US2032044A - Electrical musical instrument - Google Patents

Description

Feb. 25, 1936. L. E. A. BOURN ELECTRICAL MUSICAL INSTRUMENT Filed Jan. 31, 1935 e Sheets-Sheet 1 Feb. 25, 1936. I L. E. A. BOURN 2,032,044

ELECTRICAL MUS I CAL INSTRUMENT Filed Jan. 31, 1935 6 Sheets-Sheet 2 F g wrilwaa jzsuifilm/vflzamwpm 500/? AVVDF/V Feb. 25, 1936. v E. A. BOURN 2,032,044

ELECTRICAL MUSICAL INSTRUMENT Filed Jan. 31, 1935 6 Sheets-Sheet 3 47/197704 lisurfblmvflzamlwzaiaamv @4.

Feb. 25, 1936. E. A. BOURN 2,032,044

ELECTRICAL MUSICAL INSTRUMENT Filed Jan. 31, 1935 6 Sheets-Sheet 4 j Fighi.

Feb. 25, 1936. L. E. A. BOURN 2,032,944

ELECTRICAL MUSICAL INSTRUMENT Filed Jan. 31, 1935 6 Sheets-Sheet 5 L. E. A. BOURN ELECTRICAL MUSICAL INSTRUMENT Feb. 25, 1936,

Filed Jan. 31, 1935 6 Sheets-Sheet 6 Patented Feb. 1936 UNITED STATES PATENT OFFICE ELECTRICAL MUSICAL INSTRUMENT Application January 31, 1935, Serial No. 4,242 In Great Britain February 8, 1934 15 Claims.

This invention relates to electrical musical instruments and refers more particularly to electrical musical instruments in which each note is produced by an undulating electrical potential generated by the relative rotation of two parts one of which carries a wave or undulating form and the other a scanning form for scanning said wave form.

The object of the invention is the provision of means for compensating for constructional inaccuracies in connection with said two parts, and the invention consists broadly in the arrangement that both the wave or undulating form and the scanning form are repeated at intervals 15 wholly or partly around a circle about the axis of relative rotation, the distance apart of the wave forms and that of the scanning form's being equal or one being a multiple of the other.

In order that the invention may be more clearly understood, certain apparatus in accordance therewith will now be described, reference being made to the accompanying drawings wherein:-

Figure 1 is a plan of a single primary element for use in an apparatus for producing undulating potentials by electrostatic induction, for generating notes in an organ operating on the principle disclosed in my prior specification Serial Number 712,724, Patent No. 1,996,669 of April 2, 1935, said single primary element being adapted to generate one note.

Figure 2 is a plan of that portion of a secondary element, common to a set of such primary elements, which is adapted to immediately overlie said single primary element.

Figure 3 is a plan, partly broken away and with the elements in the space a: being omitted for the sake of clearness, of one of the sets of pri- 40 mary elements.

Figure 4 is a similar plan of the whole secondary element adapted to overlie said set, the part of said secondary element covering the space J being omitted for the sake of clearness.

Fig. 5 is a sectional side elevation illustrating a set of primary elements and a set of secondary elements in assembled relation.

Fig. 6 illustrates a modified form of secondary element.

50 Fig. 7 illustrates another modified form of secondary element.

Fig. 8 illustrates another modified form of secondary element.

Fig. 9 illustrates another modified form of secondary element.

Fig. 10 illustrates a modified form of primary element.

Fig. 11 illustrates another modified form of primary element.

Fig. 12, which is identical with Fig. 1 of my Reissue Patent No. 19,702, dated September 17, 1935, is a fundamental diagram of connections illustrating the manner of generation of each individual partial note.

Fig. 13, which is identical with Fig. 2 of said reissue patent, illustrates the correlation between the generators for six octaves of a given note (together with their partials) and the six corresponding keys of the key board. For the sake of simplicity the number of primary elements in the set shown in this figure is reduced from that shown in Fig. 3.

Fig. 14, which is identical with Fig. 3 of said reissue patent, illustrates the operation of the stops for predetermining the quality of the notes.

