US2277149A - Switching mechanism for multiple frequency band receivers - Google Patents

Description

March 24, 1942., w A, SCHAPER ErAL 2,277,149

SWITCHING MECHANISM FR MULTIXLE FREQUENCY BAND RECEIVER Y' Filed April 8, 1940 2 Sheets-Sheety 2 INVENTUM l WILLIAM A, 5CH/WEF; BY QEORQE B. MaGW-:LLM

Patented Mar. 24, 1 942 SWITCHIG MECHANISM FOR MULTIPLE FREQUENCY BAND BECEIVERS William A. Schaper, Cicero, and George B. Mc- Clellan, Chicago, Ill., assignors to Johnson Laboratories, Inc., Illinois Chicago, Ill., a corporation of Application April s, i940, serial No. 328,458

(o1. zoo- 11) 4 Claims.

- 'Ihis invention relates `to switching mechanism for radio receivers,vsuch as those used for'the reception of broadcasting, and more particularly to receivers intended to cover a very wide range of frequencies, or plural bands extending over the important portions of such a wide range.

The invention provides means by which the very considerable advantages of permeability tuning may be secured in such wide band receivers.

The switching arrangements which'we employ with our novel coil system are different from..

although not necessarily more complicated than,

those employed inA systems in which separate inductive windings are employed for each wave band. These switching arrangements, together with such modications thereof as will readily occur to those skilled in the art, taken in connection with the coil system per se constitute the novel structure which when employed with other components already well known, to form variably tunable resonant circuits, makes possible the production of highly enicient permeabilityf tuned plural-hand wide-range radio receivers in accordance with the invention.

In order that the principle underlying our invention may be properly understood, we shall first describe a coil system which provides four different air-core inductance values, and we shall then show how this coil system, `or modiiications thereof, may be employed in practical receivers, reference being had to the accompanying drawings, in which:

Fig. 1 is a diagrammatic representation of a type of winding in accordance .with thevinvention, suitable for providing four diierent.' aircore inductance values;

Fig. 2 is a diagram showing a switching method in accordance with the invention, suitable for employment with the winding of Fig. 1;

Fig. 3 is a side elevation of a coil structure having a winding such as that of Fig. l and a portion of the switch gear of Fig. 2;

asingle nat layer upon a suitable tube. In the ligure, the lower ends of these eight windings are numbered 1 to 8 respectively, the corresponding vupper ends being numbered 1' to 8' respectively, this same notation being used in "Figs, 2, 3, 4 and 6. It is preferable that the windings be spaced from each other by a distance` approximately equal to the diameter oi the conductive portion of the `wire employed. which may be either solid 4wire or conductor having plural insulated strands. In Fig. l. for clarity, the ends oi the eight windings are shown as all leaving the form or tube at the same angular point, but it will be understood that they are preferably brought oil at eight equiangularly spaced points.

Theeight windings of Fig. 1 may be made to produce numerous inductance values by. connecting them in various series, parallel, and

series parallel arrangements.

Fig. 2 shows the eiglit windings of Fig. 1 connected in four different ways, indicated by the letters a,'b, c and d. -End i of the lirst winding is one terminal of the inductor, and end 8' of the eighth winding is the other terminal of the inductor. For convenience of explanation, end I is shown as connected to a bus 9, and end 8 is shown connected to a bus I0, and the remaining terminals are each shown as connected to switch arms by which they may be connected either to a bus, or to the opposite end of the next adjacent winding. l

Maximum inductance .is secured by placing the eighijl windings in series aiding relation, as

. shown in Fig. 2a, by connecting the upper end A of each windingto the lower end of the next Fig. 4 is an end view of the coil structure l ofFig. 3:

Fig. 5 is a schematic diagram of a receiver embodying the invention; and Figs. 6 and '1 are an elevation and a section on the line 1--1 of the elevation, respectively, oi a switching arrangement to carry out the changes diagrammatically indicated in Fig. 2.

