Patent Application
20050084122
1. Field of the Invention
The present invention relates generally to the field of emitter films as used in loudspeakers. More particularly, the present invention relates to the use of a piezoelectric film as an emitter on an ultrasonic parametric transducer.
2. Related Art
Audio reproduction has long been considered a well-developed technology. Over the decades, sound reproduction devices have moved from a mechanical needle on a tube or vinyl disk, to analog and digital reproduction over laser and many other forms of electronic media. Advanced computers and software now allow complex programming of signal processing and manipulation of synthesized sounds to create new dimensions of listening experience, including applications within movie and home theater systems. Computer generated audio is reaching new heights, creating sounds that are no longer limited to reality, but extend into the creative realms of imagination.
Nevertheless, the actual reproduction of sound at the interface of electro-mechanical speakers with the air has remained substantially the same in principle for almost one hundred years. Such speaker technology is clearly dominated by dynamic speakers, which constitute more than 90 percent of commercial speakers in use today. Indeed, the general class of audio reproduction devices referred to as dynamic speakers began with the simple combination of a magnet, voice coil and cone, driven by an electronic signal. The magnet and voice coil convert the variable voltage of the signal to mechanical displacement, representing a first stage within the dynamic speaker as a conventional multistage transducer. The attached cone provides a second stage of impedance matching between the electrical transducer and air envelope surrounding the transducer, enabling transmission of small vibrations of the voice coil to emerge as expansive compression waves that can fill an auditorium. Such multistage systems comprise the current fundamental approach to reproduction of sound, particularly at high energy levels.
A lesser category of speakers, referred to generally as film or diaphragmatic transducers, relies on movement of an emitter surface area of film that is typically generated by electrostatic or planar magnetic driver members. Although electrostatic speakers have been an integral part of the audio community for many decades, their popularity has been quite limited. Typically, such film emitters are known to be low-power output devices having applications appropriate only to small rooms or confined spaces. With a few exceptions, commercial film transducers have found primary acceptance as tweeters and other high frequency devices in which the width of the film emitter is equal to or less than the propagated wavelength of sound. Attempts to apply larger film devices have resulted in poor matching of resonant frequencies of the emitter with sound output, as well as a myriad of mechanical control problems such as maintenance of uniform spacing from the stator or driver, uniform application of electromotive fields, phase matching, frequency equalization, etc.
As with many well-developed technologies, advances in the state of the art of sound reproduction have generally been limited to minor enhancements and improvements within the basic fields of dynamic and electrostatic systems. Indeed, substantially all of these improvements operate within the same fundamental principles that have formed the basics of well-known audio reproduction. These include the concept that (i) sound is generated at a speaker face, (ii) based on reciprocating movement of a transducer (iii) at frequencies that directly stimulate the air into the desired audio vibrations. From this basic concept stems the myriad of speaker solutions addressing innumerable problems relating to the challenge of optimizing the transfer of energy from a dense speaker mass to the almost massless air medium that must propagate the sound.
A second fundamental principle common to prior art dynamic and electrostatic transducers is the fact that sound reproduction is based on a linear mode of operation. In other words, the physics of conventional sound generation rely on mathematics that conform to linear relationships between absorbed energy and the resulting wave propagation in the air medium. Such characteristics enable predictable processing of audio signals, with an expectation that a given energy input applied to a circuit or signal will yield a corresponding, proportional output when propagated as a sound wave from the transducer.
In such conventional systems, maintaining the air medium in a linear mode is extremely important. If the air is driven excessively into a nonlinear state, severe distortion occurs and the audio system is essentially unacceptable. This nonlinearity occurs when the air molecules adjacent the dynamic speaker cone or emitter diaphragm surface are driven to excessive energy levels that exceed the ability of the air molecules to respond in a corresponding manner to speaker movement. In simple terms, when the air molecules are unable to match the movement of the speaker so that the speaker is loading the air with more energy than the air can dissipate in a linear mode, then a nonlinear response occurs, leading to severe distortion and speaker inoperability. Conventional sound systems are therefore built to avoid this limitation, ensuring that the speaker transducer operates strictly within a linear range.
