US2942512A - Electronic piano - Google Patents

Description

June. 28, 1960 B. F. MlEssNER ELECTRONIC PIANO 3 Sheets-Sheet 1 Filed Aug. 14, 1957 INVENTOR mzzEMressnez Jun Filed Aug. 14, 1957 e 28, 1960 B. F. MlEssNl-:R

ELECTRONIC PIANO 3 Sheets-#Sheet 2 INVENTOR June 28, 1960 B. MIESSN ER ELECTRONIC PIANO 3 Sheets-Sheet 3 Filed Aug. 14, 1957 OOOOOOOOOOOOOOOOOODO QOOOOOOOOOOOQOOOOOOC000000 l INVENTOR .Ben I /71 z'n .Z'Messner' BY I 'fr ATTORNEY United States Patent ELECTRONIC PIANO Benjamin F. Miessner, Harding Township, Morris County,I

' NJ., assgnor, by mesne assignments, to The Wurlitzer Company, Chicago, Ill., a corporation of Ohio Filed Aug. 14, 1957, Ser. No. 678,101

Claims. (Cl. 84-1.14)

present invention is the provision of an improved such instrument.

In the use of reeds instead of strings a problem is presented by the inharmonicity of the relationship of the upper partials (i.e., all above the first, or fundamental) of the vibration to the fundamentalwhereas it is a requisite of the output tone that it contain very small development of inharmonic partials and a rich development of harmonic ones. An object of this invention is the provision of a solution to this problem.

In a tone produced by a conventional piano there is a strong initial burst, including a rich harmonic development, followed in the very early instants by an apparent rapid amplitude decay or decrement. Heretofore in electronic instruments utilizing reeds as the vibrators such early rapid decrement has been lacking-or even reversed, into a slight initial increment. An object of this invention is to minimize such increment or to increase such decrement in the reed type of instrument. An allied object is to approximate the early rapid decrement characteristic of a conventional piano.

Another object is the provision of improved arrangements of translating device, or pick-up, with reed.

Other and allied objects will more fully appear from the following description and the appended claims:

This application is a continuation-in-part of' my copending application Serial No. 485,471 filed February 1, 1955, now abandoned.

This application discloses and claims subject matter disclosed in my copending application Serial No. 485,471, filed February 1, 1955, subject matter disclosed in my copending application 255,383, filed November 8, 1951, and subject matter disclosed in my copending application Serial No. 169,714, filed June 22, 1950, now abandoned.

In the description of my invention hereinafter set forth reference is had to the accompanying drawings, of which:

Figure 1 is a vertical sectional view of an electronic piano embodying my invention in one form (line 1-1 in Figure 2 indicating the plane along which Figure 1 is taken);

Figure 2 is a horizontal view taken looking upwardly toward the plane indicated by the line 2-2 of Figure 1 (or a vertical view seen when looking rearwardly toward the cover 6 of the instrument when the cover is in raised position) and, for simplicity, showing only a few of the reeds 10;

Figure 3 is an enlarged vertical view, in section, taken along the line 3 3 of Figure 1;

Figure 3a is an enlarged fragmentary view of a portion of Figure 4;

ICC

Figure 4 is a horizontal sectional view taken along line 4-4 of Figure 3;

Figure 4a is an enlarged sectional View taken along line 4a--4a of Figure 4; Y

Figure 5 is a horizontal sectional View taken along line 5-5 of Figure 3;

Figure 6 is an enlarged fragmentary view, partly in section, of a portion of Figure 1;

Figure 7 is a horizontal sectional view line 7-7 of Figure 6;

Figure 8 is an enlarged view of a righthand portion of Figure 2;

Figure 9 is a partial plan view of the instrument as seen when the cover 6 is raised, showing for simplicity only a few of the hammers 11, keys 20 and dampers 56;

Figure 10 is a schematic showing of the early portions of the electronic system of the instrument;

Figure l1 is a vertical sectional view of a base, reed and pick-up embodying my invention in another form;

Figure 12 is a perspective view of the pick-up structure of Figure 11;

Figure 13 is a front view of a portion of the assembly of Figure 1l illustrating a readjustment of the pick-up structure relative to the reed; and

Figure 14 is a perspective view of a number of reeds and pick-ups embodying my inventionin still another taken along j form.

The drawings illustrate a 73-note instrument, but it will be understood that this is by way of illustration only.

In Figure 1 the elements 1, 2, 3 and 4 respectively represent righthand and, back, bottom and front portions of the cabinet for the instrument, these portions together with the lefthand end portion (not shown) being for example permanently secured together. A removable sloping fall board 5 may extend between the two end portions, while a cover 6 may be hinged at its rear to the top of the back portion 2. As disclosed in connection with such a cabinet in my copending application Serial No. 169,714 abovementioned, the reeds and pickups may be carried by the bottom of the cover 6, the hammers may be supported by the back portion 2, and the hammer-actuating keys may be supported on the bottom portion 3.

The reeds appear as 10; their mounting, the translation of their vibrations, and related matters are set forth 1n detail hereinafter. The excitation of each reed is by a respective hammer 11 positioned therebelow, the head 12 of the hammer being propellable upwardly to strike the reed (typically, at approximately the mid-reed nodal point for the third partial vibrating of the reed, as hereinafter mentioned). The hammer head 12 may consist of a chisel-shaped block of wood, preferably covered with felt, or sponge rubber, of progressively greater thickness the lower the frequency of the associated reed. The head 12 is affixed to the forward extremity of a shank 13, which is preferably of rectangular cross section with the major dimension of that section vertically disposed. The rear extremity of the shank 13 is in turn secured in the butt 14, which is pivoted at 18 to the flange 15. All the flanges `15 are secured on top of a transverse rail 16 fixed to and extending forwardly from the cabinet back 2.

It may be mentioned that the material of the covering of the hammer head may desirably be characterized by some viscosity, to aid in the damping of upper partials of the reed vibration during they short period of hammerhead vcontact with the reed.

