telescopic mechanism

Abstract

To provide an extendable mechanism which achieves improvement of durability.SOLUTION: An extendable mechanism 2 includes: an extendable part 4 which may extend or contract by rotation of a sending / pulling part; a base part 5 which supports the extendable part 4 in a manner that allows extension and contraction. The extendable mechanism 2 has: a plate 6 attached to a tip of the extendable part 4 in an extending / contracting direction; and a plate support part 33 fixed to the base part 5. The plate support part 33 comes into contact with a base end surface of the plate 6 when the extendable part 4 is contracted at a maximum.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an extension mechanism, and for example, to an extension mechanism including an extension section that extends and retracts by rotation of a feeding / pulling section, and a base section that supports the extension section so that it can extend and retract. [Background technology]

[0002] For example, Patent Document 1 discloses an extension mechanism and a moving body that includes a telescopic extension section and a base section that supports the extension section so that it can be extended or retracted, and that includes a support section that contacts the inner or outer peripheral surface of the extension section to suppress shaking of the base side of the extension section relative to the base section, and the support section is provided on the side of the base section that faces the inner or outer peripheral surface of the extension section that the support section contacts. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-173391 Summary of the Invention [Problem to be solved by the invention]

[0004] In the telescopic mechanism described in Patent Document 1, two belts are engaged with each other while being offset from each other to form a telescopic section, and when the screw shaft rotates in one direction with an engagement pin on one belt inserted into a spiral groove formed on the circumferential surface of the screw shaft, which is the feeding section, the two belts are fed out and wound spirally, thereby extending the telescopic section. On the other hand, when the screw shaft rotates in the other direction, the two belts are retracted, unwinding and contracting the telescopic section.

[0005] This allows the plate attached to the upper end of the extension section to be displaced in the vertical direction as the extension section extends and retracts in the vertical direction. However, if the extension mechanism receives a radial load or moment load when the extension section contracts and the plate drops to the retracted end, there is a problem in that excessive force is applied to the extension section, which may cause damage.

[0006] The present disclosure has been made to solve such problems, and aims to provide an extension mechanism with improved durability. [Means for solving the problem]

[0007] The telescopic mechanism in one embodiment comprises an extension / contraction section that extends and contracts with the rotation of the feed / pull section, and a base section that supports the extension / contraction section so that it can be extended or contracted.The telescopic mechanism has a plate attached to the tip of the extension / contraction section in the extension / contraction direction, and a plate support section fixed to the base section, and the plate support section comes into contact with the base end surface of the plate when the extension / contraction section is at its maximum contraction. [Effects of the Invention]

[0008] The present disclosure makes it possible to provide an extension mechanism with improved durability. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 3 is a longitudinal sectional view showing the contracted state of the extension / contraction mechanism according to the first embodiment. [Figure 2] FIG. 2 is a vertical cross-sectional view showing the extension mechanism according to the first embodiment in an extended state. [Figure 3] FIG. 2 is a diagram illustrating an expansion / contraction section according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Embodiment 1 Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. However, the present disclosure is not limited to the following embodiments. In addition, the following description and drawings have been simplified as appropriate for clarity of explanation.

[0011] Fig. 1 is a longitudinal cross-sectional view showing the telescopic mechanism according to the first embodiment in a contracted state. Fig. 2 is a longitudinal cross-sectional view showing the telescopic mechanism according to the first embodiment in an extended state. In Figs. 1 and 2, the plate 6 and the frame 21 are shown by two-dot chain lines to clarify the configuration of the telescopic mechanism 2. Fig. 2 also shows the upper part of the telescopic mechanism 2.

[0012] The telescopic mechanism 2 comprises a telescopic section 4 and a base section 5. The telescopic section 4 is a telescopic cylindrical body that can be extended or retracted. The base section 5 supports the telescopic section 4 so that it can be extended or retracted. A plate 6 having upper and lower surfaces that extend in a substantially horizontal direction is attached to the upper end (tip) of the telescopic section 4. The plate 6 is configured to be displaced in the vertical direction between the extended end and the retracted end as the telescopic section 4 extends or retracts in the vertical direction, which is the telescopic direction. The horizontal direction is a direction perpendicular to the vertical direction (telescopic direction).

