Flexible tube for insertion apparatus, insertion apparatus, and method for manufacturing flexible tube for insertion apparatus

Abstract

A universal cord 1 of an endoscope 9 comprises: an elongated cylinder 10 including a spiral tube 20 obtained by spirally winding a strip-shaped plate and a flexible tube 30 provided on the outer circumferential surface of the spiral tube 20, the cylinder 10 having a first end 10A and a second end 10B; two substantially cylindrical bases including a first base 41 fixed to the first end 10A and a second base 42 fixed to the second end 10B; and a wire 50 having a third end 50A and a fourth end 50B, the third end 50A being fixed to the first base 41, the fourth end 50B being fixed to the second base 42, the wire 50 extending through the cylinder 10 and having a smaller elongation rate than the elongation rate of the cylinder 10.

Description

Flexible tube of insertion device, insertion device, and method for manufacturing flexible tube of insertion device

[0001] SUMMARY OF THE INVENTION Embodiments of the present invention relate to flexible tubes of insertion instruments, insertion instruments, and methods for manufacturing flexible tubes of insertion instruments.

[0002] The universal cord of an endoscope, which is a flexible tube of an insertion device, is a connection cord between the control section of the endoscope and a connector that is connected to an external device (for example, a video processor or a light source device).

[0003] Japanese Patent Application Laid-Open No. 11-332818 discloses a universal cord having a laminated structure in which a flex, which is a spiral tube made of a thin band-shaped plate wound in a spiral shape, a braid, which is a mesh tube made of thin metal wires or synthetic fibers, and an outer cover (tube) made of resin are stacked in this order.

[0004] Japanese Patent Application Publication No. 11-332818

[0005] Universal cords (flexible tubes in insertion devices) that do not have a braided tube are more likely to stretch than conventional universal cords due to external stress and changes over time, which can have a negative impact on the tubes and signal lines that pass through them, such as channels, and raises concerns about reduced reliability.

[0006] An object of the present invention is to provide a flexible tube for an insertion instrument with guaranteed reliability, an insertion instrument with guaranteed reliability, and a method for manufacturing a flexible tube for an insertion instrument with guaranteed reliability.

[0007] The flexible tube of an insertion instrument according to an embodiment of the present invention includes a helical tube formed by helically winding a strip-shaped plate and a flexible tube attached to the outer surface of the helical tube, and is further equipped with: an elongated cylinder having a first end and a second end; two mouthpieces consisting of a first mouthpiece fixed to the first end and a second mouthpiece fixed to the second end; and a wire having a third end and a fourth end, the third end fixed to the first mouthpiece and the fourth end fixed to the second mouthpiece, the wire having an elongation rate smaller than that of the cylinder, and inserted through the cylinder.

[0008] An insertion instrument according to an embodiment of the present invention is an insertion instrument to be inserted into a subject, and includes a flexible tube, the flexible tube including a helical tube formed by helically winding a strip-shaped plate, and a flexible tube provided on the outer surface of the helical tube, and further includes: an elongated cylinder having a first end and a second end; two mouthpieces consisting of a first mouthpiece fixed to the first end and a second mouthpiece fixed to the second end; and a wire having a third end and a fourth end, the third end fixed to the first mouthpiece and the fourth end fixed to the second mouthpiece, the wire passing through the cylinder and having an elongation rate smaller than that of the cylinder.

[0009] A method for manufacturing a flexible tube of an insertion device according to an embodiment of the present invention involves creating a helical tube by winding a strip-shaped metal plate spirally in the longitudinal direction, providing a flexible tube extending in the longitudinal direction on the surface side of the helical tube to form a cylinder, attaching a nozzle to each end of the cylinder, inserting a wire having an elongation rate smaller than that of the cylinder into the cylinder, and fixing each end of the wire to the nozzle.

[0010] According to embodiments of the present invention, it is possible to provide a flexible tube of an insertion instrument with guaranteed reliability, an insertion instrument with guaranteed reliability, and a method for manufacturing a flexible tube of an insertion instrument with guaranteed reliability.

