JP3802030B2 - Blow molding method - Google Patents

Description

The present invention, by applying a pressure by utilizing the gas confined in the parison, it relates to a blow molding how to mold a thin product thickness.

At present, the demand for plastics has rapidly increased in place of metal materials, and has become indispensable for daily life.
This is due to the fact that the plastic material is not only lightweight and high-strength, but also inexpensive, has a high degree of freedom in the shape of the molded product, and has good productivity, so that it is a material suitable for mass production.
In addition, various types of molding methods such as injection, extrusion, compression, and blow have been proposed along with the diversification of products.

Among the molding methods described above, the blow molding method has a feature that it can efficiently mold hollow products such as containers and bottles.
Japanese Patent Laid-Open No. 11-3461 JP 2003-308563 A

However, the blow molding method usually injects gas using a thin pin or needle into the clamped parison, so when molding a thin product, the thin pin or needle breaks, Could not be molded.
Further, even when the horizontal blowing mechanism is used, a thin pin or a needle breaks through the parison when the mold is slid, and the molding cannot be performed.
Therefore, when a thin product is formed, a product formed by vacuum forming or the like is bonded to form a hollow shape, which is expensive.

The present invention is as follows.
(1) The inventions includes a parison blocking step for closing the front end of the extruded tubular parison from the extruder at Parisonpinchi, the parison further while injecting a gas into the parison closed tip predetermined in between gas injection and extrusion step of extruding from the extruder to a length, sandwiching the parison in a state where the closed's portion of the parison was protruded outside the mold at the mold, the gas confined within said parison In a blow molding method of molding a thin product comprising a molding step of transferring an internal pressure to the parison by applying an internal pressure to form a cavity of the mold , the gas in the cavity is discharged to the mold In order to prevent the product from expanding and deforming due to the pressure of the gas inside when the mold is opened, and to tear a part of the product, And providing a gas vent hole communicating with Yabiti.
In blow molding method according to (2) (1), the gas vent hole, characterized in that provided in an inconspicuous location of the product.

According to this invention, the parison into which the gas is injected is sandwiched between the molds, and the inner pressure of the mold is transferred to the parison by applying the internal pressure with the gas confined in the parison. There is no need to inject gas into the parison after tightening, and a thin product can be molded efficiently at low cost, and a sealed molded product with a hollow interior can be molded.
Since the gas release hole provided in the mold, or to expand the gas in the open molded article from the mold clamping pressure when the mold is opened, the molded product was gas expanded by the temperature of the parison is deformed In such a case, the parison in the gas vent hole is broken by the internal pressure of the gas, so that the gas in the parison is discharged to the atmosphere outside the mold through the gas vent hole, thereby preventing the molded product from being deformed. it is Ru can.

An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory view showing a schematic configuration of a blow molding apparatus to which an embodiment of the present invention is applied , FIGS. 2 to 7 are explanatory views showing a molding process, and FIG. 8 is an explanatory view of a vent hole provided in a mold. is there.

  In these drawings, reference numeral 11 denotes an extruder, which extrudes a heat-melted thermoplastic resin as a cylindrical, for example, cylindrical parison 61.

  Reference numeral 21 denotes a parison closing mechanism, which is rotatably attached to the casing of the extruder 11 and closes the tip end of the cylindrical parison 61 pushed out of the extruder 11. 22B and a parison pinch drive unit (23) that is provided in the casing of the extruder 11 and rotates the parison pinches 22A and 22B.

31 shows a gas injection mechanism, extruded from the extruder 11, into the parison 61 to block the tip, or to prevent the parison 61 Gakuttsu rather to have the parison 61 is a negative pressure, the parison 61 It is provided in the casing of the extruder 11 so that a gas for maintaining a cylindrical shape can be injected.

  Reference numeral 41 denotes a mold, which is attached to a pair of mold plates 42A and 42B which are driven so as to be brought into and out of contact by a mold drive mechanism (51) (not shown), and opposite surfaces of the mold plates 42A and 42B. The divided molds 43A and 43B divided into the left and right parts, the frames 44A and 44B entering and exiting the divided molds 43A and 43B, and the frames 44A and 44B into the divided molds 43A and 43B. It is composed of air cylinders 45A and 45B as a frame drive mechanism for moving in and out.

