JP2884178B2 - Method for forming flange of synthetic resin corrugated tube - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method of forming a flange at an end of a synthetic resin corrugated pipe having a spiral hollow ridge on a pipe wall.

[Prior Art] The above-mentioned corrugated tube made of synthetic resin is easy to bend due to the function of a helical hollow ridge and a concave portion located between the hollow ridges, and has excellent strength in spite of being lighter than a steel tube. Therefore, it is used for water supply pipes and various fluid pipes taking advantage of its characteristics.

Conventionally, this type of corrugated tube is connected by winding a rubber packing around a helical recess formed at the end and inserting the rubber packing into a socket-shaped joint, and connecting the internal passage and the outside with the rubber packing. Was kept watertight. However, the connection structure is convenient for connecting a relatively small-diameter and light-weight corrugated tube with a diameter of about 30 cm, but it is useful for connecting a corrugated tube with a diameter of 500 mm or more that cannot be moved by human power. Is not suitable.

That is, in the case of a small-diameter and lightweight corrugated tube, the operation of winding rubber packing around the spiral concave portion and the operation of fitting the end of the corrugated tube and the joint are easy. However, in the case of a large-diameter and heavy corrugated tube, the hand may not be able to turn around the entire circumference or it may not be able to rotate at all.In addition, it is extremely difficult to move the corrugated tube manually, so the spiral concave portion has rubber. It is extremely difficult to wind the packing or to fit the end of the corrugated tube to the joint, and in many cases, it is impossible to perform such work.

On the other hand, in a fluid pipe composed of a metal pipe, a connection method of connecting flanges of a metal pipe integrally provided with a flange is generally applied. Therefore, even in the case of a synthetic resin corrugated pipe, if a flange is integrally formed at the end and the flanges are used to connect the corrugations or the corrugated pipe and a joint, workability can be improved even with a large-diameter corrugated pipe. It is considered that the connection can be made in a state where high watertightness can be maintained.

[Problems to be Solved by the Invention] However, a corrugated tube is a long tubular material, and a molded product in which a flange is integrally formed at an end of the corrugated tube has a shape in which the flange protrudes outward from the corrugated tube. Therefore, not only is it difficult to continuously extrude with a synthetic resin, but also it is difficult to perform injection molding. Under such circumstances, it may be beneficial to set the end of the corrugated tube in the mold and insert-mold the flange.

The corrugated tube used for such insert molding is generally obtained by cutting a predetermined portion of a continuous extruded long corrugated tube in a direction perpendicular to the axis,
In the corrugated tube of a predetermined length obtained in this way, the spiral hollow ridge is partially opened in a circular arc shape in a front view at the cut end face of the corrugated tube, and the hollow ridge is formed at a place where such an opening is not formed. The valley tube wall between them protrudes. Also, the cut end surfaces of the corrugated tubes are often more or less jagged, though to varying degrees.

Therefore, when it is intended to insert-mold a flange at the end of a corrugated tube having a helical hollow ridge, the end of the corrugated tube is sandwiched between an upper mold and a lower mold to form a periphery of the end. Along with forming the flange molding space, the opening of the hollow ridge opened at the end face of the corrugated tube is closed using a part of the molding die, and the molten resin injected into the molding space is hollow ridge from the opening. It is necessary to prevent intrusion into the internal space.

However, since the end face of the corrugated tube is often jagged as described above, it is difficult to reliably close the opening of the hollow ridge in a part of the mold without any gap. On the other hand, when the molten resin in the sol state is injected into the flange molding space at a predetermined pressure and ordinary insert molding is performed, the tube wall of the corrugated tube, especially the spiral hollow ridge, softens due to contact with the high-temperature and high-pressure molten resin. Then, it is melt-crushed and deformed irregularly.
For example, if the corrugated tube is a high-density polyethylene resin, its softening temperature is about 120 ° C, while the temperature of the molten resin during molding (for example, high-density polyethylene resin) is higher than that, Such a phenomenon occurs because a predetermined injection pressure is applied to the resin. Therefore, not only when the opening of the hollow ridge is not completely closed, but also when the gap is surely closed at the beginning, the molten resin is injected and the melt crush of the hollow ridge is subsequently performed. Irregular deformation occurs, and the closed state of the opening by the mold is impaired, and the molten resin tends to enter the internal space of the hollow ridge from the resulting gap. When such a situation occurs, it is difficult to accurately determine the amount of the injected resin in advance, and the yield of the material resin is reduced, and a situation in which an appropriate molded product that is previously planned cannot be obtained is caused.

