close

Вход

Забыли?

вход по аккаунту

?

JP2018516519

код для вставкиСкачать
Patent Translate
Powered by EPO and Google
Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JP2018516519
A loudspeaker diaphragm (12) comprising a woven fiber supports a damping material (25), for
example a PVA polymer, on the rear facing surface (24). The woven fiber body may be formed of
a length (14) of a non-metallic fiber material (e.g. glass fiber) coated with a thin metal coating
(32). The mass of the layer of damping material (25) may far exceed the mass of the woven fiber
body. Thus, an attractive sparkling appearance of the loudspeaker diaphragm (12) may be
provided, providing a flatter frequency response curve (50) while at the same time damping
unwanted vibrations.
Speaker diaphragm
[0001]
The present invention relates to a loudspeaker diaphragm and a method of manufacturing such a
diaphragm. More particularly, the present invention relates to a speaker diaphragm including,
but not limited to, a woven fiber body supporting a damping material. The invention also relates
to a loudspeaker drive unit and a loudspeaker housing.
[0002]
GB 149 1080 (by B & W Loudspeakers Limited-or "B & W"-) is made from an open mesh woven
fiber material, eg Kevlar®, reinforced with a thermosetting resin so that there is a space left
between adjacent fibers Disclosed is a loudspeaker diaphragm made. The space is partially filled
10-05-2019
1
with a damping material such as a PVA (polyvinyl acetate) emulsion. The spaces between the
threads of the fabric allow a good bond between the PVA emulsion and the woven fiber material.
The British company Bowers & Wilkins (see “B & W”-www.bowers-wilkins.co.uk) incorporates
a speaker diaphragm made from a woven Kevlar® fabric reinforced with resin and coated with
PVA. Commercialization of the mid range drive unit. The PVA material is brushed on the woven
fiber material in one or more layers, and typically the PVA material will form about 10% to 15%
of the total mass of the loudspeaker diaphragm. The result is a somewhat soft, showing useful
break-up behavior, more suppressed coloration, and a more even distribution of the emitted
sound, as described in more detail below. Corn (hereinafter "Kevlar corn from B & W") (still
further details are available at http://www.bowerswilkins.com/Discover/Discover/Technologies/Kevlar.html).
[0003]
The continuous vibration of the loudspeaker diaphragm, independent of the applied input signal,
responds to the given input signal as a result of "time-smearing"-a form of coloration- This can
lead to a reduction in the clarity of the sound produced and the accurate reproduction of the
sound from the input signal. PVA materials achieve damping, but the anisotropic properties of B
& W's Kevlar cones are mentioned as important: because they are woven, the mechanical
properties of B & W's Kevlar cones are fiber orientation Depends on the angle to The sound
waves travel through the material of the cone at different speeds depending on the direction of
travel. Thus, the reflection of sound waves traveling across the body of the B & W Kevlar cone
occurs at different times around the edge of the cone, resulting in less symmetrical sound wave
patterns, and the reduction of sound effects due to the formation of standing waves. Bring. Less
sound is received by the listener than would otherwise be produced by the delayed energy
emitted by the cone. As a result, undesirable "time obfuscation" noise is reduced. The cone thus
produces a radiated sound that can deliver distinct and finer details. The design details described
as providing quality control of sound reproduction include the choice of weave type, cone
geometry, and reinforcement resin and damping material types.
[0004]
B & W's Kevlar cones are used in many of B & W's products and are widely used in the midrange
drive unit supplied to B & W's speakers (www.bowerswilkins.eu/Speakers/Theatre_Solutions/FPM_VM_Series/Technologies.html) reference). Kevlar
not only has the above-mentioned advantageous properties, but also advantageously has an
attractive and distinctive appearance, which makes it suitable for use on the forward sounding
10-05-2019
2
surface of the loudspeaker drive unit's diaphragm Make it However, Kevlar is an expensive
material, and it should be beneficial to have alternative materials for this application that can be
used in a manner that provides similar or better acoustic performance. It would also be beneficial
for such materials to not only achieve technical performance and meet the required technical
features, but also have an appearance suitable for use in a high fidelity environment.
[0005]
The present invention seeks to alleviate one or more of the above mentioned problems.
Alternatively or additionally, the present invention seeks to provide an improved loudspeaker
diaphragm. Alternatively or additionally, the present invention seeks to provide an alternative to
the above B & W Kevlar cone which is substantially identical or has better acoustic performance.
[0006]
The present invention provides a loudspeaker diaphragm comprising a woven fiber body having
a forward sound emitting surface and a rearward facing surface supporting a damping material,
the damping material preferably forming the shape of the diaphragm. According to one aspect of
the invention that is important but not necessarily essential, the woven fiber body is formed of a
metal-coated non-metallic fiber material, which is coated with natural light. It is preferred that
the light from the different light sources, when illuminated by the light, appears to have a
shimmering appearance, for example as perceived by the naked eye when viewed with the naked
eye.
[0007]
The potential of being expensive and not requiring the use of Kevlar, which is limited in how it
can be presented (especially keeping in mind that Kevlar's previous color is cream yellow) It is
possible to make loudspeaker diaphragms using such metallized non-metallic fiber materials that
perform well if not better than B & W's Kevlar cone, which has the advantage of: The present
invention proposes a loudspeaker diaphragm which not only has the benefit of providing an
alternative to the prior art Kevlar fiber cone, but also has a unique and attractive look in
particular. The lengths of fibers woven to form a woven fiber body interweave with each other
such that the surface of the diaphragm has a non-smooth geometry at the local level (e.g. on the
micrometer or millimeter scale) Be A non-smooth geometry refers to the reflection of incident
10-05-2019
3
light received at a given angle of incidence (with respect to the axis or forward direction of the
diaphragm) in significantly different directions between relatively close points on the diaphragm.
Means The outer metal surface is preferably predominantly specularly reflective surface, for
example so that the surface has a mirror-like appearance as opposed to a less shiny appearance.
Thus, the diaphragm, whether natural light or light from a different light source, may have an
attractive shimmering or otherwise unusually noticeable appearance when illuminated with light.
Furthermore, it may be that the damping material may have an unattractive appearance and / or
the possibility of discoloration over time. Using a speaker diaphragm with a forward facing
surface that visually accentuates as a glitter mask or at least possibly from the unattractive
appearance of the rear damping material that would otherwise be more eye-catching It may have
the further advantage of providing something that distracts. In another aspect of the invention,
the woven fiber body may be formed of a material that is not in the form of a metallized nonmetallic fiber material but still provides benefits.
[0008]
According to another aspect of the invention that is important but not necessarily essential, the
mass of the layer of damping material exceeds the mass of the woven fiber body by more than
25%. Surprisingly, it has been found that having a relatively high ratio of mass of damping
material layer to mass of woven fiber body can provide improved acoustic performance in
embodiments of the present invention. In one embodiment of the present invention, which relates
to a 6 inch drive unit, the mass of woven fiber body and the mass of damping material may be 3
grams and 5 grams, respectively. By way of comparison, the mass of the woven fiber body of the
6 inch (prior art) B & W Kevlar cone and the mass of the damping material are 6 grams and 1
gram, respectively. Thus, B & W Kevlar cones have damping materials added to provide damping
rather than structure and have some minimal level of stiffness and structural support provided
by the woven fiber body. In embodiments of this aspect of the invention, the properties of the
damping material play a much larger role in the physical structure and acoustic performance of
the diaphragm, and the woven fiber body plays a smaller role. One role that may be considered
as the main role of the woven fiber body of the present invention is that the woven fiber body
may serve as a base or skeleton structure for supporting the damping material forming the
majority of the diaphragm. . One role that may be taken as the second role of the woven fiber
body may be that the woven fiber body provides an aesthetically pleasing forward face.
