Method and device for measuring outer circumference of pipe

Abstract

The present invention automatically measures the outer circumference length of a plain pipe during pipe production. The present invention enables the operation with a measuring device left on a line. In order to realize the foregoing, a measuring tape reel 4 is rotatably mounted on a rotating ring 3 set to be rotatable around the outer circumference of a plain pipe / pipe T. The starting point of a measuring tape 5 in the measuring tape reel 4 is fixed outside the outer circumference of the rotating ring 3, and the measuring tape 5 is wound around the outer circumferential surface of the plain pipe / pipe T as the rotating ring 3 rotates. The state of the measuring tape 5 wound around the plain pipe / pipe T one full turn or more is measured using an external field of view. During the measurement, the rotating ring 3 or the measuring tape reel 4 moves in the axial direction of the plain pipe / pipe T by a distance corresponding to the width dimension of the measuring tape 5, thereby avoiding overlap of the wound measuring tape 5 in the field of view.

Description

Pipe circumference measurement method and device

[0001] The present invention relates to a method and device for measuring the outer periphery of a blank pipe during forming, for example, in a cold roll forming machine capable of producing steel pipes with a diameter ratio of several times, in order to perform periphery control to determine whether the roll position adjustment and forming amount are appropriate when changing product dimensions.

[0002] Electric resistance welded steel pipes are manufactured on a mill line using a large number of forming roll stands, where steel strips unwound from coils are bent, welded, and drawn to produce steel pipes of the required diameter. More specifically, the steel strips are bent from edge to semicircular in the breakdown BD process, formed into a nearly round pipe in the cluster CL process, and finally formed into a blank pipe with the desired outer circumference in the fin pass roll FP process.

[0003] Next, the pipe is butt-welded using a squeeze roll SQ to form a round pipe, and then it is finished into an electric resistance welded steel pipe with the required diameter, roundness, and straightness using a sizing roll SZ and a Turks head roll TH, and is then cut to the required pipe length to complete the pipe.

[0004] When performing initial threading due to a change in steel pipe diameter, etc., the position of the forming rolls in each process is adjusted while the strip steel plate passes through the BD, CL, and FP processes in order. If the plate thickness is changed while keeping the diameter the same, there is no need to perform initial threading again, but if the plate width is changed, the roll position of each stand must be adjusted.

[0005] Whether the roll position adjustment has been performed properly is confirmed by measuring the outer periphery of the mother pipe, a process known as circumference control. That is, at the entry and exit sides of the stand after the FP process, the outer periphery of the mother pipe or welded pipe is measured with a steel tape measure (hereinafter referred to as "measure") to confirm whether the specified amount of reduction has been achieved, and the result is fed back to the roll position adjustment.

[0006] Currently, outer circumference is measured manually by wrapping a tape measure around the outer circumference of blank pipes or welded pipes while the line is stopped. Taking the initial threading of a plate in the FP process as an example, the initial roll position is adjusted according to the forming schedule for the desired diameter, and then the material is threaded once and the outer circumference is measured. The roll position is then adjusted again, the material is advanced again, and the outer circumference is measured a second time, and the effectiveness of the previous roll position adjustment is confirmed. If there is an excess or deficiency, a third outer circumference measurement will be required. When such manual measurement work is performed multiple times, concerns arise not only about safety, but also about the measurement time, which affects operating rate, and the reproducibility of measurement accuracy.

[0007] On the other hand, in order to reduce the labor required for measurement, a device has been proposed in which a welded spiral steel pipe is inserted into the belt that forms the loop, tension is applied to the belt wire using a spring or cylinder, and the length of the wound belt wire that is unwound is measured (Patent Documents 1, 2, and 3).

[0008] In addition, a device has been proposed in which a self-propelled tape measure wrapping device like a can opener is wound around the outer periphery of the end of a welded steel pipe, and the length of the tape measure that is unwound is used to measure the outer periphery (Patent Document 4).

[0009] The devices in Patent Documents 1, 2, and 3 measure the outer periphery of a spiral steel pipe that has been welded and is about to proceed to the next process, and are not suitable for online circumference management during pipe production before welding, such as in the FP process.Furthermore, Patent Document 4 is a measuring device for pipes such as steel pipes that have been cut to the required length after pipe production, and cannot be placed on the line of an operating pipe mill.