[0011] FIG. 1 is a perspective view of an endoscope according to an embodiment. FIG. 2 is a perspective view of a universal cord according to an embodiment. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. FIG. 4 is an exploded perspective view of a universal cord according to an embodiment. FIG. 5 is a partial cross-sectional view of a universal cord according to a modified embodiment. FIG. 6 is a flowchart of a method for manufacturing a universal cord according to an embodiment. FIG. 7 is a diagram of a core and a mold for manufacturing a tube according to a reference example. FIG. 8A is a cross-sectional view for explaining the method for manufacturing a tube according to a reference example. FIG. 8B is a cross-sectional view for explaining the method for manufacturing a tube according to a reference example. FIG. 8C is a cross-sectional view for explaining the method for manufacturing a tube according to a reference example. FIG. 8D is a cross-sectional view for explaining the method for manufacturing a tube according to a reference example.

[0012] <Embodiment> The universal cord of an endoscope, which is a flexible tube of an insertion instrument, will be described below using the drawings. The drawings based on the embodiment are schematic. The relationship between the thickness and width of each part in the drawings, the thickness ratio of each part, etc., differ from the actual ones. The drawings also include parts where the dimensional relationships and ratios differ. The drawings omit the illustration and reference numerals of some components.

[0013] 1 includes an insertion section 90 to be inserted into the body of a subject, an operation section 94 provided on the proximal end side of the insertion section 90, and a universal cord 1 extending from the operation section 94. A plurality of tubes such as a channel (suction conduit) 80 and a plurality of signal lines are inserted through the universal cord 1.

[0014] The endoscope 9 is, for example, a single-use endoscope that is disposed of after a single use. The endoscope 9 may be used for medical purposes or industrial purposes.

[0015] The insertion section 90 is made up of a distal end section 91 on the distal side, a bending section 92 disposed on the proximal end side of the distal end section 91, and a thin flexible tube 93 connecting the proximal end side of the bending section 92 to the operation section 94. Although not shown, an imaging unit, an illumination optical system, etc. are disposed in a hard member 91A of the distal end section 91. The hard member 91A is made of metal (e.g., stainless steel) or resin (e.g., epoxy resin, ABS resin).

[0016] The connection portions of the members of the insertion section 90 (the tip section 91 and the bending section 92, the bending section 92 and the flexible tube 93, and the flexible tube 93 and the operating section 94) are fixed by winding a thread and further reinforced with resin. The connection portions may be fixed with pins instead of winding a thread, or may be fixed only with resin. The connection portions of the members of the insertion section 90 (the tip section 91 and the bending section 92, the bending section 92 and the flexible tube 93, and the flexible tube 93 and the operating section 94) are fixed with pins, screws, rivets, etc., and further reinforced with resin such as adhesive. The connection portions may be fixed only with resin, or only with pins, screws, rivets, etc.

[0017] The operation section 94 is provided with an insertion port H80 of a treatment tool channel for introducing a treatment tool or the like into the insertion section 90. As will be described later, the channel 80 serves not only as a treatment tool channel but also as a suction tube, and therefore has a Y-shaped branch section 80Y.

[0018] The operation unit 94 is provided with various operation switches including a bending operation dial 94A. A plurality of bending operation wires (not shown) are fixed to the bending operation dial 94A, and the wires pass through flexible tubes 93 and have their ends fixed to the bending portion 92. The bending portion 92 bends in response to the rotation of the bending operation dial 94A.

[0019] Although not shown, the outer peripheral surface of the base of the flexible tube 93 is formed with a plurality of elongated protrusions that engage with a plurality of V-grooves on the inner surface of the fixing hole of the operation unit 94. This makes it easy to align the rotation direction of the bending operation dial 94A with the bending direction of the bending unit 92 during manufacturing. Note that by forming more V-grooves than protrusions, fine adjustment of the rotation direction and bending direction becomes possible. For example, if a plurality of V-grooves are formed at 5-degree intervals along the circumferential direction, the rotation direction and bending direction can be adjusted with an accuracy of within 5 degrees to fix the flexible tube 93 to the operation unit 94.