Each hammer is propelled to strike the respective reed by a respective key 20, acting through a respective coupling member 30. The keys 20 may be pivoted about conventional pins 21, each key resting on a stack 22 of washers surrounding its respective pin, and may beV guided by conventional nfront guide pins 23 each surrounded by a conventional stack 24 of washers forming a front-end downstop. The rear end of each key is bifurcated by a vertical `'slot 25 (see Figure 9), which freely embraces a respective post 26 screwed into the :.Qabinetfbottom 31 and having an ,enlarged :head A2,7 immediately .underwhich may be provided a thin slightly viscous and elastic washer 2.3; the head `2,77 and washer A2 8 form `an upstop lfor the rear end of the respective key. The relative adjustments of this rear-end tupstop ,27--28 (-eiected -by |#rotation of post 26) and of the liront-.end downstop 4(effected by choice of washer thicknesses) .agresuch that'gwhen ;thefkey is operated the primarily effective :stoptis the rear-.end ilusion 27e-28eme frontend dewnstop .being a secondary one whose function is to limit deformation xof the key which may result from front-end linger pressure lcon- -tvinued after the ,rearqend upstop has `acted.

,Near its rear extremity each vkey carries ;a respective capstan member `31 screwed into ithe key (fully seen in Figure 6). A little above the keystop -this member may have the enlarged khex portion 32 engageable by a wrench for vertical adjustment of the capstan member .-31. ,Brom thehexportion 32 upwardly the capstan member I3.1 may consist of a rod 33 preferably quite smoothly Cylindrical `excepting fora .longitudinal -ilat 34 several thousandths cf .an ,inch wide (shown in exaggerated width in Figure 6).

Ihe respective ,coupling member 3.0 .may comprise a vertically disposed cylinder 3G having, upwardly from its bottom, a circular central bore closely tting -about ltherod 33 (excepting for the flat 34 ot the latter) but slidable therealong (which action ,may be Vaidedv by a light .film Aof .silicone grease on the rod), the upper end ofthe member ,30 being solid and exteriorly rounded into substantially 4hemispherical configuration. Normally the lower extremity of the cylinder 30 rests on the capstan hex lportion 32, if desired through the intermediary of a quite thin slightly viscous Aand elastic washer 35-and when the cylinder 30 so rests the vair-chamber 36, formed between lthe bore .of the cylinder and vrod 33 at the top of the latter, may be of quite small vertical dimension. Nor- Inlly un the upper end Vof each coupling member 30 rests the forward portion of .the respective hammer butt 14., if desired through the intermediary of `a quite thin layer 17 of slightly viscous and .elastic material `secured -to the bottom of the hammer butt. When the respective lharnmer butt so rests the lower extremity of the respective vhammer head 12 is preferably slightly lspaced above a vfelt pad 29 `secured therebelow on the top of the respecy.tive key 20- Qperation of the key 20 (i.e., depression of its forward extremity by the linger), if carried out extremely slowly, will of course raise the capstan member 31 and coupling member 3.9 Without disturbance of the normal 'interrelationship between the latter members, and will swing the hammer upwardly about its pivot without any breaking of the contact of the hammer but with Vthe coupling member. Preferably the components are so geometrically interrelated that this raising will continue to, but be stopped (by the upstop 27-28), at, a position of the hammer head slightly spaced from the bottom of the respective reed 10. No impact of hammer head with reed will occur-just as there occurs in the conventional piano no hammer-string impact when the key is extremely slowly operated. When, however, the key 20 lis operated with any substantial velocity, its own sudden stoppage by the upstop 27-28 will not be accompanied by stoppage of either the coupling member 3i) or the lhammer 11. The hammer will continue under 4its own momentum, and with vnegligible change in velocity,

,to strike and rebounddownwardly ,from the reed. Correspondingly the coupling member 30 will ycontinue up- Wardly under its own momentumbutin the case of this member there is a substantial and steady loss of velocity, since this coupling-member movement can only tion.

4 occur with an enlargement of the air chamber 36, which can only occur with a tlow of air thereinto along the narrow passage formed between the bore of the coupling member 30 and the flat 34, which in turn involves substantial energy dissipation through air friction.

Assuming the key remains `operated and the capstan member 31 thus in an elevated position, then in the rela* tively high-velocity Arebound of .the hammer from the reed its downwardly moving butt 14 will quickly come into impact fftlntoug'h '17 if employed) against the :stillrising 'but Vnow relatively low-velocity Vcoupling member 30. I have found it desirable to make the mass of the coupling member several times the efectivemass of the hammer (i.e., the hammer mass as seen at the region of contact betweenhammer and coupling member). If this be done, the conditions .at the time of impact will be such that at the instant after impac-t the hammer velocity will be `very small, `while the coupling member will possess most .of .the kinetic energy previously in the rebounding hammer and will 1itself. befin downward motion toward ,its normal relationship tto the Icapsta-n member 3,1.-a motion which vvinvolves the diminution .of `.the air chamber 36 which .ca-n only .occur ,with fa .flow of `air therefrom along vthe .narrow passagway .formed aszabovementioned between the .bore lof .the .coupling member vand liiat ,34, which in `turn ,involes .substantial 4energy dissipa- 'Ihus although .the coupling member while .the key remains operated is Yin na region where fit will be .struck by therebounding hammer, 4a- 4rte-rebound .of `the hammer from it to restrike the reedwhich would occur .with .all highenvelocity key operations in a conventional system of vthis general `rio-escapefrnent typefis precluded by .the transfer of the rebounding hammers kinetic energy to ,the coupling member and the harmless .dissipation from .the coupling member of that energy.

It will be understood that a function .of the `early tenlargement of the air chamber 36 lis 4to prepare ,it ifor its later diminution and that a iunctiono-f .the energy dissipation .during that enlargement is the rapid .deceleration of the upwardly moving coupling member, while the function of the VVenergy dissipation in .the .later airchamber diminution is the ultimate one (of .precluding hammer rebound) just outlined. Y

In a preferred embodiment of the vibrator-exciting action above outlined I minimize incidental compliances which at the time of impact of the rebounding `hammer against the coupling member might yield Yand thereby divert from the coupling member some of the kinetic energy `which desirably is transferred from hammer to it for harmless dissipation as outlined above. Thus I prefer to ,avoid the use of felt or similar bushings at the pivoting point 18 .of 'but-t 1d to flange 15 and to use instead a relatively large diameter brass pivoting pin; `I prefer' to utilize the vertically still hammer stern described above; I prefer to minimize the compliance of (or even to omit altogether) the thin washer v35 -under the coupling cylinder, and likewise as to the layer 17 above .that member (on the bottom of the hammer butt); I `prefer to omit yieldable l,elements from the washer stacks 22 about the pivots 241; Vand I prefer to usea stili material for the keys 2() themselves.

l `In certain .aspects the vibrator-exciting action just outlined has some similarities to those described in U.S. Patent No. 2,767,608issued `to me October 23, 1956 and in my copending application 'Serial No. 376,543, tiled August 26 1953 (which Vis a continuationin-part `of a prier application senat ,.Ne. 292,096, .ined tune 6, 1.952 and since abandonedD-but there are several distinctions of importance.

