JPH05245889A - Manufacture of bellows tube and its molding device - Google Patents

Abstract

PURPOSE:To manufacture efficiently a bellows tube provided with dimension stability and sufficient rubber elasticity by molding the bellows tube by injection molding method in which releasing manner is planned well. CONSTITUTION:A molding space 9 is formed by a fixed mold 5, a movable mold 6 and a core 7 between both molds 5 and 6, and thermoplastic elastomer is pressure filled in said molding space 9 and then solidified to mold a bellows raw material 3 with its one end blocked by an end wall 4. Both ends 5 and 6 are mold clamped, and then the core 7 and the bellows tube raw material 3 are moved outside the molding space 9, and pressurized gas is fed into an inner face of the bellows tube raw material 3 through a passage 11 inside the core 7 to expand and deform the bellow raw material 3 and release the same out of the core 7. An end wall 4 of the bellows tube raw material 3 thus manufactured is removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manufacturing method and an apparatus for forming a bellows tube by an injection molding method.

[0002]

2. Description of the Related Art As a conventional technique for forming a bellows tube using a molding die, rubber is used as a raw material, the die is filled with vulcanization, and a plastic tube is blow-molded. It is known that a molding method is used.

[0003]

The vulcanized rubber-made bellows tube has a disadvantage that it is difficult to color the molding material, and it is difficult to apply the bellows tube especially when it is used for decoration purposes. The bellows tube formed by the blow molding method is problematic in that it lacks dimensional stability and cannot be made particularly uniform in wall thickness, and that a thermoplastic elastomer having rubber elasticity required for the bellows tube cannot be applied.

The inventor of the present invention has excellent productivity and dimensional stability,
Although research has been conducted on forming a bellows tube by an injection molding method in which there is no restriction on applied materials, an obstacle in forming a bellows tube by an injection molding method is that it is extremely difficult to release a molded product. In particular, in the case of a non-helical bellows tube in which the pleated wall of the peripheral surface of the tube is independently projected like a flange, it becomes difficult to extract the molded product from the core.

The object of the present invention is to eliminate the difficulty in mold release due to the shape of the bellows tube, to freely color the material, and to obtain sufficient dimensional stability.
An object of the present invention is to provide a manufacturing method capable of efficiently forming a bellows tube and an apparatus therefor.

[0006]

The manufacturing method of the present invention comprises:
Forming a molding space 9 with a fixed mold 5 and a movable mold 6 that form the outer surface shape of the bellows tube F, and a core 7 that is arranged between the two molds 5 and 6 and that forms the inner surface shape of the bellows tube F. , The bellows tube raw material 3 in which one end of the tube is closed by the end wall 4 by pressure-filling and solidifying the molten thermoplastic elastomer in the molding space 9.
To open the fixed mold 5 and the movable mold 6 and then move the core 7 and the bellows tube raw material 3 to the outside of the molding space 9 through the passage 11 provided inside the core 7. To release the bellows tube raw material 3 from the core 7 by supplying pressurized gas to the inner surface of the bellows tube raw material 3, and remove the end wall 4 of the released bellows tube raw material 3 to form the bellows tube. The requirement is to form F.

The molding apparatus of the present invention comprises a fixed mold 5 and a movable mold 6 for forming the outer surface shape of the bellows pipe raw material 3 having an end wall 4 at one pipe end, and between the molds 5 and 6. A core 7 that is arranged to form the inner surface shape of the bellows tube raw material 3, the core 7 is located in a molding space 9 defined by the molds 5 and 6, and It is configured so that it can be moved between the mold space 9 of the two molds 5 and 6 in the mold open state and a mold release position that projects to the outer surface, and that pressurized gas for mold release is sent to the inside of the core 7. A passage 11 for supplying the gas is provided, and a nozzle opening 12 at the end of the passage is opened in a core end wall that is inscribed in the end wall 4. The nozzle opening 12 is closed from the outer surface side by a valve body 13 to close the valve body 13. It is biased to be closed by a spring 16 and provided with a gas supply source for supplying a pressurized release gas to the passage 11. It is a requirement.

