U.S. patent number 3,892,351 [Application Number 05/488,101] was granted by the patent office on 1975-07-01 for container subassembly having a membrane-type closure.
This patent grant is currently assigned to The Procter & Gamble Company. Invention is credited to Charles Louis Johnson, Charles Donald Stuard.
United States Patent |
3,892,351 |
Johnson , et al. |
July 1, 1975 |
Container subassembly having a membrane-type closure
Abstract
A container assembly is provided which comprises a composite
tubular body having an outwardly rolled top rim which body has an
asymmetrically tabbed membrane-type closure sealingly secured to
the rolled rim so that the peripheral section of the closure
conforms radially and circumferentially to an upwardly facing
annular area of the rolled rim. The method of making the container
subassembly comprises induction heat sealing a membrane-type
closure comprising an electrically conductive sheet to a composite
tubular body comprising an electrically conductive liner with
electrical insulation means and heat activatable sealant disposed
therebetween. The method further comprises biasing the peripheral
section of the closure towards the rolled rim with a uniformly
distributed force while the induction heat sealing is being
effected.
Inventors: |
Johnson; Charles Louis
(Cincinnati, OH), Stuard; Charles Donald (Cincinnati,
OH) |
Assignee: |
The Procter & Gamble
Company (Cincinnati, OH)
|
Family
ID: |
23938329 |
Appl.
No.: |
05/488,101 |
Filed: |
July 12, 1974 |
Current U.S.
Class: |
206/508; 215/251;
229/5.5; 220/359.4; 220/258.2 |
Current CPC
Class: |
B65D
51/20 (20130101); B65D 3/22 (20130101) |
Current International
Class: |
B31B
1/66 (20060101); B31B 1/60 (20060101); B65D
43/00 (20060101); B65D 3/28 (20060101); B65D
3/26 (20060101); B65D 5/64 (20060101); B65D
51/00 (20060101); B65D 77/10 (20060101); B65B
51/10 (20060101); B65D 77/20 (20060101); B65B
51/22 (20060101); B65D 77/30 (20060101); B65D
77/22 (20060101); B23K 13/00 (20060101); B23K
13/02 (20060101); B65B 7/28 (20060101); B65D
3/00 (20060101); B65D 3/12 (20060101); B65d
005/64 (); B65d 043/00 () |
Field of
Search: |
;229/5.5,43,48T
;220/256,257,258,308,359,306 ;215/251 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Hall; George T.
Attorney, Agent or Firm: Slone; Thomas J. Gorman; John V.
Witte; Richard C.
Claims
What is claimed is:
1. A container subassembly comprising a membrane-type closure, a
composite tubular body having an outwardly rolled top rim, and heat
activatable sealant and electrical insulation means disposed
intermediate said closure and said rim of said body,
said closure comprising an electrically conductive sheet which is
configured to provide a disc portion and an integral radially
extending tab, said tab being folded so that it extends radially
inwardly from the perimeter of said disc portion and is disposed
superjacent the top surface of said disc portion,
said body comprising a liner formed form a web of electrically
conductive material which is spindled into a tabular shape so that
oppositely disposed side edge portions are sealingly secured
together in overlapped relation to form a body seam, and
said closure being sealingly secured by said heat activatable
sealant to said rim along a circumferentially extending seam with
said electrical insulation means disposed therebetween so that the
peripheral section of said disc portion conforms radially and
circumferentially to an upwardly facing annular-shape area of said
rim.
2. The container subassembly of claim 1 wherein said electrical
insulation means compises
a thermoplastic coating on the bottom surface of said sheet,
and
a layer of thermoplastic material adhered to the radially inwardly
facing surface of said liner, said thermoplastic material being
heat sealable to said thermoplastic coating,
whereby said closure is sealingly secured to said rim by heat
sealing the peripheral section of said thermoplastic coating on
said closure to the portion of said thermoplastic material of said
liner which is disposed on the upwardly facing area of said rim by
virtue of said rim being outwardly rolled.
