Abstract:
An acoustic assembly for use in a transducer includes a multi-layer structure. A first layer member includes a first center portion, a first edge portion and a first aperture separating the first center portion and the first edge portion. A second layer member includes a second center portion, a second edge portion and a second aperture separating the second center portion and the second edge portion such that the second center portion is free to move relative to the second edge portion. The first and second layers are formed into an assembly wherein the first center portion and the second center portion are coupled, the first edge portion and the second edge portion are coupled, and the first aperture and the second aperture are substantially aligned to define a passageway. The assembly has an assembly stiffness that is greater than the stiffness of either the first or second layer members. A hinge joins the assembled first and second center portions and the first and second edge portions such that the assembled first and second center portions is free to at least partially rotate relative to the assembled first and second edge portions about an axis. A flexible layer member is coupled to the assembly and provides airtight sealing of the passageway.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent claims benefit under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 60/665,700 filed Mar. 28, 2005, the disclosure of which is hereby expressly incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This patent generally relates to transducers used in listening devices, such as hearing aids or the like, and more particularly, to a composite layered structure for used in the transducers. 
     BACKGROUND 
     Hearing aid technology has progressed rapidly in recent years. Technological advancements in this field have improved the reception, wearing-comfort, life-span, and power efficiency of hearing aids. Still, achieving further increases in the performance of ear-worn acoustic devices places ever increasing demands upon improving the inherent performance of the miniature acoustic transducers that are utilized. 
     There are several different hearing aid styles widely known in the hearing aid industry: Behind-The-Ear (BTE), In-The-Ear or All In-The-Ear (ITE), In-The-Canal (ITC), and Completely-In-The-Canal (CIC). Generally speaking, a listening device, such as a hearing aid or the like, includes a microphone assembly, an amplification assembly and a receiver (speaker) assembly. The microphone assembly receives acoustic sound waves and creates an electronic signal representative of these sound waves. The amplification assembly accepts the electronic signal, modifies the electronic signal, and communicates the modified electronic signal (e.g. processed signal) to the receiver assembly. The receiver assembly, in turn, converts the increased electronic signal into acoustic energy for transmission to a user. 
     Conventionally, the receiver utilizes moving parts (e.g. armature, acoustic assembly, etc) to generate acoustic energy in the ear canal of the hearing aid wearer. The diaphragm assembly disposed within the housing of the receiver is placed parallel to and in close proximity to the inner surface of the cover. The diaphragm assembly, attached to a thin film, is secured to the inner surface of the housing by any suitable method of attachment. The motion of the acoustic assembly, and hence its performance, is dependent on the materials used to make the diaphragm assembly and its resulting stiffness. Furthermore, the materials used to make the diaphragm assembly and thin film determine the thickness of the acoustic assembly. 
     There are a number of competing design factors. It is desirable to reduce the height of the receiver; however, the acoustic assembly may require a relatively thick diaphragm assembly to ensure adequate stiffness. The resulting receiver, one with a thin housing but thick diaphragm may be limited to very small diaphragm movement, limiting its suitability for certain applications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the disclosure, reference should be made to the following detailed description and accompanying drawings wherein: 
         FIG. 1  is a is a perspective view of an acoustic assembly utilized in a transducer of one of the described embodiments; 
         FIG. 2  is an exploded view of a described embodiment of an acoustic assembly; 
         FIG. 3  is a perspective view of  FIG. 2  of the described embodiment of the acoustic assembly; 
         FIG. 4  is an exploded view of a second embodiment of an acoustic assembly; 
         FIG. 5  is a perspective view of  FIG. 4  of the second embodiment of the acoustic assembly; 
         FIG. 6  is an exploded view of a third embodiment of an acoustic assembly; 
         FIG. 7  is a perspective view of  FIG. 6  of the third embodiment of an acoustic assembly; 
         FIG. 8  is an exploded view of a fourth embodiment of an acoustic assembly; 
         FIG. 9  is a perspective view of  FIG. 8  of the fourth embodiment of an acoustic assembly; 
         FIG. 10-13  represent layers carrying a plurality of formed acoustic assemblies: 
         FIG. 14  is a perspective view of an acoustic assembly with a “S” hinge of one of the described embodiments; 
         FIG. 15  is a top view of  FIG. 14  of the described embodiment of the acoustic assembly; 
         FIGS. 16-17  is a cross section view of a described embodiment of an acoustic assembly; and 
         FIG. 18  is a cross section view of a described embodiment of an acoustic assembly. 
