US2445990A

US2445990A - Signal translating apparatus

Info

Publication number: US2445990A
Application number: US533333A
Authority: US
Inventors: Badmaieff Alexis
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1943-06-12
Filing date: 1944-04-29
Publication date: 1948-07-27
Anticipated expiration: 1965-07-27
Also published as: GB594077A

Description

July 27, 1948. A. BADMAIEFF 9 SIGNAL TRANSLATING APPARATUS Original Filed June 12 1943 I5 I7 I5 r mu n wp N fw. Mw u NV )4. w 4 D 46 7 5 I8 1 M 4Q 5 .52

4 q H3BL 1-- y ffmzzfp H B" uw #Tram/fr Patented July 27, 1.948

SIGNAL TRANSLATING APPARATUS Alexis Bad'niaieff, Indianapolis, Ind., as'sigor toYA Radio Corporation of America; a corporationl of Delaware Original application June 12', 1,943',v Serial No. 490,614. Divided and this application April 29', 1944,` Serial N0. 533,333

6 Claims.

My present invention relates generally to systems utilizing angle modulated oscillatons, and more particularly to' an improved electrical signal.K translating device' of the capacity type especially useful in connectionwith a system for providing frequency modulated oscillations in conjunction with abalanced transducer input, thenpresent applicationbeing a division of my copending application Serial No. 490,612 led June 1.2, 1943,11ow Patent No. 2,371,373, granted March-.131 1945;

In the past,. there has been shown considerableint'ferestinl frequency modulated oscillatory systems oi the type' wherein -anoscillator and discriminator are usually a short distance apart, orevenicornbinedin one unit'. Such systems have been applied` .tov sound` reproducing devices and to-measuringdevices.` Insuch prior systems, an oscillator is provided with `a frequency' changing transducer,V and the transducer is varied in response tera vibratory member `therelcyto fre'- quencyfmodulate the oscillator mean frequency. The frequency modulated' energy is thenv ied to a discriminatorcircuit whichfis tuned to a slightly different frequencyso that theA oscillator mean frequency falls ononc side ofthe discriminators resonance curve. The discriminator converts the frequency-varable' wave energyv intol amplitude- Variable wave energy. Subsequent rectication derives-the original modulatingV frequencies from the amplitude-variable Wave energy.

Ihave invented a method' of' greatly increasing they voltage output of such a` system. The method is simple and employs a minimum `of elements.V Themethodf essentially comprises the concurrent frequency variation, from one modulatlngsource, of the oscillator frequency and the diseriminatorfresonance peak in opposite' directions.

From a genericviewpoint, it may be stated that lt'fis one ofthe principal objects ofA my inventionto provide la method wherein aproperly constructedbalanced transducer isA employed to varythe'oscillator andfdscriminator circuit tuning=lin opposite directions,` or in `mopositephase relation;simultaneously. i

It\ isfan important object off my present inyentio'n'I to provide" a frequency modulated (FM for' brevity hereinafter) oscillator feeding'einto *aidiscriminator whose 'resonance i peak is subjectedtoconcurrent FM action, the two ire'- quency modul-ations'` being 180 degrees out oi pha's'ecwherebyfthe discriminatorV voltageA output will be' twiceV as? great asf would be ith-e* case if only one cffsaidfFlvfactions'y nadb'een employed:

The two forms of FM may be provided simplyv ng a symmetrical modulatingz devicethereby providing cancellationv ofy even harmonics,` greatly reducing! distortion; and'V doubling lthe output voltage froml the discriminator. i

The presentinventioni has particular utility in` an FM ksystem for reproducing :recorded sound waves. One such FM system-f has-been disclosed', for examplefbyChester M; Sinnett in application `Serial No; L159g3'75,v iiled September 23,` 1942-and assigned to'` Radio Corporation of America. The particular Sinnett `system isla single ended! frequency modulation network em'- ployinga' capacity pickup device of the ribbon type for the reproduction of sound recordings: In thel Sinnett system; `the `frequency` modulaition network consists of an electron discharge tulefwhich has one? section thereoftfunctl'ohi-ng as aA high-frequency oscillator' of constant 'ame pli-tude the frequency `of `which' is" deviatedi'by variations 1in the capacity .pickul'a` In theplate circuitv ofL theKV tube,-there are developed frequency modulated oscillaticmsV which` Aare subsequently converted into audio modulated sig:- nals'4` corresponding to the originallywrecoi'ded audioI `signals `loy a frequency 'discrimination process'. 1 y

