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Claims  |
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What is claimed is:
1. A transducer for a stringed instrument having at least one magnetically
permeable string, said transducer being of the variable reluctance type
for obtaining electrical signals respectively corresponding to vibrational
movement of the string in two mutually perpendicular planes, comprising:
first and second magnetically permeable pole pieces;
magnetic means for creating a magnetic flux in each of said pole pieces;
first and second pole faces formed respectively on said first and second
pole pieces, each said pole face for emanating magnetic flux from the pole
piece upon which said pole face is formed;
support means for supporting and positioning said first and second pole
pieces relative to the string, said support means positioning said pole
faces in stationary predetermined positions relative to said string under
non-vibratory conditions, said support means also positioning said first
pole face from said string at a predetermined distance at which vibratory
motion of said string in a first plane toward and away from said first
pole face changes the magnetic flux in said first pole piece by a
substantially greater amount than any change in the magnetic flux in said
second pole piece, said support means also positioning said second pole
face from said string at a predetermined distance at which vibratory
motion of said string in a second plane toward and away from said second
pole face changes the magnetic flux in said second pole face by a
substantially greater amount than any change in magnetic flux in said
first pole piece, said support means further positioning both pole faces
in a predetermined configuration by which vibratory motion of the string
in the first plane is substantially perpendicular to vibratory motion of
the string in the second plane, said support means including said magnetic
means,
means associated with said first pole piece for supplying a first
electrical signal related to the change in flux in said first pole piece;
and
means associated with said second pole piece for supplying a second
electrical signal related to the change in flux in said second pole piece.
2. A transducer for a stringed instrument having at least one magnetically
permeable string, said transducer being of the variable reluctance type
for obtaining electrical signals corresponding to vibrational movement of
the string in two mutually perpendicular planes, comprising:
first and second magnetically permeable pole pieces;
magnetic means for creating a magnetic flux in each of said pole pieces;
first and second pole faces formed respectively on said first and second
pole pieces, each pole face having a predetermined configuration for
orienting the magnetic flux emanating from said pole face in a
predetermined pattern within a predetermined distance from said pole face;
support means for supporting and positioning said first and second pole
pieces relative to said string and for positioning said first and second
pole faces in stationary predetermined positions relative to said string
under non-vibratory conditions, said support means also for positioning
said first and second pole faces within the predetermined distance from
said string within which the magnetic flux respectively emanating from
said first and second pole faces is oriented in the predetermined pattern,
said support means adapted also to position both pole faces at a
predetermined distance from said string within which vibratory string
motion toward and away from each pole face changes the magnetic flux in
the pole piece upon which said each pole face is formed, said support
means also adapted to position both said pole faces relative to said
string under non-vibratory conditions in a predetermined configuration by
which the predetermined flux pattern from said first pole face is
essentially mutually perpendicular to the predetermined flux pattern from
said second pole face, said support means including said magnetic means;
means associated with said first pole piece for supplying a first
electrical signal related to the change in flux in said first pole piece;
and
means associated with said second pole piece for supplying a second
electrical signal related to the change in flux in said second pole piece.
3. A transducer for a stringed instrument having at least one string, said
transducer being of the variable reluctance type for sensing vibratory
motion of the string in each of two mutually perpendicular planes,
comprising:
first and second magnetically permeable pole pieces;
magnetic means for creating a magnetic flux in each of said pole pieces;
support means for supporting said first and second pole pieces on
respectively opposite transverse sides of said string and in substantially
stationary predetermined positions relative to said string under
non-vibratory conditions, said support means including said magnetic
means;
first and second pole faces formed respectively on ends of said first and
second pole pieces, each pole face having a predetermined configuration in
regard to the predetermined position at which the pole piece is supported
relative to the string for directing magnetic flux emanating from the pole
piece substantially toward said string and for directing magnetic flux
from one pole piece toward said string substantially perpendicular to the
direction which magnetic flux from the other pole piece is directed toward
said string;
said support means adapted to support each pole piece with each pole face
spaced from said string a predetermined distance at which the magnetic
flux emanating from each pole face intersects the string and at which
vibratory string motion toward and away from one pole face substantially
only changes the magnetic flux in the pole piece upon which said one pole
face is formed;
a first winding defined by a plurality of series connected coils of an
electrical conductor formed around said first pole piece, said first
winding being adapted to supply a first electrical signal representative
of any change in flux in said first pole piece; and
a second winding defined by a plurality of series connected coils of an
electrical conductor formed around said second pole piece, said second
winding being adapted to supply a second electrical signal representative
of any change in flux in said second pole piece.
