EP0819086B1 - Process and device for manufacturing a tin can with a foil closure membrane, and semifinished can with a foil closure membrane - Google Patents

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

The invention relates to a method and an apparatus for Production of a can according to the preamble of claim 1 or Claims 7 and 8, and a semi-finished tin made of sheet metal with a Membrane film closure.

Tin cans have so far been essentially either joint crimping of the can cut edge with a metal lid sealed (e.g. according to WO 83/02577 or US-A-3,952,677), or with provided with a sheet metal ring provided with foil (according to AT-A-368.919), or the inside of the can wall (1) had to - at least in the area of the raised foil edge area (5) - be conical (e.g. according to DE-U-94 14 440), which is a more complicated can production and high Tolerances required so that when the stamp was retracted, it was always the same The position of the membrane plate in relation to the edge of the can could be achieved.

On the other hand, the cut edge of the can is not overlapping plates raised edge for cans made of plastic (e.g. DE-A1-33 05 144 or CH-A-629 984), but this was always the case relatively stable lid parts for the bottom of pressure-resistant cans or those from relatively soft walls (e.g. according to US-A-4,599,123), which for Sealing process required an external pressure recording device.

Such plates have also been proposed for tin cans (CH-A5-659633), but their installation there only works with the help of a heat-conducting one (Sheet metal) cover, through which are heated for the purpose of heat sealing must and then remains in the can.

WO-A-84/04507 has already described a device in which the sealing of a can is carried out by means of a membrane film a mechanically stretched rubber ring to the The inner wall of the can is pressed and with a hot glue is connected. However, this requires a very complicated training of the Rubber ring and that from the outside to the can wall Welding tool.

The object of the invention is now a process for the production a tin can, especially one made of tinplate or Aluminum sheet, with a simple and above all cheap closure too create. This is achieved for the first time by the in the characterizing part of claim 1 mentioned feature. Preferred developments of the invention Procedures are described in the characterizing part of claims 2 and 3.

The closure is there - as is known in another context become - from only one membrane film, possibly from (especially with thin aluminum foil laminated) paper and / or plastic, but preferably a metal foil, especially aluminum, all in following for the sake of simplicity also referred to as membrane film, and if necessary, in a manner known per se, with the aid of Tear tabs to expose the can opening. The towards the The edge of the membrane plate, which is pulled up, extends over the - preferably flanged - can edge does not make it easier Tear open and therefore leaves the edge of the can its robust outside or Footprint.

The membrane film is preferably at most 0.2 mm, in particular at most 0.1 mm thick, e.g. from a 50µ aluminum foil with 20µ Heat seal coating on the inside and 10-20µ anti-friction coating on the outside and is therefore for the closure of the later Removal opening suitable. Depending on the product or one However, the lid can also be used if necessary be produced according to the invention. Use is also preferred of embossed foils, because they are easier on cans with changing Let tolerance nestle 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 box - with is coated with a heat seal lacquer. Basically, however Inner wall of the can in the area mentioned - such as that of (e.g. combination cans coated with aluminum foil - with a primer or a heat sealable layer; otherwise the density requires Connection often the use of special - especially multi-component - Adhesives or heat seal lacquers. In any case, it can also be bare or lacquered tin cans are sealed.

So far, it has been cumbersome to have a fixed, in Inside the (relatively soft) cardboard box stamp by the Moving ring segments together or moving two together Apply conical surfaces from the outside against the stable inner punch. This is no longer the case with the method according to the invention. The much better and less cumbersome method of printing from the inside application is not possible with previous, soft cans, because for one exact, against the internal pressure directed outside bracket Diameter tolerances of the can were too large or had to The inner rim of the can and the stamp are conical. In which The method according to the invention is now no external mount at all more needed; a loose centering is sufficient.

The method according to the invention is particularly suitable the device according to claim 7 or 8. Special embodiments described in the characterizing part of claims 9 and 10.

It goes without saying that those used to close the cans according to the invention serving membrane films expediently made of material according to one of the Claims 4 to 6 are prefabricated, then with the help of method according to the invention on the corresponding can opening to be applied so that they can be used in cans with different Tolerance can be easily introduced and in the desired position partly already lie through the conical edge area 5 of the film.

Now - as mentioned - a tin can has become known from CH-PS 659.633, the end face of which is closed with a raised membrane. However, there is essential to the invention a heat-conducting lid that remains in the can until it is opened by the last consumer (FIG. 9), whereupon the membrane is also removed and the can no longer meets the requirements. The semi-finished can according to claim 11 is now only closed at one end with a membrane film and there free of a heat-conducting lid (as is customary in the industry, and is therefore suitable for filling on the opposite side, i.e. an intermediate product, while the comparable one Intermediate product according to CH-PS 659.633 has such a heat-conducting lid, which makes the can more expensive and more difficult).

