Note: Descriptions are shown in the official language in which they were submitted.
CA 02068789 1999-10-12
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CIRCUIT BREAKER FOR USE IN WALL MOUNTED PLUG
The present invention is directed towards
an electromechanical circuit breaker, and more
particularly, an electromechanical circuit breaker
which is particularly useful in wall mounted plugs.
It has become increasingly common to
utilize ground fault interrupter circuits in household
appliances to protect against hazardous electric shock
to the consumer. Such ground fault circuits are
particularly important in connection with appliances
operated around water, such as wet/dry vacuums and
appliances utilized in the bathroom.
An integral part of a ground fault
interrupter circuit is an electromechanical circuit
breaker which interrupts the application of electric
power to the load whenever a fault condition is
detected. When such a circuit breaker is used in
connection with a household appliance, it is
particularly important that the circuit breaker be
small, inexpensive, simple, and reliable. The use of a
compact circuit breaker is particularly important when
it is mounted in a standard wall plug holding the male
plug blades which fit into a standard female wall
receptacle.
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While the circuit breaker of the present invention is
particularly useful. in connection with ground fault
interrupter circuits housed in a wall mounted plug, the
present invention i.s not limited to such applications.
The circuit breaker of the present invention
comprises:
a normally open switch including first and second
contacts and a moveable leaf spring supporting the first
contact, the leaf spring is normally oriented in a first
position wherein the first contact is not electrical
contact with the second contact and is deformable into a
second position wherein the first contact is in electrical
contact with the second contact;
an armature moveable between an open position and a
closed position;
an electrical coil for generating a magnetic field
which moves the armature into the closed position when the
coil is energized;
a support member upon which the coil is mounted and
wherein the armature is hingedly connected to the support
member; and
a cam member coupled between the armature and the leaf
spring.
The leaf spring biases the armature into its open
position when the coil is not energized, the armature
causing the leaf spring to deform into the second position,
so as to place the first contact into electrical contact
with the second contact, when the coil is energized.
Preferably the cam member has a cam surface which
contacts the support member. The cam member is moved into
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the first position by the leaf spring when the coil is not
energized. When the cam member is in its first position,
the armature will be moved into its open position and the
normally open switch will be open. The cam member is moved
into a second position by the armature when the coil is
energized. In this position, the cam member causes the
leaf spring to move into its second position so as to close
the normally open switch.
In the preferred embodiment, the armature is removably
coupled to the support member by a tongue and groove
arrangement and the tongue is normally biased into the
groove by the leaf spring. The conductive core extends
through the coil and cooperates with the support member and
armature, which are also formed of conductive materials, to
define a magnetic path for flux generated by the coil when
the coil is energized.
The coil is preferably wound on a nonconductive bobbin
which is supported on the support member. The conductive
core extends through the bobbin and is separated from the
coil by the bobbin.
A support member is preferably mounted on a circuit
board via an insulation member which supports the support
member at a position spaced from the circuit board.
In the preferred embodiment, the circuit breaker and
circuit board are housed in a wall plug housing having a
viewing opening therein. A portion of the armature which
lies adjacent to viewing opening
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when the armature is in one of the open and closed
positions is preferably painted with a highly visible
paint so as to provide a visual indication through the
opening of whether the normally open switch is in the
open or closed position.
For the purpose of illustrating the
invention, there is shown in the drawing a form which
is presently preferred, it being understood; however,
that the invention is not limited to the precise
arrangement and instrumentality shown.
Fig. 1 is a side view of the circuit
breaker of the present invention located in the housing
of a wall plug, part of the housing of the wall plug
being broken away, with the circuit breaker in the open
position.
Fig. 2 is a top view of the circuit breaker
of Fig. 3, the top portion of the plug housing being
broken away.
Fig. 3 is a cross section of the circuit
breaker and plug housing taken along lines 3-3 of Fig.
2.
Fig. 4 is a front view of the circuit
breaker of Fig. 1 taken along lines 4-4 of Fig. 1.
Fig. 5 is a rear view of the circuit
breaker of Fig. 1 taken along lines 5-5 of Fig. 1.
Fig. 6 is an exploded isometric view of the
circuit breaker of Fig. l, without the winding coils.
Fig. 7 is an isometric view of the actuator
illustrated in Fig. 6.
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Fig. 8 is a side view of the circuit
breaker of the present invention located in the housing
of a wall plug, part of the housing of the wall plug
being broken away, with the circuit breaker in the
closed position.
Referring now to the drawings wherein like
numerals indicate like elements, there is shown in Fig.
1 a circuit breaker constructed in accordance with the
principles of the present invention and designated
generally as 10. In the present embodiment, circuit
breaker 10 is mounted on a circuit board 12 which also
supports electronic components forming part of the
ground fault interrupter circuit which drives the
circuit breaker 10.
In the preferred embodiment, the circuit
board 12 and the electronic components thereon,
including the circuit breaker 10, are mounted in a plug
housing 14 of a wall mounted plug.
The circuit board 12 is mounted to the plug
housing 14 in any suitable manner. The plug housing 14
preferably includes a base portion 16 and a cover
portion 18. The circuit board 12 is initially mounted
on the base portion 16 of the housing 14 and then the
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cover portion 18 is coupled to the base portion 16 to
form an enclosure housing the circuit breaker 10.
The circuit breaker ZO is coupled between a
pair of plug blades 20, 22 (Figs. 1 and 4) which are
adapted to be inserted into a standard female wall
receptacle and a power cord 24 which extends through an
opening in housing 14, and is coupled to a load such as
a household appliance.
As best viewed in Figs. l, 2 and 5, the
circuit breaker 10 includes a pair of stationery
contacts 26, 28 and a pair of moveable contacts 30, 32
coupled to respective leaf springs 34, 36. The
statianery contact 26, movable contact 30 and leaf
spring 34 together define a first normally open switch.
The stationery contact 28, the movable contact 32 and
the leaf spring 36 together define a second normally
open switch. The first normally open switch is coupled
between the plug blade 20 and a first lead 46 of power
cord 24. The second normally open switch is coupled
between the plug blade 22 and t',he second lead 48 of the
power cord 24. In the normally open position, these
switches cut off power to the load coupled to power
cord 24. In the closed position (illustrated in Fig.
8), the switches couple electrical power to the load.
Stationery contacts 26, 28 are preferably
defined by respective eyelets which are riveted to
circuit board 12 along with respective lugs 38, 40.
Each of the lugs 38, 40 includes an annular portion
which is located below circuit board 12 and has an
opening through which its respective stationery contact
is riveted. The lugs 38, 40 also include a laterally
extending I shaped portion which extends along the
bottom of circuit board 12 and then up through
respective openings 42, 44 (Fig. 2) in the circuit
board 12 to a position located above the circuit board.
Respective leads 46, 48 of the power cord 24 are
connected to the portion lugs 38, 40 located above the
circuit board 12 by any suitable means, for example by
soldering.
Referring to Fig. 1, leaf spring 34 is
coupled to plug blade 20 by an eyelet 50 which extends
through the circuit board 12 and is riveted thereto.
The rightmost end of the leaf spring 34 as viewed in
Fig. 1 extends through an opening 52 in the circuit
board 12 to provide a more stable connection to the
circuit board. The leaf spring 36 is similarly coupled
to the circuit board 12 by a corresponding eyelet 54
(Fig. 2).
The spring force in leaf springs 34, 36
cause them to be located in the positions illustrated
in Figs. 1 and 3 in the absence of any externally
applied farces. In this position, the moveable
contacts 30, 32 will be spaced from the stationery
contacts 26, 28, respectively.
When power is to be applied to the load
coupled to power cord 24, a relay 56 forming part of
the circuit breaker 10 is energized by the circuitry
(e.g, a ground fault control circuit) coupled to
circuit board 12 causing the armature 58 to pivot from
the open position illustrated in Fig, 1 to the closed
position illustrated in Fig. 8. In this position, the
cam member 60, which is coupled to the bottom end of
armature 58, rotates from its generally horizontal
orientation illustrated in Fig. 1 to its oblique
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orientation illustrated in Fig. 8 and deforms leaf
springs 34, 36 into the position illustrated in Fig. 8.
This moves the moveable contacts 30, 32 into firm
contact with the stationery contacts 26, 28,
respectively. In the preferred eanbodiment, the cam
member 60 is designed to ensure that there is an over
deformation in the leaf springs 34, 36 (that is, they
are deformed beyond the position required to first
place moveable contacts 30, 32 into contact with
stationery contacts 26, 28) in order to ensure a strong
contact between the moveable contacts 30, 32 and
stationery contacts 26, 28, respectively.
The detailed structure and operation of
relay 56 will now be described in more detail with
particular reference to Figs. 3 and 6.
The relay 56 includes a plastic bobbin 62
having a cylindrical section 64 an which the coil 66 is
wound. Opposite ends of the coil 66 pass through a
slot 68 formed in the back wall 70 of bobbin 62 and
into the channel 72 formed at the rear of the bobbin
62. One end of the coil 66 extends down the left side
of the channel 72 and is electrically connected to gin
74. The remaining end of coil 6S extends down the
right side of channel 72 and is connected to pin 76.
As best shown in Figs. 1 and 3, pins 74, 76 extend
through the circuit board 12. While not shown, the
pins 74, 76 are connected to respective circuit board
leads which are energized when the coil 66 is to be
activated.
The plastic bobbin 62 is supported on a
metallic frame 78 which in turn is supparted by a
plastic insulation piece 80 which sits on the top
surface of circuit board 12.
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The insulation piece 80 includes a planar
support surface 82 and a pair of lateral edge guides
84, 86. The width of the portion of the support
surface 82 located between lateral edge guides 84, 86
is equal to the width of the base section 96 of the
metallic frame 78 which is seated on the insulation
piece 80 to closely hold the frame 78 in place. The
planar support surface 82 is maintained at a location
above the circuit board 12 (so as to insulate the coil
28 from the circuit board) by a plurality of legs 88,
90, 92 extending downwardly from the support surface
82. A domed opening 94 is formed in the rear bottom
portion of insulation piece 80 to permit the lead 48 of
the power cord 24 to pass under the coil 66 so that it
may be soldered or otherwise coupled to lug 40.
The metallic frame 78 includes a base
section 96 which is received on the planar support
surface 82 of insulation piece l30. A pair of
downwardly projecting pins 98, :L00 are formed
integrally with the base sectioal 96 and wrap around
corresponding surfaces 102, 104 formed along the sides
of insulation piece 80. As best shown in digs. 1 and
3, the pins 98, 100 extend through corresponding
openings (unnumbered) in circuit board 12 and are
connected to circuit board 12 in any appropriate
manner.
The metallic frame 78 includes a rear
section 106 having an opening 108 formed therein.
Opening 108 receives the rear end of the metallic core
110 extending through a corresponding opening 112 in
bobbin 62, The metallic core 110, the metallic support
plate 96 and the metallic armature 58 cooperate to
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define a magnetic path for the flux generated by the
coil 66 when current is passed through the coil. The
magnetic flux will be concentrated at the front face
114 of the metallic core 110 forming a strong magnetic
field which will draw the armature 58 from the open
position illustrated in Fig. Z to the closed position
illustrated in Fig. 8.
