Note: Descriptions are shown in the official language in which they were submitted.
CA 02699185 2010-04-08
APPLICATION FOR PATENT
INVENTOR: LANNIE L. DIETLE
TITLE: HYDRODYNAMIC SEAL WITH IMPROVED EXCLUSION
AND LUBRICATION
SPECIFICATION
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional Application
Ser. No. 61/212,179
filed April 8, 2009, entitled "Rotary seal with improved environmental
exclusion," and claims
the benefit of U.S. Provisional Application Ser. No. 61/283,277 filed November
30, 2009,
entitled "Seal Carrier," and claims the benefit of U.S. Provisional
Application Ser. No.
61/284,179 filed December 14, 2009, entitled "Pressure-balanced floating seal
carrier."
Provisional Application Ser. Nos. 61/212,179, 61/283,277, and 61/284,179 are
incorporated by
reference herein for all purposes.
BACKGROUND OF THE INVENTION
1. Field of the Invention.
[0002] This invention relates to hydrodynamic rotary seals that are used to
retain lubricant and
exclude the environment in diverse applications. More specifically, this
invention relates to
features that improve exclusion edge circularity and regulate contact pressure
at the dynamic
sealing interface for improved abrasive exclusion, and improved consistency of
hydrodynamic
lubrication and flushing action.
2. Description of the Related Art.
[0003] The following commonly assigned patent documents are related to the
invention, and are
incorporated herein by reference for all purposes:
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[0004] United States Patents:
[0005] U.S. Pat. No. 7,052,020 Hydrodynamic Rotary Seal;
[0006] U.S. Pat. No. 6,767,016 Hydrodynamic Rotary Seal With Opposed Tapering
Seal Lips;
[0007] U.S. Pat. No. 6,685,194 Hydrodynamic Rotary Seal With Varying Slope;
[0008] U.S. Pat. No. 6,561,520 Hydrodynamic Rotary Coupling Seal;
[0009] U.S. Pat. No. 6,494,462 Rotary Seal With Improved Dynamic Interface;
[0010] U.S. Pat. No. 6,382,634 Hydrodynamic Seal With Improved Extrusion
Abrasion and
Twist Resistance;
[0011] U.S. Pat. No. 6,334,619 Hydrodynamic Packing Assembly;
[0012] U.S. Pat. No. 6,315,302 Skew Resisting Hydrodynamic Seal;
[0013] U.S. Pat. No. 6,227,547 High Pressure Rotary Shaft Sealing Mechanism;
[0014] U.S. Pat. No. 6,120,036 Extrusion Resistant Hydrodynamically Lubricated
Rotary Shaft
Seal;
[0015] U.S. Pat. No. 6,109,618 Rotary Seal With Enhanced Lubrication and
Contaminant
Flushing;
[0016] U.S. Pat. No. 6,036,192 Skew and Twist Resistant Hydrodynamic Rotary
Shaft Seal;
[0017] U.S. Pat. No. 6,007,105 Swivel Seal Assembly;
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[0018] U.S. Pat. No. 5,873,576 Skew and Twist Resistant Hydrodynamic Rotary
Shaft Seal;
[0019] U.S. Pat. No. 5,823,541 Rod Seal Cartridge for Progressing Cavity
Artificial Lift Pumps;
[0020] U.S. Pat. No. 5,738,358 Extrusion Resistant Hydrodynamically Lubricated
Multiple
Modulus Rotary Shaft Seal;
[0021] U.S. Pat. No. 5,678,829 Hydrodynamically Lubricated Rotary Shaft Seal
With
Environmental Side Groove;
[0022] U.S. Pat. No. 5,230,520 Hydrodynamically Lubricated Rotary Shaft Seal
Having Twist
Resistant Geometry;
[0023] U.S. Pat. No. 5,195,754 Laterally Translating Seal Carrier For a
Drilling Mud Motor
Sealed Bearing Assembly;
[0024] U.S. Pat. No. 4,610,319 Hydrodynamic Lubricant Seal For Drill Bits;
[0025] United States Patent Applications:
[0026] Pub. No. 2005/0093246 Rotary Shaft Sealing Assembly;
[0027] Pub. No. 2006/0214379 Composite, High Temperature, Dynamic Seal and
Method of
Making Same;
[0028] Pub. No. 2009/0250881 Low Torque Hydrodynamic Lip Geometry for Bi-
Directional
Rotation Seals;
[0029] Pub. No. 2007/0013143 Filled Hydrodynamic Seal With Contact Pressure
Control, Anti-
Rotation Means and Filler Retention Means;
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[0030] Pub. No. 2007/0205563 Stabilizing Geometry for Hydrodynamic Rotary
Seals; and
[0031] Pub. No. 2009/0001671 Rotary seal with improved film distribution.
[0032] Assignee Kalsi Engineering manufactures various configurations of
hydrodynamic rotary
seals, and sells them under the registered trademark "KALSI SEALS." The rotary
seals that are
marketed by Kalsi Engineering are installed with radial interference (i.e.,
compression), and seal
by blocking the leak path. The seals employ various variable width dynamic lip
geometries that
cause a lubricant-side edge of a dynamic sealing interfacial contact footprint
to be wavy. As a
consequence of the wavy lubricant-side footprint edge, the rotary motion of
the lubricant-wetted
shaft drags lubricant into the dynamic sealing interface, and causes the seal
to hydroplane on a
film of lubricant that separates the seal from the shaft. This hydrodynamic
operating regime
allows the seal to operate cooler and with less wear, even under conditions of
high differential
pressure acting from the lubricant side of the seal.
