Information
-
Patent Grant
-
6310307
-
Patent Number
6,310,307
-
Date Filed
Friday, December 17, 199925 years ago
-
Date Issued
Tuesday, October 30, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Cantor Colburn LLP
- Horton; Carl B.
-
CPC
-
US Classifications
Field of Search
US
- 200 6 R
- 200 11 R
- 200 1 R
- 200 17 R
- 200 400
- 200 401
- 200 501
- 200 244
- 200 248
- 200 287
- 200 336
- 200 337
- 200 5001
- 200 5032
- 218 22
- 218 146
- 335 16
-
International Classifications
-
Abstract
A rotary contact arrangement for circuit breakers of the type including a pair of movable contacts (30,36), one arranged on each end of the rotary contact arm (32), utilizes a single pair of contact springs (38), one spring on each side of the rotary contact arm (32). The springs (38) are aligned to intersect the axis of rotation of the rotary contact arm (32) for automatic uniform contact force adjustment throughout the operating life of the circuit breaker.
Description
BACKGROUND OF THE INVENTION
This invention relates to circuit breakers, and, more particularly, to a circuit breaker rotary contact arm arrangement.
U.S. Pat. No. 4,616,198 entitled CONTACT ARRANGEMENT FOR A CURRENT LIMITING CIRCUIT BREAKER describes the early use of a first and second pair of circuit breaker contacts arranged in series to substantially reduce the amount of current let-through upon the occurrence of an overcurrent condition.
When the contact pairs are arranged upon one movable rotary contact arm such as described within U.S. Pat. No. 4,910,485 entitled MULTIPLE CIRCUIT BREAKER WITH DOUBLE BREAK ROTARY CONTACT, some means must be provided to insure that the opposing contact pairs exhibit the same contact pressure to reduce contact wear and erosion.
One arrangement for providing uniform contact wear is described in U.S. Pat. No. 5,310,971 entitled ROTARY CONTACT SYSTEM FOR CIRCUIT BREAKERS. This arrangement includes a rotary contact arm that employs rollers between the movable contact arm and spring pins to reduce contact arm friction. A rotor assembly with four contact springs, two on each side of the rotor, offset from the center of the rotor to impart contact force between the fixed and movable contacts is also disclosed. However, the roller system used in this arrangement can cause friction between the rollers and contact arm, which will result in uneven contact forces and, therefore, uneven contact wear. In addition, a rotor with springs offset from the rotor's axis of rotation can cause a non-uniform force distribution between the fixed and movable contact pairs if one pair of contacts erodes more than the other pair. The erosion of the contact pair with lower force results in a further reduction in force that continues to accelerate the erosion process.
BRIEF SUMMARY OF THE INVENTION
In an exemplary embodiment of the invention, a circuit breaker rotary contact arrangement includes a rotor having first and second opposing sides with pin retainer slots formed on the first side and a movable contact arm disposed intermediate the first and second sides. The movable contact arm has movable contacts at opposite ends of the contact arm, with each movable contact arranged opposite a fixed contact. A pivot pin is arranged on a central portion of the movable contact arm, with the pivot pin extending within an aperture formed on a central portion of the rotor. The pivot pin allows rotation of the movable contact arm with respect to the rotor. First and second links are pivotally secured to a first side of the movable contact arm. A first spring pin extends from the first link through the first pin retainer slot, and a second spring pin extends from the second link through the second pin retainer slot. A spring is arranged proximate the first side of the rotor and extends from the first spring pin to the second spring pin. The spring exerts a spring force directed to intersect the axis of rotation of the pivot pin. The spring force urges the movable contacts towards the fixed contacts.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a front perspective view of a circuit breaker rotary cassette assembly employing the rotary contact assembly of the present invention;
FIG. 2
is a partially exploded perspective view of a cassette assembly with the cassette cover in isometric projection with the rotary contact arrangement of
FIG. 1
;
FIG. 3
is an enlarged side view of the rotary contact assembly of
FIG. 1
with the circuit breaker contacts in an initial, undamaged condition; and
FIG. 4
is an enlarged side view of the rotary contact assembly of
FIG. 1
with the circuit breaker contacts in an eroded condition.
DETAILED DESCRIPTION OF THE INVENTION
Referring to
FIG. 1
, a rotary contact assembly
12
in a circuit breaker cassette assembly
10
is shown in an electrically-insulative cassette half piece
14
intermediate a line-side contact strap
16
, load-side contact strap
18
and associated arc chutes
20
,
22
. In the embodiment shown, line-side contact strap
16
would be electrically connected to line-side wiring (not shown) in an electrical distribution circuit, and loadside contact strap
18
would be electrically connected to load-side wiring (not shown) via a lug (not shown) or some device such as a bimetallic element or current sensor (not shown). Electrically-insulative shields
24
,
26
separate load-side contact strap
18
and line-side contact strap
16
from the associated arc chutes
20
,
22
respectively. Although a single rotary contact assembly
12
is shown, it is understood that a separate rotary contact assembly is employed within each pole of a multi-pole circuit breaker and operate in a similar manner. The arc chutes
20
,
22
are similar to that described within U.S. Pat. No. 4,375,021 entitled RAPID ELECTRIC ARC EXTINGUISHING ASSEMBLY IN CIRCUIT BREAKING DEVICES SUCH AS ELECTRIC CIRCUIT BREAKERS. Electrical transport through the circuit breaker interior proceeds from the line-side contact strap
16
to associated fixed and moveable contacts,
28
,
30
at one end of a movable contact arm
32
, to the fixed contacts and movable contacts
34
,
36
at the opposite end thereof, to the associated load-side contact strap
18
. The movable contact arm
32
is arranged between two halves of a circular rotor
37
. Moveable contact arm
32
moves in unison with the rotor
37
upon manual articulation of the circuit breaker operating mechanism (not shown) to drive the movable contacts
30
,
36
between CLOSED and OPEN positions. A first contact spring
38
extends between a pair of spring pins
40
,
42
within the contact spring slot
48
formed within one side of the rotor
37
and a second contact spring (not shown) extends between pins
40
,
42
in a similar manner on the opposite side of rotor
37
. An aperture
46
extends through the rotor
37
. Aperture
46
allows for a link connection with the circuit breaker operating mechanism to allow manual intervention for opening and closing the circuit breaker contacts in the manner described within the aforementioned U.S. patent application Ser. No. 09/087,038 entitled ROTARY CONTACT ASSEMBLY FOR HIGH AMPERE-RATED CIRCUIT BREAKERS, filed May 29, 1998, which is incorporated by reference.
Referring to
FIG. 2
, the circuit breaker cassette assembly
10
is shown prior to attaching a cassette half piece
50
with cassette half piece
14
to form a complete enclosure. The contact spring
38
proximate rotor
37
is protected from contamination by the attachment of a rotor cap
52
. A cap aperture
54
in rotor cap
52
aligns with the rotor aperture
46
. A radial protrusion
56
extending from the exterior of the cap
52
sits within an aperture
58
formed within the cassette half piece
50
and acts as a bearing surface, which allows the rotor
37
to rotate freely within a slotted aperture
60
formed within the cassette half piece
50
. A side (not shown) of rotor
37
proximate cassette half piece
14
is similar to the side of rotor
37
shown in
FIG. 2
, including a spring
38
, rotor cap
52
and aperture
46
. The rotor cap
52
proximate cassette half piece
14
also includes a radial protrusion
56
and aperture
54
. The radial protrusion
56
proximate cassette half piece
14
extends within an aperture
58
in cassette half piece
14
, which also acts as a bearing surface.
With the cassette half piece
50
attached to the cassette half piece
14
by means of apertures
62
,
64
and rivets (not shown), a pair of circuit breaker operating mechanism sideframes
66
,
67
are next attached to cassette half pieces
50
,
14
by pins extending through apertures
68
,
70
. Operating mechanism lever links (side arms)
72
, on opposing sides of the sideframes
14
,
50
each connect with a crank lever
74
by a pin
76
extending through a slot
86
formed in sideframes
66
,
67
. The lever links
72
each connect with the circuit breaker operating mechanism (not shown) in the manner described within the aforementioned U.S. patent application Ser. No. 09/087,038. Crank levers
74
pivotally connect with sideframes
66
,
67
by pivots
80
for rotation of crank levers
74
in response to rotation of lever links
72
. Operative connection with crank levers
74
and the rotor
37
is provided by means of the extended rotor pin
82
that passes through the apertures
84
in the crank levers
74
, slots
86
in sideframes
66
,
67
, slotted apertures
60
in cassette half pieces
50
,
14
, the apertures
54
in the rotor caps
52
and the aperture
46
within the rotor
37
, as indicated by dashed lines.
Upon activation of lever links
72
by the circuit breaker operating mechanism (not shown), lever links
72
force crank levers
74
to pivot about pivot
80
. Extended rotor pin
82
moves in conjunction with lever links
72
, thereby rotating rotor
37
and movable contact arm
32
for driving the movable contacts
30
,
36
(
FIG. 1
) between CLOSED and OPEN positions.
Referring to
FIG. 3
, rotary contact assembly
12
is shown with contact springs
38
arranged on each side of rotor
37
, and movable contact arm
32
having fixed and movable contacts
28
,
30
,
34
,
36
arranged between load and line-side contact straps
18
,
16
. The contact springs
38
are attached between the movable contact arm
32
and the spring pins
40
,
42
by means of a pair of links
100
,
102
in the manner described within the aforementioned U.S. patent application Ser. No. 09/087,038. One end of a spring pin
40
attaches to one end of the contact spring
38
, via link
100
and is positioned within a pin retainer slot
112
formed in the rotor
37
. The other end of the spring pin
40
connects with a similar link and retainer slot (not shown) on the opposite side of the contact arm
32
and the other contact spring
38
on the opposite side of rotor
37
. One end of the spring pin
42
attaches to one end of the contact spring
38
, via link
102
and is positioned within a pin retainer slot
114
formed in the rotor
37
. The other end of the spring pin
42
connects with a similar link and retainer slot (not shown) on the opposite side of the contact arm
32
and the other contact spring
38
on the opposite side of rotor
37
. A contact arm pivot pin
104
extends from central portion of rotary contact arm
32
and is captured within the rotor
37
via an elongated clearance slot
106
disposed in rotor
37
to allow contact arm
32
to rotate and translate relative to the rotor
37
, in the manner to be described with reference to
FIG. 4. A
contact arm pin
108
connects the link
100
with the contact arm
32
and a contact arm pin
110
connects the link
102
with the contact arm
32
. The contact arm pins
108
,
110
connect the other links, although not shown, with the contact arm
32
on the other side of the contact arm
32
. Spring pins
40
,
42
are positioned in line (co-linear) with the central pivot pin
104
so that the spring force H, exerted between spring pins
40
,
42
is directed to intersect the axis of rotation of the movable contact arm
32
. The force H is transferred to the movable contact arm
32
via pins
40
,
42
, links
100
,
102
and pins
108
,
110
. Pins
108
and
110
are offset from the line created by pins
40
,
42
and pivot pin
104
, allowing the force H to rotate movable contact arm
32
. The rotation of movable contact arm
32
urges movable contacts
30
,
36
toward fixed contacts
28
,
34
. Because the force H is centered through the rotational axis of movable contact arm
32
, the force of movable contacts
30
,
36
onto fixed contacts
28
,
34
is substantially equal. The fixed and movable contacts
28
,
30
,
34
,
36
are depicted herein in an undamaged condition, that is, free from any surface erosion.
FIG. 3
shows contact arm
32
in the CLOSED position. Upon an overcurrent condition, fixed contacts
28
,
34
and movable contacts
30
,
36
are separated by magnetic repulsion that occurs between the fixed contacts
28
,
34
and movable contacts
30
,
36
, as is known the art. The force caused by magnetic repulsion acts against the force created by the contact springs
38
, which tends to maintain the fixed and movable contacts
28
,
30
,
34
,
36
in a CLOSED position. If the repulsive force exceeds the force created by springs
38
, contact arm
32
rotates in a clockwise direction, while rotor
37
remains stationary. The rotation of contact arm
32
moves pins
108
and
110
around pivot pin
104
and towards the line of force H. The motion of pins
108
and
110
is translated to spring pins
40
and
42
via links
100
and
102
, causing pins
40
and
42
to translate within slots
112
and
114
towards the perimeter of rotor
37
. The translation of pins
40
and
42
acts against the force of springs
38
. If rotary contact arm
32
rotates in a clockwise correction such that pins
108
and
110
move past the line force created by springs
38
, springs
38
will act to maintain contact arm
32
in a detented open position, with fixed and movable contacts
28
,
30
,
34
,
36
separated. Once in the detented open position, contact arm is reset to the CLOSED position by rotating the rotor
37
in a counterclockwise direction until pins
108
and
110
are returned to the position shown in FIG.
3
.
Referring to
FIG. 4
, the rotary contact assembly
12
is shown after extended use and subjected to severe contact erosion between the fixed contact
28
, and the movable contact
30
, for example, at on end of the movable contact arm
32
within the rotor
37
. It is noted that the rotor
37
has rotated in the counter-clockwise direction as indicated, driving the central pivot pin
104
downward within the elongated clearance slot
106
such that the spring force, as now indicated by H′, remains directed through the rotational axis of central pivot pin
104
, similar to the spring force depicted at H in the undamaged contacts condition shown earlier in FIG.
3
. The slight movement of the central pivot pin
104
allows the slight rotation of the spring links
100
,
102
attached to the moveable contact arm
32
by means of the spring pins
108
,
110
, which translate within the retainer links slots
112
,
114
. Elongated clearance slot
106
and pin retainer slots
112
,
114
extend along rotor
37
in the same direction (i.e. substantially parallel to each other) to allow contact arm
32
and spring pins
40
and
42
to translate in the same direction relative to rotor
37
. The arrangement of the elongated clearance slot
106
and pin retainer slots
112
,
114
allow contact arm
32
and spring pins
40
and
42
to remain in line, which allows the spring force H′ to continue to be directed through the axis of rotation of central pivot pin
104
. The arrangement of the spring force through the central pivot pin
104
causes the forces between the fixed and moveable contacts
28
,
30
,
34
,
36
to remain constant such as when the fixed and movable contacts
28
,
30
,
34
,
36
were in the undamaged condition depicted earlier in FIG.
3
. The constant force between the fixed and movable contacts
28
,
30
,
34
,
36
ensures a uniform transfer of current between the fixed and movable contacts
28
,
30
,
34
,
36
, which, in turn, prevents further erosion of the contact surfaces.
A simple arrangement of a single contact spring
38
on each side of a movable contact arm
32
in a lineal relation with the movable contact arm pivot pin
104
has herein been shown to provide an inexpensive means for reducing the effects of contact erosion over long periods of operation.
While a preferred embodiment has been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.
Claims
- 1. A circuit breaker rotary contact arrangement comprising:a rotor defining first and second opposing sides thereon, said rotor including first and second pin retainer slots formed on said first side; a movable contact arm intermediate said first and second sides, said movable contact arm defining a first movable contact at one end arranged opposite an opposing first fixed contact and a second movable contact at an end opposite said one end arranged proximate a second fixed contact; a pivot pin arranged on a central portion of said movable contact arm, said pivot pin extending within an aperture formed on a central portion of said rotor for allowing rotation of said movable contact arm with respect to said rotor; first and second links pivotally secured to a first side of said movable contact arm; a first spring pin extending from said first link and through said first pin retainer slot; a second spring pin extending from said second link and through said second pin retainer slot; and a first spring proximate said first side and extending from said first spring pin to said second spring pin, said first spring exerting a first spring force directed to intersect an axis of rotation of said pivot pin, said first spring force for urging said first movable contact toward said first fixed contact and said second movable contact toward said second fixed contact.
- 2. The rotary contact arrangement of claim 1 wherein said aperture is elongated for allowing said movable contact an to translate relative to said rotor.
- 3. The rotary contact arrangement of claim 2 wherein said aperture and said first and second pin retainer slots are arranged to allow said movable contact arm and said first and second spring pins to translate in a single direction relative to said rotor.
- 4. The rotary contact arrangement of claim 1 further including:third and fourth links pivotally secured to a second side of said movable contact arm; said rotor further including third and fourth pin retainer slots formed on said second side; said first spring pin further extending through said third pin retainer slot; said second spring pin further extending through said fourth pin retainer slot; and a second spring proximate said second side and extending from said first spring pin to said second spring pin, said second spring exerting a second spring force directed to intersect an axis of rotation of said pivot pin, said second spring force for urging said first movable contact toward said first fixed contact and said second movable contact toward said second fixed contact.
- 5. The rotary contact arrangement of claim 4 wherein said aperture and said first, second, third, and fourth pin retainer slots are arranged to allow said movable contact arm and said first and second spring pins to translate in a single direction relative to said rotor.
- 6. The rotary contact arrangement of claim 1 including first and second electrically-insulative cassette half pieces, said rotor and said movable contact an being retained intermediate said first and second cassette half pieces.
- 7. The rotary contact arrangement of claim 6 including a rotor cover arranged over said rotor, said rotor cover defining a radial protrusion extending from an outer surface thereon, said radial protrusion extending within an aperture formed within said first electrically-insulative cassette half piece.
- 8. A circuit breaker assembly comprising:a line-side contact strap arranged for connection with an electric circuit, said line-side contact strap including a first fixed contact connected to said line-side contact strap; a load-side contact strap arranged for connecting with associated electrical equipment, said load-side contact strap including a second fixed contact connected to said load-side contact strap; first and second arc chutes, said first arc chute proximate said line-side contact strap and said second arc chute proximate said load-side contact strap for quenching arcs occurring upon overcurrent transfer between said line and load-side contact straps; and a rotary contact assembly disposed between said line and load-side contact straps and said first and second arc chutes, said rotary contact assembly including: a rotor defining first and second opposing sides thereon, said rotor including first and second pin retainer slots formed on said first side, a movable contact arm intermediate said first and second sides, said movable contact arm defining a first movable contact at one end arranged opposite said first fixed contact and a second movable contact at an end opposite said one end arranged proximate said second fixed contact, a pivot pin arranged on a central portion of said movable contact arm, said pivot pin extending within an aperture formed on a central portion of said rotor for allowing rotation of said movable contact arm with respect to said rotor, first and second links pivotally secured to a first side of said movable contact arm, a first spring pin extending from said first link and through said first pin retainer slot, a second spring pin extending from said second link and through said second pin retainer slot; and a first spring proximate said first side and extending from said first spring pin to said second spring pin, said first spring exerting a first spring force directed to intersect an axis of rotation of said pivot pin, said first spring force for urging said first movable contact toward said first fixed contact and said second movable contact toward said second fixed contact.
- 9. The circuit breaker assembly of claim 8 wherein said aperture is elongated for allowing said movable contact arm to translate relative to said rotor.
- 10. The circuit breaker assembly of claim 8 wherein said aperture and said first and second pin retainer slots are arranged to allow said movable contact arm and said first and second spring pins to translate in a single direction relative to said rotor.
- 11. The circuit breaker assembly of claim 9 wherein said rotary contact assembly further includes:third and fourth links pivotally secured to a second side of said movable contact arm; said rotor further including third and fourth pin retainer slots formed on said second side; said first spring pin further extending through said third pin retainer slot; said second spring pin further extending through said fourth pin retainer slot; and a second spring proximate said second side and extending from said first spring pin to said second spring pin, said second spring exerting a second spring force directed to intersect an axis of rotation of said pivot pin, said second spring force for urging said first movable contact toward said first fixed contact and said second movable contact toward said second fixed contact.
- 12. The circuit breaker assembly of claim 11 wherein said aperture and said first, second, third, and fourth pin retainer slots are arranged to allow said movable contact arm and said first and second spring pins to translate in a single direction relative to said rotor.
- 13. The circuit breaker assembly of claim 8 including first and second electrically-insulative cassette half pieces, said rotor and said movable contact arm being retained intermediate said first and second cassette half pieces.
- 14. The circuit breaker assembly of claim 13 including a rotor cover arranged over said rotor, said rotor cover defining a radial protrusion extending from an outer surface thereon, said radial protrusion extending within an aperture formed within said first electrically-insulative cassette half piece.
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