Mechanical face seal assembly

A mechanical face seal assembly has a cylindrical retainer fixedly mounted between a rotating shaft and a stationary housing. The rotating shaft defines a longitudinal axis and a rotating sealing ring rotates with the shaft. The rotating sealing ring is axially offset from the retainer. The retainer includes inner and outer legs which extend longitudinally along the axis and are radially spaced with respect to each other. The assembly also includes a non-rotating washer disposed within the retainer. A spring biases the washer towards the sealing ring. The invention also includes a method of easily assembling a seal by deforming an outer leg of the retainer after assembly of the seal components.

BACKGROUND OF THE INVENTION 
This invention relates to a mechanical face seal assembly for rotating 
shaft assemblies which is less expensive than known seals. 
Mechanical face seals are commonly used to prevent gases and liquids from 
leaking along rotating shaft assemblies. The seal must be capable of 
sealing the shaft both statically and dynamically. That is, both when the 
shaft is rotating and when it is stopped. Further, the seal is required to 
withstand high operating pressures, temperatures and shaft speeds. 
Mechanical face seals provide longer life and less leakage than radial lip 
seals. Face seals are used in pumps due to their ability to withstand 
large changes in pressure. This type seal is also compatible with many 
fluids. 
Typically a face seal is provided between a rotating shaft and a fixed 
housing. In known face seals a seal ring is fixed to a housing wall. A 
spring biased washer rotates with the shaft and is biased toward the seal 
ring. The washer and spring must be carefully balanced, since they rotate. 
The primary sealing effect takes place at opposed faces of the washer and 
seal ring. Secondary sealing elements are often necessary to augment the 
primary seal. 
Known mechanical face seals often fail because the secondary seal between 
the shaft and the washer wears down due to vibration and shaft galling 
caused by abrasive particles in the fluid. Therefore, the seal has to be 
replaced. Replacement is costly and time consuming. It is common for the 
secondary seal to be replaced as often as once a month. More recently, in 
some applications mechanical face seals can last about 0.5 million miles 
(i.e., approximately the lifetime of a truck). However, these long lived 
seals are very expensive. 
Therefore, a major concern is reducing the cost of a long-lived face seal. 
One main factor influencing the cost of the seal is due to the rotating 
washer and the need to balance the spring and the washer. The process of 
balancing the spring and the washer is difficult. 
Further, the known rotating washer does not permit a compact mechanical 
face seal. The prior art fails to address the need to produce a mechanical 
face seal that is less costly. 
Accordingly there remains a need for a mechanical face seal that can be 
fabricated easily and economically. 
SUMMARY OF THE INVENTION 
In a disclosed embodiment of this invention, a face seal assembly for a 
rotating shaft includes a seal ring which rotates with the shaft. A spring 
biased washer is received in a retainer which is fixed to a housing 
surrounding the shaft. Thus, the washer and the spring do not rotate, and 
precise balancing of these components is not necessary. 
In other features of this invention, a non-rotation structure is provided 
between the washer and the retainer such that the washer may move axially 
toward and away from the seal, but will not rotate. 
The retainer preferably includes a leg which extends axially beyond the 
seal ring, and then is deformed radially inwardly such that a face of the 
leg secures the seal ring and washer within the retainer. Preferably, a 
labyrinth seal is also provided between the seal ring and retainer. 
In a method according to this invention, the retainer is initially formed 
without the radially inwardly extending leg. The components of the seal 
are assembled, and the outer leg is then deformed radially inwardly to 
form a unitized seal body. After assembling the seal, it is mounted into 
the housing or onto the shaft. 
The present invention discloses a long-lived, easy to assemble seal which 
is inexpensive compared to the known art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows a mechanical face seal assembly 10 including a retainer 12, a 
washer 14, a spring 16 and a sealing ring 18 for a rotating shaft 20. 
Retainer 12 is positioned within a stationary housing 24 and mounted 
radially outwardly of rotating shaft 20. Shaft 20 defines a longitudinal 
axis 22. Retainer 12 has inner leg 26 and outer leg 28 connected by a base 
29 to define a recess 27. Legs 26 and 28 are generally cylindrical and 
surround shaft 20. A sealing ring 18 is positioned axially outside recess 
27 and fixed to rotate with shaft 20. A non-rotating washer 14 surrounds 
shaft 20 and is axially movable within recess 27 and toward ring 18. A 
spring 16 is disposed in recess 27 and biases washer 14 toward ring 18. In 
mechanical face seals it may be desirable to maintain a thin lubricant 
film between washer 14 and ring 18, rather than have actual contact. 
In known mechanical face seals, the washer rotates with the shaft and is 
biased toward the seal ring. With these known seals, the washer and spring 
must be carefully balanced because they rotate. The subject invention 
includes rotating ring 18 while washer 14 does not rotate. This difference 
allows the assembly 10 to be assembled without complicated balancing 
required by known seal assemblies because washer 14 and spring 16 are not 
rotating. The washer 14 has a rim 19 at an outer periphery and a sealing 
portion 21 extending from the rim axially toward the ring 18 at a location 
radially inward of rim 19. The spring 16 applies its bias force at the 
rim. 
A shield 30 and retainer 12 form a labyrinth seal. Shield 30 is attached to 
the shaft and provides a seat 32 for ring 18. Shield 30 also extends 
radially outwardly beyond ring 18. A face 31 of the outer leg 28 opposes a 
face 33 of the shield 30 to form a labyrinth seal. The seal between 
portion 21 and seal ring 18 is particularly useful when shaft 20 is not 
rotating. The labyrinth seal prevents contaminants from reaching the 
contact seal area. 
