JP2629901B2 - Fusion joint structure of plastic pipe - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fusion joint structure for a plastic pipe such as a polyethylene pipe and a polybutene pipe.

[Prior Art] Conventionally, as one method of bonding a polyethylene pipe, there is a heat fusion joint method. For example, when connecting a pipe by a socket, as shown in FIG. 5, the inner surface 2a of the socket 2 and the outer surface 1a of the connected pipe 1 are each heated and melted, and the pipe end is pushed into the socket to connect. doing. Also,
In the case where a branch is provided in the pipe, as shown in FIGS. Then, each of the surfaces 1d is heated and melted, and then the saddle 6 is pressed and fused to the tube 1 to form a branch portion. Finally, a branch hole 1c is formed.

[Problem to be Solved] However, when the tube 1 is pushed into the socket 2, a corner portion C is formed by the inner surface 2a of the socket 2 and the end surface 1b of the tube 1 as shown in FIG. When an internal pressure or an axial force is applied to the pipe 1, stress concentration occurs at the corner C,
Considering long-term use, there is a risk that a crack may occur from this part due to the creep phenomenon peculiar to plastic.
Also, when the saddle 6 is adhered to the tube 1, as shown in FIG. 9, a corner portion C is formed at a fusion portion between the end of the hole 8a of the branch portion 8 of the saddle 6 and the tube 1, The same problem as described above occurs. In particular, since the hole 1c is formed after the saddle 6 is fused to the pipe 1 at the branch portion, there is a problem that a crack defect is easily generated in the fused portion.

An object of the present invention is to solve the above problems.

[Means for Solving the Problems] The fusion joint structure for a plastic pipe according to the present invention is to prevent a corner portion serving as a stress concentration portion from being formed at the fusion joint end of the joint member with the connected tube. And a groove having an arc-shaped cross section for reducing stress concentration.

[Operation] In order to prevent a corner portion serving as a stress concentration portion from being formed at the fusion spliced end of the joint member with the connected pipe, a conventional arc-shaped groove for reducing stress concentration is provided. The problem of stress concentration, which has been a problem, can be solved.

[Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 and 2 in which a pipe is connected by a socket 11 as a joint member 10.

A groove 12 having an arc-shaped cross section for reducing stress concentration, which is located on the inner surface 11a of the socket 11 at the pushed-in fused end of the connected tube 1.
Are formed. The radius of curvature of the groove 12 is 8 to 10 mm. The fusion of the tube 1 to the socket 11 is performed in the same manner as in the related art. FIG. 2 shows a state of fusion splicing. Since the end 1b of the tube 1 is smoothly connected to the groove 12 having an arc-shaped cross section, stress concentration at this portion is greatly reduced. That is, the conventional stress concentration coefficient of 2.5 to 3 is changed to 1.2 to
Reduced to 1.5.

Next, a case where a branch saddle 16 as the joint member 10 is fused to the pipe 1 to form a branch portion will be described with reference to FIGS.

A groove 19 for reducing stress concentration is formed at the fusion splicing end of the hole 18a of the branch portion 18 of the saddle 16 with the tube 1. Saddle 16 is fused to tube 1 in a conventional manner. FIG. 4 shows the state after fusion. Saddle 16 hole 18a
Is fused to the tube 1 through the groove 19 having an arcuate cross section, so that stress concentration at this portion can be reduced. In addition, it is possible to prevent the occurrence of cracks when drilling the hole 1c. .

[Effects of the Invention] The fusion joint structure for a plastic pipe of the present invention is as described above, and it is possible to reduce the concentrated stress at the joint of the joint member and the connected pipe.

[Brief description of the drawings]

1 and 2 are a longitudinal sectional view of a socket showing a joint structure according to an embodiment of the present invention and a longitudinal sectional view of a state where the socket is fused to a connected pipe. 3 (a) and 3 (b) are longitudinal sectional views of the branch saddle in the pipe axis direction and a direction perpendicular to the pipe axis, and FIG. 4 shows a state where the branch saddle in FIG. 3 is fused to a connected pipe. Longitudinal section, fifth
FIG. 6 and FIG. 6 are longitudinal sectional views showing a conventional socket and a connected pipe and a state in which they are fused, FIG. 7 is a perspective view showing a state in which a branch saddle is fused to the connected pipe, and FIGS. FIG. 9 is a longitudinal sectional view in a pipe axis direction and a direction orthogonal to the pipe axis in a state where the branch saddle is fused to the connected pipe. 1 ... connected pipe, 10 ... joint member, 11 ... socket, 16
…… Branch saddle, 12, 19 …… Groove with circular cross section

Claims (1)

(57) [Claims] 1. A fusion splicing end of a joint member with a connected pipe,
A fusion joint structure for a plastic pipe, wherein a groove having an arc-shaped cross section for reducing stress concentration is provided to prevent formation of a corner portion serving as a stress concentration portion.