Manufacture of roll formed tube

Abstract

A seam guide assembly (1) configured to hold longitudinal edges (101) of metal strip (102) in place prior to welding the longitudinal edges (101) of the metal strip (102) together in a weld section (201) of a welded tube roll forming apparatus (200), the seam guide assembly comprising a front seam guide tip member (2), a through passage (6) disposed in a retainer (3), the passage having an inlet opening (7) on the first side (5) of the retainer adjacent the front seam guide tip member (2) and an outlet opening (8) on the second side (9) of the retainer, the outlet opening configured to be connected to a vacuum source; a welded tube roll forming apparatus (200) comprising a vacuum extraction section (205) configured to extract solid particles generated inside a tube (100) during high frequency induction welding of tube edges and located at a position in the apparatus where edges (101) of a roll formed tube have not yet been welded together; and a method of manufacturing a tube, the method comprising extracting solid particles generated inside a tube (100) during high frequency induction welding by applying a vacuum at a section (205) of the tube where edges (101) of a roll formed tube have not yet been welded together.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the manufacture of roll formed and welded tubes, and in particular to a seam guide assembly configured for use in a roll forming apparatus for welded tubes, a roll forming apparatus comprising the seam guide assembly, and a method of manufacturing a tube comprising aluminum or an alloy thereof by roll forming a strip in a roll forming apparatus for welded tubes. BACKGROUND

[0002] Welded tubes and pipes are typically manufactured by forming a flat metal strip longitudinally into a nearly complete tube and then welding the two edges together. There are many application areas for roll formed tubes, for example in the field of the HVAC&R market (heating, ventilation, air conditioning and refrigeration). Within this technical field, environmental demands have driven the development towards air conditioning and refrigeration equipment with increased efficiency. In response to this, efforts have been made to supply smaller diameter copper tubes with a wide range of inner surface enhancements that are able to increase the heat transfer coefficient of the copper tube relative to standard smooth solutions. The use of advanced products such as small diameter welded tubes with inner surface patterns involves meeting stringent requirements in terms of internal contamination levels of the tube. With the increasing demand for cost reduction, there has been interest in providing an alternative to copper tubes in the form of aluminum tubes, which have traditionally been mainly used for air conditioning and refrigeration equipment. However, it has been found difficult to manufacture aluminum tubes with characteristics that are competitive for the purpose of applications within fields such as HVAC&R. SUMMARY

[0003] The present disclosure relates to tools and methods for manufacturing welded tubes, which provide for an efficient manufacturing of advanced tube products made of aluminium or its alloys. According to the present disclosure, a seam guiding assembly is provided, which is configured to hold the longitudinal edges of a metal strip being roll formed into a tube in place before the edges are welded together in a welding section of a welded tube roll forming apparatus. The seam guiding assembly comprises a front seam guiding tip part attached to a holder with an elongated tip protruding from a first side of the holder, and the tip is configured to be inserted between the tube edges to be welded. A through-going channel is provided in the holder, which channel has an inlet opening on the first side of the holder adjacent to the front seam guiding tip part in the longitudinal direction of the holder, and an outlet opening on a second side of the holder, and the outlet opening is configured to be connected to a vacuum source, e.g. by means of a connection fitting such as a screw fitting or a bayonet coupling, to which a connecting part of the vacuum source can be connected. The seam guiding assembly preferably comprises a rear seam guiding tip part attached to the holder with an elongated tip protruding from the first side of the holder, wherein the rear seam guiding tip part is positioned on the holder at a distance from the front seam guiding tip part in the longitudinal direction of the holder, and the channel inlet opening is located between said front and rear tip parts. Thus, the seam guiding tips are divided into two parts, with the channel inlet opening located between them. The inlet opening of the channel has a width which suitably does not exceed the outer diameter of the tube, and more preferably is about equivalent to the distance between the edges of the strip almost formed into a tube. The inlet opening of the channel preferably has an elongated shape directed in the longitudinal direction of the holder, so as to conform to the opening between the strip edges to be welded. The holder can preferably comprise guiding flanges arranged on each side of the channel inlet opening.

