JPH1016039A - Method for blow-molding double-structure body and blow molding mold for double-structure body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the defective molding of a double-structure body by blow molding by flexibly supporting a part which early contacts the molding mold of a parison. SOLUTION: A parison 3 extruded from a die 2, the lower end of which is closed at the beginning of its formation, is arranged between an open outer mold 4 and an inner mold 5 which is inserted into the outer mold 4. Air of 2.0-5.0kg/cm<2> is ejected to a part which is brought into contact early with the parison 3 of the outer mold 4 and the inner mold 5. A part which ejects air in the outer mold 4 is the peripheral part 8 of a molding surface 6 and is the corner part 9 of the molding surface 6 projected on the outer mold side in the inner mold 5d. With the progress of mold clamping, extremely thin air layers 10 are formed by the ejection of air between the peripheral part 8 of the outer mold 4 and the parison 3 and between the corner part 9 of the inner mold 5, and the parison 3 in this part is supported not in a fixed state but flexibly by the air layer 10 against the outer mold 4, the inner mold 5, and the concerned part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blow molding method for blow molding a double structure by clamping a parison, which is a cylindrical plastic, and blow molding the double structure by clamping a parison. It relates to a blow mold.

[0002]

2. Description of the Related Art For example, a shallow drawn plastic double structure 1a as shown in FIG. 14 is conventionally formed by blow molding. In addition, a molding method by blow molding is also performed on a part of the deep drawn plastic double structure 1b as shown in FIG. This blow molding method for deep drawing will be described with reference to the steps shown in FIGS. This means that the parison 3, which is a cylindrical plastic extruded from the die 2,
A method in which the molding surface is clamped by a molding die composed of an outer die 4 and an inner die 5 that can be sucked, air is injected into the parison 3, pressed against the molding surface of the molding die, and molded by suctioning the molding surface. It is.

FIGS. 15 and 16 show an initial step of molding, and the parison 3 extruded from the die 2 is a parison 3
The lower end is sealed at the early stage of the formation of the dies, and is placed between the opened outer die 4 and the inner die 5. FIGS. 17 and 18 show the initial state of the mold clamping process.
The parison 3 hits the molding surface of the outer peripheral portion 8 and the parison 3 hitting the parison 3 is fixed. In the inner mold 5, first, the parison 3 hits a molding surface protruding toward the outer mold 4,
The protruding molding surface and the parison 3 hitting it are in a fixed state.

FIGS. 19 and 20 show a middle stage of the mold clamping process. The parison 3 is brought into close contact with the molding surface of the outer mold 4 and the molding surface of the inner mold 5 by the internal air pressure which rises as the mold clamping progresses. It is stretched and molded in the direction in which it does. FIG.
1, FIG. 22 shows the state of the final stage of the mold clamping process, and a double structure 1a as shown in FIG. The needle tube 11 built in the inner mold 5 is inserted into the parison 3 slightly before the stage in FIG. 21, and the parison 3 is securely attached to each molding surface of the outer mold 4 and the inner mold 5. Air is injected into 3 and the internal air pressure is increased.

[0005]

However, in the above-mentioned conventional method of blow molding a double structure, there is no problem if the double structure 1a is shallow drawn and shallow. As the depth is increased, molding failure occurs on the peripheral side, and there is a problem that the molding is difficult or almost impossible to mold with the deep drawn deep double structure 1b as shown in FIG. In this specification,
The deep drawing refers to a drawing having a depth of more than に 対 し て with respect to the frontage of the opening, and a drawing having a depth smaller than that is referred to as a shallow drawing, but the shape is not limited to this.

That is, when the mold is moved from the initial state of the mold clamping process to the later state through the middle stage, the parison 3 fixed to the outer peripheral portion 8 of the outer mold 4 side has the peripheral wall portion of the molding surface. , And this portion is extremely thin, or is broken if the degree of stretching is large. Also, on the inner mold 5 side, the part of the parison 3 which first comes into contact with the protruding molding surface is relatively thick, and since this part is in a fixed state, the side wall part on the molding surface of the inner mold 5 becomes thin, In extreme cases, this part will break.

Accordingly, the present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a method of blow molding a double structure having few molding defects. It is an object of the present invention to provide a blow molding method for a double structure, and to provide a blow mold capable of easily performing the blow molding method.

