Device and installation for the electrostatic powder coating of objects

Abstract

A device for the powder coating of objects includes a main body on which an electrode arrangement designed for producing a powder cloud is arranged and on which a metering device is arranged above the electrode arrangement and is designed for the controlled discharge of an amount of a powder onto the electrode arrangement. A powder coating installation is equipped with at least one such device for powder coating.

Claims

1. A powder coating device for the powder coating of objects, comprising a main body, on which an electrode arrangement designed for generating a powder cloud is arranged and on which a metering device designed for a monitored discharge of an amount of a powder onto the electrode arrangement is arranged above the electrode arrangement, wherein the metering device comprises a powder outlet facing the electrode arrangement to enable powder being discharged by the metering device to reach the electrode arrangement under the effect of gravity and to produce a powder cloud that spreads out spatially as a result of electrostatic charging alone, without the application of compressed air or similar delivery of propulsive media.

2. The powder coating device as claimed in claim 1, wherein the metering device has a screen extending over the powder outlet.

3. The powder coating device as claimed in claim 2, wherein the metering device has a movably mounted slide with at least one powder receptacle, by means of which in each case an amount of powder corresponding to the size of the powder receptacle can be fed in portions to the electrode arrangement.

4. The powder coating device as claimed in claim 3, wherein the metering device is connected in a powder-conducting manner to a powder store and wherein the metering device has an electrically activatable transmitter, by means of which a supply of an amount of powder per unit of time to the electrode arrangement can be variably set, and wherein the electrically activatable transmitter interacts mechanically with the screen or with the movably mounted slide.

5. The powder coating device as claimed in claim 1, wherein the electrode arrangement is aligned in an inclined manner with respect to a horizontal, and wherein an upper-lying region of the electrode arrangement, with respect to a vertical, is at a smaller horizontal distance from the metering device in comparison with a lower-lying region of the electrode arrangement.

6. The powder coating device as claimed in claim 1, wherein the electrode arrangement is arranged pivotably on the main body.

7. The powder coating device as claimed in claim 1, wherein provided on the main body is at least one fastening element, which is designed for forming a releasable fastening with a corresponding counter-fastening element provided in a coating chamber of a powder coating installation.

8. The powder coating device as claimed in claim 1, wherein at least one wall portion is arranged on the main body and can be integrated into a boundary wall of a coating chamber of a powder coating installation.

9. A powder coating installation for the powder coating of objects, comprising at least one powder coating device as claimed in claim 1, a coating chamber and a powder storage container, and wherein the at least one powder coating device can be positioned variably in the coating chamber.

10. The powder coating installation as claimed in claim 9, wherein the coating chamber has a chamber bottom, which has at least in a portion thereof a collecting region for powder material narrowing downwardly in the form of a funnel.

11. The powder coating installation as claimed in claim 10, further comprising a powder return, which is connected by an end portion in a powder-conducting manner to the collecting region and which is connected by an opposite end portion in a powder-conducting manner to the powder storage container.

12. The powder coating installation as claimed in claim 11, wherein the powder return has an intermediate storage container.

13. The powder coating installation as claimed in claim 9, wherein a plurality of counter-fastening elements are arranged on or in the coating chamber for a variable arrangement of the at least one powder coating device.

14. The powder coating installation as claimed in claim 13, wherein at least one of the counter-fastening elements has an elongated fastening rail.

15. The powder coating installation as claimed in claim 9, wherein at least one boundary wall of the coating chamber or a wall portion belonging to the boundary wall can be released from the coating chamber and can be substituted by a wall portion of the at least one powder coating device.

16. A powder coating device for the powder coating of objects, comprising a main body, on which an electrode arrangement designed for generating a powder cloud is arranged and on which a metering device designed a for monitored discharge of an amount of a powder onto the electrode arrangement is arranged above the electrode arrangement, wherein the metering device has one of: (i) a powder outlet facing the electrode arrangement and a screen extending over the powder outlet, and (ii) a movably mounted slide with at least one powder receptacle, by means of which in each case an amount of powder corresponding to the size of the powder receptacle can be fed in portions to the electrode arrangement; and wherein the metering device is connected in a powder-conducting manner to a powder store, and wherein the metering device has an electrically activatable transmitter, by means of which a supply of an amount of powder per unit of time to the electrode arrangement can be variably set, and wherein the electrically activatable transmitter interacts mechanically with the screen or with the movably mounted slide.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

(1) Further objects, features and advantageous application possibilities of the powder coating device and the powder coating installation will be readily apparent to those of ordinary skill in the art from the following detailed description of exemplary embodiments with reference to the accompanying drawing figures.

