Patent Application
20070059965
Not Applicable.
Not Applicable.
The present disclosure relates to an electrical ground detection system, and in particular, to a non-contact electrical ground detection system that verifies the existence of an electrical path to ground by measuring the residual level of an electrical charge that is applied to a part just prior to an electrostatic paint process.
During an electrostatic painting process, a paint or coating is charged or ionized and sprayed onto a grounded part. The electrostatic attraction between the charged paint or coating and the grounded part draws the paint to the part, resulting in a more efficient painting process with less overspray which typically becomes wasted paint material. Electrostatic painting is particularly beneficial when the part has a complex shape, multiple openings, or is smaller than the effective spraying width of the equipment being used to apply the paint or coating.
Recently, there has been an emphasis on the use of polymeric or plastic materials in the manufacture of parts, particularly in automotive applications. The polymers typically used in such parts are insufficiently electrically conductive to generate the necessary difference in electrical potential to efficiently obtain a satisfactory paint thickness and coverage when the part is electrostatically painted. As such, polymeric parts require the application of an electrically conductive coating to assist in the paint process.
Briefly stated, an embodiment of the present disclosure provides a non-contact electrical ground detection system that measures residual levels of an electrical charge applied to a part just prior to an electrostatic paint process. A non-contact ground detection system for detecting the residual electrical charge on a part includes a charge generator configured to apply an electrical charge to the part. An electrostatic meter is configured to measure the level of residual electrical charge as the part moves away from the charge generator and towards the electrostatic meter. The measurement of the level of the residual electrical charge verifies a ground path from the part to electrical ground.
A method of the present invention provides for measurement of a level of residual electrical charge on a part, coupled to a programmable logic controller. During operation, the part is electrically coupled to a conveyor by a ground clip. The part is coated with a conductive coating, and an electrical charge is applied to the part. The level of the residual electrical charge is measured by measuring the level of static electricity present on the part in order to verify existence of an electrical ground path from the part.
In an alternate embodiment, an output signal is generated corresponding to a measured level of static electricity present on a part just prior to an electrostatic paint process, and is compared to a predetermined level of residual electric charge. A first signal is generated when the output signal has a value less than the predetermined level of residual electrical charge. A second signal is generated when the output signal has a value between two predetermined levels of residual electrical charge. Finally a third signal is generated when the output signal is greater than a predetermined level of residual electrical charge.
The foregoing and other objects, features, and advantages of the disclosure as well as presently preferred embodiments thereof will become more apparent from the reading of the following description in connection with the accompanying drawings.
In the accompanying drawings which form part of the specification:
Corresponding reference numerals indicate corresponding parts throughout the several figures of the drawings.
The following detailed description illustrates the disclosure by way of example and not by way of limitation. The description clearly enables one skilled in the art to make and use the disclosure, describes several embodiments, adaptations, variations, alternatives, and uses of the disclosure, including what is presently believed to be the best mode of carrying out the disclosure.
In a first embodiment, a non-contact ground detection system of the present invention is configured to identify if an electrical ground contact with a part is achieved just prior to an electrostatic painting process by verifying the existence of an electrical ground path from the part in a non-contact manner, and is optionally automated to monitor the grounding path in a hazardous environment. The non-contact ground detection system of the present invention is optionally configured to monitor multiple product lines consisting of different parts, while providing a feedback signal representative of the grounding path for any particular part.
In electrostatic painting of certain parts, problems may arise if the part to be painted can not send the charge produced by the paint applicator to an electrical ground. There is a risk of an uncontrolled electrical discharge that could result in an operator receiving an electrical shock and/or the production of a hazardous situation if flammable solvents are present (e.g. as part of the formulation being applied). Furthermore, an inability to send the electrical charge produced by the applicator to electrical ground may result in inefficient paint processes. These risks and inefficiencies can be minimized by ensuring that there is good electrical continuity for the part being painted, for instance, by making an electrical connection to the part to provide an electrical ground path for the part. As such, a non-contact ground detection system of the present disclosure verifies the existence of a path to an electrical ground.
