Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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MOISTURE PROOF TELESCOPING COUPLER ASSEMBLY FOR
ELECTRIC METAL TUBES
WITH ENHANCED GROUNDING, SEALING, AND CONTINUITY
FIELD OF THE INVENTION
This invention is generally directed to an expansion
or telescoping coupler assembly for electrical metal
tubes and more specifically to a moisture proof
telescoping or expanding coupler assembly with an
enhanced electrical grounding arrangement for coupling an
electric metal tube that is in relative sliding
relationship to a coupler body, and providing enhanced
continuity.
BACKGROUND OF THE INVENTION
There exist various known types of coupler fittings
for attaching an electric metal tube (EMT) to an
electrical installation such as an electric box or panel
or for joining at least two electrical metal tubes in an
end-to-end relationship. Such known coupler assemblies
include a coupler body to which the electrical metal
tubes are rigidly connected to the coupler body, e.g. as
disclosed in U.S. Patents 268,686; 3,976,314; 4,073,514;
4,091,523. Other known coupler assemblies include a
coupler body wherein at least one connected electrical
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,
metal tube is permitted to telescope or slide relative to
the coupler body or relative to another electrical metal
tube fixedly connected to the coupler body, e.g. as
disclosed in U.S. Patents 5,141,258 and 6,715,803.
With respect to such known sliding or telescoping
coupler assemblies, it has been noted that because of the
relatively free or sliding relationship between the
moveable electrical metal tube relative to the coupler
body, the optimal electrical grounding effect
therebetween is substantially diminished because of
insufficient contact between the complementary surfaces
of the movable electrical metal tube and the associated
coupler body due to the required tolerance necessary to
permit the desired telescoping between the moveable
electric tube and the associated coupler body. Thus, the
optimum desired amount of the electrical grounding effect
therebetween is not achieved.
Additionally, problems have been encountered in
grounding being diminished or compromised over time
resulting in poor grounding. Additionally, movement of
conduits or electric metal tubing during securing of the
electric metal tubing has often led to poor sealing.
Efforts have also been made to improve continuity in
electrical fittings or connectors. Nearly all of these
efforts have been directed to increasing contact surface
area. For example, US Patent 6,709,280 entitled "Fitting
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,
with Improved Continuity" issuing March 23, 2004 to
Gretz. Therein disclosed is a fitting for connecting a
cable to an electrically conducting junction box having a
sloped grounding tang in which the downward slope causes
the fitting to be drawn tightly against the junction box
wall. Another fitting is disclosed in US Patent 6,780,029
entitled "High Continuity Electrical Fitting" issuing
August 24, 2004 to Gretz. Therein disclosed is a fitting
for connecting a cable to an electrically conducting
junction box that has larger grounding tangs providing
much greater surface contact area, thereby improving
continuity and lowing millivolt drop.
While these prior techniques improve continuity they
have done so by increasing surface area contact. While
this may provide some improvement in continuity, there is
a limit to the increase surface area contact that can be
obtained in an electrical connector or fitting.
Therefore, there is a need for a different approach in
obtaining improved continuity or conductivity between the
electrical conductor or fitting, the electrical box, or
the cable. This has been a particularly difficult problem
for telescoping coupler assemblies that inherently must
have sliding surfaces.
Therefore, there is a need for a telescoping coupler
assembly with improved grounding, sealing, and
continuity.
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SUMMARY OF THE INVENTION
In accordance with one embodiment of the present
invention there is provided an electric metal tube coupler
assembly comprising: a coupler body having a bore extending
therethrough and having first and second opposed end
openings adapted to receive an electric metal tube, a first
seal placed adjacent the first opposed end opening, an
internal shoulder having a ramp facing the second opposed
end, and a second seal placed adjacent the internal
shoulder, whereby the internal shoulder and the ramp aids
in centering the electric metal tube within the coupler
body when the electric metal tube is placed within the
coupler body.
In accordance with another embodiment of the present
invention there is provided an electric metal tube coupler
assembly comprising: a coupler body having a bore extending
therethrough and having first and second opposed end
openings adapted to receive an electric metal tube, a first
seal placed adjacent the first opposed end opening, a
grounding spring groove formed in the interior surface of
the coupler body adjacent the first seal, a grounding
spring placed within the grounding spring groove, an
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internal should formed on the interior surface of the
coupler body adjacent the second opposed end, and a second
seal placed adjacent the internal shoulder. The grounding
spring provides electrical continuity between the coupler
body and an electrical metal tube placed within the coupler
body.
