Pipe joint structure

Abstract

To provide a pipe joint structure capable of effectively preventing collapse of a tube coupled to a joint body.SOLUTION: A pipe joint structure comprises: a tube 12; a joint body 20; a ferrule 40 that is axially adjacent to the joint body 20, through which the tube 12 passes, and that has a wedge-shaped cross-sectional shape; and a nut 50 having a cylindrical part 52 and an end plate 56. The end plate 56 extends radially inward from the cylindrical part 52 so as to sandwich the ferrule 40 between itself and a terminal surface of the joint body 20. On a surface of the ferrule 40 facing the terminal surface of the joint body 20, a stopper 46 is formed, which abuts against the terminal surface of the joint body 20 to restrict further relative movement of the joint body 20 in a direction toward the end plate 56.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This specification discloses a pipe joint structure for connecting a tube and a tubular joint body.

Background Art

[0002] Conventionally, many pipe joint structures for axially connecting two tubular bodies have been proposed. For example, Patent Document 1 discloses a quartz pipe joint structure including a quartz tube and a pipe joint. In Patent Document 1, a circumferential groove is formed on the outer peripheral surface of the quartz tube. The pipe joint includes a joint body that houses the end of the quartz tube, a ferrule that surrounds the quartz tube and closes the gap between the outer peripheral surface of the quartz tube and the inner peripheral surface of the joint body, a stopper disposed in the groove of the quartz tube, and a nut that is screwed and fastened to the outer peripheral surface of the joint body. According to the configuration of Patent Document 1, by tightening the nut, the ferrule wedges into the gap between the outer peripheral surface of the quartz tube and the inner peripheral surface of the joint body.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the case of the configuration of Patent Document 1, if the nut is tightened excessively, the ferrule may enter deep into the joint body without limit. When the ferrule enters deep into the joint body, the quartz tube is radially compressed by the ferrule accordingly. And there was a risk that the quartz tube would be crushed under this radially compressive force.

[0005] Therefore, this specification discloses a pipe joint structure that can effectively prevent the crushing of the tube connected to the joint body.

Means for Solving the Problems

[0006] The pipe joint structure disclosed in this specification includes a tube, a substantially tubular joint body into which the axial end of the tube is inserted, the joint body having a male thread formed on its outer peripheral surface, a ferrule that is axially adjacent to the joint body and through which the tube passes, the ferrule having a wedge-shaped cross-sectional shape that enters the gap between the inner peripheral surface of the joint body and the outer peripheral surface of the tube, a cylindrical portion having a female thread formed on its inner peripheral surface that engages with the male thread, and a nut having an end plate that extends radially inward from the cylindrical portion so as to sandwich the ferrule between the end plate and the end surface of the joint body. On the surface of the ferrule that faces the end surface of the joint body, a stopper is formed that restricts further relative movement of the joint body in the direction approaching the end plate by contacting the end surface of the joint body.

Advantages of the Invention

[0007] According to the technology disclosed in this specification, since the approach of the joint body to the end plate is restricted within a certain range, excessive tightening of the tube by the ferrule is effectively prevented. And thereby, crushing of the tube can be effectively prevented.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0009] Hereinafter, the structure of the pipe joint 10 will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of the pipe joint 10, and FIG. 2 is an enlarged view of part A of FIG. 1. This pipe joint 10 airtightly connects a tubular joint body 20 to the end of a resin tube 12. The tube 12 is a tubular member through which various fluids (such as hydrogen gas, etc.) flow and is made of a resin having appropriate flexibility.

[0010] The joint body 20 is a tubular member that is airtightly connected to the tube 12. Such a joint body 20 is made of, for example, metal, hard resin, or the like. The joint body 20 is substantially bilaterally symmetric, and tubes are connected to the right end and the left end of the joint body 20, respectively. Thereby, two tubes are connected via the joint body 20. Since the configurations of the right end and the left end of the joint body 20 are substantially the same, hereinafter, the structure of the left end of the joint body 20 will be described as an example.

[0011] As shown in FIGS. 1 and 2, a connecting portion 22 into which the tube 12 is inserted is formed at the end of the joint body 20. The inner diameter of the connecting portion 22 is substantially the same as or slightly larger than the outer diameter of the tube 12. Further, the inner diameter of the connecting portion 22 is larger than the inner diameter of the central portion 23 of the joint body 20, and a step 24 is formed at the boundary between the connecting portion 22 and the central portion 23. The end of the tube 12 abuts against this step 24.

[0012] The inner cavity inlet of this joint body 20 is a tapered portion 28 whose diameter decreases as it approaches the axial center. Further, a terminal protrusion 32 that protrudes axially outward is formed on the end face 30 of the joint body 20. Furthermore, a male thread 26 is formed on the outer peripheral surface of the connecting portion 22.

[0013] A ferrule 40 is disposed axially outside the joint body 20. The ferrule 40 is a sealing member that fills the gap between the inner peripheral surface of the joint body 20 and the tube 12. This ferrule 40 is substantially annular with a through-hole through which the tube 12 passes formed therein. The diameter of this through-hole is substantially the same as or slightly larger than the outer diameter of the tube 12. Such a ferrule 40 is made of a resin having appropriate elasticity.