Parametric sound systems, however, represent an anomaly in audio sound generation. Instead of operating within the conventional linear mode, parametric sound can only be generated when the air medium is driven into a nonlinear state. Within this unique realm of operation, audio sound is not propagated from the speaker or transducer element. Instead, the transducer is used to propagate carrier waves of high-energy, ultrasonic bandwidth beyond human hearing. The ultrasonic wave therefore functions as the carrier wave, which can be modulated with audio input that develops sideband characteristics capable of decoupling in air when driven to the nonlinear condition. In this manner, it is the air molecules and not the speaker transducer that will generate the audio component of a parametric system. Specifically, it is the sideband component of the ultrasonic carrier wave that energizes the air molecule with audio signal, enabling eventual wave propagation at audio frequencies.
Another fundamental distinction of a parametric speaker system from that of conventional audio is that high-energy transducers as characterized in prior art audio systems do not appear to provide the necessary energy required for effective parametric speaker operation. For example, the dominant dynamic speaker category of conventional audio systems is well known for its high-energy output. Clearly, the capability of a cone/magnet transducer to transfer high-energy levels to surrounding air is evident from the fact that virtually all high-power audio speaker systems currently in use rely on dynamic speaker devices. In contrast, low output devices such as electrostatic and other diaphragm transducers are virtually unacceptable for high-power requirements. As an obvious example, consider the outdoor audio systems that service large concerts at stadiums and other outdoor venues. Normally, massive dynamic speakers are necessary to develop direct audio to such audiences. To suggest that a low-power film diaphragm might be applied in this setting would be considered foolish and impractical.
Yet in parametric sound production, the present inventors have surprisingly discovered that a film emitter will outperform a dynamic speaker in developing high-power, parametric audio output. Indeed, it has been the general experience of the present inventors that efforts to apply conventional audio practices to parametric devices will typically yield unsatisfactory results. This has been demonstrated in attempts to obtain high sound pressure levels, as well as minimal distortion, using conventional audio techniques. It may well be that this prior art tendency of applying conventional audio design to construction of parametric sound systems has frustrated and delayed the successful realization of commercial parametric sound. This is evidenced by the fact that prior art patents on parametric sound systems have utilized high-energy, multistage-like bimorph transducers comparable to conventional dynamic speakers. Despite widespread, international studies in this area, none of these parametric speakers were able to perform in an acceptable manner.
In summary, whereas conventional audio systems rely on well accepted acoustic principles of (i) generating audio waves at the face of the speaker transducer, (ii) based on a high-energy output device such as a dynamic speaker, (iii) while operating in a linear mode, the present inventors have discovered that just the opposite design criteria are preferred for parametric applications. Specifically, effective parametric sound is effectively generated using (i) a comparatively low-energy film diaphragm, (ii) in a nonlinear mode, (iii) to propagate an ultrasonic carrier wave with a modulated sideband component that is decoupled in air (iv) at extended distances from the face of the transducer. In view of these distinctions, it is not surprising that much of the conventional wisdom developed over decades of research in conventional audio technology is simply inapplicable to problems associated with the generation parametric sound.
One specific area of transducer design that illustrates the uniqueness of parametric emitter design compared to conventional audio transducers is the adaptation of a film emitter to generate ultrasonic output at sufficient energy levels to drive air at the required nonlinear condition. As indicated above, film emitters are known to be low-energy devices. Nevertheless, film emitters have now been developed for parametric transducers as disclosed in the parent patent applications. Such emitter design has generally been characterized as an array of small emitter sections disposed across a monolithic film diaphragm. The following disclosure provides further enhancements to the development of and method of constructing an effective film emitter capable of generating high-power output, despite the traditional view that film emitters were limited to low-power applications.
In particular, the following disclosure reveals new insights in various problems that previous designers have encountered when emitting a compression wave from an emitter film that has been captured to a support member. The following disclosure also provides a method for preparing the film and capturing the film to the support member such that the above problems of previous emitter films are substantially avoided. Finally, a device is disclosed as a means for preparing the film to be captured to a support member.
It has been determined that it would be advantageous to develop a parametric speaker system, which uses a piezoelectric film as an emitter, where the film may operate in a substantially relaxed state, having minimal tension or stretching.
