Note: Descriptions are shown in the official language in which they were submitted.
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Locking Device and Method for Securing Telescoped Pipe
Specification
Background of the Invention
FIELD OF 1BE I]iVENTION
This invention relates generally to connections between lengths of pipe, or
between
pipes and fittings. More particularly, the invention is directed toward a
device and method of
connecting two lengths of pipe in a restrained joint configuration, while
employing a locking
segment that is self-braking to prevent over-rotation and penetration of a
spigot.
DESCRIPTION OF RELATED ART
Due to thrust forces, earth movement, and external mechanical forces exerted
on
pipes, the industry has focused substantial attention on the problem of
maintaining coimections
between adjacent lengths of pipe after installation. The result of this
attention is a library of
differing solutions and approaches known in the art. The majority of these
solutions can be
categorized into either "push-on" joints or "mechanical joints."
Push-on solutions are exemplified by U.S. Patent No 2,953,398, and account for
the
majority of straight-run pipe connections. In a typical configuration, a
spigot end of a pipe slides
into a bell end of another pipe past a tightly fitted gasket. A variation of
the push-on joint is
evidenced by U.S. Patent No. 2,201,372, to Miller, which employs a compression
snap-ring fitted
within a special lip of the bell, in order to exert pressure onto locking
segments and thus drive them
into the spigot, restraining the joint against thrust forces. U.S. Patent No.
3,445,120, to Barr,
likewise employs a gasket with stiffening segments completely encased therein
that are generally
disposed such that they and the gasket may roll between a locking and a free
position. As the Barr
gasket rolls under extraction forces, it is intended eventually to encounter a
position in which the
stiffened plane needs to compress for further rolling, in theory terminating
the rolling and
restraining the joint.
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Other examples of restrained push-on joints include U.S. Patent Nos.
5,295,697;
5,464,228; and 5,067,751. The securement of the connection in such references
is effected by
locking segments or wedges within the gasket that engage the spigot. The
locking segments
possess a groove that mates with an annular rib on the bell, such that the rib
acts as a rocker, or
cam, or during some movements, as a wedge. During insertion of the spigot into
the bell, the
segments rotate on the rib, but are prevented from appreciable straight-line
movement by the mating
of the rib and groove. Upon experiencing counter-forces tending to effect
removal of the spigot, the
rib acts as a cam, both causing the segments to pivot on the rib as an axis,
and exerting a radially
inward pressure as the segment attempts to slide past the rib.
BRIEF SUMMARY OF THE INVENTION
A locking segment for use in a restrained j oint avoids over-rotation and
penetration
of the inserted spigot by muring between two surfaces in the bell, thus
arresting rotation before
positions are reached in which pressures on the spigot would result in likely
penetration. The
segment therefore can rotate to an effective locking degree, upon which
rotation the radial forces by
which the segment bites into the pipe increase. By virtue of the muring that
prevents rotation
beyond a desired maximum, a graph of the relationship between a radial force
exerted by the
segment on the spigot, in relation to the thrust force experienced could show
a radial force that
generally increases as thrust forces increase, but only up to a given point.
At that point, the line
representing radial force could be made to substantially plateau. By selection
of materials and
configurations, the plateau may be fixed below a spigot penetration value.
OBJECTS OF THE INVENTION
The following stated objects of the invention are alternative and exemplary
objects
only, and no one or any should be read as required for the practice of the
invention, or as an
exhaustive listing of objects accomplished.
As suggested by the foregoing discussion, an exemplary and non-exclusive
alternative object of this invention is to provide a locking segment that is
capable under certain
conditions of self-braking, to prevent over-rotation or other un-capped
increases in radially inward
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insertion and extraction thrusts, wherein the segment is fally engaged with
the spigot to prevent
extraction.
Figure 5 is a gasket as in the present invention, shown in cut-away for
viewing a
cross-sectional profile at location of an embedded segment.
DETAILED DESCRIPTION OF THE 1NVENTION
The following is a detailed exemplary description of an embodiment of the
invention, in a number of its various aspects. Those skilled in the art will
understand that the
specificity provided herein is intended for illustrative purposes with respect
to an exemplary
embodiment, and is not to be interpreted as limiting the scope of the
invention or claims.
References to "pipe" in this document, when used with respect to the present
invention, shall be
understood equally to refer to any pipe length, appurtenance, fitting,
connection, or any other
connected or connectable device or element.