In my said Patent No. 1,996,669 an arrangement is disclosed in which the undulating potential for producing each note is generated by means of a generator consisting of a ring of conducting material having an undulating form and a scanning electrode which revolves about the axis of said ring keeping close thereto. When the undulating ring is connected to a source of potential, an undulating potential will be electrostatically induced on the scanning electrode of a frequency depending on the speed of rotation of said electrode and the distance apart of the undulation of the ring. This undulating potential is applied through a common amplifier to a loud speaker and a musical note, whose pitch depends on said frequency is accordingly produced.

For said prior arrangement the undulating rings required for the whole instrument are arranged in a number of identical sets, the rings of each set being co-planar and concentric with one another, being mounted on a common insulating disc. A common scanning electrode serves for each set, said electrode taking the form of a radial arm rotating about the axis of the set and passing close to the surface of all the rings. By a system of stops and keys the required undulating rings are connected to the source of potential and the required notes are accordingly produced by the loud speaker.

It has, however, been found exceedingly difiicult in practice to free the output from variations and irregularities due to constructional inaccuracy. For example if the axis of rotation of the scanning electrode should be slightly out of line with the axis of the undulating rings the electrode will pass slightly closer to the surface of the rings on one side than on the other and the notes produced will accordingly have an undesirable rise and fall of intensity. The same thing will occur if the disc on which the undulating rings are mounted should be slightly out of plane. Again if there should be any slight inaccuracy in the wave form of a ring at any part of its circumference this will produce a corresponding variation in the note produced.

In accordance with the apparatus now to be described with reference to the accompanying drawin Figure 1.

ings, these and other constructional inaccuracies are compensated for by constructing the scanning element with a portion proper to, and adapted to overlie, each primary element or undulating ring, said portion carrying a scanning form which is repeated at intervals equal to the wave length of the primary element which it overlies, so that as said scanning element rotates, the scanning forms of such portion are alternately in phase and out oi phase with the wave forms of the primary element which it overlies at a frequency depending on the distance apart of the wave forms of said primary element and the speed of rotation. Thus in Figure 1, the reference l designates an individual primary element or undulating ring and in a Figure 2 the reference 2 designates the portion of the scanning element which is proper to, and adapted to overlie the primary element illustrated The said portion 2 of the scanning element comprises a number of short radial scanning forms or member 21:. extending between ring supports 2b. These short radial scanning members 2a are spaced apart by a distance equal to the Wave length of the primary element i and the ring supports 21) have radii respectively just greater than the maximum, and just less than .the minimum, radii of the primary element i.

As in the disclosures of the prior patent aforesaid the individual primary elements l are arranged in concentric sets each of which sets comprises the primary elements for all the octaves of one note together with the partials thereof, so that there are in all twelve sets of primary elements for the complete musical scale. Also as in said prior patent a common scanning electrode is employed for each set of primary element. One of said sets of primary elements is shown in Figure 3 and it will thus be seen that in the present arrangement the common scanning electrode takes the form, as shown in Figure 4 of a grid consisting of a number of concentric ring supports 2b which are superimposed over the respective spaces between the undulating rings l and a set of short radial scanning members 2a extending between each adjacent pair of these concentric rings, the short radial scanning member 2a of each set lying transversely over a respective undulating ring l and these scanningmembers being spaced as stated by a distance equal to the wave length of this ring.

It is clear that if any undulating ring 5 is ener= gized an undulating potential will be electrostatically induced on the common scanning electrode by virtue of said ring being scanned by the set of scanning members 2a .which lie over it; and as these scanning members are spaced apart a distance equal to the wave length of this ring, all of them will be at the same position relative to a wave formation at any given moment and the inaccuracies such as those above referred to will not have any resultant efiect on the potential induced on the common scanning electrode. Thus if the scanning members 2a are slightly closer to the ring I on one side than the other this will not affect the mean distance of all of said scanning members from the undulating ring. Again if certain of the wave forms of a ring varies slightly from others this will not produce any irregularity in the potential induced in the common scanning electrode as each wave form is continuously being scanned and never ceases to be operative. The concentric rings 2b of the common scanning electrode between which the scanning members 2a extend will equally have no eflect on the induced potential, and the out of phase scanning members 2a which do not lie immediately above the undulating rings l under consideration are also without substantial effect on the potential induced by said undulating ring.