In accordance with a further embodiment, there is
provided an electric metal tube coupler assembly
comprising: a coupler body having a bore extending
therethrough and having opposed end openings, an electric
metal tube, the electric metal tube having an end portion
adapted to be slidably received in one of the end openings,
an inwardly extending stop means disposed within the bore
between the opposed end openings, sealing means disposed in
the one end opening circumscribing the end portion of the
electric metal tube, slidably disposed within the one end
opening, a grounding spring groove formed in the interior
surface of the coupler body adjacent the sealing means, a
grounding spring placed within the grounding spring groove,
a grounding ring connected to the electric metal tube, and
a flexible grounding strap interconnecting the grounding
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ring to the coupler body. The metal tube coupler is
grounded externally by the flexible grounding strap and
internally by the grounding spring providing enhanced
electrical grounding.
In accordance with a still further embodiment, there
is provided a coupler assembly comprising: a coupler body
having a bore extending therethrough and having first and
second opposed end openings adapted to receive a metal
tube, a first seal placed adjacent the first opposed end
opening, a grounding spring groove formed in the interior
surface of the coupler body adjacent the first seal, a
cantered grounding spring placed within the grounding
spring groove, a grounding ring, whereby the grounding ring
is capable of connecting to an electric metal tube, a
flexible grounding strap electrically interconnecting the
grounding ring to the coupler body, an internal shoulder
formed within the coupler body, a ramp adjacent the
internal shoulder facing the second opposed end, a second
seal placed adjacent the internal shoulder, and means,
adjacent the second opposed end, for fixedly securing a
metal tube to the second opposed end, wherein the coupler
assembly is grounded externally by the flexible grounding
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strap and internally by the cantered grounding spring
providing enhanced electrical grounding and the ramp
centers the metal tube within the coupler body adjacent the
second seal.
Further still, the present invention provides an
electric metal tube coupler assembly comprising: a coupler
body having a bore extending therethrough and having first
and second opposed end openings adapted to receive an
electric metal tube, a first seal placed adjacent the first
opposed end opening, an internal circumferential groove
placed in the coupler body adjacent the first seal, a
grounding spring placed within the internal circumferential
groove, a metal plating placed on the grounding spring, and
a second seal placed adjacent the second opposed end
opening, whereby the metal plating improves continuity
between the electric metal tubes placed within the electric
metal tube coupler.
Still further, the present invention provides an
electric metal tube coupler assembly comprising: a coupler
body having a bore extending therethrough and having
opposed end openings, an electric metal tube, the electric
metal tube having an end portion adapted to be slidably
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received in one of the opposed end openings and having a
first electrical conductivity, an inwardly extending stop
means disposed within the bore between the opposed end
openings, sealing means disposed in the one of the opposed
end openings circumscribing the end portion of the electric
metal tube slidably disposed within the one of the opposed
end openings, a grounding spring groove formed in the
interior surface of the coupler body adjacent the sealing
means, a grounding spring placed within the grounding
spring groove, a metal plating formed on the grounding
spring, the metal plating having a second electrical
conductivity higher than the first electrical conductivity,
a grounding ring connected to the electric metal tube, and
a flexible grounding strap interconnecting the grounding
ring to the coupler body, whereby the metal tube coupler is
grounded externally by the flexible grounding strap and
internally by the grounding spring providing enhanced
electrical grounding and continuity.
A still further embodiment provides a coupler assembly
comprising: a coupler body having a bore extending
therethrough and having first and second opposed end
openings adapted to receive a metal tube, the coupler body
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having a first electrical conductivity, a first seal placed
adjacent the first opposed end opening, a grounding spring
groove formed in the interior surface of the coupler body
adjacent the first seal, a cantered grounding spring placed
within the grounding spring groove, a metal plating formed
on the cantered grounding spring, the metal plating having
a second electrical conductivity higher than the first
electrical conductivity of the coupler body, a grounding
ring, whereby the grounding ring is capable of connecting
to an electric metal tube, a flexible grounding strap
electrically interconnecting the grounding ring to the
coupler body, an internal shoulder formed within the
coupler body, a ramp adjacent the internal shoulder facing
the second opposed end, a second seal placed adjacent the
internal shoulder, and means, adjacent the second opposed
end, for fixedly securing a metal tube to the second
opposed end, whereby the coupler assembly is grounded
externally by the flexible grounding strap and internally
by the cantered grounding spring providing enhanced
electrical grounding and continuity and the ramp centers
the metal tube within the coupler body adjacent the second
seal.
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It is a feature of one embodiment of the present
invention to provide a coupler assembly that has a coupler
body with an inlet end portion arranged for telescopically
receiving an electric metal tube in sliding relationship
relative thereto and wherein the optimum desired amount of
an electrical grounding is achieved.
Another feature of one embodiment is to provide a
coupler assembly having an arrangement for prohibiting the
seepage of moisture into the coupler assembly and the
relative telescoping members.
Another feature is to provide, in one embodiment a
coupler assembly having a coupler body for slidably
receiving an electric metal tube connected thereto that is
positively electrically grounded to the coupler body.