` Attention may now be directed to the mountingot the reeds 10 the translation of their vibrations, etc.

The reeds, being .of the fixed-free variety, are of course supported in cantilever. The baseof :each reed is preferably'surrounded by a plug 41 .of deformable material, and this plug is axially force-ttcd into a horizontal hole' i42 in an appropriate base member so that the reed effectively extends horizontally from the base member-the .base member appearing in section in Figure l being 43. This structure and method of mounting each reed to a base-.whose advantages comprise exceptionally rigid, dissipationless and determinate basing of each reed-are described in detail in my copendingrapplication Serial No. 291,829, 'filed June 5, 1952.

The base member 43 does not support all the reeds of the instrument. In may copending application Serial No. 284,133, led April 24, 1953, I have described, for an instrument of this general character, the subdivision of the total base means into a plurality of individual base members yeach supporting a respective series or group of sequentially tuned reeds; as brought ont in that application, this subdivision is so carried ont that each individual base member has a lowest natural frequency of vibration higher than the fundamental frequency of any reed extending therefrom.

In accordance with the present invention a further limitation is observed: that .the fundamental frequency of vany (in effect, of the highest-frequency) reed secured to any base member shall be higher than the secondpartial frequency of any other (in effect, of the lowestfrequency) reed secured ,to that base member. I have found this limitation important to avoid the possibility that the fundamental-frequency energy of a reed be dissipated by transfer of that energy to second-partial-frequency vibration of another reed secured to the same base member. Since the ratio of second-partial frequency :to fundamental frequency in a normal reed without special shaping, aperturing or the like is 6.27, and since even with such practises it tends to remain at least 6.0, this specification is readily met for example by limiting the fundamental-frequency ratio between highestand lowest-frequency reeds secured to any one base member to less than 6.0--or, in the tempered scale, to some 3l progressively tuned reeds.

Accordingly in the drawings it will be seen that the -base member 43 carries the thirty-one lowest-frequency reeds, Ithe base member 44 carries the twenty-four midfrequency reeds, and the base member 45 carries the eighteen highest-frequency reedsit ybeing understood that each base member individually obeys the specification set forth in .the next-to-last preceding paragraph.

All three base members are individually vibrationally insulated to some extent from the cover 6 by which they are supported and, since they may be devoid of any vibrational intercoupling other than through the cover, they may accordingly be considered as v ibrationally insulated from each other to a substantial extent. In connection with their mounting, there is secured to the bottom of the cover 6 a transverse metal plate 8 above the positions to be occupied by the base members. Extending upwardly from each base member through respective oversize holes 9 in the plate 8 and into still larger holes 7 in the cover are a pair of studs 46 each screwed into the base member, one near each end of the latter. As best seen in Figure 3, each stud terminates in an enlarged head 47, underneath which may be a metal washer 48. About each stud, between the washer and plate 8, there is disposed a conically spiralled `compression spring 49. zOne half of the weight of each base member appears at a respective spring 49, as a compressing force exerted thereon through lthe respective washer 48, each pair of these springs thus providing .the mounting `of a respective one of the base members.

The studs 46 are so located in the front-and-back dimension that the base members will have limited tendencies to rock either forwardly or rearwardly, and such tendencies are in any event restrained by strips 50 of sponge rubber or the like placed between the base members and plate 8 near the front and the back edges of the latter (each base member being in effect floated by the two respective springs 49 and the sponge rubber strips 50 just mentioned). There is, however, ample opportunity for sufficient rocking of each base member in response to forces applied thereto so that each reed is to some extent vibrationally coupled to all other reeds on the same base member-thus simulating the coupling which exists in the conventional piano between the strings of different notes. iIf desired, this effect may be carried further by deliberately introducing a modest amount (though it should not be too large) of coupling between the three base members, over and above that which occurs through their mounting to the single cover.

Each of the base members 43, 44 and 45 may comprise a main metal portion, for example of relatively hard aluminum, and a portion of insulating material appended to the metal portion. The cross-section of the metal portion of the low-frequency base member 43 may be of the shape of an inverted L whose horizontal leg is forwardly directed, is of appreciable and constant vertical dimension, and is the length or forward extent varying from a maximum at the lefthand extremity, to a moderate value at the righthand extremity, of the member 43and whose vertical leg is of constant height and of thickness varying from a minimum at the lefthand extremity, to a substantial value at the righthand extremity, of the member 43. The crosssection of the metal portion of the base member 44 may likewise be of the shape of an inverted L, and at the lefthand extremity of the base member 44 the dimensions of the legs ofthe L may be similar to those found at the righthand extremity of member 43; proceeding rightwardly, the length of the horizontal leg may continue to diminish, while the thickness of the vertical leg may continue to increase, for example so that at the righthand extremity of the base member 44 the cross-section of the metal portion has become a simple thick I. At the lefthand extremity of the base member 45 its metal portion may have the cross-section of a simple thick I, for example similar to the cross-section of the righthand extremity of member 44; proceeding rightwardly, the upper portion may be cut away in front to a small and progressive degree, so that at its righthand extremity the metal portion of the base member 45 may have -a cross-section of the shape of an upright L (as indicated by the solid and dotted lines 45 in Figure l).

It-is in the vertical legs of the base members that the reeds 10 are secured (through plugs 41 as above described) and from which they extend forwardly. It will of course be understood that with a constant width and thickness-which I prefer to employ at least for the reeds extending from base members 43 and 44-then for the required progressive tuning the reed lengths will decrease progressively from a maximum at the lefthand extremity of base member 43 to a relatively short length at the righthand extremity of base member 44. I prefer to maintain the longitudinal mid-points (more precisely, the mid-reed nodal points for third-partial vibration) of al1 the reeds in straight alignment transverse of the instrument-this being so that the hammers, which I prefer to have strike the reeds in each instance at this position, may be arranged ina straight transverse lineand I arrange the front surfaces of the vertical legs of base members 43 and 44 in a gradual curve appropriate to that maintenance. Atthe same time the rear surfaces of those legs may lie in a transverse vvertical planewhich is permitted by the thickness specifications set forth in the preceding paragraph.