[0010] JPA 1981010203JPA 1983083207JPB 1982020561 Utility Model 6-56702

[0011] The steel strip used to form the pipes has a wide variety of characteristics due to differences in the steelmaking, rolling, and width-cutting processes, and the width of the strip material is not uniform, and it may even meander slightly in the longitudinal direction. When manufacturing welded steel pipes of a certain diameter, a coil of steel strip with a specified width is used, but because the characteristics of the material vary, such as uneven width and thickness, after the steel strip is bent in the BD and CL processes, in order to weld it into a steel pipe of the required diameter in the SQ process, it is necessary to adjust the cross-sectional shape and perimeter by drawing to the amount of drawing appropriate to the characteristics of the material in the FP process just before SQ.

[0012] Furthermore, in pipe mills that can manufacture steel pipes with a diameter ratio of 2 to 3 times without changing rolls, product dimensions are often changed, and setup is changed each time. Once position adjustment is completed at the roll stand where bending is performed, the degree of drawing to be performed at the two- to three-stage fin pass FP roll stand must be determined by measuring the outer periphery of the blank pipe before and after the roll stand, so it is extremely important to adjust the roll position and manage the periphery to ensure that forming is appropriate.

[0013] For example, whether the bending radius is formed according to the design schedule in the three-stage fin pass FP roll stand region significantly affects the welding quality in the next process. Therefore, the outer circumference of the open pipe is measured as the sum of the outer circumference of the blank pipe before entering the first FP roll and the distance between the opposing edges of the blank pipe (the length of the opening portion of the blank pipe). This is then used to determine and evaluate the true outer circumference of the blank pipe, excluding the opening portion. Similarly, the outer circumference of the open pipe after passing through the first and second FP rolls is measured and used for perimeter control. Furthermore, in the SZ and TH processes, perimeter control, which measures the outer circumference of the pipe, is used to allocate the amount of drawing at each roll stand, contributing to improved dimensional accuracy of the product.

[0014] In such a pipe mill line, for example, in order to reduce the labor required for or automate the initial threading process each time a product dimension is changed, it is necessary to perform circumference management that enables the outer circumference of the blank pipe to be measured online.

[0015] An object of the present invention is to provide a method and apparatus for automatically measuring the outer periphery of a mother tube during forming.

[0016] The inventors have studied various measurement methods and device configurations with the aim of creating a circumference measurement device that can be easily installed even in spaces where the stand pitch is narrow or where there is existing equipment around the stands, and that is configured so that the measurement device can be operated while remaining on the line.

[0017] As a result, the inventors discovered that by supporting a measure bobbin with a wound measuring tape on a swivel ring that contains the mother tube and rotatably holds the outer circumference of the tube, and as the ring rotates, the measure bobbin rotates while revolving around the outer circumference of the mother tube, winding the measuring tape around the outer circumference of the mother tube, and then moving the swivel ring itself or the bobbin itself linearly in the axial direction of the mother tube by the required distance, for example, the width of the measuring tape, so that the measuring tape is wrapped around the tube more than once, so that the measuring tape is close to each other on the outer circumference of the mother tube but does not overlap, the outer circumference can be measured by observing the measuring tape scale from above, for example, visually, or in the field of view of a periscope or digital camera, and the invention was completed.

[0018] Furthermore, in this method, by ensuring that the tape measures are close to each other on the outer surface of the raw pipe when wrapping the tape around the raw pipe more than once, and that they do not overlap, the outer periphery length is not measured precisely, but it was discovered that this method allows measurements to be made in the shortest time possible and with good reproducibility each time, and the invention was completed based on this knowledge.

[0019] That is, this invention provides a method and apparatus for measuring the outer periphery of a mother pipe during pipe making and / or a pipe after welding (mother pipe / pipe) by wrapping a tape measure around the mother pipe / pipe one or more times within an observation field from the outside, the method and apparatus comprising: a swivel ring that encloses the mother pipe / pipe and rotatably holds its outer periphery; a tape measure bobbin with a tape measure wound around it is rotatably mounted on the swivel ring; the starting point of the tape measure is fixed outside the outer periphery of the swivel ring; and the holding and swivel drive mechanism has a tape measure winding function that allows the tape measure to be wound / unwound around the outer periphery of the mother pipe / pipe as the swivel ring rotates; and an axial movement means for moving the swivel ring itself or the tape measure bobbin itself in the axial direction of the mother pipe / pipe by at least the tape width dimension of the tape measure when wrapping the tape measure around the mother pipe / pipe one or more times; and the wrapped tape measures do not overlap within the observation field.

