Pipe coupling

Abstract

Provided is a pipe coupling which makes it possible to suppress pipe disconnection. A pipe coupling 10 comprises: a cylindrical main body 11; a cylindrical advancing / retracting thin tube 12 which is disposed inside the main body 11 and which is provided so as to be capable of advancing and retracting along the axial direction of the main body 11; and a cylindrical holding tube 13 which is disposed between the main body 11 and the advancing / retracting thin tube 12 and which is provided so as to be capable of advancing and retracting along the axial direction together with the advancing / retracting thin tube 12, wherein the main body 11 has: a tube insertion part 23 which is disposed on one side in the axial direction and into which a tube is inserted; and a tapered inner circumferential surface 24 which is disposed on another side from the tube insertion part 23 and which has a diameter that decreases toward the tube insertion part 23, the holding tube 13 moves toward the one side together with the advancing / retracting thin tube 12 and is thereby pressed against the tapered inner circumferential surface 24 to decrease in the diameter, to hold the tube between the holding tube 13 and the advancing / retracting thin tube 12, and the tensile elastic modulus of the holding tube 13 as measured in compliance with ISO 527 at a measurement temperature of 23±2°C and a measurement humidity of 50±10% is 8,000-11,000 MPa.

Description

Pipe fittings

[0001] The present invention relates to a pipe joint.

[0002] Pipe fittings for connecting pipes such as hoses and tubes are known. Patent Document 1 discloses a one-touch pipe fitting that can crimp and connect pipes using fluid pressure without using any crimping equipment, jigs, or the like.

[0003] The pipe fitting disclosed in Patent Document 1 includes a main body formed in a cylindrical shape with both ends open and one end serving as a hose insertion port, a retractable narrow tube provided within the main body so as to be retractable, and a retaining tube provided between the main body and the retractable narrow tube so as to be retractable. A tapered portion that narrows in diameter toward the hose insertion port is formed on the inner periphery of the main body near the hose insertion port. With a hose inserted between the retaining tube and the retractable narrow tube through the hose insertion port, the pipe fitting disclosed in Patent Document 1 moves the retractable narrow tube and the retaining tube toward the hose insertion port, and the retaining tube contracts in diameter due to the pressing force from the tapered portion, thereby holding the hose between the retaining tube and the retractable narrow tube. The retaining tube is made of synthetic resin.

[0004] Japanese Utility Model Application Laid-Open Publication No. 05-067893

[0005] A pipe fitting requires a retaining tube to hold the pipe so that it does not come loose, even when used in a variety of environments, including not only room temperature and normal pressure environments but also high temperature and pressure environments. However, in the pipe fitting disclosed in Patent Document 1, in a high temperature and pressure environment, the retaining tube's mechanical strength is insufficient, causing the retaining tube to abnormally deform and come loose from the hose insertion port, resulting in the pipe being unretained and coming loose. If the mechanical strength of the retaining tube is too high, the retaining tube will not contract, and the pipe will not be retained and will come loose.

[0006] An object of the present invention is to provide a pipe joint that can prevent a pipe from coming loose.

[0007] a retaining tube that is arranged between the main body and the advancing / retracting tapered tube and is movable forward and backward along the axial direction of the main body; and a retaining tube that is arranged between the main body and the advancing / retracting tapered tube and is movable forward and backward together with the advancing / retracting tapered tube along the axial direction. The main body is arranged on one side in the axial direction and has a pipe insertion portion into which the pipe is inserted, and is arranged on the other side opposite the one side of the pipe insertion portion and has a tapered inner circumferential surface that decreases in diameter toward the pipe insertion portion. As the retaining tube moves toward the one side together with the advancing / retracting tapered tube, it is pressed against the tapered inner circumferential surface and decreases in diameter, thereby retaining the pipe between the retaining tube and the advancing / retracting tapered tube. The retaining tube has a tensile modulus of elasticity of 8000 MPa or more and 11000 MPa or less, measured in accordance with ISO 527 at a measurement temperature of 23±2°C and a measurement humidity of 50±10%.

[0008] According to the present invention, it is possible to provide a pipe joint that can prevent a pipe from coming loose.

