JPH02112931A - Manufacture of synthetic resin pipe - Google Patents

Abstract

PURPOSE:To make a cut-out part to be closed accurately and excellently by forming protruded parts in rendering a synthetic resin belt material to be along with the surface shape of an endless molded belt, and putting integrally together the parts between the valley parts of the protruded parts, and further, leading the endless molding belt within the protruded parts outside in cutting through the small protrusions of the protruded part, and supplying synthetic resin material between the small protruded parts thereafter. CONSTITUTION:A protruded part (b) being the same as the cross-sectional shape of an endless molding belt 3 is molded by the use of a synthetic resin belt material 9, and small protrusions 10, 10 are molded on the top surface both side parts of the protruded part (b) and flat parts 11, 12 are molded integrally on both sides downward. And, a secondary winding protruded part (b) is mounted on one elongated flat belt part 11 of firstly winding protruded part (b), and the other elongated flat parts 12 of the protruded parts (b) are welded overlappedly so as to be formed with a valley part (c), and then the protruded part (b) is wound spirally therearound in turn together with the endless molding belt 3, thus, formed a synthetic resin pipe (a) having a continuous spiral protrusion. The center of the top part of the protruded part (b) is cut, and the endless molding belt 3 is extracted from the protruded part (b), after that, the synthetic resin pipe (a) provides a semi-melted synthetic resin belt material between both sides small protrusions 10, 10 and covers and closes a cut-out part 14.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for producing a pressure-resistant synthetic resin pipe suitable for use as a large-diameter electric wire protection pipe or other underground pipes that require pressure-resistant strength. be.

[Conventional Techniques] Traditionally, underground pipes are required to have high pressure resistance, so pipes such as humid pipes and cast iron pipes have been used.
The weight is large relative to the diameter, making it difficult to handle, and there are difficulties in workability.

For this reason, a synthetic resin pipe has been developed in which a spiral protrusion is integrally formed on the outer circumferential surface over the entire length using a synthetic resin material, and the pipe wall made of the helical protrusion provides pressure resistance.

As a method for manufacturing such a synthetic resin pipe, for example, several molding rotation shafts are arranged on a virtual cylinder, and one end of the molding rotation shaft is cantilevered on a base. At the same time, each rotating shaft is connected to a driving means, and the forming rotating shaft is slightly inclined in the circumferential direction with respect to the axis of the virtual cylinder, and during tube forming, a spiral reinforcing strip is formed after forming. A semi-molten band-shaped material having a hollow protruding portion and a plate-like portion forming the inner circumferential wall of the pipe is extruded from a molding gou, and the band-shaped material is spirally wound so as to span between the respective forming shafts. This wrapping is sometimes done by sequentially polymerizing and welding one side edge of the molded material and the adjacent other side edge, and while rotating the molding shaft, a synthetic resin tube with hollow protrusions spirally provided on the outer circumferential surface is formed. A continuous molding method is used.

On the other hand, a method of manufacturing a synthetic resin pipe while forming spiral reinforcing strips using a flexible belt-shaped molding core mold is also disclosed in JP-A-51-37969.

In this method, a thermoplastic synthetic resin sheet extruded from an extruder is layered on the surface of the strip-shaped core mold for molding, and then wound spirally around the molding shaft so that the edges of adjacent core molds touch each other. After cooling the resin sheet, the core mold is peeled off from the inner circumferential surface of the synthetic resin tube to produce a tube with continuous hollow protrusions in a spiral shape.

[Problem to be solved by the invention]

However, according to the former method, a semi-molten band-shaped material having a hollow protruding portion that becomes a spiral reinforcing strip after molding and a plate-like portion that becomes the inner circumferential wall of the pipe is extruded in advance using a molding die, and then the material is formed. Because it is wound spirally at high speed around the rotary shaft, the hollow protrusions may become uneven during winding, and the tube wall due to the spiral hollow protrusions becomes uneven, resulting in high precision and orderly winding. It was extremely difficult to obtain a tube body with such a shape.

