JP2000006244A - Friction gripping method of thermoplastic resin pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the cutting process of the section of a pipe and its correcting process into a true circle unnecessary by a method wherein a wearing process for smoothing the edge faces of the pipes is provided before a heating fusion process based on friction. SOLUTION: Before a heating fusion process based on friction, a wearing process for smoothing the edge faces of pipes is provided. Concretely, between two pipes 1 and 2 to be bonded, the pipe 1 is fixed to a rotary chuck 3 and the pipe 21 is fixed to travelling clamps 5, which move towards the rotary check 3 by means of a pneumatic pressure cylinder 4, so as to oppose both joint areas to each other. After that, by transmitting the power of a motor through a timing belt 6, the rotary chuck is rotatingly driven, resulting in rotating the one pipe 1 at a certain fixed rotational speed. At the fixed side pipe, an axial force is applied to the pipe 2 by means of the pneumatic pressure cylinder 4 so as to develop the surface pressure at the joint areas. In an actual friction gripping, first of all, the wearing process for smoothing edge faces, in each of which a few non-contacting part is present, is subjected and then the heating fusion process based on friction is subjected so as to join the pipes together.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for frictionally joining a thermoplastic resin pipe and a thermoplastic resin pipe or a thermoplastic resin pipe joint.

[0002]

2. Description of the Related Art Conventionally, a friction joining method has been known as a method for joining synthetic resin members. In this friction joining method, for example, one of the members to be joined is rotated about its axis, and a predetermined contact pressure is applied so that the joining surface of the rotating member and the other member are in close contact with each other. Then, the joining surface is melted by frictional heat, and then the resin is cooled and solidified to join the two members. Of these methods, a butt friction joining method for fusing both members in a state where the end faces of both members are butted against each other is disclosed in, for example,
Japanese Patent Application Laid-Open No. Sho 51-163 discloses a method of performing friction joining with a pipe fitted to a joint.
No. 75, all of these methods are capable of joining in a short time and reducing the distortion due to a small fusion zone.

However, since the bonding is performed in a short time, it is necessary that the bonding surfaces are in close contact with each other. Therefore, when the accuracy of the mating surfaces is extremely poor and there is a portion having a gap of 1 mm or more, for example, However, since the heat generation at that portion is delayed, it cannot be sufficiently melted in a short time. as a result,
If the strength is insufficient or severe, there is a problem that joining cannot be performed at all.

For example, in the case of a thermoplastic resin tube, a gap may be formed in the mating surface due to a case where the cut surface is not perpendicular to the axial direction or a contraction of the end of the tube after cutting in a circular inward direction. In addition, in joining a thermoplastic resin pipe and a thermoplastic resin pipe joint, the cross section of the pipe or the pipe joint is not a perfect circle but an elliptical shape, and the insertion of the pipe into the pipe joint is oblique. There is a problem that a non-contact portion occurs in the direction, and the strength of this portion decreases.

[0005]

In order to eliminate the gaps formed at the mating surfaces of the above-mentioned thermoplastic dendritic pipes and thermoplastic resin pipe joints, for example, the end faces of the pipes and pipe joints are cut or various jigs are used. The method of making the pipe a perfect circle by using the method, or adjusting the axis with high accuracy when inserting the pipe into the joint is considered. However, the former requires a new cutting device, and the latter requires a large-scale straightening / fixing jig. Therefore, in recent years, the friction joining method is simpler, has higher productivity, and does not cause a significant increase in cost. Had been requested. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the conventional friction joining method for thermoplastic resin pipes, and to provide a friction joining method that is simple, has high productivity, and does not cause a significant cost increase.

[0006]

The invention according to claim 1 (hereinafter referred to as "the present invention 1") provides a frictional joint in a butt friction joining between a thermoplastic resin pipe and a thermoplastic resin pipe or a thermoplastic resin pipe joint. A frictional joining method for thermoplastic resin tubes, characterized by including a wear process for smoothing the end faces of the tubes to be joined before the exothermic melting process by the above method.