In practice the undulating rings l are formed by first providing the insulating disc 3 with a coating of graphite, then dividing this coating into rings by means of longitudinal sine wave cuts a of the required wave length. Each ring I is constituted as shown by the graphite strip between two of said cuts a of the same wave length and in phase with one another. The graphite strips 6 located between the rings 1! are rendered inefiective by being earthed.

The concentric rings 2b and radial scanning members 2a of the grid electrode are formed of graphite located in channels engraved upon a disc 5 of insulating material. Thus the circular and radial channels of the required grid form having been engraved on the disc 5, the graphite is first coated over the whole disc after which the surface is rubbed down for removal of all the graphite except what is lodged in the channels.

It will be appreciated that although the fullest compensation is obtained by a complete set of the short radial scanning members 2a for each undulating ring I as described, a measure of compensation will be obtained by less than complete set of such scanning members 2a. For example, a high degree of compensation will be obtained by providing half the number of scanning members 20. spaced apart by a distance equal to twice the wave length of the corresponding ring as shown in Fig. 6. Indeed a considerable measure of compensation will be effected by providing only two scanning members 2a for each undulating ring I, located diametrically opposite to each other as shown in Fig. 7. Again, in some cases it might be preferred to arrange the scanning members 2a for each undulating ring I in two diametrically opposite groups as shown in Fig. 8, those of each group being spaced apart by a distance equal to the wave length, or in two pairs of diametrically opposite groups as shown in Fig. 9, the essential in every case being that the scanning members are in phase with the wave forms of the ring being scanned.

In like manner, where a complete set of scanning members 211 are employed for each undulating ring l, less than a complete set of undulations could be employed. Thus in Fig. 10 a ring I is shown having only two diametrically opposite undulations. In theory a single undulation would be sumcient if a complete set of scanning members 2a were provided but in practice this would produce variations similar to those produced when only one scanning member is employed for aosaou rangement would thus not come within the scope of the present invention.

In the arrangement of said prior patent each primary element I constitutes a complete ring and a number of rings of identical wave length are included in each set for the different partials of different octaves which are of the same pitch. This arrangement is usually preferred, but in ac cordance with the present invention it may be varied by employing a complete grid having a complete set of radial scanning members M for each undulating ring as in Figure 4, and dividing each undulating ring into twice as many insulated arcuate portions as there are partials requiring the frequency of said ring, and each primary element may be constituted by an electrically connected opposite pair of such arcuate portions, so that compensation for structural inaccuracy will be afforded as heretofore described.

In this way considerable economy of space will be effected, as all the primaries of identical wave length will be constituted by mutually insulated arcuate portions of the same ring. Thus Fig. 11 shows a single ring of the same wave length as that of Fig. 1 which has been divided in the man'- ner described so as to constitute two separate primary elements each having the same wave length, this being on the assumption that there are two partials of different octaves which are of the pitch represented by said wave length. As shown this ring comprises two diametrically opposite pairs of arcuate undulating portions, the portions of each pair being electrically connected together and insulated from those of the other.

It will be appreciated that the system of keys, stops and bus bars is the same as in the prior specification aforesaid. Thus referring to Fig. 12, which is identical with Fig. 1 of my Reissue Patent No. 19,702, dated September 1'7, 1935, each whole secondary element, represented diagrammatically at x, is connected to a common amplifier 6 which supplies a loud speaker I and when one of the undulating rings I in inductive relation to said secondary element is connected to a source of potential an undulating potential will be electrostatically induced on said secondary element of a frequency depending on the speed of rotation of said secondary element and the distance apart of the undulations of the ring I.

This undulating potential will be applied to the.

amplifier 6 and a musical note, whose pitch depends on the said frequency and whose intensity depends on the potential to which the ring was raised, will be emitted from the loud speaker 1.

The source of potential may be any suitable source and the connection of said ring I to said source is through the medium of a bus bar 8 adapted to be connected to the ring I by means of a contact 9 on a key I and adapted to be connected to said source by means of a contact I I on a stop I2.

In the arrangement being described by way of example we will suppose there are seventy-two keys, that is to say the keys for six octaves of each of the twelve notes of the tempered scale. Each of the octaves in the arrangement being described is capable of being produced with eight partials though in practice this number would probably be increased.

