Fluid Pressure Actuator

Abstract

To provide a fluid pressure actuator capable of preventing excessive curving when fluid pressure rises, and equipped with high repetition durability.SOLUTION: A fluid pressure actuator 1 is equipped with a tube 10 capable of expanding / contracting, a sleeve 20 that covers an outer peripheral surface of the tube 10, a pair of sealing members 30 that seals both end portions 11 of the tube 10, and a plurality of intermediate pieces 40 and 50 disposed in the tube 10. The intermediate pieces 40 at both ends in an axial direction XA of the plurality of intermediate pieces are fixed to the pair of sealing members 30. The plurality of intermediate pieces 40 and 50 is equipped with a restraining side 57 on which the adjacent intermediate pieces abut on each other, and a rocking side 59 on which a clearance 61 allowing the adjacent intermediate pieces at a position facing the restraining side 57 to rock each other, in the tube 10 that has not been pressurized by pressure of a fluid. The plurality of intermediate pieces 40 and 50 is further equipped with a restraining mechanism that maintains the intermediate pieces adjacent to each other on the restraining side 57 even in the tube 10 which is pressurized by the pressure of the fluid.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fluid pressure actuator, and more particularly to a so-called McKibben type fluid actuator. [Background technology]

[0002] Conventionally, a widely used fluid pressure actuator that uses gas or liquid to expand and contract a tube is a structure (the so-called McKibben type) that has a rubber tube that expands and contracts using air pressure and a sleeve that covers the outer surface of the tube.

[0003] Also known is a McKibben type fluid pressure actuator that bends from an axially extended state of the tube and sleeve when contracted (see Patent Document 1). Specifically, a known fluid pressure actuator has a leaf spring provided inside the sleeve of the fluid pressure actuator from one axial end to the other, and is capable of bending due to the action of the leaf spring. In such a bending McKibben type fluid pressure actuator, excessive bending of the fluid pressure actuator when the fluid pressure increases is suppressed by limiting the bending of the tube with the braid angle of the sleeve. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-88999 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in conventional bending type fluid pressure actuators, there is a risk that the leaf spring that bends the fluid pressure actuator will gradually undergo plastic deformation due to repeated bending, resulting in a decrease in restoring force.

[0006] The present invention aims to provide a bendable fluid pressure actuator that can prevent excessive bending when fluid pressure increases and that is less likely to lose its restoring force to its pre-bending state even when repeatedly bent, i.e., has high repetitive durability. [Means for solving the problem]

[0007] A fluid pressure actuator according to an embodiment of the present invention comprises a tube that expands and contracts due to fluid pressure, a stretchable structure in which fiber cords oriented in a predetermined direction are woven, and the actuator comprises a sleeve covering the outer surface of the tube, a pair of sealing members that seal both axial ends of the tube, and a plurality of center pieces arranged adjacent to each other in the axial direction inside the tube. Of the plurality of center pieces, the center pieces arranged at both axial ends are fixed to the pair of sealing members. The plurality of center pieces are configured to have a restraining side where adjacent center pieces abut against each other within the tube when not pressurized by the fluid pressure, and a swinging side at a position opposite the restraining side where a gap is formed that allows the adjacent center pieces to swing relative to each other. The plurality of center pieces further comprises a restraining mechanism that maintains adjacent center pieces abutting against each other on the restraining side even within the tube when pressurized by the fluid pressure. The restraining mechanism includes a first through hole formed in each of the center pieces so as to communicate with each other on the restraining side of the center pieces adjacent to each other, and a restraining fiber cord that is inserted into each of the first through holes from one end side to the other end side of the center pieces in the axial direction and holds the center pieces in contact with each other on the restraining side. are. [Effects of the Invention]

