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Publication numberUS3579169 A
Publication typeGrant
Publication dateMay 18, 1971
Filing dateFeb 5, 1969
Priority dateFeb 5, 1969
Publication numberUS 3579169 A, US 3579169A, US-A-3579169, US3579169 A, US3579169A
InventorsDickinson Clarence R
Original AssigneeAllen Bradley Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Variable resistor for dual operation
US 3579169 A
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Description  (OCR text may contain errors)

United States Patent inventor Appl. No. Filed Patented Assignee VARIABLE RESISTOR FOR DUAL OPERATION 7 Claims, 4 Drawing Figs.

Primary Examiner-Lewis H. Myers Assistant Examiner-Gerald P. Tolin Attorneys-Arnold J. Ericson and Richard C. Steinmetz, Jr.

ABSTRACT:. A variable resistor providing an integral as- U.S.Cl 338/170, sembly for dual operation comprising a i f arcuate 338/132 338/164! 338/167, 338/174 338/202 sistance track elements in axially spaced, face-to-face relall'llt. tion hi and having interposed therebetween a single insulat. Field of Search 338/ 128, ing rotor or b h can'ier including oppositely facing cavities, 130, 132, 162, 164, 166, 167, 170, 171, 174, 184, each cavity being recessed relative to a central plane and 202, 230 adapted to individually receive conducting brush members. Biasing springs are provided for maintaining the brush mem- References cued bers in electrical contact with the respective resistance ele- UNITED STATES PATENTS ments, as well as individual terminal assemblies for each of the 2,111,810 3/1958 Schellenger 201/55 resistance elements.

45 47 25 2+ 3 |5 23 H 43 46 Y Y |7 36 24 i 30 22 I f I) 37 I 26 42 39 2+ II 3| 4 T 0 2| BACKGROUND OF THE INVENTION The present invention relates to mechanically variable resistors having movable contacts electrically adjustable over a length of resistance element, and in particular to a variable resistor wherein there is a pair of such resistance elements in axially spaced, facing relationship and including respective movable contacts for each of the elements actuated by a single rotor, and in which all of the components are enclosed in a single, housing.

Components of the nature disclosed herein have in the past been mounted in tandem arrangement with individual movable contact elements electrically engaging separate resistance elements. The movable contact elements were attached in axially spaced relationship along a common operating shaft. This made for relatively long and cumbersome constructions.

There have also been some attempts to combine the contacts in a single rotor, but these contacts were generally of leaf spring construction with the contact buttons being made an integral part of the distal end of the lead spring and verymuch dependent upon variations in the spring material, length of spring and other factors influencing the tolerance of the construction.

SUMMARY or TIIE INVENTION device that will readily adapt itself to such applications asbridged T- and L-attenuators which require in their construction the obtainment of a specified resistance impedance in the operation of dual variable resistance. It is further important that the impedance relationship be maintainedthroughout the range of resistance values as the device is operated. The manner of construction of the present device provides a positive attainment of such impedance relationship, independent of the variations normally found in leaf spring contact constructions.

The present invention, in its preferred embodiment, adapts certain of the features of the Variable Resistance Device disclosed in US. Pat. No. 2,839,642 granted to the present inventor jointly with Bernard F. Tellkamp and assigned to the same assignee as the present invention. That is, the embodiment may utilize integrally molded resistor elements such as those set forth in the US. Pat. Nos. 2,269,136 and 2,514,682 to Tellkamp. However, it is contemplated that the construction of tee resistance elements may take other forms such as conventional cermet or thick film resistance tracks, as well as other resistance tracks well known in the art.

