US2170261A - Radio speaker control structure and circuit for use with automatic tuning devices for radio receivers - Google Patents

Description

Aug. 22, 1939. w DUNN 2,170,261 RADIO SPEAKER CONTROL STRUCTURE AND CIRCUIT FOR USE WITH AUTOMATIC TUNING DEVICES FOR RADIO RECEIVERS Filed Jan. 6, 1938 2 Sheets-Sheet l iinw Aug. 22, 1939. DUNN 2,170,261

RADIO SPEAKER CONTROL STRUCTURE AND CIRCUIT FOR USE WITH AUTOMATIC TUNING DEVICES FOR RADIO RECEIVERS Filed Jan. 6, 1938 2 Sheets-Sheet 2 v /a 4 cfizz ezz/oz 5/ I III; 7 1220272 Patented Aug. 22, 1939 RADIO SPEAKER, CONTROL STRUCTURE AND CIRCUIT FOR USE WITH AUTOMATIC TUNING DEVICES FOR RADIO RECEIVERS William L. Dunn, Chicago, 111., assignor to Belmont Radio Corporation, Chicago, 111., a corporation of Illinois Application January 6, 1938, Serial No. 183,577

13 Claims.

My invention relates in general to radio control apparatus and more in particular to means for selectively rendering the loud speakerof the radio receiver inoperative when using the con-- trol apparatus to tune the radio receiver and rendering the loud speaker operative while presetting the adjusting portions of the control aparatus to subsequently provide for tuning the radio receiver to predetermined control positions. The invention is particularly applied to so-called automatic control apparatus where the frequency controlling means of such apparatus is automatically operated to a predetermined control position or broadcast station setting. One commercial application of the invention is on control apparatus for a radio receiver including cams and levers such as is shown. in the copending application of Alexander W. Plensler Serial No. 1'70,(l70. It is understood, of course, that the application of this invention is not limited to this particular type of mechanism.

In any tuning apparatus. for radio receivers where the actual frequency control is automatically accomplished by pressing a'lever, a button or any of the other various means now employed, the operator normally makes no change in the speaker volume at the same time the automatic tuning is being accomplished. As a result, there is objectionable noise in the speaker as the control apparatus passes through. various frequencies in being tuned to the desired predetermined station. This noise is not only objectionable to the ear, but in receivers having high power output, the peak voltages created by rapidly tuning through powerful stations is likely to damage the loud speaker of the receiver.

pensive and not adapted to all types of automatic control apparatus. The present invention util-' izes the elements of the control apparatus itself for silencing the loud speaker during automatic tuning and likewise provides. for temporary operation of the speaker in the complete tuning operation merely while presetting adjustments in the automatic control apparatus are being accom- This is an old problem. in theautomatic tuning art, but the solutions to'thisj problem heretofore provided are ordinarily ex- It is an object of my invention to provide a simplified and improved speaker control system for use in connection with an automatic tuning device for a radio receiver.

A further object is to provide such a device which may readily adapt itself to automatic tuning structure and in fact utilize some of the elements of such structure for the operation of the system so that a minimum number of parts will be required.

A still further object is the provision of such speaker control apparatus particularly adapted to automatic tuning apparatus wherein the tuning apparatus includes movable levers so arranged that the end point of travel of the levers in accomplishing automatic tuning is constant regardless of the arrangement of the movable control elements corresponding to predetermined station settings themselves.

One of the features of my invention is the provision of mechanism for accomplishing silent automatic tuning in a radio receiver.

A further feature is the provision of a speaker control system which renders the radio speaker non-operative during automatic tuning, yet permits the normal operation of said speaker while one or more of the tuning control members is adjusted to a predetermined station setting.

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

Fig. l is a schematic illustration of some of the elements of an automatic tuning device using a cam and lever structure, with the circuit for the speaker control system of my invention similarly illustrated in connection with such mechanism.

Fig. 2 is a fragmentary View partly in section of the adjusting knob illustrated at the righthand side of Fig. 1 together with the switch in connection therewith.

Fig. 3 is a more extensive schematic diagram of the circuit and elements in the speaker control system of my invention, showing a different muting connection with the control apparatus.

Fig. 4 is a fragmentary end elevation of adjusting mechanism. and switch corresponding to that of Figs. 1 and 2, yet modified therefrom.

Fig. 5 is a fragmentary sectional view on the line 55 of Fig. 4.

Fig. 6 is a fragmentary front elevation partly in section of a modified embodiment of my invention applied to cam and lever tuning mechanism.

Fig. 7 is a schematic diagram of the embodiment of Fig. 6 on the line. 1-4 of Fig. 6, incombination with the circuit; diagram for this embodiment.

In the embodiment of Fig. 1 a tuning condenser is illustrated at it secured to a tuning shaft ll, supported in frame plates l2 and i3. Frame plate 83 is broken away in Fig. l merely to prevent confusion with the switch in connection with the adjusting knob as will be hereinafter more fully described, but in fact extends upwardly to carry the shaft I i as seen in Fig. 2. The rotors in the condenser it] are rotated upon rotation of the shaft II and the latter rotation is accomplished by moving a cam l4 by means of a pivoted lever IS. The cam M is normally stationary with respect to the shaft i I, but may be angularly adjusted relative to said shaft to change the station setting corresponding to such cam. This adjustment may be accomplished, as is more fully described in the above noted Plensler application, by means of a tuning and adjusting knob ll carried on the end of the shaft H as shown more particularly in Fig. 2. Although this specific structure is not a feature of the present invention, Fig. 2 might be described briefly as illustrating the knob i! keyed to a sleeve E8 on the rotary shaft H. The cams M are normally retained stationary with respect to the shaft H by means of friction washers IS on each side thereof and slidable sleeves 2! bearing against the washers 19 so that upon threadable adjustment of the cap screw 22, sleeves i8 and 2| press the cam and washer assembly in a left-hand direction as shown in Fig. 2 to bear against a rigid member (not shown) at the lefthand end of the cam assembly on shaft H. As sleeve I8 slides in a left-hand direction the knob H is carried therewith to change its axial position and inturn act upon the switch arms of the demuting switch D as will be more fully described hereinafter.

As to the speaker control structure of my invention including the demuting switch D, and as illustrated in Fig. 1, an electrical connection 23 is provided between the metal cam I4 and one side as 24 of the speaker circuit, including the output transformer 26, the voice coil 21, and field coil 28, and the speaker diaphragm itself is illustrated diagrammatically at 29. In Fig. l, the connection to the cam I4 is illustrated as leading directly to such cam, but it is understood that this may be accomplished by a stationary brush bearing against the shaft I l which is electrically common to the cam I4, or by a Wire connected to the end plate 52 which likewise is electrically common to the shaft H and cam M. A pivot rod 3! is mounted in the end plates l2 and I3 and insulated therefrom by means of fibre bushings 32, or the like, and such pivot rod 31 supports one or more tuning levers it corresponding to the cam members Hi. The rod 3i and lever 16 are each metal and an electrical connection is made from such rod 3! through the switch D by means of leads of 33 and 34 to wire 36 forming the opposite side of the speaker circuit from the wire 24.

It is apparent that connecting the wire 24 directly to the wire 36 would short-circuit the speaker circuit or, in other words, shunt out the voice coil 21. This short-circuiting or shunting out of the voice coil 27 is automatically accomplished when the lever it is depressed in the automatic tuning operation. The shunting circuit is from wire 24 through lead 23, through cam l4, through lever l6 and its pivot rod 3!, through wire 33, through the normally closed switch D and through wire 34 to wire 36. It follows that the speaker is muted during any automatic tuning operation, the muting becoming effective as soon as the lever lt'engages the cam 54 and ceasing as soon as the automatic tuning is complete and the lever it departs from the cam i i.

Presetting the cams In presetting the cam M with respect to the tuning shaft it so that operation of the lever [B will turn the tuning shaft to a predetermined position in order to tune the radio receiver to a particular frequency, the lever it is held in its fully actuated position as shown in dotted lines in Fig. '7, to hold the cam I4 in the position to which it will always be thrust by the lever l6, and the shaft H is loosened from the cam 54 by reducing the frictional pressure on the cam so that the shaft may be tuned to the frequency which the user desires to have correspond to this actuated position of cam I i. According to the muting operation as so far described, the contact of the lever it with the cam it would shunt out the voice coil 2? with the result that it would be impossible to tune the set by ear in order to select a particular station or obtain peak tuning for that station with respect to the actuated position of the cam it. This would be an undesirable effect. In other words, it is desired that the actuation of the lever It should mute the speaker during automatic tuning operations but should not mute the speaker during actuation of this lever for the purpose of presetting the cams i i on the shaft it. Of course, the actual presetting itself is accomplished when the lever is in cam holding position as previously noted. It is to provide this differential muting effect that the switch D is provided, the function of this switch being to nullify the muting circuit during presetting of the cam Hi. This switch could for convenience be called a demuting switch. Briefly stated, the switch D is normally closed to render the muting circuit effective when lever it engages cam id, but is automatically opened by operation of the knob if in the presetting operation so as to render the muting circuit ineffective during that operation.

The details of the actuation of switch D are seen in Fig. 2, When the screw 22 is loosened in order to relieve the pressure from sleeves l8 and 2 l spring pressure from one or more spring washers W in the cam assembly slides the sleeve E8 to the right and with it the knob H. The contact arms themselves in the switch D could provide this sliding pressure, and with the knob in the extended position, the cams themselves will readily loosen with respect to the shaft ii when the presetting operation is undertaken. The knob I! engages contact spring 353 of switch D and normally holds it in engagement with contact spring 39 of switch I) to close the muting circuit. When the screw 22 is loosened, however, the handle El moves to the right. This permits spring contact 38 to spring away from contact 39 and open the muting circuit, thus rendering the muting circuit ineffective. The loud speaker 29 may now function, and while cam 14 is held in its actuated position by lever it, shaft I i may be turned by knob I! to tune in the desired station accurately. This presets the cam M with respect to the shaft II. The spring washer W will act to hold this preset adjustment even though the lever I6 is released, since there will normally be several such cams i i each having a lever l6 and only one lever should be actuated at once. When all of the cams l4} have been preset, the cap screw 22 may be tightened, thus locking the cams |4 permanently in their preset "positions and drawing the knob I! in against the contact spring 38 to close the switch D. This restores the muting circuit to operative condition so that it will mute the speaker when the lever I6 is next operated.

Alternative muting connections There are various places in which the muting circuit may be connected instead of being con nected across the voice coil 21 as seen in Fig, 1. In Fig. 3, for example, it has been shown in full lines as being connected by the wires 23a. and G la toinput lead 4| and ground connection 42. The effectof this is toshort-circuit the input of the tube 43 to ground so that this tube is rendered inoperative and therefore no impulses are trans-v mitted through the remainder of the set through the speaker 29.

In dotted lines in this same figure the muting circuit is indicated as connected at an alternative position by wires 23b and 34b in. the same manner to the input connection of output tube 44 1 and to ground so as to short-circuit the signal impulses at this point. From these examples it will be apparent that the muting circuit may be connected at a variety of. points, the only requirement being that it be so connected asto directly I or indirectly mute the speaker 29.

Alternating demuting switch With different forms of presetting arrangements different switches rnay be necessary for nullifying the muting circuit during presetting.

One other presetting construction is shown in Figs. 4 and 5, in which the cap screw 22 is replaced by a threaded collar 46 to which a toothed Wheel 4'! is secured, the wheel 4? normally being free to rotate with the shaft I la. When it is desired to loosen the cam 54, a lever 48 is depressed so as to cause a dog 49 on the end thereof to engage the teeth of wheel 4'l, thus locking the wheel. The shaft 5 la may then be turned in any suitable manner as by knob 5| thereon and since the collar 46 and Wheel 41 are now restrained from turning by the dog 49, the wheel 41 will unscrew with respect to the shaft Ila along the threaded portion thereof, thus releasing the presi sure on the friction washers l9 and loosening the cam l4 sufficiently to permit the presetting adjustment thereof with respect to the shaft i la as previously described.

- The lever 48 is normally retained in a retracted position by a suitable spring 52. In such retracted position it engages the spring contact 38 of. switch D, pressing it against the springcontact 39 and thus closing the switch D to put the muting circuit in an operative condition ready to mute the 'speaker when one of the levers I5 is operated.

Restricted muting In Figs. 6 and 7 a muting arrangement has been illustrated which automatically cancels the muting efiect at the end of each tuning operation as the tuning lever reaches its fully actuated position. This makes a separately actuated demuting switch unnecessary since the presetting of the cam always takes place with the lever fully actuated to hold the cam in its actuated position. The automatic cancelling of the muting at the end of each tuning operation has the additional advantage of restoring the set to operation even though an inexperienced user should hold the tuning lever depressed.

In this form of the invention one muting connection 6| extends to a lug 62 carried by a screw 63 which is supported by but insulated from the frame member l3. Normally engaging the screw 53 is a demuting bar 64 which is pivotally carried by the pivot bar 3| which also carries the tuning lever B. The demuting bar 64 is normally urged upwardly into engagement with demuting screw 63 by a suitable spring 66. When the lever I6 is depressed, however, it will, near the end of its stroke, strike demuting bar 54 and depress it so that its contact with demuting screw 63 is broken, its depressed position being shown in dotted lines in Fig. '7. It should be noted that the spring 66 must be insulated either from the demuting bar 64 or from the frame member by which it is supported, and in Fig. 7, it has been shown as insulate-d from a cross bar 61 by a rubber sleeve 68 to which it is secured.

The cross bar 61 and rubber sleeve 68 also serve as an insulated stop for the'lever l6 in its normal position, any suitable means being provided for biasing the lever to this position. Of course, it is understood that such biasing means and a suitable insulated stop could also be provided for the tuning lever l6 in Fig. 1. It may be mentioned that bars are used for the elements 64 and 61 rather than short lugs because there are usually five or more tuning levers I6, and the elongated bars may serve them all.

In Fig. '7 the muting circuit which is closed when lever I6 strikes cam l4 extends from one side of voice coil 2'! through lug 62, through screw 63, through demuting bar 64 to pivot bar 34 and from this bar through lever l5, cam 54, shaft H and frame plate It to ground. Since the other side of voice coil 21 is also connected to ground, this muting circuit short-circuits the voice coil 21.

The .dotted line 6| in Fig. '7 indicates an alternative connection for the muting lead 6| similar to the connection 21 a or 231) of Fig. 3. With this connection the muting circuit would. mute the speaker indirectly by short-circuiting the input side of the tube 44.

The screw 63 is so positioned as to hold the demuting bar 64 out of contact with the tuning lever l6 until the latter is approximately at the end of its stroke, perhaps of an inch from the end of its stroke. At this time the lever It breaks the contact between the demuting bar 84 and demuting screw 63, and hence opens the muting circuit and renders it ineffective so that as the cam I4 reaches the position desired, the speaker will again become operative and thedesired program will be heard, or if it is desired to change the position'of cam It on shaft this may be accomplished by turning the shaft with a suitable knob, such as the knob ll of Fig. 1, while holding the lever I6 depressed. The shaft may be turned to bring the condenser ID to peak tuning of thedesired station, the proper setting being determined by ear because the loud speaker is functioning. 7

Of course, in any receiving set provided with a visual tuning indicator which shows peak tun ing visually, the demuting switch D in Figs. 1 and 4 and the corresponding demuting switch formed by demuting bar 6% andscrew 63 may be omitted, such demuting switches being necessary only to permit tuning by ear during presetting of the cam l4 on the shaft ii. Even with such visual tuning indicators, however, the arrangement of Figs. 6 and 7 is preferred since it restores the receiving set to operation immediately upon completion of the tuning, even if the tuning lever be held depressed.

From the foregoing it is seen that an extremely simple muting circuit is provided whichis suit" able for use in combination with the exceedingly simple lever and cam type of automatic tuning devices, and that suitable means is also provided for rendering the muting circuit ineffective during presetting of the cams to permit tuning by ear during such presetting cf the cams to provide peak tuning at a preset position.

The disclosures of this application are illustrative and the invention is not to be limited by them. In fact, if modifications or improvements are not at once obvious, they may be devised in the course of time to make additional use of the broad ideas taught and covered by this application. The claims are intended to point out novel features and not to limit the invention except as may be required by prior art.

I claim:

1. A radio receiver system including in combination, a radio receiver circuit having a loud speaker therein, tuning means for said receiver circuit including a rotary shaft, a tuning member on said shaft normally stationary with respect to said shaft, but selectively adjustable with respect thereto, means for moving said tuning member and said shaft, circuit means including said tuning member and said moving means therein responsive to an engagement of said moving means with said tuning member to render said loud speaker temporarily inoperative, and contact means in said circuit means responsive to the holding engagement between. said moving means and said tuning member to render said loud speaker operative during adjustment between said shaft and tuning member while the latter is held stationary.

2, A radio receiver system including in combination, a radio receiver having a loud speaker and a circuit for feeding signals to said loud speaker to be reproduced in sound, a tuner for said radio receiver including an adjustable movable tuning member, means for moving said tuning member to a predetermined station setting, and circuit means including said tuning member and said moving means therein responsive to the engagement of said moving means and said tuning member to cause a short circuit in the radio receiver circuit for preventing sound reproduction in the speaker, and means for opening said short circuit upon a presetting adjustment of said tuning member to permit sound reproduction in the loud speaker during such adjustment.

3. Means for temporarily preventing sound reproduction in the loud speaker for a radio receiver circuit having a cam and lever tuner with said cam and said lever normally insulated from one another electrically, said means including an electrical connection common to the cam and extending to the radio receiver circuit for connection into said receiver circuit ahead of the loud speaker, and an electrical connection common to the lever and extending to a corresponding point in the radio receiver circuit ahead of the loud speaker but separated from the point of connection of the first mentioned electrical connection, with said cam and lever acting upon engagement there'between to provide a short circuit across said two points in the receiver circuit to prevent signals from reaching said speaker to! provide sound reproduction therein.

4. In a radio receiver system, a radio receiver circuit, and a loud speaker connected therein, means for tuning said radio receiver including a rotary shaft, an adjustable tuning member on said shaft, means for moving said tuning mem ber to simultaneously rotate said shaft, and circuit means for muting said loud speaker during the movement of said member including a circuit connection from the tuning member to the receiver circuit, and a circuit connection from.

the moving means to the radio receiver with said moving means and tuning member normally insulated electrically from one another but acting to connect said two circuit connections upon engagement thereof for tuning, and With said circuit connections to: the radio receiver circuit being at such positions therein that signals in the receiver circuit are prevented from passing to said loud speaker during substantially all of the tuning movement of said moving means.

5. A radio receiver system including in com.- bination, a radio receiver circuit including a loud speaker, tuning means for said radio receiver comprising a movable cam, and a lever for moving said cam, with said cam and said lever normally insulated electrically from one another, and means for muting said loud speaker during movement of said cam comprising electrical connections from each said cam and said lever to the radio receiver circuit adapted to be connected upon physical engagement of said cam and lever for movement of the former to provide a short circuit across that portion of the receiver circuit intermediate said circuit connections thereto to prevent a signal input to the loud speaker such as to be reproduced as sound waves.

6. A radio receiving set including a variable tuner and automatic tuning means for operating the tuner including a member actuated to operate the tuner and which reaches its fully actuated position only as the tuning is completed, and a muting circuit including said member therein closed by this member as the tuning begins and opened by this member as the tuning is completed, said muting circuit rendering the receiving set inoperative to reproduce the received signals.

7. A radio receiver system including in combination, a radio receiver circuit, tuning means for said receiver circuit including a rotary shaft, a tuning member on said shaft normally stationary with respect to said shaft, moving means for said tuning member and said shaft normally out of engagement therewith, a muting circuit closed by engagement of the moving means with said tuning member to render the receiver circuit temporarily inoperative to reproduce received signals, releasing means operable to release the tuning member on the shaft to permit adjustment therebetween, and a switch operated by the operation of said releasing means to render the muting circuit ineffective during such adjustment and thereby prevent the receiver circuit from being rendered inoperative by the muting circuit.

