U.S. patent number 3,864,005 [Application Number 05/405,686] was granted by the patent office on 1975-02-04 for resilient electrical terminal connector.
This patent grant is currently assigned to General Electric Company. Invention is credited to Keith William Klein.
United States Patent |
3,864,005 |
Klein |
February 4, 1975 |
RESILIENT ELECTRICAL TERMINAL CONNECTOR
Abstract
A connector for making electrical connection between a terminal
strap and a wire conductor, particularly an aluminum conductor,
comprises a rigid, rectangular frame having a central opening. A
bolt, having a clamping plate mounted to its free end, is
threadingly advanced into the frame opening to engage and clamp the
wire conductor in electrically connecting relation with the
terminal strap. A lost-motion coupling incorporated in the clamping
force train between the clamping plate and the frame is equipped
with a spring to provide resilient clamping pressure on the current
carrying parts.
Inventors: |
Klein; Keith William (Simsbury,
CT) |
Assignee: |
General Electric Company (New
York, NY)
|
Family
ID: |
23604776 |
Appl.
No.: |
05/405,686 |
Filed: |
October 11, 1973 |
Current U.S.
Class: |
439/812;
24/115N |
Current CPC
Class: |
H01R
4/366 (20130101); H01R 4/363 (20130101); Y10T
24/3998 (20150115) |
Current International
Class: |
H01R
4/28 (20060101); H01R 4/36 (20060101); H01r
007/12 () |
Field of
Search: |
;339/272,259,255,254
;24/115R,135N |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
411,087 |
|
Oct 1966 |
|
CH |
|
713,146 |
|
Nov 1941 |
|
DD |
|
220,578 |
|
Jul 1942 |
|
CH |
|
1,029,440 |
|
May 1958 |
|
DT |
|
44,646 |
|
Aug 1971 |
|
SF |
|
Primary Examiner: Frazier; Roy D.
Assistant Examiner: Hafer; Robert A.
Attorney, Agent or Firm: Cahill; R. A. Schlamp; P. L.
Neuhauser; F. L.
Claims
1. A terminal connector for making an electrical connection between
a terminal strap and a wire conductor, said connector comprising,
in combination:
A. a rigid frame having a central opening and means forming an
aperture through a wall of said frame into said central
opening;
B. a sleeve accommodated in said wall aperture, said sleeve having
a threaded axial bore and terminating in inner and outer axially
spaced, radially extending flanges, said flanges engaging said wall
about said aperture to capture said sleeve in said wall aperture
and to limit the degree of reciprocal motion of said sleeve through
said wall aperture;
C. a clamping bolt threadedly engaged in said axial bore to advance
a free end thereof into said central opening;
D. a clamping plate mounted by said free end of said bolt for
clamping a wire conductor introduced into said central opening in
electrical connection with a terminal strap therein; and
E. a spring positioned within said central opening and acting
between said inner flange of said sleeve and said frame to exert a
resilient clamping force on the wire conductor.
Description
BACKGROUND OF THE INVENTION
Heretofore problems have been experienced in making lasting
electrical connections between wires and flat terminal straps
commonly used in various electrical devices, such as, for example,
molded case circuit breakers, switches, relays, etc., particularly
when one or both of the current carrying parts is formed of
aluminum. These problems are becoming more widespread as the
electrical industry increasingly resorts to the use of aluminum for
current carrying parts due to the shortage and high cost of copper.
The conventional, rigid clamping connectors, while generally quite
successful for connecting copper conductors, are not entirely
satisfactory for aluminum or other relatively soft material
conductors due to their tendency to "cold flow" or plasticly deform
under the compressing clamping forces. This permanent deformation,
in time, adversely affects the mechanical and electrical connection
between the current carrying parts. Connectors described as being
effective in overcoming this problem are disclosed in U.S. Pat. No.
2,771,591 and in my co-pending application, Ser. No. 347,127, filed
Apr. 2, 1973 and assigned to the assignee of this application.
When using clamping connectors with aluminum wire, the wire tends
to assume a permanently flat cross-sectional configuration and thus
in time becomes loosened mechanically and less intimately connected
electrically. Similarly, if the wire is clamped against a terminal
strap which is also formed of aluminum or surface coated with
aluminum or other relatively soft metal, the compressive effect of
the wire on the strap can cause material flow outwardly from under
the wire, thus further jeopardizing the connection. Due to the
desirable heat transfer and dissipation properties of aluminum, the
connector parts are advantageously also formed of aluminum.
However, here too the clamping forces can cause deformation of the
connector parts, with a consequent relaxation in the contacting
pressure between the wire and terminal strap. Any significant
relaxation in the contact pressure between current carrying
aluminum parts accelerates the formation of highly resistive oxide
films, thus greatly reducing effective life of the connection.
Furthermore, connectors embodied as terminal connectors for molded
case circuit breakers, switches and the like, must be compact as
space is often a premium. For example, in certain molded case
circuit breakers, the lateral dimensions of the terminal straps
must, owing to available space, be minimized, as must the
corresponding dimensions of the terminal connector. Yet, it is
desirable to maximize the opening in the connector for receiving
the wire to provide greater choice in the wire size that can be
employed.
