US2501575A

US2501575A - Automatic tuning control circuit

Info

Publication number: US2501575A
Application number: US521511A
Authority: US
Inventors: Jr Madison G Nicholson
Original assignee: COLONIAL RADIO CORP
Current assignee: COLONIAL RADIO Corp
Priority date: 1944-02-08
Filing date: 1944-02-08
Publication date: 1950-03-21
Anticipated expiration: 1967-03-21

Description

March 21, 1950 M. G. NICHOLSON, JR 2,501,575

AUTOMATIC TUNING CONTROL CIRCUIT Filed Fb. 8, 1944 nlml: 1"-

, ATTORNEY Patented Mar. 21,` 1950 UNITED STATES PATENToFFIcE l AUTOMATIC TUNING CONTROL CIRCUIT Madison G. Nicholson, Jr., snydor, N. Y., as-

signor to Colonial Radio Corporation, Buffalo, N. Y.

Application February 8, 1944, Serial No. 521,511

(Cl. Z50-40) Claims. l

This invention relates to an automatic tuning control circuit, andmore particularly to automatic crystal controlled radio transmitters or receivers, although it will be understood that my invention may be applied in other apparatus where automatic tuning of a circuit to any one of a series of predetermined frequencies is desired. Various forms of circuits of this type have been described and claimed in a 3o-pending application of William S. Wneld, Serial No. 463,775, led October 29, 1942. In apparatus of this type the circuits are automatically tuned to desired frequencies determined by crystals, and do not involve the setting of mechanical elements, such as pins, contactors, selecting cams,

rocker bars, or the like.

In such apparatus there may be provided a variable tuning instrumentality, such as a condenser or variometer operated by an electric vmotor through a suitable form of reduction gearing. Since the apparatus is particularly useful in airborne radios where space and weight requirements are strict, and since continuous operation is not required, the motor being in operation only when the tuning of the apparatus is equipment and parts.`v y

changed, it is customary to use a motor which is somewhat smaller and of` lighter construction than would be necessary for continuous operation. This apparatus, according to the application above referred to, is arranged so that the motor circuit is closed in the absence of a voltage in the circuit to be tuned and is opened when the voltage in the circuit rises to a predetermined level, so that when the circuit reaches resonance the motor stops operating. On the other hand, ii for any reason this predetermined voltage is not generated the motor will continue to operate indefinitely, driving the tuning instrumentality repeatedly through the tuning cycle. This is likely to produce overheating of the motor and may even burn it out. l v

In accordance with this invention I have provided a circuit which may be said to provide an automatic test of operating conditions once each tuning cycle while the motor is in operation. If this test shows that the apparatus is functioning properly, the circuit will permit continuing operation of the motor for another cycle. If not, the motor is stopped and remains stopped until the trouble is found and remedied.

It is an object of this invention to provide apparatus which will prevent sustained overloading and burnout of the driving motor, which would occur on continuous operation.v

It is a further object Of this invention to provide apparatus which will stop the operation of the driving motor. in casel .of certain failure in the associated apparatus, which would otherwise cause the apparatus .to :continually vary its tuning. y f

It is stilla further` object of this invention to provide such apparatus with a minimum of added It is still a further object of this invention to provide apparatus of the class described which will stop operation of thetuning motor in case the crystal control elements become defective or removed from their. sockets or in case of other trouble which prevents the resonant circuit from building up a voltage. Y Still other objects andjadvantages. of my invention will be apparentfrom the specification. In the drawing, the single figure is a Icircuit diagram of one form of apparatus in accordance with my invention.

Referring now more particularly to the drawing, I represents a Work circuit which may be a resonator circuit such as thev Well-known crystal and tube oscillator' l5 variably tuned bycondenser 9 connected through leads 26 and 21 or other tuning instrumentality. Customarily, a number of crystals l 6,11, I8 are provided, associated with the work circuit |,f'and some 'form of selecting means la. by which Athe operator may connect the desired crystal 'into the circuit to X the frequency of the vwork circuit. The apparatus may be a radio transmltter or, receiver or another form of circuit in which it is desired'to provide tuning to any one of a number of previously selected frequencies.

