JP2001105456A - Apparatus and method for producing hollow molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and a method for producing hollow molded article capable of obtaining a hollow molding article having excellent appearance characteristics not generating jetting or the like by a short and stable molding cycle without being affected by a raw material resin to be used and the obtained hollow molded article. SOLUTION: In an injection mold apparatus having a cavity and producing a hollow molded article by injecting a molten resin in the cavity to cool and solidify the same in the cavity, at least one movable core (A) movable unidirectionally in the cavity, a movable core moving means (B), a resin injection part (C) for injecting the molten resin in the cavity and a pressure fluid injection part (D) arranged at a position where the route communicating with the cavity is opened and closed by the movement of the movable core are provided. A hollow molded article producing method using this apparatus and the hollow molded article produced by this method are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus and a method for manufacturing a hollow molded article. More specifically, a manufacturing apparatus capable of manufacturing a molded article having a hollow portion having a desired hollow ratio or remaining wall thickness and having a smooth surface and a smooth inner wall surface, and a manufacturing apparatus for manufacturing the same. The present invention relates to a method for producing a hollow molded article used and a hollow molded article.

[0002]

2. Description of the Related Art Conventionally, methods for producing a molded article having a hollow portion include blow molding, rotational molding, injection molding using a core, injection molding using a mold having a movable core, and gas assist. Injection molding methods and the like are known. The blow molding method is an effective method for producing a molded article having a simple shape such as a tank or a bottle, but is not suitable for producing a molded article having a complicated shape. In the rotational molding method, it is difficult to mold a molded article having a complicated shape, and furthermore, since pressure is not applied to the molten resin during molding, the strength of the end portion of the molded article is often insufficient. is there.

In the case of the injection molding method using a core, a core made of metal or resin is prepared in advance, the core is disposed in the cavity of the injection molding die, and the mold surface of the cavity and the core are formed. Inject water-soluble molten resin into the space formed by the core, cool and solidify the molten resin, remove the molded product from the injection mold, and then dissolve the water-soluble core inside the molded product. By dissolving the resin, a hollow portion, which is a trace of the core, can be formed inside the molded product. The method for manufacturing a molded article using the core has a disadvantage that the production cost of the molded article is increased because the steps are complicated.

In the case of injection molding using a mold having a movable core, the movable core is disposed in the mold cavity before the molten resin is filled in the mold cavity, and the movable core is disposed in the mold cavity and the movable core. In this method, a molten resin is injected into the formed space, the molten resin is cooled and solidified, the movable core is moved out of the mold cavity, and a molded product is taken out. When the movable core is placed in the mold cavity, a large pressure is applied when filling and holding the molten resin.When moving the movable core, a large resistance is generated from the molten resin surrounding the movable core. For this reason, the shape of the movable core is limited. In particular, in the case of a long molded product or a thick molded product, a mold having a movable core cannot be molded, or even if it can be molded, a desired hollow portion is formed. However, there is a drawback that a molded article having the following cannot be obtained.

In the gas assist injection molding method, a pressurized fluid is injected into the molten resin in the cavity during or after the injection of the molten resin into the cavity provided in the mold (including simultaneously with the completion of the injection). How to According to this gas assist molding method, during cooling and solidification of the molten resin in the cavity, the molten resin is pressed against the cavity surface of the mold by a pressurized fluid, so that the obtained injection molded product is warped or sinked. Can be effectively prevented. The gas assist molding method is an efficient molding method with a short molding step.

[0006] The gas assist molding method is divided into two methods. The first method is a molding method called a full shot method. The full shot method is a method in which a mold cavity for injection molding is completely filled with a molten resin, and a shrinkage when the molten resin is cooled and solidified is supplemented by applying a pressurized gas into the molten resin. The hollow ratio is limited only slightly by the shrinkage of the molten resin.

Another method is a method called a short shot method. In the short shot method, the injection molding mold cavity is insufficiently filled with the molten resin, a pressurized gas is injected into the molten resin, and the molten resin is caused to flow to the end of the flow by the pressure of the pressurized gas, thereby forming the mold. This is a method of molding by pressing against the cavity surface. Although this method can obtain a higher hollow ratio than the full shot method, since the hollow ratio is determined by the shape of the molded product and the characteristics of the raw material resin, it is possible to obtain a desired hollow ratio or the remaining wall thickness of the molded product. There was a drawback that it was difficult. Further, in the short shot method, there is a disadvantage that gas leaks from the inside of the molten resin or a remaining thickness becomes nonuniform in each part due to a phenomenon called jetting.

Conventionally, methods for preventing the occurrence of jetting include increasing the cross-sectional area of the gate, decreasing the injection speed of the molten resin, increasing the temperature of the molten resin, and using a resin grade having a low melt viscosity. There can be mentioned a selection method and the like. However, the method of increasing the cross-sectional area of the gate portion requires a cost for post-processing of a portion corresponding to the gate portion of the molded product. In addition, the method of lowering the injection speed of the molten resin increases the molding cycle and increases the manufacturing cost of the molded product.