[0020] Furthermore, the present invention provides a method and device for measuring outer circumference, characterized in that, in the above configuration, the stage for moving the swivel ring itself in the pipe axial direction is a linear mechanical mechanism with a screw structure between the outer surface of the swivel ring and the holding mechanism of the swivel ring.

[0021] The present invention also provides a method and apparatus for measuring outer periphery length, characterized in that in the above-mentioned configuration, the means for moving the major bobbin itself in the tube axial direction uses a linear motion mechanical mechanism as a shaft support mechanism for the major bobbin.

[0022] The present invention also provides a method and apparatus for measuring outer circumference, characterized in that, in the above-mentioned configuration, the means for moving the major bobbin itself in the tube axial direction uses a linear motion mechanical mechanism as a mechanism for placing the major bobbin on the swivel ring.

[0023] The present invention also provides a perimeter measurement method and apparatus having the above-mentioned configuration, characterized in that the observation field is captured by a digital camera.

[0024] The circumference measurement method and apparatus of this invention can be used to measure the circumference of a pipe mill while the line is stopped, and after the measurement is complete, the apparatus can be left in place and pipe production operations can resume. Furthermore, it can measure the circumference of not only offline welded steel pipes, but also online blank pipes before welding, blank pipes after welding, and round or square pipes before, during, or after forming in the forming process. Furthermore, the measurement can be performed automatically, without the need for manual labor.

[0025] 5A is a simplified explanatory diagram of a measuring device for illustrating an overview of a circumference measurement method; FIG. 5B is an explanatory front view of a circumference measurement device of Example 1; FIG. 5C is an explanatory top view of a circumference measurement device of Example 1; FIG. 5D is an explanatory side view of a circumference measurement device of Example 1; FIG. 5E is an explanatory AA cross-sectional view of a circumference measurement device of Example 1, where FIG. 5A shows an initial state and FIG. 5B shows a state after one and a half revolutions; and FIG. 5F is an explanatory front view of a circumference measurement device of Example 2.

[0026] The configuration of the measuring device and the measuring method will be explained based on the simplified front view of the measuring device in Figure 1. Here, an example will be explained in which it is placed on the upstream side of the fin pass roll stand. The blank tube being formed as the object to be measured has its opposing edges open, and moves from the front to the back of the figure.

[0027] The main frame of the apparatus is, for example, a single face plate 1, with a hole 2 in the center through which the blank tube T can pass. A holding mechanism is provided on the outer periphery of this hole 2, supporting a ring plate 3 having an inner diameter similarly large enough for the blank tube T to pass through, so that the ring plate 3 can rotate about the hole 2. The hole 2 is configured to prevent interference, taking into account the size of the product formed by the pipe mill, and is designed to allow the blank tube to pass through at the center of the tube axis or the center of the tube bottom, depending on the roll forming method, for example.

[0028] A bobbin 4 is rotatably mounted on the upper surface of the ring plate 3, and has a tape-like measuring tape 5 wound around it. The starting end of the measuring tape 5 can be anywhere outside the outer periphery of the ring plate 3 in the figure, but here it is fixed to the center of the right side of the face plate 1. The measuring tape 5 is made of, for example, a thin steel tape, but its thickness is exaggerated in the figure to illustrate the wound state.

[0029] Here, if the state in which the bobbin 4 faces the vicinity of the measuring fixing point 6 is taken as the neutral position before measurement, there will be no obstacles when the blank tube T passes through the hole 2 in the face plate 1.

[0030] From the neutral position, the ring plate 3 is rotated counterclockwise as shown in the figure, and the bobbin 4 rotates about one and a half revolutions around the raw tube T, resulting in the state shown in the figure.If a camera S is placed above the raw tube T whose opposing edge portion is open, the scale markings on the tape measure can be read within the field of view of the camera S.

[0031] However, simply rotating the ring plate 3 causes the measuring tapes to overlap, making it unclear which of the measuring scales at both edge positions of the raw tube T and the scale indicating the outer circumferential length is which. Therefore, it is necessary to prevent the measuring tapes from overlapping when the bobbin 4 rotates around the raw tube T one or more times.

[0032] In other words, a means is provided for moving the bobbin 4 itself or the ring plate 3 itself in the axial direction of the tube so that when the bobbin 4 rotates one or more times around the base tube T, it moves in the axial direction of the tube by at least the width of the measuring tape, and by bringing the wrapped measuring tape close together so that they do not overlap within the observation field, the outer circumferential length of the open pipe can be measured, for example, by reading the measuring tape scales at two opposing edge positions of the base tube T.

