JPH0994844A - Method and apparatus for making hollow molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a quality hollow molding inexpensively by ejecting gas from a gas ejection opening during molding. SOLUTION: The first mold 12 in which a recessed molding surface part 15 is formed and the second mold 14 in which a projected molding surface part 16 is formed are used. The second mold 14 is advanced, the first molding space is formed between the recessed molding surface 15 and the projected molding surface 16, and the first molding 2 is formed by injecting a resin from the first gate 24. The second mold 14 is brought back, and the second molding space is formed between the recessed molding surface part 15 and the projected molding surface part 16. Gas is ejected into the second molding space, and the resin is injected from the second gate 25 to form the second molding 3 which is integrated with the first molding 2 to make a hollow molding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow molded product manufacturing apparatus and a hollow molded product manufacturing method for manufacturing a hollow molded product.

[0002]

2. Description of the Related Art Conventionally, so-called blow molding, gas injection molding and the like have been generally used as a method for producing a hollow molded article, that is, a hollow molded article.

In blow molding, for example, a parison, which is a resin material formed in a cylindrical shape, is hung between molds that have been opened, and the top and bottom of the parison are cut off by mold clamping. By injecting (blowing) gas onto the parison, the parison is brought into close contact with the cavity surface (mold surface) of the mold to form a hollow molded product having a predetermined shape.

However, in such blow molding, for example, when forming a portion that largely projects from the cylindrical surface, the parisons come into contact with the cavity surface one after another with a time difference during blowing, and at the end portion. There is a problem that the wall thickness is locally reduced, and the difference in wall thickness between the parts in the same molded product becomes large. In addition, there is a problem that finishing work (trimming) for removing the burr on the outer peripheral surface is required for the cutting part of the mold and the parting line, which increases the number of finishing steps and increases the manufacturing cost. In this respect, a method of introducing a parison into the clamped mold to reduce burrs can be considered, but the mold structure becomes complicated, the manufacturing cost rises, and the problem is limited to simple shaped products. have. In addition, PE (polyethylene), PP (polypropylene), PPO (polypropylene oxide), ABS, etc. are usually used for blow molding, but the material used is blow molding only to prevent so-called drawdown. Has a problem limited to a specific quality (grade). Further, the blow molding pressure is usually about 6~10kg / cm ^2, the pressure is usually because extremely low as compared with the resin pressure of the injection molding is approximately 400~2000kg / cm ^2, deformation and the like It is apt to occur, it is difficult to improve the dimensional accuracy, and the surface condition is difficult to improve.

In the gas injection molding, for example, a gas is injected into the molding material before the molding material injected into the mold is completely solidified to form a gas passage (gas channel).
To grow a hollow part.

However, in such gas injection molding, the gas can be injected only into a portion having a thickness dimension of a predetermined value or more, so that there is a problem that the molding portion of the hollow portion is limited. In addition, the gas injection is performed within the limit that the gas does not break through the resin, and within the limit that the wall thickness of the resin around the gas channel can be secured at a certain level or more in all parts, so the hollow ratio is blown. It is lower than that of molding and has the problem that only about 20% can be secured. Further, since the resin is pressed against the cavity surface at a gas pressure of about 100 kg / cm ² , the dimensional accuracy is better than that of blow molding, but there is a problem that injection molding is inferior. Furthermore, in order to form a gas channel, a thick part is indispensable, and the gas inside the gas channel has high temperature, high pressure, high density, low thermal conductivity, and a large amount of heat storage. There is a problem that the cooling of the product becomes slow, the molding cycle becomes long, and it becomes difficult to improve the manufacturing efficiency.

[0007]

As described above, when manufacturing a hollow molded article, in blow molding, the difference in wall thickness between the parts in the same molded article increases depending on the shape, and at the same time, the blow molding becomes difficult. Since the molding pressure is low, it is difficult to improve the dimensional accuracy, it is difficult to improve the quality, and the number of man-hours for finishing the outer peripheral surface is increased, and the materials used are also limited, which causes the problem of increased manufacturing cost ing. Further, in the gas injection molding, the molding location of the hollow part is limited, the hollow ratio is low, it is difficult to improve the dimensional accuracy, and further, the cooling of the molded product is slow and the molding cycle is long, so it is difficult to improve the manufacturing efficiency. Have a problem with.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a hollow molded product manufacturing apparatus and a hollow molded product manufacturing method capable of efficiently manufacturing a high quality hollow molded product. To do.

