JPS5837128B2 - It's a long time since I've been in the middle of a long time. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for molding a socket for connecting a packing, and more specifically, a method for molding a thermoplastic resin pipe having a socket for connecting a packing at a low cost, easily, and with high productivity. The present invention relates to an improved method for shaping.

In the present invention, a thermoplastic resin pipe is a general term for long pipes and pipe joints, and particularly refers to resin pipes used for drainage pipes and the like.

Various methods are known for connecting thermoplastic resin pipes in a liquid-tight manner, and a packing connection method is known as one of the representative methods.

In this method, the inlet pipe and the socket pipe face each other and are connected in a liquid-tight manner via a sealing packing, but it is necessary to prevent the packing from shifting or falling off during the connection process, or to prevent the resin pipe from expanding or contracting after connection. In order to prevent the packing from rolling due to thrust loads, etc., a packing engagement groove is provided on the inner peripheral surface of the socket.

By the way, the method of forming a packing engagement groove in the socket of a thermoplastic resin pipe is to form a packing engagement groove at the same time when the end of the headless long pipe is expanded in diameter by sleeve processing in the case of a long pipe. A certain secondary processing method is widely used, and for short pipes such as pipe joints, it is common to form a packing retaining groove at the same time as injection molding.

However, when forming a packing engagement groove in the socket,
The grooved part of the core inevitably becomes undercut.

In order to make the undercut part removable, a deformable core must be used, which complicates the structure of the core and significantly increases the manufacturing cost.

For example, Figures 1 to 4 are vertical cross-sectional views of the main parts of the collapsing part illustrating the conventional packing connection socket forming method, Figures 1 and 2 are sleeve processing methods, and Figures 3 and 4 are injection molding methods. It shows the form method.

According to these methods, the packing engagement groove 1b can be formed on the inner circumferential wall of the enlarged diameter portion 1a of the resin pipe 1, but the part corresponding to the hacking engagement groove 1b of the core 2 becomes an undercut 3 and the core 2 It becomes impossible to remove the mold.

Therefore, it is essential that the diameter of the undercut portion 3 is reduced as shown in the example, and when removing the core 2 from the mold, the diameter of the undercut portion 3 is reduced as shown in Figures 2 and 4. becomes.

For this reason, the core 2 is normally equipped with a complicated diameter expansion/contraction mechanism, but since the diameter expansion/contraction mechanism is extremely complex and requires high precision, the core 2 is Production costs are extremely high.

Furthermore, in this type of molding method, the core 2 must be removed from the mold only after the resin tube 1 has cooled and hardened, and in order to shorten the molding time, it is necessary to cool the resin tube 1 from the inside and outside. desired.

However, as shown in the illustration, core 1 has a built-in complicated diameter expansion/contraction mechanism.
It is extremely difficult to further provide a cooling water passage or the like inside the core, and such a core is not actually provided.

Therefore, the cooling and hardening of the resin tube 1 relies only on cooling from the outer periphery, which is unsatisfactory from the point of view of shortening the hardening time and increasing productivity.

As mentioned above, known socket pipes for connecting packing have low productivity, and the manufacturing cost of the core is high, so they are extremely expensive compared to headless pipes or sockets without undercuts. The current situation is that this has to be the case.

The present invention was made in view of the above-mentioned circumstances, and its purpose is to provide a method for forming a packing connection socket simply and inexpensively, and with high productivity. There is something to do.

The forming method of the present invention which achieves the above object is to form a packing groove by folding the end of the enlarged diameter part of a thermoplastic resin tube inward to form an inner flange. After placing a metal ring in a liquid-tight manner on the inner circumferential surface of the enlarged diameter part of a thermoplastic resin pipe whose end has been enlarged in diameter, the open end of the enlarged diameter part is folded back along the end surface of the opening side of the metal ring, The main feature is that the metal ring is stably fixed to the enlarged diameter portion, and a packing engagement groove can be formed by the enlarged inner wall surface of the thermoplastic resin pipe and the metal ring.

The structure and effects of the present invention will be specifically explained below based on Examples, but the illustrated examples are merely representative embodiments of the present invention, and various changes may be made based on the following explanation without departing from the above gist. It is also possible to implement it by

Fifth. Figures 6a and 6b are explanatory diagrams illustrating the method of forming the packing connection socket according to the present invention, and are also longitudinal cross-sectional views of the main parts.

When carrying out the present invention, first, an enlarged diameter portion 1a is formed at the open end of the thermoplastic resin pipe 1, as shown in FIG.

