JPH0144134B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for entraining a gas into a liquid, such as a plastic liquid component.

In reaction injection molding, in which molded products are manufactured by colliding and mixing at least two plastic liquid components (liquids) that react with each other, the foam structure inside the molded product is made dense, improving its physical properties and appearance, and increasing its commercial value. For the purpose of increasing the strength, air (gas) is mixed into the plastic liquid component as fine bubbles. Conventionally, a liquid pump that circulates the plastic liquid component through the flow path, a gas blowing device that mixes air into the plastic liquid component flowing through the flow path, and a gas blowing device that circulates the plastic liquid component flowing through the flow path. Although a gas content measuring device for measuring the air content in the components is provided, it has the disadvantage that the configuration is complicated and the operation is complicated.

Furthermore, if the plastic liquid component contains a filler such as glass fiber, the liquid pump will wear out quickly due to the filler, so in the conventional device using the liquid pump, the filler is not included. The drawback was that plastic liquid components could not be used.

Therefore, the applicant devised a device for mixing gas into liquid as shown in Fig. 1 (Japanese Patent Application No. 1983-
No. 163706). The device that mixes gas into this liquid is
a circulation cylinder device 3 for circulating the liquid in a liquid tank 1 through a liquid channel 2 connected to the liquid tank 1; and a gas blowing device 4 for mixing gas into the liquid flowing through the liquid channel 2. , a pressure detection means 5 for detecting the pressure inside the cylinder 3a of the cylinder device 3, and a piston 3b of the cylinder device 3.
The gas mixing rate in the liquid is calculated using the position detection means 6 which detects the position of the pressure detection means 5 and the position detection means 6, and the calculated value is compared with a predetermined set value. , and a control device 7 for controlling the gas blowing device 4 according to the results, and can also be used for plastic liquid components containing fillers,
The cylinder device 3 is provided with a liquid circulation function and a gas entrainment rate measurement function to simplify the configuration and improve operability.

By the way, although the same applies to conventional devices, in the above device, the flow rate of gas mixed into the liquid is
The flow rate adjustment valve 8 sets the flow rate to a constant value. However, increasing this set flow rate makes it difficult to accurately achieve the target gas mixture rate, and conversely, decreasing this set flow rate improves the accuracy of achieving the target gas mixture rate, but the target gas mixture rate becomes difficult to achieve. There were complaints that it took a long time to reach the target rate.

The present invention provides a liquid circulation device in the liquid flow path, a gas blowing device in both the liquid flow path and the liquid tank, and uses a measurement control device to blow the gas based on the gas mixture rate in the liquid. This device is configured to comprehensively control the mixing device to eliminate the above-mentioned dissatisfaction with the conventional method, and is capable of quickly and accurately achieving the target gas mixing rate. The purpose is to provide. Hereinafter, the present invention will be explained in detail based on the drawings.

FIGS. 2 to 4 show an embodiment of the present invention, in which numeral 10 indicates a liquid tank for storing a plastic liquid component (liquid) of a high-pressure reaction injection molding machine. The liquid tank 10 is connected to both ends 11a and 11b of a liquid flow path 11 made of piping, and is provided with a stirring blade 13 rotated by a motor 12 inside. The liquid flow path 11
In this case, the liquid in the liquid tank 10 is transferred to the liquid flow path 11.
A highly wear-resistant circulation cylinder device (liquid circulation device) 14 that circulates through the liquid flow path 11
A first gas blowing device 15 is provided for mixing gas into the liquid flowing through the liquid. That is, the liquid tank 10 is connected to the α of the first and second three-way switching valves 17 and 18 via the first switching valve 16 which is normally open.
the first three-way switching valve 1, which is connected to each end of the first three-way switching valve 1;
Cylinder 1 of the circulation cylinder device 14 is connected to the β end of 7.
One end of 9 is connected. Further, the other end of the cylinder 19 of the cylinder device 14 is connected to the β end of the second three-way switching valve 18, and inside the cylinder 19, a piston 21 provided at one end of a piston rod 20 slides. It is fitted so that it can move freely. Further, at the other end of the piston rod 20, a piston 2 that slides within the actuator 22 is provided.
3 is provided, and the piston 21 of the cylinder device 14 is configured to reciprocate from side to side in FIG. 2 by a hydraulic circuit (not shown) connected to both ends of the actuator 22. When the piston 21 moves to the reverse end (the leftmost position in FIG. 2), the first three-way switching valve 17 is switched in conjunction with the movement, so that its α end and β end are mutually switched. At the same time, the second and third method switching valve 18 is also switched, and its β
The end and the γ end communicate with each other, and when the piston 21 moves to the forward end (the rightmost position in FIG. 2), the second
The three-way switching valve 18 is switched so that its α end and β
At the same time, the first three-way switching valve 17 is also switched so that its β and γ ends are brought into communication with each other.

