Note: Descriptions are shown in the official language in which they were submitted.
3 0 -2-
In recent years, succes~ful methods have been
developed for drilling oil and gas wells at underwater
locations. A~ a result, an oil or gas well may be drilled
and completed 90 that the entire wellhead assembly i~ posi-
tioned at a depth at least sufficient to avoid being anavigation hazard to ocean-going vessels (e.g., at or near the
ocean floor). Such orfshore or underwater wells may be dri~d
from a vessel, such as a drilling barge, or from a platform
mounted on legs extending downwardly to the ocean floor.
A drilling barge or similar ~essel i9 particularly
susceptible to movements in response to wave action, even
though the barge is anchored. Drilling that ls done from a
floating vessel must accommodate both lateral and vertical
movements of the ve~sel. Accordingly, drilling equipment
such as drilling strings and riser lines, which extend down-
wardly from the drilling ves~el to the ocean floor, must
possess a degree of flexibility sufficient to prevent rupture
when the drilling ve~sel moves slightly from its designated
location. Typically, the pipe in a drilling string i9 of a
su~ficiently small diameter and has su~ficient strength to
be flexlble enough to avoid damage. The riser line or
marine conductor pipe, on the other hand, has a relatively
large diameter and encloses the drilling string 80 that
drilling ~mud" may be returned upwardly in the annulus
between the inner wall of the riser pipe and the outer wall
of the drill string. The increased diameter and rigidlty o~
the riser pipe, as compared to the drill string, requires
that the rise pipe include at least one coupling or ~oint
assembly that can be readily flexed, can withstand high
internal and external fluid pressures, and can hold up
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under the ~brasive action Or fluids, well tool~ and other
objects that pass through the ri~er pipe.
One type of flexible ~oint used in ri~er pipes
consists of a ball member having a precisely machined spherical
surface and a socket member ha~ing a complementary, precisely
machined 3pherical surface. The ~oint is flexed by sliding
one o~ the spherical surfaces relative to the other. Resilient
O-rings help ~eal the Joint at the interface between the slid-
ing sur~aces. The flexural movement of such a ball joint i9
impaired, however, when the Joint is ~ub~ected to high pres-
sures. The ~oint is al90 subJect to ~rictional wear and
deterioration o~ both the slidine surfaces and the O-ring
seals, which requires frequent repair or replacement of the
~oint.
Another type of flexible joint for fluid conduit~,
such as marine riser pipes, utilizes annular flexible ele-
ments disposea between flanges secured to adJaoent ends of
different ~ections of condu~t. The ~lexible elements ¢omprise
alternating layers of a rigid and a resilient material, uhich
are normally metal and an elastomer. The layers or lamina-
tions may be annular with ~lat surfaces~ as in the pipe Joint
of Johnson U. S. Patent No. 3J168,334, or annular with
spherical sur~aoes~ as in the flexlble Joint of Herbert et al
~. 8, Patent No. 3~680,895, Laminated ~lexlble elements permit
the necessary ~lexural movement of a Joint and also funotion
as seals. A Joint ln¢orporating a laminated element has no
~moYing" parts and is not ~ub~ect to the fri¢tionQl ~ear
encountered with the ball-and-socket Joints discussed above.
Other flexible pipe ~oints utilizing lamin~ted flexlble
elements ar~ described and illustrated in Herbert et al
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U. S. Patents Nos. 3,390,899, 3,734,546 and 3,853f337.
While joint3 utilizing laminated flexible elements
avoid the wear problem of convention ball-and-socket ~oint~,
the laminated elements have a tendency to rupture and fail
upon exposure to high axial loads and high pressure different-
ial~. In particular, the elastomer layers Or lamlnated
elements, while capabl~ of carrying high compres~ive loads,
can only with~tand relatively low tension load3. Thus, when
two adjacent lengths of pipe are sub~ected to forces that
tend to move the lengths axially away from eaoh other, the
laminated fle~ible elements are likely to fail. E~forts to
901ve the problem of tension loads have included the u~e o~
tension bars to carry the tension load~ in pre~erence to the
laminated flexible elements. Palr~ o~ laminated ~lexible
elements may al90 be utilized in a ~oint such that at least
one of the ~lexible elements is always loaded in compre9sion,
regardless of the relative axial movement between ad~acent
lengths o~ pipe. Reducing or eliminating tenæile loads on a
laminsted ~lexible element also reduces the llkelihood o~
rupture due to high pressure differentials on the element.