As is depicted in Figures 1 and 2, the locking segment 1 of the present
invention is
optimally constructed to fit within a gasket 30 that is configured to fit
within any standard push-on
bell having a gasket seat configured with an annular trough 47, also known as
a keeper groove,
without necessitating changes to the configuration of the bell or spigot.
Alternatively, the locking
segment 1 of the present invention can be used with a mechanical joint having
a thrust ring or gland
follower, rather than a cast bell lip 44, so long as an annular trough 47 is
present in the assembled
joint. In the spirit of the invention, non-standard bell configurations may be
constructed to fall
within the claims.
Looking to Figure 1, as will be understood in the art, a typical bell
configuration
(standard or non-standard) will exhibit, at a minimum, a socket area of the
bell 40, having an
increased intemal diameter as compared to the flow-area internal diameter of
the bell pipe. A bell
lip 44 extends in a generally radial direction, which serves as an externally
visible face of the bell.
Moving axially inwardly of the bell lip 44, in the direction of insertion
(shown by arrow 64), the
be1140 has a cavity for receiving and mating with the spigot 70. In assembled
operation, following
insertion of a spigot 70, the cavity will take the form of an annular gap 60
between the spigot and
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the bell cavity boundary 45, which cavity boundary 45 in the shown embodiment
is represented by a
generally cylindrical intemal wall of the bell, but which also may have
ridges, ribs, gasket retainers,
steps, varying radial depths, and other non-cylindrical characteristics such
as gasket compression rib
48, as depicted in Fig. 4.
.
In addition to the cavity boundary 45, the shown internal configuration of
be1140
includes an annular trough 47, arranged and suited in the shown configuration
for the purpose of
positioning a sealing gasket or other materials. This annular trough 47 may be
located immediately
adjacent the internal side of bell lip 40, as it appears in the shown
embodiment (Fig. 1), or it may
divide cavity boundary 45 into two axially separated sections. This annular
trough 47 is bounded at
its radial extreme by a trough terminus 42, which may be cylindrical as shown
in the figures, or may
be of other geometry, and is bounded on axially inward and outward sides a
first interior surface
and a second interior surface opposing the first interior surface, shown in
the figures as a first wall
43 and second wall 41, respectively. Trough first and second walls 43 and 41
are generally radially
extending, though they may have a curved or slanted geometry, so long as they
do not detract from
the ability to brace the mured braking effect described in summary above or in
greater detail below.
As shown in Figure 1, the second wa1141 is joined to cavity boundary 45 at a
shoulder that serves
as an insertion fulcrum 46 during assembly, but which during extraction
movements of spigot 70
bears no force and presents no radially inward cam-type influence on segment
1. Notably in the
shown embodiment, the segment 1 possesses no radially outwardly protruding
surfaces outside of
annular trough 47 that would impede substantially straight-line movement of
segment 1 as a whole
in the direction of the bell lip 44.
Moving still further inward of the annular trough 47 and the cavity boundary
45, the
bell 40 possesses a shoulder 52 stepping the interior profile of the bell 40
to a lower radius of
clearance. As will be understood in the art, this shoulder acts as a stop to
further insertion of the
spigot 70.
Looking now at Figure 5, an embodiment of a gasket 30 for use with the present
invention is shown. As will be appreciated in the art, shown gasket 30 is
configured with a bulb 32
for sealing a joint against fluid leakage. To this end, the gasket may be a
complete ring with its
outer diameter approximating or slightly greater than the inner diameter of
be1140 at the location
into which gasket 30 is to fit. This bulb may be of an elastomeric or other
resilient material sized
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with consideration taken to its elasticity and compressibility. In operation
of the joint, if the gasket
30 is intended to seal the joint, it should be sized to fit within the annular
gap 60 only upon some
compression between the spigot 70 and the bell 40. In particular, for any
given spigot 70, gasket 30
tends to have a slightly smaller inner diameter than the outer diameter of the
spigot 70.
