U.S. patent number 3,564,184 [Application Number 04/794,289] was granted by the patent office on 1971-02-16 for electric circuit breaker.
This patent grant is currently assigned to General Electric Company. Invention is credited to George E. Gauthier, Keith W. Klein.
United States Patent |
3,564,184 |
Gauthier , et al. |
February 16, 1971 |
ELECTRIC CIRCUIT BREAKER
Abstract
A movable contact-supporting arm comprising a relatively high
conductivity low strength flat plate portion disposed with its
major planar surface generally at right angles to the direction of
movement of the contact arm and a relatively low conductivity high
strength backing plate having its major planar surface disposed
generally parallel to the direction of movement of said contact arm
to form a generally T-shaped cross-sectional configuration, and a
contact member mounted on the front surface of the high
conductivity plate portion by suitable means, such as by
welding.
Inventors: |
Gauthier; George E.
(Plainville, CT), Klein; Keith W. (Simsbury, CT) |
Assignee: |
General Electric Company
(N/A)
|
Family
ID: |
25162239 |
Appl.
No.: |
04/794,289 |
Filed: |
January 27, 1969 |
Current U.S.
Class: |
200/244; 200/275;
200/270 |
Current CPC
Class: |
H01H
1/22 (20130101); H01H 1/225 (20130101) |
Current International
Class: |
H01H
1/22 (20060101); H01H 1/12 (20060101); H01h
001/02 () |
Field of
Search: |
;200/16 (CC)/ ;200/168
(A)/ ;200/169,170 ;335/23,35,46,196 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Jones; H. O.
Claims
We claim:
1. A movable contact arm assembly for an electric circuit breaker
comprising a contact; an elongated composite contact carrier
including a generally rectangular platelike current conducting
blade having a bottom surface including a substantially flat face
portion mounting said contact adjacent one end of the blade; an
elongated structural support member having a longitudinal edge
mounted in direct contact with the top surface of said blade, said
support member being secured to the blade intermediate the ends
thereof and including a pointed nose portion extending beyond the
end of said blade mounting said contact; a contact operator
pivotally mounting said carrier and including means for limiting
pivotal movement of said carrier in a first pivotal direction and
biasing means mounted on said operator for urging said carrier in
said first pivotal direction to provide releasable engagement
between said carrier and said limiting means.
2. In an electric switching device comprising a casing, a first
contact mounted in said casing, a second contact in said casing
having a surface adapted to engage a surface of said first contact,
a movable contact arm assembly mounting said second contact for
movement into and out of surface engagement with said first
contact, and drive means moving said contact arm assembly toward
and away from said first contact, the combination wherein the
contact arm assembly includes a composite contact carrier
comprising a platelike current conducting blade and a backing
member for the blade in intimate supporting engagement therewith,
said blade having a face portion disposed in confronting
relationship to the first contact during surface engagement between
said contacts; said blade being a generally rectangular strip
having a bottom surface including said face portion, said second
contact mounted on said face portion adjacent one end of said
blade, the backing member having a longitudinal edge mounted in
secured abutting relationship to said blade, and said backing
member including an arc runner portion mounted adjacent said second
contact.
3. A movable contact arm assembly for an electric circuit breaker
comprising a contact, an elongated contact carrier including a
platelike current conducting blade having a face portion mounting
said contact and a structural support member secured to the blade,
a contact operator mounting said carrier for limited movement in a
first direction and biasing means operable against said support
member for urging said carrier in said first direction, said blade
being a generally rectangular strip having a bottom surface
including said face portion, said contact mounted on said face
portion adjacent one end of the blade, the support member having a
longitudinal edge mounted in secured abutting relationship to said
blade, the contact arm assembly including a contact operator
mounting the carrier for limited movement in a first direction and
biasing means associated with said operator for urging said carrier
in said first direction.
