SAWING METHOD FOR LOOSENING A WOOD BOARD

Abstract: A sawing method for loosening from the blank (3) a woodboard or a board of non-magnetic material for improving sawing accuracy, in which method the loose sawing is carried out by means of a metallic saw blade (1) and the saw blade is steered to stay in the aimed sawing line. The blade position in relation to the aimed sawing line inside the sawed blank is measured by means of a distance measuring device (7) and the blade position is controlled to stay in the aimed sawing line by controlling for the blade needed deviation force by means of the magnetic field forming device (5) based on the distance value informed by the measuring device (7).

Description: SAWING METHOD FOR LOOSENING A WOOD BOARD The invention relates to a sawing method, with which the sawing accuracy will remarkable be improved while sawing loose from the blank specially thin wooden boards, like loosening glued woodboards from the woodbeam blank. Before known is a sawing method for glued woodboards from WO-publication 98/12030. In this method the blank is sawed split from the centre and the next halves again sawed split from the centre and so forward until in the last split the desired, thin glued woodboard is born. When the sawing is happening symmetrically the quite exact sawing result as a final result, if the blank is homogeneous and it has an equal quality. When the timber is not equal quality and homogeneous even when sorted, the saw blade does not necessarily keep its aimed direction, if the blade is going to contact in the blank assymmetrically being disturbing factor. This kind of factors are for ex. knots or their remains or sudden grain density changes. In the loose sawing of woodboards the sawing wideness is f.ex. 200 - 600 mm, or even wider, when the blade would have to keep its direction without supporting equipment equally about 300 - 700 mm ' s distance or eventually longer distance. For this reason a remarkable improvement has been developed in the way of sawing, with which improvement the blade can be guided, if it starts to turn side from the aimed exact sawing line. Characteristic to the invention is what is presented in the claims. By means of the invention noticeable advantages is reached, for that the sawing result is going to be made sure, the sawing wideness can be raised, the sawing speed can be lifted and the sawing method can be applied also for sawing other nonmagnetic materials than timber. In the following the invention is explained closer by referring to the enclosed drawing, where Figure 1 shows a sawing method according to the invention. Figure 2 shows schematically the blade guidance control. In the figure 1 there is shown from a blank 3 by means of band saw performed glued woodboard loose sawing. The sawing is done by sawing the blank split from the middle by means of a blade 1. The blade 1 is guided by means of the apparatus included rollers 2 before and after the sawing. The distance between rollers 2 is adjustable depending by the hight of the blank 3. The aimed line of sawing is straight from the middle to the split of the blank. Blade 1 should so to stay also between the area of rollers 2 in the aimed centre line. When sawing broad woodboards, the blank hightness becomes noticeable and the support points of the blades 1 , in other words rollers 2, will locate far from each other. The blade's 1 staying in the middle line is secured according to the invention by utilizing magnetic power systems. The blade 1 has to be ferromagnetic or electricity conducting material, to which by means of one or several magnetic field is caused forces for pulling or pushing farther away. The arrangement according to the invention comprises measuring of the position of the blade 1 in one or several points between the support rollers 2. The measuring device 7 is for. ex. with echo sounding princible functioning which measures throught the board the distance of the blade. The measuring principle can also be capasitive, where a capacitor is formed between the measuring device and the blade, wherein the capacitors capacitance is changing due to the distance of the blade. When the blade 1 begins to transverse due to some disturbance from the center line, begins the blade front edge, in other words the edge with teeths, first to transverse from the line. For that reason the measuring device is to be directed towards the area of the front edge of the blade. On the both sides of the blank 3 there are confront to the blade 1 an equipment to form a magnetic field 5, by means of which the blade 1 is either pulled or pushed by magnetic forces in side direction. The equipment 5 are for ex. earlier known with D.C. current formed magnets, power of which is controlled by supply of the current and one pole or both poles of the magnet are directed towards the blade-1. The equipments 5 are preferably located symmetrically on the both sides of the blade and they can operate by means of controlling either at separate time depending to which side the blade is turning, wherein only one device is pulling or pushing the blade or they are operating at the same time, wherein the other pulls and the other pushes. Also the situation is possible that both are pulling or pushing the blade at the same time. The magnetic polarity of the device 5 can be, as known change by changing the direction of D.C. current supplied to the device. If the sawing broadness (height of the blank) is big several distance measuring devices 7 can be equipped to control the blade and several devices to form the magnetic field 5 between the support rollers 2. If the blade has tendency to surging or natural vibration, these phenomenons can be removed by controlling the blade by means of magnetic forces. If the magnetic polarity is desired to obtain for the blade 1 , the blade 1 can be magne- ticed either with the help of around the blade placed D.C. current coil or with the help of on the side of the blade locating magneticing device 4. The control forces that is directed to the blade can be increased by this arrangement.. One alternative is to lead D.C. current or changing D.C. current trough the blade at least over the sawing point, wherein the blade is electric current conductiing conductor at the sawing point. The electric current to the blade 1 is got for . ex. by the help of draging current coals. By means of the magnetic field forming device 5 is equally produced to "the electric conductor" in other words to the blade 1 then force influences even in this case. In figure 2 there is shown a control system as a scheme. The system comprises a control unit 8, getting from the distance measuring gauge 7 information oft the blade position in relation to the centre line. Based on this information the unit steers the magnetic field forming devices 5 to return the blade 1 to the centre line, if it is trying to go away from it. The unit controls also the magneticing device 4 by giving it either as constant remaining or controlled magneticing power. The control system is possible to manufacture as fast reacting and back coupled, wherein the blade line can be kept stable. At the suitable point before the blade gets into the sawing situation, the magneticing can be removed from that for example by means of A.C. current. Then the blade 1 is easier either magneticed to a certain degree or left neutral when it arrives to the point of magnetic field forming devices 5. As a steerable blade according to the invention can be used a band saw blade, a broad and thin knife blade or also a circular saw blade. The stability of the circular saw blade is improved by means of the method according to the invention especially in that point when the blade is inside the sawed material. The steering of the blade can be done only from one side of the blade if both pulling and pushing force to the blade is formed by means of the magnetic field. For example when the band saw blade is in question, a band saw blade can by means of the method according to the invention be steered also to go diverging to the normal fully straight line by compelling it by means of magnetic forces, in the distance between the support rollers 2, into a bowed position and keep it in that by means of steering.