[0020] In an endoscope having an elevator in the rigid member 91A that controls the protrusion direction of a treatment tool, an elevator control wire (not shown) for controlling the elevator is inserted through the insertion section 90 and extends to an operation lever 94B of the operation section 94. Rotation of the operation lever 94B is converted into linear motion by, for example, a moving member held between two rails, and the elevator control wire is connected to a rod connected to the moving member. The rod, bending control wire, and elevator control wire are coated on their outer surfaces with a lubricating liquid (e.g., silicone oil) to improve sliding properties against bearings, etc.

[0021] The various wires passing through the insertion portion 90 and the universal cord 1 may be inserted in a resin tube. For the resin tube, a block copolymer composed of a rigid polyamide block and a flexible polyether block is preferable, instead of an expensive fluororesin. Block copolymers are relatively inexpensive, and by controlling the composition and ratio of the multiple blocks, the desired flexibility and elasticity can be achieved without the need for plasticizers.

[0022] 2 to 4 includes a tube 10, two resin bases 40, and a wire 50. The tube 10 includes a helical tube 20 around which a strip-shaped plate is wound in a spiral shape, and a flexible resin tube 30 provided on the outer circumferential surface of the helical tube 20.

[0023] The elongated cylindrical tube 10 has a first end 10A and a second end 10B opposite to the first end 10A. Of the two substantially cylindrical nozzles 40, a first nozzle 41 is fixed to the first end 10A of the tube 10, and a second nozzle 42 is fixed to the second end 10B of the tube 10.

[0024] The wire 50 has a third end 50A and a fourth end 50B opposite the third end 50A. The third end 50A of the wire 50 is fixed to the first nozzle 41, and the fourth end 50B is fixed to the second nozzle 42. The wire 50 is inserted through the tube 10, and the elongation rate ΔL50 of the wire 50 is smaller than the elongation rate ΔL10 of the tube 10.

[0025] In this specification, the elongation ΔL is calculated from the length L1 under no load at room temperature (25°C) and the length L2 when one end is fixed and a load of 40 N is applied to the other end. In other words, the elongation ΔL % is ((L2-L1) / L1)×100.

[0026] The universal cord 1 differs from conventional universal cords in that it does not have a braid, which is a mesh tube made of thin metal wires, synthetic fibers, or the like.

[0027] The universal cord 1 is less expensive and more flexible than conventional universal cords with a mesh tube. Furthermore, the universal cord 1 has lower torsional rigidity, making it easier to handle than conventional universal cords. Furthermore, the universal cord 1 does not require angle adjustment of the caps on both ends, reducing assembly time and making it easier to manufacture.

[0028] However, universal cords without a mesh tube are more likely to stretch than conventional universal cords due to external stress and changes over time, which can have a negative impact on the tubes and signal lines that pass through them, such as channels, and raises concerns about reduced reliability.

[0029] However, the universal cord 1 is provided with the wire 50 that restricts the elongation and deformation of the tube 10, and flexibility, kink resistance, and stretch prevention are guaranteed, so reliability is guaranteed.

[0030] The detailed configuration of the universal cord 1 will be described below.

[0031] The spiral tube 20 may be made of a hard resin plate having elasticity instead of a metal plate. The tube 30 is made of a soft resin such as polyurethane. The wire 50 is preferably a cable made of a plurality of twisted metal wires made of stainless steel, for example, because it has excellent flexibility. The wire 50 may be covered on its outer periphery with a resin film or inserted into a resin tube whose inner diameter is approximately the same as the outer diameter of the wire 50.