[0009]

According to a first aspect of the present invention, there is provided a hollow molded article manufacturing apparatus, wherein a hollow molding surface portion having a concave shape is inserted into the hollow molding surface portion, and the first molding is performed between the concave molding surface portion. A convex molding surface portion having a convex shape provided so as to be able to advance and retract at an advancing position forming a space and a retracted position forming a second molding space between the concave molding surface portion, and the first molding space. A first gate communicating with and injecting a molding material, a gas injecting portion provided with a gas injection port for injecting gas into the second molding space, and a molding material communicating with the second molding space to inject a molding material And a second gate that operates.

Further, in this configuration, the molding material is injected from the first gate in a state where the convex molding surface portion is inserted into the concave molding surface portion to the forward position to form the first molding space. Form the body. Then, the convex molding surface is retracted to the retracted position to form the second molding space, and gas is injected from the gas injection port of the gas injection unit into the second molding space. In this state, the molding material is injected from the second gate,
A second molded body is integrally fused with the first molded body. In this state, a hollow molded article is obtained in which a hollow portion is secured by the pressure of the injected gas in at least a part between the first molded body and the second molded body.

An apparatus for manufacturing a hollow molded article according to claim 2 is
In the hollow molded article manufacturing apparatus according to claim 1, the gas injection part is provided so as to be capable of projecting from the convex molding surface part.

With this structure, the gas is injected at an appropriate position inside the second molding space.

An apparatus for manufacturing a hollow molded article according to claim 3 is
The hollow molded article manufacturing apparatus according to claim 2, wherein the gas injection unit fixes the position with respect to the concave molding surface portion in a state where the convex molding surface portion inserted in the concave molding surface portion moves from the forward position to the backward position. It is the one that was retained.

In this structure, when the convex molding surface portion inserted into the concave molding surface portion moves from the forward movement position to the backward movement position, the gas injection portion automatically projects into the second molding space. The structure is simplified and the manufacturing process is simplified.

An apparatus for producing a hollow molded article according to claim 4 is
The hollow molded article manufacturing apparatus according to claim 1, wherein the gas injection port is closed by the convex molding surface portion in a state where the convex molding surface portion is in the forward position, and the convex molding surface portion is in the retracted position. In this state, the opening is formed in the concave molding surface portion, which is located in the portion that opens into the second molding space.

In this structure, the gas injection part automatically opens in the second molding space, and the structure for projecting the gas injection part is not required. Therefore, the structure of the apparatus is simplified and the operation is improved. Stabilize.

A method for manufacturing a hollow molded article according to claim 5 is
A first mold provided with a concave molding surface part having a concave shape and a second mold provided with a convex molding surface part to be inserted into the concave molding surface part so as to be able to move back and forth are used to form the convex molding surface part into a concave shape. The molding material is injected into the first molding space formed between the molding surface portions while being inserted to a predetermined position of the surface portions, and then,
With the convex molding surface portion retracted to a predetermined position, a gas is injected into a second molding space formed between the molding surface portions, and then a molding material is injected into the second molding space. .

With this structure, a hollow molded product in which the hollow portion is secured by the pressure of the injected gas can be obtained.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the hollow molded article manufacturing apparatus and hollow molded article manufacturing method of the present invention will be described below with reference to the drawings.

In FIG. 2, reference numeral 1 denotes a hollow molded product, which is, for example, a grill guard of an automobile, and has a first molded product 2 having a substantially U-shaped cross section and a plate-shaped product. Second
It is formed into a tubular shape having a rectangular cross section in which the hollow portion 5 is formed by fusion-bonding the molded body 3 of FIG.

In FIGS. 1, 3 and 4, reference numeral 11 is a hollow molded article manufacturing apparatus. This hollow molded article manufacturing apparatus 11 includes a first mold 12 and this first mold. And a second mold 14 combined with 12. Further, the first mold 12 is formed with a groove-shaped concave molding surface portion 15 which is a cavity surface concavely provided in a rectangular cross section, and the second mold 14 is formed with this concave molding surface portion. A convex molding surface portion 16 protruding in a ridge shape which is a cavity surface to be inserted into and loosely fitted in 15 is formed.

