Note: Descriptions are shown in the official language in which they were submitted.
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ENERGIZED RESTRAINING GASKET
FOR MECHANICAL JOINTS OF PIPES
Background of the Invention
FIELD OF THE INVENTION
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 that maximizes the advantages of both
restrained
push-on joints as well as mechanical joints, as are known commonly in the art.
The invention
has application to long-run pipe lengths as well as fittings, appurtenances,
and connections.
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
connections 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 as either "push-on" joints or "mechanical
joints." References to
"pipe" made by the inventor with respect to application or use of the present
invention shall
be understood to include fittings, connections, and any other appurtenances to
pipes.
The most common connection device used in the art for connection of
straight-run lengths of pipe is a "push-on" pipe/bell configuration. These
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. No follower ring, stuffing box, or
other external
compression means typically is present in a push-on joint. Additionally, the
typical push-on
joint does not include a restraining means, though such means as tie bars,
concrete thrust
blocks, screws, and additional ring attachments have been employed in some
cases to effect
restraining to the joints. Advancements in the art have led to innovations and
modifications
of push-on joints to include restraining means. Examples of such restrained
push-on
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joints include U.S. Patent Nos. 5,295,697; 5,464,228; and 5,067,751. The
securement of the
connection in such advancements may be effected by locking segments or wedges
within the
gasket that engage the spigot. The locking segments are oriented in such a
manner as to
allow entry of the spigot into the bell, but upon counterforces tending to
effect removal of
the spigot, the segments pivot toward a biting engagement with the spigot,
stopping further
removal. The effect is much like a child's "finger lock" toy, the stronger the
attempt to
remove the pipe, the greater the locking effect exerted by the inserts. These
push-on type
joints enjoy superior flexibility and resistance to both axial and para-axial
separative forces.
Meaningful difficulty has been experienced in the industry, however, in
applying these
connections to fittings, where it may be impracticable to secure the fitting
sufficiently to
exert the high installation pressures necessary initially to push the spigot
into the bell in such
configurations.
A "mechanical joint" is a well-known standardized connection device widely
employed in the pipe industry. Such a joint fluid-seals two lengths of pipe
together by
compressing a gasket around a spigot and within a bell at the intersection.
Mechanical joints
are characterized by an outwardly flanged bell of a receiving pipe, into which
a spigot of a
second pipe is inserted. The bell is adapted to seat a gasket that fits snugly
about the
circumference of the spigot of the second pipe, and further to receive a
supporting
compression ring or gland. In assembly, the spigot is fully advanced into the
bell and the
gasket is firmly seated within the bell and around the spigot. The gland is
then forced
against the gasket by fastening it securely to the bell flange through such
means as fastening
bolts tightened under relatively high torque. This configuration typically
includes a lip about
the inner diameter of the gland that upon securement extends axially within
the bell. The
configuration of the gland is such that as the lip is forced against the
gasket, the gasket
becomes compressed under pressures sufficient to deform the gasket. As the
gasket is
compressed between the bell and the gland, the gasket therefore is squeezed
inwards toward
and into sealing contact with both the exterior of the inserted pipe section
and the interior of
the bell. This deformation enhances the sealing effectiveness of the gasket
beyond that
which can be readily obtained in the absence of compression or high insertion
forces
The mechanical joint enjoys wide acceptance in the industry, and is the
subject of national and international standards such as ANSI/AWWA Clll/A21.11-
95.
Given the industry affinity for such joints and the embedded nature of these
standards into
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specifications, any mechanical joint should conform to these specifications to
gain optimal
acceptance. Numerous attempts have been made to improve upon the standardized
mechanical joint. These attempts are almost uniformly characterized by the
inclusion of an
additional mechanism or attachment, creating a mechanical connection resistive
to
separation of the pipes. Such attempts that require modification of the bell
or gland (or both)
are exemplified by U.S. Patent No. 784,400 to Howe, which employs locking
inserts
recessed within the gland; U.S. Patent No. 1,818,493, to McWane, which
discloses a
modified gland that relies upon specially modified bolts having toothed cams
that both pivot
on and bite into the spigot as the bolts are hooked under a modified lip of
the bell and forced
into grooves in the gland.
Further solutions employ additional restraining devices or teeth interposed
between the gasket and the gland, which are driven into the spigot as the
gland is tightened.
Included among these devices are U.S. Patent No. 4,664,426, to Ueki; and U.S.
Patent No.
5,297,826, to Percebois, which each require the use of multiple additional
locking devices in
addition to the standard mechanical joint's simple bell-gasket-gland
configuration. U.S.
Patent No. 4,878,698, to Gilchrist, U.S. Patent 5,335,946, to Dent, et al, and
U.S. Patent No.
