Paint-spray line

Abstract

A paint-spray line comprising a number of sprayers which are provided to discharge paint onto an item to be coated and are connected to a paint supply unit via a common main supply line is also suitable, to a particular extent and at an expense kept particularly low, for a need-based provision of individual quantities of paint which are kept at a particular minimum. For this purpose, the conveying device, provided for feeding paint into the main supply line is configured according to the invention as a single-piston pump.

Claims

1. A paint-spray line, comprising: a plurality of sprayers configured to discharge paint onto an item to be coated, the plurality of sprayers in fluid communication with a paint supply; a conveying device provided to feed the paint supply to the plurality of sprayers, wherein the conveying device includes a single-piston pump; a paint container comprising the paint supply, the paint container is connected to a receiving unit associated with the single-piston pump, wherein the paint container is configured to swivel about a longitudinal axis; a conveying line directly connected to a conveying side of the single-piston pump of the conveying device and to a first connection of a distributor block, wherein the distributor block is in fluid communication with the conveying device and is configured to receive the paint supply from the conveying device; a connecting line directly connected to a second connection of the distributor block and to a common supply line system, wherein the plurality of sprayers are directly connected to the common supply line system, and wherein the plurality of sprayers are in fluid communication with the distributor block and are configured to receive the paint supply from the distributor block; and a vent line directly connected to a third connection of the distributor block, wherein the vent line is in fluid communication with the distributor block and is configured to receive the paint supply from the distributor block.

2. The paint-spray line according to claim 1, wherein the single-piston pump is configured for a conveying pressure of at least 10 bar.

3. The paint-spray line according to claim 1, wherein the single-piston pump is provided with a distance sensor for determining a piston position.

4. The paint-spray line according to claim 1, wherein a flow sensor is connected downstream of the single-piston pump of the paint spray line on the conveying side.

5. The paint-spray line according to claim 1, wherein the single-piston pump is provided with a pressure sensor on the conveying side for determining a conveying pressure of the single-piston pump.

6. The paint-spray line according to claim 5, wherein a signal transmitter, associated with the pressure sensor, is configured to output a control signal if the conveying pressure exceeds a limiting value of 0.5 bar.

7. The paint-spray line according to claim 6, wherein, to transmit the control signal, the signal transmitter is connected to a switching unit associated with a branch-off point of the vent line from the conveying line.

8. The paint-spray line according to claim 1, wherein a suction pipe connected to a suction line of the single-piston pump is provided with a return stop on a free end of the suction pipe.

9. The paint-spray line according to claim 1, wherein a suction pipe connected to a suction line of the single-piston pump has a length of more than a height of the paint container comprising the paint supply.

10. The paint-spray line according to claim 1, wherein the single-piston pump can swivel in its longitudinal axis about a swivel angle of at least 180.

11. The paint-spray line according to claim 10, wherein a suction pipe of the single-piston pump is shorter than a filling level of the paint container comprising the paint supply.

12. The paint-spray line according to claim 10, further comprising a sensor which constantly measures a distance of the single-piston pump from a liquid level.

13. The paint-spray line according to claim 10, wherein a position of the single-piston pump, of a suction pipe and/or of the paint container relative to a filling level in a reservoir, which decreases during suction-removal, is automatically tracked.

14. The paint-spray line according to claim 1, wherein the common supply line system forms a loop.

15. The paint-spray line according to claim 14, wherein the common supply line system is configured to circulate paint in one direction through the loop.

16. The paint-spray line according to claim 1, wherein the common supply line system is a plurality of branch lines, and wherein each branch line corresponds to a paint sprayer in the plurality of paint sprayers.

17. The paint-spray line according to claim 1, further comprising: a second plurality of paint sprayers directly connected to a second common supply line system; and a second connecting line directly connected to a fourth connection of the distributor block and to the second common supply line system, wherein the second plurality of sprayers are in fluid communication with the distributor block and are configured to receive the paint supply from the distributor block.

Description

(1) An embodiment of the invention will be described in more detail with reference to drawings, in which:

(2) FIG. 1 schematically shows a paint-spray line;

(3) FIG. 2, 3 show details of a paint supply unit of the paint-spray line according to FIG. 1,

(4) FIG. 4a, 4b show alternative embodiments of the paint supply unit according to FIG. 2, 3, and

(5) FIG. 5a, 5b show a cover plate.

(6) Identical parts in all the figures are provided with the same reference numerals.