Because of the above situation, it was conventionally considered that it was difficult or impossible to insert-mold a flange at the end of a corrugated pipe having a spiral hollow ridge on the pipe wall. As a result, the corrugated tube in which a flange is integrally formed at an end portion by insert molding does not actually exist.

Under the circumstances described above, the present inventors have conducted intensive research and studies,
A new technology has been developed that can reliably prevent the flange forming material from entering the opening of the hollow ridge at the end of the corrugated tube having a spiral hollow ridge on the tube wall. The invention has been completed. That is, an object of the present invention is to provide a method capable of appropriately forming a flange by insert molding at an end of a corrugated tube having a spiral hollow ridge on a tube wall.

[Means for Solving the Problems] The method for forming a flange of a synthetic resin corrugated pipe according to the present invention comprises inserting a mold core into an end of a synthetic resin corrugated pipe having a spiral hollow ridge on the pipe wall. Along with supporting the inner surface of the corrugated pipe, an annular packing is disposed on the end face of the corrugated pipe,
The annular packing is pressed against the end face of the corrugated tube by the annular stepped portion provided on the mold core to close the arc-shaped opening of the hollow ridge that opens at the end face of the corrugated tube, and further, the upper end of the corrugated tube is closed. A flange forming space including at least one pitch of the hollow ridge is formed around the end of the corrugated tube sandwiched between the lower mold and the lower mold.
In that state, inject the liquid resin into the flange molding space,
The flange is integrated with the end of the corrugated pipe while restricting that the hollow ridge is melted and crushed by contact with the liquid resin.
M or cast molding.

[Operation] According to this method, the packing disposed on the end face of the corrugated pipe is pressed against the end face by the annular stepped portion of the mold core, so that even if the end face of the corrugated pipe is jagged, The opening of the hollow ridge is reliably closed, and the certainty of the closed state is improved as compared with the case where the opening of the hollow ridge is closed with a part of the mold as in the related art.

By the way, as is well known, RIM molding is a kind of injection molding method. In this RIM molding, a liquid synthetic resin monomer containing a predetermined amount of a polymerization initiator and a liquid synthetic resin monomer containing a predetermined amount of an activator are simultaneously placed in a molding space of a molding die held at a predetermined molding die temperature. This is a method in which a molded product is obtained by injecting and polymerizing both synthetic resin monomers (hereinafter, referred to as a liquid resin) in a molding space in a very short time. According to this method, the synthetic resin, which is a molding material, is injected into the molding space in a liquid state. Therefore, compared to a case where a molten resin is injected by ordinary injection molding, even if the injection pressure is small, sufficient material can be injected into the entire molding space. In addition to the wraparound, the temperature of the molding die can be lowered, and the time required for molding is reduced. Therefore, according to the RIM molding, it is possible to appropriately select the type of the liquid resin as the molding material and to suppress the injection pressure and the molding die temperature to some extent.

