US2089171A - Electrical stringed musical instrument - Google Patents

Description

Allg- 10, 1937- G. D. BEAUCHAMP 2,089,171

ELECTRICAL STRINGED MUSICAL INSTRUMENT Filed June 2, 1934 5 Sheets-Sheet l 4. 4,. "ff, "ll//f/l/ Aug. 10, 1937. G. D. BEAUCHAMP ELECTRICAL STRTNGED MuscAL INSTRUMENT 3 Sheets-Sheet 2 Filed June 2, 1934 Aug. 10, 1937. G. D. BEAUCHAMP ELECTRICAL STRINGED MUSICAL INSTRUMENT s sheets-sheet 5 Filed June 2, 1934 l y l .9.

Patented Aug. 1o, 1937 PATENT OFFICE ELECTRICAL STRINGED MUSICAL INSTRUMENT George D. Beauchamp. Los Angeles, lCalif., aslsignor to Electro String Instrument Corporation, Los Angeles; Calif., a corporation of California Application June z, 1934, serial 10,128,711

21 Claims.

This invention relates to musical instruments and it is a general object of the invention to provide a simple, practical and improved elecl musical instrument in which the vibrations of the sound producing elements or strings directly vary the reluctance of a magnetic circuit to induce an electric current in a coil within the magnetic neld, which current is suitably ampliiled l y and transformed into sounds as true reproductions oi.' the sounds produced by the vibrations of the strings. In the present invention the true sound of the vibratory string withall its char.- acteristics is accurately reproduced without the extraneous sounds and vibrations produced by instruments or devices in which a mechanical part is made to vibrate through its mechanical association with the vibratory string.

Another object of the invention is to provide 2;, an electrical musical instrument of the character mentioned including a novel, simplified and particularly effective electro-magnetic pick-up unit for converting the vibrations of the strings' into an electric current having the characteristics of 30 the string vibrations; f

Another object of the invention is to provide an electrical musical instrument oi the character mentioned including a single electro-magnetic pick-up unit for transforming the vibra- 35 tions of the several strings'of the instrument into an electric current. In the devicex of the present invention the vibrations of each of the several strings affect or vary the reluctance oi.' the magnetic circuit of a single permanent magnet 4o unit to induce an electric current in a coil superf imposed on the magnet, and the single unit is not subject to the variations necessarily inherent in devices involving a plurality of electro-magnetic 45 Another object of the invention is to provide an electrical musical instrument that does not depend upon a sound board, resonance box, or the lilrein the production or propagation of the sound of the`\desired quality, whereby the body of the 50-instrument may be.of simple, 'inexpensive construction.

Another .object of the invention is toy provide a musical instrument of the character mentioned having tensionedl vibratory strings of different 55 diameters and including ajsingle electro-magnetic pick-up unit constructed and designed to deliver an electric current to an amplifier which current is properlyand truly characteristic ci the vibrations oi the several strings.

Another object of the invention is to provide an electrical stringed musical instrument that is adapted to be played manually in any typical or desired manner and electrically reproduce the sound or music at a remote point.

Another object of the invention is to provide an electrical musicalinstrumentvoi the character mentioned that may be easily and conveniently adjusted by the vmusician'orplayer to vary the volume of the music or sound produced.

Another object oi the invention is to provide an improved electro-magnetic pickup unit'capable of embodiment in stringed musical instrume'nts of various characters with little or no modiilcation.

A further object of the invention is to provide an electrical stringed musical instrument of the character 'mentioned that is small and compact Other objects and features of the invention will be better and more fully understood from the following detailed description of typical forms and applications of the invention, throughout which description reference may be had to the accompanying drawings, in which:

Fig. 1 is/ a top or plan view of one typical embodiment of the present invention. Fig. 2 is an enlarged, transverse, detailed sectional view of the pickupr unit and body taken as indicated by line 2-2 on Fig. 1. Fig. 3 is an enlarge'd plan elevation of the main portion of the body with the magnets in cross-section, being a view taken as indicated by line 3--3 on Fig. 2.` Fig. 4 is a transverse detailed sectional view taken as indicated by Vline 4-4 on Fig. 3. Fig. 51s an en larged fragmentary `detailed sectional view taken as indicated by line 5-5 on Fig. 1. a fragmentary detailed sectional view of the body showing the socket and illustrating the plug in position to enter the socket. Fig. 7 is a Wiring diagram of the circuit involved in the present invention. Fig. 3 yis an elevation view of the present invention embodied in a. stringed musical instrument having a wooden body. Fig. 9 is a diagrammatic view illustrating the non-uniform magnetic iields of the pick up unit and Fig. l0 is an enlarged fragmentary diagrammatic View illustrating a. portion of one pole portion Fig. 6 is of the magnet and a portion of one core membert 'I'he instrument provided by the present invention includes, generally, a. body I Il, a plurality of sound propagating elements or tensloned strings II on the body I0, an electric magnetic pickup unit I2 on the body I0 for transforming vibrations of the strings Il into an induced electric current, and an amplifying unit or system I3 for amplifying the` pulsations in said current and converting them into sounds which are the 10 true sounds of the strings II.

The body Il) may be varied considerably in size. shape and construction, and may be constructed of various materials without departing from the spirit of the invention. In the lparticular form l of the invention in Figs. 1 to 7, inclusive, of the drawings, the body III is a simple integral casting of metal, such as aluminum or the like, and comprises a major or main portion I4 and a neck I5. The main portion Il of the body is sub- 20 stantially disc shaped, having flat upper and lower sides and a curved or cylindrical periphery.

The neck I5 projects radially with respect to the center of the portion I4 and is of gradually diminishing cross-section. The neck I5 has a with spaced frets I1. The-underside of the neck I5 may be convex or rounded as illustrated in Fig. 4. The body II) may be hollow-as shown in the drawings to be light in weight, it being uni derstood that in some instances it may be desirable to make the body I0 solid.`

The strings II are the sound vibration producing elements of the instrument and are adapted lto be manually plucked or otherwise manipulated to produce the desired vibrations. The strings Il extend diametrically across the top oi' the body portion Il and over the fingerboard IB to the outer end of the neck. In theparticular instrument illustrated there are six spaced strings Il in a substantially parallel series. The plurality of strings II preferably lie in the same plane, that is, their central longitudinal axes are in or adjacent a common plane. 'I'he strings II pass over a bridge I8 on the main portion Il of the body and over a similar bridge I9 on the outer portion of the neck I5. The inner ends of the strings are suitable secured in openings 20 adjacent the bridge I8 and the strings have their outer ends engaged by securing and tensioning keys 2I. The portions of the strings II extending between the bridges I8 and I! are under various degrees of tensile strain and are free to vibrate in the production of recognized musical tones. It is to be noted that the oppo- 55 site ends of the strings I I are rigidly and un yleldingly connected to the rigid metallicbody Il so that their major portions may have long periods of vibration with no dampening action due to the absorption of the vibrations by wooden 60 body parts or the like at the ends of the strings.

In accordance with the usual practice in instruments of the class illustrated the strings II are graduated in diameter. The strings II are formed wholly or in part of conducting material 65 or magnetic material having a different degree of magneticpermeability than the surrounding air to properly influence or an'ect the reluctance of the magnetic field in the unit I2.

,The pick-up unit I2 is a magnetic or electro- 70 magnetic device for converting the actual tone producing vibrations of the strings II into an induced electric current. The frequencies and the other characteristics'of the vibrations of the strings II which maybe termed the physical 75 properties or the sound produced by the strings fiat upper side forming a fingerboard IB providedA are represented in the electrical circuit in a proportional or deiinite manner with relation to the actual physical vibrations of the strings so that the amplifying unit I3 is actuated by or influenced by the physical properties of the sound to faithfully and accurately reproduce' the sound. The pick-up unit I2 comprises a magnet which, in practice, may be a of like opposed permanent magnets 22. The magnets are U-shaped or of horse-shoe design and are attached to a supporting plate 23. T'he opposed lower or inner arms A of the magnets 22 have their lower sides resting on the plate 23 and the arms A are attached to the plate by suitable screws 24. In accordance with the invention the ends of the magnets 22 are in opposed relation with their poles north to north and south to south,y as indicated in the drawings. This provides a continuous polarity at the opposite sides of the magnet or magnet unit. In the preferred construction the confronting or opposed ends of the magnets 22 are in spaced relation.