The tuning instrumentality herein referred to as a condensen although it may be any other instrumentality,' may 'be driven by any `suitable power means, such as motor l, through suitable reduction gearing 1a, and the condenser S'may be the means for 'varying the tuning of work circuit l. In order'tocontrol the motori by means of the voltage kin thel work circuit I., the voltage derived from this circuit may berectifled and passed through a resistance included in a unit 2, and the resulting voltage drop may vbe'iinpressed between cathode 3a vand control electrode3b of tube 3. Connected to the anode 3c thereof, there may be provided the energizing Winding of relay 4, having armature 4a, an energized-position fixed contact 4b, and a deenergized-position fixed contact 4c. The relay 4 controls the opening and closing of the circuit of motor 'l through source l0, through:` connections made through cam switch l5y driven bycam 8-Y synchronized with "treiuatsrstutejttttrti ne '15g-,tire sitter e t condenser 9, and having a cam segment Sa corresponding to only a relatively small part of the tuning cycle.

The came switch comprises the two movable contacts 6a and 6b, the contact 6a cooperating with a rst stationary contact 6c and a second stationary contact 6d while the contact 6b similarly cooperates with a first stationary contact Be and a second stationary contact 8f. Movable contacts Sa and 6b are mechanically connected together, as indicated by the dotted lines, for operation in unison and both n'age their r'e'- spective xed contacts 6d and Ef at all times during the tuning cycle eicept whennth'ey are moved to close their other yrespective iii'rd contacts 6c and Be by the passage of cam segment 8a, under them.

Connections may be provided between fixed contact 4c and xed contact 6c through lead 20; between iixed contact 4band fixed contact 51 through 'lead 21; between notatie ttr'rtact et and ctritrti eiettrue it through ieee `21g; aire 'between rectier 'and resistance l unit `2 and fated contact Gf through le'ad 23. Fiird contact 6e may be connected throughwaseries resistor -II d shunttond'esler (2' and through leas 2t to t "e control grid I5gI of thevvosjcillator' I5, which ma bea part of work circit i .Q Y

Do'vable Contact 4d is gliirdj'ed and movable contact 'Ea is connected tonne :side of lthe iiibt'or circuit, the 'other side of whichais .connected tl'irfngh a Suitable power sor'c'ze I0 to ground. The motor energizing circuit is thus completed in either 'of two ways. The tirst of thesereduirs that the relay 4 shall not energ'ied by the control tube 3, so, that the relay conta'ctfsjll' and fit are closed, arid further requires that the `cam segment Ba shall movemth'e contact Gu 'to `Aengage its liked 'Contact '6o. The motor circuit is then completed from the source I0 through the closed cam-switch contacts 'B and 6ta, conductor 20, and 'closed relay contacts H and le. The second manner by which the motor Vei-i'er'giaing circuit is completed requires that the relay 4 be energized by the` control tube 3,vto close the relay contacts 4a and 4b, and further requires 'thatthe cam 8 operate the movable switch-contact 6a, to close vits stationary contact 6d. -In this case the motor `circuit is completed from the source l0 through the -camlswitch 'closed contacts 6a, 6d, the conduotor 2 I', and the clsed relay contacts 4a and 4b.

It will be observed that when th'e cam `switch is not actuated by the cam segment 8o, the volt- `ag'e derived from the work lcircuit I through rectifer and 'resistance nit 2 is impressed upon the control 'electrode 3b of tube 3 through fixed Icori- -tact '6j and movable contact 6b. When 'cam switch Bb is actuated by 'cam segment im, the control electrode 3b 'ci tube 3 is connected to the 'switch 'contacts '6b and 6, the resistor 'I 1, and the frt will be 'opstarten that during the time tue control 'electrode "3U "6i 'tube 331s iectd tothe siting circuit fis 'compi-tes ty tnt uteritrgieeu operating 'teireititn er the reiay t 'the 'retten 'that the tait segrfrent sa strette nostre ci the cam-switch tttatts ta ata et. 'it 'ru-11 fui-tirer te tb'servea *that during the titre the 'centrer electrode "3b of tube 13 `i"s conne' e'd tothe tion of the relay 4 since the cam 8 now closes the cam-switch contacts 6a and 6d.

With the foregoing description of the apparatus and connections in mind, the operation of the circuit will be readily understood. Assuming that the apparatus is operating on one predetermined frequency and the operator desires to shift t'o another `f'rer'iuency, he Imay remove the operatin'g crystal from its socket and insert the new crystal, or if selecting switches are provided as shown, he may operate the selecting switch to select the new frequency. Upon disconnection or removal of the iirst crystal, the output energy of the work` circuit drops to zero, the bias voltage on tube 3 drops t'o zero, plate current increases, and contact 4d is closed against contact 4b.