[0004] According to the present disclosure, there is also provided a welded tube roll forming apparatus, the apparatus comprising a roll forming section configured to form a metal strip into a tube, followed by a welding section. The welding section comprises a seam guide assembly, a high frequency induction welding coil and a pair of welding rolls, and is configured to weld together the longitudinal edges of the metal strip being roll formed into a tube while the tube is travelling in a forward direction through the apparatus. The apparatus further comprises a vacuum extraction section configured to extract solid particles generated inside the tube during high frequency induction welding of the tube edges, the vacuum extraction section being located in the apparatus at a position where the edges of the roll formed tube have not yet been welded together. The vacuum extraction section can suitably comprise the seam guide assembly as described above arranged between the welding coil and the roll forming section. The vacuum extraction section can advantageously comprise a gap vacuum nozzle configured to be connected to a vacuum source and arranged behind the seam guide assembly in the forward direction of the tube, and the gap vacuum nozzle is configured to extract the solid particles through the opening between the yet unwelded edges of the tube. The vacuum extraction section can also comprise a tube vacuum nozzle configured to be connected to a vacuum source and arranged behind the seam guide assembly in the forward direction of the tube, said tube vacuum nozzle being configured to be positioned inside the roll formed and yet unwelded tube to extract the solid particles present inside the tube.

[0005] The apparatus can also advantageously comprise a reverse flushing device comprising a tubular member having a gas valve attached to its outlet end and a coupling attached to its inlet end, said coupling being configured to be connected to a pressurized gas source. The reverse flushing device is configured to apply a gas flow in a direction opposite to the direction of travel of the tube at a position in front of the welding coil in the forward direction of the tube, so as to force any remaining solid particles to move in a direction opposite to the direction of travel of the formed tube so that they can be extracted in the vacuum extraction section. The gas can suitably be a reverse flow nozzle. The tubular member of the reverse flushing device can comprise a straight first section having a front end to which the reverse flow nozzle is attached, said straight section having a length exceeding the distance from the rear end of the seam guide assembly to the position in front of the welding coil in the forward direction of the tube, and the straight first section having an outer diameter smaller than the inner diameter of the tube to be welded so that it can be inserted into the finished tube. The tubular member can also comprise a second section having a rear end carrying the coupling. The second section can be angled relative to the first section. The reverse flushing device is preferably arranged in the apparatus so that the metal strip is roll formed around the straight first section of the tubular member and the reverse flow nozzle is located in front of the welding coil in the forward direction of the tube.

[0006] The present disclosure also relates to a tube that has been manufactured by the apparatus described above, wherein the metal strip comprises aluminium or an alloy thereof.

[0007] According to the present disclosure, there is also provided a method of manufacturing a tube comprising aluminium or an alloy thereof. The method comprises roll forming a strip comprising aluminium or an alloy thereof into a tube in a roll forming section of a tube roll forming welding apparatus; and welding the edges of the tube together in a high frequency induction welding section of the apparatus, the high frequency induction welding section comprising a welding coil and a pair of welding rolls. The welding comprises extracting solid particles generated inside the tube during high frequency induction welding by applying a vacuum at a section of the tube where the longitudinal edges of the metal strip being roll formed into the tube have not yet been welded together. The method can preferably comprise back flushing the solid particles by applying pressurized gas in a direction opposite to the direction of travel of the tube at a position located in front of the welding coil in the direction of travel of the tube.

[0008] The detailed description and specific examples given below are presented by way of illustration only and are not intended to limit the preferred embodiments of the present disclosure in any way. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 A forming and welding apparatus is schematically illustrated;

[0010] Figure 2 A high frequency welding mechanism is schematically illustrated;

[0011] Figure 3 A position of a vacuum extraction section in a forming and welding apparatus is schematically illustrated;

[0012] Figure 4 is a perspective view of a welding section of a forming and welding apparatus comprising a seam guide assembly;

[0013] Figure 5 is a cross-sectional view of a seam guide assembly in its longitudinal direction;

[0014] Figure 6a A seam guide assembly is shown from the seam guide tip side;

[0015] Figure 6b Parts of a seam guide assembly are shown;

[0016] Figure 7a A back flushing device is shown;

[0017] Figure 7b A gas valve of a back flushing device is shown;

[0018] Figure 8 A part of a forming and welding apparatus is schematically illustrated, showing the position of a tube vacuum nozzle and a gap vacuum nozzle. DETAILED DESCRIPTION

[0019] The present disclosure relates to tools and methods for manufacturing tubes, which allow the manufacturing of advanced small diameter aluminum tube products having a diameter of 20 mm or less, preferably 5-10 mm. The tube products are preferably manufactured as continuous coils having a length of more than 500 m, preferably more than 1000 m. Such tube products can be used in the field of e.g. heating, ventilation, air conditioning or refrigeration.

