Rigid variable cable body

Abstract

To provide a rigid variable cable body which enables improvement of rigidity in a highly rigid state, elongation, and reduction of its diameter and can secure an internal space.SOLUTION: A cable body main part 11 has an elongated pipe form and flexibility and includes a hollow pressure chamber 26 therein. Two or more axial string bodies 12 are disposed so as to extend in an extension direction of the cable body main part 11 along an outer surface of the cable body main part 11. A circumferential string body 13 is disposed so as to wind in a circumferential direction of the cable body main part 11 along the outer surface of the cable body main part 11 and wound around each axial string body 12, making one or multiple loops at a position where the circumferential string body 13 intersects with the axial string body 12. When a pressure of the pressure chamber 26 is increased, the cable body main part 11 expands in a direction perpendicular to its extension direction and is pressed to the circumferential string body 13. The motion causes the circumferential string body 13 to fasten and fix each axial string body 12.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a variable stiffness cord. [Background technology]

[0002] Cord-like bodies have a structure that is suitable for working in biological, natural, and artificial environments that are difficult to access, such as narrow spaces or environments with many obstacles, and are therefore used in a variety of industrial applications, such as endoscopes for treating and treating luminal cavities and industrial videoscopes for inspecting pipes.

[0003] It is effective to increase the flexibility of a cord-like body in order to expand its range of motion, improve its ability to follow the environment, and prevent damage when it comes into contact with something. On the other hand, increasing its flexibility reduces its ability to resist external forces, which can lead to problems such as a decrease in the transmission of force to the tip and positional accuracy, and an increase in the amount of deflection due to its own weight. Therefore, by making the rigidity of the cord-like body variable, it is possible to take advantage of the properties of a flexible low-rigidity state and a high-rigidity state depending on the situation, and it is expected that it will be usable in applications that were not previously applicable.

[0004] Conventional cord-like bodies that utilize a mechanism for switching between a flexible state that is easily deformed when an external force is applied and a highly rigid state that can transmit force to the outside when contacted include, for example, a body that increases the contact force by applying tension to a wire passing through beads, thereby increasing rigidity through friction (see, for example, Patent Document 1 and Non-Patent Documents 1 or 2), and a body that increases the contact pressure between powder particles by suctioning the inside of a bag containing powder to create a negative pressure, thereby causing a jamming transition phenomenon and increasing rigidity through the frictional force (see, for example, Non-Patent Documents 3 or 4). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-202376 A [Non-patent literature]

[0006] [Non-Patent Document 1] Amir Degani and Howie Choset, “Highly Articulated Robotic Probe for Minimally Invasive Surgery”, IEEE International Conference on Robotics and Automation Orlando, May 2006, p.4167-4172 [Non-Patent Document 2] Toshiaki Fujimoto, Moriori Shimizu, Masahiro Fujita, Eri Takane, Sosuke Hayashi, Masahiro Watanabe, Kenjiro Tadakuma, Masashi Konyo, Satoshi Tadokoro, "A Torus Gripper Mechanism Using a One-Dimensional Soft-Stiff Switching Mechanism - An Example of a Structure Based on a Linear Jamming Transition Mechanism", 36th Annual Conference of the Robotics Society of Japan, 2018, RSJ2018A C3K1-01 [Non-Patent Document 3] Yong-Jae Kim and Shanbao Cheng, “A Novel Layer Jamming Mechanism With Tunable Stiffness Capability for Minimally Invasive Surgery”, IEEE TRANSACTIONS ON ROBOTICS, August 2013, Vol. 29, No. 4, p.1031-1042 [Non-Patent Document 4] Masahiro Fujita, Toshiaki Fujimoto, Moriori Shimizu, Eri Takane, Hirone Komatsu, Kenjiro Tadakuma, Masashi Konyo, Satoshi Tadokoro, "Tufted Jamming Mechanism of a Film Gripper," Robotics and Mechatronics Conference 2018, June 2018, 2P1-J06 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the cord-like body in which a wire is threaded through beads as described in Patent Document 1 and Non-Patent Documents 1 and 2, although it is possible to increase the strength and durability by constructing the beads from a hard material, there is a problem that it is difficult to achieve a high rigidity state when the length is increased because the contact area between the beads and the wire increases, resulting in a large loss of force due to friction. In addition, there is also the problem that it is difficult to secure an internal space because of the use of beads.

[0008] The powder-based cord-like bodies described in Non-Patent Documents 3 and 4 can be greatly deformed and can conform well to the shape of the object, but they use negative pressure and the pressure can only be reduced to about 0.1 MPa, so there is a problem that there is a limit to how much rigidity can be achieved. Also, in order to increase the holding power in a highly rigid state, the bag needs to be thickened, so there is a problem that it is difficult to reduce the diameter.

