JPS61179720A - Thermoforming molding method and molding equipment - Google Patents

Abstract

PURPOSE:To enable to perform molding operation smoothly and continuously, by a method wherein vacuum molding of a primary molded article is performed by a female mold which has been head and kept warm and the primary molded article is molded into a secondary molded article through air-pressure molding without almost giving stretching deformation. CONSTITUTION:A sheet S made of synthetic resin which has been heated to a predetermined temperature is molded into a primary molded article S1 through vacuum molding method by a female mold 1 which has been heated and kept warm at about the sametemperature as that of the sheet S, a male mold 5 fitted to the female mold 1 which has molded the primary molded article S1 through vacuum molding are clamped, the primary molded article S1 is molded into a secondary molded article S2 through air-pressure molding by making the male mold 5 into a mold and molding of a product is completed by making the secondary molded article S2 cut off and separated from a sheet body S4 after achievement of cooling and solidification of the secondary molded article S2. As for the parimary and secondary molded articles S1, S2, thicknesses of the whole area of them become almost uniform and it becomes that the primary molded article S1 is heated and held at the temperature, through which thermoforming is possible, through heating and heat insulation of the female mold 1, through which molding operation of the secondary molded article S2 can be achieved continuously.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a thermoforming method and mold device for molding caps, containers, etc. from a sheet-like body. The purpose is to mold products with high hardness and uniform wall thickness.

[Conventional technology]

Thermoforming is a well-known method for molding caps and containers from synthetic resin sheets.

In this conventional thermoforming molding method, there are cases in which a product is molded using only a male mold by pressure forming, and cases in which a product is molded only by a female mold by vacuum forming.

When a product is molded using only a male mold, the dimensional accuracy and shape of the inside of the product are good, which makes it suitable for molding a cap.

On the other hand, when a product is molded using only a female mold, the outer dimensional accuracy and appearance are good (this makes it suitable for molding containers).

[Problem that the invention seeks to solve]

As described above, the characteristics of the thermoforming molding method differ greatly depending on whether a male mold or a female mold is used, and this difference can cause major dissatisfaction with the product. Sometimes it happened.

For example, when thermoforming is carried out using only the male die, the dimensional accuracy on the inside is certainly good as mentioned above, but the dimensional accuracy on the outside depends on factors such as the thickness of the sheet body and the molding temperature. It will vary greatly depending on the conditions,
If it is difficult to mold to a certain size and shape, and the product is a cap, the sheet part that will be the top plate of the cap will first contact the male mold and be cooled and solidified, and then the part that will form the peripheral wall of the cap. Because the cap is stretch-molded, the peripheral wall of the molded cap becomes extremely thin compared to the top wall. A serious disadvantage has arisen in that sufficient mechanical strength of the working peripheral wall cannot be obtained.

On the other hand, when thermoforming is carried out using only the female mold, it is true that, as mentioned above, it is possible to obtain a product with good dimensional accuracy on the outside and a good appearance; Since the dimensional accuracy varies greatly depending on conditions such as the thickness of the sheet and the molding temperature, it is necessary to form a thread on the inner surface to fit it into other items, such as a screw cap. It was completely unsuitable for molding products.

[Means and effects for solving the problems] The present invention has the following features:
This was devised to eliminate the problems, inconveniences, and dissatisfaction of the conventional methods described above, and effectively combines the advantages of thermoforming using a female mold with thermoforming using a male mold. It is something that

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to drawings showing one embodiment of the present invention.

In the thermoforming method according to the present invention, a synthetic resin sheet S heated to a predetermined temperature is formed into a primary molded product S1 using a female mold 1 heated and kept at approximately the same temperature as the sheet S using a vacuum forming method. After assembling the male mold 5 into the female mold 1 which vacuum-formed this primary molded product S1 and clamping the mold, the above-described primary molded product SL is formed into a secondary molded product by air pressure forming using the male mold 5 as a molding die. After cooling and solidifying this secondary molded product S2, this secondary molded product S2 is molded into a sheet body S4.
The molding of the product S3 is completed by cutting and separating the product.

The heating temperature of the sheet S to be molded into the primary molded product S1 is determined according to the physical properties of the synthetic resin material from which the sheet S is molded, and is set to a temperature at which the sheet S can be thermoformed.

Also, the female mold 1 is heated and kept at almost the same temperature as this sheet S.
The temperature does not necessarily have to be the same as that of the sheet S, and may be within a temperature range that allows the sheet S to ripen. Considering the molding operation, it is desirable that the temperature be in a slightly lower range among the temperature ranges in which the sheet S can be thermoformed.

When the primary molded product S1 is molded by the female mold 1, the sheet S portion to be molded into the primary molded product SL is pulled into the mold part 2 of the female mold 1 by the negative pressure inside the mold part 2. The molded product enters the molding position while stretching the entire area almost uniformly, and finally comes into close contact with the molding surface of the molding part 2 over the entire area and is molded into the primary molded product S1. The wall thickness of the molded product S1 is approximately uniform over the entire area.

