CA1065753A

CA1065753A - Packing containers and a method for their manufacture

Info

Publication number: CA1065753A
Application number: CA237,888A
Authority: CA
Inventors: Kent I.E. Knutsson
Original assignee: Ziristor AB
Current assignee: Ziristor AB
Priority date: 1974-10-18
Filing date: 1975-10-17
Publication date: 1979-11-06
Also published as: SE7413152L; ES441881A1; JPS5164573A; SE381442B; FR2334572A1; DK139420B; IT1043350B; GB1515859A; DE2546590A1; FI752903A; AU8580875A; DK466275A; GB1515858A; JPS5317946B2; FR2334572B1; DE2546590B2; SU563906A3; DK139420C; BE834634A; NL7512074A

Abstract

ABSTRACT OF THE DISCLOSURE

The present invention provides a packing container of a laminated material which is formable by a heat shrinking pro-cess and which comprises a carrier layer of foamed plastics, said container having a substantially tubular part and at least one end plate said end plate comprising a material plate located within the tubular part, and adjacent an end thereof, the per-ipheral area of said material plate being sealed to a region of the tubular part folded in by shrinkage to fit against the under-side of the material plate. The present invention also provides a container in accordance with claim 1, in which the region shrunk to fit against the underside of the material plate is said end of said tubular part.

Description

iO65753 The present invention relates to a packing container of a laminated material which is formable by a heat shrinking process and which comprises a carrier layer of foamed plastics, which container has a substantially tubular part and at least one end plate. The present invention also relates to a method for the manufacture of such packing containers.
In the manufacture of packing containers of the dis-posable type, for example for liquid foods, at present a laminated material is used, which, inter a _ comprises a carrier layer of foamed plastics with thinner layers of a homogeneous plastic material on either side thereof. This material has many advant-ages, such as being very rigid, due to its "joint construction".
Furthermore it is light and cheap and has good heat insulating properties. One disadvantage, however, is that the material can only be formed by folding and not by thermoforming, since the material, if it is subjected simultaneously to heat and to pre- ;
ssure, is compressed so that the cellular structure of the carrier layer is destroyed. To avoid this disadvantage, the packing mat-erial has been developed in which the cells making up the foamed plastics are given a lenticular or elongated shape by a stretching process carried out after the extrusion of the material. Since the cells normally are spherical and try to assume their normal shape, the cells will, when the finished material is heated up again to softening, revert as far as possible to the spherical shape, thus causing the material to shrink. This means that a thermoforming of the material around e.g. a profiled mandrel can be carried out without the cell structure being altered or major variations in thickness being observed. Such a material has been used e.g. for the manufacture of a protective cover for glass bottles. For this a sleeve was formed of the material, and the same was applied around the desired part of the bottle, where-upon the unit was ~armed up so that the sleeve was shrunk tight - 1 -- ~jj,~

- , and formed in accordance with the shape of the bottle.
So far, however, no packing containers are known in which use is made of the thermoforming characteristics of the above-mentioned material in an optimum manner, so as to produce a package, the container body of which consists exclusively of the said material. Such a container should present manufacturer and distributor as well as consumer with many advantages, since it is strong, light and cheap. Beside the rules which normally apply to the shaping of packages e.g. rules concerning the stack-ability, gripping facility, stability, openability and durability,the two following points must be observed in the manufacture of a package of the said plastic material. In the first place, folding of the material must be avoided, since sharp folding lines involve a weakening of the material and moreover have a detrimental effect on the stability of the finished packing con-tainer. Secondly measures which cause a lanting compression of -the material must be avoided, since the joist construction of the material will then be lost, with consequent reduction in rigidity and deterioration of heat insulating capacity. These points ~ , failed to be observed in the construction of known containers.
The present invention provides a packing container, manufactured from the said thermoformable material, which is of ~ -such a construction that the previous disadvantages are essent-ially avoided and the characteristics of the material are util-ized to the full.
The present invention also provides a packing container which can be formed by shrinking the material around a mandrel.
The present invention still further provides a packing container, in the manufacture of which the material is utilized 3Q without the occurrence of any appreciable waste.
In accordance with the invention in a packing container of the aforesaid type the end plate of the container comprises a . . . . . . . .

