WO2020164764A1 - Method and device for the seam coating of can bodies - Google Patents

Abstract

In a method for lacquer coating the outside of the weld seam of container bodies (23 to 27) transported in a row, a spray head (31) is provided above the transported container bodies, said spray head being supplied with pressurised lacquer via a connection (8) and applying the lacquer to the weld seam via a spray nozzle (2) of the spray head. Within the spray head (31), the lacquer entering the spray head is brought to a preselected temperature and/or maintained at said temperature. In this way, the lacquer viscosity can be held within a tight tolerance using simple technical equipment, even if the surroundings in which lacquer coating takes place are subject to considerable temperature fluctuations.

Description

Method and device for seam coating of can bodies

Reference to related documents

This document claims the priority of Swiss patent application No. 0199/19, filed on February 15, 2019, the entire content of which is hereby incorporated by reference.

Field of invention

The invention relates to a method for coating the outside of the respective weld seam of container frames made of metal conveyed in a row according to the preamble of claim 1. Furthermore, the invention relates to a spray head according to claim 9 for implementing the method, a coating device for container frames with such Spray head according to claim 16 and a device for manufacturing container frames according to claim 18 with such a coating device.

background

In the production of container frames from Me tall, individual sheets are rounded and the edges of the rounded sheet are brought into an overlap and welded to the frame by seam welding. The welded frames leave the welding machine in a row with the weld seam on top and are transported in this position by a conveyor device. In the area of the weld seam of the frames, paint is applied to the outside of each frame to avoid corrosion, in particular by spraying the paint. This is done by a sta tionary above the conveyor or above the Row of conveyed frames, arranged spray head. The painting is usually carried out by means of so-called airless spraying, in which the paint to be sprayed is sucked in from a paint tank by a membrane or piston pump and fed under high pressure via a line to the spray head, also known as an airless gun which spray head a spray nozzle delivers the paint onto the weld seam. For a spatter-free application of the lacquer to the weld seam, a close tolerance of the lacquer viscosity is desirable. In commercially available systems for the paint coating of container frames, paint preheating is carried out in which the paint temperature on the way from the tank to the spray head is set to a relatively high temperature of e.g. 40 degrees Celsius by means of a heat exchanger and a circulation pump, which means that the paint on a high solid content has to be set in order not to be too thin at this temperature. However, it has been shown that this can lead to increased blistering during drying after painting. In addition, the outlay on equipment for such a procedure is great. It also shows that the known systems are influenced by the fluctuating room temperature in production, which changes over the course of the day and depending on the season, which must be corrected in practice by adjusting the proportion of thinner in the paint to the Adjust viscosity. If this is not done, the quality of the coating may not be optimal.

Presentation of the invention

The invention is based on the object of improving the coating of the weld seam on the outside of welded metal frames, even with fluctuating ambient temperatures at which the frames are produced. This object is achieved in a method of the type mentioned at the outset in that the paint entering the spray head is brought to a preselected temperature within the spray head and / or is kept at this temperature.

The effect of the desired paint temperature directly in the spray head and the thus small amount of paint to be influenced in its temperature per unit of time results in a considerable simplification of the equipment required and enables rapid adaptation to a changing ambient temperature. Furthermore, a correct paint viscosity is obtained at the start of the coating.

The preferred procedure is that the paint in the spray head passes through a paint heat exchanger arranged between the connection and the spray nozzle. This results in a simple and quick action on the paint in the spray head. The lacquer in the lacquer heat exchanger is preferably brought to and / or maintained at a preselected temperature in the range from 20 degrees Celsius to 25 degrees Celsius. A solution that can be used well for various environmental zones is obtained when the paint heat exchanger is both heated or cooled, in particular heated or cooled by a Peltier element, in order to bring the paint in the spray head to the preselected temperature. A temperature measurement in the spray head, in particular in the paint heat exchanger, is also preferably provided. In this way, a controller can ensure compliance with the preferred temperature of the paint by the controller heating or cooling the paint depending on the measured temperature. The cooling can take place particularly efficiently if the Peltier element is cooled by means of water cooling when the paint heat exchanger is cooled on the warm side of the Peltier element. An alternative method uses a constant temperature supply of water into the spray head, the spray head having a fluid inlet and a fluid outlet and the paint heat exchanger having one Fluid, in particular with water, is fed, which is fed to the spray head at the preselected temperature.

