JPS60135231A - Bending processing method of plastic rod-shaped body - Google Patents

Abstract

PURPOSE:To enhance workability through the enhancement of thermal efficiency, by using a bending mold having a cavity having a shape almost same to the outer shape of a processed rod shaped body and made of a material low in dielectric constant. CONSTITUTION:A plastic rod shaped material is received in the cavity, which has a shape almost same to the outer shape of a processed rod shaped body, of a bending mold made of a material low in dielectric constant in a deformed state. The plastic rod shaped material A received in the bending mold 3 is heated to the softening temp. thereof in a direct high frequency heating apparatus 2. At this time, the bending mold 3 is not heated because made of the material low in dielectric contsant. Therefore, quantity of heat required in processing is limited to one sufficient to heat the plastic rod shaped material A to be processed to the softening temp. thereof or more. The rod shaped material A heated to the softening temp. thereof or more loses its heat through the bending mold 3 directly after heating is finished and is cooled because said bending mold 3 is not heated. As a result, quantity of heat required in processing is reduced and the cooling speed of the rod shaped body A in the bending mold 3 is quick.

Description

[Detailed Description of the Invention] [Technical Field] As a secondary processing of plastics, a straight rod material extruded into a rod shape or a vibrator shape is made into an L-shape, S-shape, etc. at room temperature or by heating. A method is known in which the rod material is inserted into a cavity in a mold, heated above its softening point, cooled to room temperature, and processed into an L-shape, S-shape, or the like. The present invention relates to a method for bending such a plastic rod-shaped body.

[Prior Art] Conventionally, a method of bending a plastic rod-shaped body involves forming a cavity having a predetermined L-shape or S-shape into a male or
A female split mold is used, and a rod-shaped material such as a straight plastic pipe is forcibly deformed and inserted into this cavity. After the split mold is closed, the split mold containing the rod-shaped material is heated. It is placed in a medium and heated to a temperature higher than the thermal softening point of the plastic that makes up the rod-shaped body material, and the strained body produced by deformation is cooled to room temperature.Then, the mold is opened and the molded rod-shaped body is taken out. Ta. In this conventional method, it is necessary to heat and cool the split mold in order to heat and cool the rod-shaped material, which requires a huge amount of heat for processing and has poor workability.

[Objective of the present invention J] An object of the present invention is to provide a method for bending a plastic rod-shaped body with high thermal efficiency. Another object of the present invention is to provide a method for bending a plastic rod-shaped body that has high thermal efficiency and excellent workability.

[Detailed Description of the First Invention] The method for bending a plastic rod-shaped body according to the first invention includes a bending process made of a material having a small dielectric constant and having a cavity having a shape substantially the same as the outer shape of the processed rod-shaped body. Type key 1
The process of deforming and storing a plastic rod-shaped material in a 7B, irradiating the stored rod-shaped material with high-frequency electromagnetic waves, heating the rod-shaped material to a predetermined temperature, and removing the distortion caused by the deformation. A step of cooling the heated rod-shaped body from which strain has been removed to a predetermined temperature or lower in the bending die, and a step of taking out the bent rod-shaped body from the bending die. be.

In this first invention, the plastic rod-shaped material housed in the bending mold is directly heated to a temperature higher than its softening temperature by high-frequency heating. At this time, the bending die is not heated because it is made of a material with a small dielectric constant. Therefore, the amount of heat required for processing is only the amount of heat needed to heat the plastic rod material to be processed to a temperature above its softening point.

Since the bending die has not heated the rod-shaped material heated above the softening point temperature, the bending die immediately absorbs the heat and cools the rod-shaped material as soon as the heating is finished. Therefore, in the molding method of the present invention, the heat m required for processing is small and the cooling rate of the rod-shaped body in the bending die is fast.

[Detailed description of the second invention] The method for bending a plastic rod-shaped body of the second invention includes:
At least the bending mold has a cavity having a shape substantially the same as the outer shape of the rod-shaped body to be processed, and an introduction path that communicates with the cavity and has an open end through which the rod-shaped body to be processed is inserted into the cavity. a step of irradiating a plastic rod-shaped material with high-frequency radiation in a part of the introduction path of the rod-shaped material to continuously heat the rod-shaped material and deform the rod-shaped material, and storing the rod-shaped material in the cavity; The present invention is characterized by the following steps: cooling the rod-shaped body housed within the cavity; and taking out the bent rod-shaped body from the bending die.