On the other hand, according to the latter method, it is possible to form a hollow protrusion of a predetermined shape using a molding belt-like core mold, but the molding belt-like core mold can be used as an inner part over the entire length of the spiral hollow protrusion to be molded. This not only requires a long belt-shaped core mold, but also because this belt-shaped core mold is cut in one piece when cutting the continuously produced synthetic resin pipe into desired lengths. This makes it impossible to reuse the tube, which is uneconomical.Furthermore, it is necessary to remove the band-shaped core from the inner surface of the tube, resulting in a decrease in production efficiency. Furthermore, since a spirally uneven inner surface is formed at the site where the strip core mold is removed, wiring work may be difficult due to the uneven inner surface during use, and when fluid is allowed to flow inside, There is a problem that flow resistance increases.

For this reason, the inventors of the present application have constructed an endless molding belt which is spirally wound around a molding rotating shaft and rotated around it, and a synthetic resin strip material in a semi-molten state is continuously supplied onto this endless molding belt. By aligning the synthetic resin strip material to the surface shape of the endless forming belt, a protrusion is formed, and while the valleys of adjacent protrusions are polymerized and integrated, a synthetic resin pipe is formed as the endless forming belt advances. Then, during the process of molding this synthetic resin pipe, the protrusions are incised in the length direction at appropriate locations with a suitable cutter, and the endless molded heald inside the protrusions is led out through the incisions to restore the original winding. Then, by continuously supplying a semi-molten synthetic resin strip material to the top surface of the hollow protrusion formed by removing the endless forming belt and wrapping it spirally, the cut section is closed. We have developed a method for manufacturing synthetic resin pipes that is characterized by covering the tubes with synthetic resin. In this method, when the incision is sealed with a synthetic resin strip in the final step, the synthetic resin strip covers the top of the protrusion. There is a problem in that the incision may not be sufficiently sealed due to the incision being deviated laterally from the surface, resulting in a decrease in product value.

An object of the present invention is to solve these problems and provide a method for manufacturing a synthetic resin pipe having a highly accurate spiral hollow protrusion with a flat inner circumferential surface.

(Means for Solving the Problems) In order to achieve the above object, the method for manufacturing a synthetic resin pipe of the present invention includes an endless forming belt that is spirally wound around a rotating shaft for forming and moves around. The winding that is introduced onto the rotating shaft is performed by placing a half-molten synthetic resin strip at the starting part, and small protrusions protruding parallel to both sides of the strip are positioned on both sides of the top surface of the endless molded belt. By continuously supplying the synthetic resin strip material along the surface shape of the endless forming belt, a synthetic resin ridge covering the endless forming belt is formed, and the bottom side of the adjacent ridge is formed. A synthetic resin pipe having a helical protrusion is formed as the endless forming belt advances while polymerizing and integrating flat parts for forming troughs extending horizontally from the trough. Cut the center part of the top surface in the length direction with an appropriate cutter, lead out the endless molded belt inside the protruding part to the outside through the cut part, circulate it to the original winding position, and then remove the endless molded belt. The invention is characterized in that a semi-molten synthetic resin material is continuously supplied between the small protrusions on the top surface of the hollow protrusion to cover the incision.

[For production]

When the forming rotating shaft is rotated or the endless forming belt is actively circulated by a suitable drive mechanism, the endless forming belt spirally moves from one end to the other end on the forming rotating shaft. The end portion of the winding that comes off the molding rotation shaft returns to one end side of the molding rotation shaft and is spirally wound.

