CA2073987A1

CA2073987A1 - Process and device for closing an aperture in a tubular container

Info

Publication number: CA2073987A1
Application number: CA002073987A
Authority: CA
Inventors: Wilhelm Kullberg Jr.
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-11-17
Filing date: 1991-11-16
Publication date: 1992-05-18
Also published as: AU9030191A; DE59107934D1; DE4112633A1; BR9106020A; ATE139197T1; JP3089325B2; DK0511358T3; NO922815D0; EP0511358A1; EP0511358B1; JPH05504749A; WO1992008651A1; FI923256A; FI923256A0; ES2091951T3

Abstract

Abstract of the Disclosure According to a method and with an apparatus for closing an opening of a tubular container, which is intended in particular for liquids and comprises at least on one side sealably coated paper or cardboard material, the upper container opening is closed by folding together and joining the four container sides in the upper region.
In order that on the one hand the closure can be easily opened by drawing up one side of the closure/ which forms a spout, and consequently on the other hand the four folded-together container sides are joined together in a securely sealing manner, after folding together the four container sides a film-like closing element is adhesively attached to the inner face of the end face of the container. Consequently, in particular the exposed folding edges of the container sides are sealed and firmly joined to the adjacent regions of the respective neighboring sides, without folded-together faces being adhesively attached to one another. During opening of the container by drawing up a so-called spout side of the closure, the closing element is easily severed along the folding edges by which the drawn-up side is joined, so that an easy opening of the closure is possible.

Description

` ' 2~739~7 The invention relates to a method of and an apparatus for clos.ing an opening of a tubular container, which is intended in particular for liquicas and comprises at least on one side sealably coated paper or cardboard material, in which a wall of the opening, which is divided in the region of the opening of the container to be closed from the wall o the container by one or more border folding lines and surrounds the opening of the container all axound, is folded inward and together along the border folding lines and adhesively bonded together in certain regions in order to form a closure, and in which the adhesive bonding can be released during subsequent opening of the closure by drawing up at least parts of the wall of the opening.
The invention relates in particular to a method and the apparatus used for it, in which the wall of the opening comprises four sides, which are divided in the region of the opening of the container to be closed from the wall of the container by rectangularly xunning border folding lines and surround ~he opening of the container all around, are folded inward and together along ~he border folding lines, as well as following a triangular pattern of oblique folding lines on the sides, and adhesively bonded together in order to form a closure, and during subsequent opening of the closure a spout can be formed from one side by drawing it up and, if appropriatel releasing the adhesive bonding of said side.
Finally, the invention relates to a closure intended to be used in the abovementioned method.
A method of closing an opening of a ~uhular ~, container o~ paper material is known from the printed document EP-Bl-162883, which discloses a corresponding closure. This clo~ure, which is produced by the method summarized at the beginning, doas indeed have considerable advantages over other containers or packs for liquids, in particular for milk, fr~ait ~uice~ etc., such as easy producibility by an automated fabrication process, good ma~erial utilization by virtue of suitable

2 ~39~7 .
molds for the cut--to-~ize piece o~ cardboard or paper o~
the container blank, low container weight in relatio~ ~o the volume of liquid, optimum stackability and space utilization during storage and transportation as well as for keeping when it reaches the consumer, but in particular very good handling characteristics when opening the closure and pouring out the liquid. By way of explanation it may be added that the closure is produced while the container is ~till empty and the bottom is still open, filling of the con~ainer follow with said container in the inverted position and only then is the bottom opening of the container, at that time at the top, closed in the conventional way, so that a contalner of a cube shape overall is obtained.
The invention i~ based on the object of further facilitating the production and handling of the closure, but in particular of producing a liquid-tight closure in a simple and reliable way by means which are as simple as possible. In addition, the fabrication of the container parts and ~he production o the closure are to he automatable.
To achieve this object, the invention provides that - on the basis of the method mentioned ~irst at the beginning - the folded-together regions of the wall of the opening are adhesively bonded together by adhesively inserting from the in~ide of the container at least one film-like closing element, which may also be formed by applying or spraying on or the like an adhesive layer, the inner edges of the first inwardly folded regions being joined in particular in a sealing manner by the closing element to the ad~acent regions in such a way that at least the region or regions drawn up ~irst when opening the clo3ure are detachable from the neighboring regions by tearing of the closing element along the corresponding inner edges.
A corresponding way is used to achieve the ob~ect for the method which wa3 mentioned second at the beginning, that the sides in the folded-together position ' ,. ~ ,, ~, , .

