US2934732A

US2934732A - Potentiometer construction

Info

Publication number: US2934732A
Application number: US645081A
Authority: US
Inventors: Herbert M Schendel
Original assignee: Beckman Instruments Inc
Current assignee: Beckman Coulter Inc
Priority date: 1957-03-11
Filing date: 1957-03-11
Publication date: 1960-04-26
Anticipated expiration: 1977-04-26

Description

April 26, 1960 H.M. SCHENDEL POTENTIOMETER CONSTRUCTION /NVNTOI?. Hzeaskr M. SCHENDEL.

' BY HIS ATTORNEYS. HARRIS, K/acH, Fosrcz & HARRIS United States Patent POTENTIOMETER CONSTRUCTION .Herbert M; Schendel, Santa Ana, Califi, assignor, by mesne assignments, to Beckman Instruments, Inc., Fullerton, Calif a corporation of California Application March 11, 1957, Serial No. 645,081

13 Claims. (Cl. 338-143) My invention relates to constructions for potentiom- .-eters and the like. More specifically, it relates to a restainer or positioning device for holding or spacing. the turns of a multi-turn winding.

'A problem often encountered in the electrical arts is ,the arcuate positioning of such turns relative to each other and relative to a housing. A typical example is nthe positioning of a multi-turn resistive-winding in a housing to be'contacted by a movable wiper, as in the $1311. of making multi-turn potentiometers, resistors, delay .lines, etc. "While applicable to any multi-turn environ- -ment,;the invention will beparticularly exemplified with referenceqto multi-turn or helical potentiometers.

; It; is an-[important object of the inventi-onto provide ,an improved structure for accurately positioning the turns of a multi-turn winding. A further object is to provide a simple and inexpensive positioningstructure of this character comprising a tubing corrugated in the de- ,sired pattern of the multi-turn winding. -ther objects ;,-lie-. in the-novel association of such a positioning structure with a housing; also in the constructional features of the positioning structure and the manner: or method by which it is associated withthewinding orthe housmg.

.tAccordingzto the preferred practice of: the invention,

aal'thinewalled tube is=first corrugated inthedesiredtpatr-tern.-of-;the winding, the ,winding-beingthen positioned thereimlthe whole. being then positioned in .a tubular avhousing. In the potentiometer .art,- for example,. the lmulti-turn I resistance. element .will present .an inwardly- :exposed ihelical surface along which .a. suitably. guided rcontactrnay move. ;In this or similar environ-ments, the :invention provides, for. accurate placing. orspacing ar the ltiurns. .It allows the windingto be closer to the'housing ithangistthe CfiSBxWlth conventional. constructionsand permits theme of .thimwalledhousings resulting in greater tcompactness. Metal housings are particularly desirable from the standpoint of durability, shielding-compact- .DCSS, Z1Hd dissipation and equalizationof-heat. tine-addition, for anygiven outside diameter of the po- Ltentiorneter, thewmulti-turn resistance coil can have a ilarger diameter and thereby improve -resolution and slinearity. This-"becomes a striki-ngaadvantage in the socalled miniature size potentiometers now in demand for tmissileguidance, transistorized circuitsend other miniature or sub miniature control systems employing multiturn-transducers or control-devices made in accordance :withthe invention.

"The drawing illustrates preferred embodiments'of the invention andwill suggest variations within thelscope of the invention. Referring to the drawing:

Fig. l isja longitudinal cross-sectional view of a miniaturef potentiometer embodying. some .of the features of th inv n i a Fig. 2 is a transverse fragmentary view takenitlong the line 2--2 of Fig. 1;

2,934,732 Patented Apr. 26, 1960 Fig. 3. is an enlarged fragmentary view of a single turn of .the device; and

Fig.--4 is a similar fragmentary view of an alternative .;construction.

Referring particularly to Fig. 1, the potentiometer is shown as including a thin-walled tubular housing 10 having a. cylindrical interior surface 11. ,ing can ;be..made of any suitable material, distinct ad While this housvantag'es arise from the use of a metal in those instances where, compactness, increased heat dissipation or 1mproved isothermalrconditions are desired. The ends of i the housinglfl are suitably closed, as by end members .12 and 13. Pins 14 exemplify merely one way of holding the

endmembers

12 and 13 in place.

Within the housing 10 is a winding-positioning ele- -ment show-nas comprising a tube 16 corrugated in a .heIic'aI'pattern. *In this embodiment, the tube-16 is made of thinmetal, the corrugations being produced by external or internal pressure respectively applied while the tube. is over a male. die or in a female die. The resulting-corr-ugated tube 16 will have an outer surface 17 procrests. are formed by the corrugations of the tube 16.

.It is preferred that the helical crest 18 be in engagement with the interior surface 11 of the housing 10. A suflice but supplementary attachment means can be used. In thisrlatteninstance, an intervening adhesive can-be employedxor. the end turns of the crest can be pinned, asolderedyor'welded to thehousing -11. Alternatively or frictional contact in the zone of engagement will often in addition, the ends of the tube 16 may pressurally'engage

shoulders

23 and 24 of the end members 12 and--13.

.A washer'25- is shown between the shoulder 24 and the lower. end of the tube 16. The thickness of this washer will determine'the'longitudinal pressure applied to the --tube 16. '.Usually:only suflicient pressure is applied to :preventalongitudinal movement of the tube 16 but it will :be apparent that increased longitudinal pressure can be uem-ployedtorexpand the corrugations against the cylindri- -cal interior surface-11 of the housing 10. The invention .comprehcnds any suitable means for applying such longitudinal pressure to cause minute expansion of the tube 16 to clamp it within the housing.

',.'I'l1e inWard1y facing helical trough -22 forms a multiturn w mding receiving trough or space facing toward the :common axis of the tube ld an'd'the housing 10. A rmultii-turn winding '30 is disposedin this trough and will 2 be positioned orshaped thereby to conform to the predetermined multi-turn pattern of the trough. This is a dis- ;tinctly;advantagesousifeature of the present invention becausetaitroughlofpredetermined pattern can be formed in the.tube F16, after which a winding of normally different patterncan be inserted, the ultimate pattern of the *windingaconforming'to the pattern of the trough. By

-normallytdiiferentpatternI have reference to a devia- :tion in spacing or size of the'turns. For example,-=it'is :the usual practicetoproduce'the winding 30 of a helical form slightly larger than the trough 22 so that it tends to expand therein upon release from the initial contractionnecessaryto dispose it in the trough. .The winding can be retained in the trough by friction or by cementing it therein. The preferred practice is to pin or weld one end of the core of the winding relative to the tube 16 and then-exert an unwinding pressure on the other end to'iexpand the winding before this other end is similarly attachedto the tube 16.

, .Thewinding 30illustrated in Figs. 1,2 and-3 is-com posed of a multi-turn core 32, typically insulated copper Wire, with a resistance wire 33 wound therearound in contacting or spaced turns. The preferred practice is to employ a cover 34 of insulation material over the winding so that this cover will hold the resistance wire in place and will electrically insulate the wire 33 from the tube 16 if the latter is formed of metal and the resistance wire is a bare wire. The cover 34 is removed in an inwardly-facing zone 35 of the winding 30 to present an inwardly-exposed helical surface engageable by the guided contact to be described. It should be clear, however, that coreless windings 30 can be employed or that other means can be employed for insulating the resistance Wire from the tube 16. In addition, the tube 16 need not be formed of metal and if made of insulating material the wire 35 may come into direct contact therewith. In this latter connection, it is sometimes desirable to make the tube 16 of molded plastic material or other material of relatively high electrical resistivity.

Any suitable contact means can be employed to advance along the helical multi-turn winding 30 while being guided in a helical path or to advance from turn to turn of the winding 30 while being moved longitudinally of the housing 16. Figs. 1 and 2. illustrate guidance of a contact along the winding 30. As therein diagrammatically shown, a rotor 40 carries

stub shafts

41 and 42 respectively journalled in the

end members

12 and 13 to turn about the common longitudinal axis of the tube 16 and housing 10. The rotor 40 provides a longitudinal groove 44 along which a slider or block 45 may freely advance. This block carries a looped contact member 46 terminating in a contact 47 adapted to engage the zone 35 of the winding 30.

Means is provided to guide the block 45 from the tube 16 so that the contact 47 follows the convolutions of the winding 31). In this respect, the block 45 is shown as including a pair of flanges 49 extending loosely into the V-shaped space between each turn of the winding 30 and the adjacent wall of the trough 22. As the rotor 40 .turns, the flanges 49 follow this space and advance the block 45 along the groove 44. Guidance of such a block by flanges extending into a space defined by adjacent turns is disclosed in the earlier patent to Beckman No. 2,454,986 and while the present invention can employ such a sytsem it is preferred to effect guidance by a space formed in part by one turn of the Winding and in part by an adjacent wall of a trough of a memher which positions the winding, e.g. the corrugated tube 16.

Terminals connected by leads to the ends of the winding 30 may be of conventional form, being shown diagrammatically in Fig. 1 as including terminal tabs 52 extending through the

end members

12 and 13. The contact 47 can be similarly connected by a conventional pigtail lead to a corresponding terminal member, not shown.

If intermediate taps are to be employed, the leads therefor may extend through aligned

openings

53 and 54 in the tube 16 and the housing 10 respectively. If, as shown, the opening 53 lies along a crest 18, a tap wire 55 can be welded to the exposed winding and extend directly to the exterior of the housing 10. In other instances, a tap lead 56 can be connected to the winding through an opening 57 positioned remotely from the housing opening 54. In this instance, such a lead 56 may extend between an adjacent crest 18 and the housing 10 or may extend peripherally of the tube 16 to the opening 54 through a helical passage 58 formed by the trough 19 and the housing 10. This latter procedure has particular advantages when it is desired that tap connections or terminals are to be on or at either or both of the

end members

12 or 13. When tap or terminal leads extend along the helical passage 58 they are automatically electrostatically shielded from the resistance element and from external fields. The helical passage 2,934,7sa p v v 58 is of sufiicient size to receive several small leads if desired. Some of such leads may run in opposite directions along the passage 58 and may be brought out either at the front or rear of the potentiometer or both. A tap lead extending along the helical passage 58 and from the end member 12 is indicated in Fig. 1 by the numeral 59. I

It is preferable first to insert the winding 30 in the tube 16 and then position the resulting unit in the housing 10. This is particularly true when taps are to be connected to the winding 30. However, it is also within the scope of the invention to position the tube 16 in the housing 10 and then introduce the winding 30 into the tube.

In the preferred practice of the invention, both the tube 16 and the housing 10 are formed of thin metal. The resulting structure has excellent heat dissipation properties and enjoys the other advantages previously mentioned. It is within the scope of the invention to provide

tubular fittings

60 and 61 through one or both

end members

12 and 13 to provide for the ingress or egress of a heat-exchange fluid acting as a coolantor heat-regulating fluid. Such a fluid may freely circulate through the helical passage 58, being guided thereby to flow adjacent all portions of the winding 30 and in excellent heat transfer relation thereto.

It is sometimes desirable to insulate the tube 16 from the housing 10 or to further insulate the winding 30 therefrom. Fig. 4 illustrates a thin metal corrugated tube 64 coated on both sides with layers 65 and 66 of electrical insulating material. The tube 64 can thus serve as an electrostatic shield irrespective of whether the housing 10 is made of metal. Additionally, the resistance wire 33 can be a bare wire space-wound on a core 32 of insulating material or around a core space, reliance being placed upon the layer 66 to electrically insulate the corrugated tube 64 from the resistance wire.

Various changes may be made without departing from the spirit of the invention as defined in the appended claims.

I claim as my invention:

1. A multi-turn helical potentiometer including in combination: a tubular element corrugated in a multiturn helical pattern, said tubular element having an inner surface with a multi-turn helical winding-receiving trough provided by the corrugations; a multi-turn resistance winding disposed in said trough and positioned thereby as a multi-turn helical winding of a pattern determined by said trough, said helical winding bounding a rotor space and presenting an exposed helical zone facing the longitudinal axis of said tubular element; a rotor; means for journalling said rotor to turn in said rotor space about said axis; a contact turning with said rotor; and means for guiding said contact to advance along said exposed helical zone in contact with the resistance winding and follow the turns thereof as said rotor is turned about said axis.

2. A potentiometer as defined in claim 1 in which the depth of said winding-receiving trough is no more than about half the diameter of the individual turn of said multi-turn resistance winding disposed therein measured in a plane including said axis to expose at least about half of such turn to said rotor space.

