JPH09300435A - Extrusion molding of locally thick-walled synthetic resin pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently smooth the inner surface of a non-thick-walled usual pipe part in case of the molding of a synthetic resin pipe having a locally thick-walled part by making the distance between a mold and a forming tube at a time of the molding of a non-thick-wall part longer than the distance therebetween at a time of the molding of a thick-wall part. SOLUTION: A water tank 3 is moved forwardly by driving a motor 33 slightly before a thickness increase is started and an attachment 35 is stopped at the position coming into contact with an advance moving position limit switch (a) to set the distance between a mold 2 and a forming tube 4 to the distance necessary for the molding of a thick-wall part. Next, the taking-over speed of a taking-over machine 6 is changed over from a high speed mode to a low speed mode to enter a thickness increase molding state to mold a thick-wall part having predetermined length. Next, the taking-over speed of the taking-over machine 6 is changed over to a high speed mode and the water tank 3 is moved rearwardly and the attachment 35 is stopped at the position comming into contact with a retreat moving position limit switch (b) to set an interval proper to the molding of a usual smooth inner surface of a non-thick-walled part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extrusion molding method for a synthetic resin pipe having a thickened portion on the inner surface of the pipe at regular intervals.

[0002]

2. Description of the Related Art As is well known, a synthetic resin pipe material used as a fluid transport pipe or the like is drawn by cooling a tubular resin extruded from a die of an extruder while cooling it while controlling its outer diameter by a forming tube. It is manufactured by taking and then cutting to a fixed length. Synthetic resin tubing is connected by various methods, but in the tubing connected by a receiving / inserting method, one end of the above-mentioned fixed-length tubing is expanded and formed in the receiving port.

In this case, it is unavoidable to reduce the wall thickness by expanding the diameter, and in order to ensure sufficient wall thickness and guarantee the receiving strength even under such diameter expansion, for example, as shown in FIG. 2B. As described above, it is known that the thickened portion on the inner surface is molded at regular intervals, the fixed-length cutting is performed at the thickened portion end e, and the thickened end portion of the fixed-length cutting tube is radially expanded into the receiving port. is there. To mold a synthetic resin pipe with this thickened inner surface, the take-up speed is temporarily reduced from the resin discharge speed of the mold, and at the time of this deceleration, the resin discharged from the tip of the mold expands to the inner surface of the pipe. A method is used in which the pipe is made thicker than the resin discharge slit of the die.

In forming the thickened portion, a mold and a die are formed.
Since the semi-solidified tubular resin between the forming tubes is compressed in the axial direction, if the distance between the die and the forming tube is increased, the tubular resin will easily buckle, preventing such buckling. In order to achieve this, the distance between the mold and the forming tube is made shorter than in the usual case (straight tube) (about 10 mm, compared to the usual 300 mm).

[0005]

However, when the distance between the mold and the forming tube is shortened, the inner surface of the pipe becomes uneven, which leads to deterioration of the outer appearance of the inner surface and increase of fluid resistance. Such unevenness of the inner surface of the pipe shortens the distance from the mold to the forming tube (cooling water tank inlet), and shortens the air-cooling section between the mold and the forming tube. The cooling in the thickness direction becomes non-uniform because it enters the water tank so quickly and is rapidly cooled.The stress caused by this non-uniform cooling in the thickness direction causes heat shrinkage in each part of the wall thickness section due to the non-uniform kneading state. This is because the stress due to non-uniformity is superimposed.

An object of the present invention is to take out tubular resin from a die of an extruder while controlling the outer diameter by a forming tube,
When forming a synthetic resin pipe having a locally thickened portion by intermittently reducing the take-up speed, a locally thickened synthetic resin pipe that can sufficiently smooth the inner surface of the non-thickened normal pipe portion An object is to provide an extrusion molding method.

[0007]

A method of extrusion molding a locally thickened synthetic resin pipe according to the present invention is a tubular resin from a die of an extruder, which is taken while controlling an outer diameter by a forming tube.
In the method of intermittently decelerating the take-up speed to mold a synthetic resin pipe having a locally thickened portion, the distance between the mold and the forming tube at the time of non-thickened portion molding is increased. It is characterized in that it is made longer than the distance between the mold and the forming tube at the time of molding.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an extrusion molding facility used in the present invention. In FIG. 1, 1 is a barrel of an extruder, and 2 is a pipe molding die attached to the tip of the barrel. 3 is a cooling water tank, 4 is a forming tube (forming die) attached to the inlet of the cooling water tank 3.
It is.

The cooling water tank 3 is mounted on a rail 31 so that it can be moved forward and backward, and a screw rod guide 32 is attached to it.
A screw rod 34, which is normally and reversely rotated by the motor 33, is screwed into the guide 32 so that it can be moved forward and backward between the forward position limit switch a and the backward position limit switch b. Thus, the attachment 35 moves the forward position limit switch a
The space between the die 2 and the forming tube 4 at the position contacting with is set to a short space required for forming the thickened portion (approximately 10 mm).
), The mold 2 and the forming tube 4 at a position where the attachment 35 comes into contact with the retracted position limit switch b.
The interval between and is set to an appropriate interval (approximately 300 mm) for forming a normal smooth inner surface tube portion without thickening.

