JP4472248B2 - Resin pipe joint and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a resin pipe joint that can prevent problems such as cracks caused by weld lines during injection molding, and a method for manufacturing the same.
[0002]
[Prior art]
Since the resin pipe joint is intended for fluid transfer, it is generally cylindrical. When such a resin pipe joint is manufactured by injection molding of a side gate or a pin gate, a weld line always occurs. In particular, in a resin pipe joint in which a tubular body is joined by a steel ball, a weld line is always generated in a part of the hole for storing the steel ball.
[0003]
It is generally known that when a load acts on the weld line, the resin breakage occurs at a load lower than that of other portions. For this reason, a method for manufacturing a resin molded product that does not cause a weld line has been proposed. That is, at the time of injection molding, a suitable temperature is maintained by heating until the flow front of the molten resin injected into the cavity of the mold joins. (For example, refer to Patent Document 1).
[0004]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 11-179772 (page 2, FIG. 1)
[0005]
[Problems to be solved by the invention]
However, in order to prevent a weld line from occurring as in Patent Document 1, a high-temperature gas is caused to flow into the mold cavity, and the cavity surface and the flow front of the molten raw material to be filled are heated, so that the flow front Are kept at a suitable molding temperature until the time of merging, and when the flow front ends merge, it is necessary to accelerate the flow velocity of this part so that a violent collision occurs due to the rapid discharge of the hot gas.
[0006]
Thus, the present invention avoids the addition of manufacturing equipment and the complexity of the manufacturing method by allowing the generation of weld lines, while changing the position and direction of the weld lines to substantially eliminate problems such as cracks due to the weld lines. An object of the present invention is to provide a resin pipe joint that can be prevented and a method for producing the same.
[0009]
[Means for Solving the Problems]
The present invention has been made to solve the above problems, and the method for manufacturing a resin pipe joint according to the first aspect of the present invention is a method for manufacturing a resin pipe joint manufactured by injection molding. Then, resin injection gates are provided at two locations facing each other on the end face side diameter of the resin pipe joint, and a weld line is generated between the gates when the molten resin is injected into the mold cavity. And when viewed from the end face side of the resin pipe joint, a hole for storing the steel ball of the resin pipe joint that joins the pipe body with a steel ball is provided between the gate and the weld line. It is a feature.
As a result, the hole for storing the steel ball is provided between the gate and the weld line when viewed from the end face side of the resin pipe joint. Thus, a weld line comes, and problems such as cracks around the hole for storage caused by the weld line can be prevented .
[0010]
According to a second aspect of the present invention, in the method for manufacturing a resin pipe joint according to the first aspect, an air vent is provided at a position away from the hole for storing the steel ball.
That is, by providing an air vent at a position away from the steel ball storage hole, the weld line can be prevented from passing through the steel ball storage hole .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
In the resin pipe joint of the present invention, the weld line at the time of injection molding is in a part other than the load concentration part at the time of use in the resin pipe joint, and the manufacturing method injects the molten resin into the cavity of the mold. In this case, a resin injection gate is provided so that the weld line at that time comes to a portion other than the load concentration portion in use in the resin pipe joint.
[0012]
That is, the weld line itself is not eliminated, but the weld line is allowed to be generated, and the weld line is located at a portion other than the load concentration portion at the time of use in the resin pipe joint. Therefore, there is no difference in equipment from general injection molding.
[0013]
Here, in the case of the pipe joint which presses and joins a pipe body with a steel ball, the load concentration part at the time of use in a resin pipe joint is an axial direction part of the hole for storing a steel ball, for example. That is, there is a structure in which a steel ball is brought into contact with an outer collar having an inclined surface as a pressing member as a pipe joint for detachably coupling the pipe bodies. Specifically, an outer collar having an inclined surface is provided at one end of the pipe joint, and an inner collar containing a steel ball pressing member is inserted inside the outer collar.
[0014]
In such a pipe joint, when a pulling force (fluid pressure due to use) acts with the tube body inserted into the inner collar, a steel ball as a pressing member is pulled out together with the inner collar, and as a result, the inclined surface of the outer collar As a result, the steel ball is directed to the surface of the tubular body and exerts a clamping force on the tubular body. Therefore, the hole for storing the steel ball in the inner collar receives the pressure of the steel ball accompanying the pulling force at the axial direction portion of the pipe joint.
[0015]
