Note: Descriptions are shown in the official language in which they were submitted.
~;~gL6~1~
--2--
Backqround of the Invention
1. Field of ~he Invention
This invention relates to a rotary shaft seal and, more
particularly, to an annularly continuous, but axially variable
5 seal for providing hydrodynamic lubrication between the seal
and a rotating shaft. A system using differential pressures to
keep the seal compressed as it wears is disclosed.
2. DescriPtion of the Background
This invention may be adapted for use with devices having
10 tubular members which are supported for relative rotation by
means of bearings contained within a lubricant chamber in an
annular space between the members.
Such a tool is connected as part of a drilling string, and
drilling fluid is circulated downwardly through a passageway
15 foemed by the tubular members and up~ardly within the annulus
between the tool and well bore. Thus, one such member often
comprises a housing or case suspended from the lower end of the
string, while the other comprises a hollow shat rotatably
supported by ~he housing and suspending a bit on its lowez end.
20 A motor, such as a turbine, is often disposed within the annular
space be~ween the housing and shaft for rotating the shaft and
r thus the bit without the necessity for transmitting torque feom
the surface to the housing through thousands of feet of drilling
string. The passageway thus includes the annular space in which
25 the turbine is disposed and which is connected by ports through
the shaft to the bore of the shaft leading to the bit at its
lower end. Typically in such tools, the housing is connected
at its upper end to the drill steing, and the shaft is caused
to rotate with respect to the housing by means of the motor
30 therebetween, whereby spiral blades or the like ca~ried about
the tubular shaft cause a reduction of pressure of drillin~
~luids as it passes throu~h the blades and turns the blades. As
in the case of a turbodrill, the motor often comprises turbine
blades on the shaft and tubular members within the annular space
35 between them. The dril~ing fluid which is circulated through
the motor is confined for passage out through the bit.
: Due to the drop in pressure across the turbine section and
the bit, there is a substantial pressure differential across
~zg6~
--3--
the seal means of drilling tools of this type. It is well known
that a rotary seal means separating pressure in this manner is
subject to considerably greater wear than one merely separating
fluids at the same pressure. The problem of wear is even more
serious in this environment due to abrasive particles in the
drilling fluid which find their way between the surfaces of the
seal means and the eng~ged tubular members. Another factor in
seal wear is the severe axial and radial vibrations encountered
in drilling boreholes through earth formations.
Unless protected therefrom, the bearings mounted in the
annular space are also damaged by the abrasive particles in the
drilling fluid. Since bearing replacement requires the raising
and lowering of the drill string at great expense, efforts have
been made to isolate the bearings from the abrasive drilling
fluid by containing thèm in a lubricant chamber formed at least
in part by a pair of seal means in the annular space. Howe~er,
if one or both of these seal means also functions as a pressure
separation element, i~ rapidly becomes worn and permits the
abrasive drilling fluids to enter the lubricant chamber.
Because of the detrimental environment encountered by
rotating motor parts positioned in a borehole drilling opera-
tion, many of the research efforts concerning the development
of downhole "mud" motors for use in downhole drilling opera-
tions have been concerned with the protection of bearing and
25 sealing moving surfaces from the abrasive effect of drilling
fluids commonly referred to as drilling "mud. n The followin~
United States patents are particularly concerned with this
problem: United States Patents Nos. 3~659,662; 3,666,33~,
3,971,450; 4,019,591; 4,222,445; 4,256,189; and 4,260,032.
These patents deal with the problem of protecting bearing
surfaces or the like from the drilling mud by a variety of
schemes.
U.S. Patent No. 3,659,662 discloses a tool which is
intended to overcome this problem by providing a system in which
a labyrinth is provided within the annular space between the
shaft and housing. The shaft is ported in such a manner that
t~e pressure drop is taken across the labyrinth and the pressure
is equalized across the seal means forming the lubricant
~4g~
chamber in which the bearings are contained. However, if the
passages through the labyrinth are small, they tend to be become
clogged by the particles in the drilling fluidt th~reby de-
creasing the cooling effect; and, if they are sufficiently
5 large to pass a large volume of drillinq fluid, the drilling
efficiency of the bit is lowered considerably. Furthermore,
even if the labyrinth is to be replaced by a third seal means
of a non-leaking type, as disclosed in U.S. Patent No.
