Gas separation: processes – With control responsive to sensed condition – Temperature sensed
Reexamination Certificate
2001-08-30
2003-05-20
Hopkins, Robert A. (Department: 1724)
Gas separation: processes
With control responsive to sensed condition
Temperature sensed
C095S198000, C095S221000, C095S227000, C095S272000, C096S358000, C096S417000, C096S420000, C055SDIG007
Reexamination Certificate
active
06565625
ABSTRACT:
STATEMENT REGARDING FEDERALLY SOPNSORED RESEARCH OR DEVELOPMENT
Not Application
BACKGROUND OF THE INVENTION
In the paper-making industry, in textile production, and in numerous other industrial enterprises, it is often desirable to provide a chemical treatment to a roll of fabric or other work product as it is being conveyed by a standard conveyor or other means. In order to chemically treat the fabric in question, often a processing plant will include a spray or aerosol-driven liquid chemical product for application directly on the fabric or work product as it moves along a conveyor system. Typically, the aerosol spray devices
ozzles are permanently mounted above or about the conveyor and the liquid is applied to the fabric as it moves along the conveyor system. The amount of chemical applied generally varies as a function of the velocity of the conveyor, the flow rate of the spray release and the transfer efficiency of the spray system.
As chemicals are applied to the conveyed work product, a frequent and persistent problem is the overspray of chemical waste produced by the system. In order to guarantee a thorough application of the chemical upon the work product, the spray nozzles typically output more chemical than is needed for the surface since the transfer efficiency is usually much less than one hundred percent. Accordingly, the excess chemical collects on the conveying equipment or factory floor below, or is exhausted with the air effluent creating numerous problems including disposal costs, housekeeping, and the cost of the wasted chemicals themselves. Depending on the properties of the chemical, there may also be attendant environmental hazards including degradation of the equipment and personnel safety concerns. For these reasons, it is important to minimize the amount of overspray and minimize the escape of overspray.
In many chemical applications, the overspray from the applied chemical can take the form of a vapor mist with finer dispersed droplets than typical sprayed liquids. In these situations, not only does overspray result in wasted chemical product below and about the processing equipment, but airborne overspray can also travel to surrounding equipment and facilities. In these situations, it is even more important to have an adequate means for collecting and disposing of chemical overspray.
Industrial plants have been wrestling with the problems described above for decades. Accordingly, the prior art is replete with many varieties of overspray collection systems and air/liquid separators for accomplishing this purpose, as well as a wide assortment of collection basins and other forms of dealing with chemical overspray. Generally speaking, the prior art systems are marginal depending upon the task called upon to perform, and some of the prior art devices create challenges or hazards of their own.
DESCRIPTION OF THE PRIOR ART
The prior art features a wide assortment of air filters and air/chemical separation devices that have been developed over the years. Many of the prior art devices are essentially fibrous filters which are used to trap solid particulates and/or liquid solvent for separation from a gas stream. For a finely atomized mist, such devices are not adequate.
U.S. Pat. No. 1,772,037 to Bradshaw features a plurality of centrifugal separators. The Bradshaw device applies a centrifugal force on a flowing moisture stream to separate liquid from a current of gas against a plurality of baffles. The baffles increase in curvature as the inner or outer ends are approached to enhance the centrifugal effect. Likewise, U.S. Pat. No. 3,977,714 to McIlvaine features a gas separation device in which contaminant particles are entrapped in liquid droplets which are then spun to form a film on a surface of a plate. The contaminants are then discharged.
U.S. Pat. No. 4,061,478 to Hartwick discloses a self cleaning smoke filter. The filter includes a channel with multiple longitudinal sides angularly disposed, an inlet port for receiving gaseous emissions and an outlet port. The filter also contains a spraying means for producing a cleansing spray inside the channel.
U.S. Pat. No. 4,239,513 to Paul features a device for separating foreign particulates from a gas flow. The device uses wall plates to deflect the gas flow, subjecting the flow to a centrifugal force such that the foreign particulates are collected on the wall plates. The device contains spirally curved laminae to define passageways. Nozzles are arranged to feed moisture into the fluid flow to assist wet separation. While somewhat analogous to the present invention, the Paul device relies on the introduction of a water stream and a reversal of flow to form a secondary vortex to pull a film of fluid back into air suspension to mix with the solids and again be deposited on the wall plates as gas travels through the exit passages. Such a system is far more complicated and prone to error than the present system.
U.S. Pat. No. 5,906,676 to Drummond is an ejector-augmented overspray reclaim system. Drummond is directed to separating and reclaiming oversprayed powder from a powder coating spray system. In accordance with Drummond, the overspray collection system includes a trough located under a conveyor belt and an inlet passageway in fluid communication with the interior of the spray booth. A collection subsystem creates sub-ambient air flow in the inlet passageway. A rotating brush dislodges overspray articles from the conveyor. An airflow through a conduit is created by a rotating fan wheel in the collection subsystem, and the airflow is augmented by a compressed air injector that is disposed and oriented in the conduit such that it ejects compressed air in the direction of the inlet passageway. Accordingly, particulate matter settling in the trough becomes entrained in an airstream flowing into a collection subsystem. The collection subsystem includes a cyclone separator and a filter stack.
While the Drummond device is instructive, the present device features substantial innovations and improvements over Drummond. First of all, Drummond uses a rotating brush to move particulate matter to the bottom of the trough which is not necessary in the present invention. Furthermore, the use of an abrasive instrument would result in the tearing or at least scoring of a textile product, and hence, is not useful for many applications. In addition, Drummond features a compressed air injector for creating an air flow; such a subsystem is both unnecessary and counterproductive in the present device. The present device is dependant largely on a gradual or slow-velocity movement of the gas through the collection system. A compressed air injection system such as that featured in Drummond would introduce a turbulence that would frustrate the purposes of this invention.
SUMMARY OF THE INVENTION
The object of this invention is to provide an improved method and apparatus for the collection of a liquid from an overspray mist in a wide variety of manufacturing processes. Usage of this invention reduces the hazards and waste characterized by prior art methods, and provides a method and apparatus for the in-line recycling of applied liquids. In the preferred embodiment, the liquid overspray may be a chemical additive which is gas-entrained for direct application to a workpiece. The workpiece may be a paper product or a textile product, and will generally be in sheet form although other arrangements are possible. In order to achieve this objective, the present invention comprises a hooded recovery unit which is oriented above and about a conveyor system or other manufacturing line or process such that the liquid or chemical application upon the workpiece is achieved during a period in which the workpiece passes through the hooded recovery unit. The hooded recovery unit will hereafter be denoted and described as the “spray application chamber”. In this preferred embodiment, the process is a conveyor oriented such that it carries or secures the workpiece and passes through the spray application chamber. However, it is also possible
Hopkins Robert A.
Waters Law Office
Waters, Esq. Robert R.
LandOfFree
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