4. A transducer as defined in claims 1 or 3 wherein a substantial amount of
the flux respectively emanated from said first and second pole faces is
oriented to intersect said string at a respective mutually perpendicular
angle.
5. A transducer as defined in claim 3 wherein the predetermined
configurations of said pole faces result in significantly greater changes
in the magnetic flux in one pole piece than in the other pole piece, upon
vibratory movement of said string toward and away from one pole face.
6. A transducer as defined in claims 1 or 2 wherein said support means
positions said pole pieces on transversely opposite sides of said string.
7. A transducer as defined in claims 1, 2 or 3 wherein said support means
positions each pole face substantially the same distance from said string
under non-vibratory conditions.
8. A transducer as defined in claims 1, 2 or 3 wherein each pole piece
comprises an elongated bar and the pole face extends transversely across
an end of the bar and said bar is bent adjacent the end upon which the
pole face is formed.
9. A transducer as defined in claims 1, 2 or 3 wherein each pole piece
comprises an elongated bar and the pole face extends transversely across
an end of the bar generally at an acute angle relative to the length of
the bar at the end.
10. A transducer as defined in claims 1, 2 or 3 wherein said first and
second electrical signals are substantially only audio frequency signals
of predetermined strength to directly supply input to an audio amplifier,
said first and second signals being distinguishable from one another in
accordance with different vibratory string motion in each of the two
mutually perpendicular planes.
11. A transducer as defined in claims 1, 2 or 3 in combination with a
stringed instrument having a body and a plurality of strings extending in
a plane, and wherein in said combination:
a first pole piece and a second pole piece are operatively associated with
each string of the plurality of strings of the instrument; and
said support means is operatively connected to said body and positions said
pole faces of said pole pieces generally below the plane defined by said
plurality of strings, said support means also positions each first pole
face on corresponding transverse sides of each string and positions each
second pole face on the corresponding opposite transverse side of each
string.
12. A transducer as defined in claims 1, 2 or 3 wherein each said pole face
configuration is planar and the plane of said first pole face extends
substantially perpendicular to the plane of said second pole face.
13. An invention as defined in claim 11 wherein:
said support means positions the first and second pole pieces of each group
of first and second pole pieces in next adjacent relation with the one
string associated with each group and without interposition of any other
pole piece between said one string and the first and second pole pieces of
said group.
14. An invention as defined in claim 11 wherein each pole piece comprises
an elongated bar and the pole face extends transversely across an end of
said bar and said bar is bent adjacent the end upon which the pole face is
formed.
15. An invention as defined in claim 11 wherein each pole piece comprises
an elongated bar and the pole face extends transversely across an end of
said bar generally at an acute angle relative to the length of the bar at
the end. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
This invention relates to stringed instruments and more particularly to a
new and improved transducer for separately sensing the vibrational
movement of a string of the stringed instrument in two mutually
perpendicular planes and for supplying separate electrical signals related
to the vibrational movement of the string in each of the two mutually
perpendicular planes.
Transducers or pick-ups as they are commonly called have been widely
employed in a variety of different electric guitars and other stringed
instruments for the purpose of deriving electrical signals corresponding
to the vibrational movement of the string. The electrical signals are then
amplified and supplied to speakers to obtain an amplified sound over that
which would be available from vibration of the string itself. A
significant portion of musicians playing guitars and similar stringed
instruments utilize instruments employing transducers.
