US2272433A - Mounting and operating means for variable inductance devices - Google Patents

Description

Feb. 10, 1942. w. A. SCHAPER 2,272,433

MOUNTING AND OPERATING MEANS FOR VARIABLE INDUCTANCE DEVICES Filed Sept. 26, 1940 I INVENTOR. W/LL/HM r4. SCH/IP52.

BY MGM ATTORNEY.

Patented Feb. 10, 1942 MOUNTING AND OPERATING ltIEAN S FOR. VARIABLE INDUCTANCE DEVICES William A. Schaper, Cicero, 111., assignor to Johnson Laboratories, Inc., Chicago, 111., a corporation of Illinois Application September 26, 1940, Serial No. 358,464

24 Claims.

The invention pertains to improved mounting and operating mechanism for permeability tuning devices, by which inductance coils are conveniently and cheaply mounted on a supporting plate, which also supports rollers for controlling cables operatively connected with ferromagnetic cores for movement relatively to the inductance coils, all of the parts being of simple and inexpensive construction and of such a nature that needless parts are eliminated. 1

It is an object of the invention to produce mounting and operating means for permeability tuning devices by which inductance coils are placed on opposite sides of a mounting plate, an operating roller is mounted at one end portion of the plate to drive a cable connected with the ends of ferromagnetic cores movable longitudinally oi the coils, the bearings of the roller being preferably stamped sheet metal parts secured to the mounting plate and constructed at the same time to constitute a supporting base for the entire device, the mounting plate also supporting at its other. end an idler roller around which a second cablepasses and is connected at its ends with the other ends of said ferromagnetic cores, the idler'roller being mounted in a recess in the end of the mounting plate and supported for rotation on a flexible resilient rodwhich not only permits the roller to turn freely as may be required by movement of the operating roller, but also places a desired tension on the cables employed.

The above and other objects of the invention will more fully appear by reference to the accompanying drawing illustrating a preferred embodiment thereof in which:

Fig. 1 shows in plan view'a tuning unit in accordance with the invention,

Fig. 2 is aside elevation of the tuning unit shown in Fig. l,

Fig. 3 is an end elevation'of the tuning unit shown in Fi 2,

Fig. 4 is a vertical sectional view to an enlarged scale of the construction shown in Fig. 2, taken along the line ll of the latter figure, and

Fig. 5 illustrates in fragmental side elevation the manner in which a number of the tuning units may be mounted on a chassis for gang operation.

Similar numerals refer to similar parts throughout the several views.

As shown in Figs. 1, 2 and 3, the invention con-' sists of a central mounting plate it of suitable material, for example sheet metal, which has secured to its upper end portion shown in Figs. 2

and 3, two formed sheet metal members H and l2 having their mid-portions rigidly secured to the plate W in any convenient manner, for example by rivets, the end portions of said members below the said connections being bent at substantially right angles to the plate ill and extending therefrom in substantially the same plane to constitute the supporting base of the tuning device. The other end portions of the members It and I2 are bent into arcuate form as shown at Ma and Ma respectively, to receive and support a driving roller It having a shaft M to operate the same to inturn move the ferromagnetic cores of the tuning device. The roller l3 comprises a central portion of relatively large diameter and journaled end portions its and I3!) of substantially smaller diameter, which journaled portions are engaged by the curved portions lid and lid of base members ll and l2. As shownin Fig. 2, the base member ll is notched at its midportion to clear the central portion of the roller l3, and said member ll has extending therefrom partly around the journals i312 and Nb, bearing members lie and I lb, of which only the bearing member Ila is seen in Fig. 3. Similarly, as indicated in dotted lines in Fig. 2, the bearing members I211 and Hi extend from the base member l2 partly around the journals ltd and i311 to form bearing members for said journals. It will be noted that each of the bearing members lla, llb, l2a, l2b is slightly narrower than half the axial length of the corresponding journal lila, l3h as the case may be. This construction not only provides a simple and adequate bearing support for the roller it, but it also provides a convenient means for limiting the rotation of the roller l3, as follows:

As shown in Fig. l, the roller is has formed on it from its mid-portion and extending somewhat less than half the length of the journal portions I311 and ltb, stop lugs We and l3d in line respectively angularly with the bearing members lie and i219, but so disposed that they do not at any time engage the bearing members 12a and ill) respectively. The stop lugs its and ltd are displaced from each other angularly on the roller l3, so that engagement between said lugs and the ends of the bearing members lie and ltb will permit rotary movement or the roller lit to the extent desired to properly operate the tuning devices, from which it will be observed that the bearing and roller construction, althoughinclu'ding stop lugs on the roller cooperating with the ends of bearing members encircling enough of the journals of the roller angularly to positively retain the journals in engagement with the hearing members, permits the angular movement of the roller to be of much greater extent than the angular spacing between the outer ends of the bearing members themselves, by arranging one of the stop lugs to engage the end of one of the bearing members, and the ether stop lug to engage the end of a bearing member on the opposite end of the roller, and by further so arranging the bearing members that only the bearing members effective in stopping rotation of the roller I! are in line angularly with the stop lugs I30 and I311. A further advantage of the construction is that the two members I I and I2 are duplicates of each other and may be made by the same tools. As shown in Fig. l, the members II and I2 are slotted at No and He to permit the ready assembly of the cable I5, which, as shown in Fig. 3, extends one and one-half times around the central portion of the roller I3 and a has one of its ends secured to one end of the ferromagnetic core I6 of the device, the other end of the cable I as shown in Fig. 4 being secured to one end of the ferromagnetic core I! of the tuning device.

As shown in Fig. 4, the core H is supported for longitudinal movement in a tube I8 of suitable insulating material supporting an inductance coil IS, the tube I8 extending longitudinally of the tuning unit and being supported in place by a bracket I8a of sheet metal secured to the mounting plate II) in any convenient manner, for example by rivets and 2|. The core I6 is arranged to move longitudinally in a tube 23 of insulating material carrying an inductance coil 24, the tube extending longitudinally of the tuning unit and being supported by a bracket of sheet material secured to the mounting plate II] in any convenient manner, for example by rivets 2| and 22. The rivet 2| conveniently cooper ates in holding both of the brackets IBa and 25 in place, and the rivets 21 and 22 preferably engage suitable longitudinal slots in the base portion of the bracket 25, permitting the bracket and coil 24 "carried thereby to be moved relatively to the mounting plate In and longitudinally of the core I6, to secure any desired adjustment of the coil 24 relatively to and longitudinally of the core IB, for example for aligning or tracking purposes. The lower end portion of the plate In is notched to receive an idler roller 26 mounted for. rotation on a slender resilient rod 21 of spring material, for example spring steel, supported near its ends by lugs Illa and lob formed from the plate Ill. The roller 28 serves to guide a cable 28 from alignment with the core IE to the lower end of which it is secured, to alignment with the lower end of the core Il to which said cable is also secured. The roller and cable construction therefore results in moving the cores l6 and Il longitudinally and relatively to the coils 24 and I9 respectively in opposite directions, when the shaft ,I4 is rotated, the steps [30 and I3d being so disposed angularly, and the diameter of the central portion of the roller I3 being so taken, that the maximum desired movement of each of the cores I5 and I1 will result from turning the roller I3 as cient tensional force to the cables I5 and 28 to keep them in a taut condition so that the cores will be operated without lost motion when the shaft I4 is rotated.

The plate I!) is preferably provided with aflange portion Iflc to support a block of insulating material 29 carrying adjustable capacitors 30 and 3| for cooperation with the coils 24 and I9 respectively for any purposes for which the cells may be used.

As shown in Fig. 2, the shaft I4 where it extends through roller I3, is substantially half cut away as indicated at Me for engagement with a flat bent spring 32 extending through a flat slot I3e formed longitudinally through the roller adjacent the shaft I4, said spring having bent ends holding the spring in place in the roller, when the shaft is also in the roller, for which condition the spring is in a nearly straight and stressed condition holding the shaft against angular displacement relatively to the roller so that turning the shaft I4 will turn the roller I3 to operate the cores I B and ll. The spring 32 does not, however, prevent the ready insertion of the shaft I4 into and through'the roller I3, nor does it prevent the ready removal. of the shaft from the roller.

As shown in Fig. 2, one edge of the base portion of the bracket 25 is preferably provided with rack teeth 25b adjacent a centering aperture 40 in the plate ID for cooperation with a suitable pinion tool or the equivalent (not shown), for adjusting the bracket on the plate 10.

The roller I3 is preferably made of ceramic material so that it will have desired insulating value, be non-magnetic, and at the same time facilitate the molding of the stop lugs thereon, as well as the molding of the central opening therethrough, so that when the molding and firing are completed, the roller structure is ready for assembly in the tuning device. The roller 26 may be of any suitable material, for example ceramic, Bakelite, fiber, or other material adapted to the purpose,

The tuning unit construction described in connection with Figs. 1-4 inclusive is well adapted for gang operation as illustrated in Fig. 5, in which a chassis is illustrated at 33 upon which tuning units Ifld are mounted, each constructed as described in connection with Figs. 1-4 inclusive, said tuning units being mounted on said chassis so that the operating rollers I3 of said tuning units are the lowermost parts of said tuning devices and are below the top Wall of the chassis 33 and secured to said chassis with the said operating rollers I3 in alignment with each other. For this condition, a single operating shaft I4b constructed in a manner similar to the shaft I4 above described, but having a flattened portion of suliicient length to extend through all of the operating rollers i3 used in the assembly illustrated in Fig. 5, is readily inserted through all said operating rollers and cooperates with each roller by means of a flat spring 32 in the manner above described, and as a result the rollers I3 are simultaneously operated when the shaft Mb is turned. The shaft I4?) is provided with a groove I4c adjacent the side wall of chassis 33, into which a split ring 34 is compressed to. prevent the Withdrawal of the shaft I4b from the rollers l3, the engagement of the shoulder at the end of the flattened portion of said shaft with the roller I3 .nearest the ring 34, preventing longitudinal motion of the shaft I4 1n the opposite direction. The shaft Mb is extended beyond the ring 34 at 16. through the side wall oi the chassis to supporit an operating knob 35 by which the shaft Mb may be turned as desired.

It willbe observed that it 1 mounting the tuning units Hid on the chassis. 33 :as described, the only openings that need be cut through the top wail of the chassis are openings large enough thorities.

to clear the rollers l3 and that when the tuning units are in place on the cl lass'is, the base members H and ll of the tuning 'units cover said openings to thus complete :lyenclose the wiring and. accessory devices con .tained in the chassis 33., to avoid fire hazards fits required by the au- With a gang assembly of tuning units as illustrated in Fig. 5, sloield plates 36 are required between the units. if they are mounted in closely associated rela tion. but it will be ob, served that there is no need to employ shield cans for said units unless it isnecessary to shield the coils of the units .irom :other parts oi. the apparatus or to prevent outside inductive effects in operating the coils of the tuning units. It will also be observed in connection with each of the tuning units, that the "mounting plate l serves as a slneldplate between the two coils of the'unit so that there is no appreciable coupling or interaction b tween the coils of the unit.

Thetuning units'described being each self contained, may be mounted in any positiondesired, whether horizontal, vertical, or otherwise, and with the units extending in any desired directions irom their operating shafts, without in any way changing the operation of said units or the efiects secured by said operation.

The cables l5 and 28 may be pr any material adapted to the purpose, for example cord or wire, or other fibrous or metallic material, the only requirements being that it shall be sumciently flexible to bend freely around the rollers and that it mall in no way interfere with the operation of the tuning units.

it will be understood that while the invention is herein illustrated as embodied in a tunint unit construction adapted to simultaneously tune a pro-selector circuit and an oscillator )circuit cl 2. superheterodyne radio receiver, over a desired range or frequencies, the invention is not limited to that purpose, for by suitably winding the coils and suitably selecting the cores, and connecting the flexible cables to the cores in the manner reuuiredi any particular case to secure a desired relation or inductance variation of the coils, the invention may be used edectively in any case where it is required to change or vary the undue-=- tances oi two circuits, whether the change is in the same direction as illustrated, or in an opposite direction.

While I have shown my invention in. the par ticular embodiment above described, 1 do not limit myseli thereto as i may employ equivalents thereof without departing from the scope oi'the appended claims.

thus described my invention, what i cloth r V I l. in a to unit, the combination of a central mounting plate oi sheet metal ertendine lon= ciuldinally of said an inductance coil mounted on each side oi said plate and extend. i

ins loneltudiny of said unit, ferromagnetic core associated with and movable ioncitudally of each of said coils iorinductance changing purposeaan operating roller mounted for rotary movement at one end portion oi said plate, an idler roller mounted for rotary movement other end portlonof cable extending around said operating roller and having its ends connected respectively with first for angular movement,

other. end portion of said plate, a first flexible cable extending around said operating roller and having its ends connected respectively with first ends of said cores, and. a second flexible cable 5 extending around said idler roller and having its ends connected respectively with the other ends or said cores, whereby turning said operating roller moves each of said cores relatively to the associated'coll.

2. In a tuning unit, the combination of a central mounting plate of sheet metal extending longitudinally of said unit. an inductance coil mounted on each side of said plate and extending longitudinally of said unit, ,9. ferromagnetic 15 core associated with and movable longitudinally of each of said coils for inductance changing pur= poses, an operating roller mounted for rotary movement at one end portion of said plate, an idler roller mounted for rotary movement at the said plate, a first flexible ends of said cores, a second flexible cable extending around said idler roller and having'its ends 25 connected respectively with the other ends of said M cores,

whereby turning said operating roller moves each of said cores, relatively to the associated coil, and a flexible rod of resilient material extending through a central clearance hole in said idler roller and supporting said idler roller for angular movement, the end portions of said rod being held by said plate with said rod in a condition of stress tensioning said cables.

/ 3. In a tuning un't, the combination of a cen tral mounting plate of sheet metal extending longitudinally of said unit, an inductance coil mounted on each sideof said plate andextending longitudinally of said unit, a ferromagnetic core associated with and movable longitudinally so of each of said coils for inductance changing purposes, an operating roller mounted for rotary movement at one end portion of said plate, an idler roller mounted for rotary movement at the other end portion of said plate, a first flexible cable extending around said operating roller and having its ends connected respectively with first ends of said cores, a second flexible cable extendinc around said idler roller and having its ends connected respectively with the other ends of go said cores, whereby turning said operating roller moves each oi said cores relatively to the associated coil, and "flexible rod of resilient material extending through a ce tral clearance hole in said idler roller and supporting said idler roller said plate having bent and integral lugs holding the end portions oi said rod.

d. In a tuning unit, the combination of a con tral mounting plate oi sheet metal extending lonm gltudlually of said unit, an inductance coil mounted on each side oi said plate'and extendinst longitudinally oi said unit, a. ferromagnetic core wsociated with and movable longitudinally of each of said coils for inductance changing purposes, an operating roller mounted for rotary movement at one end portion of said plate, on idler roller mounted for rotary movement at the other end portion of said plate, a first iieuible cable a; w around said operating roller and 7o its ends connected respectively with ends of said cores, a second flexible cable extendinc around said idler roller and having its ends connected respectively with the other ends or said cores, whereby turning said operating roller at the it; moves each of said coresrelatively to the asso other end portion of said plate,

ciated coil, and a flexible rod oi resilient material extending through a central'clearance hole in said idler roller and supporting said idler roller for angular movement, said plate having bent and integral lugs holding the end portions of said rod with said rod in a condition oi stress tensioning said cables.

5. In a tuning unit, the combination of a central mounting plate of sheet metal extending longitudinally of said unit, an inductance coil mounted on each side of said plate and extending longitudinally of said unit, a ferromagnetic core associated with and movable longitudinally of each of said coils for inductance changing purposes, an operating roller mounted for rotary movement at one end portion of said plate, an idler roller mounted for rotary movement at the other end portion of said plate, a first flexible cable extending around said operating roller and having its ends connected respectively with first ends of said cores, a second flexible cable extending around said idler roller and having its ends connected respectively'with the other ends of said cores, whereby turning said operating roller moves each of said cores relatively to the associated coil, and sheet metal bearing members secured to the end portion of said plate and having arcuate end portions constituting bearings for said operating roller.

6. In a tuning unit, the combination of a central mounting plate of sheet metal extendin longitudinally of said unit, an inductance coil mounted on each side of said plate and extending longitudinally of said unit, a ferromagnetic core associated with and movable longitudinally of each of said coils for inductance changing purposes, an operating roller mounted for rotary movement at one end portion of said plate, an idler roller mounted for rotary movement at the other end portion of said plate, a first flexible cable extending around said operating roller and having its ends connected respectively with first ends of said cores, a second flexible cable extending around said idler roller and having its ends connected respectively with the other ends of said cores, whereby turning said operating roller moves each of said cores relatively to the associated coil, and sheet metal bearing members secured to the end portion of said plate and having arcuate end portions constituting bearings for said operating roller, said bearing members being on opposite sides of said plate and the other end portions of said bearing members being bent and extending in substantially the same plane and in opposite directions from said plate to constitute a mounting base for said tuning unit.

7. In a tuning unit, the combination or a central mounting plate 01' sheet metal extending longitudinally of said unit, an inductance coil mounted on each side of said plate and extending longitudinally of said unit, a ferromagnetic core associated with and movable longitudinally of each of said coils for inductance changing purposes, an operating roller mounted for rotary movement at one end portion of said plate, an idler roller mounted for rotary movement at the a first flexible cable extending around said operating roller and having its ends connected respectively with first ends of said cores, a second flexible cable extending around said idler roller and having its ends connected respectively with the other ends of said cores, whereby turning said operating roller moves each of said cores relatively to the assoing' around said idler ciated coil, and sheet metal bearing members secured to the end portion of said plate and having arcuate end portions constituting bearings for said operating roller, said bearing members being on opposite sides of said plate and the other end portions of said bearing members being bent and extending in substantially the same plane and in opposite directions from said plate to ccnstitute a mounting base for said tuning unit, said bearing members being of identical size and form.

8, In a tuning unit, the combination of a cen tral mounting plate of sheet metal extending longitudinally of said unit, an inductance coil mounted on each side of said plate and extending longitudinally of said unit, a ferromagnetic core associated with and movable longitudinally of each of said coils for inductance changing purposes, an operating roller mounted for rotary movement at one end portion of said plate, an idler roller mounted for rotary movement at the other end portion of said plate, a first flexible cable extending around said operating roller and having its ends connected respectively with first ends of said cores, 9. second flexible cable extending around said idler roller and having its ends connected respectively with the other ends of said cores, whereby turning said operating roller moves each of said cores relatively to the associated coil, sheet metal bearing members secured to the end portion of said plate and having arcuate end portions constituting bearings for said operating roller, and stop lugs carried-by said operating roller for engagement with said bearing members and limiting rotary movement of said operating roller.

9. In a tuning unit, the combination of a central mounting plate of sheet metal extending longitudinally of said unit, an inductance coil mounted on each side of said plate and extend ing longitudinally of said unit, a ferromagnetic core associated with and movable longitudinally of each of said coils for inductance changing purposes, an operating roller mounted for rotary movement at one end portion oi said plate, an idler roller mounted for rotary movement at the other end portion of said plate, a first flexible cable extending around said operating roller and having its ends connected respectively with first ends or said cores, a second flexible cable extendroller and having its ends connected respectively with the other ends of said cores, whereby turning said operating roller moves each of said cores relatively to the associated coil, sheet metal bearing members secured to the end portion of said plate and having arcuate end portions constituting bearings for said operating roller, and stop lugs carried by said operating roller for engagement with said bearing members and limiting rotary movement of said operating roller, said operating roller and said stop lugs comprising a unitary structure of molded material.

10. In a tuning unit, the combination of a central mounting plate of sheet metal extendng of said unit, an inductance coil said coils for inductance changing purposes, an operating roller mounted for rotary movement at one end portion of said plate, an idler roller mounted for rotary movement at the other end portion of said plate, a first flexible cable extending around said operating roller and idler roller mounted for rotary movement at.

the other end portion of said plate, a first flexible cable extending around said operating roller and. having its ends connected respectively with first ends of said cores, a second flexible cable extending around said idler roller and having its ends connected respectively with the ate end portions constituting bearings for said operating roller, and stop lugs carried by said operating roller for engagement with said bearing members and limiting rotary movement of said operating roller, said bearing members being on opposite sides of said plate, and said arcuate end portions being each of less width than the axial extent of the corresponding journal portion of the operating roller, said arcuate end portions of one of said bearing members being spaced axially of said operating roller from alignment with the arcuate end portions of the other of said bearing members, and each of said stop lugs being in alignment with an arcuate end portion of one of said bearing members for motion-limiting engagement therewith and also being free from motion-limiting engagement with the others of said bearing members.

11. In a tuning unit, the combination of a central mounting plate of sheet metal extending longitudinally of said unit, an inductance coil mounted on each side of said plate and extend ing longitudinallyof said unit, a ferromagnetic core associated with and movable longitudinally of each of said coils for inductance changing purposes, an operating roller mounted for rotary movement at one end portion of said plate,

an idler roller mounted for rotary movement at the other end portion of said plate, a first flexible cable extending around said operating roller and having its ends connected respectively with first ends of said cores, a second flexible cable extending around said idler roller and having its ends connected respectively with the other other ends of said cores, whereby turning said operating roller moves each of said cores relatively to the associated coil, sheet metal bearing members secured to the end portion of said plate and having arcuate end portions cbnstituting bearings for said operating roller, and

stop lugs carried by said operating roller for central mounting plate of sheet metal extending ends of said cores, whereby turning said operating roller moves each of said cores relatively to'the'associated coil, sheet metal bearing memhers secured to the end portion of said plate and having arcuate end portions constituting bearings'for said operating roller, and stop lugs carried by said operating roller for engagement with said bearing members and limiting rotary movement of said operating roller, said bearing members being on opposite sides of said plate, and said arcuate end portions being each of less engagement with said bearing members and limiting rotary movement of said operating roller, said bearing members being on opposite sides of said plate, and said arcuate end portions being each of less width than the axial extent of the corresponding journal portion of the operating roller, said arcuate end portions of one of said bearing members being spaced axially of said operating roller from alignment with the arcuate end portions of the other of said bearingmembers, and each of said stop lugs Being in alignment with an arcuate end portion of one of said-bearing members for motion-limiting engagement therewith and also being free from motion-limiting engagement with the others of said bearing members, the other end portions of said bearing members being bent and extending in substantially the same plane and in opposite directions from said plate to constitute a mounting base for said tuning unit.

13. In a tuning unit, the combination of a longitudinally of said unit, an inductance coil mounted on each side of said plate and extendil'lg longitudinally of said unit, a ferromagnetic core associated with and movable longitudinally of each of said coils for inductance changing purposes, an operating roller mounted for rotary movement at one end portion of said plate, an idler roller mounted for rotary movement at the other end portion of said plate, aflrst flexible cable extending around said operating roller and having itsends connected respectively withfirst ends of said cores, a second flexible cable extending around said idler roller and having its ends conwidth than the aidal extent of the correspondl ing journal portion of the operating roller, said arcuate end portions of one of said bearing members being spaced axially-of said operating roller from alignment with the arcuate end portions of the other of said bearing members, and each of said stop lugs being in alignment with 'nected respectively with the other ends of said cores, whereby turning said operating roller moves each of said cores relatively to the associated coil, sheet metal bearing members secured to the end portion of said plate and having arcuate end portions constituting bearings for said operating roller, and stop lugs carried by said operating roller for engagement with said bearing members and limiting rotary movement of said operating roller, the end journal por iii) an arcuate end portion of one of said bearing members for motion-limiting engagement therewith and also being free from motion-limiting engagement with the others of said bearing members, said bearing members being of identical size and form.

12, In a tuning unit, the combination of a central mounting plate oi sheet metal extending longitudinally of said unit, an inductance coil mounted on each side of said plate and extendinglongitudinally of said unit, a ferromagnetic core associated with and movable longitudinally oi each of said coils for inductance changing purposes, an operating roller mounted for rotary movementat one end portion of said plate, an

tions of said operating roller being of smaller diameter than the central portion thereof and said lugs extending radially from said journal portions.

id. in a tuning unit, the combination of a central mounting plate oi sheet metal extending longitudinally of said unit, an inductance coil mounted on each side of said plate and extending longitudinally of said unit, a ferromagnetic core associated with and movable longitudinally of each of said coils for inductance changing purposes, an operating roller mounted for rotary movement at one end portion of said plate, an idler roller mounted for rotary movement at the other end portion of said p ate, a first flexible cable extending around said operating roller and having its ends connected respectively with flrst ends of said cores, a second flexible cable extending around said idler roller and having its ends connected respectively with the other ends of said cores, whereby turning said operating roller moves each of said cores relatively to the associated coil, sheet metal bearing members secured to the end portion of said plate and having arcuate end portions constituting bearings for said operating roller, and stop lugs carried by said operating roller for engagement with said bearing members and limiting rotary movement of said operating roller, the end journal portions of said operating roller being of smaller diameter than the central portion thereof and said bearing members restraining said operating roller from axial movement relatively to said bearing members.

15. In a tuning unit, the combination of a central mounting plate of sheet metal extending longitudinally of said unit, an inductance coil mounted on each side of said plate and extending longitudinally of said unit, a ferromagnetic core associated with and movable longitudinally of each of said coils for inductance changing purposes, an operating roller mounted for rotary movement at one end portion of said plate, an idler roller mounted for rotary movement at the other end portion of said plate, a first flexible cable extending around said operating roller and having its ends connected respectively with first ends of said cores, a second flexible cable extending around said idler roller and having its ends connected respectively with the other ends of said cores, whereby turning said operating roller moves each of 'said cores relatively to the associated coil, said operating roller having a flat-sided central hole extending axially through it, a flat-sided operating shaft in said hole, and a flat spring in said hole and pressing against said shaft and said operating roller.

16. In a tuning unit, the combination of a sheet metal mounting plate supporting on each of its sides an inductance coil andan associated ferromagnetic core movable longitudinally of said plate and relatively to the coil for inductance changing purposes, two flexible cables connected with said cores to operate the same, an

- operating roller mounted at one end portion of said plate and engaging one oi said cables, an idler roller mounted at the other end portion of said plate and engaging the other of said cables, and arcuate sheet metal bearing elements carried by said plate and extending around and supporting said operating roller for angular movement.

1'7. In a tuning unit, the combination of a sheet metal mounting plate supporting on each ol' its sides an inductanc coil and an associated ferromagnetic core movable longitudinally of said plate and relatively to the coil for inductance changing purposes, two flexible cables connected with said cores to operate the same, an operating roller mounted at one end portion of said sheet metal mounting plate supp :rtlng on each of its sides an inductance coil and an associated ferromagnetic core movable longitudinally of said plate and relatively to the coil for inductance changing purposes, two flexible cables connected with said cores to operate the same, an operating roller mounted at one end portion of said plate and engaging one of said cables, an idler roller mountd at the other end portion of said plate and engaging the other of said cables, arcuate sheet metal bearing elements carried by said plate and extending around and supporting said operating roller for angular movement, there being two of said bearing elements at each end portion of said operating roller and spaced substantially axially from alignment with each other, and a stop carried by each end portion of said operating roller for rotationdimiting engagement with one of said bearing elements.