In this way, the wall thickness of the primary molded product S1 is almost uniform over the entire area, so the secondary molded product S2 that is pressure-formed from the primary molded product S1 using the male mold 5 is as follows: Partly because the amount of deformation from the primary molded product S1 to the secondary molded product S2 is small, the thickness of the entire area remains substantially uniform.

In addition, when pressure forming this primary molded product S1 into a secondary molded product S2, the primary molded product S
1 is heated and maintained at a temperature at which it can be thermoformed, so that the vacuum forming of the primary molded product S1 can be successively performed to form the secondary molded product S2.

In this way, the secondary molded product S2 that has been pressure-formed by the male die 5 is cooled and solidified, then released from the mold, and the sheet body S2 is released from the mold after being cooled and solidified.
4 to become product S3.

Various configurations of the mold apparatus for carrying out the method of the present invention described above are possible, and the structure is not limited, but it is thought that the structure is most suitable for carrying out the method of the present invention. An example will be explained below.

That is, this thermoforming molding device has a male mold 5 in which the cooling function portion 7 is located, and a depth and width that is approximately equal to the height and width of the mold portion 6 of the male mold 5. The mold part 2 has an inner diameter larger than the outer diameter of the mold part 6 of the male mold 5, and has a ventilation hole 3 open to the mold surface of the mold part 2, and has a heating function part. 4 and a female mold 1.

Generally, the outer circumferential surface of the mold part 6 of the male die 5 is formed with a concave-convex line or a convex-concave line for undercanting, and the mold surface of the mold part 2 of the female die l is formed with a concavo-convex line or a convex-concave line for undercanting. These uneven parts are not shaped and are simply smooth surfaces.

As is clear from the method of the present invention described above, this is because the female mold 1
This is a matter of course since it is a mold for molding the preform and the male mold 5 is the final mold for molding the product S3.

The vent hole 3 provided in the female mold 1 is for making the female mold 1 act as a mold for vacuum forming and as a jig for pressure forming. 3 performs a vacuum effect on the space formed between the mold surface formed by the mold part 2 and the sheet S, and when molding the secondary molded product S2, the primary molded product S1 is inserted into the male mold through the ventilation hole 3. This part supplies compressed air that strongly presses against the surface of the mold part 6 of No. 5.

The depth of the mold part 2 of the female mold 1 and the height of the mold part 6 of the advancement 5 are almost the same value, but strictly speaking,
When the female mold 1 and the male mold 5 are clamped, a top wall portion of the primary molded product S1 is formed between the top surface of the mold section 6 of the male mold 5 and the bottom surface of the mold section 2 of the female mold 1. It is set to a value that allows the two to be positioned so that they are in light contact with each other without being pressed.

〔Example〕

The illustrated embodiment shows the case of molding a product S3 which is a screw cap, and the mold surface of the mold part 2 of the female mold 1 is
It has a concave shape with a conical peripheral surface expanding downward and a flat bottom surface, whereas the mold surface of the mold part 6 of the male mold 5 is the outer peripheral surface of a cylindrical body with a flat top surface. The diameter of the top surface of the mold surface of the mold part 6 is a slightly smaller value than the diameter of the bottom surface of the mold surface of the mold part 2, i.e. The value is set to be smaller by the thickness of the primary molded product S1.

First, as shown in FIG. 1, a sheet S heated to a predetermined temperature is supplied between a female mold 1 and a male mold 5 which are in a released state.

At this time, the female mold 1 is heated and maintained in advance at approximately the same temperature as the supplied sheet S by the integrally assembled heating function part 4.

Once the sheet S is supplied, the female mold 1 is moved downward relative to the sheet S, and with its lower surface brought into close contact with the sheet S, vacuum is applied through the ventilation hole 3 as shown in FIG. As a result, the portion of the sheet S facing the mold portion 2 is vacuum-formed into a primary molded product S1.

At this time, since the primary molded product S1 is vacuum formed, its wall thickness is almost uniform, but strictly speaking, the top wall part is slightly thinner than the peripheral wall part. There is.

However, since the vacuum forming using the female mold 1 is carried out with the entire female mold 1 kept at approximately the same temperature as the sheet S, the peripheral wall portion of the primary molded product S1 is also sufficiently elongated and deformed. As a result, there is almost no difference in the amount of stretching between the top wall portion and the peripheral wall portion of the primary molded product S1.
There is no problem that the thickness of the top wall becomes extremely smaller than the thickness of the peripheral wall.

Simultaneously with the vacuum forming operation of the primary molded product S1, or simultaneously with the completion of the vacuum forming operation of the primary molded product S1, the male mold 5 is moved upward relative to the female mold 1, and the female mold 1 and the male mold are Clamp mold 5.

