JPH0222026Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention enables efficient dispersion of gas into liquid plastic raw materials used as raw materials for reaction-type injection molding machines, for example, and enables easy control of the content. This invention relates to a device for mixing gas into liquid.

[Conventional technology]

In reaction injection molding, in which molded products are manufactured by colliding and mixing at least two or more liquid plastic raw materials that react with each other, the purpose of this is to make the foam structure inside the molded product denser, improve its physical properties and appearance, and increase its product value. Gas is mixed into liquid plastic raw materials as bubbles.

An example of such a device is the one shown in part A of Fig. 5, which has a gas blowing port 22 at the bottom of a tank 21 that stores liquid, and blows gas into the liquid as a jet, thereby generating bubbles. Alternatively, a piping 23 for circulating the liquid in the tank 21 as shown in FIG.
There are some that have a gas blowing port 24 in the middle.

[Problem that the invention attempts to solve]

However, in the above-mentioned conventional technology, a considerable amount of the gas blown under pressure from the blowing ports 22 and 24 immediately floats to the surface and accumulates in the upper space 25 of the tank 21.
Even if the gas remains in the liquid as bubbles, it is supplied from the outside, so the pressure inside the tank 21 gradually increases and is released from the relief valve 26 provided to keep the pressure inside the tank 21 constant. It will be done. In addition, since the bubbles gradually rise and escape into the upper space, it is necessary to repeatedly blow gas in order to keep the mixing rate constant. There was a problem in that the amount of gas released into the atmosphere and wasted could not be ignored in terms of cost.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides a closed tank for storing liquid plastic raw material and supplying the liquid plastic raw material to a molding mechanism, and a space above the liquid plastic raw material in the tank. a device for supplying gas to the space and maintaining a constant gas pressure in the space; and a stirring blade inserted into the tank and rotatably provided to stir the liquid plastic raw material and the gas above the tank. a driving device that rotationally drives the stirring blade and is capable of changing the rotational speed; a measuring device that detects the content rate of the gas in the liquid plastic raw material; and a detection value of the measuring device and a preset gas. Based on the difference between the content and the target value, the rotational speed of the stirring blade for the target gas content is determined from the correlation between the rotational speed of the stirring blade and the gas content in the liquid plastic raw material, and this rotation is calculated. and a control device for controlling the drive device so that the stirring blades rotate according to the number of seconds.

[Effect]

The above-mentioned stirring blade stirs the liquid in the tank, and the gas whose pressure is maintained constant in the space above the tank is taken into the liquid and mixed uniformly, and there is a strong correlation with the rotation speed of the stirring blade. The gas content of the liquid is maintained at the required value by the relevant value.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 4.

FIG. 1 shows the first embodiment of the present invention. In this figure, 1 is a closed tank for storing liquid (liquid plastic raw material), and the bottom of the tank 1 and its vicinity are filled with air bubbles dispersed. a discharge pipe 2 that sends the liquid to a molding mechanism M such as an injection molding machine;
A return pipe 3 for returning the circulating liquid from the molding mechanism M to the tank 1 is connected to each of them. Further, a pressure gauge 5 for measuring the atmospheric pressure in the space 4 is provided at the upper part of the tank 1 .

Reference numeral 6 denotes a stirring blade that is inserted into the tank 1 so as to be located slightly below the level of the stored liquid, and stirs the liquid. It is designed to be rotated by a motor 8. The speed change mechanism 7 and motor 8 constitute a driving device for the stirring blades 6.

Reference numeral 9 denotes a gas introduction port provided above the level of the stored liquid in the tank 1, and communicates with a gas supply source A such as nitrogen through a pneumatic pipe 10.
A pressure reducing valve 11 with a relief valve provided at the tank 1 keeps the air pressure in the upper space 4 of the tank 1 constant.

12 is a device for measuring the gas content in the liquid, which is attached to the return pipe 3 from the molding mechanism M;
Reference numeral 3 denotes a control device that outputs a signal to the transmission mechanism 7 to change the rotational speed of the stirring blade 6 based on the difference between the detected value of the measuring device 12 and a preset content rate target value.

As the gas content measuring device 12, a device is employed in which the liquid to be measured is sealed in a cylinder and the gas content is measured from the relationship between the movement of a piston and the pressure of the liquid.

Note that the shape, number, etc. of the stirring blades 6 are experimentally found to be efficient and adopted.

Next, the operation of the apparatus configured as described above for mixing gas into liquid will be described.

First, Figure 3 shows the results of measuring the gas content in the liquid by changing the rotational speed of the stirring blade 6 under the condition that the pressure in the space 4 was kept constant without operating the control device in this device. and shown in FIG. From this result, it can be seen that the gas content changes following the rotation of the stirring blade 6, and that there is a substantially linear correlation therebetween.