3. The container subassembly of claim 2 wherein said thermoplastic
coating and said thermoplastic layer are selected from the group
comprising ethylene vinyl acetates, Surlyns which are ionomer
resins, and polypropylene whereby said closure is rendered peelably
heat sealable to said rim of said tubular body and said seam is
substantially hermetically sealed.
4. The container subassembly of claim 3 wherein said ethylene vinyl
acetates comprise DuPont's XBR 950, and said Surlyns comprise
Surlyn number 1652 SR.
5. The container subassembly of claim 4 wherein said thermoplastic
coating is DuPont's XBR 950, and said thermoplastic layer is
DuPont's Surlyn number 1652 SR.
6. The container subassembly of claim 2 wherein said liner is
spirally wound and said body seam is spiral-shape whereby said body
seam intersects said rim and precipitates a circumferentially
extending body-seam hump on said rim due to said overlapped side
edge portions.
7. The container subassembly of claim 6 wherein said closure is
oriented with respect to said rim that the distal end of said tab
is circumferentially spaced from said body-seam hump on said
rim.
8. The container subassembly of claim 6 wherein said closure is
oriented with respect to said rim so that the distal end of said
tab is disposed superjacent said body-seam hump.
9. The container subassembly of claim 1 further comprising an
overcap comprising a top panel and an annular skirt depending from
the periphery of said top panel, said top panel comprising
heat-deformable means for causing said radial and circumferential
conformation of said peripheral section of said closure to said rim
area when said overcap is biased towards said rim by a biasing
device which presents a planar surface to the exterior of said top
panel while said heat-deformable means is heated to a sufficiently
high temperature to enable heat-deformation thereof.
10. The container subassembly of claim 9 wherein said
heat-deformable means comprises a multiplicity of circumferentially
spaced, radially extending, depending ribs of thermoplactic
material disposed adjacent the perimeter of said top panel so that
said ribs overlie said rim.
11. The container subassembly of claim 9 wherein an aperture is
provided in said tab adjacent said disc to improve the capability
of induction heat sealing said closure to said annular area of said
rim.
12. A container subassembly comprising a body having a top rim, a
membrane-type closure, an overcap, and means for heat sealing a
peripheral section of said closure to said rim along a
circumferentially extending seam when heated to a predetermined
temperature, said overcap comprising heat-deformable means for
uniformly distributing a biasing force from a planar surface to
uniformly bias the peripheral section of said closure against said
rim when said heat-deformable means is heated to said predetermined
temperature whereby the peripheral section of said closure is
caused to conform radially and circumferentially to said rim and to
be sealingly secured thereto upon applying said biasing force while
heating said section, rim, and heat-deformable means to said
predetermined temperature, and then cooling said section, rim, and
heat-deformable means to a sufficiently low temperature to set said
circumferential seam while maintaining said biasing force.
Description
FIELD OF THE INVENTION
Providing containers comprising membrane-type closures having
integral tabs which may be grasped to enable removal of the
closure.
BACKGROUND OF THE INVENTION
Various aspects of providing containers having membrane-type
closures, and of induction heat sealing membrane-type closures to
containers are disclosed in prior art U.S. Pats. of which the
following are representative: U.S. Pat. No. 2,937,481 issued May
24, l960 to Jack Palmer; U.S. Pat. No. 3,460,310 issued Aug. 12,
1969 to Edmund Philip Adcock et. al.; U.S. Pat. No. 3,501,045
issued Mar. 17, 1970 to Richard W. Asmus et al.; U.S. Pat. No.
3,734,044 issued May 22, 1973 to Richard W. Asmus et al.; U.S. Pat.
No. 3,767,076 issued Oct. 23, 1973 to Leo J. Kennedy; U.S. Pat. No.
3,805,993 issued Apr. 23, 1974 to William H. Enzie et al.; and U.S.
Pat. No. 3,808,074 issued Apr. 30, 1974 to John Graham Smith et al.
However, the prior art does not disclose solutions to all of the
problems associated with providing containers having membrane-type
closures in the manner of or degree of the present invention.