[0020] The process of roll forming of welded tubes involves roll forming a strip into a tubular shape and welding the longitudinal edges of the strip together by means of high frequency welding in a welding coil, thereby obtaining a tube. To achieve this, the strip is fed into a forming machine or forming device, which shapes the strip through different successive forming steps performed by a plurality of forming rollers, as Figure 1 illustratively shown in Fig. 1. When the strip passes through the welding coil, an electromagnetic field is induced around the welding coil, which induces a current flowing in the strip, mainly concentrated at the edges to be joined. The electrical resistance of the metal to the current generates the necessary heat development, which rapidly reaches the melting point at these edges. While the edges are still in a molten state, they are forged together due to the interaction with the side extrusion rollers, which exert a force on the strip and thus generate the required pressure at the interface of the two edges. Oxidized metal and molten metal are extruded out of the joint when passing through the welding rollers, and clean base metal is joined. After welding, a sizing roll completes the process, providing the tube with the desired final geometry.

[0021] In high frequency welding, the current flowing in the work coil generates a magnetic field, which intersects the almost formed open tube. Two key physical phenomena are created using high frequency alternating current: the "skin effect", which means that the induced high frequency current tends to flow in the superficial skin of the conductor, and the "proximity effect", which means that the proximity of the two conductors into which the induced current flows will have a tendency to concentrate the current in the opposite surface of the conductor. Due to the skin effect and the proximity effect, the induced current will be concentrated in the "V shape" (i.e. the V-shaped space formed between the longitudinal strip edges just before the welding point), as well as in the edge "skin" volume (i.e. the outside of the strip in the area located within the welding coil). Figure 2 A high frequency welding mechanism is schematically illustrated.

[0022] In the process of manufacturing aluminum tubes by high frequency welding, a discharge of solid particles, i.e. a spattering of aluminum particles, is caused due to the presence of electromagnetic forces exerted on the liquid phase at the apex of the V shape where the strip edges meet. This discharge of solid particles spatters in all directions from the welding point, which means that it will end up also inside the welded tube. When the tube travels at high speed through the manufacturing device, the solid contaminant particles will travel with the tube away from the opening between the strip edges that have not yet been welded.

[0023] Manufacturing and use of advanced products, such as small diameter welded aluminium tubes with an inner surface pattern, involves meeting stringent requirements in terms of internal contamination levels for the tube, where cleanliness limits are often set to less than 0.5 mg / ft of internal contamination of solid particles. However, the level of solid particle contamination resulting from high frequency welding of small diameter aluminium tubes, with a diameter of 10 mm or less, results in a level of solid particle contamination that is typically 25-100 times higher than the level accepted in the final tube product. This is a problem when manufacturing small diameter tubing with a considerable length, as it is difficult to flush out these particles from the finished tube. When the tube is installed in, for example, a heating, ventilation, air conditioning or refrigeration device, it is important to avoid the presence of contaminants, for example in the form of particles, in the final tube product in order to obtain proper flow characteristics in the tube. The present disclosure therefore aims to provide a solution that facilitates the manufacturing of roll formed welded aluminium tubing. The solution relies on the removal of internal solid particle contaminants performed in parallel during the manufacturing of the welded tube by means of vacuum extraction. Thereby, the product quality of the manufactured tube product can be improved and, as a result, advanced small diameter tubes can be manufactured from aluminium or its alloys.

[0024] Hence, a seam guide assembly is provided that can be used in a welded tube forming apparatus to enable removal of emissions of solid particles resulting from high frequency welding inside the welded tube by means of applying a vacuum. The seam guide is arranged directly in front of the welding coil in the direction of travel (T) of the tube and provides for guiding the welding seam and preventing the formation of shavings in the strip edges, thereby avoiding seam rolling and providing good electrical insulation in front of the welding coil. The seam guide assembly is thus configured to hold the longitudinal edges of the metal strip being roll formed into a tube in place before the edges are welded together in the welding section of the welded tube roll forming apparatus. The seam guide assembly comprises a front seam guide tip part attached to a holder with an elongated tip protruding from a first side of the holder in a direction away from said first side, and the tip is configured to be inserted between the tube edges to be welded.

