US3003382A

US3003382A - Electric violin, and electromagnetic pickup therefor

Info

Publication number: US3003382A
Application number: US739393A
Authority: US
Inventors: Clarence L Fender
Original assignee: Individual
Current assignee: Individual
Priority date: 1958-06-02
Filing date: 1958-06-02
Publication date: 1961-10-10
Anticipated expiration: 1978-10-10

Description

Oct. 10, 1961 v c. L. FENDER 3,003,382

ELECTRIC VIOLIN, AND ELECTROMAGNETIC PICKUP THEREFOR Filed June 2, 1958 INVENTOR. Z9 GZnnenmsl.1bvo

Marty of FIGURE 2;

United S08 5 3,003,382 ELECTRIC VIOLIN, AND ELECTROMAGNETIC PICKUP THEREFOR Clarence L. Fender, 2212 E. Revere,=Fullerton, Calif. 4, Filed-June 2, 1958, Ser. No. 739,393 g 13 Claims. (Cl. s 4-1.16

This invention relates to an electric violin. More particularly, the invention relates to electromagnetic pickup means adapted to be associated with amplifier and loudspeaker means for creation of sound corresponding to movement of the strings of the violin.

An object of the present invention is to providean improved electric violin which may be mass produced economically and with a very high degree of predictability and uniformity of tone. I v Another objectis to provide an improved pickup means for an electric violin, said pickup means operating primarily upon the principle of rocking of the bridge of the violin about a longitudinal I axis, as distinguished from mere vibration of the bridge.

v Afurther object is to provide ahighly sensitive pickup apparatus for a violin, such apparatus being readily and accurately adjustable in order tocompensate for various conditions during use. V 1 I A further object is to provideran improved violin pickup means which produces .a very fast'response to all frequencies, does not. depend uponresonance of the violin bodyor of the bridge, and is not adversely'affected by the erratic vibration of ;the violin string after the bow is lifted therefrom. u

An additional object of the invention is to provide a pickup, device for violins, which device produces no adverse effect upon tuning of thestrings.

Another object is to provide a pickup device characterized by extremely small movement of an armature, and very close positioning of the armature relative to a magnetic pole piece, such positioning being adjustable to ahigh degree of accuracy. 3 I r r Anothersobject is to provide 'aviolin pickup device having great sensitivityfand fidelity with very small armaupon the correct tuning of the strings.

These and other objects and advantages of the inven-. tion will be more fully set forth in the following speci? fication and claims, considered in connection attached drawing to whichtthey relate.

Inthedrawing: FIGURE '1 is a perspective view illustrating an electric violin constructed in accordance with the present invention;

The 10 has an u per sheet sac. which is cated at 18.

The violin further includes abridge 19, over which the strings 13'are stretched. The bridge rests upon the pickup apparatus of the present invention,and which has been given .the general reference numeral 21.] Such pickup apparatus operates, as will be described subs'e-' quently, to convert the vibrations ofnstrings 13.into electrical signals which are then amplified and converted into soundby suitable amplifier and loudspeaker means, not shown. Such electrical elements are under the control of control knobs 22 and 23 which are mounted on the face sheet 18. v

Proceeding next to a description of the pickup apparatus 21, it comprises a mounting or support plate 26, armature means 27associated with bridge 19, means 36 and 37 "to support the armature means27 in relatively stable" relationship on mounting plate 26 but in such manneras to permit limited rocking or pivotal move ment of thearmature means 27 primarily about an extending longitudinally of'the strings, electromagnetic means ZQSSDClatBdYIith: armature means 27 for gener'ation' or variation of an electric current therein in response to movement of the armature means 27, and means29 toadjust in an accurate manner the positioning of the electic means 28 relative to the arma-f ture means.

' T-shaped, and is rigidly secured to sure movement, andv with no substantial adverse effect FIGURE 2 is an enlarged fragmentary sectionv taken on line-2"-2of FIGURE 1, and illustrating the rockably mounted bridge-armature means;

. FIGURE 3 is an enlarged showing of the lower portion of FIGURE 2, but omitting a showing of the mounting means for thecoil; Y p v FIGURE 4 is an enlarged fragmentary plan view of the violin, in the region .of the bridge; i i

. FIGURE 5 is an enlarged transversev section on line .FIGURE 6 is a fragmentary section taken on line.

