Open-type magnetic circuitry of loudspeaker

Electrical audio signal processing systems and devices – Electro-acoustic audio transducer – Electromagnetic

Reexamination Certificate

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Details

C381S403000, C381S405000, C381S407000, C381S419000, C381S420000, C381S400000

Reexamination Certificate

active

06584209

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an open-type magnetic circuitry of loudspeaker, and more particularly to a magnetic circuitry of loudspeaker enabling quick dissipation of internal heat produced during operation of the loudspeaker, so that the loudspeaker is free of accumulated heat and deformed or separated diaphragm due to operation for a prolonged time and could always maintain good sound quality.
As a component in a stereo sound system, a loudspeaker, or speaker, is actually a transducer that converts electrical energy into sound energy. Therefore, the loudspeaker has considerable influence on the quality of sound produced by the stereo sound system. Generally, a magnetic circuitry for a loudspeaker to operate includes at least a magnet, a voice coil, a diaphragm, a frame, an upper yoke (or ring-shaped yoke), and a lower yoke (or T-shaped yoke). According to a position of the magnet in the loudspeaker, loudspeakers are divided into two types, namely, internal-magnet and external-magnet speakers.
FIG. 1
is a sectioned side view of a conventional internal-magnet loudspeaker. The magnetic circuitry for this type of loudspeaker mainly includes a substantially U-shaped yoke
60
made of a magnetic conductive material, or soft iron, with an upper edge of the U-shaped yoke
60
bent radially inward, a magnet
61
positioned in the yoke
60
, a bobbin
63
in a predetermined length provided above the magnet
61
to project from the upper edge of the yoke
60
, and a voice coil
62
wound around the bobbin
63
to connect to a root portion of a diaphragm
64
without contacting with the magnet
61
at all. When the loudspeaker operates in a normal manner, the voice coil
62
is caused to move back and forth and therefore forces the diaphragm
64
to move back and forth at the same and thereby produces sound waves. Such continuous vibration (or work) of the voice coil
62
produces heat that accumulates in the U-shaped yoke
60
. Since the voice coil
62
of an internal-magnet speaker is in a space enclosed by the U-shaped yoke
60
and a damper
65
, the produced and accumulated heat is not easily diffused to dissipate. When the internally produced heat accumulates to a certain extent, it results in magnetic attenuation, particularly when a neodymium alnico magnet is used for the loudspeaker, and accordingly deteriorated sound quality. Another problem with the internal-magnet loudspeaker concerns the diaphragm
64
. The diaphragm
64
is made of a resin material that tends to become softened at a raised temperature. A softened diaphragm
64
has shortened usable life and results in noises and undesired resonance during sound production. All these factors result in difficulties in designing a high-power loudspeaker and increased manufacturing cost thereof.
FIG. 2
is a sectioned side view of a conventional external-magnet loudspeaker. The magnetic circuitry for this type of loudspeaker includes a lower yoke
70
substantially in the shape of a reverted letter “T”, a bobbin
71
formed from a central vertical portion of the T-shaped lower yoke
70
, a voice coil
72
wound around the bobbin
71
, a ring-shaped magnet
73
put around a lower part of the bobbin
71
, and a damper
75
and a diaphragm
74
sequentially provided above the voice coil
72
. As in the case of the internal-magnet loudspeaker, the voice coil
72
is in a space enclosed by the ring-shaped magnet
73
and the damper
75
, resulting in accumulated heat in the magnet
73
that in turn causes magnetic attenuation and softened diaphragm
74
to increase difficulties in designing a high-power loudspeaker and manufacturing cost thereof.
SUMMARY OF THE INVENTION
It is therefore a primary object of the present invention to provide an open-type magnetic circuitry of loudspeaker that eliminates the problem of accumulated heat in a closed internal space of the loudspeaker.
Another object of the present invention is to provide an open-type magnetic circuitry of loudspeaker that allows a user to see from outside of the loudspeaker an entire working process of the magnetic circuitry, that is, the movement of the voice coil, giving the loudspeaker a novel appearance showing a high-tech touch.
To achieve the above and other objects, the open-type magnetic circuitry of loudspeaker of the present invention includes a lower yoke having a central portion upward projected to form a bobbin, a magnet positioned on top of the bobbin, a voice coil wound around the bobbin and the magnet, and a diaphragm connected at a root portion to the voice coil. The magnetic circuitry of loudspeaker is characterized in that the lower yoke is provided at an upper side surrounding the bobbin with a plurality of radially equally spaced supporting posts, a top end of which being higher than at least a bottom side of the magnet, and that a ring-shaped upper yoke having a central hole is covered onto the top end of the supporting posts, such that heat produced by the voice coil during working could quickly dissipate via a space between the upper and the lower yokes. Since no heat would accumulate in the loudspeaker, the loudspeaker could always maintain good sound quality.


REFERENCES:
patent: 2727949 (1955-12-01), Lokkesmoe
patent: 4427845 (1984-01-01), Yoshida
patent: 5740265 (1998-04-01), Shirakawa
patent: 5912978 (1999-06-01), Eastty et al.
patent: 6175637 (2001-01-01), Fujihira et al.
patent: 6269168 (2001-07-01), Tagami
patent: 6359996 (2002-03-01), Ohashi

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