MEMBRAN FOR USE IN AN AUDIO CONVERTER AND METHOD FOR MAKING A MEMBRAN

Abstract

Membrane (1) for use in an audio transducer, wherein the membrane (1) has a first outer surface, a second outer surface opposite the first outer surface, and a support structure, wherein a skin (8) defines the first outer surface of the membrane (1), wherein the support structure is arranged on or in the skin (8), and wherein the support structure has a honeycomb pattern structure (110) which has an arrangement of substantially regular cells (110b) with a defined geometry, wherein the skin (8) is a first skin (108), wherein the membrane (1) further comprises a second skin (112), wherein the honeycomb pattern structure (110) is arranged between the first and second skin (108, 112) and wherein the second skin (112) defines the second outer surface of the membrane (1), wherein the honeycomb pattern structure (110) is integrally formed with the first skin (108), and wherein the second skin (112) is connected to the honeycomb pattern structure (110) but is not integrally formed with it to form the membrane (1), or wherein the honeycomb pattern structure (110) is integrally formed with the second skin (112) and wherein the first skin (108) is connected to the honeycomb pattern structure (110) but is not integrally formed with it to form the membrane (1).

Description

[0001] The present invention relates to a membrane for use in an audio transducer and to a method for manufacturing a membrane for an audio transducer.

[0002] To optimize performance, audio transducers ideally exhibit minimal mass and maximum stiffness (rigidity). Accordingly, it is desirable to use such diaphragms with a minimal amount of a high-stiffness material.

[0003] Materials that combine stiffness and low density are typically expensive and / or difficult to process. Usually, a material's stiffness increases with its density, resulting in a trade-off between the stiffness and mass of the membrane.

[0004] For the state of the art, reference should be made to the following documents: GB 2 010 637 A, US 4 351 412 A, US 2004 / 0 146 176 A1, US 2009 / 0 175 487 A1, US 2005 / 0 253 298 A1, GB 2 479 941 A, CN 105 376 679 A.

[0005] The present invention aims to provide an improved diaphragm for use in an audio transducer, with the goal of solving the aforementioned problems. The audio transducer can be a loudspeaker.

[0006] This problem is solved according to the invention by a membrane having the features of independent claim 1. Advantageous embodiments of the membrane according to the invention are specified in dependent claims 2 and 3. Likewise, this problem is solved by a method for producing a membrane comprising the steps of independent claim 4. Advantageous embodiments of the method are specified in dependent claims 5 to 8. The problem is also solved by an audio transducer having the features of claim 9.

[0007] According to a first aspect of the present invention, a membrane for use in an audio transducer is specified, wherein the membrane has a first outer surface, a second outer surface which is opposite or opposite to the first outer surface, and a support structure, wherein a skin defines the first and / or the second outer surface of the membrane, and wherein the support structure is arranged on or in the skin.

[0008] The first and second outer surfaces of the diaphragm are oriented in opposite directions, with one pointing in a first direction and the other in a second direction, which is generally opposite to the first. Preferably, the first outer surface is a front outer surface of the diaphragm; this means that, when in use, the first outer surface is positioned facing forward, towards the front of the audio transducer. Accordingly, the second outer surface is preferably a rear outer surface of the diaphragm, meaning that, when in use, the second outer surface is positioned facing backward, towards the rear of the audio transducer. The terms "front" and "rear" or "front / rear" as used in this description are to be interpreted accordingly.

[0009] In the arrangement of the present invention, the support structure acts to increase the strength of the skin. Thus, by providing a support structure, the skin can be made of a material with a relatively low density, while the required strength of the membrane is provided by the support structure. The overall mass of the membrane can therefore be reduced, while at the same time the stiffness of the membrane is increased and its performance is optimized.

