CA1063550A - Container subassembly having a membrane-type closure, and method of assembling the subassembly - Google Patents

Abstract

A CONTAINER SUBASSEMBLY HAVING A
MEMBRANE-TYPE CLOSURE, AND
METHOD OF ASSEMBLING THE SUBASSEMBLY

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 roller rim so that the peripheral section of the closure conforms radially and circumferentially to an upwardly facing annular area of the rolled rim. The container subassembly may also include an overcap comprising heat-deformable means for effecting the radial and circumfer-ential conformation of the peripheral section of the closure to the rim of the container body. 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.

Description

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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.
patents of which the following are representative: U. S. Patent No. 2,937,481 issued May 24, 1960 to Jack Palmer; U. S. Patent No. 3,460,310 issued August 12, 1969 to Edmund Philip Adcock --et al.; U. S. Patent No. 3,501,045 issued March 17, 1970 to Richard W. Asmus et al.; U. S. Patent No. 3,734,044 issued May ~ -22, 1973 to Richard W. Asmus et al.; U. S. Patent No. 3,767,076 issued October 23, 1973 to Leo J. Kennedy; U. S. Patent No.
3,805,993 issued April 23, 1974 to William H. Enzie et al.;
and U. S. Patent No. 3,808,074 issued April 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. m e 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, in one aspect,

-2-1063~i50 is to provide a thermoplastic overcap comprising heat-deformable means for causing the peripheral section of a heat-se~lable 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 major object of the present invention, in another aspect, is to provide 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 object of the present invention in a further aspect is to provide a hermetically sealable container sub-assembly comprising a spirally wound composite tubular body, and an asymmetrical shape membrane-type closure having an integral pull tab.
Still another object of this aspect of the invention is to provide the container subassembly described in the pre-ceding paragraph which subassembly comprises means for being induction heat sealed.
A further object of the present invention is to provide 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.
A still further object of the present invention, in ?
another aspect, is to provide 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.

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` ~ . ' , ~ ` 1063SS0 According to one aspect of the invention there is provided 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 ~ 10 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 from a web of electrically conductive material which is spindled into a tubular 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 20 portion conforms radially and circumferentially to an upwardly facing annular-shape area of said rim. This aspect of the invention is disclosed and claimed in Canadian Patent Application No. 231,277 of C.L. Johnson et al, filed July 11, 1975, of which the present application is a divisional. (Said Canadian Application No. 231,277 is now Canadian Patent No.
1,043,292, granted November 28, 1978).
This aspect of the invention further resides in a container subassembly comprising a body having a top rim, a membrane-type closure, an overcap, and means for heat sealing 30 a peripheral section of said closure to said rim along a circumferentially extending seam when heated to a predeter-mined temperature, said overcap comprising heat-deformable means for .'~' ~, .
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~063~50 uniformly distributing a biasing force from a planar surface to a 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 setsaid circumferential seam while maintaining said biasing force.
Said container subassembly is described and claimed in the aforementioned Canadian Patent No. 1,043,292.
The present invention, in another aspect, resides in a thermoplastic overcap for a container subassembly comprising a tubular body having an opening defining-rim and a membrane-type closure, said 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 the peripheral section of said closure to conform radially and circumferentially to said rim when said overcap is biased towards said rim by a ' - -. , .
biasing device presenting a planar surface to the exterior of : :
said top panel while said heat-deformable means is heated to a sufficiently high temperature to effect said conformation, ~ :
said heat-deformable means comprising a multiplicity of circumferentially spaced, radially extending, depending integral ribs of thermoplastic material disposed adjacent ~: .
the perimeter of said top panel so that said ribs overlie ~ ~-said rim when said overcap is applied to said container subassembly.