[0033] When wrapping the tape of the measuring tape around the outer periphery of the mother tube more than once, to prevent the tape from coming close to each other and overlapping on the outer periphery of the mother tube, if the tape unwinding speed of the measuring tape, the rotation speed of the ring plate (the orbital speed of the bobbin), and the axial feed speed of the rotating ring / measuring bobbin itself are kept constant and synchronized, the shortest length can be measured every time with good reproducibility. Furthermore, even if the above speeds are not constant, measurements can be made with consistent accuracy. Furthermore, to measure the outer periphery of the mother tube T itself, the opposing edge apexes 8 of the mother tube T shown in the figure can be confirmed, the edge opening state can be observed, and the opposing distance between the edge apexes 8 can be measured.

[0034] When winding and measuring at the maximum and minimum diameters within a diameter ratio of several times the pipe mill's planned diameter, a difference in winding speed may occur, and if moving the measuring tape width in the pipe axial direction is insufficient, the movement amount can be increased by more than one to two times.

[0035] In order to make imaging and viewing easier when measuring the circumference length and checking the edge apex 8, the type of lighting source, illuminance, and light distribution direction can be adjusted, and the measuring tape 5 itself can be provided with an identification means such as coloring or reflecting specific light.

[0036] In order to allow the bobbin 4 to wind and unwind a tape measure around the outer circumferential surface of the blank tube T as the ring plate 3 rotates, a tape measure winding means having a mechanism for applying and maintaining the necessary tension is required. For example, a winding mechanism using an elastic body such as a spiral spring as shown in the embodiment can be employed.

[0037] Various methods can be used to move the swivel ring itself in the axial direction of the tube. In the illustrated example, the ring plate 3 is supported by a support wheel 7 disposed on the outer periphery of the hole 2 of the face plate 1 so that it can be rotated. If a spiral track is provided on the outer periphery of the ring plate 3 so that the support wheel 7 can run on the track, the ring plate 3 itself can be moved in the axial direction of the tube as the ring plate 3 is rotated by the rotation drive means.

[0038] Furthermore, the support shaft of the support ring 7 itself is a screw shaft, and when the ring plate is driven to turn, the entire holding mechanism can be moved in the axial direction of the tube by the linear motion of the screw shaft.

[0039] The means for moving the major bobbin itself in the axial direction of the tube can use a linear motion mechanical mechanism for the major bobbin's axial support mechanism, and a linear motion mechanical mechanism such as a screw or copying mechanism that converts rotation into linear motion can be adopted for the axial support part of the bobbin 4.

[0040] Furthermore, a linear motion mechanical mechanism can be used for the mechanism for placing the major bobbin on the swivel ring. For example, the plate itself on which the major bobbin is placed can be moved in the axial direction of the tube by a linear motion actuator, and the plate can be raised and lowered by a wedge-shaped slider that moves horizontally between the plate and the swivel ring by an actuator.

[0041] The amount of movement in the tube axis direction depends on various factors, such as the size of the diameter of the pipe to be made, whether it revolves around the mother tube T or revolves and rotates around it, and the configuration of the driving mechanical mechanism, so that the measuring tapes do not overlap when the ring plate 3 and bobbin 4 rotate around the mother tube T more than once.By taking these factors into consideration, it is possible to determine the above-mentioned orbit length, etc.

[0042] To rotate the ring plate 3, as shown in the embodiment, the spiral track on the outer periphery of the ring and the support wheel 7 are used, and a round belt, rubber belt, etc. is hung on the spiral track and driven by a motor to rotate it.

[0043] The support wheel itself can also be driven by a mechanism that rotates it with a motor, for example, by friction with tires, gear meshing, direct drive of the rotating shaft, etc. Furthermore, a gear ring can be provided on the back surface or outer peripheral surface of the ring plate, and multiple gear motors can be arranged on the face plate 1 to drive it with gears.

[0044] The measurement of the measuring tape scale and the like can be performed using various observation fields, such as visual inspection from above the bare tube T or visual inspection from below using a periscope or endoscope. Measurements can also be performed using an observation field using a digital camera, and can be performed using anything from simple configurations such as a pan-focus lens camera or webcam to AI cameras using known image sensors and autofocusing means in the lens, allowing measurements to be performed remotely on a display device with an enlarged field of view.

