US2166691A - Tuning control system for radio receivers - Google Patents

Description

V. T. FARE TUNING CONTROL SYSTEM FOR RADIO RECEIVERS July 18, 1939.

Filed March 30, 1938 2 Sheets-Sheet 1 NO'O'O'O d nomeg July 18, 1939. v. T. PARE TUNING CONTROL SYSTEM FOR RADIO RECEIVERS 2 Sheets-Sheet 2 Filed March 30, 1938 dttorneg Patented July 18, 1939 UNITED STATES PATENT OFFlCE TUNING CONTROL SYSTEM FOR RADIO RECEIVERS Delaware Application March 30,

7 Claims.

The present invention relates to a tuning control system for radio receivers, and has for its primary object to provide an improved tuning control system which may be time-controlled to tune a radio receiver to a plurality of differing preselected broadcasting channels or stations at predetermined time intervals, and to turn off the receiver between such intervals, with but one control circuit for each channel.

It is a further object of the present invention to provide means for the preselection tuning of a radio receiver to any one of a plurality of signal receiving channels or broadcasting stations under the control of simplified contact devices with one control circuit for each broadcasting station or channel to be tuned in, which may also control the power supply for the receiver through operation of the same contact devices.

The invention relates more particularly to a preselection tuning system for radio receivers, wherein one or more tunable receiving circuits are tuned by means of adjustable tuning elements selectively connectable in circuit to effect tuning of certain of the signal selecting circuits to preselected frequencies or broadcasting stations.

In tuning systems of this character, a plurality of shunt tuning capacitors, which are preferably adjustable or variable, are connected in parallel to one side of the tuned circuit, and are selectively connectable to another point on, or to the opposite side of each signal selecting circuit, through selective switching means.

It is a further object of the present invention to provide means for controlling the energizing of the radio receiver through the selective tuning connections above referred to, whereby the control circuits are simplified.

It is also an object of the present invention to provide a tuning control system of the type above referred to having an improved timing element comprising a perforated insulating tape element between a contact drum or plate and simple spring contacts, one contact for each control circuit, the tape element being perforated to include means for readily setting up selected time intervals for the circuit tuning operations.

The invention will, however, be better understood from the following description when considered in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

In the drawings,

Figure 1 is a schematic circuit diagram of a radio receiver provided with a tuning and control circuit embodying the invention;

1938, Serial No. 198,812

Figure 2 is a view in perspective of a portion of the tuning control apparatus shown in Fig. 1, showing the mechanical and electrical arrangement of certain of the circuit elements;

Figure 3 is a plan view of a perforated insulating tape utilized in the control system shown in Figs. 1 and 2; and

Figure 4 is a rear View, on a reduced scale, of a table model radio receiver showing the location of the tuning control elements on the radio receiver chassis.

Referring to Fig. 1, a radio receiver 5 is provided with a signal input tube or first detector 6, representing any one of a plurality of signal receiving and amplifying tubes, to which is connected a tunable signal input circuit 7 comprising a tuning inductance coil 8 suitably coupled to a signal input circuit, such as an antenna circuit 9, through a winding I0 inductively coupied with the winding 8. The circuit 1 is connected at its high potential side I l with the high potential terminal I2 of the tuning inductance, and through a coupling capacitor 13 with the signal input or control grid 14 of the tube 6.

The low potential side of the input circuit "I is preferably the chassis or ground of the radio receiver indicated at l5, and is connected with the low potential terminal I6 of the tuning inductance 8 through a lead H.

The input circuit 1 is tunable to a plurality of difiering signal frequencies or broadcasting channels by means of shunt tuning capacitors indicated at l8 to 24, inclusive, connected in parallel to the high potential side of the tuned input circuit and connectable to ground or the low potential side of the input circuit through individual tuning control leads 25, 26, 21 and 28, providing for preselecting tuning to four different broadcasting stations or signal channels.

