SET CONSISTING OF A PRESSED UPHOLSTERY-PRESSED SHEET UNIT AND A HEATING PLATE OR SET CONSISTING OF A PRESSED UPHOLSTERY-HEATING PLATE UNIT AND A PRESSED SHEET, FOR USE IN A HYDRAULIC SINGLE- OR MULTI-DAY HEATING PRESS

Description

Introduction

[0001] The invention relates to a set comprising a press pad / press plate unit and a heating plate for use in a hydraulic single- or multi-opening heating press. Furthermore, the invention relates to a set comprising a press pad / press plate unit and a press plate for use in a hydraulic single- or multi-opening heating press. State of the art

[0002] The coating of wood-based panels, such as plywood, chipboard, MDF, HDF, or multiplex boards, is typically done using high-quality pulp paper impregnated with aminoplast resin. These papers can be printed with various designs or be plain. The aminoplast resins consist of pre-condensed melamine / formaldehyde resins or mixed resins of melamine and urea or phenol and cresol. The pre-condensed resins are in a liquid phase, which is why paper webs are thoroughly impregnated in special impregnation channels with drying and cooling zones. In the heated drying zone, the polycondensation of the resins is stimulated again at a temperature between approximately 150°C and 170°C. This process is interrupted in a subsequent cooling zone, depending on the desired degree of condensation.The paper webs obtained in this way have a low water content and are solid and therefore transportable for further processing in a press system, in particular in the form of a hydraulic single- or multi-daylight heating press.

[0003] The impregnated decorative papers are then placed with the appropriately selected wood-based panels in a hydraulic heating press, which can have one or more floors. Under pressure and temperature, the pre-condensed aminoplast resins first become liquid, with the viscosity of the liquid resins increasing again due to further molecular crosslinking, and finally, a solid surface is formed. To create the surface, metallic press plates with textured, matte, or glossy surfaces are brought into contact with the decorative papers or aminoplast resins. The press plates are usually chrome-plated to protect the surface against abrasion and damage. The chrome layer also serves to ensure flawless separation from the resin layer after the coating process (lamination).Metallic pressed sheets can be made of brass, the alloy MS64 or the materials AISI 410 or AISI 630, for example, although steel sheets are preferred today due to their higher hardness and longer service life.

[0004] Wood-based panels have different densities depending on their application and therefore require different pressing pressures. When manufacturing flooring panels from HDF (High Density Fibreboard), the specific pressing pressures are particularly high, ranging from approximately 400 N / cm² to 600 N / cm², as the panels' densities range from approximately 800 N / cm³ to 1000 N / cm³. The raw panels themselves have very little cushioning effect and also have thickness tolerances that must be compensated for during the coating process. In principle, all panel materials have greater or lesser thickness tolerances. Further tolerances arise from the respective press system itself, particularly the press plates and heating platens used within it.

[0005] If the aforementioned tolerances are not compensated, significant surface defects will occur during the formation of the surfaces of the coated wood-based panels. For this reason, the press systems are always equipped with appropriate press pads, particularly those in the form of pressure-equalizing fabrics or mats. The press pads are fixed between the heating platens and the press sheets. They must be heat-stable, i.e. they must not decompose even at temperatures between 200°C and 230°C, and they must possess good resilience or restoring force and high thermal conductivity. Even pressure distribution and rapid heat flow during the coating process are particularly important factors. As previously mentioned, the aminoplast resin liquefies again under pressure and heat, releasing formaldehyde and water in vapor form.Because the resin is located between the metal press plate and the wood-based panel, the system is hermetically sealed, and the corresponding vapors must diffuse into the paper web and the panel surface within the short time dictated by the press cycle. If this does not happen due to uneven pressing pressure, the gas bubbles remain trapped in the resin layer and later become visible as milky, cloudy spots on the surface. Panels with such defects are then no longer suitable for further use. Due to the high heating plate temperatures (approximately 200°C to 230°C), the selection of suitable materials for the press pads is comparatively limited. In recent decades, a silicone rubber-based elastomer material has proven suitable, although blend materials and copolymers of silicone rubber and fluorosilicone rubber or fluororubber are also used.State-of-the-art press pads are typically designed as fabrics with threads containing elastomer material or as coated mats with an inner, usually metallic, supporting fabric.

