Brush seal device

Details Brush seal device Brush seal device

2001-11-26

2003-12-02

Knight, Anthony (Department: 3676)

Seal for a joint or juncture

Seal between relatively movable parts

Brush seal

Reexamination Certificate

active

06655692

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a brush seal device having a brush for sealing a gap between two parts that move relative to each other (that make rotational movements, reciprocating movements, or the like). More particularly, the present invention relates to a brush seal device for sealing a gap between two parts which are opposed to each other and one of which is movable.
BACKGROUND OF THE INVENTION
There are various types of sealing devices for sealing a gap between two parts that move relative to each other (that make rotational movements, reciprocating movements, or the like). For example, a brush seal device as shown in
FIG. 9
is based on a generally known art.
Referring to
FIG. 9
, a brush seal
11
is composed of a brush
12
and a holding portion
14
. The brush
12
is formed of thin bristles
13
made from a highly rigid material such as metal, synthetic resin, ceramics, composite material, or the like. The thin bristles
13
are disposed in a wall shape with a certain thickness. The holding portion
14
is composed of a back plate
15
and a side plate
16
, which hold and clamp the brush
12
therebetween.
The holding portion
14
of the brush seal
11
is secured to one (a fixed body not shown in the drawing) of two parts that move relative to each other (e.g. that make rotational movements), and a free end of the brush
12
is in contact with the other part
20
(a rotor). Alternatively, the free end of the brush
12
is contiguous to the other part
20
and spaced apart therefrom by a narrow gap, whereby the gap between the two parts that move relative to each other is sealed (see
FIGS. 9
to
11
).
If the other part
20
is off-centered due to its rotation or is deformed due to a rotational force or if the gap between one part (the fixed body) and the other part
20
undergoes a change ascribable to a relative dimensional difference between the two parts as a result of a difference in thermal expansion coefficient therebetween, the entire brush
12
escapes while deflecting radially in accordance with the movement of the other part
20
. It is thus possible to prevent the free end portion of the brush
12
from wearing down and prevent the amount of leakage of sealed fluid from increasing.
In the brush seal device
11
constructed as described above, however, the brush
12
is pressed hard against the back plate
15
due to a differential pressure between upstream and downstream pressures. Therefore, if the other part
20
is off-centered during rotation or is deformed due to its rotation or if the gap between one part (the fixed body) and the other part
20
undergoes a change ascribable to a relative dimensional difference between the two parts as a result of a difference in thermal expansion coefficient therebetween, a frictional resistance between the brush
12
and the back plate
15
and a frictional resistance of the thin bristles
13
of the brush
12
prevent the brush
12
from deflecting radially and escaping. Hence, the free end portion of the brush
12
wears down (see FIGS.
12
and
13
). Also, if the degree of deformation of the other part
20
resulting from its rotation or the degree of eccentricity of the other part
20
during its rotation becomes small, the brush
12
is held while deflecting toward the back plate
15
due to the frictional resistance between the brush
12
and the back plate
15
and the frictional resistance of the thin bristles
13
of the brush
12
. Therefore, the brush
12
cannot return from its deflected state to its original state. Hence, the gap between the free end portion of the brush
12
and the other part
20
increases to the extent of causing leakage (see FIGS.
14
and
15
). In addition, since the brush
12
is free in a region affected by sealed fluid, the spaces among the thin bristles
13
in the region constitute passages into which sealed fluid flows and from which sealed fluid leaks (see FIG.
10
).
SUMMARY OF THE INVENTION
The present invention has been made as a solution to the conventional problems as described above. It is an object of the present invention to allow the brush to escape while deflecting radially in accordance with the movement of the other part if the other part is off-centered during its rotation or is deformed due to its rotation or if the gap between one part (the fixed body) and the other part undergoes a change ascribable to a relative dimensional difference between the two parts as a result of a difference in thermal expansion coefficient therebetween. It is also an object of the present invention to effectively prevent the free end portion of the brush from wearing down and to allow the brush to return smoothly from its deflected state to its original state if the degree of swell of the other part resulting from its deformation or the degree of eccentricity of the other part resulting from its rotation becomes small. Furthermore, it is also an object of the present invention to prevent the gap between a tip of the brush and the other part from increasing to the extent of causing leakage of sealed fluid. Still further, it is also an object of the present invention to prevent sealed fluid from entering the spaces among the thin bristles of the brush, and thus, to effectively prevent the free end portion of the brush from wearing down by being pressed against the other part due to a pressure of sealed fluid entering those spaces.
The brush seal device of the present invention has a brush and a holding portion. The brush has a plurality of bristles disposed in a mural manner. The holding portion holds one end side of the brush. The holding portion is secured to one of two parts that move relative to each other, and a free end portion of the brush is disposed in contact with or contiguous to the other part. An elastically deformable elastic portion for sealing is provided between opposed faces of the holding portion and the brush. The brush is pressed toward the holding portion due to an elastic force of the elastic portion so that the gap between the brush and the holding portion is sealed. Thus, sealed fluid is prevented from entering the gap between the brush and the holding portion.
Because the brush seal device of the present invention is based on the aspect as described above, the brush is pressed against the face of the holding portion which is opposed to the brush due to the elastic force of the elastic portion, so that the bristles of the brush are in close contact with one another. As a result of such close contact of the bristles, sealed fluid can be prevented from entering spaces among the bristles. Therefore, the brush can deflect in accordance with the movement of the other part without being immobilized by a pressure of sealed fluid entering those spaces. In addition, the brush can return quickly from its deflected state to its original state.
Still further, since the elastic portion for sealing seals the gap between the brush and the holding portion, it is possible to prevent sealed fluid from entering the gap between the brush and the holding portion and to prevent the brush from being exposed to a differential pressure between upstream and downstream pressures. As a result, the brush is not immobilized by being pressed against the holding portion due to such a differential pressure. Thus, it becomes easier for the brush to deflect in accordance with the movement of the other part or even to return from its deflected state to its original state.


REFERENCES:
patent: 5174582 (1992-12-01), Ferguson
patent: 5568931 (1996-10-01), Tseng et al.
patent: 5799952 (1998-09-01), Morrison et al.
patent: 6267381 (2001-07-01), Wright
patent: 2258277 (1993-02-01), None

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