WO1989004747A1

WO1989004747A1 - Method of sawing timber and timber products formed thereby

Info

Publication number: WO1989004747A1
Application number: PCT/AU1988/000454
Authority: WO
Inventors: Andrew Karl Knorr
Original assignee: Andrew Karl Knorr
Priority date: 1987-11-27
Filing date: 1988-11-24
Publication date: 1989-06-01

Abstract

The logs (16) are milled by cutting them along radial and longitudinally extending lines (17, 17', 50) to form elongated wedge shaped elements (32, 36, 36', 36'', 45, 52, 52') either separate from one another or laminated to one another such that the growth rings in the respective elements are generally perpendicular to the cut side surfaces (17, 17') of the elements, and when laminated the growth rings of all such elements are generally parallel to one another.

Description

METHOD OF SAWING TIMBER AND TIMBER PRODUCTS FORMED THEREBY The present invention relates to improved methods of milling timber and to improved timber products formed therefrom.

Conventionally, timber planks or other similar products are produced by longitudinally sawing a log in a desired pattern. Generally, planks that are quartersawn, that is with the major faces extending generally across the growth rings of the log (as opposed to generally parallel to the growth rings), provides a higher quality product. Quatersawn planks generally exhibit less lateral warping, provides a hard wearing surface with least movement across its quartersawn face, and with many species provides a more attractive appearance on the major faces. The difficulty is that if all planks formed from a log are quartersawn, there is necessarily a very high wastage of timber from any particular log. It is therefore more common to use a combination of backsawing and quartersawing to utilise the log more fully, however, even using these techniques there can be up to fifty percent wastage from any particular log. The foregoing difficulties can be aggravated by logs having specific faults, for example the centre is often formed from weak or faulty wood and needs to be excluded.

Accordingly, the present invention has for its objective the provision of a method of forming timber products from a log that enables a better utilisation of the available wood in the log. The present invention also aims at providing an improved timber product produced by the basic methods of the invention.

Accordingly, the present invention provides a method of forming a timber product from a log, said method comprising sawing said log along longitudinally extending and radially extending lines to form said timber product being substantially elongated wedge shaped elements. Conveniently, the longitudinally extending and radially extending lines extend from a peripheral surface of said log into said log to a position less than or equal to half the diameter of said log and said log is subjected to a drying or treatment step prior to separation into individual said elongated wedge shaped elements. In a second embodiment the elongated wedge shaped elements may be separated from the

- log during sawing along said longitudinally extending and radially extending lines.

In accordance with a further embodiment, two or more individually formed elongated wedge shaped elements are laminated together in a manner such that growth rings of the wood forming each said element are substantially parallel to each other in all said elements laminated. Conveniently, the timber product is formed by at least two said individual elongated wedge shaped elements such that an apex of one said element is located adjacent a wider end zone of the _ις other said element and vice versa. In an alternative embodiment the timber product is formed by two said elongated wedge elements each having two side surfaces angled with respect to each other defining an acute angle therebetween and an end surface joining said side surfaces at a wider portion of the element, said two elongated wedge shape elements being laminated by joining the respective end surfaces together such that one said side surface on one of said elements is substantially parallel to a said side surface on the other of said elements.

According to a further aspect of the present invention, a timber product is provided comprising an elongated wedge shaped element having longitudinally extending side faces forming an acute angle with each other, said side faces being formed by sawing a log along radial and longitudinally extending saw cuts to form said side faces whereby growth rings of wood forming said element are arranged substantially perpendicular to said side faces.

What is intended by the use of "perpendicular" in this context is perpendicular if the growth rings in a log were perfectly circular bearing in mind, in practice, timber is a 35 natural product subject to some imperfections. Where expressions such as "perpendicular to", "parallel to" and "tangent to" in relation to the growth rings are used herein including the accompanying claims, such expressions should be interpreted bearing in mind that timber is a natural product subject to many variations and imperfections in practice. - - - ^■■

In accordance with a preferred embodiment at least two of the aforesaid elements are laminated to one another such that the growth rings of each said element are substantially parallel to the growth rings of all other said elements^'. Conveniently, the elements may be laminated to one another with respective said side faces of adjacent said elements engaging one another and with a thinner portion of each said element being located adjacent a thicker portion of an adjacent said element. In another embodiment each said element may include an end face forming said side faces and a pair of said elements are laminated together by joining respective said end faces together such that one said side face of one said element is parallel to a said side surface of the other said element. Conveniently, the end faces may be offset relative to one another. Moreover, it is possible to arrange for the elements forming such a composite product to be formed of different timber species. The laminating of the elements may be formed by gluing, nailing (or other mechanical fasteners) or a combination of gluing and nailing (or other mechanical fasteners).