The object is also achieved with a spray head for carrying out the method, comprising a connection for a line leading to paint, a spray nozzle connected to the connection and a paint heat exchanger, the connection for the paint between the connection and spray nozzle in the spray head leads the paint heat exchanger arranged in the spray head, by means of which paint heat exchanger heat can be supplied to the paint or heat can be withdrawn. This results in the advantages mentioned before in the process.

The spray head preferably has a Pel tier element that is thermally connected to the paint heat exchanger. This results in the simple and space-saving possibility of heating or cooling the paint in the spray head, which enables a quick reaction to keep the paint temperature constant. The spray head preferably has at least one temperature measuring element. In particular, this is arranged in the paint heat exchanger of the spray head.

The spray head is preferably designed such that the Peltier element is in thermal connection on its side facing away from the paint heat exchanger with a heat exchanger through which water can flow. This allows the heat that is present on the warm side of the Peltier element that is operated to cool the lacquer to be dissipated in a simple and space-saving manner. In particular, the spray head has a heat exchanger with a fluid inlet and a fluid outlet.

In a further embodiment, the spray head has a paint heat exchanger which is provided with water connections and at least one water channel running between these in order to keep the paint heat exchanger at the temperature of the water flow by means of a water flow. In this way, too, the temperature of the paint in the spray head itself can be kept constant. A spray head which has a collecting tray for condensation water running off from the spray head is also advantageous.

The object is also achieved with a coating device for coating the respective outer side of container frames with paint, comprising a paint pressure tank, a control and a spray head according to the invention. This gives the advantages mentioned above. Instead of a paint pressure tank, a pressureless paint tank and a paint pump can also be provided.

The coating device preferably has a fastening arrangement for fastening the spray head in a position above a conveying device for the container frames, the spray head being connected to the fastening arrangement via thermal insulation. In this way, the constancy of the temperature of the paint in the spray head can be further improved, since no heat flows from or flows into the spray head via the fastening arrangement.

The object is also achieved with a device for producing container frames, which has a welding machine for welding the longitudinal seam of container frames, a conveying device and a coating device according to the invention.

Brief description of the drawings

Further embodiments, advantages and applications of the invention emerge from the dependent claims and from the description that follows with reference to the figures. Show:

Figure 1 shows a schematic representation of a welding machine, a conveyor and a coating device with a spray head for applying the paint to the container frames;

FIG. 2 shows an embodiment of the spray head in side view; and FIG. 3 shows a vertical section through the embodiment of the spray head from FIG.

Way (s) for carrying out the invention

To explain the method and the device, FIG. 1 shows a welding machine 22 and the following conveying device 28, in which the outer lacquer coating of the longitudinal seam of the welded frames is performed. In the production of container frames made of metal, individual sheets are rounded and the edges of the rounded sheet are brought into an overlap and welded to the frame by seam welding in the welding machine 22. This is known to the person skilled in the art and is not explained further here. In the area of the welded longitudinal seam of the frame, the coating usually present on the sheet metal, which protects the sheet metal from corrosion, has been removed by the weld. The welded frames, of which the frames 23 to 27 are shown as an example, leave the welding machine in a row and are transported in the direction of arrow A by the conveyor device 28. The conveyor can be configured in any manner known to those skilled in the art. The conveying takes place with the weld seam of the frames on top, just as the frames emerge from the welding machine. In the area of the weld seam, the coating device, which is generally designated by 30, is sprayed onto each frame in the area of the weld seam. This is done by a spray head 31 which is stationary above the conveying device 28 or above the row of conveyed frames and is part of the coating device 30. The painting is usually carried out using so-called airless sprays. In the preferred embodiment, a pressure tank 33 is provided for the paint, in which the paint is stored under a pressure of a few bar, in particular a pressure of 2 bar to 4 bar. This leaves the paint to be sprayed the tank with this pressure via a line 34 to the spray head 31 or to the airless gun. There a spray nozzle 13 applies the paint to the weld seam of the respective frame. A controllable valve is provided in the spray head, by means of which the spray can be activated or deactivated. The coating device shown as an example thus comprises, in addition to the spray head 31, the line 34 and the tank 33, which is a pressure tank. Furthermore, a fastening arrangement 3 is provided, by means of which the spray head 31 is fixedly attached to the conveyor device 28. The mentioned elements of the coating device are shown only schematically in FIG. The coating device can have further elements, for example valves. Such coating devices are generally known to those skilled in the art, apart from the new spray head 31 according to the present invention, which is explained below in connection with the new method for paint coating. Instead of a pressure tank for the paint, a pressureless tank can also be provided, from which a membrane or piston pump 32 draws in the paint and delivers it to the spray head with pressure.

