JPH02149369A - Coating circulating apparatus - Google Patents

Abstract

PURPOSE:To fix discharged coating at a certain amount by connecting a coating discharge amount regulator to each of branch connection pipes and providing an intermediate metering pump for measuring coating circulating pipe. CONSTITUTION:By the operation of a circulating pump 6, coating is delivered from a coating tank 1 to a coating circulating pipe 2, through which it is sent back into the tank 1. The coating flowing in from the circulating pipe 2 is set at a certain flow amount by a metering pump 11 and the pressure of the subsequent coating flow is detected by sensors 12 and 13. A control circuit 16 receives the electric signals a and b of the coating pressures from the sensors, sets the amount of the coating to be discharged from a spray gun 9 and sends a control electric signal c representing this amount to a transducer 7. The transducer 7 converts the electric signal c to the corresponding air pressure signal d, which is sent to each air-operated regulator. In this way the amount of the coating sprayed from the spray gun 9 can be controlled to thereby maintain the discharge of the coating at a predetermined amount.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a paint circulation system installed in a paint factory for automobiles or their parts, and more specifically, the present invention relates to a paint circulation system installed in a paint factory for automobiles or their parts. In addition to the returning paint circulation line,
This invention relates to a paint circulation system equipped with a paint return pipe called a so-called third line.

(Prior Art) Conventionally, in an automobile paint factory, a paint circulation pipe is installed in the factory in order to supply paint to a large number of painting work positions on a painting line, and each painting work position is connected to a paint circulation pipe from the circulation pipe. Branch pipes are branched to each branch pipe to which each painting gun can be connected, and equipment is provided to feed paint through circulation pipes and branch pipes to each painting gun and return it to the tank (for example, (See Publication No. 26350).

Recently, in order to prevent paint from settling and semi-solidifying inside the branch pipes from the circulation pipe to the painting gun, a system has been developed to communicate with each branch pipe and collect the paint inside it into a paint tank.
It is common practice to also provide a paint return pipe called the so-called third line (for example, the
No. 1100, Utility Model Application Publication No. 1-31377 (see WA).

(Problem to be Solved by the Invention) In such conventional automobile painting equipment, when the paint in the paint tank runs out during operation, it is necessary to replenish the tank with the required amount of new paint, or to replenish the paint gun by replenishing the paint. The concentration and viscosity of the paint being sent changes. Furthermore, since the paint tanks commonly used are not sealed from the viewpoint of workability, the solvent always evaporates from the paint tank, and as a result, the coating 4 tends to gradually increase in concentration and viscosity. If you replenish the solvent in a timely manner, the viscosity of the paint will suddenly decrease at that point.

In this way, in the painting process, the concentration (viscosity) of the paint
constantly changes, sometimes discontinuously. For this reason,
Even if a throttle valve for adjusting the amount of paint discharged from a paint gun is connected to a branch pipe branching from the paint circulation pipe, as shown in Japanese Patent Publication No. 59-26350, the viscosity of the paint The amount of paint discharged fluctuates due to changes in the amount of paint, and it is difficult to maintain the amount of paint discharged at a predetermined constant value only by adjusting the valve.

Therefore, there is a need for a control means that maintains the amount of paint discharged at a constant value in response to changes in the concentration and viscosity of the paint, but such a control means has not existed in the past.

As a control device for the discharge amount, as shown in Japanese Patent Publication No. 1106/1983, there is a device that calculates conditions such as the viscosity of the paint using a central processing unit and controls the amount of paint discharged using the output signal. Already proposed. However, with this device, the data of the temperature-viscosity curve of the paint is programmed into the processing unit in advance, the viscosity condition of the paint is determined by inputting the environmental temperature value, and the amount of paint discharged is controlled based on this. Moreover, the discharge amount control means could not cope with unexpected changes in paint concentration (viscosity) at all.

The present invention has been made in consideration of the above-mentioned circumstances, and its purpose is to prevent the concentration and viscosity of paint from constantly changing slightly during the painting process, even though they sometimes fluctuate rapidly. To provide a paint circulation device that can respond well to changes and always maintain the amount of paint discharged from a paint gun at a desired constant value.

(Means for Solving the Problems) The present inventor has focused on the fact that there is a nearly positive correlation between the concentration (viscosity) of paint and the pressure of paint flow, and has determined that the paint gun is controlled based on changes in paint pressure. They discovered that it is possible to maintain a constant discharge amount at all times, and completed the present invention.

Therefore, the paint circulation system of the present invention has a paint circulation pipe through which paint is supplied from a paint tank and returns to the tank, and a paint circulation pipe that connects with each connecting branch pipe that branches from the circulation pipe and connects to a paint gun. A paint circulation system comprising a paint return pipe for collecting paint into a paint tank, a paint discharge amount regulator connected to each of the connecting branch pipes, and a bypass pipe directly connecting the paint circulation pipe and the paint return pipe. A metering pump and a paint pressure detection device interposed in the passage, and a control mechanism that inputs a paint pressure signal from the detection device and outputs a discharge amount signal set based on the signal to each of the regulators. This is a characteristic feature.