[0008] According to the above configuration, it is possible to prevent excessive bending when the fluid pressure increases, and even when repeatedly bent, the force of recovery to the state before bending is unlikely to decrease, i.e., a bendable fluid pressure actuator with high durability against repeated bending can be provided. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view taken along the axial direction, schematically showing a fluid pressure actuator according to one embodiment in a state before contraction. [Figure 2] FIG. 2 is a cross-sectional view that schematically shows the fluid pressure actuator in a contracted and curved state. [Figure 3] FIG. 3 is a perspective view showing a state in which a plurality of center pieces arranged inside the fluid pressure actuator are in contact with each other. [Figure 4] FIG. 4 is a side view showing the plurality of center links before bending. [Figure 5] FIG. 5 is a side view showing the center pieces during bending. [Figure 6] 6A and 6B are perspective views of a center piece that is not directly fixed to the sealing member, among the plurality of center pieces, with FIG. 6A being a perspective view showing mainly the left side surface, and FIG. 6B being a perspective view showing mainly the right side surface. [Figure 7] Figure 7 shows six views of a center piece that is not directly fixed to the sealing member among the plurality of center pieces, and a cross-sectional view at the center line extending in the vertical direction of the side view, where Figure 7(a) is a front view, Figure 7(b) is a rear view, Figure 7(c) is a plan view, Figure 7(d) is a bottom view, Figure 7(e) is a left side view, Figure 7(f) is a right side view, and Figure 7(g) is the cross-sectional view shown by line VIIg-VIIg in Figure 7(f). [Figure 8] FIG. 8 is a cross-sectional view of the fluid pressure actuator according to this embodiment in a contracted and bent state, showing the restraining fiber cord that keeps the center pieces in contact with each other on the restraining side and the reverse warp prevention cord that is arranged on the swinging side. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment will be described below with reference to the drawings. Note that the same or similar reference numerals are used to designate the same functions or configurations, and descriptions thereof will be omitted as appropriate.

[0011] (1) Overall schematic configuration of fluid pressure actuator Fig. 1 is a cross-sectional view taken along an axial direction XA, schematically showing a fluid pressure actuator 1 according to one embodiment in a state before contraction. Fig. 2 is a cross-sectional view schematically showing the fluid pressure actuator 1 in a contracted and bent state.

[0012] As shown in Figure 1, the fluid pressure actuator 1 comprises a tube 10 that contracts and expands due to fluid pressure, a sleeve 20 that is an elastic structure made by weaving fiber cords oriented in a predetermined direction (predetermined braiding angle) and covers the outer surface of the tube 10, and a pair of sealing members 30 that seal both end portions 11 of the tube 10 in the axial direction XA.

[0013] A basic characteristic of the fluid pressure actuator 1 of this embodiment is that when the fluid pressure inside the tube 10 is increased, the fluid pressure actuator 1 expands in the radial direction while being restrained by the tension of the fiber cord forming the sleeve 20, and contracts in the axial direction XA of the fluid pressure actuator 1. Then, when the fluid pressure inside the tube 10 is reduced, the dimensions in the axial direction XA and radial direction are restored. This change in shape allows the fluid pressure actuator 1 to function as an actuator.

[0014] Such a fluid pressure actuator 1 is a so-called McKibben type fluid pressure actuator, and can be applied not only to artificial muscles but also to robot limbs (upper limbs, lower limbs, etc.) that require higher performance (contractile force). The pair of sealing members 30 may be provided with connecting portions (not shown) that can be connected to members to be connected.

[0015] In this embodiment, a McKibben type fluid pressure actuator having such basic characteristics is used, and multiple center pieces 40, 50 are arranged adjacent to each other in the axial direction XA inside the tube 10 as members that constrain (or may be called restricting or limiting, the same applies hereinafter) compression in the axial direction XA and cause the fluid pressure actuator to bend and deform.

[0016] 1, of the multiple center pieces 40, 50, the center pieces 40 located at both ends in the axial direction XA are fixed to a pair of sealing members 30. Also, as shown in Fig. 1, the multiple center pieces 40, 50 are configured to have a restraint side 57 where adjacent center pieces 40, 50 abut against each other within the tube 10 when not pressurized by fluid pressure, and a swing side 59 at a position opposite the restraint side 57 where a gap 61 is formed that allows adjacent center pieces 40, 50 to swing relative to each other.

[0017] When the inside of the tube 10 is pressurized by fluid pressure, adjacent center links 40, 50 abut against each other on the constrained side 57 of the multiple center links 40, 50 arranged between the pair of sealing members 30, and the multiple center links 40, 50 resist the compression of the tube 10 between the sealing members 30, thereby inhibiting contraction of the tube 10 along the axial direction XA. At this time, on the swinging side 59, the tube 10 can contract in the axial direction XA until the adjacent center links 40, 50 abut against each other and the gap 61 disappears (the gap 61 narrows). Therefore, the length of the tube 10 on the swinging side 59 is relatively shorter than the length of the tube 10 on the constrained side 57, and as shown in FIG. 2, the fluid pressure actuator 1 of this embodiment can deform from the state along the axial direction XA before pressurization shown in FIG. 1 to a curved state curved toward the swinging side 59.

[0018] The fluid used to drive the fluid pressure actuator 1 may be either a gas such as air, or a liquid such as water or mineral oil. The fluid pressure actuator 1 has high durability that can withstand hydraulic driving, which applies high pressure to the tube 10 and sleeve 20.