OBJECTS OF THE INVENTION
The nature and substance of the invention will be more readily
appreciated after giving consideration to its major aims and
purposes. The principal objects of the invention are recited in the
ensuing paragraphs in order to provide a better appreciation of its
important aspects prior to describing the details of a preferred
embodiment in later portions of this description.
A major object of the present invention is providing a container
subassembly comprising a composite tubular body and an asymmetrical
shape membrane-type closure having an integral pull tab and means
for induction heat sealing the closure to the body to effect a
hermetic seal therebetween.
Another major object of the present invention is providing a
hermetically sealable container subassembly comprising a spirally
wound composite tubular body, and an asymmetrical shape
membrane-type closure having an integral pull tab.
Still another major object of the present invention is providing
the container subassembly described in the preceding paragraph
which subassembly comprises means for being induction heat
sealed.
Yet still another major object of the present invention is
providing the container subassembly described in the preceding
paragraph which container further comprises an overcap having
heat-deformable means for causing the peripheral section of the
closure to conform radially and circumferentially to a rolled rim
of the tubular body.
Yet another major object of the present invention is providing a
thermoplastic overcap comprising heat-deformable means for causing
the peripheral section of a heat-sealable membrane-type closure to
conform radially and circumferentially to the rim of a container
body when the closure is heat sealed to the rim of the container
body.
A still further major object of the present invention is providing
a method of induction heat sealing an asymmetrical shape
membrane-type closure to the rim of a tubular container body so
that the peripheral section of the closure conforms radially and
circumferentially to the rim of the tubular body.
SUMMARY OF THE INVENTION
The above recited and other objects are achieved in the present
invention by providing a container subassembly comprising a
membrane-type closure having an integral pull tab, a composite
tabular body having a rolled top rim, and heat activatable sealant
and electrical insulation disposed intermediate the peripheral
section of the closure and the rim of the tubular body. The closure
comprises an electrically conductive sheet which is configured to
provide a disc portion and an integral pull tab. The tubular body
comprises a liner of electrically conductive material having a lap
seam intermediate overlapped side edge portions. The closure is
sealingly secured along a circumferentially extending seam to the
rim of the container so that the peripheral section of the disc
portion of the closure conforms radially and circumferentially to
an upwardly facing annular-shape area of the rolled rim on the
tubular body. The container subassembly may further comprise an
overcap comprising heat-deformable means for effecting the radial
and circumferential conformation of the peripheral section of the
closure to the rim of the container body. The method of induction
heat sealing an asymmetrical-shape closure comprising an
electrically conductive sheet to a tubular body comprising an
electrically conductive liner includes the step of biasing the
peripheral section of the closure towards the rim of the container
body with a uniformly distributed force while adjacent portions of
the electrically conductive sheet and the electrically conductive
liner are simultaneously heated by induction heating means.
BRIEF DESCRIPTION OF THE DRAWINGS
While the specification concludes with claims particularly pointing
out and distinctly claiming the subject matter regarded as forming
the present invention, it is believed the invention will be better
understood from the following description taken in connection with
the accompanying drawings in which:
FIG. 1 is an exploded perspective view of a preferred container
subassambly embodying the present invention.
FIG. 2 is a fragmentary perspective view of the container
subassembly shown in FIG. 1.
FIG. 3 is an enlarged scale, fragmentary perspective view of the
spirally wound and lap seamed liner of the container subassembly
shown in FIGS. 1 and 2.
FIG. 4 is a fragmentary sectional view of the liner shown in FIG. 3
taken along line 4--4 thereof.
FIG. 5 is a fragmentary, radially outwardly looking view of the
liner-seam-area of the outwardly rolled rim of the tubular
container body shown in FIG. 1.
FIG. 6 is an enlarged scale bottom view of the overcap of the
container subassembly shown in FIG. 1.
FIG. 7 is an enlarged scale, fragmentary radial sectional view of
the overcap shown in FIG. 1 taken along line 7--7 thereof.