Another feature of one embodiment is to provide a
coupler assembly for electrical metal tubes which is
relatively simple in structure, easy to manufacture,
positive in operation, and moisture proof.
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It is another feature of one embodiment of the present
invention to improve continuity and lower voltage drop
across an electrical fitting.
It is an advantage of one embodiment of the present
invention that electrical grounding is made more reliable.
It is another advantage of one embodiment of the
present invention that improved weather tight sealing is
obtained while attaching or tightening an electric metal
tube to the coupler assembly.
It is yet another advantage of one embodiment of the
present invention that a lower voltage drop across an
electrical fitting is obtained.
It is a feature of one embodiment of the present
invention that an internal grounding cantered spring is
used.
It is another feature of one embodiment of the present
invention that a cam or ramp having a predetermined radial
dimension range is placed adjacent a seal.
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It is yet another feature of one embodiment of the
present invention that a plating of high electrical
conductivity material is formed on an internal grounding
cantered spring.
The foregoing advantages and features are attained
by a coupler assembly that includes a coupler body for
securing an electrical metal tube to an electrical
structure such as an electrical box or panel or for
connecting at least a pair of electrical metal tubes in
end-to-end relationship wherein at least one of the
electric metal tubes is rendered movable relative to the
other. The coupler body includes a bore extending
therethrough to define opposed open ends. One open end
of the coupler body may be adapted to be fixedly
connected to an electric box, panel, or adapted to
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receive another electric metal tube. The other open end
of the coupler body for receiving an electric metallic
tube is sized and shaped to telescopically receive an end
portion of the electric metal tube for relative sliding
or telescoping movement with respect thereto. The end of
the coupler body adapted for securing the coupler body to
an electrical box or panel may be formed to accommodate a
lock nut or a snap fit adaptor such as disclosed in U.S.
Patents 6,555,750, 6,737,584, 6,916,688, 6,935,891 or
other like patents. Alternatively, each of the opposed
ends of the coupler body may be formed to snugly receive
an electric metal tube wherein one electric metal tube is
fixedly secured to the coupler body by means of a
fastener, and the other electric metal tube is
telescopically mounted relative to the other end of the
coupler body, as illustrated herein.
Connected adjacent to the end of the coupler body
for receiving the telescoping tube is a grounding means
that includes a grounding ring which is arranged to be
slipped onto and fixedly secured to an end portion of the
electric metal tube telescopically fitted into the
corresponding open end of the coupler body.
The grounding ring is connected to the coupler body
by a wire mesh grounding strap of a predetermined length
sufficient to provide for the relative sliding or
telescoping movement of the moveable electric metal tube
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relative to the coupler body. The arrangement is such
that the moveable electric metal tube is positively
electrically grounded to the coupler body throughout its
entire range of movement to provide for optimal
electrical grounding between the coupler body and the
associated telescoping electric metal tube.
Disposed within the bore of the coupler body are
sealing rings for rendering the coupler assembly moisture
proof without seriously limiting the relative sliding
relationship between the telescoping electric metal tube
and the associated coupler body.
Additionally, a cantered grounding spring is placed
around the internal circumferential surface of the
coupler body providing internal electrical grounding and
continuity between the coupler body and attached electric
metal tube, rigid pipe, or other conductive conduits.
To improve continuity and lower the voltage drop
across the coupler, the cantered grounding spring is
plated or coated with a metal or alloy having high
conductivity, such as tin or a tin alloy.
A ramp or cam placed within the coupler body
adjacent a sealing ring or seal improves sealing when a
set screw is used to secure the electrical metal conduit
within an adjacent end. The ramp or cam centers the
electrical metal conduit adjacent the seal so that a
uniform circumferential sealing pressure is obtained.
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BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective view of a telescoping
coupler assembly for an electric metal tube embodying the
present invention.
Fig. 2 is a perspective view of the coupler body,
absent the moveable electric metal tubes.
Fig. 3 is a top view of Fig 2.
Fig. 4 is a section view of the coupler body taken
along line 4-4 on Fig. 3.
Fig. 5 is a longitudinal sectional view of the
coupler assembly of Fig. 1.
Fig. 6 is a detail perspective view of a modified
tube retainer for fixedly securing an electric metal tube
to the coupler body.
Fig. 7 is a fragmentary sectional view of a modified
form of the invention utilizing the modified tube
retainer of Fig.6 wherein the limiting tang and retainer
tang are shown in their operative positions.
Fig. 8 is a sectional view similar to Fig. 7,
wherein the tube retaining tang is shown in the operative
position.
Fig. 9 is a perspective view illustration another
embodiment of the coupler body of the present invention.
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Fig. 10 is a cross sectional view taken along line
10-10 in Fig. 9.
Fig. 11 is a partial cross sectional view of one end
of the coupler body.
Fig. 12 is a partial cross sectional view of one end
of the coupler body illustrating the operation of the cam
or ramp.
Fig. 13 is a partial cross sectional view of the
other end of the coupler body illustrating the cantered
grounding spring.
Fig. 14 is a partial cross sectional view of the
other end of the coupler body illustrating the electrical
coupling of the cantered grounding spring with the
electric metal tube.
Fig. 15 is a partial exploded view illustrating
another embodiment of the present invention adapted for
use with threaded rigid electric metal pipe.
Fig. 16 is a partial cross section of one end of the
embodiment illustrated in Fig. 15 illustrating use with
threaded rigid electric metal pipe.
Fig. 17 is a partial cross section of the other end
of the embodiment illustrated in Fig. 15 illustrating use
with threaded rigid electric metal pipe.
Fig. 18 is a partial cross sectional view of another
embodiment of the invention illustrating the end of a
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coupler body having a cantered grounding spring plated or
coated with a high conductivity material.
Fig. 19 is an enlarged cross section of the coated
or plated cantered grounding spring illustrated in Fig.
18.
Fig. 20 is a partial cross sectional view of the
embodiment illustrated in Fig. 18 of the invention
illustrating the electrical coupling of the coated or
plated cantered grounding spring with the electric metal
tube.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings there is illustrated in
Fig. 1 a telescoping coupler assembly 10 embodying the
invention. As shown, the coupler assembly 10 includes a
coupler body 11 comprising an elongated tube or cylinder
of a predetermined length defining a bore 13 extending
therethrough that is opened at the opposed ends 11A, 11B
of the coupler body 11. In the illustrated embodiment of
Fig 1 the coupler body 11 is configured to connect at
least two electric metal tubes 14 and 15 in end-to-end
relationship wherein one electric metal tube, e.g. tube
14, is arranged to be received within the end opening 11B
of the coupler body 11 and fixedly secured thereto by
means of suitable fasteners e.g. one or more set screws
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16. The other electric metal tube 15 is adapted to be
slidably received within the other open end 11A of the
coupler body 11. The arrangement is such that tube 15 is
rendered slidably or telescopically mounted within the
open end 11A of the coupler body 11 to accommodate any
protracting or retracting movement of the electric metal
tube 15 relative to the coupler body 11 or the other
electric metal tube 14 fixedly connected to the coupler
body 11.
As best seen in Fig. 4, the coupler body 11 is
provided with a circumscribing inwardly projecting
external groove 17 to define an internal stop shoulder
17A. The shoulder stop 17A functions to limit the
distance that the fixed tube 14 may be inserted into the
open end 11B of the coupler body 11 as noted in Fig. 5.
As shown in Fig. 5, the stop shoulder 17A is located
along the length of the coupler body 11 at a point closer
to the end opening 11B than to end opening 11A. The
arrangement is such that the longer portion A of the
coupler body 11 to the right of the stop shoulder 17A has
a length sufficient for the electric metal tube 15 to be
telescopically mounted relative thereto so as to be
slidably displaced therein as the tube 15 telescopes
relative to the coupler body 11 so as to not allow the
movable tube 15 to separate from the coupler body 11.
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To prohibit any moisture or water from entering into
the coupler assembly and the tubes connected thereto, the
coupler body is provided with end seals 18-18. As shown
at least two such end seals 18-18 are provided, one to
either side of the stop shoulder 17A.
The seat 18A for accommodating the respective seals
18-18 is defined by a circumscribing internal grove 18A
which is formed in any suitable manner, e.g. by swedging,
pressure rolling or molding to deform the material of the
coupler body as illustrated in Fig. 5. While the
illustrated embodiment of Fig 5 is described as having
one seal 18 on opposite sides of the internal stop 17A,
it will be understood that the number of such seals may
be varied as required.
As shown in Fig 1, the insertion of electric metal
tube 14 into the opened end 11B of the coupler body 11 is
limited by the internal stop 17A. With the tube 14
properly seated in the open end 11B of the coupler body
11, the tube 14 is fixedly secured thereto by means of a
suitable fastener, e.g. set screw 16.
The slidable or telescoping tube 15 is inserted into
the other open end 11A of the coupler body 11. The length
A of the coupler body 11 is sufficient to permit tube 15
to be slidably disposed relative thereto without causing
the tube 15 to be separated therefrom. In other words,
the length A of the coupler body is greater than the
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maximum permitted linear displacement of the tube 15
within the coupler body 11.
Because tube 15 is slidably disposed within the
coupler body 11, the coupler body is provided with a
means for insuring the maximum optimizing of a positive
electrical ground between telescoping tube 15 and the
coupling body 11. In the illustrated embodiment, this is
attained by a grounding ring 19 which is sized and shaped
so as to be snugly fitted onto an end portion of the
slidable or telescoping tube 15. Suitable fasteners such
as set screws 20 fixedly secure the grounding ring 19 to
the telescoping metal tube 15.
A grounding strap 21 connects the grounding ring 19
to the coupler body 11. A mounting plate 21A and 21B is
connected to each end of the grounding strap 21 to
provide the means whereby the grounding strap 21 is
securely fixed to the grounding ring 21 and coupler body
11 by suitable fasteners, such as bolts or screws 22-22.
Preferably the grounding strap portion 210 connected
between the opposed end mounting plates 21A and 21B
comprises a woven wire mesh strap 21C that renders the
grounding strap 21 flexible for accommodating the
telescoping or sliding movement of tube 15 relative to
the coupler body 11. Thus the grounding strap 21 is free
to flex or stretch in accordance with the linear or
telescoping displacement of the electric metal tube 15 as
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the tube 15 telescopes or slides relative to the coupler
body 11. In doing so, the grounding effect of the movable
tube relative to the coupler body 11 is maximized
throughout the entire telescoping range of the coupler
assembly.
By providing seals 18 between the coupler body 11
and the respective associated electric tubes 14 and 15,
the coupler assembly 10, described, also prohibits
moisture or water from seeping into the coupler assembly
and the electrical tubes 14, 15 associated therewith.
While the embodiments illustrate the coupler body 11
having opposed end openings 11A, 11B of substantially
equal diameters, it will be understood that the coupler
body 11 may have opposed end openings with different
sized diameters for connecting electric metal tubes of
corresponding different diameters in end-to-end
relationship.
It will also be noted that the short end B of the
connector body 11 may be formed for accommodating a snap
fit locking ring (not shown) of the type disclosed in
U.S. Patents 6,555,750, 6,737,584, 6,860,758, 6,935,891
and 6,916,988 and the like whereby one end of the coupler
body 11 may be formed to be snap fitted or secured to an
electronic box or panel in the manner described in the
foregoing noted U.S. Patents which are incorporated by
reference herein in the event it is desirable to couple a
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telescoping electric metal tube directly to an electric
box or panel.
With the foregoing described structures it will be
noted that the electrical grounding effect between the
telescoping electric metal tube 15 and the coupler body
11 is rendered more positive than simply relying merely
upon the sliding motion of the telescoping metal tube
relative to the coupler body to produce the electrical
ground effect, which may be problematic due to a space
tolerance required between the sliding tube and the
coupler body.
Figs. 6 and 7 are directed to a modified form of the
invention. The coupler assembly 10A is similar to the
coupler assembly 10 herein described with the exception
that the means for fixedly securing the fixed electric
metal tube 25 to the coupler body 26 is achieved by a
retainer ring 27 constructed to permit the fixed tube 25
to be snap fitted into one end 26A of the coupler body 26
that will also resist any unintentional separation of the
fixed tube 25 from the coupler body 26 by an
unintentionally applied force tending to cause separation
of the fixed tube 25 from the coupler body 26.
As illustrated in Fig. 6, the retaining ring 27 is
preferably formed of spring steel with a circular
configuration capable of being inserted into the end
opening 26A of the coupler body 26. In the illustrated
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embodiment, the retaining ring 27 has its opposed ends
27A and 27B slighted spaced apart to form a split ring.
As the material of the retainer ring 27 is formed of
spring steel, the described retainer ring 27 has an
inherent resiliency which in its relaxed state is
provided with an outer diameter that is slightly greater
than the internal diameter D of the open end 26A of the
coupler body 26.
Referring to Fig. 6, the split ring retainer 27 is
provided with a leading edge 27C, a trailing edge 27D,
and a plane surface 27E therebetween. Blanked or formed
out of the plane surface 27E are one or more tube
retaining tangs, 28, one or more locking tangs 29, and
one or more limit tangs 30. As shown in Fig. 6 the tube
retaining tangs 28, the locking tangs 29 and limit tangs
30 are alternating and circumferentially spaced about the
circumference of the retaining ring 27.
The tube retaining tangs 28 are inwardly bent out of
the plane surface 27E and are inclined or angled in the
direction of the leading edge 27A of the retainer ring
27. The locking tangs 29 are outwardly bent relative to
the plane surface 27E of the retainer ring 27 and are
oppositely inclined or angled toward the trailing edge
27D of the retainer ring 27. The limit tangs 30 are also
blanked or formed out of the plane surface and outwardly
bent relative to the plane surface 27E and are angled or
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inclined toward the leading edge of the retaining ring
27.
As illustrated in Fig. 7, the retainer ring 27 being
split may be compressed to permit the retainer ring 27 to
be inserted into the open end 26A of the coupler body 26.
The arrangement is such that with the retainer ring in
its compressed state when inserted into the end opening
26A, will cause the outwardly bent limit tang 30 to
engage an internal surface portion of the coupler body
upon the removal of the compressing force thereon to
limit the distance the retainer ring 27 may be inserted
into said end opening 26A.
Upon releasing the compression force acting on the
retainer ring 27, the inherent resiliency of the split
retainer ring 27 will cause the diameter of the retainer
ring 27 to expand with a sufficient force to fixedly
secure the retainer ring 27 within the end opening 26A
whereby the outwardly bent locking tangs 29 will impart
an additional "bite" force against the inner surface of
the end opening to resist any unintentional pull out
force that may be applied on the retainer ring.
With the retainer ring 27 frictionally secure within
the open end 26A of the connector body 26, as above
described, the arrangement is such that the electric
metal tube 25 can be fixedly secured to the end opening
26A of the coupler body 26 by simply pushing the end
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portion of electric tube 25 into the end opening 26A and
through the retainer ring 27 until the end of the tube 25
engages the internal stop 31. As the end of the electric
metal tube 25 passes through the retainer ring 27 the
tube retaining tangs 29, which are inwardly bent as
described herein, will inherently exert a holding or
biting force on the electric metal tube sufficient to
resist an unintentional pulling force imparted onto the
electric metal tube 25. In all other respects, the
embodiment disclosed and described with the embodiment of
Figs. 6 and 7 is similar to the embodiments herein before
described with respect to Figs. 1 to 5.
The locking tangs 29, being outwardly bent, are
sufficiently resilient so as to flex inwardly permitting
the retainer ring to also pass through the end opening 26
of the coupler body 26 and spring outwardly, when ring 27
is fully seated, to bite into the internal surface of the
bore of the coupler body to resist or prohibit
unintentional separation of the retaining ring 27 from
the coupler body in the assembled position.
With the retainer ring 27 described, installation of
the electric metal tube 25 to the coupler body 26 may
also be effected by positioning the retaining ring 27
onto the end of the electric metal tube 25, and then
inserting the electric metal tube with the retainer ring
27 secured thereto into the end opening 26A of the
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coupler body 26 until the end of the tube engages the
stop shoulder 30 as noted in Fig. 7. In this assembled
position, as seen in Fig. 7, the tube retaining tangs 28,
which are inwardly bent and inclined in the direction of
the leading edge 270 of the retaining ring 27, are bias
to exert a biting force onto the metal tube 26 with a
force sufficient to prohibit unintentional separation of
the tube 25 therefrom. At the same time the outwardly
bent locking tangs 29, inclined in the direction of the
trailing edge 27D, will exert a biting force onto the
internal surface of the bore 32 to resist unintentional
withdrawal of the retainer ring 27 and the associated
tube 25 from the open end 26A of the coupler body 26.
Figs. 9-17 illustrate another embodiment of the
present invention. This embodiment of the present
invention utilizes an internal cantered grounding spring.
The coupler body 111 has a first opposed end 111A and a
second opposed end 111B. Adjacent the second opposed end
111B are set screws 116. Adjacent the first opposed end
111A is attached an end mounting plate 121B attached to
the coupler body 111 by screw or bolt 122. Attached to
the end mounting plate 121B is a grounding strap 121. The
grounding strap 121 is attached to grounding ring 119 by
end mounting plate 121A and screw or bolt 122. Also
attached to the grounding ring 119 are set screws 120.
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Fig. 10 more clearly illustrates the improvements in
this embodiment of the present invention that make for
better sealing or weatherproofing and enhanced grounding.
Fig. 10 is a cross section of the coupler body 111 that
more clearly illustrates the improvements in this
embodiment. In this embodiment the coupler body 111 has
several structural enhancements to provide improved
performance. To provide improved sealing or
weatherproofing, the internal shoulder 117A is utilized
having a ramp or cam 117B. The ramp or cam 117B is facing
and adjacent the second opposed end 111B. A seal 118,
which may be an 0-ring of a pliable material such as
rubber or silicone or other equivalent flexible or
compressible material, is placed within an internal
circumferential grove 118A. The seal or sealing ring 118
is placed adjacent the ramp or cam 117B facing towards
the open second opposed end 111B. An external grove 117
may be used to identify the position of the internal
shoulder 117A from the exterior of the coupler body 111.
The ramp or cam 117B greatly facilitates the
centering of an electric metal tube placed within the
second opposed end 111B. Accordingly, this improved
structure prevents leakage and improves the weather-tight
seal of the telescoping coupler assembly.
Adjacent the other first opposed end 111A is another
seal or sealing ring 118 held within another internal
CA 02707276 2010-06-10
circumferential groove 118A which is adjacent an internal
grounding spring groove 131A. Within the internal
grounding spring groove 131A is a cantered grounding
spring 131. The cantered grounding spring 131 has the
helical coils of the spring cantered, or angled, relative
to the perimeter of the spring so that the spring is
compliant or compressible in the radial direction. The
grounding spring 131 is preferably copper so as to be
electrically conductive and provides electrical
continuity or grounding to the coupler body 111 and an
electrical metal tube placed within the coupler body 111.
