JPH02174972A - Method for measuring effective amount of using paint remaining in hose - Google Patents

Abstract

PURPOSE:To calculate the effective amt. of using the paint in a hose from the time at the point of the time when the arrival of a cleaning solvent at a contraction part is known by a change in the pressure drop and at the point of the time when a valve is changed over by providing the contraction part and a pressure sensor which detects the pressure drop generated therein on the hose near the painting machine. CONSTITUTION:The contraction part 8, such as Venturi pipe, and the pressure sensor 9 for detecting the pressure drop generated therein are provided on the hose 3 near the painting machine 1. A certain paint is supplied from a valve device 2 via the hose 3 to the painting machine and the valve device 2 is changed over prior to the end of painting, by which the cleaning solvent is supplied and the paint remaining in the hose is discharged. Since the pressure drops of the solvent and the paint in the contraction part 8 vary in this case, the arrival of the solvent at the contraction part 8 is detected by the sensor 9 and the effective amt. of using the paint remaining in the hose 3 is determined in accordance with the time from the time when the valve device 2 is changed over.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention provides the following features: Before the end of painting with the paint l, which is supplied in a fixed amount from the valve device to the paint sprayer via the paint hose,
At the same time as switching the valve device to stop the new supply of the paint, the cleaning solvent is started to be supplied at the same flow rate as the paint, and the pressure of the cleaning solvent causes the paint remaining in the hose to be discharged from the sprayer. Regarding a method for measuring the effective amount of paint remaining in a hose when painting, it is particularly suitable for use in a color change painting device that uses a color change valve device as the valve device to change the color of each color of paint for each object to be painted. It is something.

[Prior art]

When performing multi-color painting by selectively supplying each color of paint according to the color of the object to be coated from a color change valve device to a coating machine that paints objects to be coated conveyed by a conveyor, it is necessary to It is desired to reduce the time required to change to the next color paint as much as possible, and to minimize waste of paint.

For example, the hose length of a top reciprocating device that reciprocates a paint sprayer horizontally is usually 7 to 1 Qm; the hose length of a side reciprocating device that reciprocates a paint sprayer vertically is usually 2 to 3 m.
Even if a hose with a diameter of 6 mm is used, the hose is filled with about 50 to 200 cc of paint, but when painting a car, the amount of paint used per paint machine is 70 cc. ~300cc is enough, so the paint inside the hose may be sufficient for painting. Therefore, if spraying and cleaning are repeated every time a color is changed, it is not possible to satisfy the demands for shortening the cleaning time for changing colors and effectively utilizing paint.

In order to simultaneously meet these two demands, the color change valve device is switched to stop the new supply of the previous color paint before the previous color paint being discharged from the paint sprayer finishes painting. At the same time, the supply of cleaning solvent is started, and the pressure of the cleaning solvent causes the previous color paint remaining in the hose connected between the color change valve device and the sprayer to be discharged from the sprayer. A method of painting using the remaining paint until the painting is completed has been proposed (Japanese Patent Laid-Open No. 60-61076).

Japanese Patent Application Publication No. 60-61077, Patent Application No. 63-273177
issue).

According to these methods, it is not necessary to waste the previous color paint remaining in the hose at the end of painting the previous color paint, and at the same time, the inside of the hose is cleaned with a cleaning solvent while the previous color paint is being applied. As a result, cleaning time is shortened and the time required to change to the next color paint is also shortened.

[Problem to be solved by the invention]

However, in reality, it is very difficult to determine the switching timing of the valve device because the amount of paint remaining in the paint hose cannot be accurately determined.

The amount of paint remaining is determined by the volume inside the hose, but the hose is bent or flexible, and its diameter changes slightly depending on the paint supply pressure. Therefore, it is extremely difficult to accurately determine the volume inside the hose.

Also, even if you can find the volume inside the hose,
When the supply of cleaning solvent is started, the cleaning solvent and paint mix at the interface, so the volume in the hose and the amount of paint that can be used effectively are different, ultimately determining the exact timing of the valve device. Can not do it.

If the switching timing of the valve device is delayed, the paint will be painted with a low viscosity paint mixed with cleaning solvent, which will cause the paint to flow when applied to a vertical surface, causing uneven streaks and puddles on the paint film. This causes paint defects such as sagging and faded finish, and if the switching timing is too early, no paint defects will occur, but there will be a problem in that paint will be wasted.

Therefore, the present invention has developed a technology to measure the volume of paint that can be effectively used in order to determine accurate valve switching timing so that the paint in the hose can be used as effectively as possible without causing paint defects. This is a major issue.