19. In a tuning unit, the combination of a sheet metal mounting plate supporting on each of its sides an inductance coil and an associated ferromagnetic core movable longitudinally of said plate and relatively to the coil for inductance changing purposes, two flexible cables connected with said cores to operate the same, an operating roller mounted at one end portion of said plate and engaging one of said cables, an idler roller mounted at the other end portion oi said plate and engaging the other of said cables, and a flexible resilient rod extending through a clearance opening in said idler roller and supplate and engaging one of said cables, an idler 1 porting said roller for angular movement, said plate having engagement with the end portions of said rod and supporting said rod in stressed condition, thereby maintaining said cables in taut condition.

20. In an assembly of self-contained tuning units each completely housed and separately operative and each including inductance coils and ferromagnetic cores movable relatively thereto for inductance changing purposes, and also including flexible cables and operating rollers for simultaneously operating said cores by means of said cables, the operating roller of each unit having its own supporting bearings constituting a Part ofsaid unit, the combination of a chassis. a plurality of said tuning units mounted side by side on said chassis, said operating rollers one for each of said tuning units being mounted in axial alignment with each other, each of said rollers having a flat-sided opening extending axially therethrough, and a flat-sided operating shaft extending through all of said rollers for simultaneously rotating the same, said shaft being freely movable axially through said operating rollers for assembling and dismantling pur- DOSES.

ing around said operating roller and said idlerroller and connected with the ends of said core, whereby turning said operating roller moves said core relatively to said coil, and a flexible rod of resilient material extending through a central clearance hole in said idler roller and supporting said idler roller for angular movement, the end portions of said rod being held by said plate with said rod in a condition of stress tensioning said flexible connection. 22. Ina tuning unit, the combination of a central mounting plate of sheet metal extending longitudinally of said unit, an inductance coil mounted on said plate and extending longitudinally of said unit, a ferromagnetic core associated With and movable longitudinally of said coil for inductance changing purposes, an operating roller mounted for rotary movement at one end portion of said plate, an idler roller mounted for rotary movement at the other end portion of said plate, a flexible connection extending around said operating roller and said idler roller and connected with the ends of said core, whereby turning said operating roller moves said core relatively to said coil, and sheet metal bearing members secured to the end portion of said plate and having .arcuate end portions constituting bearings for said operating roller. 23. In a tuning unit, the combination 'of a central mounting plate of sheet metal extending longitudinally of said unit, an inductance coil mounted on said plate and extending longitudinally of said unit, a ferromagnetic core associated with and movable longitudinally of said coil for inductance changing purposes, an operating roller mounted for rotary movement at one end portion of said plate, an idler roller mounted for rotary movement at the other end portion of said plate, a flexible connection extending around said operating roller and said idler roller and connected with the ends of said core whereby turning said operating roller moves said core relatively to said coil, sheet metal bearing members secured to the end portion of said plate and having arcuate end portions constituting bearlugs for said operating roller, and stop lugs cariied by said operating roller for engagement with said bearing members and limiting rotary movement of saidoperating roller, said operating roller and said stop lugs comprising a unitary structure of molded material.

24. In a tuning unit, the combination of a central mounting plate of sheet metal extending longitudinally of said unit, an inductance coil mounted on said plate and extending longitudi nally of said unit, a. ferromagnetic core associated with and movable longitudinally of said coil for inductance changing purposes, an operating roller mounted for rotary movement at one end portion of said plate, an idler roller mounted for rotary movement at the other end portion or said plate, and a flexible connection extending around said operating roller and said idler roller and connected with the ends of said core, whereby turning said operating roller moves said core relatively to said coil, said operating roller having a fiat-sided central hole extending axially through it, 'a flat-sided operating shaft in said hole, and a flat spring in said hole and pressing against said shaft and said operating roller.

A. SCI-LAPER.

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