[0009]
As mentioned above, much more than previously recommended in the context of the B & W
10-05-2019
4
Kevlar cone design (with a woven fiber body with a back facing surface supporting only a
relatively thin layer of damping material) It has been found that having a relatively large amount
of damping material can be surprisingly beneficial. The mass of the layer of damping material
may exceed the mass of the woven fiber body by more than 50%. The layer of damping material
may have a mass of at least twice that of the woven fiber body. The mass of the layer of damping
material may be, for example, in the range of 100 to 500 g / m <2>. The mass of the woven fiber
body may be between 25% and 80% of the mass of the layer of damping material.
[0010]
The thickness of the layer of damping material may exceed the thickness of the woven fiber
body. The thickness of the layer of damping material may for example be greater than 0.2 mm.
The thickness of the layer of damping material may be less than 0.5 mm. The woven fiber body
may form the forward sound emitting surface of the diaphragm. The layer of damping material
may form the rearward facing surface of the diaphragm. Thus, as may be the case when the
diaphragm is in the form of a sandwich structure, there may be no woven fiber present on the
rearward facing surface of the diaphragm. The damping layer may be of unitary construction.
The damping layer may be a monolithic structure having a uniform composition. Thus, the
damping layer may be such that it has little or preferably no fibrous material in its structure. As
mentioned above, in some embodiments, the woven fiber body may be made of non-metallic fiber
material. The fiber body may be formed of metal coated fibers. When a woven fiber body is
formed of metal-coated fibers, the thickness of the metal coating may be less than 10 μm. The
metallization may be less than 1 μm thick.
[0011]
The woven fiber body can include fibers and a resin, for example, fibers incorporated (at least
partially) in a cured resin matrix. The resin may be a phenolic resin. The resin can contribute to
the rigidity of the woven fiber body. Thus, the resin may take the form of a reinforcing resin. The
fibrous body and the resin may be in the form of a composite structure. If the woven fiber body
is formed of fibers that are at least partially metallic, the metal part may be protected by a layer
of lacquer. The layer of lacquer can contribute to the stiffness of the woven fiber material. If the
fiber material is further reinforced by using a reinforcing resin in addition to the lacquer, it may
be possible to use less reinforcing resin per unit area of woven fiber material. The lacquer is
preferably translucent and may be of a clear color, for example substantially transparent. The
mass per unit area of the resin may exceed the mass per unit area of the lacquer by a factor of 5
or less. The mass per unit area of the resin and the lacquer may be in the range of 20 to 60 g / m
10-05-2019
5
<2> in total.
[0012]
The diaphragm may be flat. The diaphragm may have a generally conical shape. The diaphragm
may have a diameter of at least about 50 mm. The diaphragm may have a diameter of about 200
mm or less. The woven fiber body may be formed of a glass fiber material. Glass fibers are readily
available and relatively inexpensive but are typically transparent so that light is transmitted from
one side of the woven fiber material to the other through the glass. to enable. In some cases it
may be inconvenient to pass light to and / or from the damping material on the rear facing side
of the woven fiber body, in which case the glass fiber will show the choice of the best material It
can not be received. However, if the fiberglass material is covered with an opaque coating as
provided by the above-described metal coating, such potential drawbacks can be mitigated or
overcome.
[0013]
Woven fiber bodies can have relatively regular weaves. For example, the density of thread length
per unit area may be substantially constant across the surface of the diaphragm. The collection of
fibers that together form the length of the other material and the length of the single material
interweaving in and out may itself be considered as a single thread in this context. The weave
nature of the fibrous body of the diaphragm may be such that the elongated pieces of material
weave in and out of one another to form the body. There may be gaps between adjacent material
lengths. Woven fiber bodies can define an array of such interstices. It will be appreciated that the
array of interstices typically has a relatively complex three dimensional geometry and is typically
not a regular array. Each interstice is typically formed by a pair of adjacent fibers crossing
another pair of adjacent fibers but may have a maximum dimension of at least 50 μm,
preferably at least 100 μm. Damping material may fill substantially all of the gaps so defined.
