Note: Descriptions are shown in the official language in which they were submitted.
CA 02060323 1998-08-06
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A METHOD OF MANUFACTURING A CIRCUIT BREAKER
Back round of the Invention and Prior Art
The invention relates to circuit breakers and, more particularly, to an
improved
method of manufacturing a circuit breaker.
Circuit breakers function to interrupt electrical current flow between a
source of
electricity and a load in response to an over-current condition. They are
typically
manufactured in standard sized housings and include a movable blade carrying a
contact
(movable contact) that is generally connected to the electrical source, a
mechanism
carrying a stationary contact and a spring for biasing the movable contact
away from the
stationary contact. A releasable latch mechanism opposes the spring bias to
physically
couple the movable contact and the stationary contact to permit current flow
from the
source to the load. A trip lever releases the latch mechanism, permitting the
spring bias
to separate the movable contact and the stationary contact to prevent current
flow from
the source to the load.
Prior art circuit breaker assemblies have one or more points of attachment to
the
housing. This makes preassembly of the breaker mechanism difficult because it
is held
together by the housing. The manufacture of prior art circuit breakers has
also been
difficult to automate because parts need to be assembled along three
orthogonally related
axes. The present invention provides a solution to these problems.
CA 02060323 1999-06-04
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Summary of the Invention
It is an object of the invention to provide an improved method of
manufacturing a
circuit breaker.
Another object of the invention is to provide a reliable, low cost method of
manufacturing a circuit breaker.
A feature of the invention is the provision of a modular subassembly of the
operating
parts of a circuit breaker that may be tested and adjusted prior to
installation in the breaker
housing.
In one aspect, the inventive method involves preassembling the operative parts
of
circuit breaker between a pair of frame plates that are supportable in a
housing without
attachment thereto. In one form of the invention, a functional circuit breaker
module is
assembled. The module includes the assembled working elements of the breaker,
which may
be independently adjusted and tested before final installation. A housing is
provided for
receiving and supporting the module without attachments.
An aspect of the invention is a method of manufacturing a circuit breaker
comprising
the steps of: providing a housing defining support means; providing a pre-
assembled module
containing an operating mechanism of a circuit breaker including a stationary
contact and a
movable contact, movable between an open position and a closed position with
said stationary
contact, a trip mechanism and an operating handle having electrical connection
means;
adjusting and testing said pre-assembled module; and installing said adjusted
and tested
module and said electrical connection means in said housing.
Another aspect of the invention is a method of manufacturing a circuit breaker
having
a movable load contact and a stationary load contact comprising the steps of:
pre-assembling
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a module, comprising movable parts of said circuit breaker, and said
stationary load contact,
said module being capable of being adjusted and tested before installation in
a housing;
providing a housing defining at least one compartment configured to support
said module
without attachment to said module; testing said module; placing said tested
module into said
compartment; and securing a cover to said housing.
Another aspect of the invention is a method of manufacturing a circuit breaker
comprising the steps of: pre-assembling a module, including a pair of side
plates, supporting
a movable contact mechanism, stationary contact, an operating handle and a
trip mechanism,
said module being capable of adjustment and testing before installation in a
housing;
providing a breaker housing defining a plurality of compartments for
supporting component
parts of said circuit breaker, including said module, without attachments
between said
component parts and said housing; testing said module; placing said tested
module and said
compartment parts of said breaker into corresponding compartments in said
housing; and
1 S securing a cover to said housing.
Another aspect of the invention is the method of manufacturing a circuit
breaker
comprising the steps of: pre-assembling movable parts of said circuit breaker,
including a
movable load contact, and a stationary load contact, into a module comprising
a pair of side
plates operatively supporting said movable load contact and said stationary
load contact, said
module being capable of adjustment and testing before installation of a
housing; providing a
housing including means for supporting said module without attachments between
said
moveable load contact and said stationary load contact and said housing;
adjusting and testing
said module; installing said tested module in said housing; and securing a
cover to said
housing.
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Another aspect of the invention is a circuit breaker comprising: a housing
including
a base and a cover; a module operably supporting movable parts of said circuit
breaker
including a movable load contact and a stationary load contact; and means in
said base for
supporting said module therein without attachments between said movable load
contact and
said stationary load contact and said base.
Another aspect of the invention is a circuit breaker comprising: a base
defining at least
two compartments; a cover for closing said base; a module including a pair of
side plates
operatively supporting movable parts of said circuit breaker including a
movable load contact
and a stationary load contact for testing and calibration; and said base
supporting said module
in one of said two compartments without attachments between said movable load
contact and
said stationary load contact and said base.