3,971,450, it might still be subject to damage by the tendency
10 of particles in the drilling fluid to enter between the sealing
faces.
U.S. Patent No. 3,666,333 incorporates a number of rather
~` complex features in an attempt to solve ~his problem. This
patent shows upper and lower seal systems located above and
lS below the bearings and comprised of grease and oil f}lled
chambers to prevent the entry of borehole 1uids into the
bearings. In addition, a labyrinth of mating annular parts are
positioned above the upper sealing system to further impede the
4 flow of drilling fluids, under the higher pressure of the drill
20 pipe bore, from entering the rotating bearings and surfaces of
the drilling motor.
Many devices such as that shown in U.S. Patent No.
3,971,450 utilize seals having irregular configurations which,
~hen unconfined in their assembly in the well tool, are subject
25 to extrusion and deformation due to the heat and pressures
developed in the borehole. These seals deteriorate and become
ineffective to protect the moving parts from the borehole
environment.
U.S. Patent No. 4,222,445 uses a buffer fluid to protect
30 a lubricant chamber. However, failing to take into account
other important problems such as seal wear, the ability of this
sealing system to protect the bearings is short lived.
Many approaches to this problem have simply attempted to
use brute force, i.e., using a large seal area under high
35 compression such as is shown in the lower seal of U.S. Patent
No. 4,019,591. This approach provides an initial seal but
because of high friction and ensuing heat scorching of the seal,
the seal surface wears and begins to leak lubricant
~2g6~
--5--
U.S. Patents Nos. 3,449,021; 2,867,462; and 3,831,954
deal with slanted sealing surfaces between tubular members.
U.S. Patent No. 3,449,021 illustrates such a seal for use
between relatively rotating surfaces. However, the sealing
contact surface against the rotating element is along a rather
narrow band which in the configucation illustrated is not
suited for adaptation to the environment of a borehole drilling
apparatus. In addition, the harsh and inaccessible environment
of the borehole renders it important to provide an effectual
sealing surface that can be compensated for wear to avoid the
necessity of early and frequent replacement. The above patents
directed to slanted sealing surface~ a!l utilize irregularly
shaped or nonconfined sealing members which would be deformed
un~er the conditions in which the present invention is prac-
ticed. Further, the seals are not compensated fo~ wear toprovide a relatively long sealing life.
The characteristics of lubrication of hydrodynamic seals
have been studied by the inventor and reported in several
articles. ~alsi, M.S. and G.A. Fazekas, WFeasibility Study of
a Slanted 'O-ring' as a ~igh Pressure ~otary Seal,~ ASME Paper
No. 72-WA/DE-14 (1972); Kalsi, M.S., "Elastohydrodynamic Lub-
rication of Offset O-Rinq Rotary Seal,~ ASME Paper ~o. 80-
C2/LUb-7 (1980) and in a dissertation of the same title sub-
mitted to the University of Houston in 1975.
The art has long sought a new and improved rotary shaft
seal which will provide a simple but efectual seal in an
environment of abrasive fluids while overcoming the diffi
culties and problems outlined above. The present invention
overcomes these difficulties and provides a desirable sealing
system by incorporating a continuous, axially variable hydro-
dynamic sealing surface between the shaft and housing of a
downhole mo~or. Such a sealing system operates efficiently
with a pressure differential across the seal and at a high
temperature. Further, such a system provides a means for
compensating for wear on the seal so as to maintain a seal of
high integrity.
.
~ 6~
--6--
Summary of the Invention
The present invention is directed to a rotary shaft seal
utilizing a sealing member arranged in an annularly continuous,
but axially variable path between relatively rotating parts.
