Loudspeaker with integrated spider standoff ring

A loudspeaker is provided in which the outer diameter or foot of the spider is over molded with a standoff formed of a plastic material in an injection molding tool so that the spider and standoff form an integral unit. The standoff, in turn, is glued or otherwise affixed to the frame of the speaker to provide accurate centering of the voice coil relative to the magnetic gap of the motor structure.

FIELD OF THE INVENTION

This invention relates to loudspeakers, and, more particularly, to a loudspeaker in which the outer periphery of the lower suspension is integrally molded with a plastic ring or standoff, which, in turn, is mounted to the frame of the speaker.

BACKGROUND OF THE INVENTION

Loudspeakers generally comprise a frame, a motor structure, a diaphragm, a lower suspension or spider and a surround or upper suspension. In one type of speaker, the motor structure includes a permanent magnet sandwiched between a top plate and a back plate, with a pole piece centrally mounted on the back plate so that both the top plate and magnet are concentrically disposed about the pole piece. A magnetic gap is formed between the pole piece and top plate within which a voice coil is axially movable. Preferably, the voice coil consists of a hollow, cylindrical-shaped former having an inner surface and an outer surface which mounts a winding of wire.

The voice coil is mounted within the magnetic gap by the upper and lower suspensions and the diaphragm. One end of the diaphragm is connected to the surround, which, in turn, is mounted to the upper end of the frame. The spider is connected at one end to the frame at a point between its upper and lower ends. The free ends of the diaphragm and spider are mounted to the outer surface of the former of the voice coil and support it for axial movement within the magnetic gap.

In the course of operation of speakers of the type described above, electrical energy is supplied to the voice coil causing it to axially move within the magnetic gap. The voice coil, diaphragm, surround and spider collectively form a “moving assembly” which reciprocates as a unit with the excursion of the voice coil.

To achieve highest magnetic efficiency in a loudspeaker, the magnetic gap must have a small area with tight tolerances. If the voice coil deviates appreciably from its axial path within the magnetic gap, the voice coil can contact the pole piece or top plate of the motor structure causing significant damage to the speaker. The spider permits free travel of the moving assembly while maintaining it in a centered position with respect to the magnetic gap. During excursion of the voice coil, the spider “tightens up” or stretches to an outer limit of displacement thus limiting the overall extent of excursion permitted and protecting the moving assembly from contacting other parts of the loudspeaker. Additionally, the spider is primarily responsible for exerting a restoring force on the voice coil so that it moves toward the “rest” position within the magnetic gap, i.e. where the voice coil is located when the speaker is not operating, which has a direct impact on distortion performance.

In most speaker designs, spiders are geometrically formed pieces of a cloth-like material. A resin is applied to the material before the forming operation in an attempt to ensure that the final shape of the spider is maintained. The shape of the spider is important because it determines the centering and excursion control performance of the spider.

The spider is typically glued along its inner diameter to the outer surface of the former of the voice coil. A generally flat ring section or foot is formed along the outer diameter of the spider, which, in most speaker designs, is glued to the frame. Typically, these gluing operations take place within the loudspeaker frame as an aid to fixturing the various parts in the proper spatial orientation. The spider-to-frame glue joint is especially critical because it provides the reference point for centering and axial movement of the voice coil as well as the rest of the moving assembly.

For various reasons, but most often as a result of shipping and handling, the spiders which are provided by manufacturers for assembly in loudspeakers may not be flat. That is, the attachment foot along the outer diameter of the spider often does not lie in the same plane. This geometric deformation of the spider foot not only compromises performance of the spider, but it can adversely affect the glue joint between the spider foot and frame. While some areas of the foot contact the frame and can be securely glued in place, other areas of the foot may be slightly separated from the frame resulting in a less glue-foot contact than is desired.

The problem of attaching a geometrically deformed spider foot to the speaker frame cannot be satisfactorily overcome by merely pressing the foot down onto the frame during assembly. Typically, a bead of glue is first applied to the frame and then the spider is brought into contact with the glue. Due to the nature of the glues used for the spider foot-frame joint connection, applying pressure to the foot to force it down onto the frame during assembly would cause the glue on the frame to “squirt out” from between the spider foot and frame. The displaced glue may cover the spider, thus comprising its performance, or spill onto other areas of the speaker. As a result, a relatively thick glue bead is typically used to try to ensure all areas of the spider foot are bonded to the frame. However, the glue bead itself can create geometrically uneven areas along the spider foot, particularly if the glue bead is applied unevenly to the frame.

Another problem with prior art speakers involves failure of the joint connection between the spider foot and frame. When the moving assembly approaches the limits of its excursion, a force is exerted on the spider-to-frame glue joint as the spider acts to pull the moving assembly back toward the neutral position. Since the spider is made of a cloth-like material, this glue joint is susceptible to “peel.” Starting at the inner diameter of the frame glue joint, it has been found that the spider can gradually peel away from the surface of the frame particularly in high excursion speakers such as subwoofers. If the spider detaches in one area, it's just a matter of time until the loudspeaker fails.

