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Claims  |
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I claim:
1. An electromagnetic pickup device adapted for musical instruments having
elongated magnetizable vibrating elements with each of said vibrating
elements having a different degree of magnetizability, said pickup device
comprising:
(a) a single permanent rectangular bar magnet adapted to be disposed
adjacent to vibrating elements having a lower degree of magnetizability,
and
(b) a pickup coil surrounding said permanent magnet; the improvement
comprising:
at least one metal plate means for varying the magnetic field of said
permanent magnet in proportion to the degree of magnetizability of said
vibrating elements; said metal plate means being adapted to be interposed
between said permanent magnet and said vibrating elements, and extend from
said magnet below said vibrating elements having a lower degree of
magnetizability; whereby said magnetic field is varied in accordance with
the magnetization of said vibrating elements thereby balancing the
response from each vibrating element while achieving a pickup of the
natural tone of each of said vibrating elements, and
said metal plate means is configured to provide a concave like surface
facing said vibrating elements of higher degree of magnetizability.
2. The structure of claim 1, wherein
said one metal plate means is embodied in a non-magnetic filler material.
3. The structure of claim 1, wherein
said pickup coil includes conducting means wound around said magnet and
filler material embedding said one of said metal plate means.
4. The structure of claim 1, including
covering means enclosing said permanent magnet, said metal plate means and
said pickup coil, and
said covering means including covering plates connected by an encapsulating
material.
5. In an electromagnetic pickup device adapted for musical instruments
having elongated magnetizable vibrating elements with each of said
vibrating elements having a different degree of magnetizability; wherein
said pickup device comprises:
(a) a single permanent magnet having a configured surface adapted to be
disposed adjacent to all of said magnetizable vibrating elements; and
(b) a pickup coil surrounding said magnet; the improvement comprising:
configured permanent magnet surface means and metal plate means for varying
the magnetic field of said permanent magnet in proportion to the degree of
magnetizability of said vibrating elements, with at least two metal plates
being adapted to be interposed between said configured surface and said
magnetizable vibrating elements; whereby said magnetic field is varied in
accordance with the magnetization of said vibrating elements thereby
balancing the response from each vibrating element while achieving a
pickup of the natural tone of each of said vibrating elements, and
said permanent magnet has a predetermined length and width dimension and
being magnetically polarized perpendicularly to said configured surface
means,
said surface means being a configured edge surface along said length
dimension, and
said surface means providing a varying width dimension of said bar magnet
to face said vibrating elements.
6. The structure of claim 5, wherein
a first of said two metal plates is disposed above said configured edge
surface at a portion of reduced width dimension, and
a second of said two metal plates is disposed above said configured edge
surface at a portion of relatively larger width dimension.
7. The structure of claim 6, wherein
at least a portion of said configured edge surface is tapered to provide a
tapered portion of said reduced width dimension of said bar magnet.
8. The structure of claim 6, wherein
said configured edge surface is tapered.
9. The structure of claim 6, wherein
said configured edge surface includes step edge surface portions providing
stepped portions of said reduced width dimensions of said bar magnet.
10. The structure of claim 9, wherein
said step edge surface portions provide at least two different width
dimensions of said bar magnet.
11. The structure of claim 10, wherein
said first of said two metal plates is disposed above the step edge surface
portion having the lesser of said two different width dimensions has a
square shape,
said second of said two metal plates has an elongated rectangular shape,
and
the width dimension of said square shape is greater than the width
dimension of said rectangular shape.
12. The structure of claim 6, wherein
said configured edge surface includes at least one notch edge portion
providing said reduced width dimensions.
13. The structure of claim 12, wherein
said notch edge surface portion provides at least three different width
dimensions of said bar magnet,
said second of said two metal plates being disposed above the largest width
dimension, and
said first of said two metal plates being disposed above the remaining
width dimensions.
14. The structure of claim 5, wherein
said configured edge surface includes notch and step edge portions.
15. The structure of claim 14, wherein
said notch and step edge portions provide at least four different width
dimensions.
16. The structure of claim 15, wherein
said first of said two metal plates is disposed above the smaller of said
four different width dimensions, and
said second of said two metal plates is disposed above the larger of said
four different width dimensions.
17. The structure of claim 14, wherein
the edge surface of said bar magnet is configured opposite to said
configured surface adjacent said vibrating elements.