[0006] EP 1 136 248 A discloses a press pad comprising a fabric containing a copolymer consisting of a silicone and a fluorosilicone rubber. The copolymer is incorporated into the press pad in the form of coated threads used as warp or weft threads. To increase thermal conductivity, metallic additives can be added to the elastomer material.

[0007] EP 0 735 949 A1 describes a press pad comprising a silicone elastomer in one thread system and metal threads in the other thread system. The threads comprising the silicone elastomer can be designed as sheath-core threads, with the thread core being made of wire, for example, and the thread sheath of the silicone elastomer.

[0008] In the press pad known from DE 20 2012 005 265 U, certain threads are designed as heat conducting threads which are intended to enable a more direct heat transfer due to their course being as perpendicular as possible to the press pad surfaces.

[0009] Furthermore, EP 1 300 235 A and DE 23 19 593 A each disclose a press pad made of metal fabric, which is subsequently coated essentially over its entire surface with a silicone rubber. According to the teaching of EP 1 300 235 A, the metal threads lying towards a surface of the press pad, in particular their loops or loops, are exposed by doctoring during the coating process in order to achieve metallic contact between the press pad and the heating plate or press sheet. In addition, particles can be mixed into the silicone elastomer to increase thermal conductivity. A disadvantage in this context is the fact that the addition of the particulate additives to the elastomer matrix negatively influences its elasticity and recovery properties.

[0010] From DE 10 2014 112244 A1 a press pad-press plate unit with the technical features of the preamble of claim 1 and a press pad-heating plate unit with the features of the preamble of claim 2 are known.

[0011] Common press pads often suffer from material fatigue, particularly with regard to their resilience or spring action. Common silicone elastomers, as well as alternative press pads with threads made of aromatic polymers, particularly polyamides, exhibit such aging processes at continuous temperatures above approximately 200°C to 230°C. The press pads must therefore be replaced relatively early, resulting in downtimes for the press systems and increased environmental pollution, particularly since press pads made of common materials or material blends are very difficult to recycle. Especially when coating floorboards, press pads are required that exhibit a high recovery value, even over a long period of use, as well as very high heat transfer.To date, when coating HDF boards for flooring ("laminate"), it has not been possible to change the board format using the conventional press pads, as the pads are highly compressed in the selected board format and a later change to a larger format leaves marks on the pressed material.

[0012] Furthermore, sets according to the invention can also be used in so-called high-pressure press systems, in which, for example, so-called high-pressure laminates, e.g., in the form of base materials for circuit boards, are produced by pressing under heat. A press pad for such an application, consisting of a high-temperature-resistant plastic fleece and a PTFE film bonded to it, is known from DE 200 11 432 U. Due to the long cycle times in such pressing processes, metals are not required for this high-pressure pad. Task

[0013] The invention is based on the object of providing a set comprising a press pad / press plate unit and a heating plate or a set comprising a press pad / heating plate unit and a press plate, wherein the press pad is characterized by a very high elastic recovery capacity, which is maintained fatigue-free over the longest possible period, as well as a high thermal conductivity. Solution

[0014] According to the invention, this object is achieved starting from a press cushion of the type mentioned at the beginning in that the metallic plate is a press plate or a heating plate of the single- or multi-opening heating press and the spring elements are glued and / or soldered and / or welded and / or positively connected to the plate. Metallic spring elements have two advantages over elastomer materials or aromatic polymer materials: Firstly, due to the metal material, they can have a very high modulus of elasticity, i.e. a high spring stiffness. This means that the restoring forces are already very high even with comparatively small deflections, i.e. deformations, of the spring elements. Metals with a high modulus of elasticity and, at the same time, high elongation at break include steel, in particular spring steel. In principle, however, other metallic materials such as copper alloys (e.g. beryllium copper) can also be used.Despite the large spring constants, metallic springs retain their recovery properties over very long periods of time, so that the press pads according to the invention have a correspondingly long service life.

[0015] On the other hand, metallic spring elements have a very good thermal conductivity, so that the heat transfer through the press pad according to the invention is positively influenced, especially in comparison with press pads that have large proportions of an elastomer material that is generally characterized by its comparatively poor thermal conductivity properties.

[0016] The invention thus allows for the first time the use of a press cushion component that is equally advantageous in terms of both its thermal conductivity properties and its spring properties (resilience). In the prior art, different components were always used to optimize both properties (thermal conductivity and resilience), such as elastomer materials for resilience and metal materials, in particular metal threads, for good thermal conductivity. In the context of the present invention, the support structure is formed by a metallic plate, namely a press plate or a heating plate of the single- or multi-opening heating press. In the latter two cases, where the spring elements are connected to a press plate or a heating plate, a unit is created comprising a press plate and spring elements or a heating plate and spring elements.

