Note: Descriptions are shown in the official language in which they were submitted.
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1
SEALING DEVICE
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to sealing devices,
particularly sealing devices for elongate heating cables.
Introduction to the Invention
The ends of elongate cables such as power cords or
heating cables often must be sealed in order to provide
electrical insulation, environmental protection and/or
mechanical shielding. Many methods and devices have been
used to provide a seal, including heat-recoverable tubing,
end-caps, or boots; molded adhesive-filled boots; enclosures
with gaskets or grommet seals; and wrapped tape. Such
methods have generally been unsatisfactory because of their
craft-sensitivity, difficulty of installation, limitation to
a particular size or shape of cable, or requirement for
special tools. In addition, many of these methods have
provided a seal that cannot be reentered without destroying
the seal and/or the cable.
Many elongate cables are designed to be cut to
length for a particular application, thus necessitating that
the cable end be easily sealed. For some applications using
elongate heating cables it is particularly important that
the end seal be reenterable in order to periodically
monitor the condition of the end of the cable, to check
the voltage present in the cable, and/or to monitor the
continuity of the cable. Conventional end caps and
sealing devices for protecting the ends of such cables
are known. See, for example, U.S. Patent Nos. 4,751,350
(Eaton), 4,877,943 (Oiwa) and 5,622,642 (Edwards et al).
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Such end caps often have one or more gripping members that
serve to grip the cable to prevent pullout of the cable from
the end cap. Such gripping members generally prevent
reenterability without destruction of the cable and/or the
end seal. In addition, such end caps often are filled with
a gel component in order to provide a barrier to moisture.
However, such gel-filled end caps may not be suitable for
use under conditions in which the heating cable is exposed
repeatedly to high temperature conditions. Under such
conditions, the gel may be thermally unstable, breaking down
and/or leaking from the end cap thus destroying the sealing
ability. If a sealant such as a grease which exhibits good
thermal properties at elevated temperature is used in a
rigid end seal, volume changes resulting from changes in
temperature cause shrinkage away from the cable and/or the
rigid enclosure, creating leakage paths and destroying the
sealing properties.
SUMMARY OF THE INVENTION
We have now found that a reenterable end seal with
excellent moisture-resistant properties even after repeated
exposure to high temperatures can be prepared if a sealant
such as a grease is contained in a flexible container which
has the ability to expand and contract during temperature
cycling.
Thus in a first aspect this invention provides an
apparatus for sealing the end of an elongate cable, said
apparatus comprising (1) a housing of generally cylindrical
shape, the housing comprising (a) a first open end and a
second open end; and (b) a strain relief element positioned
within the housing; (2) a flexible container which can be
positioned over the cable end, which container (i) is of
generally tubular shape, (ii) has an interior surface and an
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exterior surface, (iii) has a first open end and a second
closed end, and (iv) contains a sealant which comprises a
grease; (3) a cap which can (a) be mated with the housing at
the second open end, and (b) cover the container; and (4) a
rigid band positioned around the exterior surface of the
container, said apparatus being reenterable.
In a second aspect, the invention provides an
assembly comprising an assembly comprising (A) a reenterable
apparatus comprising (1) a housing of generally cylindrical
shape, the housing comprising (a) a first open end and a
second open end; and (b) a strain relief element positioned
within the housing; (2) a flexible container which (i) is of
generally tubular shape, (ii) has an interior surface and an
exterior surface, (iii) has a first open end and a second
closed end, and (iv) contains a sealant which comprises a
grease; (3) a cap which (a) is mated with the housing at the
second open end, and (b) covers the flexible container; and
(4) a rigid band positioned around the exterior surface of
the container; and (B) an end of an elongate cable which is
inserted through the first open end of the housing and the
first open end of the flexible container, and which directly
contacts the strain relief element and the flexible
container.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is illustrated by the drawings in
which Figure 1 is an exploded view of the components of the
apparatus of the first aspect of the invention;
Figures 2a and 2b are a plan view and a cross-
sectional view along line IIB-IIB, respectively, of an
apparatus of the first aspect of the invention with an
inserted cable prior to tightening of the cap;
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Figures 3a and 3b are a plan view and a cross-sectional view, respectively, of
the
apparatus of Figures 2a and 2b after the cap and the housing of the apparatus
have been
tightened;
Figure 4 is a perspective view of the container of the apparatus of the first
aspect of the invention;
Figure 5 is a cross-sectional view of the container of Figure 4 along line V-
V;
Figure 6 is a top view of an apparatus of the third aspect of the invention;
Figure 7 is a cross-sectional view of the apparatus of Figure 6 along line VII-
VII;
Figure 8 is a perspective view of the apparatus of the third aspect of the
invention
after an elongate cable has been inserted;
Figure 9 is a cross-sectional view of the apparatus of Figure 8 along line IX-
IX;
and
Figure 10 is a top view of another embodiment of the apparatus of the third
aspect
of the invention.
DETAILED D.S RTPTION OF TH . INV .NTION
The sealing apparatus of the invention can be used to seal the end of any
elongate
cable, including electrical heating cables such as self-limiting strip heaters
or mineral
insulated heating cables, power cables or cords, or grounded power leads.
Elongate
electrical heating cables particularly appropriate for use with this sealing
device are those
which comprise first and second elongate electrodes, a plurality of resistive
heating
elements connected in parallel between the electrodes, and at least one
insulating jacket
surrounding the electrodes and heating elements. The insulating jacket is
generally
polymeric, in the form of a continuous polymer layer, although a polymeric
braid or a
polymer tape may be used. For some applications a polymeric insulating jacket
is
surrounded by a second layer, e.g. a second polymeric insulating layer such as
a polyester
tape, or a metallized tape such as aluminized polyester. The heating cable
often
comprises an optional metallic grounding braid surrounding the insulating
jacket and the
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optional second layer. The metallic grounding braid serves
to electrically ground the heating cable and also provides
mechanical strength and abrasion resistance. When a
metallic grounding braid is present, it is generally in the
5 form of braided metal wires, although for applications in
which flexibility is not critical, it is possible to use
another type of metal layer, e.g. a sheath or metal tape.
In some applications, the grounding braid itself is
surrounded by an outer insulating jacket to provide
environmental and electrical insulation to the heating
cable. Particularly suitable heating cables are self-
regulating strip heaters in which the electrodes are
elongate wires and the heating elements comprise a
conductive polymer composition. The conductive polymer
composition, which often surrounds the elongate wires,
is often referred to as the core. Self-regulating
heaters are described in U.S. Patent Nos. 3,858,144
(Bedard et al), 3,861,029 (Smith-Johannsen et al), 4,017,715
(Whitney et al), 4,242,573 (Batliwalla), 4,334,148
(Kampe), 4,334,351 (Sopory), 4,426,339 (Kamath
et al), 4,459,473 (Kamath), 4,574,188 (Midgley et al),
and 5,111,032 (Batliwalla et al). The heating cable
generally has an approximately rectangular cross-section
with two generally parallel faces, although other
geometries, e.g. round, oval, or elliptical, can also be
effectively sealed by the sealing device of the invention.
The housing of the apparatus of the first aspect
of the invention is of generally cylindrical shape, e.g.
tubular or rectangular, although the exterior and/or
interior of the housing may vary in shape in different
sections of the housing. For example, the housing may be
generally circular in one part and generally rectangular in
another part that contacts a substrate in order to provide a
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more substantial base for positioning on the substrate. The
housing has a first open end suitable for insertion of the
elongate cable and a second open end suitable for attachment
to a cap. The housing may be a single piece, it may be
assembled into a permanent configuration from a number of
pieces, or it may comprise first and second housing members
which are capable of existing in a demated or mated
configuration. In the demated configuration, the housing
members may be separate pieces or they may be connected,
e.g. by hinges, straps or a snap-fit. When mated, the two
housing members are in contact with each other, either
directly or through a sealing member, e.g. a gasket, and in
such mated configuration, the two housing members form a
housing which has first and second openings at opposite
ends. The wall thickness of the housing may be constant,
although to provide strength, ribs, bosses, or exterior
grooves may be present.
The first open end of the housing is that which is
closest to the substrate. If the substrate is a pipe, the
first open end may be shaped, e.g. curved, in order to
accommodate the curvature of the pipe. In addition, the
perimeter of the first open end may have indented regions in
order to allow the cable to be easily inserted. The section
of the housing comprising the first open end may be designed
to allow insertion of an element other than a cable, e.g. a
pipe adapter, a light, or an electronic component such as a
thermostat, and so the open end may be shaped accordingly.
Slots may be provided near the first open end for insertion
of straps or cords to assist in securing the housing to a
substrate.
The second open end of the housing is shaped to
accommodate mating with a cap. Preferably either the
interior or the exterior surface of the housing near the
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second open end is provided with screw threads which mate
with those on the cap.
The housing may be of any length, although it
generally has a height of 63.5 to 254 mm (2.5 to 10 inches).
For many applications it is preferred that the height be
sufficient that, when the cap is placed on the housing and
the housing is installed on the substrate, the cap is
exposed and visible above any insulation that may be on the
substrate. The diameter of the housing may vary depending
on the components inserted into the housing, but generally
is 12.7 to 76.2 mm (0.5 to 3 inches).
Positioned within the housing is a strain relief
element. This element serves to hold the cable in position
with sufficient strength so that it cannot readily be pulled
out of the assembled apparatus. Generally a "pullout force"
of at least 11.4 kg (25 pounds), preferably at least 13.6 kg
(30 pounds), particularly at least 15.9 kg (35 pounds) is
required for routine use. (The pullout force can be
measured according to Factory Mutual Approval Standard,
Class No. 3820, September 1979, section 5.2.5. In that test
a known weight, e.g. 15.9 kg (35 pounds) is hung on the end
of the inserted cable at an angle of 180 for one minute.
The weight is then removed and the cable measured to
determine if any slippage from the apparatus, or cutting or
tearing of the cable jacket, has occurred.) In a preferred
embodiment, the strain relief element comprises a base
element which has a center opening which aligns with the
axial passageway of any grommet that is present. The shape
of the base element generally conforms to the shape of the
interior of the housing so that the strain relief element is
held in contact with the interior wall of the housing. To
ensure this contact, the base element may comprise an o-ring
or gasket which serves to fill any gaps between the base
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7a
element and the interior wall of the housing. Extending
from the base element toward the first open end are first
and second positioning arms which serve to orient the strain
relief element in the housing and may grip any grommet that
is present. Extending from the base element toward the
second open end are first and second gripping arms, each of
which comprises a gripping member at the end. The gripping
members, which serve to hold the cable in position, may be
the same or different. The portion of the gripping member
in contact with the cable may be smooth or it may comprise
ribs or teeth. If teeth are present, they may penetrate the
outer jacket of a polymer-insulated cable to enhance the
contact with the cable. Both the positioning arms and the
gripping arms have the ability to flex from the base element
in order to accommodate different size grommets and/or
cables. In addition, the gripping arms must be flexible
enough to be forced toward one another when the cap is mated
with the housing. Depending on the shape of the interior of
the housing and the cable, there may be more than two
positioning arms and/or gripping arms. For example, a round
cable may be held more securely by three gripping arms than
by two. The strain relief element may be a single piece or
individual components, e.g. a base element and positioning
arms, may be attached to one another to form the strain
relief element.
For most applications, inserted within the housing
is at least one grommet which is prepared from an
elastomeric material which is capable of being compressed in
the axial direction when formed into the grommet. Suitable
materials include neoprenes and fluorinated materials such
as vinylidene fluoride/hexafluoropropylene copolymer.
Particularly preferred for use at elevated temperatures is
silicone rubber which exhibits little if any degradation up
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to 150 C, and often much higher. The grommet may have any
shape that allows contact and gripping of the inserted
cable. A preferred grommet has an "hourglass" shape, i.e.
the axial passageway through which the cable is placed has
first and second inner end sections which taper inwardly
from the ends of the grommet to an inner central section.
The inner central section may be of substantially constant
cross-section. When compressed, such a grommet provides
both a longitudinal component for stress relief and a radial
component. Such a grommet, an example of which is described
in U.S. Patent No. 5,052,699 (Tucker) allows cables of
different sizes to be inserted into the grommet. The inner
surface of the grommet may be smooth or ribbed. The axial
passageway of the grommet may be of any shape, e.g. round or
elliptical, although for many applications, an elliptical
passageway is appropriate for gripping cables of different
sizes. Thus one size of housing can be used for a variety
of different sized cables. The grommet is generally
positioned between the strain relief element and the first
open end, although it can be between the strain relief
element and the second open end. For some applications, two
grommets are present, one above and one below the strain
relief element. It is important that the volume of the
inserted cable and the grommet in the housing are less than
the free volume of the
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housing cavity in which they are compressed so that it is not necessary to
compress the
grommet against its bulk modulus, which would require excessive force to
adequately
displace the strain relief element in the axial direction.
The component that actually covers the end of the cable is a flexible
container
that, when the apparatus of the first aspect of the invention is in a mated
configuration, is =
positioned within the housing in contact with the strain relief element,
between the strain
relief element and the second open end. The container is of generally tubular
shape,
having a first open end into which the cable can be inserted, and a second
closed end
which is directed to the closed end of the cap. The container may be
approximately
circular in section, a shape that is preferred for a round cable such as a
power lead;
approximately elliptical in section, a shape that is preferred for some oval
heating cables;
approximately rectangular in section; or any other appropriate shape. For some
applications, the container may be in the form of a "double" container which
allows
insertion of the cable into one container, and insertion of another component
into the
second container. In another embodiment the container may comprise a light or
other
electrical component in order to determine electrical continuity. The first
open end of the
container is shaped and sized to accept the inserted cable. For ease of
insertion, the open
end may be tapered inwardly toward the closed second end, although for some
applications, there may be a lip at the opening in order to grip the cable and
contain the
installed sealant. It is preferred that at least one rib is present on the
interior surface of the
container in order to contact the cable and wipe off the sealant when the
cable is removed
from the container. Generally at least one pair of ribs is present, and there
are preferably
two or more pair. The ribs of each pair may be directly opposite one another
on the top
and bottom interior surfaces of the container, or they may be offset. The ribs
must be
long enough to allow contact with the cable, and in order to accommodate many
different
size cables using a single size of container, the ribs may be of graduated
length. The ribs
may be positioned directly on the interior surface of the container or on a
separate insert
that is positioned within the container. The length of the container is
sufficient to allow
insertion of at least 6.4 mm (0.25 inch), preferably at least 12.7 mm (0.5
inch),
particularly at least 19.1 mm (0.75 inch), especially at least 25.4 mm (1.0
inch) of the
cable. For some applications the container can be long enough to allow
positioning over a =
light, or other component as well as the cable end.
The container is flexible, able to expand and contract as the cable is exposed
to a =
thermal cycle. The container is preferably elastomeric, comprising, for
example, a rubber
such as ethylene/propylene/diene rubber, or a silicone rubber. For good
thermal stability
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(i.e. up to 150 C, preferably up to 200 C) and good solvent resistance, it is
preferred that
the elastomer be a silicone rubber or a fluorosilicone rubber. Fillers,
including pigments
and stabilizers, can be present in the material forming the container.
Contained within the container is a sealant which has sufficient viscosity to
contact the inserted cable and maintain the contact during thermal cycling. In
addition,
the sealant acts to prevent moisture, fluids, and dust particles from
contacting the cable
end and acts as an electrical insulator. When the sealant expands and
contracts due to
thermal cycling of the inserted cable during an on/off cycle, changes in
ambient
temperature, or changes in substrate temperature, volume changes are
accommodated in a
manner which does not cause the sealant to extrude from its container, as
would be the
case with a rigid container. Thus, an excellent seal is maintained between the
sealant and
the cable. The sealant may be any suitable material but is preferably a grease
which has
good thermal stability at temperatures up to 150 C, preferably up to 200 C. A
grease is a
solid or semifluid lubricant comprising a thickening agent in a liquid
lubricant. Such
greases often comprise fillers such as clays or silica. Greases based on
silicones or
fluoropolymers are preferred. Greases having a National Lubrication Grade
Index of at
least 2 are suitable for use. It is preferred that the grease does not
compression set when
exposed to the operating temperatures required for the cable. Preferred
greases are
thixotropic silicone pastes containing silica, and perfluoroalkylpolyether oil
filled with a
telomer of tetrafluoroethylene. It is important that the grease be compatible
with the
material comprising the container so that no oils or fluids migrate from the
grease to the
container to swell and/or soften it. Thus, it is preferred that a container
comprising a
fluorosilicone be used with a silicone paste or a perfluoroalkylpolyether
lubricant, while a
container comprising a silicone rubber be used with a perfluoroalkylpolyether
lubricant
but not a silicone paste. Although the sealant can be applied by any means,
for ease of
manufacturing it is preferred that the sealant be pumpable. The container is
preferably
filled to at least 30%, particularly at least 40%, especially at least 50% by
volume with the
sealant.
For some applications, a rigid band surrounds the external surface of the
container
in the region of the ribs in order to provide adequate compression for
different cable sizes.
The band can be made of a metal, a ceramic, or a high strength polymer, e.g.
an
engineering plastic such as polyphenylsulfone or polyphenylene oxide. The
thickness of
the band is determined by the strength of the material from which it is made.
The length
of the band is sufficient to cover the ribs on the interior of the housing,
but not so great as
to limit expansion of the housing down the entire length of the housing. To
assist in the
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application of the band to the container, an extension of
the container, i.e. a "tail" can be formed at the closed end
of the container. This extension can be sized so that when
the cap is completely mated with the housing, the end of the
5 extension section away from the container contacts the inner
surface of the closed end of the cap.
When the container is located in the housing prior
to mating the housing with the cap, the container is
preferably attached to the strain relief element by means of
10 a flexible attachment strap which allows the container to be
positioned properly for installation of the cable.
Alternatively, the container can be positioned within the
cap, so that when the cap is mated with the housing, the
container comes into position with the strain relief
element.
The sealing apparatus of the first aspect of the
invention also comprises a cap which can be mated with the
second open end of the housing. Although any suitable
connection means may be used to connect the cap to the
housing, preferably the cap has screw threads at its open
end which are sized to connect to those on the housing. By
the action of screwing the cap into position, the strain
relief element is engaged by being forced down toward the
substrate and the grommet is compressed. To ensure that the
seam between the cap and the housing is sealed and to
prevent moisture ingress, the cap may also comprise an
o-ring. In a preferred embodiment, the o-ring is positioned
on the exterior surface of the cap, adjacent to the screw
threads and between the screw threads and the closed end of
the cap. When the cap is screwed into position, the o-ring
is compressed to form the seal. The length of the cap is
sufficient to completely enclose the container when the
cable is installed, as well as to provide adequate space for
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l0a
the screw threads. In order to keep the components together
before use, and for ease of installation, the cap may be
attached to the housing by means of a flexible strap. The
cap, as well as the flexible strap may be brightly colored
to assist in locating the apparatus on a substrate. The cap
may comprise ribs or bosses on its interior or exterior
surface for strength.
The housing and cap may comprise an insulated
metal or a ceramic but preferably comprise a polymer which
has an impact strength of at least 5 foot-pounds, preferably
at least 10 foot-pounds, when shaped into the final sealing
device configuration, as measured by such tests as IEEE
Test 515-1989, "Impact Test" (Test 5.1.6), Institute of
Electrical and Electronics Engineers, 1989. Preferred
polymers are of light weight, can be shaped by injection- or
transfer-molding or similar processing techniques, and will
withstand required intermittent use and continuous use
temperatures. Appropriate polymers include
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polyphenylsulfone, polyphenylene oxide, and other engineering plastics. The
polymer
may contain additional components, including fillers such as glass or graphite
fibers or
particles, pigments, stabilizers for thermal or ultraviolet stabilization,
processing aids, and
flame retardants.
The sealing apparatus of the first aspect of the invention can be used as part
of an
assembly which includes an elongate cable. When the cable comprises an
electrical
heating cable, it is preferred that the section of braid surrounding the
section of cable that
goes into the container, as well as any outer insulating jacket that covers
that section of
braid, be removed before insertion into the housing.
