Information
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Patent Grant
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6211759
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Patent Number
6,211,759
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Date Filed
Wednesday, January 12, 200024 years ago
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Date Issued
Tuesday, April 3, 200123 years ago
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Inventors
-
Original Assignees
-
Examiners
Agents
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CPC
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US Classifications
Field of Search
US
- 335 6
- 335 16
- 335 132
- 335 202
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International Classifications
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Abstract
A gas deflector for a line-in connector of a circuit breaker. The gas deflector is coupled to a collar with a top and a cavity, a threaded opening through the top, a screw threaded in the threaded opening. The collar is attached to the line-in for the circuit breaker. The gas deflector is an L-shaped shield with an integral screw sleeve and a slot sized to allow a terminal strap to pass therethrough. The terminal strap is connected to the collar. The shield device covers the collar top and the cavity and is held in place by the screw passing through the sleeve and by the terminal strap passing through the slot. The shield substantially reduces the amount of ionized gas infiltrating into the collar.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a circuit breaker and, more specifically, to a shield structure which directs ionized gases, created by separation of the circuit breaker's contacts, away from a collar assembly coupled to the line side of a circuit breaker.
2. Description of the Prior Art
Molded case circuit breakers are generally known in the art. Such circuit breakers are used to protect electrical circuits from damage due to an overload, a short circuit or both. Circuit breakers typically have a molded plastic housing enclosing at least one pair of separable contacts including a fixed contact and a moveable contact. During an overload or a short circuit, the circuit breaker will trip causing the contacts to separate thereby opening the circuit. Additionally, the circuit breaker may be tripped manually should the need arise.
When the electrical contacts within a circuit breaker separate, an electrical arc may form between the contacts creating hot ionized gases. The ionized gases formed by an electrical arc are conductive. If these ionized gases collect in the vicinity of the line terminals of the circuit breaker, they may establish a conduction path between the terminals connected to different phases of the line current, or between the terminals and an electrical ground. Such a connection can lead to electrical faults on the line side of the circuit breaker and damage the equipment. Circuit breakers typically include vents to allow the ionized gases to quickly escape as well as a shield to protect a collar assembly which connects the line to the terminal strap or contact.
A collar assembly will generally have a four sided collar defining a cavity. The collar is attached to the terminal strap which incorporates the fixed contact of the circuit breaker. The collar will also have a screw, or other such device, which may be used to clamp the line end against the terminal strap. The collar and the line end are in close proximity to the contact point of the circuit breaker and, when the circuit is broken, ionized gases are in the immediate vicinity of the line end and collar assembly. To deflect the ionized gasses away from the collar assembly and towards a vent, most collar assemblies include a gas deflector.
Prior art gas deflection devices include a generally L-shaped paper shield mounted on top of the collar which overlays the contact side of the collar, as well as a separate plastic sleeve disposed about the screw and passing through the paper shield. This design has several disadvantages. For example, because the paper shield device is not coupled to the collar assembly, it can easily be accidentally removed. Also, because the paper shield is not fixed, it may move within the circuit breaker housing, allowing a path for ionized gases to reach the collar assembly and line. Because the screw sleeve is not integral to the paper shield, another path for ionized gases to contact the collar assembly could exist through the screw sleeve hole in the paper shield. Additionally, because the paper shield and screw sleeve are separate components, there is an additional cost associated with assembling the device.
There is a need for a gas deflection device to isolate the line end terminals of a circuit breaker from each other and areas adjacent to the circuit breaker to substantially reduce the amount of ionized gases infiltrating into those spaces.
There is a further need for a gas deflection device which is compatible with collar assemblies presently used on circuit breakers.
There is a further need for a gas deflection device which is inexpensive and may be conveniently installed within a circuit breaker.
SUMMARY OF THE INVENTION
The present invention satisfies the above referenced needs by providing a one piece shield which protects the collar assembly from ionized gases. The shield has an integral sleeve which provides access for the mounting screw. Additionally, the shield is provided with a slot allowing the terminal strap to pass therethrough. The shield is made of a rigid material, such as plastic. The shield is held in place at one end by the sleeve and at the other end by the terminal strap passing through the shield. Thus, the shield is less likely to be subject to deflection than a paper shield.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
shows a perspective view of the gas deflection device and collar assembly mounted within a circuit breaker housing.
FIG. 2
shows a perspective view as in
FIG. 1
, with the top portion of the circuit breaker housing removed.
FIG. 3
is an exploded view of a terminal assembly.
FIG. 4
is a cross sectional view of the shield.
DESCRIPTION OF THE PREFERRED EMBODIMENT
A shield device
10
according to the present in invention is shown disposed within a circuit breaker housing
20
in
FIGS. 1 and 2
. The circuit breaker housing
20
includes a top portion
22
and a bottom portion
24
forming an arc chamber
26
, an movable contact chamber
28
, a collar assembly recess
30
and separation ribs
32
,
34
. A terminal assembly
40
fits mainly within the collar assembly recess
30
, with a terminal strap
80
extending between separation ribs
32
,
34
and into the arc chamber
26
. Within the arc chamber
26
is a fastener hole
36
. A fastener
38
passes through a fastener hole
90
on a terminal strap
80
into fastener hole
36
thereby attaching the terminal assembly
40
to the circuit breaker housing bottom portion
24
.
As shown in
FIG. 3
, the terminal assembly
40
for a circuit breaker includes a collar assembly
50
, a shield device
10
and a terminal strap
80
. The collar assembly has a four-sided collar
52
defining a cavity
54
with openings on the opposing first face
60
and second face
62
. As used herein, the first face
60
refers to the face of the collar
52
that will be adjacent to the arc chamber
26
when the terminal assembly
40
is installed in circuit breaker housing
20
. Conversely, the second face
62
of the collar
52
will be adjacent to the line-in when the terminal assembly
40
is installed in circuit breaker housing
20
. The collar
52
also includes a top
56
, a bottom
58
, and two sides
64
,
66
. The collar top
56
has a threaded opening therethrough with an annular ridge
68
disposed about the threaded opening. A screw
70
is engaged with the threaded opening and passes through the collar top
56
into the cavity
54
. The screw
70
may be adjusted vertically through the collar top
56
. The collar bottom
58
has a detent
72
which protrudes into cavity
54
. Each collar side
64
,
66
has a projection
74
,
76
into cavity
54
. The projections
74
,
76
are located proximal to the collar bottom
58
.
The shield device
10
is a member having a top plate
12
and a perpendicular side plate
14
. The top plate
12
is sized to cover the collar top
56
, while the side plate
14
is sized to cover the collar first face
60
and cavity
54
. The top plate
12
further includes an opening
11
, a screw sleeve
16
disposed about opening
11
which is sized to fit about screw
70
. As shown on
FIG. 4
, the lower side
13
of the top plate
12
has a circular recess
15
which has a diameter slightly larger than the annular ridge
68
. The side plate
14
includes a slot
18
at its distal end. The slot
18
is sized to allow the terminal strap
80
to pass therethrough. The shield device
10
is preferably made from a dielectric material.
As shown on
FIG. 3
, the terminal strap
80
includes a line-in tab
82
and a contact tab
84
connected by a medial portion
86
. The line-in tab
82
and the contact tab
84
are approximately in parallel planes while the medial portion
86
is perpendicular to such planes. As such, the terminal strap
80
has a Z-shape. The line-in tab
82
includes an opening
88
therethrough which is sized to fit about the detent
72
located on the collar bottom
58
. The contact tab
84
includes a fastener opening
90
and the stationary contact point
92
. In operation, the contact point
92
would touch the movable contact of the load side of the circuit breaker.
When assembled, the shield device
10
covers the collar top
52
and the first face
60
and the cavity
54
. The screw sleeve
16
fits over the screw
70
and the recess
15
encircles the annular ridge
68
. The terminal strap
80
passes through the terminal strap slot
18
. When assembled, the terminal strap is partially secured by detent
72
on housing bottom
58
which is disposed in opening
88
. Additionally, the terminal strap
80
is held by projections
74
,
76
.