The progressive decrease of reed length (and with it the curving of the front surface of lthe vertical leg of the supporting base member) may be continued throughout the highest-frequency group of reeds (and their supporting base member 45) as a sole way of accomplishing the required progressive tuning throughout this group. Because of the relatively short reed-length dimension already reached at the righthand extremity of base member 44, however, I prefer to minimize the further reduc- 7 tion of reed length throughout that highest-frequency group-'supplementing the effect Lof a small length reduction, in lachieving 'the required progressive increase in frequency, by making `the sides 4oli the reeds oblique and the free ends thus narrower kin-prog-ressively increasing degree toward the rightha-nd extremity of the lbase member 45, V'as seen in =Figure l8. A further expedient which `may `be resorted to, in minimizing the reduction of lreed length -throughout this highest-frequency group, is of course a progressive "increase in 4the thick-ness of the reeds.

The insulating "portions of the base members -are designated yas 53, 54 and 55, respectively; yeach of lthem may extend forwardly from the upper forward Asurface ofthe respective metal base-member portion. (Each of 53 Aand 54 may form a forward projection of the lvhorizontal leg of the respective metal portion of y43 or 44, and 55 may form a yforward projectionfrom the lcut-away upper part of v45.) In turn @the forward part `of each of the insulating portions 53, 54 and 55 may `conveniently be cut away at the top (as vseen in AFigure l) vr`to reduce somewhat that forward-part vertical `thickness. It Lis in this forward part of the base-member insulating portions `that the pick-ups aremounted.

Before turning to the translation of the reed vvibrations into 'electric oscillations it kwill be convenient 'to complete the 'description of the mechanical portions of the #instrument by reference 'to the tone-terminating dampers. These may be seen in 'Figures l and 9. The dampers proper, which Vare designated as 56, may each consist of a small pad of relatively soft material, preferably such as mohair which presents an active surface of generally parallel and closely spaced outwardly extending hairs. Each damper 56 may be secured on the rear upper surface of a 'respective generally vertical spring v57, of which the lower portion is secured to a rail 60 described below. Normally each damper is lightly biased by its associated spring 57 into contact 'of its active surface with Vthe free (forward) end of a respective reed 10. When in lthis relationship to that reed it will effectively suppress any signicant vibration ofthe reed-and if brought into lthat relationship `-to the reed while the reed Yis vibrating `itwillelfectively and promptly terminate that vibration.

When there is operated the lcey `20 associated with a reed against which -a respective damper 56 is biased, for excitation of that reed, "it is yof course necessary that ythe damper be removed `from contact "with the reed. To accomplish vthis each such -`key maybe provided, somewhat behind its pivot 21, with 'an upstandin'g heavy-wire arm 58 extending to -a position closely spaced behind the normal position -of the mid-portion of the respective damper spring 57, and there foldedover into a'short horizon-tal portion 59. -When the key is operated the arm portion 59 will 'be rocked diagonally "upwardly Aand forwardly, and in this movement lwill :impinge against and move `forwardly the respective damper Vspring 57, thus placing the respective damper 56 out Vof `contact with the respective reed-a condi-tion l'which `normally"will'be maintained until release of the key, ywhereupon the damper will return to contact with `the reed and `will terminate its vibration.

'To .provide the conventional loud pedal action all the dampers may collectively be removed from contact with their respective reeds. To this end the rail 60- whose rear surface may be a gradual -curvc conforming vto the similar `cu-rye formed by the Ifree ends of the reedsmay have a straight forward edge which Ein turn is inset .into -a U-cross-sectionehannel member 61. The assembly 60-6'1 .at .its extremities may v=be pivoted `to lett- .and rightha-nd standards 62 and -63.

The @assembly 60-61 may be biased about 4its pivots .(countercloekwise -as seen in Figure 11) to a predetermined position by .the combination '(partially seen in Ei-gure 9) :of an .arm [64 extending rearwardly 1therefrom,

a spring urging ythe rear extremity of that arm downwardly, and a stop 66 limiting .the response of .the arm to that bias-this predetermined .position establishing -the normal position of the rail 60 which was postulated-in prior-paragraph references lto that rail. The assembly (S0- 6l may `be rocked against its bias (i,e., .clockwise as seen in Figure 1)-thus removing all dampers collectively from contact with their associated reeds-by downward llongitudinal movement of va rod 67 which `at its upper extremity is loosely secured -to an arm .68 fextending forwardly from the channel member 6l. Such downward movement of the rod '67 may be effected in .any convenient manner, most typically by a pedal (not shown) with-'whichits lower extremity may be suitably associated. IDarnpers need -not usually be associated =with1thefvery top 'notes of the instrument, and accordingly in its righthand portion 4the damper system has been shown as embracing, of the reeds lof the highest-frequency group (i.e., those extending from base member y445), only fthe most leftward few.

`I have found -it highly desirable inthe production Aof the most pianistic tones from impulsively excited .fixedfree reeds-whose upper-partial vibrations (i.e., all above the first, or fundamental) are well known to be normally inharmonically related to the fundamental-to observe several Vspecifications (A) To utilize means in the mechanical system which is formed .by the exciting means `and the vibrator to substantially eliminate from the translated oscillations an inharmonic component correspondingto one of the lowernumbered of the upper partials at 'which the reed tends to vibrate-preferably (if the preference under B below be followed) the third parti-al;

(B) To yarrange the mechanico-electrical system which is A'formed Iby the pick-up Idevice and a portion of the vibrator so that in it is `performed the function of `substantially leliminating from the Atranslated oscillations an inharmonic component corresponding to one of the lowernumbered of the upper partials at which thereed tends to vibrate-preferably lthe second partial;

=(C) To arrange the mechanico-electrical system abovementioned so that by it is performed the function of introducing, into the electric oscillations which it translates from the reed vibrations, a series of upper partials harmonically Vrelated to the fundamental-preferably a series which diminishes in composite magnitude l(relative to the magnitude ofthe fundamental) as the vibration of the reed dies away after lits impulse excitation; and

(D) To arrange the vmechanico-electrical vsystem abovementioned so that the greater deformations ofthe reed attendant `on high-'amplitude vibration, `though involving quite inharmonic upper partials, are utilized to enhance the generation of the abovernentioned harmonically related upper partiels, as -well Ias to enhance the translation of the fundamental, in the electric oscillations during the very .initial instants following the impulse 'excitation of ,the reed.

Each `of the `lirst three of these specifications is disclosed in one or another manner in my cepending appli- .cation Serial No. 169,714 abovementioned or my `copending application Serial No. 255,383 abovernentioned. 'Iihey are, however, interrelated in -a particularly favorable manner in vthe structure of Figures ll gthrough, and with them is combined the very valuable :fourth 'specili- .cation above set forth.

