WO1996031406A1

WO1996031406A1 - Tin can with a foil closure membrane, and a process, device and foil for manufacturing the can

Info

Publication number: WO1996031406A1
Application number: PCT/EP1996/001410
Authority: WO
Inventors: Werner Grabher
Original assignee: Werner Grabher
Priority date: 1995-04-02
Filing date: 1996-03-30
Publication date: 1996-10-10
Also published as: KR20050038655A; JPH11509810A; AU694023B2; EP0819086B1; AU5398796A; GR3029457T3; KR19980703504A; DE59601055D1; CA2217311A1; CN1185138A; BR9604869A; CA2217311C; NZ305862A; KR100526838B1; ZA962628B; ATE174859T1; ES2127634T3; CN1063401C; DK0819086T3; JP3689115B2

Abstract

The tin can is closed by a paper, plastic or metal-foil membrane (2) on at least one end face in such a way that the outer side of the foil edge region (5) raised in the direction of the can's axis (A) is joined to the essentially cylindrical inner surface of the wall of the can (1) to form a seal, without covering the wall edge of the can. The membrane foil (2) with the raised foil edge region (5) is introduced into the can and forced against the inner wall of the can (1) by a die (8) with an expandable periphery (17). Heat is then applied to create a sealing join between the raised foil edge region (5) and the inner wall of the can (1) without any external pressure-absorbing device.

Description

Can with a sealing membrane made of film, as well as method, device and

Foil for making the can

The invention relates to a can according to the preamble of claim 1, to a method according to the preamble of claim 4 and to one

Device and a film for the manufacture of the can.

Up to now, metal tin cans have essentially been closed either by jointly crimping the cut edge of the can with a metal lid (e.g. according to WO 83/02577 or US-A-3,952,677), or with a foil-provided one

Sheet metal ring provided (according to AT-A-368.91 9), or the inside of the can wall (1) - at least in the area of the raised foil edge area (5) - had to be conical (e.g. according to DE-U-94 1 4 440), which is a complicated can production and high tolerances required, so that the same position of the membrane plate with respect to the can edge could always be achieved when retracting the stamp.

On the other hand, the cut edge of the can not known plates with raised edge for cans made of plastic are known (eg DE-A1 - 33 05 144 or CH-A-629 984), but it was always relatively stable lid parts for the bottom of pressure-resistant cans or those made of a relatively soft wall (for example according to US Pat. No. 4,599,123) which required an external pressure recording device for the sealing process.

The invention has now set itself the task of creating a tin can, in particular one made of tinplate or aluminum sheet, with a simple and, above all, inexpensive closure. This is achieved for the first time by the feature mentioned in the characterizing part of claim 1. The closure is made - as has become known in another context - from only one membrane film, optionally from (and in particular laminated with thin aluminum foil) paper and / or plastic, but preferably from a metal foil, in particular from aluminum, all for the sake of simplicity only as Designates the film and, if necessary, allows the can opening to be exposed in a manner known per se with the aid of tear-open tabs. The edge of the membrane plate which is pulled up in the direction of the can axis does not overlap the - preferably flanged - edge of the can, thus facilitating tearing open and therefore leaving the can edge with its robust outside or standing surface. The membrane film is preferably at most 0.2 mm, in particular at most 0.1 mm, consists, for example, of a 50μ aluminum foil with 20μ heat seal coating on the inside and 10-20μ lubricating lacquer coating on the outside and is therefore suitable for closing the subsequent removal opening. Depending on the filling material or on a lid used, however, the can base can also be designed according to the invention if required. The use of embossed foils is further preferred because these are easier to nestle on cans with changing tolerance and also result in better stability.

In general, it is preferred if the membrane film - at least in the area intended for connection to the inner wall of the can - is coated with a heat seal lacquer. In principle, however, the inner wall of the can in the area mentioned - like that of (e.g. coated with aluminum foil) combination cans - with a primer or a heat sealable

Layer provided; otherwise the tight connection often requires the use of special - especially multi-component - adhesives or heat seal lacquers. In any case, it can also be used to seal bare or painted tin cans.

The method for producing the can according to the invention uses the characterizing feature of claim 3. Preferred developments of the method according to the invention are described in the characteristics of claims 4 and 5.

In the past, it was cumbersome to exert pressure from the outside against the stable inner stamp against a fixed stamp attached inside the (relatively soft) cardboard box by moving ring segments together or moving two conical surfaces together. This is no longer the case with the method according to the invention. The much better and less cumbersome method of applying the pressure from the inside is not possible with previous, soft cans, since the diameter tolerances of the can were too large for an exact external holder directed against the internal pressure, or the inside rim and stamp had to be conical become. With the tin can according to the invention, there is no longer any need for an external bracket; a loose centering is sufficient. The device according to claim 6 is particularly suitable for carrying out the method according to the invention, preferably when at least one of the features of claim 7 is realized.

