US2041380A - Adjustable resistance - Google Patents

Description

May 19, 1936. E. R. STUEKLE 2,041,38

` vADJUSTABLE RESISTANCE Filed July 7, 1955 4 sheets-Sheet l V Abw. l

1N VEN TOR.

May 19, 1936.

Filed July '7, 1953 4 Sheets-Sheet r2 Ms 72.1% v PWM@ l ATTORNEY;

May 19, 1936. ERSTOEKLE 2,041,380

ADJUSTABLE RESISTANCE Filed July 7, 1933 4 Sheets-Sheet 5 mmw y ATTORNEY May 19, 1936. E. R, rSTQEKLE 2,041,380

ADJUSTABLE RES I STANCE Filed July '7, 1953 4 Sheets-Sheet 4 j? l @w f7/ l O fg/4;

INVENTOR.

ATTORNEY;

Petenied v,Mny i9, 193,6

UNITED STATESl PATENT l,o1-"FICE 2,041,380 ADJUSTABLE RESISTANCE Erwin R. Stoekle, Milwaukee, Wis., assignor to Central Radio Laboratories, Inc., Milwaukee, Wis., a corporation of Wisconsin Application July 7, 1933, Serial No. 679,291:

\ 25 Claims.

This invention relates to an limprovement in adjustable resistances of the type wherein a ilexible contacting strip is interposed between a resistor and an adjustable pressure pad or movable 5 contact member. I

` nection and a protection of the resistor againstV undue or injurious abrasion;

With the type of resistor contemplated by the present invention it is usually advantageous tofabricate the resistance element initially in the form of a straight flexible strip such as a. strip of cardboard or -paper or other flexible material having applied thereto a resistive coating of carbon, or the like. Afterwards the stripis flexed .into curved form as, for example, a cylindrical form whereby variations in the value of eifective resistanee may be had by rotating an adjustable contact member or pressure pad. r

With the present invention, the mounting of the resistor, its protective contacting strip and the cooperable pressure pad or movable contact is such as to provide for a substantially complete rotation of the pressure pad or movable contact member, the mounting occupying a minimum of space andthereby resulting in maximum adjust-- ability of the resistance. Furthermore, the same e means which holds the resistor iny place upon its base or housing presses terminals rmly into electrical contact therewithand does this in such manner that the terminals do not interfere with the adjustable pressure pad or contact member being brought into very close proximity thereto. The structural' organization is such as to facilitate easy removal and replacement of resistors whereby resistors of different values may be conveniently employed.

A further object is to'provide an adjustable resistance having these 'advantages and capacities,

' which is simple and durable in'construction, reliable and effective in operation, and susceptible of quantity production at a low cost.

Other objects and advantages reside in certain novel features of the construction, arrangement andcombination of parts which will be hereinafter more fully described and particularlypointed out in the appended claims, reference being had to the accompanying drawings, forming a part of this specification, and in which:

Figure 1 is a. View partly in transverse diametric cross section and partly in elevation showing an (c1. :o1- 5.5) l

adjustable resistance embodying the present invention, the cover plate for the' housing thereof being omitted;

Figures 2 and 3 are sectional-views taken on lines 2-2 and l-lvres'pectively, of Figurel, the contacting strip being omitted in Figure 3 for the sake of simplicity in illustration; y

Figure 4 is a view in cross section taken online `44 of Figure 2, parts being shown in elevation for the sake of illustration; i e

' Figure 5 is a fragmentary view in cross'section.` taken online 5-5 of Figure 3, parts being shown in elevation for the sake of illustration;

Figure 6 is a group view in perspective illustrating-the parts oi' the resistor prior to assembly, 15\

two oi' the terminals, however, being shown as; sembled with the insulating base or housing; 4

Figure 'I is a view partly in plan and partly in ysection showing another embodiment of the invention, vthe cover lplate of the housing being omitted;

Figure 8 is a view in transverse cross sectionv j taken on line 8-8 o! Figure l'7, parts being shown in elevation for the sake of. simplicity in illustration;

Figure 9 is a similar view in fragmentary cross section taken on line 9-9 of Figure 7:

Figure l0 is a viewl partly in transverse cross section and partly in. elevation, the plane of the parts shown in cross section lying in line il--I' of` Figure 7;

Figure 11 is a plan view showing still another form of the invention, the cover plate being omitted for the sake of simplicity in illustration;