3. A potentiometer as defined in claim 1 in which each turn of said winding provides a V-shaped space with an adjacent surface of the trough, and in which said means for guiding said contact includes a flnage extending loosely into said V-shaped space and mechanically connected to said contact to move same therewith.

4. A potentiometer as defined in claim 1 in which said corrugations extend less than the full length of said tubular element, leaving cylindrical non-corrugated end 5. A potentiometer as defined in claim 1 in which said tubular element is a thin metal tube and in which said multiwturn winding comprises a multi-turn core wound with resistance Wire surrounding said core in helical turns, said wire being coated with electrical insulation material engaging said metal tube.

6. A multi-turn helical potentiometer including in combination: a housing having a cylindrical inner surface; a tubular element in said housing corrugated in a multi-turn helical pattern and providing outer and inner surfaces each having a multi-turn helical crest and a helical trough formed by the corrugations, the helical crest of said outer surface engaging said cylindrical inner surface of said housing, the helical trough of such outer surface cooperating with said cylindrical interior surface to form a helical passage, the helical trough of said inner surface forming a multi-turn winding-receiving space formed by the corrugations and facing toward the longitudinal axis of said housing; a multi-turn resistance winding disposed in said winding-receiving space and shaped thereby into a multi-turn helical winding of a pattern determined by said corrugations, said helical winding bounding a rotor space and presenting an exposed helical contact zone facing said longitudinal axis; a rotor; means for journalling said rotor to turn in said rotor space about said axis; a contact turning with said rotor; and means for guiding said contact .to advance along and in contact with said exposed helical contact zone of the resistance winding as said rotor is turned about said axis.

7. A potentiometer as defined in claim 6 in which said means for journalling said rotor includes end members closing the ends of said housing, a shaft to which said rotor is connected, and bearing means carried by at least one of said end members providing a bearing means for said shaft.

8. A potentiometer as defined in claim 7 in which said corrugated tubular element is disposed between said end members and has end surfaces receiving pressure therefrom in the direction of said longitudinal axis, and including means for attaching one of said end members to said housing while applying sufiicient longitudinal force to said tubular member to compress it and expand laterally the helical crest of said outer surface thereof into pressural contact with said cylindrical inner surface of said housing.

9. A potentiometer as defined in claim 6 including a lead connected to said winding and extending along said helical passage formed by the housing and the helical trough of said outer surface of said tubular element.

10. A potentiometer as defined in claim 9 including end members closing the ends of said housing and cooperating therewith in providing an enclosing structure, said enclosing structure including an opening, and a. conductor traversing said opening and electrically connected to said lead.

11. A potentiometer as defined in claim 6 in which said housing and the helical crest of said outer surface of said tubular element provide registering openings, and including a conductor traversing said registering open ings and electrically connected to said winding at a. position intermediate its ends.

12. A potentiometer as defined in claim 6 including ingress and egress means communicating with said helical passage at positions spaced from each other along the length of such passage for circulating a heat-transfer fluid along said passage between such positions.

13. A potentiometer as defined in claim 12 including an end member closing one end of said housing, and in which at least one of said ingress and egress means includes a tubular connection member for said heatt-ransfer fluid, said tubular connection member being carried by said end member.

References Cited in the file of this patent UNITED STATES PATENTS 1,228,635 Alexander June 5, 1917 1,504,483 Klopsteg Aug. 12, 1924 2,379,530 Lederer July 3, 1945 2,454,986 Beckman Nov. 30, 1948 2,747,061 Sorber May 22, 1956 2,750,483 Voorman June 12, 1956 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2334332 April 26,, 1960 Herbert M. Schendel It is herebj certified that error appears in the-printed specification of the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column 1 line 21 for "arcuate" read accurate column 4, line 67, for "flnage" read me flange '0 Signed and sealed this 27th day of September 1960 (SEAL) Attest:

KARL H0 AXLINE Attesting Ofiicer ROBERT C. WATSON Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2 93 l 732 April 26 1960 Herbert Mo Schendel It is herebfi certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1 line 2l for "arcuate" read accurate column 4L line 67, for "oflnage" read flange Signed and sealed this 27th day of September 1960o S EAL) Attest:

KARL H AXLINE Attesting Oflicer ROBERT C. WATSON Commissioner of Patents