[0014]
The damping material may have a dynamic loss factor of at least 0.25 at frequencies between 1
kHz and 8 kHz. For example, the damping material may have a dynamic loss factor of at least 0.5
at frequencies between 3 kHz and 6 kHz. The loss factor may be greater than 0.75 at frequencies
within the operating frequency range of the diaphragm. Such damping materials may realize
10-05-2019
6
particularly strong damping at frequencies where vibration of the diaphragm may otherwise
begin to break up (i.e. deviate from simple piston-like behavior). The damping material may be an
elastomeric material. The damping material may be in the form of a synthetic resin. The damping
material may be in the form of a suitable polymer. Vinyl polymers may be appropriate. The
damping material may be a high damping polymeric material such as a PVA (polyvinyl acetate)
material. The color change over time of such materials means that their use in the hi-fi
loudspeaker diaphragm is usually limited to areas not visible in normal use. Thus, there may be
embodiments of the present invention in which the damping material is beneficially masked or
concealed or otherwise camouflaged by a metallized fibrous material body.
[0015]
The thickness of the damping material may be substantially constant over most if not all of the
rearward facing surface on which the damping material is supported. It will be appreciated that
slight changes in thickness resulting from the weave nature of the fibers and any gaps in the
weave should not be taken into account in this context. This is because it is the thickness of the
damping layer that is seen as being related to the macroscopic shape of the associated
diaphragm (and thus the change in the geometry of the diaphragm to which the weave properties
of the fiber contribute Flatten / ignore). However, the thickness of the damping material may be
selected to be thicker at specific points, for example in the area of or at the point of intersection /
node line of the vibration where break-up is observed. Therefore, there is an (middle) average
thickness of the damping material that is more than 10% greater than the (middle) average
thickness of the damping material at different contact sites between the rearward facing surface
and the damping material. There may be areas showing more than 10% of the area of the contact
area between the face and the damping material (and showing more than 10% of the total
contact area). The thickness of the damping material may vary monotonically with increasing
radial distance over at least 5% of the diameter of the diaphragm.
[0016]
According to another aspect of the present invention, there is also provided a method of
manufacturing a loudspeaker diaphragm, for example for use as a loudspeaker diaphragm as
described or claimed herein. Such methods may include the step of applying a liquid damping
material to the woven fiber body that may be rotated. Rotating the woven fiber can help to
promote uniform application of the liquid damping material. The woven fiber body can be
rotated at a relatively slow angular velocity, for example less than 100 rpm, when depositing the
liquid damping material first (e.g., in a spiral pattern) on the rearward facing surface.
10-05-2019
7
Subsequently, when rotating the woven fibrous body to promote uniform application of the liquid
damping material on the back facing surface, the woven fibrous body has a relatively high
angular velocity, for example, between about 100 rpm and 1000 rpm). It can be rotated at speed.
The woven fiber body may be rotated at over 500 rpm during the step of rotating at a relatively
high angular velocity. The process of rotating at a relatively high angular velocity comprises a
first step of rotating at a first speed between about 100 rpm and 500 rpm and then a second
step which is more than 50% faster than the first angular velocity, preferably more than 500
rpm. And second step of rotating at an angular velocity.
[0017]
There may be the step of curing the damping material such that the damping material changes
from a liquid substance to a solid (non-flowing) substance. The liquid damping material may be
applied in the form of an emulsion, for example a water based emulsion. Curing the damping
material may be performed at a temperature less than 100 degrees Celsius. When the damping
material comprises water, such as a water based emulsion of PVA material, curing at relatively
low temperatures may be important. The PVA layer may be cured between 40 degrees Celsius
and 80 degrees Celsius. The method may be performed to make a speaker diaphragm having a
woven fiber body formed of non-metallic fiber material. A method of manufacturing a
loudspeaker diaphragm may include, for example, applying a metal coating to a non-metallic
fiber material of woven fiber body. The step of depositing the metal coating may be performed
using a vapor deposition method.