[0032] The elongation rate ΔL50 of the wire 50 is preferably less than 10% of the elongation rate ΔL10 of the tube 10. If the elongation rate ΔL50 is less than 10% of the elongation rate ΔL10, the elongation deformation of the tube 10 can be restricted, and therefore the universal cord 1 has high reliability.

[0033] For example, the elongation ΔL10 of the tube 10 is 0.7%, and the elongation ΔL50 of the wire 50 is 0.03%.

[0034] 2, the first base 41 has a notch C41 which is a first through-path through which the wire 50 is inserted. The second base 42 has a notch C42 which is a second through-path through which the wire 50 is inserted.

[0035] The wire 50 has its third end 50A fixed to the outer surface 41SB of the first nozzle 41, passes through the notch C41, passes inside the tube 10, passes through the notch C42, and its fourth end 50B fixed to the outer surface 42SB of the second nozzle 42.

[0036] The third end 50A of the wire 50 is fixed to the first nozzle 41, extends along the outer surface 41SB in the direction opposite to the direction in which the second nozzle 42 is provided, passes through the notch C41, and extends through the tube 10 in the direction in which the second nozzle 42 is provided. The fourth end 50B of the wire 50 is fixed to the second nozzle 42, extends along the outer surface 42SB in the direction opposite to the direction in which the first nozzle 41 is provided, and passes through the notch C42 and extends through the tube 10 in the direction in which the first nozzle 41 is provided. The wire 50 inserted through the tube 10 may be fixed to at least one location on the inner surface of the tube 10.

[0037] The through passage may be a through hole instead of a notch, but the operation of inserting the wire 50 is easier through a notch than through a through hole.

[0038] The wire 50 is fixed to the first base 41 and the second base 42 by respective screws 62 .

[0039] 4 and 5, the second nozzle 42, although not shown, also has an annular groove T40 into which the end of the tube 10 is inserted. The groove T40 has an inner wall surface T40SA with a diameter D40A slightly larger than the inner diameter D10A of the tube 10, and an outer wall surface T40SB with a diameter D40B larger than the outer diameter D10B of the tube 10.

[0040] When the tube 10 is inserted into the groove T40, the tube 10 expands in diameter as it is pushed into the groove T40, and the inner diameter D10A becomes the diameter of the inner wall surface of the groove T40. Because the end of the spiral tube 20 made of a metal plate is inserted into the groove T40 of the base 40, there is no risk of the tubes and wiring passing through the tube 10 being damaged by the end face of the metal plate.

[0041] Since each of the two nozzles 40 is made of a transparent material, for example, polycarbonate resin, the position of the tip of the tube 10 inserted into the groove T40 can be seen from the outside. This makes it possible to confirm that the tip of the tube 10 has been inserted to a predetermined position in the groove T40. Only a portion of each of the two nozzles 40 may be made of a transparent material, as long as the tip of the inserted tube 10 can be seen from the outside.

[0042] The space between the outer diameter D10B of the tube 10 and the outer wall surface T40SB of the groove T40 is filled with adhesive 63. Since the tube 10 is fixed by the adhesive 63 while inserted into the groove T40 of the nozzle 40, the tube 10 is firmly fixed to the nozzle.

[0043] That is, the tube 10, whose tip is coated with adhesive 63, is inserted into the groove T40, and the adhesive 63 is cured. The adhesive 63 is, for example, an ultraviolet-curable resin that can be cured in a short time. The ends of the spiral tube 20 and the tube 30 are simultaneously fixed to the nozzle 40. Fixing using an adhesive is simpler and less expensive than, for example, fixing using brazing or pins.

[0044] The nozzle 40 may be joined to the tube 10 by so-called crimping. That is, the end of the tube 10 is inserted into the groove T40 of the nozzle 40, and then force is applied to the outer periphery of the nozzle 40 to plastically deform the nozzle 40, thereby firmly fixing the nozzle 40 to the tube 10. The nozzle 40 may be fixed to the tube 10 by crimping and adhesive in combination.

