US2666980A - Method of making loud-speakers - Google Patents

Description

.Fan. 26, 1954 RUSSELL 2,666,980

METHOD OF MAKING LOUD-SPEAKERS Original Filed April 2, 1947 2 Sheets-Sheet 1 iiiiiii INVENTOR. EARL L. RUSSELL ATTOQNEIS Jan. 26, 1954 RUSSELL 2,666,980

METHOD OF MAKING LOUD-SPEAKERS Original Filed April 2, 1947 2 Sheets-Sheet 2 INVENTOR. EHRL L. Russem FITToR eYs Patented Jan. 26, 1954 2,666,980 METHOD OF MAKING LOUD-SPEAKERS Earl L. Russell, Cleveland, Ohio, assignor to The Rola Company, Inc., Cleveland, Ohio, a corporation of Ohio Original application April 2, 1947, Serial No.

738,894, now Patent No.

2,524,836, dated October 10, 1950. Divided and this application November 17, 1949, Serial 1 Claim.

This application is a division of my copending application Serial No. 738,894, filed April 2, 1947, now Patent 2,524,836, issued October 10, 1950 and relates to permanent magnet loudspeakers and particularly to a method of making permanent magnet loud speakers of the type disclosed in the aforesaid application.

Loud speakers utilizing a permanent magnet for the field structure are subject to the accumulation of foreign particles in the confined space between the voice coil forms and the opening therefor in the front plate of the magnetic structure. Great care must be exercised in the manufacture and assembly of the loud speaker to avoid the possibility of magnetic particles being attracted to and held by the magnetic structure, as otherwise their presence would interfere with the normal reciprocating movement of the voice coil Within the air gap and cause a scratching noise in the reproduction. The cen tering of the voice coil form within the air gap is also important. The method of assembly must be such that the proper spacing is maintained between the component parts and at the same time must enable the speaker to withstand rough handling incident to the packing and shipment of the loud speakers from the place of production to the set manufacturer, and then to the ultimate user.

An effort heretofore has been made to overcome the aforementioned difiiculty by permanently fastening the cone and housing assembly to the field assembly after the voice coil form has been centered by means of a gauge with respect to the pole tip of the magnetic structure. The difliculty with such assembly, however, has been that if any magnetic particles should be entrapped between the voice coil form and the pole tip, or if the voice coil is not centered exactly, it

'has been necessary to destroy the diaphragm,

the spider or centering member, the voice coil and the form in order to get at the space in the region of the air gap for the purpose of freeing the gap of foreign particles or in order to recenter the voice coil. In loud speakers utilizing a permanent magnet, such occurrence is apt to be sufficiently frequent to constitute a major item in the servicing and repairing of loud speakers.

An object of the present invention is to provide a method of assembling a loud speaker wherein the cone or diaphragm and its associated housing assembly can be removed from the field as sembly without destroying or disturbing the relationship of the parts forming the diaphragm assembly, thereby enabling the field structure,

of a cone to the in the region of the air gap, to be effectively cleaned or centered and the parts reassembled in an expeditious manner.

Referring now to the drawings, Fig. l is a side elevation of a loud speaker embodying the present invention; Fig. 2 is an exploded view in side elevation of the assembly shown in Fig. 1; Fig. 3 is an end View of the field structure as viewed in the direction indicated by the arrows 3-3 in Fig. 2; Fig. 4 is a rear view of the assembled loud speaker with a portion thereof broken away; Fig. 5 is a section taken on a plane indicated by the line 55 in Fig. 4, and Fig. 6 is a section taken on a plane indicated by the line 66 in Fig. 4.

The loud speaker with which the present invention is shown has a permanent magnetic field which includes a shell type core, indicated in general at [0, and preferably comprises a strip of metal that is bent to form an open frame having a front plate H, a back plate 12, a top plate I3 and a bottom plate i l. The front plate has an opening l5 therein and the back plate has a pole piece It extending into the shell and substantially parallel to the top and bottom plates thereof. The pole piece terminates in a pole tip H which is concentrically disposed within the opening l5 and cooperates therewith to provide the air gap in which the voice coil is adapted to operate in the usual way. The pole piece 16 is held within central position within the shell by means of a resilient cup-shaped member 20 that is soldered or otherwise securely fixed to the back of the front plate and is adapted to en gage a tapered surface 21 on the pole piece to exert tension thereagainst, so as to hold it filrnlilly in central position with respect to the s e The loud speaker of the-present invention in cludes a diaphragm 25 preferablein the form throat of which a voice coil form 26 is attached. The form carries the usual voice coil 2! and is held in centered position by a spider or centering member 30 which extends from the neck of the diaphragm to the space 3| of the cone housing 32. The periphery of the cone is fastened, as by cement and gasket 33, to the periphery of the housing.

