JP4786898B2 - Intermittent indexing device - Google Patents

Description

  The present invention relates to an intermittent indexing device.

  In various automatic machines, an intermittent indexing device (index device) in which a turning operation at a constant allocation angle is intermittently repeated is often used. As a drive mechanism of this kind of intermittent indexing device, a drive mechanism using a cam mechanism has been conventionally known (Patent Document 1).

  The cam-type intermittent indexing device includes an input shaft that is rotationally driven by a rotational drive device such as a motor, and an output shaft that is supported by a housing so as to be rotatable by a rolling bearing. The input shaft is provided with a roller gear cam that rotates together with the input shaft. Further, the output shaft is provided with a plurality of cam followers over the circumferential direction, and these cam followers are engaged with the roller gear cam. The cam followers are sequentially guided by the rotation of the roller gear cam. By this cam mechanism, the rotation of the input shaft is converted into intermittent rotation drive of the output shaft.

  In such a cam-type intermittent indexing device, the above-described cam follower has been conventionally attached as shown in FIG. In FIG. 4, only the periphery of the cam follower is shown enlarged. In FIG. 4, the output shaft 31 of the intermittent indexing device is formed in a cylindrical shape, and is provided so as to be rotatable around a fixed shaft 33 disposed in the hollow portion 32 thereof. A mounting projection 34 is formed on the outer periphery of the output shaft 31, and a mounting hole 35 is formed in the mounting projection 34 along the projecting direction of the projection 34. A screw hole 36 communicating with the mounting hole 35 is formed in the outer peripheral portion of the mounting projection 34 along a direction (axial direction of the output shaft 31) perpendicular to the projecting direction of the mounting projection 34. The axial direction of the output shaft 31 corresponds to the height direction of the intermittent indexing device. The stud 37a of the cam follower 37 is inserted into the mounting hole 35, and the cam follower 37 is fixed in this state. That is, the fixing bolt 38 is screwed into the screw hole 36 in a state where the stud portion 37a of the cam follower 37 is inserted, and by tightening the fixing bolt 38, the outer peripheral surface of the stud portion 37a of the cam follower 37 is pressed. The cam follower 37 is fixed.

  By the way, since the cam follower 37 is repeatedly engaged with the roller gear cam, it is inevitable that the cam follower 37 is worn or damaged due to long-term use or accidental failure. For this reason, periodic maintenance is required, and if wear or damage is found during the maintenance, the cam follower 37 is replaced. Specifically, first, the fixing bolt 38 is loosened using a tool so that the cam follower 37 can be detached, and the cam follower 37 is pulled out from the mounting hole 35. Thereafter, the stud portion 37a of the new cam follower 37 is inserted into the mounting hole 35, and the cam follower 37 is fixed again with the fixing bolt 38 using a tool. Thereby, the cam follower 37 is replaced.

However, in such a conventional cam follower 37 mounting structure, a space for moving the fixing bolt 38 along the axial direction of the output shaft 31 at the time of replacement work, and a space for arranging a tool for operating the fixing bolt 38, It is necessary to secure in advance in the axial direction of the output shaft 31. For this reason, there is a problem that the axial direction of the output shaft 31, that is, the height direction of the apparatus cannot be compressed by the amount necessary to secure the space. And when the apparatus which compressed the height direction of the apparatus is required, since the space mentioned above cannot be secured, the replacement of the cam follower 37 must be made impossible at the expense of maintenance. . This is a significant problem because the larger the device, the more difficult it is to disassemble.
Japanese Patent No. 3515928

  The main object of the present invention is to provide an intermittent indexing device capable of compressing the height direction while making the cam follower replaceable.

  Hereinafter, effective means and the like for solving the above-described problems will be described with reference to actions, effects, and more specific means as required. In the following, in order to facilitate understanding, the corresponding configuration in the embodiment of the invention is appropriately shown in parentheses, but is not limited to the specific configuration shown in parentheses.

Means 1. The input shaft and output shaft can be rotated in the housing, the input shaft is provided with a roller gear cam, the output shaft is provided with a cam follower, and the rotation of the input shaft is converted into the rotation of the output shaft by their cam action. In the intermittent indexing device that intermittently rotates the output shaft,
A mounting hole is formed in the output shaft in a direction substantially perpendicular to the axial direction, the stud portion of the cam follower can be inserted into and removed from the mounting hole, and the output shaft is formed in a direction substantially orthogonal to the axial direction. An intermittent indexing device comprising a moving body (lock pin 16) for moving and fixing the cam follower inserted into the mounting hole.

