GB2411861A

GB2411861A - Apparatus for cutting timber

Info

Publication number: GB2411861A
Application number: GB0504778A
Authority: GB
Inventors: Per-Ke Wilklund; Lennard Svensson
Original assignee: SOEDERHAMN ERIKSSON AB
Current assignee: SOEDERHAMN ERIKSSON AB
Priority date: 2004-03-08
Filing date: 2005-03-08
Publication date: 2005-09-14
Anticipated expiration: 2025-03-08
Also published as: GB2411861B; SE0400566L; FI20050242A; GB0504778D0; DE102005009386B4; FI123147B; FI20050242A0; SE526793C2; SE0400566D0; DE102005009386A1

Abstract

A machine 1 for cutting curved timber 2 into pieces 9,10,11, with the machine having a feed device 3 and a sawing station 4. Timber is fed into the feeding device, and the feeding device feeds the timber in an axial direction into the sawing station. The sawing station is positioned downstream of the feeding device relative to the feed direction of the timber. The machine has at least three band saws 6 and at least four support rollers 12, 12'. The support rollers are remote from the feeding device and the support rollers are each individually adjustable transversally relative to the feed direction of the timber. The support rollers are grouped into pairs, with each pair being axially separated and cooperating with at least one saw band.

Description

2411 861

IMPROVEMENTS IN OR RELATING TO AN APPARATUS AND METHOD

FOR CUTTING TIMBER

Description of the Invention

The present invention relates to an apparatus and method for cutting timber, and more particularly relates to an apparatus and method for cutting curved pieces of timber.

Modern sawmills usually have many sawing lines, each with a large number of sawing stations which are highly automated to ensure that high quality timber is output from the sawmill, and to enable, for instance, board shaped timber to be cut from round logs of timber. It is of high importance in a sawmill that timber pieces which are cut from larger sections of timber have dimensions which are as accurate as possible, and also uniform along the length of the timber. If timber can be cut with high accuracy, with minimal deviations in the dimensions along the length of the timber, then that timber can be sold at a premium as high quality timber. Therefore, modern sawmills are often run with very strict tolerances in the cutting process to ensure that the output from the sawmill is of high quality.

An acceptable deviation in the thickness of a piece of timber cut in a modern sawmill, along the length of the timber, is often no more than 0.6 millimetres.

A person skilled in the art will appreciate that in order to cut a piece of timber within this tolerance using a band saw, the timber must be guided very accurately against the band saw, and the smallest deviation when guiding the timber will result in the cut timber having dimensions outside the required tolerance.

When the majority of logs of timber pass into a sawmill, they typically undergo numerous operations before a central section of each log is cut into planks or boards, by band saws in a final stage along the sawing line. In order to produce the desired timber output from a log the central section of the log, which is often known as a four-sided block, is curve sawn during a final stage in the cutting process. The reason for this is that logs are usually curved and logs often have a radius of curvature in the range of 50 to 100 meters, meaning that, for instance, a 4 meter long log has a bow of about 20 to 40 millimetres. Curve sawing of a log is achieved by feeding the log along a curved path, with the curved path corresponding to the curvature of the log.

Standard sawing stations usually incorporate three or four band saws, with each band saw having its own saw band. A timber body is cut into smaller pieces by the band saws as the timber body is fed through the sawing station.

In the case of a sawing station which incorporates four band saws, five pieces will be cut from one four-sided timber block; two outer pieces, two inner pieces and one centre piece. In conventional sawing stations, the saw bands are usually parallel to the direction in which the timber is fed, with the saw bands being arranged in pairs which are axially separated. More particularly, the saw bands are usually positioned such that the saw bands which cut the outer pieces from the timber body define a first pair of saw bands which are upstream from the other saw bands. The saw bands that cut the inner pieces of the timber from the centre piece form a second pair. The second pair of saw bands may, in some cases, be replaced by a single saw band when it is necessary to cut the inner pieces of timber from one another.

