Note: Descriptions are shown in the official language in which they were submitted.
~092588
VALVE SEAL
Background of the Invention
Field of the Invention. This invention relates to seals
for valves and, more particularly, to seals for valves that
have rotating stems.
Desc ~ tion of-the Prior Art. The prior art is replete
with various forms of valves and seals therefor; a number of
which are directed to the resolution of the problem of
,~ maintenance and integrity of the stem seals which effect the
10 rotating seal between the casing and valve stem.
In addition to the above noted problem area and also
related thereto is the problem of providing a valve which can
be readily maintained in a field environment and, more
particularly, a provision of a valve which may be maintained
15 without any interruption of the flow in the line with which it
is associated. One of the more typical field maintenance
tasks is the replacement of the stem seals and it is important
that the valve continue to function at least temporarily while
these seals are being replaced.
- ~ 20 In addition to the above noted problems, there has been a
; ~continual need for the provision of a new and improved packing
seal for valves having roting stems as contrasted to those
;~ having rising stems; particularly plug valves whose plug and
coupled stem are rotated through a limited arc. The seals
25 must have a number of characteristics to enable it to perform
effectively in such an environment. For example, a stem seal
in a plug valve environment should possess a substantial
degree of lubricity to reduce friction with respect to the
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stem and also reduce the wear on the seals themselves. With
respect to this latter point, the life of the seal can be
extended substantially if the friction between it and the
various moving parts of the valve with which it is
associated can be reduced. Another important function of
the seal is to maintain its own strength characteristics
during its operational life. This particular feature of
the seal becomes all the more important when it is compressed
by a gland ring or the like.
Examples of typical prior art forms of valves in this
general area and other art which may relate thereto are as
follows: United States Patents 1,584,699; 1,671,603;
1,680,812; 2,945,668; 3,096,070; 3,115,151; 2,231,235;
3,406,707; 3,537,682; and 3,586,289.
Summary of the Invention
~` The present invention consists of a new and improved
packing seal for valves comprising: a packing ring having
radially alternate compressed layers of polytetrafluoroethy-
lene and graphite.
In a preferred embodiment there is provided a valve
which comprises a casing having a passageway therethrough
i for the flow of fluid and a bore intersecting the passageway.
~, A flow regulating member is rotatably mounted in the bore
for blocking the passageway in the valve closed position of
the flow regulating member. The flow regulating member has
,' a port therethrough for connecting and being in communication
with the passageway in the valve open position. The flow
regulating member and the casing define a first chamber at
one end of the flow regurating member. A stem is rotatably
mounted within the casing and is mechanically coupled to the
flow regulating member to rotatably drive the flow regulating
member within the casing. The stem has an annular rim formed
toward and positioned within the first chamber. At least
one annular seal surrounds the stem to effect the seal between
.35 the stem and casing. Means are provided for introducing a -
pressure equal to or greater than the line pressure into the
;~ first chamber whereby the pressure acts on the annular rim
to move the stem in an axial direction to compress the
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annular seals which are alternate layers of polytetrafluoro-
ethylene and graphite.
It is another feature of an embodiment of the present
invention to provide a seal for a valve having a rotating
stem which seal comprises materials having compa~ability
with a wide variety of mediums.