Similarly, bondin~ ad~acent laminations into an integral
member lncreaRes the pressure-re3istance of the laminated
element.
The present inventlon i9 directed to a flexible
~oint for a fluid condult which provides an improved high-
pressure dynamic seal. According to the invention, the ~oint
comprises a pair o~ spaced rlgid rings, which are interposed
bet~een the ad~acent ends o~ two lengths of conduit. An
annular flexible element is diRposed between and sealingly
engsges the rings 80 as to define a pair of annular exposed
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side surraccs on the ~lexible element. One o~ the ~ide sur-
faces, preferably the radially innermost surface~ is to be
exposed to pressurized ~luid ~lowing through the conduit,
thereby creating a pressure difrerential across the flexible
element between its slde sur~aces. To resist the load that
results from the pressure di~rerential, the ~lexible element
incorporate~ a body of alastomer that has a thicknes~ between
the rlngs which decreases from the one side surrace of the
element to the other side surface. Because o~ lts tapering
thickness, the body of elastomer i8 dammed or held against
rupturing movement in response to the pressure o~ the rluid
in the conduit. The flexible element can thus resillently
accommodate relative motion between the rings, and hence the
lengths of conduit, while providing a fluid-tight~ pressure-
resi~tant seal between the rings.
In one embodiment of the invention, the flexibleelement also includes a plurality of spaced apart~ annular
shim of a sub~tantially inextensible material embedded in
the the body of elastomer. The shims improve the compresslon
load carrying capabilltles o~ the elastomer. To insure a
~dammlng~ action on the body of elastomer, the thickne~ses of
the shims are not included when the thickness of the body of
elastomer i9 determined. The thickness of each shim may be
con~tant or tapered. The shims may taper in thickness ~rom
the high pressure ~ide sur~ace of the ~lexible element to the
lo~ pressure side surface if the spacing between the rigid
rings tapers in a corresponding direction and to an extent
su~icient to compensate for the tapering shim thicknesses.
If the 3pacing between the rigid rings remains constant~ for
example~ the shims may be tapered in thickness from the low
104~Z30
pressure side of the flexible element to -the high pressure
side to provide the necessary "damming" effect. In a preferred
embodiment, each shim and the body of elastomer are annular in
one plane and arcuate in a perpendicular plane or planes. The
arcuate configurations of successive shims may be defined by
arcs of circles of increasing diameters so that each shim and
the body of elastomer is a spherically shaped annulus.
The joint of the present invention is normally
incorporated in a pipe joint assembly for flexibly connecting
together two lengths of pipe. One such assembly may include a
cylindrical housing having an annular body and an annular flange
at each end which extends radially inwardly of the housing body.
Each one of a pair of tubular members of smaller diameter than
the housing has a flange at one end extending radially outwardly.
The tubular members are received through opposite open ends of
the housing so that the flanges of the tubular members are
disposed between the flanges of the housing. The other ends
of the tubular members project from opposite open ends of the
housing. A pair of opposed sealing joints according to the
present invention are disposed between opposed flanges. Both
joints may be disposed between the flanges of the tubular
members or each joint may be disposed between the flange of a
different tubular member and the adjacent flange of the housing.
According to one broad aspect, the invention relates to
a pipe joint assembly for fluid conduits that receive fluid
under a pressure greater than an external ambient pressure on
the conduits, said assembly comprising a cylindrical housing
including an annular housing body and an annular flange at each
end extending radially inwardly of said housing body, and a
pair of tubular members of smaller diameter than said housing,
each tubular member including a flange at one end extending
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radially outwardly of` said member, said f1anges ol` the tut)ulclr
members being disposed between the f`langes of the housing
and the other ends of the tubular members projecting f`rom
opposite ends of the housing for attachment to fluid conduits,
the improvement of two annular joints disposed within the
housing, each joint comprising: (a) a pair of spaced rigid
rings, and (b) an annular flexible element disposed between
the rings and sealingly engaging op~(sed surfaces of the rio~C . .