At the time of achieving mold clamping between the female mold 1 and the male mold 5, 1
A slight gap is formed between the next molded product S1 and the mold surface of the mold part 6 of the male mold 5.

At this point, the primary molded product S1 is formed into the female mold l.
It remains insulated and maintained at a temperature that allows it to be thermoformed.

Once the male mold 5 has been clamped to the female mold 1, as shown in FIG. The connection is switched and the primary molded product S1 is pressed against the mold part 6 of the male mold 5 to form a secondary molded product S2 under pressure.

During pressure forming of the secondary molded product S2, the male mold 5 has already been sufficiently cooled by its cooling function part 7, so the secondary molded product S2 is cooled and solidified by the cooling from the male mold 5 and has a constant temperature. The shape is stable.

The primary molded product S1 was molded into a secondary molded product S2 by pressure forming, and when the cooling and solidification of the secondary molded product S2 using the male die 5 was completed, the connection with the compressed air function part of the vent hole 3 was cut off. In this state, as shown in FIG. 4, the male die 5 and the secondary molded product S2 are released from the female die l.

At this time, the secondary molded product S2 always adheres to the male mold 5 side due to the action of the threads formed on its peripheral wall, and is released from the female mold 1 together with the male mold 5.

Once the separation from the female mold 1 has been achieved, as shown in FIG. The secondary molded product S2 that has been molded and then released from the male mold 5 is cut and separated from the sheet body S4, as shown in FIG. 6, to complete the molding of the product S3.

〔Effect of the invention〕

As described above, the present invention vacuum-forms a primary molded product S1 using a heated female mold 1, and forms this primary molded product S1 into a secondary molded product S2 by air pressure forming with almost no stretching deformation. Therefore, the molding operation can be accomplished extremely smoothly and continuously, thereby obtaining a smooth molding operation with almost no operational complexity caused by the combination of vacuum molding operation and pressure molding operation. will be possible.

Further, by vacuum forming the primary molded product S1 using the female mold 1 heated and kept at a predetermined temperature, a primary molded product S1 having a substantially uniform wall thickness is formed as a whole, and this primary molded product S1
2 by pressure forming with almost no stretching deformation.
Since the molded product S2 is then molded, it is possible to obtain a product S3 having a substantially uniform overall wall thickness.

Furthermore, the secondary molded product S2 undergoes almost no stretching deformation from the primary molded product S1 (it is air-pressure formed, so it is molded into the final shape in a state where it is extremely easily deformed; Therefore, not only the inner peripheral surface side but also the outer peripheral surface side can be molded with extremely high dimensional accuracy and shape.

Furthermore, with regard to heat control, the female mold 1 only needs to be heated and kept warm, and the male mold 5 only needs to be cooled, so troublesome heat control can be achieved simply and easily, thereby producing high-quality products. This means that S3 can be molded.

As is clear from the above description, the present invention makes it possible to obtain high-quality products, and to obtain these high-quality products through simple, smooth, and reliable operations. It exhibits many excellent effects such as easy operation and control.

[Brief explanation of drawings]

The drawings are longitudinal cross-sectional views showing one embodiment of the present invention, and FIG. 1 shows the mutual positional relationship between the female mold, the male mold, and the sheet before the molding operation, and FIG. 2 shows the primary molding by the female mold. Figure 3 shows the state of the product during vacuum forming operation of the secondary molded product using the male mold, and Figure 4 shows the release of the male mold and the secondary molded product from the female mold. Fig. 5 shows the state of the secondary molded product being released from the male mold, and Fig. 6 shows the state of the secondary molded product being released from the male mold.
This is a next molded product, and shows the state of a product being cut and separated from the sheet body. Explanation of symbols 1; female mold, 2; mold part, 3; ventilation hole, 4; heating function part, 5; male mold, 6; mold part, 7; cooling function part, S;
Sheet, Sl; Primary molded product, S2; Secondary molded product, S3
; II product, S4; sheet body.

Claims (2)

[Claims] (1) Form a primary molded product by vacuum forming a sheet heated to a predetermined temperature using a female mold that is heated to approximately the same temperature as the sheet, and then mold the primary molded product into a female mold that was vacuum formed. After assembling and clamping the male mold, the primary molded product is air-formed using the male mold as a molding die to form a secondary molded product, and after cooling and solidifying the secondary molded product, A thermoforming method in which the next molded product is cut and separated from the sheet body to complete the product formation. (2) a male mold in which a cooling function part is located within the mold part;
a mold part having a depth and width approximately equal to the height and width of the mold part of the male mold and an inner diameter larger than an outer diameter of the mold part of the male mold; A thermoforming mold device comprising a female mold having a ventilation hole opening to the surface of the mold and a heating function part.