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-` 10~3~50 According to a further aspect of the invention there is provided a method of induction heat sealing an asymmetrical-shape closure to a tubular body having an outwardly rolled top rim with electrical insulation means disposed intermediate said closure and said rim, said closure comprising a disc portion and an integral radially extending tab, said tab being folded upwardly and radially inwardly so that it lies super-jacent the top surface of said disc portion, said closure - comprising an electrically conductive sheet, said body comprising an electri~ally conductive liner, said method comprising the ~` steps of:
a. juxtapositioning said closure on said rim with said electrical insulation means disposed intermediate the bottom surface of the peripheral section of said disc portion and said rim, b. biasing said peripheral section towards said rim - with a uniformly distributed force, c. simultaneously subjecting adjacent portions of said electrically conductive sheet, electrical insulation .
means, and said electrically conductive liner to a high frequency electrical field of sufficient constant intensity to independently inductively heat said adjacent portions of said sheet and said liner to cause heat activatable sealant disposed intermediate said adjacent portions to be conductively ~-heated to a sufficiently high bonding temperature to sealingly secure said adjacent portions together along a circumferentially extending seam, d. terminating said field to enable said sealant to cool to a sufficiently low temperature to set said seam, and e. terminating said biasing.

This aspect of the invention is claimed in Canadian Application No. 300,649 filed April 7, 1978, which is another divisional of said Canadian Application No. 231,277 (now Canadian Patent No. 1,043,292).
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~RIEF DESCRIPTION OF T~IE Dr~ IN(~S
While the specification concludes with claims particularly pointing out and distinctly claim.ing the subject matter regarded as f~rming the present invention, it S . is believed the invention will be better understood from the - following description taken in connection with the accompanying drawings in which:
Figure 1 is an exploded perspective view of a preferred container subassembly embodying the present invention.
-Figure 2 is a -fragmentary perspective-~i-ew af the container subassembly shown in Figure 1.
Figure 3 is an enlarged scale, fragmentary perspective view of the spirally wound and lap seamea liner of the container subassembly shown in Figures 1 and 2.
Figure 4 is a fragmentary sectional view of the liner .
shown in Figure 3 taken along line 4-4 th~reof. ~
Figure 5 is a fragmentary, radial~y outwardly looking ,.
view of the liner-seam-area of the outwaraly rolled rim of the tubular container body shown in Figure 1.
Figure 6 is an enlarged scale bottom view of the overcap of the container subassembly shown in Figure 1.
; Figure 7 is an enlarged scale, fragmentary radial sectional view of the overcap shown in Figure 1 taken along line 7-7 thereof. ~.
Figure 8 is an enlarged scale fragmentary circum-. ferential sectional view of the overcap shown in Figures 1, 6 and 7 taken along line 8-8 of Figure 7.
Figure 9 is an enlarged scale top view of the membrane-tvpe closure shown in Figure 1 prior to folding the integral tab of the closure to the orientation shown in Figure 1.

__ -` il)~35S~) Figure 10 is a fragmen,ary sectional view of the closure shown in Figure 9 taken along line 10-10 thereof. -Fiqure 11 is an enlarged scale radial sectional view of a top edge portion of the container subassembly shown in Figure 2 taken along line 11-11 thereof which line l extends between radially extending ribs depending from the i interior surfa~e of the overcap of the subassembly.
I Figure 12 is an enlarged scale circumferertial ~-! sectional view of the container subassembly shown in Figure 2 taken along line 12-12 thereof.
Figure 13 is a reduced scale,end view of a portion of an apparatus for induction heat sealing the closure of the container asse~bly shown in Figure 1 to the rim of the tubular body of the container assembly.
Figure 14 is a re~uced scale perspective view of the induction heating electroae of the apperatus shown in Figure 13.
Figure 15 is a fragmentary perspective vie~ of an -alternate cortainer subasser~ly embodying the present invention.
Figure 16 is ar. enlarged scale to2 view of an alternate membrane-type closure which may be incorporated in container subassemblies embodying the present invention.
Figure 17 is an enlarged scale, fragmentary top view of another alternate ~embrane-type closure which may ~e incor-porated in container subassemblies embodying the present invention 2S - Figure 18 is a sectional view of the alternate membrane-type closure shown in Figure 17 taken along line 18-18 thereof.
Figure 19 is an enlarged scale, fracmentary top view of yet another alternate mer~rane-type closure which r,ay be incorporated in container assem~lies embodying the prcsent invention.
(Figures 16-19 inciusive are located in the second sheet of drawings, together with Figures 7-10.) ~_ r~