The apparatus of the first aspect of the invention is easy to use in a three
step
operation. After preparing the cable end by removing the proper length of
outer
insulating jacket and braid (if present), the cable is inserted into the
housing. The
container is then positioned over the cable end. Finally the cap is mated with
housing. A
important feature is that, once assembled, the apparatus can be reentered to
allow
monitoring of the condition of the end of the cable and continuity checking.
The flexible container useful in the first aspect of the invention can be
modified
for use in an apparatus which allows the formation of an electrical or
physical connection
to the elongate electrodes of a heating cable. Thus, in this aspect, the core,
which
generally comprises a conductive polymer composition, is stripped away from
the
elongate electrodes, and the electrodes are inserted into the container. In
this
embodiment, the flexible container comprises a first portion of generally
tubular shape.
The first portion has a first open end with shape and dimensions suitable for
insertion of
the heating cable, and a second partially closed end. Attached to the second
end is a
second portion which comprises a first leg portion suitable for insertion of
the first
elongate electrode and a second leg portion suitable for insertion of the
second elongate
electrode. The second portion may also comprise additional leg portions for
insertion of
any additional elongate electrodes. The transition region connecting the first
and second
portions of the container may be straight, or there may be a taper between the
two
portions (and, in some cases, extending into the first and second leg
portions) to assist in
positioning the electrodes properly. The first and second portions of the
container are
designed so that, when the heating cable, with elongate electrodes free of
core material, is
inserted as far as possible into the container, the electrodes are located in
the first and
second leg portions and extend therefrom, and the edge of the core is
positioned next to
the partially closed second end.
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The first portion comprises at least one rib on an interior surface which
contacts
the inserted cable and wipes off sealant when the cable is removed from the
container. As
described for the container of the first aspect of the invention, the first
portion preferably
comprises one or more pair of ribs, which may be of the type described above.
The first
portion also comprises a sealant of the type described above.
In a preferred embodiment, at least part of the exterior surface of the
container,
preferably the exterior surface of the first portion, is surrounded by a band,
preferably a
rigid band, such as that described above.
In order to aid in the insertion of the electrodes, removable guide tubes,
with a
diameter smaller than that of the first and second leg portions, may be
inserted into the
first and second leg portions, and preferably through the first portion of the
container as
well, prior to inserting the electrodes. These guide tubes are preferably of a
rigid
material, e.g. plastic or ceramic, and allow insertion of the electrodes while
avoiding
contact between the electrodes and the sealant. If the first and second leg
portions
comprise an internal tapered section near the junction of the first and second
sections, the
tapered section grips the guide tubes prior to their removal. In addition,
when the guide
tubes are removed, the tapered section on the first and second leg portions
acts to wipe the
guide tubes clean of sealant. As a result, the section of the electrodes
protruding from the
end of each of the first and second leg portions will be clean and ready for
electrical
connection. Furthermore, the guide tubes assist in avoiding crossing of the
electrodes,
and thus electrical shorting.
The invention is illustrated by the drawings in which Figure 1 is an exploded
plan
view of sealing apparatus 1 of the invention. Housing 3, with first open end 5
and second
open end 7, comprises a notional first rectangular section 9 and a second
cylindrical
section 15. Knock-out hole 17 is positioned in housing 3 to provide an
optional drain for
water or other fluids when the housing is positioned below a substrate. (A
similar knock-
out hole may be present in the cap.) The rectangular shape of the base of
housing 3
provides good stability on a substrate and slot 11 allows a strap or cord to
be passed
through for attachment to a substrate. Located adjacent to second open end 7
is grommet
23, which, as shown, has an "hourglass" shape. Strain relief element 27
contains a base
element 29 positioned between first and second positioning arms 31,33 and
first and
second gripping arms 35,37. First gripping member 39 lies at the end of first
gripping
arm 35, while second gripping member 41 lies at the end of second gripping arm
37.