(2) FIG. 1 shows a schematic representation of an isolated powder coating device according to an exemplary embodiment of the present invention.

(3) FIG. 2a shows a metering device for the powder coating device of FIG. 1 with a slide in a receiving position.

(4) FIG. 2b shows the metering device according to FIG. 2a with the slide in the discharging position.

(5) FIG. 2c shows the metering device according to FIG. 2a and FIG. 2b with the slide located in an intermediate position.

(6) FIG. 3 shows a perspective schematic representation of an electrode arrangement for the powder coating device of FIG. 1.

(7) FIG. 4 shows a partially sectioned representation of the electrode arrangement according to FIG. 3.

(8) FIG. 5 shows a schematic representation of a powder coating installation according to the present invention equipped with the powder coating device of FIG. 1.

(9) FIG. 6 shows another exemplary embodiment of a powder coating installation according to the present invention with altogether six powder coating devices.

(10) FIG. 7 shows yet another exemplary embodiment of a powder coating installation according to the present invention.

(11) FIG. 8 shows yet another exemplary embodiment of the powder coating installation according to the present invention.

(12) FIG. 9 shows yet another exemplary embodiment of a powder coating installation according to the present invention.

(13) FIG. 10 shows yet another exemplary embodiment of a powder coating installation according to the present invention in a frontal view.

(14) FIG. 11 shows a representation of the powder coating installation according to FIG. 10 in side view.

(15) FIG. 12 shows a side view of yet another exemplary embodiment of a powder coating installation according to the present invention that is designed for run-through or in-line operation.

(16) FIG. 13 shows a plan view of yet another exemplary embodiment of a powder coating installation according to the present invention,

(17) FIG. 14 shows a side view of the powder coating installation according to FIG. 13.

(18) FIG. 15 shows yet another exemplary embodiment of a powder coating installation according to the present invention with exchangeable boundary walls or wall portions.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

(19) In FIG. 1 and FIG. 5, the construction of a powder coating device 10 is schematically shown. The powder coating device 10 has a main body 11, which at the same time acts as a carrying structure for individual components of the powder coating device 10. The powder coating device 10 has at least one electrode arrangement 12, which is designed for generating a powder cloud 2 and is arranged on the main body 11. Also arranged on the main body 11 is a metering device 14. With respect to a vertical, this device is located above the electrode arrangement 12. The metering device 14 is provided in particular with a powder outlet 24, by means of which a predetermined amount of a powder material can be discharged and can reach the electrode arrangement 12 under the effect of gravity. On the electrode arrangement 12, the powder material 1 undergoes electrostatic charging, which leads to the formation of a powder cloud 2, as schematically indicated in FIG. 5.

(20) The electrode arrangement 12 and the metering device 14 may be arranged in a fixed or variably changeable manner on the main body 11 of the powder coating device 10. The powder coating device 10 or its main body 11 can be arranged variably in a coating chamber 102 of a powder coating installation 100 schematically shown in FIG. 5. The variable arrangement, that can be configured as desired, of the powder coating device 10 in or on the powder coating installation 100 allows the generation of powder clouds 2 of a wide variety of geometries and also with different particle or powder densities.

(21) The electrode arrangement 12, which is shown separately in FIGS. 3 and 4, has an extensively planar-designed two-dimensional structure. The electrode arrangement 12 may for example be designed in a rectangular or square manner. The electrode arrangement 12 may be of a multi-layered construction. It may have a lower layer 120 and an upper layer 122. The lower layer 120 and the upper layer 122 are typically produced from an insulating material. Between the two layers 120, 122 there is an electrode 124. The electrode 124 is designed as a flat electrode and predominantly fills a region between the layers 120, 122. A pulsed high voltage is typically applied to the electrode 124. For example, a high voltage in the range of 10 kV to 25 kV may be applied to the electrode 124. Typical frequencies for the high-voltage excitation lie in the range of 20 Hz to 100 Hz, preferably in the range of 40 Hz to 60 Hz, for example in a range of approximately 50 Hz.

