Device for drying flat articles

Abstract

Device for drying sheet structures (1), comprising a housing (2) which accommodates a drying module (3), wherein the drying module (3) is configured to emit infrared radiation, wherein the drying module (3) has a support body (4) made of ceramic material, wherein at least one heating element (5) is assigned to the support body (4), wherein the support body (4) is designed as a hollow body with at least one opening.

Description

[0001] The invention relates to a device for drying sheet structures, comprising a housing which accommodates a drying module, wherein the drying module is configured to emit infrared radiation.

[0002] DE 10 2019 126 701 A1 discloses a device for drying sheet materials which uses infrared radiation for thermal drying. The sheet material is continuously fed into an irradiation zone and at least partially dried by the irradiation before being removed from the irradiation zone. Such devices are frequently used for drying coated sheet materials where a layer to be dried, such as ink, paint, varnish, or adhesive, is applied to a sheet-like substrate. The layer is preferably water-based and applied by spraying or printing. The sheet material is often a sheet-like material such as paper, cardboard, carton, or film. The device is used in particular for drying printed products. DE 10 2016 217 490 A1 discloses an infrared emitter for the heat treatment of a material web.

[0003] In previously known devices, it is known to use a drying module configured to emit infrared radiation. Furthermore, it is known to equip the devices with additional heating elements that convectively heat an incoming air which is then directed over the drying surface. While these devices offer high drying capacity, this comes at the cost of high energy consumption.

[0004] The invention is based on the objective of providing a device for drying flat structures which has a high drying capacity with low energy consumption.

[0005] This problem is solved by the features of claim 1. Advantageous embodiments are described in the dependent claims.

[0006] The device according to the invention for drying sheet structures comprises a housing which accommodates a drying module, wherein the drying module is configured to emit infrared radiation, wherein the drying module has a support body made of ceramic material, wherein at least one heating element is assigned to the support body, and wherein the support body is designed as a hollow body with at least one opening.

[0007] Because the support structure is designed as a hollow body with at least one opening, the drying module heats the air passing through it in addition to the infrared radiation. This allows the drying module to provide radiant heat in the form of infrared radiation and also convection heat in the form of heated air. The heated air can be directed onto the surface structure, in addition to the infrared radiation, to dry it through radiant and convection heat. Depending on the design of the drying module, this configuration may eliminate the need for additional heating elements in the device, which would be required in prior art devices solely for generating convection heat.

[0008] The ceramic material of the support structure is preferably selected to emit infrared radiation with a power peak in the wavelength range of 2,000 nm to 3,500 nm when heated. In this wavelength range, the radiant energy emitted by the drying module is absorbed by water to almost 100%. With regard to water-soluble substances applied to the surface structure that are to be dried, this results in particularly effective and energy-saving drying.

[0009] A particularly advantageous radiation characteristic of the infrared radiation results when the heating element is directly integrated with, and especially connected to, the support body. In this configuration, the heating element directly heats the support body, causing it to emit infrared radiation and convectively warm the air passing through the hollow support body. Integrating the heating element into the support body eliminates the need for a separate casing, such as a quartz casing. This allows the emission of infrared radiation without the filtering effect or transmission loss associated with a casing.

[0010] Preferably, the heating element is designed as an electric resistance heater. For this purpose, a meandering conductor structure can be applied to the support body. The conductor structure can be based on tungsten or platinum. When the heating element is energized, the conductor structure heats up first, followed by the ceramic support body.

[0011] The heating element is particularly firmly bonded to the support body when it is sintered together. For this purpose, the tungsten or platinum meander forming the heating element can be applied to a carrier layer, which in turn is applied to the outside of the support body. The support body then undergoes a sintering process, after which the tungsten or platinum meander is directly and firmly bonded to the ceramic material of the support body. Platinum and tungsten are particularly suitable for the design of the heating element due to their very high temperature resistance. Especially when the heating element is made of tungsten, it is advantageous for it to be embedded in the support body to prevent contact with oxygen. Alternatively, the heating element can be covered by a coating. This can extend its service life.

[0012] In principle, other heating conductor alloys are also conceivable for the design of the heating element, for example silicon carbide, molybdenum disilicide, titanium or graphite.

[0013] The heating element is preferably heated to an annealing temperature between 900 K and 1,500 K. When the ceramic support body is heated to this temperature range, it emits the preferred infrared radiation in the wavelength range between 2,000 nm and 3,500 nm. By directly integrating the heating element into the support body, particularly without a separate quartz casing for the heating element, emission of infrared radiation with wavelengths above 4,000 nm is also preferably achieved.

[0014] The support body can be rod-shaped. In this design, the support body is essentially cylindrical, thus enabling a linear radiation pattern, allowing for the drying of a flat, continuously conveyed surface along the drying module with a high area output.