[0010] The feature of the skin that defines the first and / or second outer surface of the membrane means that the skin has at least one exposed surface forming the first or second outer surface of the membrane. The skin can define only one of the first or second outer surfaces of the membrane, with the support structure located on a surface of the skin opposite its exposed surface. Alternatively, the skin can define both the front and rear outer surfaces of the membrane, with the support structure located within the skin. This means that the skin has two opposite exposed surfaces forming the first and second outer surfaces of the membrane. In some embodiments, the support structure can be completely embedded within the skin between the first and second outer surfaces of the membrane.

[0011] The support structure preferably has a higher density than the skin. In some embodiments, the support structure can be made of a first material and the skin can be made of a second material that differs from the first material, wherein the first material has a higher density than the second material. Accordingly, due to the difference in the relative densities of the first and second materials, the support structure has a higher density than the skin.

[0012] In alternative embodiments of the present invention, the support structure and the skin are formed from the same material, with the difference in their relative densities being achieved through the manufacturing process. For example, the support structure and / or the skin can be formed using an expansion forming process, wherein the material is expanded or foamed in a mold or die to create a solid cellular structure. The density of the expanded material depends on the mass of the material and the volume available in the mold or die. The density of the expanded material can be selected as desired, making it possible to form the support structure and the skin from the same material while simultaneously providing a support structure with a higher density than the skin.

[0013] The skin can have at least one area with a first density and at least one area with a second density, the second density being lower than the first. Areas of lower density can be located in areas of the skin that are inaccessible to the user when the diaphragm is located inside the audio transducer. Accordingly, the mass of the diaphragm can be further reduced without the risk of the end user damaging the diaphragm surfaces.

[0014] The support structure can include a frame, with the skin being formed around the frame to define the first and second outer surfaces of the membrane. The frame can be arranged to extend substantially over the entire area of ​​the skin, thus providing a support structure for the skin across its entire surface. This increases the membrane's strength across its entire surface. Preferably, the shape of the frame substantially corresponds to the shape of the membrane. In some preferred embodiments, the frame can be shaped like a truncated cone to form a substantially conical membrane.

[0015] In some embodiments, the frame has an outer rim that defines an outer edge of the frame, and also an inner rim that defines an inner opening of the frame. Preferably, one or more openings are formed between the outer rim and the inner rim to reduce the mass of the frame.

[0016] The support structure has a honeycomb pattern comprising an arrangement of cells with a defined geometry. The cells are hollow cavities or spaces defined by an arrangement of interconnected walls. The cells can be substantially uniform. The hollow cavities are preferably of a substantially uniform shape and size. The cells can have a substantially hexagonal geometry or, alternatively, any other suitable geometry, such as substantially circular, substantially square, or substantially pentagonal. The support structure preferably has a regular cell pattern. The cells are preferably substantially uniform.

[0017] The honeycomb structure provides the skin with additional strength due to its inherent rigidity. This increases the overall stiffness of the membrane. Because a large proportion of the honeycomb structure consists of hollow cells, the mass of the membrane is significantly less than that of a membrane with equivalent stiffness made from a solid material.

[0018] In one embodiment, some or all cells can be filled with a support material, such as liquid resin or a powder material, which provides a damping effect for the membrane and thus helps to reduce unwanted resonances of the membrane.

[0019] Preferably, at least part of the honeycomb structure is integrally formed with the skin. This can be achieved, for example, by casting the honeycomb structure (or part of it) together with the skin. By forming the honeycomb structure (or part of it) integrally with the skin, it is not necessary to add the honeycomb structure to the skin subsequently. This reduces processing time and minimizes or eliminates the need for adhesives and / or assembly accessories. This, in turn, reduces manufacturing costs. Furthermore, the structural integrity of the membrane is improved, making it more robust and resistant to damage.

[0020] In some embodiments of the present invention, the skin has a front surface that defines the first outer surface of the membrane, and the honeycomb pattern structure is arranged on a back surface of the skin that is opposite the front surface. In such embodiments, the second outer surface of the membrane can be defined by the honeycomb pattern structure. That is, the honeycomb pattern structure remains exposed on the back surface of the membrane.