[0045] Furthermore, it is equipped with an illumination light that can automatically adjust the direction of illumination and brightness, and the AI ​​camera's image sensor and program can track the observation target within the observation field even when the observation conditions change, and convert the readings of, for example, the letters, codes, calibrations on a measuring tape, etc. into image data and identify them, thereby automating measurements.

[0046] Example 1 A measuring device for implementing the perimeter measuring method shown in FIG. 1 will be described with reference to FIGS.

[0047] The frame of the device is a single main plate 10 with a passage hole 11 in the center for the blank tube to be formed. Four guide rollers 12 are journaled around the passage hole 11 at approximately 90-degree intervals, and the upper left part of the main plate 10 protrudes outward to accommodate a geared motor 13.

[0048] The four guide rollers 12 are configured so that the outer peripheries of the rollers fit into spiral grooves 20b provided on the outer periphery of a ring plate 20 having an inner diameter similar to that of the through holes, thereby supporting the rotation of the ring plate 20.

[0049] The ring plate 20 is rotated by a so-called belt drive, in which a belt rope 14 driven by a geared motor 13 is fitted into a belt groove 20a provided on the outer circumferential surface of the ring plate 20. This belt drive adjusts the position of a roller 16 of a tension adjustment unit 15 arranged on the plate adjacent to the geared motor 13, thereby maintaining an appropriate tension in the belt 14.

[0050] A bobbin 22 around which a steel tape measure 21 is wound is rotatably supported on the front surface of the ring plate 20 via a winding mechanism 23 that winds the measure using a spiral spring.

[0051] The tip of the tape measure 21 is led out to a pair of tape guide rollers 24, 24 arranged adjacent to the bobbin 22 and fixed to a tape measure fixing point 17 provided in the right center of the main plate 10. A felt pad 25 for cleaning the tape measure 21 is arranged between the pair of tape guide rollers 24, 24.

[0052] A sensor dog 26 for detecting the rotation position is placed at a required position on the top surface of the ring plate 20, and a proximity sensor 18 provided near the guide roller 12 on the lower right side of the main plate 10 detects the sensor dog 26 to determine the number of rotations of the bobbin 22. In addition to the proximity sensor, known methods and devices such as a rotary encoder can be used to detect the bobbin position, and a rotation braking mechanism can be provided on the rotation motor side to facilitate position detection. Furthermore, if the ring plate diameter is relatively small, it goes without saying that a counterweight that balances the bobbin weight can be placed on the plate.

[0053] If the state of the front view in Figure 2 is the initial state of the ring plate 20, which is in the neutral position, its cross-sectional view along the line AA is Figure 5A, and after rotating one and a half revolutions, it becomes the state shown in Figure 5B, where the ring plate 20 moves downstream by the tape width of the measuring tape 21, to the left in Figure 5, and the measuring tape wrapped around the base pipe is observed from the observation field, in this case, when viewed from above, the measuring tapes do not overlap each other.

[0054] A measuring device having the above configuration is placed on the line, for example, upstream or downstream of the fin pass roll stand, connected to an arm hanging down from above without being connected to the stand, and the outer circumferential length of the mother tube can be measured by, for example, mounting a camera on the arm. The outer circumferential length of the mother tube can be measured while the measuring device is still placed on the line, without requiring personnel with the measurement skills to ensure reproducibility, as was previously the case. Therefore, the space between roll stands that was previously required for manual measurement is no longer necessary, and the pitch between stands can be narrowed.

[0055] Second Embodiment The device shown in FIG. 6 has the same configuration as that of the first embodiment, except that the shape of the main plate 30 and the positions of the geared motor 13 and tension roller unit 15 are different.

[0056] In Example 1, the geared motor 13 is placed at the upper left side of the figure, but if the roll stand on which the measuring device is placed has a different configuration or function, there may be components that interfere with the corresponding position. In Example 2 of Figure 6, the main plate 30 is irregularly shaped and extends upward to avoid the equipment on the roll stand side.

[0057] Since the geared motor 13 is located above the ring plate 20, a pair of rollers 16, 16 are appropriately positioned to guide the belt rope 14 to the tension adjustment unit 15. An image sensor can be placed on the main plate 30 between the geared motor 13 and the ring plate 20 to measure the outer circumferential length of the blank tube.

