Devices for covering objects with electrostatic dust

• US 4,235,381 A
• Filed: 02/02/1979
• Issued: 11/25/1980
• Est. Priority Date: 04/07/1978
• Status: Expired due to Term

• Current Assignee: Juan R. Vila
• Original Assignee: Juan R. Vila
• Inventors: Vila, Juan R.
• Primary Examiner(s): Kashnikow, Andres
• Application Number:
  US06/009,060
• Time in Patent Office: 662 Days
• Field of Search: 239/690, 239/696-698, 239/704-708
• US Class Current: 239/696
• CPC Class Codes: B05B 5/032 for spraying particulate materials

Abstract

This invention is in an improvement in electrostatic spraying apparatus for coating objects with electrostatic powder, or dust. The apparatus includes a housing or body member having a discharge nozzle at one end and internal flow passages for conducting compressed gas supplied from an external source to the discharge nozzle and a deflector element coaxially disposed adjacent the discharge end of the nozzle. A source of powder or dust is provided and is mixed with the compressed gas to produce a powder gas mixture which is fed to the flow passage. Electrodes connected to a high voltage source are provided within the flow passage and at the discharge end of the nozzle to ionize the powder gas mixture. The invention provides a hollow oval shaped charging chamber within the nozzle communicating with the flow passage so that the powder gas mixture passes therethrough and is ionized therein. Auxiliary compressed gas is also passed to the nozzle and is ionized so that upon being discharged at the tip of the apparatus, it assists in augmenting the final charge of the powder which substantially improves the electrostatic application to the object being coated.

Claims

1. In an electrostatic spray coating apparatus for coating objects with electrostatic powder including a housing member, a discharge nozzle, an internal flow passage in said housing member for conducting compressed gas to the nozzle, a deflector coaxially disposed adjacent the discharge end of the nozzle, a source of compressed gas and a source of powder and means to produce a powder-gas mixture and feed it to the flow passage, means for ionizing the powder-gas mixture and a source of high voltage connected to the ionizing means, the improvement comprising a hollow charging chamber within the nozzle connected to the flow passage and through which the powder-gas mixture flows, said charging chamber having an oval shape with the long axis aligned with said flow passage, an electrode having an inner end extending into said chamber and the outer end disposed in the deflector at the discharge end of said nozzle, and means to provide an auxiliary flow of ionized gas to the discharge nozzle.

2. The apparatus as claimed in claim 1, wherein said deflector has a rod-like extension of conducting material projecting downstream within the flow passage into said charging chamber, said end projecting into said chamber being pointed and being said inner end of said electrode, said outer end of said electrode being disposed coaxially within and at the outer end of said deflector, said ionizing means comprising said chamber and electrode, said high voltage source being connected to said nozzle and said electrode.

3. The apparatus as claimed in claim 1, wherein said nozzle is comprised of an external tip member, a diffuser within said tip and a bushing of insulating material threadedly connected coaxially to the interior of said diffuser, said chamber being within said bushing, said ionizing means comprising said electrode and a second electrode within said chamber.

4. The apparatus as claimed in claim 1, wherein said nozzle is comprised of an external hollow coaxially shaped tip member, a diffuser within said tip having an outer conical surface and a bushing threadedly connected to the interior of said diffuser coaxially therewith, said chamber being within said bushing, said means to provide an auxiliary ionized gas comprising a plurality of spiral slots in the outer conical surface of the diffuser, annular flow channels surrounding said bushing and communicating with said slots, gas supply lines for supplying auxiliary compressed gas to said annular flow channels, said source of high voltage being connected to said bushing and said electrode, said auxiliary gas being ionized by passing over and in contact with said bushing.

5. The apparatus as claimed in claim 4, wherein said diffuser is adjustable to vary the flow of auxiliary gas.

6. The apparatus as claimed in claim 5, wherein said conical tip member is provided on its outer end with a radially extending flange to provide an annular chamber between said flange and the outer discharge end of said diffuser and to direct the flow of auxiliary gas in a coaxial spiral, said tip member being axially adjustable with respect to the central axis.

7. The apparatus as claimed in claim 6, wherein said tip member has a conical interior surface having a smaller apex angle than that of the conical surface on said diffuser.

8. In an electrostatic spray coating apparatus including a housing member, a discharge nozzle, an internal flow passage in said housing member for conducting compressed gas to said discharge nozzle, a deflector coaxially disposed adjacent the discharge end of the nozzle, a source of compressed gas and a source of powder material, means to produce a mixture of said gas and powder material and feed it to the flow passage, means to ionize the powder-gas mixture and a source of high voltage connected to the ionizing means, the improvement wherein said nozzle is comprised of an external hollow tip member and a diffuser made of insulating material having an outer peripheral surface engaging the inner surface of said tip member, an oval chamber within said diffuser, the long axis of said oval being coaxial with the central axis of the apparatus and through which the powder-gas mixture flows, said means for ionizing said mixture comprising at least one first electrode extending through said diffuser into said oval chamber and at least one second electrode extending through said diffuser and exposed to the powder-gas mixture at the discharge end of the nozzle, means to provide auxiliary ionized gas comprising, passageways through said diffuser, an annular outlet chamber between the outer surface of the diffuser and the inner surface of said tip member adjacent to the discharge end and communicating with said passageways, an annular orifice between the outer surface of the diffuser and the inner surface of the tip at the discharge end communicating with said outlet chamber, an annular ionization chamber between said tip member and said diffuser at the other downstream end thereof communicating with the downstream ends of said passageways remote from said discharge end, means to supply compressed auxiliary gas to said annular ionization chamber, said second electrodes passing through said annular ionization chamber to ionize the auxiliary gas passing therethrough, and said tip member being adjustable to vary the size of said annular orifice and outlet chamber.