JPH01180329A - Manufacture of pipe having irregular-shaped cross section - Google Patents

Abstract

PURPOSE:To easily manufacture a pipe having an irregular-shaped cross section and the same cross section as that of a male mold at the inner surface thereof, by inserting said male mold into said pipe made of thermoplastics, and heating said pipe up to not less than the softening temperature thereby to render the interior of said pipe at the negative pressure. CONSTITUTION:The entirety of a pipe P into which a male mold D having a desired cross section is inserted is heated up to not less than the softening temperature, so that the interior of the pipe P is rendered at the negative pressure. Consequently, the inner surface of the pipe P is deformed to be tightly adhered to an outer periphery of the male mold D. Therefore, the cross section of a pipe P1 after deformation is correctly a copy of the cross section of the male mold D. When the thus-deformed pipe P1 is cooled as it is and solidified, and the male mold D is pulled out, a pipe P2 having the desired irregular-shaped cross section can be obtained. The material for the pipe P is stable thermoplastics such as polyethylene, polypropylene etc., and it is particularly preferable to have a low melting point.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a method for manufacturing irregular cross-section pipes made of thermoplastics.

Conventional technology □ Pipe materials with irregular cross sections may be required.

For example, when manufacturing foods such as kamaboko and jelly sweets, a gel-like raw material is filled into a pipe with an irregular cross-section and sufficiently solidified, and then the product is extruded from the pipe and placed in a predetermined position. By cutting to the dimensions of , it is possible to easily mass-produce final products with any interesting irregular cross-sectional shape.

The most common method for manufacturing such irregular cross-section pipes is to extrude a molten pipe material through an extrusion die of a predetermined shape, and then cool and solidify it. According to this method, For example, it is possible to continuously mass-produce long pipes with irregular cross-sections made of thermoplastic plastic.

Furthermore, when the pipe material is a metal material, cold-dipping processing using a drawing die is often employed.

The problem to be solved by the invention is that when using such conventional techniques, not only expensive extrusion dies and drawing dies are required, but also large-scale equipment is required for the processes before and after the dies. Although it is suitable for mass production, it is unsuitable for small lot production.

SUMMARY OF THE INVENTION In view of the problems of the prior art, an object of the present invention is to manufacture a novel irregular cross-section vibrator that is particularly suitable for producing small lots of irregular cross-section pipes made of thermoplastic material with relatively short dimensions. The purpose is to provide a method.

Means for Solving the Problems The present invention has a configuration in which a male die is inserted into a pipe made of thermoplastic plastic, the pipe is heated to a temperature higher than its softening temperature, and the inside of the pipe is heated under negative pressure. The gist of this is to increase pressure.

In other words, prepare a pipe P into which a male die of an arbitrary cross-sectional shape is inserted (Fig. 1 (A)), heat the entire pipe to a temperature higher than the softening temperature of the pipe P, and create a negative pressure inside. Since the pipe P is deformed so that its inner surface is in close contact with the outer periphery of the male mold ((B) in the same figure), the cross-sectional shape of the pipe P1 after deformation accurately copies the cross-sectional shape of the male mold. can be taken as a thing.

Therefore, if the pipe P1 deformed in this way is cooled and solidified as it is, and the male shape inside is removed, a pipe P2 with a predetermined irregular cross section can be obtained (see Figure (C)
)).

The material for the pipe P that can be molded by this method is preferably a stable thermoplastic such as polyethylene or polypropylene, particularly one with a low melting point. Furthermore, when the obtained irregular cross-section vibrator P2 is used as a mold for food, it must be made of a material that does not contain harmful substances in terms of food hygiene.

The male mold is a metal bar whose maximum diameter is close to the inner diameter of the pipe P before molding (Fig. 2), and its main body D
1 is a pull-out handle D that is machined to have a predetermined cross-sectional shape that is uniform in the longitudinal direction, and has a screw carved into one end.
2 is installed protrudingly. Further, the total length of the male mold is made shorter than the pipe P so that the entire male mold can be housed inside the pipe P. Prior to inserting the male mold into the pipe P, it is preferable to apply a suitable mold release agent such as silicone oil to the surface of the male mold. Note that the male die can have any predetermined cross-sectional shape as long as the cross-sectional shape of the main body D1 is uniform in the longitudinal direction.

