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Патент USA US2121983

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June 2s, 1938.
H. G. RICHTER
-VARIABLE gEsIsTQR
. ¿M1383
'
Filed Jan. 16, 1935
lNvENToR
ATTORNEYS
'
Patented June
l2,121,983
1.938
UNITED STATES PATENT ori-‘ica '
2,121,933
vaarsnmassrs'ron
Henry G. Richter, wennen, N. J.
Application January 16, 1935, Serial No.2,001
l‘lClaims. (c1. zot-_ssi
This invention relates to variable resistors, and The specification is accompanied by a drawing
more particularly to moderately high resistance in which:
'
units of the wire-wound type.
Fig. 1 is a rear elevation of a resistor unit with
The primary object of my invention is to gen
the closure plate removed;
Fig. 2 is a section taken in the plane of the 5
5 erally improve wire-wound ,resistance elements.
A more specific object of my invention isv to pro
line 2-2 of Fig. l with the closure plate in place;
Flg.‘3 is a section taken in the plane of the line
vide a construction which will hold the resistance
wire windings tightly in place ,even when dealing I-I of Fig. l;
Fig. 4 is a perspective view' of an annular in
with fine wire wound at close pitch. Another
10 object is to obtain good electrical contact between sulation plug forming a part of the resistor as 10
'
the resistance wire and appropriate soldering lugs sembly;
Fig. 5 is a side elevation showing the manner
without soldering and while using a minimum o!
simpliiled parts.
It is common practice. particularly with radio
15 apparatus and the like, to associate a power
switch with the resistor, said power switch being
actuated during the ilrst part of the movement of
the control shaft of the resistor. It is desirable
to actuate the -power switch before rather than
20 during resistance variation, which is best accom
plished by'elongating the short-circuited or ter
minal part of the resistance element. and the ful
illment of this desideratum constitutes another
in which units may be assembled in tandem;
Fig. 6 is a front elevation of the second or
added unit shown in Fig. 5;
15
.
Fig. 'I is a side elevation showing the -manner
in which a power switch may be used for closing
the resistor;
I
' Fig. 8 is a front elevation of the power switch
closure; and -\
20
`
Fig. 9 schematically illustrates an annular
closure plug modified for a tapered or stepped
wire-wound unit.
.v
l.
Referring to the drawing and more particularly
It is sometimes sought to taper or step *the- to -Figs. 1 through 4 thereof, the resistor comprises
rate. or resistance variation, but this has been , a preferably cylindrical casing i1 having a side 25
dimcult to accomplish when dealing with wire
wall i4 and a front end wall I6, the opposite end
wound units. In accordance with a further ob
of the casing being left open. As here illustrated,
ject of my invention, I make it possible to step the casingv is molded out of a single piece of in
30 the resistance variation by simplified means, both sulation, but it may be formed of metal lined with
this and the preceding object being accomplished insulation. The resistance is formed by an appro
while using standardized production parts similar priate resistanceywire Il wound on a strip of in
to those used with a simple unit not having vthe sulation. 2l. Ittis convenient to make the strip 20
' object of my invention.
features in question.
35
,
Still another object-of my invention is to facili
bendable. the resistance windings being applied
thereto while- the strip is straight, whereupon
35
tate the production of tandem resistance units, ' the strip is bent into arcuate conilguration and
that is, two or more independent units assembled inserted within' the casing I2. An annular in
into a single compact( structure and controlled sulation plug 22 is then forced! into the casing
by a single control shaft. A further object of my within the arcuately bent yresistance element.
40y invention is to so design the resistor that the Soldering lugs 24. best shown in Figs. l and 3, are 40
casing of the unit may be interchangeably closed preliminarily ~inserted in the casing, saidlugs
by a simple back or'closure plate or a power being L-shaped and having their inner ends 26
switch lor one or more tandem resistor units. bearing _against the outside of the terminal por
Still another object of my invention is to make tions of the resistance winding. The plug 22 is
45 many of the parts of the resistor unit inter-` dimensioned for a force tit within the resistance 45
changeable with those used in a illm type resistor element, and when'pressed axially into position
shown in my application Serial No. '134,810 illed serves the dual -function of locking the individual
July l2, V1934, thereby making possible the ready resistance windings tightly inplace and of forc
assembly of tandem units having one resistance ing the terminal parts-of the windings tightly
wound and one nlm type resistor, as well as against the soldering lugs, thereby insuring good 60
simplifying the manufacturing problem >by'using contact without the necessity oi' soldering or
„a maximum number of'parts common >to both
the i‘llm and wire-wound units.
ss
`
To the accomplishment of the i'ôre'going‘and
such other objects as will hereinafter appear.
my invention consists in then resistor elements
and their relation one'to the other, as are herein-.
after more particularly described -in the speciß
œ cation and sought to be deilned in the claims.
other special precautions. " The leading or ap- _
proach edge of plug!! is preferably rounded
or/and tapered slightly. as is indicated at 23 in
Fig.
