JP2019132279A - Linear motion expansion mechanism - Google Patents

Abstract

To improve efficiency of a positioning work of an arm portion in a linear motion expansion mechanism.SOLUTION: A linear motion expansion mechanism has a plurality of flat plate-shaped first pieces 53 and a plurality of groove-shaped second pieces 54. The first and second pieces are bendably connected, and connected by a connection piece 55 at each head. A feeding-out mechanism portion 25 includes a plurality of rollers 59, to firmly hold the first and second pieces from vertical and lateral directions, and support them movably in a longitudinal direction. The first and second pieces are joined to each other by the rollers when being fed forward and linearly stiffened to constitute the pillar-shaped arm portion 5 with the connection portion, and separated from each other at a rear part of the roller when being retracted backward so that the bent state is recovered. A side face of the connection piece 55 is provided with convex positioning portions 71, 72 kept into contact with a receiving portion of the feeding-out mechanism portion to align the arm portion to a reference position with respect to the feeding-out mechanism portion.SELECTED DRAWING: Figure 4

Description

  Embodiments described herein relate generally to a linear motion expansion / contraction mechanism.

  Conventionally, articulated robot arm mechanisms have been used in various fields such as industrial robots. The inventors have developed a linear motion expansion / contraction mechanism applicable to such an articulated robot arm mechanism (Patent Document 1). The adoption of the linear motion expansion / contraction mechanism in the articulated robot arm mechanism is an extremely useful structure because it eliminates the need for an elbow joint and can easily eliminate singularities.

  The linear motion expansion / contraction mechanism includes a plurality of metal pieces having a flat plate shape (first piece) connected to bendable and a plurality of metal pieces having a groove shape connected to bendable on the bottom plate (second piece). Frame). The first and second frames are joined at the tip, and when sent forward, the first and second frames are overlapped to ensure a rigid state. Thereby, a columnar arm portion having a certain rigidity is formed. When pulled back, the first and second frames are separated, return to a bendable state, and housed inside the column. The feed mechanism is equipped with a plurality of rollers on the four sides of a rectangular tube-shaped frame, and realizes forward / backward movement while firmly sandwiching the first and second frames from four directions, and supports the arm part vertically and horizontally. .

  As is well known, when the linear motion expansion / contraction mechanism is shipped or installed, an alignment operation is required to match the control recognition length of the arm unit with the actual expansion / contraction length. Typically, the arm part is contracted to the shortest, and the position (arm reference position) is recognized by the control part as the origin for the expansion / contraction control. This operation is called “origin search” or “origin return”. In order to find the origin, it was necessary to remove the arm cover to expose the arm part and visually contract the arm part to the reference position, and the workability was not high.

  In addition, because the stretchable arm part is composed of many frames combined with a hinge structure, the arm part is relatively easy to shift even during operation, and “origin origin” is periodically performed in a relatively short period. Needed. In addition, when the expansion / contraction operation of the arm part is abnormally stopped for some reason, it is necessary to “find the origin” at any time.

Japanese Patent No. 5435679

  The purpose is to realize an improvement in the efficiency of the alignment operation of the arm portion in the linear motion extension / contraction mechanism.

  The linear motion expansion / contraction mechanism according to the present embodiment includes a plurality of flat plate-shaped first frames that are connected to bendable at the front and rear end surfaces, and a plurality of groove-shaped second frames that are connected to bendable at the front and rear end surfaces of the bottom portion. A frame, a coupling portion that couples the top of the first frame and the top of the second frame, and a plurality of the first and second frames so that the first and second frames are firmly sandwiched from above and below and from left to right and supported in a freely movable manner A feeding mechanism portion equipped with a roller. The first and second frames are joined to each other by the roller when fed forward to form a columnar arm portion together with the coupling portion and separated from each other behind the roller when pulled back. Then, a convex alignment portion is provided on the side surface of the coupling portion so as to contact the receiving portion of the delivery mechanism portion in order to align the arm portion with a reference position with respect to the delivery mechanism portion. It is done.

