JPS5814293B2 - How to form a hollow body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for molding a hollow body using a thermoplastic resin.

Conventionally, blow molding has been commonly used as this type of molding method, and direct blow molding has been particularly used as a typical molding method.

However, this direct blow molding method consists of a process of extruding the parison, a process of inserting the parison into a mold, and a process of blow molding. The problem is that there is a limit to the production volume of one molding machine due to the indispensable movement and the need for pinch-off trimming work (deburring work), and for mass production, it is necessary to use many molding machines of the same type side by side. was there.

In addition, this direct blow molding method is advantageous in that the mold cost is 33% cheaper, the molding process is simple, the entire equipment is cheaper, and the product price is also lower, but on the other hand, the accuracy of the inner shape is completely unstable. Pinch off on top of that. Even if the edges were removed during the trimming process, the residue remained and the appearance was poor, making it impossible to mold high-quality products with high precision using this direct blow molding method.

On the other hand, injection blow molding has recently come into use as an improved method of the above-mentioned direct blow molding.

This molding method first injects molten resin into a cavity to injection mold a bottomed parison, then moves it to a blow mold with the parison core still attached and blows air into it to blow mold it. Although this method solves most of the problems caused by the direct blow molding method, it has the disadvantage of releasing the parison that adheres closely to the core, and since the molding machine and mold are expensive, it is difficult to mold a large number of molds. limited to products,
Furthermore, there are problems in that it is restricted by the shape of the molded product and cannot be applied to very small molded products.

The present invention has been made in consideration of the above-mentioned problems.The cavity into which the pin is inserted is filled with molten resin, and then the plurality of side wall molds constituting this cavity are retreated, and the molten resin is filled inside the filled molten resin. By blowing air through the pins to bulge the side wall by blow molding, productivity per molding machine can be increased, molding accuracy is high, and the mold can be changed as necessary. The object of the present invention is to provide a method for molding a hollow body in which the size and shape of the hollow body in the direction perpendicular to the axis can be changed within a certain range.

The embodiment will be described below with reference to the drawings.

In the figure, 1 is a fixed template, 2 is a floating template, and both plates 1,
The mating surfaces of 2 are the parting line.

3 is a movable mold plate, and the floating mold plate 2 floats by a stroke 8 with respect to the movable mold plate 3,
An elastic material such as urethane rubber or a hydraulic cylinder is interposed between the drawing plates to urge the floating template 2 in a direction away from the movable template 3.

A cavity 4 is formed in the fixed mold plate 1 and the floating mold plate 2.

This cavity 4 is a polytacho tube cavity, and its bulging portion is located at the above-mentioned parting line.

Sliding molds 5, 5 are provided opposite to this bulging portion, and the volume of the cavity of the bulging portion is changed by sliding of these molds.

6 is a cavity pin fixed to the fixed mold plate 1, 7
are core pins fixed to the movable mold plate 3, each of which projects into the cavity 4 and forms the inner diameter portion of the polytacho tube to be molded within the cavity 4.

The core pin 7 has an air hole 8 in the axial direction, which is opened at the distal end surface of the core pin 7.

The sliding molds 5, 5 have hydraulic cylinders 9 fixed to the fixed mold plate 1.
, 9 are connected.

In the figure, 10 is an ejector bin, and 11 is a sprue runner through which the injected resin passes.

Thus, the floating mold plate 2 and the movable mold plate 3 are tightened to the fixed mold plate 1, and the sliding molds 5, 5 are connected to the hydraulic cylinder 9,
At step 9, it is moved forward and molten resin is injected and filled into the cavity 4 from the sprue runner 11 (FIG. 3).

Next, the hydraulic cylinders 9, 9 are operated to retract the sliding molds 5, 5 to a predetermined position, and the movable mold plate 3 is slightly opened to bring the tip of the core pin 7 into close contact with the tip of the cavity pin 6. A slight gap is opened from the state, and air from the air hole 8 of the core pin 7 is blown into the gap to perform air blowing.

At this time, even if the movable mold plate 3 moves slightly to open, the floating mold plate 3
is biased toward the fixed mold plate 1 side and the parting line does not open.

In addition, during injection filling and air blowing of this molten resin,
The temperature of the entire mold is controlled to the temperature required for air blow molding.

As the sliding mold 5 retreats, the resin in this area is pressed against the end surface of the sliding mold 5 by air blowing from the air hole 8, and bulges into this area as shown in FIGS. 1 and 5. A hollow part is formed.

After cooling in this state, the mold plate 3 on the movable side is moved to open the mold.

At this time, floating template 2. It can be opened with a delay of stroke S from the movable template 3.

