JP2726892B2 - Discharge method of liquid material in mixer and mixer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mixer provided with a circulation path for circulating two or more liquid substances, and intermittently discharging those liquid substances (particularly, polyurethane raw material) and mixing them at a predetermined ratio. The present invention relates to a method for discharging each liquid material and a mixer using the discharging method.

[0002]

2. Description of the Related Art For example, as is well known, a cleaning blade for an electrophotographic copying machine is used in a copying machine, a printer or the like to remove excess toner attached to a photosensitive drum after transfer. Are manufactured by casting using polyurethane or the like as a raw material. Particularly in the case of polyurethane, a liquid material as a main agent and a liquid material as a curing agent are mixed in a mixer for 50 to 1 minute.
After mixing and stirring at a temperature of 00 ° C., the mixed liquid is discharged into a predetermined mold to form the cleaning blade and the like.

In a conventional general circulating mixer having a circulation path for each liquid material, the pressure during circulation is kept constant even if the discharge pressure rises as shown in FIG. As the pressure rises, a pressure difference occurs between the pressure during circulation and the pressure. When the pressure difference between the pressure at the time of discharge and the pressure at the time of circulation is generated, the discharge amount changes as shown in FIG. 5, so that the mixing ratio does not become constant, and a molded product of constant quality and performance is obtained. I can't. This is because when the work of intermittent discharge to the mixer, mixing and casting is repeated, the liquid substance (mainly the impurities contained therein) gradually adheres to the mixing chamber and the discharge port of the mixer, It is because it hinders. Such a phenomenon is particularly noticeable when a fast-curing polyurethane is used as a raw material.

Therefore, as described in, for example, Japanese Utility Model Laid-Open No. 2-129248, a pressure difference between the time of discharge and the time of circulation is detected, and if the pressure difference exceeds an allowable range (a range in which a defective ratio does not occur). There has been proposed a mixer having a structure in which an alarm is issued to stop the operation of the mixer (and the injector).

[0005]

However, in the conventional mixer described in the above publication, a molded article having a poor ratio is not produced, but the operation of the injection machine is stopped once and the pressure at the time of discharge is reduced. It is necessary to remove the cause of the fluctuation (a liquid substance adhering to the mixing chamber or the discharge port). For this reason,
During that time, the production line is interrupted, which causes a disadvantage that the production efficiency is reduced.

The present invention has been made in view of the above points, and it is not necessary to stop the operation even if the discharge pressure of a liquid material increases, continuous operation can be performed for a long time, and production efficiency can be improved. It is an object of the present invention to provide a method for discharging a liquid material in a mixer and a mixer using the discharge method, which can produce a product of excellent quality with a constant mixing ratio.

[0007]

In order to achieve the above-mentioned object, a method of discharging a liquid material according to the present invention (Claim 1) comprises the steps of: a) Two or more liquid materials such as polyurethane raw materials are respectively supplied via a metering pump. In a mixer that mixes the liquid by intermittently discharging and mixing into the mixing chamber, b) keeping the rotation speed of each of the metering pumps constant, and c) detecting the pressure during discharge and during circulation for each liquid. The discharge amount of each liquid is made constant by adjusting the pressure during circulation to the immediately preceding discharge pressure.

Further, the mixer of the present invention for carrying out the above-mentioned method comprises the steps of: A) circulating two or more liquid substances such as polyurethane raw materials in a circulation path, and intermittently discharging and mixing the mixture into a mixing chamber. In the mixer, B) on each of the outgoing sides of the respective liquids from the storage tank to the mixing chamber in each circulation path, a metering pump and a pressure sensor are interposed, and C) the return path of each of the liquids from the mixing chamber to the storage tank. Side, each of which is provided with a throttle valve, and D) based on the pressure during discharge of each liquid detected by each of the pressure sensors, the opening degree of the throttle valve so that the pressure during the next circulation becomes equal. Control means for controlling is provided.

[0009]

According to a first aspect of the present invention, there is provided a method of discharging a liquid material, wherein two or more liquid materials are circulated, intermittently discharged into a mixing chamber, mixed and discharged to the outside. In addition, for example, by making the rotation speed of a fixed amount pump such as a gear pump constant, the liquid material is repeatedly intermittently discharged while keeping the supply amount of each liquid material at the time of circulation, whereby the liquid material is mixed with the mixing chamber and Even if the discharge pressure fluctuates (usually rises) due to adhesion to the discharge port or the like, the discharge amount becomes constant as shown in FIG. 4 if the pressure during circulation is adjusted to the pressure at the time of the immediately preceding discharge. It is based on the knowledge that.
In other words, according to the liquid discharge method of the present invention, there is no difference between the pressure during circulation of each liquid and the pressure at the next discharge, or even if there is a difference, the difference is extremely small. Since there is no need for the time required for the pressure to rise to change the pressure to the pressure, it is estimated that the discharge amount within the set time is always constant. Therefore, according to the present invention, since the ratio of each liquid material to be mixed is constant without changing, a molded product with stable quality can be obtained.