[0008]

Means for Solving the Problems In order to achieve the above object, the invention of claim 1 is to provide a method in which, during a mold clamping period in which a parison is clamped by a molding die, a portion of the parison that comes into contact with the molding die early is used. Means for flexibly supporting and clamping the relevant portion of the molding die is employed.

By adopting the above-mentioned means, the parison of the portion which comes into early contact with the molding die is not fixed to the portion of the molding die but is supported flexibly, so that the parison can be maintained as the mold clamping proceeds. Will be stretched sequentially.

In order to achieve the above object, the invention according to claim 2 is characterized in that, during a mold clamping period in which the parison is clamped by the molding die, a portion of the parison that comes into contact with the molding die at an early stage is formed between the molding die and the parison. Means for forming a thin gas layer by gas during the mold clamping period and clamping the mold is adopted.

[0011] By adopting the above means, the parison of the portion which comes into contact with the molding die early is supported by the gas layer in a flexible manner rather than being fixed to the relevant portion of the molding die. The parison will be gradually extended.

According to a third aspect of the present invention, there is provided a blow mold for blow-molding a double structure by clamping a parison, wherein the parison comes into contact with the parison early in a mold clamping period. Means having gas jetting means for jetting a gas to the molding surface.

By adopting the above-mentioned means, a gas layer is formed by the gas jetting means between the parison at a portion which comes into contact with the mold early and the portion of the mold, and the parison at the portion is not fixed but flexible. Can be supported.

According to a fourth aspect of the present invention, there is provided a blow molding die having a double structure according to the third aspect, wherein a plurality of gas ejection means are configured to be capable of supplying gas. A means for forming a small hole is adopted.

By employing the above-mentioned means, the function according to claim 3 can be exhibited by a simple configuration using small holes.

According to a fifth aspect of the present invention, there is provided a blow molding die having a double structure according to the third aspect, wherein the gas blowing means is configured to be capable of supplying gas. Means composed of sintered metal having a certain characteristic is employed.

By adopting the above means, the function according to claim 3 can be exhibited by the structural characteristics of the sintered metal, and a uniform gas layer can be formed.

[0018]

Next, an embodiment of the present invention will be described with reference to the drawings. Embodiment 1 FIG. The first embodiment is a double structure 1 made of plastic such as polypropylene as shown in FIGS.
The present invention relates to a blow molding method for blow molding a and 1b. The double structure 1a in FIG. 3 has a shallow drawing shape with a depth to the frontage of the opening of about 1/4 to 1/6, and the double structure 1a in FIG. / 4-3 /
5 is a deep drawing shape. These double structures 1a,
1b can be similarly blow-molded by replacing the outer mold 4 or the outer mold 4 and the inner mold 5. The drawing of the forming step shows the case of a deep drawing.

In this blow molding method, as shown in FIGS. 5 and 6, a parison 3 which is a cylindrical plastic extruded from a die 2 is clamped by a molding die composed of an outer die 4 and an inner die 5, and the parison 3 is formed. This is a method in which air is injected into the inside and pressed against the molding surface 6 of the molding die. The outer mold 4
The molding surface 6 of the inner mold 5 and the molding surface 6 of the inner mold 5 have a suction structure capable of suctioning. The outer peripheral portion 8 of the molding surface 6 of the outer mold 4 and the corner 9 of the molding surface 6 of the inner mold 5 that are in contact with the parison 3 are provided with a structure capable of blowing air. The air blowing structure may be a means (not shown) for guiding a hose or the like from the outside to a portion requiring air blowing to blow out a small amount of air. (Note that the molding die shown in FIG. 12 or 13 can be used for this molding die.) FIGS. 5 and 6 show the initial steps of molding, and the parison 3 extruded from the die 2 is formed in the early stage of its formation. Lower end 7
Is disposed between the closed outer mold 4 and the inner mold 5 inserted into the outer mold 4.

FIGS. 1 and 2 show the initial state of the mold clamping process. A portion of the outer mold 4 and the inner mold 5 where the parison 3 comes into contact early is about 2.0 to 5.0 kg per square centimeter. The air is blown out toward the parison 3 side. The portion of the outer mold 4 from which air is blown is the outer peripheral portion 8 of the molding surface 6 and the inner mold 5
Are the corner portions 9 of the molding surface 6 protruding toward the outer mold 4 side. As the mold clamping progresses, an extremely thin air layer 10 is formed between the outer peripheral portion 8 of the outer mold 4 and the parison 3 and between the corner 9 of the inner mold 5 and the parison 3 by jetting air. Of the outer mold 4 and the inner mold 5 is supported by the gas layer 10 not in a fixed state but with flexibility.

