US3027530A - Potentiometer - Google Patents

Description

J. F. SHEA POTENTIOMETER March 27, 1962 Filed May 25, 1959 pm. T. L g 5w. 6 f. d M a w J J/f 1` a m "J mmlm;

l/4/592/6 f' ,jgs-SUP BY rraeA/Eyg,

Unite ttes Filed May 25, 1959, Ser. No. 815,721 9 Claims. (Cl. SSS-130) This invention relates to rotary potentiometers and more particularly rotaryl potentiometers specially adapted for construction and utilization in miniature and subminiature sizes.

The herein invention provides a novel design and configuration for this type of potentiometer making possible the construction of an extremely compact device such that a potentiometer can be built having approximately one-half the size of heretofore known potentiometers having similar or superior ranges of performance.

Theinvention features a unique design wherein the potentiometer housing is formed in two sections enclosing terminals and providing a configuration having within it a toroidal or doughnu-t-like cavity in which are mounted one or more adjustable circular resistance elements, a circular preferably wafer thin contactor member n vdual turns or multiple turns in a type of device utilizing a resistance member in the form of a flat helix or spiral.

The particular configuration of the invention has the further object and provides the additional advantage of facilitating the gauging of a plurality of the potentiometers on a common shaft in such a manner as to provide a very compact ganged assembly and one which is particularly short in axial length and being an improvement over prior art devices in this respect.

- In addition to the foregoing stated objectives and advantages of the invention, it has the further objective of improving the operating and performance characteristics of the devices by providing humidity sealing individually and between ganged sections and at points of lattachment of terminals.

Another object is to improve the antivibration characteristics of a potentiometer by providing a configuration as set out in the foregoing, wherein molded in wiper contactors or brushes are sandwiched in the toroidal cavity between a resistance member and a contactor member and further by providing plural iexible lingers engaging each of the elements.

Anotheriobject is to provide a potentiometer configuration which is rotative for phasing when a group of potentiometers are ganged without breaking humidity seals between units.

Another objective is to provide a configuration as set out in the foregoing specially adapted to provide for and make possible the utilization of dual composition or multiple turn resistance units in housings of the same size as normally utilized for single turn un-ts.

-Another object is to provide a potentiometer configuration as set out in the foregoing, wherein a wire or other resistance element having a single turn for example, and a resistance up to 200K ohms may be assembled in a housing of approximately inch diameter.

Another object is to provide a potentiometer as in the foregoing having a radial stem carrying the wiper contacts or brushes and improved means for accurately guiding the rotative movement comprising a generally spherical ball on the stern moving in a toroidal guide channel in the housing. t

Another object is to provide a potentiometer design operable at temperatures of approximately 200 C.

Further objects and numerous additional advantages of atent the invention will become apparent from the following detailed description and annexed drawings wherein:

In the drawings:

FIG. l is a sectional view of a preferred form of the invention showing potentiometers ganged on a shaft;

FIG. 2 is an end view of the structure of FIG. l;

FIG. 3 is a detail view of one of the circular contact members and its connection to a terminal;

FIG. 4 is a detail view of another of the contactor members and its connection to its respective terminal member; and

FIG. 5 is a detail View of the connection of the terminal members to the circular resistance element.

FIG. l of the drawings shows in section a group of three of the potentiometers segmented together on a common shaft. Each 'of the potentiometer units individually is formed in sections. Depending upon the operating temperature to which the units are to be subjected, they may be made of different materials. For example, for higher temperatures the sections and certain other parts may be made of stainless steel and the insulative parts of molded Teflon. For lower temperature units operating at, for example, up to C., the housing sections may be made of anodized aluminum material or the sections or segments may be molded of commercial grade phenolic, that is, plastic material.

In FIG. 1 of the drawings, the three ganged potentiometers are designated generally by the numerals 10, 11 and 12. The rst potentiometer to the right designated by the numeral 10, is formed of two mating sections as designated at 14 and 15 having the shape and configuration as shown in cross-section in this figure. The section 15 has an extending boss or threaded f1tting 17 and/or servo mounting adapted for mounting the unit and the two sections have central bores as shown, for coaxially mounting them on an operating Shaft 1S. Section 14 may have molded in place bracket 9 for virtually any mounting situation. Unit 12 may have a corresponding bracket.

The sections 15 and 14 have facing annular arcuate depressions as indicated at 20 and 21 respectively; the two sections tit together and the depressions 20 and 21 are of a size to form a toroidal cavity within the housing formed by the sections, or the cavity may be considered substantially doughnut-shaped. The central parts of the sections 14 and 15 are spaced apart as shown, and the sections have additional annular grooves or depressions which are arcuate in cross-section as indicated at 23 in section 15 and at 24 in section 14. These depressions as between the two sections form a second toroidal cavity in the housing having a purpose which will be referred to presently.

The outer edges of the sections 14 and 15 lit together and at angularly spaced points the outer edges of each section have arcuate cavities or depressions so that when the sections fit together, radial openings are provided as indicated, for example, at 26 to receive the mountings of the electrical terminals. Three radial openings such as 26 are provided at the top and botto-m of the potentiometer unit or on opposite sides, as may be seen in FIG. 2 of the drawings.

The section 15 has a counter bore 27 on the inside thereof and fitting in this counterbore is a sealing member 23 having a U-shaped cross section as shown. The sealing ring 28 is of a known commercial type made of a material suitably adapted to humidity seal the unit-as rcspects the shaft 18. Alternatively a miniature ball bearing may be provided in counter bore 27 or both the ball bearing and the sealing ring may be provided. Section 14 has cavity 29 and sealing O-ring 30 which bears against stem 40. Cavity 27 may have a similar O-ring with the rings frictionally engaging stem 4) to provide for example, tive inch-ounces of drag between the shaft and stem.

j, helical winding of wire on a base iform or adjustable mandrel which, in this instance, is ring-shaped, that is, toroldal-shaped.,l Preferably in fabricating these ringshaped resistance members, this is accomplished by splitting a helical unit lengthwise along one side and thenV joining Vthe ends of individual convolutions to form a ring. Helical windings adjacent the joint are stripped away to provide for the terminal connectionsto the ends of the resistor element lthus formed. A unit thus formed vis shown in FIG. 5.

The adjustable resistance elements or units 32 and 33 "are preferably cemented into the section 14 against a side wall of the toroidal cavity as shown. FIG. shows by vWay of example one of the resistance elements and the connections of the Iterminals thereto which will be referred to again presently.

'Within rthe toroidal cavity opposite the resistance elements,that is spaced axially therefrom, on the inside of theopposite wall of the cavity, are disposed preferably wafer thin, eg. approximately .003 inch thick, ring-shaped contacter members as dsignated at 35 and 36. The two 'contactor members are spaced from each other and insulated from each other as may be seen. The configuration yof these contactor members is shown in detail in IFIGS. 3 and 4. These members are cemented against the internal side wall of Ithe toroidal cavity, that is, against lthe section 15. With reference to .the `electrical elements .1n the toroidal cavities, other types may be employed and of other materials such as carbon'or graphite.

The device bein-g described provides for a dual output, that is, there are two circular resistor elements with their cooperating circular contact members and three `terminals are provided as will be described, associated with each l'of the dual outputs.

` elements V32, and 33 and their respective contactors or l'contacting members 35 and 36. Oppositely disposed brushes or wipers are provided in diametrically opposed positions since, as stated, the unit is of the dual output type. In FIG. 1 numeral 40 designates a tube extending 'transversely through an aperture in the shaft 18 and in the space provided between the central portions ofthe sections 14 and 15. Numeral 41 designates a fabricated block of insulating material, preferably Teflon, having a cylindrical stern 42 which is self-threading and adjustable, which is threaded into the internally threaded end of the tube 40 to hold the wipers or brushes in position. The wipers or brushes themselves are in the form of a plurality of flexible contacting ngers 43 which have por- 'tions extendin-g through openings in `the block 4I and yangular portions as shown which on one side engage the resistance elements 32 and 33 and on the other side engage thercircular contact members 35 and 36. The material of the wiper fingers themselves may be a material known commercially as Palinay wire. These flexible fingers, as may be seen, bridge the resistance element 32 to the circular contactor 35- and the resistance element 33 to the con- Y tactor element 36. `Wiper fingers 43 may be molded into block 41.

annular Vgrooves or depressions 23 and 24 formed in the sectionsvlS' and 14 `which are of a size that Iball 46 engages the surface 24. The member 46 is of precision construction and rolls on its shaft for accurate and precise positioning and guidance of the Fwipercontacts in the toroidal cavity and prevents back-lash. Member 46 and a similarV member in potentiometer 12 axially position the shaft 18,.

as may be observed from the drawings.

The construction of the brushes or wipercontacts at the opposite end of the tube 40 is identical and will not therefore be described in detail. The guide rnechanismvincluding the spherical member 47 at the opposite end of the .tube 40'is also the same. The'constructionas just described contributes to precision and` vhigh resolution in the potentiometer unit and to its' improved vanti-vibration and anti-back-lash characteristics. Y

The three upper terminals of `the potentiometer unit are designatedl at S0, 51 and 52 in FIG. 2,-and the three lower terminals are designed at 53, 54 and 55. As shown, these terminals are of a turret type made of asuitable conducting material. Each of these terminals fits within a hanged insulative bushing as shown by way of example at 60 for the terminal 54 Vin FIG. 1. 26, as previously described,V is fitted with one ofthe hanged bushings 60. yThe bushing 60 has anrinternal ange as shown at 61 which engages within the toroidal cavity as shown in FIG. 1, and an external flange 62 which lits against the outside of the `housing as shown. As may be seen in FIG. 3, a contact'strip or strap 64 connects to an edge of the contact member35 and leads up into the bushing 60 and has an end portion or tab-65 which engages the end of the terminal as shown and is held thereagainst by suitable means. The connection to the contactor member 36 is similar, there being a longer contact strip or strap 63 extending up into the bushing and being similarly held against the end of the terminal member. The connections to all of the external terminals connected to circular contact strips in the unit are the same. The terminals may be of molded-in-place construction.

FIG. 5 shows the manner of connecting the terminals to the ends of the circular resistance elements, `for exam'- ple, the element 32, as shown in FIG. 5. The terminals are shown in this figure by way of example as being terminals 51 and 52 connected as by means of conducting elements 71 and 72 to the ends ofjthe winding forming the resistance element 32, this latter element having a central core, or mandrel, as shown at 73.

The section 1K4 of the potentiometer'unit lil `has a central circular depression or inset as shown at 76 the purpose of which is to provide for intertting engagement with another potentiometer unit when the units are ganged on a common shaft, the gauging being accomplished 1in a way resulting in a'minimum axial llength of the assembled unit.

The potentiometer units 11 and 12 'are the same as vthe unit 10 which has been described in detail except for specific features which in themselves will be ydescribed hereinafter. Optionally the shafts of units may bekeyed together by male and female joints as shown at 81l thus segmenting the units adapting them especially as trimmers.

Section 15 of the unit 11 has a circular boss or raised portion 77 which fits into the depression `or inset 76 in the unit 10 when the units are ganged and the units are cemented together vat this joint Vin a manner to provide for humidity sealing. Also, Vthere is vin theboss 77 an annular groove or depression 78 which fitsg'a sealing O-ring 79 of a 1material adapted for providing humidity sealing between sections. y The unit 11 has provided a 'hub 84 which may be secured on the shaft 18 by way of pressed in ipins 484. Fl`he hub 84 has Oppositely disposed radial openings or vchannels and these channels are adapted to'rec'eive tubes as shown at S5 and 86 which form legs carrying the Contact brushes or wipers, as described -in connection withk potentiometer 10. Phasing as between units \may `be Each of the holes f accomplished by circularly adjusting the position of the hub 84 on the shaft 18.

The potentiometer unit 1.2 is like 11 except that its section 14 has a central cylindrical cavity 89 having mounted in it a ball bearing including a bushing as shown at 90, and a ring member 91 forming a ball race for the ball bearings as shown. The end of theshaft 18 is received in the ball bearing which is a subminiature type wherein precision balls 91' ride in place to prevent backlash. 'l

In operation the unit 10 may be mounted by way of the screw threaded nipple or boss 17 and/ or servo-mount. The shaft 18 is rotated in response to any appropriate input and corresponding voltages are taken off from the terminals 50 to 55 with reference to the unit 10. The output is dual, as explained, the separate outputs being by way of the terminals at the top and bottom, as seen in FIG. 2.

When ganged, the potentiometers are sealed together as described and the outputs are taken off in a corresponding manner. The units are rotative for phasing when ganged without breaking the humidity seals.