The invention according to claim 2 (hereinafter referred to as “the present invention 2”)
In the method of inserting a thermoplastic resin pipe into a thermoplastic resin pipe joint and friction-joining the pipe outer wall surface and the pipe joint inner wall surface, in order to smooth the joint surface before a heat-melting step by friction. And a friction joining method for a thermoplastic resin tube, which achieves the above object.

The invention according to claim 3 (hereinafter referred to as “the present invention 3”)
Is a method for frictionally joining thermoplastic resin pipes according to claim 1 or 2, characterized in that the means for generating friction is based on rotational movement, whereby the above object is achieved.

In the present invention 1 and the present invention 2, the means for generating friction include rotational motion, regular vibration, and the like. In the present invention 1 to the present invention 3, the thermoplastic resin forming the thermoplastic resin pipe and the pipe joint is not particularly limited, and examples thereof include polyethylene, polypropylene, polybutene, polyvinyl chloride, cross-linked polyethylene, cross-linked polypropylene and the like. .

(Operation) The outline of the operation of the present invention will be described with reference to the resin phase diagram with respect to the rotation speed and pressure shown in FIG. When the amount of energy given by the rotation speed and the pressure is not sufficient, it corresponds to the lower left area in FIG. If the rotation speed exceeds a certain value, a molecular phenomenon occurs as a microscopic phenomenon. Further, if the pressure level is too high, in the case of a soft resin, abrasion (scratching) occurs, where molecular breakage occurs, and the efficiency of heat generation is significantly reduced, and it takes a long time to melt.

As described above, the problem in the friction joining method is that in the case of butt, when there is a diagonal cut or distortion due to tube end shrinkage, a non-contact portion occurs in the circumferential direction or the wall thickness direction when the tube end surfaces are joined, When a pipe is inserted into a pipe joint and joined, the non-contact portion occurs in the circumferential direction when the pipe or the pipe joint is elliptical or not aligned with the axis.

In the present invention, the joining surfaces are aligned by utilizing the relationship between the speed and the pressure in the friction joining of the resin. In FIG. 2, for example, consider the case where a rotational speed V0 is applied to one of the tubes in a butt joint by a pressure P1 (the pressing force divided by the cross-sectional area of the tube or the contact area between the tube and the pipe joint). View.

Normally, if the speed is V0, for example, the calorific value is small so that the material does not melt. However, if there is the above-mentioned non-contact portion (gap), the actual contact area is small and the pressure generated in the actual contact portion is small. Since P1 'is very high, the contact portion is abraded due to wear, the contact area gradually increases, and the surface pressure of the actual contact portion approaches P1.

Theoretically, the speed and pressure are V1 to V2, P
If the conditions are in the range of 1 'to P2 (including the checkerboard display portion) (that is, the regions A and B in the figure), the joint surface can be cut smoothly by wear without hardly melting the tube. In consideration of a preferable range of the pressure, a preferable area is a part of a lattice fringe display (that is, an area A in the figure).

Therefore, even when there is a gap between the end faces butted at the time of butt joining or when there is a non-contact portion at the time of inserting and joining a pipe to a pipe joint, it can be seen from the process flow shown in FIG. In addition, if joining by rotary heating is started immediately after the wear process, the cutting process is performed by a cutting device different from the joining device or a new straightening jig is attached to make a perfect circle at the time of butt joining. And a large fixing jig for precisely aligning the axis when inserting and joining the pipe to the pipe joint can be omitted.

