Electrostatic isolation apparatus and method

An electrostatic coating system including a source of electrically conductive coating material at a ground potential, an electrostatic coating dispensing device for dispensing electrically conductive coating material onto objects to be coated, means for electrostatically charging the coating material dispensed by the dispensing device to a high electrostatic potential, and an isolator for coupling electrically conductive coating material from the coating material source to the coating material dispensing device while maintaining electrical isolation therebetween, the isolator comprising:

• a housing;
• a charged coating material receptacle having an opening in an upper portion thereof and mounted in the housing;
• means for coupling coating material from the charged coating material receptacle through the housing to the coating material dispensing device, whereby electrically conductive coating material in the receptacle is electrostatically charged by the charging means through the conductive coating material in the coupling means;
• a grounded coating material nozzle chamber mounted above the charged coating material receptacle and having an aperture in a bottom portion thereof defining a coating material nozzle;
• means for coupling coating material from the source of coating material to the grounded coating material nozzle chamber;
• means for mechanically vibrating the coating material in the grounded coating material nozzle chamber to produce a pulsed jet droplet flow of coating material in a relatively confined path from the aperture in the bottom portion of the grounded nozzle chamber downwardly into the opening in the upper portion of the charged coating material receptacle;
• and
• a grounded electrostatic shield mounted between the receptacle and the nozzle chamber to substantially shield the grounded coating material nozzle chamber from electrical potentials below the shield including the electrical potential of the charged coating material in the charge coating material receptacle, the electrostatic shield having an aperture sized to permit pulsed jet droplet flow of coating material in a relatively confined path from the grounded coating material nozzle chamber into the charged coating material receptacle.

An isolator for an electrostatic coating system comprising:

• a housing;
• a receptacle, having an opening in an upper portion thereof and mounted in the housing, for electrostatic coating material which is at a first electrical potential;
• an outlet conduit communicating between the receptacle and the exterior of the housing for supplying electrostatic coating material from the receptacle for use by an electrostatic coating device;
• droplet supply means for supplying droplets of coating material at a second electrostatic potential at a location spaced above said receptacle for downward flow into said opening in the upper portion of said receptacle, and
• an electrostatic shield at an electrical potential substantially closer to said second potential than to said first potential, mounted between said droplet supply means and said receptacle opening to substantially electrostatically shield said droplet supply means from electrostatic potentials below said shield including the electrostatic potential of the coating material in said receptacle.

An isolator for an electrostatic coating system comprising:

• a housing;
• a receptacle, having an opening in an upper portion thereof and mounted in the housing, for electrostatic coating material which is at a first electrical potential;
• an outlet conduit communicating between the receptacle and the exterior of the housing for supplying electrostatic coating material from the receptacle for use by an electrostatic coating device;
• a nozzle chamber, for electrostatic coating material at a second electrical potential, mounted above the receptacle and having an aperture in a bottom portion thereof, to serve as a nozzle for dispensing electrostatic coating material;
• means for coupling electrostatic coating material to the nozzle chamber from an electrostatic coating material supply;
• means for forming coating material dispensed from the aperture in the bottom portion of the nozzle chamber into discrete droplets falling downwardly in a relatively confined path;
• and
• an electrostatic shield, at an electrical potential substantially closer to said second electrical potential than to said first electrical potential, mounted between the receptacle and the nozzle chamber to substantially electrically shield an area below the nozzle chamber in which said discrete droplets are formed from electrical potentials below the shield including the electrical potential of the electrostatic coating material in the receptacle, the electrostatic shield having an aperture sized to permit the passage of electrostatic coating material in a relatively confined path from the nozzle chamber to the receptacle.

An isolator for transferring liquid from a first quantity of liquid at a first electrostatic potential to a second quantity of liquid at a second electrostatic potential, different from said first potential, comprising:

• a receptacle for said second quantity of liquid, having an opening in an upper portion thereof;
• an outlet conduit coupled from the receptacle for the second quantity of liquid to a use location for said liquid;
• droplet supply means for supplying in a relatively confined downward flow path, droplets of coating material at a first electrostatic potential at a location spaced above said receptacle for flow into said opening in the upper portion of said receptacle, and
• an electrostatic shield at an electrical potential substantially closer to said first potential than to said second potential, mounted between said droplet supply means and said receptacle opening to substantially electrostatically shield said droplet supply means from electrostatic potential below said shield including the electrostatic potential of the coating material in said receptacle,
• said electrostatic shield having an aperture sized to permit the passage of said droplets in said relatively confined flow path from said droplet supply means to said receptacle.