[0019] The pair of sealing members 30 seal both end portions 11 of the tube 10 in the axial direction XA. Specifically, each sealing member 30 includes a sealing member body 31 and a crimping member 33. The sealing member body 31 seals the end portion 11 of the tube 10 in the axial direction XA. The crimping member 33 crimps the tube 10 and the sleeve 20 together with the sealing member body 31. An indentation, which is a mark left by crimping the crimping member 33 with a jig, may be formed on the outer circumferential surface of the crimping member 33.

[0020] At least one of the pair of sealing members 30 is provided with a connection port to which a hose (pipe) connected to a drive pressure source for the fluid pressure actuator 1, specifically a gas or liquid compressor, can be attached. The fluid pressure inside the tube 10 is controlled by the fluid flowing into and out of the fluid pressure actuator 1 via a fluid passage communicating with this connection port, causing the tube 10 of the fluid pressure actuator 1 to expand and contract.

[0021] (2) Configuration of fluid pressure actuator 1 As shown in FIG. 1, the fluid pressure actuator 1 is made up of the tube 10, the sleeve 20, the pair of sealing members 30, and the plurality of center pieces 40, 50, as described above.

[0022] The tube 10 is a cylindrical body that expands and contracts due to the pressure of the fluid. Since the tube 10 repeatedly expands and contracts due to the fluid, it is made of an elastic material such as butyl rubber. Furthermore, when the fluid pressure actuator 1 is hydraulically driven, it is preferable to use at least one material selected from the group consisting of highly oil-resistant NBR (nitrile rubber), hydrogenated NBR, chloroprene rubber, and epichlorohydrin rubber.

[0023] The sleeve 20 is cylindrical and covers the outer surface of the tube 10 in the fluid pressure actuator 1. The sleeve 20 is an elastic structure made by weaving fiber cords oriented in a predetermined direction relative to the axial direction XA of the tube 10 (the axial direction of the fluid pressure actuator 1) before the internal fluid pressure is increased. The oriented fiber cords cross each other to form a repeated diamond shape. Because of this shape, the sleeve 20 undergoes pantograph deformation and follows the contraction and expansion of the tube 10 while regulating it.

[0024] The McKibben type fluid pressure actuator 1 drives the fiber cord woven into the sleeve 20 so that the braid angle converges to 54.7 degrees, so that it contracts in the axial direction when the braid angle is smaller than 54.7 degrees and expands when the braid angle is larger than 54.7 degrees.

[0025] The sleeve 20 used in this embodiment is woven so that the orientation of the fiber cords of the sleeve 20 before expansion / contraction forms a predetermined braid angle smaller than 54.7 degrees with respect to the axial direction XA of the fluid pressure actuator 1 before pressurization. In other words, the orientation of the fiber cords that regulate the deformation of the tube 10 due to changes in internal fluid pressure is oriented in a predetermined direction (predetermined braid angle) in which the fluid pressure actuator 1 contracts when the tube 10 expands. Specifically, the fiber cords are woven into the sleeve 20 so that the braid angle is 15 degrees to 40 degrees.

[0026] The fluid pressure actuator 1 using this sleeve 20 contracts when the fluid pressure inside the tube 10 is increased by the braid angle of the sleeve 20 during operation becoming larger than the braid angle before contraction (approaching 54.7 degrees).

[0027] It is preferable to use fiber cords made of aromatic polyamide (aramid fiber) or polyethylene terephthalate (PET) as the fiber cords constituting the sleeve 20. However, the fiber cords are not limited to these types, and may be cords made of high-strength fibers such as PBO fiber (polyparaphenylene benzobisoxazole).

[0028] 1, in this embodiment, the multiple center pieces 40, 50 are arranged adjacent to each other in the axial direction XA inside the tube 10. Of the multiple center pieces 40, 50, the center pieces 40 arranged at both ends in the axial direction XA are fixed to a pair of sealing members 30. The multiple center pieces 40, 50 are configured so that, inside the tube 10 before pressurization, adjacent center pieces 40, 50 abut against each other on one side (restraint side 57) perpendicular to the axial direction XA, and a gap 61 is formed at a position opposite the one side (swing side 59) that allows the adjacent center pieces 40, 50 to swing relative to each other.