[0033] The environment side of the interfacial contact footprint is intended
to be circular rather
than wavy, to avoid hydrodynamic activity with the environment, and thereby
exclude the
environment. Circumstances exist where the environment side of the footprint
of prior art seals
(and the "exclusion edge" of the seal) can become wavy, as a consequence of
compression of the
variable width dynamic lip geometry. Such waviness can encourage abrasive
invasion of the
dynamic sealing interface.
[0034] The interfacial contact pressure is managed from an abrasion resistance
and interfacial
lubrication standpoint by an "exclusion edge chamfer." Independent of the
exclusion edge
chamfer, the interfacial contact pressure varies as a function of the local
width of the dynamic
lip. This lip-width induced variation causes the interfacial contact pressure
to be higher than
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desired from an interfacial lubrication standpoint at some locations, and
lower than desired from
an abrasive exclusion standpoint at other locations. Certain operating
conditions can also result
in undesirable increases in interfacial contact pressure. When lubrication
thus decreases, the seal
generates undesirable heat due to increasing asperity friction, causing a loss
of lubricant film
viscosity and seal wear. The friction further increases seal temperature,
compounding the
problem.
[00351 It is desirable to be able to overcome the shortcomings described
above. A sealing
arrangement that provides a better way to manage exclusion edge circularity
and interfacial
contact pressure would be an advantage in many applications where long sealing
life is needed to
protect critical components in difficult operating conditions.
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SUMMARY OF THE INVENTION
[0036] The present invention is a rotary sealing arrangement that overcomes
the above-described
shortcomings of the prior art. Preferably, the seals are used to establish
sealing between a
machine component (such as a housing) and a relatively rotatable surface (such
as a shaft), in
order to separate a lubricating media from an environment. Seal geometry on a
dynamic lip
interacts with the lubricating media during relative rotation to wedge a
lubricating film into the
dynamic sealing interface between the seal and the relatively rotatable
surface. A portion of the
lubricating film migrates toward, and into, the environment and thus provides
a contaminant
flushing action.
[0037] The rotary seal includes a dynamic lip having local variations in
width. The dynamic lip
deforms when compressed into sealing engagement with the relatively rotatable
surface, defining
a hydrodynamic wedging angle with respect to the relatively rotatable surface,
and defining an
interfacial contact footprint of generally circular configuration but varying
in width. A non-
circular (e.g., wavy) footprint edge hydrodynamically wedges the lubricating
film into the
interfacial contact footprint.
[0038] An important aspect of a preferred embodiment of the present invention
involves
manufacturing an exclusion edge of the seal in a wavy pattern, to improve
installed circularity of
the exclusion edge, which improves environmental exclusion. The as-
manufactured waviness of
the exclusion edge also beneficially influences interfacial contact pressure
by raising interfacial
contact pressure in some locations, and lowering it at others, compared to the
prior art.
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[0039] A preferred embodiment of the invention is a generally circular,
hydrodynamically
lubricating rotary seal that is installed in a machine component that holds
the seal in compressed
relation with a relatively rotatable surface. The preferred embodiment of the
invention manages
exclusion edge circularity and interfacial contact pressure in ways that are
advantageous to
interfacial lubrication and environmental exclusion. The preferred embodiment
of the invention
includes several desirable features. The individual features can, however, be
used separately
when it is advantageous to do so due to operating conditions and/or when
simplification is
required by circumstances such as budgetary constraints.
[0040] It is intended that the rotary seals of the present invention may
incorporate one or more
seal materials without departing from the spirit or scope of the invention,
and may be composed
of any suitable sealing material, including elastomeric or rubber-like
materials which may, if
desired, be combined with various plastic materials such as reinforced
polytetrafluoroethylene
("PTFE") based plastic. If desired, the rotary seals may be of monolithic
integral, one piece
construction or may also incorporate different materials bonded, co-
vulcanised, or otherwise
joined together to form a composite structure.
[0041] The seal can be configured for dynamic sealing against a shaft, a bore,
or a face.
Simplified embodiments are possible wherein one or more features of the
preferred embodiment
are omitted.
[0042] One objective of the preferred embodiment of the present invention is
to provide a
hydrodynamic rotary seal having improved environmental exclusion. Another
objective is
reduced torque, for reduced wear and heat generation. Another objective is
improved
distribution of lubricant across the dynamic sealing interface, and
correspondingly reduced seal
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wear, particularly in seals that are exposed to skew-resisting axial
confinement and/or high
differential pressure that may be acting from either side of the seal. Another
objective is to
enable the use of hydrodynamic inlet geometry that better accommodates high
temperature
operation in conditions of skew-resisting axial confinement.
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BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0043] So that the manner in which the above recited features, advantages, and
objects of the
present invention are attained and can be understood in detail, a more
particular description of
the invention, briefly summarized above, may be had by reference to the
embodiments thereof
that are illustrated in the appended drawings. It is to be noted, however,
that the appended
drawings only illustrate preferred embodiments of this invention, and are
therefore not to be
considered limiting of its scope, for the invention may admit to other equally
effective
embodiments that vary only in specific detail.
