KR19980703504A - Processes, apparatus and thin films for the production of cans and cans with thin film sealing membranes - 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

Processes, apparatus and thin films for the production of cans and cans with thin film sealing membranes

The metal cans were sealed by attaching flanges and cut can edges with sheet metal lids according to WO 83/02577 or US-A-3,952,677 or by having sheet metal rings with thin films according to AT-A-368.919. The inner surface of the can wall 1 is conical in accordance with DE-A-94 14 440 and at a more complex edge 5, the more complex can such that the diaphragm disc is set to the same position with respect to the can edge when punch is applied. Production and high tolerance are required.

On the other hand, discs with raised edges that cannot cover the cut edges of the can have been used in plastic cans (eg DE-A1-33 05 144 or CH-A-629 984), which have relatively soft walls and pressure A lid portion that is relatively stable against the bottom of the can that can withstand the load (eg US-A-4,599,123) but requires an external pressure absorbing device for the sealing process.

The invention relates to a can having the features described in claim 1, a process according to the features described in claim 4, and a thin film and apparatus for the production of cans.

1 shows a process sequence according to the invention.

Fig. 2-3 is an enlarged precision of II and III in Figs. 1A and 1B.

4 is a cross-sectional view of the device according to the invention.

5a and b are horizontal views of the device according to the invention in two different operating positions.

Explanation of symbols on the main parts of the drawings

1: can 2: diaphragm thin film

5: thin film edge area 6: color

8: punch 13: centering device

16, 80, 20: wedge 19: rod

22: heating device 23, 24: lid

It is an object of the present invention to provide a can consisting of a tin plate or an aluminum plate and having a simple and inexpensive sealing bag. This is achieved by the features described in claim 1. The seal consists of only one diaphragm thin film, or plastic and paper (laminated by a thin thin aluminum film). However, thin metal films, in particular aluminum, are preferred, and can opening can be accomplished by the handle of the can. The axially raised diaphragm disc edge of the can does not cover the flanged can edge, so it can be easily opened and separated from the can edge with a rigid outer surface.

The diaphragm thin film is preferably opened with a thickness of 0.2 mm or less, in particular 0.1 mm or less, and consists of a 50 μm aluminum thin film having a heat-sealed coating of 20 μm on the inner side and a 10-20 μm non-friction coated on the outside. It is suitable for resealing it. Depending on the contents or the lid used, the can bottom can be formed according to the invention if necessary. In addition, thin films are preferred to use embossed thin films because they can more easily fit into cans with variable resistance and provide greater stability.

Generally, the diaphragm thin film is heat-sealed in the area for connection to the inner surface of the can. In principle, however, in the case of the inner surface of a composite can (eg lamination with a thin aluminum film), the inner surface of the can is heat-sealed coated; Otherwise special adhesives or heat-sealing coatings are required to ensure tight bonding. Thus the coated can can be closed with a rigid seal.

The production process of the can according to the invention follows the features of claim 3. The improved process according to the invention is described in the characterizing part of claims 4 and 5.

According to the prior art, pressure has to be exerted on the outside against a fixed, stable punch applied to the interior of a relatively soft cardboard by joining annular portions together or joining two conical surfaces together. This is no longer necessary according to the process of the invention. The diameter error of the can is too large to accurately maintain the external pressure direction against the internal pressure, and since the can inner edge and the punch have to be kept conical, a rather uncomfortable method of applying pressure inside the conventional flexible can is not available. In the case of the can according to the invention, no external support is required; A loose center of gravity is enough.

The device according to claim 6 is suitable for carrying out the process according to the invention when at least one of the features described in claim 7 is realized.

Of course, the diaphragm thin film used to seal the can according to the invention is conveniently conveniently pre-created with the material according to claim 9 and then applied to the can opening by the process according to the invention. They have the feature according to claim 10 that can be easily fitted into cans with different tolerances and are simply placed in the desired position due to the conical thin film edge part 5. This fixing action can be further improved by the features of claim 11.