[0009] Fig. 7 is a cross-sectional view cut in half of the pipe joint according to the present embodiment. Fig. 8 is a cross-sectional view cut in half of the advancing / retracting tapered cylinder. Fig. 9 is a perspective view of the retaining cylinder. Fig. 10 is a front view of the retaining cylinder. Fig. 11 is a cross-sectional view cut in half of the retaining cylinder. Fig. 12 is a cross-sectional view cut in half showing a state in which a pipe is inserted into the pipe joint. Fig. 13 is a cross-sectional view cut in half showing a state in which a pipe is connected to the pipe joint. Fig. 14 is an enlarged view of part A shown in Fig. 7 .

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The following description will discuss in detail preferred embodiments of the present invention with reference to the accompanying drawings. The preferred embodiments are merely examples of the present invention, and the present invention is not limited thereto.

[0011] <Configuration of Pipe Joint> Figure 1 is a cross-sectional view cut in half of a pipe joint 10. The pipe joint 10 is used to connect pipes (not shown) for circulating various fluids such as liquids and gases. Any type of pipe may be connected to the pipe joint 10, and examples of such pipes include hydraulic hoses, hoses for circulating liquids, and hoses for circulating gases.

[0012] 1 , pipe fitting 10 includes main body 11, advancing / retracting tapered cylinder 12, and retaining cylinder 13. Pipe fitting 10 is configured such that main body 11 is formed in a cylindrical shape with both ends open, one end of which is an insertion port for a pipe, and inside main body 11, advancing / retracting tapered cylinder 12 and retaining cylinder 13 are arranged coaxially with main body 11, and when advancing / retracting tapered cylinder 12 and retaining cylinder 13 move toward the insertion port side of the pipe with the pipe inserted between advancing / retracting tapered cylinder 12 and retaining cylinder 13, the diameter of retaining cylinder 13 contracts and presses the pipe against advancing / retracting tapered cylinder 12, so that the pipe is clamped between advancing / retracting tapered cylinder 12 and retaining cylinder 13.

[0013] The main body 11 is formed in a hollow cylindrical shape. The main body 11 has a joint body 14, a socket 15 into which a pipe is inserted, and a connection part 16 that is connected to equipment such as hydraulic equipment (not shown). The socket 15 is disposed on one side Z1 in the axial direction of the main body 11, and the connection part 16 is disposed on the other side Z2 opposite to the one side Z1 in the axial direction of the main body 11. The joint body 14 is disposed between the socket 15 and the connection part 16.

[0014] The joint body 14 has a large diameter portion 17 and a small diameter portion 18 provided on the other side Z2 of the large diameter portion 17. The inner diameter of the large diameter portion 17 is larger than the inner diameter of the small diameter portion 18. A step 35 is provided between an inner circumferential surface 33 of the large diameter portion 17 and an inner circumferential surface 34 of the small diameter portion 18. A large diameter portion 42 of the retractable narrow cylinder 12, which will be described later, abuts against the step 35.

[0015] The large diameter portion 17 has an annular surface 36 facing one side Z1 in the axial direction of the main body 11. An annular lock ring 37 is provided on the annular surface 36. A plurality of claws 38 are provided on the inner periphery of the lock ring 37. The plurality of claws 38 are inclined with respect to the axial direction of the main body 11, with their tips facing the one side Z1.

[0016] The socket 15 has a fixed portion 20, a cylindrical portion 21, a tapered portion 22, and a pipe insertion portion 23. The socket 15 has a configuration in which the fixed portion 20, the cylindrical portion 21, the tapered portion 22, and the pipe insertion portion 23 are integrally formed.

[0017] The fixing portion 20 is fixed to the large diameter portion 17 of the joint body 14. Specifically, with a portion of one side Z1 of the large diameter portion 17 inserted into the other end of the other side Z2 of the fixing portion 20, the other end of the fixing portion 20 is fixed to the large diameter portion 17 by a method such as crimping. The internal space of the fixing portion 20 is in communication with the internal space of the large diameter portion 17.

[0018] The cylindrical portion 21 is provided on one side Z1 of the fixed portion 20. The other end of the cylindrical portion 21 on the other side Z2 is connected to one end of the one side Z1 of the fixed portion 20. The internal space of the cylindrical portion 21 is in communication with the internal space of the fixed portion 20.

[0019] The inner and outer diameters of the cylindrical portion 21 are uniform around the entire circumference. Note that "uniform" includes not only cases where they are strictly uniform, but also cases where they are approximately uniform, i.e., cases where they vary within a range that does not deviate from the spirit of the invention (for example, cases where they vary within a tolerance range determined at the time of design).

