Abstract:
A speaker driver has a detachable motor and basket to allow attachment or separation of the motor assembly from the basket assembly. Two embodiments are disclosed, a thread-on detachable motor and a bolt-on detachable motor.

Description:
RELATED APPLICATIONS 
   This application is a continuation of prior application Ser. No. 10/395,765, filed Mar. 24, 2003 now U.S. Pat. No. 7,301,490, which claims priority to U.S. provisional patent application 60/367,659 filed Mar. 26, 2002 entitled “Detachable speaker driver with bolt on motor” and U.S. provisional patent application 60/367,584 filed Mar. 26, 2002 entitled “Detachable speaker driver with screw on motor” 

   BACKGROUND 
   Speaker drivers convert an electrical signal to sound by inducing a current in a voice coil that is within a permanent magnetic field. The magnetic field produced by the voice coil current interacts with the permanent magnet field and causes movement of the voice coil. The voice coil is wound around a voice coil former and is attached to a cone which causes air movement and sound to propagate. A basket provides a frame to support the large diameter of the cone through a flexible surround. The former attached at the small end of the cone is stabilized by a spider, which allows movement along the axis of the cone and voice coil and restrains lateral motion. 
   Drivers are produced in a range of sizes. The smallest, a tweeter, is used for reproducing the high frequency end of the audio range. A midrange driver is used for reproducing the mid range of the audio spectrum. A woofer driver is used for the lower end of the audio spectrum. At the extreme low end of the audible range, and below, a sub-woofer driver is used. At lower audio frequencies more air volume needs to be moved. This requires a larger cone and a higher displacement in the motion of the cone. In order to move a large volume of air with a speaker driver mounted in a small enclosure, a large permanent magnet is needed and a high voice coil current. 
   The permanent magnet, T-yoke, and gap plate are referred to as the motor. In a conventional speaker driver, the motor is attached to the basket using screws that are inserted from inside the basket, underneath the cone, passing through holes in the basket and threading into the gap plate. Once the surround is attached to the basket, the removal of the motor is prevented because the attachment screws are no longer accessible. This arrangement dictates a specific sequence in manufacturing, where the motor must be attached to the basket prior to the voice coil, cone, and surround being assembled. 
   U.S. Pat. No. 4,234,766 “speaker assembly” issued to Cacho describes a speaker assembly with a detachable cone unit that may be removed from a base and replaced with a larger or smaller capacity speaker. This disclosure is directed to a small speaker and does not address the problem of removing the motor portion of the speaker driver from the basket after assembly. The detachable cone unit is a complete speaker driver including a cone, coil, and magnet. 
   Large drivers present manufacturing, shipping, and installation difficulties due to the heavy product. The cost is higher due to the large components. A substantial portion of the weight of the driver is represented by the motor. When damage occurs to the surround, cone, voice coil, or spider the driver must be shipped to a repair facility for replacement of the damaged parts. 
   SUMMARY OF THE INVENTION 
   A speaker driver has a detachable basket assembly and detachable motor assembly to allow attachment or separation of the motor from the basket after assembly of the completed driver. The basket and motor have corresponding attachment mechanisms that are engaged with each other to complete assembly of the speaker driver. This arrangement facilitates separate manufacturing of the motor and basket assemblies, either at two facilities or on two production lines. The detachable arrangement enables easier repair of a damaged driver, either during manufacture of the driver or a returned product. Reduced shipping costs are possible because a driver can be separated and the only section needing repair or replacement is shipped. 
   In one embodiment of the detachable driver, the motor is attached to the basket using a basket mounting ring attached to the basket and secured using externally accessible screws. The screws pass through holes in the basket mounting ring and thread into the gap plate. 
   In another embodiment of the detachable driver, the motor has a threaded member that engages a threaded section of the basket. The motor is rotated to screw it into the basket. Locking threads, thread locking liquid such as Loctite®, set screws, or elastomer locking ring can be used to prevent unintentional unthreading of the motor. The basket and gap plate can be manufactured with threaded sections, or an adapter plate with threads can be attached to the respective pieces to create the threaded mating regions. 
   Both embodiments of the detachable driver allow the motor and the basket to be produced as separate sub-assemblies and to be attached together into a complete speaker driver and to be detached from each other. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a cross sectional view of the bolt-on detachable driver with the motor detached. 
       FIG. 2  shows a cross sectional view of the assembled driver. 
       FIG. 3  shows an exterior side view of the bolt-on detachable driver. 
       FIG. 4  shows an exterior side view of the assembled driver. 
       FIG. 5  shows a gap plate for use with a detachable motor. 
       FIG. 6  shows a basket mounting ring for use with a detachable basket. 
       FIG. 7  shows a cross sectional view of the thread-on detachable driver with the motor detached. 
       FIG. 8  shows a cross sectional view of the assembled driver. 
