US3618185A - Oval loudspeaker basket and method of manufacturing same - Google Patents

Abstract

A METHOD OF MANUFACTURING AN OVAL LOUDSPEAKER BASKET EMPLOYING EXPANDED METAL TECHNIQUES. A FLAT BLANK OF MATERIAL IS PIERCED (E.G. PUNCHED) TO FORM A CENTRAL ANNULAR REGION, A PERIPHERAL OVAL FLANGE AND A NETWORK OF CONCENTRIC WEBS, RADIAL INTERCONNECTING WEBS AND CONCENTRIC SLOTS. THE ANNULAR PORTION IS DISPLACED FROM THE PERIPHERAL PORTION BETWEEN A PAIR OF DIE MEMBERS, EXPANDING THE WEBS TO FORM GENERALLY DIAMOND-SHAPED OPENINGS IN THE EXPANDED BASKET.

Description

Nov. 9, 1971 A. L. COEN Original Filed June 5. 1967 5 Sheets-Sheet l INVENTUW moo L. 605M mm m A. L. COEN Nov, 9, 1971 OVAL LOUDSPEAKER BASKET AND METHOD OF MANUFACTURING SAME 5 Sheets-Sheet 2 Original Filed June 5, 1967 HVWEWTflW 4.400 1. Com

461W TOIWME Y Nov. 92, 1971 A. L. COEN OVAL LOUDSPEAKER BASKET AND METHOD OF MANUFACTURING SAME Original Filed June 5, 1967 5 Sheets-Sheet 5 Nov. 9, 1971 A. a... com

OVAL LOUDSPEAKER BASKET AND METHOD OF MANUFACTURING SAME Original Filed June 5, 1967 5 Sheets-Sheet 4 TQM n F? mm M E ii W Cam Nova 9, 1971 A. L... GOEN OVAL LOUDSPEAKER BASKET AND METHOD OF MANUFACTURING SAME Original Filed June 5, 1967 5 Sheets-Sheet 5 3,618,185 OVAL LOUDSPEAKER BASKET AND METHOD OF MANUFACTURIING SAME Aldo L. Coen, Chicago, 1111., assignor to RCA Corporation Original application June 5, 1967, Ser. No. 643,473, new Patent No. 3,497,928. Divided and this application Feb. 12, 1969, Ser. No. 810,075

lint. Cl. BZId 31/04 U.. C]. 29-61 4 Claims AlBfiTRACT (IF THE DKSCLOSURE A method of manufacturing an oval loudspeaker basket employing expanded metal techniques. A flat blank of material is pierced (e.g. punched) to form a central annular region, a peripheral oval flange and a network of concentric webs, radial interconnecting webs and concentric slots. The annular portion is displaced from the peripheral portion between a pair of die members, expanding the webs to form generally diamond-shaped openings in the expanded basket.

This is a division of application Ser. N0. 643,473, filed June 5, 1967 now Pat. No. 3,497,928.

This invention relates to loudspeakers and, more particularly is concerned with a support structure or basket for supporting the diaphragm and magnet assembly of a loudspeaker and a method of manufacturing such a basket.

Generally, loudspeaker baskets are made by punching a blank from a sheet of metal (e.g. steel) and then forming the blank into a basket shape between a pair of dies. The blank is punched so as to provide, in the formed speaker basket, a central annular plateau region for mounting of a voice coil and magnet assembly and a peripheral flange for attaching the outer edge of the speaker cone or diaphragm to the basket and for attaching the entire assembly to a speaker enclosure. Sufficient material is punched from the sheet of material so as to leave between the central annual region and the periphery of the blank generally radial ribs separated by substantial open spaces. The outside dimensions of the blank are substantially greater than the outside dimensions of the finished basket. During the forming process, the edge of the blank is restrained but not clamped tightly so that as the central annular region is displaced perpendicularly from the plane of the edge portion of the basket, metal from the edge portion is permitted to slip" towards the center and, at the same time, the radial ribs are stretched slightly, the combined effect of edge slipping and rib stretching providing the total required displacement of the central annular region from the peripheral flange. In such a construction, the initial size of the blank must be substantially greater than the outside dimension of the finished basket in order to accomplish the required displacement.

In accordance with the present invention, speaker baskets are manufactured utilizing expanded metal techniques which are substantially more economical of metal than the prior method. In the expanded metal method, the outside dimensions of the starting blank for a given size basket are only slightly larger than the outside dimensions of the finished basket and substantially smaller than the blank for the same size basket manufactured by the former method.

