Mechanical seal device

Details Mechanical seal device Mechanical seal device

2002-11-27

2004-07-06

Miller, William L. (Department: 3677)

Seal for a joint or juncture

Seal between relatively movable parts

Relatively rotatable radially extending sealing face member

C277S377000

Reexamination Certificate

active

06758476

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a two-half type mechanical seal device comprising two halves each having a splitting face extending axially that are combined from the radial direction of a rotational shaft to couple together, and more particularly to a two-half type mechanical seal device constituted as an outside seal device for sealing a high pressure fluid.
2. Description of the Related Art
As a first related art relating to the invention there exists a mechanical seal device, as shown in FIG.
3
.
FIG. 3
is a sectional view, showing the upper half of a mechanical seal device
100
according to the first related art. The mechanical seal device
100
is an inside seal device. A rotational shaft
148
passes through a passage
151
in the housing
150
to which the mechanical seal device
100
is mounted. To the end face of the housing
150
is secured a gland assembly
140
with screw bolts (not shown) through a gasket. The gland assembly
140
is also comprised of two halves that are split along the axial plane. In the gland assembly
140
, those two halves are joined together at their mating faces with a plurality of screw bolts (not shown).
A mechanical seal is disposed inside of the inner face
141
of the gland assembly
140
. Tis mechanical seal is provided with a holder assembly
102
that is also comprised of two halves and mounted on the rotational shaft
148
for rotation therewith. The two halves of the holder assembly
102
are joined together at their splitting faces with a plurality of screw bolts. Between the outer face of the holder assembly
102
and the inner face
141
of the gland assembly
140
is formed a fluid passage
142
through which the sealed fluid flows. Further, a first O-ring
131
for sealing the fitting section between the rotational shaft
148
and the holder assembly
102
is fitted in an annular groove
105
formed in the inner face of the holder assembly
102
.
At one end face of the holder assembly
102
is formed a recess
146
having a bottom surface to which one or more drive pins
135
are fixed and having a step section
145
on which an O-ring is seated.
Within the recess
146
of the holder assembly
102
is installed a rotational seal ring
101
that is also comprised of two halves that are split in the axial direction. The rotational seal ring
101
has a rotational sealing face
106
at one end and one or more engagement sinks
103
at the other end for the engagement with the corresponding drive pins
135
. Between the step section
145
of the holder assembly
102
and the outer face of the rotational seal ring
101
is provided a space
133
in which a second O-ring
132
is disposed. The second O-ring
132
is adapted to fasten the splitting faces to closely contact the two halves of the rotational seal ring
101
and adapted to seal the space
133
. An inlet
144
is also formed to allow the sealed fluid to enter the space
133
.
An axial two-half type stationary seal ring
110
having a stationary sealing face
111
in close contact with the rotational sealing face
106
is fitted to the rotational shaft
148
with a gap therebetween. The stationary seal ring
110
is disposed within the space defined by the inner space defining face
143
of the gland assembly
140
and is movably fitted to a fitting surface S. The stationary seal ring
110
is biased toward the rotational seal ring
102
by a plurality of leaf springs
130
mounted at the end of the gland assembly
140
. Further, a space chamber
114
is formed between the outer face of the stationary seal ring
110
and the inner space defining face
143
. A third O-ring
137
is provided in the space chamber
114
. The third O-ring
137
is adapted to fasten the mating surfaces to closely contact the two halves of the stationary seal ring
110
and adapted to seal the space chamber
114
.
In the mechanical seal device
100
of the first related art constituted in such a way described, it is required to provide the two-half type gland assembly
140
in which a mechanical seal is build. The gland assembly
140
necessarily has a complicated structure due to its two-half constitution in which the two halves are assembled with screw bolts and due to the attachment of the gland assembly
140
to the end face of the housing
150
with screw bolts. Accordingly, there is a problem that the gland assembly
140
becomes larger in size. Also, the two-half type holder assembly
102
assembled with screw bolts has a complicated structure and a large size because it contains the rotational seal ring
101
. The large size of the holder assembly
102
makes the mechanical seal device larger in its overall size. The higher the pressure of the fluid to be sealed is, the larger the thickness required for the components of the gland assembly
140
becomes, causing the entire structure to be large in size.
A plurality of leaf springs
130
circumferentially located at the end of the gland assembly
140
make the structure further complicated. There is also a problem that it becomes more difficult to fabricate the entire seal device because of the increase of the total number of parts.
Further, when the pressure of the sealed fluid is high, the high pressure fluid from the fluid passage
142
acts on the second O-ring
132
and the third O-ring
137
. This causes the deformable seal rings
101
and
110
of silicon carbide or carbon of the split structure to be easily deformed by the pressure of the sealed fluid and as a result, the sealing faces
106
and
111
, specifically the rotational sealing face
106
is deformed, which leads the sealed fluid to leak between the sealing faces
106
and
111
.
Further, there exists a two-half type, outside mechanical seal device
200
as a second related art, as shown in FIG.
4
.
In
FIG. 4
, the two-half mechanical seal device
200
is provided for sealing the sealed fluid between a rotational shaft
148
and a housing
150
through which the rotational shaft
148
passes. The fluid is sealed by a stationary sealing face
161
through the inner face side of a stationary seal ring
160
.
The axial two-half type stationary seal ring
160
for sealing the fluid on its inner face side has an inner face fitted to the rotational shaft
148
with a gap therebetween. This gap formed between the inner face of the stationary seal ring
160
and the outer face of the rotational shaft
148
defines a fluid passage for the sealed fluid.
The stationary seal ring
160
has an outer face fitting to the inner face
167
on one side of an annular gasket
165
comprised of combined two thick halves each having the L shaped sectional area. The end face
166
on the other side of the gasket
165
is in close contact with the end face of the housing
150
. The gasket
165
is also split into two halves. Those two halves can be in close contact with each other in a way that projections and recesses formed on the splitting faces of two halves are closely fitted to each other.
The stationary seal ring
160
is secured through the gasket
165
to the inner face
167
on one side of an axial two-half type stationary holder
168
, the other end of which is fitted and secured to the projection formed in one end of the housing
150
. In order to assemble the stationary two-half type holder
168
, two halves of the two-half stationary holder
168
are fastened with two screw bolts
153
and coupled together.
In the two-half stationary holder
168
, in order to compensate for holding the stationary seal ring
160
fittingly secured on other side while one end is fittingly secured to the projection of the housing
150
, one of the fitting sections has a recess or undercut. In this recess structure, the part of the gasket
165
sandwiched by the two-half holder
168
and the stationary seal ring
160
is made thick.
The two-half type rotational seal ring
170
is fitted to the rotational shaft
148
with a gap therebetween and has at one end a rotational sealing face
171
in close contact with the stationary sealing face
161
to

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