Specifications A and 3, taken together and utilized with respect to the second and third reed-vibrationjpartrials., serve .the highly important function of rendering harmless the .significant ones `of the -inharmonic (-i;e., all upper) partials lat which the reed tends to `vibrate-'since partials above the third lare normal-ly suiciently'weak so that their translation has a .negligible deleterious effect on .output tone. tated in other words, they cause the reed-#though actually still excited in the simple impulsive manner required for a pianistic type of tone-#to approximate in its effect a vibrator whose vibration is free of partial development (i.e., whose vibration occurs only at its fundamental frequency).

The function just mentionedhighly important since substantial inharrnonic components, especially continuing (as distinguished from transient) ones, are intolerable in tones intended to be pianistio--would result, taken alone, in an unusably dull output tone, quite unpianistic `because it would lack the rich development of upper partials harmonically related to the fundamental which is characteristic of the piano. It is to cure this lack, by creating just such a rich development of harmonic .upper partials, that specification C is combined with A and B.

It will be convenient iirst to describe the pick-up means and how the structure meets specifications A, B and C, `and then to bring out the importance of specification D and how the structure meets it.

Specification C may be met by arranging the pick-up means so that it is principally influenced by an edge portion of the reed, which preferably Iwill most fully influence it twice in each cycle of vibration at substantial amplitude-it being preferably so arranged that the instants of greatest inuence, though bicyclic, are never separated by precisely 180 degrees (thus avoiding pure double-frequency translation). Reference being had to Figures 3, 3a, 4 and 4a, there Will be seen for each reed a pick-up means 70. Each such pick-up means may comprise a threaded portion 73 conveniently passing vertically through the forward part of the associated base-member insulating portion (e.g., through the forward part of 53) and there anchored by means of two nuts 74 threaded on the portion 73 and tightened against the base-member insulating portion, one on top and the other on the bottom. Each pick-up means may lfurther comprise a rod portion 72 preferably of reduced diameter forming a downward projection of the `threaded portion, and may finally comprise an active pick-up portion 71-typically in the form of an abrupt enlargement of the rod portion at its end into a thin transverse end plate (for example,

of thickness generally similar to that of the associated reed). Seen in plain view of reed and end plate (e.g., in Figure 3a), the end plate 71 is closely spaced from an edge portion of the reed'. Vertically, the pick-up means may be so adjusted (by nuts 74) that the end plate 71 is very nearly at the level of the reed when the latter is in its at-rest position, for example (see ligure) so that its central plane approximately coincides with the plane of the bottom of the at-rest reed.

It is of course desirable that the natural frequency of each pick-up device be higher than the fundamental frequency of the highest-frequency reed of the instrument. It is further desirable that the material be soft enough to permit accurate placement of the end plate 71 horizontally, relative to the reed, by slight bendings of the rod portion 72, preferably effected with the aid of an appropriate bending tool.

It will be understood (I) that when the reed moves upwardly the capacity betweenit and the end plate 71 will progressively reduce; that as the reed moves downwardly from an upward excursion that capacity will progressively increase, reaching its original value when the reed reaches its at-rest position; that as the reed continues to move downwardly that capacity will at the very first still further increase somewhat, to a maximum when the reed and end plate are in alignment (ie, when the central planes of the two coincide), and will then progressively decrease; and that as the reed moves upwardly from a downward excursion that capacity will progressively increase, reaching its abovementioned maximum when the central planes of reed and end plate coincide, and will then decrease to reach its somewhat smaller original value when the reed reaches its at-rest position-this analysis of course assuming that the reed movement is of suiiicient amplitude so that in its downward excursion it proceeds beyond a position of alignment with Ythe end plate 71. It will further be understood (Il) that the higher the amplitude of the reed movement, or vibration, and thus the greater its velocity in passing its positions of maximum capacity abovementioned, then in the waveform of the capacity variations the greater will be the Steepness of the approaches to and recessions from maximum capaci-ty. It will still further be understood (III) that if the reed be vibrating at very high amplitude the intra-cyclic instants of maximum capacity-both occurring in the downward-excursion half-cycle-Will be separated by almost (but never fully) 180 degrees; that as the amplitude reduces that separation will reduce; and that when the reducing amplitude has reached a value only sutlicient (at the peak of the downward excursion) to align the reed with the end plate that separation will have reached zero-after which there will be in each cycle only one instant of maximum capacity.

As will hereinafter more fully appear, with this type of pick-up means the translated oscillations are a function of the variations of the capacity between the reed and the pick-up means. Also, as is well understood, an intracycle departure from pure sinusoidal character, if repeated from cycle to cycle (subject to no more than minute amplitude shifts from one cycle to the next) gives rise to the generation of partials which are limited to integral multiples in frequency, or true harmonics, of the fundamental. Accordingly it is the action described in (I) above (in fully understanding which (II) and (III) above are helpful) which meets the basic portion of speciiication C-that the pick-up means, in its translating action, introduce into the translated oscillations a series of upper partials harmonically related to the fundamental. Further, it is the actions `described in (II) and (III) above which meet the supplementary portion of specification C-that the series of harmonic upper partials diminish in composite magnitude as the vibration of the reed dieS away (magnitude being used in the sense of amplitude relative to the amplitude of the fundamental).

In the structure specifically illustrated in Figures l through 9 the edge portion of the reed which principally inuences the active portion of the pick-up (i.e., end plate 71) is an internal edge portion, created for example by piercing the reed with a somewhat elongated hole 80. The outer portion (i.e., the portion toward the free extremity of the reed) of the periphery of the hole may, for example and as illustrated in Figure 3a, be of semicircular formation, and it is from this portion that the active pick-up portion or end plate'71-which in this case may for example be circular-is closely spaced. In Figure 3a the dash-dot line 79 may be taken as very approximately illustrating the region, longitudinally of the reed, of average influence of the reed' on the pick-up. To meet specification B this region, as to each reed, may most desirably be at the longitudinal position of the node for the second partial of the reed vibration. In the case of an unpierced reed of uniform cross-section this node falls at a position removed from the base of the reed by approximately 78% (and from the free end of the reed by approximately 22%) of the reed length-and the piercing of the reed appears to make no first-order change of this position, so that a positioning of the hole to bring the line of average influence of read on pick-up at a position removed from the base of the reed by approximately 78% of the reed length represents a close compliance with specification B.

