US3635401A — Electrostatic spraying methods and apparatus

Claim 1

Independent Claim 168 words

An electrostatic spray gun of the type in which a spray of coating material particles is produced by interacting streams of coating material and air under pressure comprising: an electrically conductive spray head for issuing intersecting streams of coating material and air to produce a spray of coating material particles, means, including an emitter electrode disposed in the path of the particle spray in downstream spaced relation to the spray head, for establishing a rearwardly directed corona discharge terminating at the spray head to charge the coating material particles electrostatically, and means for preventing sparking between the emitter electrode and the spray head, the spark-preventing means including switch means responsive to the flow of air to the spray head for energizing the emitter electrode, whereby air flows from the spray head and over the emitter electrode prior to the initiation of the corona discharge, said flow of air being effective to prevent sparking between the emitter electrode and the spray head in the absence of the particle spray.

Claim 2

Dependent Claim 168 words

An electrostatic spray gun of the type in which a spray of coating material particles is produced by interacting streams of coating material and air under pressure comprising: an electrically conductive spray head for issuing intersecting streams of coating material and air to produce a spray of coating material particles, means, including an emitter electrode disposed in the path of the particle spray in downstream spaced relation to the spray head, for establishing a rearwardly directed corona discharge terminating at the spray head to charge the coating material particles electrostatically, and means for preventing sparking between the emitter electrode and the spray head, the spark-preventing means including switch means responsive to the flow of air to the spray head for energizing the emitter electrode, whereby air flows from the spray head and over the emitter electrode prior to the initiation of the corona discharge, said flow of air being effective to prevent sparking between the emitter electrode and the spray head in the absence of the particle spray.

Claim 3

Dependent Claim 43 words

A spray gun according to claim 1 further comprising: means defining at least one passage within the gun for conducting air to the spray head, the switch means being located within the gun in communication with the air passage to the spray head.

Claim 4

Dependent Claim 86 words

A spray gun according to claim 2 further comprising: individually operable valves for controlling the flow of coating material and air from the spray head, and operator means for sequentially opening the air and coating material valves, the operator means being arranged to open the air valve prior to opening the coating material valve so that air is delivered to and discharged from the spray head, and the airflow-responsive switch is actuated to energize the emitter electrode, before coating material is issued from the spray head.

Claim 5

Dependent Claim 85 words

A spray gun according to claim 3 in which the spray head includes a centrally disposed coating material orifice and an annular air discharge orifice in surrounding relation to, and substantially coaxial with, the coating material orifice, and in which the emitter electrode comprises a needlelike member having a pointed tip, the tip being disposed substantially on the longitudinal axis of the coating material and air discharge orifices, whereby air exiting from the annular air discharge orifice surrounds the electrode tip in a spark-preventing airflow.

Claim 6

Dependent Claim 84 words

A spray gun according to claim 4 in which the emitter electrode is supported by the spray head and extends transversely into the spray and thereafter curves rearwardly to terminate at a point in front of the coating material orifice, and in which the annular air discharge orifice is inclined with respect to the axis of the coating material orifice to an extent that the air exiting from the air discharge orifice converges toward and impinges upon the rearwardly extending portion of the electrode.

Claim 7

Dependent Claim 64 words

A spray gun according to claim 1 further comprising means for issuing a moving air shroud in surrounding relation to the particle spray simultaneously to control turbuleNce within the particle spray and to control radial and rearward dispersal of the charged spray particles downstream of the spray head, thereby causing the particles to move principally in the downstream direction and acquire increased charge potentials.

Claim 8

Dependent Claim 39 words

A spray gun according to claim 6 in which the shroud air issuing means includes means for adjusting the velocity of the shroud air to allow regulation of spray turbulence and the extent of dispersion of the spray particles.

Claim 9

Dependent Claim 48 words

A spray gun according to claim 7 further comprising means defining at least one passage within the gun for conducting the shroud forming air, and in which the velocity adjusting means includes a valve located in the air passage for regulating the flow of air through the passage.

Claim 10

Dependent Claim 83 words

A spray gun according to claim 8 in which the spray head includes a centrally disposed orifice for discharging the particle spray, and in which the shroud air issuing means includes means at the forward end of the gun defining a plurality of separate air passage opening in the downstream direction and disposed in a generally circular pattern around the centrally disposed orifice, the shroud air being issued from the plurality of separate air passages in a corresponding number of separate air jets.

