Sleeve for joining tubular conduits

A sleeve for coupling together two fluid-handling conduits includes a compressible and resilient tubular core and a protective fabric cover which covers at least portions of the outer surface of the core and is substantially inexpansible in the radial and circumferential directions so as to resist radial and circumferential expansion of the core. The core is preferably a cellular elastomeric foam and the fabric cover advantageously is integrally molded into the core. The core is sized slightly smaller in diameter than the conduits to be joined so that it is expanded radially when installed onto a conduit. Expansion of the core is resisted by the fabric cover, and thus the core is radially compressed and provides a continuous restoring force urging the sleeve against the conduit. The sleeve preferably includes strike-through regions in which the foam material of the core penetrates through to the outer surface of the sleeve so as to form slip-resistant surfaces for engagement by plastic tie-wraps or other clamping devices. The inner surface of the core at both ends preferably includes a fabric layer which provides a slip-enhancing surface facilitating sliding the sleeve over the ends of the conduits or hoses to be joined. In a further preferred embodiment, a pressure-activated or thermally activated adhesive band covers the inner surface of the sleeve for sealing the sleeve to a conduit.

FIELD OF THE INVENTION 
The present invention relates to coupling devices for joining together two 
tubular conduits to effect a fluid-tight seal therebetween. 
BACKGROUND OF THE INVENTION 
In many industrial and manufacturing applications it is necessary to couple 
the ends of two fluid-handling conduits to effect a fluid-tight coupling 
therebetween, and accordingly a host of coupling devices have been 
developed for the purpose. Many of these coupling devices rely on metal 
band clamps tightened about a sleeve which is slipped over the ends of the 
conduits so that the sleeve is inwardly compressed against the conduits. 
Where the fluid within the conduits is under significantly higher pressure 
than ambient, some provision must be made for preventing the sleeve from 
"ballooning" outward and possibly failing or causing the sleeve to slip 
out from under the clamps. Thus, in some coupling devices a single metal 
band clamp is used which extends continuously over the joint between the 
two conduits and is tightened at its two ends about the conduits, for 
example as shown in U.S. Pat. Nos. 4,101,151 and 3,836,182. 
In other types of coupling devices, the sleeve itself is made relatively 
stiff and rigid so as to resist ballooning. For example, in fluid systems 
for some aircraft, a coupling device sometimes used comprises a sleeve 
formed of multilayered fiberglass coated with silicone elastomer. The 
sleeve is sized to fit over the ends of the conduits to be joined and is 
secured by metal band clamps or the like. A difficulty associated with 
such coupling devices is that the stiff sleeve is frequently not able to 
adequately conform to the exterior contour of the conduit to form a 
reliable seal. For instance, misaligned conduits are difficult to seal 
with the stiff sleeve because the sleeve is not readily bendable. Sealing 
difficulties can also be encountered when the interface surface of the 
conduit is not smooth or has become dented or scratched, when the conduit 
is sized slightly larger or smaller than nominal, or when the conduit has 
become otherwise misshapen. If any of the aforementioned circumstances 
occur, leaks can develop. Thus, where the conduits are misaligned, a 
worker frequently must rework the conduits to bring them into alignment 
prior to installing the coupling device. Where the conduits are not smooth 
or are scratched or dented, a worker must polish and/or fill the surface 
of the misshapen conduit to provide a smooth surface for the sleeve to 
seal against. However, such procedures are labor-intensive and 
time-consuming. Leaks can also develop when relative movement occurs 
between the two conduits that are joined, because the stiff sleeve does 
not have enough "give" to compensate for the movement. The usual solution 
to leaks is to further tighten the clamps, but overtightening the clamps 
can cause damage to the conduit and/or to the sleeve, leading to potential 
loss of pressure. The consequences of the pressure loss can include loss 
of passenger comfort, loss of system performance, damage to or failure of 
a component, etc. 
The coupling device employing the stiff fiberglass/elastomer sleeve also 
requires a separate wrap of insulation around the joint to prevent thermal 
and acoustics loss. The insulation typically comprises moisture-resistant 
insulation batting wrapped with fiber-reinforced perforated plastic film 
that is heat sealed, stitched, or taped in place. This method of assembly 
is expensive, labor-intensive, heavy, and unreliable. Moreover, the 
insulation typically requires periodic replacement if the plastic film 
becomes torn, if the insulating performance degrades as a result of 
shifting of the batting and/or repeated wetting and drying of the batting, 
or if the tape used to secure the plastic film fails or becomes loose 
because of age. 
Thus, it would be desirable to provide a coupling device which has thermal 
and acoustical insulating functions without the necessity of wrapping a 
joint with insulation as in existing coupling devices employing stiff 
sleeves, and which does not degrade in insulating performance as a result 
of wetting, shifting insulation, or the like. It would also be desirable 
to provide a coupling device able to satisfactorily seal against scratched 
or dented conduits, conduits that are slightly larger or smaller than 
nominal, or conduits that are misshapen, so that reworking of the conduits 
can be avoided. Additionally, particularly in aircraft applications where 
a substantial number of coupling devices may be used in a single aircraft, 
it would be desirable to provide a coupling device having lower cost and 
lighter weight than existing coupling devices incorporating stiff sleeves 
and metal clamps and separate insulation materials. 
SUMMARY OF THE INVENTION 
The above needs are met and other advantages and objects are achieved by 
the present invention, which provides a coupling sleeve that does not 
require a separate wrapping of insulation for achieving thermal and 
acoustical insulating functions. The sleeve is able to satisfactorily seal 
against scratched or dented conduits, conduits that are slightly larger or 
smaller than nominal, conduits that are misshapen, and conduits that are 
oval or other non-round shapes. The sleeve can also be made and installed 
at lower cost and is lighter in weight than existing coupling devices 
incorporating stiff sleeves and metal clamps and separate insulation 
materials. 
To these ends, a coupling sleeve in accordance with one preferred 
embodiment of the invention comprises a tubular core formed of flexible 
and resiliently compressible slip-resistant material, and a tubular fabric 
cover. At least a central portion of the inner surface of the core forms a 
conduit-engaging surface of the sleeve. The tubular fabric cover is joined 
to the core and forms at least a portion of an outer surface of the 
sleeve. The core preferably is slightly smaller in inner diameter than the 
outer diameter of the conduits being joined. Furthermore, the cover 
preferably is relatively inexpansible in the circumferential and radial 
directions so that it prevents ballooning of the core. Thus, the sleeve is 
stretched over the conduits such that the compressible core is radially 
compressed between the conduits and the generally inexpansible cover. 
Preferably, the core comprises an elastomeric foam material, and thus 
provides thermal and acoustical insulating properties to the sleeve. In a 
preferred embodiment of the invention, the foam material of the core 
impregnates partially through a thickness of the fabric cover such that 
the cover is partially embedded in the core. 
The foam core also provides slip-resistant properties so that the sleeve 
does not readily slip relative to the conduits. Additionally, in 
accordance with a further preferred embodiment of the invention, the 
sleeve includes at least one strike-through region in which the foam 
material of the core impregnates completely through the thickness of the 
cover and is exposed at the outer surface of the sleeve so as to provide a 
slip-resistant outer surface. Thus, a clamp such as a band clamp or 
plastic tie-wrap can be wrapped about the strike-through region for 
clamping the sleeve onto a conduit, and the strike-through region tends to 
prevent the clamp from slipping relative to the sleeve. Where a pair of 
clamps are used for clamping the sleeve onto a pair of conduits, two 
strike-through regions preferably are provided so that each of the clamps 
engages one of the strike-through regions. 
In accordance with another preferred embodiment of the invention, a fabric 
layer covers a portion of the inner surface of the core adjacent one end 
of the core. The fabric layer forms a slip-enhancing surface to facilitate 
sliding the sleeve over the end of a conduit. Preferably, both ends of the 
core have fabric layers on their inner surfaces. The fabric layers in one 
embodiment comprise extensions of the fabric cover which are wrapped over 
the ends of the core so as to extend onto the inner surface of the core. 
The wrapped extensions of the cover also seal and protect the end surfaces 
of the compressible core. 
Strike-through regions as described above preferably are provided over a 
portion of the core which is not covered by the slip-enhancing fabric 
layers on the inner surface, so that clamps tightened about the sleeve 
compress the slip-resistant inner surface of the core against the 
conduits. Because the core is compressible and resilient, partial 
loosening of a clamp causes the core to resiliently expand so as to take 
up any additional space created by the loosening of the clamp, so that 
frequent checking and retightening of clamps in many cases can be avoided. 
Moreover, the core tends to fill in and conform to irregularities in the 
surfaces of the conduits. Thus, the sleeve tends to be self-sealing so 
that reworking of scratched or dented conduits in many cases is 
unnecessary. Additionally, the sleeve is capable of sealing against oval 
or other non-round conduits, which are typically difficult to join with 
conventional sleeves employing substantially rigid band clamps because of 
the tendency of the clamps to nonuniformly compress the sleeve about the 
circumference of the conduits. The flexible core and flexible cover of the 
present sleeve, however, are able to adapt to a variety of conduit shapes. 
Advantageously, the inner surface of the core adjacent one or both ends 
thereof is flared to facilitate sliding the sleeve over the end of a 
conduit. In one embodiment of the invention, both the inner and outer 
surfaces of the core adjacent one or both ends are flared so as to form a 
bell mouth at one or both ends of the sleeve. 
As described above, the sleeve may be used in conjunction with clamps for 
compressing the sleeve against a pair of conduits. However, in many 
applications where relatively low pressures exist in the conduits to be 
joined, a sleeve in accordance with the present invention is suitable for 
use without a clamp. Additionally, a further preferred embodiment of the 
invention provides a sleeve having adhesive applied over at least a 
portion of the inner surface of the core for sealing the sleeve to a 
conduit. A sleeve in accordance with this embodiment is suitable for use 
in many cases even where the pressure within the conduits is relatively 
high. Various types of adhesives may be used, including but not limited to 
thermally activated adhesives which may be activated by heating after the 
sleeve has been placed over a conduit, or pressure-activated adhesives 
which for example may be activated by pressure exerted when the sleeve is 
slid over the end of a conduit. 
A further advantage of the sleeves having a fabric cover in accordance with 
the invention is that the fabric cover tends to prevent not only 
ballooning which is a problem when the conduit pressure is higher than 
atmospheric, but also collapsing of the sleeve which is a problem when a 
vacuum exists within the conduit. In contrast, some conventional coupling 
devices employing a flexible sleeve clamped by one or more metal band 
clamps can be susceptible to collapsing of the sleeve under vacuum.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
The present invention now will be described more fully hereinafter with 
reference to the accompanying drawings, in which preferred embodiments of 
the invention are shown. This invention may, however, be embodied in many 
different forms and should not be construed as limited to the embodiments 
set forth herein; rather, these embodiments are provided so that this 
disclosure will be thorough and complete, and will fully convey the scope 
of the invention to those skilled in the art. Like numbers refer to like 
elements throughout. 
With reference to FIG. 1, a sleeve 10 in accordance with one preferred 
embodiment of the invention is shown installed on the ends of a pair of 
conduits C to effect a coupling therebetween. The sleeve 10 comprises a 
compressible and resilient core 12 and an outer cover 14 which is joined 
to the outer surface of the core. The core 12 preferably should have good 
rebound properties so that when a force compressing the core 12 is removed 
the core tends to rebound to its original dimensions and shape even when 
the compressing force is exerted for extended periods of time. An 
advantageous material for the core 12 is closed-cell silicone foam, which 
can be made with various compressibilities to suit particular 
applications. Silicone foam also has good thermal and acoustical 
insulating characteristics, and thus the sleeve 10 reduces thermal and 
acoustic loss from the coupling between the conduits C. 
The cover 14 preferably is a woven fabric which has good resistance to 
tearing so that the core 12 is protected from tearing or the like during 
installation and use of the sleeve. The cover 14 preferably also limits 
the extent to which the sleeve 10 can expand outwardly so that substantial 
ballooning of the sleeve under pressure loads is prevented. A small amount 
of ballooning may be tolerable in many applications. The degree of 
expansibility of the fabric cover can be selected to suit a particular 
application. The expansibility of the fabric in the lengthwise, radial, 
and circumferential directions is primarily a function of the weave and 
the material. Various fibers can be used for making the cover, including 
natural and synthetic materials. Synthetic fibers which are suitable 
include polyesters such as Dacron, or the like. The weave of the fabric 
cover 14 preferably allows the cover to stretch in the length direction of 
the sleeve but does not allow substantial expansion in the radial and 
circumferential directions so that ballooning is controlled as noted 
above. However, a limited degree of expansion in the radial and 
circumferential directions may be desirable in order to allow the sleeve 
10 to fit a range of conduit diameters, which for example might occur as a 
result of variations in manufacturing tolerances during manufacture of the 
conduits. 
The sleeve 10 in a relaxed state advantageously has an inner diameter about 
equal to the inner diameter of the conduits C. Accordingly, the sleeve 10 
must be expanded radially and circumferentially in order to fit over the 
ends of the conduits C. Preferably, the majority of the expansion occurs 
through compression of the core 12, and the cover 14 has significantly 
less propensity to expand so that it resists the expansion of the core 12. 
This can be seen most readily in the area of the outwardly protruding bead 
B formed on the outer surface of the conduit C on the left side of FIG. 1. 
The bead B causes the core 12 to be compressed between the cover 14 and 
the bead B because the cover 14 does not substantially expand. The 
compressible core 12 is essentially a spring which tends to have greater 
restoring force the more it is compressed. Accordingly, the restoring 
force tending to urge the sleeve 10 against the outer surface of the 
conduit C is greater in the area over the bead B than for the rest of the 
sleeve 10 and thus tends to provide a greater resistance to leakage past 
the interface between the sleeve 10 and the conduit C. Thus, in some 
applications such as higher-pressure applications, it may be desirable to 
include a bead on one or both of the conduits. However, even without a 
bead on the conduit, the core 12 is compressed between the cover 14 and 
the conduit outer surface so that a restoring force of the core 12 urges 
the core against the conduit and thus seals the interface therebetween. 
Advantageously, the core 12 undergoes a maximum compression of about 60 
percent of its relaxed radial thickness when the sleeve is installed on a 
conduit. 
The core 12 and cover 14 thus work together to form a flexible and 
stretchable sleeve 10 which is able to accommodate variations in conduit 
size and/or shape. The resilient core 12 of the sleeve 10 tends to conform 
to dents, scratches, or other non-smooth regions of the conduit outer 
surfaces, in contrast to coupling devices employing rigid sleeves of 
fiberglass or the like which are substantially incapable of conforming to 
such non-smooth contours. Additionally, the sleeve 10 works well on oval 
or other non-round conduits in order to form a fluid-tight coupling. 
With reference to FIG. 2, the sleeve 10 preferably includes a fabric layer 
16 on the inner surface 18 of the core 12 adjacent at least one end, and 
preferably adjacent both ends, of the sleeve. The fabric layer 16 provides 
a slip-enhancing surface that facilitates sliding the sleeve 10 over the 
end of the conduit C. The fabric layer 16 has a limited lengthwise extent 
so that most of the inner surface 18 of the sleeve 10 in the central 
portion of the sleeve is formed of the foam core material, which tends to 
be slip-resistant. In this way, the sleeve 10 is provided with slip 
resistance so that it tends not to slide on the conduits once installed 
thereon. The sleeve 10 without any clamp is capable of providing an 
essentially leak-free coupling at positive and negative gage pressures 
having magnitudes up to 2.0-2.5 psig. The preferred construction 
comprising a silicone foam core and a Dacron fabric sleeve enables the 
sleeve to be used over a broad range of temperatures, for example from 
about -65.degree. F. to +500.degree. F., for transferring air, other 
gases, or fluids. 
Where higher gage pressures must be contained, the sleeve 10 can be 
adhesively joined to the conduits C by an adhesive layer 19 interposed 
between the inner surface 18 of the core 12 and the outer surface of the 
conduits. Advantageously, the adhesive layer 19 is applied to the inner 
surface 18 of the sleeve prior to the sleeve being slid over the end of 
the conduit C. For example, the adhesive layer 19 may be formed during 
manufacturing of the sleeve so that it is an integral part of the sleeve. 
Suitable adhesives include thermally activated adhesives which are 
activated by heating the sleeve and conduit after the sleeve is installed 
onto the conduit, and pressure-activated adhesives which may be activated, 
for example, by the sliding action between the sleeve and the conduit when 
the sleeve is initially installed onto the conduit. Alternatively, a 
brushable type of adhesive may be applied to the outer surface of the 
conduit and/or the inner surface of the sleeve immediately prior to 
installation of the sleeve onto the conduit. 
To further facilitate sliding the sleeve over the ends of the conduits, an 
alternative preferred embodiment of a sleeve in accordance with the 
invention is shown in FIG. 3. The sleeve 20 includes a resilient core 22 
and outer cover 24, and a fabric layer 26 on the inner surface 28 adjacent 
one end, and preferably adjacent both ends, of the sleeve. In addition, 
the sleeve 20 also includes a chamfered portion 28' of the inner surface 
28 at one end, and preferably at both ends, of the sleeve such that the 
inner surface is flared outwardly. The flared inner surface 28' further 
facilitates initial insertion of a conduit C into the sleeve and also 
provides a larger entrance to the sleeve for accommodating variations in 
conduit size. The fabric layer 26 preferably covers the flared portion 28' 
and terminates slightly inward of the flared portion. 
FIG. 5 depicts yet another embodiment of the invention in which the sleeve 
30 has both the inner surface 38 and the outer surface 39 of the core 32 
flared or curled outwardly to form a bell mouth 40 at one or both ends of 
the sleeve for facilitating insertion of the conduit C into the sleeve. A 
fabric layer 36 covers the inner surface of the core 32 in the bell mouth 
portion of the sleeve and terminates slightly inward of the bell mouth 40. 
The outer cover 34 if desired may be terminated in the region of the bell 
mouth 40, but preferably extends over the bell mouth 40 to provide 
resistance to damage such as tearing or the like, which the bell mouth 40 
may be particularly susceptible to because of its larger diameter relative 
to the rest of the sleeve 30. 
In the embodiments of the invention described above in connection with 
FIGS. 1-3 and 5, the outer cover and the fabric layers on the inner 
surface at the ends of the sleeve are depicted as being separate pieces of 
material. However, it may be advantageous to form the cover and inner 
fabric layers as one integral piece of material. FIG. 4 depicts a sleeve 
50 in accordance with a further preferred embodiment of the invention, in 
which the cover 54 is extended beyond the end of the core 52 and is 
wrapped over the end and onto the inner surface 58 of the core so as to 
form a fabric layer 56 on the inner surface adjacent the end of the 
sleeve. Both ends of the sleeve 50 preferably include the wrapped 
extensions of the cover 54 forming fabric layers 56 at both ends of the 
sleeve. The wrapped extensions of the cover 54 provide protection for the 
end surfaces 60 of the core 52. 
Although the sleeves 10, 20, 30, and 50 can be used without clamps as 
described above, the invention is not limited to sleeves used without 
clamps. In some applications, it may be desirable to provide clamps for 
further compressing the foam core of the sleeve against the conduit in 
order to achieve a tighter seal with the conduit. Thus, a further 
preferred embodiment of the invention is shown in FIGS. 6 and 7, in which 
a sleeve 70 comprises a resilient core 72 and an outer fabric cover 74 
which extends the length of the core 72. The sleeve 70 includes at least 
one strike-through region 76 adjacent one end of the sleeve, and 
preferably includes a pair of strike-through regions adjacent both ends of 
the sleeve. The strike-through region 76 is a region of the sleeve in 
which the material of the foam core 72 penetrates through the fabric cover 
74 such that the foam material is exposed at the outer surface of the 
sleeve 70. The strike-through region 76 thus provides a slip-resistant 
surface about which a clamp K can be encircled for compressing the sleeve 
70 against the conduit C. The slip-resistant surface of the strike-through 
region 76 tends to resist slipping of the clamp K relative to the sleeve 
so as to reduce the tendency of the sleeve to be pulled out from under the 
clamp by pressure loads. 
FIG. 7 schematically illustrates an advantageous feature of the present 
invention. A sleeve 70 is shown installed on a conduit C with the aid of a 
clamp K which compresses the sleeve against the conduit. The resilience of 
the core of the sleeve causes restoring forces F to be exerted on the 
clamp K and on the conduit C so as to constantly urge against the conduit. 
Even if the clamp K should expand outwardly, as long as the radial 
expansion of the clamp does not exceed the unclamped radial thickness t of 
the sleeve, the sleeve 70 will expand to fill the space between the clamp 
and the conduit and a continuous restoring force will be exerted keeping 
the sleeve sealed against the conduit. Thus, the sleeves of the present 
invention are suitable for use with nylon tie-wraps, which are prone to 
hygroscopic expansion, as well as with other types of clamps such as metal 
band clamps or the like. FIG. 7 also illustrates the inclusion of a bead B 
on the conduit C for helping to prevent the sleeve 70 and clamp K from 
being pulled off the end of the conduit. 
Any of the sleeves described above may be manufactured in various ways. One 
advantageous method of making a sleeve in accordance with the invention is 
to place a tubular fabric cover into a tubular mold and inject a 
foam-forming composition into the mold on the inner surface of the fabric 
cover. The composition expands to fill the mold and in the process of 
expansion partially penetrates through the fabric cover. Strike-through 
regions can be provided by causing total penetration of the composition 
through the fabric in selected regions thereof, as understood by those 
skilled in the art. Upon curing of the composition, the foam material 
which penetrates into the fabric cover causes the cover to be integrally 
joined to the core. 
Alternatively, a foam core may be molded in tubular form, and then a fabric 
sheet may be wrapped about and adhesively joined to the outer surface of 
the core. The fabric may be configured to cover only a central portion of 
the core so that the opposite end portions have foam material exposed at 
the outer surface of the sleeve for providing slip-resistant surfaces for 
clamps, as previously described. 
Still another method for making a sleeve comprises forming a composite 
sheet of foam material having a fabric sheet joined to one side thereof, 
wrapping the composite sheet into a tubular form such that the two 
lengthwise-extending edges of the composite sheet come together, and 
adhesively joining the two lengthwise-extending edges of the composite 
sheet to form a tubular sleeve. The edges of the sheet may be joined with 
any suitable adhesive capable of providing a sufficiently strong bond to 
prevent splitting of the sleeve along the seam in view of the expected 
pressure or vacuum loads that the sleeve must withstand in use. 
Many modifications and other embodiments of the invention will come to mind 
to one skilled in the art to which this invention pertains having the 
benefit of the teachings presented in the foregoing descriptions and the 
associated drawings. Therefore, it is to be understood that the invention 
is not to be limited to the specific embodiments disclosed and that 
modifications and other embodiments are intended to be included within the 
scope of the appended claims. Although specific terms are employed herein, 
they are used in a generic and descriptive sense only and not for purposes 
of limitation.