It is to meet specification A that the hammers have been called for above preferably to strike the reed at the mid-reed node for the third-partial reed vibration-- which node in the case of an unpierced and uniform cross-section reed falls almost precisely at the longitudinal mid-point of the reed, and is not substantially altered by the piercing. Other means of meeting specification A have been disclosed in my copending application Serial No. 169,714 abovementioned; in my copending application Serial No. 189,345, filed October 5, 1950; now

`11 abandoned and in my VU.S. Patent No. 2,755,697 issued July 24, V1956---consisting generally in rendering integral thenormally nonfintegral ratio between the frequencies ofthe second and iirst partials ofthe reed vibration, and thus rendering the second partial a useful harmonic of the fundamental. Still `another means of meeting Yspecification A yhas been disclosed in my copending application ,SerialNa 248,947, tiled September 29, 1951, which is now abandoned .but whose subject vmatter is vcontinued in vmy `copending application Serial No. 549,589, filed November ,29, 1955-.consisting generally of .the use of a substantially -softer-than-normal hammer to substan tially eliminate the excitation of the upper partials, at least of those `above .the second, .of the reed vibration.

It Will of course be understood that the manner in which the mid-reed vnodal striking of the ,reed meets specification A-i.e., Iin which it substantially eliminates from the translated oscillations 4an inharmonic ,component corresponding to the third partial at which the reed tends to vibrateis by vsubstantially eliminating the presence of that partial in the reed vibrations on a selective basis. The difference between this and each of the other means of meeting specification A above referred to will be apparent.

When -a fixed-free reed is vibrated at high amplitudewhich ,is the case linitially after strong excitation-at Va plurality of its partial frequencies the deformation attendant on the upper-partial vibration components produces -a-n eifective shortening of the reed; this might be termed a temporary or dynamic shortening. Considering the fiirst-partial (or fundamental) vibration, which is the one ofcourse relied on in the abovementioned functioning ofthe structure, this dynamic shortening will temporarily increase the spacing of the locus of the vibratingfreed extremity from any picloup located just beyondvthat yextremity (such as the one disclosed in -most ,of the -iigures of my copending application Serial No. 169,714 abovementioned). Since the eiciency of translation is a sharp inverse function of such spacing, there takes place during the initial high-amplitude vibration a very noticeable reduction of translation eiciency. Thus, with a pick-up located just beyond the free extremity of the reed, there can and `does occur an actually observable increase of amplitude `of the translated oscillations during the early instants after reed excitation, as the dynamic deformation `subsides and the translation efficiency therefore increases.

This time is one when, in a normal piano, avery noticeable decrement of the output sound occurs; indeed, an especiallyhigh.initial decrement--i.e., decrement during the first few instants of a tone-is a strong .distinguishing feature of piano tone.

By arranging the pick-up means so that the edge portion of the reed which most actively iniiuences it is a longitudinally.intermediate edge portion, or portion other than the free extremity ofthe reed, the disadvantage just discussed is obviated. Thereby a worthwhile improvement in respect of tone-inception characteristics is achieved. 'The arrangement of the pick-up in .the `strueture .of Figures 1 through 9 of course observes this specification (in addition to which it .observes a furtherl one, hereinafter set forth, for the obtainment of still further advantage). In meeting the specification of this paragraph, however, itrwillbe understoodV that the edge portion of the reed which most actively or fully iniiuences the pick-up neednot be aninternal edge portion. Thus .in my copending .application Serial No. 255,383 and in Figure y54 .of irny .copending application Serial No. 169,714, bothabovementioned, I showed structures in which that edge'portioniwas a .side-edge region; .such structures ,I now describe.

:Reference `beingihadto .Figure 11, there will be `seen an alternative constructiontinfwhch the metal reed base, of approximately ltr-cross-sectiomis designated .as 115, a treed as 116'and11the associated' pick-up structure as 117; :it will be understood that the base 115 will carry other reeds and pick-ups therefor, not here necessary to show. Each reed may for example be individually clamped in position between upper and lower largediameter fine-thread socket-head hardened-steel setscrews, 118 and 121 respectively, having slightly concave ends resulting in respective small circumferential ridges 120 and 122 axially aligned with each other and biting into the respective reed surfaces thereby to provide -a sharply defined and positive securing of the reed; a respective horizontal hole '125, larger than the width of the reed, through the-downhanging part of the ibase 115 provides clearance space through which .the reed reaches its clamping set-.screws and Within which the forwardly extending or active part ofthe reed may freely vibrate; Extending forwardly from the front surface ofthe forwardly extending part of the base 115 may be a yrespective insulating bushing 126 internally threaded to accommodate a respective screw 127 by which the respec- Ytive conductive pick-up structure is secured.

As shown in Figure 12, the pick-up structure may be ypunched from a `sheet of suitable metal and may be generally of inverted-U formation, its downhanging ends 12B-which form the pick-ups proper being Yinternally widened and folded forwardly so that when the pick-.up issecured in position against the ,front of .bushing 12.6, by the screw 127 passing through an upwardly .extending central notch in the pick-up structure, these ends l1128 will be in a plane substantially parallel to thatof the yrespective reed. The pick-ups .(i.e., ends) *128 straddle that reed, forming therefor a pair of pick-ups,

fand the transverse center line of the pick-ups may -be made to coincide with the nodal point of the second partial of the reed vibration (which is typically removed from the secured end of the reed by 78%, and from the lfree end by 22%, of the active length .of the reed). Appropriate vertical elongation of the notch 130 permits vertical adjustment of the pick-ups relative to the reedfwhich is illustrated by the fact that in Figure 11 the pick-ups appear as having their bottoms .above the top of the reed, whereas in the front view constituted :by Figure 13 they appear in the more typical position of `partial overlap (vertically) between their thicknesses and that of the reed. Other precise adjustments of pick-ups relative to reed are readilyl made by appropriate bendings of the pick-up.

An electromagnetic pick-up may be yused if the reeds be of magnetic material-'such a pick-up being desirably provided with only a relatively weak magnetic bias in order to minimize shifting of the frequencyof @the Yreed at low amplitudes of vibration due to the magnetic attraction between the reed Vand pick-up structure. For effective use in the development of the series of'upper partials harmonically lrelated to the fundamental, `an electromagnetic pick-up may be placed at the reed edge near the reed tip; it should develop veryisteep voltage pulses as the reed sweeps past it, and accordingly may have a pole tip very closely spaced from 'the reed. One type of design utilizes a non-rnagneticallybiased pick-up construction in which the entire core and pole-piece structure is made of high-quality magneticmaterial such-as Permalloy having a very high initial permeability; for a pick-up of this type the biasor magnetomotive force may be provided by the reed (or some otherfs'ource .fclose by), Whose magnetic influence on `the pick-up-will `be modied abruptly by the passage ofthe reed adjacent the pick-up. VFigure 14 illustrates an arrangementl lof an electromagnetic pick-.up in which the electrical coils 187 are wound upon individual .cores 188, each core being disposed .between adjacent reeds 190 which are laterally magnetized as indicated by the polar markings N and S.