Claims: CLAIMS 1. A sawing method for loosening a woodboard or a board of other non-magnetic material from the blank (3) to achieve better sawing accuracy and to stabilize the blade movements, in which method the loose sawing is carried out by means of a metallic saw blade (1) and the saw blade is steered to stay in the intended sawing line, characterized in that - the blade (1) position (side deviation) in relation to the aimed sawing line inside the sawed blank (3) is measured by means of a distance gauge device (7), - the blade side position is controlled to stay in the aimed sawing line by controlling needed steering force in the side direction by means of the magnetic field forming device (5) based on the distance value informed by the measuring device (7). 2. A method according to the claim 1 characterized in that to the blade (1) is caused magnetic polarity by means of a magneticing device (4). 3. A method according to the claim 1 characterized in that to the blade (1) is caused magnetic polarity by forming it as a D.C. conductor at least at the point of sawing. 4. A method according to any of the previous claims 1 -3 characterized in that the devices (5) for forming a magnetic field locate on both sides of the blade. 5. A method according to any of the previous claims 1 -4 characterized in that the distance measuring from the blade and the inluence of magnetic force to the blade are centralized to happen from the edge of the blade, which has toothing. 6. A method according to any of the previous claims 1 -5 characterized in that the magnetic steering power influence to the blade (1) and the blade distance measuring are carried out through the board which is loosened by sawing. 7. A method according to any of the previous claims 1-6 characterized in that in the method the blank (3) is sawed split in the middle.

Inventors: VILJANEN REIJO, VILJANEN, REIJO
Applicants: JOINT CAPITAL OY SOLWO, VILJANEN REIJO, VILJANEN, REIJO
Application year: 2000
Main classification: B27B13
IPC codes: B23D55, B23D59, B27B13