- 3 - 2~3~87 are adhesively bonded toge~her by adhesively inserting from the inside of the con~ainer at least one film like closing element, which may also be formed by applying or spraying on or the like an adhesive layer, the inner edges of the initially inwardly folded sides being joined in particular by the closing element to the adjacent regions of the subsequently folded sides in such a way that at least the side drawn up first when opening the closure is detachable from the neighboring sides by tearing of the closing element along the corresponding inner edges.
The difference between the two methods described above is, in particular, that the second method involves a right-parallelepipedal container, or at least a container of rectangular cross section, whereas the eross section in the case of the method mentioned first is virtually unrestricted. The invention can be applied equally to bo h methods, because the essential idea of the invention is to attach adhesively onto the inner face of the end face of the container on the closure side a film-like closing element which joins together the inwardly exposed edges and the adjacent faces in such a way that the closure can be produced in ~his way, namely by the folded-together parts of the wall of the opening or the folded-together sides of the opening being joined together in a sealing manner without adhesively bonding face to face.
In other words, in the ca~e o th~ method according to the invention, the sides - four in the case of a right-parallelepipedal container - are folded together as before for closing the subsequent pouring opening - it goes without saying while the container bottom is still open - and in this position the folded-together sides are ~oined together from inside, that i9 from the in3ide o~ the container, by adhe~ively inserting or attaching a sheet-like closing element.
Instead of the closing element, an adhesive layer may also be formed, by spraying on a suitable adhesive, which ' ~ ' , ' , , , 2~3~8~

joinC the neighboring edges and face~ together in such a way that an undesired unfelding of the folded-~ogether wall parts or sides cannot occur and, in particular, the closure is absolutely liquid~-tight, because ik covers all regions or intermediate spaces, openings, slits or the like through which liquid can escape in an undesired way.
It is very important that during opening of the closure by the consumer, this film-li.ke closing element or the adhesive layer can readily tear appropriately along the edges of the side which is folded up first during opening of the container. Thus, the invention accomplishes a mechanically high-strength closing and an absolutely liquid-tight sealing of the closure, without the opening of the closure by the consumer being hindered or hampered. This is so since only the folding edges of the first inwardly folded ides, which in the case of a rectangular container cross section form triangles, are joined in a sealing manner by the closing element to the adjacent regions of the sides folded thereafter onto these triangles. As a rasult, the ~ide subsequently forming the pouring opening can ea~ily be detached from the closure and ~olded upright by simple drawing up. The regions of this spout side folded together and onto the side~ lying underneath are not adhesively bonded together.
The other ~olding edges are al~o ~o be correspondingly detachable if further sides o~ the container opening are also drawn up and folded upright.
The introduction and adhesive attachment or insertion of such a closing element or else the formation of a corresponding adhesive layer is readily pos~ible in production terms, in particular if, while the closure i5 being produced, the tubular container blank is held on a mandrel, on the outer end ~ace of which an appropriate closing element can be arranged and held in ~uch a way that the sides of the container opening are able to be folded toge~her at the mandrel and are thu~ able to be brought into contact wi~h ~he closLng element.

~' ; .'. "~ , .
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`` - 5 - 2~739~7 For easy openirlg of the closure, use is preferably made of a tear-open tab, which is known per se.
In any event, with the method according to khe invention th~ ob~ect mentioned above is achievsd in an optimum manner.
Preferably a cl~sing element of sealable film or of a material coated with film which is sealable at least on one side, for example PE-coated, is used and, by heating the closing element and pressing onto the closing element the inner faces of the container to be secured is adhesively inserted. The welding of such a closing element to the outer coating of the container sides can be carried out in fabrication by relatively simple means as well as at very high speed and in a reliable way.
The film-like closing element may be of any form, as long as the function of the closing element is ensured. The closing element preferably covers the entire inner face of the end face of the container on the cloA~ure side, but at least the edge regions, for joining mutually adjacent regions or sides.
According to the invention, it is preferably provided that, first of all, the corners of the inside of the container are sealed, preferably by heating and pressing, and the remaining regions are sealed by adhe~ively in~erting the closing element, it being possible to use a closing element of a smaller surface area than the size of the inner surface area of the container.
A clo~ure according to the invention for closing an opening of a tubular container which is intended in particular for liquids and comprise~ at lea~t on one side sealably coated paper or cardboard material, to be precise produced by one of the two known methods mentioned at the beginning, is defined according to the invention by the fact that, on the inner face of the end face of the container on the closure side, which is formed by the inwardly exposed regions ~f the i ,:

~., . . : .