The method of increasing the temperature of the molten resin impairs the thermal stability of the molten resin and causes problems such as poor appearance of molded articles and reduced properties due to generation of gas from the molten resin and reduction in the molecular weight of the resin. In addition, in the method of selecting a resin grade with a low melt viscosity, when excellent physical properties such as high impact resistance and high fatigue resistance are required for molded products, high-molecular weight type synthetic resin or cross-linked type synthetic resin or It is necessary to use a synthetic resin having a high viscosity at the time of melting, such as a synthetic resin alloy.

Further, in order to generally improve the strength of a molded product, a resin may be filled with a fiber filler.
The stable flow of the molten resin is hindered, and when the pressurized gas is injected, the gas inside the molten resin leaks and the remaining wall thickness becomes uneven. Especially on the inner wall surface of the hollow part, the tip of the fiber filler protrudes from the inner wall surface into the hollow part or rises to the surface as it is, causing roughness, and if the protrusion or protrusion is remarkable, a large bump that closes the hollow part There may be a large thickness deviation due to the protrusion of the projection.

Furthermore, due to the time difference between the filling of the molten resin into the cavity and the filling of the pressurized gas, the flow of the molten resin is stopped, and a boundary line called a hesitation line having a clearly different gloss is formed on the surface of the molded product. There is a problem that a defect that the appearance of the molded article is impaired occurs.

[0012]

Under such circumstances, the present inventors have intensively studied to provide a technique for manufacturing a hollow molded article which at once has solved the above-mentioned disadvantages of the prior art. As a result, the present invention has been completed. The objects of the present invention are as follows. 1. An object of the present invention is to provide a production apparatus capable of efficiently producing a hollow molded article having excellent appearance characteristics without jetting or hesitation lines without being affected by a raw material resin used. 2. An object of the present invention is to provide a manufacturing apparatus capable of manufacturing a synthetic resin hollow molded product having a desired hollow ratio or remaining wall thickness. 3. An object of the present invention is to provide a method for producing a molded product having a desired hollow ratio or remaining wall thickness of a hollow portion and having a hollow portion having a smooth inner wall surface as well as the surface.

[0013]

According to the present invention, there is provided a hollow molded product having a cavity, injecting a molten resin into the cavity, and cooling and solidifying the molten resin in the cavity. (A) at least one movable core disposed in the cavity and movable in one direction in the cavity, and (B) movable core moving means for moving the movable core And (C)
A resin injection unit for injecting the molten resin into the cavity, and (D) a pressurized fluid injection unit installed at a position where a path communicating with the cavity is opened and closed by movement of the movable core,
The present invention provides an apparatus for producing a hollow molded article, characterized by comprising:

Further, according to the present invention, after a molten resin is injected from a resin injection portion into a cavity of an injection molding die, the resin is cooled and solidified in the cavity to produce a hollow molded product. At least one movable core disposed in the cavity and movable in one direction in the cavity;
(B) a movable core moving means for moving the movable core, (C) a resin injection section for injecting the molten resin into the cavity, and (D) a path communicating with the cavity by moving the movable core. Using a pressurized fluid injection unit installed at a position to be opened and closed, using a hollow molded product manufacturing apparatus, each of which (a) before the start of injection of the molten resin into the cavity, the movable core by the movable core moving means Moving, closing the injection part communicating with the cavity of the pressurized fluid, and holding the same at that position, (b) moving the movable core in one direction in the cavity by the movable core moving means after injecting the molten resin from the resin injection part. Moving, and opening the injection part communicating with the cavity of the pressurized fluid, (c) from the pressurized fluid injection part, at least the movable core surface, the cavity surface and the molded product surface formed by the movable core Pressurizing fluid into or out of the closed space defined by the movable core during or after moving the movable core, for a predetermined time during which the molded product is cooled, and maintaining a predetermined pressure, (d) molding the molded product into a mold And a step of discharging the pressurized fluid from the molded article after cooling inside the molded article, and then taking out the molded article from the mold.

The present invention also provides a hollow molded product obtained by injecting a molten resin from a resin injection part into a cavity of an injection molding die and then cooling and solidifying the molten resin in the cavity. ) At least one movable core disposed in the cavity and movable in one direction in the cavity;
(B) a movable core moving means for moving the movable core, (C) a resin injection section for injecting the molten resin into the cavity, and (D) a path communicating with the inside of the cavity by moving the movable core. Using a pressurized fluid injection unit installed at the position to be opened and closed, using a hollow molded product manufacturing device, respectively, (a) before the start of injection of the molten resin, move the movable core by movable core moving means, Closing the injection part communicating with the cavity of the pressurized fluid, and holding the injection part at that position, (b) moving the movable core in one direction in the cavity by the movable core moving means after injection of the molten resin from the resin injection part, And (c) opening at least two of the movable core surface, the cavity surface, and the molded product surface formed by the movable core from the pressurized fluid injection portion. A step of injecting a pressurized fluid into the closed space while the movable core is moving or after the stop, and maintaining the predetermined pressure for a predetermined time during which the molded product is cooled, and (d) after the molded product is cooled in the mold. And a step of discharging a pressurized fluid from a molded article and then removing it from a mold.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an apparatus for manufacturing a hollow molded product (also referred to as an injection molding die apparatus) according to the first invention of the present invention will be described in detail. An apparatus for manufacturing a hollow molded product according to the present invention is provided with a cavity, injects a molten resin into the cavity, and then cools and solidifies the molten resin in the cavity to produce a hollow molded product.
The manufacturing apparatus includes (A) at least one movable core disposed in the cavity and movable in one direction in the cavity, (B) a movable core moving means for moving the movable core, C) a resin injection section for injecting the molten resin into the cavity, and (D) a pressurized fluid injection section provided at a position where a path communicating with the cavity is opened and closed by movement of the movable core. I have.