[Means to solve the problem]

In order to solve this problem, the present invention switches the valve device to stop the new supply of paint before the painting with the paint that is being supplied in a fixed amount from the valve device to the paint sprayer via the hose is completed. At the same time, a cleaning solvent is started to be supplied at the same flow rate as the paint, and the paint remaining in the hose is discharged from a sprayer using the pressure of the cleaning solvent to perform painting. Method for measuring the effective usage amount of paint remaining in a hose. A pressure sensor for detecting a constriction section and a pressure loss occurring in the constriction section is provided in the vicinity of the sprayer of the hose, and a cleaning solvent arrives at the constriction section based on a change in the pressure loss. is detected, and the effective usage amount of the remaining paint is calculated based on the time it takes for the cleaning solvent, which is started to be supplied at a predetermined flow rate, to reach the condenser part from the time when the valve device is switched.

[Function] According to the present invention, the hose that connects the valve device and the sprayer is provided with a constriction section, and the pressure loss at the constriction section changes depending on the properties of the flowing fluid. When the paint mixed with the cleaning solvent reaches the contraction part when the paint is forced out, the viscosity of the paint changes and the pressure loss changes.

This change in pressure loss is detected by a pressure sensor, and based on the detection signal from the pressure sensor, it is possible to detect that the liquid mixture with the cleaning solvent has arrived at the contraction part.

At this time, if the time from when the valve device is switched until the cleaning solvent supplied at a predetermined flow rate reaches the condenser section can be measured in advance, if the condenser section is located close to the sprayer, The effective amount of paint that can be applied can be calculated from the product of paint flow rate and time.

Furthermore, if the paint flow rate is constant, the effective amount of paint used can be determined by subtracting the measured time from the total painting time from the start of painting to the end of painting, using only time as a parameter.

Furthermore, if the pressure sensor cannot be installed very close to the electrostatic sprayer, such as when using an electrostatic sprayer that uses high voltage, install the condenser section and pressure sensor a certain distance away from the sprayer. Then, from the relationship between the installation position and the measurement time, it is possible to estimate the time it takes for the unusable paint to reach the coating machine, and determine the effective usage amount of the paint.

〔Example〕

Embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 is a flow sheet of a color change coating apparatus to which the method of the present invention is applied.

In this coating device, a paint hose 3 is connected between a coating machine 1 for painting an object to be coated and a valve device 2, so that paint of a predetermined color is selectively supplied in a fixed amount from the valve device 2. being done.

The valve device 2 is provided with a large number of color change valves 4, and a paint pump 5 circulates and supplies each color paint at a constant rate, and a pressure pump 6 supplies a cleaning solvent (thinner) at the same flow rate as the paint flow rate. A cleaning solvent supply valve 7 and a compressed air supply valve V are provided to supply each color of paint, cleaning solvent,
Compressed air is selectively supplied to the coating machine 1.

In addition, a flow contraction section 8 such as a bench pipe is provided in the vicinity of the sprayer 1 of the hose 3, which causes pressure loss that varies depending on the properties of the fluid flowing inside the hose 3, and a flow contraction section 8, such as a bench pipe, is provided on the upstream side of the hose 3 to prevent changes in the pressure loss. A pressure sensor 9 for detection is installed.

Reference numeral 10 denotes a control device for controlling the switching timing of the valve device 2 based on the detection signal of the pressure sensor 9, and the cleaning solvent is supplied from the time when the valve device 2 is switched and the supply of the cleaning solvent is started. The time required to reach the contraction section 8 is measured in advance, and a control signal is output to the valve driving device 11 at a predetermined timing.

Next, the method of the present invention will be explained in more detail with reference to FIG. 2. FIG. 2 is a graph showing an example of a pressure diagram detected by the pressure sensor 9.

First, a fixed amount of paint is supplied under the same conditions as for painting, and at the same time the valve device 2 is switched, timing is started. At this time,
At the same time as the new supply of the paint is stopped, the cleaning solvent is started to be supplied at the same flow rate as the paint, and the paint is forced out of the coating machine I by the pressure of the cleaning solvent.

In this case, in the hose 3, the cleaning solvent and paint are mixed at the boundary, and from the sprayer l side, there are three parts: a part with only paint, a part with a mixture of paint and cleaning solvent, and a part with only cleaning solvent. As time passes, the paint, liquid mixture, and cleaning solvent will pass through the condenser section 8 at 111α.

At this time, the viscosity of each fluid is relatively high for the paint, the mixed liquid gradually decreases depending on the amount of cleaning solvent mixed, the cleaning solvent is low, and the pressure loss that occurs in the contraction section 8 increases the viscosity. It changes accordingly.