The typical prior art transducer employs a pole piece of magnetically
permeable material which conducts and emanates magnetic flux. The pole
piece is positioned sufficiently close to the string so the vibratory
movement of the string toward and away from the pole piece changes the
reluctance through the air gap adjacent the pole piece. Reluctance changes
cause the flux in the pole piece to change in a related manner, and the
flux changes induce the electrical signals. Conventional transducer
assemblies typically sense vibrational movement of the strings in a plane
perpendicular to the plane collectively defined by all the strings of the
instrument.
It is known that a string which is plucked or strummed will typically
vibrate in a complex pattern. The center point of a plucked string may
vibrate in a linear, circular, oval, figure eight or a variety of other
complex patterns. Prior art transducers, however, have sensed the string
movement only in a single plane, although the actual audible effect
created by the vibrating string itself may contain frequencies and effects
which are distinguishable from the vibrational movement of the string in
that single plane. Consequently the electrical signals generated by the
prior art single-sensing plane transducers may not accurately reflect the
sound effect created by the vibrating string.
Certain prior art transducers have even attempted to eliminate the effects
of the string vibrations in planes other than the single-sensing plane.
U.S. Pat. No. 3,453,920 discloses a piezo-type bridge pick-up for a
guitar. Two piezoelectric crystals are mechanically contacted with the
string at a bridge to sense any string vibration. The piezoelectric
crystals are mechanically oriented to sense horizontal and vertical string
vibrations, although the crystals may also dampen the string movement. The
piezoelectric crystals are electrically connected to electrically cancel
the signals developed from the horizontal string vibration.
Prior art relating to deriving signals representative of the string
vibration in two mutually perpendicular planes is disclosed in U.S. Pat.
No. 4,143,575. The arrangement described in U.S. Pat. No. 4,143,575
employs a pair of radio frequency coils oriented with their axes in
non-intersecting relation with each string, a signal generator for
conducting radio frequency signals through each string of the stringed
instrument, signal processing circuitry including an AM detector for
detecting the modulation in the radio frequency signal of the string as
sensed by the radio frequency coils, and an amplifier and speaker for
amplifying the audio signal obtained from the AM detector. The radio
frequency signal processing equipment and radio frequency coils have
heretofore been regarded as necessary to detect string vibration in each
of the two mutually perpendicular planes with sufficient signal separation
to obtain two audibly distinguishable signals from string vibration in the
two mutually perpendicular planes.
Other shortfalls and deficiencies in the development in this art may be
known. In general, however, a greater appreciation for the significance of
the present invention should be revealed by a more complete understanding
of the previous developments in this art.
SUMMARY OF THE INVENTION
General objectives of the present invention are to provide a new and
improved variable reluctance and flux transducer for sensing the
vibrational movement of a string in two mutually perpendicular planes,
which has the significant advantages and features of more perfectly
reproducing the complex movement of the vibrating string, which allows an
accomplished musician to obtain two distinguishable audio effects from a
single vibrating string and to increase the distinctiveness of the playing
style of the musician, which can be utilized with conventional audio
amplifying equipment without the necessity of costly complex signal
processing equipment and the like, and which can be utilized with various
signal processing equipment to obtain unique musical effects. Another
objective is simply to increase the number and distinctiveness of sounds
attainable from a stringed instrument utilizing an electrical transducer
for sensing the string vibration.
The transducer of the present invention can generally be summarized as
comprising a pair of pole pieces, means for creating magnetic flux flowing
through the pole pieces and means for sensing changes in magnetic flux. A
pole face of predetermined configuration is formed on each pole piece. The
predetermined configuration of the pole faces emanates the magnetic flux
flowing out of the pole pieces into a predetermined pattern in the air gap
in the vicinity of the string. Vibrational movement of the string in one
plane parallel to the magnetic flux pattern emanated from the pole face of
the first pole piece induces minimal or insignificant flux changes in the
second pole piece, and vice versa. In this manner, vibrational movement of
the string in one plane is sensed independently of, and with a minimum of
influence over, the sensing of the vibrational movement of the string in
the other mutually perpendicular plane.
The present invention is defined in the appended claims. A more complete
understanding of the invention can be obtained from the following
description of its preferred embodiments and from the drawings consisting
of a number of figures.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a generalized view of a guitar to which there is attached a
transducer assembly including at least one transducer according to the
present invention. Electrical output terminals for the transducer assembly
and various other electrical apparatus are also schematically illustrated.