[0044] In the drawings:
[0045] FIGS. IA and 113 are fragmentary cross-sectional views representing an
uncompressed
cross-sectional configuration of a ring-shaped hydrodynamic seal having a
dynamic sealing lip
according to a preferred embodiment of the present invention, FIG. IA is a
view taken along
lines IA-IA of FIG. 1C at a narrow location of the dynamic sealing lip and
FIG. 113 is a view
taken along lines 1 B-1 B of FIG. 1 C at a wide location of the dynamic
sealing lip;
[0046] FIG. 1 C is fragmentary plan view representing the uncompressed
condition of the
hydrodynamic features between the first and second body ends of the
hydrodynamic seal of
FIGS. 1A and 113;
[0047] FIG. ID is a fragmentary cross-sectional view of the hydrodynamic seal
showing the
compressed cross-sectional configuration in conjunction with first and second
machine
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components, the view corresponding to the narrow location of the dynamic
sealing lip shown in
FIG. IA;
[0048] FIG. I E is a fragmentary cross-sectional view of the hydrodynamic seal
showing the
compressed cross-sectional configuration in conjunction with first and second
machine
components, the view corresponding to the wide location of the dynamic sealing
lip shown in
FIG. I B;
[0049] FIG. 1 F is a schematic representation of an exclusion edge of the
hydrodynamic seal in
the installed compressed condition and the uninstalled uncompressed condition,
and includes a
representation of the tendency of the prior art exclusion edge in an installed
compressed
condition;
[0050] FIG. 2 is a schematic representation similar to FIG. 1 F in which the
hydrodynamic seal
has a different hydrodynamic inlet wave form than the seal of FIG. IF; and
[0051] FIG. 3 is a fragmentary cross-sectional view of an alternate embodiment
of the present
invention showing the compressed cross-sectional configuration of a
hydrodynamic seal in
conjunction with first and second machine components.
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DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0052] The ring-like rotary seal according to the preferred embodiments of the
present invention
is generally referred to as reference number 2 in the drawings. Features
throughout this
specification that are represented by like numbers have the same basic
function.
[0053] FIGURES 1A-IF
[0054] FIGURES 1A-1F are views representing a preferred embodiment of the
present
invention, and should be studied together, in order to attain a more complete
understanding of
the invention.
[0055] FIGURES 1A & 1B
[0056] FIGURES 1A and I B are fragmentary views that represent the cross-
sectional
configuration of the rotary seal 2 at respective first and second locations
before installation, and
FIG. 1 C is a fragmentary view of the seal that identifies the cutting planes
that relate to the cross-
sections of FIGS. IA and 1B. FIGURES 11) and I E are fragmentary views that
represent the
cross-sectional configuration of the rotary seal 2 at the same first and
second locations after
installation.
[0057] Referring now to FIGS. 1A and I B, the rotary seal 2 is shown in an
uncompressed,
uninstalled condition. The rotary seal 2 has a ring-like seal body 4 of
generally circular
configuration. The term "ring-like" is used with the understanding that the
term "ring" is
commonly understood to encompass shapes other than those that are perfectly
circular. As an
example, a decorative finger ring often has beaded edges or a sculpted shape,
yet is still called a
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ring. As another example, the key ring of U.S. Pat. No. 1,462,205 is not
everywhere circular.
There are thousands of precedents for using the term "ring-like" in a patent,
and many patents
use the term in conjunction with a seal or a body of a seal. For example, see
U.S. Pat. Nos.
612,890, 4,361,332, 4,494,759, 4,610,319, 4,660,839, 4,909,520, 5,029,879,
5,230,520,
5,584,271, 5,678,829, 5,833,245, 5,873,576, 6,109,618, and 6,120,036. Note
that in many of the
examples, the seal in question has features that result in the shape not being
everywhere circular;
for example, in some cases the dynamic lip of the ring-like seal has a wavy
lubricant-side shape.
[0058] The rotary seal 2 includes a dynamic sealing lip 6 of generally annular
form that projects
from the seal body 4. The rotary seal 2 incorporates a static sealing surface
32. The rotary seal 2
preferably also includes a static sealing lip 8 that projects from the seal
body 4 in generally
opposed relation to the dynamic sealing lip 6, as taught by the prior art.
[0059] As used herein, the "modulus" or "elastic modulus" of an elastomer can
be estimated in
accordance with FIG. 1 of ASTM D 1415-83, Standard Test Method for Rubber
Property--
International Hardness. Rotary seal 2 is constructed of sealing material which
is preferably an
elastomer compound or a combination of one or more elastomer compounds, or a
combination of
a suitable plastic and an elastomer compound, as taught by the prior art. For
example, the region
of the seal comprising the dynamic sealing lip 6 could be made from a first
material, and the
region comprising the static sealing surface 32 and/or the static sealing lip
8 could be made from
a second material. As taught by commonly assigned U.S. Pat. No. 5,738,358, the
first material
could have a higher elastic modulus, compared to that of the second material.
As taught by
commonly assigned Canadian Pat. No. 2601282, the first material could be
selected based on its
dynamic characteristics, and the second material could be selected based on
its compression set
resistance characteristics.
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[00601 It is commonly understood by those having ordinary skill in the art
that elastomers used
in seal construction are compounds that include one or more base elastomers.
Such base
elastomers include, but not limited to, HNBR (highly saturated nitrile
elastomer), FKIVI
(fluorocarbon rubber), FEPM (also known as TFE/P or Tetrafluoroethylene and
Propylene
Copolymer), and EPDM. Such compounds may include other compounding agents
including
fillers, processing aids, anti-degradants, vulcanizing agents, accelerators
and activators. The
effects of the ingredients used are generally understood by those of ordinary
skill in the art of
compounding elastomers. Likewise, the ingredients used in manufacturing
plastics that are used
in seal construction are generally understood by those of ordinary skill in
the art of developing
plastic seal materials.
[00611 The seal body 4 has a first body end 10 and a second body end 12. The
seal body 4,
being a generally circular, ring-like entity, defines a theoretical
centerline/axis (not shown). For
orientation purposes, it should be understood that in all of the cross-
sectional views herein, the
cutting plane of the cross-section is aligned with and passes through the
theoretical axis of the
rotary seal 2. The first body end 10 of rotary seal 2 is located in generally
opposed relation to
the second body end 12. Within the seal industry, the first body end 10 of
rotary seal 2 is
sometimes referred to as the "lubricant end," and the second body end 12 is
sometimes referred
to as the "environment end."
