Background of the Invention The present invention relates generally to loudspeaker cones, and more particularly to a novel annular suspension rim for a loudspeaker cone wherein the rim has, in a preferred embodiment, a mounting gasket formed integral therewith, and a method for making the same.

Loudspeaker cones, alternatively termed loudspeaker vibration diaphragms, are well known. They may employ a generally frustoconical shaped fibrous or felted-paper cone or diaphragm adapted to be supported on a similarly shaped support frame or basket through an annular suspension member or rim secured to the outer marginal edge of the cone and having predetermined elastic or flexibility properties. The suspension member or rim may be formed as an integral generally radially directed extension of the periphery of the cone or diaphragm, as disclosed in U.S. patent Nos. 1,872,583, 2,302,178 and 4,646,874, or may be formed as a separate annular supporting flange or rim affixed to an outer peripheral edge of the cone, such as are disclosed in U.S. patent Nos. 2,840,177 and 3,684,052. Alternatively, the loudspeaker cone or diaphragm may be formed of plastic material such as that disclosed in U.S. patent No. 3,858,680.

With the advent of relatively sophisticated sound reproduction systems, such as in stereophonic sound systems, the dynamic or moving coil-type loudspeaker cones used for the mid and low frequency ranges have become subject to relatively high amplitude vibrations in the axial direction of the cone. In the past, many

manufacturers of larger size loudspeaker cones have made the suspension rims from rubber in order to achieve desired flexibility and durability. A drawback to the use of rubber suspension rims is their relatively high cost.

In mounting the loudspeaker cone or diaphragm on a support frame or basket, the annular suspension rim on the cone is conventionally adhesively affixed to an annular mounting flange surface on the basket with the speaker cone extending into a generally conical or concave portion of the basket. The annular axially extending mounting flange is on the outer periphery of the basket. The mounting flange thereby supports the circumference of the speaker cone suspension rim.

The speaker cone and associated frame or basket are then usually mounted within a speaker cabinet so that the axially extending flange on the basket is concentric to a circular speaker opening formed in a forward wall of the cabinet. The speaker cabinet, or at least the forward wall in which the speaker opening is formed, is conventionally made of wood or the like to facilitate securing of the annular basket rim to the forward wall by screw fasteners or the like. A suitable speaker cloth may cover the otherwise exposed speaker cone.

With a loudspeaker cone and cabinet mounting arrangement as thus described, an annular resilient gasket is frequently secured to the outwardly facing or exposed surface of the speaker cone suspension rim. See, for example, the aforenoted U.S. patent Nos. 2,840,177 and 3,858,680. When the speaker cone support frame or

basket is mounted against a wall within a speaker cabinet, the annular gasket is slightly compressed between the gasket mounting flange on the basket and the speaker cabinet peripherally of the speaker opening, and serves to take up small irregularities in the mounting surface to which the basket is secured and also act as a shock absorber. An acoustically transparent fabric cover, termed a grill cloth, is generally supported to overlie the otherwise exposed speaker cone and suspension rim.

In more recent loudspeaker cabinets, the speaker cones and associated baskets are mounted within circular openings in the speaker cabinets so that upon removal of the speaker cone grill cloth, which some purists believe impedes true sound reproduction, the basket mounting flange and speaker cone suspension rim are visually exposed. This also gives the loudspeaker a high-tech look. Because an irregular gap is frequently created between the outer edge of the speaker cone suspension rim and the annular outer flange on th« ^* associated cone support basket during assembly some loudspeaker manufacturers have mounted s. ^~ annular gasket-like member on the outer -xpos- . surface of the speaker cone suspension rl h, <?. any such gaps and thereby provide a mor< ii; or cosmetically pleasing look to the conr j-er _* the known prior loudspeakers, the annular gasx^s on the speaker cone suspension rims have been made as separate members and adhesively secured to the suspension rim. The gaskets have conventionally been made of rubber, although gaskets of a paper construction having a foam layer attached to the outer or forward surface have also been employed.

Summary of the Invention

One of the primary objects of the present invention is to provide a novel suspension rim for a loudspeaker cone wherein the suspension rim has an annular gasket formed integral therewith.

A more particular object of the present invention is to provide a novel loudspeaker cone suspension rim and method of making the rim from a plastic foam so as to form an annular gasket integral with the suspension rim and extending forwardly thereof for engaging a cabinet mounting surface or providing a cosmetically pleasing appearance when the speaker cone and suspension rim are exposed in a speaker cabinet assembly.

Another object of the present invention is to provide a novel loudspeaker cone assembly as aforedescribed, and a method of making the same, wherein the suspension rim is formed from a plastic foam in a manner to form high density closed-cell outer skin surfaces on the suspension rim and on the integral annular gasket, the outer skin surfaces forming an integral sandwich construction with a low density closed-cell inner core to provide a suspension rim and gasket having improved strength, flexibility and durability.

Another object of the present invention lies in the provision of a tool for making a speaker cone suspension rim having an integral annular gasket, wherein the tool includes a female mold and male die cooperative to define an annular cavity taking the form of the desired cone suspension rim and annular gasket so that liquid plastic introduced into the cavity forms the annular gasket integral with the suspension rim.

A color coating may be applied to the tool cavity in a manner to selectively color coat the external surface of the suspension rim and integral gasket. In one embodiment, the female mold and male die cooperate to receive a speaker cone body so that an outer peripheral edge of the cone body communicates with the annular suspension rim forming cavity, whereby the suspension rim is formed integral with the peripheral edge of the cone body.

Another object of the present invention is to provide an improved loudspeaker cone assembly having a novel suspension rim which exhibits desired strength, flexibility and durability, which is economical to manufacture, and which has high strength adhesion to the perimeter of the speaker cone.

A further object of the present invention is to provide an improved loudspeaker cone assembly suspension rim which has an annular flange that attaches to the loudspeaker basket without the need for an integrally formed annular gasket.