An opening 25 is provided in the top or upper side of the body portion Il to receive the pickup unit I2. The plate 23 carrying the magnets 22 is inserted in the opening 25 and studs or bolts 26 project upwardly from the opposite ends of the plate to extend through openings in plates 21 on the body. The plates 21 may carry sleeves 28 for receiving the bolts 2i. It is preferred to mountor support the unit I2 so that it may be adjusted and accurately set with relation to the strings II. Nuts 29 are threaded on the outer ends of the bolts 26 and bear against the outer sides of the plates 21. The nuts 25 may be tightened down to adjust or shift the unit l2 outwardly. Springs III surround the bolts 2E and are arranged under compression between the plate 23 and the plates 21 to normally urge the unit inwardly and hold it against movement.

With the unit I2 mounted or supported as-just described the pair -of opposed -magnets 22 are disposed transversely of the series of strings II and their upper or outer arms B are spaced above the top surface of the body.' The strings Il pass under the magnet arms B with considerable clearance. A'The strings Il pass through the magnetic field of the magnets 22. The outer arms B of the magnets may be slightly inclined toward their opposing ends to compensate for the widened magnetic field at their poles or ends. The above described inclination of the magnetic arms B is such that the spaces between the arms and strings vary substantially-in proportion to the intensity of the magnetism of said arms. l

The pickup unit I2 includes a coil C arranged on or superimposed on the permanent magnet. The coil C is supported on the inner arms A of the pair of magnets 22 and is to receive an induced, electric current when the reluctance of Y the field of the magnet or magnet unit is varied.

The coil C includes a coil form or spool 3i having spaced upper and lower flanges 32. A winding 33 of suitable enameled wire is provided on the spool )I between the flanges 32. The spool 3| is formed of a suitable insulating material. The number of turns In the winding 23 and the gauge of the wire of the coil depends upon the particular amplifying unit I3 with which the instrument is to be used. In accordance with the invention the coil C is positioned between the north and south poles of the magnet and is related to the strings II. to be influenced or affected by their vibration in the' magnetic field.

' make the members 35 in the form of posts or pins as illustrated throughout the drawings. The lower ends of the pins rest on or engage the lower arms A of the magnetswhile the upper ends of the pins project from the spool 3I. 'I'he upper ends of the core pins 35 are spaced directly below the strings II as clearly illustrated in Figs. 2 and 3 of the drawings. In order to properly compensate for differences in the extent or degree of variation of the magnetic reluctance in the spaces between the outer ends of the members 35 and the adjacent arms of the magnet due to the differences in the diameter of the strings II, the spaces between the upper ends of the -pins 35 and the strings II are graduated substantially in proportion to the graduation in the diameter of the strings.

To eliminate the necessity of aground lead from the coil C one or both of the end pins 35 project from the surface of the spool 3I and are vengaged by the inner windings 33 which have the enamel removed therefrom to electrically contact or connect with the pins. -The pins 35 thus electrically connected with the inner winding or windings of the coil Care grounded to the body I0 through the magnet arms A, the plate 23, bolts 25 and plates 21. By thus grounding the coil winding to the body through the magnets the sounds or noises that are characteristics o f the coil and magnets are eliminated or avoided. It,

is believed that it will be apparent how the nuts v29 may be employed to set or position the unit where the pins 35 are related to the strings II to provide for the desired operation of the pickup unit I2. The pins 35 in extendinginto the coil C operate to concentrate the magnetic force. in spaced zones or fields in the spaces between their outer ends and the adjacent arms of the magnet and carry the magnetic force into the center of `the field of the coil. The strings passing be- The particular amplifying unit I3 illustrated in.