Still further, it is desirable and, in fact essential from a
salability standpoint, that the parts of the connector be adapted
for cooperating in a manner which facilitates the making of a
dependable initial electrical connection in a rapid manner and for
minimizing any undesirable relative motion between the connector
parts and the current carrying parts which could adversely affect
the useful life of the connection.
It is accordingly an object of the present invention to provide an
electrical connector adapted for assuring a reliable electrical
connection between current carrying parts, wherein at least one of
the parts is formed of aluminum or other relatively soft, plasticly
deformable metal.
Another object of the present invention is to provide an electrical
connector of the above character which is capable of providing a
dependable electrical connection of relatively long life.
Still another object of the present invention is to provide an
electrical connector of the above character embodied as a terminal
connector for molded case circuit breakers and the like, wherein
the connector is compact in size, inexpensive to manufacture, and
conveniently operable in a rapid manner.
Other objects of the invention will in part be obvious and in part
appear hereinafter.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided an
electrical connector which is particularly adapted as a terminal
connector for molded case circuit breakers, switches, and the like,
wherein the conductor to be connected is formed of aluminum or
other soft, readily plasticly deformable metal. Generally stated,
the electrical connector of the present invention includes a rigid
frame having walls defining a central opening for receiving the
bared end of a wire conductor to be connected. A clamping bolt
having a free end to which is mounted a clamping plate is
threadingly advanced into the frame opening through one of the
walls to bring the plate into clamping engagement with the wire
conductor, thus to electrically connect the wire conductor with a
terminal strap of the circuit breaker, etc.
The electrical connector further includes, in accordance with the
invention, the incorporation of a lost-motion coupling in the
clamping force train between the clamping plate and the frame. A
spring element is incorporated in this lost-motion coupling such
that the clamping force exerted on the current carrying parts is
resilient in character. As a consequence, any cold flow or plastic
deformation of the current carrying parts of the electrical
connection, which would otherwise result in a lessening of the
contact pressure therebetween, is taken up by the resilient
lost-motion coupling. As a consequence, the integrity of the
electrical connection is preserved over a longer useful life than
would otherwise be possible.
In one embodiment of the invention, the clamping bolt is
threadingly advanced through a sleeve mounted in an aperture formed
in one of the frame walls. The resilient lost-motion coupling of
the invention is provided in the mounting of the sleeve to the
frame.
In another embodiment of the invention, the resilient lost-motion
coupling is provided in the mounting of the clamping plate to the
clamping bolt.
In still another embodiment of the invention, the resilient
lost-motion coupling of the invention is provided in the connection
of the terminal strap to the frame; the wire conductor being
clamped against the terminal strap by the advancement of the
clamping bolt and clamping plate into the frame opening.
In all embodiments of the invention, the clamping force providing
the requisite continuing contact pressure between the current
carrying parts is provided by the resilient lost-motion coupling
included in the clamping force train between the clamping plate and
frame.
The invention accordingly comprises the features of constructions,
combinations of elements and arrangements of parts which will be
exemplified in the constructions hereinafter set forth, and the
scope of the invention will be indicated in the claims.
For a fuller understanding of the nature and objects of the
invention, reference should be had to the following detailed
description taken in connection with the accompanying drawing, in
which:
FIG. 1 is a side elevational view, partially in section, depicting
one embodiment of the invention;
FIG. 2 is a side elevational view, partially broken away, of
another embodiment of the invention;
FIG. 3 is a side elevational, sectional view of still another
embodiment of the invention; and
FIG. 4 is a sectional view taken along line 4--4 of FIG. 3.
DETAILED DESCRIPTION
The embodiments of the invention shown in FIGS. 1 through 3 are for
the purpose of effecting an electrical connection between a flat
terminal strap 10 and a wire conductor 12. The strap is elongated,
rectangular in cross section, and typical of the terminal straps
used in many electrical devices, such as molded case circuit
breakers, switches, relays, and the like. The wire conductor 12 may
be a single conductor, as shown in FIGS. 2 and 3, or a multi-strand
conductor, as illustrated in FIG. 1. As will become apparent from
the following detailed description, the electrical connector
embodiments of the present invention are most advantageously
employed when the wire conductor and/or the strap is formed of
aluminum or other, readily plasticly deformable conductive
metals.
In the embodiment of the invention seen in FIG. 1, the electrical
connector includes a rectangular frame 14 having top, bottom and
sidewalls defining a central opening 16 into which terminal strap
10 and wire conductor 12 are introduced. If desired, strap 10 may
be suitably configured so as to be captured within central opening
16 or attached to the frame bottom wall or floor 18 so as to be
maintained in place prior to effecting the electrical connection.
Top wall 20 is provided with an opening 21 for receiving a sleeve
22. This sleeve is flanged at its lower end, as indicated at 24,
and staked over at its upper end, as indicated at 26, so as to be
mounted to the frame while permitting a limited degree of relative
or lost motion therebetween. Taking up the slack in this lost
motion connection is a suitable spring, such as a spring washer 29,
acting between the flanged portion 24 of sleeve 22 and the top wall
20 of frame 14. The central bore of sleeve 22 is threaded to
accommodate the advancement of a clamping bolt 28 into the central
opening of frame 14. An arcuate clamping plate 30, freely rotatably
mounted on the end of clamping bolt 28, is provided to clamp
terminal strap 10 and wire conductor 12 against the floor 18 of
frame 14, pursuant to effecting the electrical connection
therebetween.
From the foregoing description of FIG. 1, it is seen that as the
clamping bolt 28 is turned down to exert clamping pressure on the
wire conductor 12 and terminal strap 10, spring 29 is compressed.
Once the desired contact pressure between wire conductor 12 and
terminal strap 10 is achieved by clamping bolt 28, the resiliency
of the clamping force generated by spring 29 is effective to
maintain the contact pressure between the terminal strap and wire
conductor relatively constant despite deformation of either or both
of these current carrying parts.
In the embodiment of the invention seen in FIG. 2, terminal strap
10 is provided with a tapped hole 34 into which is threaded the end
of a bolt 36 having an enlarged diameter intermediate portion 38
slidingly received in an opening 40 formed in the bottom wall or
floor 42 of a generally rectangular frame 44. A spring washer 46 is
positioned to operate between busbar 10 and the floor 42 of frame
44. A clamping screw 48 is threaded through a tapped hole 50 in the
top wall 52 of frame 44 to advance a bi-planar clamping plate 54,
rotatably mounted to the free end thereof, downwardly to
resiliently press the wire conductor 12 against the terminal strap
10. It is seen that the resilient lost-motion connection afforded
by bolt 36 slidingly mounted by frame 44 and spring washer 46 acts
in the clamping force train to maintain the requisite continuing
contact pressure between terminal strap 10 and wire conductor 12
despite plastic deformation in either of these current carrying
parts.
In the embodiment of the invention seen in FIG. 3, the terminal
strap 10 is secured in electrical contacting engagement with the
bottom surface of the floor 60 of an open interior electrically
conductive frame 62 by a bolted connection afforded by bolt 64. The
top wall 66 of frame 62 is provided with a threaded bore 68 in
which is threaded a clamping bolt 70. Clamping bolt 70 is provided
with a stepped, axial bore having a reduced diameter portion 72 in
which is received a rod 74 carrying at its lower end a clamping
plate 76. The upper end of rod 74 is staked, as indicated at 78, so
as to connect the clamping plate to the end of clamping screw 70
with a limited degree of lost or relative motion accommodated
therebetween. A spring washer 80 is positioned between the clamping
plate 76 and the lower end of clamping screw 70. The upper end of
the axial bore through clamping screw 70 is formed with a hex
socket 82 accommodating a wrench for advancing the clamping plate
76 into clamping engagement with wire 12. Spring 80 acts to
maintain the requisite contact pressure between the wire conductor
and the floor 60 of frame 62, thus insuring a lasting electrical
connection with terminal strap 10. As seen in FIG. 4, rod 74 and
bore 72 may be rectangular in crosssection, such that the clamping
plate 76 rotates with clamping bolt 70. This produces a beneficial
wiping action on wire conductor 12 to remove surface oxides, thus
insuring a good current path through the clamping plate, rod,
clamping bolt and frame body to the terminal strap to supplement
the more direct current path through the floor 60 of the frame.
In any of the various embodiments of the invention, it is often
desirable to have the terminal strap either wholly formed of
aluminum and coated with tin, or formed of another metal and
surface coated with tin or aluminum, and to form the connector
parts of aluminum also, all for the purpose of enhancing thermal
and electrical conductivity, achieving weight and material cost
savings, and avoiding corrosion due to galvanic action. Using the
same material for the terminal strap, wire conductor and connector
also affords greater uniformity in the coefficients of expansion of
the various parts and thus minimizes the effects of differences in
the thermal expansion and contraction of the parts. It is
anticipated, however, that the resilient clamping force afforded by
the present invention will compensate for the otherwise prejudicial
effects of thermal expansion and contraction of the parts on the
integrity of the electrical connection.
It will be observed from the foregoing detailed description and the
accompanying drawings that the electrical connector of the present
invention is quite compact in size, taking up virtually no more
space than is consumed by conventional terminal connectors.
Consequently, the terminal connector embodiments disclosed herein
may be readily accommodated in the confined spaces being allotted
for terminal connectors in currently available molded case circuit
breakers, switches, and the like. Moreover, the making of
electrical connections during installation by an electrician using
the terminal connectors of the present invention is as
straightforward and convenient as with conventional terminal
connectors exerting rigid clamping forces.
It will thus be seen that the objects set forth above, among those
made apparent from the preceding description, are efficiently
attained and, since certain changes may be made in the above
constructions without departing from the scope of the invention, it
is intended that all matter contained in the above description or
shown in the accompanying drawings shall be interpreted as
illustrative and not in a limiting sense.
Having described my invention, what I claim as new and desire to
secure by Letters Patent is:
* * * * *