EP2631200B1 - Device for thermosealing waste - Google Patents

Description

The invention relates to a device for welding waste according to the preamble of claim 1.

Devices for welding waste are mainly used in laboratories and medical facilities for safe and low-contamination disposal of toxic or infectious waste and hazardous waste, the waste to be disposed of by means of the device aerosol and liquid-tight sealed in foil bags.

From the DE 2 364 180 A device for packaging waste by welding in foil bag is already known, which comprises a housing having a receiving space for a folded film tube and extending through the receiving space funnel. At the lower end of the funnel, a welding unit with two movable heatable welding jaws is arranged, between which an inwardly folded, guided from top to bottom through the hopper hose section of the film tube can be clamped and welded along a transversely extending over the hose section away weld. For transporting the film tube or hose section, a conveyor unit with two pairs of conveyor rollers is arranged below the welding unit, between which the tube section extends. The conveyor rollers of each pair of rollers are pressed from opposite sides against an edge strip of the tube portion and driven to transport the tube portion in the opposite direction of rotation. The emerging from the conveyor unit film tube consists of a series of contiguous bags, between each of which a weld is arranged.

Next is from the DE 695 17 207 T2 already known a device for welding waste with a combined welding and separating unit, which is able to heat the plastic of the film tube during welding along a cutting seam to flow to separate each foil bag when welding its upper end of the hose section simultaneously. In this device, both the heating temperature for welding the tubular film and the duration of the mutual pressing of the two heatable welding jaws preset, the latter by a predetermined delay. As a result, either only individual separate bags or a single long bag can be produced, which is closed only at its two opposite ends, but not several contiguous bags, each containing separately welded waste. In addition, the lower end of the hose portion located below the welding and separating unit with the last filled or welded bag is only safely separated, if the weight of this lower end or the therein welded waste is greater than the resistance force, along the Trennnaht contrary to flow heated tubular film a separation opposes. If the shrink-wrapped waste has only a very low weight, such as used syringes that are contaminated with toxic or infectious material, a safe separation is not always guaranteed. Moreover, since the tubular film is heated to flow along the dividing seams, it can not be ruled out that bags with welded waste at their ends along one or both dividing seams will leak leaking toxic or infectious material. Last but not least is considered in the known device as disadvantageous that the conveyor rollers of the conveyor unit over the entire width of the Foil tube extend. This can lead to the welding of pulpy or pasty waste to the fact that the waste are distributed by the contact pressure of the two conveyor rollers on the inside of the film tube over a larger area and hinder the subsequent welding of the film tube.

The DE 696 06 219 T2 discloses an apparatus for packaging products in mesh bags having a shaft through which an inwardly turned portion of a mesh tube extends, and two roller pairs of a conveyor disposed outside the shaft. The pairs of rollers may be driven in a reversible direction to lift the outer portion of the mesh tube and thus bring it into the tube and lower its free end in the tube or to lift the mesh tube within the tube until its free lower closed end determines a particular one Height in the tube reached before a bag with open top created and the product is filled into the bag. By lifting the mesh tube in the tube to avoid that the product filled in the bag falls from high altitude down to the bottom of the bag.

Next discloses the FR 2 841 229 A already a device according to the preamble of claim 1, wherein the conveyor unit comprises as drive an electric motor and thus a motor whose direction of rotation is reversible by reversing, which would inherently lead to a reversal of the transport direction of the conveyor unit. In addition, the known device comprises a controller with which the various functions of the device can be controlled.

Proceeding from this, the invention has the object, a device of the type mentioned above to improve the fact that the waste to be welded can optionally be sealed in individual separate bags or in several connected bags and that in the former case a secure separation of the bags is ensured even if the weight of the welded-in waste is very small.

This object is achieved by the features of claim 1.

When wastes are to be sealed in individual separate bags during a separation welding cycle, the conveying unit can be started or put into operation when separating a filled and sealed bag with the reverse transport direction by the feature according to the invention to the above the filled bag between the conveyor unit and the welding and separating unit located part of the hose section to exert an upward pulling force and thereby pull this part of the hose section upwards. This ensures that this part of the hose section along a seam referred to below as a separating seam is reliably separated from the last filled and welded bag and thus from the lower end of the hose section below the welding and separating unit as soon as the upward pulling force is greater than the resistance, which opposes the heated separating seam located between the welding jaws of a separation. The last filled and welded bag then falls either immediately or at the latest when moving apart of the two welding jaws down in a arranged below the welding and separating unit collecting container.