Accordingly, as illustrated in Fig. 10, the
telescoping coupler assembly has internal grounding
through the grounding spring 131 and external grounding
through the grounding strap 121. Therefore, should the
external grounding strap 121 be compromised or severed,
for whatever reason, the internal grounding spring 131
will provide adequate grounding. Accordingly, the present
invention by providing an internal cantered grounding
spring 131 provides enhanced or additional electrical
grounding.
Figs. 11 and 12 more clearly illustrate the improved
sealing or weather-tight feature of the present
invention. In Fig. 11 the ramp or cam 1178 positioned
between the internal shoulder 117A and the seal or
sealing ring 118 is more clearly illustrated. The ramp or
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cam 117B has a larger diameter 1170 and a smaller
diameter 117D. The distance between the diameters or
radial height between 117C and 117D is selected to be in
the range of the radial dimensional tolerances of an
electrical metal tube 114 intended to be placed within
the second opposed end 111B. The positioning of the seal
or sealing ring 118 adjacent the ramp or cam 117B greatly
improves the ability of the telescoping coupler assembly
111 to be sealed so as to be weatherproof or weather-
tight and more fully assures that a uniform seal is
formed around the entire outer circumference of the
electric metal tube 114. This is especially important
when the set screws 116 are tightened to securely hold
the electric metal tube 114 in position. As the set
screws 116 are tightened they tend to force the portion
of the electric metal tube 114 adjacent the set screw 116
to be non-concentric within the coupler body 110. Without
the ramp or cam feature of the present invention, this
may result in an uneven gap circumferentially formed
around the electric metal tube 114 making it difficult to
seal or resulting in an unreliable seal. However with the
ramp or cam 117B placed adjacent the seal or sealing ring
118, at least in the portion of the electric metal tube
114 adjacent the seal or sealing ring 118 the gap formed
around the external surface of the electric metal tube
114 will be substantially uniform and therefore provide a
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much improved uniform seal less prone to leakage. The end
of the pipe 114A will be wedged at a point longitudinally
or axially along the ramp or cam 117B. If the external
diameter of the electric metal tube 114 is at the low end
of the design specification, the end 114A of the electric
metal tube 114 will be nearly adjacent the internal
shoulder 117A. When the external diameter of the electric
metal tube 114 is at the larger end of the design
specification, the end 114A of the electric metal tube
114 will come to rest closer to the larger diameter 117C
of the ramp or cam 117B and closer to the seal or sealing
ring 118. Accordingly, by providing a uniform spacing
adjacent the seal or sealing ring 118 improved sealing
and weatherproofing is obtained with little likelihood of
leakage.
Figs. 13-14 illustrate the enhanced grounding
feature of the present invention. Figs. 13-14 more
clearly illustrate the structure and function of the
internal grounding feature of this embodiment of the
present invention.
Fig. 13 more clearly illustrates the cantered
electrical grounding spring 131 retained within the
internal grounding spring groove 131A. The electrical
grounding spring 131 forms a circle or ring of helical
coils. The helical coils of the grounding spring 131 are
cantered or angled so as to make them readily compliant
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in the radial direction. The helical coils of the
grounding spring 131 are in a plane that is angled
relative to the radial direction of the circle or loop
formed by the helical coils. Accordingly, when a radial
pressure is applied to the cantered grounding spring 131
the helical coils comply in the radial direction to
maintain continuous contact with the inserted electric
metal tubing.
Fig. 14 illustrates the placement of an electric
tube 115 within the first opposed end 111A so as to
compress the cantered grounding spring 131. Accordingly,
the cantered grounding spring 131 creates an electrical
grounding connection between the electric metal tube 115
and the coupler body 111. Therefore, this embodiment of
the present invention provides both internal and external
grounding. This improves safety and enhances overall
grounding of the telescoping coupler assembly. Therefore,
should the external grounding strap be severed or
removed, the internal grounding will prevent an
electrical grounding fault or discontinuity.
Fig. 15-17 illustrates another embodiment of the
present invention that is adapted to mate with electric
rigid pipe that is threaded. In Fig. 15 a sliding rigid
pipe adaptor 140A has a sliding insert end 142A adapted
to be inserted into the first opposed end 111A. A
threaded end 114A has female threads 146A therein. The
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,
female threads 146A are adapted to mate and thread onto
the male threads of a rigid pipe. Fixed rigid pipe
adapter 1403 has a fixed insert end 142B adapted to be
inserted within the second opposed end 111B of the
coupler body 111 and fixed therein by set screw 116.