For example, even when a non-contact portion is 1.0 mm or more when a pipe is inserted into and joined to a pipe joint at a gap between butted end faces at the time of butt joining (for example, when the diameter is 200 mm).
(If the non-contact portion is 5.0 mm or less in the case of a tube of about mm), it is possible to produce a bonded product having stable strength by the method of the present invention. It is also advantageous in terms of the joining cycle from a comprehensive viewpoint.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 is a side view showing an example of an apparatus suitable for use in carrying out the method of the present invention 1.
Of the two pipes 1 and 2 to be joined, the pipe 1 was fixed to the rotary chuck 3, and the pipe 2 was fixed to the moving clamp 5 which advances and retreats in the direction of the rotary chuck 3 by the pneumatic cylinder 4, so that both joining faces faced each other. Thereafter, the power of the motor 7 is transmitted via the timing belt 6 to rotate the rotary chuck 3,
A mechanism for rotating one of the tubes 1 at a constant rotational speed about the central axis of the joint surface, and a mechanism for applying an axial force to the tube 2 by a pneumatic cylinder 4 to generate a surface pressure at the joint surface. Has become.

At the time of actual friction joining, first, the pipes are joined to each other through an abrasion process for smoothing the end face where a slight non-contact portion exists, and then through a heat melting process by friction. FIG. 7 is a side view showing an example of an apparatus suitable for performing the method of the present invention 2. After fixing the pipes 1 and 2 with the clamps 5 and 5 in a state where the two pipes 1 and 2 to be joined are inserted into the pipe joint 9 attached to the joint rotating jig 8,
The power of the motor 7 is transmitted via the timing belt 6 to rotate the joint rotating jig 8 to rotate the joint 9 at a constant rotational speed about the central axis of the pipes 1 and 2. The joint surface between the pipe joint 9 and the pipes 1 and 2 has a mechanism for generating a surface pressure by the pneumatic cylinder 4.

In actual friction joining, first, a pipe joint and a pipe are joined through a wear step of smoothing a joining surface where a slight non-contact portion exists, and then through a heat melting step by friction. is there.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail based on embodiments. (Example 1) The apparatus shown in FIG.
High-density polyethylene tube (Eslohyper, Sekisui Chemical Co., Ltd., melting point 128 ° C., density 0.952 g / cm 3)
Are set on the rotary chuck 3 and the clamp 5, respectively, and the set pressure is 0.04 when the end faces are fully contacted in a state where the distance between the concave portions on the pipe end faces is a maximum of about 1.5 mm.
At 9 MPa, the rotation speed is 300 rpm (the peripheral speed is 2.6 m /
When one of the tubes was rotated at (sec), a wear phenomenon occurred (FIG. 5).

At this time, the end face of the tube was actually cut obliquely, and the actual contact pressure of the contact portion was about 0.83 MPa (FIG. 5). With the wear, the contact pressure of the contact portion gradually approached 0.049 MPa, and was 15
In about a second, the gap at the pipe end face was almost eliminated. From this state, bonding was performed under the speed and pressure conditions shown in FIG.

That is, in the joining step, the clamp 5 is operated two seconds after the drive switch is turned on, and the joint surfaces of the two tubes are pressed against each other at a pressure of 0.25 MPa. 4, the pressure of the bonding surface was lowered to 0.088 MPa by lowering the pressure of 3 and further 3 seconds later, the pressure of the clamp was lowered to hold the pressure of the bonding surface at 0.039 MPa for 10 seconds. At the same time, the pressure of the pneumatic cylinder 4 was increased to 0.49 MPa at the joint surface and then reduced to 0.098 MPa to finally obtain a joined tube in which the two were joined.

When creep performance evaluation (JIS K6774 “Appendix 1 of polyethylene pipe for gas”) was performed on the obtained joined pipe, the fracture time was about 350 hours equivalent to that of the base material at a load stress of 7 MPa.

(Embodiment 2) Using the apparatus of FIG.
Two cross-linked polyethylene pipes of 0 mm (27 mm in outer diameter) (Eslopex, manufactured by Sekisui Chemical Co., Ltd.) and a cross-linked polyethylene tapered pipe joint shown in FIG. 8 were joined. At this time, the pipe and the pipe joint were joined to each other with a slightly elliptical cross section and a maximum clearance of 0.3 mm.