Based on this correlation, the stirring blade 6
By setting the rotation speed in advance in accordance with the target gas content, it is possible to obtain a liquid having a gas content that roughly matches the target value. If this method is used, a relatively simple device can be obtained.

Here, if the above-mentioned correlation is unknown or when performing more stable control, if the detected value of the gas content measuring device 12 is lower than the target value, the rotation speed of the stirring blade 6 is increased to achieve the target value. If the rotation speed is higher than that, the control device 13 performs feedback control to lower the rotation speed.

What is shown in FIG. 2 shows a second embodiment of the present invention, in which a storage tank 14 is provided between a gas mixing tank 1 and a forming mechanism M.
4 and the tank 1 for gas mixture, the pump P
The liquid is circulated through the circulation pipe 15, and the spaces 4 and 4 above the tanks 1 and 14 are
16 are made to communicate with each other via a pneumatic tube 10. Such a device is required when a large amount of liquid is used and it would be more convenient to store more liquid, or when a new gas mixing device is added to an existing storage tank.

In the embodiments shown in FIGS. 1 and 2 above,
Since gas is directly supplied to the spaces 4 and 16 and mixed with the liquid, the air pressure in the spaces 4 and 16 does not rise more than necessary, and there is no loss of gas at all. Gases can be mixed into liquids efficiently and at extremely low cost.

Furthermore, it is easy to control the gas content, and therefore automatic control is also easy, and high-quality molded products can be produced.

When feedback control is performed by the control device 13, the gas content in the liquid can be kept extremely constant at an arbitrary value. Coupled with the ability to make the gas content extremely uniform, the quality of the molded product molded by the molding mechanism M can be greatly improved.

[Effect of idea]

The present invention includes a closed tank that stores liquid plastic raw material and supplies the liquid plastic raw material to a molding mechanism, and a closed tank that stores a liquid plastic raw material and supplies the liquid plastic raw material to a forming mechanism; a device for maintaining a constant pressure; a stirring blade inserted into the tank so as to be freely rotatable and stirring the liquid plastic raw material and the gas above it; a drive device capable of changing the content of the gas in the liquid plastic raw material; a measuring device that detects the content of the gas in the liquid plastic raw material; From the correlation between the rotational speed of the stirring blade and the gas content in the liquid plastic raw material, the rotational speed of the stirring blade for the target gas content is determined, and the driving is performed so that the stirring blade rotates at this rotational speed. Since the device is equipped with a control device that controls the device, the content of gas in the liquid plastic raw material is maintained at a constant target value by the stirring action of the liquid plastic raw material and the gas above the liquid plastic raw material. be able to.

In other words, the gas content in the liquid plastic raw material can be kept extremely constant at any value, and the gas content in the liquid plastic raw material in the tank can be made extremely uniform by the stirring action of the stirring blade. Moreover, since there is no waste of releasing gas into the atmosphere, unlike when blowing gas from the outside, gas can be mixed into the liquid plastic raw material at an extremely low cost.

Therefore, the quality of the molded product formed by the molding mechanism can be greatly improved, and the cost of the molded product can be reduced, which is an excellent effect.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the first embodiment of the present invention, Figure 2 is a schematic diagram of the second embodiment, and Figures 3 and 4 are the rotation speed and gas content of the stirring blade in the first embodiment. FIG. 5 is a schematic diagram of a conventional example. 1... Tank, 4... Space, 6... Stirring blade,
7... Speed change mechanism, 8... Motor, 9... Inlet,
DESCRIPTION OF SYMBOLS 10... Pneumatic pipe, 11... Pressure reducing valve, 12... Gas content measuring device, 13... Control device, M... Molding mechanism.

Claims (1)

[Scope of Claim for Utility Model Registration] A closed tank for storing liquid plastic raw material and supplying the liquid plastic raw material to a molding mechanism, and supplying gas to a space above the liquid plastic raw material in the tank. a device for maintaining a constant gas pressure in the space; a stirring blade inserted into the tank and rotatably provided to stir the liquid plastic raw material and the gas above it; and rotating the stirring blade. a driving device that can be driven and whose rotational speed can be changed; a measuring device that detects the content rate of the gas in the liquid plastic raw material; and a detection value of the measuring device and a preset target value of the gas content rate. Based on the difference, the rotation speed of the stirring blade for the target gas content is determined from the correlation between the rotation speed of the stirring blade and the gas content in the liquid plastic raw material, and the stirring blade is rotated at this rotation speed. An apparatus for mixing gas into liquid plastic raw material, characterized in that it is equipped with a control device for controlling the drive device so as to control the driving device.