Note: Descriptions are shown in the official language in which they were submitted.
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HIVOTINa CIRCUIT HREARER TERMINAL
MELD OF THE INVENTION
The present invention relates generally to the
terminals) of a circuit breaker. In particular, the
present invention relates to a pivoting terminal which can
be pivoted to engage a cable extending from the back of the
circuit breaker or from one side of the circuit breaker.
BACKGROUND OF THE INVENTION
Typical circuit breakers include load and line
terminals which provide electrical connections between the
load and line conductors and the circuit breaker. These
terminals have a fixed position or configuration depending
upon the application for the circuit breaker. More
specifically, the terminals can have a number of. positions
or configurations depending upon whether the conductors
connected to the circuit breaker are connected at the side
or back of the circuit breaker. However, these positions
and configurations are established when the circuit breaker
is manufactured, and are not readily modified when the
circuit breaker is used in the field. Additionally,
regardless of the position or configuration of the
terminals, these terminals are rigidly positioned in the
circuit breaker and, in use, can not be repositioned to
accommodate conductors which are oriented such that they
are difficult to connect to the terminal {e. g. a 0o gauge
conductor which is skewed and must be deflected with
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substantial force to be properly connected to the lug
associated with the terminal).
In addition to the problem of connecting poorly
oriented conductors to the terminals of a circuit breaker,
there is a need to reduce the size of circuit breakers for a
given current interrupting rating. Accordingly, circuit
breakers have been designed with moving load contacts which
increase the speed and distance between the line and load
contacts when separating in response to a short circuit
condition. An example of such a circuit breaker is disclosed
in U.S. Patent No. 4,594,567, issued on June 10, 1986. This
type of circuit breaker is typically smaller than a circuit
breaker of equal rating having a fixed load contact, but
requires added components such as a load contact pivot and
camming arrangement. Accordingly, elimination or reduction in
size of any of these added components would further reduce the
size of the circuit breaker.
In view of the circuit breaker configurations
discussed above, it would be desirable to provide an improved
terminal configuration to improve the ability to connect a
conductor to the circuit breaker. Additionally, it would be
desirable to provide a terminal configuration which reduces
the size of a circuit breaker for a given rating.
SUMMARY OF THE INVENTION
The present invention provides an electric switch
including an enclosure, a first contact moveable between first
and second positions within the enclosure, and an operating
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mechanism supported by the enclosure and coupled to the first
contact to move the first contact between positions. The
switch also includes a terminal pivotally supported by the
enclosure and exposed to the exterior of the enclosure, and a
contact arm including a second contact, and pivotally and
electrically connected to the
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terminal at the interior of the enclosure. The contact
arms are arranged so the first contact engages the second
contact when the first contact is in the first position.
The present invention further provides a circuit
breaker including a base including a top side and a bottom
side, a first contact arm including a first contact
moveable between first and second positions, and an
operating mechanism supported by the top side of the base
and coupled to the first contact arm to move the first
contact arm between positions. The circuit breaker also
includes a terminal pivotally connected to the top side of
the base, and a second contact arm including a second
contact and pivotally connected to the terminal. The
contact arms are supported so that first contact engages
the second contact when the first contact arm is in the
first position.
Another configuration of the circuit breaker
includes three phases. This multi-phase circuit breaker
includes a base, at least three line contact arms each
including a line contact and moveable between first and
second positions, and an operating mechanism supported by
the base and coupled to the line contact arms to move the
line contact arms between positions. The circuit breaker
also includes at least three load terminals pivotally
connected to the base, and at least three load contact arms
each including a load contact. Each of the load contact
arms being pivotally connected to one of the respective
load terminals, where the first contacts engage the second
contacts when the first contact arms are in the first
position.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a side elevation view, partly broken
away, of the molded case circuit breaker according to the
present invention with the contact blades shown in the
closed position:
21~~~1~'~
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Figure 2 is a partial view of Figure 1 showing
the contact blades in the open position:
Figure 3 is a view similar to Figure 2 showing
the contact blades in the blown open position:
Figure 4 is a perspective view of the load
contact blade assembly:
Figure 5 is a perspective view of the load
contact blade assembly:
Figure 6 is a view taken on line 6-6 of Figure 2
showing the contact pressure spring assembly:
Figure 7 is a view taken on line 7-7 of Figure 6:
Figure 8 is a view taken on line 8-8 of Figure 3:
Figure 9 is a view taken on line 9-9 of Figure 8;
and
Figure 10 is a view of an alternate terminal
connection arrangement.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Figure 1, a circuit breaker 10
includes an enclosure having a base 17, a line contact
blade assembly 11, a load contact blade assembly 12, an arc
chamber 19 supported by the enclosure above the contact
blade assemblies 11 and 12 and a contact operating
mechanism 14. The blade assemblies 11 and 12 are pivotally
supported by base 17. The line contact blade assembly 11
is shown in the closed position in Figure 1, and in the
open position in Figure 2. Assemblies 11 and 12 are shown
in the blown open position in Figure 3. Line contact blade
assembly 11 generally includes a blade 13 having an
electrical contact 15 on the upper end. Blade 13 is
pivotally supported by base 17.
Operating mechanism 14 is supported by base 17
and provided for moving blade assembly 11 between open and
closed positions with respect to load contact blade
assembly 12. Depending upon the application (i.e. single
or multi-pole), operating mechanism 14 will interact with
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a crossbar to move multiple assemblies 11 simultaneously.
The present embodiment of circuit breaker 10 includes three
poles. However, for purposes of clarity, only a single
pole of circuit breaker 10 is described herein. By way of
example, operating mechanism 14 can be configured as shown
and described in United States Patent No. 4,594,567 noted
above.