The two pipes are inserted, and an axial force is applied so that the 9 mm width of the joint surface between the outer wall surface of the tube and the inner wall surface of the pipe joint is 0.049 MPa when the entire surface is in contact with the tube. When the pipe joint was rotated at a speed of several 1800 rpm (peripheral speed of 2.6 m / sec), a wear phenomenon occurred while the pipe was inserted (FIG. 5). This was because the pipe had an elliptical cross section at the beginning of rotation as described above, so that it was in local contact with the inner wall surface of the pipe joint, and in fact, had a contact pressure higher than 0.049 MPa.

With the abrasion, the surface pressure of the contact portion gradually becomes 0.04.
As the pressure approached 9 MPa, the gap on the pipe end face almost disappeared in about 3 seconds from the start of rotation. From this state, the rotation speed 260
Bonding was performed at 0 rpm and a pressure of 0.04 MPa for 20 seconds. The test specimens shown in FIG. 9 were taken out from eight places in the circumferential direction of the joined product and subjected to a peel test.

[0027]

According to the joining method of the present invention, in the butt friction joining of the thermoplastic resin pipe and the thermoplastic resin pipe or the thermoplastic resin pipe joint, before the exothermic melting step by friction,
Since it includes a wear process to smooth the end face of the pipe to be joined, it goes through major separate processes such as a cutting process and a rounding correction process to develop a round shape of the cross section of the tube before the heat melting process It is possible to provide a friction joining method that is unnecessary, simple, has high productivity, and does not cause a significant cost increase.

The joining method according to the second aspect of the present invention is a method for frictionally joining an outer wall surface of a pipe and an inner wall surface of the pipe joint by inserting a thermoplastic resin pipe into a thermoplastic resin pipe joint, wherein the step of exothermic fusion by friction is performed before the step of melting. Includes an abrasion process to smooth the joint surface, so a large-scale separate process such as a cutting process, a rounding correction process, and a shaft alignment process to develop a round shape of the cross section of the tube before the heat melting process Thus, it is possible to provide a friction joining method that is simple, has high productivity, and does not cause a significant increase in cost.

In the joining method according to the third aspect of the present invention, since the means for generating friction is the joining method according to the first or second aspect of the present invention, the effect of the first or second aspect of the present invention is more simply and reliably achieved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a resin state with respect to a rotation speed and a pressure of a tube in a method of the present invention.

FIG. 2 is a diagram for explaining a condition of surface matching of a rotation speed and a pressure of a tube to which the present invention can be applied.

FIG. 3 shows a process flow of the method of the present invention.

FIG. 4 is a side view showing an example of an apparatus suitable for performing the method of the present invention.

FIG. 5 is a view for explaining tube surface matching conditions in Examples 1 and 2.

FIG. 6 is a diagram showing the passage of the circumferential speed and the surface pressure of the pipe in the wear step and the joining step in Example 1.

FIG. 7 is a side view showing another example of an apparatus suitable for carrying out the method of the present invention.

8A and 8B are diagrams showing the shape of a tapered pipe joint used in Example 2, (a) is a front view, and (b) is a cross-sectional view.

FIG. 9 is a diagram schematically showing the shape of a peel test piece of a joined product obtained in Example 2.

[Explanation of symbols]

 1, 2 thermoplastic resin pipe 9 thermoplastic resin pipe joint

Claims (3)

[Claims] In a butt friction joining of a thermoplastic resin pipe and a thermoplastic resin pipe or a thermoplastic resin pipe joint, a wear step for smoothing an end face of the pipe to be joined is performed before a heat generation melting step by friction. A friction joining method for a thermoplastic resin tube, comprising: 2. A method of inserting a thermoplastic resin pipe into a thermoplastic resin pipe joint to frictionally join an outer wall surface of the pipe and an inner wall surface of the pipe joint, wherein the joining surface is smoothed before an exothermic melting step by friction. Joining method for a thermoplastic resin tube, comprising: 3. The method according to claim 1, wherein the means for generating friction is a rotational movement.