Prior proposed cutting machines usually have four pairs of vertical rollers located in a feeding device, which is located upstream from the sawing station, to guide a curved timber body. The rollers press against two vertical opposing sides of the timber body as the timber body is fed along the sawing line. The rollers of the feeding device are divided into two rows, which are parallel to the sawing line and which may move collectively at an angle relative to the sawing line. This configuration often gives rise to the rollers pressing excessively against the timber body, which causes undesirable stress on the timber body and the feeding device. Additionally, the rear pair of rollers in the feeding device, which are positioned closest to the sawing station, press against the timber body at a relatively large distance from the second pair of saw bands.

This relatively large distance between the rear pair of rollers and the saw bands results in the inherent curvature of the timber body contributing to deviations in the position of the timber body in relation to the sawing line, which may reduce the accuracy of the cutting process.

In an attempt to overcome this guiding problem, it has been proposed previously to move the rear pair of rollers closer to the second pair of saw bands. When this adjustment was carried out more accurate guidance of the timber was obtained, but at the same time a new problem was created. When these adjustments were made to the feeding device, the front rollers caused the first pair of saw bands to become clamped between the outer pieces of timber and the remaining part of the timber body, which potentially caused damage to the saw bands as well as the sawn timber. In addition, despite this alteration to the feeding device, the remaining part of the timber body still diverged from its intended path due to lack of guidance.

Referring now to Figure 1, a prior proposed cutting machine 1 cuts a curved piece of timber 2. The cutting machine 1 is usually provided at the end of a sawing line to carry out the final cutting operation of the sawing line.

Therefore, it should be appreciated that, before the timber body 2 reaches the cutting machine 1, the timber body 2 may have undergone various other machining processes by other machines (not shown for the sake of simplicity) along the sawing line. These other processes are usually to machine a round log into a shape suitable for feeding into the cutting machine 1.

Before reaching the cutting machine 1 a round log is fed into the loading end of the sawing line, where the shape and curvature of the log is determined to calculate the maximum amount of cut timber obtainable from the log. In practice, logs are often curved in several different planes. However, the curvature of a log is often particularly marked in one main plane. As the log progresses along the first half of the sawing line, a number of edge boards and/or lateral boards are cut from the log, to leave a heart piece of the log having a rectangular cross-section, known as a four-sided block. After the timber body has undergone these procedures to produce the four-sided block the timber body resembles a banana having a rectangular cross-section.

It should be noted that the curvature of the timber body 2 in the accompanying drawings is slightly exaggerated for the sake of explanation.

Once the four-sided block of timber 2 has been cut it is then sawn into individual planks or boards by the cutting machine 1 at the end of the sawing line. A person skilled in the art will appreciate that there may be other different machines along the sawing line, as well as different types of conveyers (e.g. chain conveyers) between the machines along the sawing line, none of which are shown in the accompanying drawings for the sake of simplicity.

The cutting machine 1 incorporates a feeding device 3 and a sawing station 4.

The feeding device 3 is positioned upstream of the sawing station 4 in relation to the feeding direction of the timber body 2. The feeding device 3 has a base 19 and a plurality of rollers 5, with the rollers 5 each being rotatable about a respective vertical axis. The rollers 5 are rotatably driven, for instance by electric motors (not shown), and the rollers 5 press against the timber body, so that as the rollers 5 rotate they move the timber body 2 in an axial direction, into the sawing station 4.

The sawing station 4 incorporates four band saws 6, which are each individually adjustable transversally relative to the feeding direction of the timber body 2. The band saws 6 are grouped into pairs along the axial direction of the feeding direction of the timber body 2, with one band saw 6 of a pair to one side of the sawing line and the other band saw 6 of that pair to the other side of the sawing line. Each band saw 6 incorporates a saw band 8, 8', with each saw band being carried by a carrier 7. The teeth of each saw band 8, 8' are directed upstream of the feed direction of the timber body 2.

The saw bands 8, 8' are parallel to one another and parallel to the feed direction of the timber body 2, and the saw bands 8, 8' are axially separated in pairs from one another.

