EP1349715B1

EP1349715B1 - Apparatus and method for handling logs

Info

Publication number: EP1349715B1
Application number: EP01999466A
Authority: EP
Inventors: Esko METSÄNRANTA; Seppo Lehtola; Bengt Klockars; Tapani Rossi
Original assignee: Tahka Oy AB
Current assignee: Tahka Oy AB
Priority date: 2000-12-07
Filing date: 2001-12-07
Publication date: 2007-02-14
Anticipated expiration: 2021-12-07
Also published as: EP1349715A1; ATE353743T1; AU2002217173A1; DE60126662D1; FI20002683A0; WO2002045925A1

Abstract

The present invention relates to an apparatus and a method for handling logs (5). They provide a quicker handling of logs (5) in the vicinity of crosscut saw (4) and, at the same time, reduce the generation of waste material. These improvements are achieved by the design and the movement of longitudinal conveyors (1, 2, 3), by optimising the movements of the crosscut saw (4) in accordance with the data obtained from a measurement conveyor, and by measuring the length of the blocks without a detent by means of photocell and a pulse detector.

Description

The present invention relates to the handling of logs and, more precisely, to a method and an apparatus for a quicker and more effective handling of logs in a crosscut saw and in its vicinity.
In the following, one apparatus and a method commonly used at present in bark stripping and cutting stations of veneer logs are briefly described. Before handling, logs are kept in a tank incubator, where the logs are in water at a temperature of about 60°C to become soft. From there, the logs are lifted one by one or in small bundles onto a front table, using a crane/log loader. From the front table, the logs are transferred transversely onto a breaker table, the purpose of which is to break the high log bundles into lower layers. After the breaker table, the logs are transferred to a feeder log hoist, which guides the logs individually onto a longitudinal conveyor so that, when moving onto the longitudinal conveyor, the logs are sequentially as close to one another as possible. This longitudinal conveyor conveys the logs to a bark-stripping machine, where the logs are stripped and, from there, another longitudinal conveyor conveys the stripped logs further to a measurement conveyor. On the measurement conveyor, the log is accurately measured, and the data on the log is recorded in a computer. The values to be measured include, among others, length, diameter, ovality, angle of taper, springing, crooked-growth, surface contour, etc. Regarding the values to be measured, the timber volume and optimum use in further processing are calculated, among others. Furthermore, grading is carried out and defects in the butt end and the like are observed.
After measurement, the logs are pushed transversely to a roadside landing. At this stage, the order of logs must not be changed any more, because then the log-specific data measured by the measurement conveyor gets mixed up. From the roadside landing, the logs are transferred individually onto the longitudinal conveyor. The conveyor takes the logs through a metal detector, and if there are any metal particles in the log, these parts are removed from the log automatically or manually using the crosscut saw.
The longitudinal conveyor, typically, a chain conveyor, brings the logs from the metal detector to the crosscut saw, which typically is a circular saw. The end of the log is driven past the crosscut saw blade against a mechanical detent behind it. There are several detents available for cutting pieces of different lengths on the basis of the data obtained from the measurement conveyor. There are also movable detents, the location of which can be changed, so that a block of a correct size can be cut from the log. After the log has been driven against the desired detent, the conveyor that comes to the crosscut saw and leaves from there is stopped for the time of sawing. A problem occurring, when the log is driven against the detent, is to make the log stop so that it adheres to the detent, because, when hitting the detent, the log always tends to slightly bounce backwards on the conveyor. Therefore, for safety's sake, the block must always be cut slightly overlong, in order not to lose the whole block because it is too short for further processing. Cutting the block properly overlong results in wasting more material in further processing. Furthermore, since the log does not stop immediately near the detent, it takes time to arrange it, which slows down log handling.
For the time of sawing, the log is firmly gripped with pliers. Typically, the pliers are located both before and after the saw. After sawing, the mechanical detent is removed and, after disengaging the pliers, the cut log is moved forward to further processing, using the longitudinal conveyor after the saw. The detent is returned to its place and the remaining log is driven against it for cutting a new block. After all the blocks have been cut from the log and moved forward, the remaining piece of log is dropped through a slot between the conveyors and next to the crosscut saw to the collection point below the conveyor. If the piece of log is longer than the existing slot, it is possible to enlarge the slot by turning downwards by 90° the pivoted conical roller parts, which are located before and/or after the crosscut saw.
In document CA-A-2305850 is presented an other apparatus and method for bucksawing a log with improved throughput speed. The method comprises the steps of advancing the log endwise along an infeed conveyor, raising the log above the level of said infeed conveyor while advancing the log, measuring the advance of the log while raised, stopping the log at the desired length, sawing the log to produce a forward log segment and lowering the forward log segment onto an outfeed conveyor while advancing the remaining log segments.
Problems with previously known apparatuses include controlled transportation of logs by the longitudinal conveyor, large variations in the dimension of the block cut from the log, causing unnecessary waste of material, the unnecessary movement of the crosscut saw from one extreme position to another during each cutting operation, an increase in the distance between the logs on the longitudinal conveyor, which thus slows down the production in connection with cutting, and the delays of production caused by the use of the mechanical detent.
The apparatus and the method according to the present invention provide a solution to the problems described above, and the following advantages. The apparatus according to the invention speeds up log handling by implementing a more stable longitudinal conveyor solution and design of the conveyor that comes to the crosscut saw, a proactive and optimising crosscut saw, a movable conveyor subsequent to the crosscut saw, and cutting without a detent. These solutions, which are described in detail hereinafter, provide, among others, acceleration of the production and a decrease in noise and the waste of material.
The apparatus and the method according to the invention are defined by the features of claims 1 and 9 respectively.
In the following, the apparatus and the method according to the invention are described in detail with reference to the appended drawings, in which