In the cavity, at least one movable core can reciprocate (forward / backward) in one direction in the cavity and form a space (gap) between the inner surface of the cavity and the surface of the movable core. It is arranged to be. This space (gap) cools and solidifies the injected molten resin,
The movable core is moved (moved forward / backward) in one direction in the cavity by a moving means described later to form a molded article having a hollow portion inside. The number of movable cores provided in the cavity may be one, but may be two or more depending on the use, shape, structure, etc. of the hollow molded article. Even when two or more movable cores are provided in the cavity, each movable core is provided so as to be able to reciprocate in one direction in each cavity portion. In this case, the moving direction of each movable core is usually different. In the present invention, “one direction in the cavity” generally means a direction in which the cavity extends, and is preferably a direction along a direction in which the molten resin flows in the cavity.

In the apparatus for manufacturing a hollow molded product according to the present invention, the mold block, the cavity, the movable core disposed in the cavity, and the like are preferably prepared from a metal material.
Examples include carbon steel, alloy steel, ordinary steel, and special steel. The inner surface of the cavity, the surface of the movable core disposed in the cavity, and the like are preferably subjected to hard chrome plating or the like and mirror-finished for the purpose of preventing corrosion.

The space (gap) formed between the inner surface of the cavity and the surface of the movable core needs to be large enough that the movable core does not contact the inner surface of the cavity when the movable core moves. The movable core has a cross-sectional area obtained by cutting the cavity at a right angle to the moving direction of the movable core with respect to a sectional area obtained by cutting the cavity at a right angle to the moving direction of the movable core.
Preferably, the ratio is 1 to 0.9. If the ratio of the cross-sectional area is less than 0.1, the hollow ratio becomes too small,
Conversely, if the ratio exceeds 0.9, the residual wall thickness becomes too small, and in any case, a preferable hollow molded article cannot be obtained, which is not preferable.

The cross section of the movable core disposed in the cavity at a right angle to the moving direction has substantially the same shape in the moving direction of the movable core. The cross section when cut at right angles to the moving direction has the same shape in the moving direction of the movable core. With the same shape, even if the movable core is held by the molten resin in the cavity, the movable core can be retracted in the cavity by the movable core moving means. However, the cross section of the movable core cut at right angles to the moving direction may be changed to a range that does not hinder the movement of the movable core. Undercuts. The cross-sectional shape cut at a right angle to the length direction of the movable core is not particularly limited as long as it can move (forward / backward) in the cavity.
It can be elliptical, triangular, square, and the like. When two or more movable cores are provided, they do not all need to have the same shape, and can be changed according to the structure of the molded product.

The movable core can be moved (advanced / retracted) in the direction along the length of the cavity by moving means disposed outside the mold block of the injection molding apparatus. It is preferable that the sliding portion (the portion to be sealed) between the movable core and the mold block has no gap so that the molten resin does not leak. As for the shape of the sliding portion of the movable core with the mold block, the cross-sectional shape cut in the flow axis direction of the molten resin is similar to the cross-sectional shape of the cavity at the same position.

The moving (sliding) means of the movable core includes a fluid cylinder, an electric motor, a screw mechanism such as a ball screw, a cam mechanism, and the like. In the case of a fluid cylinder, a liquid such as hydraulic oil or a gas such as air may be used, and in the case of an electric motor, a fluid drive motor using a liquid such as hydraulic oil or a gas such as air, It may be an electric servomotor or the like. The movable core can be directly moved by a fluid cylinder, a fluid drive motor, an electric servomotor, or the like. Especially, a fluid cylinder etc. are suitable. When two or more movable cores are arranged in one injection mold,
It is preferable that all the moving means of the movable core be of the same type, but different types may be combined.

A fluid cylinder as a means for moving (sliding) the movable core is provided with a fluid cylinder connected to the outside of the mold block. (Opposite side) and can be operated by a mechanism equipped with a solenoid, a fluid pressure control valve, a flow control valve, and the like.

Regardless of the moving means of the movable core, it is preferable to select the axial force of the driving device in the range of 500N to 400KN. If the axial force of the driving device is less than 500N, the axial force is not enough and the shaft may be damaged when moving the movable core. If the axial force exceeds 400KN, the shaft becomes too expensive, Not preferred.

The apparatus for manufacturing a hollow molded product according to the present invention includes:
A resin injection unit for injecting the molten resin is provided in the cavity. Usually, a sprue portion or a runner portion is provided between the end of the heating cylinder of the injection molding die device and the mold cavity as a channel for flowing molten resin, and there are various types between the runner portion and the cavity. Gate part is provided. In some cases, the molten resin is directly injected into the cavity by a hot runner, a valve gate, or the like. In the present invention, these gate portions provided in the injection molding die apparatus are collectively referred to as a resin injection portion.

