U.S. patent number 3,836,941 [Application Number 05/376,601] was granted by the patent office on 1974-09-17 for electrical connector with resilient pressure pad.
This patent grant is currently assigned to Thomas & Betts Corporation. Invention is credited to Hyman Izraeli.
United States Patent |
3,836,941 |
Izraeli |
September 17, 1974 |
ELECTRICAL CONNECTOR WITH RESILIENT PRESSURE PAD
Abstract
The connector of the present invention is arranged to couple an
electrical conductor to a terminal point and to compensate for the
different coefficients of expansion between the connector and the
conductor. A resilient pressure pad is added to the normal metallic
pressure plate of a mechanically operated connector to force a
conductor, placed within the connector, against a contact portion
of the connector regardless of changes in the dimensions of the
conductor and connector resulting from thermal expansion and
contraction of the dissimilar metals. The connector consists of a
tubular body for the receipt therein of an electrical conductor and
a pressure plate, operated by a mechanical screw, to exert
connecting pressure between the conductor and the connector body. A
resilient pad member, added to the pressure plate, permits the
connector to accommodate dimensional changes, while the coupling
between the pressure plate and resilient pad member limits
tightening of the connector to prevent destruction of the resilient
pad member.
Inventors: |
Izraeli; Hyman (West Caldwell,
NJ) |
Assignee: |
Thomas & Betts Corporation
(Elizabeth, NJ)
|
Family
ID: |
23485673 |
Appl.
No.: |
05/376,601 |
Filed: |
July 5, 1973 |
Current U.S.
Class: |
439/431;
439/810 |
Current CPC
Class: |
H01R
4/363 (20130101) |
Current International
Class: |
H01R
4/28 (20060101); H01R 4/36 (20060101); H01r
011/20 () |
Field of
Search: |
;339/95,97,272 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
719,991 |
|
Dec 1954 |
|
GB |
|
496,659 |
|
Oct 1953 |
|
CA |
|
Primary Examiner: McGlynn; Joseph H.
Attorney, Agent or Firm: Teschner; David Woldman; Jesse
Claims
I claim:
1. In a connector for coupling an electrical conductor to a
terminal position of the type having a tubular body having first
and second spaced apart portions for receipt of an electrical
conductor therebetween; a terminal portion for engagement with a
terminal position at a first end and having its second end
positioned adjacent said second portion of said tubular body for
receipt thereon of an electrical conductor; a clamping screw
threadably engaging a threaded hole in said first portion of said
tubular body; said clamping screw having a slot for receiving a
tool at a first end thereof for advancing and retracting the second
end thereof into and out of said tubular body and a pressure plate
coupled to said second end of said clamping screw, the improvement
comprising: resilient pad means coupled to said pressure plate for
engaging an electrical conductor placed in said tubular housing
when said clamping screw is completely advanced into said tubular
body and holding said electrical conductor in intimate contact with
said second end of said terminal portion.
2. A connector as defined in claim 1, wherein said resilient pad
means is so proportioned and contoured that when said resilient pad
means is brought into contact with said electrical conductor said
resilient pad means forms a seal about said electrical conductor
within said connector.
3. A connector as defined in claim 1, wherein said second end of
said terminal portion has a plurality of insulation and oxide
piercing teeth formed on the portion of its surface arranged to
engage an electrical conductor.
4. A connector as defined in claim 1, wherein said pressure plate
has first and second extensions extending from first and second
transverse ends, said extensions centering said pressure plate
within said tubular body.
5. A connector as defined in claim 1, wherein said tubular body is
formed of a length of elongated material formed to provide said
first and second portions with an open seam adjacent said second
portion; apertures in the portions of said body extending between
said first and second portions; and tabs on said terminal portion
adjacent said second end to engage said apertures in the portions
of said body extending between said first and second portions to
assemble said terminal portion to said body and to retain the ends
of said body member adjacent said seam.
6. A connector as defined in claim 5, wherein said second end of
said terminal portion has a plurality of insulation and oxide
piercing teeth formed on the portion of its surface arranged to
engage an electrical conductor.
