Note: Descriptions are shown in the official language in which they were submitted.
CA 02466396 2004-05-05
577-596 PATENT
HIGH TEMPERATURE LIOUIDTIGHT FLEXIBLE METAL CONDUIT FITTING
CROSS-REFERENCE TO RELATED APPLICATIONS:
[0001] This application claims priority to U.S. Provisional Application No.
60/466,921,
filed May 1, 2003.
FIELD OF THE INVENTION:
[0002] The present invention relates generally to a fitting for terminating a
flexible
metallic conduit. More particularly, the present invention relates to a
liquidtight fitting for
terminating flexible metallic conduit, having high temperature resistant
characteristics.
BACKGROUND OF THE INVENTION:
[0003] It has long been known to use fittings to terminate electrical conduit,
especially
electrical conduit of the flexible metallic variety. Such conduit typically
includes the plurality of
insulated electrical conductors surrounded by a flexible metallic armor. An
insulated jacket is
positioned over the metallic armor. Fittings of the liquidtight variety are
used to attach such
conduit to a panel structure such as one for an electrical enclosure. It is
desirable that the fittings
engage the conduit in a liquidtight relationship as defined by the National
Electrical Code
(NEC). Also, the fitting itself should be placed in ground continuity with the
metallic armor of
the conduit.
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[0004] Various fittings of this type are well known in the art. U.S. Patent
No. 3,448,430
issued June 3, 1969, entitled Ground Connector, shows a typical fitting used
to terminate flexible
metallic conduit. Similarly, U.S. Patent No. 3,603,912 issued September 7,
1971 entitled
Raceway Terminator, shows such a fitting attached through the knockout of a
wall of an
electrical enclosure. Each of these patents are incorporated by reference
herein, in their entirty
for all purposes. Additionally, U.S. Patent No. 5,929,383, issued July 27,
1999 entitled
Rotationally Unrestrained Grounding Coupling for External Grounding of
Fittings, shows a
liquidtight fitting terminating a conduit to a panel of an enclosure. The
fitting of the '383 patent
allows external grounding of the fitting. This patent is also incorporated by
reference herein, in
its entirety for all purposes.
[0005] Each of the above referenced fittings effect liquidtight termination of
the conduit
by employing a sealing ring interposed between the body of the fitting and a
gland nut used to
tighten the fitting to the conduit. The sealing ring is typically formed of a
resilient plastic
IS material which compresses upon tightening of the gland nut to the body to
effect a seal thereat
about the jacket of the conduit. The sealing ring is typically formed of a
material which is
sufficiently pliable so as to effect a liquidtight seal with the cable upon
attachment of the gland
nut to the body.
[0006] Recently fittings have been developed which are designed to work in
high
temperature environments. Fittings in the prior art are typically rated for
105"C or less. New
demands on such fittings now require that fittings be rated for up to 150"C.
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[0007] While the basic construction of the existing fitting would satisfy such
requirement
the material which forms the sealing ring can not withstand such high
temperatures. Moreover,
many of the fittings of the type described above also include an insulated
throat for protecting the
insulating conductor which extend therethrough. This insulated throat is also
formed of a plastic
material. It has been found that the plastic material used for the insulated
throat also is not able
to withstand such high temperatures. It is therefore desirable to provide a
liquidtight fitting for
permeating flexible metallic conduit which is rated for high temperature
applications.
SUMMARY OF THE INVENTION:
[0008] An electrical fitting is provided for terminating a flexible metallic
conduit. The
fitting includes an elongate connector body having a conduit receiving end and
a wire egressing
end. A gland nut is attachable to the conduit receiving end of the body. The
sealing ring is
interposed between the gland nut and the body to establish a seal thereat upon
attachment of the
glad nut to the conduit. The sealing ring is formed of high temperature
resistant material.
[0009] The connector body and the gland nut are formed of conductive metal for
establishing ground continuity with the metallic conduit.
BRIEF DESCRIPTION OF THE DRAWINGS:
(0010] Figure 1 is a cross-sectional view of the high temperature liquidtight
flexible
metal conduit fitting of the present invention used for straight through
applications.
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[0011] Figure 2 is a cross-sectional view of a fitting similar to that of
Figure 1, used for
45° applications.
[0012] Figure 3 is a cross-sectional view of a fitting similar to Figure 1
used in 90°
applications.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:
[0013] The present invention provides a high-temperature liquidtight flexible
conduit
fitting useful for terminating a jacketed metal-clad flexible conduit (not
shown) having a
plurality of insulated conductors extending therethrough. Further, the
invention will be
described with respect to the embodiment of Figure 1 showing a fitting for
straight through
applications. It, however, may be appreciated that the present invention may
be practiced with
respect to 45° and 90° fittings 110, 210 shown in Figures 2 and
3, respectively.
[0014] Fitting 10 of the present invention is a muitipart component including
body 12,
gland nut 14, a sealing ring 16, a ground cone 18, an insulated throat 20, and
a locking nut 22.
As will be described in further detail hereinbelow, body 12, gland nut 14,
ground cone 18, and
locking nut 22 may be formed of conductive materials, preferably zinc plated
steel. As will also
be described hereinbelow, the sealing ring 16 and the insulated throat 20 are
formed of high-
temperature resistant insulative plastic materials.
[0015] Body 12 of fitting 10, is an elongate member having a conduit receiving
end 30, a
conductor egressing end 32, and a central bore 34 extending therethrough. The
central bore 34
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of body 12 accommodates the flexible conduit therethrough so that the
insulated conductor
extends through the conductor egressing end 32. In order to insulate the
conductors from the
metallic body 12 and provide protection for the insulation of the conductors,
a cylindrical
insulated throat 20 is interposed into the conductor egressing end 32 of body
12.
[0016] Gland nut 14 is attachable to the conduit receiving end of body 12. The
gland nut
14 may be internally screw threaded to threadingly attach to the external
screw threads of the
conduit receiving end 30 of body 12.
[0017] Interposed within the conduit receiving end 30 of body 12 is ground
cone 18
which, upon termination of the conduit to the fitting 10 establishes ground
connection between
the metal jacket of the conduit and the metallic body 12 of fitting 10. A
locknut 22 is threadingly
attached to the conductor egressing end 32 of body 12 so that the body of the
terminated conduit
can be attached to a panel of an electrical enclosure (not shown). The locknut
22 is also formed
of metallic material so that it can establish ground connection between the
panel and body 12.
The present invention also contemplates attachment of fitting 10 to an
enclosure by screw
threaded attachment of the externally threaded conductor egressing end 32 of
body 12 to a
threaded aperture. In this situation the locknut 22 need not be used.
[0018] Interposed between gland nut 14 and the conduit receiving end 30 of
body 12 is a
sealing ring 16. Sealing ring 16 is formed of suitably resilient material so
that upon screw
attachment of the gland nut 14 to the body 12, the sealing ring will effect a
seal therebetween
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with the jacket of the conduit inserted therein. Sealing ring 16 is formed of
a resiliently
compressible material so as to effectuate such a seal.
[0019] The fitting 10 of the present invention is particularly designed for
high-
temperature application. In accordance therewith, the material forming sealing
ring 16 is formed
of high- temperature resistant resilient plastic. More specifically, by way of
a preferred material,
the present invention provides a sealing ring formed of a nylon 4/6 material.
This material is
sold under the trade name Stanyl TW341 available from DSM Engineering
Plastics. The nylon
4/6 material of the present invention has a higher temperature resistance than
the material
previously used for sealing ring 16 which is commonly nylon 6/6 sold under the
trade name
Zytel 101. Use of nylon 4/6 material for sealing ring 16 allows the fitting of
the present
invention to be rated for applications of 150°C.
[0020] In addition, in order for the fitting 10 to achieve such a rating, the
insulated throat
20 of the present invention may also be formed of the same high-temperature
resistant material.
Thus, the entire connector may be used in an environment where temperatures
reach 150°C and
still maintain adequate liquidtight electrical and mechanical connection.
[0021] Various changes to the foregoing described and shown structures will
now be
evident to those skilled in the art. Accordingly, the particularly disclosed
scope of the invention
is set forth in the following claims.
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