The apparatus for manufacturing a hollow molded product according to the present invention is provided with a pressurized fluid injection portion communicating with the cavity. The pressurized fluid injection unit is installed at a position that is opened and closed by moving the movable core in the cavity. That is, before injecting the molten resin into the cavity, the pressurized fluid injection unit moves the movable core to the most advanced end position by the movable core moving means, and injects the pressurized fluid communicating with the cavity into the cavity. Close the part and "close"
During the injection of the molten resin from the resin injection section into the cavity, or after the injection is completed, the movable core is moved in the direction along the length direction of the cavity by the movable core moving means. Immediately after the start, during the movement, or after the completion of the movement to the predetermined position, the injection portion communicating with the cavity of the pressurized fluid is provided in an “open” state.

A check valve or the like is arranged at the injection section of the pressurized fluid, and injection is performed from a pressurized fluid tank disposed at a position distant from the injection molding die apparatus through a metal or resin thin tube as a path. It is connected to the injection part of the pressurized fluid of the molding die apparatus.
When two or more movable cores are provided in one injection mold, the number of injection portions of the pressurized fluid is set to a number corresponding to the number of movable cores.

The pressurized fluid that can be used is preferably an inert fluid that is a gas or a liquid at normal temperature and does not react when injected into the molten resin. Specifically, nitrogen gas,
Carbon dioxide, air, helium gas and the like can be mentioned. Preferably, nitrogen gas and helium gas are used, and particularly preferably, nitrogen gas is used.

Next, the method for producing the hollow molded article of the second invention according to the present invention will be described in detail. In the method for manufacturing a hollow molded article according to the second invention of the present invention, the apparatus for manufacturing a hollow molded article (injection molding apparatus) described in detail above is used, and a resin injection section is formed in a cavity of an injection molding die. After the molten resin is injected from the cavity, the molten resin is cooled and solidified in the cavity to produce a hollow molded article having a hollow portion inside. The injection mold may be either a single-cavity mold or a multiple-cavity mold.

In the manufacturing method according to the second aspect of the present invention, in the first step, the mold of the injection molding apparatus is closed and placed in the cavity before starting injection of the molten resin into the cavity. The movable core is moved (slid) to the forward end position by the movable core moving means, and the distal end of the movable core is brought into contact with the injection portion of the pressurized fluid in which the check valve and the like are disposed, so that the cavity of the pressurized fluid is The injection part communicating with the inside is set to the "closed" state,
A space (gap) where the molten resin is injected is formed between the inner surface of the cavity and the surface of the movable core.

In the next step, the molten resin is injected from the resin injection section into the space (gap), and after the injection is completed, the movable core is moved by the movable core moving means in a direction along one direction in the cavity. Move (retreat). The amount of the molten resin injected into the cavity may be an amount (full shot) sufficient to manufacture a molded product. During the injection of the molten resin or after the injection is completed, the movable core is moved, and immediately after the start of the movement, during the movement, or after the movement to the predetermined position, the injection of the pressurized fluid into the cavity. Open the part. When a plurality of movable cores are provided, a timing (timing) for starting the movement (retreat) of each movable core, a timing for ending the movement of each movable core,
The moving speed and the like of each movable core may be the same or different, and the optimum conditions can be appropriately determined according to the characteristics of the resin used, the molding conditions, and the like.

In the third step, the pressurized fluid injection section is opened,
Immediately after the start (movement) of the movable core,
Alternatively, after the movement to the predetermined position, the pressurized fluid is injected into a closed space defined by at least two of the surface of the movable core, the surface of the cavity, and the surface of the molded product formed by the movable core. The pressurized fluid injected into the closed space maintains a predetermined pressure for a predetermined time until the molten resin is cooled and solidified. By holding the pressure for a predetermined time, the molten resin is kept pressed against the cavity surface, preventing the surface of the hollow part from being roughened and preventing the resulting injection molded product from warping or sinking. can do.

In order to maintain the pressurized fluid at a predetermined pressure for a predetermined time, (i) a method of maintaining a constant pressure while continuing to inject the pressurized fluid injected into the closed space, or (ii) ) A method of injecting the pressurized fluid into the closed space while simultaneously allowing the pressurized fluid to flow out of the mold and adjusting the injection speed of the pressurized fluid and the speed of the pressurized fluid to flow out of the mold may be maintained. The time required for the molten resin to cool and solidify depends on the temperature of the molten resin, the hollow ratio of the molded product, the remaining wall thickness, and the like. The pressure of the pressurized fluid is preferably a pressure that can maintain the state in which the molten resin is pressed against the cavity surface, and can be selected in the range of 1 to 30 Mpa.

In the final fourth step, after the molded article is cooled in the mold, the pressurized fluid is discharged from the molded article in the mold, and the molded article is taken out of the mold cavity. In order to discharge the pressurized fluid from the mold cavity from the mold cavity, a method of discharging the pressurized fluid from a path provided separately from the path for pressurized fluid injection is performed. In this case, the narrow tube, which is the path of (1), is made to flow backward, and a purge valve provided in the middle of the narrow tube is opened to discharge. When the pressurized fluid is maintained at a constant pressure, the pressurized fluid is simultaneously injected into the closed space described in (ii) and simultaneously discharged out of the mold. In the case of adopting a method of adjusting the flow rate to the pressurized fluid, the pressurized fluid is discharged from a path provided separately from the injection path. After discharging the pressurized fluid, open the mold and remove the molded product from the mold, the preparation for the next molding cycle is completed, and the mold can be closed to start the next molding cycle. it can.