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Still other features of embodiments of the invention
are:
(i) to provide a seal for valves having rotating
stems which seal comprises materials having significant
temperature ranges beyond that of rubber and other con-
ventional sealing materials;
- (ii) to provide a packing seal for valves comprising
a packing ring having radially alternate compressed layers
of polytetrafluoroethylene and graphite. The polytetra-
fluoroethylene layer is formed from a continuous ribbon of
polytetrafluoroethylene and the graphite layer is formed
from a continuous ribbon of graphite;
(iii) to provide a packing seal for valves wherein
the graphite layer is substantially, approximately five times,
thicker than the polytetrafluoroethylene layer;
(iv) to provide a packing seal for valves wherein
each layer is compressed into a serpentine configuration in
cross section;
tv) to provide a packing seal for valves wherein
the ring is compressed to approximately 50~ of its original
height;
(vi) to provide a packing seal for valves wherein
each of the continuous ribbons are of equal height and are
-~ wrapped to form the seal one ribbon superimposed on the
i 25 other;
- (vii) to provide a packing seal for valves wherein
the continuous ribbon of polytetrafluoroethylene is sub-
stantially U-shaped in cross section and is wrapped to form
the seal with the graphite ribbon being inserted within the
U-shaped polytetrafluoroethylene ribbon;
(viii)to provide a packing seal for valves comprising
the steps of wrapping about a mandrel at least two ribbons,
one of graphite and one of polytetrafluoroethylene to form
multiple alternate layers of the ribbons and compressing the
alternate wrapped ribbons to form a seal;
. (ix) to provide a packing seal for valves wherein
: the ribbons are compressed into a forming cup;
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(x) to provide a packing seal for valves wherein
the ribbons are compressed to approximately 50% of their
original height;
(xi) to provide a packing seal for valves wherein
the ribbon of polytetrafluoroethylene is formed into a
V-shaped cross section and the graphite ribbon is inserted
with the U-shaped polytetrafluoroethylene ribbon before
compressing the ribbons;
(xii) to provide a tapered plug valve which is
highly `effective and efficient and which includes a unique
and ~dvanced stem seal;
(xiii) to provide a tapered plug valve which may be
effectively serviced in a field environment;
(xiv) to provide a tapered plug valve which is
inexpensive to manufacture yet is highly reliable and
easily maintained;
(xv) to provide a valve wherein the flow regulating
member is a tapered plug rotatably mounted~in the bore which ::is tapered to conform to the tapered plug with the plug and
casing defining the first chamber at the smaller end of -:-
the plug; -~(xvi) to provide a tapered plug valve wherein the
outside diameter of the annular rim formed on the stem is
less than the inside diameter of the first chamber;
(xvii) to provide a tapered plug valve wherein a ring
- surrounds the stem to rotate therewith. The ring has a - -
.~ radially extending face which sealingly contacts the
annular seal;
(xviii) to provide a tapered plug valve wherein a
; 30 pressure tight seal is effected by the annular seal with
moving contact between the outer surface of the stem and the
inward facing surface of the annular seal and between the
radially extending face of the ring and the radially extend-
ing surface of the annular seal in contact with the radially
extending face;
.: (xix) to provide a tapered plug valve wherein the
means for introducing a pressure to the first chamber
includes valving means for the introduction of a pressurized
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- 6 109258ff
sealant lubricant medium into said first chamber and into
grooves provided on the outer surface of the plug;
(xx) to provide a tapered plug valve which includes
a pressure responsive valve means in the plug to allow line
pressure to enter the first chamber when the pressure in
the first chamber is reduced to a level below line pressure;
and
(xxi) to provide a tapered plug valve wherein biasing
means is provided between the stem and the plug to bias the
plug toward its larger end. The biasing means is a spring
member received within a cavity in the stem.
Further features of embodiments of the invention will
become apparent as the description proceeds in connection
with the appended claims and annexed drawings described
below.
Brief Description of the Drawings
Figure 1 is a partial sectional view of a tapered plug
valve in accordance with an embodiment of ~he present
invention.
Figure 2 is another sectional view of the tapered plug
valve wherein the tapered plug valve in Figure 1 is rotated
approximately 90 degrees.
Figure 3 is a top view of the tapered plug valve of
' Figure 1.
Figure 4 is a cross sectional view of one of the seals
used in the plug valve of Figure 1 in its uncompressed state.
Figure 5 is a cross sectional view of the seal of
Figure 4 in its compressed state.
Figure 6 illustrates the wrapping of the seal of
Figure 4.
Figure 7 is a cross sectional view of yet another type
of seal that might be used in the plug valve of Figure 1 in
its uncompressed state.
Figure 8 is a cross sectional view of the seal of
Figure 7 in its compressed state.
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Figure 9 illustrates the wrapping o~ the seal of Figure
7.
Figure 10 is a cross sectional view of the ribbons of
Figure 9 taken along the line 10-10.