The parallel arrangement of the capacitors is for the purpose of providing a series of narrow tuning ranges which cover the full tuning range 'of the receiving system. Three of the variable capacitors, 20, 22 and 24, are provided with fixed shunt capacitors 19, 2| and 23, respectively, for spacing the tuning ranges of the variable 01' adjustable capacitors. The four-channel tuning is shown only by way of example, and it is obvious that additional tuning channels may be provided by additional capacitors and control leads, or that a lesser number of channels may be provided as may be desired.

The leads 25 to 28, inclusive, are selectively connectable to the low potential side of the tuned circuit through spring contact elements 29 to 32,

inclusive, which are arranged in parallel relation to each other to engage at their free ends the periphery of a metallic cylinder or drum 33 as a contact plate. The drum is rotatable on a shaft 35 which is driven by a time clock 35 or other timing device through a suitable drive connection indicated at 3B. The drum or cylinder 33 is grounded, as indicated by the lead 31', to complete the connection for the tuning capacitors to the low potential side of the signal circuit.

The drum carries a perforated insulating tape element 3? having elongated formable contact areas or openings 38 spaced longitudinally for time separation of the contact operation, and arranged in four rows in alignment with the contact fingers to permit the various tuning capacitors to be connected in shunt with the tuned circuit at predetermined time intervals.

The mechanical and electrical arrangement of the contacts and drum, together with the tuning capacitors, is indicated in Fig. 2, to which attention is now directed along with Fig. 1, and in which figure the same reference numerals are applied to like parts and circuit elements as in Fig. l. The capacitors iii to 24 are arranged in a group for screw adjustment at the top and may be connected to the tube 6 through the various elements mounted on and supported by an insulating plate it. This unit may also be mounted close to the contact fingers 29 to 32, which may be carried in an insulating block ill adjacent to the drum 33.

The perforated tape 3"! is preferably arranged as shown in Fig. 3, having the contact openings or areas arranged to be formed or broken out from longitudinal marginal perforations 13 defining four rows 34, 45, Lit and l! of openings, spaced to move under and in alignment with the contact fingers, and having additional transverse marginal perforations 18 in each row definin the length of the areas which may be broken out, to cover successive short time intervals such as 15-minute periods, corresponding to the usual program time, and the entire length of the tape being timed to move under the contact fingers once in 12 to 24 hours, or other total time, as may be desired.

By arranging the transverse perforations 48 for short time intervals, the contact areas for the contact fingers may be elongated in sections to cover any predetermined length of time for operation of the. receiver in any one wave band. For example, as shown in Fig. 2, the perforations or openings 38 are of various lengths, depending upon the number of blocks or areas broken out from the tape in the various rows.

By placing along the edge of the tape the time or clock intervals as shown in Fig. 3 at 5! the time of operation of the four selector circuits may be set up at desired times and for desired time intervals by referring to the time designation opposite the areas to be broken out to form the contact opening in the tape. With the tape made of heavy paper, this operation may be accomplished without the aid of any tools or cutting devices other than an ordinary pencil point, for example.

After the tape is blocked out to provide the desired contact openings, it is placed upon the drum in such a position that the contact fingers are opposite the time designation on the tape corresponding to the time at which the tape is placed upon the drum. The tape is then secured in place by any suitable means, and this is all that is necessary to correlate the tape with the timing means or clock 35.

Referring again to Fig. 1, it will be seen that a single contact and control circuit is provided for each signal channel to be tuned in. In operation, the capacitor i8 is adjusted to tune the receiver to a selected signal channel in the higher frequency portion of the tuning range of the receiver, and the capacitors 2B, 22 and 24 are adjusted to tune the receiving system to other signal channels in lower frequency portions of the tuning range, the contact finger connected with each of the capacitors being connected with the drum 33 during each tuning adjustment, while the other contact fingers are insulated therefrom by a strip of insulating material or paper such as the tape 3!.