On the other hand, the γ end of the second three-way switching valve 18 is connected to the first three-way switching valve 17 via the second switching valve 24.
is connected to the γ end of the first gas blowing device 15 and one end of the first gas blowing device 15, respectively.
The other end is connected to the liquid tank 10 via a check valve 25 and a third switching valve 26 which is normally open.

A gas supply source 28 is connected to the first gas blowing device 15 via a pipe 27, and a gas pressure control valve 2 is connected to the pipe 27 in order from the gas supply source 28.
9, gas pressure gauge 30, first gas flow rate adjustment valve 31,
First gas flow meter 32, first gas solenoid valve 33, first
A gas check valve 34 is provided. Further, the liquid tank 10 is provided with a second gas blowing device 35 that mixes gas into the liquid in the liquid tank 10 . This second gas blowing device 35 is connected to the gas pressure control valve 2 of the pipe 27 via a pipe 36.
9 and the gas pressure gauge 30, and in this piping 36, in order from the second gas blowing device 35, a second gas check valve 37, a second gas solenoid valve 38,
A second gas flow meter 39 and a second gas flow rate adjustment valve 40 are provided.

Further, the piston rod 20 is provided with a measuring element 41, and a rack 41a formed on one side of the measuring element 41 is provided with a measuring element 41.
A pinion 42a of an encoder 42 for measuring the zero position is engaged. Further, the cylinder 19 of the cylinder device 14 is provided with a pressure sensor 43 for detecting internal pressure, and these encoders 42 and pressure sensors 43 are connected to the control device 4.
4 is attached.

The control device 44 includes a calculation unit 45 that calculates the gas mixture rate in the liquid using the outputs from the encoder 42 and the pressure sensor 43, and a storage unit that stores the measured value of the gas mixture rate calculated by the calculation unit 45 in advance. 46 and a predetermined set gas mixing rate smaller than the target value. If the rate is lower than the above-mentioned first and second gas solenoid valves 33, 3
8, and when the measured value of the gas mixing rate is lower than the target value and higher than the set gas mixing rate, only the first gas solenoid valve 33 is opened, and the measured value of the gas mixing rate is opened. is higher than or equal to the target value, the first and second gas solenoid valves 3
3 and 38, the calculation section 45 is connected to the encoder 42 and the pressure sensor 43, and the command section 48 is connected to the encoder 42 and the pressure sensor 43.
They are connected to second gas solenoid valves 33 and 38, respectively. Then, the encoder 42, pressure sensor 43, control device 44, etc. measure the gas mixture rate in the liquid, and comprehensively control the first and second gas blowing devices 15, 35 based on the measured value. A measurement control device 49 is configured.

As is well known, a measuring cylinder device 50 and a mixing head 51 are connected to the liquid tank 10, and the plastic liquid component supplied from the liquid tank 10 is sent to the mixing head 51 for other measuring operations (not shown). By mixing with other plastic liquid components sent from a cylinder device or the like, molded products can be obtained by reaction of the flowing liquid components. Further, numeral 52 in the figure is a level meter for measuring the liquid level of the plastic liquid component in the liquid tank 10.

Next, the operation of the apparatus for mixing gas into a liquid according to the present invention configured as described above will be explained.