[0015] The support structure may have at least one recess. The recess is either in contact with the hollow body incorporated into the support structure or forms the hollow body itself. The air contained in the recess or passing through the hollow body heats up, so that the drying module generates convective heat in addition to infrared radiation through the heating of the air.

[0016] The recess can extend axially through the support body. In this configuration, the support body can be tubular, allowing air to enter at one end and exit at the other. Alternatively, air can enter at one end and exit at the other and / or through additional air outlets. During heating operation, the drying module emits infrared radiation from its outer surface, while the air flowing through the hollow body inside heats up. It has proven particularly advantageous to use a blower to force air through the support body. The air heated by the drying module can then be applied to the surface structure, and together with the infrared radiation, it supports the drying process. The air flowing through the support body also acts as a cooling element.

[0017] Several recesses can be provided, radially integrated into the support body. In this configuration, it is conceivable that multiple recesses extend radially through the support body. Air can also be guided through the support body in this configuration. The recesses can form nozzles, and the heated air guided through the support body can be directed directly onto the surface structure.

[0018] In an alternative embodiment, the support body has a recess that extends axially through it, with several recesses branching off from this axial recess and penetrating the support body in a radial direction. In this embodiment, an air supply can be introduced centrally into the support body and heated within the recess. The heated air can then exit the support body through the radially extending recesses and be directed onto the surface structure.

[0019] The supporting structure can be colored black. The uncolored ceramic material is usually white, light gray, or beige. Coloring it black increases the emissivity of the dry modulus. The emissivity of an uncolored ceramic material is typically around 0.8 and improves to approximately 0.95 with black coloring.

[0020] A conveying system can be provided that directs air through the drying module. This creates a forced airflow, resulting in particularly good and efficient heat transfer. It is advantageous that the air cools the drying module and maintains the temperature within the range of the desired annealing temperature; simultaneously, the heated air can be directed onto the surface structure to support the drying process.

[0021] The housing can be equipped with a nozzle through which the process air heated by the drying module is directed towards the surface structure. This results in a directed flow of the heated air, enabling a particularly efficient drying process.

[0022] The housing can contain a reflector associated with the dry module. The reflector reflects the infrared radiation emitted by the dry module and directs it towards the surface structure. This prevents the infrared radiation from heating the housing or the components located within it, thus improving the efficiency of the device.

[0023] Some embodiments of the device according to the invention are explained in more detail below with reference to the figures. These show, schematically: Fig. 1 a dry module according to a first embodiment; Fig. 2the dry module according to Fig. 1 with a changed flow direction; Fig. 3 a dry module according to a second embodiment; Fig. 4 a device according to a first embodiment; Fig. 5 a device according to a second embodiment.

[0024] Figure 1Figure 1 shows a drying module 3 for a device for drying sheet structures 1. The drying module 3 comprises a support body 4 made of ceramic material and a heating element 5, which is associated with the support body 4. The support body 4 is rod-shaped in the form of a cylinder and is provided at one end with a fastening device 10. The fastening device 10 is in the form of a bayonet fitting. The heating element 5 is designed as an electrical resistance heater and comprises meandering heating wires made of tungsten. In an alternative embodiment, the heating wires are made of platinum. The heating element 5 is firmly and metallurgically bonded to the support body 4 by means of a sintering process.

[0025] The heating element 5 is designed to be heated to an incandescent temperature between 900 K and 1,500 K. The support body 4 also heats up, and at these temperatures it too begins to incandescent, emitting infrared radiation in a spectrum with wavelengths ranging from 2,000 nm to 3,500 nm.

[0026] The ceramic material of the support body 4 is colored black and has an emissivity of 0.95.

[0027] In the design according to Figure 1A recess 6 is provided in the support body 4, extending axially through it. This makes the support body 4 a hollow body with at least one opening. In the embodiment with the axially extending recess 6, the support body 4 is essentially tubular. Air can flow transversely through the support body 4 via the recess 6, which on the one hand tempers the support body 4 and on the other hand, as outgoing warm air, convectively supports the drying process of the surface structure 1. Because the recess 6 extends axially through the support body 4, openings are formed at both end faces of the support body 4, with the fastening device 10 being arranged at one end face, so that the fastening device 10 is also provided with the axially extending recess 6. In the embodiment according to Figure 1 Air flows longitudinally through the entire drying module 3.

[0028] Figure 2 The dry module 3 shows according to Figure 1 , wherein in this embodiment air flows in via the end face opposite the fastening device 10 and flows out via the fastening device 10. In this respect, in the Figure 1 and 2 In the dry module 3 shown, a flow through in both directions is conceivable.