(22) Arranged on the upper side of the upper layer 122 that is facing away from the lower layer 120 is a grid electrode 126. This has a grid-shaped structure and extends almost over the entire outer surface of the upper layer 122. A high-voltage DC voltage in the range of 5 to 50 kV is typically applied to the grid electrode. The grid electrode 126 provides electrostatic charging of the powder material 1 located on the upper side of the electrode arrangement 12. The pulsed electrode 124 brings about a kind of periodic pulse charging of the powder material 1 and assists the formation of a powder cloud 2 moving away spatially from the upper side of the electrode arrangement 12. Both electrodes, the electrode 124 and the grid electrode 126, are connected to a control unit 50. The electrodes 124, 126 may be galvanically isolated from one another.

(23) As also shown in FIGS. 1 and 5, the electrode arrangement 12 is arranged in a tilted manner with respect to a horizontal. It has with respect to the vertical an upper region 13 and a lower region 15. With a planar design of the electrode arrangement 12, the upper region 13 and the lower region 15 mark opposite side edges of the electrode arrangement 12. In the present case, it is provided that, with respect to a horizontal, the upper region of the electrode arrangement 12 is arranged closer to the outlet 24 of the metering device 14 than the lower region 15. In this way, it can be ensured that the powder material 1 discharged from the metering device 14 first impinges on the upper region 13 of the electrode arrangement 12 and from there is discharged to a powder cloud 2.

(24) Since the deposition rate of powder material 1 from the powder cloud 2 onto an object to be coated is limited and the powder cloud is subject to the effect of gravitational force, individual powder particles of the powder cloud steadily sink down onto the electrode arrangement 12. As a result, a uniform distribution of powder material 1 takes place on the upper side of the electrode arrangement 12, as is indicated in FIGS. 1 and 5. Moreover, the inclined alignment of the electrode arrangement 12 allows the geometry of the powder cloud 2 that is formed to be influenced and monitored. The electrode arrangement 12 may in particular be arranged pivotably on the main body 11 of the powder coating device 10. It may in particular be mounted pivotably on the main body 11 with regard to a horizontally running pivot axis. It is also conceivable that the electrode arrangement can be fastened multiply and separately to the main body 11 by regions that are opposite one another or at a distance from one another. Thus, an alignment and arrangement and also fixing of the electrode arrangement 12 that can be inclined as desired can also take place in this way on the main body 11.

(25) As shown in particular in FIG. 1, the main body 11 may form a kind of closed housing of the powder coating device 10. Above or to the side of the electrode arrangement 12, the main body 11 has in this case an outlet opening 17 for the powder cloud. As a departure from this, however, it is also conceivable that the electrode arrangement 12 is arranged outside an enclosure or a housing of the main body 11.

(26) In the specific design of the metering device 14 according to FIG. 1, it has a screen 26 that is made to extend over the powder outlet 24. The screen 26 prevents unrestrained trickling down or falling down of powder material 1 from a powder store 16 located above the powder outlet 24. The powder store 16 may be enclosed by a powder storage container 104. The powder storage container 104 may likewise be a component part of the powder coating device 10. It may however also be arranged outside the powder coating device 10 and merely be connected or coupled in a powder-conducting manner to the metering device 14.

(27) The metering device 14 according to FIG. 1 has adjacent to the screen 26 and counter to the delivery direction for the powder material 1 a deformable or flexible powder guide 20. The powder guide 20 may be for example a flexible tube or a flexible piece of line, by means of which the powder outlet 24 is connected to the powder storage container 104. The powder storage container 104 may have in particular a connection piece 104a for the powder guide 20. Facing away from the powder storage container 104, the powder guide 20 may have a stub 21 for receiving and/or fastening the screen 26. The stub 21 may have a flange-like widening. The powder guide 20 may also have respectively in the direction of the connection piece 104a and in the direction of the stub 21 a flange-like widening 20a, 20b, by means of which a form-fitting fastening of the powder guide 20 with respect to the powder storage container 104 and with respect to the stub 21 is possible. The powder guide 20 may be designed for example in the form of a flexible silicone tube.