:' : ~ ,. . . ' . ' ~06S753 material plate located in the tubular container part and near to the one end of the same, the peripheral area of which mat-erial plate is sealed to a region of the tubular container part folded in by shrinkage to fit against the underside of the mat-erial plate.
According to the present invention therefore there is provided a packing container of a laminated material which is formable by a heat shrinking process and which comprises a carrier layer of foamed plastics, said container having a sub-stantially tubular part and at least one end plate said end plate comprising a material plate located within the tubular part~ and adjacent an end thereof, the peripheral area of said material plate being sealed to a region of the tubular part folded in by shrinkage to fit against the underside of the mat-erial plate.
Such packing container may be made by forming a strip of said material into a cylinder, whereupon the ends of the strip are sealed to one another, so as to form the tubular container part, introducing a material plate adapted to the shape and size ` 20 of the container part into one end thereof, which end is shrunk s ; by heating to partly enclose the material plate, whereupon the plate and the end of the tubular container part are sealed to one another.
The present invention thus also provides a method for the manufacture of a packing container which comprises forming a strip of a laminated material which is formable by a heat shrink-ing process and which comprises a carrier layer of foamed plastics into a cylinder, sealing the ends of the strip to one another so as to form a tubular container part, introducing a material plate adapted to the shape and size of the tubular part into one end thereof, heating said end to effect shrinkage thereof and partly to enclose the material plate, and sealing the plate and the end -:: :

