Electromagnetic transducer for generating sound in hearing aids, particularly electronic hearing aids

1. Field of the Invention

The present invention is directed to an electromagnetic transducer for generating sound in hearing aids.

2. Description of the Prior Art

An electromagnetic transducer which serves the aforementioned purpose is known, for example, from I. Veit, Technische Akustik, Vogel Verlag, Würzburg, 1978, and has a housing containing an electromagnetic drive that is comprised of a coil, a drive magnet and an armature arrangement. A membrane arrangement that is mechanically coupled to the armature arrangement in order to convert movements of the armature arrangement into sound signals is secured in the housing.

This known electromagnetic transducer has only one armature and one membrane, so that the efficiency of the transducer is limited, and, moreover, the moving parts lead to vibrations of the overall transducer arrangement during operation of the transducer.

An object of present invention is to provide an electromagnetic transducer wherein the efficiency of the transducer arrangement is improved and feedback phenomena of the device caused by vibrations are avoided or at least diminished.

This object is achieved in accordance with the invention in a transducer of the type described above wherein the membrane arrangement is formed by two separate membranes that are arranged at opposite sides of the drive but are otherwise identically fashioned and are oppositely driven such that the overall mechanical pulse occurring due to the movement of the driven or driving parts is minimized.

The basis of the invention is to consistently implement two principles in the transducer arrangement, namely a highly symmetrical movement of the driving and driven parts and strictly opposed operation of the moving and moved parts such that the overall mechanical pulse occurring due to the movement of these parts is minimized. This results in vibrations being avoided, and thus feedback phenomena can be largely suppressed from the very outset.

In a preferred embodiment, the two membranes are symmetrically arranged relative to the drive. This is a consistent development of the symmetry concept.

In a further embodiment, an air space in communication with an output connecting piece of the housing is enclosed between the two membranes. Due to the opposite drive of the movement of the two membranes, a considerable improvement in the efficiency is achieved, so that an adequate performance of the transducer can be fundamentally achieved with smaller, i.e. less disruptive, movements of the driving and driven parts, which in turn assists in the reduction of the vibrations causing feedback.

In a further embodiment, the armature arrangement has two separately movable armatures. Each armature is connected to one of the membranes. This leads to a further symmetry of the overall structure and of the individual components. The two armatures can be identically fashioned and can be pre-mounted in conjunction with the two membranes.

In an embodiment of the invention two separate armatures are arranged between the respective poles of a drive magnet and the middle region of the membranes and proceed parallel to the membranes, at least in sections. The membranes are centrally connected to the armatures. Given excitation of the field coil, the armatures are either opposite attracted or repelled in common by the drive magnet, leading to an opposite but symmetrical movement of the membranes as well as of the drive parts.

In another embodiment the drive magnet arranged between the membranes is centrally divided, but the armatures are not arranged between the ends of the drive magnet and the membranes, but in the form of armature tongues, proceed parallel side-by-side in a center gap of the drive magnet. The connection of the armature tongues to the membranes ensues via a rigid connector element that is secured to the free end of each armature tongue. Both armature tongues merge via intermediate regions bent outwardly from their common plane into a U-shaped end region that is surrounded by a coil. The armature tongues, the middle regions and the U-shaped end region of the armature elements thus form a closed magnetic circuit, which leads to an especially advantageous compensation of the constant magnetic force given employment of the double membrane principle with two armatures.

FIG. 1 is a schematic illustration, in section, of an electromagnetic acoustic transducers constructed in accordance with the principles of the present invention.

FIG. 2 is a schematic illustration in section of an electromagnetic acoustic transducer with compensated constant magnetic force constructed in accordance with the principles of the present invention.

FIG. 3 shows a section along the section line III—III in FIG. 2 .

FIG. 4 shows a section along section line IV—IV in FIG. 2 .

The electromagnetic transducer 1 shown in FIG. 1 has a housing 2 in which an electromagnetic drive 3 is arranged, formed by a coil 4 , drive magnets and an armature arrangement 6 . A membrane arrangement also is provided, formed by two separate membranes 7 , 7 ′ that are arranged at opposite sides of the drive 3 , and that are identically fashioned and that are oppositely driven such that the overall mechanical pulse occurring due to the movement of the driven or driving parts is minimized.

The two membranes 7 , 7 ′ are symmetrically arranged with reference to the drive 3 and enclose an air space 9 in communication with an output connector piece 8 .

The armature arrangement 6 is composed of two separately movable armatures 10 , 10 ′, whereby each armature 10 , 10 ′ being connected to one of the membranes 7 , 7 ′. In the exemplary embodiment shown in FIG. 1, the armatures are arranged between the drive magnet 5 and the middle region of the membranes 7 , 7 ′ and proceed parallel to the membranes 7 , 7 ′ in sections. The two armatures 10 , 10 ′ are formed by a U-shaped, resilient element. The coil 4 is arranged in the middle region 12 of the U. The drive magnet 5 is seated between the legs 13 of the U-shaped element.

In a second exemplary embodiment shown in FIGS. 2 through 4, the drive magnet 5 is centrally divided. Two armature tongues 15 , proceeding essentially parallel side-by-side in the same plane, are arranged in a middle gap 16 of the drive magnet. Each armature tongue 15 is rigidly connected to one of the two membranes 7 , 7 ′ via a connector element 18 .

The two armature tongues 15 have outwardly bent intermediate regions 20 that proceed from a common plane into a U-shaped end region 21 of the armature arrangement 6 that penetrates the coil 4 .

The armature tongues 15 , the intermediate regions 20 and the U-shaped end region 21 of the armature arrangement 6 form a closed magnetic circuit.

In all exemplary embodiments, the membranes 7 , 7 ′ proceed parallel to the side walls 25 of the housing. In space-saving fashion, the drive magnet that interacts with the two membranes 7 , 7 ′ lies therebetween. In the exemplary embodiment shown in FIGS. 2 through 4, the parts of the drive magnet 5 separated by the middle gap 16 are held in a magnetic yoke 27 .

It can be clearly seen in FIGS. 3 and 4 that the regions of the armature tongues 15 , 15 ′ proceeding parallel to one another and in the same plane are separated from one another by a narrow air gap 30 .

Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventor to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of his contribution to the art.