In practice the rings I for the partials of all six octaves of each note are included in one set so that there are in all twelve sets of rings I each set having associated with it six keys I0. One such set of rings I together with the associated six keys I II is illustrated in Fig. 13, which is identical with Fig. 2 of my reissue patent aforesaid.

In practice each set of generators is made identical and the whole tempered musical scale is covered by rotating the successive secondary elements of each set at a speed of 12 /2 times that of the preceding.

Each of the six keys I0 associated with each set of rings is provided with eight contacts 9 for the eight partials of the octave represented by that particular key, each contact 9 being connected to the appropriate ring as illustrated in Figure 12.

Eight of the bus bars 8 are provided which are common throughout the whole scale and it will be seen from Figure 12 that when any key I0 is depressed all of its contacts 9 will be connected to respective bus bars, the first to the first bus bar, the second to the second bus bar and so on.

Thus the note appertaining to that key will be produced in a quality which depends upon which of the eight bus bars are energized.

The energization of the bus bars is controlled by the stops i2. Each of the stops I2 has a number of contacts II each connected to the source of potential, which contacts II when the stop is drawn, engage with, and effect energization of, selected ones of the bus bars 8 according to the quality of notes which it is required to be produced by the keys. A stop I2 is illustrated by way of example in Figure 14, which is identical with Fig. 3 of my reissue patent aforesaid, which upon depression eflects energization of the first, third and seventh of the bus bars 8 so that when this stop is drawn the subsequent depression of each key III will sound the first, third and seventh partial of the note appertaining to that key.

Each bus bar 8 is permanently connected to earth through a resistance I3 of say 100,000 ohms and its connection to the source of potential by each contact II is through an independent path including a resistance I5 of the same order. Thus when the bus bar 8 is energized through two different contacts I I simultaneously, owing to two different stops I2 being simultaneously actuated,

its potential will be higher than if it were energized through only one of said contacts and thus the correct additive effect will be obtained.

Each contact 9 is connected to its proper ring I through an adjustable resistance I6 and a leak 20 of say 20 megohms in series, a leak 2i of say 5 megohms extending to earth from a point between said resistance I6 and leak 20, and a condenser I8 being connected between the earth and the ring I.

Fig. 5 illustrates the structional details of one of the generator units showing the rings I mounted on the insulating disc 3, and the secondary element mounted on the disc 5 rotatable about the common axis of the two discs. As shown said d'sc 5 is mounted on a spindle 22 carrying a driving pulley 23.

What I claim and desire to secure by Letters Patent is:-

1. In an electrical musical instrument, an electrostatic generator adapted to electrostatically induce a varying potential for producing a single individual sound tone, comprising two relatively rotatable electrodes in electrostatically inductive relation, one of which constitutes a plurality of wave forms and the other a plurality of scanning forms therefor, both said wave and scanning forms being repeated about the axis of relative rotation at such intervals that, at any given moment, the wave and scanning forms of every constitutes a plurality of wave forms, and a pluinductively cooperating pair are at the same re tion.

2. In an electrical musical instrument, an elec trostatic generator adapted to electrostatically induce a varying potential for producing a single individual sound tone, comprising two relatively rotatable electrodes axially spaced and at a substantially common radius so as to be in electrostatically inductive relation, one of which constitutes a plurality of wave forms and the other a plurality of scanning forms therefor, both said wave and scanning forms being repeated about the axis of relative rotation at such intervals that at any given moment, the wave and scanning forms of every inductively cooperating pair are at the same relation.

3. In an electrical musical instrument, an electrostatic generator adapted to elecn'ostatically induce a varying potential for producing a single individual sound tone, comprising two relatively rotatable electrodes in electrostatically inductive relation, one of which is constituted by a ring of undulating form concentric with the axis of relative rotation and the other of which comprises a plurality of scanning members arranged so as to scan said ring as relative rotation takes place, said scanning members and the undulations of the ring being at such intervals that, at any given moment, the undulation and the scanning member of every inductively cooperating pair are at the same relation.

