Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
  • B05D7/22—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to internal surfaces, e.g. of tubes
  • B05D7/222—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to internal surfaces, e.g. of tubes of pipes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05C5/00—Apparatus in which liquid or other fluent material is projected, poured or allowed to flow on to the surface of the work
  • B05C5/001—Apparatus in which liquid or other fluent material is projected, poured or allowed to flow on to the surface of the work incorporating means for heating or cooling the liquid or other fluent material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D1/00—Processes for applying liquids or other fluent materials
  • B05D1/26—Processes for applying liquids or other fluent materials performed by applying the liquid or other fluent material from an outlet device in contact with, or almost in contact with, the surface
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
  • B05D7/14—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to metal, e.g. car bodies
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
  • B05D7/22—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to internal surfaces, e.g. of tubes
  • B05D7/227—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to internal surfaces, e.g. of tubes of containers, cans or the like

Definitions

• the invention relates to a method and apparatus for applying a continuous protective film of a thermoplastic material to the inside of the longitudinal weld seam of sheet metal tubes, which are fed to each other practically frontally lying on the welding arm of a welding machine and a subsequent application arm, wherein the continuously fed thermoplastic in the Preheated area of the order arm, melted and passed to the homogenous liquefaction to an applicator, and the liquid plastic metered over at least the entire width of the weld is applied.
• Welding machines are known which have an "in-line" application system for a thermoplastic material which applies a protective film to the longitudinal weld seam of sheet metal tubes, in particular longitudinally welded can and can shells a powder, which are processed in situ to a seam covering layer.
• the application of a protective film is carried out, depending on the machine type, top or bottom, wherein the metal sheet to be treated when applying the protective film in the upper region on a request arm hanging, while applying in the lower area while standing on a conveyor belt, transported in the longitudinal direction of the order.
• the generic EP 0885085 B1 allows economical, accurate application of an inside weld of tin cans.
• an applicator nozzle and a follower roller are mounted, wherein the applicator nozzle is mounted more projecting by the adjustable thickness of the applied thermoplastic layer than the follower roller, which serves as a spacer.
• This role can also be replaced by a carriage or a shoe.
• the continuous melting of a supplied plastic wire on the one hand and the design of the application nozzle on the other allow an economical process of high quality and great reliability. Even the strict regulations of the food regulation are fulfilled.
• the inventor has set himself the task of providing a method and a device of the type mentioned, which allows a faster and more simplified application to the inside longitudinal weld seam of sheet metal tubes without increasing the melting temperature of the thermoplastic material, without a loss of quality occurs.
• the object according to the invention is achieved in that the preheated thermoplastic material in a liquefaction zone with metal contact along a first contact surface by at least one metallic fuse link back and after the at least partial liquefaction along a larger second contact surface is returned.
• thermoplastic which forms the weld seam protection must necessarily have good adhesive properties and is therefore also referred to as "hot melt adhesive” or “hotmelt.”
• hot melt adhesive or hotmelt
• Suitable thermoplastics include, first and foremost, polyesters which are relatively expensive, yet resistant and, above all, food safe.For nonfood grade industrial cans, polyurethanes or, in some cases, even curable epoxy resins can also be used
• thermoplastic material is guided in the form of a wire through the welding arm in the application, first preheated in a preheating to a temperature of preferably about half the melting temperature and then in the liquefaction zone introduced with little play in a running in the same direction channel of the metallic fuse link.
• the pushed with metal contact along a first contact surface in this channel plastic wire is initially solid and then melts continuously.
• the molten plastic flows at least partially melted into a frontal recess of the fuse link, is redirected there and then along at least a larger second contact surface, formed by axial longitudinal channels, brought back to the inlet side of the plastic wire and redirected to a leading homogenizing in the direction of the applicator zone.
• This zone is also heatable and preferably equipped with a metallic Homogenmaschineshus, which structurally corresponds approximately structurally about the use of melt.
