PROCEDURE AND APPARATUS FOR STRAIGHTENING A CIRCULAR-SAW BLADE INTO A DESIRED SHAPE

Abstract: Procedure for straightening a circular-saw blade (2), in which procedure the blade (2) is mounted on a shaft (3). The geometry of the blade is measured, the measured values are compared with reference values, deformations in the blade are straightened by means of blade treating elements (10, 11, 12, 13, 14, 15, 16, 23, 24), the blade is tensioned by means of working devices (13, 14), the blade (2) is rotated, lateral forces are applied to the blade (2), the effect of the forces on the blade (2) is measured while the blade is rotating, the measured values are compared with the reference values, and some or all of the operations mentioned above are repeated, if necessary, in a desired order, until the desired rigidity and straightness of the blade (2) have been achieved. The invention also relates to an apparatus for straightening a blade.

Description: PROCEDURE AND APPARATUS FOR STRAIGHTENING A CIRCULAR-SAW BLADE INTO A DESIRED SHAPE The present invention relates to a procedure as defined in the preamble of claim 1 for straightening a circular- saw blade into a desired shape. The invention also re¬ lates to an apparatus as defined in the preamble of claim 6 for straightening a circular-saw blade into a desired shape. Circular-saw blades lose their original shape during use. The tensions in the blade change during use as a result of mechanical lateral forces and the thermal effects pro¬ duced by such forces. Depressions are formed in the blade and the blade may get twisted, leading to a deteriorated sawing result. So far, the straightening of circular-saw blades has usually been performed manually by hammering, which means that the quality of work has been dependent on the craftsmanship of the person carrying out the op- eration. Manual straightening takes time and a successful result is not guaranteed. Moreover, different circular- saw blades having different damages require different treatment. An advantageous circular-saw blade design is one with a slightly Λ cup-like' shape, i.e. with a slightly curved cross-sectional form. When the blade is rotated at nominal speed, its cuplike shape is straight¬ ened. The cup-like shape varies depending on things like the size and material of the blade and the rotational speed it is designed for. Also, manual straightening and repair of blades whose thickness is reduced radially from the centre towards the edges of the blade has been very difficult, even impossible. Some devices for straightening a circular-saw blade are also known. From EP application 0521824 Al, a machine for straightening a circular-saw blade is known in which the straightening is effected by means of rollers placed on opposite sides of the blade and controlled on the basis of a measurement performed by means of a dial indicator. Again, US patent specification 2964248 presents a proce¬ dure and machine for the tensioning and straightening of a circular-saw blade, in which dents are straightened by hammering with a hammering device. The blade is hammered from one side only. Among the drawbacks of the solutions known in the art is the inaccuracy of the measurement used for controlling the straightening treatment. In the known solutions, the straightening treatment is performed in a random order, and this has led to unsatisfactory straightening results. Furthermore, treating the blade with rollers and hammers creates unnecessary tensions or expansion of the blade, and these have a deteriorating effect on the final result of the treatment. The object of the present invention is to achieve a com¬ pletely new type of procedure and apparatus for straight¬ ening circular-saw blades into a desired shape, avoiding the drawbacks of the solutions previously known in the art. The invention is characterized by what is presented in the claims. The solution of the invention has several significant ad¬ vantages. The procedure of the invention can be used to automatically straighten circular-saw blades without the need for special skill. The procedure is fast and accu¬ rate. It makes it possible to achieve a straightened and tensioned circular-saw blade having a maximal rigidity, which also remains very accurately in alignment while ro¬ tating. Blades repaired by applying the procedure and apparatus of the invention are tested in conditions cor¬ responding to an actual operating situation, ensuring that they will also work properly in their real place of use. The measurement of blade geometry forming the basis of the treatment is very accurate. The tools used in the treatment produce a very accurate effect on the blade. This means that unnecessary tensions and expansion of the blade are avoided. The blade is mounted in a manner cor¬ responding to its mounting on a real sawing machine. The behaviour of the blade can be observed while it is rotat- ing at a correct speed. The procedure and apparatus of the invention make it possible to produce a report giving blade-specific information about the faults detected and corrected as well as about the repair operations per¬ formed. Moreover, information about the repaired blade is obtained, e.g. relative rigidity, surface hardness, size of saw kerf/side clearance, straightness and magnitude of vibration/critical speed of rotation. The blade can be marked with these data, making it easy to select a blade that best suits the sawing situation. In the following, the invention is described by the aid of examples of preferred embodiments by referring to the attached drawings, in which Fig. 1 presents a top view of an apparatus as provided by the invention. Fig. 2 presents a detail of a blade treating element used in the apparatus of the invention, seen from the direction of the blade, and Fig. 3 presents a detail of the blade