FIG. 2 is a generalized schematic view of a transducer illustrating certain
principles and elements of the transducer in operative relation with one
string of a guitar or other stringed instrument, in accordance with the
invention.
FIG. 3 is a side view, partially in elevation and partially in section of
one embodiment of a transducer of the present invention viewed in a plane
perpendicular to the longitudinal extension of a string of a stringed
instrument.
FIG. 4 is a view similar to FIG. 3 of another embodiment of the transducer
of the present invention.
FIG. 5 is a section view taken substantially in the plane of lines 5--5 in
either of FIGS. 3 or 4.
FIG. 6 is a perspective view of one transducer assembly including a number
of individual transducers positioned relative to the strings of the guitar
shown in FIG. 1.
FIG. 7 is one exemplary electrical connection of two transducers of the
transducer assembly.
DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention is intended for use in conjunction with a stringed
instrument such as a guitar 10 which has a plurality of strings 12, as
shown in FIG. 1. The present invention is embodied by one or more
individual transducers 14 illustrated in FIGS. 2, 3 and 4. The transducers
14 of the present invention sense the vibratory motion of the strings 12
in essentially two mutually perpendicular planes and provide separate
signals relating to the string vibratory motion in each of the two
mutually perpendicular planes. Prior art transducers or pick-ups are
commonly employed for essentially sensing the vibratory motion of the
string in only a single plane.
When plucked or strummed the string 12 will typically vibrate in various
complex patterns and not in a single plane. The complex patterns result
essentially because of the non-uniform manner in which the string is
plucked or because of multiple angles of attack on the string by the
picking device. Any complex pattern will involve components of vibration
or movement in two mutually perpendicular planes extending parallel to the
string under non-vibratory conditions, designated as an X plane and a Y
plane in FIG. 2. In fact, any movement of the string, except in a single
plane parallel to either the X plane or the Y plane, will involve a
component of movement in both planes. The transducer 14 of the present
invention separately senses the component of string vibratory movement in
each of the two mutually perpendicular X and Y planes and provides
separate electrical signals relating to the vibratory motion of the string
in each plane.
The transducers 14 are typically assembled into a transducer assembly 16
and attached to the guitar or stringed instrument as shown in FIGS. 1 and
6. The transducer assembly 16 is preferably positioned below a plane
defined by the plurality of strings 12 and is connected to a body 18 of
the guitar 10. The transducer assembly 16 is positioned between two
bridges 20 and 22 of the guitar 10 over which the strings 12 pass. The
bridges 20 and 22 thus define the maximum longitudinal length along which
the string 12 is allowed to vibrate, since the bridges dampen the string
vibrations to the guitar body. The transducer assembly 16 is positioned at
some point along the suspended length of the strings where they undergo
vibrational movement as a result of stimulation by plucking, strumming,
bowing, impacting, or the like.
Separate electrical signals respectively representative of the string
motion or vibration in each of the two mutually perpendicular planes are
directly supplied to audio amplifiers 24 and 25 which drive speakers 26
and 27, as shown in FIG. 1. The signal supplied to amplifier 24 represent
the string vibratory motion in one of the two mutually perpendicular
planes, and the signal applied to amplifier 25 represents the string
vibratory motion in the other mutually perpendicular plane. Terminals 28
and 30 are provided on the guitar to electrically connect the transducer
assembly 16 with the amplifiers 24 and 25. As shown in FIG. 2, a separate
pair of terminals 28a and 30a could be provided for each individual
transducer 14 of the assembly 16 thereby providing a pair of separate
signals from each individual string, or various electrical signals can be
summed together at the single terminals 28 and 30 as shown in FIG. 7.
