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Патент USA US3028581

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April 3, 1962
G. J. MUCHER
3,028,571
MULTITURN POTENTIOMETER
Filed Sept. 28, 1960
2 Sheets-Sheet l
GEORGE
BY
Km!
INVENTOR.
J. MU CHER
April 3, 1952
G. J. MUCHER
3,028,571
MULTITURN POTENTIOMETER
Filed Sept. 28, 1960
2 Sheets-Sheet 2
as
34
3e‘
35'
29
3|
42
32
4|
4o
.
39
36
38
37
30
FIG. 3 .
l7'
l8'
l9‘
u‘
l6‘
F I G. 4 .
GEORGE
INVENTOR.
J. MUCHER
BY
KM
United States Patent'Q
"ice
3,028,571
Patented Apr. 3, ‘1962
2
1
viewed in the direction of the arrow designated with the
3,028,571
numeral 2;
MULTITURN POTENTIOMETER
George J. Mucher, Rochester, N.H., assignor to Clarostat
3-—3 in the direction of the arrows as indicated in PEG.
1. showing in cross-section the contact driver, contact car
rier, and ‘contact arm utilized in the potentiometer; and
lgf’lfglk Co., Inc, Dover, N.H., a corporation of New
Filed Sept. 28, 1960, Ser. No. 59,080
or
'
FIG. 3 is a partially sectional view taken along the line
>
FIG. 4- is a circuit diagram of one possible winding cir
10 Claims. (or. 338-143)
cuit arrangement.
’
I
In FIG. 1 a molded cylindrical casing 10 is shown hav
This invention relates generally to an electrical con
trol device and more particularly to a variable resistance 10 ing a resistance Wire in the form of a helix 11 embedded
in the internal surface thereof. The axis of the helix and
multiturn potentiometer whose value is determined by the
the axis of the casing are identical. As seen also in
longitudinal position of a contact arm which is adjusted
FIG. 2, casing 10 is formed with a helical groove 12
by rotation of a shaft.
on its internal surface so that each turn of resistance wire
Multiturn potentiometers generally consist of a resist
ance wire wound in the form of a helix and a contact arm 15 11 is separated from adjacent turns by a portion of helical
groove 12 which extends throughout the effective length
which moves along the longitudinal axis of the helix to .
of casing 10 as does wire 11.
traverse the various turns thereof in order to alter the
It should be noted that because of the precise manner
value of the resistance. -The most common method of
in which the casing 10, helically formed wire 11, and
moving the contact arm 'is through use of a rotatable
shaft mechanically connected with the contact arm so 20 groove 12 are combined with respect to one another the
ment of the contact arm. Such an assembly is utilized in
central axis for each of these elements is identical with
the central axis for the remainder of the elements. In
equipment wherein high accuracies are sought and the
other words, the longitudinal axis of the casing Iii’, grooves
movement of the contact arm must be accomplished in
12 and coil 11 is identical.
In its preferred form the casing 10‘ is molded. from a
that rotation of theyshaft will effect longitudinal move
such a manner that little or no electrical error results 25
from the mechanical construction of the device. The
rotation of the shaft in assemblies of this type is usually
plastic material, however, any suitable non-conducting ma
terial can be used for this purpose. In its preferred form,
vthe external surface of casing 10 is formed with longi
accomplished by a servo motor‘ and because of the ac
tudinal slots 13 and through openings 14 in order to aid
curacies involved it is theoretically desirable to have the
extreme of rotation of the servo motor coincident with 30 in assembling certain portions of the device and in order
to aid in placing external casing 15 over casing 10 when
the extreme movement of the contact arm'in both direc
the assembly has been completed.
tions. This, of course, is impossible in a practical physical
External casing 15 is shown in FIG. 1 and in the ?nal
embodiment and one of the main sources of difficulty in
‘assembly the casing 10 lies within casing 15 and concen
the utilization of multiturn potentiometers results from
tric therewith. Openings 14 are used to aid in the assem- .
the requirement that if the movement of the shaft and
bly and to allow leads to be brought‘ from within casing
the movement of the contact arm are not precisely syn
.10 to posts 16, 17, 18 and 19 of terminal block 20 which
chronized, the potentiometer is in serious danger of being
is rigidly fastened to the external surface of casing 15‘.
damaged. To this end various methods have been used
Openings21 in casing 10 and 22 in casing 15‘ are utilized
and constructions made to effect a stopping of they con
to maintain the two casings rigidly together in the ?nal
tact arm at its extreme position without damaging the as
assembly steps.
I
sembly even if the shaft is further rotated.
One end of casing 15 is closed and a bearing member 23
The invention herein disclosed has as its principal ob
is embedded in the internal surface thereof and designed
ject the furnishing of a new multiturn potentiometer of
to receive corresponding bearing member 23’ which is
such construction that it can resist a high degree of turn
‘ ing torque applied to its shaft without damaging the 45 fashioned at one end of shaft 24 which is the axis of
the driver member indicated generally by the numeral 25
structure even though the contact arm has reached an
in the ?gures. As shown in the ?gures, the combination
extreme position.
of bearing members 23 and 23’ form a sleeve bearing sup
Another object of this invention is to provide a multi
porting one end of shaft 24 which is preferably steel but
turn potentiometer of rugged construction which suffers
vary little backlash and which will not alter its electrical 50 which could be formed from any suitable material. Al
though a sleeve bearing assembly is illustrated in the
characteristics because of dirt forming in the track in
?gures, other types of bearings can be utilized.
which the contact carrier moves.
Circular cover 26 is formed with a portion 27 of ex
A further object of this invention is to provide a multi
ternal diameter so that it can be received within casing
turn potentiometer whose movable parts are light in mass,
one thatrequires low torque to move the contact arm, 55 or housing 15 and maintained therein by utilization of
openingsv 21, 22and 23. The cover 26 is formed also
and one that exhibits superior vibration characteristics.
from any suitablematerial which is a non-conducting ma
The invention disclosed herein is described in. terms of ,
712a potentiometer by way of example only and it should be
terial. 'In the preferred form, control housing 15 and
cover 26 are moldedv from diallyl phthalate. The cover
understood that the inventive concept set forth herein
can be applied by one reasonably skilled in the art to 60 or liner 10 as set forth above is also molded from a
non-conducting material. In its preferred form the ma
other variable parameter components whose value is
terial of which liner '10 is molded is epoxy resin, how
altered by moving a contact arm by rotation of a shaft.
ever, any suitable material can be used for this purpose.
A multiturn potentiometer embodying the invention
Bearing member 28 is set in cover 26 to receive corre
' and the manner of using the same is described herein with
sponding bearing member‘28', in order to support the
references to the drawings in which:
remaining end of shaft 24. Shaft 24 forms the axis for
FIG. 1 is an exploded top perspective view of a multi
the driver member 25 whose major or body portion 29 is
turn potentiometer constructed in accordance with the
molded from diallyl phthalate to give it an irregular cross
teachings of this invention with portions thereof broken
section with radially projecting portions 3-0, 31 and 32.
away to disclose detailed views of portions thereof;
FIG. 2 is a segmentary view of a portion of the casing
.and winding of the potentiometer shown in FIG. 1 as
70 Body 29 extends longitudinally between bearing members
23' and 2-8’ and the length of body 29 is substantially the
same as the length of liner 10. '
I
'
3,028,571
3
.
vBody 29 which is-originally attached to shaft 24 con
tains longitudinal slot 33 extending throughout its length.
Longitudinal slot 33 is formed to receive metallic ‘U
channel 34 which in turn forms the track for sliding stop
35.
Channel 34 is U-shaped in cross-section forming a
substantially rectangular track in which sliding stop 35
is maintained against rotational movement but free to
move longitudinally.
.
Light weight disk 36 with a section removed from the
d
sert or channel 34' carries the contact and also the stop
and resists turning at the ends. The light mass contact
assembly gives superior vibration characteristics and the
disk 36 is slightly loaded in the helical groove and
twisted in order to increase the vibration resistant ability
of the resultant assembly. The one point drive resulting
in the substantially glove '?t of radial member 30‘ within
opening 37 provided therefor results in :an excellent drive
with very little backlash. The placing of the spring con
central portion thereof corresponding generally to the 10 tact near the drive point maintains the necessary portion
outline of driver member 25 so that it can receive the
of the disk in the groove in the proper place giving maxi:
same therein, is utilized as a contact carrier.
As seen
best in FIG. 3 contact carrier 36 is formed to receive the
cross-sectional con?guration of driver body 29 ‘and to
mum drive force. The helical groove in which the .con
tact carrier 36 travels is displaced from the coil 11 itself
and as a result the formation of dust or dirt of any kind
receive radial projecting portion'iitl‘ thereof within cut 15 within the groove 12 cannot affect the electrical charac
out section 37 of carrier member 36. Carrier member
teristics of the device. Additionally, the concentricity of
36 is disk-like and has a depth substantially equal to the
the major components of the device results in a highly.
width of helically grooved channel 12 of the liner 10'.
accurate assembly.
>
Carrier member 36 is formed of a light weight material,
Thus, among others, the several objects in the invention
preferably a plastic, which is non-conducting. An edge 20 as speci?cally aforenoted, are achieved. Obviously, nu~
thereof at section 36’ is received within slot 35' of mov
merous changes in construction and rearrangement of
ing stop 35. The moving stop is preferably metallic and
parts might be resorted to without departing from the
‘the slot 35 formed therein is preferably of su?icient width
spirit of the invention as de?ned by the claims.
i claim:
.
that section 36' of the carrier member 36 is maintained
therein relatively snugly. ‘Resilient contact arm 38 is 25
1. A multi-turn potentiometer including in combination‘
‘fastened at one end 39 by means of bracket 40 and eye
a cylindrical hollow casing, a helical groove formed on
lets {i-l to contact carrier 36 and electrical lead 42 is
‘electrically in contact with contact member 38.
Contact 38 is designed to engage coil 11 when sector
3'6’ of contact carrier 36 is engaged in slot 35' of moving
stop 35 and groove 12 of liner it). Further, contact 33
the inner surface of said casing, a resistance wire consist
ing of a plurality of continuous turns ‘in the form of a
. is positioned on contact carrier 36 so that the resiliency
‘with its axis of rotation concentric with the vaxis of said
groove and said wire, a longitudinal slot formed in said
driver member, a contact carrier, a portion of said con
of arm 38 will yieldingly urge’ sector 36’ Within groove
12. In order to accomplish this, the point whereat con
helix disposed in the cylindrical plane of said ‘casing with
turns thereof separated by portions of said ‘helical groove,
a driver member rotatably supported within said casing ‘
tact 38 will engage resistance wire‘lll is displaced from 35 tact carrier having the Width of said groove and disposed
therein, a second portion of said contact carrier disposed
With such con?guration when the driver ‘member 25 ' within said slot, means preventing relative rotational
sector 36? which is to be urged'thereby'within groove 12.
i isdisposed with its ends supported in the appropriate bear
movement of said contact carrier and said driver mem
ber, a contact arm rigidly supported by said contact car
of a rotational forcev to contact carrier 36 through the 40 rier and in engagement with one turn of said cell, and
radially projecting portion 30? of driver 25. This force
conducting means forming an electrical circuit with said
ings, rotation of shaft 24 will result in the transmission
will tend to turn contact carrier 36 and move it with ‘
‘contact arm and said coil.
groove 12 serving as a track therefor so that contact 38
will traverse wire 11 and such traverse can be accom
.2. A multiturn potentiometer in accordance with claim ’
1 in which the contact carrier is a lightweight electrically
'
plished throughout the length of wire 11.
non-conductive disc section and the contact arm is a
Fixed stops 43 and 4-4 are provided at either end of
channel 34 in the completed assembly. These stops are
resilient electrical conductor rigidly fastened at one end
preferably metallic and have surfaces facing channel 34
‘coil adjacent the portion of the helical groove ‘in which
so that at either of the extreme positions of contact car
the contact carrier is disposed.
to a surface of the contact carrier so that it engages the
'
rier 36 movable stop member 35 will abut stop 43 or 44 50
3. A multiturn potentiometer in accordance with claim
to prevent further movement of the contact carrier 36
1 in which the ‘casing is formed with one surface at each
longitudinally. Stop 43 is rigidly fastened by any suit
end against which the contact carrier can abut upon reach
ing the ‘extremity of ‘travel in that direction.
able means to the bottom of housing 15 in the general
vicinity of bearing 23. vStop 44 is rigidly fastened to
7 4. A multiturn potentiometer in accordance with claim
cover 26 by'any suitable manner in the vicinity of bear 55 2 in which the portion of the contact carrier within the
ing member v28.
.
helical groove is displaced from the contact arm whereby
Electrically the circuit of the potentiometer shown and
it is yieldingly urged thereby within saidhelical groove.
5-. A 'multiturn potentiometer in accordance with claim
described herein is diagrammatically illustrated'in FIG.
4 in which the contact carrier is formed with a radial
4. In FIG. 4 the variousv points of interest are given
numbers corresponding to the numbers given the posts. on 60 .slot and the driver member is formed‘ with a radial‘pro
.jection disposed within said radial slot ‘in substantiallya '
terminal board 20 in FIG. '1. In FIG.‘ 4, however, in
glove ?t by which turning moments applied to the driver
order to avoid error, the corresponding numbers are set
member can be imparted to the contact carrier.
6. A multiturn potentiometer including in combination .
of wire 11. Physically, post 16 is electrically connected 65 a cylindrical hollow casing, a helical groove formed on
the inner surface of said casing, .a resistance wire con?
, to collector arm 45’ shown in FIG. lvwhich is designed to
forth as prime numbers and as tap points on resistance
11' which is a diagrammaticindication of the resistance
engage collector 46 which is electrically connected with
sisting of 'a plurality of continuous turns in the form of
.arm 38. For this purpose wire 42 is utilized and cutout
a helix concentric with said helical groove with turns
portion 4'7 ofv body 29?. Post 17 is connected electrically
thereof vseparated by ‘portions of said helical groove, a
to one end of wire 11 and post‘19 is connected to the re 70 driver member rotatably supported within said casing
vmaining end. Post 18 is an optional terminal which can
be utilized if desired.
‘With such a device ‘many advantages result. The de
' vice is low in backlash and there is very little relative ro
with its axis of rotation concentric with the axis of said
groove and said wire, a longitudinal slot formed in said
driver member, a light weight electrically non-conducting
contact carrier, a sliding stop slidably disposed in .said
tational motion between the various parts. The metal in 75 slot, a recess in said sliding stop, a section of said con
3,028,571
5
6
tact carrier having a portion within said recess and a
resistance wire from adjacent turns, a driver member
rotatably supported with its axis of rotation concentric
with the axis of said casing, a contact member mounted
portion in said helical groove, means preventing relative
rotational movement of said contact carrier and
driver member, a contact arm rigidly supported by
contact carrier and in engagement with said coil,
conducting means forming an electrical circuit with
contact arm; and ‘said coil.
I,
V V
said
said
and
said
.
on said driver member so that it is longitudinally movable
relative thereto and maintained against rotational move
ment relative thereto, a longitudinal ‘groove formed in
. said driver member, a section of said contact member
movably disposed in said longitudinal groove, and Ya
7. A multiturn potentiometer in accordance with claim
6 in which the casing is formed with one surface at each
portion of said contact member disposed withinv said
end against which the sliding stop can abut upon reaching 10 helical groove whereby rotation of said driver member
the extremity of travel in that direction.
can cause said contact member to move longitudinally
and traverse the turns of said resistance wire.
8. In a mnltiturn potentiometer a cylindrical hollow
casing, a resistance wire consisting of a plurality of con
10. In a multiturn potentiometer, a cylindrical hollow
casing, a resistance wire consisting of a plurality of con
said casing, a helical groove formed in said casing 15 tinuous turns in the form of a helix concentric with said
throughout its e?ective length, a driver member rotatably
casing, a helical groove formed in said casing throughout
its effective length and separating each turn of said re
supported within said casing and said wire with its axis
sistauce wire from adjacent turns, a driver member ro
of rotation concentric with the axis of said casing, a
tinuous turns in the form of a helix concentric with
tatably supported with its axis of rotation concentric
contact member mounted on said driver member so that
it is longitudinally movable relative thereto and main 20 with the axis of said casing, a contact member, an irregu
tained against rotational movement relative thereto and a
lar slot formed in said contact member, said driver mem
her being formed to be received in said irregular slot so
portion of said contact member disposed within said heli
cal ‘groove whereby rotation of said driver member can
that said contact member is longitudinally movable rela
cause said contact member to move longitudinally and
tive thereto and maintained against rotational movement
traverse the turns of said resistance wire, said contact 25 relative thereto and a portion of said contact member
' member being formed ‘with an irregular slot therein and
disposed within said helical groove whereby rotation of
said driver member is formed to be received in said slot,
said driver member can cause said contact member to
and a longitudinal groove is formed in said driver mem
ber and said contact member is formed with a section
move longitudinally and traverse the turns of said re
sistance wire.
thereof to be movably disposed in said longitudinal 30
groove.
'
I
9. In a multiturn potentiometer, a cylindrical hollow
casing, a resistance wire consisting of a plurality of con
tinuous turns in the form of a helix concentric with
said casing, a helical groove formed in said casing through
out its e?ective length and separating each turn of said
References Cited in the ?le of this patent
UNITED STATES PATENTS
Beckman ____________ __ Nov. 30,
2, 45 4, 9 8 6
2,813,956
1948
Sorber ______________ __ Nov. 19, 1957
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