8. A radio receiver system including in combination, a radio receiver circuit, tuning means for said receiver circuit including a rotary shaft, a tuning member on said shaft normally stationary with respect to said shaft, moving means for said tuning member and said shaft normally out of engagement therewith, a muting circuit including said tuning member and said moving means closed by engagement of the moving means with said tuning member to render the receiver circuit temporarily inoperative to reproduce received signals, and a demuting switch in said muting circuit for rendering the muting circuit ineffective even while said moving means is in engagement with said tuning member.

9. A radio receiver system including in combination, a radio receiver circuit, tuning means for said receiver circuit including a rotary shaft, a tuning member on said shaft normally stationary with respect to said shaft, moving means for said tuning member and said shaft normally out of engagement therewith, a muting circuit including said tuning member and said moving means closed by engagement of the moving means with said tuning member to render the receiver circuit temporarily inoperative to reproduce the received signals, and a demuting switch in said muting circuit for rendering the muting circuit ineffective even while said moving means is in engagement with said tuning member, said demuting switch being operated by said moving means at the end of its moving stroke.

10. A radio receiving system including a receiving circuit adapted to be tuned to different frequencies by means of a tuning shaft, a plurality of cams on the shaft normally lockedon the shaft to rotate therewith but releasable at will for adjustment with respect to the shaft, a tuning lever for each cam adapted to be actuated to rotate the cam to a predetermined position whereby the receiving circuit may be tuned automatically to any one of a plurality of frequencies by selective actuation of the levers, a muting circuit for rendering the receiving circuit inoperative to reproduce signals during such automatic tuning connected through the actuating lever and the cam whereby the circuit is closed by the en-.

gagement of the lever on the cam, and a normally closed switch in the muting circuit including a bar positioned to be engaged for opening the switch by each of the actuating levers as it reaches the end of its stroke.

11. A radio receiver including in combination a radio receiver circuit, means for tuning said radio receiver circuit including a rotatable shaft and a movable control member thereon, an actuator for moving said control member, friction varying means acting on said control member to prevent or permit angular adjustment of said control member with reference to said shaft depending upon whether friction is applied to or removed therefrom, a muting circuit including said control member and said actuator therein and connected into said receiver circuit and including a demuting switch, with said switch being mounted in a position with reference to said friction varying means whereby said switch is open to continuously maintain said muting circuit open when the friction is substantially removed from said control member and closed to maintain said muting circuit closeable when the friction is applied to said control member, with said muting circuit adapted to be closed when the demuting switch is closed upon engagement of said control member and said actuator.

12. A radio receiver including in combination a radio receiver circuit, means for tuning said radio receiver circuit including a rotatable shaft and a movable control member thereon, an actuator for moving said control member, friction varying means acting on said control memher to prevent or permit angular adjustment of said control member with reference to said shaft depending upon whether friction is applied to or removed therefrom, said friction varying means including a knob unit on said shaft having threadable axially adjustable means therein for causing axial movement of said knob unit, a muting circuit including said control member and said actuator therein and connected into said receiver circuit, said muting circuit including a demuting switch mounted in a position with respect to said knob unit whereby said switch is open to continuously maintain said muting circuit open when the friction is substantially removed from said control member and said switch is closed to maintain said muting circuit closeable when the friction is applied to said control member, with said muting circuit adapted to be closed when the demuting switch is closed upon engagement of said control member and said actuator.

13. A radio receiver including in combination a radio receiver circuit, means for tuning said radio receiver circuit including a rotatable shaft and a movable control member thereon, an actuator for moving said control member, friction varying means acting on said control member to prevent or permit angular adjustment of said control member with reference to said shaft depending upon whether friction is applied to or removed therefrom, said friction varying means including an internally threaded toothed unit vertically carried on said shaft and operatively connected with said control member, and a pivoted lever for engaging said teeth of said internally threaded toothed unit for maintaining said unit fixed while rotating said shaft with reference thereto, a muting circuit including said control member and said actuator therein and connected into said receiver circuit, said muting circuit including a demuting switch mounted in a position in respect to said lever whereby said switch is open to continuously maintain said muting circuit open when said lever is in engagement with said teeth and said switch is closed to maintain said muting circuit closeable when said lever is out of engagement with said teeth, with said muting circuit adapted to be closed when the demuting switch is closed upon engagement of said control member and said actuator.

WILLIAM L. DUNN.

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