[0013] The telescopic mechanism 2 according to this embodiment can be applied to a mobile body including a drive unit equipped with drive wheels, a motor (drive source), etc. The drive wheels, motor, etc. that constitute the drive unit of the mobile body may be supported on a base covered by, for example, a base cover. Such a mobile body moves forward, backward, and turns, for example, by independently rotating and driving the left and right drive wheels. Incidentally, the mobile body may operate by autonomous control or may operate according to external instructions.

[0014] Next, the configuration of the extension mechanism 2 of this embodiment will be described in detail. As shown in FIG. 3, the extension section 4 of the extension mechanism 2 includes a first belt 11 and a second belt 12. Here, FIG. 3 is a diagram for explaining the extension section of embodiment 1. The first belt 11 is, for example, a steel strip, and has engagement pins 11a provided at approximately equal intervals along the opposing long sides. The second belt 12 is, for example, a steel strip of the same thickness as the first belt 11, and has engagement holes 12a provided along the opposing long sides to correspond to the pitch of the engagement pins 11a.

[0015] The first belt 11 and the second belt 12 are spirally wound in a mutually offset state, with the second belt 12 positioned inside the first belt 11 in advance, to form the stretchable section 4. At this time, the engagement pins 11a of the first belt 11 protrude toward the inside of the stretchable section 4, and the engagement pins 11a on the upper side of the first belt 11 engage with the engagement holes 12a on the lower side of the second belt 12, which is positioned offset upward with respect to the first belt 11, and the engagement pins 11a on the lower side of the first belt 11 engage with the engagement holes 12a on the upper side of the second belt 12, which is positioned offset downward with respect to the first belt 11.

[0016] As shown in Figures 1 and 2, the upper ends of the first belt 11 and the second belt 12 after the stretchable portion 4 is formed are held by a belt holding portion 13 that is arranged at the upper end of the stretchable portion 4. Therefore, the plate 6 is attached to the belt holding portion 13. In addition, the upper ends of the first belt 11 and the second belt 12 after the stretchable portion 4 is formed are covered by a cylindrical belt cover 14 that is arranged outside the first belt 11.

[0017] As shown in Figures 1 and 2, the base unit 5 includes a frame 21, a main shaft 22, a first roller holding unit 23, a screw shaft (feed unit) 24, a belt guide 25, a first belt holder 26, a second belt holder 27, a second roller holding unit 28, a first roller unit 29, a second roller unit 30, a first drive unit 31, a second drive unit 32, and a plate support unit 33.

[0018] The frame 21 includes a first plate 21a, a second plate 21b, and a support pillar 21c. The first plate 21a is a plate-like body having a substantially flat upper surface. The second plate 21b is a plate-like body having a substantially flat upper surface and is disposed above the first plate 21a. A through hole is formed in the second plate 21b. The support pillar 21c is disposed on the edge of the first plate 21a and connects the first plate 21a and the second plate 21b.

[0019] The main shaft 22 includes a cylindrical portion 22a and a flange portion 22b that protrudes outward from the lower end of the cylindrical portion 22a, and the lower end of the main shaft 22 is rotatably supported by the first plate 21a. The upper end of the cylindrical portion 22a of the main shaft 22 is inserted into a through-hole of the second plate 21b of the frame 21 and protrudes upward from the second plate 21b.

[0020] The first roller holding portion 23 is a cylindrical body, and grooves 23a extending in the up-down direction are formed on the outer circumferential surface of the first roller holding portion 23. The grooves 23a are, for example, arranged at approximately equal intervals in the circumferential direction of the first roller holding portion 23. The first roller holding portion 23 is fixed to the upper end of the cylindrical portion 22a of the main shaft 22.

[0021] The screw shaft 24 includes a cylindrical portion 24a and a flange portion 24b. A spiral groove portion 24c is formed on the outer peripheral surface of the cylindrical portion 24a, into which the engagement pin 11a of the first belt 11 is inserted. The flange portion 24b protrudes outward from the lower end of the cylindrical portion 24a.