The invention provides a method for constructing a parametric transducer, which includes preparing a support member having opposing front and back surfaces, the support member extending along an x-axis and a y-axis. The support member is structured to retain an array of parallel ridge locations extending along the x-axis and spaced apart along the y-axis at predetermined separation distances. The ridge locations have forward, film contacting faces to support an emitter film in a desired film configuration for emitting parametric output. An electrically sensitive and mechanically responsive (ESMR) film is disposed over the support member with one side of the ESMR film being captured at the film contacting faces, and with arcuate sections aligned with and positioned between the parallel ridges. The film contacting faces mechanically isolate each of the arcuate sections of ESMR film from adjacent arcuate sections.
The invention also provides a method for preparing an electrically sensitive and mechanically responsive (ESMR) emitter film for a parametric transducer, which includes heating the ESMR film to a predefined temperature, thereby altering the dimensions of the film in at least one direction. The formed ESMR film is then captured at a support member while the film is in its heated state, thereby maintaining captured portions of the film at their altered dimensions when the film is subsequently cooled, and allowing free-moving portions of the film to return to approximately their original state when the film is subsequently cooled. The method may also include forming the ESMR film to a predetermined configuration while the film is in its heated state, prior to capturing the ESMR film to the support member.
The invention also provides a device for preforming an electrically sensitive and mechanically responsive (ESMR) film to be disposed over a support member of a transducer. The device includes a forming plate having opposing front and back surfaces, the forming plate having an array of parallel arcuate surfaces with respect to the front surface. The arcuate surfaces are separated by an array of parallel ridges. A plurality of apertures provides for airflow through the forming plate at the front surface. A vacuum source is attached to the apertures for creating negative pressure at the front surface.
Additional features and advantages of the invention will be apparent from the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate, by way of example, features of the invention.
The following drawings illustrate exemplary embodiments for carrying out the invention. Like reference numerals refer to like parts in different views or embodiments of the present invention in the drawings.
a is a perspective view of an ultrasonic, parametric transducer, including a support member and a piezoelectric type film to be applied to the support member, in accordance with the method of
b is a perspective view of the transducer of FIG. a, wherein the film has been applied to the support member;
c is a drawing of one embodiment of the support member;
a is a perspective view of a transducer, wherein the film is configured in the form of alternating concave and convex arcuate sections, in accordance with an embodiment of the present invention;
b is a perspective view of a transducer, wherein the film is configured with arcuate sections protruding away from the support member;
a is a flow chart illustrating a method for constructing another parametric transducer, in accordance with an embodiment of the present invention;
b is a perspective view of a transducer, wherein the support member has a front face surface in a smooth continuous configuration, in accordance with the method of
a is a perspective view of a transducer, wherein the support member configures the film to have a concave dish curvature for focusing a propagated wave;
b is a perspective view of a transducer, wherein the support member configures the film to have a convex dish curvature for dispersing a propagated wave;
a is a representation of multiple electrically isolated conductive portions of film being driven by multiple parametric signals created by providing a passive delay line;
b is a representation of a transducer having multiple electrically isolated conductive portions of film in a progressively larger ring configuration;
c is a representation of one method for connecting electrical contacts to the transducer in
d is a representation of one method for connecting electrical contacts to the transducer in
a is a perspective view of a forming plate used to preform the film, in accordance with an embodiment of the present invention;
b is a perspective view of a second forming plate used to preform the film, in accordance with an embodiment of the present invention;
c is a perspective view of a third forming plate used to preform the film, in accordance with an embodiment of the present invention; and
Reference will now be made to the exemplary embodiments illustrated in the drawings, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Alterations and further modifications of the inventive features illustrated herein, and additional applications of the principles of the inventions as illustrated herein, which would occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the invention.
In accordance with
Method 100 may also include forming a backplate on the back surface of the support member, thereby creating an array of parallel channels on the front surface, each channel having a channel cross section and a front face of a predetermined depth and configuration.
a is a depiction of the transducer disclosed in the method of
Generally, the support member, as applicable to method 100, may consist of any structure that retains the ridges 108 in a substantially parallel configuration.
The parallel ridges of method 100 may consist of any structures that provide film contacting faces 112 for capturing the film and forming intermediate arcuate sections 116 of film. The cross sections 111 and parallel channels 112 created by the parallel ridges need not be rectangular in shape as illustrated in
The film contacting faces of method 100 may consist of any structures that are capable of capturing the film between the arcuate sections 116 of film. The film contacting faces should be configured such that when they capture the film, each intermediate arcuate section of film 116 is substantially isolated from all other arcuate sections.