Accordingly, insertion of spigot 70 into be1140 will require exertion of force
sufficient to compress
gasket 30 against cavity boundary 45. In addition to the bulb 32, gasket 30
possesses a retainer heel
31, configured to mate with annular trough 47 in such a manner that when
gasket 30 is installed in
bell 40, retainer hee131 fits within annular trough 47 and positions bulb 32
such that gasket 30 is
appropriately oriented. Typically, though not necessarily, retainer heel may
be constructed of an
elastomer of a higher durometer rating than that of bulb 32. As will be
understood in the art, this is
because bulb 32 should desirably be capable of flexibility and compression for
sealing efficiency,
while an increased firmness of retainer hee131 may allow the retainer heel 31
to remain mated
within annular trough 47 despite axial movement of spigot 70.
In addition to sealing, gasket 30 retains locking segment 1 within a range of
desired
orientations during assembly. It thus should be understood that the gasket 30
need not necessarily
effectively perform a sealing function to fall within the scope of the
invention. Although in the
shown embodiment and the remainder of this description the gasket 30 is
sufficient to provide a
sealing function, the inventors recognize within the spirit and scope of one
altemative embodiment
that the shown gasket 30 may be substituted with a simple positioning body, or
retainer, operating
to hold the locking segments 1 in a desired range of orientations during
assembly. In such
alternative, the gasket 30 need not have sealing properties, nor be continuous
about the perimeter.
It is possible in such alternative that the retainer be a wire or snap ring
urging the locking segment 1
radially outward.
Tuniing now to Figure 2, an embodiment of a locking segment 1 is depicted.
Reference to directions and orientation in this description of the shown
locking segment 1 is made
with respect to the orientation of the locking segment 1 as installed in a
bell 40, seen in Figure 1.
Locking segment 1 generally may be divided for discussion purposes into a
first portion, or brake
12, and a second portion, or toe 13. Brake 12 extends radially outwardly of
toe 13. Toe 13 is
constructed to engage spigot 70, at least upon movement of spigot 70 in an
extraction direction. To
facilitate this engagement, the shown toe 13 is configured as a wedge or
triangular shape, and
possesses on its radially inward bottom 9 as a toothed surface with at least
one tooth 7, which is
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constructed of a material having a hardness sufficient to penetrate the
surface of spigot 70. 7n the
shown embodiment, the radially outward side of toe 13 opposite bottom 9 is top
8, is shown
without teeth or any protrusion or extension that could impinge, rotate, or
resistively meet cavity
boundary 45. As shown top 8 joins to axially inward heel side 14 at a
transition point 6. Similarly,
bottom 9 joins an axially outward side of brake 12 at a braking elbow 2.
Outward side 11 and
inward side 14 are connected at their radial extremes by a mating surface 10.
In the shown
embodiment, the transition from inward side 14 to mating surface 10 serves
also as forward brake 3,
though it will be understood from the discussion below that the forward brake
3 need not
necessarily be at the intersection of inward side 14 and mating surface 10
(e.g., it could be a
protrusion or nub in the middle of inward side 14, or adapt a functionally
similar alternative
location). Similarly, the shown embodiment features an insertion brake 5
located as a portion of
outward side 11 near outer comer 4, though the insertion brake 5 and outer
coiner 4 can in some
embodiments be coincident, and, indeed, even in the shown embodiment the outer
comer 4 may
perform the insertion braking function of insertion brake 5 to some degree. In
the shown
embodiment, segment 1 appears with the angle between the toe and the heel
between approximately
120 degrees and 170 degrees.
As can be seen readily from Figure 1, brake 12 is held by gasket 30 (or other
retainer
used in place of gasket 30) at least partially within annular trough 47, and
having at least a portion
of toe 13 extending exteriorly of the annular trough 47, and radially inward
of the same, to allow
contact between a tooth 7 and the spigot 70 in some orientations of locking
segment 1. While the
figures show an embodiment having the toe 13 extending from the annular
trough, it is conceivable
within the scope of the invention that the locking segment 1, including all
portions of toe 13, may in
some alternative embodiments reside entirely within the annular trough 47, so
long as the toe 13 is
capable of making resistive contact with spigot 70, whether by altemative
configurations of the bell
40 or the spigot 70. For ease of application to a wide range of spigots 70 and
bells 40 as are already
present in the market, the inventors have shown the particular embodiment
having a toe 13
extending from annular trough 47 to meet spigot 70, rather than an embodiment
that may rely on
special configurations of spigot 70.
In assembly, locking segment 1 is molded into or inserted into gasket 30, with
the
brake 12 of locking segment 1 extending into the retainer heel 31 of gasket
30, as maybe seen from
the cut-away of Figure 5. Although not shown, the brake 12 can, in addition to
extending into
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retainer heel 31, extend beyond the retainer heel 31, such that the brake 12
is visible from outside
the retainer heel 31. As shown, the tooth 7 should be sufficiently near the
surface of bulb 32 to
allow penetration of the bulb and direct contact with spigot 70. It will be
understood in the art that
some alternative embodiments may not require or encourage direct spigot 70-to-
tooth 7 contact. In
such cases, the operation of the invention may continue in effect, though
appropriate modifications
may be necessary to provide a sufficient resistance between the locking
segment 1 and spigot 70,
such as special ribs or notches formed onto the spigot 70. Regardless of the
mode of contact
between locking segment 1 and spigot 70, typically, though not absolutely
necessarily, anumber of
locking segments 1 will be dispersed about gasket 30. In the shown embodiment,
fifty-six locking
segments 1 are dispersed about a thirty-six inch diameter spigot 70. The
inventors' experiments
suggest the invention will bring ready improvements over the art to at least
thirty through sixty-four
inch pipe; the invention is applicable to smaller diameters and possibly to
larger diameters as well,
and, though not empirically tested, is expected to provide excellent results.
Furthering the assembly, the gasket 30 is placed within bel140, such that
retainer
heel 31 mates with annular trough 47. This assembly arrangement will cause
brake 12 also to be at
least partially within annular trough 47, and toe 13 to extend out of the
annular trough 47 and into
the cavity 49 (i.e., in presence of a spigot 70, the annular gap 60). In this
orientation, prior to
extraction movements of a spigot, segment 1 is in a resting position. The
presence of the retainer
heel 31 in annular trough 47 tends to secure the gasket 30 in place against
axial displacement. In
some embodiments, the locking segments 1 may further this securement, as well.
Following
insertion and seating of the gasket 30, spigot 70 is inserted into the bell 40
by movement in the
direction of arrow 64. As spigot 70 passes lip 44, it will come into contact
with gasket 30. Upon
insertion pressures, spigot 70 will tend to push gasket 30 axially inwardly,
but as a body, gasket 30
resists such movement due to the securement of retainer heel 31 in annular
trough 47.
Consequently, bulb 32 is compressed within the annular gap 60, as may be seen
in Figure 3. It will
be understood that this compression has a number of effects. Among the effects
are the sealing of
the joint against fluid flow through the annular gap 60, and the relative
centering of the spigot 70
within the cavity 49 due to circumferentially distributed pressures of the
gasket 30.
As the gasket is compressed, it will be evident to those in the art that the
locking
segment 1 will rotate such that the toe 13 moves radially outwardly, but heel
12, being engaged
with the annular trough 47, has a limited range of radial movement. In
operation, during insertion
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the shown locking segment 1 rotates against insertion fulcrum 46, pivoting
about this point as an
axis of rotation. It will be understood by those in the art that although the
insertion fulcrum 46 is
shown as a right-angle shoulder, alternative embodiments of the joint
described and claimed herein
may form insertion fulcrum 46 as a rib raised in a radially inward direction
from the cavity
boundary 45, or as a depression at the intended location for locking segment
1, recessed radially
outwardly from cavity boundary 45 to create a more gentle or a cammed fulcrum
or other effect.
The locking segment 1 is constructed and oriented in such a manner as to allow
the locking segment
1 enough rotational freedom within the annular trough 47 and the annular gap
60 to accommodate
entry of the spigot 70 into the cavity 49. With the particular embodiment
shown, due to the closely
mated profiles of the heel 12 and the annular trough 47, the radially outward
rotation of toe 13 as it
pivots on insertion fulcrum 46 may be limited by the contact between insertion
brake 5 (which may
be coincident with outer corner 4) and a wall of trough 47. In addition to
other reasons, the
inventors have drawn the locking segment 1 in this manner to take advantage of
the enhanced
retention of the gasket 30 in annular trough 47 made possible by braking
rotation of the locking
segment 1 on insertion. The shown configuration allows sufficient rotation to
allow insertion of
spigot 70 without extrusion or gouging of the surface of spigot 70. In some
applications, the user
may desire to provide a tighter fit, even one that causes such gouging or
scraping, in order to ensure
an early bite of the tooth 7 into spigot 70.