6-6 of FIGURE 1, and showing a detent-type control means; and w FIGURE 7. isran enlarged perspective view of detent washer employed in thecontrol means of FIGQ violin also includes a bow 16, and a chin piece 17. 6 FIGURE 3, such holes are sufilciently large to I Themounting' or support plate 26 should be formed -of a non-magnetizable material, such as aluminum, and is mounted over an opening in face sheet 18 beneath the bridge19'. "The illustrated mounting plate2 6 isf face sheet 18 by means" ofthreescrews31fi The armature '27 isformed of amagnetizable material, such as'steel and comprises an upper portion disposed parallel tomounting plate 26, and upon which the bridge 19 rests. In order to prevent sliding ofthe I bridge'on the armature 27, a raised bead 32 is formed thereon around the'base oftthe bridge. Provided at one end of'the upper, horizontal portion of armature means 27, laterally of the bridge 19, is "a downwardly extending armature portion33. Such portion 33 extends through a slot 34 inmounting plate 26 and in non-interfering relationship so that there is no engagement between the portion 33 and the mounting plate. Portion 33 is preferably sufficiently long that the electromagnetic means 28. may be spacedrelatively far from mountins plate 26 while still being close to the lower end of portion 33. This prevents or minimizes eddy currents in the mounting plate '26, and eliminates the damping action which'would otherwise be produced by such eddy currents. The' armature means 27 is preferably a one-piece or integral structure, as described, although it ispossible to employ a non-magnetizable. horizontal portion beneath bridge 19, and'a magnetizable portion near the electromagnetic means 28. f The means tomount armature 27 in relatively stable relationship, but in such manner as to permit limited dented inwardly from the upwardly-extending edge portions 'of the bridge 19 as best illustrated in FIGURES 2 i and 3. The screws 37 are provided on opposite sides-of the bridge 19 and along a line which extends longitudinally of' the strings 13. These screws are threaded downwardly into the mounting plate 26, and extend through holes in the armature 32 and pad 36. As illustrated in p tod Oc L 3 limited rocking movement of the armature relative to plate 26.

The screws 37 are screwed down firmly, but not sufliciently tightly to squash the pad 36. -It is pointed out, however, that the strings 13 exert a' considerable downward force against the pad 36. Such downward forces against the pad, in combination with the relatively large area of the pad, limit the amount of motion of armature 27 to an extremely small value. 'It follows that the bridge 19 moves very slightly, andthat such slight movement is not .suflicient to create any adverse elfectupon the tuning of strings 13.

The electromagnetic means 28 is illustrated to comprise a pair of permanent magnet elements (or pole pieces) 38, formed of a permanent magnet alloy such as Alnico. Magnet elements 38 are shown as cylindrical in shape, and located in vertically disposed, spaced parallel relationship directlybeneath the portion 33 of the armature. The poles of the magnets 38 correspond, so that either both north poles or both south poles are disposed upwardly. A coil 39, comprising a large number of turns of fine electrically-conductive wire, is wound around the magnets or pole pieces 38, being held in position between two horizontally-disposedinsulating sheets 41'which are preferably formed of fibrous material.

The means 29 to accurately adjust'theposition of electromagnetic means 28 relative to armature portion 33 comprises a pair of screws which are inserted downwardly through support plate 26 and are threaded through edge portions of the insulating sheets 41. Helical compression springs 43, or other suitable resilient elements, are provided around the screws -betweenp'late 26 and'the upper insulating sheet 41, thereby maintaining the electromagnetic means 28 in the lowermost position permitted by the screw adjustment. I

Proceeding next to a description of the control knobs 22 and 23, each is mounted on a control shaft 44 which is associated with a potentiometer or rheostat 4.6. 'The shaft, which extends through .a mounting plate 47, rotates in a nut 48 adapted to lock the assembly 'in position. A washer 49 (HS. 7) .is locked imposition beneath nut 48, and has an upwardly extending resilient edge portion 51 which rubs .against the lower surface of the knob 23. A projection 52, on the upper surface of spring portion 51, is adapted to seat selectively in one of aplurality of circumferentially spaced dimples 53 on the lower knob surface. .A detent action is thereby provided which tends to stop .rotation of the knob and associated shaft when the projection 52 is seated in a dimple. With the described construction, the violinist .may set the knobs 22 and 23 to the desired positions, even in a darkened room, since it is merely necessary for :him to turn the knobs to one extreme position and then return them a predetermined number of steps to the desired .s'etting.

Operation "In the operation of the electric violin apparatus the knobs .22 and 23 are first turned to the "desired settings, after which the how '16 is drawn over the strings 13 in the conventional manner. As the bow is drawn over a string 513, such string moves a slight distance with the bow because of the sticking (friction) action produced by-the rosin on the bow, "after whichthe string breaks away from the bow and moves 'in the opposite direction. This action repeats many times during each bow move ment. Such string motion (and also a vibration of the string caused by picking, for example) produce a torque effecting rocking of the bridge 1-9 and associated armature 27 on the pad 36. Such rocking or pivoting is, as previously indicated, primarily about an axis extending longitudinally of the strings. The. extremely slight rocking or pivoting action thus eifected causes upward and downward movement of the portion '33 of the armature, which disturbs the magnetic fields of the magnets '01 pole pieces 38. This causes generation of a-voltage 'in the 4 coil 39, which voltage is suitably amplified and transmitted to a loudspeaker. It has been found from numerous tests and performances that the sound emanating from the loud speaker isa highly faithful representation of the string movement.

