JPH0147290B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming an enlarged diameter socket on the end of a thermoplastic synthetic resin pipe material or a pipe joint member by injection molding, and in particular to a method for forming an enlarged diameter socket on the inner circumferential surface of the enlarged diameter socket. This is a method in which a fitting ring groove for arranging a gasket is formed at the same time as the diameter of the socket is expanded by a simple mold construction means, and the dimensional accuracy is achieved by using the mold. It is designed to improve the

In thermoplastic synthetic resin pipes, the ends of straight pipes,
Alternatively, an enlarged diameter socket (hereinafter simply referred to as a socket) may be formed at the end of a bent pipe or short pipe used as a joint.In this case, an extruded pipe is generally used as the material. It is often formed by subsequent molding means. It may also be injection molded as a joint pipe. Packets are installed in these sockets, but
One way to attach these gaskets to a predetermined position is to provide an annular groove on the inner circumferential surface of the socket to prevent the gasket from coming off.

On the other hand, in such secondary forming, a push-forming mold is used, but since the annular groove portion becomes an undercut portion, conventionally, a combination core mold with a diameter expansion/contraction function had to be used. Ta. However, these core molds are composed of many parts and have a complicated structure, which is technically extremely difficult, especially for small diameter pipes.

On the other hand, I learned that thermoplastic synthetic resins, when heated and shaped to a state where they exhibit fluidity, have a temperature range in which they can recover even if they are subjected to considerable deformation during the curing process. . Here, this condition range is referred to as the thermoelastic state range. Utilizing this property, we have proposed a molding method in which the core mold is pulled out as it is while forcibly deforming the undercut portion in the thermoelastic state region. That is, the mold for molding the opening end of the expanded diameter socket is composed of a movable core mold and an outer mold, and a protruding part for molding the undercut part is formed on the core mold. The molds are joined and held to form a molding gap, and the molding gap is filled with a resin material. After reaching the temperature in the thermoelastic state range, or while maintaining the temperature, the outer mold on the socket end side is first detached and retracted, and then the core mold is extracted from the opening side while deforming the end part. It is. The open end portion from which the core mold has been removed is restored to the state in which it was shaped by its elastic recovery force, and is therefore hardened in this restored state.

For example, an annular groove 2 for fitting a seal is formed in an enlarged diameter socket 1 formed into a single-sided straight tube as shown in Fig. 1 (top half cut side view), and an annular groove 2 for fitting a gasket is formed in the opening tube to be inserted and joined. The sealing gasket that maintains the watertightness of the ring groove 2
will be installed on the

By the way, when such an enlarged diameter socket D of the annular groove 2 is formed by the above-mentioned proposed method, the core mold having the protrusion for forming the annular groove is removed from the mold at once, so that from the annular groove 2 to the open end 3 of the socket. The amount of deformation is large, and the molded tube is easily stretched and deformed into a thin wall. Furthermore, even if these deformations are restored, the inner surface of the ring groove may not be uniform, which may cause the seal to come off. Therefore, even if the above-described molding method utilizing the thermoelastic state is employed, a restoring means is required.

The present invention has been made in view of the above-mentioned circumstances, and in particular, after the core mold on which the ring groove molding protrusion has been formed is pulled out from the diameter expansion socket, the ring groove that has been retracted once is removed. Slide the diameter-expanding sliding outer mold for molding from the socket open side to the original molding position, shape the diameter-expanding socket open end and the outer peripheral surface of the ring groove, and move from the core mold side to the inner surface of the ring groove. The gist is that the inner surface of the annular groove is blow-shaped by blowing air.

The present invention will be explained in detail below based on the drawings, but the drawings show specific embodiments of the present invention and can be similarly applied to enlarged diameter sockets of other shapes. Further, a specific example of the molding die is shown, and the present invention is not limited to these illustrated examples, and other configurations or partial modifications may be made in accordance with the spirit described above and below. It can be implemented in the same way even if the design is changed.

FIG. 2 is a partially cutaway side view showing an example of a molding device 4 for carrying out the present invention, and shows a molding die used as a secondary molding means. By attaching a device, it can also be used as an injection mold. That is, in secondary molding, a softened pipe end is inserted, and its tip end is heated by a heating device installed in the mold to a temperature at which it exhibits at least fluidity, and is pressed into shape. . In addition, in injection molding, resin in a molten state is press-fitted and shaped, and the mold configuration and molding operation of the expanded diameter socket 1 are the same, so the following explanation will be made using two methods. Next, let's talk about the next forming.