A wide collar running parallel to the diaphragm plate, e.g. in the US-A-4,599,123 has been found to be extremely unfavorable proven that when it is pulled into the can - without the cut edge of the Reaching over the edge of the can - must lead to wrinkles forming difficult a tight connection of the film with the inner wall of the can or even make it impossible.

There are, of course, numerous possibilities for the final attachment after the State of the art. But since the film used according to the invention is relatively thin and preferably a film with good thermal conductivity to use a hot joining process, such as one Apply hot glue to the outside.

Fig. 1

den Ablauf des erfindungsgemässen Verfahrens;

Fig.2und 3

vergrösserte Details II und III aus der Fig.1a bzw. 1b;

Fig.4

einen Schnitt durch die erfindungsgemässe Vorrichtung;

Fig. 5a und b

einen horizontalen Teilschnitt durch die erfindungsgemässe Vorrichtung in zwei verschiedenen Arbeitspositionen.

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

Fig. 1

the sequence of the method according to the invention;

Fig. 2 and 3

enlarged details II and III from FIGS. 1a and 1b;

Fig. 4

a section through the inventive device;

5a and b

a partial horizontal section through the inventive device in two different working positions.

According to the representation a) in Figure 1, a can 1 made of sheet metal with a Membrane film 2 are closed. The membrane film 2 can with a tear tab 3 connected in any way, for example by gluing be. In contrast to conventional tear-open tabs, the tab 3 can do this can be used, the introduced into the box 1 and connected to it at the edge Tear off membrane film 2 as a whole. This is cheaper because in the conventional design either a predetermined breaking point, e.g. by Punching, or a separation of the membrane film edge overlapping the can cutting edge created by the membrane foil plate spanning the can opening had to become. With a thin film of preferably at most 0.2 mm, generally even at most 0.1 mm, still meant this Difficulties.

It goes without saying that such a thin film, which is only used for keeping fresh or to preserve the aroma or to prevent contamination, relatively is difficult to handle. According to the invention, it now has one perimeter Cover area 4 an all around raised foil edge area 5, the the membrane plate part spanning the can opening provides a certain stiffening mediated. The membrane film closing the can base preferably has 2 for stiffening (and also for achieving a slight radial Elasticity during deep drawing and / or sealing) preferably at least one circular bead. The membrane film 2 reinforced in this way can now form-fitting (so that the film shape does not when inserted into the can opening is changed), e.g. by means of a suction gripper known per se and be placed on the top of the can 1 in a first step. Here there is another difficulty associated with a thin film: it it must be ensured that the film remains on the top of the can 1, so that in the next step they are tightly connected to the inner wall of the can can be. In itself, it would be conceivable to cover the upper edge of the can 1 with a To provide adhesive such that the film on it in the desired position Remains. According to the invention, however, this advantageously takes place in one Way, as can be seen better from Fig.2.

Accordingly, the raised edge is at least slightly conically divergent, i.e. it results in a vertical V, if only very small, but it does measurable angle ß, the size of less than 5 °, in particular less than 2 °. In a practical embodiment, the diameter at the bottom of the membrane plate, i.e. in the area of the cover surface 4 only a few tenths of a mm smaller than the opening diameter of the membrane plate , the height measured along the vertical V being only about 5 mm must be.

The upper, larger diameter of the membrane film 2 becomes natural expediently chosen so that they are frictionally engaged when placed on by the suction pad is held at the top of the can 1. Another measure to secure the membrane sheet 2 on the top of the can 1 can in consist of a cross-section hook-shaped collar 6, which with the upper Edge of can 1 interacts. The upper, mostly sharp-edged edge of the can Incidentally, 1 is preferably flanged to the outside (7 in Fig. 1a, 3) to a Prevent damage to the thin film or injury to the user.

The membrane film 2 is thus firmly seated with this collar 6 on the edge of the can. This is, however, only an intermediate step when closing the box 1, the subsequent ones Steps should not hinder. This includes the action of a, in Fig. 1b only schematically shown stamp 8, the membrane sheet 2 in the 1b apparent position presses. The collar 6 slides out of the in Fig. 3 dash-dotted position in which he is before depressing of the stamp 8 was in the interior of the can and lies down due to the ductility the film material (with sufficient toughness at the same time) in the position shown in Figure 3 with full lines on the inner circumference box 1. The conicity illustrated on the basis of FIG. 2 also applies here the film edge area 5 with the small angle ß in a cylindrical shape, so that the film edge area 5 fits closely to the can circumference. Because of the low Tapering is the formation of wrinkles and wrinkles - as in US-A-4,599,123 expressly mentioned - avoided.