[0009] The present invention has been made with attention to such problems, and aims to provide a variable rigidity cord-like body that can increase the rigidity in a high rigidity state, can be made longer and thinner, and can ensure internal space. [Means for solving the problem]

[0010] In order to achieve the above object, the present invention provides a variable stiffness cord having a long, slender, flexible tubular shape, a hollow pressure chamber provided inside along the extension direction, and a cord body provided so as to be expandable in a direction perpendicular to the extension direction when the pressure in the pressure chamber is increased; and two or more axial cords each arranged so as to extend in the extension direction of the cord body along the outer surface of the cord body; and axial cords arranged so as to be wound in the circumferential direction of the cord body from one end to the other end of the cord body along the outer surface of the cord body, and each axial cord is arranged at a position where it intersects with each axial cord. and a circumferential string wound around the pressure chamber one or more times, wherein one end of each axial string is fixed to one end or the other end of the rope-like body main body, and the other end is arranged to be relatively slidable along the extension direction of the rope-like body main body so as to follow the shape of the rope-like body when the rope-like body main body is bent, and when the pressure in the pressure chamber is increased, the rope-like body main body expands in a direction perpendicular to its extension direction and is pressed against the circumferential string, thereby tightening and fixing each of the axial strings at the positions where the circumferential string intersects with them.

[0011] The variable stiffness cord according to the present invention is arranged so as to extend in the extension direction of the cord body along the outer surface of the cord body when the flexible cord body is bent, and each axial cord around which the circumferential cord is wound slides relatively along the extension direction of the cord body to conform to the shape of the cord body. When the cord body is bent or straight, if the pressure in the hollow pressure chamber of the cord body is increased, the cord body expands in a direction perpendicular to the extension direction, so that the cord body is pressed against the circumferential cord arranged to be wound around the cord body in the circumferential direction along the outer surface of the cord body, and tension is generated in the circumferential cord. At this time, since the circumferential cord is wound around each axial cord at a position where it intersects with each axial cord, each axial cord is tightened by the tension of the circumferential cord. As a result, contact pressure is generated between the circumferential cord and each axial cord, and friction increases, so that each axial cord is fixed to the circumferential cord. This restricts the sliding movement of each axial cord relative to the cord body, making it possible to maintain the shape of the cord body.

[0012] In the variable stiffness cord according to the present invention, the pressure chamber is provided inside the cord body along the extension direction, so that when the pressure in the pressure chamber is increased, the cord body can expand from one end to the other end of the cord body. In addition, since the circumferential cords are disposed from one end to the other end of the cord body, the movement of each axial cord can be restricted from one end to the other end of the cord body, and the overall shape of the cord body can be maintained.

[0013] In the variable stiffness cord according to the present invention, the circumferential cord may be wound any number of times around each of the axial cords. The more the number of turns of the circumferential cord around each of the axial cords, the greater the friction between the circumferential cord and each of the axial cords when the pressure in the pressure chamber is increased, and the greater the force with which the cord body can maintain its shape.

[0014] The variable stiffness cord according to the present invention can increase the stiffness in a high stiffness state in which the shape of the entire cord body is maintained by increasing the pressure applied to the pressure chamber, but can also increase the stiffness in the high stiffness state by increasing the number of turns of the circumferential cord around each axial cord or by increasing the number of positions at which the circumferential cord and each axial cord cross. In addition, the length and diameter can be increased without decreasing the stiffness in the high stiffness state while maintaining the configuration of the cord body, the circumferential cord, and each axial cord. In addition, the internal space of the cord body can be secured by dividing the internal space into, for example, an internal space in the center and a pressure chamber on the outer periphery.

[0015] The variable stiffness cord according to the present invention, when there are two axial cords, can maintain the shape of the cord body in a high stiffness state against bending of the cord body along a predetermined plane. When each axial cord is made up of three or more axial cords, it is preferable that the interval between adjacent axial cords is less than 180 degrees around the central axis of the cord body, and this arrangement allows the shape of the cord body in a high stiffness state to be maintained regardless of the bending direction of the cord body.

[0016] In the variable stiffness cord according to the present invention, each axial cord is preferably composed of two or more sets, with two cords in each set being arranged side by side, one end of one axial cord being fixed to one end of the cord body, one end of the other axial cord being fixed to the other end of the cord body, and the circumferential cord being wound around each set of axial cords one or more times so as to bundle the two axial cords of each set at a position where the circumferential cord intersects with each set of axial cords. In this case, the friction between the circumferential cord and each axial cord when the pressure of the pressure chamber is increased can be made substantially equal, regardless of the position where the circumferential cord intersects with each axial cord along the extension direction of the cord body. Therefore, the cord body can be maintained in a substantially uniform high stiffness state.