- .
:., ' : ' ' ' ' ' 2~73987 folded-together opening wall or sides, there is adhesively attached in a manner sealing the interior of the container on the closure side a sheet-like closing element which can be severed during opening of the closure by drawing up at least one part o the openiny wall or the sides and which may also comprise an applied adhesive layer. A closure produced in this way, which can be produced by any of various methods, ensures an absolutely liquid-tight closing o~ the subsequent spout of the container from the inside of the container, that i~ while the bottom of the container is s~ill open, without folded-together ~aces of the sides of the closure being adhesively bonded to one another and thereby possibly hampering opening.
For the fixed-cycle adhesive insertion of the closing elemen~ for closing the opening o the tubular container, according to a further development of the invention it is provided that the closing element consisting of PE film or PE-coated material is laid on the free end face of a mandrel, preferably a multi-armed rotor having corrasponding mandrels on the outer end, is hea~ed there and pressed against the inner faces of the four folded-together ~ides of the upper container part, that is against the end inner face of the upper container part. In this way, with appropriate refinement of ~he method and the device used for i~, a hish number of working cycles can be achieved and so too can an absolutely liquid-tight closing of the upper container part.
To be speciic, for the adhesive insertion of the closing element it is pre~errad according to the invention that, after drawing the tubular container, open at both ends, onto the mandrel and after laying the closing element onto the ~ree end ~ace of the mandrel, the upper container part is .olded clo~ed - preferably after activating the corner regLon~ - and the closing element is then heated, or is already heated during the folding closed, and is adhesively attached onto the end -~
.
. .; . '~ ~ :
.

~073987 inner face of the upper container park under pressure exerted from the outside onto the end outer face of the upper container part and from the inside by the mandr~l onto said end inner face thereof. Similarly, it is 5 conceivable initially to lay the closing element on the free end face of the mandrel and only then draw the tubular container, open at both ends, onto the mandrel.
The result is essentially the same in both cases.
The working speed in execution of the method depends decisively on the apparatuses used. Therefore, for the heating and adhesive insertion of the closing element, according to the invention an apparatus is proposed which is defined by the fact tha~ the head of the mandrel consist~ of insulating material such as ceramic or plastic, the end face of which is coated by an extremely fine coating of ferritic material, which is coated by an antiadhesive layer, for example by a PTFE
skin, and ~hat, for pressing the end faca of the upper container part against the end face of the mandrel head against which the closing element can be laid, a pressing ram is provided, in which an induction coil for extremely brief inductive heating, for example for a period of 0.4 sec~ of the ferritic coating of the mandr~l head is arranged. Instead of the coating, a very thin metal plate which can be electrically heated by means of current pulse may also be provided. If appropriate, the region of the mandrel head lying underneath the ferrltic coating or the plate ma~ also be cooled, in order to avoid heating up to an unde~irably high temperature level and in this way to ensure the heating cycle - heating up/cooling down - with a short cycle tLme.
This apparatus according to the invention allow~
a very high number of working cycles by heating and adhesively inserting the closing element in the ~hortest time. Since electrical heating is only carried out briefly, inductively in the case of the extremely thin ferritic coating on the end face of the mandrel head or on the basi~ of it~ ohmic re~i~tance in the ca~e of the .

~ .

