Brush seal device

Details Brush seal device Brush seal device

2002-06-14

2003-08-05

Knight, Anthony (Department: 3676)

Seal for a joint or juncture

Seal between relatively movable parts

Brush seal

C415S174400

Reexamination Certificate

active

06601853

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a brush seal device. More particularly, the present invention relates to a brush seal device having a brush seal mounted on one of two components displaceable relatively between the two components, wherein the brush seal is capable of resiliently deforming to follow the change of the clearance between the two components even if the relative change between the two components occurs.
2. Description of the Related Art
As one related to the present invention there exists a brush seal device
100
, as shown in FIG.
8
.
FIG. 8
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 casing
110
is a component disposed on the stationary side of a steam turbine or gas turbine. The brush seal device
100
is mounted to the casing
110
to seal fluid by separating the space between the casing
110
and the rotary shaft
120
.
The brush seal device
100
is formed in a ring shape and attached to a channel section
112
in the casing
110
. Main components of the brush seal device
100
are a brush seal
109
, a backing plate
102
and a holding plate
103
. In the brush seal
109
, a number of bristles
101
are arranged around the circumference to form a partition wall, and on end of the bristles are coupled together to form an attachment section
104
. A free end
105
as the other end of the brush seal
109
faces the rotary shaft
120
. The diameter of the bristle
101
generally used is 0.02 to 0.5 mm. Tens of thousands or hundreds of thousands of bristles are used.
An annular backing plate
102
is located on one side face of the brush seal
109
with its side face
108
contacting the one side face of the brush seal
109
and supports the bristles
101
against pressure action of the sealed fluid.
A support plate
103
formed as a ring plate is disposed on the other side face of the brush seal
109
to sandwich, in cooperation with the backing plate
102
, the brush seal
109
on its attachment section
104
side. The brush seal
109
is exposed at its free end
105
so that the side surface of the brush seal
109
is not wholly sandwiched.
One ends of the backing plate
102
, the attachment section
104
of the brush seal
109
, and the support plate
103
are welded together to form a connecting section
106
.
FIG. 9A
is a partial front view of the brush seal
109
. The brush seal device
100
in
FIG. 9A
is in a state that the brush seal
109
and the rotary shaft
120
are normally fitted without oscillation, such that a number of bristles
101
extend straight and oriented to incline relative to the radial direction of the circumefrence of the rotary shaft
120
. In the normal state of the brush seal
109
, the rotary shaft
120
is in contact with or close to the free end
105
, as shown by the solid line in FIG.
8
.
FIG. 10A
is a perspective view of the free end side of the brush seal
109
. In
FIG. 10A
, the free end
105
is precisely processed by wire electronic discharging or the like such that the brush seal
109
fits the rotary shaft
120
after the process. The bristles
101
are however apt to be deformed, so it is extremely difficult to process them. Moreover, it is also difficult to precisely process the free end
105
.
A brush seal device
100
B shown in
FIG. 11
is another related art to the present invention.
FIG. 11
shows thin plates as seals
209
that are piled in the direction of a circumference of a rotary shaft
120
and seal a high pressure area P
1
and a low pressure area P
2
.
Outer circumference portion of the seal
209
is brazed and formed on an attachment section
104
as well as attached to the channel section of the casing
110
through the brazed attachment section
104
. Also, a backing plate
102
is located at a side face of the seal
209
in a low pressure area P
2
, a holding plate
103
is located at a side face in a high pressure area P
1
, and both the plates
102
and
103
support both sides of the seal
209
, respectively.
However, when the rotary shaft
120
eccentrically presses to contact the seal
209
formed in the above way, the piled seals
209
forming an annular body have no space for compensation and thus the spring constant corresponding to the resilient deformation is increased, and thus it is difficult to follow the eccentric behavior of the rotary shaft
120
. Thus, clearance between the seals
209
and the outer circumference surface of the rotary shaft
120
is large, and it causes a problem relating to sealing ability for sealed fluid.
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
. 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 between thin plates on the outer circumference. However, gaps still remain between the surfaces of the piled plates. In this viewpoint, there also exists the problem of sealing ability. Also, in this constitution such that the flexibility thereof may be reduced, the free end
105
of the brush seal
209
be worn quickly.
In the brush seal device
100
A constituted as described above, when the rotary shaft
120
contacts the brush seal
109
involved in any oscillation, 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.
9
B.
If the pressure of the sealed fluid is the higher P
1
in this state, the differential pressure (P
1
-P
2
) between the P
1
and the low pressure P
2
is increased, and the whole straight bristles
101
of the brush seal
109
are pressed against the backing plate and become less deflective, and thus the ability to follow the rotary shaft
120
is worsened.
FIG. 10B
is a front view of the brush seal
109
in
FIG. 10A
, viewed from the free end
105
at inner side.
In FIG.
10
A and
FIG. 10B
, if the sealed fluid flows into gaps between straight bristles
101
, each bristle
101
arranged as shown in
FIG. 10A
, seen from the inner circumference side is pushed aside such that gaps between the bristles
101
are increased as shown in
FIG. 10B
, and then the sealed fluid leaks from those separated clearances. If this operation is combined with a condition that the bristles
101
in the inclined condition are separated by pressure, one separated side tends to displace such that the inclined angle is decreased, whereby the bristles
101
is deformed such that its length in the radial direction is large, and therefore it increases pressure to the rotary shaft
120
and causes wear.
In addition to a condition like this, with respect to
FIG. 8
, compared to a position of the brush seal
109
pressed to the rotary shaft
120
(in the condition of FIG.
9
B), in the opposite side to the radial direction from axis, a clearance C between a free side surface
105
and the rotary shaft
120
swings as shown in imaginary lines in the rotary shaft
120
of FIG.
8
and opens widely, causing leakage of the sealed fluid from the clearance C.
Also, with respect to a seal
209
in
FIG. 11
, because thin plates are attached in the direction to which the sealed fluid affects, attached surfaces of the thin plates are separated in the same way as in
FIG. 10B
if the sealed fluid affects, so that the sealed fluid leaks. In addition, because flexibility of the free end
105
of the seal
209
is inhibited, distance from the rotary shaft
120
should be large, and it causes a problem

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