The second mold 14 is driven to move back and forth by a hydraulic cylinder 18 so as to move between a forward movement position shown in FIG. 3, a backward movement position shown in FIGS. 1 and 4, and a mold opening position (not shown). It has become. Then, in the state where the second mold 14 is positioned at the forward position, the first molding space having a substantially U-shaped cross section, which is a cavity for forming the first molded body 2.
21 is formed, and a second molding space 22 having a substantially rectangular cross section, which is a cavity for forming the second molded body 3, is formed in a state in which the second mold 14 is located at the retracted position. It has become.

Further, the first mold 12 is provided with a first gate 24 and a second gate 25 connected to an injection molding machine (not shown) for injecting a resin material as a molding material. The first gate 24 communicates with the first molding space 21 and is opened and closed by the first valve 24a which is driven forward and backward. The second gate 25 communicates with the second molding space 22 and is driven back and forth.
And the third valve 25a, 25b. The third valve projects into the first molding space 21 and secures a passage of the resin material that penetrates the first molded body 2.

Further, the second mold 14 is formed with a through hole 26 which opens to the front end face, and a nozzle pin 27 as a gas injection portion is inserted into this through hole 26. Then, the nozzle pin 27 is driven to move back and forth separately from the second mold 14, and the second molding space 22 is kept in a state where the second mold 14 is located at the retracted position.
It is possible to project to. Also, this nozzle pin 27
In the shape of a double pin having an annular gas passage, a gas injection port 28 opening to the outer peripheral surface is formed in the vicinity of the tip, and at the tip, the front end surface of the convex molding surface portion 16 is formed. It becomes flush with and closes the through hole 26, that is, the gas injection port 28 (seal).
A possible lid 29 is formed.

Next, a method of manufacturing the hollow molded product 1 using the hollow molded product manufacturing apparatus 11 will be described. First, as shown in FIG. 3, the second mold 14 is moved to the forward position to move the first mold 14 to the first position.
Of the nozzle pin 27, the gas injection port 28 of the nozzle pin 27 is closed, the first valve 24a is opened to open the first gate 24, and the second valve and the third valve 25a,
5b is closed.

In this state, when a resin material is injected from the injection molding machine, the resin material is injected into the first molding space 21 through the first gate 24 and the first molded body 2 is formed. .

Then, after the first molded body 2 is cured,
As shown in FIG. 4, the second mold 14 is retracted to the retracted position to form the second molding space 22. At this time, the front end surface of the convex molding surface portion 16 is flush with the end surface of the first molded body 2, and this portion becomes a parting line. Further, the nozzle pin 27 is retracted to a predetermined position separated from the parting line by a predetermined dimension so that the gas injection port 28 is opened in the second molding space 22, and the first valve 24a is closed. The first gate 24 is closed. In this state,
Gas is injected from the gas injection port 28 into the second molding space 22.

Next, with the pressure in the second molding space 22 increased to a predetermined value, as shown in FIG. 1, the second valve and the third valve 25a, 25b are opened to open the second gate. Open 25, and from this second gate 25 to the second molding space 22
The resin material is injected into. Then, since the pressure in the second molding space 22 is increased by the gas, the injected resin material is held along the front end surface of the convex molding surface portion 16, and the second molding body 3 in plate shape is held. Is formed, and both ends of the second molded body 3 are welded to the ends of the first molded body 2,
A hollow molded article 1 which is a composite body of the first molded body 2 and the second molded body 3 is formed.

Further, the injection pressure of the resin material from the second gate 25 is set to be slightly lower than the injection pressure of the resin material from the first gate 24, and the gas pressure against it is set to a relatively low level. It can be suppressed. In particular, the second molded body 3
When the outer surface of the second molded body 3 is a surface to be attached to another member or in a position where it is not visible, this method is easy to adopt because the allowable range of appearance quality of the second molded body 3 is wide. This is because it is preferable that the gas pressure is low in view of the load on the gas pressurizer and measures against gas leakage.