  According to the means 1, the cam follower is fixed or unfixed by moving the moving body in a direction substantially orthogonal to the axial direction of the output shaft. For this reason, a space for moving the moving body in the axial direction of the output shaft and a space for arranging a tool for operating the moving body become unnecessary. Thereby, while the cam follower can be replaced, the axial direction of the output shaft, that is, the height direction of the apparatus can be greatly compressed.

  Here, the configuration of the intermittent indexing device will be described in more detail. The output shaft is provided with a plurality of cam followers at equal intervals in the circumferential direction at the same position in the axial direction, at least one of which is provided on the side surface of the housing. It is arranged near the opening. A work space is provided around the cam follower disposed in the vicinity of the opening so that the cam follower can be exchanged through the opening.

Mean 2. The input shaft and output shaft can be rotated in the housing, the input shaft is provided with a roller gear cam, the output shaft is provided with a cam follower, and the rotation of the input shaft is converted into the rotation of the output shaft by their cam action. In the intermittent indexing device that intermittently rotates the output shaft,
A mounting hole is formed in the output shaft in a direction substantially perpendicular to the axial direction, the stud portion of the cam follower can be inserted into and removed from the mounting hole, and the output shaft enters from the outer peripheral surface to the back. An intermittent indexing device comprising a movable body (lock pin 16) which is fixed in a state where the cam follower is inserted into the mounting hole and is moved backward to be unfixed.

  According to the means 2, the cam follower is fixed or unfixed when the moving body enters the back from the outer peripheral surface of the output shaft or retreats therefrom. For this reason, a space for moving the moving body in the axial direction of the output shaft and a space for arranging a tool for operating the moving body become unnecessary. Thereby, while the cam follower can be replaced, the axial direction of the output shaft, that is, the height direction of the apparatus can be greatly compressed.

  Means 3. A first lock hole is formed on the inner surface of the mounting hole, an interposed member (steel ball 15) is provided in the first lock hole, and intersects with the first lock hole around the cam follower on the outer peripheral surface of the output shaft. Forming the second lock hole, providing the moving body in the second lock hole, and pressing the interposition member that contacts the moving body against the stud of the cam follower as the moving body enters, The intermittent indexing device according to means 1 or 2, wherein the intermittent indexing device is configured to be fixed.

  According to the means 3, the cam follower is fixed by pressing the interposition member that contacts the moving body against the stud portion of the cam follower as the moving body enters. Then, by interposing the interposition member provided in the first lock hole between the moving body and the cam follower, the moving direction of the moving body related to fixing / non-fixing of the cam follower is substantially the same as the axial direction of the output shaft. It is possible to realize a configuration that directs in an orthogonal direction or a configuration in which the moving body enters the back from the outer peripheral surface of the output shaft. Such a configuration is a simple configuration in which two holes are formed, and a moving body and an interposition member are respectively provided there, and a complicated configuration is unnecessary, so that an increase in cost can be suppressed.

  Here, the first lock hole is preferably formed as follows. That is, the output shaft is formed in a cylindrical shape, a fixed shaft fixed to the housing is provided in the hollow portion, and the output shaft is rotatably supported with respect to the fixed shaft by rolling bearings provided at both ends in the axial direction. Then, a housing recess for housing the rolling bearing is formed on the inner surface of the output shaft, and the first lock hole is formed by forming a hole along the axial direction from the inner surface forming the housing recess.

  According to such a configuration, since the first lock hole is formed by using the housing recess for housing the rolling bearing, it is formed for the first lock hole as compared with the case where the hole is formed from the end surface of the output shaft. The entire length of the hole to be made can be shortened. Thereby, the formation work of the 1st lock hole becomes easy.

  Means 4. 4. The intermittent indexing device according to claim 3, wherein the stud portion of the cam follower is formed with a locking recess that engages with a part of the interposition member.

  According to the means 4, a part of the interposition member is engaged with the locking recess formed in the stud portion of the cam follower, so that the interposition member is not simply pressed against the stud portion, but also prevents the disengagement due to the engagement. Join. For this reason, the cam follower can be more reliably fixed.