By applying the generic method ofn my invention'to the' particular Sinnett system, lor in gen,- eralI` to any system l off record( reproduction; various advantages :are secured; The advantages in my system result in reduction of the massr'oil bratory system" which is' utilized-` acrossffthe'lfoscillator "tank circuit.l Furthermore, the dualvcapacity' variations may be' so correlated' thatrthe 3 changes in the oscillator frequency and the discriminator circuit resonance occur 180 degrees out of phase, whereby a push-pull frequency deviation effect is secured. Cancellation of even harmonics, reduction of inter-modulation and higher audio vvoltage output, are immediately realized` by such a system. The higher audio voltage output can be employed to advantage because the size of the pickup condenser plates*` can be reduced;

Accordingly, it may be stated that it is another object of my present invention to provide an FM network for use with a simple; specially-designed capacity pickup device which is adapted to reproduce either lateral i' vertically cut records, a frequency modulated signal' being provided the frequency deviation of which is the cumulative effect of oscillator and discriminator frequency variation in push-pull relation whereby the various aforementioned advantages may be secured f I.

VIn a pickup, it is most important to keep the mass of `the vibratory system as low as possible. Thisraises the frequencyzof the peak and reduces the mechanical impedance, thereby permitting a reduction ofv needle pressure and the accompanying reduction of surface noise. Accordingly, it may be stated that it is another important object ofmylinventionto provide an improved capacity pickup device wherein the stylus supporting wire acts as the center plate of a push-pull condenser working into a balanced, or push-pull, FM oscillator-discriminator network whereby the mass of the pickup is reduced to a minimum, since nothing else would be mechanically coupled to the stylus except its own-support; and the supporting wire being small in cross-section so that no eXtra mas's would be added in transforming the mechanicalvibrationsto electrical signals at corresponding frequencies.

- Yet another object of lmy present invention is to provide an improved mounting for the pickup device whereby the coupling elements between the pickup `and the supporting arm therefor will serve both as electrical and mechanical couplingelements therebetween to thereby eliminate eX- traneous parts.- the mechanical coupling also having compliance to flexibly mount the .pickup on the arm. f'

Still other objects of my invention are to improve generally the simplicity and efficiency of record reproducing equipment ofthe FM type, and more especiallyA to provide a high fidelity, low cost and low distortion record reproducer system which is easily manufactured and readily assembled. 1. y

The novel features which I believe tobe characteristic of 'my invention are set forth in particularityV in the appended claims; the invention itself, ho'we'ver, as to both its organization `and method of operation, will best be understood by reference tothefollowing description, takenv in connection with the accompanying drawings, in which Figure 1 is a side elevation of one form of pickup devic'eaccording to the present invention with one of th'estationary condenser plates omitted for the sake of clearness; A f i 'Figure12 is a bottom plan view of the pickup;

" Figure 3 is a detail viewshowing particularly the stylus supporting wire which constitutes the movable condenser plate or electrode;

Figure 4 is a section along line IV-IV of Fig. 3;

'Y Figure 5shows the circuit-diagramof ajpreferred reproducing circuit according to the. pres.-

i ent invention and employing my improved pickup device;

Figure 6 is a bottom plan view of a modified form of pickupv device according to the present invention and employing an improved form of mounting;` and Y j Figure 7 is a centralsectional view of the latter form of pickup device shown connected to a mounting therefor.

Referring more particularly to the drawings, wherein similar reference characters designate corresponding parts throughout, there is shown, in

Figs. l to 4, a pickup supporting arm to which is connected a capacity pickup device 3 by means of one or more spring plates 5. The pickup 3 come prises a yblock i of Bakelite or other suitable dielectric material to the front end of which is secured a brass block 9 by means of a screw or the like II. A steel wire I3 is secured to and eX- tends from the bottom of the block 9, the wire I3 terminating at its free end in -a loop or eye I5v in which a needle or stylus Il is mounted for cooperation with a `phonograph record.` The wire I3 and its needle Il maybe of the type disclosed in the Hasbrouck Patent No. 2,326,460, the stylus supporting wire I3 being preferably rectangular in cross section, as clearly shown in Fig..4.- ,Preferably, the wire I3 is ground flat along itsvertical plane on both sides along its entire length to a thickness of about 0.008 inch.- By lWay of` illustration, it may be pointed out that the vertically extending portion of the supporting wire I3 in Fig. 3 may have a dimension of 0.09,inch, the distance between the bend in the wire and the sapphire point may be equal to 0.13 inch, and the sapphire |point may have a radius of 0.0028inch. Also, as shown in Fig. 4, the long cross-sectional dimension of the wire I3 may be 0.014 inch,.whi1e the short dimension thereof may be, 0.008 inch.,

