EP2075073B1 - Colour change system and method for changing colours - Google Patents

Description

The invention relates to a color changer system for the selective supply of at least two colors to a device for dispensing the colors and a corresponding color change method.

In the automotive industry, for example, robots are frequently used in paint shops for painting body parts with paints. In this case, colors are understood as meaning colored and colorless, usually liquid paints, lacquers, primers or similar fluids. In known systems, a plurality of robots are usually arranged in a paint booth, in whose robot arms the different colors, on average about 20 colors, are led as a hose package and connected there to a color changer so that the body parts can be painted in any desired color order. The individual colors are often passed through ring lines from larger color tanks under a pressure of up to 20 bar up to the color changer. The color changer can be formed by a block with a central channel into which the feed channels of the individual colors flow. These supply channels are each closed by a selectively openable valve or the like color port. In addition, opens in the channel a detergent connection. The channel then leads via a paint or Lackdosierpumpe to the means for dispensing the colors, for example to a pneumatically or electrostatically operated atomizer, a spray gun or the like.

In a color change, the previously opened color valve of the currently used color is first closed and as long as flushing agent from the detergent connection through the channel up to the device for dispensing the colors directed to the central channel of the color changer and all downstream thereof located lines including the paint or Lackdosierpumpe and the device for dispensing the colors of the previous color cleaned and partially dried. The color contained in the color changer and the downstream lines is lost and must be disposed of. This leads to high costs. In addition, it is considered to be disadvantageous that the opening and closing of the valves of the feed channels opening into the color changer are not always carried out without errors, so that an unwanted escape of two colors may occur simultaneously.

From the EP 1 245 295 A2 a color change system is known, which has a plurality of color supply valves connected to each color supply line and a atomizer-side connection valve, wherein the connection valve with one of the ink supply valves can be coupled. For this purpose, a coupling device is provided, which allows a relative movement of the ink supply unit combined color supply valves to the port valve. When the connection valve is open, color can reach adjacent application devices, such as the color pressure regulator, dosing pump and atomizer. For rinsing during a color change, the color change system has a rinse line associated with the atomizer-side connection valve with an additional valve arrangement for the rinsing agent or compressed air.

From the DE 199 62 220 A1 For example, a coating material change system is known in which a color picker can be assigned to different couplings. The color output of the colorant can lead to a color pressure regulator and metering pumps. In the paint collector openings may be provided for the supply of detergent and / or the compressed air.

In the DE 10 2006 005 341 A1 a painting device is described with a color changing device, which consists of two partially abutting parts that are movable relative to each other. Between the color changing device and an atomizer, a metering pump can be provided.

Object of the present invention is to provide a cost-effective and compact color changer system that can be cleaned well, as well as a method for changing a color in which as little as possible color is lost and at the same time a particularly reliable operation without Farbverschleppung is possible.

This object is achieved according to the invention substantially with a color changer system according to claim 1, which is suitable for the selective supply of at least two colors to a device for dispensing the colors. The color changer system comprises a first element, into which feed channels for the at least two colors open, and a second element, which can be rotated, swiveled and / or displaced relative to the first element, into which at least one with the device for dispensing the paint connectable conduit opens and which has a channel connected to the conduit with an opening which is selectively connected to each other by turning, pivoting and / or moving the two elements with each one of the feed channels of the first element, the supply channels this occlusive and selective openable paint ports or the like shutter assemblies are associated, and wherein in the line between the means for discharging the colors and the channel in the second element, a pump for conveying color is provided. According to the invention, the opening of the channel is fluidly connected to the pump.