treating ele¬ ments in a diagrammatic form, partly sectioned. The figures show an apparatus as provided by the inven¬ tion for straightening a circular-saw blade into a de¬ sired shape and for tensioning the same. The circular-saw blade 2 is mounted on a shaft 3, between flanges 4, 5 on the shaft. The manner of mounting the blade corresponds to normal mounting of the blade on a circular saw. The shaft 3 preferably consists of two parts. The shaft 3 is rotatably mounted with bearings on the frame 1 of the ap¬ paratus. The shaft is rotated by means of a drive 6, such as an electromotor. The shaft is provided with a detector 7 which transmits the angular position of the shaft 3 to a control unit 8. By means of the control unit 8, the shaft 3 and therefore the circular-saw blade 2 can be ro- tated by the drive precisely to the desired position. The apparatus is provided with elements 9 for determining the geometry of the blade. Using a measuring device 9, the shape, possible deflections, dents and convex- ity/concavity of the circular-saw blade 2 are determined. The measuring elements consist of e.g. at least one sen¬ sor 9, the sensor 9 or the blade 2 or both being moved in relation to each other so that substantially the whole surface of the blade is measured. Measurement of shape is an ordinary task for a person skilled in the art, so the shape of the blade can be measured using any known method or detector. It is possible to use e.g. laser measurement to determine the shape of the blade 2 and transmit it further to the control unit 8. The sensor 9 is preferably attached to a support 12 which is movable at least in the radial direction of the blade 2, permitting the whole blade area to be measured by simultaneously rotating the blade 2. In addition, the apparatus comprises blade treating ele¬ ments for correcting any deformations, such as dents and deflections, as well as means for tensioning the blade. These elements preferably consist of arms 10, 11 placed on opposite sides of the blade, the blade 2 to be treated being located between the arms. The arms 10, 11 are pref¬ erably pivoted on the support 12, which is movable at least in a direction transverse to the axis 3 of rotation of the blade (e.g. in the radial direction of the blade) . The support 12 can be moved e.g. on guide rails 20 by means of a motor 21. The arms 10, 11 are provided with blade treating elements 13, 14, 15 ,16, 23, 24 placed at the arm ends closer to the blade. The blade treating ele¬ ments consist of working devices 13, 14 and/or shaping devices 15, 16, 23, 24. The working devices 13, 14 pref¬ erably consist of surfaces formed in the arms 10, 11, de¬ signed to apply a force to the blade 2 by means of actu¬ ating devices 17, 18. The shaping devices 15, 16, 23, 24 comprise a press part 15, 16 and a counter press part 23, 24, at least one of which is adjustable. The shaping de¬ vice is e.g. a hydraulically operated mandrel. The arms are moved by means of the actuating devices 17, 18, which are e.g. piston-cylinder combinations operated by means of a pressure medium, preferably electrohydraulic servo cylinders. The moving mechanism is controlled by means of the control unit 8. The arms 10, 11 are preferably moved together so that they are moved to the desired location on the blade 2 with the arms located on opposite sides of the blade 2. At least one of the arms 10, 11 is brought into contact with the surface of the blade 2, whereupon it is moved preferably in a direction perpendicular to the blade surface so that the desired straightening move¬ ment is produced. The working devices 13, 14 are preferably provided with protuberances 13, 14 protruding from their surface. The press part 15, 16 of the shaping devices is surrounded by a preferably annular projection 23, 24 slightly protrud- ing from the surface of the blade treating elements, said projection acting as a counter press element while the blade is being shaped from the opposite side. In addition, the apparatus comprises elements 19 for ap- plying a load on the blade 2, especially in the axial di¬ rection. These elements consist of at least one nozzle 19 through which a jet of compressed air is directed at the blade 2, preferably in a direction perpendicular to the lateral surface of the blade. The compressed air is sup- plied to the nozzle via ordinary air supply means from a compressed-air source, such as a compressor (not shown) . The nozzle 19 is placed near the blade 2, e.g. on an arm 10, 11, at the arm end closer to the blade. The process of straightening the blade to a desired shape and tensioning it is e.g. as follows. The blade 2 is fixed onto the shaft, between the flanges 4, 5 provided for this purpose. This manner of mounting the blade es¬ sentially corresponds to a normal circular-saw operating situation. The blade 2 mounted on the shaft is rotated slowly, e.g. 10 - 100 r/min, by means of the drive 6. The geometry of the blade 2 is measured by means of a measur- ing device 9 preferably mounted on the support 12 at least on one side of the blade 2. Determining the blade geometry includes the measurement of the blade's diame¬ ter, number of teeth, tooth shape, number, shape and lo¬ cation of cleaning teeth, as well as the measurement of possible cut-outs in the blade, such as thermal gaps, and blade thickness and defects of shape. After the blade ge¬ ometry has been determined, the measured results can be displayed on a monitor connected to the control unit 8. The measuring device 9 used may consist of any known sys- tern that can be connected to the control unit 8. The most suitable measuring system is laser measurement. The meas¬ urement is preferably performed on both sides of the blade 2, which makes it possible to achieve a geometric analysis of even blades that have a cross-sectional form tapering in the