DE9106610U1 - Spray coating device - Google Patents

Description

Patent Attorney E. O. VETTER, Bahnhof-Straße 30, D-8900 Augsburg, Federal Republic of

Ransburg GmbH

Our ref: G 670 DE 24 May 1991

Spray coating device

The invention relates to a spray coating device according to the preamble of claim 1.

Such a spray coating device is known from DE-PS 32 01 930 C2. During the coating process, coating material (colored or transparent, paint, varnish) flows from one or more coating material containers to a

Coating material changer and from there via a flow path to an atomizer device, which sprays the coating material onto an object to be coated. If no more coating material is supplied to the coating material changer, the

Flow path continues to be filled with coating material. To ensure that this coating material is not lost, it is pushed out of the flow path by an additional flow medium (air, but preferably liquid, in particular solvent) starting from the coating material changer up to the atomizing element of the atomizing device and sprayed by the atomizing device onto the object to be coated. The residues that then remain in the flow path are expelled from the flow path by the same or another flow medium through a continuous or intermittent flow medium pulse. These details also apply to the present invention. Further details can be found in the aforementioned DE-PS 32 01 930 C2.

The invention is intended to solve the problem of reducing the time required for cleaning the flow path when changing from one coating material to another coating material and the amount of solvent required for this. At the same time, the problem is to be solved of being able to clean the atomizer device alone in a shorter time than previously required during coating breaks, when work is subsequently continued with another or the same coating material, and using less solvent than was previously required.

This object is achieved according to the invention by the characterizing features of claim 1.

Further features of the invention are contained in the claims .

The invention is described below with reference to the drawing using a preferred embodiment as an example.

The drawing shows a spray coating device according to the invention for the automatic application of liquid coating material to, in particular, motor vehicle bodies by means of an atomizer device 2 for several, for example three coating materials, in particular paints in a pressure vessel 4, 6 and 8. The atomizer device 2 contains known means for electrostatically charging the coating material. A coating material changer 10, hereinafter referred to as a paint changer, contains, depending on the number of different coating materials, for example six valves, preferably 2/2-way valves 12/1, 12/2, 12/3, 12/4, 12/5 and 12/6, so that depending on the open way valve, the coating material in question reaches the atomizer device 2 via a flow path 14. In the flow path 14 there is a pressure regulator 16 which is effective for all coating materials and is referred to below as the paint pressure regulator 16. For the sake of simplicity, it is assumed that there is a first paint in the pressure vessel 4, a second paint in the pressure vessel 6, a third paint in the pressure vessel 8 and a solvent in a further pressure vessel 18. A compressed air source 20 is connected via a check valve 22/1 and a 2/2-

Directional valve 12/4 of the color changer 10 can be connected to the flow path 14. The solvent of the pressure vessel 18 can be connected to the flow path 14 via a solvent pressure regulator 24/1, a check valve 22/2 and a 2/2-directional valve 12/5 of the color changer 10. Furthermore, the solvent pressure vessel 18 can be connected to the flow path 14 via a pressure regulator 24/2, a check valve 22/3 and a

2/2-way valve 12/6 of the color changer 10 can be connected to the flow path 14. In addition, the solvent pressure vessel 18 can be connected to a 2/2-way valve 12/7 of a secondary flushing device 30 via a pressure regulator 24/3 and a subsequent check valve 22/4. The secondary flushing device 30 also contains a 2/2-way valve 12/8, which is connected to a compressed air source 20 via a check valve 22/5. The outputs 32 and 34 of the two 2/2-way valves 12/7 and 12/8 are connected to one another and connected to a fluid connection 36 of a first switching device 38. The first switching device 38 is preferably a 3/2-way valve. The first switching device 38 divides the flow path 14 into a first path section 40 leading from the color changer 10 to the first switching device 38 and a second path section 42 leading from the first switching device 38, from its flow connection 36, to the atomizing element 44 of the atomizing device 2. The atomizing element 44 is preferably a rotating bell. A measuring cell 46 is located in the first path section 40. The 3/2-way valve of the first switching device 38 connects the first path section 40 with the second path section 42 in the switching position shown. In this switching position of the first switching device 38, paint from one of the pressure vessels 4, 6 or 8 can reach the first path section 40 via the relevant valve 12/1 or 12/2 or 12/3 of the color changer 10 and from there via the first switching device 38 and the adjoining second path section 42 of the flow path 14 to the atomizing element 44 of the atomizing device 2. If, after this paint supply, all valves 12/1, 12/2 and 12/3 of the different colors are closed, the paint remains in the