Then, with the nozzle pin 27 retracted into the second mold 14, the second mold 14 is retracted to the mold open position, and an unillustrated ejection pin or the like is operated to form a hollow molded product. I'm supposed to take out 1.

Further, according to the present embodiment, there is no need for a step of stretching the once injected resin material or a step of cutting off the injected resin material, unlike the blow molding, and unlike the gas injection molding, There is no need to inject a gas into the injected resin material, and the first and second molded bodies 2 and 3 that form the hollow molded product 1 can be molded into the molding spaces 21 and 22 by using an injection machine. It can be formed by injection. Therefore, there are few restrictions on the resin material, the molding cycle can be shortened, and the peripheral finishing work such as the work for removing the surface burrs can be reduced, and the manufacturing cost can be reduced.

Further, since the resin material can be formed by injection, by increasing the molding pressure, the dimensional accuracy can be improved, the surface condition can be improved, and the quality of the molded product can be improved.

Further, since the hollow molded product 1 in which the hollow portion 5 is secured by the pressure of the injected gas can be manufactured and there is no step of stretching the resin material, the hollow ratio can be made constant and the convex molding surface portion 16 can be formed. The hollowness can be freely set by the moving dimension.

The first and second molds 12, 14 are
Since only a simple advancing / retreating operation is required, the molding cycle can be shortened, the die driving device is not complicated, and the manufacturing cost can be reduced.

Further, since the nozzle pin 27 is provided in the second mold 14 so as to be capable of projecting and retracting, the gas can be injected to an appropriate position inside the second molding space 22, and the nozzle pin 27 can be retracted to form a hollow shape. The protrusion of the molded product 1 can be facilitated.

In the above embodiment, the nozzle pin
The nozzle pin 27 can be fixedly provided at a fixed position on the second mold 14 side, although the nozzle 27 is provided so as to be retractable from the second mold 14. That is, as shown in FIGS. 5 and 6, the nozzle pin 27 can be fixed at a position where the lid 29 closes the gas injection port 28 in a state where the second mold 14 is positioned at the forward position.

That is, as shown in FIG. 5, the second mold
With the nozzle 14 positioned at the forward position and the nozzle pin 27 buried in the second mold 14, the resin material is injected from the first gate 24 as in the first embodiment shown in FIG. To form the first molded body 2. Then, after cooling the first molded body 2, as shown in FIG. 6, the second mold 14 is positioned at the retracted position, and the front end face of the convex molding surface portion 16 is aligned with the parting line to form the second mold 14. A molding space 22 is formed. In this state, since the nozzle pin 27 is fixed to the mold part that is unrelated to the movement of the convex molding surface portion 16, it remains at a fixed position in the second molding space 22. Then, gas is injected from the gas injection port 28 of the nozzle pin 27 into the second molding space 22, and subsequently, the resin material is injected from the second gate 25 to form the second molded body 3, The hollow molded article 1 can be formed by fusion-bonding and integrating with the first molded body 2.

Then, according to the second embodiment,
When the second mold 14 is retracted from the forward position to the retracted position, the nozzle pin 27 automatically projects into the second molding space 22, so that the structure of the device can be simplified and the manufacturing process can be simplified. It is possible to improve the manufacturing efficiency.

Further, as in the third embodiment shown in FIGS. 7 to 10, a gas injection portion 31 is provided at the longitudinal end portion of the first mold 12 and the wall portion 32 of the concave molding surface portion 15 is provided. It is also possible to form the gas injection port 33 opening to the. Further, this configuration forms a hollow molded product 1 having a long longitudinal dimension L and having one end opened, and a convex molding surface portion 16 is slidably contacted with the wall portion 32. The gas injection port 33 is
In a state where the convex molding surface portion 16 is in the advanced position, the convex molding surface portion 16 is closed by the convex molding surface portion 16 and in a state where the convex molding surface portion 16 is in the retracted position, a portion which opens into the second molding space 22 The opening is formed at the position.