4.. In an electrical musical instrument, an electrostatic generator adapted to electrostatically induce a varying potential for producing a single individual sound tone, comprising two relatively rotatable electrodes in electrostatically inductive relation, one of which is constituted by a ring of undulating form concentric with the axis of relative rotation and the other of which comprises a plurality of scanning members spaced axially from, and at substantially the same radius as, said ring so as to be adapted to'scan said ring as relative rotation takes place, said scanning members and the undulations of the ring being at such intervals that, at any given moment, the undulation and-the scanning member of every inductively cooperating pair are at the same relation.

5. In an electrical musical instrument, an electrostatic generator unit adapted to electrostatically induce varying potentials for producing a plurality of individual sound tones, comprising two relatively rotatable parts, a plurality of electrodes carried by one of said parts, each of which electrodes constitutes a plurality of wave forms, and a plurality of sets of electrically connected scanning forms carried by the other part for scanning the respective wave form electrodes in inductive relation therewith, both the wave and scanning forms of each inductively cooperating wave form electrode and scanning form set being repeated about the axis of relative rotation at such intervals that, at any given moment, the wave form and scanning form of every inductive ly cooperating pair are at the same relation.

6. In an electrical musical instrument, an electrostatic generator unit adapted to electrostatically induce varying potentials for producing a plurality of individual sound tones, comprising two relatively rotatable parts, a plurality of elec trodes carried by one of said parts in a common plane at right angles to the axis of relative rotation and at diilerent radii with respect to said axis of relative rotation, each of which electrodes rality of sets of electrically connected scanning forms, for the respective wave form electrodes, carried by the other part in another common plane at right angles to said axis of relative rotation and at substantially the same radii as the respective wave form electrodes so as to be adapted to scan the same in electrostatically inductive relation, both the wave and scanning forms 01 each inductively cooperating wave form electrode and scanning form set being repeated about the axis of relative rotation at such intervals that, at any given moment, the wave form and scanning form of every inductively cooperating pair are at the same relation.

'7. In an electrical musical instrument, an electrostatic generator unit adapted to electrostatically induce varying potentials for producing a plurality of individual sound tones, comprising two relatively rotatable parts, a plurality of rings of undulating form carried by one of said parts concentric with the axis of relative rotation and at difierent radii in a common plane at right angles to said axis of relative rotation, and a plurality of sets of electrically connected scanning members for scanning the respective undulating rings in electrostatically inductive relation, carried by the other part in another common plane at right angles to said axis of relative rotation and at substantially the same radii as the respective rings, both the undulations and the scanning members of each inductively cooperating ring and set of scanning members being repeated about the axis of relative rotation at such intervals that, at any given moment, the undulation and the scanning member of every inductively operating pair are at the same relation.

8. In an electrical musical instrument, an electrostatic generator unit adapted to electrostatically induce varying potentials for producing a plurality of individual sound tones, comprising two relatively rotatable parts, a plurality of electrodes electrically insulated from one another carried by one of said parts, each of which electrodes constitutes a plurality of wave forms, and a plurality of sets of scanning forms all electrically connected to one another carried by the other part for scanning the respective wave form electrodes in inductive relation therewith, both the wave and scanning forms of each inductively cooperating wave form electrode and scanning form set being repeated about the axis of relative rotation at such intervals that, at any given moment, the wave form and scanning form of every inductively cooperating pair are at the same relation.

9. In an electrical musical instrument, an electrostatic generator unit adapted to electrostatically induce varying potentials for producing a plurality of individual sound tones, comprising two relatively rotatable parts, a plurality of rings of undulating form carried by one of said parts in insulating relation to each other concentric with the axis of relative rotation and at different radii in a common plane at right angles to said axis of relative rotation, and a plurality of sets of scanning members, for scanning the respective undulating rings in electrostatically inductive relation, carried by the other part in conductive relation to one another in another common plane at right angles to said axis of relative rotation and at substantially the same radii as the respective rings, both the undulations and the scanning members of each inductively cooperating ring and set of scanning members being repeated about the axis of relative rotation at such intervals that, at any given moment, the undulation and the scanning member of every inductively cooperating pair are at the same relation.