A color liquid column is formed in the flow path 14 (40, 42). This can be pushed out of the flow path 14 by solvent from the pressure vessel 18 via one of the two regulators 24/1 and 24/2 and the connected valves 12/5 or 12/6 of the color changer 10 until the end of the color column and thus only a small amount of color remains immediately in front of the atomizing element 44. The atomizer device 2 contains a second switching device 50 in the form of two valves 52 and 54. One valve 52 is located in the second path section 42 immediately upstream of the atomizer element 44, and the said paint column end of the ejected paint column lies on the short intermediate piece 56 between this valve 52 and the atomizer element 44. The other valve 54 of the second switching device 50 connects the second path section 42 immediately upstream of the one valve 52 to a second return line 58 which leads to a collecting container 60. During the conveyance of coating material through the flow path 14 to the atomizer element 44, and also during the ejection of the material column remaining in the flow path 14 after the coating material has been supplied, the one valve 52 is open and the other valve 54 of the second switching device 50 is closed. Furthermore, during this coating material supply and during the ejection of the remaining material column after its conveyance, the two valves 12/7 and 12/8 of the secondary flushing device 30 are closed. The coating material and the solvent are conveyed by compressed air sources 20 connected to them.

When no more coating material is fed to the atomizer device 2 and the remaining coating material remaining in the flow path 14

material column has been pushed out of it in the manner mentioned, the flow path 14 must be cleaned of coating material residues. To do this, it is possible to convey solvent from the pressure vessel 18 via one or the other of the two pressure regulators 24/1 and 24/2 and one of the valves 12/5 or 12/6 connected in terms of flow into the first path section 40 and from there via the first switching device 38 also through the second path section 42. Depending on the design of the atomizer device 2, the solvent can exit through the one valve 52 of the second switching device 50 on the atomizing element 44, or preferably be conveyed into the collecting container 60 with the valve 52 closed and the other valve 54 of the second return line 58 open. However, in order to save time and solvent for this cleaning process, according to the invention, the 3/2-way valve of the first switching device 38 is switched to another position, to a so-called "flushing" position. In this "flushing" position, the two path sections 40 and 42 are no longer fluidically connected to one another via the fluid connection 36 of the first switching device 38, but are separated from one another in the first switching device 38. Instead, in this "flushing" operating position, the first path section 40 is connected via the first switching device 38 to a first return line 62, which also leads into the collecting container 60. As a result, the solvent (or another rinsing agent) which is conveyed from the color changer 10 through the first path section 40 to the first switching device 38 does not reach the second path section 42, but directly from the first switching device 38 into the collecting container 60. At the same time, while the one valve 52 of the atomizer device 2 is opened and the

other valve 54 is closed, the valves 12/7 and 12/8 of the secondary flushing device 30 are opened and closed alternately and as a result, with a relatively high frequency sequence, a solvent (or another flushing agent) is alternately conveyed from the pressure vessel 18 via the pressure regulator 24/3 and the 2/2-way valve 12/7 and, the next time, compressed air from the compressed air source 20 is conveyed via the 2/2-way valve 12/8 of the secondary flushing device 30 at the fluid connection 36 of the first switching device 38 into the upstream beginning of the second path section 42 and through it, whereby this solvent or, alternately, the air, reaches the collecting container 60 via the valve 54 of the second switching device 50. One valve 52 is therefore always closed and the other valve 54 of the second switching device 50 is always open. To expel coating material residues in the short section 56 between one valve 52 and the atomizing element 44, one valve 52 can be opened briefly and the other valve 54 closed at the same time, so that a burst of solvent and/or air is then released from the secondary flushing device 30 through the second path section 42 via the atomizing element 44.

