Adhesive melting device for an edge-banding machine and method for controlling the adhesive melting device

Abstract

The invention relates to an adhesive melting device (10) for an edgebanding machine, comprising a melting chamber (34) for receiving adhesive material (32) and a heatable melting element (34) for melting the adhesive material (32). To further develop the adhesive melting device (10) in such a way that crosslinking of reactive hot melt adhesive, for example PUR adhesive, remaining in the melting chamber (34) after completion of an adhesive bonding process can be easily avoided, it is proposed that the adhesive melting device (10) include a suction device (46) for extracting air from the melting chamber (34).

Description

[0001] The invention relates to an adhesive melting device for an edgebanding machine, comprising a melting chamber for receiving adhesive material and a heatable melting body for melting the adhesive material.

[0002] Furthermore, the invention relates to a method for controlling such an adhesive melting device.

[0003] Adhesive melting devices are used in edgebanding machines, that is, machines that feed an edgebanding material, often also referred to as "edging" or "banding," to one long side of a workpiece moving in a transport direction and bond it to that long side. The workpiece with the edgebanding material can then typically be processed further, for example, to achieve a continuous transition between the top and bottom surfaces of the workpiece and the edgebanding material.

[0004] To bond the edgebanding material, which is supplied as strips or rolls, to the long edge of the workpiece, adhesive is melted using an adhesive melting device of the type discussed here. The molten adhesive is then fed into an adhesive application system of the edgebanding machine to apply the adhesive to the long side of the workpiece, so that the edgebanding material can subsequently be bonded to the long side. The adhesive application system can, for example, have an application nozzle to apply the molten adhesive to the long side of the workpiece.

[0005] The adhesive melting device has a melting chamber for receiving adhesive material, which is supplied, for example, in the form of granules or cartridges. The device features a heated melting element for melting the adhesive material. Commonly used adhesive materials include thermoplastic resins based on ethylene vinyl acetate (EVA adhesives), polyolefin-based hot melt adhesives (PO adhesives), or reactive hot melt adhesives, particularly reactive polyurethane hot melt adhesives (PUR adhesives). PUR adhesives offer the advantage that the edge material can be bonded to the longitudinal side of the workpiece, forming very thin adhesive joints. The resulting bond exhibits high adhesion strength and good resistance to higher temperatures and various media, especially high resistance to water and steam. The adhesive bond is thus resistant to moisture, water, and heat.

[0006] PUR adhesives contain isocyanate groups which, after the initially liquefied and subsequently solidifying adhesive is joined, cross-link through reaction with atmospheric humidity, thereby converting the adhesive into a non-meltable state.

[0007] When using PUR adhesive, care must be taken to ensure that adhesive material remaining in the melting chamber of the adhesive melting device after the completion of a bonding process does not come into contact with humidity, as otherwise the isocyanate groups of the adhesive will react with the humidity, resulting in cross-linking and preventing the adhesive material in the melting chamber from being liquefied again.

[0008] To prevent cross-linking of the PUR adhesive remaining in the melting chamber after a bonding process, it is known to detach the entire adhesive melting device from the edgebanding machine and store it in a nitrogen or vacuum tank. Such storage results in the PUR adhesive solidifying but not cross-linking, so that even after several days, it can be reliquefied by reheating the adhesive melting device and used again for a bonding process. However, storing the adhesive melting device in a nitrogen or vacuum tank when not in use is time-consuming and labor-intensive.

[0009] The object of the present invention is therefore to further develop an adhesive melting device of the generic type in such a way that, after completion of an adhesive process, cross-linking of the PUR adhesive remaining in the melting chamber can be avoided in a simpler manner.

[0010] This problem is solved according to the invention in an adhesive melting device of the type mentioned at the outset by the fact that the adhesive melting device has a suction device for extracting air from the melting chamber.

[0011] The suction device used in the adhesive melting unit according to the invention makes it possible to extract air from the melting chamber after a bonding process using PUR adhesive has been completed, so that a negative pressure is created in the melting chamber and only minimal residual amounts of humidity remain. This prevents any remaining PUR adhesive in the melting chamber from crosslinking without the need to disconnect the adhesive melting unit from the edgebanding machine and store it in a nitrogen tank or a vacuum tank. After the melting element cools, the PUR adhesive still in the melting chamber may solidify, but no further crosslinking occurs, so that the PUR adhesive can be reliquefied and used again at a later time for another bonding process.