In this second invention, when the plastic rod-shaped material is charged into the cavity of the bending mold, the rod-shaped material is continuously heated in a part of the introduction furnace communicating with the cavity. Therefore, the rod-shaped material is softened by heating before being inserted into the cavity, and is easily deformed to conform to the shape of the cavity. Moreover, when charging the rod-shaped material into the cavity, the part of the rod-shaped material on which the charging pressure acts has not yet been heated, so even if sufficient pressing force is applied to insert the rod-shaped material into the cavity. ,
The plastic rod material is not crushed. In particular, if the plastic rod-shaped material can be heated above its softening point in the introduction path, the deformation strain that occurs when it is stored in the cavity is removed by heat, so that after the rod-shaped material is completely stored in the cavity. , there is no need to heat the rod material within the cavity. Therefore, productivity is improved accordingly.

The second invention makes it easy to store the rod-shaped material in the cavity, and the amount of heat required for processing is only the amount of heat required to heat the molding material above its softening point temperature, resulting in high thermal efficiency and even higher productivity. expensive.

[Detailed description of the structure of the invention of the first invention] The bending die used in the first invention has a cavity with a shape almost the same as the outer shape of the processed rod-shaped body, and is made of a material with a small dielectric constant. There is. As materials with a low dielectric constant, ceramics such as alumina and silicon nitride, fluororesins, and the like are known.

The cavity shape and external shape of this bending die may be the same as those of the conventional bending die used for bending.

Further, the bending die may be a divided die such as a male die and a female die.

Furthermore, the bending mold can be provided with an introduction channel communicating with the cavity. Preferably, the open end of the introduction furnace is funnel-shaped so that the plastic rod material to be molded can be easily inserted into the introduction channel.

In such a case, it is preferable that the wall surfaces of the introduction path and the cavity have a smooth surface or a surface with a small coefficient of friction that has low sliding resistance against the rod material.

Bookcase - In the method of the invention, a bending mold made of the above-mentioned material with a low dielectric constant is used, and a plastic bar material to be molded is housed in the cavity of the bending mold.

This storage method can also be carried out by deforming the rod-shaped material at room temperature with the split mold open, and then pushing it into the cavity and closing the mold, as in the conventional method. Further, in the case of a bending mold having an introduction path, it is also possible to insert the rod-shaped material from the introduction furnace and store it in the cavity while deforming the rod-shaped material by the insertion force. If the rod material cannot be easily deformed at room temperature, it may be heated to a predetermined temperature below its softening temperature to deform the rod material in a slightly softened state and housed in the cavity.

The rod-shaped material housed in the cavity is directly heated by high-frequency heating. Depending on the type of plastic, there are some that are easy to heat with high frequency and others that are not.

In the method of the present invention, it is preferable to use resins such as polyvinyl chloride resins, polyester resins, and polyether resins. The degree of heating is similar to conventional heating, and is heated to a temperature higher than the softening point of the plastic material to be molded. By heating above the softening point temperature, the deformation strain that occurs when the rod is deformed into a cavity shape is removed by the thermal movement of the polymer constituting the rod material.

After this, heating is stopped.

When heating is stopped, the bending die is not heated, so the heat of the bar material is transferred to the bending die, and the bar material is rapidly cooled. Then, by cooling the plastic to a temperature below the softening point, the thermal motion of the polymer forming the resin is frozen, and the plastic is molded into a cavity shape. The molded rod-shaped body is then removed from the cavity. To take out the rod-shaped body from the inside of the cavity, the mold is opened as in the conventional method, or if the molded rod-shaped body has an introduction hole, the molded rod-shaped body is pulled out from the introduction hole. Bookcase-
In the method of the invention, the entire plastic rod material inside the cavity A is directly heated by high frequency heating, and the bending die itself is not heated. Therefore, the amount of heat required for heating is extremely small. Furthermore, when the heating is stopped, the bending die is not heated, so the heat of the heated bar material is immediately transferred to the forming die and is effectively cooled. Therefore, the bookcase-invention has high thermal efficiency (good workability).