On the other hand, if the wastes are to be sealed in a plurality of contiguous bags during a welding cycle, the conveying unit is not started or put into operation in the reverse transporting direction, so that no upward pulling force is exerted on the welded seam being formed and the bags along the Weld seam can not be separated.

Since the resistance force which the heated separating seam opposes to a separation during the separation welding cycle depends on how strongly the tube section heats up between the welding jaws, a preferred embodiment of the invention provides for a separation welding cycle for separating the lower end of the tube section from the welding section. and separation unit along the cutting seam in the tube portion supplied amount of heat is greater than the amount of heat that is supplied during a welding cycle of the welding and separating unit in the tube section to only weld this, but not separate. In this way, on the one hand, the separation of the lower end of the tube section can be facilitated without, on the other hand, jeopardizing a hermetic welding of the waste by excessive heating of the seam.

The greater amount of heat supplied as the lower end of the tube section is cut into the tube section along the dividing line results in the thermoplastic material of the tube being heated to a flow temperature along the dividing line, while the reduced amount of heat supplied to the tube section during welding along a weld the thermoplastic material of the film tube along the weld is heated only to a lower temperature, which in the sufficient pressure exerted by the welding jaws to hermetically weld the hose section.

Due to the possibility of reversing the transport direction of the conveyor unit when necessary and to change the amount of heat supplied by the welding and separating unit into the seam, a waste batch to be welded can be placed both in one individually segregated bag or in one of several contiguous bags.

The reversal of the transport direction of the conveyor unit during the separating welding cycle is preferably triggered as a function of a state of the separating seam, expediently when the separating seam has been heated by the welding and separating unit until it has flowed. The devices provided for this purpose advantageously comprise a time control which triggers the reversal of the transport direction of the delivery unit as a function of the time elapsed since the beginning of the heat supply to the separating seam.

A further advantageous embodiment of the invention provides that the conveyor unit comprises at least one pair of conveyor rollers, which are driven in opposite directions of rotation, and that for separating the lower end of the tube section, the direction of rotation of both conveyor rollers is reversible. Suitably, the conveyor unit has two pairs of narrow conveyor rollers, which are arranged on opposite sides of the shaft and extend only over part of the width of the hose section in the shaft, wherein the direction of rotation of the conveyor rollers of both roller pairs is reversible. Compared to the one from the DE 695 17 207 T2 known device can be increased by the two narrow pairs of rollers, the receiving volume of the tube section above the welding and separation unit.

The welding and separating unit preferably comprises two heatable welding jaws which, for welding the hose section, approach the hose section by means of a welding jaw drive from opposite sides and can be pressed against the latter.

In order to avoid sticking of the welding jaws on the hose portion and to ensure uniform welding, the two welding jaws each have a connectable to a power source heating wire, which is arranged between a Teflon tape on its side facing the hose section and a rubber band on its side facing away from the hose section is.

A still further advantageous embodiment of the invention provides that at least one of the two welding jaws is resiliently mounted counter to the direction of movement when approaching the hose section and provided with a contact for reversing the direction of the welding jaw drive when the spring outside of a central welding position of the welding jaw by a Resistance in the same movement path is compressed and triggers the contact. The contact is preferably a reed contact, which is triggered by the approach of a permanent magnet during compression of the spring. In this way, a squeezing of a hand or a finger of a user can be prevented, provided that unexpectedly the hand or finger should be introduced from above or from below between the approaching welding jaws. A possible combustion on one of the heating wires is prevented by the fact that the power supply to the heating wires is switched on only when the welding jaws have reached a central welding position.

The device according to the invention has a control which serves to activate the conveyor unit and the welding and separating unit when the device is put into operation. Among other things, this control advantageously comprises a device which monitors the power supply to the electric welding jaw drive during a movement apart of the welding jaws and the power supply to the drive motor interrupts and preferably reverses briefly when a predetermined current threshold is exceeded. As a result, a squeezing of a hand or a finger of a user can be prevented, as long as the hand or finger unexpectedly from above or below between one of the diverging welding jaws and an opposite rigid part of the welding and separating unit should introduce.