[0058] The method and apparatus of the present invention enable remote or automatic measurement of the outer circumferential length of the blank pipe before, during, or after forming on a stopped line during the initial roll adjustment process when changing product dimensions on a cold roll forming machine capable of producing steel pipes with a diameter ratio of several times larger. This makes it easy to adjust the position of the rolls on each forming roll stand and to manage the circumferential length to ensure that the amount of forming is appropriate, and also makes it possible to automate the various operations involved in such measurement and management.

[0059] 1 Face plate 2 Hole 3, 20 Ring plate 4, 22 Bobbin 5, 21 Measuring tape 6, 17 Measuring tape fixing point 7 Support wheel 8 Edge top 10, 30 Main plate 11 Pass-through hole 12 Guide roller 13 Geared motor 14 Belt 15 Tension adjustment unit 16 Tension roller 17 Measuring tape holder 18 Proximity sensor 20a Belt groove 20b Spiral groove 23 Winding mechanism 24 Tape guide roller 25 Felt pad 26 Sensor dog S Camera T Blank tube

Claims

1. A method and device for measuring the outer periphery of a mother pipe during pipe making and / or a pipe after welding (mother pipe / pipe) by wrapping a tape measure around the mother pipe / pipe one or more times from an external observation field, the method comprising: a swivel ring that encloses the mother pipe / pipe and holds its outer periphery rotatably; a tape measure bobbin with a tape measure wound around it placed rotatably on the swivel ring; the tape measure's starting point is fixed outside the outer periphery of the swivel ring; the holding and swivel drive mechanism has a tape measure winding function that allows the tape measure to be wound / unwound around the outer periphery of the mother pipe / pipe as the swivel ring rotates; the swivel ring or tape measure bobbin has a tube axial movement means that moves the swivel ring itself or the tape measure bobbin itself in the axial direction of the mother pipe / pipe by at least the tape width dimension of the tape measure when wrapping the tape measure around the mother pipe / pipe one or more times; and the wrapped tape measures do not overlap within the observation field.

2. A method for measuring outer circumference length according to claim 1, characterized in that the stage for moving the slewing ring itself in the pipe axial direction is a linear motion mechanical mechanism with a screw structure between the outer surface of the slewing ring and the holding mechanism of the slewing ring.

3. A method for measuring outer circumference according to claim 1, wherein the means for moving the major bobbin itself in the tube axial direction uses a linear motion mechanical mechanism as the axial support mechanism for the major bobbin.

4. A method for measuring outer circumference according to claim 1, wherein the means for moving the major bobbin itself in the tube axial direction uses a linear motion mechanical mechanism for placing the major bobbin on the swivel ring.

5. The method for measuring circumference according to claim 1, wherein the observation field is captured by a digital camera.

6. A circumference measuring device that measures the circumference of a mother pipe during pipe making and / or a pipe after welding (mother pipe / pipe) by wrapping a tape measure around the mother pipe / pipe one or more times in an observation field from the outside, comprising a swivel ring that encloses the mother pipe / pipe and holds its outer circumference rotatably, and a holding / swivel drive mechanism for the same; a tape measure bobbin with a tape measure wound around it is rotatably mounted on the swivel ring, the starting point of the tape measure being fixed outside the outer circumference of the swivel ring, and the holding / swivel drive mechanism has a tape measure winding function that allows the tape measure to be wound / unwound around the outer surface of the mother pipe / pipe as the swivel ring rotates; and a tube axial movement means for moving the swivel ring itself or the tape measure bobbin itself in the axial direction of the mother pipe / pipe by at least the tape width dimension of the tape measure when wrapping the tape measure around the mother pipe / pipe one or more times, and the wrapped tape measure does not overlap within the observation field.

7. A peripheral length measuring device according to claim 6, characterized in that the stage for moving the slewing ring itself in the pipe axial direction is a linear mechanical mechanism with a screw structure between the outer peripheral surface of the slewing ring and the holding mechanism of the slewing ring.

8. The circumference measuring device according to claim 6, wherein the means for moving the major bobbin itself in the tube axial direction uses a linear motion mechanical mechanism for the axial support mechanism of the major bobbin.

9. The peripheral length measuring device according to claim 6, wherein the means for moving the major bobbin itself in the tube axial direction uses a linear motion mechanical mechanism for the mechanism for placing the major bobbin on the swivel ring.

10. The circumference measuring device according to claim 6, wherein the observation field is captured by a digital camera.

Images