Fig. 1 shows a drawing in principle of longitudinal conveyors and a crosscut saw as viewed from the side,
Fig. 2 shows a partial enlargement of Fig. 1, wherein part of the chain structure of the longitudinal conveyors is viewed from the side,
Fig. 3 shows a cross section of the longitudinal conveyors in accordance with the section I-I of Fig. 1,
Fig. 4 shows the cross section II-II of Fig. 1, the centring holding pliers being preferably located next to the cross-section,
Fig. 5 shows the cross section III-III of Fig. 1, the presses preferably being located next to the cross section,
Fig. 6 shows the crosscut saw as viewed from the side to the direction of sawing,
Fig. 7 shows the crosscut saw waiting for cutting, and
Fig. 8 shows the crosscut saw in the extreme position after cutting.

Fig. 1 shows a drawing in principle of longitudinal conveyors 1, 2, and 3, and a crosscut saw 4. A log 5 is moved to the crosscut saw 4, and the conveyors 2 and 3 and, as necessary, also the conveyor 1, are stopped so that the selected cutting point of the log is next to the blade of the saw 4. The cutting point is automatically calculated on the basis of the data coming from the measurement conveyor (not shown in the figure) by means of a computer. For optimum use, the computer program calculates one or more alternatives for the log 5 for cutting the blocks. The user of the apparatus, who is in the immediate vicinity of the crosscut saw 4, selects any of the alternatives, or (s)he also has the opportunity to cut the log 5 in accordance with his own choice. In that case, the computer program calculates a new optimum use plan for the remaining log.
The log 5 is moved to the right location with respect to the crosscut saw 4 by driving the end of the log past a photocell (not shown in the figure) located after the saw, whereby the forward movement of the conveyors 1, 2, and 3, and at the same time, also of the log can be stopped in a controlled way. Thus, the distance of the photocell from the saw 4 is known, and the displacement measure of the conveyor coming from the pulse detector of the conveyor 3 is added to it, whereby the dimension of the piece of log that has travelled past the blade of the crosscut saw, i.e., the length of the block to be cut, is obtained. Accordingly, there is no need to drive the end of the log 5 against the mechanical detent, whereby the log always bounces slightly backwards and causes dimensional error. This method is used to decrease any waste created at subsequent further processing stages and to accelerate sawing. The conveyor 3 is preferably controlled by means of the feedback provided by a frequency transformer and a cutter location probe, i.e., the pulse detector.
The possibility to cut the log 5 effectively without the detent and without great dimensional errors is based on the new structure of the longitudinal conveyors 1, 2, and 3 presented in Fig. 2. The longitudinal conveyor 3 and preferably also the other longitudinal conveyors 1 and 2 are composed of parts 7, which are connected by articulation and contain sharp forms 6, the sharp forms of the parts being against the surface of the log 5. The parts 7 form a chain-like structure, on which the log 5 rests, and which is used to move the log forward in a controlled way. There are at least two, preferably 5, chain-like structures side by side in the longitudinal conveyors 1, 2, and 3. The sharp forms 6 are preferably spikes or barbs, which prevent the log 5 from sliding with respect to its direction of motion, and it is possible to measure the location of the end of the log with respect to the crosscut saw 4 by using the photocell and the pulse detector of the conveyor 3.
In Fig. 3, one preferred embodiment of the longitudinal conveyors 1, 2, and 3 is described as a cross section I-I of Fig. 1, wherein the chain-like structures combined from the parts 7 are located in a group of a V-shape. The spikes 6 together with the preferably V-shaped cross section of the group formed by the chain-like parts of the conveyors 1, 2, and 3 described herein contribute to a more stable forward transportation of the log 5. In addition, the more stable transportation and cutting without a detent also provide a lower noise level compared with prior art.
Fig. 4 shows the cross section II-II of Fig. 1. Holding pliers 8, which are not shown in Fig. 1, are located next to the cross section II-II. The holding pliers 8 are used to centre the log 5 on the middle of the longitudinal conveyor 2 during cutting. The holding pliers 8 are fitted on both sides of the longitudinal conveyor 2 above it, so that they are pivoted on bearings to the body of the longitudinal conveyor at their upper parts, and interconnected by means of their tooth systems of the tooth system.
In that case, by preferably using one hydraulic cylinder 9, a uniform compression is provided due to the tooth system, which interconnects the holding pliers 8, on both sides of the log 5, whereby it moves to the middle of the conveyor 2. The design of the holding pliers 8 at their lower parts is preferably implemented in accordance with Fig. 4, so that the holding pliers are capable of effectively centring the logs 5 of all diameters, which come to the saw 4, on the middle of the conveyor 2, so that no lateral movement of logs is allowed to happen. The contact surface of the holding pliers 8, which comes against the log, is provided with a serrated pattern to improve adhesion.
