Fluid actuator

Abstract

This fluid actuator comprises: a cylindrical tube 24 that expands and contracts depending on the pressure of a fluid; a sleeve 26 that covers the outer peripheral surface of the tube 24; a pair of sealing members that seal the end portions of the tube; a long restraining member 28 that is disposed to extend from one side to the other side in an axial direction S on the outside in a radial direction of the tube 24 and the inside in a radial direction of the sleeve 26, resists compression in the axial direction S, and can be curved in an intersecting direction that intersects the axial direction S; and a fixing member 36 that fixes the sleeve 26 and the restraining member 28 to an insertion portion 32B from the outside of the sleeve 26 at a position corresponding to a restraining end portion 29 that is one end of the restraining member 28. The restraining end portion 29 is fixed, in the insertion portion 32B, to an outer surface of the tube 24 on a radially outer side than the outer surface corresponding to a portion of the tube 24 which is not inserted into the insertion portion 32B before being curved.

Description

Fluid Pressure Actuator

[0001] The present invention relates to a fluid pressure actuator.

[0002] Patent Document 1 discloses a fluid pressure actuator that includes a cylindrical tube that expands and contracts due to fluid pressure, an elastic structure made by weaving fiber cords oriented in a predetermined direction, a sleeve that covers the outer surface of the tube, and a sealing member that seals the axial end of the tube, and includes a restraining member that is provided inside the sleeve from one end to the other end in the axial direction, and the restraining member resists compression along the axial direction and is deformable in a direction perpendicular to the axial direction.

[0003] Japanese Patent Application Laid-Open No. 2021-088999

[0004] In such a fluid pressure actuator, the restraining member is fixed to the sealing member together with the tube and sleeve, but when the fluid pressure actuator is operated, the pressure inside the tube increases, causing the outer shape of the unfixed central portion to expand relative to the fixed portion. As a result, the restraining member bends at the boundary between the fixed portion and the central portion, and as this bending becomes larger, the load on the restraining member increases.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to provide a fluid pressure actuator that suppresses the load on a restraining member.

[0006] a pair of sealing members having insertion portions inserted from their tip ends into one and the other axial ends of the tube, respectively; a long restraining member arranged radially outside the tube and radially inside the sleeve, extending from one side to the other in the axial direction, resisting compression in the axial direction and bendable in a direction intersecting the axial direction; and a fixing member for fixing the sleeve and the restraining member to the insertion portion from the outside of the sleeve at a position corresponding to a restraining end, which is one end of the restraining member. The restraining end is fixed to the outer surface of the tube in the insertion portion, radially outside of an outer surface corresponding to a portion of the tube that is not inserted into the insertion portion before bending.

[0007] In the fluid pressure actuator of the first aspect, the restraining end portion is fixed to the outer surface of the tube at a position in the insertion portion radially outward of the outer surface corresponding to the portion of the tube that is not inserted into the insertion portion before bending. Therefore, even if the outer shape of the central portion of the tube increases when the tube expands in response to fluid pressure, the degree of deformation of the restraining member can be reduced, thereby suppressing the load.

[0008] In the fluid pressure actuator of the second aspect, at maximum internal pressure, the maximum diameter of the tube is within 160% of the portion of the insertion section where the restraint end section is located.

[0009] By setting it in this way, it is possible to suppress the load on the restraining member while ensuring deformation during operation of the fluid pressure actuator.

[0010] In the fluid pressure actuator of the third aspect, the insertion portion has a diameter that increases from the distal end toward the proximal end.

[0011] In this way, by making the diameter small at the tip of the insertion part and increasing toward the base end, the restraining end of the restraining member can be smoothly deformed and positioned along the outside of the insertion part.

[0012] According to the present invention, it is possible to provide a fluid pressure actuator that suppresses the load on the restraint member.

[0013] FIG. 1 is a plan view of a fluid pressure actuator according to an embodiment of the present disclosure. FIG. 2 is an exploded perspective view of one axial end side of a fluid pressure actuator according to an embodiment of the present disclosure. FIG. 3 is a perspective view illustrating a sealing member connector according to an embodiment of the present disclosure. FIG. 4 is a cross-sectional view of a connection portion (when not driven) between a sealing member connector on one end side and an actuator main body according to an embodiment of the present disclosure. FIG. 5 is a cross-sectional view of a connection portion (when driven) between a sealing member connector on one end side and an actuator main body according to an embodiment of the present disclosure. FIG. 6 is a cross-sectional view illustrating an operation of a fluid pressure actuator according to an embodiment of the present disclosure. FIG. 7 is a cross-sectional view of a connection portion (when not driven) between a sealing member connector on one end side and an actuator main body according to a conventional example. FIG. 8 is a cross-sectional view of a connection portion (when driven) between a sealing member connector on one end side and an actuator main body according to a conventional example.