Another object of the present invention is to provide a method of making a loudspeaker cone having a suspension rim formed from a plastic foam to produce a high density closed-cell outer skin surface and a low density closed-cell inner core. A still further object of the present invention lies in the provision of a tool for making a speaker cone suspension rim having an integral annular flange wherein the tool includes a female mold and male die cooperative to define an annular cavity taking the form of the desired cone suspension rim and annular flange so that

liquid plastic foam introduced into the cavity forms the annular flange integral with the suspension rim. A color coding may be applied to the tool cavity in a manner to selectively color coat the external surface of the suspension rim and annular flange.

Brief Description of the Drawings

Further objects, features and advantages of the present invention, together with the organization and manner of opposition thereof, will become apparent from the following detailed description of preferred embodiment of the invention when taken in conjunction with the accompanying drawings, in which like reference numerals designate like elements throughout the several views, wherin:

FIG.l is a front elevational view of a loudspeaker cone assembly constructed in accordance with a preferred embodiment of the present invention;

FIG. 2 is a transverse sectional view taken substantially along line 2-2 of FIG. 1;

FIG. 3 is a perspective view illustrating the step of depositing a bead of liquid plastic foam into a female mold to form the suspension rim and integral annular gasket in accordance with the method of the preferred embodiment of the present invention;

FIG. 4 is a perspective view illustrating a further step in forming the suspension rim in integrally connected relation to the speaker cone body in accordance with the preferred embodiment of the present invention;

FIG. 5 is a vertical longitudinal sectional view illustrating the female mold and male die in cooperating relation during forming of a foam suspension rim on the outer edge of a speaker cone body in accordance with the preferred embodiment of the present invention;

FIG. 6 is an enlarged fragmentary vertical sectional view illustrating the female mold and male die in sealing relation with the cone body to form the cone suspension rim and integral gasket in accordance with one embodiment of the invention;

FIG. 7 is a fragmentary exploded perspective view illustrating a portion of the cone suspension rim and integral gasket in relation to a support frame or basket to which the rim is secured in a speaker cone/support basket assembly;

FIGS. 8 and 9 are fragmentary sectional views illustrating two alternative techniques for mounting the speaker cone and basket of FIG. 7 to a speaker cabinet;

FIG. 10 is a fragmentary sectional view illustrating an alternative annular cone suspension rim and integral gasket secured on a support basket which is mounted on a speaker cabinet;

FIG. 11 is a front elevational view of a loudspeaker cone assembly constructed in accordance with a second embodiment of the present invention;

FIG. 12 is a transverse sectional view taken substantially along line 12-12 of FIG. 11;

FIG. 13 is a perspective view illustrating the step of depositing a bead of

liquid plastic foam into a female mold to form the suspension rim in accordance with the method of the alternate embodiment of the present invention; -: ^~ -- F G. 14 is a perspective view illustrati g a further step in forming the suspension rim of the alternate embodiment where the suspension rim is integrally connected to the speaker cone body in accordance with the present invention; FIG. 15 is a vertical longitudinal sectional view illustrating the female mold and male die in cooperating relation during the forming of a film suspension rim on the outer edge of a speaker cone body in accordance with the alternate embodiment of the present invention;

FIG. 16 is an enlarged fragmentary sectional view illustrating the sealing relation of the female mold and male die with the cone body in accordance with the alternate embodiment of the present invention; and

FIG. 17 is an enlarged fragmentary detail view similar to FIG. 16 but illustrating an alternative manner of sealing the cone body between the female mold and male die and with the suspension rim affixed to the outer free edge of the cone body through a butt joint connection.

Detailed Description

Referring now to the drawings, and in particular to FIGS. 1 and 2, a loudspeaker cone assembly constructed in accordance with one embodiment of the present invention is indicated generally at 10. The loudspeaker cone assembly 10, which may alternatively be termed a speaker cone or acoustic diaphragm, includes a sound

radiating cone body or element 12 and an annular suspension rim 14. The suspension rim 14 is integrally connected to an outer peripheral edge 12a of the cone body 12 and facilitates attachment of the loudspeaker cone assembly to a mounting flange of a support means such as a basket of conventional design, a fragmentary portion of which is indicated at 16 in FIG. 7. The cone body 12 has a generally frustoconical configuration having a convex curvilinear cross-sectional profile, as viewed in FIG. 2. The cone body 12 has a circular outer peripheral edge 12a and an annular generally cylindrical neck portion 12b extending in the axial direction of the cone and to which a voice coil or the like may be attached in a conventional manner. Alternatively, the cone body 12 may have an elliptical or square outer peripheral edge, with the peripheral wall of the cone body being correspondingly modified from a generally conical configuration to accommodate the shape of the selected outer edge.

In the illustrated embodiment, the cone body 12 has a fibrous or felted paper construction which may be formed by a conventional felting process as conventionally employed in the manufacture of paper cones. For example, the cone body or diaphragm 12 may be formed by a feramonous form, such as a screen, having the desired configuration of the finished cone or diaphragm. The feramonous form is submerged in a water suspension of paper fibers and suction is applied to one side of the form so as to draw the suspension therethrough. Felting of the paper fibers occurs on the form opposite the side through which the suction is applied until the

desired thickness of fibers are built up on the form to establish a peripheral wall of generally uniform thickness from the free edge of the neck portion 12b to the outer free edge 12a of the cone body. The felted form is then dried sufficiently to enable removal of the fibrous cone body from the feramonous form. Conventionally, the cone body 12 is formed to a thickness in the range of approximately .006-.070 inch. The making of felted or fibrous cone bodies is a well established art as exemplified by the aforementioned U.S. patent No. 1,872,533 which is incorporated herein by reference. Alternatively, the cone body 12 may be made of a suitable plastic material having a configuration substantially identical to the described cone body 12.