[0020] The tapered portion 22 is provided on one side Z1 of the cylindrical portion 21. The other end of the tapered portion 22 on the other side Z2 is connected to one end of the cylindrical portion 21 on the one side Z1. The internal space of the tapered portion 22 is in communication with the internal space of the cylindrical portion 21. The inner diameter and outer diameter of the tapered portion 22 decrease toward the one side Z1.

[0021] The pipe insertion portion 23 is disposed on one side Z1 in the axial direction of the main body 11 and forms an insertion port through which the pipe is inserted. The pipe insertion portion 23 is provided on one side Z1 of the tapered portion 22. The other end portion on the other side Z2 of the pipe insertion portion 23 is connected to one end portion on one side Z1 of the tapered portion 22. The internal space of the pipe insertion portion 23 communicates with the internal space of the tapered portion 22. The inner diameter and outer diameter of the pipe insertion portion 23 are uniform around the entire circumference.

[0022] A tapered inner peripheral surface 24 is disposed on the other side Z2 of the pipe insertion portion 23. The tapered inner peripheral surface 24 constitutes the inner peripheral surface of the tapered portion 22. The tapered inner peripheral surface 24 becomes smaller in diameter as it moves toward one side Z1 in the axial direction of the main body 11, i.e., toward the pipe insertion portion 23. The tapered inner peripheral surface 24 is connected to the inner peripheral surface of the pipe insertion portion 23.

[0023] The socket 15 has a through hole 25 into which an insert (not shown) is inserted to remove the pipe inserted into the pipe insertion portion 23. The through hole 25 is provided in the tapered portion 22. The number of through holes 25 is not particularly limited. For example, one or more through holes 25 may be provided at different positions in the circumferential direction of the tapered portion 22. As the insert, for example, an insert disclosed in Japanese Patent Laid-Open No. 4-151089 or the like may be used.

[0024] The connection part 16 is detachably connected to the device. In this example, the connection part 16 is configured as a hexagonal cap nut with a through hole, and one end on one side Z1 and the other end on the other side Z2 are each open. The connection part 16 has a female thread on its inner circumferential surface. The female thread on the connection part 16 is threadedly engaged with a male thread on the device. The connection part 16 is not limited to a configuration having a female thread on its inner circumferential surface, and may also have a male thread on its outer circumferential surface.

[0025] The connecting portion 16 is rotatably attached to the small diameter portion 18 of the fitting body 14. Specifically, with a portion of the other side Z2 of the small diameter portion 18 inserted into one end of the one side Z1 of the connecting portion 16, the one end of the connecting portion 16 is rotatably attached to the small diameter portion 18 by a method such as crimping. The internal space of the connecting portion 16 is in communication with the internal space of the small diameter portion 18.

[0026] The retractable thin cylinder 12 is formed in a hollow cylindrical shape, is disposed inside the main body 11, and is provided so as to be retractable along the axial direction of the main body 11. The retractable thin cylinder 12 is also called a nipple.

[0027] 2 is a cross-sectional view cut in half of the retractable narrow cylinder 12. As shown in Fig. 2, the retractable narrow cylinder 12 has a small diameter portion 40, a medium diameter portion 41 having an outer diameter larger than that of the small diameter portion 40, and a large diameter portion 42 having an outer diameter larger than that of the medium diameter portion 41.

[0028] The small diameter portion 40 is inserted into the inside of the pipe. The outer peripheral surface of the small diameter portion 40 contacts the inner peripheral surface of the pipe. The outer peripheral surface of the small diameter portion 40 is provided with an annular groove 45 and a seal groove 46.

[0029] The annular groove 45 has a corner 47 connected to the outer peripheral surface of the small diameter portion 40. The corner 47 of the annular groove 45 comes into close contact with the inner peripheral surface of the pipe inserted through the pipe insertion portion 23. The corner 47 has an R-shape. The R-shaped corner 47 comes into close contact with the curved surface of the pipe so that the inner peripheral surface of the pipe fits along it.

[0030] The small-diameter portion 40 of the retractable narrow cylinder 12 has a so-called annular shape, and has a plurality of annular grooves 45 formed on its outer peripheral surface. A plurality of the annular grooves 45 are formed on one side Z1 of the seal groove 46 in the axial direction of the main body 11, and a plurality of the annular grooves 45 are formed on the other side Z2 of the seal groove 46 in the axial direction of the main body 11. Corners 47 of the plurality of annular grooves 45 come into close contact with the inner peripheral surface of the pipe inserted through the pipe insertion portion 23.

