US2130153A

US2130153A - Tuning device for radio receivers

Info

Publication number: US2130153A
Application number: US170070A
Authority: US
Inventors: Alexander W Plensler
Original assignee: BELMONT RADIO CORP
Current assignee: BELMONT RADIO Corp
Priority date: 1937-10-20
Filing date: 1937-10-20
Publication date: 1938-09-13
Anticipated expiration: 1955-09-13

Description

Sept. 13, 1938. A. w. PLENSLER 2,130,153

TUNING DEVICE FOR RADIO RECEIVERS Filed Oct. 20, 193,7 4 Sheets-Sheet 2 MII M iff y my( '1 'Inl U ILIM i Sem. i3, 193s. A, w. PLENSLER 2,130,153

TUNING DEVICE FOR RADIO RECEIVERS Filed Oct. 20, 1957 4 Sheets--Sheetl 3 Sept. I3, 1938. A. w. PLENSLER 1309153 TUNING DEVICE FOR RADIO RECEIVERS Filed Oct. 20, 1957 4 Sheets-Sheet 4 Patented Sept. i3, 19

TUNING DEVICE FOR RADHO RECEIVERS Alexander W. Plensler, Chicago, lill., assigner to Belmont Radio Corporation, a corporation of lillinois Application october 2c,

17 Claims.

My invention relates in general to so'called automatic tuning devices for radio receivers and particularly to a mechanically operated device for connection with the tuning mech-anism for g a radio receiver to accomplish rapid tuning of the receiver to a predetermined broadcast station.

Mechanical tuning of a radio receiver to a predetermined station setting has been accomplished in the prior art by means of a rotatable cam and movable lever structure, but there have been certain disadvantages to the structure heretofore employed which have prevented or at least handicapped the commercial exploitation of such devices. These disadvantages were primarily related to unsatisfactory structure for securing a cam to its corresponding shaft, yetpermitting rotation thereon for original setting or resetting of said cam to a desired tuning position, and further were related to the complexity and relatively high costs for the structure without producing comparable operating advantages.

It is an object of the present invention to provide an improved automatic tuning device for a radio receiver.

A still further object is to provide a simplied, mechanically operated tuning device which will operate smoothly and efficiently, yet of such simple construction that it may be produced at 30 a very low cost for use with any radio receiver, and particularly the inexpensive table models or so-called midget radio receivers.

One of the features of my invention is the provision of locking means for the rotatable cams on their corresponding shaft to positively prevent movement of the cam with respect to the shaft during the tuning operation so that after the cam is once positioned on the shaft for a desired station setting, such position will be retained during subsequent tuning operations. 'Ihese tuning operations are, in effect, somewhat violent, by virtue of the fact that the operator in pressing the operating lever for the cam downwardly will apply a substantial force against the cam surface. f. f

A still further feature of my/invention is the provision of novel and simple/means for varying the locking pressure on the yindividual cams so as to permit the setting or angular positioning of such cam with respect to `the shaft to provide a desired predetermined station Setting for Athe tuning device. With respect to this locking pressure, there is sufficient frictional pressur'e on each cam even when ready for resetting, so that all cams may be reset individually while the lock- 1937, Serial No. 170,070

(Cl. 'i4-10) ing pressure is off, and then retain the set position until all others are similarly acted upon, after which the. locking pressure may be applied to all cams simultaneously with a single operation..

A further feature of my invention is the provision of coupling means between the tuning condenser and cam shaft to prevent misalignment of the condenser elements and to prevent undesirable microphonics to arise as between the condenser and automatic tuning device.

In practicing my invention I may also provide the tuning cams, and tuning condenser rotors on the same shaft, eliminating the necessity for coupling a cam shaft to a tuning shaft and thus simplifying the 4complete assembly.

In the commercial embodiments of my invention I also provide various stopping means to limit the movement of the cam on its carrying shaft to substantially 180 or the degree of rotation of the variable condenser for the radio receiver. I also provide stopping means acting upon the rotatable carrying shaft mechanism for my tuning device to cooperate with the normal stopping means on the variable condenser for the receiver to reduce jarring and consequently the possibility of misalignment of the variable condenser elements to a minimum.

Other objects and features of my invention will be apparent in the following description taken with the drawings, of which:

Fig. 1 is a front elevation of the complete automatic tuning device of my invention.

Fig. 2 is a top plan view, partly in section, of the tuning device of a portion of the variable condenser shown in Fig. 1.

Fig. 3 is a detailed sectional view along the line 3-3 of Fig.' 2.

Fig. 4 is a detailed view, partly in section, of the coupling mechanism between the rotatable cam shaft and the variable condenser for the radio receiver.

Fig. 5 is an enlarged view of a portion of,the coupling mechanism.

Fig. 6 is a fragmentary view, partly in section, of a 'modification of the manual tuning structure, and friction tensioning' means for the tuning cams.4

Fig. 7 is a fragmentary view, partly in section, of a further modification of the tuning and tensioning means.

Fig. 8 is a front elevation of a modication of the friction pressure adjusting means.

Fig. 9 is a sideelevation of an element thereof.

Fig 10 illustrates a still further modiilcation of the friction adjusting means.

Fig. 11 illustrates a modification of the tuner and condenser structure in which a common shaft is provided for both members.