[0014] Hereinafter, embodiments for realizing the technology of the present disclosure will be described in detail with reference to the drawings.

[0015] In addition, components and processes that perform the same actions and functions are given the same reference numerals throughout the drawings, and duplicated explanations may be omitted as appropriate. Furthermore, the present disclosure is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the purpose of the present disclosure.

[0016] As shown in FIG. 1, a fluid pressure actuator 20 according to an embodiment of the present disclosure includes an actuator body 22, a first sealing member 30A, and a second sealing member 30B.

[0017] As shown in FIG. 2 , the actuator main body 22 includes a tube 24, a sleeve 26, and a restraining member 28. The tube 24 is cylindrical and elastically deformable, expanding and contracting with changes in the pressure of the fluid inside. The axial direction S of the tube 24 is referred to as the "axial direction S." The tube 24 may be made of an elastic material such as butyl rubber. Air may be used as the fluid supplied to the tube 24, in which case the fluid pressure actuator 20 becomes a pneumatic actuator. Note that when the fluid pressure actuator 20 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.

[0018] The sleeve 26 is cylindrical and covers the outer periphery of the tube 24. The sleeve 26 is an elastic structure made by weaving fiber cords oriented in a predetermined direction, and the oriented cords intersect at a predetermined angle θ with respect to the axial direction S. By having such a shape, the sleeve 26 undergoes pantograph deformation that changes the angle θ, and follows the contraction and expansion of the tube 24 while regulating this contraction and expansion.

[0019] It is preferable to use fiber cords made of aromatic polyamide (aramid fiber) or polyethylene terephthalate (PET) as the cords constituting the sleeve 26. However, the cords are not limited to these types of fiber cords, and other high-strength fiber cords such as PBO fiber (polyparaphenylene benzobisoxazole) may also be used.

[0020] The restraining member 28 is provided between the tube 24 and the sleeve 26. The restraining member 28 is in the form of a long plate, and is arranged such that its longitudinal direction is along the axial direction S of the tube 24. The restraining member 28 covers part of the outer periphery of the tube 24 and is arranged from one end of the tube 24 to the other end.

[0021] The restraining member 28 includes a restraining main body 28A and a restraining end portion 29. The restraining main body 28A is a portion that is arranged along the axial direction S of the tube 24 and is not covered by a fixing member 36, which will be described later. The restraining end portion 29 is formed at one end of the restraining member 28. The restraining end portion 29, together with the tube 24 and the sleeve 26, is fixed to an insertion portion 32B, which will be described later, by the fixing member 36, which will be described later.

[0022] The restraint member 28 is formed of a material that does not expand or contract when pressurized, and is capable of bending and deforming in the direction in which its ends approach each other. A so-called leaf spring can be used as the restraint member 28. The dimensions of the leaf spring are determined depending on the size of the fluid pressure actuator 20, the required bending output, and other factors. The material of the leaf spring is not particularly limited, but typically, any material that is easily bendable and resistant to compression, such as a metal such as stainless steel, may be used. Alternatively, the leaf spring may be formed of a thin plate of carbon fiber reinforced plastic (CFRP).

[0023] The first sealing member 30A includes a sealing member connector 32, a locking wire 34, and a fixing member 36.

[0024] 3 and 4, the sealing member connector 32 has an integrally molded base end portion 32A and an insertion portion 32B. The base end portion 32A is generally rectangular parallelepiped with a diameter larger than the outer diameter of the tube 24, and the insertion portion 32B extends from one end side of the base end portion 32A in the axial direction S. The insertion portion 32B has, in order from the base end portion 32A side, a small diameter portion 48, a tapered portion 49, a large diameter portion 50, and a bamboo-like portion 52.

[0025] The shoot portion 52 protrudes from the distal end of the insertion portion 32B, and the tube 24 is inserted from the distal end of the shoot portion 52. The large diameter portion 50 is formed continuously with the base end 32A of the shoot portion 52 and has a disk shape with a larger diameter than the shoot portion 52. A step 42 is formed between the large diameter portion 50 and the shoot portion 52.

[0026] The tapered portion 49 is formed continuously from the large diameter portion 50 on the base end 32A side of the large diameter portion 50 (the back side of the insertion portion 32B), and is tapered so that the diameter becomes smaller as it approaches the base end 32A side.

[0027] The small diameter portion 48 is formed between the tapered portion 49 and the base end 32A, and has the same diameter from the tapered portion 49 to the base end 32A. The outer diameter of the small diameter portion 48 is smaller than the tip of the barbed portion 52. A step 35 is formed between the small diameter portion 48 and the base end 32A.

