JPH0376650B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) This invention relates to a blow molding method.

(Prior art) When manufacturing a molded article by blow molding, a thermoplastic material heated and melted in an extruder 1 is extruded as a cylindrical parison 2, as shown in FIG. 4b due to the compressed gas injected from the nozzle 4 while being held between 3a and 3b.
As shown in FIG. 3, a hollow molded product 5 is manufactured by expanding within the molds 3a and 3b. In this way, the conventional blow molding method can only mold a hollow molded product 5, so when manufacturing a product 6 with one side open, it is necessary to divide the hollow product molded by blow molding. (See Figure 5), there is a problem that not only is it time-consuming to divide, but also that a large amount of resin unnecessary for the product 6 is required during molding, resulting in a poor yield. Moreover, when manufacturing a product 6 having a flange 6a as shown in FIG. 6, secondary processing is required, which again poses the problem of labor and material yield of the secondary processing.

(Problems to be Solved by the Invention) This invention can mold products with one side open, which could not be achieved with conventional blow molding methods, and can also mold products with complex shapes similar to injection molded products. A novel blow molding method is provided.

Structure of the Invention (Means for Solving the Problems) That is, in order to solve the above problems, the present invention provides a plurality of molds each having an independent molded product cavity, and a cavity of the molds. Using a blow molding machine having a gas blowing member provided to cover the opening, a parison extruded by an extruder is placed between the gas blowing member and at least one side of the mold. This method employs a method in which the parison is held between a mold and the parison is pressed against the cavity surface of the mold by blowing out compressed gas from the outlet of the gas blowing member.

(Operation) In the present invention, a parison is extruded from an extruder between the gas blowing member and at least one of the molds with the gas blowing member disposed inside a plurality of molds. Then, a plurality of molds are moved and clamped, and compressed gas is blown out from a number of outlets formed in the gas blowing member with the parison being held between the gas blowing member and the molds. The parison is pressed against the mold along the cavity shape of the mold by the action of compressed gas, and is molded into a predetermined shape. Next, after cooling of the parison is completed, the mold is opened and the molded product is taken out from inside the mold, thereby producing a molded product with one side open.

(Example) Examples 1 and 2 which embody this invention will be described below.
This will be explained according to the diagram. The mold 11 is placed in the center of a pair of left and right molds 11a and 11b that are symmetrically formed.
A gas blowing member 12 is arranged, which includes an air chamber 12a having a height and width approximately equal to those of the air chamber 12a, a plurality of blowing ports 12b formed on both sides of the air chamber 12a, and a connecting pipe 12c connected to a compressed air source (not shown). It is set up. An extruder 14 is disposed above the gas blowing member 12 to heat and melt the raw resin and extrude it as two sheet-shaped parisons 13.

Now, when forming a molded article using this apparatus, as shown in FIG.
A sheet-like parison 13 is transferred to the gas blowing member 12.
The parisons 13 are pushed out until the lower end of each parison 13 reaches the lower end position of both the left and right molds 11a, 11b, and then the left and right molds 11a, 11b are inserted into the gas blowing member 1.
move the parison 13 to the gas blowing member 1
2 and both left and right molds 11a and 11b. After the parison 13 is clamped, the gas blowing member 12
Compressed air is blown out from each outlet 12b, and the parison 13 is pressed against both the left and right molds and is molded into a shape that follows the cavity of the mold. After the compressed air is introduced into the air chamber 12a, it is blown out from each outlet 12b, so that air at approximately the same pressure is blown out from each outlet 12b, and each part of the parison 13 is pressed uniformly. Furthermore, since the cavity of the mold is divided by the gas blowing member 12, by opening the molds 11a and 11b after cooling is completed and taking out the molded product 15, it is possible to simultaneously obtain two products with one side open. .

Note that the present invention is not limited to the above-mentioned embodiments, and for example, as shown in FIG. It can also be applied to the cylindrical parison 13 in the same way as the blow molding. Moreover, the molds 11a, 11b
does not necessarily have to be formed in a symmetrical shape, but may be formed asymmetrically. Furthermore, according to the blow molding method of the present invention, it is possible to manufacture products with complex shapes similar to injection molded products, but the injection pressure is usually as high as 800 to 2000 kg/cm ² . The mold also needs to be pressure resistant, which increases the cost, but when carrying out the blow molding method of this invention, the pressure of compressed air is 3 to 3, which is the same as in the normal blow molding method.
Since the pressure is 10 Kg/cm ² , the mold is not required to have much pressure resistance, and it is possible to reduce mold cost and energy.

Effects of the Invention As detailed above, according to the present invention, it is possible to mold a product that is not hollow and has one side open, and even though it is blow molded, it has a complex shape similar to injection molded products. This has the excellent effect of reducing mold costs and energy consumption.

[Brief explanation of drawings]

Figures 1 a to c are cutaway front views showing the sequence of the blow molding method embodying the present invention, Figure 2 is a sectional view taken along line A-A in Figure 1 a, and Figure 3 is a perspective view showing another parison. Figures 4a to 4c are cross-sectional views showing the order of the conventional blow molding method, Figure 5 is a cross-sectional view showing the state in which the hollow molded product is divided, and Figure 6 is a cross-sectional view showing the conventional blow molding method. It is a sectional view of the required product. Mold...11a, 11b, gas blowing member...1
2. Air chamber...12a, Air outlet...12b, Parison...13, Extruder...14, Molded product...1
5.

Claims (1)

[Scope of Claims] 1. Using a blow molding machine having a plurality of molds each having a cavity for an independent molded product, and a gas blowing member provided to cover the cavity opening of the mold, After disposing the parison extruded by an extruder between the gas blowing member and at least one side of the mold, the plurality of molds are moved to separate the parison between the gas blowing member and the mold. A blow molding method characterized in that the parison is pressed against a cavity surface of a mold by blowing compressed gas from an outlet of the gas blowing member. 2. The blow molding method according to claim 1, wherein the plurality of molds are asymmetrically formed. 3. The blow molding method according to claim 1, wherein the plurality of molds are formed symmetrically. 4. According to any one of claims 1 to 3, the parison is extruded in the form of two sheets, and is sandwiched and molded between a pair of molds and a gas blowing member. blow molding method.