The operational concept of the transducer 14 is generally illustrated in
FIG. 2. Each transducer comprises a first pole piece 32 and a second pole
piece 34. Each pole piece is formed of magnetically permeable material
which, in association with the adjacent structures and the space in close
proximity, possesses a certain magnetic reluctance. Means for creating
magnetic flux flowing within and out of the pole pieces 32 and 34 is also
provided. In the transducer 14 shown in FIG. 2, the pole pieces 32 and 34
are permanent magnets and the magnetic material thereof creates the
magnetic flux. Each pole piece 32 and 34 is formed with a pole face 36 and
38, respectively, of predetermined configuration for orienting the
magnetic flux flowing out of the pole piece into a predetermined pattern.
The magnetic flux emanating from the pole faces 36 and 38 into the space
or air gap area adjacent the string 12 is a predetermined pattern aligned
substantially parallel to the two planes X and Y, respectively.
A planar configuration is one predetermined configuration of the pole faces
36 and 38 which achieves the effect of orienting the flux patterns in the
vicinity of the string in the mutually perpendicularly intersecting
relation. The magnetic flux tends to emanate from or exit the pole piece
in a direction substantially perpendicular to the plane of the pole face
surface at the point of exit. As the flux travels into space beyond the
pole face, the flux lines may bend according to other influences. It is
possible that other non-planar pole face configurations can be utilized
which particularly arrange the flux lines in the area adjacent the
non-vibrating string into an intersecting, mutually perpendicular flux
pattern.
The pole pieces 32 and 34 and their pole faces 36 and 38 respectively are
positioned and supported in predetermined relation to the string 12. This
predetermined supported relation causes the magnetic flux exiting from
pole piece 32 at its pole face 36 to intersect the string 12 in a manner
generally parallel to the X plane. The magnetic flux exiting the pole
piece 34 at its pole face 38 intersects the string 12 in a pattern
generally parallel to the Y plane and substantially perpendicular to the X
plane.
The strings 12 of a typical musical instrument are generally of
magnetically permeable material such as steel. However, non-magnetically
permeable strings can be made magnetically permeable by attaching a small
foil of magnetically permeable material around the strings in the vicinity
where the magnetic flux from the pole pieces intersects the string. The
string 12 is positioned at a predetermined distance from the pole faces 36
and 38 and within the flux pattern emanating from the pole pieces whereby
string vibratory motion in the X and Y planes influences the magnetic
reluctanace of the path in which the flux flows. As the string 12 vibrates
toward and away from the pole face 36, the reluctance of magnetic flux
path through the pole piece 32 changes in relation to the distance of the
string 12 from the pole face 36. Since the distance of the string from the
pole face 36 varies directly in accordance with the vibrational frequency
of the string in the X plane, the reluctance changes are directly related
to the vibrational frequency of the string. A similar effect creates
reluctance changes in the magnetic flux path through pole piece 34 as a
result of vibratory motion of the string 12 in the Y plane toward and away
from the pole face 38.
A change in reluctance in each magnetic flux path causes a related change
in the magnitude of magnetic flux flowing in the pole piece within the
magnetic flux path. In order to supply an electrical signal related to the
change in flux in each pole piece, electrical coils 40 and 42 are formed
around pole pieces 32 and 34, respectively. The electrical coils 40 and 42
are defined by a plurality of series connected individual loops or coils
of electrical conductors 44 and 46 respectively. Changes in magnetic flux
through the pole pieces induce an electrical voltage signal in the sensing
coils 40 and 42, and the signals are applied over the conductors 44 and 46
to a pair of terminals 28a and 30a respectively connected to the
conductors 44 and 46.
Since the pole pieces and pole faces are supported to cause the magnetic
flux from each pole face 36 and 38 to respectively intersect the string 12
in a mutually perpendicular relationship, movement of the string in one
plane does not cause magnetic flux changes in the pole piece emanating
magnetic flux parallel to the other plane. For example, movement of the
string in the X plane does not cause substantial flux changes in the pole
piece 34 because the string 12 remains essentially at the same distance
from the pole face 38, and vice versa. Some bending and interaction of the
magnetic flux emanated from the pole faces 36 and 38 may occur in the
vicinity of the string 12, but this distortion from a strictly
perpendicular orientation in the vicinity of the string is not so
significant to prevent separate flux changes in the pole pieces 32 and 34
in accordance with the reluctance changes caused by vibratory string
motion in the X and Y planes, respectively.