[0008]

According to the present invention, the bellows tube raw material 3 whose one end is closed by the end wall 4 is molded by the injection molding device, and then pressurized gas is blown into the inside of the bellows tube material 3 to expand the raw material. The bellows tube raw material 3 is released from the core 7 by pressure. In order to ensure the mold release, the rubber elasticity of the thermoplastic elastomer is used for the mold release, and the passage 11 is provided inside the core 7 for feeding the pressurized gas for the mold release. There is. Further, the core 7 can be moved to the outside of the molding space 9 of the fixed mold 5 and the movable mold 6 which are opened. The thermoplastic elastomer does not require vulcanization and can be colored freely. Nozzle 12 to valve body 1
The reason for blocking with 3 is to prevent molten resin from entering the passage 11 through the nozzle opening 12 during molding.

[0009]

According to the present invention, the bellows tube raw material 3 which is in close contact with the core 7 through the corrugated wall 1 having a corrugated cross section is formed into a bottomed tubular shape in which one tube end is closed by the end wall 4. By injecting a pressurized gas into the interior of the tube to expand the entire tube wall, the core 7 can be reliably released from the mold. Therefore, for forming the bellows tube F using the molding die, it is possible to adopt an injection molding method which is excellent in mass productivity, has dimensional stability and sufficient rubber elasticity, and has a limited degree of freedom in coloring. It has become possible to efficiently manufacture the bellows tube F which is not present.

[0010]

1 to 4 show an embodiment of a method of manufacturing a bellows tube and a molding apparatus therefor according to the present invention. As shown in FIG. 4, the bellows tube F has a circumferential wall formed in a continuous corrugated form, and each fold wall 1 is independently formed for each turn, and is formed as a non-helical bellows tube. The fold wall 1 adjacent to the inner surface of the pipe
Six ribs 2 for connecting the two are provided at equal intervals in the circumferential direction, and a ring portion 19 is provided at each of the pipe ends.

The bellows tube F is formed by forming the bellows tube raw material 3 by an injection molding method and removing the end wall 4 of the raw material 3 after releasing the mold.
Specifically, as shown in FIG. 2, the movable mold 5 and the movable mold 6,
And the molding space 9 is formed by the three members of the core 7 arranged between the molds 5 and 6, and the molding space 9 is filled with the thermoplastic elastomer under pressure to solidify and one end is closed by the end wall 4. The peeled bellows tube raw material 3 is formed. The fixed mold 5 and the movable mold 6 form the outer surface shape of the bellows tube raw material 3, and the core 7 forms the inner surface shape. As the thermoplastic elastomer, vinyl chloride-based, styrene-based, olefin-based, urethane-based, ester-based, amide-based, etc. thermoplastic elastomers can be used.

In order to remove the molded bellows tube raw material 3 from the core 7, as shown in FIG. 1, the movable mold 6 is separated from the fixed mold 5 and the mold is opened, and the two molds 5 and 6 are separated from each other. The release gap E is secured. In this state, the core 7 is relatively pushed toward the fixed mold 5 side by the operation shaft 10 provided in the movable mold 6 to separate the core 7 and the bellows tube raw material 3 on the outer surface thereof from the mold release gap E.
And is located outside the molding space 9.

The core 7 is supported by an operating shaft 10 in a cantilevered manner, and a passage 1 for guiding the release of pressurized release gas therein.
1, a valve body 13 for opening and closing the nozzle opening 12 at the end of the passage, a valve case 14, and the like. The nozzle opening 12 is open at the core end wall inscribed in the end wall 4 of the bellows tube raw material 3. The valve body 13 is formed in the shape of a poppet valve, is vertically slidably supported by a boss 15 provided in the inner surface of the valve case 14, and is biased by a spring 16 to be closed. The valve seat portion formed of the tapered surface of the valve body 13 is the nozzle opening 12
It has become. A communication hole 17 for passing a pressurized gas is provided in the boss 15.

The pressurized gas is compressed air supplied through a control valve from a gas supply source such as an air compressor (not shown), and the passage in the movable mold 6 and the operation shaft 10 are provided.
It is fed to the passage 11 via the passage 10a provided in the.
The operating shaft 10 is operated by a hydraulic cylinder (not shown) to move the core 7 between a molding position located inside the molding space 9 and a releasing position protruding to the outer surface of the molding space 9.