PreEerably, the seal is of a slanted O-ring or multiple con-
volution configuration. Upper and lower seal contacting mem-
bers have surfaces matingly engaging the surfaces of the
sealing member, preferably slanted surfaces or surfaces with
multiple convolutions. The upper and lower seal contacting
members are arranged for relative movement to compress the
sealing member therebetween.
Differentia~ pressures are generated by the arran~ement
of tool elements to move at least one of the seal contac~îng
members toward the other.
In a presently preferred embodiment, the unsupported area
principal is employed to generate a differential pressure by
providing a multiplication of differential pressure forces
acting to compress the seal contacting members to cause the seal
to fill the groove within which it is carried as the seal wears.
Additionally, a spring biasing member urges the seal contacting
members to compress the seal during low differential pressure
situations encountered during starting and stopping of the
motor. This additional biasing minimizes or prevents otherwise
considerable leakage of lubrican~ from the bearing and sealin~
sub during these times.
The arrangement of parts causing the seal carrying groove
to compress the seal under a controlled pressure provides a
system which does not rely on the original shape of the seal
being maintained. The seal, whatever its original shape, is
compressed within the confines of the seal contacting members
and thus assumes the shape afforded by such members.
Another feature of the present invention includes the use
of a lubricant contained in a chamber above the sealing member,
wherein the high pressure of a pressure differential is com-
municated to the lubricant which in turn acts on one of the sealcontacting members to move that seal contacting member toward
~he other and thereby compr~ss the seal.
Still another feature oE the present inventivn includes a
~61~;~
--7--
lower chamber located below the lower seal contacting member
and filled with a highly viscous material such as grease for
impeding the encroachment of environmental fluids into the
sealing system while peemitting the pressure o environmental
S fluids to impinge upon the lower seal contacting member~
61~
Brief Description of the Drawings
Other features and intended advantages of the invention
will be more readily apparent by reference to the following
detailed description in connection with the accompanying draw-
ings wherein:
Fig. 1 illustrates a vertical, partial cross-sectional
view of ~ well tool for use in a downhole drilling system into
which a lower sha~t seal ln accor~ance wlth the present inven-
tion may be incorporated;
Fig. 2 illustrates a detailed vertical cross-sectional
view of the lower shaft seal area of Fig. 1 and incorporating
a rotary shaft seal in accordance with the present invention;
Fig. 3 illustrates a vertical cross-sectional view of a
portion of the lower shaft seal area of Fig. 1 and incorporating
an alternative embodiment of a rotary shaft seal in accordance
with the present invention;
Fig. 4 illustrates a partial top view of the upper support
member 77 of Fig. 3; and
Fig. 5 illustrates a diagramatic view of an offset O-ring
seal with a corresponding velocity diagram.
While the invention will be described in connection with
a presently preferred embodiment, it will be understood that it
is not intended to limit the invention to that embodiment. On
the contrary, it is intended to cover all alternatives, modifi-
cations and equivalents as may be included within the spirit ofthe invention as defined by the appended claims.
~2
_9_
Descri tion of the Preferred Embodiment
P~
Referring first to Fig. 1 of the drawings, there is
illustrated a bearing and sealing sub-section 11 suitable for
incorporation into a drill string. In a typical drill string
assembly, a bit sub would be connected at 12 to the lower end
of sealing sub 11. Sub 11 would be connected below housing 13
of a motor sub, preferably a deep oil well ~otor such as
illustrated and described in U.S. Patent No. 3,966,369. Motor
sub 13 would normally include a turbine motor, a positive
displacement motor or the like having an output shaft (not
shown) connected to shaft 14 rotatably positioned within hous-
ing 16 of sub 11.
