Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Patent
1997-10-08
1999-06-22
Ball, Michael W.
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
1562746, 156296, 156312, 1563803, 264120, 264405, 264DIG65, 425 83, 425174, 425371, H05B 100, B29C 4322
Patent
active
059139900
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns a method for continuously producing panels of lignocellulose-containing particles, whereby the binder is continuously applied to the particles, which are continuously shaped to form a mat. The mat is continuously pre-compressed and at the same time continuously preheated by the effect of a high-frequency high-voltage energy field. The mat which is guided onto a planar surface, is compressed to form the panels under the effect of further heat. Furthermore the invention concerns a device for carrying out such a method with a gluing machine for continuously applying glue onto the particles, with a mat-forming machine for continuously forming the particles to a mat, a prepress for continuously pre-compressing the mat, with a high-frequency heating unit for continuously preheating of the mat through applying a high-frequency high-voltage field and with a heatable press, which consists of two sheets of metal, which presses the mat which was guided onto a planar surface to panels by applying further heat.
2. Description of the Related Art
The invention thus refers only to methods and devices, which include at a minimum the pre-press and the high-frequency device which allows work continuously, this minimal equipment does not include sawing devices. The invention later considers methods and devices which hot-presses the mat, which was guided onto one planar surface into panels. Thus the application of calander-presses, which can be used only for panels with limited thickness and special material is excluded. In contrast the invention is not limited to a special binder, the invention is also not limited to a defined particle size or composition of the lignocellulose-containing particles. This means it does not matter whether the binder is urea-formaldehyde resin or a binder free from formaldehyde. In the same way it does not matter, whether the manufactured panels are particle boards, medium density fibre boards (MDF) or oriented strand boards (OSB). However the invention has distinguished advantages when manufacturing certain type of boards. A method and a device of the sort described in the preceding are described in "Proceedings 27.sup.th International Particle board/- Composite Materials Symposium" W.S.U. 1993, page 55 to 66:
SUCCESS STORY. MODERN PARTICLEBOARD USING EASTERN HARDWOODS. There a device for the continuous manufacturing of particleboard is described which establishes the continuous preheating of the mat using a high-frequency heating device before the pre-press for mat compression. The high-frequency heating unit increases the mat temperature from room temperature by about 40.degree. C. It was reported there that by using high-frequency heating, the productivity of the line significantly increases because the pre-heated mat is pressed for a significantly shorter time in the finishing press. The heating-capacity of a high-frequency heating unit directly depends upon the field strength of the working alternating electrical field. For example, in order to reach the same heating-capacity when doubling the distance between the electrode platens the alternating voltage is to be doubled. Increasing the voltage increases the threat of high-voltage break downs which may lead to severe damaging of the high-frequency heating device. Additionally electric- magnetic impulses, which accompany break downs, may damage other electric or electronic installations. Finally, while producing panels, break downs may lead to ignition of the mat or to damaged areas on the finished boards.
Taking these problems into consideration, it is therefor necessary to locate a high frequency heating unit, for the continuous pre-heating of the mat, which has a working high-frequency alternating high voltage field, after the pre-press for continuous compressing of the mat, where the mat has only a reduced thickness. Therefor a significantly reduced distance between the electrodes of the high. frequency device is possible. In "Taschenbuch der Spanplattentechni
REFERENCES:
patent: 4216179 (1980-08-01), Lamberts et al.
patent: 4293509 (1981-10-01), Bucking
patent: 4420357 (1983-12-01), Neubauer et al.
Ball Michael W.
Yao Sam Chuan
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