[0017] In addition, when the two axial cords in each set are arranged side by side, when there are two sets of each axial cord, the shape of the cord body can be maintained in a high rigidity state against bending of the cord body along a predetermined plane. In addition, when each axial cord consists of three or more sets, it is preferable that each set is arranged at an interval of less than 180 degrees between adjacent sets around the central axis of the cord body, and this arrangement allows the shape of the cord body in a high rigidity state to be maintained regardless of the bending direction of the cord body.

[0018] In addition, when the two axial cords of each set are arranged side by side, the cord body has a plurality of pulleys provided at one end thereof, each axial cord is composed of an even number of sets of four or more, each set is arranged at equal angular intervals around the central axis of the cord body, each pulley is provided corresponding to a combination of two sets of axial cords arranged on the opposite side of the central axis of the cord body, and among the two axial cords included in each of the two sets of each combination, the axial cords fixed to the other end of the cord body may be connected to each other at one end to form a single cord, and the cord may be wound around the corresponding pulley to be slidable. In this case, the cord wound around the pulley is arranged along the opposite outer surface of the cord body with the pulley sandwiched between them, so that one side of the pulley sandwiched between them can slide through the pulley in the compression direction and the other side in the extension direction in accordance with the deflection of the cord body. In addition, the length of the cord wound around the pulley can suppress the extension of the cord body in the extension direction.

[0019] In the variable stiffness cord according to the present invention, the circumferential cord may be wound helically around the outer surface of the cord body multiple times from one end to the other end of the cord body. Alternatively, the circumferential cord may be made up of three or more cords, spaced apart from one end to the other end of the cord body, and each wound around the outer surface of the cord body once in an annular shape. In either case, the shape of the entire cord body can be maintained by increasing the pressure in the pressure chamber.

[0020] In the variable stiffness cord according to the present invention, the circumferential cord is preferably wound around each of the axial cords such that the axial cords are located on the inside of the outer circumferential portion wound around the cord body at the intersection with the circumferential cord. In this case, when the pressure in the pressure chamber is increased, the tension of the circumferential cord not only tightens each of the axial cords but also presses each of the axial cords against the outer surface of the cord body. This increases the force that maintains the shape of the cord body and stabilizes the intersection positions of the circumferential cord and each of the axial cords so that they do not shift. Effect of the Invention

[0021] According to the present invention, it is possible to provide a variable stiffness cord-like body that can have a higher stiffness in a high stiffness state, can be made longer and thinner, and can ensure an internal space. [Brief description of the drawings]

[0022] [Figure 1] 1 is a perspective view showing a variable stiffness cord according to an embodiment of the present invention; [Diagram 2] 1A is a plan view, FIG. 1B is a front view, FIG. 1C is a cross-sectional view taken along line AA, and FIG. 1D is a cross-sectional view taken along line BB, showing a variable stiffness cord-like body according to an embodiment of the present invention. [Diagram 3] FIG. 1 shows an embodiment of a variable stiffness cord of the present invention, in which (a) one circumferential cord is wound spirally around the outer surface of the cord body and one circumferential cord is wound around each pair of axial cords; (b) one circumferential cord is wound spirally around the outer surface of the cord body and two circumferential cords are wound around each pair of axial cords; and (c) a perspective view showing a plurality of circumferential cords wound in a circular shape around the outer surface of the cord body and one circumferential cord is wound around each pair of axial cords. [Figure 4] FIG. 1A is a cross-sectional view of a variable stiffness cord of an embodiment of the present invention, showing a state when the circumferential cord is wound around each axial cord so that each axial cord is positioned inward relative to the outer circumferential portion wound around the cord body, and the pressure in the pressure chamber is not increased; FIG. 1B is a cross-sectional view showing a state when the circumferential cord is wound around each axial cord so that each axial cord is positioned inward relative to the outer circumferential portion wound around the cord body, and the pressure in the pressure chamber is increased; and FIG. 1C is a cross-sectional view showing a state when the circumferential cord is wound around each axial cord so that each axial cord is positioned outward relative to the outer circumferential portion wound around the cord body, and the pressure in the pressure chamber is not increased. [Diagram 5] 3A and 3B are longitudinal cross-sectional views showing a variable stiffness cord-like body according to an embodiment of the present invention in a straight state and in a bent state when the pressure in a pressure chamber is not increased. [Figure 6]FIG. 2 is a side view showing a state in which the variable stiffness cord-like body according to the embodiment of the present invention is bent into an S-shape. [Figure 7] FIG. 13 is a perspective view showing a modified example of the variable stiffness cord-like member according to the embodiment of the present invention, in which the axial cords are formed of 12 sets of cords. [Figure 8] FIG. 1A is a perspective view showing a modified example of a variable stiffness cord of an embodiment of the present invention, in which two pairs of axial cords arranged on opposite sides of the central axis of the cord body are connected to each other, and FIG. 1B is a perspective view showing a modified example in which each of the connected axial cords is wound around a pulley. [Figure 9] 10 is a longitudinal sectional view showing a modified example of the variable stiffness cord-like body according to the embodiment of the present invention in which the inside of the expansion tube is entirely used as a pressure chamber and a coil spring is disposed inside the expansion tube. FIG. [Figure 10] 13 is a perspective view showing a modified example of the variable stiffness cord-like body according to the embodiment of the present invention, which has an outer tube and a braided tube that covers each of the axial cords and the circumferential cords. FIG. [Figure 11] FIG. 11 is a perspective view showing a modified example of the variable stiffness cord-like body of the embodiment of the present invention, in which a protective cloth is used instead of the braided tube shown in FIG. 10, and a circumferential cord is sewn to the cloth. [Figure 12] FIG. 13 is a side view showing a modified example of the variable stiffness cord according to the embodiment of the present invention for actively bending the cord body in a desired direction. [Figure 13] FIG. 13 is a side view showing a modified example in which a plurality of variable stiffness cord-like bodies are connected in series according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 to 13 show a variable stiffness cord according to an embodiment of the present invention. As shown in FIG. 1 and FIG. 2, the variable stiffness cord 10 has a cord body 11, axial cords 12, and circumferential cords 13.