SUMMARY OF THE INVENTION

This invention is directed to a loudspeaker in which the foot of the spider is over molded with an annular plastic ring or standoff in an injection molding tool so that the spider and standoff form an integral unit. The standoff, in turn, is glued or otherwise affixed to the frame of the speaker to provide accurate centering of the voice coil relative to the magnetic gap of the motor structure.

This invention is predicated on the concept of ensuring that the outer diameter of the spider is flat and can be securely mounted to the speaker frame. As noted above, the spider foot is over molded with a plastic ring or standoff to form an integral unit. During the molding operation, the spider is clamped in a flat position by an injection molding tool to ensure its dimensional and geometric integrity. This molding operation further provides for precise concentricity of the standoff and spider. The standoff can then be glued or otherwise affixed to the frame to obtain a secure connection at that joint, and to accurately locate the spider so that the voice coil is centered relative to the magnetic gap of the motor structure of the speaker.

In one embodiment, the standoff is glued to the speaker. Alternatively, metal pins are placed in the injection molding tool and over molded with the standoff and spider foot. A portion of these metal pins protrude from the bottom surface of the standoff and are inserted within corresponding locator holes formed in the frame to properly position the spider. In another embodiment, the injection molding tool may be configured to form integral plastic pins extending from the bottom surface of the standoff which function in the same fashion as the metal pins noted above.

Using metal or plastic locator pins, the standoff is glued in position to the frame. The assembler may press down on the standoff during the gluing operation to ensure that a tight joint is created with the glue evenly distributed because the spider foot is embedded in the standoff and remains out of contact with the glue. As an alternative to a glue attachment, the standoff may be formed with a number of internal locator holes extending upwardly from its bottom surface which align with holes in the frame. Screws are then inserted through the frame holes into the standoff to secure it in place without the use of glue.

The use of a plastic ring or standoff to secure the spider foot allows for flexibility in the type of frame which can be used. Typically, speaker frames have a continuous spider plateau or seat which supports and connects to the spider foot. With the standoff of this invention, a frame having spaced arms may be employed with each arm being formed with a hole to receive a screw for attachment to the standoff as noted above. Alternatively, the standoff may be glued to the frame arms.

Another advantage of the standoff of this invention is that other elements may be over molded with the standoff and spider foot for mounting to the frame. For example, electrical terminals may be inserted in the injection molding tool and integrally attached to the standoff. When standoff is mounted to the frame, such terminals may be used to receive lead wires from the voice coil.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring initially toFIGS. 1 through 4, a loudspeaker10is illustrated which, inFIG. 1, includes a standard, prior art connection between the spider and frame, as described below, and inFIG. 3an improved means of connecting the spider to the frame according to the present invention.

The speaker10generally comprises a motor structure12, a frame14mounted to the motor structure12, a diaphragm16, a lower suspension or spider18and an upper suspension or surround20. Conventionally, the motor structure12includes a top plate22and a back plate24which are spaced from one another and mount a permanent magnet26between them. A pole piece28is integrally formed with and extends upwardly from the back plate24into a central bore30formed in both the magnet26and top plate22. A magnetic gap32is formed between the top plate22and the pole piece28. A voice coil34is also provided which includes a hollow, cylindrical-shaped former36having an inner surface38and an outer surface40which mounts a wire winding42. The former36is concentrically disposed about the pole piece28, and the voice coil34is axially movable within the magnetic gap32during operation of the speaker10.

The voice coil34is held in place with respect to the pole piece28by the diaphragm16, spider18and surround20. The inner diameter of the diaphragm16is affixed to the former36by adhesive or the like, and its outer diameter connects to the surround20. The surround20, in turn, is mounted to the upper end44of the frame14as shown. In the prior art speaker10shown inFIGS. 1 and 2, the spider18is connected to the outer surface40of the former36along its inner diameter, and a foot46formed at the outer diameter of the spider18is glued directly to a seat or spider plateau48formed in the frame14.

A dust cap50is mounted to the diaphragm16in position to overlie the voice coil34and pole piece28in order to protect such elements from dirt, dust and other contaminants. A dust cap cavity is therefore formed in the area defined by the lower portion of the diaphragm16, the dust cap50, the voice coil34and the pole piece28. In response to the input of electrical energy to the wire winding42, the voice coil34is moved axially with respect to the fixed motor structure12. Because the diaphragm16, spider18, surround20and dust cap50are operatively connected to the voice coil34, such elements also move with the excursion of the voice coil34forming a moving assembly.