During operation of the cutting machine 1 the first pair of saw bands 8, cuts two outer pieces 9 from the timber body 2, and a second pair of saw bands 8' cuts two inner pieces 10 from the remaining centre piece 11 of the timber body 2.

As a result of the band saws 6 each being moveable transversally to the feeding direction of the timber body 2, each of the saw bands 8, 8' may be moved away from the sawing line, to adjust the position at which each saw band 8, 8' cuts the timber body 2. For instance, a pair of saw bands 8 may be moved away from the sawing line so as to not cut the timber body 2 to reduce the number of pieces 9 which are cut. Alternatively, the second pair of saw bands 8' may be replaced by a single saw band, which would result in the two inner pieces 10 of timber being cut in half by the single saw band, without the centre piece 11 of timber being cut.

The present invention seeks to provide an improved apparatus and method for cutting timber.

According to one aspect of this invention, there is provided a machine for cutting timber into pieces comprising a feeding device for feeding the said timber in an axial direction into a sawing station, the sawing station being positioned downstream of the feeding device relative to the feed direction of the timber, the machine further comprising at least three band saws, with each band saw having a respective saw band which is carried by a respective carrier, the or each saw band being substantially parallel to the feed direction of the timber, and at least one saw band being axially offset along the feed direction in relation to the other saw bands, the machine further incorporating at least four support rollers, with each support roller being remote from the feeding device and individually adjustable relative to the feed direction of the timber, the support rollers being grouped into pairs with each pair being axially separated and co-operating with at least one saw band by contacting the said timber body along an imaginary georretric reference line, with the or each reference line extending transversally relative to the feed direction and being located in close proximity to a corresponding saw band.

Preferably each support roller is moveably mounted to a respective said carrier.

Conveniently each support roller is moveably mounted to a respective carrier by a respective guide system which extends from the carrier at least partly into a volume between a respective saw band.

Advantageously the said feeding device is switchable between an active state in which it feeds the timber towards the sawing station, and an inactive state in which the feeding device is free to follow the curvature of the timber.

According to another aspect of this invention, there is provided a method for cutting timber into pieces comprising the steps of: feeding the timber using a feeding device in an axial direction into a sawing station which is located downstream from the feeding device; and feeding the timber towards at least three saw bands which are operating in the sawing station, with a saw band in each said band saw generating saw cuts in the timber which are substantially parallel to the feed direction of the timber, at least one of said saw bands being offset relative to the other saw bands along the feed direction, wherein at least four support rollers, which are each remote from the feeding device and each individually adjustable transversally relative to the feed direction, the support rollers being provided in pairs, with the pairs being axially separated from one another and each pair co-operating with at least one saw band, the support rollers pressing against the timber along two imaginary geometric reference lines which extend transversally relative to the feed direction of the timber, with the reference lines being located in close proximity to a respective saw band which co operates with a respective pair of support rollers.

Preferably the at least one saw band which is located upstream relative to the other saw bands generates a first saw cut in the timber, and the other saw bands generate saw cuts in the timber adjacent the said first saw cut.

Conveniently the support rollers press against the timber upstream from the saw band which is associated with the respective pair of support rollers.

A preferred embodiment of the present invention may provide a cutting machine which offers good guidance of a timber body throughout the complete cutting process.

The preferred embodiment of the present invention may provide a machine that cuts pieces from a timber body, with the pieces having dimensions within a high tolerance along the length of each timber piece.

The preferred embodiment of the present invention may provide a cutting machine in which the guidance of a timber body during the cutting process does not have to be precisely defined.

The preferred embodiment of the present invention may provide a cutting machine in which the guidance of a timber body during the cutting process is not carried out by a feeding device.

In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described, by way of example, with reference to the accompanying drawings in which: FIGURE 1 is a schematic plan view of a prior proposed cutting machine.

