WO1999011440A1

WO1999011440A1 - A method for operation of a saw mill and a wood unit

Info

Publication number: WO1999011440A1
Application number: PCT/SE1998/001522
Authority: WO
Inventors: Lars Hammarström
Original assignee: Hammarstroem Lars
Priority date: 1997-08-29
Filing date: 1998-08-26
Publication date: 1999-03-11
Also published as: SE9703116L; SE9703116D0; SE512883C2; AU8895698A; ZA987849B

Abstract

In the operation of a saw mill logs (1) received are converted into wood units (2) with a substantially rectangular cross section and an inner longitudinal hollow space (14), and these wood units are after that divided into wood pieces depending upon orders coming into the saw mill. The conversion of logs into wood units is carried out in a time independent connection to a demand correspnding to said orders. In the case a difference between the flow of logs to the saw mill and demand arises a storage of said wood units takes place.

Description

A method for operation of a saw mill and a wood unit

FIELD OF THE INVENTION AND PRIOR ART

The present invention relates to a method for operation of a saw mill, in which logs arriving to the saw mill are received and these are then divided into wood pieces depending on orders coming in to the saw mill.

In operation of a saw mill there is in practise seldom a complete correspondence between the flow of logs into the saw mill and said orders coming to the saw mill, which means that logs have to be stored, sometimes over a longer period of time, before they are divided into wood pieces, such as boards and deals. It is then of course also possible that the storage of logs takes place outside the actual saw mill region, maybe at a compara- tively large distance to the saw mill, for example in connection to the felling place, but such a storage is in this context also intended to be comprised in the method for operation of the saw mill.

However, the storage of such logs or so called round timber means problems, since this round timber ages and has a tendency to split. The storage also requires some handling of the round timber, which is sensible to such handling and is by that easily damaged. These problems result in the end in a lower quality of the wood pieces produced later on. However, this is a fact that has been accepted as something inevitable until now. SUMMARY OF THE INVENTION

The object of the present invention is to provide a method for operation of a saw mill, which solves the problems mentioned above of such methods already known to a large extent and by that makes it possible to obtain wood pieces of an improved quality from logs.

This object is according to the invention obtained by firstly converting the logs received in a method defined in the introduction into wood units having a substantially rectangular cross-section and an inner longitudinal hollow space by applying two longitudinal cuts substantially perpendicularly to each other and crossing each other in the centre of the log on the respective log, so that four elongated wood members are obtained, and material is cut away from each such member in the longitudinal direction thereof along the entire member according to two lines being substantially parallel to the cut surfaces emanating from the cuts for forming substantially plane glue surfaces and the wood members are glued together with these plane surfaces against each other and turned so that said cut surfaces are directed outwardly, these wood units are after that divided into wood pieces depending on said orders coming in, the conver- sion of logs into wood units is carried out in a time independent connection to a demand corresponding to said orders and should this demand be lower than the flow of logs to and received by the saw mill such wood units are stored to such an extent that this difference between the flow of logs to the saw mill and the demand is substantially compensated, and in the case that such a difference between the flow of logs into the saw mill and the demand arises that a longer storage is required before the division into wood pieces this storage mainly takes place in the form of storage of said wood units. By ensuring that wood units of the type defined above will constitute the very storage article in the saw mill process in this way the quality of the wood pieces produced later on may be improved considerably. Any storage of logs depending upon a dis- crepancy between orders coming into the saw mill and the flow of logs to the saw mill or the felling speed in the forest has not to be there any longer, but the logs may be immediately converted into said wood units, which are excellent as storage articles, independently of such orders. Thus, a bulk commodity is in this way converted into another bulk commodity having considerably improved properties. Such wood units are easy to handle without damaging them, and their tendency to age or split when stored are extremely low, since contractions and expansions of the different wood members glued to each other co-operate so that formation of splits is counteracted. The characterizing feature for wood units of this type, which are already known through for example the Swedish patent 1 15 667 and the SE- publication 465 412 is that the annual rings extends substantially perpendicularly to the surfaces of the wood unit, which means that these surfaces get very resistant to wear and the wood unit may therefore withstand the handling thereof necessary before the continued division thereof into wood pieces.

Exactly the latter fact of annual rings extending substantially perpendicularly to the surfaces of the wood unit also contributes to improving the quality of the wood pieces resulting from the continued division of the wood unit, since the surfaces of such wood pieces get an advantageous design with respect to the extension of the annual rings for a number of different division patterns.

As a not neglectable bonus to the advantages of the method according to the invention with respect to the very storage, a possibility is achieved, which has turned out to be very valuable, namely to produce wood pieces with a high quality starting from said wood unit through a number of different division patterns, which may be created thanks to the advantageous appearance and the geometry of said wood unit with respect to a normal log.