  Means 5. 5. The intermittent indexing device according to means 3 or 4, wherein the interposition member is a steel ball, and a tip of the moving body is provided with a tapered portion that comes into contact with the steel ball.

  According to the means 5, since the interposition member is a steel ball, the contact between the stud portion and the interposition member becomes a point contact, and a stronger pressing force can be obtained. In addition, the tip of the moving body is provided with a tapered portion that comes into contact with the steel ball, so that the steel ball is gradually pressed against the stud portion as the moving body enters, and a certain pressing force is required to fix the cam follower. Can be obtained. One or more steel balls are provided depending on the length and size of the first lock hole into which the steel ball is inserted.

  Hereinafter, an embodiment embodying the present invention will be described with reference to FIGS. 1 is a partial sectional view showing the entire apparatus of the intermittent indexing device, FIG. 2 is a front view when viewed from the direction A in FIG. 1, and FIG. 3 is a partially enlarged view of FIG. . For convenience of explanation, the terms “upper and lower” and “left and right” are based on the state shown in the drawings.

  As shown in FIG. 1, the intermittent indexing device 1 of the present embodiment includes a housing 2, an input shaft 3, and an output shaft 4 that form a hollow box. The input shaft 3 is supported by the housing 2 with its axis line oriented in the horizontal direction and projecting at both ends from the housing 2 as shown in FIG. The input shaft 3 is provided so as to be rotatable about its axis, and is connected to a rotation driving device such as a motor (not shown) to be driven to rotate. The input shaft 3 is provided with a roller gear cam 5 that rotates with the input shaft 3 in the housing 2. This roller gear cam 5 constitutes a cam mechanism together with a cam follower 9 described later.

  Further, the output shaft 4 is provided in a state in which its axis line is oriented in the vertical direction and protrudes from the upper end of the housing 2. The output shaft 4 is a hollow shaft, and a fixed shaft 7 fixed to the housing 2 is accommodated in the hollow portion 6. The output shaft 4 is supported with respect to the fixed shaft 7 via roller bearings 8 provided at both ends in the axial direction, and is rotatable about the axis. In the present embodiment, the output shaft 4 does not have the same cross-sectional shape along the axial direction, and the upper end portion 4a is formed in a table shape. For this reason, in FIG. 1, the width in the left-right direction differs between the upper end portion 4 a of the output shaft 4 protruding from the upper end of the housing 2 and the shaft portion 4 b in the housing 2.

  The output shaft 4 is provided with a plurality of cam followers 9 on the outer periphery of the housing 2. These cam followers 9 are provided at equal intervals in the circumferential direction at the same position in the axial direction of the output shaft 4. Among the plurality of cam followers 9, several cam followers 9 are engaged with the taper rib 5a formed on the roller gear cam 5 described above. Then, as the roller gear cam 5 rotates as the input shaft 3 rotates, the cam follower 9 engaged with the roller gear cam 5 is guided to the cam 5 and sequentially fed out. At the same time, the other cam followers 9 are sequentially engaged with the roller gear cam 5. The cam mechanism of the roller gear cam 5 and the cam follower 9 is configured to convert the rotation of the input shaft 3 into intermittent rotation drive of the output shaft 4.

  In the intermittent indexing device 1 configured as described above, the input shaft 3 is rotated by a rotary drive device such as a motor. Then, the rotation of the input shaft 3 is transmitted to the output shaft 4 by the aforementioned cam mechanism, and the output shaft 4 is driven to rotate intermittently at a predetermined allocation angle. The allocation angle is arbitrarily determined by appropriately changing the number of cam followers 9 and the shape of the tapered rib 5a of the roller gear cam 5.

  By the way, the cam follower 9 is attached to the output shaft 4 in the following configuration. First, as shown in FIG. 1, the cam follower 9 includes a stud portion 9 a inserted into the output shaft 4 and a roller portion 9 b that engages with the roller gear cam 5. As shown in FIG. 3, a locking recess 11 is formed on the outer peripheral surface of the stud portion 9a.

