Woodworking – Process – Mechanical cutting or shaping
Reexamination Certificate
1993-09-03
2001-09-11
Dexter, Clark F. (Department: 3724)
Woodworking
Process
Mechanical cutting or shaping
C144S345000, C144S346000, C144S347000, C144S355000, C144S359000, C144S360000, C144S363000, C144S376000
Reexamination Certificate
active
06286571
ABSTRACT:
The present invention relates to a method of sawing a log for high yield extraction from the log of vertical-grained lumber, i.e. pieces with growth rings more or less perpendicular to the widest surfaces of the cut piece.
It is common practice, for special uses of wood, that it is desirable to extract vertical-grained lumber, i.e. pieces of lumber which are sawn out essentially radially to the log. Vertical-grained lumber is less susceptible to cracking when dried and does not cup but remains planar and has less of a tendency to become warped and twisted and have other defects caused by contraction anisotropism in the wood substance. Surfaces which are been cut radially into a log are harder than tangentially cut surfaces. Furniture, floors and other woodwork are of recognized higher quality if the wood used is vertical-grained.
An older method of obtaining vertical-grained lumber is so-called quarter sawing. The yield used in this method is, however, low, and only certain pieces of lumber are vertical-grained when this method is used.
DE-C-692 987 describes a method of manufacturing an intermediate layer from plywood or similar products with vertical-graining, whereby a log is sawn with radial, longitudinal cuts into a plurality of sector- or wedge-shaped pieces of lumber, which, after tangential edging are glued together in blocks in which the wedges alternate. From the block there can then be sawn planks or sheets with vertical-graining.
WO 89/04747 describes a method of sawing logs where they are sawn with longitudinal radial cuts into wedge-shaped vertical-grained pieces of lumber.
The lumber yield when sawing with these two methods described immediately above is rather good.
Practically all of the lumber obtained according to these two methods must be glued prior to use. This is expensive and sometimes technically or aesthetically unsatisfactory.
A primary purpose of the present invention is to extract from logs, primarily logs of intermediate or large diameter, i.e. logs with a diameter of about 18 cm and above, an improved yield of vertical-grained pieces of lumber. In principle, this is achieved according to the invention by sawing out pieces of not only triangular or sector-shaped cross-section but also planks with essentially parallel sides between adjacent pairs of the triangular or sector-shaped pieces. Specifically, the log is divided with at least two parallel, longitudinal and nearly diametrical cuts, which are parallel to the pith, to obtain at least one essentially diametrical and plane-parallel board and a pair of blocks with substantially semi-circular cross-section and, with parallel, substantially radial, longitudinal cuts, which are substantially parallel to the pith, dividing each of the blocks into at least three pieces of lumber which are essentially sector-shaped or triangular in cross-section and at least one substantially plane-parallel board between adjacent pairs of the pieces of lumber which are sector-shaped or triangular in cross-section. This method of sawing provides, especially for big logs, improved yield of vertical-grained lumber which can be used as raw material for high quality construction, wood-working and furniture products.
According to a preferred embodiment of the method according to the invention, the blocks divided with the parallel, nearly radial cuts are spaced at 60° angular intervals to extract from an essentially round log six substantially uniform pieces of lumber having a cross-section which is an equilateral triangle after tangentially edging of each piece of lumber, and at least five essentially plane-parallel boards. By virtue of the division of the log into six pieces, each having a cross-section which is an equilateral triangle, they can, after drying, be either glued together to either be rip sawn in a manner known per se into desired products, preferably vertical-grained, or be used for flooring, counters or the like where an end-grained working surface is desired.
It is suitable to divide the essentially diametrical piece of lumber into at least two parts by removing the pith with the central, undesirable juvenile wood.
For very large logs, it can be suitable to extract from between each pair of sector-shaped or triangular pieces of lumber a plurality of essentially radial, plane-parallel boards.
According to a preferred embodiment, the planar supporting surfaces on the outer surface of the log are prepared prior to division of the log, said supporting surfaces being the external sides of the pieces with triangular cross-section. These supporting surfaces can also be used to guide the log during continuing sawing.
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Dexter Clark F.
Hollander Law Firm, P.L.C.
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