10. In an electrical musical instrument, an electrostatic generator unit adapted to electrostatically induce varying potentials for producing a plurality of individual sound tones, comprising two relatively rotatable parts having respective insulating surfaces in proximity to each other, a plurality of electrodes constituted by separated portions of a thin metallic layer on one of said surfaces, each of which electrodes constitutes a plurality of wave forms, and a plurality of sets of electrically connected scanning forms constituted by a metallic substance in grooves on the other surface for scanning the respective wave form electrodes in electrostatically inductive relation thereto, both the wave and scanning forms of each inductively cooperating wave form electrode and scanning form set being repeated about the axis of relative rotation at such intervals that, at any given moment, the wave form and scanning form of every inductively cooperating pair are at the same relation.

11. In an electrical musical instrument, an electrostatic generator unit adapted to electrostatically induce varying potentials for producing a plurality of individual sound tones, comprising two relatively rotatable parts having respective insulating surfaces at right angles to the axis of relative rotation and in proximity to one another, a plurality of rings of undulating form concentric with the axis of rotation and constituted by divided portions of a thin metallic layer on one of said surfaces and a plurality of sets of electrically connected scanning members for the respective rings constituted by a metallic substance in grooves in the other surface, both the undulations and the scanning members of each inductively cooperating ring and set of scanning members being repeated about the axis of relative rotation at such intervals that, at any given moment, the undulation and the scanning member of every inductively cooperating pair are at the same relation.

12. In an electrical musical instrument, an electrostatic generator unit adapted to electrostatically induce varying potentials for producing a plurality of individual sound tones, comprising two relatively rotatable parts having respective insulating surfaces in proximity to each other, a

plurality of electrodes in insulated relation to one another constituted by separated portions of a thin metallic layer on one of said surfaces, each of which electrodes constitutes a plurality of wave forms, and a plurality of sets of scanning forms all in conductive relation to one another constituted by a metallic substance in grooves on the other surface for scanning the respective wave form electrodes in electrostatically inductive relation thereto, both the wave and scanning forms of each inductively cooperating wave form elec- 'trode and scanning form set being repeated about the axis of relative rotation at such intervals that, at any given moment, the wave form and scanning form of every inductively cooperating pair are at the same relation.

13. In an electrical musical instrument, an

electrostatic generator unit adapted to electrostatically induce varying potentials for producing a plurality of individual sound tones, comprising lated relation to one another concentric with the .axis of rotationand constituted by divided portions of a thin metallic layer on one oi said surfaces, anda plurality of sets of scanning members for the respective rings all in conductive relation to one another constituted by a metallic substance in grooves in the other surface, both the undulations and the scanning members of each inductively cooperating ring and set of scanning members being repeated about the axis of relative rotation at such intervals that, at any given moment, the undulation and the scanning member of every inductively cooperating pair are at the same relation.

14. In an electrical musical instrument, an electrostatic generator unit adapted to electrostatically induce varying potentials for producing a plurality of individual sound tones, comprising two relatively rotatable parts having respective insulating surfaces at right angles to the axis of relative rotation and in proximity to one another, a plurality of rings of undulating form in insulated relation to one another concentric with the axis of rotation and constituted by divided portions of a thin metallic layer on one of said surfaces, and a plurality of sets of scanning members for the respective rings constituted by a metallic substance in grooves in the other surface and all in conductive relation to one another by virtue of extending between concentric conducting rings also constituted by a metallic substance in grooves in the other surface, both the undulations and the scanning members of each inductively cooperating ring and set of scanning members being repeated about the axis of relative rotation at such intervals that, at any given moment, the undulation and the scanning member of every inductively cooperating pair are at the same relation.

15. In an electrical musical instrument, an electrostatic generator unit adapted to electrostatically induce varying potentials for producing a plurality of individual sound tones, comprising two relatively rotatable parts having respective insulating surfaces at right angles to the axis of relative rotation and in proximity to one another, a plurality of rings of undulating form in insulated relation to one another concentric with the axis of relative rotation and constituted, together with intermediate permanently earthed ring portions, by dividing a thin metallic layer on one of said surfaces, and a plurality of sets of scanning members for the respective rings all in conductive relation to one another constituted by a metallic substance in grooves in the other surface, both the undulations and the scanning members of each inductively cooperating ringandsetofscanningmembersbeingrepeated about the axis of relative rotation at such intervals that, at any given moment, the undulation and the scanning member of every inductively cooperating pair are at the same relation.

LEI-II EDWIN ALEXANDER HOUR-N.

Images