4. In an electric switching device of the type comprising a casing,
a normally stationary contact supported in said casing, a movable
contact arm assembly supported in said casing and including a
movable contact portion movable along a predetermined path into and
out of engagement with said stationary contact, the combination
wherein said movable contact arm assembly comprises:
a. an elongated relatively wide, thin, flat current conducting
member;
b. a movable contact member rigidly and conductively mounted on a
first wide surface of said current conducting member adjacent one
end thereof;
c. a backing member of relatively high strength material rigidly
affixed to said current conducting member at a second wide surface
thereof opposite said first wide surface, said backing member
comprising a relatively wide, thin, flat member having its wide
surfaces extending generally perpendicular to said wide surfaces of
said current conducting member and having a longitudinal edge
portion mounted in abutting relationship to said second wide
surface of said current conducting member; and
d. said contact arm assembly disposed in said casing with said
first and second wide surfaces of said current conducting member
extending substantially perpendicular to said predetermined path of
movement of said movable contact member.
5. The combination as set forth in claim 13 wherein:
a. said current conducting member comprises a relatively high
electrical conductivity metallic material;
b. said backing member comprises a metallic material having an
electrical conductivity substantially lower than that of said
current conducting member; and
c. said backing member further being composed of a material having
a mechanical strength greater than that of said current conducting
member.
6. The combination as set forth in claim 4 wherein:
a. said current conducting member comprises copper; and
b. said backing member comprises steel.
7. The combination as set forth in claim 4 wherein said backing
member is disposed substantially along the longitudinal center line
of said current conducting member and is attached thereto by means
of integral lug portions which extend through corresponding holes
in said current conducting member.
8. The combination as set forth in claim 4 wherein said one end of
said current conducting member is offset from the general plane of
said current conducting member in a direction toward said first
wide surface, and said backing member has its said longitudinal
edge portion conforming to the contour of said offset at the
portion abutting thereagainst.
9. The combination as set forth in claim 4 wherein said backing
member has a nose portion extending beyond said current conducting
member at said one end thereof and having a depending portion
extending in the direction of said contact, said nose portion
having a longitudinal edge portion extending substantially flush
with the contacting face of said contact to provide an arc runner
capable of readily accepting transfer of an arc from said
contacting face of said contact.
10. The combination as set forth in claim 4 wherein said
combination also comprises means supporting said contact arm
assembly for pivotal movement in said casing between open and
closed circuit positions with respect to said stationary contact,
and flexible conductor means connected directly to said current
conducting member of said contact arm assembly adjacent the end
thereof opposite said one end whereby all current entering said
current conducting member enters directly and without having to
first pass through any portion of said backing member.
Description
BACKGROUND OF THE INVENTION
Our invention relates generally to electric circuit control devices
and more particularly is directed to new and improved contact arm
assemblies for electric switches, circuit breakers and the
like.
Heretofore movable electric contact arm assemblies for switches
such as circuit breakers and the like have conventionally consisted
essentially of a flat plate of relatively highly conductive
material with a contact mounted on one edge thereof. The conductive
plate was disposed generally perpendicular to the abutting surfaces
of the contacts in the closed circuit position in order to best
resist the high compressive forces exerted thereagainst during
operation. Unfortunately such assemblies inherently possess the
structural weaknesses associated with the use of high electrical
conductivity materials. Accordingly it has been necessary to
increase the cross-sectional area of such parts for purely
structural purposes beyond the size required to carry the current
of the switch or circuit breaker. This, of course, unnecessarily
adds to the cost of the device, since the high conductivity
materials (such as copper) are comparatively expensive.
In addition, such prior art contact arms presented a problem in
that the mounting of the contact member on one edge portion of the
contact arm member was difficult to accomplish. This is because the
welding of contact members to supporting metallic members is best
accomplished by an assembly which presents two opposed generally
flat relatively wide planar surfaces which may be engaged by
opposed electrodes of a welding machine, sandwich fashion, during
the welding process. Contact arm assemblies of the type referred to
of the prior art, however, present an edge portion of the support
member as one of the two opposed surfaces which must be engaged by
the welding electrodes. This makes the welding process more time
consuming and also causes a higher number of defective welds to
occur.
Furthermore, in addition to the above, the relatively small area of
engagement between the edge portion of the supporting member and
the generally planar back surface of the contact member of such
prior art constructions does not provide a very good path for the
conduction and dissipation of heat generated between the contacts
in closed circuit position.
