US2145953A

US2145953A - Variable resistance device

Info

Publication number: US2145953A
Application number: US721728A
Authority: US
Inventors: Newton C Schellenger
Original assignee: CHICAGO TELEPHONE SUPPLY CO
Current assignee: CHICAGO TELEPHONE SUPPLY Co
Priority date: 1934-04-21
Filing date: 1934-04-21
Publication date: 1939-02-07
Anticipated expiration: 1956-02-07

Description

Feb. 7, 1939. u N. c. SCHELLENGER 2,145,953

VAR IAB -E HES ISTANCE DEVICE Filed Aprii 21, 1934 3 Sheets-Sheet l w H 25 57 n 11153 95 M ZNVENTOR NEWTON U. 5 c1151: zzzvazfi.

A TT'Y.

Feb. 7, 1939. c. SCHELLENGER 2,145,953

" VARIABLE RESISTANCE DEVICE Filed April 21, 1934 37Sheets-Sheet s E 1 NsUl-HT/ON 5235 34 EC; Jfl. E51].

INVENTOR.

NEW TON 6f SCHELLENGER. D1. 'MMZV- I ATT'Y.

Patented Feb. 7, 1939 UNITED STATES PATENT OFFICE Chicago Telephone Supply 00.,

a corporation of Indiana Application April 21, 1934, Serial No. 721,128 9 cm... (01. 201-55) This invention relates to a variable resistance device of the type-in which an actuating arm moves a contactorover, the redstance element andapplies more particularly to variable resistance devices of thetype used in volume control or tone control circuits in radios or public address systems. v

It has often been found-desirable to actuate other control devices, positioned in near proxi imity to the variable resistance device, by the same actuating meanswhich is used to operate the variable resistance device.

I am. aware of the fact that others have proposed various means for the actuation of coni trols arranged adjacent to a variable resistance device such as the transient operation of a switch or the actuation of a series of similar controls arranged in tandem relationship by means a single actuating member. But in all these prei viously proposed devices the single actuating means is positioned, relative to the variable resistance control and the additional control so that a complete actuation of one of thecontrols must of necessity also actuate the other control as or controls. In other words, the various controls to be actuated by the single actuating means were arranged in such operative relationship to the latter that when one of the controls is actuated in its entirety the other control or con- 30 trols must of necessity also be operated. In a plurality of adjacent controls, -all of which are to be actuated by a single actuating means, it may often be desirable to refrain from actuating one or more ofthe controls even though the adjacent control or controls are actuated in their entirety. b It is an object of the present invention to provide a variable resistance control device with an actuating means which at the option of the op- 40 erator may be made to actuate an adjacent control device, but which need not actuate the adjacent control device even though the variable resistance device is actuated throughout its-full range.

45 It is another object of this invention to provide a single actuating means for a plurality of control devices which actuating means is'normally arranged for actuation of one or more control devices but which upon being actuated 50 in a particular manneris adapted to actuate one or more additional control devices. f

It is a further object of my invention to provide an enclosed resilient element for maintaining the actuating means of a control device-in a 1 normal operating relationship wit on or more control devices and upon application of force against said resilient element the actuating means is adapted to be placed in operating relationship with one or more additional control devices.

, It is a further object of my invention to provide a substantially enclosed, electrically shielding coverfor a control device having a rotatable and axially movable actuating means and means integral with said cover operable as a journal bearing and thrust bearing for an actuating shaft. 7

It is a further object of my invention to provide a control device with a metallic cover member having stop elements for limiting the move- 16 'ment of the control mechanism struck therefrom at such portion of said cover member which has the greatest supporting strength for said stop elements. A further object of my invention is to pro- 20 vide a control device having an actuating shaft and bearings for said shaft, positioned at extreme opposite portions of said device so as to afford the maximum support for said shaft and to prevent binding of said shaft upon slight defeotivealignment of the bearings.

