JP2004202811A - Resin pipe joint and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin pipe joint which makes it possible to avoid the addition of manufacturing facilities and the complication of a manufacturing method by allowing the generation of a weldline while substantially preventing the problems of cracking or the like due to the weldline from occurring by changing the position or direction of the weldline, and a method for manufacturing the resin pipe joint. <P>SOLUTION: The resin pipe joint is manufactured by injection molding and constructed so that the weldline L which is generated when a molten resin is injected in the cavity of a mold to be injection-molded, appears at a part other than a load concentrating part of the resin pipe joint during use. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a resin pipe joint capable of preventing a problem such as a crack caused by a weld line at the time of injection molding, and a method for manufacturing the same.
[0002]
[Prior art]
Since the resin pipe joint is for transferring a fluid, 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 pipes are connected by steel balls, a weld line always occurs in a part of the hole for storing the steel balls.
[0003]
It is generally known that when a load is applied to the weld line, the resin breaks at a lower load than other parts. Therefore, a method of manufacturing a resin molded product that does not generate a weld line has been proposed. That is, during injection molding, the molten resin injected into the cavity of the mold is heated until the leading edge of the molten resin joins to maintain an appropriate temperature for molding. (For example, see Patent Document 1).
[0004]
[Patent Document 1]
JP-A-11-179772 (page 2, FIG. 1)
[0005]
[Problems to be solved by the invention]
However, in order to prevent a weld line from being generated as in Patent Document 1, a high-temperature gas is caused to flow in the cavity of the mold, and the cavity surface and the flow front of the molten raw material to be filled are heated, thereby causing a flow front. Must be maintained at a suitable molding temperature until the merging, and when the flow fronts merge, it is necessary to accelerate the flow velocity in this portion so that a sharp collision occurs due to rapid discharge of the hot gas.
[0006]
Therefore, the present invention allows the generation of weld lines, thereby avoiding the addition of manufacturing equipment and complicating the manufacturing method, while changing the position and direction of the weld lines substantially eliminates problems such as cracks caused by the weld lines. It is an object of the present invention to provide a resin pipe joint which can be prevented and a method for manufacturing the same.
[0007]
[Means for Solving the Problems]
The present invention has been made to solve the above problems, and a first gist of the present invention is a resin pipe joint manufactured by injection molding, wherein a weld line at the time of injection molding is a resin pipe joint. The present invention relates to a resin pipe joint in a portion other than the load concentrated portion during use in the above.
[0008]
In particular, in the case of a resin pipe joint in which pipes are joined by steel balls, a weld line passing through a hole for accommodating the steel balls relates to a resin pipe joint that is not in the axial direction of the pipe joint.
[0009]
A second aspect of the present invention is a method for manufacturing a resin pipe joint by injection molding, wherein a weld line when a molten resin is injected into a cavity of a mold is a part other than a load concentrated portion when the resin pipe joint is used. The present invention relates to a method of manufacturing a resin pipe joint in which a resin injection gate is provided so as to come to a portion of (1).
[0010]
In particular, in the case of a resin pipe joint in which pipes are joined by steel balls, a resin injection gate is provided so that a weld line passing through a hole for storing steel balls does not face the axial direction of the pipe joint. The present invention relates to a method for manufacturing a resin pipe joint. In this case, it is preferable to provide an air vent at a position distant from the hole for storing the steel ball.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
In the resin pipe joint of the present invention, the weld line at the time of injection molding is located at a portion other than the load concentrated portion at the time of use in the resin pipe joint, and the manufacturing method is such that molten resin is injected into the cavity of the mold. The gate for resin injection is provided so that the weld line at this time is located in a portion other than the load concentrated portion during use in the resin pipe joint.
[0012]
That is, instead of eliminating the weld line itself, the weld line is allowed to occur, and the weld line is located in a portion other than the load concentrated portion in use of the resin pipe joint. Therefore, there is no difference in terms of equipment from general injection molding.
[0013]
