Coating apparatus – Solid member or material acting on coating after application – Rotary member
Reexamination Certificate
1998-11-24
2001-03-20
Edwards, Laura (Department: 1734)
Coating apparatus
Solid member or material acting on coating after application
Rotary member
C118S126000, C118S413000, C118S419000
Reexamination Certificate
active
06203615
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention.
The present invention relates to a device for leveling and/or metering a layer of liquid or viscous coating medium onto a moving background. With direct application of the operating medium, the moving background is a material web, preferably a paper or cardboard web. With indirect application, it is the surface of a transfer element which transfers the liquid or viscous medium onto the material web.
2. Description of the Related Art.
When leveling and/or metering the coating medium layer on the background, precise positioning of the leveling and/or metering element against the background is of utmost importance. If the leveling and/or metering element is positioned too far from the background during operation, it will not remove the desired amount of coating medium from the background, resulting in a total coating weight that is too high. In extreme instances, the leveling and/or metering element may not even be in a position to smooth the coating medium layer to the desired extent. If, in contrast, the leveling and/or metering element is positioned too closely to the background, it will remove an excessive amount of coating medium, resulting in an overall coating weight that is too low. In extreme instances, this may even result in damage to the material web, the transfer element or the leveling and/or metering element.
Because of the aforementioned reasons, precisely adjustable power components must be utilized with conventional leveling and/or metering devices. However, such precisely adjustable power components are expensive with regard to purchase and maintenance.
Therefore, it was suggested in European patent document no. EP O 418 476 B1 to provide a lever mechanism between the power transfer device acting upon the doctor blade (=leveling and/or metering element) and the power components, which would reduce the regulating distance of the applicable power component into a correspondingly shorter regulating distance of the power transfer device. However, the suggested lever mechanisms permit only a relatively small reduction so that relatively precisely adjustable power components would still have to be used.
SUMMARY OF THE INVENTION
The invention provides a leveling and/or metering device of the generic type, which is more cost effective with regard to purchase and maintenance.
At least one power component positions a leveling and/or metering element against the background. The at least one power component acts upon the leveling and/or metering element through a power transfer device. The at least one power component acts upon the power transfer device through at least one spring arrangement.
The leveling and/or metering device according to the invention replaces the previously conventional method of regulating distance reduction by converting a power component's regulating distance into a definable adjustment force through a spring arrangement. With the spring arrangement, the leveling and/or metering element is positioned against the background through the power transfer device. This permits precise selection of the distance-power ratio even on very large regulating distances, resulting in positioning of the leveling and/or metering element against the background at the desired level of accuracy. This is because the reaction of the spring arrangement to a preselected regulating distance of the power components may be selected within wide limits as desired through an appropriate selection of the spring constants and pre-tensioning of the spring. The method in accordance with the invention, which includes at least one spring arrangement, also offers the advantage over the rigid distance-distance reduction according to European patent document no. EP O 418 476 B1 that the leveling and/or metering device may be designed“softer” in its entirety. Thus, the leveling and/or metering device may get out of the way of the momentarily thicker material layer without difficulty should the need arise, for example at the pass-through of the splice point of two material webs. This reduces the danger of damaging the leveling and/or metering element and the material web. Even if the material web winds itself around a backing roll following a web break, which would lead to a considerable enlargement of the effective diameter of this backing roll within a very short period of time, the leveling and/or metering unit according to the invention is able to withstand this diameter enlargement longer than conventional leveling and/or metering devices would be able to. This means that there is a better chance that the leveling and/or metering device would not be damaged, or not be damaged too severely during such a web break.
When it was stated earlier that the at least one power component acts “through” the at least one spring arrangement upon the power transfer device, this was meant to include design forms in which the at least one spring arrangement is located between the at least one power component and the power transfer device. It was also meant to include design forms in which the power component is mounted to the power transfer device and acts upon at least one spring arrangement which is supported on a rigid frame.
Leveling and/or metering elements may take the form of all conventional elements, such as doctor blades, metering rods, metering bars, etc., regardless of whether these elements perform a reciprocating motion transversely to the material web or whether they rotate around an axis which is arranged substantially parallel transversely to the material web.
The power transfer device is mounted on a support on which the at least one power component is also mounted. The power transfer device is flexible under the influence of the at least one power component and the at least one spring arrangement. In this instance, the power transfer device does not have to be moved relative to the support in order to be able to influence the leveling and/or metering element in various positions. This also eliminates the need of having to overcome the friction that is always associated with such a relative movement, especially static friction at the beginning of a motion. Therefore, lower efficiency and consequently cheaper power components may be utilized.
When the power transfer device is manufactured at least partially of synthetic material, manufacturing costs, as well as the forces that are necessary to achieve a pre-established distortion of the power transfer device, are reduced as compared to power transfer devices manufactured from rigid materials, such as metal. This also allows the use of lower efficiency power components.
In order to be able to remove the leveling and/or metering element from the moving background, at least one spring arrangement includes a tension spring, a compression spring and/or a tension/compression spring.
In a cost-effective design variation, at least one spring arrangement includes a coil spring. In addition, this design variation distinguishes itself in low susceptibility to dirt accumulation. Other forms of additional or alternative spring arrangements may also be used. Some examples are gas springs, resilient rubber elements and leaf springs.
In a further embodiment of the invention, at least one damper arrangement can be provided between the at least one power component and the power transfer device. This damper arrangement counteracts development of vibrations in the leveling and/or metering device, which would manifest themselves in cross streaks or so-called “barring” in the coating layer. When laying out the damping characteristics for the damping unit, it should be ensured that the ability of the leveling and/or metering unit to get out of the way of the passing splicing area is not significantly impaired. The leveling and/or metering device can accommodate the enlargement of the backing roll diameter that may result from a web break, even when utilizing the damper arrangement, due to the relatively high time constant associated with this diameter enlargement.
The damper arrangement and
Edwards Laura
Taylor & Aust P.C.
Voith Sulzer Papiertechnik Patent GmbH
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