First, the liquid in the liquid tank 10 is transferred to the liquid channel 11.
In order to circulate the water through the air, the cylinder device 14 may be operated. That is, the cylinder device 14
When the piston 21 is retracted and moved to the leftmost position in FIG. The 2-3 mode switching valve 18 is switched, its β end and γ end are communicated, and the first, second, and third switching valves 16, 24, and 26 are each in an open state. When a hydraulic circuit (not shown) is operated from this state to move the piston 23 in the actuator 22 forward to the right in FIG. 2, the piston 21 of the cylinder device 14 is moved to the right in conjunction with this, so that The liquid in the device 14 is transferred from the other end of the cylinder 19 to the second and third type switching valve 1.
The liquid flows into the cylinder device 14 through the β and γ ends of the first three-way switching valve 17 and the second switching valve 24, and the liquid flows into the cylinder device 14 through the α and β ends of the first three-way switching valve 17. The water is allowed to flow in from one end of the cylinder 19. Therefore, the liquid in the liquid tank 10 is
As indicated by the arrows in FIG.
4, first gas blowing device 15, check valve 25, third
The liquid is fed under pressure in the order of the switching valve 26 and circulated to the liquid tank 10. Next, when the piston 21 of the cylinder device 14 moves to the rightmost position in FIG. The 2-3 mode switching valve 18 is switched, and its α end and β end are connected. When the hydraulic circuit is switched and the piston 23 in the actuator 22 is moved back to the left in FIG. 2, the piston 21 of the cylinder device 14 is moved to the left in conjunction with this, so that Liquid is in cylinder 1
The liquid flows out from one end of 9 into the liquid flow path 11 through the β and γ ends of the first three-way switching valve 17, and the α and β ends of the second three-way switching valve 18 are injected into the cylinder device 14. through which liquid is allowed to flow from the other end of the cylinder 19. Therefore, the liquid in the liquid tank 10 is sucked into the cylinder device 14 in the order of the first switching valve 16 and the second three-way switching valve 18, as shown by the arrow in FIG. 1
7, first gas blowing device 15, check valve 25, third
The liquid is fed under pressure in the order of the switching valve 26 and circulated to the liquid tank 10.

In this way, by switching the hydraulic circuit and reciprocating the piston 23 in the actuator 22 to the left and right, the piston 23 of the cylinder device 14
1 is reciprocated from side to side, and the liquid in the liquid tank 10 is circulated through the liquid channel 11.

Therefore, gas is mixed into the liquid by the first and second gas blowing devices 15 and 35, but at that time, the control device 44 is controlled based on the outputs from the encoder 42 and the pressure sensor 43. Therefore, the gas mixing rate in the liquid is calculated, and the first and second gas blowing devices 15 and 35 are generally controlled based on the calculated value.

That is, when calculating the gas mixture rate in the liquid, first, the α end and the β end of the second three-way switching valve 18 are communicated with each other, and the piston of the cylinder device 14 is opened with the second switching valve 24 closed. 21 from the right to the left to draw liquid into the cylinder 19 from the other end (see Figure 3A). Then, in order to reduce the internal pressure of the liquid, the β end and the γ end of the second three-way switching valve 18 are communicated with each other, and the piston 21 of the cylinder device 14 is moved further to the left while preventing the liquid from flowing in from the α end. (See Figure 3 B). Next, the piston 21 of the cylinder device 14
Move to the right and move on to compression. Then, the pressure sensor 43 detects that the first pressure (low pressure) P ₁ preset by the control device 44 has been reached, and the piston stroke l ₁ at that point is read by the encoder 42 (see Fig. 3). reference). moreover,
The pressure sensor 43 detects when the second pressure (high pressure) P ₂ preset by the control device 44 is reached, and the encoder 42 reads the piston stroke l ₂ at that point. These measurement data P ₁ , P ₂ , l ₁ , l ₂ are stored in the calculation unit 45 of the control device 44.
The gas mixing rate Xa in the liquid under atmospheric pressure is calculated using the following equation.

Xa=πD ² lP ₁ P ₂ /N However, N=4.132 (V ₀ + V _P −πD ² l ₁ /4) × (P ₂ − P ₁ ) + πD ² lP ₂ × (P ₁ −1.033) This formula is determined as follows. In other words, (1) the state equation for gas (PV = constant) holds true even when mixed with liquid.

(2) Liquids are incompressible.

