Patent DE-19858152-A1 (DE)
Title: Continuous press for wood or recycled thermoplastic boards has structured sections for heating and heating/cooling and cooling to ensure that finished board material has no water or vapor pockets
Inventor: GRAF MATTHIAS
IPC: B30B5/06
Filed: 1998-12-16
Abstract: The continuous press assembly, for the production of wood chip- and fiberboards, and plastics boards, has a press stretch (L) which is divided into a heated press stretch (LH) of 50-75% of the length, a heated/cooled press stretch (LH/K) of 15-25% of the length, and a press cooling stretch (LK) of 10-25% of the length.  The continuous press assembly, for the production of wood chip- and fiberboards, and plastics boards, has a press stretch (L) which is divided into a heated press stretch (LH) of 50-75% of the length, a heated/cooled press stretch (LH/K) of 15-25% of the length, and a press cooling stretch (LK) of 10-25% of the length. Each section has its press plate system with a recirculating low friction unit (21,22). The press heated/cooled stretch has a single or multiple structure, where the segments (S1-S3) can be heated and/or cooled. A low friction support is at the transit (TB) between the two recirculating systems or press part-sections (I,II). The low friction units are roller rods (22) on chains (21) across the press width, or they are roller bearing carpets. The supports are in the wedge-shaped path section (TB) between the press sections (I,II), which are rotating roller bodies, static rollers, sliding shoes or hydrostatic press cushions, air or steam cushions. The low friction units are between the press cooling plates (18) and the steel belts (12,13), as a non-stick cladding or an air or steam cushion surface at the press plates (18). Additional vertical drillings at the cooling press plates (18) and the heating press plates (17) are at intervals in a number of rows across the press width, to deliver cold softened water at the low friction units (22) and the steel belts (12,13). The evaporated water is extracted as steam from the roller zone and/or flat through the drillings in the press plates or at the sides of the steel belts (12,13). Heat taken from the low friction units (22) at the press part section (I) is fed back through a heater. The low friction units (22) can be tubes. Insulation strips (37) are between the final press heated plates (16) and the leading press heated/cooled plate (17). The press plate cassettes are separated from each other by insulation strips (37) and against the adjacent press heated plate (16). Independent claims are also included for: (1) a continuous board press plate control where the press heated/cooled stretch within the press stretch is switched on when the temperature in the center of the pressed board material has achieved 85-95% of the bonding agent reaction temperature; (2) a continuous board press operation, where the press heated/cooled stretch (LH/K) has a number of working fields (S1-S3) with a variable action either for the heated (LH) or the cooling (LK) stretches to match the reaction temperature of the bonding agent and/or the type and consistency and thickness of the pressed board material.  Preferred Features: The final moisture content of the pressed board material over the press cooled stretch is 0-3% below the initial moisture content level. The recovery of the heat loss from the press plate cooling, the cooling of the low friction units and the steel belts is used for initial heating of the water supply to be heated for steam at the initial warming of the board material and/or the water supply for the steam dryers at the wood chip/fiber preparation stages and/or as the heating medium for the press heated plates in the continuous press. The heat extracted from the press units in the press heated/cooled stretch (LH/K) is fed to the full height of the steel belts as they return to the start point, together with heating. The cooling of the low friction units and the steel belts is set according to the hardening temperature of the bonding agent at not more than 120 deg C for wood boards and not more than 100 deg C for plastics boards. The surfaces of the pressed board material are cooled by coolant fed through the drillings in the press cooled plates and/or by spraying cold water on the low friction units and the steel belts through vertical drillings at the press plate cassettes and/or the press cooled plates and/or by press cooled plates. The water delivered is only sufficient to give a volume of evaporated steam which can be extracted. The extracted steam is fed through a water basin to condense into water. Any oil residue is taken from the water surface by separation or suction, and the condensed water is recirculated in a closed water spray circuit.