BRIEF DESCRIPTION OF DRAWINGS
Other objects, features and advantages of the invention will be apparent from
reading
the following description in conjunction with the drawings, in which:
FIG. 1 is a view of a circuit breaker constructed in accordance with one
aspect of the
invention;
FIG. 2 is a partial view of the unitary breaker assembly of FIG. 1 in a closed
position;
FIG. 3 is a partial view of the unitary breaker assembly of FIG. 1 in an open
position;
FIG. 4 is a view of the operating handle mechanism of the unitary breaker
assembly
as viewed from behind;
FIG. 5 is an exploded perspective showing assembly of the circuit breaker of
FIG. 1;
FIG. 6 is a view of a circuit breaker constructed in accordance with another
aspect of the
CA 02060323 1998-08-06
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invention; and
FIG. 7 is an exploded perspective showing
assembly of the circuit breaker of FIG. 6.
Description of the Preferred Embodiments
A circuit breaker 10 constructed in
accordance with the first aspect of the invention is
illustrated in FIG. 1. An additional description of
the general features of a similar type circuit breaker
can be found in the following patents,
(a ) Westermeyer, U.S. Patent No. 4, 617, 540,
entitled "Automatic Switch, Rail-tdounted",
(b) Westermeyer, U.S. Patent No. 4,614,928,
entitled "Automatic Switch with an Arc Blast Field",
(c ) Westermeyer, U.S. Patent No. 4, 609, 895,
entitled "Automatic Switch with Integral Contact
Indicator", and
(d) Westermeyer, U.S. Patent No. 4,608,546,
entitled "Automatic Switch with Impact-Armature
Tripping Device".
The circuit breaker 10 has a housing 11 and
includes a resilient clamp type line terminal 12 for
connection to a source of electricity (not shown) and a
screw type load.terminal 14 for connection to a load
circuit (not shown). A current path is established
between the line terminal i2 and the load terminal 14
which includes a line conductor 16, a support 18 for a
bimetal thermal element 20, a braided pigtail 22, and a
blade 24 including a movable contact 26. Continuing
from the movable contact 26, the current path includes
a stationary contact 28, a trip coil 31 and a load
conductor 32.
The blade 24 is shown in a closed position
with the movable contact 26 engaging or mating with the
stationary contact 28. The blade 24 is pivotable
between the closed position shown and an open position,
wherein the movable contact 26 is separated from the
stationary contact 28 to prevent current flow.
CA 02060323 1999-06-04
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The stationary contact 28 comprises a layer of copper
28a laminated to a layer of steel 28b with a
silver/graphite composition contact 28c welded to the '
copper. The blade 24 is an element of a unitary
5 breaker assembly, generally designated 40, which
controls the position of the blade 2~1 relative to the
stationary contact 2$.
The circuit breaker 10 also includes a line-
side arc arresting plate 29a, a load-side arc arresting
10 plate 29b and a stack of deionization plates, or arc
stack, 30, which cooperate to break the electrical arc
formed when the circuit breaker 10 is opened while
supplying current to a load. The specific operation of
the arc arresting plates 29a, 29b and the arc stack 30
15 is disclosed in greater detail in the above
identified patents. The elements 16, 18, 20 and 29a
are joined together by welding at their various
interfaces.
In FIG. 2, unitary breaker assembly 40
20 includes a first frame member or plate 42 having first,
second and third upright members 43, 4~4, ~5,
respectively. A pivot pin 48 extends upwardly through
a hole in the first frame plate ~t2. A trip lever 50 is
pivotally supported on the pivot pin 48. The trip
25 lever 50 includes a solenoid actuator surface 52 and a
bimetal actuator surface S~I. The blade 2u includes an
elongated slot 24a for receiving the pivot pin 48. The
blade 24 further includes a notch 56 to which a first
end of a toggle spring 58 is attached.
30 A latch spring 60 is disposed about the pivot
pin 48 between the trip lever 50 and the blade 2~1. The
latch spring 60 includes a first end 62 which engages
the first upright member ~3 and a second end 63 which
engages the solenoid actuator surface 52 of the trip
35 lever 50. The latch spring 60 provides
counterclockwise bias to the trip lever 50.
A cam 64, having an operating handle 65
attached thereto, includes a recesse~~ n~rr; ~., ~~ ; n
FCT/US90/03664
wo9m6~zo 2~~~3~3
_5_
which a cam spring 68 is placed. Referring also to
FIGS. 3 and ~4, a first cam spring end 69a extends from
recessed portion 66 and engages the third upright
member 45. A second cam spring end 69b engages a wall
of the recessed portion 66. The cam spring 68 imparts
a clockwise bias to the cam 64 as viewed in FIG. 2. A
link 70 couples the cam 64 to a pawl 72. The pawl 72
is pivotally connected to a flag end 74 of the blade 24
by a pin 76. The flag end is visible through a window
75 in the housing 11 (FIG. 1) and indicates the status
of the circuit breaker contacts, i.e. whether they are
opened or closed. The trip lever 50 further includes
an engaging surface 78 which engages the pawl 72.