[0017] The spring elements are glued and / or soldered and / or welded and / or positively connected to the respective plate, for example by inserting spring sections into corresponding recesses or openings in the plate. A combination of a metallic plate and a textile fabric is also possible. In this variant, the spring elements are preferably connected to the textile fabric and the metallic plate. Furthermore, a suitable connection between the textile fabric and the metallic plate is required, for example in the form of gluing, welding, or soldering, or a positive connection between threads of the textile fabric and the plate, e.g. guiding threads of the textile fabric through openings or recesses in the metallic plate.

[0018] In particular, the textile fabric can be designed as a knitted fabric or a nonwoven fabric or a woven fabric, wherein at least some of the threads forming the textile fabric consist of metal or contain metal, wherein the metal can be formed in particular from brass, copper, bronze, steel, in particular stainless steel.

[0019] Disc springs or coil springs or leaf springs or wave springs can preferably be used as metallic spring elements.

[0020] According to a preferred embodiment of the invention, it is proposed to connect the spring elements to threads of the textile fabric, in particular to connect them in a form-fitting manner, preferably at intersection points of warp threads and weft threads. For this purpose, the spring elements can have openings through which threads of the textile fabric, in particular the aforementioned warp and weft threads, are passed. A particularly preferred embodiment is formed by a press pad in which the spring elements each have four openings, two of which carry a warp thread and the other two carry a weft thread. The intersection points of the respective threads can be designed particularly advantageously in this way.

[0021] To achieve the best possible homogeneity of the spring properties of the press cushion, the spring elements should be arranged equidistant from each other, especially in intersecting rows, and especially along the weft and / or warp threads of a fabric serving as the supporting structure. This results in a kind of matrix structure and a particularly simple arrangement of the spring elements.

[0022] In a further development of the invention, it is provided that the spring elements can be partially embedded in an elastomer material, preferably in a silicone elastomer or a fluorosilicone elastomer or a blend polymer or copolymer of the two aforementioned elastomers. Preferably, sections or parts of the spring elements on both opposite sides of the press pad each form part of the surface of the press pad. In this way, particularly good heat transfer is achieved, since the heat is transferred from both surfaces of the press pad to the press plate or heating plate via metallic contact surfaces of the press pad. In this context, it is particularly advantageous if the spring elements extend completely through the entire thickness of the press pad in order to optimize heat transfer.

[0023] When combining metallic spring elements with an elastomer material, it may be useful to add particles to the elastomer material to increase the thermal conductivity of the press pad. These are particularly particles made of a metal or mineral, and these particles should preferably be in the form of nanoparticles. Example

[0024] The invention is explained in more detail below using exemplary embodiments illustrated in the figures. It shows: Figure 1 shows a schematic view of a press pad not according to the invention, Figure 2 shows a vertical section through a spring element from Figure 1 , Figure 3 a schematic view of another press cushion not according to the invention, Figure 4 a vertical section through the press cushion from Figure 3, Figure 5 shows a vertical section through a single-daylight heating press according to the prior art, Figure 6 shows a vertical section through a press cushion-heating plate unit of a set according to the invention and Figure 7 shows a vertical section through a press cushion-press plate unit of a further set according to the invention.

[0025] An example of implementation that is shown in the Figure 1 , comprises a press cushion 1' not according to the invention for use in a hydraulic single- or multi-opening heating press. As in the prior art, the press cushion 1 is arranged between a heating plate and a press plate of a single- or multi-opening heating press in order to compensate for thickness tolerances present in the press plate or heating plate and simultaneously enable the heat emanating from the heating plate to be transferred to the press plate.

[0026] The press pad 1, not according to the invention, comprises a flat support structure 2 and a plurality of spring elements 3. The flat support structure 2 is designed in the form of a woven fabric comprising two thread systems 4, 5, namely warp threads 6 and weft threads 7. The warp threads 6 and the weft threads 7 are in the form of brass wire strands and are woven together to form a plain weave. The warp threads 6 thus run alternately over and under the weft threads 7 and vice versa.

