Mechanical sealing device

Details Mechanical sealing device Mechanical sealing device

2002-08-29

2004-03-23

Pickard, Alison K. (Department: 3676)

Seal for a joint or juncture

Seal between relatively movable parts

Relatively rotatable radially extending sealing face member

C277S387000, C277S408000

Reexamination Certificate

active

06708980

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a mechanical sealing device and, particularly to the technical field of a mechanical sealing device capable of effectively sealing high viscosity fluid or slurry-contained fluid.
2. Description of the Related Art
There has been a conventional mechanical seal as a related art of the invention, as shown in
FIG. 5
, which is a half sectional view of a conventional mechanical sealing device.
The mechanical seal
100
as the first related art shown in
FIG. 5
is constituted as a set that is mounted on a rotary shaft
151
and installed within a stuffing box
150
through fastening bolts
160
.
The mechanical seal
100
includes, as principle components thereof, a liquid sealing device
101
, a fist seal flange
110
, a second seal flange
120
and a gas sealing device that are arranged in order, from the inside of the stuffing box
150
toward the outside thereof, in the axial direction.
The liquid sealing device
101
is mounted on the outer circumference of a sleeve
153
secured onto the rotary shaft
151
through a screw socket
152
. Between the rotary shaft
151
and the sleeve
153
fitting thereto is disposed an O-ring
154
for sealing therebetween.
In the liquid sealing device
101
, a rotary seal ring
102
formed with a rotary seal face
103
is resiliently biased by a spring
105
through a U-shaped gasket
107
and a spacer
108
.
Also, a stationary seal ring
112
having a stationary seal face
113
in contact with the rotary seal face
103
is fitted to the inner circumference of the first seal flange
110
through an O-ring
116
. Further, at least one pin
115
secured to the stationary seal ring
112
engages a groove provided in the inner circumference of the first seal flange
110
to engage the stationary seal ring
112
with the first seal flange
110
.
A gas-sealing device
121
is installed inside of the inner circumference of the second seal flange
120
coupled with the first seal flange
110
. The gas-sealing device
121
is provided with a drive sleeve
125
that is secured to the sleeve
153
through at setscrew
126
. A second rotary seal ring
122
having a second rotary seal face
123
is fitted in the drive sleeve
125
to slide therein. One end of a fluid passage formed in the second rotary seal ring
122
for creating dynamic pressure is opened at the second rotary seal face
123
.
A second stationary seal ring
132
having a second stationary seal face
133
in close contact with the second rotary seal face
123
of the second rotary seal ring
122
is fitted to the inner circumference of the second seal flange
120
through an O-ring
136
. In the second stationary seal face
133
are formed a plurality of grooves for creating dynamic pressure, in cooperation with the second rotary seal face
123
. Also, the second rotary seal ring
122
is resiliently biased by a coil spring
127
toward the second stationary seal ring
132
side.
The mechanical seal
100
is assembled to the rotary shaft
151
and then the assembly is inserted and installed inside of inner circumferential surface
156
of the stuffing box
150
.
An intermediate chamber
130
in which the gas-sealing device
121
is housed is constituted such that the pressure within the intermediate chamber
130
is approximately equal to the atmospheric pressure due to the presence of a drain
128
in the second seal flange
120
.
On the other hand, there has been a tandem mechanical seal having a constitution approximately identical to that shown in
FIG. 5
(not illustrated in the accompanying drawings. Because the corresponding components are different each other in geometry, each component identical to that in
FIG. 5
shall be represented by a combination of the same numeral and a succedent alphabet.) However, the mechanical seal
100
A as the second related art is different from the first related art in that the pressure within an intermediated chamber (buffering chamber)
130
A is less than that within a liquid chamber
157
and more than the atmospheric pressure (the pressure within the intermediate chamber
130
A is approximately a half of that within the liquid chamber
257
.). The pressure within the intermediate chamber
130
A can be derived from, for example, reducing the pressure within the liquid chamber
157
.
It is also a difference from the first related art that a gas sealing device
121
A is not a contact type sealing device employed in the first related art but is a non-contact type sealing device. Additionally, in a first seal flange
10
A engaging a stationary seal ring, the inside diameter, on the intermediate chamber
130
A side, of the first seal flange
110
A is approximately equal to that of the stationary seal ring and it is adapted to prevent the pressure within the intermediate chamber
130
A from acting on the side face of the stationary seal ring
112
A.
If any high viscosity fluid or slurry contained fluid is intended to be sealed using such mechanical seals
100
,
100
A that are constituted as previously described, then slurries or the like that is contained in the fluid to be sealed will stick on the spacer
108
, the spring
105
, the gasket
107
and others. Then, those slurries and solid matters will enter between the sliding faces of those components to cause the axial response of the rotary seal ring to be reduced and the surface pressure of the rotary seal face
103
to be worsen, resulting in poor sealing ability.
Specifically, if the response of the rotary seal ring
102
is worsen in the state that the rotary seal face
103
of the rotary seal ring
102
is pushed against the stationary seal face
113
, then the rotary seal face
103
will slides relative to the mating surface
113
in the state that the former is subject to a large pressure. Both seal faces will be therefore damaged due to heat generation from sliding action therebetween, causing the sealing ability to be worsen rapidly.
Contrary, if the response is worsen in the state that the surface pressure applied on the rotary seal face
103
is reduced, then the sealing ability of the mating seal faces will be reduced and slurries or the like enter between the rotary seal face
103
and the stationary seal face
113
, which causes those seal faces to be damaged.
In such a structure of the mechanical seal
100
shown in
FIG. 5
, it is difficult to prevent the rotary seal face
103
from being damaged due to heat generation from sliding action, because it is difficult to cool the rotary seal face
103
and the proximity thereof by supplying coolant. This causes the sealing ability of the seal faces
103
,
113
to be reduced.
Further, there exists, as the third related art of the invention, a mechanical seal
100
B shown in
FIG. 6
, which has been used as a shaft sealing device in a stirrer, a pump and others for handling magnetic paint for a video tape. In other words, the fluid to be sealed contains slurry.
In
FIG. 6
, the mechanical seal is installed between a casing
201
and a rotary shaft
202
.
As shown in
FIG. 6
, the rotary shaft
202
fits to and passes through a through-hole
201
a
. Between the rotary shaft
202
and the casing
201
is disposed a mechanical seal
100
B that functions to divide off or tightly seal between a slurry contained fluid area
204
and a sealed liquid area
205
.
The mechanical seal
100
B is so constituted that a rotary seal ring
206
is fixedly fitted to the rotary shaft
202
and rotates therewith. An O-ring is disposed for sealing between the rotary shaft
202
and the rotary seal ring
206
in order to prevent fluid leakage. The rotary seal ring
206
has a rotary seal face, which in turn closely contacts a mating stationary seal face, thereby to function to seal.
On the other hand, a stationary seal ring
207
is slidably fitted in a through-hole
201
A in the casing
201
through an O-ring
209
. The O-ring
209
is inserted to fit in an annular groove
211
formed in the through-hole
201
A of the casing
201
to seal the space
214
formed between the casing

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