[0029] The multiple center links 40, 50 are arranged inside the tube 10 in a number that matches the length of the axial direction XA of the fluid pressure actuator 1 so that adjacent center links 40, 50 are in contact with each other on the constraint side 57 from one sealing member 30 to the other sealing member 30 before the fluid pressure actuator 1 is pressurized. Note that if the length of the axial direction XA of the tube 10 is short, the center link 50 adjacent to only one of the pair of center links 40 fixed to the pair of sealing members 30, or the center link 50 adjacent to neither of the pair of center links 40, may be omitted, and the multiple center links may be formed using only two center links 40. Note that if the length of the axial direction XA of the tube 10 is long, the center links 40 may be in contact with each other on the constraint side 57 by increasing the number of center links 50 arranged between the center links 40 or by changing the length of the center links 50.

[0030] The material of the multiple center blocks 40, 50 may be selected from materials that have compressive rigidity that prevents deformation, particularly in response to compressive stress on the restraint side 57, when the fluid pressure actuator 1 is pressurized and the tube 10 is driven to contract in the axial direction XA. The material of the multiple center blocks 40, 50 may be resin such as a thermoplastic synthetic resin, hard plastic, or hard foam material such as hard foam synthetic resin, or may be metal such as stainless steel. Note that, if it is desirable to reduce the weight of the fluid pressure actuator 1, it is preferable to use resin, hard plastic, or hard foam material.

[0031] The specific shapes of the plurality of center pieces 40, 50 in this embodiment will be described with reference to FIGS.

[0032] FIG. 3 is a perspective view showing a state in which multiple center pieces 40, 50 arranged inside the fluid pressure actuator 1 are in contact with each other. FIG. 4 is a side view showing the multiple center pieces 40, 50 before bending. FIG. 5 is a side view showing the multiple center pieces 40, 50 after bending. FIG. 6 is a perspective view of a center piece 50, of the multiple center pieces 40, 50, that is not directly fixed to the sealing member 30, with FIG. 6(a) being a perspective view mainly showing the left side. FIG. 6(b) being a perspective view mainly showing the right side. FIGS. 7(a) to 7(f) are six-view views showing a center piece 50, of the multiple center pieces 40, 50, that is not directly fixed to the sealing member 30. FIG. 7(g) is the cross-sectional view taken along line VIIg-VIIg in FIG. 7(f). Of the six views in Figures 7(a) to 7(f), Figure 7(a) is a front view, Figure 7(b) is a rear view, Figure 7(c) is a plan view, Figure 7(d) is a bottom view, Figure 7(e) is a left side view, and Figure 7(f) is a right side view.

[0033] 3 and 4 show multiple center pieces 40, 50 arranged inside the tube 10 of the fluid pressure actuator 1 in a state before pressure is applied inside the tube 10 (a state before the fluid pressure actuator 1 is bent, a state shown in the schematic diagram of FIG. 1). The center pieces 40, 50 are arranged such that adjacent center pieces abut on their restraint sides 57, with gaps 61 formed on their oscillation sides 59. As shown in FIG. 4, the multiple center pieces 40, 50 are adjacent to each other and form a generally cylindrical shape with the axial direction XA as its axis, matching the shape of the space inside the tube 10.

[0034] 5 shows the multiple inner links 40, 50 arranged inside the tube 10 of the fluid pressure actuator 1 in a state after pressurization inside the tube 10 (a state after the fluid pressure actuator 1 has been bent, a state shown in the schematic diagram of FIG. 2). In this state, the multiple inner links 40, 50 are bent to a state where there is no gap 61 on the oscillation side 59 or where the gap 61 is narrowed while maintaining the abutting state of the restraint side 57.

[0035] Next, with reference to Figures 6(a) to 6(b) and Figures 7(a) to 7(g), the specific structure of the center link 50 (the center link other than the pair of center links 40 arranged at both ends) that is not directly fixed to the sealing member 30 will be described.

[0036] As shown in Figures 6(a) and 7(g), a first convex portion 63 is provided on the restraining side 57 (lower side in Figure 7(a)) and a first concave portion 65 is provided on the swinging side 59 (upper side in Figure 7(a)) on the left side of the middle piece 50 when viewed from the front in Figure 7(a). Then, as shown in Figures 6(b) and 7(g), a second convex portion 67 is provided on the swinging side 59 and a second concave portion 69 is provided on the restraining side 57 on the right side of the middle piece 50.

[0037] When multiple inner links 50 are arranged adjacent to one another, on the restraint side 57, the first convex portion 63 of one inner link 50 enters and abuts against the second concave portion 69 of the other inner link 50. In contrast, on the swing side 59, the second convex portion 67 of one inner link 50 enters the first concave portion 65 of the other inner link 50 but does not abut against the first concave portion 65, forming a gap 61. In other words, in each inner link 50, the protrusion amount of the first convex portion 63 in the axial direction XA is equal to or greater than the recess amount of the second concave portion 69, so that adjacent inner links 50 abut against each other on the restraint side 57. Furthermore, the protrusion amount of the second convex portion 67 in the axial direction XA is less than the recess amount of the first concave portion 65, so that a gap 61 is formed between adjacent inner links 50 on the swing side 59.