the drawings is a one stage audiofrequency amplifying circuit and is merely typical of the various amplifying systems that may be employed. Means is provided for conveniently connecting the coil C with the amplifying unit I3. In the form-of the invention being described a socket or jack 40 is provided in the body III and is electrically connected with the coil C by a conductor Il. The socket 40 'is adapted to removably receive a plug on the end of a flexible two-conductor cord 42 extending from the amplifying unit I3. Means is interposed between the coil C and the amplifying unit I3 for varying the amplification ci sound.. The volume control is preferably provided on the instrument proper to be conveniently accessible to the player. In the drawings I have shown a typicalvariabieresistance element 43 connected between the socket 40 and the coil C and including a control or regulating knob I4 projecting from the upper I surface of the body.

Fig. 8 of the drawings illustrates the invention embodied 'in an instrument in the form of a guitar having a wooden body III". The body IIIIa has the usual resonance -box I4* and the neck I5. The strings IIa extend across the upper surface of the body and are maintained under the required tension by keys 2li. The electromagnetic pickup unit I2 is supported on the body Ita so that the strings Il" pass under its outer `magnet arms A1.

'I'he strings II*i pass between the magnet arms A1 andthe coil of the unit.

The unit I2a operates in the same manner as the v unit I2 and suitable conductors extend from the 'board I6 by the fingers of the player or by a steel or playing ybar held in the -players hand.

Asbest illustrated in Figs. 9 and 10 of the drawings. the magnetic flux passes between the upper or outer arms of the magnets 22 and the members 35 in concentrated non-uniform fields F. That is, the lines of magnetic force asv illustrated diagrammatically by the spaced lines L in Figs. 9 and 10 are relatively concentrated in the spaces or fields F between the outer arms of `the magnets and the exposedends of the pole members 35 and converge td or iiare outwardly from trie relatively limited surfaces presented by ends of the members 35. ing in Figs. 9 and 10 are not intended to illustrate the total lines of 'magnetic force in the fields F and merely illustrate the general grouping and the general direction of the lines of force in the fields when the strings Il are in their normal positions. The vibratory strings II of magnetic material pass through these concentrated non-uniform elds F and when they are stationary or unmoved there is a fixed or stable condition of magnetic flux and reluctance in the fields F. Movement or vibration of a string I I in any direction alters this fixed condition of the field F through Whch it passes varying the reluctance in the space or field F. 'Ihe variation in the reluctance of the field F induces a current in the coil C. The current induced in the coil C has characteristics proportional to the characteristics of the movement of the strings II. As the fields F are non-uniform or composed of fiaring or converging lines L' of magnetic force, movement-or vibration of the strings II in the directionof the longitudinal axes of the members 35 and movement of the strings II in a direction transverse of said axes both vary the reluctances of the fields F and thus induce a currentin the coil. However, lthe tone or the character of the tone produced by the amplifier I3 resulting from the current induced in the coil C by variation in the reluctance of a given field F caused by movement or vibration of the string II therein inv a direction substantially transverse ofthe longitudinal axis of the The lines L appcaradjacent member 85 is different from that resulting from vibration of the string in a direction substantially axially of said axis. Assuming that a string Ii is vibrated to move substantially 5 transversely through its eld F relative tothe general direction of the lines of force L, the magnetic path through the string il is longervor greater when the string is in the end positions oi its vibratory motion than when the string is l in the intermediate position of such' motion. The reluctance of thespace or field F therefore is greaterwith the string Il'kin the end positions ofits vibratory motion" than with the string in the intermediate position of its movement. 'Ihus l vibration of the string Ilhorlzontally or substantially transverse of the longitudinal axis of the member l induces a current in the coil VC which isconverted by the amplifier Il into a tone in which the second harmonic of the note ofthe string predominates. Assuming that the above-mentioned string Il is vibrated in a general vertical direction or in a direction substantially parallel with or axially of the longitudinal u axis of the member 35, the effect of the string in reducing the reluctance of the ileld F is greater when at the end of its vibratory travel nearest the member l5 than when at the end of its travel nearest the arm oi the,` magnet 22. This is due to this 'particular movement of the string Il in the non-uniform -or substantially fan shaped field F made up of the lines L of force converging. to or flaring from the end of the member 35. Vibration of the string II in a substantially vertical direction or in a direction substantially axial of the member II induces a current in the coil C whichact'uates the amplliler to produce a tone which is strongly that of the fundamental .note of the string. While it may not be practical to vibrate the strings Il in truly vertical or truly 40'horiaontaldirections thev player or musician may at will readily vary and control the character of the tones produced electrically by the instrument.