[0024] The cord-like body main body 11 has an inflation tube 21, an inner tube 22, an outer tube 23, a pair of caps 24, and a connection part 25. The inflation tube 21 is made of a long and thin silicone rubber tube and is flexible. The inner tube 22 is made of a long and thin resin corrugated tube and is flexible. The inner tube 22 has an outer diameter smaller than the inner diameter of the inflation tube 21 and a length slightly shorter than that of the inflation tube 21. The inner tube 22 is disposed inside the inflation tube 21 with a gap between it and the inner surface of the inflation tube 21. In the cord-like body main body 11, the hollow space between the inner tube 22 and the inflation tube 21 forms a pressure chamber 26.

[0025] The outer tube 23 is formed by dividing a long and thin corrugated tube made of resin, whose inside diameter is slightly larger than the outside diameter of the expansion tube 21, into four approximately equal parts around the central axis along its central axis. Each of the four divided parts of the outer tube 23 is flexible and has the same length as the expansion tube 21. The four divided parts of the outer tube 23 are arranged along the outer surface of the expansion tube 21 with a gap between them in the circumferential direction.

[0026] The pair of caps 24 are provided so as to cover both ends from the inner tube 22 to the outer tube 23, respectively, and have a communication port 24a that communicates with the inside of the inner tube 22. Each cap 24 is attached using an adhesive or the like so as to airtightly close the opening between the inner tube 22 and the expansion tube 21 and seal the pressure chamber 26. At least one of the caps 24 has a supply port 24b that communicates with the pressure chamber 26.

[0027] The connection part 25 is attached to the supply port 24b of one of the caps 24, and has a connection port 25a that communicates with the supply port 24b. As shown in Fig. 12, the connection part 25 is provided so that a hose 51 of a pump (not shown) can be connected to it. The connection part 25 is configured so that, when the hose 51 of the pump is connected, the connection part 25 can supply and discharge fluid to and from the inside of the pressure chamber 26 from the connection port 25a via the supply port 24b. The fluid supplied to the inside of the pressure chamber 26 may be either a gas or a liquid.

[0028] The cord-like body main body 11 can expand in a direction perpendicular to the extension direction by supplying fluid to the inside of the pressure chamber 26 to increase the pressure in the pressure chamber 26. When the cord-like body main body 11 is in an expanded state, the cord-like body main body 11 can contract from the expanded state to its original state by discharging the fluid from the inside of the pressure chamber 26 to reduce the pressure in the pressure chamber 26. When not inflated, the cord-like body main body 11 is configured to bend and curve in a direction perpendicular to the extension direction.

[0029] The axial cords 12 are made of eight stainless steel wires, and are divided into four sets of two. Each axial cord 12 is arranged so as to extend in the extension direction of the cord body 11 along the outer surface of the outer tube 23 of the cord body 11, and the two axial cords 12 of each set are arranged side by side. Each set of the axial cords 12 is arranged in the gap between each of the four divided parts of the outer tube 23, and the interval between adjacent sets is arranged at about 90 degrees around the central axis of the cord body 11. One axial cord 12 of each set of the axial cords 12 is fixed at one end to one cap 24, and the other end is provided to pass through the other cap 24. The other axial cord 12 of each set of the axial cords 12 is fixed at one end to the other cap 24, and the other end is provided to pass through the one cap 24.

