JP2010260111A - Rotation transmission device for screw parts automatic fastening machine - Google Patents

Abstract

An object of the present invention is to provide a rotation transmission device for a screw component automatic fastening machine that enables a slight reverse rotation with a reaction force caused by twisting of a driver bit after completion of screw component fastening.
One end of one of a rotary coupling body 22 arranged around a drive shaft 2 rotated by a single drive motor 4 capable of rotating in the forward and reverse directions and a fixing member 7 fixed to a transmission shaft 6. The pin member 8 from which the protrusion protrudes is fixed, and a drive transmission groove 23 having a circular long groove shape extending along the circumferential direction is formed on the other fixing member 7 or the rotary connecting body 22 to which the pin member 8 is not fixed. Since the pin member 8 is fitted in the drive transmission groove 23 and the rotation transmission between the drive shaft 2 and the transmission shaft 6 is cut off within a predetermined angle range, the driver is immediately stopped when the drive motor is stopped when the final screw tightening is completed. The bit can be rotated in reverse by a predetermined amount, so that the bite between the screw driving portion and the driver bit is eliminated, and even if the machine is lifted after the screw tightening is completed, the work does not get stuck and go up.
[Selection] Figure 1

Description

  The present invention is an automatic screw part fastening machine that first screws a screw part such as a screw, a bolt or a nut with high speed and low torque rotation, and then fastens the screw part to a workpiece with low speed and high torque up to a preset final fastening torque. The present invention relates to a rotation transmission device that removes the biting of a driver bit into a drive part of a screw part that occurs when screw part fastening is completed.

  2. Description of the Related Art Conventionally well-known screw component fastening machines such as bolts, nuts, and screws are well-known machines that automatically supply these components every work cycle and screw them into a workpiece. In such a machine, a screw tightening machine as an example uses a driver bit that can be engaged with a rectangular shaped drive hole such as a cross or a hexagon hole formed on the head of the screw. Is connected to an electric driver via a drive shaft. When a screw is screwed into a workpiece with this screw tightener, the electric driver is driven in a state where a driver bit is engaged with a screw driving hole. Thereby, a rotational force is transmitted from the driver bit to the screw, and the screw is fastened to the workpiece.

  Such a screw tightening machine is not suitable for screw tightening work where high screw tightening accuracy (fastening torque with little variation) is required, and it is not much when tightening torque needs to be as specified. Not adopted. Therefore, as a screw part fastening machine that has recently been used as such a part fastening machine with stable fastening torque, there is a fastening machine as shown in FIG. 7 as an example. As shown in Patent Document 1, this is a screw tightening machine in which two of a low-speed high-torque driver 102 and a high-speed low-torque driver 103 are arranged, and after a screw is held in a chuck unit (not shown). The low speed high torque driver 102 and the high speed low torque driver 103 are driven simultaneously. At this time, since the outer ring 121 slips with respect to the inner ring 122 by the one-way clutch 120, the driver bit (not shown) is rotated by the rotation of only the high-speed and low-torque driver 103 via the drive shaft 104, and the screw is turned. Screwed at high speed. In this operation, when the rotational speed of the high speed / low torque driver 103 decreases as the screw is screwed in and decreases below the rotational speed of the low speed / high torque driver 102, the rotation of the low speed / high torque driver 102 is controlled by the action of the one-way clutch 120. It is transmitted to the connected drive shaft 104 and screwed until it reaches the final fastening torque at a low speed.

  Recently, a screw tightening machine as shown in FIG. 6 has also been developed. This is because rotation is transmitted from the first rotation transmission path 220 directly connected to the drive shaft 205 located on the extension center line of the motor shaft by the drive motor 204 disposed at the rear to tighten the drive shaft 205. Rotating at high speed and low torque, temporarily tightening the screw parts, and at the same time the seating surface of the screw parts is seated on a work (not shown), the rotation direction of the motor shaft is switched, and the transmission path of the rotational power is changed to change the motor shaft This is a screw tightening machine configured to transmit low-speed high-torque rotation from a second rotation transmission path 230 disposed around the extended center line (see Patent Document 2). In this screw tightening machine, three-way clutches 211, 221, 231 for interrupting transmission of rotation when the rotation direction of the drive motor 204 for screw tightening is changed are provided at three locations, Thereby, the rotation transmission path is smoothly changed.