According to the invention, the flow path 14 is thus divided into two path sections 40 and 42 during the cleaning process, which are preferably each approximately the same length, at least each path section should still have a significant length. If the flow path 14 is halved into two path sections, the time required for rinsing or cleaning the two path sections is also approximately halved if this cleaning or rinsing takes place in parallel, i.e. simultaneously, according to the invention. At the same time, the consumption of cleaning agent or solvent is reduced.

because the cleaning effect is greater over short distances than over long distances and less contaminated cleaning material or solvent is more absorbent to the paint to be cleaned.

The process sequence of the spray coating device according to the invention is described in detail below:

coating with the first color from the pressure vessel 4;

Close color valve 12/1 of the color changer 10;

Open solvent valve 12/5 and supply solvent from pressure vessel 18 at a solvent pressure adapted to the viscosity of the coating material, whereby the solvent pressure can decrease as the residual coating material column in flow path 14 decreases;

using this solvent, push the paint column out through the flow path 14 until the end of the paint column is just in front of the atomizing element 44;

Close solvent valve 12/5 of the color changer 10;

Switch solvent pressure regulator 24/1 to the pressure required for flushing with solvent (this also sets the solvent quantity at the same time);

at the same time, set the paint pressure regulator 16 to maximum value so that the solvent can flow through freely;

simultaneously switching the 3/2-way valve of the first switching device 38 so that no solvent can flow from the color changer 10 via the first switching device 38 to the atomizer device 2, but the flow path for solvent and air from the color changer via the first switching device 38 and the first return line 62 into the collecting container 60 is open;

simultaneously closing the atomizing valve 52 of the second switching device 50 in the downstream end section of the second path section 42;

simultaneously opening the flushing valve 54 of the second switching device 50 in the atomizer device 2 so that the second return line 58 into the collection container 60 is open;

then pulsating alternating supply of air and solvent

a) Air from the air source 20 via the valve 12/4
of the colour changer 10 or solvent from the pressure vessel 18 via the solvent pressure regulator 24/2
and the valve 12/6 of the colour changer 10 by
the first section 40 of the flow path
14 to the first switching device 38 and from
this directly through the first return line 62
into the collecting container 60, and at the same time
in parallel

b) from the secondary flushing device 30 air from the
Air source 20 via the 2/2-way valve 12/8 and
Alternately, solvent from the pressure vessel 18 via the solvent pressure regulator 24/3

and the 2/2-way valve 12/7 of the secondary flushing device 30 to the fluid connection 36
and thus into the beginning of the second path section 42 and through this second path section 42, at the end of which it is
closed valve 52 and open valve 54
via the second secondary line 58 into the
collecting container 60;

The solvent quantity in the second path section 42 is controlled by the solvent pressure regulator
24/3 set (fixed value or variable in
Dependence on the flushability of the
rinsing coating material and/or
variable depending on time);

then switch off the solvent supply;

then blow the first path section 40 from the color changer with air and blow the second path section 42 from the secondary flushing device 30 with air;

turn off air;

Prepare for the supply of another coating material or color by following steps:

Switching the first switching device 38 back to the position shown in the drawing, in which it connects the two path sections 40 and 42 of the flow path 40 with each other in terms of flow, the collecting container 60 is separated in terms of flow, and the secondary flushing device 30

- 11 is switched off;

the color pressure regulator 16 remains at maximum pressure setting ;

the flushing valve 54 of the atomizer device 2 remains open and the atomizer valve 52 of the second switching device 50 remains closed;

opening the valve 12/1 or 12/2 or 12/3 of the color changer 10 for the pressure vessel 4, 6 or 8 of the relevant selected color;

the selected color is conveyed through the flow path 14 until just before the flush valve 54 of the second switching device 50, and then at this moment the color pressure regulator 16 switches from its maximum setting to the color pressure required for the coating process and the color is conveyed through the still open flush valve 54 (atomization valve 52 closed) until just behind this flush valve 54;

Closing the flush valve 54;

opening the atomization valve 52 of the second switching device 50, and conveying the paint through this spray valve 52 either only to the connecting piece 56 between this spray valve 52 and the atomization element 44 or completely to the atomization element 44, depending on whether the spray coating process is only to be prepared (pressing paint on) or the spray coating process is already to be carried out, i.e. paint is to be sprayed onto an object to be coated.