[0025] The holder typically can have a generally elongated shape adapted to be positioned along the tube, and the first side is the side of the holder that is intended to face the tube to be welded during the welding process. During the welding process, when the longitudinal tube edges are pressed towards each other by means of the pressing rolls, the longitudinal tube edges are pressed against the side surfaces of the tip, so that the tip of the seam guiding assembly is held in place by the seam guiding tip component assisted by the pressing rolls. The front seam guiding tip component can also extend from the holder in the longitudinal direction of the holder, so that its outermost tip edge can extend further forward along the tube, which would not be possible for the holder due to lack of space. A through channel is provided in the holder. The channel has an inlet opening on the first side of the holder, i.e. the side facing the tube to be welded, and an outlet opening on the second side of the holder, i.e. the side of the holder that does not face the tube, e.g. on the side opposite to the first side or perpendicular to the first side.

[0026] The inlet opening of the through channel is located adjacent to the front seam guiding tip component in the longitudinal direction of the holder, and the outlet opening is configured to be connected to a vacuum source. By means of the vacuum source, the emissions of particles that have been ejected inside the tube due to the high-frequency welding can be removed from the inside of the shaped and welded tube through the channel of the seam guiding assembly. A connection part can be attached to the outlet opening to facilitate the connection to the vacuum source.

[0027] The seam guiding assembly preferably comprises a rear seam guiding tip component attached to the holder in such a way that the elongated tip protrudes from the first side of the holder, wherein the rear seam guiding tip component is positioned on the holder at a distance from the front seam guiding tip component in the longitudinal direction of the holder, and the channel inlet opening is located between said front and rear tip components. Thus, the seam guiding tip is divided into two parts, with the channel inlet opening located between them. This allows the edges of the strip to be welded to be properly guided along a greater length of the roll-formed strip. The holder of the seam guiding assembly can suitably be made of brass, and the seam guiding tip components are suitably made of electrically insulating material, preferably ceramic material. The inlet opening of the channel has a width that suitably does not exceed the outer diameter of the tube, and more preferably is about equivalent to the distance between the edges of the strip to be welded, which is almost shaped into a tube. Thus, the vacuum applied through the channel will effectively act on the inside of the roll-formed strip. The inlet opening of the channel preferably has an elongated shape directed in the longitudinal direction of the holder, so as to conform to the opening between the edges of the strip to be welded. To facilitate the correct positioning of the seam guide, the holder can preferably comprise a guide flange arranged on each side of the channel inlet opening. The seam guiding assembly does not comprise any components that need to travel inside the tube during the welding process. Thus, the seam guiding assembly of the invention allows the welding of very small diameter tubes, such as 20 mm or less, preferably 5-10 mm.

[0028] According to the present disclosure, there is also provided a welded tube roll forming apparatus comprising a roll forming section configured to form a metal strip into a tube, followed by a welding section. The welding section comprises a seam guide assembly, a high frequency induction welding coil and a pair of welding rolls, and is configured to weld together the longitudinal edges of the metal strip being roll formed into a tube while the tube is advancing in a travel direction through the apparatus. The welding coil is typically a copper tube bent to create a plurality of windings perpendicular to the tube direction.

[0029] The apparatus further comprises a vacuum extraction section configured to extract solid particles generated inside the tube during the high frequency induction welding of the strip edges. The vacuum extraction section is located in the apparatus at a position where the edges of the roll formed strip have not yet been welded together, i.e. behind the welding section (201), i.e. upstream of the welding section in the travel direction of the tube. The vacuum extraction section is preferably arranged in the apparatus such that it covers the gap between the not yet welded strip edges adjacent to the welding coil. The vacuum depression should be chosen to sufficiently remove the particles present inside the tube, for example an suction force of about 10 m / s or higher for a vacuum tube diameter of 2-5 cm.

