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Патент USA US2080811

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Patented May 18, 1937
2,080,811 ' -
UNITED STATES
‘
‘PATENT OFFICE “f
2,080,811
'
nnnc'rrncar. CONTACT
Kenneth L. Emmert, Indianapolis. Ind., assignm
to P. It. Mallory & Co., Inc., Indianapolis, 1nd,.
a corporation of Delaware
.
No Drawing. Application, June 12, 1936,
Serial No. 84,980
4 Claims. (Cl. 200—166)
This invention relates to electric contacts. -
An object of the invention is to improve the
characteristics of electric contact elements con
taining silver.
6
~
Other objects of the invention will be apparent
from the following description taken in connec
tion with the appended claims.
'
The present invention comprises the combina
tion of elements, methods of manufacture, and
10 the product thereof brought out and exempli?ed
metal transfer and build-up and reduces the
tendency of the contacts to fuse together.
The contacts of the present invention are par
ticularly satisfactory for use on low frequency
relays and on contact applications where the con
tacts are subject to momentary overload where
prior contact materials cause undue failure by
fusion and sticking.
'
Comparative tests have been made on contacts -
of the ?rst preferred composition given above 10
in the disclosure hereinafter set forth, the scope and contacts of fine silver. coin silver and an
of the invention being indicated in the appended alloy of 80% silver plus 20% cadmium.
claims.
The various contact materials were tested on
While a preferred embodiment of the invention Cutler-Hammer relays using one pair of con
15 is described herein, it is contemplated that con
tacts 0.187 diameter one of which was ?at faced 15,
siderable variation may be made in the method of and the other having approximately a 1" ra
procedure and the combination of elements with-, di'us. The contacts were riveted on phosphor
out departing from the spirit of the invention.
The present invention comprises an improve ‘bronze reeds with .the maximum opening about
1A". The frequency of operation was 1.4 sec 20
ment in silver electric contact elements and es
pecially in contact elements formed of silver and ends on, 1.4 seconds oil’, making 1285 operations
per hour. The load was resistive at a power fac
cadmium. According to the invention the con
tor of 100%. Tests were run at both 2 and 10
tacts are improved by the addition of nickel.
The contacts accordingly may be composed of ounces total contact pressure. The test period
25 cadmium nickel and silver. The ingredients may consisted of 72 hours of operation or in-excess of 25
' be present in approximately the following propor
92,000 operations.
'
tions:
The following current ratings were main
Per cent tained at the voltages indicated.
Nickel
30 Cadnnum
1
0.25 to 5
A
6 volts D. C.—
12 volts D. C.—
110 volts D. C.18 .volts A. C.--
5 to 25
Silver
balance
A preferred contact material has the composi
tion:
'
35
30
110 volts A. C.-- 6.7 amperes '
.
' '
Nickel
__
-
’
0.6
22.4
Silver
77.0
A second preferred composition contains:
40
'
Silver
2.0
_-__
vention:
‘
Sticking or failure due to arcing
40'
____..
_
During a test period of 72 hours’ operation at .
_ 20.0
110 volts D. C. failure occurred before the end of
78.0
the period on all the _ comparison materials
Contacts of the present invention are suitable
for use as make-and-break contacts for control
ling either A. C. or D. C. circuits. They may be
used in pairs of the same composition or an in-v
dividual contact of this composition may be used
with a co-operating contact -of entirely di?erent
composition.
35
The principal results discussed below show the
superiority of the contacts of the present in
Per cent
Nickel
Cadmium
220 volts A. C.—10.0 amperes
Per cent
Cadmium
45
1.5 amperes
2.1 amperes
1.8 amperes
6.7 amperes
whereas the contacts of the present invention
were still operating at the 'end of the test period 45
as indicated in the table below:
~ Material
Lg‘
'
Number of operations
50
'
The addition of nickel as set forth above ma
02.
terially improves the contact characteristics. It
also increases the resistance of the contact ma~
' terial to cold working and thereby maintains con
60
2.520
tact spacing. The nickel increases the fusing
temperature of the contacts thus greatly reducing
the possibility of the contacts melting and stick
ing together during heavy current surges.
toward pitting and transfer, followed in order
The cadmium reduces the tendency toward
by the 80-20 alloy and the alloy of the present
Metal transfer and pitting
Fine silver showed the greatest tendency
55
.
2,080,811
invention. Coin silver was not compared in this Coin silver showed a decrease. The alloy of the
regard.
present invention was generally more constant
Oxidation
with all current loads and with light-and heavy
5
_
10
15
The alloy of the present invention showed
slightly less oxidation than the 80-20 alloy,
'contact
Contacts
pressures.
made of materials containing
2
normal
fine silver or coin silver.
amounts of impurities are contemplated as with
in the scope of the present invention. 1
Contact wear
While the present invention as to its objects
Contact wear is closely related to‘v pitting and and advantages, has been described herein .as
transfer. Therefore the comparison-materials. carried out in speci?c embodiments thereof, it
showed a tendency toward greater wear than the is not desired to belimited thereby but it is in
tended to cover the invention broadly within the
alloy of the present invention.
.
spirit'and scope of the appended claims.
Contact resistance
What is claimed is:
The change in contact resistance during oper- '
1. An electric contact member consisting of 15
ation is in general an indication of the operating
characteristics of the contact material. An in
creasing contact resistance with length .of oper
0 ation indicates the formation of a high resistance
an alloy of 5 to 25% cadmium, 0.25 _to_5% nickel
‘and the balance silver.
' oxide or a pitting or wearing of the contact face.
and, the balance silver.
Increased resistance causes an increased tend
ency toward overheating and contact sticking.
The initial resistance of contacts made of the
5 alloy of the present invention was lower than that
r P of the 80—20 alloy and of coin silver. Fine silver
generally has a lower initial resistance than all
the others and remains constant on low current
2. An electric contact member comprising an
alloy of about 22.4% cadmium, about 0.6% nicke
,
'
_ '
20
3. An electric contact member comprising ‘an
alloy of about 20% cadmium, about 2% nickel
and the balance silver.
_
4. An electric contact member comprisingan
alloy consisting substantially of cadmium, nickel
and silver, the cadmium comprising substantially
5 to 25% of said alloy, the nickel comprising
operation._ However, its contact resistance in ,substantially 0.25 to 5% of said alloy‘ and the
0 creases very greatly with heavy loads frequently remainder of said_alloy_y_,conslsting substantially
resulting in sticking.
The 80-1-20 alloy showed a greater increase in
resistance during operation‘ than any. others.
of silver.
'
.‘
'
_
.
,
_
J
L. "EMMERT.
30
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