The inventive design of the color changer system on the one hand ensures that the comparatively long central channel known color changer can be omitted, so that only the downstream of the color changer located lines need to be emptied and cleaned, This is not only the amount of discarded paint and the required detergent but it can also significantly reduce the cleaning time during a color change. Since in the color changer system according to the invention, only one feed channel can always be in communication with the channel leading to the device for dispensing the colors, the simultaneous emergence of two colors is excluded. The color connections or similar closure arrangements assigned to the feed channels additionally ensure that ink does not escape unintentionally. The assignment of a feed channel to the line leading to the atomizer or the like means for delivering the colors by a relative movement of the two elements to each other. This can be done, for example, by lifting the second element from the first element and then moving and / or rotating relative to it. In particular, when using an electrostatic atomizer, the plates should be able to be lifted apart by more than 200 mm. In principle, however, it is sufficient to lift the plates only so far during a color change that they do not rub. Alternatively, the pivoted two elements and then rotated or moved. Even a pure rotation and / or displacement without prior lifting or swinging away the two elements is possible, but then there is a risk of scoring on the facing surfaces of the elements.

By the invention provided in the line between the means for delivering the colors and the channel in the second element pump color can be pushed back during a color change in the respective Farbzuführkanal. The opening of the channel is fluidly connected to the pump, i. no valves or the like are provided downstream of the paint connection in front of the pump. This allows in the color changer system according to the invention the pushing back of the color from the lines in the Farbzuführkanal. Further, due to the absence of a valve or the like in the conduit or channel, there is no risk of a conduit bursting during the repressurization of the paint when a valve is not opened or is stuck or otherwise defective.

According to a preferred embodiment of the invention, the second element has an actuating member for opening and / or closing the paint connections. The paint connections can thus be designed, for example, as closing arrangements which are loaded by the fluid pressure in the feed channels and / or by an elastic element, so that an accidental discharge of color is prevented. The paint connections or similar closure arrangements can thus be opened only by the actuator when the corresponding supply channel is in a position assigned to the channel, while all other color connections or closure arrangements always remain closed. The actuator is arranged at any position so that it can cooperate with the paint connections.

In a further development of this inventive idea, it is provided that the second element comprises, for example, a plunger as actuator, softer is designed and arranged such that the plunger a hollow needle, a ball or the like one of the paint connections to open against the force of the hollow needle, the Ball or the like acting elastic element lifts from a seat. The actuator need not be formed as a plunger, but may be formed by any element suitable for opening a shutter or paint terminal, i. For example, a linear actuator, a needle, a solenoid valve or the like.

According to the invention, the restoring force of the elastic element is smaller than the pressure force of the fluid from the channel which is active during operation of the pump during the repressing of paint on the ball or hollow needle. Thus, the paint fitting simultaneously acts as a safety valve which automatically opens to repress the paint even if the actuator fails.

If the first and / or the second element, a stepper motor or other suitable, for example. Pneumatic drive for relative rotation of the two elements to each other and / or a linear actuator or the like for relative movement of the two elements are assigned to each other in an axial direction, the For a color change required rotation and translation are carried out with particularly simple means. Preferably, the first element is designed as a stationary, circular disc-like plate, in which the feed channels open, while the second element is formed as an example below this plate lying second plate with the stepping motor by 180 ° to 360 ° to the left or right is rotatable. To distinguish the two elements from each other before twisting, one or more linear actuators or the like may be provided be to achieve a stroke of, for example, about 20 mm to about 30 mm between the two elements. In principle, even an even smaller stroke can be sufficient to move the two elements relative to one another without these rubbing against one another. For cleaning purposes, it is preferable if a larger stroke of, for example, about 200 mm is made possible.

For the cleaning of the color changer system and the lines connected downstream of the latter during operation, a flushing agent channel for supplying flushing agent via a flushing agent connection, which communicates with the channel in the second element, is formed in the first and / or second element. Preferably, the detergent channel is designed in such a way that when cleaning the last used closure element or the color connection of the last used color is partially cleaned with and also the actuator and all channels are cleaned, especially in the second element. As a rinsing agent, for example, an air and solvent mixture can be used. Also, water or gases such as nitrogen are suitable as a rinse in some applications. The liquid or gaseous rinsing agent can be used simultaneously to push back the color in the Farbzuführkanal. For this purpose, the rinsing agent is, for example, supplied to the pump and / or to the atomizer or the like. Thus, the pump and the lines can pre-purify already during the pushing back of the color, so that at most only a short after-cleaning must be done.