Therefore, in the third embodiment, as shown in FIG.
And as shown in FIG. 8, the convex molding surface portion of the first mold 12
16 is positioned at the forward position to form the first molding space 21 and close the gas injection port 33. Further, the first valve 24a is opened to open the first gate 24, and the second valve and the third valves 25a and 25b are closed. In this state, when the resin material is injected from the injection molding machine, the resin material passes through the first gate 24 and the first molding space 21.
And the first molded body 2 is formed.

Then, after the first molded body 2 is cured,
As shown in FIG. 9, the second mold 14 is retracted to the retracted position to form the second molding space 22. In this state, the gas injection port 33 opens, and gas is injected from the gas injection port 33 into the second molding space 22.

Then, as shown in FIG. 10, the second valve and the third valve 25a, 25b are opened to open the second gate.
25 is opened, and a resin material is injected from the second gate 25 into the second molding space 22 to form a plate-shaped second molded body 3
Is formed and is welded to the end of the first molded body 2 to form the hollow molded product 1.

In addition, in the third embodiment, the gas injection port 33 can be automatically opened and closed with the movement of the convex molding surface portion 16, and the structure for projecting the gas injection portion 31 is not required. The structure can be simplified, the operation can be stabilized, and the manufacturing efficiency can be improved. Further, in the case of forming a hollow molded product 1 having a long hollow portion 5 with one end opened, a long die is inserted into the hollow portion 5 and is formed by a single injection molding. Compared with, the moving distance of the mold (drawing stroke) becomes too large and the mold is easily bent or damaged, and there is no problem that the hydraulic cylinder does not operate stably, and the inside becomes a vacuum and the mold is released. The hollow molded article 1 can be easily manufactured without causing a problem such as failure.

Further, as in the case of the fourth embodiment shown in FIGS. 11 to 14, when the hollow molded product 1 having a long longitudinal dimension L and both ends thereof being open is formed, the third embodiment is also used. The hollow molded article 1 can be easily manufactured as in the embodiment.

Although the resin material is injected from the second gate 25 after the gas is injected in the above embodiment, the gas may be injected at the same time as the injection.

[0046]

According to the hollow molded article manufacturing apparatus of the first aspect, the work of stretching the injected molding material, the work of cutting off the injected molding material, and the operation of injecting gas into the injected molding material. Since the first and second molded bodies constituting the hollow molded article can be formed by injecting the molding material into each molding space, there is less limitation on the molding material, the molding cycle can be shortened, and the surface can be shortened. The work of removing burrs can be reduced, and the manufacturing cost can be reduced.
Further, since the molding material can be formed by injection, by increasing the molding pressure, the dimensional accuracy can be improved, the surface condition can be improved, and the quality of the molded product can be improved. Furthermore, it is possible to manufacture a hollow molded product in which the hollow part is secured by the pressure of the injected gas, and there is no step of stretching the molding material, so that the hollow ratio can be made constant, and the moving size of the convex molding surface part allows the hollow ratio to be increased. Can be set freely.

According to the hollow molded article manufacturing apparatus of the second aspect, in addition to the effect of the first aspect, since the gas injection portion is provided so as to project from the convex molding surface portion, the inside of the second molding space is formed. The gas can be injected at an appropriate position in.

According to the hollow molded article manufacturing apparatus of the third aspect, in addition to the effect of the second aspect, when the convex molding surface portion inserted in the concave molding surface portion moves from the forward movement position to the backward movement position, it is automatically operated. Since the gas injection part protrudes into the second molding space, the structure of the apparatus can be simplified, the manufacturing process can be simplified, and the manufacturing efficiency can be improved.

According to the hollow molded article manufacturing apparatus of the fourth aspect, in addition to the effect of the first aspect, the gas injection port is closed by the convex molding surface portion in a state where the convex molding surface portion is in the forward position. In addition, since the convex molding surface portion is located at the portion that opens in the second molding space in the retracted position and the opening is formed in the concave molding surface portion, the gas injection unit automatically operates in the second molding space. The structure for opening the gas injection part and for projecting the gas injection part is not necessary, the structure of the device can be simplified, the operation can be stabilized, and the manufacturing efficiency can be improved.