2.
‘
-
.
-
p
'
55
resistance is varied vby a sliding contact
Il formed'at the-end of a preferably long resilient
arm'Ilsecured-«to a radial ann 32y mounted.. on
Athe control shaft “.- Arms Il and $2 are here
illustrated as secured together by a tenon 38 on 60
2
9,191,988
arm 32 passing through arm l2 and riveted there
over. The inner end of arm 22 is pressed to form
a dished hub 38 within which there is placed an
insulation washer lli. The inner end of shaft Il
is squared at 42 and receives a metallic washer
M, an insulation washer It, hub 28 with its in
sulation washer I0, and a stop arm SII, these parts
all being riveted tightly on shaft Il, as is indi
cated at 52. The hole in hub Il is, „of course,
10 made larger than the squared end 42, so that the
entire contact arm assembly is insulatediy
mounted on the control shaft.
Electrical connection with the contact arm is
made through soldering lug". 'The inner end
which are secured bearing surfaces 9| which pro
ject through a window Ill in plate 80. Bearing
fingers 2l lie in the path of movement of stop
arm l0, and the parts are so arranged that when
the stop arm reaches its end position, the switch
is turned loff, this being the condition of the
parts shown in Fig. 8 in which the stop arm il
is indicated by broken lines. It will be under
stood that when the resistor is turned from its
end position, the switch is tripped during the nrst
part of the movement.
.
To avoid having the switch tripped only after
traversing part of the resistance element, I short
circuit the resistance winding for an appreciable
distance at the starting terminal. This is accom
15 of this soldering lug forms a ring Il which
surrounds insulation washer I8 and bears in an ' pllshed in a convenient manner at minimum cost
axial direction against the face of hub 2l. The
ring 56 has struck thereon diametrically opposed
teats 58 which ride on hub 3l.
'I'he soldering
lug is formed of sheet metal sufficiently resilient
to insure good electrical contact. It will be
noted in Fig. 1 that soldering lug I4 enters casing
I2 at the ends of the resistance element, thus
avoiding contact with the resistance windings.
25 The lug is preferably recessed into the end_wall
i6 of the casing, as is best shown at il in Fig. 2,
in order not to interfere with proper seating of
the resistance element. The lug is held in place
by insulation plug 22. The latter is preferably
30 recessed at t2 to insure proper registration of the
parts, and this recess is occupied by a bend Il
20
by coating a part of the periphery of plug 22 with
metallic paint, as is indicated at |02 in Fig. 4.
I prefer to use a non-oxidizing metal like silver.
When plug 22 is forced into place, the resistance
windings in contact with the silver coating |02
are short-circuited and rendered ineffective. 'I'he
coating is dirnensioned to compensate for tripping
of the power switch. This feature may be used.
of course, only with units intended to be equipped
with a power switch, but the expense is so slight
that I flnd it more convenient to use the metallic
coating il! on all units, thereby standardizing
the resistance value and adapting all units for
the addition of a power switch.
This general idea of coating the periphery of
the plug 22 may also beV used to provide a so
called tapered resistance unit. that is., a unit in
Control shaft 34 is carried by a threaded me
which the rate of change of the resistance is
tallic bushing C8 whichisflanged at il and riv
eted to casing wall I 0 at 10. The shaft is held ì not uniform. Tapering is valuable and vhas been sa
against axial movement by thrust washer Il at - used with considerable success in film type resist
one end of the bushing, and a split thrust washer ance units but has been too costly for use in wire
wound units. as by varying the pitch of the wind
12 sprung into a mating groove 1I on the con
ing or changing the size or material of the resist
trol shaft at the other end of the bushing.
ance wire. In accordance with my invention, the
> The resistor is completed by a preferably me
tallic closure plate 1B secured at the open end of plug 22 may have a part of the periphery coated
with a very low resistance film i“, as is indi
the casing.- Cylindrical casing wall Il is prei’
erably recessed at'" to receive closure plate'lß. cated in Fig. 9. When such a plug is forced
into contact with the wire windings, a part of the
The closure plate is circular except for a regis
tration proiection Il which nts into a recess I2 winding is changed to a compound wire and nlm
on casing wall I4. While closure plate 1l is not type unit, thereby lowering the resistance value
shown in plan, the projection Il is similar to that of part of the element while still retaining a
shown on the switch closure in Fig. 8. A ring of current carrying capacity better than is attain
insulating material I2 may be interposed between able'with a simple film type resistor. The short
circuiting terminal or metallic coating il2 may,
50 the closure plate and the casing when assembling
the parts. The closure plate is held in place by of course, also be used.
A further feature of my invention concerns
a single assembly screw I4 which passes through
the front wall I8 of the casing, then through tandem units. Such units are troublesome to
a hole I8 in the plug 22, and finally is threaded stock because of the variety of combinations re
into
the closure plate at Il. This assembly screw quired. I simplify this problem by adding one or
55
Il is so located as not to interfere with the full more tandem units lin to the standard resistor
desired range of movement of the contact arm I2. R, as is indicated in Fig. 5. Instead of closing
Plate 10 has struck inwardly therefrom a stop the back of resistor R with a closure disc or
power switch, the unit I IllA is added which in turn
lug B8 which cooperates with the store-men
tioned stop arm l0 to limit the movement of the is open at its back face and preferably made ex
actly like the back edge of the standard unit, so
control shaft.
'
If desired, the resistor may be combined with that the regular closure plate or power switch
a power switch by substituting a switch closure may in turn be used to close the casing of the
for the simple closure .plate heretofore described. tandem unit lili. The casing of unit Ill is
molded like that of unit R except that the for
65 Such an arrangement is shown in Figs. 7 and 8.
The resistor R corresponds to thatV heretofore ward edge is stepped or shouldered at l|2 and
described. The switch closure S comprises a plate provided with a locating projection Ill, so that
III having the same outline as closure plate 1l. the units will mate snugly together. 'I'he as
This plate includes a registration lug Il and sembly screw i Il is approximately twice as long as
70 threaded hole I1, like those heretofore described. before and passes through both units from end to
and a. stop lug 92 which allows for the switch end. Unit lill in Figs. 5 and. 6 is intended to
The switch is mounted on plate Il, generically represent a tandem unit of either
. movement.
film or wire-wound type. If wire wound, the
and electrical connection is made through soi
dering lugs 84. The switch is preferably of the , internal mechanism of the unit is like that of
75 toggle type and is controlled by a rocker Il to unit R, the essential difference being that the
in soldering lug Il.
'
‘
3
bushing and control shaft of unit l I0 terminate
at the unit, and the control shaft has riveted
thereto a drive disc H8. This disc is slotted at
|20, and the waste metal is bent outwardly to
form bearing surfaces l2! dimensioned to receive
the stop arm 5|! of unit R. Stop arm 50 then
functions as a coupling rather than a stop arm,
but the stop arm of unit H0 assumes the motion
limiting function.
'
An important feature of the present invention
10
resides in the fact that the external dimensions
of casing l2, stop arm 50, disc Ill, closure plate
16, and switch S are identical with the corre
sponding dimensions in the film type unit shown
15 in my copending application Serial No. 734,810
heretofore mentioned. This makes- it possible
not only to connect wire-wound units in tandem
with one another and nlm type units in tandem
with one another, but more important, to con
20 nect wire-wound and film type units in tandem.
Such flexibility of combination is valuable in
meeting the varied requirements which arise in
practice. In Figs. 5 and 6 the tandem unit lill
equally well represents a unit of the film type
or of the wire-wound type. 'If desired, the first
unit (replacing R) may be of the nlm type and
the second unit of the wire-wound type.
It is believed that the mode of constructing
and using, as well as the many advantages of my
30 resistor, will be apparent from the foregoing de
tailed> description thereof. The windings and
soldering lugs are locked tightly in place and are
held in good electrical contact by their assembly
plug, and a removable closure for closing the
open back end of the casing.
2. A variable resistor comprising a-cylindrical
casing closed at one end, a bushing secured to
said end, a control shaft passing through said
bushing, a contact arm mounted on said control
shaft, an arcuate wire-Wound resistance element
placed inside the cylindrical wall of the casing,
one or more soldering lugs having their inner
ends next to the windings, an annular insulation 10
plug forced within said wire-wound strip, a stop
arm mounted at the end of the control shaft, and
a closure for the open end of the casing, said clo
sure having a stop cooperating with said stop
' arm.
3. A variable resistor comprising a. cylindrical
casing closed at one end and open at the other
end, a bushing secured to the closed end, a con
trol shaft passing through said bushing, a con
tact arm and hub insulatedly mounted on the A20
inner end of said control shaft, an arcuate wire
wound resistance element placed inside the cy
lindrical wall of the casing, one or more solder
ing lugs having their inner ends next to the
windings, an annular insulation plug forced 25
within said wire-wound strip, another soldering
lug passing beneath said plug and bearing at
its inner end against said hub, a stop arm mount
ed at the end of the control shaft, and a clo
sure for the open end of the casing, said clo 30
sure having a stop lug cooperating _with said
stop arm.
>
4. A variable resistor comprising a cylindrical
between an external ring and an internal plug. ' casing closed at one end and open at the other
end, a bushing secured to the closed end, a con
35 This internal plug serves dual yfunctions in re
trol shaft passing through said bushing, a con
ceiving a metallic coating for short-circuiting ter
-rninal windings and in receiving a resistance or tact arm and metallic hub insulatedly mounted
on the inner end of said control shaft, an ar
other conductive coating for tapering the resist
ance value. The assembly of tandem units is cuate wire-wound vresistance element placed in
side the cylindrical wall of the casing, one or
40 facilitated and the combination of wire-wound
and ñlm type units made possible.' Many of the more soldering lugs having their inner ends inter
parts of the wire-wound unit are identical with posed between Athe windings and the casing, an
«annular insulation plug forced within said'wire
parts used in a film type unit, thereby simplify
ing manufacture. Sliding contact is made at the wound strip in order to bind the windings and
press the same into contact with the soldering
45 side rather than the edge of the resistance -ele
lugs, another soldering lug passing beneath said
ment, thus presenting ‘a larger surface for con
tact. The contact arm is long and readily yield---- plug and having at its inner end a contact mem
>ber bearing against the aforesaid hub, a stop
able, making for smooth even control.
It will be apparent that while I have shown arm mounted at the end of the control shaft,
and described my invention in preferred forms, a closure for the open end of the casing, said
many changes and modifications 'may be made closure having a stop cooperating with said stop
in the structures disclosed without departing arm, and a single assembly screw passing through
from the spirit of the invention defined Ain the' said casing, plug, and closure, said screw being
so located as not to interfere with the desired
following claims.
55
I claim:
1. A variable resistor comprising a one-piece
casing having -an end and a cylindrical side-wall,
a bushing secured to said end, a control shaft
35
40
45
50
55
range of movement of the contact arm.
5. A variable resistor comprising a continuous
wire-wound resistance element, a contact mov
able thereover, and an insulation support ex
ternal of the elements and forced against the
outside of said element, said support being coated
with a conductive coating contacting with a part
shaft, an arcuate wire-wound resistance element of said element.
placed inside the cylindrical wall of the casing,
6. A variable resistor comprising a cylindrical
said resistance element being small in radial casing wall, an arcuate wire-wound resistance
dimension but broad in axial dimension, saidy strip carried within said wall, and a circular es
65 cylindrical side wall having» an axial breadth insulation plug forced within said arcuate re
greater than that of the resistance element, an sistance element, a part of the periphery of the
annular rigid insulation plug forced within said plug being coated with a conductive coating.
'1. A variable resistor comprising a cylindrical
wire-wound element tovhold the same tightly
casing wall, an arcuate resistance element car 70
against
the
cylindrical
wall
of
the
casing,
said
70
ried within said wall, and a circular insulation
plug being-substantially smaller in axial dimen
sion than the element and bearing against the plug forced within said arcuate resistance ele
forward part of the inner wall of the element, ment. the periphery of the plug at oneend of
said contact arm bearing against the remainder the element being coated lwith a metallic coating
75
75 of the inner wall of said element in back of said- ,in order'to short-circuit a part of the element.
passing through said bushing, an arcuately bent
60 resilient contact arm mounted on said control
4
53,121,993
,
8. A variable resistor comprising a cylindrical
casing wall, an arcuate _wire-wound resistance
strip carried within said wall, one or more solder
inglugs having `their inner ends next to the
' resistance element„ and an insulation plug forced
l 1o
within said arcuate resistance element, the pe
riphery of the plug at one end of the wire
wound element Íbeing coated- with a metallic
coating in order to short-circuit a part of the
element. said plug acting to force the soldering
a different resistance value than the remainder
of the element.
'
14. _A variable resistor comprising a cylindrical
casing closed at one end and open at the other
end, a bushing secured to the closed end, a con
trol shaft passing through said bushing, a con
tact arm mounted on said control shaft, an ar
cuate wire-wound resistance element placed inside the cylindrical wall of the casing,_an an
nular insulation plug forced within said wire l0
~ - lugs and the metallic coating into contact with
wound strip, the periphery of said plug at one .
the resistance element.