If a preferably optionally forward and backward running paint or Lackdosierpumpe is arranged close to the two elements, the conduction path between the paint or Lackdosierpumpe and the two elements can be kept short, thereby further shortening the channel to be cleaned at a color change. In addition, a reverse-running paint or Lackdosierpumpe, in a color change that is still in the lines residual color against the flow direction during operation, ie when Painting to bring back, so that the previously used color is forced back into the feed channel. Thus, it is only the largely colorless lines to be cleaned by the detergent. This not only simplifies cleaning, but the color loss during a color change is reduced to almost zero. This leads to a considerable cost savings. At the same time, the entire color changer system can be constructed in a comparatively simple and cost-effective manner, since a total of only one paint or paint metering pump has to be provided, while all the supply channels are closed only by closure arrangements or the like.

According to a preferred embodiment of the invention, the paint or Lackdosierpumpe is formed as a two-way operable gear pump. However, other suitable pumps or piston-cylinder units for delivery and metering may also be used as a paint or paint metering pump.

The paint or Lackdosierpumpe is preferably fixed to one of the two elements, in particular to the second element, wherein the paint or Lackdosierpumpe can be driven by a particular in a hollow shaft for relative rotation of the two elements to each other arranged drive shaft. This allows a particularly space-saving design, which is particularly suitable for installation in a robot arm. Alternatively, the drive shaft for the paint or Lackdosierpumpe can also be guided laterally outside the shaft for pivoting the two elements. This is particularly useful when additional sensors or the like. Are provided, which complicate the arrangement of the drive shaft in a hollow shaft. If the means for dispensing the paint, which is, for example, a spray gun or an atomizer bell, is designed as an electrostatic atomizer, sufficient distances must be maintained between the atomizer and the other elements of the system.

Alternatively, the paint or Lackdosierpumpe be arranged in or on the means for dispensing the colors, in particular the spray head assigned. The paint or Lackdosierpumpe preferably has a separate from the hollow shaft and the first and the second element drive connection, for example, a drive shaft or a hydraulic connection.

The color changer system according to the invention is designed in such a way that a flushing agent inlet channel, which can be closed by means of a shut-off device, for the supply of flushing agent opens into the channel in the second element. In addition, from the channel in the second element and / or from the flushing agent inlet channel, a flushing agent return channel, which may be closed by means of the blocking member, branches off, which can be connected to the pump for supplying flushing agent to the pump. The flushing agent inlet channel is thus looped through the channel and supplies the pump with flushing agent via the flushing agent return channel, so that color can be forced back out of the pump and the lines between the pump and the color connection through the flushing agent column.

In order to avoid an unwanted escape of color in the contact plane of the two elements formed, for example, by circular plates, the contact surfaces abutting one another during painting or the like, for example, are ground. In addition, sealing means are provided in the mutually facing surfaces of the two elements, which prevent unwanted color leakage. For this purpose, either the channel provided in the second element can be surrounded by a seal and / or seals can be assigned to each of the feed channels or paint connections.

For exact and coordinated operation of the individual components of the color changer system according to the invention preferably at least the actuator and / or the paint or Lackdosierpumpe a control device are assigned. This may possibly also for the relative movement the two elements required drives, shutter assemblies of the color changer system and / or the detergent supply control.

During operation, the paint connections may become dirty or otherwise defective. The replacement of a paint connection is facilitated by the fact that the feed channels are connected to the first element in each case via a quick coupling device, wherein each feed channel is assigned in addition to the color connection, a further shut-off device. A paint feed channel can thus be quickly separated from the first element without any paint leakage when one of the paint connections needs to be repaired or replaced.