Figure 1 shows a construction which is suitable forv use with our invention with a coil sys- Y i Vtem in the-case in which four different inductance values are to be provided.' Thecoilcomprises eight windings arranged spirally side by side in adjacent winding.y To secure the next lower value of inductance, the windings are thrown into two groups each having four windings in series. This is accomplished, as shown in Fig. 2b, by switching end 5 to bus 9 and end l to bus I0. To secure the next lower value of inductance the windings are thrown into four groups each having two windings in series. 'I'his is accomplished, as shown in Fig. 2c, by switching ends 3, and 'I to bus 9, and ends 2' and i' tobus. I0. Tosecure the lowest value oi inductance all eight windings are placed in parallel. This is Y accomplished, as shown in Fig. 2d, by switching lower end of the structure. then the switching may be accomplished entirely at the lower end. A convenient structure for securing this result and mounting the switching mechanism, is shown in Figs. 3 and 4. The eight windings of Figs. 1 and 2 are wound upon a suitable thin-walled tube II of insulating material, core I2 being arranged to slidably enter tube II from the far end thereof. At either end of tube II there are discs I3 and I4, also of insulating material, and running between these discs, staked or otherwise suitably' fastened into equi-angularly spaced lholes around the peripheries thereof are small wire bus bars I" to 8" inclusive. The'ends I to 3' inclusive, oi the eight windings are soldered respectively to bus bars i" to 8" inclusive and are thus returned to the opposite end of the form, where the bus bars are terminated in suitable switch contact points. The ends I' to 8 inclusive, of the eight windings are connected directly to eight switch-points, also equi-angularly spaced, but at a smaller radius than the bus bars. It will be apparent that by bringing suitable sets of switch-arms into contact with switch-points I to 8 and I to 8, the four different connections of 'the windings explained in connection with Fig. 2 can be secured, and switching of the associated capacitors can be accomplished in the same switch-gear.

It will be noted that for all four inductance values each ofthe switch-points in Fig. 2 is connected either to an adjacent switch-point or to one terminal of the complete coil. Thus switch-point 4' is connected to switch-point 5 for position a of Fig. 2 and to bus bar I8 (not shown in Figs. 3 and 4) for positions b, e and d of Fig. 2. Similarly, switch- points 2 and 8 are connected respectively to switch-points 3 and 1 for positions a and b, and to bus bar III for positions e and d. And finally, switch-points I', 3', 5' and 1' are connected respectively to switch- points 2, 4, 8 and 8 for positions a, b and c and to bus bar I for-position d. Switch-points 2 to 8, when not connected to switch-points I to 1' respectively as just described, are connected to bus bar 9.

Ou1 improved switching mechanism is illustrated in Figs. 6 and 'I to be employed in combination with a coil structure such as that shown in Figs. 3 and 4 to secure the switching functions indicated diagrammatically in Fig. 2. In Fig. 6, switch contact points 2 3 and I'1 are arranged in seven radial pairs, spaced 45 degrees apart in the same manner as in Fig. 4, upon a suitable disc of insulating material which may be cam slots 48-54 in ring 31. Contactors 45 are of such shape that in the outward position of each arm, the inner contacter connects together the corresponding radial pair oi' switch contact points, while the outer contactor restsupon the ring 31. Upon moving the arm inwardly, the inner contactor connects the inner switch contact point to contact ring 38, and the outer contacter connects the outer switch contact point to the ring 31.

Ring 31 is rotatably supported in peripheral guides, not shown, and has gear teeth around 45 degrees of its periphery, which engage a pinion 58 mounted upon a shalt 51 to which an operating knob, not shown, may be attached. Arms 38--44 are restrained to radial motion in slots in upwardly projecting inner rim 58 of ring 36 and by similar slots in guide members 5S at their outer ends.

