Патент USA US2138210код для вставки
Nov. ¿29, 1938. N. c. SCHELLENGER 2,138,210 CONTROL DEVICE Filed Feb. 17, 1934 4 Sheets-Sheet l 7 9 @7231/76/5 __“ “umnuunununnnnn O O NOV- 29, w38- N. c. SCHELLENGER I ¿M8210 CONTROL DEVICE Filed Feb. 17, 1954 4 Sheets-Sheet 2 .772 Iren to?? Newtm 6.’ Sc/LeZZeníe?? Nov., 29, 1938u N.f f:A sci-IELLENGER CONTROL DEVICE Filed Feb. 17, 1954 4 Sheets-Sheet 3 204' Nßm? c@„w/dal@œgß wn 6Z n.4/ a Nov. 29, 1938. n N_ C SCHELLENGER 2,138,210 CONTROL DEVI CE Filed Feb. 17, 1934 4 SheeÍs-Sheeî. 4 .7m/@néon New Zan ¿î Sc/zeZZeîz- Q72 Patentedv Nov. 29, 1938 _ i l UNITED STATES PATENT OFFICE> 2,138,210 CONTROL DEVICE Newton C. Schellenger, Elkhart, Ind., assignor to Chicago Telephone Supply Co., Elkhart, Ind., a corporation of Indiana - Application February 17, 1934, Serial No. 711,1644 7 Claims. (Cl. 5301-55) This invention relates to improvements in variable resistance devices of the type commonly ing through the terminal sector on a part of the resistance element that could not be used other employed as volume and tone control apparatus Wise, the present invention allows this to be done in radio sets,`public address systems and the like. more satisfactorily as no portions of the terminal 5 More particularly this invention relates to ter- member lie in the path of the contactor and the 5 minals for variable resistance devices in which contactor can be moved through 360° if desired the resistance element is of the flat composition » Since no portion of the terminal lies in the path type against which. the terminals are adapted to of movement of the contactor, there is no pos be clamped, and relates also, to aterminal co- l Sibilîty 0f engagement between these members 10 operating with other means to make connection with a movable contact member. This invention further relates to a combination variable resistance device of the aforementioned type and a switch or other associated .de-' .15 vice operatively connected to the variable resistance device for operation thereby when the con-tactor or other. adjustable element is moved through a predetermined portion of its travel >normally beyond the end of effective portion of 20 the resistance element. For some time, the radio trade has been de>manding the smallest possible rheostat for volurne and tonev control purposes that can be furnished without sacriñeing smoothness of opera- and hence the present invention eliminates any 10 possibility of sudden variations in resistance due to transient metal to metal contact between the contactor and terminal, and also eliminates any possibility of the scoring of the polished surface of the contactor by the terminal. l 15 It is well known that terminal members have been used to clamp onto wirewound resistance elements in various ways but none of them Vsolved the above mentioned problems. In fact none of them were adapted to clamp onto airagile re- 20 sistance element of the composition type regard less of whether or not the other problems were Solved. One object of this invention is to provide a 25 tion or accuracy of the resistance gradient. In terminal for a variable resistance device that can 25 -order to meet this demand it was necessary to »y be securely clamped in place so that no auxiliary reduce the width of the sector occupied by the holding means are required. resistance element end terminals and the mov- ~ Another object 0f this inVentìOn iS to DI‘OVÍde a »able `contactor terminal to the lowest possible 30 limit in order that the maximum length of effec'tive resistance element might be maintained for useful variation in resistance. - In many cases it is also required that a power switch be added to the variable resistance device 35 and be- operated by angular movement of the operating shaft of the variable resistance device, usually through an angle adjacent one of the , . terminal that makes good electrical contact with the resistance element outside the path 0f the 30 contactor and has no parts directly engageable by the contactor, _ Another object of this invention is to provide a terminal with an ear that can easily be bent into contact with the resistance element without 35 damaging the resistance element. \ Another object of this invention îS t0 Dl‘OVíde rotational limits of the movable contactor. Prior a ñxed terminal means for tapping the resistance to the invention disclosed in my application Se- v element _Outside the Def/h 0f the mOi/able C011 40 rial N0_ 692,665, med October '7I 1933,11; was com.. taeter and at a position intermediate the end 40 mon practice to operate the switch as the movable terminals Without appreeìably affecting the total contactor of the variable 'resistance device apresistance of the resistance element and also pro proached one of the end terminals of the resistviding a low minimum resistance between the ance element. However, to permit this, it was 4 5 necessary to short circuit that portion of the' resistance element vtraversed by the contactor during the switch operating portion of the contactor movement and as a result the expense of l manufacture was increased and the eiîective‘por- terminal and the‘contactor. Another object of this invention is to provide 45 a terminal for the movable contactor which pro vides a positive electrical and mechanical con nection with a member in the electrical circuit between the terminal and the movable contactor. . 