Therefore, the output of the pressure sensor 9 is approximately constant (JP (second Figure T).

When the paint passes through the condenser section 8 and the mixture of paint and cleaning solvent reaches the condenser section 8, the viscosity of the paint decreases and the pressure loss due to the constriction section 8 decreases. The pressure detected by the pressure sensor 9 drops rapidly (Fig. 2 T).

Therefore, it can be seen that the paint has passed through the contracted flow section 8 at the point when the measured value suddenly decreases.

In this way, the time T (m
In) is measured once in advance and set in the control device IO, and the time T (win) and the paint flow 1v (cc/m1) at that time are measured and set in the control device IO.
The effective usage amount of the paint remaining in the port 3 can be determined by multiplying by n), and if the switching timing of the valve device 2 is determined based on this effective usage amount, the paint can be used without wasting it. It is possible to do this without causing coating defects.

Further, if the paint flow rate during painting is the same as the condition at the time of time measurement, the switching timing can be determined using only time as a parameter.

For example, the total painting time from the start of painting to the end of painting is Ta
Then, the switching timing T0 of the valve device 2 is Ta
-T can be obtained.

Furthermore, in cases where it is not possible to provide the constriction section 8 and the pressure sensor 9 in the immediate vicinity of the atomizer 1, such as in an electrostatic sprayer, the hose The switching timing of the valve device 2 is determined by estimating the time it takes for the paint in the valve device 3 to reach the coating machine.

For example, if the total length of the hose 3 is 10 meters and the installation position of the condenser section 8 is 1 meter from the sprayer 1 side, then at the measured time T, the cleaning solvent will reach the hose 3 by 9 meters.
Since this is the time it takes for the cleaning solvent to travel a meter, the time for the cleaning solvent to reach the coating machine 1 can be expressed as (10/9)xT.

In addition, in the above embodiment, a case was explained in which a venturi tube was used as the flow contraction section 8, but the present invention is not limited to this, and an orifice or other arbitrary tube may be used as long as it causes a pressure loss. can.

Furthermore, although the case has been described in which the pressure sensor 9 is provided only on the h flow side of the contraction section, it is possible to provide the pressure sensor 9 on both the upstream and downstream sides.
If pressure loss is detected based on the pressure difference, pressure changes caused by disturbances can be offset.

Furthermore, as a control method, even if time data is taken under the same conditions before the start of painting, measurements are taken every time the object to be painted5 is applied, and the gain obtained from the painting performed on the previous object is measured. The switching timing may be corrected little by little by using the obtained data for painting the next object to be painted.

(Effects of the Invention) As described above, according to the method of the present invention, a constriction section of the hose is provided near the sprayer, a pressure sensor detects that the paint passes through the constriction section, and the valve device is activated. This has the excellent effect that the effective usage amount of the paint inside the hose can be easily and accurately determined based on the time from the time of switching until the cleaning solvent reaches the contraction part.

Further, even if the mixing range of the paint and the cleaning solvent differs depending on the coating conditions, the effective usage amount can be easily determined based on the pressure change.

Therefore, the switching timing can be determined accurately and easily based on the effective usage amount without considering the volume inside the bent or bendable hose and various other coating conditions, and there is no need to waste paint. At the same time,
It has the excellent effect of not causing coating defects due to the mixture of paint and cleaning solvent.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet of a coating apparatus to which the method of the present invention is applied, and FIG. 2 is a graph showing changes in pressure loss due to the contraction section. Explanation of symbols 1 - Painter, 2... Valve device, 3 - Hose, 4 Color change valve, 7 - Cleaning solvent supply valve, 8 Contraction section, 9 -
Pressure sensor, 10-control device, 11-pulp drive device.

Claims (1)

[Claims] Before the completion of painting with the paint that is being supplied at a constant rate from the valve device to the coating machine via the hose, the valve device is switched to stop the new supply of the paint, and at the same time, the cleaning solvent is supplied at the same flow rate as the paint. This is a method for measuring the effective amount of paint remaining in a hose when supply is started and painting is performed by discharging the paint remaining in the hose from the sprayer using the pressure of the cleaning solvent. A pressure sensor is provided to detect a pressure loss occurring in the flow section and the contraction section, and based on a change in the pressure loss, it is detected that the cleaning solvent has arrived at the contraction section, and at the time when the valve device is switched. A method for measuring the effective usage amount of residual paint in a hose, characterized in that the effective usage amount of the residual paint in a hose is calculated based on the time it takes for the cleaning solvent, which is started to be supplied at a predetermined flow rate, to reach the contraction part.