[00621 Preferably, the size of the dynamic sealing lip 6 is not uniform, but
instead varies, to
produce a sealing interface of variable width when installed, in order to
cause hydrodynamic
wedging activity in response to relative rotation. For example, the size of
dynamic sealing lip 6
is smaller at the first location of FIG. 1 A, compared to the size at the
second location of FIG. I B,
as taught by the prior art. This intentional variation in the size of the
dynamic sealing lip 6 is
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accomplished by varying one or more dimensions of the dynamic sealing lip 6,
in accordance
with the teachings of the commonly assigned patents and patent applications
noted above.
[0063] Prior art patents and patent publications teach that almost any
dimension of the dynamic
sealing lip 6 can be varied to cause the size of the dynamic sealing lip 6 to
vary, and produce a
dynamic interface of variable width when installed, and to cause hydrodynamic
wedging activity
in response to relative rotation when installed. For example, U.S. Pat. No.
4,610,319 teaches that
the width of the dynamic lip can be varied to achieve hydrodynamic wedging
activity, U.S. Pat.
No. 6,685,194 teaches that the slope and/or curvature of the dynamic lip can
be varied to produce
hydrodynamic wedging activity, and U.S. Pat. Nos. 6,109,618 and 7,562,878 show
that the
geometry of a dynamic sealing lip can be varied in complex ways to achieve
hydrodynamic
wedging activity.
[0064] When pressed against a relatively rotatable surface, the dynamic
sealing lip 6 establishes
a sealing interface with respect to the relatively rotatable surface that has
a non-circular, wavy
lubricant-side edge, in accordance with the above-noted commonly assigned
patents and patent
applications. Examples of such a wavy lubricant-side edge can be seen in FIGS.
2-8 of U.S. Pat.
No. 4,610,319, FIG. 13 of U.S. Pat. No. 5,230,520, FIG. 2F of U.S. Pat. No.
6,109,618, and
FIGS. 2 and 2A-2C of U.S. Pat. No. 7,562,878. The sealing interface is
sometimes referred to as
the interfacial contact footprint, to facilitate visualization of what is
being referred to.
[0065] The dynamic sealing lip 6 incorporates a dynamic sealing surface 14.
The cross-sectional
profile of the dynamic sealing surface 14 can be any suitable shape, including
straight or curved
lines or line combinations, and including shapes that vary at different
locations of the dynamic
sealing lip 6. Many such shapes are taught by the prior art.
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[00661 The dynamic sealing lip 6 preferably has a lubricant side flank 16 that
is non-circular;
and preferably wavy. The lubricant side flank 16 is preferably blended to the
dynamic sealing
surface 14 by a blending feature 18 over at least part of the circumference of
seal body 4. This
blending feature 18 can take many different forms, including forms that vary
in shape about the
circumference of the seal body 4. Many such shapes are taught by the prior
art.
[00671 The dynamic sealing surface 14 of the dynamic sealing lip 6 also
incorporates an
exclusion edge 20 that preferably has generally abrupt form. If desired, the
exclusion edge 20
can be formed by an intersection between the dynamic sealing surface 14 and a
flexible
transitional heel 22, as shown. The flexible transitional heel 22 can also be
referred to as the
"exclusion edge chamfer."
100681 The exclusion edge 20 of the preferred embodiment of the present
invention differs
radically and counter-intuitively from that of the prior art. In the prior
art, the exclusion edge is
manufactured to be circular in the uninstalled condition. It has recently been
discovered that the
exclusion edge of the prior art becomes slightly wavy/less circular upon
installation. The
exclusion edge 20 of the preferred embodiment of the present invention is
intentionally
manufactured to be non-circular in the uncompressed condition of the rotary
seal 2, so that it is
slightly wavy in a manner that is timed to the varying size of the dynamic
sealing lip 6. This
uninstalled waviness has a waviness height 24.
[00691 Unlike the prior art, the exclusion edge 20 of the present invention is
intentionally wavy
in the uninstalled condition, but becomes more circular/less wavy upon
installation of rotary seal
2. This provides improved environmental exclusion, compared to the prior art,
by minimizing
skew-induced wear. The waviness of the exclusion edge 20 in the uncompressed
condition of
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the rotary seal 2 is engineered to compensate for the trend toward waviness
that compression of
the dynamic sealing lip 6 causes, so that in the compressed condition, the
exclusion edge 20
becomes much less wavy than would otherwise be the case.
[0070] The flexible transitional heel 22 has a heel width 26 which, in the
uncompressed
condition, is different in size at the first location, represented by FIG. IA,
compared to the
second location, represented by FIG. 1 B. This variation in size from one
location to another is a
wavy variation in size that is substantially in time with the locally changing
size of the dynamic
sealing lip 6, and is substantially in time with the waviness of the exclusion
edge 20.
[0071] This variation in size of the heel width 26 from one location to
another influences local
interfacial contact pressure near the exclusion edge 20 when the rotary seal 2
is compressed. For
example, consider a comparison to a prior art seal with a fixed, non-varying
heel width that has a
width dimension of "X" inches. In the present invention, the local interfacial
contact pressure
near the exclusion edge 20 would be greater than that of the prior art near
where the heel width
26 is larger than dimension "X", and would be less than that of the prior art
near where the heel
width 26 is less than dimension "X".
[0072] Fittingly, the increases in interfacial contact pressure over that of
the prior art occur
where such increases are desirable from an environmental exclusion standpoint,
and the
reductions in contact pressure over that of the prior art occur where such
reductions are desirable
from an interfacial lubrication standpoint.
[0073] In the example of FIGS. IA and 113, the variation in the heel width 26
establishes the
waviness height 24 of the exclusion edge 20. The heel width 26 variations that
are needed to
establish the correct uncompressed waviness of the exclusion edge 20 are also
the variations that
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are desirable to beneficially manage interfacial contact pressure in the
manner discussed in the
previous two paragraphs.