Various types of film may be used as the emitter film. The important criteria are that the film be capable of (i) deforming into arcuate emitter sections at the cavity locations or displaced spaces from the support member, and (ii) responding to an applied electrical signal to constrict and extend in a manner that reproduces an acoustic output corresponding to the signal content. Although piezoelectric materials are the primary materials that supply these design elements, new polymers are being developed that are technically not piezoelectric in nature. Nevertheless, the polymers are electrically sensitive and mechanically responsive in a manner similar to the traditional piezoelectric compositions. Accordingly, it should be understood that reference to piezoelectric films in this application is intended to extend to any suitable film that is both electrically sensitive and mechanically responsive (ESMR) so that acoustic waves can be realized in the subject transducer.
In accordance with method 100 of
The embodiment shown in
When the emitter film 318 is applied to the support member 302 of
c is a drawing of one embodiment of the support member. The support member has a width along the y-axis of 131 millimeters, or 5.15 inches. The support member has a length along the x-axis of 133 millimeters, or 5.23 inches. The height of the support member is 6 millimeters, or 0.24 inches. The width of each film contacting face, labeled “slot width” in
[Jim-do you want to add new measurements for current preferred embodiment?]
Method 100 may include the more specific step of configuring the channel cross sections with a curvature approximately corresponding to the arcuate sections of the ESMR film extending into the channel cross sections.
As depicted in
The concepts from
As depicted in
As illustrated in
In accordance with
b is a depiction of the constructed transducer as disclosed in the method 700. The transducer 710 is comprised of the support member 712 having opposing front 714 and back 716 surfaces, wherein at least the front surface 714 is in a smooth continuous configuration, meaning that the support member does not have the ridges as shown in
The resonance frequency of the film is dependant on ‘r’. As ‘r’ gets smaller, the resonance frequency of the film rises. To optimize the interaction of the parametric waves in the air so that maximum decoupling of the waves occurs, it may be beneficial to position the arcuate sections 320 such that L≦½ λ.
In another embodiment of the invention, the distance ‘L’ and/or the radius ‘r’ may vary throughout the transducer structure. In order to vary the distance ‘L’, the separation distances of the parallel ridges 308 must also vary by the same amount. By varying the distance ‘L’, the radius ‘r’ of the arcuate sections 320 may also be altered. As stated above, altering ‘r’ will affect the resonance frequency of the film. Therefore, varying the radius ‘r’ and/or the distance ‘L’ will create multiple resonance frequencies, which may be desired if a wide frequency spectrum is required.
The distance from the arcuate sections 320 of the film 318 to the front face 313 of the parallel channels may also affect the performance of the transducer. The variable ‘d’ represents the distance from the central peak depth of the film's arcuate sections 320 to the front face 313 of a parallel channel 310. In one embodiment, d≦½ λ. When d=½ λ, the propagated wave that is emitted from the back of the film 802 may reflect off of the support member 302, and return out of phase with the wave emitted from the front of the film 318. Consequently, the extra sound pressure may drive the arcuate sections 320 of the film 318 out of their desired polarity, and may cause destructive interference with the wave emitted from the front of the film 804. In a preferred embodiment, where d≦¼ λ, the interference and cancellation that may occur when d=½ λ is avoided. Therefore, it may be preferred that not only the central peak of the arcuate section of the film be less than ½ λfrom the front face of the parallel channel, but also that the entire length of film be less than ½ λ from the front face of the parallel channel 110.
In a preferred embodiment, the arc lengths of the arcuate sections 320 are defined by a central angle, labeled ‘θ’ in
Once the ESMR film is captured at the support member 302 of
It may also be preferred that the width of ESMR film emitters of methods 100 and 700, labeled ‘width’ in
As depicted in
As depicted in
Methods 100 and 700 may further include biasing the ESMR film into the arcuate sections at the film contacting faces without application of negative pressure to the ESMR film at the array of parallel ridges.
As previously mentioned, methods 100 and 700 may include capturing the ESMR film at the film contacting faces using an adhesive substance. The adhesive substance is denoted as 810 in
Methods 100 and 700 may include configuring the parallel channels of support member to have opposing ends that are maintained open to airflow to avoid pressure differentials of varying altitudes and to provide cooling.