The annular suspension rim 14 is made from a plastic foam material so that an inner peripheral edge 18 of the suspension rim 14 may be affixed to the outer free edge 12a of the cone body 12. As will be described, the plastic foam annular suspension rim 14 is formed with an integral annular gasket 20 in a manner to establish high density closed-cell skin surfaces on both the inner exposed surface of the suspension rim and the outer exposed surface of the rim and gasket, as indicated at 22a and 22b, respectively, in FIG. 2. The high density closed- cell skin surfaces 22a and 22b are formed in an integral sandwich construction on opposite sides of a closed-cell inner core having lower density than the high density skin surfaces.

In the illustrated preferred embodiment, the suspension rim 14 is formed to define a forwardly extending convex annular surface 24

which is of generally uniform radius, as considered in transverse cross section in FIG. 2, and which is integral with the inner peripheral edge portion 18 and a generally radial outer peripheral flange portion 26 of the suspension rim 14. The forwardly extending annular surface 24 need not have a uniform radius, but may have a curvature which provi „r a variable rim thickness from its inner periph ral edge 18 to the outer flange portion 26, if desired.

The plastic foam material from which the suspension or supporting rim 14 is formed preferably comprises a closed-cell polyurethane foam such as is available in liquid state from Plast-O-Meriσ, Inc. , North Baltimore, Ohio, under its product identification No. SSF-1782 Polyurethane System. If desired, one or more filler materials such as microscopic size glass beads, talcum powder or other desired filler, may be added to the liquid plastic foam prior to forming the suspension rim 14.

The suspension rim 14 is formed by an open-mold process wherein a predetermined volume of the liquid polyurethane foam is deposited into a tool at atmospheric pressure, as indicated generally at 28 in FIG. 5. The liquid foam is preferably deposited in a continuous bead into an open annular cavity in a female mold portion 30 of the tool 28. In the illustrated embodiment, the female mold 30 supports a cone body 12 with its outer peripheral edge 12a exposed within the annular cavity after which a male die 32 is brought into cooperation with the female mold to establish a substantially closed annular chamber having a configuration identical to the desired

configuration of the suspension rim 14 and integral gasket 20. The liquid foam is deposited in sufficient volume to totally fill the annular chamber when expanded and cured. The foam impregnates the exposed outer peripheral edge 12a of the cone body 12 to form an integral connection therewith. Upon curing, the foam forms the high density closed-cell outer skin surfaces 22a and 22b in an integral sandwich construction with a lower density inner core. After curing, the suspension rim 14 with the integral gasket 20 and associated cone body 12 are removed from the tool 28 in substantially the form of the loudspeaker cone assembly 10. In the following described method of making the suspension rim 14 and integral gasket 20 so that the suspension rim is integrally connected to the outer edge 12a of the cone body 12, the suspension rim, except at the annular gasket 20, is preferably formed to a thickness in the range of approximately .015 to .070 inch, depending upon the intended application of the loudspeaker cone assembly being manufactured, although other rim thicknesses, or a rim having a variable thickness across its transverse section, may be desirable for some applications.

Referring now to FIGS. 3-6 for a more detailed description of the method for making the loudspeaker cone assembly 10, the female mold 30 is made of a suitable rigid material, such as a suitable metallic or plastic material, and has a base 34 having a flat base surface 34a adapted to be placed on a turntable or the like, such as indicated at 36 in FIG. 3, coaxially with the axis of rotation of the turntable. In the illustrated

embodiment, the base 34 is generally circular. However, where the suspension rim 14 is to have a non-circular configuration, such as an elliptical or square plan configuration, the base 34 may have a corresponding outer periphery. The female mold 30 has an upper annular surface 34b formed parallel to the lower base 34a. An annular cavity or groove 34c of substantially uniform radius or semi-circular transverse cross section is formed in the surface 34b and is generally radially intersected by an annular recessed planar surface 34d of a radial width substantially equal to the radial dimension of the annular flange 26 on the suspension rim 14. The inner peripheral boundary of the annular cavity 34c terminates in an annular, generally conical surface 34e which is concentric with, but inclined from, a conical surface 34f having a contour substantially equal to the contour of the cone body 12 adjacent its outer free edge 12a. The annular surface 34f intersects an upper planar surface 34g on the female mold and serves as a pilot surface to be engaged by the inner surface of the cone body 12 when placed on the female mold 30 during the manufacturing process. As will be described, the conical surface 34f also cooperates with a similarly configured and mutually opposed conical surface 54e on the male die 32 to secure and seal the outer peripheral edge portion of a cone body during forming of a suspension rim integral with the outer edge of the cone body.

Referring particularly to FIGS. 3 and 6, an annular channel or recess 35 is formed in the generally planar surface 34d on the female mold 30 to create the annular gasket 20 on the speaker

cone suspension rim 14. The channel 35 has a rectangular transverse cross section having a vertical height and radial width which may vary depending on the size of the speaker cone with which the suspension rim 14 is to be used. For example, the channel or recess 35 may be sized to form a gasket having a vertical height in the range of approximately one-quarter inch to one- half inch and a radial width of approximately one- quarter inch to one inch for speaker cones having an outer diameter of approximately eight inches up to fifteen inches or greater.

The gasket forming channel or recess 35 is formed in the surface 34d so that an inner annular wall 35a is spaced radially outwardly from the outer edge of the annular concave recess 34c a distance of approximately one-sixteenth inch, thereby forming a connecting web 25 between the outer edge of rim portion 24 and the annular gasket 20. An annular chamfer 37 is preferably formed at the intersection of an outer annular wall 35b of the channel 35 with the planar surface 34b so as to create an annular beveled edge 20a on the outer peripheral flange portion 26 of the suspension rim peripherally of the base of gasket 20.

In the illustrated embodiment, a cone body locating post 38 is mounted on the base portion 34 of the female mold 30 in coaxial relation therewith. The post 38 has a cylindrical outer surface 38a sized to receive the neck portion 12b of a cone body 12 in sliding relation when the cone body is supported on the female mold in coaxial relation engaging the surface 34f and with the free outer edge portion of the cone body

extending above the recessed conical surface 34e on the female mold. The post 38 has a smaller diameter coaxial cylindrical boss 38b formed coaxially in the base portion 34 and is fixed therein by means of a bolt 40. The small diameter boss 38b allows different diameter posts each having a small diameter boss to be mounted on the female mold so that mold 30 can thereby accommodate cone bodies having different diameter neck portions 12b.