Also mounted ony the supporting block. in spaced and electrically insulated relation to each other are a pair of rod-like or bar-like, stationary, condenser plates I9 and 2|, as best seen inFigjZ. The plates I9 and 2| are substantially parallel f to each other and are disposedone on each side of the stylus wire I3. Each of vthe xed or sta-1 tionary condenser plates I9 an-d 2| is spaced a distance preferably of about 0.003 inch to 0.005 inch from the stylus wire I3. The two Xed condenser plates |9 and 2| form the two outside plates of a balanced condenser, while the movable condenser plate or wire I3, which is connectedto ground, constituted the movable electrode-of the condenser. v I' The spring plates 5 permit movement ofthe pickup -device 3 in a vertical direction relative to the supporting arm I. The purpose of this compliance is to prevent damage to the pickup head when it is accidentally dropped on a record. The arm consists of a conventional U-shaped channel but has a supporting shieldf23 running length-- wise thereof and forming: two separate channels. therein. The two leads 25 and 21 from the pickup head 3, which, with the shield23, may be regarded as radio `frequency transmission lines,are con,- nected to the fixed Iplates lil-and 2|-, respectively, and are placed inside of the two corresponding channels in the arm and are supported .centrally therein 4by-means of small blocks of suitable damping material, preferably of the type and in a manner more particularly disclosed inthe copending application of C. M. Sinnett, Serial No. 414,305,.led October .9, 1941, nowPatent No. 2,376,456, granted May 22, 1945. This'lis done so as to permit the least. capacity andmaxie,

mum. shielding between the transmission lines. Dampingof the vibratile fstylus wire I3 may be obtained by means` of a Viscoloid damping block 29 inorderto suppresstorsional resonance of the styluswire il A pickup device such` as described above may be employedin any suitablel'M circuit,the capacity changes in the ,condensers I9, I3 and" I3, 2I which result from vibration of the wire I3 in response to a` `recordr `groove being utilized to vary the frequency of atuned oscillator circuit, and the "output of the oscillator being applied tothe resonant `input of a suitable discriminator which converts the frequency variable oscillations into amplitude Variable oscillations in known manner. One such circuit is shown, by way of illustration, in Fig; 5 and comprises a tube 3I of the 6SF'1 type or any other suitable type capable of serving as anelectron coupled oscillator, discriminator and detector. The tube 3l is'provided with a cathode 32,'an oscillatorgri'd 33, an oscillator anode `3f! whic'his the screen grid of the tube, a suppressor 35, afplate 3E and an auxiliary anode 31. The auxiliary anode 31 cooperateswith the cathode 32 to provide the necessary rectification While the suppressor 35 acts as an electrostatic shield between thevplate 36 and the other elements of the tube." i

The cathode 32 of the tube 3l is grounded and connected to a low tap von an oscillator coil 38, preferably one which has an adjustable core of comminutecliron and is therefore of the Variable inductance type. The controlgrid 33, which functions as the oscillator section grid, is connected through a D.C. blocking condenser 40 `to the high potential side of the coil 38 and to one of the fixed plates of the `pickup device 3 (for example, thejplate I9). The second ilXed plate 2! of the device 3`is connected through a D.C. blocking condenser 42 `to the output plate 3G of the tube 3`I. The plate 35 is also connected to the high potential side of a discriminator coil 44 which, like the coil 38, has a core ofcomminuted iron and is of the variable inductanoe type. However, if Athe turns in the coils 38 and 44 are properly adjusted, it is possible to have only one of them variable, preferably the oscillatorcoil 38. The coil 44 can 'have a slightly higher inductance by addition of `one o-r two turns, so that its tuning Will coincide with thetuning of the coil `3B with its iron core half way in. This affords enough range to position the oscillator mean frequency on the discriminator resonance curve in its proper relation thereto;