[0031] A seal member 48 (see FIG. 1) is provided in the seal groove 46. The seal member 48 seals the gap between the small diameter portion 40 and the piping, ensuring fluid-tightness between the small diameter portion 40 and the piping. The seal member 48 is, for example, an O-ring.

[0032] A pressing portion 49 (see FIG. 1 ) is provided on the outer peripheral surface of the small diameter portion 40 to press the retaining tube 13 (described later) toward one side Z1. The pressing portion 49 abuts against a step portion 50 provided between the outer peripheral surface of the small diameter portion 40 and the outer peripheral surface of the medium diameter portion 41. The pressing portion 49 is formed in an annular shape. The pressing portion 49 presses the retaining tube 13 by moving together with the reciprocating narrow tube 12 toward one side Z1 in the axial direction of the main body 11. The pressing portion 49 is also called a pressure ring.

[0033] The outer peripheral surface of the medium diameter portion 41 is composed of a first cylindrical surface 51 provided on one side Z1 in the axial direction of the main body 11, a second cylindrical surface 52 provided on the other side Z2 in the axial direction of the main body 11 and having an outer diameter larger than that of the first cylindrical surface 51, and a tapered surface 53 connecting the first cylindrical surface 51 and the second cylindrical surface 52 and decreasing in diameter toward the one side Z1. The first cylindrical surface 51 is not in contact with the multiple claws 38 of the lock ring 37. The second cylindrical surface 52 and the tapered surface 53 come into contact with the multiple claws 38 of the lock ring 37 when the retractable tapered cylinder 12 moves toward the one side Z1.

[0034] The second cylindrical surface 52 has an uneven shape. The uneven second cylindrical surface 52 engages with the multiple claws 38 of the lock ring 37. The uneven second cylindrical surface 52 and the lock ring 37 form a ratchet mechanism that allows movement of the retractable tapered cylinder 12 to one side Z1 and restricts movement of the retractable tapered cylinder 12 to the other side Z2. The uneven shape of the second cylindrical surface 52 is formed, for example, by grooves. The grooves are circumferential grooves that extend around the entire circumference of the second cylindrical surface 52, or spiral grooves that extend spirally along the axial direction of the main body 11. In this example, multiple circumferential grooves are provided on the entire surface of the second cylindrical surface 52. Note that the grooves are not limited to being provided on the entire surface of the second cylindrical surface 52, and may be provided on only a portion of the second cylindrical surface 52.

[0035] A seal groove 55 is provided on the outer circumferential surface of the large diameter portion 42. A seal member 56 (see FIG. 1) is provided in the seal groove 55. The seal member 56 closes the gap between the large diameter portion 42 and the large diameter portion 17. This ensures fluid tightness between the large diameter portion 42 and the large diameter portion 17. The seal member 56 is, for example, an O-ring.

[0036] The large diameter portion 42 abuts against a step 35 provided between the inner circumferential surface 33 of the large diameter portion 17 and the inner circumferential surface 34 of the small diameter portion 18. When the large diameter portion 42 abuts against the step 35, the movement of the reciprocating narrow cylinder 12 toward the other side Z2 in the axial direction of the main body 11 is restricted.

[0037] The retaining cylinder 13 is formed in a hollow cylindrical shape and is disposed between the main body 11 and the advancing / retracting thin cylinder 12. The retaining cylinder 13 is provided so as to be able to advance and retreat along the axial direction of the main body 11 together with the advancing / retracting thin cylinder 12 (see FIG. 1). When the retaining cylinder 13 moves together with the advancing / retracting thin cylinder 12 toward one side Z1 in the axial direction of the main body 11, the retaining cylinder 13 is pressed against the tapered inner circumferential surface 24 of the tapered portion 22, reducing its diameter and pressing the piping against the small-diameter portion 40 of the advancing / retracting thin cylinder 12, thereby retaining the piping between the retaining cylinder 13 and the advancing / retracting thin cylinder 12. The retaining cylinder 13 is also called a gripper.