In this way, the belt-like synthetic resin material in a semi-molten state is placed on the winding start part of the endless forming belt that circulates spirally on the forming rotation shaft, and small protrusions protruding parallel to both sides of the belt form the endless forming belt. When the belt-shaped synthetic resin material is fed while being positioned on both sides of the top surface, when the belt-shaped synthetic resin material is flat, it deforms to closely fit the outer shape of the endless molding heddle and covers the endless molding belt, forming an endless molding belt. If it has been previously formed to follow the cross-sectional shape of , it is polymerized and coated onto the endless forming belt as it is, and is spirally wound together with the endless forming belt around the forming rotating shaft.

In this way, when the belt-shaped synthetic resin material is spirally wound around the molding rotating shaft together with the endless molding belt, the part that is in close contact with the endless molding belt forms a continuous spiral protrusion, and the protrusion of the protrusion The flat parts extending horizontally from both ends are superimposed and integrated with the horizontally extending flat part wound next along the inner circumferential surface of the endless forming heald, so that the inner circumferential surface is flat on the forming rotation axis, and A synthetic resin pipe having a spiral protrusion on the outer peripheral side is continuously formed.

The synthetic resin tube thus formed is appropriately cooled while traveling on the molding rotating shaft, and when it reaches the cutter position, a part of the spiral protrusion is continuously cut in the length direction by the cutter. The endless molding belt is separated from the molding rotating shaft while pushing the incision apart.

The spiral protrusion, which became hollow when the endless molding belt was pulled out, immediately returns to the direction that closes the spread of the cut part, while the endless molding belt, which has separated from the molding rotation shaft, starts to wrap around the belt-shaped synthetic resin material again. It circulates to the end side and is wound around the molding rotating shaft in the same manner as described above to mold the belt-shaped synthetic resin material, thereby producing a synthetic resin pipe.

Furthermore, while the hollow spiral protrusion is progressing on the molding rotating shaft, semi-molten synthetic resin material is continuously supplied between the small protrusions on the top surface of the hollow spiral protrusion and wound in a spiral shape. This allows the incision to be covered while preventing displacement by the small protrusions.

In this way, a pressure-resistant synthetic resin pipe having uniform hollow protrusions and a flat inner circumferential surface having a constant diameter can be manufactured.

〔Example〕

An embodiment of the present invention will be described with reference to the drawings. A plurality of molding rotating shafts (2) (2)...(2) are arranged concentrically at predetermined intervals. ), one end of which is rotatably supported by the base frame (1), and a plurality of molding rotating shafts (2) arranged concentrically at predetermined intervals.
On top, an endless molded belt (3) with a trapezoidal cross section is wound spirally several times at a desired pitch, and along between the wound endless molded belts (3), a manufacturing process is carried out. An endless shaping belt (4) along the trough (C) of the synthetic resin pipe (a)
) are wound as necessary, and these endless forming belts (3) and shaping belts (4) are separated by the shaping rotating shaft (2) at the end of the winding, as shown in Figure 2. , so as to continuously circulate around the original winding start end via appropriate guide rolls (5) and (6).

These endless molded belts (3) and shaped belts (4) can also be made of rubber, synthetic resin, leather, synthetic rubber with a reinforcing core, or by continuously joining a large number of aluminum block pieces in the length direction. In addition to the above trapezoidal shape, the cross-sectional shape may also be semicircular, square, etc., and the cross-sectional shape may not be the same over the entire length.
It is also possible to use belts with different cross-sectional shapes for each predetermined length.

Now, each molding rotating shaft (2) is rotated in the same direction, and a semi-molten material having a constant width larger than the circumference of the endless molding belt (3) is melted from the molding guide (8) of the extrusion molding means (7). The synthetic resin strip material (9) in the state is attached to the endless molded belt (3).
) onto the starting end of the winding.

At this time, the synthetic resin strip material (9) is
) on both sides of the surface of the endless molded heald (3) while forming a small protrusion 00)0ω with a gap between both corners of the top surface of the endless molded heald (3), and then extrude the small protrusion 0n)00) into an endless molded belt ( 3)
When the synthetic resin strip material (9) is formed into a flat strip shape, the center portion thereof is supplied so as to coincide with both corners of the top surface of the endless molded belt (3). After molding the protrusions (b) so that both sides are in close contact with each other along both sides of the endless molded belt (3), the protrusions (b) are formed in a horizontal direction from the bottom of the endless molded belt (3) toward both sides. The molding material is fed onto the molding rotating shaft (2) while being bent into an extending flat portion (11) θ2).