[0038] 7(b), 7(c), 7(g), etc., on the restraint side 57 and the swinging side 59, side walls 71 are provided on both sides of the central portion where the first convex portion 63, the first concave portion 65, the second convex portion 67, and the second concave portion 69 are formed, protruding in the axial direction XA from both sides of the portion where the first concave portion 65 and the second concave portion 69 are formed. Note that, as shown in FIG. 7(g), the protruding direction of the side walls 71 is such that the side walls 71 formed on the sides of the first concave portion 65 protrude toward the first convex portion 63, and the side walls 71 formed on the sides of the second concave portion 69 protrude toward the second convex portion 67.

[0039] The side wall 71 restricts relative movement, such as rotation about the axial direction XA, between the center pieces 40, 50 within the tube 10. Furthermore, even when stress perpendicular to the axial direction XA is applied to the fluid pressure actuator 1, the side wall 71 abuts against the adjacent first convex portion 63 or second convex portion 67, thereby preventing bending of the fluid pressure actuator 1 in any direction other than the bending direction. As shown in FIG. 7(g), the side wall 71 is formed to protrude by an amount that does not hinder the swinging of the center piece 50 or the bending of the fluid pressure actuator 1.

[0040] 7(e) and 7(f), an air vent 51 is formed through the center of the circular outer periphery of the center piece 50. Furthermore, two first through holes 53 are formed on the restraint side 57, and a second through hole 55 is formed on the swing side 59.

[0041] As shown in Figures 6(a), 7(a), 7(b), and 7(d), one end of the first through hole 53 opens into the first protrusion 63, and the other end opens into the second recess 69, as shown in Figure 6(b). As shown in Figures 6(a) and 7(g), one end of the second through hole 55 opens into the first recess 65, and the other end opens into the second protrusion 67, as shown in Figures 6(b), 7(c), and 7(g).

[0042] FIG. 8 is an explanatory diagram showing a cross-sectional view of the fluid pressure actuator 1 according to this embodiment in a contracted and bent state, illustrating a restraining fiber cord 80 that keeps the center pieces 40, 50 in contact with each other on the restraining side 57, and a reverse warp prevention cord 90 that is arranged on the swinging side 59.

[0043] 1 and 8, center piece 40, which is arranged at both ends in the axial direction XA and configured to be fixed to a pair of sealing members 30, has vent holes 41 formed therethrough to allow fluid to flow in and out of sealing members 30. Also, similar to center piece 50 shown in FIGS. 6(a) to 6(b) and 7(a) to 7(g), two first through holes 43 are formed on restraining side 57 and one second through hole 45 is formed on swinging side 59.

[0044] In this embodiment, the end of the second through hole 45 on the sealing member 30 side opens into a notch (positioning portion) 47 formed on the swing side 59 of the center piece 40 and on the sealing member 30 side. The notch 47 also functions as an eye mark that indicates the swing side 59 where the center pieces 40, 50 can be bent.

[0045] In this embodiment, as shown in Fig. 1, a rubber cushion member 100 is disposed in the gap 61 formed on the swinging side of the adjacent center pieces 40, 50. The cushion member 100 is compressible so as not to significantly restrict the swinging of the center pieces 40, 50 when the fluid pressure actuator 1 is bent and deformed, and is a member that restores the center pieces 40, 50 to the pre-pressure position shown in Fig. 1 when the pressure inside the tube 10 of the fluid pressure actuator 1 is released.

[0046] The cushion member 100 is preferably made of a material such as rubber or urethane foam that has the desired compressibility that does not significantly restrict the oscillation of the center pieces 40, 50 when the fluid pressure actuator 1 is bent and deformed, and also has excellent resilience that allows the center pieces 40, 50 to return to their pre-pressure state after repeated compressive deformation.

[0047] In addition, the gap 61 in which the cushion member 100 is placed may be provided with a clearance that takes into account the shape of the compressed and deformed cushion member 100 so that the bending deformation of the middle pieces 40, 50 is not hindered when the cushion member 100 is deformed.

[0048] The structure for fixing the center piece 40 to the sealing member 30 may be such that the vent hole 41 is in communication with the sealing member 30 so as not to impede the inflow and outflow of fluid from the sealing member 30.

