The covering of the fin F with sealant is desirable in order
to prevent contact of raw metal with the contents of the can.
As those skilled in the art will appreciate, the steps shown in
FIGS. 6 and 7 may be performed in one die operation. Similarly, the
steps shown in FIGS. 8 and 9 may also be performed simultaneously,
the sealant application normally being a separate operation.
The downward and upward turning of the free edges of the opening
and the closure member respectively is of course achieved by the
use of suitably shaped dies. Using known techniques, the dies are
also designed so that the closure member is resiliently biased
towards the opening as previously mentioned.
The desirable amount of overlap x depends inter alia on the size of
the closure, the properties of the sheet metal, and the pressure in
the container for which the can end is made. By way of example, an
end for a beer can made from high temper tinplate about 0.012
inches (0.3 mm) thick, we have found that an overlap x of 0.015
inches (0.38 mm) is very satisfactory.
It will be appreciated that complete overlap between the free edges
17 and 18 may be desirable and in such a case, the free edge 17 is
preferably disposed outwardly of and above the lever of free edge
18. Here the contact or close proximity may be between free edge 17
and the outside surface of free edge portion 19 or between free
edge 18 and the interior surface of can end 10 adjacent opening 16.
However, it should be appreciated that complete overlap is not
essential and that the embodiment described above is a commercially
workable and acceptable embodiment.
Many alternatives exist for obtaining the desired overlap between
the closure member and the opening although some of these have
obvious disadvantages. For example, the whole of the bulge or only
the central portion of it falling within the shoulder may be formed
downwardly. In this case, there is contact (or close proximity)
between the interior surface of the can end and the exterior
surface of the free edge portion of the closure member.
Another alternative construction is shown in FIGS. 13 to 17 where
parts similar to those of the first embodiment are indicated by the
suffix c. As in the first embodiment, the closure member 12c
remains connected to the end 10c by a neck 14c l of metal and the
free edge 18c of the free edge portion 19c is disposed beyond or
outside the free edge 17c of the opening 16c. However, the edge
portion 19c and the edge 17c are not turned upwardly and downwardly
but remain in their severed orientation as clearly shown in FIG.
14. It will be seen that there is contact (or close proximity)
between the free edge 17c and the exterior surface of the free edge
portion 19c.
The method of forming the closure 12c is illustrated in its
successive stages in FIGS. 15, 16 and 17. In the first stage (FIG.
15) an upward flat-topped bulge 20 is formed to the height of
shoulder 22 of the first embodiment. In the second stage (FIG. 16)
a generally central portion 24c of the bulge 20 is severed from end
10c, except for a portion defining the neck 14c, and the severed
portion is displaced downwardly so that its free edge 18c is below
the free edge 17c of the opening. The final stage (FIG. 17)
involves the partial flattening of the truncated bulge around the
opening to reduce the opening to a size smaller than the size of
the closure member 12c, and then the application of a sealant S as
in the first embodiment.
Alternatively again, the bulge may be annular in shape with the
central portion being in the plane of the undeformed sheet or at
any rate lower than the height of the annulus. Severance of the
metal around the highest part of the annulus then defines an
opening and a closure member each having a raised rim which when
partially flattened reduces the size of the opening and increases
the size of the closure member.
In the can end shown in FIGS. 4 and 11, where parts similar to
those of the previous embodiment are indicated by the suffix a,
suitable for contents at atmospheric pressure or below, the closure
member 12a has some of its free edge portion 19a at 25 in contact
with or closely overlying the exterior surface of the can end 10.
This prevents the closure member 12a from being opened by
accidental contact or by atmospheric pressure. In practice, the
width of the overlap between edge 15 and the periphery of the
opening would be much less than that shown in FIG. 4 and even in
FIG. 11. At each extremity of the overlap 25, a short incision may
be made in the edge of the closure member 12a in order to
facilitate the change in position of the edge 18a from the interior
surface to the exterior surface of the can end.
FIGS. 5 and 12, where the suffix b is used, shows an alternative
easy-opening closure which has three segments 25b of free edge 19b
on the exterior surface of the can end.
In each of the embodiments, the easy-opening closure and the
immediately surrounding parts of the can end may be covered by a
removable adhesive covering strip of paper, plastic film or other
suitable material if this is found desirable for reasons of
hygiene.
The ebodiments described are primarily intended for cans having
liquid contents. Cans for powdered, granular or other non-liquid
contents would not essentially require a sealant since a small dab
of adhesive in one or more places around the closure member would
be satisfactory. The closure would of course be designed so that
any gap between the closure and opening would not allow the
contents to escape. For substances such as salt and pepper,
perforated caps may be provided to fit into the opening after the
closure member has been displaced.
In the easy-opening closure defined above, and all other closures
embodying the essential features of the invention there is an
essential difference between our invention and that disclosed in
U.S. Pat. No. 3,334,775. Whereas in our invention, the closure
member is larger than the opening as defined by its free edge, the
gate panel or closure member in said disclosure is larger than the
opening defined by the convex rim of the upper 180.degree. fold and
is not larger than the opening defined by the score cut. In fact,
the gate panel may be considered to be smaller than the opening
defined by the score cut by an amount of the width of the cut.
Furthermore our closures do not require severe metal deformation
during their formation. Accordingly, when our closures are formed
from high temper (e.g., Temper 6) or double reduced steel the metal
does not suffer from stress cracks and therefore such closures have
distinct advantages over the above U.S. art. When formed from low
temper steel (such as for contents at atmospheric pressure) the
closures have the advantage that their formation is simple and
economic.
* * * * *