Fig. l2 is a modification of the structure of Fig. l1.

Fig. 13 is a modification of the selector lever structure of Fig. 1. 2

y Fig. 14 is a fragmentary top plan view of the selector lever.

Fig. 15 is a modification of the indicator structure of Fig. 1.

Fig. 16 is a fragmentary plan view of the indicator of Fig. l5; and

Fig. 17 is a fragmentary sectional view of the pointer unit for this indicator.

Referring to Fig. 1, my tuning device is illustrated with a frame comprising a pair of side members I0 and II for rotatably supporting a cam shaft structure I2 including a central shaft I3 (Fig. 2) with a plurality of independent sleeves I4"surro unding the shaft. A bushing I3 slidable with respect to said shaft supports the same in the frame member I3. while a corresponding bushing I1 supports the shaft I3 in the opposite lframe member II.- A plurality of cams I3 are the shaft for receiving the key lug 23 on the washer I3 to prevent the rotation of the washer on said shaft. 'I'he cam I3 will rotate on the shaft-when the friction pressure is reduced as will be hereinafter explained, but this rotary movement is limited to substantially 180 by means of the integral stop lug 24 on the cam, engaging shoulder 23 or 21 on the washer I3,

the particular shoulder engaged depending on` the angular position of'the cam with respect to the shaft I3. Washer 2I may be identical with washer I3 and non-rotatable on the shaft I3, but a stop lug is provided on only one side of the cam I3. The key way 22 is shown in Fig. 2 of the drawings, and extends from the threaded end portion 28 of the shaft substantially to the opposite condenser coupling end 23.

The tuning ofthe radio receiver to a particular broadcast station is accomplished by moving the rotors of the tuning condenser 3| secured to a shaft 32 to a particular position with respect to the condenser stators to provide a particular capacity therebetween. The rotary movement of the rotors is limited to 180, and suitable stops are provided on the condenser structure. By virtue of the lug 24 on a cam I3, and the shoulders 23 and 21 on axed washer I9, the movement of each cam is limited to the same 180 arc travelled by the rotors of the variable condenser 3i. To provide a predetermined station setting within this path a cam I3 is set to an angular position with respect to the shaft I3 corresponding to the position of the rotors of the variable condenser 3I for that station. So far as the positioning of a cam on a shaft to correspond with the tuning condenser is concerned, this has been previously accomplished in the art. However, locking the cams in the desired position and'then resetting those cams for a predetermined station setting is accomplished in the present invention by much more positive yet simpler means than anything provided in the prior art.

The cams frictio'nally retained against rotary movement on the shaft I3 when in operating position, are selectively moved to provide a predetermined station setting for the variable condenser by means of selector levers 33 pivoted on a fixed rod or shaft 34 secured in the frame plates I3 and II.v The selector levers act as their own spacers, but are retained on a limited length of the rod as shown by means of split locking washers 33 pressed into corresponding grooves at that point in the rod. A sleeve 33' separates the two groups of levers at the dial portion of the assembly. Bushings 35 of insulating material support the shaft 34 at each end in the frame members to electrically insulate said shaft from said frame members. Each selector lever comprises a onepiece key and lever member 31 having a finger portion 33 formed at one end, and apertured intermediate the ends to fit over the rod 34. The member 31 is reinforced and supported against undesirable play on the shaft by means of a lever frame bar 33 riveted or otherwise secured to the lever member 31 at 4I and extending rearwardly in an offset position substantially parallel to the member 31 to cooperate therewith at its outer end in carrying a rotatably mounted roller 42. 'I'he two

members

31 and 33 act as their own spacers on the rod. Pivoted about the rod 34 as a center, the selector lever 33 is depressed until it engages the cam surface as shown in the first dotted position in the illustration of Fig. 3 when it causes the cam I3 itself to move by virtue of the rounded surface of its edge until the roller is'in the depression 43 formed by the two halves of the substantially heart-shaped cam. This position of the cam is shown in full lines in Fig. 3 and the corresponding position of the roller 42 is shown in the upper dotted line position. After the lever has been depressed to rotate the cam to this position, the spring 44 fastened to an insulating strip 44 acts to pull it back to the normal non-operating position shown in Fig. l. As is apparent, in Fig. 3 one side of the cam from tip to Y depression 43 is longer than the other side, and the tip is olf-center with respect to the aperture for the shaft I3. The cam and lever structure described above compensates for any wear on any of the engaging portions of the complete assembly and the roller 42 always seats in the depression 43 so that the. latter is always in the saine angular position and consequently the same station will always be tuned in for a particular setting of a cam. The' angular position of the condenser rotors of cour'sle corresponds to the position of the cam in the set position described.

The frictional pressure or tension on the cams I3 is adjusted by structure as shown in one embodiment in Fig. 2, which includes a knob unit 43 comprising an inner -s1eeve 41 having an integral downwardly extending lug 43 for fitting in thekey-way 22 of the shaft I3 as heretofore described. A knob 43 molded or provided in other material and rigidly secured to the sleeve 41, is left open at the end to receive a cap screw 5I which flts into the sleeve 41 and is apertured and anV tapped at one end to screw onto the corresponding threadsection 23 of the shaft I3. It is noted in Fig. 2 that shoulders 52 are provided on the under side of the head of the cap screw k.'il V to -bear against -the end of the sleeve 41 which sleeve the washer 2i carries therebetween a spring washer 54 bowed over its body portion as shown clearly in Fig. 2. In the position of these members as illustrated in Fig. 2, the screw I has been turned outwardly enough to reduce the tension in the spring Washer 54, to in turn reduce the friction tension on the individual cam-washerand-collar units over the length of the shaft I3 so that such shaft I3 may be moved relative to the cam I8. Such movement of the shaft I3 is accomplished while holding a cam i8 in fixed position by means of a roller 42 on the lever 33 engaging the depression 43. This holding position is illustrated in the full-line position of the cam I3 in Fig. 3, and the uppermost dotted line position of the roller 42. Meanwhile the tuning knob B9 is rotated to rotate the shaft I3 and in turn the shaft 32 coupled thereto, of the condenser 3l. Even in the position of Fig. 2 the spring washer 54 exerts sufiicient force on the movable assembly on the shaft to provide such frictional engagement on the cams as to keep them from rotating freely. As a result each cam may be reset while the locking pressure is oi; and then with them all in the desired positions the locking pressure is applied in a single operation as will be explained.

After a particular setting of the cam I8 is accomplished, the screw 5i is tightened on the threaded portion 28 to pull the threaded portion 29 into the threaded cavity of the cap screw 5I, and thereby cause the collar 41 on the tuning knob to press against the bushing I8 vwhich in turn presses the washer 53 against the spring washer 5B to gradually atten the same against the washer 2l and thus increase the friction pressure between each member of the complete assembly. This causes sufficient frictional pressure between the washers I9 and 2i and the adjacent surfaces of the cam I8 to securely lock the cam IB against rotation with respect to the shaft I3. The slot 5 I in the head of the cap screw is of such size that it will accommodate a relatively thin coin for turning the same so that no screwdriver is required.

' In order to prevent rotation of the shaft I3 as the screw 5I is being threaded onto the section 28, the shaft is turned by means of the turning knob 49 until a stop bar 56 keyed to the iiattened 'portion 29 of the shaft I3 engages a lug 51 punched out of the end wall il of the tuner frame. Inasmuch as the bar Vis keyed to the shaft. this engagement prevents further rotation of the shaft. The stop bar 56 is an element in the coupling structure between the shaft 32 of the tuning condenser and theshaft I3 of the automatic tuning' device. As shown in the enlarged illustration of Fig. 5, the end portion 29 of the shaft I3 is attened on each side at 58. These flattened sides correspond in angular position to the key-way 22 in such a manner that all of the elements making up the tensioning and locking means for the tuner can be aligned in the original assembly thereof to permit a rapid alignment with the rotor sections of the tuning condenser 3|. In this manner the arcuate path of 180 for the tuning condenser and the cams on, the tuner will exactly correspond when the device is in operation. This will be more readily apparent in the following description.

I n the structure of Figs. 1 to .5 particularly an indirect coupling between the shaft 32 and shaft I3 is provided. This is accomplished by a spring spider 59 rigidly secured toabushingGI whichmay be slipped over the end of the shaft 32 and se- 'cured thereto by the set screw 62. The spring spider 59 in turn is mounted on a pair of bosses 63 cooperating mechanism thereon is mounted in the l frame members I8 and II, the shaft I3 may be pushed in a left-hand-direction as viewed in Fig.

2 to cause the4 flattened portions 58 to extend through the end member i I. A fibrewa sher 62 is slipped over the end of the shaft to lay against the outside surface of the wall II and the spider collar and stop bar assembly is then slipped over the end of the shaft with the attened sides 65 of the slot or aperture in the stop bar 55 snugly engaging the flattened portions 5B of the shaft I3 to cause the stop bar to be keyed thereon in the position shown in Figs. 4 and 5. Ihis assembly is then rigidly secured on the end of the shaft by means of a screw 61 fitting in a threaded cavity in the end portion 23 of the shaft I3 and accessible through the opening 88 of the collar BI. With this lassembly completed, the shaft I3 is then turned until the stop bar 56 butts a lug 51 as shown in Fig. 4. This, of course, represents one of the extreme positions in the 180 arc travelled by rotors of the condenser 3| and the shaft I3. In originally setting or resetting a cam I8, the cam, as stated above, remains stationary while the shaft I3 is rotated by the knob 49. Because of the lug 2li on the cam I8 and the abutting shoulder 25 limiting rotation of the shaft, such shaft must be' turned in a counter-clockwise direction as' viewed in Figs. 3 and 4, and this, of course, is also true because of the fact that the stop bar 55 abuts the lower lug or projection 51. With the con-` denser 3| mounted in the position'on the end of the tuner frame shown in Fig. l, the rotors of such condenser will be entirely tted into the stators thereof at maximum capacity position when v'the cam and coupling structure is in the position shown in Figs. 3 and 4. 'I'hereforarotating the shaft I3 in a counter-clockwise direction by means of the tuning knob 49 will move the rotors of the condenser outwardly to the position of minimum capacity 180 from the initial position. This operation is utilized .in coupling the condenser shaft to the shaft I3 by means of the collar 5I, inasmuch as alignment between the tuner and condenser may be accomplished with each at one of the5 extreme positions on the-180 arc. After the set screw 62 is turned tightly .against the shai`t32 to secure'the coupling device onto said shaft. the mounting arms A on the condenser frame are secured by means of screws or the like to a rubber mounting member or grommet R on the end memberl II of the tuning frame to cushion the condenser with respect to the tuning device.

Tuning-indication is provided in a dial assembly including a drum 69 on thebushing 1I which in turn is secured to a movable sleeve on the shaft I3 asheretoforeide'scribed. The dial scale is printed on a plate or the like 12 transparent at the figures themselves to transmit light from dial light to the rear thereof. The plate 12 is secured on a boxlike frame 13 which in turn is supported on the n' bars 10 and 10', and then the vedge of the frame adjacent .the slots is peened to spreadthe frame and rigidly secure the bar in the frame. This Asame securing means is employed for fastening pulled against the same by the' spring. The u table model or so-called midget radio receiver.

The entire cabinet and receiver chassis is, of course. compact and relatively small, and the knob 43 is adapted to extend through an end wall 13 of the cabinet. No other manual tuning knob is employed for the condenser 3| and setting or resetting ofthe cams as well as tuning to stations other than those provided for on the automatic tuning device, is accomplished by such knob. In the case of a larger console model or the like where the large chassis and large cabinet is employed, it is not convenient from the standpoint of operation t'o have the manual tuning knob on theA side of the cabinet nor desirable in that it necessitates an extremely long tuning shaft reaching through the side wall of the cabinet. To overcome this dlillculty a modiflation of the invention is illustrated in Fig. 6 in which is provided alright-angled drive with the usual tuning knob at the front of the cabinet rather than on the side of the cabinet'as is provided for the structure of Fig. l. The shaft I3 in the Fig. 6 embodiment extends through the side wall I3 -of the tuning device and is encircled by a collar 11 having a downwardly prolecting'lug 13 keyed in the key-way 22 of the shaft I3, and bearing against the bushing I3 at one end, and against the shoulder 13 of a screw 3| at the other end. A drum 32 suitably journalled in a frame 33 is splined to the collar 11 at 3l. A pulley and shaft assembly 36 carries a belt or cord 31, and upon rotation of the shaftl and pulley 36 by means of a knob on the front of the radio cabinet, the pulley 32 is rotated to in turn rotate the shaft I3, and consequently the condenser shaft 32 as heretofore described.

The frictional pressure on the individual cams Il is varied in the manner substantially as previously described by turning the screw 3I to the right or left in th'e same manner as described with the cap screw I. A wing nut 33 is -provided on the end of the screw and is large enough to provide sufilcient leverage for finger move-` ment of said screw. In turning the cap screw, the collar 11, and consequently all of the axiallymovable cam unit elements on the shaft I3 in the tuning unit, are moved into tight frictional eny gagement with one another. and the spring washer 54 is compressed to maintain this frictional pressure as heretofore described. After the frictional pressure has been removed, the selector lever 33 may be employed-to engage the depression 43 in the substantially heart-shaped'cam, to

hold such cam against rotation while the shaft I3 is turned by means of the tuning knob on the shaft and pulley assembly 33. The cams are re set in this manner to vary the thereof.

A still further modification of the manual tuning tensioning means for the cam units is illustrated in Fig. '1. With this structure it is possible to eliminate the internal cap screw of the structuning position tures of Figs. l to 6 and utilize merely a-s'ngle tuning knob I3' for varying the frictional pressure on the elements on the shaft. InV the position illustrated in Fig. "l, the frictional pressure on the cam units is reduced to permit resetting of a cam I3, and for the purpose of illustration, this structure and the operation thereof will be described in connection with the step of increasing the frictional pressure on the individual cams. Axial movement of the washer I3 to the left on the shaft I3', as viewed in Fig. 7, to increase the frictional pressure, is accomplished by-an internally threaded gear or toothed wheel 33 threadably secured on the thread portion 23' of the shaft I3'. A piniongear 33' is provided, having a stub shaft 33 with a flattened side or sides 3I at the end thereof. A rim or collar 32 on the shaft 33 cooperates with the wall I3 to retain a coiled spring 33 on the shaft. The spring is shown in its compressed position in Fig. 7, but when the inward pressure on the shaft 33 is removed, as will 'be explained, the spring presses the shaft to the right to disengage the gear 33 from the gear 33.

In the structure of Fig. 7 the knob 43' is provided with an integral or rigid collar 41' having a cavity 33 therein corresponding in shape to the end of the shaft 33 including the flattened portion 3|. A corresponding vflattened portion 33 is provided on the end of the tuning shaft I3' to receive the knob and hold it against rotation thereon.. The internally threaded gear or toothed wheel 33 correspondsto a nut threaded on the shaft I3' and a gear rigid with respect thereto. The shaft I3 is turned by the knob 33 until the stop bar 53 (Fig. 4L on the end thereof, as heretofore described, engages a stop lug 51. This prevents further rotation of the shaft. The knob 43 is then removed from the shaft I3' and is slipped onto the end of the stub shaft 33 to push the shaft and gear 33' into the position illustrated, and then by turning the latter shaft in a direction to move the gear 33 axially to the left on the thread portion 23 of the shaft I3', the washer S3 is likewise moved to the left and the friction pressure i s increased on the individual cam units over the entire length of the shaft I3'. 'I'he knob 33' may then be removed from the stub shaft 33 and placed onto the shaft I3 and again utilized for manual tuning in the manner described above.

It is understood that the modification of Fig. 'I is employed primarily on midget sets and the knob 33' is positioned on the outside of the end wall of the cabinet as described with respect to Fig. 1. It is further understood, of course, that the loosening operation for the gear. is Just shaft I3'.

Although the adjusting means for the embodiments of my invention illustrated in Fig's. l to 7 include removable elements such as the cap screws and knobs, the invention is successfully practiced with adjusting means for the friction pressure on the cam by structure including nonremovable elements. One such embodiment, representing a modification of the previously described structure, is illustrated in Figs. 8 and 9. In the illustration of Fig. 8, a sleeve 33 for a knob member such as that shown in Figs. l and 7 is rigidly secured to a shaft I3' by means of a set screw 33 or the like. An apertured wheel IIII internally threaded or rigidly secured to a collar as |32 is threadably carried on the shaft rim of the Wheel to be engaged by a spring detent |04, including a movable pin having a pointed end |06 and having suitable stop collars and spring collars to retain the pin in the wall |'0 of the frame member for the tuner device. A coiled spring |01 on the pin |05 normally holds the same in the position shown in Fig. 8 out of engagement with the apertures |03 s or not it is desired to increase or decrease the frictional pressure on the cam units as has been explained. With the shaft I3 retained against rotation in one direction, the button |08 is pressed to cause the projection |06 to engage a corresponding aperture |03 in the wheel and while holding this engagement, the shaft |3 is turned in a direction away from the stop lug 51 by the tuning knob on the collar 98. 'I'his structure will permit the shaft to turn 180 and the threads on the shaft I3' and corresponding threads on the wheel unit are provided in such a manner that the 180. of movement will be sufficient to compress the spring washer 54, or permit the expansion thereof a sufficient amount to lock, or loosen. the cam units on such shaft, and in the latter case permit adjustment thereof. After the adjusting operation is completed the spring |01 will move the projection |06 out of engagement with the wheel |0I.

A still further modification of the adiustingr means is illustrated in Fig. 10. This includesa one-piece lever |09 pivotally 'secured on a pin normally mounted on the wall |0 of the tuner frame. The lever |09 is provided with a dog or projection -||2 for engagement with a tooth of a toothed wheel ||3 similar to, or identical with, the gear'89 of Fig. 7. When it is desired to adjust the frictional pressure on the elements on the shaft I3', the shaft |3' is turned.

by means of a knob (not shown) rigidly secured, if desired, to the end of the shaft |3 to a stop position with the stop bar 56 engaging a lug 51. Instead of a detent such as unit |04 ofl Fig. 8, the lever |09 is depressed to cause the engagement of the dog ||2 on a tooth at the stopped position of the wheel and the knob on the shaft |3 is then turned to move the shaft-180 as heretofore described. The spring ||4 pulls the dog ||2 out of engagement with the toothed wheel when the operators finger is removed from the lever. This lever may extend out of the rear of the cabinet or could extend from the front of the cabinet in a manner to correspond with the selector levers 33.

Modifications of the cam and condenser assembly are illustrated in Figs. 11' and 12. In Fig. 11, a one-piece shaft ||6 is rotatably mounted in a frame including a pair of end plates ||1 and ||8 corresponding in general to frame plates |0 and of the structure of Fig. 1. The rotor members.

of the tuning condenser 9 are rigidly secured to the shaft ||6 in the usual manner, and the cams |2| are supported on such shaft in the identical manner as described with respect to the structure of Fig. 1. The selector lever mechanism is likewise similar to that previously described. In fact, the illustrations of Figs, 11 and 12 are primarily schematic.

A slight modification of th one-piece rotatable shaft is illustrated in Fig. 12 with the condenser frame |22 being substantially identical with the frame of the condenser 3| except that the Wall |23 of the tuning unit frame is common to the condenser frame as well as the tuning frame. The shaft I6, however, is journalled in the frame member |23 and |24 and carries both the rotors of the condenser and the cams for the tuning unit. The coupling structure shown in Figs. 2 and 4 particularly, is, of course, eliminated in the devices of Figs. 1l and 12. This structure necessitates such a correlation between the condenser unit and the tuning unit that vthe entire assembly is completed in a single continuous operation rather than assembling each unit independently as is the case with the preferred embodiment in Fig. 1. However, where large production is attained on one particular structure of the tuning device, it is profitable to design the tuning and condenser units for assembly on a single shaft as shown in Figs. l1 and 12 to eliminate the extra parts and labor of the coupling device in the preferred embodiment. With the variations in sizes for a number of models, as is the usual practice with radio manufacturers, the two-unit assembly of Fig. 1 is ordinarily preferred.

l'I'heusual stops are provided in the rotor and stator assembly of Figs. 11 and 12, and a stop bar performing in the same manner as bar 54 is provided von the one-piece rotatable shaft intermediate the condenser unit and the cam unit, for engagement With a lug on the Wall or frame member intermediate these two units in the manner previously described.

When utilizing the tuning device of my invention with a midget set having a one-piece molded cabinet, with a decorative front Wall and no supplementary escutcheon plates, the slots in the wall for receiving a finger portion as 38 would ordinarily have to be too Wide to be acceptable from a decorative standpoint. In order to overcome this difficulty, a multi-part lever (Figs. 13 and 14) is provided having a stub end which may be conveniently inserted in a relatively narrow slot and having a supplementary finger portion for attachment to the main body of the selector lever. A lever member |26 similar to the lever 31 without the key portion 38, is provided with a pair of bumped out straps |21 at the forward l portion thereof. A spring member |28 is riveted to the lever |26 and includes a pair of spring fingers |29 having detents |3| thereon to engage corresponding notches |32 in a removable pin |33 for insertion through the front wall of the cabinet. A molded finger portion |34 is molded directly onto the pin |33. .When the pin is inserted through the straps |21, the detents |3| on the fingers |29 snap into the notches |32, and cooperate with the straps |21 to rigidly, but removably, retain the pin |33 therein.

In the event that a longitudinal rather than a vertical indicating scale is desired with the tuning structure previously described, a stampedout frame |36 is mounted on the tuner frame, preferably to one side or the other of the selector levers. Frame |36 is adapted to Support thereon a plurality of pulleys, including two longitudinally mounted pulleys |31 at one end and two vertically mounted pulleys |38 at the end end. A drive pulley |39 is secured to either the condenser shaft 32 or the cam shaft I3, and in this illustration such one or the other shaft Will be designated generally by reference character |40. Any dein a slot |44 in the frame member |36. Thel carriage is illustrated in section in Fig. 17 and includes a block |46 having shoulder portions |41 engaging one side of the frame |34. The block |48 is retained in this position by a plate |48 secured to the front of the block by a bolt or screw I4! also utilized to secure the pointer |42 to the plate |48. A cord ISI extends around the drive pulley |39 and over the two sets of pulleys |31 and |38, and each end of such cord is inserted through apertures |52 in the block |44 to be knotted at the under surface thereof and retained against removal. This is shown more particularly in Fig. 17.v Upon rotary movement of the shaft I, the carriage |43 travels longitudinally in the slot |44 with the pointer |42 indicating the changed position of the radio receiver.

From the foregoing description and the drawings it is apparent that I have provided a simple and compact tuning device, which will quickly and accurately tune the radio receiver to a deaired predetermined station setting. The cams are so rigidly retained in position on the tuning shaft when they. are set thereon that they will withstand any normal amount of pressure on the selector keys without varying in angular position. 'I'his makes it possible to obtain the same peak-timing for a predetermined station upon continued operations. Yet the friction tension'- ing means for the cam is such that it may be very quickly and easily adjusted.

Although my invention has been described and illustrated in its preferred embodiments, it is undersood that I do not limit my invention thereby but the invention is limited only by the scope of the appended claims.

I claim:

1. Radio tuning, apparatus for movement through no more than 180, including in combination, a rotatable shaft, a pair of spaced apart parallel frame members supporting said shaft, with the latter extending through each frame member, rotating means for said shaft on one end thereof, and a. stop member keyed to said shaft at the other end thereof for engagement with corresponding stops on the adjacent framev with respect to said shaft, and means for limiting the rotational movement of each cam with respect to said shaft, said means including a rigid stop lug on one sideof each cam, with said adjacent washer having a pair of integral shoulders spaced apart circumferentially thereon for engaging said lug on said cam to limit the rotary movement of the cam to the distance between control membersv on said shaft, spacing and friction means intermediate the control members and axially slidable therewith on said shaft substantiaily as an assembly, means at one end of the assembly for limiting axial movement of the assembly on the shaft at that end, tuning and adjusting means at the other end of the assembly directly on the threaded end of the rotary shaft and operable adjacent an end wall of the housing for varying the frictional pressure on the control members'and adapted for rotation of the shaft directly at the shaft for tuning, said means including threaded means on the threaded end of the rotary shaft, and" with said means movable and operatively connected with the slidableassembly to cause relative movement between the slidable assembly on the shaft and the limiting means at the one end of the assembly for applying sumcient frictional pressure on the control members in the assembly to prevent rotation of said control members with respect to the rotary shaft.

4. Selector tuning mechanism for a radio repeiver having a housing including in combination, a rotary shaft threaded at one end, a plurality of control members on said shaft, axially slidable means intermediate the control members for normally frictionally retaining said members against rotation relative to said shaft, said members and said slidable means movable axially together substantially as an assembly on said shaft, means at one end of the assembly for limiting axial movement of the assembly on the shaft at that end, and tuning and friction adjusting means at the` other end of the assembly directly on the threaded end oi' the rotary shaft including aknob on the outside 0f the receiver housing having a central bore and carried axiallyslidable on said shaft but non-rotatable thereon, a cap screw rotatable in said knob bore adjustably secured on the threaded end of the rotary shaft having an enlarged head at the outer end thereof for engagement against the knob, with said tuning and adjusting means operatively connected with said slidable assembly to cause relative movement between said assembly and said limiting means at the one end of the assembly upon rotation of said cap screw in said knob to apply frictional pressure on the control members.

5. Selector tuning mechanism for a radio receiver including in combination, a rotary shaft threaded at one end. a plurality of control members on said shaft, spacing and friction means intermediate the control members and axially slidable therewith on said `shaft substantially as an assembly, means at .one end of the assembly for limiting-axial movement of the assembly on the shaft at that end, tuning and friction adjusting means at the other end of the assembly directly on the threaded end of the rotary shaft including a tuning and friction adjusting device having a central bore and carried axially slidable but non-rotatable on said shaft, an adjusting member within the device bore having an internally threaded cavity at one end for threaded engagement with the end of the rotary shaft and having an enlarged head at the other end engaging a corresponding shoulder'on the device at the bore, with said tuning and friction adjusting means operatively connected with said slidable assembly to cause relative movement between said assembly and the limiting means at the one end of said assembly upon rotation of said adjusting member on said device to apply frictional pressure on the control members.

6. Selector tuning mechanism for a radio receiver having a housing with a. front and side walls including in combination, a rotary shaft threaded at one end portion, a plurality of control members on said shaft, spacing'and friction means intermediate the control members and axially slidable therewith on said shaft substantially as an assembly, means at one end of the assembly for limiting axial movement of the assembly on the shaft at that end, tuning and friction adjusting means at the other end of the assembly on the rotary shaft directly on said threaded end thereof including a tuning member for operation outside an end wall of the housing non-rotatably supported on said rotary shaft, and an adjusting unit operable outside said end wall of the housing at the tuning member having a threaded portion threadably secured on the threaded end of vthe rotary shaft, a relatively rigid washer and a resilient washer adjacent one another on said shaft intermediate the tuning and friction adjusting means and the slidable assembly, and with saidtuning and friction adjusting means acting on said washers and slidable assembly upon rotation of said adjusting unit from the outside of the end Wall of the housing to provide relative movement between the slidable assembly on the shaft and the limiting means at one end of the assembly for applying frictional pressure on the control members.

7. Selector tuning mechanism for a radio receiver having a housing including in combination, a rotary shaft threaded at one end thereof, a plurality of control members on said shaft, spacing and friction means intermediate the control members and axially slidable therewith on said shaft substantially as an assembly, means at one end of the assembly for limiting axial movement of the assembly on the shaft at that end, and tuning and friction adjusting means at the other end of the assembly directly on the threaded end, said means including an elongated memberthreadably secured at one end of the threaded end of the rotary shaft extending outwardly toward a side wall of the housing for adjusting the frictional pressure on the control members and adapted for direct engagement to turn the rotary shaft for tuning, structure axially slidable but non-rotatable relative to said shaft on said shaft intermediate said assembly and the elongated member acting upon said assembly upon threadable adjustment of said elongated member on said shaft to provide relative movement between said assembly and said limiting means at the one end of said assembly to apply frictional pressure on the control members.

8. Radio tuning apparatus for mounting in the housing for a radio receiver including in combination, a rotary shaft threaded at one end, a plurality of control members on said shaft, spacing v and friction means intermediate the control members and axially slidable therewith on said shaft substantially as an assembly, means at one end of the assembly for limiting axial movement of the assembly on the shaft at that end, a tuning and friction adjusting unit at the other end of the assembly directly on the threaded end of the said assembly acting together and said limiting means at one end of said assembly to apply frictional pressure on the control members.

9. Radio tuning apparatus for movement through no more than 180, including in combination a rotatable shaft, a pair of spaced apart parallel frame portions supporting said shaft, station selecting means on said shaft intermediate the frame portions with said shaft extending at each end through the corresponding frame portion, rotating means for said shaft on one end thereof, outside the corresponding frame portion, and a stop bar secured to said shaft against rotation relative thereto at the other end of said shaft outside the other frame portion, stop lugs extending laterally from such other frame portion on the outside thereof and positioned in the path of movement yof said stop bar in a manner to limit the degree of rotation of said bar to not more than 180.

10. Radio tuning apparatus including a rotary shaft, a plurality of control members spaced apart on said shaft and rotatable relative to said shaft, a washer on at least one side of each control member, non-rotatable relative to said shaft, means for maintaining each of said washers substantially in abutting relationshipto the corresponding sideof said control member, and means for limiting the rotational movement of each control member relative to said shaft, said means including a rigid lateral projection on the side of each control member with th corresponding washer for each member having a pair of integral abutments spaced apart circumferentially thereon for engaging the lateral projection on the control member to limit the relative rotary movement between the control member and the shaft to the distance between the abutments on the washer.

l1. Radio tuning apparatus including a rotary tuning shaft, a plurality of control members spaced apart on said shaft for selective rotation relative to said shaft to vary the control position of each of said member-s, a rotational limiting member on said shaft on at least one side of each control member non-rotatable relative to said shaft, means for limiting the angular rotational movement of each control member with respect to said shaft to a degree no more than the normal tuning movement of the rotary tuning shaft, said means comprising engaging abutments on a limiting member and its corresponding control member, with a single abutment' on one of said members and a pair `of angularly spaced apart abutments on the other of said members, said abutments being on adjacent portions and said pair of abutments defining the limit of relative movement between said two members.

