CA2107050A1 - Weld seam covering on metal tubes - Google Patents
Weld seam covering on metal tubesInfo
- Publication number
- CA2107050A1 CA2107050A1 CA 2107050 CA2107050A CA2107050A1 CA 2107050 A1 CA2107050 A1 CA 2107050A1 CA 2107050 CA2107050 CA 2107050 CA 2107050 A CA2107050 A CA 2107050A CA 2107050 A1 CA2107050 A1 CA 2107050A1
- Authority
- CA
- Canada
- Prior art keywords
- hot
- application
- weld seam
- melt
- longitudinal weld
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 239000002184 metal Substances 0.000 title claims abstract description 42
- 239000012943 hotmelt Substances 0.000 claims abstract description 72
- 238000003466 welding Methods 0.000 claims abstract description 37
- 238000000034 method Methods 0.000 claims abstract description 22
- 239000011241 protective layer Substances 0.000 claims abstract description 11
- 238000000576 coating method Methods 0.000 claims abstract description 9
- 239000011248 coating agent Substances 0.000 claims abstract description 8
- 238000004659 sterilization and disinfection Methods 0.000 claims abstract description 4
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims abstract 2
- 239000000126 substance Substances 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 claims description 3
- 239000000155 melt Substances 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims description 3
- 230000001939 inductive effect Effects 0.000 claims description 2
- 238000005096 rolling process Methods 0.000 claims description 2
- 238000005507 spraying Methods 0.000 claims description 2
- 238000003892 spreading Methods 0.000 claims description 2
- 239000004922 lacquer Substances 0.000 abstract description 11
- 238000001035 drying Methods 0.000 abstract description 3
- 230000008030 elimination Effects 0.000 abstract description 2
- 238000003379 elimination reaction Methods 0.000 abstract description 2
- 239000010410 layer Substances 0.000 description 9
- 238000002844 melting Methods 0.000 description 4
- 230000008018 melting Effects 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 230000001419 dependent effect Effects 0.000 description 3
- 238000011065 in-situ storage Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000001681 protective effect Effects 0.000 description 2
- 230000001954 sterilising effect Effects 0.000 description 2
- 239000004593 Epoxy Substances 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000007688 edging Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229920000728 polyester Polymers 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K11/00—Resistance welding; Severing by resistance heating
- B23K11/06—Resistance welding; Severing by resistance heating using roller electrodes
- B23K11/061—Resistance welding; Severing by resistance heating using roller electrodes for welding rectilinear seams
- B23K11/062—Resistance welding; Severing by resistance heating using roller electrodes for welding rectilinear seams for welding longitudinal seams of tubes
- B23K11/063—Lap welding
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K11/00—Resistance welding; Severing by resistance heating
- B23K11/0006—Resistance welding; Severing by resistance heating the welding zone being shielded against the influence of the surrounding atmosphere
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Lining Or Joining Of Plastics Or The Like (AREA)
- Application Of Or Painting With Fluid Materials (AREA)
- Coating Apparatus (AREA)
Abstract
ABSTRACT
In the process for the continuous application of protective layers to cover a longitudinal weld seam of metal tubes, a hot-melt mass is passed continuously as a flexible hot-melt thread (28,58) through the welding arm (18) of a welding machine, deflected to the inside of the longitudinal weld seam of the metal tubes, pressed by an application device (40,54), melted and spread homogenously over the width of the longitudinal weld seam (12). Preferably at the same time as the inner coating, an outer protective layer is applied which allows the elimination of the baking or drying ovens for lacquer with their high requirements for space and energy.
One particularly advantageous application of the process lies in the application of a sterilisation-resistant hot-melt strip to the inside or inside and outside of the longitudinal weld seam of a tin casing.
(Fig. 3)
In the process for the continuous application of protective layers to cover a longitudinal weld seam of metal tubes, a hot-melt mass is passed continuously as a flexible hot-melt thread (28,58) through the welding arm (18) of a welding machine, deflected to the inside of the longitudinal weld seam of the metal tubes, pressed by an application device (40,54), melted and spread homogenously over the width of the longitudinal weld seam (12). Preferably at the same time as the inner coating, an outer protective layer is applied which allows the elimination of the baking or drying ovens for lacquer with their high requirements for space and energy.
One particularly advantageous application of the process lies in the application of a sterilisation-resistant hot-melt strip to the inside or inside and outside of the longitudinal weld seam of a tin casing.
(Fig. 3)
Description
2 1.~7~
~ ~e~L cl~yQ~a on~tal ~ubes The invention relates to a process for continuous application of a protective layer to cover a longitudinal weld seam of 5 metal tubes on a welding machine with a welding arm, an application arm connected to the welding arm, removable means fQr the transport of the metal tubes lying and to end in an axial direction and an application device for the protective layer. The invention also relates to a process for the 10 performance and an application of the process.
Welding machines are known which have an application system fitted "in line" which applies a protective strip to the longitudinal weld seam of metal tubes, in particular 15 longitudinally welded tins and cans. In principle, these differ by the application of a lacquer and a powder which are processed in situ to give a seam-covering layer.