[0018]
According to another aspect of the present invention there is also provided a speaker drive unit
comprising a diaphragm according to any aspect of the present invention as described in the
claims or described herein. Such a speaker drive unit may be configured for use as a midrange
drive unit for a high fidelity speaker. The speaker drive unit may have an operating range over a
frequency band including a frequency of 20 Hz. The loudspeaker drive unit may have an
operating range over a frequency band ranging at least 6 kHz and possibly at least 8 kHz in
height. For example, the operating range may include 200 Hz to 5 kHz. If the diaphragm of the
loudspeaker drive unit has a diameter of less than 80 mm, the drive unit may also have an
operating range over a frequency band that extends at least 10 kHz, possibly even at least 15
kHz.
10-05-2019
8
[0019]
According to yet another aspect of the present invention, there is also provided a speaker
housing comprising a speaker drive unit according to any aspect of the present invention as
described in the claims or as described herein. Of course, it will be understood that the features
described in relation to one aspect of the invention may be incorporated into other aspects of the
invention. For example, the method of the present invention may include any of the features
described with respect to the device of the present invention, and vice versa. Embodiments of the
invention will now be described, by way of example only, with reference to the accompanying
schematic drawings.
[0020]
FIG. 1 is a perspective view of a speaker housing incorporating a woven fiber cone according to a
first embodiment of the present invention. It is a figure which shows the direction of the fiber of
the woven fiber cone of FIG. Figure 2 is a side view of the cone of Figure 1; FIG. 2 includes an
enlarged view of a portion of the woven fiber cone of FIG. 1; 5 is a cross-sectional view of a
portion of the woven fiber cone shown in FIG. 4 along the plane represented by line A-A in FIG. 4;
FIG. 6 is an enlarged cross-sectional view of one of the lengths of material of FIG. 5; FIG. 2 shows
frequency response curves comparing the acoustic performance of the loudspeaker of FIG. 1 with
an equivalent loudspeaker of the prior art. FIG. 2 shows frequency response curves comparing
the acoustic performance of the loudspeaker of FIG. 1 with an equivalent loudspeaker of the
prior art. 5 is a flow chart illustrating a manufacturing method according to a second
embodiment of the present invention.
[0021]
FIG. 1 shows a high fidelity speaker enclosure 2 in the form of a generally cubic cabinet 4. The
cabinet 4 accommodates the mid / low drive unit 6 and the tweeter 8. The speaker is vented by
the forward port 10. The drive unit 6 comprises a cone-shaped diaphragm 12 which has a
generally concave shape when viewed from the front (as shown in FIG. 1). The diaphragm has a
diameter of about 150 mm (6 inch drive unit) and operates over frequencies in the range of 20
Hz to 6 kHz. The diaphragm is formed from a woven fiber cone as schematically shown in FIGS. 2
and 3, which show the cone as a front view and a side view, respectively. Thus, there are adjacent
fiber lengths 14 extending substantially parallel to one another, these fiber lengths 14 being of
other corresponding adjacent fiber lengths extending transversely to them. Weaving in and out
10-05-2019
9
to form a woven mat. The length of fiber material 14 is curved and intersected at different angles
to define the desired (concave) conical shape of the diaphragm. Diaphragm 12 defines a forward
sound emitting surface and a rearward facing surface that supports the damping material. FIG. 2
shows the longitudinal extent of only some of the fiber lengths 14 and shows the non-linear
shape that the fiber lengths of the diaphragm 12 have.
[0022]
The generally concave shape of the cone-shaped diaphragm 12 is formed by a wall extending
360 degrees around the central axis 12a, and the wall 16 has a convex shape which is gently
curved when viewed in cross section It will be understood from FIG. 3 that it has. FIG. 3 also
shows the forward sound emitting surface 22 (also seen in FIG. 1) and the rearward facing
surface 24 of the diaphragm. FIG. 4 shows an enlarged view 18 of the cone 12 and a portion
thereof. As can be seen from FIG. 4, each fiber length 14 is such that there is a space 20 between
generally parallel adjacent fiber lengths 14 extending in a given direction. Interwoven in a
relatively coarse weave. FIG. 5 very schematically shows a cross section of a length 14 of three
parallel fiber materials, which is taken along the line A-A shown in FIG. The forward facing sound
emitting surface 22 is located at the top of FIG. 5, while the rearward facing surface 24 is located
at the bottom of FIG. The layer of woven glass fiber material has a thickness Tf of about 0.2 mm
to 0.3 mm. The rearward facing surface 24 of the diaphragm supports a layer 25 of damping
material, which fills the space 20 between the woven fiber lengths 14. The damping material is in
the form of a cured PVA polymer and has a mass of about 240 g / m <2>. The damping material
has an average thickness Td that is not much different from the thickness Tf of the glass fiber
layer, which is about 0.2 mm to 0.3 mm. The cured PVA layer 25 fills the interstices 20 between
the lengths of fibrous material 14 and thus acts as a sealant (the cone will be full of holes without
the sealant).