As noted above, and as shown in
FIG. 1
, a circuit breaker housing top portion
22
is attached to the circuit breaker housing bottom portion
24
. The circuit breaker housing top portion
22
has chambers corresponding to the arc chamber
26
, the movable contact chamber
28
, the collar assembly recess
30
as well as has a screw access hole
21
positioned over screw
70
. The line side cable (not shown) fits within cavity
54
of the collar assembly
50
. The cable is secured within the collar assembly
50
by tightening screw
70
thereby clamping the cable against line-in tab
82
of terminal strap
80
. The load side of the circuit breaker is coupled to the moveable contact assembly (not shown) which is mounted adjacent to the movable contact chamber
28
and which has a contact passing into the arc chamber
26
which touches contact point
92
of terminal strap
80
when the circuit breaker is in the closed position.
In operation, the contacts will be closed. When a current interruption occurs in the circuit breaker, or when the circuit breaker is intentionally tripped, the electrical contacts separate and may form an electric arc therebetween. The electrical arc may create ionized gases which can conduct electricity. These gases are initially in the arc chamber
26
but may travel to the collar assembly chamber
40
. A substantial amount of these gases, however, are prevented from reaching the collar assembly
50
by shield device
10
. Because the shield device
10
substantially covers the collar assembly
50
, the gases will pass over the shield device
10
and exit the circuit breaker housing
20
through the back of the collar recess
30
.
While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangement disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breath of the appended claims and any and all equivalence thereof.
Claims
- 1. A gas deflecting terminal assembly for a circuit breaker comprising:a collar having a top, and a cavity; said cavity having an opposing first face and second face, each face having an opening to said cavity; a threaded opening through said collar top; a screw, threaded in said threaded opening; a shield device having a top plate and a perpendicular side plate; said top plate having an opening therethrough and an integral screw sleeve; a terminal strap; said terminal strap connected to said collar; said shield device coupled to said collar with said top plate covering said collar top, said side plate covering said first face and said first face cavity opening; and; wherein said shield device side plate has a slot passing therethrough and said terminal strap passes through said slot.
- 2. The terminal assembly of claim 1, wherein said collar top includes an annular ridge disposed about said threaded opening and said shield device includes a recess disposed about said top plate opening, where said recess has a diameter larger than said annular ridge.
- 3. The terminal assembly of claim 2, wherein;said collar has a bottom and two sides forming said cavity; said collar bottom having a detent protruding into said cavity; said collar sides each having a projection into said cavity; said terminal strap having a opening corresponding to said detent; wherein said terminal strap is frictionally held in said collar by said detent and said projections.
- 4. A circuit breaker comprising;a circuit breaker housing having an arc chamber and an adjacent collar recess communicating with said arc chamber; a collar assembly comprising: a collar having a top and a cavity; said cavity having an opposing first face and second face, each face having an opening to said cavity; said collar seated in said collar assembly recess with said first face adjacent to said arc chamber; a threaded opening through said collar top; a screw threaded in said threaded opening; a shield device having a top plate and a perpendicular side plate; said top plate having an opening therethrough and an integral screw sleeve; a terminal strap coupled to said collar extending from said arc chamber into said cavity through said first face opening; said shield device coupled to said collar with said top plate covering said collar top, said side plate covering said first face and said first face cavity opening; and wherein said shield device side plate has a slot passing therethrough and said terminal strap passes through said slot.
- 5. The circuit breaker of claim 4, wherein;said collar top includes an annular ridge disposed about said threaded opening and said shield device includes a recess disposed about said top plate opening, where said recess has a diameter larger than said annular ridge.
- 6. The circuit breaker of claim 5, wherein said collar has a bottom and two sides forming said cavity;said collar bottom side having a detent protruding into said cavity; said collar sides each having a projection into said cavity; said terminal strap having a opening corresponding to said detent; wherein said terminal strap is frictionally held in said collar by said detent and said projections.
US Referenced Citations (5)