Turning to
In an embodiment, the backside of the buck 20, extension 22, arm 16, stand 14 and conveyor 12 comprises metal material. As such, the ground detection system 10 incorporates a ground path 24 to electrical ground 26, such as an electrical ground, from the buck 20 and through the conveyor 12 via the extension 22, the arm 16 and stand 14. Ground clips 28, meanwhile, attach to the outside portion of the part 18 and attach to the top side of the buck 20 to electrically couple the part 18 to the buck 20. Accordingly, the part 18 is electrically coupled to the conveyor 12. In
As shown in
Referring to
A static monitor 40 is connected to the electrostatic meter 36. The static monitor 40 is configured to convert the output signal 38 of the electrostatic meter 36 into a suitable standard value, such as kilovolts. A controller 42 in communication with the static monitor 40 is configured to compare the output value to a range created by two different predetermined levels of residual electrical charge 44 and 45, as will be discussed. The controller 42 generates a first signal 46 when the output signal 38 has a value greater than the upper predetermined level of residual electrical charge 45. A second signal 48 is generated when the output signal 38 has a value equal to or greater than the lower predetermined level of residual electrical charge 44 and equal to or less than the upper predetermined level of residual electrical charge 45. The third signal 50 is generated when the output signal 38 has a value less than the lower predetermined level of residual electrical charge 44. In an embodiment, the controller 42 may convert the output signal 38 to the standard value.
Turning to
The part 18 is next moved towards the charge generator 34, which applies an electrical charge to the part 18 (Box 104). The factors needed to convert the measured levels of residual electrical charge to a standard measurement are then loaded into the controller 42 (Box 106).
The conveyor 12 then conveys the part 18 toward the electrostatic meter 36, which measures the level of residual electrical charge by measuring the level of static electricity present on the part 18 (Box 108). The electrostatic meter 36 generates the output signal 38 corresponding to the measured static electricity level. The electrostatic meter 36 communicates the output signal 38 to the static monitor 40 which converts the output signal 38 to a standard value and subsequently communicates the output signal to the controller 42. As previously noted the controller 42 utilizes the output signal 38 directly and converts the raw output signal 38 to an appropriate standard via the loaded factors which are determined by the physical characteristics of the part 18 such as, but not limited to, size, shape, and material composition, with the use of the static monitor 40.
The controller 42 evaluates the converted output signal 38 by comparison with predetermined levels of residual charge 44 and 45 (Box 110). If the electrical charge of the part 18 dissipates completely, or the output signal 38 has a value greater than the upper predetermined level of residual charge 45, the controller generates a first signal 46 (Box 112) to notify the operator that the ground path 24 to electrical ground 26 exists for the part 18 and that the ground clip 28 has properly connected the part 18 to the buck 20. Thus, measuring the residual electrical charge verifies the existence of ground path 24 to electrical ground 26 by the conductive coating 32 and the ground clips 28.
If the output signal 38 has a value equal to or greater than the lower predetermined level of residual charge 44 and equal to or less than the upper predetermined level of residual charge 45, the controller 38 generates the second signal 48 (Box 114) to notify the operator that the ground path 24 to electrical ground 26 is inadequate.
The third signal 50 is generated when the output signal 38 is less than the lower predetermined level of residual charge, indicating to the operator that either the conductive coating 32 has not been adequately applied to the part 18, or that the ground clip 28 is missing or not making proper contact to couple the part 18 and the buck 20. When the controller 42 generates the third signal 50, the operator preferably inspects the part 18 before transferring the part 18 to the electrostatic paint process (not shown).
In view of the above, it will be seen that the several objects of the disclosure are achieved and other advantageous results are obtained. As various changes could be made in the above constructions without departing from the scope of the disclosure, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