Here, the load concentrated portion during use in the resin pipe joint is, for example, in the case of a pipe joint that presses and joins a pipe body with a steel ball, is an axial portion of a hole for accommodating the steel ball. That is, as a pipe joint for detachably connecting a pipe body, there is a structure in which a steel ball as a pressing member is brought into contact with an outer collar having an inclined surface. More specifically, a structure in which 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-out force (fluid pressure due to use) acts while the pipe body is inserted into the inner collar, the steel ball as the 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 toward the surface of the tube, and exerts a tightening force on the tube. Therefore, the hole for accommodating the steel ball in the inner collar receives the pressure of the steel ball due to the pulling force in the axial direction portion of the pipe joint.
[0015]
Therefore, in the inner collar constituting the pipe joint, the axial portion of the hole for storing the steel ball becomes the load concentrated portion, and if the inner collar is made of resin, the weld line accompanying the injection molding becomes the axial direction of the pipe joint. In this case, there is a concern that a crack may be generated by the fluid pressure acting when the pipe joint is used. Therefore, in the resin pipe joint of the present invention, the risk of cracks is eliminated by setting the weld line passing through the hole for storing the steel ball not 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, since a weld line is generally formed in the middle portion of the gate for resin injection, the number and position of the gates are set so that the middle 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 mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram showing the occurrence of weld lines 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 from the upper gate G as indicated by arrows, and merges at the lower part 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 ways as indicated by arrows, and flows in the middle part of the gate G. The weld lines L are merged. Therefore, the gate G is provided so that the weld line L is located at a portion other than the load concentration portion during use in the resin pipe joint.
[0019]
In this regard, a resin pipe joint in which the pipes are joined by steel balls will be further described. FIG. 2 is a conceptual diagram showing a situation where the weld line is oriented in the axial direction of a pipe joint passing through a hole for storing a steel ball. That is, as shown in FIG. 2 (A), when the pin gates G (four points) are at the vertices of a square, the weld line L passing through the holes 2 for storing the steel balls 1 provided on the upper, lower, left and right sides is a pipe. Orients in the axial direction of the joint.
[0020]
Here, when a fluid pressure or a tensile load at the time of using the pipe joint acts on the steel ball 1, the steel ball 1 moves in the axial direction of the pipe joint, and thus 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 occur) with a low load.
[0021]
However, as shown in FIG. 3, when the pin gate G is reduced to two diagonally opposite places and an air vent is provided in the middle part, a weld line L is generated in the middle part, so that the steel ball 1 is stored. In the axial direction. That is, the weld line L comes to a portion other than the load concentrated portion during 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 FIG. 3, since no weld line L exists in the hole 2 hit by the steel ball 1, no crack was observed even in a pressure test under more severe conditions.
[0023]
【The invention's effect】
The resin pipe joint and the method for manufacturing the same according to the present invention are required when a weld line is not generated because the weld line at the time of injection molding is located at a portion other than the load concentrated portion during use of the resin pipe joint. It is possible to substantially prevent a problem such as a crack due to a weld line while avoiding the addition of a manufacturing facility and a complicated manufacturing method.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing the occurrence of weld lines when a resin pipe joint is manufactured by injection molding.
FIG. 2 is a conceptual diagram showing a situation where a weld line is directed 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 where a weld line does not face an axial direction of a pipe joint passing through a hole for storing a steel ball.
[Explanation of symbols]
1 steel ball 2 hole L weld line G gate

Claims (5)

A resin pipe joint manufactured by injection molding, wherein a weld line (L) at the time of injection molding is located in a portion other than a load concentrated portion in use of the resin pipe joint. A weld line (L) passing through a hole (2) for accommodating a steel ball (1) of a resin pipe joint for connecting a pipe body by a steel ball (1) is not in the axial direction of the pipe joint. Item 4. The resin pipe joint according to Item 1. A method of manufacturing a resin pipe joint by injection molding, wherein a weld line (L) when a molten resin is injected into a cavity of a mold is located in a portion other than a load concentrated portion in use of the resin pipe joint. And a gate (G) for resin injection. In order to prevent the weld line (L) passing through the hole (2) for accommodating the steel ball (1) of the resin pipe joint connecting the pipes with the steel ball (1), the resin pipe joint does not face the axial direction of the pipe joint. The method for manufacturing a resin pipe joint according to claim 3, wherein an injection gate (G) is provided. The method for manufacturing a resin pipe joint according to claim 4, wherein an air vent is provided at a position away from the hole (2) for storing the steel ball (1).

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