2~73987 thin plate, and since the heat .imparted during a heating cycle duration of, for example, 0.4 sec. is immediately removed again or used for heating up by the closing element consisting of PE film and the adjacen~ inner face of the upper container part, there occurs virtually a heat or temperature oscillation, the heating of the PE
film of the closing element taking place in particular during the temperature peaks in the ferritic coating or the plate, whereas when the induction coil is switched off and no heat is generated in the ferritic coating the temperature of the ~erritic metal or the plate drops considerably. Due ~o the antiadhesive skin with which the ferritic coating or the plate is coated, adhesion of the closing element or parts of the sealable film forming the closing element to this receiving surface for the closing element is avoided. When pressing the pressiny ram against the end outer face of the upper container part, the heated closing element, preferably PE closing element, merges completely with the end inner face of the upper container part and brings about the desired complete liquid-tight sealing of this inner face.
Bores to which negative pressure can be applied are preferably provided in the end face of the mandrel head for securing the closing element during heating etc.
It goes without saying ~hat, like the respec~ive period of action of the inductive or other heating, ~he time period of the negative pressure feeding must be coordinated exactl~ with the individual phases of ~he working cycle provided for adhesively inserting the closing element.
As an alternative to the above method of heating the closing element by mean~ o~ inductive heat, according to the invention an apparatus is .provided which i5 defined by the fact that a heatable plate, which is for heating the closing element and i8 coated on the outside by an antiadhesive layer, for example by PTFE, close~ off the mandrel at the end and the end face of the plate forms the receiving surface for the. closing element , :~. ":
, .

.
,, .. :

2~73~87 before and during adhesive insertion.
The plate is preferably easily exchangeable by means of a snap closure or other type of quick fastening.
In contrast to inductive heating, in the case of this plate a heating means arranged in the plate i5 used to reach and keep constant a temperature level on the free end face of the plate which brings abou~ at least a softening of a closing element of PE film laid on the plate. In this state, the closing element can, in the same way as an induc~ively heated closing element, be pressed against the end inner face of the upper container part and be adhesively inserted there in a sealing manner. The PTFE coating of the plate, preferably consisting of lightweight metal such as aluminum, prevents adhesion of PE film to the end face of the plate. Rather, after softening and pressing against the end inner face of the upper container par~, the closing element consisting of PE film merges completely wLth this inner face~
Illustra~ivQ embodiments of ~he invention are described in more detail below with reference to the drawings, in which;

Fig. 1 shows a perspective view o~ an upper part of a tubular container blank with still open opening, but with already adhesively inserted draw-up tab;

Fig. 2 shows a perspective view of the upper part of the container after folding together the four sides surrounding the opening of the container;

Fig. 3 shows a plan view of the inner face of the end face of the container of Fig. 2, that i~ viewed from the interior o~ the container;

Figs 4, 5 and 6 show plan view~ o a sheet-like closing element in various de~ign8;
.

:: ~

2~73~87 Fig. 7 shows a plan view of the punched-out cut-to-size piece of the container blank for the purpose of illustrating activatabl~ region~ of a PE coating;

Fig. 8 shows a plan view of the inner f ac2 of the 5container end face as in Fig. 3, but after the adhesive insertion of the shee~-like closing . element according to Fig. 4;

Fig. 9 in turn shows a plan view of the inner face of the end face of the containe~ as in Figs. 3 and 108, but after opening the container by drawing up the so~called ~pout side of the container opening for opening the clo~ure;

Fig. 10 shows a plan view of the closure of the container opened as in Fig. 9~ but seen from out~ide and 15. from above;

Fig. 11 shows a diagrammatical cross sec~ional view of a heating and pres~ing apparatu~ at the outer end of a mandrel for heating and adhasively inserting a closing element consisting o~ PE film;
0 Fig. 12 show~ a detail o~ the apparatus of Fig. 11, marked by X in Fig. 11;
.
Fi~. 13 shows a sectional view of a further heatin~ and pressing apparatus for the same purpo6e as the apparatus represented in Figs. 11 and 12;
5 Fig. 14 show~ a plan ~iew of the apparatus o~ Fig. 13 in sec~ion along the line XIV-XIV of Fig. 13.

In Fig. 1, an upper part, with respect to the subsequent position for u~e, of a container generally denoted by 1 is represented, which comprises a cut-to-size container piece 2 of paper material PE-coated .

