Patent Application
20140333012
1. Field of the Invention
The invention relates to a method of manufacturing a hearing aid component, such as a part of a hearing aid housing.
2. Description of Related Art
Hearing aids are miniaturized devices which incorporate electronic, mechanical and electrochemical components such as microphones, loudspeakers, coils, switches, processors, amplifiers, various kinds of sensors, electrical connectors and batteries in a housing. These components require seals against humidity and dirt and damping structures against shock and vibrations in order to prevent failure of the components and improve performance of the device. Hearing aid loudspeakers are also called receivers. Typically, receivers and microphones have hard, metallic housings and require damping structures to be mechanically isolated from their surrounding in order to reduce feedback. Receivers and microphones are vibration sensitive components. The problem of feedback caused by vibration is due to the fact that during normal operation of the hearing aid the receiver is outputting an amplified signal of the microphone of the hearing aid. Since vibrations are transmitted between components which are in close mechanical contact also these components are considered to be vibration sensitive. Therefore, a housing of a hearing aid or a part of a hearing aid which contains a receiver or a microphone is vibration sensitive.
Examples for non-vibration sensitive components are, for example, earpieces which do not contain receivers or microphones.
Switches and battery compartments comprise movable mechanical parts which may cause openings to the inner parts of a hearing aid housing and therefore require adequate sealing against humidity and dirt. Since all electronic components are humidity sensitive also such mechanical components are regarded as to be humidity sensitive components.
Usually, such seals and damping structures are made of a soft material and are located on a curved substrate made of a harder material, such as a hard plastic material or a ceramic material. Typically, the housing of a hearing aid containing such components is manufactured by an injection molding process. Seals and damping structures on some areas of the housing can be created contemporarily when a two-component injection molding process is applied. However, often such process is not easy to control and the required tools are expensive. Further, the capability of injection molding processes to create fine structures is limited. The choice of acceptable soft performing material which can be processed in a two-component injection molding process is limited.
The raw material for the injection molding process may contain additional non-organic materials like powders of metals or glas to reach specific optical, electrical or mechanical properties. For creation of ceramic materials, an additional sintering step might be necessary, a contemporary creation of damping structures is not possible.
It is known that three-dimensional structures can be produced by inkjet printing. Such 3D inkjet printing is an additive manufacturing process which is typically used for rapid prototyping. For example, a 3D printing system may generate a 3D prototype based on data provided by a CAD system. Such 3D printing systems are already commercially available, for example, from the company Objet Geometries or from the company Z Corporation.
It has been proposed to use a 3D inkjet printing process for manufacturing hearing instrument earpieces, see for example, U.S. Patent Application Publications 2010/0017006 A1, ]2007/0116311 A1, US 2004/0107080 A1 corresponding to U.S. Pat. No. 8,032,337 B2, and UK Patent Application Publication GB 2344556 A, and U.S. Pat. No. 7,660,427 B2.
U.S. Patent Application Publication 2008/0070181 A1 and corresponding U.S. Pat. No. 8,291,912 B2 relate to an oral appliance used for coupling sound from a hearing instrument into a tooth, which oral appliance may be manufactured by using a 3D inkjet printing process.
International Patent Application Publication WO 2011/000375 A1 relates to an earplug of a receiver-in-the-ear-hearing aid, which earplug comprises a shell individually shaped according to the measured shape of the user's ear. The outer surface of the shell is provided with electrodes for measuring brain wave signals. The electrodes are applied onto the shell by an inkjet printing process using conductive ink.
It is an object of the invention to provide a method of manufacturing a hearing aid component, which is cost effective, which has as little geometrical and topological constraints as possible, which is easy to control and which is highly flexible in case of design changes and has better acoustical and mechanical properties and allows to combine multiple functions in one component.
According to the invention, this object is achieved by a method as described herein.
The invention is beneficial in that, by applying, by an inkjet printing process utilizing a jet of droplets having a volume from 0.1 nl to 10 nl, a functional structure of a viscoelastic material having a thickness of at least 50 μm onto a surface of a substrate component, a relatively hard substrate can be provided with a relatively soft functional structure in a simple, effective and contactless manner. The method of the invention has only little constraints regarding the geometry and topology of the functional structure and is highly flexible in case of redesign of the hearing aid component. In particular, such manufacturing method may replace a two-component injection molding process, thereby saving the costs resulting from the tools required for injection molding. Thus, the manufacturing method according to the invention is particularly suited for small series and for individually shaped components.
Moreover, the invention is also suitable for modification of existing components like receivers, microphones, coils, switches or knobs. The inventive method offers the possibility to apply a damping or sealing structure on such a component instead of creating it inside the hearing aid shell. This alternative process creates a damping structure between the hearing aid shell and a receiver or microphone or another vibration sensitive component.
Hereinafter, examples of the invention will be illustrated by reference to the accompanying drawings.
In
Three-dimensional structures can be created, for example, by scanning the substrate surface 20 repeatedly in such a manner that the structures are built up layer-by-layer (i.e., each point of the substrate surface area 20 is brought several times into the jet of droplets 18; in
An example of the generation of a 3D structure is illustrated in
The substrate component may be, for example, a polymer or a glass reinforced polymer. It may also be made of a metal or a ceramic, or it may contain metallic and/or ceramic materials.
The substrate component is typically produced by an injection molding process and is preferably made of a relatively hard plastics material or of a ceramic material.
Alternatively, the substrate may be made of metal, for example, a receiver or a microphone.
The hardness of synthetic or metallic substrate material may be classified in accordance with the Vickers scale; if the material is a metal, it may have a hardness ranging from 10 to 3000 HV 3; for plastic materials the hardness may range from 1 to 10000 HV 0.01.
In view of the fact that injection molding processes often produce surfaces of relatively low roughness, it may be necessary to apply a surface treatment to the surface of the substrate component prior to applying the functional structure. For example, the surface of the substrate component may be activated and/or conditioned by irradiation, such as x-rays, accelerated electrons, UV laser light, visible laser light or IR laser light, prior to applying the functional structure. However, also other surface treatment, in particular, for roughening the surface of the substrate component, may be applied. Preferably, the surface of the substrate component has a surface roughness of with an Ra value between 12 to 33 according to VDE 3400 prior to applying the functional structure.
The functional structure, after having been applied onto the substrate component, may be cured by applying heat or radiation.
The functional structures have a thickness of at least 50 μm and preferably not more than 500 μm.
The hardness of the functional structures is lower than the hardness of the substrate component. The functional structures are made of a viscoelastic material which preferably has a hardness in the range of 10-80 Shore A.
For example, the material of the functional structures may be polyamide 6.6, polyamide 12, propylene, polyurethane, pebax, TPE, a silicone compound or an acryl material.
In
According to the example of
Any hearing aid component which requires seals and/or damping elements may be provided with a functional element applied by an inkjet printing process according to the invention. Examples of such components are shown in
In
Preferably, the hearing aid is a BTE (behind-the-ear) or ITE (in-the-ear) hearing aid.
Inkjet printing processes also could be used to provide hearing instrument components with two-dimensional (i.e., thinner than 50 μm) surface coatings in order to impart certain surface properties to the respective hearing instrument component, such as to provide for a hydrophobic surface or for an electrically conductive surface. However, such processes do not form part of the present invention which relates to the generation of 3D functional structures on hearing aid components.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2012/050634 | 1/17/2012 | WO | 00 | 7/16/2014 |