  On the other hand, the output shaft 4 is formed with a plurality of attachment holes 12 into which the stud portions 9a of the cam followers 9 are inserted at positions where the cam followers 9 are attached. The attachment hole 12 is formed in a direction substantially orthogonal to the axial direction of the output shaft 4 and toward the central axis of the output shaft 4. Further, the output shaft 4 is formed with a first lock hole 13 from the inner surface upper side of the mounting hole 12 toward the axial direction of the output shaft 4, and the second lock is formed on the outer peripheral surface above the opening of the mounting hole 12. A hole 14 is formed.

  The first lock hole 13 is formed by using an accommodation recess 22 for accommodating the lower rolling bearing 8. That is, the first lock hole 13 is formed by forming a hole from the inner upper surface of the housing recess 22 upward in the axial direction of the output shaft 4 and further upward after reaching the mounting hole 12. Is formed. The second lock hole 14 is formed so as to be parallel to the mounting hole 12 and intersect the first lock hole 13. The first lock hole 13 and the second lock hole 14 are formed for each mounting hole 12.

  A stud portion 9 a of the cam follower 9 is inserted into the mounting hole 12 in a state where the positions of the opening of the lock recess 11 and the first lock hole 13 are aligned. In this state, a plurality (three in the present embodiment) of steel balls 15 as interposition members are introduced into the first lock hole 13. In this case, the number to be charged is determined so that a part of the uppermost steel ball 15 is disposed in the hole in which the two lock holes 13 and 14 are shared. On the other hand, the lowermost steel ball 15 is in a state where a part thereof is engaged with the locking recess 11. The steel ball 15 has a diameter that matches the size of the first lock hole 13.

  The second lock hole 14 is screwed with a lock pin 16 as a moving body. For this reason, the moving direction of the lock pin 16 is the direction in which the second lock hole 14 is formed, that is, the direction substantially orthogonal to the axial direction of the output shaft 4. A hexagonal hole is formed in the base end surface of the lock pin 16, and a tapered portion 16a is formed at the tip. When the lock pin 16 is inserted into the second lock hole 14, the tapered portion 16 a at the tip thereof and the steel ball 15 come into contact with each other. When the lock pin 16 is further advanced from there, the steel ball 15 is pressed against the stud portion 9 a of the cam follower 9. The cam follower 9 is fixed to the output shaft 4 by this pressing action.

  In the housing 2, a work space 17 is secured around the cam follower 9 and around the opening of the second lock hole 14 on the opposite side of the roller gear cam 5 (right side in FIG. 1). The housing 2 is formed with an opening 18 that opens the work space 17 to the outside. As shown in FIG. 2, the opening 18 has a size that allows the entire roller portion 9b of the cam follower 9 and the opening of the second lock hole 14 to be viewed from the outside. As described above, since the work space 17 is secured around the cam follower 9, the cam follower 9 and the second lock hole 14 can be directly viewed from the outside of the housing 2 through the opening 18. Also, work on them is possible.

  The housing 2 is provided with a plurality of screw holes 19 around the opening 18. A window lid 20 is detachably attached to the housing 2 using the screw holes 19 as shown in FIG. Normally, when the intermittent indexing device 1 is used, the opening 18 is covered with the window lid 20, and the window lid 20 is removed when work is required for the cam follower 9 due to maintenance or the like.

  Next, an operation performed when the cam follower 9 is replaced in the intermittent indexing device 1 configured as described above will be described.

  First, the drive of the intermittent indexing device 1 is stopped, and then the window lid 20 provided on the housing 2 is removed. Then, as shown in FIG. 2, the roller portion 9 b of the cam follower 9 in the housing 2 and the second lock hole 14 are visible from the opening 18. Thereafter, as shown in FIG. 3, the tip of the hexagon wrench T is inserted into the housing 2 from the opening 18 and engaged with the hexagon hole of the lock pin 16, and the hexagon wrench T is rotated to operate the lock pin 16. Is loosened and removed from the second lock hole 14. As a result, the pressing of the cam follower 9 against the stud 9 a by the steel ball 15 is released, and the cam follower 9 can be removed from the mounting hole 12. After this state, the operator removes the cam follower 9 from the output shaft 4.

  If the cam follower 9 that needs to be replaced is not visible when the window lid 20 is removed, the input shaft 3 or the output shaft 4 is appropriately rotated to place the desired cam follower 9 at a workable position. Further, when the cam follower 9 is removed, the steel ball 15 introduced into the first lock hole 13 falls into the mounting hole 12 and further into the housing 2, but it can be taken out from the opening 18.