It goes without saying that the membrane foils used to close the cans according to the invention are expediently prefabricated from material according to claim 9, in order then to be applied to the corresponding can opening using the method according to the invention. They then preferably have the feature of claim 10, so that they can easily be introduced even in cans with different tolerances and in some cases already lie in the desired position through the conical film edge area 5. This security function can be further improved by the feature of claim 11.

A wide collar running parallel to the diaphragm plate, e.g. in the

US-A-4,599. 1 23 has proven to be extraordinarily unfavorable, since when it is drawn into the can - without overlapping the cut edge of the can edge - it has to lead to folds which make it difficult for the film to be tightly connected to the inner wall of the can or even make it impossible.

There are, of course, numerous possibilities according to the prior art for final attachment. However, since the film used according to the invention is relatively thin and preferably a film with good thermal conductivity, use will be made of a hot joining process, for example one

Apply hot glue to the outside.

Further details of the invention result from the following description of exemplary embodiments explained in the drawing. Show it:

Fig. 1 the sequence of the method according to the invention, for which the

Fig. 2-3 illustrate enlarged details II and III from Fig. 1 a and 1 b, while Fig. 4 shows a section through the inventive device. Fig. 5a and b show a horizontal partial section through the inventive

Device in two different working positions. According to representation a) in FIG. 1, a can 1 made of sheet metal is to be closed with a membrane film 2. The film 2 can be connected to a tear-open tab 3 in any way, for example by gluing. In contrast to conventional tear-open tabs, the tab 3 can be used as a whole to tear off the membrane film 2 which has been introduced into the can 1 and connected to it at the edge. This is cheaper because either a predetermined breaking point, for. B. by punching, or a separation of the membrane cutting edge overlapping the can cutting edge from the membrane opening plate spanning the can opening had to be created. With a thin film of preferably at most 0.2 mm, in general even at most 0.1 mm, this still meant difficulties.

It goes without saying that such a thin film, which is only used to keep fresh or to preserve the aroma or to prevent contamination, is relatively difficult to handle. According to the invention, it now has, on the circumference of a covering area 4, a film edge area 5 which is pulled up all round and which provides the membrane plate part spanning the can opening with a certain stiffening. The membrane film 2 closing the can bottom preferably has at least one annular bead for the purpose of stiffening (and also for the purpose of achieving a slight radial elasticity during deep drawing and / or sealing). The film 2 reinforced in this way can now be form-fitting (so that the film shape is not changed when inserted into the can opening), e.g. are picked up by means of a suction gripper known per se and placed in a first step on the top of the can 1. Here there is another difficulty associated with a thin film: it must be ensured that the film remains on the upper side of the can 1 so that it can be tightly connected to the inner wall of the can in the next step. As such, it would be conceivable to provide the upper edge of the can 1 with an adhesive in such a way that the film remains attached to it in the desired position. Advantageously, however, this is done according to the invention in a manner which can be seen better in FIG.

Accordingly, the raised edge is at least slightly conically divergent, i.e. it results in a vertical V, even if only a very small but measurable angle β, which will have a size of less than 5 °, in particular less than 2 °. In a practical embodiment, the Diameter on the underside of the membrane plate, ie in the area of the cover surface 4, should be only a few tenths of a mm smaller than the opening diameter of the membrane plate, the height measured along the vertical V only having to be about 5 mm.

The upper, larger diameter of the film 2 is, of course, expediently chosen such that it is held frictionally on the top of the can 1 when it is placed on by the suction gripper. A further measure for securing the film 2 on the upper side of the can 1 can consist in a collar 6 which is hook-shaped in cross section and which interacts with the upper edge of the can 1. The upper, mostly sharp-edged edge of the can 1 is, by the way, preferably flanged outwards (7 in FIG. 1a, 3) in order to prevent damage to the thin film or injury to the user.

The film 2 is so firmly with this collar 6 on the edge of the can. However, this is only an intermediate step when closing the can 1, which should not hinder the subsequent steps. This includes the action of a stamp 8, shown only schematically in FIG. 1b, which presses the film 2 into the position shown in FIG. 1b. The collar 6 slides out of the position indicated by dash-dotted lines in FIG. 3, in which it is before the stamp is pressed down

8 was located in the interior of the can and, because of the ductility of the film material (with sufficient toughness at the same time), lies against the inner circumference of the can 1 in the position shown in full lines in FIG. 3. The conicity of the film edge area 5 with the small angle β illustrated in FIG. 2 also changes into a cylindrical shape, so that the film edge area 5 lies closely against the can circumference. The low conicity prevents the formation of folds and wrinkles - as expressly mentioned in US Pat. No. 4,599,123.

