Tube-fitting machine and a method for tube end seating in such a machine The invention relates to tube-fitting machines and a method for tube end sealing in such machines. More precisely, the invention relates to processing of double tubes. This means a tube of the kind which has an inner tube and, surrounding this with a gap, an outer tube, both connected to a common tube shoulder which has means for delivering product from the inner tube and the outer tube through an emptying opening in a desired way.

STATE OF THE ART Double tubes of said kind and also other types of two-chamber or mufti- chamber tubes are used for inter alia packing different types of products or components which, on mutual contact, react easily with one another chemically or in another way. It is desirable that such reaction occurs only in connection with the contents, in portions or completely, being emptied from the tube. Under such conditions, the components therefore have to be stored separately in the tube.

Applications other than that mentioned also exist. A double tube or other mufti-chamber tube can be used, for example, to deliver l'striped toothpaste".

For rapid and reliable processing of said double tubes, however, an effective tube end-sealing step and thus a commercially competitive tube-fitting machine are lacking at present.

Such a tube-fitting machine is to be capable of being used, with precision and high capacity, for producing defect-free, filled tubes without operational stoppages of the machine as a consequence of, for example, contamination in connection with fitting, poor sealing of filled tubes or other hitches which disrupt functioning.

In order to achieve high output capacity, it is also to be possible when necessary for the processing in the machine to carry out the tube end sealing in a parallel manner with a large number of tubes simultaneously in the sealing station.

THE OBJECT OF THE INVENTION Double tubes of the kind mentioned in the introduction have previously caused major problems, and it has not been possible effectively to seal the ends of such tubes in tube-fitting machines without encountering the disruptions mentioned above.

The object of the invention is therefore to eliminate this disadvantage and to provide effective processes and a tube-fitting machine for the double tubes.

THE INVENTION The object of the invention is achieved by the sealing methods according to the method claim 1 and also by the tube-fitting machines according to the machine claim 3.

Dependent claims linked to the respective main patent claims indicate advantageous developments.

DESCRIPTION OF THE DRAWINGS The accompanying drawings show in a number of basic and detailed illustrations major structural elements forming part of the tube-fitting machine for realization of the abovementioned object, in which drawings : Figure 1 shows a double tube in principle in its state before insertion into the tube-fitting machine according to the invention,

Figure 2 shows the double tube in Figure 1 in its state when it leaves the tube-filling machine, Figure 3 shows a basic diagram of the hot-gas nozzle for thermal activation of the heat-sealable end portions of the inner and outer tubes intended for end seating, Figure 4 is a section along the ! ine A-A in Figure 3, Figure 5 is a section along the line B-B in Figure 3, and Figure 6 is a perspective illustration of the hot-gas nozzle in Figure 3.

PREFERRED EMBODIMENT OF THE INVENTION The double tube 10 in Figure 1 has an inner tube 11 and an outer tube 12.

These two tubes are connected to a tube shoulder 13, in which there are passages (not shown) for separate dispensing and subsequent mixing of the contents of the inner tube 11 and the gap-shaped space between the inner tube and the outer tube. There is a tube cap 14 on the tube shoulder.

In the embodiment shown, the inner tube, the outer tube, the tube shoulder and the tube cap all have a circular cross section, which is to be preferred with the tube end sealing step which will be described below.

In principle, however, other cross-sectional shapes are possible.

The selection of material for the double tube components depends on the intended application. Thermoplastics of the polyolefin type, for example polyethylene, polypropylene etc. with or without barrier layer, are usually used. In order to apply the hot-gas activation technique and heat-seating method which will be described below, however, it is essential that the open

end portions of the double tube in Figure 1 comprise material which is heat- salable.

The double tube 10 is inserted into the tube-fitting machine directly from transport packs filled with a large number of tubes and supplied by a tube manufacturer. The tubes can be greatly deformed and deviate considerably from their nominal (circular) cross section at the open end. The double tube shown in Figure 1 intended for insertion into the tube-fitting machine deviates moderately from the nominal cross section. In view of the fact, however, that the gap between the inner tube and the outer tube has a relatively small width, for example of the order of 5 mm, handling is inevitably a delicate operation, in connection with fitting the gap space as disclosed in one co- pending Swedish patent application No 0104166-4, but also during thermal activation for subsequent seating.