~0739~

on both sides, which is shown in part in Fig. 7.
The wall 3 of the container, tubularl~ folded and joined along a seam 9, has in the upper region a correspondingly rectangularly surrounding border folding line 4, above which the four sides involved in the closure lie, namely a spout side 5, from which namely a spout can be formed during opening o~ the closure, a rear neighboring side 6, a front neighboring side 7 and a ~ide 8 which is opposite the spout side and along which th~
seam 9 run~. These foux sides form the opening of the container 1, generally denoted by 10.
Impressed into the spout side 5 are oblique folding lines 11, virtually forming a triangle with the corresponding border folding line. The two neighboring sides ~, 7 have corresponding folding lines 12. To be emphasized in particular is the arcuately arched border 13 of the spout side 5, which namely brings about the necessary overlap with respec~ to the side 8 during folding together and, furthexmore, provides a favorable shape ~or the subsequent spout.
It can be seen from the cut-to-size container piece 2 in Fig. 7 that the ~pout side S i8 longer than the opposite side 8, so that subsequently during folding the conditions evident from Fig. 2 for example are obtained. Correspondingly, the upper border of the neighboring sides 6, 7 follows a pa~h rising to the spout side 5. An air outlet opening 14 results when the closura is opened, said opening being represented in Fig~ 10 and intended to make it easier ~or air to flow in when liquid is ~lowing out of the container 1.
In the position represented in Fig. 1, there has already been attached to the inner face of the spout side a draw-up tab 20, which for example a~sumes the position seen in Figs. 2 and 3 when the container 1 is closed at its upper opening 10, 50 that it can be ea~ily drawn up or opening the container.
A closing element, represented in various designs in Figs. 4, 5 and 6 and generally denoted by 15 i~ to be :' ' .: '' : :
, ' - 12 - 2~73~
integrated in the closure. Said element comprises a piece of PE film as a square 16 according to Fig. 4, with clearances 17 at the border~ according to Fig. 5 and has crossed tape strips 18, 19 according to Fig. 6. It is essential for the design of the closiny elPment6 15 that the edges 31, 32, 33, 34 of the inner faces of the ~ides 6, 7, produced during folding together of the four sides 5, 6, 7, 8, as represented in Fig. 3, are joined in an absolutely sealing manner to the respec~ively ad;acent inner faces of the two sides 5, 8. As a result, the gaps which the edges 31, 32, 33, 34 form with the adjacent regions of the sides 5, 8 are bridged and closed by the closing element 15. In the case of the square 16 of Fig.

4, the closing elemen~ 15 covers the rectangular inner face, represented in Fig. 3, of the upper end face of the container. As still to be explained later, narrow border strips o~ the inner face may remain free, if appropriate, if the corners of the inner face are closed and sealed in some other way, as explained later. Irrespective of whether the embodiment according to Fig. 4, 5 or 6 is chosen, if the closing element 15 is adhesi~ely inserted in this way, the triangle regions expoRed in the interior of the container of the sides 5, 6, 7 and 8 (cf. Fig. 3) are joined together in a mechanically fixed and sealing manner along the edge~ 31, 32, 33, 34.
The closing of the opening lO is expediently perormed in the following steps:
First of all the corner regions E of the sides 5, 6, 7 and 8 are activated on the inside by hot air. In Fig. 7, a folding line pattern of a developed projection of the container is represented by vertical hatching. The activated regions are the lower tips of the t~iangle~
represented by hatching.
Subsequently, the neighboring sides 6, 7 are folded first along their obliyue folding lines 12 and inward along their border folding lines 4. rrhe ~olding of the side 8 opposite the spout side 5 follows, whereupon the spout side 5 i~ the last oi the four sides; to be . .

.. .

` - 13 - 2~73~87 folded along the border folding line 4 and i5 folded with the arcuate border 13 and the draw-up tab 20 onto the outer face of the opposite side 8. In this position, the heated closing element 15 is pressed from the inside of the container onto the inner face of the container end face, as shown in Fig. 3 and adhesively attached, so that the image according to Fig. 8 is ob~ained. At the same time, ~he activated corner regions E are also pressed together and adhesively bonded for the purpose o sealing the four corners. As stated, the corner regions and/ if appropriate, in general the border regions of the inner face of the container end face need no~ be covered by the closing element 15 if the corners are first of all adhesively bonded in a sealing manner.
In any event, during the course of the method ~he situation according to Fig. 8 is obtained - if appropriate leaving border strips all around - where the closing element 15, by joining the edges 31, 32, 33, 34 to the adjacent face regions, closes the intermediate ~paces or slit-shaped openings present there in a continuously sealing manner and at the same time ~oins the four sides 5, 6, 7, 8 firmly together from the inside of the container.
Expediently, the draw-up tab 20 is adhesively attached when producing the adhesive bond or else at a different time to the outer face of the side 8 in the sense of tacking on, in order that it rests as flat as possible on the outer face of the side 8 during transportation.
After filling with a liquid and after clo~ing the bottom of the container 1 in any conventional way, the container 1 goes to the retailer and from there to the consumer, who opens the container 1 again. For this purpose, using two fingers, the draw-up tab is easily detached from the side 8 and the spout side 5 drawn up with it. During drawing up of the spout side 5, the triangular inner ~ace (c~. Fig. 3 or 8) o~ the spout side

5 tears along the edges 31, 32 from the center outward ,. : ..
: , .