FIG. 8 is an enlarged scale fragmentary circumferential sectional
view of the overcap shown in FIGS. 1, 6 and 7 taken along line 8--8
of FIG. 7.
FIG. 9 is an enlarged scale top view of the membrane-type closure
shown in FIG. 1 prior to folding the integral tab of the closure to
the orientation shown in FIG. 1.
FIG. 10 is a fragmentary sectional view of the closure shown in
FIG. 9 taken along line 10--10 thereof.
FIG. 11 is an enlarged scale radial sectional view of a top edge
portion of the container subassembly shown in FIG. 2 taken along
line 11--11 thereof which line extends between radially extending
ribs depending from the interior surface of the overcap of the
subassembly.
FIG. 12 is an enlarged scale circumferential sectional view of the
container subassembly shown in FIG. 2 taken along line 12--12
thereof.
FIG. 13 is a reduced scale, end view of a portion of an apparatus
for induction heat sealing the closure of the container assembly
shown in FIG. 1 to the rim of the tubular body of the container
assembly.
FIG. 14 is a reduced scale perspective view of the induction
heating electrode of the apparatus shown in FIG. 13.
FIG. 15 is a fragmentary perspective view of an alternate container
subassembly embodying the present invention.
FIG. 16 is an enlarged scale top view of an alternate membrane-type
closure which may be incorporated in container subassemblies
embodying the present invention.
FIG. 17 is an enlarged scale, fragmentary top view of another
alternate membrane-type closure which may be incorporated in
container subassemblies embodying the present invention.
FIG. 18 is a sectional view of the alternate membrane-type closure
shown in FIG. 17 taken along line 18--18 thereof.
FIG. 19 is an enlarged scale, fragmentary top view of yet another
alternate membrane-type closure which may be incorporated in
container assemblies embodying the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIGS 1 and 2, the preferred embodiment of the
present invention is a container subassembly 40 which comprises a
spirally wound, composite tubular body 41, a membrane-type closure
42 having an integral pull tab 43, and an overcap 44.
Briefly, overcap 44 comprises heat-deformable means such as a
multiplicity of circumferentially spaced, radially extending ribs
85 which means are heat-deformed or molded when container
subassembly 40 is assembled to cause the peripheral section of
closure 42 to conform radially and circumferentially to the rim of
tubular body 41 regardless of minor irregularities in the rim of
tubular body 41. Further, the container subassembly comprises means
for induction heat sealing closure 42 to the rim of tubular body 41
and for causing the heat-deformable means to effect the above
described radial and circumferential conformation of the peripheral
section of closure 42 to the rim of tubular body 41.
Tubular body 41, FIG. 1, of the preferred embodiment container
assembly 40 is a glue bonded, composite, spirally wound tube
construction which tube, after being cut to length, has its top rim
48 rolled outwardly to form a circumferentially extending bead and
has its bottom rim 49 flared to enable crimping a bottom closure
thereto.
Referring now to FIG. 11, the multi-ply sidewall of tubular body
41, FIG. 1, is shown to comprise three major plies: an innermost
ply hereinafter referred to as liner 50, an outermost ply
hereinafter referred to as label 51, and a middle ply 52. In the
preferred embodiment container assembly 40, FIG. 1, label 51
comprises 55 pound litho paper coated with a moisture barrier
which, in turn, is printed and coated with an overprint lacquer;
and the middle ply 52 is 19 point kraft paper can board.
Liner 50, FIG. 3, comprises a web of four layer construction as
shown in FIG. 4. The innermost layer 53 is a thermoplastic material
which forms the radially inwardly facing portion of body 41 when
the web is spirally wound and spirally lap seamed as indicated in
FIG. 3. The thermoplastic material of the preferred embodiment is a
12 pound coating of Surlyn, DuPont number 1,652 SR, an ionomer
resin, although polypropylene and other thermoplastic materials may
be used. Surlyn is a registered trademark of the E.I. DuPont de
Nemours Company. The second layer 54 is aluminum foil having a
preferred thickness of about thirty-five one-hundred-thousandths of
an inch which is adhered to the outermost layer 56 by the third
layer 55 of the construction which third layer may be a 7 pound
coating of low density polyethylene. The outermost layer 56 may be
25 pound machine finish natural kraft paper.