[0022] The cylindrical portion 22a of the main shaft 22 is passed through the inside of the screw shaft 24, and the screw shaft 24 is arranged between the flange portion 22b of the main shaft 22 and the first roller holding portion 23 in a state where it can rotate relative to the main shaft 22.

[0023] The belt guide 25 has a basic cylindrical shape and comprises a first portion 25a having a first outer diameter, and a second portion 25b having a second outer diameter smaller than the first outer diameter and positioned above the first portion 25a.

[0024] The first portion 25a of the belt guide 25 has an opening through which the second belt 12 passes. Department The second portion 25b of the belt guide 25 has an opening through which the first belt 11 is passed. Department It is formed.

[0025] The cylindrical portion 24 a of the screw shaft 24 is passed through the inside of the belt guide 25 , and the lower end of the belt guide 25 is fixed to the flange portion 24 b of the screw shaft 24 .

[0026] This allows the screw shaft 24 and the belt guide 25 to rotate around the main shaft 22. At this time, a gap is formed between the outer peripheral surface of the cylindrical portion 24a of the screw shaft 24 and the inner peripheral surface of the belt guide 25, allowing the first belt 11 and the second belt 12 to pass through in an overlapping state.

[0027] The first belt holder 26 accommodates the second belt 12 in a belt state before the formation of the stretchable portion 4. The first belt holder 26 is basically a cylindrical body with a bottom, and a through hole 26a is formed in the bottom of the first belt holder 26.

[0028] The belt guide 25 is passed through the through hole 26a of the first belt holder 26, and the first belt holder 26 is supported by the flange portion 24b of the screw shaft 24 in a state in which the first belt holder 26 is rotatable relative to the belt guide 25.

[0029] The second belt holder 27 accommodates the first belt 11 in a belt state before forming the stretchable portion 4. The second belt holder 27 has substantially the same shape as the first belt holder 26, and has a through hole 27a formed in the bottom portion of the second belt holder 27.

[0030] The second belt holder 27 is disposed above the first belt holder 26. The belt guide 25 is passed through a through-hole 27a of the second belt holder 27, and the second belt holder 27 is supported by a step portion between a first portion 25a and a second portion 25b of the belt guide 25 in a state in which the second belt holder 27 is rotatable relative to the belt guide 25.

[0031] The second roller holding portion 28 includes a cylindrical portion 28a and a flange portion 28b. The cylindrical portion 28a has an inner diameter larger than the outer diameter of the first roller holding portion 23, and grooves 28c extending in the up-down direction are formed on the inner circumferential surface of the cylindrical portion 28a. The grooves 28c are arranged, for example, at approximately equal intervals in the circumferential direction of the cylindrical portion 28a. The flange portion 28b is formed to protrude outward from the lower end of the cylindrical portion 28a.

[0032] Then, with the first roller holding portion 23 inserted inside the second roller holding portion 28, the flange portion 28b of the second roller holding portion 28 is fixed to the second plate 21b of the frame 21. At this time, it is preferable that the groove portion 23a of the first roller holding portion 23 and the groove portion 28c of the second roller holding portion 28 are arranged so as to roughly face each other.

[0033] The first roller unit 29 includes rollers 29a and a fixing jig 29b. The rollers 29a are rotatable around rotation shafts 29c that extend substantially horizontally, and a plurality of rollers 29a are arranged vertically.

[0034] Fixing jig 29b is formed in a substantially C-shape when viewed from above, and supports roller 29a via rotation shaft 29c with roller 29a disposed inside fixing jig 29b. First roller unit 29 is fitted into groove 23a of first roller holding part 23 and fixed.

[0035] The second roller unit 30 has the same configuration as the first roller unit 29, and therefore a detailed description thereof will be omitted, but the second roller unit 30 has a configuration in which a plurality of rollers 30a arranged in the vertical direction are rotatably fixed to a fixing jig 30b via a rotation shaft 30c. The second roller unit 30 is fixed by being fitted into a groove 28c of the second roller holding part 28.