[0030] The vacuum extraction section can suitably comprise a seam guide assembly as described above, which is arranged between the welding coil and the roll forming section, preferably as close as possible to the welding coil. The vacuum extraction section can advantageously comprise a gap vacuum nozzle configured to be connected to a vacuum source and arranged behind the seam guide assembly in the travel direction of the tube, and configured to extract solid particles through the opening between the not yet welded edges of the tube. The gap vacuum nozzle can suitably be positioned on top of the opening between the edges of the strip forming the tube, having a width not exceeding the outer diameter of the tube, and being larger than the distance between the edges, thereby covering all or part of the length of the strip forming the tube comprised between the tube roll forming section of the apparatus and the seam guide tip assembly. The vacuum extraction section can further comprise a tube vacuum nozzle configured to be connected to a vacuum source and arranged behind (i.e. upstream of) the seam guide assembly in the travel direction of the tube, said tube vacuum nozzle being configured to be positioned inside the roll formed and not yet welded tube to extract solid particles present inside the tube. In this way, the internal particle contamination can be further reduced.

[0031] As mentioned above, it is difficult to flush small diameter tubes having a considerable length. However, according to the present disclosure, the apparatus can advantageously comprise a reverse flushing device in order to further improve the removal of any particles inside the finished tube. The reverse flushing device comprises a tubular member having a gas valve attached to its outlet end and a coupling attached to its inlet end, said coupling being configured to be connected to a pressurized gas source, preferably a neutral gas such as nitrogen. The reverse flushing device is configured to apply a gas flow in a direction opposite to the direction of travel of the tube at a position in front of the welding coil in the direction of travel of the tube in order to force any remaining solid particles to move in a direction opposite to the direction of travel of the shaped tube so that they can be extracted in the vacuum suction section, thereby further facilitating the removal of particles inside the welded tube which are still remaining after the welding point, i.e. downstream of the welding point, preferably also downstream of the extrusion roller which can be part of the welding section. Thus, the reverse flushing of gas from the inside of the tube beyond the position of the forging point results in a final increase of the vacuum suction efficiency and the amount of foam removal.

[0032] The gas valve can suitably be a counterflow nozzle. The tubular member can be a flexible pipe made of a heat resistant material such as PTFE. The tubular member of the reverse flushing device can comprise a straight first section having a front end to which the counterflow nozzle is attached, said straight section having a length exceeding the distance from the rear end of the joint guide assembly to the position in front of the welding coil in the direction of travel of the tube, and the straight first section having an outer diameter which is smaller than the inner diameter of the tube to be welded so that it can be inserted into the finished tube. The tubular member can further comprise a second section having a rear end carrying the coupling. The second section can be angled with respect to the first section. The reverse flushing device is preferably arranged in the apparatus so that the metal strip is roll formed around the straight first section of the tubular member and the counterflow nozzle is in front of the welding coil in the direction of travel of the tube. The part of the tubular member of the reverse flushing device which is closest to the induction coil can be made of a glass fiber reinforced epoxy resin material or a ceramic material in order to be able to withstand the high local temperatures generated during welding and to avoid damages due to contact with solid particles. The gas valve can have an outer diameter which is smaller than the inner diameter of the tube. It should be noted that the reverse flushing device can be used independently in an apparatus for manufacturing roll formed and welded tubes, i.e. it does not necessarily require the presence of a vacuum suction device or a joint guide assembly.

[0033] The present disclosure also relates to a tube which has been manufactured by the apparatus described above, wherein the metal strip comprises aluminum or an alloy thereof.

[0034] A method of manufacturing a tube comprising aluminium or an alloy thereof is also provided. The method comprises: roll forming a strip comprising aluminium or an alloy thereof into a tube in a roll forming section of a welded tube roll forming apparatus; and welding the tube edges together in a high frequency induction welding section of the apparatus, the high frequency induction welding section comprising a welding coil and a pair of welding rollers. The welding comprises extracting solid particles generated inside the tube during high frequency induction welding by applying a vacuum at a section of the tube where the longitudinal edges of the metal strip being roll formed into the tube have not yet been welded together. The method can preferably comprise backflushing the solid particles by applying pressurised gas in a direction opposite to the direction of travel of the tube at a location in front of the welding coil in the direction of travel of the tube. The strip forming the tube preferably has an enhanced surface obtained by an embossing pattern to increase the heat transfer properties of the tube product. The strip width is chosen so that the formed tube reaches a desired diameter of preferably 20 mm or less, preferably 5-10 mm.