7. In a connector for coupling an electrical conductor to a
terminal position of the type having a tubular body having first
and second spaced apart portions for receipt of an electrical
conductor therebetween; a terminal portion for engagement with a
terminal position at a first end and having its second end
positioned adjacent said second portion of said tubular body for
receipt thereon of an electrical conductor; a clamping screw
threadably engaging a threaded hole in said first portion of said
tubular body; said clamping screw having a slot for receiving a
tool at a first end thereof for advancing and retracting the second
end thereof into and out of said tubular body and a pressure plate
coupled to said second end of said clamping screw, the improvement
comprising: resilient pad means coupled to said pressure plate for
engaging an electrical conductor placed in said tubular housing
when said clamping screw is completely advanced into said tubular
body and holding said electrical conductor in intimate contact with
said second end of said terminal portion; said resilient pad means
having first and second generally parallel sides, each of said
sides having a groove therein and said coupling between said
pressure plate and said resilient pad means is provided by turning
lateral edges of said pressure plate adjacent said first and second
sides of said resilient pad means inwardly into the grooves of said
first and second sides of said resilient pad means.
8. In a connector for coupling an electrical conductor to a
terminal position of the type having a tubular body having first
and second spaced apart portions for receipt of an electrical
conductor therebetween; a terminal portion for engagement with a
terminal position at a first end and having its second end
positioned adjacent said second portion of said tubular body for
receipt thereon of an electrical conductor; a clamping screw
threadably engaging a threaded hole in said first portion of said
tubular body; said clamping screw having a slot for receiving a
tool at a first end thereof for advancing and retracting the second
end thereof into and out of said tubular body and a pressure plate
coupled to said second end of said clamping screw, the improvement
comprising: resilient pad means coupled to said pressure plate for
engaging an electrical conductor placed in said tubular housing
when said clamping screw is completely advanced into said tubular
body and holding said electrical conductor in intimate contact with
said second end of said terminal portion; said resilient pad means
having an aperture extending generally from a first face to a
second face thereof and said pressure plate having a protrusion
thereon; said protrusion arranged to extend into and through said
aperture of said resilient pad means to retain said resilient pad
to said pressure plate and to limit the advancement of said
clamping screw into said tubular body.
9. In a connector for coupling an electrical conductor to a
terminal position of the type having a tubular body having first
and second spaced apart portions for receipt of an electrical
conductor therebetween; a terminal portion for engagement with a
terminal position at a first end and having its second end
positioned adjacent said second portion of said tubular body for
receipt thereon of an electrical conductor; a clamping screw
threadably engaging a threaded hole in said first portion of said
tubular body; said clamping screw having a slot for receiving a
tool at a first end thereof for advancing and retracting the second
end thereof into and out of said tubular body and a pressure plate
coupled to said second end of said clamping screw, the improvement
comprising: resilient pad means coupled to said pressure plate for
engaging an electrical conductor placed in said tubular housing
when said clamping screw is completely advanced into said tubular
body and holding said electrical conductor in intimate contact with
said second end of said terminal portion; said resilient pad means
having an aperture extending generally from a first face to a
second face thereof; said pressure plate means having an aperture
extending therethrough and said clamping screw having a protrusion
thereon at said second face thereof; said clamping screw protrusion
extending through said aperture in said pressure plate to
releasably mount said pressure plate to said screw and into and
through said aperture of said resilient pad means to retain said
resilient pad to said pressure plate and to limit the advancement
of said clamping screw into said tubular body.
10. A connector as defined in claim 9, wherein said resilient pad
means has first and second generally parallel sides, each of said
sides having a groove therein and the lateral edges of said
pressure plate adjacent said first and second sides of said
resilient pad means being turned inwardly into the grooves of said
first and second sides of said resilient pad means to assist in
coupling said resilient pad means to said pressure plate.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to the field of connecting conductors to
one another or connecting conductors to a connection point or
terminal points such as a bus bar, transformer or the like.
2. Description of the Prior Art
Mechanically operated connectors of the type generally described
herein have been employed for large sized conductors for many
years. These connectors were fabricated from copper or copper
alloys, in order to be employed with copper conductors. The
relative rates of thermal expansion and contraction of the
connector and conductor were the same due to the similarity of
material used. Vibration of the joint did at times cause loosening
of the mechanical clamping screw removing some of the pressure
between the connector and conductor and thus degrading the joint.