- 14 - 2~3~8~
progressively from these inner folding edgPs of the two neighboring ~ides 6, 7. Consequently, only ~his tearing of the inner folding edges 31, 32 of ~he neighboring sides 6, 7 cons~itutes ~ha drawing-up resi~tance, which is thus easily overcome. The folded-together faces are namely adhesively bonded together only in the corner regions and otherwise re~t adhesively unattached one on the other.
As represented in Figs. 9 and 10, a ~pout 30 can be easily formed from the spout side 5 by appropriate folding o~ the spout side 5 along the oblique ~olding lines 11. Air has easy access to the interior of the container through the air outlet opening 14, so that the flowing out o~ liquid from the container 1 is not hindered.
The draw-up tab 20 can be easily torn off the spout side 5, so that it does not constitute any hindrance when pouring the liquid out from the spout 30.
Figs. 9 and 10 illustrate the form of the opened container as well a~ in particular of ~he spout 30, to be precise both viewed from the interior of the container (Fig. 9) and seen from outside toward the upper container part.
Producing the closure by machine may proceed as follows:
. In a machine for processing the container blanks for filling and closing the containers there iS arranged a multi-armed rotor, which rotates by being driven in ~ixed cycles and, during one revolution, closes what is the upper opening of the container~ in use securely in a sealing manner.
For this purpose, the tubularly folded contain~r is in each case drawn in a lower angular po~ition onto a correspondingly rectangular mandrel, which corresponds in cross ~ection to the con~ainer blank. The activation of the corner region~ o the sides forming the opening of the container then takes place. Subsequently,~the four side~ are folded together in the way described, ~nd then . . . ~ -: , , .~ ,.
.

~ - 15 - 2~73987 the likewise activated closing element of PE film is brougnt against the inner face of the contain~r end face and firmly pressed against there, the folded-together sides being held at the rear by corresponding counterpressure. In this way, the closing element is adhesively attached in a firm and sealing manner against the inner face of the container end face. The operation of activating the corner regions of the ~riangle faces and the folding of the sides, may, however, as already stated above, proceed in the reverse sequence. In any event, the closure is produced in its finished foxm once the closing element has been adhesively inserted into the container.
At that s~age, the container can be removed from the mandrel and automatically transported further for filling with ~he liquid.
Two apparatuses for activating as well as heating and adhesively inserting the closing element 15 consisting of PE film during the working cycle described 20above are represented in Figs. 11 and 12 as well as 13 and 14, respectively.
In the case o~ the first apparatus according to FigR. 11 and 12, khe head 38 of the mandrel, on which the container 1 is received, consis~s of ceramic or plastic, in any event of an electrically insulating material. The end face 39 of the mandrel head 38 i~ provided with a coating 40 o~ ferritlc metal of a thickness of about 20 m~, which in turn is coated by a PTFE skin 41. The sur~ace o~ ths PTFE skin 41 forms a receiving surface 42 for the closing element 15. During the working cycle of adhesively inserting the closing element 15 into the container 1, opposite the mandrel head 38 thexe lies a presRing ram 43, in which an induction coil 44 is arranged and is provided with a corresponding power supply.
For adhesively inserting the clo~ing element 15 into the con~ainer 1, the closing element 15 is laid on the receiving ~urface 42 o the P~FE skin 41 and held .
. , . .- .
. ~ . .
. .
~ , . . .