[0027] The spring elements 3 of the press cushion 1 are designed in the form of metallic disc springs 8. When used in a single- or multi-opening heating press, the disc spring 8, in an undeformed state, is in contact only with a circular, circumferential upper edge 9 with a heating plate of a single- or multi-opening heating press and with a likewise circular, circumferential lower edge 10 with a press plate of a single- or multi-opening heating press, with the two edges 9, 10 each forming a circular contact line 11, 12. However, a reversed orientation of the spring element 3 is also conceivable, in which the upper edge 9 is in contact with the press plate and the lower edge 10 is in contact with the heating plate.

[0028] Furthermore, the disc springs 8 have bevelled (conical) side sections 15, which cause a reduction of the diameter of the first contact line 11 compared to the diameter of the second contact line 12. A section through a disc spring 8 is shown in the Figure 2 shown and illustrates a truncated cone shape.

[0029] During a pressing process in a single- or multi-opening hot press, the spring element 3 is deformed such that a flat, upper contact surface 13 is formed. At the same time, a flat, lower contact surface 14 is formed. When used in a single- or multi-opening hot press, one of the contact surfaces 13, 14 is in contact with the heating plate, while the other contact surface 13, 14 is in contact with the press plate. The disc spring 8 thus essentially assumes the shape of a hollow cylinder during the pressing process.

[0030] In an edge region 16, the disc springs 8 are provided with four openings 17, which are arranged at an angle of 90° to one another on a circle. To simplify production, each of these openings can also be open to the circular outer edge of the disc spring 8, so that the weft threads 7 or warp threads 6 do not have to be "threaded through" with one thread end, but can be "threaded in" laterally. A thread 6, 7 of a thread system 4, 5 is passed through two opposite openings 17 of the spring elements 3, while the remaining two openings 17 are intended to receive a thread 6, 7 of the correspondingly other thread system 4, 5. A crossing point 18 of a warp thread 6 and a weft thread 7 essentially corresponds to a central axis 19 of the spring element 3. The disc springs 8 are arranged equidistantly in the press cushion 1 and form rows crossing at an angle of 90° in the press cushion 1.The press pad 1 is therefore easy to roll up and transport.

[0031] Due to an increased untensioned (force-free) length 21 of the disc springs 8 compared to a diameter 20 of the warp threads 6 and weft threads 7, an upper contact surface of the press cushion 1 is formed by the total of the upper contact surfaces 9 of the individual disc springs 8, while a lower contact surface of the press cushion 1' is determined by the total of the lower contact surfaces 10 of the individual disc springs 8. This ensures that different thicknesses in the heating plate and / or the press sheet are compensated for by means of a resilient effect of the disc springs 8, wherein the degree of the resilient effect can be varied by changing an outer diameter 22, an inner diameter 23, a material thickness 24 and the untensioned length 21 of the disc spring 8 and can thus be adapted to the specific requirements in the single- or multi-opening heating press. The warp threads 6 and the weft threads 7 therefore do not come into contact with the press sheet orthe heating plate. Due to the heat-conducting properties of the disc springs 8, which extend very directly, ie, over a short distance, through the press plate, the heat emanating from the heating plate is effectively transferred to the press plate.

[0032] A further embodiment of a press pad 1' not according to the invention is shown in Figure 3 The press pad 1' also comprises a flat support structure 2 in the form of a fabric and a plurality of metallic spring elements 3. In contrast to the Figure 1 The press cushion 1' shown in the drawing has the press cushion 1' according to the Figure 2 a double-sided coating 25 made of a heat-stable elastomer material. Figure 1The pressing pad 1' shown is therefore essentially embedded in the elastomer material. To ensure that the contact of the heating plate or the pressing plate continues to be made only with the spring elements 3, the coating 25 is removed in the area of ​​each spring element 3, as can be seen in the Figure 4 can be seen. A lower surface and a lower surface 26 of the press pad 1' are thus partially formed by the spring elements 3.

[0033] A single-daylight heating press 27 according to the state of the art is shown in Figure 5shown. The single-opening heating press 27 comprises two heating plates 28 and two pressing plates 29. As already provided in the prior art, a pressing pad 1', 1 is arranged between each heating plate 28 and a pressing plate 29 of the single-opening heating press 27. A wood-based panel 30 to be coated is inserted between the two pressing plates 29 and is covered with a decorative paper (not shown in the figure). The decorative paper is bonded to the wood-based panel 30 by means of the heat emanating from the single-opening heating press 27 and the pressure exerted on the wood-based panel 30.