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Flexible container 43 is attached to strain relief element 27 by means of
attachment strap
45. Container 43 has first open end 47 for insertion of the cable and second
closed end
49. Also shown is extension section 51. Compression band 59 surrounds
container 43
near first open end 47. Cap 61 has first open end 63 and second closed end 65.
Screw
threads 67 sized to match those on the interior of housing 3 near second open
end 7 are
positioned near first open end 63. 0-ring 69, designed to ensure a good seal
when cap 61
is mated to housing 3, is positioned adjacent to screw threads 67. External
ribs 71
provide a good gripping surface for mating the cap with the housing and
actuating the
strain relief system. Flexible connection strap 21, positioned under the lip
surrounding
second open end of the housing 3, may also be attached to cap 61.
Figures 2a and 3a show apparatus 1 of the invention in plan view before
(Figure
2a) and after (Figure 3a) mating of cap 61 with housing 3. Figures 2b and 3b
show cross-
sectional views of apparatus 1 along line IIB and IIIB, respectively, of
Figures 2a and 3a.
Cable 73, shown here as a heating cable, is inserted into first open end 5
through
indention 13. Cable end 75 passes through axial passageway 25 of grommet 23
which is
in contact with first and second positioning arms 31,33 of strain relief
element 27.
(Grommet 23 is held in place by pins which protrude from the bottom of base
element 29,
but are not shown.) Cable end 75 then passes through an opening in base
element 29 and
is gripped by first and second gripping members 39,41. Cable end 75 is
inserted into first
open end 47 of container 43 and is in contact with ribs 57. Compression band
59 is pre-
positioned over ribs 57. Extension section 51 extends toward closed end 65 of
cap 61.
When cap 61 and housing 3 are completely mated (Figures 3a and 3b), grommet 23
is
compressed axially as well as radially due to the tapered shape of the grommet
and the
cavity of the housing. In addition, first and second gripping arms 35,37 are
compressed
against the sides of the cable to ensure that first and second gripping
members 39,41 are
in good contact with cable 73.
Figure 4 is a perspective view of container 43 and Figure 5 is a cross-
sectional
view along line V-V of Figure 4 (without showing extension section 51).
Container 43
has a generally tubular shape with first open end 47 and second closed end 49.
As shown
in this embodiment, first open end 47 has an opening of generally elliptical
shape,
although other shapes, e.g. circular or rectangular, may be suitable. Ribs 57
are in contact
with interior surface 53, while compression band 59 contacts exterior surface
55 in the
region of ribs 57. Contained within container 43, is sealant 77.
CA 02230591 1998-02-26
WO 97/08798 PCT/US96/13803
14
Figure 6 is a top view of apparatus 80 of the third aspect of the invention.
Flexible container 80 is made of first portion 83 and second portion 89. First
portion 83
has first open end 85 and second partially closed end 87. Extending from
second portion
89 are first leg portion 91 and second leg portion 93 which are joined at
second partially
closed end 87. The transition region 111 between first and second portions is
tapered.
Surrounding first portion 83 is rigid band 95, which may be held in place by a
ridge or
edge portion (not shown) around first open end 85.
Figure 7 is a cross-sectional view of the apparatus of Figure 6 along line VII-
VII.
Visible are ribs 97 which extend from interior surface 98. Surrounding
exterior surface
99 is rigid band 95.
Figure 8 is a perspective view of apparatus 80 after elongate heating cable
101 has
been inserted, and Figure 9 is a cross-sectional view along line IX-IX. Core
material, e.g.
conductive polymer, has been removed from first electrode 105 and second
electrode 107
prior to their placement in first and second leg portions 91 and 93,
respectively. Core 103
has been inserted so that exposed end of core 113 is in contact with the
interior surface of
second partially closed end. Ribs 95 contact core 103.
Figure 10 is a top view of apparatus 80 in which first and second guide tubes
115,117 are inserted into first and second leg portions 91,93, respectively,
and through
first portion 83. The diameter of the guide tubes is less than that of the leg
portions but
greater than that of the first and second electrodes.
Though the invention has been described with regard to certain preferred
embodiments thereof, it should be understood that the invention is not
intended to be
limited thereby. The various elements described can be combined as
appropriate, and the
invention is to be limited only by the appended claims.