18. The structure of claim 17, wherein
said two configured edge surfaces provide at least four different width
dimensions of said bar magnet.
19. The structure of claim 18, wherein
said first of said two metal plates is disposed above the smaller of said
four different width dimensions, and
said second of said two metal plates is disposed above the larger of said
four different width dimensions.
20. The structure of claim 6, wherein
said coil includes conducting means wound against said magnet at an end
having larger width dimensions, and
said conducting means being overlappingly wound upon itself at an end of
said magnet having smaller width dimensions.
21. The structure of claim 5, including
covering means enclosing said magnet and said coil, comprising
a first plate covering said configured surface, and
a spacer between at least a portion of said configured surface and said
first plate providing a taper therebetween.
22. The structure of claim 21, wherein
at least two metal plates are embedded in said first plate,
23. The structure of claim 21, wherein said spacer includes lead material.
24. The structure of claim 22, wherein said two metal plates comprises thin
steel shims.
25. In an electromagnetic pickup device for musical instruments having
elongated magnetizable vibrating elements with each of said vibrating
elements having a different degree of magnetizability; wherein said pickup
device comprises:
(a) a single permanent magnet, and
(b) a pickup coil surrounding said magnet; the improvement comprising:
horizontal plate means for varying the magnetic field of said permanent
magnet in proportion to the degree of magnetizability of said vibrating
elements; said horizontal plate means is disposed adjacent to said magnet;
whereby the magnetic field of said magnetic is shaped by maximizing the
magnetic field adapted to effect the wound vibrating elements having a
lower degree of magnetizability and minimizing the magnetic field adapted
to effect the vibrating elements having a higher degree of
magnetizability, and
said plate means is configured to provide a concave-like surface which when
said pickup device is adapted to said vibrating elements, will face said
vibrating elements of higher degree of magnetizability.
26. The structure of claim 25, wherein
said plate means is embedded in non-magnetic filler material.
27. The structure of claim 26, wherein
said pickup coil includes conducting means wound around said magnet and
filler material embedding said plate means.
28. The structure of claim 27, including
covering means enclosing said magnet, said plate means and said pickup
coil, and
said covering means including cover plates connected by an encapsulating
material. |
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Claims |
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Description |
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The present invention relates to improved electromagnetic pickups for
stringed musical instruments. In this regard, an improvement is provided
for the type of pickup, described in my previous application, having a
permanent bar magnet with a configured shape or surface adjacent to the
strings of the musical instrument for varying the magnetic field effecting
the respective strings in accordance with their magnetizability, wherein
thin metal plates or shims are interposed between the configured surface
of the magnet and the strings. A further improved arrangement of this type
is provided wherein the magnet is a regular bar magnet extending beneath
only some of the strings, while the metal shim provided between the
surface of the magnet and the strings is extended below the remaining
strings, not adjacent the magnet, with the shim itself being configured
with respect to these strings.
Various arrangements have been contemplated for magnetic pickups for
stringed musical instruments for the purposes of achieving volume
amplification of the vibrating strings, together with providing an
acceptable tone quality and uniformity of the amplified sounds produced by
the musical instrument. Such arrangements have included the provision of a
plurality of magnetic elements adjacent to each of the strings of the
musical instrument which magnetic elements may be adjustable with respect
to the strings to achieve natural tones and desired amplification of these
tones. Although such arrangements consider the variation of the magnetic
field associated with the respective strings, each of which has varying
degrees of magnetizability because of their construction, these prior
arrangements have involved complex constructions which leave the selection
of the tone quality of the strings subject to considerable adjustments.
Other arrangements have contemplated permanent magnet type structures which
vary the magnetic field effecting the various strings of the musical
instruments by placing a plurality of permanent magnets having variable
magnetic polarizations adjacent to the respective strings. These prior
arrangements also involve considerably complex constructions. A further
prior arrangement for a magnetic pickup for an electric guitar has
contemplated the use of separate pickups for the wound and unwound strings
of the electric guitar. The diameter of the string, as well as the
winding, provide different magnetizability of the wires which are effected
by the magnetic field of the respective pickups.
The present invention achieves an improved pickup of the structure of my
above-mentioned application in which the natural tone response is provided
for each string with high clarity. This electromagnetic pickup, according
to the present invention, allows high volume amplification techniques
while still retaining a true natural tone for each string, and reducing
hum and feedback in the amplified sound of the musical instrument.