The control also serves to control the welding of the tube section in the welding cycle and the separation of the lower end of the tube section in the separation welding cycle, in which case the tube section is first welded along a weld, then the lower end of the tube section is separated along a separating seam arranged above the weld and finally the remaining tube section is welded along a weld arranged above the dividing seam.

In order to make it possible to freely choose the length of a bag, for example, depending on the size of the waste to be welded, a further preferred embodiment of the invention provides that in the welding cycle and in the separation welding cycle, first a transport of the film tube takes place, wherein the length of the transport path is freely selectable.

• Fig. 1 eine perspektivische Ansicht einer erfindungsgemäßen Vorrichtung zum Einschweißen von Abfällen in einen Folienschlauch;
• Fig. 2 eine Oberseitenansicht eines Gehäuses der Vorrichtung;
• Fig. 3 eine Oberseitenansicht des Gehäuses nach dem Abnehmen eines Gehäusedeckels;
• Fig. 4 eine perspektivische Ansicht des Gehäuses;
• Fig. 5 eine perspektivische Ansicht des Gehäuses nach dem Abnehmen eines Gehäusedeckels;
• Fig. 6 eine schematische Schnittansicht des Gehäuses zur Erläuterung der Funktionsweise der Vorrichtung;
• Fig. 7 eine auseinander gezogene perspektivische Ansicht einer Fördereinheit, einer Schweiß- und Trenneinheit und eines Gehäuseunterteils des Gehäuses;
• Fig. 8 eine perspektivische Ansicht der Fördereinheit;
• Fig. 9 eine perspektivische Ansicht der Schweiß- und Trenneinheit.

In the following the invention will be explained in more detail with reference to an embodiment shown in the drawing. Show it:

• Fig. 1 a perspective view of a device according to the invention for welding waste into a film tube;
• Fig. 2 a top view of a housing of the device;
• Fig. 3 a top view of the housing after removing a housing cover;
• Fig. 4 a perspective view of the housing;
• Fig. 5 a perspective view of the housing after removing a housing cover;
• Fig. 6 a schematic sectional view of the housing for explaining the operation of the device;
• Fig. 7 an exploded perspective view of a conveyor unit, a welding and separating unit and a housing lower part of the housing;
• Fig. 8 a perspective view of the conveyor unit;
• Fig. 9 a perspective view of the welding and separating unit.

The apparatus 10 of the invention shown in the drawing is used to weld waste into a foil tube 12 made of a thermoplastic film which, during welding, is subdivided by transversal welds into a series of aerosol and liquid tight pouches, each containing a batch of wastes.

With the device 10, a plurality of sealed bags can be dispensed either as a continuous strand or in the form of individual separate bags from a housing 12 of the device 10, from which they extend downwardly into a container (not shown) positioned below the housing 12 will fall.

The apparatus 10 includes, in addition to the flat parallelepiped housing 12, a chassis 14 having four elongated legs 16 supporting the housing 12, which are provided with rollers 18 at their lower ends, and a platform 20 mounted on the legs 16 near the lower ends for parking the collecting container. The housing 12, the chassis 14 and the platform 20 are made of stainless steel. However, the apparatus 10 can also be integrated without the carriage 14 into a work table or into a wall, e.g. as a built-in device.

The essentially consisting of a lower housing part 22 and a removable cover part 24 housing 12 surrounds an electronics unit 26, a welding and separation unit 28 and a conveyor unit 30, which are housed inside the housing. How best in Fig. 7 shown, the electronics unit 26, the welding and separating unit 28 and the conveyor unit 30 with the lid part 24 removed successively from above into the housing base 22 (in Fig. 7 not shown) are used before the lid part 24 is finally placed.

How best in Fig. 1 shown, the cover member 24 has a circular insertion opening 32 for injecting the waste to be welded, which is surrounded by a flat funnel-shaped edge 34.

How best in Fig. 6 illustrated, the in-outline square trough-like housing base 22 has a flat bottom 36 which is provided with a central bottom opening 38.

As in Fig. 7 illustrated, the electronics unit 26 has a flat bottom plate 40 with a central opening 42 which is aligned with the bottom opening 38 after insertion into the housing lower part 22. About the floor panel 40 is a sheet-metal bent frame-like wall portion 44 with a square outline perpendicular to above, to which, inter alia, a power supply, a rechargeable battery 46 and mounted on a circuit board electronic controller 48 of the device 10 are attached.

