US3614703A

US3614703A - Miniature potentiometer with friction wheel drive

Info

Publication number: US3614703A
Application number: US24689A
Authority: US
Inventors: Ronald L Froebe
Original assignee: Bourns Inc
Current assignee: Bourns Inc
Priority date: 1970-04-01
Filing date: 1970-04-01
Publication date: 1971-10-19
Anticipated expiration: 1988-10-19

Abstract

A miniature rotary potentiometer having an arcuate resistance element and a rotary contact movable through less than one complete turn or revolution in brushing over the active extent of the resistance element. The rotary contact is mounted upon a rotatable carrier which also carries the pivots of a plurality of friction planet wheels the peripheries of which frictionally engage and travel along a circular path on the inner wall of the potentiometer housing and which peripheries are frictionally engaged by and driven by a small rotary spindle or hub carried by a tool-rotatable actuator disposed in the top or upper end of the potentiometer. Rotation of the actuator frictionally rotates the friction planet wheels which through their pivots drive the carrier at reduced rotary speed relative to the actuator, whereby the actuator must be rotated several complete revolutions to drive the contact along the extent of the resistance element.

Description

D United States Patent 13,614,703

[72] Inventor Ronald L. Froebe 3,469,225 9/1969 Wood 338/163 21 1 pp No. git zg i Primary Examiner-Laramie E. Askin Assistant Examiner-Gerald P. Tolin [22] Filed Apr. 1,1970 F B P t 451 Patented Oct. 19,1971 e [73] Assignee Bourns, Inc.

ABSTRACT: A miniature rotary potentiometer having an arcuate resistance element and a rotary contact movable [54] MINIATURE POTENTIOMETER WITH FRICTION through less than one complete turn or revolution in brushing WHEEL DRIVE over the active extent of the resistance element. The rotary 7 Claims, 8 Drawing Figs contact lS mounted upon a rotatable carrier which also carries the pivots of a plurality of friction planet wheels the periphe- [52] US. Cl 338/174, ries of which f i i ll engage and travel along a circular 338/163 path on the inner wall of the potentiometer housing and which [51] Int. Cl H0lc 9/02 peripheries are frictionany engaged by and driven by a Small [50] Field Of Search ..338/l62l64, :otary spindle hub carried by a too| rotatab1e actuator 174 disposed in the top or upper end of the potentiometer. Rota- References Cited tion of the actuator frictionally rotates the friction planet wheels which through their pivots drive the carrier at reduced UNITED STATES PATENTS rotary speed relative to the actuator, whereby the actuator 3,355,693 I 1/1967 Van Benthuysen 338/164 X must be rotated several complete revolutions to drive the con- 3,388.365 6/1968 Wood 338/162 tact along the extent of the resistance element.

MINIATURE POTENTIOMETER WI'I'II FRICTION WHEEL DRIVE BRIEF SUMMARY OF THE INVENTION a. The environment of the invention and the prior art.

In prior art potentiometric instruments of the type popularly called single-tum adjustment or trimming potentiometers and which are characterized by an arcuate resistance element of slightly less than 360 angular extent, a shaft or rotor is generally employed to carry a movable potential-adjusting contacting in an arcuate brushing or wiping path along the surface of the resistance element. Stop means are commonly provided for restricting movement of the contact off either end of the element. In the case of such potentiometers in the largesize range (of the order of 1 inch diameter and larger), a shaft is provided on which a manually rotatable knob is secured, thus increasing the leverage that may be exerted in adjusting the contact and the precision with which adjustment may be made. In the case of medium-size potentiometers of the noted type (of the order of 55 inch to 1 inch diameter), a contactcarrying rotor is generally employed, which rotor has an end protruding from, or at least accessible from, the exterior or housing of the potentiometer, the rotor having a slotted end for reception of a tool such as a screwdriver that is manually rotated to eflect potential-adjusting movement of the contact along the resistance element. That means of adjusting such medium-size adjustment potentiometers in many instances leaves something to be desired as to fineness or accuracy of adjustment easily accomplished; and as a consequence, it has been previously proposed to interpose reduction gearing between the manually rotatable rotor and a member carrying the rotary contact, whereby several turns or revolutions of the screwdriver and rotor are required to traverse the contact along its arcuate path of less than 360". Such speedreducing" gear means have been found to be feasible, mechanically if not economically, in the larger models of medium-size single-tum adjustment potentiometers; but have been found to be impractical in small-size potentiometers (less than 9% inch maximum dimension) because of lack of space for operable gears, weakness of gear teeth and gear spindles of the small sizes required, and allied reasons, such as excessive cost. It may be noted that the contact must be rotatable through all of its prescribed path and from any position therealong to either end of the path as defined by stop means, but is generally prohibited from being moved beyond either end by the stop means. Thus gearing interposed between the manually driven actuator and the contact carrier, although capable of transmitting the required torque without damage other than normal wear, must survive relatively large torque overloads incident to arrest of the contact carrier by the stop means when the contact is driven to either extreme of its path and the operator continues to apply torque to the actuator. Thus such gearing, will in theory offering advantages of increasing value as the size of the potentiometer is decreased, has been found to be economically impractical in miniature single-tum rotary potentiometers.

b. the present invention.

The invention disclosed hereinafter in detail is a miniature single-tum rotary potentiometer comprising a driving mechanism which provides all of the advantages of the noted reduction-gear or speed-reducing driving means for the contact, without any of the disadvantages. The novel driving mechanism is such that several turns or revolutions of the manually operated actuator are required for rotation of the potential-adjusting contact through its entire traverse of the resistance element of somewhat less than 360 angular extent; and it is such that continued application of torque and driving rotation to the actuator after arrest of contact rotation by the stop means is permissible and does not result in any damage to the mechanism. Additionally, the expense of forming or cutting gears is avoided, and the parts are easily and inexpensively produced and assembled, whereby the potentiometer may be of very small size and is economically practical. The

reduction-gear or speed-reducing effect is attained in a simple and highly effective way by forming the contact carrier as a planet carrier with means for supporting or carrying in driving relation thereto a set of planet members of wheel form, each rotatable on its own axis on the planet carrier and each having a rim frictionally engaging a circular path on the interior wall of the potentiometer housing and each further frictionally engaging a driving stub preferably formed as an axial extension of the manually driven actuator. Whereby the forces created and involved are balanced, the planet members or wheels are preferably uniformly spaced apart relative to the circular path or track. While the set of planet members may comprise three or four wheels, a set comprising only two wheels has been found to operate with complete satisfaction. In all cases, each wheel contacts the circular path and the driving stub of the actuator. Thus rotation of the small diameter driving stub of the actuator causes rotation of the planet members about their respective axes and consequent rotational travel of the planet members along the circular path engaged by their rims. The planet members thus partake of orbital motion around the axis of the stub; and since they are supported by the rotatably supported carrier, the latter is also slowly rotated about that axis. The number of revolutions of the actuator and stub required to rotate the carrier and its contact through the full traverse of the resistance element is dependent upon the relationship between the diameters of the driving stub and the circular friction path defined on the inner wall of the potentiometer housing, and may be, for example, four revolutions. Thus precision of adjustment of the potentiometer, despite its very small dimensions, is excellent, and precise adjustment is easily accomplished. Further, when the actuator has driven the contact carrier to the point where motion of the contact is arrested, continued rotation or overdriving" of the actuator merely causes slipping of the planet member rim surfaces relative to the surface of the driving stub, without any harmful or undesired effect. Following such overdriving, reverse rotation of the actuator is immediately effective to reversely rotate or drive the carrier and the contact. In a preferred embodiment of the invention, the planet members are formed as wheels, each having an integral stub axle and pivot, and a frictional rim. The carrier is, in the preferred form of the invention, formed as a rotary plate having recesses or nests and bearings providing guides for the respective planet wheels, each recess or nest being open adjacent the outer edge of the carrier to permit the frictional rim of the associated planet wheel to engage the arcuate friction path on the inner wall of the housing. The carrier is thus a dual-function member, carrying the electrical contact on one face and the planet wheels on the opposite face. The carrier is preferably constrained to rotate about the axis of the driving stub by having a central bore or bearing in which an axle on the lower end of the driving stub rotates, and/or by being confined at its circular periphery by suitably formed portions of the inner wall of the potentiometer housing. In the embodiments herein illustrated, an extension of the driving stub forms a rotary gudgeon or axle on which the contact carrier rotates.

