JPS59104905A - High-speed pressure forming method - Google Patents

Abstract

PURPOSE:To make high-speed operation of a pressure forming machine possible, by making sharp the rising of air pressure that acts on a resin sheet from an assistant plug side, and cutting off the feeding of the pressurized air after the rising, thereby preventing the air pressure from rising. CONSTITUTION:In a pressure molding machine wherein a heated resin sheet (a) is clamped between a mold 1 and a closed mold 4, vacuum is applied via suction holes 3 of the mold 1, and pressurized air is fed from an air housing 6 of the mold 4 thereby carrying out the molding, a pressure regulating valve 20 that is set to apply pressure higher than the required air pressure, a receiver tank 21, and an electromagnetic change-over valve 22 are provided in the intermediate section of the feed pipe 19 connecting a pressurized air feeding hole 17 of the closed mold 4 and a pressurized air feeding source 25. The closed mold 4 is provided with a pressure detecting hole 18 to which a pressure switch 24 is connected via a detecting pipe 23. The pressure of the feeding source 25 is higher than that of the conventional feeding source, and when the pressure that is the same as the conventional pressure is detected by the detecting pipe 23, the supply of the pressurized air is cut by the pressure switch 24 and the electromagnetic switch-over valve 22.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of performing a conventional pressure forming method at twice the speed or more.

As shown in FIG. 1, one mold 1 is provided with a mold cavity 2.
and the other closed mold 4 provided with an assist plug 5 loosely inserted into the mold hole 2 and an air surface 6 (in some cases, only the air surface is provided without providing an assist plug etc.),
A heated resin sheet a is sandwiched between one mold 1 and the other sealed mold 4, and the air surface 6 is sealed, and the air on one side of the resin sheet a is drawn from the suction hole 3 of one mold. A pressure regulating valve (2) is installed in the compressed air supply pipe 7 which is connected to the air source and communicates with the air surface 6 to provide vacuum suction.

The compressed air molding method is conventional, in which compressed air set at, for example, 3 kv/cm2 is applied to the other side of the resin sheet (a), and the resin sheet (a) is tightly pressed against the wall of one of the molds. It is publicly known. In this case, there is a limit to the compressed air pressure applied to the other side of the resin sheet a, and if the compressed air pressure is too high, the resin sheet a will be pressed against one mold 1, compressing the mold, and the reaction will cause There is a risk that the other sealed mold will be pushed back and the airtightness of the air cylinder 6 will be broken, causing a leak of compressed air or making pressure molding impossible. Although it is possible to increase the hydraulic pressure switched and supplied, increasing the compressed air pressure requires consideration of the strength of the entire molding apparatus, which is economically disadvantageous.

For this reason, the set pressure of the pressure regulating valve Vl is set to a pressure commensurate with the compressed air molding pressure, for example, around 31 csI/cm2. In addition, an electromagnetic switching valve 2 is inserted in the compressed air supply pipe 7, but this valve has a common function of operating in accordance with the timing of molding and cutting off the supply of compressed air until the condition shown in Figure 1 is reached. It is nothing more than a switching valve. However, for example, 3
When using a known pressure forming method in which the air pressure is set at around 1 cf/cm2, the rise of the air pressure is the third
The curve line A shown in the figure takes a long time to apply a compressed air pressure of, for example, 3 leg/ca'' to the resin sheet a in the air plane, and this increases the air forming speed. The method of the present invention aims to eliminate such drawbacks, and the method of the present invention is to provide a pressurized air supply pipe in which the other sealed pressurized air supply port is connected to a pressurized air supply source. A pressure regulating valve set to a pressure higher than the compressed air pressure, a receiver tank, a switching valve, and a pressure switch for detecting the compressed air pressure in the other closed mold are provided inside, and the high pressure air is supplied from the pressurized feed pipe to the above. The compressed air is supplied to a supply port, a rise in compressed air pressure is detected by the compressed air pressure set in a pressure switch, the switching valve is closed based on the detection signal, and the compressed air supply is analyzed every month. This makes high-speed air forming possible by making the rising edge a straight line with a steep angle.

An embodiment of the method of the present invention will be described with reference to FIG.