Cam slots 4Ii-54 are so shaped that upon rota- -tion of ring 31 through successive angles o! 11.25 the four diderent connections shown in Fig. 2 oi' the eight windings of a coil such as shown in Fig. l are accomplished. In the position shown in Figs. 6 and 7, the connections correspond to those of Fig. 2a, all eight windings being connected ln series. Cam slot 5i is of such shape that immadiately upon clockwise rotation of ring 31 arm 4I is moved inwardly to connect switch contact point 4 to ring 31 and switch contact point 5 to ring 38, to secure the arrangement oi Fig. 2b. Upon further rotation of ring 31, arm 4I remains in its inward position and arms 39 and 43 are moved inwardly to secure the arrangement of Fig. 2c, Upon still further rotation of ring 31, arms 39, 4I and 43 remain in their inward positions and arms 38, 40, 42 and 44 are moved inwardly to secure the arrangement of Fig. 2d. Upon counterclockwise rotation of ring 31 the reverse operations occur. Suitable notches and a pawl, not shown, may be provided to indicate the four positions of ring 31, and to hold the,

ring in a selected position. A suitable stop, not shown, may be provided eitheron ring 31 or on shaft 51 to prevent rotation of ring 31 beyond its proper end positions.

Terminal I of the first winding is permanently connected to ring 38, and terminal 3' of the eighth winding is permanently connected to ring 31. The ungrounded terminals of condensers I8, I1, I8 and I3 oi' Fig. 5, are brought to contact points 88, 8|, 82 and 83 respectively oi.' the switch in Fig. 6. Mounted upon ring 31 and rothe end disc I4 of the form shown in Figs. 3 and an inner switch contact point to the adjacent outer switch contact point,A proceeding always in a clockwise direction (or vice versa) except for terminals I and 8' to be described later. Inwardly of the radial pairs of contact points, there is a contact ring 38 corresponding to bus 8 of Fig. 2. Outwardly oi' the radial pairs of switch contact points, there is a ring 31, which corresponds to bus I 0 of Fig. 2. Positioned over the switch contact points 4and the rings 38 and 31 are seven radially movable arms 38-44 of insulating material. In the drawing, arms 38, 39 and 40 are broken away to -show the radial pairs of switch contact points. Each of these arms carries two contactors, 45, which have pins 48 tating therewith vin a small contacter 84. As ring 31 is rotated to select a desired connection of the coil windings, contactor 84 moves over contacts SI1-83 to connect the appropriate condenser 'into circuit, as explained in connection with Fig. 5. For convenience in the drawings, ring 31 is shown radially outside the switch contact points and in the same piane, but it may alternatively be made of an outside diameter corresponding to the outer circle oi' switch contact points and may be positioned above them, by suitable repositioning of the contactors 45 and the follower pins 41.

In the switch gear shown by way of illustrative example in Figs. 6 and '1, ring 31 acts as a rotary cam to actuate arms 38-44 and also as a bus bar and electrical terminal of the compound coil.

If preferred, ring 31 may be made o! insulating material, and a separate ring of suitable contact metal may be added to act as a b us corresponding to bus I0 of Fig. 2. Numerous other modications will occur to those skilled in' the art.

in the higher frequency bands.

As is known, the inductance change produced by a particular core depends upon the dimensions and proportions of the coil with which it is used, but is independent of the inductance value of the coil. Thus, using a single core, the in- Yductance change and therefore the ratio of maxiquencies in each band will, in general, be greater This fact makes advisable a compromise in the choice of the material from which the core is made, so that the inductance-to-resistance of the circuit will be decreased by the core only in the highest frequency band, or the two highest frequency bands, will remain substantially constant in the second or third band, and will be increased in the fourth or lowest frequency band. It is to be remembercd thatthe coil construction in accordance with the invention provides exceptionally good quality coemcient, Q, on the higher frequency bands, so that while the change in Q over the frequency band is more pronounced in the higher frequency bands, nevertheless very satisfactory gain and selectivity can be secured in all bands.