FIG. 1 shows an appearance of a robot arm mechanism equipped with a linear motion expansion / contraction joint according to the first embodiment. FIG. 2 is a side view of the robot arm mechanism of FIG. FIG. 3 is a diagram showing the internal structure of the robot arm mechanism of FIG. 1 from the side. FIG. 4 is a diagram showing the structure of the alignment portion of the arm portion of FIG. FIG. 5 is a view showing the structure of the delivery mechanism of FIG. FIG. 6 is a diagram illustrating how the origin is obtained using the alignment unit of FIG.

  Hereinafter, the linear motion expansion / contraction mechanism according to the present embodiment will be described with reference to the drawings. In addition, the linear motion expansion-contraction mechanism which concerns on each embodiment can be used as a single mechanism (joint). In the following description, a robot arm mechanism in which one joint portion among the plurality of joint portions is configured by the linear motion extension mechanism according to each embodiment will be described as an example. As the robot arm mechanism, a vertical articulated robot arm mechanism provided with a linear motion expansion / contraction mechanism will be described here, but other types of robot arm mechanisms may be used. In the following description, components having substantially the same function and configuration are denoted by the same reference numerals, and redundant description will be given only when necessary.

  FIG. 1 shows the appearance of a robot arm mechanism equipped with a linear motion extension mechanism in the first embodiment. FIG. 2 is a side view of the robot arm mechanism of FIG. FIG. 3 is a side view showing the internal structure of the robot arm mechanism of FIG.

  The robot arm mechanism includes a base 1, a turning part (supporting part) 2, an undulating part 4, an arm part 5, and a wrist part 6. The swivel unit 2, the undulating unit 4, the arm unit 5, and the wrist unit 6 are arranged in order from the base 1. The plurality of joint portions J1, J2, J3, J4, J5, and J6 are arranged in order from the base 1. The rotary joint mechanism according to the present embodiment is realized by the torsional joint of the fourth joint portion J4. The base 1 is typically provided with a swivel portion 2 that forms a cylindrical body vertically. The swivel unit 2 houses a first joint J1 as a swivel rotary joint. The first joint portion J1 includes a torsional rotation axis RA1. The rotation axis RA1 is parallel to the vertical direction. The swivel unit 2 has a lower frame 21 and an upper frame 22. One end of the lower frame 21 is connected to the fixed portion of the first joint portion J1. The other end of the lower frame 21 is connected to the base 1. The lower frame 21 is covered with a cylindrical housing 31. The upper frame 22 is connected to the rotating portion of the first joint portion J1, and rotates about the rotation axis RA1. The upper frame 22 is covered with a cylindrical housing 32. As the first joint portion J1 rotates, the upper frame 22 rotates with respect to the lower frame 21, whereby the arm portion 5 pivots horizontally. First and second frame rows 51 and 52 of a third joint portion J3 serving as a linear motion extending / contracting mechanism to be described later are housed in the hollow interior of the swivel portion 2 forming a cylindrical body.

  On the upper part of the swivel unit 2, a undulating part 4 that houses a second joint part J2 as a undulating rotary joint part is installed. The second joint portion J2 is a bending rotation joint. The rotation axis RA2 of the second joint portion J2 is perpendicular to the rotation axis RA1. The undulating part 4 has a pair of side frames 23 as a fixing part (support part) of the second joint part J2. The pair of side frames 23 are connected to the upper frame 22. The pair of side frames 23 is covered with a bowl-shaped cover 33. The pair of side frames 23 supports a cylindrical body 24 as a rotating portion of the second joint portion J2 that also serves as a motor housing. A delivery mechanism 25 is attached to the peripheral surface of the cylindrical body 24. The delivery mechanism 25 includes a frame 26. The frame 26 holds a drive gear 56, a guide roller 57, and a roller unit 58. As the cylindrical body 24 rotates, the delivery mechanism 25 rotates, and the arm portion 5 supported by the delivery mechanism 25 undulates up and down. The delivery mechanism 25 is covered with a hard cylindrical cover 34. The gap between the bowl-shaped cover 33 and the cylindrical cover 34 is covered with a U-shaped bellows cover 14 having a U-shaped cross section. The U-shaped bellows cover 14 expands and contracts following the up-and-down movement of the second joint portion J2.