Fig. 5 shows the cross section III-III of Fig. 1. Presses 10, which are not shown in Fig. 1, are located next to the cross section III-III. The presses 10 are fitted on both sides of the longitudinal conveyor 3 so that they are attached by bearings to the body of the longitudinal conveyor at their other ends. By means of the hydraulic cylinders 11, the presses 10 preferably press the log 5, which is centred by the holding pliers 8, against the longitudinal conveyor 3 for the time of cutting the log. The ends of the presses 10 on the side of the log 5 and opposite to the bearing are designed so that they are capable of effectively pressing logs of all sizes, which come to the saw 4, against the conveyor 3. In that case, the design is preferably the shape of a butter-knife, the surface of which coming against the logs 5 is provided with a serrated pattern.
During sawing, the log 5 is compressed against the conveyors 2 and 3 by means of the holding pliers 8 or the presses 10 located either before the saw 4 and/or after the saw, being correspondingly presented in Figs. 4 and 5. One preferable embodiment locates the centring holding pliers 8 before the saw 4 and the presses 10 after the saw.
Fig. 6 shows a drawing in principle of the crosscut saw 4 of Fig. 1. The saw 4 is mounted by a bearing to the framework at its centre of gravity 12 and it is preferably moved to and fro by means of a hydraulic cylinder 13, which is attached between the frameworks and the saw, on the basis of the data coming from the measurement conveyor in accordance with an arrow 14. The blade 15 of the saw 4 is preferably rotated by means of an electric motor 16 in accordance with an arrow 17. The electric motor 16 is located above the bearing 12, whereby it balances the mass of the blade 15.
Figs. 7 and 8 show in detail the operation of the crosscut saw 4, when the log 5 is cut. After the log 5 has been driven to a proper location in the crosscut saw 4, the blade 15 of the saw is already at the right distance 18 from the surface of the log, waiting for the cutting in accordance with Fig. 7. The data on the thickness of the log 5 at the cutting point comes from the measurement conveyor. The saw 4 starts to cut so that, in the beginning, the feed of the saw blade 15 is at its maximum, and it slows down, when approaching the maximum length of the cutting line, after which the blade feed is again accelerated. In this way, blocking and a possible seizure of the blade 15 are prevented in the vicinity of the longest cutting line, when cutting thick logs 5. After cutting the log 5, the saw blade 15 is not driven to its extreme position, which is enabled by the movement of the hydraulic cylinder, but on the basis of the data obtained from the measurement conveyor, immediately after the log has been cut, the saw blade returns to wait for the next cutting at the proper distance 18 from the surface of the log. In connection with cutting, the blade 15 of the saw 4 moves by a dimension 19 only in accordance with Fig. 8, without the blade having anything to cut. When there is no need to drive the blade 15 from one extreme position to another, but the blade is only moved for the distance required by the cutting, this procedure saves the time taken by the cutting.
While the preceding log 5 is still being cut, the next log is driven by the conveyor 1 to be ready and waiting as near the conveyor 2 as possible, which leads to the saw 4. The length of the conveyor 2, which leads to the saw 4, is optimised in accordance with the maximum length of the block, and the length of the conveyor 1 is optimised in accordance with the maximum length of the log 5.
After cutting the blocks, generally, a waste piece remains of the log 5, which must be removed from the conveyor 2 after the last cutting. This is carried out by dropping it through a slot between the conveyors 2 and 3 on both sides of the crosscut saw 4 to a collection point below the saw. Previously, the slot has been increased by means of conical roller parts, which turned downwards by 90°. The parts were located before and/or after the saw.
In the solution according to the invention, the waste piece is preferably removed by means of the conveyor 3, which is mounted to move in the longitudinal direction. When needed, it is possible to move the conveyor 3, which is located after the saw 4, forward by preferably about 0.3 m, whereby the slot between the conveyors 2 and 3 next to the saw increases, and the waste piece of the log 5 has enough room to drop to the collection point under the crosscut saw. The conveyor 3 is moved forward fully automatically, programmed by the computer, and the conveyor returns back to its extreme position near the saw 4 to wait for the next log 5. Moving can take place so that there is no next log 5 yet on top of the conveyor 3, or that the next log is already on the conveyor or moving onto it, whereby the rotational speed of the conveyor chains are adjusted as necessary by means of the frequency transformer.
The solution according to the invention provides a quicker handling of logs next to the crosscut saw. This is made possible by decreasing the distance between the logs, when coming to the cutting, because the next log can be driven by the conveyor to be already waiting near the end of the previous log. Another accelerating factor is the optimised movement of the crosscut saw regarding the cutting movement and the saw feeding; both it and the saw are already waiting in the right place, when a log of a certain size comes to the cutting. A third factor is to implement measurement without a detent, whereby there is no need to drive the log against the detent. When driving against the detent, the log often bounces towards the detent before settling sufficiently near. In measurement without the detent, the log can be made to settle in the right place with a smaller tolerance and in a controlled way, and it can be cut faster.