so as to define a pair of annular exposed side suriaces of
said flexible element, the flexible element including a body
of elastomer which when measured substantially normal to at
least one of the opposed surfaces of the rings has a tapered
thickness between the rings that decreases from one side
surface to the other side surface of the flexible element,
the body of elastomer being closely confined in its tapered
: configuration along surfaces that extend from the one side
surface to the other side surface of the flexible element so
as to resist deflection of the elastomer from between the
rings in response to pressure exerted on the one side surface
of the flexible element, one ring of one joint being in load
and motion transmitting engagement with the flange of one
tubular member and being sealingly engaged with said one
tubular member, one ring of the other joint being in load
and motion transmitting engagement with the flange of the other
tubular member and being sealingly engaged with said other
tubular member, the other ring of each joint being sealing
engaged with a fluid-tight portion of the pipe joint assembly
such that the two joints together define at least part of a
fluid-tight passageway that interconnects the tubular members
to permit a flow of fluid between the tubular members, the
joints being oriented such that the one side surface of each
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flexible element is exposed to fluid in said passageway and to
pressure exerted by fluid in the passageway, the one side
surface being the only side surface of each flexible element
which is exposed to fluid in sagd passageway, each flexible
element resiently accommodating relative motion between the
rings that engage the element and providing a fluid-tight seal
that is particularly resistant to pressure exerted on the one
side surface of the element.
According to another aspect, the invention relates to
a pipe joint assembly for a conduit that receives fluid under
a pressure greater than an external ambient pressure on the
conduit, said assembly comprising a first annular member
including a radially extending flange, and a second annular
member spaced from and axially aligned with the first annular
member, the second annular member including a radially
extending flange that is spaced from and disposed in opposed
relation to the flange of the first annular member, the
improvement of an annular joint disposed between said flanges,
said joint being fluid-tight and comprising an annular flexible
20 element having a pair of annular exposed side surfaces and a
pair of annular and opposed end surfaces, the flexible element
including (a) a body of elastomer which when measured
substantially normal to at least one of the end surfaces of
the flexible element has a tapered thickness that decreases from
one side surface to the other side surface of the element, the
b~dy of elastomer being clo-sely confined in its tapered
configuration along surfaces that extend from the one side
surface to the other side surface of the flexible element so
as to resist deflection of the elastomer from between the
flanges in response to pressure exerted on the one side surface
of the flexible element, and (b) a plurality of spaced annular
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shims of a suhstantially inextensible material eml~edded in the
body of elastomer, the thickness of the body of elastomer being
exclusive of the thicknesses of the shims, the joint being in
load transmitting engagement with the flange of at least one
of the first and second annular members and the end surfaces of
the flexible element of the joint being sealingly engaged with
fluid-tight portions of the pipe joint assembly so that the
flexible element defines at least part of a fluid-tight passage-
way that interconnects the annular members to permit a flow of
fluid between the annular members, the joint being oriented
such that the one side surface of the flexible element is
exposed to fluid in the passageway and to pressure exerted by
fluid in the passageway, the one side surface being the only
side surface of the flexible element which is exposed to fluid
in the passageway, the flexible element resiliently
accommodating relative motion between the annular members and
providing a fluid-tight seal that is particularly resistant to
pressure exerted on the one side surface of the flexible
element.
According to a further aspect, the invention relates
to a flexible joint for a conduit that receives fluid under a
pressure greater than an external ambient pressure on the
conduit, said joint comprising a pair of spaced rigid rings,
and an annular flexible element disposed between the rings and
sealingly engaging opposed surfaces of the rings so as to define
a pair of annular exposed side surfaces of said flexible
element, the flexible element including a body of elastomer
which when measured substantially normal to at least one of the
opposed surfaces of the rings has a tapered thickness between
the rings that decreases from the radially innermost one of the
side surfaces to the other side surface of the flexible element,
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~040230
the body of elastomer being closely confined in its tapered
configuration along surfaces that extend from the one side
surface to the other side surface of the flexible element so
as to resist deflection of the elastomer from between the
rings in response to pressure exerted on the one side surface
of the flexible element, the flexible element resiliently
accommodating relative motion between the rings that engage
the element and providing a fluid-tight seal that is
particularly resistant to pressure exerted on the one side
surface of the element.