by pluclring or otherwise vibrating the strings Il to vibrate in a generally vertical direction or a generally horizontal direction. The soundproduced by the'system or unit I3 therefore has all the tonal qualities of the sound which results from the physical vibration of the strings il. 'I'he element `Il may be employed to control or varythe volume of the sound produced by the uniti) and ls conveniently accessible to the hand of the player or musician employed to pluck or vibrate the strings. The sound is reproduced without the mechanical vibration of any part at the pickup unit l2 yother than the 'strings Ii. The resultant music or sound accordingly does not have any extraneous vibrations or unwanted p qualities.

Having described only typical preferred forms a0 and applications ofA my invention I do not wish to be limited or restricted to the speciiic forms and applications herein set forth, but wish to reserve to myself any modiilcations or variations that may appear to those skilled in the art or fall within the scope of 4vthe following claims.

Having described my invention, I claim:

l; A pick up unit 'for use with the vibratory strings of a musical instrument, including a permanent magnet, a coil supported by the magnet between its poles, means mounting themagnet to have thestrings pass between one of its' poles and the coil, and core members within the coil each having anend facing a string.l

2. In combination, a series of tensioned strings of' magnetic material of different diameters, a

' single magnet having its pole portions at opposite sides of the series of strings, a coil between the pole portions of the magnet, andA magnetic core members extending from one of the pole Portions toward the other and terminating to form string ,spaces which vary in size with,the strings.

l 3. In combination, a plurality of spaced vibratory strings of magnetic material, and a pick up unit including, a pair, of permanent magnets arranged to surround the strings with their corresponding poles opposed, a coil within the field of the magnets, and means supporting the magnets and coil for adjustment yrelative to the strings.

'4. A musical instrument comprising, a body to be held by the player, a plurality of spaced vibratory strings of magnetic material at the exterior of the body having portions accessible to be engaged by the player, a permanent magnet having a polar part extending over the strings to cover the same adjacent said portions and form a guard therefor and a rest for the operator, and

a coil within the ileld of the magnet sensitive to disturbances therein.

5. A musical instrument comprising, a body to be held by the player, a plurality of spaced vibratory strings of magnet material at the exterior4 of the body having portions accessible to be engaged by the player, a. permanent magnet having its polar parts spaced above and below the lstrings whereby the strings pass through a dense portion of the field of the magnet, the upper polar parts extending over the strings adjacent said portions to cover the same and form a guard i'or the strings and a hand rest for'the player, and a coil insaid field sensitive to disturbances therein.

6. A musical instrument comprising, a pluralment, said pick up unit comprising, an elongate magnet unit disposed transversely of the strings to have a polar part above the strings, a coil carried by the magnet to receive an inducedl current from its field, and means for shifting the magnet from eitherend to move it relative t0 the strings to tune the pick up unit.

8. A" pick up unit for use in combination with the vibratory string of an instrument including, a magnet having spaced polar parts, an induc- I tion coil positioned between the said polar parts,

and means ior supporting the magnet and coil so that the string passes through the space' between the coil and one of said parts whereby vibration of the string varies the reluctance of the said space to induce a current in the coil.`

9. A pick up means for use in combination with a musical instrument havinga vibratory string of. magnetic material,said pick up means including, a magnet having spaced polar parts, a coil positioned between the said parts, the magnet and coil being positioned so that the stringv passes through the space between the coil and one of said parts whereby vibration oi' the string varies the reluctance of a relatively dense portion of the magnetic ileld to induce a current in the coil,

and means carrying the magnet and coil for adjustment relative to the string.