The movable plate or stylus wire I3 of the pickup device 3 is connected through a lead 45 to the grounded, negative terminal of a suitable directcurrent energizing source. The positive terminal of this source may be at +300 volts and is connected through a resistor 48 to the screen grid 34, thelow potential end of the coil 44 being connected tothe positive terminal of the '+300 volt source'and by passed to ground by a capacitor 46; l The screen grid 34,3which functions as an oscillator plate or anode, feeds into the `lovver nated `to a meanV or `center frequency Fc which r 6. may be in the range fof about-l5 mc. to 60 mclper second and which4 is to` bedeviated in accordance with theamplitude of` the modulation frequene cies. The deviation range ofthe mean frequency is dependent on the capacity change of the condenser I3, I9 and the-meansfrequencyemployed.` The factors governing the :mean frcquencywof` the oscillator aremore fully set forth in my abovementioned copending application and are not believed to require further discussion here.` Inany case, it will be apparent that thecondenser I3, I9 is connected across `the oscillator coil 38,\While the condenser I3, 2| is s'hunted across `thediscriminator coil 44. i The discriminator coil `should be slightly olf-tune from the oscillator mean fre@ quency, either above or below the latter, and the oscillator mean frequency should be tuned tothe middle portion of a linear part of the discriminator curve side. i i

A pickup device as described above and -con nected to an oscillator anda discriminator as shown in Fig. 5 constitutes a balanced transducer for Varying the tuning of the oscillator andthe discriminator in opposite directions or phaserelations simultaneously. In operation, variations in the capacity of the `condensers I3, IBand I3, ZI produce corresponding variations in tuning of the oscillator and the discriminato-r and will cause shifting of the oscillator frequency infra direction opposite to that of the discriminator resonance peak frequency. Since the oscillator and the discriminator are coupled electronically in the tube 3|, the frequency variations of the oscillator will be applied to the discriminator to provide FM oscillations in the plate circuit of the tube. The discriminator coil 44 `feeds its output energy through a coupling condenser 54 to the diode anode 31 of the rectifier or detector section of the tube 3|, and thus an audio signal results.

A radio frequency choke coil 56is insertedtto` prevent the RF voltage frombeing present in the output circuit, which would be of audio frequency in the case of phonograph reco-rd reproduction; As pointed out above, the resistor 52His thedetector load resistor. The audio output energy may be amplified and reproduced in any suitable way. i

In Figs. 6 and '1, I have shown `a somewhat modified Aform of pickup device and mounting therefor constructed according to the present yinvention. Here, thestationary plates of the condenser are constituted byi a pair of conductive inserts I9a and 2 la in a molded supporting block la of suitable electrical insulating material, such as `phenol-formaldehycle resin `While thewwire I3 is `secured by soldering i or `in lany `other suitable manner -to a third conductive linsert sa. in the block 1a. To the inserts I9a, 9c and 2in are spot Welded or otherwise `suitably secured spring `steel coupling members` 6i and $2, respectively, the `members 1ll,\6l and 52 being secured to their respectivev condenser electrode plates prior to the molding vof the block la, of course, and extending from the block 1a, as shown. A molded mounting member or holder 63 includes three terminal inserts 64, one for each of the springs .60, 5I and G2. The spring members 6U, 5i and 62 are placed against the block t3 in contact with theirv respective ter minal members 64, as clearly shown in FigyT, and they are heldagainst the terminals 64wby `means of a clamping plate 65 of suitable electrical insulating` material, which .may be similar to the material of the supporting block 1a, and .one or `v`more screws 6E. The terminals dfprovfide an,

external' connection of the pickup'fcondensery plates to a suitable transmission line of the type shown in Fig. 2, for example... The advantage offeredv by this form of my ,invention is that the

spring members

60, 6l and 62 serv-e both as supports forv the 4pickup device and electrical coupling members to the electrode plates thereof, while at the same time providing a compliant coupling between the pickup 3 and the support or holder 63 which may or may not be a part of the pickup armproper. With this form of plugin typemounting, it is apparent that the pickup device-may be easily and quickly removed from the holder 63 by merely loosening the screws 66 and replaced by another one which is suitable for a particular requirement.