[0035] Description of example embodiments

[0036] The tools and methods of the present disclosure will now be described with reference to the drawings, wherein are shown preferred example embodiments of the present disclosure. The present disclosure may, however, be embodied in other forms and should not be interpreted as limited to the embodiments disclosed herein. The disclosed embodiments are provided to comprehensively convey the scope of the present disclosure to those skilled in the art.

[0037] Figure 1 A conventional welded tube roll forming apparatus 200 is schematically illustrated, comprising a roll forming section 202 configured to form a metal strip into a tube, followed by a welding section 201, a high frequency induction welding coil 203 and a pair of welding rollers 204. The apparatus does not comprise a seam guide assembly.

[0038] Figure 2 A high frequency welding mechanism is schematically illustrated in more detail, wherein a metal strip 102 is almost formed into a tube 100. The illustration shows how the strip is formed to bring the longitudinal edges into abutment with each other and how the almost closed tube is moved through the welding coil.

[0039] Figure 4 is a perspective view of a welding section of a forming and welding apparatus comprising the seam guide assembly of the present disclosure. Figure 4 It is also illustrated how the backflushing device 300 is inserted into the almost closed tube. The opening between the longitudinal side edges of the strip is somewhat exaggerated for illustrative purposes.

[0040] Figure 5 is a cross-sectional view of the seam guide assembly in its longitudinal direction. Figure 5 The small arrows in show the travel path of the solid particles to be extracted. Figure 6a is shown from the side of the seam guide tip andFigure 6b Parts of a seam guiding assembly are shown.

[0041] The seam guiding assembly 1 is configured to hold the longitudinal edges 101 of the metal strip 102 being roll formed into a tube 100 in place prior to welding the edges together in a welding section 201 of a tube roll forming apparatus 200. The seam guiding assembly 1 comprises a front seam guiding tip part 2 attached to a holder 3 such that an elongated tip 4 protrudes from a first side 5 of the holder 3. The tip 4 is configured to be inserted between the tube edges 101 to be welded. A through channel 6 is provided in the holder 3. The channel has an inlet opening 7 on the first side 5 of the holder adjacent the front seam guiding tip part 2 in the longitudinal direction of the holder and an outlet opening 8 on a second side 9 of the holder. The outlet opening is configured to be connected to a vacuum source. A connection part 18 is couplable to the outlet opening, e.g. by means of a screw joint. A rear seam guiding tip part 10 is attached to the holder 3 such that an elongated tip 11 protrudes from the first side 5 of the holder 3. The rear seam guiding tip part 10 is positioned on the holder at a distance from the front seam guiding tip part 2 in the longitudinal direction of the holder and the channel inlet opening 7 is located between said front and rear tip parts 2, 10. The holder 3 comprises a guiding flange 12 arranged on each side of the channel inlet opening 7.

[0042] Figure 3 A tube roll forming apparatus 200 is schematically illustrated, the apparatus comprising a roll forming section 202 configured to form a metal strip 102 into a tube 100, followed by a seam guiding assembly and / or vacuum extraction section 205 and a welding section 201 comprising a high frequency induction welding coil 203 and a pair of welding rolls 204. The apparatus is configured to weld the longitudinal edges 101 of the metal strip 102 being roll formed into a tube 100 together while the tube is forwarded through the apparatus in a forward direction (T). Figure 3 The position of the vacuum extraction section 205 in the forming and welding apparatus is schematically illustrated. The figure illustrates how the vacuum extraction section, which can comprise both a seam guide and vacuum suction equipment, is arranged on a tube that has not yet been closed and welded, without details of the equipment, which are more clearly shown in the following figures. The high frequency induction welding coil 203 can be designed in various ways, as shown for example in Figure 2 to Figure 4 and Figure 7a .

[0043] The apparatus also comprises a vacuum extraction section 205 configured to extract solid particles generated inside the tube 100 during the high frequency induction welding of the tube edges, the vacuum extraction section 205 being located in the apparatus at a position where the edges 101 of the roll formed tube have not yet been welded together. The vacuum extraction section 205 comprises a joint guide assembly 1 arranged between the welding coil 203 and the roll forming section 202.