Yet another aspect of the invention relates to a
flexible joint for a conduit that receives fluid under a
pressure greater than an external ambient pressure on the
conduit, said joint being fluid-tight and comprising an
annular flexible element having a pair of annular exposed side
surfaces and a pair of annular and opposed end surfaces,
the flexible element including (a) a body of elastomer which
when measured substantially normal to at least one of the end
surfaces of the flexible element has a tapered thickness
that decreases from the radially innermost one of the
side surfaces to the other side surface of the flexible element,
and (b) a plurality of spaced annular shims of a substantially
inextensible material embedded in the body of elastomer, the
thickness of the body of elastomer being exclusive of the
thicknesses of the shims, the joint resiliently accommodating
relative motion between adjacent sections of conduit and
providing, when sealingly engaged with said adjacent conduit :
sections, a fluid-tight seal that is particularly resistant
to pressure exerted on the one side surface of the flexible
element.
For a better understanding of the invention, reference
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1040230
may be made to the following description of an exemplary
embodiment, taken in conjunction with the figures of the
accompanying drawings, in which:
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~igure 1 is a diagrammatical view of a drilling
barge at an ofrshore location positioned above a wellhead
a~sembly on the ocean ~loor;
Figure 2 is a longitudinal view, partly in cross
section, o~ one pipe joint assembly illustrated in Figure 1
and incorporating the joint of the present invention;
Figure 3 i9 a fragmentary view, on an enlarged scale,
o~ the joint illustrated in Figure 2; and
Figure 4 is a view corresponding to ~igure 3 but
illustrating an alternate embodiment of the ~oint of the
present invention.
Figure 1 of the drawings illustrates a drilling barge
10 floating on the surfaoe 12 of a body of salt water 1~.
Belo~ the barge 10, an underwater wellhead a~sembly 16 i8
positioned on the ocean floor 18. The lower end of a large
diameter marine riser pipe 20 is secured to the wellhead
assembly 16 by a wellhead connector ?2. Ths upper end of the
marine riser pipe 20 is se¢ured to the barge 10 in any conven-
tional manner~ 3uoh as by cables 24. The cables 24 position
the top of the marine rlser pipe 20 more or less centrally in
a drilllng slot 26 that extends throush the barge 10. During
drilling operations, a strlng of drilling pipe 32 passes
through a rotary table 34 on the drilllng barge 10 and extends
throughout the lengt.h o~ the riser pipe 20 into the well.
Although the riser pipe 20 i8 depicted as a continuou9
plpe or tubular member in Flgure 1, the pipe i9 normall~ made
up of a multipliclty o~ relatively short tubular seotlons
secured together ln any conventional manner. ~ositloned in
the riser 20, adJaoent each of its ends, are flexible pipe
~olnt assemblies 28 and 30. Joint assembl~es 28 and 30
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accommodate the ma~or lateral movements o~ the riser pipe 20
due to movements of the barge 10, ~or example. Inasmuch as
the ~lexible pipe ~oint assemblies 28 and 30 are essentially
identical in construction, they will be described in detail
with re~erence only to the joint 30, a~ ~hown in Figure 2.
The pipe joint assembly 30 has a cylindrical outer
housing 36 that compri~es an open-ended tubular or annular
body 38 and a pair of annular flange members 40a and 40b.
The flange members 40a and 40b are positioned at opposite ends
of the body 38 and are releasably secured to the body by lug
bolts 42, ~or example. When mounted on the body 38, the ~lange
members 40a and 40b extend radially inwardly from the body.
Ad~acent the flange 40a o~ the hou~ing 36 19 a tubular
member 44a that extends through the central opening in the
rlange 40a. A flange 46a is ~ormed at the end o~ the tubular
member 44a which i8 inside the housing 36. The ~lange 46a
extends radially outwardly of the tubular member 44a and over-
laps the M ange 40a of the housing 36. The overlapping or
inter~ering relationship of the flanges 40a and 46a requires
the flange 40a to be separable from the body 38 of the housing
36 to permit assembly o~ the tubular member 44a within the
housing. An identical tubular member 44b that has a ~lange
46b is dlsposed ad~acent the other end o~ the housing 36 in a
corresponding overlapping relationship with the flange 40b.
Annular replaceable wear bushing 43a~ 43b, 45a, 45b, 47a and
47b oover the interior circum~erence o~ each Or the tubular
members 44. The bushings 43~ 45 and 47 protect the tubular
members 44 against the abrasive action o~ well tools passing
through the Joint assembly 30 and drilling mud flowing through
the assembly outside the drilling pipe 32.
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_9_
Between the ~langes 40a and 46a and bGtween the
~langes 40b ~nd 46b are annular laminated bearings 48a and 48b,
respectively. Each of the bearings 48 includes two relatively
massive, annular end plates 50 and 52 and an intermediate
flexible element 54. The end plates 50 and 52 are received on
appropriately con~igured sur~aces of the flange~ 40 and 46,
respectively. The interfaces between the plates 50 and 52
and the flanges 40 and 46 are not sealed. The ~lexible element
54 is bonded to the end plates 50 and 52 and incorporate~ a
plurality of alternating layers of elastomeric material and a
material that is substantially inextensible or nonextensible
compared to the elastomeric material. The inextensible layers
are preferably ~ormed o~ steel, while the elastomeric layers
are preferably formed of natural rubber. Other inexten~ible
and elastomeric materials may be substituted for the steel and
rubber where appropriate. Alternate elastomeria materials
include synthetic rubber, while alternate inextensible mater-
ials include other metals, ~iberglass, and reinforced plastics.
The layers o~ eaah flexible element 54 and the adjaoent sur-
faces o~ the assoaiated end plates 50 and 52 have circular
conrigurations in longitudinal section. The over-all
spherical shapes o~ the bearlngs 48a and b permit the bearings
to ~unction QS universal ~oints with the relative motion be-
t~reen ad~acent relatively rigid components (i.e., the in-
extensible layers and the end plates) being accommodated by
~lexing or shearlng o~ the elastomer layers.
Interposed between the flanges 46a and 46b o~ the
tubular members 44 are a pair o~ flexible ~oints ~;6a and b.
Eaah of the ~oints 56a and b includes two relatively massive,
rigid rings 58 and 60 and an annular flexible element 62
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~S~40230
located between the ring~. The ~lexible element 62, which
includes elastomer, ls relatively so~t or more flexible
compared to the flexible elements 54 of the bearings 48. ~he
difference in ~lexibility or stirfness may be achieved b~
utilizing a "sorter" elastomer or by constructing the flexible
element 62 to have a lower shape factor than the flegible
elements 54, for example. The element 62 is bonded to each
o~ the rings 58 and 60 so as to define on the ~lexible element
a pair of annular side surraces 64 and 66 which are exposed
or ~ree. As in the bearings 48a and b, the ~lexible elements
62a and b and the ad~acent surfaces of the end rings 58a and
b have circular shapes in longitudinal section. The ~oints
56a and b may thus functlon as universal joints, like the
bearing~ 48a and b.
The end rings 58a and b Or the ~oints 56a and b are
carrled on and engage sur~aces o~ the flanges 46a and b appro-
priately configured to prevent radial shi~ting Or the rings.
Grooves 63a and b formed in the ad~acent surfaces of the
flanges 46a and b reoeive resilient 0-rings 65a and b (See
also Figure 3) to seal the interfaces between the ~langes and
the rlngs 58. End rings 60a and 60b engage each other and
rit together. Axially extendlng, annular flanges 68a and 68b
on the rings 60a and b overlap in an axial direction to prevent
relative radial move~ent between the rings. As best sho~n in
Figure 3, grooves 67a and 67b are ~ormed in the rings 60a and
b to accept resilient 0-rings 69a and b, which seal the inter-
~ace between the rings 60. None o~ the rings 58a, 58b, 60a
or 60b is secured to the ad~acent metal sur~ace that the ring
contacts. The seallng action o~ the 0-rings 65a and b and
the 0-ring 69b is insured by constantly maintainlng a
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compression load on the Joints 56a and 56b, as will be
described herein.