[Detailed Description of the Second Invention] The bending die used in the second invention has a cavity having a shape substantially the same as the outer shape of the plastic to be processed, and an introduction path for introducing the rod-shaped material into the cavity. At least a portion of this introduction path has a heating portion that transmits high-frequency electromagnetic waves to the plastic rod material. This bending mold can also be made entirely of a material with a low dielectric constant. Alternatively, the entire mold may be made of a radio wave reflector such as a metal, and a radio wave introduction portion into which radio waves are introduced is provided in a part of the introduction path, and high frequency radio waves may be introduced from the radio wave introduction portion. If the plastic rod material cannot be heated above its softening temperature in the introduction path, the surface portion forming the cavity should be made of a material through which high-frequency radio waves are transmitted, that is, a material with a dielectric constant, so that the rod material can be heated within the chirality. It can be made from a small material, or the entire mold can be made from a material with a low dielectric constant. In addition, the device for supplying high-frequency electromagnetic waves to the introduction path or the introduction path and cavity is installed inside the mold.
Either method may be used, or a method may be used in which electromagnetic waves are introduced into the bending die from outside the bending die.

In the method of the second invention, the rod-shaped material is inserted into the cavity through the introduction path. When the rod material passes through this introduction path, the entire surface and interior of the rod material is heated almost uniformly by high frequency heating, and the rod material softens and easily deforms in response to the heating. Therefore, the rod-shaped material can be easily pushed along the complex shape of the cavity. If the rod material is easily deformed like a round rod,
The heating in the introduction path can be performed to a temperature higher than the softening point temperature of the rod material. In such a case, there is no need to reheat the rod-shaped material housed in the cavity, and only the rod-shaped material is cooled in the cavity. In addition, if heating above the softening point temperature causes the rod material to deform abnormally, or if the rod material cannot be reliably stored in the cavity, the heating in the introduction path should be lowered slightly, and the rod material When the rod material is completely accommodated in the cavity, the rod material is heated again to a temperature above its softening point. Thereafter, the heating is stopped, and the heat of the heated rod-shaped material is transferred to the bending mold, and the plastic is cooled to below its softening point temperature and molded. The method of taking out the molded plastic from the bending mold is the same as the conventional bending method, and in the case of a split mold, it is processed by opening the mold or, if it is possible to pull it out, directly through the introduction channel. The rod-shaped body can be pulled out.

In the second aspect of the present invention, even when it is difficult to deform the rod-like material into a cavity shape at room temperature, the rod-like material can be efficiently stored in the cavity. Particularly, the portion of the rod material to be housed in the cavity that requires pressing force is heated and not softened, so that sufficient pressing force can be applied. In addition, the part that is pressed and deformed along the cavity shape has already been heated by high-frequency heating in the introduction path and has become soft, so it deforms with a relatively small force and is efficiently accommodated in the cavity. Ru.

Example [Example 1] The first example shows an example of the first invention, in which a bending die 1 whose front view is shown in FIG. 1 and a plan view of the lower die 12 is shown in FIG. 2 is used. This bending die 1 is made of fluororesin and is a split die consisting of an upper die 11 and a lower die 12. Upper mold 11 and lower mold 12
As shown in FIG. 2, an introduction path 14 having an L-shaped cavity 13 and a funnel-shaped opening 14a is formed on the mating surfaces of the two. Using this bending die 1, as schematically shown in FIG.
4a into the cavity 13. The rod material A is made of nylon and has an outer diameter of 4 mm.

Inner diameter 1. ．． A pipe with a length of 5 mm and a length of 710 mm was used.

Next, as schematically shown in FIG. 4, a bending mold 1 is inserted between the electrodes 23 and 24 of the high-frequency heating device 2, which has high-frequency electrodes 23 and 24 on the upper part 21 and the lower part 22. The rod-shaped material was placed and subjected to high-frequency heating. In this example, the heating time was 6 to 10 seconds, and each electrode distance was 1111145.
The rod material A was heated to about 90 to 100°C by irradiating high frequency under the condition of -5 omm. After discontinuing high frequency heating,
After 10 seconds, the rod-shaped body was pulled out from the bending die 1 and processed into the L-shape shown in FIG.