When the web from which liner 50 is spirally wound into the tubular
shape shown in FIG. 3, one side edge portion 60 is doubled back so
that the oppositely disposed second side edge portion 61 can be
overlapped therewith with the thermoplastic innermost layer 53 of
side edge portions 60, 61 in abutting relation. This enables the
overlapped side edge portions 60, 61 to be heat sealed together to
form a spiral lap seam or body seam 62 having a spiral inner edge
63 and a spiral outer edge 64.
As is shown in FIG. 3, spiral lap seam 62 comprises three
thicknesses of the web from which the liner 50 is formed. The two
extra thicknesses of liner material in spiral seam 62 precipitate a
circumferentially extending hump 65, FIG. 5, in the top rim 48 of
tubular body 41, which hump 65 is shown in exaggerated proportions
in FIG. 5 to more clearly disclose that it causes the top rim 48 to
have elevational differences around the top opening 66 of tubular
body 41 as indicated in FIG. 5 by delta E; (.delta.E).
As will be described more fully hereinafter, elevational
differences of rim 48 around top opening 66 which differences are
precipitated by lap seams and/or other aspects of making spirally
wound composite tubular bodies such as 41 having outwardly rolled
top rims require special attention to hermetically seal a
membrane-type closure such as closure 42 to the top rims.
The membrane-type closure 42, FIG. 9,, has an asymmetrical shape,
and comprises a disc portion 70 and an integral radially extending
tab 43 having its proximal end 71 hingedly secured to the perimeter
72 of disc portion 70. An annular-shape section of disc portion 70
which extends radially inwardly from perimeter 72 is designated
peripheral section 73.
As shown in FIG. 10, closure 42 is a three layer construction
comprising a top layer 74, a middle layer 75, and a bottom layer
76. In the preferred embodiment closure 42, middle layer 75 is an
electrically conductive sheet of type 1145-0 aluminum having a
nominal thickness of about 3 mils, top layer 74 is a 1/2 pound
vinyl washcoat such as Adcoat 41C available from Morton Chemical
Company, Chicago, Ill., and the bottom layer is a 1 mil
thermoplastic coating of DuPont type XBR 950 ethylene vinyl
acetate. The vinyl washcoat is provided as a means for protecting
the top surface of the aluminum sheet from oxidation, and the XBR
950 coating is provided on the bottom surface of the aluminum sheet
to make the peripheral section 73 of closure 42 peelably heat
sealable to an upwardly facing annular-shape area of the
thermoplastic innermost layer 53 of liner 50 of tubular body 41
which layer 53 is disposed on the top of rim 48 by virtue of rim 48
being rolled outwardly as described hereinbefore.
Together, the portions of the XBR 950 coating and the thermoplastic
layer 53 of the liner 50 of tubular body 41 comprise electrical
insulation means and heat activatable sealant disposed intermediate
the aluminum sheet 75 of closure 42 and the aluminum layer 54 of
liner 50 whereby the peripheral section 73 of closure 42 is
susceptible to being induction heat sealed to the top rim 48 of the
tubular body 41 to form a hermetic circumferential seam
therebetween.
Overcap 44, FIG. 1, of the preferred embodiment is made of
thermoplastic material such as low density polyethylene resin type
1400 available from Gulf Oil Chemicals Co., Orange, Texas. Overcap
44, FIGS. 6 and 7, comprises a top panel 80 and an annular skirt 81
depending from the periphery of the top panel 80.
The top panel further comprises an annular-shape stacking flange 82
which extends upwardly from the exterior surface 83 of top panel
80. The stacking flange 82 has a planar, annular-shape top surface
84. The stacking flange 82 has a mean diameter substantially equal
to the mean diameter of rim 48 of container body 41 so that the
stacking flange 82 is superjacent the rim 48 when the overcap 44 is
applied to the tubular body 41 as shown in FIGS. 2 and 11.