It is a further object of my invention to provide a variable resistance device having a rotatable and axially movable actuating means and a resilient contact arm adapted to expand in unison so with the axial movement of said actuating means to maintain a driving engagement with said actuating means and maintain electrical contact between a resistance element and a plurality 01' current conducting members in all axial positions of said actuating element. 7

It is a further object of my invention to provide a variable ce device comprising a rotatable and axially movable shaft and a substantially enclosed metallic housing for electri- 4o cally shielding said variable resistance device from associated control devices.

Another object of my invention is to provide a variable resistance device housing in which parts of the housing may be fastened to each other without leaving any undesirable and unsightly parts projecting therefrom.

Still further advantages of my invention will become evident by reference to the following description taken in connection with the accompanying illustrations of one specific embodiment thereof, the. scope of the invention to be limited only as deflned'by the appended claims.

g In the drawings: I

Fig.1 is a planview of a variable resistance device constructed in accordance with my inventicn, with the top of the housing and the resilient spring member removed to show the relationship of the various parts.

Fig. 2 is a vertical sectional view, taken along line 2-2 of Fig. 1, and showing the shaft in its normal position spaced from the thrust bearing.

Fig. 3 is a vertical sectional view similar. to Fig. 2 and showing the shaft forced into position against the thrust bearin'g.

Fig. 4 is a top plan view, on a slightly reduced scale, of the variable resistance device shown in Fig. 1 with the shaft shown in section adjacent the top of the housing.

Fig. 5 is abottom plan view of the device shown in Fig. 1 and illustrating the means of connecting the housing to the grounding plate.

Fig. 6 is a vertical elevational view of the device shown in Fig. 4.

Fig. '7 is an exploded isometric assembly view of a variable resistance device constructed in accordance with the invention and illustrating the relationship of the various parts to each other.

Fig. 8 is an enlarged fragmentary view of a section of the grounding plate at an intermediate stage of manufacture.

Fig. 9 is a sectional view taken along the line 99 of Fig. 8.

Fig. 10 is an enlarged fragmentaryview of a the cup-shaped control housing for the variable resistanc'e control. The control housing 20 is provided with a circular, substantially flat .end wall 2! from which extends a cylindrical side wall 21 (see Fig. 7). The free edge of the side wall is provided with a plurality of extensions 2| spaced from each other and hereinafter referred to as ears. A section 22 of the free edge of the cylindrical side wall (see Figs; 3 and 7) is cut away to prevent contact with the current carrying terminals of the variable resistance device. Stop members 23 are struck from the side wall of thehousing. These stop members for limiting the angle of rotation of the control mechanism must be of substantial height and .are therefore struck from a section of the side wall which is spaced a substantial distance from the cut away section 22, in order to provide the necessary strength and rigidity to these stop members.

The central portion of the housing is provided with an annular depressed portion 25, substantially U-shaped in cross-section, the innermost portion of which consists of a cylindrical section I 25 which is concentric with the cylindrical side wall 21 of the housing. The inner surface of section' 26 is constructed to fit snugly about the reduced portion 81 of a shaft 36 and is adapted to function as a journal bearing for said shaft. The flatinner surface 25a of the annular depressed portion 25 is adapted .to function as a stop member and thrust bearing for shoulder 38 of the shaft 36.-

An insulation strip 28 having narrow slots 29 of strip28 will abut against the end wall 24 of the housing whereas the opposite edge of the strip will abut against an insulating base plate 96.

The base plate 96 is provided with an integral arcuate, extended shelf section 98 and supported on the base plate is a resistance element 91. In the particular embodiment disclosed herein, the resistance element is of the planar carbonaceous type although other known types of resistance element may be used equally well to fulfill the requirements of this invention. The planar, car"- bonaceous type, resistance element 91 may comprise a coating of carbon or graphite composition 11 on a sheet of, tough, yieldable, insulating material such as parchment paper as is clearly illustrated in Figs. 1 and 2. The resistance element is provided with a break 89 between the ends thereof, or may comprise a coating of suitable carbonaceous resistance material applied directly onto the base plate. 7

A substantially circular metallic grounding plate 98 is positioned directly on the rear surface of the base plate. The grounding plate 98 is provided with a plurality of tongue sections 93 spaced from each other on the outer marginal periphery thereof. The tongue sections are flattened so as to produce depressed offset portions on the outer surface of the grounding plate.

