Note: Descriptions are shown in the official language in which they were submitted.
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Atty Docket No. CTH/104
STAB JOINT FOR PIPE ASSEMBLY INCORPORATING COMPRESSIBLE
GASKET SECURED BY COMPRESSION STRAP
Field of the Inv ne tion
The invention is generally related to connecting pipes, and in
particular to connecting pipes through the use of a stab joint.
Backc,~round of the Invention
Forming a seal between adjoining spirally or helically formed
corrugated mEaal pipes has been problematic in a number of drainage and
culvert applications. One particular difficulty associated with forming such
seals stems from the availability of a wide array of diameters of corrugated
pipe, available, for example, in diameters between 12-144 inches.
11: is desirable for a seal formed between adjoining lengths of pipe
to be both reliable and easy to assemble. One conventional practice is to
recorrugate the ends of helically formed pipe with annular corrugations. A
gasket, typically an O-ring, is placed within an annular corrugation. The pipe
is then placed in an abutting relationship with a similar recorrugated pipe
having a similar 0-ring disposed in an annular corrugation thereof. A
compression hand is then placed around both pipes and tightened through the
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use of bolts, which tension the bands and compress the gasket between the
outer surface of each pipe and the inner surface of the band.
While the aforementioned type of joint usually forms a reliable
seal, in practice the joint is difficult and time consuming to assemble in the
field - especiall'y in trenches or ditch-like conditions where a large
percentage
of corrugated pipe is used. Particularly when extremely large diameter pipe is
used, recorrugating the pipe ends, orienting a band around abutting pipes and
tightening the band to achieve the seal is extremely unwieldy and inefficient
to assemble.
As an alternate to the use of a compression band, various types
of stab joints have been developed. With a stab joint, a pipe, acting as a
spigot, is inserted into a larger diameter bell formed on another pipe, or
alternatively, on a sleeve that functions as a bell for adjoining pipes.
Typically,
the joint is formed by initially placing a gasket on either the outer surface
of
the pipe or the 'inner surface of the bell. A seal is then formed between the
gasket and the other structure by inserting the pipe in a direction along its
longitudinal axis into the bell. Tightening of a band within the field is
typically
not required, and as such, a stab joint is often faster and less difficult to
install.
Conventional stab joints, however, also have a number of
drawbacks. A number of stab joint designs, for example, are not suitable for
use with spirally formed corrugated pipe, and thus often require pipe end
recorrugation to form annular corrugations. Moreover, for those joints that do
not require recorrugation, often a gasket material is wound within the valley
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of a single corrugation without any form of retainer. Without such a retainer,
however, a risk exists that the gasket will become dislodged during insertion
of the pipe into the bell. Any dislodgement of the gasket may compromise the
seal and cause leakage lif not corrected.
Some stab joint designs also incorporate a retaining ring to initially
secure a gasket to the inner surface of a bell or an annular outer surface of
a
pipe. Typically, the engagement with the opposing structural member,
however, is formed through the use of one or more deformable lips. In
practice, such joints require a consistent circurnferential profile of both
the bell
and the pipe to form a reliable seal, and thus" such joints are not suitable
for
use with spirally formed pipe. Moreover, the ~deformable lips typically do not
completely fill 'the space between the pipe and bell, and as such, may not
provide for a reliable seal in all circumstances.
Therefore, a significant need continues to exist in the art for a
reliable and easy to install sealing arrangement for use with spirally formed
corrugated pipe.
Summary of the Invention
The invention addresses these and other problems associated
with the prior art by providing a stab joint, a pipe assembly incorporating
the
same, and a method of forming a seal between a corrugated pipe and a bell in
which an annular gasket is secured to a corrugated pipe through the use of a
compression strap that applies a compressive force to the gasket to form a
seal between the gasket and the outer engagement surface of the pipe. The
annular gasket overlays .an adjacent crest and valley on the outer engagement
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surface of the pipe and is formed of a compressible material having an
uncompressed radial thickness that is greater than the radial distance between
the inner engagement surface of the bell and a crest on the outer engagement
surface of the pipe. When compressed by the compression strap, at least a
portion of the annular gasket has a diameter that is greater than that of the
strap such that the annular gasket forms a sea/ with the inner engagement of
the bell when tine pipe i,s inserted into the bell.