Then, according to the opening movement of the floating template 2, the ejector pin 1
0 extrudes the molded product.

FIG. 6 is a perspective view of a polytacho tube obtained by this molding method.

FIG. 7 and subsequent figures show a bottle molding method according to another embodiment.

That is, two sliding molds 17a and 17b which are slidable in a direction perpendicular to the direction of movement of the movable mold 16 are placed between a fixed mold 15 that molds the bottom surface of the bottle and a movable mold 16 that molds the mouth part.
are respectively connected to a cylinder device 18, and are configured to slide in symmetrical directions over a predetermined stroke by this cylinder device 18.

The core pin 19 passes through the movable mold 16 and the movable mold 16,
The core pin 19 protrudes into the cavity formed between the fixed mold 15 and the sliding molds 17a and 17b, but is separated into a fixed side member 19a and a movable side member 19b, so that the core pin 19 is separated from the air passage 20. By blowing air, the movable member 19b moves against the spring 21, and the air moves against the core pin 19.
The air is blown into the cavity from around the area.

The fixed mold 15 is provided with an injection hole 22 facing the center of the cavity, and the area around the injection hole 22 is a heater 2.
3, the temperature can be controlled.

The movable mold 16 for molding the mouth of the bottle has a two-part structure.

Therefore, when molding a bottle, there is a fixed mold 15 and a movable mold 1.
6 and both sliding molds 17a and 17b are clamped, molten resin is injected into the cavity from the injection hole 22 (7th
(upper half of the figure and Figure 8).

Then, while retracting both sliding molds 17a and 17b, air from the air passage 20 is blown from around the core pin 19 (lower half of FIG. 7 and FIG. 9).

In this way, the resin in the cavity retreats into the sliding mold 17a.
, 17b and bulges out while being pressed by air to form a hollow portion.

After molding, the mold is cooled and the mold is opened to take out the molded product.

At this time, the movable mold 16 for forming the mouth part is divided into two parts, so that even if a screw is screwed into the mouth part, it can be easily taken out.

FIG. 10 is a partially cutaway front view of a bottle obtained by this molding method.

In each of the above embodiments, air is blown into the sliding type 5, 5.
Although the air blowing is performed while retracting the slide molds 17a and 17b, this is not limited to this, and air may be blown after the sliding mold completes its retraction.

According to the method for molding a hollow body according to the present invention, as described in detail above, there are two end molds for molding both ends of the hollow body in the axial direction, and a mold that is located between the two end molds and slides laterally. A space between a cavity composed of a plurality of movably opposed side wall molds for forming the side walls of a hollow body and a pin protruding into the cavity is filled with molten resin, and then each of the side wall molds is are moved back from each other, and air is blown into the inside of the filled molten resin from the pin to bulge the side wall part by blow molding, compared to the conventional direct blow molding method for molding hollow bodies. The process of extruding the parison and inserting it into a mold is omitted, filling with resin can be done by injection, and there is no need to remove parison, which reduces production per molding machine. It can greatly improve your sexual performance.

Further, the outer shape of the hollow body can be formed with high molding accuracy without forming any cracks.

Furthermore, by appropriately changing the retraction distance of the side wall mold, it is possible to change the size and shape of the hollow body in the direction perpendicular to the axis within a certain range. Molded products with a wide variety of cross-sectional shapes can be obtained.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of the molding device for carrying out the present invention, and Fig. 2 is a front view of the molding device, with the fixed side being above the center line and the movable side being below the center line. shows. Fig. 3 is a sectional view showing the injection state of molten resin, Fig. 4 is a sectional view taken along the line IV-IV in Fig. 3, Fig. 5 is a blowing state diagram, and Fig. 6 is a sectional view showing the injection state of molten resin.
The figure is a perspective view showing a polytaco tube which is a molded product, and Figure 7 and the following figures show other embodiments of the present invention. is a sectional view showing the blow molding state, FIGS. 8 and 9 are operation explanatory views, and FIG. 10 is a partially cutaway front view of the bottle, which is a molded product. 4 is a cavity, and 5, 5 and 17a, 17b are sliding types.

Claims (1)

[Claims] 1. Both end molds for molding both ends in the axial direction of a hollow body, and a plurality of side wall molds located between the two end molds and facing each other so as to be able to slide laterally to mold the side walls of the hollow body. The space between the constructed cavity and the pin projected into the cavity is filled with molten resin, and then the side wall molds are moved back from each other, and air is introduced from the pin into the inside of the filled molten resin. A method for forming a hollow body, characterized by blowing air into the side wall to bulge it by blow molding.