When the various components of the joint assembly 30
are assembled as shown in Figure 2, the exposed end~ of the
tubular members 44a and 44b are connected to the ends o~
ad~acent lengths of riser pipe (not shown). The riser pipe
20, throughout its length, is normally malntained in tension.
This tension load, which is transmitted to the joint assembly
30, is carried by compression loading of the laminated elasto-
meric bearings 48a and 48b. The load is applied through theflanges 46a and b and is transmitted to the housing 36. Since
a compression load on the bearings 48a and b wlll result in
de~lection o~ the elastomer in the bearings, the flanges 46a
and b of the tubular member~ 44a and b wlll tend to move away
from each other and away from the ~olnts 56a and b. To prevent
such movement ~rom interrupting the seals at the inter~aces
between ~langes 46 and rings 58 and between rings 60a and 60b,
the internal oomponents of ~oint assembly 30 are prede~leoted
and thus preloaded~ on assembly, between the housing ~langes
40a and 40b. The assembly prede~lection or preload derlects
the Joints 56a and b in preferen¢e to the bearings 48a and b
due to the di~erence in the sti~nesses of the ~lexible
elements 54 and 62, Thus, when the tension load on the riser
pipe 20 is transmitted to the tubular members 44a and 44b and
the bearings 48a and 48b, the resulting de~lection of the
bearings i8 not su~ficient to relieve completely the
compres~ion load on the ~oints 56a and 56b. Consequently,
the 0-rings 65a, 65b and 69b are always loaded in compre99ion
to seal the lnter~aces between ~langes 46 and rings 58 and
between ring 60a and ring 60b The preload also pro~ides
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limited frictional engagement between adjacent metal surfaces
to prevent relative rotation between the flanges 46 and the
rings 58, for example.
The spherical configurations Or the joints 56a and
56b, together with the ~pherical configurations of the bearings
48a and 48b, permit angular misalignment~ between the lengths
of riser pipe 20 on either side of the joint assembly 30.
Angled relative orientations of the lengths of riser pipe 20
are accommodated by shearing of the elastomer in the elements
54a, 54b, 62a and 62b, as indicated above. The elastomer in
the ~lexible elements 54a, 54b, 62a and 62b will also shear to
accommodate rotational movements of the riser pipe sections
about their longitudinal axes, During their de~lections~ the
~lexible element3 62 maintain a rluid-tight ~eal against the
highly pressurized and abrasive drilling mud, ~or example,
that ~lows through the riser pipe 20 along the outside Or the
drilling pipe 32. (As noted above, the bearing~ 48 need not
provlde a fluid-tight seal against the sea water surrounding
the ~oint assembly 30.) The sealing action Or the ~oints 56a
and 56b is facilitated by thelr unique design, as discussed
ln detail below with parti¢ular reference to ~oint 56b.
A9 disoussed above and illustrated in Figure 2, the
radially inner side surfaoes 64 of the flexible elements 62
Or ~oints 56 are normally exposed to a highly pressurized
~luid, such as drilllng mud. The drilling mud is at a pre~-
sure substantially higher than the pressure o~ the fluid, such
as sea water, to which the opposite side ~urfaces 66 of the
flexible elements 62 are exposed. The pressure di~ferential
across the elements 62 tends to ~orce the elements radially
outwardly from between the rigid rings 58 and 60. To
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1~4(J~ 30 -i3-
counteract the ef~ects of the pressure differential~ the
flexible elements 62 comprise outwardly tapered bodies of
elastomer 70. As best shown in Figure 3 with regard to joint
56b, the body o~ elastomer 70b has a thickness (measured
5 substantially normal to the curved surfaces of rings 58b and
60b) which decrease3 from the high pressure side surface 64b
of the flexible element 62b to the low pressure side surface
66b of the element. The tapering thickness of the body of
elastomer 70b, which has been exaggerated for purpose~ of
lO illustration in Figure 3~ is achieved b~ tapering the spacing
between the ad~acent arcuate surfaces of the rigid rings 58b
and 60b. The taper effectively results in the elastomer being
'tdammed" or retained between the two rings 58b and 60b against
radially outward and upward rupturing movement. This positive
15 mechanical interlock provides a more effective high pressure
~eal than is ~ound in similar flexible ~oint~ that rely solely
on the strength of the bond between the body Or elastomer and
the ad~acent metal part9.
