JP2008036713A - Clamp mechanism, measuring device - Google Patents

Abstract

To provide a clamp mechanism capable of gripping a round bar-shaped workpiece in a correct posture and a measuring device capable of measuring the outer shape of the round bar-shaped workpiece with high accuracy.
A clamping mechanism 10 includes a receiving base 1 having a groove portion 2 into which an extremely fine round rod-shaped workpiece R is inserted, and a pressing portion 5 having a tip portion 6 that fits in the groove portion 2. And the tip 6. The cradle 1 is provided so as to be opposed to each other with the groove 2 interposed therebetween, and two pairs of recesses are provided in the extending direction of the groove 2 so as to cut out all or part of the sandwiched groove 2. Two pairs of convex portions corresponding to the two sets of concave portions are provided at the distal end portion 6 of the holding portion 5, and each convex portion guides the workpiece R inserted into the groove portion 2 along the slope of the groove portion 2. Fits into two sets of recesses. Thereby, the workpiece | work R is hold | gripped with the correct attitude | position which the extending direction of the groove part 2 and the axis line Ra of the workpiece | work R corresponded.
[Selection] Figure 1

Description

  The present invention relates to a clamp mechanism that grips a round bar-shaped workpiece and a measuring device that measures the outer shape of the round bar-shaped workpiece.

  As a clamping mechanism for gripping a round bar-shaped workpiece, a chuck 80 for gripping a blade as shown in FIG. 7 is known (Patent Document 1). The chuck 80 has a tool clamping part 81 whose tip side is divided into three parts, and an operating body 82 that clamps the tool clamping part 81 and grips a workpiece.

  Further, as a measuring device having a clamping mechanism such as the chuck 80, a tool holding means as a clamping mechanism, a rotation driving means for rotating the tool holding means about an axis, and a rod-like shape held by the tool holding means. 2. Description of the Related Art A measuring apparatus for a rod-shaped cutting tool is known that includes an imaging unit that images the tip of a cutting tool from two directions in the Z-axis direction orthogonal to the axis and the axis (Patent Document 2).

JP 2003-334706 A JP 2001-59713 A

  When gripping an extremely thin round bar-shaped workpiece using the chuck 80, if the workpiece is inserted into the tool clamping portion 81 and tightened with the operating body 82, the workpiece is pinched and damaged in the gap 83 on the divided tip side, or There was a problem that it was difficult to hold in a correct posture.

  Further, when measuring the external shape of an extremely thin round bar-shaped workpiece using the measuring device, if the axis of the held workpiece and the rotation axis of the chuck 80 do not match, the focal point when the workpiece is rotated and imaged. There was a problem that could not be determined. Therefore, there has been a problem that the focus position must be sequentially adjusted in accordance with the rotation of the workpiece.

  The present invention has been made in consideration of the above problems, and provides a clamp mechanism capable of gripping a round bar-shaped workpiece in a correct posture and a measuring device capable of measuring the outer shape of the round bar-shaped workpiece with high accuracy. With the goal.

  The clamping mechanism according to the present invention includes a cradle having a groove portion including at least two inclined surfaces, and a pair of recesses provided on the cradle so as to cut out all or part of the sandwiched groove portion. And a pressing part having a tip part that fits in the groove part, and a pair of convex parts provided at the tip part so as to fit in the pair of concave parts and cross the groove part, and the round bar-shaped workpiece inserted in the groove part is the groove part And the tip part.

  According to this configuration, the cradle having the groove portion is disposed with the groove portion interposed therebetween, and the pair of concave portions are provided so as to cut out all or a part of the sandwiched groove portion. Moreover, a pair of convex part is provided in the front-end | tip part so that it may fit in a pair of recessed part and may cross | intersect a groove part. Therefore, the work in which the pair of convex portions is inserted is guided along the inclined surface of the groove portion and fits in the pair of concave portions. Therefore, the workpiece can be gripped by the groove portion and the tip portion so that the direction in which the groove portion extends matches the axis of the round bar-shaped workpiece. That is, it is possible to provide a clamp mechanism that can be gripped in a correct posture even when the round bar-shaped workpiece is extremely fine.