[0021] The skin is a first skin, and the membrane additionally has a second skin. In such embodiments, the honeycomb pattern structure is arranged between the first and second skins, and the second skin defines the second outer surface of the membrane. Accordingly, the honeycomb pattern structure is enclosed by the first and second skins.

[0022] At least part of the honeycomb pattern structure is integrally formed with either the first skin or the second skin, which offers the aforementioned advantage of an integrally formed honeycomb pattern structure.

[0023] The honeycomb structure can be formed integrally with the first skin, with the second skin being connected to the honeycomb structure to form the membrane. Alternatively, the honeycomb structure can be formed integrally with the second skin, with the first skin being connected to the honeycomb structure to form the membrane.

[0024] In alternative embodiments, a first part of the honeycomb structure is formed integrally with the first skin and a second part of the honeycomb structure is formed integrally with the second skin, the first and second parts of the honeycomb structure being joined together to form the membrane. The first and second parts of the honeycomb structure can preferably be joined by welding. When the first and second parts of the honeycomb structure are welded together, the solidified bond between them provides the membrane with additional strength.

[0025] If the supporting structure consists of a honeycomb pattern, the membrane can be made from two components joined together to form the membrane. Accordingly, a membrane with a honeycomb supporting structure can be manufactured by joining just two components, thus simplifying the manufacturing process.

[0026] For example, a first membrane component can consist of the first skin and the honeycomb structure, and a second membrane component can consist of the second skin, with the two membrane components being connected by linking the second skin to the honeycomb structure. Alternatively, a first membrane component can comprise the first skin and a first part of the honeycomb structure, and a second membrane component can comprise the second skin and a second part of the honeycomb structure, with the two membrane components being connected by linking the first part of the honeycomb structure to the second part of the honeycomb structure.

[0027] Each of the two membrane components can be manufactured by molding, machining, 3D printing, thermoforming, casting, or any other suitable method known to a person skilled in the art. Preferably, each of the two membrane components is formed by expansion molding.

[0028] The membrane according to one of the embodiments of the present invention described above can preferably be made from a single material, more preferably from foamed or expanded polypropylene or foamed or expanded polyethylene.

[0029] According to a second aspect of the present invention, a method for manufacturing a membrane for an audio transducer is specified, wherein the method comprises the following steps, which may be carried out in any order: - Formation of a skin shaped to define the anterior and / or posterior outer surface of the membrane; - Forming a supporting structure; and - Arranging the support structure on or in the skin.

[0030] Preferably, the supporting structure has a higher density than the skin.

[0031] The process can involve, in a first step, the formation of the support structure, followed by the formation of the skin around the support structure, so that the support structure is located within the skin. The membrane can be formed by overmolding the skin over the support structure, or alternatively, the support structure and the skin can be formed sequentially in a multi-stage injection molding process.

[0032] In preferred embodiments, the skin and / or the support structure is formed by an expansion forming process.

[0033] The procedure further comprises the following steps: - Placing an initial expandable material into an initial form and stretching or expanding the initial expandable material within the initial form to form the support structure; - Arranging the support structure and a second expandable material in a second mold and stretching or expanding the second expandable material within the second mold to form the skin with the support structure arranged inside the skin.

[0034] The first and second extensible materials are the same material, but the ratio of the mass of the extensible material within the first form to the volume within the first form is greater than the ratio of the mass of the extensible material within the second form to the volume within the second form. Accordingly, the density of the supporting structure is greater than the density of the skin.

[0035] In some embodiments, the support structure has a honeycomb pattern structure, and the method comprises the following steps: - Formation of a first membrane component and a second membrane component; and - Connecting the first membrane component to a second membrane component to create the membrane.

