JP3747661B2 - Measuring device for bending amount of rod-shaped body - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for measuring the amount of bending on-line in a conveying line that conveys a rod-shaped body such as a steel bar or a tube rod in the longitudinal direction.
[0002]
[Prior art]
As a conventional method for measuring the bending of a rod-shaped body, a first method described in JP-A No. 51-132856 is known.
As shown in FIG. 11, when the measured bar 1 moved in the direction orthogonal to the longitudinal direction by the handling device 5 comes to the position of the solid line, the light substantially perpendicular to the length direction of the bar 1 is obtained. The light is irradiated by a parallel light source 2 that has an axis and is opposed to each other with a rod 1 interposed therebetween, and an image thereof is captured by a light receiving system that includes an imaging lens 3 and a photoelectric conversion element array 4 at right angles to each other. Then, three image forming apparatuses having two optical systems perpendicular to each other can be arranged along the length direction of the rod 1 to be measured, and an image of the rod 1 can be obtained two-dimensionally. It is what I did.
[0003]
Since this image can be converted into an electric signal by the photoelectric conversion element array 4 and the image forming position of the image can be obtained as an electric signal, a straight line can be obtained by comparing this position with preset linear data. Is obtained two-dimensionally. This will be described with reference to FIG. Assuming that the two optical systems are in the X and Y directions, relative deviations Δx1, Δx2, Δx3, Δy1, Δy2, and Δy3 with respect to preset linear data are obtained as shown in the figure. Thus, when the deviations dx and dy between the dotted line and the intermediate point shown in the figure are obtained and the square root of the sum of these squares (√dx ² + dy ² ) is obtained, the deviation from the two-dimensional straight line is obtained, and this value is obtained. Is divided by the distance between the optical systems in the length direction of the bar to obtain the degree of bending per unit length.
[0004]
On the other hand, as a second method using only one detector instead of a plurality of detectors, a method described in Japanese Patent Laid-Open No. 8-94348 is known. This is because the material to be measured is supported in the state of a fixed beam at one end, and when the material to be measured is straight, a straight line parallel to the material to be measured is used as a reference line, and the cross section of the material to be measured from a point on the reference line. The distance in the first direction perpendicular to the reference line to the center and the distance in the second direction perpendicular to the first direction and the reference line are detected, the detected distance is corrected by the amount of deflection due to its own weight, and the amount of bending is calculated. It is a method to do.
[0005]
[Problems to be solved by the invention]
Among such prior arts, the first method is to measure the amount of bending when the measured material moved in the direction orthogonal to the longitudinal direction reaches a predetermined position. Although the bend can be measured, it is not possible to measure the running distance while the material to be measured is conveyed in the longitudinal direction, and the bend per unit length of the material to be measured conveyed in the longitudinal direction is a predetermined pitch (for example, 100 mm pitch). It cannot be measured over the entire length of the material to be measured. Conversely, when it is desired to measure in detail over the entire length, it is necessary to install a large number of detectors at short intervals. For these reasons, the first method cannot cope with the local bending of the material to be measured with three imaging devices.
[0006]
On the other hand, in the second method, since the amount of bending of the tube is measured in a cantilever supported state, it is possible to measure the amount of bending only at the tip of the tube, and bending occurs with the same curvature continuously like a tube. In the case, there is no problem, but the second method cannot be adopted when the same curvature is not always obtained continuously other than the pipe, such as a steel bar.
[0007]
Further, the second method has the following problems.
(1) Equipment such as a pinch roll and a bite detection load cell for supporting the material to be measured in the state of a single-end fixed beam is required, and if these are not present in the existing equipment, it will be necessary to add new equipment. This increases the cost when introducing the device.
(2) Although the amount of deflection is corrected by its own weight, the operator must input the amount of deflection calculated for each type of tube in advance, which puts a burden on the work and a certain length of material to be measured. It is also one of the factors that make it difficult to measure the hitting bend over the entire length of the material to be measured at a pitch of 100 mm, for example.