  In the direction in which the groove extends, at least two pairs of recesses are provided at an interval, and a pair of protrusions is set at a position corresponding to at least two sets of recesses at the tip of the pressing portion. It is preferable that at least two sets of convex portions are provided. According to this, the workpiece inserted into the groove portion is guided along the slope of the groove portion by at least two sets of convex portions provided at intervals. Therefore, the posture of the workpiece can be easily corrected so that the extending direction of the groove and the axis of the workpiece coincide with each other by fitting at least two sets of convex portions separated in the extending direction of the groove into the corresponding concave portions. it can.

  Of the at least two sets of recesses, it is preferable that one set of recesses located on the side where the workpiece is inserted is disposed inside the cradle. According to this, one set of convex portions is provided on the pressing portion side in correspondence with the one set of concave portions disposed inside the cradle. Therefore, when the workpiece is inserted into the groove portion, the position of the groove portion can be easily recognized without being hidden by the one set of convex portions provided on the pressing portion. Therefore, even an extremely fine workpiece can be reliably inserted into the groove, and damage to the workpiece due to an insertion error can be reduced.

  It is preferable to further include a biasing portion that biases the pressing portion toward the groove portion of the receiving portion. According to this, the work inserted into the groove portion can be pressed by the biased pressing portion and securely fixed along the groove portion.

  The measuring device of the present invention is a measuring device for measuring the outer shape of a round bar-shaped workpiece, and is arranged with a cradle having a groove portion composed of at least two inclined surfaces and the groove portion, and all or one of the sandwiched groove portions. A pair of concave portions provided in the pedestal so as to cut out the portion, a holding portion having a tip portion that fits in the groove portion, and a pair of convex portions provided in the tip portion so as to fit in the pair of concave portions and cross the groove portion And a clamp mechanism that grips the workpiece inserted into the groove portion by the groove portion and the tip portion, and an imaging device that images the workpiece from a direction orthogonal to the axis of the workpiece gripped by the clamp mechanism. It is characterized by.

  According to this configuration, even if the round bar-shaped workpiece is extremely fine, it is guided to the groove portion by the pair of concave portions and the pair of convex portions, and can be gripped by matching the extending direction of the groove portion and the axis of the workpiece. A possible clamping mechanism is provided. Therefore, the workpiece can be gripped in a correct posture at a determined position and the outer shape can be imaged by the imaging device. That is, it is possible to provide a measuring device that can accurately measure the outer shape of a round bar-shaped workpiece.

  In the direction in which the groove extends, at least two pairs of recesses are provided at an interval, and a pair of protrusions is set at a position corresponding to at least two sets of recesses at the tip of the pressing portion. It is preferable that at least two sets of convex portions are provided. According to this, the workpiece is guided to the groove portion by at least two sets of convex portions provided apart from each other, and can be easily gripped by the groove portion and the tip portion in a correct posture.

  Of the at least two sets of recesses, it is preferable that one set of recesses located on the side where the workpiece is inserted is disposed inside the cradle. According to this, one set of convex portions is provided on the pressing portion side in correspondence with the one set of concave portions disposed inside the cradle. Therefore, when inserting a workpiece into the groove portion, the groove portion can be easily visually recognized and inserted without being hidden by the one set of convex portions provided on the pressing portion. Therefore, during measurement, even an extremely thin workpiece can be reliably inserted into the groove, and it is possible to reduce the occurrence of abnormal measurement of the outer shape due to the workpiece being damaged due to an insertion error.

  It is preferable to further include a biasing portion that biases the pressing portion toward the groove portion of the receiving portion. According to this, the pressing portion can be urged by the urging portion, and the round bar-shaped workpiece can be fixed in a correct posture between the urging portion and the groove portion. Therefore, the workpiece can be fixed at a more accurate position and imaged by the imaging device.

  The image pickup apparatus includes a camera for picking up a work and a focus mechanism for focusing the camera on the work. According to this, since the focus mechanism for focusing the camera on the workpiece is provided, the outer shape of the workpiece can be measured with higher accuracy.