[0049] 8, a recess in the axial direction XA that can fit onto the outer periphery of sealing member 30 may be provided at the axial end of core 40, or the fluid passage of sealing member 30 may be formed with a larger diameter than necessary for the fluid flow path, and core 40 may be formed with a portion that protrudes in the axial direction XA to fit onto the inner circumferential surface of the fluid passage of sealing member 30. Note that while vent hole 41 in core 40 is essential for allowing fluid to flow in and out of sealing member 30, vent hole 51 in core 50 does not have to be formed in core 50 because fluid can flow in and out of tube 10 from the position where core 40 and core 50 are adjacent to each other.

[0050] The sealing member 30 seals the end 11 of the tube 10 in the axial direction XA of the fluid pressure actuator 1. The sealing member 30 is composed of a sealing member body 31 and a crimping member 33.

[0051] The sealing member main body 31 is inserted into the tubular tube 10. Specifically, the sealing member main body 31 has a head portion whose dimension is larger than the inner diameter of the tube 10 and a body portion whose outer diameter is large enough to be inserted into the inner diameter of the tube 10. The body portion is inserted into the tube 10.

[0052] The sealing member body 31 is preferably made of a metal such as stainless steel, but is not limited to such a metal and may be made of a hard plastic material or the like.

[0053] The crimping member 33 crimps the tube 10 inserted into the sealing member body 31 and the sleeve 20 covering the outer peripheral surface of the tube 10 together with the sealing member body 31. Specifically, the crimping member 33 is provided on the outer peripheral surfaces of the tube 10 and the sleeve 20 at the portions where the sealing member body 31 is inserted, and crimps these members to the sealing member body 31.

[0054] Metals such as aluminum alloy, brass, and iron can be used for the crimping member 33. When the crimping member 33 is crimped by a crimping jig, an indentation may be formed in the crimping member 33.

[0055] The sealing member 30 may include a locking ring (not shown) that locks the sleeve 20 to the sealing member body 31. Specifically, the sleeve 20 may be folded back radially outward via the locking ring.

[0056] The locking ring may have a shape that allows it to engage with the sealing member main body 31. The locking ring may be made of the same material as the sealing member main body 31, such as metal or hard plastic material, or natural fiber (natural fiber thread), rubber (for example, an O-ring), or the like.

[0057] (3) Configuration of restraint mechanisms 43, 53, and 80 The fluid pressure actuator 1 of this embodiment further includes a restraint mechanism 43, 53, 80 that holds adjacent inner links 40, 50 in contact with each other on the restraint side 57 within the tube 10 when the plurality of inner links 40, 50 are pressurized by fluid pressure.

[0058] The first through-hole 43 of the center link 40 and the first through-hole 53 of the center link 50 are formed so as to communicate with each other when adjacent to each other. Similarly, the second through-hole 45 of the center link 40 and the second through-hole 55 of the center link 50 are formed so as to communicate with each other when adjacent to each other.

[0059] The restraining mechanism 43, 53, 80 includes a first through hole 43, 53 formed in each of the middle pieces 40, 50 so as to communicate with each other on the restraining sides 57 of the adjacent middle pieces 40, 50, and a restraining fiber cord 80 inserted into each of the first through holes 43, 53 from one end side to the other end side in the axial direction XA of the multiple middle pieces 40, 50, and holding the middle pieces 40, 50 in contact with each other on the restraining sides 57.

[0060] The restraint mechanism may have a plurality of first through holes 43, 53 formed in each of the center links 40, 50. In this embodiment, as shown in Figures 6(a) and 6(b), two first through holes 43, 53 are formed in each of the center links 40, 50.

[0061] Each of the plurality of first through holes 43, 53 communicates from one end side to the other end side in the axial direction XA of the plurality of center pieces 40, 50, and a restraining fiber cord 80 is inserted into each of the first through holes 43, 53.

[0062] In this embodiment, two restraining fiber cords 80 are inserted from one end to the other end of the multiple center pieces 40, 50 in the axial direction XA. The ends of the restraining fiber cords 80 are configured not to enter the first through holes 43, 53 when inserted through the first through holes 43, 53. When inserted through the first through holes 43, 53, the restraining fiber cords 80 restrain relative movement between adjacent center pieces 40, 50. Furthermore, because the center pieces 40, 50 are restrained by the two restraining fiber cords 80, relative movement, such as rotation, between the center pieces 40, 50 within the tube 10 can be restrained.

[0063] The material of the restraining fiber cord 80 may be selected from among the fiber cords that can be used for the sleeve 20, taking into consideration the desired tensile strength and the like.