. Although .I have shown and described two forms of my present invention, it will undoubtedly be obvious to those skilled in the art that many other modications thereof, as well as variations in those herein described, are possible. For example, instead of making the center plate or wire I3 the movable element, it may be held stationary and the needle Il mounted on an insulated cross-piece which connects the lower or outer ends of the plates I9 and 2 l, the latter then being made of resilient material and constituting the movable elements of the two condensers. Moreover, While I have shown, for the purpose of illustration only, a pickup device especially suitable for operation on a lateral cut type of record, it will undoubtedly be apparent to those skilled in the art that the pickup may be arranged for operation with hill and dale records as well.` Other changes of a similar nature are also pos' sible. I therefore desire that my invention shall not be limited except insofar as is made necessary bythe prior art and by the spirit of the appended claims.

yI'claim as my invention:

. l. A phonograph record signal translating device comprising, in combination, a support, a pair of conductive members carried by said support, said members extending downwardly from and to one side of said support in physically spaced and lelectrically insulated relation to each other,

a third conductive member carried by said sup-V port in electrically insulated relation to each of said pair of members, said third member also extending downwardly from and to one side of ,said support between and in spaced relation to each of said pair of members and having a freely suspended end terminating in a loop, and a needle mounted in said loop for cooperation with a phonograph record, said three members cooperating to provide a pair of capacitor components, and said third member being movable laterally relative to each of said pair of members in response to movement of said needle by a record to therebyvary the capacities of said components simultaneously and in opposite phase.

i 2. A phonograph record signal translating device comprising, in combination, a support, a pair of conductive members carried by said support, and said members extending downwardly from and yto one side of said support in physically spaced and electrically insulated relation to each other, a resilient element constituting a third conductive member carried by said support in electrically insulated relation to each of said pair of members, said resilient element also extending downwardly from and to one side of said support between and in spaced relation to each of said pair of members and terminating in a loop at one end, and a needle mounted in said loop for co- LAl() operation with a phonographrecord, said three `members cooperating to provide a pair of capace. itor components, and said resilient element being anchored at its opposite end whereby it is adapted to flex for movement relative to said pair of members in response to movement of said needle by the record to thereby vary the capacities of said components simultaneously in opposite phase.

3. In signal translating apparatus, the combination of an electro-mechanical transducer head including electro-conductive signal converting elements, a mounting for said transducer including` terminal members, and means coupling saidl elements mechanically and electrically to said terminal members, said coupling means Acomprising the sole connection between said transducer and said mounting.-

4. In signal translating apparatus, the com.- bination of an electro-mechanical tranducer head including electroeconductive signal converting elements, a mounting for said transducer including terminal members, and resilient means coupling said elements mechanically and electrically to said terminal members, said coupling means serving as the sole connection between said transducer head and said mounting, and the resilience of said coupling means affording a compliance therebetween.

5. In signal translating apparatus, the combination of a transducer head including a support, a pair of conductive elements carried by said support and constituting a first electrode unit, said elements extending from said support in physically spaced and electrically insulated relation to each other, a third conductive element carried by said support in electrically insulated relation to each of said pair of elements, said third element constituting a second electrode unit and extending from said support between and in spaced relation to each of said pair of elements, said three elements cooperating to provide a pair of capacitor components and one of said units being movable laterally relative to the other of said units for varying the capacities of said components simultaneously and in opposite phase, a mounting for said transducer including a plurality of terminal members, one for each of said elements, and resilientmeans coupling said elements mechanically and electrically to said terminal'members, said coupling means serving as the sole connection between said transducer head and said mounting, and the resilience of said coupling means affording a compliance therebetween. Y

6. In signal translating apparatus, the combination of a trans-ducer head including ka support, a pair of conductive elements carried by said support, said elements extending from said support in physically spaced and electrically insulated relation to each other, a third conductive element carried by said support in electrically insulated relation to each of said pair of elements, said third element extending from said support between and in spaced relation to each of said pair of elements, .said three elements cooperating to provide a pair of capacitor components and said third` element being movable laterally relative to each of said pair of elements for varying the capacities of said components REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,786,436 Leffler Dec. 30, 1930 Number 10 Number Name Date Leiiler Mar. 10, 1931 Weibusch Feb. 25, 1936 Murphy Mar. 10, 1936 Dudek Feb. 14, 1939 Hunt Apr. 29, 1941 Hausz Oct. 2, 1945 FOREIGN PATENTS Country Date Great Britain Apr. 30, 1929