AXIAL DYNAMIC BRUSH SEAL
FIELD OF THE INVENTION
This subject invention relates to brush seals and in particular a new axial,
dynamic brush seal and brush seal system.
BACKGROUND OF THE INVENTION
Brush seals are well known. See U.S. Patent No. 6,231,047 incorporated
herein by this reference. Typically, the bristles of the brush seal are disposed between
a front plate and a back plate surrounding a rotating shaft. The free ends of the
bristles engage the shaft sealing it with respect to a housing. Most prior art brush
seals are thus radial in design in that the bristles extend radially towards the rotating
shaft.
U.S. Patent No. 5,480,162, also incorporated herein by this reference,
proposes an axial brush seal for sealing a combustor assembly with respect to an
adjoining stator assembly in a gas turbine engine. The stator assembly does not move
but the combustor assembly does move towards and away from the stator assembly.
The brush seal bristles provide a seal between the combustor assembly and the stator
assembly and the back plate of the brush seal is designed to bear against the stator
assembly to transmit axial loads. See also U.S. Patent Nos. 6,170,831 and 5,114,159
also incorporated herein by this reference. U.S. pending Patent Application Nos. U.S.
2005/0110218 and U.S. 2003/0131602, also incorporated herein by this reference,
propose axial brush seal arrangements which are floating but require complex housing
arrangements and have no provisions for pressure induced blow-down of the bristles

against the mating ring or runner.
To our knowledge, the prior art does not disclose a flexible axial brush seal
which can be easily implemented into a sealing system used dynamically to seal a
rotor such as a rotating shaft with respect to a housing through which the rotor
extends.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide an axial brush seal for
sealing a rotor such as a rotating shaft and useful in turbine engines, steam turbines,
compressors, blowers, fans, mixers, turbocharges, and other rotating hardware such as
spindles.
It is a further object of this invention to provide such an axial, dynamic brush
seal which is easy and economical to manufacture.
The subject invention results from the realization that if a brush strip element
of a radial brush seal is bent 90° out of plane, it can now be used as an axial, dynamic
seal and manufactured easily and economically.
The subject invention, however, in other embodiments, need not achieve all
these objectives and the claims hereof should not be limited to structures or methods
capable of achieving these objectives.
This subject invention features an axial and dynamic brush seal system. A
mating ring is attached to a rotor and has a sealing surface. A plurality of bristles are
disposed about the rotor and extend axially so the terminal free ends of the bristles
engage the sealing surface of the mating ring. la one example, the rotor extends along a
longitudinal axis and the sealing surface of the mating ring is angled with respect to an

axis perpendicular to the longitudinal axis. The sealing surface can be angled away
from the bristles or towards the bristles. In another example, the bristles are angled
with respect to the sealing surface of the mating ring. The sealing surface of the
mating ring can be angled to match the terminal free ends of the bristles in a blow
down condition.
There is typically a housing for the bristles. In one example, the housing
includes an axially extending front plate and an axially extending back plate about the
bristles. Further included may be a retainer for the bristles sandwiched between the
front and back plates.
In one example, the housing includes a subsystem configured to urge the free
ends of the bristles against the sealing surface of the mating ring. For example, the
housing may include a first magnet and a second magnet is associated with the bristles
to urge the free ends of the bristles against the sealing surface of the mating ring.
An axially extending dynamic brush seal in accordance with the subject
invention features a plurality of bristles configured to be disposed about a rotor. The
terminal ends of the bristles are designed to engage a sealing surface attached to the
rotor. There is also a housing for holding the bristles.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features and advantages will occur to those skilled in the art
from the following description of a preferred embodiment and the accompanying
drawings, in which:
Fig. 1 is a schematic cross-sectional view of a typical prior art radial brush
seal;

Fig. 2 is a schematic side cross-sectional view showing one embodiment of a
brash seal assembly in accordance with the subject invention;
Fig. 3 is a schematic cross-sectional side view showing another embodiment
of a brush seal assembly in accordance with the subject invention;
Fig. 4 is a schematic cross-sectional side view showing still another
embodiment of a brush seal assembly in accordance with the subject invention;
Fig. 5 is a schematic cross-sectional side view showing still another
embodiment of a brush seal assembly in accordance with the subject invention;
Fig. 6 is a schematic cross-sectional side view showing still another
embodiment of a brush seal assembly in accordance with the subject invention;
Fig. 7 is a schematic cross-sectional side view showing still another
embodiment of a brush seal assembly in accordance with the subject invention; and
Fig. 8 is a schematic cross-sectional side view showing an embodiment of a
brush seal assembly in accordance with the subject invention including a subsystem
for urging the free ends of the bristles against the mating ring.
DISCLOSURE OF THE PREFERRED EMBODIMENT
Aside from the preferred embodiment or embodiments disclosed below, this
invention is dapable of other embodiments and of being practiced or being carried out
in various ways. Thus, it is to be understood that the invention is not limited in its
application to the details of construction and the arrangements of components set forth
in the following description or illustrated in the drawings. If only one embodiment is
described herein, the claims hereof are not to be limited to that embodiment.
Moreover, the claims hereof are not to be read restrictively unless there is clear and