  The third joint portion J3 is provided by a linear motion expansion / contraction mechanism. The linear motion expansion / contraction mechanism has a structure newly developed by the inventors, and is clearly distinguished from a so-called conventional linear motion joint in terms of a movable range. Although the arm portion 5 of the third joint portion J3 is freely bendable, the bending is restricted when the arm portion 5 is fed forward along the center axis (extension / retraction center axis RA3) from the base feed mechanism 25 of the arm portion 5, and linear rigidity is obtained. Is secured. When the arm part 5 is pulled back, the bending is recovered. The arm unit 5 includes a first frame row 51 and a second frame row 52. The first frame row 51 is composed of a plurality of first frames 53 that are connected to be freely bent. The first frame 53 is formed in a substantially flat plate shape. The first frame 53 is connected to bendable at the end portion. The second frame row 52 includes a plurality of second frames 54. The second frame 54 is configured as a grooved body having a U-shaped cross section or a cylindrical body having a rectangular shape. The second frame 54 is connected to bend at the end portion of the bottom plate. The bending of the second frame row 52 is limited at a position where the end surfaces of the side plates of the second frame 54 come into contact with each other. At that position, the second frame row 52 is linearly arranged. The first frame 53 at the top of the first frame sequence 51 and the second frame 54 at the top of the second frame sequence 52 are connected by a combined frame (combining unit) 55.

  The first and second frame rows 51 and 52 are pressed and joined to each other by the roller 59 when passing through the roller unit 58 of the feed mechanism 25. By joining, the first and second frame rows 51 and 52 exhibit linear rigidity and constitute a columnar arm portion 5. A drive gear 56 is disposed behind the roller unit 58 together with the guide roller 57. The drive gear 56 is connected to a motor unit (not shown). The motor unit generates power for rotating the drive gear 56. A linear gear is formed along the connecting direction in the center of the inner surface of the first frame 53, that is, the width center of the surface joined to the second frame 54. When the plurality of first frames 53 are arranged in a straight line, adjacent linear gears are connected in a straight line to form a long linear gear. The drive gear 56 is meshed with the linear gear of the first frame 53 pressed by the guide roller 57. The linear gear connected in a straight line forms a rack and pinion mechanism together with the drive gear 56. When the drive gear 56 rotates forward, the first and second frame rows 51 and 52 are fed forward from the roller unit 58. When the drive gear 56 rotates in the reverse direction, the first and second frame rows 51 and 52 are pulled back to the rear of the roller unit 58. The pulled back first and second frame rows 51 and 52 are separated from each other between the roller unit 58 and the drive gear 56. The separated first and second frame rows 51 and 52 are returned to a bendable state. The first and second frame rows 51, 52 that have returned to the bendable state are both bent in the same direction (inner side) and stored vertically in the turning unit 2. At this time, the first frame row 51 is stored in a state of being substantially aligned with the second frame row 52 substantially in parallel.

