Electrical sound translating device



June/29, 1914 1.. B. CORNWELL I ELECTRICAL SOUND TRANSLATING DEVICE 2 Sheets-Sheet 1 Filed Jan. 50, 1946 T v R w t K P Q m w m N W N T a l R A J A m C L n k, w c in L a M a L i \Q r @N EN 2 Q NP WI Q h f 7 June 29, 1948. B. CORNWELL ELECTRICAL SOUND TRANSLATING DEVICE 2 Sheets-Sheet 2 Filed Jan. so, 1946 If z 4 ATTORNEYS. Patented June 29, 1948 ES PAT ENT QFFICE 2,444,336 EBECTRIGAL soU ND TRANSLATING DEVICE Lio'iiei B. Cornwall, New Canaan, Conn. Application January 30, 1946, Serial No. 644,283 i 2 Claims. Thisi-nvention relates to electrical sound trans-- =1 atin'g devices of these-cabled magnetic type. The invention is useful in translating mechanical motion into electricali-mpuises as wen es in transflating electriczpiimpulses into mechanical motion. A-s exemplified inthe present embodiment the invention takes theiorm of a phonograph :pickup {for use with lateral out sound records; and the foilowing disclosure of such-embodiment will be sufficient to permit those skilled in. the art to understand the invention and the vanious uses to which it may be put. :It is to be understood that its broader aspects the invention maybe usefully embodied in microphones or other devices to react to any inotion of steamy-nature or to Another 0 adevicewhich'maybefproduced "at relatively low cost and yet be capable of translating sound in thefdesiredimanner. n I The invention consists of the "novel features, aireng neiits, construction and combination of iia'iatu's 'to be hereinafter more 'fiilly Ziescritud as 'inustratin-g "a present-prefer ed form of the invention, and "the invention will be more particu nnynointed out in the appendedclaims. rt'heran' "morespecificobjects-features and advantages of "the invention will more clearly "appj'al'r from "the "detailed description to be given "foil taken in connection with the accomnalnying'drztwings in whichz Fig. "1 is "an enlarged scale front 'eleva'tional view of a foicku'p device, in which the coil windings are shown "somewhat diagrammatically; Fig. 12. is fa. long'itiidifial sections view "taken a the lin'e 2 -'2 of Fi'gRI; g. '3 is a n'aftial'nttom view-"of Fig. '1 showing fiirti'feiiiafticular's as to the "mountin the dfmdtii're and showing the lateral "spacing between the armature arid cooperating pole pieces 'iiag gerated -for the ipurposes iof clarity; s rewn a soirfewhat :uregmmmanc viewshowcorded on a lateral cut record and which will invention is toprovide a 2 ing the relationship of certain parts somewhat more clearly; Fig. 5 is a. side elevat'ionol fragmentary View, partly in section and on on enlarged scale, showing a modification of my invention. relative to the arrangement of pole ends and armature mount- Fig 6 a bottom View of certain parts shown in FigIS; and 7 is it somewhat diagrammatic front elevational view, partly in section, showing the relationship of certain parts of the modification shown in Figs. 5 and 6 out further enlarged lfor greater clarity. Referring to the drawing and more particularly to Fig. l, the device comprises a main. body member i formed of aluminumor other non-m'agnetic material, such as plastic, and a supporting plate 2 secured to the block I as byscrews 3 (see also Fig. '3) The plate 2 provides a convenient means for attaching the device to a supporting arm. the forward end of which is designated as 4 to the bottom. flange of which the plate is attache-ci as by screws such as 5. The magnetic field provided by a suit-able magnet '5 which is polarized, asshmvn by the letters N 'a'n'd'S, which in turn serves to .pol'a-rize a pair of "laminated transformer "iron pole pieces 1 and B (see also Figs. 2 and 3) of the same or north polarity, and the magnet 6 also pcictrices a pole piece! of 0pposite or south polarity. The pole piece 9 i in the 'form of a strap secured to the'ba-c'k of the block i by screws such as T0 and to the underside of block "i by heing'clamped between the block and plate 2. The upperend ofithe pole piece strep '9 extends upwardly heyon'd'the block I and together therewith forms a. recess in which the 5magn8t :5 is seated. magnet'fii'srclemped between the strapt anda softiron plate M Tby means of screws such as 12, which=pass'throughthe plate -i Loisposed on opposite sides "of the :magnet 26 and are in "threaded engagement with vthe strap .9. The screws L2 also :pagss through a, .plate L3 between which and the plate II the upper ends of the 3301811316065 1 ends areifirrrilynlamped. .The'pole pieces 1 ends extend downwardlyand forwardly through suitable