Patent DE-19836789-A1 (DE)
Title: Continuous embossing press for embossing cold board surfaces has short movement path into a transfer stretch where water is sprayed followed by embossing stages with controlled temperature and pressure effects for a durable embossing
Inventor: BIELFELDT FRIEDRICH B
IPC: B27N3/24
Filed: 1998-08-13
Abstract: For the production of boards with a structured surface, the finished and cold board material is sprayed with water on one or both surfaces before passing through a heated stage to evaporate the water before the board surfaces are embossed.  The cold board is moved along a short path (A) into a covered transfer stage (B) where water is sprayed on to the board surface(s) at a rate of 112.5-225 g/m<2> before it passes through a continuous embossing press where a continuous structure belt round the press ram is pressed against the surface, while a steam pressure is increased to about 0.5 N/mm<2> in a steam pressure increase stage (C1) within the press stretch (L). The next press stage (C2) gives a steam pressure plasticizing effect on the board surface where the board is subjected to an increasing embossing pressure up to 3.5-4.0 N/mm<2> and at an increasing temp. up to 200 deg C. The embossing pressure and the plasticizing temp. are held in a high pressure and embossing stretch (D). The final stage (E) of the press stretch (L) gives a drying and structure fixing action with a reducing embossing pressure down to about 0.5 N/mm<2>. The time for the board material to pass through the five process stages (B,C1,C2,D,E) is sufficient to give a durable embossed structure at the board surface. The specification is an addition to DE19718770.6. The temperature of the sprayed water is from 20 deg C to  <= 100 deg C. At the steam pressure increase stage (C1), the steam pressure increase is 1.5-2.0 N/mm<2>. The board material takes about 18 secs. to pass through the five process stages (B,C1,C2,D,E) of the embossing press. Steam generated in the steam pressure increase stage (C1) is extracted, condensed and returned as water to be sprayed to the board surface at the transfer stage (B).  An Independent claim is included for a continuous board embossing press (10), separated from the feed point for the cold board (1) by a short movement path (A) into the transfer stage (B) where water is sprayed at the board surface within a spraying hood (6). The sprayed board is moved directly into the angled entry gap into the embossing press with an embossing length (L). The temp. and pressure for embossing, within the press length (L), is divided into four working stages with different temp. and pressure effects. The leading stage (C1) builds up the steam pressure, followed by a stage (C2) where the board surface is plasticized by the steam pressure. The next high pressure and embossing stage (D) is followed by the final drying and structure fixing stage (E).  Preferred Features: The board material (1) is carried between continuous steel belts (25,26), moved by powered drums (27,28) at the entry, to pass round rigid semi-circular deflectors (17,18) at the other end. They pass round the press table and press ram, with friction-reduction units giving support at the heated press plates (11) at the press table (22) and press ram (23). A continuous structured belt (19) of a woven metal wire mesh moves round the press ram (23) with the upper steel belt (25), with its own deflection drums (20,21). The upper sliding support plates can be heated. The press ram (23) and press table (22) are held together by tie straps (14), with a setting mechanism to adjust the press gap between them. The tie straps can be swung out, and telescopic tubes extended, for a change of structured belt (19).