JOINT MECANIQUE

MECHANICAL SEAL ASSEMBLY

Abrégé anglais

078257-BJ(V)

MECHANICAL SEAL ASSEMBLY

Abstract:


A mechanical seal assembly (10) especially
adaptable for use in the chemical industry in
which a jacket (36) impervious to the chemical
involved surrounds a spring means (24) which urges
the seal faces (20,22) toward one another, the
spring being capable of transmitting torque and
provides axial support to the jacket.

Revendications

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A mechanical seal assembly especially adaptable
for use in the chemical industry and which is associated with a
rota-table shaft and a stationary housing which may contain
chemically active fluid, comprising:
a stationary sealing ring associated with said
housing;
a rotatable sealing ring associated with said shaft;
said sealing rings having seal faces opposed to
one another;
a retainer connected to said shaft;
resilient means connected at one end to one of said
seal rings and at its other end to said retainer for urging
said one of said seal rings toward the other of said seal rings;
fluid impervious means surrounding, separate from
and supported by the outside of said resilient means for
protecting said resilient means from said chemically active
fluid;
said fluid impervious means comprising a jacket of
shrinkable plastic shrunk onto said resilient means; and
means encircling said jacket and sealing the ends
thereof to one of said seal rings and to said retainer.
2. A mechanical seal assembly as recited in Claim
1, wherein said resilient means comprises a coil spring.




3. A mechanical seal assembly as recited in Claim
2, wherein said encircling means comprises O-rings and said
resilient means is connected at one end to said rotatable seal
ring.
4. A mechanical seal assembly especially adaptable
for use with chemically active fluids and comprising:

a stationary seal ring adapted to be connected to
a housing;
a rotatable seal ring adapted to be connected to
a rotatable shaft;
said seal rings having faces opposed to one another;
a coil spring urging said rotatable seal ring toward
said stationary seal ring;
a retainer adapted to be connected to the rotatable
shaft for positioning one end of said spring;
a fluid impervious jacket surrounding and separate
from and supported by the outside of said spring; and
means sealing the ends of said jacket to said
retainer and said rotatable seal ring,
said fluid impervious jacket comprising a fluour-
ethylene-propylene plastic shrunk onto said spring;
said means sealing the ends of said jacket to
said retainer and said rotatable seal ring comprising O-rings
around said jacket and received in grooves in said retainer and
said rotatable seal ring, respectively.

Description

73




ME~e~llCAI ~ MBLY
Descrlption

Mechanical sPal assemblies for sealing fluids
from each other and associated with a stationary
housing and a rotatable shaft are well known in the
art. The housing may house a pump impeller connected
to ~he rotatable shaft. To substantially eliminate
leakage of the pump fluid from the housing, a mechanical
seal assembly is used. Generally these mechanical
seal assemblies comprise a seal ring connected to
the housing and a seal ring connected to the shaft,
the rings having opposing seal faces one or both of
which are resiliently urged toward the other. Such
construction can leave the resilient means exposed
to one of the fluids - i.e., 1) fluid being pumped
and 2) air or other fluid. ]:f the fluid being pumped
is chemically active, it can corrode and damage the
resilient means and/or other par~s of the assembly.
A mechanical seal assembly is disclosed herein
constructed especially for use in chemical applications
where corrosive fluids are handled and in which a
chemically impervious covering is used to protec~
various parts of the assembly from contact with the
corrosive fluids. Speci~ically, the assembly comprises
a conventional rotatable and stationary seal rings of

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a coil spring for urging -the rings toward one another.
Preferably, a heat shrinkable plastic tubing surrounds the
spring and is sealed at one end of the spring retainer and at
the other end to a seal ring, the tubing being of a fluor-
ethylene-propylene material. Other elastomers may be used to
encase the spring, in which case other methods of joining the
sleeve or jacket to the end pieces would be necessary.
Therefore, in accordance with the present invention
there is provided a mechanical seal assembly especlally adaptable
for use in the chemical industry which is associated with a
rotatable shaft and a stationary housing which may contain
chemically active fluid. The assembly comprises a stationary
sealing ring associated with the housing, a rotatable sealing
ring associated with the shaft, the sealing rings having seal
faces opposed to one another, a retainer connected to the shaft,
resilient means connected at one end to one of the seal rings
and at its other end to the retainer for urging the one of the
seal rings toward the other of the seal rings, fluid impervious
means surrounding, separate from and supported by the outside
of the resilient means for protecting the resilient means from
the chemically active fluid. The fluid impervious means
comprising a jacket of shrinkable plastic shrunk onto the
resilient means. The assembly further includes means encircling
the jacket and sealing the ends thereof to one of the seal rings
and to the retainer.
The single figure is a longitudinal, partial sectional
view of a mechanical seal assembly according to this invention.
The mechanical seal assembly is generally identified
as 10 and comprises a stationary seal ring 12 sealed to a

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multiple part housing 14 by an O-ring 16 and a rotatable seal
ring 18 the rings 12 and 18 having opposed seal faces 20 and
22, respectively. The seal ring 18 is urged toward the seal
ring 12 by a coil spring 24, one end of which surrounds and
frictionally engages a reduced portion of the ring 18 and the
other end of which surrounds and frictionally engages a reduced
portion 20 of a spring retainer 30, the latter being adapted
to be connected to a rotatable shaft 32 by a set screw 34 and
sealed thereto by an O ring 35. Because of the connection of
the retainer 30 with the shaft 32 and the spring 24, the seal
ring 18 is rotatable with the shaft 32.
A sleeve or jacket 36 surrounds the spring 24 and
extends over parts of the seal ring 18 and the spring retainer
30. One end of the sleeve 36 is received in an annular groove
38 in the ring 18 and is fixed therein by an O-ring 40. The
other end




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of the sleeve 36 is received in an annular groove
42 in the retainer 30 and is fixed therein by an
O-ring 44.
Preferably the sleeve 36 comprises a heat
shrinkable tubing of a fluor-ethylene-propylene
(FEP). A portion of the seal 10 can be constructed
as a cartridge, i.e., a retainer 30, a seal xing
18 and a spring can be assembled in a mandrel.
A length of FEP tubing is slipped over the assembled
parts followed by assemblying the O-rings 40 and 44
in the appropriate grooves 38, and 42, respectively.
Warm air is then directed onto the tubing which
causes it to shrink and assume the shape as shown
in the drawi~g. The parts can then be removed from
the mandrel for future assembly with a seal ring 12.
For high pressure uses, multiple ply sleeves
or jackets can be used.
It is to be understood that other elastomers
may be used to encase the spring 24, in which case
other methods of joining the sleeve or jacket to
the end pieces would be necessary. The spring 24
serves to radially support the sleeve or jacket and
enables the seal assembly to be used at much higher
pressures than in the absence of such radial support.