AU620185B2 - Shallow loudspeaker with slotted magnet structure - Google Patents

Description

Personal Signature of Declarant (no seal, witness or legalisation).

this day of Mar. 19 91 HARMAN INTERNAION INDUS S, INCORPORATED O (h (Signature of Declarant) Frank Meredith, Assistant Secretary To THE COMMISSIONER OF PATENTS.

CUi Cinl IAIArCD ATCP OT A" fllCll CC r 110Pd(' CT YCT qVncllV AlIQThAi IA C %Af4 LL i~U~LV~lnlC nllrlnlLynuc~,~irr ~nnl~c~o~rrc,~ llOW I UV fi a~ i:;.lll i OPI DATE 28/05/90 AOJP DATE 05/07/90 APPLN. ID 46268 89 PCT NUMBER PCT/US89/04501 13r-"Cr INTERNATIONAL APPLICATI IU lSIC UN ERB E PkjNT COOPERATION TREATY (PCT) (51) International Patent Classification 5 (11) International Publication Number: WO 90/05435 H04R 9/00, 7/16 A l (43) International Publication Date: 17 May 1990 (17.05.90) (21) International Application Number: PCT/US89/04501 (74) Agent: CONARD, Richard, Barnes Thornburg, 11 South Meridian Street, Suite 1313, Indianapolis, IN (22) International Filing Date: 12 October 1989 (12.10.89) 46204 (US).

Priority data: (81) Designated States: AT (European patent), AU, BE (Euro- 268,376 7 November 1988 (07.11.88) US pean patent), CH (European patent), DE (European patent), DK, FR (European patent), GB (European patent), IT (European patent), JP, LU (European patent), Parent Application or Grant NL (European patent), SE (European patent), US.

(63) Related by Continuation US 268,376 (CON) Filed on 7 November 1988 (07.11.88) Published With international search report.

(71) Applicant (for all designated States except US): HARMAN INTERNATIONAL INDUSTRIES, INCORPORAT- ED [US/US]; 8500 Balboa Blvd., P.O. Box 2200, Northridge, CA 91329 (US).

2) Inventor; and Inventor/Applicant (for US only) HOUSE, William, Neal [US/US]; 1401 East Prairie Drive, Bloomington, IN 47401 (US).

(54) Title: SHALLOW LOUDSPEAKER WITH SLOTTED MAGNET STRUCTURE 36 (57) Abstract 4 2 4 6 An electrodynamic transducer includes a 38 magnet structure (14, 28, 30) having inner (31) and outer (14) poles defining between them an air gap a diaphragm and a voice coil Openings (18) are provided in the outer pole 44 -26 40 the openings (18) extending generally parallel with the air gap (17) and the direction of motion of the voice coil (44) in the air gap The voice coil (44) is coupled to the diaphragm (12) by ribs (40) extending transversely across the air gap (17) and through the openings (18) for secur- 12 ing the voice coil (44) to the diaphragm 16 24 1 26 32 14 18 28 r

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a t t i ib i ii g I o 0 WO 90/05435 PCT/US89/04501 SHALLOW LOUDSPEAKER WITH SLOTTED MAGNET STRUCTURE 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. Patents: 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 .6 inch (1.5 cm) peak to peak excursion, a space of at least .3 inch (.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 j and magnet assembly must be avoided to prevent the audible distortion which accompanies such collisions.

It is an object of the present invention to I provide an electrodynamic transducer structure in which

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r i! /i -2is it 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, in an electrodynamic transducer comprising a magnet structure including first and second poles defining between themselves an air gap, a diaphragm, a voice coil, and means for coupling the voice coil to the diaphragm, openings are provided in at least one of the poles, the 10 openings extending substantially parallel with the air o• gap and the direction of motion of the voice coil in the egos air gap and the means for coupling the voice coil to the Sdiaphragm comprises ribs extending transversaly across the air gap and through the openings, securing the voice coil to the diaphragm.

Illustratively, according to an embodiment of the invention, the first and second poles comprise an inner pole and an outer pole, respectively, the voice coil having a substantially cylindrical configuration, and the air gap having a substantially cylindrical 1 configuration, the ribs extending substantially radially of the axes of the voice coil and air gap between the voice coil and diaphragm.

Further, illustratively according to an embodiment of the invention, the diaphragm comprises an opening having an inner sidewall and the ribs are secured at their radially outer extents to the inner sidewall.

Additionally, illustratively according to an embodiment of the invention, the inner sidewall of the 30 opening in the diaphragm is substantially cylindrical.

Illustratively, according to an embodiment of the invention, the inner sidewall of the opening in the diaphragm is substantially right circular cylindrical.