[0012] The adhesive melting device can remain on the edgebanding machine during operation of the suction device or can be detached from the edgebanding machine.

[0013] Preferably, the adhesive melting device comprises a storage container with an airtight, sealable filling opening for storing adhesive material to be melted. The melting chamber is connected to the interior of the storage container for receiving adhesive material from the container, and the storage container, together with the melting chamber, can be vacuumed by means of the suction device. The storage container allows for the storage of a larger quantity of adhesive material to be melted. The melting chamber is connected to the interior of the storage container for receiving adhesive material from the container. The interior can be filled via the filling opening, which is airtight.This allows, after completion of an adhesive bonding process using PUR adhesive, air to be extracted not only from the melting chamber but also from the reservoir using the suction device, in order to prevent the PUR adhesive remaining in the reservoir and the melting chamber from crosslinking.

[0014] In an advantageous embodiment of the invention, the adhesive melting device comprises a pressure piston movable within the melting chamber for pressing the adhesive material located in the melting chamber against the melting body, and a feed unit for moving the pressure piston. The melting body may have through channels extending in the feed direction of the pressure piston. The melting body is heatable, in particular electrically heated, to melt the adhesive material. The molten adhesive material can be fed to the adhesive application system of the edgebanding machine via the through channels.

[0015] It is advantageous if the adhesive melting device has a control unit for controlling the suction unit. The operation of the suction unit can be controlled using this control unit without requiring a separate machine control system for the edgebanding machine.

[0016] It is particularly advantageous if the temperature of the melting element can be detected by a temperature sensor, with the temperature sensor being connected to the control unit and the control unit configured to regulate the suction device depending on the melting element's temperature. After the bonding process is complete, the heating of the melting element is switched off, causing its temperature to decrease. The PUR adhesive remaining in the melting element after the bonding process solidifies but does not cross-link due to the lack of contact with air. This prevents air from entering the melting chamber via the melting element and, if a storage container is used, from entering the storage container via the melting chamber. Once the melting element has cooled, the suction device can be activated by the control unit to extract any air present in the melting chamber and, if applicable, in the storage container.If the melting body is reheated at a later time for another bonding process, causing its temperature to rise, the control unit can deactivate the suction device again. The PUR adhesive, which liquefies again due to lack of cross-linking when the melting body is reheated, can then be fed into the adhesive application system of the edgebanding machine for the next bonding process.

[0017] The temperature sensor can be thermally connected to the molten body; in particular, it can be arranged directly on the molten body. It is especially advantageous if the temperature sensor is integrated into the molten body.

[0018] In a particularly simple design, the temperature sensor is connected to the control unit via a sensor cable.

[0019] It is advantageous if the control unit is configured to activate the suction device only when the temperature of the melting element is lower than a predefinable or predetermined temperature limit. In such a configuration of the adhesive melting device according to the invention, the control unit activates the suction device only when the temperature of the melting element falls below the predetermined or predefinable temperature limit, so that the PUR adhesive in the melting element solidifies and thus ambient air cannot flow into the melting chamber via the melting element.

[0020] Preferably, the adhesive melting device according to the invention has a pressure sensor which is connected to the control unit and provides the control unit with a pressure signal corresponding to the atmospheric pressure prevailing in the melting chamber and preferably also in the storage container, wherein the control unit is configured to control the suction device depending on the pressure signal. Such a design has the advantage that, after completion of an adhesive process and cooling of the melting body, the suction device is not operated continuously but rather depending on the atmospheric pressure prevailing in the melting chamber.After the bonding process is complete and the melting body has cooled, the suction device can be activated. This causes the air pressure in the melting chamber, and preferably also in the reservoir, to drop, resulting in virtually no humidity remaining in the melting chamber and, if a reservoir is used, in the reservoir itself. The suction device can then be switched off by the control unit. If the air pressure subsequently rises again gradually due to leaks, the control unit can reactivate the suction device.

