US2138210A

US2138210A - Control device

Info

Publication number: US2138210A
Application number: US711644A
Authority: US
Inventors: Newton C Schellenger
Original assignee: CHICAGO TELEPHONE SUPPLY CO
Current assignee: CHICAGO TELEPHONE SUPPLY Co
Priority date: 1934-02-17
Filing date: 1934-02-17
Publication date: 1938-11-29
Anticipated expiration: 1955-11-29

Description

Nov. 29, 1938. N. c. SCHELLENGER CONTROL DEVICE 4 Sheets-Sheet l Filed Feb. 17, 1934 umnuunununnnnn NOV- 29, w38- N. c. SCHELLENGER I M8210 CONTROL DEVICE Filed Feb. 17, 1954 4 Sheets-Sheet 2 .772 Iren to?? Newtm 6. Sc/LeZZene?? Nov., 29, 1938u N.f f:A sci-IELLENGER CONTROL DEVICE Filed Feb. 17, 1954 4 Sheets-Sheet 3 n.4/ a g Z 6 dal@ w/ c@ n w m? N Nov. 29, 1938. n N C SCHELLENGER 2,138,210

CONTROL DEVI CE Filed Feb. 17, 1934 4 Shees-Shee. 4

.7m/@non New Zan Sc/zeZZez- Q72 More particularly this invention relates to termember lie in the path of the contactor and the 5 minals for variable resistance devices in which contactor can be moved through 360 if desiredthe 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 posbe clamped, and relates also, to aterminal col Sibilty 0f engagement between these members operating with other means to make connection and hence the present invention eliminates any 10 with a movable contact member. possibility of sudden variations in resistance due This invention further relates to a combinato transient metal to metal contact between the tion variable resistance device of the aforemencontactor and terminal, and also eliminates any tioned type and a switch or other associated .de' possibility of the scoring of the polished surface .15 vice operatively connected to the variable resisof the contactor by the terminal. l tance device for operation thereby when the con- It is well known that terminal members have -tactor or other. adjustable element is moved been used to clamp onto wirewound resistance through a predetermined portion of its travel elements in various ways but none of them Vsolved normally beyond the end of effective portion of the above mentioned problems. In fact none of the resistance element. them were adapted to clamp onto airagile re- 20 Patentedv Nov. 29, 1938 i l UNITED STATES PATENT OFFICE 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 varing through the terminal sector on a part of the iable resistance devices of the type commonly resistance element that could not be used otheremployed 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 For some time, the radio trade has been desistance element of the composition type regardmanding the smallest possible rheostat for volless of whether or not the other problems were urne and tonev control purposes that can be furn- Solved. ished without sacrieing smoothness of opera- One object of this invention is to provide a 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 inVentOn iS to DIOVde a able `contactor terminal to the lowest possible terminal that makes good electrical contact with limit in order that the maximum length of effec'- the resistance element outside the path 0f the 30 tive resistance element might be maintained for contactor and has no parts directly engageable by useful variation in resistance. the contactor,

In many cases it is also required that a power Another object of this invention is to provide switch be added to the variable resistance device a terminal with an ear that can easily be bent and beoperated by angular movement of the into contact with the resistance element without 35 operating shaft of the variable resistance device, damaging the resistance element. usually through an angle adjacent one of the Another object of this invention S t0 DlOVde rotational limits of the movable contactor. Prior a xed terminal means for tapping the resistance to the invention disclosed in my application Sev element Outside the Def/h 0f the mOi/able C011- 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 appreeably affecting the total contactor of the variable 'resistance device apresistance of the resistance element and also proproached one of the end terminals of the resistviding a low minimum resistance between the ance element. However, to permit this, it was terminal and thecontactor.

5 necessary to short circuit that portion of the' Another object of this invention is to provide 45 resistance element vtraversed by the contactor a terminal for the movable contactor which produring the switch operating portion of the convides a positive electrical and mechanical contactor movement and as a result the expense of nection with a member in the electrical circuit l manufacture was increased and the eiectiveporbetween the terminal and the movable contactor.

tion of the resistance element was crowded into Another object of this invention is to provide 50 a much shorter space which greatly impaired the a terminal that occupies an extremely narrowl smoothness of control of the radio set. z sector of the variable resistance device base.

While the above mentioned invention made Another object of this invention is to provide available for operation of the switch, the portion a combined variable resistance device and

switch

5,5. of rotation during whichthe contactor was movin which the switch can be operated while the movable contactor is moving through the sector of the base of the variable resistance device occupied by the terminals.

With the above and other objects in view which will appear as the description proceeds, my invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly dened by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

In the accompanying drawings, I have illustrated complete examples of the physical embodiment 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 completed terminal;

Fig. 5 is an isometric view of a. 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 resistance element sectioned;

Fig. 8 is a view taken from the opposite end of 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 completed terminal of slightly modified construction;

Fig. 11 is an end View similar to Fig. 8 of a slightly modied terminal;

Fig. 12 is an isometric view of one element of a two piece terminal;

Fig. 13 is an isometric view of the other element 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 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 rotation of the rheostat shaft;

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 movable parts in a certain position;

Fig. 2O is a partial plan view showing the movable contactor in a certain position;

Fig. 21 is a partial plan view showing the movable contactor in another position;

Fig. 22 is another partial plan view showing the movable contactor adjacent the tap termina 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,

terminal ready variable resistance device comprises o.

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 directly to the base 2. Usually it is desirable to deposit 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 resistance 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 application Serial No. 666,444, iiled April 17, 1933.

End terminals

4 and 5 make connection with the ends 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 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 opposed ears II and I2 formed up from the body portion of the arm 1 on a center line which is at 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 corresponding shape in the drive plate, and a washer I6 fitted over the reduced atted end I5 of the shaft I4 and the flatted end peened over to hold 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 swaging the shoulder 20 of the bushing into engagement 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 planar. The shaft I4 is journaled in this bushing 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 between 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 collector ring 24 that is insulated and spaced 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 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), projecting 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. Rotation in the other direction/is limited by the drive plate I8 striking the stop ear 85 and bringing the contactor to rest between the bent over

ears

45 and 46 of terminalv5.

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 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 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 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 narrower and1 is adapted to be clinched over onto the base or resistance element to hold the terminal 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 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 terminal 36 is a connection extension (commonly called at solder lug) having a perforated portion 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 suitable material to shape shown in Fig. 4 with the exception that the ear 35 sheared out of the body portion 36 and formed at right angles has no reduced section 31. A separate trimming operation is employed to cut notchesout of the sides and create this reduced section 31 that serves to force the bending line to the desired point when the tip 32 is bent over on the resistance element.

Another. forming operation gives the terminal of Fig. 4 the shape shown in Fig. 5, the shape in which it is positioned on the base. The extending wings 38' and 38", formed on a head portion 38 of the terminal proper 36 are hooked over the lobe 39 which is integral with the base 2' and extends beyond the periphery of the cover (Fig. 18) to actas a terminal support. The terminal is then slid into the notches 40 and 4l in the base until the end 34 starts to enter the hole 42 in the base 2. The body portion 36 of the terminal 4 is then pushed up against the under side of the base 2 so that 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 the reduced

sections

43 and 31 extend slightly 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 surfaces will be substantially parallel with the surface of the resistance element 3 when they meet the latter, due, as previously stated, to the bends occurring at a point predetermined by the location of the reduced sections. The reduced sections also permit the end 34 and the ear 35'to be bent over onto the resistance element 3 with a more even `and accurately predetermined pressure 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 elements 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 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 surface 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 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 kind and thickness of metal used for the terminal and can best be determined by trial.

Where it is desired to provide a variable resistance device having an extremely low contact resistance between the terminal and the resistance element, a soft pad of conducting material is interposed 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 pushed up against the base 2d. The terminal 4d is then inserted in a manner similar to that described 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 of the resistance element 3d.

As the pad y80 is soft it adapts itself to the contours of the surfaces of the resistance element 3d and the terminal 4d respectively and thus has an area of intimate contact with both members respectively which is greater than the area of contact between the terminal and resistance element when these latter elements are in direct contact and no pad is employed.

An equivalent result may be obtained by interposing between the resistance element and the tips which are bent over against the resistance element a section of soft wire, such as fuse wire; when the tips are bent ove'r to clamp the terminals on the base, the interposed wire is fiattened out into intimate contact with the surface of the resistance element and the tips.` This wire thus serves as a cushion for the tips and provides a low contact resistance between the terminal and the resistance element.

No auxiliary parts are required to hold the terminal in place against the resistance element as this is accomplished by the tips 3| and 32 of the end 34 and ear/35 respectively that are bent over onto the resistance element 3 clamping Ithe terby the dotted lines.

minal 4 tightly to the base 2 and making good electrical contact with the resistance element 3.

The reduced portion 44 in the connection extension is provided so that it will bend and thereby prevent damage to the variable resistance device if any excessive bending force is applied to the connection extension, such as might occur when leads to the external circuit are being connected.

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 extension 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 back part of the terminal body 3S against the underside of the base 2. With pressure n the other direction there will be a slight pressure increase of the bent over tip 3| on the resistance element 3 and a pressure of the body portion 36 adjacent the notch 40 upward against the base 2.

In Figs. l0 and l1 I have shown another method of obtaining a reduced or weakened section in the upstanding ear and upturned end to pos'- 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.

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 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 on the base 2b (Fig. 14) before the clinching operation 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 ts snugly against the inside wall of the notch 4|b in the base and the creased section 237 falls at a position that permits bending the tip 232 over against the resistance 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 with the tip 23| of ear 234 in the position shown Member 284 is placed in position with the

wings

238 and 238 of the terminal bearing against the upper side of the lobe 39D, the body portion 236 against the body portion 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 rm 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.

All of the above terminals have the tips long enough to bend over onto the resistance element 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 the terminal when the contactor is between the terminal ears and allows a very low minimum resistance to be obtained and also allows the contactor to be moved past -the terminal if desired, without touching it or producing any discontinuity in the nature of the contact between the contactor and the surface of the resistance element, such as might occur if the contacter made direct contact with the terminal.

W'hen a switch is to be used in combination 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), to a position between the ears 3|, 32 of terminal 4 as shown in Fig. 2l, at which point the effective 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 8| mounted on the cover 8U of the variable resistance device. For constructional details of this switch, reference may be made to my copending application Serial No. 599,490, filed November 24, 1933.

Movement of the contactor 6 on past the terminal 4 onto the portion B operates the switch 8| so that the latter is thrown into the open circuit position before the stop ear 85 in the cover 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 the contactor 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 produce any variation in the effective resistance furnished 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 practically the same as though the contacter 6 were short circuted 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 engaged by the pin 84, and the switch 8| is thrown to the closed circuit position before the contactor E passes out from between the terminal ears 3|, 32 and onto the effective portion A of the resistance 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 connection on the resistance element at a point intermediate 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 ner in which lobe 39 is notched for either of the

end terminals

4, 5. The terminal 48 is assembled in the same manner as the end terminals 4, 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 terminals

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 resistance element 3 a considerable proportion of the total 'resistance would be short circuited since the inner marginal portion of the resistance element 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 the tap terminal 48 and the movable contactor 6 is desired a low resistance composition is deposited, 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. Preferably 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 element 3 where the ear 50 of the tap terminal 48 will be clinched over and with the apex of this triangle toward the center of the variable resistance 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 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 general shape and position no appreciable amount of the effective resistance of the resistance element 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 the apex of the low resistance triangular sector 5l is made to extend toward the ear 49 will depend upon the conditions desired.

The terminal 21, electrically connected to the movable contactor 6, is also of the clinch-on type which permits rapid assembly and requires no auxiliary parts to hold it in place. The connection extension 51 has a reduced section 58 which will bend before the base 2 or any other part of the terminal 21 is damaged by a bending or twisting force applied tcLthe end of the terminal 21, such as might occur when a wire is being attached to the terminal 21. The extending wings 60 and 6I bear against the upper side of lobe 39 on base 2 when the portion 63 is seated in the 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 extends through the hole 61 in the base 2 fitting snugly against the outer edge of this hole. Approximately 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 shoulder on the tail 28 at the base of the reduced section 26 bears against the terminal adjacent the wall of the hole 28. The tip 68 of end 29 is then 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 connection of low electrical resistance and great mechanical strength is formed between these members 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 resistance element comprising a support and a conductive film carried by said support, disposed on said base between said apertures and having a relatively smooth contact surface, a terminal for said resistance element extending between said apertures and having portions registering therein for eiiecting self-clamping engagement with said base and said resistance element, and adjustable contacting means engageable with said resistance element for varying the effective resistance of the device.

2. A variable resistance devicecomprising a base, a plurality of apertures in said base, a resistance element comprising a support and a conductive film carried by said support, disposed on said base between said apertures and having a relatively smooth Contact surface, a terminal extending between said apertures having portions registering therein for engaging said base, said portions being bent over into clamping engagement with the conductive lm of said resistance element, and adjustable contacting means associated with the contact surface of said resistance 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, 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 shouldered portion away from said other side of the base, and means extending through said base for securing said body portion to said base.

4. A current controlling device comprising a base having a recess in the peripheral portion thereof and a terminal seated in said..recess, said terminal having a shouldered portion engaging a first face of said base, a wire connecting portion extending from said shouldered portion away from said rst face of said base, and a body portionY extending along the second face of said base and extending through an opening in said base, the end of said body portion being bent over toward said base to clamp said end against said 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, 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 contact 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.

6. A variable resistance device comprising a base, a resistance element comprising a support and a conductive lm 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 engaging the surface of said resistance element.

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:

claim l, for the word "assistance" co lumn, line ll,

Page 5, second 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.

(Seal) tHenry AVan Arsdale.

Acting Commissioner of Patents.