DESCRIPTION OF T~E PREFEP~RED ~!`5BODlr~.MT
__ Referring now to Figures 1 and 2, the preferred embodiment of the present invention is a container sub-assembly 40 ~hich comprises a spirally ~ound, composite tubular body 41, a membrane-type closure ~2 having an integr21 pull t2b 43, and an overcap 44. - ~
Briefly, overcap 44 comprises heat-deform2ble means such zs ~ multiplicity of circumferentially spacea, radially extending ribs 85 (See Figs. 6, 8 and 12) which means are heat-deformed ` 10 or molded when container sub2ssembly 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 tub~lar body 41. Further, ~ the container subassembly comprises means for induction heat ; 15 sealing closure 42 to the rim of tubular body 41 and for causing the heat-deform2ble means to effect the above described radial :~.
and circumferential conformation of the peripheral section of closure 4 to the rim of tubular body 41. ~:.
: Tubular boay 41, Figure 1, of the preferred embodiment container assembly 40 is a glue bonded, composite, spirally - wound tub-e 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 botto~ closure thereto.
Referring now to FiGure 11, the multi-ply sidewall of tubular body 41, Figure 1, is shown to comprise three ~ajor plies: an innermost ply hereinafter referred to as liner aO, an outermost ply hereinafter referred to as label 51, and a ~iddle ply 52. In the preferred em~odiment cor.tainer asse~bly 4D, Figure 1, label 51 comprises fifty-five pound litho paper .

