JPH0929831A - Bending method for resin tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for bending a resin tube holding excellent accuracy of an inner diameter without kicking (breaking) by bending and without a parting line on the outer surface of the tube. SOLUTION: A resin tube (e.g. made of a soft vinyl chloride resin) 1 inserted with a conductive core rod (e.g. made of brass) 2 having a shape coincident with a desired bending shape is engaged with a groove 4 coincident in the bending shape provided at the conductive base (e.g. made of brass) 3, a high-frequency current flows between the rod 2 and the base 3 to heat the tube 1, and then to deenergize the current and to cool it.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method of bending a resin tube.

[0002]

2. Description of the Related Art Conventionally, the method of bending a resin tube is
The method is to put the tube in a working mold and leave it in an atmosphere of high temperature (about 120 to 180 ° C.) (5 to 30 minutes) and then cool it, but there is a drawback that the working time is extremely long. Therefore, various improvement methods have been proposed,
For example, Japanese Patent Laid-Open No. 61-41524 proposes a method in which a synthetic resin tube in a preheated and softened state is fitted into a spiral bending jig, and then the bending jig is resistance-heated to a predetermined temperature for a short time. However, this method may cause kinks (breaks) in the bent portion of the tube, and
The pattern of the spiral bending jig may remain on the tube.

Further, in Japanese Patent Laid-Open No. 2-32831,
A metal tube piece having an inner diameter slightly larger than the outer diameter of the resin tube, which is located on the outer peripheral side of the portion to be bent of the small-diameter resin tube as the work piece that has been cut into a predetermined length in advance, is used. It has been proposed to apply and then to integrally bend the adhered part into a desired shape by manual bending with a bending jig or automatic bending with a bender device. Since it is wound, there is a risk that the outer circumference of the bent portion becomes thick, and there is a problem that it is difficult to use when a thin tube is required.

Various methods are proposed in Japanese Patent Laid-Open No. 6-190913. A predetermined portion of a straight tubular resin tube to be bent is partially heated by a partial heating means, and the heated predetermined portion is partially bent by a partial bending mold to obtain the resin tube. Although a method (claim 1) of imparting a required bending shape to the tube has been proposed, this method may cause a kink at the bent portion of the tube.

[0005] Further, the same publication proposes a method of heating a tube with ultrasonic waves or high frequencies and partially bending it with a partial bending mold (claims 2 and 5). In the case of a tube, it is difficult to heat it with ultrasonic waves, and both methods may cause kinks in the bent portion of the tube. Further, a method has been proposed in which a tube formed body containing a conductive powder is used for heating at a high frequency and a partial bending process is performed by a partial bending process (claims 3, 4, and 6). , Kink may occur in the bent part of the tube. Further, there is also a problem that a tube molded body containing a substance such as metal powder cannot be used for medical purposes.

Further, in the publication, a mandrel made of rubber or the like in which powder such as metal powder is mixed is inserted inside the resin tube, and the mandrel is heated by a high frequency to heat the resin tube to form a partially bent mold. Although a method has been proposed in which the mandrel is pulled out after partially bending it (claim 7), the use of metal powder makes it difficult to use for medical purposes even if it is washed. In addition, in the case of a tube in which a thin groove is dug in the thick portion of the tube because it is clamped with a working die (see FIG. 4 described later), this groove may be crushed unless the mandrel is inserted into the thin groove. However, it is difficult to insert the mandrel into the narrow groove and it is difficult to remove it. Further, there is a problem that the mating surface of the processing mold has a softened resin and has a parting line.

[0007]

SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and its object is to prevent kinking (breaking) due to bending and to maintain good inner diameter accuracy. It is an object of the present invention to provide a method for bending a resin tube in which a parting line does not occur on the outer surface of the tube.

[0008]

According to the present invention, a resin tube in which a conductive core rod having a shape matching a desired bending shape is inserted is matched with the bending shape provided on a conductive base. A method for bending a resin tube is characterized in that the resin tube is fitted in a groove, a high-frequency current is passed between the core rod and the base to heat the resin tube, and then the energization is stopped to cool the resin tube.

The resin used in the present invention is not particularly limited as long as it is a resin that generates heat and softens when a high-frequency current is applied, and examples thereof include thermoplastic resins such as vinyl chloride resin.

The present invention will be described below with reference to the drawings.
FIG. 1 is a perspective view showing a bending process according to the present invention. A resin tube 1 in which a conductive core rod 2 having a shape matching a desired bending shape is inserted is fitted into a groove 4 provided on a conductive base 3 and matching the bending shape.

In the present invention, in this state, the core rod 2 and the base 3 are
The resin tube 1 is bent by applying a high-frequency current to generate heat in the resin tube 1, and then the energization is stopped to cool the resin tube 1.