Housing 16 is illustrated having an annular upper end
sleeve 17 assembled within the housing bore and connected at its
lower end to spacing sleeve l8. Bearing collar 19 is connected
to the bottom of spacing sleeve 18. An alternating dependin~
vertical arrangement of spacing sleeves 18, 18a, 18b and 18c and
bearing collars 19, l9a and l9b is shown positioned in the bore
of housing 16 to carry the elements comprising the main port~cn
of sub 11.-
These elements further include movable piston 21 slidablypositioned between spacing sleeve 18 and wear sleeve 22 on the
outer surface of shaft 14. Spring 23 is arranged between the
top end of piston 21 and annular inwardly facing shoulder 24
formed on upper end sleeve 17. An annular recess on the inner
wall of pisto~ 21 carries annular spring 26 for compressing
annular packing assembly 27 positioned in the annular recess of
piston 21. O-rings Inot shown) on the outer side wall of piston
21 sealingly engage the inner bore oE spacing sleeve 18.
A series of interconnected chambers and annular spaces 28
formed between housing 16 and shaft 14, are filled with a
lubricating oil to provide an oil bath for the bearings housed
in sub 11. Radial bearing assembly 29 is illustrated between
wear sleeve 22 and spacing sleeve 18 to provide for concentric
mounting of shaft 14 ~ithin housing 18 and to accommodate
lateral forces acting on sub 11 such as are caused by hole
aeviations acting against the sub. The lower end of wear sleeve
22 has an outwardly projecting annular shoulder portion 31
~61i~
! !
--10--
which is arranged to hold thrust bearing 32 against upwardly
pro3ecting portion 33 of bearing collar 19. Downwardly pro-
jecting portion 34 of b~earing collar 19 is arranged to form the
top of a circumferential chambec for housing non-compressible
thrust ring 36. The lower and inner wall portions of the
cir~umferential chamber are provided by an "~" shaped annular
ring member 37 riding on top of thrust bearing 32a. The bottom
of thrust bearing 32a is supported by rotor shaft collar 38
clamped about shaft 14 and having a shoulder portion extending
into the annular space between shaft 14 and housing 16 to hold
bearing 32a in its vertical position in the bearing and seal
assembly of sub 11.
Thrust bearings 32b and 32c are arran~ed in a similar
manner to the arran~ement described above for locating bearing
lS 32a in the assembly. Lower radial 'bearing assembly 29a is
illustrated between shaft 14 and housing 16. In the bearing
arrangement described above, uppermost thrust bearing 32 is
arranged to carry thrust forces acting downwardly on sha~t 14
relative to housing 16. This would occur when the drill strin~
is positioned above the bottom of the hole. When the drill bit
is resting on the bottom and weight is placed on the drill
string, thrust bearings 32a, 32b and 32c carry the upward
loading on shaft 14. The bearing and seal arrangement described
above is shown in greater detail in U.S. Patent No. 4,086,788.
25The lower shaft seal assembly generally indicate~ by the
reference numeral 41 and which is the subject of the present
invention is illustrated and described in greater detail with
respect to Figs. 2 and 3 of the drawings. Referring now to Fig.
2 of the drawings, lower shaft seal assembly 41 is illustra~ed
30between shat 14 and housiny 16 below radial bearing 29a. One
of annular chambers 28~ containing the oil for lubricating the
bearing assembly, is illustrated extending below bearing 29a
and into fluid communication with the upper end of lower seal
assembly 41. Annular space 35 for mounting the lower seal
assembly is formed between shaft 14 and housing 16 and ter-
minates at its upper end at inwardly proj2cting shoulder 42 on
~ousing 16. ~nnular abutment ring 43 is threadedly received in
the lower end of housing 16 to form the lower end of annular
~gL6~
--11--
space 35 for housin~ seal assembly 41.