As in Fig. 8 illustrated, the conveyor unit 30 has a bottom plate 50, an outline in square inner wall 52 made of sheet metal and an outline square outer wall 54 made of sheet metal, which are bent from the floor panel 50 upwards. The inner wall 52 of the conveyor unit 30 defines a square shaft 56 and is provided on opposite sides of the shaft 56 with two pairs of narrow conveyor rollers 58 in the form of friction wheels, each projecting inwardly into the shaft 56. A first of the two conveyor rollers 58 of each pair has a fixed axis, while a second of the two conveyor rollers 58 of each pair is pivotally mounted and acted upon by a pressure ram 60 with a spring force to press with its peripheral surface against the peripheral surface of the first conveyor roller 58 , The two conveyor rollers 58 of each pair are non-rotatably connected by the inner wall 52 with meshing gears 62, of which the gear 62 of the fixed shaft conveyor roller 58 via a toothed belt 64 and an output shaft 66 of an electric drive motor 68 can be driven, so that the Always turn gears 62 in opposite directions. The drive motor 68 is a drive motor 68 with a reversible direction of rotation, which is arranged in the intermediate space between the inner and outer walls 52, 54.

As in Fig. 9 illustrated, the welding and separating unit 28 has an outline square frame 70 which defines a passage opening 72 and an outer wall 74 of sheet metal, whose dimensions correspond to those of the outer wall of the conveyor unit 28. In the frame 70, two movable parallel welding jaws 76 are arranged, the opposite ends of which are mounted on slides, which can be approximated by a welding jaw drive 78 along parallel guides 80 to each other or moved apart. The movement and the respective position of the welding jaws 76 are monitored by the controller 48 via microswitches according to the quiescent current principle. Each welding jaw 76 has a heating wire which can be connected to a current source and which is arranged between a Teflon strip on its side facing the passage opening 72 and a rubber band on its side facing away from the passage opening 72.

The heating wires of the two welding jaws 76 are supplied with power from the controller 48 when the welding jaws 76 are in an intermediate welding position in which they are pressed against the welding between the welding jaws 76 extending hose portion 82 from opposite sides, as in Fig. 6 shown schematically.

In order to prevent injury to a hand or fingers of a user who accidentally get between them in the mutual approach of the two welding jaws 76, the welding jaws 76 are resiliently supported against the direction of movement in their approach to the carriage. Further, a reed contact is disposed on one of the slides, which is triggered by a permanent magnet attached to the welding jaw 76 when the spring is compressed outside the central welding position and thereby the magnet is approximated to the contact.

The welding jaw drive 78 is an electric drive motor, to which power is supplied for the mutual approaching or moving apart of the welding jaws 76. When the welding jaws 76 are moved apart, the power supply to the drive motor 78 is monitored. If the current consumption of the drive motor 78 exceeds a predetermined current threshold, which indicates that there is an obstacle in the path of movement of the welding jaws 76 between these and opposite parts of the frame 70, the direction of movement of the welding jaws 76 is briefly reversed by reversing the drive motor 78. Thus, if the obstacle is a user's hand or finger, it may pull the hand or fingers out of the gap between the welding jaw 76 and the frame 70 without the risk of injury.

The outer wall 54 of the conveyor unit 30 and the outer wall 74 of the welding and separating unit 28 have corresponding lateral dimensions, while the wall portion 44 of the electronic unit 26 has larger lateral dimensions. In this way, a receiving space 84 for a folded film tube 86 is formed between the outer walls 54, 74 on the one hand and the wall portion 44 on the other hand, as in Fig. 6 shown.

Before the device 10 is put into operation, the film tube 86 which has been folded into an annular packet is inserted into the receiving space 84, which is accessible from above when the cover part 24 is removed. Subsequently, the upper end of the film tube 86 is folded inward or everted and passed through the limited by the inner wall 52 of the conveyor unit 30 shaft 56. In this case, between the two pairs of conveyor rollers 58 opposite and double superimposed edge strips of the folded inwards and through the shaft 56 and between the Welding jaws 76 downwardly guided hose portion 82 of the film tube 86 is clamped. In this way, the tube portion 82 can be transported downwardly through the housing 12 to and from the bottom opening 38, as indicated by the arrow A in FIG Fig. 6 illustrated by the conveyor rollers 58 are driven in the opposite direction of rotation, as indicated by the arrows B in Fig. 6 displayed. After closing the lid part 24, the device 10 can be put into operation.