In the figure, the outer molds include an enlarged-diameter sliding outer mold 5 that forms the outer surface on the open end side of the socket from the maximum diameter part of the outer periphery of the ring groove 2 for fitting the seal, and a sliding mold 5 that forms the outer surface on the open end side of the socket. It consists of an enlarged-diameter outer mold 6 for molding the outer surface, and each of these has a circumference divided into an appropriate number of pieces (in the illustrated example, divided into six pieces). In addition, these divided pieces are respectively connected to the piston of the working cylinder, and the enlarged diameter outer 6
An actuating cylinder 14 is provided in each group, and an actuating cylinder 12 is provided in each of the five groups of enlarged sliding outer molds. The actuating cylinder 14 is attached to a frame member (not shown) surrounding the forming device 4, while the other actuating cylinder 12 is an annular sliding member configured to move in the axial direction of the forming socket tube. They are fixedly provided on the guide plate 10, respectively. The diameter-expanding sliding outer mold 5 is a dovetail groove 10 formed radially on the guide plate 10.
It is desirable to configure the device so that it can be moved by fitting into a portion a (FIG. 4). 13 is a sliding cylinder for the guide plate 10 and is fixed to a frame (not shown).

On the other hand, the core mold 7 has a core mold main body 7a provided with a protrusion 9 that forms the inner surface of the annular groove 2, and a core mold main body 7a that is attached to the tip side of the core mold main body 7a when the core mold main body 7a slides a certain distance backward. Guide core type 7 that follows and moves
b, and its structure is such that a small-diameter stepped portion 7d is formed at the center of the leading end side of the core mold body 7a, and a fitting portion that slides on the narrow-diameter stepped portion 7d is formed on the guide core mold 7b. A recess is formed, and an engagement device is provided between the distal end surface of the narrow diameter stepped portion 7d and the fitting recess surface. That is, such an engagement device 17 includes a plated member 17a formed separately and attached to the tip of the core body 7a side, and a flange ring that engages with the plated member 17a on the bottom side of the fitting recess. 17b is attached to the guide core mold 7b side. For these engagements, a gap 17c is formed.
A step is formed at the root of the narrow diameter step 7d, and an air blowhole 15a is formed in a part of the step. Pressure air emitted from the blowhole 15a is sent through a guide hole 15 provided in the core body 7a. Further, the blowhole 15a is configured to be closed by a peripheral end 16 formed on the guide core mold 7b, and is closed when the core mold main body 7a and the guide core mold 7b are joined (during molding in FIG. 2). . 7c is a core-shaped moving rod connected to an actuating cylinder (not shown).

The present invention is carried out in the following order using the mold configured as described above. That is, FIG. 5 and the following are operational explanatory diagrams showing enlarged main parts in FIG.
(FIG. 2), and the expanded diameter socket 1 is shaped in a molten state as described above. When the shaping is completed, as shown in FIG. 5, the operating cylinder 12 is first operated to cause the diameter-expanding sliding outer mold 5 to detach and retreat in the centrifugal direction perpendicular to the tube axis. Then, when the shaping section 18a is in the above-mentioned thermoelastic state range, or after waiting until this temperature condition is reached, the core body 7a is retreated to separate the protrusion 9 from the shaping section 18a. The retracted position is a position rearward of the sliding core mold 5 from which the protrusion 9 is detached and retracted.
Due to this retreat, the forming portion 18a is formed by the dotted line (FIG. 6).
It is deformed as shown in , but it is immediately restored as described above. The shaped portion 18a is once strongly deformed.
is subjected to a tensile force by the protrusion 9 when the core body 7a slides, so the forming portion 18a is slightly stretched compared to before the core mold 7 is removed from the mold.

