US2151275A - Radio station center tuning control - Google Patents

Description

March 21, 1939. A. LESTl ,1

RADIO STATION CENTER TUNING CONTROL Filed April 1'7, 1937 4 Sheets-Sheet l INVENTOR March 21, 1939. A. LESTI RADIO STATION. CENTER TUNING CONTROL Filed April 1'7, 1937 4 Sheets-Sheet 2 March 21, 1939. A E 2,151,275

RADIO STATION CENTER TUNING CONTROL Filed April 17, 1957 4 Sheets-Sheet 5 F'IGJ INVENTOR March 21, 1939. A -r 2,151,275

RADIO STATION CENTER TUNING CONTROL Filed April 17, 1957 4 Sheets-Sheet 4 INVENTOR Patented Mar. 21, 1939 UNITED STATES BATENT FFEQE RADIO STATION CENTER TUNING CONTROL Arnold Lesti, Los Angeles, Calif.

Application April 17, 1937, Serial No. 137,509

13 Claims.

My invention is in a radio tuning control to permit accurate tuning of radio receivers to radio transmitting stations and to render inaccurate tuning impossible. My invention also constitutes a radio station indicator to give a visible indication of radio stations that are transmitting.

An object of my invention is to provide radio receivers with a tuning control whereby radio stations are not heard in the loud speaker unless the tuning is in the proper point of resonance.

In radio reception a station will not be received properly when detuned.

Another object of my invention is to provide a light signal when the receiver to which my invention is applied, is accurately tuned to the center of the frequency band which constitute the radio signal, while simultaneously the audible tones or modulations of the station are heard in the loud speaker. In radio reception there is a considerable range over which the carrier frequency gives equal response and it is difficult to determine where the proper center of response should be. When the response curve has several peaks or is substantially flat over a wide range tuning meters or indicators give the same readings for various positions of the tuning control and thus accurate tuning is diflicult.

In the construction of my invention I have found that shutters may be utilized to represent a range of frequencies from corresponding detuned portions on both sides of the exact tuning point of a signal and that the center of these shutters automatically may switch an electrical circuit to control the above mentioned loud speaker or lamp when all tuned circuits are in perfect alignment.

An important feature of my invention is that it provides interstation noise suppression between substantially accurate and very narrow points of resonance of radio stations received.

Another detailed object of my invention is to provide a simultaneous visible indication of all radio transmitting stations within the receptive range of any radio receiver to which my novel .3 invention is applied and to provide such indication while the radio receiver is use-d in its normal function and also to utilize the apparatus already inherent in the receiver to obtain the above objects.

I have found that while a radio receiver may be in tune with only one station at a time, it is possible to utilize a series of shutters to give a simultaneous indication of many radio stations. Each shutter may operate separately and independently as the tuning element of the receiver is varied and the full sweep of the tuning element will bring each individual shutter in succession into operative influence. As the proper shutters are operated I found that they may be held operated even after the operating influence has passed.

A further detailed feature is to provide an adequate, simple and inexpensive indicator of the above type in which the shutters are self restoring whenever certain stations may cease transmitting or if the wave band to which the receiver is receptive may be changed; the effect is brought about whenever the tuning element is again varied throughout its entire range.

Another object of my invention is to eliminate the crowding of stations on the low wavelength side of the dial and to provide substantially an evenly calibrated dial on conventional radio receivers. It is well known that conventional radio receivers do not have straight line frequency response of the tuning control; 1. e., the rate of change of frequency with respect toangular movement of the tuning control is not a constant. As a result there is a crowding of stations on the low wavelength side of the tuning range.

While I have. shown my invention as applied to radio reception it should not be considered as being so limited. It may be used generally for electrical control and indication.

With the foregoing and other objects and features in view which will be made manifest in the following detailed description and pointed out in the claims, reference is had to the accompanying drawings for an illustrative embodiment of the invention wherein:

Fig. 1 is a front view of the indicator with the escutcheon and attachments removed.

Fig. 2 is a sectional View on the line 2-2 of Fig. 1, showing also the escutcheon and attachments in section and the relay.

Fig. 3 is a view of the line 33 of Fig. e with the relay removed showing the centering feeler assembly.

Fig. 4 is an enlarged view on the line 2-4 of Fig. 1 showing the centering feeler and feeler lift assembly. The shutters are shown on the line [5-45 of Fig. 1.

Fig. 5 is a view of the feelers and shutters when the relay is energized.

Fig. 6 is a view illustrating the action of the feelers when detuned to the right.

Fig. 7 is a View illustrating the action of the feelers when detuned to the left.

Fig. 8 is a view illustrating the action of the feelers at perfect center tuning.

Fig. 9 is a view of the elliptical gears on line 9-9 of Fig. 2.

Fig. 10 is a perspective view of part of the shutters and feelers.

Fig. 11 is a View on the line |l|| of Fig. 4.

Fig. 12 is a front reduced view of the indicator.

Fig. 13 is a view of part of the movable slotted disc with feelers thereon.

Fig. 14 is a diagrammatic View of a conventional radio receiving circuit of a general type showing a method of applying the invention thereto.

Referring to the accompanying drawings wherein similar parts are represented by similar numbers throughout, l6 represents the movable relay which is rotatable when the variable tuning element of the radio receiver is moved. This tuning element is usually a series of ganged variable condensers. The shaft of these condensers ll connects to the shaft i9 by universal joint coupling I9. The movable relay I6 is rotatable with shaft 2| and the disc 22 is held by screws not shown to the base of the relay H5. The entire relay and its assembly moves through substantially 180 degrees as the tuning element is turned throughout its entire range. Armature 23 is hinged by pivot screws 24, 25, and finger 29 is held to the back face of the armature. When the relay coil 27 is energized the armature will be moved towards the core 29 and the finger 29 will move several shutters 29 inwards towards the rotatable disc 22. Only one shutter will be moved through the slot 39. As the disc moves the shutters that have been moved through the slot 39 will remain on the back face 3| of the disc. If the relay is energized and the shaft rotated all shutters will be moved through the slot and held by the back face 3| of the disc 22. If the armature 23 is restored to normal every shutter will also be restored to normal as rotation takes place ex cept where the armature may be held operated. As a result of discontinuous operations of the armature a series of shutters may be moved towards the back face of disc 22 while others may remain adjacent to the front face 32. The result of this procedure is an appearance such as is shown generally by 33 in Fig. 1. I prefer to energize the relay as described below, when the radio receiver is detuned, in which case the series of shutters held normally adjacent to the front face 32 will constitute an indication of radio stations received as the tuning element of the receiver is varied. The front face 32 of the disc 22 is of a finish to provide contrast with the shutters 29 which may be either black, dark blue or any other suitable shade.

The position of the shutters adjacent the front face 32 may be considered their operated position, in the preferable form of the invention, and after going through the slot, while held on the back face 3!, they may be considered as being in their normal position. However, in the alternative method of indicating the stations received, wherein blank spaces adjacent the front face 32 may correspond to the stations received, the opposite nomenclature may be used, i, e., adjacent the front face 32 the shutters may be considered as being in their normal position, while in the back face they may be considered as being in the operated position. Knobs 34 and 35 are turned during the tuning operation. I prefer a planetary reduction box 39 of conventional design to give the knob 34 high speed and 35 low speed. These knobs turn pulley 3'! to move friction belt 38 which turns pulley 39. This pulley is integral with gear 40 which engages gear 4! fastened to pinion 42 to drive gear 43 fixed to the shaft 2| by a set screw. This arrangement gives a large reduction in speed to turn the relay I6 and its assembly, together with the disc 22 and its assembly. Other suitable arrangements may be used. The elliptical gear 44 also turns integrally with shaft 2| as does likewise pointer 46 to show the particular shutters or tuning to which the radio instrument is set. The elliptical gear 44 is coupled to its mate by springs 41, 48 and both gears engage elliptical gear 49. The arrangements of the three gears 44, 45 and 49 permits coupling between shafts l8 and 2| without back-lash.

In order to allow each shutter to cover the same frequency change in all parts of the dial and also to eliminate the defect of crowding, the elliptical gears are used to provide a stepup ratio between shafts l8 and 2| whereby 2| travels faster than l8 at the low wave length settings of the variable tuning element of the receiver and 2| travels slower than l8 at the high wave length settings, The efiect is made sufficient to obtain substantially a constant for the rate of change of frequency with respect to angular movements. This system is preferable, but if the radio has straight line frequency response it may be eliminated, in which case 2! is directly coupled to H. The universal joint coupling I9 is used to relieve the load on elliptical gear springs 41, 48 if shaft 18 is placed slightly out of alignment with H.

The opening 59 permits light from the lamps 5| to provide indirect illumination. I prefer a convex transparent glass 52 held by snap ring 53 on the escutcheon 54 as shown to cover the scale 55 and pointer 46.

While I have shown the shutters 29 in a preferably semicircular form, this arrangement is not absolutely necessary. may extend in a complete circle or, where space is ample, the shutters may extend substantially in a straight line. In this latter case the movable relay would move in a straight line. The shutters 29 are preferably made from very thin sheet steel with clearances or openings 59. Each shutter has a free end 5.! and wide end 58 to give strength. I have shown only 138 shutters in Fig. 1 in order to illustrate detail but actually a large number is necessary. I have used 380 shutters for radio receivers to cover a range of about one megacycle for a complete sweep of the tuning control, While I have shown my invention in a preferable form it should not be considered as being so limited as various obvious changes may be made by those skilled in the art without departing from the broad aspect of this invention.

When the shutters are moved by the finger 26 the free end 51 moves in a direction perpendicular to the plane of the material from which the shutters are made towards the slot 30, referring to Fig. 5, to the rear 59 of the disc 22. Referring to Fig. 3 the feelers 69 and GI are riveted to disc 22 at 62 and bear down towards the shutters 29 at the slot 30. These feelers move independently by spring action and have tapered edges 63 and 54, as shown in. Fig. 4, and the center between the feelers 65 coincides with the slot 39. The feeler springs 66 and 61 make In some cases they.

A closed circuit may be traced from lead 13 to springs I5 and I39 to feeler spring 66, to feeler spring tip I I, to feeler 60 and to feeler 6|, feeler spring tip I2 and feeler spring 61 to 14. This circuit may be opened as illustrated in Figs.

5, 6 and 7.

Link I8 is fixed to 26 and movable with the armature. There is a hole in the link to receive pin I9 held to piece 80 pivoted by} pivot screws 82, 82 so that any movement of the armature is linked to 80 causing a small rotation of this member. Feeler lift BI is fixed to 80 and provides a magnified movement to lift the feelers when the armature is operated as shown in Fig. 5 and thereby allow the shutters to move freely through the slot. When the armature is restored the feeler lift releases the feelers which exerts pressure on any shutter which may be present in the back face 3|. This aids the normal self restoring springing action of the shutters and insures positive and complete restoration.

As explained below, radio stations give an indication such as 83, 84 and 85, Fig. 6. The width of these indications is related to the strength of the station to which they correspond. In Fig. 10 is shown how the feelers 60, 6| engage the operated shutters in the back face of the disc 22. The slot opening 89 allows a free movement of the feelers. For a wide indication the feelers will move by spring action towards the front face 32 to a greater degree than for a smaller indication. In Fig. 6, when a station is detuned to the right, feeler BI is raised higher than 60 by the end of a shutter. This moves the entire spring assembly to break contact at 60 to 'II. In Fig. '7, when a station is detuned to the left feeler 60 is raised higher than 6I by the end of the shutter which corresponds to a detuned portion of the radio station, similarly to the detuned portion on the other side of the exact center 81 which caused the raising of feeler 6I. Feeler 60 may thus cause a breaking between contact at BI and I2. The breaking or the opening of the circuit of leads I3 and I4 silences the radio speaker and turns off a lamp as mentioned above and as is explained in detail below. Fig. 8 illustrates how exact tuning is achieved when both feelers are raised by a similar amount and both make contact with the feeler spring tips II and I2 to close the circuit of leads I3 and I4. I prefer to render the loud speaker operative at this time and to light a lamp to indicate exact resonance. Line 88 indicates the amount of detuning of the entire movable assembly and tuning system with respect to the position of exact tuning of station 84 represented by the dotted line 87. I prefer to provide an insulating washer 20 of the universal joint I9 to insulate the shaft I8 from the chassis of the radio to which this device is applied. The frame H8 should also be insulated from the chassis when it is fixed thereon. Referring to Fig. 14 radio frequency currents present in the antenna I to ground are coupled to the imput grid of tube 89 and tuned by variable condenser IN. The amplified currents are transformed from the plate circuit of tube 89 to the imput of the mixer tube 90 and tuned by the variable condenser I02. The variable condenser I03 tunes the local oscillator circuit with tube 95 and this oscillator frequency is fed into mixer tube 90. The heterodyned output of tube 90 is fed to an intermediate amplifier having tubes 9I and 92. The output of the intermediate amplifier is rectified by tube 93 and demodulated currents appear across I04 to ground. These currents are fed to the audio frequency tube 94 the amplified output of which at I05, I06 may be connected to an audio frequency amplifier not shown. The amplifier is supplied by a source of plate current connecting positive to lead I01 and negative from I08. Leads I09 and H0 furnish tube heater currents and also serve for lighting the indicator lamps I.

Variable condensers IOI, I02 and I03 are ganged together and their common shaft is N, Fig. 2. In the tuning operation the radio receiving circuit will amplify any radio station with which it may be in tune and place a negative potential due to the carrier frequency, at point I04,the magnitude of which is proportional to the intensity of the received signal. This negative potential is fed to the grid of the tube 96 through the battery or source of potential I32. When no signals are present switches I3I and I09 are adjusted to cause the tube to pass current to energize coil 21. When signals are present and a negative potential is placed at I04 tube 96 cuts off and no current flows through coil 21. Adjustment of switches I3I and I09 will give accurate control so that signals above a specified minimum will cause tube 96 to sharply cut off. As the shaft I1 is turned during the tuning operation and the entire tuning range is covered certain shutters will be moved through the slot 30 to the back face 3| leading a series of shutters in their normal position to give a visible indication of stations that are on the air. I prefer to indicate stations as normal unmoved shutters instead of the alternative of moving the shutters to indicate stations, as there is no current flowing through coil 21 when the re-' ceiver is tuned to a station in the system which I disclose in Fig. 14. The center tuning feature may be eliminated by grounding lead I4.

In Fig. 14 lead I3 is shown grounded and lead I4 is connected to the grid of the audio amplifier tube 94. If spring assembly I I3 and the feelers and feeler springs all make contact, tube grid return lead H4 is grounded and amplification of currents from II5 takes place. However, if the circuit is broken, as mentioned above in connection with Figures 5, 6, and '7, then a high negative potential from lead I08 will charge the grid of tube 94 and cut off its plate circuit to stop amplification of audio currents and silence the loud speaker. I prefer a neon lamp 98 to furnish light when the tube 94 is amplifying and to darken when this tube is cut off. Since the grid is practically an open circuit resistance II2 may be very high and I have found that five megohms may be used to reduce to a very low value the current that fiows through the feeler contacts, in order to prevent arcing and insure long life. If more light is required than can be furnished by lamp 98, a separate tube 91 may be used with a powerful lamp 99. Leads H6 and III are then connected together. The procedure to obtain center tuning is to first sweep the dial and then turn to any station desired as indicated by the pointer 46. When the exact center is reached the neon lamp 98 will light and the loud speaker of the radio will simultaneously translate the demodulated and amplified audio currents into sound.

Various changes may be made by those skilled in the art in detail of construction of my invention without departing from. the spirit thereof as set forth in the drawings, specifications and claims.

I claim:

1. A radio dial comprising in combination, a series of shutters, a movable member having a slot adapted to allow the passage of the shutters, a radio tuner coupled to said movable member and means responsive to a tuned-in signal to move any of the said shutters through the said slot to indicate the signals received by the said tuner.

2. A radio station indicator comprising in combination a series of shutters each having a normal and an operated position, .a radio tuner, a movable member coupled to the said tuner and having a slot adapted to allow the passage of substantially one shutter, means responsive: to a tuned-in signal to move any of the shutters through the said slot corresponding to the settings of the tuner and means to hold the operated shutters from returning to their normal position.

3. A radio station indicator comprising in combination, a series of shutters, a radio receiver having a tuner, a movable electro-magnet coupled to the said tuner and having means cooperating therewith to move any of the said shutters, when operated, corresponding to stations received by the said tuner, and means for holding any of the said moved shutters from returning to their normal positions whereby a simultaneous indication of shutters is attained corresponding to radio stations received.

4. A radio stations indicator comprising in combination, a series of shutters arranged sub- .stantially in a circular form and forming a portion of a disc with each shutter having a free end close to the center .of the disc and edges that are substantially radii of the disc and a fixed end close to the periphery of the disc, a movable member adapted to be energized and move any of the said shutters and means for holding the moved shutters from returning to their normal positions whereby a series of shutters is held, corresponding to the energized positon of the movable member.

5. A radio station indicator comprising-in combination, a series of shutter-s, a movable member having a slot to pass substantially one shutter at a time and. a front face adjacent to the shutters, a back face on the movable member to hold any moved shutter, a relay held to the movable member and movable therewith, a radio receiver having a loud speaker, meansfor energizing the relay when the said receiver isdetunedfrom signals, an armature adapted ,to move anyshutters through the said slot to the back'face of themovable member when the relay is energized, a centering switch engaging the moved shutters with means cooperating therewith tosilence the loud speaker 'for'detuned settingsof the said receiver.

6. .A radio station indicator.comprising-in combination, aseries of shutters, a movablemember :having a slot adapted to allow the passage of substantially one shutter at.atime,.a radio am- .plifier and tuner-having a variable element linked and tuner having a variable tuning element coupied to the said movable member, a relay held to the movable member and having an armature with means cooperating therewith to move any shutter through the said slot when the relay is energized, an automatic volume control in the said amplifier to furnish potential proportional to the received signals, a radio tube with means cooperating therewith to energize the relay by the automatic volume control potential when signals are detuned whereby shutters are held in their normal positions corresponding to radio signals received.

8. A radio stations centering switch comprising in combination, two feeler members each having a tapered edge and movable independently, a movable member engaging each feeler member and means for disengaging one feeler member from the movable member by the movement of the other feeler member.

9. A'radio stations centering switch for spaced protuberances, comprising in combination, two feeler members each having a tapered edge and adapted to move independently when passed over for placing a series of shutters on the back face of the movable member to indicate the radio station received by the said receiver, two feeler members movable independently and having tapered edges engaging the shutters on the .back face of the movable member,-means for utilizing the said feeler members to switch .an electrical circuit when the center position of spaced shutters is attained corresponding to resonance of the radio station tuned.

11. A centering SWitCh'fOI radio receivers comprising in combinationa series of shutters having movable .ends,,a movable member having a slot to pass any of the said shutters, a back face on the said movable member to hold the moved shutters, a relay integral with the said movable member and having an armature adapted tomove substantially one shutter through the said slot when energized, two feeler springs on the back .face of the movable member having tapered edges engaging the moved shutters, a contact member engaging the said feelers, and means for switchinganelectrical circuit by the action of thefeelersand the contact member when the slot on the m va le mem er coincid s w th h ente of a series f sh tte s eld i th i n rma pet tions- 12. The method of switching an electrical circuit when obtaining substantially exact tuning of a radio signal with shutters which consists, in utilizing spaced shutters to correspond to specifled detuned portions on both sides of the point of exact resonance of a radio signal and utilizing the center between these shutters to switch the electrical circuit corresponding to exact tuning.

13. The method of visibly indicating radio signals and electrically switching at exact tuning by shutters which consists, in utilizing a series of shutters to cover a range from specified detuned portions on each side of the position of exact tuning to give a visible indication and utilizing the center of the series of shutters for switching at exact tuning.

ARNOLD LES'I'I.

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