Presses – Methods – With heating or cooling
Reexamination Certificate
2000-04-21
2002-08-27
Gerrity, Stephen F. (Department: 3721)
Presses
Methods
With heating or cooling
C100S152000, C100S154000, C100S041000
Reexamination Certificate
active
06439113
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of pressing mats of a compressible material, usually a material made from wood and containing cellulosic fibers or particles, with or without a binder, and, more particularly, to a method of operating a continuous press for the production of pressed board and, of course, to a continuous press for the production of pressed board operated by the method of the invention.
BACKGROUND OF THE INVENTION
Continuous presses for the production of pressed board generally comprise a pair of belts, usually of steel, passing a mat of a material which can be consolidated into pressed board between upper and lower press platens mounted respectively on the upper and lower parts of the continuous press.
Such presses are used in the production of pressed board from wood particles or fibers, more generally cellulosic particles and fibers, with or without binders which may be thermally activated and for that purpose, the press platens are usually heated to a temperature such that, upon compression of the mass to a nominal thickness, namely, a standard thickness of the finished board, the combination of heat and pressure consolidates the mass to a rigid board which can then be trimmed to standard length and width dimensions outside the press. The boards which may be produced in this manner are known generically as particle board and can include fiber board, chip board and the like.
The press can have at an inlet side, a pair of bendable plates, referred to herein as inlet plates, which converge toward the gap between the platens and define a mouth for the press. These plates may have high bending elasticity, i.e. tend to restore their original shape when subjected to bending at high pressures, e.g. from a plurality of piston and cylinder units mounted on the upper and lower parts of the press and bearing upon the upper and lower plate. These piston and cylinder units are usually hydraulically operated to vary the shape of the mouth.
The plates themselves may be heated and between the plates and platens and the steel belts, roller rods may be provided to reduce the friction between the belts and the surfaces along which the belts are guided of the plates and platens.
The piston and cylinder units can be connected to a hydraulic controller or a hydraulic regulator for the system, operated by a computer or the like. Usually this ability to modify the inlet contour of the inlet mouth of the press serves to allow a steplessly-continuous compression of the mat and is in the form of a continuous bend of the inlet plates producing a monotonic convergence between them (see German patent document 197 40 325).
OBJECTS OF THE INVENTION
It is the principal object of the present invention to provide an improved method of pressing compressible mats of a material adapted to form a press board under heat and pressure whereby the production of pressed board and, in particular, the compaction of the mass prior to entry between the press platen is optimized.
Another object of this invention is to provide an improved method of operating a continuous press of the type described.
It is also an object of the invention to provide an improved continuous press for the production of pressed board whereby drawbacks of earlier systems are obviated.
SUMMARY OF THE INVENTION
These objects are attained, in accordance with the invention by automatically and at the beginning of the inlet phase at the inlet portion of the mouth subjecting the mat to an accelerated heat transfer by rapidly and strongly compressing the mat utilizing the bendable plates and the aforementioned hydraulic units.
More particularly, the method of pressing a compressible mat for producing pressed board in a continuous press can comprise controlling the gap between the upper and lower press plates by operation of the piston and cylinder units to rapidly and strongly compress the mat and thereby accelerate heat transfer to the compressed mass by the heated plates before passage of the mat between the platens.
The method is also a method of operating the continuous press which comprises an upper press part and a lower press part, a heated lower platen on the lower press part, a heated upper platen on the upper press part defining with the lower platen a pressing space having a width for producing a pressed board of a nominal thickness, a pair of belts displaceable along the platens for conveying a mat between the plates and a pressed board out of the space, an upper bendable inlet plate and a lower bendable inlet plate extending from the upper and lower platen toward an inlet side of the press and defining between them a variable contour mouth through which the mat enters the press, and a plurality of piston and cylinder units acting on one of the plates and braced upon the respective press part for varying the contour of a gap between the plates, the method comprising controlling the unit so that a respective mat at a beginning of an inlet phase is rapidly and strongly compressed at an inlet region of the mouth with accelerated heat transfer to the mat.
The continuous press itself can comprise a continuous press for the producing of mats of a compressible material for the production of pressed board, the press comprising an upper press part and a lower press part, a heated lower platen on the lower press part, a heated upper platen on the upper press part defining between then a pressing space having a width for producing a pressed board of a nominal thickness, a pair of belts displaceable along the platens for conveying a mat between the plates and a pressed board out of the space, an upper bendable inlet plate and a lower bendable inlet plate extending from the upper and lower platen toward an inlet side of the press and defining between them a variable contour mouth through which the mat enters the press, and a plurality of piston and cylinder units acting on one of the plates and braced upon the respective press part for varying the contour of a gap between the plates, and automatic control means connected to the units for controlling the units whereby controlling the unit so that a respective mat at a beginning of an inlet phase is rapidly and strongly compressed at an inlet region of the mouth with accelerated heat transfer to the mat.
The invention is based upon the fact that the flexible but highly elastic and shape-restorative configuration of the inlet plates of the mouth enables at least one of these plates to be deformed toward the other of these plates to form a compression zone at the inlet side of these plates whereby the heated plates rapidly transfer heat to the high-density mass formed by the compression.
With the system of the invention, depending upon the characteristics of the compressible material, the mat thickness, the liquid density of the material forming the mat and the other pressing properties thereof, the compression of the mats can be controlled in the longitudinal direction and as the mat passes through the mouth between the plates because the spacing between the plates is variable in the direction of advance in the material.
With the system of the invention, it is no longer necessary to have the minimum width of the gap between the plates immediately at the point at which the plates are joined to the press platens. Rather the minimum spacing between the plates can be at another location substantially upstream therefrom and toward the inlet side of the mouth. In fact, the location of the minimum spacing between the plates can be varied to lie anywhere along the length of the mouth. The result is that the position of the minimum spacing and thus highest degree of compression of the mass can be located at an optimum position depending upon the parameter mentioned earlier of the compressible mass to obtain a more effective compaction of and heat transfer to the material of the mats and a more uniform and higher quality product.
The earlier compaction of the mass of compressible material not only enables higher densities to be achieved than have been attainable heretofo
Gawlitta Werner
Schürmann Klaus
Sebastian Lothar
Weiss Horst
Dubno Herbert
G. Siempelkamp GmbH
Gerrity Stephen F.
Huynh Louis
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