With the female mold 30 positioned coaxially on the turntable 36 as illustrated in FIG. 3, a plastic foam mixing and dispensing head 44 having a discharge nozzle 44a is brought into position overlying the female mold such that the discharge nozzle directly overlies the annular channel 34c. The mixing and dispensing head 44 is of conventional design and has controls associated therewith (not shown) operative to provide a timed discharge of liquid foam from the discharge nozzle orrelated to the rotational speed of the turntable 36. The dispensing head 44 may be supported by an articulated support arm (not shown) enabling movement of the dispensing head from a position spaced from the turntable to a position overlying the anr\lar groove or cavity 34c, and vice-versa. If desired, a suitable release agent may be wiped onto the female mold to lightly coat the annular groove 34c, the adjacent recessed surfaces 34d and 34e, and the annular channel or recess 35. As described in greater detail below, a color coating, such as paint, used for coloring the rim, makes a suitable release agent. The use of paint as a release agent also

has been found to prevent pinholes and other defects in the finished product.

With the dispensing head 44 so positioned, a bead of liquid plastic foam of the aforedescribed type is discharged into the annular groove 34c simultaneously with rotation of the turntable 36 at a predetermined rotational speed in relation to the rate of discharge from the dispensing head. If desired, the dispensing head 44 may have a pair of discharge orifices operative to simultaneously deposit a small bead of liquid plastic foam into the channel or recess 35. The rotational speed and rate of discharge are established so that a predetermined volume by weight of plastic foam is deposited into the annular groove 34c and channel 35 in a continuous but not overlapping bead. Conversely, the female mold 30 may be supported on a stationary support and the dispensing head 44 moved through a path generally overlying the annular groove or cavity 34c to discharge a bead of foam along the full periphery of the groove or cavity 34c and the channel 35. The volume by weight of liquid plastic foam discharged into the annular groove 34c and channel 35 is substantially equal to the volume and weight of foam in the suspension rim 14 and integral gasket 20 after curing.

After depositing a bead of liquid plastic foam into the annular groove 34c and channel 35, rotation of the turntable 36 is terminated and the dispensing head 44 is moved away from the turntable. The female mold 30 is then transferred to a curing work station. In the illustrated embodiment, the curing station includes a horizontal support surface 48 which is

preferably closely adjacent and substantially coplanar with the upper support surface on the turntable 36. The support surface 48 may comprise a portion of a substantially larger rotatable turntable which defines a plurality of work stations about its periphery at substantially equal circumferentially spaced positions on the surface 48. A pair of upstanding locating or stop brackets 50a and 50b serve to abut and locate the female mold 30 at the curing work station when moved onto the support surface 48.

The male die 32 has an annular wall 54 defined between coaxial outer and inner cylindrical surfaces 54a and 54b, respectively. The outer surface 54a has a diameter substantially equal to the outer diameter of the base portion 34 of the female mold 30 adjacent the annular surface 34b. The annular wall 54 is formed integral with and depends from a circular plate 56 which is fixed at its center to the lower end of a vertically reciprocable piston rod 58. The piston rod 58 extends axially from a vertically disposed double acting pneumatic or hydraulic cylinder (not shown) and is guided through a guide bushing 60 supported on a bracket 62 between a pair of support posts 64a and 64b. The male die 32 is vertically movable through selective actuation of the double acting cylinder from a position spaced above the female mold 30, as illustrated in FIG. 4, to an operating position wherein an annular planar surface 54c on the annular wall 54 engages or bottoms against the annular surface 34b on the female mold 30. Preferably, vent means in the form of one or more radial grooves, one of which is indicated at 65 in FIG. 6, are formed in the

annular surface 34b on the female mold to accommodate expansion of the foam deposited into the cavity 34c. The venting grooves 65 thus serve as a pressure relief or expansion path for the liquid plastic foam during expansion and curing as will be described.

A pilot boss 56a is formed coaxially on the underside of the circular plate 56 for sliding entry into a cylindrical recess 38c formed coaxially in the cone locating post 38. Preferably an annular chamfer surface 38d is formed on the post 38 concentric with the cylindrical recess 38c. An annular chamfer 56c is also formed at the lower end of the pilot boss 56a to facilitate entry into the recess 38c.

In the illustrated embodiment, the annular wall 54 of the male die 32 also has an annular convex surface 54d and an annular frustoconical surface 54e formed on its lower end which are configured to lie in predetermined generally parallel spaced relation to the concave cavity surface 34c and annular surfaces 34e and 3 f on the female mold 30 when the male die is in its lowered operating position relative to the female mold, as shown in FIGS. 5 and 6. The annular surface 54e on the male die 32 is spaced above the annular inclined or conical surface 34f by a distance slightly less than the nominal wall thickness of the cone body 12 so that the mutually opposed surfaces 34f and 54e engage the cone body and maintain it firmly in position between the male die and female mold when the male die is lowered to its operating position relative to the female mold. The mutually opposed surfaces 34f and 54e effect a sealing relation with the

interposed wall of the cone body 12 to prevent blow-by or the passage of liquid plastic foam from the suspension rim cavity established between recessed surface 34e and the mutually opposed annular recessed surface 54f on the lower end of the male die.

If desired, the suspension rim 14 and integral annular gasket 20 may be formed independently of a speaker cone body 12, and thereafter secured to the outer peripheral edge of a speaker cone through a suitable adhesive. In this embodiment, the female mold 30 and male die 32 may be readily modified so that the suspension rim 14 and integral gasket 20 are formed without integrally joining the inner peripheral edge 18 of the suspension rim to the outer peripheral edge of a speaker cone. More particularly, the female mold 30 and male die 32 would be modified so that the conical surfaces 34f and 54e engage each other and enable formation of an annular suspension rim having a free inner edge 18 which can subsequently be secured to the outer edge of a speaker cone.