radial direction towards the circumfer¬ ence. The yield strength of the blade 2 is preferably de¬ termined by applying a shaping test to the blade by means of the shaping devices on the arms 10, 11 and measuring the effects of the shaping on the blade. The apparatus also preferably comprises a device for hardness measure¬ ment (not shown) to allow the hardness of the blade to be determined. A hardness measurement is performed on sev¬ eral points in the lateral surface of the blade. The hardness of the blade has a substantial influence on the determination of the working resistance/yield strength of the blade. After the measurements, the blade 2 is straightened into the desired shape. The straightening is performed using blade treating ele¬ ments, preferably arms 10, 11 moved by drives and special shaping devices 15, 16, 23, 24 mounted on the arms. Larger deflections are straightened by means of the arms 10, 11 and the working devices 13, 14 , and depressions and dents in the blade 2 by means of the shaping devices 15, 16, 23, 24. During the straightening shaping process, an arm on the opposite side of the blade 2, preferably a counter press element 24 of the shaping device on the arm, pushed out into an outer position, the press element 16 of the shaping device on said arm being in an inner position, acts as a stop face, preferably a circular one, supporting the blade. When the arm on the opposite side of the blade, preferably the press element 15 of the shaping device on it, is pushed out into an outer posi¬ tion and the counter press element 23 is in its inner po¬ sition. By forcing the arms 10, 11 by means of actuating devices, preferably servo cylinders, in a controlled man¬ ner towards each other, a dent or bump in the blade 2, brought into the region of the gap of the counter press element 24, can be pressed so as to straighten it by ap¬ plying such pressure to one or more points on the blade, depending on the extent of the dent/bump. The aim of the straightening process is that, when rotating at nominal speed, the blade 2 is substantially perpendicular to the axis 3 of rotation. Tensioning of the blade body is usu¬ ally started when the circumference of the blade is ro¬ tating in the same plane with the centre. After the straightening, the blade is tensioned by means of the shaping devices 13, 14 so that a maximum rigidity is achieved with the rotational speed used. A tension is created by pressing the blade body by means of cylinders from both sides, causing the protrusions 22 of the shap¬ ing devices 13, 14 to be pressed against each other. The shape of the tool 13, 14 is such that the working takes place in the direction of the circumference, so that even the smallest deformation produces a sufficient increase in the tension. The elements used to treat and shape the blade are placed on arms 10, 11 moved by servo cylinders, by means of which it is possible to achieve very accurate treatment. Therefore, the procedure produces no unneces¬ sary tension or blade expansion as when rollers or con- ventional hammers are used. After the tensioning, while rotating at nominal speed, the blade 2 is subjected to a lateral load e.g. by applying an air blast to it. This is preferably achieved by using a nozzle 19 to which com¬ pressed air is supplied via suitable piping (not shown) e.g. from a compressor. Nozzles may be provided on both sides of the blade. The effects of the air blast load are monitored by means of a measuring device 9, preferably the same laser measurement device used for measuring the blade shape as described above. The measuring device preferably monitors the displacement of the blade. The measuring, tensioning and straightening operations described above are repeated several times if necessary, controlled by the control unit 8, until a circular-saw blade 2 is obtained that has the greatest possible rigid¬ ity and remains most accurately in alignment while rotat¬ ing. In this manner, by repeating treatment operations, the load resistance of the blade body can be optimized. The measuring, bending and tensioning operations are re- peated until the displacements in the loading tests are at a minimum. This optimization of firmness and rota¬ tional stability is the most significant advantage of the procedure and apparatus of the invention. The control unit 8, e.g. a PC, regulates the operating elements of the apparatus in the desired manner. The con¬ trol unit is supplied with reference values with which it compares the measured values and which form the basis on which the required operations are performed. The control unit preferably controls the apparatus in such a way that defects requiring correction in the first place, such as large deflections and bumps, are treated first. In addi¬ tion, the control unit is preferably so designed that it will take the effect of a treatment operation on other defects in the blade into account. In a preferred case, the control unit is equipped to collect and analyze data about the blades treated by the apparatus, thus continu- ally expanding the reference material. In this case, the procedure and apparatus of the invention have a self- teaching capability. It is possible to print out from the control unit a blade-specific report indicating e.g. defects discovered in the blade and corrective treatment applied to it. The properties of the straightened blade that can be printed out include relative rigidity, surface hardness, saw kerf/side clearance, straightness and magnitude of vibra- tion/critical speed of rotation. Based on these data it will be easy to select a blade that best suits each saw¬ ing situation. It is obvious to a person skilled in the art that the in- vention is not restricted to the embodiments described above, but that it may instead be varied in the scope of the following claims.