[0008]
Therefore, in view of the above points, an object of the present invention is to measure the amount of bending per unit length of a rod-shaped body conveyed in the longitudinal direction on the entire surface in real time, and immediately in response to product abnormality. Another object of the present invention is to provide an apparatus for measuring the amount of bending of a rod-shaped body that can cope with the problem and prevent the generation of a mass rejected product.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems and achieve the object of the present invention, the invention according to claim 1 is characterized in that the bending amount of the rod-shaped body conveyed by being guided by the guide roll in the longitudinal direction at a predetermined conveying speed is determined from the reference position. In the apparatus for measuring the amount of bending of a rod-shaped body, which is measured based on the amount of displacement of the rod-shaped body, in a plane perpendicular to the conveyance direction of the rod-shaped body, which is disposed at a necessary interval along the conveyance path of the rod-shaped body. At least three displacement detecting means for detecting the rod-like body displacements in the first and second directions intersecting each other at every required sampling period, and the rod-like body displacements in the first and second directions sampled by the respective displacement detecting means. Bending amount calculation means for continuously calculating the amount of bending per unit length of the rod-like body based on the required pitch, and each displacement detecting means is half the unit length of the rod-like body In length The regular guide rolls are arranged at intervals, and are arranged at the closest positions upstream of the respective displacement detection means to contact the rod-like body from below and guide the regular guide rolls on the most upstream side and the most downstream side. The auxiliary guide rolls are arranged close to each other on the upstream side of the regular guide rolls on the downstream side .
[0010]
As described above, in the invention according to the first aspect, the displacement of the rod-shaped body in the first and second directions is detected for each required sampling period during the conveyance of the rod-shaped body, and the unit length of the rod-shaped body is determined based on the detected displacement. The amount of bending per hit is calculated continuously for each required pitch. For this reason, the amount of bending per unit length of the rod-shaped body can be measured in real time over the entire length of the rod-shaped body. As a result, it is possible to respond immediately to product abnormalities of product abnormalities and to prevent the occurrence of mass rejected products.
[0012]
In the invention according to claim 1 , in addition to the regular guide roll, an auxiliary guide roll is arranged. For this reason, even when there is a local bend at the tip or tail end of the rod-shaped body, the influence of bending due to the weight of the rod-shaped body can be ignored, and thus when calculating the amount of bending per unit length of the rod-shaped body, It is not necessary to correct the amount of deflection due to its own weight.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below with reference to the drawings.
This embodiment demonstrates the case where the bending amount measuring apparatus of the rod-shaped body of this invention is applied to the measurement of the bending of the rod-shaped body a conveyed by a predetermined conveyance line. Here, the rod-shaped body a is a steel bar, a tube rod, or the like, and hereinafter, a case where the bar-shaped body a is a steel bar having a vertical cross section of a circle and a diameter of about 20 to 80 mm will be described.
[0014]
As shown in FIG. 1, guide rolls 11 to 13 are disposed on the lower side of the conveyance path of the rod-shaped body a that is conveyed with the longitudinal direction as the Z direction, and the guide rolls 11 to 13 are displaced to the immediate downstream side. At least three (three sets) of the first distance meter 21, the second distance meter 22, and the third distance meter 23 constituting a part of the detection means are arranged at predetermined intervals determined by the inspection standard of the rod-shaped body a. Has been. The guide rolls 11 to 13 are formed in a drum shape whose diameter gradually increases from the central portion in the axial direction toward both ends.
[0015]
As shown in FIG. 1, the arrangement interval of the first distance meter 21, the second distance meter 22, and the third distance meter 23 is determined when the inspection standard of the rod-shaped body a evaluates the amount of bending per unit length L. Is L / 2. For example, when evaluating the bending amount per meter of the rod-shaped body a, the arrangement interval is 500 mm.
[0016]
As shown in FIG. 1, the guide rolls 11 to 13 are in the immediate vicinity of the first distance meter 21, the second distance meter 22, and the third distance meter 23, and on the upstream side in the conveying direction of the rod-shaped body a. It arrange | positions so that arrangement | positioning space | intervals of this guide roll 11-13 may be L / 2 similarly to the arrangement | positioning space | interval of the distance meters 21-23.
[0017]
The three first rangefinders 21, the second rangefinders 22, and the third rangefinders 23 are in two directions substantially perpendicular to each other in a plane perpendicular to the transport direction, that is, perpendicular to the horizontal X direction shown in FIG. The position of the rod-shaped body a being conveyed in both the Y direction is measured.
[0018]
Therefore, each of the distance meters 21 to 23 includes a distance detector 21a that measures the position of the rod-shaped body a in the X direction and a distance detector 21b that measures the position of the rod-shaped body a in the Y direction. It is configured.