According to the mixer of the present invention, when each liquid is discharged into the mixing chamber, the pressure during discharge is detected by the pressure sensor, and when each liquid is circulated after the discharge is completed. Then, the pressure during circulation is detected by the pressure sensor. During the circulation of each liquid material, the control means compares the pressure at the time of discharge with the pressure at the time of circulation, and when the circulation pressure is smaller (or larger) than the discharge pressure, a throttle valve interposed on the return path side. Is reduced (or opened) to reduce (or increase) the opening, and control is performed so that the circulating pressure becomes equal to the immediately preceding discharge pressure. The determination as to whether the liquid is being discharged or circulating when detecting with the pressure sensor is performed, for example, by determining the direction of a switching valve for switching between discharging and circulating the liquid in the mixing chamber, This is performed based on the position and the like. During the next discharge of each liquid, the circulating pressure before switching is adjusted to the immediately preceding discharge pressure, so that even if the discharge pressure is higher than the immediately preceding discharge pressure, the difference between the two is extremely small. Therefore, if the rotational speed of the metering pump is kept constant, the amount of each liquid discharged within the set time should be equal regardless of the fluctuation of the discharge pressure. The amount is always constant.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the mixer according to the present invention will be described below with reference to the drawings, together with a method of discharging a liquid material in the mixer.

FIG. 1 is a system diagram of a urethane elastomer (polyurethane) mixer used for casting a cleaning blade. As shown in FIG.
This is for mixing a main agent (prepolymer) and a curing agent (crosslinking agent) when molding with a urethane elastomer using a casting machine (not shown).

The mixer 1 is provided integrally with a mixing head 2 at its lower end for mixing and stirring the above two kinds of liquid components in a mixing chamber 1a and discharging the mixture to a casting mold (not shown). Below the mixing head 2, dies (not shown) for casting a cleaning blade are arranged in a line at predetermined intervals and are conveyed at a constant conveyance speed. Then, the urethane elastomer is intermittently discharged from the lower end (discharge nozzle) of the mixing head 2 to the mold sequentially conveyed at a constant speed, and the cleaning blade is formed.

In the mixing chamber 1a of the mixer 1, stirring blades (not shown) are rotatably arranged. A circulation path 1 for a main agent (hereinafter referred to as a liquid material A) is provided in the mixing chamber 1a.
0 passes through a three-way switching valve 11, and a circulation path 20 of a curing agent (hereinafter, referred to as a liquid material B) passes through a three-way switching valve 21.
Each is connected. The circulation path 10 includes a storage tank 12 for the liquid material A, and a forward pump 13 connecting the storage tank 12 and the switching valve 11 is provided with a gear pump 15 and a pressure sensor 16 as a metering pump in order. .
Further, a throttle valve 17 is interposed in the return pipe 14 connecting the switching valve 11 and the storage tank 12.

The circulation path 20 has a storage tank 22 for the liquid B, and a forward pump 23 connecting the storage tank 22 and the switching valve 21 is provided with a gear pump 25 as a fixed-quantity pump and a pressure sensor 26 in this order. Have been. Switching valve 2
A throttle valve 27 is interposed in the return pipe 24 connecting the tank 1 and the storage tank 22. The throttle valve 27 and the throttle valve 17 are provided with a servomotor 2 for controlling the opening degree.
8 and 18 are provided.

A computing unit 3 is provided as control means for controlling the opening of the throttle valves 17 and 27.
, Signals from the switching valves 11 and 21 (signals of the circulation position and the discharge position) and signals from the pressure sensors 16 and 26 (detected pressure value signals) are respectively inputted.
Thus, a signal for operating these motors is output to the servo motors 18 and 28 of the throttle valves 17 and 27. The arithmetic unit 3 is composed of a microprocessor or the like, and the pressure sensor 1
6.26 is not a simple display type, but is of a type in which the detected pressure is output as a signal such as a voltage (or a current or a capacitance). The pressure sensors 16 and 26 constantly (or periodically) detect the pressures of the liquid materials A and B, and circulate their pressures (pressures circulating in the circulation paths 10 and 20) and discharge pressures (switching valves 11 and 21). The pressure at the time of switching and discharging to the mixing chamber 1a) is output to the calculating unit 3, and the calculating unit 3 compares and calculates the difference between the most recently output circulating pressure and the immediately preceding discharging pressure. Thus, the opening degree of the throttle valves 17 and 27 is controlled. As a signal for causing the calculation unit 3 to determine whether the switching valves 11 and 21 are in the circulation position or the discharge position, for example, in the case of an electromagnetic switching valve, a signal of an electromagnetic force generating switch may be used.