The wide collar parallel to the diaphragm disc described in US-A-4,599,123 is very disadvantageous. Because when introduced into the can without covering the can's cut edges, it forms a pleat, which makes it harder or harder to bond between the inner surface of the can and the thin film.

There are many means of realization according to the prior art for final mounting. However, the thin films used according to the invention are relatively thin and have good thermal conductivity, and high temperature bonding processes can be used, for example heat-sealing coatings on the outer surface.

The details of the invention are apparent from the description of the embodiments shown in the accompanying drawings.

In FIG. 1A, a can 1 made of sheet metal is sealed with a diaphragm thin film 2. This thin film 2 can be connected to the handle 3 by bonding with an adhesive. Unlike conventional handles, the handle 3 can be used to remove the entire diaphragm membrane 2 that fits into the can 1 and engages the can at the edge. This is more convenient because in the prior art, it is necessary to have a predetermined break point that punches, or a portion of the diaphragm thin film covering the cut edge of the can from a diaphragm thin film that extends throughout the can opening. This presents difficulties for thin films of 0.2 mm or less, especially for thin films of 0.1 mm.

Of course, thin films that serve to maintain freshness and fragrance or to prevent contamination are relatively difficult to handle. According to the invention, it has a thin film edge 5 along the circumference of the lid 4, which gives the diaphragm disc part which is raised as a whole and which extends a certain intensity over the can opening. The diaphragm membrane 2 covering the bottom of the can preferably comprises at least one annular bead to impart relatively small, radial elasticity and strength during deep drawing and sealing. The thin film 2 reinforced in this way can be picked up to be connected by the suction gripper so that the thin film shape does not change upon insertion into the can opening. The thin film may be assembled on the top of the can 1 in the first step. Here, one encounters the difficulties associated with the thin film: in fact it is necessary to keep the thin film on top of the can 1 to ensure that it can be firmly bonded to the inner surface of the can in the next step. In principle, an adhesive is applied to the upper edge of the can 1 so that the film can remain attached to the desired position. However, it is advantageous to carry out the method more clearly shown in FIG. 2 according to the invention.

Referring to the accompanying drawings, the raised edge branches conically. That is, it is inclined at an angle β with the vertical part V, which is very small but measurable and has an angle of less than 5 °, in particular less than 2 °. The diameter of the lower surface of the diaphragm disk, ie in the region of the cover surface 4, should be 0.2 to 0.3 mm smaller than the diameter of the opening of the diaphragm disk, and the height measured along the vertical portion V should be about 5 mm.

The larger diameter of the upper part of the membrane 2 can be conveniently selected, so that it is held at the top of the can 1 by the suction gripper via frictional force when assembled. The method of fixing the thin film 2 to the top of the can 1 is made by a collar 6 which interacts with the upper edge of the can 1 and has a hooked cross section. In order not to damage the thin film and injure the user, it is preferable to flange the top, pointed corners of the can 1 towards the outside (7 in FIG. 1A).

It fits tightly into the collar 6 at the edge of the can of thin film 2. However, this should not interrupt the next steps with only an intermediate step in the sealing of the can 1. This involves the operation of the punch 8, schematically shown in FIG. 1B and pressing the thin film 2 to the position shown in FIG. 1B. The collar 6 slides to the position indicated by the dotted line in FIG. 3, where it is in the state before being pressed into the can by the punch 8, and because of the ductility of the thin film material having sufficient simultaneous toughness, the inner periphery of the can 1. In a solid line at the position shown in FIG. 3. The conical shape of the film edge region 5 with angle β shown in FIG. 2 is in the form of a cylinder, so that the film edge region 5 is in firm contact with the can circumference. Because of the cone shape, the wrinkles mentioned in US-A-4,599,123 are not formed.

As explained below, the process according to the invention and the device according to the invention tightly couple between the diaphragm membrane 2 and the cylindrical region of the inner surface of the can under the can edge.