The bending process is essentially the resin tube 1
This is done by generating heat only in the portion that comes into contact with the table 3 (the portion shown by the diagonal lines in FIG. 2), but the desired bending shape can be obtained by processing only one side like this, but the required dimensional accuracy is If it is high or if the heat load applied to the resin tube after processing is large, the portion of the resin tube 1 that was not in contact with the base 3 is further fitted into the groove 4 and bent in the same manner to perform the resin tube processing. It is recommended that both sides be processed.

The procedure of double-sided processing described above will be described with reference to FIG. 3. After bending one side in the state shown in FIG. 3A, FIG. 3A, FIG. 3B and FIG. The resin tube 1 in which the core rod 2 is inserted as indicated by the arrow in FIG.
Is reversed and the other surface is bent similarly in the state shown in FIG. 3 (D).

(Operation) The resin tube 1 in which the conductive core rod 2 having a shape corresponding to a desired bending shape is inserted,
Grooves 4 provided on the conductive base 3 and conforming to the above-mentioned bending shape
The resin tube 1 is internally heated by high frequency induction heating to be softened by fitting a high frequency current between the core rod 2 and the base 3 so that the resin tube 1 follows the shape to be bent. Then, when the energization is stopped and the resin is cooled, the resin is solidified and fixed in a shape that tends to bend. In the method of the present invention, since the core rod 2 and the base 3 are in contact with the resin tube that has generated heat, the temperature rises slightly due to heat transfer, but since it is not directly heated by the high frequency current, it is essentially Does not get hot. Therefore, when the high frequency current is cut off, the core rod 2 and the base 3
Due to this, the resin tube is cooled in a short time. Further, since the resin tube 1 is securely supported in the desired shape by the groove 4 and the core rod 2 during the bending process, the resin tube 1 is not kinked by the bending process.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 is a sectional view of the resin tube 1 used in this example. The resin tube 1 is made of soft vinyl chloride resin and has an inner diameter of 8 mm, an outer diameter of 12 mm and a wall thickness of 2
mm and the length was about 100 mm. As can be seen in FIG. 4, a thin groove with a diameter of 0.5 mm has an angle of 90 mm in the thick part.
There were 4 dug at a time interval. In this embodiment, the resin tube 1 was bent to have a radius of curvature of 50 mm.

A conductive core rod 2 having a shape corresponding to a desired bending shape was inserted into the resin tube 1 described above.
FIG. 5 shows a side view of the core rod 2 used. The core rod 2 is made of brass and is a rod-shaped body with a diameter of 8 mm.
1 and a bent portion 22 having a radius of curvature of 50 mm.

Next, as shown in FIG. 1, the core rod 2 described above is used.
The resin tube 1 in which was inserted was fitted into the groove 4 provided on the conductive base 3 and conforming to the above-described bending shape. FIG.
A side view of the stand 3 used in (A) and a plan view thereof are shown in FIG. 6 (B). The pedestal 3 was made of brass, and the pedestal 3 had a semicircular bottom section with a diameter of 12 mm, and was provided with a curved groove 4 with a radius of curvature of 50 mm.

Next, a frequency of 40.4 is applied between the core rod 2 and the base 3.
A high frequency current of 6 MHz is passed for 4 seconds to heat the resin tube 1, and then the current is stopped and cooled, and then the resin tube 1 in which the core rod 2 is inserted is inverted as shown in FIG. In the state shown in (D), bending was performed by passing a high frequency current in the same manner as above.

After cooling, the core rod 2 was pulled out from the resin tube 1 to obtain a resin tube which had a desired bending radius of 50 mm. The obtained resin tube had no kink, the inner diameter accuracy was kept good, and no parting line was generated on the outer surface of the resin tube.

[0020]

The structure of the present invention is as described above. When the method of bending a resin tube according to the present invention is used, the resin tube is not kinked by the bending process, and the inner diameter accuracy is kept good. In addition, since no external force is applied to the tube because it is not clamped by the working die, no parting line is generated on the outer surface of the tube. Also,
It is not necessary to mix conductive powder into the resin tube molding material for bending, and no mandrel made of a material mixed with conductive powder for bending is used, so contaminants on the inner surface of the resin tube are removed. The present invention is particularly suitable for bending a resin tube for medical use, because no cleaning is required to do so.

[Brief description of drawings]

FIG. 1 is a perspective view showing a bending process according to the present invention.

FIG. 2 is an explanatory diagram showing a heat generating portion of a resin tube 1.

FIG. 3 is a perspective view showing a procedure of double-sided processing.

FIG. 4 is a sectional view of a resin tube used in an example.

FIG. 5 is a side view of the core rod used in the examples.

FIG. 6 is a diagram showing a table used in an example.
6A is a side view of the table, and FIG. 6B is a plan view thereof.

[Explanation of symbols]

 1 Resin tube 2 Core rod 3 units 4 Groove

Claims (1)

[Claims] 1. A resin tube in which a conductive core rod having a shape corresponding to a desired bending shape is inserted is fitted into a groove corresponding to the bending shape provided on a conductive base, and the core rod and A method for bending a resin tube, characterized in that a high-frequency current is passed between the bases to heat the resin tube, and then the energization is stopped to cool the resin tube.