The advantages achieved by the performance of the present invention, or preferred aspects thereof, are numerous. The log sawing method produces wedge shaped elements with major side surfaces that are always perfectly quartersawn. The method also utilises the available wood in any log to a far higher extent than with other conventional milling methods. Up to 80% effective utilisation can be achieved with methods of the present invention. With laminated wood products according to the present invention it is possible to laminate the weaker thinner wood sections with the stronger thicker sections to achieve a strong and stable end product. This form of lamination also has the effect of relieving internal stresses in the wood in a balanced fashion while enabling the presentation of either a perfectly quartersawn surface or a backsawn surface on certain surfaces of the product formed in various preferred embodiments of the method of the present invention.

The methods of the present invention also makes it possible to utilise smaller logs than would be necessary with conventional milling methods. This then makes it more attractive to use plantation forestry or regrowth timbers where valuable timber products can be formed from small tress thinned out as well as the larger trees when fully grown. The ability of milling smaller logs also makes their handling easier at all stages of production. This method is particularly advantageous with small diameter trees with high growth stresses which cause problems when being converted by conventional methods.

A number of preferred embodiments will hereinafter be described with reference to the accompanying drawings in which :

Figure 1 is a schematic cross-sectional view of a log demonstrating the difficulties associated with products of conventional milling techniques due to different shrinkage rates across and parallel to the growth rings;

Figure 2 is a view similar to Figure 1 showing a sawing pattern according to one embodiment of the present invention;

Figure 3 illustrates schematically one form of apparatus for sawing a log according to Figure 2;

Figure 4 illustrates schematically a second form of cutting a log in accordance with the present invention;

Figures 5, 6, 7 and 8 illustrate schematically different forms of laminated timber products according to the present invention;

Figure 9 illustrates a second form of laminated timber product;

Figure 10 illustrates the use of the laminated product of Figure 9; Figure 11 illustrates a still further form of laminated product;

Figure 12 illustrates schematically a means for . drying timber sawn initially in accordance with the present invention;

Figure 13 illustrates schematically a further preferred embodiment of cutting a log into wedge shaped elements; and

Figures 14 to 16 are illustrative of various laminated products formed from cutting a log as shown in Q Figure 13.

