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Патент USA US2404157

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Jul)’ 15, 1946- '
_
_
F. w. AHALT
2,404,157
METHOD OF BONDING STRUCTURES
Filed Sept. 8; 1943
INVENTOR.
BY [WA/MAT
ATTO/PA/f)’
2,404,157
Patented July 16, i946
UNITED STATES PATENT OFFICE
2,404,157
METHOD OF BONDING STRUCTURES
Frank W. Ahalt, Downers Grove, Ill., assignor to
Western Electric Company, Incorporated, New
York, N. Y., a corporation of New York
Application September 8, 1943, Serial No. 501,544
6 Claims. (01. 219-10)
1
This invention relates to a method of bonding
structures, and more particularly to a method of
bonding structures comprising a plurality of
parts formed of tungsten.
In the manufacture of incandescent lamps
and of electronic emission devices, such as may
be positioned in‘ a vacuum tube, it is sometimes
the practice to employ a ?lament of tungsten,
which is capable of withstanding considerable
2
Referring to the drawing, and particularly to
Fig. 1, an apparatus is there shown which may
be employed in following the method of this in
vention. As shown in Fig. l, a hood 5, or bell,
is positioned on a table 6 and may be supplied
with hydrogen through a port 1 formed in the
upper portion of the hood 5, it being desirable
that the bonding operation take place in a non
oxidizing atmosphere, such as hydrogen, in order
heat over long periods of operation. This ?la 10 to reduce so far as possible oxidation of the me
tallic elements. Positioned within the hood 5
ment may be mounted between a pair of spaced
and mounted on the table 6 is a base plate 8
tungsten lead wires which serve as electrodes
which serves as a support for a base member 9
and supporting elements and the ?lament may
of an assembly to be welded. As shown in this
be attached to the upper ends of the lead wires
drawing, two spaced parallel glass tubes H) ex
15
by welding.
tend vertically through the assembly base 9 and
One method of welding has been to arc weld
two lead wires H, which are made of tungsten,
the tungsten ?lament to the tungsten lead wires
are positioned in these tubes and extend sub
in a hydrogen atmosphere using a carbon elec
trode.
However, because of the high tempera
stantially beyond the ends thereof.
The glass
tubes, which may be fused to the lead wires,
ture present in a carbon arc and necessary to 20
serve to insulate the lead wires from the base
melt the tungsten, both the tungsten ?lament
member 9. The upper end of each lead wire II
and lead wires were sometimes embrittled in the
is provided with a notch l5, as shown in Fig, 2,
areas adjacent the joints due to the formation
and the ends of a tungsten ?lament wire 16 rest
of tungsten carbide in that area because of car
these notches, the ?lament being positioned
bon mixing with the tungsten, the carbon being 2-5 in
between and supported by the lead wires which
supplied from the carbon electrode, and also due
are substantially thicker than the ?lament wire
to crystallization of the tungsten caused by the
l6.
excessive heat, which is on the order of 7000° F.,
An electrode holder I8 is universally supported
generated during the welding process. Since the
in
a ball and socket joint l9 mounted in the hood
30
welded assembly may be employed in lamps or
5 and serves as a support for an electrode 20
tubes which may be subjected to considerable
which is made of nickel. In changing from a
shocks and vibrations during use, this embrit
carbon-type
electrode to a metallic electrode, a
tlement of the ?lament and lead wires tends to
metal must be selected which will itself with
reduce their useful life.
An object of the present invention is to pro 35 stand the high temperatures encountered when
the tungsten ?lament becomes incandescent dur
vide an improved and an efficient and effective
ing operation, as well as a metal which will form
method of bonding structures.
a mechanically strong joint between the tung
In accordance with the present invention, a
sten
lead wires and the tungsten ?lament.
tungsten ?lament may be bonded to a tungsten
lead wire by using a nickel electrode and a cur
rent su?icient to cause the nickel to be deposited
over the juncture of the tungsten elements to
form in effect a brazed union between the ele
ments, the union being made at a temperature
40 Nickel, as used in accordance with this inven
tion, meets these requirements fully.
It will be noted that the electrode holder I8
is so positioned that the end of the nickel elec
trode 20 may be moved into contact with the
substantially lower than the melting temperature 45 upper end of the lead wire I I. In some cases, the
of the tungsten.
Other objects and advantages of the present
invention will be apparent from the following de
tailed description taken in conjunction with the
accompanying drawing, wherein
‘
Fig. 1 shows diagrammatically an apparatus
which may be used in accordance with the pres
bonding operation may be expedited by making
the supporting plate 8 rotatable and providing a
mechanism (not shown) operable from outside
of the hood 5 to rotate the table to bring each
50 lead wire into position adjacent the electrode 20.
The electrode 20 is connected to one side of a
source ‘2| of direct current, such as a direct cur
rent generator, and each lead wire II is con
ent invention; and
nected to the other side of the same source. As
Fig. 2 is an enlarged sectional view along the
55 may be seen in Fig. 1, the mounting plate 8 is
line 2-2 of Fig. 1 showing a. completed joint.
3
2,404,157
4
provided with recesses 23 through which the
lower portions of the lead wires ll extend, the
table 6 being similarly apertured, and a pair of
clips 24 of electrically conductive material is at
is deposited on the parts acts as a reinforcement
to the wires in that area, Results obtained by
following this process have been exceptionally
satisfactory and have resulted in an appreciable
tached to the lower ends of the lead Wires 1 l and
reduction of failures as a result of breaking of the
connected to the direct current source 2|.
?lament wires, which is largely due to embrittle
In the operation of this apparatus, it is general
ment of the tungsten adjacent the welding areas
ly preferable to strike the arc between the elec
during subsequenthandling of the welded assem
trode 2i] and the lead wire l I rather than between
bly.
the electrode 20 and the ?lament it‘ since the fila 10
What is claimed is:
ment is usually formed from a substantially
1. A method of uniting tungsten parts compris
smaller diameter wire than the lead wire and,
ing assembling the parts in the desired relation,
consequently, is more likely to be burned through
and applying an are from a nickel electrode to the
than are the lead wires, In practice, an arc
junction of the parts to deposit nickel thereon
voltage of 25 to 30 volts at from 12 to 15 amperes 15 and unite the parts.
may be used and the are is held for a short period
2. A method of uniting tungsten parts com
of time, generally less than a second. Under
prising assembling the parts in the desired rela
these conditions, and using as an electrode a wire
tion, applying an are from a nickel electrode to
having a diameter of approximately .03", a read
the junction of the parts, and depositing nickel
ily visible deposit 25 of nickel will be formed at 20 on the junction of the parts to reinforce the junc
the junction of the lead wire and the ?lament
tion.
wire and will provide a mechanically strong joint
3. A method of uniting tungsten parts compris
therebetween.
ing assembling the parts, and. applying an are
In uniting the parts, in accordance with this
from a nickel electrode to the junction of the
invention, an are having a temperature substan
tially below the melting point of tungsten, which
is approximately 61000 F., but considerably‘ above
the melting point of nickel, which is approxi
25 parts to deposit nickel‘ thereon and unite thev
parts, the are being applied in a hydrogen at,
mosphere.
‘i. A method of’ uniting tungsten parts compris
mately 2645"
is used. The speed of the opera
ing assembling the parts, and applying an are
tion is such that substantially no nickel is lost in 30 from anickelv electrode to the junction of the parts
spite of the relatively high temperature, while
to deposit nickel thereon and unite the parts, the
on the other hand, the high temperature is suf?
are being applied in a non-oxidizing- atmosphere.
cient to cause the surface of the tungsten lead
5. A method of’ uniting tungsten parts com
wire and the tungsten ?lament wire to soften
prising assembling the parts, and applying an
somewhat inv the area of the joint, thus forming
are from a nickel electrode to the junction of the
a joint very similar to that obtained by brazing.
parts to cause nickel to be deposited on the junc
By using an arc having a temperature below the
tion of the parts to reinforce the junction, the
melting point of tungsten, crystallization of the
are being applied in a hydrogen atmosphere.
tungsten is kept at a minimum since very little
6. A method of uniting tungsten parts com
grain growth occurs in the tungsten when ex
prising assembling the parts, drawing an arcfrom
posed to the temperature used for the short weld
a nickel electrode at a temperature below the.
ing period required in accordance with this inven
melting point of tungsten and above the melting
tion. At the same time, ‘by eliminating the car
point of nickel, and depositing nickel over the
bon electrode, the formation of tungsten carbide,
which is very brittle, in the area of the joint is 45
completely avoided. In addition, the nickel which
juncture of said parts,
‘
FRANK: W.v AI-IALT.
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