Figures 12 and 13 are views in transverse cross .section taken on lines IZ-I 2 and |3-I3, respectiveLv, of Figure 11, and parts being shown in elevation for the sake of simplicity in illustration;

and

in elevation for the sake of illustratiom Referring to the drawings, and more particu- 1an-1y to Figures 1 to s, inclusive, it'wiu be seen 'such .as shown generally at '4 in Figure ,6.v

Within the housing la resistor 5 is provided. The resistor 5 may be of any'suitable type. It may be a wire wound resistor but usually and preferably it consists of a flexible strip such as 55 Figure 14 is a fragmentary sectional view taken 4 on' line I4-H of Figure 11 and with parts shown.

cardboard or paper or other flexible material which has a resistive coating such as carbon or the like applied to its inner face. initially the resistor 5 is fabricated in the form ot a straight exible strip which is afterwards exed or curved to cylindrical form to correspond in contour to the cylindrical body 2 of the housing whereby it may be dispose-d flush up against the inner sur face of the body portion 2 of this housing. In the assembly, the ends of the resistor 5 abut ribs 6 which may be molded integral with the housing I. Terminals 1 and 6 are provided and have electrical connection with the ends oi the re-l sist-or 5.

The terminals 'I and B are oi similar construc tfon and each has a stepped body portion il which, in the assembly, is snugly seated in a correspondingly formed recess il! provided thereu for in the end wall 3 of the housing i as shown to advantage in Figures 5 and 6. lntegral'with. the body portion 9 of each terminal is a tang il of less width than its body portion il and which extends out through an opening Vi provided in the housing to facilitate connection of yconcluetors with the terminals. A clamping lug lEi is integrally formed with the body portion of each terminal and is of arcuate form so as to have .firm clamping engagement with the adjacent portion of the resistor 5 for the purpose of establishing electrical contact `therewith and to aid, to some extent, in holding the resistor in position.

In the assembly, the clamping lugs i3 of the terminals are pressed into hrm clamping engagement with the resistor and the resistor is clamped against the housing by suitable means and preferably by means of an expansible Washer I5. The washer may be notched as at l5', the notches accommodating the lugs I3 and allowing the periphery of the washer to clamp the resistor against the housing` The washer I5 consists of a flat disc of insulating material, the center of which is cut out as at I6. At one point the washer I5 is split as indicated at l1. The central cut-out in the disc is bounded in part by surfaces I6 designed to eoact with an expanding member as will hereinafter appear.

On the top of the washer I5 is a flanged conducting ring 2D secured in position on the Washer by means of a rivet 2I which also serves to connect this ring 20 with. a third terminal 22. In the assembly, the washer I5 rests flatly against the bottom wall 3 of the housing I and its terminal 22 projects exteriorly of the housing through` an opening 23 provided therefor. The washer I5 is centered or located in proper position in the assembly by means of a centering or locating pin 24 which may be molded integral with the end wall of t'ne housing and which projects up through the split I1 of the washer and through a notch 25 in the ring 20.

A flexible contacting ring 26 is provided and may be formed from a strip ofsuitable flexible metal, the strip being bent into circular form and has itsends overlapped and soldered or otherwise suitably secured together. A slot 21 is formed in the overlapped ends of the strip and receives a tongue 28 integral with the flange 20 of the ring 20. The lower edge portion of the' ring 26 is inwardly curved as at 26 so as to be interlocked with the correspondingly curved flange 20' of the ring 20. The interengagement of the curved edge 26' and the engagement of the tongue 28 with the slot 21 holds the strip 26 against axial displacement while leaving the same free to be bushing 35 is threaded to receive a nut lill.

deformed radially outward into contact with the resistor li throughout the extent of the strip.

Substantially any portion oi the flexible con tact strip 26 may be pressed into engagement with the conductive coating of the resistor 5 by means of a pressure pad or button 3i] of insulat ing material carried by a spring arm 3l or arcuate form, one end of which is riveted or otherwise suitably fastened to the outer end of a radial arm 3l. The arm 32 is riveted er otherwise fixed to the inner end of a rotatable shaft 33, the outer end of which carries a knob 3l! whereby it can be conveniently turned. The shaft 33 is rotatably iitted in a mounting bushing 35 which extends through the cut-out or opening in the washer i5 and Ithrough an opening 3 provided thereier the end wall 3. Adjacent its inner end this mounting bushing 35 has a shoulder 36 which, in the assembly, abuts the apertured plate portion 3l of a stop finger 3B, The inner portion of this tween'the threaded portion 39 of the bushing 35 and the shoulder 36 thn outer periphery of the bushing is smooth and tapered. as at lli.

is pulled through the washer l5 and engages the surface lil to expand the Washer thereby causing the periphery oi the washer to press against the lugs i3 and cause these lugsto have clamping engagement with the resistor to secure the same in place and establish electrical Contact between the terminals and the resistor. The shoulder holds the stop plate 3l and Washer I5 in posi tion and as the flexible contacting strip 26 is in tercngaged with the contact ring 26 and as the y latter is fastened to the washer l5, the Contact ring Ztl is also held in position. Thus, a single fastening means, the nut 49, secures all of the parts in proper assembly and provides for the easy removal and replacement of any of `these parts. lt will be understood that the stop finger 38 is engageable with the arm 32 to limit the rotation of this arm in either direction. Lugs 3l" en the plate 3l engage the shoulder 36 and in a recess 3' in the end wall 3 to locate the stop fin ger 38 and to secure the bushing 35 against turning. Stop finger 38 also exten-dsV through slot `IIL* in the cover 4 and on being bent at a right angle serves to prevent the cover from coming off.

The arm 32 isshown as provided lwith a pro jection 32 utilized in many instances for interlocking the adjustable resistance with a switch mechanism (not shown) but as the switch mechanism and interlocking feature form no part of the present invention they need not be described.

contacting strip 26. As shown in Figures 7 and 9 the terminals 'I' and 8 for the resistor 5 may be provided with lugs Ii and 6a firmly clamped against the resistor 5 by the expansible washer I5. As illustrated in Figures 7 and 10, the contacting strip 26 has its overlapped ends secured by i means of a rivet 5|) Ito the upstanding portion 5I of the third terminal -53 which is fitted in and projects beyond an opening 54 provided therefor in the housing.

The adjustable contact means or pressure pad When the nut Ml is tightened up the tapered portion 1li in this embodiment includes as before a shaft 33 rotatably mounted in a bushing 35 held in position by means of a nut 40 and having a tapered or inclined portion 4| for expanding the washer in this form of .the invention. However, the pressure pad 30, its spring arm 3| and radial arm 32 are omitted and in lieu thereof a rotatable ring 55 is provided and has its hub 56 appropriately fastened to the inner end of the shaft 33. 'Ihe radial arm 51, which is integral with and connects the hub with the ring 55, is

provided with a radial socket or recess 58 in which a pressure pad? or button 59 is slidably fitted. A spring 60 urges the pad or button outwardly.

It is to be understood that the ring 55, its hub 56 and the arm 51 may -be molded from suitable insulating material, such as phenol condensat composition or the like. l s.

In the embodiment of the invention shown in Figures 11 to 14, inclusive, the insulated base or housing is designated generally -at 6| and has flaring side walls of body portion 6| with an invtegral end Wall 62 at the small end thereof. The open end of the housing may, asin the previous embodiments, be closed by a removable cap or closure.V ,A resistor 63 in the form of a carbon coated flexible strip or the like is fitted against the inner surface of the body portion 6| of the housing and is held inl proper position thereagainst by means of an expansible Washer of insulating material designated at |5' and corresponding in structure and operation to the washer |5 of the embodiments previously described, in

Vthat it is split as shown at 64 and is expanded to cause lugs 65 of the terminals 66 to clamp the resistor in position. As in the previous embodiments a mounting bushing 35 having a tapered portion 4| acts under the influence of a nut 40 .to expand the washer I5.

In the present embodiment of the invention a conducting ring 61 is held in position on the washer 'l5' by the action of the bushing 35 exerted through a washer 68 and by lmeans of a rivet 58` which secures the ring and a terminal 69 to the washer and electrically connects the ring and terminal. An intermediate contact strip is provided and is 'of conical form, the

lower and smaller end of the strip 10 being interengaged with a correspondingly viormed flange r|51' of the ring 61, and being further held in position by means of ak lug 1| integral with the ring 51 and extending through anropening or slot 12 in the strip.

, To the inner end/vof the lshaft 33 a movable contact arm 13 is riveted'or otherwise securely fixed. 'I'his arm13-is of resilient metal land carries 'at its outerrend a contact button or pad of insulating material. The arm 13 is so bent and 'flexed or-tensioned that under the influence of its inherent resiliency the button or pad 14 presses against the contacting strip 10 whereby the portion of the strip engaged by thepad or button L will be deformed or flexed outwardly into contact with the resistor as will be understood from Figures 11 and V12. A stop finger 15 is provided Vand is engageable with 'the arm 13 for positively-limiting its movementA in either direction. The finger has an integral attaching platen connned between nut 4l and the housing Il and the intermediate portions of the finger passes vthrough opening provided' therefor vin the end wall l! of the housing, the washer I il and the conducting ring or disc I1.

` In all of the embodiments of the invention the advantages of compactness, simplicity and economical manufacture, along with efficiency in operation and durability, are realized. Furthermore, the elements of the adiustable resistance are 'organized in such a novelV manner as to be 5 conveniently assembled and disassembled for the purposes of replacement or repair. Along with these practical advantages there is preserved the features of protecting the resistor from undue abrasion upon adjustment and of obtaining a large range of adjustment and utilizing a maximum ,of effective length of resistor.

The invention lends itself to the use of any desired number of terminals and, if desired, to the use of the sfo-called tap terminals. The several modifications may be employed singly or in multiple as desired. For example, several units of the same type may be clamped together and simultaneously operated. In the forms of the invention utilizing the contact rings such as the contact ring (Figures 1 to 6) or the contact ring 61 (Figures 11 to 14) the third terminal may be omitted or not used and the contact ring may be grounded by connecting it to the bushing 35.

While I have shown and described several constructions in which the invention may be embodied, it is to be understood that the constructions shown have been selected merely for the purposes of illustration and that various changes in the size, shape and arrangement of the parts and in the materials employed may be resorted to'without departing from the spirit of the in-l vention or the scope of the subjoined claims.

'Ihe invention claimed is:

1. An adjustable resistance comprising a housing, a resistor therein, terminals engageable with said resistor for establishing electrical contact therewith, a member within the housing for pressing said terminals against the resistor, means for securing the member in position in the housing and having an expanding action on Said member to press the terminals against the resistor, and adjustable contact means cooperable with said resistor, said member securing p means also providing a mounting for the adjust- .45

, minals to clamp them against the resistor and tofclamp the resistor against said housing and ,55 means for deforming said member and securing it in positionin the housing.

3. An adjustable resistance comprising a housing, a resistor disposed against a wall thereof,

terminals engageable with said resistor, a deformable member engageable with said terminals to clamp them ,against the resistor, adjustable conf tact means cooperable with said resistor, a'mounting for said adjustable means, said mounting, in

vits operative position, being cooperable with said 55 deformable memberto deform the same to press the terminals against the resistor, and means for securing said mounting in operative position in said housing. i

4. An adjustable resistance comprising a hous- .70 ing, a resistor disposed within thehousing and comprising a strip and resistance means carried thereby, terminals projecting exteriorly of the vhousing and having portions therein overlapping the inner surface of the resistor, adisc-like expansible member Within the housing, and having peripheral engagement with the last named portions of the terminals, means for expanding said member into edgewise abutting engagement with the portions of `the terminals overlapping the resistor to clamp the terminals against the resistor, and adjustable contact means cooperable with said resistor.

5. An adjustableV resistance comprising ahous lng having a curved interior wall, a resistor dis posed in the housing against and conforming to the curvature of said Wall and comprising a strip carrying resistance means thereon, an adjustable contact means cooperable with said resistor and disposed in the housing for rotation about an axis substantially' co-axial 'with the said curved interior Wall, an cxpansible Washer in the housing in transverse relation to said axis and having peripheral engagement with said resister, and means for expanding the Washer in the plane thereof to clamp the resistor against said wall.

6. An adjustable resistance comprising ahous ing, a resistor disposed within the housing and against a wall thereof, an expansible washer in said housing, means for expanding said Washer to cause it to clamp said resistor against the wall of the housing, a flanged contact member carried by `said Washer, a contact strip intercngaged with the flange of said member and overlying said resistor and adjustable means for pressing various portions of said strip along its length into engagement with said resistor.

'1. An adjustable resistance comprising a housing, a. resistor disposed within the housing and against a wall thereof, a'n expansible washer in said housing, a mounting bushing having a tapered portion engageable with the expanding washer, means coacting with the bushing for causing said tapered portion to expand the washer, and adjustable contact means supported on said mounting bushing and cooperable with said resistor.

8. An adjustable resistance comprising a housing, a. resistor disposed within the housing, a i

contact ring xed n said housing, terminals for said resistor and said contact ring, a flexible contact strip overlying saidvresistor, said contact strip and said contact ring lying in different planes and having portions loosely, but positively interengaged to prevent axial shifting of the contact strip while providing for lateral displacement thereof, means for preventing bodily displacement of said contact strip, and adjustable contact means cooperable with said strip for displacing portions thereof into engagement with said resistor.

9. An adjustable resistance comprising a housing, a resistor disposed within the housing, a flanged contact ring fixed within the housing, terminals for said resistor and said contact ring, a contact strip overlying ,the resistor in transverse relation to said contact ring and having a portion engageable with the flange of said, contact ring, means for preventing bodily displacement of said contact strip and adjustable pressure means cooperable with said strip for displacing portions thereof Ainto engagement with the resister.

1`0. An adjustable resistance comprising a housing. a resistor disposed within the housing, a contact member xed within the housing, termlnals for the resistor and the contact member, a contact strip overlying said resistor, said contact member and said contact strip having portions at least of approximately conical form,

said portions being interengaged to hold the contact strip against axial displacement while providing ijor lateral outward displacement thercoi", and adjustable pressure means cooperable with said strip for displacing portions thereof laterally outward and into engagement with said resistor'.

ll. An adjustable resistance comprising ahous ing, a resistor disposed within the housing, a

contact member fixed Within the housing, a conl.

having portions engageable with the resistor. a i

split expansilole Washer having its periphery err1 gageable 'with said portions of the terminals, means for expanding the Washer `to cause it to press said portions against the resistor and thereby clamp the resistor in position as Well as establish electrical connection between the terminals and the resistor, and adjustable contact means cooperable with said resistor.

13. An adjustable resistance comprising an insulating housing, a resistor disposed Within the 1"" housing and against a wall thereof, terminals having portions engageable with the resistor, a split expansiblc washer having its periphery en gageable with said portions of the terminals, a

mounting bushing having a tapered portion engageable with said split Washer for expanding the same, a nut threaded on said bushing and cooperable with the housing for securing the bushing in place and causing its tapered portion to expand the washer into engagement with the L terminals whereby to cause the terminals to clamp the resistor in position, and rotatable contact means mounted on said bushing and cooperable with the resistor.

14. An. adjustable resistance comprising a housing, a resistor disposed Within the housing and against the wall thereof, terminals engageable with the resistor, expansible Washer of insulating material positioned within the housing and engageable with the terminals, a Contact .strip overlying the resistor and mounted on said Washer, a terminal carried by the washer and connected to the contact strip,` means for expanding the washer, and adjustable pressure means for displacing the strip into engagement with the resistor.

l5. An adjustable resistance comprising a housing having a curved interior Wall, a ilexible resistor strip bent to Acorrespond to the curvature of the wall and disposed ilush thereagainst, terminals having portions overlapping the inner surface of the resistor, a disc-like expansible member in said housing in substantially transversel relation to the axis of said resistor and having peripheral engagement with the last named portions of the terminals, acting when expanded to press said terminal portions against the resistor to secure the terminals in position and establish electrical connection therewith, and

Illl

and securing resistor, an expansible member in said housing,

acting when expanded to press the terminals against the resistor to secure the same in position and establish electrical connection therewith, means for expanding said member, in combination with a contacting strip overlying theresistor, means for holding the contacting strip in position while providing for outward displacement of portions thereof into engagement with the resistor, and an adjustable pressure means for displacing various portions of the contacting strip into engagement with the resistor, said expansible member serving as a part of the mounting for the adjustable pressure means.

17. An adjustable resistance comprisingv a housing having a curved interior wall, a ilexible resistor strip bent to correspond to the curvature of the wall and disposed ush thereagainst, terminals having portions engageable with the resistor, an expansible member in said housing, acting when expanded to press the terminals against the resistor to secure the same in position and establish electrical connection therewith, means for expanding said member, in combinationw-ith a protective contacting strip, means for securing said contacting strip to the exp'ansible member to prevent axial movement thereof while providing for outward lateral displacementof portions of said contacting strip, and adjustable pressure means for displacing various portions of said contacting strip into engagement with various portions of the resistor.

18. An adjustable resistance .comprising a housing, a resistor disposed within the housing and against the wall thereof, an expansible washer in said housing, a contacting strip overlying the resistor, means carried by said expansible -washerfor holding the strip against bodily dis- Vvplacement while providing for outward lateral displacement of portions thereof into engagement with the resistor, a rotatable pressure pad for displacing portions of said strip into engagement with the resistor, a mounting for said rotatable pressure pad, and means cooperable with the housing for releasably securing said mounting in position, said mounting having means for expanding said washer to secure the resistor in position and also to secure the washer in position.

19. An adjustable resistance comprising a housing, a. resistor disposed within the housing and against the wall thereof, an expansible washer in said housing, a contacting strip overlyingv the resistor, means carried by said expansible washer for holding the'strip against bodily displacement while providing for outward lateral' displacement of portions thereof into engagement with the resistor, a rotatable pressure pad for displacing portions ofsaid strip into engagement with the resistor, a mounting for said rotatable pressure pad, and means cooperable'with the housing for releasably securing said mounting in position, said mounting having means for expanding said washer to secure the resistor ,in

' position and also to secure the washer in position, in combination with a stop secured in posi- 4 tion in said housing by said mounting.

20. An adjustable resistance comprising a housing having a curved interior wall, a resistor for holding the contacting strip against bodily movement while providing for displacement of portions thereof entirely about the strip into engagement with portions of the resistor, a rotatable member mounted in said housing within said curved interior wall, a spring arm carried by said rotatable member and a pressure pad carried by said arm and engageable with the contacting strip for displacing portions thereof into engagement with portions of said resistor, the resistor and the contact strip being arranged with their cngageable surfaces in substantially parallel relation to each other and to the axis of rotation of said rotatable member.

21. An adjustable resistance comprising a housing, a resistor disposed within the-housing and insulated therefrom, terminals electrically connected to the ends of said resistor, a conducting disc ofsmaller diameter than the inside diameter of said resistor mounted within the confines of the latter in spaced relation thereto and concentric therewith, the periphery of said disc and the opposed surface of said resistor defining spaced contact surfaces, a flexible conducting ring loosely fitting about said disc between the latter and said resistor, a terminal electrically connected to said disc, and adjustable means adapted to ex said ring into rm contact with saidy resistor at-.a variable location along the latter and simultaneously to engage said ring in rm though correspondingly variable contact with the peripheral contact surface of said disc whereby the resistance between said last mentioned terminal and either of said first mentioned terminals may be varied.

22. An adjustable resistance comprising a housing, a resistor in the form of an annulus disposed within the housing and insulated therefrom, terminals electrically connected to the ends of the resistor, a conducting member mounted Awithin the housing and having an arcuate conresistor at a variable location about the latter,

said strip having a loose connection with the arcuate contact surface of the conducting member whereby the strip under' the action of. .the pressure means will retain iirmly contact with the arcuate contact surface as to one portion of the strip as the other portion is displaced member into contact with the resistor.

23. A resistance comprising a housing having a circular wall, a resistor comprising a flexible backing strip having a resistivevcoating applied to one face thereof, said strip being flexed in the assembly with its backing strip disposed against the circular wall of the housing and with its resistive coating spaced from said wall, a. clamping member in said housing and having a substantially circular periphery engaged with the resistor for substantially the entire length thereof, means for causing the clamping member to stantially the entire length ofthe resistor, and

from the adjustable contact means cooperable with 'the resistor.

24. A resistance comprising n housing having a circular Wall, u resistor comprising riexible backing strip having a resistive coating applied to one face thereof, said strip 'being ilexesl in the assembly with its backing strip disposed against the circular Wali of the housing :and with its resistive coating spaced from snm Wall, terminais engageable with the resistive coating' of the re" sistor for establishing elecirieni eontaei there with, and a clamping member imi/ing e, simuler periphery engaged with a portion of the resistor for substantially the entire length thereof and also engaged with the terrnineisT ioi causing the clamping member to einem the resistor between its periphery and. the eireulm" imll oi."

time housing and also to clamp the terminals elg'ainst the resistor7 and adjustable Contact :means eooperabie with the resistor.

25. A resistance comprising a housing having a curved Wall, a resistor comprising a, flexible nack- :ing strip having a, resistive coating on e. surface i? Yi'eoi, said resistor being flexed in essern-l io'iy with its back disposed against salici euri/fed 'mili oi the housing, a clamping member disposed. in tine housing and having e. curved periphery engaged with a. portion of." the resistor for sub stentially iziie entire length thereof, anti means associated with the housing iolm causing the eienn'ping member to clamp the resistor between itself and the housing 'for substantially 'the iuil length of the resistor.

ERWIN R.

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