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Патент USA US2413043

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Dec. 24, 1946.
Filed Aug. 14, 1943
Patented Dec. 24, 1946
Charles J. Ganci, Rldgewood, N. Y., assignor to
Ward Leonard Electric Company, a corpora
tion of New York
Application August 14, 1943, Serial No. 498,651
6 Claims. (01. 201-63)
This invention relates to‘improvements in re
sistive devices such as tubular resistive units and
other forms.
In making resistive units, such as of tubular
form, in which a solid conductor, usually in the
form of a wire or ribbon, or a conductor of vari
obtain a, device which will have a uniform and
smooth surface throughout its length and sub
stantially overcome rejects in the process of
manufacture due to failure of the connection be
tween the conductor and the stranded lead wires.
A further object is to produce a process of manu
ous forms and cross-sections, is utilized as the
facture which may be conveniently accomplished
resistive conductor, it is desirable to provide
and carried out with assurance of dependability
stranded wire connections thereto, or so-called
and durability. Other objects and advantages
pigtail leads, owing to their ?exibility and con 10 will be understood from the following description
venience in making connections to the circuit in
which the device is to be used and owing to their
comparative freedom from breaking after re
peated bending and twisting. It has been com
mon to twist the stranded wire around the solid
wire and solder the connection but this forms an
objectionably enlarged joint; and particularly in
and accompanying: drawing which illustrate em
bodiments of the invention and the steps in the
method of making.
P18‘. 1 is a side view of a resistive device of
tubular form showing the tubular support and
, the conductor applied thereto before the applica
tion of the insulating coating; Fig. 2 is a side view
of the completed unit; Fig. 3 is a diagram show
ing a step in the process of preparing the strand
joint is objectionable not only in increasing the 20 ed conductor for welding; Fig. 4 is a diagram
outside dimension of the unit but in the difficulty
showing a further step in the process; Fig. 5 is
of properly covering and embedding the joint
a similar diagram showing the ?nal step in the
with the insulating coating.
process; and Figs. 6, 7 and 8 are side views of
According to the'present invention, the ends
joined conductors as illustrative examples.
of the conductors are butt welded together to pro
Referring to Fig. 1, the main support is a tube
duce a joint not appreciably larger than the size
i of insulating material such as porcelain. On
of the conductors and give the joined conductors
this is wound a solid conductor 2 forming the re
the appearance of a continuous conductor. When
sistive conductor. This is of a proper size, length
a resistive conductor with such welded terminal
and. number of turns to give the desired resistance
leads of stranded wire is utilized in a resistive
to the unit. It may be of any suitable metal or
device, there are no enlarged joints to contend
alloy, such as Nichrome composed of nickel, chro
with in applying the insulating coating, result
mium and iron, or may be an alloy of nickel and
ing in a final product having a uniform and
copper, or of nickel and chromium, various al~
smooth appearance throughout. But the butt
loys of iron, or any other metal or alloy accord
welding of the end of a stranded wire cannot be
ing to particular requirements.
accomplished properly if it be attempted to weld
At each end of the resistive conductor 2 is a
by joining the ends of the stranded wire to the
joint 3 between it and the stranded wires 4 and
end of a conductor; because some of the strands
5 forming the ?exible terminal connections. The
may be welded while others will not. This results
lead 4 continues from its joint 3 around the tube
in a poor electrical connection and in the spread 40 and then passes within the tube through a hole
ing out of the unwelded strands or of some of
6 and then out from the end of the tube to form
them, giving an awkward joint to properly and
the outside lead. The lead 5 continues from its
fully cover by the insulating coating. It also re
joint 3 around the tube and then passes within
sults in a portion protruding from the unit at
the tube through a notch l and through the length
the joint. Furthermore, during the maturing of,
of the tube to form the other outside lead.
the insulating coating, as by firing in a furnace,
As to the joint 3, it is shown as a solid con
the strains imposed on the few welded strands are
nection between the solid conductor 2 and the
likely to- rupture the connection, giving an open
stranded wire leads 4 and 5; and this joint is no
circuit in the completed article. The number of
larger than the conductor 2 or the leads, giving
rejects from this cause alone may be considerable. .50 the appearance of a continuous conductor of uni
Even if the opening of the circuit does not occur,
form size having no protruding portions or ob
the few strands remaining connected will, dur
jectionable enlargement. It therefore forms a‘
ing use of the device, cause excessive heating local
joint which may be readily and conveniently cov-'
ized at the joint which is likely to cause a break
ered by the insulating coating. In fact it is just
down of the device after a short period of use.
as easily and fully covered as any other portions of
The present invention overcomes these various
the conductor. The device as shown in Fig. 1
is ready for the application of the insulating
One object of the invention is to produce a re
coating which may be of any suitable mate
sistive device which will be durable and depend
rial but is preferably of vitreous enamel mate
able in long continued use. Another object is to 60 rial. The coating is matured by flring in a fur
resistive units wherein the resistive conductor is
coated with an insulating coating, the enlarged
gether and fused in the manner described with
nace if vof vitreous‘ enamel, and by drying or
reference to Fig. 5.
other'wiseaccording to the character of the coat
ing material.
A stranded wire 35' thus
fused to a larger braided wire 20 is'shown as an '
example in Fig. 8 at the solid joint 2 I. All strands
Fig. 2 shows the completed unit with the in-,'
of each of the two conductors are thus fused to
the common joint and insure complete electrical
connection between all strands of both conduc
sulating coating 8; and it is obvious that the de
vice is of uniform size throughout with a smooth
Y surface and no objectionable protruding portions.
This particular resistive unit was for an immen
_ Although preferred embodiments have been de
' sion heater and was adapted to slide into a quite
' closely ?tted tube or casing; any projection from 10 scribed as illustrative examples, the invention
may be embodied in other typesvand forms of re- .
the unit due to enlarged. joints or connections
between the conductor and leads would prevent it
sistive devices and modi?cations made without
vdeparting from the scope of the invention.
from ?ttingwithinthe tubular casing. In mak- ,
ing the unit, the resistive conductor is ?rst made
' of proper length and then-the stranded wire ter
minals-Pare joined'fthereto'_ in ‘the manner later
described;?Thee-freeei‘id‘of the lead 6 is passed
I claim:
1. A resistive device comprising an insulating‘
' support, a‘ solid resistive conductor carried there
by, and a lead of a stranded conductorjoined _
thereto, the end of the stranded conductor hav
ing a fused solid end butting against the end of
the lead 4 and the conductor;’ is wound around
solid conductor and fused thereto in a solid
the tube and also a portion of the lead 5. The 20 the
of a size approximately equal to that of
remaining portion of the lead 5 is then-passed
the larger of the two conductors.
through the length of the tube and held in place
2-. A resistive device comprising an insulating
by being drawn into the notch l. The insulat-__ : ,._'support;, _a,-s,olid gresistiveiconductor carried there
ing' coating is thenapplied. _
' through thehole s and then the inner portion of
As to-the making of?the"joint,‘fE‘ig'.'3‘shows'
the ?rst step. A length of stranded wire 9 is
clampedbetween the jaws 10. of .a butt welder,‘
' a portion of the‘ wire extending vbetween the two
by,‘ ‘and a"l'e"ad"'of""a stranded conductor joined
thereto, the end?of; each strand of the stranded
> oonductoribeing =fused'into1a:solidsend, and the
'said solid end beingfusedlto the" end of the solid
pairs of fljaws.‘
The Ewelder ‘is supplied with cur- rent from a suitable source, such as ‘from the "
3; A resistive ‘device vcomprising ;__an insulating
a vsolid resistive’conductor ‘carried there-_
secondary‘!l‘oféatransformer l2. The heating
by, a lead of a stranded conductor joined there~
is concentrated at the midportion of the stranded
to, the fused solid end of the stranded conductor
' wire and fused there, resulting in the separation '_ butting against they end of the‘ solid conductor
of the wire to-form two. separate leads and in a
and fused thereto in a solid joint of a"'jsize-ap
fused solid end [3 on each-of the leads, as shown .35 . proximately equal to that of theilargeii of the
in Fig. 4'; This solid fused end is not materially
two conductors, and an insulating coating cov
larger or smaller than thejsize or diameter of \ - ering said resistive conductor and'sla'eid joint.
the stranded wire and all of the strands areipers '
. 4. A resistive'device comprising; an insulating
manently fused andiconnected to this solid end. 40 support, a solid resistive conductor-1 carried there‘,
The next step isshown in
5. Here one of
there- '
by, a lead of a‘stranded conduct " 'oine'd
the stranded wires or leads ‘9 having the fused
to,'thejend of each strand of ‘the stranded con
solid end-is-zf'placed in one of‘ the jaws of' the ' ductor being fused into a solid end, andjjthe said
welder' and ‘the solidhresist‘ive conductor 2 is
" solid end being. fused to the end oft-the solid con.‘
placed in. the other jaw. 'One of the vjaws is then
ductor, and an insulating .coating'fcoverihg said
moved towards the-"other toi brlngtogether the
resistive conductor and said joint.
solid end-[l3 of the lead and the end-of the solid‘
.5. A resistive vdevice comprising-1 an insulating
conductor. . Thiscauses. the fusing-of the meeting ._ supporting tube, a solid resistive conductor wound f
ends givinga solidjointZ Messhown :in-Flgg?? : ' thereon, aleadrofastrandedrconductor joined to
and the (:onnection of :all-o?thé-strands'tojithe
' mt or: ' each end -'of said solid conductor respectively, the
solid conductor-is insured with ‘fai'sdlid'j
Ifuséadsolidjehds of thesai’dis'tranded conductor
about the ~ ‘same "size "as xii-emerges 'or‘thé tea,
v-buttingagainst the, ends'of 'said‘sdlid conductor and fused thereto in solid joints of ‘a ‘size'fdpprox
imately' equal to the size of theilarger ofjthe con
wires. Another stranded leadis "in'i'il'a?y Q0111 .
nect-ed td't'h‘e other end'iioffthehlsolid conductor,
2; and thevlj-combined conductor is ,then readyv
for applieationj to the tube 1 , :the device ‘being;
completed m'the’mannerza‘lready-described; "
This method of forming- the joint is applicable, ‘I
Eductors, and an insulatingicoatinggcovering said
'solidconductor and coveringsaidéjeints
'ftion's of each ofv said stranded conductors;
jii;v A resistive} device comprising an insulating
to the joining-of- strandisdcondirctois, or'xnulé/
supporting §~tub_e»,;§ a - solid;- ‘resistive
, _ conductor
tiple condactors. ‘of different‘; sizes/"toI solidIcpn-j" “ Y iwoundth'erjeo'n; a lead'i'of Estrandedé conductor
ductors of" "jdi?erent sizes massages‘
shows a stranded conductor}
Fig. 265 .,,n
Solid wire’ll'? let the. joint H5. the,..wire; is being:
“joined to each-end ‘of jsaid‘solid i: lductor respec
-'-tively;:"tj_he ends of the ‘leaf "s't Ii rd wire being
., .. said:
fusedjtq solid"; ends,;
mis butting
of much larger size ‘than thes‘trandedwir'ei Fig.3 "lagairist‘?hé' "é‘n‘dswof vsaid solid conductor and
'7 shows the stranded wire l5 connected at the
joint 18 to a solid wire ld‘of smaller size. This
method of forming the joint is applicable like- v_ I
wise to the joining of two stranded or braided
wires or conductors. In. that'case a solid end'i
?rst formed on the ends of each of such con
ductors in the manner described with reference _
to Figs. 3 and 4. The fused ends of the two
conductors to be joined are then brought to
fused thereto in solid joints of a size approxi
mately equal to the size of the larger of the con
ductors, and an insulating coating covering said
[solid conductor and covering said joints and por
Itions of each of said stranded conductors, the
uncovered ends of said stranded conductors being
passed through openings in said tube to form ex
ternal leads.
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