An isolator for transferring liquid from a first quantity of liquid at a first electrostatic potential to a second quantity of liquid at a second electrostatic potential, different from said first potential, comprising:

• a receptacle for said second quantity of liquid, having an opening in an upper portion thereof;
• an outlet conduit coupled from the receptacle for the second quantity of liquid to a use location for said liquid;
• a nozzle chamber for the first quantity of liquid, mounted above the receptacle for the second quantity of liquid and having an aperture in a bottom portion thereof, to serve as a nozzle for dispensing liquid;
• means for coupling liquid to the nozzle chamber for the first quantity of liquid from a liquid supply;
• means for forming the liquid dispensed from the nozzle chamber for the first quantity of liquid into discrete droplets falling downwardly in a relatively confined path;
• and
• an electrostatic shield, at an electrical potential substantially closer to the electrical potential of the first quantity of liquid than to the electrical potential of the second quantity of liquid, mounted between the receptacle and the nozzle chamber at a location to substantially electrically shield areas of droplet formation beneath the nozzle chamber for the first quantity of liquid from electrical potentials below the shield, including the electrical potential of the second quantity of liquid, the electrostatic shield having an aperture sized to permit the passage of liquid droplets from the first quantity of liquid in a relatively confined path to the second quantity of liquid.

An isolator for transferring liquid from a first quantity of liquid at a first electrostatic potential to a second quantity of liquid at a second electrostatic potential, different from said first potential, comprising:

• a receptacle for said second quantity of liquid, having an opening in an upper portion thereof;
• a nozzle chamber for the first quantity of liquid, mounted above the receptacle for the second quantity of liquid and having an aperture in a bottom portion thereof, to serve as a nozzle for dispening liquid;
• means for mechanically vibrating the first quantity of liquid to produce a pulsed jet droplet flow of liquid in a relatively confined path, from the aperture in the bottom portion of the nozzle chamber for the first quality of liquid, downwardly into the opening in the upper portion of the receptacle for the second quantity of liquid;
• and
• an electrostatic shield, at an electrical potential substantially closer to the electrical potential of the first quantity of liquid than to the electrical potential of the second quantity of liquid, mounted between the receptacle and the nozzle chamber at a location to substantially electrically shield locations of droplet formation beneath the nozzle chamber for the first quantity of liquid from electrical potentials below the shield including the electrical potential of the second quantity of liquid, the electrostatic shield having an aperture sized to permit the passage of liquid droplets from the first quantity of liquid in a relatively confined path to the second quantity of liquid.

A method of transferring liquid from a source of liquid at a first electrostatic potential to a supply of liquid at a second electrostatic potential, different from said first potential, comprising the steps of:

• forming liquid supplied from the source at the first electrostatic potential into droplets at a predetermined location for establishing a downward droplet flow therefrom,
• collecting the droplets of liquid in the droplet flow in a receptacle, mounted below the predetermined location, having an opening in an upper portion thereof for receiving said droplets;
• electrostatically shielding the predetermined location from the liquid collected in the receptacle to substantially prevent electrostatic charging of the droplets formed at said predetermined location while permitting the droplets to flow downwardly for collection in the receptacle with an electrostatic shield between the predetermined location and the receptacle, and
• coupling liquid collected in said receptacle to the liquid supply at the second potential.

A method of transferring liquid from a source of liquid at a first electrostatic potential to a supply of liquid at a second electrostatic potential, different from said first potential, comprising the steps of:

• coupling liquid from the source to a chamber having an aperture in a bottom portion thereof;
• dispensing liquid in the chamber to form discrete droplets of liquid falling downwardly in a relatively confined path beneath the chamber;
• electrostatically shielding areas of droplet formation below the chamber to substantially prevent induction charging of the droplets at formation while permitting the passage of droplets falling downwardly in a relatively confined path;
• collecting the droplets in a receptacle, mounted below the chamber, having an opening in an upper portion thereof for receiving said droplets;
• and
• coupling liquid collected in said receptacle to the liquid supply.

A method of transferring liquid from a source of liquid at a first electrostatic potential to a supply of liquid at a second electrostatic potential, different from said first potential, comprising the steps of:

• forming liquid supplied from the source at the first electrostatic potential into droplets at a predetermined location for establishing a downward droplet flow therefrom,
• sensing droplet separation at a location below the predetermined location;
• controlling the droplet formation at the predetermined location dependent upon the sensed separation of the droplets being sensed below the predetermined location;
• collecting the droplets in a receptacle, mounted below the chamber, having an opening in an upper portion thereof for receiving said droplets;
• electrostatically shielding the predetermined location from the liquid collected in the receptacle to substantially prevent electrostatic charging of the droplets formed at said predetermined location while permitting the droplets to flow downwardly for collection in the receptacle with an electrostatic shield between the predetermined location and the receptacle, and
• coupling liquid collected in the receptacle to the liquid supply at the second potential.