US2052238A - Radio tuning and indicating apparatus - Google Patents

Description

1936. E. F. MCDONALD. JR 2,052,233

RADIO TUNING AND INDICATING APPARATUS Filed Sept. 1, 1934 2 Sheets-Sheet l .ZZzv/entofl V 'BI QMFMJDOW Aug. 25, 1936.

E. F. M DONALD JR 2,052,238 RADIO TUNING AND INDICATING APPARATUS Filed Sept. 1, 1934 2 Sheets-Sheet 2 W I" .3 W V fiuxwzion' @QRQMDOYZQMfi Patented Aug. 25, 1936 UNITED STATES PATENT OFFICE RADIO TUNING AND INDICATING APPARATUS Eugene F. McDonald, Jr., Chicago, 111., assignor to Zenith Radio Corporation, Chicago, IlL, a

corporation of Illino Application September 1, 1934, Serial No. 742,470

3 Claims.

marks upon the tuning scale to determine such positioning. Fine calibrations of tuning scales are difficult to read,and whilethis has long been recognized as obtaining in the accurate adjustment of the radio tuning elements of the more selective types of broadcast-band receivers, and has always been an objectionable feature in the tuning of short-wave receivers, the advent of the so-called all-wave receiver has accentuated the need of tuning and indicating apparatus through which the careful positioning of the tuningelements may be both quickly and accurately effected and definitely and accurately determined.

In such all-wave receivers, in which the tuning range extends over and between the short-wave and the broadcast bands, and in which a single set of adjustable tuning elements is used to cover this greatly extended range, the exact positioning of the tuning elements is absolutely necessary throughout the shorter wave-bands, and the tuning and indicating apparatus should be such as will permit the operator to both obtain and ob serve extremely accurate and delicate adjustments and also enable him to obtain such adjustments as quickly as he has been accustomed to do when tuning for broadcast band reception.

It is impracticable to employ a continuous graduated tuning scale which will embrace the full tuning range of an all-wave receiver, and it is the common practice to break up the scale into sections, such as I have illustrated upon the dial shown in Figure l, leaving that portion covering the broadcast band substantially as it has beenthat is to say, with ten-kilocycle calibrations, but, in using the arrangements so far provided in allwave receivers the result has been to add to the confusion of the operator in definitely determining the proper positions ofthe tuning elements for short-wave reception, and I have added a graduated circular scale, spread circumferentially upon the dial so that the graduations thereof may be easily and conveniently observed, and a corresponding pointer'to indicate in connection therewith fractional adjustments of the tuning elements between the graduation marks of each and all of the several tuning scales.

The principal radio apparatus.

Another object of my invention is to provide 10 an arrangement through which such accurate and delicate adjustment may be obtained simply and quickly, so that, while the apparatus is parproviding for 15 tuning elements throughout the possible confusion of the operator will be minimized; and so that he will not find it necessary to depend upon hearing the desired signal to determine if he has properly adjusted the tuning elements to receive it.

These and other objects and advantages of my invention will appear in the following description.

In the drawings- Figure l is a front elevational view, showing the operating knob and the indicating devices forming a part of my invention;

Fig. 2 is a vertical sectional view, taken upon the line 2-2 of Fig. 1, showing the complete operating mechanism embodying my invention; 40 and Fig. 3 is an enlarged fragmentary sectional view, illustrating in detail the construction and arrangement of some of the parts shown in Fig. 2.

Referring to Fig. 2, I have shown a conven- 45 tional form of variable condenser having statorplates i and rotor-plates 2, the latter being fixed upon the rotatable condenser-shaft 3, and the entire condenser structure being secured in any desirable manner upon the fixed support 4. Condenser-shaft 3 is centrally bored at its forward end-part, and into this boring 5 is tightly pressed the rearward end-Dart of the arbor-shaft 6, the arbor-shaft thus forming a forward extension of said condenser-shaft, and this method of attach- 55 ment being one which affords accurate alinement and secure attachment of my device with shafts of various types of variable condensers.

Shaft 1 is rotatably supported in bearings 8 and 9 and p'ojects forwardly through the instrument panel l0, adjusting knob ll being removably fixed upon the outwardly presented end-part. A friction-drive-wheel I2 is fixed upon shaft 1 and is formed by two rim-flared disks l3 and i4 tightly pressed together (Fig. 3) upon a hub l5. These disk's I3 and i4 bear upon the opposite circumferential edges of a relatively larger drive-disc l6 of celluloid, pyralin, or other suitable material, the central mounting-plate ll of which drive-disc is removably fixed upon condenser-shaft 3 by means of set-screw I8. The above described mechanism constitutes a frictiondrive vernier adjusting means, by which the operator may quickly and accurately adjust the rotor-plates 2 of the variable condenser. This particular construction of the vernier adjusting means does not form a part of this invention, however, and any other construction of this part of my device may be used, if desired, and the r turning ratio of the shaft 1 with respect to the condenser-shaft 3 may be changed without departing from the spirit and scope of my invention.