[0023]
A length of single fiber material 14 is shown in cross section in FIG. The length of fibrous
material comprises a collection of individual glass fibers 26 (not individually shown in FIG. 6)
arranged in parallel to form a thread 28. Woven glass fibers have an open weave with a mass
density of about 120 g / m <2> (as dry). The interstices 20 between the fiber lengths 14 have a
width of about 400-500 μm. The fibers 26 forming the threads 28 are embedded in a resin
substrate 30, the outer surface of the resin substrate 30 is covered with a thin layer 32 of
aluminum and the thin layer 32 of aluminum is protected by a layer 34 of lacquer. The amount
of resin used per unit area alone is less than the amount ideally needed to provide the desired
10-05-2019
10
stiffness to the glass fiber layer. However, the layer 34 of lacquer contributes to the stiffness of
the woven fiber material and has a mass per unit area less than but still comparable to that of the
resin. The mass per unit area of the combined resin and lacquer is typically in the range of 20 to
60 g / m <2>, depending on the particular application. (Thus, woven glass fibers, including resins
and lacquers, have mass densities on the order of about 160 gm <2> ± 20 g / m <2>). The layer
32 of aluminum has a thickness of about 0.1 μm and therefore has a negligible mass compared
to the mass of the other component materials of the diaphragm. The presence of the layer 32 of
aluminum provides opacity, without which the PVA layer 25 behind the glass fiber thread and /
or the resin substrate 30 around the glass fiber thread would be desired It may be exposed to
more light and / or become more visible. The aluminum layer 32 has a silver appearance and
provides the thread with a glossy, highly reflective outer surface. The weave of the thread causes
incident light to be reflected in a variety of different directions, giving the diaphragm a shiny or
sparkling appearance. The warp and weft catch light in different ways, which also contributes to
the visually noticeable appearance. Furthermore, slight changes in the viewing angle may
significantly affect the way light is reflected, which also causes a slight relative movement,
especially when viewed with both eyes and / or between the observer and the diaphragm. This
leads to the diaphragm having weird optical properties and appearance for the loudspeaker
diaphragm when viewed with the
[0024]
The amount of PVA damping material used in the embodiments described herein provides the
improved performance of the diaphragm with respect to mechanical resonance (also described as
break up). Proper handling of mechanical resonances is very important to the performance of the
loudspeaker diaphragm. For lower frequency units operating at frequencies up to about 500 Hz,
cones can be designed with mechanical resonance out of band by choosing the correct shape and
material. Material specific modulus (Young's modulus divided by density) is a good metric to
quantify the stiffness of the structure. By selecting a high specific modulus material (such as
aluminum or carbon fiber), the cone breakup is pulled far beyond 500 Hz, so the unit operates
only in a piston-like manner. For mid or low to mid drive units, they must cover a wide range of
frequencies, for example from 20 Hz to 6 kHz, which designs a cone that does not show a
breakup in this (wide) band Dealing with the problem is not so easy, as it makes it more difficult
to do. The prior art Kevlar weave's anisotropic nature and other mechanical properties of the
diaphragm have been used to alleviate the problems with the breakup mode in the frequency
range of operation.