[0028] The shoot portion 52 is tapered in three stages (tip 52A, middle stage 52B, and base end 52C) with the diameter increasing toward the base end 32A. The outer diameter of the shoot portion 52 is smallest at the tip 52A and increases in the order of the middle stage 52B and base end 52C, so that the shoot portion 52 as a whole gradually expands in diameter from the tip end to the base end in the axial direction S. The angle with the axial direction S is largest at the tip 52A and smallest at the base end 52C, and when viewed in a cross section along the axial direction S, the slope gradually becomes gentler from the tip 52A side to the base end 52C side.

[0029] The largest diameter portion of the bamboo shoot portion 52 (the portion of the base end 52C on the base end portion 32A side, hereinafter referred to as the "outermost bamboo shoot portion 53") is larger than the inner diameter of the tube 24 when not inserted.

[0030] The sealing member connector 32 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.

[0031] 4, the sealing member connector 32 has a flow path R formed in the center of the insertion portion 32B as viewed in the axial direction S, which extends in the axial direction S and communicates with a connection hole H on the side surface of the base end portion 32A (see also FIG. 6). An air supply hose (not shown) is connected to the connection hole H, and compressed air is supplied to the flow path R.

[0032] As shown in Fig. 4, the restraining end 29 of the restraining member 28 is disposed in a position in the axial direction S that corresponds to the barbed portion 52 of the sealing member connector 32. The restraining main body 28A and the restraining end 29 of the restraining member 28 are disposed radially outward from the outer surface of the central portion that is not inserted into the insertion portion 32B of the tube 24. That is, as shown in Fig. 4, the restraining main body 28A and the restraining end 29 of the restraining member 28 extend linearly, and are disposed so that the restraining main body 28A is separated from the tube 24 (so that a gap is formed). The tip of the restraining end 29 is disposed opposite the step 42 of the large diameter portion 50.

[0033] The locking wire 34 is formed into a ring shape by winding the wire multiple times, and is wound around the outside of the sleeve 26 so as to sandwich the sleeve 26 between the small diameter portion 48 and the locking wire 34. The sleeve 26 is also folded back onto the outer periphery via the locking wire 34. This allows the sleeve 26 to be locked to the sealing member connector 32. A metal wire can be used as the locking wire 34.

[0034] The fixing member 36 is disposed so as to cover the insertion portion 32B on the outer periphery of the actuator main body 22. The barb portion 52, the tube 24, the restraining main body 28A of the restraining member 28, the sleeve 26 (before folding), and the sleeve 26 (after folding) are disposed in a portion of the fixing member 36 corresponding to the barb portion 52. The small diameter portion 48, the restraining end portion 29 of the restraining member 28, the sleeve 26 (before folding), the locking wire 34, and the sleeve 26 (after folding) are disposed inside the fixing member 36.

[0035] The tube 24 , restraining member 28 , and sleeve 26 can be secured to the sealing member connector 32 by crimping the securing member 36 radially inward.

[0036] When fixed by the fixing member 36, the restraining end 29 of the restraining member 28 is positioned radially inward relative to before fixation due to compressive deformation of the tube 24. The portion of the restraining end 29 corresponding to the outermost bamboo shoot portion 53 is positioned radially outward relative to the outer surface of the tube 24 corresponding to the restraining main body portion 28A.

[0037] The second sealing member 30B has the same structure as the first sealing member 30A, except that the flow path R is not formed therein.

[0038] Next, the assembly procedure for the fluid pressure actuator 20 in this embodiment will be described.

[0039] <Assembly of the fluid pressure actuator 20>

[0040] At one end of the fluid pressure actuator 20 in this embodiment, the first sealing member 30A and the actuator main body 22 are assembled as follows.

[0041] First, the tube 24 is inserted into the insertion portion 32B of the sealing member connector 32 until one end of the tube 24 abuts against the step 42. Next, the restraining member 28 is positioned so that the tip of the restraining end portion 29 is in the same position as the tip of the tube 24.

[0042] Next, the sleeve 26 is placed over the tube 24 and the base end 32A of the sealing member connector 32 to cover the outer surface of the restraint member 28, and the locking wire 34 is wound around the sleeve 26 from the radial outside and attached to the position of the small diameter portion 48.

[0043] Next, the sleeve 26 is folded back onto the insertion portion 32B of the sealing member connector 32 so that the locking wire 34 is on the inside, and the fixing member 36 is positioned so that it spans from the radial outside of the sleeve 26 to the end of the small diameter portion 48 of the insertion portion 32B, and is then crimped and fixed in place. As a result, the tube 24, the restraining member 28, and the sleeve 26 are fixed to the sealing member connector 32 on one side of the actuator body 22 in the axial direction S.

[0044] Next, on the other side in the axial direction S, the second sealing member 30B and the actuator body 22 are assembled in the same manner as the first sealing member 30A.