The two types of liquids A and B normally circulate in the circulation paths 10 and 20, respectively (the state shown in the figure), but when the switching valves 11 and 21 are switched, they are transferred to the storage tanks 12 and 22. It is discharged into the mixing chamber 1a of the mixer through the discharge pipes 11a and 21a without returning. Discharge line 11a
There is a small-diameter nozzle (not shown) in the discharge portion from 21a to the mixing chamber 1a, and a predetermined time is set by setting the switching time (period) of the switching valves 11 and 21 (usually 2 to 5 seconds). The discharge amount can be obtained. At this time,
The rotation speeds of the gear pumps 15 and 25 are also set,
Thereafter, it is kept constant. In order to satisfy the physical properties (hardness, elastic modulus, etc.) required for the molded article, the mixing ratio (weight ratio) of the liquid B to the liquid A is constant (for example, 7% ±
0.2%). Then, in order to discharge the two liquids to the mixing chamber 1a within the range of the ratio, the diameters of the nozzles are set so that the discharge amount per unit time becomes the above ratio, and the switching valve 11 and the 21 are switched and operated for the same time.

Next, a description will be given of a mode of discharging the liquid material by the mixer 1 having the above configuration.

In FIG. 1, each gear pump 15, 25
, The liquid material A in the storage tank 12 is circulated by the circulation path 10 through the switching valve 11 of the mixing chamber 1a of the mixer 1, and the liquid material B in the storage tank 22 is circulated. It is circulated by the passage 20 via the switching valve 21 of the mixing chamber 1a of the mixer 1. The operating section 3 controls the throttle valves 17 and 27 so that the circulation pressure at this time is equal to the discharge pressure when the switching valves 11 and 21 are switched to discharge the liquids A and B into the mixing chamber 1a. Is controlled.

In the above-described state, the switching valves 11 and 21 are switched to simultaneously discharge the liquid materials A and B into the mixing chamber 1a, and are mixed at a predetermined ratio in the mixing chamber 1a. The cleaning blade is injected into a casting mold (not shown).

The above operation and the above operation are intermittently repeated. During this time, the liquid materials A and B are mixed in the mixing chamber 1a.
When discharging to the pressure sensors 16 and 26
When the switching valves 11 and 21 are switched after the end of discharge and the liquids A and B circulate, the circulating pressure is detected by the pressure sensors 16 and 26. However, for a while after the start of the work, there is little change in the discharge pressure because there is almost no foreign matter adhering to the discharge nozzle and the mixing chamber 1a. Therefore, there is no need to change the circulation pressure. The opening of the valves 17, 27 is kept constant.

When the operation is continued for a long time and foreign substances adhere to the discharge nozzle and the mixing chamber 1a, the pressure at the time of discharge gradually increases. During the circulation of the liquids A and B, the calculation unit 3 compares the pressure at the time of discharge with the pressure at the time of circulation, and when the circulation pressure is smaller than the discharge pressure, the servo motor 18.2.
An operation signal is output to 8 and the throttle valves 17 and 27 are throttled to reduce the opening degree, and control is performed so that the circulating pressure becomes equal to the immediately preceding discharge pressure. In this way, at the time of discharging the next liquids A and B, since the circulation pressure is adjusted to the immediately preceding discharge pressure, even when the discharge pressure is higher than the immediately preceding discharge pressure, both of them are discharged. Since the difference is extremely small, the gear pumps 15, 2
If the rotation speed of 5 is kept constant, the discharge amount of each of the liquids A and B into the mixing chamber 1a does not fluctuate, so that the mixing ratio is always kept constant.

