JPS6315130B2 - - Google Patents

Description

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

For vacuum forming of plastic plates, for example, as shown in Fig. 1, a female mold 2 is mounted on a base plate 1 that is set in a press machine and moves up and down. 2 is provided with a lower vacuum suction chamber 3, an inner surface 4 of the mold, and small suction holes 5 at corners or ridges of the inner surface of the mold, and is further provided with a vacuum pump 6 and a vacuum tank for evacuating the vacuum suction chamber 3 of the female mold 2. A vacuum piping device consisting of a vacuum pipe 7 and a vacuum pipe 8 is provided.

The conventional vacuum piping consists of only one circuit, which includes a vacuum pump 6, a vacuum tank 7, a vacuum piping 8 to the suction chamber 3, and a solenoid valve 9, which are indicated by a dashed line in FIG. Therefore, the inside of the vacuum tank 7 is always
Even if the vacuum is close to 10 ^-4 Torr, the degree of vacuum drops immediately when valve 9 is opened. Further, the temperature of the heated plastic plate 15 decreases, and its tensile strength rapidly increases over time, making it difficult to conform to the mold.
Therefore, in order to quickly reach and maintain the maximum degree of vacuum in the temperature range where tensile strength is low and elongation reaches its maximum value, the present invention adopts a two-stage suction system. In other words, the feature is that two vacuum tanks are installed in parallel between the vacuum suction port of the mold and the vacuum pump, and the A circuit consisting of a series circuit of vacuum tank A and solenoid valve A is connected to the vacuum pump. , a check valve B, a vacuum tank B, and a B circuit consisting of a series circuit of a solenoid valve B.

The solid line in FIG. 1 is a mold cross section and piping system diagram showing a specific example of the present invention, and a vacuum tank A7 and a solenoid valve are connected between the vacuum pump 6 and the vacuum piping 8 leading to the vacuum suction port 10 of the vacuum suction chamber 3. Circuit A has A11 in series circuit, check valve B12, another vacuum tank B13, and solenoid valve B14 in series circuit.
The circuits are installed in parallel.

The A circuit is the conventional piping indicated by the dashed line at the bottom of Figure 1. First, the solenoid valve A11 and the solenoid valve B14 of the B circuit are connected.
, and then operate the vacuum pump 6 and keep it pulled to evacuate the vacuum tank A7 and the vacuum tank B13. Next, when the solenoid valve A11 is opened, the plastic plate 15 is pulled downward from the vacuum suction chamber 3 of the female mold 2 through the small suction holes 5 provided in the bottom corners and ridges of the female mold 2, and the plastic plate 15 is drawn downward onto the inner surface 4 of the mold. Transform until they fit together. At this time, the female mold 2 is deep drawn,
If the plastic plate 15 is thick, the vacuum tank A alone may not be able to pull it out sufficiently. Therefore, solenoid valve A11 is closed, and solenoid valve B14 is closed.
Open it, switch to vacuum tank B13, and use the high degree of vacuum of B circuit to perform a two-stage pull-out.

Since the B circuit has a check valve B12 that prevents air from moving from the direction of the vacuum tank A7 to the direction of the vacuum tank B13, the degree of vacuum in the vacuum tank A7 decreases by simply operating the solenoid valve B14. Despite this, the movement of air into the vacuum tank B13 is prevented, and 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 15 is clamped around the periphery by a clamping frame 16, and heated with a heater to heat and soften the plate from both upper and lower sides or from one side. Although the heater is not shown, there is a female mold 2 and an upper cover 1.
7 are released upward and downward, respectively, and the heater is moved forward to efficiently heat the plastic plate 15 in a state in which it is sandwiched therebetween. A communication hole 18 is made in the cover 17 to communicate with the atmospheric pressure, and a valve 19 and an air compressor 20 are connected to this through a compressed air piping 21. At the same time as the above-mentioned two-stage suction, air is compressed by the air compressor to create a vacuum. Pneumatic molding can also be performed.

Note that it is convenient to connect the air compressor 20 to the female vacuum suction chamber 3 via the valve 22 and use it for mold release blowing of the molded product.

The two-stage vacuum suction described above enables sharp forming and deep drawing that could not be achieved with conventional vacuum forming, and has the effect of making vacuum forming and vacuum/pressure forming even more useful. be.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the mold and a piping system diagram. 2... Female type, 6... Vacuum pump, 7... Vacuum tank A, 8... Vacuum piping, 10... Vacuum suction port, 11... Solenoid valve A, 12... Check valve B, 13
...Vacuum tank B, 14...Solenoid valve B, 15...
Plastic board, 17... cover, 20... air compressor.

Claims (1)

[Claims] 1. In a vacuum forming device that vacuums 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 a vacuum pump is used to draw a vacuum from the vacuum pump. Circuit A consists of a series circuit of tank A and solenoid valve A, and circuit A consists of a series circuit of check valve B, vacuum tank B, and solenoid valve B that prevents air from moving from vacuum tank A7 to vacuum tank B13. A plastic vacuum forming apparatus characterized in that a B circuit is provided in parallel.