Metallic coating device and method, and holding unit for the device

Abstract

The invention relates to a device and a method for the metallic coating of a work piece with a mobile coating lance (20), by means of which a metal plasma jet can be generated to create the coating consisting of metal particles. According to the invention, an extraction hood (30) is provided, which at least encloses an axial section of the coating lance (20) in a ring-shaped manner, and the extraction hood (30) has a ring-shaped holding unit (50), which is configured to take up the metal particles.

Claims

1. A device for metallic coating of a workpiece having a coating lance, through which a metal plasma jet can be generated to form the coating of metal particles, wherein ambient air can be removed from the coating lance with an overspray of metal particles via a waste air pipe, wherein an extraction hood, which annularly encloses at least an axial portion of the coating lance, is provided to draw off the ambient air, the extraction hood and the coating lance are arranged on a mobile base carriage, the coating lance is mounted so that the coating lance can be moved on the mobile base carriage at least in one direction, the extraction hood has, on the mobile base carriage, an annular holding unit which is designed for depositing of metal particles, the extraction hood has a cover hood and a bottom plate, which is arranged on a lower side of the cover hood, the annular holding unit is arranged releasably on the bottom plate, the annular holding unit is mounted within the extraction hood so that the annular holding unit can be replaced, the annular holding unit comprises a drum-shaped base body, which is provided with a peripheral wall, an annular upper edge element, and an annular lower edge element, wherein each of the annular upper edge element and the annular lower edge element is arranged at an end of the peripheral wall and extends radially inwards, and the annular holding unit is designed to be releasably arranged on the bottom plate of the extraction hood of the device.

2. The device according to claim 1, wherein the bottom plate is releasably fastened to the cover hood by means of at least one quick release device.

3. The device according to claim 1, wherein the bottom plate has a central opening, on which an annular flange is provided, which has a radially inwardly falling conical surface.

4. The device according to claim 3, wherein the conical surface is formed with an anti-adhesion property.

5. The device according to claim 1, wherein a removable cover plate is arranged at an upper side of the cover hood.

6. The device according to claim 1, wherein the extraction hood is mounted so that the extraction hood can be moved on the mobile base carriage at least in one direction.

7. The device according to claim 1, wherein the base body is produced from sheet metal.

8. The device according to claim 1, wherein the base body is constructed from sub-segments.

9. A method for metallic coating of a workpiece, wherein a metal plasma jet is generated by means of a coating lance, through which the coating of metal particles is formed on the workpiece, wherein a device is used, wherein ambient air can be removed from the coating lance with an overspray of metal particles via a waste air pipe, the device comprising: an extraction hood, which annularly encloses at least an axial portion of the coating lance, is provided to draw off the ambient air, wherein the extraction hood and the coating lance are arranged on a mobile base carriage, the coating lance is mounted so that the coating lance can be moved on the mobile base carriage at least in one direction, the extraction hood has, on the mobile base carriage, an annular holding unit which is designed for depositing of metal particles, the extraction hood has a cover hood and a bottom plate, which is arranged on a lower side of the cover hood, the annular holding unit is arranged releasably on the bottom plate, the annular holding unit is mounted within the extraction hood so that the annular holding unit can be replaced, the annular holding unit comprises a drum-shaped base body, which is provided with a peripheral wall, an annular upper edge element, and an annular lower edge element, wherein each of the annular upper edge element and the annular lower edge element is arranged at an end of the peripheral wall and extends radially inwards, and the annular holding unit is designed to be releasably arranged on the bottom plate of the extraction hood of the device, the method comprising: arranging the extraction hood and the coating lance on the mobile base carriage, and the extraction hood has, on the mobile base carriage, the annular holding unit, wherein at least the axial portion of the coating lance is enclosed annularly by the extraction hood, through which an air flow is generated, by means of which ambient air containing metal particles is removed, moving the coating lance, with continuing metal plasma jet, into the annular holding unit, and depositing metal particles on the holding unit in the extraction hood on the mobile base carriage, wherein the extraction hood has the cover hood and the bottom plate, which is arranged on the lower side of the cover hood, and the annular holding unit is arranged releasably on the bottom plate.

10. The method according to claim 9, wherein the air flow is generated by means of a flow device which is connected via a ventilation duct to the extraction hood.

11. The method according to claim 9, wherein the coating lance is moved out of the workpiece into the extraction hood with a holding unit, wherein the metal plasma jet is directed onto the holding unit and metal particles deposit on a peripheral wall of the holding unit.

12. The method according to claim 11, wherein the holding unit is exchanged at predefined time intervals and/or when a predefined amount of deposits is reached.

Description

(1) The invention will be described further below by reference to the preferred exemplary embodiments that are schematically shown in the attached drawings, in which:

(2) FIG. 1 shows a schematic perspective view of a device according to the invention for metallic coating;

(3) FIG. 2 shows a schematic perspective view of the device of FIG. 1, but without a coating lance;

(4) FIG. 3 shows an enlarged cross-sectional view with respect to the extraction hood according to the device of FIGS. 1 and 2; and

(5) FIG. 4 shows an enlarged perspective view of a holding unit according to the invention.

(6) A device 10 according to the invention for the metallic coating of a workpiece (not shown) is illustrated in its main parts in FIGS. 1 and 2. The workpiece can be in particular an engine block, of which the cylinder bores are provided with a metal coating. To form the metal coating, a rod-shaped coating lance 20 is used, which is known in principle and generates a metal plasma jet. Through this substantially radially directed metal plasma jet, metal particles are applied at high speed to the workpiece wall to be coated, wherein a solid, thin-walled metal coating is formed. The structure and the operating mode of such a coating lance have long since been known. The device 10 can additionally have a base frame (not shown) as well as feed and positioning devices for the workpiece.