As described below, the method according to the invention and the device according to the invention bring about the tight connection of the membrane film 2 with the cylindrical region of the inner wall of the can directly below the (preferably flanged) edge of the can:

According to a preferred embodiment, the stamp 8 is in accordance with FIG

Fig. 4 section shown. It consists of several parts, namely the actual stamp surface 9, which protrudes upwards over pins 10 (only one is shown, preferably there are three) connected to the attachment 1 1 of a stamping head 1 2. A centering ring 1 3 is placed around the stamp surface 9 and can be displaced along guide pins 14 and against the action of at least one compression spring 15. Normally, the ring 1 3 assumes the lowered position on the left in FIG. 4, in which it is supported, for example in a manner not shown, on the upper side of the stamp surface 9, but may also be held by other means.

In this position, the centering ring 1 3 receives the edge of the can and has a small recess 1 6 'for this purpose. The process can now proceed in such a way that the can 1 stands on a lifting table and is lifted up, as a result of which the centering ring 1 3 moves against the action of the spring 1 5 into the upper position shown on the right. At the same time, the stamp surface 9 emerges from the inside of the ring 1 3 and thus presses the film plate 2 into the position shown in FIGS. 1 b and 3.

Alternatively, the ring 1 3 could also be stationary and hold the can centered while the stamp surface 9 is moved downwards. In this case, for example, approach 11 would be designed as a piston rod of a fluidic unit, preferably a pneumatic piston-cylinder unit. However, it goes without saying that there is a lot of leeway here in terms of design considerations, since it is only a question of the relative movement of the parts shown and the can. The centering of the can or, relative to it, of the film 2 could also take place in a wide variety of ways.

From the previous explanations, it is clear that it is important to place the raised film edge area 5 of the membrane film 2 as close as possible to the inner circumference of the can (as shown in FIG. 3) in order to connect it firmly to it. For this purpose, the punch 8 has a spreading device, which in the exemplary embodiment according to FIG. 4 is formed by a wedge arrangement.

A series of wedge segments 16 is guided along the top of the stamp surface 9 in such a way that they can be displaced radially outward with respect to the central axis A of the stamp 8. For guidance purposes, the rear side of the stamp surface 9 could have grooves or slots (not shown), for example. However, it also likes the flat back of the stamp surface

Sufficient guidance. Although the wedge segments 1 6 themselves could be used to press the raised foil edge area 5 of the foil 2 against the inner circumference of the can 1, it is advantageous if they are spanned by elastic piston rings 17 or snap rings. This creates a more uniform circumferential surface when these rings 17 are pressed against the film edge region 5 of the film 2 and moreover also results in a double function in a double function, which acts on the segments 16.

In order to press the wedge segments 1 6 radially outwards, a conical wedge 1 8 is provided, which can be moved downwards by means of an actuating rod 1 9 by a drive, preferably of a pneumatic type, and between the wedge segments with their wedge surfaces 20. The reason for preferring a pneumatic drive is that there is hardly any risk of contamination from oil or leakage liquid, and it is particularly easy to set a maximum pressure that does not widen the can. If the conical wedge 1 8 is now moved downwards against the stamp surface 9, it spreads the wedge segments 1 6 apart and thus presses the elastic rings 1 7 against the foil edge region 5 (which is indicated in fragments at the bottom right in FIG. 4), where the edge of the can is stuck in the recess 1 6 '. In this way, the position of the film 2 according to Fig. 1 b reached.

In this position, however, the film 2 must now also be secured and generally also sealed. This can be done in a conventional manner by means of adhesive, preferably by means of heat sealing, because the thin film 2 allows the heat to pass through relatively well. For this purpose, the outside of the

Film edge be coated with a hot glue 21 (Fig.2). A heating device is then assigned to the spreading device 1 6-1 8. This could in itself be formed by heating windings accommodated in the wedge segments 1 6, but the space at this point is very narrow, and movable connections must also be provided. Although this possibility should not be excluded, a (e.g. annular) radiant heating source 22, e.g. B. above the wedge segments 1 6 and the rings 1 7 are provided, which heats these parts in order to heat the hot glue 21 (FIG. 2) and to fuse with the inner wall of the can 1. The wedge segments 16 can be formed, for example, from a ceramic material with good heat storage properties, which also improves the wear properties. Fig. 5a shows the wedge segments 1 6 and a snap ring 1 7 in the closed, Fig. 5b (by the wedge pieces 1 8 of the stamp 8, not shown here, moved perpendicular to the plane of the drawing) in a spread position for the purpose of heat sealing the film 2 to the inner wall of the can.