In addition to the above problems, the process of welding, as is
well known, creates intense heat in the parts to be welded, with
the result that the support member is softened or "annealed" by the
welding. This weakens the support member at the precise point where
strength is important, that is, at the point at which force is
exerted thereon because of the engagement of the contacts in the
closed position.
OBJECTS OF THE INVENTION
Accordingly, it is a general object of the present invention to
provide a new and improved contact arm assembly for circuit control
devices of the type described which uses a minimum of relatively
expensive high electrical conductivity material.
It is another object of the invention to provide a supporting arm
for a movable contact member including mounting means for the
contact on the supporting arm which is readily adapted to standard
welding processes and machines.
A further object of the invention is to provide a supporting arm
for a movable contact member which also provides for good heat
conductivity and dissipation of heat from the movable contact, and
which furthermore nevertheless utilizes a minimum of relatively
expensive high conductivity material.
It is another object of the present invention to provide a contact
arm assembly for supporting a movable contact member of an electric
switch or circuit breaker in which a minimum of relatively
expensive high conductivity metallic material is required, but
which nevertheless presents a contact supporting portion to which a
contact may be welded, which is generally wide and flat in a
direction parallel to the back surface of the contact member to be
attached thereto, while yet providing required structural strength
in the assembly.
It is a further object of the invention to provide a contact
supporting arm construction of the type including a contact support
member having a contact engaging portion of relatively high
conductivity material, the contact being attached thereto by
welding, the nature of the assembly being such that softening or
weakening of the contact engaging portion of the assembly by said
welding process does not detract from the required structural
strength of the assembly.
A further general object of the present invention is to provide an
improved contact arm assembly comprised of a composite metal
construction exhibiting high strength, endurance and dependable
operating characteristics.
A further object of the invention is to provide a switch or circuit
breaker including a composite contact supporting arm comprising a
minimum amount of relatively expensive high conductivity material
combined with relatively inexpensive low conductivity high strength
material in which the high conductivity portion is disposed and
arranged to shield the main body of the low conductivity material
from direct impingement by an arc drawn between the contacts.
SUMMARY OF THE INVENTION
In accordance with the present invention these and related objects
are attained by providing an electric circuit breaker of the type
described with a new and improved movable contact arm assembly
comprising an elongated contact carrier mounted for pivotal
movement along a path between open and closed circuit positions and
including a conductor blade disposed substantially perpendicular to
a plane lying along the carrier's path. The contact carrier is a
composite member comprising a platelike current conductor blade
mounting the contact on its wide surface at one end thereof and a
structural support member upstanding from the conductor at
substantially a right angle thereto.
The invention accordingly consists in the features of construction,
combination of elements and arrangement of parts which will be
better understood from the following detailed description taken in
conjunction with the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
In the drawing:
FIG. 1 is a side elevation view of a circuit breaker, partly broken
away and partly in section, illustrating one embodiment of the
contact arm assembly of the present invention in its closed circuit
position, its open circuit position being shown in phantom;
FIG. 2 is a fragmentary plan view illustrating only the movable
contact arm assembly of FIG. 1;
FIG. 3 is an exploded isometric view of the contact arm assembly
shown in FIG. 2;
FIG. 4 is a sectional view of the contact carrier of the assembly
illustrating one manner of securing the backing member to the
conductor blade; and
FIG. 5 is a side elevation view of another embodiment of a contact
carrier of the present invention.
DESCRIPTION OF PREFERRED EMBODIMENT
Referring now to the drawing in greater detail, wherein like
reference numerals indicate like parts throughout the several
FIGS., the invention is shown in FIG. 1 as incorporated in a
multipole electric circuit breaker having an insulating housing or
casing comprised of a generally rectangular base member 10 and an
overlying cover 12 mounted thereon. A manually operated ON/OFF
button 14 protrudes through the cover 12 and is suitably connected
through an operating mechanism, such as the spring driven
overcenter toggle linkage 16 (shown in phantom), to each of the
circuit breaker's contact arm assemblies, generally designated by
the numeral 20. As illustrated in FIG. 1 the assembly 20 is mounted
within the insulating casing for movement between its closed
circuit position shown in full line and its phantom line open
circuit position.