In operation, the device 10 is controlled by means of a contactlessly above the housing lower part 24 protruding infrared sensor 88 which projects into a punched next to the opening 32 opening 90 in the cover part 24. As in FIGS. 2 and 3 illustrated, the sensor 88 comprises a pulse operating, emitting IR radiation transmitter 92 and an adjacent to the transmitter 92 arranged IR receiver 94. The receiver 94 is responsive when vertically upwards from the transmitter 92 emitted IR radiation from one above of the sensor 88 at a distance of less than 0.2 m in the radiation path of the IR radiation moving object is reflected back to the receiver 94. In addition to the transmitter 92 and the receiver 94, the sensor 88 also includes an indicator light 96, which indicates various operating states of the device 10 by different colors.

After switching on a arranged on the bottom of the housing 12 battery disconnect switch 98 for connecting the battery 46, the device 10 is in stand-by mode, in which the device 10 can not be controlled by means of the sensor 88. The activation takes place by pressing a reset button 100 on the lower housing part 22, whereupon the indicator lamp 96 lights up in a first color. When first using the device 10 after inserting a new film tube 86th into the receiving space 84, the hose section 82 of the film tube 86, which is folded inwards and is passed through the shaft 56 and the remaining housing 12, is closed in the welding and separating unit 28 between the welding jaws 76 by a weld extending transversely across the tube section 82, which then forms the lower end of the first bag.

In use of the device 10, with the sensor 88 activated, one of the user may select one of two desired modes of operation, namely, a welding cycle and a separation welding cycle.

The welding cycle is triggered by moving an object, for example the user's hand, over the sensor 88 into the IR radiation path. Thereafter, the indicator light 96 begins to flash in a different color, indicating that the device 10 is waiting and waiting for another input from the user. When the user again moves the hand over the sensor 88, transport of the hose portion 82 is initiated by driving the two pairs of conveyor rollers 58 of the conveyor unit 30. The transport takes place until the user again moves the hand away from the sensor 88 or until an adjustable maximum bag length is reached. The user can thus control by the residence time of the hand above the sensor 88, the length of the film bag to be formed to receive the waste. Before or during transportation, the user may throw a batch of the waste into the throw-in port 32 from where they fall into the upwardly open hose section 82 or bag which has previously been welded in the welding and separation unit 28 at the lower end. When the user moves his hand away from the sensor 88, a welding operation is then initiated again to close the top of the bag.

In the welding operations, the two welding jaws 76 are approached from opposite sides of the hose portion 82 and pressed against it. Then, current is supplied to the heating wires in the welding jaws 76 to weld the hose portion 82 therebetween along a weld extending transversely across the hose portion 82 and thus hermetically seal the film bag. Between the upper end of a bag and the lower end of a subsequently formed bag a single weld is arranged in each case. The film tube is not severed in the welding cycle to form a continuous string of bags which are closed at both ends by parallel welds, the contents of each bag being hermetically separated from the contents of the adjacent bags.

The splice cycle is triggered by holding an object, such as the user's hand, over the sensor 88 for a period of more than 2 to 3 seconds. In this case, the indicator light 96 flashes in still another color and the separation welding cycle is initiated. As with the welding cycle, a hand-controlled transport of the hose portion 82 is first initiated, which lasts until the user moves the hand away from the sensor 88 again or a maximum adjustable bag length is reached. Before or during transport, the user can, as in the welding cycle throw the waste into the insertion opening 32, from where they fall into the already sealed at the bottom of foil bag. As the user moves his hand away from the sensor 88, a first welding operation is initiated in which the bag is welded at the top by a transverse weld, as previously described for the welding cycle. However, after the welding jaws 76 have been moved apart again, in the separation welding cycle the hose section 82 is removed from the Feed unit 30 again moves down a short distance, preferably by about 5 centimeters. Thereafter, the two welding jaws 76 are again approximated to the hose portion 82 and pressed against this, but the heater wires more power than in the welding process is supplied. Due to the greater amount of heat generated thereby, the hose portion 82 between the welding jaws 76 is heated to flow. If this is the case after expiration of a preset period of time previously determined by tests, the direction of rotation of the drive motor 68 of the conveyor unit 30 is reversed by reversing the polarity and power is again supplied to the drive motor 68 for a short time. As a result, the part of the hose section 82 located between the conveying unit 30 and the welding and separating unit 28 is moved backwards, ie upwards, and thus along a separating seam extending between the welding jaws 76 from the lower end of the hose section 82 projecting downwards beyond the welding jaws 76 demolished the last welded bag. This latter then falls either immediately or at the latest when moving apart of the welding jaws 76 down into the receptacle. After the welding jaws 76 have been moved apart, the hose section 82 is once again moved downwards a short distance by the conveyor unit 30 and then welded again along a weld before the next cycle can be initiated. In this way, individual bags are produced at the Trennschweißzyklus with shrink-wrapped waste, which are closed at both ends by two parallel seams, a weld adjacent to the bag contents and a arranged directly at the bag end seam.

