GB2275920A - Method and apparatus for deforming container closures - Google Patents

Abstract

A method and apparatus for deforming container closures made of an electrically conductive metal, wherein the effect of the magnetic field generated by an electromagnetic pulse is concentrated on the projecting edge 4a of the closure 3 lying on the edge 2 of a container opening, and is kept away from the region of the closure not to be deformed. The magnetic field is shielded from the region of the closure not to be deformed by a pressure pad or a pressure plate 8 made of a highly electrically conductive metal such as copper, aluminium, silver or the like, overlapping the bottom 4 of the closure. This prevents deformation of the closure foil in the region of the bottom 4 of the closure cap. The pressure pad or pressure plate 8, which is heated by the eddy currents occurring during the pulses, can also be utilized in the same work operation for sealing the closures on the container edge. Part of the pressure pad or pressure plate may be cooled by gas or liquid (figs 3 and 4). <IMAGE>

Description

Method and Apparatus for Deforming Container Closures The invention concerns a method of deforming container closures made of an electrically conductive metal, by the electromagnetic pulse of a current pulse coil which acts on the closure and, furthermore, relates to devices for implementing the method during the closing and/or sealing of such container closures, particularly closures of aluminium or a light metal alloy.

It is known to close containers with metal caps which are mechanically folded or flanged onto and around the container opening. On account of the folds, said known method does not provide a secure closure of a drinks bottle, for example. Consequently, additional sealing or bonding on the edge of the container is carried out in order to seal the closure.

A device for closing vessels with electrically conductive caps by means of current pulse coils is also already known from DE-OS 29 38 168, said current pulse coils each being arranged on a capping head. The capping head consists of a guiding bell, a casing with a pusher, a rod loaded by a spring, a main inductor surrounding the head of the sprung rod and an auxiliary inductor arranged coaxially to said main inductor. This apparatus is used, in particular, for closing drinks bottles with screw caps. The main inductor and the auxiliary inductor are supplied with voltage via control electrodes by the discharging of a working capacitor. As a consequence of this, the cap is compressed in the threaded part of the neck of the bottle or vessel.

Before the, electrode which is electrically allocated to the auxiliary inductor of the capping head, has approached the control electrode for the main inductor, the working capacitor is discharged once more.

When the capacitor discharges, whilst delivering its voltage to the auxiliary inductor, the lower cap ring is compressed and adapted to fit the collar of the neck of the bottle or vessel.

On account of the rod, which is displaceably mounted against the pressure of a spring, above the main inductor and the auxiliary inductor, on the casing of the capping head, the head of said rod lying on the container closure during the closing operation, such an apparatus is only suitable for closing containers or bottles with comparatively thick-walled closure caps such as, in particular, screw caps for drinks bottles with a securing ring, and not for closing and/or sealing particularly thin-walled containers such as yoghurt pots, milk drink bottles, cream pots or the like, with a thin aluminium foil which overlaps the edge of the container opening with a comparatively narrow edge region in comparison to the width or the diameter of the container opening. With such container closures, there is, to a large extent, a risk that the closure foil is completely deformed in the region of the comparatively wide container opening by the magnetic field generated by the electromagnetic pulse of the current pulse coil and, as a consequence thereof, can also no longer be moulded with the edge of the closure around the edge of the container opening.

This is similar to another method, revealed in DE-OS 15 32 501, of closing containers, for example bottles, with a closure similar to a crown cap, in which the closure blank is punched from a metal strip with a surge current discharge directed via a coil and, at the same time, is pressed on over the toric edge or a similar moulded part of the container in a single work operation. With the closing machine provided for implementing this method, the surge current coil serving to deform the container closures is arranged at a distance above a punching die such that a metal strip is guidable between the coil and the punching die, the container closures being punched from said metal strip by the effect of the electromagnetic pulse from the surge current coil and being pressed onto the toric edge of the container. The closing machine working according to this known method is also unsuitable for closing yoghurt pots, milk drink bottles and the like, with a comparatively large container opening, by means of a thin aluminium foil or the like, on account of the very severe effect, which is directed downward, of the magnetic field generated by the surge current coil.

With this known closing machine, it is also provided that the metal strip is coated on one side with a sealant, which can optionally also be applied in the form of a strip of foil between the metal strip and the die, although sealing of the container closures is not provided.

GB-PS 1 165 116 and the associated DE-OS 17 52 470 also reveal an apparatus for electromagnetically deforming workpieces in the form of closures on containers such as, in particular, bottles. Magnetic field forming elements are used to deform the closures, said magnetic field forming elements consisting of a plurality of abutting field forming plates, which have a plurality of openings with current pulse coils for generating magnetic field by which the closures are moulded onto the container openings.