Outer leg 28 has a hollow annular collar 36 which in an undeformed 
orientation has portion 37 extending beyond shield 30. Portion 35 of outer 
leg 28 extends outwardly along a face of housing 24, and collar 36 extends 
from portion 35. As can be appreciated, portion 35 extends radially 
outwardly from the nominal position of outer leg 28. The radially 
outermost end of shield face 33 is radially outward of the nominal 
location of the outer leg 28. However, portion 35 extends radially beyond 
the radially outermost end of shield face 33. Collar 36 extends beyond the 
radially outermost portion of the shield face 33, and face 31 then extends 
back radially inwardly. This combination forms an effective labyrinth seal 
preventing leakage. A resilient ring 39 rests between retainer 12 and 
housing 24. Ring 39 maintains retainer 12 secure, and prevents retainer 12 
from vibrating between housing 24 and shaft 20. 
A bellows 42 is mounted within the retainer 12 for supporting the spring 16 
and moving the washer 14 longitudinally along the axis 22. Bellows 42 also 
has a pair of axially spaced first and second ends 44, 46. End 46 is 
complementary with rim 19 surrounding the washer 14. End 44 fits flush 
with base 29 of retainer 12. The bellows 42 provides an expandable seal. 
Rubber strip 54 is disposed between ring 18 and the shield 28. Ring 18 and 
strip 54 are press fit into seat 32. Rubber strip 56 is disposed between 
the shield 30 and the shaft 20. 
An end of inner leg 26 has at least one bent portion 40. As shown in FIG. 
2, bent portion 40 is engaged in groove 43 in washer 14. Inner leg 26 thus 
prevents washer 14 from rotating with ring 18. Preferably, there are a 
plurality of portions 40 and grooves 43. 
FIG. 3 shows a second embodiment 80 of the present invention. In general, 
the assembly is similar to the FIG. 1 embodiment. A wave spring 82 biases 
the washer 14 in this embodiment. A bellows 122 is mounted within retainer 
98 for supporting the spring 82 and moving the washer 14 longitudinally 
along the axis 22. Seal ring 84 includes a ring shaped plastic spacer 86 
press fit at an outer periphery of the rotating sealing ring 84. Plastic 
spacer 86 has a cylindrical portion 88 and a rim 90 that extends radially 
outward from an end of the cylindrical portion 88. Rim 90 has a set of 
labyrinth grooves 92. Grooves 92 are adjacent to the portion 94 of the 
outer leg 96 of retainer 98. Rotating sealing ring 84 has a flange portion 
100 extending from a central portion 102 radially outward from the 
longitudinal axis 22. Further, rotating sealing ring 84 has a guideway 104 
within the central portion 102. The plastic spacer 86 extends beyond the 
central portion 102 of rotating sealing ring 84 such that the tip of 
spacer portion 88 surrounds the washer 14. An O-ring 106 fits within the 
guideway 104 of rotating ring 84. 
Portion 108 of outer leg 96 has an indentation 110 at the point of 
deformation to produce face 112 which is deformed radially inward. 
The O-ring 106 allows the shaft 20 to pivot within the seal ring 84 and 
O-ring 106 to allow adjustment. At the same time, the O-ring 106 is 
tightly received within guideway 104 such that it does ensure the seal 
ring 84 does rotate with the shaft 20. 
In the prior art, it was very difficult to assemble the seal components 
within the tight space between the housing and the shaft. The present 
invention simplifies this assembly process, and allows the use of a less 
complex, less expensive system. 
FIG. 4 schematically shows a method of assembling a seal according to the 
present invention. With both the FIGS. 1 and 3 embodiments, the spring, 
washer and seal ring and associated parts are all placed within the outer 
leg of the retainer, with the outer leg of the retainer being in its 
undeformed position. The outer leg of the retainer is then deformed 
radially inwardly to provide a unitized seal pack. 
As shown in FIG. 4, the unitized seal pack 120 is then placed within the 
stationary housing 24. The shaft 20 is then forced axially within the seal 
pack 120. 
With the FIG. 1 embodiment, a force to insert the seal pack 120 into the 
housing may be placed on the face 31. The spring 16 will tend to bias the 
face 33 against the face 31 until the shaft abuts the shield member 30 and 
may force it axially inwardly slightly relative to the face 31 as shown in 
FIG. 1. 
In assembling the FIG. 3 embodiment, it is preferable that the force to 
insert the seal pack 120 into the housing be applied along a radially 
outer portion of flange portion 100 of seal ring 84. That force is then 
transmitted through spacer 86 to portion 94 of outer leg 96. 
Further in this embodiment, since the seal ring 84 is not fixed to the 
shaft 20, the O-ring 106 and seal ring 102 may adjust slightly relative to 
the shaft 20. In addition, in some applications it is possible that the 
O-ring 106 and seal ring 102 may move axially inwardly along with the 
shaft such that the plastic spacer portion 90 is brought into contact with 
the portion 94 of the outer leg 96. Upon continued rotation of the seal 
ring 84 and spacer 86, the face of the portion 90 abutting portion 94 of 
the outer leg 96 may wear. 
Obviously, many modifications and variations of the present invention are 
possible in light of the above teachings. It is, therefore, to be 
understood that within the scope of the appended claims, the invention may 
be practiced otherwise than as specifically described.