[0036] In some embodiments, the skin is a first skin, the first membrane component has at least a part of the honeycomb pattern structure that is integrally formed with the first skin, and the second membrane component has a second skin, wherein the method includes connecting the second membrane component to the first membrane component to arrange the honeycomb pattern structure between the first skin and the second skin.

[0037] In some embodiments, the first membrane component can contain the entire honeycomb pattern structure, which is integrally formed with the first skin. In such embodiments, the step of joining the first membrane component to the second membrane component includes joining the second skin to the honeycomb pattern structure.

[0038] In alternative embodiments, the first membrane component can have a first part of the honeycomb structure that is integrally formed with the first skin, and the second membrane component can contain a second part of the honeycomb structure that is integrally formed with the second skin. In such embodiments, the step of joining the first membrane component to the second membrane component comprises joining the first region of the honeycomb structure to the second region of the membrane structure. During the joining process, the cells of the honeycomb structure of the respective membrane component are preferably aligned with each other.

[0039] In each of the embodiments described above, in which a first membrane component is connected to a second membrane component, the two membrane components are preferably joined by welding, and more preferably by hot plate welding, ultrasonic welding, or vibration / friction welding. Such welding processes involve melting the material of each component on a corresponding surface, whereupon said surfaces are brought into contact and the molten material is cooled to solidify and fuse the two membrane components together. The solidified material at the weld joint has a higher density than the material of the respective components, so that the weld joint has the further advantage of imparting additional strength to the membrane.

[0040] Non-restrictive embodiments of the invention are described below by way of example only, with reference to the accompanying drawings, in which: Fig. 1 a perspective view of a membrane according to a first embodiment of the present invention; Fig. 2 a perspective view of the membrane of Fig. 1 is where an area of ​​the skin is cut out to show the frame; Fig. 3 a perspective view of a frame of the membrane of Fig. 1 is; Fig. 4A is a perspective front view of a membrane according to a second embodiment of the present invention; Fig. 4B a perspective rear view of the membrane of Fig. 4A is; Fig. 5A a cutaway, perspective front view of the membrane of Fig. 4A is where a section of the membrane has been cut out; Fig. 5B a cutaway, perspective rear view of the membrane of Fig. 4A is where a section of the membrane has been cut out; Fig. 6 is a perspective rear view of a membrane according to a third embodiment of the present invention; Fig. 7 a perspective front view of a membrane according to a fourth embodiment of the present invention, wherein a second skin of the membrane has been removed to show the honeycomb pattern structure of the membrane; Fig. 8A is a cutaway view of an area of ​​a membrane according to a fifth embodiment of the present invention; Fig. 8B a cutaway view of an area of ​​the membrane of Fig. 8A is the one that shows the two membrane components; Fig. Figures 9A to 9D are schematic illustrations depicting a heating element welding process for forming a membrane according to the present invention; and Fig. 10A and Fig. Figure 10B shows schematic illustrations of an ultrasonic welding process for forming a membrane according to the present invention.

[0041] With reference to the Fig. Figures 1 to 3 show a diaphragm 1 according to a first embodiment of the present invention. The diaphragm 1 is suitable for use in an audio transducer, e.g., a loudspeaker. As shown in Fig. 1 and Fig. As shown in Figure 2, a surround 2 can be connected to an outer circumference of the diaphragm 1, with the surround 2 forming a connection between the diaphragm 1 and a housing of an audio transducer (not shown).

[0042] The diaphragm 1 has a front outer surface 4 and a rear outer surface 6, which are arranged opposite the front outer surface 4. In use, the front outer surface 4 is oriented forward towards the front of the audio transducer, while the rear outer surface 6 is oriented in the opposite direction towards the rear of the audio transducer. The terms "front" and "rear," as used in this description, are to be interpreted accordingly.