Referring now toFIGS. 3 through 13, the loudspeaker10is depicted with alternative embodiments of a novel means of mounting the spider foot46to the frame14according to this invention. Each embodiment is described separately below with reference to specific Figs., it being understood that structure of the loudspeaker10common to each embodiment, and to the prior art speaker shown inFIGS. 1 and 2, is given the same reference numbers throughout.

In the embodiment ofFIGS. 3 and 4, the foot46of spider18is over molded with an annular plastic ring or standoff56to form an integral joint connection between the two. For purposes of this discussion, the term “over molded” refers to a process in which an item already formed is placed in a mold and then becomes integrally attached to an object formed in the mold. The spider foot46is placed in a plastic injection molding tool (not shown) where it is clamped in place in a flat position, and then molten plastic is injected into the mold. The molten plastic flows over and around the spider foot46and cools to form the standoff56, which because of the plastic injection molding tool, is precisely concentric to the foot46. Consequently, the foot46of the spider18is concentrically embedded within the standoff56forming a joint connection which is not susceptible to peeling or other break down of the layers of the cloth-like material forming the spider18.

In this embodiment, the standoff56is affixed to the spider plateau48with a bead of glue. Although the bottom surface of the standoff56is substantial planar, in the event of any irregularities between the standoff56and spider plateau48the standoff56may be pressed downwardly against the plateau48and the bead of glue thereon. Even if the glue squirts out from between the standoff56and plateau48, it will not cover any portion of the spider foot46or other area of the spider18since the spider foot46is spaced from the bottom surface of the standoff56as best seen inFIG. 4.

The embodiments of this invention shown inFIGS. 5-8depict related, alternative arrangements for locating the standoff56in the proper position along the spider plateau48. InFIGS. 5 and 6, the standoff56is provided with a number of circumferentially spaced metal pins58, two of which are shown in the drawings, each having a head section60embedded within the standoff56and a stem section62, a portion of which protrudes from the bottom surface of standoff56. The metal pins58are placed in the injection molding tool with the spider18and over molded with the standoff56. Each pin58is received within a locator hole64formed in the spider plateau48which ensures that the spider18is placed in the proper position to center the voice coil34within the magnetic gap32.

Alternatively, as shown inFIGS. 7 and 8, plastic pins66are integrally molded in the standoff56at spaced intervals along its circumference. The injection molding tool is formed with wells (not shown) to form the pins66during the molding operation. These pins66are inserted within the locator holes64in the spider plateau48in the same manner and for the same purpose as the metal pins58ofFIGS. 5 and 6. In each of the embodiments ofFIGS. 5-8, the standoff56is affixed to the spider plateau48by glue.

Referring now toFIGS. 9 and 10, the standoff56is shown with a number of spaced holes68which extend from its bottom surface to a location short of where the spider foot46is embedded. Each hole68in the standoff56aligns with a locator hole64in the spider plateau48and receives a screw70. Each screw70extends from the underside of the spider plateau48, through one of the locator holes64and then threads into a hole68in the standoff56. The holes68may be smooth, in which case self-tapping screws70are used, or the holes68may be molded with internal threads (not shown). In this embodiment, no glue is need to secure the standoff56to the spider plateau48.

In each of the embodiments of speaker10shown inFIGS. 1-10, the spider plateau48of the frame14is formed as a continuous circular surface. This construction of the spider plateau is essential in prior art designs because such surface formed the only point of attachment of the spider18to the frame14. The standoff56of this invention allows for more flexibility in the design of frames which may be employed, as seen inFIGS. 11 and 12. In that embodiment, a frame72is shown which includes a number of circumferentially spaced arms74each extending from the top plate22of the motor structure12to an upper rim76of the frame72. A seat78is formed in each arm74having a locator hole80which aligns with a hole82formed in the standoff56. A screw70is provided at each seat78to attach the standoff56to the frame arms74in the same manner as the standoff56is attached inFIGS. 9 and 10. Because the spider foot46is embedded in the standoff56, which is a rigid plastic structure, there is no need for continuous attachment along the entire periphery of the foot46or standoff56to the frame72.

It is also contemplated that use of the standoff56of this invention may permit other speaker elements to be over molded in the injection molding tool, as desired. For example, one or more electrical connectors84may be embedded in the standoff56to receive the lead wires86of the speaker10as shown inFIG. 13. This eliminates the need to mount the connectors84to another part of the speaker10in a separate assembly operation, and provides a convenient and secure connection for same.

While the invention has been described with reference to a preferred embodiment, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. For example, in the embodiments ofFIGS. 5-8, metal or plastic pins58,66are employed to locate the standoff56on the spider plateau48where it is glued in place. It should be understood that screws could be employed instead of glue to secure the standoff56to the spider plateau48. Additionally, the standoff56is depicted as being attached by screws70to the frame arms74in the embodiment ofFIGS. 11 and 12. If desired, the standoff56could be attached by gluing to the seat78of each arm74thus eliminating the screws70.

Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.