Atlas Copco Aktiebolag

Rolf T Spongh

Peter N Kling

Bo A Hankvist

A method and apparatus for insulating a spray liquid source from the high tension voltage of an electrostatic spray gun (13) when using an electrically conductive spray liquid. A spray liquid supply line (12) couples the spray liquid source to the spray gun and comprises an insulating device (14) in the form of a closed vessel (16; 26; 36) containing an electrically non-conductive liquid which is not mixable with the spray liquid and which has a density different from that of the spray liquid. A sprinkler nozzle (21; 31; 41) is arranged to disintegrate the spray liquid into separated drops which are transported through the insulating liquid (17; 27; 35) in the closed vessel at least by the influence of the difference in gravity acting on the two liquids. The separated spray liquid drops form a discontinuation of the electrical lead through which the high tension voltage propagates upstream through the supply line. Thereby, the parts of the supply line upstream of the insulating device, which may include a spray liquid feed pump (11) and a spray liquid receptacle (10), are electrically insulated from the high tension voltage. The closed vessel (26; 36) of the insulating device may comprise passages (27, 28; 37, 38) and a pump (30;40) to forcibly circulate the insulating liquid within the passage in the closed vessel such that a movement is superimposed upon the gravity influenced spray liquid transportation movement to increase the spray liquid flow capacity through the insulating device.

Method and apparatus for insulating a spray liquid source from high

A device for insulating the spray liquid source from the high tension voltage of an electrostatic spray system when using an electrically conductive spray liquid. The device comprises a spray gun (13), a supply line (12) which connects the spray gun (13) to a spray liquid reservoir (10) and which includes a vessel (16) containing a barrier forming liquid (17) of low electrical conductivity and a density other than that of the spray liquid. The vessel (16), which is substantially non-conductive is connected at its inlet end (24) to ground potential and at its outlet end (19) to the same high potential as the spray gun (13). An electrode means (22; 25) is provided in the vessel (16) to expose the spray liquid passing through the vessel (16) to at least one intermediate potential for controlling the tension gradient in the barrier forming liquid by limiting and controlling the charging of the spray liquid.

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Tyreso, Sweden

Rolf T Spongh