The pipe P into which the male mold has been inserted is sealed at one end and then immersed entirely in the oil OL of the oil bath device B (the third
figure). However, the oil bath device B is a band heater BH.
, BH, . . . A thermometer 82 is attached to the oil tank B1, and a drain B3 is formed.

Further, an airtight adapter pa is attached to the other end of the pipe P, and the pipe P is connected to a vacuum generator V via this adapter Pa. The vacuum generator V may be constructed by combining a vacuum tank v1 and a simple rotary pump 2, and a vacuum gauge V)1 is attached to the vacuum tank v1.

The oil 01 for the oil bath is one whose boiling point is higher than the softening temperature of the pipe P. For example, when the pipe P is a polyethylene vibrator, white squeezed oil can be used.

Further, during heating of the oil OL, it is preferable to uniformize the temperature distribution by appropriately stirring the oil OL.

Maintaining the temperature of oil 01 higher than the softening temperature of pipe P,
When the vacuum generator V is activated, the pipe P is deformed so as to fit tightly into the female shape and becomes the pipe P1. Thereafter, the pipe P1 is taken out from the oil tank B1, cooled, and solidified. Thereafter, a suitable extraction tool is attached to the handle D2 of the male mold, and the male mold is removed from the pipe P1, thereby producing the irregular cross-section pipe P2 as the final product.

In the above explanation, heating using an oil bath is just an example, and it goes without saying that heating in an air atmosphere within the membrane may be used as long as a uniform heating state and an appropriate heating temperature can be obtained. It is. Furthermore, if the vacuum generator (2) is branched and connected to a plurality of pipes P, it is possible to deform and process a large number of pipes at once.

Further, the cross-sectional shape of the main body D1 can be roughly arbitrary as long as the male mold can be handled from the pipe P1 that has been deformed so as to fit closely around the male mold. For example, the main body portion D1 can be made thinner continuously in one direction (FIG. 4), and it is possible to manufacture an irregular cross-sectional pipe P2 whose internal cross-sectional shape is continuously smaller.

Roughly speaking, the male body portion D1 may be formed into a thread shape with equal pitches (FIG. 5). Since the male shape can be handled by twisting it with respect to the pipe P1, the irregular cross-section pipe P2 can be manufactured in the same way. In addition, when removing the male mold from the deformed pipe P1, it is possible to easily handle the male mold by drilling an air intake port at the tip of the pipe P1 or cutting both ends. shall be able to do so.

As described in detail, according to the present invention, a male mold is inserted into a pipe made of thermoplastic plastic, the pipe is heated to a temperature higher than its softening temperature, and the inside of the pipe is subjected to negative pressure, thereby softening the pipe. is 1. Since it is deformed so as to fit tightly around the outer periphery of the male mold, it is possible to easily manufacture a pipe with an irregular cross section on the inside that has the same cross-sectional shape as the male mold. Since each pipe is processed individually, it has the advantage of being able to easily accommodate small-lot production.

Example A male die with a star-shaped cross section was inserted into a polyethylene pipe with an inner diameter of 25 m and a wall thickness of 3 JISIl, and heated in an oil bath at a temperature of 150 to 155° C. for 15 to 20 minutes using white squeeze oil. Next, when the inside of the pipe was brought to a negative pressure of 7,538 g, the pipe deformed so as to closely fit the male mold, and almost no uneven distribution of wall thickness was observed at that time. Therefore, the male mold was removed from the deformed pipe to obtain an irregular cross-sectional pipe having a star-shaped cross-sectional shape on the inner surface.

[Brief explanation of the drawing]

Figures 1 to 3 show examples, Figure 1 (A> to C) is a schematic cross-sectional view showing the process order, Figure 2 is an overall configuration diagram of the male mold, and Figure 3 is a heating deformation process. FIG. FIGS. 4 and 5 are a perspective view and a side view, respectively, showing another male embodiment. PSPL, P2...Pipe D...male type

Claims (1)

[Claims] 1) An irregular cross-section pipe characterized by inserting a male die into a pipe made of thermoplastic plastic, heating the pipe to a temperature higher than its softening temperature, and creating a negative pressure inside the pipe. Production method. 2) The method for manufacturing an irregular cross-section pipe according to claim 1, wherein the heating is performed using an oil bath.