50 tion of the resistance element was crowded into a much shorter space which greatly impaired the smoothness of control of the radio set. z Another object of this invention is to provide 50 a terminal that occupies an extremely narrowl sector of the variable resistance device base. While the above mentioned invention made available for operation of the switch, the portion 5,5._ of rotation during _whichthe contactor >was mov- Another object of this invention is to provide a combined variable resistance device and switch _in which the switch can be operated while the 55 o Á 2 2,138,210 movable contactor is moving _through the sector of the base of the variable resistance device oc cupied by the terminals. With the above and other objects in view which will appear as the description proceeds, my in vention resides in the novel construction, com bination and arrangement of parts substantially as hereinafter described and more particularly deñned by the appended claims, it being under stood that such changes in the precise embodi ment of the hereindisclosed invention may be made as come within the scope of the claims. In the accompanying drawings, I have illus trated complete examples of the physical embod 15 iment of my invention in which: Fig. 1 is a plan view of the variable resistance device of my invention with the cover removed; Fig. 2 is a partial elevational view in section taken along the line 2-2 of Fig. 1; Fig. 3 is a sectional elevational view taken along line 3-3 of the rheostat shown in Fig. 1; Fig. 4 is an isometric view of a partially com pleted terminal; Fig. 5 is an isometric view of a. terminal ready 25 to be mounted on the rheostat; Fig. 6 is an end view of one of the terminals of my invention assembled in place in the rheostat; Fig. '7 is an elevational view of the terminal after assembly in the rheostat With the base and 30 resistance element sectioned; Fig. 8 is a view taken from the opposite end of 35 that shown in Fig. 6; Fig, 9 is a plan view of a part of the rheostat base showing notches and holes for mounting of terminals; Fig. l0 is an isometric view of a partially com pleted terminal of slightly modified construction; Fig. 11 is an end View similar to Fig. 8 of a slightly modiñed terminal; 40 Fig. 12 is an isometric view of one element of a two piece terminal; Fig. 13 is an isometric view of the other ele ment of the two piece terminal; ' Fig. 14 is a side View of a two piece terminal assembled in the rheostat, with other parts of the rheostat shown in section; Fig. 15 is an enlarged portion of Fig. 14 showing the bent over end of the terminal; Fig. 16 is a plan view of the terminal of Fig. 14 50 assembled in the rheostat; Fig. 17 is an elevational view, with some parts broken away, of a rheostat with a switch mounted on the cover -and adapted to be operated by ro tation of the rheostat shaft; 55 60 ~ Fig. 18 is a sectional plan view of the rheostat and switch operating member taken along the line l8-i8 of Fig. 17; Fig. 19 is a partial plan view showing the mov able parts in a certain position; Fig. 2O is a partial plan view showing the mov able contactor in a certain position; Fig. 21 is a partial plan view showing the mov able contactor in another position; Fig. 22 is another partial plan view showing the movable contactor adjacent the tap termi na ; Fig. 23 is ariothM partial plan view showing the movable contactor in another position; Fig. 24 is a reduced bottom plan vier.' showing the base with terminals attached; and Figs. 25 and 25 are enlarged frag and sectional views respectively show of - modified construction. Referring to the drawings more in detaii dan, variable ‘resistance device comprises o. i formed of insulating material, such as a phenol condensation product, or the like, on which is mounted a resistance element 3, which may be formed by coating a strip of heavy paper with a carbonaceous conductive composition. In other cases the resistance element may preferably be formed by applying the conductive coating di rectly to the base 2. Usually it is desirable to de posit a low resistance coating on the section of the resistance element that will be engaged by terminals 4 and 5 so that a low minimum re sistance between the terminal and the movable contactor can be obtained. These low resistance coatings are preferably tapered in thickness at the ends so that there will be no sudden change inthe rate of resistance variation as the movable contactor passes from one section to the other, as is shown and described in my copending applica tion Serial No. 666,444, iiled April 17, 1933. End terminals 4 and 5 make connection with the ends 20 of the effective portion of the resistance element 3 and provide a means of connecting