Claim 11

Dependent Claim 42 words

A spray gun according to claim 9 in which the separate air passages are inclined with respect to the longitudinal axis of the particle spray so as to discharge the shroud air along a generally cone-shaped path diverging in the downstream direction.

Claim 12

Dependent Claim 56 words

A spray gun according to claim 9 further including an annular air reservoir located upstream of the separate air passages and having a volume substantially greater than the combined volumes of the separate air passages, so that a continuous flow of air of substantially equal velocity is maintained through each of the separate air shroud passages.

Claim 13

Dependent Claim 199 words

In an electrostatic spray system, the combination comprising: a spray gun having a spray head for interacting streams of coating material and air under pressure to produce a spray of coating material particles, means for supplying air under pressure to the spray gun, means for supplying coating material under pressure to the spray gun, means, including an emitter electrode disposed in the path of the particle spray in downstream spaced relation to the spray head, for establishing a rearwardly directed corona discharge terminating at the spray head to charge the coating material particles electrostatically, a high-voltage power supply for energizing the emitter electrode, and means for preventing sparking between the emitter electrode and the spray head, the spark preventing means including switch means disposed within the spray gun and responsive to the flow of air to the spray head for electrically connecting the high-voltage power supply to the emitter electrode to establish the corona discharge, whereby air flows from the spray head and over the emitter electrode prior to the initiation of the corona discharge, said flow of air being effective to prevent sparking between the emitter electrode and the spray head in the absence of the particle spray.

Claim 14

Dependent Claim 199 words

In an electrostatic spray system, the combination comprising: a spray gun having a spray head for interacting streams of coating material and air under pressure to produce a spray of coating material particles, means for supplying air under pressure to the spray gun, means for supplying coating material under pressure to the spray gun, means, including an emitter electrode disposed in the path of the particle spray in downstream spaced relation to the spray head, for establishing a rearwardly directed corona discharge terminating at the spray head to charge the coating material particles electrostatically, a high-voltage power supply for energizing the emitter electrode, and means for preventing sparking between the emitter electrode and the spray head, the spark preventing means including switch means disposed within the spray gun and responsive to the flow of air to the spray head for electrically connecting the high-voltage power supply to the emitter electrode to establish the corona discharge, whereby air flows from the spray head and over the emitter electrode prior to the initiation of the corona discharge, said flow of air being effective to prevent sparking between the emitter electrode and the spray head in the absence of the particle spray.

Claim 15

Dependent Claim 60 words

An electrostatic spray system according to claim 12, further comprising: means defining at least one passage within the spray gun for conducting air to the spray head, the switch means being located in communication with the air passage and being responsive to the flow of air through the passage to connect the high-voltage power supply electrically to the emitter electrode.

Claim 16

Dependent Claim 70 words

An electrostatic spray system according to claim 13, further comprising means for confining the charged spray particles downstream of the spray gun, thereby to control dispersal of the particle spray and to cause the particles to move principally in the downstream direction and acquire increased charge potentials, the spray-controlling means including means associated with the spray head for issuing a moving air shroud in surrounding relation to thE particle spray.

Claim 17

Dependent Claim 39 words

An electrostatic spray system according to claim 14, in which the spray-controlling means includes means for adjusting the relative velocity between the shroud air and the spray particles to regulate the extent of radial dispersal of the spray particles.

Claim 18

Dependent Claim 81 words

An electrostatic spray system according to claim 15, in which the spray head includes a centrally disposed orifice for discharging the coating material, and in which the spray confining means includes means associated with the spray head defining a plurality of separate air passages opening in the downstream direction and disposed in a generally circular pattern around the central coating material orifice, the air jets issuing from the plurality of separate air passages constituting the air shroud surrounding the particle spray.

Claim 19

Dependent Claim 97 words

An electrostatic spray system according to claim 16, further comprising: individually operable valves in the spray gun for controlling the flow of coating material and air from the spray head, and operator means associated with the spray gun for sequentially opening the air and coating material valves, the operator means being arranged to open the air valve prior to opening the coating material valve so that the air is delivered to and discharged from the spray head, and the airflow-responsive switch is actuated to energize the emitter electrode, before coating material is issued from the spray head.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1975-01-17	1975-07-19	1976-01-18	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1979-01-17	1979-07-19	1980-01-18	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1983-01-17	1983-07-19	1984-01-18	$7700.00	Window Closed / Lapsed

Electrostatic spraying methods and apparatus

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