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JPS5217732

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DESCRIPTION JPS5217732
■ Speaker's cone edge ■ Japanese Patent Application No. 46-49725 [phase] Application No. 46
(1971) published on July 5 48 to 16628 @ Akira 48 (1973) March 2 @ inventor 柘 保 吹 千 1 西
25 7 7 same Koizumi To Hirakata City Dejima Higashicho 3 13 ■ Applicants Sekisui Kogyo
Kogyo Co., Ltd. Kita-ku, Osaka Shikisocho 2 same Matsushita Electric Industrial Co., Ltd. Kadoma
City Oji Kadoma 1006 Detailed explanation of the invention This invention is a speaker Concerns
the corn edge of Conventionally, a frusto-conical diaphragm called a speaker cone is used for the
speaker, and further, the lateral edge of the speaker cone attenuates the lateral vibration of the
speaker cone, adjustment of the lowest resonance frequency, and the propagation of sound. A
band called "corn edge" is provided for this purpose. Conventionally, as a cone edge of a speaker,
a thick paper or a resin-processed cloth is used widely (although it has a drawback that
generation of sound due to split resonance and formability are bad, recently the defect that these
cone edges have is improved As a material, a corn edge made of polyurethane foam is used.
However, since there are open cells at the [111111] edge made of polyurethane foam, ventilation
also occurs between the front and back of the cone edge, and particularly in the piston area
vibration, sound pressure is generated. There is a drop in weight and an increase in weight to
reduce the air permeability to a density of about 0.1 to 0.2 r / C, which affects the speaker sound
pressure level and is not yet satisfactory. Furthermore, there is a drawback that the moldability is
also poor. The present invention has been made in view of the above-mentioned disadvantages of
conventional corn edges, and the gist of the invention is ethylene-vinyl acetate coweight having a
composition of 65 to 90% by weight of ethylene and 35 to 10% by weight of vinyl acetate. It
exists in the cone edge of the speaker which consists of a closed-cell foam of the mixed resin of
50 weight% or more of combined, and 50 weight% or less of polyethylene. In the present
invention, as the resin constituting the foam used for the cone edge of the speaker, at least 50%
by weight of an ethylene-vinyl acetate copolymer consisting of 65 to 90% by weight of ethylene
and 35 to 10% by weight of vinyl acetate A mixed resin with 50% by weight or less of
polyethylene is used. The closed-cell foam in the present invention may be prepared, for example,
by mixing a decomposition type foaming agent such as azodicarbonamide into the mixed resin
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and heating and foaming, or evaporating the mixed resin in the molten state such as
dichlorodifluoromethane. It can be easily manufactured by a conventionally known method such
as a method in which pressure is released and foaming is performed after pressing in the
foaming agent.
In addition, in order to foam the mixed resin so as to be completely closed cells and uniformly
fine cells, and to improve the heat resistance and molding processability of the resulting foam, it
is preferable to dik the above mixed resin before foaming. Preferably, they are crosslinked by
ionizing radiation such as an organic peroxide such as mill peroxide or electron beam. The
degree of crosslinking may be a degree of crosslinking such that the residual gel content by
xylene extraction is 35 to 95% by weight. [111111] EndPage: 1 As described above, in the
present invention, it is pliable to use a mixed resin of 50% by weight or more of ethylene-vinyl
acetate co-electromer of a specific composition ratio and 50% by weight or less of polyethylene.
Foam made of ethylene-vinyl acetate copolymer alone, which is a synthetic resin, becomes too
soft and there is also a problem with heat resistance, and there is a risk of deformation or the like
when used for a long time or under high temperature As such, even though the ethylene-vinyl
acetate copolymer has excellent acoustic properties as a speaker cone edge, it becomes difficult
to use practically, but mixing of 50% by weight or less of polyethylene These problems are
eliminated by Thus, the cone edge of the speaker of the present invention can be put to practical
use by taking advantage of the excellent acoustic properties of the ethylene-vinyl acetate
copolymer by using polyethylene together with the ethylene-vinyl acetate copolymer. It is
something that can be done. Next, an embodiment of the present invention will be described with
reference to the drawings. FIG. 1 shows the cone edge of the present invention, and 6 is a cone
edge formed of a closed-cell circular band-shaped foam having a thickness of 1.5 mm and an
inner diameter of 25 cIIL, said cone edge having a vinyl acetate content of 25 weight Of a mixed
resin of 75% by weight of ethylene-vinyl acetate copolymer and 25% by weight of low density
polyethylene, the expansion ratio of which is about 15 times. Reference numeral 61 denotes a
bulging portion provided at the center of the circular band foam so as to transmit a good
vibration. The above-mentioned cone edge is formed by heating and pressurizing a foam sheet.
