JPS6132128B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of forming curved tubes made of blow-molded plastic material for various applications.

Conventionally, this kind of bent pipe has been formed by blow molding by manually introducing a small parison into the cavity of a split mold to obtain the bent pipe, or by blow molding between upper and lower split molds installed in a molding machine. However, the former method not only requires hot kneading techniques to manually introduce the parison into the mold by splitting it, but also requires mold clamping. It is extremely dangerous for workers to put their hands between the molds, and there are problems such as delays in the molding cycle. The latter uses a molding machine that uses an NC device, which inevitably makes the molding equipment expensive, making it difficult to save money.

The present invention solves the above-mentioned conventional drawbacks and facilitates industrial production of bent pipes by devising a means for supplying parisons.

That is, in the present invention, a concave bent part and a convex bent part are formed in the joint surfaces of a pair of male and female molds to form a curved pipe shape in a direction perpendicular to the joined surfaces, respectively, and are bored in the shape of a groove. The parison is fed downwardly from the die of the extruder located above toward the open space of the cavity, and then the parison is sucked into the female mold by air suction means of an appropriate number of small air suction holes provided in the cavity of the female mold. Air blowing means is provided in an appropriate number of small holes for blowing heated air provided in the cavity of the male mold, while the male mold is moved toward the parison. By pressing the parison against the cavity of the female mold, the parison is blown onto the female mold, the male and female molds are clamped, and the upper end of the parison, which is shaped like a curved tube inside the cavity, is sprayed onto the female mold. It is an object of the present invention to provide a method for forming a curved pipe made of plastic material by injecting pressurized air from a separate air supply pin and performing hollow forming.

In the present invention, a pair of male and female split molds are used for forming a male and female mold.One of the half molds containing a cavity forming a convex bent part for a bent pipe is called a male mold, and the concave bent part is referred to as a male mold. This is based on the fact that the other half-split mold containing the cavity forming the mold is called the male mold. The diameter of the parison is set to be smaller than the diameter of the groove in the cavity since a curved pipe will be obtained by hollow molding. The diameter of the small holes for air suction and blowout in the cavity is suitable to be around 0.3 to 0.5 mm, and it is desirable that they are distributed approximately evenly, but the number of holes should be adjusted so that the effect of suction and pressure can be obtained. It may be selected appropriately depending on the aerodynamic force and the degree of curved pipe.

The present invention will be described in detail below with reference to drawings of embodiments.

As shown in Fig. 1, the parison is made from a die 1 at the tip of an extruder (not shown) located above a pair of left and right split molds consisting of a female mold 3 and a male mold 4 arranged in a blow molding machine. 2 between the female mold 3 and the male mold 4 5
droop towards. The male and female molds 3 and 4 have a female cavity 7 and a male cavity 7', and small holes 8 are carved at equal intervals along the valley of the female cavity 7, and these communicating holes 10 and a discharge pipe 13 are formed. arrow 7b on the cavity surface by means of a vacuum pump (not shown).
The parison 2 is sucked in the direction of , and is exhausted as shown by the arrow 10b. On the other hand, while the male mold 4 is moving, the male cavity 7' of the male mold 4 has a small hole 8 similar to the female mold 3.
It has a communication hole 10, and heated pressurized air is blown out from the small hole 8 as shown by an arrow 7a. The heated pressurized air is forced into the suction pipe 13' connected to the communication hole 10 as shown by the arrow 10a. Note that the symbol 12 indicates a hydraulic mold clamping rod.

In this way, as shown in FIG. 2, the male mold 4 moves considerably, and the left and right female and male molds 3 and 4 move toward the parison 2, pushing the parison 2 into the female cavity 7,
The parison 2 is sandwiched between the male cavity 7' and the small hole 8 in the female cavity 7 adsorbs the parison 2, and at the same time, the small hole 8 in the male cavity 7' presses the parison with pressurized air as shown by the arrow 7a. When the male and female molds 3 and 4 on the left and right move forward and clamp the parison 2 between the female cavity 7 and the male cavity 7' to complete the mold clamping, the parison 20 is formed into a curved tube shape as shown in Fig. 3. is formed within the cavity.

Next, as shown in FIG. 5, 5 to 10 kg of high-pressure air is pumped through the upper end 26 of the parison 20, which has a curved tube shape.
cm ² is injected through the air supply pin 25, and a curved tube molded product 6 is formed as shown in FIG. Note that the recesses 27 near both ends of the molded product 6 are filled with air supply pins 25 after molding.
It shows a guide groove that is injected with more pressurized air and cut out in the mold or cut in post-processing.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional front view showing a state in which a parison is supplied to a split mold for curved pipe forming, Fig. 2 is a longitudinal sectional front view showing a state in which the split mold in Fig. 1 is advanced, and Fig. 3 is Figure 2 is a front view of the mold after mold clamping, Figure 4 is a front view of the molded product and bent tube, and Figure 5 is an enlarged view of the curved tube-shaped parison with an air supply pin injected into it. show. 3...Female mold, 4...Male mold, 6...Bent pipe, 7
...Female cavity, 7'...Male cavity, 8...
...Small hole, 10...Communication hole, 25...Air supply pin.

Claims (1)

[Claims] 1 Open space between cavities bored in the form of grooves with concave and convex bends formed on the joining surfaces of a pair of male and female molding molds to form a curved pipe shape in a direction perpendicular to the joint surfaces. The parison is fed downward from the die of the extruder located above, and then the parison is sucked into the cavity of the female mold by the air suction action of an appropriate number of small air suction holes provided in the cavity of the female mold. At the same time, while moving the male mold toward the parison, the parison is blown out by the air blowing action of an appropriate number of heated air blowing holes provided in the cavity of the male mold. The parison is attracted to the female mold by pressing against the cavity of the female mold to clamp the male and female molds, and a separate air supply pin is inserted toward the upper end of the curved tube-shaped parison inside the cavity. A method for forming a curved pipe made of plastic material, characterized by hollow forming by injecting pressurized air.