DE29615000U1 - Device for dosing liquid dye - Google Patents

Description

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2a/nn;f6osn

ABB Flexible Automation AS N-4341 Bryne, Norway

Device for dosing liquid dye

6 TECHNICAL AREA

The invention relates to a device for dosing liquid dye, in particular for spray painting. More specifically, the invention relates to a device that enables the dosing of multi-component dyes and/or a quick change between different colors.

12 STATE OF THE ART

Spray painting on an industrial scale, for example 14 painting of vehicle bodies, places high demands on the supply of dyes. These include:

16 - Precise dye dosing in terms of quantity and volume flow,

18 - Quick change between different colors,

- Dye emulsions or suspensions must not separate at 20 shear,

- Dye suspensions with abrasive effect,

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- Providing mixed multicomponent dyes,

- Transport of electrically conductive dyes, such as water-based paints , from a grounded supply to a high-voltage electrostatic spray device,

- Easy and quick cleaning.

In most cases, several of these requirements must be met simultaneously.

A common method, which has the advantage of precise dosing, is based on the use of piston pumps in the broadest sense. However, problems arise with this, such as sealing and wear problems due to the movement between the piston and the cylinder wall and difficult cleaning. The same applies to gear pumps.

Peristaltic pumps avoid the problem of relative movement between mutually touching pump parts and enable good dosing accuracy, but are subject to rapid wear and are difficult to clean.

Pressurizing the dye out of a container using compressed air does not require any moving parts, but suffers from inaccurate dosing and delay effects due to the compressibility of the air.

BRIEF DESCRIPTION OF THE INVENTION

The invention is based on the object of developing a device for dosing liquid dye which fulfills the above-mentioned requirements for such a device without having the disadvantages of the known devices.

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To solve this problem, a device for dosing liquid dye according to the preamble of claim 1 is proposed, which according to the invention has the features mentioned in the characterizing part of claim 1.

Further embodiments of the invention are mentioned in the subclaims.

The basic principle of the device according to the invention is the dosing of the dye by forcing a working fluid into a pump chamber in which the working fluid and dye are separated by a membrane that is deformable due to its shape and/or the material used. When using several such pump chambers a color change and/or the provision of multi-component dyes is possible.

Since the working fluid, in contrast to compressed air, is almost incompressible, the fluid volume flow and the quantity of working fluid and dye integrated over a working cycle correspond to one another without any time delay. In the dye, there is no relative movement of contacting pump parts. When designing the pump chambers and the membrane, there is great freedom to take into account minimal material fatigue of the membrane and easy flushing for cleaning. The device can also be designed in such a way that the shearing remains below a limit value above which a separation of dye suspensions or emulsions could occur.

When using an electrically insulating working fluid together with valves, for example according to WO 93/23173, which can insulate a high electrical voltage, a device according to the invention can also be used for electrostatic spray painting with electrically conductive dyes

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This application is gaining popularity due to the good

2 Environmental compatibility of water-based paints, which are increasingly required by the legislator, is becoming increasingly important.

4 From a high-voltage point of view, it is particularly advantageous to accommodate the electrically insulating valves

6 tile in common containers with the pump chambers containing the membrane, where they are separated from the

8 working fluid serving as the eluent.

In order to achieve the largest possible displacement with given external dimensions, the diaphragm must have considerable

Allow for shape changes. This can be easily achieved 12 by shaping, for example bellows shape, by choice of material, e.g. rubber-elastic polymers, or 14 by a combination of shaping and choice of material.

DRAWINGS

16 The invention is explained in more detail below with reference to the attached drawings.

18 Figure 1 shows a pumping chamber with a flat membrane at rest.

20 Figure 2 shows a pump chamber with a bellows-shaped membrane.

22 Figure 3 shows a device for dosing two-component dye for a spray device with the 24 possibility of choosing between several colors.

Figure 4 shows a pump chamber with integrated electrically isolating valves and a high voltage

guide for the electrically conductive dye.

28 DESCRIPTION OF PREFERRED EMBODIMENTS

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Fig.l shows a pump chamber 1 which is divided by a deformable, preferably rubber-elastic, membrane 2 into a working chamber 3 filled with a working fluid and a dye chamber 4 filled with a liquid dye. If working fluid is pressed into the working chamber through a connection 5, the membrane deforms so that the volume of the dye chamber is reduced and dye is pressed out through another connection 6. This is indicated by arrows. If working fluid is instead sucked out of the working chamber, a corresponding amount of dye is sucked into the dye chamber. To make it easier to rinse the dye chamber, it is provided with one or more connection(s) 7 for cleaning fluid and/or compressed air. Due to the negligible compressibility of working fluid and dye, the flows through connections 5 and 6 correspond exactly to one another.

While the deformability of the membrane in the pump chamber shown in Fig. 1 is achieved by a high elasticity of the membrane material used, Fig. 2 shows a pump chamber in which the deformability is achieved by shaping the membrane 2 as a bellows. Bottles made of a polymer material in this shape are inexpensively available and are preferably used. Since cleaning them is more difficult than a flat membrane according to Fig. 1, it is often more practical to replace the membrane with a new (or cleaned) one, for example when changing the dye.

For the purpose of easy replacement, a part 8 of the pump chamber can be designed to be easily opened. An opening 9 in this part of the pump chamber is designed for easy replacement of the bottle and a tight connection to it.

