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Патент USA US3053965

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Sept. 11, 1962
2 Sheets-Sheet 1
Filed May 18, 1959
% '7
sept- 11, 1962
Filed May 18' 1959
2 Sheets-Sheet 2
$42010 Zmaey 3420M”
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United States Patent U” 1QC
‘ Patented Sept. 11, 1962
FIGURE 7 is a plan view from below of a modi?ca
The drawings as shown in FIGURES 1 to 4 illustrate
the invention applied to a three phase circiut breaker
Harold Townley Baldwin, Eyre St., Sheffield, England
in which the contactor or circuit breaker comprises a
Filed May 18, 1959, Ser. No. 814,045
Claims priority, application Great Britain Mar. 14, 1959
1 Claim. (Cl. 200--147)
This invention relates to improvements in contactors
or circuit breakers of the type in which the contacts are
mounted within but out of contact with a shroud pro
tecting the contacts from the entry of air during the
breaking of the contacts.
As it is well known upon the breaking of electrical
casing formed in two sections, 1, 2 and bolted together
by bolts passing through holes 3 therein between which
is mounted a slid-e 4 carrying moving contacts 5. Each
section '1 or 2 is divided by partition walls 6 into com
partments, the partition walls 6 extending inwardly of
the casing to engage grooves 7 in the slide 4 to form
interphase barriers therefor.
A shroud 8 of magnetic or non-magnetic material sub
stantially semi-circular or D shape with ?anges 10 to
enter recesses in the casing is mounted in each compart
contacts an are or electron discharge occurs between 15
ment of the casing and is enclosed at each end by end
the two contacts. The are occurs with explosive sud
plates 16, 17, the outer periphery of the shroud being
denness and the accompanying ?ame may propagate
exposed to the atmosphere. A stationary contact 9 is
itself to great length and cross sectional area compared
mounted in the end plate 16 of the casing to project
with the are core proper, and consequently the ?ame
into the chamber A enclosed by the shroud and the slide
itself must be effectively controlled by means of addi 20 and at the ends by end plates 16, 17. Intermediate the
tional to the mechanism for are rupture in order to break
ends of the chamber A a disc or plate 11 of magnetic
the circuit with maximum efficiency.
material of the same contour as the shroud is secured
Attempts have been made in prior art circuit breakers
therein as shown or it may enter a groove in the shroud.
to house or con?ne the ?ame by walls or barriers to
The stationary contact 9 extends in close proximity to
prevent damage to adjacent parts and to prevent the
the disc or plate but out of contact therewith. The
?ame from bridging metal parts causing a short circuit
contact 9 may be provided with a shoulder to engage a
in the contacts and the ?ame must therefore be dealt
recess in the casing and is formed with a screwed or
with concurrently with the are proper.
other shank to receive a nut for attachment of the lead
The invention comprises a shroud formed of substan
tially semi-circular or D shape exposed to the atmosphere 0 thereto.
The shroud is shown as being of metal to provide good
and closed at both ends by end plates with a stationary
heat conductivity so that, as the outer surface is exposed
contact mounted in one end plate to project near to
to atmosphere, heat is readily transferred thereto and
but out of contact with ‘a ring or plate of magnetic ma
the shroud is cooled, but the shroud may be formed of
terial mounted intermediate the ends of the shroud, and 5 insulating material provided this material will withstand
a moving contact projecting into the chamber enclosed
the heat generated by the arc.
by the shroud and mounted on a slide for movement
vertically into and out of engagement with the stationary
contact, the ring or plate producing a circular magnetic
?eld which prevents the arc from spreading sideways and
promotes ef?cient arc control.
Where the surface area of the contact is large the
normal requirements of electrical clearance will result
in a chamber of large volume and the et?ective volume
of air contained in the shroud chamber may be reduced
by the employment of an inner shroud of substantially
semi-circular or D shape, carried by the closed end of
the outer shroud, and projecting from the closed end to
adjacent the ring or plate.
For a double break contactor or circuit breaker a
common slide carrying both movable contacts is mounted
between the substantially semi-circular or D-shaped
shrouds mounted in casings bolted together to sandwich
the slide therebetween.
Two or more shrouds may be mounted side by side in
the casing for simultaneously breaking single or multi
phase circuits.
The invention will be described with reference to the
accompanying drawings:
FIGURE 1 is a perspective exploded view of a three
phase double pole contactor or circuit breaker showing
the upper and lower end plates and the intermediate
slide carrying the moving contacts;
FIGURE 2 is an elevation partly in section showing
one shroud chamber;
FIGURE 3 is a horizontal section through the casing
and slide on line 3-3, FIGURE 4;
FIGURE 4 is a vertical section at right angles to FIG
URE 3, and
FIGURE 5 is an elevation of one shroud chamber
showing an inner shroud therein;
FIGURE 6 is a section on line 6—6, FIGURE 5;
The slide 4 is provided with the grooves 7 on both
surfaces to receive the partition walls 6 which act as
interphase barriers. The moving contacts 5 for a double
break contactor or circuit breaker are mounted on the
ends of a bar 12 supported on a member 13 spring
mounted in the slide 4 with the bar 12 projecting at each
side of the slide to extend into the chamber A in line
with the stationary contacts 9. The bottom of the slide
4 is provided with a member 14 by which slide 4 is
actuated to make or break the contacts.
On the breaking of the contacts the are thereby pro
duced is controlled by the magnetic ?eld which is pro
duced in the disc or plate 1.1 which is of the general
shape shown, the break taking place in the vicinity of
the disc or plate 11. The heat generated by the arc
passes to the shroud and is dissipated thereby. It has
been found that the volume of air in the chamber A
should be kept to a minimum consistent with a clearance
between the contacts and the shroud and that after re
peated operations removal of metal from the contacts
is minimised thereby increasing the life of the contacts
nor does erosion or other high temperature effects take
place on the casing and end plates.
A limited volume of air can enter the chamber A along
the bars 12 but no air will enter during the formation of
an are on breaking of the contacts since the heat gen
erated by the arc causes the air in the chamber A to
expand and accordingly the pressure in the chamber A
rises to more than atmospheric.
Where the contacts have to carry a high current the sur
face area of the contacts is increased and this increase in
the surface area of the contacts necessitates a correspond
ing increase in the diameter of the shroud thereby increas
ing the volume of air in the chamber A. In order to re
70 duce the effective volume of ‘air at the moment of break a
second shroud 15, FIGURES 5 and 6, is arranged inside
the shroud 8, the shroud 15 being mounted on the end wall
of the casing remote from the stationary contact 9 and
extending adjacent to the stationary contact, the end of the
shroud 15 adjacent the stationary contact being open. An
the opposite end of said chamber, a member extending
into said chamber and mounting said movable contact in
a position facing said stationary contact, displacement
annular air cushion B (FIGURE 6) is provided between
chamber for displacing said member together with said
movable contact along said longitudinal axis, said movable
contact being displaceable by said displacement means be
means mounted on said housing but exteriorly of said
the two shrouds 8, 15, which does not participate in the
breaking operation. The shroud 15 is preferably metal
tween a ?rst position in electrical contact with said surface
and provided with an end plate of similar material to with
of said stationary contact and a second position spaced
stand the heat generated by the are but it may be of insu
lating material provided this latter will withstand the tem 10 therefrom along said longitudinal axis but within said
chamber, said housing comprising opposed end walls
spaced apart along said longitudinal axis in transverse re
lationship thereto and delimiting the opposite ends of said
Where a single break contactor or circuit breaker is re
quired the casing is moulded to accommodate a single
shroud 8 and the slide 4 moves in the casing and carries a
single movable contact 5.
The movement of the moving contacts 5 in each cham
ber A will substantially change the air in each chamber
' chamber with one of said end walls ?xedly mounting said
stationary contact, and a curved side wall portion in at
least semi-encircling relationship to said stationary and
movable contacts and extending between said end walls
and delimiting said chamber to control and protectively
between each break.
enclose an ‘are formed between said contacts, said side wall
An alternative form of shroud (FIGURE 7) comprises
metal laminates 18 of magnetic or non-magnetic material 20 portion comprising a plurality of stacked abutting layers of
alternating members of electrically insulating material and
of U or ring form insulated from each other by laminates
of magnetic material with each of said layers extending
of insulating material 19 and projecting into ‘the arc cham
transversely with respect to said longitudinal axis, said
her to a less extent than the metal laminates 18. In this
members of magnetic material being free of engagement
way the insulation material 19 is kept at a safe distance
from the high temperature arc, and the projecting metal 25 with said contacts but projecting transversely inwardly into
said chamber by a further distance than said insulating
members to reduce the effective volume of said chamber
and to enable said insulating members to be spaced at a
sufficiently safe distance from said arc for withstanding
laminates 18 forming the shroud reduce the volume of air
in the arc chamber.
For breaking of low current circuits all these laminates
18 forming the shroud may be of U shape, but for the
breaking of higher currents one or more of these laminates 30 the heat generated thereby.
18a should be of magnetic material and of ring form, and
References Cited in the ?le of this patent
of the general shape shown in FIGURE 7, to control the
magnet ?eld and thus the arc movement and operate as
described in connection with the plate 11.
I claim:
In an electrical contact making and breaking device
having a stationary contact ‘and a movable contact engage
able with said stationary contact and substantially aligned
therewith long a longitudinal axis, a ?xed housing de?ning
a substantially enclosed chamber wherein said stationary’ 40
and movable contacts are disposed and engage, said sta
tionary contact being disposed near one end of said cham
ber and having an engagement surface extending radially
with respect to said longitudinal axis and facing toward
Anderson ____________ __ Oct. 27, 1936
Hara ________________ __ Dec. 31, 1940
Lindstrom ____________ __ May 6,
Dawe ________________ __ Sept. 1,
Few et al ______________ __ Oct. 19,
Morschel ____________ __ May 28,
Russell ________________ __ June 4,
Moyer _______________ __ Feb. 17,
France ______________ __ Dec. 29, 1958
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