Following insertion, thrust forces and other forces tending to urge separation
of the
bell 40 and the spigot 70 will typically cause the spigot 70 to move in an
extraction direction (e.g.,
along the direction of arrow 63) relative to bell 40. By virtue of the
pressure exerted by bulb 32 of
gasket 30, tooth 7 will be in proximity to spigot 70, if not in direct
contact. In one embodiment,
tooth 7 is, in the uncompressed state of gasket 30, already exposed. This
exposure may be by
protrusion from the surface of gasket 30, or by slight recessing beneath the
surface in combination
with the absence of gasket material covering the teeth. An alternative
embodiment presents tooth 7
slightly recessed within gasket 30, and covered by a membrane or thin layer of
compressible or
puncturable material, so long as the depth and placement of tooth 7 are
adapted to ensure
engagement between tooth 7 and spigot 70 upon compression of gasket 30. In the
shown
configuration, locking segment 1 possesses a plurality of teeth 7, the tips of
which are arranged in
an arcuate relationship. The arcuate relationship enhances the ability of at
least one tooth 7 to bite
into spigot 70 despite any variations in circumference of spigot 70 or the
inner dimensions of bell
40. This is because a larger annular gap (frequently due to manufacturing
tolerances) will cause
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locking segment 1 in assembly to be rotated toward a less acute engagemcnt
angle 62 than exists in
an installation having a larger spigot 70. Given the arcuate relationship of
teeth 7, upon such
rotation of locking segment 1 the teeth nearest the end of toe 13 rotate into
contact with spigot 70.
The arcuate configuration farther urges at least two teeth 7 to be in contact
with spigot 70,
regardless of the rotation of segment 1, because a straight line can be drawn
between any two
adjacent teeth 7.
In response to extraction movements of the spigot 70, locking segment 1 will
attempt to move in an extraction direction along with spigot 70, but axial
movement of the entire
body of locking segment 1 is prevented by the pressing of brake 12 against
first wall 43. Locking
segment 1 then rotates such that toe 13 moves radially inwardly toward spigot
70. As the locking
segment 1 of the shown embodiment rotates, the slope of brake 12 allows that
portion of locking
segment 1 to slide upwards against the wall of annular trough 47, preventing
premature binding.
The rotation of locking segment 1 is caused even in the absence of a pre-
existing engagement of
tooth 7 with spigot 70 due to friction between the spigot 70 and the bulb 30
in which locldng
segment 1 is disposed. If not already in biting engagement, as such rotation
continues, tooth 7
engages with spigot 70 by digging into the surface of spigot 70. Thus the
further movement of
spigot 70 causes a concomitant radially inward rotation of toe 13. Those in
the art will understand
that the relationship between the force of the axial thrust pressures on
spigot 70 is by this process
transferred in part into a radially inward force between the spigot 70 and the
locking segment. The
dynamic nature of the relationship results in increased biting, or digging of
tooth 7, into spigot 70 as
the pressures increase. To a point, this increasing radial pressure is
advantageous, as greater radial
pressure and the bite of tooth 7 exerted thereby may be necessary in response
to greater axial
extraction forces. It will be understood, however, that each spigot 70 will
have a maximum
sustainable radial pressure threshold, above which radial pressures exerted by
the locking segment 1
cause or make likely a complete penetration of the spigot 70 by locking
segment 1, and thus failure
of the joint. As described below, the arrangement of lock.ing segment 1 in
concert with bell 40
prevents exceeding such pressures in the current invention.
The brake 12 of the locking segment 1 fits within annular trough 47 in such a
manner that it has limited rotational freedom. Upon rotation of toe 13
radially inwardly, it will be
understood that brake 12 also rotates. Due to the confines of annular trough
47, rotation of brake 12
is arrested by the muring of brake 12 between the first wall 43 and the second
wall 41. As shown,
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the braking elbow 2 is forced during this muring against the first wall 43,
and the forward brake 3 is
forced against the second wall 41, resulting in a braked position for segment
1. It should be
understood that, while forward brake 3 and braking elbow 2 are shown in the
figures as terminating
points on the inward side 14 and of the outward side 11 of brake 12, the
invention is not so limited.