106;~5~0 c~ated with a moisture barrier whi~h, in turn, is printed and coat~d with an overprint lacq~er; and the middle ply 52 is nineteen point kraft paper can board.
~iner 50, Figure 3, comprises a web of four layer - -5 constr~ction as shown in Figure 4. The innermost la~er 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 indicatea in Figure 3. The thermoplastic ~ material of the preferred embodiment is a twelve pound coating `` 10 of Surlyn, DuPont number sixteen-hundred-fifty-two S~, an ionomer resin, although polypropylene and other the~moplastic 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 preferre~ 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 seven pound coating of low density polyethylene. The outermost layer 56 may be twenty-five pound machinè finish natural kraft paper.
~i 20 When the web from which liner 50 is spirally wound into the tubular shape shown in Figure 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 thermo-plastic innermost layer 53 of side edge portions 60, 61 in - 25 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 h2ving a spiral inner edge 63 and a spiral outer edge 64.
As is shown in Figure 3, spiral lap seam 62 comprises three thicknesses of the web from which the liner 50 is fo-med.
The two extra thicknes~es of liner material in spiral seam 62 precipitate a circumferentially extending hump 65, Figure 5, . . .
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in the top rim 48 of tubular body 41, which hu~p 65 is ~;ho~,~n in ex2ggerated proportions in Figur~ 5 to more clearly disclose that it causes the top rim 4 8 to have elevational differences around the top opening 66 of tubular body 41 as S indicated in Fiaure S by delta E; (~ E ~
As will be described more fully hereinafter, elev2tional differences of rim 48 around top opening 66 ~hich 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 re~uire special atten.ion to - hermetically seal a membrane-type closure such 2S closure 42 to the top rims The membrane-type closure 42, Figure 9, has an asymmetrical shape, and comprises a disc portion 70 and an inte-gral radially extending tab 43 having its proximal end 71 hinged~
secured to the peri~eter 72 of disc portion 70 An annular-shape section of disc portion 70 which extends radially inwardly from perimeter 7Z is designated peripheral section 73 As shown in Figure 10, closure ~2 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 ~onductive sheet of type 1145-;--aluminum having 2 nominal thickness of about three mils, top layer 74 is a one-half pound vinyl washcoat such as "Adcoat ilC"* available from Morton Chemical Company, Chicago, Illinois, and the bottom layer is a one mil thermcplastic coating of DuPont type XBR 950 ethylene vinyl acetate The vinyl washcoat is provided as a means for protecting the top surface of the al~inum sheet from oxida.ion, and the XBR 950 coating is provided o~ the bottom surface of the aluminum sheet to m2~e the peripheral section 73 of closure 42 peelably heat *Trademark , _g_ ' ' , ' .: :
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, `- iO6;~50 sealable to an upwardly facing annular-shape area of the thermo?lastic 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 a_ described hereinbefore.
Together, the portions of the XBR 950 coa,ins and the thermopl2stic 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 L0 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, Figure 1, of the preferred embodiment is made of thermoplastic material such as low density poly-S ethylene resin type 1400 available from Gulf Oil Chemicals Co., Orange, Texas. Overcap 44, Figures 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 ;0 stacking flange 82 which extends upwardly from the exterior sur-face 83 of top panel 80. The stacking flange ~2 has a planar, annular-shape top surface 84. The stacking flange 82 has a mean diameter subst2ntially e~ual to the mean diameter of rim 48 of container body 41 so that the stacking flange 82 is super-jacent the rim 48 when the overcap 44 is applied to the tubular body 41 as shown in Figures 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, Figures 6, 7 and 8, ~hich o depend from the interior surface of the top panel 80 of overc2p 44. The ribs 85 2re so disposed that they underlie the stacking l(~ti3~50 flang~ 82 whereby they radially span the rim 48 of the tubular body 41 when the container su~assembly 40 is assembled as shown in Figure 11. Figure 7 is a radial sectional view taken between two ribs 85 to.show the radially extending profile of a rib 85 ~ .
S and Figure 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 ~en the container subassembly 40 is assembled as shown in Figures 11 and 12. In the preferred embodiment, ribs 85 have a radial length L, Figure 7, of about one-quarter of one inch, a width W, Figure 8, of about six-thousandtns of one inch, are spaced circumferentially about ten-thousandths of one ~5 inch center-to-center, and have a height H, Figure 8, of about eight-thousandths of one 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 t~bular 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 Figure 11.
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5~0 The container subasse~bly 40, Figures 1 and 2 is assembled as shown in the greatly enlarged scale radial sectional view of Figure 11 taken along line 11-11 of ~igure 2, and as shown in the greatly enlarged scale circumferential sectional view of Figure 12 taken along line 12-12 of Flgure 2. Briefly, the preferred methcd 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 g section 73 of closure 42 to conform radially, Figure 11, and ~-circumferentially, Figure 12, to rim 48 as shown, and to be hermetically sealed thereto along a circu~ferentially extending seam 89. By virtue of heat-deform-ng ribs 85 as shown in Figures : 11 and 12, the peripheral section 73 of closu~e 42 can be made to so conform to rim 48 regaraless of elevational differences ~ caused by the seam 62 of the liner 50 (i.e.: hump 65, Figure -~20 5), or the presence of tab 43, Figure 12.
. Preferably, the biasing force is applied from a planar surface 95 of a biasing device such as spring 96 incor-porated in an induction heating device 97 to the planar surface - 84 of overcap 44 as shown in Figure 13 while carriage 98 is -:25 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 upstand-ing ends 105, 106 respectively of carriage 98, and by virtue of a pinion gear 107 being drivingly secured to shart 103 and ~30 drivingly engaged with a stationary rack gear 108, à loosely assembled container subassembly 40 can be supported between ~' i(~ 550 cups 109,11o, and rolled past the non-contacting linear sections 111, 112 of induction heating electrode 113, Figure 14, -as the carriage 98 is moved. As shown in Figure 13, linear section 111 of electrode 113 is disposed substantially tbut not touching) tubular body 41 subjacent the top rim of the body, and the linear section 112 of electrode113 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-elect-rically conducti~e sheet ~5 of -closure 42 - and the electrically conductive layer 54 of liner 50 can be . . .
simultaneously induction heated whereby adjacent portions of . . . :
the ribs 85 of the overcap 44, the thermoplastic coating 76 ~
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of closure 42, and the thermoplastic innermost layer 53 of liner 50 are simultaneously conduc'ively 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, Figure 12, illustrate the heat-deformation of the ribs which causes the biasing force to be equally dis-tributed around the peripheral section 73 of closure 42 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.

