BRUSH SEAL WITH A CORE RING WRAPPED BY BRISTLE BUNDLES

JOINT A BROSSE A ANNEAU CENTRAL ENTOURE DE FAISCEAUX DE POILS

English Abstract

A brush for sealing a gap between a rotor/stator system
comprises a rotor-concentric clamping ring whose interior chamber
receives bristle bundles that project into gap. The bundles are
wrapped around core ring that extends into the interior of
clamping ring. The core ring has separating disks that are
spaced apart from one another in the circumferential direction
by an angular pitch .alpha., and by winding ribs that are wrapped by
the bundles. The winding ribs connect adjacent separating disks
in such fashion that as a result of the diagonal positioning of
separating disks in the circumferential direction, bundles are
aligned at an angle .beta. to radius R. This makes it possible to hold
bristle bundles securely with a predetermined angular
orientation.

French Abstract

L'invention concerne un joint à brosse servant à obturer un espace compris entre un rotor et un stator. Ledit joint à brosse comporte un anneau de serrage (4) qui est concentrique au rotor et dont l'intérieur (I) loge les faisceaux (6) dont les extrémités (7) font saillie dans ledit espace (S), lesdits faisceaux (6) entourant un anneau central (5) s'étendant à l'intérieur (I) de l'anneau de serrage (4). L'objectif de l'invention est de créer un joint à brosse qui permet aux poils (6) d'être positionnés obliquement dans le sens de la circonférence pour compenser des déplacements radiaux du rotor ou de l'arbre. A cet effet, il est proposé que l'anneau central (5) soit constitué de disques de séparation (10) espacés les uns des autres selon un angle de pas alpha , dans le sens de la circonférence, et de pièces transversales d'enroulement (11) autour desquelles les faisceaux de poils (6) sont enroulés. Lesdits éléments transversaux d'enroulement (11) relient des disques de séparation (10) adjacents de façon alternée, de sorte que les faisceaux de poils (6) soient alignés par le positionnement oblique de disques de séparation (10) dans le sens de la circonférence, à un angle beta par rapport à la ligne radiale (R). Ainsi, les faisceaux de poils (6) peuvent être fixés de façon sûre selon un angle prédéterminé.

Claims

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:

1. A brush seal for sealing an annular gap between a
rotor/stator arrangement, having a rotor-concentric clamping ring
with a toroidal interior chamber that receives bristle bundles
whose ends project out of a circumferential slot of the clamping
ring toward the gap, such bundles being wrapped around a core
ring that extends in the interior chamber, wherein:
the core ring comprises separating disks that are spaced apart
in the circumferential direction by an angular pitch .alpha., and
winding ribs that are wrapped by bundles;
the winding ribs and separating disks are arranged in
alternating sequence; and
the separating disks are disposed diagonally in the
circumferential direction, whereby the bundles are aligned at an
angle to a radius of the rotor.

2. The brush seal according to claim 1, wherein an angle
between adjacent separating disks corresponds to the angular
pitch .alpha..

3. The brush seal according to claim 1 or 2, wherein the
separating disks have a matching outside diameter to receive the
clamping ring in a toroidal interior chamber.

4. The brush seal according to claim 1, 2 or 3, wherein the
separating disks are elliptical.

5. The brush seal according to any one of claims 1 to 4,
wherein the winding ribs have a circular cylindrical cross
section.

6. The brush seal according to any one of claims 1 to 5,
wherein the angular pitch .alpha. is less than or equal to 10° C.



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7. The brush seal according to any one of claims 1 to 6,
wherein the bristles comprise a silicon carbide material.

8. The brush seal according to any one of claims 1 to 7,
wherein adjacent separating disks and winding ribs form H- or N-
shaped angle sections of the core ring in the circumferential
direction.

9. A method of manufacturing a core ring for a brush seal in a
rotor/stator arrangement having a core ring disposed in a
circumferentially extending clamping ring, said core ring
comprising a plurality of separating disks which are aligned at a
predetermined angle relative to a radius of said rotor/stator
arrangement, are connected by a plurality of winding ribs and are
spaced apart in circumferential direction by a predetermined
angular pitch, said method comprising:
providing a wire with a diameter that corresponds to a diameter
of an interior chamber of the clamping ring, at least along a
circumferential length of the interior chamber;
a clamping the wire;
relative cutting circumferential grooves in the wire at an
angle relative to a lengthwise axis of the wire which angle is
approximately equal to the predetermined angle, said grooves
being spaced apart from one another along said lengthwise axis at
a separation which corresponds to said predetermined angular
pitch; and
bending and connecting ends of the wire to form a core ring.