' 2~3987 fi~m by means o~ negative pre~sure, which is effective in the end region of the mandrel head 38 via bores 45 to which negati~e pre~sure can he applied.
As soon as the container 1 is then drawn onto the mandrel head 38 in the diagr~mmatically represented way, or the tubular container 1, open at both ends, is drawn onto the mandrel head 38 and has been folded closed at its outer end in the way already described abo~e, to be precise with simultaneous activating of the ~riangular inner sides 5, 6, 7, 8, the pressing ram 43 is brought against the mandrel head 38 (cf. axrow 46). By actlvation of the induction coil 44 fox a brief heating time of, for example, 0.4 sec. the closing element 15, consisting of 15-20 m~ PE filmt is then heated by the inductive heat genexated in the coating 40 of ferritic metal, whereupon the pressing ram 43 is brought again~t the mandrel head 38 and the end ~aces of the container 1 and o~ the closing elemenk 15 are thereby pressed together between the lower face 47 o~ the pressing ram 43 and the receiving sur~ace 42 in such a way that the heated and activated clo~ing element 15 adhesively attaches firmly to the likewise activated PE coating o~ the inner face 37 of the end ~ace of the container l. After removing the pressing ram 43 from the mandrel head 38, the closing element 15 is adhesively inserted in the container 1 in a sealing manner.
In the case o~ the secend heating and pressing apparatus according to Figs. 13 and 14, to be used as an alternative, at the outer end of the mandrel 58 thexe is a plate 50, which is fastened by means of screws 51 to the head 52 of the mandrel 58, with an insulating plate 53 interposed. The head 52 has underneath a shank 60, which can be inserted into a bore 61 and can be fastenad there by means of screws 54, the înner end~ of which engage in corresponding clearances 55 in the wall o~ the shank 60. With the guick ~a~tening ~ormed in this way, the head 52 aan be rapidly exchanged.

2~73~8~

Arranged in the plate 50 is a heating means 59, in order to keep the PTFE-coated end face o~ the plate 50, which forms the receiving surface 57 for the closing element 15, at a temperature lavel at which a closing element 15 laid on the receiving surface 57 can be made to soften or be made tacky to such an extent that it is adhesively attached to khe end inner face 37 of the container 1 when appropriate pressure is applied (pressing ram not shown). Th~ closing eLement 15 laid on the receiving surface 57 can be held firm by means of bores 56 in the plate 50 to which nega~i~e pressure can be applied.
Otherwise, the function of this second heating and pressing apparatus and similarly the working cycle of adhesively inserting the closing elsment 15 which can be carried out with it are similar to in the case of the first heating and pressing apparatus described above, so that there is no need for any further description.
Reference numeral~ requiring explanation in Figs.
11 and 12:

15 - PE film 40 - Ferritic metal 1 - Cardboard, PE-coated 38 - Material: ceramic/plastic 43 - Pressing ram 44 - Induction coil available heating tim~ 0.4 sec.

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Claims

Patent Claims

1. A method of closing an opening of a tubular container, which is intended in particular for liquids and comprises at least on one side sealably coated paper or cardboard material, in which a wall of the opening, which is divided in the region of the opening of the container to be closed from the wall of the container by one or more border folding lines and surrounds the opening of the container all around, is folded inward and together along the border folding lines and adhesively bonded together in certain regions in order to form a closure, and in which the adhesive bonding can be released during subsequent opening of the closure by drawing up at least parts of the wall of the opening, wherein the folded-together regions of the wall of the opening are adhesively bonded together by adhesively inserting from the inside of the container at least one film-like closing element, which may also be formed by applying or spraying on or the like an adhesive layer, the inner folding edges of the first inwardly folded regions being joined in a sealing manner by the closing element to the adjacent regions in such a way that at least the region or regions drawn up first when opening the closure are detachable from the neighboring regions by tearing of the closing element along the corresponding inner folding edges.

2. A method as claimed in claim 1 in which four sides, which are divided in the region of the opening of the container to be closed from the wall of the container by rectangularly running border folding lines and surround the opening of the container all around, are folded together inward along the border folding lines, as well as following a triangular pattern of oblique folding lines on the sides, and adhesively bonded together in order to form a closure, and during subsequent opening of the closure a spout can be formed from one side by drawing it up and, if appropriate, releasing the adhesive bonding of said side, wherein the sides are adhesively bonded together in the folded-together position by adhesively inserting from the inside of the container at least one film-like closing element, which may also be formed by applying or spraying on or the like an adhesive layer, the inner folding edges of the initially inwardly folded sides being joined in particular by the closing element to the adjacent regions of the subsequently folded sides in such a way that at least the side drawn up first when opening the closure is detachable from the neighboring sides by bearing of the closing element along the corresponding inner folding edges.