If cai'n switch 6 is positioned at this time to close its contacts Ea, 6d and 6b, 5f, which it is except for a small part of the tuning cycle, then the motor circuit is closedthrough contact 6d and Sa and the 'motor operates, var-yimg the tuning of the Awork circuit I through condenser 9. When the work circuit b'eciiies resonant to the new frequency, it begins to deliver output voltage, the bias voltage impressed on tube 3 from the recter and resistance 2 reduces the plate current of tube 3 to the Vpoint 'where the lrelay 4 'opens and contact la moves out of engagement with Contact 4h and into engagement with con- 'tact 4c, thus interrupting the `ni'c'utor circuit- The apparatus will remain tuned to tlri'e neit7 frequency until the operator changes it again, or until the work circuit 'stops 'd'elve1`"`1n"gl 'a 'voltage for 'some other reason. l

It the crystal 'or oscillator should suddenly become inoperative, the work circuit `v'rould stop delivering voltage to the rbtier and resistance 2, bias 'voltage on tube 3 would be reduced so that relay 4 would again be energized, 'and contact -lI-a 'would move into engagement with 'contact 4b, thus closing the Vmotor 'circuit and operating the tuning I'condenser 9. v'This 'condition would contiue, resulting as aboveV explained in possible overheati'n'g or burnout of 'the motor 1, but for the operation o the can operated switch 6. At o' point in the tuning cycle, the 'ca'm' segment 8a actuat'es th switch "6, 'closing movable 'contact 6a `agaist3ie`d Contact 5c 'and movable Contact '6h against fixed contact Ec 'as 'already explained.

With Contact 4c against contact 4b as last described, the cam actuation of switch 6 momentarily opens the motor lcir :1'1it, 'and the motor 'stops with the switch contacts ta, te and sb, 'se in closed position. With 'the 'contacts in this po- 'sition control electrode 3b of t'b'e 3 is now connfected through switch cofritacts '619,15 to the oscillater 'tube control ygrid I5y in the work circuit I. If the oscillator 'is o'atiri'g properly, a voltage is being 'produced (even though the work circuit is not delivering any voltage) which is 'suiiicifent 'to reducetle 'plate current of tube 3 to 'the point where the relay 4 becomes degener- `ized and contact 4a is permitted to lclose against Contact 4c.

With 'the contacts of the switch in the position rlast described, this' "deenergization of the fr'elay 4 closes the motor 'circuit and the motor begins operation 'again and will continue to operate until the cam 'segment Ba is moved sufficiently that lthe vswitch -B is actuated again toclose 'its contacts 6a, "6d and 617,61. This action now disconnectsfcontrol `electrode 3b 'from the oscillater grid 15g Sand 'restores it to rectifier and re- "s'istance 2, and if no voltage is 'present 'therein the plate current of tube 3 will rise and the relayv 4 will close its 'contact 4a against contact 4b, thereby again closing the motor circuit to con' tinue the tuning operation.

If switch 6 happens to have its contacts 6a, 6c and 6b, 6e closed when initial operations are attempted, as when the apparatus is first turned on, as soon as tube 3 heats up and the oscillator begins to oscillate plate current in`r tube 3 drops because of the bias on its control electrode 3b; the motor circuit is closed by closure of the relay contacts 4a and dcand the motor begins to opcrate the tuner. From here on, the operation is as already described.

If, however, when the contacts of cam switch 6 are moved into upper contact position and the control grid 3b connected tothe oscillator control grid, there is no voltage on the oscillator control grid (which would be the case if the tube had stopped oscillatingr due to a defective or missing crystal), the plate current of tube 3 would be of suiiicient value to hold contact 4a against contact 4b, thereby keeping the motor circuit open. In other words, the operation of the circuit may be summed up as follows:

Once during each tuning cycle, with the operation of the cam switch, tube 3 teststhe oscillating circuit, and if it is operating properly, the motor circuit is closed and operation continues, but if the oscillatoris not working, the motor circuitis opened and will remain open until the trouble is found and remedied; so it will be seen that should trouble develop; i. e., should the oscillator tube burn out or should the crystal become inoperative, the motor is prevented from operating. On the other hand, if the oscillator is functioning properly, operation of the motor continues through the next tuning cycle.