[0043] As in Fig. As can be seen most clearly in Figure 2, the membrane 1 has a skin 8, the skin 8 defining the front outer surface 4 and the rear outer surface 6 of the membrane 1. A frame 10 is arranged within the skin 8 between the front outer surface 4 and the rear outer surface 6. In the illustrated embodiment, the skin 8 is formed around the frame 10 such that the frame 10 is completely embedded in the skin 8.

[0044] In the illustrated embodiment, the frame 10 has the shape of a truncated cone and thus defines a substantially conical shape for the membrane 1, with the front outer surface 4 of the membrane 1 having the shape of an inverted cone. It is evident that in alternative embodiments, the frame can have any desired alternative shape to give the membrane a desired geometry. The frame can be symmetrical or asymmetrical.

[0045] The frame 10 has a higher density than the skin 8 and thus acts as a supporting structure, providing additional strength to the skin 8 and increasing the stiffness of the diaphragm 1. Accordingly, the skin 8 can be made of a relatively low-density material, thereby minimizing the overall mass of the diaphragm 1 while maintaining the necessary stiffness to optimize its performance within an audio transducer.

[0046] In order to minimize the mass of the frame 10 and thus minimize the total mass of the membrane 1, the frame 10 has a plurality of openings 12 formed between an outer edge 14 and an inner edge 16 of the frame 10, as shown in Fig. 3 is most clearly recognizable. The outer edge 14 defines an outer circumference 15 of the frame, and the inner edge 16 defines an inner opening 17 of the frame, which in turn defines an outer circumference and an inner opening of the membrane 1, the inner opening being circular in this embodiment. Accordingly, the frame 10 provides a support structure over essentially the entire surface of the skin 8.

[0047] The membrane 1 can be formed by any suitable method known to those skilled in the art. In particular, the membrane 1 can be formed using an overmolding process in which the skin 8, with relatively low density, is formed over the preformed frame 10, with relatively high density, such that the skin 8 defines the outer surfaces of the membrane 1.

[0048] In some embodiments, the frame 10 can be made of a first material and the skin 8 of a second material that differs from the first material, the first material having a higher density than the second material. Accordingly, due to the different relative densities of the first and second materials, the frame 10 has a higher density than the skin 8.

[0049] In preferred embodiments of the present invention, however, the frame 10 and the skin 8 are produced from the same material, e.g., polypropylene or polystyrene, using an expansion forming process. In an expansion forming process, small particles of the material (e.g., chips or beads) are placed in a mold and expanded (e.g., by applying heat and pressure and / or by adding an expansion agent) so that the small particles expand and fuse together to form a solid cell structure, with the material filling the space within the mold. The density of the component formed by the process depends on the mass-to-volume ratio: the ratio of the mass of the expandable material placed in the mold to the volume of the space within the mold during the expansion process.The lower the mass-to-volume ratio, the greater the extent to which the material can expand, and thus the lower the density of the expanded material. Accordingly, the frame and skin of the membrane can be formed from the same material by producing the frame using expansion forming with a higher mass-to-volume ratio than is used for the skin.

[0050] With reference to the Fig. Figures 4A to 5B show a diaphragm 100 according to a second embodiment of the present invention. The diaphragm 100 is suitable for use in an audio transducer, e.g., a loudspeaker. As shown in the Fig. As shown in 4A to 5B, a surround 102 can be connected to an outer circumference of the diaphragm 100, the surround 102 forming a connection between the diaphragm 100 and a housing of an audio transducer (not shown).

[0051] The membrane 100 has a front outer surface 104 and a rear outer surface 106, which is opposite to the front outer surface 104. In use, the front outer surface 104 is arranged so that it faces forward towards the front of the audio transducer, while the rear outer surface 106 faces in the opposite direction towards the rear of the audio transducer.