According to the method for manufacturing a hollow molded article according to the second invention of the present invention, the timing of injection of a molten resin, movement (sliding) of a movable core, injection of a pressurized fluid, etc., when manufacturing a hollow molded article. Timing) can be selected in various ways, and examples of selectable modes are schematically shown in FIGS. 1A to 1E as timing charts.

In FIG. 1, a straight line indicates a time that elapses from the left side to the right side, and a length of the straight line indicates a length of the elapsed time. The left end of the straight line drawn on the right side of the section “Injection of molten resin” indicates the start of injection of the molten resin, and the right end of the same straight line indicates the completion of injection of the molten resin. In addition, the left end of the straight line drawn on the right side of the section “Injection of pressurized fluid” indicates the start of injection of the pressurized fluid, and the right end of the same straight line indicates the completion of injection of the pressurized fluid. Further, the left end of the straight line drawn on the right side of the section “movement of the movable core” means the start of the movement of the movable core, and the right end of the same straight line means the end of the movement of the movable core.

The resin applicable to the injection molding method of the present invention is not particularly limited, and may be a synthetic resin capable of injection molding, specifically, a thermoplastic resin, a thermoplastic elastomer, an alloy thereof, or a thermosetting resin. Examples of the thermoplastic resin include olefin resins such as polyethylene and polypropylene, styrene resins such as polystyrene, ABS resin and AS resin, vinyl resins, vinylidene chloride resins, acrylic resins such as polymethyl methacrylate, and fluorine resins. Resins, polyamide resins, polyester resins, polycarbonate resins, polyacetal resins, polysulfone resins, modified polyphenylene ether resins, and the like.

Various kinds of conventionally known resin additives can be added to the above-mentioned synthetic resin within a range that does not adversely affect the properties of the molded article. As resin additives, heat stabilizers, light stabilizers, coloring agents, lubricants, plasticizers,
In addition to foaming agents, ultraviolet absorbers, etc., inorganic fillers such as calcium carbonate, talc, mica, glass fiber,
Reinforcing materials such as whiskers can also be incorporated.

The hollow molded product according to the third invention which can be produced by the production method of the second invention of the present invention includes a cylindrical shape, a rod shape, a straight tube, a curved tube, a T-shaped tube, and a cross shape having a hollow portion inside. Examples include a pipe, a Y-shaped pipe, a modified U-shaped pipe in which a branch pipe is provided at the bottom of a U-shaped pipe, and a modified S-shaped pipe. The cross-sectional shape of the molded product when cut at a right angle to the flow axis direction of the molten resin is not particularly limited, and may be any shape such as a circle, an ellipse, a rectangle, and a polygon. The molded article does not need to have a hollow part in all parts, and may have a hollow part in a part of the molded article.

Applications of these hollow molded articles include a motor cooling system piping member, a motor intake manifold, an exhaust gas system piping member, a braking system hydraulic system piping member, etc. in the field of automobiles and auto cycles. In addition, refrigerant piping members of refrigerators in the electric and mechanical fields, and actuator piping members by fluid control, and the like can be mentioned. further,
Examples include water supply / hot water supply piping members, shower heads, gas piping members, and the like in the field of construction and building materials, and circulatory medical device piping members and respiratory medical device piping members in the medical field. Among them, a handle-shaped hollow molded product is particularly preferable.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings and manufacturing examples, but the present invention is not limited to the following description examples. In the following drawings, the same parts or the same components are denoted by the same reference numerals.

FIGS. 2 to 4 are schematic longitudinal sectional views showing an example of the apparatus for producing a hollow molded article according to the first invention of the present invention. A cylindrical molded article having a hollow portion therein can be produced. . The hollow molded product manufacturing equipment a1 has a cavity a3
A movable core a4 and a resin injection section c2 for injecting the molten resin a6 from the cylinder c1 of the injection molding machine into the cavity a3 are provided therein. The cross section of the movable core a4 cut at right angles to the length direction has the same shape at any cut position. A space (gap) a5 is formed between the inner surface of the cavity a3 and the surface of the movable core a4.
Then, the molten resin a6 is injected and cooled and solidified to form a molded product a7.

Mold block a2 of hollow molding product manufacturing apparatus a1
A movable core moving means for moving the movable core a4 in a direction substantially parallel to the direction along the length (extending) direction of the cavity a3, and a fluid cylinder b1 is provided outside the movable core a4. Inside the cavity a3, a pressurized fluid tank (not shown) is arranged outside the mold block a2 and away from the mold block a2. From the pressurized fluid tank, the pressurized fluid tank is loaded into the cavity a3 by a thin tube d1. An injection part d2 for injecting the pressurized fluid is provided. The injection part d2 of the pressurized fluid is installed at a position where the injection part d2 communicating with the cavity a3 is opened and closed by moving the movable core a4 within the cavity a3.

