Patent Application
20080083846
The invention may best be understood by referring to the following detailed description and accompanying drawings which illustrate the invention. In the drawings:
Coating material to be atomized is supplied to the inner surface 30 of bell cup 28 through a feed tube 32 from a grounded coating material supply 34, all in accordance with known principles. External charging device 22 includes electrodes 36 which are coupled through conductors provided within device 22 and a high voltage cable 38 to a high magnitude potential source 40, for example, a source of the type illustrated and described in U.S. Pat. Nos. 6,562,137; 6,423,142; 6,144,570; 5,978,244; 5,159,544; 4,745,520; 4,485,427; 4,481,557; 4,324,812; 4,187,527; 4,075,677; 3,894,272; 3,875,892; and, 3,851,618. The turbine motor 24 and electrically non-insulative components electrically coupled thereto are grounded through a ground connection 42 to the turbine motor 24 housing 43.
The feed tube 32 typically is constructed from electrically non-insulative material, for example, stainless steel. Feed tube 32 is mounted at its rearward end 44 in a recess 45 provided for this purpose in an atomizer mounting manifold 46 typically constructed from electrically relatively non-conductive resin such as, for example, Delrin® acetal resin. See, for example, U.S. Pat. Nos. 5,622,563; 5,633,306; 5,662,278; and, 6,896,211. To promote grounding of feed tube 32 and thus charging of the coating material supplied through feed tube 32 to bell cup 28, it is desirable to couple feed tube 32 electrically to housing 43.
Referring now particularly to
Brushes 52-1 are placed in the brush holder 50 so that, and are of sufficient length that, the free ends of the brushes 52-1 very lightly contact the outside surface 54 of electrically non-insulative feed tube 32 to provide relatively constant, relatively low impedances on the order of a few tenths of ohms to a few tens of ohms between surface 54 and the mountings of the brushes 52-1 in the brush holder 50.
Brushes 52-2 are placed in the brush holder 50 so that, and are of sufficient length that, the free ends of the brushes 52-2 lightly contact the outside surface 56 of electrically non-insulative shaft 26 to provide relatively constant, relatively low impedances on the order of a few tenths of ohms to a few tens of ohms between surface 56 and the mountings of the brushes 52-2 in the brush holder 50. The lengths of the brushes 52 and positioning of the brushes 52 adjacent surfaces 54, 56 are not such as to significantly load the motor 24, so that motor 24 control is not significantly compromised by the contact. The brushes 52 are all electrically coupled to each other and to turbine motor 24 housing 43 and/or directly to ground connection 42 through (an) electrical conductor(s), such as (a) length(s) of metal wire electrically connected to all of brushes 52, imbedded in brush holder 50 and providing an output terminal 58 facilitating electrical connection with turbine motor 24 housing 43 and/or directly to ground connection 42.
In another embodiment illustrated in
Brushes 152-1 are placed in the brush holder 150 so that, and are of sufficient length that, the free ends of the brushes 152-1 approach very closely (to within about 0.001 inch or so, about 0.025 mm or so), but do not contact, the outside surface 154 of an electrically non-insulative feed tube 132 to provide relatively constant, relatively low impedances on the order of a few tenths of ohms to a few tens of ohms between surface 154 and the mountings of the brushes 152-1 in the brush holder 150.
Brushes 152-2 are placed in the brush holder 150 so that, and are of sufficient length that, the free ends of the brushes 152-2 approach very closely (to within about 0.001 inch or so, about 0.025 mm or so), but do not contact, the outside surface 156 of an electrically non-insulative turbine 124 shaft 126 to provide relatively constant, relatively low impedances on the order of a few tenths of ohms to a few tens of ohms between surface 156 and the mountings of the brushes 152-2 in the brush holder 150. The mounting of the brushes 152 and positioning of the brushes 152 adjacent surfaces 154, 156 do not load the motor 124 in this embodiment since the brushes 152 do not physically contact surfaces 154, 156, so that motor 124 control is not compromised. The brushes 152 are all electrically coupled to each other and to turbine motor 124 housing 143 and/or directly to a ground connection, such as connection 42 in the embodiment illustrated in
Brushes 52, 152 may be of any suitable types and constructed from any suitable materials. By way of example only, and not by way of limitation, brushes 52, 152 can be of any suitable types described in United States Patent Application 20060007609 or United States Patent Application 20040233592. Also, while specific numbers of brushes 52, 152 are illustrated, it should be understood that a device constructed according to the present invention may include any suitable number of brushes, or a single continuous brush surrounding one or the other or both of feed tube 32, 132 and shaft 26, 126.
The disclosures of all of the references listed herein are hereby incorporated herein by reference. These listings are not intended to be representations that a complete search of all relevant art has been made, or that no more pertinent art than that listed exists, or that the listed art is material to patentability. Nor should any such representation be inferred.