  Next, a new cam follower 9 is attached to the output shaft 4. At the time of attachment, the stud portion 9a of the cam follower 9 is inserted into the attachment hole 12 with the locking recess 11 facing upward. Thereby, in the state where the stud portion 9 a is inserted, the locking recess 11 is arranged at a position that matches the opening of the first lock hole 13. Next, the steel ball 15 is introduced into the first lock hole 13 from the opening of the second lock hole 14. Thereafter, the lock pin 16 is screwed into the second lock hole 14 using the hexagon wrench T, and the tapered portion 16a at the tip thereof is brought into contact with the steel ball 15. When the lock pin 16 continues to be screwed, the stud 9 a of the cam follower 9 is pressed by the steel ball 15. Thereby, the cam follower 9 is fixed to the output shaft 4.

  After the cam follower 9 is attached to the output shaft 4 in this way, the window cover 20 is attached to the housing 2, thereby completing the cam follower 9 replacement operation.

  As described above in detail, the present embodiment has the following excellent effects.

  In the present embodiment, the cam follower 9 is fixed or unfixed by screwing the lock pin 16 inward from the outer peripheral surface of the output shaft 4 or by retracting the lock pin 16 therefrom. More specifically, when the lock pin 16 is screwed and retracted, the lock pin 16 moves in a direction in which the second lock hole 14 is formed, that is, in a direction substantially orthogonal to the axial direction of the output shaft 4. The cam follower 9 is set in a fixed state or a non-fixed state. For this reason, it is not necessary to secure a space in which the lock pin 16 moves during the replacement of the cam follower 9 or a space in which a tool such as a hexagon wrench T for operating the lock pin 16 is arranged in the axial direction of the output shaft 4. Thereby, while the cam follower 9 can be replaced, the axial direction of the output shaft 4, that is, the height direction of the intermittent indexing device 1 can be greatly compressed.

  Such an effect becomes more remarkable as the intermittent indexing device 1 becomes larger. The intermittent indexing device 1 is more difficult to disassemble as the size of the intermittent indexing device 1 increases. In the conventional configuration, when the height direction is compressed, it is virtually impossible to replace the cam follower 9. This is because the cam follower 9 can still be replaced even if the height is compressed.

  Moreover, since the rotation axis of the lock pin 16 is the moving direction of the lock pin 16, that is, the direction substantially orthogonal to the axis of the output shaft 4, the rotation operation of the hexagon wrench T that rotates the lock pin 16 is performed on the opening 18. There is no limit to the range. In this regard, conventionally, since the rotation axis of the fixing bolt is in the axial direction of the output shaft 4, the rotation operation of the tool is limited within the range of the opening 18. Since there is no such limitation, the operation of fixing / non-fixing the cam follower 9 is facilitated, and the replacement operation can be easily performed.

  In the present embodiment, the cam follower 9 is fixed by pressing the steel ball 15 against the stud 9 a of the cam follower 9 as the lock pin 16 is screwed. Then, by moving the steel ball 15 introduced into the first lock hole 13 between the lock pin 16 and the stud portion 9a of the cam follower 9, the movement of the lock pin 16 related to fixing / non-fixing of the cam follower 9 is performed. A configuration in which the direction is a direction substantially orthogonal to the axial direction of the output shaft 4 can be realized. And since this structure is a simple structure which forms the two holes 13 and 14 in the output shaft 4, and each provides the lock pin 16 and the steel ball 15, it can suppress the increase in cost.

  In addition, since the first lock hole 13 is formed by using the housing recess 22 for housing the roller bearing 8, the first lock hole 13 is a hole that is not used as compared with the case where the hole is formed from the end surface of the output shaft 4. The length of the hole below the lock hole 13 can be shortened. Thereby, the operation | work which forms the 1st lock hole 13 can be performed easily.

  According to the present embodiment, since a part of the steel ball 15 is engaged with the locking recess 11 formed in the stud portion 9a of the cam follower 9, not only the steel ball 15 is pressed against the stud portion 9a. Moreover, the prevention action by the engagement is also added. For this reason, the cam follower 9 can be fixed more reliably.