[0014] Of the ferrule 40, the end portion on the side adjacent to the joint body 20 functions as a wedge portion 42 that enters the gap between the inner peripheral surface of the joint body 20 and the outer peripheral surface of the tube 12. This wedge portion 42 has a wedge-shaped cross section that becomes thinner as it approaches the joint body 20. Further, the outer peripheral edge of this wedge portion 42 is folded back at an acute angle in the direction approaching the joint body 20. Due to this folding, a housing recess 44 into which the terminal protrusion 32 can enter is formed in the wedge portion 42. The bottom surface of the housing recess 44 functions as a stopper 46 for preventing excessive tightening of the tube 12 by the ferrule 40, which will be described later.

[0015] The pipe joint 10 further has a nut 50. The nut 50 has a cylindrical portion 52 that covers the outer periphery of the connecting portion 22 and the ferrule 40, and an end plate 56 that extends radially inward from the cylindrical portion 52. Such a nut 50 is made of metal or a hard resin, for example, the same material as the joint body 20. A female thread 54 that engages with the male thread 26 of the joint body 20 is formed on the inner peripheral surface of the cylindrical portion 52. Further, the end plate 56 is located on the opposite side of the joint body 20 with the ferrule 40 interposed therebetween. Therefore, the ferrule 40 is sandwiched between the end plate 56 and the end surface 30 of the joint body 20.

[0016] When such a nut 50 is tightened, the nut 50 moves to the right side of the paper surface, and the distance between the end plate 56 and the end surface 30 of the joint body 20 decreases. As a result, the ferrule 40 receives an axially compressive force. Here, the cross-sectional shape of the end portion of the ferrule 40 is wedge-shaped as described above. Therefore, a part of the axially compressive force applied to the ferrule 40 is converted into a radially inward force. As a result, by tightening the nut 50, the wedge portion 42 of the ferrule 40 presses the tube 12 radially inward while closely adhering to the end (taper portion 28) of the joint body 20. Thereby, the gap between the inner peripheral surface of the joint body 20 and the outer peripheral surface of the tube 12 is hermetically filled with the wedge portion 42, and the expected leakage flowing inside the tube 12 is effectively prevented.

[0017] Thus, in order to prevent gas leakage, it is important to tighten the nut 50 sufficiently. However, if the nut 50 is tightened excessively, there is a risk of crushing the tube 12. That is, when the nut 50 is tightened excessively, the ferrule 40 compresses the tube 12 in the radial direction accordingly. And due to this compressive force, the tube 12 may be crushed.

[0018] In this example, in order to prevent such crushing of the tube 12, a stopper 46 is provided on the ferrule 40. As described above, the stopper 46 is the bottom surface of the accommodation recess 44. As the nut 50 is tightened, the end protrusion 32 of the joint body 20 abuts against this stopper 46. And when the end protrusion 32 abuts against the stopper 46, further approach of the joint body 20 to the end plate 56 is restricted. And when the approach of the joint body 20 to the end plate 56 is restricted, the ferrule 40 is prevented from being tightened excessively, and crushing of the tube 12 is effectively prevented.

[0019] Also, as described above, a part of the end face of the ferrule 40 is folded back at an acute angle toward the joint body 20. As a result, an accommodation recess 44 for accommodating the end protrusion 32 is formed on the end face of the ferrule 40. In other words, there is a wall 45 formed by folding on the outside in the radial direction of the end protrusion 32. And due to the presence of this wall 45, the joint body 20 is prevented from spreading outward in the radial direction. As a result, an increase in the gap between the inner peripheral surface of the joint body 20 and the outer peripheral surface of the tube 12 is prevented, and leakage of the gas flowing in the tube 12 can be effectively prevented.

[0020] As is clear from the above description, according to this example, it is possible to effectively prevent crushing of the tube 12 while preventing gas leakage. Note that the configurations described so far are examples, and other configurations may be appropriately changed as long as they have the configuration of claim 1. For example, the shapes of the joint body 20 and the ferrule 40 may be appropriately changed.

Explanation of Reference Numerals

[0021] 10 Pipe joint, 12 Tube, 20 Joint body, 22 Connecting part, 23 Central part, 24 Step, 26 Male screw, 28 Tapered part, 30 End face, 32 End protrusion, 40 Ferrule, 42 Wedge part, 44 Receiving recess, 45 Wall, 46 Stopper, 50 Nut, 52 Cylindrical part, 54 Female screw, 56 End plate.

Claims

【Claim 1】 a tube and a substantially tubular joint body into which an axial end of the tube is inserted, the joint body having a male thread formed on an outer peripheral surface, a ferrule that is axially adjacent to the joint body and through which the tube passes, the ferrule having a wedge-shaped cross-sectional shape that enters a gap between an inner peripheral surface of the joint body and an outer peripheral surface of the tube, a nut having a cylindrical portion with a female thread formed on an inner peripheral surface that engages with the male thread, and an end plate extending radially inward from the cylindrical portion so as to sandwich the ferrule between the end plate and an end surface of the joint body, and a stopper is formed on a surface of the ferrule facing the end surface of the joint body so as to contact the end surface of the joint body and restrict further relative movement of the joint body in a direction approaching the end plate of the joint body. A pipe joint structure characterized by the above.

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