FIG. 2 shows the change over time of the pressure (pressure signal) of the liquid material B detected by the pressure sensor 26 of the mixer 1 of the above embodiment and the discharge amount. Although the change over time of the pressure on the pressure sensor 16 (liquid B) side is not shown,
Basically they are common. Further, in FIG. 2, the difference between the pressure value at the time of circulation and the pressure value at the time of discharge is slightly different from the pressure signal shown in FIG. Because the difference is clearer,
Actually, there is no difference between the pressure at the time of circulation and the pressure at the time of the immediately preceding discharge (this point is the same for the diagram of FIG. 3 described later).

FIG. 3 shows the change over time of the pressure (pressure signal) of the liquid material B and the discharge amount in a conventional general mixer. For a while (several hours) from the start of the casting (mixing / discharging) work, the discharge amount does not change because there is no pressure difference between the discharge pressure and the circulation pressure. And the mixing chamber 1 over time.
The foreign matter adheres to the nozzle which discharges into a, and the discharge pressure gradually increases. However, it is confirmed from FIG. 3 that since the pressure during the circulation is kept constant, the difference between the two gradually widens and the discharge amount decreases accordingly.

In the mixer 1 of the present invention as well, as the time elapses, foreign matter adheres mainly to the nozzles discharged into the mixing chamber 1a, and the discharge pressure gradually increases. Accordingly, the pressure during circulation is reduced by the throttle valve 17,
Since the opening degree of the opening 27 is reduced and automatically increased, there is no pressure difference between the circulation pressure and the discharge pressure even if the discharge pressure increases. Therefore, as can be seen from FIG. 2, the discharge amount is always kept constant. You.
Therefore, a molded product of stable quality can be continuously cast for a long time without cleaning and replacing the nozzle and cleaning the inside of the mixing chamber 1a.

While the embodiment of the mixer of the present invention has been described above, the present invention can also be carried out as follows.

A) The present invention is not limited to the mixing of two kinds of liquids, but can be similarly carried out when three or more kinds of liquids are mixed.

B) The present invention can be widely applied not only to the mixing of liquid materials relating to molding of rubber and plastics but also to the mixing of liquid materials relating to painting, adhesion or chemical addition.

[0029]

As is apparent from the above description,
The liquid material discharging method and the mixer according to the present invention have the following effects.

(1) Since the discharge amount is kept constant even if the discharge pressure of the liquid material increases, continuous operation can be performed for a long time, and the production efficiency can be improved. Also, the mixing ratio is constant,
High quality products can be manufactured, and the yield increases.

(2) The mixer according to claim 2 can reliably carry out the liquid material discharging method of the present invention (claim 1).
Since all operations are performed automatically, unmanned operation is possible and production efficiency can be further improved.

[Brief description of the drawings]

FIG. 1 is a system diagram of a urethane elastomer mixer used for casting a cleaning blade.

FIG. 2 is a diagram showing a change over time in a circulation pressure and a discharge pressure (pressure signal) of a liquid material detected by a pressure sensor of the mixer of FIG. 1 and a discharge amount.

FIG. 3 is a diagram showing a change with time of a circulation pressure and a discharge pressure (pressure signal) of a liquid material and a discharge amount detected by a pressure sensor of a conventional general mixer.

FIG. 4 is a diagram showing a discharge amount and a discharge pressure when there is no difference between a discharge pressure and a circulation pressure in a mixer.

FIG. 5 shows a pressure difference between a discharge pressure and a circulation pressure in a mixer;
FIG. 3 is a diagram illustrating a discharge amount.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mixer 1a Mixing chamber 3 Operation part (control means) 10.20 Circulation path 11.21 Switching valve 12.22 Storage tank 15.25 Gear pump (quantitative pump) 16.26 Pressure sensor 17.27 Throttle valve

Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location G05D 16/20 G05D 16/20 D

Claims (2)

(57) [Claims] 1. A mixer for circulating two or more liquid materials such as polyurethane raw materials via a metering pump, and intermittently discharging and mixing them into a mixing chamber, wherein the rotational speed of each metering pump is constant. A method for discharging a liquid material in a mixer, wherein the pressure at the time of discharge and at the time of circulation is detected for each liquid material, and the pressure at the time of circulation is adjusted to the immediately preceding discharge pressure. 2. A mixer for circulating two or more liquid substances such as a polyurethane raw material in a circulation path and intermittently discharging the mixture into a mixing chamber to mix each liquid substance from a storage tank in each circulation path to the mixing chamber. A metering pump and a pressure sensor are interposed on the outward path of the substance, respectively, and a throttle valve is interposed on the return path side of each liquid substance from the mixing chamber to the storage tank. A mixer provided with control means for controlling the opening degree of the throttle valve based on the pressure during discharge of an object so that the pressure during the next circulation becomes equal.