The object underlying the invention is further achieved by a method according to claim 12 or 14 for changing a color in particular between two coating steps (or the like. Steps for dispensing and / or applying a fluid), in particular with a color changer system of the type mentioned above. The method according to the invention has the following steps:

Supplying a first color from a paint container to a device for dispensing the ink, wherein the ink flows through a first supply channel with an opened paint connection in a first element, through the channel in a second element, which sealingly abuts the first element, and by a Direction to a acting in a first direction of paint or Lackdosierpumpe and from there to a means for delivering the colors, reversing the direction of the paint or Lackdosierpumpe for a period of time until the color substantially completely from the lines downstream of the paint terminal in the first supply channel is pushed back, closing the color connection associated with the first color, carrying out at least one relative movement of the two elements relative to one another until a second color connection of a second color faces the channel and the two elements or at least their seal (s) abut each other, opening of the color associated with the second color terminal and supply of the second color from a paint container to the means for dispensing the colors, wherein the color through the second feed channel with opened paint connection opens into the first element the channel in the second element sealingly abutting the first element and passing through the conduit to the paint or paint metering pump, again acting in the first direction, and from there to the ink dispensing means. In particular, the relative movement of the two elements may initially comprise a removal, pivoting away or lifting of the two elements from each other, a subsequent rotation and / or displacement and then an approximation of the two elements.

The emptying of the paint residues in the feed channel according to the invention not only saves ink but also the cleaning of the lines, i. This is done especially when, after reversing the direction of operation of the paint or Lackdosierpumpe the color from the lines downstream of the paint during the painting downstream of the respective paint connection extending channels including the paint and Lackdosierpumpe the color connection is forced back into the first supply channel by sucking a liquid or gaseous rinsing agent into at least some of the lines from the washing means channel assigned to the pump by the pump and / or from a washing agent channel associated with the device for dispensing the colors.

Alternatively, to change the colors between two painting steps or the like steps for applying and / or applying a fluid according to the invention, it is possible to close the color connection associated with the first color before the end of the first painting step and the first painting step continue until at least a portion of the first color is discharged from the lines downstream of the paint terminal from the color dispenser. In this case, preferably, the actuating member and / or the paint or Lackdosierpumpe controlled by a control device such that the first painting step is continued after closing the color associated with the first color terminal until the color substantially completely from the lines downstream of the paint terminal of the device for dispensing the colors is delivered. Therefore, the ink does not have to be discarded or pushed back, but can be applied far enough from the lines downstream of the paint connection during the first painting step that these lines are virtually free of ink residues.

According to the invention, it is provided that, after closing the color connection associated with the first color, flushing agent is introduced into the lines downstream of the color connection before the end of the first painting step during the continuation of the first painting step. The lines are thus cleaned during the first painting and filled with detergent. This facilitates and shortens the color change process significantly.

To eliminate the disturbing effects of air inclusions in the line, it is provided according to a development of the described method that an air inclusion in the line out of the line is forced into a flowing into the channel detergent return line and, for example, the pump is supplied. The forced out can be done both by detergent and by paint or paint.

The methods according to the embodiments described above are preferably operated such that a residual color amount remaining in the lines when the color changes is less than 10 ml, in particular less than 5 ml.

This is made possible for example by a time- and / or sensor-controlled control of the paint or Lackdosierpumpe or / and at least one of the closure arrangements.

Before the two elements are removed from one another, it is preferable to supply rinsing agent through the rinsing agent feed channel for the purpose of cleaning the first paint connection and the line downstream thereof. This may be an air and solvent mixture.

The rinsing agent is used according to a preferred embodiment of the invention not only for cleaning the downstream of the paint connection lines but also for cleaning the atomizer or the like. In this case, it is preferred if the rinsing agent is initially conducted together with any paint residues of the first color to a valve upstream of the paint dispensing device and from there to a collecting container and only after cleaning of the downstream of the paint connection lines by switching the valve in and / or via the device for dispensing the colors. The atomizer or the like is thus cleaned only with one of the previous color largely unloaded detergent.

In order to allow the rest of the color to restrain in the downstream of the paint port lines, the paint or Lackdosierpumpe is operated at a pressure higher than that prevailing in the feed channels pressure. Thus, the paint or Lackdosierpumpe can build up a pressure of, for example, about 70 bar, while prevail in the ring lines and the feed channels only up to about 20 bar.