Referring initially to Figure 1, a log is illustrated schematically in cross-section showing some forms of milling. The plank shown at 11 is quartersawn, that is the growth rings are as near as possible arranged at 5 right angles to the major side surfaces of the plank. The shrinkage that occurs with planks thus sawn is primarily parallel to the major side surfaces, however the cross-section remains essentially rectangular without any lateral warping. The square sections and round sections ffi shown at 12 and 13 are more or less quartersawn although because of their greater width there is a greater tendency for lateral warping to occur when the product shrinks. The plank shown at 14 is then backsawn and is the exact opposite to the quartersawn plank 11. In this case there is the 5 greatest risk of lateral warping as illustrated upon the plank shrinking during drying. Moreover, the plank major surfaces have a minimum of the harder growth rings and consequently in some species its appearance and wearing or strength characteristics are impaired. Finally, the square section at 15 is equally likely to shrink and become distorted as shown because of its arrangement relative to the log growth rings. Clearly a quartersawn plank provides the best stability and the hardest wearing product and in many species may combine this with the most attractive appearance, however, it is impossible to cut most logs economically to achieve completely quartersawn products. Figures 2 and 3 illustrate a sawn cross-section of log and schematically a cutting apparatus to achieve this cutting pattern in accordance with the present invention. As shown in Figure 2, the log 16 is cut by a plurality of radial (and longitudinally extending saw cuts 17 extending from the periphery 18 of the log towards its centre. In most instances the angular spacing between the cuts 17 will be equal although with the preparation of some laminated products, as explained hereinafter, it may be desirable to have some of the cuts at different angular spacings, for 0 example, half the angle of the majority of the other saw cuts. Figure 3 illustrates schematically a cutting machine 19 for achieving the configuration shown in Figure 2. The machine 19 comprises two circular saw working heads 20,21 mounted to travel along supporting and guiding rails 22. 5 The rails 22 are mounted parallel to the longitudinal axis of the log 16 to be sawn which is mounted on spindles 23 permitting selective rotation of the log through a predetermined angle of movement. Each working head 20,21 is mounted on support arms 24,25 that are pivotable about the δ point 26. Each head 20 or 21 can be lowered a prescribed amount into the log 16 by rotating the heads around the point 26 by use of a control device 27. Each cutting head is rotated in the desired direction and cuts are made by relative movement of the log and cutting head. Cuts can be 5 made towards the centre of the log in each direction of travel or in one complete pass. Furtherjnore, it is possible to have one of the heads 21 cutting radially while the other cutting head cuts tangentially (or at an angle to the tangent). Drive means for the respective working heads may 0 be from a common drive to the point 26 with pulleys or the like transferring this drive to the working head, or alternatively, or in combination with, by separate electric or hydraulic motors arranged at the working head. The cutting heads themselves may be any desirable cutter or 5 shaper elements including circular saws and other cutting saws, hoggers and shapers. It is possible also to arrange two or more cutting or shaping elements in the one head. The spindles 23 that hold the log during cutting may dog into the end of the log so that the inner end 28 of the radial saw cuts 17 extend longitudinally along most of the log at a uniform depth but at each end the line 28 diverges outwardly to leave an amount of uncut timber to hold the section together. In addition, as shown in Figure 2, the inner end of the saw cuts may terminate less than half way through the log to leave a central portion 29 uncut. Alternatively, these cuts can go right to the centre with the log being held together only by the end sections adjacent the spindles 23. Alternatively, spindles could dog into ends of a log allowing cuts at predetermined angles to go to the centre of the log through ends of the log leaving segments held by fingers of the sprindle dogging into the log. The machine may include auxiliary devices for inserting spacers into the cuts made, for compressing softwood logs and supporting long hardwood lodgs and in some instances, for enabling sideways travel of the working heads. Figure 4 illustrates another method of cutting a log in accordance with the present invention. In this case the log 16 is bandsawn in half and each log half is separately attached to an offset table 30 and is rotated around the cutting axis 31. In this case individual segments 32 are produced which may be used green or dried using conventional methods or any of the methods hereinafter described.

After the log has been initially cut as described in the foregoing, it may be dried using any of the following techniques. One such technique might be simply to leave the log cut but not separated until the log has naturally dried. Another method might be to wrap the cut logs in a porous or non-porous membrane and have hot air forced through it. Alternatively, the log might be placed in a cylinder of similar but slightly larger dimensions and dried by vacuum or by forced movement of air through the cylinder. These cylinders might operate as individual units for precise control of the drying environment or a number of logs might be placed in a long cylinder or dried on a continuous feed system as the logs move through the cylinder. Figure 12 illustrates a still further possible drying arrangement where the logs are placed in a container 33 with an inclined bottom surface 34 such that they roll downwardly thereon to be eventually discharged at the lower end. New logs 16 are loaded sideways at the upper end of the container 33 with hot air 35 being introduced at the lower end.

Once a log 16 has been cut according to Figure 2, (and dried and treaded, if desired, as aforesaid), it may be cut into individual wedge shaped elements by dividing the log in half, separating the log halves and passing a rotary cutter centrally down the log halves to remove the central uncut wood portions. If the radial cuts have passed to the centre of the log and the log is held together only by uncut end sections, then it is only necessary to remove the uncut end sections to separate the individual wedge shaped elements.

Figures 5 to 11 illustrate various forms of laminated wood products using wedge shaped segments formed as aforesaid. Figure 5 shows two elements 36 (glued, nailed or combination of gluing or other mechanical fasteners, nailing) at side faces 37 to form a laminated product. The portions 38 shown in dotted outline may be removed either before or after laminating to form a rectangular product with the major outer faces 39,40 providing perfectly quartersawn faces. Figure 6 shows a somewhat similar lamination technique wherein a plurality of wedge shaped elements 36 are laminated together at mutually engaging side faces 37. In this case the two end elements 36' and 36" are half the angle of the other elements 36 to form a rectangular product. Again the portions 38 shown in dotted outline might be removed before or after lamination. With this product it might be possible to further divide the section by cutting along one or more lines parallel to the outer surfaces 41 and 42. Figure 7 is similar to Figure 6 except that only one element 36 is laminated with half angled elements 36' and 36" to form the laminated end product. Again with this product the major outer surfaces

43 and 44 are perfectly quartersawn. Figure 8 illustrates a variation of Figure 5 wherein the lamination line 37 does not extend from corner to corner of the end product. The sections 38' and 38" may be removed before or after 5 lamination. In all the aforesaid products the growth lines of the wood of each element are substantially parallel.