[0038] The tensile modulus of the retaining tube 13, measured in accordance with ISO 527 at a measurement temperature of 23±2°C and a measurement humidity of 50±10%, is 8000 MPa or more and 11000 MPa or less. If the tensile modulus of the retaining tube 13 is less than 8000 MPa, when the piping inserted between the retractable tapered tube 12 and the retaining tube 13 via the piping insertion portion 23 moves toward one side Z1 in the axial direction of the main body 11 (i.e., the direction in which the piping is removed), the retaining tube 13 pressed against the tapered inner circumferential surface 24 of the main body 11 (socket 15) may be excessively crushed or otherwise abnormally deformed, causing the retaining tube 13 to slip out of the gap between the socket 15 and the piping, resulting in the piping being unretained and removed. The retaining tube 13 may also be destroyed by the abnormal deformation. If the tensile modulus of the retaining tube 13 is less than 8000 MPa, abnormal deformation of the retaining tube 13 is likely to occur in a high-temperature, high-pressure environment. If the tensile modulus of the retaining tube 13 exceeds 11,000 MPa, when the piping inserted between the retractable tapered tube 12 and the retaining tube 13 via the piping insertion portion 23 moves in the removal direction, the retaining tube 13, which is in contact with the tapered inner circumferential surface 24 of the main body 11 (socket 15), does not sufficiently contract in diameter against the pressing force from the tapered inner circumferential surface 24, causing the movement of the retaining tube 13 to stop toward the one side Z1. The piping is not pressed against the small-diameter portion 40 of the retractable tapered tube 12, and the piping may not be held and may come out. By making the tensile modulus of the retaining tube 13 8,000 MPa or more and 11,000 MPa or less, abnormal deformation of the retaining tube 13 is suppressed, and the retaining tube 13 can be appropriately contracted in diameter to crimp and hold the piping. The tensile modulus of the retaining tube 13 is preferably 8,500 MPa or more and 9,600 MPa or less.

[0039] The material of the retaining tube 13 is fiber-reinforced plastic (FRP), that is, composed of synthetic resin and reinforcing fiber. Examples of synthetic resins include polyacetal resin (POM), polyamide resin (PA), and polyether ether ketone resin (PEEK), and these are used alone or in combination. Examples of polyamide resins include polyamide 12 (PA12) and polyamide 6 (PA6). Examples of reinforcing fiber include glass fiber.

[0040] The retaining tube 13 is preferably made of synthetic resin and glass fiber. The glass fiber has excellent mechanical strength and heat resistance, and improves the tensile modulus of elasticity of the retaining tube 13. The synthetic resin is preferably at least one selected from the group consisting of polyacetal resin, polyamide 12, polyamide 6, and polyether ether ketone resin.

[0041] The glass fiber content of the entire material of the retaining tube 13 may be 23 wt % or more and 35 wt % or less. By setting the glass fiber content of the entire material of the retaining tube 13 within this range, it becomes easier to adjust the tensile modulus of elasticity of the retaining tube 13 within a desired range.

[0042] Fig. 3 is a perspective view of the retaining barrel 13. Fig. 4 is a front view of the retaining barrel 13 (a view of the retaining barrel 13 from one side Z1). Fig. 5 is a cross-sectional view of the retaining barrel 13 cut in half.

[0043] 3 to 5, the retaining tube 13 has a plurality of first slits 61 that open to one side Z1 in the axial direction of the main body 11, and a plurality of second slits 62 that open to the other side Z2 in the axial direction of the main body 11. The plurality of first slits 61 and the plurality of second slits 62 are alternately provided at equal intervals in the circumferential direction of the retaining tube 13. In this example, the retaining tube 13 has four first slits 61 and four second slits 62.

[0044] When the advancing / retracting tapered cylinder 12 and the retaining cylinder 13 move to one side Z1 in the axial direction of the main body 11 with the piping inserted between them via the piping insertion portion 23, the outer circumferential surface of the retaining cylinder 13 is pressed against the tapered inner circumferential surface 24 of the main body 11 (socket 15), and the gaps between the plurality of first slits 61 and the gaps between the plurality of second slits 62 become smaller, thereby reducing the diameter of the retaining cylinder 13. The piping is clamped between the retaining cylinder 13 and the advancing / retracting tapered cylinder 12.

[0045] The outer peripheral surface of the retaining tube 13 is composed of a cylindrical surface 63 provided on the other axial side Z2 of the main body 11 and a tapered surface 64 provided on one axial side Z1 of the main body 11 and having a diameter that decreases toward one side Z1. The outer diameter of the cylindrical surface 63 is uniform around the entire circumference.