Further developments, advantages and applications of the invention will become apparent from the following description of exemplary embodiments and the drawings.

They show schematically:

Fig. 1

in a partially sectioned view of the color changer system according to the invention according to a first embodiment,

Fig. 2

a view of the color changer system seen in the direction of arrow A from Fig. 1 .

Fig. 3

a schematic diagram of the color change system according to the invention and

Fig. 4

in a partially sectioned view of the color changer system according to the invention according to a second embodiment.

The color changer system has two circular disk-like elements 1 and 2, which in the illustration of Fig. 1 abut each other. In the top of the figure in the figure 1 open several feed channels 3, of which in Fig. 1 only one is shown. Each of the feed channels 3 is assigned a color connection 4 formed by a closure arrangement in the first element 1. As from the representation of Fig. 2 it can be seen, a plurality of feed channels and paint connections are arranged on a circular path of the first element 1.

The second element 2, however, is provided only with a bore, which can be brought into each case with one of the paint terminals 4 in coverage. In this hole, a plunger 5 is introduced, which lift the ball of the paint terminal 4 against the force of the spring of the paint terminal 4 from its seat may be to establish a flow connection between the feed channel 3 and the bore in the second element 2.

In the channel 6, an opening 6a is formed, which faces the first element 1, so that the respectively associated with the second element 2 color terminal 4 directly opposite the opening formed as a bore in the end face of the second element 6a. Further, in the second member 2, a channel 6 is formed with a free passage, which is in communication with the bore 6 a of the actuator 5. The bore 6a forms a connection portion of the channel 6 for selective connection with one of the paint connections 4. In this channel 6 also opens a detergent connection 7, which with a in Fig. 3 In addition, a shut-off valve 15 may be provided for the detergent channel 7, which, however, does not affect the free passage of the channel 6. Alternatively, the channel 7 can also be used as a return or discharge channel for rinsing agent and / or residual color, for example. When during the cleaning phase rinsing agent from the atomizer 9 or the pump 8 is directed toward the paint terminal 4.

Via a line 10, the channel 6 is connected to a paint or Lackdosierpumpe 8, which in turn is connected via a line, not shown, with a device for dispensing the colors, which is formed by an atomizer 9 in the illustrated embodiment. The paint or Lackdosierpumpe 8 is rigidly connected to the second element 2, wherein a drive shaft 11 for the paint or Lackdosierpumpe 8 through a central bore in the two elements 1 and 2 leads.

The drive shaft 11 of the paint or Lackdosierpumpe 8 is guided by a hollow shaft 12 which is rigidly connected to the second element 2 and is rotatably guided through a bore in the first element 1. The hollow shaft 12 thus makes it possible to rotate the second element 2 relative to the first element 1. For this purpose, the hollow shaft 12 is assigned, for example, a stepping motor, not shown in the figures. Next is also not shown in the figures device for lifting the two elements 1 and 2 relative to each other in the axial direction of the hollow shaft 12 is provided. This device can be formed for example by a suitable linear drive.

In operation, ink is passed from a paint line from a paint reservoir at a pressure of, for example, up to 20 bar via the feed channel 3 to the first element 1. The actuator 5 opens the paint port 4, so that the paint is passed through the channel 6 to the paint or Lackdosierpumpe 8. From there, the ink is passed under increased pressure to the atomizer 9, from which it is applied, for example, to body parts. With the exception of the opened by the actuator 5 color port 4 all other paint connections are closed on the one hand by the force of the spring and on the other hand by the fluid pressure in the supply channels, so that no color can escape from these other supply channels.

