Electrical audio signal processing systems and devices – Electro-acoustic audio transducer – Electromagnetic
Reexamination Certificate
2000-01-11
2004-05-18
Ni, Suhan (Department: 2643)
Electrical audio signal processing systems and devices
Electro-acoustic audio transducer
Electromagnetic
C381S412000, C381S413000
Reexamination Certificate
active
06738490
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of loudspeakers, and more particularly to loudspeakers with independent magnetic dampening and excursion control.
BACKGROUND OF THE INVENTION
Conventional loudspeakers produce audible sounds by displacing air via the movement of a diaphragm. Specifically, the diaphragm is attached to and moves under the control of a voice coil, through which electric currents associated with the sounds to be reproduced are driven. The voice coil is disposed in an annular air gap defined by a pole assembly. The pole assembly includes a permanent magnet that provides radial flux in the air gap. Current through the voice coil interacts with this flux to provide axial forces on the coil and thereby displace the coil and attached diaphragm.
The displacement or movement of the voice coil is controlled by the magnitude and direction of current in the coil and the resulting axial forces. If sufficiently high current is provided to the coil, the movement of the voice coil is limited only by the construction of the loudspeaker. Specifically, the outward movement is limited by the diaphragm or spider reaching their respective full extension. The inward movement is similarly limited by the diaphragm or spider reaching full excursion and additionally through direct contact with the pole assembly by the dust cap or the spider, or by the voice coil contacting the backplate. Over a period of time, the repeated use of these components of the loudspeaker to limit the movement of the voice coil can have significant and detrimental effects on the component parts, as well as the overall performance of the loudspeaker.
Thus, an important aspect of the present invention is, to substantially reduce, if not eliminate, the use of the component parts of the loudspeaker as movement limiters. Of course, the present invention achieves the stated goals without negatively affecting the overall performance of the loudspeaker.
SUMMARY OF THE INVENTION
Accordingly, it is a primary object of the present invention to provide an apparatus and related method for overcoming the limitations of the prior art, and to substantially reduce, if not eliminate, detrimental contact between or over extension of component parts of a loudspeaker.
Another object of the present invention is to provide an apparatus and related method for utilizing magnetic flux to provide independent dampening and excursion control.
Yet another object of the present invention is to utilize magnetic flux to limit the movement of a loudspeaker voice coil to prevent detrimental contact between or over extension of the component parts of the loudspeaker.
Still another object of the present invention is to utilize magnetic flux to maintain the component parts of the loudspeaker such as a diaphragm and/or a spider in proper position thus reducing deformation, fatigue or mechanical failure over an extended period of time.
Additional objects, advantages, and other novel features of the invention will be set forth in part in the description that follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned with the practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects, and in accordance with the purposes of the present invention as described herein, there is provided a loudspeaker with independent magnetic dampening and excursion control for generating sound from an electrical current. The loudspeaker includes a basket, a voice coil through which the current flows, a diaphragm and a spider attached to the voice coil and basket, a pole assembly for locating the voice coil, a permanent magnet for producing a magnetic field interacting with the current to produce a movement of the voice coil, and first and second magnets that produce magnetic flux forces that provide independent dampening and excursion control. The effect of the dampening and limiting magnets is to substantially reduce, if not eliminate, detrimental contact between or over extension of the component parts of the loudspeaker.
More specifically, the pole assembly includes a pole yoke supported by a backplate, and a top plate. The pole yoke extends from the backplate through the permanent magnet and the top plate thereby defining the inner diameter of an annular gap within which the voice coil moves. The top plate and permanent magnet define the outer diameter of the gap.
Preferably, the first dampening magnet is supported by the pole yoke and the second dampening magnet is supported by and moves in concert with the voice coil. As the voice coil moves within the annular gap, the interaction of the magnetic flux forces between the dampening magnets provides a repelling or dampening force that increases as the distance between the magnets decreases. Of course, the overall make up and strength of the dampening magnets and necessarily the resulting forces are selectively controlled dependent upon the desired result.
Depending upon the placement of the second magnet relative the first magnet, the resulting dampening force may be used to prevent movement in either of two distinct directions, i.e., outward or inward. For example, an adapter mounted to an end of the voice coil may be used to support the second magnet between the first magnet and a dust cap, thus limiting the movement of the voice coil in the first, inward direction. Alternately, the adapter may be modified to support the second magnet between the first magnet and the backplate, thus limiting the movement of the voice coil in the second, outward direction.
In accordance with another important aspect of the present invention, the loudspeaker may include a third magnet to provide an additional dampening force. The forces of the first and second dampening magnets and the additional force of the third dampening magnet act to limit the movement of the voice coil independent of the direction of its movement.
It is contemplated that the third magnet may be positioned a fixed distance from the second magnet and supported by the voice coil, thus further limiting the movement of the voice coil in the outward direction. Alternatively, the third magnet may be positioned a fixed distance from the first magnet and supported by the pole assembly, thus further limiting the movement of the voice coil in the inward direction.
In addition to limiting the movement of the voice coil during use the first and second dampening magnets, and the third dampening magnet in the alternate embodiment, act to maintain the component parts of the loudspeaker such as the diaphragm and/or the spider in proper position. Advantageously, maintaining the parts in proper position helps prevent deformation from repeated over-extension and/or component-component contact thus insuring that maximum and uniform efficiencies are maintained over an extended service life interval of the loudspeaker.
In accordance with the method of the present invention, a magnetic field is generated within the loudspeaker by the permanent magnet which interacts with the current flowing through the voice coil to move the voice coil. The movement of the voice coil, however, is, limited by magnetic flux forces generated by dampening magnets. Advantageously, the dampening magnets substantially reduce/prevent fatigue of the component parts of the loudspeaker and detrimental contact between the voice coil and its supporting parts and the remaining component parts of the loudspeaker.
The method of limiting the movement of a voice coil within a loudspeaker may include the additional steps of dynamically supporting a first magnet for movement with the voice coil, and statically supporting a second magnet with the pole assembly in order to generate the desired magnetic flux forces.
Still other objects of the present invention will become apparent to those skilled in this art from the following description wherein there
King & Schickli PLLC
Ni Suhan
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