With the ESMR film and the support member in the configurations disclosed in the present invention, many benefits are acquired over the prior art. First, the use of an ESMR film is superior to the use of an array of hundreds or even thousands of bimorph transducers. An array of bimorph transducers requires separate wiring to drive each bimorph transducer. This adds to the complexity and cost of manufacture. Conversely, the use of an ESMR film may only necessitate one electronic coupling in order to drive the film. Furthermore, when an array of bimorph transducers is used, each transducer will likely be positioned at a slightly different angle, creating undesired phase differentials and a non-uniform wave front. Because ESMR film is a uniform, continuous surface, the waves emitted by the film are also uniform, with very little undesired phase differential.
The use of ESMR film in a substantially non-pressured state also has benefits over the prior art method of using a permanent vacuum to shape the film. A permanent vacuum will apply continuous pressure to form the film into its desired configuration. This continuous stress may stretch the ESMR film and cause the film to have a variable resonance frequency depending on the tension of the film at a particular point, and may cause the emitted waves to contain unwanted distortion. However, capturing the film in a substantially non-pressured state at a support member in accordance with the present invention avoids the use of a permanent vacuum, while maintaining the film in its desired configuration. Because the film is in a substantially non-pressured state, the frequency response of the film is more consistent, and the waves emitted from the film more closely resemble the intended waveform.
Furthermore, use of a permanent vacuum applies pressure on only one side of the film. In this condition, the vibrations of the film tend to expand further in one direction than the other. This effect can generate even-order, or asymmetric distortion in the emitted wave. Even-order distortion causes spurious even harmonics (2nd, 4th, 6th, etc.) to be added to a signal passing through a device. Because the present invention provides a method of maintaining the arcuate sections in the film without the permanent application of a vacuum, the film is free to vibrate equally in both directions, thus substantially eliminating even-order distortion in the emitted wave.
Finally, use of a permanent vacuum requires additional structure for maintenance and the containment of the vacuum. Such a structure adds to the mass, volume, and manufacturing complexity of the speaker. The support member 102 of the present invention is much thinner than the drum or other support member previously used to provide the vacuum chamber in the prior patent application, and is also more durable.
As depicted in
As illustrated in
It has also been discovered that techniques applied to generation of printed circuit boards may be used to develop a support member useful with the present monolithic film emitter. For example, the support member may be formed by etching or other known procedures for preparing a printed circuit board. The structure of the support member would conform to the design parameters set forth herein. This is particularly suitable for use with the illustrated embodiments in
In another embodiment of
While
The ESMR film 1052 may be placed on any support member 1064, including but not limited to the support members disclosed in the present invention. Because the support members disclosed in the invention may be square or rectangular in shape, the corners of the support member 1064a may not conform to the ring configuration of the conductive portions of film. Therefore, the corners 1064a may be left bare (without film) as shown in
Various techniques of creating electrical contacts to the conductive portions of film may be employed. One technique, illustrated in
Another technique of creating electrical contacts to the conductive portions of film, illustrated in
An example of a focusing parametric transducer as described in
As depicted in
In addition to electronically coupling the edges of the film to the signal source using the C-channels, the film may be electronically coupled to the signal source in various positions throughout the center of the film. When using large pieces of ESMR film, and when coupling the signal source to the edges of the film, the resistive losses of the film's metallization may attenuate the signal near the center of the film. By electronically coupling the film to the signal source in various positions throughout the center of the film, the signal strength remains substantially consistent throughout the film. One method of electronically coupling the center of the film to the signal source is by applying the signal source to one or more conductive film contacting faces, which are electronically coupled to the corresponding captured portions of film.
In the above cases, the separate conductive regions of the film diaphragm may be isolated on both the front and back surface sides of the film or may be only isolated from each other on one surface side, with the remaining surface side of the film being conductively continuous across that surface side. In the later case, the continuous side may be driven from a common ground potential of an amplifier system with alternate polarity, phases or delays driving the isolated regions on the opposite surface side.
