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Патент USA US2407651

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Sept 17, 19461»
J. T. BUTTERFIELD ETAL,
2,407,550
WIPER CONTACT FOR ELECTRICAL DEVICES
Filed 001;. 21 , 1945
2 Sheets-Sheet 1
FIG]
J. 7'. BUTTERF/ELD
MM, K/VAPP
B. F. RU/VYON
INVENTORS
(9 2pm % W(@@(
19V
'
A TTORA/EK
2,407,650
Patented Sept. 17, 1946
UNITED STATES PATENT OFFICE
2,407,650
WIPER CONTACT FOR ELECTRICAL DEVICES
Joseph 'I‘. Butter?eld, Summit, N. J., Harry M.
Knapp, Flushing, N. Y., and Benjamin F. Run
yon, Basking Ridge, N. J., assignors to Bell
Telephone Laboratories, Incorporated, New
York, N. Y., a corporation of New York
Application October 21, 1943, Serial No. 507,140
3 Claims. (Cl. 201-56)
2
1
This invention relates to wiper contacts and
more particularly to wiper contacts suitable for
ance element is clamped in place at therequired
spaced points, parts of the resistance element be
use in rheostats or potentiometers.
tween the points of clamping are often more or
The object of the invention is to provide in a
rheostat or potentiometer, having a plurality of
turns of wire on a support, a wiper contact that
will successively engage the turns of wire with
out skipping any of the traversed turns when
the contact making parts of the rheostat or
less bulged away from the drum-type support,
and the edge of the resistance element presented
for engagement by the wiper contact is in wave
like form. In such cases, if the contact end of
the wiper contact were of pin-point form the
Wiper contact might run off the resistance ele
ment at the bulged points during its traverse of
the resistance element. The edge of the resist
ance element presented for engagement by the
‘ potentiometer are relatively moved.
A feature of the invention resides in the con
ducting means provided in the Wiper contact.
Another feature resides in means provided for
supporting the conducting means of the wiper
contact.
wiper contact may also in some cases have some
of its parts in slightly higher or lower planes than
15
In the drawings:
other parts due to slight inaccuracies in clamp
ing the resistance element in place with respect
with part of a casing broken away to obtain a
to a desired line of travel of the wiper contact
or slight differences in the distance the Various
turns of wire extend beyond an edge of the sup
View of the wiper contact and its supporting
porting card.
Fig. 1 is an under-surface plan view of a
potentiometer in Which the invention is used and
Fig. 2 is an enlarged view of the wiper contact
and its supporting means;
Fig. 3 is a side view, partly in section, of the
wiper contact and its supporting means and taken
on the line 3—3 in Fig. 2;
Fig. 4 is an enlarged view, partly in section,
of parts of the wiper contact and means pro
vided for supporting the wiper contact;
_
In the present invention we provide a wiper
means;
contact which will faithfully perform its function
25
of successively engaging the turns of wire on the
resistance element. The wiper contact will not
run off the resistance element during its traverse
thereof and will not skip or bounce over any of
the turns of wire the wiper contact is required to
engage during its operation along the resistance
element.
For the purpose of simpli?cation in explaining
the invention, and not in the sense of limiting it
in application, the device in which it is used will
be considered to be and hereinafter referred to
Fig. 5 corresponds to Fig. 4 but shows one of 3.0
the parts adjusted to a different position;
Fig. 6 is an enlarged View, in perspective and
partly in section, of a contact element; and
as a potentiometer.
Fig. '7 is a side view, partly in section, of the
As shown in Fig. 1 the potentiometer 8 com
wiper contact and its supporting means and 3.5
prises a casing 9 in which is suitably supported
shows in full and dot-dash lines parts of the in
an annular support 10 around the outer curved
vention adjusted to different positions.
surface of which is supported a resistance ele
In some potentiometers now required and in
ment ll comprising a card-like support [2 on
volving a winding of resistance wire on a card
like support and a wiper contact to selectively 40 which is wound a resistance wire, the turns of
which extending over one, edge of the card-like
engage the turns of wire, it is found quite im_
support 12 are indicated at 43 in Fig, 1. Con
portant to insure that the wiper contact will not
centric with the support In and the resistance
skip or bounce over some of the turns of wire and
element II is a hoop 14 in which screws I5 are
a precise predetermined pressure will be main
tained by the wiper contact against the turns of 45 supported at spaced points, the hoop l4 being
drilled and tapped to receive the screws [5 and
resistance wire it engages. In some of the
the inner ends of the screws [5 having bearing
potentiometers, above mentioned, the resistance
engagement with blocks l6 so that when the
element involving the wire-wound card is
screws i5 are tightened the blocks I6 will clamp
clamped at predetermined spaced points to a
drum-type support in order that certain prede 50 the resistance element H to the support I0 at
required spaced points, the spaced points being
termined electrical potentials will be obtained
predetermined and indicated by the marks I‘! on
when the potentiometer is operated in an electri
the support I0. It will be seen that between
cal system and the wiper contact engages the
points in line with the marks I‘! where the re
resistance element at points in direct radial line
with the points of clamping. When the resist 55 sistance element l l is clamped the resistance ele
5
2,407,65G
6
of the free end of the arm 29'. A convenient way
of bending the bracket 30 is to insert a screw
driver in the aperture 591and use the screw
metal fork IQ of the wiper contactv I8 is so
mounted relative to the resistance element that
an initial spring pressure is developed in the
sheet metal fork l9. As shown in Fig. 3 the sheet
metal fork l9 extends diagonally from its point
driver as a lever to bend the bracket 3!) to a
required form; one of the forms of the bracket
33 may be made to take that shown in Fig. 7
in which the bracket 30 has been bent to pro
of support on the insulating plate 48 to a point
considerably below the 4 level of the arm 29.
vide an off-set form as indicated at 80.
It will be seen as shown in Fig. 1 that the arm
When the arm 29 is mounted in the potentiometer
8 shown in Fig. 1, the arm 29 is in a plane only
29 extends from the shaft 21 in the central por
tion of the potentiometer 8 and toward the loca
tion of the resistance element H, the bracket 38
extends angularly of the free end portion of the
arm 29 and the tines 2| and 22 of the sheet metal
fork l9 extend in spaced relation with the bracket 15
slightly above the plane of the edge of the resist
ance element H, the contact piece 23 is resting
on the edge of the resistance element II and
wire on the resistance element H are wound on
the sheet metal fork i9 is slightly bowed to ob
the tines 2| and 22 of the wiper contact are ?exed
so that a required initial spring pressure is de
veloped in the tines. In some of the potenti
30 and so that the contact piece 23 crosses and
ometers, for instance, we have stressed the tines
is in engagement with the resistance element I I.
2| and 22 so that the contact piece 23 bears
By turning the shaft 27 thecontact piece 23 may
against the resistance element It with a pres
be caused to sweep over and frictionally engage
sure of the order of 65 grams. The pressure may
the turns of resistance wire extending over the 20 be increased or reduced as desired simply by
edge of the card-like support l2. .
bending the free portion of the bracket 33 as
In potentiometers in which the present inven
shown in Fig. '7 in which two of the many pos
tion is found of particular value, the potenti
sible forms to which the bracket 39 may be shaped
ometers are sometimes operated at a substantially
are shown. In the full-line position shown in
constant and relatively high speed, the turns of 25 this ?gure the bracket 36 has been bent so that
the card-like support at a constant pitch and the
wiper contact must therefore traverse a predeter
tain a certain desired spring pressure and in the
dot-dash line position the bracket 3i! has been
mined number of turns of the resistance wire on
further bent so that the sheet metal fork i9 is
the engaged edge portion of the resistance ele 30 bowed still more to obtain a greater spring pres
ment and arrive on a predetermined turn of the
sure. The bracket 36 may be bent to the forms
resistance wire at the end of a predetermined
shown simply by placing the blade of a screw
period of time. The potentiometer must be so
driver in the elongated aperture 59 and using the
constructed and arranged that certain-predeter
screw-driver as a lever to bend the bracket. By
mined voltages will be obtained when the wiper 35 increasing or decreasing the spring tension of
contact reaches points in line with the marks I‘!
the sheet metal fork Hi the amplitude of vibra
on the support l0 and in line with which are
tion of the wiper contact may be changed to meet
clamped predetermined points of the resistance
a required condition and if the amplitude of
element II. To insure that the contact piece 23
vibration is ‘found not suincient to make the
of the wiper contact 18 will engage a ‘predeter 40 contact piece 23 come into engagement with cer
mined turn of the resistance wire on the resist
tain turns of the resistance wire extending in a
ance element | I when in line with a predeter
slightly lower plane than other turns the spring
mined mark |‘| and will not skip or bounce over
pressure may be increased to make the wiper
the turn of resistance wire at that point, the
contact have a, su?icient overthrow in its move
sheet metal fork I9 is made to have a natural 45 ment to reach the lower turns of resistance
frequency of vibration such that the contact piece
wlre.
will engage the required turns of resistance wire.
The particular structure and arrangement
Theoretically, and as an example, in the case
shown for mounting the bracket 39 on the arm
when the pitch of winding the wire on the card
29 permit adjustment of the bracket 3i! in regard
like support is 160 turns per inch and the maxi 50 to its extension from the arm 29. As already
mum speed of movement of the wiper contact is
pointed out in the speci?cation, the screws 3|
6 inches per second, the natural frequency of
the wiper contact is made so that its tracking
frequency of vibration is a minimum of 960
cycles per second. In this case and assuming 55
that there are 160 turns of wire per inch of travel
of the wiper contact, the contact piece on the
wiper contact will engage each turn of Wire in
succession and will arrive on a predetermined
and 32 are securely mounted on the arm 29 and
the plate 33 is secured against movement since
the holes therein for the screws 3| and 32 snugly .
‘accommodate the screws. The holes 4| and 42
in the bracket 30 are considerably larger in diam
eter than the enlarged portion 3% of the screws
3| and 32 and by loosening the screws 3| and 32
the bracket 33 may be released for movement
60 on the arm 29 within limits permitted by the
enlarged portions 38 of the screws 3| and 32 and
turn of wire at the end of the predetermined
period of time. In this example it is also as
sumed that the turns of wire traversed are in a
the relatively large apertures 4| and 42 in the
common plane. In cases where the number of
bracket 38. The angle of extension of the bracket
turns of wire per inch of travel of the wiper con
30 relative to the arm 29 may be changed by
tact and the maximum speed of travel of the 65 loosening the screws 3| and 32 and by manually
wiper contact are greater than the above ex
turning the bracket 30 on its point of support
ample, the wiper contact would be made to have
on the arm 29 and within the limits permitted
a natural frequency of vibration greater than the
by the screws 3| and 32 and the apertures 4|
frequency above mentioned.
and 42. By turning the bracket 38 in this manner
In order to obtain a required pressure of the
the angle of extension of the contact piece 23
contact piece of the wiper contact against the
relative to the direction the resistance wire in
turns of resistance wire and to obtain a suf?cient
the resistance element || extends over an edge
amplitude of vibration to make the wiper con
of the card-like support l2 may be changed.
tact reach a turn of wire located in a slightly
The wiper contact l8 may, therefore, be adjusted
lower plane than an adjacent turn the sheet 75 so that the contact piece 23 extends either angu
2,407,650
8
larly or in parallel relation with turns of the
resistance wire on an edge of the card-like sup
port [2.
The bracket 39 may be also adjusted longitu
dinally to extend a shorter or longer distance
from the arm 29 so that when the arm 29 is in
a given position and the contact piece 23 is found
tions relative to turns of wire on the resistance
element.
What is claimed is:
1. A wiper contact to frictionally traverse an
electrical element, said wiper contact comprising
an arm, a bendable bracket supported at one end
on said arm, a reed-type conducting member
secured at one end on the unsecured end of said
to be either forward or backward of a predeter
‘bracket and having an unsecured end portion
mined turn of resistance wire it is desired to
select for the given position of the arm 29, the 10 extending into contact with the electrical ele
ment, and said bracket having an aperture formed
bracket 30 may be, in effect, shortened or length
therein between the secured end of said ‘bracket
ened to bring the contact piece 23 to the desired
and said conducting member to provide a hold
turn of resistance wire.
for means to be applied to said bracket to bend
The pitch of winding the resistance wire on the
said bracket to change the pressure of said reeds
card-like support 12 is usually so short that it
type conducting member on the electrical ele
would be difficult to adjust the wiper contact l8
to engage a desired turn of the wire simply by
ment.
shifting the bracket 36 longitudinally by hand.