Fig. 5 is a schematic diagram of a receiver embodying the invention, of the superheterodyne type, and employing a series-tuned antenna cir.

cuit and an oscillator circuit, 'followed by the usual oscillator-modulator, intermediate-frequency amplifier, detector, audio-frequency ampliier and loud speaker as indicated. Coils, and switch-gear to accomplish the necessary inductance and capacitance changes for the different frequency bands, of the type above described are indicated by the blocks marked Antenna coil and switch and Oscillator coil and switch. The antenna I5 is permanently connected to one terminal oi the antenna coil, the other terminal of the coil being connected to a grid of the oscillatormodulator tube. The antenna coil switch automatically selects one ofthe condensers I6, l1, I8 or it for the selected frequency band. The oscillator circuit is of conventional type, and as shown employs shunt coils and 2| and'series coils 22 and 23 on the two lower frequency bands respectively, capacitors 24 and 25 beingA connected permanently across shunt coil 20 and capacitorsv 25 and 21 being permanently connected across shunt coil 2|. The proper complete combination of shunt coil, series coil, and capacitors is selected by the coil switch. Similar shunt and series'coils may also be employed on the two higher frequency bands. although they are usually not necessary. As shown, for the two higher frequency ranges, the oscillator circuit employs capacitors' 23-29 and capacitors -31 respectively. The antenna coil switch and the oscillator coil switch arevmechanically con nected for simultaneous operation by means of a single knob, as indicated by the dotted line 32. Ferromagnetic cores 33 and 34 are associated with the antenna coil and the oscillator c'oil will occur to those skilled in the art. For example, the arrangement according to the invention may equally well be/ employed in parallel-tuned input circuits, and in either the plate circuits or the grid circuits of tuned radio-frequency amplifier stages. Additionally, as already noted, the arrangement according to the invention may be employed in receivers having less than four frequency bands, and in cases in 'which itis" preferred to employ separate coils permanently connected as above described.

In the detailed description of our invention we have chosen an arrangement for providing four frequency bands, since this example is adequate to illustrate the principles involved. it

will be understood, however, that the invention is not limited to a maximum of four frequency bands, and that it may be .applied to live or more bands as may be required.

Having thus described our invention, what we claim is:

1. As a means for selectively connecting a plurality of permeability tuned inductance coils in differentones of series, parallel and seriesparallel arrangements, the combination of a mounting plate, concentric flat metal rings mounted on said plate and spaced from each other radially by a substantial amount, pairs of electrical contacts for connection with the terminals of said coils and each pair mounted on said plate between said rings and spaced therefrom and from each other, said rings constituting bus-connections for the selective connecting means, movable switch arms having conductive contactors for selectively connecting said electrical contacts and said rings, and cam mechanism for actuating said switch arms.

2. As a means for selectively connecting a plurality of permeability tuned inductance coils in different ones of series, parallel and seriesparallel arrangements, the combination of a mounting plate, mounted on said plate and spaced from each other radially by a substantial amount, pairs of electrical contacts for connection with the terminals of said coils and each pairmounted on said plate between said rings and spaced therefrom and from each other, said rings constituting bus-connections for the selective connecting means, movable switch arms having conductive contactors for selectively connecting said electrical contacts and said rings, and cam i mechanism for actuating said switch arms, said switch arms being mounted on said plate in respectively and are arranged for movement in radial arrangement for longitudinal movement and respectively in line with said pairs of contacts.

3. As a means for selectively connecting a pl rality -of permeability tuned induotance coils in different ones of series, parallel and lseries-parallel arrangements, the combination of a mounting plate, concentric flat metal rings mounted on said plate and spaced from each other radiallyY by a substantial amount, pairs of electrical contacts for connection with the terminals of said coils and each pair mounted on said plate between said rings and spaced therefrom and from each other, said rings constituting bus-connections for the selective connecting means, movable switch arms having conductive contactors for selectivelyV connecting said electrical contacts and said rings, and cam mechanism' for actuating 'said switch arms, said switch arms being of insulating material and each of said cntactors .being adapted to electrically connect concentric fiat metal rings tween said rings and spaced therefrom and from each other, said rings constituting bus-connections for the selective connecting means, movable switch arms having conductive contactors for selectively connecting said electrical contacts and said rings, and cam mechanism for actuating said switch arms, each pair of said contacts cooperating with one of said switch arms and constituting terminal connections one for 10 each to two of said coils.

WILLIAM A. SCHAPER. GEORGE B. MCCLELLAN.

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