  It is preferable to measure the outer shape of the workpiece by rotating the workpiece in a plurality of times, gripping the workpiece by a clamp mechanism, and capturing an image corresponding to the plurality of times. According to this, since the workpiece is rotated a plurality of times and imaged a plurality of times, not only the outer shape of the workpiece but also the eccentricity can be accurately measured.

  The embodiment of the present invention will be described by taking as an example a clamp mechanism for gripping an extremely thin round bar-shaped workpiece and a measurement apparatus including the clamp mechanism. In addition, each figure used for description is appropriately enlarged or reduced in scale so that the embodiment can be described.

<Clamp mechanism>
The clamp mechanism of this embodiment is demonstrated using FIGS. 1-3. 1 is a schematic perspective view showing the structure of a clamp mechanism, FIG. 2 (a) is a perspective view showing details of a cradle, FIG. 1 (b) is a plan view seen from the direction A of FIG. (A) is the perspective view which shows the detail of a holding | suppressing part, The same figure (b) is the top view seen from the B direction of the same figure (a).

  As shown in FIG. 1, the clamping mechanism 10 of the present embodiment includes a cradle 1 having a groove portion 2 into which a very thin round bar-shaped workpiece R is inserted, and a presser having a tip portion 6 that fits in the groove portion 2 of the cradle 1. The workpiece R is gripped by the groove portion 2 and the tip portion 6.

  Behind the cradle 1 in the insertion direction (Y-axis direction) of the work R is a support base 22 that functions as a stop for the work R, and a T-shaped presser arm supported by the support base 22 by a shaft 24. 23. The pressing portion 5 is fixed to one end portion 23 a of the pressing portion arm 23 with a screw 26. Further, a spring 25 as an urging portion is provided between the other end portion 23 b of the pressing portion arm 23 and the support base 22. The pressing portion 5 is urged by a spring 25 with the support portion 23 c of the pressing portion arm 23 as a fulcrum, and the distal end portion 6 is configured to fit in the groove portion 2 of the cradle 1. The biasing portion is not limited to the spring 25, and an elastic body such as rubber may be used.

  As shown in FIG. 2 (a), the cradle 1 includes a V-shaped groove portion 2 composed of two inclined surfaces 2a and 2b, and four concave portions 3a provided in a direction orthogonal to the extending direction of the groove portion 2. 3b, 4a, 4b. When viewed from above the cradle 1, the pair (one set) of recesses 3 a and 3 b provided with the groove 2 interposed therebetween is provided at a position entering the inside from the insertion side of the workpiece R. The other pair of recesses 4a and 4b is provided so as to be separated from the one recess 3a and 3b and to cut out the side surface of the cradle 1. In other words, it is provided facing the support base 22 (see FIG. 1) having a function of stopping the workpiece R.

  As shown in FIG. 2 (b), the pair of recesses 4a and 4b are provided so as to be smaller than the depth of the groove 2 corresponding to the diameter of the workpiece R, and to cut out part of the corresponding inclined surfaces 2a and 2b. It has been. Therefore, the workpiece R is inserted along the groove portion 2 and abuts against the support base 22. Moreover, insertion of the workpiece | work R is not inhibited by the recessed parts 4a and 4b.

  When the diameter of the workpiece R is very thin, a pair of recesses 4a and 4b may be provided so as to cut out all the corresponding two inclined surfaces 2a and 2b. Further, if the workpiece R can be supported by at least two inclined surfaces 2a and 2b, the bottom of the groove 2 may be a flat surface. The method for forming the recesses 3a and 3b is the same.