(28) The metering device 14 is also equipped with a transmitter 18. This is arranged at the height of the powder outlet 24, therefore at the height of the screen 26. In the present case, the transmitter 18 is arranged at the height of the stub 21 and outside the stub 21, laterally adjacent to the stub 21. The transmitter 18 has in the present case an electrically activatable solenoid 38, which is designed to respond to the application of an electrical control signal by correspondingly striking laterally against the stub 21 in a regular and/or repeated manner, in order thereby to exert a mechanical pulse on the movably mounted screen 26. In this way, the solenoid 38 can exert a kind of knocking movement on the flexibly mounted screen 26, so that a defined amount of powder is discharged from the screen. The design shown here is advantageous to the extent that the movably mounted parts do not undergo any friction or abrasion, which could for example contaminate the powder material 1. Any powder material 1 that may become attached to the outside of the powder guide 20 can be knocked off by means of the transmitter 18. To this extent, the transmitter 18 counteracts attachment of powder to the movable components of the metering device 14.

(29) In FIGS. 2a to 2c, a further design of a metering device 14 is shown. Instead of a powder guide 20 forming an extension of a powder store 16 and a screen 26, this device has a movable slide 28. The slide 28 has a receptacle 30 for an amount of powder. The slide 28 is guided longitudinally displaceably on the metering device 14, between a receiving position shown in FIG. 2a and a discharging position shown in FIG. 2b. The receptacle 30 is upwardly and downwardly open. In the receiving position shown in FIG. 2a, the receptacle 30 is located under an outlet of the powder storage container 104. In this position, the receptacle 30 can be filled with powder material 1. Then, the slide 28 can be transferred into the discharging position shown in FIG. 2b, in which the slide 28 protrudes with its receptacle 30 out of a housing of the metering device 14. Since the receptacle 30 is downwardly open, the amount of powder 1 located in the receptacle 30 can be discharged downwardly and fed to the electrode arrangement 12. In FIG. 2c, an intermediate position of the slide 28 is shown. The arrow reproduced there shows the momentary direction of movement of the slide 28 toward the receiving position.

(30) As an alternative to the exemplary embodiment of FIGS. 2a to 2c, it is conceivable that the slide 28 is not mounted horizontally and longitudinally displaceably, but rotatably. For this case, a through-opening may be provided on an underside of the housing of the metering device 14, arranged offset in relation to an outlet of the powder storage container 104. By means of a rotatable slide 28, the receptacle 30 can be moved into the region of a through-opening on the underside of the housing of the metering device 14, through which through-opening the amount of powder can be discharged. It is equally conceivable that the slide 28 is moved completely within the housing of the metering device 14 and that the receptacle 30 in the discharging position comes to lie in line with a downwardly open through-opening of the housing.

(31) As shown in FIG. 5, the powder coating installation 100 has at least one previously described powder coating device 10. The powder coating device 10 may also have a wall portion 41, which is designed for and dimensioned in such a way as to substitute a wall portion 103a or an entire boundary wall 103 of the coating chamber 102. In the exemplary embodiment shown in FIG. 5, a boundary wall of the powder storage container 104 coincides with the wall portion 41 of the powder coating device 10.

(32) The powder coating device 10 can be releasably arranged together with this wall portion 41 on the coating chamber 102 or on a carrier structure 111 that is not explicitly shown in FIG. 5. In the configuration shown in FIG. 5, the electrode arrangement 12 is located above a chamber bottom 106. It protrudes laterally from a side wall portion 103 of the coating chamber 102 into the interior volume of the coating chamber. As indicated in FIG. 5, a powder cloud 2, which ideally fills as completely as possible a coating region 101 designed for receiving coating objects, forms during the operation of the powder coating installation 100.