FIG. 2 shows a state in which the movable core a4 is moved to the forward end position to bring the tip of the movable core a4 into contact with the pressurized fluid injection section d2, and the pressurized fluid injection section d2 is closed to be in a "closed" state. Is shown. FIG. 3 shows that after injecting the molten resin a6 from the resin injection part c2 into the cavity a3, the movable core a4 is slightly retracted from the most advanced end position to make the injection part d2 "open", and the injection part d2 of the pressurized fluid.
This shows a state in which a pressurized fluid is injected into a closed space c5 formed by the distal end portion of the movable core a4 and the inner surface of the molded product a7.

FIG. 4 is a schematic longitudinal sectional view showing a state in which the movable core a4 has been retracted to the retracted end position by the fluid cylinder b1 as movable core moving means. Fluid cylinder b1
The movable core a4 can be controlled by equipping a combination of a solenoid, a fluid pressure control valve, and the like (not shown). By retreating the movable core a4 to the retreat end position, a hollow part a8 is formed in the molded product a7. The molded product a7 cooled and solidified in the mold can be discharged by opening the mold.

The hollow molded article according to the third invention of the present invention is as described above, and sectional views of various hollow molded articles are shown in FIGS. FIG. 5 shows a T-shaped tube, which can be manufactured by an injection molding die apparatus combining two movable cores. When combining two movable cores, one T-shaped horizontal bar (horizontal core) and one T-shaped vertical bar (vertical core) are combined at right angles to form a T-shape. After filling the cavity by injecting the molten resin from the resin injection section provided at one end of the horizontal core, the horizontal core starts retreating, and at the same time, pressurized fluid is injected from the forward end position side of the horizontal core. Start, start the retraction of the vertical core when the horizontal core reaches the portion of the vertical core, after the horizontal core and the vertical core reach the retreat end position, maintain the pressurized fluid at a predetermined pressure for a predetermined time, It can be manufactured by cooling and solidifying a molten resin.

FIG. 6 shows a cross-shaped tube, which can be manufactured by a hollow molded product manufacturing apparatus in which three movable cores are combined. When combining three movable cores, one long movable core (long core) and two short movable cores (short core) are combined and arranged in a cross shape.
After injecting the molten resin from the resin injection section provided at one end of the long core to fill the cavity, the retreat of the long core starts, and simultaneously, the injection of the pressurized fluid from the forward end position side of the long core starts. When the core reaches the portion of the short core, the retraction of the short core starts, and after the long core and the short core reach the retreat end position, the pressurized fluid is maintained at the predetermined pressure for a predetermined time to remove the molten resin. It can be manufactured by cooling and solidifying.

FIG. 7 shows a Y-shaped tube, which can be manufactured by a hollow molded product manufacturing apparatus in which three movable cores are combined. When three movable cores are combined, one (vertical core) is arranged at the vertical bar portion below the Y-shape with the V-shaped corner as the forward end position, and one at each of the left and right of the upper V-shape. (V core), each is arranged in a Y-shape in combination, and molten resin is injected from a resin injection portion provided at the tip of the vertical core (near the V corner on the Y-shape) to fill the cavity, The retraction of the vertical core and the two V cores is started at the same time, and the pressurized fluid injection port provided near the V on the Y-shape and closed by the tip of the vertical core is opened to start injection of the pressurized fluid. Then, after the vertical core and the two V cores reach the retreat end positions, the pressurized fluid can be maintained at a predetermined pressure for a predetermined time to cool and solidify the molten resin.

FIG. 8 shows a modified U-shaped tube, which can be manufactured by a hollow molded article manufacturing apparatus in which three movable cores are combined. When three movable cores are combined, one (branch core) is attached to the branch pipe at the bottom of the U-shape.
Place the curved surface of the U-shape as the forward end position, and
After bending cores (bending cores) are combined and arranged in a U-shape with a branch pipe, molten resin is injected from a resin injection portion provided at the tip of the branch core to fill the cavity, and then the branch core and two pieces are formed. At the same time, starts retreating the bent core and opens the pressurized fluid injection port provided on the U-shaped curved surface and closed by the tip of the branch core to start injection of the pressurized fluid.
After the bent cores reach the retreat end position, the pressurized fluid can be maintained at a predetermined pressure for a predetermined time to cool and solidify the molten resin.

FIG. 9 shows a piping member for water supply and hot water supply.
It can be manufactured by a hollow molded article manufacturing apparatus in which a plurality of movable cores are combined. When three movable cores are combined, one end of one long movable core (long core) is set to the forward end position, and two short bent cores (bent cores) are used.
Are arranged in combination as shown in FIG. After injecting the molten resin from the resin injection section provided near the long core to fill the cavity, start retreating the long core, open the pressurized fluid injection port closed by the tip of the long core, and pressurize Start injection of fluid, retreat two curved cores sequentially,
After the long core and the two bent cores reach the retreat end position, the pressurized fluid can be maintained at a predetermined pressure for a predetermined time to cool and solidify the molten resin.

[Production Example] FIG.
A mold for manufacturing a bathroom handle part shown in FIG.
A cylindrical movable core having a length of 600 mm and a diameter of 20 mm is provided in a mold cavity, and a nylon resin (manufactured by Mitsubishi Engineering-Plastics Co., trade name: Novamid 1015G30, glass fiber reinforced) Grade) is plasticized and melted at a cylinder temperature of 260 ° C., the injection pressure is 50 MPa, and the temperature is 100 ° C.
Into the mold cavity. After the injection of the molten resin into the mold cavity was completed, the retracting of the movable core was started. In this case, an axial force of 40 KN was applied to the movable core by a hydraulic device as a reaction force to oppose the pressure of the molten resin.