It is a particular object of the present invention to provide an oval loudspeaker basket (i.e. a basket for supporting a diaphragm having an oval outer periphery) manufactured by expanded metal techniques.

3,618,185 Patented Nov. 9, 1971 It is a further object of the present invention to provide a method for producing an oval expanded metal loudspeaker basket.

In accordance with the present invention, a method of forming a support structure for a loudspeaker assembly comprises the steps of piercing a sheet of mechanically deformable material to provide, within an oval boundary, a central annular ring, a plurality of closely spaced concentric webs of substantial linear dimension disposed between the ring and the oval boundary and interconnecting radial Web portions interconnecting each concentric web alternately with adjacent inner and outer ones of the concentric Webs, the radial and concentric webs defining concentric apertures having a linear dimension less than that of the concentric webs but substantially greater than that of the radial webs, rigidly clamping the edge portion of the pierced sheet outside the oval boundary, and displacing the annular ring along an axis substantially perpendicular to the plane of the edge portion while conforming the concentric and radial. webs to a substantially smooth surface defined at one extreme by the oval boundary and defined at the opposite extreme by the annular ring for expanding the pierced sheet to form a loudspeaker basket.

In accordance with a further aspect of the present invention, a support structure for a loudspeaker assembly comprises an annular central portion, an oval peripheral flange, the oval flange having associated major and minor axes, and an apertured transition portion extending between the oval flange and the central portion, the transition portion comprising a network of relatively long, generally circumferential webs and relatively short interconnecting radial webs, a plurality of the long webs extending across the major axis and linking together segments of the oval flange disposed on each side of the major axis in adjacent quadrants of the oval.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation as Well as additional objects thereof will best be understood from the following description when read in connection with the accompanying drawing in which:

FIG. 1 is a partial top view of an oval expanded metal loudspeaker support structure or basket constructed in accordance with the present invention.

FIG. 2 is a front view, partially in section, of the support structure shown in FIG. 1.

FIG. 3 is a top view of a punched blank utilized for producing the structure shown in FIGS. 1 and 2. 1

FIG. 4 is a diagrammatic sectional view taken through a punch press showing a step in the manufacture of the structure of FIGS. 1 and 2.

FIG. 5 is a diagrammatic sectional view taken through a forming press showing a further step in the manufacture of the structure of FIGS. 1 and 2.

Referring now to FIGS. 1 and 2 of the drawing, the loudspeaker assembly comprises a magnet structure 10 mounted upon a central annular, plateau-like portion 12 of a speaker basket indicated generally by the reference numeral 14. A cylindrical voice coil assembly 16 is mounted by means of a flexible suspension member 18 within a circular opening 20 in annular portion 12. Voice coil assembly 16 extends adjacent magnet structure 10 and is coupled by means of an electrical lead wire assembly 22 to a terminal board 24 mounted adjacent a barrel-shaped access opening 26a in basket 14. A similar opening 26b is provided diametrically opposite opening 26a adjacent annular portion 12. A dust cap 28 is provided over the exposed end of voice coil assembly 16. A speaker cone or diaphragm 310 having a central circular edge 30a and a peripheral oval edge 30b (i.e. an oval cone) is suspended between voice coil assembly 16 and a second suspension member 32. Suspension member 32 is retained within a peripheral flange 34 by means of a gasket 36 and is fastened by means of a suitable adhesive against a lip 38. Mounting holes 40 are provided in the lip between flange 34 and an oval boundary 42 of basket 14. Central annular portion 12, lip 38, flange 34, and the transition portion 14a of basket 14 all are formed from a unitary piece of metal such as steel or other suitable material.

The central annular portion 12 of basket 14 is displayed from the plane of lip 38 along an axis which is perpendicular to that plane (see FIG. 2). Annular portion 12 and lip 38 are joined together by transition portion 14a which comprises a plurality of relatively long generally circumferential webs 44 joined together by relatively short interconnecting radial web portions 46. Webs 44 and interconnecting radial web portions 46 define a plurality of apertures 48 which are generally diamond-shaped along the major and minor axes of basket 14 but are irregularly shaped at points intermediate those axes. The outermost ends of the outermost ones of apertures 48 lie along the oval boundary 42. Stated differently, the webs 44 which extend across the major axis of basket 14 are joined together to form continuous links between the portion of oval boundary 42 on one side of the major axis and the portion of oval boundary 42 on the other side of the major axis.

