Seal for a joint or juncture – Seal between relatively movable parts – Brush seal
Reexamination Certificate
2002-09-27
2004-10-19
Pickard, Alison K. (Department: 3676)
Seal for a joint or juncture
Seal between relatively movable parts
Brush seal
C277S416000, C277S547000
Reexamination Certificate
active
06805356
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a strip-like brush seal having a plurality of thin plates that are processed to have thin, cantilever beams at their one end and relates to a brush seal device, for sealing between a rotational shaft and a mating component movable relatively thereto, for example in an aircraft and a gas turbine. More particularly, the present invention relates to a technical field of a brush seal and a brush seal device capable of following the rotation or minute variation of one component with respect to other component to deform during relative movement for effectively sealing between both components.
2. Description of the Related Art
There exists, as shown in
FIG. 12
, a brush seal device
100
as one related art of the present invention.
FIG. 12
is a sectional view of a brush seal device
100
mounted between a rotational shaft
120
and a casing
110
through which the rotational shaft
120
passes. The casing
110
is a component of a steam turbine or gas turbine. The brush seal device
100
separates the casing
110
and the rotational shaft
120
so as to seal fluidly.
In
FIG. 12
, the brush seal device
100
is formed in a ring shape and attached to a channel section
112
of the casing
110
. Main components of the brush seal device
100
are a brush seal
109
, a back plate
102
and a retaining plate
103
. In the brush seal
109
, a number of bristles
101
in the form of a wall are arranged circumferentially, and one end of the bristles are coupled together to form an attachment section
104
. The free end face
105
as the other end of the brush seal
109
faces the rotational shaft
120
. The diameter of each bristle
101
used in general is 0.02 to 0.5 mm. However its sealing ability will be reduced because the brush seal device is formed of linear bristles
101
in the form of a wall that has been merely brought together. In order to overcome such a drawback the thickness of the wall formed with the bristles
101
must be increased and thus tens of thousands or hundreds of thousands of bristles
101
are necessarily used.
An annular back 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 bears each of the bristles
101
against the action of the sealed fluid pressure.
A retaining plate
103
formed as a ring plate is disposed integrally on the other side face of the brush seal
109
to sandwich, in cooperation with the back plate
102
, the brush seal
109
on its attachment section
104
side. The retaining ring
103
has a small thickness in its radial direction so that the brush seal
109
is exposed to allow the brush seal
109
to deform corresponding to the contact of the rotational shaft
120
therewith.
The back plate
102
, the attachment section
104
of the brush seal
109
and the retaining plate
103
are welded at one end together to form into a connecting section
106
.
In
FIG. 12
, the rotational shaft
120
shown by an actual line is in a state that the rotational shaft
120
is normally fitted without oscillation and every bristle
101
extends straight and inclines in the rotating direction, relative to the radial direction of the rotational shaft
120
. Accordingly, the free end face
105
will be precisely finished after fabrication of the brush seal
109
so as to fit the rotational shaft
120
normally. It is however difficult to process the free end face
105
because tens or hundreds of thousands of bristles
101
arrayed in the form of a wall in the free end face
105
are apt to deform.
When the rotational shaft
120
then contacts the brush seal
109
, the brush seal
109
is pressed against the rotational shaft
120
while its tilt angle is increased. At the same time there are created gaps between neighboring bristles
101
due to their movement and/or deformation.
In this state, as shown in
FIG. 12
, if the pressure of the sealed fluid is a high pressure P
1
, the differential pressure (P
1
-P
2
) between P
1
and a low pressure P
2
is increased, and then the gaps formed between neighboring bristles
101
will be further enlarged, resulting in the sealing ability to be worsened.
FIGS. 13 and 14
are partial front views of the brush seal
109
, seen radially from its inner side.
In
FIGS. 13 and 14
, if the sealed fluid enters the gaps between straight bristles
101
, each bristle
101
arranged as shown in
FIG. 13
, seen from their inner circumferential side, is pushed aside such that each gap width between the bristles
101
is increased as shown in
FIG. 14
, and as a result the sealed fluid leaks from those gaps.
If neighboring bristles
101
inclined are separated apart each other by the pressure described above, one of the bristles
101
separated apart tends to displace to reduce its tilt angle, and it is therefore deformed such that its length along the radial direction is long. Accordingly, the pressure applied to the rotational shaft
120
is increased to cause wear. This wearing action will be accelerated as the thickness of the bundle of the bristles
101
becomes large for improving the sealing ability.
In this state, with the increase of the gap C formed between the free end face
105
of the bristles
101
and the rotational shaft
120
(Refer to the rotational shaft shown by a phantom line in
FIG. 12
) on the diametrically opposite side, the sealed fluid leaks from the gap C.
Further, there exists a seal device as another related art, as shown in FIG.
15
. In the figure, thin plate like leaves are piled as a seal
209
along the circumferential direction of the rotational shaft
120
to seal between a high pressure side area P
1
and a low pressure side area P
2
.
Outer circumferential portion of the seal
209
of plate like leaves is brazed to form an attachment section
104
. Then the seal
209
is attached to the channel section of the casing
110
through the brazed attachment section
104
.
Also, a back plate
102
is disposed on the side face of the seal
209
at the low pressure side area P
2
, a retaining plate
103
is disposed on the side face at the high pressure side area P
1
, and both the plates
102
and
103
retain both sides of the seal
209
, respectively.
However, when the rotational shaft
120
eccentrically presses against the seal
209
formed in the above manner, the seal
209
having piled thin plate like leaves to form an annular body has no space for accommodating own elastic deformation and thus the spring constant corresponding to the resilient deformation is increased. It is therefore difficult for the seal
209
to follow the eccentric behavior of the rotational shaft
120
.
Further, in the seal
209
in which thin plate like leaves are piled in the direction of the action of the sealed fluid pressure, gaps are forced to create between two neighboring plates. This causes a problem relating to its sealing ability for fluid leakage.
Moreover, the seal
209
forming an annular body includes hundreds of thousands of thin plate like leaves that are piled in the annular direction. Therefore, it is extremely difficult to fabricate the seal
209
. Further, as the length along the outer circumference of the annular body of the seal
209
is longer than that along the inner circumference, spacers for compensating the difference in length theretween are necessarily disposed between thin plate like leaves at their outer circumferential sides. However, gaps still remain between the surfaces of the piled plate like leaves. In this viewpoint, there also exists the problem of sealing ability. Also, in this constitution whose flexibility may be reduced, the free end face
105
of the seal
209
be worn quickly due to its worsened elastic response.
In the brush seal device
100
constituted as described above, when the sealed fluid acts on the bristles
101
, gaps are created therebetween, as shown in
FIG. 14
, because the bristles
101
are randomly gathered together to form a bundle in the shape of a wall.
Further, when the r
Arent & Fox PLLC
Eagle Industry Co. Ltd.
Pickard Alison K.
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