[0021] It is advantageous if the pressure sensor is connected to the melting chamber or to a suction line through which the suction device is connected to the melting chamber. If a storage container is used, the pressure sensor can alternatively be connected to the storage container. Using a suction line has the advantage that the suction device can be positioned at a distance from the melting chamber and, if necessary, also at a distance from the storage container, allowing it to draw air from the melting chamber and, if a storage container is used, also from the storage container.

[0022] The use of a suction line makes it possible, for example, to position the suction device on a rear side of the edgebanding machine that faces away from the operating side of the edgebanding machine.

[0023] In a preferred embodiment of the invention, the pressure sensor is connected to the control unit via a sensor line.

[0024] It is advantageous if the control unit is configured to switch on the suction device only when the atmospheric pressure prevailing in the melting chamber, and preferably also in the storage container, is greater than a predetermined or predefinable upper pressure limit, and to switch off the suction device when the atmospheric pressure prevailing in the melting chamber, and preferably also in the storage container, is less than a predetermined or predefinable lower pressure limit. The suction device thus exhibits hysteresis behavior, with the switching points of the suction device being provided by the control unit.

[0025] Alternatively or additionally to controlling the suction device based on the atmospheric pressure prevailing in the melting chamber and preferably also in the storage container, the control device can be configured to switch the suction device on and off at predetermined or predefinable time intervals. With such a design of the control device, the use of a pressure sensor can be omitted.

[0026] The adhesive melting device preferably has a vent valve through which ambient air can be supplied to the melting chamber and which is controllable by the control unit. During an adhesive melting process, the suction device is switched off and the vent valve can be opened, allowing air to flow into the melting chamber and preferably also into the reservoir, or to be released from the melting chamber and preferably also from the reservoir to the environment, thus equalizing the pressure. If the suction device is activated after completion of an adhesive melting process, the vent valve can be closed, preventing pressure equalization with the ambient air via the vent valve and instead allowing the melting chamber, and if a reservoir is used, also the reservoir, to be pressurized.

[0027] In a preferred embodiment of the invention, the vent valve is connected to a suction line, via which the suction device is connected to the melting chamber and preferably also to the storage container. This allows the vent valve to be positioned at a distance from the melting chamber and, if a storage container is used, also at a distance from the storage container.

[0028] In an advantageous embodiment of the invention, the adhesive melting device has a manually operated main switch for switching the control unit and / or the suction unit on and off. The adhesive melting device according to the invention is suitable not only for use with PUR adhesive but also for use with adhesive materials that do not react with atmospheric moisture, such as EVA adhesive. With such adhesive materials, it is not necessary to activate the suction unit after completion of an adhesive application. Instead, the control unit and / or the suction unit can be switched off by an operator using the main switch. If PUR adhesive is used at a later time, the operator can switch the control unit and / or the suction unit back on using the main switch.

[0029] The main switch is advantageously connected to a status indicator that shows an operator the operating status of the control unit and / or the suction unit.

[0030] The invention further relates to a method for controlling an adhesive melting device of the type mentioned above, wherein the melting chamber is evacuated after completion of an adhesive bonding process of the edgebanding machine, depending on the temperature of the melting element and / or depending on the air pressure prevailing in the melting chamber. As already explained, such a method reliably and without significant time and effort prevents cross-linking of the PUR adhesive remaining in the melting chamber after completion of an adhesive bonding process using PUR adhesive, and, if a reservoir is used, of the PUR adhesive remaining in the reservoir.After switching on the control device, it can put the suction device into operation, in particular if the temperature of the melting body is lower than a predetermined or predefinable temperature limit and if the atmospheric pressure prevailing in the melting chamber and preferably also in the storage container is higher than a predetermined or predefinable lower pressure limit.

[0031] The following description of an advantageous embodiment of the invention, in conjunction with the drawing, serves for further explanation. The drawing shows: Figure 1: a perspective view of an adhesive melting device for an edgebanding machine, wherein the adhesive melting device is connected to an adhesive application system of the edgebanding machine; Figure 2: a partially cutaway view of the adhesive melting device and the adhesive application system made of Figure 1 .