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Illustratively, the diaphragm is substantially planar.

Further, illustratively according to an embodiment of the invention, the air gap and voice coil are substantially right circular cylindrical.

Additionally, illustratively according to an embodiment of the invention, the openings are in the outer pole and are in the shape of slots which are elongated in the direction of the air gap and voice coil .o 10 .axes and narrow in a direction transverse to the air gap Sand voice coil axes.

Further, illustratively according to an embodiment of the invention, 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.

Additionally, illustratively according to an embodiment of the invention, the means for coupling- the voice coil to the diaphragm further comprises a voice 20 coil form for supporting the voice coil in the air gap, the ribs secured at their radially inner extents to the voice coil form.

i 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 i{ constructed according to the present invention; and ii Fig. 2 illustrates a fragmentary sectional side elevational view of the electrodynamic transducer of Fig.

1, taken generally along section lines 2-2 of Fig. 1.

Referring to both figures, the transducer includes a back plate 10 which can be constructed from Si Mrvty, 0K

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-3aany suitable material such as a metal or filled or unfilled resin. Back plate 10 extends outward from the transducer components illustrated in the figures and typically supports the outer perimeter (not'shown) of the diaphragm 12 of the transducer by some suitable 4 Oe 0 S

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0000 00 0* 4 00 0 00 0* KNT 0 WO 90/05435 PCT/US89/04501 -4configuration which is not the subject of this invention. An outer pole, or shell, 14 is mounted, such as by a suitable adhesive, on back plate 10. Shell 14 is constructed from a material which has a high magnetic permeability, a ferromagnetic material. Shell 14 defines within it a generally right circular cylindrical space 17, open at the top 16. Slots 18 extend along the length of the sidewall 20 of shell 14 from its floor 22 to its upper lip 24. Slots 18 are elongated in the direction of the axis 26 of the right circular cylindrical space and narrow in the direction around sidewall 20 transverse to axis 26.

A right circular cylindrical ferromagnet 28 and slug 30 are stacked on the floor 22 of shell 14 to form the inner, or core, pole 31 of a yoke 32 with shell 14.

A right circular cylindrical air gap 34 coaxial with space 17 and core pole 31 is thus formed.

Diaphragm 12 includes an inner circular opening 36 defined by a right circular cylindrical wall 38 having a radius larger than the radius of shell 14 so that diaphragm 12 will slide down around the shell 14.

Several ribs 40 extend radially inward from wall 38 and join the outer sidewall of a right circular cylindrical voice coil form 42. The dimensions of ribs 40 and voice coil form 42 are such that the ribs 40 move freely without contact in slots 18 and voice coil form 42 and the voice coil 44 which is provided on the radially inner surface 46 thereof move freely without contact in air gap 34.

*.i M i:i :i i WO 90/05435 PCT/US89/04501 It will be appreciated with reference to Fig. 2 that the entire excursion of diaphragm 12 between its peak limits T and B is below the level of lip 24 of shell 14. Thus, the object is achieved of providing a transducer structure wherein space between the diaphragm 12 and magnet structure 14, 28, 30 in the direction in which excursion of the diaphragm 12 occurs is eliminated.

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Claims (8)

1. 2. The apparatus of claim 1 wherein the first and second poles comprise an inner pole and an outer pole, respectively, the voice coil having a substantially cylindrical configuration, and the air gap having a substantially cylindrical configuration, the ribs .extending substantially radially of the axes of the voice 20 coil and air gap between the voice coil and diaphragm.
2. 3. The apparatus of claim 2 wherein the diaphragm comprises an opening having an inner sidewall and the ribs are secured at their radially outer extents to the inner sidewall.
3. 4. The apparatus of claim 3 wherein the inner sidewall of the opening in the diaphragm is substantially cylindrical. The apparatus of claim 4 wherein the inner sidewall of the opening in the diaphragm is substantially right circular cylindrical.
4. 6. The apparatus of claim 5 wherein the diaphragm is substantially planar. A ;LtX" L i 1 1 nP L r it -7-
5. 7. The apparatus of claim 2 wherein the air gap and voice coil are substantially right circular cylindrical.
6. 8. The apparatus of claim 2 wherein the openings are in the outer pole and are in the shape of slots which 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.
7. 9. The apparatus of claim 8 wherein the ribs 10 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.
8. 10. The apparatus of claim 2 wherein 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 secured at their radially inner extents to the voice coil form. DATED this 29th day of November, 1991 HARMAN INTERNATIONAL INDUSTRIES, INCORPORATED Attorney: LEON K. ALLEN Fellow Institute of Patent Attorneys of Australia S" of SHELSTON WATERS Sr 1 1 1 1 1 i~t 2