As best shown in Fags. 3, 6 and 7, the
armature 58 is fixedly coupled to plastic cam member 60
and is hingedly coupled to the metallic frame 78. The
armature 58 includes a foot portion 116 and a face
portion 118. Foot portion 116 is fitted into a slot
120 formed in cam member 60. Part of the metal forming
the foot portion 116 is cut and forced upwardly to form
a projection 122. As the foot portion 116 is forced
into the slot 120 in cam member 60, the upper wall 119
of cam member 60 will be deformed upwardly until the
projection 122 is received in the slot 124 formed in
the rear of cam member 60. As a result of this snap-
fit arrangement, the cam member 60 is securely attached
to the foot portion of 116 of armature 58.
As best shown in Figs. 6 and 7, an inverted
U-shape opening is formed in face portion 118 of
armature 58 to form an upwardly projecting tongue 126.
The tongue 126 is received in a corresponding groove
128 formed in a narrow projection 130 extending from
the front end of metallic frame 78.
As best shown in Figs. 1 and 3, the cam
member 60 is pressed against the bottom of base section
96 of metallic frame 78 by the spring force of leaf
springs 34, 36. As a result of the spring force, the
tongue 126 formed in the face portion 118 of armature
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58 is forced up through the groove 128 in frame 78.
Since the upper and lower faces 132, 134 (Fig. 6) of
the cam member 60 are aligned parallel to one another,
and since the face portion 118 of armature 58 forms an
oblique angle with the foot portion 116 thereof, the
face portion 118 of armature 58 will be spaced from the
front face 114 of care 110 whenever the coil 66 is not
energized. When electrical current flows through the
coil 66, the armature 58 pivots about a pivot point
defined by the bottom portions 115 of the U-shaped
opening in armature 58 and the bottom 117 of projection
130. As a result, the face portion l18 of armature 58
is drawn into contact with the front face 114 of core
110 causing the rear lower edge 138 of cam member 60 to
rotate caunterclockwise as viewed in Figs. 1 and 3
thereby deforming leaf springs 34, 36 into the position
illustrated in Fig. 8 and moving moveable contacts 30,
32 into firm contact with stationery contacts 26, 28.
~,s best seen in Figs. 1 and 6, the top of
the front face 118 of armature !58 defines an indicator
section 140 which is preferably painted with an easily
visible color, such as iridescent orange. hs best
viewed in Fig. 1, a viewing opening 142 is formed in
housing 14 at a location corresponding to the location
of indicator section 140 when armature 58 is in the
open position illustrating Fig, 1. In the preferred
embodiment, a viewing lens 144 is located in the
viewing opening 142. This lens may be a magnifying
lens so as to make it easier to view the indicator
section 140 through the opening 142.
When power is being applied to the load,
the armature 58 is located in the closed position
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illustrated in Fig. 8 and the indicator section 140 is
moved away from the viewing opening 142. The user will
not see the brightly colored indicator section 140
which will inform him that power is being applied to
the load.
When power is cut off from the load, the
armature 58 returns to the open position illustrated in
Fig. 1 and the user can view the indicator section 140
through the viewing opening 142. Tn this position, the
viewer will see the brightly colored paint Located on
the indicator section 40 which will let the viewer know
that the circuit breaker is open and that power is
disconnected from the load.
Tn the preferred embodiment, the viewing
opening 142 is placed at the location of the indicator
section 140 when the armature 58 is in the open
position. Alternately, the viewing opening 142 can be
located at the position of the indicator section when
armature 58 is in the closed position. Tn such case, a
bright color such as green is preferably used to
indicate an OK condition -- that is, that the circuit
breaker is closed and power is being applied to the
load a
The foregoing structure provides a very
simple, reliable, and inexpensive circuit breaker with
the minimum of moveable parts. The circuit breaker can
be constr-acted very compactly so as to fit within the
housing of a wall plug while retaining full electrical
capacity, low manufacturing costs, and reliable, fully
automatic operation.
The present invention may be embodied in
other specific forms without departing from the spirit
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or essential attributes thereof and, accordingly,
reference should be made to the appended claims, rather
than to the foregoing specification, as indicating the
scope of the invention.