2. A wiper contact comprising an arm, an aper
In order that very precise longitudinal adjust
tured bracket supported at one end on said arm
and extending angularly of said arm, spaced
ment of the bracket 30 may be made, the slots
43 and 45 are provided in the bracket 35 and the
screws mounted on said arm and extending
plate 33, respectively, the slot 43 being enlarged
and beveled at 44. For a normal setting of the
bracket 30 the slots 43 and 45 will be in registry
as shown in Fig. 3. To move the bracket 38
longitudinally from the position shown in Fig. 3,
through the apertures in said bracket, the aper
tures in said bracket being larger than the diam
eter of said screws, an apertured plate disposed
between the heads of said screws and said
bracket, the apertures in said plate being of sub
stantially the same diameter as said screws, said
and after the screws 3! and 32 are loosened, the
plate and said screws cooperating to clamp said
blade of a screw-driver may be inserted in the
slots 45 and 43 and the screw-driver operated as
bracket to said arm, a reed-type contact sup
a lever to move the bracket 39, the wall of the 30 ported at one end on the free end of said bracket,
slot 45 being used as a fulcrum point in the oper
and said bracket and said plate, each, having a
ation of the screw-driver.
slot formed therein and into which the blade of
In Fig. 4 the bracket 30 has been moved longi
a screw-driver may be inserted to longitudinally
tudinally to the left from the position shown in
move said bracket when said screws are loosened.
Fig. 3 to make the bracket 3i) extend a greater 35
3. In a variable electrical resistance device, in
distance from the arm 29. To move the bracket
which the resistance element is a resistance wire
30 slightly back from this position very precise
wound in a plurality of turns, a wiper contact,
movement may be accomplished by simply plac
means to cause relative movement of said resist
ing the screw-driver blade in the slot 45 and
ance element and said wiper contact, said wiper
driving the blade end down against one side of 40 contact being operable to selectively engage the
the beveled portion 44. In Fig. 5 the bracket 30
turns of said resistance wire and comprising, in
has been moved longitudinally to the right of the
combination, an arm having a free end extending
positions shown in Figs. 3 and 4 and presumably
in the vicinity of said resistance element, screws
mounted in spaced relation on the free end of
by means of a screw-driver. This movement is,
in effect, the same as shortening the bracket 33. 45 said arm, a bracket mounted at one end on and
After the required longitudinal adjustment of the
extending angularly of the free end of said arm,
said bracket having apertures formed therein to
bracket 39 has been made to bring the contact
piece 23 to a required position on a predeter
receive said screws and of larger diameter than
mined turn of the resistance wire on the card
said screws, a plate apertured to accommodate
like support l2, the screws 3| and 32 are tight 50 said screws and cooperating with said screws to
ened to press the plate 33 against the bracket 30
clamp said bracket to said arm, a slot formed
and thus clamp the bracket 39 in the required
in said plate, a second slot formed in said bracket,
said slots being normally in registry with each
position on the arm 29.
other and providing apertures through which a
It will be seen from the foregoing description
and the drawings that we have provided a wiper 55 tool may be inserted to longitudinally move said
bracket to change the distance said bracket ex
contact suitable for use in a precision potenti
tends from said arm, a fork of conducting mate
ometer, the wiper contact may be made to have
rial having its closed end mounted on said
a predetermined natural frequency of vibration
bracket, means to mount said fork on said
to meet certain requirements, the wiper contact
will not skip or bounce over turns of a Wire 60 bracket, tines on said fork extending backwardly
along and in spaced relation with said bracket
wound resistance element when the potentiom
and a bar of contact material bridged across and
eter is operated, and the structure and arrange~
secured to said tines and arranged to friction
ment of the parts permit increasing or decreas
ally engage the turns of resistance wire on said
ing the contact pressure, adjustment of the am- 65 resistance element.
plitude of vibration of the wiper contact and
JOSEPH T. BUT'I'ERFIELD.
adjustment of the position of a contact piece
HARRY M. KNAPP.
embodied in the wiper contact to required posi
BENJAMIN F. RUNYON.
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