As shown in FIG. 2, the distance detector 21b is a laser-type steel bar end detection sensor composed of a light projector 211 and a light receiver 212 arranged to face each other in the horizontal direction X with the rod-shaped body a interposed therebetween. A laser beam having a strip shape in the Y direction from 211 is received by a light receiver 212 in which photoelectric conversion elements are arranged in the Y direction.
[0019]
In the distance detector 21b having such a configuration, the position of the rod-shaped body a in the X direction is measured by the shadow portion (arrow portion in FIG. 2) caused by the rod-shaped body a blocking the light from the projector 211. The length is detected by the light receiver 212, and the position of the lower edge of the rod-shaped body a can be known from the detection signal, and the detection signal is output as a position signal of the rod-shaped body a.
[0020]
As shown in FIG. 1, the distance detector 21a includes a light projector 211 and a light receiver 212 that are arranged to face each other in the vertical direction Y with the rod-shaped body a interposed therebetween, and is configured in the same manner as the distance detector 21b.
Position signals from the distance detectors 21b of the distance meters 21 to 23 are input to the arithmetic device 30 via the corresponding controllers 31, 32, and 33, and the distance detectors of the distance meters 21 to 23 are input. The position signal 21a is input via the corresponding controllers 34, 35, and 36, respectively. The controllers 31 to 36 function as input interfaces.
[0021]
In addition, a signal related to the start of measurement is input to the arithmetic device 30 from a rod-like body tip detection sensor 37 provided on the upstream side of the guide roll 11, and data related to an inspection standard described later is input. The device 30 is configured to output an alarm signal as described later to the alarm indicator 38.
[0022]
Further, the arithmetic unit 30 takes in each position signal from each distance detector 21a of the distance meters 21 to 23 and each distance detector 21b of the distance meters 21 to 23 at every required timing to be described later, and takes this position. Based on the signal, a bending amount S1 per unit length of the rod-shaped body a, which will be described later, and a bending amount S2 of the entire length of the rod-shaped body a are obtained.
[0023]
Next, operation | movement of the calculating device 30 in the bending measuring apparatus which concerns on embodiment comprised in this way is demonstrated with reference to the flowchart of FIG.
Now, when the arithmetic device 30 receives a signal indicating that the tip of the rod-shaped body a has arrived from the rod-shaped body tip detection sensor 37 and a predetermined time has elapsed, the arithmetic device 30 starts the following measurement (step S1). . By starting this measurement, in step S2, measurement of the bending amount S1 per fixed length of the rod-shaped body a is started (step S2), and this measurement is performed at a required sampling period.
[0024]
Here, it is assumed that the required sampling period is determined in advance by the conveying speed of the rod-shaped body and the pitch for evaluating the bending amount S1 per unit length L of the rod-shaped body. For example, when the conveyance speed of the rod-shaped body is about 90 mpm and the bending amount S1 per unit length L of the rod-shaped body is measured in real time over the entire length of the rod-shaped body a at a pitch of about 15 mm, the sampling period is 10 msec.
[0025]
Next, the measurement of the bending amount S1 per fixed length of the rod-shaped body a will be described with reference to the flowchart of FIG.
First, the arithmetic unit 30 takes in each position signal in the X direction from each distance detector 21a of the distance meters 21 to 23 and each position signal in the Y direction from each distance detector 21b of the distance meters 21 to 23 ( Step S21). Next, the displacements X1, X2, and X3 of the rod-shaped body a in the X direction are calculated based on the captured position signals in the X direction and preset reference positions, and the captured rod-shaped body a. Based on each position signal in the Y direction and each reference position set in advance, each displacement amount Y1, Y2, Y3 of the rod-shaped body a in the Y direction is calculated (step S22).
[0026]
Here, regarding the calculation example of the displacement amount, calculation of the displacement amount Y1 in the Y direction of the rod-shaped body a will be described with reference to FIG. The lower edge position ym in the Y direction of the rod-shaped body a is obtained based on the position signal from the distance detector 21b of the distance meter 21, and the difference between this position ym and a preset reference position yo is A displacement amount Y1 of the rod-shaped body a in the Y direction is set.
[0027]
The reference position yo is the same as in the case of the rod-shaped body a when a reference rod that can be regarded as having no bending is set on the conveyance rollers 11 to 13 in the installation portion of the distance meters 21 to 23 with the conveyance line stopped. Prior to measurement, the position of the lower edge of the reference bar in the vertical direction Y is obtained in advance, and the obtained edge position is stored in advance in the memory of the arithmetic unit 30 as a reference position (see FIG. 3). .
