Coating processes – Spraying
Reexamination Certificate
1998-05-22
2001-03-20
Beck, Shrive (Department: 1762)
Coating processes
Spraying
C118S326000
Reexamination Certificate
active
06203857
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an improved fluid application system, useful in applying application fluids to work pieces for coating or lubrication in preparation for subsequent manufacturing operations on such work pieces.
More specifically, this invention describes a new and improved closed loop controllable fluid application system, which involves one or more controllable atomizing spray devices located inside a substantially enclosed housing for spraying a coating of application fluid, such as drawing oil, onto work pieces such as metal sheets or blanks passing into and out of the housing, with the application fluid delivered through circulation lines connected to a fluid source. Through the use of controllable spray devices and a mist collector, application fluid losses to the environment surrounding the system are minimized; desired coverage of work pieces with fluid may be accomplished with substantially reduced atomizing pressure and corresponding fluid pressure at the spray device; and optional use of a heater enables application fluids with temperature variable viscosity to be controllably sprayed regardless of their room temperature characteristics.
In many manufacturing processes, work pieces such as continuous sheet metal strips or metal blanks are coated with an application fluid appropriate to the manufacturing operation to follow. This may be a fluid chosen to principally coat the work piece, and/or to lubricate the work piece in preparation for a stamping operation, or other metal forming, treatment or assembly.
As an example, in the metal stamping industry, drawing oil compounds are applied to blanks or roll stock in open atmosphere of the manufacturing facility using rollers, brushes, drip bar systems, or uncontrolled spray devices. This may result in uncontrolled dispensing of the fluid.
At times this application takes place at a location independent of other manufacturing machinery and equipment. At other times it occurs at remote locations on a ram of a stamping press, with the spray coating the die and the work piece in an uncontrolled fashion.
Where spray devices are the technique of choice, this application typically takes place with pressurized fluid forced through an orifice, or with atomizing gas or liquid introduced into a stream of application fluid under relatively high pressure. In each case, this causes atomization of the application fluid and uncontrolled spraying of that application fluid toward the work piece. This may result in heavy runoff of application fluid from the die, the work piece and/or the press, and emission of fluid to the ambient atmosphere in a mist, to which operators and other employees are exposed. This fluid, in runoff and mist form, must be contained, removed and disposed of due to hazardous chemical laws and potential health hazards of its exposure to humans. Where application fluid is incompatible with any manufacturing step after metal stamping operations, that fluid must be washed off and properly disposed of, adding another stage at which it is advantageous to have the minimum required amount of fluid present on the work piece.
Conventional application systems may also incur a substantial loss of fluid volume during coating operations, from emissions of fluid into the air in a mist, or excessive volume of the application fluid directed toward the work piece. This results in undesirable down time, cost and extra manufacturing operations to replenish such fluid.
Because of uncontrolled application of fluid, conventional systems also frequently expose the dies and other machinery and work pieces to damage from inappropriate lubrication. This may, for example, arise due to inadequate lubrication, or excessive lubrication and consequent damaging die movement (“hydraulic cylindering”). Wearing and structural damage to the dies may occur in such cases. Inadequate lubrication causes significant increases in scrappage rate for work pieces. Each circumstance may increase down time, add to manufacturing steps and the cost of cleaning the environment and replacing lost fluid.
A cabinet structure may be used to partially contain the runoff of excess application fluid, and emitted application fluid given off in a mist from a coating operation. However, the necessary entry and exit slots for work pieces to traverse the cabinet, along with high pressure atomizing spray, typically permit application fluid to escape from such cabinets. This virtually negates the containment effect of enclosing the operation.
To the extent that other devices such as drip bars, brushes or similar techniques take the place of high pressure spraying, problems also arise in clogging of the applicator device, wearing of the brushes, and excessive down time for maintenance (such as brush replacement) and dealing with work pieces which receive inadequate or excessive application fluid. Such techniques also suffer from the problems of uncontrollable application, as well as lack of uniformity in dispensing fluid across the work piece. Problems with such techniques are in large part a reason for the use of high pressures in spraying operations. Use of high pressure is an attempt to ensure that sufficient application fluid is applied to avoid any damage to die or work piece—as any such problems either result in scrapping of the work piece, or costly and time consuming repairs to the die.
One attempt to improve fluid application systems uses an electrostatically charged drip bar. By introducing an electric charge to a conductive drip bar in such a system, the application fluid flowing through the system also becomes electrostatically charged. As this occurs, the fluid is caused to atomize upon exiting the drip bar at a series of spaced openings in the drip bar. This approach requires additional components and costs (such as adding a source of electric charge) and limits the system to operating with conductive fluids. In addition, such systems may result in electrically charging and attracting of air-borne contaminants. This may contaminate the application fluid sprayed onto a work piece, and lead to clogging of drip bar components, thus increasing rather the decreasing down-time for maintenance. These problems in turn lead to addition of potentially complex filtration sub-systems, difficult cabinet design, and more difficult, complicated maintenance steps. Such systems may lack the capability of operating within a compact, portable enclosure, and lack the simplicity and reliability of design and operation sought in fluid application systems.
Conventional systems further do not permit controllable application of the volume, depth and directional reach of application fluid spray that is applied to the work piece in the context of a reliable, portable closed loop system that can operate at relatively low atomizing pressures regardless of the application fluid viscosity encountered.
Thus it can be seen that a need exists for a controllable fluid application system, operating in a closed loop such that application fluid escaping to the plant environment is minimized, a desired coating of application fluid may be applied to the work piece, but the system is portable, of simple and cost effective construction, and operates efficiently without substantial down time, and with relatively low atomizing pressure and fluid pressure at the spray device, regardless of the viscosity of the application fluid in use.
It is, therefore, an object of the present invention to provide a controllable closed loop system for delivering application fluid to a work piece.
It is another object of the present invention to provide an improved fluid application system which permits controllable atomized spray of application fluid onto a work piece at substantially reduced atomizing pressures and fluid pressures, regardless of fluid viscosity.
It is a further object of the present invention to provide an improved fluid application system which controls temperature dependent viscosity of application fluid to maximize atomizing spray efficiency using relatively low atomizi
Beck Shrive
Calcagni Jennifer
Young & Basile P.C.
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