[0074] The static sealing lip 8 preferably incorporates a static exclusionary
intersection 34. If
desired, the static exclusionary intersection 34 can be formed by an
intersection between the
second body end 12 and the static sealing surface 32, as shown. The specific
shape of the static
sealing lip 8 can vary from the shape that is shown without departing from the
spirit or scope of
the invention. For example, the static sealing surface 32 could be slightly
conical/sloped, as
taught by commonly assigned U.S. Pat. No. 7,052,020. Preferably, a static lip
flank 36 intersects
the static sealing surface 32 to form a static lip corner 38.
[00751 For the sake of the description that is needed in conjunction with the
illustration of FIG.
1 C, the theoretical intersection 28 between the lubricant side flank 16 and
the dynamic sealing
surface 14, and also the body intersection 30 between the lubricant side flank
16 and the seal
body 4 are identified on the seal that is illustrated in FIGS. IA and 1B. This
is being done
simply for the sake of discussion and comprehension, with the understanding
that not every
hydrodynamic seal that has a dynamic sealing lip 6 of varying size will have a
theoretical
intersection 28 and/or a body intersection 30.
[0076] FIGURE 1 C
[0077] FIGURE 1 C is a fragmentary view that represents the same rotary seal 2
that is shown in
FIGS. IA and 1B, and like those figures, also represents the uncompressed
condition of rotary
seal 2. FIG. 1A corresponds to the location identified by cutting plane IA-IA,
and FIG. 1B
corresponds to the location identified by cutting plane lB-lB. To minimize
curvature-related
foreshortening in FIG. 1 C, for ease of comprehension, FIG. 1 C has been drawn
to represent how
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a seal that is relatively large or infinite in diameter would appear, or how a
smaller seal would
appear if a short portion thereof was forced straight. By using this
illustration premise, the
visually confusing effects of curvature-related foreshortening are absent or
negligible, and can be
ignored.
[0078] Several features in FIG. 1 C are numbered for the purpose of orienting
the reader; namely:
first body end 10, second body end 12, dynamic sealing surface 14, lubricant
side flank 16,
exclusion edge 20, flexible transitional heel 22, waviness height 24, heel
width 26, theoretical
intersection 28, and body intersection 30. In keeping with American drafting
third angle
projection conventional representation, the theoretical intersection 28 is
represented by a solid
line even though the intersection would typically be blended by a blending
feature. For a
discussion of this general blended intersection illustration practice, see
paragraph 7.36 and FIG.
7.44(b) on page 213 of the classic drafting textbook "Technical Drawing,"
(Prentice-Hall, Upper
Saddle River, N.J., 10th edition (1997)).
[0079] The theoretical intersection 28, which is not applicable on all
hydrodynamic seal designs,
is illustrated merely to convey the sense that the dynamic sealing lip 6
varies in size, as a matter
of convenience. It is understood that, as taught by the various commonly
assigned prior art, seal
designs are possible where the dynamic sealing lip 6 varies in size, but the
surfaces of the
dynamic sealing lip are such that no theoretical intersection can be defined.
[0080] The main point of FIG. 1 C is that it shows the variation in size of
the heel width 26 of the
flexible transitional heel 22, and shows the waviness and waviness height 24
of the exclusion
edge 20. The waviness of the theoretical intersection 28 and body intersection
30 show that the
dynamic lip varies in size from cutting plane 1 A-1 A to cutting plane 1 B-1
B.
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[0081] FIGURES I D & 1E
[0082] Referring now to FIGS. 1 D and 1 E, the rotary seal 2 is shown in its
installed condition.
The cross-sections of FIGS. 1 D and 1 E are fragmentary longitudinal cross-
sectional illustrations
that correspond to the uncompressed cross-sections of FIGS. IA and 1 B,
respectively. The
cross-sections of FIGS. ID and I E relate to cutting planes that pass through
the theoretical
centerline/axis of the seal; i.e., the theoretical centerline lies on the
cutting plane. The
circumferential direction of relative rotation is normal (perpendicular) to
the plane of the cross-
section, and the theoretical centerline of rotary seal 2 generally coincides
with the axis of relative
rotation.
[0083] Rotary seal 2 is oriented (i.e., positioned) by the first machine
component 40 for sealing
with respect to a relatively rotatable surface 56 of a second machine
component 42. For the
purpose of illustrating a typical application, the first machine component 40
is illustrated as
having a generally circular seal groove that is defined by a first wall 44, a
second wall 46 and a
peripheral wall 48.
[0084] An extrusion gap bore 64 establishes an extrusion gap clearance 66 with
respect to the
relatively rotatable surface 56 of the second machine component 42. Part of a
chamber 50 is
typically formed by a component bore 68 and the relatively rotatable surface
56. The transition
between the second wall 46 and the extrusion gap bore 64 and the transition
between the first
wall 44 and the component bore 68 preferably takes the form of a corner break
70, such as a
radius or other form of curve, or such as a chamfer (the latter being
illustrated). The corner
break 70 preferably has a width 72 and a depth 74. The width 72 and depth 74
may be the same
size, or different in size relative to one another. The first wall 44 and the
second wall 46 are in
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CA 02699185 2010-04-08
generally opposed relation to one another. Within the seal industry, the first
wall 44 is
sometimes referred to as the "lubricant-side wall," and the second wall 46 is
sometimes referred
to as the "environment-side wall."