As described above, according to the method of the present invention, in addition to the fact that the opening of the hollow ridge is securely closed by the packing, the injection pressure of the liquid resin and the temperature of the molding die are increased by employing RIM molding. Is reduced, and the time required for molding is shortened, so that they act synergistically to deform the tube wall at the end of the corrugated tube, especially the hollow ridge, due to the melting and crushing, and to form the liquid into the hollow ridge. Intrusion of the resin is minimized as much as possible or does not occur at all. In other words, in the method of the present invention, since the RIM molding is adopted, a liquid resin having a difficult sealing property is used as a molding material as compared with a molten resin having only fluidity similar to starch syrup used for normal injection molding. However, in addition to the fact that the opening of the hollow ridge is closed by the packing pressed against the end face of the corrugated pipe, the liquid resin injection pressure is low, and at the same time, the deformation due to the melt crush of the hollow ridge is unlikely to occur. This makes it difficult for the liquid resin to penetrate into the inside of the hollow ridge during molding, and such a novel technique makes it possible to insert-mold the flange at the end of the corrugated tube.

Cast molding is a method in which a liquid resin as a molding material is poured into a molding space without applying pressure. Therefore, even in the case of casting, the opening of the hollow ridge is reliably closed by the packing, and the injection pressure of the liquid resin and the temperature of the molding die are kept low. The deformation due to the melt crushing of the hollow ridge and the intrusion of the liquid resin into the hollow ridge are minimized as much as possible, or they do not occur at all.

According to the method of the present invention, at least one of the hollow ridges is provided.
Since the flange is formed in the portion including the pitch, the end of the corrugated pipe and the flange are joined together, considering the linear width of the overlapping portion of the resin layer forming the flange and the resin layer forming the corrugated pipe. By ensuring a large area of the portion, the joining strength of the flange to the corrugated tube is increased.

[Embodiment] FIG. 1 is an explanatory view of an embodiment method of the present invention. That is, the figure shows a mold core 1 attached to the end of a synthetic resin corrugated tube 100.
Is inserted to support the inner surface of the corrugated tube 100, and an annular packing 2 made of a heat-resistant material such as silicone rubber is disposed on the end face 101 of the corrugated tube 100. The packing 2 is attached to the mold core 1. Corrugated tube end face 101 is provided by annular stepped portion 11 provided.
To close the arc-shaped opening 111 of the hollow ridge 110 which is opened at the end face 101 of the corrugated tube. The state where the molding space S is formed is shown.

The corrugated tube 100 is formed by continuously extruding the inner wall resin layer having a smooth inner surface and the outer wall resin layer forming the helical protrusion into a two-layer shape while continuously extruding the molding resin from the molding machine head. The ridge 110 is spirally formed by a part of the inner wall resin layer and the outer wall resin layer. The corrugated tube 100
May be made by other molding methods. Also,
The corrugated tube 100 is, for example, a long product continuously extruded from a high-density polyethylene resin and cut at a predetermined position in a direction perpendicular to the axis, and the end surface 101 is a cut surface. Therefore, the hollow ridge 110 is open in an arc shape in a part of the end face 101, and the valley 120
Are projected in an arc shape. 11
Reference numeral 2 denotes an arc-shaped tube wall protruding in such a manner. Furthermore, the end face 101 is more or less jagged because it is a cut end face.

The mold core 1 has an annular step 12 having a diameter larger than that of the annular step 11. The annular groove formed in the large step 12 is made of a heat-resistant material such as silicon rubber. The formed annular packing 5 is held, and the annular packing 5 faces the flange forming space S.

In addition to the flange forming space S, the upper die 3 has a material reservoir 32 connecting the air vent hole 31 and the flange forming space S, a slit-shaped material passage 33, and a spiral ridge 34 meshing with the valley 120 of the corrugated pipe 100. Etc. are formed. In addition, a packing 6 made of a heat-resistant material such as silicon rubber is interposed in a gap between the upper mold 3 and the corrugated tube 100, and the packing 6 prevents leakage of the liquid resin. The lower mold 4 has a material mixing head 41 and a material injection port of the mixing head 41.
A slit-shaped material passage 44 connecting the material pool 43 and the material reservoir 43 to the flange forming space S, and a spiral ridge 45 meshing with the valley 120 of the corrugated tube 100 are formed. Lower mold 4 and corrugated tube 10
In the gap with 0, the packing 6
The packing 6 prevents leakage of the liquid resin. The upper mold 3 and the lower mold 4
A packing for preventing leakage of the liquid resin is interposed, if necessary, in the gap between the mating surfaces. This packing is also made of a heat-resistant material such as silicon rubber.