The field structure is attached to the cone assembly by fastening members 35 which extend through openings 36 in a plate 37 and are in threaded engagement with registering openings in the baseof. the cone housing. As is shown in Fig. 6, theopenings 35 are larger than the diameter of the threaded shank of the fastener 35,

as a result of which adjustment may be made between the field structure and the cone assembly whenever the screws are loosened.

The foregoing described the component parts of the assembly,.but for carrying .out the assembly, the plate 3'! isgstaked or-iotherwise securely fastened to the front plate H, as by bosses 40 which are extruded from the front plate and are adapted to enter correspondingly shaped openings in the plate 37. Additionally, the attachment is made by threadedjastenmg.members-4l, as is shown in Fig. 3. The plate. andshell as a unit are then fastened to the cone housing 32 by means of the securing members 55, these being accessible from the rear of the housing as is shown in 4, inasmuch-as the plate 311s wider than the material of which the 1shell i0 .is made.

After the shell has been assembled to the housing, then the pole piece it is centrally located therein by means of asuitable gaugev placed between the pole tip and the wall of the opening 15, and is locked in place by; the resilient center- :ing member 20, after which solder is applied to hold the pole piece to the back wall of the shell and'to hold the centering member to theiront plate of theshell.

After the assembly of the magnetic structure,

the. centering member 30 is cement-ed at its outer periphery to the base 3| of the cone housing, while being centered with respect to the axisof the pole tip by means ,of a gauge that is inserted within the air gap. lihe assembly of the cone and its associated-voice coil rorm to the centering member 30 is made by applying cement to theineck of the cone .on the outer portion thereof and-then inserting the voice coil ,form into the --air gap, using a customary centering gauge to space ,it with respect to the pole piece. The .form isinserted until the centering member fits snugly against the neck of the cone,whereu pon the cement operates efiectivelyto join the two parts together. While the centering gauge is -stillrin position,-the base of the cone is cemented to thevcone housing and sealed by means .of the gasket 33 which is cemented thereto.

In the-event of the voice coil form being inaccurately centered with respect to the polepiece, then itis only necessary to loosenthe screws .35

and move the field assembly with respectto the ,cone assembly, using the customary centering gauge between the voice coil ,form and the .pole

tip, and then tightemng theimembers e5.

Heretofore it has been necessary to destroy the cone, together with its associated centering .member, voice coil and voice coil iormin ,order to relocate a form with respect .to the walls of the air gap, or to make the air gap accessible for cleanirgpurposes. Anadvantage of .the present invention, however/is that the adjustment and the component parts, and without disturbing the 0 ;clean1ng can .bemade-without destroying anyof 6 Moreover, the invention is advantageous in that the cone assembly and field structure may be quickly adjusted merely by the insertion of a centering gauge between the voice coil form and the pole tip at the time of tightening of the fastening members, which are readily accessible from xthe-exteriorpart of the unit.

1 claim: In alloud speaker having a permanent magnet shell type field structure with an air gap in one F iace a pole pieceand pole piece centering member,-a cone assembly including a housing, and a diaphragm having a voice coil and form at one end with a retaining spider having a central opening for accommodating the voice coil and form, a plate having an air gap opening for coupling the-shell and pole piece to the cone assemblyythe plate having a width greater than the air gap race of the shell and having oversize holes through portions thereof ez-ztendingbeyond the air face of the shell adapted to loosely receive securing screws therethrough, the method of assembly comprising, positioning and securing the plateto the air gapface of the shell so that the air gap opening of'the plate is centered with respect to the air gap of the shell, securing the housing to the plate by means of screws extending through the oversize holes in theplate and toward the housing, centering and securing the pole piece in the shell by means of the'pole piece centering member, centering the spider with respect to the pole piece and securing the outer periphery of the spider to the housing, centering the voice coil and form of the diaphragm through the central opening of the spider in the air gap between'the pole piece and shell, securing the adjacent end of the diaphragm to the spider and securing the outer end of the diaphragm to the adjacent portion of the housing.

EARL L. RUSSELL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,836,076 Kingsiord ec. 15, 1931 1,859,518 Kingsford May 24, 1932 1,856,774 Mayer May 3, 1932 1,886,735 Prldham Nov. 8, 1932 1,905,702 vI-lardisty Apr. 25, 1933 1,906,196 Fisher ,Apr. 25, 1933 1,941,476 Jensen Jan. 2,1934 2,020,212 Quam, Nov. '5, 1935 2,174.,355 .Sundstrom Sept..26,'1939 2,306,291 .Alons Dec. 22, 1942 2,423,037 Marquis June 24, 19937 2,524,836 .Russell -1 Oct. 10,1950

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