Example 2] The second example corresponds to the example of the second invention of the present invention. In this embodiment, a bending die 3 consisting of an upper die 31 and a lower die 32, whose front view is shown in FIG. 6 and a plan view of the lower die 32 is shown in FIG. 7, was used. This bending mold 3 is made of fluorine resin, and the cavity 33 is S-shaped.
An introduction path 34 having a funnel-shaped opening 34a is communicated with. In the introduction path 34, electrodes 35 forming a pair of high-frequency electrodes are embedded in the upper mold 31 and the lower mold 32, respectively. Using this bending mold 3, a nylon round bar with a diameter of 4 mm is used as the rod material B, and the rod material B is passed through the opening 34a of the bending mold 3 through the introduction path 34 as in Example 1.
was inserted into the cavity 33 of. In this case, the heating temperature in the introduction path 34 is 40 to 50°C, and the insertion speed is 30 m.
The rod-shaped material B was inserted into the cavity 33 while being continuously subjected to high-frequency heating under the conditions of m/sec. After inserting the rod material B securely into the cavity 33, stop the high-frequency heating, leave it for about 10 seconds, and bend the rod material B into the mold 3.
The molded rod-shaped body was cooled inside the mold, and the mold was opened and taken out. A plan view of the obtained rod-shaped body is shown in FIG.

Conventionally, rod-shaped materials such as those in this example, which are difficult to deform to fit the cavity shape at room temperature, are heated in a heating furnace to soften the material slightly before being stored in a bending mold cavity. was. However, in this embodiment, the rod material at room temperature can be inserted into the cavity by directly pushing it into the cavity of the bending mold without heating, and the rod material can be heated within the cavity. There is no need for the process of Therefore, the processing method of this embodiment has high thermal efficiency and high productivity.

[Brief explanation of the drawing]

Figures 1 to 5 show the first embodiment, where Figure 1 is a front view of the bending mold, Figure 2 is a plan view of the lower mold, and Figure 3 is a rod-shaped material inserted into the bending mold. FIG. 4 is a side view showing the heating process, and FIG. 5 is a plan view of the processed rod-shaped body. Figures 6 and 8 show the second embodiment, with Figure 6 being a front view of the bending mold, Figure 7 being a plan view of the lower mold, and Figure 8 being a plan view of the processed rod-shaped body. It is. 1.3... Bending mold 2... Heating device patent applicant Toyoda Gosei Co., Ltd. agent Patent attorney Hirotoshi Okawa Patent attorney Raw materials Modification Patent attorney Akio Maruyama Figure 1 Figure 2 Figure 7 Figure 8 1. Indication of the case 2. Name of the invention Method for bending plastic rod-shaped bodies 4. Agent address: Hi Kodama, 3-3-4 Meieki, Nakamura-ku, Nagoya, Aichi Prefecture 450 L (7a052-583-972 (+) 5, Date of amendment order: March 70, 1982 (Date of dispatch: March 270, 1982) 6. Clarification of the subject of the amendment' Title of the invention in the letter R, Patent claim Scope column Detailed explanation of the invention column, Brief explanation of drawings column 7, Contents of amendment The type print has been retyped in black and large type as shown in the attached sheet. 8. List of attached documents (1) Details after amendment ■j 1 copy

Claims (1)

[Claims] (1) The processed rod-shaped body has a cavity with the same external shape, and the plastic rod-shaped body material is deformed into the cavity of a bending die made of a material with a low dielectric constant. irradiating the stored rod-shaped material with high-frequency electromagnetic waves to heat the rod-shaped material to a predetermined temperature to remove distortion caused by deformation; 1. A method for bending a plastic rod-shaped body, comprising the steps of: cooling the body to a predetermined temperature or lower in the bending die; and taking out the bent rod-shaped body from the bending die. (The 2-inch bending mold communicates with a cavity formed inside the mold, and has an O-shaped introduction path at the opening. By forcibly inserting the rod-shaped material through the introduction path, the rod material is inserted into the cavity.) The bending method according to claim 1, in which the rod-like material is deformed and stored. (3) The bending method according to claim 1, wherein the rod-like material is pipe-shaped. At least the bending mold is introduced into a bending mold having a cavity having a shape substantially the same as the external shape of the rod-shaped body, and an introduction path communicating with the cavity and having an open end through which the rod-shaped body to be processed is inserted into the cavity. A step of irradiating a plastic rod-shaped material with high-frequency electromagnetic waves in a part of the path to continuously heat the rod-shaped material and deform the rod-shaped material, and storing the rod-shaped material in the cavity. A method for bending a plastic rod-shaped body, comprising the steps of: cooling the bent rod-shaped body in the cavity; and taking out the bent rod-shaped body from the bending die. (5) A bending die. The bending method according to claim 4, wherein the opening of the introduction path is funnel-shaped. (6) The bending method according to claim 1, wherein the rod-shaped body is pipe-shaped.