In accordance with
In the above methods, and in various parent applications, the inventors have disclosed transducers employing a piezoelectric film emitter captured to a support member, such that captured portions of the film are fixed in one position. The inventors have now discovered that when an electronic audio signal is applied to an emitter film to produce an audio compression wave, the electronic current passing through the resistive losses of the film's metallization may cause the temperature of the film to rise by a significant amount. As the temperature of the emitter film rises, the film expands and/or contracts in at least one dimension by up to approximately 2%. While the free-moving portions of film will expand and/or contract, the captured portions of film are fixed, creating tension between the free-moving portions and the captured portions of film. This tension creates buckling and folds in the free-moving portions of the film. Consequently, the amplitude of the propagated wave decreases, and distortion is created.
To resolve the tension occurring in the free-moving portions as described above, a method 1300, in
By heating 1302 the film prior to forming 1304 the film or applying 1306 the film to the support member, the film dimensions will expand and/or contract to approximately the same dimensions the film will assume during operation, when a voltage is applied causing the temperature of the film to rise. When the heated film is captured 1306 to the support member, the film may subsequently be cooled to an ambient temperature. The cooled film attempts to contract to approximately its original size, but the captured portions are forced to remain in their expanded form. When the film is subsequently driven by an electronic signal during operation, the film's temperature rises, causing the free-moving portions of film to expand and/or contract yet again. Because the entire film will then have assumed the expanded form, the film will operate in a substantially untensioned state, with minimal unwanted buckling or folding in the film. Consequently, the amplitude of the propagated wave will be maximized, with minimal distortion.
Method 1300 focuses on all ESMR emitter films that are or will be captured at a “support member.” Various support members are provided herein by way of example. However, the method 1300 is equally applicable to all ESMR films that are to be captured at a support member and that generate heat during operation. The defining characteristic of a “support member”, as applied to method 1300, is any device capable of retaining an emitter film in a predefined configuration.
The defining characteristic of a film being “captured” at a support member, as applied to method 1300, is that the film be fixed in at least one dimension to at least one point of the support member. To be captured, the captured portions of film should not be able to slide substantially or adjust substantially when lateral pressure is exerted to the film. All films that are captured to a support member, as defined herein, fall within the scope of method 1300.
The inventors have found method 1300 to be particularly helpful when preparing an ESMR film for use in parametric ultrasonic transducers. Parametric ultrasonic transducers commonly require high levels of power in order to drive the surrounding air into nonlinearity, as is required for acoustic heterodyning. Consequently, the temperature of the film rises considerably, causing significant expanding and/or contracting of the film.
While method 1300 is useful in the field of parametric ultrasonic speakers, the method has other applications as well. These applications include preparing an ESMR film for use in conventional speaker transducers (not using parametric technology), and preparing an ESMR film for use in microphone-type transducers, or other types of sensors.
The heating performed on the film in method 1300 should not be confused with thermal forming. In thermal forming, the film is heated to such a high temperature that the film will permanently retain its molded configuration when the heat is removed. In method 1300, the heat is chosen such that the heat causes the film to expand, but does not necessarily cause the film to retain a new shape. If the film were not captured at the support member, the entire film would be free to contract to approximately its pre-expanded shape when subsequently cooled. However, because the film is captured at the support member while heated, which alters the film's dimensions, the captured portions of the film are forced to retain their expanded and/or contracted states even when cooled, while the free-moving portions of film may contract to their approximate pre-expanded shapes.
The ideal temperature to produce this result may be the approximate temperature reached by the film while it is being driven by an electronic parametric ultrasonic signal. The ideal temperature may be the approximate temperature reached by the film while it is being driven by a conventional electronic audio signal. The temperature may be approximately 50 degrees Celsius. Even when the above temperatures are used, there is a possibility that minor thermal forming may still occur, because minor thermal forming is unavoidable whenever certain types of film are heated to any degree. However, because minor thermal forming may be unavoidable, it is preferable that the thermal forming occur prior to capturing the film to the support member. Otherwise, a similar amount of thermal forming would occur after capturing the film to the support member, because similar temperatures are produced during operation. When minor thermal forming occurs during operation, the results are largely uncontrollable, and may be less than desirable. Thus, the unavoidable minor thermal forming that may occur during heating 1302 prior to capturing the film 1306 minimizes any potential thermal forming that would have occurred after capturing the film to the support member had the film not been preheated.