[0044] As Figure 8 schematically illustrated in Figs. 1 and 2, the welding vacuum extraction section 205 of the tube roll forming apparatus can comprise a gap vacuum nozzle 206 and a tube vacuum nozzle 207. The arrows in the figures show the travel path of the solid particles to be extracted. The gap vacuum nozzle 206 is connected to a vacuum source and arranged behind the joint guide assembly 208 in the travel direction (T) of the tube 100 and is configured to extract solid particles through the opening between the not yet welded edges of the tube. The tube vacuum nozzle 207 is also connected to a vacuum source and arranged behind the joint guide assembly 208 in the travel direction (T) of the tube 100. The tube vacuum nozzle 207 is positioned inside the roll formed and not yet welded tube to extract solid particles present inside the tube.

[0045] Figure 7a A reverse flushing device is shown, and Figure 7b shown is its gas valve 302 in the form of a counterflow nozzle. The reverse flushing device 300 comprises a tubular member 301 having a gas valve 302 attached to its outlet end 303 and a coupling 304 attached to its inlet end 305. The coupling is connected to a source of pressurized gas and the reverse flushing device applies a gas flow in a direction opposite to the travel direction (T) of the tube 100 at a position (P) in front of the welding coil 203 in the travel direction (T) of the tube. In the example shown, the tubular member 301 of the reverse flushing device 300 comprises a straight first section 306 having a front end 303 to which the counterflow nozzle 302 is attached. This straight section 306 has a length L exceeding the distance from the rear end 13 of the joint guide assembly 1 to the position (P) in front of the welding coil 203 in the travel direction (T) of the tube 100 (as seen for example in Figs. 1 and 2). Figure 8 The tubular member 301 comprises a second section 307 having a rear end carrying the coupling 304, said second section 307 being angled with respect to the first section 306. As Figure 4 and Figure 8 shown in Figs. 1 and 2, the reverse flushing device 300 can be arranged such that the metal strip 102 is roll formed around the straight first section 306 of the tubular member 301 and the counterflow nozzle 302 is located in front of the welding coil in the travel direction (T) of the tube 100.

[0046] The skilled person realizes that the present disclosure is not limited to the preferred embodiments described above. The skilled person further realizes that modifications and variations are possible within the scope of the appended claims.

Claims

1. A seam guide assembly (1) configured to hold longitudinal edges (101) of a metal strip (102) being roll-formed into a tube (100) in position before the longitudinal edges (101) of the metal strip (102) are welded together in a welding section (201) of a welded tube roll-forming apparatus (200), the seam guide assembly (1) comprising a front seam guide tip component (2) attached to a retainer (3) with a first elongated tip (4) protruding from a first side (5) of the retainer (3), the first elongated tip (4) configured to be inserted between the longitudinal edges (101) of the tube to be welded, wherein A through-channel (6) is provided in the holder (3), the through-channel having an inlet opening (7) on the first side (5) of the holder adjacent to the front seam guide tip part (2) in the longitudinal direction of the holder, and an outlet opening (8) on the second side (9) of the holder, the outlet opening being configured to be connected to a vacuum source, Characterized in that the through-channel (6) is configured for removing emissions of solid particles generated within the tube due to welding by applying a vacuum at the outlet opening (8), and that the inlet opening (7) of the through-channel (6) has an elongated shape pointing in the longitudinal direction of the holder (3).

2. The seam guide assembly according to claim 1 , further comprising a rear seam guide tip component (10) attached to the holder (3) with a second elongated tip (11) protruding from the first side (5) of the holder (3), wherein The rear seam guide tip part (10) is positioned on the holder at a distance from the front seam guide tip part (2) in the longitudinal direction of the holder, and the inlet opening (7) of the through-channel is located between the front seam guide tip part (2) and the rear seam guide tip part (10).

3. The seam guide assembly according to claim 1 or 2, wherein: The inlet opening (7) of the through-channel (6) has a width that does not exceed the outer diameter of the tube (100).

4. The seam guide assembly according to claim 3, wherein: The inlet opening (7) of the through-channel (6) has a distance corresponding to the distance between the longitudinal edges of the strip (102) formed almost as a tube.

5. The seam guide assembly according to claim 1 or 2, wherein: The holder (3) comprises a guide flange (12) which is arranged on each side of the inlet opening (7) of the through-channel.

