Brush seal

Details Brush seal Brush seal

1998-05-29

2001-05-15

Dayoan, B. (Department: 3626)

Seal for a joint or juncture

Seal between relatively movable parts

Brush seal

Reexamination Certificate

active

06231047

ABSTRACT:

FIELD OF INVENTION
This invention relates to an improved brush seal, and more particularly to such a brush seal which has uniform pack density throughout the extent of the bristles.
BACKGROUND OF INVENTION
Presently there are a number of techniques for making a brush seal using a plurality of tufts of bristles. In one technique the bristles are gathered at one end into a tuft; the tufted end of a plurality of such tufts are embedded in series in an epoxy retainer or rail. The rail is bent into an annular shape with the unattached ends of the tufts extending radially outwardly and across a back plate. A front plate is attached with unattached ends of the tufts sandwiched between the plates. The unattached ends of the bristles are trimmed and attached as by welding at the O.D. of the back plate and become the fixed ends of the bristles in the seal while the tufted ends of the bristles are trimmed off beyond the I.D. and become the free sealing ends of the bristles which ride on a shaft for example. The tufts of bristles are oriented with the tufted ends radially inwardly and the bristles spread with increasing radius. This makes the bristles non-parallel and makes their pack density (number of bristles per in
2
) non-uniform; this introduces a number of problems. Since the bristles are not uniformly distributed there is inconsistent wear and inconsistent leakage with resulting reduced life and performance. The non-uniform density produces weak spots where the fluid being sealed may tunnel through and cause leakage. Bristle blow down can occur where air or other fluid turns downward at the seal toward the shaft and displaces the bristles causing gaps and leakage and increased uneven wear. In another technique the tufts of bristles are positioned in slanted radial grooves on an annular jig with the tufted ends being radially outward and the unattached ends being radially inward. A retainer such as a back plate fits within the center hole of the annular jig so that the tufts extend slanted radially across it. The tufts are fixed to the back plate typically with a front plate and welding and the tufted ends are trimmed off at the O.D. of the back plate. The unattached ends of the tufts are trimmed off radially inwardly of the I.D. of the back plate. In this latter technique in contrast to the former, the tufted ends become the fixed end of the bristles while the unattached ends become the free sealing ends of the bristles. But the same non-uniform pack density results with the same problems in performance, wear, life and leakage including tunnelling and bristle blow down. In both approaches, since tufts have a predetermined size, unique tufts must be manufactured for different I.D. seals. This is so because as more and more of the bristles toward the O.D. are trimmed off to enlarge the I.D. of the seal, the pack density decreases until a practical seal is no longer possible.
SUMMARY OF INVENTION
It is therefore an object of this invention to provide an improved brush seal.
It is a further object of this invention to provide such an improved brush seal that has uniform pack density throughout the extent of the bristles.
It is a further object of this invention to provide such an improved brush seal which is simpler and less expensive.
It is a further object of this invention to provide such an improved brush seal which has improved wear, life, performance and sealing.
It is a further object of this invention to provide such an improved brush seal which reduces effects of tunnelling and bristle blow down.
It is a further object of this invention to provide such an improved brush seal which is modular and provides the same uniform pack density independent of the seal radial cross-section.
The invention results from the realization that a truly improved brush seal can be achieved by individually attaching a multiplicity of single bristles to the retainer at the same angle in a continuous array so that the bristles have a uniform pack density throughout their entire extent from the fixed end to the sealing end.
This invention features a brush seal including a retainer and a multiplicity of single bristles each bristle having a fixed end and a free sealing end. The fixed ends are individually attached in a continuous array at the same angle to the retainer. The bristles have a uniform pack density throughout the extent of the bristles from the fixed to the sealing end.
In a preferred embodiment the retainer may include a retainer element or a pair of spaced retainer elements with the bristles between them. The retainer element may include a weld or a braze or an epoxy element for attaching the bristles to the retainer. The retainer element may include a backing plate and/or a front plate. The retainer element may be a flexible member. The flexible member may have a moment of inertia of approximately 5×10
−5
or in
4
or less. The angle of the bristles may be between 30° and 90°. The retainer may be linear, curved or annular. The bristles may be a metal alloy such as a cobalt based metal alloy, Haynes 25, Haynes 214 or stainless steel. The retainer may be a metal alloy such as a nickel-based metal alloy including Inconel 625.
The invention also features an annular brush seal including an annular retainer and a multiplicity of single radially extending bristles each having a fixed end and a free sealing end. The fixed ends are individually attached in a continuous array at the same angle to the retainer. The bristles have a uniform pack density throughout the radial extent of the bristles from the fixed end to the sealing end.
The invention also features a linear brush seal including a linear retainer and a multiplicity of single parallel bristles each having a fixed end and a free sealing end. The fixed ends are individually attached to the retainer at the same angle in a continuous array. The bristles have a uniform pack density throughout the parallel extending bristles from the fixed to the sealing end.


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