FIGURE 2 is a schematic plan part cut away view of a cutting machine in accordance with the preferred embodiment of the invention, FIGURE 3 is a schematic perspective side view of a band saw of the cutting machine shown in Figure 2, and FIGURE 4 is a diagrammatic perspective side view of two of the band saws shown in Figure 3 mounted on a stand.

Referring now to Figure 2 a cutting machine 1 in accordance with the preferred embodiment of the present invention incorporates many of the same parts of the cutting machine shown in Figure 1, and thus corresponding parts will be allocated the same reference numerals and will not be redescribed below.

The cutting machine 1 has a first pair of vertical support rollers 12 and a second pair of vertical support rollers 12'. The two pairs of support rollers 12, 12'are each axially spaced from one another, and are axially spaced from the feeding device 3. Each support roller 12, 12' is individually adjustable in a direction which is transverse to the feed direction of the timber body, so that the timber body 2 may be held firmly during the cutting process.

The first pair of support rollers 12 is associated with the first pair of saw bands 8, and the second pair of support rollers 12' is associated with the second pair of saw bands 8'. The pairs of support rollers 12, 12' press against the timber body 2 along two imaginary geometric reference lines R and R', which are each transverse to the axial feed direction of the timber body 2, and each located in close proximity to their respective saw band 8, 8'. The reference lines R and R' are each located upstream from their respective co-operating saw band 8, 8'. In this preferred embodiment the axial distance between the reference lines R and R' is approximately 300 millimetres, and the axial distance between each reference line R. R' and the respective co-operating saw band 8, 8' is between 30 and 40 mlllimetres.

Each of the pairs of support rollers 12, 12' guides the timber body 2 during the cutting process. The feeding device 3 is adjustable between an active state, in which it feeds and guides the timber body 2 into the sawing station 4, and an inactive state, in which the base 19 of the feeding device 3 is free to follow the curvature of the timber body 2. In other words, when the feeding device 3 is in the inactive state, the feeding device 3 becomes "free flowing" perpendicular to the feed direction of the timber body 2, whilst all four of the support rollers 12, 12' are still pressed against the timber body 2. The feeding device 3 becomes free flowing in order to reduce the risk of the support rollers 12, 12' and the feeding device 3 pressing excessively against the timber body 2. In this preferred embodiment the feeding device 3 continues to feed the timber body 2 axially through the sawing station 4 when the feeding device 3 is in its inactive free flowing state. However, in alternative embodiments, the timber body 2 may be fed by one or more of the support rollers 12, 12', with the feeding device 3 being omitted from the cutting machine 1.

In the preferred embodiment, the support rollers 12, 12' are connected to the carriers 7 which carry the band saws 6, so that the support rollers 12, 12' are moveable in response to movement of the carriers 7. Each support roller 12, 12' is rotatably mounted to a respective holder 13. Each of the holders 13 is mounted on a respective guide system 14, and each of the guide systems 14 is mounted to a respective carrier 7. In this preferred embodiment, the guide system 14 is formed by a slideable mount, but in other embodiments an alternative system, such as a piston and cylinder arrangement, may be used.

The first pair of support rollers 12 and their respective guide systems 14 are all mounted on the same side of the first saw band 8. However the second pair of support rollers 12' are positioned on an opposite side of the second saw band 8' compared with their respective guide systems 14. This ensures that the second pair of rollers 12' presses against the timber body 2 at a position which is upstream of the second saw band 8'.

The radii of each of the support rollers 12, 12' is greater than the axial distance between each of the saw bands 8, 8' and their respective reference lines R. R'. This prevents the support rollers 12, 12' being offset past one another, without colliding with one another. As the support rollers 12, 12' are mounted to their respective carriers 7, the risk of collision between support rollers 12, 12' and the saw bands 8, 8' is greatly minimised as a result of the guide system 14 being limited to a maximum length of stroke which is less than the distance between the carrier 7 and its respective saw band 8, 8'.