According to a special embodiment of the invention, it is possible to provide a second coating material changer 210 for other different types of coating material and to connect it to the same flow connection 36 at the beginning of the second path section 42 via a further first path section 240 and a further first switching device 238, so that then either the one color changer 10 and the one first path section 40 or the other color changer 210 and its first path section 240 are connected to the second path section 42 and can thus use the latter together alternately. The further first switching device 238 can in turn be formed by a 3/2-way valve and be connected in terms of flow to the collecting container 60 via a third return line 262. This avoids interruptions in operations even when a large number of different coating materials are used alternately and individual material strands or pressure vessels containing coating material have to be replaced or cleaned in between.

An advantage of the invention is that by dividing the flow path into sections 40 and 42 or 240 and 42 it is possible to clean the atomizer device 2 in a short time with little solvent through the secondary flushing device 30, without cleaning the first path section 40. This is useful when, when using the same coating material, cleaning only the atomizer device 2 is required, for example during breaks in operation.

If so-called water-based paint is used as the coating material, it is also possible within the scope of the invention to provide a further flushing device 330 that is structurally similar to the secondary flushing device 30, with which it is possible, if necessary, to clean only the atomizing element 44 of the atomizing device 2 with solvent and/or air.

91 OB610.

Claims (9)

Patent Attorney E. O. VEnER, Bahnhof-Straße 30, D-8900 Augsburg, Federal Republic of Germany Ransburg GmbH Our Ref. No.: G 670 DE 24 May 1991 Claims 1. Spray coating device for the automatic application of liquid coating material, in particular to motor vehicle bodies, by means of an atomizer device for several coating materials, with a flow path for the coating materials from a coating material changer to the atomizer device, wherein the flow path can be flushed with fluid when the coating material is changed, characterized,
that the flow path (14) of the coating material contains a first switching device (38) with which it can be divided for the rinsing process into at least two path sections (40, 42) which can be rinsed separately but simultaneously, of which the first path section (40) extends from the coating material changer (10) to the first switching device (38) and the second path section (42) extends from the first switching device (38) to the atomizing element (44). 6 610. 2. Spray coating device according to claim 1,
characterized, that the first path section (40) and the second path section (42) each have their own fluid supply device (10, 30) for supplying the fluid used for flushing. 3. Spray coating device according to claim 2,
characterized, that the fluid supply device of at least the second path section (42) is a device (30) which releases a plurality of air or solvent pulses in a fluid-wise manner. 4. Spray coating device according to one of claims 1 to 3, characterized,
that the end of the first path section (40) can be connected in terms of flow for the rinsing process by means of the first switching device (38) via a first return line (62), and the atomizer device (2) can be connected in terms of flow to a collecting container (60) by means of a second switching device (50) via a second return line (58), and that the two switching devices (38, 50) separate the two return lines (62, 58) from the two path sections (40, 42) in terms of flow and instead release the full flow path (14) continuously for coating material when they are switched from "rinsing" back to "coating". 91 08 610. 5. Spray coating device according to claim 4,
characterized, that the second switching device (50) can be switched selectively from "rinsing" to "coating" and then vice versa, while the first switching device (38) is switched to "rinsing". 6. Spray coating device according to one of claims 1 to 5, characterized, that the first switching device (38) is a switchable multi-way valve. 7. Spray coating device according to one of claims 1 to 6, characterized,
that the second switching device (50) consists of two valves (52, 54), of which one valve (52) is arranged in the end section of the second path section (42) leading to a spray element (44) of the atomizer device (2), and of which the other valve (54) forms the beginning of the second return line (58) which branches off from the second path section (42) immediately upstream of the one valve (52). 8. Spray coating device according to one of claims 1 to 7, characterized,
that a rinsing agent supply device (330) for separately supplying rinsing agent to the spray element (44) of the atomizer device (2) is provided separately from the flow path (14) of the coating material. 9. Spray coating device according to one of claims 1 to 8, marked by
at least one second coating material changer (210) for a plurality of coating materials, the flow path (14) of which for its coating materials is formed by a separate first path section (240) from it to a further first switching device (238) and by the second path section (42) which can be used selectively for all coating materials from the first switching devices (38, 238).