5,398,946, to Hunter, et al., appear susceptible to, possible early engagement
of the biting
teeth prior to full seating of the gland. U.S. Patent No. 5,803,513, to
Richardson and others
attempt to solve this potential problem by use of sacrificial skid pads to
prevent early
engagement of the teeth.
Additional solutions employ a bolting assembly attached to (or incorporated
into) the bell, which assembly is oriented such that upon tightening of
certain specially
configured bolts, the bolts or a device actuated thereby are driven into the
outer surface of
the spigot. These bolting schemes are exemplified by devices sold by EBAA
Iron,
commonly known in the art under the trademark MEGALUG (Registration No.
1383971)
Further examples of this type of solution include U.S. Patent No. 4,647,083,
to Hashimoto,
which modifies the standard gland to include bolts that act upon locking
wedges when
tightened. When a pipe is installed in a ground-bedded environment, it is
typically
inconvenient to have multiple additional bolting requirements on the underside
of the pipe as
laid. Such underside boltings increase the cost and time of installation. If,
however, the
bolt-in locking scheme employs only a few bolt locations, the inward pressure
of the bolts
may in some conditions tend to deform the cross-sectional profile of the
spigot. For
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example, employment of only three bolt locations in some circumstances may
exhibit an
undesirable possibility of deforming the spigot into a slightly triangular
shape.
It will be noted by those reasonably skilled in the art that each of these
configurations also suffers from practical issues, such as the expense of
manufacture of
additional components and the fact that additional components increase the
potential for
unacceptable failure.
Furthermore, each of these solutions may be considered a "static" connection.
Although pipelines are traditionally considered to be rigid and immobile
structures, a durable
connection must allow for a certain amount of flexibility and "play" at
joints. Such
accommodation to movement is necessary because the environments in which
pipelines lay
are not truly static. Thrust forces may create non-longitudinal, or para-
axial, loads that tend
to drive a pipe length toward an angle from the longitudinal axis of the
lengths to either side
of such axis. As the pressures of the material being transported within the
pipe vary, the
forces will similarly vary. Additionally, locations in which pipes are run
rarely are as stable
as commonly believed. In fact, pipes may be run above ground, in which cases
such pipes
do not enjoy the benefit of any stability enhancing factors of bedding or
trenched
installation. Finally, even typical earth-bedded pipes must endure shifting
due to
sedimentation, erosion, compaction, mechanical forces (such as nearby
construction), and
earth movement (such as earthquakes).
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 the locking segments and thus drive them into the
spigot. Alternatives
in Miller similarly drive locking segments into the spigot upon installation.
U.S. Patent No.
3,445,120, to Barr, likewise employs a gasket with stiffening segments
completely encased
therein that are generally disposed in a frustroconical arrangement. Such
segments are stated
to give the gasket a resistance to compression along the plane that includes
both ends of the
segment. When a spigot is subjected to withdrawing forces, the gasket rolls
with the
movement of the pipe. As the gasket rolls, it is intended to eventually
encounter a position
in which the stiffened plane needs to compress for further rolling. In optimal
conditions, due
to the stiffening, the gasket cannot compress and therefore cannot roll
further. As the rolling
stops, the gasket becomes a static friction- based lock between the spigot and
the bell.
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Notably, among other distinctions, the arrangement taught by Barr remains a
rubber-to-pipe
frictional connection.
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 an exemplary and non-exclusive
alternative object of this invention is to provide a gasket interchangeable
with gaskets of
standard mechanical joints which allows for the transformation of the joint
into a restrained
joint without the need for any reconfiguration or adaptation of the bell,
spigot, or gland of
the mechanical joint involved.
A further exemplary and non-exclusive alternative object is to provide a
dynamic connection for pipes that does not require high insertion pressures.
A further exemplary and non-exclusive alternative object of the invention is
to provide for a cost effective manner and device of restraining a typically
configured pipe
joint.
The above objects and advantages are neither exhaustive nor each
individually critical to the spirit and practice of the invention, except as
stated in the claims
as issued. Other objects and advantages of the present invention will become
apparent to
those skilled in the art from the following description of the invention.
