Electrostatic high voltage isolation system with internal charge generation

• US 4,544,570 A
• Filed: 01/26/1984
• Issued: 10/01/1985
• Est. Priority Date: 01/26/1984
• Status: Expired due to Fees

• Current Assignee: Nordson Corporation
• Original Assignee: Nordson Corporation
• Inventors: Plunkett, Robert T., Inculet, Ion I.
• Primary Examiner(s): Bueker, Richard
• Application Number:
  US06/574,286
• Time in Patent Office: 614 Days
• Field of Search: 427/27, 118/621, 118/627, 239/3, 239/690, 239/691, 239/704-708
• US Class Current: 427/475
• CPC Class Codes: B05B 5/043 using induction-charging
• CPC Class Codes: B05B 5/1616 and the arrangement comprising means for insulating a grounded material source from high voltage applied to the material
• CPC Class Codes: B05B 5/165 by dividing the material into discrete quantities, e.g. droplets
• CPC Class Codes: B05D 1/04 involving the use of an electrostatic field B05D1/025 and B05D1/14 take precedence

Abstract

An electrostatic high voltage isolation system with internal charge generation in which conductive coating material to be sprayed is electrostatically charged by charging discrete droplets of coating material transferred from a coating material source to a supply of coating material for a spray gun. The source of coating material includes an electrically grounded reservoir of coating material having a nozzle aperture in a bottom portion thereof, and the coating material in the reservoir is mechanically vibrated to produce a pulsed jet droplet flow of coating material from the nozzle into a supply container for the spray gun. A high voltage electrode at the location of droplet formation induces an electrostatic charge on the droplets in order to electrostatically charge the coating material transferred to the gun supply container for use by the gun for electrostatic coating.

Claims

1. An electrostatic coating system comprising:

a source of coating material;

means for applying electrostatically charged coating material to objects to be coated;

a supply of coating material, electrically isolated from the source of coating material, coupled to the means for applying electrostatically charged coating material;

means for transferring coating material from the source of coating material to the supply of coating material by forming transferred coating material into discrete droplets; and

means for inducing an electrostatic charge on the discrete droplets of transferred coating material to establish an electrostatic charge on coating material in the supply of coating material which is coupled by means of a fluid conduit to the means for applying electrostatically charged coating material.

2. The electrostatic spray coating system of claim 1 in which the means for transferring coating material comprises means for producing a pulsed jet droplet flow of coating material into the supply of coating material.

3. The electrostatic coating system of claim 2 in which the source of coating material comprises a coating material reservoir positioned above the supply of coating material and having a nozzle aperture in a bottom portion thereof, and the pulsed jet droplet flow emanates from the nozzle aperture.

4. The electrostatic coating system of claim 1 in which the means for inducing an electrostatic charge comprises a high voltage generator coupled to an electrode positioned at a droplet formation location of the transferred coating material.

5. The electrostatic coating system of claim 4 in which the high voltage supply imposes a voltage on the electrode which is lower than the electrostatic charge on the coating material in the supply of coating material which is coupled to the means for applying electrostatically charged coating material.

6. A method of applying electrostatically charged coating material to objects to be coated comprising the steps of:

transferring coating material from a source of coating material to a supply of coating material, which is electrically isolated from the source of coating material, by forming transferred coating material into discrete droplets;

inducing an electrostatic charge on the discrete droplets of transferred coating material to establish an electrostatic charge on coating material in the supply of coating material; and

coupling the electrostatically charged coating material in the supply of coating material by means of a fluid conduit to a coating material dispenser for applying electrostatically charged coating material to objects to be coated.

7. An electrostatic spray coating system comprising:

a source of coating material including a grounded coating material reservoir having a nozzle aperture in a bottom portion thereof;

a spray gun for spraying electrostatically charged coating material onto objects to be coated;

a supply container having an opening in an upper portion thereof for coating material, which is electrically isolated from the coating material reservoir and from ground;

means for coupling coating material by means of a fluid conduit from the container to the spray gun;

means for transferring coating material from the reservoir to the container by producing a pulsed jet droplet flow of coating material from the nozzle aperture into the opening of the container; and

means for inducing an electrostatic charge on droplets in the pulsed jet droplet flow of transferred coating material to establish an electrostatic charge on coating material in the container which is coupled to the spray gun.