These and other advantages and features, which characterize the
invention, are set forth in the claims annexed hereto and forming a further
part
hereof. However, for a better understanding of the invention, and of the
advantages and objectives attained through its use, reference should be made
to the Drawing:c, and to the accompanying descriptive matter, in which there
is described exemplary embodiments of the invention.
Brief Descr~tion of the Drawings
FIGURE 1 is a partially-exploded elevational view of a pipe
assembly consistent with the invention, with portions thereof cut away to
illustrate internal components of the assembly.
FIGURE 2 is a cross-sectional view illustrating the profile of the
annular gasket in the pipe assembly of Fig. 1 .
FIGURE 3 is an alternate cross-sectional profile to that of Fig. 2.
FIGURE 4 is an enlarged fragmentary cross-sectional view
illustrating the seal formed upon insertion of an annular pipe into the sleeve
of
Fig. 1 .
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FIGURE 5 is an elevational view of an alternate pipe assembly
consistent with the invention, incorporating a recorrugated pipe.
FICiURE 6 is another alternate pipe assembly consistent with the
invention, incorporating a spiral rib-type pipe.
FIGURE 7 is yet another alternate pipe assembly consistent with
the invention, incorporating a sleeve having a plurality of deformable tongues
for use in securing a corrugated pipe within the sleeve.
FIGURE 8 is an enlarged fragmentary cross-sectional view of a
seal formed between the sleeve and pipe of Fig. 7.
Detailed Description
Turning to the Drawings, wherein like numbers denote like parts
throughout the several views, Fig. 1 illustrates a pipe assembly 10 consistent
with the invention. Pipe assembly 10 is illustrated including first and second
corrugated pipes 12, 14 joined in an abutting relationship by an annular
sleeve
24. Each corrugated pipe 12, 14 is illustrated as a spirally wound pipe
including a plurality of corrugations 16 defined on an outer engagement
surface 18 of the pipe. The corrugations 16 form a plurality of alternating
crests 20 and valleys 22 that are spirally wound on the outer surface of the
pipe. It will be .appreciated that each pipe 12, 14 may have an inner surface
having the same; profile as the outer surface of the pipe, or in the
alternative,
a liner may be secured to the inner surface of the pipe to provide a smooth
profile for the pipe.
Sleeve 24 includes first and second bell portions 26, 28, which
respectively receive the ends of pipes 12, 14 to effect a joint therebetween.
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An annular center stop 30 is optionally provided between bell portions 26, 28
to prevent insertion of the sleeve too far onto a pipe when the sleeve is
first
inserted over a first pipe, as well as to prevent movement of the sleeve when
a second pipe is inserted into the sleeve.
An inner engagement surface 32 is defined along the interior of
each bell portion 26, 28, and sleeve 24 also optionally includes annular entry
flares 34, 36 formed on the end portions thereof to facilitate alignment of a
pipe with the sleeve during assembly.
Each of pipes 12, 14 and sleeve 24 may be formed of a number
of different mai:erials, including various metals and alloys, as well as
different
plastics that provide suitable rigidity for the application. Moreover, while
Fig.
1 illustrates thc: use of a sleeve having opposing bell portions for joining
two
lengths of pipe, it will also be appreciated that the sleeve may be
permanently
secured to or formed on the end of one length of pipe, whereby formation of
a seal between pipes requires only the insertion of another length of pipe
into
the sleeve. The sleeve, for example, may be integrally formed on the end of
a pipe through molding or metal forming, or may be a separate member that
is secured in ainy number of fashions to the end of a pipe prior to use in the
field.
To effect a seal between each pipe 12, 14 and inner engagement
surface 32 of sleeve 24, a seal 40, including a gasket 42 and compression
strap 44, is initially secured to the end of each corrugated pipe.