The annular convex surface 54d on the male die 32 is substantially semi-circular in transverse cross-section so that when the male die is lowered into operating position with the lower female mold 30, a substantially closed chamber is established having a transverse cross-sectional profile and volume substantially equal to the desired cross-sectional configuration of the suspension rim 14 and integral gasket 20 on the loudspeaker cone assembly 10. With a cone body 12 mounted on the female mold over the post 38, the free outer peripheral edge 12a of the cone extends a predetermined distance, such as approximately

.0625-.125 inch, into the cavity established between the mutually opposed surfaces 34e and 54f. In similar fashion to the female mold 30 and its annular cavity or groove 34c, the male die 32 may be modified so that the wall 54, and its planar surface 54c, have a circumferential configuration corresponding to the shape selected for the female mold which, in turn, is dependent on the configuration of the cone body 12 and corresponding suspension rim selected. Similarly, the transverse curvature of the annular convex surface 54d on the male die 32 may be configured so that it is not parallel to the cavity surface 34c on the female mold, thereby providing a variable thickness rim as desired.

Lowering the male die 54 into operating position with the female mold 30 causes the deposited bead of liquid plastic foam to substantially fill the closed suspension rim and gasket chamber and simultaneously embed the exposed peripheral edge 12a of the cone body 12 exposed between surfaces 34e and 54f. During expansion and curing, the liquid plastic foam impregnates the exposed inner and outer surfaces of the cone body adjacent its outer free edge 12a. As previously described, as the plastic foam expands, it forms high density closed-cell outer skin surfaces on the suspension rim 14 and annular gasket 20 in an integral sandwich construction with an interposed lower density cellular core. The high density closed-cell skin surfaces protect the suspension rim 14 and gasket form the adverse effects of environmental conditions, such as ultraviolet rays which can lead to premature

deterioration as experienced with prior foam speaker cone suspension rims.

As an alternative to the aforedescribed manner of integrally connecting the inner edge 18 of the suspension rim 16 to the outer peripheral edge 12a of the speaker cone 12, the opposed surfaces of the female mold 30 and male die 32 may be formed with mutually facing annular pinch beads so as to pinch the cone body 12 between the pinch beads closely adjacent the outer peripheral edge 12a of the cone body. The pinch beads prevent flow of liquid foam upwardly onto the cone wall but without crushing or damaging the cone wall. During expansion of liquid plastic foam deposited within the annular channel 34c in the female mold, the liquid foam impregnates the edge 12a of the cone body in a butt-joint connection. Excess expansion of the plastic foam is accommodated by one or more relief or escape vent grooves 65. This alternative embodiment is described in greater detail below.

Referring to FIG. 6, the male die 32 in the preferred embodiment has a plurality of cylindrical bosses, one of which is indicated at 66, fixed to the annular lower surface 54c so as to depend into the annular recess 35 in the female mold 30. The bosses 66 are equidistantly spaced about the circumference of recess 35 and are sized to create blind bores in the molded annular gasket 20, such as indicated at 68 in FIG. 9. The bores 68 intersect the rearward or inner surface 22a of the suspension rim 14 outwardly from the annular convex portion 24. In assembling the loudspeaker cone 10 onto a support frame or basket 16, the inner surface 22a of the suspension rim 14

outwardly from the convex portion 24 is adhesively secured to a radial generally planar flange portion 16a of the basket 16. The flange 16a may have a plurality of circumferentially spaced mounting screw openings therethrough, one of which is indicated at 16b in FIG. 9, to receive mounting screws, such as indicated at 70. The mounting screws 70 facilitate mounting of the basket 16 and associated speaker cone to a wooden wall or the like of a speaker cabinet, as indicated at 72 in FIG. 9. The blind bores 68 in the suspension rim 14 are formed so as to overlie the screw openings 16b in the basket flange 16a. With this construction, and with the suspension rim 14 and gasket 20 being made of a plastic foam material, a slit, such as indicated at 68a in FIG. 9, may be readily cut in the outer surface of the gasket 20 to intersect each of the bores 68. The slits 68a enable entry of a mounting screw 70 and screwdriver to attach the basket 16 to the speaker cabinet 72, and close off after removing the screwdriver so as to provide a clean uninterrupted look to the annular gasket 20. In the embodiment illustrated in FIG. 9, the basket 16 has an outer annular flange 16c which seats within a counterbore 72a in the cabinet wall 72 so that a peripheral edge 16d on the flange 16b is flush with an outer surface 72b of the speaker cabinet wall. FIG. 7 illustrates an embodiment of the speaker cone suspension rim 14 wherein a plurality of external recesses, one of which is indicated at 76, are formed circumferentially about the gasket 20 so as to intersect an outer annular surface 20b on the gasket. To form the recesses 76 during

molding of the suspension rim 14 and integral gasket 20, suitable convex, generally semicircular projections (not shown) are formed on the wall surface 35b of the annular channel or recess 35 in the female mold 30. The recesses 76 are located to coincide with mounting screw slots or openings in the basket flange 16a, one of which is indicated at 78 in FIG. 7. The recesses 76 thus provide clearance for screwdriver access to mounting screws inserted through the openings 78 for mounting the basket 16 to a speaker cabinet.

Returning again to FIG. 5, t e upper male die 32 is moved into its operating position with the female mold 30 in a manner to prevent separation or lifting of the male die fv^s. the female mold during expansion and curing -yf the liquid plastic foam. This may be accomplished by pressurizing the associated double acting cylinder to prevent upward movement of the male die during the foam expansion and curing cycle. Alternatively, the male die 32 may be maintained in fixed relation with the female mold 30 by toggle linkages or the like which may be manually or automatically actuated to prevent upward movement of the male die until intended release of the applied retaining force. It has been found that when a quantity of liquid plastic foam sufficient to form the suspension rim 14 and integral gasket 20 is deposited within the annular cavity 34c and recess 35 in the female mold 30 and caused to expand with the male die 32 positioned to establish a substantially closed chamber with the annular cavity, a reactive pressure is created within the chamber. This pressure is resisted by applying sufficient pressure to the double acting

cylinder which actuates the piston 58, or by selective use of toggle linkage type clamps acting on the male die 32.

