Brush seal device

Details Brush seal device Brush seal device

2002-01-23

2004-05-25

Browne, Lynne H. (Department: 3676)

Seal for a joint or juncture

Seal between relatively movable parts

Brush seal

C277S387000, C277S388000, C277S926000

Reexamination Certificate

active

06739592

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a brush seal device for sealing a gap between two parts that move relative to each other about a rotating shaft of an airplane, gas turbine or the like. More particularly, the present invention relates to the field of a brush seal device for sealing a gap between two parts by causing a brush seal to elastically deform according to movement of one part even when the dimension of the gap is changed and thus preventing contact wear.
BACKGROUND OF THE INVENTION
There is a brush seal device
100
of
FIG. 13
as an example of the related art of the present invention.
FIG. 13
is a cross-sectional view of the brush seal device
100
. The brush seal device
100
is mounted between a rotating shaft
120
and a hole formed in a casing
110
, and the rotating shaft
120
extends through the hole. This casing
110
is a part of a steam turbine. The brush seal device
100
separates the gap between the casing
110
and the rotating shaft
120
so as to seal a sealed fluid (steam fluid) flowing in the gap.
The brush seal device
100
has a ring shape, and is mounted in an annular groove
112
in the casing
110
. The brush seal device
100
mainly includes a brush seal
109
, a back plate
102
and a retaining plate
103
. The brush seal
109
is formed from bristles
101
radially arranged into a wall shape along the circumference. The bristles
101
are connected together at one end to form an attachment portion
104
. A free end face
105
of the brush seal
109
faces the rotating shaft
120
. The bristle
101
of the brush seal
109
commonly has a diameter of 0.25 mm or more.
The annular back plate
102
has its side surface
108
in contact with one side surface of the brush seal
109
. The annular back plate
102
supports the bristles
101
against the pressure of the sealed fluid.
The retention plate
103
has a ring shape, and is mounted on the other side surface of the brush seal
109
. The attachment portion
104
of the brush seal
109
is thus held between the retaining plate
103
and the back plate
102
. The retention plate
103
has a small width in the radial direction of the brush seal
109
so that the brush seal
109
is exposed to the sealed fluid.
The back plate
102
, the attachment portion
104
of the brush seal
109
and the retaining plate
103
are welded together to form a connected portion
106
.
FIG. 14
is a front view of the brush seal
109
, illustrating the present invention or the related art. The brush seal device
100
of
FIG. 14
is in a normally fitted state in which the brush seal
109
and the rotating shaft
120
do not move relative to each other. In this normal state, the rotating shaft
120
shown by the virtual line in
FIG. 13
is located in contact with or near the free end face of the brush seal
109
.
Although not shown in the figure, a brush seal device according to another example of the related art has a small gap between the side surface
108
of the back plate
102
and the side surface of the brush seal
101
. However, the bristle
101
having a diameter of 0.25 mm or more hinders the function of the gap. In other words, the bristles
101
will not be deflected according to movement of the rotating shaft
120
. This accelerates wear of the free end face
105
of the bristles
101
. Moreover, such a large diameter of the bristle
101
makes it impossible to form a thicker wall of the bristles in view of the friction with the rotating shaft. This results in degraded sealing capability.
In the above brush seal device
100
, when the rotating shaft
120
contacts the brush seal
109
due to vibration or the like as shown in
FIG. 13
, the brush seal
109
is further tilted in the rotation direction under the pressure from the rotating shaft
120
as shown in FIG.
15
.
If the sealed fluid has a high pressure P
1
in this state, the brush seal
109
is pressed against the side surface
108
of the back plate
102
due to a large difference between the high and low pressures P
1
and P
2
(P
1
−P
2
), as shown in FIG.
16
.
In the state of
FIG. 16
, the bristles
101
of the brush seal
109
are less likely to be deflected because they are pressed against the side surface
108
of the back plate
102
. In other words, the bristles
101
are less likely to be deflected according to movement of the rotating shaft
120
. Moreover, the sealed fluid enters between the bristles
101
, whereby one bristle
101
is raised relative to the other. As a result, the tilted bristles
101
try to reduce the tilting angle of the raised bristles
101
. Since the raised bristles
101
have a long radial length, the pressure from the rotation shaft
120
is increased, causing wear of the brush seal
2
.
When the vibration of the rotating shaft
120
is reduced as shown in
FIG. 17
, the gap C between the worn free end face
105
of the bristles
101
and the rotating shaft
120
is increased as shown in FIG.
18
. As a result, the sealed fluid leaks through the gap C. Moreover, when the pressure P
1
of the sealed fluid is reduced (i.e., when the difference between the pressure P
1
and the pressure P
2
in the downstream region (P
1
−P
2
) is reduced), the rotation force of the rotating shaft
120
becomes dominant. Accordingly, the gap C between the rotating shaft
120
and the free end face
105
of the bristles
101
may be increased due to the rotation force. In this case as well, the sealed fluid leaks through the gap C.
The preset invention is made in view of the above problems. It is an object of the present invention to improve flexibility of a brush seal against the pressure of a rotating shaft, and reduce the wear due to friction between the brush seal and the rotating shaft by the flexibility of the brush seal.
It is another object of the present invention to improve sealing capability by improving the ability of the brush seal to deflect according to movement of the rotating shaft.
It is still another object of the present invention to improve sealing capability by densely arranging bristles of a smaller diameter into a wall shape.
It is yet another object of the present invention to improve sealing capability and prevent friction-induced damages by preventing abnormal movement of the aligned bristles.
It is a further object of the present invention to enable the brush seal to be deformed according to the pressure value of a sealed fluid by controlling in balance the front pressure of the sealed fluid acting on the bristles and the back pressure of the sealed fluid in a recess passing through the brush seal.
SUMMARY OF THE INVENTION
The present invention is made to solve the above problems. Means for solving the problems are structured as follows:
A brush seal device according to the present invention is mounted to one of two parts that move relative to each other with a gap therebetween, and seals the gap between the parts by a brush seal. The bush seal device includes: a brush seal formed from bristles arranged into a wall shape, and including an attachment portion formed by connecting the bristles together at one end, and a free end face facing an opposing surface of the other part; a back plate connected to the attachment portion of the brush seal, and including a support surface for supporting a side surface of the brush seal; and a retaining plate for retaining the attachment portion of the brush seal between the retaining plate and the back plate. The support surface of the back plate and an opposing surface of the brush seal are disposed at a distance from each other. The bristle of the brush seal has a diameter of 0.15 mm to 0.008 mm.
In the brush seal device of the present invention, the bristles are disposed at a distance from the support surface of the back plate, and the bristle has a diameter of 0.15 mm to 0.008 mm. Therefore, even when the other part contacts the free end face of the bristles, the bristles can be elastically deformed toward the support surface. For example, even if the bristles abut on the rotor, they are moved while reducing the contact pre

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