[0034] An embodiment of a press pad heating plate unit 31 of a set according to the invention, which is shown in the Figure 6The assembly shown comprises a press pad 1, 1', as described above, for example, and a heating plate 28 of a single- or multi-opening heating press. The press pad 1, 1' is bonded to the heating plate 28 in such a way that a single component is formed.

[0035] An embodiment of a press pad-press plate unit 32 of a further set according to the invention is shown in the Figure 7 shown. In contrast to the press pad-heating plate unit 31, the press pad 1', 1, as described above, is not connected, for example, by adhesive bonding, to a heating plate 28, but rather to a press plate 29 of a single- or multi-opening heating press, and thus also forms a single component. List of reference symbols

[0036] 1' Press pad 1 Press pad 2 Supporting structure 3 Spring element 4 Thread system 5 Thread system 6 Warp thread 7 Weft thread 8 Disc spring 9 Upper edge 10 Lower edge 11 Contact line 12 Contact line 13 Upper contact surface 14 Lower contact surface 15 Side section 16 Edge area 17 Opening 18 Crossing point 19 Central axis 20 Diameter 21 Untensioned length 22 Outer diameter 23 Inner diameter 24 Material thickness 25 Coating 26 Surface 27 Single-daylight heating press 28 Heating plate 29 Press plate 30 Wood-based panel 31 Press pad-heating plate unit 32 Press pad-press plate unit

Claims

1. Set made of a press pad-press plate unit and a heating plate for use in a hydraulic single or multi-level heating press, comprising a flat support structure (2) and a plurality of metallic spring elements (3), which are connected to the support structure (2) and are distributed therein or arranged thereon, the support structure (2) being a metallic plate, the metallic plate being a press plate for use in a single or multi-level heating press, and the spring elements (3) are glued and / or soldered and / or welded and / or positively connected to the plate, characterized in that the spring elements (3) are arranged between the press plate and the heating plate.

2. Set made of a press pad-heating plate unit and a press plate for use in in a hydraulic single or multi-level heating press, comprising a flat support structure (2) and a plurality of metallic spring elements (3), which are connected to the support structure (2) and are distributed therein or arranged thereon, the support structure (2) being a metallic plate, the metallic plate being a heating plate for use in a single or multi-level heating / hot press, and the spring elements (3) are glued and / or soldered and / or welded and / or positively connected to the plate, characterized in that the spring elements (3) are arranged between the press plate and the heating plate.

3. Set according to claim 1 or 2, characterized in that the metallic plate is connected to a textile fabric, the spring elements (3) being connected to the textile fabric and to the metallic plate.

4. Set according to claim 3, characterized in that the textile fabric is a knitted or a crocheted fabric or non-woven or a woven fabric, at least one portion of the threads (6, 7) which form the textile fabric, consisting of metal or contain metal, the metal being formed in particular from brass, copper, bronze, steel, in particular stainless steel.

5. Set according to one of claims 1 to 4, characterized in that the spring elements (3) are plate springs (8) or helical springs or leaf springs or wave springs.

6. Set according to one of claims 3 to 5, characterized in that the spring elements (3) are connected, in particular positively connected to threads (6, 7) of the textile fabric, the spring elements (3) being preferably arranged at crossing points (18) of warp threads and weft threads (6, 7) of the textile fabric.

7. Set according to claim 6, characterized in that the spring elements (3) have openings (17), through which the threads (6, 7) of the textile fabric are passed.

8. Set according to claim 7, characterized in that the spring elements (3) have at least four openings (17), a warp thread (6) is passed through two of said openings and a weft thread (7) is passed through the other two.

9. Set according to one of claims 6 to 8, characterized in that the spring elements (3) are arranged equidistantly from one another, in particular in intersecting rows, in particular along the weft threads and / or warp threads (6, 7).

10. Set according to one of claims 1 to 9, characterized in that the spring elements (3) are embedded at least partially in an elastomeric material, are preferably embedded in a silicone elastomer or a fluorosilicone elastomer or a blend polymer or a copolymer of the two previously mentioned elastomers, the spring elements (3) on both opposite sides of the press pad (1, 1') preferably forming in each case a portion of the surface (26) of the press pad (1, 1').

11. Set according to claim 10, characterized in that particles to increase thermal conductivity, in particular particles made from a metal or a mineral, in each case preferably in particular in the form of nanoparticles, are contained in the elastomeric material.