FIG. 2 shows a speaker using the above-mentioned cone edge 6, wherein 1 is a frame, 2 is a yoke,
3 is a damper, 4 is a dust cap, and 5 is a polymethyl methacrylate foam board having an
expansion ratio of about 20 times. A cone, 7 is a voice coil, 8 is a magnet, and 9 is a gasket. The
side edge of the cone edge 6 is adhered to the end edge of the speaker cone 5 with an adhesive,
and the other side edge is held and fixed to the frame 1 by a gasket 9.
When the sound pressure-frequency characteristics were measured with the above-mentioned
speaker using the cone edge having the above-mentioned structure, the result as shown in FIG.
3A was obtained. Also, instead of the above-mentioned mixed resin of ethylene-vinyl acetate
copolymer and low density polyethylene [111111], thickness 1.5 im and inner diameter
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consisting only of ethylene-vinyl acetate copolymer with vinyl acetate content of 25% by weight
The sound pressure-frequency characteristics were measured using a speaker of the same
construction, using an annular cone-shaped foam of closed-cell circular ring-shaped foam having
an expansion ratio of about 15 times that of 25 to 35 as shown in FIG. 3B. The results were
obtained. In addition, the sound pressure-frequency characteristic is the speaker which is
identically constructed, using the cone edge of the ring-shaped polyurethane foam having a
thickness of 1.57 nm, an inner diameter of 25 c IrL and an expansion ratio of about 15 times that
of the open-celled annular foam. The results shown in FIG. 3C were obtained. As apparent from
the sound pressure-frequency characteristic curve in FIG. 3 (the speaker using the cone edge
according to the present invention has a so-called piston band of 50 to 1000 Hz as compared to
the speaker using the cone edge made of conventional polyurethane foam). There is an increase
in sound pressure level of about 2 db on average, and the sound effect is good. As described
above, since the corn edge of the present invention 6 is made of a foam of ethylene-vinyl acetate
copolymer resin or a mixed resin of ethylene-vinyl acetate copolymer and polyethylene, it is
possible to use a conventional polyurethane foam made of cone edge. In comparison, the heat
molding process can be performed in a very short time and easily. For example, in the case of a
foam comprising the ethylene-vinyl acetate copolymer resin or the mixed resin of ethylene-vinyl
acetate copolymer and polyethylene in the above-mentioned example, the heat molding time is
about 6 to 7 seconds. In the case of the polyurethane foam in the comparative example, it took
about 60 seconds. Furthermore, in the present invention, since the foam is closed cell, the
acoustic characteristics are improved as compared with the open-celled one such as the
conventional polyurethane foam. That is, in the case of an open-cell foam, when it is used as a
cone edge, aeration occurs between the front surface and the back surface bounded by the cone
edge, so that the sound pressure generated by the cone is faithful to the vibration of the electrical
system. However, in the closed-cell foam as in the present invention, the sound pressure level
may be cut because the air flow as described above is blocked. The cone edge made of
polyurethane foam also has a hygroscopicity and can absorb moisture in the air gradually.
[111111] EndPage: 2 The weight of the cone edge is also gradually increased to control the
inertia of the speaker. Although the adverse effect is exerted and the damping effect is
deteriorated and the acoustic characteristics are deteriorated, the cone edge of the present
invention is extremely low in hygroscopicity (about 15% foaming and about 0.13% Without
giving rise to differences in sound effects by speaker installed the environment for, can and
withstand without any long-term use that Kon'etsuji by moisture is undermined.
Also, in the present invention, by using a foam made of a mixed resin of ethylene-vinyl acetate
copolymer and polyethylene, compared to the case where a foam made of a single resin of
ethylene-vinyl acetate copolymer is used. The heat resistance is improved and the resin does not
become too soft, and it has appropriate q flexibility, has excellent properties as a cone edge, and
is practically problematic (it can be used). [111111]
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BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially cutaway perspective view showing a
cone edge of the present invention, FIG. 2 is a longitudinal sectional view of a speaker using the
cone edge of the present invention, and FIG. 3 is a speaker using the cone edge of the present
invention Fig. 18 shows sound pressure-frequency characteristic curves of a speaker using a
cone edge of and f [. 1・・・・・・フレーム、2・・・・・・ヨーク、3・・・・・・ダンパー
、4・・・・・・ダストキャップ、5・・・・・・スピーカーコーン、6・・・・・・コーンエ
ツジ、7・・・・・・ボイスコイノに8・・・・・・マグネット、9・・・・・・ガスケット。
[Phase] Citation of Japanese Literature 34-18107 [111111] EndPage: 3
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