EP0603456B1 - Process, apparatus and coating material for coating can seams - Google Patents

Abstract

The invention makes it possible, in the case of a system (2) for coating can bodies, to make the space-consuming secondary treatment section unnecessary according to the state of the art, by use of a coating material which hardens quickly. Furthermore, the can body coating system (2) is itself considerably simplified in that the coating material is introduced untreated, in its basic form, until shortly before it reaches the preparation unit (41), i.e. it is not liquefied to make it suitable for coating until it reaches the said preparation unit (41). <IMAGE>

Description

The present invention relates to a method and an apparatus the steps indicated in the preamble of claim 1 and the features specified in the preamble of claims 5. A such a method and such an apparatus are known from the US-A-3 077 171.

Metal sheets are welded together to form individual pieces with different alloy and / or e.g. of different thicknesses new board to form which sections with different Has material properties. Will such a new, compound The sheet of metal then drawn from animals creates a spatial one Structure with (due to the different material properties) predetermined, changing properties across the dimension. In this way e.g. Beams manufactured in the automotive industry, which show defined properties in the event of a crash and So the basis for the desired training are Crumple zone.

Car tanks are e.g. from deep-drawn, superimposed Halves formed by welding along the edge areas. Today it is foreseeable that the weld seams will no longer be in one Level, but to complete the spatial conditions during installation to be able to use, will be three-dimensional.

Other metal parts are known from the prior art Founders welded together or to meet new needs to satisfy.

All these examples have in common that after the welding process, especially by roller seam welding, the weld seam possibly protected with slag, but otherwise completely raw, unprotected and therefore susceptible to corrosion. Will not be one provided the actual coating, one usually helps with brushing the freshly made weld seam so that the To remove slag and oil it.

Accordingly, it is an object of the present invention to provide a process and to create a device with which the weld seams coated with reasonable effort, thus be protected can.

Where below for clarity of can coating lines or the coating of weld seams of can bodies this is done to relieve the description. The However, the invention is not to be applied with regard to Limited coating of can welds.

Metal sheets, which are intended to metal containers, such as for example metal cans or food cans, processed to are first coated on that side or painted, which is intended to the interior of the container to build. These metal sheets are then used, for example bent or folded to form the container. The respective End edges of the bent or folded metal sheets are put together and for example by means of a can welding device welded close together, but the existing coating destroyed by the melting process and is removed, so that the weld seam is again uncovered. This makes the weld seam susceptible to corrosion, which is why it subsequently to the welding process using suitable coating agents is to be covered or coated.

Continuous can seam coating systems, e.g. downstream a welding device on a welding arm are known. Here is on the same machining arm in the machining direction A coating system arranged downstream of the welding head, by means of which the can seam by applying, for example, one Wet paint or powder coated.

These coating systems must be designed, the freshly welded ones Can frames with an average speed of 50 Meters per minute and a high speed of 100 meters per Minute to be able to carry on. For the immediately above Future is a high speed area of 130 meters each Expect minute, even higher speeds are already emerging specifically. This means that every second of treatment time the coating system for coating the can seam must be 1 to 2 meters or more in length.

US-A-3 077 171 describes a method and an apparatus for coating weld seams described on sheet metal parts such as can frames, in which a band or a layer of synthetic resin is applied to the weld seam. The layer has a thickness of at least one mil and preferably three mils, with approximately 10 mils being considered the upper limit for the thickness becomes. The layer is applied with the help of a preformed film or tape a roll is pressed onto the weld seam. The layer hardens by exposure from heat, either from the still hot weld seam or from an additional burner. The disadvantage, however, is that a complex support and control device for the pressure roller is required. Another disadvantage is that with the known device a continuous Operation is not possible because after emptying a cylinder a piston is withdrawn and the Cylinder must be refilled before an extrusion process can continue.

EP-A-0 062 965 describes a device for coating the seams of can bodies Wet paint described. A wet paint is placed in a circulation device above room temperature held and sprayed over spray arrangements on the inner seams of the can body, where it is solidified and hardened at room temperature. Only coating materials can be used with this device like wet paint that is sprayable, taking care that the coating materials do not come to a standstill and already harden in the spray device, what is conceivable in the event of a business interruption.