Accordingly, these aspects are enhanced efficiently and economically in a
relatively simple construction over that of my above-mentioned application
in which a permanent magnet having a configured surface adjacent to the
strings of the musical instrument for varying the magnetic field effecting
the respective strings of the musical instrument was provided, wherein
additionally thin metal plates or shims are arranged in the pickup
structure between the configured surface and strings.
The configured surface itself provides a varying size of one dimension of a
permanent bar magnet in accordance with the degree of magnetizability of
the adjacent string. Thus, the magnetic mass adjacent to each respective
string is varied in accordance with the magnetization of the string,
thereby balancing the response from each string, while achieving a pickup
of the natural tone of the string. However, the addition of the thin metal
plates, particularly arranged specifically with the respective different
sizes of the magnet, results in a considerable improvement in the quality
and amplification of the pickup tones.
In particular, the magnetic pickup in accordance with the improved
invention advantageously enables the strings of an acoustic guitar to be
amplified at a high gain without destroying the natural response and
clarity of each string, and considerably reduces hum and feedback of the
amplified sound. Accordingly, the acoustic guitar can be electronically
amplified while retaining the natural tone quality of each of the strings.
An acoustic guitar utilizes bronze strings which are wound, and thereby
have varying degrees of magnetization in terms of the magnetic mass and
magnetic material of the respective strings. The construction of the
magnetic pickup in accordance with the present invention enables a
variation of the magnetic field effecting these strings of the acoustic
guitar in order to bring out the natural tone without severe amplification
of some strings over others such that the response from each string is
balanced.
In a particularly preferred arrangement of the present invention, the
magnetic mass adjacent the treble strings, which have the smallest
diameter and are not wound, is significantly reduced by eliminating the
permanent bar magnet at this location, whereas a thin plate covering the
bar magnet extends below the treble strings to magnetically balance the
pickup from these strings. The portion of the thin plate or shim extending
under the treble strings is configured to shape the magnetic field derived
from the permanent bar magnet relative to the treble strings, thereby
configuring the magnetic field to suit the magnetic pickup of the strings
without configuring the bar magnet. This preferred arrangement of the
present invention offers the ultimate stability and simplicity of the
pickup.
It is an object of the present invention to provide an improved
electromagnetic pickup device for a musical instrument of the type having
elongated magnetizable vibrating elements, which pickup device achieves a
balanced, natural tone quality of the musical instruments at high
amplification without the complexities and disadvantages of the
above-described prior arrangements.
Another object of this invention is to provide an improved electromagnetic
pickup device for musical instruments having elongated magnetizable
vibrating elements, which pickup device comprises a permanent magnet
having a configured surface adjacent to the magnetizable vibrating
elements to provide variation of the magnetic field effecting the
respective elements in accordance with their magnetizability, and having a
pickup coil surrounding the permanent magnet, wherein the improvement
comprises the interposition of thin metal plates or shims between
respective configured portions of the configured surface and the vibrating
magnetizable elements.
Still another object of the present invention is to provide an improved
electromagnetic pickup device of the aforementioned type having the thin
metal plates or shims in combination with a pickup device which includes a
permanent rectangular bar magnet being magnetically polarized
perpendicularly to two edge surfaces of the rectangular bar, with one edge
surface adjacent to the vibrating elements being configured to provide a
varying cross-sectional thickness or width dimension of the rectangular
bar magnet in accordance with the variation of magnetic field effecting
the respective vibrating elements with respect to their magnetizability.
A further object of the invention resides in the use of an improved
electromagnetic pickup of the aforementioned type having in combination
thin metal plates or shims arranged relative to a permanent magnet being
configured with different cross-sectional dimensions adjacent the
respective strings of an acoustic guitar in accordance with their
magnetizability, thereby improving natural tone quality and balance for a
pickup of the acoustic guitar at high amplification.
Yet another object of the present invention is to provide an improved
electromagnetic pickup device for musical instruments having elongated
magnetizable vibrating elements, which pickup device comprises a permanent
bar magnet arranged adjacent the vibrating elements of lower degrees of
magnetization and a thin plate or shim interposed between the magnet and
the vibrating elements with the thin plate extending out from the magnet
to balance the magnetic pickup of the vibrating elements of higher degrees
of magnetization.