(33) The chamber bottom 106 is aligned in an inclined manner, at least in a portion thereof. It may have a recessed collecting region 108. In particular, the chamber bottom 106 may be designed in the form of a funnel, for instance one-dimensionally or two-dimensionally in the form of a funnel. The chamber bottom 106 may taper downwardly, narrowing in the form of a cone, in the manner of a tetrahedron or in the manner of a truncated pyramid. In this way, a narrowing collecting region 108 can be formed, by means of which the powder material 1 trickling down for example from the electrode arrangement 12, in particular from its lower region 15, can be caught and collected.

(34) The collecting region 108 is also connected to a powder return 110. The powder return 110 has an end portion 112, which is connected in a powder-conducting manner to the collecting region 108 at the bottom of the coating chamber 102. An opposite end portion 114 of the powder return 110 is connected in a powder-conducting manner to an intake or a supply for the powder storage container 104. In this way, excess powder material 1, or powder material 1 collecting on the chamber bottom 106, can be fed once again to the coating process. In this way, a closed circulation is formed. The powder consumption can be minimized.

(35) The powder return 110 may also optionally have an intermediate storage container 116, which is connected in a powder-conducting manner to the end portion 112. The intermediate storage container 116 may also be connected in a powder-conducting manner to the end portion 114. The provision of an intermediate storage container 116 allows frequent removal of powder material 1 from the collecting region 108, without the amount of powder thereby recovered each time having to be fed directly to the powder storage container 104. In particular with the provision of a metering device 14 with a screen 26 provided at the powder outlet 24, it may be advantageous if the powder storage container 104 is not replenished with any further powder material 1 from above during an ongoing coating process.

(36) A filling level sensor 113, by means of which a removal, for example suction removal, of collected powder material 1 from the collecting region 108 can be initiated or triggered, may also be provided at or in the collecting region 108. The filling level sensor 113 is typically coupled to a central controller, for example to the control unit 50. Delivery means, for instance a blower or a suction extractor, for transporting the powder material 1 from the collecting region into the intermediate storage container 116 and into the powder storage container 104 are not explicitly shown in the present case. They may have one or more blowers or suction blowers, which are provided in or on the powder return.

(37) In the exemplary embodiment according to FIG. 15, the optional modular construction of a coating chamber 102 is shown by way of example in the example of a boundary wall 103, which in the present case is designed as a side wall. The boundary wall 103 has a number of side wall portions 103a. These are provided in each case with one or more fastening elements 40, which can be connected to counter-fastening elements 60 designed as corresponding thereto of a carrier structure 111 that is only schematically represented in FIG. 15. The carrier structure 111 may provide a load-bearing framework for the coating chamber 102 or parts thereof.

(38) The mutual connection of fastening elements 40 and counter-fastening elements 60 is releasably designed. In this way, individual side wall portions 103a can be released from the carrier structure and removed. Sometimes, the individual side wall portions 103a are also releasably connected to one another, thus for instance by means of connecting elements 42. Instead of a wall portion 103a designed for example in a planar manner, there may thus also be a powder coating device 10 arranged on the carrier structure 111. The powder coating device 10 has in this case along with the electrode arrangement 12 and the metering device 14 also a wall portion 41, which is formed with regard to size and geometry largely identically to the previously removed side wall portion 103a that is represented by dashed lines in FIG. 15. Consequently, the side wall portion 103a is substituted by the wall portion 41 of the powder coating device 10. At the same time, this can achieve the effect of arranging the powder storage container 104 outside the coating chamber 102 and the electrode arrangement 12 inside the coating chamber 102.

(39) As an alternative to this, it is of course also conceivable to arrange individual counter-fastening elements 60, for example in the form of elongated fastening rails 62, on the inner side of boundary walls 103, 105, 107 inside the coating chamber 102. Thus, for example, in the exemplary embodiments according to FIG. 13 and FIG. 14, provided on the opposite side wall portions 103, 105 there are in each case a number of horizontally running, elongated fastening rails 62, which are arranged one above the other with respect to a vertical and allow a variable arrangement, displaceable in the longitudinal direction, of individual powder coating devices 10 inside the coating chamber 102.