The resistance elements each provide an arcuate track which may be of constant resistance throughout its length or variable, as desired, and in the case of otentiometers, a centrally disposed collector track of conducting, low-resistance material. The resistance elements are retained in axially spaced, face-to-face relationship by means of a tubular enclosure or casing. An operating shaft protrudes through a central aperture of one of the resistance elements and has attached to its internal end portion an insulating rotor elementincluding two oppositely disposed cavities recessed inwardly relative to a central plane dividing the rotor perpendicularly of its axis. Within each of the cavities there is located a conducting brush which is rotatable with the rotor about an axis substantially concentric with the respective resistance tracks and having collector engaging portions in sliding contact with the collector track and a resistance engaging portion in sliding contact with the resistance track. Relatively flat spring elements are seated in the respective cavities to bias the brushes outwardly of the cavities and towards their respective resistance elements.

It is therefore among the objects of the present invention to provide a variable resistor of diminutive size which includes among its various features the provision of well proven and commercially accepted resistance elements and brush constructions and which combine all of these features in the device to provide a dual functioning, variable resistor enclosed within a single housing to thereby reduce both its radial and axial length when compared to conventional tandem operated variable resistors.

BRIEF DESCRIPTION OF THE DRAWING The attached drawing, which comprises a part hereof, discloses the invention, as follows:

FIG. 1 is a longitudinal view, partially in section, of a variable resistor in the form of a potentiometer incorporating the teachings of the present invention;

FIG. 2 is a cross-sectional view taken along lines 2-2 of FIG. 1 and illustrating, more particularly, a construction of the rotor or brush carrier;

FIG. 3 is a cross-sectional view taken along lines 3-3 of FIG. I, and illustrates the configuration of the resistance track and collector track as used in the dual resistance elements; and

FIG. 4 is an enlarged fragmentary view of another embodiment of the brush construction.

DESCRIPTION OF THE FREE ERRED EMBODIMENTS Referring now to the drawing, and in particular to the views of FIGS. l3, there is shown a resistance element in the form of a molded base 10 of insulating material. The base 10 provides a surface 11 preferably of circular configuration. The configuration of the resistance and collector tracks of the surface 11 is similar to the interior surface 12 of an axially spaced resistance element 13, except for a rotative positioning relative to the longitudinal plane of the device for purposes hereinafter described. Attention is directed to'FlG. 3 which more clearly shows the configuration of the surface 12 of the element 13. Embedded within the base 10 and the element 13, and exposed flush with the respective faces 11 and 12, are circular resistance tracks 14 and 15, respectively, each in the form of a nearly completed ring. The tracks 14,15 each comprise a shallow layer of conducting material in the form of distributed carbon-black particles dispersed within the molded material of the respective base 10 and element 13 to have become an integral portion thereof upon molding. Substantially concentric with the resistance tracks 14, 15 are respective collector tracks 16 and 17, also exposed fiush with the respective faces 11 and 12. The tracks 16, 17 cover a circular area at the center of the respective faces 11 and 12 and, like the tracks 14, 15 are formed of a plurality of conducting particles molded integrally with the respective base 10 and element 13 in a shallow layer near the surface. The particles comprising the collector tracks 16, 17 are more densely distributed only rather than a potentiometer, in the form of thick film or cermet surfaces as is well known in the art.

Returning to the description of the base 10, a set of threeterminal leads 20 (one of them not being shown) are embedded within the base 10 at the time of molding and there disposed with the embedded end of one in electrical contact with the collector track 16 and the embedded ends of the others in contact with the end portions of the resistance track i 14. The terminals 20 are shown in longitudinal projection The terminals 21 of the element '13 are molded in {place in similar manner to terminals 20, and project downwardly relative to FIG. 1. Should it be desired to provide the aforementioned means for including downwardly projecting terminals 20, the setsof terminals 20,21 will be chosen dimensionally to fit into known circuit board constructions.

- Both the molded base 10 and the resistance element 13 also have embedded therein metallic heat extracting and housing anchoring inserts 22 and 23, preferably composed of a :metal having high heat conductivity. The inserts are more clearly shown and described in detail in the Dickinson et al. US. Pat. No. 2,839,642. They generally take the form of an interrupted cylinder with a plurality of perforations through which the material of the-base 10 and theelement 13 may flow, upon molding, to rigidly secure the inserts 22, 23. Each of the in serts 22, 23 with its respective forward edge 24, 25 behind, spaced from but very, near the respective resistance tracks 14, 15, as shown in FIG. 1, to readily receive heat released within the resistance tracks l4, 15 and to conduct the same to the exterior of the'base 10 and resistance element 13.

' The base 10 and resistance element 13 are retained in axially spaced relationship by means of a housing or casing-26 which is preferably of a metallic heat-conducting material. At the bottom of the housing, as viewed in FIG. 1, it will be noted that'a portion of the housing is lanced inwardly from its right end withtheseparated portion bent inwardly to formya rotor stop as will. be Iaterdescribed. The casing'26'is provided'with a set of ears (not shown) which act to retain a threaded bushing 30 having a circular base 31 resting against the resistance elenient 13.v The free ends of the aforementionedears are bent over the bushing base 31 to secure the bushing 30 in position. Extending through the bushing 30 is an operating shaft-32 hav ing a reduced cross section33 and a'knurled end 34 withirijthe casing '26. The knurled end 34 and the reduced portion 33 are embedded within a'molded contact carrier or rotor 35 composed of an insulating material. The rotor is provided with a projecting molded portion 39 which acts to insulate the shaft 32 -from the collector ring 17 in addition tojproviding a "bearingsurface for thero'tor 35. The bushing 30 is recessed at 36 to receive an -O-rin'g gasket 37 which is compressed between the interior circular wall of the recessed cavity 36 and the shaft 32 to provide a seal. The brush carrier or rotor 35 is slotted at 38 for purposes of assembly in order to clear the inwardly folded portion 27 of the casing. Although not shown, the rotor'35 is molded'to proyide a projection which will engage either side of the portion 2 7 for purposes of limiting rotation thereof. The movement of of a novel modification of the brush carrier or rotor 35 to permit this dual function. That is, the brush carrier 35 is recessed to provide diametrically opposed cavities 40 :for respectively receiving electrically conducting brushes 42 and 43 of carbon and the respective pair of biased springs 44 and 45. With reference to FIGS. 1 and 2, it will be noted that each of the brushes has a substantially identical configuration, the rear- I ward side of brush 43 and the forward side of brush 42 being shown in the cross-sectional view of FIG. 2. As viewedin FIG. l5and 2, itwill be noted that the brush carrier 35 is provided with an arcuate protruding portion 46 which acts as a stop for the rotor 35 on any endward, axial thrust being placed upon the shaft 32 during adjustment. That is, the rotor 35 will in no way touch the resistance'track 15 or the collector track 17 as the *protruding'portion 46 is disposed to rest against the inner 'face 11 of the base 10 intermediate the said tracksl5 and 17.

Each of the brushes 42,43 are of general 'triangular'configuration to be respectively seated in the generally triangular configured recesses 40 and 4-1 of the rotor 35, respectively. As shown in FIG. 2 and as particularly'illustrated with regard to brush 42, each of the brushes 4 2,43 are provided with three 'co ntacttoes47, 48 and 49. The two radially inwardly disposed toes 48, 49 rest upon and electrically engage the respective collector tracks 10 and 17 of the baselfl'and the resistance element 13. whereas the outwardly positioned toe 47'rides upon and electrically engages the resistance-tracks 14 and 15. The triangular disposition and spacingtofthe toes 47, 48 and 49'also provides stability for the respective brushes 42, 43.

As shown on FIG. 2, the springs 44, are disposed in laterally projecting recessed portions of the cavities 40 and 41. The laterally projecting recesses are formed with abutments at their extremities 50 to receive the ends of the respective springs 44,45. The intermediate portion'of each of the springs 44, 45 bears againstthe angled back surface 51 of the respective brushes 42,43 and is bowed to'provide necessary contact pressure between-the brush toes 47 and the exposed surface areas of the tracks 14, 1'5 and 16, 17. It will be further observed that the force exerted by the springs 44, 45 against the angled back surface'SI'divides into two components,-one biasing the respective brush 42, 43 towards the respective faces 11 and 12, and the other force component biasing the respective brush in adirection towards the forward surface defining the toe 47. The latter-component acts to retain the brush'in its cavity, which is especially helpful during assembly of the device. The use of a plurality of springs 44, 45permitscontacting engagement-with the angled backsurface 51 of the brush'to provide a spring characteristic similar to that of a flat spring.

It will be apparent from the above description that manual rotation of the shaft 32 willcause the rotor 35 molded to the inward endof the shaft to rotationally move the conducting brushes 42 and 43 circumferentially of the concentric resistance and'colle'ctor tracks 14, 1'6 and 15 17, respectively. This dual operation is performed in a minimum axial dimension between the resistance elements 10 and 13 by seating the respective brushes-42 and 43in cavities 40 and '41 which are disposed inwardly of aplane cross-sectionally bisecting the ro- FIG. 4 is illustrative'of another brush embodiment, and like parts are described by referring to like numerals. As stated above,'the springs .44, 45 bear against the angled back surface 51 of the brushes 42, 43. This arrangement provides desired contact pressure between the toe 47 and the respective resistor track 14, 15. However, such arrangement also tends to wedge the apex forming the outer surface of the toe 47 of the triangular brush against the mating surface of the triangular recess of the rotor 35.

In order to minimize the wedging condition and thereby permit freedom ofbrushaction when the rotor is operated, the surface of the recess engaging the toe 47 is preferably formed as shown in FIG. 4. That is, the apex is further defined by the planar surface portions 52iand 53, which lie in angular planes intersecting at the-terminus of the apex. This provides a two point" contact for the rounded toe 47. The brush 43 (shown in FIG. 4) and the brush 42 will then be assured freedom of movement in the recess 41 of the rotor 35 even under bias of the respective springs 45,-44.

I claim: 1. A variable resistance apparatus comprising: a housing; J I a pair of spaced-apart, stationary insulating substrate element supported by said housing, at least one of which includes'a shaft-receivingaperture; an arcuate resistance track and a conducting collector track supported by each of said substrate elements and in respective facing relationship;

a rotatable shaft received in the apertured substrate element and extending inwardly of said housing;

an integrally formed insulated contact brush carrier supported on the inner end of said rotatable shaft and positioned intermediate said resistance elements, said contact brush carrier containing a pair of reentrant brush-receiving cavities on opposite sides thereof and disposed'angularly relative to one another, the operi ends of said cavities facing respective resistance tracks and collector tracks supported by the respective substrate elements, the said reentrant cavities of said brush carrier each having a depth exceeding one-half the axial length of said brush carrier;

conducting contact brushes disposed on opposite sides of said contact carrier and positioned in the respective cavities of said contact brush carrier and slidably electrically bridging the respective facing resistance and collector tracks;

biasing means at opposite sides of said contact carrier disposed in said respective cavities intermediate a respective inner end of said cavities and its respective brush, thereby biasing said brush into electrical bridging engagement with said resistance track and said conducting collector track supported by the respective substrate elements; and

terminal connections for said respective resistance tracks and said respective collector tracks.

2. The variable resistance apparatus of claim 1, wherein said respective brushes are of triangular configuration and include three protruding toes each being located at the respective apices of each of said brushes, one of said toes being in sliding electrical contact with said arcuate resistance track and the remaining toes being in sliding electrical contact with said collector track. 1

3. The variable resistance apparatus of claim 1, wherein each of the brush-receiving cavities are triangularly shaped and disposed with on apex positioned for rotational alignment with its respective arcuate resistance track and said one apex being further configured at its terminus to define planar wall surfaces lying in angular intersecting planes, said wall surfaces being normal to said respective resistance track, and said respective brushes being triangularly shaped and seated in a respective cavity with one apex being arcuately configured and in linear engagement with each of the respective said planar wall surfaces of said one apex of said cavity.

4. The variable resistance apparatus of claim 1, wherein the distal end surface of the shaft-supported brush carrier includes a protruding portion spaced from said arcuate resistance track to prevent the said end surface from wiping against said track during rotation of said shaft.