(7) The shaft-form coating lance 20 with the associated base unit 22 is held on a lance carriage 14 which can be moved relative to a base carriage 12, which is only indicated schematically, in a vertical direction along a lance guide 15 by means of a lance linear drive 16. Furthermore the coating lance 20 is mounted so that it can be rotated and driven around its vertical longitudinal axis in order to coat an inner wall of a cylinder bore with a radially directed metal plasma jet.

(8) Furthermore an extraction hood 30 is mounted on the base carriage 12 by means of a hood carriage 17 so as to be movable in the vertical direction and parallel to the direction of movement of the lance carriage 14. Two rail-like hood guides 18 are arranged for this purpose on the base carriage 12, with which the hood carriage 17 is connected in a guiding manner via sliding blocks. A linear displacement is brought about by means of a linear drive 19. The base carriage 12 itself is mounted so that it can be moved relative to the base frame of the device 10 in several directions. A cylindrical or drum-shaped cover hood 32 is fastened to the frame-like hood carriage 17 of the extraction hood 30.

(9) By reference also to FIG. 3, the structure of the extraction hood 30 is explained in more detail. The cover hood 32 is produced from sheet metal and is arranged in a holding frame 31 which is fastened to the hood carriage 17. The cover hood 32 has a cylindrical wall 33 which is closed at its upper side by a cover plate 34. The cover plate 34 is designed in two parts and has a central through opening 35 for passage of the coating lance 20. A discharge opening 46 is incorporated in the cylindrical wall 33, via which ambient air containing metal particles can be drawn out of the inner space of the cover hood 32 during operation via a ventilation duct 48 by means of a flow device (not shown), in particular a pump, and carried away to a filter device. The cover plate 34 is releasably arranged and can be removed to influence the flow conditions.

(10) At its lower side the cover hood 32 is closed by an annular bottom plate 36 which is fastened in the present exemplary embodiment via three quick release devices 40 releasably on a lower annular brace 37 of the holding frame 31. For this, radially projecting hook elements 41 are provided on the radial outer edge of the bottom plate 36 which can be connected to a clamping bracket of the quick release device 40.

(11) To allow the coating lance 20 to pass through the bottom plate 36, the bottom plate 36 has a central opening 38, along which an annular flange 42 is mounted resiliently via spring elements 43 and is held on the bottom plate 36. The resilient mounting of the annular flange 42 allows a precisely fitting, flexible placing of the extraction hood 30 on a workpiece.

(12) The annular flange 42 has on its radial inner side a conical surface 44 with an upwardly directed angle of inclination of approximately 30. Upon passage of the coating lance 20 out of the workpiece into the extraction hood 30 during a continuous metal plasma jet, metal particles impacting on the conical surface 44 are deflected to a great extent and guided into a drum-shaped holding unit 50, which is mounted on the bottom plate 36 in the extraction hood 30. To avoid undesired deposits on the conical surface 44, this conical surface 44 is provided with an anti-adhesion property through a corresponding material selection and surface treatment.

(13) The structure of a holding unit 50 according to the invention for the device 10 according to the invention is shown in more detail in FIG. 4. The drum-shaped holding unit 50 has a base body 52 of sheet metal which comprises a cylindrical peripheral wall 54 produced from a curved and welded sheet metal strip. At the upper end of the peripheral wall 54 an annular upper edge element 56 is welded. Correspondingly an annular lower edge element 58 is welded at the lower end of the peripheral wall 54. Both edge elements 56, 58 are radially inwardly orientated and enclose an annular collection space.

(14) The lower edge element 58 has a larger radial extension than the upper edge element 56 and is adapted to an annular recess 39 in the bottom plate 36. The lower edge element 58 extends as far as the central opening 38 in the bottom plate 36, at which the conical surface 44 of the annular flange 42 begins. It is hereby ensured that, when the coating lance 20 is moved in with continuous metal plasma jet, the metal particles in the extraction hood 30 extensively reach an inner side of the peripheral wall 54 of the holding unit 50. When the coating lance 20 is moved in the extraction hood 30 in a moved-in end position, the metal plasma jet is directed approximately centrally onto an inner side of the peripheral wall 54. The upper edge element 56 and the lower edge element 58 ensure that metal particles do not leave the holding unit 50 upwards or downwards.

(15) During operation the coating lance 20 is moved into the extraction hood 30 with continuing metal plasma jet whenever the coating lance 20 is moved relatively from one workpiece bore to be coated to the next workpiece bore to be coated. During this movement process with the base carriage 12 the coating lance 20 is further rotated so that the continuous metal plasma jet forms a metal deposit on the inner side of the peripheral wall 54 of the holding unit 50. As soon as this metal deposit has reached a predetermined maximum amount, which can be a few kilos, the holding unit 50 is replaced by a new holding unit 50. For this, the quick release devices 40 are released so that the bottom plate 36 with the holding unit 50 lying on it is separated from the cover hood 32 arranged above. In this state the holding unit 50 can be removed and replaced by a new holding unit 50. Subsequently the cover hood 32 is placed on the bottom plate 36 again and both parts are reconnected by means of the quick release devices 40. Subsequently the coating of the workpieces can be continued. Furthermore ambient air of the coating lance 20 is drawn off via the suction hood 30. The suction or drawing-off is realised both during the coating of the workpiece and also while the coating lance 20 has been moved into the extraction hood 30. In this way overspray, which in particular is also produced if the metal plasma jet is directed onto the holding unit 50, is removed.