Coating apparatus – Gas or vapor deposition – Means to coat or impregnate particulate matter
Patent
1994-11-23
1995-11-28
Bueker, Richard
Coating apparatus
Gas or vapor deposition
Means to coat or impregnate particulate matter
118723EB, 118726, 20429823, 20429826, 20429828, C23C 1400
Patent
active
054703883
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to a device for the all-sided coating of relatively small parts in large numbers (mass produced products). The coatings are applied by vacuum evaporation, vacuum deposition (magnetron sputtering) and/or ion plating (plasma-assisted vacuum evaporation). The parts to be coated are preferably machine components (bolts, screws), but also other parts, which are to have a decorative, hard, wear-reducing, electrically conductive or corrosive-preventing surface. Other, not specified characteristics of surfaces are also to be produced or improved. It is also possible to coat according to this process small parts made from plastics or ceramics.
It is known in connection with vacuum coating to fix the parts to be coated in suitable holding devices and to guide them one or more times through the coating zone of a vacuum evaporator, a sputtering source or some other vapor source for physical vapour deposition (PVD) and then remove the holding devices again after applying the coatings. Apart from the costs of the holding devices and the time taken for fixing and removing parts, the fundamental disadvantage exists that areas of the surface of the parts are always covered and remain uncoated.
In much the same way as for electrochemical coating deposition (CVD), it is known to receive the parts in the form of mass produced products in a basket made from partly permeable materials (wire gauze, perforated metal plates) and bring the same into the vapor zone of a PVD vapor source for coating purposes. The basket rotates about a horizontal axis in order to achieve a mixing movement of the parts, while making use of gravity. Unlike in the case of electrochemical deposition from the liquid phase, such methods are not very suitable for PVD coatings. There is a poor vapor utilization and the openings in the basket are closed by the coating after a short operating period and are no longer effective (JP-A 61-194177). An inclined position of the drum or an eccentric mounting thereof lead to the same deficiencies (U.S. Pat. No. 3,511,644).
An attempt has therefore been made to replace the basket by chains or perforated belts, optionally combined with vibrators, in order to better realize the aim of the coating operation. However, the described deficiencies have not been effectively removed and the apparatus costs are unacceptably high in view of the minor advantage obtained.
It is also known to receive the parts to be coated as mass produced products in a rotary basket and place one or more sputtering sources within said basket (East German patent 257 552 A3, East German patent 257 554 A3). By means of devices fixed to the basket it is ensured that the parts are carried along over a portion of the circumference and then roll back due to gravity. This leads to a mixing movement of the parts during the coating process and therefore to an all-sided coating. However, it is a disadvantage of this process that it is only possible to coat "from top to bottom", i.e. the coating sources can only be constituted by magnetrons, so that the disposition rate is limited. The resulting high coating costs are the reason why this process is only used for very special coatings, e.g. very thin resistance coatings. As all the parts are always under the action of gravity in a spatially confined area in the lower portion of the basket, it has also not been possible to simultaneously introduce into the process plasma sources during the coating process (for ion plating) or an effective cooling of the heat-sensitive parts. Therefore some known rotary basket sputtering plants are limited to specific uses.
For coating granular materials in vacuo it is known to introduce the same into a rotary drum housing and evaporator. This drum rotates at such a high speed that the granular materials to be coated are pressed against the wall by centrifugal force. As a result of a pulsating speed change the granular materials are circulated on becoming detached from the circumference (East German patent 293
REFERENCES:
patent: 2846971 (1958-08-01), Baer et al.
patent: 3395674 (1968-08-01), Burham et al.
patent: 4116161 (1978-09-01), Steube
Goedicke Klaus
Heisig Ullrich
Metzner Christoph
Reschke Jonathan
Schiller Siegfried
Bueker Richard
Fraunhofer-Gesellschaft Zur Foederung der angewandten Porschung
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