This process of forming the enlarged diameter part 1a is not different from the conventional method, and a sleeve molding method or an injection molding method can be adopted, but in any case, the core 2 that regulates the inner surface of the enlarged diameter part 1a is Undercuts cannot be created.

Therefore, as shown in FIGS. 1 to 4, the core 2 does not need to have a complicated structure that can be expanded and contracted in diameter, so its manufacture is extremely simple and inexpensive.

Furthermore, since there is no need to incorporate a complicated mechanism inside the core 2, cooling channels 4 can be provided inside the core 2, as shown in FIG. 5, for example.

Therefore, in the forming step of the enlarged diameter portion 1a, it is possible to cool not only the outer circumferential surface but also the inner circumferential surface thereof, so that the enlarged diameter portion 13 can be cooled and hardened in a short time, and the shaping time can be significantly shortened.

The enlarged diameter portion 1a shaped in this way has the sixth a
A metal ring 5 is inserted and arranged as shown in the figure.

The metal ring 5 of this example is shaped so that its outer diameter is equal to the inner diameter of the enlarged diameter portion 1a of the resin tube 1, and its cross-sectional shape is L-shaped with the open end bent toward the inner circumference. shape into a shape.

After bonding the metal ring 5 to the deep inner surface of the socket portion 1a by adhesive or baking bonding, etc., the enlarged diameter portion 1a is
By bending the open end in the direction of arrow A, a socket portion having a packing engagement groove 6 on the inner periphery of the open end is obtained as shown in FIG. 6b.

Such a socket part is easy to shape, and since the packing engagement groove 6 is formed by the metal ring 5 itself, its shape can be made precise; Since it is reinforced, it has excellent strength.

Figures 7a and 7b show other embodiments of the invention,
It is also possible to adopt a joining method in which a sealing packing 7 is arranged on the outer peripheral surface of the metal ring 5 and the packing 7 maintains liquid tightness.

Figures 8a, 8b and 9a, 9b show still other embodiments of the present invention, in which a donut-shaped metal ring 5 is used.

In such a case, a first enlarged diameter section 1a and a second enlarged diameter section 1a' are formed at the open end of the resin tube 1, but in any case, an undercut section is formed on the core used for diameter expansion shaping. I can't.

After the metal ring 5 is placed in the inner part of the second enlarged diameter part 1a', by folding the enlarged diameter end inward, a socket part having a packing engagement groove 6 on the inner periphery of the open end is obtained as described above. .

As is clear from the illustrated example, the shape of the metal ring 5 used in the present invention can be appropriately selected depending on the shape of the packing retaining groove 6 to be formed, and is not a limitation of the present invention. It's not a thing.

Further, the shape of the enlarged diameter portion 1a (and 1a') of the resin pipe 1 should be appropriately selected depending on the shape of the packing engagement groove 6 and the metal ring 5 to be formed, and is not particularly limited. In order to avoid creating an undercut in the core, it is natural that the shape should be such that the diameter increases toward the opening.

In the illustrated example, the packing engagement groove 6 is rectangular in shape, but the shape of the enlarged diameter portion 1a and the metal ring 5 may be changed depending on the shape of the sealing packing to be engaged with the engagement groove 6. It goes without saying that various appropriate packing engagement grooves 6 other than those illustrated can be formed by appropriately selecting the following.

Next, a method of folding back the open end of the resin tube 1 will be explained according to the embodiment shown in FIG. 10.11.

This folding process is intended to stably fix the metal ring 5 and improve the product value by making the appearance of the socket part beautiful, and can be folded along the opening end surface of the metal ring 5. Any method may be used, but the example shown in FIG. 10.11 is an extremely practical method from the viewpoint of ease of processing operation and reliability.

That is, the illustrated example shows a method of using a folded member 9 having an elastic tube 8 disposed on its inner periphery, and the elastic tube 8 is expanded by the fluid pressure sent from the fluid pressure inlet 10.

Therefore, the enlarged diameter part 1a with the metal ring 5 disposed on the inner circumferential surface and whose open end is heated and softened is inserted into the folded member 9 (
(Fig. 10), when fluid is pressurized into the elastic tube 8, the elastic tube 8 expands and compresses the opening of the enlarged diameter portion 1a, causing the opening to extend along the opening end surface of the metal ring 5 as shown in Fig. 11. Process by folding.

If you adopt the method of using the elastic tube 8 in this way,
The structure of the folding member 9 is simple, and since the folded portion can be uniformly compressed from the entire circumference, the machined surface can be beautifully finished, which is extremely suitable for carrying out the present invention.

