Coating apparatus – Condition responsive control
Reexamination Certificate
1999-02-19
2001-02-13
Bueker, Richard (Department: 1763)
Coating apparatus
Condition responsive control
C118S400000, C118S603000, C118S610000, C118S719000, C134S060000, C134S104200, C134S110000
Reexamination Certificate
active
06187099
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an installation for the treatment of objects in a defined gas atmosphere.
In many production procedures for the manufacture, refining and quality improvement, substances are applied which for the improved handling are enriched with solvents. During the production these part substances evaporate and as a rule are led to the production outgoing air.
On account of existing technical regulations outgoing air purification systems must be applied in order to filter production substances which are damaging to the environment. It is known for this to use incineration installations and adsorption and absorption installations.
The occurring outgoing air volume flows are normally dependent on the intensity of the applied solvent. For safety reasons the outgoing air volume flows are considerably higher than is required caused by production. This means in each individual case an uneconomically high volume of the installation for the purification of the outgoing air. For example with the application of combustible solvents the minimum outgoing air quantity is to be selected such that during the continuing production and in particular at the start or stop of the installation under no circumstances may a mixture capable of ignition occur. This is achieved in that the outgoing air quantity is increased in such a manner that no concentrations capable of ignition may occur in the outgoing air. According to safety regulations the distance to the ignitable concentration of flammable substances in production installations is maximally 20% below the limit of inflammability. This means generally that for safety reasons at least five times the outgoing air volume is needed in order to be able to securely operate a production installation. Furthermore the high quantity of outgoing air also after its purification is contaminated with residual substances from the production.
On the basis of a substance of material class III, according to TA-Luft (Official Standard for Clean Air) then a maximum concentration of 150 mg/Nm
3
is permitted after outgoing air purification. With a quantity of outgoing air of e.g. 100,000 Nm
3
/h this would mean an immission of 15 kg/h which would be given to the environment.
It is known to subject certain objects to a surface treatment method, for example with suitable plastics, which for curing the coating, use UV-energy or the electron beam method. With such cases the product quality may be increased by reducing the oxygen concentration in the irradiation region. Since in the irradiation region there is a danger of ignition in any case, the concentration of oxygen is to be limited to a maximum value. An example of such a surface treatment is the coating of glass containers with a polymer.
BRIEF SUMMARY OF THE INVENTION
It is the object of the invention to provide an installation for the treatment of objects in a defined gas atmosphere, whose O
2
content is smaller than that of air and with which environmentally damaging treatment gases are produced, which ensures a secure production operation, causes only slight environmental damage and may be operated economically.
This Object is Achieved by the Invention Disclosed Herein.
With the installation according to the invention there is provided an almost completely closed housing which is only connected to the environment via at least two openings, wherein the objects get into the housing via one opening and go out of the housing via another. With closed containers (reactors) or with installations operating with the batch procedure it is possible to produce a volume of gas sealed from the environment and to set it to a desired concentration of any gaseous components. With objects on the other hand which continuously travel through the housing in a conveyed manner there is present a constant connection to the environment. Since however according to requirements the oxygen concentration must not exceed a maximum value, corresponding measures are needed in order to minimise the influence to the surrounding atmosphere. The housing in the inside is subdivided into at least two zones of which the one is connected to the entry opening and the other to the exit opening. In the first treatment zone the process gas is formed by a part of the treatment gas which is produced in the first zone, for example for coating or vaporizing the accommodated objects, for example with a suitable polymer. In this case the treatment gas contains also a component of solvent so that the coating may be effected in the desired manner. The first zone is connected to the second treatment zone via a passage opening. The second zone is furthermore connected to the exit opening. In this zone the drying or the end reaction of the deposited material takes place, for example with the help of a suitable heat source, or an UV irradiation. Alternatively also electron beam treatment may be carried out. It is essential that for the quality improvement and/or for avoiding an ignition in the second treatment zone the oxygen concentration is minimal.
For achieving and maintaining the desired data the installation according to the invention envisages three sluices of which in each case one is allocated to the entry or exit opening and a further to the passage opening. The first and third sluices prevent the entry of normal air into the treatment zones. The second sluice prevents the entry of process air into the second treatment zone. The sluices form “gas curtains”through which the objects run. In the first sluice the gas curtain is formed by purified process air, just as in the second sluice. Since in the second treatment zone there is supplied an inert gas this is effected preferably in that the third sluice is flowed upon by inert gas by which means it is ensured that in the second treatment zone there prevails a largely inert atmosphere. As an inert gas for example nitrogen or carbon dioxide may be applied.
The process gas is suctioned out of the treatment zone and sent via a filter device so that pollutant gas, for example solvent, is removed. The purified process gas may then be fed back into the treatment zones, somewhat, as mentioned, via the first and second sluice. Since by way of the inert gas supply an excess of gases in the housing arises, the installation according to the invention finally envisages an outgoing air branch for process gas which preferably is connected to the first sluice, in the conveying direction, in front of the entry of the purified process gas into the sluice.
With the installation according to the invention the atmosphere required for the production is purified via a purification installation and the thus purified process gas is led to a closed circuit system of the production installation. The outgoing air delivered to the environment is minimal since as a maximum it corresponds to the volume which is supplied in the form of inert gas. By way of the directed encapsulation of the production and a defined guiding of the flow whilst using the mentioned sluices, leakage losses may be kept low and correspond to a fraction of the normally occurring purified outgoing air quantity. The installation according to the invention can be particularly preferably applied where with the guiding circulation combustible and chlorinated substances are used.
On account of the relatively well encapsulated production the inert gas consumption may be kept low. In the production atmosphere ignition processes are not at all possible since there lacks a suitable oxygen concentration. The circulation volume flow may be reduced to that measure which is required for the production without problems arising with regard to safety technology. As is known each volume flow reduction for the production atmosphere reduces the expense, with regard to installation technology, for the purification systems which are integrated into the process circulation.
Since the process gas volume flow is very small also the scope of the filter device may be selected correspondingly small. Preferably as a filter device an adsorber is prov
Bueker Richard
Knaack & Jahn GmbH
Vidas Arrett & Steinkraus P.A.
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