[0036] At this time, a gap is formed between the roller 29a of the first roller unit 29 and the roller 30a of the second roller unit 30, through which the first belt 11 and the second belt 12 can pass in an overlapping state, and when viewed from the top and bottom, the gap is positioned so as to approximately overlap with the gap between the outer surface of the cylindrical portion 24a of the screw shaft 24 and the inner surface of the belt guide 25.

[0037] The rollers 29a of the first roller unit 29 and the rollers 30a of the second roller unit 30 are arranged so that when the first belt 11 and the second belt 12 pass through the gap between the rollers 29a of the first roller unit 29 and the rollers 30a of the second roller unit 30 while overlapping each other, the rollers 29a of the first roller unit 29 come into contact with the inner surface of the second belt 12 and the rollers 30a of the second roller unit 30 come into contact with the outer surface of the first belt 11.

[0038] The first drive unit 31 includes a motor 31a and a drive transmission unit 31b. Although not shown in detail, the motor 31a is supported by the second plate 21b of the frame 21. The drive transmission unit 31b includes a pinion gear 31c, a pulley 31d, and a belt 31e.

[0039] The pinion gear 31c is fixed to the output shaft of the motor 31a. The pulley 31d is a ring gear with teeth formed on its outer circumferential surface, and the inner circumferential portion of the pulley 31d is fixed to the upper end of the belt guide 25 so as to be able to transmit driving force. The belt 31e is an endless belt with teeth formed on its inner circumferential surface, and is stretched between the pinion gear 31c and the pulley 31d.

[0040] The second drive unit 32 includes a motor 32a and a drive transmission unit 32b. Although not shown in detail, the motor 32a is supported by the first plate 21a of the frame 21. The drive transmission unit 32b includes a pinion gear 32c, a ring gear 32d, an external tooth portion 32e, a planetary gear 32f, and a belt 32g.

[0041] The pinion gear 32c is fixed to the output shaft of the motor 32a. The ring gear 32d is rotatably supported by the flange portion 22b of the main shaft 22, and teeth are formed on the outer and inner peripheral surfaces of the ring gear 32d. The external teeth 32e are formed on the outer peripheral surface of the flange portion 24b of the screw shaft 24.

[0042] The planetary gear 32f includes a rotating shaft 32h, a first gear portion 32i, and a second gear portion 32j. The rotating shaft 32h extends in the vertical direction, and a lower end portion of the rotating shaft 32h is rotatably supported by the flange portion 22b of the main shaft 22. The first gear portion 32i is a gear provided on the rotating shaft 32h, and is engaged with teeth formed on the inner peripheral surface of the ring gear 32d.

[0043] The second gear portion 32j is a gear provided on the rotary shaft 32h, and is meshed with the external teeth portion 32e formed on the flange portion 24b of the screw shaft 24. In this case, in the illustrated example, the second gear portion 32j is disposed above the first gear portion 32i, but the second gear portion 32j may also be disposed below the first gear portion 32i.

[0044] When the rotational speed transmitted to the screw shaft 24 by the first drive unit 31 to rotate the screw shaft 24 and the rotational speed transmitted to the screw shaft 24 by the second drive unit 32 to rotate the screw shaft 24 are equal, the telescopic unit 4 rotates via the main shaft 22, and when the rotational speeds are different, the telescopic unit 4 telescopes.

[0045] In other words, when the rotation speed of the screw shaft 24 caused by the first drive unit 31 to rotate the screw shaft 24 and the rotation speed of the screw shaft 24 caused by the second drive unit 32 to rotate the screw shaft 24 are equal, the telescopic unit 4 rotates via the main shaft 22, and when the rotation speeds are different, the telescopic unit 4 extends and retracts. Here, when viewing the telescopic mechanism 2 from above, the rotation of the screw shaft 24 in one direction is represented as "+" and the rotation of the screw shaft 24 in the other direction is represented as "-".