Either or both forward brake 3 and brake elbow 2 can be protrusions from the
respective sides, not
necessarily located at the corners, so long as they are capable of muring
between the first wall and
the second wall in response to rotation. Additionally, given the variations in
spigot and bell
diameters experienced in real world appiications, some configurations of brake
12 having a more
rounded profile may not have a discreet pinpointable forward brake 3 or
braking elbow 2, so long as
rotation of brake 12 causes points to mure between the first wall and the
second wall. By operation
of this muring, the rotation of brake 12 is arrested; in tum, as will now be
evident, the rotation of
the entire loclcing segment 1 is arrested (except, perhaps, for defonnation
that may occur to the
locking segment 1 or to first wall 43 or second wal141). As the rotation of
locking segment 1
cannot continue, the radial pressures exerted by toe 13 on spigot 70 will not
increase, despite an
increase in axial thrust pressures. Contrast is drawn to the continuing
increase in radial pressure
that would be expected in the absence of a rotational braking mechanism. The
invention may be
used to cause the plateau for this pressure line, if graphed, to occur below a
pressure at which spigot
70 is deemed likely to fail.
As described, by means of the rotational braking, the radially inward
pressures
exerted on spigot 70 may be capped. In fact, the muring mechanism taught
herein will cause a
segment 1 to cease rotation at its maximum desired rotational point even in
the absence of a spigot.
Mathematically, despite the capping of radial pressures by muring, the forces
in the system must
remain net zero. In effect, the inventors believe (without wishing to be
limited to theory) that the
cantilever effect of the muring multiplies the axial forces applied by the
locking segment 1 to the
first wall 43 to offset the forces not transferred into radial pressures on
the spigot 70, though it is
recognized that the system is sufficiently dynamic with multiple variables
that this mechanism may
not always or purely be in play.
In the shown embodiment, the profile of the brake 12 is complimentary to the
internal profile of the annular trough 47. Those skilled in the art will
understand by reference to
the claims and the preceding discussion that the profiles need not match
precisely, nor even nearly,
so long as the brake 12 is fitted within annular trough 47 in such a manner as
to mure between first
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wall 43 and second wall 41 upon reaching a maximum rotation. Furthermore,
those in the art will
understand that while the first wall 43 and the second wal141 are discussed
herein as if they were
discrete walls of the annular trough 47, the walls may be staggered or may
have varying radial
separations. By way of example, Figure 1 shows first wall 43 as coincident
with the inner face of
bell lip 44. As further shown in this figure, braking elbow 2 actually would
cantilever into aportion
of the first wal143 that is more radially inwardly extended than any existing
point on second wall
41. It is possible that a bell configuration may have a radially extending
wall offset from the annular
trough 47. In such cases, the offset radial wall will be considered an
extension of the first wall 43,
even though it is offset from first wall 43 axially.
It should be noted that in the shown embodiment, the axis of rotation of the
locking
seginent during insertion is located in or about insertion fulcrum 46, while
the rotational axis occurs
at a different point during extraction. More particularly, the inventors
believe that the axis of
rotation during extraction is a "floating" axis that is located in the brake
12 itself. T'liis floating
characteristic of the axis allows the locking segment to seek its own
orientation for locking spigots
and bells of varying tolerances (e.g., situations in which the annular gap 60
varies between one joint
and the next). It is possible that in some installations, outer corner 4 may
never contact any portion
of annular trough 47. Alternatively, in tighter installations (e.g., those
having a narrower annular
gap 60), the outer corner 4 may contact trough terminus 42 and may even act as
a cain in some
respects. In normal operation, the shown embodiment does not take advantage of
or exhibit any
cam-type action outside of the annular trough. Further, the locking segment 1
of the current
invention does not require any.bell surfaces forward of the brake 12 that
exert any radially inward
pressures or that resist axially outward movement of the locking segment 1.
CONCLUDING REMARKS
The foregoing represents certain exemplary embodiments of the invention
selected to teach the
principles and practice of the invention generally to those in the art such
that they may use their
standard skill in the art to make these embodiments or variations based on
industry skill, while
remaining within the scope and practice of the invention, as well as the
inventive teaching of this
disclosure. The inventor stresses that the invention has numerous particular
embodiments, the
scope of which shall not be restricted further than the claims as allowed.
Unless otherwise
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specifically stated, Applicant does not by consistent use of any term in the
detail description in
connection with an illustrative embodiment intend to limit the meaning of that
term to a particular
mean.ing more narrow than that understood for the term generally.
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