EP0351725A2 - Procédé et dispositif de revêtement par pulvérisation électrostatique - Google Patents

Procédé et dispositif de revêtement par pulvérisation électrostatique Download PDF

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Publication number
EP0351725A2
EP0351725A2 EP89112926A EP89112926A EP0351725A2 EP 0351725 A2 EP0351725 A2 EP 0351725A2 EP 89112926 A EP89112926 A EP 89112926A EP 89112926 A EP89112926 A EP 89112926A EP 0351725 A2 EP0351725 A2 EP 0351725A2
Authority
EP
European Patent Office
Prior art keywords
powder
weight
coating
coated
coating powder
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP89112926A
Other languages
German (de)
English (en)
Other versions
EP0351725A3 (fr
Inventor
Robert Lehmann
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Gema Switzerland GmbH
Original Assignee
Gema Switzerland GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Gema Switzerland GmbH filed Critical Gema Switzerland GmbH
Publication of EP0351725A2 publication Critical patent/EP0351725A2/fr
Publication of EP0351725A3 publication Critical patent/EP0351725A3/fr
Withdrawn legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/14—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas designed for spraying particulate materials
    • B05B7/1404—Arrangements for supplying particulate material
    • B05B7/1472—Powder extracted from a powder container in a direction substantially opposite to gravity by a suction device dipped into the powder
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B12/00—Arrangements for controlling delivery; Arrangements for controlling the spray area
    • B05B12/08—Arrangements for controlling delivery; Arrangements for controlling the spray area responsive to condition of liquid or other fluent material to be discharged, of ambient medium or of target ; responsive to condition of spray devices or of supply means, e.g. pipes, pumps or their drive means
    • B05B12/12—Arrangements for controlling delivery; Arrangements for controlling the spray area responsive to condition of liquid or other fluent material to be discharged, of ambient medium or of target ; responsive to condition of spray devices or of supply means, e.g. pipes, pumps or their drive means responsive to conditions of ambient medium or target, e.g. humidity, temperature position or movement of the target relative to the spray apparatus
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
    • B05B5/001—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means incorporating means for heating or cooling, e.g. the material to be sprayed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
    • B05B5/16—Arrangements for supplying liquids or other fluent material
    • B05B5/1683—Arrangements for supplying liquids or other fluent material specially adapted for particulate materials