From WO-A-89/06165 a method is known, in which a coating powder plastic Application device supplied and sprayed in dry form on the can seam using compressed air becomes. The substrate to which the powder is applied is previously at the melting temperature of the coating powder plastic has been brought. It is further provided that in a line conveyor section the coating powder plastic is preheated or that a microwave generator is provided is.

It is true that the measures described can be used to adequately melt the Shorten the required post-treatment distance for coating powder plastic, but do so additional equipment is required.

From US-A-4 361 113 is another example of known the use of wet paint. One in the lower area in a paint bath roller is in the upper Run over the area of the can frame at the seam so that the varnish picked up and carried by the roll at the bottom is deposited on the seam of the can. The problems that arise with this procedure can be done with some equipment Effort to be solved; in any case, the space required for that Apply relatively modestly. In contrast, the following needs Drying stretch a considerable amount of space because of the fresh applied wet paint dried when passing through a heating section must become. It is possible to apply the wet paint within approx. 15 Drying enough seconds, but what a post-treatment route of a length of 15 to 30 meters. Also fall considerable amounts of solvents, which are environmentally harmful are and must be disposed of.

Similar conditions arise when using powder as coating material. The powder is charged statically and applied to the can seam at the coating location. Also here, as with wet paint coating, is quite a considerable one equipment expenditure inevitable. The powder must be before and during of the order should be kept cool so that it does not clump together. Further the static charge must be such that the correct one The powder is distributed over the seam of the can. The whole process needs a humid atmosphere due to the specific Properties of the powder. There will also be a post-treatment line of a good 20 to 30 meters because the cold applied Powder in the aftertreatment line above his Melting point must be heated so that it flows away can. Powder coatings also have the disadvantage that they turn out to be relatively thick, which is the case with the enormously high production Pieces of cans can be crucial. already a two-shift can manufacturing line with 500 Doses per minute well over half a million doses per day.

Overall, it follows that today's can seam coating systems the disadvantage inherent in that it is particularly at the job site are expensive in terms of equipment and one extraordinary long aftertreatment line need what in a manufacturing line is undesirable. In addition, harmful solvents either fall in considerable quantities, especially when Powder a lot of raw material is consumed.

The object of the invention is a method and an apparatus in the preamble of the claims 1 or 5 specified type so that a thin seam coating in a continuous Operation in a simple and fail-safe manner is possible.

This object is achieved according to the invention by the claims 1 and 5 Steps or features solved.

According to the invention, a thermoplastic wire is used for the coating, which is easy to use can be transported close to the point of inquiry. At the request point, it turns into a flowable one Condition brought and then applied with the help of an application agent. This makes it easy to Way that the weld seam with a precisely positioned, film-thin coating is covered.

The coating material supplied according to the invention in the form of wire can be easily Handle in a manner without the risk of interrupting the coating material supply and without a long aftertreatment distance after the application of the coating material is required.

According to the coating material in an insensitive Basic form brought to the job site so that the outlay on equipment at the coating site can be considerably simplified.

If a hotmelt material or hot melt adhesive is used for the coating used success results beyond the task at hand, that there is no need for a post-treatment route. Such hot melt materials are also known under the name Hot melt or hot melt adhesive. You are special known from the adhesive technology, where they are used for gluing or joining two parts can be used. Especially in the automotive industry as well as in the textile and packaging industry become such hot melt materials for gluing the most diverse Materials used.

The hot melt material, applied to a seam of the can, solidifies by cooling, which takes place quickly, since the metallic Can body dissipates the heat from the seam area within seconds. Cooling is superfluous and post-treatment is not necessary.

Even where e.g. for a polymerisation of the applied coating a further heat supply or initially a slower one Cooling is indicated, a heating distance of a maximum of a few is sufficient a few meters, which is not comparable to the apparatus Effort according to the state of the art.

This gives the advantage that a partial Hardening or foaming of paint or a Clumping of powder between the processing unit and the Order point can be avoided. When using Hotmelt material can be fed through a heated hose to the order point, what concerns the risks regarding hardened Areas in the feed material eliminated. There is a risk of clumping or hardening, especially during maintenance work on the can seam coating system or the upstream one Can welding machine, because between the processing unit and the order point with a distance of several meters must become.

Further advantages of the invention result from the further subclaims.

The invention is described below using the exemplary embodiments described in more detail.