• the melting and homogenizing insert are integrally formed, that is, machined or eroded out of a common, in particular cylindrically formed, metal block.
• the channels and applicator are preferably dimensioned and matched to the feed of the plastic thread that the liquefied plastic flows out metered, and can build up pressure in the melting apparatus.
• wire also includes threads, cords and the like. Compared to the cross section long masses.
• the plastic wire is heated, for example, to 140 to 160 0 C and pushed through a sealed opening in the channel of the liquefaction zone, where the temperature is increased depending on the material to a range of, for example, about 220 to 280 0 C.
• the preheating zone has the advantage, among other things, that no heat can flow back when the machine is turned off and the plastic wire can melt outside the apparatus.
• the preheating zone expediently remains cold for the time being, this is switched on for about 10 minutes after the heating cartridge for liquefying.
• thermoplastic material can be added not only in wire form, but also in other suitable form, for example in powder or granular form.
• a 10 to 150 .mu.m, in particular 20 to 50 microns thick protective film is applied, which is suitably 3 to 30 mm wide depending on the formation of the weld and use of the sheet metal tubes.
• the thickness of the protective film over the entire width is constant or in the middle, just above the weld, where usually an increased protection is desired, applied slightly thicker.
• the sheet metal tubes with the internally coated weld seam can be guided in-line through a heating zone after the coating.
• the applied protective film is further homogenized. This is particularly necessary when a relatively hard meltable epoxy resin is used, here a longer heat zone than usual is necessary.
• Another major advantage of using a doctor blade is the massively increased throughput speed of the sheet metal tubes, which can be significantly increased without reducing the quality of the protective film.
• a doctor blade throughput speeds of up to about 90 m / min possible, optimally they are in the range of 60 to 80 m / min.
• the optimal throughput speeds are around 30 to 40 m / min.
• the invention according to a first variant is achieved in that in the liquefaction zone, a metallic fuse link with at least one heating cartridge to a longitudinally extending supply channel for the preheated thermoplastic as the first contact surface, at least one return passage of a larger second contact surface for liquefied thermoplastic plastic and a front-side communicating recess for diverting the supply channel to the return ducts is arranged.
• a metallic, in the application direction of the liquefied thermoplastic plastic Kunststoffflosse- NEN homogenization insert is arranged, which expediently structurally substantially corresponds to the use of melt.
• the melt insert and the homogenization insert can in particular be designed as cylindrical individual elements or worked parallel from a metallic insert.
• the supply channel of the fuse link is cylindrical, coaxial with the in practice likewise cylindrically shaped fuse insert itself.
• thermoplastic material When leaving the feed channel of the thermoplastic material is already at least partially liquefied or at least pasty, which allows a deflection in the return ducts.
• These are expediently partially open in the longitudinal direction against the supply channel and extend outwards, which corresponds with respect to the cross section of the shape of a rosette.
• the geometric shape of the cross sections of the return channels is only of secondary importance, it is essential that the second contact surface of the metal to the returning liquefied plastic is as large as possible, preferably at least twice as large as the first contact surface of the feed channel.
• the heat transfer in the feed channel it has proved to be advantageous to taper this in the feed direction, with respect to the cross-sectional area to about 10%.
• the heat transfer from the metal to the plastic can also be optimally carried out during the transition from the solid to the liquid form.
• the object of the invention with respect to the device is achieved in that the applicator is in the form of a doctor blade, which has a reservoir for the liquefied thermoplastic and a frontal, extending transversely to the device comb for stripping excess entrained plastic.
• a squeegee basically allows a much higher throughput speed of the sheet metal tubes than an application nozzle.
• the inner weld seam surface of the sheet metal pipes is pulled or pushed over the surface of the reservoir of liquid, thermoplastic plastic and takes by adhesive forces liquefied plastic. An excess amount of plastic is stripped off the squeegee and retained in the reservoir.