[0052] The membrane 100 consists of a skin 108, the skin 108 having a front surface that defines the front outer surface 104 of the membrane 100. A honeycomb pattern structure 110 is arranged on a rear surface of the skin 108. The honeycomb pattern structure 110 has a structured arrangement of walls 110a extending substantially perpendicular to the rear surface of the skin 108, the walls 110a defining an arrangement of substantially uniform hollow cells 110b with a predefined geometry. The ends of the walls 110a of the honeycomb pattern structure 110 together define the rear outer surface of the membrane 100. In alternative embodiments, the honeycomb pattern structure 110 can be arranged on a front surface of the skin 108, such that the honeycomb pattern structure 110 defines the front outer surface 104 of the membrane.

[0053] In the Fig. In the embodiments shown in Figures 4A to 5B, the hollow cells 110b have a hexagonal geometry. However, it should be noted that alternative embodiments of the present invention may have a honeycomb structure with any other suitable geometry. For example, Figure 4A shows that the hollow cells 110b have a hexagonal geometry. Fig. 6 a third embodiment of the present invention, which is described in Fig. The second embodiment shown in 4A to 5B essentially corresponds to the second embodiment, wherein the hollow cells 110b have a circular geometry.

[0054] In the second and third embodiments, which are described in Fig. As shown in Figures 4A to 6, the honeycomb pattern structure 110 is integrally formed with the skin 108. In alternative embodiments, the skin 108 and the honeycomb pattern structure 110 can be formed as separate components that are subsequently joined together.

[0055] The honeycomb structure 110 acts as a supporting structure and, due to its inherent strength, imparts additional strength to the skin 108, thereby increasing the overall stiffness of the membrane 100. Since a large part of the honeycomb structure 110 consists of hollow cells 110b, the mass of the membrane 100 is significantly less than that of a membrane with equivalent stiffness made of a solid material mass.

[0056] A fourth embodiment of a membrane 100' according to the present invention is in Fig. Figure 7 shows the membrane 100'. The membrane 100' essentially corresponds to the membrane 100 according to Fig. 4A to 5B and the corresponding features are identified by the same reference numerals. In the embodiment according to Fig. In section 7, the skin 108 is a first skin, and the membrane 100' further comprises a second skin 112. The honeycomb structure 110 is integral with the first skin 108, such that the walls 110a of the honeycomb structure 110 extend from a posterior surface of the first skin 108. The second skin 112 is connected to the honeycomb structure 110 at the distal end of the walls 110a, so that the honeycomb structure 110 is enclosed between the first skin 108 and the second skin 112. The second skin 112 thus defines the posterior outer surface 106 of the membrane 100'.

[0057] The membrane 100' according to Fig. 7 therefore consists of only two components: a first component, comprising the first skin 108 and the honeycomb pattern structure 110, and a second component, comprising the second skin 112. The two components can be joined together by any suitable method. For example, the two components can be joined by a snap-fit ​​connection. In preferred embodiments, the two components can be bonded or welded together, preferably using hot plate welding, ultrasonic welding, or vibration welding (described in more detail below). The individual components can be formed by demolding or molding, preferably by expansion forming, or alternatively by other suitable manufacturing processes such as machining, 3D printing, thermoforming, or casting.

[0058] The Fig. 8A and Fig. Figure 8B shows a small section of a membrane 200 according to a fifth embodiment of the present invention. The structure of the membrane 200 essentially corresponds to that shown in Fig. Figure 7 shows the structure of the membrane 100', wherein a honeycomb pattern structure 210 is arranged between a first skin 208 and a second skin 212, each defining a front outer surface 204 and a rear outer surface 206 of the membrane 200. The honeycomb pattern structure 210 has a structured arrangement of walls 210a extending substantially perpendicular to the rear of the skin 208, the walls 210a defining an arrangement of substantially uniform hollow cells 210b with a predetermined hexagonal geometry.