[0032] The drawing schematically illustrates an advantageous embodiment of an adhesive melting device 10 according to the invention, which is used in an edgebanding machine. Such edgebanding machines are known to those skilled in the art. Figure 1 The adhesive melting device 10 is connected to an adhesive application system 12 of the edge banding machine, which is also shown schematically.

[0033] With the aid of the adhesive melting device 10, an adhesive material, for example an EVA adhesive, a PO adhesive or a PUR adhesive, can be melted, and by means of the adhesive application system 12, the molten adhesive material can be applied by means of an application nozzle 14 of the adhesive application system 12 to a longitudinal side 16 of a plate-shaped workpiece 18, which is moved in a transport direction 20 by means of transport elements known per se and therefore not shown in the drawing, for example by means of transport rollers or transport chains. After the adhesive material has been applied to the longitudinal side 16, an edge banding material can be bonded to the longitudinal side 16 by means of the edge banding machine in a manner known per se.

[0034] In the exemplary embodiment shown, the adhesive melting device 10 has a storage container 22 for holding the adhesive material to be melted. The storage container 22 has a filling opening 24 which can be sealed airtight by means of a closing element. In the illustrated embodiment, the closing element 26 is designed in the form of a lid 28.

[0035] The interior 30 of the storage container 22 can be filled via the filling opening 24 with adhesive material 32 to be melted, which in the illustrated embodiment is provided in the form of cartridges.

[0036] The interior 30 of the storage container 22 is adjoined by a melting chamber 34 for receiving adhesive material 32 from the storage container 22.

[0037] For melting the adhesive material 32, the adhesive melting device 10 has an electrically heated melting element 36 in the melting chamber 34, to which an outlet channel 38 is connected. Molten adhesive material can be fed to the application nozzle 14 via the outlet channel 38, so that it can subsequently be applied to the longitudinal side 16 of the workpiece 18.

[0038] In the illustrated embodiment, a pressure piston 40 is displaceable back and forth in a feed direction 42 within the melting chamber 34. The pressure piston 40 presses the adhesive material 32 located in the melting chamber 34 against the melting body 36. The pressure piston 40 is driven by a feed unit 44 of the adhesive melting device 10. In the illustrated embodiment, the feed unit 44 is designed as a piston-cylinder unit. Alternatively, the feed unit 44 could, for example, include an electric motor. Such feed units 44 are known to those skilled in the art.

[0039] The melting body 36 has a multitude of through channels that extend in the feed direction 42 and through which the molten adhesive material 32 can pass to the outlet channel 38.

[0040] The adhesive melting device 10 also includes a suction device, which in the illustrated embodiment is configured as a suction pump 46. Furthermore, the adhesive melting device 10 includes a control unit 48. The control unit 48 controls the operation of the suction pump 46 and is connected to the suction pump 46 via a first control line 50.

[0041] The melting chamber 34 has a suction port 52 to which a suction line 54 is connected. The melting chamber 34, and via this the interior 30 of the storage container 22, is connected to the suction pump 46, so that air can be extracted from the storage container 22 and the melting chamber 34 by means of the suction pump 46.

[0042] Alternatively, the storage container 22 can have a suction port so that the suction line 54 can be connected to the suction port of the storage container 22 in order to extract material from the storage container 22 and the melting chamber 34.

[0043] The control unit 48 is connected via a first sensor line 56 to a temperature sensor (not shown in the drawing for clarity), which in the illustrated embodiment is integrated into the melting body 36. The temperature sensor provides the control unit 48 with a sensor signal that depends on the temperature of the melting body 36.

[0044] The control unit 48 is connected to a pressure sensor 60 via a second sensor line 58. The pressure sensor 60 is connected to the suction line 54 and provides the control unit 48 with a pressure signal that depends on the atmospheric pressure prevailing in the suction line 54 and consequently on the atmospheric pressure prevailing in the storage container 22 and in the melting chamber 34.