With the male die 32 in operative relation with the female mold 30, and with liquid plastic foam deposited within the rim cavity 34c as described, the closed tool 28 is heated to approximately 120°F during expansion and curing of the foam. Heating of the female mold 30 and male die 32 of the tool may be carried out by any suitable heating means. In a preferred embodiment, the closed tool 28 is moved into a heating oven which may be formed to extend partially about the turntable 48 so that indexing the turntable causes the closed mold to be disposed within the heating oven for a predetermined period of time.

In accordance with another feature of the invention, a color coating such as paint may be applied to selected exposed surface areas on the annular suspension rim 14 and/or the annular gasket 20. If color coating is desired, such as on the forward exposed surface 22b of the rim 14 and the exposed surface on the gasket 20, a release agent, such as commercially available from Moline Paint Manufacturing Co., Moline, Illinois, under its product identification No. MPM 11-X153A, is applied to the female mold surface 34c-e and gasket recess 35 prior to depositing the liquid foam into the annular cavity 34c in the female mold. A selected urethane color coating, such as a urethane color coating available from Moline Paint Manufacturing Co. under its ALIPHLEX® System, is then applied as by spraying onto the mold surfaces 34c-e and 35. If desired, a color

coating having a release agent mixed therein may be used, thereby eliminating application to the female mold of a separate release agent. Also, fillers such as microscopic size glass beads, talcum powder or additives giving the coating a pearlescent finish could be added to the color coating applied to the mold surfaces 34c-e.

Preferably a shield, such as a paper shield having the shape of the cone body 12, is placed over the cone guide post 38 to mask off and shield the surfaces 34g and 34f from the color coating spray. Alternatively, the color coating may be sprayed onto the female mold surface 34c-e and within the channel 35 by an electrostatic process so that no shield is needed. During curing of the liquid foam within the closed cavity between the female mold and male die, the color coating, as selectively applied to the female mold, is transferred to and adheres to the corresponding outer exposed surface areas of the suspension rim 14 and/or gasket 20. After curing of the liquid foam, the male die 32 is raised from the female mold and the resulting finished loudspeaker cone assembly is removed. It will be appreciated that selected surface areas on the inner surface 22a of the suspension rim 14 may be provided with a color coating in a similar manner. In addition to providing a desired aesthetic appearance, the color coating further enhances the resistance of the suspension rim and gasket to adverse environmental conditions.

If desired, an air pressure conduit, such as indicated at 80 in FIGS. 4 and 5, may be secured at one end to the annular wall 54 of the male die 32 so as to communicate with the open

space above a cone body 12 supported between the female mold 30 and male die 32, as through an air passage 82 formed in the annular wall 54. The opposite end of the pressure conduit 80 is connected through a control valve (not shown) to a suitable air pressure source. Air pressure may be manually or automatically introduced into the annular chamber above the cone body 12 when the male die is raised from the female mold to assist in the release of the speaker cone assembly from the male die.

FIG. 8 illustrates another manner of mounting the loudspeaker cone 10 and basket 16 to a wall 84 of a speaker cabinet wherein the annular gasket 20 is interposed between the basket flange 16a and the wall 84 peripherally of a suitable opening 84a formed in the cabinet wall. Mounting screws, one of which is indicated at 86, are inserted through openings 78 spaced circumferentially about the basket flange 16a and secure the basket to the cabinet wall 84. In this manner, the gasket 20 serves to compensate for any irregularities or unevenness in the opposed surface of the speaker cabinet wall 84 and also acts as a shock absorber. A grill cloth (not shown) may be mounted on the speaker cabinet, such as within the opening 84a, to overlie the otherwise exposed speaker cone.

FIG. 10 illustrates an alternative speaker cone suspension rim, indicated at 14*, which has an annular gasket 20' formed integral thereon. The gasket 20 ^• differs from gasket 20 in that gasket 20' has greater radial width and has an annular recess 20'a formed therein to receive the annular flange 16c on the support basket 16.

The embodiment of FIG. 10 finds particular application where it is desired to mount the speaker cone and associated basket within a counterbore 88a in a speaker cabinet 88 through mounting screws (not shown) in similar fashion to FIG. 9. The gasket 20', together with the remainder of the suspension rim 14', effectively hides the basket 16 and provides a pleasing finished appearance, particularly when a grill cloth is not employed to overlie the loudspeaker cone.

Thus, in accordance with the present invention, a loudspeaker cone assembly is provided which includes a flexible suspension or supporting rim 14 having an integral annular gasket 20 and having high density closed-cell skin surfaces on the rim and gasket which are disposed on opposite sides of a lower density closed-cell internal core in an integral sandwich construction. The inner peripheral edge 18 of the suspension rim is impregnated into and integrally connected to the outer circumferential edge 12a of the cone body 12 either in overlapping relation on both sides of the peripheral edge of the cone body such that the outer edge of the cone is embedded within the suspension rim, as illustrated in FIG. 6, or by a butt-joint connection as described. Further, a selected color coating may be economically applied to selected exposed surface areas of the flexible mounting rim 14 and annular gasket 20. For example, when the speaker cone 10 and support basket 16 are mounted within a loudspeaker cabinet, such as within the counterbore 72a in the wall 72 as shown in FIG. 9 or within the counterbore 88a in the speaker cabinet wall 88

shown in FIG. 10, so that the outer exposed surfaces of the suspension rim and annular gasket are visible, color coating of the outer surfaces of the suspension rim and gasket may be desirable to provide a particular color scheme. The integral sandwich construction of the suspension rim .and gasket greatly improves the strength, flexibility and durability of the suspension rim and gasket over prior foam loudspeaker suspension rims.