Pressure problems could usually be corrected by the use of a
Belleville washer or the like to accommodate any loosening which
might take place within the connector. However, with the
introduction of aluminum conductors, attempts to use connectors
fabricated of copper and copper alloys with such conductors were
generally unsuccessful due to radically different rates of thermal
expansion and contraction in the copper or copper alloys of the
connector and the aluminum of the conductor. The normal heating and
cooling of the conductor and connector, as a result of the cycling
found in the electrical equipment, caused sufficient loosening of
the connector to provide a very high resistance contact, commonly
known as a "hot joint," which might ultimately lead to the
destruction of the joint. In addition to the use of specially
formed pressure plates, or the addition of Bellevile washers, it is
also well known in the prior art to use specially formed connector
bodies having deflectable sections to make up for expansion of the
conductor. However, in each of these cases the introduction of the
aluminum conductor produced such strain upon the existing
connectors that they could no longer perform as needed, unless the
connectors were very often inspected and retightened to desired
torque levels.
SUMMARY OF THE INVENTION
The present invention overcomes the difficulties noted above with
respect to prior art devices by providing a mechanically actuated
connector which introduces a resilient pressure pad to the pressure
plate of the connector to compensate for wide variations in the
thermal expansion and contraction characteristics of the material
of the connector and the material of the conductor. This is
achieved by providing a resilient, elastomeric pressure pad on the
pressure plate operated by the mechanical clamping screw of the
connector and forcing the conductor into intimate contact with a
portion of the connector body throughout the operation of the
connector to permit changes in the pressure applied by the
resilient pressure pad to accommodate differences in thermal
expansion of the conductor with respect to the connector. To
prevent overtightening of the mechanical clamping screw the
pressure plate itself is fabricated with a protrusion which engages
the pressure pad and when fully tightened upon a conductor inserted
within the connector, engages the surface of the conductor in such
a manner as to prevent further tightening of the connector to the
point where the pressure pad might be destroyed. Also, the
protrusion engaging the conductor increases the mechanical strength
of the joint and increases the pullout forces required to remove
the conductor from the connector. Further, by the inclusion of
insulation and oxide piercing teeth to the lower, inner portion of
the connector body, as the connection is made the oxide of the
aluminum conductor is successfully broken through and contact is
made between the connector and newly exposed material of the
conductor to assure the best possible contact therebetween. It is
therefore an object of this invention to provide an improved
mechanically operated connector.
It is yet another object of this invention to provide an improved
mechanically operated connector for aluminum conductors.
It is still another object of this invention to provide an improved
mechanically operated connector fabricated of copper or copper
alloy, for use with aluminum conductors.
It is still another object of this invention to provide an improved
mechanically operated connector employing a pressure pad to
compensate for difference in thermal expansion between the material
of the connector and the material of the conductor to insure a good
electrical and mechanical joint therebetween throughout the
operation of the connector and the conductor.
It is yet another object of this invention to provide an improved
mechanically operated connector having a resilient pressure pad
having means for limiting torque applied to such pressure pad to a
point below that which would destroy it.
It is yet another object of this invention to provide an improved
mechanically operated connector for use with aluminum conductors
having an insulation and oxide piercing portion thereon to insure a
good mechanical and electrical joint between said conductor and
said connector.
Other objects and features of the invention will be pointed out in
the following description and claims and illustrated in the
accompanying drawings, which disclose, by way of invention, the
principles of the invention and the best modes contemplated for
carrying it out.
BRIEF DESCRIPTION OF THE DRAWING
In the Drawings:
FIG. 1 is a side elevation of a connector constructed in accordance
with the concepts of the invention.
FIG. 2 is a front elevational view of the device of FIG. 1.
FIG. 3 is a top plan view of the device of FIG. 1.
FIG. 4 is an elevational view in section of the pressure plate and
pressure pad of the device of FIG. 1.
FIG. 5 is a front elevational view of an alternative construction
of a pressure pad and pressure plate.
FIG. 6 is a front elevational view of an alternative form of lug
for use with the device of FIG. 1.
FIG. 7 is a front elevational view of the device of FIG. 1 applied
to a conductor of large diameter.
FIG. 8 is a front elevational view of the connector of FIG. 1
applied to a conductor of small diameter.
FIG. 9 is a front elevational view of yet another connector
constructed in accordance with the concepts of the invention
applied to a small conductor.
FIG. 10 is a front elevational view, in section, of the device of
FIG. 1 taken along the lines 10--10.
FIG. 11 is a front elevational view, in section, similar to that
shown in FIG. 10 but shown applied to a conductor.
Similar elements are given similar reference characters in each of
the respective figures.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Turning now to FIGS. 1, 2 and 3, there is shown a connector 20
constructed in accordance with the concepts of the invention.
Connector 20 has a tubular body portion 22 consisting of a base
portion 24 and two generally parallel extending legs 26 which
terminate at inwardly turned ends 28. Inwardly turned ends 28 of
the legs 26 are brought closely together to form an open seam 30
therebetween. Bridging the open seam 30 and extending across the
inwardly turned ends 28 of the legs 26 is a lug 32 (see FIG. 2)
whose ends 34 pass through slots 36 (see FIG. 1) within the
parallel extending legs 26 of the body portion 22. Ends 34 are
turned downwardly as at 38 to permit the retention of th lug 32
within the body portion 22. By using the body portion 22 formed in
the manner just described and by bridging the open ends of seam 30
with a lug member such as 32 anchored to the side walls 26 of the
body portion 22 it is possible to employ flat stock for the
formation of the body portion 22 to avoid expensive castings, or
drilling, or machining operations to form such a tubular body from
solid stock. Base portion 24 has a raised boss 40 thereon
internally threaded to receive a clamping screw 42 therethrough.
Clamping screw 42 has a hexagonal recess 44 therein (see FIG. 3)
for receipt of an appropriate tool, such as an Allen wrench, in
order that the clamping screw 42 may be advanced or retracted with
respect to the cavity within the tubular body portion 22. Although
a hexagonal slot 44 is shown it should be understood that any other
convenient shape, including a slot, may be employed to accept a
tool to cause the advancing or retracting of the clamping screw
42.
At the lower end of the clamping screw 42, which is best seen in
FIG. 4, is fabricated a protrusion 46 to which the pressure plate
48 is rotatably fastened. Forming the protrusion 46 with a
bulbaceous end it is possible to slip the pressure plate 48 over
the protrusion 46 and to cause it to be loosely retained thereby.
Pressure plate 48 has upturned ends 50, as is best seen in FIG. 1,
to help center pressure plate 48 with respect to the connector body
portion 22. The protrusion 46 of the clamping screw 42 also extends
into the central aperture 54 of the pad 52 and due to the
resiliency of the pressure pad 52 it is maintained on the
protrusion 46 although the protrusion 46 is free to move within
central aperture 54 of the pressure pad 52. Also, this loose
fitting arrangement of the protrusion 46 with the pressure pad 52
permits the pressure pad 52 to be replaced to provide pressure pads
of other contours, if desired. In addition to retaining pressure
pad 52 and the pressure plate 48 on the clamping screw 42,
protrusion 46 will, as described below, serve the additional
function of limiting the tightening of the clamping screw 42 in
such a manner that the pressure pad 52 will not be distorted beyond
its resilient limits and thereby render it incapable of functioning
in the manner to be described below. As will be set forth below,
the protrusion 46 is partly embedded into the conductor and as such
aids in gripping the conductor, thus increasing the pullout
strength of the conductor from the connector. Lug 32 is extended to
a terminal tab 56 which has an aperture 58 therein for receipt
therethrough of a terminal screw or similar fastening device. With
the availability of such a terminal tab 56, connector 20 may be
employed to connect a conductor to a terminal point on a bus bar or
terminal block or similar device. However, if it is desired,
terminal tab 56 may be omitted and connector 20 used to connect two
or more conductors as a splice.
Turning now to FIGS. 10 and 11, the operation of the connector 20
will be better appreciated. In FIG. 10 there is shown a front
elevational view, in section, of the connector in the fully open
position so that the relative positions of the component portions
of the connector 20 may be viewed. As can be seen, the clamping
screw 42 is in a fully retracted position, that is, with the major
portion of its threaded shank extending out of the threaded boss 40
of the body portion 22. As such, the pressure plate 48 is held
close to the inner surface of the base portion 24 of the body 22
and the pressure pad 52 is also held close to the under surface of
the base portion 24. The protrusion 46 of the clamping screw 42 is
fully within the central aperture 54 of the pressure pad 52. Now a
conductor 60, as is shown in FIG. 11, is inserted and rested on the
upper surface of the lug 32 and the connection between the
connector 20 and the conductor 60 is made by means of tightening
the clamping screw 42.