A still further object of this invention resides in an improved
electromagnetic pickup of the aforementioned type having a thin metal
plate extending out from the permanent magnet to balance the pickup of the
less magnetizable vibrating elements, wherein the thin plate is configured
relative to the less magnetizable vibrating elements to shape the magnetic
field effecting these elements in accordance with their magnetizability.
These and other objects of the present invention may be achieved in an
improved electromagnetic pickup device including at least one thin metal
plate or shim in combination with a permanent magnet, and having a pickup
coil surrounding the permanent magnet and thin metal plate or shim,
wherein a configuration of the magnetic field is achieved relative to
magnetizable vibrating elements of a musical instrument, either by
configuring the magnet or the thin plate or shim. Moreover, the
improvement of this combination also resides in that the permanent magnet
may be a rectangular bar magnet being magnetically polarized perpendicular
to the two longitudinal edge surfaces thereof, and in one embodiment of
the present invention, wherein the magnet may have a configured surface
with one of the two edge surfaces providing a cross-sectional varying
thickness or width dimension of the bar magnet facing the vibrating
elements.
In this arrangement of the present invention, the improved pickup may be
used with a variation of the cross-sectional thickness or width of the bar
magnet being achieved in a tapered form, a step form, a notch form and a
combination of a notch and step form. The respective variations of the
cross-sectional thickness or width of the permanent magnet are dimensioned
in accordance with the amount of pickup to be achieved with the respective
strings of the musical instrument. Moreover, it has been found
particularly advantageous that respective ones of thin metal plates or
shims be placed in relationship to the respective cross-sectional
variations of the thickness of the magnet.
A preferred arrangement of these thin metal plates or shims in this
embodiment results from using different dimensioned plates or shims
relative to the different configured surfaces of the magnet. Thus, at the
side of the magnet extending below the treble strings of an acoustic
guitar, for example, which magnet has a tapered or stepped configuration
of the magnet, a square-like plate or shim can be interposed, while a
longer rectangular plate or shim can cover the remaining surface of the
magnet. The square-like plate preferably includes a width dimension larger
than the width dimension of the longer rectangular plate. By this means,
variations in the shielding between the magnet and strings can be balanced
so as to result in a more balanced output of the pickup.
This embodiment of the present invention further contemplates the improved
pickup with the provision of a covering structure for enclosing the
permanent magnet and the coil surrounding the permanent magnet. The thin
metal plates or shims may be embedded in the covering structure which may
be non-magnetic and include a spacer material which enables a tapering of
the surface of the covering structure adjacent to the configured edge
surface of the permanent magnet. In this respect, the covering structure
can include two non-magnetic plates adjacent the two edge surfaces of the
bar magnet, having the pickup coil surrounding the permanent magnet, and
connected to one another by means of an epoxy resin further surrounding
the construction of the permanent magnet and coil. The epoxy resin
material may be also utilized as the spacer material between the top cover
plate and the configured surface of the permanent magnet providing a taper
therebetween. This top cover and configured surface are those placed
adjacent to the strings of the musical instrument.
A further arrangement of this embodiment of the present invention resides
in the use of a lead filler as the spacer material between the configured
surface of the magnet and the top cover plate. The remaining structure of
the pickup is as described with the thin metal plates or shims embedded
into the top cover plate above the lead filler material.
In another preferred embodiment of the present invention, the improved
combination of the electromagnetic pickup may reside in that the permanent
bar magnet may be a rectangular bar magnet being magnetically polarized
perpendicular to the two longitudinal edge surfaces thereof, and in that
the bar magnet extends only under, or adjacent, the strings of the musical
instrument which have the lower magnetization, while a thin metal plate
covering the bar magnet extends out from the longitudinal edge surface
facing the strings to effect the magnetic field with respect to the
strings of higher magnetization, i.e. the treble side strings. In
particular, the thin plate is configured or bent in the area adjacent the
treble strings to provide a somewhat concave-like surface facing the
treble strings. The thickness of the metal plate or shim can be selected
to further balance the amount of magnetic energy required for the pickup
of the sounds by the treble strings.