convincing evidence manifesting a certain exclusion, restriction, or disclaimer.
In a typical radial brush seal installation, brush seal 10, Fig. 1 is arranged such
that bristles 12 surround shaft 14, extend towards the shaft, and the free end of the
bristles engage the shaft as shown in Fig. 1.
Axial brush seal system 20, Fig. 2 in accordance with this subject invention, in
contrast, includes rotor 22, typically a rotating shaft, and mating ring 24 attached to
rotor 22 to rotate with it. Mating ring 24 includes or defines sealing surface 26.
Bristles 28 of axially disposed brush seal 30 are disposed about rotor 22 and
extend axially in the same direction as the longitudinal axis of rotor 22 such that the
terminal free ends of bristles 28 engage sealing surface 26 of mating ring 24. Bristles
28 provide for adequate sealing even when mating ring 24 and rotor 22 move in the
axial direction shown by arrow 29 and/or in a direction transverse to arrow 29.
One example of a brush seal in accordance with the subject invention includes
a stationary housing fixed to a non-rotating component of the structure (not shown)
through which rotor 22 extends. The brush seal housing includes front plate 34 and
back plate 32 with retainer 36 sandwiched therebetween to hold the non-free ends of
the bristles. See U.S. Patent No. 6,231,047. Fastener 38 secures back plate 34 to
front plate 32. In other embodiments, however, the back plate and the front plate may
be welded or otherwise fixed to each other. Neither the front nor the back plates
contact sealing surface 26. Other designs for the housing of the bristles of the brush
seal are known to those skilled in the art. This brush seal element does not require
complex front plate or back plate components but rather a groove in the supporting
housing with a simple retainer. The axial brush seal of the subject invention
maintains a seal through large axial excursions. The flexible brush strip of U.S.

Patent No. 6,231,047 requires only minimal required radial height to implement the
brush seal element.
In another embodiment, bristles 28, Fig. 3 are angled with respect to sealing
surface 26 to take advantage of the bristle spread caused by the rotation of rotor 22 in
the direction shown in Fig. 3 by arrow 31.
In still another example, the sealing surface is angled with respect to an axis A
perpendicular to the longitudinal axis L of rotor 22 as shown in Figs. 4 and 5. Such a
design assists in sealing and the slant angle of the sealing surface better tolerates axial
travel. In the example of Fig. 4, sealing surface 26' of mating ring 24' is angled at an
angle 0i away from bristles 28 in the case where the higher pressure is located at the
outside of the bristles. This design is particularly useful for 0 layer angle. Since the
bristles in a 0 layer angle brush seal are parallel to the shaft centerline, the pack is
much stiffer and provides high resistance to axial travel. Thus, placing an angle on
the mating ring helps the seal during axial travel by allowing the bristles to displace in
a radial motion while still providing a seal against the tapered surface. In the example
of Fig. S, sealing surface 26" of mating ring 24" is angled at an angle 62 towards
bristles 28 in the case where the higher pressure is located at the inside of the bristles.
0i may be between 0° and 45°; 82 may be between 0°and 45°.
In another embodiment, bristles 28, Figs. 6 and 7 are angled with respect to
the sealing surface during high-pressure induced blow-down where the bristles
adjoining back plate 32 attempt to straighten out. This condition produces a tapered
shape on the free ends of the bristles as shown. By matching the sealing surfaces 26'"
and 26|V angles to the bristle blow-down condition, the seal will essentially run in a
line-to-line state with the rotating surface during operation.

In any embodiment and in any implementation, such an axial, dynamic brush
seal is fairly simple to manufacture and readily accommodates movement of the shaft.
The brush strip element of the radial brush seal disclosed in U.S. Patent No.
6,231,047 can be bent 90° out of plane so it can now be used in an axial seal
implementation and manufactured easily and economically. The brush seal flexible
element, due to its small size, can be easily integrated into the supporting housing
with the addition of a groove cut into the housing and a simple retaining feature. The
brush seal flexible element is also light weight and therefore can be made to track the
sealing surface by use of permanent magnets to create a closing force.
In the embodiment of Fig. 8, for example, back plate 32 includes permanent
magnet insert 50 and brush seal retainer 36 includes permanent magnet 52 of the same
polarity as permanent magnet 50 to urge retainer 36 and thus the free ends of bristles
28 against sealing surface 26 of mating ring 24. Other subsystems configured to urge
the free ends of bristles 28 against the sealing surface 26 of mating ring 24 may also
be employed including the combination of magnets 54 and 52.
Although specific features of the invention are shown in some drawings and
not in others, this is for convenience only as each feature may be combined with any
or all of the other features in accordance with the invention. The words "including",
"comprising", "having", and "with" as used herein are to be interpreted broadly and
comprehensively and are not limited to any physical interconnection. Moreover, any
embodiments disclosed in the subject application are not to be taken as the only
possible embodiments. Other embodiments will occur to those skilled in the art and
are within the following claims.
In addition, any amendment presented during the prosecution of the patent

application for this patent is not a disclaimer of any claim element presented in the
application as filed: those skilled in the art cannot reasonably be expected to draft a
claim that would literally encompass all possible equivalents, many equivalents will
be unforeseeable at the time of the amendment and are beyond a fair interpretation of
what is to be surrendered (if anything), the rationale underlying the amendment may
bear no more than a tangential relation to many equivalents, and/or there are many
other reasons the applicant can not be expected to describe certain insubstantial
substitutes for any claim element amended.
What is claimed is:

1. An axial and dynamic brush seal system comprising:
a rotor;
a mating ring attached to the rotor and having a sealing surface; and
a plurality of bristles about the rotor and extending axially, the terminal
free ends of the bristles engaging the sealing surface of the mating ring.
2. The brush seal system of claim 1 in which the rotor extends along a
longitudinal axis and the sealing surface of the mating ring is angled with respect to
an axis perpendicular to the longitudinal axis,
3. The brush seal system of claim 2 in which the sealing surface is angled
away from the bristles.
4. The brush seal system of claim 2 in which the sealing surface is angled
towards the bristles.
5. The brush seal system of claim 2 in which the sealing surface of the
mating ring is angled to match the terminal free ends of the bristles in a blow down
condition.
6. The brush seal system of claim 1 further including a housing for the
bristles.
7. The brush seal system of claim 6 in which the housing includes an

axially extending front plate and an axially extending back plate about the bristles.
8. The brush seal system of claim 7 further including a retainer for the
bristles sandwiched between the front and back plates.
9. The brush seal system of claim 6 in which the housing includes a
subsystem configured to urge the free ends of the bristles against the sealing surface
of the mating ring.
10. The brush seal system of claim 9 in which the subsystem is magnetic.
11. The brush seal system of claim 10 in which the housing includes a first
magnet and there is a second magnet associated with the bristles to urge the free ends
of the bristles against the sealing surface of the mating ring.
12. The brush seal system of claim 1 in which the bristles are angled with
respect to the sealing surface.
13. An axial and dynamic brush seal system comprising:
a rotor;
a mating ring attached to the rotor and having a sealing surface; and
a stationary housing including a plurality of bristles extending
therefrom disposed about the rotor, the bristles extending axially and the terminal free
ends of the bristles engaging the sealing surface of the mating ring.

14. The brush seal system of claim 13 in which the rotor extends along a
longitudinal axis and the sealing surface of the mating ring is angled with respect to
an axis perpendicular to the longitudinal axis.
15. The brush seal system of claim 14 in which the sealing surface is
angled away from the bristles.
16. The brush seal system of claim 14 in which the sealing surface is
angled towards the bristles.
17. The brush seal system of claim 13 in which the sealing surface of the
mating ring is angled to match the terminal free ends of the bristles in a blow down
condition.
18. The brush seal system of claim 13 in which the housing includes an
axially extending front plate and an axially extending back plate about the bristles.
19. The brush seal system of claim 18 further including a retainer for the
bristles sandwiched between the front and back plates.
20. The brush seal system of claim 13 in which the housing includes a
subsystem configured to urge the free ends of the bristles against the sealing surface
of the mating ring.

21. The brush seal system of claim 20 in which the subsystem is magnetic.
22. The brush seal system of claim 21 in which the housing includes a first
magnet and there is a second magnet associated with the bristles to urge the free ends
of the bristles against the sealing surface of the mating ring.
23. The brush seal system of claim 9 in which the bristles are angled with
respect to the sealing surface.
24. An axially extending dynamic brush seal comprising:
a plurality of bristles configured to be disposed about a rotor wherein
the terminal ends of the bristles engage a sealing surface attached to the rotor; and
a housing for holding the bristles.
25. The brush seal system of claim 24 in which the housing includes an
axially extending front plate and an axially extending back plate about the bristles.
26. The brush seal system of claim 25 further including a retainer for the
bristles sandwiched between the front and back plates.
27. The brush seal system of claim 24 in which the housing includes a
subsystem configured to urge the free ends of the bristles against the sealing surface
of the mating ring.

28. The brush seal system of claim 27 in which the subsystem is magnetic.
29. The brush seal system of claim 28 in which the housing includes a first
magnet and there is a second magnet associated with the bristles to urge the free ends
of the bristles against the sealing surface of the mating ring.
30. An axial and dynamic brush seal for a system including a mating ring
attached to a rotor and defining a sealing surface, the brush seal comprising:
a plurality of bristles to be disposed about the rotor, the bristles
extending axially to engage the sealing surface of the mating ring.

An axial and dynamic brush seal system wherein a mating ring is attached to a
rotor and has a sealing surface. The bristles of the brush seal are disposed about the rotor
and extend axially so that the terminal free ends of the bristles engage the sealing surface
of the mating ring.