Coating apparatus – Control means responsive to a randomly occurring sensed... – Condition of coated material
Reexamination Certificate
1999-01-22
2001-06-19
Edwards, Laura (Department: 1734)
Coating apparatus
Control means responsive to a randomly occurring sensed...
Condition of coated material
C118S679000, C118S688000, C118S708000, C118S712000, C118S713000, C118SDIG004
Reexamination Certificate
active
06248174
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an apparatus in which liquid or pasty coating medium is applied directly or indirectly onto a traveling material web, especially of paper or cardboard.
2. Description of the Related Art
The application of liquid or pasty coating medium by use of a paint curtain or paint veil, the so-called “curtain coating” itself, is already known. U.S. Pat. No. 5,624,715, for example, shows a paint curtain applicator mechanism for the direct coating of a material web. To put it more precisely, U.S. Pat. No. 5,624,715 deals with the impairment/disturbance problem of the coating medium-veil's even distribution onto the material web caused by the carried-on air of the traveling material web. Furthermore, from the German patent document no. EP 0 517 223 B1, an apparatus is known with the help of which air bubbles are to be removed from the coating medium in the run-up of the application process so that the bubbles cannot influence the regularity/evenness of the application.
A further problem, which arises during “curtain coating,” and with which the above mentioned printing does not deal, is the dosage of the coating medium. Usually, the coating medium applied by use of curtain coating is not metered out by a subsequent doctor device, so high demands are made on the measured emission/discharge of the coating medium from the paint curtain applicator mechanism.
SUMMARY OF THE INVENTION
The present invention provides an apparatus for direct or indirect application of liquid or pasty coating medium onto a traveling material web, especially of paper or cardboard. Besides a paint curtain applicator mechanism, this apparatus includes at least one sensor equipment to register the flow quantity of the applied coating medium layer and to prepare a corresponding flow-quantity signal. Additionally, it includes at least one regulator device to change at least one manipulated variable of the paint curtain applicator mechanism, of which the flow quantity of the applied coating-medium-layer onto the material web depends. Finally, it includes a regulation unit which receives the prepared flow-quantity signal from at least one sensor device, which, dependent on this flow quantity signal, determines at least one face value for the at least one manipulated variable. The sensor transmits the at least one manipulated variable-face value to the at least one regulator device.
Through the inventional planned flow quantity regulation, the coating medium can be emitted well-dispensed from the paint curtain applicator mechanism so that the desired even layer application onto the material web results. Furthermore, inventional planned flow quantity regulation is constructed in a simple way, because it does not monitor each of the application result influencing parameters separately, nor does it maintain them at a preset face values. Rather, dependent on the registration of the flow quantity, it regulates the per unit time dispensed quantity of the coating medium. The paint curtain applicator mechanism can, for example, include a distribution arrangement which evenly distributes the coating medium in cross direction of the material web. The distribution arrangement, for this purpose, includes a distribution channel, a supply opening/feed opening for introducing the coating medium into the distribution channel, at least one outflow/exit slot for evenly depositing the coating medium in the form of a coating-medium-curtain or veil, as well as, if desired, a depositing opening to divert superfluous coating medium which has been introduced into the distribution channel.
In order to be able to ensure the application's evenness not only in lengthwise direction of the material web, but also in its cross direction, it is suggested to influence the coating medium quantity, which is emitted per unit time from the paint curtain applicator mechanism by several successive application sections installed in cross direction of the material web and which are independent from each other. This can, for example, be carried out by ensuring that the regulator device includes some regulator units which are arranged in cross direction of the material web in order to adjust, section by section, the width of the least one outflow exit slot of the paint curtain applicator mechanism.
In a majority of cases, however, it will suffice to adjust the overall coating medium quantity which has been emitted from the paint curtain applicator apparatus per unit time to a desired value. For this purpose, the regulator device can include, for example, a device to adjust the output conveying capacity of the coating-medium-pump, which has been assigned to the paint curtain applicator apparatus. Additionally or alternatively, the regulator device can include a valve arrangement to influence the quantity of the coating medium which is introduced per unit time through the supply opening feed opening into the distribution channel. Again, additionally or alternatively, the regulator device can include a regulator unit to adjust the width of the at least one exit slot of the paint curtain applicator apparatus. Furthermore, it is possible for the regulator device to include a valve arrangement to influence the exit opening redischarged fraction of the coating medium which is introduced into the distribution channel via the feed supply opening.
The flow-quantity-sensor-equipment can be developed for the direct or indirect registration of the flow quantity of the coating medium layer applied onto the material web.
For a direct registration, the flow quantity sensor equipment can display a first sensor unit which is arranged in running course direction of the material web in front of the paint curtain applicator apparatus, and it can provide a first sensor signal. Furthermore, it can display a second sensor unit, which is arranged in running direction of the material web behind the paint curtain applicator apparatus and provides a second sensor signal. Finally, it can display a difference formation unit which deducts the first sensor signal from the second one and provides the difference signal as the flow quantity signal.
Through this process, the first sensor unit measures the characteristics properties of the material web in its rough state natural condition, i.e., before the herein discussed coating process, which, however, does not exclude that the material web has been coated already once or several times. The second sensor unit measures the achieved final condition so that the coating is reflected as such in the difference of the two measured signals. The running time of the material web between the first sensor unit and the second sensor unit can be taken into consideration through the formation of the difference signal. In principle, however, it is also possible to assume that the signals produced by the two sensor units are quasi stationary signals which change only slowly, so that the running time does not have to be considered.
The flow quantity can be determined, for example by an optical measuring procedure, during which the luminous reflectance or the coefficient of transmission of the material web can be measured. But there are also known radioactive measuring procedures, during which the radiation extinction of a radioactive source, usually a radiation source, of known intensity is determined through the material web. The latter measuring method can be calibrated from time to time by putting the radiation source next to the material web or by determining the intensity of the not evaporated radioactive sources. All the above mentioned measuring procedures are suitable for determining the flow quantity, independent from its locale in cross direction of the material web. For this purpose, for example, a measuring head along a guide running in cross direction of the material web can be moved back and forth.
An indirect flow quantity registration can be effected, for example, by use of a flow quantity sensor device, which includes a first sensor unit assigned to the feed openi
Edwards Laura
Taylor & Aust P.C.
Voith Sulzer Papiertechnik Patent GmbH
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