[0025]
10-05-2019
11
FIG. 7 is measured by the microphone position along the axis of the diaphragm of the first
embodiment at a distance of 1 meter from the plane of the outer diameter of the diaphragm
while increasing the frequency of the sine input signal (along the x axis) A frequency response
curve 50 is shown as a graph of sound pressure levels (along the y-axis). As can be compared, the
corresponding frequency response curve 52 of a speaker using a B & W Kevlar cone of
comparable diameter is also shown in the graph, which is identical in all other respects. A portion
54 of the graph of FIG. 7 is shown in the enlarged view of FIG. It can be seen from FIGS. 7 and 8
that the frequency response curve 52 of the B & W Kevlar cone is relatively flat over the 200 Hz
to 6 kHz range, but there is room for further improvement. Although PVA based damping
material is already used in the (prior art) Kevlar diaphragm to achieve damping, this embodiment
is much more expensive than that made from Kevlar Suggested in conjunction with glass fiber
weave cone. It is surprising that using glass fibers instead of Kevlar fibers can give better results
when involving the use of much larger amounts of PVA material. Thus, it can be seen that the
frequency response of the diaphragm of the first embodiment (see curve 50 in FIG. 8) is better
than the frequency response of the Kevlar diaphragm (see curve 52 in FIG. 8) . The frequency
response of the Kevlar diaphragm has two peaks 56 around 3.5 kHz and 5 kHz, but the
frequency response of the diaphragm of the first embodiment is more flat at such frequencies.
The frequency response of the diaphragm of the first embodiment (see curve 50 of FIG. 8) is also
as flat as the frequency response of the Kevlar diaphragm (see curve 52 of FIG. 8) at lower
frequencies. As can be seen from FIG.
[0026]
The type of high damping polymer material used, such as PVA material, has a high dynamic loss
factor (greater than 0.5) in the frequency band of interest (around 3.5 kHz and around 5 kHz in
the first embodiment above) ) Can be presented. The dynamic loss factor can be measured by the
DMTA (Dynamic Thermal Mechanical Analysis) test. Such tests are conveniently performed at 25
degrees Celsius.
[0027]
FIG. 9 is a flow chart illustrating a method according to a second embodiment of the present
invention. Thus, as a first step 162, a disc-shaped woven glass fiber mat is provided, in which a
bundle 114 of bundles of aligned glass fibers is woven to form a fibrous material mat. As the next
step 164, the fiber material is coated with resin so that the fibers are coated (and partially preimpregnated) with uncured resin 130 (thus forming a "prepreg" mat). Be done. The resin-coated
10-05-2019
12
mat is then heat treated in a vacuum-forming mold apparatus using a mold that shapes the
resulting resin-infused glass fiber mat into the required cone shape of the diaphragm. Be done.
Once the resin is cured, gaps 120 remain in the product between the lengths of resin-infused
glass fiber bundles. Then, in the next step (box 166 in FIG. 9), a metal deposition system is used
to apply an aluminum coating 132 to the fiber length. The lacquer 134 is then attached to the
metal coating using a lacquer spray system (step 168). Then, a thick layer 125 of PVA material is
deposited on the back of the cone of material using a cone-spinning application system described
in more detail below (step 170). The cone is then trimmed and integrated into the speaker drive
unit in a manner conventional in the art.
[0028]
The result of the cone-rotating PVA deposition step 170 is the use of centrifugal force to spread
the liquid across the surface of the cone of bulk liquid PVA (PVA held in a water-based emulsion)
to the back of the inverted cone It is a deposit. This is achieved as follows. A continuous ball of
liquid (PVA) is pushed out and deposited in the spiral path on the back of the cone of material
rotating at low speed (less than 100 revolutions per minute). An air stream is used to disperse
the liquid on the surface of the cone to create a continuous and continuous coverage of the liquid
on the cone. The air flow used also pushes the PVA into the interstices in the weave of woven
fiber material. The cone is then spun at high speed in a two-stage process as follows. The first
stage of rotation is to try to level the PVA over the cone prior to the second stage. The first phase
of rotation aims to remove any non-PVA islands in order for the second phase to rotate properly.