[0045] By the above procedure, one side and the other side of the tube 24 are sealed with the first sealing member 30A and the second sealing member 30B, and the fluid pressure actuator 20 is assembled.

[0046] Next, the operation of the fluid pressure actuator 20 in the present disclosure will be described.

[0047] <Operation of the fluid pressure actuator 20>

[0048] As shown in FIG. 6, the fluid pressure actuator 20 is used with a first sealing member 30A on one end side fixed and a second sealing member 30B on the other end side being a free end.

[0049] When compressed air is introduced through the connection hole H, the pressure inside the fluid pressure actuator 20 increases. Due to the increase in internal pressure, the tube 24 elastically deforms and expands, the sleeve 26 undergoes pantograph deformation so that the angle θ increases, and a force acts in a direction that shortens the length of the actuator main body 22. Because the shortening of the outer peripheral side wall on which the restraining member 28 of the actuator main body 22 is arranged is restricted, the outer peripheral wall of the actuator main body 22 on the side where the restraining member 28 is not arranged shortens when viewed from the axial direction S. This causes the restraining member 28 to flex and deform, and the entire actuator main body 22 bends as shown by the two-dot chain line in FIG. 7 .

[0050] At this time, as shown in FIG. 5 , the portion of the tube 24 not secured by the fixing member 36 expands near the end of the actuator body 22 adjacent to the first sealing member 30A. Because a gap is formed between the tube 24 and the restraining member 28 at the initial stage of expansion, the boundary between the restraining main body 28A and the restraining end 29 of the restraining member 28 does not bend radially outward until the tube 24 contacts the restraining member 28. When the internal pressure of the tube 24 increases, the restraining main body 28A is pushed by the tube 24 and bends radially outward near the end of the first sealing member 30A, as shown in FIG. 6 . It is preferable that, at the maximum internal pressure of the tube 24, the outer diameter A2 of the portion where the restraining end 29 is located be set to within 160% of the outer diameter A1 of the outermost portion 53 of the bamboo shoot. The portion of the restraining member 28 that is not secured by the fixing member 36 bends radially outward, while the portion corresponding to the fixing member 36 remains unchanged.

[0051] In the fluid pressure actuator 20 of this embodiment, the restraint end 29 is fixed to the outer surface of the tube 24 at a position in the insertion section 32B radially outward of the outer surface corresponding to the portion of the tube 24 that is not inserted into the insertion section 32B. Therefore, as described above, when the actuator main body 22 expands, the degree of deformation of the restraint member 28 can be reduced, thereby suppressing the load.

[0052] In addition, in this embodiment, the bamboo shoot portion 52 gradually expands in diameter at a gentle slope from the tip end 52A side to the base end 52C side, so that the restraint end portion 29 can be smoothly deformed and positioned along the outside of the insertion portion 32B.

[0053] Furthermore, at the beginning of expansion, a gap is formed between the tube 24 and the restraining member 28, so that the burden on the boundary between the restraining main body 28A and the restraining end 29 of the restraining member 28 can be reduced until the tube 24 comes into contact with the restraining member 28.

[0054] As shown in Figure 8, in the conventional configuration, the tube 24 is in contact with the restraint main body portion 28A of the restraint member 28 before operation, so as shown in Figure 9, the restraint member 28 bends radially outward from the early stage of expansion, increasing the load.

[0055] The above describes an embodiment of the present disclosure with reference to the accompanying drawings. However, it is clear that a person with ordinary knowledge in the field of technology to which the present disclosure pertains can conceive of various modifications or applications within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure.

[0056] The disclosure of Japanese Patent Application No. 2024-026898, filed on February 26, 2024, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A fluid pressure actuator comprising: a cylindrical tube that expands and contracts in response to fluid pressure; a sleeve that covers the outer peripheral surface of the tube and expands the tube radially as the tube expands while restricting axial extension; a pair of sealing members having insertion portions that are inserted from their tip sides into one and other axial ends of the tube, respectively, and that seal the tube ends; an elongated restraining member that is arranged radially outside the tube and radially inside the sleeve, extending from one axial end to the other, resisting compression in the axial direction and being bendable in a direction intersecting the axial direction; and a fixing member that fixes the sleeve and the restraining member to the insertion portion from the outside of the sleeve at a position corresponding to a restraining end that is one end of the restraining member, wherein the restraining end is fixed to the outer surface of the tube at the insertion portion, radially outside of an outer surface that corresponds to a portion of the tube that is not inserted into the insertion portion before bending.

2. The fluid pressure actuator according to claim 1, wherein, at maximum internal pressure, the maximum diameter of the tube is within 160% of the portion of the insertion section where the restrained end is located.

3. The fluid pressure actuator according to claim 1, wherein the insertion section has a diameter that increases from the tip to the base end.

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