Woodworking – Process – Mechanical cutting or shaping
Patent
1992-01-17
1993-04-06
Bray, W. Donald
Woodworking
Process
Mechanical cutting or shaping
100176, 144 2R, B27M 102
Patent
active
051994763
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to the field of treating wood chips prior to their impregnation.
BACKGROUND OF THE INVENTION
Impregnation of wood chips prior to the manufacture of pulp therefrom, either chemically or semi-chemically, or prior to producing pulp mechanically from said chips, for instance in a disc refiner, can be made easier and improved by compressing the chips between rotating rollers. See CA 773,835. The wood chips preferably contain 40-55 percent by weight water and are compressed to a thickness of from 1/5-1/10 of their original thickness in the roll nip defined between a pair of rollers. The rollers act on the mutually opposite flat sides of the chips to loosen the bonds between the fibres and to render the chips more porous. The chips return almost to their original shape subsequent to compression.
Thicker chips are compressed more thoroughly than thinner chips between the rollers. This results in an increase in the porosity of the thicker chips, so as to render the entire cross-section of the thicker chips accessible to an impregnating liquid and to achieve comparatively uniform impregnation. The thinner chips do not benefit from as high a degree of compression and have a lesser increase in porosity. Infeed of the chips into the roll nip can be made easier by roughening the roller surfaces.
WO 89/02951 relates to improving uniformity during the impregnating process. This is accomplished by sawing mutually identical wood pieces having a length of, e.g., 100 mm in the fibre direction and a width and thickness of 40.times.10 mm transversely to the fibre direction, and compressing the wood pieces at right angles to the fibre direction prior to impregnation. For instance, the wood pieces can be compressed between rollers or press plates which act on the mutually opposite flat sides of said wood pieces. When rollers are used, the rollers may be shallowly serrated or fluted, so as to facilitate movement of the wood pieces into the roll nip.
OBJECTS AND SUMMARY OF THE INVENTION
The object of the present invention is to provide a novel and advantageous method for treating wood chips prior to impregnation. The method will impart greater porosity and liquid-absorption properties to the chips.
It is another object of the present invention to provide an apparatus capable of compressing chips so as to impart greater porosity and liquid-absorption properties to the chips.
In accordance with these objections and in one aspect of the present invention there is provided a method of treating a plurality of wood chips, the wood chips having an average thickness ranging between a low average thickness and a high average thickness, prior to impregnating the plurality of wood chips, including the steps of: providing a plurality of wood chips; and compressing the plurality of wood chips to an average thickness which is less than the low average thickness without damaging fibers of the wood chips and while imparting to the plurality of wood chips an undulating configuration in at least one direction so as to produce a plurality of wave-shaped wood chips having at least one wave crest and at least one wave trough, the wood chips thereby having greater porosity and liquid absorption properties.
There is also provided an apparatus for compressing a plurality of wood chips having an average thickness ranging between a low average thickness and a high average thickness, so as to improve their porosity and liquid absorption properties including: a plurality of compression rolls, the compression rolls including a plurality of grooves and being disposed relative to each other so as to compress the plurality of wood chips to an average thickness which is less than the low average thickness without damaging fibers of the wood chips and so as to impart to the plurality of wood chips an undulating configuration and in least one direction so as to produce a plurality of wave-shaped wood chips having at least one wave crest and at least one wave trough, the apparatus capable of producing wood c
REFERENCES:
patent: 266763 (1882-10-01), Burk
patent: 1150805 (1915-08-01), Beran
patent: 3447352 (1969-06-01), Millen
patent: 4319473 (1982-03-01), Franke, Jr. et al.
patent: 5007271 (1991-04-01), Boegli
Bray W. Donald
Sunds Defibrator Industries Aktiebolag
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