Brush Seal Assembly And Method Of Making

Abstract

A bristle pack for use in a brush seal includes a support and a plurality of bristles. The bristles are folded over the support defining a fold, and are joined together adjacent the support opposite the fold.

Description

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/894,949, filed Mar. 15, 2007, and the entire disclosure of which is incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable.

BACKGROUND OF THE INVENTION

This invention relates generally to brush seals for sealing a gap between a high pressure and a low pressure area and, more particularly, to a brush seal made from bristles joined together around a support.

The use of brush seals for sealing gaps, such as those found in gas turbine engines, is known in the art. For example, in gas turbine engines brush seals are often utilized to minimize leakage of fluids at circumferential gaps, such as between a machine housing and a rotor, around a rotary shaft of the engine, and between two spaces having different fluid pressure within the engine. The fluid pressure within the system, which may be either liquid or gas, is greater than the discharge pressure (the pressure outside the area of the engine housing, toward which the fluid will tend to leak), thus creating a pressure differential in the system. As used herein, the system pressure side of the brush seal is referred to as the high pressure side, while the discharge pressure side of the brush seal is referred to as the low pressure side.

Known brush seals can be made from metallic or non-metallic fibers. Metallic brush seals typically include fibers made from cobalt or nickel-base high temperature superalloy wire products suitable for elevated temperature operation. Non-metallic brush seals can include fibers made from ceramic or polymeric materials.

FIG. 1 shows a portion of a conventional brush seal. Conventional brush seals include a bristle pack 1, which is traditionally flexible, and includes a plurality of bristles 2 for sealing the gap, the bristles 2 having a free end for contacting one component, such as the rotor. The bristles 2 in the prior art bristle pack 1 are typically secured to a support 3 by crimping a channel 4 over the the bristles 2. Securing the bristles 2 using the clamping channel 4, such as shown and described in U.S. Pat. No. 4,730,876, is often difficult because the bristles 2 are not secured until the clamping channel 4 is crimped over the support 3 and bristles 2. As a result, this method of fabrication is time consuming and expensive. Therefore, a need exists for a bristle pack and resulting brush seal that is simple and easy to fabricate.

SUMMARY OF THE INVENTION

The present invention provides a bristle pack for use in a brush seal, a brush seal, and method of making the bristle pack. The bristle pack includes an elongated support and a plurality of bristles. The bristles are folded over the support defining a fold, and are joined together adjacent the support opposite the fold.

A general objective of the present invention is to provide a bristle pack, brush seal, and method of making a bristle pack that is simple and easy to manufacture. This objective is accomplished by providing a bristle pack that includes bristles folded over a support and joined together adjacent the support opposite a fold.

These and still other objects and advantages of the present invention will be apparent from the description which follows. In the detailed description below, preferred embodiments of the invention will be described in reference to the accompanying drawings. These embodiments do not represent the full scope of the invention. Rather the invention may be employed in other embodiments. Reference should therefore be made to the claims herein for interpreting the breadth of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

It should be understood that the drawings are provided for the purpose of illustration only and are not intended to define the limits of the invention. The present invention is not limited to the precise arrangements and instrumentalities shown in the drawings, and the drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles disclosed herein, wherein:

FIG. 1 is a perspective view of a mechanically captured prior art brush seal;

FIG. 2 is a schematic illustration of a brush seal design including a flexible front and back plate mounted in a housing;

FIG. 3 is a front view of the bristle pack of FIG. 2 incorporating the present invention;

FIG. 4 is a detailed view along line 4-4 of FIG. 3;

FIG. 5 is a perspective view of a group of bristles of FIG. 3;

FIG. 6 is a front view of a partially assembly bristle pack of FIG. 3;

FIG. 7 is a front view of an another embodiment of the bristle pack of FIG. 2 incorporating the invention;

FIG. 8 is a front perspective view of three groups of bristles of FIG. 7; and

FIG. 9 is a rear perspective view of the three groups of bristles of FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring initially to FIG. 2, there is illustrated a brush seal 10 having a bristle pack 12 including a plurality of bristles 14 folded around a support 16, such as a rod or core. The bristles 14 wrap around the support 16 as shown schematically in FIG. 2 to form the bristle pack 12. In the embodiment shown in FIG. 2, the bristle pack 12 is mounted in a brush seal housing 18 which can be attached to a rotor 26 with the bristles 14 extending radially inwardly engaging a rotating shaft 24. Of course, the brush seal housing 18 can be attached to the rotating shaft 24 with the bristles 14 engaging the rotor 26 without departing from the scope of the invention.

The support 16 is preferably a solid or braided core wire formed from a flexible metal. The support 16 is formed into any desired shape required for the brush seal application. Although a flexible support is preferred, the support 16 can be a rigid frame without departing from the scope of the invention. Most preferably, the support 16 does not have any rough edges that can cut or severe the bristles 14 secured thereto.

The bristles 14 are wrapped or folded over the support 16 defining a fold 28 at an outer diameter of the support 16 when the support 16 has a circular shape, such as shown in FIG. 3. Distal ends 32 of each bristle 14 extend radially inwardly for engagement with the shaft 24. Of course, if the brush seal 10 is mounted onto the shaft 24, the bristle folds 28 would be defined at an inner diameter of the circular support 16 and the distal ends 32 of the bristles 14 would extend radially outwardly.

The bristles 14 are secured to the support 16 by joining the bristles 14 together adjacent to the support 16 opposite of the fold 28. In the embodiment disclosed in FIGS. 3-6, the bristles 14 are secured onto the support 16 by a sewn thread 36 which joins the bristles 14 together adjacent the support 16 opposite the folds 28 in the bristles 14. The thread 36 used to join the bristles 14 can be the same material as the bristles 14 or any other suitable thread, such as cotton, metal, polymer, ceramic, and the like. The bristles 14 can be grouped or banded together into discrete tufts, as shown in FIGS. 3-6, or into a long continuous strip without departing from the scope of the invention.

A clamping channel 4, such as the conventional channel shown in FIG. 1, or U-ring, may be utilized to further secure the bristles 14 to the support 16 by crimping the channel 4 over the folded bristles 14. For added security, the bristles 14 may be glued or cemented to the support, as desired.

In one embodiment of the present invention, the bristles 14 are formed from twisted or braided ceramic or polymeric filaments of about 0.02-0.05 inches in diameter. The ceramic bristles can be made from suitable high temperature ceramic filaments, including, but not limited to: ceramic oxides such as Aluminum Oxide, Silicon Oxide, Boron Oxide, and Nextel™ fiber; Silicon carbide fiber; and other ceramic fibers generally made for ceramic/metal or ceramic/ceramic composites. Polymeric bristles can be made from suitable high temperature polymeric materials, including, but not limited to: KEVLAR® brand filaments for extremely high strength; and NOMEX® filaments for high strength and moderate temperature (˜300° C.) applications. Both KEVLAR® and NOMEX® are synthetic aromatic polyamide polymer manufactured by DuPont. Other suitable polymeric materials may be utilized for the twisted or braided filaments for brush seals, as would be known to those of skill in the art.

In one embodiment, NOMEX® fibers are preferred because the NOMEX® fibers are generally made into strong fabrics for applications where thermal and flame resistant properties are essential. NOMEX® fibers are very thin, in the range of about 25 micrometers to 0.001 inches in diameter, and have a low modulus of elasticity. The twisted NOMEX® fibers are much thicker than the individual fibers, the twisted fibers having a thickness in the range of about 900 micrometers to 0.036 inches in diameter and they are rigid enough to make brush strips using the conventional automatic brush strip manufacturing process. This helps to reduce the fabrication cost of NOMEX® brush strips which will be formed or rolled into brush seal inserts as explained below.

In order to facilitate bending of polymeric fibers during rotor excursions, the fiber strip can be inclined axially in the direction of the fluid flow, toward the low pressure (L_P) side. To provide some rigidity, the flexible bristle pack 12 can be held in an axially inclined position between a thinner front plate 44 and back plate 48 which are attached to more rigid front plate 52 and rigid back plate 54 forming the brush seal housing 18 as shown in FIG. 2. Of course, the bristle pack 12 can be inclined toward the high pressure side, if desired, without departing from the scope of the invention.

The flexible plates may extend a predetermined length of the bristles 14 so as to expose only the bristle distal ends 32, and protect the softer polymeric fibers from being damaged (luring installation and mishandling. The polymeric brush seal may be attached to the stator housing or to a rotor 26 at a first end for an intershaft seal configuration and contact rotating shaft 24 at a second end. For a rotating seal, the stresses in the polymeric fibers resulting from the centrifugal force are minimized as the bristle pack is supported by flexible metallic back plate segments. The metallic segments are designed to withstand the maximum bending stress due to centrifugal force. By securing the bristles 14 between axially inclined coned front and back plates 44, 48, 52, 54 in the direction of the fluid flow, the plates 44, 48, 52, 54 including the rigid plates 52, 54 at the outer diameter and the thinner plates 44, 48 at the inner diameter, bristle pack displacement is controlled and stresses in the bristle pack 12 are minimized.