[0028]
Next, using the obtained displacement amounts X1, X2, and X3, as shown in the equation (1), the average of the displacement amounts X1 and X3 of the upstream and downstream distance detectors 21a and the center distance detection. A deviation from the displacement amount X2 of the vessel 21a is obtained (step S23), and the obtained deviation is defined as a bending amount dx per unit length in the X direction of the rod-like body a.
[0029]
dx = [(X1 + X3) / 2] −X2 (1)
Next, using the taken displacement amounts Y1, Y2, and Y3, as shown in the equation (2), the average of the displacement amounts Y1 and Y3 of the upstream and downstream distance detectors 21b and the central distance detector A deviation from the displacement amount Y2 of 21b is obtained (step S24), and the obtained deviation is set as a bending amount dy per unit length of the rod-shaped body a in the Y direction.
[0030]
dy = [(Y1 + Y3) / 2] -Y2 (2)
Next, a vector sum of the bending amount dx per unit length in the X direction and the bending amount dy per unit length in the Y direction obtained in this way is obtained by the following equation (3) (step S25). The obtained absolute amount is defined as a bending amount S1 per unit length of the rod-shaped body a (see FIG. 6).
[0031]
S1 = √dx ² + dy ² (3)
Here, the right side of equation (3) means the sum of the square of the bending amount dx and the square of the bending amount dy, and means the square root of this sum.
Note that the processes of steps S21 and S22 and the distance meters 21 to 23 in the flowchart of FIG. 5 correspond to the displacement detecting means, and the processes of steps S23 to S25 correspond to the bending amount calculating means.
[0032]
Next, as shown in step S3 of FIG. 4, it is determined whether or not the obtained bending amount S1 is equal to or less than the inspection reference value S1a. As a result of the determination, the bending amount S1 exceeds the inspection reference value S1a, and the rod-shaped body. If there is an unacceptable local bend in a, an alarm display (alarm, patrol, etc.) is displayed by the alarm indicator 38 (step S4), and this is notified to the operator. On the other hand, as a result of the determination, if the bending amount S1 is equal to or smaller than the inspection reference value S1a, the process proceeds to the next step S5.
[0033]
In step S5, since each process for calculating | requiring the bending amount S2 of the full length of the rod-shaped body a is performed, the process is demonstrated with reference to FIG.7 and FIG.8.
FIG. 7 is an explanatory diagram for obtaining the profile of the rod-shaped body a on the XZ plane. The X direction, the Y direction, and the Z direction described in FIG. 7 and below correspond to the horizontal direction, the vertical direction, and the transport direction in FIG. 7 indicates the position of the rod-shaped body when sampling i = N, and the dotted line indicates the position of the rod-shaped body when sampling i = N + 1.
(1) First, the amount of displacement from a certain reference straight line (reference position) to the measurement points X1 _N and X2 _N X3 _{N in} the X direction of the rod-like body is calculated from the position signal from the distance detector 21a (see FIG. 7). Similarly, the distance from a certain reference line to the measurement points Y1 _N and Y2 _N Y3 _{N in} the Y direction of the rod-like body is calculated from the position signal from the distance detector 22b. Note that the displacement amount calculated in this way corresponds to the displacement amount obtained in step S22 of FIG. 5, and therefore this displacement amount may be used.
(2) Next, a quadratic approximate curve F _N on the XZ plane passing through the three measurement points X1 _N and X2 _N X3 _N is obtained as shown in FIG. Similarly, a quadratic approximate curve F _N on the YZ plane is also obtained for the Y direction.
(3) Next, a deviation δ _N of the distance in the distance measuring direction between the point X1 ′ _N on the quadratic curve shifted from the measurement point X1 _N by the sampling interval L2 and the measurement point X1 _N is obtained (see FIG. 8). ), Integrating the deviation δ _N of the distance so far. Also in the Y direction, the deviation is obtained and integrated as in the X direction.
[0034]
When the processes from (1) to (3) are completed, the process proceeds to the next step S6, and it is determined whether or not all the measurement of the rod-shaped body is completed.
As a result of this determination, if all the measurements of the object to be measured are not completed, the process proceeds to the next step S7, waits until the next sampling time, returns to step S2, and repeats the processes of steps S2 to S7.