In addition to providing pressurized air supply hole 7 in the other sealed mold 4,
A pressure detection hole 18 is provided in a feed pipe 19 that communicates the supply hole I7 with the compressed air supply source 25, and a pressure regulating valve 2 is installed at a pressure of 61 Cg/cIII2, which is significantly higher than before.
0, the receiver tank 21 of the pressure pool, and the electromagnetic switching valve 2-2 are inserted in the illustrated arrangement, and the pressure switch 24 is connected to the detection pipe 23 connected to the pressure detection hole 18. The pressure switch 2a is the same as before when the pressure inside the air cylinder 6 is 3.
The pressure is set to 3 kg/cm 2 so as to detect the increase in pressure to 1 cg/c+a 2 , and the detection operation instructs the electromagnetic switching valve 22 to close via the signal line 26 . The electromagnetic switching valve 22 connects to another signal line 27 at the timing of starting supply of pressurized air during the molding cycle.
command to open the valve.

In the method of the present invention, as shown in the figure, one mold I and the other closed mold 4 are closed with a resin sheet a sandwiched between them by the actions of arrows x, y, and a vacuum suction 28 is applied through the suction hole 3. At the same time, the electromagnetic switching valve 22 is opened, and the pressure regulating valve 20 receives pressurized air 29 at a high pressure far exceeding 6 kg/cm 2 in the example described above and 31 cg/cm 2 in the conventional compressed air pressure example. The air cylinder 6 is fed from the tank 21 to the air cylinder 6. Since the air cylinder 6 is at normal pressure due to the previous molding cycle, the rise in pressure due to the feeding of the high pressure pressurized air 29 is caused by the pressure line B in Fig. 3. The rising part Ba is straight and steep, and the pneumatic pressure acting on the resin sheet a is extremely high.
Reaching 1cg/cI12. However, as mentioned above, if the compressed air pressure exceeds a predetermined pressure, it is harmful to resin sheet molding, but as soon as the predetermined pressure is reached, the pressure switch 24 accurately detects and
A command is given to the valve 22 to close the valve, and the pressure increase is interrupted by closing the valve 22.

In the pressure forming method, pressurized air 29 supplied to the air box 6
As mentioned above, the shorter the rise time of the pressure, the faster the pressure forming speed can be. As is clear, the rising portion Ba is steep, and as is clear from the comparison of the times t1 and t2 for reaching a predetermined pneumatic pressure, the method of the present invention can shorten the culm degree to 1/3 to 1/2. Furthermore, if the pressurized air 29 is fed without limit, the compressed air pressure will rise as shown by the dotted line in Figure 3, and the set pressure of the pressure regulating valve 20 will be reached in about the same time t2 as when the curve line is entered, but by the dotted line pressure. Doing so is harmful to the air pressure forming machine, and at the same time the pressure at the rising portion Ba becomes the same air pressure as before, the pressure detection by the pressure switch 24 cuts off the pressure increase, resulting in an excessive increase in the air pressure forming pressure. There is no danger, and for example 6 kg / c + n 2
For example, the pressure of 3 kg/c is set by the pressure switch 24.
m 2 or so, and the cooling of the resin sheet a due to the latent heat of expansion at that time can also be improved.

As is clear from the above explanation, the method of the present invention makes the rising time of the compressed air pressure applied to the resin sheet a from the assist plug 5 side steep, and after the rising time, the compressed air pressure is fed without increasing. Since it automatically shuts off, the mold closing time required for pressure forming of one mold 1 and the other closed mold 4 is shortened, enabling high-speed molding by high-speed operation of the pressure molding machine, and improving the molding rate ++1i. It has the effect of significantly improving

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the conventional pressure forming method, FIG. 2 is an explanatory diagram of the method of the present invention, and FIG. 3 is a comparison graph of the Vt conventional method and the method of the present invention.

Claims (1)

[Claims] Consisting of one mold and the other closed mold with an air surface, a heated resin sheet is interposed between the one mold and the other closed mold, and air is formed on one side of the resin sheet. In a compressed air molding method in which pressurized air is sucked through a suction hole provided in one mold and pressurized air is supplied to the other closed mold to suppress the other side of the resin sheet, pressurization of the other closed mold is performed. A pressure regulating valve set at a pressure higher than the compressed air pressure, a receiver tank, a switching valve, and a compressed air pressure in the other closed mold are installed in the pressurized feed pipe that communicates the air supply port with the pressurized air supply source. A pressure switch for detection is provided, high pressure air is supplied from a pressurized feeder to the supply port, a rise in the pressure of the compressed air is detected by the pressure of the compressed air set in the pressure switch, and the switching valve is closed by the detection signal. A high-speed pressure forming method characterized by interrupting the supply of compressed air.