When in the closed position, the movable
contact 26 is physically coupled to the stationary
contact 28. The pin 76 operates as a fulcrum on the
blade 24, causing the toggle spring 58 to keep the
movable contact 26 and the stationary contact 28
closed.
Referring again to FIG. 1, the blade 24 can
be moved to the open position by operation of the
bimetal thermal element 20, by action of a spring
loaded rod 80 disposed within the operating or trip
coil 31, or by manipulation of operating~handle 65.
Load current passing through the bimetal thermal
element 20 heats the bimetal thermal element 20 which
deflects downwardly in the direction of the arrow 82.
The amount of deflection depends upon the temperature
reached by the bimetal thermal element 20, which is a
function of the magnitude and duration of the load
current. When the bimetal thermal element 20 deflects
sufficiently, a calibration screw 84 engages the
bimetal actuator surface 54 of the trip lever 50,
causing the trip lever 50 to rotate clockwise about the
pivot pin 48 and against the. bias of the latch spring
60 (FIG. 3), tripping the circuit breaker 10 as
discussed in greater detail below.
The circuit breaker 10 can also be tripped by
the trip coil 31. The rod 80 is downwardly biased by a
w~ 9ms~zo Pcrms9o~o36~
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~.~ ~D
~~,~sb~enoid spring 86. Rod 80 may be coupled to, or a
part of (or simply in gravitational contact with), a
movable armature in coil 31. Load current passes
through the coil 31 (one end of which is welded to
stationary contact.28), establishing an electromagnetic
field that affects the coil armature (and hence rod
80). When the electromagnetic force in coil 31 exceeds
the biasing force of the solenoid spring 86, the rod 80
is moved (up) to engage the solenoid actuator surface
52, causing the trip lever 50 to rotate clockwise,
tripping the circuit breaker 10, as discussed below.
Referring to FIGS. 1, 2 and 3, when either
the bimetal thermal element 20 or the rod 80 causes the
trip lever 50 to rotate clockwise, the engaging surface
78 of trip lever 50 moves away from pawl 72 which
permits cam spring 68 to rotate cam 64 in a clockwise
direction. Cam 64 pulls downwardly on the link 70,
causing counterclockwise rotation of pawl 72 about pin
76. When pawl 72 is released from engagement with the
engaging surface 78, blade 24 moves downwardly at its
right side due to the action of toggle spring 58,
initially causing the pivot pin ~8 to engage the upper
surface of the elongated hole 2~4a, which operates as a
floating point. The pivot pin 48 then operates as a
fulcrum about which blade 24 rotates, causing the
toggle spring 58 to move movable contact 26 away from
stationary contact 28, thus opening the circuit. ,
In the event that the operating handle 65 is
Locked in its upward, or on, position and either
bimetal thermal element 20 or rod $0 causes the trip
lever 50 to rotate clockwise, link 70, which is under
compression between cam 64 and pawl 72, causes the pawl
72 to rotate clockwise about pin 76, again releasing
the engaging surface 78 from engagement with the pawl
72. When the engaging surface 78 no longer engages the
pawl 72, the blade 2~I lowers, causing the pivot pin 48
to operate as a fulcrum about which the blade 24
rotates, permitting the toggle spring 58 to move the
wo 91/16?20 ~ ~ ~ ~ ~ ~ ~ Cf/U~90/03664
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movable contact 26 away from the stationary contact 28.
The cam 64 is shown from its reverse side in
FIG. 4 to better illustrate the recessed portion 66 and
cam spring 68. The cam spring 68 is centered on a cam
pivot axis 88. The second cam spring end 69b is biased
against wall b6a of the recessed portion 66. The first
cam spring end 69a is biased by torsion loading against
the third upright member 45. The torsion loading of
the cam spring 68 urges the cam 64 and attached
operating handle 65 in the downward position.
The circuit breaker 10 is illustrated in an
exploded perspective view in FIG. 5. The first, second
and third upright members 43, 44, 45 of the first frame
plate 42 terminate in connecting tabs 43a, 44a, 45a,
respectively. A second frame plate 89 includes
corresponding tab receiving openings ~43b, 44b, 45b
which provide an interference fit with the respective
connecting tabs 43a, ~44a, 45a to secure the f:Erst frame
plate 42 to the second frame plate 89. In this
embodiment of the invention, the first and second frame
plates 42, 89, respectively, are separate pieces;
however it is to be understood that the frame plates
could be formed from a single piece folded over to form
the opposing frame surfaces.
With the first frame plate 42 secured to the
second frame plate 89, it will be noted that all
elements of the unitary breaker assembly 40 are secured
together. As illustrated, the unitary breaker assembly
and other individual components of the circuit breaker
10 are simply installed into the circuit breaker base
11a and require no attachments thereto.
The housing 11 has a base 11a and a cover
11b. The base 1la defines x, y and z axis supporting
elements and surfaces. These include internal and
external walls and parts that are perpendicular to the
base 11a, i.e. extend along the z-axis. The elements
define an arc stack section 90, a unitary breaker
assembly section 92 and a coil section 94 as well as
support slots such as 96a and 96b.
WO 91116720 PCT/LJS90/03664
'~ ~0'~'~3 _8_
End portions 18a and 18b of the bimetal
support 18 are slid into and retained within respective
support slots 96a and 96b. The line=side arc arresting
plate 29a is slid into and retained within an arc
runner slot 98. The unitary breaker assembly CIO is
then simply placed in.the unitary breaker assembly
section 92, and requires no attachments to the housing
11. Suitably placed and configured additional
indentations and protrusions (not shown) may be
incorporated in base 11a and cover 11b for assuring
adequate support for the various elements, if desired.
The load terminal 1~4 is slid into and retained in a
load terminal compartment 99. Suitable fasteners, not
shown, are used to secure cover 11b in place on base
11a and thereby retain the elements of the circuit
breaker in housing 11. The blade 24 is a tapered plate
on edge, operating structurally as a beam so as to
prevent flexing. If additional current carrying
capacity is required, the width of the blade 24 may
simply be increased.
The embodiment of the invention illustrated
in FIGS. 6 and 7 provides a very attractive solution
for a circuit breaker manufacturer who wishes to do
final assembly of circuit breakers at different
locations. The operative parts of the circuit breaker,
including the unitary breaker assembly and the trip
coil and stationary contact, are preassembled into a
module that may be tested and calibrated before final
installation in the breaker housing. Therefore, the
critical manufacturing steps may be carefully
controlled where the modules are constructed.
In FIG. 6, circuit breaker 10' has a base 111
that is modified to accept a module 100 without the
need of fasteners. Module 100 h.as a pair of supporting
side plates or frame members (only one of which-105-is
visible) that function to support the movable elements
for operation as was accomplished by the frame members
X12 and 89 above. That is, one of the side plates of
WO 91f16720 PCT/US90l03664
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module 100 has an internal configuration that
cooperates with the other side plate to operatively
support the working elements of the circuit breaker.,
As illustrated by the dotted line wall portions 103 and
the fastener points 102, the frame members are
configured to provide suitable openings for parts of
the circuit breaker that extend outside the module
which includes the unitary breaker assembly and the
trip coil assembly. These parts include the cam 64,
ZO operating handle 65, line terminal '12, load terminal
14, flag end 7~, calibration screw 84 and line and load
side arc plates 29a and,29b. Thus the essential
mechanis~i of the breaker may be handled and tested as a
separate module 100. The frame members are preferably
made of plastic with suitable interior coatings or
barrier plates adjacent to the contact areas to
withstand the effects of heating due to opening and
closing of the contacts under load. The frame members
also support the pivot pins X48 and define the pivot
axis 88. The differences between this embodiment and
that described in FIGS. 1-5 are that the stationary
contact and trip coil and the bimetal and calibration
screw are also secured in their final positions by the
module 100, which permits full operation and adjustment
of the breaker before installing it in housing 111.
All that needs to be added during final assembly is the
arc chute 30. Securing the trip coil and stationary
contact and the thermal element support 18 in module
100 renders the unitary breaker assembly capable of
full operation apart from housing 111 and cover 112 and
represents a preferred implementation of the invention.
In FIG. 7, the internal configuration of base
111 for supporting module 100 (without fasteners is
shown. It will be appreciated that suitable fasteners
(not shown) are used to secure module 100 between base
111 and cover 112 via apertures 10u and 105. It will
also be noted that the particular configuration of the
base, cover and module is dependent upon the specific
breaker construction.
WO 91 f 16720 PCf/US90/03664
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Thus it can be seen that a unitary breaker
assembly has been provided which can be preassembled
and which requires no attachments to secure it within a
circuit breaker housing. In addition, assembly of the
unitary breaker assembly can readily be automated,
because the assembly steps are performed along a single
axis.
It will be understood that the invention may
be embodied in other specific forms without departing
from the spirit or central characteristics thereof.
The present examples and embodiments, therefore, are to
be considered in all respects as illustrative and not
restrictive, and the invention is not to be limited to
the details given herein.