[0046] In this case, the first drive unit 31 and the second drive unit 32 may satisfy, for example, the following conditions: The extension / contraction movement of the extension / contraction unit 4 is the difference in the amount of rotation between the main shaft 22 and the screw shaft 24, and can be expressed by the following equation 1.

number

[0047] where v p is the expansion / contraction speed of the expansion / contraction section 4, p is the pitch length of the groove section 24c of the screw shaft 24, ω s is the rotation speed of the screw shaft 24, ω m indicates the rotation speed of the main shaft 22.

[0048] At this time, the rotation speed ω of the frame 21 relative to the main shaft 22 is p corresponds to the rotation speed of the main shaft 22, and can be expressed by the following equation 2.

number

[0049] Further, due to the relationship of the planetary gear 32f, the following equation 3 is satisfied.

number

[0050] Here, Z1 is the number of teeth of the second gear portion 32j of the planetary gear 32f, Z s is the number of teeth of the external tooth portion 32e formed on the flange portion 24b of the screw shaft 24, and ω y is the rotation speed of the planetary gear 32f, ω i is the rotation speed of the ring gear 32d, Z2 is the number of teeth of the first gear portion 32i of the planetary gear 32f, Z i indicates the number of teeth formed on the inner peripheral surface of the ring gear 32d.

[0051] In this case, assume that <Number 4>

number

[0052] From the above, ω y can be eliminated to derive number 5.

number

[0053] Therefore, if we use <Number 6>, we can derive <Number 7>.

number

number

[0054] Using the inverse matrix, it can be expressed as <Equation 8>.

number

[0055] Also, from the statics relationship, it can be expressed by equation 9.

number

[0056] where τ s is the torque input to the screw shaft 24, τ i is the torque input to the ring gear 32d, F p is the stretching force of the stretchable part 4, T P indicates the output torque of the frame 21 relative to the main shaft 22.

[0057] In addition, when the expandable portion 4 only performs expansion and contraction operations, if the conditions of the following <Equation 10> and <Equation 11> are satisfied, it can be expressed by <Equation 12> and <Equation 13>.

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number

number

[0058] On the other hand, when the extension / contraction section 4 only performs a turning motion, if the conditions of the following <Equation 14> and <Equation 15> are satisfied, it can be expressed by <Equation 16> and <Equation 17>.

number

number

number

number

[0059] Therefore, in both the extension and retraction operation of the extension section 4 and the rotation operation, the outputs of the motor 31a of the first drive section 31 and the motor 32a of the second drive section 32 can be combined.

[0060] Note that <Equation 4> assumed along the way is intended to obtain the above relationship when equivalent outputs can be obtained from the motor 31a of the first drive unit 31 and the motor 32a of the second drive unit 32. Therefore, <Equation 4> does not necessarily have to be satisfied when the outputs of the motor 31a of the first drive unit 31 and the motor 32a of the second drive unit 32 are different.

[0061] The plate support portion 33 includes a cylindrical portion 33a and a flange portion 33b that protrudes inward from the upper end of the cylindrical portion 33a. The cylindrical portion 33a has an inner diameter that is larger than the outer diameter of the flange portion 28b of the second roller holding portion 28. The flange portion 33b has an inner diameter that is larger than the outer diameters of the belt holding portion 13 and the belt cover 14. The flange portion 33b has a substantially flat upper surface. The upper surface of the flange portion 33b is disposed so as to extend substantially horizontally at the position of the contracted end.

[0062] Then, with the extension / contraction unit 4, the belt holding unit 13, and the belt cover 14 passing through the inside of the plate support unit 33, the lower end of the tubular unit 33a is fixed to the second plate 21b of the frame 21. In other words, the plate support unit 33 is fixed to the base unit 5. Therefore, the plate support unit 33 does not move when the extension / contraction unit 4 extends or contracts. Furthermore, the plate support unit 33 is disposed with a gap between it and the outer peripheral surfaces of the belt holding unit 13 and the belt cover 14. Therefore, the plate support unit 33 does not interfere with the extension / contraction unit 4 when the extension / contraction unit 4 extends or contracts. In this way, the plate support unit 33 does not affect the movement of the extension / contraction unit 4.