[0035]
If such processing proceeds and it is determined in step S6 that all measurement of the object to be measured has been completed, the process proceeds to the next step S8.
In step S8, the overall profile in the X direction of the rod-shaped body in the XZ plane obtained in step S5 and the profile in the Y direction of the rod-shaped body on the YZ plane are synthesized. It is calculated as the bending S2 of the full length of the body.
[0036]
Next, it progresses to step S9 and it is determined whether the calculated | required bending amount S2 of the full length of the rod-shaped body a is below the inspection reference value S2a. As a result of this determination, if the bending amount S2 of the entire length is not equal to or less than the inspection reference value S2a but is a defective product, an alarm is displayed by the alarm indicator 38 (step S10), and this is notified to the operator. On the other hand, when the bending amount S2 is equal to or less than the inspection reference value S2a and the rod-shaped body is an acceptable product, the series of processes is terminated.
[0037]
As described above, according to this embodiment, the displacement amount from the reference position of the rod-shaped body in the X direction and the Y direction is detected for each required sampling period during the transportation of the rod-shaped body, and the detected displacement amount is obtained. Based on this, the amount of bending per unit length of the rod-like body is continuously calculated for each required pitch. For this reason, the amount of bending per unit length of the rod-shaped body can be measured in real time over the entire length of the rod-shaped body.
[0038]
Further, according to this embodiment, the bending amount S1 per unit length of the rod-shaped body and the bending amount S2 of the entire length of the rod-shaped body are obtained and compared with the inspection reference value, and the rod-shaped body has its inspection reference value. When the above condition is not satisfied, an alarm display to that effect is provided, so that it is possible to respond immediately to product abnormalities and to prevent the occurrence of mass rejected products.
[0039]
Furthermore, in this embodiment, it is only necessary to install at least three distance meters 21 to 23 along the conveyance line. Therefore, when this embodiment is applied to an existing conveyance line, the application is performed at the time of application. No major equipment modifications or additions are required.
Furthermore, according to this embodiment, the amount of bending in the X direction is obtained, the amount of bending in the Y direction is obtained, and the amount of bending per unit length of the rod-like body is obtained from the vector sum of these. The amount can be obtained with high accuracy.
[0040]
In this embodiment, since the three distance meters 21 to 23 and the three guide rolls 11 to 13 are appropriately arranged in relation to the distance meters 21 to 23, 3 The table distance meters 21 to 23 can accurately measure the position of the rod-shaped body.
[0041]
Next, another embodiment of the present invention will be described with reference to FIG.
In this other embodiment, when there is a local bend at the tip or tail end of the rod-shaped body a, the original position of the rod-shaped body cannot be detected due to the influence of bending due to its own weight, and the detection accuracy decreases. Therefore, the amount of bending can be ignored, and correction of the amount of bending due to its own weight is unnecessary.
[0042]
For this reason, in this other embodiment, as shown in FIG. 9, an intermediate position between the upstream guide roll 11 and the central guide roll 12 in the transport line, or an intermediate and upstream guide roll, as shown in FIG. 9. The auxiliary guide roll 14 is added at a position close to 11, and the auxiliary guide roll 14 is provided at an intermediate position between the center guide roll 12 and the downstream guide roll 13 or at a position between them and close to the downstream guide roll 13. A guide roll guide roll 15 is added.
[0043]
In addition, in this other embodiment, since the structure of the other part except the addition of the auxiliary | assistant guide rolls 14 and 15 is the same as FIG. 1, the structure of the same part is abbreviate | omitted in FIG.
The reason why the auxiliary guide rolls 14 and 15 are added as described above will be described below with a specific example. That is, as shown in FIG. 10, the bending of the rod-like body a with the cantilever is greatly affected by the length of the arm. For example, the length of the arm is 500 mm as shown by the curve A in FIG. When the interval between the guide rolls is equivalent to 500 mm, when the diameter of the rod-shaped body a decreases, the amount of deflection at the leading end of the rod-shaped body a cannot be ignored. However, when the arm length is 250 mm and the distance between the guide rolls corresponds to 250 mm as shown by the curve B in the figure, even if the diameter of the rod-shaped body a is small, the leading end of the rod-shaped body a The amount of bending at can be ignored. Therefore, the auxiliary guide rolls 14 and 15 are added as described above.