  As shown in FIG. 3A, the pressing portion 5 has a tip portion 6 that fits in the groove portion 2 of the cradle 1. The tip 6 has two slopes 6 a and 6 b having the same inclination angle as the slopes 2 a and 2 b of the groove 2, and a plane 6 c that is parallel to the extending direction of the groove 2. Moreover, it has the convex parts 7a and 8a which protruded on the slope 6a side so that it may orthogonally cross the plane 6c, and the convex parts 7b and 8b which protruded on the slope 6b side. The pair (one set) of convex portions 7 a and 7 b is formed at the tip portion 6 at a position corresponding to the pair of concave portions 3 a and 3 b formed in the cradle 1. Similarly, a pair of convex parts 8a and 8b are formed in the front-end | tip part 6 in the position corresponding to a pair of recessed parts 4a and 4b.

  As shown in FIG. 3B, the convex portions 7a, 7b, 8a, 8b are arranged in the horizontal direction on the paper surface so that the bottom surfaces 7c, 8c form the same plane as the plane 6c of the tip portion 6. It protrudes from the slopes 6a and 6b. That is, the tip 6 is formed so as to cross the groove 2 of the cradle 1. Further, the presser part 5 is provided with a notch 9 that fits into one end part 23a of the presser part arm 23 and a hole 9a through which a fixing screw 26 passes.

  According to such a clamping mechanism 10, the workpiece R inserted into the groove 2 is supported by the two inclined surfaces 2 a and 2 b and is pressed and held between the flat surface 6 c of the pressing portion 5. Therefore, the workpiece R is gripped so that the axis line Ra (see FIG. 1) of the workpiece R and the extending direction of the groove portion 2 coincide with each other. Therefore, it is possible to grip the round bar-shaped workpiece R without causing shaft shake.

  Further, the two sets of convex portions 7a, 7b, 8a, 8b provided in the pressing portion 5 are provided so as to be accommodated in the two sets of concave portions 3a, 3b, 4a, 4b. Therefore, even if the workpiece R is inserted into the groove portion 2 in an inclined state, each of the convex portions 7a, 7b, 8a, 8b guides the workpiece R so as to fit in a predetermined position along the inclined surfaces 2a, 2b of the groove portion 2. . Therefore, it is possible to easily grip the workpiece R in a correct posture without axis shake.

  Further, for example, in order to place the workpiece R in the groove portion 2 in a more correct posture, in the insertion direction of the workpiece R, the recesses 3a and 3b are provided on the side surface of the cradle 1 in the same manner as the recesses 4a and 4b. Can be considered. Then, when inserting the workpiece R into the groove 2, when viewed from the operator, the groove 2 is hidden by the convex portions 7 a and 7 b of the pressing portion 5, which may cause an insertion error. In this case, since the recesses 3a and 3b are provided on the inner side of the cradle 1, the entrance of the groove 2 is not hidden by the protrusions 7a and 7b that fit into this, and the workpiece R can be inserted into the groove 2 more reliably. Is possible.

  In addition, each convex part 7a, 7b, 8a, 8b does not necessarily need to be provided in the direction orthogonal to the extension direction of the groove part 2. FIG. For example, it is preferable to form the convex portions 7a, 7b, 8a, and 8b and the corresponding concave portions 3a, 3b, 4a, and 4b so as to open in a reverse C shape with respect to the insertion direction of the workpiece R. . According to this, insertion of the workpiece | work R is hard to be inhibited by each recessed part 3a, 3b, 4a, 4b. Furthermore, the slopes 6a and 6b are not essential, and the front end portion 6 may have a flat surface 6c for gripping the workpiece R and each of the convex portions 7a, 7b, 8a and 8b. Further, the convex portions are not limited to two sets, and even one set can be expected to have the effect, and may be increased further.

<Measurement device>
Next, the measurement apparatus of this embodiment will be described with reference to FIG. FIG. 4 is a schematic perspective view showing the configuration of the measuring device. The measuring apparatus 100 according to the present embodiment includes the clamp mechanism 10 according to the above-described embodiment that grips the workpiece R, the table 21 on which the clamp mechanism 10 is disposed, and the Z axis that is orthogonal to the axis Ra of the gripped workpiece R. And an imaging device 30 that images the workpiece R from the direction. The imaging device 30 includes a camera 31 as an imaging unit, an illumination 32 arranged to face the camera 31, and an autofocus mechanism 33 that adjusts the focus by moving the camera 31 in the Z-axis direction. . The camera 31 uses, for example, a combination of a CCD as an image sensor and an objective lens that enlarges the measurement location of the workpiece R. As the illumination 32, for example, a halogen lamp capable of obtaining high luminance is used.