The exemplary embodiments relate to the coating of can seams. However, the organs for the coating themselves do not have to or are only slightly modified to coat them To be able to use weld seams from metal sheets or car tanks. The main modifications then relate to the transport device in any case for the workpiece to be coated. Such transport facilities are known in the art; think for example after-treatment of weld seams by brushing, in which according to a brushing station by a coating station of the present invention could be replaced.

Figur 1 schematisch eine Beschichtungsanlage gemäss einer ersten Ausführungsform , bei welcher die Auftragseinheit ein Reservoir für im verfliessfähigem Zustand sich befindendes Material besitzt;

Figur 2 schematisch eine Beschichtungsanlage gemäss einer zweiten Ausführungsform, bei welcher die Beschichtungseinheit nur sofort aufzutragendes Beschichtungsmaterial verarbeitet;

Figur 3a schematisch eine Beschichtungsanlage gemäss einer dritten Ausführungsform, bei welcher die Beschichtungseinheit das Beschichtungsmaterial auf die Dosennaht aufträgt, wobei der verfliessfähige Zustand erst auf der Dosennaht erreicht wird.

Figur 3b den Querschnitt entlang der Linie A von Fig 3a.

It shows:

Figure 1 schematically shows a coating system according to a first embodiment, in which the application unit has a reservoir for material in the flowable state;

FIG. 2 schematically shows a coating system according to a second embodiment, in which the coating unit only processes coating material to be applied immediately;

3a shows schematically a coating system according to a third embodiment, in which the coating unit applies the coating material to the seam of the can, the flowable state only being reached on the seam of the can.

Figure 3b shows the cross section along the line A of Figure 3a.

Figure 1 shows schematically a welding machine 1 with one on it coupled can body coating system 2.

The welding machine 1 has a frame 3 and is arranged thereon a round apparatus 4, a welding arm 5 and welding rollers 6 and 7. From the drawing is the vertically movable suspension the upper welding roller 6 can be seen. It is also shown the suspension 8, the welding arm 5 and a Z-rail 9. A just rounded still open can body 10 is in the round apparatus; a can frame 11 standing in front of the welding is running on the Z-rail 9. The can frame 12 is in the welding process.

The can body coating system 2 has one on a foot 20 resting, frame 21 which has one end 22 fixed to the Welding arm 5 is connected.

On the frame 21 there is a transport device 23 for welded Can frames 24 arranged.

The transport device 23 has a conveyor belt 24, 25 and 26 for further transport of the welded can frames. The conveyor belts 24, 25 and 26 are arranged as parallel double conveyor belts carried out such that e.g. the one above Welded seam 54 of the can frame 12 between the side attacking parallel belts of the conveyor belts 24, 25 and 26.

With the conveyor belt 24, 26, the can rests on the belts; at the Conveyor belt 25 hangs, e.g. held by magnetic force to which two bands running in parallel.

Next to the frame 21 is a heater 28 and a heater 29 provided. The heater 29 is an additional heater educated. Both heating devices 28, 29 act in particular on the weld seam 54 of the can bodies.

To relieve the drawing, a drive is omitted as well a control device for the various organs of the can coating system. Drive and control device are conventional trained and arranged in Gesges 21.

A wire-shaped, semi-finished coating material 30 is wound on a spool 31. A conveyor 35 for coating material has rollers 36 for the wire-shaped Coating material 30. The conveyor 35 has further as drive rollers 37 for the coating material 30 trained feed means, which in the conveying direction in front of a Application unit 40 for the coating material are arranged. A processing unit 41 is included in the application unit 40 a reservoir 42 for those in a flowable state Coating material provided. Trained as a spray head 43 Order funds are omitted to relieve the drawing Pump connected to the reservoir 42.

A pressure variable chamber 39 designed as a pressure sensor 38 stands over a wall section 65 with the contents of the reservoir 42 as well as the control of the plant 2 operable in connection with what allows the pressure in the reservoir 42 to be in the desired range hold. The controller, in turn, works with one Valve 66 of the spray head 43 together.

Figure 2 shows the same can body coating system 2 as Figure 1, but the processing unit 41 is modified is.