It Vwill readily vbe appreciated that in lthe lstructures of Figures l1 through13 and of '.Figure14 thelocus `ofl vibration of the-portion of the reed which principally modulating, or on a frequency-modulating basis.

v 13 influences the pick-up is left unchanged, in effect on the pick-up, by the dynamic shortening of the reed, thereby avoiding any temporary diminution of the translation efficiency at and immediately after the excitation of thel reed. I have found, however, that important still further improvement is possible. It is achieved by arranging the pick-up means so that the locus of the portion of the reed which principally influences it-instead of being brought further away from it, or left unchanged, by the dynamic shortening of the reed-is by that dynamic shortening brought closer to it. It is for this reason that I have employed, for the portion of the reed which principally influences the pick-up means, an internal edge portion-and have selected for that edge portion the outer (rather than the inner or an intermediate) peripheral portion of the hole 30. This represents a longitudinally intermediate edge portion specially selected for positive additional advantages.

It will be understood that the effect of this favorable utilization of the dynamic shortening of the reed during the early instants following the excitation of the reed is not only to enhance the translation of the fundamental (thereby increasing the initial decrement, as is desirable),

but also then to increase the generation of harmonically related upper partials-since the steepness of the waveform of capacity variation is likewise increased by this utilization. It is so that specification D is met. This is of especial importance since a distinguishingv feature of piano tone, over and above the high initial decrement, is a very initial burst of momentarily accentuated harmonic development.

The pick-up means of Figures 1 .through 9 and of Figures l1 through 13 will be recognized as of the capacitative type, and those of Figure 14 as of the electromagnetic type, and as to broader aspects of the invention it will be understood that no limitation as to type is intended. For the capacitative type, in turn, no limitation as to broader aspects is intended, as between those operating for example on a D.C., on an amplitude- I have preferred, however, to employ the capacitative type of pick-up means operating on a frequency-modulating basis-Le., to employ a system in which variations of the capacity between the pick-up means and the reeds, each taken collectively, are used to modulate a high-frequency carrier, which in turn is demodulated to produce the translated tone-representing oscillations, which in turn may be amplified and translated into sound by a final audio amplifier and electro-acoustic translating device (not shown).

Reference being had to Figure 10, there will be seen an electronic system comprising a pentagrid converter tube 89 such, for example, as a 6BA7, of which the second and fourth grids'are interconnected and, by-passed by condenser 105, are supplied with positive potential through voltage divider S-104 from a source B-l of plate current, and of which the first grid 91 is connected to the upper extremity of an oscillator coil 100 through grid condenser 102 and also `to the cathode 90 or tube 89 through grid leak 98. The lower extremity of the 'coil 100 is connected to ground, while the cathode 90 may be connected to a tap 101 on the coil 100 appropriate to the setting up of the system 100-90-91-92 as a high-frequency oscillator system. In tube 89 the third grid 93 may be Aconnected to cathode 90 and the fth (or suppressor) grid to ground; in the plate current flowing between plate 96 and the source B1 of plate the oscillations generated by the high-frequency oscillator abovementoned, amplified by the action of tube 89 and rendered suitable, impedancewise, for feeding into that load.

The several reeds may be electrically interconnected, as by interconnection of the metal 'portions of the three base members 43, 44 and 45 by flexible wires 51, and

current, through the load mentioned below, will appear 14 connected to ground. The several pick-up means 70 may be electrically interconnected in any suitable manner, as by a conductor intertwined around the upper extremities of the threaded portions 73, and connected to a suitable tap on the coil MiG-several such taps being provided so that they may be selected between. These connections place the aggregate capacity, between reeds and pick-up means, in parallel with a selected portion of the coil that portion will be selected so that the combination of that capacity with the coil will resonate the oscillator system abovementioned to approximately the desired frequency, fine tuning to that frequency being accomplished for example by adjustment of a variable iron core 99 associated with the coil.

It will be understood that upon vibration of a reed the aggregate reed-to-pick-up capacity will be varied `oscillatorily,A and that as a result the frequency of the oscillator system abovementioned will be varied oscillatorily-i.e., will be modulated by the reed vibrations, it being the thus frequency-modulated oscillations which appear in the plate current of the tube 89. The load connected in the plate circuit of that tube may be the input of a discriminator-transformer 107 (tuned to the carrier frequency) of any conventional type, to the output of which may be connected in conventional fashion a doublediode discriminator tube 108 and the demodulatedoscillation load system 109 of any conventional type. It will accordingly be understood that across the demodulated-oscillation load system 109-i.e., between its upper terminal 110 and ground-will appear the electric oscillations translated from the reed vibrations.

Between the terminal 110 and the final amplifier and electro-acoustic translating device (not shown) the translated electric oscillations may be passed through a lowpass filter 111-112 to eliminate supersonic components; may be attenuated to any desired amplitude by attenuator 113-114; and may be preliminarily amplified by tube 115, shown for example as a triode-connected pentode with load resistance 116, bleed resistance 117 and cathode .resistancetand condenser 118-119. From load resistance 116 the oscillations may be applied through condenser 120 to a volume control 121, preferably of the `well-known amplitude-compensated type illustrated.

From the Ioutput of the volume control 121 the oscillations may be fed to the final amplifier through a network 122 which, in cooperation with the input impedance lof the amplifier 130, serves to impart thereto a frequency characteristic rising with increasing frequency. Additionally there may be associated with the output of the volume control, as by shunting thereacross, a resonant circuit (which should be of the series variety for the shunt connection) consisting of variable inductance 123 and variable capacity 124, for further shaping of the frequency characteristic of the system. I have found that for most pianistic tones it is desirable that the series circuit 123-124 be resonated at a frequency correspond- 'ing to the fundamental of a tone at or near the bottom effect thus cumulative with that of the network 122. `Interesting and important variations of effect can, however, be achieved by varying the resonance of 123-124. The electronic system above described (other than the amplifier 130 and the controls proper of elements 121,

l123 and 124) may be mechanically arranged in the form of a compact unit 88 which, if desired and as indicated in Figures 1 and 2may be physically disposed below the cover 6 behind the base members 45 and 44 at the treble extremity of the instrument.