And, Pa: Atmospheric pressure (1.033Kg/cm ² ) P ₁ : First pressure condition Kg/cm ² (absolute pressure) P ₂ : Second pressure condition Kg/cm ² (absolute pressure) Vm: Volume of liquid cm ³ Va: Volume of entrained gas under Pa, cm ³ V ₁ : Volume of entrained gas under P ₁ , cm ³ V ₂ : Volume of entrained gas under P ₂ , cm ³ V ₀ : Volume of cylinder 19, cm ³ Vf: P ₁ Total volume of liquid and gas in the lower cylinder 19 cm ³ Vs: P ₂ Total volume of liquid and gas in the lower cylinder 19 cm ³ V _P : Internal volume of the pipe cm ³ l ₁ : Pressure from encoder 42 origin a Distance cm from point b where the pressure becomes P ₁ cm: Distance cm from point b where the pressure becomes P ₁ to point c where the pressure becomes P ₂ (l = l ₂ − _{l 1} ) D: Cylinder 19 The diameter is cm. From the gas state equation, 1.033Va=P ₁ V ₁ = P ₂ V ₂ Therefore, V ₁ = 1.033Va/P ₁ ………(1) V ₂ = 1.033Va/P ₂ ………(2) V ₁ −V ₂ =1.033Va×(1/P ₁ −1/P ₂ )……(3) Also, Vf＋V _P =V ₁ +Vm……(4) Vf＝V ₀ −πD ² l ₁ /4 ………(5) From formulas (1), (4), and (5), Vm=Vf+V _P −V ₁ =V ₀ −πD ² l ₁ /4 +V _P −1.033Va/P ₁ ………(6) Furthermore, V ₁ −V ₂ = πP ² l/4 ………(7) (3) From equation (7), Va=πD ² lP ₁ P ₂ /{4×1.033(P ₂ −P ₁ )} …( 8) Since the gas mixing rate Xa is determined by Xa=Va/(Vm+Va), from equations (6) and (8), Xa=πD ² lP ₁ P ₂ /N where N=4.132 (V ₀ +V _P −πD ² l ₁ /4) (P ₂ - _{P 1} ) + πD ² lP ₂ (P ₁ - 1.033) In this way, based on the measurement data P ₁ , P ₂ , l ₁ , l ₂ , the calculation unit 45 of the control device 44 calculates the When the mixture rate is calculated, the calculation result is compared with a target value of the gas mixture rate stored in advance in the storage unit 46 and a predetermined set gas mixture rate lower than the target value, and the result is The signal is sent to the command unit 48 and the first and second gas blowing devices 15 and 35 are controlled. That is, when the comparator 47 determines that the measured value of the gas mixture rate obtained by the calculation unit 45 is lower than the set gas mixture rate, the command unit 48 controls the first and second gas solenoid valves 33 and 38. Open both.
Then, the gas sent from the gas supply source 28 is mixed into the liquid in both the liquid flow path 11 and the liquid tank 10 by the first gas and second gas blowing devices 15 and 35, and the gas is mixed into the liquid in both the liquid flow path 11 and the liquid tank 10. The liquid is transferred to the liquid flow path 1 by the switching valves 17, 18, and 24.
1 and is circulated within the liquid tank 10. On the other hand, when the comparison unit 47 determines that the measured value of the gas mixture rate is higher than the set gas mixture rate and lower than the target value, the command unit 48 opens only the first gas solenoid valve 33 and Solenoid valve 38 is closed. Then, the gas from the gas supply source 28 is mixed into the liquid in the liquid flow path 11 only by the first gas blowing device 15, and the liquid is circulated in the same manner as described above. Furthermore, when the comparison unit 47 determines that the measured value of the gas mixing rate is higher than or equal to the target value, the command unit 48 controls the first and second gas solenoid valves 3.
3 and 38 to stop the mixture of gas.
Then, the liquid is circulated in the same manner as above, but
At that time, if necessary, the liquid tank 10 is replenished with liquid that is not mixed with gas.