These offset tongue portions 93 are produced by cutting sections from the outer periphery of the grounding plate thereby leaving a plurality of pairs of parallel sided notches 83, 84 and a tongue 94 which is shorter than the circumference of the main portion of the grounding plate (see the dotted line in Fig. 8.) The tongue 94 is then flattened by pressing the same to the desired thickness, forcing themetal of the tongue into a part of the space of matches, 84 and the tongue is also thereby lengthened to extend substantially to the circumference of the main portion of the plate. A section 92 (see Figs. 5 and 7) of the grounding plate is cut away to prevent contact with current carrying terminals 19, 85, 19 of the variable resistance device. A plurality of locating projections 95 (see Fig. 6) are formed on the outer surface of the grounding plate. These projections 95 are adapted to fit into suitable apertures lll8 of a panel ID! or other supporting surface, whereby the variable resistance device may be easily, quickly and accurately positioned against a panel or surface to which it is to be fastened. y

The grounding plate is adapted to reinforce the base plate as well as to constitute a metallic cover for the housing to electrically shield the variable resistance device from electrical dis"- turbances of adjacent devices.

The base plate 96 and the grounding plate are constructed with openings 88 and 9| respectively for cooperation with a circular bushing 19. The bushing 10 is formed with an externally threaded portion 12 for connection of the same to a panel or the like, and is provided with an anflange 19a and the shoulder 15 is fitted in the openings 88 and 9| of the base plate and ground-f ing plate respectively with the sharp ridge ll of grounding plate and thereby securely fasten the base plate and grounding plate together.

The housing is securely fastened to the grounding plate by bending. the ears 2! thereof over onto the depressed tongues 93 of the grounding plate thereby forcing the base plate firmly against the insulation strip 28. The ears 2| are adapted to be retained within the said depressed tongue. portions 93 of the grounding plate, thereby providing a smooth even outer surface on the 15 said plate 90. This even outer surface will permit connection of the variable resistance device to a panel or other plane surface without distortion of the grounding plate or base plate when it is drawn up tightly against the panel I01 by screwing a nut I09 onto the threaded portion 12 of the bushing projecting through an opening I Ill of the panel.

The bushing 19 has a longitudinal bore through the center thereof. The greater part of the length of said bore is preferably of a diameter considerably larger than the external diameter of the shaft 36 so as to provide a very loose fit with the shaft 36. The end of the bushing extending from the variable resistance device contains a comparatively short bored section 13 of a diameter \very, slightly larger than the external diameter of the shaft 38 so as to constitute a journal bearing for the shaft. The shaft extends through andv has a portion thereof projecting from the vbushing to constitute a handle for imparting axial or rotatable movement to said shaft.

When the two journal bearings 25, I3 for the shaft are positioned at extreme opposite sides of the varpble resistance device as disclosed in the preferred embodiment of the invention, a much greater rigidity and stability is imparted to the shaft than would be possible if the bearings were positioned closer together. Furthermore, the exact alignment of bearings is not as critical and the allowable tolerances need not be so close when the bearings are comparatively short and are spaced a substantial distance from each other as would be the case if the bearings were long or spaced close together.

The arcuate extended shelf section'98 of the base plate 96 contains a plurality of parallel sided notches I34, I05 and Ill (see Figs. 3 and 5t in which are positioned a plurality of current carry-.

ing terminals I9; I9, and 35. The grounding plate which overlies the base plate has the section 92 thereof removed to prevent making contact with these'terminals. The end terminals 19, I9 are positioned into notches I94 and I08 and are .0 adapted to contact the ends-of the'resistance elefiled February 17,1934;

As pointed out above, the actuating shaft 39 is reduced in diameter adjacent the end wall. of the housing, the reducds'ection 31 of the shaft extending through and projecting from p the said end wall 24. -A drive arm 39 is fixed to the main portion of shaft adjacent the reduced portion thereof.

The drive arm 39 comprises a fiat plate having an integral cylindrical collar portion 40 formed' therein, the collar portion 40 being arranged perpendicular to the flat surface of the plate and may be formed by drawing the same from the One end of t e plate' metal of the flat plate. terminates in a downwardly directed nger 4| and the other end of the plate terminates in a blunt section having oppositely directed

sides

44, 45. A second downwardly directed finger 42 is formed on the arm intermediate the collar 40 and the

sides

44, 45. This finger 42 is preferably spaced from the collar 40 a distance equal to that between finger 4| and the collar 40. In order to construct the finger 42 according to exact dimensional requirements by a punching operation, it is preferable that a section of the metal surrounding the finger be first removed to leave a finger of the exact desired dimensions which may then be bent downwardly to the position shown in Fig. '7 of the drawings. The inner surface, of the collar 49 is knurled or otherwise provided with axially extending teeth 46 (see Fig. 2) which are adapted to be forced into the metal of the shaft 36 when the arm is forced thereon, and thereby dispenses with the necessity of fastening elements such as set screws or key members between the shaft and arm. If desired, similar teeth 46a may be provided on the shaft for coengagement or to mesh with the teeth 46 of the drive arm.

The fingers 4| and 42 of the drive arm are 3 adapted to fit into

notches

49 and 43 respectively of a motion-transmitting plate. This motiontransmitting plate is made of insulating material and has an opening 52 into which the shaft 36 is positioned and thus permitting the fingers of the drive'arm to engagethe sides of the

notches

49 and 48. The plate 41 is considerably wider than the drive arm 39 as is clearly shown in Fig. 1, and at least one end of this plate is arranged to substantially overlie the converging ends of the resilient contact arm members 53, 59 to prevent dislodg'ing of the contact shoe in case of violent vibration. For simplicity in assembly, both ends of the plate are constructed alike. The plate 41 is further provided, on opposite sides thereof, with notches and 5! for engagement with

upstanding projections

54, 54 of a contactor arm 53 and thereby transmit motion from the drive arm 39 to the contactor arm 53.

The contactor arm 53 is composed of resilient metallic material having a'substantially circular slip ring portion with an opening 56 therein which is sufiiciently large that the shaft 36 may extend therethrough without contacting the sides of the opening. A pair of comparatively long converging

arms

58, 58 extend from the slip ring portion and are joined at their converging ends. Extending from the junction of the converging ends is a downwardly directed toe 51 whichis adapted to project into an opening 6| of the contact shoe 60. The contact shoe is constantly maintained in contact with the resistance ele-. ment 11, and is pressed against the resistance element by the resilient contactor arm 53. The

upstanding projections

54, 54 are adapted to prevent contact of the contactor arm with the shaft by their engagement with the notches 53, 5| of the motion-transmitting plate. The

projections

54, 54 are prevented from making contact with the drive arm 39 due to the fact that the plate 4'I is-wider than arm 39. The contactor arm is bent, warped or dished so as to function as a the resistance element 'I'I as will be more particularly described below.

A collector ring 62 is positioned directly below the body portion of the contactor arm 53 and is constructed to substantially the same size as the slip ring portion of the contactor arm so as to be constantly maintained in contact therewith. An extending arm 65 is provided on the collector ring (see Fig. 3) which terminates in a narrow finger portion 66. This finger portion 66 is adapted to be projected through a small opening 81 in the end 86 of the central terminal 85. The end 86 of the terminal is'then bent over onto the base plate thereby clinching the end 86 and the finger 66 securely together. Care must be taken to prevent contact between the resistance element and the bent over end 86 of the terminalf. This may be done, as shown in Fig. 7, by cutting out a section I6 of the resistance element. The collector ring 62 is provided with alarge opening 61 of substantially the same size as opening 56 of the contactor arm, and also with

guide projections

63, 64 to prevent contact of the collector ring with the shaft 36. An insulating washer 68 is positionedbetween the collector ring 62 and the circular bushing I0 for the purpose of preventing contact between the collector ring and bushing. The washer 63 is slightly larger in diameter than the flange 10a' of the bushing so that the: downwardly directed

guide projections

63 and 64 of the collector ring will be prevented from contacting the flange 10a. The

guide projections

63, 64 engage diametrically opposite portions of the insulating washer 68 to thereby prevent contact of any portion of the collector ring with the shaft 36.

A dished spring member 3| having a plurality of outwardly directed arms 32 and a centrally positioned opening 33 for the shaft 36 is positioned between the drive arm 39 and the end wall 24 of the housing to normally maintain .the shaft in the position shown by Fig. 2, with the drive arm, motion-transmitting plate, contactor arm, collector ring and insulating washer all forced into close contact with each other and against the flange 10a of the circular bushing. A washer 34 preferablyformed of insulating material, may, if desired, be positioned between the spring 3| and the drive arm 39. The washer 34 is provided with a centrally positioned opening 35 sufliciently large to snugl fit about the collar of the drive arm.

An actuating arm I00 may be mounted on the reduced end 31 of the shaft which projects from the end wall of the housing. This arm I00 can be fixed to the reduced end of the shaft in any in Fig. 2. In order to actuate the adjacent control device 'the shaft 36 must be moved axially against the action of spring 3|, that is, before the eccentrically mounted projection |0| can engage the element I03 of the adjacent control, the shaft must be moved axially to the position shown in Fig. 3.

It will beobvious that many other means of driving engagement of the reduced end of the shaft with an adjacent control device, for operation of the control device when the shaft is in its advanced axial position, may be devised by anyone skilled in the art and the specific embodiment herein disclosed is for illustrative purposes only and the invention is not to be limited thereby.

When the shaft'is moved axially against the action of spring 3|, as shown in Fig. 3, the shoulder 38 of the shaft is adapted to contact the surface 250. of the thrust bearing, the surface 25a functioning both as a means for limiting the axial movement of the shaft as well as providing a surface against which the shoulder 38 may turn. It will be furthermore readily apparent that when the shaft is forced against the thrust bearing the resilient contactor arm will assume its natural bent or dished shape so as to maintain a contact with the collector ring as well as maintaining a pressure on the contact shoe to preserve an electrical contact between the latter and the resistance element.

' As has been pointed out above the

stop members

23, 23 are struck from the sidewall of housing 20 at a substantial distance from the portion 22 of the side wall which is removed to prevent contact with the terminals. The

stop members

23, 23 are positioned to be engaged by cars 44, of'the drive arm 33 when the contact shoe is adjacent an end of the resistance element. Inasmuch as the drive arm willbe moved axially with the shaft, the stop members 23 must be of considerable height to insure engagement at all times with the ears ll, 45 of the drive arm 33 and it is primarily for this reason. that the members 23 are struck from the housing'at a distance from the cut-out section 22.

In this connection it willbe noted that the-rotational movement of the shaft andassociated elements is limited by direct impact of the drive arm against the stop members. The drive arm is directly connected to the shaft in a very rigid manner, consequently there is much less danger of damaging the control device by the shock of the impact with the stop members than if some other element of the device were used as a means for limiting the rotational movement.

In the operation of the variable resistance device herein disclosed, when used as a simple rheostat, the current is adapted to pass from an end terminal to the resistance element, .then to the contact shoe, then to the contactor arm, from the contactor arm to the collector ring and from the collector ring to the central terminal. When the shaft is in its normal retracted position shown in Fig. 2, rotation of the shaft will actuate only the variable resistance device.' If the, shaft is rotated in a clockwise direction, the side 45 of the drive arm will eventually abut against one of the

stop members

23, 23 at which position the contact shoe will be adjacent one end of the re-- sistance element. Upon'rotation in the other direction the side 44 of the drive arm will abut against the other stop member and the contact shoe will be positioned adjacent the other end of the resistance element. It is preferable that the contact shoe can be moved on the'resistance element

adjacent portions

82, 82 of the terminals without making a contact with the same, as any direct contact between the end terminals and the shoe is undesirable.

The contact shoe is moved over the resistance element by means of the contactor arm 53. The

' rigidity to the entire device and to eliminate a binding of the axially and rotatably movable shaft because of slight inaccuracies in the manufacture of the various parts, the journal bearings for the shaft are spaced from-each other as far as possible in opposite extreme positions of the housing and bushing. Thrust bearing means are provided in the housing adjacent the journal bearing, to function as an impact absorbing means, and to aid in withstanding the endwise rotational thrust of the shaft.

In the modified form of variable resistance device shown in Fig. 12, the shaft 36' is mounted in the housing 20 and its associated bushing 10' for rotational movement only and illustrates the manner in which the control device may be constructed in a narrow compact unit when the axial movement of the shaft can be dispensed with. This modified construction retains the advantages of the other features of the invention to provide an exceptionally rugged, uniformly and smoothly operating unit, which can be constructed very economically and without the usual critical requirements of variable resistance devices known heretofore that each individual element be maintained within severely fine tolerances.

The shaft 36 is supported by the widely separated comparatively short journal bearings 26' of the housing 20' and 13' of the bushing 10'. As in the case of the variable resistance device shown in Figs. 2 and 3, this feature will permit smooth, uniform rotation of the shaft even though there is a slight malalignment between the two bearings. The shoulder 38 of the shaft will be continuously maintained in direct contact with the thrust bearing 25', thus permitting a considerable narrowing of the side wall of the housing. If an exceptionally smooth operation is desired, a small, smooth thrust washer I05 may be positioned between the shoulder 38' and the thrust bearing 25'. When no additional control is positioned adjacent the variable resistance device for actuation by the shaft 36' the'reduced end of the shaft 3'! may be out off evenly with the end wall 24 of the housing 20' as shown in Fig. 12. Nevertheless, it will be obvious that the reduced end of the shaft may be extended beyond the end wall 24' for thepositive actuation of an adjacent control in a known manner. It is not necessary that the stop member 23' be made as longas stop member 23 by reason of the fact that the drive arm 39' is not moved axially as is drive arm 39 in the modification described above, nevertheless it is preferably struck from a portion of the housing spaced from the terminals to prevent cutting through the free end of the side wall of the housing as would be the case if it were struck from the section of the'housin adjacent the terminals.

The grounding plate 9.0 is provided with depressed tongues 93'. corresponding to the depressed tongues 93 as previously described, and the ears 2| of the housing'are bent over onto the tongues 93 so as to prevent troublesome projections on the external free surface of the grounding plate 90.

The various other parts of this modified construction of variable resistance device are constructed and assembled inthe same manner and relationship as above described with references to Figs. 1-11.

It is to be understood that the specific embodiment of the invention illustrated and described may be varied in many details of its construction within wide limits without departing from the spirit of the invention, and that the invention is to be limited only within the terms of the appended claims.

I claim:

1., A variable resistance control device havin in combination, a housing, a shaft rotatably mounted in said housing, a journal bearing in one side of said housing, a bushing extending from the opposite end of the housing, a narrow journal bearing in the outer end of the bushing, said journal bearings being positioned at extreme opposite ends of said housing, whereby main'mum rigidity with minimum bearing surfaces may be obtained between said shaft and bearing in the bushing and the bearing in the housing.

2. A variable resistance device having in combination, a metallic open-ended housing member, a metallic plate overlying the open end of said housing member, said metallic plate being formed with a plurality of peripherally arranged tongues depressed below the plane of the exterior face of said plate, a plurality of ears integral with said housing member, said housing and plate being secured to each other by bendingsaid ears over onto said depressed tongues, and an actuating shaft extending through said plate and housing.