[0085] Although the first wall 44 and the second wall 46 are shown to be in
fixed, permanent
relation to one another, such is not intended to limit the scope of the
invention, for the manner of
positioning the rotary seal 2 admits to other equally suitable forms. For
example, the first wall
44 and/or the second wall 46 could be configured to be detachable from the
first machine
component 40 for ease of maintenance and repair, but then assembled in more or
less fixed
location for locating the rotary seal 2. For another example, it is common in
some types of
equipment for the first wall 44 to be part of a ring that is spring-loaded to
force the rotary seal 2
into contact with the second wall 46 for reasons of skew avoidance. For yet
another example, a
detachable gland wall may be mandated when the rotary seal 2 is small in
diameter, because such
small seals cannot be deformed sufficiently to be installed within a groove
that has fixed, non-
detachable gland walls. The first body end 10 of rotary seal 2 generally faces
the first wall 44,
and the second body end 12 of rotary seal 2 generally faces the second wall
46.
[0086] First machine component 40 and second machine component 42 together
typically define
at least a portion of the chamber 50, which is typically used for locating a
retained fluid 52 and
for defining a lubricant supply. The retained fluid 52 is preferably exploited
in this invention to
lubricate the dynamic sealing interface between rotary seal 2 and the second
machine component
42 during relative rotation thereof. Retained fluid 52 is preferably a liquid-
type lubricant such as
a synthetic or natural oil, although other fluids including greases, water,
and various process
fluids are also suitable in some applications. An environment 54 may be any
type of
environmental media that the rotary seal 2 may be exposed to in service, such
as any type of
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CA 02699185 2010-04-08
solid, liquid, or gaseous environmental media including, but not limited to,
dirt, crushed rock,
drilling fluid, manure, dust, lubricating media, a process media, seawater,
air, a partial vacuum,
etc. For purposes of this specification, the term "fluid" has its broadest
meaning, encompassing
both liquids and gases.
[0087] The purpose of rotary seal 2 is to establish sealing engagement with
the relatively
rotatable surface 56 of the second machine component 42 and with the first
machine component
40, to retain a volume of the retained fluid 52, to partition the retained
fluid 52 from the
environment 54, and to exclude the environment 54 and prevent intrusion of the
environment 54
into the retained fluid 52.
[0088] Relatively rotatable surface 56 of second machine component 42 and
peripheral wall 48
of first machine component 40 are in spaced relation to each other. The
spacing of relatively
rotatable surface 56 and peripheral wall 48 is sized to hold rotary seal 2 in
compression. In the
same manner as any conventional interference-type seal, such as an O-ring or
an O-ring
energized lip seal, the compression of rotary seal 2 establishes sealing
between static sealing lip
8 of rotary seal 2 and peripheral wall 48 of first machine component 40, and
establishes sealing
between the dynamic sealing lip 6 of rotary seal 2 and the relatively
rotatable surface 56 of
second machine component 42.
[0089] A portion of the static sealing surface 32 is typically in compressed
contact with the
peripheral wall 48. At least a portion of the dynamic sealing lip 6 is held in
compressed,
contacting relation with relatively rotatable surface 56 of the second machine
component 42. In
dynamic operation, the relatively rotatable surface 56 has relative rotation
with respect to
dynamic sealing lip 6 of the rotary seal 2 and with respect to the first
machine component 40.
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CA 02699185 2010-04-08
The preferred embodiment of the present invention has application where either
the first machine
component 40 or the second machine component 42, or both, are individually
rotatable.
[0090] The compression (i.e., compressed, contacting relation) of dynamic
sealing lip 6 against
the relatively rotatable surface 56 establishes and defines a sealing
interface/interfacial contact
footprint between dynamic sealing lip 6 and relatively rotatable surface 56,
as taught by the
commonly assigned prior art identified above. The sealing interface has a
footprint width 58 that
is greater at the location of FIG. 1 E, compared to FIG. I D. The footprint
has a non-circular first
footprint edge 60 that faces the retained fluid 52, and a second footprint
edge 62 of generally
circular configuration that faces the environment 54 (the footprint edges
identified by referencing
the extension lines of the dimension for the footprint width 58).
[0091] Thus, the footprint width 58 varies about the circumference of seal
body 4 from a
minimum width to a maximum width, as taught by the commonly assigned prior
art. FIGURE
1D is representative of a location of the dynamic sealing lip 6 that produces
the minimum
footprint width 58, and FIG. 1E is representative of a location of the dynamic
sealing lip 6 that
produces the maximum footprint width 58.
[0092] The exclusion edge 20 of dynamic sealing lip 6, which was manufactured
slightly wavy,
becomes less wavy and more circular when installed. Because of this unique
feature, the present
invention provides better alignment between the exclusion edge 20 and the
direction of relative
rotation, and is adapted to better-exclude intrusion of the environment 54,
compared to the prior
art. Exclusion edge 20 is of a configuration intended to develop substantially
no hydrodynamic
wedging activity during relative rotation between dynamic sealing lip 6 and
relatively rotatable
surface 56. Exclusion edge 20 presents a scraping edge to help exclude
contaminant material
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CA 02699185 2010-04-08
from the interfacial contact footprint between dynamic sealing lip 6 and
relatively rotatable
surface 56, in the event of any relative movement occurring perpendicular to
the direction of
relative rotation between dynamic sealing lip 6 and relatively rotatable
surface 56 (i.e.,
movement occurring from right to left or left to right in FIGS. 1 D and 1 E).
[0093] When relative rotation is absent, a liquid-tight static sealing
relationship is maintained at
the interface between dynamic sealing lip 6 and relatively rotatable surface
56, and between
static sealing surface 32 and peripheral wall 48. When relative rotation
occurs between first
machine component 40 and relatively rotatable surface 56, the rotary seal 2
preferably remains
stationary with respect to peripheral wall 48 of first machine component 40
and maintains a
static sealing relationship therewith, while the interface between dynamic
sealing lip 6 and
relatively rotatable surface 56 of second machine component 42 becomes a
dynamic sealing
interface, such that relatively rotatable surface 56 slips with respect to
dynamic sealing lip 6 at a
given rotational velocity. When relative rotation between dynamic sealing lip
6 and relatively
rotatable surface 56 ceases, the sealing interface/interfacial contact
footprint between dynamic
sealing lip 6 and relatively rotatable surface 56 returns to being a static
sealing interface.