an external circuit with the ends of the resistance element. A movable contactor 6 is pressed into contact with the resistance element 3 by the pressure 25 arm l which terminates in a tip 8 that is tapered to engage the edges of the hole 9 in the contactor 6 so as to accurately position the latter on the resistance element. The pressure arm 'I is posi? tioned on the drive plate I0 by two diametrically 30 opposed ears II and I2 formed up from the body portion of the arm 1 on a center line which is at 90° to the center line passing through the tip 8 so as to engage two corresponding notches on the drive plate I0. The drive plate IU is secured to the shaft I4 through the co-operation of a flatted reduced end I5 on the saft I4, a hole of corre sponding shape in the drive plate, and a washer I6 fitted over the reduced ñatted end I5 of the shaft I4 and the flatted end peened over to hold 40 the members all in pressure engagement. Centrally located in the base 2 is a bushing I1 having a shoulder I8 which is knurled around its outer portion to provide teeth which penetrate the surface of the base 2 when the bushing is pressed into place. On the other side of the base 2 is a washer I9 that fits over another shoulder 20 on the bushing. The base 2, bushing I1 and washer I9 are all held securely together by swag ing the shoulder 20 of the bushing into engage ment with the washer I9. Preferably the washer i9 has a tapered hole formed with the large end away from the base so that the portion of the shoulder 20 that extends beyond the washer I 9 before swaging, can be swaged into the hole leaving the mounting surface substantially 55 planar. The shaft I4 is journaled in this bush ing I'I and is positioned longitudinally by a shaft collar 2l and washer 22 bearing against one end of the bushing Il and opposing the thrust be 60 tween the drive plate I 0 and the bushing Il which is exerted by a spring member 23 located between the drive plate I0 and the pressure arm l. This spring member is spaced from the shaft by projections on the rim that form notches which engage the ears II and I2 bent up from the body portion of the pressure arm 1. The body portion of the pressure arm l is pressed against spaced collector ring 24 that is insulated and the bushing by a washer 25 of fibre or other sui"able material and connected to the terminal by a reduced section 2S’ of tail 26 extendir. through a hole §23 in the ear 28 of the 3 2,138,210 drives the pressure arm 1 which is in'engagement with the contacter 6 so that the contacter is moved along the resistance element and passes very close to the bent over ear 50 of the tap terminal 48 and, when no switch is used, the drive plate I8 strikes a suitably positioned stop ear, not shown but similar to 85 (Fig. 18), pro jecting in from the cover 80 so that the contacter 6 comes to rest between the bent over ears 3l and 32 of terminal 4 at one end of rotation. Ro tation in the other direction/is limited by the drive plate I8 striking the stop ear 85 and bring ing the contactor to rest between the bent over ears 45 and 46 of terminalv5. 15 _ Referring more particularly to the terminals of my invention, it is to be noted that` they may be brought very close together and yet allow a I sufficient spacing between terminals to provide the necessary insulation and also to provide a 20 maximumeffective length of resistance element. I have accomplished this by tapering the body section of the terminal so that the angle occupied by the terminal is approximately the same'or in some cases slightly more at the outer end than V25 at the inner end, which provides sufficient strength at the outer portion to withstand the forces that may be imposed during attachment of a conductor. This same effect could be obtained by any means of narrowing the inner end of the 30 terminal such as by providing one or more steps in width of the body portion. The inner end, where great strength is not required, is much nar rower and1 is adapted to be clinched over onto the base or resistance element to hold the terminal 35 in place and in the case of the end terminals, also make contact with the resistance element. Referring more in detail to Figs. 4 to 8, the terminal comprises a terminal proper or body portion 36 which is formed with a head portion 40 38 having ‘ laterally extending wings 38', 38" constituting shoulders, an upturned end portion 34, and an upstanding ear 35. Integral with and extending from the head portion 38 of the ter minal 36 is a connection extension (commonly called at “solder lug”) having a perforated por tion 33 and a neck 44 of reduced width. Adjacent the tip 3l of the upturned end 34 is a reduced section or neck 43 and adjacent the tip 32 of the ear 35 is a reduced section or neck 31. This terminal 4 can be easily manufactured by punching a piece out of sheet brass or other suit below the surface of the resistance element 3 so that when the ltips 3l and 32 are bent over onto the resistance element 3, their contacting sur faces will be substantially parallel with the sur face of the resistance element 3 when they meet the latter, due, as previously stated, to the bends occurring at a point predetermined by the loca tion of the reduced sections. The reduced sec tions also permit the end 34 and the ear 35'to be bent over onto the resistance element 3 with a 10 more even `and accurately predetermined pres sure than would otherwise be possible; Thus a uniform contact pressure between the terminal 4 and the resistance element 3, and consequently, al uniform contact resistance between these ele 15 ments can readily be obtained. Furthermore the provision of reduced sections makes it possible to obtain these results without damage to the very thin and fragile conductive coating of the 20 resistance element. The thickness of this coating is in most cases only one or two thousandths of an inch and as a result the resistance element can be very easily damaged by any excessive pressure on any part of its surface such as would be created by the sur face of the terminal ears meeting the conductive coating unevenly _as they are bent over into their final position. The exact width, length and position of these reduced sections necessary to iorce the bending 30 to occur in them without distorting other parts of the ears and to allow the end to bebrou-ght into viirrn coplanar contact with the resistance element over the maximum area depends largely upon the ' 35 kind . and thickness of metal used for the ter minal and can best be determined by trial. Where it is desired to provide a variable resist ance device having an extremely low contact re sistance between the terminal and the resistance element, a soft pad of conducting material is in terposed between these elements. _ Such an arrangement is shown in Figs. 25 and 26 wherein a pad 38 is constituted of soft sheet metal or metal foil having originally a U shape and is inserted in the openings did, 42d and 45 pushed up against the base 2d. The terminal 4d is then inserted in a manner similar to that de scribed in connection with the terminal 4 and the tips 3 Id, 32d are bent over to clamp the ends 9i, 92 of the pad 9D against the contact surface 50 of the resistance element 3d. ' ` . As the pad y80 is soft it adapts itself to the con able material to shape shown in Fig. 4 with the exception that the ear 35 sheared out of the body tours of the surfaces of the resistance element portion 36 and formed at right angles has no re ' 3d and the terminal 4d respectively and thus has duced section 31. A separate trimming operation an area of intimate contact with both members is employed to cut notchesout of the sides and respectively which is greater than the area of create this reduced section 31 that serves to force contact between the terminal and resistance ele the bending line to the desired point when the ment when these latter elements are in direct contact and no pad is employed. tip 32 is bent over on the resistance element. An equivalent result may be obtained by inter Another. forming operation gives the terminal 60 of Fig. 4 the shape shown in Fig. 5, the shape in posing between the resistance element and the tips which are bent over against the resistance which it is positioned on the base. The extend element a section of soft wire, such as fuse wire; ing wings 38' and 38", formed on a head por tion 38 of the -terminal proper 36 are hooked when the tips are bent ove'r to clamp the ter over the lobe 39 which is integral with the base 2' minals on the base, the interposed wire is fiat and extends beyond the periphery of the cover tened out into intimate contact with the surface of the resistance element and the tips.` This wire (Fig. 18) to actas a terminal support. The ter minal is then slid into the notches 40 and 4l «in thus serves as a cushion for the tips and provides the base until the end 34 starts to enter the hole a low contact resistance between the terminal 42 in the base 2. The body portion 36 of the and the resistance element. No auxiliary parts are required to hold the ter terminal 4 is then pushed up against the under side of the base 2 so that the tips 3| and 32 of the minal in place against the resistance element as this is accomplished by the tips 3| and 32 of the ` end 34 and the ear 35 project beyond the face of the resistance element 3. When in this position end 34 and ear/35 respectively that are bent over 75 the reduced sections 43 and 31 extend slightly 25, 55 60 65 70 onto the resistance element 3 clamping Ithe ter 75 2,138,210 minal 4 tightly to the base 2 and making good electrical contact with the resistance element 3. The reduced portion 44 in the connection ex tension is provided so that it will bend and there by prevent damage to the variable resistance de vice if any excessive bending force is applied to the connection extension, such as might occur when leads to the external circuit are being con nected. Any side thrust applied to the connection eX tension is resisted by the sides of notches 4i) and ¿il and sides of hole 42 bearing against the sides of the terminal. Pressure on the connection ex tension in a direction parallel to the axis of the shaft ill is resisted in one direction by pressure of extending wings 38’ and 38" against the lobe 39 of the base 2 and by a light pressure of the terminal ears and allows a very low minimum resistance to be obtained and also allows the con tactor to be moved past ~the terminal if desired, without touching it or producing any discontinu ity in the nature of the contact between the contactor and the surface of the resistance ele ment, such as might occur if the contacter made direct contact with the terminal. W'hen a switch is to be used in combination back part of the terminal body 3S against the underside of the base 2. With pressure ín the adjacent the notch 40 upward against the base 2. to a position between the ears 3|, 32 of terminal 4 as shown in Fig. 2l, at which point the effec tive portion of the resistance element 3 ends. However, at this point a pin 84 on the drive plate I0 engages an operating member 82 of a switch In Figs. l0 and l1 I have shown another method 25 of obtaining a reduced or weakened section in the upstanding ear and upturned end to pos'í tion the bending line at a point that will allow the tips to bend over onto the resistance element and accomplish the same results outlined above. 30 The reduced section is provided in this terminal |04 by piercing a hole |31 in the ear |35, and a hole |43 in the ear |34 at suitable positions. All other parts of the terminal function in exactly the same manner as described above. Another modification of the terminal is shown in Figs. l2 to 16. In this form of ~terminal the ears that extend through the base are creased transversely to definitely locate the bending line instead of having a section cut away as in the 40 previously described forms, and -two pieces are used so that together they function in a manner similar to the terminal 4. A member 204 (Fig. 12) is punched from sheet metal and portions of each end formed up so that when it is in place 45 on the base 2b (Fig. 14) before the clinching op eration has been performed it will have the shape shown by the dotted lines. When in this position the ear 234’ projects into the hole 42h in the base 2b and fits closely against the wall of the hole closest to the outer rim of the base 2b. The other ear 235 on this member ñts snugly against the in side wall of the notch 4|b in the base and the creased section 237 falls at a position that per mits bending the tip 232 over against the resist 55 ance element 3b and making good contact with it over the maximum area and without damage to the conducting surface. A second flat member 204’ (Fig. 13) is punched from sheet metal and formed as shown in Fig. 14 60 with the tip 23| of ear 234 in the position shown ~ by the dotted lines. Member 284’ is placed in po sition with the wings 238’ and 238” of the ter minal bearing against the upper side of the lobe 39D, the body portion 236 against the body por 65 tion 236’ of the member 204, and the ear 234 extending up through the hole 4217 in the base 2b and fitting snugly against the ear 234’ of the member 204. The creased section 243 is at a point that permits bending the tip 23| into ñrm 70 engagement with and over a maximum area of the resistance element 3b. In other respects the parts of this two piece terminal function in the same manner as the corresponding parts of the single piece terminals. 75 as far as possible and still fall short of the 'path of movement or race-way of the contactor by several thousandths of an inch. This provides two very short paths between the contactor and Ul the terminal when the contactor is between the with the variable resistance device, the switch is preferably located so that it is not engaged while the contactor 6 is being moved from the effective portion A of the resistance element 3 (Fig. 18), 20 other direction there will be a slight pressure in crease of the bent over tip 3| on the resistance element- 3 and a pressure of the body portion 36 35 enough to bend over onto the resistance element ’ All of the above terminals have the tips long 8| mounted on the cover 8U of the variable re sistance device. For constructional details of this switch, reference may be made to my co pending application Serial No. 599,490, filed No vember 24, 1933. ~ Movement of the contactor 6 on past the ter 30 minal 4 onto the portion B operates the switch 8| so that the latter is thrown into the open cir cuit position before the stop ear 85 in the cover 80 is engaged by the drive plate I0. When the switch 8| is in the open circuit position and the drive plate IO is against the stop 85 the con tactor 6 will be in the position shown in Fig. 20. The portion of the resistance element 3 over which the contacter 6 travels during operation of the switch 8l and which is ineffective to pro duce any variation in the effective resistance fur nished by the variable resistance device |, may have a very low resistance coating deposited on its surface so that the effect on the external circuit will be practicall’y the same as though the contacter 6 were short circuíted to the adjacent end terminal 4 or, when this effect is not desired, a high resistance coating may be applied to the resistance element 3 over this range. If desired, the coating may be terminated at or just beyond . the terminal 4 by providing a wider section 95 which carries no conductive coating, so that the contactor 6, when moving through the greater part of the switch operating portion of its travel, does not engage the conductive surface of the resistance element. When the drive plate is rotated in the opposite direction the switch operating member 82 is en gaged by the pin 84, and the switch 8| is thrown to the closed circuit position before the contactor 60 E passes out from between the terminal ears 3|, 32 and onto the effective portion A of the re sistance element 3. When the shaft |4 is rotated to its limiting position in this same direction the stop ear 85 will be engaged by the other side ol' the stop portion of drive plate l0 at which time the contactor 6 is directly between the bent over ears 45 and 46 of terminal 5 as shown in Fig. 23. It is often desirable to provide a fixed tap con nection on the resistance element at a point in termediate the end terminals and „when this is desired a terminal of the type shown in Figs. '7, 11 or 14 can be used. An extension or lobe 41 (Figs. 1 and 22) is provided on the base 2 and is notched for terminal 48 similar to the man-v 75 5, 2,188,210 ’ ner in which lobe 39 is notched for either of the end terminals 4, 5. The terminal 48 is assem bled in the same manner as the end terminals 4, 5 except that the ear 49 closest to the center of the base 2 is not bent over onto the resistance element 3 but is bent over onto the insulating base 2 instead. In order that no appreciable amount of the resistance between the end termi nals 4, 5 be short circuited,` only the outer ear is bent into contact with the resistance element 3. If the inner ear 49 were bent over onto the re sistance element 3 a considerable proportion of the total -'resistance would be short circuited since the inner marginal portion of the resistance ele ment 3 is the shortest and provides the lowest resistance path between the end terminals 4, ‘5 and consequently exerts the greatest influence on the overall resistance of the resistance element 3. When a very low minimum. resistance between 20 the tap terminal 48 and the movable contactor 6 is desired a low resistance composition is de » posited, prior to the assembly of the tap terminal 48, on that portion of the resistance element 3 where the tap terminal 48 is to be located. Pref 25 erably this low resistance coating 5l (see Fig. 18) is applied in the general shape of a triangle with the base at the outer rim of the resistance ele ment 3 where the ear 50 of the tap terminal 48 will be clinched over and with the apex of this 30 triangle toward the center of the variable re sistance device I. In most cases it is desirable that the edges of this low resistance coating 5l be tapered so that there will be no suddenchange in the rate of resistance variation as the movable 35 contacter 6 moves onto or 01T of this section of the surface of the resistance element 3. With the low resistance coating 5| applied'in this gen eral shape and position no appreciable amount of the effective resistance of the resistance ele 40 ment 3 is short circuited and a very low minimum resistance is obtained between the contactor t and the tap terminal 48 when the contactor 6 is adjacent the tap terminal 48 and bearing on the low resistance coating 5l. The distance that 45 the apex of the low resistance triangular sector 5l is made to extend toward the ear 49 will de pend upon the conditions desired. bent over onto the base into the position shown in Fig. 3. This securely clamps the reduced section 26’ of ‘the tail 26 under the terminal and also locks, the section 26’ into the hole 28 due to the sides of the holesqueezing in against the sides of section 26' when thefear is bent over. Thus a connec tion of low electrical resistance and great me chanical strength is formed between these mem bers with a minimum of parts and labor. I claim: , l. A variable assistance device comprising a base, a plurality of apertures in said base, a re sistance element comprising a support and a conductive film carried by said support, disposed on said base between said apertures and having a 15 relatively smooth contact surface, a terminal for said resistance element extending between said apertures and having portions registering therein for eii‘ecting self-clamping engagement with said base and said resistance element, and ad 20 justable contacting means engageable with said resistance element for varying the effective re sistance of the device. 