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Description 1, title of the invention
Electric precursor converter
3. Detailed Description of the Invention The present invention relates to an emitter and receiver
of sound waves in which the non-expanding conversion element converts alternating voltage into
vibration or vice versa. More particularly, it relates to a loudspeaker and microphone rophone in
which the dome shaped membrane is formed by a self-supporting structure made of a polymer
material. The relief surface of this structure is covered with capacitor-forming electrodes -1 The
conversion effect used in these structures appears over the whole of the electrical sensing zone
located between the electrodes, so that An active dome is formed. The polymeric material used to
make the active dome has a uniform film or double-layered film tights, the thickness of the film
generally being a few tens to a few microns. In this case, the final molded product is obtained by
thermoforming or electroforming. Self-supporting structures with very thin walls can also be
obtained by casting or coating, and the dome obtained with any manufacturing technique is
distinguished from flat films with similar thickness It has good mechanical power due to its selfsupporting properties. In addition, by applying a thrust to the center of the convex surface of the
dome, a mechanically stable stove-in portion is formed, which changes the sphymo-acoustic
properties altogether. Although this strain phenomenon is reversible, the thrust must be applied
in the opposite direction to that which caused the dent to regain the initial shape. In practice, the
user does not approach the convex surface of the dome-shaped membrane, but this also includes
the subtle removal of the transducer if the membrane is punctured by accident. Although the six
emitting surfaces of the active dome may be grid protected to alleviate this disadvantage, this
method can not be applied if the holes are caused by overpressure. In addition, the holes cause
damage such that the dome can not fully return to its original shape again. It should also be
taken into account that during use of the active dome electro-acoustic transducer an accident
may cause a hole and additionally a non-excitation mode, which may cause irregular deformation
due to standing waves. Furthermore, the vibration of the active dome is easily amplified by the
resonance in the narrow range of the acoustic spectrum, which makes it unrealistic for the
reproduction of high quality sound. The control of the frequency response of the polymer active
dome is based on the damping of its natural resonance and the damping that can be actuated by
acoustic coupling. However, the moderate effect of piezoelectric Holmer transducers can not be
expected to have a reliable electrical damping of the resonance as having a practical and
sufficient effect.
In order to alleviate the above disadvantages, the present invention provides an acoustically
transparent and elastic support corresponding to the shape or its concave form with an active
self-supporting structure made of a polymeric material It is a thing. The pressure generated by
this support can prevent I-holes from being punctured, and can provide mechanical damping of
the dome EndPage: dual damping. The invention consists of a rigid case covered with a selfsupporting active radiation film made of a polymeric material, having at least one raised portion,
said case being acoustically transparent and of the radiation film in shape The shape of the
support surface of the support, including the elastic support corresponding to the shape of the
recess on the inner surface, is determined by the shape of the thin radiation film.
Electric precursor converter
Hereinafter, the present invention will be described in detail based on the attached drawings. FIG.
1 shows an electro-acoustic transducer which can operate as a loudspeaker, an earphone or a
microphone. The transducer consists of a self-supporting active thin film obtained by
thermoforming, electroforming, molding or coating with a film 3 of piezoelectric polymer
material. The film 30 is coated on both sides with conductive deposits 1 and 2 forming a
capacitor electrode. The membranes 1.2 and 3 are in the form of domes, for example spherical
wedges with a center O and a radius of curvature R. The thin film assembly is electrically
capacitively equivalent, and when an alternating voltage is applied between the electrodes, the
active structure vibrates according to the mode of thickness, with alternating tangential
extension modes. The thin films 1, 2 and 3 cover the rigid case 8 and the periphery thereof is
fixed to the flange of the case 8 by a gold collar 4. A gold ring 7 arranged in an annular housing
in the flange of the case 8 makes electrical contact with the electrode 2 forming the concave
surface of the membrane. The ring 7 is electrically connected to the terminal 6. The collar 4
clamping the periphery of the thin film also plays a role of elastic connection of the electrode 1
forming the convex surface of the thin film. The terminal 5 is fixed to the collar 4. The interior of
the case 8 is in communication with the outside through an orifice 9, which serves to maintain
the balance of the static pressure acting on each side of the membranes 1, 2 and 3. The internal
volume of the case is partially filled with absorbent material 10 to prevent the formation of
standing waves. The volume 11 in the vicinity of the electrode 2 is an air cushion under the static
pressure of the ambient air 12, in which the emitted or received sound waves propagate. The
frequency response characteristics of the electro-acoustic transducer depend on the diameter D
of the vibrating piston formed by the radiating films 1, 2 and 3 as well as its compliance and
inertance and also the acoustic impedance formed by the case 8. The acoustic and literary
impedance of Case 8 decreases to the closed volume of air and the active surface force of the
vibrating piston and the resulting acoustical capacity, and the sound absorbing material 10
increases this capacity and reduces the damping effect. Leading, the balance hole 9 connects the
series acoustic inertia in parallel with the acoustic resistance. The thin film shown in FIG. 1 is
formed of a uniform film of piezoelectric polymer material. The piezoelectric effect is dipole
origin. Materials used for thin film formation are polymers such as vinylidene polyfluorocide
PVF, -substituted vinyl polyfluorolide PVF and vinyl polychloride.