Furthermore, it should be noted that while the radial webs 46 which lie along the major and minor axes of oval flange 34 are radially aligned, the radial webs 46 between such axes are not radially aligned. The positioning of the radial webs is selected so as to provide a length for each segment of the long webs 44 suflicient to provide the necessary deformation thereof without fracturing. It has been found, for example, in the illustrated structure that a maximum permissible angle between two segments of webs 44 meeting at a common radial web 46 is approximately sixty degrees.

The manner in which the basket 14 is manufactured now will be described referring initially to FIG. 4. In FIG. 4, there is shown a sectional view through a portion of a punch press designated generally by the reference numeral 458. The principal parts of the press 458 for purposes of this description consist of a stationary apertured base plate 460 and a reciprocating head 462 having a plurality of curved punches 464, the punches 464 lying along concentric circles. Apertures 448 are provided in base plate 460 for receiving the punches 464 as head 462 is lowered and for permitting removal of material from a fiat strip of sheet metal 450 which is placed upon base plate 460 for punching. In practice, sheet metal 450 may be fed from a roll across base plate 460 from right to left in FIG. 4 against an indexing stop (not shown) located at the left end of base plate 460. When the sheet metal 450 contacts the indexing stop, head 462 is brought rapidly downward such that punches 464 produce a predetermined plurality of apertures in sheet metal 450.

Where a large number of closely spaced apertures are required in the sheet 450, the punching operation preferably is carried out utilizing a multi-station punch press. For example, two separate heads, each containing onehalf the required punches (i.e. alternate rows of the required punches) and two separate base plates, each containing one-half the required apertures, may be provided in a single machine. In that case, as the sheet material 450 is fed into the press, the first punching operation will result in half the required apertures being punched in a first blank. The sheet 450 is then advanced and the second punching operation will result in a simultaneous punching of the second half (i.e. the alternate rows) of the required apertures in the first blank and the first half of the apertures being punched in a second blank. In this manner, one blank will be completed for each punching operation 4 after the first one. On the third punching sequence, a cutoff device may be provided for cutting off the first blank which now passes out of the punch press. 'In such an arrangement, the tools (punches and base plate) more readily may be fabricated.

Referring to FIG. 3, a flat punched blank 50 is shown which is produced in the manner described in connection with FIG. 4. The punched blank 50 is utilized, in accordance with the present invention, for forming the basket 14 shown in FIGS. 1 and 2. In FIG. 3, elements of the blank 50 prior to forming which correspond to elements of the basket 14 (FIG. 1) after forming are indicated by the same reference numerals as are used in FIGS. 1 and 2 with the addition of a prime notation following the numerals in FIG. 3.

As shown in FIG. 3, the blank 50 from which basket 14 is formed comprises a generally octagonal sheet of, for example, one thirty-second inch thick steel of aluminum killed grade. A plurality of discontinuous concentric apertures 48', a central circular pilot aperture 52 and a pair ofmodified rectangular apertures 26a and 26b having curved ends (preferably segments of concentric circles) and straight sides are punched in the sheet material. Continuous concentric webs 44' bounded at the inside by annular portion 12', at the outside by an oval boundary 42' (shown in dotted lines) and interrupted by apertures 26a and 26b are formed as a result of the punching. Webs 44' are joined together by interconnecting radial web portions 46' which extend between adjacent apertures 48'. Central aperture 52 and two relatively small apertures 54 and 56 lying along the major axis of blank 50 serve as pilot holes for positioning blank 50 during the forming process as will be described below.

Referring to FIG. 5, the manner in which punched blank 50 (FIG. 3) is formed into basket 14 (FIGS. 1 and 2) now will be described. 'In FIG. 5, there is shown a sectional view through a portion of a forming press designated generally by the reference number 510. For purposes of this description, the principal parts of forming press 510 consist of a stationary base plate 512 including a male basket-forming die 514. A floating ring 516 supported on an air cushion encircles the uppermost plateau region 518 of male die 514. Ring 516 is coupled by means of supporting pins 520 to a piston assembly 522 which extends within an air (or other hydraulic) cylinder 524. Pressure is maintained within cylinder 524 by means of a conventional pressurized air supply 526.

The forming press 510 further comprises a movable female basket-forming die 530 and driving means (not shown) coupled to the female die 530 for reciprocating female die 530 along a vertical axis.

The punched blank 50 (shown in FIG. 3) is located upon plateau region 518 and floating ring 516 by indexing means (e.g. pin 528) for forming.