In order that the receiver may be turned off during time intervals when no reception is desired and turned on when the receiver is adjusted for response to any one of the selected signal channels, by operation of the timing drum and tape, a low current relay 5! having operating contacts 52 is connected with its operating coil 53in circuit with the control leads 25 to 28, inclusive. The connection With each of the control leads 25 to 28 for the relay coil is made through a lead 54, and individual radio frequency choke coils 55, one connected between the lead 54 and each of the control leads 25 to 28, as shown. The choke coils are of such inductive value that they offer a relatively high impedance to signal currents at the lowest frequency in the tuning range of the receiver, whereby they serve to isolate electrically the tuning capacitors and control circuits from the relay circuit 54.

The relay circuit is provided With operating current from a suitable low potential source, such as a battery 56 connected between the relay operating coil 53 and chassis or ground 51.

With this arrangement, it will be seen that as each contact is closed with the drum, a circuit is completed from the source 56 through the operating coil 53, the common lead 54, and one of the choke coils 55 to the operating or control circuits 25-28, and through one of the contact fingers to the drum 33 and ground If back to the source 56, through the ground 5?. The relay thus becomes energized whenever a tuning contact is closed, without interfering with the tuning operation, because of the isolation of the relay circuit 54 from the tuning circuits. In the present example, the relay contacts 52 are connected in the power supply circuit 58 for the radio receiver, Whichis energized when the contacts 52 are closed by operation of the relay.

When the receiving system is detuned by opening of a contact at the drum, the relay operating circuit is opened, the contacts 52 become opencircuited, and the receiver is deenergized.

Referring now to Fig. 4, in which the same reference numerals are used for like parts as in the preceding figures, a radio receiver 69, having a chassis BI, is arranged to have mounted thereon the tuning drum 33 and the insulating plate 40, with the tuning capacitors arranged for rear operation, as indicated at 62.. The insulating block 4! and contact fingers are arranged as in Fig. 2, to engage the drum at the top, and the remainder of the apparatus is mounted on the chassis in the usual manner. This facilitates adjustment of the receiver for the various stations to be tuned in and for placing the tape on the drum from the rear of the cabinet. This type of preselection, time-controlled tuning is adapted for use in low cost receivers because of its simplified construction.

In the receiver shown, the drum 33 may be driven by a small synchronous motor 63, geared to the drum through a gearing 64, the gear train being such that the synchronous motor, operating on the usual BO-cycle current, revolves the drum once in 12 or 24 hours. In the present example, the motor is of the usual clock type, having internal gearing (not shown) for reducing the speed of the motor to the usual speed required for clocks. As this type of motor is of relatively low cost, it does not add appreciably to the cost of the receiver.

Referring to Fig. 1, it will be seen that the circuit arrangement is such that there is provided across the tuned circuit, in parallel with the tuning inductance thereof, a tuning capacitor connected with the high potential side of the circuit, and two parallel branch circuits to ground and the low potential side of the circuit, comprising a pair of time controlled contacts in one branch and a high frequency choke coil, the operating coil of a control relay, and a source of operating current for the relay in the other branch. When the time controlled contacts are open, the relay circuit is ineffective to provide a tuning connection for the tuning capacitor to ground by reason of the choke coil.

When the contacts are closed, the tuning capacitor or tuning element is simultaneously connected to ground or the low potential side of the circuit and in shunt with the coil therein, to tune it to a predetermined frequency, and the relay circuit is completed through the same contacts. Thus, the contacts serve to control both the relay and the tuning simultaneously, without interfering with the tuning operation of the circuit when the contacts are open.

From the foregoing description, it will be seen that the automatic tuning of a small low cost radio receiver may be made practicable by the device and system herein described, which may be arranged to automatically turn on a radio receiver and tune in any one of a number of preselected signals at predetermined time intervals, together with controlling the energizing of the receiver during the periods that operation is desired in any one of the selected signal channels. Furthermore, it will be seen that the apparatus embodying the invention is adapted for mounting on a small radio chassis, in a position to be adjusted readily and without interfering with the other apparatus contained in the receiver.