It goes without saying that the wedge arrangement shown is only one possible exemplary embodiment, which may be preferred with regard to the service life of the device, and that numerous modifications are conceivable within the scope of the invention. For example, the conical wedge 1 8 could simply be formed by a pressure plate movable relative to the stamp surface 9, a rubber bellows may be provided between the top of the stamp surface 9 and this pressure plate. This expands when a pressure medium is applied through the pressure plate used in place of the part 18, which would then also be connected to the rod 19 for its actuation, from the top to the side and thus presses on the displaceable parts 1 6 or directly the rings 1 7. A horizontally running drive, radially outwards, would be conceivable for the individual segments 16, but would be structurally complex. Especially in this case, but also in other cases, heating the upper edge of the can from the outside for heat sealing may be the simpler solution.

As soon as the can 1 is closed in the position according to FIG. 1 b, additional measures may be advantageous. In order to protect the vulnerable film 2, for example, a cover 23 or 24 (FIG. 1 c) can also be applied.

A particular advantage of the present invention is also that the foils can be manufactured separately and, if necessary, kept in stock, whereby - with the same diameter of the cans 1 - cans with different volumes with the prefabricated and due to their design with the foil edge area 5 are sufficient stable foils 2 can be loaded.

This film edge area 5 can also be easily coated with the adhesive 21, which would be difficult to attach to the inner circumference of the can due to the risk of contamination. On the other hand, the invention is of course not limited to the use of an adhesive, as has already been explained. The invention is not restricted to the illustrated embodiments. Thus, the output of the device according to the invention with - z. B. arranged on a turntable - multiple tools can be increased in a conventional manner.

Claims

PATENT CLAIMS

1 . Tin made of sheet metal with a sealing membrane (2) made of paper, plastic or metal foil provided on at least one end face, which closes the at least one end face in such a way that the outside of the foil edge area (5) drawn up in the direction of the can axis (A) ) is sealingly connected to the inside of the can wall (1), preferably glued or heat-sealed, without overlapping the edge of the can wall, characterized in that the inside of the can wall (1) - at least in the area of the raised film edge area (5) - is essentially cylindrical.

2. Can according to claim 1, characterized in that the can wall edge (7) is flanged to the outside and / or the film edge area (5) lies essentially without wrinkles and wrinkles on the inner wall of the can (1).

3. A method for producing a can according to claim 1 or 2, wherein the membrane film (2) with raised foil edge area (5) is inserted into the can, which is then by means of a stamp (8) with an expandable circumference (17) against the inner wall of the can (1) is pressed, whereupon, under the influence of heat, the tight connection of the raised film edge area (5) - essentially over its entire vertical extent - to the inner wall of the can (1), characterized in that the expansion takes place without an external pressure recording device he follows.

4. The method according to claim 3, characterized in that the expansion of the punch circumference is carried out by a combination of wedges (1 6, 1 8, 20) and piston rings or snap rings (1 7).

5. The method according to claim 3, characterized in that the spread of the

Stamp circumference is done by a pneumatically operated rubber bellows.

6. Apparatus for performing the method according to claim 4 or 5, with a displaceably mounted plunger (8) with a width that can be expanded transversely to the direction of displacement, a displacement device (1 9) for the

Stamp and a spreading device (1 6-1 8) for generating the corresponding movements is provided, characterized in that at least one of the following features is provided: a) a centering device (1 3) for the membrane film (2) and / or the can (1); b) a heating device (22) for the circumference of the stamp (8).

7. The device according to claim 6, characterized in that the Aufspreiz¬ device (1 6- 1 8) a combination of on the one hand at least two, preferably three to four radially expandable piston or snap rings (1 6) with mutually offset openings , and on the other hand at least three, preferably four to eight, in particular six, arranged in a ring

Wedges (1 8.20) includes.

8. The device according to claim 6, characterized in that the Aufspreiz¬ device from an arranged along the circumference of the stamp elastic ring (1 7), preferably from at least one fluidically or pneumatically actuated unit, such as a rubber bellows.

9. film (2) for a can according to claim 1 or 2, characterized in that it is a - in particular embossed or grained - metal foil of at most 0.2 mm, preferably at most 0.1 mm.

1 0. film (2) for a can according to claim 1 or 2, characterized in that it has on its radial outer side a raised - preferably 0.2 to 0.3 mm upwards to conically divergent - film edge area (5), preferably an adhesive coating on the outside

(21), in particular with a hot glue.

1 1. Film (2) according to claim 1 0, characterized in that it has at the free end of the film edge region (5) a radially outwardly facing, in cross-section approximately hook-shaped collar (6).