Electrostatic coating apparatus of spray-gun type

Claim 1

ELECTROSTATIC SPRAY COATING APPARATUS COMPRISING, IN COMBINATION, A NOZZLE SUPPORT BODY HAVING SEPARATE FLUID COATING MATERIAL AND AIR PASSAGES FOR RESPECTIVE CONNECTION TO A SOURCE OF COATING MATERIAL AND A SOURCE OF AIR UNDER A PRESELECTED RELATIVELY LOW PRESSURE OF THE ORDER OF SEVEN P.S.I.; A PLURALITY OF ATOMIZING NOZZLES ON SAID BODY HAVING THEIR DISCHARGE AXES LYING IN SUBSTANTIALLY THE SAME PLANE AND SUBSTANTIALLY PARALLEL TO EACH OTHER FOR DISCHARGE OF ATOMIZED COATING MATERIAL TOWARD A COMMON WORK SURFACE; EACH OF SAID NOZZLES HAVING A RELATIVELY SMALL DIAMESTER CENTRAL ORIFICE OF THE ORDER OF 0.5 MM. CONNECTED TO SAID COATING MATERIAL PASSING AND EACH HAVING AIR DISCHARGE ORIFICE MEANS ARRANGED AROUND SAID CENTRAL ORIFICE AND CONNECTED TO SAID AIR PASSAGE, SAID AIR DISCHARGE ORIFICE MEANS DIRECTING COMPRESSED AIR INWARDLY TOWARD THE FLUID COATING MATERIAL DISCHARGED FROM SAID CENTRAL ORIFICE TO ATOMIZE THE MATERIAL SOLELY BY COMPRESSED AIR; THE VALUE OF SUCH LOW PRESSURE, AT NOZZLES, BEING OF THE ORDER OF SEVEN P.S.I. AND BEING COORDINATED WITH THE RELATIVELY SMALL DISCHARGE AREA OF EACH OF SAID RELATIVELY SMALL DIAMETER CENTRAL ORIFICES TO EFFECT THOROUGH ATOMIZATION OF THE COATING MATERIAL DISCHARGED THERETHROUGH; AND MEANS FOR ESTABLISHING AN ELECTROSTATIC POTENTIAL GRADIENT BETWEEN SAID NOZZLES AND THE WORK SURFACE TO MOVE THE THUS COMPRESSED-AIR ATOMIZED COATING MATERIAL PARTICLES TO THE WORK SURFACE TO COAT THE LATTER; THE ATOMIZED PARTICLE VELOCITY AT A SELECTED DISTANCE OF THE ORDER OF 30 CM. FROM THE TIPS OF SAID NOZZLES, BEING OF THE ORDER OF 0.5 MM./SEC.; THE SUM OF THE DISCHARGE RATES OF FIVE OF SAID NOZZLES BEING OF THE ORDER OF THE DISCHARGE RATES OF A SINGLE SPRAY NOZZLE OPERATING AT A NOZZLE PRESSURE OF THE ORDER OF 40 P.S.I. AND WITH AN ATOMIZED PARTICLES VELOCITY, AT A DISTANCE OF THE ORDER OF 30 CM. FROM ITS TIP, OF 15 MM./SEC.