The definition "saw mill" is as already mentioned here to be given a very broad sense, and the invention also comprises the case in which the wood units are produced on one place in a saw or a so called saw mill and the continued division into wood pieces takes place in another saw or saw mill in another place, in which the storage of the wood units may take place in one or the other place, or even in another place than these places. Thus, it is not at all necessary that the conversion of logs into wood units takes place in the same saw mill line as normally regarded as the division of wood units into wood pieces.

The invention also relates to a wood unit intended to be used for later production of wood pieces through division thereof, which is defined in the appended independent claim for such a wood unit and which results from the idea according to the invention to constructing a method or operation of a saw mill according to the above. The advantages of such a wood unit for storage have been thoroughly penetrated above.

Further advantages as well advantageous features of the invention will appear from the following description and the other de- pendent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, below follows a spe- cific description of a preferred embodiment of the invention cited as an example.

In the drawings:

Fig. 1 is a perspective view of a log cut for producing a wood unit having a square cross-section, Fig. 2 is a perspective view of a wood unit formed by gluing the wood members resulting from the cut according to Fig. 1 to each other,

Fig. 3 is a very simplified cross-section view of storage of wood bulk commodity, in which wood units according to Fig. 2 are stored,

Fig. 4 is a cross-section view of a wood unit according to

Fig. 2 illustrating how cuts are applied thereon for division thereof,

Fig. 5 is a cross-section view illustrating wood pieces obtainable through the division indicated in Fig. 4,

Fig . 6 and 7 are cross-section views corresponding to Figs. 4 and 5, respectively, illustrating how the division of wood units into wood pieces according to a second preferred embodiment may takes place,

Fig. 8 is a view corresponding to Fig. 4 with a different application of cuts, and

Figs. 9 and 10 are views illustrating wood pieces obtainable through a division indicated in Fig. 8 according to a third preferred embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

It is schematically illustrated in Figs. 1 and 2 how a log already reduced and received in a saw mill is converted into a wood unit 2 intended to be divided into different wood pieces depending upon orders coming in to a saw mill. It is not necessary that the log is round reduced, and it is neither necessary that the cross- section of the wood unit 2 is made square, as shown in the figures, but a different rectangular cross-section is also possible.

It is illustrated how two longitudinal cuts being substantially perpendicular to each other and crossing each other substantially in the centre of the log are applied, so that four elongated wood members 3 are obtained, and material is cut away from each such member in the longitudinal direction along the entire mem- ber according to two lines being substantially parallel to the cut surfaces 4 emanating from said cuts for forming substantially plane glue surfaces 5. It is then completely possible and in practise maybe most often desired that the cutting away for forming the glue surfaces takes place before the cutting into wood members.

Glue is then applied on said glue surfaces and the wood members are turned with these against each other, so that the cut surfaces 4 are directed outwardly, in which the gluing may take place either in direct connection to the very cutting in a wet gluing method or after an intermediate drying step.

An alternative to the procedure just described for obtaining a wood unit 2 consists in carrying out said cutting away for form- ing the plane glue surfaces substantially in parallel with the natural conicity of the log in question and for two wood members so obtained shift one end for another end before the gluing of the wood members to each other, so that a wood unit with a substantially constant cross-section along the length thereof is obtained without any previous round reduction of the log .

The method described so far, i.e. the way to obtain the wood units in question , belongs to the prior art and has been described inter alia in the two Swedish patents mentioned above. The characterizing feature of the present invention is that wood units of the type illustrated in Fig. 2 are produced from logs in time independent connection to the demand of wood pieces reflected by orders coming in to the saw mill, which means that in the case that storage of bulk commodity has to take place before the division into wood pieces this may take place in the form of storage of wood units while avoiding storage of so called round timber resulting in the advantages of the former storage with respect to the latter and which have been discussed in de- tail above. It is illustrated in Fig . 3 how a number of such wood units may be stored waiting for a continued division into wood pieces.

Thus, the invention may be said to also comprise a method for production of a wood unit intended to be a storage article for a later division thereof for forming wood pieces, in which a tree is felled and cut into logs and then a wood unit with a substantial rectangular cross-section and a longitudinal inner hollow space is produced according to above.

A first possible division pattern applicable to a said wood unit 2 for obtaining wood pieces is illustrated in Fig . 4. It is illustrated how cuts 6-9 are applied substantially in parallel with the sides 10 of the wood unit, in which the wood pieces 1 1 and 12 are preferably firstly formed by applying cuts 6 and 7, respectively, and the cuts 8 and 9 are then applied on the remaining member. A wood piece 13 with a longitudinal inner hollow space 14 and two additional members 15, 16, which are preferably glued together to a beam-like wood piece 17 results then. Wood pieces of high value with wear resistant surfaces on the main part of the size thereof thanks to annual rings with an extension making angles close to 90° therewith are obtained in this way. These wood pieces may stipulate a considerably higher price than the wood pieces obtainable in a division of a log , especially with defects from storage, into wood pieces. It has been illustrated in Figs. 4-8 and 10 how the longitudinal inner hollow space 14 has a substantially square cross-section distinguished from what is shown in Fig. 2 and 3, which may be obtained through a corresponding removal of material before the gluing to form the wood unit, but it is of course also possible that the inner hollow space has such an appearance as indicated in Fig. 3 or any completely different cross-section shape in the embodiments according to Figs. 4-10.