The top panel 83 of overcap 44 also comprises heat-deformable means
such as a multiplicity of circumferentially spaced, radially
extending ribs 85, FIGS. 6, 7 and 8, which depend from the interior
surface of the top panel 80 of overcap 44. The ribs 85 are so
disposed that they underlie the stacking flange 82 whereby they
radially span the rim 48 of the tubular body 41 when the container
subassembly 40 is assembled as shown in FIG. 11. FIG. 7 is a radial
sectional view taken between two ribs 85 to show the radially
extending profile of a rib 85 and FIG. 8 is a circumferential
sectional view taken through the ribs 85 to show their transverse
cross-sectional shape. Such heat deformable means as ribs 85 are
provided to cause the peripheral section 73 of closure 42 to
conform radially and circumferentially to the rim 48 of tubular
body 41 by being heat-deformed when the container subassembly 40 is
assembled as shown in FIGS. 11 and 12. In the preferred embodiment,
ribs 85 have a radial length L, FIG. 7, of about one-quarter of 1
inch, a width W, FIG. 8, of about six-thousandths, of 1 inch, are
spaced circumferentially about ten-thousandths of 1 inch
center-to-center, and have a height H, FIG, 8, of about
eight-thousandths of 1 inch.
The annular skirt 81 of overcap 44 comprises means for cooperating
with overcap engaging means provided on the tubular body 41
adjacent the top rim 48 of the body 41. In the preferred
embodiment, the radially inwardly and downwardly extending shoulder
87 comprises the means for cooperating with overcap engaging means
on the tubular body 41, and the radially outwardly disposed,
radially inwardly and downwardly extending distal portion 88 of the
outwardly turned top rim 48 of tubular body 41 comprises such
overcap engaging means, all as shown in Fig. 11.
The container subassambly 40, FIGS. 1 and 2 is assembled as shown
in the greatly enlarged scale radial sectional view of FIG. 11
taken along line 11--11 of FIG. 2, and as shown in the greatly
enlarged scale circumferential sectional view of FIG. 12 taken
along line 12--12 of FIG. 2. Briefly, the preferred method of so
assembling container subassembly 40 comprises biasing the overcap
44 towards the rim 48 of the tubular body 41 while adjacent
portions of the peripheral section 73 of closure 42, rim 48, and
ribs 85 are simultaneously heated by induction heating means to a
sufficiently high temperature to heat-deform the ribs 85 to cause
them to evenly distribute the biasing force across the closure-rim
interface to cause the peripheral section 73 of closure 42 to
conform radially, FIG. 11, and circumferentially, FIG. 12, to rim
48 as shown, and to be hermetically sealed thereto along a
circumferentially extending seam 89. By virtue of heat-deforming
ribs 85 as shown in FIGS. 11 and 12, the peripheral section 73 of
closure 42 can be made to so conform to rim 48 regardless of
elevational differences caused by the seam 62 of the liner 50
(i.e.: hump 65, FIG. 5), or the presence of tab 43, FIG. 12.
Preferably, the biasing force is applied from a planar surface 95
of a biasing device such as spring 96 incorporated in an induction
heating device 97 to the planar surface 84 of overcap 44 as shown
in FIG. 13 while carriage 98 is drawn along cylindrical guides 99,
100 by a chain 101 attached to the carriage 98 is drawn around a
driven sprocket 102. By virtue of shafts 103, 104 being freely
rotatable in the upstanding ends 105, 106 respectively of carriage
98, and by virtue of a pinion gear 107 being drivingly secured to
shaft 103 and drivingly engaged with a stationary rack gear 108, a
loosely assembled container subassembly 40 can be supported between
cups 109, 110, and rolled past the non-contacting linear sections
111, 112 of induction heating electrode 113, FIG. 14, as the
carriage 98 is moved. As shown in FIG. 13, linear section 111 of
electrode 113 is disposed substantially (but not touching) tubular
body 41 subjacent the top rim of the body, and the linear section
112 of electrode 113 overlies the overcap 44 and closure 42
radially inwardly from the rim of the body and extends chordally
with respect to the rim. Thus, by energizing electrode 113 by a
suitable RF source (not shown) adjacent portions of the
electrically conductive sheet 75 of closure 42 and the electrically
conductive layer 54 of liner 50 can be simultaneously induction
heated wherby adjacent portions of the ribs 85 of the overcap 44,
the thermoplastic coating 76 of closure 42, and the thermoplastic
innermost layer 53 of liner 50 are simultaneously conductively
heated. When thus heated to a sufficiently high temperature, the
biasing force will precipitate the above described radial and
circumferential conformation, and the hermetic circumferential seam
89 will be formed.
