JPH0564567B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method and apparatus for molding a fiber-reinforced synthetic resin pipe, particularly a resin pipe having threads at both ends.

BACKGROUND ART Conventionally, when forming a male thread for a joint at the end of a fiber-reinforced synthetic resin pipe (hereinafter referred to as a resin pipe), the thread was directly formed on the pipe surface by cutting.

Problems to be Solved by the Invention According to the above-mentioned conventional cutting process, the reinforcing fibers laminated inside the resin pipe are cut, which has a negative impact on the strength of the resin pipe itself and also limits the processing accuracy of threads. There is a problem that there is. In addition,
In order to prevent the strength of the resin pipe from decreasing, it may be possible to form a tip strand layer on the outer periphery of the end of the resin pipe and then cut threads into this tip strand layer, but it is also possible to cut the tip during cutting. The strand itself is damaged, the strength of the screw is reduced, and there is also a limit to the accuracy of screw processing.

Therefore, an object of the present invention is to provide a method and apparatus for molding a fiber-reinforced synthetic resin pipe that can solve the above problems.

Means for Solving the Problems In order to solve the above-mentioned problems, the method for molding a fiber-reinforced synthetic resin pipe of the present invention involves adding a tapered screw to the outer periphery of the end when molding a fiber-reinforced synthetic resin pipe by centrifugal molding. This is a method in which the pipe is integrally molded, and the outer circumferential surface of the tapered thread is located inside the outer circumferential surface of the straight pipe portion of the resin pipe.

Furthermore, the fiber-reinforced synthetic resin pipe molding apparatus of the present invention includes a straight pipe part mold for molding a straight pipe part of a resin pipe, an annular thread part mold for forming a tapered thread part at the end of a resin pipe, and a mold for forming a straight pipe part of a resin pipe. It is composed of a connector that connects both molds together, and a support that is inserted inside the end of the resin tube during demolding and supports the end of the resin tube from the inside.

Effects In the above-mentioned molding method of the present invention, the tapered thread is integrally formed on the outer periphery of the end of the fiber-reinforced synthetic resin pipe by centrifugal molding, so there is less damage to the threaded part than when using conventional cutting processing. Because there is no screw, the strength is high and the screw precision is also good. Furthermore, since the outer circumferential surface of the tapered screw is located inside the outer circumferential surface of the straight pipe part, there is no problem in demolding the mold for the straight pipe part.

Furthermore, in the molding apparatus of the present invention, the mold for the tapered threaded portion is annular and integral.
For example, compared to a two-piece mold, there is no misalignment at the mating portion, so it is possible to improve screw precision and reduce the manufacturing cost of the mold. Furthermore, since a support for the end of the resin tube is provided, the resin tube will not be deformed during demolding.

Embodiment Hereinafter, an embodiment of the present invention will be described based on the drawings.

As shown in FIG. 1, a fiber-reinforced synthetic resin pipe (hereinafter referred to as a resin pipe) 1 according to the present invention is molded by a centrifugal molding method, and tapered threaded portions 1a are integrally formed at both ends of the pipe by centrifugal molding. It is molded into. That is, as shown in Figure 2,
When the straight tube part mold 2 and the screw part molds 3, 3 at both ends are integrally connected and rotating, molten resin and reinforcing fiber (for example, glass fiber) are contained in the molds 2, 3. These materials are added to form a resin tube 1 having tapered threaded portions 1a on the outer periphery of both ends. After molding, the screw part molds 3, 3 at both ends are
After removing the resin pipe 1 from the straight pipe mold 2, a tension fitting is screwed onto one of the tapered threaded parts 1a and the resin pipe 1 is pulled out from the straight pipe mold 2. In this way, in order to pull out the resin pipe 1 from the straight pipe part mold 2, as shown in FIG. It is located inside the outer circumferential surface of. The dimensions of this tapered threaded portion 1a are as follows (1) ~
Equation (3) is satisfied.

t ₁ /5<t ₂ <t ₁ /3 −(1) 5t ₁ <l<15t ₁ −(2) t ₁ /10<h<t ₁ /3 −(3) However, t ₁ : Straight pipe section Thickness t ₂ : Taper height at the tapered end l : Length of the taper threaded part h : Thread height Next, a molding apparatus for centrifugally molding the resin pipe will be explained based on FIG. 3.