       FIG. 9  shows an exterior side view of the detachable driver. 
       FIG. 10  shows an exterior side view of the assembled driver. 
       FIG. 11  shows a basket mounting ring for use with a thread-on detachable basket. 
       FIG. 12  shows a gap plate for use with a thread-on detachable motor. 
       FIG. 13  shows an alternate basket mounting ring. 
       FIG. 14  shows a gap plate adaptor to adapt a gap plate without threads to use in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   First Embodiment, Bolt-on Detachable Motor 
   Referring to  FIG. 1 , a cross sectional view, basket assembly  100  is comprised of basket  110 , cone  112  attached to basket  110  through surround  114 , voice coil former  118  around which voice coil  120  is wound, spider  116 , and basket mounting ring  125 . Spider  116  and surround  114  allow cone  112  and voice coil former  118  to move in and out while providing lateral support and alignment. Basket mounting ring  125  can be attached to basket  110  with screws  126 . Other configurations of attachment of mounting ring  125  to basket  110  are possible using screws or welding. Alternatively basket mounting ring  125  can be an integral part of basket  110 , formed as a single molded or machined part. Basket mounting ring  125  has an overhanging region. The basket can be formed by casting, machining, or a combination of casting and machining. 
   Motor  140  is comprised of T-yoke  144 , magnet  142 , and gap plate  147 , which has internal threaded holes. When assembled, coil  120  develops a force, that is transferred to voice coil former  118  and cone  112 , resulting from the interaction of signal current flowing through coil  120  and the magnetic field of magnet  142 . 
   Motor  140  is attached to basket assembly  100  by engaging gap plate  147  with basket mounting ring  125  and securing with screws  127 , which pass through basket mounting ring  125  overhanging region and enter threaded holes in gap plate  147 . A bolt is another name for a screw, both being described as a fastening rod with external threads and having a head used for applying rotating force to engage the threads into an internally threaded object. 
     FIG. 2  shows a cross sectional view of the assembled speaker driver.  FIG. 3  shows an exterior view of the motor and basket assembly prior to attachment.  FIG. 4  shows an exterior view of the assembled speaker driver. 
     FIG. 5  shows details of a gap plate with radially positioned internally threaded holes.  FIG. 6  shows details of a basket mounting ring. 
   In an alternative design, gap plate  147  can be formed with an overhang region and basket mounting ring  125  can be formed with internal threaded holes. 
   Second Embodiment, Thread-on Detachable Motor 
   Referring to  FIG. 7 , a cross sectional view, basket assembly  200  is comprised of basket  210 , cone  212  attached to basket  210  through surround  214 , voice coil former  218  around which voice coil  220  is wound, spider  216 , and basket mounting ring  222 . Spider  216  and surround  214  allow cone  212  and voice coil former  218  to move in and out while providing lateral support and alignment. Basket mounting ring  222  can be attached to basket  210  using adhesive or mechanical attachment devices such as screws or welding. Alternatively basket mounting ring  222  can be an integral part of basket  210 , formed as a single molded or machined part. Basket mounting ring  222  has threaded region  224 , which are internal threads. The threads are coaxial to the axis through the center of the speaker driver. The basket can be formed by casting, machining, or a combination of casting and machining. 
   Motor  240  is comprised of T-yoke  244 , magnet  242 , and gap plate  246 , which has threaded region  248 . When assembled, coil  220  develops a force, that is transferred to voice coil former  218  and cone  212 , resulting from the interaction of signal current flowing through coil  220  and the magnetic field of magnet  242 . 
   Motor  240  is attached to basket assembly  200  by engaging threaded region  248  with threaded region  224  and rotating Motor  240  relative to basket assembly  200 . Set screws, locking threads, or thread locking compound can be used to prevent unscrewing of motor  240 . 
     FIG. 8  shows a cross sectional view of the assembled thread-on speaker driver.  FIG. 9  shows an exterior view of the motor and basket assembly prior to attachment.  FIG. 10  shows an exterior view of the assembled speaker driver. 
     FIG. 11  shows details of a basket mounting ring.  FIG. 12  shows details of a gap plate. 
     FIG. 13  shows an alternate basket mounting ring for assemble with a basket. 
     FIG. 14  shows a gap plate adaptor to adapt a gap plate without threads to use in accordance with the present invention. 
     FIG. 12  shows detail of a gap plate with a threaded region, with M140×3 metric threading (140 mm diameter with a thread pitch of 3 mm) over an approximately 15 mm region. This results in a thread engagement of up to approximately 5 threads.  FIG. 14  shows a gap plate adaptor with a threaded region of 6.10 mm, providing at least 2 full threads. 
     FIG. 11  and  FIG. 13  show detail of mounting rings with threaded regions of 15.49 mm and 24.38 mm, respectively, to provide thread engagement of at least approximately 5 threads at a pitch shown of 3 mm.