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

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 from the pin 10 (only one is shown, preferably there are three) with the approach 11 of a stamp head 12 is connected. There is a centering ring 13 around the stamp surface 9 placed along guide pins 14 and against the effect at least a compression spring 15 is displaceable. Usually the ring takes 13 the left in Fig.4, lowered position, in which it is not, for example supported on the top of the stamp surface 9, if necessary but is also held by other means.

In this position, the centering ring 13 takes up the edge of the can and has a recess 13 'for this purpose. The process can now proceed that the can 1 is on a lifting table and is lifted up, whereby the centering ring 13 against the action of the spring 15 in the one shown on the right top layer shifts. At the same time, the stamp surface 9 emerges from the inside of the Ring 13 and thus presses the membrane film 2 in that shown in Fig.1b and 3 Location.

Alternatively, the ring 13 could also be stationary and hold the can centered, while the stamp surface 9 is moved down. In this case, for example the approach 11 as a piston rod of a fluidic unit, preferably of a pneumatic piston-cylinder unit. It it goes without saying, however, that constructive considerations leave a lot of leeway is granted, since it is only on the relative movement of the parts shown and the Can arrives. The centering of the can or relative to it could also Membrane film 2 done in a variety of ways.

From the previous explanations, it is clear that it is important to pull up Foil edge area 5 of the membrane foil 2 as close as possible to the inner circumference the can (as shown in Fig.3) to secure it with this connect. For this purpose, the stamp 8 has a spreading device which in the embodiment of Figure 4 is formed by a wedge arrangement. Along a row of wedge segments 16 is guided at the top of the stamp surface 9, that they are radially outward with respect to the central axis A of the punch 8 can be moved. The back of the stamp surface could be used for guidance 9, for example, have grooves or slots (not shown). It however, the flat back of the stamp surface may also be sufficient for guidance.

Although the wedge segments 16 on themselves to press the hoisted Film edge area 5 of the membrane film 2 is used on the inner circumference of the can 1 , it is advantageous if they are made of elastic piston rings 17 or circlips can be spanned. This creates a more even one Circumferential surface when pressing these rings 17 against the film edge area 5 of the membrane film 2 and also results in a double function Restoring force that acts on the segments 16.

In order to press the wedge segments 16 radially outwards, there is a conical wedge 18 provided, preferably by means of an actuating rod 19 of a drive pneumatic type, downwards and between the wedge segments with their Wedge surfaces 20 can be moved. The reason for preferring one pneumatic drive is that there is a risk of contamination is hardly given by oil or leakage liquid and a maximum pressure is particularly easy can be set that does not expand the can. If the conical wedge 18 is moved down against the stamp surface 9, it spreads the Wedge segments 16 apart and thus presses the elastic rings 17 against the film edge area 5 outwards, where the can rim is stuck in the recess 13 '. To this The position of the membrane film 2 according to FIG. 1b is achieved.

In this position, however, the membrane film 2 must also be secured and in general also be sealed. This can be done in a conventional manner Gluing, preferably done by means of heat sealing, because of the thin membrane film 2 yes the heat lets through relatively well. For this purpose the outside the edge of the film may be coated with a hot glue 21 (FIG. 2). Of the A heating device is then assigned to the spreading device 16-18. This could formed by heating coils accommodated in the wedge segments 16 be, but the space is very narrow at this point, and still movable Connections are to be provided. So although this possibility is not excluded may be a (e.g. annular) radiant heat source 22, e.g. above the wedge segments 16 and the rings 17 are provided which heat these parts, to heat the hot glue 21 (Fig.2) and with the inner wall of the Merge can 1. The wedge segments 16 can for example consist of one Ceramic material with good heat storage properties can be formed, which also improves wear properties.

5a shows the wedge segments 16 and a snap ring 17 in the closed, 5b (through the wedge pieces 18 of the not shown here, perpendicular to the plane of the drawing moving stamp 8) in the spread position for the purpose of heat sealing the membrane film 2 to the inner wall of the can.

It is understood that the wedge arrangement shown is only one possible, under certain circumstances preferred embodiment with regard to the life of the device is and that numerous modifications within the scope of the invention are conceivable. For example, the tapered wedge 18 could be simply relative be formed to the stamp surface 9 movable pressure plate, wherein between a rubber bellows is provided on the top of the stamp surface 9 and this pressure plate may be. This expands when a pressure medium is applied by the pressure plate used in place of part 18, which then also with the rod 19 would be connected to operate, from the top to the side and thus presses on the displaceable parts 16 or directly on the Rings 17. A horizontal drive, radially outwards, would also be suitable for the individual segments 16 conceivable, but structurally complex. Especially in In this case, but also in other cases, the upper edge of the can may be heated represent the simpler solution from the outside for the purpose of heat sealing.