  A wrist portion 6 is attached to the tip of the arm portion 5. The wrist 6 is equipped with fourth to sixth joints J4 to J6. The fourth to sixth joint portions J4 to J6 are each provided with three orthogonal rotation axes RA4 to RA6. The fourth joint portion J4 is a torsional rotary joint centered on a fourth rotation axis RA4 that substantially coincides with the expansion / contraction center axis RA3, and the end effector is swung and rotated by the rotation of the fourth joint portion J4. The fifth joint portion J5 is a bending rotation joint about the fifth rotation axis RA5 arranged perpendicular to the fourth rotation axis RA4, and the end effector is tilted back and forth by the rotation of the fifth joint portion J5. Is done. The sixth joint portion J6 is a torsional rotational joint about the sixth rotational axis RA6 that is arranged perpendicular to the fourth rotational axis RA4 and the fifth rotational axis RA5. By the rotation of the sixth joint portion J6, The end effector is pivoted.

  The end effector (hand effector) is attached to the adapter 7 provided at the lower part of the rotating part of the sixth joint part J6 of the wrist part 6. The end effector is a part having a function of directly acting on a work target (work) by the robot, and various tools such as a gripping part, a vacuum suction part, a nut fastener, a welding gun, and a spray gun exist. The end effector is moved to an arbitrary position by the first, second, and third joint portions J1, J2, and J3, and is disposed in an arbitrary posture by the fourth, fifth, and sixth joint portions J4, J5, and J6. In particular, the length of the expansion / contraction distance of the arm portion 5 of the third joint portion J3 enables the end effector to reach a wide range of objects from the proximity position of the base 1 to the remote position. The third joint portion J3 is a characteristic point that is different from the conventional linear motion joint in the linear expansion / contraction operation realized by the linear motion expansion / contraction mechanism constituting the third joint portion J3 and the length of the expansion / contraction distance.

  The arm portion 5 formed into a columnar body by joining the first and second frame rows 51 and 52 has, for example, a flexible resin-made bellows structure whose cross section is formed in a rectangular shape or a nearly cylindrical shape. Covered by a cover 15. One end portion of the arm cover 15 is connected to a joint portion of the wrist portion 6 with the arm portion 5, and the other end portion is connected to a cylindrical cover 34 that covers the undulating portion 4. The arm cover 15 is stretchable by adopting a bellows structure, expands and contracts linearly in accordance with the linear movement of the arm unit 5, and always covers the entire arm unit 5.

  In the linear motion expansion / contraction mechanism according to the present embodiment, an operation for adjusting the arm portion 5 to the reference position with respect to the delivery mechanism 25 is required to match the control recognition length of the arm portion 5 with the actual expansion / contraction length. . In the present embodiment, the arm portion 5 is most contracted, and the most contracted position is set as an origin for expansion / contraction control (extension distance is zero). The alignment operation is referred to as “origin search” or “origin return”. By aligning at the most contracted position, and by constructing the linear motion expansion / contraction mechanism so that the most contracted position is the structural contraction limit, the alignment error can be reduced to zero or minimized. In the linear motion expansion / contraction mechanism according to the present embodiment for this “origin search”, a convex alignment that abuts the receiving piece provided on the frame 26 of the feed mechanism 25 on the connecting piece 55 on the distal end side of the arm portion 5. Department. The receiving part is typically the front edge of the frame 26.