Claims

An apparatus for handling logs comprising a crosscut saw (4), a longitudinal conveyor, which comes to the saw and consists of at least two separate, first and second conveyor parts (1, 2), characterized in comprising a third, shorter conveyor part (3), which is after the crosscut saw (4) and mounted to be moved in its longitudinal direction, and a subsequent fourth conveyor part and that first, second, and third conveyor parts (1, 2, 3) consist of a conveyor means formed from parallel, longitudinal, interconnected pieces (7), and which conveyor means, when there are more than two, are located with respect to one another so that they form a surface with a curved or V-shaped cross section, and which conveyor means have gripping members (6).
An apparatus according to Claim 1, characterized in that the length of the first conveyor part (1) is in the same order as the average length of a log (5).
An apparatus according to Claim 2, characterized in that the length of the second conveyor part (2) is as great or slightly greater than the maximum length of the block to be cut.
An apparatus according to Claim 3, characterized in that the conveyor means is a simple conveyor chain or a conveyor chain with rakes or lamellas.
An apparatus according to Claim 4, characterized in that the gripping members (6) are spikes, barbs or other kinds of pieces containing sharp edges.
An apparatus according to any of the preceding Claims, characterized in that while the crosscut saw (4) is a circular saw controlled in an optimised way, the crosscut saw (4) comprises a hydraulic control cylinder (13) for the movement of the saw blade (15) transversely to the direction of travel of the track, and that the bearing (12) of the saw blade (15) and the drive (16) is at the gravity point formed by them.
An apparatus according to any of the preceding Claims, characterized in that the apparatus comprises holding members (8, 10) of the log (5), located before and/or after the crosscut saw (4).
An apparatus according to Claim 7, characterized in that the holding members (8, 10) comprise centring holding pliers (8) fitted before the crosscut saw (4) and/or presses (10) fitted after the crosscut saw (4).
A method for handling logs using apparatus according to any of Claims 1-8, wherein the logs (5) are optimised by means of a measurement conveyor, transported to the crosscut saw (4), cut to a fixed size, and transported forward to be further processed, characterized in that the transportation of the logs (5) to the crosscut saw (4) and from the crosscut saw (4) is done with conveyor parts (1, 2, 3) containing sharp forms against the surface of the logs (5) so that the logs (5) are moved forward and cut to the fixed size in a controlled way without the detent and without sliding of the log (5) with respect to its direction of motion.
A method according to Claim 9, characterized in that the movement of the crosscut saw (4) is optimised in accordance with the data coming from the measurement conveyor so that no unnecessary sawing movement takes place and the saw blade (15) moves to be waiting at the right distance from the surface of the log (5) in accordance with the data obtained from the measurement conveyor, and that the feeding rate of the saw blade (15) is optimised in accordance with the thickness of the log (5), so that the feeding rate of the saw blade (15) slows down, when coming towards the longest cutting line, and speeds up again after it.
A method according to Claim 9 or 10, characterized in that the conveyor part (3) after the crosscut saw (4) moves forward, when necessary, whereby the waste piece of the log (5) to be cut has enough room to drop through the conveyors (2, 3), after which the moving conveyor part (3) returns to its extreme position nearer the crosscut saw (4).