Brush seal device

Details Brush seal device Brush seal device

2002-06-18

2004-07-20

Pickard, Alison (Department: 3676)

Seal for a joint or juncture

Seal between relatively movable parts

Brush seal

Reexamination Certificate

active

06764078

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a brush seal device for sealing a clearance formed between a shaft and its mating component that are relatively displaceable. More particularly, the present invention relates to a brush seal device for sealing a clearance formed between two components relatively displaceable, wherein a split brush-seal piece of a thin plate has a brush section on its one side and a base section on the other side and is formed with a projection on its one split face and a recess on its other split face, both the projection and recess being able to engage the corresponding recess and projection on the mating brush-seal pieces, respectively, and a plurality of split brush-seal pieces are connected in order to obtain a brush seal in any size.
2. Description of Related Art
As one related art to the present invention there exists a brush seal device
100
, as shown in FIG.
14
.
FIG. 14
is a sectional view of a brush seal device
100
mounted between a rotary shaft
120
and a casing
110
through which the rotary shaft
120
passes. The rotary shaft
120
and the casing
110
are components, such as of a steam turbine or gas turbine. The brush seal device
100
seals fluid by separating the space formed between the casing
110
and the rotary shaft
120
that displace relatively.
In
FIG. 14
, the brush seal device
100
is formed in a ring shape and secured in a channel section
112
of the casing
110
. The brush seal device
100
has a brush seal
109
to which a backing plate
102
and support plate
103
are attached as its accessories. In the brush seal
109
, bristles
101
are arranged in a circle to form a wall and coupled together at one end to form an attachment section
104
. The free end
105
of the brush seal
109
faces the rotary shaft
120
. The diameter of the bristle
101
used is generally 0.02 to 0.5 mm. Tens or hundreds of thousands of bristles are used for this purpose.
On one side of the brush seal
109
is located an annular backing plate
102
with its side face
108
in contact with the brush seal
109
and supports the bristles
101
against the action of the pressure of the sealed fluid.
Also, on the other side surface of the brush seal
109
is integrally placed a support plate
103
in the shape of a ring so as to, in cooperation with the backing plate
102
, sandwich the brush seal
109
at its attachment section
104
side. The length of the support plate
103
in radial direction is made small so as to allow the brush seal
109
to be exposed to deform. One ends of the backing plate
102
, attachment section
104
of the brush seal
109
, and support plate
103
are welded together to form a coupling section
106
.
FIGS. 15A and B
are front views of part of the brush seal
109
shown in FIG.
14
. The brush seal device
100
in
FIG. 15A
is in a state that the brush seal
109
and the rotary shaft
120
are normally fit each other such that there occurs no relative oscillation therebetween and the bristles
101
are straightly inclined in the rotational direction with respect to the radial direction of the rotary shaft
120
. The normal state of the brush seal
109
is that the rotary shaft
120
contacts or approximates to the free end
105
, as shown by the solid line in FIG.
14
.
In the brush seal
109
formed in such a way described above, the larger the diameter of the brush seal
109
is, the more difficult the production thereof, due to the increase of the number of the bristles
101
to hundreds of thousands. Specifically, fixing the bristles
101
between the backing plate
102
and the support plate
103
while slanting the bristle
101
, further increases its manufacturing cost.
Additionally, because the brush seal
109
, backing plate
102
, and support plate
103
are welded together into one piece, the backing plate
102
and the support plate
103
must have a larger thickness for strengthening them in a larger brush seal device
1
. Thus, not only the yield of material is reduced by the increase of the number of the bristles, but also yield of material involved in the number of the backing plates
102
or the support plates
103
that can be cut out from one steel plate is reduced.
A brush seal device shown in
FIG. 16
is another related art to the present invention. The brush seal device in
FIG. 16
, has a number of thin plates as a brush seal
209
, that are piled in the circumferential direction of the rotary shaft
120
and seals a high pressure area P
1
and a low pressure area P
2
.
Outer peripheral of the brush seal
209
is brazed to form an attachment section
104
and then mounted in a channel section of a casing
110
through the brazed attachment section
104
. Also, a backing plate
102
is located on the side surface of the brush seal
209
that faces the low pressure area P
2
, a support plate
103
is located on the opposed side surface that faces the high pressure area P
1
, and thus both the plates
102
and
103
support the both side surfaces of the brush seal
209
, respectively.
However, when the rotary shaft
120
eccentrically presses against the brush seal
209
that are formed in the way above, the brush seal
209
of piled thin plates forming an annular body is not given a space ample to deform itself, and the spring constant corresponding to the elastic deformation is therefore increased, which causes a problem such that it is difficult to follow the eccentric movement of the rotary shaft
60
. To overcome this drawback, the clearance between the seal
209
and the outer circumference surface of the rotor
120
has been selected larger, but a problem concerning to the capability to prevent the leakage of fluid to be sealed is also present.
Additionally, the pressure of the sealed fluid acts on the seal
209
in the direction of the surfaces of the piled thin plates forming the seal
209
and, as the result, gaps are forcedly increased between the piled plates. Accordingly, also in this case, a problem concerning to the capability to prevent the leakage of fluid to be sealed is present.
Moreover, the brush seal
209
forming an annular body includes some hundreds of thousands thin plates used. Therefore, it is extremely difficult to fabricate the brush seal
209
and the yield of material is also poor. Further, as the length along the outer circumference of the annular body of the brush seal
209
is longer than that along the inner circumference, spacers are necessarily disposed on the outer circumference to compensate the difference in the circumferential length between the outer and inner circumferences. However, gaps still remain between the surfaces of the piled plates. In this viewpoint, there also exists the problem of sealing ability. Also, as a whole, the brush seal
209
constitutes a ring, thereby to cause its elasticity to be lost, so that the flexibility thereof may be reduced and the free end
105
of the brush seal
209
be worn quickly.
In the brush seal device
100
constituted as described above, when the rotary shaft
120
contacts the brush seal
109
involved in any vibration, oscillation or the like, the brush seal
109
is pressed to contact the rotary shaft
120
, and at he same time its tilt angle is increased, as shown in FIG.
15
B.
Referring to
FIG. 14
, the clearance C generated between the free end
105
of the bristles
101
, at the position diametrically opposite to the position where the rotary shaft
120
presses against the brush seal
101
(in the state shown in
FIG. 15B
) becomes larger due to the oscillation of the rotary shaft
120
, as shown by phantom line in
FIG. 14
, which will cause leakage of the sealed fluid though the clearance C. In order to prevent this leakage, the bristles
101
are slanted toward the rotational direction of the rotary shaft. However, because hundreds of thousands of bristles
101
are arranged to form a wall in a bundle as a seal device, the yield of material may become poor, and it may be extremely difficult to fabricate an attachment structure for slanting

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