US2483105A - Combined inductance and capacity tuner - Google Patents

Description

Sept. 27, 1949. J. RENNICK 2,483,105

COMBINED INDUCTANCE AND CAPACITY TUNER Filed Oct. 3, 1945 HIS ATTORNEYS Patented Sept. 27, 1949 COMBINED INDUCTANUE AND CAPACITY TUNER John L. Renniok, Elmwood Park,

Zenith Radio Corporation,

Illinois 111., asslgnor a corporation of Application October 3, 1945, Serial No. 020,088

The present invention relates to tuners for radio apparatus particularly of the type which are arranged to receive or transmit energy in different frequency bands.

It is desirable in commercial radio apparatus arranged to transmit or receive energy in a plu- 4 rality of allocated bands in the frequency spectrum useful for radio apparatus to be able to tune such apparatus easily, with the least number of inexpensive parts arranged compactly.

It is an object of the present invention to provide improved apparatus for obtaining the above mentioned desiderata and yet position the tuning elements where they cause the least electrical interference, coupling, etc., to the other elements in the composite apparatus.

Another object of the present invention is to provide improved apparatus wherein an inductance or condensermay be varied or adjusted by actuation of a common control element.

A further object of the present invention is to provide an improved construction for tuners useful in radio apparatus tunable to different frequency bands.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The present invention itself, both as to itsorganization and manner of operation, together with further ob- Jects and advantages thereof, may best be understood by reference to the followingdescription taken in connection with the accompanying drawing in which:

Figure 1 is a perspective view, partly in section, of apparatus incorporating the present invention, and

Figs. 2 and 3 are views, partly in section, showing some of the details of the apparatus of Fig. 1.

The tuning arrangement described isespecially applicable in radio receivers arranged to receive amplitude modulated signals in the standard broadcast band ranging from 550 to 1600 kilocycles and also to receive frequency modulated signals in the broadcast band assigned thereto. The arrangement is such that a condenser I of the rotary type is varied for receiving amplitude modulated signals and an inductance 2 of the variable core type is varied for receiving frequency modulated signals, the condenser and inductance each being varied by actuation of a single common control shaft 3.

The condenser I is shown of the rotary interleaved type of which the one set of spaced leaves rotatably mounted are each arranged to be sandwiched in varying degrees between adjacent 2 leaves one second relatively stationary set oi spaced leaves as the control shaft 3 is rotated between its extreme limits of movement.

The condenser I is mounted resiliently on the chassis 4, rubber or other similar elastic material I being interposed between the chassis 4 and condenser supports 8 each of which has one end thereof fixed to the stationary frame portions of condenser I and the other end thereof resiliently mounted in the doughnut-shaped resilient material 5.

Control shaft 3 fixed to the rotatably mounted plates of condenser I has permanently mounted thereon by means of set screw 1 cam member I having a hub 9 fixed to shaft 3. The angular position of cam 8 is related to the magnitude of inductance unit 2 as will appear from the following description;

Inductance unit 2, comprising stationary coil III wound on coil form II and movable core member I2, is mounted on the stationary portion of condenser I by means of bracket I3, one end of bracket I3 being fixed to the stationary portion of condenser 'I by means of a suitable fastener I4 and the other end of the bracket being fixed to coil form II. Core member I! is fastened to a flexible actuating member I 5 which has a threadlike outer surface arranged to be held in adjusted position in a cooperating threaded insulating member I8 forming a part of a carriage II. The flexible actuating member I5 is made preferably as set forth and claimedin the Patent Number 2,423,275, July 1, 1947, to Clarence W. Wandrey,

and assigned to the same assignee as the present application.

Obviously the actuating member I 5 must not be flexible in the direction of its length because the tuning core members I2 must be moved in unison with each other accurately to maintain accurate tuning. That is, the members It must be inextensible and incompressible within the range of forces which they encounter in the tuner. The term "inextensible is used to mean that members I 5 must not increase or decrease their length within the range of forces which they encounter in the tuner, yet, at the same time, they must be flexible laterally to allow sideward bending. This lateral flexibility of members I5 makes it possible for'the tuning cores I2 to slide in accurately defined passages through the coil forms II when moved by the carriage I1 even though the portion I6 of carriage I'l moves through the arc of a circle. By this arrangement, linkages with their inevitably associated play and backlash or complicated arrangements for essence 3 eliminating play and backlash are entirely avoided.

The carriage it, the angular position of which determines the position of core members 12 and hence the magnitude of the inductance unit 2, is pivotally mounted on the stationary frame portion of the condenser unit I. These pivots i8 and i9 consist of antifriction balls and 21, respectively, being set into their respective seats. These seats for the balls 20 and 2| are formed by drilling or punching undersized holes, on'the same longitudinal axis, through a carriage flange 22, a pair of stationary frame portions 22, 24 of condenser unit I and a flexible extension of carriage 11. Ball 20 is held in its seats between members 22 and 23, and ball 2| is held in its seats between members 24 and 25 due to the resilient nature of the spring 25 thus providing the pair of antifriction pivot points l8, IS on the stationary portions 23, 24 of condenser 1 upon which the carriage I1 is pivoted.

A tension spring 26, having one of its ends fastened to the carriage H at a point 21 and its other end fastened to an extension 28 of the stationary frame portion of the condenser I,

biases the carriage ll counterclockwise about the pivot points l8, l9 and holds a flat surface 29, forming a part of carriage II, in positive engagement with cam member 8. Not only the inherent friction between the rotating parts of the condenser and the frame of the condenser, but also the friction between the cam edge and the surface 29 is suilicient to keep the cm from moving until the cam is rotated by the control shaft 2.

In Figure -3, upon counterclockwise rotation of the cam 8, the flat surface 29 rides smoothly without binding on the cam because the surface of the cam approaching the flat surface 29 is of ever decreasing radius.

Upon counterclockwise rotation of the control shaft 3, the cam 2 is rotated counterclockwise and by reason of the biasing spring 20 biasing the flat surface 29 against the cam 8 and also because the pivotal position of the carriage i1 is determined by the radius of that portion of the cam against which it bears, the carriage is pivoted more and more counterclockwise as that portion of the cam against which it bears reduces its radius. As the carriage i1 is pivoting counterclockwise on pivots l8, l9 by its interaction with the ever decreasing radius portion of the cm 8, its portion I0 is rising in an arc. As flexible actuating member I! is a non-extensible connection between portion I2 and the movable core member 12, the rising motion of portion 19 is transmitted without backlash to the core member, to raise the core member and change the tuning of the inductance 2.

Conversely, clockwise rotation of the cam I results in pivoting the carriage clockwise, to lower the core member and change the tuning of the inductance 2.

Control shaft 3 is arranged to be rotated by rotating manual control knob 30, shaft 2| of knob 30 being connected to shaft 2 through belt 22 and pulley 23. The shaft 2| may be connected to station indicating apparatus for indicating the tuned condition of condenser l and inductance 2. One of the features of the present invention is that the tuning inductance unit 2 may be mounted underneath the chassis l in close proximity to the terminals of tube sockets of conventional construction and yet be resiliently mounted with respect to the chassis l by providing a clearance opening be between the chassis d and coil form Another feature is that the chassis 4, since it has condenser unit l mouhted on the one side thereof and the inductance unit 2 mounted on the other side thereof, serves as an electrostatic shield for shielding such units one from the other.

This combination condenser and inductance tuning unit has particular advantages in that only a single tuning knob is effective for tuning any desired signal in the broadcast band. This tuning is accomplished by adjustment of the condenser connected in conventional manner through conventional band switch with the oscillator and radio frequency circuits in a superheterodyne receiver. Alternatively, in a second position of such conventional band switch the unit is tuned with the same knob to any desired signal in the frequency modulation band by adjustment of the inductance coils connected in conventional manner through terminals 21, 28 and such switch with the oscillator and radio frequency circuits in the receiver.

While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects, and, therefore, the aim in the appended claim is to cover all such changes and, modifications as fall within the true spirit and scope of this invention.

I claim:

A tuning device including a frame member, a shaft member rotatably mounted on said frame member, a cam member fixedly mounted on said shaft member, a carriage member pivotally mounted on said frame along an axis of said carriage and having portions extending on either side of said axis, a further member formed on one of said portions and adapted to coast with the edge of said cam, an inductance coil having a longitudinally movable core member mounted therein, a longitudinally inextensible and laterally flexible connecting element coupling said core to the other of said portions, spring means for biasing said carriage about said axis in a direction to urge said further member against the edge of said cam and to cause said last mentioned portion to describe an are moving said core longitudinally in said inductance to a certain position by means of said connecting element, whereby rotation of said shaft causes said last mentioned portion to describe further said are and said core to move in substantially a straight line within said inductance.

JOHN L. RENNICK.

REFERENCES CITED The following references are of record in the file of this patent:

Number Name Date 1,659,417 Washington Feb. 14, 1928 2,206,820 Mydlll July 2, 1940 2,217,984 Kirk Oct. 15, 1940 2,270,117 Fill Jan. 13, 1942 2,320,483 Stocker June 1, 1943 FOREIGN PATENTS Number Country Date 112,516 Australia Feb. 7, 1941

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