A covering structure for this embodiment of the present invention may have
non-magnetic plates covering the top and bottom of the bar magnet with the
top plate also covering the configured magnetic metal shim or plate. In
this arrangement, configured portion of the metal plate extending beyond
the magnet may be surrounded by a filler material, such as an epoxy resin
or other nonmagnetic material so as to substantially fill the volume
between the top and bottom covering plates. The configured metal shim is
effectively embedded in position by the filler material so that the pickup
coil can be wound about the magnet on one end and about the configured
metal shim and filler material at the other end of the pickup device.
The high pickup coil, or spool, plays an important part in the pickup of
the tones of the vibrating strings, and may be either low impedance or
high impedance. In accordance with a further aspect of the present
invention, the coil is wound about the bar magnet having a varying
cross-sectional dimension, or about the bar magnet and configured shim, in
such a manner as to be tight against the magnet at one end, but wound
overlappingly at the end of the pickup relative to the treble side of the
musical instrument. Thus, at the treble side, the coil windings are
spread-out away from the pickup end, thereby adding depth to the field
created by the magnet. This adds depth, or a more distant response, and a
pleasing tone to the sounds picked-up at treble side of the musical
instrument. On the other hand, the coil windings will be wound tight
against the magnet at the bass end which tend to compress the bass tones,
thereby reducing super-low frequencies which cause annoying acoustic
feedback. This construction acts as a filter of the super-low frequencies
at the bass side, while the musical tones picked up at the treble side are
mellowed in that the super-high frequencies are limited and not heard as
occurs in natural acoustic sounds.
These and other aspects of the present invention may be achieved and
understood by reference to the drawing figures, which provide in
non-limitative example the features of the present invention, and wherein
FIG. 1 illustrates an acoustic guitar utilizing the electromagnetic pickup
according to the present invention;
FIG. 2 illustrates in perspective view one embodiment of the improved
electromagnetic pickup in accordance with the present invention;
FIGS. 3a-3g illustrate respective examples of configured cross-sectional
thicknesses or widths of the magnet in relation to the strings of a
musical instrument for use with the improved electromagnetic pickup device
in FIG. 2;
FIGS. 4a and 4b illustrate a preferred construction of the embodiment in
FIG. 2 in elevation and plan view, respectively;
FIGS. 5a and 5b illustrate in cross-section and plan view, respectively, a
preferred construction of another embodiment in accordance with the
present invention; and
FIG. 6 illustrates an arrangement of the pickup coil of the present
invention.
An electromagnetic pickup 2 in accordance with the present invention is
illustrated in FIG. 1 being placed under the strings 5 of an acoustic
guitar 1. The placement of the pickup may be between the bridge 3 of the
guitar and the sound hole thereof with a preferred placement being
approximately two inches from the bridge 3 and between the top of the
guitar 1 just below the strings 5.
FIG. 2 sets forth an arrangement of one embodiment of the electromagnetic
pickup of the present invention in which two thin metal plates or shims 21
and 22 are placed in the top cover 10 of nonmagnetic material. The
remaining pickup structure in accordance with my aforementioned copending
patent application includes the bar magnet 12 having a generally
rectangular shape with respective length, width and thickness dimensions,
being provided between the top and bottom covers 10 and 11. The coil 13
surrounds the outer periphery of the bar magnet 12 and includes the leads
14 which may be attached to conventional amplifying equipment including
pre-amplifiers.
The thin metal plates or shims 21 and 22 are illustrated in FIG. 2 as being
embedded into the top cover plate 10, but this top plate may be dispensed
with. In such an arrangement, the pickup is encapsulated in a synthetic
resinous material, and the thin metal plates or shims 21 and 22 are
arranged over the top of the magnet 12 embedded into the encapsulating
material. Thus, the top cover, as well as the bottom cover, may be of a
plastic non-magnetic material with the metal plates 21, 22 fixed in the
top cover, or alternatively, the top cover may be comprised of the thin
metal plates or shims being a metallic magnetic shielding structure.
As may be further seen in FIG. 2, the respective thin metal plates or shims
21 and 22 are of different sizes. That is, the plate 22 is an elongated
rectangular plate while the plate 21 is a generally square plate having
width dimensions greater than that of the width dimension of the plate 22.