Depending on machine type, the lacquer is applied from above 20 or below, where the metal tube to be processed normally hangs from an application arm or for application in the lower area stands on a conveyor belt, and is transported in the longitudinal direction of the application arm.
;
25 The lacquer can be supplied without air at high pressure through tubes of small diameter to the spray nozzle, atomised with an air flow or in another variant applied with a wheel.
2 3 ~ ~ ~ O
~ 2 --The weld seam is covered with a wet lacquer, and the resulting dry layer is around lO ~lm thick but relatively porous in comparison with a white inner lacquer.
5 Furthermore, a dlsadvantage with the use of known lacyuer application processes is that the tips o~ the butt and matrix welded points are not covered with lacquer, as it flows off.
In other known application devices on welding machines, the 10 inner longitudinal weld seams of metal tubes are protected in that a powder strip is applied in even thickness and melted in situ. The rehardened layers are us-~ally around 30 - 60 ~m thick and are essentially pore-free.
15 All lacquers and powders known to the specialist in this application can be used.
'~
In particular ~or the cans used in the foodstuf~ industry, a clean sterilization-resistant inner cover of the weld seam lS
20 extremely important. The food-resistance requirement means ~ that the protective layer must also resist hard mechanical -~ stresses such as the application o~ beading or edging.
Tests for the application of sterilization-resistant "hot-25 melts", as thermoplastic adhesives are known for short, which also resist mechanical stress have previously failed in that ~ ,, ~ :~ n ~ ^ Q
they could not be applied with the technical means adapted to the conditions.
The inventor has therefore faced the problem of creating a 5 process of the type described above and a device ~or its performance which allows the use of hot-melt in a simple, economic and effective manner. All undesirable dif~usion processes to a filling, in particular food, should be prevented.
With regard to the process, the task is solved according to the invention in that a hot-melt mass is fed continuously through the welding arm as a flexible hot-melt thread, deflected in the application arm to the inside o~ the 15 longitudinal weld seam of the metal tube, pressed by the ` application device against the hot longitudinal weld seam, melted and spread homogeneously over its width. Special and more advanced design forms of the process are the subject of the dependent patent claims.
The term "hot-melt thread" comprises also cords, wires, strips, tapes, foils, films etc. and hot-melt masses which are very long in comparison with their cross-section. In a special design form, the term "hot-melt thread" also covers a 25 hot-melt piece or compact hot-melt powder without conveyor medium passed through a flexible guide tube to the application device. The term "in the application arm" also - -~7~ ~r3 cover~ the ~pace present where applicable between the welding arm and the application arm.
Simultaneously with the inner coating of the weld seam, a 5 second flexible also pre~erably cold hot-melt thread is passed continuously to the outside of the longitudinal weld ssam, pressed by a second application device against the hot longitudinal weld seam, melted and/or spread homogeneously over its width. This second hot-melt thread can have the 10 same chemical composition as the first applied internally.
The internal and external coating of a longitudinal weld seam with a hot-melt layer has the essential advantage that baking or drying ovens for lacquers with their high requirements for space and energy can be eliminated.
The arrangement of the weld arm and application arms with the coating device immediately behind each other has the further advantage that the longitudinal weld seams of the metal tubes ~passing through are still very hot at the application head, ;20 usually still glowing faintly red. In particular with a low layer thickness, these can give the metal tube enough inherent warmth to melt one or both hot-melt threads on contact and guarantee the required coating without the provision of further heat. In addition, the still hot weld 25 seam gives a far better adhesion of the protective layer.
With insufficient heat transfer through the hot longitudinal weld seam, in particular with greater layer thicknesses to be applied and/or coating on both sides, additiorlal heat is applied to one or both hot-melt threads in the area of the application device by the application head being heated, for example by inductive or resistance heating, a gas flame or a 5 radiator.
If a hot-melt thread, in the most common variant o~ the design, is supplied and pressed in the ~irection of feed of the metal tubes, with a corresponding design of the 10 application head, an automatic advance of a hot-melt thread is possible, primarily on the outside. In particular with heating of the application head and~or with a hot-melt thread applied at a steeper angle to the longitudinal weld seam, this is drawn by at least one additional drive element and 15 pushed towards the application device.
A hot-melt thread pushed between the application head and the metal tubes approximately vertical to or even in the opposite direction to the advance of the metal tubes can be pressed 20 against the hot longitudinal weld seam with generation of friction heat, thus generating further heat.
In a special design form, the application device can he - designed such that the flexible hot-melt thread melted 25 between the application head and the hot longitudinal weld seam can where applicable be moved before application in a rotation movement to eliminate any air inclusions. Thus air ,i a inclusions which have a negative effact in the protective layer can be avoided.
In a first preferred variant o~ the material feed, the hot-5 melt thread is unwound from a storage roll and passed through the welding arm to the application device. Ths coatiny process need be interrupted without special measures only when the roll is finished and the hot-melt thread from the next roll must be fed in. The end of the hot-melt thread of 10 one roll can for example be bonded e.g. by the attachment of reserve loops to the start of the hot-melt thread of the second roll, so as to guarantee a completely continuous operation.