In the specification I have explained the prin# ciples of my invention and the best mode in which I have contemplated applying those principles so as to distinguish my invention from other inven# tions, and I have particularly pointed out and distinctly claimed the part, improvement, or combination which I claim as my invention or discovery. y

While I have shown and described certain preferred embodiments of my invention, it will be understood that'modications and changes may be made without departing from the spirit and scope of my invention, as will be those skilled in the art.

Iclaim:

1. In automatic tuning apparatus, in combination, a frequency determining element, a work circuit including an oscillator for delivering energy limited to -a frequency determined by said element, said work circuit having a variable tuning instrumentality power operated means for varying said tuning instrumentality, energy responsive means for interrupting operation of said power means either in responseto delivery by said work circuit of a predetermined level of energy or in response to failure of the oscillator to deliver a predetermined level of energy, and means for periodically opera-tively associating said energy responsive means alternately with said work circuit and with said oscillator.

2. In automatic tuning apparatus, in combina.- tion, a frequency determining element, a work circuit including an oscillator for delivering energy limited to a frequency determined by said element, said work circuit having a variable tunapparent to ving instrumentality, power means for varying said instrumentality, energy responsive means for 6 interrupting loperation of said-power means either in response to delivery by said'work circuit of a predetermined level of energy Vor inlresponse to failure of the oscillator totdeliver a predetermined level of energy, and means for periodically operatively associating said energy responsive means alternately with said work circuit and with said oscillator, said energy responsive means being arranged to be operatively associated with said oscillator during a small part only of each tuning cycle. l ,y

3. In automatic tuning apparatus, in combination, a frequency determining element, va work circuit including van oscillator' for delivering energy limited to a frequency determined by said element, said work circuit having a variable tuning instrumentality power' operated means for varying said tuning instrumentality, energy responsive means for interrupting operation of said lpower means either in response to delivery by said work circuit of a predetermined level of energy or in response to failurel of the oscillator to deliver a predetermined level of energy, and means for periodically operatively associating said energy responsive means alternately with said work circuit and with said oscillator, said energy responsive means being arrangedtobeoperatively associated with said work circuit during the major part of each tuning cycle and with said oscillator during a small part only 'of each tuning cycle;

4. In :automatic tuning apparatus, in combination, a frequency determining element, a work circuitv including anoscillator for delivering energy limited to a frequency determined by said element, said work circuit having a variable tuning instrumentality, power means for varying said instrumentality, energy responsive means for interrupting operation of said power means either in response to delivery by said work circuit of a predetermined levelv of energy orv in response to failure of the oscillator to deliver a predetermined levelv of energy, and means synchronized with said tuning instrumentality for periodically and alternately connecting said energy responsive means -to said work circuit and to said oscillator.

5. In automatic tuning apparatus, in combination, a frequency-determining element, a work circuit including an oscillator for delivering energy limited to a frequency determined by said element, said work circuit having a variable tuning instrumentality, power means for varying said instrumentality, a power control circuit including a thermionic vacuum tube having a current relay in the plate circuitthere'of having an' armature biased 'to'one contact position and closable to another contact position by the current of said relay, and'acam actuated switchhaving at least .two contacts closable yin individual ones of a rst and asecond operating positionof said switch and arranged in' circuit'with said power means and withsaid armature for Ypreparing said power circuit for closure eitherin said'rst or said second operating position of said cam switch, whereby closure'arid opening of said power circuit may be `controlled by'said thermionic'relay, `and a lsecond set of contacts-on said cam switch and effective in said rst and said second operating position thereof for selectively connecting the control electrode of said thermionic'vacuum tube to the output of said work circuit orto said oscillator, said cam switch being synchronized with said tuning instrumentality.

` 6. In automatic tuningapparatus; in combination, a frequency-determining elemerit,v a work 'circuit including any oscillator. for :delivering enasentar.

elementsaid, work; circuit having a variable tun,-

ingv instrumentality; power means. for var-ying said instrumentality, a power control circuit including: athermionic vacuum tube having a current relay in the plate circuit thereof, said relay having an emmaturebiased to one contact position andA closable to4 another contact position by the current of said relay; and a cam switch hav.- ing; a rstset or iixed. and, movable contacts preparing said power control circuit for. closure. on either said one or said: other contact positions of said' relay armature-andp a` second set of iixed and movable: contacts for selectively connecting the control circuitoff-said thermionic relay to the outputv f; said. work` circuit. or to said oscillator respectively,` saidcam switch beingy synchronized with said'. tuning instrumentality, whereby in one positionV of; said canrswitch. predetermined current in said; relay causes closure of said power circuit while in the other position of said cam switch predetermined current in said relay causes opening ci said power circuit.