When a liquid resin as a molding material is injected from the material of FIG. 1 into the flange molding space S from the mixing head 41, the flange is integrally formed with the end of the corrugated tube 100 by RIM, and at the same time, of the flange formed by molding. The annular packing 2 around
Is held. Further, the annular packing 5 is held on the surface of the flange. The RIM molding is performed while restricting the hollow ridge 110 from being melt-crushed by contact with the liquid resin. That is, the molding conditions (such as the temperature of the molding die, the injection pressure into the flange molding space S, the time required for molding, etc.) so that the hollow ridge 110 does not melt-crush or suppress the melt-crushing to such an extent that molding is not hindered Perform RIM molding under).

The liquid resin injected into the flange forming space S from the mixing head 41 is a mixture of a liquid resin containing a polymerization initiator and a liquid resin containing an activator. Is completed to form the flange. As the liquid resin, for example, resin monomers such as urethane and dicyclopentadiene are selected. In the case of dicyclopentadiene, the temperature of the molding die is suitably about 80 ° C., and the injection pressure is about 5 kg / cm ^{2. In} such a case, the time until the completion of polymerization is between several seconds and several minutes. If the molding die temperature, the injection pressure and the polymerization time (time required for molding) are in such a range, the hollow ridge 110 of the corrugated tube 100 in contact with the liquid resin injected into the flange molding space S may be melted and crushed. Hollow ridges 11 that are effectively restricted and associated with their melt crush
0 does not cause irregular deformation, or even if it occurs, the opening 1
The closed state of 11 is not impaired, and the liquid resin in the flange forming space S does not enter the hollow ridge 110.

When the corrugated tube 100 is a high-density polyethylene resin and a polyethylene resin is used as the liquid resin, the allowable mold temperature is about 40 to 100 ° C., and the injection pressure is 0.3 to 10 kg / c.
m ² , the polymerization time is about 5 to 3600 seconds, which depends on the amount of liquid resin injected. In other words, the temperature of the molding die, the injection pressure, the polymerization time and the like can be adjusted. In addition,
If the amount is outside the above range, proper molding is not performed due to deterioration of the resin surroundings, or the material yield is reduced due to melting or crushing of the hollow ridge 110, or the hollow ridge 110 due to intrusion of the resin.
May be blocked and the material yield may be reduced.

FIG. 2 shows a use state of the corrugated tube 100 having the flange 7 formed at the end portion by the above method, and a broken line a in FIG. 2 shows a contour of the hollow ridge 110 before the flange 7 is formed. Represents. The flange 7 is in close contact with a cylindrical resin layer 71 provided at the root portion of the flange 7 in a state where the cylindrical resin layer 71 and the resin layer forming the corrugated tube 100 overlap and strongly contact each other. The resin layer
The outer shape of 71 may be enlarged to make the whole of the flange 7 and the resin layer 71 of the same figure a thick flange. However, such a method requires a large amount of material resin and deteriorates appearance. Since there is no inconvenience and there is no need to make the flange thicker in terms of strength, it is desirable to keep the flange as shown in the figure.

The flange 7 is RIM-formed in the above-described flange forming space S and is integrally formed at the end of the corrugated tube 100.
The flange forming space S is at least one of the hollow ridges 110.
Since it is formed in a portion including the pitch, the joined portion of the flange 7 and the corrugated tube 100 by fusion is also in a range including at least one pitch of the hollow ridge 110. Therefore, a large joint area is ensured for the straight width L of the overlapping portion of the flange 7 and the corrugated tube 100, and a large joint strength is obtained. If the joining portion is shorter than one pitch of the hollow ridge 110, there is a concern that the joining strength may be insufficient.

