JPS5983614A - Apparatus for vacuum molding of plastics - Google Patents

Abstract

PURPOSE:To improve close adhesiveness to a mold surface to make the finish of a product sharp and to enable deep drawing processing, by a method wherein two vacuum tanks are provided between the vacuum suction port of a female mold and a vacuum pump in parallel and a two-stage suction system is employed. CONSTITUTION:Two vacuum tanks 7, 13 are provided between the vacuum suction port of a female mold 2 and a vacuum pump 6 in parallel. A heat softened plastic plate 15 is placed on a female mold 2 and covered with a cover lid 17 while a vacuum pump 6 is operated to reduce the pressure of the interior 3 of a female mold through an A-circuit consisting of the vacuum tank 7 and a solenoid valve 11 to closely adhere the plastic plate 15 to the inner surface 4 of the female mold. In this case, when pressure reduction is not sufficient only by the vacuum tank 7, the solenoid valve 11 is closed while a solenoid valve 14 is opened to change over said tank 7 to a vacuum tank 13 and two-stage sucking is performed by utilizing the high vacuum degree of a B-circuit to closely adhere the plastic plate 15 with the inner surface 4 of the female mold.

Description

[Detailed Description of the Invention] The present invention relates to a vacuum forming apparatus that molds a heated and softened plastic sheet or plastic plate by applying vacuum to the mold surface, or using pressure in combination with vacuum. This is related to improving vacuum/pressure forming equipment, allowing products to have a sharp finish with good adhesion to the mold surface.
The present invention also relates to a vacuum forming apparatus that can be applied to deep-drawn products.

In the vacuum forming of plastic plates, for example, as shown in Figure 1, a female mold (
2) is attached, and the female mold (2) has a lower vacuum suction chamber (
3) The inner surface of the mold (4), small suction holes (5) are provided at the corners or ridges of the inner surface of the mold, and a vacuum pump (3) is provided to vacuum the vacuum suction chamber (3) of the female mold (2) A vacuum piping device consisting of a vacuum tank (7), a vacuum pipe (8), and a vacuum tank (7) is provided.

Conventional vacuum piping consists of only one circuit: the vacuum pump (6), the vacuum tank (7), the vacuum piping (8) to the suction chamber (3), and the solenoid valve (9) shown by the dashed line in Figure 1. There wasn't. Therefore, the inside of the vacuum tank (7) is 1O-4 at all times.
Even if the vacuum is close to Torr, the degree of vacuum drops immediately when the pulp (9) is opened. Furthermore, as the temperature of the heated plastic plate α decreases, its tensile strength increases rapidly over time, making it difficult to conform to the mold. Therefore, with low tensile strength,
In order to quickly reach and maintain the maximum degree of vacuum in the temperature range where elongation reaches its maximum value, the present invention employs a two-stage suction system. That is, the feature is that two vacuum tanks are installed in parallel between the vacuum suction port of the mold and the vacuum pump, and vacuum tank A is connected from the vacuum pump to vacuum tank A.
A circuit consisting of a series circuit of and a solenoid valve A, and a check valve B,
It is provided with three circuits consisting of a vacuum tank B and a series circuit of a solenoid valve B.

The solid line in FIG. 1 is a mold cross section and a piping system diagram showing a specific example of the present invention. A circuit with a series circuit of vacuum tank A (7) and a solenoid valve ACII), one check valve Bα, and 3 circuits with a series circuit of another vacuum tank B03 and a solenoid valve BO■ are connected in parallel. It is set up.

The circuit is the conventional piping shown by the dashed line at the bottom of Figure 1.
Close the solenoid valve AOη and the 3-circuit solenoid valve B (M), operate the vacuum pump (6) and turn it on to evacuate the vacuum tank A (7) and the vacuum tank B Q3. Next, when the solenoid valve Aα◇ is opened, the vacuum suction chamber (3) of the female type (2) passes through the small suction holes (5) in the bottom corners and ridges of the female type (2), and then the glass plate. αG is pulled downward and deforms until it aligns with the inner surface of the mold (4). At this time, if the female mold (2) is deep-drawn 9 or if the glass plate θ~ has a large thickness, the vacuum tank A alone may not be able to draw it sufficiently. Therefore, close solenoid valve AOυ, open solenoid valve B Q4, and switch to vacuum tank B (13).
Utilizes the high degree of vacuum of 3 circuits to perform 2-stage evacuation.

Since there is a check valve B (U) in the 3rd circuit, it is just a solenoid valve B.
By operating u4), the degree of vacuum in the vacuum suction chamber (3) is maintained at a high vacuum. Switching between solenoid valves A and B can be performed automatically using an electrical control circuit.

The plastic plate Q0 is clamped around the circumference by a clamping frame uQ and heated with a heater to heat and soften the plate from both the upper and lower sides or from one side. Although the heater is not shown, the female mold (2) and the upper lid α force are released upward and downward, respectively, and the heater is moved forward to efficiently heat the plastic plate αO while sandwiching it. A communication hole 0→ that communicates with atmospheric pressure is made in the cover 025, and a bubble α is inserted into this hole.
It is also possible to connect the pump and the near compressor (a) with a full-pressure air pipe (21), and perform vacuum/pressure forming by compressing air with the near compressor at the same time as the two-stage suction described above.

In addition, from the near compressor (1) to the valve +221'
It is convenient to connect the pipe to the female vacuum suction chamber (3) via r and use it for releasing the molded product.

The two-pronged vacuum suction tool described above enables sharp forming and deep drawing that cannot be achieved with conventional vacuum forming.
This had the effect of making vacuum forming and vacuum/pressure forming metals even more useful.

[Brief explanation of the drawing]

Figure 1 shows a cross-sectional view of the mold and a diagram of the piping system. (2) Female type (6) Vacuum pump (7
) Vacuum tank A (8) Vacuum piping OI Vacuum suction port aυ Solenoid valve A @ Check valve B
IJ3 Vacuum tank Ba< Solenoid valve B
(1119) 0 running board 0η cover lid
(E) Air conditioner, 76v or more 64-

Claims (1)

[Claims] 1. In a vacuum forming device that vacuum-suctions a heat-softened plastic plate to form it along the mold surface, two vacuum tanks are installed in parallel between the vacuum suction port of the mold and a vacuum pump, and the vacuum pump's A circuit consisting of a series circuit of vacuum tank A and solenoid valve A, check valve B, vacuum tank B,
A plastic vacuum forming apparatus characterized in that eight circuits consisting of a series circuit of solenoid valves B are provided in parallel.