Further, another paint circulation device of the present invention includes the paint circulation pipe and the paint return pipe described above, and further comprises a paint discharge amount regulator connected to each of the connecting branch pipes, and the paint circulation pipe. A metering pump and a paint pressure detection device are interposed in a paint circulation pipe for measurement through which paint is supplied from a paint tank and returned to the same tank through a pipe separate from the pipe, and a paint pressure signal is input from the detection device. and a control mechanism that outputs a discharge amount signal set based on this to each of the regulators.

The paint circulation pipe and the paint return pipe may basically have the same configuration as conventional ones. For example, the paint circulation pipe includes a circulation pump, and branch pipes branching from this are equipped with a pressure reducing valve and a paint gun. The paint return pipe may be one in which a check valve or the like is interposed in the return branch pipe communicating with each of the above-mentioned branch pipes.

The paint discharge amount regulator in the present invention may be any element that can adjust the amount of paint discharged from a coating gun, and for example, an air-operated regulator may be used. The regulator is interposed in a branch pipe between the paint circulation pipe and the paint gun.

The bypass line is a line that directly connects the paint circulation line and the paint return line, and is equipped with a metering pump and a paint pressure detection device in this order. The metering pump maintains a constant flow rate of paint through the conduit, and the device detects the pressure of the paint flowing at a constant rate and outputs it as an electrical signal. The paint pressure detection device in this case is composed of, for example, two pressure sensors, an orifice inserted between them, a capillary tube, etc., and detects the difference between the paint pressure in the paint circulation pipe and that in the paint return pipe. You can use the one that is designed to detect it.

The control mechanism inputs, for example, an electric signal of the detected paint pressure, and based on this input, for example, the following formula (1)% formula % (1) [where ■ is the magnitude of the electric signal for discharging ( C1 represents the initial value of the pressure difference detected by the two pressure sensors (before painting), C2 represents the elapsed value of the pressure difference detected by the two pressure sensors (during painting), D represents the proportionality coefficient or the magnitude of the electrical signal of the discharge amount before coating. ], a control circuit that determines and outputs an electrical signal for the amount of paint to be dispensed, and an electrical/pneumatic converter that converts the output electrical signal into a pneumatic signal and sends it to the air-operated regulator mentioned above. configured.

The measuring paint circulation pipe used in the second aspect of the present invention is a pipe separate from the paint circulation pipe, and is a circulation pipe in which the paint leaves the paint tank and returns to the same tank again. A metering pump and a paint pressure detection device are also installed in this conduit in this order. The metering pump may have the same configuration as described above, and the paint pressure detection device may be configured, for example, by a negative pressure sensor and an orifice, as long as it detects the pressure itself of the paint flowing through the circulation pipe.

(Function) The paint circulation device of the present invention first makes the flow of paint flowing into the bypass pipe or the measurement circulation pipe a constant amount using a scaffolding pump, and in this state detects the pressure of the paint using a pressure sensor or the like. , and the control mechanism sets the amount of paint to be discharged from the paint gun based on this pressure signal, and adjusts the amount of paint to be discharged from the paint gun.
It works by sending a signal to the regulator through a discharge installed in a branch pipe that communicates with the paint circulation pipe.

In other words, the device of the present invention immediately recognizes changes in paint concentration or viscosity as changes in paint pressure, accurately sets the amount of paint to be discharged from this pressure fluctuation value, and adjusts the discharge amount regulator based on this. By controlling the operation, the amount of paint discharged from the paint gun can be kept constant regardless of changes in paint concentration (viscosity).

(Example) Embodiments of the present invention will be described below with reference to the drawings.

Example 1 As shown in Fig. 1, the paint circulation system of this example was installed in a paint booth for an automobile. It comprises a circulation pipe 2 and a paint return pipe 3.

In the paint tank 1, paint is constantly mixed by a propeller type mixer 23 to prevent the paint from settling.

The paint circulation pipe 2 branches off into a connecting branch pipe 4 at each painting work site in the booth, and can be connected to a paint gun 9 through the branch pipes 4. Each branch pipe 4 is provided with an air-operated regulator 7 for adjusting the amount of paint discharged from the paint gun 9.

The paint return pipe line 3 has return branch pipes 5 (including check valves, etc.) that communicate with the switching terminals 8 in each of the connection branch pipes 4, and is connected to the paint tank 1, which is the main pipe that brings them together. It becomes.

Therefore, by operating the circulation pump 6, the paint is fed from the paint tank l to the paint circulation line 2, and after circulating through the line 2, returns to the tank l (in the direction of arrow p). The paint flowing into the connecting branch pipe 4 is supplied to the paint gun 9, but when not painting, it enters the return branch pipe 5 from the switching terminal 8, passes through the paint return pipe 3, and is collected directly into the paint tank l ( (direction of arrow q).

In the embodiment, as shown in FIG. 2, the circulation pipe 2 and the return pipe 3 are directly connected to each other by a bypass pipe 10 immediately before entering the coating source, and a pressure reducing valve 15 and a metering valve are connected to this pipe IO. A pump 11 and a paint pressure detection device 18 are installed in this order.