[0059] The membrane 200 consists of two components 200a and 200b. A first membrane component 200a comprises the first skin 208 and a first part 220a of the honeycomb pattern structure 210. A second membrane component 200b comprises the second skin 212 and a second part 220b of the honeycomb pattern structure 210. Each of the individual membrane components 200a and 200b is formed in one piece, with the two separate components 200a and 200b subsequently being joined together to form the entire membrane 200. The individual membrane components 200a and 200b can be formed by molding, preferably by expansion molding, or alternatively by other suitable manufacturing processes such as machining, 3D printing, thermoforming, or casting.

[0060] The two membrane components 200a, 200b can be joined by any suitable means or method and are preferably joined using an adhesive-free fastening method, more preferably by welding. Fig. Figures 9A to 9D show a preferred heating element welding method for joining the two membrane components 200a, 200b. As shown in Fig. 9A and Fig. As shown in Figure 9B, the two membrane components 200a, 200b are brought into close proximity to a heating plate 214, the heating plate 214 being arranged between the exposed surfaces of the first and second regions 220a, 220b of the honeycomb structure 210. The heated plate 214 transfers heat to the exposed surfaces of the first and second regions 220a, 220b of the honeycomb structure 210 in order to raise said exposed surfaces to a temperature above the melting point of the material from which the membrane components 200a, 200b are formed ( Fig. 9B). Once the desired temperature is reached, the heated plate 214 is removed and the two membrane components 200a, 200b are brought together to establish contact between the molten surfaces of the honeycomb pattern structure 210 ( Fig. 9C). As the molten material cools and solidifies, the respective surfaces of the first and second regions 220a, 220b of the honeycomb structure 210 fuse together to connect the two membrane components 200a, 200b. The layer of fused, solidified material that connects the respective surfaces of the honeycomb structure 210 forms a compound 216, the material at which this compound 216 has a higher density than the rest of the membrane. Accordingly, the compound 216 contributes to additional stiffness of the membrane 200, thereby improving the membrane's performance without a significant increase in mass.

[0061] The use of the heating plate 214 enables a controlled and uniform distribution of heat to the respective surfaces of the honeycomb structure 210. The temperature of the heating plate 214 and the duration of heating can be carefully controlled depending on the size of the membrane and the material from which it is made, so that a joint 216 of adequate strength and strength is created. However, it should be noted that, alternatively, direct heat welding with hot air can be used, provided that a controlled and uniform distribution of heat to the respective surfaces of the honeycomb structure can be achieved.

[0062] The Fig. 10A and Fig. Figure 10B presents a further preferred method for joining the two membrane components 200a, 200b using ultrasonic welding. In the illustrated embodiment, the first membrane component 200a is securely held so that it remains motionless during the welding process. The second membrane component 200b is positioned such that the respective exposed surfaces of the two regions 220a, 220b of the honeycomb structure 210 are brought into contact, with the hollow cells 210b being suitably oriented. The second membrane component 200b is held against the first membrane component 200a with some pressure and moved back and forth in a direction parallel to the plane of the respective contact surfaces of the first and second regions 220a, 220b of the honeycomb structure 210 at ultrasonic frequencies.This rapid movement generates sufficient friction between the adjacent surfaces of the first and second regions 220a, 220b of the honeycomb pattern structure 210 to heat the material above its melting point and thus melt the adjacent surfaces.

[0063] Once the ultrasonic movement of the second membrane component ceases, the molten material cools and solidifies, allowing the respective surfaces of the honeycomb structure 210 to fuse together and join the two membrane components 200a and 200b in the same manner as described above with regard to the heating element welding process. The layer of molten, solidified material that joins the respective surfaces of the honeycomb structure 210 forms a joint 216, the material at this joint 216 having a higher density than the rest of the membrane. Accordingly, the joint 216 contributes to an additional stiffness of the membrane 200, thereby improving the membrane's performance without a significant increase in mass.

[0064] It should be noted that in alternative embodiments the second membrane component 200b can be held statically and the first membrane component 200a can be brought into position and subjected to rapid movement at ultrasonic frequencies in order to weld the two membrane components 200a, 200b together.