Moreover, the magnet 12 in FIG. 2 is illustrated as including a single
step, similar to the arrangement in FIG. 3c, and the thin metallic plate
21 covers the area of reduced cross-sectional thickness of the magnet,
while the thin metallic plate 22 covers the greater thickness portion of
the magnet 12. By such an arrangement, the thin metallic plate or shim
being at the treble side of the pickup increases the magnetic shielding
and/or improves the balance of the pickup with respect to the remaining
strings of the guitar.
Various configurations of the bar magnet have been found to be effective in
achieving the high volume amplification of the acoustic guitar strings in
accordance with the improved structure including the thin metallic shims
21 and 22. These various configurations of the bar magnet may be seen by
reference to FIGS. 3(a-g), which correspond to the various configurations
utilized in my abovementioned copending application.
Accordingly, the rectangular bar magnet 12a in FIG. 3a has a tapered edge
surface adjacent to the strings of the guitar in order to provide a
continuously varying change of magnetic mass adjacent to the strings 5,
which includes steel wound bronze strings at the base side and unwound
steel strings at the treble side. A further example of this structure is
seen in FIG. 3b in which the taper is provided only over a length of the
bar magnet 12b at the treble side of the pickup.
The configured bar magnet 12c in FIG. 3c includes a step 16 at the treble
side of the pickup. In this instance, a spacer material may be placed
between the face 15 of the reduced step cross-sectional portion of the
magnet 12c with the thin metallic plate or shim, such as 21, placed
thereabove, similarly to that illustrated in FIG. 2. As mentioned above,
the shim 21, as well as shim 22 may be provided above the magnet, between
the top surface of the magnet and the strings 5, with or without the use
of the top cover 10.
A further arrangement of the bar magnet may be seen in FIG. 3d, wherein the
bar magnet 12d is stepped at the step 16, and further includes a notch
edge surface portion 17 with a further step edge surface portion 19 at the
step 18. In this respect, the thin metallic shim 21 may cover the major
portion of the notch edge surface portion 17, as well as the edge step
surface portion 19, as may be further seen in FIGS. 4a and 4b.
The pickup in FIGS. 3e, 3f, and 3g show various other configurational
arrangements of the bar magnets 12e, 12f, and 12g. In these various
configurational arrangements of the magnets, respective different
thicknesses of the magnet are disposed relative to the different strings
of the guitar. Moreover, each of these configurational arrangements of the
bar magnets in FIGS. 3a through 3g may be appropriately dimensioned in
accordance with the strings of the guitar, as described in my
aforementioned copending patent application.
In this respect, the various configurational arrangements of the bar
magnets result in differing advantageous features of the pickup of the
present invention, as discussed in my copending application. For example,
ease of manufacture, as well as varying balanced outputs of the pickup,
may be achieved with the respective different configurational arrangements
of the bar magnet.
FIGS. 4a and 4b illustrate in respective elevational and plan views a
preferred arrangement of this embodiment of the present invention in which
the thin metal plates or shims 21 and 22 are arranged above the top
surface of the configured bar magnet. In these figures, a configuration of
the bar magnet, such as appears in FIG. 3d, is provided with the shims 21
and 22 being embedded into the top cover 10.
In this regard, FIG. 4a illustrates the embedding of the shims 21 and 22
into the top cover 10, and a filler material 23 included between the top
cover 10 and the stepped surfaces 17 and 19 of the bar magnet 12. This
filler material may be lead, and the pickup then embedded in a synthetic
resinous material with the coils wrapped around the edges of the magnet.
FIG. 4b shows in plan view the arrangement of this embodiment of the
present invention wherein the covers 10 and 11 are not illustrated for
purposes of clarity. This figure also emphasizes the difference in
dimensions of the respective thin meallic plates or shims 21 and 22, as
well as their respective placement with respect to the stepped or
configured surfaces of the pickup.
Although this preferred arrangement in FIG. 4 is described with respect to
the bar magnet, such as that in FIG. 3d, of course, the shims 21 and 22
may be utilized with any of the different configured magnets, such as
those previously described.
In each of the embodiments described above, the bar magnets may have a
cross-sectional thickness ranging from 0.125 to 0.425 inches. Moreover,
the permanent bar magnets may be formed of a rubber magnetic material, an
alnico magnetic material, a Cu-Ni-Fe magnetic alloy, or a ceramic magnet.
The length of the magnet will be appropriate to extend under all of the
strings of the guitar, and may be approximately 21/2 inches, for example.
