Coating apparatus – Immersion or work-confined pool type – Running length work – longitudinally traveling
Patent
1998-02-12
2000-07-11
Lamb, Brenda A.
Coating apparatus
Immersion or work-confined pool type
Running length work, longitudinally traveling
118419, B05C 302
Patent
active
060866748
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for applying at least one magnetizable dispersion containing pigments and polymeric binders to the front of a linearly transported nonmagnetic substrate by means of an extrusion coater, the orifice of the slot transporting the dispersion being essentially opposite the edge of the pole surface of a magnet arranged adjacent to the back of the substrate.
2. Description of the Prior Art
Apparatuses of the abovementioned generic type are disclosed, inter alia, in DE-B-19 07 212, DE-A-42 26 139 and German Patent Application P 44 43 896 of the same Applicant. A major advantage of this coating arrangement is that the applied amount of dispersion depends only on the dose supplied but, within certain limits, is independent of the distance from the extruder orifice to the substrate. As is evident from the example of the abovementioned DE-B-19 07 212, coating speeds of 100 m/min can thus readily be achieved.
Recently, substantially higher coating speeds have been required for greater cost-efficiency of the coating procedure and in addition the magnetic properties of magnetic recording media thus achieved must meet higher requirements; in particular the smoothness of the surface should be improved to achieve constant contact between the head and the magnetic recording medium.
SUMMARY OF THE INVENTION
It is an object of the present invention to start from the abovementioned prior art and improve the coating apparatus with respect to these required properties.
It is an object of the present invention to obtain a coating which is satisfactory over the coating width and has a very smooth surface, even at high coating speeds which are higher than 100, in particular higher than 500, m/min.
As is clearly evident from FIG. 1 of DE-B-19 07 212, the substrate (6) glides directly past the edge (3a) of the soft iron strip of the magnet (3). With slight fluttering of the substrate and in the case of a substrate which is wavy transverse to the web running direction, there is accordingly the danger of scratching the back of the magnetic recording medium, resulting in abrasion which adversely affects the mechanical and magnetic properties when the coated substrate is rolled up.
We have found that this object is achieved, according to the invention, by an apparatus having the features stated in the defining part of claim 1. Further details of the invention are evident from the subclaims, the description and the drawings.
With the novel apparatus it was possible to obtain a coating which is satisfactory over the coating width and has a very smooth surface, even at high coating speeds, in particular greater than 500 m/min. By the further use of a guide element having a curved guide surface, it was furthermore possible to avoid scratching the back of the substrate.
The invention is described in more detail below with reference to the Figures, in which
BRIEF DESCRIPTIONS OF THE DRAWINGS
FIG. 1 shows a schematic overview of the novel apparatus and
FIG. 2 and
FIG. 3 show two different embodiments, based on FIG. 1, on a larger scale.
DESCRIPTIONS OF THE PREFERRED EMBODIMENTS
FIG. 1 shows that the substrate (1), which consists, for example, of a thin polyethylene terephthalate film, passes through the extrusion coating arrangement to be described in more detail, between two rotatably mounted guide rolls (10, 20) in the direction indicated by the arrow. The extrusion coater head (2) consists of an upper part (14) and a lower part (15); the dispersion is transported between said upper and lower part (in the direction indicated by the arrow) through the coater slot (4) by means of a metering apparatus (not shown) and leaves the coater through the orifice (3). The dispersion is applied as a magnetizable layer (11) to the front of the substrate (1). An essentially cuboid magnet (5) is present essentially opposite the extruder orifice (3) and adjacent to the back of the substrate (1) and is arranged in such a way that its magnetization direc
REFERENCES:
patent: 4357370 (1982-11-01), Alheid
patent: 5601647 (1997-02-01), Pertzsch et al.
patent: 5641355 (1997-06-01), Munch et al.
Brotz Friedrich
Nagler Eberhard
Wagner Hans-Gunter
EMTEC Magnetics GmbH
Lamb Brenda A.
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