  FIG. 4 is a view showing the structure of the alignment portions 71 and 72 of the arm portion 5 of FIG. FIG. 5 is a view showing the structure of the frame 26 of the delivery mechanism 25 of FIG. 6 is a view showing a state in which the alignment portions 71 and 72 in FIG. 4 are in contact with the receiving portions 234 and 235 in FIG. In the present embodiment, the alignment portion is provided on the connecting piece 55 of the arm portion 5. The arm unit 5 includes a connecting piece 55 for connecting the first and second pieces 53 and 54. The connecting piece 55 is typically a rectangular cylindrical body that approximates an outer shape in which the first piece 53 and the second piece 54 are joined by being shifted by ½ of the piece length. An annular flange 551 projects outward from the tip of the connecting piece 55. A cylindrical part (fixed part) 61 of a fourth joint part J4 as a torsional rotary joint part is connected to the connecting piece 55 of the arm part 5. An annular flange 61 is attached to the rear end of the cylindrical portion 60 so as to stick outward. The flange 61 at the rear end of the cylindrical portion 61 is coupled to the flange 551 of the coupling piece 55 by a spiral. As a result, the wrist 6 including the fourth joint J4 is fixed to the tip of the arm 5. When the wrist portion 6 and the arm portion 5 are fixed via the flanges 61 and 551, the hollow region of the cylindrical portion 60 of the fourth joint portion J4 communicates with the hollow region of the coupling piece 55. A motor unit 62 composed of a motor and a gear box for generating power for driving the fourth joint portion J4 is inserted into the communicating hollow region. The motor unit 62 is fitted into the cylindrical portion 60 and fixed to the inner wall thereof. An output shaft (drive shaft) 63 of the motor unit 62 projects from the tip opening of the cylindrical portion 60 and is connected to a substantially central portion of the long shaft of, for example, a strip-shaped rotating plate 64 that forms the rotating portion of the fourth joint portion J4. . The rotating plate 64 is supported by the output shaft 63 of the motor unit 62 and is driven to rotate.

  The fourth joint J4 is covered with a wrist cover 8. The wrist cover 8 covers the front portion of the coupling piece 55 together with the cylindrical portion 60 and the rotating plate 64 of the fourth joint portion J4. When the motor unit 62 is driven, the rotating plate 64 rotates with respect to the cylindrical portion 60.

  The alignment portions 71 and 72 are attached to, and typically attached to, the left side surface and the right side surface of the connecting piece 55 at the distal end portion of the arm portion 5, respectively. Needless to say, when machining the joining piece 55 from the ingot or the like, the alignment portions 71 and 72 may be machined together with the joining piece 55 in the machining process. The alignment portions 71 and 72 are typically fixed with respect to the connecting piece 55, but of course, they may be detachably provided so that the origin position can be arbitrarily changed.

  The alignment portions 71 and 72 are typically metal strip-shaped thin flat plates. The thickness of the alignment portions 71 and 72 is smaller than the distance between the side surface of the coupling piece 55 and the arm cover 15, for example, several mm. The width of the alignment portions 71 and 72 is shorter than the width of the side surface of the connecting piece 55, for example, 1/3 to 2/3, preferably 1/2 of the width of the side surface of the connecting piece 55. The alignment portions 71 and 72 are provided in parallel to the length direction of the coupling piece 55 (the direction along the telescopic axis RA3). With respect to the width direction of the side surface of the joining piece 55, the alignment portions 71 and 72 are arranged not at the upper and lower surfaces of the joining piece 55 but at the width center of the side surface. Depending on the thickness, width, and mounting position, the risk of the alignment portions 71 and 72 coming into contact with the arm cover 15 is reduced. As a result, the positioning portions 71 and 72 are attached to the tip of the arm portion 5, specifically the connecting piece 55, and the positioning portions 71 and 72 are covered with the connecting piece 55 with the arm cover 15, and the arm portion The steady operation can be continued without obstructing the expansion and contraction operation. In other words, no additional preparatory work such as removing the arm cover 15 or attaching the positioning portions 71 and 72 to the connecting piece 55 is required during the origin-finding work.

  Further, the alignment portions 71 and 72 are coupled so that the rear end positions of the alignment portions 71 and 72 are located at a position equivalent to or slightly longer than the contracted length of the arm cover 15 from the front end of the coupling piece 55. It is attached to the top 55. When the arm portion 5 is contracted most, the rear ends of the alignment portions 71 and 72 abut against the receiving portion of the frame 26 of the delivery mechanism 25, typically the front edge. The most contracted position of the arm unit 5 can be set as the origin for expansion / contraction control (extension distance is zero), and the alignment error is reduced to zero or minimized by mechanical collision.