Also, the endless forming belt (3) is formed by the forming die (8).
A protrusion (b) having the same cross-sectional shape as the protrusion (b) is formed, and small protrusions 00)θ0) are formed on both sides of the top surface of the protrusion (b), and flat portions (Ill(12)) are formed on the lower sides of both sides. The protrusions (b) may be covered by the endless molded belt (3) by extruding them while integrally molding them.

In this way, the protrusions (b) made of the synthetic resin strip material (9) coated on the surface of the endless molded heald (3), together with the endless molded heald (3), form the molding rotating shaft (2) (2)... (
2) Wrapped in a spiral on top.

At this time, the protruding part (b) to be wound next is placed on one of the extended flat parts (11) of the protruding part (b) to be wound first, and the protruding part (b) to be wound next is The other extended flat part 02) is polymerized and welded to form the valley part (C), and the protruding part (b) is sequentially wound helically together with the endless molded belt (3) to form a continuous spiral protruding part. A synthetic resin pipe (a) having the following properties is formed.

The inner circumferential surface of this synthetic resin pipe (a), that is, the surface along the virtual circle formed by the plurality of molding rotating shafts (2) (2)...(2), A flat surface having a uniform diameter is formed by the flat part (II) sealing the bottom surface of b) and the flat part θ2) polymerized and welded to the flat part (11).

The shaping belt (4), which circulates in a spiral manner in synchronization with the endless forming belt (3), has endless forming belts on both sides of the protrusion (b) (b) that covers the endless forming belt (3). belt(
3) to hold it in a predetermined shape while correcting the pitch of the endless molded belt (3), but it is not necessarily necessary.

In this way, the synthetic resin pipe (a) having a spiral protrusion formed on the molding rotating shaft (2) is suitably cooled and hardened while traveling on the molding rotating shaft (2), and the endless molding belt (3) ), when the cutter 02) is placed at a suitable location outside the cutter 02).
As shown in FIG. 3, the center of the top of the protrusion (b) is continuously cut into a slit by the cutter 03), and the endless forming belt (3) is opened while expanding the incision side. ) is pulled out and separated from the molding rotating shaft (2),
The synthetic resin strip material (
9) is wound spirally to continuously form a synthetic resin pipe (a).

Note that when the endless molded heald (3) is removed from the protrusion (b), the protrusion (b) has been cooled to the extent that no deformation occurs, and the incision side is After the endless molded belt (3) is pulled out by pushing it apart, the cut side elastically returns to its original state.

In this way, after the endless molded belt (3) is extracted from the protrusion (b), the synthetic resin pipe (a) further advances along the molding rotation shaft (2), and on the way, the synthetic resin belt A narrow half-molten synthetic resin strip or string material θω, different from the material (9), is attached to small protrusions on both sides of the protrusion portion (b) (00θ0)
After being continuously supplied between the molding parts and spirally wound to cover and close the cutout part 04), the molding material is removed from the molding rotation shaft (2) and becomes a product.

At this time, if the synthetic resin material 05) in a semi-molten state is in the form of a flat band, it will not be prevented from shifting to both sides by the small protrusions 00)00) on both sides of the protrusion (b); In the case of a string-like material, it is welded to the top surface of b) and stretched into a flat strip using an appropriate roller.

In addition, each molding rotation shaft (2) is wound on the molding rotation shaft (2) by rotating the molding rotation shaft (2) all at once in the same direction via a suitable drive mechanism from the motor a5') on the base frame (1) side. The endless forming belt (4) is moved integrally, but instead of using such a rotational drive mechanism, the endless forming belt (4) is operated by a rotational drive pulley at a location separated from the forming rotating shaft (2). The molding rotating shaft (2) may be rotated together by forcibly moving the molding shaft (2) through the molding shaft.