3. A method as claimed in claim 1 or 2, wherein a closing element of sealable film or of a material coated with film which is sealable at least on one side, for example PE-coated, is used and, by heating the closing element and pressing onto the closing element the inner faces of the container to be sealed, is adhesively inserted.

4. A method as claimed in one of claims 1 to 3, wherein the closing element covers the inner face of the end face of the container on the closure side, but at least the folding edge regions, for joining and sealing mutually adjacent regions or sides.

5. A method as claimed in one of the preceding claims 1 to 4, wherein the corners of the inside of the container are sealed, preferably by heating and pressing, and the remaining regions are simultaneously sealed by adhesively inserting the closing element, it being possible to use a closing element of a smaller surface area than the size of the inner surface area of the container.

6. A method as claimed in one or more of claims 1 - 5, wherein the closing element consisting of PE film or PE-coatad material is laid on the free end face of a mandrel, heated there and pressed against the inner faces of the four folded-together sides of the upper container part, that is against the end inner face of the upper container part.

7 . A method as claim in claim 6, wherein, after drawing the tubular container, open at both ends, onto the mandrel and after laying the closing element onto the free end face of the mandrel, the upper container part is folded closed and the closing element is heated then or already during the folding closed, and i adhesively attached onto the end inner face of the upper container part under pressure exerted from the outside onto the end outer face of the upper container part and from the inside by the mandrel onto said end inner face thereof.

8. An apparatus for carrying out the method as claimed in claim 6 or 7, wherein the mandrel head (38) consists of insulating material such as ceramic or plastic, the end face (39) of which is coated by an extremely fine coating (40) of ferritic metallic material which is coated by an antiadhesive coating, for example by a PTFE skin (41), and wherein, for pressing the end face of the container (1) against the end face (39) of the mandrel head against which the closing element (15) can be laid, a pressing ram (43) is provided, in which an induction coil (44) for extremely brief inductive heating of the ferritically metallic coating (40) of the mandrel head (38) is arranged, or wherein, instead of the coating (40), there is on the mandrel head (38) a metal plate which can be heated electrically by means of current pulse.

9. An apparatus as claimed in claim 8, which comprises bores (45), to which negative pressure can be applied, in the end face of the mandrel head (38) for securing the closing element (15).

10. An apparatus for carrying out the method as claimed in claim 6 or 7, which comprises a heatable plate (50), which is for heating the closing element (15) and is coated on the outside by an antiadhesive layer, for example by PTFE, and preferably consists of lightweight metal such as aluminum, closes off the mandrel (58) at the end and the end face of the plate (50) forms the receiving surface (57) for the closing element (15) before and during adhesive insertion.

11. An apparatus as claimed in claim 10, wherein the plate (50) with the head (52) can be easily detached from the mandrel (58) by means of a quick fastening (54, 55) and consequently can be exchanged quickly.

12. A closure for closing an opening of a tubular container, which is intended in particular for liquids and comprises at least on one side sealably coated paper or cardboard material, in which a wall of the opening, which is divided in the region of the opening of the container to be closed from the wall of the container by one or more border folding lines and surrounds the opening of the container all around, is folded inward and together along the border folding lines and adhesively bonded together in certain regions in order to form a closure, and in which the adhesive bond can be severed during subsequent opening of the closure by drawing up at least parts of the wall, in particular if the opening of the tubular container is formed in square or rectangular arrangement by four sides which are divided in the region of the opening of the container to be closed from the wall of the container by rectangularly running border folding lines and surround the opening of the container all around, are folded together inward along the border folding lines, as well as following a triangular pattern of oblique folding lines on the sides, and adhesively bonded together in order to form a closure, and during subsequent opening of the closure a spout can be formed from one side by drawing it up and, is appropriate, releasing the adhesive bonding of said side, wherein, on the inner face of the end face of the container on the closure side, which is formed by the inwardly exposed regions of the folded-together opening wall or the folded-together sides, there is adhesively attached in a manner sealing the interior of the container on the closure side a film-like closing element which can be severed during opening of the closure by drawing up at least one part of the opening wall or of the folded-together sides and which may also comprise an applied adhesive layer.