  The frame 26 is formed by connecting a pair of side plates 261 and 262 having the same size and shape in parallel by an opening plate 263. The rear portions of the pair of side plates 261 and 262 are formed, for example, in an arc shape that can be joined to the peripheral surface of the cylindrical body 24 as the rotating portion of the second joint portion J2 that also serves as the motor housing. The pair of side plates 261 and 262 rotatably support the roller 59 and the guide roller 57 that support the arm portion 5. The opening plate 263 is a rectangular flat plate, and a rectangular opening is formed at the center thereof, which is the same as or slightly larger than the cross-sectional shape of the arm portion 5. The aperture plate 263 includes concave receiving portions 264 and 265 with which the rear ends of the alignment portions 71 and 72 of the arm portion 5 abut in order to align the arm portion 5 with the reference position with respect to the delivery mechanism 25. The receiving portions 264 and 265 are grooves having a rectangular cross section having the same shape as the rear end surfaces of the alignment portions 71 and 72 or a slightly larger bottom surface. The depths of the receiving portions 264 and 265 are the same as the depth of the cylindrical cover 34 to which one end of the arm cover 15 is connected while the alignment portions 71 and 72 are in contact with the bottom surfaces of the receiving portions 264 and 265, respectively. The distance between the rear end of the wrist cover 8 to which the end is connected is adjusted to be equivalent to or slightly longer than the most contracted length of the arm cover 15. The receiving portions 264 and 265 are not limited to being provided on the opening plate 263. For example, the receiving portions 264 and 265 may be provided on the side plates 261 and 262 as convex portions that contact the rear ends of the alignment portions 71 and 72. . In this case, the strip-shaped alignment portions 71 and 72 are formed so that their rear ends slightly protrude from the rear end of the connecting piece 55.

  “Origin origin” is an operation for determining the origin (the arm reference position of the linear expansion / contraction joint) in the operation control of the arm unit 5. Therefore, by carrying out “origin search” with the arm portion 5 being most contracted, the controllable expansion / contraction range of the arm portion 5 can be maximized. In this embodiment, since the arm part 5 is covered with the arm cover 15, the state in which the arm part 5 is most contracted is equivalent to the state in which the arm cover 15 is most contracted. The arm portion 5 includes convex alignment portions 71 and 72 that come into contact with the opening plate 263 in a state where the arm portion 5 is most contracted. The alignment portions 71 and 72 are such that the distance between the tip of the cylindrical cover 34 and the rear end of the wrist cover 8 is the most contracted of the arm cover 15 in a state where the alignment portions 71 and 72 are in contact with the opening plate 263. The position is adjusted to be equivalent to or slightly longer than the length. As a result, the user can accurately contract the arm unit 5 to a position where the alignment units 71 and 72 collide with the opening plate 263, and the position can be set to the origin on the operation control of the arm unit 5 (the linear expansion / contraction joint). The origin reference operation can be performed without removing the arm cover 15. In addition, by providing the concave receiving portions 264 and 265 on the opening plate 263, the direction perpendicular to the telescopic axis RA3 in a state where the rear end surfaces of the alignment portions 71 and 72 are in contact with the bottom surfaces of the receiving portions 264 and 265, respectively. The displacement of the arm portion 5 with respect to the opening portion is limited, and as a result, the “origin origin” can be performed more accurately than when the receiving portions 264 and 264 are not provided on the opening plate 263.

  In the present embodiment, the alignment portions 71 and 72 are provided integrally with the joining piece 55, but may be detachable from the joining piece 55. For example, screw holes are provided on both side surfaces of the connecting piece 55, and the alignment portions 71 and 72 are fastened to the connecting piece 55 with screws.

