# US 8,540,924 B2 · Method and device for preheating a pressed material mat during manufacture of wood material boards > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,540,924 B2 - Document ID: US8540924B2 - Status: Granted - Kind: B2 - Application number: 12/811,109 - Filed: 2008-12-27 - Published: 2011-04-21 - Granted: 2013-09-24 - Earliest claimed: 2007-12-30 - Assignees: Dieffenbacher GmbH Maschinen- und Anlagenbau - Applicants: Werner Hoffman; Ulf Konekamp; Gernot von Haas - Inventors: Werner Hoffman; Ulf Konekamp; Gernot von Haas - Web page: https://patentgrep.com/patent/US8540924B2 ## CPC - B27N 3/18: Auxiliary operations, e.g. preheating, humidifying, cutting-off - B27N 3/24: characterised by using continuously acting presses having endless belts or chains moved within the compression zone - F26B 3/20: the heat source being a heated surface {, e.g. a moving belt or conveyor}(F26B3/22 takes precedence) - F26B 3/347: Electromagnetic heating, e.g. induction heating or heating using microwave energy - F26B 7/00: Drying solid materials or objects by processes using a combination of processes not covered by a single one of groups F26B3/00 and F26B5/00 {(F26B1/005, F26B5/04, F26B23/026 take precedence)} - F26B 17/026: {the material being moved in-between belts which may be perforated} - B27N: MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL (containing cementitious material B28B; shaping of substances in a plastic state B29C; fibreboards made from fibrous suspensions D21J; drying F26B17/00) - F26B: DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM (drying devices for combines A01D41/133; racks for drying fruit or vegetables A01F25/12; drying foodstuffs A23; drying hair A45D20/00; body-drying implements A47K10/00; drying household articles A47L; drying gases or vapours B01D; chemical or physical processes for dewatering or like separating liquids from solids B01D43/00; centrifugal apparatus B04; drying ceramics C04B33/30; drying yarns or fabrics in association with some other form of treatment D06C; drying frames for laundry without heating or positive air circulation, domestic laundry-or spin-driers, wringing or hot pressing laundry D06F; furnaces, kilns, ovens F27) ## Abstract The invention relates to a method for preheating a pressed material mat (14) spread on an endlessly and continuously circulating molding band (6) during manufacture of wood material boards, wherein microwaves from one or both press surface sides are beamed into the pressed material mat (14) to preheat the pressed material mat (14) and the pressed material mat (14) is compacted and hardened by application of pressure and heat after transfer to a continuously operating press (1). The invention consists of microwaves in a frequency range of 2400-2500 MHz being used to heat the pressed material mat (14), wherein the microwaves for each press surface side are generated from 20 to 300 microwave generators (26) with magnetrons (20) of a respective output of 3 to 50 kW. A device for preheating pressed material mats (14) is also provided, in which 20 to 300 microwave generators (26) with magnetrons (20) with an output of 3 to 50 kW and with a frequency range of 2400-2500 MHz are arranged in a conveyor furnace (4) per area side. ## Claims ### Claim 1 A method for preheating a press material mat spread on an endless, continuously revolving shaping belt during production of wooden boards, the method comprising: preheating the press material mat in a continuous furnace by emitting microwaves having a frequency ranging from 2400-2500 MHz into the press material mat from one or both press surface sides using 20 to 300 microwave generators for each press surface side, each microwave generator comprising at least one magnetron having a power ranging from 3 to 50 kW. ### Claim 2 (depends on 1) The method according to claim 1, further comprising examining the press material mat for metal parts having a dimension longer in length than ¼ of a wavelength of a microwave frequency. ### Claim 3 (depends on 1) The method according to claim 1, wherein an entry, an exit or a combination thereof of the continuous furnace is automatically adjusted in height and width to the press material mat. ### Claim 4 (depends on 1) The method according to claim 1, further comprising guiding the press material mat directly through the continuous furnace via a shaping belt that is microwave-compatible. ### Claim 5 (depends on 1) The method according to claim 1, further comprising heating a plastic belt used in the continuous furnace less than 10° C. during a pass. ### Claim 6 (depends on 1) The method according to claim 1, wherein by using an upper endlessly revolving plastic belt in the continuous furnace, escape of moisture from the press material mat is prevented. ### Claim 7 (depends on 1) The method according to claim 1, wherein absorption elements in the continuous furnace are brought as close as possible to the press material mat during passage of the press material mat. ### Claim 8 (depends on 7) The method according to claim 7, wherein the absorption elements comprise absorber bricks or water vessels. ### Claim 9 (depends on 1) The method according to claim 1, further comprising reintroducing excess scattered radiation back into the press material mat via reflectors. ### Claim 10 (depends on 1) The method according to claim 1, further comprising automatically switching off the microwave generators in areas in the continuous furnace in which no press material mat is conveyed, in areas in the continuous furnace in which foreign metal objects are detected or a combination thereof. ### Claim 11 (depends on 1) The method according to claim 1, further comprising converting cooling power by heat feedback for remote heat. ### Claim 12 (depends on 1) The method according to claim 1, further comprising checking the press material mat for sparks or fires during passage of the press material mat through the continuous furnace. ### Claim 13 (depends on 12) The method according to claim 12, further comprising automatically extinguishing the sparks, the fires or a combination thereof. ### Claim 14 A method for preheating a press material mat spread on an endless, continuously revolving shaping belt during production of wooden boards, the method comprising: preheating the press material mat in a continuous furnace by emitting microwaves having a frequency ranging from 2400-2500 MHz into the press material mat from one or both press surface sides using 20 to 300 microwave generators for each press surface side, each microwave generator comprising at least one magnetron having a power ranging from 3 to 50 kW, wherein the preheating produces a uniform temperature distribution of ±7° C. in the press material mat over a length and a width of the press material mat.