5Description of the Embodi~ents
Referring now to the drawings, there is shown an improved
tapered plug valve 10 according to a preferred embodiment of
the present invention. The tapered plug valve 10 is highly
adaptable to many applications and requirements as is well
known by those having ordinary skill in this art. For
example, the tapered plug valve as contemplated by this
invention may be used in oil and gas production, refining and
transmission apparatus, flow systems of all kinds and the
like.
15The tapered plug valve 10 is provided with a casing 12.
Typically, the casing 12 is a cast part which, in turn, is
machined and otherwise suitably prepared for the operational
introduction of its various parts. The casing 12 is so
arranged as to receive an end cap 14. The end cap 14 may be
adapted to the casing by suitable attaching means such as a
series of threaded bolts 16. With the end cap removed, all the
various operational parts, which will be below further
described, may be introduced into the casing 12, i.e., the
stem 18, coupling member or equalizing ring 20 and plug 22 may
all be loaded or assembled within the casing from the bottom.
The stem 18 is rotatably mounted within the casing 12 and
is mechanically coupled to the equalizer ring 20. The
equalizer ring 20 is mechanically coupled to the plug 22 which
is rotatably mounted within the casing 12 at a tapered
interface 24. As can immediately be seen, rotation of the
stem 18 will, in turn, cause rotation of the plug 22 through
the equalizer ring 20 which mechanically couples the stem 18
to the plug 22. The end cap 14 is also provided with a
threaded cavity 28 which is adapted to threadably receive a
plug adjusting screw 30 and a protective cap 32. The plug
adjusting screw 30, as the name implies, is adapted to adjust
the axial position of the plug 22 within the casing 12. This
adjustment is achieved through the provision of a spherical
plug thrust ball 34 supported within a cavity 36 in the lower
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--8--
end of the plug 22 and on ball seat 38. The ball seat 38 is
responsive to axial movement of the plug adjusting screw 30
which, for example, when threadably moved inwardly with
respect to the end cap 14 drives the plug 22 and thereby drives
the spherical plug thrust ball 34 toward the apex of the
taper.
A band seal 40 may also be provided around the juncture
of the casing 12 and end cap 14 to seal the void 42 between the
two members from the environment. The sealing of the void i5
further enhanced by the provision of a grease fitting 44
provided in a bore 46 in the end cap 14 for applying grease
under pressure to the above noted void 42. It should be noted
that the grease will completely fill the void 42 and surround
the threaded bolts 16 thereby preserving the threads on the
threaded bolt 16 from any adverse substance or environment.
The stem 18, as before mentioned, is rotatably supported
within the casing 12. The stem 18 is provided with an annular
rim 48 which is located in the area of the upper chamber 76.
The upper chamber 76 will be described in further detail
` 20 below. The annular rim 48 may be formed integrally with the
stem 18 and is generally of a lesser diameter than the
interior of the upper chamber 76. More particularly, the
outside diameter 19 of the annular rim 48 is of a lesser
diameter than the inside diameter of the upper chamber 76 and
freely rotates there within. The stem 18 is further provided
with an additional annular rim 21 which has a radially
-.extending surface 23 facing outwardly from the upper chamber
76. This annular rim 21 may also be formed integ~ally with the
stem 18 to rotate therewith. As with the annular rim 48, the
30 outer surface 25 of the annular rim 21 is of a lesser diameter
than the inner surface of the upper chamber 76 so as to allow
it to freely rotate therein.
The plug valve 10 is further provided with a ring 27
which surrounds the stem 18 and rotates therewith. The
35 annular ring 27, while being generally fixedly attached to the
stem 18 by means of a close fit thereon, does not contact the
inner surface of the casing but rotates with the stem free and
clear thereof.
A plurality of annular pac~ing seals 56 are provided in
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~0~2588
g_
the casing above the ring 27 and below the stem cap 62. As can
be seen in Figures 1 and 2, the stem cap 62 i9 fixedly attached
to the casing 12 by suitable fastening means such as a series
of threaded bolts 64. The stem cap 62, in addition to
providing a positive positioning means for the seals 56, also
provides for the environmental sealing of the stem by the
provision of a weather seal 66 as tyically manufactured by
Johns Manville as their Wiper Construction II, Type P. The
stem cap 62 performs the further function of acting as a stop
member in that a stop member portion 68 may be formed on the
stem cap 62 to coact with a stop collar 70 which is affixed to
the stem 18 to rotate therewith. The stop collar 70 is
provided with a cut away section 72 with lands 74 at each end
thereof which restrict the rotational movement of the stem 18
to a predetermined arc. The restriction of the movement of
the stem 18 is effected by the stop collar 70 abutting the stop
member 68 at either of its lands 74.
~As can be seen in either of the sectional views of the
-~valve 10, the casing 12 and the tapered plug 22 define an upper
chamber and a lower chamber 78. A check valve assembly 80 is
provided for the introduction of a sealant lubricant into the
upper chamber 76 and the sealant lubricant may be introduced
therein under pressure. The sealant lubricant, as it flows
into and fills the upper chamber 76, will also flow into
;25 axially extending grooves 82 and circumferential grooves 84.
As the name sealant lubricant implies, the material serves the
dual purpose of lubricating the various operational parts of
the valve 10 while at the same time seals the plug with respect
to the casing.
The casing 12 is provided with a radially extending port
; which is in communication with a pressure relief screw
arrangement 86. The pressure relief screw arrangement 86
includes a partially threaded cavity 90 disposed within the
casing 12. The pressure relief screw arrangement 86 relieves
;35 the line pressure in the first chamber 76 when the cap 68 is
removed. Suitable stop means such as a solid spherical ball
88 is received within the threaded cavity 90 and is seated in
the cavity 90 on a ball seat (not shown). The spherical ball
88 is maintained on the ball seat in a sealed condition by a
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109Z588
--10--
set screw 92 which is threadably received within the threaded
cavity 90.
The plug valve is immune to the lockup phenomenon by the
provision of dynamically balancing the plug 22 in the casing
12 when the plug 22 is partially or fully open, i.e., when the
port 94 of the plug 22 is connected to and in communication
with the passageway 96 through the casing 12. The dynamic
balancing feature of the valve 10 is achieved by the provision
of a first axially extending opening 98 in the plug 22
connecting the port 94 to the lower chamber 78 and the
provision of a second axially extending opening 100 in the
plug 22 connecting the port 94 to the upper chamber 76. The
opening 98 may be offset from the longitudinal axis of the
plug 22 while the opening 100 may also be disposed from the
longitudinal axis.
At this juncture, it can be seen that the pressure seen
by the port 94 when the plug 22 is in its partially open or
fully open position is also simultaneously seen by the upper
chamber 76 and the lower chamber 78. Accordingly, the
pressure seen by the chambers 76 and 78 will also be seen by
the smaller end 102 of the plug 22 and the larger end 104 of
the plug 22, respectively. ~ydraulic pressure exerted on the
smaller end 102 and the larger end 104 of the plug 22 will tend
to maintain the axial position of the plug 22 with respect to
the tapered interface 24 within the casing 12 at all times
even through pressure and temperature transient. However,
there has been noted that there will tend to be a slight
unequal pressure exerted toward the apex of the taper due to
secondary forces such as the relatively large cross sectional
areas of the larger end 104 with respect to the smaller end Qf
the plug as well as the unequal weight distribution of the
plug 22, i.e., the plug obviously is heavier at its larger end
than at its smaller end. Depending upon the position of the
valve with respect to its associated line, gravity, therefore,
may also play a role in axially dislocating the plug 22 along
its longitudinal axis. To offset these secondary forces, a
helically wound spring 106 which may be disposed on the
longitudinal axis of the plug 22 biases the plug 22 along the
longitudinal axis away from the apex of the taper. The spring
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1092588
--11--
106 may be received within a cavity 108 in the stem and, as
before mentioned, abuts and biases the plug 22. Therefore,
the plug 22 will see virtually no axially dislocating forces
as it experiences pressure and temperature transient in its
partially open or fully open position. The avoidance of such
axial dislocation of the plug also avoids the lockup
phenomenon in that the plug 22 maintains its axial position
within the casing 12 and is not driven into the taper and thus
pinched by the casing after the stabilization of a pressure or
temperature transient.
The second axially extending opening 100 is also provided
with a spherical ball 110 seated therein. The spherical ball,
which is not biased by the spring 106, is free floa~ing within
the second axially extending opening and serves as a check
valve, checking the flow of the sealant lubricant into the
port 94 of the plug 22 when the sealant lubricant is
introduced into the upper chamber 76 under pressure.
The new and improved sealing means 56 comprises a
plurality of annular rings and, as shown in the plug valve of
Figures 1-3, there are three such rings. The three rings, as
will be further described and discussed, are fixed at an
axial position along the stem between stem cap 62. In the plug
valve 10 of Figure 1 the ring 27 exerts a compressing load on
the seals 56. The points of rotating contact of the seals 56
with respect to the stem 18 and ring 27 will be explained in
further detail below but it should be pointed out that these
seals are not necessarily limited to a plug valve as herein
described. The seals as contemplated by the present
invention, while ~eing particularly adapted for such
applications, can be used in other applications where their
unique characteristics are found to be applicable. As can be
seen in Figures 4-10, the new and improved seals 56 generally
comprise radially alternate compressed layers of
polytetrafluoroethylene and graphite. More particularly, it
can be seen in Figure 6 that the seal of Figure 4 is formed by
wrapping a ribbon of polytetrafluoroethylene 51 and a ribbon
of graphite 53. These ribbons which are substantially the
same height are wrapped about a mandrel 55 to form the
uncompressed ring 57 as illustrated in Figure 4 in which each
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alternate strata is polytetrafluoroethylene and graphite. The
polytetrafluoroethylene may be one of many commercially
available forms such as TEFLON (a trademark of E.I. Dupont
DeNemours & Co.). The graphite similarly can be purchased
commercially such as GRAFOIL (a trademark of Union Carbide).
The ribbons 51 and 53 are wrapped about the mandrel 55 in such
a fashion as to generally approximate the final dimensions of
the sealing chamber into which it is to be inserted (both
inside and outside diameters thereof). The height, however,
of the rib~bons is generally twice as great as the desired
final dimension. After the ring 57 is formed it is compressed
within a forming cup 59 by a suitable compressing means (not
shown) such that it is compressed to approximately one-half
the height of the ring 57 to form the ring 61 as shown in
Figure 5. It can be seen from the cross section of Figure 5
that the relatively parallel ribbon strata of Figure 4 has
been compressed into a generally serpentine configuration,
i.e., each alternate layer has been compressed such that they
follow a serpentine or sinusoidal path.
- 20 Referring now to Figures 7-10, there is shown another
improved seal 131 which also employs alternate strata of
- polytetrafluoroethylene and graphite as was employed in the
seal 61 of Figures 4-6. As can be seen in Figure 9, the seal
is formed by wrapping two ribbons about a mandrel 133 to form
; 25 the uncompressed ring 135 of Figure 7. While the ribbon 137 of
graphite is wrapped about the mandrel in a manner similar to
that as shown in Figure 6, there is a difference in the
configuration of the polytetrafluoroethylene ribbon 139. This
can be best seen in Figure 10, which is a sectional view taken
along line 10-10 of Figure 9. The polytetrafluoroethylene
ribbon 139 is formed in a substantially U-shaped manner and
the graphite ribbon 137 is inserted within the U-shaped
polytetrafluoroethylene 139. Accordingly, as these two
ribbons in the above noted configuration are wrapped about the
mandrel 133, the uncompressed seal 135 is formed with each U-
shaped polytetrafluoroethylene ribbon being concentrated at
one end thereof. As with the previously described seal, the
uncompressed seal 135 is compressed to substantially one-half
of its original height within the forming cup 141 by suitable
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forming means (not shown) to form the seal 131 of Figure 8.
The seal 131 of Figure 8 in its compressed state presents a
lower radially extending face 143 compressed entirely of
polytetrafluoroethylene whose purpose will be defined and
S discussed below.