Copolymers such as co-polymers of vinylidene and polyfluorolide and co-polymers of ethylene
and polytetrafluoroethylene may also be used. The emergence of the piezoelectric properties is
associated with a pretreatment comprising an electrical polarity phase of strength preceded or
not preceded by the mechanical tension phase. Within the scope of the present invention, the
thin film shown in FIG. 1 is capable of replacing the thin film whose cross-sectional view is shown
in FIG. 2 and the thin film of FIG. It's phibe. The thin film preferably consists of two layers 13 and
14 of polymeric material adhering to one another. Layers 13 and 14 may be backed from a
dielectric material lacking piezoelectric properties. At least one of these layers must have been
subjected to a charge injection process that causes excessive hydraulic damage. When an
alternating excitation voltage is applied to the electrodes 1 and 2, the action of the electrostatic
force causes an elongation, but this EndPage: 3 can be made different by an appropriate choice
of material and overcharge. A bending torque M is obtained which is responsible for the
alternating bending of the thin film, with a different elongation which is proportional to the
exciting electric field. By way of non-limiting example, for example, a conformal thin film may be
formed by using a charged ethylene polytetrafluorolite film, preferably affixed to a polyvinyl
chloride film. Of course, the homogeneous shaped structure may be wholly or partially formed of
a piezoelectric polymer material. FIG. 3 shows the main part of the above structure. The case 8
closing the air part is covered by a self-supporting active film, the resting shape of which is
indicated by the dashed line 15. This thin film vibrates generally when electrical or acoustical
excitation is applied. However, because the surroundings are fixed, steady-state liquid
phenomena do not move at a certain frequency 17 (single point chain? IM) may occur.
Furthermore, under the influence of the thrust force due to the accident on the convex surface,
the thin film may be permanently dented as shown in FIG. Since the thin film is fixed to the case
8, it is impossible to stretch this indented portion. This is because it is impossible to access the
concave surface late after the delicate removal. This depression may be due to the rough
handling of the user or due to overpressure on the convex surface of the membrane. Whatever
the cause, the self-supporting property of a non-expanding surface of a spherical wedge or
truncated cone shape with a corrugation on a straight or exponential function, with concentric
corrugations, is a few tens or tens of micrometers thick of thin film It must be considered that it
cooperates with the substantial reduction of).
As a result, these thin films are susceptible to dents in their projections. FIG. 4 shows a crosssectional view of an electroacoustic transducer according to the invention. This converter has an
insulating case 8 with a bottom 26 with connection terminals 27 and 28. A thin film 18 similar to
that of FIGS. 1 and 2 covers the circular opening at the top of the case 8. The membrane 18 rests
on the seven rungs of the circular opening of the case 8 through the embedded metal ring 21.
The membrane is clamped with its metal collar 4 around its flat annular circumference. In this
way, the electrodes covering both sides of the membrane 18 are electrically connected to the
collar 4 and the ring 21, these metal parts in turn being connected to the output of the booster
transformer 29. The transformer 290 input terminals are connected to terminals 27 and 28,
which pass through the bottom of the case 8. According to the invention, the case 8 comprises an
acoustically transparent elastic support directly below the membrane 18. The resilient support
comprises at least two elements, namely a cushion 19 and a grid 20, which lightly press the first
side of the membrane 18 but are not a support. In fact, since the membrane 18 is a selfsupporting support, it presses its shape through the raised features of the grid 20 onto the
cushion 19. A top view of the grid 20 is shown in FIG. The organization of the material used to
form the cushion 19 is shown in FIGS. As shown in FIG. 7, a low density felt pad may be used, the
compression of which is stabilized with a binder but maintains high porosity and good sound
transmission. Examples include glass wool used in the field of thermal or acoustic insulation. FIG.
8 is made of cellular material having cells in communication. Because of the low density, this
open cell-like structure is shortened to the simplest representation, ie called a three-dimensional
mesh network. Various polymer foams such as polyurethane and polyester foams can also be
mentioned EndPage: 4. Because the cushion 19 is slightly compressed between the membrane 18
and the grid 20, it is the ridges provided to the grid that determine the thickness of the cushion
19 as well as the concave shape of the membrane 18. The above thickness may vary from the
center of the film to the periphery, or may be reversed uniformly if the center of the radius of
curvature of the film 18 coincides with the center of the radius of curvature of the grating 20.
The grid 20 is fixed to the flange inside the case, the flange defining a circular opening covered
by a thin film.