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, - . : ~ - . , : ' ' The Model 5000 R.F.C. High ~'requency Generator which is available from the Radio Frequency Compar.y, 44-46 Park Street, Medfield, Massachusetts is such a suitable RF source referred to above.
S During the assembly and sealing of the preferred con-tainer subassembly described hereinabove which subassembly 40 comprises a tubular body 41 having an inner diameter of about two-and-seven-eighths inches, the R.F.C. Generator was operated - at a plate cu-rent of about one-and-three-tenths amperes, a spring biasing force of about thirty pounds was applied, and the carriage was drawn past the linear sections 111, 112 of electrode 113 at about two feet per second. The linear sections 111, 112 of electrode 11' were approximately twelve inches long.
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During such induction heat sealing as described above, ~15 and with the tab 43 of the closure 42 oriented away from *he seam 62 in liner 50 of body 41 as shown in Figures 1 and 2, the maximum temperature achieved under the proximal end 71 of tab 43 was in the range of from about two-hundred-thirty to about two-hundred-thirty-nine degrees Fahrenheit while the maximum temperature achieved around the rest of the rim 48 was in the range of from about two hundred-seventy to about two-hundred-seventy-nine degrees Fahrenheit.
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The tensile streng~h of the peelable bond achieved between XB~ 950 and Surlyn ~registered tradem2rk of the DuPont Company) or ~olypropylene is directly related to the tempera-ture achieved during the heat sealing operation. Thus, because S 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 circumfer-ential 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 co~ductive layer is o~itted from the tubular body, the tensile strength of the circumferential seam is, as compared to the preferrea embodiment container sub-; assembly, inferentially, much lower as witnessed by the following examples.
;~ When a container subassembly like the preferred embodiment but for omitting the electrically conductive sheet ~20 from the closure was subjected to the -ealing 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 one-hundred-twen'.y to about one-hundred-twenty-nine degrees .
Fahrenheit; less than one half that achieved in the preferred embodiment. ;
Similarly, when a container subassembly like the ; preferred embcdiment but for omitting the electrically con-ductive layer in the rim of the tubular body was subjected to -the same sealing conditions, the maximum temperature achieved ~ . .

: , ' ' under the pro~imal end of the tab was in the range of from about one-hundred-ten to about one-hundred-nineteen desrees Fahrenheit and the maximum temperature in the circumferential seam area spaced a~lay fron the tab and the S body seam was in the range of from about one-hundred-thirty to about one-hundred-thirty-nine degrees Fahrenheit; also less than about one half that achieved in the preferred embodiment.
From the foregoing, it is clear that both the ,10 electrically conductive sheets in the closure 42 and theelectrically conductive layer in the liner of tubular body 41 are required to enable inductively sealing those members of the sub~ssembly together in the manner described herein-before. Also, by virtue of making the electrically conductive sheet and layer of aluminum, the resulting cont~iner 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 mem~ers must be electrically insulated from each other to prevent arcing during induction heating.
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Referring now to Figure 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, Figures 1 and 2. Indeed, the subassemblies 40 and 4ba are identical but for the fact that closure 42 of subassembly 40, Figure 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 tubular body in the preferred assembly 40, whereas the closure 42 of subasse~bly 40a, ~igure ~0 15, is oriented with respect to the rim of the tubular body . .