FIGS. 7 and 8 show the middle stage of the mold clamping process. The parison 3 is formed by the internal air pressure which rises with the progress of the mold clamping and the molding surface 6 of the outer mold 4 and the molding surface 6 of the inner mold 5. It is stretched in the direction in which it comes into close contact with and is molded. At this time, the parison 3 is elastically supported by the air layer 10 formed by the air ejected from the outer mold 4 and the inner mold 5, so that the parison 3 is sequentially expanded. FIGS. 9 and 10 show the final stage of the mold clamping process, in which a double structure 1a, 1b as shown in FIGS. Shortly before the stage shown in FIG. 9, the ejection of air is stopped,
The needle tube 11 built in the inner mold 5 is pierced into the parison 3, and 6.0 to 7.0 k per square centimeter in the parison 3.
g of air is fed in, and a vacuum is applied to the molding surface 6 of the outer mold 4 and the molding surface 6 of the inner mold 5 to adsorb the parison 3 to the molding surface 6. The parison 3 is securely adhered to the molding surface 6.

FIG. 11 shows the transition of the pressure state of the gas layer 10, the internal pressure of the parison 3, and the vacuum (vacuum pressure) with the elapsed time of the mold clamping step on the horizontal axis and the pressure on the vertical axis. In FIG. 11, a indicates the pressure of the gas layer 10, b indicates the internal pressure of the parison 3, and c indicates the vacuum (vacuum pressure).

According to this blow molding method, the parison 3 is formed on the outer mold 4 side by the flexible support by the gas layer 10 when the mold is advanced from the initial state to the middle state in the mold clamping step. 6 along the peripheral wall portion 12. Therefore, it is almost impossible for this portion to be extremely thin or to be broken due to an excessively large degree of stretching. Also, on the inner mold 5 side, the protruding corner 9 of the molding surface 6 and the parison 3 do not become thick due to the flexible support of the gas layer 10, and thus the molding surface of the inner mold 5 is formed. The parison 3 near the side wall portion 13 in 6 does not become thin or break. Accordingly, a blow molding method for the double structures 1a and 1b with less defective products and a good yield is provided. This blow molding method is particularly effective for a deeply drawn double structure 1b which cannot be formed by the conventional blow molding as shown in FIG. The heavy structure 1a is also effective in improving the yield as compared with the conventional blow molding. In addition, this blow molding method
Naturally, the present invention can be applied to plastics other than polypropylene.

Embodiment 2 FIG. The second embodiment relates to a blow mold for performing the blow molding method described in the first embodiment. FIG. 12 is a sectional view showing the blow mold. Note that the same components as those described in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and description thereof will be omitted.

The molding die according to the second embodiment is characterized in that it has gas ejection means for ejecting gas to the molding surface 6 at the portion where the parison 3 comes into contact early in the mold clamping period. . That is, the air distribution pipes 14 are respectively provided inside the outer mold 4 and the inner mold 5 which constitute the forming dies. The inlet end of each air distribution pipe 14 is opened outside the mold as a connection port, and an air supply hose 15 is connected to each.
The air distribution pipe 14 of the outer mold 4 applies approximately 2.0 to 5.0 kg of air per square centimeter to the outer peripheral portion 8 of the molding surface 6 with which the parison 3 comes into contact in the initial stage of mold clamping.
It communicates with a plurality of small holes 16 opened in the outer peripheral portion 8 of the molding surface 6 so as to be ejected toward the side. The air distribution pipe 14 of the inner die 5 has 2.0 to 5.0 kg per square centimeter at the corner 9 of the molding surface 6 protruding toward the outer die 4 where the parison 3 comes into contact in the initial stage of mold clamping. The air is communicated with a plurality of small holes 16 opened in the corner portion 9 so as to blow out a certain amount of air toward the parison 3. Each small hole 1 of outer mold 4 and inner mold 5
Reference numeral 6 denotes a hole having a radius of about 0.5 mm, which jets air to form a very thin air layer 10 between the parison 3 and the outer die 4 and the inner die 5.