JP-A-60-52268 JP 2008-114303 A

  However, although these parts fastening machines are capable of properly obtaining the predetermined fastening torque in this way, the driver bits remain engaged with the screw drive holes when the final screw tightening is completed. When the machine is lifted after the completion of the screw tightening, the workpiece may be lifted together, resulting in a product defect. In addition, since a clutch is used in any of these machines, when the drive shaft is reversed by a reaction force caused by twisting of the driver bit when screw tightening is completed, this reverse rotation is prevented by the clutch, and the screw tighten state Is becoming difficult to unlock. In addition, when the workpiece is relatively thin as in recent years due to such problems, the workpiece is often damaged when mounting parts automatically, and automation is difficult to progress. Has produced.

  The object of the present invention is to eliminate such problems and fasten the screw component at a high speed and low torque at the beginning of screwing of the screw component, and fasten the screw component at a low speed and high torque when the screwing is completed and torsion of the driver bit after the screwing is completed. It is to obtain a rotation transmission device of a screw part automatic fastening machine that enables a slight reverse rotation with force.

  An object of the present invention is to connect a rotary connecting body 22 disposed around a drive shaft 2 rotated by a single drive motor 4 capable of rotating in the forward and reverse directions so as to be integrally rotatable at the time of forward rotation, and to rotate at the time of reverse rotation. A first one-way clutch 21 for blocking is provided, and the drive shaft 5 is connected to the transmission shaft 6 to which the rotation of the rotary coupling body 22 is transmitted to drive at high speed and low torque. An output speed reduction means for reducing the rotation and rotating in the direction opposite to the rotation direction of the drive shaft 2 is arranged, and between the rotary connecting member 32 to which the rotation from the output speed reduction means is transmitted and the transmission shaft 6. In the screw component automatic fastening machine in which the second one-way clutch 31 for rotating the drive shaft 2 in the forward direction is blocked during the forward rotation and rotating the transmission shaft 6 in the forward direction with the low speed and high torque drive during the reverse rotation, Fixed to transmission shaft 6 The pin member 8 whose one end protrudes is fixed to one of the fixed members 7 and the other fixed member 7 or the rotary connecting body 22 to which the pin member 8 is not fixed has the same center as the rotary connecting body 22. The drive transmission groove 23 having a circular long groove shape along the circumferential direction is formed, and the pin member 8 is fitted into the drive transmission groove 23. The drive shaft 2 and the transmission shaft 6 are rotated within a predetermined angle range. This is achieved by providing a rotation transmission device that is configured to block transmission.

  In order to achieve this object, in the rotation transmission device, the drive transmission groove is on the turning locus of the pin member 8, and the pin member 8 is capable of turning back and forth while standing on the turning locus. Therefore, the reaction force generated in the drive shaft 5 and the driver bit at the time of screw tightening can be removed immediately after the fastening is completed, and the screw part drive portion and the driver bit can be caught. It will be resolved.

  According to the present invention, one of these members is interposed between the rotary coupling body fixed to the first one-way clutch to which the drive shaft is connected only during normal rotation and the fixed member of the transmission shaft to which the rotation is transmitted. Since the drive member is provided with a drive transmission groove in which the pin member is fitted and the other member is fitted with these to transmit the rotation, the driver bit is placed immediately after the drive motor stops when the final screw tightening is completed. Since the rotation can be reversed only by a fixed amount, the engagement between the screw drive portion and the driver bit is eliminated, and the workpiece does not come up and rise even when the machine is raised after the screw tightening is completed. This eliminates the occurrence of product defects. Further, in a screw tightening machine provided with a clutch in the rotation transmission system, it is easy to reverse the drive shaft after the completion of screw tightening, so that the screw tightened state can be easily released. Furthermore, since the reverse rotation of the drive shaft is possible within the predetermined range in this way, when the work is relatively thin as in recent times, the occurrence of damage to the work when automating the parts mounting is reduced, Specific effects such as progress in automation can be obtained.