(7) The paint-spray line 1 according to FIG. 1 is configured in the embodiment to have multiple sections, is configured in particular as a two-section line and comprises a first painting section 2 and a second painting section 4. However, the paint-spray line 1 could naturally also be equipped with only a single painting section. To coat items or to apply paint, each painting section 2, 4 respectively comprises a plurality of sprayers 6 which, with the formation of the respective painting section 2, 4, are arranged in tandem, are provided for applying paint onto the coated item and are connected to a paint supply unit 12 common to both painting sections 2, 4 via a main supply line 8 and 10 which is common to the sprayers 6 inside the respective painting section 2, 4. In this respect, in the embodiment, the paint supply to the sprayers 6 is provided via the main supply lines 8, 10 which thus form a supply line system 8, 10 common to the sprayers 6. Alternatively, the supply line system 8, 10 could also be configured as a plurality of individual branch lines or the like which lead to the individual sprayers from a common branching point.

(8) The length of the main supply lines 8, 10 of the painting sections 2, 4 can be freely selected and the main supply lines 8, 10 lead to a number of colour changers 14 which are arranged in a painting booth (not shown) and from which a respective branch line leads to the respective sprayers 6. The main supply line 8, 10 is configured to be piggable in each case and can be formed as a branch or ring line. In this respect, the respective main supply line 8, 10 has at its start or at its conveying pump-side end a respective release valve 56 which is followed by a first parking station 58 for a pig. Provided downstream of the last removal area is a second parking station 59 for the pig, where the pig can let through the fluid which flows past it during normal operation. Connected to the pig parking station is a combination of valves which comprises at least one valve for release into a collecting line or into a collecting container, as well as a valve for rinsing agent and a valve for a propelling medium, preferably compressed air. Otherwise, the respective main supply line 8, 10 is appropriately configured by drawing on the pigging method, as described for example in EP 1 142 649 B1, the disclosure of which in respect of the pigging method used is explicitly fully incorporated by reference.

(9) The paint-spray line 1 is specifically configured to also allow the discharge of very small quantities of paint and is thereby also configured for the need-based coating of very small batches or individual parts, involving a particularly low material consumption, while keeping operational costs particularly low. For this purpose, on the one hand basically the feed of need-based calculated colour or paint packages into the respective main supply lines 8, 10 is provided, using the pigging method, so that residual quantities of paint in the adjoining systems can be kept particularly low. To further improve the reduction, achievable thereby, of the operational effort and material expense, in the paint-spray line 1, the paint supply unit 12 is also configured, however, to a particular extent for the processing of very small quantities, while substantially reducing the ensuing waste, even during frequent colour changes.

(10) For this purpose, on the one hand the paint supply unit 12 is configured to keep to a particular minimum the quantity of paint which is required in the manner of an operating material for maintaining the operational procedures and, on the other hand, the corresponding line volumes and the like are kept comparatively low. To make this possible, the conveying device 20 of the paint supply unit 12 which causes the paint to be fed into the main supply line 8, 10 from a paint container 22 provided for the paint supply, is configured as a single-pump piston 20. The single-pump piston 20 is configured for a conveying pressure of at least 10 bar, so that line cross sections with comparatively small dimensions can also be reliably fed (filled) with paint. The minimised line cross sections promote the fact that even in the case of restricted volumes of the fed-in paint, an adequate conveying length inside the respective line is traveled by the paint, so that an adequately precise positioning of the respective paint package in relation to the discharge point is possible without an appreciable operational expense.

(11) The single-pump piston 20 comprises a piston 26 which is guided in a cylinder 24 and can be moved inside the cylinder 24 by a piston rod 28. The cylinder 24, the piston 26 and a cover plate 30 form a conveying chamber 32, the volume of which can be varied by moving the piston 26 inside the cylinder 24. The conveying chamber 32 is connected on the suction side to the interior of the paint container 22 via a suction system 34 and is connected on the conveying side to the main supply line 8 and 10.

(12) The configuration of the conveying device 20 of the supply unit 12 as a single-piston pump ensures that the suctioned quantities of paint brought into the conveying chamber 32 can be fed virtually completely and without residue into the main supply lines 8, 10. In this respect, a comparatively very precise discharge of precisely metered quantities of paint is made possible by a correspondingly precise control of the piston position inside the cylinder 24, so that the single-piston pump 20 can also be used in the manner of a metering cylinder for a very precise paint feed. To further improve the accuracy of a specific and need-based paint feed, the paint supply unit 12 is also provided with a number of sensors to accurately determine the delivered quantity of paint.