Claims: CLAIMS 1. Procedure for straightening a circular-saw blade (2), in which procedure the blade (2) is mounted on a shaft (3), preferably between flanges (4, 5), characterized in that - the geometry of the blade is measured by means of a measuring device (9) , - the measured values are compared with reference values, - controlled by a control unit (8) on the basis of the measured values and the reference values, - deformations in the blade are straightened by means of blade treating elements (10, 11, 12, 13, 14, 15, 16, 23, 24), - the blade is tensioned by means of working devices (13, 14), - the blade (2) is rotated preferably at its nominal speed, - lateral forces are applied to the blade (2), - the effect of the forces on the blade (2) is measured while the blade is rotating, - the measured values are compared with the reference values, and - some or all of the operations mentioned above are re- peated, if necessary, in a desired order, until the de¬ sired rigidity and straightness of the blade (2) have been achieved. 2. Procedure as defined in claim 1, characterized in that the geometry of the blade (2) is measured from both sides of the blade. 3. Procedure as defined in claim 1 or 2, characterized in that lateral forces are applied to the blade (2) by blasting with compressed air. 4. Procedure as defined in any one of claims 1 - 3, char¬ acterized in that the yield strength and/or hardness of the blade (2) is determined at least before the straight¬ ening. 5. Procedure as defined in any one of claims 1 - 4, char- acterized in that measured values about the blades treated by the procedure are collected in the control unit (8) and, when necessary, the straightening and ten¬ sioning treatment, including e.g. the treatment opera¬ tions, their application to the blade and their duration, is modified on the basis of the material collected. 6. Apparatus for straightening a circular-saw blade (2), in which apparatus the blade (2) is placed on a shaft ro- tatably mounted with bearings, which apparatus is pro- vided with means (10, 11) for straightening the blade, said means being placed on both sides of the blade (2), and with at least one measuring device (9) for the meas¬ urement of the shape of the blade, characterized in that the means for straightening the blade consist of arms (10, 11) movable at least in the radial direction of the blade (2) and at least one blade treating element (13, 14, 15, 16, 23, 24) designed to produce an effect on a lateral surface of the blade (2), and that the control unit (8) controls the operation of the blade straighten- ing means on the basis of measured values transmitted by the measuring device (9) . 7. Apparatus as defined in claim 6, characterized in that the blade treating elements consist of working devices (13, 14) and/or shaping devices (15, 15, 23, 24) mounted on the arms (10, 11) . 8. Apparatus as defined in claim 6 or 7, characterized in that the working devices (13, 14) preferably consist of surfaces formed in the arms (10, 11), which are used to produce an effect on the blade (2) by means of devices (17, 18) actuating the arms. 9. Apparatus as defined in any one of claims 6 - 8, char¬ acterized in that the shaping device (15, 16, 23, 24) comprises a press element (15, 16) and a counter press element (23, 24), at least one of which is adjustable. 10. Apparatus as defined in any one of claims 6 - 9, characterized in that the apparatus comprises means (19) for applying an air blast load to the blade (2) .

Inventors: RAUTIO KAI, RAUTIO KAUKO, RAUTIO, KAI, RAUTIO, KAUKO
Applicants: RAUTIO KAI, RAUTIO KAUKO, VEISTO RAKENNE RAUTIO OY, RAUTIO, KAI, RAUTIO, KAUKO, VEISTO-RAKENNE RAUTIO OY
Application year: 1996
Main classification: B23D63
IPC codes: B23D63