The processing unit 41 has a processing space 44, in which the wire-shaped coating material 30 directly through the Drive rollers 37 is conveyed into it. One works in this room Heater 45, which is used as an electric heater, microwave radiator etc. is trained. A schematically illustrated screw conveyor 46 is designed such that it is the coating material convey to the spray head 43 under the necessary pressure can.

The screw conveyor thus acts as a pump for the material to be dispensed Coating material. The mixing process for multi-component Material or the melting process for a thermoplastic containing Material takes place in room 44. Accordingly, that progressing mixing or melting process or the increase in pressure accordingly, the diameter of the helix and / or the spindle body yourself or change the pitch of the helix.

FIG. 3a shows the can body coating system 2 from FIG. 1, however, the processing unit 41 is also modified is shown.

The processing unit 41 has one on two processing rollers 50, 51 revolving endless belt 52, which is a device 60 for applying the coating material to the interface 54 form. The processing roller 50 acts with one roller 53 together as drive rollers, which the wire-shaped coating material 30 pull between them and onto the endless belt 52 lead. At the same time, one can by the rollers 50, 53 Pre-profiling is done. The preparation roller 51 presses the coating material 30 against the transported can frame 55, the frame in turn against this pressure from a support roller 56 is supported. Accordingly, the wire-shaped coating material 30 profiled (see Fig. 3b).

Figure 3b shows a cross section through the support roller 56 and Order role 51 at the point of common contact. Shown is the weld seam 57, the profiled wire-shaped coating material 30, the endless circulating belt 52.

Because of the overlap of the welded can edges a stage 58 which is characterized by an accumulation of coating material 30 must be covered, since the flow process consists of physical Reasons the coating material tends to from the edge 59 of the step 58 runs away to the side and exposes it.

During operation of the welding machine 1, they reach a can frame 10 to be rounded sheet metal sections in the round apparatus 4 and there rounded to a frame 10. The freshly rounded one wraps around Can frame that running on the rollers 36, wire-shaped Coating material 30. A not shown in the figures Frame conveyor moves the just rounded frame 10 on; the frame runs, now shown as frame 11 in the figure, with its edges in the Z-rail 9. The frame 1 passes the suspension 8 of the welding arm 5 runs on the welding arm 5 continue until it is welded as a frame 12 by the welding rollers 6, 7 becomes. The frame 12 still wraps around the coating material 30 and the welding arm 5, but is now through the welding sealed to a can jacket.

The freshly welded can frame 12 is from the welding machine 1 ejected and from the conveyor belt 24 of the can body coating system 2 taken over. Since the can frame 12 is closed everyone has to get on the inside of the can wall, i.e. on too organs acting in the area of the frame 21 are located, the end 22 firmly coupled to the welding arm 5 is. While the frame 12 runs over the conveyor belt 25, it becomes kept warm by a heater 28. This means in essential that the cooling from the welding process Weld seam is kept at an elevated temperature. After that the can frame 12 taken over by the conveyor belt 26, which Conveyor belt 26 transports the frame past the application unit 40. The coating material is now in the processing unit 41 prepared as follows to coat the can seam:

The coating material 30 is in its basic form, as a semi-finished product, unwound from the roll 31 and through the conveyor 35 with the help of the rollers 36 and the drive rollers 37 to the processing unit 41 at least partially drawn. This funding process of the coating material in its basic form 30 is very simple and does not require any other equipment Expenditure. In the event that the can body coating system is used for maintenance work 2 must be separated from the welding arm 5, can simply cut through the wire-shaped coating material become. The two loose ends are put back into service the can body coating system 2 e.g. with the help of a soldering iron simply welded together. A complex cleaning or a special treatment of the transport route of the conveyor 35 is completely eliminated.

Through the drive rollers 37, the coating material 30 in the processing unit 41 pushed in, where it is for coating suitable flowable condition is brought.

In the case of a multi-component coating material, this is Condition by mixing the components e.g. in the processing room 44 of the processing unit 40 reached. In the event that Coating material contains at least one hot melt, this is Hot melt through a heater 45 in a flowable state brought. The pump, which was omitted to relieve the figures, delivers then the coating material prepared for coating from the reservoir 42 into the spray head 43 of the application medium.