     
    
    
     The drawings are for illustrative purposes only and are not intended to be to scale. 
     DETAILED DESCRIPTION 
     While the present disclosure is susceptible to various modifications and alternative forms, certain embodiments are shown by way of example in the drawings and these embodiments will be described in detail herein. It will be understood, however, that this disclosure is not intended to limit the invention to the particular forms described, but to the contrary, the invention is intended to cover all modifications, alternatives, and equivalents falling within the spirit and scope of the invention defined by the appended claims. 
     It should also be understood that, unless a term is expressly defined in this patent using the sentence “As used herein, the term ‘______’ is hereby defined to mean . . . ” or a similar sentence, there is no intent to limit the meaning of that term, either expressly or by implication, beyond its plain or ordinary meaning, and such term should not be interpreted to be limited in scope based on any statement made in any section of this patent (other than the language of the claims). To the extent that any term recited in the claims at the end of this patent is referred to in this patent in a manner consistent with a single meaning, that is done for sake of clarity only so as to not confuse the reader, and it is not intended that such claim term by limited, by implication or otherwise, to that single meaning. Unless a claim element is defined by reciting the word “means” and a function without the recital of any structure, it is not intended that the scope of any claim element be interpreted based on the application of 35 U.S.C. §112, sixth paragraph. 
       FIG. 1  illustrates an exemplary embodiment of a transducer  100 . The transducer  100  may be adapted as either a microphone, receiver speaker, accelerometer, Microelectromechanical System (MEMS) devices or other such device, and may be useful in such devices as listening devices, hearing aids, in-ear monitors, headphones, electronic hearing protection devices, very small scale acoustic speakers, and MEMS devices. The transducer  100  includes a motor assembly  120 , a coupling assembly  130 , and an acoustic assembly  140  disposed within a housing  110 . The housing  110  may be rectangular and consists of a cover  102  and a base  104 . In alternate embodiments, the housing  110  can be manufactured in a variety of configurations, such as a cylindrical shape, a D-shape, a trapezoid shape, a roughly square shape, a tubular shape, or any other desired geometry. In addition, the scale and size of the housing  110  may vary based on the intended application, operating conditions, required components, etc. Moreover, the housing  110  can be manufactured from a variety of materials, such as, for example, stainless steel, alternating layers of conductive materials, or alternating layers of non-conductive layers (e.g., metal particle-coated plastics). The base  104  may include a plurality of supporting members (not shown) adapted to support the motor assembly  120 . In alternate embodiments, the base  104  may include an opening and a portion of the motor assembly  120  may then extend into the opening such that the motor assembly  120  and the base  104  are mutually interconnected. 
     The motor assembly  120  includes a drive magnet  122  and a magnetic yoke  124 . The magnetic yoke  124  forms a frame having a central tunnel defining an enclosure into which the drive magnet  122  mounts. The magnetic yoke  124  may be made of a Nickel-Iron alloy, an Iron-Cobalt-Vanadium alloy or of any other similar materials. The drive magnet  122  may be made of a magnetic material such as Ferrite, AlNiCo, a Samarium-Cobalt alloy, a Neodymium-Iron-Boron alloy, or of any other similar materials. The motor assembly  120  may further include an armature  126  and a drive coil (not shown). In the embodiment shown in  FIG. 1 , the armature  126  is generally U-shaped. One of ordinary skill in the art will appreciate that the armature  126  may be E-shaped or of a different configuration such as disclosed in U.S. patent application Ser. Nos. 10/769,528 and 10/758,441, the discloses of which are incorporated herein by reference. A movable end of the armature  126  extends along the drive coil (not shown) and the magnetic yoke  124 , which in turn connects to the acoustic assembly  140  via the coupling assembly  130  to drive the acoustic assembly  140 . The coil (not shown) is located proximate to the drive magnet  122  and the magnetic yoke  124 . 
     Adhesive bonding may secure the acoustic assembly  140  to the inner surface of the housing  110  and to the motor assembly  120  via the coupling assembly  130 . Any other suitable attachment means may be used to couple the acoustic assembly to the motor assembly  120  via the coupling assembly  130 . The arrangement of the acoustic assembly permits the transfer of electrical signal energy to vibrational energy in the acoustic assembly  140  or to transfer vibrational energy in the acoustic assembly  140  into electrical signal energy. In alternate embodiments, the acoustic assembly  140  is secured to the outer surface of the motor assembly  120  by bonding with adhesive or any other suitable method of attachment. The coupling assembly  130  may be a drive rod, a linkage assembly, a plurality of linkage assemblies, or the like. As depicted in  FIG. 1 , the coupling assembly  130  is a linkage assembly. The linkage assembly  130  typically fabricated from a flat stock material such as a thin strip of metal or foil may be formed into variety of shapes and configurations based on the intended application, operating conditions, required component, etc to amplify motion or force. Alternately, the linkage assembly  130  may be formed of plastic or some other compliant material. 
     The acoustic assembly  140  may be rectangular and consists of a first layer  142 , a second layer  144 , and a flexible layer  146 . However, the acoustic assembly  140  may utilize multiple layers, and such embodiment will be discussed in greater detail. In alternate embodiments, the acoustic assembly  140  may be formed of various shapes and have a number of different of sizes in different embodiments based on the intended application. The first and second layers  142 ,  144  can be manufactured from a variety of materials such as aluminum, stainless steel, beryllium copper, titanium, tungsten, platinum, copper, brass, or alloys thereof, non-metals such as, plastic, plastic matrix, fiber reinforced plastic, etc., or multiples of these could be used. The first layer  142  is attached to the second layer  144  for example, by adhesive bonding, for example, ethylene vinyl acetate thermoplastic adhesive, thermo set adhesive, epoxy, polyimide, or the like. The flexible layer  146  attached to the composite layered structure may be made of Mylar, urethane, rubber or of any other similar materials. 
       FIGS. 2-3  illustrate an embodiment of the acoustic assembly  140  that can be used in a variety of transducers, including receivers similar to the receiver  100  illustrated in  FIG. 1 . The acoustic assembly  140  includes a first layer  142 , a second layer  144 , and a flexible layer  146 . The first layer  142  and the second  144  are attached together, for example, by bonding with adhesive, welding compression, or mechanical attachment. The combined first and second layers  142 ,  144  may then be attached to the flexible layer  146  to constitute the acoustic assembly  140 , which then may be operably attached to the linkage assembly  130  as shown in  FIG. 1 . In one example, the first layer  142  is made of stainless steel having a thickness of about 0.0005″ to about 0.002″. The first layer  142  includes a central portion  148 , an edge portion  150 , a hinge portion  154 , and a passageway  152  formed between the central portion  148  and the edge portion  150 . Two legs  153  connecting the central portion to the edge portion form a hinge  154 . The legs may each have a width and length of approximately about 0.01″. The hinge  154  allows the central portion of the acoustic assembly  140  to rotate easily around an intended axis while suppressing other forms of motion at the hinge such as shear motion or rotation along other axes. The second layer  144  includes a central portion  156 , an edge portion  158 , and a passageway  160  formed between the central portion  156  and the edge portion  158 . The second layer  144  may optionally include a hinge (not shown) formed from legs. 
     In one example, the second layer  144  is made of stainless steel having a thickness of about 0.002″ to about 0.015″. Other materials having a density about 2 g/cm 3  to about 15 g/cm 3 , or an elastic modulus of about 1.0E+10 Pascals (Pa) to about 2.5E+11 Pa may be employed separately of the first layer  142  to affect the resonant frequency of the overall acoustic assembly  140  or the moving mass of the acoustic assembly  140 . It is to be understood that thickness, width, length, and materials other than those described above may be utilized as well. In this example, the overall thickness of the acoustic assembly  140  is less than the typical acoustic assembly, thereby taking up less space in the output chamber of the receiver  100 . The flexible layer  146  may be made of Mylar, urethane, or of any other similar materials. As shown in  FIG. 2 , the flexible layer  146  is attached to the composite two layer structure. The flexible layer  146  includes a folded portion  147  that is disposed within the passageways  152 ,  160  between the edge portions  150 ,  158  and the central portions  148 ,  156  to form an airtight partition from a first side of the acoustic assembly to the second side of the acoustic assembly. The flexible layer  146  allows relatively unrestricted rotating movement of the central portions relative to the edge portions about the corresponding hinge portions. 
     In a lamination process, a temporary connecting material (not shown) may be disposed in the passageway  160  of the second layer  144  aligning and retaining the central portion  156  of the second layer  144  to the central portion  148  of the first layer  142 . The central portion  156  of the second layer  144  is then attached to the central portion  148  of the first layer  142 , for example, by bonding with adhesive, welding, compression, or mechanical attachment. The flexible layer  146  is attached to the second layer  144  and thus the second layer  144  to the first layer  142 . Such fabrication process will be discussed in greater details. In alternate embodiments, a structural enhancing feature may be provided to the hinge. For example, hinge legs may be enlarged or provided with ribs or other structural enhancing structures. Alternatively, a large mass of adhesive may be applied to the hinge portion  154  to increase the rigidity around the hinge and enhance control of the movement of the acoustic assembly  140 . The pivoting movement about the hinge provides control of the movement of the acoustic assembly  140  while delivering acoustic output sound pressure. It is to be understood that materials other than those described above may be utilized as well to control the rotational flexibility around the hinge. 
       FIGS. 4-5  illustrate another embodiment of an acoustic assembly  240 . The acoustic assembly  240  includes a first layer  242 , a second layer  244 , a third layer  246 , and a flexible layer  248 . The second layer  244  is attached to the first layer  242  and the third layer  246  is attached to the second layer  244 . The composite three layer structure may be a metal-polymer-metal construction, which forms the diaphragm. The flexible layer  248  attaches thereto to complete the acoustic assembly  240 , which may then be operably attached to the linkage assembly  130  as is shown for the acoustic assembly  140  in  FIG. 1 . 
     The first, second and third layer  242 ,  244 ,  246  includes central portions  250 ,  256 ,  264 , edge portions  252 ,  258 ,  266 , and passageways  254 ,  260 ,  268 , respectively. The passageways  254 ,  260 ,  268  are formed between the central portions  250 ,  256 ,  264  and edge portions  252 ,  258 ,  266 . The second layer  244  further includes a hinge portion  262  which provides the same function as the hinge portion  154  as shown in  FIG. 2-3 , although it will be appreciated that the first and/or third layers may incorporate the hinge. In one example, the first and third layers  242 ,  246  can be formed from a material of high elastic modulus such as stainless steel, copper, brass, or alloys thereof, or beryllium copper (BeCu). The second layer  244  can be a dry adhesive sheet. For example, the second layer  244  may be formed from a material of low density such as modified ethylene vinyl acetate thermoplastic adhesive, a thermo set adhesive, an epoxy, or polyimide, that acts as an adhesive and spacer layer for joining and positioning the first and third layers of the structure while increasing the bending moment of the acoustic assembly  240  hence raising the resonant frequency of the central portion without adding significantly to the mass or thickness. In this example, the overall thickness of the acoustic assembly  240  is less than a typical acoustic assembly, thereby taking up less space in the output chamber of the receiver  100 , which will be discussed in greater detail. As shown in  FIG. 4 , the flexible layer  248  may be made of Mylar, urethane, rubber or of any other similar materials, and includes a folded portion disposed within the passageways  254 ,  260 ,  268  to form an airtight partition while allowing unrestricted rotational movement between the edge portions  252 ,  258 ,  266  and the central portions  250 ,  256 ,  264  about the hinge portion  262 . In this configuration, the composite three layer structure, such as the discussed metal-polymer-metal sandwich structure, enables control of resonant frequency of the central portion independent of the moving mass. 
     Typically, resonances of the central portion of the acoustic assembly  240  take the form of bending or twisting motions at certain frequencies, resulting in deviation of the moving mass of the central portion of assembly  240 . To control the moving mass of the central portion of acoustic assembly  240  over a specified frequency range, it is generally desirable to control the lowest frequency of such resonant motion, in particularly, the bending motion of the central portion of assembly  240 . The composite three layer structure enables control of the resonant frequencies independent of the moving mass. For given length and width dimensions of the central portion and for a hinged connection between the edge portion and the central portions of the composite three layer structure, the resonant frequencies are dependent on the ratio of mass per unit area to the stiffness of the central portion, which enables the paddle mass and paddle resonance characteristics to be independently pursued. The mass per unit area of the central portion is strongly influenced by the overall thickness and density of the metal layers since the metal layers have considerably higher densities than polymers. The stiffness of the central portion is influenced by both the thickness of the metal layers due to their high elastic modulus and the vertical separation between them as established by the polymer layer. A direct design approach is to allocate a total metal thickness, divide the thickness between the two metal layers that satisfies the paddle mass requirement and then set a polymer thickness which achieves sufficient plate stiffness in the overall acoustic assembly  240 . The desired rotational and translational stiffness of the hinge further depends on having chosen a polymer material with the correct elastic modulus. 
       FIGS. 6-7  illustrate yet another embodiment of an acoustic assembly  340 . The assembly  340  is similar in construction and function as the assembly  140  illustrated in  FIGS. 2-3 , and similar elements are referred to using like reference wherein, for example  340  and  342  correspond to  140  and  142 , respectively. In this embodiment, a central portion  356  of the second layer  344  is formed with pattern of apertures to facilitate control of the center of mass of the central portion  356 . In alternate embodiments, the second layer  344  can be attached to the top surface of the first layer  342  and the flexible layer  346  is attached to the bottom surface of the first layer  342 , which permits additional control of the resonant frequency of the acoustic assembly  340 , thus requiring less space in the output chamber of the receiver  100 , as depicted in  FIG. 1 . The pivoting movement about the hinge portion  354  also allows control of the movement of the acoustic assembly  340  while delivering maximum acoustic output sound pressure. 
       FIGS. 8-9  illustrate still another embodiment of an acoustic assembly  440 . The acoustic assembly  440  is similar in construction and function to the acoustic assembly  240  illustrated in  FIGS. 4-5 , and similar elements are referred to using like reference numerals wherein, for example  440  and  442  correspond to  240  and  242 , respectively. In this embodiment, central portions  450 ,  464  of the first and third layers  442 ,  446  in a pattern of apertures to facilitate controlling the center of mass of the acoustic assembly  440 . A flexible layer  448  is attached to the composite, multi-layer structure. Also, the acoustic assembly  440  provides for controlling the resonant frequency in a thin design, thus requiring less space in the output chamber of the receiver  100 , as depicted in  FIG. 1 . The pivoting movement about the hinge area  462  also allows control of the movement of the acoustic assembly  440 , as well as stiffness of the moving mass of the acoustic assembly  440 , while delivering acoustic output sound pressure. 
       FIGS. 10-13  are plan views illustrating a panel  500  for forming a plurality of acoustic assemblies. The acoustic assemblies are distributed on the panel  500  in an array. Fewer or more acoustic assemblies may be disposed on the panel  500 , or on smaller or larger panels. As described herein, the acoustic assemblies include a number of layers, such as first layers, second layers, third layers, flexible layers, and the like. To assure alignment of the portions as they are brought together, each portion may be formed to include a plurality of alignment apertures  502  and inserts  504 . To simultaneously manufacture several hundred or even several thousand acoustic assemblies, a first layer  506 , such as described herein is provided. An adhesive layer, such as a sheet of dry adhesive is positioned under the first layer  506 , and a second layer  508  is positioned under the first layer  506 . The temporary legs located away from the hinge portion of the second layer  506  are then removed simultaneously in a second blanking operation. A flexible layer  510  is positioned under the second layer  508  and thus the second layer  508  to the first layer  506 . The dry adhesive layer and the flexible layer are activated, such as by the application of heat and/or pressure. The panel  500  is then separated into individual acoustic assemblies using known panel cutting and separating techniques. In alternate embodiments, a three layer structure is laminated by any suitable method of attachment, e.g. adhesive. The three layer structure is typically patterned by lithography and/or laser milling having a central portion, an edge portion, a passageway, and hinge portion. In this embodiment, the hinge portion of middle layer of the three layer structure is formed a using photolithographic patterning process to create openings in the first and third layers, leaving an exposed portion of the middle layer. The flexible layer  510  positioned under the three layer structure is formed within the passageway to form an airtight partition while allowing unrestricted relative motion between the edge portion and the central portion. Yet in another embodiment, a forming sequence process using any type of circuit board fabrication to deposit, form, or otherwise create a layer of material. The acoustic assembly includes a first substrate, a second substrate, and a flexible layer. The first and second substrates may be made any material allowing processing in circuit board panel form and the flexible layer may be made of polyimide with a finishing layer of copper is applied on top surface of the flexible layer. The combined first and second layers are formed on the top surface of the flexible layer. 
       FIGS. 14-18  illustrate an acoustic assembly  640  with a contoured hinge area. The acoustic assembly  640  is similar in construction and function as the assemblies illustrated in  FIGS. 2-9 . In this embodiment, a contour shape hinge  642  is formed at a position in the vicinity of the front end between the edge portion  646  and the central portion  644  of the acoustic assembly  640 . The hinge  642  may be a thin strip of flexible metal such that the central portion  644  of the acoustic assembly  640  is non-parallel to the inner surface of the cover  602  while an aperture  650  is formed in the vicinity of the rear end of the acoustic assembly  640 . The linkage assembly  630 , as depicted in  FIG. 18  corresponding to the aperture  650  in the acoustic assembly  640  is bonded to the aperture  650  by any suitable method of attachment, e.g. adhesive, to drive the acoustic assembly  640 . In alternate embodiment, the aperture  650  is not required and the linkage assembly  130  is coupled to the inner surface of the acoustic assembly  640  as opposed to the hinge  642  by any suitable method of attachment. In this configuration, the front volume  652  between the acoustic assembly  640  and the inner surface of the cover  602  is reduced and the resonant frequencies of the receiver  600 , which depend on the air volume contained in the front volume  652 , are increased. Further, it may be possible to maximize the bandwidth as compared to a receiver utilizing an acoustic assembly parallel to and in close proximity to the inner surface of the cover  602 . In alternate embodiment, the hinge  642  is formed at a position in the vicinity of the front end between the edge portion  646  and the central portion  644  of the acoustic assembly  640  such that the hinge  642  is in close proximity to the inner surface of the cover  602  and the central portion is non-parallel to the inner surface of the cover  602  of the receiver  600 . Yet in alternate embodiment, the hinge  642  having a thickness is formed at a position in the vicinity of the front end and an unhinge end portion  654  depicted in  FIG. 18  as opposed to the hinge  642  having a thickness less than the thickness of the hinge  642  is formed in the vicinity of the rear end of the acoustic assembly  640 . 
     Still in alternate embodiment, the acoustic assembly  640  having a concavity is formed partially or wholly at the central portion  644 . A preformed member may be made of conducting layers, non-conducting layers, layers of conducting/non-conducting, or any other similar materials is attached to the inner surface of the cover  602  to partially or wholly fill a portion of the concavity such that the central portion  644  of the acoustic assembly  640  is in close proximity to the inner surface of the cover  602 , thus reduces the front volume. In a fifth aspect, the acoustic assembly  640  does not require a concavity. A fillable means is provided to partially or wholly fill the cover  602  with liquids, grease, gel, foam, latex, silicone, curable adhesive, plastic, metal, or any other similar materials. In a sixth aspect, a fillable means is provided to partially or wholly fill the space between the composite multi-layer structure of the acoustic assembly with foam rubber, trapping air bubbles, or any other similar materials. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
     Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. It should be understood that the illustrated embodiments are exemplary only, and should not be taken as limiting the scope of the invention.