[0045] The universal cord 1 has a first base 41 fixed to an operation section 94 of the endoscope 9, and a second base 42 fixed to a connector 95 that is connected to an external device.

[0046] <Method of Manufacturing Universal Cord> A method of manufacturing a universal cord will be described with reference to the flowchart of FIG.

[0047] <Step S10> A strip-shaped metal plate is spirally wound in the longitudinal direction to produce an elongated spiral tube 20.

[0048] <Step S20> The helical tube 20 is inserted into the flexible tube 30 to produce the cylinder 10. As a specific method, for example, the flexible tube 30 is provided on the surface side of the helical tube 20 to produce the cylinder 10. For example, air is blown into the tube 30, and the helical tube 20 is inserted into the tube 30 in an expanded state. It is preferable that the inner diameter of the tube 30 is slightly larger than the outer diameter of the helical tube 20.

[0049] <Step S30> A nozzle 40 is attached to each end of the tube 10. That is, the end of the tube 10 to which the adhesive 63 has been applied is pressed into the groove T40 of the nozzle 40, and then the adhesive 63 is cured. The adhesive 63 is, for example, an ultraviolet-curable urethane acrylate resin. The adhesive is cured by ultraviolet irradiation or a combination of ultraviolet irradiation and thermal curing.

[0050] <Step S40> The wire 50, which has an elongation rate smaller than that of the tube 10, is inserted into the tube 10, and the third end 50A and the fourth end 50B of the wire 50 are fixed to the respective nozzles 40. That is, the screw 62 around which the end of the wire 50 is wound is inserted into the threaded hole of the nozzle 40. The wire 50 may be fixed by a fixing device including a screw or a pin, or by adhesive.

[0051] The wire 50 is set to a length that allows the wire 50 to be substantially straight inside the tube 10 when the tube 10 is arranged in a straight line. In other words, the length of the wire 50 is substantially the same as the length of the tube 10.

[0052] According to the method for manufacturing a universal cord of this embodiment, an inexpensive universal cord can be easily manufactured.

[0053] As shown in Fig. 3, in the universal cord 1, the wire 50 is inserted through the inner surface 20SA of the helical tube 20. To prevent the wire 50 from moving within the helical tube 20, the wire 50 may be fixed to a guide member (not shown) provided on the helical tube 20. As already explained, the inner diameter of the tube 30 is slightly larger than the outer diameter of the helical tube 20, and therefore, as shown in Fig. 5, the wire 50 may be inserted between the outer surface 20SB of the helical tube 20 and the inner surface 30SA of the tube 30.

[0054] <Reference Example> As already explained, the channel 80 (suction tube) of the endoscope 9 has a branching portion 80Y. The endoscope 9 is also provided with other channel conduits, such as an air and water supply tube (not shown). The air and water supply tube also has a location where multiple tubes are connected together, like the branching portion 80Y. If the location where multiple tubes are connected together (the branching portion) is constructed with a metal Y-shaped tube, the cost will be high, and even if it is constructed with a resin Y-shaped tube, the assembly cost will be high and the resin will become waste when the endoscope is disposed of. For this reason, there has been a demand for cost reduction without using a Y-shaped tube.

[0055] To manufacture a channel 81 such as an air / water pipe having a branched section, an upper die 71, an upper core 72, a lower core 73, and a lower die 74 are used, as shown in Figure 7. The outer peripheral surface of a core set formed by combining the upper core 72 and the lower core 73 has the same shape as the inner peripheral surface of the hollow portion of the channel 81. The upper core 72 and the lower core 73 have a circular cross section at one end and a semicircular cross section at the other end. The upper core 72 and the lower core 73 are combined so that the flat surfaces of the semicircular cross sections face each other, and are used as a core set.

[0056] The inner peripheral surface of one mold set, which is a combination of the upper mold 71 and the lower mold 74 , has the same shape as the outer peripheral surface of the hollow portion of the channel 81 .