When painting the weld seam, a tight tolerance of the paint viscosity is required for good quality coverage of the seam. For example, the preferred viscosity can be 18 seconds +/- 10%, this at a given temperature and determined with a discharge cup according to DIN EN ISO 2431, ASTM D 5125 with a 4 mm discharge nozzle. In the event of fluctuations in the temperature in the factory building in which the paint is being coated, the paint viscosity must therefore be adjusted or, according to the state of the art, paint is preheated to a relatively high temperature of e.g. 40 degrees Celsius in the coating device before the paint gets into the spray head.

According to the invention, the procedure is different, in that the paint temperature is only increased in the spray head itself given temperature is brought or is kept at this ge. The paint entering the spray head is heated or cooled in it, depending on whether the paint has a lower or higher temperature than the specified temperature when it enters the spray head. The given temperature is preferably in the range of 20 degrees Celsius to 25 degrees Celsius. If the entry temperature of the paint into the spray head happens to be in the range of the specified temperature, this is maintained in the spray head. This is also the case if the spray head is deactivated for a time, since then the paint in the spray head can also be kept at the predetermined temperature and has the desired temperature and thus also viscosity when operation is resumed.

A preferred example of the spray head 31 is shown in FIGS. As can be seen schematically in FIG. 1, the spray head is controlled by a control device 37. This can be an independent control of the coating device 30 or it can be part of a higher-level control, for example the control of the welding machine or the entire system for manufacturing container frames. The spray head has a paint connection 8 to which the line 34 coming from the paint pressure tank 33 or possibly from a pump can be connected. From the paint connection 8, the paint passes into the spray head 31 to its spray nozzle 2, which forms the paint emerges 13. The spray head preferably has a pneumatically controllable paint valve 1 which can be controlled to enable or block the paint flow from the paint connection 8 to the spray nozzle 2, or in other words to activate or deactivate the spraying of the paint. In the preferred embodiment, a pneumatic connection 11 is therefore provided for controlling the paint valve. In the schematic view of FIG. 1, the spray device 31 is supplied with compressed air (and, as will be explained below, with electrical energy and a fluid) through the box 38 and through the this box to the spray head pointing arrow shown simplified. The provision of compressed air, electricity and fluid is known to those skilled in the art and this does not have to be presented in detail here. The combination of the provision of these resources in box 38 is one possibility, but completely separate sources for compressed air, electricity and the fluid can also be provided. It is thus shown in the example of FIG. 1 that the controller 37 can apply compressed air to the spray head via the box 38 or can interrupt it in order to control the paint valve 1 via the pneumatic connection 11.

In the spray head 31, a paint heat exchanger 5 is provided for heating or cooling the paint or for keeping its temperature constant, through which the paint flows on the way from the paint connection 8 to the paint nozzle 2 (with the paint valve 1 open) or lingers ( with the paint valve closed 1). The paint valve 1 can be arranged upstream of the paint heat exchanger 5 or after the paint heat exchanger 5, as seen from the paint connection 8. The paint heat exchanger in the spray head removes heat from the paint or cools the paint if its entry temperature into the spray head is above the specified temperature. The paint heat exchanger heats the paint when its entry temperature into the spray head is below the specified temperature. If the paint temperature happens to be at the desired predetermined temperature when it enters the spray head, it remains at this value in the paint heat exchanger. A paint heat exchanger, which provides one or more channels for the paint and determines the temperature of the paint in the heat exchanger via the contact of the paint with the surface of the channels, is an element familiar to the person skilled in the art and need not be described in detail here.