slots provided in "the block I and are rigidlyclampeii to-said block by means of set screws such as 'l'li. The lower eniis of tine pole pieces i and 8 extend inwardly toward each other in e lateral direction zcle'a'rly shown in Figssl and 3' totprovide pole endswhichare designated Ni and N2. i'I-he "pol-e piece plate 9 is bifurcated at itSslOWGl forwardly extending end itseecalso-Figsn 2nnd 3) :so QSL-tO-PIOVide polesends designated SI and S2 which are disposed beneath the respective pole ends of opposite polarity N! and N2 and the fixed spacing vertically between the pole ends of opposite polarity is provided by suitable means which takes the form of spacer blocks such as l5 (Fig. l). The arrangement of these pole ends is more clearly shown in Fig. 4, from which it will be seen that the disposition of these pole ends in the magnetic circuit above described provides laterally spaced air gaps across which flux flows in the same direction between the pole ends NI-N2 and SIS2. An armature A is substantially horizontally disposed intermediate the said pole pieces in both a vertical and lateral direction, and the armature carries rigidly secured thereto a stylus S which extends downwardly in a substantially vertical direction and is provided with a suitable point for engagement with a sound record. Ihe armature A (Fig. 3) is provided with a rearwardly extending tongue or arm l6 and a forwardly or oppositely extending corresponding tongue or arm I 7. The said arms Iii-l1 are rigid with the armature A and are preferably formed from the same piece of material and are rectangular in cross section. The center line of the arms l6--|'l passes through the center of the armature A and is centrally disposed in a lateral direction between the pole ends NISI and N2S2 and defines a torsion axis about which the armature may move angularly, in the manner to be more fully pointed out. The arms l6 and I! are disposed in cooperating openings provided in respective supporting blocks l8 and I 9 which are made of rubher or the like material providing the necessary or desirable compliance. In the present embodiinent I have obtained entirely satisfactory results in using rubber having a compliance of -40 durometer. One of the advantages of the invention resides in the ability to readily obtain the desirable operation of the device by varying the compliance of the supporting blocks, and in the fact that such blocks also provide a damping agent to dissipate any excess vibratory energy that otherwise might produce a non-linear response characteristic over the desired audio range. This means of support provides the desired torsional resiliency permitting angular movement of the armature in response to lateral movements of the stylus point by the lateral undulations of a record, and additionally provides sufficient re siliency in a vertical direction to accommodate such ancillary unevenness of the sound track in a vertical direction as is usually present on a lat eral cut record. The block I8 is firmly held in position by bracket which is secured to the block 5 by a screw 2 I; and the block I9 is similarly supported by a bracket 22 which is rigidly secured to the block I by the screws 23-24. The brackets 20 and 22 together with the block I provide recesses entirely enclosing the blocks on five sides so as to firmly secure the blocks in the desired position, and this means of support also makes it possible for limited adjustment of the initial compression of the blocks to thereby provide a certain degree of variation in the compliance relative to the torsional movement of the armature. The pole pieces 1 and 8 (Figs. 1 and 2) are provided with corresponding coils 25-26 which are preferably identical in dimension, number of turns and impedance and serve to transform magnetic fluctuations into corresponding alternating electrical potentials in the manner to be: more particularly pointed out following. The coils are wound and connected in the manner schematically shown in Fig. 1 and the coil terminals 2'! and 28 are connected to a suitable receiving circuit, in the manner well known to those skilled in the art. Assuming a lateral vi-- bratory movement to be applied to the stylus, as by the undulations on a lateral cut record, the following magnetic and electrical action takes place. The resilient supporting means is so constructed and arranged that with the stylus S resting on the record as in operating position the armature A is disposed centrally in a vertical direction between the pole pieces of opposite polarity and