Definitions

  • the invention relates to a method for electrostatic spray coating according to the preamble of patent claim 1.
  • the invention further relates to a device for electrostatic spray coating according to the preamble of patent claim 4.
  • US Pat. No. 4,500,560 shows a device for the electrostatic spray coating of objects with coating powder, with a moisture adjusting device for adjusting the moisture content of the coating powder by moistening and / or heating, before this coating powder is electrostatically charged by a spraying device and sprayed onto objects to be coated.
  • the coating quality and the efficiency of the coating process depend, in particular with enamel powder, on the moisture content of the coating powder.
  • the spray device is connected to a closed powder container in which the coating powder is in a fluidized state. Fresh powder, powder recovered from a spray booth, gas for fluidizing the coating powder, and steam for moistening the fluidized powder are fed to the powder container. There is a heating device in the gas supply line.
  • the coating quality and the efficiency of the coating process depend on the electrical resistance of the powder.
  • the electrical resistance of the powder, especially enamel powder is heavily dependent on its moisture.
  • US Pat. No. 4,500,560 the moisture content of the mixture of gas and particles of coating powder suspended in it is measured in the powder container. Depending on the measured value, either steam is supplied or the gas is heated. Despite these measures, there are great fluctuations in practice in the type of spraying and in the coating quality, especially if the powder is an enamel powder.
  • the development of a so-called "orange peel effect" and other undesirable irregularities in the powder layer applied to an object is particularly disadvantageous.
  • the object of the invention is to improve the coating quality and the efficiency when spray-coating objects with coating powder, in particular with enamel powder.
  • the invention enables both very thin and relatively thick layers of coating material to be sprayed onto objects without the back-spraying effect or orange peel effect occurring and without coating powder falling off the object. This gives you better coating quality and better coating efficiency.
  • these advantages result from the fact that, for powder conditioning, the weight of the powder which was deposited on an object by a spray device is measured directly or indirectly.
  • the object can be the object to be coated or a test object. A direct measurement of the moisture content of the powder is no longer necessary.
  • the weight of the coating powder adhering to an object can be determined according to the invention by measuring the weight of the object before and after coating with powder. If the weight of the uncoated object is known, it is sufficient to measure the weight of the coated object.
  • the difference in weight between uncoated and coated object is the weight of the powder deposited.
  • the measured weight of the coated object minus the weight of the uncoated object corresponds to the weight of the powder adhering to the object, and it also corresponds to a certain thickness of the powder adhering to the object.
  • the measured weight of the coating powder on the object serves as an actual value and is compared according to the invention with a target value.
  • the moisture and thereby the electrical resistance of the coating powder to be sprayed is regulated, that is to say the moisture and thereby the electrical resistance is maintained or increased or decreased.
  • the strength of the adhesion of the coating powder to the object is also measured and used as an additional actual value of the coating powder to adjust the moisture content. This prevents coating powder from falling off the object due to excessive moisture.
  • the device according to the invention shown in FIG. 1 for spray coating objects with powder, in particular enamel powder contains a cabin 2, at least one spray unit 4, a powder container 6, a weight measuring device 8, an air humidifier 10, and an electronic control device 12.
  • a conveyor chain 14 transports objects 16 hanging from it through the cabin 2.
  • a pneumatic conveyor device 18 sucks powder from the powder container 6 according to the Venturi injector principle and conveys it to the spray unit 4, which sprays it onto the objects 16 which are in the cabin 2 are located.
  • Conveying air flows from a compressed air network 20 via a conveying gas line 22 with an adjustable electromagnetic valve 24 axially through a venturi channel 26 of the conveyor device 18.
  • Control air flows from the compressed air network 20 via a control gas line 28 with an adjustable electromagnetic valve 30 into the vacuum region 32 of the venturi channel 26 for controlling the Delivery rate.
  • the powder container 6 is divided by a gas-permeable porous intermediate floor 34 into a gas chamber 36 and a powder chamber 38 located above it.
  • Air flows from the compressed air network 20 through a gas supply line 40, then via a clean gas line 42 with an adjustable electromagnetic valve 44 and / or via the air humidification device 10 to a connecting line 46, and then from this into the gas chamber 36, through the intermediate floor 34 into the powder space 38 in which it keeps the powder in a state of suspension.
  • Fresh powder and powder recovered from the booth 2 can be fed into the powder chamber 38 of the powder container 6 from above through an opening 48.
  • the heating device 50 is electrical and is connected to an electrical power source 53 via a relay 52. Instead of a heating device 50 surrounding the powder container 6, a heating device projecting into it can also be used.
  • the aforementioned regulation of the moisture content of the powder in the powder chamber 38 of the powder container 6 is carried out by the control device 12 as a function of the weight of the objects 16 or a test object 54 which have been coated with the powder from the powder container 6.
  • the actual weight value of a powder-coated object 16 or test object 54 measured by the weight measuring device 8 is a measure of the powder layer thickness on the objects 16, since the weight difference of the objects 16 before and after coating with powder is the weight of the powder adhering to the objects corresponds, and this weight corresponds with respect to the size of the coated surface of the objects 16 to a certain powder layer thickness.
  • the test object 54 can be the same as the objects 16 or have a certain size ratio to them, so that the weights of a test object 54 measured by the weight measuring device 8 can be used instead of the Measure weights of objects 16.
  • the weight measuring device 8 can measure the weights of the objects 16 or the test object 54 before and after coating with powder and report the measured actual weight values to the electronic control device 12 via electrical lines 56.
  • the actual weight value of the uncoated object 16 is stored in the control device 12 or is defined as a fixed value such that it suffices if the weight measuring device 8 only measures the weight of the coated object 16 or test object 54 and a corresponding electrical signal via the lines 56 sends to the control device 12.