• the comb of the doctor blade in the longitudinal center region has a recess, which corresponds in particular to the width of the welded seam of the sheet metal tubes. This ensures that a thicker protective film is applied in the region of the weld seam than in the edge region.
• thermoplastic material namely the formation of a metallic fusible body and a doctor blade
• the optimized melting of the thermoplastic material and the optimal design of the application device which are already advantageous separately, leads to a far greater than expected combination effect with respect to the application speed and the quality of the protective film.
• FIG. 1 is a block diagram of the area of the welding arm and of the
• FIG. 2 shows a melting apparatus with a preheating, liquefaction and homogenizing zone
• FIG. 4 shows a cross section through a metallic homogenizing insert
• FIG. 5 shows an exploded, perspective view of a combined one-piece melting and homogenizing insert with a doctor blade
• FIG. 6 shows a fusible insert with a frontal recess
• FIGS. 5 and 6 show a perspective view of a ready-to-use insert according to FIGS. 5 and 6,
• FIG. 9 shows a squeegee in view
• FIG. 11 shows an enlargement of the region A according to FIG. 10.
• the sheet metal tubes 10 in the present case steel tubes, there is an endless conveyor belt 22, which is tensioned and driven by a deflection roller 24.
• the metal tubes 10 are transported in the direction of the arrow 26 and passed through a subsequent, not shown, heat zone W.
• the plastic wire 28 having a diameter in the range of about 2 to 4 mm is in the direction indicated by the arrow 34 feed direction via a preheater 36 in a melting apparatus 38th encountered.
• the melting apparatus 38 is as a whole in order the suspension 40 pivotable.
• a pivoting movement delimiting slot 42 is penetrated by a limiting bolt 43 for the melting apparatus 38.
• An application nozzle 44 for applying the protective film 20 and a follower roller 46 as a spacer are attached to the apparatus frame of the melting apparatus 38.
• the melting apparatus 38 is pressed over the follower roller 46 and the distance a (FIG. 2) of the outflow opening of the application nozzle 44 is kept constant.
• FIG. 2 shows the material flow 48 shown by arrows in the region of the melting apparatus 38 and illustrates the heating cartridges 50, 52 used in the region of the preheating zone 36, a liquefaction zone 54 and a homogenization zone 60.
• the plastic wire 28 is heated in the preheating zone 36 to about 150 ° C.
• the preheated plastic wire 28 enters the fusing apparatus 38 through a sealed opening 56 and is pushed through a feed channel 64 (FIG. 3) of a metallic fusible insert 58.
• plastic wire 28 of at least partially liquefied plastic in a front side of the fuse link 58 arranged closed recess 59 is deflected and recirculated through the inlet channel 64 surrounding surrounding return channels 66 (Fig. 3), which is indicated by two arrows. Then, the liquefied mass is deflected again and pushed into an overhead homogenization zone 61 with a metallic homogenization insert 60, where finally takes place an extremely homogeneous liquefaction of the thermoplastic material.
• this homogeneously liquefied mass passes over a support channel 62 to the application nozzle 44, a slot die with respect to the supply of application material, ie the advance of the plastic wire 28, large outflow opening, which prevents pressure build-up in the melting apparatus 38.
• This outflow opening of the application nozzle 44 is arranged less high by the distance a than the follower roller 46.
• the application nozzle 44 is replaced by a doctor blade 82 (FIG. 5) shown below.
• both the supply channel 64 and the return channels 66 are heated by external heating cartridges, which may also be heating sleeves.
• the melting apparatus 38 arranged in the application arm 18 can be pivoted. According to embodiments not shown, the pivot axis may also be arranged in the welding arm 12 (FIG. 1).
• Fig. 3 is a cross section through the fuse link 58 of Fig. 2 drawn.
• the plastic wire 28 which is guided in a metal-contact-coaxial feed channel 64 coaxial with the melt insert 58, is already partly melted or doughy. From the supply channel 64 extend in the radial direction longitudinal return channels 66, which have about an inner tube of the same diameter about three times larger surface and thereby have a correspondingly increased heat transfer thanks to the increased metal contact.