[0094] Because the footprint between dynamic sealing lip 6 and relatively
rotatable surface 56
has a first footprint edge 60 that is intentionally non-circular (e.g., wavy),
it, in conjunction with
the deformed shape of dynamic sealing lip 6, produces a hydrodynamic wedging
action in
response to relative rotation between the rotary seal 2 and relatively
rotatable surface 56. This
hydrodynamic wedging action forces a film of the retained fluid 52 into the
interfacial contact
footprint between the dynamic sealing lip 6 and relatively rotatable surface
56 for lubrication
purposes, which reduces wear, torque and heat generation. In other words,
dynamic sealing lip 6
slips or hydroplanes on a film of lubricating fluid during periods of relative
rotation between the
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CA 02699185 2010-04-08
dynamic sealing lip 6 and relatively rotatable surface 56. When relative
rotation stops, the
hydroplaning activity stops, and a static sealing relationship is re-
established between dynamic
sealing lip 6 and relatively rotatable surface 56 due to the compression of
dynamic sealing lip 6
against relatively rotatable surface 56.
[00951 The hydroplaning activity that occurs during relative rotation
minimizes or prevents the
typical dry rubbing wear and high friction associated with conventional non-
hydrodynamic
rubber and plastic seals, prolonging the useful life of the rotary seal 2 and
the life of the
relatively rotatable surface 56, and making higher speed, compression and
differential pressure
practical. During relative rotation, a net hydrodynamic-pumping related
leakage of the retained
fluid 52 occurs as lubricant is transferred across the dynamic sealing
interface and into the
environment 54.
[00961 Due to second footprint edge 62 being substantially circular and
substantially aligned
with the possible directions of relative rotation, second footprint edge 62
does not produce a
hydrodynamic wedging action in response to relative rotation between the
dynamic sealing lip 6
and the relatively rotatable surface 56, thereby facilitating exclusion of the
environment 54.
[0097] Since perfect theoretical circularity is seldom if ever obtainable in
any feature of any
manufactured product in practice, it is to be understood that when "circular,"
"substantially
circular," or "substantial circularity" or similar terms are used to describe
achievements or
feature attributes of the invention that is described and claimed herein, what
is meant is that
circularity is improved, so that there is less waviness or other deviation
from perfect theoretical
circularity, compared to the prior art under similar installed conditions. For
example, it is one
objective of a preferred embodiment of the current invention to improve the
circularity (i.e.,
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CA 02699185 2010-04-08
achieve less waviness) of the exclusion edge 20 and the corresponding
environment side of the
interfacial contact footprint in conditions of little or no differential
pressure compared to the
prior art. This objective is not to be misconstrued as an intent to achieve
the unobtainable; i.e.,
perfect theoretical circularity.
[0098] The non-circular, wavy configuration of first footprint edge 60 can
take any desirable
form where at least a portion is skewed with respect to the direction of
relative rotation, and can
take the form of one or more repetitive or non-repetitive convolutions/waves
of any form
including a sine, saw-tooth or square wave configuration, or plural straight
or curved segments
forming a tooth-like pattern, or one or more parabolic curves, cycloid curves,
witch/versiera
curves, elliptical curves, etc. or combinations thereof, including, but not
limited to, any of the
lubricant-side footprint edge configurations shown in U.S. Pat. Nos.
4,610,319, 6,109,618,
6,685,194, and 7,562,878.
[0099] Compared to the prior art, the wavy as-manufactured geometry of the
flexible transitional
heel 22 as shown in FIGS. IA-IC causes the interfacial contact pressure
between the dynamic
sealing lip 6 and the relatively rotatable surface 56 to be greater where such
is desirable for
improved exclusion, and causes the interfacial contact pressure to be less
where such is desirable
for improved lubrication. In the prior art, the heel width was constant in the
as-manufactured
state, but varied in a wavy pattern when the seal was installed. In the
present invention, the heel
width and the exclusion edge 20 are wavy in the as-manufactured state, and
become less wavy in
the installed state. In other words, the as-manufactured waviness of the heel
width, and of the
exclusion edge 20, are designed to compensate for and largely correct the
tendency of the
features to otherwise become wavy due to compression. The as manufactured
waviness is made
in a form that is opposite the compression-induced waviness tendency, in order
to compensate
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CA 02699185 2010-04-08
for the compression-induced waviness tendency. This concept is clarified below
in the
description of FIG. 2.
[001001 The seal body 4 of rotary seal 2 is illustrated as having an installed
length that
causes it to simultaneously contact the second wall 46 and the first wall 44
in certain operating
conditions, in accordance with the axial constraint teachings of commonly
assigned U.S. Pat. No.
6,315,302. In other words, the first body end 10 of seal body 4 is illustrated
as contacting the
first wall 44 of first machine component 40, and the second body end 12 of
seal body 4 is
illustrated as contacting the second wall 46 of first machine component 40, in
order to inhibit
skew-induced wear. This is not meant to imply that the invention is limited to
seals that have
axial constraint. The teachings of the invention are also applicable to seals
where seal body 4
has an installed length that is shorter than the distance between the second
wall 46 and the first
wall 44.
[001011 Relatively rotatable surface 56 can take the form of an externally or
internally
oriented substantially cylindrical surface, as desired, with rotary seal 2
compressed radially
between peripheral wall 48 and relatively rotatable surface 56, in which case
the axis of relative
rotation would be substantially parallel to relatively rotatable surface 56.