According to the method for manufacturing a hollow molded article according to the fifth aspect, it is necessary to stretch the injected molding material, cut off the injected molding material, and inject gas into the injected molding material. Since the first and second molded bodies constituting the hollow molded product can be formed by injecting the molding material into each molding space, there are few restrictions on the molding material, the molding cycle can be shortened, and the surface burrs can be reduced. It is also possible to reduce the work of removing, etc., and reduce the manufacturing cost. Further, since the molding material can be formed by injection, by increasing the molding pressure, the dimensional accuracy can be improved, the surface condition can be improved, and the quality of the molded product can be improved. Furthermore, it is possible to manufacture a hollow molded product in which the hollow part is secured by the pressure of the injected gas, and there is no step of stretching the molding material, so that the hollow ratio can be made constant, and the moving size of the convex molding surface part allows the hollow ratio to be increased. Can be set freely.

[Brief description of drawings]

FIG. 1 is an explanatory view of a manufacturing process following FIG. 3 showing an embodiment of a hollow molded article manufacturing apparatus of the present invention.

FIG. 2 is a cross-sectional view of the above hollow molded article.

FIG. 3 is an explanatory diagram showing a manufacturing process same as above.

FIG. 4 is an explanatory view showing the manufacturing process following FIG. 1 above.

FIG. 5 is an explanatory diagram of a manufacturing process according to the second embodiment of the present invention.

FIG. 6 is an explanatory view showing the manufacturing process following FIG. 5 above.

FIG. 7 is an explanatory diagram of a manufacturing process according to the third embodiment of the present invention.

8 is an explanatory view showing a cross section taken along the line CC of FIG.

FIG. 9 is an explanatory view showing the manufacturing process following FIG. 8 above.

FIG. 10 is an explanatory view showing the manufacturing process following FIG. 9 above.

FIG. 11 is an explanatory diagram of a manufacturing process according to the fourth embodiment of the present invention.

FIG. 12 is an explanatory view showing a DD cross section of FIG. 11 of the above.

FIG. 13 is an explanatory diagram showing the manufacturing process following FIG. 12 above.

FIG. 14 is an explanatory diagram showing the manufacturing process following FIG.

[Explanation of symbols]

 1 Hollow Molded Product 11 Hollow Molded Product Manufacturing Device 12 First Mold 14 Second Mold 15 Concave Molded Surface 16 Convex Molded Surface 21 First Molding Space 22 Second Molding Space 24 First Gate 25 Second gate 27 Nozzle pin as gas injection part 31 Gas injection part 28, 33 Gas injection port

Claims (5)

[Claims] 1. A concave molding surface portion having a concave shape, and a second molding between the concave molding surface portion and an advance position which is inserted into the concave molding surface portion and forms a first molding space between the concave molding surface portion and the concave molding surface portion. A convex molding surface portion that is provided so as to be able to move forward and backward at a retracted position that forms a molding space, and a molding material that is in communication with the first molding space and injects a molding material.
A gate, a gas injection part provided with a gas injection port for injecting gas into the second molding space, and a second gas injection part that communicates with the second molding space and injects a molding material.
And a gate for manufacturing the hollow molded article. 2. The hollow molded article manufacturing apparatus according to claim 1, wherein the gas injection section is provided so as to be able to project from the convex molding surface section. 3. The gas injecting portion is fixedly held in position with respect to the concave molding surface portion in a state in which the convex molding surface portion inserted into the concave molding surface portion moves from the forward movement position to the backward movement position. The hollow molded article manufacturing apparatus according to claim 2. 4. The gas injection port is closed by the convex molding surface portion in a state where the convex molding surface portion is in the forward position, and
The hollow molded article manufacturing apparatus according to claim 1, wherein the convex molding surface portion is located at a portion that opens to the second molding space in the retracted position and is formed in the concave molding surface portion. . 5. A first mold provided with a concave molding surface portion having a concave shape, and a second mold provided with a convex molding surface portion which is inserted into the concave molding surface portion so as to be capable of advancing and retracting, and this convex shape is used. With the molding surface portion inserted to the predetermined position of the concave molding surface portion, the molding material is injected into the first molding space formed between these molding surface portions, and then the convex molding surface portion is retracted to the predetermined position. A method for producing a hollow molded article, comprising injecting a gas into a second molding space formed between these molding surface portions, and then injecting a molding material into the second molding space.