  Moreover, the position where the alignment parts 71 and 72 are provided is not limited to this embodiment. For example, the arm cover 15 may be provided with a reinforcing plate that reinforces the arm cover 15. The reinforcing plate is a thin plate-shaped annular member typically made of resin, the center of which is cut out in a rectangular shape in accordance with the rectangular shape of the cross section of the arm portion 5. The outer peripheral shape of the reinforcing plate has an outer shape corresponding to the shape of the cross section of the arm cover 15. The reinforcing plate separates the arm cover 15 from the internal structure (the frame row) such as the arm portion 5 (movable portion) of the linear motion joint mechanism, and allows the arm cover 15 to be deformed in the direction of the movement axis RA3, and the movement thereof. The upper surface of the arm portion 5 is slid inside the arm cover 15 to prevent deformation (collapse) of the arm cover 15 in a direction other than the direction, that is, typically in a direction orthogonal to the moving direction. Mounted movably. Therefore, providing the alignment portions 71 and 72 on both side surfaces of the arm portion 5 as in the present embodiment does not disturb the reinforcing plate that slides on the upper surface of the arm portion 5. Of course, when the reinforcing plate is slidably mounted on both side surfaces of the arm portion, alignment portions may be provided on the upper and lower surfaces of the coupling piece 55. Further, in the case where the arm cover 15 is not provided with a reinforcing plate, alignment portions may be provided on each of the upper, lower, left and right surfaces. As described above, the alignment portion may be provided on at least one of the upper, lower, left, and right surfaces of the connecting piece 55.

  Furthermore, the present embodiment can be applied to a case where the arm portion 5 is not covered with the arm cover 15. At this time, in a state where the alignment portions 71 and 72 are in contact with the opening plate 263, the alignment portions 71 and 72 are formed so that a slight gap is formed between the front end of the cylindrical cover 34 and the rear end of the wrist cover 8. The position of is adjusted.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  4 ... undulating part, 5 ... arm part, 6 ... wrist part, 8 ... wrist cover, 15 ... arm cover, 26 ... frame 263 ... top plate, 264, 265 ... receiving part, 53 ... first frame, 54 ... second Frame, 55... Combined frame, 71, 72.

Claims (9)

A plurality of plate-shaped first pieces that are connected to bendable at the front and rear end surfaces;
A plurality of groove-shaped second pieces which are connected to bendable at the front and rear end faces of the bottom part;
A coupling unit coupling the top of the first frame and the top of the second frame;
A feeding mechanism portion equipped with a plurality of rollers for firmly sandwiching the first and second frames from above and below and from the left and right and supporting them in a freely movable manner;
The first and second frames are joined to each other by the roller when fed forward to form a columnar arm portion together with the coupling portion and separated from each other behind the roller when pulled back. Returned to the bent state,
A convex alignment portion that abuts against a receiving portion of the delivery mechanism portion is provided on a side surface of the coupling portion to align the arm portion with a reference position with respect to the delivery mechanism portion. Dynamic expansion and contraction mechanism. The arm portion is covered with a stretchable arm cover,
The linear motion expansion / contraction mechanism according to claim 1, wherein a thickness of the alignment portion is thinner than a gap distance between a side surface of the coupling portion and the arm cover.   3. The linear motion expansion / contraction according to claim 2, wherein the rear end of the alignment portion is provided at a position equivalent to or slightly longer than the contracted length of the arm cover from the front end of the coupling portion. mechanism.   The linear motion expansion / contraction mechanism according to claim 1, wherein the alignment portion has a flat plate shape.   The linear motion expansion / contraction mechanism according to claim 1, wherein the alignment portion is provided in the center of the width of the side surface of the coupling portion.   The linear motion expansion / contraction mechanism according to claim 1, wherein the alignment portion is provided on each of both side surfaces of the coupling portion.   The linear motion expansion / contraction mechanism according to claim 1, wherein a width of the alignment portion is shorter than a width of a side surface of the coupling portion.   The linear motion expansion / contraction mechanism according to claim 1, wherein the receiving portion is a front edge of the delivery mechanism portion, and a concave portion for receiving the alignment portion is provided on the front edge.   The linear motion expansion / contraction mechanism according to claim 1, wherein the alignment portion is detachable from the coupling portion.

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