On the other hand, the guide core mold 7b starts to move as the core mold main body 7a moves by the engagement device 17 formed in the double core mold as described above, and a gap is formed between it and the core mold main body 7a. . Then, it slides to a position where the blowhole 15a faces the inner surface of the shaping portion 18a. At this time, the fumarole 15a opens due to the gap formation. Next, while moving the sliding plate 10, the diameter-expanding sliding outer mold 5 is moved toward the outer peripheral surface of the core mold body 7a. Note that the movement of the diameter-enlarging sliding outer mold 5 in the tube axis direction may be performed together with the removal movement of the core mold 7, or after that. Then, before returning the sliding plate 10 to the original molding position, the diameter-enlarging sliding outer mold 5 is reduced in diameter (Fig. 7), and then the sliding plate 10 is returned by sliding toward the opening side of the socket. Even if the shaped portion 18a is stretched as described above, it is shaped so that it is pushed back by the diameter-expanding sliding outer mold 5. By the way, in the annular groove 2 shaped in this manner, only the outer circumferential surface is molded, so that the resin is easily pushed out toward the inner surface of the unrestricted shaped portion 18a. However, in the present invention, air is forced in from the blowhole 15a at the same time as the diameter-expanding sliding outer mold 5 is returned to its original position. It is shaped into a smooth surface without bulging on the inner surface side. Moreover, since the outer surface of the forming part 18a is also regulated by the outer molds 5 and 6 when air is press-fitted, the forming part 18a is molded by air press-fitting in a manner similar to so-called blow molding, and is extremely accurate. An annular groove is formed. When the enlarged diameter socket 1 is molded in this way, the enlarged outer molds 5 and 6
After retracting, the molding is completed by moving the core mold 7 or pulling out the molded product.

In this way, in the present invention, air is injected from the core mold and the outer mold that has been temporarily retracted is returned to shape the diameter-expanding molded area from both the inside and outside, thereby ensuring that the shaped part in the thermoelastic state region is It can be restored to Therefore, the molding accuracy of the enlarged diameter socket is improved, and the socket can stably hold the packing. In addition, molding becomes easy, and a wide variety of uniform products from small diameters to large diameters can be provided at low cost.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway side view of an expanded diameter socket to which the present invention is applied, Fig. 2 is a partially cutaway side view showing a molding die to which the present invention is applied, and Fig. 3 is the same as in Fig. 2. Line sectional view, Fig. 4 is a - line sectional view of Fig. 3, Fig. 5
8 are explanatory views of the operation of FIG. 2. 1... Expanded diameter socket, 2... Ring groove for fitting the seal,
3... Socket open end, 4... Molding device, 5... Diameter enlarged sliding outer mold, 6... Diameter enlarged outer mold, 7... Core mold for forming inner peripheral surface, 7a... Core mold body, 7b...Guide core type, 9
... Protrusion, 10 ... Sliding guide plate, 12, 13, 1
4...Cylinder.

Claims (1)

[Claims] 1. A method for forming a socket in which an annular groove for fitting a seal is formed on the inner circumferential surface of an enlarged diameter socket of a thermoplastic synthetic resin pipe or an enlarged diameter socket of a pipe joint member, wherein the outer mold for molding the outer circumferential surface thereof is It consists of an enlarged-diameter sliding outer mold that molds the open end side of the socket with the maximum diameter part of the outer periphery of the ring groove for fitting the seal as a boundary, and an enlarged-diameter outer mold that molds the base side of the socket, and the other molds the inner peripheral surface. The core mold has a protrusion on its outer periphery that forms the ring groove for fitting the seal, and is composed of a movable core mold that forms a blowhole for blow shaping the ring groove by moving the core mold. The cavity formed by combining these outer molds and core molds is filled with the resin of the material tube while at least having fluidity or fluidity, and when the resin is in a thermoelastic state region, first, the resin is expanded. The diameter sliding outer mold is retracted, and then the core mold is retreated toward the socket opening side while elastically deforming the pipe wall on the socket opening side, and the retracted position is such that the protrusion is at least connected to the expanded diameter sliding outer mold. When the elastically deformed part is restored or after it has been restored, the diameter-expanding sliding outer mold is returned toward the base of the socket along the outer periphery of the core mold, and the seal is fitted. After shaping the mounting ring groove and the outer circumferential surface on the opening side of the socket, blow air into the ring groove to shape the inner circumferential surface of the seal fitting ring groove, and then remove these outer molds and cut out the shape. A method for molding a socket of a thermoplastic synthetic resin pipe, which is characterized by: