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Патент USA US2115777

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May 3, 1938.
Filed May 8, 1936
717/0’? ,5: n/é/wvso/v.
Patented May 3, 1938
Thor S. Johnson, Irvington, N. Y., assignor to
Anaconda Wire & Cable Company, New York,
N. Y., a corporation of Delaware
Application May s, 1936, Serial No. ‘78,559
3 Claims. (c1. 148-6)
My invention relates to uninsulated electrical
ther enhanced by using somewhat roughened rolls,
conductors such as busses or other switchboard
although smooth rolls will still permit a much less
re?ective surface, aside from the darkened color,
apparatus carrying heavy currents.
Copper busbars are commonly used in sub-sta
5 tions and other switchboard installations in a
wide variety of shapes and cross sections such as
?at, rectangular, round or channel, with a view to
obtaining the greatest current carrying capacity
forthe conditions of installation.
The current
10 carrying capacity of such conductors is limited by
the temperature rise, the usual limit of permis
sible temperature rise generally ming 30° C.,
above the surrounding air temperature of 40° C.
The maximum capacity will therefore be a our
15 rent having an energy or resistance loss which
will be dissipated by a temperature difference of
30° C., over the ambient air. The current carry
ing capacity of the busbar or other conductor is
therefore governed not only by its conductivity
and cross sectional area, but also by its ability to
' 26
dissipate heat rapidly.
' Heretofore copper busbars and other con
ductors have been given arhighly polished smooth
surface as, for example, by a cold drawing proc
2-5 ess or other means. The busbars retain their light
color and smoothness with little change through
age or use.
The heat generated by the passage
of the current through such conductors is given
off to the surrounding air by conduction and con
“ vection and is given up by radiation. In my in
vention the radiation of heat from such conduc
than would be obtained without the super?cial
oxide coating. The outer layer of the oxide will 5
be a cupric oxide which may merge into a red
cuprous oxide which, in turn, merges into the un
oxidized metallic copper. This results in the for
mation of a ?rm, lasting bond between the copper
oxide and the underlying metal.
The invention is illustrated by way of example
in the accompanying drawing which shows, in
perspective,» a busbar of channel shape treated ac
cording to’ my invention to provide a black ad
herent copper oxide, parts of the oxide coating 15
being shown as removed to show position and
In the conductor shown in the accompanying
drawing, the metallic copper structure I is cov
ered by a layer of oxides 2 in which the red cu
prous oxide predominates. This is, in turn, cov
ered with a layer 3 in which the black cupric
‘oxide predominates or composes the entire layer.
These layers adhere closely to each other and to
the underlying metal forming one integral struc
ture. The oxide- coating’ is a permanent one,
highly resistant to change, particularly in a dry
atmosphere and, being completely oxidized, is un- affected by oxygen or by heating. v
Inasmuch as the amount of heat given off by 30
radiation for any given temperature is directly
proportional to the emissivity of the surface, a
- amount of current may be carried by a given‘ perfectly black body has the most radiating ef
fect or emissivity, and the‘black voxide coating.
conductor without exceeding the maximum tem
closely approaches this ideal. For example, un- 35
35 perature rise.
tors is very greatly increased .so that a larger
In accordance with my invention I form on the
surface of the conductor a non-polished or rough
ened dark or black ?nish integral with the bus
bar structure, thereby increasing the radiation ef
‘ 40 fects or efficiency over what can be obtained by a
light colored highly polished surface. This black
or darkened and roughened surfaceis obtained
der a given set of conditions in which a polished
copper‘su'rface dissipated heat at a rate vof 0.0027
watt per square inch when freshly washed, the
rate of dissipation of heat increased to- 0.0029
after being tarnished in service,'whereas a similar 40
conductor treated according to my invention
showed a heat dissipating capacity of 0.0038 watt
‘ by a superficial oxidation of the surface, of the ' per square inch, an increase of about 30%. The
busbar preferably accompanied by a working of
45 the oxide thus formed on the surface of the metal.
For this purpose the copper is heated to a sum
ciently high temperature to cause a super?cial
_ oxidation, and is, then rolled in suitable rolls
.whichmay serve to give the‘busbar its final shape
50 and dimensions. This is in contrast to the cold
rolling heretofore used which imparts a bright
burnished surface to the metal.
The super?cial oxidation forms a roughened or
matte-like surface which also serves to increase
66 its radiating properties. ‘This may be still fur
formation of the black matte 'or roughenedv sur- 45
face as an integral part of the conductor has the
advantage over the exteriorly applied coatings or
surfaces in that it is not affected by age nor by
deterioration, and incurs no maintenance expense
or difficulties.
While the invention has been shown as applied
to achannel-shape busbar, it will be understood
that it may be applied to any of the usual cross
sectional shapes such as bar, rectangle, circular
or special forms, the invention being in the -sur- ‘5
' w
face formed on such structures and not in the
per electric conductors which‘ comprises oxidizing
shape of the structure itself.
the surface thereof to cupric oxide, and then hot
What I claim is- .
working said surface.
1. A method of ?nishing the surfaces of cop
5 per electric conductors which comprises oxidizing
the surface thereof to cupric oxide, and then hot
rolling said surface.
2. A method of ‘finishing the surfaces of cop
3. A copper electric conductor having a black
matte surface of cupric oxide and an underlying 5
layer of cuprous oxide hot rolled into an integral
structure with the underlying metal.
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