In a preferred embodiment, the punch 8 is formed according to the section shown in FIG. It consists of several parts, i.e. comprises the actual punch surface 9, which is connected to the lug 11 of the pinch head 12 by a raised-projection pin 10. The central ring 13 is arranged around the punch surface 9 and can move along the guide pin 14 against the action of the at least one pressure spring 15. Usually, the ring 13 is arranged at the bottom in the left part of FIG. 4, which is held at the top of the punch 9 but may be supported by another device.

In this position, the central ring 13 supports the can edge and has a small recess 16 'for this purpose. This process occurs such that the can 1 is placed on the lifting table and raised so that the central ring 13 moves to the upper side shown on the right with respect to the operation of the spring 15. At the same time, the punch surface 9 is formed inside the ring 13 to press the thin film disc 2 to the position shown in FIGS. 1B and 3.

Alternatively, the can is held in the center and the ring 13 is fixed while the punch surface 9 moves downward. In this case, lug 11 should be in the form of a piston rod of the fluid assembly or in the form of a hydraulic piston / cylinder assembly. Since the relative motion of the can and the part shown in the figure is important, the width is determined in consideration of the shape. In addition, the center arrangement of the can or the center arrangement of the thin film 2 relative to the can can be made in various ways.

In the above description, it can be clearly seen that it is important to arrange the raised thin film edge portion 5 of the diaphragm thin film 2 as close as possible to the inner circumference of the can in order to firmly connect the edge portion to the inner circumference. For this purpose, the punch 8 has a diffusion device, which is formed as a wedge device in the embodiment shown in FIG. The row of wedge portions 16 is guided along the top of the punch surface 9 so that it can be disposed radially outward with respect to the central axis A of the punch 8. For guiding, the rear of the punch surface 9 may have grooves or slots. However, even a flat rear portion of the punch surface can sufficiently guide.

Although the wedge portion 16 is used to press the raised thin film edge of the thin film 2 against the inner circumference of the can 1, it is advantageous if the elastic piston ring 17 or cigar circlip ring extends around the wedge. The ring 17 is pressed against the membrane edge portion 5 of the membrane 2 and generates a restoring force applied to the wedge portion 16 to provide a more uniform circumferential portion when performing the dual function.

A conical wedge 18 is used to radially press the wedge portion 16 outwards, which can be moved between and below the wedge portion having the wedge surface 20 by a hydraulic actuation rod 19. have. The reason for favoring hydraulic drives is that it is easy to set the maximum pressure that little risk of contamination by oil or leaking liquid and does not act on the can. When the conical wedge 18 moves downward with respect to the punch surface 9, it stretches the wedge portion 16 and presses the elastic ring 17 outward against the thin film edge, the area 5, where the can edge Is tightly fitted in the recess 16 '. The positioning of the thin film 2 according to FIG. 1B is also made in this way.

In this position, the thin film 2 must be fixed and sealed. This can be done by bonding, heat-sealing with an adhesive. This is because the thin film 2 can transfer heat relatively easily. For this purpose, the outside of the film edge is provided with a heat-sealing coating 21 (FIG. 2). The thermal device is then co-ordinated and mounted with the diffusion device 16-18. The thermal arrangement can be formed by heating the coil contained within the wedge portion 16, but the space is very limited and there is a need to provide a movable connection. Although this possibility should be ruled out, over the wedge portion 16 and the ring 17, a radiant heat source 22 can be provided, which heats the heat-sealing sheath 21 (FIG. 2). Heat to fuse with the inner surface of can 1. The wedge portion 16 is formed of a ceramic material having good heat storage properties, which improves durability.

FIG. 5A shows the wedge portion 16 and the spring ring 17 in the closed state and FIG. 5B shows a punch moving at right angles to the plane of the drawing, although not shown in the accompanying drawings to heat seal the membrane 2 to the inner surface of the can. The wedge portion 16 and the spring ring 17 are shown in a position diffused by the wedge piece 18 of (8).