For a color change, the paint or Lackdosierpumpe 8 is actuated in the opposite direction, so that the remaining in the lines 10 between the paint terminal 4 and the atomizer 9 residual color is conveyed through the paint terminal 4 back into the feed channel 3. In this case, a gas, for example air or nitrogen, and / or a liquid rinsing agent is sucked into these lines 6, 10 located downstream of the paint connection 4. This is a pre-cleaning of the lines. After emptying these lines, first flushing agent is supplied through the flushing agent connection 7, which cleans both the lower side of the color connection 4, ie the ball, and the elements of the actuating element 5 projecting into the channel 6, and all lines located downstream of the color connection 4 flushed. It can be between the paint or Lackdosierpumpe 8 and the atomizer 9 a Can be provided multi-way valve, which makes it possible to first run rinsing agent with paint residues in a collecting container and only then rinsing agent, which contains substantially no paint residues, for cleaning the atomizer 9 through or through it.

Alternatively, it is also possible that rinsing agent is sucked into the lines when the color or Lackdosierpumpe 8 actuated in a reverse direction for a color change and thereby the remaining in the lines between the paint terminal 4 and the atomizer 9 residual color through the paint terminal. 4 is fed back into the feed channel 3. The lines are thus filled after the expulsion of the residual color already with the detergent and can then be cleaned by supplying more detergent, dried by supplying air or filled directly with the new color.

Before this flushing operation, the actuating member 5 is retracted so far that the paint connection 4, which faces the actuating member 5, is closed by the fluid pressure in the feed channel 3 and by the elastic element of the paint terminal 4. The pressure of the rinsing agent is less than the pressure in the feed channel 3, so that the paint connection 4 remains closed during the rinsing process.

After rinsing, the first element 1 is first lifted off the second element 2 or vice versa, with a small stroke of, for example, about 30 mm already being sufficient for the spacing of the two elements 1 and 2 from each other. Subsequently, the second element 2 is rotated as far as the first element 1 by actuation of the stepping motor until the supply channel and the color connection of the next required color is opposite the actuating member 5. The two elements 1 and 2 are then brought back into contact with each other and the actuator 5 can open the paint connection to a new painting.

For a better overview, see Fig. 3 a schematic diagram of the line system shown. The line system comprises the feed channel 3, which is closed by the closure assembly 4. By the actuator 5, not shown, the shutter assembly 4 can be opened so that color by the in Fig. 3 not shown opening 6a can flow into the channel 6. Detergent can be introduced from a detergent inlet channel 13 via the detergent connection 7 in the channel 6 and be forwarded via the flushing agent return channel 14, for example, to the pump 8. The flushing agent connection 7 is assigned a shut-off element 15, which blocks the supply of flushing agent or makes it possible, if necessary.

At the in Fig. 4 In the illustrated embodiment, the first element 1 is not formed as a circular disc but as an elongate rail, wherein the paint terminals 4 may be arranged in one or more rows on the rail. As a result, particularly many color connections can be provided on the first element 1. The feed channels 3 assigned to the paint attachments 4 can open into the first element 1 from above or from the side, wherein the closure arrangement 4 does not have to be provided on the same side as the feed channels.

The second element 2 can be kept compact in this embodiment and has the channel 6 with the opening 6a and possibly the actuating element 5 on. As in Fig. 4 indicated by dashed lines, the actuating element 5 can also be arranged on the side facing away from the opening 6a of the first element in order to open the closure arrangements defined and close.

LIST OF REFERENCE NUMBERS

1

first plate-shaped element

2

second plate-shaped element

3

feed

4

Color connection (closure arrangement)

5

Actuator (ram)

6

channel

6a

opening

7

Detergent connection (or return)

8th

Paint or paint metering pump

9

atomizer

10

management

11

drive shaft

12

hollow shaft

13

Dishwashing liquid supply channel

14

Dishwashing liquid return channel

15

shutoff

Claims (18)