This molding device 4 includes a straight pipe part mold 2 for molding the straight pipe part 1b of the resin pipe 1, and a tapered threaded part 1 of the resin pipe 1.
a Thread part mold 3 for molding, and both these molds 2, 3
An annular connector 5 that connects the two pieces to each other, and a cylindrical connector that is inserted inside the end of the resin pipe 1 through the hole 3a of the threaded mold 3 during demolding and supports the end of the resin pipe 1 from the inside. It is composed of a support tool 6. The straight pipe mold 2 has a cylindrical shape, and a plurality of connecting claws 7 are protruded from the outer periphery of the end thereof at predetermined intervals, and the end surface of the straight pipe mold 2 has an annular shape. A protrusion 8 is formed, and the outer peripheral surface thereof is formed into an annular inclined convex surface 9. The threaded part mold 3 has an annular structure, and a predetermined tapered threaded part 3b is formed on the inner surface of one end thereof, and an annular inclined convex surface of the straight pipe part mold 2 end is formed at one end. 9 is formed with an annular inclined concave surface 10 that can be fitted onto the outside, and an annular engaging protrusion 11 is formed on the outer periphery of one end. Furthermore, ring teeth 12 are formed at the other end on the threaded part mold 3 side for rotating this threaded part mold 3 during demolding, and a straight pipe is provided in the middle part of the threaded part mold 3. An injection hole 13 for injecting a mold release material (silicon) is formed in the contact surface with the part mold 2. Note that 14 is a connection flange for the injection hole 13, and 15 is a sealing material attached to the annular inclined concave surface 10 on the threaded part mold 3 side. In addition, the connecting tool 5
An annular recess 16 is formed on the inner circumferential surface of the mold, and the claws 7 and engagement protrusions 11 of both molds 2 and 3 fit into this annular recess 16, so that both molds 2 and 3 are integrated. be done. Therefore, a notch (not shown) through which the claw portion 7 can be inserted is formed in one side edge of the connector 5, and the connector 5 is fitted onto the engagement protrusion 11. When performing the connection, it is sufficient to align the ends of both molds 2 and 3 with each other, position the claw portion 7 within the annular recess 16, and rotate it in a predetermined direction. Note that the contact surface between the claw portion 7 and the annular recess 16 is tapered, and when the connecting tool 5 is rotated, both molds 2 and 3 are pressed against each other.

In the above configuration, when centrifugally molding a resin pipe with threaded ends, first the threaded part mold 3 is fitted to both ends of the straight pipe part mold 2, and the pipes are integrally connected to each other by the connector 5. At this time, since the annular inclined concave surface 10 of the threaded part mold 3 fits into the annular inclined convex surface 9 of the straight pipe part mold 2, mutual alignment is easily and accurately performed. Next, the above molds 2 and 3
is rotated, molten resin, reinforcing fibers, etc. are alternately introduced into the molds 2 and 3, and the resin tube 1 is centrifugally molded. When centrifugal molding is completed, the support 6 is inserted into the resin tube 1 through the hole 3a of the threaded mold 3, and then the flange 6a is attached to the threaded mold 3 by bolts 17.
Fix it by. Next, a mold release material (for example, silicone) is injected into the inner surfaces of both molds 2 and 3 through the injection hole 13, and the connector 5 is rotated to
Unlink comrades. Next, after meshing the driving gear 18 with the ring teeth 12 of the threaded part mold 3, the driving gear 18 is rotated by a motor (not shown) to move the threaded part mold 3 into the tapered part 1a of the resin tube 1. to separate from After the threaded part mold 3 is removed from both ends, a tension fitting (not shown) is screwed onto one tapered screw 1a of the resin pipe 1, and the resin pipe 1 is pulled from the straight pipe part mold 2. Just pull it out.

Effects of the Invention According to the above-mentioned molding method of the present invention, the tapered thread is integrally formed on the outer periphery of the end of the fiber-reinforced synthetic resin pipe by centrifugal molding, so there is less damage to the threaded part than when using conventional cutting processing. Since it does not stick, the strength is high and the screw precision is also good. Furthermore, since the outer circumferential surface of the tapered screw is located inside the outer circumferential surface of the straight pipe part, there is no problem in demolding the mold for the straight pipe part.

In addition, according to the above-mentioned molding apparatus of the present invention, the mold for the tapered thread part is annular and integrated, so there is no misalignment at the mating part compared to, for example, a two-piece mold, which improves thread accuracy. It is possible to improve the performance of the mold and reduce the manufacturing cost of the mold. Furthermore, since a support for the end of the resin tube is provided, the resin tube will not be deformed during demolding.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is an enlarged sectional view of a tapered threaded portion of a resin pipe, FIG. 2 is an overall vertical sectional view, and FIG. 3 is an enlarged sectional view of the main part of a mold. . DESCRIPTION OF SYMBOLS 1...Fiber-reinforced synthetic resin pipe, 1a...Tapered thread part, 1b...Straight pipe part, 2...Straight pipe part mold, 3...
...Thread part mold, 3a... Hole part, 3b... Taper thread mold part, 4... Molding device, 5... Connector, 6...
Support.

Claims (1)

[Scope of Claims] 1. When forming a fiber-reinforced synthetic resin pipe by centrifugal molding, a tapered thread is integrally molded on the outer periphery of the end thereof, and the outer periphery of this tapered thread is placed inside the outer periphery of the straight pipe part of the resin pipe. A method for molding a fiber-reinforced synthetic resin pipe, characterized in that the pipe is positioned at 2 An apparatus for molding fiber-reinforced synthetic resin pipes by centrifugal molding, which includes a straight pipe part mold for molding the straight pipe part of the resin pipe, and an annular thread part mold for molding the tapered thread part at the end of the resin pipe. , a fiber-reinforced synthetic resin tube comprising a connector that connects these two molds together, and a support that is inserted inside the end of the resin tube during demolding and supports the end of the resin tube from the inside. molding equipment.