  In addition, the measuring apparatus 100 moves the table 21 in the X-axis direction and the Y-axis direction so that at least a part of the gripped work R is positioned on the optical axis 32a of the camera 31 and the illumination 32 ( (Not shown). The drive unit has an X-axis motor and a Y-axis motor. For example, servo motors are used as the X-axis motor and the Y-axis motor.

  Furthermore, the control apparatus 40 which controls each part of the measuring device 100 is provided. The control device 40 includes a CPU 41, a memory 42 such as an EPROM, an image processing unit 43, an X-axis motor control unit 44, and a Y-axis motor control unit 45. The control device 40 is configured using a personal computer or the like, for example.

  A measurement method using the measurement apparatus 100 will be described. The operator first inserts the workpiece R into the groove portion 2 and presses it with the pressing portion 5 to cause the clamp mechanism 10 to grip the workpiece R (gripping step). Then, the control device 40 is operated to start the measurement operation. First, the CPU 41 sends a control signal to the X-axis motor control unit 44 and the Y-axis motor control unit 45 based on the measurement program input to the memory 42. The X-axis motor control unit 44 and the Y-axis motor control unit 45 drive the X-axis motor and the Y-axis motor based on the control signal so that the measurement location of the workpiece R is positioned on the optical axis 32a. Move (positioning step). In addition, a control signal is sent to the autofocus mechanism 33 to drive the autofocus mechanism 33 so that the work R illuminated by the illumination 32 is in focus. More specifically, the image processing unit 43 identifies the outer shape of the workpiece R based on image information captured by the camera 31, and drives the autofocus mechanism 33 so as to obtain a predetermined sharpness. (Focus position adjustment step). The image processing unit 43 converts the image information captured in a focused state into bitmap data and sends it to the CPU 41. The CPU 41 calculates the dimension of the measurement location from this bitmap data and outputs it (measurement process). Further, the operator releases and rotates the workpiece R by the clamp mechanism 10 and rotates it, and repeats the dimension measurement for gripping and imaging the workpiece R a plurality of times, and the output data is statistically processed by the CPU 41 (dimension data). Processing step). Thereby, an average value and variation are obtained from a plurality of sampling data at the measurement location. Further, by rotating the work R in a plurality of times, dimensional information such as eccentricity can be obtained.

  Since the measuring apparatus 100 includes the clamp mechanism 10 that holds the workpiece R so that the axis Ra does not shake, the camera for the workpiece R is measured in the first measurement when the sampling data is to be obtained a plurality of times. If the focal position of 31 is adjusted, it is not necessary to adjust the focal position again even if the workpiece R is rotated, and measurement can be performed. The same applies to the case where the workpiece R is replaced and measurement is continued for another workpiece R. That is, the outer shape of the workpiece R can be measured with high accuracy, and the focal position adjustment between the workpiece R and the camera 31 accompanying a plurality of measurements is simplified.

  If such a measuring device 100 further includes a display device or a printing device, it is possible to display the dimension data output by the CPU 41, record it on paper, or display the image information of the workpiece R.

The effect of the said embodiment is as follows.
(1) In the clamp mechanism 10 of the above embodiment, two sets of convex portions 7a, 7b, 8a, 8b of the pressing portion 5 guide the work R inserted into the groove portion 2 of the cradle 1 along the inclined surfaces 2a, 2b. To do. And two sets of convex parts 7a, 7b, 8a, 8b are settled in two sets of concave parts 3a, 3b, 4a, 4b provided so that the groove part 2 may be crossed. Therefore, the workpiece R can be supported by the tip portion 6 and the groove portion 2 at three points, and can be gripped by matching the extending direction of the groove portion 2 with the axis line Ra of the workpiece R. Furthermore, since the pressing part 5 is urged toward the groove part 2 by the spring 25, the work R can be pressed and fixed.