[0030] The circumferential cord 13 is made of braided para-aramid fibers and is arranged so as to be wound in the circumferential direction of the cord body 11 along the outer surface of the outer tube 23 from one end to the other end of the cord body 11. The circumferential cord 13 is arranged in a groove of the outer tube 23 and is wound spirally around the outer surface of the outer tube 23 multiple times along the groove. As shown in FIG. 3(a), the circumferential cord 13 is wound around each pair of axial cords 12 at a position where it intersects with each pair of axial cords 12 so as to bundle the two axial cords 12 of each pair. Also, as shown in FIGS. 4(a) and (b), the circumferential cord 13 is wound around each axial cord 12 at a position where it intersects with each pair of axial cords 12 so that each axial cord 12 is located inside the outer circumferential portion wound around the cord body 11.

[0031] As shown in Fig. 4(a) and Fig. 5, the variable stiffness cord 10 is freely bent when the pressure in the pressure chamber 26 is not increased, and the other ends of the two axial cords 12 in each set are configured to be relatively slidable along the stretching direction of the cord body 11 so as to conform to the shape of the cord body main body 11 at that time. For example, the axial cords 12 on the inside of the bend of the cord body main body 11 slide in the compression direction, and the axial cords 12 on the outside of the bend slide in the stretching direction. The bend of the cord body main body 11 is not limited to a uniform curvature, and may be a locally curved shape, an S-shape as shown in Fig. 6, or a three-dimensional curved shape.

[0032] 4(b), when the pressure in the pressure chamber 26 of the variable stiffness cord 10 is increased, the cord body 11 expands in a direction perpendicular to the direction of extension and is pressed against the circumferential cords 13 via the outer tube 23, generating tension in the circumferential cords 13. As a result, the circumferential cords 13 tighten and fix the axial cords 12 at positions where they intersect. This restricts the sliding movement of the axial cords 12, making it possible to maintain the shape of the cord body 11.

[0033] The axial cord 12 preferably has high strength and rigidity to prevent buckling, and is moderately slippery with respect to the circumferential cord 13. The axial cord 12 is preferably, for example, a metal wire or a highly elastic resin monofilament. The circumferential cord 13 is preferably, for example, a material having high strength, a large bending curvature, and springiness so that the tightened axial cord 12 can be easily released. The circumferential cord 13 is preferably, for example, a braided para-aramid fiber, an ultra-high molecular weight polyethylene fiber, or a PBO fiber.

[0034] Next, the operation will be described. When the pressure in the pressure chamber 26 is not increased, the stiffness variable cord 10 can freely bend and curve the cord body 11. When the pressure in the hollow pressure chamber 26 of the cord body 11 is increased with the cord body 11 bent or straight, the stiffness variable cord 10 expands in a direction perpendicular to the direction of extension of the cord body 11, and the circumferential cord 13 tightens the axial cords 12. This generates contact pressure between the circumferential cord 13 and each axial cord 12, increasing friction, so that each axial cord 12 is fixed to the circumferential cord 13, and the shape of the cord body 11 can be maintained. When the pressure in the pressure chamber 26 is reduced in this state, the expanded cord body 11 contracts, and the circumferential cord 13 releases each axial cord 12, allowing the cord body 11 to return to a freely bent state again.

[0035] In the variable stiffness cord 10, the pressure chamber 26 is provided inside the cord body 11 along the extension direction, so that when the pressure in the pressure chamber 26 is increased, the cord body 11 can expand from one end to the other end of the cord body 11. In addition, at this time, since the circumferential cords 13 are arranged from one end to the other end of the cord body 11, the movement of each axial cord 12 can be restrained from one end to the other end of the cord body 11, and the overall shape of the cord body 11 can be maintained.

[0036] Furthermore, since each set of axial cords 12 of the variable stiffness cord body 10 is arranged at intervals of approximately 90 degrees around the central axis of the cord body main body 11, the shape of the cord body main body 11 in a high stiffness state can be maintained regardless of the bending direction of the cord body main body 11.

[0037] In the variable stiffness cord-like body 10, two axial cords 12 are arranged in a set, and the two axial cords 12 of each set are fixed to the caps 24 on the opposite sides, so that the friction between the circumferential cords 13 and each axial cord 12 when the pressure in the pressure chamber 26 is increased can be made substantially equal, regardless of the position where the circumferential cords 13 intersect with each axial cord 12 in the stretching direction of the cord-like body main body 11. Therefore, the cord-like body main body 11 can be maintained in a substantially uniform high stiffness state.

[0038] 4(a) and (b), in the variable stiffness cord 10, the circumferential cord 13 is wound around each axial cord 12 so that each axial cord 12 is located inside the outer circumferential portion wound around the cord body 11, so that when the pressure in the pressure chamber 26 is increased, the tension of the circumferential cord 13 not only tightens each axial cord 12 but also presses each axial cord 12 against the outer surface of the cord body 11. This increases the force that maintains the shape of the cord body 11 and stabilizes the intersection positions of the circumferential cord 13 and each axial cord 12 so that they do not shift.