15 In another preferred variant, the flexible hot-melt thread is generated in-line from a fluidised mass and then it is continuously extruded or drawn for example. By the attachment of reserve loops and by bonding the ends, ~ully continuous operation is possible, even during any temporary 20 interruptions in the in-line production of hot-melt filament.
The process according to the invention with the essential feature of the thread-like supply of hot-melt mass through the welding arm to an application device has numerous 25 technical solutions which however all have as an object an inner or an inner and an outer sealing of the longitudinal weld seam of metal tubes.
2 ~ Q ~
In tha application of the protective strip(s), the longitudinal weld seam can be positioned not only on the kop ~ut also underneath or in any side position. This depends on 5 the position of the application devices, the arrangement of the transport device and for "in-line" welding machines, the alignment of the welding wire on the application devices. In practice, the hot-melt strip is u~ually applied on the top where the metal tubes are suspended on the transport device.
lO The metal tubes can be advanced further in axial direction simply by an upper conveyor belt or preferably by two side conveyor belts.
The hot-melt masses used according to the invention usually 15 ha~e a melting point in the range of lO0 to 300OC, including those resistant to foodstuffs. The application heads are if necessary controlled by sensors, brought to a corresponding temperature and held there by programmed control.
20 The width of the hot-melt strips applied or sprayed on differs according to the weld seam and in practice lies in a range of 3 to 20 mm. The hot-melt strips become hard immediately, with preferred layer thicknesses of lO to 150~1m, in particular 20 - 50~lm, and the tips created during welding 25 do not press through as can be the case with the lacquer coating process for example.
~ `
J I?l. ~
With reference to the device, the task is solved according to the inven-tion in that the welding arm ha~ at lea~t one integral supply line for the flexible hot-melt thread, and the application arm with at least one hollow chamber in the 5 area oE the coating has a melting head to apply the hot-~elt thread to the inside of the longitudinal weld seam. Special and more advanced forms of the device are the subject of corresponding dependent claim~.
10 The application arm is connected in a known manner at one end to the welding arm of the welding machine and at the other end is preferably supported to move freely in an axial direction.
15 The supply line for the hot-melt thread integrated into the welding arm corresponds to the service channel in known systems. These can be converted for operation according to the invention without problem. The same supply line can also be used for electrical lines or similar where the hot-melt 20 thread with a diameter of 2 - 6 mm for example allows. The electrical lines or similar can also be arranged in another supply line in the welding arm.
A large number of hot-melts are suitable for use according to 25 the invention, where foodstuff-resistant hot-melts are of particular interest, for example based on polyester or epoxy resinO
2~ ~7n~
In a preferred design form, the device according to the invention also comprises an outer second application head to apply a second flexible hot-melt thread on the outside 5 of the longitudinal seam. Like the inner first melt head, the outer can also be suitably heated in a known manner, e.g.
by induction, ohmic resistance, a gas flame or a radiator.
One application head, either the inner or the outer, is 10 designed such that the corresponding weld seam cover can be applied adjustable in the width or thickness by programmed control. The term "application" here comprises rolling, spreading or spraying on, where the application head comprises the corresponding known means for performance, for 15 example a spreader, a scraper or a nozzle.
The pulling or pushing force exerted by the advancing metal tube on the pressed hot-melt thread can be supported by a drive element with a rotating or reciprocating movement which 20 is driven electrically, pneumatically or hydraulically. With a feed of the flexible hot-melt thread vertical to or in the opposite direction to the advance movement of the metal tubes, this drive is essential, and the thread must not only be pulled but also pushed to the application point.
At least the inner first hot-melt thread can be passed through a flexible tube and protected by this. In the area of a drive el~ment, the flexible tube can also be opened so that for example the torque o a drawiny roller can be applied. This flexible tube can also be used for the supply, without compressed air, of pelletised or powdery hot-melt 5 substance which reaches the application head as a single-piece hot-melt thread and is melted.
The process according to the invention and the device for its performance have the advantage not previously attainable 10 industrially that a hot melt layer can be applied to the inside of a longitudinal weld seam of metal tubes adjacent to the welding wire. Therefore firstly the heat transferr~d to the metal tube during welding can now be used, and secondly the longitudinal weld seams of the metal pipes are still 15 accurately aligned. The invention also offers the possibility of applying a hot-melt protective layer to the longitudinal weld seam internally and externally. The resulting elimination of baking and drying ovens for lacquer and similar, due to the far lower requirements for 20 investment~ space and energy, offers the filler the possibility of producing his own cans to suit his production.
This in turn brings not only economic but also ecological advantages that bulky transport of cans is no longer required.
~, .
~ :1 Q 7 ~; 3 The invention is explained in more detail using the design examples shown in the drawing which are also subjects o~ the dependent claims. The diagrams show:
- Fig. 1: a partial cross-section through a metal tube in the area of the longitudinal weld seam - Fig. 2: a partially cut-away view of a device for continuous application of a hot-melt thread - Fig. 3: a detailed representation with external application of the hot-melt strip, and - Fig. 4: a part view in axial direction with offset conveyor belts.