From the start of retreat of the movable core, a closed space formed by the tip of the movable core and the inner surface of the molded product
Injection of 20 MPa nitrogen gas was started, and after reaching the retracted end position of the movable core, the pressure of the nitrogen gas was increased to 7 MPa for 90 seconds.
After cooling, the nitrogen gas remaining in the hollow part of the molded product was discharged into the atmosphere by retracting the thin tube from the pressurized fluid injection part. The mold was opened, and the molded product was removed from the mold.

FIG. 11 is a schematic view for explaining the movement of the mold cavity and the movable core when the bathroom handle part shown in FIG. 10 is manufactured, and (i) injects the molten resin into the mold cavity a3. In the previous state, a state in which the pressurized fluid injection part d2 is closed by the movable core a4 is shown, and (ii) shows a state in which the molten resin a6 is injected into the mold cavity a3 from the resin injection part c2. (iii) is to retreat the movable core a4, inject a pressurized fluid from the pressurized fluid injection part d2 into the space created by the retreat of the movable core a4, and pressurize the pressurized fluid until the molded article a7 is cooled. (Iv) shows the pressurized fluid injection part d2 and the movable core a4 in the mold cavity a3.
, The pressurized fluid is discharged, and the state immediately before the molded product a7 is removed from the mold is shown.

The obtained molded article has a hollow grip portion,
The mounting part is solid, and the outer diameter cross-sectional area of the grip part is 30m
m, having a hollow section of 20 mm and a total length of 700 mm. There are no irregularities in the hollow part inside,
The molded product had a uniform remaining thickness and a beautiful appearance.

[0055]

The present invention has been described in detail above, and has the following particularly advantageous effects, and its industrial value is extremely large. 1. When using the apparatus for manufacturing a hollow molded product according to the present invention,
It is possible to produce a hollow molded article having excellent appearance characteristics free from jetting or the like by a short and stable cycle without being affected by the raw material resin used. 2. When using the apparatus for manufacturing a hollow molded product according to the present invention,
A hollow molded article having a desired hollow ratio or remaining wall thickness can be manufactured. 3. ADVANTAGE OF THE INVENTION According to the manufacturing method of the hollow molded article which concerns on this invention, the hollow molded article which has the hollow rate of a desired hollow part or the remaining wall thickness can be manufactured with high efficiency. 4. ADVANTAGE OF THE INVENTION According to the manufacturing method of the hollow molded article which concerns on this invention, a hollow molded article whose surface of a hollow part is smooth can be manufactured with high efficiency. 5. According to the method of manufacturing a hollow molded product according to the present invention, a hollow molded product having a branch structure such as a T-shaped tube, a cross-shaped tube, and a Y-shaped tube can be easily and inexpensively manufactured. 6. The hollow molded article according to the present invention can be used as a piping member in a wide field such as an automobile, an auto cycle field, an electric field, a mechanical field, a building material field, and a medical field.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing timing of injection of a molten resin, injection of a pressurized fluid, movement of a movable core, and the like.

FIG. 2 is a schematic longitudinal sectional view showing an example of the apparatus for manufacturing a hollow molded product according to the present invention, and shows a state in which an injection portion of a pressurized fluid is closed.

FIG. 3 is a schematic longitudinal sectional view showing a state in which a pressurized fluid is injected into a closed space formed by a pressurized fluid injection section, a distal end portion of a movable core, and an inner surface of a molded product.

FIG. 4 is a schematic longitudinal sectional view showing a state where the movable core is retracted to a retracted end position by a fluid cylinder.

FIG. 5 is a cross-sectional view of a T-shaped tube having a molded product.

FIG. 6 is a cross-sectional view of a cross-shaped pipe having a molded product.

FIG. 7 is a sectional view of a Y-shaped tube having a molded product.

FIG. 8 is a cross-sectional view of a modified U-shaped tube in which a molded product is formed.

FIG. 9 is a cross-sectional view of a piping member for supplying water / hot water to a molded product.

FIG. 10 is a side view of an example in which the molded article is a bathroom handle part.

FIG. 11 is a schematic diagram illustrating movement of a cavity and a movable core when manufacturing the bathroom handle part shown in FIG. 10;

[Explanation of symbols]

 a1: Hollow molded product manufacturing apparatus a2: Mold block a3: Cavity a4: Movable core a5: Space (gap) a6: Molten resin a7: Molded product a8: Hollow part b1: Fluid cylinder c1: Cylinder of injection molding machine c2 : Resin injection part d1: Thin tube d2: Pressurized fluid injection part

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Yoshihiro Chino 5-6-1, Higashi-Yawata, Hiratsuka-shi, Kanagawa Prefecture Inside the Technology Center of Mitsubishi Engineering-Plastics Co., Ltd. No. 6-2, Mitsubishi Engineering Plastics Co., Ltd. Technology Center (72) Inventor Kazuhiro Sakai 4-26 Odabuchi-cho, Toyokawa-shi, Aichi Pref. Kunitachi Die & Mold Co., Ltd. (72) Inventor Mitsuo Suzuki Aichi (72) Inventor Toshiyuki Suzuki 4-26 Odabuchi-cho, Toyokawa-shi, Aichi Fuku term (reference) 4F202 AG07 AG29 AR01 AR02 CA11 CB01 CK12 CK73 CK74 4F206 AG07 AG29 AR01 AR02 JA05 JL02 JM04 JM05 JN25 JN27 JQ81