Because of .the above-described very small movement of the armature 32, the armature portion 33 may be disposed very close to the pole pieces 38 without danger of actual engagement therebetween. It is highly important that the electromagnetic means 28 be adjustable, as described, in order to permit the minimum spacing between the pole pieces 38 and the lower end of armature portion 33. Such spacing is accomplished by tightening the screws '29'until the pole pieces 38 abut the lower end of the armature. The screws 29 are then loosened a very slight amount, for example a quarter or half turn, to provide a very short space between the armature and the pole pieces. The space should not be more than ,4 of an inch, and is preferably about ,4 of an inch.

Since the armature portion 33is disposed very close to the pole pieces 38, it follows that .even a slight movement of the .armature produces a substantial effect upon the magnetic fields of the pole pieces, and thus generates in coil 39 a voltage which accurately represents the movements of the strings. It is to be understood that the magnetic field strength of each pole piece 38 varies in accordance with the square of the distance that the armature portion 33 is spaced above the pole piece. It follows that when the armature portion 33 is disposed very close to the pole pieces, as described, the slight movement of the armature portion '33 produces a very substantial disturbance in the magnetic field. If, on the other hand, the portion 33 were spaced a substantial distance above the pole pieces, the slight vibration of the portion 33 would produce relatively little disturbance in the magnetic field, and consequent poor reproduction of the string movements. Stated otherwise, because of the above-mentioned square relationship, the identical armature movement produces a very much greater disturbance in the magnetic field when the armature is close to the pole pieces than when it is remote therefrom.

Various embodiments of the present invention, in addition to what has been illustrated and described in detail, may be employed without departing from the scope of the accompanying claims.

I claim:

, 1. An electrical musical instrument of the violin type having a body, strings, and a bridge therebetween, an electrical pickup for said instrument comprising a support upon which said bridge is mounted, a resilient compressible pad disposed between said support and said instrument body, and adjustable compression means extending between .saidsupport and said body to adjust the degree of compression of said resilient compressible pad, said support comprising at least part of an armature of said pickup, whereby movement of said bridge by said strings will cause movement of said armature which may be .electroacoustically translated into sound.

2. The invention as claimed in claim 1, in which said adjustable compression means extending between said support andsaid body is adapted to permit limited rocking movement of said :bridge relative to said body about an axis generally parallel to said strings.

3. The invention as claimed in claim 1-, in which said armature has at least one magnetizable portion which is operatively associated with a permanent-magnet pole piece and associated coil of wire, whereby movement of said magnetizable portion :disturbs the field of said pole piece and induces a'voltage in "said coil of wire.

4. The invention as claimed in claim 1, in which said support comprises a rigid element having openings therein along a line longitudinal to said strings, and in which said adjustable compression means extending between said support and said body comprises fasteners extending through said openings .in saidurigid element and into said body, said fasteners having smaller diameters than said openings to thus permit rocking of said support.

5. The invention as claimed in claim 1, in which said pad is located beneath the center portion of said bridge, and in which the edge portions of said pad are indented inwardly from the outermost ones of said strings.

6. The invention as claimed in claim 1, in which said pad is formed of elastomeric material.

7. The invention as claimed in claim 1, in which said support has associated therewith a'magnetizable portion adapted to move in a predetermined direction in response to rocking of said bridge aboutan axis generally parallel to said strings, and in which electromagnetic means are disposed adjacent said magnetizable portion and adapted to generate a voltage in response to said movement thereof.

8. The invention as claimed in claim 7, in which said electromagnetic means, is in general alignment with said direction of movement of said magnetizable portion caused by said rocking of said bridge, and in which means are provided to effect accurate adjustment of the distance, in a direction parallel to said direction of movement, between said electromagnetic means and said magnetizable portion.

9. The invention as claimed in claim 1, in which said support is rigid, in which said adjustable compression means extending between said support and said body comprises adjustable fasteners adapted to move said rigid support toward said body to compress said pad, in which said support has a portion formed of magnetizable material and extending downwardly into the interior of said body, in which electromagnetic means are disposed within said body and include an elongated permanent-magnet the distance between said downwardly-extending portion i and said magnet element varies in response to movement of said bridge.

10. The invention as claimed in claim 9, in which means operable from the exterior of said body are provided to adjust the spacing between said magnet element and said downwardly-extending portion of said support.

11. The invention as claimed in claim 9, in which said body includes a mounting plate disposed beneath said bridge and supporting said pad, said mounting plate being formed of non-magnetizable material and having an opening therein through which said downwardly-extending portion of said support extends.

12. The invention as claimed in claim 9, in which said downwardly-extending portion of said support is disposed laterally of said bridge.

13. The invention as claimed in claim 9, in which said 7 pad is formed of solidelastomeric material.

7 References Cited in the file of this patent UNITED STATES PATENTS