The detection device 18 includes two pressure sensors 12 and 13 and an orifice (or capillary tube) 1 provided between them.
It is composed of 4.

Therefore, the paint (in the direction of arrow r) flowing from the circulation pipe 2 is made to flow in a constant amount by the metering pump 11, and the pressure of the subsequent flow is detected by sensors 12 and 13.

a and b indicate electrical signals of detected pressure.

Furthermore, the apparatus of the embodiment includes a control circuit 16 and an electric/pneumatic converter 17, as shown in FIG. The control circuit 16 receives paint pressure electrical signals a and b from the above-mentioned sensor.
is input, and the amount of paint to be discharged from the paint gun 9 is set based on the above-mentioned equation (1), etc., and a control electric signal C representing it is output and sent to the converter 17. Transducer 17 converts electrical signal C into a corresponding pneumatic signal d and sends it to each air-operated regulator (FIG. 1). Therefore, the operation of the regulator is adjusted according to the signal level from the control circuit 16, and the amount of paint discharged from the paint gun 9 is controlled.

With the apparatus of Example 1, even if the concentration and viscosity of the paint fluctuates, not only during continuous painting but also when replenishing paint and solvent,
The amount of paint discharged could be maintained at a desired constant amount.

Embodiment 2 As shown in FIG. 4, the paint circulation device of this embodiment includes a measurement paint circulation pipe separate from the paint circulation pipe 2 instead of the bypass pipe and its intervening (connection) parts. 22 are provided. The measurement circulation pipe 22 is connected to the metering pump 11. A paint pressure detection device 21 is interposed in order. The detection device 21 is composed of a pressure sensor 19 and an orifice (capillary tube) 20. Therefore, painting by the operation of the pump 11;
A constant amount of paint flows through the circulation pipe 22 (in the direction of arrow S), and the sensor 19 detects the pressure of the paint flowing there. e
indicates an electrical signal of the detected pressure, which is sent to the control circuit 16. The control circuit 16 sets the amount of paint to be discharged from the paint can according to a predetermined calculation based on the input signal e, and sends a control electric signal C representing the amount to the electric/pneumatic converter 17. Other configurations, operations, etc. are the same as in the first embodiment.

In the apparatus of Example 2 as well, even if the concentration and viscosity of the paint varied, the amount of paint discharged from the coating gun could be maintained at a desired constant amount.

Although the above embodiments have been described with reference to the case where a manual painting gun is used, it goes without saying that the present invention is equally applicable to the case where an automatic painting gun is used. In this case, instead of the switching terminal 8, an automatic three-way valve is used.

(Effects of the Invention) As described above, the paint circulation device of the present invention constantly changes the concentration and viscosity of the paint even slightly during the painting process.
Even if there are sometimes sudden changes due to paint or solvent replenishment, the effect is that the amount of paint discharged from the paint gun can always be maintained at a desired constant value by successfully responding to these changes.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a schematic configuration diagram showing a paint circulation device according to Embodiment 1 of the present invention, Fig. 2 is an enlarged view showing the part of frame A in Fig. 1, and Fig. 1 is a diagram showing the control mechanism of the apparatus, and FIG. 4 is a schematic configuration diagram showing the paint circulation device of Example 2. In the figure, l... φ paint tank 2... paint circulation pipe 3... paint return pipe 4 φ ・ 5 ・ ・ 7・ fist 9− ・ 10 ・ ・ 11 − φ l 2, 1 16 ・ ・l 7 ・ φ l 8, 2 22- ・ ・Connecting branch pipe, return branch pipe, air-operated regulator, painting gun, bypass pipe line, metering pump 3.19...Pressure sensor, control circuit, electrical/pneumatic conversion Instrument 1...Paint pressure detection device/Measurement paint circulation pipes a, b, e...Pressure detection signal C...Control electric signal d...Control air signal/Paint circulation flow/Paint return flow Flow, bypass flow, circulation flow of measuring paint

Claims (2)

[Claims] (1) A paint circulation pipe through which paint is supplied from a paint tank and returned to the tank, and a paint that connects with each connecting branch pipe that branches from the circulation pipe and connects to a paint gun, and collects the paint into the paint tank. a paint circulation device having a return pipe, a paint discharge amount regulator connected to each of the connecting branch pipes, and a metering pump interposed in a bypass pipe directly connecting the paint circulation pipe and the paint return pipe. and a paint pressure detection device; and a control mechanism that inputs a paint pressure signal from the detection device and outputs a discharge amount signal set based on the signal to each of the regulators. (2) A paint circulation pipe through which paint is fed from the paint tank and returned to the tank, and a paint that connects with each connecting branch pipe that branches from the circulation pipe and connects to the paint gun, and collects the paint into the paint tank. In the paint circulation device, the paint is supplied from the paint tank through a paint discharge rate regulator connected to each of the connecting branch pipes, and a pipe different from the paint circulation pipe. A metering pump and a paint pressure detection device are interposed in the measurement paint circulation pipe that returns to the same tank, and a paint pressure signal is input from the detection device, and a discharge amount signal set based on this is output to each of the regulators. A paint circulation device comprising a control mechanism.