I claim as my invention:

1. In a radio receiving system, means for tuning said system comprising a tuning element connectable to ground, a circuit providing said last named connection, time controlled contact means in said circuit, a parallel branch circuit for said last named circuit comprising a high frequency choke coil, a relay coil and a source of potential, and contacts controlled by said relay coil for energizing said receiver.

2. In a radio receiving system, means for tuning said system comprising a tuning element conneotable to ground, a circuit providing said last named connection, time controlled contact means in said circuit, said last named means comprising a time-controlled rotatable drum, a. spring contact engaging the periphery of said drum and connected with said circuit, and an insulating tape element carried by said drum having openings therein for permitting contact between the periphery of said drum and the spring contact during predetermined time intervals, a parallel branch circuit for said last named circuit comprising a high frequency choke coil, a relay coil and a source of potential, and contacts controlled by said relay coil for energizing said receiver.

3. In a radio receiving system, the combination with a tunable signal receiving circuit and a power supply circuit for said system, of means for tuning said circuit to a plurality of differing signal frequencies including an adjustable tuning element for each of said frequencies connected in parallel to one side of said circuit an having individual control circuits connectable with the opposite side of said circuit, each of said last named circuits including electrical contact means for selectively completing said connections, a relay operating circuit connected between the low potential side of the tunable input circuit and each of said circuit connections, a high frequency choke coil between each of said circuit connections and contacts and the relay circuit, and a relay in said relay circuit having contacts connected with said power supply circuit to control the flow of current therethrough.

4. In a radio receiving system, the combination with a tuning inductance, of a plurality of tuning elements connected in parallel relation with said tuning inductance and having individual tuning control circuits, time controlled contact means for selectively connecting each of said control circuits with said tuning inductance, a low current relay, a relay circuit including a source of operating current, a choke coil connected between said relay circuit and each of said control circuits, whereby said relay is energized through said control circuits while being electrically isolated therefrom at signal frequencies, and a control circuit for energizing said receiver in response to operation of, the relay.

5. In a radio receiving system, a tunable signal circuit comprising a plurality of tuning elements connected in parallel relation thereto at the high potential side thereof, and having individual ground connections to the low potential side thereof including a series of control circuits, a plurality of contact elements one for each of said control circuits, a grounded contact member movable in engagement with said contacts, a strip of insulating material between said contacts and said member having perforations forniing rows of formable contact areas corresponding to predetermined time intervals, timing means for moving said member and insulating strip at a predetermined rate with respect to time, a low current relay connected in circuit With said receiver for controlling the energizing thereof, said relay having an operating coil connected to ground and with each of said control circuits, and a choke coil between each of said last named circuits and the relay circuit, said choke coils having a relatively high impedance at the lowest frequency to be received.

6. The combination, with a radio receiver having a tunable radio signal receiving circuit, of means for tuning said receiver to one of a plurality of preselected signal channels and controlling the energization of said receiver in response to the tuning operation, comprising a plurality of tuning capacitors connected in parallel relation to each other to one side of said circuit and being adjustable to tune said circuit to a plurality of differing signal frequencies, said circuit being grounded at its loW potential side, a control circuit providing a connection for each of said tuning elements with the low potential side of said circuit and ground, comprising a circuit lead and a contact element for each of said tuning elements, a second contact element time controlled for movement in connection with said first named contacts, an insulating tape carried by said second element having formable openings in alignment with said first named contacts for selectively permitting contact between said first named elements and said second contact element, a relay controlling the operating current supply to said receiving system having an operating coil and an operating circuit therefor connected to ground, said coil having a common circuit connecticn with each of said control circuits, and a choke coil in said last named connections between each of said control circuits and the relay circuit, said choke coils having a relatively high impedance at the lowest frequency to be received, whereby said relay circuit and control circuits are electrically isolated.

7. In a radio receiving system, thecombination circuit and each of said control circuits, means providing a circuit connection whereby said relay is energized through said control circuits while being electrically isolated therefrom by said impedance. means at signal frequencies, and a circuit for controlling the operation of said receiver in response to operation of, said relay.

VICTOR T. FARE.

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