  According to the present embodiment, since the steel ball 15 is used to press the stud portion 9a of the cam follower 9, the contact between the two becomes a point contact, and a stronger pressing force is obtained. Further, as the lock pin 16 is screwed in, the tapered portion 16a at the tip thereof gradually presses the steel ball 15 against the stud portion 9a of the cam follower 9, so that a wedge effect is obtained and it is reliable to fix the cam follower 9. A pressing force can be obtained.

  In addition, this Embodiment is not limited to the above content, For example, you may implement as follows.

  In the above embodiment, the lock pin 16 is screwed into the second lock hole 14. However, the lock pin 16 may be allowed to enter the second lock hole 14 with other configurations. For example, a locking portion that locks the lock pin 16 at a position where a constant pressing force can be obtained may be provided on the inner surface of the second lock hole 14 and the lock pin 16.

  In the above embodiment, the steel ball 15 is used as the interposed member, but other members may be used. For example, it may be a rod-shaped member with a narrowed tip on the stud 9a side.

  In the embodiment described above, the movement direction of the lock pin 16 is set to a direction substantially orthogonal to the axial direction of the output shaft 4. However, if the lock pin 16 is advanced from the outer peripheral surface of the output shaft 4, It is not limited. However, in view of the ease of operation of the lock pin 16, it can be said that a configuration in which the direction is substantially orthogonal as in the above embodiment is most preferable.

  In the above embodiment, the hexagon wrench shown in FIG. 3 is used to screw in or retract the lock pin 16, but other tools such as a screwdriver may be used. In this case, the lock pin 16 is not formed with a hexagonal hole, but is formed with an engaging portion that matches the tool.

The partial cross section figure which showed the whole apparatus of the intermittent indexing apparatus. The front view at the time of seeing an intermittent indexing device from A direction in FIG. The partially expanded sectional view of FIG. The partially expanded sectional view which shows the attachment structure of a cam follower in the conventional intermittent indexing apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Intermittent indexing device, 2 ... Housing, 3 ... Input shaft, 4 ... Output shaft, 5 ... Roller gear cam which comprises a cam mechanism, 9 ... Cam follower, 9a ... Stud part of cam follower, 11 ... Locking recessed part, 12 ... Installation Hole: 13 ... 1st lock hole, 14 ... 2nd lock hole, 15 ... Steel ball as interposition member, 16 ... Lock pin as moving body, 16a ... Tapered part.

Claims (4)

The input shaft and output shaft can be rotated in the housing, the input shaft is provided with a roller gear cam, the output shaft is provided with a cam follower, and the rotation of the input shaft is converted into the rotation of the output shaft by their cam action. In the intermittent indexing device that intermittently rotates the output shaft,
The output shaft is a hollow shaft having a hollow portion, a fixed shaft fixed to the housing is accommodated in the hollow portion, and the output shaft is supported with respect to the fixed shaft by bearing members provided at both ends in the axial direction. Supports pivoting,
The first bearing member of the bearing member opposite to the output end of the output shaft is housed in a housing recess formed on the inner peripheral surface of the output shaft, and the housing recess is formed in the output shaft. The part is formed thinner than other parts ,
A mounting hole is formed in the output shaft in a direction orthogonal to the axial direction, the stud portion of the cam follower can be inserted into and removed from the mounting hole, and further, the output shaft enters from the outer peripheral surface to the back. Fix the cam follower inserted in the mounting hole, and provide a moving body that is unfixed by moving backward ,
A first lock hole is formed on the inner surface of the mounting hole, an interposition member is provided in the first lock hole, and a second portion is formed around the cam follower on the outer peripheral surface of the output shaft so as to intersect the first lock hole. A lock hole is formed, the moving body is provided in the second lock hole, and the cam follower is fixed by pressing an interposition member that contacts the moving body against the stud portion of the cam follower as the moving body enters. And
The intermittent indexing device according to claim 1, wherein the first lock hole is a hole formed along an axial direction of the output shaft from an inner surface of the housing recess . The first lock hole is formed by further forming a hole after reaching the mounting hole along the axial direction of the output shaft from the inner surface of the housing recess. The intermittent indexing device described. 3. The intermittent indexing device according to claim 1, wherein a locking recess that engages with a part of the interposition member is formed in a stud portion of the cam follower. The intermittent indexing device according to any one of claims 1 to 3 , wherein the interposed member is a steel ball, and a tapered portion that abuts the steel ball is provided at a tip of the moving body.

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