The above-described frames 44A and 44B are configured in a square shape (square) in side view with the left and right surfaces open.
Further, the split molds 43A and 43B for accommodating the frames 44A and 44B are provided with a square-shaped (rectangular) groove so that the frames 44A and 44B can move back and forth, and a portion that forms a cavity inside the groove. (Inner surface shape) is provided.
Note that at least one of the divided molds 43A and 43B, for example, the divided mold 43B, is provided with a gas vent hole 43h (FIG. 8) for communicating the cavity and the atmosphere.
The vent hole 43h may penetrate the mold plate 42B.

Next, molding will be described.
First, as shown in FIG. 1, the parison pinch drive section (23) is operated to expand the parison pinches 22A and 22B, and the mold drive mechanism (51) is operated to separate the mold plates 42A and 42B. At the same time, the air cylinders 45A and 45B are operated to cause the frames 44A and 44B to protrude from the divided molds 43A and 43B.
In this state, as shown in FIG. 2, the thermoplastic resin heated and melted from the extruder 11 is extruded into a cylindrical shape to form a parison 61.

Next, if the parison 61 is pushed out to such a length that the lower end portion of the parison 61 can be sandwiched and closed by the parison pinches 22A and 22B, the parison pinch drive unit (23) is operated as shown in FIG. Then, the lower end portion of the parison pinch 61 is sandwiched and closed by the parison pinches 22A and 22B to form the closed portion 62, and then the parison pinch drive unit (23) is operated to move the parison pinches 22A and 22B as shown in FIG. While being separated so as not to contact the parison 61, the gas injection mechanism 31 is operated to further push out the parison 61 from the extruder 11 while injecting gas, for example, air, into the parison 61 at atmospheric pressure.

As shown in FIG. 5, if the parison 61 is pushed out from the extruder 11 until the closed portion 62 of the parison 61 protrudes downward from the split molds 43 </ b> A and 43 </ b> B, the extruder 11 is stopped and the parison 61 is stopped. Is stopped, the gas injection mechanism 31 is stopped, the gas injection into the parison 61 is stopped, and the mold drive mechanisms (51) are operated to bring the mold plates 42A and 42B closer to each other, As shown in FIG. 6, the upper and lower sides of the parison 61 are sandwiched between frames 44A and 44B.
Thus, when the upper and lower sides of the parison 61 are sandwiched between the frames 44A and 44B, the parison 61 in the frames 44A and 44B swells to the maximum extent because both ends are closed.

  From the state in which the upper and lower sides of the parison 61 are sandwiched between the frames 44A and 44B as described above, the mold drive mechanism (51) molds the molds 43A and 43B so as to sandwich the upper and lower sides of the parison 61 as shown in FIG. When the divided molds 43A and 43B are moved by moving the panels 42A and 42B, the frames 44A and 44B are retracted into the divided molds 43A and 43B, so that the parison 61 in the frames 44A and 44B is separated from the outside. The inner surface of the molds 43A and 43B is pushed by the inner surface forming the cavity, and the inner surface is pushed by the internal pressure of the gas in the parison 61 to the inner surface forming the cavity of the split molds 43A and 43B. 61 is transferred.

  When the Harrison 61 is sandwiched between the divided molds 43A and 43B, the frames 44A and 44B are divided by the air cylinders 45A and 45B according to the approach of the divided molds 43A and 43B so that the air cylinders 45A and 45B are not broken. The frames 44A and 44B may be retracted into the split molds 43A and 43B by the air cylinders 45A and 45B until the split molds 43A and 43B are closed.

After a predetermined time, the mold drive mechanism (51) is operated to separate the mold plates 42A and 42B as shown in FIG. be able to.
When such taking out the molded article with the mold 41 burrs around the parison 61 leading to the lower side of the extruder 11 is also removed together.
In addition, when the parison 61 between the extruder 11 and the metal mold 41 is cooled, the parison 61 on the lower side of the extruder 11 may be cut off and removed.
Next, a desired product can be obtained by removing the burrs from the mold 41 by removing it from the mold 41.
Thereafter, it can be molded in the same manner.