Threaded end 144B has female threads 1463 adapted to
receive the male threads of a rigid pipe. When the fixed
rigid pipe adaptor 140B is placed within the second
opposed end 111B the set screws 116 are tightened,
securely holding the fixed rigid pipe adaptor therein.
Similarly, the sliding rigid pipe adaptor 140A is placed
within the first opposed end 111A and slidably retained
therein. In this embodiment the telescoping coupler
assembly is adapted to be used with threaded rigid
electric pipe that is used as a conduit to contain
electric wires.
Fig. 16 illustrates an end of the coupler body 111
holding the fixed rigid pipe adaptor 1403 with female
threads 146B inserted into the opposed end 111B. The
fixed rigid pipe adaptor 140B is held securely in place
by a set screw 116, fastener, or other equivalent means
for fixedly securing a metal tube. A rigid electric pipe
148 having male threads 150 is illustrated mating with
the fixed rigid pipe adaptor 140B.
Fig. 17 illustrates the other end of the coupler
body 111 holding sliding rigid pipe adaptor 140A with the
CA 02707276 2010-06-10
threaded end 146A. Threaded within the threaded end 146A
is rigid electric pipe 152 having male threads 154. The
grounding ring is attached to the external grounding,
strap and end mounting plate 121B may be attached to the
sliding rigid pipe adaptor 140A or the rigid electric
pipe 152 depending upon the length of the sliding rigid
pipe adaptor 140A. The sliding rigid pipe adaptor 140A is
internally grounded by the grounding spring 131.
Accordingly, this embodiment of the present
invention provides for an improved and enhanced
telescoping coupler assembly that has improved
weatherproofing and grounding. Even when the external
grounding strap 121 is severed or removed, the internal
grounding spring 131 remains in grounding contact
providing electrical continuity for grounding.
Figs. 18-20 illustrate another embodiment of the
present invention. In this embodiment electrical
continuity is enhanced. This embodiment is similar to the
embodiment illustrated in Figs. 13 and 14 except that
cantered grounding spring 231 is plated with a metal or
alloy 232 having high conductivity, such as tin or a tin
alloy. The copper or copper alloy cantered grounding
spring 231 is plated with a metal having electrical
conductivity higher than the electric metal tube or
coupler body and preferably higher than zinc, such as and
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preferable tin or a tin alloy. The plating of a high
conductivity metal on the cantered grounding spring 231
is preferably formed on the entire surface. The tin plate
or plating may be a matte or bright finish and preferable
has a thickness of between 0.00015 and 0.00030 inches, or
between 0.0381 and 0.0762 millimeters. The tin plating
may be electrodeposited using standard techniques, such
as per ASTM B545 (Type I) standards. Different high
conductivity metals and tin or tin alloys may be used,
such as tin-zinc, tin-lead, or tin-nickel. Tin has a much
higher conductivity than zinc, and is similarly corrosion
resistant. Additionally, high conductivity metals other
tin or tin alloys may be used such as silver or gold. The
plating of the copper cantered grounding spring 232
substantially improves the conductivity and continuity of
the telescoping coupler assembly. Corrosion is also
reduced which may adversely affect continuity.
The reduced surface area contact and the lower
contact pressures of the cantered grounding spring in the
telescoping coupler assembly versus a non-telescoping
coupler assembly often results in lower continuity and
increased voltage drop across the coupler assembly.
Typically, there are electrical standards, such as
Underwriters Laboratory or UL standards, that have a
maximum permitted voltage drop across an electrical
fitting, such as a coupler assembly. These standards
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assure for a safe electrical connection that is
adequately bonded or grounded. In experiments using a
copper alloy spring that was bright tin plated, a voltage
drop across the telescoping coupler of only 6mV or lower
was obtained. The appropriate Underwriters Laboratories
specification, UL 514B, requires less than a 10mV voltage
drop.
While the terms bonding and grounding or often used
synonymously, the present invention is more accurately
directed to electrical bonding. The National Electric
Code defines bonding as a low impedance path obtained by
securely joining all non-current carrying metal parts to
assure electrical continuity and having the capacity to
conduct safely any current likely to be imposed upon it
and defines grounding as a permanent and continuous
conducting path to the earth with sufficient ampacity to
carry any fault current liable to be imposed upon it, and
of sufficiently low impedance to limit the voltage rise
above ground and to facilitate the operation of the
protective devices in the circuit. Therefore the present
invention improves continuity of telescoping coupler
assemblies that may be applied to either electrical
bonding or grounding. The present invention quite
surprisingly results in a substantial decrease in voltage
drop across the telescoping coupler assembly. As a result
continuity of the telescoping coupler assembly is
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improved resulting in a telescoping coupler assembly
having better electrical properties.
While the invention has been described with respect
to the different embodiments, other variations and
modifications can be made without departing from the
spirit or scope of the invention.
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