When the pressurized gas is fed into the passage 11, the valve element 13 is slightly pushed outward against the spring 16 to open the nozzle opening 12, as shown in FIG. Therefore, the pressurized air is jetted from the nozzle port 12 and filled between the end wall 4 and the core 7, and further flows along the peripheral surface of the core 7 to the operation shaft 10 side, and the bellows tube raw material is obtained. The whole 3 is expanded and deformed. In this state, an inner pressure substantially equal to the pressure of the pressurized air acts on the inner surface of the bellows tube raw material 3, and the inner surface of the fold wall 1 floats from the peripheral surface of the core 7. Moreover,
Part of the pressurized air blows out from the upper end of the bellows tube raw material 3. Therefore, the bellows tube raw material 3 is extruded downward along the peripheral surface of the core 7 and discharged from the release gap E to the product outlet.

As shown in FIG. 4, by removing the end wall 4 of the raw material 3 for the bellows tube, a bellows tube F having both ends open is obtained. Regarding the removal of the end wall 4, the end wall 4 is cut into a disc shape, but the pipe end may be cut into a sliced shape depending on the shape of the end portion. The bellows tube F according to this embodiment has an outer diameter of 39 mm and a total tube length of 260 mm, and is mainly used as a decorative body for a bent pipe portion of a pipe chair or as a decorative body for a column made of pipe material.

As described above, the bellows tube F is manufactured by the injection molding method.
By forming, the bellows tube F can be molded with a thermoplastic elastomer having sufficient rubber elasticity, and its color can be arbitrarily selected. Since the elasticity of the thermoplastic elastomer is used to release the core 7 from the core 7 by the pressurized air, the mold can be released without difficulty and the molding can be performed efficiently.

A plurality of nozzle openings 12 can be provided,
It is also possible to adopt an arrangement form in which the core 7 is open at the peripheral surface.
The pleated wall 1 of the bellows tube F can be continuously formed in a spiral shape, and the outer diameter can be changed in size along the tube axis direction if necessary. The wall thickness can be partially changed. The core 7 can be supported on the fixed mold 5 side, or can be independently supported between the fixed mold 5 and the movable mold 6.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a molding die showing a state where a bellows tube is being released.

FIG. 2 is a vertical sectional view of a molding die in a mold clamped state.

FIG. 3 is a vertical cross-sectional view of a core showing a state of a valve and a bellows tube at the time of release.

FIG. 4 is a front view of a bellows tube with a part cut away.

[Explanation of symbols]

 3 Raw material for bellows pipe 4 End wall 5 Fixed mold 6 Movable mold 7 Core 9 Molding space 11 Passage 12 Nozzle mouth 13 Valve body 16 Spring F Bellows pipe

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Claims (2)

[Claims] 1. A molding space formed by a fixed mold 5 and a movable mold 6 that form the outer surface shape of the bellows tube F, and a core 7 that is arranged between the two molds 5 and 6 to form the inner surface shape of the bellows tube F. 9 is formed, and the melted thermoplastic elastomer is pressure-filled and solidified in the molding space 9 to form the bellows tube raw material 3 in which one end of the tube is closed by the end wall 4, and the fixed mold 5 and After the movable mold 6 is opened, the core 7 and the bellows tube raw material 3 are moved to the outside of the molding space 9, and the inner surface of the bellows tube raw material 3 is pressed through the passage 11 provided inside the core 7. A method for manufacturing a bellows tube, in which a bellows tube raw material 3 is released from a core 7 by feeding gas, and an end wall 4 of the released bellows tube raw material 3 is removed to form a bellows tube F. 2. A fixed mold 5 and a movable mold 6 which form an outer surface shape of a bellows tube raw material 3 having an end wall 4 at one pipe end, and the bellows which are arranged between the molds 5 and 6. A core 7 that forms the inner surface shape of the pipe raw material 3 is provided, and the core 7 is located in the molding space 9 defined by the molds 5 and 6 and both molds in the mold open state. The molds 5 and 6 are configured so that they can be moved between a molding space 9 and a releasing position that protrudes to the outer surface, and a passage 11 is provided inside the core 7 for supplying pressurized releasing gas. The nozzle opening 12 at the end of the passage is opened in the core end wall inscribed in the end wall 4, and the nozzle opening 12 is closed by the valve body 13 from the outer surface side to form the valve body 1.
3. A bellows tube forming apparatus having a gas supply source configured to urge 3 to be closed by a spring 16, and to supply a pressurized release gas to the passage 11.