Seal for a joint or juncture – Seal between fixed parts or static contact against... – Contact seal for other than internal combustion engine – or...
Patent
1997-05-20
1999-07-27
Reichard, Lynne A.
Seal for a joint or juncture
Seal between fixed parts or static contact against...
Contact seal for other than internal combustion engine, or...
427571, F16J 1502
Patent
active
059277270
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
A sealing element of the above type having a hard material layer which comprises a hard layer component applied to the working surface of the shut-off body and a subsequent covering layer component and the associated plasma CVD coating process for applying the hard material layer to the working surface of the shut-off body is known from DE-A 38 32 692.
According to this document, shut-off bodies are, to coat their working surfaces, placed in the coating chamber on a specimen holder having a negative potential relative to the plasma. For initial physical etching of the working surfaces of the shut-off bodies with argon, the coating unit is first operated as cathode atomization (sputtering) unit. For subsequent deposition of the bonding layer component of the hard material layer on the etched working surface, the same unit is then operated under certain first process parameters as high-frequency plasma CVD unit, with the argon gas in the coating chamber being replaced, for example, by tetramethylsilane. With altered second process parameters, the covering or sliding layer component is then deposited from a gas mixture of tetramethylsilane and hexane after deposition of the bonding layer component.
The sealing elements obtained by this method (these can advantageously be coated ceramic plates for water valves, e.g. single-hand mixers) have, thanks to the hard material layer applied, sufficiently low coefficients of sliding friction and static friction when sliding over one another, even in the presence of water, so that greasing of the sealing surfaces as has hitherto been required for uncoated ceramic plates is no longer necessary.
A disadvantage of the known sealing elements, which are coated with a single-layer and multilayer hard material layer, is that their hot-water resistance is unsatisfactory. This is the case particularly when a hot-water resistance of more than 1000 operating hours is to be achieved without the hard material layer applied becoming detached from the shut-off body.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a sealing element which has both sufficiently low coefficients of static friction and sliding friction on the sliding layer surface and a high hot-water resistance. Preferred sealing elements, in particular in the form of discs, should have a hot-water resistance at 95.degree. C. over a sufficient operating period, for example of at least 1000 hours without, in particular, the adhesion of the hard material layer on the shut-off body being significantly impaired.
The invention relates to a sealing element, particularly for shut-off and regulating valves. It comprises a disc-shaped, piston shaped or spherical shut-off body. The shut-off body can comprise a metallic or nonmetallic material. This material can be, for example, a ceramic material, including aluminum oxide Al O and the various silicon carbides SiC, Si C and silicon nitride Si N.
On a working surface (sealing surface) of the shut-off body, a hard material layer containing carbon and silicon is applied by plasma CVD or plasma polymerization in a coating chamber.
The hard material layer can be essentially homogenous. However, it can also have a lamellar structure. Advantageously, the hard material layer can comprise a bonding layer component applied to the working surface of the shut-off body and a subsequent covering layer (sliding layer) component. The bonding layer component can have a first silicon content favouring adhesion to the working surface of the shut-off body, and the subsequent carbon-containing covering layer component can have a second silicon content lower than that of the bonding layer component, to achieve low coefficients of sliding friction and static friction. The bonding layer component can also be silicon-free.
The deposition from the plasma is carried out by ion bombardment, e.g. by means of a glow discharge of by means of an additional ion gun. From a hydro-carbon-containing atmosphere a wear-resistant, carbon-containing layer having suffici
REFERENCES:
patent: 5137398 (1992-08-01), Omori et al.
patent: 5645900 (1997-07-01), Ong et al.
patent: 5674438 (1997-10-01), Patel et al.
Strelow Hans-Peter
Wagner Friedrich
Bochna David E.
Friedrich Grohe AG
Reichard Lynne A.
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