As long as the operating valve 47, 66 of the spray head 43 is open, the pumped, flowable and for Coating suitable material from the spray head 43 onto the through the conveyor belt 26 applied can body 12 applied. Of the to relieve the figures omitted drive of the can body coating system 2 and also no further in the figures shown control device of the can body coating system 2 now coordinate the operation of the spray head 43 accordingly the can bodies 12 and the ones in the processing room 44 acting pump and the drive rollers 37th effect of the conveyor 35.

Overall, it follows that the base material is immediate in front of the coating point in a suitable coating flowable condition prepared and immediately on the Can seam is applied. The warm by the heater 29 held can seam facilitates or enables it to flow the freshly applied coating compound, insofar as this should have been applied irregularly by the spray head 43 or by the endless belt 52 in the solid state on the frame wall was created.

The spray head 43 is preferably also heated, so that at Interruptions in operation of a hot melt material do not solidify can.

The freshly coated can frame is now from 24 Conveyor belt 27 taken over and guided past an afterheater 29. This post-heating is not absolutely necessary. Here but the heat from the weld seam through the metallic can walls is quickly transported away, solidified hot melt material solidifies very fast. For visual reasons, it can now be reheated the surface of the seam coating is smoothed.

It is also conceivable to provide post-heating where hot melt material is concerned should polymerize; usually a polymerization process take a little longer than through self-cooling time is available for the weld.

The coating process begins as soon as coating material is on the can seam is applied, and is complete once the material distribution over the weld seam has been formed. The distributed material solidifies in the area of the conveyor belt 27. A complete hardening or hardening takes place without any post-treatment on the way to the next processing station the can frame.

With the can body coating system shown, the Realized advantage that the system itself e.g. only a third or a quarter of the usual length, which is when planning of the entire production line as a decisive advantage is. Moreover, the design effort of the can coating system itself significantly simplified because of the can coating material 30 in its basic form, e.g. stored as a semi-finished product and can be used up to the order point. Elaborate Facilities, e.g. the supply of molten material from the roll 31 through heated hoses from the round apparatus 4 via the welding arm 5 to the processing unit 41 are eliminated, as are the problems with partially solidifying on the above-mentioned transport route or clumping coating material such as powder or paint.

Last but not least, the structure mentioned can be scaled down Realize can diameter.

These advantages described also result in one embodiment according to Figures 3a and 3b.

The supplied wire-shaped coating material 30 (which can also have a band shape or another cross-section) is pulled from the rollers 50, 52 to the processing unit 41, where the coating material reaches the endless belt and between the application roller 51 and the can frame 55 are squeezed together, is profiled. The frame 45 is due to the action the heater 28 in heat, so that a hot melt to immediately flow away at least coating material 30 contained begins. It is possible that the auxiliary heater 61 Melt coating material 30 so that it is on the frame 55 is immediately liable. Furthermore, the applied coating material can also flow from the inside of frame 55 brought by appropriate means after the Roll 51 are provided.

An advantage of this profiling is that the material distribution of coating material 30 over the weld can be achieved optimally and without major technical effort can. In Figure 3b it can be seen that the Level 58 of the overlapping sheet edges of the can weld seam one Accumulation of material is formed, so that the sensitive edge 59 is definitely covered enough.

Another advantage of this embodiment is that a heater and a pump for that suitable for coating Conditioned, flowable coating material omitted, likewise of course a spray head 34 is omitted.

This embodiment allows a perfect coating make and the equipment expenditure of the can coating system 2 to keep to a minimum.

The support roller 56 fulfills the fixation of the can frame 55 another function. With a simple regulation, the Can frames with a constant, minimal distance from the conveyor belts 25, 26, 27 can be transported further. This means, that with continuously working coating, the support roller 56 is coated every time there is no frame 55 between it and the application roller 51 is located. A doctor blade 57 simply scrapes the coating material 56.

This function of the roller 56 can of course also be used in the further Embodiments described above can be realized.

Not shown in the figures is the case where not one, but several components of the coating material 30 in the Processing unit 41 are processed. That way you can various components of the coating material use Find.

In the event that the coating material 30 as a semi-finished product is not optimal cross-section on the coil 31, a Pre-profiling, e.g. can be provided by the rollers 50, 53.

It is also possible to place the endless belt 52 in an area or Section in front of the order point 48 for further elements Bring the preparation of the coating material past, e.g. on a heater for softening the surface or on an output unit for another component of the coating material or on a unit for adding a plasticizer.

