Woodworking – Process – Mechanical cutting or shaping
Patent
1996-05-14
1997-10-21
Bray, W. Donald
Woodworking
Process
Mechanical cutting or shaping
144380, 100 93P, 100240, B27M 102
Patent
active
056786182
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method of producing hard wooden elements, and then in particular sawn wooden elements.
BACKGROUND OF THE INVENTION
It is known to produce hard wooden elements, such as sheets of floor boarding, by compressing different types of wood products in conventional presses. DE 0 601 162 describes one example of a wood pressing technique. Wood sheets of limited size layered with steam-heated metal plates are stacked in a steam operated press. A piston driven by pressurized steam functions to press vertically on the stack of metal plates/wood sheets from beneath the stack. Side plates are located on two of four sides, therewith enabling the wood to expand in two directions as it is compressed. Because of this possibility for the wood to expand, there is a limit on the maximum pressure to which the wood can be subjected. Deformation of the wooden sheet becomes very pronouned when the wood is subjected to high pressure, and there is also a danger that the wooden sheet will be forced out of the press. It is not therefore possible to produce hard wooden elements under very high pressures with the technique taught by DE 0 601 162.
U.S. Pat. No. 3,621,897 describes a method of pressing wooden pieces of limited size in a press mould so as to obtain a patterned surface. The wood is pretreated by immersing the wood in a water/pyridine mixture for some minutes. After being dried, the wood is pressed under hot conditions (at about 180.degree. C.) in a metal mould that will produce the desired pattern. Nothing is mentioned as to which pressure shall be applied. According to this patent specification it is well known that the plasticity and compressibility of natural wood is very low. The pyridine treatment makes the wood soft and pliable, therewith enabling the wood to be pressed in the mould without the wood cracking. However, the pyridine impregnation process constitutes an additional treatment stage which complicates the manufacturing process. Furthermore, pyridine is a skin irritant and is extremely toxic. This technique does not allow wood to be compressed without prior impregnation of the wood with pyridine, if the wood is not to crack. This is a serious drawback, in view of the toxicity of pyridine. Furthermore, it is evident that the wood is pronouncedly deformed when practicing this technique. As shown in the figures, the wood is flattened pronouncedly when compressed. Neither does this technique enable hard wooden elements to be obtained while essentially retaining the shape of the wood after compression, since the technique is based on the wood being pressed in a mould, and moulds, after all, are not so flexible as to provide a perfect fit with each piece of wood.
U.S. Pat. No. 2,666,463 describes a wood pressing technique in which the wood is first heated quickly so as to reduce its moisture content to about 15% and to render the lignin plastic, whereafter the heated wood is pressed in a mould to reduce its volume instead of obtaining flattening of the wood at a constant volume. According to this patent specification, the wood is compressed at high pressures 800-2000 psi (55-138 bars). When pressures of these high magnitudes are applied from one direction, the material is subjected to high stresses and strains and in order to obtain an acceptable result it is necessary for the wood starting material to be even and relatively homogenous. Since knots are generally much harder than the remainder of the wood, compression of a knot-rich piece of wood is liable to give rise to ugly crack formations and may totally pulverize the knots. The pressed wooden element is also deformed to the shape of the mould used. The technique taught by U.S. Pat. No. 2,666,463 cannot therefore be applied to compress knot-rich wooden elements or wooden elements which are inhomogeneous in other ways, or to compress wooden elements of any chosen and/or irregular shapes with acceptable results.
The press devices described in the aforesaid patent specifications generate all of their pre
REFERENCES:
patent: 1480658 (1924-01-01), Bostock
patent: 2023687 (1935-10-01), Klein
patent: 2586308 (1952-02-01), Curtis
patent: 2787306 (1957-04-01), Lundstrom
patent: 2793859 (1957-05-01), Darling et al.
patent: 3166110 (1965-01-01), Hartesveldt et al.
patent: 4017980 (1977-04-01), Kleinguenther
patent: 4428410 (1984-01-01), Strandberg
patent: 4606388 (1986-08-01), Favot
patent: 5343913 (1994-09-01), Tanahashi et al.
by T. UEDA, "Microwave Recipt Yields Straight Logs", The Nikkei Weekly, vol. 30, No. 1521, Jun. 1992.
Castwall Lennart
Lindhe Curt
LandOfFree
Process for producing hard elements of wood does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for producing hard elements of wood, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing hard elements of wood will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-999547