US-PS 3 808 074 also reveals a method of heatsealing container closures made of a metal diaphragm with a layer of adhesive by high frequency sealing, wherein, however, the diaphragms are only sealed with the edge of the container, and are not deformed.

The invention present aims to create a method and suitable devices for implementing the method with which it is possible in a technically accurate manner on the one hand perfectly to close and/or optionally to seal containers such as, in particular, milk bottles and other suitable containers,without deformation in the region of the container opening, with container closures made of an electrically conductive metal, even if they consist, in particular, of a thin aluminium foil.

According to the invention there is provided a method for deforming container closures made of an electrically conductive metal by the electromagnetic pulse of a current pulse coil which acts on the closure, wherein the effect of the magnetic field generated by the electromagnetic pulse is concentrated onto the projecting edge of the closure which is to be deformed and which is lying on the edge of a container opening, and is kept away from the region of the closure not to be deformed.

Particularly when using thin aluminium foils or foils made of a light metal alloy, there is a risk that the central part of the closure will be bowed upwards, damaged or torn by the electromagnetic pulse.

According to a particularly advantageous development of the method according to the invention, this risk can also be overcome by shielding the magnetic field generated by the electromagnetic pulse from the region of the closure which is not to be deformed by means of a pressure pad or a pressure plate, overlapping the bottom of the closure, made of a highly electrically conductive material such as copper, aluminium, silver or the like.

The effect of such a pressure pad or pressure plate, which ideally consists of copper, is essentially that the magnetic field of the current pulse is displaced from the middle, towards the edge of the closure by the pressure pad or pressure plate so that, on the one hand, the magnetic field deforming the projecting edge of the closure is intensified and, on the other hand, the field acting on the middle of the closure is weakened. In this way, deformation of the closure foil is prevented in the region of the bottom of the closure cap.

In a further embodiment of the invention, the pressure pad or the pressure plate, which is heated by the eddy currents occurring during the pulses, is utilized in the same work operation for sealing the closures on the edge of the container. In this case, the inside of the closure is provided with an adhesive or a foil which bonds and hardens during heating.

Furthermore, the heated pressure plate or pressure pad can be additionally heated and/or cooled for precise temperature regulation.

The apparatus for implementing the method according to the invention comprises a holder for the current pulse coil, a pressure plate or a pressure pad for the bottom of the closure and a pulse generator, the pressure plate or the pressure pad being firmly connected to the current pulse coil such that at least half of the coil height of the current pulse coil projects downwards from the pressure plate or pressure pad seated on the bottom of the closure, in the direction of the coil axis, over the lower edge of the pressure plate or pressure pad and completely surrounds the edge region to be deformed of the closure on the neck of a container, over its entire circumference and at a close radial or lateral distance.

Particularly advantageous developments of such apparatus are set out in claims 8 to 11.

Preferred embodiments of the invention are represented in diagrammatic form in the drawings, in which: Figure 1 shows a section through a drinks bottle or a similar container with a coil holder and a pressure plate placed on the neck of the bottle or container; Figure 2 shows an enlarged partial representation, compared with Figure 1, of a modified embodiment of such a closing apparatus; Figure 3 shows a further modified embodiment of the closing apparatus with a pressure plate or pressure pad, additionally heated or cooled by a liquid or a gas, for simultaneous sealing during the deformation of the closure; and Figure 4 shows an embodiment corresponding to Figure 3 with regulation of the temperature of the pressure plate or pressure pad, with simultaneous sealing, by means of air cooling.

Figure 1 shows a container or a drinks bottle 1 with a container edge or container neck 2 and a closure 3 in the form of an aluminium closure cap, which has already been permanently deformed on the container edge 2 by an electromagnetic pulse. The closure or the closure cap 3 is provided with an annular, all-over adhesive foil or layer 4b, shown in Figure 3 and 4, on the underside of the bottom 4 of the closure.

A current pulse coil 6, together with a pressure plate or a pressure pad 8 for the bottom 4 of the closure, are located on a coil holder 5.

The current pulse coil 6 is excited by a pulse generator, which is not shown, and the pressure plate or pressure pad 8 is firmly connected to the current pulse coil 6 such that at least half of the coil height of the current pulse coil 6 projects downwards from the pressure plate or pressure pad 8, seated on the bottom 4 of the closure 3, in the direction of the coil axis 6a, over the lower edge of the pressure plate or pressure pad 8, and completely surrounds the projecting edge 4a to be deformed of the closure 3 over its entire circumference and at a close radial or lateral distance.

The pressure plate or the pressure pad 8 consists of a highly electrically conductive material such as copper, aluminium, silver or the like, in order to shape the magnetic field by the formation of eddy currents (skin effect).