10. In combination, a series of vibratory strings of magnetic material of different diameters, a magnet,a coil in the field of the magnet, the magnet being positioned so that the strings pass through its field, magnetic core members extending from one pole portion of the magnet and passing through the coil toward the other pole portion of the magnet and terminating at points spaced from the said other pole portion to leave spaces through which the strings pass, and means for shifting the magnet to vary the relation between the strings and said spaces.

11. A musical instrument comprising a body to be held by the player, a plurality of vibratory strings of magnetic material extending across an exterior face of the body in spaced relation thereto, a permanent magnet on the body havinga polar part related to the strings to cover the strings and form a guard therefor and a hand rest for the player, and a coil in the field of the magnet sensitive to disturbances therein.

12. In a musical instrument, a series of spaced vibratory strings of magnetic material, an cion-- gate magnet unit disposed. transversely of the strings where the strings pass through its field, a coil carried by the magnet unit to receive an induced current from the magneticeld, and means for shifting the magnet from either end to adjust it relative to the strings.

13. In a musical instrument, a series of spaced Vibratory strings of magnetic material, an elongate magnet unit disposed transversely of the strings where the strings pass through its field, a coil in the magnetic field of the unit to receive an induced current therefrom, and means for rocking the magnet unit in a plane substantially transverse of the strings to adjust it relative to the strings. V

14. In a musical instrument, a series of spaced vibratory strings of magnetic material, an elongate magnet unit disposed transversely of the strings where the strings pass through its field, a coil in the magnetic field of the unit to receive an induced current therefrom, and means for tilting the magnet unit in a plane substantially' transverse of the strings, said means including supportsfor the magnet unit at points at opposite sides of the series of strings.

15. In combination, a vibratory string of magnetic material, a magnet having pole portions at opposite sides of the string, a coil between the pole portions of the magnet, a .magnetic core member extending from one of the pole portions toward the other pole vportion and terminating at a point spaced therefrom to forma space' through which the string passes, and means for shifting the magnet to vary the positions of the core member and the said other pole portion with relation to the string.

16. A musical instrument comprising a body, a

plurality of exposed vibratory strings extending across a face of the body in' spaced relation thereto, a pair of opposed magnets on the body having polar portions disposed transversely of the strings and related to the strings to form a guard therefor, said guard extending over the strings to cover the same, and a coil in the field of the pair of magnets sensitive to disturbances therein.

17. In a pick up unit, vibratory strings of magnetic material, a magnet having spaced pole portions and positioned so that the strings pass between said pole portions, a plurality of magnetic pole members on one of said pole portions, each member having a limited surface of magnetic attraction adjacent one string whereby the strings act in zones wherein the lines of magnetic force flare inwardly to said limited surfaceavand Va coil surrounding the pole members.

18. In a pick up u nit, vibratory strings of magnetic material, a single permanent magnet having a series of projecting pole parts of like polarity, each pole part presenting a limited surface adjacent a string whereby the lines of magnetic force flare outwardly from said surfaces about the strings, and an induction coil surrounding said series of parts.

19. In a pick up unit, a plurality of vibratory strings of magnetic material, a magnet having spacedpole portions positioned so that the strings pass between the pole portions in closer proximity to one than the other, magnetic posts extending from said other ,pole portion and each having a surface of limited extent adjacent a string and opposing the first mentioned pole portion whereby the strings vibrate in a zone where the lines of magnetic force converge to said surfaces, and a coil in the field of the magnet.

20. In a pick up unit, a plurality of vibratory strings o'f magnetic material having their axes in a common plane, amagnet having a pole portion adjacent the strings and` inclined with respect to said plane so that the spaces between said portion and the strings vary substantially in proportion to the intensity of the magnetism of said pole portion, and a coil in the field of the magnet.

21. In a pick up unit, a plurality of vibratory strings of magnetic material having their axes in a common-plane, a magnet having a pole portion adjacent the strings and inclined with respect lto said plane so that the spaces between said

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