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Патент USA US2407171

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Sept. 3, 1946.
Filed llay 16, 1944' >
10 I
12 i3
16. 11*
Patented Sept. 3, 1946
Lawrence McFarren, Indianapolis, Ind., assign.
or to P. R- Mallory & 00-, Inc-J Indianapolis,
Ind., a corporation of Delaware
Application May 16, 1944, Serial No. 535,788
1 claim-
(Cl- 201-67)
The. present invention relates to resistors, and,
moreparticularly, to wire-wound resistors of the
type employed in connection with electrical
measuring instruments for extending the range
of measurement.
As those skilled in the art know, precision ex
ternal meter resistors of the described character
essentially comprise a glass or ceramic enclosure
with ferrules at the ends thereof. Within the en:
closure the, windings of resistance wire are pro
external meter resistor which is. simple in struc
ture, is capable of passing the most severe test,
and which may be readily manufactured and sold
on a practical and commercial scale at a low cost.
Other and further objects and advantages of
the. invention will become apparent from the fol-.
lowing description, taken in conjunction with the
accompanying drawing; in which
Fig. 1 illustrates a side elevational view of a
vided on a suitable base likewise constituted of
ferrule type resistor embodying the principles of
the present invention;
glass or of ceramic material. These units are
very di?icult to make since their resistance has
the unitary resistor;
to be. within very close tolerances, they. have to
Fig. 2 depicts a longitudinal sectional View. of
Fig. 3 shows a similar sectional view of one of
be non-inductively. wound and in addition have 15 the resistance elements or units which maybe
to pass severe tests. Another practical difficulty
experienced in connection with these resistors
employed in the preferred form of the invention;
was that they had to be manufactured in a large
Fig. 4 is a longitudinal sectional view of a mod
number. of different sizes and resistance values in
i?ed form of the resistance element or unit which
accordance with the, speci?c application contem
may be incorporated into the resistor of the in
plated. Of course, manufacturing and carrying
in stock a large number of different resistance
While a preferred embodiment of the inven
values was connected with considerable incon
tion is described herein, it is contemplated that
venience as it necessitated tying up a great deal
considerable variation may be made in the meth
of capital and raw material in the form of resis 25 od of procedure and the construction of parts
tors of different values including such values for
without departing from the spirit of the inven
which there was very little demand. Various.
tion. In the following description and in the
suggestions and proposals have been made to
eliminate this. difficulty but, as far as is known,
none of these suggestions and proposals, was com
pletely satisfactory. and successful when carried
into practice. on a practical and commercial
It is an object of the present invention to pro
vide a precision meter resistor which completely
eliminates the foregoing difficulties,
It is another object of the present invention to
provide a resistor of novel and improved charac
ter which permits building up any practically
desirable resistance value from a plurality of
claims, parts will be identi?ed by speci?c names,
for convenience, but they are intended to be asv
generic in their application to similar parts as
the art will permit.
Referring now more particularly to Figs. 1 to
3 of the drawing, reference character It] denotes
a cylindrical casing constituted of moisture and
heat-resistant insulating material such as, for
example, glazed porcelain, “Isolantite,” “Pyrex,”
and the like. The ends of casing Ii] are closed
by means of ferrules ll of brass, bronze, or some
other metal.
Within casing 10 there are disposed end to end
standard values.
a plurality of resistance elements or units. Each
It is a further object of the present invention
of these comprises a cylindrical spool 12 with in
tegrally formed barriers l3 de?ning winding
to provide an external meter resistor of the fer
rule type comprising an insulative enclosure with
spaces I4 within which there are disposed wind
ferrules at the ends thereof, within which there 45 ings l5 of resistance wire. In accordance with
are disposed a plurality of serially connected uni
the usual practice, an even number of winding
tary resistors selected from a few standard val
spaces is provided for one unit and the direction
ues in accordance with the desired application.
of Winding is reversed for adjoining winding
It is also within the contemplation of the in
spaces in order to make the ?nished resistance
vention to provide a ferrule type meter resistor 50 substantially non-inductive. Barriers l3 are also.
which may be assembled from appropriately se
provided with the usual radial slots for the pas
lected standard elements to constitute a preci
sage of the interconnecting portions l6 of the re
sistance wire. Cylindrical spools [2 may be con
sion resistance of any desired value within a wide
stituted of the same materials as casing [0, such
The invention also contemplates a precision 55 ar particularly “Isolantite.”
The end faces of spools I2 may be provided
with a metalized layer I‘! to which the ends of
the resistance wire may be soldered. Electrical
connection between the adjoining ends of the
Fig. 3 is a longitudinal sectional view of a
resistance unit which is in every respect identical
with the units shown in Fig. 2 with the only dif
several spools may be established by brazing or
ference that four Winding spaces I4 are de?ned
therein by means of a corresponding number of
soldering the silvered ends of the spools together.
As an alternative, jumpers (not shown) may be
barriers I3. The structure and the operation of
the resistance unit should be self-explanatory.
soldered across from one spool to the next one
in a manner well understood.
Fig. 4 is a similar view of a modified form of re
be readily assembled with considerable savings
said tube, a plurality of stacked unitary resist
sistance unit which is also practically identical
Electrical connection between the serially con 10 with the structures shown in Figs. 2 and 3, similar
nected resistance units and the end ferrules II
reference characters being used to denote corre
may be secured in a great variety of ways. One
sponding parts. The difference resides in that
form of construction which was found satisfac
one end of spool I2 is provided with a head 30 of
tory comprises an apertured disc or spider I8 of
conical shape while the other end of the spool is
spring metal having an opening I9 in the center
provided with a conical depression 3| of conform
thereof and having its circumferential edges 20
ing shape. Both head 30 and depression 3I are
clamped between the ends of casing I0 and
coated with a metalized layer 32 to which the ends
?anges 2I' of the ferrules. Disc or spider I8 will
of the resistance wire are electrically connected.
resiliently hold the stacked resistance units
A plurality of such resistance elements or units
within tubular casing it). A conductor 22 has 20 may be readily stacked or mounted end to end by
one of its ends extending through opening I9 in
inserting the conical head of one unit into the
disc I8 and soldered to metallic layer I‘! at the
corresponding depression of the next one. Elec
end of the spool at 23 while its other end extends
trical connection between the several stacked
through a corresponding opening 24 in ferrule
units may be made by brazing metalized layers
I I and is soldered thereto at 25. Ferrules I I may 25 32 together or by means of soldered jumpers, as
be secured to the ends of easing II! in various
it is set forth more fully in the foregoing.
ways such as by cementing or by silvering the
While the present invention, as to its objects
ends of the casing tube and soldering the flanges
and advantages, has been described herein as
of the ferrules thereto.
carried out by speci?c embodiments thereof, it is
From the foregoing description the operation 30 not desired to be limited thereby but it is in
of the resistor of the invention and its advan
tended to cover the invention broadly within the
tages will be readily understood by those skilled
spirit and scope of the appended claims.
in the art. Obviously, by manufacturing re
What is claimed is:
sistance elements orunits in a few standard val~
An electrical resistor comprising in combina
ues, a very large number of resistor values may 35 tion an insulative tube, a ferrule at each end of
in manufacturing cost.
ance values which have
greatly reduced and at
sired value within the
The number of resist
ance elements mounted Within said tube, each of
to be carried in stock is
said resistance elements including an insulative
the same time any de
spool with windings of resistance Wire thereon
practical range is in 40 having one of its ends formed with an external
stantaneously available.
conical surface and its other end formed with a
The advantages of the present invention are
corresponding internal conical surface and a
particularly accentuated by recent efforts in the
metalized layer on each of said surfaces consti
direction of standardizing meter resistors. Thus,
the American Standards Association has issued
speci?cations for ferrule type meter resistors
covering three mechanical sizes and thirteen re
sistance values from 0.5 to 6 megohms. Each
tuting terminals for said windings, the external
and internal conical surfaces of adjoining spools
being adapted to mate with each other to main
tain the relative position of the spools in the
stack, means including a fused metallic bond be
tween each pair of adjoining metalized layers for
megohm, 0.5 megohm and 1.0 mego‘nm. The re
connecting all of said windings in series, and
means for connecting the terminals of said seri
sistor of the present invention, of course, is ex~
cellently adaptable for the manufacture of such
ally connected Windings to said ferrules.
standard resistors since by carrying in stock only
resistance units of three different values, any
resistance within the standard range may be 55
standard resistance value is a multiple of 0.3
immediately assembled.
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