[0064] On the swinging sides 59 of the center pieces 40, 50 that are adjacent to each other from one end to the other in the axial direction XA of the center pieces 40, 50, the second through-holes 45, 55 communicate from one end to the other in the axial direction XA of the center pieces 40, 50. A reverse warp prevention cord 90 is inserted into the second through-holes 45, 55 to prevent the gap 61 on the swinging side 59 from widening beyond a state where it is not pressurized by fluid pressure.

[0065] When the anti-reverse warp cord 90 is not bent as shown in Figures 3 and 4, it has a length equivalent to the distance between the openings of the second through holes 45 in the notches 47 on the oscillating side 59 of the center pieces 40 arranged at both ends, and is structured so that the ends do not enter the inside of the second through holes 45, as shown in Figure 8.

[0066] 8, when the fluid actuator 1 is bent, the end of the reverse warp prevention cord 90 is away from the opening of the second through-hole 45 in the notch 47, i.e., no tensile force is generated in the reverse warp prevention cord 90. If the fluid actuator 1 attempts to bend from its extended state in a direction that widens the gap 61 on the oscillation side 59 compared to when it is not pressurized by fluid pressure, the end of the reverse warp prevention cord 90 will come into contact with the opening of the second through-hole 45 in the notch 47, generating tensile force in the reverse warp prevention cord 90, thereby preventing reverse warp of the fluid actuator 1.

[0067] The material of the reverse warp prevention cord 90 may be selected from among the fiber cords that can be used for the sleeve 20, taking into consideration the desired tensile strength and the like.

[0068] (4) Sealing mechanism configuration 1, 2, and 8, the tube 10 is inserted into the body of the sealing member body 31 of the sealing member 30. The tube 10 and the sleeve 20 covering the outer peripheral surface of the tube 10 are crimped to the sealing member body 31 by a crimping member 33.

[0069] The crimping member 33 is larger in outer diameter than the body of the sealing member main body 31, and is inserted through the body and then crimped with a jig. The crimping member 33 crimps the tube 10 and the sleeve 20 together with the sealing member main body 31.

[0070] (5) Actions and Effects The fluid pressure actuator 1 has the following features.

[0071] Large bending angle (bends over 180 degrees) -Large generated force (approximately 40N) -Easy to control force (generated force is proportional to pressure) Simple structure - By coating the surface, it is possible to directly touch the object to be operated. Furthermore, the fluid pressure actuator 1 of this embodiment can be bent into a predetermined curved shape based on the structure of the center pieces 40, 50 that restrict the expansion and contraction of the tube 10. Therefore, even if the pressure inside the tube 10 rises excessively, the fluid pressure actuator 1 will not bend beyond the predetermined curved shape.

[0072] Furthermore, even when the fluid pressure actuator 1 is repeatedly bent, the fluid pressure actuator 1 is bent by providing the restraining side 57 and the swinging side 59 on the center pieces 40, 50, which are made of a material with compression rigidity, so no deformation occurs in the center pieces 40, 50. Therefore, even when the fluid pressure actuator 1 is repeatedly bent, its restoring force to its pre-bending state is less likely to decrease, and it has high repetitive durability.

[0073] Furthermore, the restraint mechanisms 43, 53, and 80 restrain the relative movement of adjacent center pieces 40 and 50, so that the curved structure of the fluid pressure actuator 1 is maintained even if, for example, the pressure inside the tube 10 rises excessively and tensile stress is applied between the sealing members 30.

[0074] Furthermore, in the fluid pressure actuator 1, the tube 10 is sealed by the sealing member 30 with the center pieces 40, 50 disposed within the tube, so the volume within the tube 10 is smaller than the volume within the tube 10 when the center pieces 40, 50 are not disposed. Therefore, in the fluid pressure actuator 1 of this embodiment, the pressure within the tube can be increased more easily than in a case where the center pieces 40, 50 are not used, and the response speed of the fluid pressure actuator 1 can be improved.

[0075] (6) Other embodiments The present invention has been described above in accordance with the embodiments, but it will be obvious to those skilled in the art that the present invention is not limited to these descriptions and that various modifications and improvements are possible.

[0076] 3 and 4, when the multiple inner pieces 40, 50 arranged inside the body pressure actuator 1 are in contact with each other, they have a generally cylindrical shape with the axial direction XA as their axis, and the restraint sides 57 where adjacent inner pieces 40, 50 are in contact with each other are always arranged on the same first side in the circumferential direction with respect to the tube 10, and the oscillating sides 59 are arranged on the second side opposite the first side. However, the arrangement of the restraint sides 57 and oscillating sides 59 with respect to the tube 10 of the multiple inner pieces 40, 50 arranged inside the body pressure actuator 1 is not limited to this.