Ribs 85a, FIG. 12 illustrate the heat-deformation of the ribs which
causes the biasing force to be equally distributed around the
peripheral section 73 of closure 43 during the induction sealing
operation described above. Were the tabs 85a disposed superjacent
the tab 43 not so deformed, the biasing force would be concentrated
in the tab area. This concentration of bias might precipitate
damage to the underlying portion of rim 48 and/or reduce the bias
around the remainder of the rim to a value too low to effect good
sealing.
The Model 5,000 R.F.C. High Frequency Generator which is available
from the Radio Frequency Company, 44--46 Park Street, Medfield,
Mass. is such a suitable RF source referred to above.
During the assembly and sealing of the preferred container
subassembly described hereinabove which subassembly 40 comprises a
tubular body 41 having an inner diameter of about 27/8 inches, the
R.F.C. Generator was operated at a plate current of about 1 3/10
amperes, a spring biasing force of about 30 pounds was applied, and
the carriage was drawn past the linear sections 111, 112 of
electrode 113 at about 2 feet per second. The linear sections 111,
112 of electrode 113 were approximately 12 inches long.
During such induction heat sealing as described above, and with the
tab 43 of the closure 42 oriented away from the seam 62 in liner 50
of body 41 as shown in FIGS. 1 and 2, the maximum temperature
achieved under the proximal end 71 of tab 43 was in the range of
from about 230 to about 239.degree. Fahrenheit while the maximum
temperature achieved around the rest of the rim 48 was in the range
of from about 270 to about 279.degree. Fahrenheit.
The tensile strength of the peelable bond achieved between XBR 950
and Surlyn (registered trademark of the DuPont Company) or
polypropylene is directly related to the temperature achieved
during the heat sealing operation. Thus, because the maximum
temperatures achieved under the proximal end 71 of tab 43 and above
the body seam 62 in the rolled rim of body 41 were lower than in
the remainder of the circumferential seam 89, it follows that the
tensile strength of the circumferential seam 89 is smaller under
the tab 43 and above the body seam 62 than in the remainder of the
circumferential seam 89.
However, in similar subassemblies wherein either the electrically
conductive sheet is omitted from the closure or the electrically
conductive layer is omitted from the tubular body, the tensile
strength of the circumferential seam is, as compared to the
preferred embodiment container subassembly, inferentially, much
lower as witnessed by the following examples,
When a container subassembly like the preferred embodiment but for
omitting the electrically conductive sheet from the closure was
subjected to the sealing conditions described hereinabove, the
maximum temperature achieved intermediate the peripheral section of
the closure and the rim of the tubular body was in the range of
from about 120 to about 129.degree. Fahrenheit; less than one half
that achieved in the preferred embodiment.
Similarly, when a container subassembly like the preferred
embodiment but for omitting the electrically conductive layer in
the rim of the tubular body was subjected to the same sealing
conditions, the maximum temperature achieved under the proximal end
of the tab was in the range of from about 110 to about 119.degree.
Fahrenheit and the maximum temperature in the circumferential seam
area spaced away from the tab and the body seam was in the range of
from about 130 to about 139.degree. Fahrenheit; also less than
about one half that achieved in the preferred embodiment.