  (2) In the clamp mechanism 10 of the above-described embodiment, the pair of recesses 3a and 3b of the cradle 1 is provided at a position inside the entrance side in the insertion direction of the workpiece R. Accordingly, when the workpiece R is inserted into the groove portion 2, the groove portion 2 is not obstructed by the set of convex portions 7a and 7b of the pressing portion 5 corresponding to the set of concave portions 3a and 3b. It is easy to do, and even a very thin workpiece R can be easily inserted into the groove 2.

  (3) Since the measuring device 100 of the above embodiment includes the clamp mechanism 10, the workpiece R is gripped so that the extending direction of the groove 2 matches the axis Ra, and the dimension of the workpiece R is accurately measured. can do. Further, when the workpiece R is rotated and measured in a plurality of times, or when a plurality of workpieces R are exchanged and measured, the workpiece R is gripped with high positional accuracy, so that the focus position adjustment by the autofocus mechanism 33 is performed. Even if it is not performed frequently, accurate dimensional data can be obtained.

  As mentioned above, although embodiment of this invention was described, various deformation | transformation can be added with respect to the said embodiment in the range which does not deviate from the meaning of this invention. For example, modifications other than the above embodiment are as follows.

  (Modification 1) In the clamp mechanism 10 of the above embodiment, the shapes of the cradle 1 and the pressing portion 5 are not limited to this. FIG. 5 is a schematic view showing a pressing portion and a cradle according to a modification. FIG. 6A is a perspective view of a modified pressing portion, and FIG. 5B is a plan view showing the relationship between the modified pressing portion and a cradle. As shown in FIG. 5A, the holding portion 50 of the modification includes a tip 51 having two inclined surfaces 51a, 51b, a ridge 51c, and two sets of convex portions 52a, 52b, 53a, 53b. ing. Each convex part 52a, 52b, 53a, 53b protrudes so as to be orthogonal to the ridge 51c. As shown in FIG. 5B, the cradle 60 corresponding to the pressing portion 50 has a V-shaped groove portion 61 and crosses the groove portion 61 corresponding to the two sets of convex portions 52a, 52b, 53a, 53b. Thus, two sets of recesses 62a, 62b, 63a, 63b are provided. The bottom surface 53c (bottom surface 52c) of the pair of convex portions 53a and 53b (convex portions 52a and 52b) has an inverted V shape, and the work R is supported at four points by the bottom surface 53c (bottom surface 52c) and the groove portion 61. Thus, the extending direction of the groove 61 and the axis line Ra of the workpiece R can be easily matched and gripped.

  (Modification 2) In the above embodiment, the workpiece R is not limited to a simple round bar. FIG. 6 is a plan view showing the shape of the workpiece. As shown in FIG. 6, for example, the workpiece 70 is a round bar having different shaft diameters d1, d2, and d3. The width decreases from the main shaft 71 to the sub shaft 72 and the tip shaft 73. The shaft diameter of the tip shaft 73 is approximately 20 μm. Tapered portions are formed between the main shaft 71 and the sub shaft 72 and between the sub shaft 72 and the tip shaft 73, respectively. If the measuring device 100 is used, each shaft diameter d1, d2, d3 and each dimension a, b, c, e can be measured with high accuracy. Thereby, the external shape of each axis | shaft 71,72,73 and the length of a taper part can be calculated | required. Further, the eccentricity of the auxiliary shaft 72 and the tip shaft 73 with respect to the main shaft 71 can also be measured.

  (Modification 3) In the measurement apparatus 100 of the above-described embodiment, the arrangement of each part such as the clamp mechanism 10, the table 21, and the imaging apparatus 30 is not limited to this. For example, in FIG. 4, the clamp mechanism 10 is arranged so that the axis Ra of the round bar-shaped workpiece R and the Z-axis direction coincide with each other so that the optical axis 32 a comes in a direction perpendicular to the axis Ra of the workpiece R. In addition, the camera 31 and the illumination 32 may be arranged to face each other. According to this, the workpiece R is inserted into the groove 2 from the Z-axis direction, and the operation is relatively easy.