It should be noted that the inner surface 33 of the lug 32, shown
in FIG. 2, is smooth, and in such case it will be necessary, if the
conductor 60 is aluminum, that the conductor 60 be scraped clean
and protected with proper oxide inhibiting agents prior to the
insertion within the connector 20. Alternatively, as shown in FIG.
6, the lug 32 may be replaced with a lug 70 having along its inner
surface 72 a plurality of insulation and oxide piercing teeth 74 so
formed that they will pierce through the aluminum oxide formed on
the outside of the aluminum conductor 60 and contact fresh aluminum
in the conductor 60 itself. In such case it is not necessary to
prepare the conductor 60 prior to insertion within the connector
20. Lug 70 is affixed by means of tabs 76 at its ends through slots
such as 36 in the side walls 26 of the connector 20 of FIG. 1 and
the ends 78 downturned as was true of the ends 38 of the lug 32 of
FIG. 2.
With the conductor 60 properly placed upon the upper surface of the
lug 32 of FIG. 2, clamping screw 42 is tightened by inserting an
appropriate Allen wrench, or the like, in the hexagonal recess 44
and driven downwardly so as to cause first the outer surface of
pressure pad 52 to contact the outer surface of the conductor 60.
The tightening operation will continue until the leading edge of
the protrusion 46 extends completely through the central aperture
54 of the pressure pad 52 and contacts the outer surface of the
conductor 60 and slightly thereafter partially compressing the
conductor 60. (See FIG. 11). With the protrusion 46 so contacting
the conductor 60, the operator is assured that proper tightening
has taken place and is warned against such further tightening that
could cause the crushing of the resilient pressure pad 52 and its
destruction. The urging of the clamping screw 42, the pressure
plate 48 and the pressure pad 52 press the conductor 60 against the
upper surface 33 of the lug 32 and thereby assure an intimate
contact between such conductor 60 and the connector 20. The
limitation of the compression of the resilient pressure pad 52 will
permit the pressure pad 52 to continue to be compressed as the
conductor 60 expands to a degree greater than the connector 20, and
will also allow the pressure pad 52 to recover and expand as the
connector 20 and conductor 60 are caused to contract during
cooling. The resilience of the pad 52 will permit it to match the
disparity between the contraction of the conductor 60 and the
smaller contraction of the connector 20.
When the conductor being employed with a connector such as 20 is
more irregular or flatter than the generally round shape of the
conductor 60, shown in FIG. 11, the pressure plate and pressure pad
may be modified, as shown in FIG. 5, to accommodate such change in
the profile of the conductor. As is shown in FIG. 5, clamping screw
80 has affixed at its lower end by means of a pin 82, a pressure
plate 84. Pin 82 makes it possible for the clamping screw 80 to
turn freely without causing the pressure plate 84 to rotate. Plate
84 has two downturned legs 86 contoured so as to be able to fit
within grooves 90 of a pressure pad 88 placed partially within the
pressure plate 84. Downturned legs 86 will thereby act as a
limitation on the tightness of the clamping screw 80 and will also
serve to retain the pressure pad 88 to the clamping screw 80.
Turning now to FIGS. 7 and 8, the position of the relative elements
of the connectors 20 are shown with conductors of different sizes.
For example, in FIG. 7, connector 20 is applied to a conductor 92
of rather large diameter. Very little distortion of the pressure
pad 52 is necessary because of the rather large size of the
conductor 92. However, as shown in FIG. 8, the pressure pad 52 is
greatly distorted when a very small sized conductor 94 is placed
within the body portion 22 of the connector 20. Great distortion of
the pressure pad 52 may be used to advantage to provide a seal for
the conductor within the connector, as is shown in FIG. 9, by
providing a pressure pad 96 which when installed about a small
conductor such as 98 distorts to form a complete enclosure about
the conductor 98 as the conductor 98 is fitted upon the inner
surface 33 of the lug 32 of the connector of FIG. 1. Pressure pad
96 because of the loose fit on protrusion 46 is easily
interchangeable with pressure pad 52 of FIG. 10.
While there have been shown and described and pointed out the
fundamental novel features of the invention as applied to the
preferred embodiments, it will be understood that various omissions
and substitutions and changes of the form and details of the
devices illustrated and in their operation may be made by those
skilled in the art, without departing from the spirit of the
invention. The embodiments of the invention in which an exclusive
property and privilege is claimed are defined as follows:
* * * * *