A still further embodiment of the present invention is illustrated in FIGS. 11-17, and in particular FIGS. 11 and 12, wherein a loudspeaker cone assembly is indicated generally at 110. This loudspeaker cone assembly is similar to that described above with respect to FIGS. 1 and 2, except that it does not include the integral gasket 20. The loudspeaker cone assembly 110 includes a sound radiating cone body or element 112 and an annular suspension rim 114. The suspension rim 114 is integrally connected to an outer peripheral edge 112a of the cone body 112 and facilitates the mounting of the loudspeaker cone assembly to a speaker cabinet, as is known. In the illustrated embodiment, the cone body 112 has a generally frustoconical configuration having a concave curvilinear annular profile, as illustrated in FIG. 12. The illustrated cone body 112 has a circular outer peripheral edge 112a and an annular generally cylindrical neck portion 112b extending in the axial direction of the cone into which a voice coil or the like may be attached in a conventional manner. Alternatively, the cone body 112 may have an eliptical or square outer peripheral edge, with the peripheral wall to the

cone body being correspondingly modified from a general conical configuration to accomodate the shape of the selected outer edge.

In accordance with one feature of the alternative embodiment of the present invention, the annular suspension rim 114 is made from a plastic foam material such as that described above. The rim has an inner peripheral edge 118 which is integrally affixed to the outer free edge 112a of the cone body 112. As described above, the plastic foam annular suspension rim 114 is formed in a manner to establish high density closed-cell skin surfaces on both the inner and outer exposed surfaces 120 and 122, respectively, of the suspension rim. Here again, the high density closed-cell skin -surfaces 120 and 122 are formed in an integral sandwich construction on opposite sides of a closed cell cellular inner core having a lower density than the high density skin surfaces.

The suspension rim 114 defines a forwardly extending annular surface 124 which is of a generally uniform radius, as shown in the transverse cross section of FIG. 12, and is integral with the inner peripheral edge portion 118 and a generally radial outer peripheral flange portion 126 of the suspension rim 114. The forwardly extending annular surface 124 need not have a uniform radius, but may have a curvature which provides a variable rim thickness from its inner peripheral edge 118 to its outer free edge shown in FIG. 12 at the extreme terminus of outer peripheral flange 126. The plastic foam material from which the suspension or supporting

rim 114 is formed is the same closed-cell polyurethane foam described above.

The suspension rim 114 is formed by the low pressure casting described above, process wherein a predeterimend volume by weight of the liquid polyurethane foam is deposited into a tool indicated generally at 128 in FIG. 15, at atmospheric pressure. The liquid foam is preferably deposited in a continuous bead into an open angular cavity in a female mold portion 130 of the tool 128. The female mold 130 supports a cone body 112 with its outer peripheral edge 112a exposed within the annular cavity, after which a male die 132 is brought into cooperation with the female mold to establish a substantially closed annular chamber having a configuration identical to the desired configuration of the suspension rim 114. As before, the liquid foam is deposited in sufficient volume to totally fill the annular chamber when expanded and cured. The foam both impregnates the outer peripheral edge 112a of the cone body 112 to form an integral connection therewith. Upon expansion, the foam forms the high density closed cell outer skin surfaces 120 and 122 in an integral sandwich construction with a lower density cellular inner core. After curing, the suspension rim 114 and associated cone body 112 are removed from the tool 128 in substantially the form of the loudspeaker cone assembly 110. The suspension rim 114 is integrally connected with the outer edge 112a of the cone body 112. The suspension rim is preferably formed to a thickness in the range of approximately 0.015 to 0.070; the thickness selected depending upon the intended application

of the loudspeaker cone assembly being manufactured. Other rim thicknesses, or a rim having a variable thickness across its section, may be desirable for some applications. Referring now to FIGS. 13-17 for a more detailed description of the method for making the loudspeaker cone assembly 110, the female mold 130 is similar to that described above for the preferred embodiment of the invention. The difference is that female mold 130 does not include an apature for the integrated gasket 20. The mold 130 is made of a suitable rigid materialm, and has a base 134 having a flat base surface 134a adapted to be placed on a turntable of the like, such as is indicated at 136 in FIG. 13 coaxially with the axis of rotation of the turntable. In this embodiment, the base 134 is generally circular. However, where the suspension rim 114 is to have a noncircular configuration such as an elliptical or square plan configuration, the base 134 may have a corresponding outer periphery. The female mold 130 has an upper annular planar surface 134b formed parallel to the lower base 134a. An annular cavity or groove 134c of substantially uniform radius or semicircular transverse cross section is formed in the planar surface 134b and is radially intersected by an annular recessed plane or surface 134d of radial width substantially equal to the radial dimension of the annular flange 126 of the suspension rim 114. The inner peripheral boundary of the annular cavity 134c is intersected by an annular conical surface 134e which is concentric but depressed from a conical surface 134f having a contour

substantially equal to the contour of the cone body 112 adjacent to its outer free edge 112a. The annular surface 134f intersects an upper planer surface 13 g on the female mold and serves as a pilot surface to be engaged by the inner surface of the cone body 112 when placed on the female mold 130 during the manufacturing process. Here again, the conical surface 134f cooperates with a similarly configured and mutually opposed conical surface 154e on the male die 132 to secure and seal the outer peripheral edge portion of a cone body during forming of a suspension rim on the outer edge of the cone body.

A cone body locating post 138 is mounted on the base portion 134 of the female mold 130 in coaxial relation therewith. In this embodiment, the post 138 has a cylindrical outer surface 138a sized to received the neck portion 112b of a cone body 112. This part of the casting tool is similar to that described above, in FIG. 5.

When the female mold 130 is positioned coaxially on the turntable 136, as illustrated in FIG. 13, a plastic foam mixing and dispensing head 144 having a discharge nozzle 144a is brought into position overlying the female mold so that the discharge nozzle directly overlies the annular channel 134c. The mixing and dispensing head 144 is similar to that described above. The dispensing head 144 here again may be supported by an articulated support arm enabling movement of the dispensing head from the position spaced above the turntable to a position overlying the annular groove or cavity 134c and vice versa. If desired, a suitable release agent such as Teflon or paint may be wiped on to the female mold to lightly coat

the annular groove 134c and the adjacent recess surfaces 134d and 134e.