It is a schematic perspective view which shows the decomposition | disassembly structure of the principal part of this invention. It is a partial cross section front view showing the whole composition concerning the present invention. It is a principal part expanded sectional view which shows this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic perspective view which decomposed | disassembled and showed the rotation transmission state which is the principal part of this invention in the state just before a combination, (a) shows a high-speed low torque rotation transmission state, (b), (c) is low-speed high torque. The rotation transmission state is shown, and (d) shows the fastening completion state. It is an operation | movement flowchart which shows the operation state of the rotation transmission system which concerns on this invention, (a) shows the high speed low torque rotation transmission state, (b) has shown the low speed high torque rotation transmission state. It is principal part sectional drawing which shows the structure of the prior art example of this invention. It is a block diagram including the principal part cross section which shows another prior art example of this invention.

  Embodiments of the present invention will be described below with reference to FIGS. In FIG. 2, reference numeral 1 denotes a screw component automatic fastening machine that is placed on a lifting platform (not shown) and moves up or down. The screw component automatic fastening machine 1 belt-drives a drive pulley 3 fixed to a drive shaft 2 and can rotate forward and reverse, and a rotation transmission system that transmits rotation from the drive motor 4 to the inside. And a drive shaft 5 that receives rotation from a rotation transmission system. A drive shaft 5 for fixing a driver bit (not shown) is disposed on a central extension line of the drive shaft 2 to which the drive pulley 3 is fixed. Between the drive shaft 2 and the drive shaft 5, a drive shaft 5 is disposed. Two rotation transmission systems are configured. One of the transmission systems is a first rotation transmission system 20 that rotates the drive shaft 5 at high speed and low torque, and the other is a second rotation transmission system 30 that rotates the drive shaft 5 at low speed and high torque. .

  As shown in FIG. 3, the first and second rotation transmission systems 20 and 30 have a structure that operates when the drive motor 4 rotates in the forward and reverse directions. The first rotation transmission system 20 includes a drive shaft. When the drive shaft 2 is connected to the tip of the drive shaft 2 to rotate it in the forward direction (clockwise) to transmit the rotation and to rotate in the reverse direction (counterclockwise direction) Is one of the first one-way clutches 21 that is disconnected and blocks transmission of rotation, and the other one of the first one-way clutches 21 is connected to a cylindrical rotary connecting member 22 having the same center as the drive shaft 2. It is fixed. The rotary connection body 22 is rotatably supported by a hollow first connection body 32a constituting a second rotation transmission system 30 supported by the casing 10 so as to be rotatable around the rotation connection body 22. The body 22 is concentric with the fixing member 7 fixed so as to be integrated with the transmission shaft 6 disposed on the central extension line of the drive shaft 2.

  A pin member 8, one end of which protrudes on the side facing the rotary connecting body 22, is fixed to the fixing member 7 so as to turn around the center of the fixing member 7, while the fixing member 7 of the rotary connecting body 22 is fixed. A drive transmission groove 23 into which the protruding end of the pin member 8 is fitted is formed on the side opposite to the side. The drive transmission groove 23 has the same center as the rotary coupling body 22 and is formed in a circular long groove shape along the circumferential direction. The rotary coupling body 22 that rotates by receiving the rotation from the drive shaft 2 is the pin member. The rotation is transmitted to the transmission shaft 6 that transmits the rotation to the drive shaft 5 via 8. As shown in FIG. 1, the circumferential length of the drive transmission groove 23 is such that the transmission shaft 6 to which the pin member 8 is fixed can freely turn with respect to the rotary connecting body 22 by a predetermined rotation angle. Well, in this embodiment, when the drive shaft 5 is reversed by a slight angle, the drive shaft 2 is rotated by a large angle by the output reduction means described later, so that the angle range is relatively large around the center of the rotary coupling body 22. Is set. Therefore, the rotation transmission between the drive shaft 2 and the transmission shaft 6 is cut off within the range of this angle, and the rotation is transmitted to the transmission shaft 6 by rotating more than this angle. Further, this angle can be arbitrarily set within the range depending on the reduction ratio of the output reduction means.

  In other words, the drive transmission groove 23 is on the turning locus of the pin member 8 as shown in FIG. 1, and the length of the pin member 8 is such that the turning locus can be moved back and forth while standing on the turning locus. Is formed. In this embodiment, the pin member 8 is fixed to the fixing member 7, and the drive transmission groove 23 into which the pin member 8 is fitted is formed in the rotary coupling body 22. However, these configurations are reversed, that is, the pin member 8 is rotated. Even if the drive transmission groove 23 is formed on the fixing member 7 while being fixed to 22, the same action can be obtained.