[0063] When the telescopic unit 4 is fully contracted, the plate support part 33 comes into contact with the lower surface (base end surface) of the plate 6 attached to the upper end of the telescopic unit 4. That is, when the telescopic unit 4 contracts and the plate 6 descends, the lower surface of the plate 6 comes into contact with the upper surface of the plate support part 33 at the contracted end position. Therefore, in the telescopic mechanism 2, the plate 6 located at the contracted end is supported by the plate support part 33. Furthermore, when the telescopic unit 4 is fully contracted, if the belt holding part 13 is displaced horizontally due to stress, the outer peripheral surface of the belt holding part 13 (more specifically, the outer peripheral surface of the upper end of the belt holding part 13) comes into contact with the inner peripheral surface of the flange part 33b of the plate support part 33. At this time, the belt holding part 13 is supported horizontally by the plate support part 33 fixed to the base part 5, and therefore at least a portion of the stress generated in the belt holding part 13 can be supported by the base part 5 via the plate support part 33.

[0064] The telescopic mechanism 2 configured in this manner can realize the extension and retraction motions and the swinging motions of the telescopic section 4 by using the first drive unit 31 and the second drive unit 32. Moreover, the extension and retraction motions and the swinging motions of the telescopic section 4 can be realized by combining the outputs of the motor 31a of the first drive unit 31 and the motor 32a of the second drive unit 32. Therefore, the motors 31a and 32a can be made smaller than when two motors are used and the extension and retraction motions and the swinging motions of the telescopic section 4 are realized individually using the outputs of each motor.

[0065] Hereinafter, the operation of the extension / retraction unit 4 of the extension / retraction mechanism 2 of this embodiment will be described. The motor 31a of the first drive unit 31 and the motor 32a of the second drive unit 32 are rotationally driven so that the rotation speed transmitted to the screw shaft 24 by the first drive unit 31 to rotate the screw shaft 24 is different from the rotation speed transmitted to the screw shaft 24 by the second drive unit 32 to rotate the screw shaft 24. The rotational drive force of the motor 31a is transmitted to the screw shaft 24 via the drive transmission unit 31b of the first drive unit 31 and the belt guide 25, and the rotational drive force of the motor 32a is transmitted to the main shaft 22 and the screw shaft 24 via the drive transmission unit 32b of the second drive unit 32.

[0066] This causes the screw shaft 24 to rotate differentially relative to the main shaft 22, and as the screw shaft 24 rotates, the first belt 11 and the second belt 12 are sent out and wound spirally, causing the stretchable section 4 to extend, or the first belt 11 and the second belt 12 engage with each other and unwind from their wound state, causing the stretchable section 4 to contract.

[0067] In this case, in the telescopic mechanism 2 of this embodiment, the lower part of the telescopic section 4 is sandwiched between the roller 29a of the first roller unit 29 and the roller 30a of the second roller unit 30 in the thickness direction of the telescopic section 4, thereby suppressing vibration of the telescopic section 4.

[0068] Next, a description will be given of the operation of the telescopic unit 4 of the telescopic mechanism 2 of this embodiment when it rotates. The motor 31a of the first drive unit 31 and the motor 32a of the second drive unit 32 are rotationally driven so that the rotation speed transmitted to the screw shaft 24 by the first drive unit 31 to rotate the screw shaft 24 is equal to the rotation speed transmitted to the screw shaft 24 by the second drive unit 32 to rotate the screw shaft 24. The rotational drive force of the motor 31a is transmitted to the screw shaft 24 via the drive transmission unit 31b of the first drive unit 31 and the belt guide 25, and the rotational drive force of the motor 32a is transmitted to the main shaft 22 and the screw shaft 24 via the drive transmission unit 32b of the second drive unit 32.

[0069] As a result, the main shaft 22 and the screw shaft 24 rotate equally, and the main shaft 22, the screw shaft 24, the belt guide 25 and the extension / contraction unit 4 rotate integrally, resulting in the extension / contraction unit 4 turning relative to the base unit 5.