As soon as the can 1 is closed in the position according to FIG further, additional measures are an advantage. About the vulnerable membrane film To protect 2, a cover 23 or 24 (Fig.1c) can be applied will.

A particular advantage of the present invention is that the Foils can be manufactured separately and if necessary kept in stock, where - with the same diameter of the cans 1 - cans with different Volume with the prefabricated and due to their training with the foil edge area 5 but sufficiently stable foils 2 can be loaded. This Film edge area 5 can also be easily coated with the adhesive 21, which is difficult to attach to the inner circumference of the can due to the risk of contamination would. On the other hand, the invention is of course not based on the use of an adhesive, as already explained.

The invention is not restricted to the illustrated embodiments. So the output of the device according to the invention can be - e.g. on a rotary table arranged - multiple tools in a conventional manner be increased.

Claims (12)

1. Process for manufacturing a tin can with a paper, plastic or metal foil membrane (2) which is provided on at least one end face and is inserted into the can with raised foil edge region (5) and which closes at least one end face so that the outside of the foil edge region (5) raised in the direction of the can axis (A) is tightly connected, preferably adhesively bonded or heat-sealed, to the inside of the can wall (1), which inside is essentially cylindrical at least in the raised foil edge region (5), characterized in that the foil membrane (2) is pressed by means of a stamp (8) having a spreadable (17) circumference against the inner surface of the can (1), the spreading being effected without being opposed by a force from a pressure-absorbing device, and the tight connection between the raised foil edge region (5) - essentially over its total vertical dimension - and the inner surface of the can (1) then being produced under the action of heat.
2. Process according to Claim 1, characterized in that the spreading of the stamp circumference is effected by a translation of the axial movement of a stamp (3) into a radial movement of pressure elements, in particular of wedge segments (16) and/or spring rings and/or piston rings (17).
3. Process according to Claim 1, characterized in that the spreading of the stamp circumference is effected by a pneumatically operated rubber bellows.
4. Process according to any of the preceding Claims, characterized in that the foil (2) used has, on its radially outer surface, a foil edge region (5) which is raised - preferably diverging conically upwards by 0.2 to 0.3 mm - and which preferably has an adhesive coat (21), in particular comprising a hotmelt adhesive, on its outer surface.
5. Process according to any of the preceding Claims, characterized in that the foil (2) used has, at the free end of the foil edge region (5), a collar (6) which points radially outwards and is approximately hook-shaped in cross-section.
6. Process according to any of the preceding Claims, characterized in that the foil (2) is embossed or grained.
7. Apparatus for carrying out the process according to any of the preceding Claims, having a displaceably mounted stamp (8) with a circumference spreadable transversely to the displacement direction, the displacement means (19) for the stamp and a spreading means (16, 18) for producing the corresponding movements being provided, characterized in that the stamp (8) is displaceably mounted inside a centring means (13) for the foil membrane (2) and the can (1), and a heating means (22) for the circumference of the stamp (8) or for the upper can edge is provided from the outside.
8. Apparatus for carrying out the process according to any of Claims 1 to 6, having a displaceably mounted stamp (8) with a circumference spreadable transversely to the displacement direction, a displacement means (19) for the stamp and a spreading means (16, 18) for producing the corresponding movements being provided, characterized in that a centring means (13) for the foil membrane (2) and the can (1) and a heating means (22) for the circumference of the stamp (8) are provided.
9. Apparatus according to Claim 7 or 8, characterized in that the spreading means (16, 18) comprises a combination of, on the one hand, at least two, preferably three or four, radially expandable piston rings or spring rings (16) with openings offset relative to one another and, on the other hand, at least three, preferably four to eight, in particular six, wedges (18, 20) arranged in the form of a ring.
10. Apparatus according to any of Claims 7 to 9, characterized in that the spreading means consists of a hydraulically or pneumatically operable rubber bellows arranged along the stamp circumference.
11. Semifinished can comprising a sheet metal cylinder which is open at one end face for filling but is closed at the other end face by a foil membrane (2) comprising paper, plastic film or metal foil in such a way that the outside of the foil edge region (5) raised in the direction of the can axis (A) is tightly connected, preferably adhesively bonded or heat-sealed, to the inside of the can wall (1) without overlapping the edge of the can wall, characterized in that the inside of the can wall (1) is cylindrical - at least in the raised foil edge region (5) - and the foil edge region (5) is free of a heat-conducting cover.
12. Can according to Claim 11, characterized in that the edge (7) of the can wall is flanged in an outward direction and/or the foil edge region (5) rests against the inner surface of the can (1) essentially without folds and creases.

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