  The drive shaft 2, the first one-way clutch 21, the rotary connecting body 22, and the transmission shaft 6 constitute the first rotation transmission system 20, and the rotation from the first rotation transmission system 20 is The drive shaft 5 that is connected to the transmission shaft 6 so as to rotate integrally is transmitted at high speed and low torque.

  On the other hand, in FIG. 2, there is output deceleration means around the intermediate position of the drive shaft 2 as an output reduction means for reducing the rotation of the drive shaft 2 at high speed and low torque with a large reduction ratio and converting the rotation to low speed and high torque. A reduction gear 40 is arranged. The speed reducer 40 has a structure called a Harmonic Drive (registered trademark) speed reduction mechanism, and this means that the rotation of the drive shaft 2 transmitted from the drive motor 4 via the drive pulley 3 is the rotational direction of the drive shaft 2. Is a configuration in which it is converted into a low-speed high-torque rotation in the reverse direction and output. This configuration is disclosed in, for example, Japanese Patent Application Laid-Open No. 58-196349 or Japanese Patent Application Laid-Open No. 59-113342, and is already known prior to the filing of the present invention.

  A generator 41 on the input side of the speed reducer 40 is operated on the drive shaft 2, and the operation of the generator 41 outputs reduced rotation to the flexible gear 42 on the output side of the speed reducer 40. It has become. The output side of the speed reducer 40 is connected to a cylindrical first connection body 32a that is rotatably supported by the casing 10, and a second connection body 32b is concentrically connected to the first connection body 32a. Similarly to the first connection body 32 a, the first connection body 32 a and the second connection body 32 b constitute a rotation connection member 32. A second one-way clutch 31 is interposed between the second connection body 32b and the transmission shaft 6. The second one-way clutch 31 is connected to the transmission shaft 6 when the rotary connection member 32 rotates forward. This rotation is transmitted. The drive shaft 2, the speed reducer 40, the rotation connection member 32, the second one-way clutch 31, and the transmission shaft 6 constitute the second rotation transmission system 30, and the second rotation transmission system 30 The rotation of the drive shaft 5 transmits the drive shaft 5 at low speed and high torque.

  Further, in the state where the rotation is transmitted from the first rotation transmission system 20, that is, in the state where the drive shaft 2 is rotating forward, the second rotation transmission system 30 is also decelerated as an output reduction means. The low speed rotation in the reverse rotation direction is transmitted from the machine 40, but the transmission shaft 6 is rotating in the normal rotation at high speed and the rotary connecting member 32 is rotating in the reverse direction. Is cut off. On the other hand, in a state where the rotation is transmitted from the second rotation transmission system 30, that is, in a state where the drive shaft 2 is reversely rotated, the output from the speed reducer 40 of the second rotation transmission system 30 is forward rotation. The rotation is low speed, and this rotation is transmitted to the second one-way clutch 31 via the rotation connecting member 32. At this time, the first one-way clutch 21 of the first rotation transmission system 20 is in a state in which the reverse rotation from the drive shaft 2 is cut off, so that the low-speed high torque rotation from the second rotation transmission system 30 is the transmission shaft. 6 is converted from high-speed low-torque rotation to low-speed high-torque rotation by switching the forward / reverse rotation of the drive shaft 2. In addition, the first and second rotation transmission systems 20 and 30 are built in the casing 10, and the rotary connection member 32 is rotatably supported by the casing 10. Each of the 22 is rotatably supported.

  Furthermore, a driver bit (not shown) such as a box bit or a cross bit that engages with the head of a screw component (not shown) is connected to the tip of the drive shaft 5, and this driver bit is In response to the rotation transmitted from the first and second rotation transmission systems 20 and 30, the screw component is rotated at a high speed and a low torque at the initial stage of screwing, and at a low speed and a high torque when the screwing is completed.

  In addition, as shown in FIG. 2, a cylindrical strain generating tube 50 covering the drive shaft 5 is fixedly disposed on a spacer 11 fixed to the lower end of the casing 10. The pipe 50 receives a reaction force of the drive shaft 5 generated when a threaded part is seated on a work (not shown) and is fastened with a high torque. The strain pipe 50 is twisted. A strain gauge 51 for detecting a strain corresponding to the twist as an electric signal is attached. A torque sensor is constituted by the strain generating tube 50 and the strain gauge 51, and the fastening torque is determined by the control unit 60 from the signal of the strain gauge 51 so that a predetermined fastening torque is obtained.