12. Radio tuning apparatus including in combination, a rotary shaft, supporting means for said shaft, a plurality of control members normally frictionally retained against rotation relativeto said shaft, spacing and friction means on at least one side of each of said control members axially slidable therewith as an assembly on said shaft, friction adjusting means at onev end of said shaft bearing against one end of said assembly for axially adjusted movement to vary the friction on each control member in accordance with the adjusted position of said friction adjusting means, said spacing and friction means for each control member'I including a washer member adjacent said control member and keyed on said shaft with means on said two members to limit the relative rotation for one with respe'ct to the other, said means including an abutment on one member and a pair of spaced apart abutments on the other member for engagement by the one abutment to limit the degree of rotation of said control member relative to said shaft when the friction adjusting means is in a reduced friction position.

13. Radio tuning apparatus including in combination, a rotary shaft, supporting means for said shaft, a plurality of control members nor- `mally frictionally retained against rotation relative to said shaft and each control member having a projection extending laterally from onev side thereof, spacing and friction means on each side of each of said control members axially slidable therewith as an assembly on said shaft, friction adjusting means on one end of said shaft bearing against one end of said assembly for axially adjusting movement to vary the friction on each control member in accordance with the adjusted position of said friction adjusting means, said spacing and friction means 'including a washer against the extending projection side of each control member, each of said washers having a pair of circumferentially spaced abutments for engagement by the lateral projection of said control memberto limit the degree of lrotation of -said control member relative to said shaft when the friction adjusting means is in a reduced friction position. v

14. Radio tuning apparatus including in combination a rotary shaft, a pair of frame portions spaced apart and supporting said rotary shaft, rotating means for the shaft on one end thereof, a plurality of control members rotatable on said shaft intermediate theframe portions, means for limiting the angular rotation of said shaft to less than 360 comprising a stop bar on said shaft keyed against rotation thereon and a pair of laterally projecting abutments spaced apart on a frame portion adjacent said stop bar for limiting the movement of said stop bar and thereby limiting said shaft to angular movementv correspending to the space between said abutments, and means for limiting the angular rotation of each of said control members on said shaft to less than 360, said latter means comprising a washer for each control member keyed against rotation on the shaft and positioned adjacent one side of the control member, with one of said elements as between a washer andl a control member having'A an abutment thereon and the other of said elements having a pair of abutments thereon spaced apart angularly less than 360 for engagement by the single abutment to limit relative movement between the two elements.

l5. Radio tuning apparatus including in combination, a rotary shaft, a frame for supporting said shaft, rotating means for said shaft at one end portion thereof, a plurality of control members on said shaft within said frame, means for limiting the angular rotation of said shaft to less than 360, and means-for limiting the angular rotation of each control member on said shaft relative to said shaft to a similar amount less than 360, said latter means comprising a washer member for each control member keyed against rotation on the shaft and positioned adjacent one side of the control member, with one of said two members having a pair of abutments spaced apart lessthan 360 corresponding to the limitation of movement of said shaft and the other of said two members having a single abutment thereon for engagement with the pair of abutments and for angular movement within the limits vof the corresponding distance between said pair of abutments whereby to maintain each of said control members in an angular position within the limits of angular movement of said shaft.

. 16. Radio tuning mechanism for mounting in a housing, said mechanism including in combination a rotary shaft having a threaded portion at one end,'tuning control means on said shaft inoluding a plurality of spaced apart control members for controlling the angular rotation of said shaft and spacing and friction means therefor, tuning and adjusting means at one.end of the `tuning control means directly on the threadedportion end of the rotary shaft for operation at an end wall of the housing for varying the frictional pressure on the control members andl for rotation of the shaft directly at said-shaft for tuning purposes, said tuning and adjusting means including a finger engaging tuning member axially movable on said shaft and an adjusting member therewith having a securing portion for adjustable securing engagement with the threaded portion end of the rotary shaft, with said adjusting member operativelyconnected with said finger engaging member, and with said finger engaging member operatively connected with the tuning control means to cause relative axial movement between the tuning control means and the shaft upon adjustable movement of said adjusting member for causing a variation in the frictional pressure between the control members and the spacing and friction means therefor to prevent or to permit rotation of ,the control members relative to the rotary shaft depending upon whether the frictional pressure is applied to, or removed from, said control members.

17. Radio tuning mechanism for mounting in a housing, said mechanism including in combination a rotary shaft having a threaded portion at one end, tuning control means on said shaft including a plurality of spaced apart control members for controlling the angular rotation of said shaft and spacing and friction means therefor, tuning and adjusting means at one end of the tuning control means directly on the threaded portion end of the rotary shaft for operation at an end wall of the housing for varying the frictional pressure on the control members and for rotation of the shaft directly at said shaft for tuning purposes, said tuning and adjusting means including a finger-engaging-shaft-rotating member on said 'shaft adapted for yrelative axial movement with respect to said shaft and a threaded adjusting member operatively connected with said finger-engaging member for threadable engagement with the threaded portion of said shaft to govern such relative axial movement of the finger-engaging member, with said fingerengaging member operatively connected with the tuning control means to cause relative axial movement between the tuning control means and the shaft upon said relative axial movement between the finger-engaging member and said shaft to vary the frictional pressure between the control ALEXANDER W. PLENSLER.