Fig.3 shows a device for dosing liquid two-component dye, which allows a quick change between

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see different colors. It contains a number of pump chambers la, 1b,..., which corresponds to the number of colors that can be switched between, as well as at least one pump chamber lh for a hardener. The pump chambers are shown here as an example with bellows membranes. Each pump chamber is assigned an inlet valve 10a, 10b,... and an outlet valve 11a, 11b,... for the working fluid and an inlet valve 12a, 12b,... and an outlet valve 13a, 13b,... for the dye. To fill the dye chamber 4b with a dye B, for example, dye B is pressed/sucked into the dye chamber from a dye source (not shown) through the valve 12b, which is open or opens automatically as a one-way valve, until the membrane 2b has reached its maximum deflection, mediated by a sensor 14b. Then, a control unit (not shown) causes the valve 12b to close. The working fluid that is thereby pressed/sucked out of the working chamber 3b is pressed through the opened valve 11b into a storage container 15. The pump chamber 1h is accordingly filled with a hardener H. The device is now prepared for spraying with paint B. During the following spraying process, working fluid is pressed into the working chamber 3b by a first pump 16 via the valves in Fig. 3 that are opened by the control unit during this process, and working fluid is pressed into the working chamber 3h by a second pump 16h. Hardener and dye, the latter after passing through valve 17, then enter a static mixer 18 and from there through another valve 19 to a dye spraying device 20. After the amount specified by the control unit has been used up, which can also be controlled in terms of volume flow, but at the latest when the minimum deflection of the membrane for dye and/or hardener, mediated by a sensor 21b or 21h, is reached, the spraying process is completed by closing at least valve 19. After the spraying process has been completed, the lines

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with the aid of a first rinsing liquid forced in through a valve 22, compressed air forced in through a valve 23 and a second rinsing liquid forced in through a valve 24. The rinsing liquids escape through the valve 19 and any other valves not shown. The second rinsing liquid is especially intended for the removal of already mixed multi-component dye.

The sensors and control lines connected to the control unit are not shown in Fig. 3 for the sake of clarity. The valves and pumps can be controlled electrically, hydraulically, pneumatically or by other transmission means.

With devices similar to that shown in Fig.3, mixed colors can also be dosed by using additional pumps by simultaneously feeding at least two dyes of different colors, with or without additional hardener. Multi-component dyes can also be dosed, which require, for example, the mixture of a dye, a hardener and a liquid auxiliary agent, for example an accelerator.

Of course, a device according to Fig. 3 can also be used for quick color changes for single-component paints by not using or omitting the pump chamber lh for the hardener and the mixer.

When using an electrically insulating working fluid and electrically insulating valves 12, 13 designed for high voltage, for example with a structure described in WO 93/23173, a device of this type is also suitable for the electrostatic spraying of electrically conductive dyes by means of a spray device under high voltage.

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Fig. 4 shows an advantageous embodiment of a pump chamber 1 for pumping an electrically conductive dye which enters the dye chamber 4 through a grounded inlet connection 25 and is dosed to an electrostatic spray device through a high-voltage outlet connection 26. The working chamber 3 filled with insulating working fluid also includes the inlet valve 12 and the outlet valve 13 for the electrically conductive dye. When the dye is admitted into the dye chamber 4 formed by the membrane 2, the dye chamber is earthed via the open inlet valve 12. The high voltage is kept away by the outlet valve 13, which is electrically insulating when closed. When the dye is pressed out, the valves swap roles. The dye is decoupled from earth by the closed inlet valve 12 and is connected to high voltage via the open outlet valve 13. Due to the much higher electrical flashover field strength of the area surrounded by the working fluid compared to air, the high voltage is reduced. The valves can be designed very compactly on the outside of the two valves. Together with the high-voltage bushing 27 for the outlet connection 26 and a design of the pump chamber as a grounded metal container, this results in a high-voltage-compatible design. To increase the electrical flashover voltage of the bushing, it can be provided with shields 28. This is particularly useful in damp and dirty environments.

Claims (1)

21.08.96 9 22 764 G Protection claims 1. Device for dosing liquid dye with a pump chamber (1), characterized in that the pump chamber is divided by a membrane (2) into a working chamber (3) and a dye chamber (4), that both chambers are provided with at least one connection for liquids located therein and that the membrane is designed and arranged in such a way that a liquid volume flow forced through an open connection of one chamber causes a corresponding liquid volume flow through an open connection of the other chamber by displacing the membrane. 2. Device according to claim 1, characterized in that the membrane consists of elastic, preferably rubber-elastic, material. 3. Device according to claim 1 or 2, characterized in that the membrane is at least partially designed as a bellows. 4. Device according to one of claims 1-3, characterized in that the pump chamber is provided with at least one connection (7) for cleaning liquid and/or compressed air. 5. Device according to one of claims 1-4, characterized in that at least two pump chambers are arranged together with valves (10, 11, 12, 13) which enable a change between different dyes. 6. Device according to one of claims 1 - 5, characterized by that at least two pump chambers together with valves and at least one sta- 21.08.96 10 22 764 G tic mixer (18) are arranged so that at least two dyes can be dosed and mixed together. 7. Device according to one of claims 1 - 6, characterized in that at least two pump chambers together with valves and at least one static mixer (18) are arranged so that at least one dye and at least one hardener and/or another liquid auxiliary substance can be dosed and mixed together. 8. Device according to one of claims 1-7, characterized in that at least one inlet valve (12) to a dye chamber (4) and one outlet valve (13) from a dye chamber (4) form an insulation against a high electrical voltage in the closed state of the valve. 9. Device according to claim 8, characterized in that the working fluid is electrically insulating. 10. Device according to claim 9, characterized in that the valves (12, 13) which are electrically insulating in the closed state are arranged in the working chamber (3). 11. Device according to one of claims 8-10, d a - characterized in that the pump chamber (1) is designed as a grounded metal container. 12. Device according to one of claims 8-11, characterized in that the working chamber is provided with an electrical high-voltage feedthrough, which can be provided with shields (28) and by 21.08.96 11 22 764 G which has an outlet connection (6, 26) for the liquid to be displaced from the dye chamber (4).