A terminal strap 22 associated with a line terminal of the circuit
breaker is fixedly secured to the base member 10 of the casing and
mounts a stationary contact 24 at one end thereof. As will be
appreciated each of the movable contact arm assemblies 20 are
operable in unison by the overcenter operating linkage 16 through a
common contact cross arm 26 which extends transversely of the
casing and provides a common pivot axis therefor. A flexible
electric conductor or braid 28 is connected to each movable contact
arm assembly 20 and is suitably associated with a load terminal on
the opposite end of the breaker to complete the circuit
thereacross.
Upon movement of the manually operated button 14 to its OFF
position, the overcenter toggle linkage 16 moves the pivotal
contact arm assembly 20 to the phantom line position shown in FIG.
1, opening the circuit and preventing the flow of electric current
therethrough. Conversely, upon movement of the manually operated
button 14 to its ON position illustrated in FIG. 1, the contact arm
assembly is rapidly and effectively driven in a clockwise direction
as viewed in FIG. 1 causing firm pressurized surface engagement
between the movable contact 32 carried by the contact arm assembly
20 and the stationary contact 24 carried by the load terminal strap
22.
Upon the occurrence of an abnormally high current condition in the
circuit controlled by the breaker, a suitable tripping mechanism,
not shown, which may be of a thermal or magnetic character or a
combination thereof, is activated to cause movement of the toggle
linkage 16 a sufficient distance to permit operation of the
overcenter mechanism and the resultant counterclockwise movement of
the contact arm assembly 20 to its open circuit position. Upon
correction of the condition resulting in the high current short
circuit, the breaker may be manually reset by moving the manually
operated button 14 to its OFF position.
In accordance with the present invention the pivotal contact arm
assembly 20 comprises a contact operator 34 firmly mounted on the
common cross arm 26 and a composite contact carrier including a
current conducting blade 38 and support member 40 pivotally mounted
on the contact operator 34 by means of an interconnecting pivot pin
42. The contact operator 34, best shown in FIG. 3, is a generally
U-shaped member comprised of a substantially flat base portion 44
which rests against a flat surface 46 of the cross arm's square hub
48 and a pair of opposed sides 52 provided with aligned generally
square openings 54 at their point of juncture with the base portion
44 for receiving the common cross arm 26 therethrough. As shown in
FIGS. 1 and 2, the base portion 44 is held in secure fixed
engagement with the common cross arm 26 by means of the fastener 56
whose tabs 58 extend through apertures 50 in the base portion 44
and bend over the outside surface thereof in locking engagement.
The spaced generally parallel sides 52 of the contact operator are
each provided with forwardly extending pinched-in journal tabs 60
spaced in substantial parallelism by a distance approximately equal
to the width of the contact carrier's support member 40. In this
manner the tabs 60, which are provided with aligned apertures 62
for receiving the pivot pin 42, securely mount the contact carrier
therebetween for limited pivotal movement as discussed in greater
detail hereinafter.
The current conducting blade 38 of the contact arm assembly is an
elongated, generally rectangular strip or bar of copper or other
suitable conductive material to which the movable contact 32 is
affixed at one end thereof. It is an advantage of the present
invention that the blade 38 is mounted in such a manner that the
plane thereof is disposed at substantially a right angle to the
assembly's path of travel between its open and closed circuit
positions. More particularly the conductive blade 38 presents its
wide bottom surface to the arcing area of the circuit breaker so
that the blade's flat face portion 36 which mounts the contact 32
lies in confronting planar relationship to the terminal strap 22
and the stationary contact 24 mounted thereon. As mentioned, the
blade 38 is preferably a flat copper strip or bar which provides
excellent current conducting properties and is of sufficient length
to provide for the secure attachment of the flexible conducting
braid 28 which electrically interconnects the movable contact 32
with the load terminal of the circuit breaker.