The outer die 4 and the inner die 5 are provided with small suction holes 18 on their molding surfaces 6 for applying a vacuum for adsorbing the parison 3 to the molding surface 6 by a vacuum supply hose 17. I have. Shortly before the final stage of the mold clamping process, the inner die 5 has a built-in needle tube 11 that pierces the parison 3 and sends about 6.0 to 7.0 kg of air per square centimeter into the parison 3. I have. By using the blow mold having such a configuration, the blow molding method described in Embodiment 1 can be easily performed.

That is, when the process proceeds from the initial state of the mold clamping process to the middle state, the small holes 1 of the outer die 4 and the inner die 5 are formed.
The parison 3 is made to be in a flexible support state by the gas layer 10 by blowing air out of the outer mold 4, and the parison 3 is gradually extended along the peripheral wall portion 12 of the molding surface 6 on the outer mold 4 side. Therefore, this part becomes extremely thin,
The degree of stretching is too large to be almost broken. Also, on the inner mold 5 side, the corner 9 of the protruding molding surface 6 and the parison 3 do not become thicker due to the flexible support of the gas layer 10, so that the inner mold 5 does not become thicker. The parison 3 of the side wall portion 13 on the molding surface 6 does not become thin or break. Therefore, the blow molding die of the double structures 1a and 1b having less defective products and having a good yield can be obtained. This blow mold is particularly effective for a deep drawn double structure 1b that cannot be formed by the conventional blow molding as shown in FIG. The double structure 1a is also effective in improving the yield as compared with the conventional blow molding die.

Embodiment 3 The third embodiment also relates to a blow mold for performing the blow molding method described in the first embodiment. FIG. 13 is a sectional view showing the blow mold. Note that the same components as those described in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and description thereof will be omitted.

The molding die according to the third embodiment has gas ejection means for injecting gas to the molding surface 6 where the parison 3 comes into contact early in the mold closing period, similarly to the blow molding die according to the second embodiment. There is a structural feature in what we do. That is,
The entire molding surface 6 side of the outer mold 4 and the inner mold 5 constituting the molding die is made of sintered metal 19 having high air permeability. A two-system air passage 21 is provided between the sintered metal 19 and the outer mold body 20.
22 are formed. Also, two systems of air passages 21 and 22 are formed between the sintered metal 19 and the inner die body 23. One air passage 21 of the outer mold 4 is configured to face behind the sintered metal 19 on the outer peripheral portion 8 of the molding surface 6 with which the parison 3 comes into contact in the initial stage of mold clamping, and is formed by the air supply hose 15. Air can be sent in from the outside. The other air passage 22 is formed so as to face behind the sintered metal 19 on the molding surface 6 excluding the outer peripheral portion 8, and can be vacuumed from outside by the vacuum supply hose 17. The one air passage 21 of the inner mold 5 is configured to face behind the sintered metal 19 of the corner portion 9 of the molding surface 6 protruding toward the outer mold 4 to which the parison 3 comes into contact in the initial stage of mold clamping. The air can be supplied from the outside by the air supply hose 15. The other air passage 22 is formed so as to face behind the sintered metal 19 of the side wall portion 13 excluding the corner portion 9 of the molding surface 6 protruding toward the outer mold 4, and can be vacuumed from outside by the vacuum supply hose 17. it can.

The blow mold of the third embodiment can form the gas layer 10 shown in the second embodiment by utilizing the air permeability of the sintered metal 19, Vacuum can also be applied using sex. Functionally, it is the same as that of the second embodiment, but it is not necessary to adopt a complicated structure such as the air distribution pipe 14 and the small hole 16, and furthermore, the uniform gas layer 10 is formed at the portion where the gas layer 10 is formed. And the support function of the parison 3 is also improved.
The other functions are the same as those of the second embodiment, and the description thereof will be omitted.

[0031]

According to the first aspect of the present invention, since the parison of the portion which comes into contact with the mold early is not fixed to the portion of the mold but is supported flexibly, the subsequent parisoning is performed. As the process proceeds, the parison is successively stretched, which can be a blow molding method suitable for forming a deep-drawn double structure which is less likely to become thin or break.

According to the second aspect of the present invention, since the parison of the portion which comes into contact with the mold early is not fixed to the portion of the mold but is supported flexibly, the subsequent progress of mold clamping As the parison is gradually stretched, a blow molding method suitable for forming a deep-drawing double structure which is less likely to become thin or break can be obtained.