Load contact blade assembly 12 generally includes
a blade 16 having V-shaped offset bearing section 18 at the
lower end and an electrical contact 20 at the upper end
which is positioned to engage electrical contact 15 on line
contact blade 13. A terminal strap 22 having a multi-sided
(e. g., octagonal) cross piece or shaft 23 which is seated
in bearing section 18 and retained therein by a leaf spring
24 which is secured to the blade 16 by a rivet 26.
Alternatively, shaft 23 could have a circular cross-
section. The lower end of the spring 24 projects into an
opening 28 in the terminal strap 22. Strap 22 is pivotally
supported at the end bearing portions 23a and 23b of piece
23 by an appropriate bearing structure in base 17 (e. g.
molded recess). For example, portions 23a and 23b could be
captured between base 17 and the top portion of the circuit
breaker 10 enclosure when base 17 and the top portion are
joined. Thus, strap 22 can pivot about the axis of shaft
23 relative to base 17.
A feature of this arrangement is the dual
function of terminal strap 22 which allows load contact
blade 16 to pivot or rotate generally about the axis of
cross piece 23 and allows terminal strap 22 to rotate into
a plurality of positions relative to base 17. With this
arrangement the terminal strap 22 can be pivoted to engage
a clamp-type line connector 34, as shown in Figure 1, or
pivoted to engage a threaded line connector 36, as shown in
Figure 10. Connector 36 includes a threaded fastener 36a
which passes through an opening in terminal 22 and engages
the threads of a threaded wire end 36b. The conductor is
attached to terminal 22 so the axis of the end portion of
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the conductor is substantially coincident with the axis of
fastener 36a.
Load contact blade assembly 12 is pivoted about
piece 23 and biased into engagement with the line contact
blade assembly 11 by a return spring 35 in the form of a
torsion spring which is mounted on base 17 in a position to
engage lower end 27 of load contact blade 16.
Another advantage of the present configuration is
the provision of v-shaped offset bearing section 18 of load
contact blade 16 which makes contact with the cross piece
23 of terminal strap 22. The crosspiece 23 is seated
against the angled sides of the V-shaped bearing section
18. This configuration increases the contact forces
between the blade 16 and the strap 22. The contact forces
with the V-shaped bearing are greater than they would be
with, for example, a circular-shaped journal bearing. It
is advantageous to increase these contact forces for two
reasons. First, because electrical current is conducted
through this bearing, the increased contact forces tend to
reduce the resistance to electrical current flow through
the bearing surfaces. Accordingly, by reducing electrical
resistance, this also reduces the amount of heat produced
in the bearing. Second, it is important to have
sufficiently high contact forces in order to counteract the
effects of current constriction forces in the bearing
interface. Typically, when two electrical conductors make
physical contact with each other, and an electrical current
flows from one conductor into the other through the contact
interface, an electrodynamic repulsion force, due to the
phenomenon of current constriction, arises between the two
parts which tends to separate them. In the bearing surface
between the load contact blade 16 and the terminal strap
22, such separation would be undesirable because it would
result in an electric arc which would damage the bearing
surfaces. The increased contact forces of the present
configuration help to prevent separation from occurring.
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A contact pressure wire spring 30 is mounted on
the front of the load contact blade 12 by rivet 26 for leaf
spring 24. Spring 30 as shown in Figures 6 and 7 includes
a semi-circular loop 25 fixed to blade 16 by rivet 26. A
pair of legs (i.e., beam spring portions) 29 are provided
on the ends of loop 25 which diverge outwardly. A second
semi-circular loop 31 is formed at the upper end of each of
the legs 27. Loops 31 are bent at a right angle to the
upper end of each leg 29. Loops 31 are biased outwardly by
diverging legs 29 on loop 25.
A U-shaped channel member 40 is formed from a
single piece of sheet steel or other ferrous material and
includes a pair of side walls 42 extending outwardly from
a base 44. A pair of opposed spring cam surface are
provided by a surface 46 on the outer edges of each of side
walls 42 extending at a predetermined angle (e.g. 25-65
degrees) from the parallel portion 46a of member 40. U-
shaped member 40 is magnetically attracted to the loops 31
and blade 16 due to the magnetic field produced by the
current in blade 16. This attraction delays the release of
blade 16 and loops 31 from U-shaped channel member 40 until
the arc between contacts 15 and 20 is extinguished. When
the arc is extinguished and the blow apart forces subside,
the return spring 35 will bias load contact blade assembly
12 to its original position.
In operation, loops 31 are initially in direct
engagement with cam surfaces 46 when the load contact blade
assembly 12 is in the closed position. The wire form
spring 30, in combination with the return spring 35, and
the interaction of piece 23, section 18 and leaf spring 24,
holds the electric contact 20 on the load contact blade 16
in engagement with the electric contact 15 on the line
contact blade 13 with an appropriate force. When the
electromagnetic forces (i.e., blow apart) caused by the
substantially parallel and opposite currents in blades 13
and 16 exceed a predetermined limit (i.e., during short
circuit conditions), loops 31 slide along cam surfaces 46,
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are compressed and move to engage side walls 42 of U-shaped
member 40. Upon engaging walls 42, the force loops 31
produce to restrict movement of blade 16 (i.e., counter
clockwise rotation) are greatly reduced to facilitate
contact blow apart.
Although the invention has been described in
conjunction with specific embodiments thereof, it is
evident that alternatives, modifications and variations
will be apparent to those skilled in the art. For example,
the position of springs 30 and U-shaped channel member 40
could be reversed so that member 40 is fastened to arm 16
and spring 30 is fixed relative to base 17. It is intended
that the claims embrace all such alternatives,
modifications and variations that fall within the spirit
and broad scope of the appended claims.