BRIEF SUMMARY OF THE INVENTION
The present invention may be described basically as a gasket for converting a
standard mechanical joint into a restrained mechanical joint without the need
for altered
configuration of the bell, spigot, or gland of the joint, and without the need
for additional
fittings or devices. In the practice of the present invention, a standard
mechanical joint's bell
and gland configuration can be employed to connect a spigot end of one pipe
length to the
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bell end of another pipe length in a restrained relationship (restraint being
defined as
resistance to axial separation of a mated bell and spigot), with the restraint
based on forces
superior to rubber-to-pipe friction. In more particular discussion of some of
the
embodiments taught, the invention includes forming the gasket to fit within
the bell in such a
manner that a void exists during rest, into which void the gasket deforms,
which in turn
influences the rotational motion of the segment. In this manner, the
configuration of the
gasket influences the timing and extent of rotation during the process of
securing the gland
to the bell. Overpenetration may be avoided, while at the same time ensuring
sufficient
penetration at the proper moment in time. Controlling the timing and extent of
locking
segment rotation influences gasket performance and is addressed by the
described
embodiments of this invention. The extent of segment rotation affects the
application of
restraint. Once restraint occurs, which typically is when the segment has
rotated into an
interference position between bell and spigot, further meaningfully helpful
gasket
compression typically no longer occurs. Rotating the segment too early yields
insufficient
gasket compression for adequate sealing. Rotating the segment too late may not
sufficiently
restrain the joint.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows an diagram of the typical mechanical joint, having a gasket in
place.
Figure 2 depicts a cross-sectional view of an un-stressed gasket of the
present
invention in the initial phase, at a location in which the position and cross-
section of the
locking segment can be viewed.
Figure 3 demonstrates the cross-sectional view of an embodiment of the
gasket.
Figure 4 is a depiction of the gasket and segment in the joint during the act
of
assembly, in the transition phase.
Figure 5 shows an embodiment of a locking segment configuration useful in
the present invention.
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Figure 6 shows the joint of the present invention following compression and
in a locked state, restraining the joint.
Figure 7 is an alternative embodiment of the locking segment useful in a
gasket of the current invention.
Figure 8 is a cross-sectional view of a gasket for use in the current
invention,
showing an alternate embodiment of the locking segment in place.
DETAILED DESCRIPTION OF THE INVENTION
The following is a detailed description of the invention. Those skilled in the
art will understand that the specificity provided herein is intended for
illustrative purposes
with respect to the inventor's most preferred embodiment, and is not to be
interpreted as
limiting the scope of the invention. References to "pipe" herein shall be
understood equally
to refer to any pipe length, appurtenance, fitting, or any other connected
device or element
regardless of the method or material of manufacture.
Turning now to the drawings, Figure 1 presents a diagram of a typical
mechanical joint. Assembly of the joint according to the current invention is
practiced as
known in the art. Particularly, but without limitation of the known variants
which shall be as
equally applicable to the present invention as they are to the known art, the
joint contains the
following elements in the following relationship. Compression ring or gland 11
is placed on
spigot 10, following which gasket 2 is placed around the exterior of spigot
10. Spigot 10 is
then advanced within bell 12 until the end 41 of spigot 10 is stopped by an
annular shoulder
42 within bell 12. Gasket 2 is advanced into bell 12 until it seats in the
annular recess seat
43, as shown. Gland 11 is then abutted against gasket 2 and is secured to bell
12 by
securing devices 44, which are presented for illustration here as bolts 45
passing through
perforations 46 and engaged by nuts 47. As is evident, upon drawing up or
tightening of
nuts 47, gland 11 is compressed against gasket 2, causing it to compress.
Alternative
securing means will be apparent to those in the industry, such as overcenter
clamps, cam
locks, ramped wedges, ramped annular rings, and rivets, and could include any
mechanism
that may be used to decrease the axial spacing between the gland 11 and the
bell 12.
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Due to the constraining presence of recess seat 43 and gland 11, deforming of
gasket 2 may
be directed primarily radially inward toward and into sealing engagement with
spigot 10.
The invention of the present disclosure builds upon this interrelationship and
requires no
changes to the spigot, bell, or gland, though such changes may be accommodated
within the
spirit of the invention if such modifications are otherwise desired.
As will be known in the art, traditional understanding counsels that the
profile
of the gasket 2 in a resting state substantially match with the internal
profile of the bell 12 at
the location in which the gasket 2 is intended to reside in final assembly.
The purpose of
such matching profiles is to allow for tight mating of the gasket 2 into the
bell 12 to enhance
fluid seal. In the shown embodiment, this conventional wisdom would counsel
for the
radially outward profile of the gasket 2 to have approximately the same
configuration as
recess seat 43 of bell 12. As shown in Figure 1, in a resting state the
primary mating
surfaces of a prior art gasket would mate smoothly with the internal surfaces
of the bell 12.
Accordingly, in prior art gaskets, following assembly the profile of the
gasket at these areas
of sealing interface is substantially the same as the profile of the gasket in
the resting state.
As is depicted in Figures 2 and 8, the locking segment 1 of the present
invention may be constructed to fit within a gasket 2 that is configured to
fit within any
standard mechanical joint without necessitating changes to the configuration
of the bell,
gland, or spigot. Gasket 2 is an elastomeric or other resilient or deformable
material, such as
those in the art will understand may be used in the practice of a mechanical
joint. A useful
configuration of the gasket 2, as shown in Figure 3, is an annular ring with a
radially inner
surface 4 that is adapted to be in contact with spigot 10, a gland face 7 that
is adapted to be
compressed by a gland or compression ring 11, a front face 61 that leads in
axial insertion,
and a radially outer surface, shown in the drawings as having a configuration
that does not
mate smoothly with the recess seat 43 in a resting state. Particularly, in the
shown
embodiment, the radially outer surface of the gasket 2 has a compression seat
surface 9 at the
leading portion of the gasket 2 near the front face 61 that is designed to
mate with and seal
against an area of the recess seat 43. Also characterizing the shown
embodiment is a
distortion control surface 62 that in the resting state leads away from the
recess seat 43 to
form a radially depressed gutter 63, before the profile of the gasket 2
extends once again
radially outward to meet the bell 12 in the area of rear seal 64. Although
these surfaces are
readily distinguishable in the drawings and as discussed herein, though the
transition among
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surfaces may not be as readily apparent in the uncompressed state as in the
configuration
shown. In the shown embodiments, gasket 2 conforms to all of the requirements
of
ANSI/AWWA C111/A21.11-95. In particular, for any given spigot 10, gasket 2
tends to
have a slightly smaller inner diameter than the outer diameter of the spigot
10. Accordingly,
placement of gasket 2 over the exterior of spigot 10 typically will require
exertion of force to
expand gasket 2 to fit around spigot 10.
Alternatively described, it will be noted that the gutter 63, being an annular
depression (radially speaking) is characterized by the fact that if gasket 2
is advanced into
the bell 12 as fully as is possible in the resting state (e.g., prior to
deformation), and rotated
to contact the bell 12 in the area of the recess-seat 43 as much as possible
without
deformation, a void remains between the gasket 2 and the recess seat 43; such
depression or
void is the gutter 63. As shown Figures 2 and 4, in this embodiment a portion
of the gutter
63 remains vacant of gasket material, even during some advanced stages of
compression and
assembly. It will be noted that the gutter 63 in other embodiments could be
covered by a
film of rubber or otherwise be a void below the radially outward surface of
gasket 2, and still
be and operate as a gutter 63 in the spirit and scope of the invention.
Without limiting the application of the structure, effects, or scope of the
invention or other possible advantages of practice of the invention, the
operational aspects of
having this void are believed in the shown embodiment to confer at least two
advantages,
either of which alone would be an advance in the art. it should be noted that
applicant does
not limit the invention by this discussion to only embodiments that possess
one or more of
these advantages. First, the compression of compression seat surface 9, and
separately of
distortion control surface 62, against recess seat 43 in different locations
is believed to create
two separate areas of sealing, with gradients of compression between the
points of initial
contact with the recess-seat 43, such that sealing efficiency is enhanced.
Also, rear seal 64
in compressive contact with gasket land 49 may create yet another area of
sealing. This
appears to create maximum pressure against at least one point in the area of
the gasket 2,
which serves to resist high fluid escape pressures, while still taking
advantage of the
fiexi,_r_iity and other advantages of high surface-area, lower-pressure
sealing.
A second perceived benefit is an operational effect on the motion of the
segment 1, which is described in more detail, below.
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Gasket 2 incorporates at least one locking segment 1, which may be
configured as shown in Figure 5, also shown as embedded in the gasket 2 in
Figure 8. In the
usual practice of the invention, a number of locking segments 1 will be
circumferentially
dispersed about and within gasket 2, and though preferable, the placement need
not be
precisely or even nearly symmetrical. The number of such segments 1 may be
selected with
reference to the expected separative forces to be encountered by the joint,
with a higher force
tending to recommend a larger number of segments 1. The inventor prefers to
use no fewer
than three such segments 1, but the invention is not so limited. For example,
a preferred
configuration of segments 1 for use with a pipe of eight inch diameter
intended to carry
fluids at pressures of 350 p.s.i. includes eight to ten segments 1 uniformly
spaced around the
spigot-facing circumference of gasket 2 (e.g., the radially inner surface 4).
An alternative
would allow a single segment 1 of a circumference appreciable to (at least one-
half the size
of) the circumference of gasket 2.
Separative forces (shown diagramatically as vectors 50, 50a and 50b in
Figure 1) tend to extract spigot 10 from bell 12. As indicated by directional
arrow 50, some
separative forces follow in-line with the common axis of assembled pipe
lengths. Other
separative forces are para-axial, as shown by vectors 50a and 50b, which may
be due to
bedding shifting or non-uniform securement around the periphery of spigot 10.
Segment 1
is intended to grip spigot 10 and to translate separative forces into forces
at least partially
opposing bell 12. To this end, segment 1 possesses teeth 6 that are adapted to
protrude from
inner surface 4 of gasket 2, at least upon compression of gasket 2 by gland
11. Teeth 6 are
adapted to contact spigot 10, and are most preferably fashioned of a substance
that is harder
than the material comprising the exterior of spigot 10. In a particular
embodiment, teeth 6
are, in the uncompressed state of gasket 2, already exposed from the inner
surface 4 as
shown by Figure 8. This exposure may be by protrusion from the inner surface
4, or by
slight recessing beneath inner surface 4 in combination with the absence of
gasket material
covering the teeth, which is the embodiment shown in Figure 3 and subsequent
images. As
shown in Figure 3 and 8, the gasket 2 may be configured with a recess about
teeth 6 to
prevent interference with penetration of such teeth 6 into spigot 10. An
alternative preferred
embodiment presents teeth 6 slightly recessed within gasket 2, and covered by
a membrane
or thin layer of compressible or puncturable material. The inventors suggest
that at least
some of the area between teeth 6 or immediately adjacent to teeth 6 be free of
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to allow penetration of the spigot 10. An advantage of initial concealment is
that it allows
for greater advancement of gland 11, and thus greater compression of gasket 2,
prior to
substantial engagement of teeth 6 into spigot 10. A greater sealing
effectiveness therefore
may be achieved.
Preferably, segment 1 possesses a plurality of teeth 6. In a tested
configuration, the tips of teeth 6 are arranged in an arcuate relationship.
The arcuate
relationship enhances the ability of teeth 6 to bite into spigot 10 despite
any variations in
circumference of spigot 10 or the inner dimensions of bell 12. This is because
a larger gap
(frequently due to manufacturing tolerances) between spigot 10 and the inner
dimensions of
bell 12 (particularly annular gasket recess seat 43) will cause segment 1 in
assembly to be
rotated upon compression of gasket 2 toward a steeper angle relative to spigot
10 than exists
in the unstressed configuration as displayed in Figure 2. Given the arcuate
relationship of
teeth 6, upon such rotation of segment 1 the most axially inner teeth rotate
into contact with
spigot 10. The arcuate configuration further urges at least two teeth 6 to be
in contact with
spigot 10, regardless of the rotation of segment 1. This is because in the
arcuate
configuration, a straight line can be drawn between any two adjacent teeth 6.
Beneficially,
the presence of additional teeth 6 to either side of any biting tooth 6 tends
to assist in
preventing overpenetration of the spigot 10 by segment 1, due to the fact that
these adjacent
teeth will be pointed at an angle to spigot 10 such that they are not
optimally positioned for
biting; rather, adjacent teeth 6 will tend to contact spigot 10 at an angle
substantially more
parallel to spigot 10 than those teeth 6 that are biting into spigot 10.
Accordingly, because of
the more-parallel angle, adjacent teeth 6 act as stops to further penetration.
In a shown configuration as detailed in Figure 5, segment 1 in cross section
has a toothed edge 16, with teeth 6 extending therefrom in the arcuate pattern
as above
discussed; and a back face 13, extending radially and axially along a slope
towards
protrusion 17. Back face 13 as shown is adapted to be in a close proximity to,
or even in
direct contact with, gland 11 when the mechanical joint is assembled.
Connecting protrusion
17 in the axially inner direction with toothed edge 16, is a surface, or a
series of surfaces,
denoted compression faces 15. In this embodiment, back face 13 is in close
proximity to
gland 11 when the joint is assembled, and upper protrusion 17, being the most
radially outer
area of the segment, is in close proximity to gasket land 49 of the bell. A
greater volume of
elastomeric material of gasket 2 exists between compression seat surface 9
(particularly
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shoulder 8) and segment 1 than is present between back face 13 and gland 11.
Upon insertion of spigot 10 into gasket 2, toothed edge 16 of segment 1 may
be forced radially outwardly by the presence of spigot 10, and may cause
pivoting of
segment 1. The volume of compressible material present between the segment's
compression faces 15 and recess seat 43 allows for such outward movement or
pivoting
without compromising the integrity of gasket 2. Given the arcuate
configuration of teeth 6
along toothed edge 16, even when rotated radially outwardly, at least one
tooth 6 will be
poised for contact with spigot 10 upon compression (though the inventor
recognizes within
the spirit of the invention that any or all of teeth 6 may be removed from
direct physical
contact with spigot 10 due to teeth 6 of segment 1 being recessed in gasket 2
or the presence
of a thin layer of elastomeric material, or other substance, so long as the
material, or
substance is not sufficient to interfere with the effective grip of at least
one of teeth 6 into
spigot 10 upon full compression of gasket 2, as is described below). Spigot 10
may be
advanced as in the prior art until stopped by annular shoulder 42.
Following such insertion of spigot 10 into bell 12, gasket 2 will be in a
position basically as represented in Figure 2, and the gasket 2 may be already
in contact with
recess-seat 43 at some point. In any event, substantial compression of gasket
2, as in
compression sufficient to effect the sealing and securement of the joint is
not at this point
effected. Further assembly is carried out by advancing of gland lip 71 against
the gasket 2
gland face 7, and into the bell 12. As will be evident to those skilled in the
art, this advance
of gland 11 will by contact with gasket 2 force gasket 2 inwardly into contact
or more
forceful contact with recess seat 43. As shown from Figure 4, gasket 2, and in
the shown
embodiment specifically compression seat surface 9, begins deformation against
recess-seat
43. Deformation of gasket 2, particularly in the area of distortion control
surface 62, begins
to occur in the shown embodiment prior to substantial rotation of segment 1.
This phase of
the assembly operation is considered the initial phase and is characterized by
substantially
translational motion of the segment. The forces acting on the segment are
principally
balanced between gland 11 acting on the back face 13 of segment 1 and the
compression
energy stored in the gasket rubber trapped between segment 1, spigot 10 and
bell 12. This
compression energy acts on segment 1 at a location known as the "center of
pressure" that is
believed in the shown embodiments to be substantially in line with the force
vector imparted
by gland 11 acting on segment 1.
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As gland 11 continues to advance into bell 12 beyond the point shown in
Figure 4, segment 1 begins to rotate. This phase of the assembly operation is
the transitional
phase and is characterized by a relatively decreasing amount of translational
motion of
segment 1 and a relatively increasing amount of rotational motion of segment
1. In other
words, upper protrusion 17 advances into the bell at a faster rate than teeth
6 for a given
input by gland 11. This occurs because the center of pressure of the
compression energy
stored in the gasket moves closer to the teeth 6 of segment 1 and away from
upper protrusion
17 as the gasket is compressed. Rotation of segment 1 at this point is
influenced by the
gutter 63 and is related to the movement of the center of pressure of the
gasket toward teeth
6. Because gutter 63 presents the area of least resistance to compression, and
hence to
deformation (it being known in the art that rubber tends to deform, but not to
compress), the
upper (as seen in the Figures) portion of the segment 1 rotates toward the
gutter 63, reducing
the size of the gutter 63 as the gasket material deforms into the area.
Rotation of segment 1 continues substantially in this manner as the gland 11
advances until the point at which segment 1 is in resistive contact with both
spigot 10 and
bell 12. This phase of the assembly operation shall be known as the final
phase and in the
shown embodiment is characterized by a substantially rotational motion of
segment 1 and a
substantial collapse of gutter 63. This segment and gasket orientation is
depicted by Figure
6. The resistive contact in the shown embodiment is specifically between a
tooth 6 and
protrusion 17 of segment 1 and the corresponding joint surfaces of spigot 10
and bell 12.
Until the final phase of assembly is entered, if a tooth 6 is in resistive
contact with spigot 10,
or protrusion 17 is in resistive contact with bell 12 it will be understood
that this contact is of
a sliding nature. Upon the substantial collapse of gutter 63 and the start of
the final phase of
assembly, further gasket deformation is extremely limited which effectively
prevents further
translation of segment 1 further in the axial direction. Any additional
clamping force applied
to the securing mechanism between gland 11 and bell 12 (e.g. the bolts 44)
imparts a large
rotational energy to the segment due to the imbalance between the force vector
created by
contact of gland 11 and segment 1 vs. the vector between the center of
pressure of gasket 2
and segment 1. Any further rotation of segment 1 now causes a penetration of
segment 1
into spigot 10 by teeth 6 and a penetration of segment 1 into bell 12 by
protrusion 17 via
plastic deformation of spigot 10 and bell 12. This penetration provides a
mechanical lock
between spigot 10 and bell 12 via segment 1 and thus joint restraint is
obtained.
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Following installation, it will be evident from the foregoing description that
at
least one tooth 6 remains in gripping contact with spigot 10 and protrusion 17
remains in
contact with bell 12. Any attempt of the spigot 10 to move outwardly of bell
12 urges at
least this one tooth 6 to move axially outwardly of bell 12 along with spigot
10, but axial
movement is not possible due to the resistive contact between back face 13 and
lip 71 of the
gland and a rotation of the locking segment in a direction that exerts axial
resistance as well
as radial pressure among the segment 1, the bell 12, and the spigot 10. This
axial resistance,
or restraint, is caused by the segment rotating into a direction in which its
length is greater
than the distance between the spigot 10 and the bell 12. The balance between
the axial load
and the radial load imparted to the bell and spigot affects the performance of
the invention
and may be influenced by the configuration of segment 1. As the forces trying
to separate
bell 12 and spigot 10 increase so does the axial resistance imparted to bell
12 and spigot 10
by segment 1. The radial load also imparted keeps teeth 6 and protrusion 17 of
segment 1
engaged with spigot 10 and bell 12 respectively. If the radial component is
too low, then the
segment 1 will disengage spigot 10 or bell 12. If the radial component is too
high, then
excessive deformation or penetration of spigot 10 by segment 1 may occur.
The inventors note that this feature, like others shown in the embodiments,
may exhibit particular advantages, but that the presence or absence of these
features and
advantages required of the scope of the invention only as limited in each
particular claim.
Except to the extent expressly included in a claim, the inventors do not
consider these
advantages, configurations, or possibilities to be limitations on the
invention.
Manufacturing tolerances for spigots and bells are not precise; accordingly,
in
some installations, the distance between spigot 10 and bell 12, including
features of bell 12
such as recess seat 43, will be greater or less than such distance in other
installations. Under
the above described embodiment of segment 1, where the gap between spigot 10
and recess
seat 43 is as intended or smaller, upon securement of gland 11 at least on of
teeth 6 of
segment 1 is driven into spigot 10 and and upper protrusion 17 is driven into
bell 12. The
inventor believes that due to the supportive pressures of the gasket material,
segment 1 does
not begin biting engagement with spigot 10 until a generally effective seal
among bell 12,
spigot 10 and gasket 2 has been effected by compression. Accordingly, teeth 6
are unable
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to prematurely engage spigot 10 in a manner that may adversely affect the
ability to obtain
optimal compression of gasket 2. This delayed engagement can be manipulated by
the
means discussed above; namely, the configuration of the gasket, notably the
gutter 63,
compression seat surface 9, distortion control surface 62, elastomeric
characteristics of the
gasket 2, shape of segment 1, position of segment 1 in gasket 2 or various
combinations of
these features. Due to contact with bell 12 in addition to gland 11,
separative forces are
transferred by segment 1, not just against gland 11 but also against bell 12.
This is
significant in that it reduces a potentially substantial force that is
resisted by bolts 45 and
gland 11. Under high loads, bolts 44 and gland 11 may distort, reducing
sealing
effectiveness of gasket 2; the current invention's ability to transfer a
significant portion of
the magnitude of the separative vector directly to bell 12 via segment 1
therefore enhances
the effectiveness of sealing.
In contrast to situations as in the previous paragraph, in which the distance
between spigot 10 and gasket recess seat 43 is relatively small, an
exaggerated pivoting
mechanism is believed to occur in segment 1 when the gap is larger, as
follows:
The condition that exists in a large gap situation (e.g. when the
manufacturing
tolerances and assembly conditions exist such that bell 12 dimensions are at a
maximum
diameter condition and spigot 10 dimensions are at a minimum diameter
condition) is such
that upon initial assembly, neither gasket 2 or segment 1 may be in contact
with either one or
both spigot 10 or bell 12. During the transition phase gasket deformation will
occur, as
previously described, due to compressive forces acting on gasket 2 by spigot
10, gland 11
and bell 12 forcing gasket 2 into contact with both spigot 10 and bell 12. At
this point
however, segment 1 may still not be in contact with either spigot 10 or bell
12. Approaching
the end of the transitional phase of assembly, as gutter 63 of gasket 2 closes
up due to elastic
deformation of gasket 2 caused by compression of gasket 2, a dramatic rotation
of segment 1
will occur due to the previously described shift in the center of pressure of
the compressed
gasket and its relationship to segment 1. This dramatic rotation allows
segment 1 to bridge
large gaps for which restraint would otherwise be impossible to provide. The
final phase of
assembly then proceeds as previously described with teeth 6 embedding in
spigot 10 and
protrusion 17 embedding in bell 12.
In an embodiment of segment 1, upper protrusion 17 may be formed in an
angular configuration. Such an angular configuration will cause such points to
bite into
CA 02536500 2006-01-24
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bell 12 when sufficient pressure is exerted between segment 1 and bell 12.