In the embodiment shown in FIGS. 3-6, the bristle pack 12 is made by folding or wrapping the bristles 14 around the support 16 until a desired bristle density is achieved. Wrapping or folding the bristles 14 around the support 16 forms the fold 28 in each bristle 14. As described above, the bristles 14 can be made out of metals, ceramics, polymers, organic materials or any combination of materials. The bristles 14 are secured onto the support 16 by the sewn thread 36 which joins the bristles 14 together adjacent the support 16 opposite the folds 28 in the bristles 14.

Once the desired length of bristle pack 12 is achieved, the ends 42 of the support 16 are welded together. Ideally this is a butt weld, but the ends 42 could also be glued or held together by other means. The final assembly of the embodiment disclosed herein is then formed into a hoop and can be assembled into adaptive hardware, such as the housing 18, of the brush seal assembly 10. Preferably, the support 16, and thus the bristle pack 12, is formed into a loop or circle. However, the bristle pack 12 can be shaped into any form, such as a square, rectangle, oval, triangle, and the like, without departing from the scope of the invention.

In another embodiment shown in FIGS. 7-9, a bristle pack 112 is made by wrapping bristles 114 around a support 116 forming a fold 128 in each bristle 114, as described above. In the embodiment shown in FIGS. 7-9, a metal clip 132, such as staple, is wrapped, such as by stapling, around a discrete group of the bristles 114. The clip 132 joins the bristles 114 together adjacent the support 116 opposite the folds 128 in the bristles 114 forming an individual tuft 144. An adjacent tuft 114 is formed by an adjacent clip 132 wrapped around an adjacent group of bristles 114. Advantageously, each clip 132 quickly and efficiently secures the respective group of bristles to the support.

It will be understood that various modifications may be made to the embodiments disclosed herein. Therefore, the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments. Those skilled in the art will envision other modifications within the scope, spirit and intent of the invention.

Claims

1. A bristle pack for use in a brush seal comprising:

a support; and

a plurality of bristles folded over said support and defining a fold, said bristles being joined together adjacent said support opposite said fold.

2. The bristle pack as in claim 1, in which at least some of said bristles are joined together by a sewn thread.

3. The bristle pack as in claim 1, in which at least some of said bristles are joined together by a clip.

4. The bristle pack as in claim 1, in which said bristles are metallic.

5. The bristle pack as in claim 1, in which said bristles are non-metallic.

6. The bristle pack as in claim 1, in which said support is a flexible wire.

7. The bristle pack as in claim 1, in which said plurality of bristles are formed into a plurality of groups of bristles, each of said groups of bristles being banded together adjacent said support opposite said fold.

8. The bristle pack of claim 7, wherein at least one of said groups of bristles is banded by a clip.

9. The bristle pack as in claim 7, in which at least one of said groups of bristles is banded by a sewn thread.

10. A method of making a bristle pack comprising:

folding a plurality of bristles over a support and forming a fold in each of said bristles; and

joining adjacent bristles together adjacent said support opposite said fold to secure said bristles to said support.

11. The method as in claim 10, in which joining adjacent bristles together includes attaching a clip to at least some of said bristles.

12. The method as in claim 10, in which joining adjacent bristles together includes sewing at least some of said bristles together into a group.

13. The method as in claim 10, including forming said support into a ring.

14. The method as in claim 13, including joining a first end and a second end of said support together.

15. A brush seal comprising:

a bristle pack including a support and a plurality of bristles folded over said support and defining a fold, said bristles being joined together adjacent said support opposite said fold.

16. The brush seal as in claim 15, in which at least some of said bristles are joined together by a sewn thread.

17. The brush seal as in claim 15, in which at least some of said bristles are joined together by a clip.

18. The brush seal as in claim 15, in which said bristles are metallic.

19. The brush seal as in claim 15, in which said bristles are non-metallic.

20. The brush seal as in claim 15, in which said support is a flexible wire.

21. The brush seal as in claim 15, in which said plurality of bristles are formed into a plurality of groups of bristles, each of said groups being banded together adjacent said support opposite said fold.