Lower seal support member 44 is comprised of an annular
sleeve having upwardly extending support portion 46, support
member 44 being sized for reception in the lower end of annular
space 35. The lower end of support member 44 rests on top of
abutment ring 43. A pair of annular felt seal rings 47 are
illustrated spaced apart longitudinally on the inner facing
wall of support member 44 for providing a barrier against the
encroachment of drilling fluids into the lower end oE seal
assembly 41. While preventing the encroachment of such fluids
in conjunction with a viscous material such as ~rease posi~
tioned ~hereabove, the ~elt seals are not suf~icient to preven~
the transmittal of pressure from the borehole annulus into the
lower end of annular space 35. Port 48 is provided through the
wall of housing 16 to accommodate the insertion of grease into
annular space 35 and is arranged with a fitting to seal the port
closed when grease is not being injected. The grease is
communicated to the inner side of support member 44 by means of
port 51 in the wall of upwardly extending support portion 460
0-ring seal 30 is positioned in a groove on the outer wall of
support member 44 between member 44 and the inner bore of
housing 16. Upper surface 53 of support portion 46 is contoured
to matingly conform to the lower surface of lower seal member
52. Seal member 52 and matingly contoured surface 53 are
characterized by an axial variat:ion, and preferably are slant-
ed or multiply convoluted.
Referring now to the upper end of seal assembly 41, annular
spring array 57, e.g., Beleville springs, is positioned in
annular space 3S just below shoulder 42. The bottom of spring
3G array 57 acts downwardly upon top surface 58 of upper annular
support member 59. Support member 59 has downwardly extending
annular portion 62 which extends about the inner wall of the
annular space and beyond seal 52, with the lower end of annular
portion 62 being unsupported therebelow and in communication
with the fluid pressure in the annular spac~ below or outside
housing 16. Annular 0-ring seal 63 is positioned in a groove
around the outer wall oE upper support melnber 59 to seal the
lower end of portion 62 from the higher differential pressure
~246~
-12-
of oil in chamber 28. Lower surface 64 is formed on the ~ottom
side of a shoulder formed on the inner wall of upper support
member 59. Surface 64 is arranged to matingly conorm ~o the
upper surface of upper seal member 66. Seal member 66 and
surface 64 are characterized by an axial variation, and pre-
ferably are slanted or multiply convoluted. Accordingly, in a
presently preferred embodiment, surfaces 64 and 53 are parallel
and provide an annular slanted groove in which is housed lower
annular seal 52 and upper annular seal 6~. In the embodiment
illustrated in Fig. 2, upper seal 66 is illustrated as an O-ring
and lower seal 52 is illustrated as a braided layer of packing.
Because of the compressive effect of the seal assembly de-
scribed above, the seal materials will be compressed to ~ill the
groove formed by upper and lower surfaces 64 and 53 respectively
and the outer wall of shaft 14 and vertical inner wall o
portion 62. Thus, regardless of the specific shape of packing
or seal used in the assembly, the seal will be deformed into the
shape of the groove. Additionally, the seals are constructed
so that radius 67 is formed by the inner edges of the ver~ical
sealing surfaces of seal members 52 and 66 facing shaft 14.
Referring now to Fig. 3 of the drawings, an alternative
embodiment of seal assembly 41 is illustrated. Annular space
35 between housing 16 and shaft 14 is arrange~ between upper
shoulder 42 and lower abutment ring 43 as in Fig. 2. Lower
support member 71 also similarly has felt seals 47 arranged on
its inner wall to engage the outer surface of shaft 14. O-ring
30 is positioned on the outer wall of lower supp~rt member 71
to seal against the bore of housing 16. Grease injection port
and fitting 48 peovides for the filling o~ annular space 35 at
the lower end of the ~eal assembly with a viscous material.
Lower support member 71 has an enlarged annular portion 7~ at
its upper end which is sized to fill the space between the
housing 16 and shaft 14.
Vertical holes 73 are formed in a radial series about upper
end portion 72 of support member 71. The upper surface of
enlarged portion 72 has a surface 74 for matingly engaging an
~nnular sealing member 76. These surfaces are characteri~ed by
an axial variation, and preferably they are slanted or multiply
~29~
-13-
convoluted. Upper support member 77 is positioned above seal
member 76 and has lower surface 78 for matingly contacting the
top of seal member 76. An array of springs 57 is positioned
between shoulder 42 and the top of upper support 77. A radial
series of vertical holes 79 is also formed in upper support 77
and are aligned with vertical holes 73 in upper portion 72 of
lower support member 71. The top portion of holes 79 is
enlarged to receive head 81 of pin 82 sized for reception within
aligned holes 79 and 73. Vertical passage 83 conneots the
bottom of each hole 73 with annular space 35 in the lower
portion of the seal assembly. Oil fills the chamber or spaces
2a above upper support 77. Fig. 4 of the drawings illustrates
a top view of upper support 77. Heads 81 of pins 82 are
illus~rated in the assembled position within the radial serie~
of vertical holes 79.
Seal 76 is comprised of layers of suitable sealing ma-
terial arranged in a continuous annular configuration with an
axial variation, preferably slanted or multiply convoluted, to
fit within the groove defined by surfaces 78 and 74 on upper and
lower support members 77 and 71, respectively. Radius 86 is
formed on the top and bottom inner facing edge of seal 76 to
accommod~te the lifting of such inner facing edge of the seal
by the hydrodynamic force of lubricating oil moving past the
seal.
The hydrodynamic effect of the lubricating oil film on the
seal is appreciated more clearly by reference to Fig. 5 of the
drawings. Fig. 5 is a schematic representation of the circum-
ferentially developed path of seal 76 of Fig. 3 moving in
relation to shaft 14 during one revolution of the shaft.
Because of the axial variation of the seal, e.g., the slanted
configuration of seal 76 with respect to the path of rotation
of shaft surface 14, the seal, having a vertical width S, moves
through a path having a vertical width P during one revolution
of shaft 14. As the shaft rotates relative to the seal,
lubricant tends to move in a substantially horizontal direction
about the shaft. The horizontal velocity being applied to the
~il is represented by the line VO in Fig. 5. The velocity
represented by YO can be divided into two vector components,
~24L6~
i.e., VI, which is the velocity moving the oil in a lateral
direction along the path of the seal and VT which is the
velocity acting transversely to the side wall of s~al 76.
Co~ponent VT causes oil, in conjunction with the radius 86 at
the edges of seal 76 to lift the seal and flow under the seal
thereby forming a thin layer of lubricating oil between seal 76
and shaft 14. In addition, because there is a pressure
differential across seal 76 due to the pressure developed
across the downhole motor, e.g., there is a net downward force
on the oil moving back and forth across the seal as the sh~Et
moves rel~tive thereto. The back and forth movement o~ the oil
is due to the undulating or sinusoidal path taken by the seal
relative to the shaft having the effect of alternately placing
portions o~ the sha~t above and below the seal. The e~fect of
this seal system and ~he hydrodynamic ~low generated with
respect thereto is to provide a lubricating surface at all times
between seal 76 and shaft 14 which tends to reduce the tempera-
ture of the seal as well as to lubricate the rotating shaft,
thus preventing the seal from scorching and becoming brittle.
Prevention of ~corching and brittleness greatly reduces wear on
the seal. The net flow of oil in one direction also aids the
temperatuse reducing function of the system by carrying ~eat
away from the sealing surface.
When a drilling tool having a seal assembly in accordance
with the present invention as described above is operatedr a
pressure differential is developed across the tool whereby a
hi~her pressure exists in the section of the tool above the
drill bit than exists below the bit. The higher pressure in
this tool is communicated to the upper end of bearing and
sealing sub 11 (Fig. 1) by means of piston 21 at the upper end
of sub ll. This pressure is carried by the lubricant in
chambers 28 throughout ~ub 11 to the lower end of the sub
bordering seal assembly 41. Referring now to Fig. 2, this
pressure is passed to the upper end of upper support member Sg
and acts downwardly across the area Al. This downward force is
passed to the top surface of seals S2 an~ 66. Bottom support
member 44 is held againstdownward movement by abutment ring 43~
thus compressing the seal between upper and lower support
~2~
-15-
members 59 and 44, respectively. As the inner facing surfaces
of seals 52 and 66 wear, the predictable force between the
support members is appropriately closing the groove defined by
surfaces 53 and 64 to continuously maintain the seal confined
as it wears down and to press the seal into sealing engagement
with the shaft and upper support member.