A washer 22 held in place by a post 30 pressing against the bottom of the case 26 ensures
clamping around the grate 20. Due to the acoustic transparency of the thin film probe 18,
another active self-supporting thin film such as 24 may be provided on the inside of the case.
This inner membrane 11124 is clamped between two adjoining rings 23 and 25 which are
inserted between the washer 22 and the post 30. Since the rings 23 and 25 are also connected to
the transformer 29, the two films can cooperate in acoustic radiation. The inside of the case 8
can be lined with an absorbing material 40 to increase the acoustic capacity of the case and to
counter standing waves. The mechanical compliance of the grating 20 and the mass of the
grating will reciprocate to form a mechanical resonator that is coupled to the membrane 18
using the cushion 19. As a non-limiting example, the grid 20 can be formed by polyvinyl chloride,
a grid of thickness 2IIII +, whose diagonal dimensions of its rhombus mesh are 6 and 4.5 wm.
The cushion 19 is in this case formed from two stacked discs cut from an unstressed polyester
wool pad of thickness 3 *. For a thin [18 with a piston diameter of 7 cPn, one of the discs has a
diameter of 7 cIn and the other has a diameter of 4]. The distance between the membrane 18 and
the grid 200 is on the order of 3 w, which ensures the compression of the superposed discs. FIG.
6 shows two frequency response curve records corresponding to the transducer of FIG. 4 with
the dimensions indicated immediately above. Sound pressure level 8 PL is measured with a
microphone located on the axis of the transducer at a distance of 30 to 30 countries from
membrane 18. The response of the converter, support) 19.20 and without the membrane 24 is
shown. Curve 32 is of the same converter. This time it represents the response with support
19.20. The natural resonance of the membrane 18 ranging between 10 and 18 kH3 becomes
duller with the cushion 19, which improves the response in this region of the acoustic spectrum.
The response is also improved between 063 and 5 kHz. Because the thin film support's
resonance is used to enhance its vibration amplitude. The depression that occurs between 2kH
and 5kH2 of curve 32 can be filled by introducing the spontaneous emission of thin film 24
which can be designed to emit in this region of the spectrum. Due to the presence of the thin film
support of the present invention, the transducer is paired with the disc 1.. It is known empirically
that it has great resistance. This is because the thin film 18 is punched in its shape after being
lowered to the surface of the surface shape.
The membrane 18 also resists finger pressing. As far as the damping of the parasitic oscillations
of the membrane 18 is concerned, the cushion 19 \ 'i introduces a mechanical coupling which
cooperates with the dissipative properties of the material forming this cushion. The cushion also
acts as a coupling element between the membrane 18 and the resonant structure formed by the
grating 20. In this way it is also possible to mechanically increase the radiation ability of the thin
film in the other acoustic spectral region of the region where the natural resonance of the thin
film is located, the acoustic transparency of the assembly of the cushion 19 and the grating 20 is
also Provide acoustic coupling with other passive or active impedances included in case 8.
EndPage: 5 Although the essential features of the invention as applied to the preferred
embodiment of the invention have been described and illustrated above, those skilled in the art
will appreciate it without departing from the scope of the invention. It will be apparent that any
change in shape or detail may be made. In particular, the sound transmission will be closely
related to the breathability of the cushion and of the grid supporting this cushion, but instead of
the cushion a self-supporting shell with good mechanical compliance and small mass The sound
transmission will also be reduced when using and when cellular foam with closed cells is used as
a cushion. The two elements of the elastic membrane support can be merged into one support,
for example by treating one of the faces of the cushion with a suitable binder, such that the fiber
cushion performs the function of a grid or thin support wall. Of course, the proposed device
extends to structures that scrape into thin films to provide non-uniform values of static pressure.
This result may be caused by the choice of the non-homogeneous unloaded thickness of the
damping cushion and / or by the geometry of the grid, such as varying the thickness of the gap
separating the grid from the membrane. It is also possible to squeeze the thin @ 18 between the
two) 19.20, one of these supports of the electro-acoustic transducer! -It spreads outside the race
4. Brief description of the drawings. FIG. 1 is a cross-sectional view of an electro-acoustic
transducer having a piezoelectric polymer thin film, FIG. 2 is a cross-sectional view of a thin film
of the same construction, and FIG. FIG. 4 is a cross-sectional view of another electro-acoustic
transducer according to the present invention, FIG. 5 is a plan view of a thermoformed grating,
FIG. 6 is accompanied by a thin film support or FIG. 7 and FIG. 8 are perspective views of the
acoustically transparent and compressible structure without the accompanying case. 1, 2.3
Metal ring, 8 иии Case, 9 иии balance Hole, 10 ... wicking material. 1- ? ? 12 12 12 Gono EndPage:
6 ? 6 ? EndPage: 7 ? 1 Continued 0 Inventors Vinyl и Love In France Country 92340 Pool и
Race и Ryu и Andre и Teyuire 5 End Page: ?
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