To increase the capacity of the joint 56b of Figure 3
20 to Y ithstand pressure differentials across the body of elasto-
mer 70b and/or to reduce the stress in the elastomer for a
given pressure differential~ metal shims 72 are embedded in
the elastomer 70b at spaced apart locstions between the rings
58b and 60b. The shims 72, which are substantially inexten-
25 sible compared to the elastomer 70b, are continuous annularmembers and have arcuate con~igurations in longitudinal
section. The arcuate lines of the shims 72 are pre~erably
circular arcs. Such a configuration best accommodates the
ball-and-socket type operation of the ~oint 56b and ls more
30 convenient to manu~acture than other curved shapes. The
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arcs may be taken from a single circle Or ~ixed diamete~, or
from different diameter circles such that the diameters of
successive shims increase ~rith increasing radial distance of
the particular shim from the nominal center of the joint. The
5 spacing between the individual shims 72 and between the endmost
shims and the adjacent surf`aces of the rings 58b and 60b
decreases from the high pressure side 64b of the flexible
element 62b to the low pr essure side 66b. With shims defined
by circular arcs, the tapering in the spacing is achieved by
10 axially displacing the center of the circle that defines the
arcuate shape of each shim ~rom the center of the circle de-
flning the arcuate configuration of the adJacent~ radially
inwardly locatad shim, While the damming effect in joint 56b
i8 provided by a decrease in the spacing between the end rings
15 58b and 60b, the tapering of the thickness of the elastomer
body 70b may be accomplished through other techniques. For
example, the thicknesses of the shims 72 r~y be tapered from
the low pressure side 66b of the flexible element 62b to the
high pressure side 64b without tapering the spacing between
20 the end rings 58b and 60b.
It should be noted that the use of tapered layers of
elastomer in a laminated elastomeric bearing is kno~m in the
art~ as illustrated by Figure 3 of Krotz U~ S. Patent No.
3~179,400 and by Figure 7 of Hinl{s U. S. Patent No. 3~071,422.
25 Neither patent, however, recognizes the construotion and use
o~ such an elastomeric bearing as a sealing pipe ~oint.
Figure 4 o~ the application illustrates an alternate
embodiment of the ~oints 56. In the embodiment of Figure 4
not only does the thickness of the body of elastomer 70bt
30 diminish from the high pressure side ~urface 64bt of the
-, . :~'
,, - - ., ~ .
~ 15-
flexible element 62b' to the low pressure surface 66b', but
the shims 72t similarly taper from the high pressure side to
the low pressure side of the fleYible element 62bt, The
tapering Or the sims 72l permits a reduction in the amount of
metal used in the flexible element 62bt, as compared to the
element 62b of Figure 3. The basis for tapering the shims
may best be understood by considering that the annular shims
72' are everwhere subjected to radiall~ directed forces which
place each shim 72' in what may be termed Ithoop tension". The
"hoop tension" i8 greatest at the edges of the shims 72'
adjacent the high pre~sure side 64bl of the flexible element
62bl. The tension diminishes with increasing distance from
the longitudinal axis of the pipe joint assembly 30. Thus,
the ends of the shims 72' which are uppermost in Figure 4 are
15 subject to a lesser "hoop tension" than the lower ends of the
shims. The smaller tlhoop tension" requires a smaller thick-
ness of metal to resist the tension load and the shims may be
tapered accordingly.
It will be understood that the embodiment desoribed
above is merely exemplary and that persons skilled in the art
may make many variations and modifications without departing
from the splrit and scope of the invention. For example,
indivldual rings 58 and 60 may be fabricated in one piece with
ad~acent metal oomponents such as flanges 46. The ~oints 56
may also be utilized as combined bearings and seals in a
variety of dif~erent pipe ~oint assemblies~ suoh as those
shown in the var~ous Figures of Herbert etal U. S. Patent
No. 3,6Bo,8g5. ~11 such modifications and variations are
intended to be within the scope of the invention as defined
in the appended claim~.
.