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41 so th2' the proximal end of the tab 43 is disposed supe~-jacent the portion of the lapped body seam 62 of the tubular b~dy 41 disposed in the rim 48 of the tubular body in the alter-. nate container subassembly 40a.
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.5 As will become apparent from the.. following example, the circumferential seam 89, Figure ll, of pre-ferred e~bodiment container subassembly 40, Figures 1 and 2, has greater structural integrity than the circu~ferential seam in the alternate subassembly 40a, Figure 15. However, 10 because the tensile strength of the circumferential seam sub-jacent tab 43 of subassembly 40a is less than in subassembly . 40, the initial pull re~uired to begin peeling closure 42 from the tubular body 41 is commensurately less. Therefore, ~ a container comprising subassembly 40a is easier to open than .15 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, Figure 15, is inferred .20 from the fact that when such an as~embly is subjected to the -ame : sealing conditions described in con3unction with the preferred .
embodiment container subassembly, the maxim~ temperature .
achieved subjacent the proximal end of the tab of the closure is in the range of from about one-hundred-seventy to about one-hundred-seventy-nine degrees Fahrenheit, wnile the ma~imum ~` . temperature achieved in the remaining portion of the circum-ferential seam is in the range of from about two-hundred-. seventy to about two-hundred-seventy-nine degrees Fahrenheit;
over twice the differential measured in the preferred container assembly 40, Figures l and 2, as set forth hereinabove. Indeed, .' ' ' .

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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 ~ubassembly 40a.
Referring now to Figure 16, an alternate closure embodiment 42a is shown which has an aperture 120 disposed in the proximal end 71a of tab ~3a adjacent the disc portion 70a of the closure. In such a closure having a three-sixteenths-inch diameter aperture in a one-half-inch wide tab, the .emp-erature differential experienced between the area under the tab and the other portions of the circumferential seam during induction heat sealing was reduced by about twenty-five percent from the differential experienced in the preferred embodiment described hereinbefore. Thus, container subasse~blies com-lS prising 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 aga-nst the need therefor and the cost thereof.
. _ 2~ Other alternate closure embodiments 42b, and 42c are shown in Figures 17 and 19 respectïvely. However, the elongate apertures 121 disposed in the proximal end of the tab are formed by making C-shape cuts to form flaps 122, Figure 18, and by folding the flaps 122 as shown in Figure 18. Such a method of ~25 providing apertures obviates scrap removal which would be -~ required in the manufacture of alternate closures 42a, Figure 16.

-lB-io~;~ 5 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.

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Claims (2)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A thermoplastic overcap for a container subassembly comprising a tubular body having an opening defining-rim and a membrane-type closure, said 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 the peripheral section of said closure to conform radially and circumferentially to said rim when said overcap is biased towards said rim by a biasing device presenting a planar surface to the exterior of said top panel while said heat-deformable means is heated to a sufficiently high temperature to effect said conformation, said heat-deformable means comprising a multiplicity of circumferentially spaced, radially extending, depending integral ribs of thermoplastic material disposed adjacent the perimeter of said top panel so that said ribs overlie said rim when said overcap is applied to said container subassembly.

2. An overcap for a container body having an opening-defining rim and overcap engaging means disposed on said container body adjacent said rim, said overcap comprising a top panel and an annular skirt depending from the periphery of said top panel, said skirt being provided with means for cooperating with said overcap engaging means to releasably interlock said overcap on said container, said top panel being provided with a multiplicity of circumferentially spaced, radially extending, depending ribs of thermoplastic material disposed adjacent the perimeter of said top panel so that said ribs overlie said rim when said overcap is inter-locked with said container.