The speed of rotation of the first stage is about 150 rpm and lasts approximately 5 seconds. The
second stage of rotation is 750 rpm for about 5 seconds (but for larger diameter cones, longer
duration may be required). These high speed rotation stages have a surprising effect in terms of
leveling the PVA over the surface of the cone, providing a clean finish with a relatively constant
PVA thickness over the entire area of the cone. The PVA is then rapidly cured at about 65
degrees Celsius to dry the liquid so that it can be handled and to reduce the risk of the PVA
flowing and losing its shape. A relatively low air temperature (<100 ° C.) is used to cure the PVA
to reduce the risk of water boiling in the emulsion. In this embodiment, the PVA polymer used
has a loss factor of more than 0.5 at 5 kHz, 25 degrees Celsius. The PVA layer is deposited to
form 2/3 (2/3) of the total mass of the cone. By having the cone form a portion of the PVA layer
that significantly exceeds half of the mass of the cone, as mentioned above, a particularly useful
level of damping is provided. The PVA layer acts like a free-layer damping system, but also serves
to seal the diaphragm (without the PVA layer, the cone will be full of holes).
[0029]
10-05-2019
13
Although the present invention has been described and illustrated with respect to particular
embodiments, it will be understood by those skilled in the art that the present invention is
suitable for many different variations not specifically shown herein. I will. Next, by way of
example only, several possible variants are described. It has been mentioned above that
providing a particularly useful level of damping is provided by the cone having a PVA layer
forming much more than half of the mass of the cone. It will be appreciated that a PVA layer
forming 62.5% or more of the mass of the cone, which will be judged to be well over half the
mass of the cone, is particularly beneficial.
[0030]
The constant thickness of the PVA coating is not essential. In fact, it may be advantageous to
provide PVA coatings having varying thicknesses. Materials other than PVA, such as other
synthetic resin elastomeric materials with high dynamic loss, can be used if they adequately
provide high loss at the relevant frequency. Materials with high viscosity and high hysteresis can
be suitable substitutes. A vinyl resin based thermoplastic material sold by Barrett Varnish Co as
Cone Edge Dampener E-5525 may be a suitable alternative. Another potential candidate is PVB
(polyvinylbutyl), which is also usable as an emulsion and exhibits good damping properties.
[0031]
Rather than using a PVA deposition method that utilizes a rotating cone, the polymer may be
deposited by brushing, sponging or otherwise adding a continuous layer of polymer . Many
layers may be required to obtain the required thickness. As used herein, the term "woven
material" (e.g., in the context of "woven fiber material") is a mesh that includes spaces between
threads (or longs of material) that form the primary substructure of the material. Including any
material formed from threads or strips of material woven or knitted or otherwise arranged to
interlock to form a fabric having a like structure. In the described embodiment, the material used
is in the form of a woven glass fiber fabric, although other woven or knitted materials may be
used. For example, embodiments of the present invention may have applications where the fiber
material is made of aramid (aromatic polyamide) fibers, or similar materials such as, for example,
Kevlar.
[0032]
10-05-2019
14
The resin used to impregnate the woven fiber material, which resin is used as a reinforcing
material, may be a synthetic resin, such as a phenolic resin, an epoxy resin, or a melamine resin.
However, any other flexible heat resistant thermosetting resin or high temperature thermoplastic
resin may be used. In the above description, where whole numbers (integers) or elements with
known equivalents, obvious equivalents, or foreseeable equivalents are mentioned, such
equivalents are as if they were individually described. As incorporated herein. Reference should
be made to the appended claims in order to determine the true scope of the invention, and the
true scope of the invention should be construed to encompass any such equivalents. Also, the
completeness or features of the present invention described as being preferred, advantageous,
advantageous, etc. are optional and are not intended to limit the scope of the independent claims.
Would be understood. Moreover, such optional completeness or features may provide benefits in
some embodiments of the present invention, but may not be desirable in other embodiments and
thus may not be present. But should be understood.
10-05-2019
15
Документ
Категория
Без категории
Просмотров
0
Размер файла
32 Кб
Теги
jp2018516519
1/--страниц
Пожаловаться на содержимое документа