The units may provide one turn or dual turns or multiple turns, which would be by way of a fiat helical resistance element, or composition substantially filling the cavity 21. The device has the advantage that the same size housing may be utilized for a single turn or dual turn or multiple turn element. Units having an unusually wide resistance range can be made in smaller sizes and particularly with a shorter axial length. In addition to the advantages previously set forth, it has been found that potentiometers constructed in accordance with this invention have shown improvement in noise level characteristics, life of instrument, torque, moment of inertia, linearity, and in other respects due to simplification and compactness of the design.

The foregoing disclosure is illustrative of a preferred form of the invention and is to be interpreted in an illustrative rather-'than a limiting sense. Various modifications and alternatives may occur to and be adopted by those skilled in the art without departing from the spirit and scope of the invention, which is to be in accordance with the claims appended hereto.

What is claimed is:

l. In a potentiometer, in combination: a resistance element of circular form, a circular contact member spaced axially from the resistance element, housing means having a central shaft enclosing said resistance element and contact member, rotatable contacting means disposed between the resistance element and the contact member and engageable with them, said shaft having a rigid radial stern carrying said rotatable contact means, the said housing means having a configuration to form an internal cavity of toroidal shape having the resistance element and circular contacting member disposed in said cavity and the contacting member being arcuate in cross-section adapting it to fit against the interior of the toroidal cavity.

2. In a potentiometer, in combination: a plurality of resistance elements of circular form, a plurality of circular contact members spaced axially from the resistance elements, housing means having a central shaft enclosing said resistance elements and contact members and rotatable contacting means disposed between the resistance elements and the contact members and engageable with them, said shaft having a rigid radial stem carrying said rotatable contact means and said housing having aconiiguration to form an internal cavity of toroidal shape having the resistance elements and circular contacting members disposed in said cavity.

3. In a potentiometer, in combination: a resistance element of circular form, a circular contact member spaced axially from the resistance element, housing means having a central shaft enclosing said resistance element and contact member, rotatable contacting means disposed between the resistance element and the contact member and engageable with them, said shaft having a rigid radial stem carrying said rotatable contact means, the housing means having a configuration to form an internal cavity of toroidal shape having the resistance element and circular contacting member disposed in the cavity, and the housing being formed by two generally circular sections each having a cavity portion formed in it.

4. A potentiometer as in claim 3, including a second similar potentiometer adapted to be ganged therewith on a common axial shaft, said two potentiometers having adjacent sections having configurations adapting them to closely interft together.

5. A structure as in claim 4, including humidity sealing means interposed between the two interftting sections of the potentiometers.

6. A potentiometer housing comprising generally cir-l cular mating sections having a configuration to form a structure having a toroidal-shaped cavity within it, circular resistance means and a circular contact member within the cavity spaced axially from each other, rotatable electrical contacting means positioned between the resistance member and the contact member, an axial shaft having a radial stem for rotating the contacting means, said sections having a space between their central portions to accommodate said stem, rotatable contacting means including a guide member disposed on the radial stem, and said housing sections having oppositely disposed annular grooves forming a circular channel in which said guiding member moves.

7. A potentiometer as in claim 6, wherein said channel is toroidal and said guide member is generally spherical having engagement with one side of said channel.

8. A potentiometer housing comprising generally circular mating sections having a configuration to form a structure having a toroidal-shaped cavity within it, circular resistance means and a circular contact member within the cavity spaced axially from each other, rotatable electrical contacting means positioned between the resistance member and the contactor member, an axial shaft having a radial stem for rotating the contacting means, said sections having a space between their central portions to accommodate said stern, a second similar potentiometer adapted to be ganged with said first potentiometer and mounted on a common shaft, said two potentiometers having adjacent housing sections having a configuration to interft each other forming a ganged structure of relatively short axial length, and humidity sealing means' interposed between the two potentiometers around the coaxial shaft.

9. A potentiometer structure as in claim 8, including two circular resistance elements of different adjustable diameters within the cavity in the housing and two circular adjustable contact members of different diameters within the housing, and a plurality of radially extending terminals extending radially from the cavity within the housing, said terminals being in two sets diametrically opposed on the housing, one set having connections with one potentiometer formed by a resistance element and a contacting member, and the other having electrical connection with a second potentiometer formed by a resistance element and a contacting member.

References Cited in the file of this patent UNITED STATES PATENTS 2,551,989 Wilson May 8, 1951 2,595,189 Dewan Apr. 29, 1952 2,798,926 Mucher July 9, 1957 2,881,295 Brown Apr. 7, 1959 2,898,567 Drewitz et al. Aug. 4, 1959

Images