(13) For this purpose, on the one hand the piston rod 28 of the single-piston pump 20 is provided with a distance sensor 40. Said distance sensor 40 makes it possible to very accurately determine the piston position inside the cylinder 24, from which it is possible to precisely determine the given paint volume, while considering the other configuration parameters, such as in particular the cylinder cross section. In particular, the movement increments of the piston 26 in the single-piston pump 20 can be detected sensorially and can be evaluated as conveyed-quantity signals.

(14) Alternatively or additionally, on the conveying side, a flow sensor can also be connected downstream of the single-piston pump 20 to determine the conveyed-out quantity of paint. Flow sensors of this type, which are not shown in the embodiment, can be associated in particular with the connection lines 36, 38.

(15) To be able to detect and determine the discharged quantity of paint in a particularly precise sensorial manner, in a starting procedure of the paint transportation, as often occurs when there are frequent colour changes, the time at which paint starts to be fed into the main supply lines 8, 10 is also automatically recorded. In this respect, it is specifically taken into account that during the suctioning procedure and before the start of the actual paint transportation, the single-piston pump 20 only releases air on the conveying side first of all and as long as the conveying volume 32 has not been completely filled with paint. Since air is a compressible medium, whereas the paint to be conveyed is incompressible, the commencing discharge of paint on the conveying side of the single-piston pump 20 results in a corresponding increase in pressure in the conveying chamber 32 of the single-piston pump 20 at the moment when the conveying chamber 32 is completely filled with paint. To be able to suitably determine this moment, a pressure sensor 46 for determining the conveying pressure is associated with the single-piston pump 20 on the conveying side.

(16) Associated with the pressure sensor 46 is a signal transmitter 48. The signal transmitter 48 is configured to output a control signal in the event that the conveying pressure exceeds a limiting value, which can be adjusted in a system-dependent manner, of 0.5 bar, for example. Thus, by presetting this limiting value, the control signal emitted by the signal transmitter 48 is characteristic of a differentiation as to whether or not the conveying chamber 32 of the single-piston pump 20 is completely full of paint. The control signal can therefore be used for a corresponding recognition of the start of the actual conveying of the paint.

(17) This control signal can be evaluated in an automation unit or in a central control station for the paint-spray line 1. However, in the embodiment, it is provided in the sense of an additional and further integration of the system procedures in the manner of an automated utilisation of this control signal that the operating state of the paint-spray line 1 switches over from ventilation to paint conveyance directly subject to this control signal. For this purpose, for transmitting the control signal the signal transmitter 48 is connected on the signal side to a switching unit 56 associated with the branch-off point 50 of a vent line 52 from a paint line 54 connected downstream of the single-piston pump 20 on the conveying side.

(18) The paint supply unit 12 is also configured for an integrated and thus particularly compactly maintained construction. For this purpose, directly connected to the single-piston pump 20 on the conveying side is a distributor block 60, in which the conveying line of the single-piston pump 20 branches into the connecting lines 36, 38 for the main supply lines 8, 10 on the one hand and branches into the vent line 52 on the other. The distributor block 60 is directly flange-mounted onto the single-piston pump 20 for an integrated and compact construction, which cannot be seen in FIG. 1 due to the schematic illustration. Further valves for rinsing agent, compressed air and/or for the release of various rinsing or ventilation paths are arranged in the distributor block 60, depending on requirements.

(19) To further reduce the residual quantities of paint which have to be accepted, the suction system 34 of the supply unit 12 is also configured appropriately. In particular, the suction system 34 of the single-piston pump 20 has suction pipe 72 which is connected via a suction line 70 to the conveying chamber 32 of the single-piston pump 20. The suction line 70 is kept particularly short, so that the corresponding volumes can be kept particularly low, and it has a length of at most 200% of the height of the reservoir. The suction line 70 is thereby particularly shorter than double the height of the container 22. Furthermore, the suction pipe 72 is also appropriately configured in respect of the discharge of very small residual quantities from the paint container 22 and, for this, it has at its free end 74 a return stop, particularly in the form of a check valve, preferably a ball check valve. Furthermore, the suction pipe 72 can also be configured to discharge a remaining residual quantity of paint during emptying of the container 22, for example by a piston guided in the suction pipe 72 or by a ball floating therein which transfers the residual quantity of paint remaining inside the suction pipe 72 into the conveying volume 32.