1. A colour change system for selectively supplying at least two colours to a colour-transfer device (9) with a first element (1) into which lead supply channels (3) for the at least two colours, with in particular a twistable, pivotable and/or slidable second element (2) movable relative to the first element, into which second element leads at least one line (10) connectable with the colour-transfer device (9) and which comprises a channel (6) connected with the line and comprising an opening (6a) facing the first element (1), which channel is selectively connectable by a relative movement of the two elements (1, 2) in relation to each other with respectively one of the supply channels (3) of the first element (1), wherein the supply channels (3) are associated with these closable and selectively openable colour connections (4), wherein a detergent flow channel (13) for supplying detergent and closable by means of a shut-off device (15) leads into the channel (6) in the second element (2), characterised in that a preferably selectively forward and backward running pump (8) for conveying colour is provided in the line (10) between the colour-supplying device (9) and the channel (6) in the second element (2), wherein the opening (6a) of channel (6) is in flow-connection with pump (8) such that downstream of the respective colour connection (4) no shut-off device is provided ahead of the pump (8) and in that a detergent return channel (14) possibly closable by means of the shut-off device (15) branches off from the second element (2) and/or from the detergent flow channel (13), which return channel is connectable with pump (8) for supplying detergent to the pump (8).
2. The colour-change system according to claim 1, characterised in that the second element (2) comprises an actuating device (5) for opening and/or closing the colour connections (4).
3. The colour-change system according to claim 2, characterised in that the second element (2) comprises a plunger (5) as actuating device, which is designed and disposed such that the plunger (5) lifts a hollow needle or a ball of one of the colour connections (4) off a seat for opening, against the force, an elastic element acting upon the hollow needle or the ball.
4. The colour-change system according to claim 3, characterised in that the restoring force of the elastic element is smaller than the compressive force of the fluid from the channel (6), acting upon the ball or hollow needle during operation of the pump (8)
5. The colour-change system according to one of the preceding claims, characterised in that the first and/or second element (1, 2) are associated with a step motor or a pneumatic drive for twisting the two elements (1, 2) relatively to each other and/or with a linear actuator for moving the two elements (1, 2) relatively to each other in an axial direction.
6. The colour-change system according to one of the preceding claims, characterised in that an optionally forward- or backward-running colour- or varnish-metering pump (8) is disposed close to the two elements (1, 2).
7. The colour-change system according to claim 6, characterised in that the colour- or varnish-metering pump (8) is fixed on one of the two elements (2), wherein the colour- or varnish-metering pump (8) can be driven by a drive shaft (11) disposed in particular in a hollow shaft (12) for twisting the two elements (1, 2) relatively to each other.
8. The colour-change system according to one of claims 1 to 5, characterised in that the colour- or varnish-metering pump (8) is disposed in or on the colour-transfer device (9), in particular in association with a spray head (9).
9. The colour-change system according to one of the preceding claims, characterised in that sealing means are provided in the surfaces of the two elements (1, 2) facing each other, which sealing means surround the channel (6) and/or the supply channels (3).
10. The colour-change system according to one of the preceding claims, characterised in that the actuating device (5) and/or the colour- or varnish-metering pump (8) has a control device associated with it.
11. The colour-change system according to one of the preceding claims, characterised in that at least one of the supply channels (3) is connected with the first element (1) via a quick-coupling device, wherein the supply channel (3), in addition to the colour connection (4), has a further shut-off device associated with it.
12. A method for changing colour, in particular between two varnishing steps in a colour change system according to one of the preceding claims, comprising the following steps:

    - supplying a first colour from a colour reservoir to a colour-transfer device (9), wherein the colour flows through a first supply channel (3) into a first element (1) when the colour connection (4) is open, through an opening (6a) into a channel (6) in a second element (2) sealingly supported against the first element (1), and through a line (10) to a colour- or varnish-metering pump (8) acting in a first working direction and from there to the colour-transfer device (9),

    - reversing the working direction of the colour- or varnish-metering pump (8) for a period of time, until at least substantially all colour has been urged back into the first supply channel (3) from the lines (6, 8, 9, 10) downstream of the colour connection (4),

    - closing the colour connection (4) associated with the first colour,

    - performing at least one relative movement of the two elements (1, 2) to each other, until a second colour connection of a second colour lies opposite the opening (6a) of channel (6) and the two elements (1, 2) or at least their seal(s) are resting against each other,