Although it is most common to use a gas such as compressed air as the fluid here, using a liquid such as cold water to accelerate cooling and hardening at the same time as the folding process is even more effective in terms of shortening the processing work. It's practical.

However, there is no reason why the folding method that can be adopted in the present invention is limited to the example shown above, and other methods that utilize the expansion force of an elastic material or folding members that can be mechanically expanded and contracted in diameter may be used. In short, as long as the opening end of the enlarged diameter portion 1a can be folded back along the opening end surface of the metal ring 5, the folding mechanism itself can be adapted as appropriate depending on the actual situation at the work site. It is something that can be selected and determined.

Figures 12a and 12b illustrate a more preferred embodiment of the present invention, and show a method of adhering the sealing elastic packing 11 in advance to the metal ring 5 to be placed in the enlarged diameter portion 1a.

If the packing 11 is bonded to the metal ring 5 in advance in this manner, the bonding is simpler and more accurate than in the case where the packing 11 is bonded after the socket is formed, which is extremely convenient.

13-14 are cross-sectional side views of main parts showing still another embodiment of the present invention, and can be understood in the same manner as FIGS. 6-12 except that the shape of the metal ring 5 is slightly changed.

The present invention is constructed as described above, and a socket portion can be easily obtained by simply arranging a metal ring on the inner circumferential surface of the enlarged diameter portion of a resin tube and then folding back the tip.

In particular, in the process of shaping the enlarged diameter part in the present invention, even in the case of collapse in the sleeve shaping method or the injection shaping method, an undercut cannot be formed in the core that regulates the inner surface of the enlarged diameter part. , the shape and structure of the core are simplified, the manufacturing cost of the core is significantly reduced, and a certain shaping process is also simplified.

Further, since the core has an extremely simple structure, it is easy to provide a cooling section inside the core, and the advantage of shortening the cooling hardening time of the processed section can also be enjoyed.

Further, according to the present invention, the packing engagement groove can be shaped with high precision, and its shape and dimensions can be easily and freely changed according to the shape and dimensions of the sealing packing to be engaged. .

This makes it possible to make efficient packing connections by maximizing the contact area of the sealing packing.

Furthermore, the socket part of the present invention has the significance of reinforcing the socket part, which is most susceptible to unbalanced loads against external forces such as earth pressure and thrust loads, and is extremely effective in practical use. There are some preferable ones.

In this way, a socket having excellent characteristics in terms of strength and precision can be provided at a low price with high productivity.

[Brief explanation of drawings]

The drawings are for explaining the present invention, and FIGS. 1 to 4 show known examples,
5 to 11 are vertical cross-sectional views of essential parts of the folding machine illustrating a certain method according to the present invention. Figures 1 and 2 show a known example in which a socket for connecting a packing is formed by secondary processing a resin pipe using a core whose diameter can be expanded and contracted, and Figures 3 and 4 show a structure that can be expanded and contracted in diameter. This is a known example in which a pipe joint having a packing connection socket is injected or formed using a certain core. 5 to 9b are explanatory diagrams illustrating the process of shaping the packing connection socket according to the present invention, and FIGS. 10 and 11 are explanatory diagrams illustrating the folding method employed in the present invention. Figures 12a and 12b show another embodiment of the present invention, and are explanatory diagrams illustrating a method of joining the sealing packing with the socket shape. FIGS. 13 and 14 are side views in cross-section of essential parts of still another example of the socket obtained by the present invention. 1...Thermoplastic resin pipe, 1a, 1a'...
... Expanded diameter part, 1b... Packing engagement groove, 2...
...Middle child, 3...Song undercut section, 4...
...Cooling path, 5...Metal link, 6...
・Packing engagement groove, 7...Packing for curved seal, 8...
...Elastic tube, 9...Folding member,
10...Liquid inlet, 11...Elastic packing for sealing 0

Claims (1)

[Claims] 1 When creating a packing groove by folding the end of the enlarged diameter part of the thermoplastic resin pipe inward to form an inner flange, the opening end of the thermoplastic resin pipe is expanded or shaped. After placing the metal ring on the inner peripheral surface of the diameter part in a liquid-tight manner, the opening end of the enlarged diameter part is folded back along the opening side end surface of the metal ring to stably fix the metal ring to the enlarged diameter part. . A method of forming a socket for connecting a packing, characterized in that a packing engagement groove is formed by the enlarged-diameter rear wall surface of the thermoplastic resin pipe and a metal ring.