Because the pole pieces, the pole face configurations, and the
predetermined magnetic flux pattern in the vicinity of the string are
arranged in accordance with the invention to have maximum affect on the
flux in one pole piece and a minimum or no effect on the flux of the other
pole piece from string vibration in a single plane, separate electrical
signals are derived from the string movements in each of the two mutually
perpendicular planes. The predetermined distance of the string from the
pole faces, the amount of flux flowing through and created within each
pole piece and the number of individual conductor coils of each sensing
coil are all related in a predetermined manner to provide voltage output
signals on terminals 28a and 30a which themselves are sufficient to drive
an audio amplifier 24 or 26 (FIG. 1) directly without the necessity for
further elaborate electronic signal processing, conditioning and the like.
A skilled musician can utilize the transducers of the present invention to
create uniquely sounding musical styles and effects not previously
appreciated. Significantly perceptible differences in sound result from
the string vibration in each of the two mutually perpendicular planes. The
overall sound available from the transducer of the present invention, when
compared to the sound available from conventional transducers, may be
subjectively described as fuller or fatter with greater dimension. The
different signals from the sensing coils create a stereo-type image
determined by the manner in which the instrument is played. By plucking
the string back and forth in a transverse direction between the two pole
pieces, the initial linear vibration of the string in a transverse
direction will alternately induce the primary signals in the pole pieces.
The back and forth string plucking will cause the sound image to move back
and forth across a stereo dimension defined by the space between the two
separated speakers 26 and 27 (FIG. 1). A musician can also fret the string
in such a manner to bend or displace the string from its normal position
between the two pole faces toward one of the pole pieces and away from the
other. Bending the string closer to one pole face increases the amplitude
of the signal supplied by one sensing coil decreases the amplitude of the
signal supplied by the other sensing coil, which will cause the amplitude
of the sound image to move toward one side of the stereo dimension between
the two separated speakers. It is also possible for a skilled musician to
create a subtle flanging or phasing effect. This phasing or flanging
effect is controlled by plucking the string at successive intervals along
the length of the string, thereby causing successive variations in
vibration attack and sustain patterns of the vibrating string. The rate at
which the phasing occurs is determined by the rate at which the plucking
is moved along intervals of the string. These and other unique effects are
under the simultaneous yet independent control of the musician.
The described unique musical effects achieved by the transducers of the
present invention are the direct result of the vibration sensing
capabilities. No elaborate additional electronic equipment, such as signal
processing equipment and the like, is necessary other than the
conventional audio amplifiers 24 and 25 and the conventional speakers 26
and 27. The transducers of the present invention are directly adaptable to
a conventional guitar or other stringed instrument, or can be substituted
for a conventional pick-up without significant modification to the
instrument or the audio amplifying equipment of the musician.
Preferred structure of one actual embodiment 14a of the transducer can be
understood by reference to FIG. 3. The pole pieces 32 and 34 are
preferably formed from elongated bars of magnetically permeable material.
Coil forms 48 generally take the configuration of a reel or a bobbin and
include center openings 50 within which the pole pieces are received. The
sensing coils 40 and 42 are defined by a predetermined plurality of turns
of an electrical conductor wound around the middle portion of the coil
form 48 between end flanges 52 and 54 of each coil form. A permanent
magnet 56 contacts ends 58 and 60 of the pole pieces 32 and 34
respectively. The permanent magnet 56 creates the magnetic flux flowing in
the pole pieces 32 and 34. A metallic magnetically permeable shield 62
(FIG. 5) extends between the end flanges 52 and 54 and completely
surrounds each sensing coil 40 and 42. The shield 62 may be formed of a
single piece of metallic material shaped in a figure eight as shown in
FIG. 5, to simultaneously slide over both sensing coils and coil forms.