As best shown in Fig. 2, gasket 42 includes inner and outer
engagement surfaces 46, 48, which are respf:ctively configured to engage the
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pipe and the bell portion of sleeve 24. The gasket also includes a tapered
leading edge 50 that facilitates alignment of the sleeve prior to assembly
onto
the pipe. An annular groove 52 is formed by a pair of annular shoulders 54,
56 intermediate the leading edge 50 and outer engagement surface 48 of the
gasket. Groove 52 is sized and configured to receive strap 44 and compress
the gasket onto the spiral corrugations of a pipe.
Strap 44 is typically formed of metal or plastic, and is used to
compress the gasket onto the outer engagement surface of the pipe. For this
reason, gasket 42 is preferably formed of a compressible material such as a
low durometer rubber. ~'Vhile various natural or synthetic rubber compositions
(including multiple layers and other combinations of materials) may be used to
form gasket 42, closed cell formed rubber is preferably utilized in the
illustrated embodiment.
The material used to form the gasket preferably has less than
about a 45 (Shore 00) durometer, more preferably a durometer of less than
about 30 (Shore 00), to permit the gasket to account for the variable
compression to which the gasket is subjected across the inner engagement
surface 46 thereof. Specifically, as can be seen in Fig. 1, inner engagement
surface 46 of the gasket overlays at least one adjoining crest and valley
forming a corrugation. In many instances, more than two valleys and/or crests
may be overlaid by the gasket, and as such, it is often desirable to provide a
sufficiently low durometer gasket material to permit the gasket to completely
fill each overlaid corrugation valley while sufficiently compressing over each
overlaid corrugation crest. As such, a reliable seal around the entire
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circumference o~f the pipe may be provided regardless of the particular
profile
of the outer enc,~agement surface thereof.
A wide variety of alternate profiles may be utilized for gasket 42
consistent with the invention. For example, as shown in Fig. 3, a gasket 42'
may include a lip 60 disposed distal from the leading edge of the gasket
relative to a groove 62 to provide additional material and thereby form a
tighter
seal between the pipe and the sleeve. As another example, it may be desirable
to utilize a different leading edge profile, including one without a taper.
The
use of a tapered leading edge, however, does facilitate the alignment of the
sleeve and also minimize, the bulging of the gasket proximate the leading edge
thereof. In addition, alternate groove profiles may be utilized in a gasket,
and
in some implennentations it may be possible to omit the groove and simply
allow the strap to compress the gasket along the outer engagement surface
thereof. In addition, while the illustrated gasket includes a smooth, circular
cylindrical profile, the inner engagement surface of the gasket may assume
other profiles as well. It is important to note, however, that the profile of
the
inner engagement surface, when in an uncompressed state, usually need not
match the cross-sectional profile of the overlaid portion of the outer
engagement surface of the corrugated pipe. As will become more apparent
below, permitting the inner engagement surface of the gasket to assume the
profile of the pipe through a compression permits the gasket to be assembled
onto pipes of varying profiles, and without the need to align the gasket at
any
specific orientation relative to the profile of t:he pipe.
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A~; shown in Figs. 2 and 4, gasket 42 preferably has an
uncompressed radial thickness t that is greater than the radial distance d~
between the inner engagement surface 32 of the sleeve and a crest 20 formed
on the outer engagement surface 18 of the pipe. By providing such a
thickness, the c,~asket is ensured of forming a seal at least between the
crest
of a corrugation and the sleeve. Moreover, it is desirable for the
uncompressed thickness t of the gasket to also be greater than the radial
distance d~ between the inner engagement surface 32 and a valley 22, such
that sufficient rnaterial is provided in the gasket to completely fill the
adjacent
valley 22 of the pipe. However, in some implementations, it may not be
necessary to provide sufficient thickness in the gasket to completely fill
each
valley overlaid by the gasket.
In operation, a joint is formed between a corrugated pipe and a
sleeve by first securing gasket 42 to the end of pipe 12 through the use of
strap 44. Typically, gasket 42 is placed in a circumscribing relationship over
the end of pipe 12, and strap 44 is placed around the gasket and tightened by
means of a manual or pneumatic tensioner. A wide variety of strap
constructions and tightening mechanisms may be utilized consistent with the
invention, e.g., various band angles or other 'fasteners. It will be
appreciated
that securing the gasket to the pipe may be performed in the field, or more
typically, prior to delivery of the pipe to the field.
Tightening the strap performs two functions. First, the strap
compresses the gasket to fill the corrugation valleys or other areas between
the corrugations and l:hereby form the seal between the gasket and the
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corrugated pipe. Second, the strap holds the gasket in place while the stab
sleeve is assemlbled onto the pipe, and serves to reduce the risk of the
gasket
rolling or pushing ahead of the sleeve when the joint is assembled. It is also
desirable for at least a portion of the annular gasket to bulge outwardly to
provide a diameter greater than the strap after compression to assist in
forming a seal with the inner engagement surface of the sleeve.
Once the gasket is secured to the pipe, the joint is formed by
inserting the end of the pipe into the sleeve in a longitudinal direction
until the
end of the pipe contacts the center stop formed in the sleeve. Doing so forms
a compression ;seal within the gasket and the inner engagement surface of the
sleeve.
Se:curement of a second pipe 14 to the opposite bell 28 formed
in sleeve 24 occurs in the same manner as for pipe 12. Moreover, it should
be appreciated that the sleeve may be secured to one of the pipes prior to
delivery of the pipe to the field, whereby adjoining a sequence of pipes
merely
requires that each pipe be supplied with a sleeve secured to one end thereof,
with the opposing end of each pipe sequentially inserted into the exposed
sleeve end of a preceding pipe.
It may be seen that the compression of the gasket into the valleys
of the annular corrugations, combined with the compression of the bulged
" areas of the outer edge of the gasket adjacent the strap by the inner
s
engagement surface of the sleeve assists in forming a water-tight seal
between the pipe and the sleeve.
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The herein-described sealing arrangement may also be utilized to
form other joint assemblies consistent with the invention. For example, as
illustrated by joint assembly 10' in Fig. 5, seal 40 may be utilized to form a
seal between sleeve 24 and a recorrugated pipe 12' having an end thereof
recorrugated to form annular corrugations 70 including adjacent crests and
valleys 72, 74. Similarly, as illustrated by pipe assembly 10" in Fig. 6, seal
40 may also bE: used to form a seal between sleeve 24 and a spiral rib-type
corrugated pipe 12" including a spiral formed rib 80 defining alternating
crests
and valleys 82, 84.
In certain implementations, it may be desirable to specifically
configure the gasket and strap 42, 44 of seal 40 for use with specific types
of corrugated pipe. However, one advantage of the invention is that in many
instances the same gasket and strap configuration may be utilized for a given
diameter of corrugated pipe, regardless of the specific type of corrugations
utilized thereon.
Aa another alternative, Fig. 7 illustrates a joint assembly 10"' in
which a corrugated pipe 12 is secured to a sleeve 24' through the use of seal
40. In addition to the compression seal formed by seal 40, sleeve 24' includes
a plurality of deformable tongues 90 formed around the periphery thereof.
Each deformable tongue; is cantilevered with a free end 92 extending generally
' in the direction of insertion of the pipe. As best illustrated in Fig. 8,
after pipe
s
12 is inserted into sleeve 24', the deformable tongues 90 may each be
pressed downvvardly into engagement with the outer engagement surface of
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pipe 12 ltypically on the back side of a crest 20) to restrict removal of the
pipe
from the sleeve.
Typically, deformable tongues are integrally formed on a metal
sleeve, and are defined by slots 94 circumscribing the free end 92 of each
tongue 90. The tongues typically may be deformed by simply hammering
down on the tongues after the pipe is inserted into the sleeve. Various tongue
profiles, including U-shaped, V-shaped, semi-circle-shaped, etc. may be used
to define each i:ongue, and any number of tongues may be disposed about the
periphery of the sleeve. Other modificatians will be apparent to one of
ordinary skill in the art.
Various additional modifications may be made without departing
from the spirit .and scope of the invention. Therefore, the invention lies in
the
claims hereinafter appended.
llVhat is claimed is:
