The invention generally relates to acoustic transducers having a connector between an actuator and a diaphragm.
A loudspeaker is a transducer that produces sound in response to an electrical audio signal input. The vast majority of loudspeakers in use today are electromagnetic transducers. Referred to as dynamic loudspeakers, this class has essentially remained unchanged since the 1920's. Typically, a linear motor, such as an electromagnetic or electrostatic motor, actuates a diaphragm, which causes sound waves to be emitted by the speaker.
More recently, a new class of mechanical-to-acoustical transducers has been developed. Those transducers may have an actuator that may be coupled adjacent to an edge of a speaker diaphragm or diaphragm that may then be anchored and spaced from the actuator. In such transducers, the actuator is typically a piezoelectric actuator. Mechanical motion of the actuator is translated into the movement of the diaphragm, generally in a direction that is transverse to the direction of the motion of the actuator. The diaphragm radiates acoustic energy. Mechanical-to-acoustical transducers are exemplified in each of U.S. Pat. Nos. 6,720,708 and 7,038,356.
A problem with this new class of mechanical-to-acoustical transducers is durability. For example, the piezoelectric actuator is coupled to the diaphragm, and that coupling point is under significant mechanical stress. That may lead to the actuator becoming separated from the diaphragm and the diaphragm becoming damaged at or near the coupling point.
The invention provides more durable mechanical-to-acoustical transducers that are designed to better withstand the environment in which they will be used without breaking. Particularly, the invention recognizes that the connection point between the actuator and the diaphragm is subjected to large localized separation forces when an external force is applied to the transducer, such as from dropping, normal contacts, or other events. The magnitude of the separation force is a result of the large change in bending stiffness of the diaphragm and the relatively indefinite stiffness of the actuator acting nearly perpendicular to the diaphragm. A singular point of transition in the thickness from the coupling element and the diaphragm results in a concentration of separation forces on one small area of the bond, precipitating early failure.
The invention solves that problem by providing a tapered connector between the diaphragm and the actuator. The connector element has tapered flanges radiating outward from the actuator beam. The tapering of the flange serves to distribute the stress of any deforming forces over a wider area of the diaphragm.
Connectors of the invention may have any type of taper. For example, the connector may have a planar proximal end that tapers to a distal end. Furthermore, any or all sides of the connector may taper. For example, two sides of the connector may taper form the proximal end to the distal end. In more specific embodiments, the left and right sides of the connector taper from the planar proximal end to the distal end. In other embodiments, the top and bottom sides of the connector taper from the planar proximal end to the distal end. In other embodiments, three sides of the connector may taper from the proximal end to the distal end. In particular embodiments, all sides of the connector taper from the planar proximal end to the distal end.
Any connecting mechanism may be used to couple the connector to the diaphragm. For example, the connector may be coupled to the diaphragm by an adhesive, thermal bonding, or a mechanical fastener. In certain embodiments, the connector is integrally formed with the diaphragm. The connector also needs to couple to the actuator. An exemplary way to make this connection is to configure the connector such that a portion of the actuator fits within the distal end of the connector. The connector may also be integrally formed with the actuator. Any material known in the art can be used to make the connector. In certain aspects, however, the connector is made of a soft or compressible material. For example, the connector is made of silicone or rubber. Typically, the connector has a stiffness greater than a stiffness of the diaphragm and less than the stiffness of the actuator.
In other aspects of the invention, the connector further includes a damping element. The damping element provides an additional measure for suppressing the harmful vibration that can result when the transducer is dropped or struck against an object. Typically, the damping element is sandwiched between two relatively stiff components that lack sufficient damping on their own. When the system flexes during vibration, shear strains develop in the damping element and energy is lost through shear deformation of the material. Accordingly, the damping element serves to dissipate the impact transmitted from the diaphragm to the actuator or vice versa. In certain aspects of the invention, the damping element is located at the proximal end of the connector in between the connector and the diaphragm.
In certain aspects, the damping element includes an optically clear material or film. In other aspects, the damping element is an adhesive. Suitable adhesives include pressure sensitive adhesives, in which the adhesive forms a bond when pressure is applied. Pressure sensitive adhesives exhibit viscoelastic, i.e., viscous and elastic properties, both of which are used in proper binding. In further aspects of the invention, the adhesive is an acrylic-based adhesive that is prepared from high strength, acrylic polymers.
With respect to the other components, such as the diaphragm or the actuator, transducers of the invention can use any type of diaphragm and actuator for moving the diaphragm. For example, the diaphragm can be prepared from any solid material, such as a plastic, an optical-grade material, glass, a metal, a carbon-fiber composite, a fabric, a foam, paper, or any combination of these. In certain aspects of the invention, the diaphragm is formed with one or more curvatures. Actuators suitable for use with the invention include piezoelectric actuators. In further aspects, the actuator is a bending type piezoelectric actuator. These can include unimorph, bimorph, trimorph, or other multimorph type benders. Transducers of the invention can include additional components as well, such as a support for supporting the diaphragm.
The invention generally relates to acoustic transducers. In certain embodiments, the transducers of the invention have bending type piezoelectric actuators where the diaphragm is curved, the piezoelectric actuator is mechanically attached to the diaphragm and where the movement of the mid-point of the diaphragm between actuator and support or between two actuators moving against each other is mechanically amplified relative to the movement of the actuator by virtue of its mechanical construction. Such a transducer is subsequently called a mechanically amplified transducer.
Transducers of the invention may include a diaphragm 101. The diaphragm 101 may be a thin, flexible sheet. The diaphragm may be flat or formed with curvature, for example a parabolic section. In certain embodiments, the diaphragm includes several curvatures. In certain embodiments, when in its resting position the diaphragm is curved in the section between the piezo actuator attachment point and a support (or a second actuator). The diaphragm may be any solid material including such plastics as Kapton (poly amide-imide), polycarbonate, PMMA, PET, PVDF, polypropylene, or related polymer blends; or optical quality materials such as tri-acetates, and tempered glass; or aluminum, titanium or other metals; or carbon fiber composite; or paper; or resin doped fabrics; or foams; or other composites. The diaphragm in certain embodiments is made of a material with no or with only negligible piezoelectricity. The diaphragm may be made to be opaque or optically clear. The diaphragm may include a light polarizing layer or a damping element, or both. Polarizing and damping elements are described for example in Booth (U.S. patent application number 2012/0186903), the content of which is incorporated by reference herein in its entirety. The diaphragm may also be coated with a light diffusion texture or coating to facilitate the projection of images or light. The diaphragm may be composed of a flexible display component.
The diaphragm 101 couples to the support 100. When the diaphragm 101 is curved, the support 100 may include a curve that matches the curve of the diaphragm. The exemplary coupling in
It is important to note that the above description is exemplary and not limiting of the invention. Numerous other coupling configurations are possible and the invention is not limited to any specific coupling configuration. For example, transducers of the invention can be configured so that the coupling points are one actuator and one support, or one actuator and multiple supports, or two or more actuators (opposing each other) and no support at all, as well as two or more actuators and one or more supports.
Transducers of the invention include at least one actuator 104 that is coupled to the diaphragm. In certain embodiments, the actuator is a bending type piezoelectric actuators such as for example unimorph, bimorph, trimorph, or multimorph type benders. In certain embodiments, a single actuator designed transducer has the actuator coupled to a center line of the diaphragm.
Any type of actuator known in the art may be used with methods of the invention, and an exemplary actuator is a piezoelectric actuator. A piezo bimorph is one type of suitable drive mechanism or actuator for this invention. An example of a Piezo Multimorph is a five layer device consisting of four plates of piezo material with a conductive coating on each side bonded to a central substrate. The substrate provides some spring force. It also can act as a dampener. The piezo plates are available for example from CTS Electronic Components, Inc. Piezoelectric Products 4800 Alameda Blvd NE Albuquerque, N. Mex. 87113. A type that may be used is 3195STD. The piezo plates expand or contract in the X- and Y-axis (a direction generally aligned with vertical axis and lying in the plate). In one configuration the plates are stacked up with alternating poling direction on each side and driven with a signal that is inverted relative from one side to the other. As a result, two plates expand, and the other two plates contract at the same times, which causes the actuator to bend in the z-direction. The final bending motion far exceeds the expansion of a single piezo wafer's movement.
The coupling of the actuators 104 to the diaphragm 101 is such that movement of the actuators causes the diaphragm to move in a direction transverse to the movement of the actuators. Further description of how the actuators cause movement of the diaphragm is described in Athanas (U.S. Pat. Nos. 6,720,708; 7,038,356), Johnson (U.S. Pat. No. 7,884,529), Carlson, et al. (U.S. Pat. No. 8,068,635), and Booth, et al. (U.S. Pat. No. 8,189,851), the content of each of which is incorporated by reference herein in its entirety.
The base 100 may hold the electronics of the acoustic transducer. Electronics for loudspeakers are described for example in Burlingame (U.S. patent application number 2011/0044476), the content of which is incorporated by reference herein in its entirety. The base may also optionally hold a speaker.
Furthermore, in
As the diaphragm is mechanically attached to the bender the diaphragm will see a component of its excursion F and G that are perpendicular to plane P. F and G are observed half way along the curvature of the diaphragm between the attachment point of the actuator D and the support S. Typically, the displacement of the diaphragm F is larger than the sum of displacements X and Y. If the piezo bender moves in the opposite direction correspondingly displacement G is larger than the sum of displacements X′ and Y′. This type of transducer is mechanically amplified.
By coupling the distal end of a piezo actuator to a curved diaphragm the lateral component of the motion of the distal end of the actuator is converted to a larger perpendicular motion of the diaphragm surface.
Definitions: the arc-length is the length of the diaphragm segment between points D and S. The chord-length d is the straight line distance between points D and S. The chord-depth T is the maximum perpendicular distance between the diaphragm segment and plane P. This is illustrated in
The geometry and material properties of the curved diaphragm are chosen such that when the actuator or actuators exert a lateral force on the segment of the diaphragm between D and S the diaphragm will react by flexing and increasing or decreasing its curvature. This can be seen in
The geometry of the diaphragm is relatively thin and relatively long and its modulus is selected from a group of materials such as plastics, metals, paper, carbon fiber, foam, composites of the before and similar materials.
If such a diaphragm is curved between the attachment point D of the actuator and the support S, it has a substantially fixed arc-length. The lateral motion of the distal end of the actuator results in a change of the chord-length d of the arc. Due to geometric principles when the chord-length d changes and arc-length remains fixed the corresponding chord-depth T will change. In the case that the chord-depth T is less than half of the chord-length d, any incremental changes in the chord-length d will result into a larger incremental change in the chord depth T as long as the diaphragm does not take up a flat shape. We call this effect mechanical amplification. We call the ratio of the incremental change of chord depth T to chord-length d the amplification ratio. As the ratio of chord-length d to chord depth T increases so does the amplification ratio.
The amplification ratio is observed at a frequency significantly below the first mechanical resonance of the transducer and within a range of frequencies between 20 hertz and 20 kilohertz. In a preferred embodiment, the amplification ratio is, for example, at least 1.2, at least 1.5, at least 1.7, at least 2, at least 2.5, at least 3, at least 3.5, at least 4, at least 4.5, at least 5, at least 5.5, at least 6, at least 6.5, at least 7, at least 7.5, at least 8, at least 8.5, at least 9, at least 9.5, at least 10, at least 10.5, at least 11, at least 11.5, at least 12, at least 12.5, at least 13, at least 13.5, at least 14, at least 14.5, at least 15, at least 15.5, at least 16, at least 16.5, at least 17, at least 17.5, at least 18, at least 18.5, at least 19, at least 19.5, or at least 20. In other embodiments, the amplification ratio is any ratio between those recited above.
In the construction of a speaker transducer the angle A formed between the distal end of the actuator and the plane P can be varied from perpendicular to very shallow angles which result in different proportions of mechanical amplification and motion in different regions of the diaphragm.
Mechanical amplification occurs for angles A larger than zero degrees and less than 180 degrees. It is noted that actuators can also be attached at the opposite side of the diaphragm at the same point D. Furthermore, mechanical amplification only occurs when the cord-depth T is less than two times the cord-length d.
It is noted that in addition to diaphragm motion due to mechanical amplification the diaphragm will also move with a superimposed displacement equal to the vertical component of the motion of the distal end of the actuator. There is no such superimposed displacement if the angle A is 90 degrees.
At rest position the diaphragm has a neutral shape determined by the relaxed shape of the diaphragm as well as the constraints imposed by the actuator attachment and support. The positive to negative oscillation of the signal voltage to the actuators results in a corresponding positive and negative displacement of the diaphragm relative to the neutral position. This displacement of the diaphragm creates an acoustic air pressure change and allows this design to act as an audio transducer.
Various combinations of the length of the actuator, baseline chord depth T and chord length d result in different speaker transducer performance in terms of maximum sound pressure level and frequency response.
It is noted that the piezoelectric bender can attach at a wide range of angles relative to the diaphragm. In certain embodiments, transducers of the invention are configured such that movement of the actuator has a component x that is larger than 0 and where the displacement of the diaphragm F is larger than the sum of displacements X and Y. If x were zero than there would be no mechanical amplification of the diaphragm displacement relative to the bender displacement. It is further noted, that the diaphragm can overhang the actuator by any amount. Other variants of the amplified transducer include: actuator or actuators on two opposing sides, no support S; and actuator on two opposing sides, with support S in-between.
In certain embodiments, the transducer is configured such that the piezoelectric effect is limited to the actuator. This means that a piezoelectric actuator, that is separate and distinct from a diaphragm composed of non-piezoelectric material, is used to excite the diaphragm. In case there is any piezoelectric effect in the diaphragm, this is not utilized to actuate the diaphragm. There is no electrical connection between the diaphragm and the audio amplifier.
Acoustic transducers of the invention may optionally include additional features so that the transducer of the invention can better withstand the environment in which they will be used without breaking. For example, piezo actuators are relatively brittle and will get damaged under high dynamic loads and sudden impacts. Additionally, thin diaphragms, as may be used with transducers of the invention, may be fragile due to their relative thinness. If a user drops a transducer onto a floor (for example from 120 cm height) than several reliability problems can occur. For example, the piezo actuator may be damaged or the diaphragm may be damaged.
Reliability problems of this type can often be so severe that the intended use of the transducer is no longer possible. The damage to the piezo actuator typically occurs due to an impact on the transducer in the direction of plane P for example dropping of the product on the floor. The weight of the diaphragm will force the piezo actuator to bend beyond its mechanical breaking limit. A typical example of damage is cracks being created inside the piezoelectric material that cause a dielectric breakdown when voltage is applied and thus preventing the actuator from moving as designed.
A typical damage to the diaphragm is a crack, a hole or a discoloration that typically occur in close proximity to the attachment points between the diaphragm and the actuator or the diaphragm and support. The extent of the damage to the actuator or diaphragm depends on the specific material and design chosen for both. In general the damage will be more severe or will occur more easily the heavier and larger the diaphragm is for a given design. The damage will also be more severe or will occur more easily if the transducer design is of a frameless type. It will also be more severe if the impact is increased for example by increasing the drop height, the weight of the product or the stiffness of the surface the transducer is dropped on.
Particularly for frameless transducers, there is an additional reliability problem as the diaphragm can be bent or torn due to the lack of a frame or speaker grille. As an example, if such a frameless transducer is dropped from 120 cm height onto a hard surface, such as concrete or wood, damage to the piezo actuator or the diaphragm or to both is observed. Moreover, if the transducer is dropped in a plane of the diaphragm on the top side of the diaphragm the diaphragm will bend and create a high stress at the attachment points that leads to cracking of the diaphragm near the attachment point.
Exemplary features that can protect transducers of the invention include: (a) mechanical stop or stops to limit the maximum bending of the actuator; (b) connector piece or pieces with tapered edges; (c) actuator substrate with tapered edges; (d) diaphragm with integrated connector piece with tapered edges; (e) removable and re-attachable diaphragm; (f) mechanical stop to limit bending of diaphragm; (g) member to prevent edge impact onto diaphragm, (h) a relatively soft connector piece between support and diaphragm; and (i) auxiliary supports on the left and right sides, coupled at the top left and right corner. The preferred implementation for each of these measures is described below. The measures can be used individually or in conjunction to improve the reliability of mechanically amplified acoustic transducers with piezoelectric actuators.
The figures show a transducer that includes the additional features a), b), f), g) and h), although transducers of the invention do not need to include all of the features or can include more features at the same time. For example, transducers of the invention can be provided with none of the additional features, with one of the additional features, or with all of the additional features. Stated another way, the additional features described herein are optional, and no embodiment of the invention should be interpreted to require any of the additional features. Also, any combination of the features may be used with transducers of the invention.
A first feature may be a member that limits bending of the actuator. That member can be seen as 106 in
The member that limits bending of the diaphragm 101 is shown as 108 in
The member may be any component that limits bending of the actuator. The member may be composed of any material, and exemplary materials include plastics, metals and rubbers. A specific exemplary configuration for the member is shown in
The member may also be an integral feature of the “base/support” instead of a separate part.
Prior art teaches the use of a substrate with a bent over top section against which the diaphragm is attached. The disadvantage of this construction is that a sharp transition corner all around the attachment point or attachment area is formed. That stiffness of the diaphragm changes dramatically at that corner and the corner acts as a stress concentrator. Any sudden impact on the transducer will create a localized very high force at the corner where the diaphragm attaches to the substrate. This high force then causes cracks or holes in the diaphragm or separation of the diaphragm from the substrate or damage to the substrate or a combination of those when dropped, for example from a height of 120 cm, onto a concrete or wood floor.
In order to overcome that problem, a connector with tapered flanges is introduced. The connector is shown as 107 in
Connectors of the invention may have any type of taper. For example, in certain embodiments, the left and right sides of the connector taper from the planar proximal end to the distal end, as shown in
The size of the connector can be determined as necessary. In an exemplary embodiment, the planar proximal end has dimensions of 9 mm×30 mm. The distal end has dimensions of 4 mm×25 mm. The distance from the planar proximal end to the distal end can be 7 mm. In addition, the size of the tapered flanges can be determined as necessary. In certain embodiments, the taper can be very gradual. In preferred embodiments, the ratio of the flange thickness near the center of the connector to the thickness at the edge of the flange is 3:2. It is desirable to have the thinnest practical tip thickness of the flanges in order to create the smallest possible increase in the bending stiffness of the diaphragm where it is coupled to the connector. The provided taper can include any number of cross sectional profiles, as shown in
Any connecting mechanism may be used to couple the connector to the diaphragm. For example, the connector may be coupled to the diaphragm by adhesives, friction, clamp, fasteners, rivets, material connection such as those made by laser welding or ultrasonic welding, or magnetic connection. When the diaphragm is flat, the proximal end of the connector may also be flat, as shown in
The connector also needs to couple to the actuator. An exemplary way to make this connection it to configure the connector such that a portion of the actuator 104 fits within the distal end of the connector 107, as shown in
Connectors of the invention can be made from any material known in the art. In certain embodiments, however, the connector is made from a soft or compressible material. These materials confer a certain level of flexibility to the connector, which facilitates the distribution of force upon impact.
Any method known in the art can be used to produce connectors in accordance with the invention. The actual method may vary depending on the configuration of the connector, for example, whether the connector comprises a single, contiguous unit or whether the connector is made from multiple components. In certain embodiments, extrusion is used to produce the provided connectors. This method can be used when multiple components are needed to assemble the connector. This method is less suitable for monothilic or contiguous connector units, due to the tapering required in the final form.
Extrusion is a process used to create objects of a fixed, cross-sectional profile in which the material used to create the object is pushed or drawn through a die of the desired cross-section. Extrusion is suitable for producing objects with very complex cross-sections. Extrusion may be continuous (producing indefinitely long material) or semi-continuous (producing many pieces). The extrusion process can also be performed using hot or cold starting materials. Extruded materials suitable for preparing connectors of the invention include, without limitation, metals, polymers, ceramics, and combinations thereof.
In the basic hot extrusion process, the starting material is heated and loaded into the container in the press. In cold extrusion, the starting material is kept at room temperature or near room temperature. In either case, a dummy block is placed behind the loaded container where the ram then presses on the material to push it out of the die. Afterward the extrusion is stretched in order to straighten it. If better properties are required then it may be heat treated or cold worked.
In certain aspects, the provided connector comprises multiple components. In this case, dies are prepared for each of the separate components, such as the two tapering sides the non-tapering sides. The starting material is again pushed through the various dies, resulting in the production of multiple components which are then connected. Any means can be used to connect the components, including welding, the use of adhesives, interlocking components, etc.
Molding is another process that can be used to produce connectors in accordance with the invention. Molding is especially advantageous in that it can be used to produce monolithic units and multicomponent units. In molding, a rigid frame or model is used to shape pliable raw material into the desired form.
The mold is typically a hollowed-out block that is filled with a liquid like plastic, glass, metal, or ceramic raw materials. The liquid hardens or sets inside the mold, adopting its shape. A release agent is often used to facilitate the removing the hardened/set substance from the mold. Types of molding suitable for use in producing connectors of the invention include without limitation, blow molding, compression molding, extrusion molding, injection molding, and matrix molding. Unlike the extrusion processes described above, molds can be used to easily prepare contiguous, monolithic connectors with tapering sides. For example, a single mold can be used to produce the monolithic members while several different molds can be used to the various components in a multi-component unit.
An exemplary process for making a connector in accordance with the invention will now be provided. Plastic injection molding is well known in the art. To mass produce the connector a mold block with the shape of the connector provided as a hollow cavity coupled to a reservoir that can inject molten plastic resin is made. The mold is made in two halves such that a completed part can be removed from one of the halves without any portion being impeded by portions of the mold cavity. Persons skilled in the art are readily familiar with the requirements. The mold is placed in a processing machine capable of clamping the two halves of the mold together with many tons of force. Molten plastic resin is injected into the cavity at very high pressure in order to facilitate rapidly filling thin or distant volumes of the mold. The need for rapid filling is due to the limited time before the molten plastic cools into a solid. Within a cycle time generally less than two minutes the mold may be closed, filled and emptied of completed parts. In order to optimize the cost and throughput of molded parts in the machine the mold may be comprised of several identical cavities. Molds can have 1, 2 or even dozens of cavities and produce a commensurate number of parts in each cycle.
The material properties of the plastic resin may be selected to optimize the stiffness, damping properties and also the compatibility with the joining processes used to attach the diaphragm to the connector and the connector to the actuator.
Connectors of the invention can also include additional components that further help disperse the force associated with an impact. In certain aspects of the invention, the proximal end of the connector that couples to the diaphragm features a damping element or elements. The use of a damping material may lead to a desired damping characteristic for the entire connector. Stated another way, the overall damping of the connector is higher than the damping that would be otherwise present without the damping element.
The term “damping” in this disclosure (also called tan delta or using the symbol 6) is known to be the ratio of loss modulus (E′) to storage modulus (E″). It is a characteristic generally associated with viscoelastic materials. Adding these elements may provide a means to reduce or eliminate undesirable vibration modes in the diaphragm.
In certain aspects, the damping elements comprise viscoelastic materials inserted between the connector and diaphragm. The damping elements may also provide adhesive as between the connector and diaphragm as shown in
The damping elements can be incorporated into the connector as separately manufactured elements or they may be molded concurrently with the rigid portion of the connector in a process that provides for two steps of injecting first one then another plastic resin into a mold that has changeable portions to allow the completion of a two component part in one molding operation.
(c) Actuator Substrate with Integrated Connector Piece with Tapered Edges
In some embodiments, the tapered edge or edges as described in (b) above that connect the diaphragm to the actuator are not a separate connector piece but are integrally formed with the substrate element of the actuator, as shown in
A preferred implementation is a substrate of the actuator that is produced as an injection molded or cast part out of plastic or metallic material and that combines the tapered feature of the connection area with the desired geometry of the actuator substrate.
(d) Diaphragm with Integrated Connector Piece with Tapered Edges
In some embodiments, the connector as described in (b) above is integrally formed with the diaphragm, as shown in
The tapering features as well as a recess or other feature designed to couple the diaphragm to the end of the actuator are incorporated into the connector portion molded with the diaphragm.
A distal end of the actuator attaches to the connector as described above, for example by a portion of the actuator fitting within the distal end of the connector. A preferred implementation is a diaphragm made by injection molding, casting or thermoforming that combines the general shape of the connector described above with the desired geometry of the diaphragm into one part.
In certain embodiments, transducer of the invention are designed such that the diaphragm is removable coupled to the actuator. The strength of the connection is designed such that the diaphragm will release from the actuators at a force that is less than an impact force that would damage the diaphragm. In that manner, the diaphragm releases from the actuator prior to a force being applied to the diaphragm that would damage either the diaphragm or the actuators. Any type of releasable connection may be used. In exemplary embodiments, the releasable connection is accomplished using magnets or friction based claims. The strength of the magnets are tuned such that the magnets come loose before a force impact would damage either the diaphragm or the actuator. Other connections may be formed using tapered wedges that create very stiff connections laterally but may be separated easily in a direction parallel to the plane of the actuator.
One of the potential ways the diaphragm can get damaged during a drop from for example 120 cm onto a floor is by the transducer dropping onto the diaphragm itself and causing it to bend. This is a particular problem for a transducer with a frameless diaphragm as shown in
The mechanical stop of the invention may have any type of orientation or distance relative to the diaphragm. For example, in certain embodiments, the mechanical stop has the form of a slot and forms a stop on both planar sides of the diaphragm. The position of the diaphragm within the slot may be symmetric or asymmetric relative to the two mechanical stops. In other embodiments, the mechanical stop only interacts with the front or the back side diaphragm in case of a drop with a diaphragm bending of 180 degrees. This can be achieved by having a mechanical stop only on one side of the diaphragm or by having two stops with the one on one side being too far removed to act as a stop.
In particular embodiments, a slot is protecting the diaphragm from bending in both sides at equal distance as is shown in
(g) Member to Prevent Edge Impact onto Diaphragm
Another durability problem can arise from a direct edge impact onto the diaphragm, in particular in a frameless design. This can create high shear forces onto the interface of diaphragm to actuator or connector that can create damage in the diaphragm or actuator or connector or interface layer. This is a particular problem on the edge or edges of the diaphragm that is attached to the actuator and that is moving as these cannot be protected through firm coupling with a frame. A solution is to introduce a member that physically prevents an edge impact onto one side of the diaphragm. A preferred implementation is shown in
Another area of the diaphragm that can get damaged when dropping the transducer is the connection of the diaphragm to the support. As discussed above a stress concentrator can cause damage to the diaphragm. A solution to this problem is a tapered design of the interconnection point between the diaphragm and the support to achieve a gradual stiffness change. This can be achieved with a tapered connector piece, with a tapered edge that is integral to the diaphragm or with a support that includes a tapered feature. Another solution is the use of a relatively soft and compressible connector piece between the diaphragm and the support. In a preferred implementation the connector piece has a lower modulus than the diaphragm and the support and it is made out of a rubber or silicone. Other materials can be used as well. The relative softness and compressibility of the connector material will allow for a bending of the diaphragm around a larger radius and a reduction of maximum stresses. A soft and compressible connector piece can be combined with a tapered design. A preferred implementation is shown in
In certain embodiments, the transducers of the invention include auxiliary support.
In a three sided frameless transducer design such as those shown in
The invention also encompasses soundbars, as shown in
Similar to the transducers described above, soundbars of the invention may optionally include additional features so that the transducers of the invention can better withstand the environment in which they will be used without breaking. Exemplary features that can protect transducers of the invention include: (a) mechanical stop or stops to limit the maximum bending of the actuator; (b) connector piece or pieces with tapered edges; (c) actuator substrate with tapered edges; (d) diaphragm with integrated connector piece with tapered edges; (e) removable and re-attachable diaphragm; (f) mechanical stop to limit bending of diaphragm; (g) member to prevent edge impact onto diaphragm, (h) a connector piece between support and diaphragm; and (i) auxiliary supports on the left and right sides. The preferred implementation for each of these measures is described above. The measures can be used individually or in conjunction to improve the reliability of a mechanically amplified acoustic transducers with piezoelectric actuators.
Similar to above, the soundbars of the invention do not need to include all of the features. For example, soundbars of the invention can be provided with none of the additional features, with one of the additional features, or with all of the additional features. Stated another way, the additional features described herein are optional, and no embodiment of the invention should be interpreted to require any of the additional features. Also, any combination of the features may be used with soundbars of the invention.
Various modifications of the invention and many further embodiments thereof, in addition to those shown and described herein, will become apparent to those skilled in the art from the full contents of this document, including references to the scientific and patent literature cited herein. The subject matter herein contains important information, exemplification and guidance that can be adapted to the practice of this invention in its various embodiments and equivalents thereof.
This application claims the benefit of and priority to Provisional U.S. Patent Application Ser. No. 61/791,355, which was filed on Mar. 15, 2013, the entirety of which is incorporated by reference herein.
Number | Date | Country | |
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61791355 | Mar 2013 | US |