[0039] The variable stiffness cord-like body 10 can prevent the expansion tube 21 from expanding and contracting along the expansion direction when the pressure in the pressure chamber 26 is increased or decreased, by the inner tube 22 and the outer tube 23. In addition, the variable stiffness cord-like body 10 can prevent the expansion tube 21 from buckling when it is bent, by the inner tube 22.

[0040] As shown in Fig. 2, the variable stiffness cord-like body 10 can secure a space inside the inner tube 22. Therefore, the internal space can be used as a storage space, and the internal space and the communication opening 24a of each cap 24 can be used to pass various devices such as a camera or a cable 52, as shown in Fig. 12. As a result, the variable stiffness cord-like body 10 can be used as a device for exploring narrow spaces, such as an endoscope or a videoscope.

[0041] The stiffness of the stiffness-variable cord 10 can be increased in a high stiffness state in which the overall shape of the cord body 11 is maintained by increasing the pressure applied to the pressure chamber 26, but the stiffness can also be increased by increasing the number of turns of the circumferential cord 13 around each axial cord 12 or by increasing the number of positions at which the circumferential cord 13 and each axial cord 12 cross. The stiffness can also be increased in a high stiffness state by increasing the diameter of the cord body 11, increasing the coefficient of friction between the circumferential cord 13 and each axial cord 12, increasing the coefficient of friction between each pair of axial cords 12, increasing the number of axial cords 12, or decreasing the bending stiffness of the circumferential cord 13. By adjusting one or more of these in combination, the length and diameter can be increased without decreasing the stiffness in the high stiffness state while maintaining the configuration of the cord body 11, the circumferential cord 13, and each axial cord 12. In addition, the bending resistance when the cord-like body 11 is bent in a state where the pressure in the pressure chamber 26 is not increased can also be reduced.

[0042] In the variable stiffness cord 10, each axial cord 12 may be wound spirally around the cord body 11 so that the angle between the axial cord 12 and the extension direction of the cord body 11 is smaller than that between the circumferential cord 13. In this case, the stiffness of the cord body 11 can be increased in a twisted state, and the shape can be maintained.

[0043] The stiffness variable cord 10 may also be made up of two sets of axial cords 12. In this case, the shape of the cord body 11 can be maintained in a high stiffness state against bending of the cord body 11 along a predetermined plane. The set of axial cords 12 may also be three as shown in FIG. 4, or five or more as shown in FIG. 7. In the example shown in FIG. 7, the axial cords 12 are made up of 12 sets. Each set of axial cords 12 may also be made up of three or more axial cords 12. When the set of axial cords 12 is made up of three or more sets, the set of axial cords 12 is arranged so that the interval between adjacent sets is less than 180 degrees around the central axis of the cord body 11, thereby allowing the shape of the cord body 11 in a high stiffness state to be maintained regardless of the bending direction of the cord body 11.

[0044] In addition, the variable stiffness cord 10 may have the axial cords 12 arranged independently, rather than in pairs, and one end of each axial cord 12 may be fixed to one of the caps 24. Even in this case, when there are two axial cords 12, the shape of the cord-like body main body 11 can be maintained in a high stiffness state against bending of the cord-like body main body 11 along a predetermined plane. When there are three or more axial cords 12, the shape of the cord-like body main body 11 in the high stiffness state can be maintained regardless of the bending direction of the cord-like body main body 11 by arranging each axial cord 12 at an interval smaller than 180 degrees around the central axis of the cord-like body main body 11.

[0045] In addition, in the variable stiffness cord 10, the circumferential cord 13 may be wound around each axial cord 12 two times, or three times or more, as shown in Fig. 3(b). The more the number of turns of the circumferential cord 13 around each axial cord 12, the greater the friction between the circumferential cord 13 and each axial cord 12 when the pressure in the pressure chamber 26 is increased, and the greater the force that maintains the shape of the cord body 11. However, the more the number of turns of the circumferential cord 13, the greater the bending resistance when the cord body 11 is bent in a state where the pressure in the pressure chamber 26 is not increased, so it is considered that at most two or three turns are preferable.

[0046] Moreover, the variable stiffness cord 10 is not limited to one in which one circumferential cord 13 is wound helically around the cord body 11, but may have a plurality of circumferential cords 13 wound helically around the cord body 11 in the same or opposite directions. Also, as shown in Fig. 3(c), three or more circumferential cords 13 may be arranged at intervals from one end to the other end of the cord body 11, and each may be wound around the outer surface of the cord body 11 in a circular shape. Even in these cases, the overall shape of the cord body 11 can be maintained by increasing the pressure in the pressure chamber 26.