The wedge shown in the figures is a preferred embodiment for the life of the device, and many modifications can be made within the scope of the invention. For example, the conical wedge 18 may be formed by a pressure plate that is movable relative to the punch surface 9, which may have a rubber bellows between the pressure plate and the top of the punch surface 9. The bellows may be used in place of the wedge 18 and then extend transversely from the top to the displacement portion 16 or loop when provided with a pressurized medium through a pressure plate connected to the rod 19 to actuate the wedge. Directly press (17). A radially outwardly extending horizontal drive is available for each part 16, but is complex. The heating of the top can edge extended outwards for heat sealing will be simpler.

Alternative methods may be advantageous if the can 1 is sealed in the position shown in FIG. 1B. For example, lids 23 and 24 (FIG. 1C) may be mounted to protect the weak thin film 2.

Another advantage of the present invention is that the thin films can be produced separately and stacked if necessary-wherein the cans 1 are formed of the same diameter-the cans of different volumes are pre-produced and the thin film edge regions 5 can be produced. The branch has a sufficiently stable thin film 2 because of its shape. The thin film edge region 5 can be easily coated with an adhesive 21, which is difficult to apply to the inner circumference of the can due to the risk of being soiled. The present invention does not limit the use of adhesives as already described.

The invention is not limited to the described embodiments. The production of the device according to the invention with multiple tools can therefore be increased in a known manner.

Claims (11)

The outer surface of the film edge region 5 raised in the direction of the can axis A, without covering the edge of the can wall, is at least one end so as to be firmly connected to the inner surface of the wall of the can 1 by adhesive bonding or thermal bonding. In a sheet metal can comprising a sealing diaphragm 2 of paper, plastic film or metal foil provided on the side surface and sealing one or more end faces, the inner surface of the wall of the can 1 is cylindrical in the raised membrane edge region 5. Can characterized by taking. 2. The can according to claim 1, characterized in that the edge (7) of the can wall is flanged outward and the thin film edge region (5) is arranged on the inner surface of the can (1) without pleating. The diaphragm membrane (2) according to claim 1 or 2, wherein the diaphragm membrane (2) with raised membrane edge regions (5) is sandwiched by a can, the membrane edge regions being driven by a punch (8) having an inflatable circumference (17). The thin film edge region 5, which is pressed against the inner surface of the can 1 and then raised, is connected to the inner surface of the can 1 under the action of heat—over its entire vertical distance—the aforementioned expansion absorbs external pressure. A can, which can be made without a device. 4. Process according to claim 3, characterized in that the expansion of the punch circumference is by a combination of wedges (16, 18, 20) and piston rings or spring rings (17). The process according to claim 3, wherein the expansion of the punch circumference is made by rubber bellows actuated hydraulically. 6. A device as claimed in claim 4 or 5, in which a movable mounting punch (8) having a circumference capable of expanding transverse to the displacement direction, a displacement device (19) for said punch, and an expansion device for generating a corresponding movement (16-18), a) centering device 13 for diaphragm thin film 2 and / or can 1; b) Process execution apparatus characterized by including the heating device 22 for the circumference of the punch (8). The expansion device 16-18 comprises a combination of radially expandable piston rings or spring rings 16 with at least two, preferably three or four staggered openings, At least three, preferably four to eight, in particular six wedges (18, 20) arranged annularly. 7. The device according to claim 6, wherein the expansion device consists of an elastic ring (17) arranged along the punch circumference and preferably comprises at least one hydraulic unit, such as a rubber bellows. The thin film for cans according to claim 1 or 2, wherein the diaphragm thin film (2) is an embossed metal thin film having a thickness of 0.2 mm or less, in particular 0.1 mm or less. 3. The diaphragm thin film (2) according to claim 1 or 2, having a thin film edge portion (5) raised at its radially outer portion, which branched conically upwards from 0.2 to 0.3 mm and coated with adhesive on the outer surface. 21), in particular a thin film for cans, characterized in that a heat-adhesive is applied. The thin film according to claim 10, wherein the diaphragm thin film comprises a collar (6) at the free end of the thin film edge region (5) which is radially outward and almost cross-sectional in shape.