(20) In respect of the choice of material for the suction pipe 72, said suction pipe 72 is also of an adequately rigid construction and is calculated in length such that it exceeds the overall height of the container 22 such that, when the suction pipe 72 immerses into the paint container 22, a local deformation of the container base by the free end 74 of the suction pipe 72 is made possible. Thus, during immersion of the suction pipe 72 into the paint container 22, a local depression in the container base can be produced in which residual quantities of paint can collect, thereby furthering a specific discharge of even very small residual quantities of paint. The suction system 34 also comprises at least one release valve 35, the opening of which can clear the suction line to the conveying chamber 32. The release valve 35 is closed when the paint in the conveying chamber 32 is to be pushed again in the direction of the connecting line. Compactly connected to the output system 34 is a valve unit 31 into which are integrated different valves, by which the output system 34 and the path to and in the distributor block 60 can be rinsed. Contained in the valve unit 31 are at least valves for supplying rinsing agent and compressed air, and also, if required, release valves for the choice of rinsing paths and/or associated pump valves which conduct the soiled rinsing agent into disposal lines.

(21) Details of the paint supply unit 12 are presented in FIGS. 2 and 3. As shown by these figures, the paint supply unit 12 and therewith also a receiving unit 80, associated with the single-piston pump 20, for the paint container 22 can swivel in the longitudinal axis. Starting from a straight starting position, as shown in FIG. 2, by swiveling the entire system, a tilted position, as shown in FIG. 3, can be adjusted if required. This tilting movement ensures that small residual quantities of paint remaining in the container 22 collect in the base region in the immediate vicinity of the free end 74 of the suction pipe 72, so that the tilting movement promotes a specific discharge of even very small residual quantities of paint.

(22) Alternatively, the single-piston pump 20 for its part can advantageously swivel with a swivel range of at least 180, or can be installed in a fixed upside-down position, as shown in FIG. 4. Thereby, the adjustment of an upside-down position for the single-piston pump 20 is possible, so that the single-piston pump 20 can be directly immersed with its suction region in the container 22, while dispensing with a longer suction line or the like. By appropriately re-positioning the single-piston pump 20 in relation to the respective liquid level of the paint in the paint container 22, a reliable discharge of the paint is thereby particularly promoted.

(23) As shown in FIGS. 4a and 4b, the suction line 34 can be significantly shortened and can be configured with a shorter length than the overall height of the reservoir 22. In this case, the suction line is immersed into the paint (the liquid to be conveyed) with an immersion depth of only a few centimeters and the distance of the pump from the liquid level 81 is measured using an optical, acoustic, electric or inductive distance sensor 82. With the evaluation of this signal, the pump or the suction line thereof tracks the liquid level 81, which falls as the contents of the container are removed by suction, by a motor-driven positioning means 83, so that the lower end of the suction line 74 always remains below the liquid level. This configuration means that the length of the suction line 34 can be significantly less than the filling level of the liquid in the reservoir. In the case of upside-down operation of the single-piston feed pump, the discharge of the suctioned paint (liquid), or the guidance of the ventilation valve 52 can take place centrally through the piston rod of the pump, so that the air which is unavoidably also drawn up by suction during the first suctioning procedure of the liquid can escape upwards above the liquid in the conveying chamber 32 of the pump.

(24) In this respect, the positioning means 83 can be directly associated with the pump or with the suction line thereof and can suitably track them according to the change in height of the liquid level 81. However, in the embodiment, the positioning means 83 is associated with the reservoir 22 in the manner of a telescopically extensible support mechanism, so that the height thereof can be appropriately adjusted to the position of the pump.

(25) FIG. 5a, 5b are respective longitudinal sectional views of the cover plate 30, as configured in particular for upside-down operation of the single-piston pump. In a particularly advantageous configuration, as shown in FIG. 5a, 5b, integrated into the cover plate 30 are valves and connections 90 for branch lines which are contained in the distributor block 60 in the embodiment according to FIG. 1. This configuration allows a positioning of the junctions for the branch lines and/or of the distributor block 60 in the immediate vicinity of the single-piston pump 20, which again requires a very compact construction with correspondingly short conveying paths. Furthermore, a pig launching station can also be integrated into the cover plate 30.

LIST OF REFERENCE NUMERALS

(26) 1 paint-spray line 2,4 painting section 6 sprayer 8, 10 main supply line 12 paint supply unit 14 colour changer 20 single-piston pump 22 paint container 24 cylinder 26 piston 28 piston rod 30 cover plate 32 conveying chamber 34 suction system 38, 38 connecting line 40 distance sensor 46 pressure sensor 48 signal transmitter 50 branch-off point 52 vent line 54 paint line 60 distributor block 70 suction line 72 suction pipe 74 free end 80 receiving unit 81 liquid level 82 distance sensor 83 positioning unit for pump/container distance