Seal for a joint or juncture – Seal between relatively movable parts – Close proximity seal
Reexamination Certificate
2001-06-12
2002-11-12
Knight, Anthony (Department: 3676)
Seal for a joint or juncture
Seal between relatively movable parts
Close proximity seal
C277S421000
Reexamination Certificate
active
06478304
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
This application claims the priority of German Patent Document 199 33 445.5 filed in Germany on Jul. 16, 1999 and PCT/DE00/02309 filed in Germany on Jul. 14, 2000.
The invention relates to a sealing ring for non-hermetic fluid seals with a restricted passage between coaxial sealing elements rotating relative to one another especially as a rotating sealing element for labyrinth seals in gas turbine engines, with a carrier leading to at least one component and with at least one sealing rib extending radially outwards or inwards and around the entire carrier, the exposed, circumferential edge of which rib in operation forms a flow restriction with a running-in surface situated radially opposite, the sealing rib presenting an abrasive geometry to the running-in surface.
Thus German Patent Document DE 4341 216 C2 protects a seal component for controlled-gap or labyrinth seals having a coating composed of a compound containing metal and hard material particles, the latter being arranged in the form of regularly shaped bodies with leveled surfaces lying on the same level. This construction is intended to ensure that the running-in surface material is not only removed by abrasion but displaced by hot plastic flow. This presupposes a large amount of heat generated by friction, which can in turn damage the fin material.
Numerous measures are known, which are intended to remedy this problem and come under the term “fin tip armouring”.
Thus DE 4341 216 C2 protects a seal component for controlled-gap or labyrinth seals having a coating composed of a compound containing metal and hard material particles, the latter being arranged in the form of regularly shaped bodies with levelled surfaces lying on the same level. This construction is intended to ensure that the running-in surface material is not only removed by abrasion but displaced by hot plastic flow. This presupposes a large amount of heat generated by friction, which can in turn damage the fin material.
German Patent Document DE 197 30 008 C1 protects armouring for a metal engine component, which is worked into a running-in surface as this is skimmed, comprises a ceramic layer and is profiled with peaks and intervening spaces for the discharge of abraded material, the profiling being created by deforming of the surface of the component prior to coating, preferably by knurling. The entire sealing fin is therefore constructed like a saw blade with a plurality of teeth uniformly distributed over its periphery, the surfaces of which teeth are ceramic-coated. This solution has the disadvantage, among others, that the many spaces between the teeth/tips generally impair the sealing effect. Owing to the small material cross sections in the tips and the punctual introduction of heat, local heat flux densities occur here, which may be higher than in the case of smooth sealing fins and hence very detrimental to the material grain structure. In addition, the V-shaped spaces having sharp edges at the foot form stress-increasing notches from which dangerous cracks can originate. A coarser toothing would be advantageous with a view to effective abrasion and hence a thermally non-critical running-in process. This is inconsistent with the need for a good sealing effect, so that in fact only a very fine, flat toothing can be used. In this respect, this solution also tends to result in a wear process with the thermal disadvantages already referred to.
This object is achieved by the sealing ring for non-hermetic fluid seals with a restricted passage between coaxial sealing elements rotating relative to one another, especially as a rotating sealing element for labyrinth seals in gas turbine engines, with a carrier leading to at least one component and with at least one sealing rib extending radially outwards or inwards and around the entire carrier, the exposed, circumferential edge of which rib in operation forms a flow restriction with a running-in surface situated radially opposite, the sealing rib presenting an abrasive geometry to the running-in surface, characterized in that the/each sealing rib has a smooth, rotationally symmetrical contour over the greater part of its periphery, and in that one or a few cutting elements are arranged at one or a few points on the/each sealing rib in such a way that each cutting element projects radially and axially on one or both sides from the contour of the sealing rib. a suitable , mechanically abradable running-in surface.
This object is achieved by the features characterized in claim
1
, in conjunction with the generic features of its pre-characterizing clause.
The sealing ring according to the invention advantageously combines the features of a conventional design with at least one smooth, rotationally symmetrical sealing rib, and an abrasive design, one or a few cutting elements, which project from the sealing rib contour, being arranged at only one or a few discrete points on the sealing rib. The cutting elements are intended to be of a really cutting or chip-forming design and robust, that is mechanically resistant, so that sufficient surface material is abraded in the shortest possible time and without much friction work, thereby producing the desired clearance with the smooth, sealing contour of the sealing rib.
BRIEF DESCRIPTION OF THE DRAWINGS
A chip-forming machining process is known, which is referred to as “thread whirling” and which uses a hollow tool with one or a few inwardly projecting teeth rotating at high speed, in order to machine a slowly rotating work-piece. Although the tool and the work-piece are not guided co-axially with one another in thread whirling, this process nevertheless gives some idea of the running-in process involved in a sealing ring according to the invention.
Preferred configurations of the invention are characterized in the subclaims.
REFERENCES:
patent: 3537713 (1970-11-01), Matthews et al.
patent: 3846899 (1974-11-01), Gross
patent: 4148494 (1979-04-01), Zelahy et al.
patent: 4227703 (1980-10-01), Stalker et al.
patent: 4390320 (1983-06-01), Eiswerth
patent: 4671735 (1987-06-01), Rossmann et al.
patent: 43 41 216 (1995-06-01), None
patent: 197 30 008 (1998-10-01), None
Beres John L.
Crowell & Moring LLP
Knight Anthony
MTU Aero Engines GmbH
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