The schematic perspective view which shows the structure of a clamp mechanism. (A) is a perspective view which shows the detail of a receiving stand, (b) is the top view seen from the A direction of (a). (A) is a perspective view which shows the detail of a holding | suppressing part, (b) is the top view seen from the B direction of (a). The schematic perspective view which shows the structure of a measuring device. (A) is a perspective view of the holding part of a modification, (b) is a top view which shows the relationship between the holding part of a modification, and a receiving stand. The top view which shows the shape of a workpiece | work. The schematic perspective view which shows the chuck | zipper as a conventional clamp mechanism.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base, 2 ... Groove part, 2a, 2b ... Slope, 3a, 3b, 4a, 4b ... Concave part, 5 ... Holding part, 6 ... Tip part, 7a, 7b, 8a, 8b ... Convex part, 10 ... Clamp mechanism 25 ... Spring as an urging unit, 30 ... Imaging device, 31 ... Camera, 33 ... Auto-focus mechanism as a focus mechanism, 50 ... Holding unit, 51 ... Tip, 52a, 52b, 53a, 53b ... Projection, DESCRIPTION OF SYMBOLS 60 ... Receptacle, 61 ... Groove part, 62a, 62b, 63a, 63b ... Recessed part, 70 ... Round bar-shaped workpiece, 100 ... Measuring device, R ... Round bar-shaped workpiece, Ra ... Axis.

Claims (10)

A cradle having a groove comprising at least two slopes;
A pair of recesses provided in the cradle so as to cut out all or a part of the sandwiched groove part, which is arranged across the groove part;
A holding part having a tip part that fits in the groove part,
A pair of convex portions provided in the tip portion so as to fit in the pair of concave portions and cross the groove portion;
A clamping mechanism characterized in that a round bar-shaped workpiece inserted into the groove is held by the groove and the tip. In the direction in which the groove extends, at least two pairs of the pair of recesses are provided at intervals,
The at least two pairs of convex portions, each of which includes the pair of convex portions, are provided at positions corresponding to the at least two pairs of concave portions at the distal end portion of the pressing portion. The clamp mechanism described in 1.   The clamp mechanism according to claim 2, wherein one set of recesses located on the side into which the workpiece is inserted is disposed inside the cradle among the at least two sets of recesses.   The clamp mechanism according to any one of claims 1 to 3, further comprising an urging portion that urges the pressing portion toward the groove portion of the receiving portion. A measuring device for measuring the outer shape of a round bar-shaped workpiece,
A pedestal having a groove portion composed of at least two slopes, a pair of recesses disposed on the pedestal so as to cut out all or part of the sandwiched groove portion, and the groove portion A pressing portion having a tip portion that fits into the pair, and a pair of convex portions provided in the tip portion so as to fit in the pair of recesses and cross the groove portion, and the workpiece inserted into the groove portion A clamping mechanism gripped by the groove and the tip;
A measuring apparatus comprising: an imaging device that images the workpiece from a direction orthogonal to an axis of the workpiece held by the clamp mechanism. In the direction in which the groove extends, at least two pairs of the pair of recesses are provided at intervals,
The at least two pairs of convex portions, each of which includes the pair of convex portions, are provided at positions corresponding to the at least two pairs of concave portions at the tip portion of the pressing portion. The measuring device described in 1.   The measuring apparatus according to claim 6, wherein one set of recesses located on the side into which the workpiece is inserted is disposed inside the cradle among the at least two sets of recesses.   The measuring device according to claim 5, further comprising an urging portion that urges the pressing portion toward the groove portion of the receiving portion.   The measurement apparatus according to claim 5, wherein the imaging apparatus includes a camera that images the workpiece, and a focus mechanism that focuses the camera on the workpiece. 8. The outer shape of the workpiece is measured by rotating the workpiece in a plurality of times, gripping the workpiece by the clamp mechanism, and taking an image corresponding to the plurality of times. The measuring device according to item.

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