the supporting blocks allow the armature to rotate about the said torsion axis and provide a restoring force that returns the armature to its horizontal neutral position, as more clearly shown in Fig. 4, as soon as the lateral displacing force such as L is removed from the stylus S. Thus the armature may be displaced in relatively opposite angular directions due to relatively opposite lateral force on the stylus and restore to neutral position when such lateral dis placement ceases. Such an arrangement permits very close control of the mechanical impedance of the stylus S to the lateral force encountered on a lateral cut record by controlling or predetermining the compliance of the supporting blocks l8 and IS. The magnetic pull of the poles NIS| and N2-S2 tends to hold the armature in the horizontal neutral position and therefore the only remaining forces tending to move the stylus to one side or the other are the actuating forces such as are provided b the laterally cut undulating groove of the record. The device is so balanced in use that the stylus rides in the groove under a pressure of the order of 10-25 grams weight and hence these actuating forces are relatively ver small allowing the use of supporting blocks having extreme compliance assuring perfect tracking at all frequencies and amplitude encountered in the standard lateral cut phonograph record. Assuming a lateral force L 4) moving the stylus to the ri ht, the right hand edge of the armature A closer to the pole end N2 and away from t"e pole end wlb' the left hand edge of the attire moves nearer to the pole end Si and a from the pole end Ni, thereby reducing the flux flowing fi m N! and increasing the flux flowing from N2 3. consequently inducing an electr potential in the coils l and The coils are so connected. that these electrical impulses are additive as a result of angular motion of the armature but are out of phase one with respect to the c l to any flux induced from vertical motion of the a 'ure, hence all scratch noise from vertical forces :ejected thus reducing the scratch amplitude that would otherwise result. Furthermore, with the coils thus connected they are 139 out of phase to all external magnetic induction, thereby providing an effective shielding against all. A. C. hum, etc. It will be understood that with the force L applied on the opposite side or the stylus S similar electrical potentials are produced in the coils With similar results, 'but in this instance the flow of flux from N i is increased while simultaneously being decreased from N2. It is noted that the armature is of less lateral extent than .the lateral space between the ends Nl-N2, and accordingly if the device should be carelessly handled so as to exert an abnormal force upwardly on the stylus S the armature will not strike the pole pieces. It is further noted that the armature cannot freeze to any of its adjacent magnetized poles and has unrestricted motion within the maximum limits of all lateral out records. It will be understood from the foregoing description that in the neutral position shown in Fig. 4 there is substantially no flux flow through the armature and that neutral stabilizing force is exerted upon the armature; if the armature should move in a clockwise angular direction about its torsional axis the flux will flow from N l laterally through the armature A into the opposite pole end Si; and as the armature moves in the opposite angular direction the flux flow will pass from N: laterally through the armature A into the opposite pole end 82. lhe parts are preferably so constructed and arranged that within the of operation the armature in its angular movements does not overlap any of the pole ends and its normal vertical movement due to said ancillary undulations in the record does not exceed the vertical spacing of the armature from the pole ends. In practice, I have found it satisfactory to use an armature having a lateral width w of approximately a" and a thickness t of .014"; and to space the armature laterally from the pole pieces .0085" on each side as indicated at .r and vertically from the pole pieces a distance of the order of .001", respectively, from the pole pieces of opposite polarity when the armature is in neutral position, as indicated at y. Modification In Figs. 5, 6 and 'l I have illustrated a modification as to certain details. For instance, instead of bifurcating the pole end of the pole piece i! so as to provide a pair of poles Sl-S2 disposed as in the embodiment previously described, a single pole is