In the operation of forming press 510, base plate 512 and male die 514 remain stationary. Punched blank 50 is located on floating ring 516 and plateau region 518. Female die 530 is then moved vertically downward such that initial contact is made between female die 530 and blank 50 along the edge of blank 50 which rests on ring 516. The air pressure provided by supply 526 (e.g. 80. p.s.i.) is selected such that the edge of blank 50 is clamped between ring 516 and die 530 and thereby is substantially restrained from sideways movement. As female die 530 is advanced downwardly, the webs 44' and 46" of punched blank 50 (see FIG. 3) are displaced and the apertures 48 between webs 44' are enlarged, thereby expanding blank 50 into the desired basket shape (see FIG. 1). Female die 530 is then lifted permitting removal of the formed basket. The dimensions of ring 516, rods 520 and dies 514 and 530 are arranged such that the interconnecting webs 44 and 46 of the finished basket all lie along the smooth surfaces of the dies 514 and 530.

After removal from the forming press 510, the formed basket is trimmed along its outer edge and mounting holes 40 (FIG. 1) and the larger central voice coil hole 20 are punched by means of a conventional vertical punch press. In the final trimming operation, only a very narrow strip of material is discarded since, as was mentioned above the outside dimensions of blank 50 are only slightly greater than the outside dimensions of finished basket 14. The increase in the dimensions along the surface of transition portion 14a required to permit vertical displacement of annular portion 12 from lip 38 is provided substantially solely by the rearrangement of the webs 44 and 46 during the forming or expansion operation. In a typical 8 x 12" oval basket, the savings in material realized by virtue of the present invention is of the order of twenty percent.

It should also be noted that, while the transition portion 14a of basket 14 extends between a circular inner portion 12 and an oval outer boundary 42, the apertures 43 and the Webs 44 (FIG. 3) in the blank 50 all lie on concentric circles. Such an arrrangement permits relatively simple and therefore not excessively costly manufactun ing of the tooling (i.e. punches 464 and apertured base plate 460 of punch press 458) required for producing the punched blank 50.

What is claimed is: 1. A method of forming a support structure for a loudspeaker assembly comprising the steps of piercing a fiat sheet of mechanically deformable material to provide, within an oval boundary having associated major and minor axes, a central annular ring, a plurality of closely spaced concentric webs of substantial circumferential dimension disposed between said ring and said oval boundary and radial web portions interconnecting each said concentric web alternately with adjacent inner and outer ones of said concentric Webs, at least some of said concentric Webs terminating at said oval boundary between said major and minor axes, said radial and concentric webs defining concentric apertures having a circumferential dimension less than that of said concentric Webs but substantially greater than that of said radial webs, rigidly clamping the edge portion of said pierced sheet outside said oval boundary, and displacing said annular ring along an axis substantially perpendicular to the plane of said edge portion while conforming said concentric and radial webs to a substantially smooth surface defined at one extreme by said oval boundary and defined at the opposite extreme by said annular ring for expanding said pierced sheet to form a loudspeaker basket.

2. A method of forming a support structure for a loudspeaker assembly according to claim 1 wherein said radial Web portions being radially aligned along said axes and being radially mis-aligned intermediate said axes to provide sufiicient length for said concentric webs intermediate said axes to prevent fracture thereof upon displacement of said annular ring.

3. A method according to claim 2 and further comprising piercing said sheet of material to form at least a first access opening disposed adjacent said annular ring along said major axis, said access opening being defined by first and second side ribs and an end rib.

4. A method according to claim 3 wherein said radial webs intermediate said major and minor axes are dis placed from each other and from said access opening ribs such that each segment of each said concentric web between adjacent inner and outer radial webs is of sufiicient length to prevent fracture upon deformation.

References Cited UNITED STATES PATENTS 865,173 9/1907 Eichberg 296.2. X 1,144,668 6/1915 Rizzardi 2962 1,287,298 12/1918 Halvorson et al. 240102 2,895,578 2/1946 Perganoe 40-1241 3,497,928 3/1970 Coen 296.1

FOREIGN PATENTS 767,336 1/1934 France 29163.5

JOHN F. CAMPBELL, Primary Examiner R. J. CRAIG, Assistant Examiner US. Cl. X.R. 296.2, 163.5

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. ,185 Dated November 71 Inventor (x) Aldo L. Coen It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 42, that portion reading "annual" should read annular Column 2, lines 25-36, that portion should be deleted. Column 3, line 12, that portion reading "displayed" should read displaced Signed and sealed this 18th day of July 1972.

(SEAL) ttest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PO-lOSCI [10-69] USCOMM- 99 75.;159

ll 5v GOVERNMENT HUNTING OFFICE: 1," O'lC-L\l

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