2. A variable resistance device?comprising a base, a plurality of apertures in said base, a re sistance element comprising a support and a con ductive film carried by said support, disposed on said base between said apertures and having a relatively smooth Contact surface, a terminal ex tending between said apertures having portions 30 registering therein for engaging said base, said portions being bent over into clamping engage ment with the conductive ñlm of said resistance element, and adjustable contacting means asso ciated with the contact surface of said resistance 35 element for varying` the effective resistance of the device.' 3. A current controlling device comprising a base having a recess in a peripheral portion, a wire _connecting terminal mounted on said base, 40 said terminal having a body portion mounted on one side of said base and extending to seat in said recess, a shouldered portion bearing against the other side of said base adjacent the recess, a wire connecting portion extending from said shoul 45 dered portion away from said other side of the base, and means extending through said base for said body portion to said base. The terminal 21, electrically connected to the securing 4. A current controlling device comprising a movable contactor 6, is also of the clinch-on type ‘base having a recess in the peripheral portion 50 50 which permits rapid assembly and requires no thereof and a terminal seated in said..recess, said auxiliary parts to hold it in place. The connec having a shouldered portion engaging a tion extension 51 has a reduced section 58 which terminal first face of said base, a wire connecting portion will bend before the base 2 or any other part of extending from said shouldered portion away the terminal 21 is damaged by a bending or twist from said ñrst face of said base, and a body por 55 55 ing force applied tcLthe end of the terminal 21, tionY extending along the second face of said base such as might occur when a wire -is being at tached to the terminal 21. The extending wings and extending through an opening in said base, 60 and 6I bear against the upper side of lobe 39 the end of said body portion being bent over to on base 2 when the portion 63 is seated in the ward said base to clamp said end against said 60 notch 64 in the lobe 39 of base 2 and the body portion of the terminal 21 bears against the other side of the base 2. The end 29 of the terminal 21 is bent up from the body portion 62 and ex tends through the hole 61 in the base 2 fitting snugly against the outer edge of this hole. Ap proximately even with the inner surface of the base 2 is a hole 28 in the end 29 and beyond is a tip portion 68 clinched over against the base 2. The collector ring 24 has a tail 26 formed as shown in Fig. 3 that terminates in a reduced tapered section 26’,which is> projected through the hole 28 in the terminal 21 so that the shoul der on the tail 28 at the base of the reduced sec tion 26’ bears against the terminal adjacent the 75 wall of the hole 28. The tip 68 of end 29 is then 60 base. 5. A variable resistance device comprising a base, a resistance element comprising a support and a conductive film carried by said support, disposed-on one surface of said base, a contactor engaging the surface of said resistance element, 65 means for -moving said contacter over the surface of said resistance element, and a terminal secured to said base and having a body portion extending along the under surface of said base and a con tact portion extending through said base and bent. into engagement with the upper surface of said resistance element, said terminal having a reduced transverse cross-sectional area provided at the point of bending, adjacent said contact y portion. 76 6 2,138,210 6. A variable resistance device comprising a base, a resistance element comprising a support and a conductive ñlm carried by said support, on said base and a terminal for said resistance element including a member extending along said base, said member having a portion projected through a perforation in said base and bent over to secure said member on said base and a second ` member comprising a pad 0f soft conductive material clamped between said base and the body of said first member and having a portion engag ing the surface of said resistance element. '7. In a variable resistance device, a base, a resistance element comprising a support and a. conductive film carried by said support, on said base, a contacter movable on said resistance ele ment through a predetermined path, a terminal Ol for said resistance element, tail-like portions on said terminal extending through said base, one of said tail-like portions being bent over into en gagement with the conductive surface of said resistance element outside the path of said con- 10, tactor. NEWTON C. SCHELLENGER., CERTI- FI CA TE OF|` CORRECTI ON.. Patent No. 2,158,210. November 29, 1958 . NEWTON C., SCHELLENGER. it is hereby certified that error appears in the printed specification ofthe abo ve numbered patent requiring correction as follows: Page 5, second co lumn, line ll, claim l, for the word "assistance" read resistance; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office. Signed and sealed this 7th day of February, A. D. 1959. tHenry AVan Arsdale. (Seal) Acting Commissioner of Patents.