Coating apparatus – Immersion or work-confined pool type – Work-confined pool
Reexamination Certificate
1999-09-21
2001-11-20
Edwards, Laura (Department: 1734)
Coating apparatus
Immersion or work-confined pool type
Work-confined pool
C118S413000, C118S119000, C118S126000, C118S261000
Reexamination Certificate
active
06319320
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a coating machine to coat material webs, more particularly, material webs made from paper or carton.
2. Description of the Related Art
Reference is made to German patent document DE 3236991 and DE 33111081. It should be noted here that the moving surface which is to be coated is a material web in the case of direct application. In the case of indirect application, the moving surface is an applicator roll which transfers the medium onto the material web.
The machines described in the above-mentioned patent documents require different coater rods for different mediums to be applied, i.e., different coater rods having various diameters and contact pressure characteristics had to be selected to suit different medium viscosities. This required significant machine time and readjustment of the contact pressure onto the material web each time a new coating medium, and therefore a new coater rod, was selected.
In order to achieve a satisfactory coating quality on the material web, it was necessary to pre-meter the medium in significant excess quantities, which subsequently had to be removed by the coater element in order achieve the required coating weight. As a general rule, approximate 90 to 95% of the pre-metered medium had to be removed from the moving surface. In order to be able to handle the excess coating, it was necessary to maintain a high metering pressure in metering chamber. Therefore, this method required high pumping power (for the supply and discharge of the medium). The removal of excess material was typically performed by groo coater rods which, because of their ability to volumetrically meter the medium, were better for the task. However, these rods are more complex to manufacture and maintain. Furthermore, these particular rods are prone to substantially greater wear compared to smooth coater rods.
SUMMARY OF THE INVENTION
The present invention provides a coating machine which avoids the above-stated disadvantages with a minimum of technical complexity.
The inventor has recognized that the provision of counter force F
G
in the metering chamber, which opposes force F
1
acting upon the coater rod, can be built up to a level so that the contact force of the coater rod no longer is the only deciding factor in achieving the desired coating weight on the material web.
Force F
1
is dependent on the pressure in a pressurized hose, which generates the coater pressure, for example. This force F
1
is determined by this formula:
F
1
=F
H
+F
G
,
whereby, F
H
is the hydrodynamic force which forces the coating medium against the coater rod in the metering chamber. The hydrodynamic force is a function of the viscosity of the coating medium, the diameter of the coater rod and the machine speed setting.
The pre-load force F
1
and the hydrodynamic force F
H
relate to each other in a favorable way. Therefore, the force F
1
acting upon the coating element is more finely adjustable than before.
There are several ways to generate the counter force F
G
. It is possible, for example, to employ a fixed-movable bearing combination. It is especially advantageous to employ a pre-load panel. Such a panel is very simple to procure and manufacture. Depending on the thickness of the pre-load panel, different pre-load forces can be generated, assuming a constant geometry of the coating machine. This allows the use of only one size coater rod regardless of what coating medium is used, which, in turn, requires only a single coater rod bed supporting the coater rod. The diameter of the coater rod is now only 20 mm, for example.
It is preferred for the coater rod of the present invention to have a smooth outer surface. As mentioned above, this coater rod is simple to manufacture and wears substantially less than grooved rods or rods with wires wound around them.
A further feature of the present invention consists of the advantage that it is no longer imperative to maintain the pressure in the metering chamber. The key factor to achieve the required coating weight and a uniform coating of the material web is simply the supply of the required amount of coating medium. The conditions for a so-called “1:1 coating” are therefore established. In other words, it is only necessary to supply the amount of coating medium that is indeed used. The present invention eliminates the need to supply and remove large amounts of excess coating material. This results in substantial savings on equipment, pump power, coating medium, and operational resources.
REFERENCES:
patent: 4245582 (1981-01-01), Alheid et al.
patent: 4773351 (1988-09-01), Sollinger
patent: 4859507 (1989-08-01), Damrau
patent: 5433781 (1995-07-01), Bernert
patent: 5738726 (1998-04-01), Kaipf et al.
patent: 6004394 (1999-12-01), Gottwald
patent: 6106619 (2000-08-01), Eng
patent: 32 36 991 A1 (1984-04-01), None
patent: 33 11 081 A1 (1984-09-01), None
Edwards Laura
Taylor & Aust P.C.
Voith Sulzer Papiertechnik Patent GmbH
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