[0044]
In the above description, the distance meters 21 to 23 are arranged at equal intervals as shown in FIG. 1, but the arrangement intervals of the distance meters 21 to 23 are not necessarily equal, You may make it arrange | position at arbitrary intervals. In this case, when obtaining the bending amount S1 per unit length of the rod-like body, the bending amount may be corrected according to the arrangement interval.
[0045]
In the above description, the distance meters 21 to 23 are arranged so that the pair of distance detectors 21a and the distance detectors 21b are substantially orthogonal to each other in substantially the same plane, but are not necessarily orthogonal to each other. It is also possible to arrange them so as to intersect at a predetermined angle. In this case, if the displacement amount of one of the distance detector 21a and the distance detector 21b is corrected according to the crossing angle, the displacement amount in the orthogonal state can be obtained.
[0046]
Furthermore, in the above description, the distance detectors 21a and 22b are so-called transmission type sensors. Instead, a rod-like body is imaged by an imaging device, and the image data is subjected to image processing to detect displacement. May be.
[0047]
【The invention's effect】
As described above, in the invention according to claim 1, the displacement of the rod-shaped body in the first and second directions is detected at every required sampling period during the conveyance of the rod-shaped body, and the rod-shaped body is based on the detected displacement. Since the amount of bending per unit length is continuously calculated for each required pitch, the amount of bending per unit length of the rod-shaped body can be measured in real time over the entire length of the rod-shaped body. As a result, it is possible to respond immediately to product abnormalities of product abnormalities and to prevent the occurrence of mass rejected products.
[0048]
Further, in the invention according to claim 1 , since the auxiliary guide roll is arranged in addition to the regular guide roll, the rod-shaped body of the rod-shaped body can be obtained even when there is a local bend at the tip or tail end of the rod-shaped body. The influence of bending due to its own weight can be neglected, and therefore correction of the bending amount due to its own weight becomes unnecessary when determining the amount of bending per unit length of the rod-shaped body.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration in a case where a bending amount measuring apparatus for a rod-shaped body according to the present invention is applied to bending measurement of a rod-shaped body conveyed by a steel bar conveying line.
FIG. 2 is a front view showing a configuration of a distance detector.
FIG. 3 is a diagram for explaining a measurement principle of a distance detector.
FIG. 4 is a flowchart showing an example of the operation of the embodiment of the present invention.
FIG. 5 is a flowchart showing a calculation process for obtaining a bending amount S1 per unit length of a rod-shaped body.
FIG. 6 is an explanatory diagram for obtaining a bending amount S1 per unit length as a vector sum.
FIG. 7 is an explanatory diagram for obtaining a profile in the X direction of a rod-shaped body.
FIG. 8 is an explanatory diagram for obtaining a profile in the X direction of the rod-like body.
FIG. 9 is a diagram schematically showing a configuration of another embodiment of the present invention.
FIG. 10 is a diagram showing an example of the relationship between the diameter of a rod-like body and its deflection.
FIG. 11 shows a conventional apparatus.
FIG. 12 is an explanatory diagram for explaining a measurement method of a conventional apparatus.
[Explanation of symbols]
11-13 Guide rolls 14, 15 Auxiliary guide roll 21 First distance meter 22 Second distance meter 23 Third distance meters 21a, 21b Distance detector 30 Arithmetic devices 31-36 Controller 38 Alarm indicator

Claims (1)

In the bending amount measuring apparatus for the rod-shaped body, which measures the bending amount of the rod-shaped body guided and conveyed by the guide roll in the longitudinal direction at a predetermined conveying speed based on the displacement amount from the reference position,
The rod-shaped body displacements in the first and second directions that are arranged along the transport path of the rod-shaped body and are maintained at a necessary interval and intersect each other in a plane orthogonal to the transport direction of the rod-shaped body are measured for each required sampling period. At least three displacement detection means for detecting
Bending amount calculating means for continuously calculating the amount of bending per unit length of the rod-like body for each required pitch based on the rod-like body displacement in the first and second directions sampled by each displacement detecting means; Prepared,
Each displacement detection means is arranged at equal intervals with a length that is half the unit length of the rod-shaped body,
A regular guide roll that guides the rod-shaped body by contacting it from below at the closest position on the upstream side of each displacement detecting means,
And the bending amount measuring apparatus of the rod-shaped body characterized by having arrange | positioned the auxiliary | assistant guide roll adjacent to the downstream of the regular guide roll in the most upstream side, and the upstream of the regular guide roll in the most downstream side , respectively.

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