Figure 9 illustrates a further preferred embodiment, particularly suited for forming a flooring or panel board product. In this instance two wedge shaped

10 elements of similar cross-sectional shape 45 and 45' are laminated together (preferably by gluing) along the edge surfaces 46 and 46' joining the respective side surfaces 37 and 37' at the thicker edge of the elements. The arrangement is such that the growth lines of each element

15

45,45' are essentially parallel with one another and the respective faces 37 and 37' of each element are parallel with one another and present a perfectly quartersawn face.

Furthermore, the two elements 45 and 45' are offset relative to one another to form upper and lower steps 47,48. Figure

20)

10 illustrates the use of a laminated product as shown in

Figure 9 as flooring. In this flooring construction the laminated products are laid overlapping one another and adjacent one another and can in each instance be nailed through the hidden surface 37' of each product. As is

25 apparent from the drawings, the narrow edge of the wedge locks under the angled step in the edge of the exposed end face which mechanically locks the boards together in addition to the nailing. These angles may need to be machined into the product. The respective upper surfaces 37

30 are all perfectly quartersawn providing a high quality hard wearing appearance. The respective elements 45 and 45' might be produced from different timber species to provide a cheaper but compatible wood for the lower element 45'.

Laminated products according to Figure 9 may also be used in

35 larger laminations where two or more such products are joined with adjacent elements being laminated by gluing surfaces 37' together. A single wedge shaped element may then be glued to either end. Figure 11 illustrates a further form of laminated product where individual wedge elements 47 are glued together into an annular shape. The outer surface 48 might be circular or might be shaped as desired, as indicated by _ς. the line 49. This type of product might be useful as poles, masts or turning blanks.

The individual wedge shaped segments should have a dimensionally stable cross-sectional shape (i.e. not warped), be straight along the longitudinal plane at right angles to the face tangential to the growth rings, but may

Z be curved longitudinally as a result of varying growth stresses. Segments may need to be machined before they are laminated. Segments, sitting on their tangential faces may be passed over two fixed rollers and onto further movable rollers controlled by a sensing device which determines the

15 degree of curvature of each segment. The segment may be held to the tangential rollers by angled rollers placed strategically. The segments may be machined after passing over the fixed rollers by the desired number of angled zσ cutters, rotary planers or sanders. Segments may then be glued together using forces causing the curvature of the segments to an advantage. One means of achieving this is to place the machined segments to form a rectangular section with the segments being held to a desired width and adhesive applied between the contacting surfaces. Subsequently

25 pressure can be applied by rollers operating from a central zone towards the longitudinal ends of the segments to achieve pressure application with a minimum of clamping devices. Segments might also be nail laminated by clamping one end together in the desired position and forcing a

30 roller from this end to the other end nailing as the roller passes. If the segments are green, the nail can protrude to assist with stacking and drying and the segments pressure rolled after drying to clinch nails and remove shrinkage gaps between segments.

35

Figures 13 to 16 illustrate a further alternative method according to the present invention. In this embodiment (Figure 13) cuts are made by a suitable saw 54 radially along longitudinal planes 50 from the centre of the log 16 to a distance approximating a veneer thickness from the outside periphery 18 of the log. This may be done as illustrated by the application of heat and/or chemicals to the log with the outside circumference being laid flat in the direction of the arrow 51 with distortion of the fibres in the uncut section similar to that which occurs with rotary cutting of veneers. As an alternative to that which is shown in Figure 13, the log might be halved prior to cutting in a similar fashion. In either case the wedge shaped elements 52 are interconnected by veneer width portions 53 as shown in Figure 14 where a section of log is shown laid out in an extended fashion. The tips of the wedge shaped elements 52 are removed along line 55 so that the shape of the wedge shaped elements 52 will be essentially complimentary to the spaces therebetween. In one embodiment shown in Figure 15, the length of the wedge shaped elements might be halved by cutting along line 56 so that the removed tip parts 57 might be laminated between the remaining parts 58 of the wedge elements 52 to form a completed laminated timber product. Figure 16 illustrates a second embodiment where two cut members according to Figure 14 having individual wedge shaped elements 52 and 52' are laminated together. Subsequent to lamination, the product may be machined as desired to achieve the required cross-sectional shape.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS;

1. A method of forming a timber product from a log (16), said method comprising sawing said log along longitudinally extending and radially extending lines (17,50) to form said timber product being substantially elongated wedge shaped elements (32,36,45,52,52').