5. The variable resistance apparatus of claim 3, wherein the inner back surface of each of the respective brushes is angularly disposed relative to the plane intersecting the end of said brushes in electrically bridging engagement with said tracks, and wherein the biasing means comprises an elongated spring disposed transversely of and pressing against said angularly disposed back surface to provide a resultant force acting to concurrently force the respective brush in a direction into engagement with its respective resistance track and to force said arcuately formed apex of said brush into said linear engagement with said planar wall surfaces of said cavity.

6. In a variable resistance apparatus comprising:

a housing;

a stationary insulating substrate element supported by said housing and including an interiorly facing surface supporting an arcuate resistance track and a conducting collector track;

a rotatable shaft extending inwardly of said housing and supporting at its inner end a contact brush carrier;

the combination therewith of;

triangularly shaped, brush-receiving cavities in said brush carrier and disposed with one apex thereof positioned for rotational alignment with the said arcuate resistance track, and said one apex being further configured at its terminus to define planar wall surfaces lying in angular intersecting planes, said wall surfaces being substantially normal to the surface of said substrate element supporting said resistance track;

a conducting brush seated in said cavity and having an exposed surface in slidably electrically bridging engagement with said tracks, said brush being triangularly shaped with one apex being arcuately configured and in linear engagement with each of the respective planar wall surfaces of said one apex of said cavity; and

biasing means disposed in said cavity intermediate the inner end of said cavity and said brush, to thereby bias said brush into electrical bridging engagement with said tracks.

7. ln the variable resistance apparatus of claim 6, the inner back surface of said'brush being angularly disposed relative to the plane intersectingthe end of said brush in electrically bridging engagement with said tracks, and wherein the said biasing means comprises an elongated spring disposed transversely of and pressing against said angularly disposed back surface of said brush to provide a resultant force acting to concurrently force the brush in a direction towards engagement with said tracks and to force said arcuately formed apex of said brush into said linear engagement with said planar wall surface of said cavity.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2111810 *Oct 7, 1935Mar 22, 1938Chicago Telephone Supply CoRheostat
US2506491 *Nov 8, 1948May 2, 1950Phillips Petroleum CoVolume control
US2514682 *Apr 9, 1948Jul 11, 1950Allen Bradley CoVariable resistor apparatus
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3760323 *Sep 25, 1972Sep 18, 1973Continental Wirt ElectronicInsulated wire wound resistor
US3932831 *Jun 25, 1974Jan 13, 1976Spectrol Electronics CorporationVariable resistance device
US4310824 *May 14, 1979Jan 12, 1982Preh Elektrofeinmechanische Werke Jakob Preh Nachf. Gmbh & Co.Rotary variable resistor
US5745025 *Jan 26, 1996Apr 28, 1998Preh-Werke Gmbh & Co. KgSnap-engaging apparatus for a rotable component
US5986421 *Aug 14, 1998Nov 16, 1999Koito Manufacturing Co., Ltd.Safety device for power window
US6040757 *Feb 25, 1999Mar 21, 2000Murata Manufacturing Co., Ltd.Variable resistor
US6275140Nov 1, 1999Aug 14, 2001Alps Electric Co., Ltd.Rotary variable resistor
US7167075 *Dec 3, 2004Jan 23, 2007Jefferson Science Associates, LlcDual design resistor for high voltage conditioning and transmission lines
US7369033 *Feb 15, 2005May 6, 2008Alps Electric Co., Ltd.Rotating type variable resistor
CN100458985CFeb 6, 2005Feb 4, 2009阿尔卑斯电气株式会社Rotating type variable resistor
EP0999561A1 *Oct 28, 1999May 10, 2000Alps Electric Co., Ltd.Rotary variable resistor
Classifications
U.S. Classification338/170, 338/164, 338/174, 338/202, 338/132, 338/167
International ClassificationH01C10/20, H01C10/00, H01C10/34
Cooperative ClassificationH01C10/20, H01C10/34
European ClassificationH01C10/20, H01C10/34