Contrary to the order of the organs shown in the figures (Feed means 35, processing unit 41, application unit 40) this can be reversed, with the consequence that the Spray head 43 is located directly next to the welding rollers 6.7. As a result, e.g. the heater 28 can be dispensed with can. The coating material can then e.g. first on the above Organs bypassed and in a direction of transport the cans to the rear of the pulley against the direction of transport returned and placed in the processing unit 40 become.

Although the embodiments of the coating system, the coating of can seams, the invention is not based on the Coating of can seams limited.

The inventive method can in particular for Coating of sheet metal, e.g. deep-drawn sheet metal, applied become. The task and solution remain essentially the same.

Claims (11)

1. Process for coating welded seams (54) in sheet metal parts such as can bodies (12) and automobile fuel tanks by means of a coating material (30) which is fluid during coating, which is composed of one or more components and which solidifies and hardens spontaneously soon after the coating has been completed, which contains at least one thermoplastic component, wherein the coating material (30) is introduced into a device (2) adapted for coating welded seams and is transported directly and essentially unchanged toward an applicator unit (40) of device (2) where, prior to being applied, it is brought within a preparation unit (41) into a state of flowability suitable for coating by melting the thermoplastic component through the application of heat, characterized in that the coating material (30), in the form of a wire, is pulled toward the preparation unit (41) by means of a transport device (35) located ahead of the preparation unit and is applied to the welded seam (54) by an applicator means (43) after being brought into the flowable state.
2. The process of claim 1 characterized in that the coating material (30) is stored in the flowable state inside a reservoir (42) and is applied by the applicator unit (40) as needed to the seam weld (54) while a controller or regulator immediately replaces the applied material inside the reservoir (42) in such manner that the contents of the reservoir (42) can be maintained at a minimum.
3. Process according to claim 1, characterized in that the coating material (30) is pumped onward to the applicator means (43) and applied in the same step in which it is brought into the flowable state.
4. Process according to one of claims 1 to 3, characterized in that the wire is a hot-melt material and that the hot-melt material is essentially a thermoplastic polymer and/or that the hot-melt material is a polyester or a copolyester and/or the hot-melt material is a PVC, polyethylene, polyamide or a copolyamide and/or the thermoplastic polymer which is utilized is at least partly cross-linkable and/or the hot-melt material includes at least one additive such as an adhesion promoter for improving the adhesion to the metal surface and/or a flowability promoter for improving the flowability of the hot-melt material onto the seam weld (54).
5. Apparatus for performing the process according to one of claims 1 to 4, having a support frame (21), a drive, a control apparatus, a transport apparatus (24, 25, 26) for the sheet metal parts which are to be welded, a conveyor apparatus (35) for the coating material (30) a preparation unit (41) with accompanying heating apparatus (45) for causing the coating material (30) to be in the flowable state suitable for coating and an applicator unit (40) for the coating material (30), wherein the preparation unit (41) is placed immediately ahead of the location (48) at which the coating material (30) reaches the seam weld (54) characterized in that the applicator unit (40) has an applicator means (43) for applying the coating material (30).
6. Apparatus according to claim 5, characterized in that a reservoir (42) for the flowable coating material (30) is placed immediately bead of the applicator unit (40) and that the heating apparatus (45) cooperates with the reservoir (42).
7. Apparatus according to claim 6, characterized in that the reservoir (42) is of closed construction and its filling level is detected by a sensor which preferably takes the form of pressure sensor (38).
8. Apparatus according to claim 7, characterized in that the sensor (38) takes the form of a chamber (39) which cooperates with the contents of the reservoir (42) and preferably has a pressure-variable volume and that the pressure inside the reservoir is detected by the volume of the sensor chamber (39).
9. Apparatus according to claim 5, characterized in that the preparation unit (40) has a space (44) for the preparation of the coating material (30) and a pumping apparatus (46) located inside that space.
10. Apparatus according to claim 9, characterized in that the pumping apparatus (46) takes the form of a single- or multi-flight screw conveyor having a diameter and/or a pitch which increases in the direction of pumping and in that the pumping apparatus (46) itself is preferably adapted to be heated.
11. Apparatus according to one of claims 5 to 10, characterized in that the applicator means takes the form of a spray nozzle (43).

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