[0047] 4(c), in the variable stiffness cord-like body 10, the circumferential cords 13 may be wound around each axial cord 12 so that each axial cord 12 is on the outside of the outer circumferential portion wound around the cord-like body main body 11 at the position where it intersects with each set of axial cords 12. Even in this case, when the pressure in the pressure chamber 26 is increased, the tension of the circumferential cords 13 can tighten each axial cord 12, and the shape of the cord-like body main body 11 in the high stiffness state can be maintained.

[0048] Furthermore, as shown in Figures 6 and 8(a), in the variable stiffness cord-like body 10, each axial cord 12 is composed of an even number of groups of four or more, and each group is arranged at equal angular intervals around the central axis of the cord-like body main body 11, and for a combination of two groups of axial cords 12 arranged on opposite sides of the central axis of the cord-like body main body 11, of the two axial cords 12 included in each of the two groups in each combination, the axial cords 12 fixed to the other end of the cord-like body main body 11 may be connected to each other at one end to form a single cord, and the axial cords 12 fixed to one end of the cord-like body main body 11 may be connected to each other at the other end to form a single cord.

[0049] Furthermore, as shown in FIG. 8(b), a plurality of pulleys 41 may be provided at both ends of the cord-like body main body 11 in correspondence with the positions where the two axial cords 12 of each combination are connected, and the two connected axial cords 12 may be wound around the corresponding pulleys 41 to be slidable. In this case, the cords wound around the pulleys 41 are arranged along the opposite outer surfaces of the cord-like body main body 11, sandwiching the pulleys 41, so that one side sandwiching the pulley 41 can slide in the compression direction and the other side in the extension direction via the pulleys 41 in accordance with the bending of the cord-like body main body 11. In addition, the length of the cords wound around the pulleys 41 can suppress the stretching of the cord-like body main body 11 in the extension direction.

[0050] 4, 5 and 9, the variable stiffness cord-like body 10 may have no inner tube 22, and the entire inside of the expansion tube 21 may be made into a pressure chamber 26, with each cap 24 airtightly sealing both ends of the expansion tube 21. Even in this case, the pressure in the pressure chamber 26 can be increased to create a high stiffness state, and the shape of the cord-like body main body 11 can be maintained. Also, as shown in FIG. 9, a coil spring 42 may be disposed inside the expansion tube 21 to increase the flexibility and elasticity of the cord-like body main body 11.

[0051] As shown in FIG. 10, in order to protect the whole, a braided tube 43 may be provided on the outer surface of the outer tube 23 so as to cover each of the axial cords 12 and the circumferential cords 13 together with the outer tube 23. The braided tube 43 may be made of any material as long as it is flexible, for example, polyester. As shown in FIG. 11, instead of the braided tube 43, a protective cloth 44 may be provided. In this case, the circumferential cords 13 may be sewn to the braided tube 43 or the cloth 44. The braided tube 43 or the cloth 44 may be provided on the outside of the inflation tube 21 without using the outer tube 23. In this case, the diameter can be made smaller than when the outer tube 23 made of a corrugated tube is used.

[0052] As shown in FIG. 12, the stiffness-variable cord 10 may have an operating means 45 for pulling or releasing the end of each axial cord 12 that is not fixed to each cap 24 toward one end side or the other end side of the cord body 11. In this case, the cord body 11 can be actively bent in a desired direction by pulling any of the axial cords 12 with the operating means 45, and the bent shape can be maintained by increasing the stiffness. For this reason, when used as a device for exploring narrow spaces such as an endoscope or a videoscope, it can be deformed or moved according to the environment. It can also be used as a gripper, a robot joint, a finger, etc.

[0053] Furthermore, the variable stiffness cord-like body 10 may cover the outside of an actuator that can be curved and deformed by inserting the actuator into the inside of the inner tube 22 or the communication opening 24a of each cap 24. In this case, too, the actuator can be curved and deformed and its shape can be maintained by increasing its stiffness.

[0054] Also, as shown in FIG. 13, the stiffness variable cord-like body 10 may be made up of a plurality of members connected in series. In this case, it is preferable that the communication openings 24a of the caps 24 of the stiffness variable cord-like body 10 are connected so as to communicate with each other. In order to make each stiffness variable cord-like body 10 independently in a high stiffness state, the pressure of the pressure chambers 26 of each stiffness variable cord-like body 10 may be adjustable at the hand side. In addition, in order to make the whole body in a high stiffness state, the pressure chambers 26 of all the stiffness variable cord-like bodies 10 may be configured to communicate with each other. In this case, it is possible to make the length even longer, and a sensor 53 such as a camera, a swing mechanism, a gripper, etc. may be attached to the tip of the cable through the communication hole 24a of each stiffness variable cord-like body 10, and it can be suitably used for searching in a narrow environment or an environment with many obstacles. EXAMPLES