  The drive motor 4 outputs a signal indicating its rotation state, and this signal enters the control unit 60 and is processed together with a signal from the sensor. In addition, the control unit 60 outputs a signal for rotating the drive motor 4 forward and backward, which is a stall state of the drive motor 4 (stall means that the motor shaft of the drive motor 4 cannot rotate). In this stalled state, the high-speed, low-torque drive by the forward rotation of the drive motor 4 is switched in response to the signal, and the drive shaft 2 rotates in the reverse direction. Thus, low speed and high torque drive is transmitted to the drive shaft 5. In addition, the control unit 60 causes the screw component to be screwed at a high speed by the forward rotation of the drive motor 4 with respect to the final fastening torque set according to the type of the screw component, and the screw component is seated on the workpiece. In this case, the maximum rotational speed of the drive motor 4 is determined so that the generated impact torque does not exceed the final fastening torque.

  Next, the operation of the present invention will be described. In a screw component automatic fastening machine having a screwdriver bit in a state where the screw component is engaged and held, when a start signal is input with the screw component positioned at the work fastening position. 5A, the drive motor 4 causes the drive shaft 2 to rotate at high speed in the forward direction, that is, the clockwise direction that is the screwing direction (the direction of arrow (A) in FIG. 4A). At this time, the first one-way clutch 21 is connected to the drive shaft 5 so that the drive shaft 2, the rotary connecting body 22, the transmission shaft 6 and the drive shaft 5 rotate together. In this rotation, the pin member 8 fitted in the drive transmission groove 23 of the rotary connecting body 22 is engaged with the drive transmission groove 23 and transmitted to the transmission shaft 6 as shown in FIG. On the other hand, as shown on the right side of FIG. 5, the reduction gear 40 is also rotated by this rotation, and the reverse rotation direction, that is, the low-speed rotation in the counterclockwise direction (arrow (B) direction in FIG. 4A) is reduced by the reduction gear 40. However, the second one-way clutch 31 is activated to interrupt transmission of the low-speed rotation to the transmission shaft 6. As a result, the drive shaft 5 rotates at high speed and low torque without receiving any resistance, the rotation is transmitted to the driver bit, and the screw part is screwed into the work (not shown) at high speed and low torque.

  Thus, when the screw component is screwed in at a high speed and the screw component is seated on the work, the drive motor 4 is in a stalled state, and a reverse rotation start signal is input from the control unit 60 to the drive motor 4, and FIG. As shown in b), the drive shaft 2 rotates at high speed in the reverse direction, that is, in the counterclockwise direction due to the reverse rotation of the motor shaft of the drive motor 4. For this reason, the 1st one way clutch 21 will be in an idling state, and rotation will be interrupted | blocked, and the transmission shaft 6 will be in the state from which high speed reverse rotation was interrupted | blocked. On the other hand, since the speed reducer 40 is connected to the drive shaft 2, the reverse rotation of the drive shaft 2 is output as a forward rotation that is decelerated from the output side of the speed reducer 40, that is, a clockwise low-speed rotation. The rotation connection member 32 is transmitted to the second one-way clutch 31. Since the rotation from the rotation connecting member 32 is coupled to the second one-way clutch 31, a normal rotation of low speed and high torque is transmitted from the transmission shaft 6 to the drive shaft 5. In this rotation, as shown in FIGS. 4 (b) and 4 (c), the rotation of the pin member 8 engaged with the drive transmission groove is not transmitted from the rotation coupling body 22, but from the rotation connection member 32. Low speed rotation is transmitted to the transmission shaft 6 via the second one-way clutch 31.

  When the fastening torque reaches the final fastening torque set in advance to a predetermined value by the torque sensor during the rotation of the low speed and high torque, the fastening motor is in a fastening completion state as shown in FIG. Stops. At this time, the driver bit and the drive shaft 5 are twisted, but the drive transmission groove 23 in which the pin member 8 is fitted does not have a wall of the groove 23 in the reverse direction of the drive shaft 5, that is, play. Therefore, simultaneously with the stop of the drive motor 4, the drive shaft 5 reverses by this play due to the reaction force of the torsion, so that the engagement between the screw drive hole and the driver bit is eliminated. In this operation, the flexible gear 42 of the speed reducer 40 is also reversely rotated by the reverse rotation of the drive shaft, whereby the generator 41 is normally rotated and the drive shaft 2 is also normally rotated, but since the range of the drive transmission groove 23 is long, The reverse rotation of the drive shaft 5 is not hindered.