10. A brush seal for sealing a circumferentially extending gap
in a rotor/stator arrangement, said brush seal comprising:
a rotor concentric clamping ring having a circumferentially
extending interior chamber;
a core ring arranged in said interior chamber and having a
cross sectional shape and diameter that correspond to a cross
sectional shape and diameter of said interior chamber; and



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a plurality of radially inwardly extending bristle bundles
connected on said core ring; wherein
the core ring comprises a plurality of separating disks which
are aligned diagonally at a predetermined first angle relative to
a radius of said rotor/stator arrangement, are connected by a
plurality of winding ribs and are spaced apart in a
circumferential direction by a fixed angular pitch; and
said bristle bundles are wrapped on said core ring and
separated by said separating disks, whereby said bristle bundles
extend radially diagonally inward at an angle relative to said
radius of said rotor/stator arrangement, which angle corresponds
to said first angle.

11. The brush seal according to claim 10, wherein said cross
sectional shape of said interior chamber of said clamping ring is
substantially circular, and said diagonally aligned separating
disks are substantially elliptical shaped.



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Description

CA 02223156 2004-04-05
Brush Seal with a Core Ring Wrapped by Bristle Bundles
BACKGROUND AND SUNll~IARY OF THE INVENTION
The invention relates to a brush seal for sealing an annular
gap between a rotor/stator arrangement, and to a method for
.5 manufacturing such a brush seal.
The brush seals are mounted in a stator housing surrounding
a rotor concentrically, with the bristles fitting together
closely and being arranged at an angle to the radius. The ends
of the bristles touch the rotor at its circumference, or end
shortly before, so that they provide a seal between chambers
which are subjected to different pressures on both sides of the
seal under all operating conditions. Because of their elasticity
and their angular position relative to the rotor, the bristles
can bend to compensate for eccentricities of the rotor and/or
shaft and for rotor imbalance.
A brush seal of the generic type is disclosed in German
patent document DE-OS 39 07 614. However, because the bristles
are wrapped around a rotor-concentric clamping ring- and
surrounded by a C-shaped clamping ring, diagonal alignment of the
bristles relative to the rotor is not possible, especially at
larger angles, and the bristles cannot maintain a given diagonal
angular pitch during operation. In addition, stronger clamping
of the bristles, especially in the case of ceramic fibers, is not
possible since high pressure at the edge causes premature wear
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CA 02223156 2004-04-05
or breakage of the bristles. This is especially true with regard
to the desirable use of very fine and/or extremely thin bristles.
The object of the invention, therefore, is to provide a
brush seal that permits diagonal positioning of the bristles
relative to the rotor and ensures the functional reliability of
the brush seal while maintaining the angular pitch of the
bristles over the entire operating range. A method is also
provided for simple manufacture of the core ring of such a brush
seal_
These and other objects and advantages are achieved
according to the invention by using a plurality of separating
disks spaced apart from one another at an angular pitch a, so
that a uniform diagonal angular pitch is assumed over the entire
circumference of the brush seals. The bristle bundles thus
aligned by the separating disks each surround a winding rib which
is located between the separating disks and also connects
adjacent separating disks with one another. Together with the
clamping force exerted by the clamping ring, it is possible to
secure the bristle bundle reliably at the predetermined angular
orientation.
One advantage of the invention is that by using separating
disks mounted at an angle in the interior of the clamping ring,
the bristle bundles are forcibly aligned at an angle ~i relative
to the circumference of-the rotor without extreme clamping force
25. being required to hold the bristle bundles..
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Another advantage of the invention is that by using a
straight blank (for example a wire) the core ring, consisting of
separating disks and winding ribs arranged alternately, can be
manufactured in an economical fashion by sawing or milling. When
a disk milling cutter is used, whose disk thickness corresponds
to the distance between two adjacent separating disks, it cuts
circumferential grooves in the wire as it makes a pass in a
circular movement around the wire so that a winding rib of the
desired diameter remains between two adjacent separating disks.
20 The position of the axis of the disk milling cutter relative to
the lengthwise axis of the wire, at an angle that corresponds to
the angular pitch of the separating disks relative to the radius,
permits a diagonal orientation of the separating disks relative
to the axis of the core ring as well as an elliptical shape of