With the dispensing head 144 so positioned, a bead of liquid plastic foam is discharged into the annular groove 134c simultaneously with the rotation of the turntable 136 and a predetermined rotational speed in relation to rate of discharge from the dispensing head. This relationship is established so the predetermined volume by weight of plastic foam is deposited into the annular groove 134c in a continuous but not overlaping bead. The volume by weight of liquid plastic foam discharged into the annular groove 134c is substantially equal to the volume and weight of the foam in the suspension rim 114 on the completed loud speaker cone assembly 110. Conversly, the female mold 130 may be supported on a stationary support and the dispensing head 144 moved through a path overlying the annular groove or cavity 134c to effect discharge of a bead of foam about the full periphery of the groove or cavity.

The remainder of the method is identical to that described above for making the rim with the integral gasket.

The male die 132 is also substantially the same as that described above. As shown in FIG. 14, the male die is actuated along rod 158 which is guided through a guide bushing 160. The bushing 160 is supported on a bracket 162 which is itself supported between a pair of support posts 164a and 164b, as in the previous embodiment.

The connection between the annular suspension rim 114* and the periphery of the cone 112a is shown in the embodiments of FIGS. 16 and

17. In FIG. 16, the female mold has an aperture defined by surface 13 e which, in cooperation with the surface 154f on the male mold, provides a space which allows foam to surround and impregnate the edge of the loudspeaker cone 112a.

FIG. 17 illustrates and alternative, and often preferred, embodiment of the manner of attaching an annular suspension rim 114' to the outer peripheral edge 112a of a cone body 112 in a butt joint connection. In the embodiment of FIG. 17, structural elements similar to the elements of FIG. 16 are represented by corresponding primed referenced numerals. The angular recessed surface 134e on the female mold 130 and the angular recessed surface 154f on the male die 132 of FIG. 16 are eliminated. Instead, the lower surface of the annular wall 154* of the male die 132' has an annular or conical surface 154'e which intersects the inner margin of the convex surface 154'd. Similarly, the annular or conical surface 134'f on the female mold intersects the inner marginal edge of the concave cavity surface 134'c.

In FIG. 17, a pair of mutually opposed annular pinch beads 166 and 168 are formed, respectively, on the annular conical surface 134'f on the female mold 130' and on the opposed surface 154*e of the male die 132* . These beads pinch the cone body 112 near its outer peripheral edge 112a. The beads 166 and 168 are sized to pinch and seal the cone body 112, thereby preventing a flow of liquid foam upwardly into the cone wall but without crushing or damaging the cone wall. In other respects, the inner facing surfaces of the female mold 130• and the male die 132' are

substantially identical to the embodiment illustrated in FIG. 16.

The manner of depositing a bead of liquid plastic foam within the annular channel 134'c in a female mold 130' and bringing the male die and female mold into cooperating relation so as to fill the resulting substantially closed cavity with liquid plastic foam and with the annular surfaces 134'b and 154'c on the female mold 130' and male die 132' in abutting relation, is the same as described with respect to the preferred embodiment, described above. During expansion, the liquid foam impregnates the edge 112a of the cone body in a butt joint connection. Excess expansion of the plastic foam is accommodated by one or more release or escape vent grooves 165' .

As an alternative to the pinch beads 166 and 168, a pair of mutually opposed annular grooves could be formed in facing surfaces 134'f and 154'e in tfea female mold 130' and the male die 132', respect-T'^ly. The annular grooves could receive O-ring type resiliant seals for sealing relation with the cone body, if desired. Annular spring bias compression springs could also be used to seal the outer cone edge so as to prevent foam from contacting the cone body upwardly from the annular seal means. The latter alternative cone sealing means; namely, resiliant O-rings and spring bias compression rings, are particularly desirable where the tool 128 is used tc make different thickness suspension rims, or is used with different thickness cone bodies. When it is desired to increase the thickness of the suspension rim 114, annular shims may be mounted

between the abutting stop surfaces 134b and 154c in the female mold and male die.

Turning now to FIG. 15, the upper die 132 is moved into its operating position with the female mold 130 in a manner to prevent separation or lifting of the male die 154 from the female mold during expansion and carrying of the liquid plastic foam just as in the preferred embodiment, described above. With the male die 132 in operative relation with the female mold 130 and with the liquid plastic foam deposited within the rim cavity 134c as described, the closed tool 128 is heated to approximately 120°F so that the liquid foam within the annular cavity is subjected to approximately 120°F during expansion and curing of the foam. Heating of the female mold 130 and the male die 132 of the tool may be carried out by any suitable heating means. A color coating may be applied to a selected exposed surface area on the annular suspension rim 114 by the same methods and for the same purposes as described above for the preferred embodiment. Thus, in accordance with this embodiment, a loudspeaker cone assembly is provided which includes a flexible suspension or supporting rim 114 having high density closed-cell skin surfaces disposed on opposite sides of a lower density closed cell internal core in an integral sandwich construction. The suspension rim is impregnated into and integrally connected to the outer circumferential edge 112a of the cone body 112 either in overlapping relation on both sides of the peripheral edge of the cone body such

that the outer edge of the cone is embedded within the suspension rim, as illustrated in FIG. 16, or by a butt joint connection, as illustrated in FIG. 17. Further, a selected color coating may be economically applied to selected exposed surfaces of the flexible mounting rim. The integral sandwich construction of the suspension rim 115 greatly improves the strength, flexibility, and durability of the suspension rim over prior foam loudspeaker suspension rims.

While preferred embodiments of the loudspeaker cone assembly in accordance with the present invention and a preferred method of manufacture have been illustrated and described, it will be understood that changes and modifications may be made therein without departing from the invention and its broader aspects.

Various features of the invention are defined in the following claims.