9. A variable resistor comprising a cylindrical
casing wall, an arcuate wire-wound resistance
15 strip carried within said wall, and a circular in
end of the wire-wound element being coated with
sulation plug forced within said arcuate resist-ance element. the periphery of the plug at one
closure including a power switch adapted to be
operated by said arm, the parts being so pro
`end of the wire-wound element being coated for
portioned that the switch is operated while the
a substantial distance with a metallic coating in
arm is at the metallic coated part of the plug.
a metallic coating for a substantial distance, an
arm mounted at the end of the control shaft, and
a closure for the open end of the casing, said 15
20 order to short-circuit a part of the element, a
15. A variable resistor comprisingA a cylindrical _
contact arm for varying the resistance, a power
switch, and means associated with the contact
casing closed at one end and open at the other
end, a bushing secured to the closed end, a con
trol shaft passing ‘through said bushing, a con
tact arm mounted on the control shaft, an arcu»
_ate wire-wound resistance element placed inside ,
arm for operating the power switch while the
contact arm is at the short-circuiœd end of the
25 element.
10. A variable resistor comprising a cylindrical
casing wall, an arcuate wire-wound resistance
strip carried within vsaid wall, one or more solder- `
the cylindrical 4wall of the casing, on'e or more
soldering lugs having their inner ends interposed
between the windings and the casing, an annular
insulation plug forced Within said wire-wound
ing lugs having their inner ends interposed be»
30 tween the resistance element and the cylindrical
wall. a circular insulation plug forced within said
strip, the periphery of said plug at one end of .
35 stantial- distance in order to short-circuit a part
sure including a power switch adapted to be oper- ,
of the element,-a contact arm for varying the
resistance, a power switch, and means associated
with the contact arm for operating the power
switch while the contact arm is at the short~
40 circuited end of the element.
1l. A variable resistor comprising a cylindrical
casing wall, an arcuate wire-wound resistance
ated by said stop arm, the parts being so propor
tioned that the switch is operated while the arm
the wire-wound element being coated for a sub
arcuate resistance element, the periphery of the y stantial distance with a metallic coating, a stop
plug at one end of the wire-wound element arm mounted at the nend of the control shaft, a
being coated with a metallic coating for a sub
closure> for the open end of the casing, said clo
is at the metallic coated part of the plug. f
16. A non-uniform variable resistor comprising
a uniform wire-wound resistance element> includ
ing an insulation core and a uniform resistance
wire wound thereon, an insulation support wall
element carried within said wall, and a‘circulari bearing against said element, a part of said wall
insulation plug forced within said arcuate re
'being coated with a carbonaceous resistance nlm
in order to give part of the wire-wound element
45 sistance element, a portion of the periphery of
said plug being coated with a carbonaceous re~
al different `resistance value than the remainder
sistance film whereby a part of the element is of the element.
given a different resistance value than the re
17. A variable resistor comprising a one-piece
mainder of the. element.
.
casinghaving an end anda cylindrical side wall,
12. A variable resistor comprising a cylindrical a bushing secured to said end, a control shaft
` casing wall, an arcuate wire-bound resistance ele
passing through said bushing, an arcuately bent
ment carried within said wall. one o‘r more solder
ing lugs having their inner ends next to the re
sistance element, and a circular insulation plug
55 forced within said arcuate resistance element, a
portion of the periphery of said plug being coated
witha carbonaceous` resistance illm whereby a
.part of the element is given a different resistance
value than the remainder oi' the element, said
plug acting to‘force the soldering lugs and the
resistance film into contact with the resistance
element._
`
13. A variable resistor comprising a cylindrical
casing wall, an arcuate wire-wound resistance
resilient contact arm mounted on said control
shaft, an arcuate wire-wound resistance element'
placed inside the cylindrical wall of the casing.
said resistance element being small in radial di
mension but broad in axial direction, said cylin
drical side wall having an axial breadth greater
than that of the resistance element, soldering
lugs projecting outwardly from said casing and
having their inner ends bent to lie between the
outside of the resistance element and the inside
of the cylindrical wall of the casing, a rigid an
nular insulation plug forced within the wire
strip carried within said wall. one or more sol
wound element to hold the same tightly against
the soldering lugs and the cylindrical wall of the
dering lugs having their inner ends interposed
casing, said plug being substantially smaller in
between the resistance element and the cylindri
axial dimension than theV element and bearing
cal wall. and a circular insulation plug forced` against the forward part of the inner wall of the
within said arcuate resistance elementfin order element, said contact arm bearing against -the re
70 to bind the wire windings in place and `in order mainder of the> inner wall of said. element in
to force the windings and soldering lugs into good back of said plug, and a removable closure for
electrical contact, a portion of the periphery of
said plug being coated with a low resistance film
whereby a part of the' resistance element is given
closing- the open back end of the casing.
HENRY G. RICHTER. _
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