Referring now to Figures 3 and 4, each band saw 6 is moveably mounted to a stand 15, to allow each of the band saws 6 to undergo a translatory movement in a direction transverse to the feed direction of the timber body 2. Each of the band saws 6 is moveable from an outer position, in which the timber body 2 may pass through the sawing station 4 without contacting that band saw 6, and an inner position, in which at least one saw band 8, 8' is positioned at the centre, or beyond the centre of the timber body 2. In the preferred embodiment, each band saw 6 may be moved through a distance of approximately 400 millimetres. However, in other embodiments, depending upon the application in which the saw is being used, the length by which the band saws 6 may be moved may vary greatly.

Each band saw 6 incorporates a support column 7 which supports a driving wheel 16 at its lower end via a driving shaft (not shown). An upper wheel 17 is rotatably mounted to an upper end of the support column 7. The driving wheel 16 and the upper wheel 17 are aligned, and in the same plane as one another, and a saw band 8' extends around the peripheries of the wheels 16, 17. The driving wheel 16 and the upper wheel 17 are biased away from one another to tension the saw band 8', and cause the saw band 8' to be moved by means of friction as the driving wheel 16 rotates.

A blade guide 18 is mounted to the support column 7 above where the timber body 2 is to be cut. The blade guide 18 guides the saw band 8', and limits movement of the saw band 8' in a transverse direction in relation to the direction of movement of the saw band 8', thus minimising the possibility of parallel deviation of the saw band 8' during the cutting process. This preferred embodiment only incorporates one guide element 18, but in other embodiments, a further guide element may be provided below the level of where the timber body 2 is to be cut, to provide further stabilization of the saw band 8'.

In this preferred embodiment, the function and positioning of the two pairs of support rollers 12, 12' in the sawing station 4, combined with the adjustable positioning of the saw bands 8, 8' provide improved accuracy in the cutting process. The reason for this is because the first pair of saw bands 8 are for separating the centre piece 11 from the timber body 2, and the second pair of saw bands 8', which is axially remote from the first pair of saw bands 8 in the downstream direction, are provided to cut the outer pieces 9 from the inner pieces 10. This means that when the timber body 2 reaches the second pair of saw bands 8' there are no saw cuts in the timber body 2 between the support rollers 12' and the saw bands 8', which ensures that the outer pieces 9 and also the inner pieces 10 are cut to precise dimensions.

A horizontal roller (not shown) during the cutting process, presses against the upper side of the partially cut timber pieces from the sawing station 4. The basic function of the horizontal roller is to press the timber pieces against the conveyor on which they are being carried. It has been shown that as this horizontal roller presses down on the timber pieces, the timber pieces are caused to diverge from one another. In other words, the horizontal roller causes the timber pieces to move in a diverging motion downstream from the support rollers 12'. Accordingly, when the inner pieces 10 and the outer pieces 9 are about to be cut, a good contact is achieved between the second pair of support rollers 12' and the timber body 2. The second pair of support rollers 12' may also, because of the diverging movement of the timber pieces, be pressed against the timber body 2 downstream of the teeth of the saw bands 8', without the risk of the saw band 8' becoming jammed during the cutting process.

As a result of the moveable support rollers 12, 12' and their position, the cutting machine 1 of the preferred embodiment described above allows accurate guidance of the timber body 2 during the entire cutting process.

Also, the support rollers 12, 12' permit the first pair of saw bands 8 to generate the inner saw cuts and the second pair of saw bands 8' to generate the outer saw cuts. This minimises the chances of small dimensional variations occurring during the cutting process as a result of the guidance by the support rollers during the cutting process. This allows pieces of timber which have small dimensional variations along each axis to be cut, which improves the quality of the output from the sawing line.

As a result of the feeding device 3 being in free flow operation during the cutting process, the timber body 2 is not excessively held and no excessive stresses are placed upon the timber body 2 or the saw bands 8, 8'.

Whilst the cutting machine 1 has been described thusfar as having three pairs of vertical rollers 5 in the feeding device 3, in other embodiments, the feeding device 3 may only incorporate two pairs of vertical rollers 5.