As shown in Figure 1, the lines of flux 9 of the magnetic field are kept away from the bottom 4 of the closure 3 by the pressure plate or pressure pad 8, which is arranged fixed to the coil holder 5 above the magnetic pulse coil 6, and is concentrated onto the edge 4a of the closure 3 lying on the container opening or the container neck 2.

Tests have shown that particularly favourable results are obtained with such a closing apparatus if the underside of the pressure plate or the pressure pad 8 coincides, at the coil holder 5, with the centre plane 6b of the current pulse coil 6. This is shown in figure 2. Here, the lines of flux 9 of the magnetic field are kept completely away from the bottom 4 of the closure 3 by the pressure plate 8 consisting of a highly electrically conductive metal and are concentrated at the projecting edge region to be deformed of the closure 3, beneath the pressure plate or the pressure pad 8, so that the projecting edge 4a of the closure 3 lies tightly around the container or bottle neck.

Figures 3 and 4 show the cooling or heating of the pressure plate or pressure pad 8 with the circulation 10 of a liquid or a gas. In the embodiment in Figure 3, the pressure plate or pressure pad 8 has an attachment 11 on the back for the circulation of a preferentially liquid coolant, whilst in the embodiment in Figure 4, the pressure plate or pressure pad 8 has cooling ribs 13 pointing outwards from a body 12, a gaseous coolant 14 such as cooling air flowing around said cooling ribs 13. The body 12, together with the cooling ribs 13, is connected in a single piece with the pressure plate or pressure pad 8. In both cases, the temperature of the pressure plate or pressure pad is regulated according to the desired bonding or sealing temperature, for example in a suitable temperature range between 50 and 100 OC, In addition to the temperature regulation, the underside of the pressure plate or pressure pad 8 can also contain recesses in the form of characters, not shown in the drawing, which are mapped onto the bottom 4 of the closure 3 during deformation. Thus, certain markings and use-by dates can be applied to the closures 3 when the container 1 is closed.

The containers 1 to be closed can also be capsules for sheathing or sealing solid bodies, in order, for example, to protect them against corrosion or to prevent the egress of undesirable materials.

Claims (14)

CLAIMS:

1. A method for deforming container closures made of an electrically conductive metal by the electromagnetic pulse of a current pulse coil which acts on the closure, wherein in that the effect of the magnetic field generated by the electromagnetic pulse is concentrated onto the projecting edge of the closure which is to be deformed and which is lying on the edge of a container opening, and is kept away from the region of the closure not to be deformed.

2. A method according to claim 1, wherein the magnetic field generated by the electromagnetic pulse is shielded from the region of the closure not to be deformed by a pressure pad or pressure plate made of a highly electrically conductive material overlapping the bottom of the closure.

3. A method according to claim 2, wherein, during deformation of the closure, the pressure plate or the pressure pad is simultaneously heated to a temperature sufficient for sealing the closure on the edge of the container opening.

4. A method according to claim 3, wherein the heated pressure plate or pressure pad is additionally heated and/or cooled for precise temperature regulation.

5. Apparatus for implementing the method according to any of claims 1 to 4 comprises a holder for the current pulse coil, a pressure plate or pressure pad for the bottom of the closure and a pulse generator, the pressure plate or pressure pad being firmly connected to the current pulse coil such that at least half of the coil height of the current pulse coil projects downwards from the pressure plate or pressure pad, seated on the bottom of the closure, in the direction of the coil axis, over the lower edge of the pressure plate or pressure pad, and completely surrounds the projecting edge region of the closure which is to be deformed on a container neck, over its entire circumference and at a close radial or lateral distance.

6. Apparatus according to claim 5, wherein the pressure plate or the pressure pad consists of a highly electrically conductive material.

7. Apparatus according to claim 6, wherein the pressure plate or the pressure pad consists of copper, aluminium or silver.

8. Apparatus according to any of claims 5 to 7, wherein the underside of the pressure plate or the pressure pad coincides with the centre plane of the current pulse coil.

9. Apparatus according to any of claims 5 to 8, wherein the pressure plate or the pressure pad has an attachment on the back for the supply of a gaseous or liquid coolant.

10. Apparatus according to any of claims 5 to 8, wherein the pressure plate or the pressure pad has cooling ribs pointing outwards, around which flows a gaseous coolant such as cooling air.

11. Apparatus according to any of claims 5 to 10, wherein recesses in the form of characters are contained on the underside of the pressure plate or pressure pad, said recesses in the form of characters being mapped onto the bottom of the closure during deformation.

12. Apparatus according to any of claims 5 to 11, wherein the container closures are made of aluminium or a light metal alloy.

13. A method of deforming container closures substantially as hereinbefore described with reference to the accompanying drawings.

14. Apparatus for deforming container closures substantially as hereinbefore described with reference to the accompanying drawings.