The heating or cooling of the paint in the spray head is preferably carried out by means of a plate-shaped Pel tier element 4, one surface of which rests on the outside of the paint heat exchanger and thus the borrowed paint can heat or cool. A good heat flow connection is created between the outside of the paint heat exchanger 5 and the adjacent surface of the Peltier element in that the surface of the Peltier element is connected to the outside of the heat exchanger over as full a surface as possible and, if necessary, using a commercially available thermal paste. On the spray head 31 electrical contacts 7 are provided, which allow the electrical Spei solution of the Peltier element 4. In the schematic view of FIG. 1, this also takes place via the box 38 and under control by the controller 37. At least one temperature measuring element 15 is preferably provided in the spray head, the measuring signal of which is also output via the electrical contacts 7. This can be done directly to the controller 37 or via the box 38 to the controller.

By reversing the polarity of the electrical supply to the Peltier element, it can be cooled on the side connected to the paint heat exchanger. Heat is thus extracted from the paint located in the heat exchanger, so that it assumes a temperature in the predetermined range, even if the paint reaches the spray head 31 at a higher temperature from the tank 33. The heat extracted from the paint must be dissipated on the side of the Peltier element 4 facing away from the paint heat exchanger. For this purpose, a heat sink and a fan can be provided on this side. It is preferred, however, if a water heat exchanger 6 is provided on the side of the Peltier element 4 facing away from the paint heat exchanger 5, which allows the heat generated by cooling the paint in the paint heat exchanger 5 on the Peltier element to be dissipated by cooling water. The Kühlwas water can also be supplied via the box 38 and all if also discharged via this. To connect the corresponding water lines, the water connections 9 and 10 are provided on the spray head 31, which feed the water into the heat exchanger 6 and discharge it from it. The water supply to the Peltier element can take place continuously, when the coating device is in operation or it is also controlled by the controller 37.

The predetermined temperature value for the paint in the spray head can thus be set on the controller 37. The control is informed by the at least one temperature sensor 15 about the actual temperature of the paint. This temperature sensor 15 is preferably located in the paint heat exchanger of the spray head, as indicated in FIG. 3 by the box in the paint heat exchanger 5. A temperature sensor can additionally or alternatively also be arranged in the tank 33 and / or in the line 34, and / or also in the spray head directly when the paint enters. It is indicated in FIG. 1 by the arrow 37 'that the controller 37 receives the information about the paint temperature from the spray head. If the controller determines that the temperature of the paint that is fed to the spray head is below the predetermined temperature, the controller can cause the paint heat exchanger 5 to be heated by the Peltier element 4 by supplying it with electric current in the appropriate polarity becomes.

If the controller determines in the other case that the temperature of the paint supplied to the spray head 31 is above the desired predetermined temperature (i.e. above the desired temperature value in the range of 20 to 25 degrees Celsius), the controller 37 can cool the paint heat exchanger 5 by means of of the Peltier element 4 wir ken. The heat extracted from the paint is dissipated on the warm side of the Peltier element, which is in contact with the heat exchanger 6. The surface of the Peltier element lying on the heat exchanger 6 is also mounted on the heat exchanger, possibly using thermal paste, so that there is a good heat flow connection between the Peltier element 4 and the heat exchanger 6.

If the controller 37 determines, in particular by means of the mentioned temperature sensor 15 or the mentioned alternative or additional temperature sensors, that If the paint supplied to spray head 31 is already at the predetermined temperature, either no cooling / heating at all or the Peltier element 4 can be operated by the controller so that it also maintains this temperature with its surface adjacent to the paint heat exchanger 5 .

As an alternative to the cooling / heating by means of the Peltier element or possibly another heating and cooling source, it can be provided that the paint heat exchanger 5 is operated with a water flow of constant temperature in the predetermined desired temperature range. In Figure 1, the additional box 38 ', which is shown with broken lines, indicates that a water source of constant temperature, in particular in the range of 20 to 25 degrees Celsius, is available by means of which the paint heat exchanger 5 in the spray head 31 is constant the desired temperature is kept rich in the said Be. It then results via the paint heat exchanger 5 an adaptation of the paint entering the spray head to this constant temperature of the water. For this purpose, the paint heat exchanger is provided with water connections and at least one channel running between these connections, so that the paint heat exchanger can be kept at this temperature by means of the water at a constant temperature, which is transferred to the paint according to the function of the heat exchanger. In such an embodiment, the water connections 9 and 10 are seen as the connections for the constant temperature water flow and lead this water flow directly into corre sponding channels in the paint heat exchanger 5 and not in the heat exchanger 6, which is not taken in such an embodiment.