When molding is performed as described above, the gas in the molded product released from the clamping pressure expands when the split molds 43 and 43B (mold 41) are opened, or the gas expands depending on the temperature of the parison 61. When the molded product is deformed, as shown in FIG. 8, the parison 61 in the gas vent hole 43h provided in the split mold 43B is broken by the internal pressure of the gas, so that the gas in the parison 61 is changed. It is discharged to the atmosphere outside the mold 41 through the gas vent hole 43h.
Therefore, it is possible to prevent the molded product from being deformed when the split molds 43A and 43B are opened.
In addition, what is necessary is just to block | close the torn part of the molded product corresponding to this gas vent hole 43h by post-processing.

As described above, according to one embodiment of the present invention, the parison 61 into which the gas has been injected is sandwiched between the molds 41 and the inner pressure is applied to the parison 61 by applying the internal pressure with the gas confined in the parison 61. Since it is transferred, it is not necessary to inject gas into the parison 61 after clamping using a thin pin or needle, etc., and a thin product can be molded efficiently at low cost and the inside is hollow. It is possible to form a hermetic molded product.
And, since there is provided a gas vent hole 43h to the mold 41, or to expand the gas in the open molded article from the mold clamping pressure when the mold is opened 41, the gas expands with the temperature of the parison 61 When the molded product is deformed, the parison 61 in the gas vent hole 43h is broken by the internal pressure of the gas, so that the gas in the parison 61 is discharged to the atmosphere outside the mold 41 through the gas vent hole 43h. molded articles Ru can be prevented from being deformed.

In the above-described embodiment, an example in which the gas injection mechanism 31 is blown upward has been described. However, when the lower blow air pin is inserted into the parison and the lower pinch is performed as it is and air is injected, the lower blow may be used.
Although the example in which the frame driving mechanism is the air cylinder 45A, 45B has been shown, the frame 44A, 44B is divided into the divided molds according to the approach of the divided molds 43A, 43B even in the case of the frame driving mechanism having other configurations. What is necessary is just to make it control to retract in 43A, 43B.
Moreover, although the example which provided the frames 44A and 44B in the metal mold | die 41 was shown, even if it does not provide the frames 44A and 44B, it can shape | mold similarly.
Furthermore, it is desirable to provide the vent hole 43h in a place where the molded product is not conspicuous.

It is explanatory drawing which shows schematic structure of the blow molding apparatus to which one Example of this invention is applied . It is explanatory drawing which shows a shaping | molding process. It is explanatory drawing which shows a shaping | molding process. It is explanatory drawing which shows a shaping | molding process. It is explanatory drawing which shows a shaping | molding process. It is explanatory drawing which shows a shaping | molding process. It is explanatory drawing which shows a shaping | molding process. It is explanatory drawing of the vent hole provided in a metal mold | die.

Explanation of symbols

11 Extruder 21 Parison closing mechanism 22A, 22B Parison pinch 31 Gas injection mechanism 41 Mold 42A, 42B Mold plate 43A, 43B Split mold 43h Gas vent holes 44A, 44B Frame 45A, 45B Air cylinder (frame drive mechanism)
61 Parison 62 Blocked part

Claims (2)

A parison closing step of closing the tip of a cylindrical parison extruded from the extruder with a parison pinch;
A gas injection / extrusion step of extruding the parison from the extruder to a predetermined length while injecting gas into the parison whose tip is blocked;
The closed but part of the parison pinching the parison in a state where the protruded to the outside of the mold at the mold, the inner surface shape to form the mold cavity by applying a pressure in the gas confined within said parison A molding step for transferring to the parison;
In a blow molding method for molding a thin product comprising:
While exhausting the gas in the cavity to the mold, the product is prevented from expanding and deforming due to the pressure of the gas inside when the mold is opened, and a part of the product is torn. For this purpose, a vent hole connected to the cavity is provided.
A blow molding method. The blow molding method according to claim 1,
Providing the vent hole in an inconspicuous place of the product;
Blow molding how, characterized in that.

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