In a radial sealing
configuration, dynamic sealing lip 6 is oriented for compression in a
substantially radial
direction, and peripheral wall 48 may, if desired, be of substantially
cylindrical configuration,
and first wall 44 and second wall 46 may, if desired, be of substantially
planar configuration.
[001021 Alternatively, relatively rotatable surface 56 can take the form of a
substantially
planar surface, with rotary seal 2 compressed axially between peripheral wall
48 and relatively
rotatable surface 56 in a "face-sealing" arrangement, in which case the axis
or relative rotation
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CA 02699185 2010-04-08
would be substantially perpendicular to relatively rotatable surface 56. In an
axial (face) sealing
configuration, dynamic sealing lip 6 would be oriented for compression in a
substantially axial
direction, peripheral wall 48 may be of substantially planar configuration,
and first wall 44 and
second wall 46 may, if desired, be of substantially cylindrical configuration.
In the most
common configuration, relatively rotatable surface 56 is an external
cylindrical surface formed
by an exterior surface of a shaft or sleeve.
[001031 In summary, the seal can be used as a radial seal or a face seal by
configuring the
dynamic sealing lip 6 to be located at either the inside diameter, the outside
diameter, or the end
of the seal, while maintaining the advantages of the invention that are
disclosed herein. In a
preferred embodiment, a performance advantage is realized by implementing the
depth 74 and
width 72 in such a manner that the former is at least 2.5 times greater than
the latter, and
preferably approximately three times greater. Simplified embodiments are
possible wherein one
or more of the features that are described above are omitted. Alternate
embodiments are also
possible, where one or more of the features that are described above are
combined with different
features of the prior art. For example, in the uncompressed condition thereof,
dynamic sealing
surface 14 and/or static sealing surface 32 may, if desired, be of sloped
configuration, angulated
with respect to the respective mating surfaces of the first machine component
40 and second
machine component 42, in accordance with the teachings of commonly assigned
U.S. Pat. No.
6,767,016.
[001041 FIGURE IF
[001051 FIG. IF is a schematic of the exclusion edge 20 of the seal that is
disclosed in
FIGS. 1A-1E. A solid line shows the wavy shape of exclusion edge 20 before
seal installation.
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CA 02699185 2010-04-08
A phantom line shows the more circular shape of exclusion edge 20 after seal
installation. A
phantom line 76 shows what the installed exclusion edge waviness would have
been if the
exclusion edge had been circular before installation. FIGURE 1 F shows that
the pre-installation
shape of the exclusion edge 20 is engineered to compensate for the waviness
that would
otherwise occur.
[00106] FIGURE 2
[00107] FIGURE 2 is a schematic that shows that the principles taught herein
can be
applied to seals that have hydrodynamic inlet wave forms other than the simple
sine wave that is
shown in FIG. 1 C. Referring to FIG. 2, a solid line shows the wavy shape of
exclusion edge 20
before seal installation. A phantom line shows the more circular shape of
exclusion edge 20
after seal installation. A phantom line 76 shows what the installed exclusion
edge waviness
would have been if the exclusion edge had been circular before installation.
In FIG. 2, the
waviness of the exclusion edge 20 before installation is not sinusoidal;
rather it has more of the
character of a zig-zag with blended corners, in order to be used with dynamic
lips that vary
locally in size in the manner shown by FIGS. 2A, 3, 4, 8, and 10 of commonly
assigned U.S.
Patent Application Publication No 2009/0001671.
[00108] FIGURE 3
[00109] FIGURE 3 shows an alternate embodiment of the present invention, where
the
rotary seal 2 is shown in its installed condition. FIG. 3 illustrates that the
principles taught
herein are applicable to assemblies that do not use the principle of axial
constraint that is taught
by commonly assigned U.S. Pat. No. 6,315,302, and illustrated in FIGS. ID and
1E herein. Note
that the seal body 4 is not in simultaneous contact with the first wall 44 and
the second wall 46 of
Page 28
CA 02699185 2010-04-08
the groove of the first machine component 40. In FIG. 3, various features of
the seal and
machine components are labeled to orient the reader, bearing in mind that
features throughout
this specification that are represented by like numbers have the same basic
function.
[00110] In FIG. 3, the rotary seal 2 is shown located in a position within the
seal groove
that would occur if the pressure of the retained fluid 52 were higher than the
pressure of the
environment 54. In such pressure conditions, the hydrostatic force resulting
from the lubricant
pressure acting over the area between the relatively rotatable surface 56 and
peripheral wall 48
forces the second body end 12 of the rotary seal 2 against the second wall 46.
This leaves a gap
between the first body end 10 and the first wall 44. If the pressure were in
the opposite direction,
such that the pressure of the environment 54 were higher than the pressure of
the retained fluid
52, the seal would slide in response to the differential pressure, bringing
the first body end 10
into supporting contact with the first wall 44, and opening up a gap between
the second body
end 12 and the second wall 46.
[00111] In view of the foregoing it is evident that the present invention is
one that is well
adapted to attain all of the objects and features hereinabove set forth,
together with other objects
and features which are inherent in the apparatus disclosed herein. Even though
several specific
hydrodynamic rotary seal and seal gland geometries are disclosed in detail
herein, many other
geometrical variations employing the basic principles and teachings of this
invention are
possible.
[00112] The foregoing disclosure and description of the invention are
illustrative and
explanatory thereof, and various changes in the size, shape and materials, as
well as in the details
of the illustrated construction, may be made without departing from the spirit
of the invention.
Page 29
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The present embodiments are, therefore, to be considered as merely
illustrative and not
restrictive, the scope of the invention being indicated by the claims rather
than the foregoing
description, and all changes which come within the meaning and range of
equivalence of the
claims are therefore intended to be embraced therein.
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