Method for manufacturing diaphragm for loudspeaker

Details Method for manufacturing diaphragm for loudspeaker Method for manufacturing diaphragm for loudspeaker

2000-05-22

2003-09-30

Tentoni, Leo B. (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

Direct application of electrical or wave energy to work

Plasma

C264S129000, C264S320000, C264S328100, C427S536000

Reexamination Certificate

active

06627140

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to the field of methods for manufacturing speaker diaphragms employed in a range of audio equipment, speaker diaphragms made using such methods, and speakers employing such diaphragms.
BACKGROUND OF THE INVENTION
The configuration of a conventional speaker is described with reference to its sectional view in
FIG. 7. A
magnetic circuit
15
includes a magnet
15
a
, lower plate
15
b
, and upper plate
15
c.
A frame
16
is bonded to the magnetic circuit
15
. A damper
17
holds a voice coil
18
. The outer circumference of the damper
17
is bonded to the frame
16
, and its inner circumference is bonded to the voice coil
18
whose coil
18
a
is embedded in the magnetic gap
15
d
of the magnetic circuit
15
.
A speaker diaphragm
19
is bonded to the frame
16
via an edge
19
a
bonded to its outer circumference, and the inner circumference of the speaker diaphragm
19
is bonded to the voice coil
18
. This speaker diaphragm
19
is generally made mainly of paper or thin resin plates, which is selected depending on the need for weather resistance and required acoustic characteristics.
A method for manufacturing a typical speaker diaphragm
19
made of resin, more specifically a polyolefin polyethylene speaker diaphragm, is described next.
A speaker diaphragm made of polyethylene, which is a type of polyolefin system, has low material density which gives the speaker diaphragm a low mass. It also has relatively large internal loss with respect to mechanical vibration, which improves the frequency characteristic of the speaker. Accordingly, polyethylene speaker diaphragms are commonly used in speakers. However, a polyethylene speaker diaphragm has low adhesivity, making it essential to activate the surface of the speaker diaphragm to improve bonding strength.
Common conventional methods for activating the surface of the speaker diaphragm
19
include the application of primer after corona discharge, and surface treatment of the speaker diaphragm
19
by the gas plasma treatment method using parallel flat electrodes
20
and
21
as shown in
FIGS. 8 and 9
.
However, the conventional surface activating technology for treating the surface of the speaker diaphragm has the following disadvantages.
As for the method involving surface activation by corona discharge and primer application, a large processing apparatus is required because only the areas close to electrodes
20
and
21
are activated if the electrodes are small, causing a deviation in wettability of the speaker diaphragm
19
. In addition, this treatment takes about 30 seconds for one face of the speaker diaphragm
19
. The workpiece then needs to be flipped or the speaker diaphragm
19
needs to be flipped to apply treatment to the other face, requiring more than one minute for each piece and seriously degrading productivity.
Furthermore, it has another problem that the speaker diaphragm may deform during corona discharge due to high temperatures above 80° C. in the reactive chamber.
The method using the parallel flat electrode
20
in
FIG. 8
also creates the risk of heat deformation and low productivity of the speaker diaphragm
19
. The method using the parallel flat electrode
21
in
FIG. 9
may also cause low productivity. If more than one speaker diaphragm
19
is handled at once to solve the problem of low productivity, it may still have the risk of heat deformation, and significant difference in wettability between the periphery and the center.
The present invention aims to solve these disadvantages. By offering a method for manufacturing a speaker diaphragm assuring stable quality and high productivity, the present invention offers a speaker diaphragm with stable quality and a speaker employing such diaphragm.
SUMMARY OF THE INVENTION
To solve the conventional disadvantages, the method for manufacturing a speaker diaphragm of the present invention involves the next steps. A resin speaker diaphragm made by injection molding or sheet forming by heating is disposed in a reactive chamber, and electrodes are provided outside of the reactive chamber. Plasma is applied to the speaker diaphragm to activate the surface. Provision of electrodes outside the reactive chamber enables to keep the temperature of the reactive chamber below the heat deformation temperature of the speaker diaphragm during plasma treatment. Accordingly, heat deformation of the speaker diaphragm is preventable and defects caused by heat deformation can be suppressed.


REFERENCES:
patent: 60048696 (1985-03-01), None
patent: 5-168903 (1993-02-01), None
patent: 6-225388 (1994-08-01), None
Japanese search report for PCT/JP99/03140 dated Aug. 24, 1999.
English translation of Form PCT/ISA/210(Aug. 24, 1999).

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