  In the fastening operation of the screw parts, since the stall state by the drive motor 4 is driven and controlled by the control unit 60 so as to be generated with an impact torque lower than the final fastening torque, the inertia in the drive motor 4 is small. The final fastening torque can be accurately obtained by the reverse drive of the drive motor 4. Therefore, the fastening operation from the start of screwing in the forward rotation of the drive motor 4 to the seating on the work can be performed at a high speed.

  On the other hand, when the screw part is seated on the workpiece by the high-speed and low-torque screwing operation with the drive motor 4, the control unit 60 reverses the drive motor 4 until the final fastening torque is reached. The stalling state is detected and the drive motor 4 is controlled, and it is determined whether or not the screw component is seated and the final fastening torque is reached. Thus, the fastening operation can be comprehensively controlled by transmitting and receiving signals from the drive motor 4 and the torque sensor to and from the control unit 60, and the screw parts can be fastened efficiently.

  Thereafter, when the screw component fastening operation cycle is completed, the drive motor 4 returns to the normal rotation state and enters a standby state until the next work cycle. When the next start signal is input again, the above fastening operation is performed. Repeated.

  In this embodiment, the forward direction is shown as a clockwise direction, and the reverse direction is shown as a counterclockwise direction. However, the forward direction may be taken as a counterclockwise direction, and the reverse direction may be taken as a clockwise direction. The screw is a right-handed screw, which is shown from the fact that the screwing direction seen from above is regarded as the positive direction, and it is easy to understand that the left-handed screw is the opposite. .

  According to the present invention, when screw parts are fastened, a screwing operation with a preset fastening torque can be accurately obtained without causing screw floating, and the biting of the driver bit into the drive part of the screw parts is released. It is suitable for.

DESCRIPTION OF SYMBOLS 1 Screw component automatic fastening machine 2 Drive shaft 3 Drive pulley 4 Drive motor 5 Drive shaft 6 Transmission shaft 7 Fixed member 8 Pin member 10 Casing 11 Spacer 20 First rotation transmission system 21 First one-way clutch 22 Rotation coupling body 23 Drive Transmission groove 30 Second rotation transmission system 31 Second one-way clutch 32 Rotation connection member 32a First connection body 32b Second connection body 40 Reduction gear 41 Generator 42 Flexible gear 50 Strain tube 51 Strain gauge 60 Control unit

Claims (2)

A rotary connecting body (22) arranged around the drive shaft (2) rotated by a single drive motor (4) capable of rotating in the forward and reverse directions is connected so as to be integrally rotatable during forward rotation, and rotated during reverse rotation. A first one-way clutch (21) for blocking is provided, and a drive shaft (5) is connected to a transmission shaft (6) to which the rotation of the rotary coupling body is transmitted to drive at high speed and low torque. An output speed reduction means for reducing the rotation of the rotation speed and rotating the rotation direction opposite to the rotation direction of the drive shaft is disposed around the rotation connecting member (32) to which the rotation from the output speed reduction means is transmitted and the transmission. In a screw component automatic fastening machine in which a second one-way clutch (31) is arranged that rotates between the shaft and the drive shaft during normal rotation, and at the time of reverse rotation, the transmission shaft rotates forward at low speed and high torque drive.
The pin member (8), one end of which protrudes, is fixed to either one of the rotation coupling body and the fixing member (7) fixed to the transmission shaft, and the other fixing member or the rotation of which the pin member is not fixed. A drive transmission groove (23) having a circular long groove shape having the same center as that of the rotary connection body and extending in the circumferential direction is formed in the connection body, and the pin member is fitted into the drive transmission groove, and the drive shaft, the transmission shaft, Is a rotation transmission device characterized in that transmission of rotation is cut off within a predetermined angle range.   2. The drive transmission groove is on a turning locus of the pin member, and the pin member is formed to have a length capable of turning in the front-rear direction while standing on the turning locus. The rotation transmission device described.

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