The water tank 3 itself has a mechanism for preventing displacement so that the center lines of the mold 2 and the forming tube 4 are always aligned not only before and after the movement of the water tank 3 but also during the movement. It is provided, but not shown.
In FIG. 1, 5 is a measuring roll, 6 is a take-off machine, and 7 is a standard length cutting device. FIG. 1 shows a state in which the attachment 35 is brought into contact with the retreat position limit switch b, and the normal portion of the non-thickened part is being extruded under the high-speed mode.

In order to extrude a locally thickened synthetic resin pipe by the method of the present invention, the motor 3 is added shortly before the thickening is started.
The water tank 3 is moved forward by driving 3 and stopped at a position where the attachment 35 comes into contact with the forward movement position limit switch a, and the distance between the mold 2 and the forming tube 4 is set to a distance required for forming the thickened portion. Set to. After that, the take-up speed of the take-up machine 6 is switched from the high-speed mode to the low-speed mode, the thickening molding state is entered, the thickened portion of a predetermined length is formed, and then the take-up machine 6 is drawn. The take-up speed is switched to a high-speed mode (normal take-up speed), and the water tank 3 is moved backward by the reverse rotation drive of the motor 33, and stopped at a position where the attachment 35 comes into contact with the backward moving position limit switch b. The distance between the mold 2 and the forming tube 4 is set to an appropriate distance (approximately 300) for forming a normal smooth inner surface of the non-thickened portion.
(mm)), and in this state, a normal pipe part without thickening is extruded.

This normal pipe portion has a predetermined length (length between thickened portions)
Shortly before, the water tank 3 is moved forward by the normal rotation drive of the motor 33, and stopped at a position where the attachment 35 comes into contact with the forward movement position limit switch a, and between the mold 2 and the forming tube 4. The distance is set to the distance required for forming the thickened portion, the take-up speed 6 is switched to the low speed mode, and the next thickened portion is molded, and thereafter, the above is repeated.

In the above, the water tank 3 is moved forward by the normal rotation drive of the motor 33, the high speed mode of the take-up machine 6 is switched to the low speed mode, and the water tank 3 is driven by the reverse rotation drive of the motor 33. The backward movement and switching of the take-up machine 6 from the low speed mode to the high speed mode are performed by the count signal generated from the measuring roll 5, and the start timing of the pipe length is about 200 mm with respect to the start of the. It is considered to be on the front side, and the start timing of is after the thickness increase is started immediately after the thickness increase length is formed.

In the present invention, any appropriate foaming tube may be used as long as it is located at a position separated from the mold and the tubular resin from the mold can be sized to the final product size. Forming method (vacuum evacuation hole for sucking the outer surface of the tubular resin to the inner surface of the forming tube is provided in the forming tube, and the evacuation tube is connected to the outer surface of the tube). When moving the water tank, loosen the degree of vacuum and form the outer surface of the tubular resin
It is preferable to reduce the friction between the inner surfaces of the bushes.

In the locally thickened synthetic resin pipe extruded according to the present invention, as shown in FIG. 2A, the central position of the thickened portion n and the central position of the non-thickened normal portion m are set. By cutting, the thickened end portion of the cut pipe is expanded and shaped to form a receiving port, or as shown in (b) of FIG. 2, the thickened end e is cut and the thickened portion of the cut pipe is thickened. By expanding the end portion and forming it into a receiving port, a pipe material having a receiving port at one end is formed.

2A, the length of the thickened portion of the synthetic resin pipe and the length of the non-thickened normal portion are the same as those of FIG. 2B. The length of the thickened portion of the synthetic resin pipe and the length of the non-thickened normal portion are almost doubled.

[0017]

In the extrusion molding method of the locally thickened synthetic resin pipe according to the present invention, the distance between the mold and the forming tube is sufficiently long during the extrusion molding of the non-thickened normal portion. Therefore, it is possible to prevent the rapid cooling of the tubular resin from the mold and to mitigate the uneven cooling in the thickness direction, and the stress caused by the uneven cooling in the thickness direction causes the wall thickness due to the uneven kneading state. It is possible to prevent well the unevenness of the inner surface of the pipe caused by the overlapping stress due to the non-uniform heat shrinkage in each section.

On the other hand, during extrusion molding of the thickened portion, since the distance between the mold and the forming tube is sufficiently short, the tubular resin between the mold and the forming tube is buckled. It is possible to easily form the thickened portion by bulging the inner surface of the pipe while preventing it. Although unevenness occurs on the inner surface of the thickened portion, the unevenness does not appear in the appearance of the product because it is formed in the receiving opening by expanding the diameter from the inner surface side of the receiving die.

Therefore, according to the present invention, it is possible to obtain a synthetic resin pipe material having one end having a smooth inner surface of a non-thickened ordinary pipe portion.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an apparatus used in a method for extrusion molding a locally thickened synthetic resin pipe according to the present invention.

FIG. 2 is an explanatory view showing a method of manufacturing a synthetic resin pipe material having a receiving end at one end from a locally thickened synthetic resin pipe.

[Explanation of symbols]

 2 Extruder mold 3 Cooling water tank 4 Forming tube 6 Take-off machine

Claims (1)

[Claims] Claim: What is claimed is: 1. A tubular resin from a die of an extruder is taken while controlling the outer diameter by a forming tube, and the take-up speed is intermittently reduced to have a synthetic resin pipe having a locally thickened portion. In the method of molding, it is necessary to make the distance between the mold and the forming tube at the time of forming the non-thickened portion longer than the distance between the mold and the forming tube at the time of forming the thickened portion. A method for extrusion-molding a locally thickened synthetic resin pipe.