The support member 40 of the composite metal contact carrier is a
flat, generally rectangular plate formed from rigid, high strength
material, such as steel. The support member 40 is disposed at
substantially a right angle to the conductor blade 38 so that its
bottom longitudinal edge 64 rests on the broad top surface 66 of
the blade imparting a generally T-shaped cross-sectional
configuration to the contact carrier, as best seen in FIG. 4. A
pair of depending securing lugs 68 extend downwardly from
longitudinal edge 64 and interfit within central apertures 70
provided in conductor blade 38 to provide a secure interconnection
therebetween when staked in the manner illustrated in FIG. 4. The
support member 40 is further provided with a central aperture 72
for receiving the pivot pin 42 and facilitating pivotal
interconnection with the operator 34 of the contact arm assembly.
Thus, the upright support member 40 provides a strong, durable
support backing for the current conducting blade 38 in the form of
a beam capable of imparting to the assembly the strength and
durability necessary for prolonged trouble-free operation.
Although the contact carrier is pivotally mounted on its contact
operator 34, the pivotal movement thereof is substantially limited.
For example, when the circuit breaker is fully assembled with the
contact arm assembly 20 mounted on the common cross arm 26, the
clockwise rotation of the contact carrier assembly when the parts
are in the open circuit position is limited by the interfering
engagement of a tapered tail portion 74 of the support member 40
with the fastener 56. Additionally, rotation in a counterclockwise
direction as viewed in FIG. 1 is resisted by a wire spring 76 held
by the operator 34 and pivot pin 42 for engagement with the top
longitudinal edge 78 of the support member 40. As shown in FIG. 1
the spring 76 passes beneath pivot pin 42 and rests within its
locking grooves 82 while the spring's free ends 80 are held within
the side apertures 84 of the operator 34. Thus, it will be
appreciated that as the snap action of the overcenter mechanism
drives the contact arm assembly 20 in a clockwise direction toward
the closed circuit position and brings movable contact 32 into
surface engagement with stationary contact 24, the spring 76
permits only limited counterclockwise rotation of the current
conducting blade 38 and support member 40. Consequently, clockwise
rotational movement of the common contact cross arm 26 beyond that
necessary for engagement between the contacts will load spring 76
and assure full pressurized engagement between the contacts at
their closed circuit position and a minimum electrical contact
resistance.
The support member 40 of the assembly is also provided with a
forwardly protruding nose portion 86 which advantageously provides
a terminal point 88 suitable for operation as an arc runner for the
movable contact arm assembly. As shown in FIG. 5 an alternative
embodiment of the nose portion is depicted. In the latter
embodiment the nose portion 90 extends below the flat face portion
36 of the blade's bottom surface toward the terminal strap 22.
As will be seen from the foregoing detailed description, the
present invention provides a new and improved composite metal
contact arm assembly which exhibits improved interruption
characteristics on high current short circuits. The assembly is
comprised of a current conducting blade oriented so as to dispose
its broad flat surface toward the arcing area of the circuit
breaker and a structural backing member capable of imparting
increased rigidity and durability to the assembly. The T-shaped
cross-sectional configuration of the contact arm assembly not only
provides the desirable strength and electrical conductivity
characteristics required for circuit breaker operation but also
appears to provide a beneficial heat dissipating effect over the
large conductive surface presented to the arc during the circuit
breaking operation. In addition, an important advantage of the
T-shaped cross-sectional configuration disclosed is that the wide
dimension of the highly conductive blade 38 shields the support
member 40, which is desirably of a higher strength but lower
conductivity material, from the action of an arc drawn between the
contacts. Thus as previously noted, the blade portion 38 is
preferably constructed of copper or a copper alloy, while the
portion 40 is preferably constructed of steel or a steel allow. In
the form of FIG. 5, the portion 40 is extended to provide an arc
runner portion 90, but damage to this portion, such as by erosion
due to effects of arcing, will not adversely affect the function of
the part 40 as a strength beam or reinforcing member.
As will be apparent to persons skilled in the art, various
modifications and adaptations of the structure above-described will
become readily apparent without departure from the spirit and scope
of the invention.
Certain aspects of the structure disclosed herein, particularly
relating to the spring means for biasing the contact carrier
assembly with respect to the contact operator 34, are disclosed and
claimed in our copending application Ser. No. 4,836 filed
1-22-70and assigned to the same assignee as the present
invention.
* * * * *