[0057] <Method of Manufacturing Channel> A method of manufacturing the channel will be described with reference to Figures 8A to 8D, which are cross-sectional views along the longitudinal direction of the channel.

[0058] 8A , the cylindrical portion of the upper core 72 is inserted into the first resin tube 82, and the cylindrical portion of the lower core 73 is inserted into the second resin tube 83. The cylindrical portion of the combined upper core 72 and lower core 73 is inserted into the third resin tube 84.

[0059] The first resin tube 82, the second resin tube 83, and the third resin tube 84 are made of a resin that melts when heated.

[0060] As shown in Figure 8B, a core set into which a first resin tube 82, a second resin tube 83, and a third resin tube 84 are inserted is placed in the space between the upper mold 71 and the lower mold 74.

[0061] As shown in FIG. 8C, when the portions where the first resin tube 82, the second resin tube 83 and the third resin tube 84 face each other are heated, the facing portions melt, and the three tubes are welded together.

[0062] As shown in FIG. 8D, the upper mold 71 and the lower mold 74 are removed, and then the upper core 72 and the lower core 73 are removed, thereby completing the channel 81 having the branch portion 80Y.

[0063] As described above, the method for manufacturing a channel 81 such as an air / water supply pipe of the endoscope 9 includes arranging a first resin tube 82, which passes a first fluid from the outside to the operation unit 94, in parallel with a second resin tube 83, into which a treatment tool is inserted from the operation unit 94. A third resin tube 84, one end of which is disposed at the distal end 91 of the insertion unit 90 to be inserted into the subject and the other end of which is disposed at the operation unit 94, is opposed to the first resin tube 82 and the second resin tube 83. An upper core 72 is inserted through the first resin tube 82 and the third resin tube 84, and a lower core 73, which is combined with the upper core 72, is inserted through the second resin tube 83 and the third resin tube 84. The first resin tube 82, the second resin tube 83, and the third resin tube 84, which have passed through the upper core 72 and the lower core 73, are mounted between the upper mold 71 and the lower mold 74. The portion where the first resin tube 82, the second resin tube 83, and the third resin tube 84 face each other is heated between the upper mold 71 and the lower mold 74. The portions where the three tubes face each other are welded together to form a channel 81 in which the first resin tube 82, the second resin tube 83, and the third resin tube 84 communicate with each other via a branch portion.

[0064] The manufacturing method of the channel 81 described above is intended to be used for the branching portion of the air and water supply pipe, but a similar manufacturing method may also be applied to 80Y, which is the branching portion of the channel 80 including the suction pipe, etc.

[0065] Although the above description has been given taking the example of a universal cord for an endoscope as the flexible tube of an insertion device, the flexible tube may also be a catheter or the insertion portion of an endoscope.

[0066] The present invention is not limited to the above-described embodiments, and various modifications, combinations, and applications are possible within the scope of the invention.

[0067] This application claims priority from U.S. Provisional Patent Application No. 63 / 621,631, filed in the United States on January 17, 2024, the disclosure of which is incorporated herein by reference in its entirety, including its claims and drawings.

[0068] REFERENCE SIGNS LIST 1: Universal cord 9: Endoscope 10: Cylinder 20: Spiral tube 20SA: Inner surface 20SB: Outer surface 30: Tube 30SA: Inner surface 40: Base 41: First base 41SB: Outer surface 42: Second base 42SB: Outer surface 50: Wire 63: Adhesive 71: Upper mold 72: Upper core 73: Lower core 74: Lower mold 80, 81: Channel 82: First resin tube 83: Second resin tube 84: Third resin tube 90: Insertion section 91: Tip section 92: Bending section 93: Flexible tube 94: Operation section

Claims

1. A flexible tube for an insertion device, comprising: a spiral tube in which a strip-shaped plate is spirally wound; a flexible tube provided on an outer peripheral surface of the spiral tube; an elongated cylinder having a first end and a second end; two caps including a first cap fixed to the first end and a second cap fixed to the second end; and a wire having a third end and a fourth end, wherein the third end is fixed to the first cap, the fourth end is fixed to the second cap, and the wire is inserted through the cylinder and has an elongation rate smaller than that of the cylinder.