Therefore, in the inner collar that constitutes the pipe joint, the axial part of the steel ball storage hole becomes the load concentration part, and if the inner collar is made of resin, the weld line accompanying the injection molding is the axial direction of the pipe joint. If this is the case, there is a concern that cracks may occur due to the fluid pressure acting when the pipe joint is used. Therefore, in the resin pipe joint of the present invention, the possibility of cracking is eliminated by preventing the weld line passing through the hole for storing the steel ball from being in the axial direction of the pipe joint.
[0016]
Such a resin pipe joint of the present invention can be manufactured by setting a predetermined number of resin injection gates at predetermined positions. That is, generally, since a weld line is formed at an intermediate portion of the resin injection gate, the number and positions of the gates are set so that the intermediate portion of the gate does not coincide with the load concentration portion. In order to reliably guide the weld line, it is preferable to provide an air vent.
[0017]
【Example】
Hereinafter, the best embodiments of the resin pipe joint and the manufacturing method thereof according to the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram showing the occurrence of a weld line when a resin pipe joint is manufactured by injection molding. FIG. 1 (A) shows a case of a side gate, and FIG. 1 (B) shows a case of a pin gate. Show.
[0018]
As shown in FIG. 1A, in the case of a side gate (one point), the resin flows in two ways as indicated by an arrow from the upper gate G, and joins at the lower portion to generate a weld line L. Also, as shown in FIG. 1B, in the case of a pin gate (three points), the resin flows from the gate G at each vertex of the equilateral triangle in two hands as indicated by arrows, and at the middle part of the gate G. The weld lines L are generated by joining. Therefore, the gate G is provided so that the weld line L comes to a portion other than the load concentration portion in use in the resin pipe joint.
[0019]
This point will be further described by taking as an example a resin pipe joint that joins pipe bodies with steel balls. FIG. 2 is a conceptual diagram showing a situation when the weld line is oriented in the axial direction of the pipe joint passing through the hole for storing the steel ball. That is, as shown in FIG. 2A, when the pin gate G (four points) is at each vertex of the square, the weld line L passing through the holes 2 for storing the steel balls 1 provided on the top, bottom, left and right is a tube. It faces in the axial direction of the joint.
[0020]
Here, when a fluid pressure or a tensile load is applied to the steel ball 1 when the pipe joint is used, the steel ball 1 moves in the axial direction of the pipe joint, and therefore hits the weld line L of the hole 2. Then, as shown in FIG. 2B, the load concentrates on the weld line L and breaks (cracks) with a low load.
[0021]
However, as shown in FIG. 3, when the pin gate G is reduced to two diagonally opposite locations and an air vent is provided in the middle portion, a weld line L is generated in the middle portion, and the steel ball 1 is stored. No longer passes through the hole 2 in the axial direction. That is, the weld line L comes to a portion other than the load concentration portion at the time of use in the resin pipe joint.
[0022]
As a result, in the pressure resistance test, the resin pipe joint injection-molded by the four pin gates G shown in FIG. 2 was cracked by the steel ball 1 hitting the weld line L of the hole 2, In the case shown in FIG. 3, since no weld line L exists in the hole 2 where the steel ball 1 hits, no crack was observed even in a pressure test under more severe conditions.
[0023]
【The invention's effect】
The resin pipe joint of the present invention and the manufacturing method thereof are required when the weld line is not generated because the weld line at the time of injection molding is in a part other than the load concentration part at the time of use in the resin pipe joint. While avoiding the addition of manufacturing equipment and complication of the manufacturing method, problems such as cracks due to weld lines can be substantially prevented.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a conceptual diagram showing a state of occurrence of a weld line when a resin pipe joint is manufactured by injection molding.
FIG. 2 is a conceptual diagram showing a situation when a weld line is oriented in the axial direction of a pipe joint passing through a hole for storing a steel ball.
FIG. 3 is a conceptual diagram showing a situation when the weld line does not face the axial direction of the pipe joint passing through the hole for storing the steel ball.
[Explanation of symbols]
1 ... steel ball 2 ... hole L ... weld line G ... gate

Claims (2)

A method of manufacturing a resin pipe joint manufactured by injection molding,
Resin injection gates are provided at two locations facing each other on the diameter on the end face side of the resin pipe joint, and a weld line when molten resin is injected into the cavity of the mold is generated between the gates,
When viewed from the end face side of the resin pipe joint, a hole for storing the steel ball of the resin pipe joint that joins a pipe body with a steel ball is provided between the gate and the weld line. A method of manufacturing a resin pipe joint. The method for producing a resin pipe joint according to claim 1, wherein an air vent is provided at a position away from the hole for storing the steel ball.

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