In addition, in the above embodiment, in order to manufacture synthetic resin pipes with different diameters, in FIG. The virtual circle formed by the molding rotation shaft may be changed in size by expanding or contracting the connected links 07).

(Effects of the Invention) As described above, according to the method for manufacturing a synthetic resin pipe of the present invention,
An endless molding belt is spirally wound around a rotating shaft for molding and rotated, and a semi-molten synthetic resin strip is continuously supplied onto the endless molding belt to form an endless molding belt. The synthetic resin pipe is molded by following the progress of the endless forming belt while molding the protrusions along the surface shape of the endless forming belt while polymerizing and integrating the valleys of adjacent protrusions. By using the molding heald, it is possible to manufacture a synthetic resin pipe with high accuracy while molding a spiral protrusion in an orderly and predetermined shape without creating a ζ-shaped mold surface. The endless molded belt inside the protrusion is led out from the cut in the longitudinal direction with a suitable cutter and circulated to the original winding position, so the endless molded belt of a certain length Synthetic resin pipes can be manufactured efficiently by repeating helding and continuously moving around on the molding rotating shaft.Furthermore, since the protrusions are formed hollow by removing the endless molding belt, The synthetic resin pipe can be made lighter, making it easier to transport and handle, and the hollow spiral protrusion increases the pressure resistance of the pipe wall.

Furthermore, in the present invention, a semi-molten synthetic resin strip is provided at the starting portion of the winding where the circulating endless forming belt is introduced onto the rotating shaft for forming, protruding parallel to both sides of the strip. Since the small protrusions are continuously supplied while being positioned on both sides of the top surface of the endless forming belt, it is possible to accurately position the synthetic resin strip material with respect to the endless forming belt, and also to ensure that the small protrusions are positioned on both sides of the top surface of the endless forming belt. After removing the endless molded belt from the cutout in the center of the spiral protrusion of the synthetic resin pipe, a semi-molten synthetic resin material is continuously applied between the small protrusions on the top surface of the protrusion. When feeding, these small protrusions can reliably prevent the synthetic resin material from shifting, and the incision can be accurately and beautifully covered and closed.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is a simplified vertical sectional side view of the apparatus during the production of synthetic resin pipes, FIG. FIG. 4 is an enlarged cross-sectional view of a part of the tube wall. (2)...Rotating shaft for molding, (3)...Endless molding belt, (9)05)...Synthetic resin strip material, (10) (
10)...Small protrusion, (I+)02)...Flat part, 0
3)...cutter, circle...incision, (a))...
Synthetic resin pipe, (b)... projecting portion.

Claims (1)

[Claims] 1. An endless molding belt that is spirally wound around a molding rotating shaft and traveling around is introduced into the molding rotating shaft and a half-molten synthetic resin strip is placed on both sides of the belt. Continuously supply the endless forming belt so that the small protrusions protruding parallel to the parts are located on both sides of the top surface of the endless forming belt, respectively.
By aligning the synthetic resin strip material along the surface shape of the endless molded belt, a synthetic resin protrusion covering the endless molded belt is formed, and a trough extending horizontally from the bottom side of the adjacent protrusion is formed. A synthetic resin pipe having a spiral protrusion is molded as the endless forming belt advances while the flat part is polymerized and integrated. During the molding of this synthetic resin pipe, the center part of the top surface of the protrusion is cut with an appropriate cutter. The endless molded belt inside the protrusion is led out from the cut in the length direction and circulated to the original winding position, and the protrusion formed hollow by removing the endless molded belt is removed. A method for manufacturing a synthetic resin pipe, characterized in that a semi-molten synthetic resin material is continuously supplied between the small protrusions on the top surface to cover the incision.