2. The flexible tube for an insertion device according to claim 1, wherein the elongation rate of the wire is less than 10% of the elongation rate of the cylinder.

3. The flexible tube for an insertion device according to claim 1, wherein the wire is inserted through an inner surface of the spiral tube.

4. The flexible tube for an insertion device according to claim 1, wherein the wire is inserted between an outer surface of the spiral tube and an inner surface of the tube.

5. The flexible tube for an insertion device according to claim 1, wherein the first cap has a first through-passage through which the wire is inserted, and the second cap has a second through-passage through which the wire is inserted.

6. The flexible tube for an insertion device according to claim 5, wherein the third end of the wire is fixed to an outer surface of the first cap, the wire passes through the first through-passage, through the cylinder, through the second through-passage, and the fourth end is fixed to an outer surface of the second cap.

7. The flexible tube for an insertion device according to claim 1, wherein the wire is fixed to each of the two caps by a fixture including a screw or a pin.

8. The flexible tube for an insertion device according to claim 1, wherein the third end of the wire is fixed to the first cap, the wire extends in a direction opposite to the direction in which the second cap is provided, and then extends in the direction in which the second cap is provided.

9. The flexible tube for an insertion device according to claim 1, wherein the fourth end of the wire is fixed to the second cap, the wire extends in a direction opposite to the direction in which the first cap is provided, and then extends in the direction in which the first cap is provided.

10. The flexible tube for an insertion device according to claim 1, wherein the two caps have an annular groove into which the first end or the second end of the cylinder is inserted.

11. The flexible tube of the insertion device according to claim 10, wherein the groove has an inner wall surface with a diameter larger than the inner diameter of the cylinder and an outer wall surface with a diameter larger than the outer diameter of the cylinder.

12. The flexible tube of the insertion device according to claim 11, wherein each of the two caps allows the cylinder inserted into the groove to be visually recognized from the outside.

13. The flexible tube of the insertion device according to claim 12, wherein at least a part of each of the two caps is made of a transparent material.

14. The flexible tube of the insertion device according to claim 11, wherein the cylinder is fixed to the groove with an adhesive.

15. The flexible tube of the insertion device according to claim 1, wherein the wire includes a cable in which a plurality of metal strands are twisted together.

16. The flexible tube of the insertion device according to claim 1, wherein the insertion device is a single-use endoscope that is disposed of after a single use.

17. The flexible tube of the insertion device according to claim 16, which is a universal cord of the endoscope and does not include a blade that is a net-like tube braided with metal wires or synthetic fibers covering the spiral tube.

18. The flexible tube of the insertion device according to claim 17, wherein the first cap is fixed to the operation unit of the endoscope, and the second cap is fixed to a connector connected to an external device.

19. An insertion device including a flexible tube inserted into a subject, the flexible tube including a spiral tube in which a strip-shaped plate is spirally wound, a flexible tube provided on an outer peripheral surface of the spiral tube, an elongated cylinder having a first end and a second end, two caps including a first cap fixed to the first end and a second cap fixed to the second end, a wire having a third end and a fourth end, the third end being fixed to the first cap, the fourth end being fixed to the second cap, and the wire passing through the cylinder and having an elongation rate smaller than the elongation rate of the cylinder.

20. A method for manufacturing a flexible tube of an insertion device, the method including: manufacturing a spiral tube by spirally winding a strip-shaped metal plate in a longitudinal axis direction; providing a flexible tube extending in the longitudinal axis direction on a surface layer side of the spiral tube to manufacture a cylinder; attaching caps to both ends of the cylinder; inserting a wire having an elongation rate smaller than the elongation rate of the cylinder into the cylinder; and fixing both ends of the wire to the respective caps.

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