A metal tube 10 partly shown in Fig. 1 has a longitudinal weld seam 12 which is covered on the inside with a longitudinal hot-melt strip 14 of polyesterO On the outside 20 runs a corresponding hot-melt strip 16.
In the device for continuous application of the hot-melt strips to cover the inside ~Fig. 2) and optionally also the outside of a longitudinal weld seam as in Fig. 3, the metal 25 tubes lying end to end have not been shown for the sake of clarity. On welding arm 18 of a standard welding machine, not shown, is arranged a welding wire 26 passing over a 2~ ~`i9 deflection roller 2~ in the area of face ~0. The welding arm 18 has for example a diameter of 60 mm and is particularly suitable for welding metal tubes with a diameter of 65 to 200 mm. The diam~ter of the metal tube can therefore be not only 5 slightly but also very much larger than that of the welding arm 1~. For smaller or larger metal tubes, a correspondingly dimensioned welding arm 18 could be used.
Coaxially connected with welding arm 18 is an application arm 10 22 which consists for example of a steel tube. The application arm 22 with the same longitudinal axis L as the welding arm 18 is attached by fixing means 30.
The metal tubes 10, not shown (Fig. 1), joined together on 15 welding arm 18, run in-line to the application arm 22 where they are advanced further by an endless conveyor belt 32 guided by two deflector rollers 34,36, one of which is the drive roller. The conveyor belt 32 has a magnetic support for the metal tubes and a variable speed drive. The 20 transport device 32,34,36 can be hinged up out of the way.
A hot-melt thread 28 is pressed by an application head 38 of an application device 40 against the longitudinal weld seam 12 (Fig. 1) of a metal tube, not shown in Fig. 2, which is in 25 turn held down by conveyor belt 32. Under the effect of the longitudinal weld seam still glowing faintly red and of the 23 ~r!~rt3 melting head 38, the hot-melt thread 28 mel-ts and thus forms a reqular protective layer.
The continuously melting hot-melt thread, squeezed between 5 the hold-down metal tube and the application head, is automatically pulled forward by the thrust of the advancing metal tuhe. The hot~melt thread 28 is also in this case passed over an additional drive element 42 which is arranged in the application arm ~8 and driven electrically. The hot-10 melt thread 28 is drawn through a supply line 44 in weldingarm 18 and passed over the rotating drive element 42 from where it is pushed between the metal tube and the application head 38.
15 Further details can be seen in the detailed representation in Fig. 3 extended hy the outer application.
The hot-melt thread 28 does not completely fill the supply line 44 integrated in the weldiny arm 18. Therefore 20 additional electrical lines 46 can also be passed through the supply line 44` to an electric motor 48 with gearing 49 for the drive element 42.
, The cold hot-melt thread 28 is passed throu~h the inner 25 chamber in the application arm 22 in the direction of the drive element 42 and is partly guided and protected by a flexible pipe 52.
7 ~
Above the metal tube is arranged an outer second application device 54 with a second application head 56. An outer second cold hot-melt thread 58 of the same chemical composition as 5 the inner first hot-melt thread 28 is passed between the second application head 56 and the outside of the longitudinal weld seam of the metal tube and there also melted to form an outer hot-melt layer 16 on the longitudinal weld seam 12.
With a device according to Fig. 3, a longitudinal weld-seam can be coated internally and externally at the same time.
Fig. 4 shows that the metal tubes 10 are moved by two 15 conveyor belts 32 drawn to them magnetically. The conveyor belts 32 are offset by an angle a of around goo to the longitudinal axis L with an approximately vertical median.
The upper longitudinal weld seam 12 is generated by welding wire 26 shown on the deflecting roller 24.
~ ~e~L cl~yQ~a on~tal ~ubes The invention relates to a process for continuous application of a protective layer to cover a longitudinal weld seam of 5 metal tubes on a welding machine with a welding arm, an application arm connected to the welding arm, removable means fQr the transport of the metal tubes lying and to end in an axial direction and an application device for the protective layer. The invention also relates to a process for the 10 performance and an application of the process.
Welding machines are known which have an application system fitted "in line" which applies a protective strip to the longitudinal weld seam of metal tubes, in particular 15 longitudinally welded tins and cans. In principle, these differ by the application of a lacquer and a powder which are processed in situ to give a seam-covering layer.
Depending on machine type, the lacquer is applied from above 20 or below, where the metal tube to be processed normally hangs from an application arm or for application in the lower area stands on a conveyor belt, and is transported in the longitudinal direction of the application arm.
;
25 The lacquer can be supplied without air at high pressure through tubes of small diameter to the spray nozzle, atomised with an air flow or in another variant applied with a wheel.
2 3 ~ ~ ~ O
~ 2 --The weld seam is covered with a wet lacquer, and the resulting dry layer is around lO ~lm thick but relatively porous in comparison with a white inner lacquer.
