JPH0651349B2 - Tube flare processing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluororesin pipe joint used for transferring chemicals, pure water, etc. used in a semiconductor manufacturing process and a method for flaring a fluororesin tube used in combination therewith. It is a thing.

[0002]

2. Description of the Related Art A large amount of various chemicals and pure water are used in the semiconductor manufacturing process. With the automation of the manufacturing process, these chemicals and pure water are pumped or gas-pumped according to the application. It needs to be transported in a wide variety of ways. Therefore, many joints and tubes made of fluorine resin, which are stable and resistant to chemicals, are used. The tubes, joints, and nuts used for the transfer of these liquids do not come out of the tubes with respect to the temperature and pressure of the liquid to be transferred, and liquid leakage and fine particles caused by the creep property of the fluororesin are caused. There should be no dust, no bacteria from the pool. Dust, bacteria, and the like cause formation defects during formation of fine patterns during the semiconductor manufacturing process, and significantly deteriorate the yield of semiconductor products. Various pipe joints have been devised and used from these viewpoints, but while fluororesin is superior in terms of heat resistance, chemical resistance, and purity of physical properties in semiconductor manufacturing, on the other hand, it has fluororesin. Due to the drawback of large plastic deformation due to creep, none was satisfactory.

The pipe joints and tubes which have been used conventionally have a combination of structures as shown in FIGS. 7 to 10.

FIG. 7 shows an inner ring type, in which when the inner ring 50 is inserted into the tube 51 for connecting to the joint 55, the inner surface of the tube is scratched to generate dust, and the dust is contained inside. Since a liquid pool is created around the inner ring, dust easily collects and becomes a source of bacteria. Further, although the strength against withdrawal is strong, the sealing point is the outer surface of the tube, so that the liquid leaks due to the deformation of the material and the reduction of the tightening force of the nut 52 due to the heat cycle.

In the combination shown in FIG. 8, the groove 56 is cut into the tube 51 and the tongue portion 58 provided on the inner surface of the nut 57 is inserted into the groove 56 to seal the tip end edge of the tube 51 against the inner surface step 59 of the joint 55. Although the tube has a pull-out resistance, it is difficult to cut the tube at right angles to the axial direction for sealing, the cutting condition is poor, and the tube cross section deforms into an elliptical shape when tightened. Leakage will occur. In addition, since the groove is cut on the outer surface of the tube, the wall thickness of the tube is halved, and there is a danger of insufficient strength when used at high temperatures.

FIG. 9 shows a structure in which a wedge-shaped ferrule 60 is pressed against the outer surface of the tube 51 for sealing, which is inexpensive and has good workability, but has a weak pulling resistance and a liquid leakage.

In FIG. 10, the tube 51 is flared 61.
And with the structure where the seal point is placed on the inner surface of the tube,
Does not stagnate garbage and has little liquid pool. However, when the tube is subjected to a heat cycle, the contraction of the tube and the deformation of the joint body and the nut weaken the tightening force of the nut 52, and as a result, the tube is easily pulled out.

[0008]

In the combination which is subjected to flare processing as shown in FIG. 10, the tube is easily pulled out because the flared tube portion is repeatedly subjected to expansion and contraction motions because the tube is flared. This is because the physical force of this portion causes the portion to return to its original shape before being flared, and the fastening force of the nut is reduced. An object of the present invention is to provide a method for processing a tube which can prevent the tube from coming off due to the above causes.

[0009]

The constitution of the present invention is as follows. A circumferential groove consisting of a vertical surface and an inclined surface with respect to the tube axis is formed on the outside of the tip of the fluororesin tube, and this tube is heated and a jig is inserted inside to perform flare processing. By forming a vertical step surface and a parallel surface with respect to the tube axis by the circumferential groove on the tube, the tube is fitted into a fitting made of fluororesin, and a nut made of fluororesin is screwed into the fitting, to the inner surface of the nut. A flare processing method for a tube in which the vertical step surface of the tube is abutted against the step portion of the retaining wall provided.

[0010]

According to the present invention, as shown in FIG. 1, a circle composed of the vertical surface 3a and the inclined surface 3b shown in FIG. 3 so that the inner surface F of the nut and the outer surface G of the tube are parallel to each other after flaring the tube 1 in advance. Since the flaring process is performed after the circumferential groove 3 is formed, the cutout portion J is formed in the tube 1 as shown in FIG. 6, and the tube P after the flaring process returns to the original straight tube P ₂ ′. Becomes very small and fits well to the shape of the jig 4, and it is possible to maintain this state even if the hand is released after the flaring process is completed. Therefore, if this flared tube is inserted into the joint 7 as shown in FIG.
Fits well with the shape of the joint 7, and therefore the sealing performance at the seal point C is exhibited, and at the same time, the inner surface F of the nut and the outer surface G of the tube are fastened in parallel, so that the retaining wall break 6 and the circumferential groove vertical step surface 3A are securely fitted, and the tube 1 can be effectively prevented from coming off.