Claims (11)

[Claims] An apparatus for manufacturing a hollow molded article by providing a cavity and injecting the molten resin into the cavity and then cooling and solidifying the molten resin in the cavity, wherein (A) the cavity is disposed in the cavity. And at least one movable core movable in one direction in the cavity; (B) a movable core moving means for moving the movable core; and (C)
A resin injection unit for injecting the molten resin into the cavity, and (D) a pressurized fluid injection unit installed at a position where a path communicating with the cavity is opened and closed by movement of the movable core,
A manufacturing apparatus for a hollow molded product, comprising: 2. The apparatus according to claim 1, wherein the cross section of the movable core cut at right angles to the moving direction is substantially the same in the moving direction of the movable core. 3. A sectional area of a cross section of the movable core cut at right angles to a moving direction of the movable core is 0.1 to 0.1 with respect to a cross sectional area of a cross section of the movable core cut at right angles to the moving direction of the movable core. Claim 1 or Claim 2 which is 0.9.
2. The apparatus for manufacturing a hollow molded product according to item 1. 4. The apparatus for manufacturing a hollow molded article according to claim 1, wherein the movable core moving means has an axial force of a driving device of 500 N to 400 KN. 5. The apparatus for manufacturing a hollow molded article according to claim 1, wherein the movable core moving means is a fluid cylinder. 6. The apparatus for manufacturing a hollow molded product according to claim 1, wherein the movable core moving means is an electric motor. 7. Injecting a molten resin from a resin injection portion into a cavity of an injection molding die, and then cooling and solidifying the resin in the cavity to produce a hollow molded product, wherein (A)
At least one movable core disposed in the cavity and movable in one direction in the cavity, (B) a movable core moving means for moving the movable core, and (C) a molten resin in the cavity. An apparatus for manufacturing a hollow molded article, which includes a resin injection section for injection and a pressurized fluid injection section installed at a position where a path communicating with the cavity by the movement of the movable core is opened and closed. Used, (a) before the start of injection of the molten resin into the cavity, moving the movable core by movable core moving means, closing the injection portion communicating with the cavity of the pressurized fluid, holding the position, (b) Moving the movable core in one direction in the cavity by the movable core moving means after injecting the molten resin from the resin injection section, and opening the injection section communicating with the cavity of the pressurized fluid, (c) pressurized fluid Injection part A pressurized fluid is injected into the closed space defined by at least two of the movable core surface, the cavity surface, and the molded product surface formed by the movable core during or after moving the movable core, and the molded product is cooled. Maintaining a predetermined pressure for a predetermined time, (d)
A method of manufacturing a hollow molded article, comprising: cooling a molded article in a mold, discharging a pressurized fluid from the molded article, and removing the molded article from the mold. 8. The pressurized fluid is an inert gas.
The method for producing a hollow molded article according to the above. 9. The hollow molded article according to claim 7, wherein the predetermined pressure of the pressurized fluid is determined by an inflow speed of the supplied pressurized fluid and an outflow speed of the pressurized fluid out of the mold. Manufacturing method. 10. A hollow molded product obtained by injecting a molten resin from a resin injection portion into a cavity of an injection molding die, and then cooling and solidifying the molten resin in the cavity.
(A) at least one movable core disposed in the cavity and movable in one direction in the cavity; (B) movable core moving means for moving the movable core; and (C) melting in the cavity. (D) a resin injection section for injecting the resin;
Using a pressurized fluid injection unit, which is provided with a pressurized fluid injection unit installed at a position where a path communicating with the cavity is opened and closed by movement of the movable core, and (a) before starting injection of molten resin Moving the movable core by the movable core moving means, closing the injection portion communicating with the cavity of the pressurized fluid, and holding the injection position, (b) the cavity by the movable core moving means after the molten resin is injected from the resin injection portion. Moving the movable core in one direction, and opening an injection portion communicating with the cavity of the pressurized fluid, (c) from the pressurized fluid injection portion, formed by the movable core surface, the cavity surface and the movable core A pressurized fluid is injected into the closed space defined by at least two of the molded product surfaces during or after the movable core is moved, and a predetermined pressure is maintained for a predetermined time during which the molded product is cooled. (D) after the molded article is cooled in the mold, discharging the pressurized fluid from the molded article, and taking out from the mold. A hollow molded article made of a thermoplastic resin. 11. A hollow molded article made of a thermoplastic resin is a handle-shaped molded article having an attachment portion at least at one end, wherein (i) the grip portion is hollow, and (ii) the outer diameter of the grip portion is reduced. (Iii) the ratio of the outer diameter to the length of the grip portion is 5 or more, and (i) the ratio of the area to the hollow sectional area is in the range of 0.1 to 0.9;
The thermoplastic resin molded product according to claim 10, wherein (v) the hollow portion has two or more openings, and (v) the mounting portion is solid.