The preceding brief description of the invention relative to the prior art indicates that it is a primary object of the invention to provide improvements in miniature single-tum adjustment potentiometers.

It is another object of the invention to provide a miniature rotary potentiometer having a simple and economical speedreduction rotary driving mechanism.

Another object of the invention is to provide an improved driving mechanism for a miniature single-tum rotary potentiometer.

Other objects and advantages of the present invention will hereinafter be set out or made evident in the appended claims and the following description of a presently preferred physical embodiment of the invention as illustrated in the accompanying drawings.

THE DRAWINGS The presently preferred embodiments of the invention is illustrated in the accompanying drawings which are part of this description or specification and in which drawings:

FIG. I is a pictorial view, grossly enlarged, of the miniature single-tum adjustment potentiometer comprising the present invention;

FIG. 2 is a vertical cross-sectional view of the potentiometer depicted in FIG. 1, on a larger scale, showing the vertical arrangement of the rotary operating components relative to the external shell or housing of the potentiometer, the sectioning being as indicated by directors 22 in FIG. 1;

FIG. 3 is a vertical cross-sectional view of the illustrative exemplary potentiometer according to the invention and depicted in FIG. 1, the section being taken as indicated by directors 3--3 in FIG. 2, and substantially at right angles to the section of the latter figure;

FIG. 4 is a transverse sectional view, the section being taken as indicated by directors 4-4 in FIG. 2, showing the presently preferred arrangement of the actuator and driving hub, first and second planet wheels, and the circular track or path on the interior surface or wall of the potentiometer housing means;

FIG. 5 is a transverse sectional view of portions of the exemplary potentiometer, the section being taken as indicated by the directors 5-5 in FIG. 2, and showing in detail the geometrical arrangement of orientation and stop devices and showing the nature of the movable contact device;

FIG. 6 is an isometric view of the base device of the exemplary potentiometer, the base device comprising a substrate, resistive and conductive devices, and termination members in the form of wirelike pins;

FIG. 7 is a vertical section, in isometric, of the manually operable actuator of the potentiometer, and a ring seal that is employed to bar entrance of undesired foreign material into the interior of the potentiometer; and

FIG. 8 is an exploded pictorial representation of the combined planet carrier and contact carrier of the illustrated potentiometer, and the displaced planet wheels, one of the latter being shown in section.

DETAILED DESCRIPTION OF THE INVENTION In the accompanying drawings to which reference is herein made, the illustrative potentiometer (FIG. 1), according to the invention, is illustrated grossly enlarged for the wake of clarity. The potentiometer depicted is actually about 5/l6 inch diameter and about /4 inch high excluding terminal pins. Thus to adequately and clearly portray details, gross enlargement is necessary. The depicted structure and mechanical arrangement, while conforming substantially exactly to an eminently successful embodiment of the invention, is exemplary only and the nature and scope of the invention are as defined by the appended claims.

The illustrated potentiometer comprises a generally hollow cylindrical inverted cuplike housing 22, the bottom of which is open and the top of which is provided with a circular aperture 22a, as shown in FIGS. 1, 2 and 3. Rotatable in the circular aperture 220 is the upper tool-receiving stub 24a of a manually rotatable actuator 24. As shown in FIGS. 3 and 7, the actuator stub is provided with a driver-receiving depression in the form of a slot 240 for reception of a torque-applying rotary tool such as the blade of a screwdriver. The stub is of cylindrical configuration and has applied thereto an O-ring seal 26 as indicated, for example, in FIG. 7. The apertured web of the housing 22 is provided with an annular recess 22r against the walls of which recess the O-ring seal engages, as indicated in 'FIG. 3. The actuator has an annular flange 24f which rotatably bears on the inner face of the transverse web of the housing 22, and is retained in that attitude by a ringlike housing insert 28 (FIGS. 2, 3 and 5), the upper generally annular flat face of which bears in part against the lower faceof the flange. The insert 28 performs orientation functions, as will be presently explained.

Protruding or extending downwardly from the lower face of flange 24f of the actuator, and preferably formed as integral portions of the actuator, are a driving hub 24h and a rotary gudgeon 24g, both coaxial with the potentiometer axis and both of cylindrical form and arranged as indicated in FIGS. 3 and 7. The hub 24h serves as a frictional driving member presently more fully explained, and gudgeon 24g serves as a guide or pivot about the axis of which a rotatable carrier 30 is arranged for rotation. The axis about which the hub, gudgeon and stub of actuator 24 are rotatable is for convenience defined as the axis of the potentiometer.

The carrier 30 is of circular plan form, as indicated in FIG. 4, and rotates in free bearing relationship, within presently described angular stop-defined limits, inside an upper inner cylindrical wall surface 28b (FIG. 3) of the fixed housing insert 28. As indicated in FIG. 8, carrier 30 is provided with a central longitudinally ribbed or fluted bore 30b that is dimensioned for reception of gudgeon 24g of the actuator 24, and is provided with a shallow transverse recess 30r of dumbbell shape for accommodation of hub 24h of the actuator and the disc portions of a set of substantially identical frictional planet wheels 32. The relative dispositions of the carrier, hub, gudgeon and planet wheels are as indicated in FIG. 2.

As is further indicated in FIG. 8, the carrier 30 is formed or provided with a set (two, as shown) of radially extended slots 30:; centrally disposed in respective outer enlargements of the shallow recess 30r. The slots are formed and dimensioned to accommodate, with clearance for some radial movement as well as for rotation, the downwardly extending hubs or axles 32p of the planet wheels 32. The recess 30r is dimensioned, as indicated in FIGS. 2 and 4, so as to form, with the overlying flange of actuator 24, a set of interconnected cells in which the respective planet wheels are confined with capacity for easy rotation about their respective axes and for orbital motion with the rotary carrier.

In assembling the parts thus far described, the O-ring seal is fitted onto stub 24s and the actuator is lowered, topside down, into the inverted housing 22. The orienting housing insert 28 is then secured in place against an ofiset or shelf formed on the interior of housing 22, as shown, adhesive means or pressfitting or the like being preferred for retaining the insert in fixed position. The insert is formed with unequally spaced longitudinal slots such as 28n (FIG. 4) which accommodate respective complementary inwardly extending longitudinal keys such as 22k formed along the interior wall of housing 22. The unequally spaced keys serve to facilitate and insure correct orientation during assembly of the parts and proper positioning of a fixed stop means. Following installation of the insert 28, the assembly is inverted to upright position, the planet wheels are placed in position in the recess 30r of the carrier with their axles in respective ones of slots 30c and the subassembly thus formed moved into position in the housing, care being taken that projecting rotary stop 30s (FIG. 8) thereon is displaced out of line with a stationary or fixed stop 28s (FIG. 5) formed on the interior of insert 28. Thus the rims of the planet wheels are brought into compressional contact with a circular friction path conveniently provided by the previously mentioned surface 28b on the interior of the housing insert. Thereafter a base device 34, presently described, is rotationally oriented relative to the housing and is pressed into place with outer edge portions of its upper flat face abutting the lower annular face 28f (FIG. 1) of insert 28, and the base device is sealed in place with potting compound or other sealant means which in the interest of clarity of illustration has been omitted from the drawings.

The carrier 30 is a dual-purpose member or device of the potentiometer machinery, serving as a carrier and rotator for an electrical contact devices 36 (FIG. 5) affixed to the lower face of the carrier, and as a support and guide for the planetwheel portion of the "speed-reducing" driving means of the potentiometer. The contact device 36 is preferably formed from an integral thin sheet of precious (noncorroding) metal, with a folded base portion 36b (FIG. 3) pressed into and corn pressively engaging the walls of a slot or recess 30c formed in the base of carrier 30, and with first and second sets of

resilient contact fingers

36m and 36n (FIG. 5) extending angularly away from the lower face of the carrier but adapted to be stressed into a shallow extension 30f of the recess 30e in the bottom face of the carrier, as indicated in FIGS. 3 and 5. The contact device, which may herein be termed the contact in the interest of brevity, may if desired be additionally secured in place in the recess in the carrier by filling the base-receiving recess 30e with cement or potting compound (not shown in the interest of clarity of illustration).

The base device 34 (FIG. 6) is formed with key slots such as 34n that are complementary to and dimensioned and disposed to receive respective ones of the keys 22k of the housing 22, whereby proper angular relationship or orientation between parts is assured. The base device comprises an insulation substrate 34a that preferably is of alumina or the like, and on the flat upper face of which substrate are formed first and second

conductive termination films

34c and 34d, a. central conductive film 34c, and an arcuate resistive film or element 34r. The resistance element 34r is preferably of cen-net material, fired in place, but may be of other composition. The conductive films are formed from applied conductive metal paint, in known manner. The base device further comprises terminal conductors that are in the form of wirelike pins, 34x, 34y and 34z (FIG. 6), that are each secured in a respective one of through-holes formed in the substrate, by solder or conductive cement for example, as indicated at 34s in H0. 2, with their upper ends in conductive contact with respective ones of the conductive films. Thus pin 34x is electrically connected to one end of element 34r by way of film 34c, pin 34y is similarly electrically connected to the other end of the element 34r, and pin 34z is connected to the central conductive film 34c which is herein termed the return conductor.

When the base device is moved into position in the housing, the element 34r is brought into contact with and compresses contact fingers 36m, and return conductor 34c similarly contacts and compresses contact fingers 36", and thus the variable electrical circuit of the potentiometer is established. Rotation of the carrier moves contact fingers 36m along an arcuate brushing or contact path extending between

termination films

34c and 34d, the extent of possible rotary movement being restricted by arrestment of stop 30s on the carrier by the stop 28: formed on the inner face of housing insert 28 and positioned in the circular path in which the rotary stop 30s moves. The dimensioning and dispositions of the stops, contact device and element 34r are such that rotation of the carrier from either extreme or limit of its prescribed extent of rotational movement causes brushing of element 34r by contact fingers 36m from one electrical end of the element to the other, the total arcuate traverse being less than 360.

Rotation of the carrier and the contact device is effected by rotation of the actuator 24. When the latter is rotated, the frictional surface of hub 24h rotates and, due to frictional engagement of rim portions of each of the set of planet wheels with both the hub 24/1 and the circular interior friction surface 28b of the housing insert, the planet wheels rotate about their respective axes and travel along the circular friction path provided by surface 28b on which they bear or press. As they so travel, their axles 32p force the carrier to rotate about the resistance element. As is indicated in FIG. 4, the planet wheels have resilient deformable frictional rim portions, and are dimensioned to be slightly diametrically compressed when in operable position in the potentiometer, whereby the noted driving action occurs. The planet wheels may have rims of, or be entirely composed of, resilient frictional material such as resilient synthetic rubber or resin polymer, and, depending upon the 'material used for driving hub 2411, the latter may be smooth or rough, It is thus evident that, due to the difference between the diameter (or circumference) of driving hub 24h and the diameter (or circumferential length) of the clrcular frictional path on surface 28b, several rotations or turns of the actuator hub (and of the actuator) are necessary to cause the planet wheels to travel along the permitted extent of the circular path 28b formed on the interior of the housing. The rotary motion is effected without the necessity of gears. ln the illustrated potentiometer, the planet wheels have a maximum diameter of approximately five sixty-fourths of an inch and the actuator hub is of the order of one thirty-seconds of an inch, whereby it is evident that gear teeth would be impractical in such miniature single-tum adjustment potentiometers. When an operator overdrives the actuator 24, as is extremely easy due to the very small size of the instrument, harmless slipping occurs between the driving hub 24h and the planet wheels as soon as the stops 28s-30s arrest rotation of the carrier, and thus no damage to the parts occurs. As is evident, even if very strong and expensive fine gauge gears were employed, stripping and ruinous damage could easily occur. The described arrangement and construction, in which the housing, actuator, planet wheels and carrier are easily produced from inexpensive synthetic polymer material by molding techniques, avoids any possibility of overdriving damage while concurrently affording the much desired speed-reduction effeet between the manually operated actuator and the movable contact and an economically feasible potentiometer. While the housing 22 has been illustrated as being of circular form having standoff feet 22f, it is evident that the exterior plan form of the housing may be octagonal, or square, or of other geometrical form, it being essential only that a circular interior track (or an equivalent pair of arcuate tracks) be provided for travel of the planet wheels, and an axis of rotation for rotary parts such as the actuator and the carrier.

Having disclosed and explained in detail the presently preferred embodiment of the invention, it is evident that the mentioned objects have been attained, and 1 claim:

1. A miniature single-tum adjustment potentiometer comprising, in combination:

first means including housing means, providing a smooth circular friction path on the interior of said housing means;

second means, including a manually-rotatable actuator supported by said first means and having a portion exposed for application of driving torque thereto, and a second portion comprising a rotary friction driving surface;

third means, including base means, supported by said first means in a lower portion of said housing means, said third means including an arcuate resistance element and return conductor means;

fourth means, including a rotatable carrier arranged for rotation in said housing means interposed between said rotatable actuator and said base means, said fourth means including an electrical contact movable by said carrier along an arcuate path of contact with said resistance element, said contact brushing on said return conductor means;

and fifth means, including a set of rotatable friction wheels carried by said carrier and pivotally supported thereon each with a rim surface pressing radially in operative frictional engagement with said friction path and pressing radially in operative frictional engagement with said friction driving surface, said rotatable carrier and said rotatable friction wheels comprising cooperating means permitting radial adjustment movement of said wheels whereby radial forces exerted on said wheels are equalized,

whereby incident to rotation of said actuator said friction wheels are rotated by said friction driving surface and travel along said circular friction path and rotate said carrier to move said contact along said arcuate path of contact at a rotational rate less than that of said actuator.

2. A potentiometer according to claim 1, in which said first means includes a fixed stop means and in which said fourth means includes a movable stop means disposed and arranged to be arrested by said fixed stop means at predetermined extremes of the movement of said contact along said arcuate path of contact. whereby said contact is prevented from moving of? either extremity of said arcuate path of contact of said resistance element.

3. In a miniature single-turn rotary adjustment potentiometer of the type comprising housing means, an arcuate resistance element, a return conductor, a rotary contact brushing on the resistance element and connected with the return conductor, and a manually rotatable actuator means to receive applied torque for effecting movement of the contact along the resistance element; mechanical means interposed between the rotatable actuator and the contact whereby more than one revolution of the actuator is required for movement of the contact throughout the arcuate extent of the resistance element, said mechanical means comprising a carrier rotatably supported in said housing means for rotation about an axis and carrying the said contact, a set of friction planet wheels carried by the carrier, a smooth circular driving friction surface on said actuator means in frictional driving relationship with said planet wheels, and said housing means providing smooth arcuate paths coaxial with said axis for travel therealong by respective ones of said planet wheels and in frictional contact with respective ones of said wheels, said carrier and said friction wheels comprising cooperating means permitting free radial adjustment of said wheels to equalize radial forces on said wheels, whereby incident to rotation of said driving friction surface said planet wheels are rotated and travel along respective ones of said arcuate paths and along orbital paths relative to said axis to thereby rotate said carrier and move said contact along said resistance element, and whereby a plurality of revolutions of said actuator means are required to move said contact from either end of said arcuate resistance element to the other end thereof to permit very fine adjustment of said contact.

4. A potentiometer according to claim 3, in which said housing means comprises a circular aperture in which said actuator is rotatable and defines an axis, and in which said rotatable carrier and said actuator comprise cooperating bearing means coaxial with said axis and comprise a rotatable pivot on one of said actuator and said carrier and a pivot-receiving bore in the other of said actuator and said carrier, whereby said carrier is constrained to rotation about said axis and said planet wheels are constrained to circular orbital paths having said axis as a center.

5. A potentiometer according to claim 3, in which said housing means and said carrier comprise fixed and movable stop means, respectively, so positioned as to restrict said carrier and the contact carried thereby to rotational movements of less than one complete revolution, said driving friction surface and said frictional contact of said path with said wheels permitting slipping of frictional surfaces in said mechanical means incident to continued rotation of said driving surface following engagement of said fixed stop means by said movable stop means, whereby damage to said mechanical means and said contact is avoided.

6. A potentiometer according to claim 3, in which said carrier comprises slot-shaped axle-receiving bearing means and said planet wheels each comprise a stub axle rotatably received in a respective one of said bearing means, whereby said planet wheels may assume positions in which opposed forces exerted on their rims by said driving friction surface and said arcuate paths are equalized to provide freedom from binding of said planet wheels.

7. A potentiometer according to claim 3, in which said carrier is provided with recesses in its upper face, in which recesses said planet wheels are nested for rotation, and in which potentiometer said rotatable actuator means comprises a flange overlying said planet wheels and confining said planet wheels to said recesses, whereby said mechanical means is made simple and inexpensive.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 614, 703 Dated October 19, 1971 Inventor(s) Ronald L. Froebe It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 10, "contacting" should read contact. Column 1, line 54, "will" should read while-. Column 2, line 61, insert --board after "primary". Column 3, line 4, insert aafter "are". Column 3, line 22, insert opposed-- after "second". Column 3, line 32, "conductive" should read conductor-. Column 3, line 47, "wake" should read sake-. Column 3, line 61, "24a" should read --24s. Column 4, line 72, "devices" should read device--. Column 5, line 63, insert potentiometer axis, carrying the contact along the after "rotate about the".

Signed and sealed this 25th day of July 1972.

(SEAL) Attest:

EDWARD M.FLETCHER.JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM 304050 uscoMM-Dc 60376-P69 a U S. GOVIRNHENY FRINYING OFFICE 1969 0-366-33

Claims

1. A miniature single-turn adjustment potentiometer comprising, in combination: first means including housing means, providing a smooth circular friction path on the interior of said housing means; second means, including a manually-rotatable actuator supported by said first means and having a portion exposed for application of driving torque thereto, and a second portion comprising a rotary friction driving surface; third means, including base means, supported by said first means in a lower portion of said housing means, said third means including an arcuate resistance element and return conductor means; fourth means, including a rotatable carrier arranged for rotation in said housing means interposed between said rotatable actuator and said base means, said fourth means including an electrical contact movable by said carrier along an arcuate path of contact with said resistance element, said contact brushing on said return conductor means; and fifth means, including a set of rotatable friction wheels carried by said carrier and pivotally supported thereon each with a rim surface pressing radially in operative frictional engagement with said friction path and pressing radially in operative frictional engagement with said friction driving surface, said rotatable carrier and said rotatable friction wheels comprising cooperating means permitting radial adjustment movement of said wheels whereby radial forces exerted on said wheels are equalized, whereby incident to rotation of said actuator said friction wheels are rotated by said friction driving surface and travel along said circular friction path and rotate said carrier to move said contact along said arcuate path of contact at a rotational rate less than that of said actuator.

2. A potentiometer according to claim 1, in which said first means includes a fixed stop means and in which said fourth means includes a movable stop means disposed and arranged to be arrested by said fixed stop means at predetermined extremes of the movement of said contact along said arcuate path of contact, whereby said contact is prevented from moving off either extremity of said arcuate path of contact of said resistance element.