Method and apparatus for use in surface treatment of conveyor supported workholders

The method of improving electrical conductivity of contact between an electrically conductive workpiece and an electrically conductive work carrier while the workpiece is supported on a work carrier prior to moving the workpiece through an electrocoating treatment zone while supported by said work carrier comprising the steps of:

• (1) suspending the workpiece on the carrier prior to entry into the treatment zone, and
• (2) impressing a high voltage on the suspended workpiece prior to entry into the zone to cause an arc discharge between the workpiece and carrier so as to carbonize or burn away any treatment coating accumulated on the hanger from previous passage through the treatment zone to thereby increase the electrical conductivity of the interface between the workpiece and the carrier prior to entry of the workpiece into the electrocoating treatment zone.

In electrocoating equipment having a conveyor rail with a trolley movable therealong for carrying parts through a bath to be electrocoated, said trolley comprising wheels, arms dependent from said wheels below said rail and a part carrier suspended from said arms, and drive means for the trolley, the improvement comprising shoe means electrically connected to one side of a capacitor discharge power supply system, said shoe means being disposed in sliding electrical contact with at least one of said arms of said trolley and extending along the path of travel thereof prior to transitting the electrocoating bath of said equipment, said shoe means being yieldably biased into such contact with said arm, said power supply system including wiper means connected to the other side of said power supply system for applying a relatively high voltage to a workpiece while the same is carried on said part carrier to cause a spark discharge via the interface of said workpiece and part carrier to improve the electrical contact therebetween.

Apparatus for use in coating electrically conductive objects comprising in combination an electrically conductive coating tank adapted to contain an aqueous bath having organic film-forming material dispersed therein and to contain a first electrode, conveyor means for transporting a line of electrically conductive objects into said tank, means for providing a flow of electrical energy between each of said objects and said first electrode when the object is in contact with said bath, means for providing a difference of electric potential between each of said objects and said conveyor prior to the entry of each such object into said tank and means for applying said potential difference across the object-conveyor interface to cause a flow of electrical energy between each such object and said conveyor while said object is in movement to said tank of sufficient magnitude and duration to break-down the electrical resistance of any of the film forming material existing in the object-conveyor interface prior to entry into the tank.

System for removing electrically insulative material accumulated on carriers suspended from an overhead conveyor used to continuously move articles through a zone for applying an electrical surface treatment to the articles by electrical conduction through the workpiece and associated carrier, said system comprising,

• means for making electrical contact with the article or the carrier during transit thereof prior to entry of said zone, and
• circuit power supply means for supplying to said contact means a predetermined voltage applicable upon engagement with the article or the carrier so as to produce an arc discharge across a metal-to-metal interface surface area of the carrier located in electrical series circuit with the workpiece during the surface treatment thereof in said zone, said predetermined voltage being of sufficient magnitude to carbonize or burn away accumulated insulative material from said interface of the carrier in the course of such movement.

The method of improving electrical conductivity of support contact between an electrically conductive workpiece and an electrically conductive work carrier prior to moving the workpiece through an electrocoating treatment zone while supported by said work carrier comprising the steps of:

• (1) moving the workpiece carrier through an arc discharge station prior to entry into the electrocoating treatment zone, and
• (2) in said arc discharge station impressing a high voltage across a surface area of the carrier on which the workpiece is suspended in said treatment zone to cause an arc discharge so as to carbonize or burn away any treatment coating accumulated on said surface area from previous passage through the treatment zone to thereby increase the electrical conductivity of the interface between the workpiece and the carrier prior to entry of the workpiece into the electrocoating treatment zone.

In surface treatment equipment having a conveyor rail with a trolley movable therealong for carrying parts through a zone for applying an electrically induced surface treatment to the parts by electrical conduction through the trolley means, said trolley comprising rail tracking wheels, arm means dependent from said wheels below said rail and a part carrier suspended via articulated joint structure from said arm means, and drive means for the trolley, the improvement comprising shoe means electrically connected to one side of a capacitor discharge power supply system, said shoe means being disposed in sliding electrical contact with at least one of said arm means of said trolley and extending along the path of travel thereof prior to transmitting the electrocoating bath of said equipment, said shoe means being yieldably biased into such contact with said arm means, said power supply system including contact means connected to the other side of said power supply system for applying a relatively high voltage to said part carrier to cause a spark discharge via the interface of said articulated joint structure to improve the electrical contact.