In other embodiments, the support rollers 12, 12' may not necessarily be connected to the carriers 7 of the band saws 6, but may instead be mounted onto individual free standing supports, for instance frames connected to the support stand 15 of the band saws 6.

In the described embodimen; each support roller12, 12' is described as a roller, but this may alternatively be any other mechanism which is capable of guiding and support the timber body 2 during the cutting process.

In the described embodiment the saw bands 8, 8' operate vertically (i.e. impart vertical cuts to the timber body 2). However, in other embodiments the saw bands 8, 8' may be angled horizontally, or at any other angle.

The cutting part of the saw bands 8, 8' may include any kind of grain tearing means, for instance teeth, inserts, grit, or the like.

The support rollers 12, 12' and their associated guide systems 14 may, as well as being moveable transversally relative to the feed direction of the timber body 2, also be moveable in an axial direction, to enable precise adjustment of the location of the points where the rollers 12, 12' contact the timber body 2, as well as to facilitate the mounting and removal of the saw bands 8, 8'.

A person skilled in the art will appreciate that although, in this described embodiment, the cutting machine is to be positioned at the final stage along a sawing line, the cutting machine 1 may alternatively be used at any other position along a sawing line, or indeed as a standalone cutting machine.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

Claims 1. A machine for cutting timber into pieces comprising a feeding

device for feeding the said timber in an axial direction into a sawing station, the sawing station being positioned downstream of the feeding device relative to the feed direction of the timber, the machine further comprising at least three band saws, with each band saw having a respective saw band which is carried by a respective carrier, the or each saw band being substantially parallel to the feed direction of the timber, and at least one saw band being axially offset along the feed direction in relation to the other saw bands, the machine further incorporating at least four support rollers, with each support roller being remote from the feeding device and individually adjustable relative to the feed direction of the timber, the support rollers being grouped into pairs with each pair being axially separated and co-operating with at least one saw band by contacting the said timber body along an imaginary geometric reference line, with the or each reference line extending transversally relative to the feed direction and being located in close proximity to a corresponding saw band.
2. A machine according to Claim 1, wherein each support roller is moveably mounted to a respective said carrier.
3. A machine according to Claim 1 or claim 2, wherein each support roller is moveably mounted to a respective carrier by a respective guide system which extends from the carrier at least partly into a volume between a respective saw band.
4. A cutting machine according to any one of the preceding Claims, wherein the said feeding device is switchable between an active state in which it feeds the timber towards the sawing station, and an inactive state in which the feeding device is free to follow the curvature of the timber.
5. A method for cutting timber into pieces comprising the steps of: feeding the timber using a feeding device in an axial direction into a sawing station which is located downstream from the feeding device; and feeding the timber towards at least three saw bands which are operating in the sawing station, with a saw band in each said band saw generating saw cuts in the timber Which are substantially parallel to the feed direction of the timber, at least one of said saw bands being offset relative to the other saw bands along the feed direction, wherein at least four support rollers, which are each remote from the feeding device and each individually adjustable transversally relative to the feed direction, the support rollers being provided in pairs, with the pairs being axially separated from one another and each pair co-operating with at least one saw band, the support rollers pressing against the timber along two imaginary geometric reference lines which extend transversally relative to the feed direction of the timber, with the reference lines being located in close proximity to a respective saw band which co operates with a respective pair of support rollers.
6. A method according to Claim 5, wherein the at least one saw band which is located upstream relative to the other saw bands generates a first saw cut in the timber, and the other saw bands generate saw cuts in the timber adjacent the said first saw cut.
7. A method according to claim 5 or Claim 6, wherein the support rollers press against the timber upstream from the saw band which is associated with the respective pair of support rollers.
8. A machine for cutting timber substantially as herein described with reference to and as shown in Figures 2 to 4 of the accompanying drawings.
9. A method for cutting timber substantially as herein described with reference to Figures 2 to 4 of the accompanying drawings.
10. Any novel feature or combination of features disclosed herein