of the tubular part to one another.
The present invention will be further described with reference to the accompanying drawings wherein Fig. 1 is a perspective view of a packing container provided with lid in accordance with one embodiment of the pres-ent invention, Fig. 2 is a cross-section of the packing container in accordance with Fig. 1, and Fig. 3 shows a stage in the manufacture of a packing container of Figs. 1 and 2.
The packing container in accordance with the invention is manufactured from a laminated material which has a central carrier material of foamed plastics and a homogeneous plastics ; layer situated on either side of this. The plastic material may consist e.g. of polyethylene or polystyrene. The material is formable by a heat shrinking process and can be sealed, by a method in which at least the surface layer in the portions which are to be sealed to one another are heated to softening, where-upon they are pressed together.
~' 20 The packing container shown in Fig. 1 comprises a sub- -stantially tubular wall part 1 and two end plates 2 and 3 resp-ectiveIy. The tubular wall part 1 has an upper, substantially cylindrical part 4 and a lower substantially conical part 5, which tapers off downwardly in the direction of the end plate 3 .,.~
which forms the bottom of the package. The tubular container part 1 is manufactured from a rectangular material strip, the ; short ends of which are sealed to one another, and the package has therefore a vertical overlap joint 6 which extends over the entire height of the package (Fig. 1). At the upper end of the 3Q joint 6 is a luy 7 which is not attached to the underlying mat-- erial and which projects from the overlap joint and runs substant-.
ially adjoining the underlying material. This lug 7 serves for .. , - . ~ .
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:: , -10657~i3 .
the opening of the package as a pull flap and is therefore con-nected to a tearing thread 8 located around the upper end of the package and directly below the end plate or lid 2. The tearing thread 8 is partially embedded in the inner homogeneous layer forming the tubular container part 1 and extends therefore also out into the pull lug 7 formed by the packing material.
The lower, conical end S of the tubular container part 1 is closed at the bottom by a shrunk edge 9, which fits against and is sealed to a material plate 10 introduced into the bottom end of the tubular container part 1. The shrunk edge 9 is sealed in an overlap joint 11 to a circumferential edge area of the lower surface of the material plate 10. ~-The upper end plate 2 or lid of the packing container is constituted by a lid with recessed inner part adapted to the diameter of the upper tubular part 4 of the packing container.
The lid is butt welded to the top edge of the tubular packing -container 1. On opening of the packing container by pulling in the projecting pull lug 7, the lid as well as the part of the package located between the lid and the tearing thread 8 are -detached.
In the manufacture of the above described packing con- -tainer, the container is formed around a mandrel 12 (Fig. 3).
The mandrel has a shape corresponding to the shape of the tubular container part , i.e. an upper cylindrical part 13 and a lower, conical part 14. The bottom end of the mandrel 12 is substant-ially plane and joins onto the conical part 14 of the mandrel via a rounded, circumferential edge. The diameter of the cylindrical mandrel part 13 corresponds to the desired inside diameter of the ~ ;
finished package.
3~ In the method a rectangular material strip is heated up and is wrapped round the cylindrical part 13 of the mandrel 12.
The material strip has a length ~so adapted to the periphery of the mandrel 12, that the strip ends after completion of the wrapping round extend somewhat over one another. The ends overlapping one another are then heated up, so that the surface layer of the material softens, whereupon they are pressed together to form the vertical overlap joint 6. The tubular and cylindrical part 1 so formed is then displaced in relation to the mandrel 12, so that a portion at the one end of the cylindrical part 1 extends beyond the lower end of the mandrel 12. To this lower end of the mandrel 12 is placed with the aid of a device 15 fitted up with a suction head the material plate 10 and is retained there in a suitable manner, e.g. by means of a vacuum. Then the tubular part 1 and the peripheral area of the material plate 10 are heat-ed up. During heating, the tubular part 1 shrinks so that its upper part situated on the cylindrical portion 13 of the mandrel 12 accurately fits to the latter. The bottom part of the con-tainer part 1, situated below the transition between the cylind-rical part 13 of the mandrel 12 and the conical part 14 of the mandrel 12, on heating up, also shrinks and accurately fits to the conical part 14. The portion located at the bottom edge is heated particularly strongly and through shrinkage is folded in over the peripheral area of the material plate 10 fitting against the bottom surface of the mandreI 12.
To ensure a tight seal between the peripheral surface of the material plate 10 and the folded in edge of the container part 1, and so as to provide an appropriate shaping of the bottom sur-face of the packing container, it is desirable to press a device, moulding the outside of the container base, against the folded in edge. Since the edge as well as the peripheral area of the plate are heated up particularly strongly, a circumferential, imperm-eable overlap joint is achieved between the plate 10 and thecontainer part 1 at the same time as the folded in edge 9 is given an even surface so that the packing container stands stably.

;, . , - . :

10t;5753 After this operation the packing container is drawn off the mandrel and is placed on a conveyor belt, on which it is taken to a filling station where it is filled with the desired contents. Finally the filled container passes a lid fitting station, where the upper edge of the container is heated up and the prefabricated lid is joined onto it by means of a butt weld.
Finally the finished, filled packing containers are placed into transport packages or the like.
The general, relatively gentle heating for making the rectangular material blank bendable and formable, as well as the more vigorous heating on producing the overlap joints and the forming of the bottom, may both be carried out by applying hot air to the parts which are to be heated. Naturally it is also possible to use radiant heat or the like.
The material plate 10 facilitates the forming of an impervious bottom part and makes it possible to form packages with considerable diameter, since the folding zone remains in- -variably narrow. This makes it also simpler to produce an even and impervious base.
The tearing thread located at the upper end of the package may be situated in the inner homogeneous plastic layer from the start, and does not affect, or is damaged by, the form-ing operations in accordance with the invention. Naturally it is also possible to omit the tearing thread, if some other opening arrangement is considered appropriate, e.g. a pull-off strip arranged on the lid which covers a punched out pouring opening.