6. A welded tube roll forming apparatus (200) comprising a roll forming section (202) configured to form a metal strip (102) into a tube (100), followed by a welding section (201), the welding section (201) comprising a high frequency induction welding coil (203) and a pair of welding rollers (204) configured to weld together longitudinal edges (101) of the metal strip (102) being roll formed into the tube (100) while the tube is passed forwardly through the welded tube roll forming apparatus in a direction of travel (T), characterized in that The welded tube roll forming apparatus further comprises a vacuum extraction section (205) configured to extract solid particles generated inside the tube (100) during high-frequency induction welding of the longitudinal edges of the tube, the vacuum extraction section (205) being located between the high-frequency induction welding coil (203) and the roll forming section (202) at a position where the longitudinal edges (101) of the roll-formed tube have not yet been welded together. Wherein, the vacuum extraction section (205) comprises a seam guide assembly (1) according to any one of claims 1 to 5.

7. The welded tube roll forming apparatus according to claim 6, wherein: The vacuum extraction section (205) includes a gap vacuum nozzle (206) configured to be connected to a vacuum source and arranged behind the seam guide assembly (1) in the travel direction (T) of the tube (100), the gap vacuum nozzle (206) configured to extract solid particles through an opening between the edges of the tube that have not yet been welded.

8. The welded tube roll forming apparatus according to claim 6 or 7, wherein: The vacuum extraction section (205) includes a tube vacuum nozzle (207) configured to be connected to a vacuum source and arranged behind the seam guide assembly (1) in the travel direction (T) of the tube (100), and configured to be positioned inside a roll-formed and unwelded tube to extract solid particles present inside the tube.

9. The welded tube roll forming apparatus (200) according to claim 6 or 7, further comprising a backflushing device (300), the backflushing device (300) comprising a tubular member (301), the tubular member (301) having a gas valve (302) attached to a front end portion (303) thereof and a connector (304) attached to an inlet end portion (305) thereof, the connector being configured to be connected to a pressurized gas source, the backflushing device being configured to apply a gas flow in a direction opposite to the direction of travel (T) of the tube (100) at a position (P) in front of the high-frequency induction welding coil (203) in the direction of travel (T) of the tube.

10. The welded tube roll forming apparatus (200) according to claim 9, wherein: The gas valve (302) is a counter-flow nozzle.

11. The welded tube roll forming apparatus according to claim 10, wherein: The tubular member (301) of the backflushing device (300) includes a straight first section (306) having the front end (303), the backflow nozzle being attached to the front end (303), the straight first section (306) having a length (L) exceeding the distance from the rear end (13) of the seam guide assembly (1) to a position (P) in front of the high-frequency induction welding coil (203) in the travel direction (T) of the pipe, and wherein the straight first section (306) of the tubular member (301) has an outer diameter that is smaller than the inner diameter of the pipe (100) to be welded.

12. The welded tube roll forming apparatus according to claim 11, wherein: The tubular member (301) comprises a second section (307) having a rear end portion carrying the coupling (304), the second section (307) being angled relative to the straight first section (306).

13. The welded tube roll forming apparatus according to claim 12, wherein: The backflushing device (300) is arranged in the welded tube roll forming apparatus so that the metal strip (102) is roll-formed around the straight first section (306) of the tubular member (301), and the countercurrent nozzle is located in front of the high-frequency induction welding coil in the travel direction (T) of the tube (100).

14. A pipe manufactured by the welded pipe roll forming apparatus according to claim 6 or 7, wherein: The metal strip comprises aluminum or an alloy thereof.

15. A method of manufacturing a tube comprising aluminum or an alloy thereof, comprising: A strip comprising aluminum or an alloy thereof is roll-formed into a tube (100) in a roll-forming section (202) of a welded tube roll-forming apparatus (200); and longitudinal edges (101) of the tube are welded together in a high-frequency induction welding section (201) of the welded tube roll-forming apparatus comprising a welding coil (203) and a pair of welding rollers (204); characterised in that the welding comprises extracting solid particles generated inside the tube (100) during high-frequency induction welding by applying a vacuum at a section (205) of the tube located between the welding coil (203) and the roll-forming section (202) with the aid of a seam guide assembly (1) according to any one of claims 1 to 5, where the longitudinal edges (101) of the roll-formed tube have not yet been welded together.

16. The method according to claim 15 further comprises backflushing the solid particles by applying pressurized gas in a direction opposite to the direction of travel (T) of the tube (100) at a position (P) ahead of the welding coil (203) in the direction of travel (T) of the tube.

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