[0065] Since the ultrasonic welding process relies on friction between the membrane components 200a, 200b, the effectiveness of the process depends on the size and shape of the individual components and the material from which they are made. If the membrane components are made of an extended foam material (e.g., expanded polypropylene or expanded polyethylene), the foam material has inherent damping properties that can absorb some of the ultrasonic energy. Therefore, the effectiveness of the ultrasonic welding process may be limited in some applications.

[0066] To overcome these difficulties, the membrane components 200a, 200b can alternatively be joined using a vibration welding process, which is essentially the same as described above with reference to Fig. 10A and Fig. The vibration welding process corresponds to the ultrasonic welding process described in Section 10B. The vibration welding process differs from the ultrasonic welding process in that the dynamic component is moved with a higher amplitude of the reciprocating motion and at a lower frequency. This means that with each reciprocating motion, the dynamic component is moved over a greater distance, and the frequency of the reciprocating motions is lower. Accordingly, the vibration welding process is less susceptible to the damping effect of the extended foam and may therefore be better suited for welding membrane components made from an extended foam material.

[0067] The invention has been described above by way of example only, with reference to specific embodiments. It should be noted that various embodiments are possible, which fall within the scope of the attached patent claims.

Claims

[1] Membrane (1) for use in an audio transducer, wherein the membrane (1) has a first outer surface, a second outer surface opposite the first outer surface, and a support structure, wherein a skin (8) defines the first outer surface of the membrane (1), the support structure being arranged on or in the skin (8), and wherein the support structure has a honeycomb pattern structure (110) which has an arrangement of substantially regular cells (110b) with a defined geometry, wherein the skin (8) is a first skin (108), wherein the membrane (1) further comprises a second skin (112), wherein the honeycomb pattern structure (110) is arranged between the first and second skin (108, 112) and wherein the second skin (112) defines the second outer surface of the membrane (1), wherein the honeycomb pattern structure (110) is integrally formed with the first skin (108), and wherein the second skin (112) is connected to the honeycomb pattern structure (110) but is not integrally formed with it to form the membrane (1), or wherein the honeycomb pattern structure (110) is integrally formed with the second skin (112) and wherein the first skin (108) is connected to the honeycomb pattern structure (110) but is not integrally formed with it to form the membrane (1). [2] Membrane (1) according to claim 1, wherein the support structure has a higher density than the skin (8). [3] Membrane (1) according to claim 1 or 2, wherein the membrane (1) is made of a single material. [4] Method for manufacturing a membrane (1) for an audio transducer, the method comprising the following steps which may be carried out in any order: - Forming a skin (8) shaped to define an anterior outer surface and / or a posterior outer surface of the membrane (1) and embedding a frame (10) completely in the skin (8); - Forming a supporting structure; and - Arranging the supporting structure in the skin (8); - Placing an initial expandable material in an initial form and stretching or expanding the initial expandable material within the initial form to create the support structure; - Placing the support structure and a second extendable material in a second mold and stretching or expanding the second extendable material within the second mold to form the skin (8) with the support structure arranged in the skin (8), wherein the first extendable material and the second extendable material are the same material, and wherein the ratio of the mass of the extendable material placed in the first mold to the volume within the first mold is greater than the ratio of the mass of the extendable material placed in the second mold to the volume within the second mold. [5] Method according to claim 4, wherein the support structure has a higher density than the skin (8, 108). [6] Method according to claim 4 or 5, comprising forming the support structure and subsequently forming the skin (8, 108) around the support structure, such that the support structure is arranged in the skin (8, 108). [7] Method according to any one of claims 4 to 6, wherein the skin (8, 108) is formed over the support structure. [8] Method according to any one of claims 5 to 7, wherein the skin (8, 108) and / or the support structure is formed by means of expansion forming. [9] Audio transducer comprising the membrane (1, 100, 100') according to any one of the preceding claims 1 to 3.

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