[0070] When a moving body equipped with the telescopic mechanism 2 moves or performs other operations, the telescopic mechanism 2 may be subjected to a load (external force) due to an unexpected movement of the moving body or the moving body accidentally coming into contact with something. For example, in a configuration in which the plate support part 33 is omitted from the telescopic mechanism 2, the plate 6 cannot be supported by the base part 5. Therefore, when the telescopic part 4 contracts and the plate 6 drops to the contracted end position, if the telescopic mechanism 2 receives a radial load or a moment load, excessive force may be applied to the telescopic part 4. As a result, there is a risk that the telescopic part 4 may be damaged.

[0071] In contrast, in this embodiment, when the extension / contraction section 4 contracts and the plate 6 drops to the contracted end, it is supported by the plate support section 33 fixed to the base section 5. At this time, at least a portion of the radial load and moment load received by the extension / contraction mechanism 2 is supported by the base section 5 via the plate support section 33, thereby reducing the force that may be applied to the extension / contraction section 4 and preventing damage to the extension / contraction section 4. In this way, according to this embodiment, the durability of the extension / contraction mechanism 2 can be improved.

[0072] The present invention is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the invention. For example, the extension / contraction unit 4 in the above embodiment has been described as a telescopic extension / contraction unit 4, but the extension / contraction unit 4 may be configured to be extendable and contractable by rotation of the retracting unit. For example, in the telescopic mechanism 2 of the above embodiment, the telescopic part 4 is configured to be rotatable, but it may be configured to be non-rotatable. For example, although the extension mechanism 2 in the above embodiment includes the first roller unit 29 and the second roller unit 30, the first roller unit 29 and the second roller unit 30 may be omitted. [Explanation of symbols]

[0073] 2 Telescopic mechanism 4 Telescopic part 5 Base 6 plates 11 first belt, 11a engagement pin 12 second belt, 12a engagement hole 13 Belt holder 14 Belt cover 21 frame, 21a first plate, 21b second plate, 21c support 22 main shaft, 22a cylindrical portion, 22b flange portion 23 first roller holding portion, 23a groove portion 24 screw shaft, 24a cylindrical portion, 24b flange portion, 24c groove portion 25 Belt guide, 25a first part, 25b second part minutes 2 6 First belt holder, 26a Through hole 27 second belt holder, 27a through hole 28 second roller holding portion, 28a cylindrical portion, 28b flange portion, 28c groove portion 29 first roller unit, 29a roller, 29b fixing jig, 29c rotating shaft 30 second roller unit, 30a roller, 30b fixing jig, 30c rotating shaft 31 First drive unit 31a Motor 31b drive transmission part, 31c pinion gear, 31d pulley, 31e belt 32 Second drive unit 32a motor 32b drive transmission part, 32c pinion gear, 32d ring gear, 32e external teeth part 32f planetary gear, 32g belt, 32h rotating shaft 32i 1st gear, 32j 2nd gear, 32g Belt 33 plate support portion, 33a cylindrical portion, 33b flange portion

Claims

[Claim 1] An extension mechanism including an extension unit that extends and retracts by rotation of a feeding / pulling unit, and a base unit that supports the extension unit so that the extension unit can extend and retract, a belt holding portion that is disposed at a tip end of the stretchable portion in the stretching direction and that holds a first belt and a second belt that are wound spirally in a mutually offset state to form the stretchable portion; a plate attached to the belt holding portion; a plate support portion fixed to the base portion; a first roller holding portion provided on the base portion so as to be disposed between the belt holding portion and the feeding portion, and having a first roller unit fixed thereto that contacts an inner peripheral surface of the extension portion; and the expansion / contraction section is regulated by the belt holding section contacting the first roller holding section when contracting, and contracts to the maximum extent; The plate support portion contacts the base end surface of the plate when the expansion / contraction portion is fully contracted, and contacts the outer peripheral surface of the belt holding portion when the belt holding portion is displaced in a direction perpendicular to the expansion / contraction direction due to stress when the expansion / contraction portion is fully contracted.

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