The differential pressure described above, actinq to
force the support members together, is further enhanced by an
unbalanced area effect, which results from the configuration of
upper and lower seal supports and their cooperative rela-
tionship in the assembly. As dis~ussed above, a downward force
on top of the seals i~ represented by a higher pressure PH in
the tool bore acting across area Al as illustrated in Fi~. 2.
The downward pressure is the produc~ of Al x P~. The lower
pressure PL of the borehole annulus acts across area A2 on
unsupported portion 62 depending from support member 59. The
hydraulic force thus acting upwardly on upper support member 5~
i~ PL x A2~ A ~hird upwardly acting force acting upon support
; member 59 is represented by an unknown pressure Ps acting across
the seals or area A3 also represented by Al - A2. A simple force
diagram can be drawn with examples of pressures and areas to
show that the pressure Ps ac~ing across the seals is always
greater than the pressure of the lubricant in chamber 28 above.
The pressure P~ across the seals is calculated as Ps = ~P~-Al
- Pl-A2)/(Al - A21. This unsupported area effect thereby
enhances the wear compensating feature of the system. The seals
not only last longer but uncontrolled leakage of oil past the
seal at a rate greater than that of the desired leakage rate is
prevented.
The portion of the seal assembly below seals 66 and 52 is
filled with a highly viscous material such as grease, which~ in
conjunction with Eelt seals 47, prevents drilling fluids from
passing into the seal area. Felt seals 47 also become impreg-
nated with the grease. The grease below the seals together with
the net flow of oil downwardly as described above, prevents
drilling 'luids from encroaching into the assembly from below.
The system, however, does permit the pressure of drillin~
fluids in the borehole annulus to be transmitted to the grease
~;~46~0
-16-
chamber below seals 66 and 52.
When the tool oE Fig. 1 is stationary, is co~mencing or is
ceasing its rotation, it is likely that the pressure dif-
ferential relied upon to compress the seals will not be suEfi-
S ciently high to be operative to prevent leaka~e of lubricantpast the seals. Spring areay 57 thus acts downwardly on upper
support member 59 during periods of little or no rotation, in
addition to holding the components in assembly.
The embodiment illustrated in Fig. 3 operates similarly to
the embodiment of Fig. 2 as described above except that pins 82
represent the unsupported area which provides the multiplying
effect of pressure differential across seal 7~.
The foregoing description of the invention has been di-
rected primarily to a pa~ticular pre~erred embodiment in ac-
cordance with the requirements of the patent statutes and forpurposes of explanation and illustration. It will be apparent,
however, to those skilled in the art that many-modifications and
changes in the specifically described and illustrated appa-
ratus and method may be made without departing from the scope
and spirit of the invention. For example, while the disclosure
of the system has been described primarily with regard to a
slanted seal member, it may be appreciated from the present
description and illustrations that any seal member having a
confi~uration with sufficient axial variation, e.g., multiple
convolutions, to produce the desired hydrodynamic lubrication
may be substituted for the slanted seal of the illustrated
embodiment. Further, various changes in the size, shape and
materials as well as the details of the illustrated embodiment
will be evident to those skilled in the art without departing
from the present invention in its broadest aspects. Finally,
although this seal device was described with relation to use in
a drillin~ tool) it is adaptable for use in any device employing
a rotary seal. Therefore, the invention is not restricted to
the particular form of construction illustrated and described,
but covers all modifications which may fall within the scope of
the following claims.
It is Applicant's intention in the following claims to
cover such modifications and variations as fall within the ~rue
~;~46~
--17--
spirit and scope of the invention.