However, in both the welding cycle and the separation welding cycle, the thermoplastic material of the film tube is heated along the seams to such a temperature that there are also several along the seams hermetically connect superimposed or overlapping layers of plastic material.

By pressing the reset button 100, the welding cycle and the separating welding cycle can be stopped at any time.

Claims (11)

1. Device (10) for welding waste into a tubular film (56), having a housing (12) which surrounds a receiving space (84) for the folded-up tubular film (86), a duct (56) through which an inwardly folded-over tubular portion (82) of the tubular film (82) extends from the top to the bottom, a conveying unit (30) which conveys the tubular portion (82) downwards through the duct (56) and the conveying direction of which is reversible, having a welding and separating unit (28), which is disposed below the conveying unit (30), for welding the tubular portion (82) along transversely running seams and for severing a lower end of the tubular portion (82), and having a controller (48) for activating the conveying unit (30) and the welding and separating unit (28), characterized in that the controller (48) is disposed in such a manner that the conveying direction of the conveying unit (30) is reversed in the event of the lower end of the tubular portion (82) being severed.
2. Device according to Claim 1, characterized by installations for reversing the conveying direction of the conveying unit (30), depending on the state of a seam which is produced for severing the lower end of the tubular portion (82) in the welding and separating unit (28).
3. Device according to Claim 2, characterized in that the installations comprise a time controller.
4. Device according to one of the preceding claims, characterized in that a heat quantity which is supplied by the welding and separating unit (28) into the tubular portion (82) for severing the lower end of the tubular portion (82) is larger than a heat quantity which is supplied by the welding and separating unit (28) into the tubular portion (82) for welding the tubular portion (82).
5. Device according to one of the preceding claims, characterized in that the conveying unit (30) comprises at least one pair of conveying rollers (58) which are driven so as to have opposing directions of rotation, and in that for severing the lower end of the tubular portion (82) the direction of rotation of both conveying rollers (58) is reversible.
6. Device according to Claim 5, characterized in that the conveying unit (30) comprises two pairs of narrow conveying rollers (58) which are disposed at opposite sides of the duct (56) and extend only across part of the width of the tubular portion (82), the direction of rotation of the conveying rollers (58) of both roller pairs being reversible.
7. Device according to one of the preceding claims, characterized in that the welding and separating unit (28) comprises two heatable welding jaws (76) which are pressable against the tubular portion (82) from opposite sides.
8. Device according to Claim 7, characterized in that the two welding jaws (76) comprise in each case one heating wire which is connectable to a power source and which is disposed between a Teflon tape on the side of said heating wire which faces towards the tubular portion (82) and a rubber tape on the side of said heating wire which faces away from the tubular portion (82).
9. Device according to Claim 7 or 8, characterized in that when approaching the tubular portion (82), the two welding jaws (76) are supported counter to their direction of movement by springs and in that, in the event of one of the springs being compressed, installations for reversing the direction of movement of the welding jaws (76) are provided.
10. Device according to one of Claims 7 to 9, characterized by installations for monitoring the power supply to an electric drive motor (78) of the welding jaws (76) during moving-apart of the welding jaws (76), and a controller (48) for reversing the power supply to the drive motor (78) when a predefined power threshold value is exceeded.
11. Device according to one of the preceding claims, characterized in that the controller (48) is disposed in such a manner that, in the event of the lower end of the tubular portion (82) being severed, first the tubular portion (82) is welded along a welding seam, in that the lower end of the tubular portion (82) is then severed along a separating seam which is disposed above the welding seam, and in that finally the remaining part of the tubular portion (82) is welded along a welding seam which is disposed above the separating seam.

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