Abstract This invention concerns a spray nozzle fed with the powder conveyed in an air stream constructed so that expansion of the air conveying the powder is effected in the nozzle and the spread of the spray jet issuing from the nozzle is adjusted by regulating the flow of an auxiliary jet of air which whirls about the air stream conveying the powder. In a specific embodiment the nozzle comprises a conduit having a downstream portion of larger cross-section than the cross-section of an upstream portion thereby forming an expansion chamber in the nozzle; and the jet of whirling air is admitted to the nozzle conduit downstream of the expansion chamber. A conductive core is mounted coaxially in the nozzle conduit and is adapted to be connected to a source of high voltage. The ionization means for ionizing the air conveyed powder are at the outlet of the nozzle.
Apparatus for coating an object with a layer of powder, said apparatus comprising a nozzle defining a conduit for a gaseous stream conveying the powder, the downstream portion of said nozzle conduit being substantially larger cross section than its upstream portion, a conductive core mounted coaxially in said nozzle conduit and adapted to be connected to a source of high voltage, ionization means at the outlet of said nozzle, and means for forming an adjustable spray of air coaxially whirling about the gaseous stream conveying the powder, in which said sprayforming means discharge into said downstream portion of said nozzle conduit.
Claim 2
Dependent Claim
101 words
Apparatus for coating an object with a layer of powder, said apparatus comprising a nozzle defining a conduit for a gaseous stream conveying the powder, the downstream portion of said nozzle conduit being substantially larger cross section than its upstream portion, a conductive core mounted coaxially in said nozzle conduit and adapted to be connected to a source of high voltage, ionization means at the outlet of said nozzle, and means for forming an adjustable spray of air coaxially whirling about the gaseous stream conveying the powder, in which said sprayforming means discharge into said downstream portion of said nozzle conduit.
Claim 3
Dependent Claim
57 words
Apparatus according to claim 1, wherein the nozzle has an outlet portion defining a terminal part of the nozzle conduit which outlet portion widens outwardly to a rounded edge, and the means for forming a spray of coaxially whirling air comprises a plurality of passages in said nozzle discharging into said conduit upstream of said terminal part.
Claim 4
Dependent Claim
17 words
Apparatus according to claim 2, wherein the passages are all inclined to intersect the conduit substantially tangentially.
Claim 5
Dependent Claim
12 words
Apparatus according to claim 3, wherein the passages are slightly inclined forwardly.
Claim 6
Dependent Claim
47 words
Apparatus as claimed in claim 1 in which the portion of said nozzle defining the downstream portion of said conduit is made of an electrical insulating material, and the portion of said nozzle defining the upstream portion of said conduit is made of an electrically conductive material.