According to the third aspect of the present invention, a gas layer is formed between the parison at a portion which comes into contact with the mold early and the portion of the mold by the gas blowing means, and the parison at the portion is fixed. It can be supported with flexibility.
Therefore, the parison can be successively stretched even as the mold clamping progresses, and a blow mold that is less likely to become thin or break is suitable for forming a deep drawn double structure.

According to the fourth aspect of the present invention, the effect according to the third aspect can be obtained with a simple configuration using small holes.

According to the fifth aspect of the present invention, the effect according to the third aspect can be obtained with a simple configuration due to the structural properties of the sintered metal, and a uniform gas layer can be formed.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing an initial state of a mold clamping step in a blow molding method according to a first embodiment.

FIG. 2 is a plan sectional view showing an initial state of a mold clamping step in the blow molding method according to the first embodiment.

FIG. 3 is a diagram of a double structure formed by the blow molding method according to the first embodiment. (A) is a plan view, and (B) is a cross-sectional view.

FIG. 4 is a diagram of a double structure formed by the blow molding method according to the first embodiment. (A) is a plan view, and (B) is a cross-sectional view.

FIG. 5 is a side sectional view showing an initial step of molding in the blow molding method of the first embodiment.

FIG. 6 is a plan sectional view showing an initial step of molding in the blow molding method of the first embodiment.

FIG. 7 is a side sectional view showing a middle state of a mold clamping step in the blow molding method according to the first embodiment.

FIG. 8 is a plan sectional view showing a middle stage of a mold clamping step in the blow molding method according to the first embodiment.

FIG. 9 is a side sectional view showing a state in a final stage of a mold clamping step in the blow molding method according to the first embodiment.

FIG. 10 is a plan sectional view showing a final state of a mold clamping step in the blow molding method according to the first embodiment.

FIG. 11 is an explanatory diagram showing the relationship between the elapsed time of the mold clamping step and the pressure of each part in the blow molding method according to the first embodiment.

FIG. 12 is a side sectional view showing a blow mold according to a second embodiment.

FIG. 13 is a side sectional view showing a blow mold according to a third embodiment.

FIG. 14 is a sectional view of a double structure formed by a conventional blow molding method.

FIG. 15 is a side sectional view showing an initial step of molding in a conventional blow molding method.

FIG. 16 is a cross-sectional plan view showing an initial molding step in a conventional blow molding method.

FIG. 17 is a side sectional view showing an initial state of a mold clamping step in a conventional blow molding method.

FIG. 18 is a plan sectional view showing an initial state of a mold clamping step in a conventional blow molding method.

FIG. 19 is a side sectional view showing a middle stage of a mold clamping step in a conventional blow molding method.

FIG. 20 is a plan sectional view showing a middle stage of a mold clamping step in a conventional blow molding method.

FIG. 21 is a side sectional view showing a final stage of a mold clamping step in a conventional blow molding method.

FIG. 22 is a plan sectional view showing a state of a final stage of a mold clamping step in a conventional blow molding method.

FIG. 23 is a sectional view of a deep-drawn double structure.

[Explanation of symbols]

 Reference Signs List 1a Double structure 1b Double structure 3 Parison 4 Outer die 5 Inner die 6 Molding surface 8 Outer peripheral part 9 Corner part 10 Air layer 16 Small hole 19 Sintered metal

Claims (5)

[Claims] In a mold clamping period in which a parison is clamped by a mold, a portion of the parison, which comes into early contact with the mold, is flexibly supported and clamped to the portion of the mold. A blow molding method for a double structure. 2. In a mold clamping period in which a parison is clamped by a molding die, gas is generated during the clamping period between the molding die and the parison in a portion where the parison comes into contact with the molding die early. A method for blow molding a double structure, comprising forming a thin gas layer and clamping the mold. 3. A blow molding die for blow-molding a double structure by clamping a parison, wherein a gas blowing means for blowing gas to a molding surface of a portion where the parison comes into contact early in a mold closing period is provided. A blow mold having a double structure, characterized in that the mold is provided. 4. A double-molded blow mold according to claim 3, wherein the gas jetting means comprises a number of small holes configured to supply gas. Blow mold for body. 5. The blow molding die according to claim 3, wherein the gas jetting means is made of a gas-permeable sintered metal capable of supplying a gas. Double structure blow mold.