It is illustrated in Figs. 6 and 7 how according to a second preferred embodiment the division of a wood unit 2 takes place by only applying the two cuts 6 and 7 substantially in parallel with one side 10 of a wood unit so as to obtain the three wood pieces 1 1 , 12 and 18 shown in Fig. 7. It may here be mentioned that the wood pieces 1 1 and 12 are very well adapted for use where wear resistant surfaces are asked for, such as for floors, in which the sides 19 are then turned upwardly.

A third way of dividing a said wood unit 2 for obtaining a wood piece is illustrated in Fig. 8-10, in which the cuts 20 are here applied in an angle of substantially 45° with the sides 10 of the wood unit for cutting elongated wood pieces 21 with the cross- section of right-angled triangles away, which may be pair-wise glued together with the surfaces 22 emanating from the cuts 20 against each other for obtaining the very wear resistant wood piece 23 shown in Fig. 9, in which all the surfaces have annual rings extending substantially perpendicularly thereto. The wood piece 24 illustrated in Fig. 10 remains, and this has a comparatively large cross-section area and may by that stipulate a com- paratively high price. It would of course also be possible to apply one or more further cuts in parallel with the cuts 20 but closer to the respective corner of the wood unit according to Fig . 8, after which the wood members resulting from the outermost cuts may be glued together for forming a wood piece corre- sponding to that shown in Fig. 9, whereas the other wood pieces so formed may also be glued to each other in different ways for forming different wood pieces, such as four and four, with the sides emanating from the side of the wood unit in Fig. 8 as glue surfaces for forming a frame-like structure or with the same glue surfaces but alternatingly turned 180° about the longitudinal axis thereof for forming a plate-like wood piece.

The invention is of course not in any way restricted to that described above, but many possibilities to modifications thereof would be apparent to a man skilled in the art without departing from the basic idea of the invention.

It is for example also within the scope of the claims to store logs to a certain extent, should this be desired or difficult to avoid for any reason. Thus, could for example any shorter storage of logs, for example in the felling place, take place before the conversion into wood units takes place and after that the storage of some of these takes place before the division into wood pieces or would the number of logs delivered to the saw mill during a certain period of time be that high that it would not be possible to produce wood units with the same speed, a certain storage of logs may also take place at the saw mill, and this is to be considered to lie within the scope of the invention.

Claims

1 . A method for operation of a saw mill, in which logs (1 ) arriving to the saw mill are received and these are then divided into wood pieces depending on orders coming in to the saw mill, characterized in that the logs received are first converted into wood units (2) having a substantially rectangular cross-section and an inner longitudinal hollow space (14) by applying two longitudinal cuts substantially perpendicularly to each other and crossing each other in the centre of the log on the respective log, so that four elongated wood members (3) are obtained , and material is cut away from each such member in the longitudinal direction thereof along the entire member according to two lines being substantially parallel to the cut surfaces (4) emanating from the cuts for forming substantially plane glue surfaces (5) and the wood members are glued together with these plane surfaces against each other and turned so that said cut surfaces are directed outwardly, that these wood units are after that divided into wood pieces depending on said orders coming in, that the conversion of logs into wood units is carried out in a time independent connection to a demand corresponding to said orders and should this demand be lower than the flow of logs to and received by the saw mill such wood units are stored to such an extent that this difference between the flow of logs to the saw mill and the demand is substantially compensated, and that in the case that such a difference between the flow of logs into the saw mill and the demand arises that a longer storage is required before the division into wood pieces this storage mainly takes place in the form of storage of said wood units.

2. A wood unit intended to be stored for later production of wood pieces through division thereof, characterized in that it is formed by four elongated wood members (3) obtained by ap- plying two longitudinal cuts substantially perpendicularly to each other and crossing each other substantially in the centre of a log to a log, from which members material is cut away along the entire length of the members according to two lines being substantially parallel to the cut surfaces (4) of the respective wood member emanating from the cuts for forming substantially plane glue surfaces (5), and the members are glued to each other with these plane surfaces against each other and so turned that said cut surfaces are directed outwardly and the wood unit has a substantially rectangular cross-section and an inner longitudinal hollow space.

3. A wood unit according to claim 2, characterized in that it has a cross-section being substantially constant over the length thereof by the fact that said cutting away for forming the plane glue surfaces is carried out substantially in parallel with the natural conicity of the log in question and end is shifted for end for two of the wood members before gluing the wood members (3) together.