[0046] A helical protrusion 65 extending along the axial direction of the main body 11 is provided on the inner peripheral surface of the retaining tube 13. The retaining tube 13 can be manufactured using a mold for injection molding a molded product having a threaded portion. The helical protrusion 65 becomes the threaded portion when the retaining tube 13 as a molded product is unscrewed from the mold.

[0047] <Functions and Effects of Pipe Fitting> The connection portion 16 of the pipe fitting 10 is connected to, for example, hydraulic equipment. As shown in Fig. 6, a pipe 70 is inserted into the pipe insertion portion 23 of the main body 11 of the pipe fitting 10. In Fig. 6, the tip of the pipe 70 is disposed between the retractable tapered cylinder 12 and the retaining cylinder 13, and abuts against the pressing portion 49. Before pressurization of the pipe fitting 10, by inserting an inserting tool into the through hole 25 provided in the tapered portion 22 of the socket 15, the pipe 70 can be moved to the one side Z1 and pulled out of the pipe insertion portion 23 while restricting movement of the retaining cylinder 13 to the one side Z1. This makes it possible to adjust the length of the pipe 70, etc.

[0048] When the hydraulic device is activated, a fluid at, for example, 80°C flows through the pipe fitting 10, pressurizing the inside of the pipe fitting 10. The internal pressure of the pipe fitting 10 becomes, for example, 21 MPa. The fluid pressure acts on the retractable tapered cylinder 12. As shown in FIG. 7 , the retractable tapered cylinder 12 moves toward one side Z1 in the axial direction of the main body 11 in response to the fluid pressure. As the retractable tapered cylinder 12 moves, the retaining cylinder 13 is pressed by the pressing portion 49 and moves toward the one side Z1, and the outer circumferential surface of the retaining cylinder 13 abuts against the tapered inner circumferential surface 24 of the main body 11 (socket 15). As the retractable tapered cylinder 12 and the retaining cylinder 13 move further toward the one side Z1, the outer circumferential surface of the retaining cylinder 13 is pressed against the tapered inner circumferential surface 24, and the retaining cylinder 13 contracts in diameter. As the diameter of the holding cylinder 13 is reduced, the piping 70 is pressed against the retractable thin cylinder 12 , and the piping 70 is held between the retractable thin cylinder 12 and the holding cylinder 13 .

[0049] After the pipe fitting 10 is pressurized, a ratchet mechanism formed by the second cylindrical surface 52 having an uneven shape of the retractable thin cylinder 12 and the multiple claw portions 38 of the lock ring 37 of the main body 11 allows the retractable thin cylinder 12 to move to one side Z1 and restricts the retractable thin cylinder 12 from moving to the other side Z2.

[0050] 8, the pipe 70 pressed against the retractable tapered cylinder 12 by the retaining cylinder 13 is in tight contact with each corner 47 of the multiple annular grooves 45 of the retractable tapered cylinder 12 and is firmly connected to the pipe fitting 10. The pipe fitting 10 is a one-touch type pipe fitting that can crimp and connect the pipe 70 using fluid pressure without using any crimping equipment, jigs, or the like.

[0051] The pipe fitting 10 conforms to ISO 527, and the tensile modulus of the retaining tube 13 measured at a temperature of 23±2°C and a humidity of 50±10% is 8000 MPa or more and 11000 MPa or less. This prevents abnormal deformation of the retaining tube 13, and the retaining tube 13 reduces in diameter to hold the pipe 70, thereby preventing the pipe 70 from coming loose.

[0052] Since the retaining tube 13 is made of synthetic resin and glass fiber, the tensile modulus of elasticity of the retaining tube 13 is improved.

[0053] The retaining tube 13 has a plurality of first slits 61 that open to one side Z1 in the axial direction of the main body 11 and a plurality of second slits 62 that open to the other side Z2 in the axial direction of the main body 11. When the retaining tube 13 moves to the one side Z1 in the axial direction of the main body 11 and the outer circumferential surface of the retaining tube 13 is pressed against the tapered inner circumferential surface 24 of the main body 11 (socket 15), the gaps between the plurality of first slits 61 and the gaps between the plurality of second slits 62 become smaller, and the retaining tube 13 becomes more likely to contract in diameter.