3. A variable resistance device having in combination, a metallic open-ended housing, a plurality of ears extending from the open end of said housing, a metallic plate adapted to close the open end of said housing, a plurality of tongues at the marginal periphery of said plate, said tongues being depressed below the plane of the exterior surface of said plate, said housing and plate connected to each other by bending of said ears over onto said depressed tongues whereby an even exterior surface is provided on said plate.

4. A variable resistance control device having in combination, a housing having a perforation therethrough and an annular depressed portion immediately surrounding said perforation, a resistance element in said housing, contacting means cooperating with said resistance element,.

means for actuating said contacting means including a rotatable shaft extending into said housing, said annular depressed portion constituting a combined journal and thrust bearing for said shaft.

5. A variableresistance device having in combination, a cup-shaped metallic housing having a cylindrical wall, a variable resistance in said housing, a rotatable contact driving member in said housing, lugs struck' inwardly from the wall of said housing, a strip of insulating material against the inner surface of the cylindrical wall of the housing, the lugs extending through the insulating material to position the same, the insulating material covering the openings in the housing wall from which the lugs are struck, and portions on the rotatable contact driving member adapted to engage the lugs to limit rotation of said member.

6. A variable resistance device having in combination, a housing, a resistance in said housing,

housing for an end surface of the shoulder on said shaft, stop means limiting movement of the shaft in the direction away from the second bearing, the contactor being maintained in ena shaft extending through at leastione wall of gagement with the resistance strip throughout said housing, a contactor engaging the resistance axial movement of the shaft, means for yieldingly and moved by rotation of the shaft, means carmaintaining the shoulder spaced from the second ried by the shaft and rotatable therewith conbearing, actuating means on the end of the shaft nected to the contact, said means engaging a fixed beyond the second bearing, and a second control connector carried against the inner face of one device located to be actuated by said means when 10 Wall of the housing, and resilient means engagthe shaft is in engagement with the second ing the opposite inner wall of the housing to urge bearing. said first means against the fixed connector and 9. A multiple circuit control device comprising toward the first wall. a variable resistance having in combination, a

7. A variable resistance device having in comhousing, a shaft rotatably mounted in and exbination, a housing, a resistance in said housing, tending through said housing, a resistance strip a shaft extending through at least one wall of in the housing, a contactor engag the s said housing, a contactor engaging the resistance ance strip and rotated by the shaft, a shoulder and moved by rotation of the shaft, conducting on said shaft, a journal bearing formed integrally means connected to the contact and carried by with said housing at one end thereof, a second and rotatable with the shaft, a second conducting journal bearing at the opposite end of said housmeans carried by an inner wall of the housing, ing, a thrust bearing formed in the wall of said and resilient means engaging the opposite inner housing adjacent said first-named journal bearwall of the housing and urging the shaft toward ing within the housing, stop means limiting movethe first-named Wall to cause contact between the ment of the shaft in the direction away from the said conducting means. i thrust bearing, the contactor being maintained in 8. A multiple circuit control device comprising ng em nt with the r sis an e strip throu h a variable resistance having in combination, a axial movement of the shaft, means for yieldingly housing, a shaft rotatably mounted in and exmaintaining the shoulder spaced from the thrust tending through said housing, a resistance strip bearing and againstsai p e a ati in the housing, a contactor engaging the resistance strip and rotated by the shaft, a shoulder on said shaft, a bearing surface integral with said housing for a circumferential surface of said means on the end of the shaft beyond the second nearing, and a second control device located to be actuated by said means when the shaft is in engagement with the thrust bearing.

shaft, a second bearing surface integral with said NEWTON C. SCHEU ENGER.

CERTIFICATE OF CORRECTION. Patent No. 2,1Lr5,955c February 7, 1959.

' NEWTON C. SCHELLENGE R.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correctionas follows: Page 5, second column, line 25, claim 1, for "bearings" read bearing;

lines

27 and 28,

strike out the words "in the bushing and the bearing in the housing" and insert the same before "being" in line 25,same c1aiml; 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 Gffice. Signed and sealed this 11th day of April, A. D. 1959.

Henry Van Arsda'le (Seal v Acting Commissioner of Patents.