Drying and gas or vapor contact with solids – Apparatus – With means to treat gas or vapor
Patent
1990-12-27
1992-09-08
Bennet, Henry A.
Drying and gas or vapor contact with solids
Apparatus
With means to treat gas or vapor
34 44, 34 54, 34 51, 34233, 34243C, F26B 300
Patent
active
051447541
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for controlling the supply and the discharge of hot and/or cold gases to and from, respectively, a tunnel-shaped arrangement for drying and/or cooling vehicles or parts thereof, said arrangement being divided longitudinally into a number of sections each of which is provided with a plurality, preferably 60-250, of nozzles which are substantially evenly distributed over the curved inner surface of the section and through which the gases are supplied and blown against the vehicle or parts thereof passing through said arrangement.
In the car industry, there has been a switch over the past years to water-base paints, entailing certain problems in drying the paint on the vehicle parts. This is especially the case when a layer of non-water-base paint should be applied over a layer of water-base paint.
One problem of water-base paints is that these paints do not withstand such high temperatures as the paints previously used. This means that since it is desirable, for reasons of economy and efficiency, to use the same drying units (blowing tunnels) and the same throughput rates as earlier, it will be necessary to supply a larger amount of hot air per unit of time than earlier, to compensate for the necessary reduction of the temperature of the hot air. This, of course, places increased demands on the system supplying and discharging the hot air to and from the blowing tunnel.
Another problem is that, in order to meet the increasing demands for optimum energy utilisation, it is desirable to be able to control the supply of heat to the different parts of the blowing tunnel, so that there is supplied precisely the amount of heat necessary for drying, e.g., the different parts of a car body placed in the blowing tunnel.
Yet another problem when using water-base paints is that they give off water vapour when drying. This means that the exhaust air from the blowing tunnel will have a relatively high moisture content. If the moisture content inside the blowing tunnel becomes too high, the surface layer of the car body will dry very slowly. This means that recirculation of the exhaust air must be limited, although it is desirable for better energy economy to recirculate as much hot exhaust air as possible.
A further problem encountered when using water-base paints is that if the moist air forming during the drying of the paint in the blowing tunnel would leak out into the surrounding atmosphere at the ends of the blowing tunnel, there would be a risk both of condensation and, thus, of corrosion on objects, such as spray booths, placed around the blowing tunnel, and of impaired function in the spray booth. Nor is it of course desirable from energy aspects that the hot drying air is emitted directly into the surrounding atmosphere without any previous energy exchange with cold supply air.
If the blowing tunnel is used for drying an outer layer of enamel on a vehicle body, dangerous solvent vapours are instead emitted to the drying air within the blowing tunnel. Nor is it of course desirable that these vapours are emitted into the surrounding atmosphere.
The primary object of the present invention therefore is to provide a solution ensuring efficient supply of heat to the different parts of the blowing tunnel.
According to the invention, this object is achieved by a method of the type stated in the introduction to this specification, which is characterised by the steps of measuring the pressure drop of the gases across the nozzles, measuring the temperature of the gases before the nozzles, comparing the measured pressure drop values with desired values corresponding to the prevailing temperature, and supplying a pressure increase or a pressure reduction signal to first pressure changing means for supplying the gases to said arrangement, depending on whether the measured values are below or above said desired values.
The nozzles are suitably arranged in groups comprising a certain number of nozzles, preferably 15-90, and the pressure drop and the temperature of the gases can be measur
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patent: 4635381 (1987-01-01), Hubbert
patent: 4656758 (1987-04-01), Nakayama
patent: 4761894 (1988-08-01), Hamasaki et al.
ABB Flakt AB
Bennet Henry A.
Fournier, Jr. Arthur E.
Gromada Denise L. F.
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