Offset ends 64 overlap the middle portion of the metallic shield and
assure a complete magnetic shield around each sensing coil. The shield 62
shields the sensing coils 40 and 42 from the influence of external
spurious magnetic flux and helps reduce the induction of spurious
electrical signals in the sensing coils. Each transducer 14a is held in
assembled relation and positioned on the guitar body 18, and the pole
pieces and pole faces are positioned relative to the string 12 by a
support means or housing 66 having an upper wall 68 and a lower wall 70.
Openings 71 are formed in the upper wall 68 to allow ends of the pole
pieces 32 and 34 to protrude therethrough and be supported adjacent the
string on opposite transverse sides of the string.
In the embodiment 14a of the transducer shown in FIG. 3, the pole faces 36
and 38 are formed on the pole pieces 32 and 34 respectively, by making a
planar cut at approximately a 45.degree. angle with respect to the
longitudinal extention of the pole pieces. The pole faces 36 and 38 both
directly face the string 12 and are approximately the same distance from
the string 12 under non-vibratory conditions. Imaginary lines 72 which
extend perpendicularly from the planar pole faces 36 and 38, respectively,
intersect at the string 12. Magnetic flux emanating from the pole faces 36
and 38 generally intersects the string 12 in essentially a mutually
perpendicular relationship due to the described geometry. Of course, the
planes defined by the pole faces 36 and 38 are also mutually perpendicular
with respect to one another.
In the embodiment 14b of the transducer shown in FIG. 4, the ends 74 and 76
of the pole pieces 32 extend above the top surface 68 of the housing 66
and are bent in a direction to converge toward the string 12. The
configuration of the pole faces 36 and 38 is planar. The pole faces 36 and
38 extend transversely and generally perpendicularly with respect to the
extension of the ends 74 and 76. The planar orientation of the pole face
configurations 36 and 38 in the embodiment 14b shown in FIG. 4 defines
essentially similar pole face geometry and produces an essentially similar
flux pattern in the vicinity of the string as has been previously
described.
A plurality of individual transducers, for example those referenced 14a,
are assembled into the transducer assembly 16, as shown in FIG. 6. One
individual transducer is provided in the assembly 16 for each string 12 of
the stringed instrument. Each individual transducer provides signals
representative of the vibrational movement of the string with which the
transducer is associated. Screws 80 or other conventional fastening
devices are utilized for attaching the housing 66 of the transducer
assembly 16 to the guitar body 18. It should be noted that the pole faces
36 and 38 in the assembly 16 are positioned in a line extending
transversely with respect to the longitudinal extension of the strings and
are positioned in next adjacent relation to the string whose vibrations
are sensed. Therefore, it can be seen from FIG. 6 that no other pole piece
is interposed between each string 12 and the two pole pieces presenting
the pole faces 36 and 38 operative with respect to that string. Each
transducer senses the vibrational movement of its associated string at
approximately corresponding places along the length of the strings.
The sensing coils of each transducer of the transducer assembly may be
electrically connected in a variety of different manners, one of which is
illustrated in FIG. 7. Two individual transducers 14c are schematically
illustrated. The sensing coils 40 of the two pole pieces 32 on the same
transverse side of the strings 12 are electrically connected through
resistors 82 and 84 to the terminal 30 which also serves as a summing
junction. Resistors 82 and 84 are of value selected to provide the desired
magnitude of the individual signals derived from each of the sensing coils
40. Similarly, the sensing coils 42 surrounding the pole pieces 34 are
electrically connected through resistors 86 and 88 to the terminal 28. The
electrical arrangement illustrated in FIG. 7 sums all of the first set of
electrical signals derived from vibrational movement of all or a plurality
of strings in one set of parallel planes and sums the second set or the
remainder of the electrical signals derived from vibrational movement of
the strings in the set of mutually perpendicular planes. Although not
shown, the signals supplied by each individual sensing coil could be
separately supplied to a separate amplifier, or connected by one of the
known techniques to achieve interference cancellation, e.g. "Humbucking".
Preferred embodiments of the transducer of the present invention, as well
as its operational principles and significant improvements and advantages
over the prior art have been described with a degree of particularity. It
should be understood, however, that the specificity of the present
disclosure has been made by way of example, and that changes in detail of
structure and features may be made without departing from the spirit of
the invention defined by the appended claims.
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