The thin metallic plates or shims will have corresponding dimensions
appropriate to the improvement of these elements. Namely, in the
embodiment of FIGS. 4a and 4b, for example, the thin metallic plate or
shim 21 may be generally one square inch, while the thin metallic
rectangular plate 22 may have a length slightly greater than about 11/2
inches and a width somewhat less than one inch.
The metal plates or shims may be formed of steel or preferably any magnetic
shielding material.
A preferred embodiment of the present invention is illustrated in FIGS. 5a
and 5b, wherein the magnet 52 extends only beneath the strings 5 of lower
magnetizability, and the thin plate or shim 50, covering the top of the
magnet, extends from the magnet to below the strings 5' of higher
magnetizability. These strings are at the treble side of the musical
instrument, and are constituted of small diameter and are not wound, so as
to have a high degree of magnetizability. Thus, in order to achieve
excellent balance for these strings which require only a small amount of
magnetic energy, then the metal plate 50 being magnetized by the magnet 52
effects only the magnetic field necessary for the strings 5'.
In this regard, in order to improve the pickup, the thin plate 50 extending
beyond the magnet 52 is configured by a dip or bend 51. This achieves a
variation of the magnetic field relative to the strings 5' in a similar
manner to that of the configured bar magnet 12 in the embodiment above,
but with a much simpler construction achieved with a higher degree of
stability. As may be seen in FIG. 5a, the volume between the upper and
lower cover plates 10 and 11 is filed with a filler 53, which may be of an
epoxy resin material, or a similar filler material to that described in
the embodiment above.
This filler material 53 embeds the configured portion 51 of the shim 50 so
as to hold it into position, as well as provides a base or support for
winding the coils 13 about the end of the freely extending shim 50. The
magnet may be of the same magnetic material used in the embodiment
discussed above, while the cover plates 10 and 11 may also be of
non-magnetic synthetic resinous materials or non-magnetic metals, which
are bonded together by an encapsulating material, such as described above.
The thin metal plate or shim 50 may be formed of a steel or a magnetic
material, as above, and preferably has a thickness of about 0.030 inches.
The rectangular dimensions of the thin plate or shim 50 correspond to that
of the magnet, as may be seen in FIG. 5b, wherein the magnet may have a
length of about 11/2 inches, for example, wich a width or thickness
similar to that described above.
On the other hand, the shim 50 extends beyond the edge of the magnet 52
sufficiently to be located beneath the strings 5', such as by a distance
of at least one inch. Moreover, the curvature 51 of the plate 50 in this
area may be determined on the basis of the balance of the magnetic pickup
of the strings 5'. As may be seen in FIG. 5a, the curvature is such as to
provide a concave-like surface facing the strings 5' with the distance
between the strings and the shim 50 varying in accordance with the
magnetizability of the respective strings. That is, the shim 50 is
farthest away from the larger diameter string having a greater magnetic
mass than the right-hand most string.
The arrangement of the coil 13 has been found to be of considerable
importance in the quality of the pickup in both embodiments of the present
invention, as also discussed in my aforementioned copending patent
application. Accordingly, FIG. 6 shows a view of the pickup in FIG. 3d in
the direction of the arrows 6--6 wherein the coil 13 may be wound above
the bar magnet 12" to be tight against the magnet at the wider dimension
end, or base side, while being wound spreadout away from the magnet at the
outer width end, or treble side. This winding occurs as a natural
consequence of the winding of the wire about the magnet of different
widths in order to maintain the presence of the coil about the body of the
magnet. A similar arrangement of the coil windings may be seen in FIG. 5a.
This arrangement of FIG. 6 has been found to considerably enhance the
quality of the acoustic pickup in that the super-high frequencies of the
treble side, as well as the super-low frequencies of the base side, are
essentially filtered out.
In each of the embodiments of the present invention, the coil may be a low
impedance coil of about 150 to 1000 ohms, and, for example, may be No. 37
wire with an impedance of about 200 ohms. The size or gauge of the wire
may vary considerably, however, ranging from No. 37 wire to No. 44 wire
with a corresponding impedance ranging from 200 to 1000 ohms. Also, a high
impedance coil of from 6000 to 14000 ohms for wire ranging from No. 40 to
No. 44 may be used.
While I have shown and described several embodiments in accordance with the
present invention, it is understood that the same is not limited thereto | | |