A device as shown in
Specifically, the device 1400 shown in
b illustrates an alternate device 1420 that may be used to preform the ESMR film into its designated shape. A forming plate 1422 having opposing front 1432 and back (hidden) surfaces and having an array of parallel, convex arcuate surfaces 1424 separated by inverted ridges 1426 is provided as a mandrel or mold for shaping the film 1434. Small apertures 1428 are provided in the forming plate 1422 creating a means for airflow to the front surface 1432 of the forming plate 1422. A vacuum source 1430 is attached to the apertures 1428 for creating negative pressure at the front surface 1432. A film 1434 may be rolled onto the forming plate 1422 such that the film is sequentially preformed in each successive channel 1424 without applying any undue tension or stretching to the film along the y-axis. Once the film 1434 has been preformed to the shape of the forming plate, it may be captured at a support member, completing the basic transducer structure. In the embodiment shown in
c illustrates an alternative device 1440 that may be used to preform an ESMR film to be disposed over a support member. Particularly, the device 1440 may form the film to the configuration shown in
As illustrated in
Method 1300 may also include forming the support member to have an array of parallel ridges separated from one another in a spacing configuration corresponding to the captured portions of the film. The ridges have forward, film contacting faces to capture the ESMR film in a desired film configuration.
As illustrated in
By way of example, the transducer of
Because the film 318 is captured at the support member 302 while in its heated state, being expanded along the y-axis, the captured portions of the film are maintained in their expanded states when the film is subsequently cooled. Therefore, the captured portions are stretched in an outward direction, as indicated by the arrows 326. The free-moving portions of film are allowed to return to approximately their original state when the film is subsequently cooled, as indicated by the arrows 324. However, when an electronic signal is applied to the film during operation, the film temperature rises, causing the free-moving film portions 320 to expand. Because the entire film 318 will have assumed the expanded form, the film will operate in a substantially relaxed, untensioned state, with no undesired buckling or folds in the film. Consequently, the amplitude of the propagated wave will be maximized, with minimal distortion.
Method 1300 may also include the step of forming the support member having opposing front and back surfaces, wherein at least the front surface is in a smooth continuous configuration. An ESMR film is disposed over the front surface of the support member, said ESMR film being configured for emitting parametric output. The ESMR film is also configured with an array of parallel convex arcuate sections alternatively separated by parallel captured portions.
Method 1300 may also include adhering the formed film to the support member by applying a thin, uniform layer of adhesive to the film contacting faces of the support member, and capturing the film contacting faces of the support member to the back surface of the ESMR film while the ESMR film is in its heated, expanded state, such that captured portions of the ESMR film at the film contacting faces are fixed in their expanded state, and the arcuate sections are free to contract into their original state at ambient temperature.
As discussed above, the forming devices of
The method 1300 and the devices of
It is to be understood that the above-referenced arrangements are illustrative of the application for the principles of the present invention. Numerous modifications and alternative arrangements can be devised without departing from the spirit and scope of the present invention while the present invention has been shown in the drawings and described above in connection with the exemplary embodiments(s) of the invention. For example, an array of parallel, cylindrical fingers or rods forming a grid could serve as a forming surface to apply the desired curvature for the channel structure of the film. The intermediate, suspended film between the rods could then be directly captured at the flat ridges of the support member by means of vacuum openings on the face of the flat ridges. Once the film is secured to these ridges, the rods could be pulled free from the film, leaving the curved channels in an operable mode. Accordingly, it will be apparent to those of ordinary skill in the art that numerous modifications can be made without departing from the principles and concepts of the invention as set forth in the claims.
Priority of application Ser. No. 60/496,385 filed Aug. 21, 2003 in the U.S. Patent Office is hereby claimed. Prior Application This application is a continuation-in-part of Ser. No. 09/787,972 filed Jan. 17, 2002, and of Ser. No. 09/159,442 filed Sep. 24, 1998, and of Ser. No. 09/478,114 filed Jan. 4, 2000. The above disclosures are hereby incorporated herein by reference. The parametric transducer apparatus corresponding to the present invention is disclosed in co-pending application entitled “Parametric Transducer Having An Emitter Film”
| Number | Date | Country | |
|---|---|---|---|
| 60496835 | Aug 2003 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 09787972 | Jan 2002 | US |
| Child | 10923288 | Aug 2004 | US |
| Parent | 09159449 | Sep 1998 | US |
| Child | 10923288 | Aug 2004 | US |
| Parent | 09478114 | Jan 2000 | US |
| Child | 10923288 | Aug 2004 | US |