Thermal insulation 14 is preferably provided on the fastening arrangement 3 of the coating device, which is only partially shown in FIGS. 2 and 3, for example made of plastic of low thermal conductivity, to thermally decouple the spray head from the mounting arrangement. Furthermore, it is preferred if a condensation collecting tray 12 is arranged on the spray head 31, which collects the condensation resulting from the cooling of the lacquer or the Peltier element and preferably discharges it via a condensation line, not shown.

While preferred embodiments of the invention are described in the present application, it should be clearly pointed out that the invention is not restricted to these and can also be carried out in other ways within the scope of the following claims.

Claims

Claims 1. A method for lacquer coating the outside of the respective weld seam of container frames (23 to 27) conveyed in a row, in particular can frames, with a spray head (31) arranged in a stationary manner above the conveyed container frames, which has a connection (8) is supplied with pressurized paint and applies the paint to the respective weld seam via a spray nozzle (2) of the spray head, characterized in that the paint entering the spray head is brought to a preselected temperature within the spray head (31) and / or is held on it. 2. The method according to claim 1, wherein the paint passes through a paint heat exchanger (5) arranged in the spray head (31) between the connection (8) and the spray nozzle (2). 3. The method according to claim 1 or 2, wherein the paint in the paint heat exchanger is brought and / or held at a preselected Tempe temperature in the range of 20 degrees Celsius to 25 degrees Celsius. 4. The method according to claim 2 or 3, wherein the paint heat exchanger (5) is heated or cooled, in particular heated or cooled by a Peltier element (4) in order to bring the paint in the spray head to the preselected temperature. 5. The method according to claim 4, wherein the Pel tier element (4) is cooled during the cooling of the paint heat exchanger on the warm side of the Peltier element by means of a water cooling system (6). 6. The method according to claim 2 or 3, wherein the spray head has a fluid inlet (9) and a fluid outlet (10) and the paint heat exchanger (5) is fed with a fluid, in particular with water, which wel ches the spray head with the preselected temperature is supplied. 7. The method according to any one of claims 1 to 6, wherein the temperature of the paint in the spray head is measured and output to a control device, which control device controls the heating or cooling of the paint in the spray head. 8. The method according to claim 2 and 7, wherein the temperature of the paint heat exchanger is measured as the temperature of the paint in the spray head by means of a sensor element. 9. Spray head (31) for performing the method according to one of claims 1 to 8, comprising a connection (8) for a paint-carrying line, a spray nozzle (2) connected to the connection (8) and a paint heat exchanger (5) ), the connection for the paint between connection (8) and spray nozzle (2) in the spray head through the paint heat exchanger (5) arranged in the spray head, by means of which paint heat exchanger heat can be supplied or heat can be extracted from the paint. 10. Spray head according to claim 9, comprising a fer ner with the paint heat exchanger in thermal connec tion standing Peltier element (4). 11. Spray head according to claim 10, wherein the Peltier element (4) on its side facing away from the paint heat exchanger (5) is in thermal connection with a heat exchanger (6) through which water can flow. 12. Spray head according to claim 11, wherein the heat exchanger (6) has a fluid inlet and a fluid outlet (9 and 10). 13. Spray head according to claim 11, wherein the paint heat exchanger (5) has water connections and at least one water channel running between these in order to keep the paint heat exchanger at the temperature of the water flow by means of a water flow. 14. Spray head according to one of claims 9 to 13, wherein this has a collecting tray (12) for draining condensation water from the spray head. 15. Spray head according to one of claims 9 to 14, wherein it has a temperature sensor (15) for measuring the paint temperature, in particular for measuring the paint temperature by measuring the temperature of the paint heat exchanger (5). 16. Coating device (30) for coating the respective outside of container frames (23 to 27), comprising a paint tank (33), a control (37) and a spray head according to one of claims 9 to 15. 17. Coating device according to claim 16, comprising a fastening arrangement (3) for fastening the spray head in a position above a conveyor device (28) for the container frames, the spray head being connected to the fastening arrangement via thermal insulation (14). 18. Device for the production of Behäl terzargen comprising a welding machine (22) for Welding the longitudinal seam of container frames, a conveying device (28) and a coating device according to claim 16 or 17.