On the other hand, in the conventional flare tube, flare processing is performed without previously forming the circumferential groove 3 as in the present invention. Therefore, the flare tube obtained as shown in FIG. 6'is the original straight tube. It acts large force P _{2 'of} returning, after flaring ends and release the hand shape of the resulting tube by the shape of the jig 4 becomes incomplete flared can not be maintained. Even if this incomplete flare tube is inserted into the joint 7 and fastened with the nut 5, the gap between the tube inner slope 9 and the joint slope 8 becomes large, and the horizontal portion of the tube 1 in contact with the horizontal portion 10 of the joint 7 Since the length L of 11 is smaller than that of the present invention, the tube 1
The seal point of 1 and the seal point of the joint 7 deviate from each other, an effective seal point C cannot be obtained, and the tube 1 easily comes out of the joint 7.

Further, when the flare ratio is increased during the flaring process, the wall thickness of the tube 1 becomes thinner, and when the step E formed by the vertical step surface 3A and the parallel surface 3B is cut after the flaring process, the extremely thin portion is found. It is easy to do and there is a risk of the tube breaking. In such a case, flare processing is performed again, and workability is poor.

In actual processing, the tube 51 is often short in length as shown in FIG. 11, and both sides thereof are flared and fastened with nuts in many cases. In such a case, unless the circumferential groove 3 is formed before the flaring process, the nut 5 is already formed after the flaring process.
Since No. 2 cannot be pulled out from the tube 51, it is obvious that the nut 52 cannot be processed because the nut 52 interferes when cutting the step E. This is another great advantage that occurs in the present invention by forming the circumferential groove 3 in advance and then performing flaring.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, first of all, as shown in FIG. 3, a vertical surface 3a and a sloped surface 3b are formed on the fluororesin tube 1 shown in FIG.
A circumferential groove 3 composed of and is formed. This tube 1 is heated (about 230 ° C.), and the jig 4 shown in FIG. 4 is inserted into the tube 1 having the circumferential groove 3 and flared. (FIG. 5) Thus, the vertical step surface 3A and the parallel surface 3B are formed. As shown in FIG. 1, the nut 5 used in the method of the present invention has a retaining wall break portion 6 formed on the inner surface thereof to prevent the nut 5 from coming off due to the vertical step surface 3A formed by the circumferential groove of the flared tube 1 abutting against the inner surface. I am doing it. The joint 7 into which the nut 5 is screwed has a beveled surface 8 at its tip, and the tube 1 is fitted therein. At that time, the force of pressing the tube 1 toward the joint 7 side and sealing at the basic sealing point C (tightening force) is P, and the force of shrinking the tube 1 to its original shape due to flaring is P ₂ , the slope 8 is P ₂ ′ as the component force of P ₂ and P ₂ ′ as the component force of P ₂ , and P _{2 as} the component force of tube 1
_Set to ₁ . The joint 7 seals by closely contacting the horizontal portion 10 of the joint by the force P ₂ of the tube 1 which tends to shrink to its original shape due to its physical properties, and at the basic seal point C by the force P generated by the tightening force of the nut 5. Sealed by line contact. In addition, the stepped structure of the step E obtained by performing the flaring process after the groove process is performed on the tube 1 and the step D provided on the nut prevents the force P ₁ for pulling out the tube. The outer surface G of the tube and the inner surface F of the nut are parallel to each other to ensure the step alignment of the tube step E and the nut step D. Further, the inner surface of the tube that is in contact with the basic seal point C of the joint 7 is deformed by the tightening force of the nut so as to fit the basic seal point C of the joint.

[0015]

According to the present invention, since the flaring is performed after the groove is formed in the tube, it is extremely easy to surely flare the fitting portion of the nut and the tube and the tube closely attached to the seal point at the same time. Therefore, it is possible to exert a great effect on the sealing property at high temperature of the present joint and the prevention of the tube from coming off, which were the conventional defects. For this reason, during the transfer of chemical liquids and pure water fluororesin pipe joints and tubes required during the semiconductor manufacturing process, there is no leakage, no heat cycle, no dust, and no liquid pool. It is possible to construct joints and tubes that satisfy the above requirements.

[Brief description of drawings]

FIG. 1 is a vertical side view of the present invention.

2 to 5 are sectional views showing a flare processing sequence.

FIG. 6 is a sectional view for explaining the operation of the present invention.

7 to 10 are cross-sectional views showing a joined state of a conventional pipe joint and a tube.

FIG. 11 is a cross-sectional view of a short tube flared on both sides and fastened with a nut.

[Explanation of symbols]

 1 tube 2 groove cutting edge 3 circumferential groove 4 jig 5 nut 3A vertical step surface 3B parallel surface 6 retaining wall section 7 joint 8 slope of joint 9 tube flare inner surface 10 joint horizontal portion 11 tube horizontal portion

Claims (1)

[Claims] 1. A flare is formed by forming a circumferential groove on the outside of the tip of a fluororesin tube, the circumferential groove consisting of a vertical surface and an inclined surface with respect to the tube axis, and heating the tube to insert a jig therein. By processing, thus forming a vertical step surface and a parallel surface with respect to the tube axis in the tube by the circumferential groove, insert the tube into a fitting made of fluororesin, and screw a nut made of fluororesin into the fitting. , A method of flaring a tube in which the vertical step surface of the tube is abutted against the retaining wall step portion provided on the inner surface of the nut.