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Патент USA US3058090

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Oct. 9, 1962
Filed Feb. 20. 1961
United States Patent O ”
Patented Oct. 9, 1962
is fitted with end plates l2, 13. End plate 12 carries
three terminals 14, 15, 16. Terminals 14 and 15 are
Clarence R. Laubeniels, 333 Scholl Drive,
coil terminals, and terminal 16 is a brush terminal. In
Glendale, Calif.
Filed Feb. 20, 1961, Ser. No. 90,462
sulating inserts 17, 18, 19 are fitted in holes in the end
plate to pass the terminal leads and insulate them from
8 Claims. (Cl. 3138-143)
the end plate.
A splined shaft 20l is journaled in the two end plates.
This invention relates to a potentiometer.
made in three sections: Spline section 2.1 with splines
An object of this invention is to provide a structure and
extending parallel to the axis 24 of the device,
means for assembling the structure whereby a device is 10
connecting pin section 25, and drive section Z6. The
produced whose performance equals or exceeds that of
»expensive precision potentiometers, at a cost comparable
spline section and drive section are made of metal to
resist Wear. Also, the spline section should be electrically
conductive. The connecting pin is made of insulation ma
to insulate the splined section from the outside
potentiometer without backlash, with low hysteresis, good 15 terial
potentiometer except through terminal 16. An in
repeatability, high resolution, and high linearity. In at
spacer 27 is placed between the spline section
tempting to attain »these objectives, precision potentiom
and «the drive section. It bears against right-hand end
eters become very expensive, and their designs impose
plate 13.
to that of ordinary potentiometers.
A related object of the invention is to provide a rotary
undesirable limitations on the device produced. For ex
A rotor 30 (FIG. 3) comprises a disc having an exterior
ample, in a potentiometer a relatively high resistance is 20
thread 31 which extends peripherally around the rotor,
desirable, but there is an inherent limitation imposed by
except for a cut-out portion 32. The thread thus extends
the way conventional precision potentiometers have been
the major portion of the periphery, and, with
built and assembled. The usual ten-turn precision po
minor modifications could extend around lthe full periph
tentiometer in a 7/s inch diameter size ordinarily has a
ery. A brush 33 has one end attached to the cut-out por
maximum standard resistance of about 125,000 ohms, 25 tion
of the rotor. Its -free end 34 rides the interior surface
and this is about as great as can be attained. To illus
.trate the advantages of the instant invention, a 7% inch
»diameter precision potentiometer made according to it
can be produced with a maximum resistance of 300,000
of a winding 35. A Whisker 36 makes electrical contact
with brush 33 and bears against the splined shaft.
A second Whisker 37 rides the left-hand end of the
shaft and constitutes a portion of terminal 16.
It will
ohms. As to the other characteristics above mentioned, 30 now be seen that when the shaft is turned, the rotor will
`it provides approximately twice .the performance of pre
turn, carrying with it brush 33, an electrical connection
viously known, commercially available precisie-n poten
thereby being made between the Winding and terminal
16. Note that only the litee end of the brush rides the
A potentiometer according to this invention comprises
a frame having a bore yformed by an interior wal-l, the 35 winding. The rotor is supported and guided by the case,
and not the winding. Any lost motion of the brush and
bore having a central axis. A helical groove is formed
in this wall, the helical groove forming a means for re
ceiving a helical winding, and also forming a helical track
between adjacent convulutions of the groove for a rotor
to ride on.
The rotor has an exterior thread by which it is engaged
to the helical track. Preferably the rotor makes an in
terference fit With the track, and this is possible when
10W-friction materials are used, thereby eliminating play
any appreciable wear on the winding are eliminated.
The case encloses a frame 40 which is made of two
frame sections 4l, 4Z, each of which includes a concavely
formed section 43, 44, respectively. Neither of the sec
40 tions rforms more than 180° of the interior wall of the
bore which is formed by assembling them together. Each
of the frame sections includes a fragment 45, 46 of a
continuous groove, which when the case sections are as
sembled together, `form a continuous helical groove. Be
in the rotor. The rotor has a central non-circular open 45
»tween the groove sections, there are formed track sections
ing which receives a shaft. The shaft is also non-circular,
47, 48, which when assembled `form a continuous helical
track to which the thread 3l of the rotor is engaged. The
extreme edges of the cut-out portion are slanted to elimi
The rotor carries a brush which moves along the wind
abrupt shoulders adajacent to the thread which might
ing as the rotor is turned and advanced along the helical 50 interfere
with rotation when the edges encounter the split
edges of the frame.
According to a prefer-red but optional feature of the
FIG. 4 shows a frame embodiment which can be used
invention, the frame is expansible, such as by being slit,
in place of frame 40. Frame 60 comprises a piece of
enabling the edges of the slit to be pried apart, or by pro
viding it in a plurality of iframe sections which can be 55 tubing 61 with an internal helical groove 62 and helical
track 63. An axial slit 64 is formed without removal
assembled together. This enables the frame to be as
of material. The material of the frame is sufficiently
sembled around the winding, so that the winding is placed
flexible that the slit can be pried open.
in the groove in its relaxed condition without any distor
When the winding is placed in either embodiment of
so that the shaft and rotor are in a torque-transmitting,
but axially slidable relationship to each other.
tion along its length.
The above and other `features of this invention will be 60 the frame, and the frame is put in the casing, the helical
track is continuous, and preferably the rotor makes an
yinterference fit with it. Ordinarily this would make for
and the accompanying drawings in which:
too great a drag, but this is avoided by making the rotor
FIG. l is a cross-section of »the presently preferred em
of a low-friction material, such as Teflon. This totally
bodirnent of lthe invention;
eliminates play between the rotor and the track, and cor
fully understood from the following detailed description
FIG. 2 is a left-hand end view of FIG. l;
FIG. 3 is a cross-section taken at line 3-3 of FIG. l;
FIG. 4 is a cross-section of an alternate embodiment
of frame for use in the invention.
rects one of the greatest deficiencies in conventional po
tentiometers: play in the system between the shaft, brush
and winding.
The preferred embodiment of shaft is a splined one.
The term “splined” is not intended to be restrictive to
A potentiometer 10 according to the invention is shown 70 mean a circular shaft having axial, rectangular flanges.
in FIG. l. It is assembled within an exterior cylindrical
It comprehends all generally prismatic shapes, which
case 11 (which may be »tubular as shown). The case
might be such as triangular, square, or polygonal. The
shaft shown does, however, have significant advantages.
The circular portion `of the shaft is smaller than the cir
cular portion of the rotor opening, and the two splines
are defined by -a pair of parallel planes. Also, the splines
are shorter than the corresponding part of the rotor open
ing. The shaft is thereby rendered self-aligning. ln
addition, the driving faces make an interference fit, so
economies, because the spoilage rates in previous pre
cision potentiometers have been quite high due to the dis
torted Iforces which had to be exerted on the helix when
the device was put together.
This invention thereby provides a simple device capable
of Ibeing readily and inexpensively assembled, and which
provides exceptional performance in a potentiometer
which costs no more than conventional potentiometers.
that there is no lost rotational motionbetween shaft and
This invention is not to be limited by the embodiment
rotor. This tight lit is tolerable because the area of con
tact is small, and low-friction material is used. Thus 10 shown in the drawings and description which is given by
way rof example and not of limitation, but only in ac
there is no substantial frictional drag against axial move
cordance with the scope of the appended claims.
ment of the rotor along the shaft.
I claim:
While the invention is useful for many types of po
l. A potentiometer comprising: a plurality of frame
tentiometers, its principal use is in connection with pre
sections, each having a concavely for-med section; a trag
cision potentiometers. The device shown is a ten-turn
ment of a continuous helical groove in each trame sec
device (7/s” O.D.) which can be made with va total re
tion, said groove forming a fragment of a continuous
sistance as high as 300,000 ohms, which is much higher
helical track, said frame sections being assembled to form
than attai-nable with conventional potentiometers. A
a cylindrical bore, each section forming no more than
winding suitable for use with it is conveniently formed by
taking an initially straight piece of insulated wire 49 20 180° of the interior wall of said bore and «forming a
continuous interior helical groove and track, all having
:and Wrapping a coil 50 of resistance wire around it and
a common central axis; a helical winding Seated within
then forming the coil-wound wire 49 into a helix. Then
the groove between adjacent convolutions of the track;
to assemble the device of FIG. 1, this helix in its relaxed
a rotatable splined shaft in said bore on the central axis;
condition is first lowered into one of the frame sections.
Then the other yframe section is placed over it, few drops 25 a rotor having a splined central opening and an exterior
thread, the splined opening making a driving connection
of cement placed between the two frame sections, if de
sired. Then the case is slid over the assembled case sec~
with the splined shaft, and the thread riding the helical
track; and a contact carried by the rotor riding the wind
tions »to hold them together. The rotor, shaft, and end
ing, whereby driving the shaft 1rotates .the rotor to ad
plates are put in position, the internal electrical connec
tions are made, and the potentiometer is ready for use. 30 vance it along the track, -and with it, to advance the
contact along the winding, the rotor making no contact
When the frame of FIG. 4 is used, the slit is pried open
with the winding.
to admit the winding.
2. A potentiometer according to claim l in which each
The advantages of the aforesaid technique of assembly
end of the cylindrical bore is closed by an end plate,
and the construction described which makes it possible will
be best appreciated by comparison with previously used 35 the splined shaft' being journaled in the plates.
3. A potentiometer according to claim 2 in which the
methods of assembling conventional precision potentiom
eters. In the past, the frame was internally grooved, and
the wire-wound resistance element in helix form was
screwed into the frame. This, of course, caused distor
tion during the insertion, resulting in errors of linearity. 40
As can easily be understood, more end Aforce must be
exerted on the helix to get it in the last turn than at the
ñrst turn which results in uneven `forces exerted over the
`splined shaft is made of three sections: a splined section
bearing the splines; a drive section outside the bore;
and a connecting pin section made of insulating material
joining the pin section to the drive section.
4. A potentiometer comprising: a plurality of frame
sections, each having a concavely-formed section; a frag
nient of a continuous helical groove in each frame section,
said groove forming a fragment of a continuous helical
length of it so that the helix is not loaded down uniform
ly over its whole length in the groove. In addition, the 45 track, said frame sections being assembled to» form a cyl
indrical bore, each section Áforming no more than 180°
previously known methods of rotating the contact have
of the interior wall of said bore and forming a continuous
required considerable clearance between the parts, re
interior helical groove and track, all having a common
sulting in back lash which shows up as a hysteresis error
central axis; 4an exterior case surrounding and embracing
and results in non~repeating readings. All of this is
avoided by means of either of the construction shown, 50 the frame sections to hold them assembled; a pair of end
plates, one at each end of the cylindrical bore; a helical
whereby in FIG. l, a completely relaxed winding is placed
winding seated within the groove between adjacent con
between frame sections, and the frame sections are then
ñxed together, or in FIG. 4, where the frame is opened
to admit a relaxed winding. With either technique, there
are no» end `forces at all'exerted on the helix so that the
helix condition is unifonm from end to end, thereby over
coming the aforesaid problems. In addition, there are
volutions of the track; ya rotatable splined sha-ft in said
bore on the central axis and journaled in the two end
plates; a rotor having a splined central opening and an
exterior thread, the splined opening making a driving
connection ywith the splined shaft, and the thread riding
the helical track; and a contact carried by the rotor rid
ing the winding, whereby the shaft rotates the rotor to
As to the accuracy of the contact mounting, it will be
advance it along the track, and with it, to advance the
contact along the winding, the rotor making no contact
seen that in FIG. l the rotor rides a continuous helical
thread and because it overlaps more than 180° of the
with the Winding.
5. A potentiometer according to claim 4 in which the
periphery, keeps the case sections in proper alignment.
In FIG. 4, the material‘springs back to alignment. Fur
rotor has a cut-out portion for the Contact, said cut-out
thermore, when the low `friction material, such as Teilon, 65 portion having slanted edges adjacent the thread to elimi
nate «sharp shoulders which might interfere with rota
is used, the fit between the rotor and the track can be
tion by engaging the edges of the frame.
an interference lit so that there is no tolerance or spacing
no problems of clearance as to getting .the helix in be
canse the lit in this device can be an exact one.
of any kind which would permit random motion of the
contact. Thus, the device shown is totally Without as
6. A potentiometer laccording to claim 4 in which the
exterior thread on the rotor extends substantially around
sembly errors and without errors which would result'
the full perimeter of the rotor.
from the necessity of providing clearances throughout 70 7. A potentiometer according to claim 4 in which the
the device. This is the reason i hat this invention provides
a precision potentiometer whose performance-character
istics are at least twice as good as any of those known
end plates and in which arthir-d terminal is connected to
a brush which rides the splined shaft and in which the
contact is electrically connected to the splined shaft, the
This also results in
in the prior art, and it will be seen thatthe assembly
technique is very much simpler.
winding has a pair of terminals mounted to one of the
splined shaft' being made of conductive material whereby
said third terminal 'acts as a brush connection to the po
References Cited in the lilc of this patent
tentiometer winding.
8. A potentiometer according to claim 4 in which the
rotor is made of material having a low coeñ’icient of
friction, and the rotor makes an interference lit with the
helical track.
Lock ________________ __ Dec, 3, 1957
MacLaren ___________ __ Sept. 2, 1958
Gach et al ____________ __ Aug. 18, 1959
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