As described above, in the device for mixing gas into liquid of the present invention, when the gas mixing rate is lower than the set gas mixing rate, the first and second gas blowing devices 13, 3
Since gas is mixed into the liquid by both of 5,
The gas mixing rate is fast and the gas mixing rate increases rapidly, but when the gas mixing rate reaches the set gas mixing rate,
Since the second gas blowing device 35 is stopped and gas is mixed only by the first gas blowing device 15, the gas mixing speed is reduced and the target gas mixing rate can be achieved with high accuracy. can. That is, if the amount of gas blown by the first gas blowing device 15 is increased, the gas mixture rate can be rapidly increased, but the measurement interval of the gas mixture rate is, for example, about 30 seconds, and it is impossible to further shorten this. Since this is not possible, too much gas is blown in when the gas mixing rate approaches the target value. On the other hand, if the amount of gas blown is reduced, it will take a long time until the gas mixing rate reaches the target value. For this reason, in the apparatus of the present invention, the second gas blowing device 35 is provided in the liquid tank 10, and gas is blown into the liquid tank 10 by both gas blowing devices 10 and 35 to rapidly reduce the gas mixing rate. It was designed to increase the

Here, it is possible to provide a plurality of gas blowing devices only in the liquid flow path 11, but the liquid tank 1
0 capacity is, for example, about 250, whereas the amount of liquid circulated by the cylinder device 14 is, for example, about 10.
Since the flow rate is as small as /min, a large amount of gas is blown into the liquid flow path 11 where the amount of liquid is small, and the gas may not form fine bubbles. Therefore, in order to rapidly increase the gas entrainment rate,
Preferably, gas is blown into the liquid tank 10.

Incidentally, the liquid mixed with gas is sent from the liquid tank 10 to the mixing head 51 by the measuring cylinder device 50 at regular time intervals.
Even when the liquid in tank 10 decreases to a low level and a new liquid without gas is supplied to the liquid tank 10 to a high level, and the amount of liquid without gas increases rapidly, this mixing continues. head 49
The supply of liquid continues. Therefore, in order to maintain a uniform rate of gas mixture in the liquid, it is necessary to particularly increase the gas mixture rate in the above cases, and the apparatus of the present invention is extremely effective in such cases.

In the above embodiment, the cylinder device 14 was used for liquid circulation in consideration of wear resistance, etc., but if there is no need to take wear resistance etc. into consideration, the cylinder device 14 may be used as in the conventional case. A liquid pump may also be used. Furthermore, in the above description, the liquid channel 11 and the liquid tank 10 are each provided with one first and second gas blowing device 15, 35, but both the liquid channel 11 and the liquid tank 10 are provided with a plurality of gas blowing devices. If a loading device is provided, the above effects can be exhibited even better. Furthermore, the control device 4 has a control function that controls the gas blowing devices 15 and 35 according to the level of the liquid tank 10 to change the gas mixing speed.
It is also possible to have it held at 4.

As explained above, in the device for mixing gas into liquid according to the present invention, gas blowing devices are provided in both the liquid flow path and the liquid tank, and these gas blowing devices are used to mix gas in the liquid. Since it is equipped with a measurement control device that measures the mixing rate and comprehensively controls these gas blowing devices based on the measured value, it is possible to freely change the gas mixing rate according to the gas mixing rate and inject the target gas. Incorporation rates can be achieved quickly and with high tactility.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an improved conventional device for mixing gas into liquid; FIGS. 2 to 4 show an embodiment of the present invention; FIG. 2 is a schematic configuration diagram; Figures A, B, and C are explanatory diagrams showing the procedure for measuring the gas inclusion rate, and Figures A, B, and C are explanatory diagrams showing the states under each pressure. 10...Liquid tank, 11...Liquid channel, 14
... cylinder device (liquid circulation device), 15 ... first gas blowing device, 35 ... second gas blowing device, 49 ... measurement control device.

Claims (1)

[Claims] 1 In the liquid flow path connected at both ends to the liquid tank,
A liquid circulation device is provided for circulating the liquid in the liquid tank through the liquid flow path, and a gas blowing device is provided in both the liquid flow path and the liquid tank for mixing gas into the liquid therein. In addition, the gas blowing device is provided with a measurement control device that measures the gas mixture rate in the liquid and controls the gas blowing devices overall based on the measured value. A device for mixing gas into a liquid, characterized by comprising: