US2453252A - Tuning control mechanism for radio receivers - Google Patents

Description

Nov. 9, 1948. w. E. NEWMAN TUNING CONTROL MECHANSM FORRADIO RECEIVERS Filed Deo. 5, 1944 3 Sheets-Sheet l bwl SCHH H TTOR/Vf' Nov. 9, 1948.

w. E. NEWMAN TUNING CONTROL MECHANISM FOR RADIO RECEIVERS Filed Dec. 5, 1944 3 Sheets-Sheet 2 W/LL/AM ,4 rrokA/EV Nov. 9, 1948. w. E. NEWMAN TUNING CONTROL MECHANISM FOR RADIO RECEIVERS Filed Dc.

5 Sheets-Sheet 3 Patented Nov. 9, 1948 TUNING CONTEROL MECHANISM FOR RADIO RECEIVERS William Edward Newman, Chicago, Ill., assigner to Radio Corporation of America, a corporation of Delaware Application December 5, 1944, Serial No.'566,666

(Cl. Z50-40) 8 Claims. l

This invention relates in general to tuning control mechanism for Vradio receivers, and more particularly to control mechanism for effecting in a sequential manner the automatic adjustment of the tuning device of a radio receiver to a plurality of transmitted carrier waves having a signal strength above a predetermined minimum.

In control systems of this general type an electric motor is utilized to effect the tuning, the motor being set into operation by manually actuated means and rendered inoperative automatically when the receiver has been tuned to the carrier wave of a broadcasting station received with sunicient strength.

vIt is one of the objects of the present invention to provide a high degree of tuning accuracy in a control system of the type mentioned wherein there is utilized a high ratio gearing between the tuning element and the stationselector means.

A further object of the invention is to provide a combination scanning and hunting type of selector which permits of eiecting in the rst instance a rough adjustment of the receiver to a station of sullcient signal strength followed by an accurate adjustment of the receiver tuning means.

A still further object of the invention is to provide in combination with an adjustable tuning device of a radio receiver tunable through a certain vfrequency range, a reversible electric motor, means operable in response to manual control for energizing the motor to actuate the tuning device in a manner such that it is permitted to scan said :frequency range for a signal wave having an amplitude above a predetermined minimum, and

means operable upon reception of such signal carrier wave for discontinuing the scanning operation and effecting operation of the motor in a manner such that the tuning device is permitted to hunt for said received carrier wave prior to final adjustment ci said tuning device to said carrier wave.

A more specic object is to provide a control mechanism for effecting the automatic adjustment of the tuning device of a radio receiver to a transmitted signal carrier wave having an amplitude above a predetermined minimum, which includes a reversible the tuning device, a rotary member movable with the tuning device carrying a pair of commutator segments separated by an insulating gap or dead .spot for determining the direction of motor o oeration, means for actuating said member from ihr' motor, a contact nin cooperatively related with said rotary member, means -or effecting roelectric motor for actuatingv tation of the segment carrying member and contact pin in unison, means in response to a signal carrier wave having an amplitude above said predetermined minimum for stopping the ccntactpin in a radial position corresponding to said carrier wave, and means for effecting closure of the motor circuit through the contact pin and one or the other of the commutator segments to cause continued operation of the motor inthe corresponding direction until'the dead spot between segments contacts the contact pin at which time the motor will be deenergized to stop the tuning device.

Thenovel features characteristicof my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its construction and mode of operation together with `further objects and advantages thereof, Will best be understood by reference to the following description taken in connection with the -accompanying drawings, in which:

Fig. 1 is a view, partly in section, disclosing schematically the control mechanism according to one form of the invention;

Fig. 2 is a cross-sectional view taken on the line 2 2 of Fig. 1;

Fig. 3 is a partial view of Fig. 1 showing the condition of the apparatus when operating as a scanning type of tuner; y

Fig. 4 is a view similar to Fig. 3 showing the condition of the apparatus when operating as a hunting type of tuner;

Fig. 5 is a modied form of Vthe invention; and

Fig. 6 is an end View of Fig. 5.

In accordance with the invention, the station selector means of the control mechanism consists of a motor-actuated two-segment commutator separated by a dead spot or insulating gap which upon arriving in contact with a single contact, adjustably positioned in reference to the station carrier to be received, `stops the hunting operation of the motor. The motor is of the reversible type having its field windings connected to the two segments of the commutator in the conventional manner. The selector Contact and commutator both rotate together when the selector is scanning or running from one station to the next, but when a station carrier is found by the tuning element the selector contact is locked in position. .and the coiimutator and tuning element continue in their original direction of rotation due to inertia. Eventually they stop and then reverse their direction of rotation due to the motor torque being reversed. The moment the signal carrier is found by the tuning element, the selector contact locks itself to a fixed part of the mechanism and becomes a marker or reference point to which the selector finally cornes to rest. The contact is carried by a rotatable arm of low mass so that it has practically no overtravel and will therefore stop almost instantly whereas the tuning element and the commutan tor have in comparison a much greater mass.

Briefly, the device functions as a scanning type of selector` when running from one station to the next, having a motor reversing means at each limit of the tuning stroke, and is automatically converted to a hunting type of selector when the tuning element arrives at a station carrier of sufficient strength. With the use of this principle only one contact point is required for stopping at any angular position, since the contact point and the commutator rotate together until the two are separated by the incoming signal. It is possible, therefore, to obtain extreme accuracy in the stopping positions of the tuning element by gearing down so that the selector makes thousands of revolutions to one revolution of the tuning element.

Referring now to the drawings, and more particularly to Figs. l and 2, there is shown at IU the tuning device of a radio receiver represented as a conventional type of rotary variable condenser, suitably supported from a bracket II mounted on a support I2 which may be the receiver chassis. On the shaft I3 of the rotary element of the tuning device is mounted a worm wheel I4 which meshes with a worm I5 formed at one end of a motor-driven shaft i5. The shaft is `iournalled in a bearing I1 carried by a bracket IS also affixed to the receiver chassis I2. Affixed to the shaft I6 is a friction wheel I9 which is adapted to be driven by a second friction wheel 2f! mounted on a shaft 2i of an electric motor indicated generally at 22.

The motor is of the reversible type being provided with an armature 23 to which the driving shaft 2| is attached and with a pair of field windings 2li and 25. Thearmature is capable of slight axial movement, being constrained, by spring means not shown, to assume the nondriving position shown in Fig. l.. Upon the motor becoming energized, the armature is thrust outwardly in an axial direction in opposition to the spring means to effect the coupling or driving relation between the `driving wheel 20 and the driven wheel I9,

The common terminal of the motor field windings 24 and 25 is connected by way of a conductor 25 to one side of a source of power 21 which is constituted by a step-down transformer for stepping down the 110 volts available at the house current power supply mains to about 24 volts necessary for operating the motor, The other side of the power source (transformer secondary) is connected through a conductor 23 to a movable contact 29 of a switch 3B, to be described later. The opposite terminals of windings 2d and 25 are connected, respectively, by way of conductors 3I and 32 to fixed contacts 33 and 34 of a motor reversing switch 35. The moveable element of this switch is in the form of a blade 36 which is centrally pivoted at 31 and is provided with an operating lever 38 disposed in the path of travel of a pair of pins 39 and Ali affixed to the side of worm wheel Sli. The pins are spaced apart 180 to correspond with the two limiting positions of the tuning device.

In the position shown in Iiig` l the tuning de vice has just reached one of its limits (the minimum capacity position) whereat switch blade 36 is snapped into the position shown, by action of pin against lever 3S. rhis closes the motor circuit through the field winding 25 which causes the motor to operate in the reverse direction, that is in the direction opposite to that which moved the tuning device to the minimum capacity position. The motor will so operate until the tuning condenser is moved to its other limit (the maximum capacity position) whereat switch blade 35 is snapped into its other position by action of pin iii against lever 33. This closes the rnotor circuit through the other eld winding 2li which causes the motor to again reverse its direction of operation. rEhe back-and-forth movement of the tuning device between minimum and maximum capacity positions brought about by the motor when under control of the reversing switch 35 will here-- inafter be referred to as the scanning operation.

Afiixed to the motor-driven tuning shaft I6 at the right is a drum member il provided with a flange 42 to which there is attached a plate 43. Carried by this plate is a strip of insulation 44 to which there is attached a pair of conimutator segments 'l5 and 46 separated by a narrow gap or dead spot 4i. An insulating sleeve 43 is provided on the outer surface of the drum and carried on the sleeve are a plurality of collector rings 49, 5e, 5i and '52. Rings 49 and 5u are electrically connected, respectively, to commutator segments and it, and rings 5I and 52 are electrically connected to the opposite terminals of a solenoid 53 contained within and adapted to rotate with the drum 4 I. Each ring has associated with it a contact brush, these being shown respectively at 54, 55, 5t and 5l, suitably supported on an insulating block 53 carried on a bracket 59. Contact brushes 5&1 and 55 are connected respectively to the uncommon terminals of the motor field windings 25 and 24 by way of conductors B0 and 60', and contact brushes 56 and 5'! have connected to them1 respectively, a conductor iii which leads to the -B terminal, and a conductor 62 which leads to the +B terminal of the receiver power supply through a solenoid-controlled armature, later to be described.

A bracket 63 mounted on the receiver chassis I2 has its upper part 63' offset slightly toward plate 4S to present a surface in parallel relation therewith. Formed integral with bracket part 53 or otherwise attached thereto is a bushing 64 which serves as a bearing for an axially shiftable and rotatable shaft 55, disposed in axial relation with reference to shaft I5. The left end of shaft 65 carries a'plunger 56 which in the deenergized state of solenoid 4I extends partly into the drum in the manner shown in Fig. 1. The shaft 65 also carries to the right of the plunger a contact arm @l which is provided on its opposite faces, in concentric relation with the plunger, with annular layers 68 and 59 of friction material, such as rubber. In the position shown for contact arm 51 the friction layer 5S is in contact relation with the side of bracket part 53' facing it, shaft 55 and contact arm 61 being urged to that position by means of an expansion spring 'Iii `disposed between a pair of washers 'II and 12. The latter is keyed to move` with the shaft while the former always remains in xed position in contact with the end of bushing 561. With shaft 65 and arm G'l axially shifted to the left, due to energization of solenoid 4I, the friction layer 68 on the opposite side of the arm is forced into Contact relation with the rotary drum plate 43. rAsfa-consequencecontactarm161 is caused to=berotated along with vdrum 4|.

Contact arm I6"! lhas affixed to it an insulating member 73 which `carries 'a contact pin 14. In order that contactimaybe had between the pin and thecommutator --41 at all times regardless of Vthe 'axial position `of the contact arm, the shank 15 of the pin .isslidably mounted with a bushing lfcarried byzmember 13 and a coil spring 1111s `disposed between the iiange of the bushing and the 4`pin head 4'|8.

`A...ilexible 'conductor '|9 vis connected between the contactxpinpandga collector ring insulatingly mounted on the bushing .64. A brush contact f8| suitably `supported on an insulating bracket 82land arranged to contact with vring 8U is-connected by way of 4'a conductor '83.and a resistor 84 to aflxed contact 185 yof `the switch 30. A second fixed contact86 lof the switch 30 is connected by way of a `conductor 81 to the center contact 88 of motorreversing switch 35 which is electrically connected to the pivoted switch blade 36. Switch 301s' supported from the :chassis |-2 'by abracket 99.1andzis so positioned ythat its center flexible contact 29 is disposed adjacent to land in the path of an .insulating member 90 carried at the end of Ashaft .65, .the position of switch contact 29 being .determined by the .axial position of the shaft 65.

At 9| is shown a control tube which may constitute one of the radio frequency or intermediate frequency stages of the radio receiver to be controlled or a separate tube which is arranged to have impressed on its input electrodes a portion of the received signalenergy. A solenoid `92 is connected in the plate circuit of tube 9|, that is, between the `plate electrode of the tube and the +fB terminal of the receiver power supply. The armature 93 iis alsoconnected to the -l-'Blterminal and is arranged by spring means 94 -to assume the inormal vposition shown, that is, away 'from a'xed contact 95 to which `conductor f62 is connected. For initiating operation `of thecontrol mechanism, `there is connected between-the plate side of LAthe'solenoid Z92 and the -`B terminal -or ground a Ymanual station Vselector switch'orpushbutton 96.

The control mechanism above described operates =in the -following manner: 'For `-tuning in a station all that'need be done by the operator is to actuate pus`h-button 96. This completes .-a circuit through `solenoid 92 as follows: from -l-B, solenoid92, closed switch 1`96, to -B or ground. As a result armature '93 `will vbe pulled Jover to contact I95 -in lopposition to spring 9'4 to close a the :position yof blade`36 of motor reversing 'switch 35. This condition of 4themechanisni :for :carrying out the scanning operation is shown :diagrammatically in Fig. 3, the motor actuating the tuner I0 between Iits .two limiting positions inorder to scan the frequency range ;0f the `receiver. During the :scanning oper-ation :com-

mutator-M-M and-contactpin .1.4 will .rotatein unison but `.due to the axial .movement `of :shaft 65 vcontacts 29 and 85 which provide continuity from the contact pin to `the motor vare broken.v The motor having started rotating, the station selector button 96 may be released but thesolenoid remains energized due to the .flow of "current inthe plate circuit of control ytube 9| and will continue to .be energized Has long as the tuner is 4not tuned to a carrier wave of requisite signal strength.

When, however, the tuner is actuated to aposition where the receiver is tuned to a station carrier of predetermined strength the plate current through control tube 9| willbevreduced suiciently to cause release of plunger -66 and, :incidentally, contact arm 6'| which, due to action of spring `1|) is forced against the face of bracket part 63', arm remaining fixed in .a radial vdirection as determined by the point of release.

l The commutator 45-41, however, continues'in its original direction of Arotation due to inertia. Switch contacts 29 and S5 are now closed by reason of `the return of 'shaft 65 .to the right, sothat contact pin '|4 on one .or the other of commutator segments 45, 46 provides continuity forlthe'motor circuit. This condition .of the mechanism for carrying out the "hunting operation is shown diagrammatically in Fig. 4, the motor driving the commutator back and .forth until .its gap 41 coincides with contact pin 14 -when the motor circuit is broken, deenergizing `the motor and causing the .tuner l0 to stop at the tuned-in position at which the receiver is adjusted to the carrier wave having a signal strength of predetermined value.

During the hunting operation the commutator gap passes the vcontact pin several times, the commutator coming to rest when the energy due to inertia is used up. In order to reduce the motor speed and therefore the number of back and forth movements of vthe commutator during the hunting operation, the resistor 84 is connected in series with the motor circuit. The motor-reversing switch .35, it will be noted, is not included in the motor ycircuit when the commutator is hunting since switch 3B isfopen at its contacts y29, 86;

After a station is tuned-in in the manner described, the next station in sequence of requisite signal strength can be tuned-inby-actuating the station selector button anew.

It Awill be seen .therefore from the description given above that by reason of the instantaneous setting of the low mass -contact arm in response to a predetermined signal and 'by reason also 'of the high ratio gear reduction between the commutator and .the tuning element there is secured a .high degree-of tuning accuracy.

A modified form of the invention is disclosed in Figs. and-Gfin whichthe positions of the contact pin "I4 andthe commutatorAE-H aretransposed, the .same yreference characters as Vemployed in Figs. l land 2 being used to designate the same'or equivalent elements. vExcept for the fact `that the commutator is shifted in an axial direction upon energization 'of the solenoid 53 tofbe locked for rotation with drum i during the scanning operation, and that contact -pin 'M is .oscillated back and forth with respect to the commutator segments during the hunting operation, the vcontrol mechanism shown. in Figs. 5 and 6 operates in exactly the same manner as that disclosed in Figs, l and 2. A yfurther description thereof is therefore believed unnecessary.

While I have shown and :described preferred embodiments of the invention, it will be `under-- 7 stood by those skilled in the art that modications and changes may be made without departing from the spirit and scope of the invention.

What claim is:

1. The combination in a radio receiver, oi an adjustable tuning device tunable through a certain frequency range, a reversible electric motor for actuating the tuning device, first control means including a solenoid and a two-position switch which is under the control of the armature of said solenoid, said control means being operable in response'to manual control for energizing the solenoid and, through said switch in one of its positions, also the motor to actuate the tuning device in a manner such that it scans said frequency range in search for a carrier wave of a signal strength above a predetermined minimum, and second control means operable upon reception of such signal carrier Wave adapted to deenergize said solenoid thereby to move the switch to its other position for deenergizing the motor and discontinuing the .scanning operation, and circuit means closed through the switch in said other position for eifecting operation of the motor in a manner such that the tuning device hunts for said received carrier wave prior to final adjustment thereof to said carrier wave.

2. The combination in a radio receiver, of an adjustable tuning device tunable through a certain frequency range, a reversible electric motor for actuating the tuning device having associated with it alternative energizing circuits, first control means including a solenoid and a two-position switch which is under the control of the armature oi said solenoid, said control being operable in response to manual control for energizing the solenoid and, through said switch in one of its positions, also the motor through one of its circuits to actuate the tuning device in a continuous manner such that it scans said frequency range for a carrier wave of a signal strength above a predetermined minimum, and second control means operable upon reception of such signal carrier wave adapted to deenergize said solenoid thereby to move the switch to its other position for deenergizing said one motor circuit to thereby discontinue the scanning operation, and circuit means closed through the switch in said other position for effecting operation of the motor through its other circuit in a manner such that the tuning device hunts for said received carrier wave prior to final adjustment thereof to said carrier wave.

3. Control mechanism for effecting the automatic adjustment of the tuning device of a radio receiver to a transmitted signal carrier wave having an amplitude above a predetermined minimum, comprising a reversible electric motor for actuating the tuning device, a rotary member movable with the tuning device carrying a pair of commutator segments separated by a dead spot for determining the direction of motor operation, means for actuating said member from the motor, a contact pin cooperatively related with said rotary member, means for effecting rotation of the segment carrying member and contact pin in unison, means in response to a signal carrier Wave having an amplitude above said predetermined minimum for stopping the contact pin in a radial position. corresponding to said carrier wave, and means for eiiecting closure of the motor circuit through the contact pin and one or the other of the commutator segments to cause continued operation of the motor in the corresponding direction until the dead spot between segments contacts the contact pin at which time the motor will be deenergized to stop the tuning device.

4. Control mechanism for efecting the automatic adjustment of a radio receiver tuning device to a transmitted signal carrier wave having an amplitude above ,a predetermined minimum, comprising a reversible electric motor, a commutator provided with a pair of conducting segments spaced apart by an insulating strip, means operable during operation of the motor for actuating the tuning device and the commutator, a rotary contact pin arranged in cooperative relation with the commutator, a control member adapted upon actuation to initiate operation of the mechanism, means operable in response to actuation of the control member for effecting rotation of the commutator and contact pin in unison, and means operable in response to a signal carrier wave having an amplitude above said predetermined minimum for making the last-mentioned operable means ineffective, whereby the contact pin is stopped in a radial position corresponding to said carrier wave, the contact pin in its stopped position remaining in contact with one or the other of the commutator segments to thereby determine the direction oi motor operation which continues until the insulating strip of the commutator arrives in contact with the contact pin to deenergize the motor and cause the tuning device to stop at thc position which tunes the receiver to said carrier wave.