utilized; and instead of utilizing the rubber block supports the anmature may be suspended on a torsion spring. In this modification the structure is identical with that previously described except in the particulars otherwise shown in Figs. 5, 6 and '7 and only such details as differ from those previously described will be described in detail. The lower end of the pole piece strap, designated 9 is provided with a stamped out recessed portion forming a pole piece common to and of opposite polarity to the poles N!N2 and is designated So. The portion So has a central area disposed beneath the armature and is provided with a hole through which the stylus S extends and provides sufficient clearance for lateral motion of the stylus. A torsion spring 39 is rigidly secured to the upper face of the armature A intermediate the ends of the spring which extend outwardly beyond the armature and are rigidly supported as by screws 3 |-32 passing through the plate 9 and vin threaded engagement with suitable portions provided on the block I. This spring is centrally disposed with respect to the armature in a lateral direction and its longitudinal axis otherwise corresponds to the torsion axis previously described. The lateral and vertical spacings of the armature with respect to the pole pieces NI-NZ and So 623 are substantially as previously described with ref erence to the preferred embodiment. Having thus described my invention with partioularity with reference to a preferred embodiment thereof, and having referred to certain modifications, it will be obvious to those skilled in the art, after understanding my invention, that other chances and modifications may be made therein without departing from the spirit and scope of the invention, and I aim in the appended claims to cover such changes and modi fications as are within the scope of the invention. What I claim is: 1. In a pickup device of the magnetic type, the combination of a magnetic circuit having two flux paths providing a pair of laterally spaced upwardly and downwardly extending air gaps across which flux flows in the same direction to supply a pair of fields for an armature, electrical coils surrounding respective of said paths on the same polarity side only of said gaps, an armature centrally disposed relative to said fields, torsion resilient means supporting said armature for rocking motion within the fields of influence of both of said paths and also providing compliance to ancil1ary vertical movement of said armature, and an electrical circuit including said coils for generating electrical impulses in accordance with flux modulation responsive to said armature motion in a lateral direction while rejecting electrical impulses due to motion of said armature in a vertical direction. 2. In a magnetic pickup device, the combination of a magnetic circuit providing a flux field including a pair of laterally spaced and upwardly and downwardly extending air gaps, an armature disposed in the field of influence of said flux field and extending in a direction transverse the flux fiow across said gaps, said armature in neutral position being substantially horizontal, a stylus rigidly secured to said armature and extending substantially vertically downwardly therefrom, and resilient supporting means for said armature including a torsion spring secured intermediate its ends to said armature and having oppositely disposed ends extending in a direction forwardly and rearwardly beyond said armature secured to relatively rigid portions of said device, to thereby yieldingly torsionally support said armature in said neutral position for movement about a torsion axis disposed intermediate said air gaps and extending in a forwardly and rearwardly direction. LIONEL B. CORNWELL. REFERENCES CITED The following references are of record in the file of this patent: UNITED STATES PATENTS Number Name Date 1,804,961 Thomas May 12, 1934 1,916,703 White et al. s July 4, 1933 2,108,275 Vermeulen Feb. 15, 1938 FOREIGN PATENTS Number Country Date 355,227 Great Britain Aug. 17, 1931



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Cited By (4)

    Publication numberPublication dateAssigneeTitle
    US-2508783-AMay 23, 1950Lionel B Cornwell, John F NielsenElectrical sound translating device
    US-2554696-AMay 29, 1951Henry H BruderlinMagnetic phonograph pickup head with two pairs of pole pieces
    US-3031536-AApril 24, 1962Pickering & Co IncMultiple coil electromagnetic sound reproducer
    US-3683128-AAugust 08, 1972Joseph F GradoFlux-bridging stereophonic pickup