  • the control device 12 compares the actual weight values with a desired weight value and, depending on the comparison result, regulates the moisture content of the powder in the powder container 6 in the manner mentioned by supplying air partially or completely saturated with water and / or non-humidified air into the container 6 or / and by heating the container 6. By heating the container 6 with the heating device 50, moisture is evaporated.
  • the humidifier 10 can have various embodiments. In the embodiment shown in the drawing, it contains a container 60 filled with water, to which the gas supply line 40 is connected at the bottom via an intermediate line 62 with an adjustable electromagnetic valve 64.
  • the gas supply line 40 contains a valve 68 and a pressure regulator 70. Air from the intermediate line 62 rises through the water in the container 60, becoming completely or partially saturated with water, and then flows via a further intermediate line 72, which is on the container 60 above is connected to the connecting line 46 of the powder container 6.
  • the further intermediate line 72 contains a manometer 74 and an adjustable electromagnetic valve 76.
  • a water supply line 77 with an adjustable electromagnetic valve 79 is connected to the water container 60 at the bottom.
  • All adjustable valves 24, 30, 44, 64, 76 and the relay 52 are connected to the control circuit 12 and are regulated by it as a function of actual weight value signals from the weight measuring device 8.
  • the air which is fed to the powder container 6 is not or only slightly moistened or completely saturated with water.
  • water instead of water, another liquid can also be used, or an additive can be added to the water.
  • the water tank 60 is provided with a float switch 61 which reports the water level to the control device 12 and regulates it via the valve 79, a heater 63 controlled by the control device, a thermostat 65 and a water drain valve 67.
  • the weight measuring device 8 can be designed in various ways and can be arranged at any desired locations.
  • the weight measuring device 8 is attached to the cabin 2 and it contains a motor 80, the shaft 82 of which protrudes through a slot 84 in the cabin roof 86 and carries a test object 54.
  • the test object 54 can be of the
  • Spray unit 4 are coated with powder for a certain period of time. Thereafter, the motor 80 pivots the test object 54 by 90 o from the car 2 up and out into the measurement position shown 54/2, in which the motor 80 puts the test object 54 on a measuring rod 88 of a balance 90th
  • the dipstick 88 can be retracted so that the test object 54 can be pivoted and, after the test object 54 has been pivoted up, can be advanced into the advanced position shown in FIG. 1, in which the motor 80 places the test object 54 on the Dipstick 88 sets so that the scale 90 can measure the weight of the coated test object 54 and can give an actual weight value signal corresponding to the weight of the coated test object 54 to the electronic control device 12 via the lines 56.
  • the control device 12 compares the actual weight value signal with a desired weight value and regulates the moisture of the powder in the powder container 6 as a function of the comparison result in the manner mentioned.
  • the desired weight value can be contained in the electronic control device 12 as a fixed value or as a variable value.
  • the moisture content of the powder in the powder container 6 is adjusted so that the actual weight value essentially corresponds to the desired weight value.
  • the actual weight value corresponds to a certain amount of coating powder on the coated object 16 or on the coated test object 54 and thus also a certain layer thickness of sprayed powder on each of the objects 16.
  • a vibration device 91 is provided. This is formed by a stop pin 91, which is normally in a position laterally outside the slot 84 of the cabin 2 and can be moved into the position shown in FIG. 1, in which it projects over the slot 84. This allows the motor 80 to strike the test object 54 against the stop pin 91 when swiveling up from the lower position 54/1 to the upper position 54/2, in order to check whether part of the powder falls off the test object 54 in the process. Then the stop pin 91 is withdrawn into the position not shown outside the slot 84, the test object 54 is moved up to the position 54/2 shown in FIG.
  • the measuring rod 88 is extended into the position shown, and the test Object 54 placed on the measuring rod 88 and thus brought into the position 54/2 shown in FIG. 1.
  • the difference in weight of the test object 54 before and after tapping powder on the stop pin 91 is a measure of the strength of the adhesion of the powder to the test object 54.
  • the electronic control device 12 holds the function of this strength of the adhesion of the powder Moisture content of the powder in the powder container 6 always below a critical adhesion value even if the amount of coating of the uncapped test object 54 determined by the weight measurement of the balance 90 would allow a greater moisture content of the powder.
  • the vibration device 91 could have a firing pin 92 instead of the stop pin 91, which strikes the test object 54 while it is lying on the measuring rod 88.
  • a third variant consists in vibrating the test object 54 by the motor 80.
  • the device according to FIG. 1 enables a method for optimizing the degree of coating by conditioning the moisture content of powdered coating material, in particular enamel powder, which is applied to objects by an electrostatic spraying method.
  • the conditioning takes place by moistening and / or heating the powder in the powder container 6 as a function of a weight comparison.
  • an object which can be an object 16 to be coated or a test object 54, is coated for a specific period of time.
  • a control variable is formed from the weight of the object coated in this way and is used to control the moisture conditioning process.
  • the adhesion of the powder to the object can also be taken into account by shaking or tapping the coated object and then determining the amount of powder that has fallen off by tapping the weight and the value obtained in this way with that originally the object applied amount of powder is compared.
  • the maximum moisture content of the powder in the powder container 6 can be limited during the moisture conditioning.
  • the invention regulates the electrical resistance of the coating powder, in particular enamel powder, as a function of the weight measurement.
  • the type of moisture conditioning of the powder is not limited to the embodiment described, but other types of moistening gas or directly moistening the powder with liquid can also be used.
  • liquid and gas can be fed separately to the powder container 6. Air is preferably used as the gas, but other gases can also be used. Instead of pure water, water with additives or other liquids can be used as the liquid.
  • the powder is removed from the coated test object 54 after each weight determination.
  • the powder may be blown off the test object by air from nozzles 96, or removed by the test object by a powder wiper, e.g. a pair of brushes.