    - opening the colour connection associated with the second colour and supplying the second colour from a colour reservoir to the colour-transfer device (9), wherein the colour flows through the second supply channel into the first element (1) when the colour connection (4) is open, and is directed through the opening (6a) into the channel (6) in the second element (2) sealingly resting against the first element, and through the line to the colour- or varnish-metering pump (8) acting again in the first working direction and from there to the colour-transfer device (9), characterised in that after reversing the working direction of the colour- or varnish-metering pump (8) the colour is urged back into the first supply channel (3) from the lines (6, 8, 9, 10) downstream of the colour connection (4), in that a liquid or gaseous detergent is sucked from a detergent channel (14) associated with pump (8) and/or a detergent channel associated with the colour-transfer device (9) into at least some of the lines (6, 8, 9, 10).
13. The method for changing a colour according to claim 12, characterised in that prior to the relative movement of the two elements (1, 2) a detergent is supplied through a detergent flow channel (7) for cleaning the first colour connection (4) and the lines (6, 8, 9, 10) downstream therefrom, which flow channel is, at least from time to time in flow-connection with channel (6).
14. The method for changing a colour, in particular between two varnishing steps in a colour-change system according to one of claims 1 - 11, comprising the following steps:

    - supplying a first colour during a first varnishing step from a colour reservoir to a colour-transfer device (9), wherein the colour flows through a first supply channel (3) into a first element (1) when the colour connection (4) is open, through an opening (6a) into a channel (6) in a second element (2) sealingly supported against the first element (1), and through a line (10) to a colour- or varnish-metering pump (8) acting in a first working direction and from there to the colour-transfer device (9),

    - closing the colour connection (4) associated with the first colour prior to the end of the first varnishing step and continuing with the first varnishing step, until at least part of the first colour has been discharged by the colour-transfer device (9) from the lines (6, 8, 9, 10) downstream of the colour connection (4),

    - performing at least one relative movement of the two elements (1, 2) to each other, until a second colour connection of a second colour lies opposite the channel (6) and the two elements (1, 2) or at least their seal(s) are resting against each other,

    - opening the colour connection associated with the second colour and supplying the second colour during a second varnishing step from a colour reservoir to the colour-transfer device (9), wherein the colour flows through the second supply channel into the first element (1) when the colour connection (4) is open, and is directed through the opening (6a) into the channel (6) in the second element (2) sealingly resting against the first element, and through the line (10) to the colour- or varnish-metering pump (8) acting again in the first working direction and from there to the colour-transfer device (9), characterised in that after closing the colour connection (4) associated with the first colour and prior to the end of the first varnishing step detergent is introduced, during the continuation of the first varnishing step, into the lines (6, 8, 9, 10) downstream of the colour connection (4).
15. The method for changing the colour according to claim 14, characterised in that the actuating device (5) and/or the colour- or varnish-metering pump (8) is controlled by the control device such that the first varnishing step, after closing the colour connection (4) associated with the first colour is continued until substantially all colour has been discharged by the colour-transfer device (9) from the line (6, 8, 9) downstream of the colour connection (4).
16. The method for changing the colour according to one of claims 12 to 15, characterised in that the relative movement of the two elements (1, 2) comprises the following steps:

    - distancing the two elements (1, 21) from each other and subsequent rotating and/or displacing of the two elements (1, 2) relative to each other, until a second colour connection of a second colour lies opposite the channel (6),

    - bringing the two elements (1, 2) closer together until these or at least their seal(s) come to rest against each other.
17. The method for changing the colour according to one of claims 13, 14 or 15, characterised in that the detergent is directed initially together with any residues of the first colour as far as a valve upstream of the colour-transfer device (9) and from their into a collecting reservoir and is not directed into and/or via the colour-transfer device (9) until after cleaning the line (6, 8, 9, 10) downstream of the colour connection (4) by a switch-over of the valve.
18. The method for changing the colour according to one of claims 12 to 17, characterised in that the colour- or varnish-metering pump (8) is operated at a higher pressure, preferably up to approximately 70 bar, than the pressure prevalent in the supply channels, preferably up to approximately 20 bar.

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