5 Furthermore, a dlsadvantage with the use of known lacyuer application processes is that the tips o~ the butt and matrix welded points are not covered with lacquer, as it flows off.
In other known application devices on welding machines, the 10 inner longitudinal weld seams of metal tubes are protected in that a powder strip is applied in even thickness and melted in situ. The rehardened layers are us-~ally around 30 - 60 ~m thick and are essentially pore-free.
15 All lacquers and powders known to the specialist in this application can be used.
'~
In particular ~or the cans used in the foodstuf~ industry, a clean sterilization-resistant inner cover of the weld seam lS
20 extremely important. The food-resistance requirement means ~ that the protective layer must also resist hard mechanical -~ stresses such as the application o~ beading or edging.
Tests for the application of sterilization-resistant "hot-25 melts", as thermoplastic adhesives are known for short, which also resist mechanical stress have previously failed in that ~ ,, ~ :~ n ~ ^ Q
they could not be applied with the technical means adapted to the conditions.
The inventor has therefore faced the problem of creating a 5 process of the type described above and a device ~or its performance which allows the use of hot-melt in a simple, economic and effective manner. All undesirable dif~usion processes to a filling, in particular food, should be prevented.
With regard to the process, the task is solved according to the invention in that a hot-melt mass is fed continuously through the welding arm as a flexible hot-melt thread, deflected in the application arm to the inside o~ the 15 longitudinal weld seam of the metal tube, pressed by the ` application device against the hot longitudinal weld seam, melted and spread homogeneously over its width. Special and more advanced design forms of the process are the subject of the dependent patent claims.
The term "hot-melt thread" comprises also cords, wires, strips, tapes, foils, films etc. and hot-melt masses which are very long in comparison with their cross-section. In a special design form, the term "hot-melt thread" also covers a 25 hot-melt piece or compact hot-melt powder without conveyor medium passed through a flexible guide tube to the application device. The term "in the application arm" also - -~7~ ~r3 cover~ the ~pace present where applicable between the welding arm and the application arm.
Simultaneously with the inner coating of the weld seam, a 5 second flexible also pre~erably cold hot-melt thread is passed continuously to the outside of the longitudinal weld ssam, pressed by a second application device against the hot longitudinal weld seam, melted and/or spread homogeneously over its width. This second hot-melt thread can have the 10 same chemical composition as the first applied internally.
The internal and external coating of a longitudinal weld seam with a hot-melt layer has the essential advantage that baking or drying ovens for lacquers with their high requirements for space and energy can be eliminated.
The arrangement of the weld arm and application arms with the coating device immediately behind each other has the further advantage that the longitudinal weld seams of the metal tubes ~passing through are still very hot at the application head, ;20 usually still glowing faintly red. In particular with a low layer thickness, these can give the metal tube enough inherent warmth to melt one or both hot-melt threads on contact and guarantee the required coating without the provision of further heat. In addition, the still hot weld 25 seam gives a far better adhesion of the protective layer.
With insufficient heat transfer through the hot longitudinal weld seam, in particular with greater layer thicknesses to be applied and/or coating on both sides, additiorlal heat is applied to one or both hot-melt threads in the area of the application device by the application head being heated, for example by inductive or resistance heating, a gas flame or a 5 radiator.
If a hot-melt thread, in the most common variant o~ the design, is supplied and pressed in the ~irection of feed of the metal tubes, with a corresponding design of the 10 application head, an automatic advance of a hot-melt thread is possible, primarily on the outside. In particular with heating of the application head and~or with a hot-melt thread applied at a steeper angle to the longitudinal weld seam, this is drawn by at least one additional drive element and 15 pushed towards the application device.
A hot-melt thread pushed between the application head and the metal tubes approximately vertical to or even in the opposite direction to the advance of the metal tubes can be pressed 20 against the hot longitudinal weld seam with generation of friction heat, thus generating further heat.
In a special design form, the application device can he - designed such that the flexible hot-melt thread melted 25 between the application head and the hot longitudinal weld seam can where applicable be moved before application in a rotation movement to eliminate any air inclusions. Thus air ,i a inclusions which have a negative effact in the protective layer can be avoided.
In a first preferred variant o~ the material feed, the hot-5 melt thread is unwound from a storage roll and passed through the welding arm to the application device. Ths coatiny process need be interrupted without special measures only when the roll is finished and the hot-melt thread from the next roll must be fed in. The end of the hot-melt thread of 10 one roll can for example be bonded e.g. by the attachment of reserve loops to the start of the hot-melt thread of the second roll, so as to guarantee a completely continuous operation.
15 In another preferred variant, the flexible hot-melt thread is generated in-line from a fluidised mass and then it is continuously extruded or drawn for example. By the attachment of reserve loops and by bonding the ends, ~ully continuous operation is possible, even during any temporary 20 interruptions in the in-line production of hot-melt filament.
The process according to the invention with the essential feature of the thread-like supply of hot-melt mass through the welding arm to an application device has numerous 25 technical solutions which however all have as an object an inner or an inner and an outer sealing of the longitudinal weld seam of metal tubes.
