2,3o0,28o

2,3o0,28o
Patented Oct. 27, 1942
UNITED STATES PATENT ‘OFFICE,
ELECTRICAL CONTACT
Childress B. Gwyn, In, Bannockburn, I'lL, assign
or to Fansteel Metallurgical Corporation, North ‘
Chicago, 111., a corporation of New York
- No Drawing. Application May 3, 1941,
Serial No. 392,487
6 Claims. (01.200-166) '
tive side is characterized by the \presenceof an
' This invention relates to electric contacts.
, An object of the invention is to improve the
appreciable quantity of a platinum group element
and the contact on the negative side is made up
of a refractory metal such ‘as tungsten in combi
nation with silver and in some cases modifying
compositions and combinations of compositions
for electric make-and-break contacts for applica
tions such as voltage regulators, relays and the
like.
.
-
.
~
element.
,
Other objects of the invention will be apparent
from the following description taken in connec
tion with the appended claims.
'
'
.
'
I have found the most'suitable materials for
the positive side to be alloys of a precious metal,
e. g._ of the platinum group or gold with or with
, The present invention comprises the combina 10 out silver, which may also include small amounts
tion of elements, methods of manufacture, and ' of hardening metals such as the metals of the
iron group or copper.
the product thereof brought out and exempli?ed
For most applications the contacts for the pos
' in the disclosure hereinafter set forth, the scope
itive side may be formedvof alloys in the following . '
of the invention being indicated in the appended
' claims.
While a preferred embodiment ofKthe invention
15
is described herein, it is contemplated that con
siderable variation may be made in the method »
of procedure and the combination of elements
Q‘ without departing from the spirit of the inven 20
tion.
.
ance with a relative’ small contact pressure and
be capable of maintaining low resistance in serv
,
'
'
-
.
I
Per cent
Platinum and/or palladium and/or gold" 0-98
Other metals of the platinum group____..'_T 0-15 _Silver____
‘
_
0-50, '
Iron group or copper______'____-___; ______ __ 0-5_\
.
In voltage regulators or relays the contacts
should'be non-fusing, have a low contact resist
iceafter a large number of operations.
range of compositions:
.
The .preferred contact materials for the nega
tive side are' hard alloys of high conductivity
characterized by a wear-resisting ingredient such
as tungsten, molybdenum or their carbides or
borides, plus a conductive ingredient such as sil
It is of importance in contact applications to
consider the type of ‘current load placed upon the
ver, copper or alloys made up principally of these
This load will normally be through a
ments such‘ as one of the iron ‘group metals,
cadmium, zinc, arsenic or the alkali or alkali
contacts.
resistive circuit in voltage regulators. I For relay .
applications, on the other hand, the load may
varyfrom purely resistive to purely inductive. It
elements modified by lesser amounts of other ele
earth metals.
‘
'
.
For_most uses the negative contacts may be
may be a combination of resistance and induct
formed of alloys having their ingredients present
ance. It may also include capacitative loads as
in the following range of proportions:
.
well.
O3 in
It has. been found that contacts in such serv
Tungsten, molybdenum or the carbides
ices as mentioned above frequently fail on ac
thereof‘
20-80
count of excessive material transfer. This trans
Silver or copper ________ ..‘_ _____ __ _____ __ 75-15
fer is a function of the electrical conditions at the
Modifying element ____________________ __ 0-5
time of make or break and it is also dependent 40
upon the materials which are used for the con
‘Examples of preferred compositions for use
tacts. It is well known that di?erent metals and
different alloys have widely di?ferent characteris
tics in their ability to withstand transfer.
It is known that the tendency of the contact
materials to transfer and of the contacts to fail is
according to the invention are: ' .
Positive side:
Per cent 1
a. Palladium? _____________________ _. 71
also dependent upon the contact polarity. That '
is, if one material is used for the positive contact
Platinum
'
_
_
4
b. Palladium __________ _; _______ __'___. 84
a D. C. circuit ~the tendency to contact failure will 50
Platinum -
be di?erent from a combination in which the ma- I
Nickel
terials of the positive and negative contacts arev
reversed. This is apparently dependent upon the
characteristics of the different materials in the
0. Platinum‘
Iridium
voltages, ionization potentials, sticking or non
fusing characteristics and the like.
According to the present invention, there is
proposed the use of contact combinations for
D. C. purposes wherein the contact on the posi 60
25
Nickel
and another material for the negative contact in
composition, including such factors as the arcing, ‘
.
-
l4
_
d, Palladium
'_
2
92
8
90
Ruthenium
’
>
10
e. Palladium"; ____________________ _- 60
.Silver _______________ __'_____' _____ ..- 40
j. Gold
Silver
Nickel
'
“
'
71
25
4
2
2,300,286
Negative side:
'
and the contact on the other side being made up
of a wear-resistant constituent selected from the
sixth group or the periodic system and a con
a. Molybdenum ____ _._ ______________ __ 35
Tungsten carbide ________________ __ 25
Silver
- 20
Copper
ductive constituent of the class consisting of sil
ver, copper and alloys predominating in these
20
b. Molybdenum ____________________ __ 64
Silver-
metals.
35
Nickel
‘
1
c, Tungsten
75
Copper
24
Cobalt
1
-
>
.
3. An electric contact combination for D. C.
operation, the contact on one side of said com
bination being formed of an alloy rich in at least
10 one noble metal and the contact on the other side
of said combination having the composition I
d. Tungsten carbide _______________ -l- 75
Silver
'
-
-
24.6
Copper
' 0.4
e. Tungsten _____________________ -____. 50
15 Silver or copper__________________ _'____
Silver ___________________________ _._ 45
Cadmium _______________________ __
Percent
Tungsten, molybdenum or the carbides
thereof
20-80
15-75
Modifying agent selected from the class
5
consisting of iron, cobalt, nickel, cad
In comparison tests of various of the preferred
mium, zinc, arsenic, the alkali metals
combinations of the present invention with» other
and the alkaline earth metals _______ __
0-5
contact combinations, it has been found that 20
4. An electric contact combination wherein one
combinations selected according to the invention
contact is made up of platinum group metals con
operate for periods of the order of 300 to 5,000
taining a small amount of iron group metal as a
hours which is far in excess of known previous
modifying‘ agent and the other contact is made up
combinations. of a tungsten group metal in combination with
While the present invention as to its objects 25 silver.
‘
and advantages has been described here as car
5. An electric contact combination wherein one
ried out in speci?c embodiments thereof, it is not
contact is made up of a platinum group alloy
desired to be limited thereby but it is intended to
and the other contact is made up of a tungsten
cover the invention as broadly as the spirit and
group
metal, silver, and a small amount of an
30
scope of the appended claims permit. '
What is claimed is:
.
other metal which serves as a modifying agent
'
for the silver.
1. In combination a co-operating pair of elec
6. An electric contact combination wherein one
tric make-and-break contacts, one contact being
contact is made of a platinum group alloy and
,formed of an alloy rich in at least one noble metal
the other contact is made up of a tungsten group
and the other contact being made up of a wear 35 metal, a small amount of a modifying agent for
resistant constituent selected from the sixth
said metal selected from the class consisting of
group of the periodic system and a conductive
carbon and boron and silver.
constituent of the class consisting of silver, cop
per and alloys predominating in these metals.
CHILDRESS B; GWYN, JR.
2. An electric contact combination for D. C. op
eration the contact on one side of said combina
tion having the composition
,
'
At least one metal of the group platin
Per cent
,
palladium, gold _____________________ .._
45
0-98
At least one metal of the group ruthenium,
'
rhodium, osmium, iridium ___________ __
0-15 -
Silver
At least one metal of the group iron cobalt,
nickel, copper _____ _"_'"_\__ _____________ __
0-50
50'
0-5

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