Claims to the vibrator-exciting action disclosed herein are not made kin this application, the same having been 'made in vmy copending application Serial No. 660,787,

led May 22, 1957; likewise claims to the subdivision of base means in accordance with specifications. set forth above are not made herein but rather in that copending application just mentioned. Furthermore, claims to structure taking positive advantage of the dynamic shortening of the reed are not made herein, the same having been presented in my copending application Serial No. 673,725, filed July 23, 1957.

While I have disclosed my invention in terms of particular embodiments thereof, .it will be -understood that unnecessary limitations are not thereby intended, 4since by the disclosure various modifications will be suggested to those skilled in the art. Such modifications will not necessarily constitute departures .from the scope of the invention, which I undertake Ato express in the appended claims.

I claim:

.1. In combination in an .electricalmusical instrument, .a fixed-free reed, an impulse .exciting means comprising a key actuated hamrner'adjacent the' reed selectively engageable with the individual reed for setting it into Adecadent free vibration, and an electric translation pick-up adjacent the reed, said pickup having atone producing portion located alongside and being vibratorily passed by a longitudinally intermediate edge portion of the reed and being of an-etfective thickness, inthe direction of reed vibration, smaller than the high-amplitude stroke of-said edge portion -of the reed.

2. In combination in anelectrical musical instrument,

a fixed-free reed, an impulseexciting means comprising a key actuated hammer adjacent thereed.selectivelylengageable with the individual reed forsetting it into Vdecadent free vibration, andan electric translation pick-up adjacent the reed, said pickup having a tone producing portion located alongside and .being vibratorily passed by a longitudinally intermediate edge portion of the reed, being of an eiective thickness, `in the direction `of reed vibration, smaller than the-high-amplitude stroke ofsaid edge portion of the reed, and being oiset in saiddirection from effective alignment with the rest position ofthe reed.

3. The combination claimed in claim 1, wherein said edge portion of the reed is located substantially at ia node for .a lower one of the upper partials ofthe free vibration of the reed. i i Y 4. The combination claimed rin claim 1, wherein said edge portion of rthe reed is substantially nodal `for the second partial of the kfree vibration of the reed.

5. The combinationclairned in claiml, wherein said edge portion -of the reed is substantially nodal for Ythe second partial of the free vibration of the reed and wherein, in the direction of reed vibration, said pickup portion has an effective mid-pointoffset from the rest position of the eifective mid-point of said vedge portion of the reed. i

6. In combination in anelectrical musical instrument, a mechanical system comprising a fixed-free reed and an impulse exciting means comprising a key actuated harnmer adjacent the reed selectively engageable with the .findividual reed for setting it into decadent free vibration, an electric translation pick-up adjacent the reed, said pickeup havinga tone producing portion located alongside and being vibratorily passed by a longitudinally intermediate edge portion of the reed and being of an effective thickness, in the direction of reed vibration, smaller than the high-amplitude stroke of said edge portion of the reed, and means comprised in said mechanical system for at least substantially eliminating from the free vibration of the reed ailower one of `itsnormally present upper partials.

7. The combination claimed in claim 6, wherein said edge portion of the reed is substantially -nodal -for 4 another lower one of the lupper partialsrof the free vibration of the reed.

8. In combination vin an electrical musical instrument,

a ,ixed-freerced, an impulse Iexciting means adjacentthe reed andeffeotive thereon substantially ata node yfor one of the two lowest of the upper partials of the free vibration of the reed for setting the reed into decadentfree vibration, and an ,electric translation pick-up -adjacent the reed, said ,pickup having a tone producing portion located alongside and being vibratorily passed by alongitudinally lintermediate edge portion of the reed and being of an effective thickness, in the direction of reed vibration, smaller than the lhigh-amplitude stroke of said edge portion o-f the reed, saidedge vportiono'f ,the reed 4being substantially .nodal for the other offsaid two lowest upper partials. l

9. In combination in a musical instrument, a iixed-free reed,`singleimpulse exciting means comprising akey actuated hammer selectively engageable with ,the individual reed for setting it into decadent .freevibratiorn a mechanico-electrical system consisting of a portion of the reedand pick-upimeans associated with and influenced 'by said portion -for translatinglelectric oscillations from the reed vibrations, 4means comprised in said mechanico- `electrical system forat least substantially eliminatingfrom said oscillations aninharmonic component corresponding toa lowerone of the Aupper partials V at which the reed `tends to vibrate, and means `also comprised in said mechanico-electrical system `for introducing into the oscillations translatedfrom v`the fundamental reed vibrations Va series of upper partials harmonically related thereto.

110. `combination in a musical ins trument, a mechanical system comprising axed-free reed and single-impulse exciting means for setting it into decadent free vibration, a mechanicofeleotrical system consisting of aportion of said reed and pick-up means associated with and V,inuencedby said portion for translating electricoscillations'frorn the reed vibrations, means comprisedin `Said Amechanical system for at least substantially eliminating from said oscillations an inharmonic component corresponding to one ofthe two lowest ofthe upper partials at which the reed tends to vibrate, means comprised in said mechanico-electrical system for at least substantially eliminating from said oscillations an inharmonicvcomponent corresponding to the other of said two partials, .and means also comprised in said mechanicofelectrical system for introducing into the oscillations `translated fronithe fundamental reed vibrations ,a Aseries of upper partials Yharmonically related thereto.

References Cited in the ile of this patent UNITED STATES PATENTS 1,016,094 Richmond Jan. 30,1'912 1,853,728 VGranstrom Apr. 12,1932 1,906,250 Devol jMayn2, 193.3 l1,906,985 Morrison May2, 1933 1,915,858 Miessner June 27,y 1933 1,947,020 Ranger Feb. `13, 1934 2,015,014 Hoschke Sept. 17, 1935 2,201,388 Curtis May 21, `1940 2,261,346 Demuth Nov. 4, `17941 2,275,252 Demuth Mar. 3, 1942 2,318,936 Fisher yMay 11, `11943 2,413,062 Miessner Dec. y24,V 1.946 2,414,886 Miessner Jan. 28, 1947 2,462,531 Minshall Feb. 22, v1949 2,540,327 Felici Feb. `6, 1951 2,581,963 Langloys Jan. v8,1952 2,622,467 lKunz D,ec.'23, 1952 2,656,755 Miessner Oct. 27,"1953 l2,724,819 Peterson Nov. 22,*1955 YOTHER i REFERENCES VPublication Musical Engineering by Olson, Mc'raw- Hill (c) .1952, pgs. 76, 77, 2 22 and 223, received Library US. Patent, September 23, 1952.

Images