[0045] The adhesive melting device 10 also has an electrically controlled vent valve 62, which is connected to the suction line 54 and to the control unit 48 via a second control line 64. The vent valve 62 has a valve housing 66 that includes a vent opening 68. The vent opening 68 can be opened and closed by means of the vent valve 62. The control unit 48 controls the vent valve 62. During an adhesive melting process, the vent opening 68 is opened, allowing pressure equalization to occur via the vent opening 68 and the suction line 54. This occurs as air from the environment flows into the melting chamber 34 and the reservoir 22 via the vent opening 68 and the suction line 54, and air can be released from the reservoir 22 and the melting chamber 34 to the environment.After completion of a bonding process, the ventilation opening 68 is closed, so that air can be extracted from the melting chamber 34 and from the storage container 22 via the suction line 54 using the suction pump 46.

[0046] For switching the control unit 48 on and off, the adhesive melting device 10 has a manually operable main switch 70, which is coupled to a status indicator 72.

[0047] As already mentioned, the adhesive melting device can melt 10 different adhesive materials, which can then be applied to the longitudinal side 16 of the workpiece 18 via the adhesive application system 12 to bond an edge material to the longitudinal side 16. If the edge banding machine is switched off after completion of a bonding process, the heating effect of the melting body 36 ceases, so that adhesive material remaining in the melting chamber 34 and especially in the melting body 36 after completion of a bonding process gradually solidifies.When using a PUR adhesive, care must be taken after the gluing process to ensure that the PUR adhesive does not come into contact with humidity, as otherwise the isocyanate groups of the PUR adhesive will react with the humidity, causing it to solidify not only due to the loss of heating effect but also to cross-link through contact with humidity and subsequently no longer be liquefiable.

[0048] The PUR adhesive remaining in the melting body 36 and also in the outlet channel 38 is practically free from crosslinking due to the lack of contact with air. The PUR adhesive remaining in the application nozzle 14 can be flushed out of the application nozzle 14 via a flushing channel in the usual manner. To prevent crosslinking of the PUR adhesive remaining in the melting chamber 34 and the reservoir 22, the operator can switch on the control unit 48 using the main switch 70. The control unit 48 is configured to control the suction pump 46 depending on the temperature of the melting body 36 and the atmospheric pressure prevailing in the reservoir 22 and in the melting chamber 34. For this purpose, the control unit 48 is in signal-conducting communication via the first sensor line 56 with the temperature sensor integrated in the melting body 36 and via the second sensor line 58 with the pressure sensor 60.The control unit 48 switches on the suction pump 46 if the temperature of the melting body 36, as detected by the temperature sensor, falls below a predetermined or predefinable temperature limit after the heating of the melting body 36 has been switched off, and the atmospheric pressure prevailing in the storage container 22 and the melting chamber 34 exceeds a predetermined or predefinable upper pressure limit. After completion of an adhesive bonding process, the PUR adhesive can solidify due to the cessation of the heating effect in the melting body 36. If the temperature limit of the melting body 36 is undershot, the suction pump 46 is activated by the control unit 48, and the vent valve 62 is controlled such that the vent opening 68 closes.The reservoir 22 and the melting chamber 34 are then evacuated by means of the suction pump 46 until the atmospheric pressure prevailing in the reservoir 22 and the melting chamber 34 falls below a predetermined or predefinable lower pressure limit. This ensures that the PUR adhesive remaining in the reservoir 22 and the melting chamber 34 after completion of the bonding process no longer comes into sufficient contact with atmospheric moisture and thus cannot crosslink. To keep the energy consumption of the adhesive melting device 10 low, the control unit 48 only switches the suction pump 46 on again when the atmospheric pressure prevailing in the reservoir 22 and the melting chamber 34 exceeds the upper pressure limit again due to leaks.

[0049] Alternatively or additionally to switching the suction pump 46 on and off depending on the atmospheric pressure prevailing in the reservoir 22 and the melting chamber 34, the control unit 48 can be configured to switch the suction pump 46 on and off at predetermined or predefinable time intervals. In this case as well, it is ensured that the concentration of humidity present in the reservoir 22 and the melting chamber 34 is low enough to prevent cross-linking of the PUR adhesive remaining in the reservoir 22 and the melting chamber 34 after completion of a bonding process, thus allowing it to be liquefied again for a subsequent bonding process.

[0050] If, for example, an EVA adhesive is used instead of a PUR adhesive, it is not necessary to pump out the reservoir 22 and the melting chamber 34 after completion of an adhesive application. The operator therefore has the option of switching on the control unit 48 using the main switch 70 only when a PUR adhesive has been used.

Claims

1. Adhesive melting device for an edgebanding machine, comprising a melting chamber (34) for receiving adhesive material (32) and a heatable melting body (36) for melting the adhesive material (32), characterized by the fact that The adhesive melting device (10) has a suction device (46) for extracting air from the melting chamber (34).

2. Adhesive melting device according to claim 1, characterized by the fact that The adhesive melting device (10) comprises a storage container (22) with an airtight sealable filling opening (24) for storing adhesive material (32) to be melted, wherein the melting chamber (34) adjoins the interior (30) of the storage container (22) for receiving adhesive material (32) from the storage container (22), and wherein the storage container (22) together with the melting chamber (34) can be vacuumed by means of the suction device (46).

3. Adhesive melting device according to claim 1 or 2, characterized by the fact thatthe adhesive melting device (10) has a pressure piston (40) movable in the melting chamber (34) for pressing the adhesive material located in the melting chamber (34) against the melting body (36) and a feed unit (44) for moving the pressure piston (40).

4. Adhesive melting device according to claim 1, 2 or 3, characterized by the fact that the adhesive melting device (10) has a control device (48) for controlling the suction device (46).

5. Adhesive melting device according to claim 4, characterized by the fact that the temperature of the melting body (36) can be detected by means of a temperature sensor, wherein the temperature sensor is connected to the control device (48) and the control device (48) is configured to control the suction device (46) depending on the temperature of the melting body (36).

6. Adhesive melting device according to claim 5, characterized by the fact that the temperature sensor is integrated into the melting body (36).

7. Adhesive melting device according to claim 5 or 6, characterized by the fact that the temperature sensor is connected to the control unit (48) via a sensor line (56).

8. Adhesive melting device according to claim 5, 6 or 7, characterized by the fact that the control device (48) is set up to switch on the suction device (46) only when the temperature of the melting body (36) is less than a predetermined or predeterminable temperature limit.

9. Adhesive melting device according to one of claims 4 to 8, characterized by the fact that the adhesive melting device (10) has a pressure sensor (60) which is connected to the control device (48) and provides the control device (48) with a pressure signal corresponding to the atmospheric pressure prevailing in the melting chamber (34), wherein the control device (48) is configured to control the suction device (46) depending on the pressure signal.

10. Adhesive melting device according to claim 9, characterized by the fact thatthe pressure sensor (60) is connected to the melting chamber (34) or to a suction line (54) via which the suction device (46) is connected to the melting chamber (34).

11. Adhesive melting device according to claim 9 or 10, characterized by the fact that the pressure sensor (60) is connected to the control unit (48) via a sensor line (58).

12. Adhesive melting device according to claim 9, 10 or 11, characterized by the fact that the control device (48) is configured to switch on the suction device (46) only when the atmospheric pressure prevailing in the melting chamber (34) is greater than a predetermined or predefinable upper pressure limit, and to switch off the suction device (46) when the pressure prevailing in the melting chamber (34) is less than a predetermined or predefinable lower pressure limit.

13. Adhesive melting device according to one of claims 4 to 12, characterized by the fact thatthe control unit (48) is set up to switch the suction device (46) on and off at predetermined or predeterminable time intervals.

14. Adhesive melting device according to one of claims 4 to 13, characterized by the fact that the adhesive melting device (10) has a ventilation valve (62) through which ambient air can be supplied to the melting chamber (34) and which can be controlled by means of the control device (48).

15. Adhesive melting device according to claim 14, characterized by the fact that the ventilation valve (62) is connected to a suction line (54) via which the suction device (46) is connected to the melting chamber (34).

16. Adhesive melting device according to one of claims 4 to 15, characterized by the fact that the adhesive melting device (10) has a manually operated main switch (70) for switching the control device (48) and / or the suction device (46) on and off.

17. Method for controlling an adhesive melting device (10) according to one of the preceding claims, characterized by the fact that The melting chamber (34) is emptied after completion of a gluing process of the edge banding machine depending on the temperature of the melting body (36) and / or depending on the air pressure prevailing in the melting chamber (34).

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