7. In automatic tuningl apparatus, in combination, a frequency-determining elem-ent, a work circuit including an oscillator for delivering energy limited toA a frequency determined by said element, said work circuit having a variable tuning instrumentality, power means for Varying said instrumentality, a power control circuit including a thermionic, vacuum tube having a current, relay. the plate circuit thereof, said relay having an arnfiature-biasedV to one contact position and closable to.v another contact position by the current of said. relay, and a cam switchhaving a. rst. set of fixed and movable contacts preparing said powerv control. circuit for closure on either said one or said other. contact positions of said relay armature, and, a second set of fixed and movable contacts forselectively connecting the control circuit of said thermionic relay to the output. of said work circuit or tosaid oscillator respectively, saidcamy switch being` synchronized with said tuning instrumentality, whereby in one position of saidcam switch predetermined current insaid relay causes closure of said power circuit while in the other position of said cam switch .predetermined current in said relay causes opening oi saidl power circuit, said cam switch being arranged to prepare said powerA circuit for closure through said other contact of said relay during the major part of the tun-ing cycle;

8. In automatic tuning apparatus, in combination, a frequency-determining element, a work circuit including an oscillator for deliveringr energylimited to a, frequency determined by said element, said work circuit havinga variable tuning instrumentality, power means for varying said instrumentality; apower control circuit including athe-rmienic vacuum tube. having a current relay in the plate circuit thereof, said relay having an armature biased to one contact position l and closable to another contact position by the current offsaid relay, and a cam switch having a nrst set of fixed and movablecontacts preparing said power control circuit for closure on either said one or said other contact positions of said relay armature, and a second setr of' fixed and movable contacts for selectively connecting the control circuit of said thermionic relay to the output of said work circuit or to said oscillatorrespectively, said cam switch being synchronized with said tuning instrumentality, whereby in one position of said camy switch predetermined current in said relay causes. closure of` said power-circuit while in the other; position of said camswitch predetermined current in said relay causes opening of said power circuit, said cam 4 switch being arranged to prepare the power circuit for closure on said one contact. of said relay during a small part only of each tuning cycle.

9, In automatic tuning apparatus, inl combination, a frequency-determining element, a work circuit including an oscillator for delivering energy limited to a frequency determined by said. element, said work circuit having a variable tuning instrumentality', power means for varying said instrumentality, a power contr-ol circuit including a thermionic vacuum tube havingA a current relay in the plate circuit thereof, said relay having anr armature biased to one contact position and closablel to another contact position by the current of said relay, and a cam switch having a rst setoi fixed and movable contacts preparing said. power control circuit for closure on either said one or said other contact positions of said relay armature, and a second set of fixed and movable contacts for selectively connecting the control circuit of said thermionic relay to the output of said work circuit or to said oscillator respectively, saidcam switchy being synchronized with saidtuning instrumentality, whereby in one position of said cam switch predetermined current in said relay causes closure of said power circuit while in the other position of said cam switch predetermined current in said relay causes opening of saidl power circuit, said cam switch being arranged to prepare said power circuit for closure through said other contact of said relay during the major' partY of the tuning cycle and for closure on said one contact of said relay during a small part onlyof each tuning cycle.

l0. Infautomatic tuning apparatus, in combination, a frequency-determining element, a work circuit including an oscillator for delivering energyhaving a frequency determined by said element,` said work circuit including a variable tuning instrumentality, powermeans for varying said instrumentality,l and a control system for controlling the energization of said power means, said system including means operating in synchronized relation with said tuning instrumentality for selectively coupling said control system during one portion of each tuning cycle to the output of said Work circuit and during another portion thereof to said oscillator, and means also operating in synchronized relation with said tuning instrumentality for reversing as between said one and said other portion of said each tuning cycle the mode of control effected by said control system over the energization of said power means.

MADISON G. NICHOLSON, J n.

REFERENCES errno `The.l following references are of record in the le of this patent:

UNITED. S'IA'IESA PATENTS i Number Name Date 11,8971252 Gardner Feb. 14, 1933 1,932,925 Chauveau Oct. 31, 1933 2,056,200 Lowell" Oct. 6, 1936 2,182,352 Prochnow Dec. 5, 1939 2,304,871 Andrews Dec. 15, 1942 FOREIGN PATENTS Number Country Date Great Britain Mar. 19, 1935