It is an important task, with the narrow gap space and where appropriate different kinds of material in the inner tube and the outer tube, to bring about leakproof and aesthetically attractive end sealing of the double tube. Such end sealing can be seen in Figure 2. The invention provides a special thermal activation process for this important task.

In a station in the tube-fitting machine according to the invention, the open end portion of the double tube 10 is to be thermally activated, then to be heat-seated by clamping jaws, which are preferably cooled, in a subsequent work station.

Figure 3 shows in principle the way in which a hot-gas nozzle, preferably a hot-air nozzle, according to a preferred embodiment of the invention is designed.

The hot-air nozzle 22 comprises an outer annular part 24 provided with outlet openings 23 and intended to be inserted with play into the open end of the

gap-shaped space filled with product, without touching the product. A supply duct 25 conducts hot air to the annular part 24 via a separate passage 26 for this annular part.

From the outlet openings 23, hot air flows against the inner side of the end of the outer tube 12, thermally activates the tube material there and is conducted off via an outflow duct 27.

The hot-air nozzle 22 also has a second part 28, which is essentially circular- cylindrical, provided with outlet openings 29 and dimensioned to be inserted with play into the open end of the inner tube 11 filled with product, but without touching the product. Said second part 28 of the hot-air nozzle is fed with hot air from the same supply duct 25 as the part 24, but has a separate (individual) passage 31 for supply of hot air to the outlet openings 29.

After the hot air has left said openings 29, it is applied to the inner side of the end of the inner tube filled with product in order to activate thermally the heat- salable material of the end portion for the purpose of end-sealing the double tube in a following work station working with clamping jaws.

After this thermal activation, the air from the outlet openings 29 is collected together in the same outflow duct 27 as the air from the outlet openings 23 in the annular part of the hot-air nozzle 22.

Arranged peripherally around the annular part 24 of the hot-air nozzle is a centring sleeve 30 with a gap forming a clearance between the centring sleeve and the annular part 24 dimensioned to receive the open end of the outer tube. The centring sleeve 30 shapes the tube end to and maintains it at nominal cross-sectional dimension and centres the outer tube rotative to the hot-air nozzle and thus the whole double tube 10.

As mentioned previously, the tube materials of the inner tube and the outer tube may be different and thus not have the same thermal activation characteristics. The individual (separate) passages 26 and 31 can be adapted in order by empirical trials to overcome any problem caused by different kinds of material.

The centring sleeve 30 has an all-round recess 34 intended to form a part wall for a cooling duct for cooling the centring sleeve, for example with water, and thus regulating the temperature of the outer side of the outer tube, In combination with the individual passages for supplying hot air, this affords excellent possibilities for setting the correct thermal activation temperature for bringing about aesthetically attractive and acceptable end-sealing of the double tube.

In Figures 4 and 5 there are shown sections through the hot air nozzle along lines A-A and B-B respectively, in Figure 3.

Figure 6 shows a perspective view of the hot-air nozzle made up of two parts which operate with hot air, the peripheral arrangement of outlet openings 23 in the annular part 24 being clearly visible, as are peripherally located outflow ducts 27 and the conical entry end 32 of the circular-cylindrical inner part 28.

It can also be seen from Figure 6 that the annular part 24 is bevelled at its end 33 in order to facilitate introduction into the gap-shaped space between the inner tube and the outer tube.

The invention thus provides a tube-filling machine, and a preferred tube end sealing method for handling double tubes has been described. In the description made with reference to the drawings, the principles underlying the invention are shown on the one hand diagrammatically and on the other hand by specific embodiments of components.

Such components can of course vary in their design within the scope of the accompanying patent claims, and the intention is that the invention is to be limited only by the content of the accompanying patent claims.