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Claims

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

1. A method for the manufacture of a packing container which comprises wrapping a strip of a laminated material, which is formable by a heat shrinking process and which comprises a carrier layer of foamed plastics around a mandrel to form a cylinder, the inner diameter of which coincides with the dia-meter of the mandrel sealing the ends of the strip on said mandrel to one another so as to form a tubular container part, introducing a material plate of not greater than that of the mandrel adapted to the shape and size of the tubular part into one end thereof, heating said end to effect shrinkage thereof and partly to enclose the material plate, and sealing the plate and the end of the tubular part to one another.

2. A method in accordance with claim 1, in which the ends of the strip are heated up to softening and pressed together to form an overlap joint.

3. A method in accordance with claim 1, in which the tubular container part is displaced along the mandrel so that a portion at the one end of the container part extends beyond the end of the mandrel, whereafter the material plate is disposed so as to fit against the end of the mandrel, and the said end of the container part is heated to shrink and to enclose the mandrel and the material plate.

4. A method in accordance with claims 1, 2 or 3 in which the end of the tubular container part and the plate, are heated up to softening, whereafter a moulding device is pressed against the plate and the end of the container enclosing the plate for form a base for said container.

5. A method in accordance with claim 1, 2 or 3 in which the material is hated with hot air.

6. A method for making, filling and sealing packing containers for liquids composed of a heat-shrinkable laminated material having a carrier layer of foamed plastics and at least one layer of a thermoplastic, heat-sealable material, said method comprising wrapping a strip of the laminated material about a cylindrical mandrel to overlap the opposed ends of the strip, heating the overlapping end portions of the strip to heat seal the strip end portions together to form a tubular member of inner diameter which coincides with that of the diameter of the mandrel, moving said tubular member relative to the mandrel so that one end thereof extends beyond the corres-ponding end of said mandrel, placing a bottom forming plate mem-ber against the end of the mandrel, the plate member having a diameter not greater than the diameter of the end of the mandrel, heating the extended end of the tubular member of laminated material to shrink the extended end portion of the tubular mem-ber inwardly to embrace the marginal surface of the plate member and to heat seal the inwardly shrunk end of the tubular member to the marginal surface of the plate member to form a seal, applying pressure to the end of the tubular member and plate member while still in a heated condition, to provide a liquid tight seal therebetween and to provide the base portion of the container with a flat, substantially uniform surface for stabi-lity, removing the container from the mandrel, filling the container with liquid contents, heating the upper edge of the container to a heat-sealing temperature, and pressing a lid member thereonto in abutting relation to the heated upper edge of the filled container to form a liquid-tight butt seal there-with.

7. A method for making, filling and sealing packing containers to liquids composed of a heat shrinkable laminated material having a base layer of foamed plastics material and at least one layer of a thermoplastic, heat sealable material, said method comprising: wrapping a strip of the laminated material about the cylindrical portion of a cylindrical mandrel having a truncated conical portion at one end thereof to overlap the opposed ends of said strip, heating the overlapping end portions of the strip to heat seal the strip end portions together to form a tubular member of inner diameter which coincides with that of the diameter of the mandrel, moving said tubular member relative to the mandrel so that one end thereof extends beyond the conical end portion of said mandrel, placing a bottom forming plate member against the truncated conical end of the cylindrical mandrel, the plate member having a diameter not greater than the diameter of the truncated conical end of the mandrel, heating the extended end of the tubular member of laminated material to shrink the laminated material to conform with the conical portion of the mandrel and to shrink the extended end portion of the tubular member inwardly to embrace the marginal surface of the plate member and to heat seal the inwardly shrunk end of the tubular member to the marginal surface of the plate member to form a seal, applying pressure to the end of the tubular member and plate member while still in a heated condition to provide a liquid tight seal therebetween and to provide the base portion of the container with a flat, substantially uniform surface for stability, removing the container from the mandrel, filling the container with liquid contents, heating the upper edge of the container to a heat-sealing temperature, and pressing a lid mem-ber thereonto in abutting relation to the heated upper edge of the filled container to form a liquid-tight butt seal therewith.