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  • Application Of Or Painting With Fluid Materials (AREA)
  • Paints Or Removers (AREA)
EP19890112926 1988-07-22 1989-07-14 Procédé et dispositif de revêtement par pulvérisation électrostatique Withdrawn EP0351725A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3824908A DE3824908A1 (de) 1988-07-22 1988-07-22 Verfahren und vorrichtung zum elektrostatischen spruehbeschichten
DE3824908 1988-07-22

Publications (2)

Publication Number Publication Date
EP0351725A2 true EP0351725A2 (fr) 1990-01-24
EP0351725A3 EP0351725A3 (fr) 1991-01-23

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EP19890112926 Withdrawn EP0351725A3 (fr) 1988-07-22 1989-07-14 Procédé et dispositif de revêtement par pulvérisation électrostatique

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EP (1) EP0351725A3 (fr)
DE (1) DE3824908A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996005734A1 (fr) * 1994-08-19 1996-02-29 Sunkist Growers Regulateur et procede reglant selectivement la quantite de cire pulverisee sur des fruits
AU693215B2 (en) * 1994-06-27 1998-06-25 Kimberly-Clark Worldwide, Inc. Improved nonwoven barrier and method of making the same

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4121455C2 (de) * 1991-06-28 1994-10-27 Wagner Int Einrichtung zum Speisen von Pulverbeschichtungsgeräten mit einem Pulver-Luft-Gemisch
DE4140490B4 (de) * 1991-12-09 2004-05-27 EISENMANN Maschinenbau KG (Komplementär: Eisenmann-Stiftung) Spritzkabine für das Aufbringen von stark wasserhaltigen Email- oder Keramik-Glasuren auf entsprechende Werkstücke mit Rückgewinnungseinheit zur Overspray- Rückgewinnung sowie Verfahren zum Betreiben einer solchen Anlage
DE4319726A1 (de) * 1993-06-15 1994-12-22 Gema Volstatic Ag Pulverfördereinrichtung
DE4344701A1 (de) * 1993-12-27 1995-09-14 Eisenmann Kg Maschbau Verfahren und Anordnung zur Überwachung des Pulverausstoßes an Pulverspritzanlagen
DE19537089A1 (de) * 1995-10-05 1997-04-10 Abb Research Ltd Verfahren und Einrichtung zum Pulversprühen
DE19645261A1 (de) * 1996-11-02 1998-05-07 Gema Volstatic Ag Vorrichtung zum Sprühbeschichten von Objekten

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4500560A (en) * 1982-02-09 1985-02-19 De Dietrich & Cie Process for enamelling objects electrostatically by means of a gun

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU2643077A (en) * 1976-07-29 1979-01-04 United States Gypsum Co Spraying calcium sulfate hemi-hydrate
DE2636898A1 (de) * 1976-08-17 1978-02-23 Gema Ag Verfahren zur herstellung von pulverbeschichtungen mit vorgegebener feinstruktur
US4526804A (en) * 1982-08-30 1985-07-02 Ball Corporation Method for providing sheet metal stock with finely divided powder

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4500560A (en) * 1982-02-09 1985-02-19 De Dietrich & Cie Process for enamelling objects electrostatically by means of a gun

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU693215B2 (en) * 1994-06-27 1998-06-25 Kimberly-Clark Worldwide, Inc. Improved nonwoven barrier and method of making the same
WO1996005734A1 (fr) * 1994-08-19 1996-02-29 Sunkist Growers Regulateur et procede reglant selectivement la quantite de cire pulverisee sur des fruits

Also Published As

Publication number Publication date
EP0351725A3 (fr) 1991-01-23
DE3824908A1 (de) 1990-02-01

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