5. Control mechanism as defined in claim 4 wherein the means operable during operation of the motor effects actuation of the tuning device and commutator in unison, the latter at a greater speed than the former.

6. Control mechanism as dened in claim 4 wherein the actuating means for the commutator includes a direct drive from the motor and that for the tuning device includes reduction gearing.

7. Control mechanism for effecting automatic adjustment of the tuning device of a radio receiver to a transmitted signal carrier wave having an amplitude above a predetermined minimum, comprising a reversible electric motor for driving the tuning device, a pair of alternative circuits for energizing the motor, a, rotary member movable with the tuning hdevice in a predetermined relation carrying a pair of commutator segments separated by a dead spot, an axially shiftable shaft, a rotary arm aiTiXed to said shaft and carrying a Contact pin, a twoposition switch controlled by said shiftable shaft adapted in one position to energize the motor through one of said alternative circuits and in the other position to energize the motor through the other motor circuit which includes the commutator segments and contact pin, a control member upon actuation adapted to initiate operation of the mechanism by energizing said one motor circuit, means operable in response to actuation of the control member for effecting rotation of the commutator and contact pin in' unison, and means operable in response to a signal carrier wave having an amplitude above said predetermined minimum for making the ylastmentioned operable means ineective whereby the contact pin is prevented from rotating with the commutator and is stopped at a radial position corresponding to said carrier wave, said contact arm in said stopped position cooperating with one or the other of the commutator segments to cause continued operation of the motor in the corresponding direction until the dead spot between segments is moved in contact with the contact pin at which time the motor is deenergized to stop the tuning device at the point of adjustment Whereat the radio receiver is tuned to said signal carrier Wave.

8. Mechanism for eiecting automatic adjustment of a radio receiver tuning device to a transmitted signal carrier Wave having an amplitude above a predetermined minimum, comprising a reversible electric motor, means including reduction gearing for actuating the tuning device from the motor, a rotary member carrying a pair of commutator segments for determining the direction of motor operation, a fixed member spaced from the rotary member, means including a direct drive for actuating said rotary member from the motor, a rotary contact arm adapted for axial movement between said rotary and fixed members, a contact pin carried by said arm and arranged to cooperate with said commutator segments, a solenoid upon being energized arranged to shift the contact arm in driving rela tion with the rotary member, a normally open switch included in the motor circuit actuated to closed position with the shifting of the Contact arm, means for energizing the solenoid in the absence of a signal carrier Wave having an amplitude above said predetermined minimum and for deenergizing the solenoid upon reception of such carrier wave, manual means for initiating operation of the mechanism, means in response to a signal carrier wave having an amplitude above said minimum for deenergizing the solenoid to thereby release the contact carrying arm which assumes a fixed position in a radial direclll REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,911,021 Gunther et al May 23, 1933 2,021,476 Bertschinger Nov. 19, 1935 2,025,218 Reinken Dec. 24, 1935 2,046,910 Barrett July 7, 1936 2,100,609 Mitchell Nov. 30, 1937 2,112,687 Barton Mar. 29, 1938 2,174,566 Case Oct. 3, 1939 2,208,549 Plensler July 16, 1940 2,231,806 Goldsborough Feb. 11, 1941 2,262,218 Andrews Nov. 11, 1941 2,326,737 Andrews Aug. 17, 1943 2,326,738 Andrews Aug. 17, 1943 2,369,542 Dietrich Feb. 13, 1945 FOREIGN PATENTS Number Country Date 425,626 Great Britain Mar. 19, 1935

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