• the homogenization insert 60 shown in cross-section in FIG. 4 has longitudinal channels 64, 66 comparable to FIG. 3, which are likewise produced by erosion.
• the central longitudinal channel 64 of the homogenizing insert 60 has a substantially smaller diameter than that of the melting insert 58.
• the melting apparatus 38 shown in Fig. 5 shows in a substantially cylindrically shaped metal block 68 with an eroded liquefaction zone 54 and a homogenization zone 61.
• With the metal block 68 is a substantially disc-shaped headpiece 74 which is sealingly screwed onto the end face 76 of the metal block 68.
• Concealed recesses in the header 74 allow the molten plastic to flow back into the return passages 66 of the melt insert 58 and to transfer the homogenized liquid plastic mass from the homogenizing zone 61 to an exit slot 78 in a flattened surface 80 of the header 74.
• a doctor blade 82 can be screwed with its flat side onto this flattened lateral surface 80 in a sealing manner.
• This doctor blade 82 has a recess for forming a reservoir 84 of liquefied thermoplastic material, which flows in metered manner out of the outlet slot 78.
• this reservoir 84 is delimited by a comb 86 running perpendicular to the conveying direction, which strips off excess coating material.
• the metal block 68 has, in the direction of the invisible end face 92, two diagonally opposite recesses 88 for fastening holding struts 90 (FIG. 7).
• FIG. 6 shows a perspective view of the metal block 68 according to FIG. 5, viewed in the direction of the other end side 92.
• a front-side recess 94 connects the two rosette-shaped liquefaction zone 54 and homogenization zone 61.
• the plastic wire 28, not shown, is pushed into the central supply channel 64 of the liquefaction zone 54.
• the liquefied plastic exits via the rosette-shaped return channels 66 on the end face 92.
• the supply channel 64 and the return channels 66 are communicatively connected to each other. Via the recess 94, the liquefied plastic enters the homogenization zone 61 and is guided to the end face 76.
• FIG. 7 shows a melting apparatus 38 which is fastened and screwed by way of two holding struts 90 and having a preheater 36, a metal block 68 with the invisible liquefaction and homogenization zone and a bar. 82 with the reservoir 84 and the comb 86. The already mentioned holding struts 90 are inserted.
• FIG. 8 shows the outflow opening 96 of an application nozzle 44, a slot die.
• This outflow opening 96 is substantially elongated.
• the two opposite longitudinal walls of the application nozzle 44 are formed recessed in the central region, in other words, the material of the sidewalls thickening in the direction away from the outflow opening 96 is removed.
• the protective film 20 FIG. 10
• substantially more coating material flows out in the middle region of the nozzle.
• the recess 98 in the longitudinal walls of the nozzle may in principle be of any shape.
• the reinforcement of the protective film in the central region is the greater, the more material of the side walls is removed.
• a doctor blade 82 shown in FIG. 9 has a comb 86 with a longitudinal central recess 98, the effects are the same as in FIG. 8, the center of the protective film 20 is thickened.
• a sheet metal tube 10 is shown with a longitudinal weld 16, which is covered on the inside 100 with a protective film 20.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Wood Science & Technology (AREA)
• Lining Or Joining Of Plastics Or The Like (AREA)
• Coating Apparatus (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Rigid Containers With Two Or More Constituent Elements (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=39536371

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Country Status (4)

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• 2008
  • 2008-01-10 EP EP08700518A patent/EP2111307A2/de not_active Withdrawn
  • 2008-01-10 US US12/522,865 patent/US20100055309A1/en not_active Abandoned
  • 2008-01-10 WO PCT/CH2008/000013 patent/WO2008083510A2/de active Application Filing
  • 2008-01-10 CN CN200880007826A patent/CN101668595A/zh active Pending

Non-Patent Citations (1)

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