Reference numeral 200 denotes a synthetic resin joint. The joint 200 has a flange 210 at an end portion and an annular convex portion 220 on an inner peripheral portion of the flange 210. The joint 200 is
0 is inserted into the inside of the flange 7 of the corrugated tube 100, the end surface of which contacts the packing 2 held by the flange 7, and presses the packing 2 against the end surface 101 of the corrugated tube 100. Further, the packing 5 held by the flange 7 is pressed by the flange 7 and the flange 210 on the joint 200 side opposed thereto. The two flanges 7,210 are connected to each other by bolts and nuts or clamp-type fastening means.

In the connection state described above, the packing 2 and the joint
Since the contact portion of the 200 with the end face of the convex portion 220 is water-tightly sealed, water leakage from the contact portion is prevented. Further, the contact point between the packing 2 and the end face 101 of the corrugated pipe 100 is also sealed watertight. Further, the packing 5 provides a watertight seal between the flange 7 and the flange 210. Here, packing 2
If the watertightness is reliably maintained, it is considered that it is not always necessary to maintain the watertightness by the packing 5 on the outer side, but the structure in which the watertightness is doubled by both of the packings 2 and 5 is considered. Therefore, there is an advantage that the reliability is dramatically increased.

FIG. 3 shows a modification of the annular packing 5 held on the flange 7. The packing 5 has a projection 51, and the projection 51 is embedded in the resin layer of the flange 7 to exert an anchoring action. As described above, such a packing 5 is previously disposed in the flange forming space S, and is held by the flange 7 by RIM forming the flange 7.

In the above embodiment, the case where RIM molding is performed has been described. However, cast molding may be performed instead of RIM molding, and the method is also included in the present invention.

[Effects of the Invention] As described above, according to the method of the present invention, there is an excellent effect that insert molding of a corrugated tube and a flange, which has been considered extremely difficult or impossible in the past, becomes possible. .

[Brief description of the drawings]

FIG. 1 is an explanatory view of a method according to an embodiment of the present invention, FIG. 2 is a partially cutaway side view showing a use state of a corrugated tube having a flange formed at the end portion by the above method, and FIG. FIG. 10 is a partial cross-sectional view showing a modified example of the annular packing portion of the corrugated tube having a flange formed at the end at the end. 1 ... mold core, 2 ... annular packing, 3 ... upper mold, 4
…… Lower mold, 11… Circular stepped part, 100 …… Corrugated tube, 101 ……
End face of corrugated tube, 110: hollow ridge, 111: opening of hollow ridge, S: flange forming space.

────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification symbol FI B29C 57/00 B29C 57/00 // B29L 23:00 (56) References JP-A-62-256628 (JP, A) JP-A-62-256628 JP-A-62-116119 (JP, A) JP-A-61-293821 (JP, A) JP-A-57-128527 (JP, A) JP-A-58-148159 (JP, A) (58) Fields investigated (Int .Cl. ⁶ , DB name) B29C 45/00-45/84 B29C 39/00-39/44 B29C 57/00

Claims (1)

(57) [Claims] 1. A corrugated tube made of synthetic resin having a helical hollow ridge on a tube wall, a mold core is inserted into an end of the corrugated tube to support an inner surface of the corrugated tube, and an annular packing is provided on an end surface of the corrugated tube. Is disposed, the annular packing is pressed against the end face of the corrugated tube by the annular stepped portion provided on the mold core to close the arc-shaped opening of the hollow ridge opened at the end face of the corrugated tube, A flange molding space including at least one pitch of the hollow ridge is formed around the end face of the corrugated tube by sandwiching the end between the upper mold and the lower mold, and in this state, a liquid resin is injected into the flange molding space. Flange formation of a synthetic resin corrugated pipe characterized in that the flange is formed integrally with the end of the corrugated pipe by RIM molding or casting while restricting the hollow ridge from being melted and crushed by contact with the liquid resin. Method.