[0029] Figure 3 shows a dry module 3 according to Figure 1 , wherein in the present embodiment several recesses 6 are provided which are radially incorporated into the support body 4. The support body 4 additionally has the in Figure 1The described axially extending recess 6 is located. However, this recess is only open towards the end face associated with the fastening device 10. The axially extending recess 6 through the support body 4 is flow-conductingly connected to further recesses 6 that are radially integrated into the support body 4. In this configuration, supply air can flow into the support body 4 via the fastening device 10 and flow out through the radially extending recesses. The radially extending recesses 6 have a relatively small cross-section and thus form nozzles, allowing the heated air flowing out of the radial recesses 6 to be directed directly onto the surface structure 1.

[0030] Figure 4 Figure 1 shows a first embodiment of a device for drying sheet structures 1, comprising a housing 2 which contains a drying module 3 according to Figure 1 , Figure 2 or Figure 3 records.

[0031] Drying module 3 is designed to emit infrared radiation and to heat air convectively. In its configuration according to... Figure 1A conveying device 7 in the form of a blower is provided, which conveys air through the housing 2 in the form of a forced flow. The housing 2 is provided with an outlet opening 11, from which a nozzle 8 is formed. Furthermore, the outlet opening 11 has a cross-sectional constriction, the cross-section of which widens again in the direction of flow upstream of the nozzle 8. This creates a Venturi nozzle in the area of ​​the cross-sectional constriction. The recess 6, which is incorporated into the end face of the support body 4 of the drying module 3, opens into the area of ​​the cross-sectional constriction. This makes it possible to passively convey air through the drying module 3. Due to the Venturi effect, air is drawn in through the recess 6 and, together with the other conveying air, is directed towards the nozzle 8 and finally onto the surface structure 1.

[0032] The sheet material 1 can, for example, be paper or cardboard coated with printing ink, varnish, or other coating. Preferably, the printing ink, varnish, or coating is water-based and therefore exhibits a particularly high absorption capacity for radiant energy in a wavelength range between 2,000 nm and 3,500 nm. In conjunction with the drying module 3 according to the invention, which emits infrared radiation in this wavelength range due to its ceramic support body 4, a particularly effective and energy-saving drying process is achieved. The drying process is supported by the air conveyed onto the sheet material 1 via the nozzle 8, which has been convectively heated inside the support body 4 of the drying module 3.

[0033] Inside the housing 2, a reflector 9 is arranged. This is positioned above the drying module 3 and reflects the infrared radiation emitted by the drying module 3 and directs it towards the surface structure 1 passing below the drying module 3. The nozzle 8 is designed as a slot nozzle and enables a linear flow towards the surface structure 1.

[0034] Figure 5 shows further training of the in Figure 4 The device shown. In this embodiment, two conveying devices 7 are provided, wherein a first conveying device 7 directs air through the housing 2 and a second conveying device 7' directs air through the support body 4 of the drying module 3. A nozzle 8 is associated with the housing 2, in which the two air streams mix and are directed onto the surface structure 1.

Claims

1. Device for drying flat articles (1), comprising a housing (2), which accommodates a drying module (3), wherein the drying module (3) is designed to emit infrared radiation, wherein the drying module (3) has a support body (4) made of ceramic material, wherein at least one heating element (5) is assigned the support body (4), characterised in that the support body (4) is designed as a hollow body having at least one opening, wherein air is guided through the hollow body in such a way that the drying module also provides convective heat in the form of heated air.

2. Device according to claim 1, characterised in that the heating element (5) is designed as an electrical resistance heater.

3. Device according to claim 1 or 2, characterised in that the support body (4) is rod-shaped.

4. Device according to one of claims 1 to 3, characterised in that at least one recess (6) is formed in the support body (4).

5. Device according to claim 4, characterised in that the recess (6) engages axially through the support body (4).

6. Device according to claim 4 or 5, characterised in that a plurality of recesses (6) are formed radially in the support body (4).

7. Device according to one of claims 1 to 6, characterised in that the support body (4) is coloured black.

8. Device according to one of claims 1 to 7, characterised in that the heating element (5) is assigned directly to the support body (4).

9. Device according to one of claims 1 to 8, characterised in that the support body (4) emits infrared radiation in a wavelength range of between 2,000 nm and 3,500 nm.

10. Device according to one of claims 1 to 9, characterised in that a conveying device (7) is provided, which guides air through the drying module (3).

11. Device according to one of claims 1 to 10, characterised in that a nozzle (8), through which the process air heated by the drying module (3) can be guided in the direction of the flat article (1) is is assigned to the housing (2).

12. Device according to one of claims 1 to 11, characterised in that a reflector (9) assigned to the drying module (3) is arranged in the housing (2).

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