A double-ended pointer I9 is fixed upon the forward end-part of a sleeve 20 which extends rearwardly through a central aperture in the indicator-dial 2| and is snugly fitted in frictional engagement over the major part of arbor-shaft 6, the frictional engagement being such as to insure the turning of the pointer 19 by the condensershaft 3 and yet permit it to be adjustably positioned in the testing of the assembled apparatus to accurately indicate upon the dial 2| the various tuning positions of the rotor-plates 2. The double-ended pointer l9 co-operates with a plurality of tuning scales, A, B, C, D and E (Fig. 1),

some of which are calibrated to indicate megacycles for short-wave tuning, and one of which E, is calibrated to indicate kilocycles for broadcast-band tuning. I have not shown the usual tuning coils and the circuit connections therefor, since neither their construction nor arrangement is involved herein, and I do not wish my invention to be considered as limited in any respect to the use of the scale arrangement I have shown for illustrative purposes upon the indicator-dial 2|. Different scales and different arrangements of scales may be employed as occasion may require or as may e preferred.

A second pointer 22 is fixed upon the forward end-part of a sleeve 23 which is fitted to turn freely upon sleeve 20 and extends rearwardly therewith through the'central aperture in the indicator-dial 2i and through bearing- plates 24 and 25. Sleeve 23 carries a pinion-gear 26 fixed tightly thereupon between bearing- plates 24 and 25 and in mesh with a gear-wheel 21. Gearwheel 21 is fixed upon a counter-shaft 28 which is supported in bearing- plates 24 and 25 and carries a pinion-gear 29 tightly fixed thereupon at or near its rearward end-part. Pinion-gear 29 meshes with a gear-wheel 30 tightly fixed upon arbor-.shaft 6. A cover 3| of glass or other transparent material is positioned over the indicator-dial 2| and pointers l9 and 22 to permit observance thereof and to prevent tampering with their proper adjustment.

The ratio of movement of the various parts is.

such that a single turn of the adjusting knob H will effect a partial rotation or Vernier adjustment of the condenser-shaft 3 and pointer l9, and at the same time effect'more than one revolution of pointer 22. It will be observed that pointer 22 traverses a graduated scale 32, the calibration of which is easy to read, and that the relative positions of the two pointers l9 and 22 are as convenient for observation as the hour and minute hands of a timepiece.

The operation of the device is simple. It consists in the turning of the adjusting knob ll until the double-ended pointer 19 indicates upon the proper scale the approximate tuning position desired, this adjustment being obtainable quickly, the more accurate and delicate adjustment of the tuning devices being had by observing the position of the pointer 22 with relation to the scale 32.

I claim- 1. In apparatus of the character described, the combination of a dial having a plurality of concentrically arranged sets of arcuate scales and a circular scale displayed thereupon, a plurality of pointers arranged to turn upon a common axis, one of said pointers being double-ended with its diametrically opposite end-parts registering with different scales of said sets of arcuate scales and a second of said pointers registering with said circular scale, driving means, speed-reducing transmission means connecting said driving means with said one of said pointers, and speedincreasing transmission means connecting said one of said pointers with said second of said pointers.

2. In apparatus of the character described, the combination of a dial having a plurality of differently graduated semi-circular scales and an evenly graduated circular scale displayed thereupon, said plurality of scales being concentrically arranged and representing different tuning wavebands andsaid circular scale surrounding said plurality of scales and representing fractional adjustments only, a plurality of pointers of different length arranged to turn upon a common axis, one of said pointers registering with said plurality of scales and a second and longer one of said pointers registering with said circular scale, and driving means connected with said pointers to effect their simultaneous operation at relatively different speeds.

3. The combination, of an adjustable radio tuning element, a driving shaft, and transmission means connecting said shafts whereby one revolution of said driving shaft will effect a partial revolution of said rotatable shaft, of a dial having a plurality of differently graduated semi-circular scales and an evenly graduated circular scale displayed thereupon, said plurality of scales being concentrically arranged and representing difierent tuning wavebands and said circular scale surrounding said plurality of scales and representing fractional adjustments only, a plurality of pointers of different length arranged to turn upona common axis, one of said pointers registering with said plurality of scales and a second and longer one of said pointers registering with said circular scale, and transmission means connecting said pointers with each other and with said rotatable shaft whereby the operation of said driving shaft will effect the simultaneous movement of said pointers at relatively different speeds.

EUGENE F. MCDONALD, JR.

with the rotatable shaft

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