US 3,937,180 AGranted

Apparatus for electrostatically charging workpieces for spray coating application

AssigneeThe Gyromat Corporation

InventorRichard F. Wiggins

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Abstract

Disclosed herein are a method and apparatus for progressively charging an electrically isolated conductive workpiece from ground potential to high potential while the workpiece is supported by a moving grounded conveyor. A portion of the conveyor is selectively included in circuit with a high voltage source and a voltage divider to charge the isolated conveyed workpieces to high electrostatic potential with respect to ground. The highly charged workpieces are conveyed past a grounded spray device dispersing atomized particles (i.e., liquid or powder) which are at electrical ground potential. In accordance with well known electrostatic coating principles, the particles will be attracted to the high potential workpiece parts and will adhere thereto. As a more specific aspect of the invention, the high potential is applied to the workpieces through a unique "brush and commutator" apparatus which sequentially and gradually increases the charging of the workpiece from ground potential to a predetermined desired level for electrostatic spray deposition in a spray zone and thereafter sequentially gradually decreases the charge on the workpiece to ground potential after exiting the spray zone.

Claims4

Dependent claims

Apparatus for transporting workpieces along a predetermined path through a coating zone of uncharged coating particles, including a conveyor structure having

a. a plurality of conductive work supporting elements adapted to support a workpiece and to convey said workpiece along said path;
b. isolating means adapted to provide a nonconductive barrier between selected ones of said supporting means and the remainder of said conveyor structure;
c. charging means adapted to apply a high electrical potential to said selected ones of said supporting means in said coating zone;
d. said charging means including contact means engageable with said support means and forming a progressive charging zone, a high voltage zone, and a discharging zone,
e. said charging zone including a plurality of successively arranged charging contact elements engageable in sequence with work supporting elements being advanced by said conveyor structure,
f. a high voltage charging source,
g. a multiple step voltage divider system connected to said high voltage source and to said charging contact elements, whereby successive such elements are charged at progressively higher voltages for progressive charging of a workpiece being conveyed along said charging zone,
h. said high voltage zone comprising contact means connected to said high voltage charging source and adapted for charging a workpiece to a predetermined high voltage,
i. said high voltage zone being located downstream of the progressive charging zone in the direction of movement of a workpiece carried by the conveyor structure,
j. said discharge zone comprising discharge contact means for grounding workpieces upon exit thereof from said high voltage zone.

7 more elements

Dependencies are inferred from the claim text.