Z5 the separating disks.
After each pass, the wire is advanced by the constant
distance between the separating disks in the clamp, so that the
separating disks together with the winding ribs are gradually cut
from the wire. When the wire has been machined over its entire
20 length, it is bent into a core ring and joined. The finished core
ring can then be provided with the bristles and placed _in the
clamping ring. Final machining to produce a brush seal then
follows.
Other objects, advantages and novel features of the present
25 invention will become apparent from the following detailed
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CA 02223156 2004-04-05
description of the invention when considered in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a partial sectional view of a_rotor/stator
arrangement in which two bristle bundles are shown as an example
in an angular position;
Figure 2 is a cross section through a brush seal taken along
line z-z in Figure 1; and
Figure 3 is a schematic view of a clamping device with wire
for the manufacture of a core ring_
DETAILED DESCRIPTION OF DRAWINGS
Figure 1 shows a brush seal 1 for a turbo machine (not shown
in greater detail). The seal is formed concentrically between
a rotor 2 and a stator 3, and serves to provide a seal between
two chambers subjected to different pressures. To receive the
numerous bristle bundles 6, brush seal 1 has a clamping ring 4
with a toroidal interior Chamber i as well as a core ring 5 that
is likewise concentric with respect to the rotor, and is located
inside core ring 4.
As is also shown in Figure 2, the free- ends 7 of bristle
bundles 6 project out of a circumferential slot 8 that opens
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CA 02223156 2004-04-05
radially inward from clamping ring 4. The free ends 7 abut a
sealing surface 9 that surrounds rotor 2, thus sealing gap S
between rotor 2 and stator 3.
As can also be seen from Figure 1, bristle bundles 6 are
mounted diagonally at an angle~~ of 45° relative to a radius R.
The ends thus abutting sealing surface 9 at an angle produce an
improved sealing effect for the entire system by contrast with
bristles that are aligned exactly radially.
As can also be seen from Figure 2, bristle bundles 6 are
to held by core ring 5 and surrounded by clamping ring 4. For this
purpose, the core ring 5 is composed of alternatively arranged
elliptical separating disks 10 and winding ribs 11 in the shape
of a circular cylinder. The separating disks 10 are spaced apart
from one another, and aligned relative to one another at an angle
y, (Figure 1), and for alignment of bristle bundles 6, are
mounted diagonally at an angle a = 45° to rotor axis A, so that
they hold bristle bundles 6 in the desired alignment. Winding
ribs 11 that join adjacent separating disks 10 to one another are
mounted diagonally at a 45° angle relative to the tangential
alignment so they can be wrapped by a bristle bundle 5. As a .
result of all the bristles forming a loop around a winding rib
11, assurance is provided that all the bristles are equally
protected against pulling out of clamping ring 4.
Brush seal Z shown in Figure 2 has a welded sealing housing
12 which surrounds clamping ring 4 and opens radially inward to
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accept bristle bundle 6 in a circumferential slot 8' _ A brush
seal 1 housed in this fashion can then be used in a rotor/stator
arrangement.
Figure 3 shows a work step for manufacture the core ring 5
with its H-shaped angular sections by means of a disk milling
cutter 13.. A straight wire 4 mm in diameter is used as the blank
for core ring 5 and is clamped in a clamping device 15 at an
angle b = 45° to a work plane for milling circumferential grooves
14. This clamping angle b results from the desired angular pitch
~B of the bristle bundle and separating disks 10. A disk milling
cutter 13 (whose disk thickness b matches circumferential groove
14 or the space between adjacent separating disks 10) gradually
cuts circumferential grooves 14 into the wire. For this purpose,
disk milling cutter 13 performs a circular movement around an
axis that is identical to the axis of symmetry W of 'the angle rib
11 to be cut out.
One circuit of disk milling cutter 13 around axis of
symmetry W cuts the diagonal circumferential groove 14, and a
cylindrical winding rib 11 remains. The wire is then pushed
outward from clamping device 15 for a distance that corresponds
to the arcuate spacing of separating disks 10, and the wire is
clamped again to cut the next circumferential groove.
This workstep is repeated as frequently as:necessary until
the desired length of the wire is provided with circumferential
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grooves 14. Then the wire is bent into a core ring 5 and the ends
are joined together.
Although the invention has been described and illustrated
in detail, it is to be clearly understood that the same is by way
of illustration and example, and is not to be taken by way of
limitation. The spirit and scope of the present invention are
to be limited only by the terms of the appended claims_
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Representative Drawing