2 ~ Q ~
In tha application of the protective strip(s), the longitudinal weld seam can be positioned not only on the kop ~ut also underneath or in any side position. This depends on 5 the position of the application devices, the arrangement of the transport device and for "in-line" welding machines, the alignment of the welding wire on the application devices. In practice, the hot-melt strip is u~ually applied on the top where the metal tubes are suspended on the transport device.
lO The metal tubes can be advanced further in axial direction simply by an upper conveyor belt or preferably by two side conveyor belts.
The hot-melt masses used according to the invention usually 15 ha~e a melting point in the range of lO0 to 300OC, including those resistant to foodstuffs. The application heads are if necessary controlled by sensors, brought to a corresponding temperature and held there by programmed control.
20 The width of the hot-melt strips applied or sprayed on differs according to the weld seam and in practice lies in a range of 3 to 20 mm. The hot-melt strips become hard immediately, with preferred layer thicknesses of lO to 150~1m, in particular 20 - 50~lm, and the tips created during welding 25 do not press through as can be the case with the lacquer coating process for example.
~ `
J I?l. ~
With reference to the device, the task is solved according to the inven-tion in that the welding arm ha~ at lea~t one integral supply line for the flexible hot-melt thread, and the application arm with at least one hollow chamber in the 5 area oE the coating has a melting head to apply the hot-~elt thread to the inside of the longitudinal weld seam. Special and more advanced forms of the device are the subject of corresponding dependent claim~.
10 The application arm is connected in a known manner at one end to the welding arm of the welding machine and at the other end is preferably supported to move freely in an axial direction.
15 The supply line for the hot-melt thread integrated into the welding arm corresponds to the service channel in known systems. These can be converted for operation according to the invention without problem. The same supply line can also be used for electrical lines or similar where the hot-melt 20 thread with a diameter of 2 - 6 mm for example allows. The electrical lines or similar can also be arranged in another supply line in the welding arm.
A large number of hot-melts are suitable for use according to 25 the invention, where foodstuff-resistant hot-melts are of particular interest, for example based on polyester or epoxy resinO
2~ ~7n~
In a preferred design form, the device according to the invention also comprises an outer second application head to apply a second flexible hot-melt thread on the outside 5 of the longitudinal seam. Like the inner first melt head, the outer can also be suitably heated in a known manner, e.g.
by induction, ohmic resistance, a gas flame or a radiator.
One application head, either the inner or the outer, is 10 designed such that the corresponding weld seam cover can be applied adjustable in the width or thickness by programmed control. The term "application" here comprises rolling, spreading or spraying on, where the application head comprises the corresponding known means for performance, for 15 example a spreader, a scraper or a nozzle.
The pulling or pushing force exerted by the advancing metal tube on the pressed hot-melt thread can be supported by a drive element with a rotating or reciprocating movement which 20 is driven electrically, pneumatically or hydraulically. With a feed of the flexible hot-melt thread vertical to or in the opposite direction to the advance movement of the metal tubes, this drive is essential, and the thread must not only be pulled but also pushed to the application point.
At least the inner first hot-melt thread can be passed through a flexible tube and protected by this. In the area of a drive el~ment, the flexible tube can also be opened so that for example the torque o a drawiny roller can be applied. This flexible tube can also be used for the supply, without compressed air, of pelletised or powdery hot-melt 5 substance which reaches the application head as a single-piece hot-melt thread and is melted.
The process according to the invention and the device for its performance have the advantage not previously attainable 10 industrially that a hot melt layer can be applied to the inside of a longitudinal weld seam of metal tubes adjacent to the welding wire. Therefore firstly the heat transferr~d to the metal tube during welding can now be used, and secondly the longitudinal weld seams of the metal pipes are still 15 accurately aligned. The invention also offers the possibility of applying a hot-melt protective layer to the longitudinal weld seam internally and externally. The resulting elimination of baking and drying ovens for lacquer and similar, due to the far lower requirements for 20 investment~ space and energy, offers the filler the possibility of producing his own cans to suit his production.
This in turn brings not only economic but also ecological advantages that bulky transport of cans is no longer required.
~, .
~ :1 Q 7 ~; 3 The invention is explained in more detail using the design examples shown in the drawing which are also subjects o~ the dependent claims. The diagrams show:
- Fig. 1: a partial cross-section through a metal tube in the area of the longitudinal weld seam - Fig. 2: a partially cut-away view of a device for continuous application of a hot-melt thread - Fig. 3: a detailed representation with external application of the hot-melt strip, and - Fig. 4: a part view in axial direction with offset conveyor belts.
A metal tube 10 partly shown in Fig. 1 has a longitudinal weld seam 12 which is covered on the inside with a longitudinal hot-melt strip 14 of polyesterO On the outside 20 runs a corresponding hot-melt strip 16.