[0054] The inner peripheral surface of the retaining tube 13 is provided with a spiral protrusion 65 extending along the axial direction of the main body 11. When the retaining tube 13 is manufactured by injection molding, the retaining tube 13 injection-molded in a mold can be easily removed from the mold by unscrewing. Note that if the retaining tube is made of a material with excellent mechanical strength and multiple annular protrusions are provided on the inner peripheral surface of the retaining tube, the annular protrusions will become undercuts during injection molding, making it difficult to forcefully remove the retaining tube as a molded product from the mold.

[0055] An annular groove 45 and a seal groove 46 are provided on the outer peripheral surface of the small diameter portion 40 of the retractable narrow cylinder 12. A corner 47 of the annular groove 45 comes into close contact with the inner peripheral surface of the pipe 70, thereby increasing the contact surface pressure of the corner 47 against the inner peripheral surface of the pipe 70. A seal member 48 is provided in the seal groove 46, sealing the gap between the retractable narrow cylinder 12 and the pipe 70. In this way, fluid-tightness between the retractable narrow cylinder 12 and the pipe 70 is improved. The R-shaped corner 47 comes into close contact with the inner peripheral surface of the pipe 70 so that it fits along the curved surface, further improving fluid-tightness.

[0056] A plurality of annular grooves 45 are provided on one side Z1 in the axial direction of the main body 11 relative to the seal groove 46, and a plurality of annular grooves 45 are provided on the other side Z2 in the axial direction of the main body 11 relative to the seal groove 46. The corners 47 of the plurality of annular grooves 45 are in close contact with the inner peripheral surface of the piping 70, thereby further improving the fluid-tightness between the retractable narrow tube 12 and the piping 70. Note that if the small-diameter portion of the retractable narrow tube inserted into the piping has a so-called bamboo shoot shape and is provided with an annular protrusion with a triangular cross section on its outer peripheral surface, the contact area between the outer peripheral surface of the small-diameter portion and the inner peripheral surface of the piping is large, and therefore the contact surface pressure of the outer peripheral surface of the small-diameter portion against the inner peripheral surface of the piping is low, resulting in insufficient fluid-tightness between the retractable narrow tube and the piping, which may result in fluid leakage.

[0057] <High-Temperature Destruction Test> Three types of retaining tubes 13 (grippers) were manufactured by changing the type of synthetic resin and the glass fiber content, and these were designated Examples 1 to 3. Five types of retaining tubes (grippers) were manufactured by changing the type of synthetic resin and the glass fiber content, and these were designated Comparative Examples 1 to 5. Pipe joints were constructed using a main body 11 having a socket 15, a retractable narrow tube 12 (nipple), and the retaining tubes (grippers) of Examples 1 to 3 and Comparative Examples 1 to 5, and high-temperature destructive tests were conducted on each pipe joint. Table 1 summarizes the configurations of Examples 1 to 3 and Comparative Examples 1 to 5 and the results of the high-temperature destructive tests.

[0058]

[0059] The synthetic resin used in Example 1 was POM (grade: GH-25) manufactured by Polyplastics. The synthetic resin used in Example 2 was PA12 (grade: 3020GX9) manufactured by Ube Industries. The synthetic resin used in Example 3 was PA6 (grade: 1015GC6) manufactured by Ube Industries. The synthetic resin used in Comparative Example 1 was POM (grade: F10-01) manufactured by Mitsubishi Engineering Plastics. The synthetic resin used in Comparative Example 2 was PA12 (grade: 3014U) manufactured by Ube Industries. The synthetic resin used in Comparative Example 3 was PA6 (grade: 1013B) manufactured by Ube Industries. The synthetic resin used in Comparative Example 4 was PA6 (grade: 1015GC9) manufactured by Ube Industries. The synthetic resin used in Comparative Example 5 was PEEK (grade: 450GL30) manufactured by Victrex.

[0060] The tensile modulus was measured in accordance with ISO 527. The flexural modulus was measured in accordance with ISO 178.

[0061] The high-temperature fracture test involves applying static pressure at a constant rate to a hose (piping) connected to pipe fittings at both ends until the hose breaks. After circulating oil at 100°C through the hose for 10 minutes at room temperature (approximately 23°C), the high-temperature fracture test was performed, and the fracture mode (i.e., fracture mode) of the pipe fitting or hose was observed.