[0077] The restraint side 57 and the swinging side 59 of the multiple center pieces 40, 50 do not always need to be on the same side relative to the tube 10, and the positions of the restraint side 57 and the swinging side 59 relative to the tube 10 may be switched midway.

[0078] Specifically, from one end of the tube 10 in the axial direction XA to a predetermined position, the restraint side 57 is arranged on the first side and the oscillating side 59 is arranged on the second side, and from the predetermined position to the other end, the restraint side 57 is arranged on the second side and the oscillating side 59 is arranged on the first side, so that the deformation of the tube 10 when bent may be S-shaped.

[0079] In this case, the middle piece 50 may be configured such that, for example, the arrangement of the first convex portion 63 and the first concave portion 65 on the left side remains the same, but the second convex portion 67 is formed in the location where the second concave portion 69 was formed on the right side, and the middle piece with the second concave portion 69 is positioned at the location where the second convex portion 67 was formed, and further, the first through hole 53 is formed within the middle piece to connect the first convex portion 63 and the second concave portion 69, and the second through hole 55 is formed to connect the first concave portion 65 and the second convex portion 67.

[0080] Furthermore, in this embodiment, the cushion member 100 is made of rubber, urethane foam, or the like, but the cushion member 100 is not limited to these. Any material may be selected as the cushion member 100 as long as it can easily compress and deform when the inside of the tube 10 is pressurized, thereby ensuring the bendability of the fluid pressure actuator 1, and can restore the positions of the center links 40, 50 to their pre-pressure state when the inside of the tube 10 is depressurized. For example, a spring having an elastic modulus that satisfies the above conditions may be disposed in the gap 61 as the cushion member 100. Furthermore, if the greatest possible amount of bending is required, the cushion member 100 may be omitted.

[0081] Although the embodiments of the present invention have been described above, the descriptions and drawings that form part of this disclosure should not be understood to limit the present invention. Various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art from this disclosure. [Explanation of symbols]

[0082] 1. Fluid pressure actuator 10 tubes 11 Tube end 20 sleeves 30 Sealing member 31 sealing member body 33 Caulking material 40 Center pieces on both ends 41 Ventilation hole 43 First through hole 45 Second through hole 47 Notch (positioning part) 50 Middle piece 51 Ventilation hole 53 First through hole 55 Second through hole 57 Restraint side 59 Swing side 61 Gap 63 First convex part 65 First recess 67 Second convex part 69 Second recess 71 Side wall 43,53,80 Restraint mechanism 80 Restraint textile cord 90 Anti-warping cord 100 cushion member XA Axial direction

Claims

1. a tube that expands and contracts due to fluid pressure; a sleeve having an elastic structure in which fiber cords oriented in a predetermined direction are woven, the sleeve covering the outer circumferential surface of the tube; a pair of sealing members that seal both axial ends of the tube; a plurality of center pieces disposed adjacent to each other in the axial direction inside the tube, the plurality of center pieces are configured to have a restraint side where adjacent center pieces abut against each other in the tube when it is not pressurized by the pressure of the fluid, and a swing side where a gap is formed at a position opposite the restraint side to allow the adjacent center pieces to swing relative to each other, the plurality of center pieces further include a restraining mechanism that holds the center pieces adjacent to each other on the restraining side in contact with each other even in the tube in a state in which the tube is pressurized by the pressure of the fluid, The restraining mechanism includes a first through hole formed in each center piece so as to communicate with adjacent center pieces on the restraining side, and a restraining fiber cord that is inserted into each of the first through holes from one end side to the other end side of the plurality of center pieces in the axial direction to hold the center pieces in contact with each other on the restraining side.

2. 2. The fluid pressure actuator according to claim 1, wherein a plurality of the first through holes of the restraining mechanism are formed in each center piece, and a plurality of the restraining fiber cords are inserted into the plurality of first through holes.

3. 3. The fluid pressure actuator according to claim 1, further comprising: second through holes formed on the pivoting sides of adjacent center pieces from one end side to the other end side in the axial direction of the center pieces; and reverse warp prevention cords inserted into the second through holes from one end side to the other end side of the center pieces in the axial direction of the center pieces to prevent the gaps on the pivoting sides from widening beyond a state in which they are not pressurized by the pressure of the fluid.

4. A cushion member is disposed in the gap formed on the swinging side of the adjacent center pieces, 4. The fluid pressure actuator according to claim 1, wherein the cushion member restores the postures of the plurality of center pieces to a state in which the inside of the tube is not pressurized by the pressure of the fluid.

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