In the device for continuous application of the hot-melt strips to cover the inside ~Fig. 2) and optionally also the outside of a longitudinal weld seam as in Fig. 3, the metal 25 tubes lying end to end have not been shown for the sake of clarity. On welding arm 18 of a standard welding machine, not shown, is arranged a welding wire 26 passing over a 2~ ~`i9 deflection roller 2~ in the area of face ~0. The welding arm 18 has for example a diameter of 60 mm and is particularly suitable for welding metal tubes with a diameter of 65 to 200 mm. The diam~ter of the metal tube can therefore be not only 5 slightly but also very much larger than that of the welding arm 1~. For smaller or larger metal tubes, a correspondingly dimensioned welding arm 18 could be used.
Coaxially connected with welding arm 18 is an application arm 10 22 which consists for example of a steel tube. The application arm 22 with the same longitudinal axis L as the welding arm 18 is attached by fixing means 30.
The metal tubes 10, not shown (Fig. 1), joined together on 15 welding arm 18, run in-line to the application arm 22 where they are advanced further by an endless conveyor belt 32 guided by two deflector rollers 34,36, one of which is the drive roller. The conveyor belt 32 has a magnetic support for the metal tubes and a variable speed drive. The 20 transport device 32,34,36 can be hinged up out of the way.
A hot-melt thread 28 is pressed by an application head 38 of an application device 40 against the longitudinal weld seam 12 (Fig. 1) of a metal tube, not shown in Fig. 2, which is in 25 turn held down by conveyor belt 32. Under the effect of the longitudinal weld seam still glowing faintly red and of the 23 ~r!~rt3 melting head 38, the hot-melt thread 28 mel-ts and thus forms a reqular protective layer.
The continuously melting hot-melt thread, squeezed between 5 the hold-down metal tube and the application head, is automatically pulled forward by the thrust of the advancing metal tuhe. The hot~melt thread 28 is also in this case passed over an additional drive element 42 which is arranged in the application arm ~8 and driven electrically. The hot-10 melt thread 28 is drawn through a supply line 44 in weldingarm 18 and passed over the rotating drive element 42 from where it is pushed between the metal tube and the application head 38.
15 Further details can be seen in the detailed representation in Fig. 3 extended hy the outer application.
The hot-melt thread 28 does not completely fill the supply line 44 integrated in the weldiny arm 18. Therefore 20 additional electrical lines 46 can also be passed through the supply line 44` to an electric motor 48 with gearing 49 for the drive element 42.
, The cold hot-melt thread 28 is passed throu~h the inner 25 chamber in the application arm 22 in the direction of the drive element 42 and is partly guided and protected by a flexible pipe 52.
7 ~
Above the metal tube is arranged an outer second application device 54 with a second application head 56. An outer second cold hot-melt thread 58 of the same chemical composition as 5 the inner first hot-melt thread 28 is passed between the second application head 56 and the outside of the longitudinal weld seam of the metal tube and there also melted to form an outer hot-melt layer 16 on the longitudinal weld seam 12.
With a device according to Fig. 3, a longitudinal weld-seam can be coated internally and externally at the same time.
Fig. 4 shows that the metal tubes 10 are moved by two 15 conveyor belts 32 drawn to them magnetically. The conveyor belts 32 are offset by an angle a of around goo to the longitudinal axis L with an approximately vertical median.
The upper longitudinal weld seam 12 is generated by welding wire 26 shown on the deflecting roller 24.
Claims (14)
1. Process for continuous application of a protective layer (14) to cover a longitudinal weld seam (12) of metal tubes (10) on a welding machine with a welding arm (18), an application arm (22) connected to the welding arm (18), removable means (32,34,36) for the transport of the metal tubes (10) lying end to end in an axial direction (L) and an application device (40) for the protective layer (14), characterised in that a hot-melt mass is passed continuously through the welding arm (18) as a flexible hot-melt thread (28), deflected in the application arm (22) to the inside of the longitudinal weld seam (12) of the metal tubes (10), pressed by the application device (40) against the hot longitudinal weld seam (12), melted and spread homogenously over its width.
2. Process according to claim 1 characterised in that at the same time a second flexible hot-melt thread (58), preferably of the same chemical composition as the first, is passed continuously to the outside of the longitudinal weld seam (12), pressed by a second outer application device (54) against the hot longitudinal weld seam (12), melted and spread homogenously over its width.
3. Process according to claim 1 or 2, characterised in that with insufficient transfer of heat through the hot longitudinal weld seam (12), additional heat is supplied to one flexible hot-melt thread (28,58) in the area of the application device (40,54), preferably by inductive or resistance heating, a gas flame or a radiator.
4. Process according to any of claims 1-3, characterised in that a flexible hot-melt thread (28,58) is pulled by at least one additional drive element and pushed to the application device (40,54).
5. Process according to claim 4 characterised in that a hot-melt thread (28,58) is pushed to the application device (40,54) approximately vertically or in the opposite direction to the advance of the metal tubes (10) and pressed against the hot longitudinal weld seam (12) with generation of friction heat.
6. Process according to any of claims 1-5, characterised in that the flexible hot-melt thread (28,58) melted between the application device (40,54) and the hot longitudinal weld seam (12) is moved before application in a rotation movement to eliminate air inclusions.