2. A method according to Claim 1, wherein said longitudinally extending and radially extending lines (17) extend from a peripheral surface of said log (16) into said log to a position up to half the diameter of said log (16) and said log is subjected to a drying and treating (if necessary) step prior to separation into individual said elongated wedge shaped elements (32,36,45).

3. A method according to Claim 1, wherein said elongated wedge shaped elements (32,36,45) are separated from said log (16) during sawing along said longitudinally extending and radially extending lines (17).

4. A method according to anyone of Claims 1 to 3, wherein two or more individually formed said elongated wedge shaped elements (32,36,45) are laminated together in a manner such that growth rings of the wood forming each said element are substantially parallel to each other in all said elements (32,36,45) laminated.

5. A method according to Claim 4, wherein the timber product is formed by at least two said individual elongated wedge shaped elements (32,36) such that an apex of one said element is located adjacent a wider end zone of the other said element (32,36) and vice versa.

6. A method according to Claim 4, wherein the timber product is formed by two said elongated wedge shaped elements (45) each having two side surfaces (37,37') angled with respect to each other defining an acute angle therebetween and an end surface (46,46') joining said side surfaces at a wider portion of the element, said two elongated wedge shaped elements (45,45') being laminated by joining the respective end surfaces (46,46') together such that one said side surface (37) on one of said elements (45) is substantially parallel to a said side surface (37) on the other of said elements (45').

7. A method according to Claim 1, wherein said radially extending lines (50) extend from a central zone of the log (16) towards but not through the periphery (18) of the log (16) leaving thin section zones (53) enabling the wedge shaped elements (52,52') to be laid out in line interconnected only by said thin section zones (53) and defining wedge shaped spaces between said wedge shaped elements (52,52').

8. A method according to Claim 7, wherein said wedge shaped elements (52) are cut along a plane (56) parallel to the thin section zones (53) after being laid out and tip portions (57) removed thereby are laminated to the remaining parts (58) of said wedge shaped elements (52) in the spaces therebetween.

9. A method according to Claim 7, wherein two members each comprising a series of said interconnected wedge shaped elements (52,52') are laminated to each other with the spaces between said wedge shaped elements (52) being occupied by the wedge shaped elements (52') of the other said member.

10. A timber product comprising an elongated wedge shaped element (36,36' ,36",45,52,52' ) having longitudinally extending side faces (37,37',50) forming an acute angle with each other, said side faces being formed by sawing a log along radial and longitudinally extending saw cuts (17,50) to form said side faces whereby growth rings of wood forming said element are arranged substantially perpendicular to said side faces (37,37' ,50).

11. A timber product according to Claim 10, comprising at least two said elements (36,36' ,36",45,52,52' ) laminated to one another such that the growth rings of each said element are substantially parallel to the growth rings of all other said elements (36,36' ,36",45,52,52' ) .

12. A timber product according to Claim 11, wherein said elements (36,36' ,36") are laminated to one another with respective said side faces (37) of adjacent said elements engaging one another and with a thinner portion of each said element (36,36',36") being located adjacent a thicker portion of an adjacent said element (36,36' ,36") .

13. A timber product according to Claim 11, wherein each said element (45,45') includes an end face (46,46') joining said side faces (37,37') and a pair of said elements are laminated together by joining respective said end faces (46,46') together such that one said side face (37) of one said element (45) is parallel to a said side surface (37) of the other said element (45^f).

14. A timber product according to Claim 13, wherein the end faces (46,46') are offset relative to one another.

15. A timber product according to Claim 13 or Claim 14, wherein respective pairs (37,37 and 37' ,37') of said side surfaces of separate said elements (45,45') are parallel to each other.

16. A timber product according to anyone of Claims 13 to 15, wherein the pair (45,45') of said elements are formed from wood of different species.

17. A timber product according to anyone of Claims 11 to 16, wherein said elements (36,36' ,36",45,52,52' ) are laminated with assistance of glue, nailing (or other mechanical fasteners), or a combination of glue and nailing (or other mechanical fasteners).

SKP.JC (11.2)