[0062] The failure modes include "hose rupture," "hose slippage," "gripper slippage," and "oil leakage." The following explains the meanings of these failure modes. "Hose rupture" refers to the hose bursting before the pipe coupling breaks due to the extremely good sealing performance of the connection between the hose and the pipe coupling. "Hose slippage" refers to the occurrence of an abnormality in which the gripper is pressed and moved by the pressing part when pressurized, and the gripper does not sufficiently contract, causing the gripper to stop moving when it comes into contact with the tapered inner surface of the socket, resulting in insufficient hose retention and the hose slipping out. "Gripper slippage" refers to the occurrence of abnormal deformation of the gripper as it is pressed and moved by the pressing part when pressurized, causing the gripper to slip out of the gap between the socket and the hose. "Oil leakage" refers to the occurrence of insufficient fluid-tightness between the nipple and the hose, allowing oil to enter between the nipple and the socket and leak from the socket's through-hole, etc.

[0063] As shown in Table 1, Examples 1 to 3, which had a tensile modulus of elasticity of 8,000 MPa or more and 11,000 MPa or less, were able to withstand the high-temperature fracture test, and it was confirmed that the hose continued to be held even when a "hose rupture" occurred, in which the hose burst. Comparative Examples 1 to 3, which had a tensile modulus of elasticity of less than 8,000 MPa, underwent abnormal deformation due to insufficient mechanical strength, resulting in "gripper slippage," in which the hose slipped out of the gap between the socket and the hose. As a result of "gripper slippage," the hose was no longer held in place and came out. Comparative Examples 4 and 5, which had a tensile modulus of elasticity of more than 11,000 MPa, had too high a mechanical strength to sufficiently reduce the diameter, resulting in "hose slippage," in which the hose was no longer held in place and came out.

[0064] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be modified as appropriate within the scope of the spirit of the present invention.

[0065] The socket 15 is not limited to having the fixing portion 20, the cylindrical portion 21, the tapered portion 22, and the pipe insertion portion 23. The socket 15 may have the fixing portion 20, the tapered portion 22, and the pipe insertion portion 23, but may not have the cylindrical portion 21.

[0066] The outer peripheral surface of the holding tube 13 is not limited to being configured with the cylindrical surface 63 and the tapered surface 64. The outer peripheral surface of the holding tube 13 may be configured with either the cylindrical surface 63 or the tapered surface 64.

[0067] REFERENCE SIGNS LIST 10 Pipe joint 11 Main body 12 Retractable narrow cylinder (nipple) 13 Holding cylinder (gripper) 14 Joint body 15 Socket 16 Connection portion 23 Pipe insertion portion 24 Tapered inner peripheral surface 45 Annular groove 46 Seal groove 61 First slit 62 Second slit 65 Spiral projection Z1 One side Z2 Other side

Claims

1. A pipe joint for connecting pipes, comprising: a main body formed in a cylindrical shape; a retractable cylinder formed in a cylindrical shape, disposed inside the main body, and provided so as to be retractable along the axial direction of the main body; and a holding cylinder formed in a cylindrical shape, disposed between the main body and the retractable cylinder, and provided so as to be retractable along the axial direction together with the retractable cylinder. The main body has a pipe insertion portion disposed on one side in the axial direction into which the pipe is inserted, and a tapered inner peripheral surface disposed on the other side opposite to the one side of the pipe insertion portion and having a reduced diameter toward the pipe insertion portion. The holding cylinder moves toward the one side together with the retractable cylinder, is pressed against the tapered inner peripheral surface and reduced in diameter, and holds the pipe between the retractable cylinder. The pipe joint has a tensile elastic modulus of the holding cylinder measured in accordance with ISO 527 at a measurement temperature of 23 ± 2°C and a measurement humidity of 50 ± 10% of 8000 MPa or more and 11000 MPa or less.

2. The pipe joint according to claim 1, wherein the holding cylinder is composed of a synthetic resin and glass fiber.

3. The pipe joint according to claim 2, wherein the synthetic resin is at least one selected from the group consisting of polyacetal resin, polyamide 12, polyamide 6, and polyetheretherketone resin.

4. The pipe joint according to claim 1, wherein the holding cylinder has a plurality of first slits opening to the one side and a plurality of second slits opening to the other side.

5. The pipe joint according to claim 4, wherein a spiral protrusion extending along the axial direction is provided on the inner peripheral surface of the holding cylinder.

6. The pipe joint according to claim 1, wherein an annular groove and a seal groove are provided on the outer peripheral surface of the retractable cylinder.

7. The pipe joint according to claim 6, wherein one or more annular grooves are provided on the one side of the seal groove and one or more annular grooves are provided on the other side of the seal groove.

Images