As before mentioned, the ring 27 is generally fixedly
attached to the stem 18 to rotate therewith and, therefore, it
will have moving contact at its radially extending face 29
with the radially extending face 31 defined by the downward
facing face of the lowermost seals 56. In addition, the seals
56 will have moving contac~ with the outer surface of the stem
18. As indicated above, the upper chamber 76 sees the higher
of line pressure or sealant lubricant pressure. ~his pressure
will act upon the various surfaces of the annular rims 21 and
48 which are generally located within the upper chamber 76.
It can be seen from Figures 1 and 2 that such pressure will
tend generally to bias the stem 18 along its longitudinal axis
generally outwardly away from the plug. More particularly, it
can be seen from Figures 1 and 2 that the pressure will act
upon the lower radially extending face 33 of the annular rim
48 and the overall differential biasing force generated
thereby will tend to move the stem 18 outwardly away from the
plug 22. As the stem 18 moves in such a direction the annular
- rim 21 will act upon the ring 27 which, in turn, will be biased
along the same direction as stem 18. The ring 27 which rotates
with the stem 18 will thereupon tend to compress the seals
against the stationary stop member 68 which is bolted to the
~- casing 12. As the ring 27 compresses the seals 56 they will
tend to be forced in greater intimate contact with the stem 18
to further effect the seal therebetween. Additionally, the
ring 27 will be forced in greater intimate contact with the
seals 56 at its radially extending face 29. As before
mentioned, there will be rotating contact between the outer
surface of the stem 18 and the seals 56 as well as between the
seals 56 and the radially extending face of the ring 27.
The seals 56 may comprise three separate rings. The
lowermost ring of the seals 56 would typically be ring 131 of
Figure 8. More particularly, it can be seen that the radially
extending polytetrafluoroethylene face 143 of ring 131 would
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be in moving contact with the radially extending face 31 of
the ring 27. In addition, the upward projecting alternate
layers of the polytetrafluoroethylene will provide a suitable
bearing surface for the moving contact between the outer
surface of the stem 18 and the inner axially extending surface
of the seal 131. Further, the seal 61 of Figure 5 could be
suitably utilized in the top two seals 56. These two uppermost
seals would primarily be in moving contact with the outer
surface of the stem 18 and the inner axially extending
surfaces of~the seals.
It can be seen from the above, that the line pressure
and/or the sealant lubricant pressure can be considered to be
an energizing force which ultimately results in the seals 56
being brought into intimate sealing contact with the stem 18
and the ring 27 as well as the inner surface of the casing 12
and the downward radially extending face of the stop member
68.
It should also be noted that the annular rim 48 performs
a backseat function as well as the functions above noted. If,
for example, it is necessary to replace the seals 56, it can be
seen fr~m Flgures 1 and 2 that upon removal of the threaded
bolts 64 which allow removal of the stop member 68 after
removal of the stop collar 7Q the seals will be exposed. When
` the stem cap 62 is so removed the stem 18 will tend to move in
an axial outward direction and at that point the annular rim
4~ at its outward facing radially extending face 35 will
backseat on a radially extending face 37 formed on the casing
12.
As before mentioned, the various operational parts of the
valve 10 may be assembled through the end of the casing
through the opening covered by the end cap 14, i.e., the stem
18, thrust bearing and seal 50, equalizer ring 20, spring 106,
spherical ball 110, plug 22, spherical plug thrust ball 34
etc. As the stem 18 is removed through the bottom of the
casing 12, the ring 27 will abut the angular protrusion 39
provided on the casing 12 and will slide off the stem as it is
withdrawn from the casing.
There is thus provided a uniquely configured plug valve
10 which incorporates pressure actuated rotating seals which
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109Z588
--15--
effect an efficient and effective seal between the rotating
stem 18 and casing 12. In addition, the plug valve 10 may be
field maintained without any interruption of line flow. In
addition, the plurality of seals 56 may be removed and
replaced while the valve is installed in an operational mode.
Obviously, the present invention is not limited to the
specific details as herein described, but is capable of other
modifications and changes without departing from the spirit
and scope of the appended claims.
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