(40) The exemplary embodiments of FIG. 6 to FIG. 14 are greatly simplified and schematized. Only the electrode arrangements 12 and powder storage containers 104 of the respective powder coating devices 10 are shown there. In the design according to FIG. 6, three powder coating devices 10, arranged one above the other with respect to the vertical, are provided in each case on opposite side wall portions 103, 105. These allow the formation of a comparatively elongated, vertically aligned coating region 100. In FIG. 7, only the left-hand side wall portion 103 is provided with three powder coating devices 10 arranged one above the other. Perpendicularly to the opposite side wall portions 105 in the horizontal direction, the powder coating installation 100 according to FIG. 7 to FIG. 9 may also have a number of powder coating devices 10 arranged one behind the other, as shown for example in FIG. 11 and FIG. 14.

(41) In the exemplary embodiment according to FIG. 8, a powder coating device 10 is respectively arranged on opposite side wall portions 105. The respective electrode arrangements 12 are arranged approximately at the same height, considered in the vertical direction. They have a clear distance between them that is smaller than the horizontal extent of the electrode arrangements concerned. As a difference from this, in FIG. 9 a coating chamber 102 of a comparatively wide design is provided. This has two collecting regions 108, lying next to one another and respectively designed as narrowing downwardly. Above each collecting region 108 there is in each case an electrode arrangement 10.

(42) In the further exemplary embodiment according to FIG. 10, a powder coating device 10 is respectively arranged on opposite side wall portions 103, 105. In addition to this, at least one further powder coating device 10 is also arranged on an underside of a top portion 107 upwardly closing the chamber 102. This device has an electrode arrangement 12 comprising two parts or designed in a saddle-like or gable-like manner, with two limbs 12a, 12b. The limbs 12a, 12b go over seamlessly one into the other.

(43) With their ends remote from one another, the limbs 12a, 12b are in each case aligned as slightly inclined downwardly. Each of the limbs 12a, 12b may have a substantially planar structure. In the transitional region of the limbs 12a, 12b is the highest point of the electrode arrangement 12, which is typically arranged, with respect to the horizontal, approximately in the middle under the powder outlet 24 of the metering device 14.

(44) The powder coating installation 100 is shown in FIG. 10 in a frontal view. In FIG. 11, a corresponding side view is reproduced. There it can be seen that the powder coating devices provided in the region of the side wall portions 103, 105 extend over the entire length of the side wall portions 103, 105 and that two powder coating devices 10, at a distance from one another in the longitudinal direction or in the horizontal, are arranged on the top portion 107.

(45) In the representation of a further exemplary embodiment according to FIG. 12, a number of powder coating devices 10 are arranged inside an elongated coating chamber 102. The coating chamber 102, and consequently the entire powder coating installation, is designed for run-through operation. It has a feed opening 130 for coating objects 70 and also an outlet opening 132 for the coated objects 70, provided at an opposite end portion of the coating chamber 102. From the feed opening 130 to the outlet opening 132 there extends a delivery section 134, along which the coating objects are transported.

(46) At least two or more powder coating devices 10 are arranged along the delivery section 134. The powder coating devices 10 are arranged here at a distance from side wall portions 103, 105 on elevated base portions 140 in the middle of the coating chamber 102. Provided between the elevated base portions 140 are collecting regions 108 for powder material 1 occurring in the coating process. As already described above, the collecting regions 108 are connected in a powder-conducting manner to a powder return 110. In the region of the feed opening 130 and the outlet opening 132, air locks may be provided, which are not explicitly shown in the present case and by means of which a hermetic separation of the coating chamber 102 from the outer surrounding area can be obtained. The powder coating installation 100 shown in FIG. 12 allows pressure-less coating of elongated coating objects 70 in a continuous run-through process under atmospheric pressure without the aid of compressed air or similar delivery media.

(47) For the coating process, the coating objects 70 are typically electrically grounded. Even if many of the exemplary embodiments shown in the drawing figures show a metering device 14 that is provided with a movable slide, all of the exemplary embodiments may also be provided with a metering device, as shown in FIG. 1.