Electrical audio signal processing systems and devices – Electro-acoustic audio transducer – Having electrostatic element
Patent
1991-03-21
1992-01-14
Isen, Forester W.
Electrical audio signal processing systems and devices
Electro-acoustic audio transducer
Having electrostatic element
381202, H04R 2500
Patent
active
050816845
DESCRIPTION:
BRIEF SUMMARY
This invention relates to electrodynamic transducers and more specifically to a novel configuration of the magnet structure and diaphragm which permits a shallower transducer to be realized than is permitted by prior art designs.
Various shallow and flat diaphragm designs are known. There are, for example, the designs illustrated by the following U.S. Pat. Nos. 1,766,612; 2,498,825; 2,858,377; 3,153,463; 4,379,951; 4,385,210; 4,508,941; and, 4,520,237. This listing is only intended as illustrative of the prior art and specifically is not intended as a representation that no closer prior art exists to the claimed invention. Although the listed prior art generally illustrates what are believed to be the shallowest transducer designs available with existing technology, the illustrated designs suffer from the weakness that the transducer must be designed with space between the diaphragm and magnet assembly when the voice coil is unexcited so that no collisions occur between the diaphragm and magnet assembly when the voice coil is excited. For example, in a transducer whose design is intended to provide a 0.6 inch (1.5 cm) peak to peak excursion, a space of at least 0.3 inch (0.75 cm) must be provided between the diaphragm and adjacent surfaces of the magnet assembly when the voice coil is unexcited. Of course, collisions between the diaphragm and magnet assembly must be avoided to prevent the audible distortion which accompanies such collisions.
It is an object of the present invention to provide an electrodynamic transducer structure in which it is not necessary to provide space between the diaphragm and magnet structure in the direction in which excursion of the diaphragm occurs.
According to the invention, an electrodynamic transducer includes a magnet structure including a first inner, or core, pole and a second outer pole, or shell, defining an air gap between them. The air gap has a generally cylindrical configuration. The transducer further includes a diaphragm, a voice coil having a generally cylindrical configuration for displacement axially within the air gap, and means for coupling the voice coil to the diaphragm so that movement of the voice coil in response to current flow through the voice coil generates corresponding movement of the diaphragm. Openings are provided in the outer pole. The openings extend generally parallel with the axes of the air gap and voice coil. The means for coupling the voice coil to the diaphragm comprises ribs extending from the voice coil with a component radially of the axes of the air gap and voice coil. The ribs are secured to the diaphragm.
Illustratively, the diaphragm comprises an opening having an inner sidewall, and the ribs are secured at their radially outer extents to the inner sidewall, the diaphragm is generally planar, and the inner sidewall is right circular cylindrical.
Further, illustratively, the air gap and voice coil are generally right circular cylindrical in configuration.
According to the illustrative embodiment, the openings in the outer pole are generally slot-shaped. The openings are elongated in the direction of the air gap and voice coil axes and narrow in a direction transverse to the air gap and voice coil axes. Also according to the illustrative embodiment, the ribs are elongated in the direction of the air gap and voice coil axes and narrow in a direction transverse to the air gap and voice coil axes.
According to the illustrative embodiment, the means for coupling the voice coil to the diaphragm further comprises a voice coil form for supporting the voice coil in the air gap. The ribs are secured at their radially inner extents to the voice coil form.
The invention may best be understood by referring to the following description and accompanying drawings which illustrate the invention. In the drawings:
FIG. 1 illustrates an exploded fragmentary perspective view of an electrodynamic transducer constructed according to the present invention; and
FIG. 2 illustrates a fragmentary sectional side elevational view of the electrodynamic transduc
REFERENCES:
patent: 1766612 (1930-06-01), DeForest
patent: 2498825 (1950-02-01), Richards
patent: 2858377 (1958-10-01), Levy
patent: 3153463 (1964-10-01), Novak
patent: 4379951 (1983-04-01), Gabr
patent: 4385210 (1983-05-01), Marquiss
patent: 4508941 (1985-04-01), Wiggins
patent: 4520237 (1985-05-01), Murakami
Harman International Industries Incorporated
Isen Forester W.
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