From the foregoing, it is clear that both the electrically
conductive sheets in the closure 42 and the electrically conductive
layer in the liner of tubular body 41 are required to enable
inductively sealing those members of the subassembly together in
the manner described hereinbefore. Also, by virtue of making the
electrically conductive sheet and layer of aluminum, the resulting
container subassembly is subject to being hermetically sealed by
crimping a suitable hermetic closure to the bottom end of the
tubular body. However, the electrically conductive members must be
electrically insulated from each other to prevent arcing during
induction heating.
Referring now to FIG. 15, an alternate container subassembly 40a is
shown which comprises the same tubular body 41, closure 42, and
overcap 44 as the preferred container subassembly 40, FIGS, 1 and
2. Indeed, the subassemblies 40 and 40a are identical but for the
fact that closure 42 of subassembly 40, FIG. 2, is oriented with
respect to the rim of the tubular body 41 so that the proximal end
of the tab 43 is not disposed superjacent the portion of the lapped
body seam 62 disposed in the rim of the tabular body in the
preferred assembly 40, whereas the closure 42 of subassembly 40a,
FIG. 15, is oriented with respect to the rim of the tubular body 41
so that the proximal end of the tab 43 is disposed superjacent the
portion of the lapped body seam 62 of the tabular body 41 disposed
in the rim 48 of the tabular body in the alternate container
subassembly 40a.
As will become apparent from the following example, the
circumferential seam 89, FIG. 11, of preferred embodiment container
subassembly 40, FIGS. 1 and 2, has greater structural integrity
than the circumferential seam in the alternate subassembly 40a,
FIG. 15. However, because the tensile strength of the
circumferential seam subjacent tab 43 of subassembly 40a is less
than in subassembly 40, the initial pull required to begin peeling
closure 42 from the tubular body 41 is commensurately less.
Therefore, a container comprising subassembly 40a is easier to open
than a container comprising subassembly 40 and for that reason more
desirable for some container applications than a container
comprising a subassembly 40.
The reduced initial pull required to peel a closure from an
alternate container subassembly 40a, FIG. 15, is inferred from the
fact that when such an assembly is subjected to the same sealing
conditions described in conjunction with the preferred embodiment
container subassembly, the maximum temperature achieved subjacent
the proximal end of the tab of the closure is in the range of from
about 170 to about 179.degree. Fahrenheit, while the maximum
temperature achieved in the remaining portion of the
circumferential seam is in the range of from about 270 to about
279.degree. Fahrenheit; over twice the differential measured in the
preferred container assembly 40, FIGS. 1 and 2, as set forth
hereinabove. Indeed, the pull required on the tab of the closure to
initiate peeling the closure from the preferred embodiment 40 is
greater than two times that required for the alternate container
subassembly 40a.
Referring now to FIG. 16, an alternate closure embodiment 42a is
shown which has an aperture 120 disposed in the proximal end 7la of
tab 43a adjacent the disc portion 70a of the closure. In such a
closure having a 3/16 inch diameter aperture in a one-half-inch
wide tab, the temperature differential experienced between the area
under the tab and the other portions of the circumferential seam
during induction heat sealing was reduced by about 25 percent from
the differential experienced in the preferred embodiment described
hereinbefore. Thus, container subassemblies comprising the
alternate closure 42a would have greater structural integrity than
the preferred embodiment. It is believed that the benefit of
increased structural integrity available through using alternate
closures 42a must be balanced against the need therefore and the
cost thereof.
Other alternate closure embodiments 42b, and 42c are shown in FIGS.
17 and 19 respectively. However, the elongate apertures 121
disposed in the proximal end of the tab are formed by making
C-shape cuts to form flaps 122, FIG. 18, and by folding the flaps
122 as shown in FIG. 18. Such a method of providing apertures
obviates scrap removal which would be required in the manufacture
of alternate closures 42a, FIG. 16.
While particular embodiments of the present invention have been
illustrated and described, it will be obvious to those skilled in
the art that various changes and modifications can be made without
departing from the spirit and scope of the invention and it is
intended to cover, in the appended claims, all such changes and
modifications that are within the scope of this invention.
* * * * *