7. Process according to any of claims 1-6, characterised in that the flexible hot-melt thread (28,58) is uncoiled in-line or generated from a fluidised phase.
8. Device for the performance of the process according to any of claims 1-7, characterised in that the welding arm (18) has at least one integrated supply line (44) for the flexible hot-melt thread (28), and the application arm (22) with a hollow chamber at least in the area of the coating has an application device (40) with a melt head (38) for applying the hot-melt thread (28) on the inside of the longitudinal weld seam (12).
9. Device according to claim 8 characterised in that it has a preferably heatable outer second application device (54) with an outer application head (56) for applying the second hot-melt thread (58) on the outside of the longitudinal weld seam (12).
10. Device according to claim 8 or 9, characterised in that the melt head (38,56) has means for applying, rolling, spreading or spraying the melted hot-melt mass onto the longitudinal weld seam (12).
11. Device according to any of claims 8-10, characterised in that at least the inner flexible hot-melt thread (28,58) engages with a drive element (42) which has a rotating or reciprocating movement.
12. Device according to any of claims 8-11, characterised in that at least the first flexible hot-melt thread (28,58) is at least partly passed through and protected by a flexible pipe (52), where this flexible pipe (52) is also open over part of its periphery in the area of a drive element (42).
13. Device according to any of claims 8-12, characterised in that in the area of the application arm (22) two conveyor belts (32) for the metal tubes (10) are arranged, which are offset in relation to the longitudinal axis (L), preferably by an angle (.alpha.) of around 90° with an approximately vertical median.
14. Application of the process according to any of claims 1-7 to apply a sterilisation-resistant hot-melt strip (14,16) to the inside or inside and outside of the longitudinal weld seam (12) of a tin casing (10).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH302392 | 1992-09-28 | ||
| CH03023/92 | 1992-09-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2107050A1 true CA2107050A1 (en) | 1994-03-29 |
Family
ID=4246904
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2107050 Abandoned CA2107050A1 (en) | 1992-09-28 | 1993-09-27 | Weld seam covering on metal tubes |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0591107A1 (en) |
| JP (1) | JPH06218315A (en) |
| AU (1) | AU4759593A (en) |
| BR (1) | BR9303942A (en) |
| CA (1) | CA2107050A1 (en) |
| NO (1) | NO933404L (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB9413754D0 (en) * | 1994-07-07 | 1994-08-24 | Boc Group Plc | Liquid dispensing apparatus |
| WO1997032685A1 (en) * | 1996-03-06 | 1997-09-12 | Frey Ernst M | Internal weld protection of sheet metal pipes |
| DE102006055462A1 (en) * | 2006-11-24 | 2008-05-29 | Gebhardt-Stahl Gmbh | Production of a hollow body made from a metal strip material for forming fence posts comprises contacting the longitudinal edges of the metal strip material and connecting together using laser welding |
| CN106930707B (en) * | 2017-02-22 | 2019-01-18 | 中国石油大学(华东) | Hollow carbon fiber coiled rod connector and its automatic welding device |
| RU2716789C1 (en) * | 2019-06-20 | 2020-03-16 | Александр Георгиевич Чуйко | Device for robotised internal insulation of pipeline welded joint |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2941067A (en) * | 1958-05-07 | 1960-06-14 | R L Kitrell | Welding apparatus and flexible dam for use therewith |
| FR2455945A1 (en) * | 1979-05-11 | 1980-12-05 | Framatome Sa | DEVICE FOR SUPPLYING LONG PRODUCT OF COVERING TO AN INTERNAL PIPING COATING SYSTEM |
| FR2574012B1 (en) * | 1984-12-05 | 1987-01-30 | Ballan De Ballensee Pierre | DEVICE FOR APPLYING WELDING SUPPORTS TO JOINTS OF METAL SHEETS BY SINGLE-SIDED ELECTRIC ARC WELDING |
| SU1563912A1 (en) * | 1988-07-19 | 1990-05-15 | Киевский институт автоматики им.ХХУ съезда КПСС | Method of protecting weld back side |
| CH684524A5 (en) * | 1991-12-17 | 1994-10-14 | Ernst M Frey | Weld on the inside cover of sheet metal pipes. |
-
1993
- 1993-09-22 EP EP93810671A patent/EP0591107A1/en not_active Withdrawn
- 1993-09-24 NO NO933404A patent/NO933404L/en unknown
- 1993-09-27 CA CA 2107050 patent/CA2107050A1/en not_active Abandoned
- 1993-09-27 AU AU47595/93A patent/AU4759593A/en not_active Abandoned
- 1993-09-27 JP JP26289893A patent/JPH06218315A/en active Pending
- 1993-09-28 BR BR9303942A patent/BR9303942A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| JPH06218315A (en) | 1994-08-09 |
| NO933404L (en) | 1994-03-29 |
| EP0591107A1 (en) | 1994-04-06 |
| BR9303942A (en) | 1994-05-17 |
| AU4759593A (en) | 1994-04-14 |
| NO933404D0 (en) | 1993-09-24 |
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