Although such
biting can occur in any event under appropriately high pressures, particularly
in the small-
gap situation addressed above, the propensity to bite can be controlled by
adjusting the
acuteness of the angle. The inventor notes that the more acute the angle at
either given
point, the earlier along a pressure curve the point will likely bite into bell
12. Accordingly, it
is possible to adjust the tendency toward desired points of final rotation of
segment 1 by
adjusting the acuteness of angle of the upper protrusion 17, which will in
turn adjust the
maximum probable radially outward movement of upper protrusion 17. It should
be noted
that at pressures sufficient to drive upper protrusion 17 into bell 12,
rotation of segment 1
will be substantially prevented and will occur under conditions of plastic
deformation of
either segment 1, spigot 10 or bell 12. This mechanism can be employed to
balance the
rotation of segment 1-and control the point of engagement.
Similarly, if upper protrusion 17 is configured in a radiused fashion,
movement of segment 1 may be adjusted to allow axial movement of segment 1
until upper
protrusion 17 obtains non-compressible abutment with bell 12, at which point
the axial and
radial forces acting on segment 1 at upper protrusion 17 cause the pivot point
to occur in its
near vicinity. Variations of this allow further control of segment engagement
and the balance
of axial and radial loading distributed to all load carrying components of the
invention.
An alternative embodiment, as shown in Figure 7, may be to incorporate an
elbow 3 into the back face of segment 1. Elbow 3 will contact gland 11 during
securement
of the restraining devices 44 in the initial stages of the transitional
assembly phase. The
location and configuration of elbow 3 may be tailored to further alter the
behavior of
segment 1 during rotation, engagement and lockup. The location and
configuration of elbow
3 may be further explained by addressing several characteristics of elbow 3
which may be
modified to alter segment behavior. If elbow 3 is given a sharp radius, elbow
3 may be
made to penetrate gland 11 at the contact point. This penetration will impart
additional
resistance to further rotation of segment 1 when the final assembly phase is
complete thus
relieving some of the reliance on the angle of the line of action segment 1
makes relative to
spigot 10 and bell 12 when balancing the segments axial and radial load
carrying
distribution. Additionally, elbow 3 may be positioned radially outward or
inward on
segment 1. Placing elbow 3 radially outward on the segment will increase the
rotational
tendency of the segment during the transitional phase of assembly promoting
earlier
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engaement and lockup of segment 1. Placing elbow 3 radially inward on segment
1 will
have a correspondingly opposite effect.
If elbow 3 is made such that it penetrates gland 11 while at the same time
upper protrusion 17 penetrates into bell 12, a situation may be created
whereas both axial
and radial loads transferred into bell 12 may be balanced along multiple load
paths.
Building upon the concept of altering the acuteness of elbow 3 and upper
protrusion 17, the transition between such points may be less pronounced than
in Figure 2.
In fact, the transition may be so smooth as to create a general curve that
acts as both elbow 3
and upper protrusion 17. A curve could be adapted to effect biting engagement,
whether by
altering the radius of curvature, or by including nubs or other points to
operate as
engagement points (which, for purposes of this invention could be considered
to be elbow 3
or upper protrusion 17).
Further alternative embodiments that may be included with the foregoing or
otherwise substituted for gutter 63 or the area around gutter 63 include the
strategic
positioning of a secondary or tertiary elastomeric material having different
deformation
characteristics than the remainder of gasket 2. Such strategic positioning may
optimally
include placement between frontal slope 15 of segment 1 in the vicinity of
upper protrusion
17. This placement would influence the potential of upper protrusion 17 to
move toward
annular recess seat 43, thereby causing upper protrusion 17 to cease
substantial rotation prior
to biting into bell 12. Similarly, such secondary or tertiary rubber may be
placed radially
outwardly of elbow 3 to influence the maximum ability of elbow 3 to move
radially
outwardly of spigot 10.
Although much of the foregoing is discussed in terms of initial installation
of
a mechanical joint, the inventor notes the value and applicability of use of
the present
invention to "retrofit" or repair existing mechanical joints. By simply
rejoinably severing
the ring of gasket 2 (preferably at an angle to the radius) the gasket 2 can
be fit over an
existing spigot, and moved into place after removal of the old gasket. The
gland 11 can then
be re-attached, completing retrofitting of a standard mechanical joint to a
gasket-restrained
mechanical joint.
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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 so
that they may use their standard skill in the art to make these embodiments or
other and
variable embodiments of the claimed invention, 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 issued.
Unless otherwise
specifically stated, applicant does not by consistent use of any term in the
detailed
description in connection with an illustrative embodiment intend to limit the
meaning of that
term to a particular meaning more narrow than that understood for the term
generally.
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