[0055] A prototype of the stiffness-variable cord-like body 10 shown in FIG. 1 was manufactured. In the prototype, a silicone rubber tube with an outer diameter of 27 mm, a thickness of 1 mm, and a length of 200 mm was used as the expansion tube 21. A corrugated tube with a thickness of 2 mm, a wave period of 4.2 mm, and a length of 200 mm was used as the inner tube 22 and the outer tube 23. A braided Kevlar® thread with a diameter of 0.5 mm was used as the circumferential cord 13, and a SUS304 wire with a diameter of 1.6 mm was used as the axial cord 12. The prototype had a diameter of 32 mm and a mass of 49.1 g. The wall thickness from the inner tube 22 to the outer tube 23 was about 5 mm.

[0056] A shape retention test was carried out using the manufactured prototype. First, when no pressure was applied to the pressure chamber 26, the prototype could be curved with a radius of curvature of about 100 mm or S-shaped. It was also confirmed that the shapes were retained when a low pressure of about 30 kPa was applied to the pressure chamber 26. It was also confirmed that the retention force and rigidity were increased by further increasing the pressure applied to the pressure chamber 26. [Explanation of symbols]

[0057] 10 Variable stiffness cord 11 Cord body 21 Inflation tube 22 Inner tube 23 Outer tube 24 Cap 24a Communication port 24b Supply port 25 Connection 25a Connection port 26 Pressure Chamber 12 Axial string 13 Circumferential string 41 Pulley 42 Coil spring 43 Braided Tube 44 Cloth 45 Operating means 51 Hose 52 Cable 53 Sensors

Claims

1. a cord-like body main body having an elongated tubular shape and flexibility, a hollow pressure chamber provided inside along the extension direction, and configured to be expandable in a direction perpendicular to the extension direction when the pressure in the pressure chamber is increased; Two or more axial cords each extending in the extension direction of the cord body along the outer surface of the cord body; a circumferential cord arranged to be wound around the circumferential direction of the cord body along an outer surface of the cord body from one end to the other end of the cord body, and wound around each axial cord one or more times at a position where the circumferential cord intersects with each axial cord; Each of the axial cords has one end fixed to one end or the other end of the cord-like body, and the other end is relatively slidable along the extension direction of the cord-like body so as to follow the shape of the cord-like body when the cord-like body is bent, When the pressure in the pressure chamber is increased, the cord-like body expands in a direction perpendicular to the direction of expansion and is pressed against the circumferential cord, thereby tightening and fixing each of the axial cords at positions where the circumferential cord intersects with each of the axial cords. A variable stiffness cord-like body.

2. The variable stiffness cord described in claim 1, characterized in that the axial cords consist of three or more cords, and the spacing between adjacent axial cords is less than 180 degrees around the central axis of the cord body.

3. Each axial cord is composed of two or more sets, each set consisting of two axial cords, and each set has two axial cords arranged side by side, one end of one axial cord is fixed to one end of the cord body, and one end of the other axial cord is fixed to the other end of the cord body, The circumferential cord is wound around each pair of axial cords one or more times at a position where the circumferential cord intersects with each pair of axial cords so as to bundle the two axial cords of each pair.

2. The variable stiffness cord according to claim 1.

4. The stiffness-variable cord body according to claim 3, characterized in that each axial cord body consists of three or more sets, and each set is arranged at an interval between adjacent sets less than 180 degrees around the central axis of the cord body main body.

5. A plurality of pulleys are provided at one end of the cord body, Each axial cord is composed of an even number of groups of four or more, and each group is arranged at equal angular intervals around the central axis of the cord-like body, Each pulley is provided corresponding to a combination of two axial cords arranged on opposite sides of the central axis of the cord body, Of the two axial cords included in each of the two sets of each combination, the axial cords fixed to the other end of the cord-like body are connected to each other at one end to form a single cord, and the cord is wound around a corresponding pulley and configured to be slidable.

5. The variable stiffness cord according to claim 3 or 4.

6. The variable stiffness cord described in any one of claims 1 to 4, characterized in that the circumferential cord is wound spirally multiple times around the outer surface of the cord body from one end to the other end of the cord body.

7. The variable stiffness cord described in any one of claims 1 to 4, characterized in that the circumferential cords consist of three or more cords, which are arranged at intervals from one end to the other end of the cord body, and each is wrapped around the outer surface of the cord body in a circular shape once.

8. The variable stiffness cord described in any one of claims 1 to 4, characterized in that the circumferential cord is wound around each axial cord so that at the positions where it intersects with each axial cord, each axial cord is on the inside of the outer circumferential portion wound around the cord body.

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