Method for producting strip cable

In the present invention, a method for producing strip cable provided on its periphery with the meshed conductive metal or the woven fiber coated with a conductive material. The method produces a flat cable having multiple signal conductive members encase in an insulating material with the mesh metal outer layer fastened to the outer surface of the insulating material. The strip cable is thus protected from electromagnetic waves. Since the strip cable fails to function as an antenna, the electronic equipment connected to the strip cable does not require a shielding material. By using the strip cable provided with a electromagnetic-shielding effect, electromagnetic waves can be avoided easily and inexpensively. In addition, the varieties of design can be allowed for the electronic equipment.

BACKGROUND OF THE INVENTION 
The present invention relates to a strip cable comprising multiple signal 
conductors and being connected to electronic equipment. 
Since the strip cable receives and transmits a weak control signal for 
driving and controlling the electronic equipment connected to the strip 
cable, signal conductors composing the strip cable have a small diameter 
and high impedance. The strip cable is a bundle of long, thin signal 
conductors because it must connect electronic equipment scattered at 
various distances. The strip cable may function like an antenna and 
receive and send electromagnetic noise. 
Conventionally, the strip cable is positioned far from the electronic 
equipment which may be a source of electromagnetic noise and each piece of 
electronic equipment connected to the strip cable is electromagnetically 
shielded, so that the strip cable will not pick up electromagnetic noise. 
However, the above solution is insufficient and the following problem still 
remains. 
Since the strip cable must be positioned far from the electronic equipment 
such as an electronic typewriter or a printer, the design of the 
electronic equipment connected to the strip cable is limited. 
These days, the electronic equipment increasingly use microcomputers. To 
increase the processing speed of the microcomputers, the clock frequency 
is set at high a value. As a result, the number of electromagnetic-noise 
sources as well as the amount of electromagnetic noise increase. The cost 
for shielding the sources is also increased. 
SUMMARY OF THE INVENTION 
Consequently, the object of the present invention is to provide a strip 
cable that is easily and inexpensively shielded from electromagnetic noise 
and that allows a variety of the electronic equipment designs. 
This object is achieved by a strip cable that is resistant to 
electromagnetic noise. The strip cable comprises a plurality of signal 
conductors coated with insulating material, and a meshed outer layer 
fastened to an outer surface of the insulating material. The meshed outer 
layer is made of conductive material for reducing electromagnetic noise on 
the signal conductors.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As shown in FIG. 1, a flat cable 1 comprises eight copper signal conductors 
3 arranged in parallel, an insulating layer 5 for insulating the signal 
conductors 3, and a meshed metal 7 adhered onto the outer periphery of the 
insulating layer. The meshed metal 7 is composed of copper wire with a 
linear diameter of 0.02 mm to 0.2 mm. 
The flat cable 1 is manufactured as follows: 
First, the signal conductors are arranged in parallel on the same plane of 
a strip-shaped metal mold. Insulating resin such as polyvinyl chloride, 
polyester or polyimide resin is then poured into the metal mold to form 
the insulating layer 5. After curing, the insulating layer 5 including the 
signal conductors 3 is extracted from the metal mold. Subsequently, a 
low-melting film composed of polyvinyl acetate, ethylene-vinyl acetate 
copolymer, phenoxy resin, or the like is adhered onto the outer periphery 
of the insulating layer 5, and the meshed metal 7 is formed on the surface 
of the film. Finally, by heating, the low-melting film is melted to join 
the meshed metal 7 with the outer periphery of the insulating layer 5. The 
meshed metal 7 can be coated with a low-melting film in advance, and, by 
heating, the meshed metal 7 can be adhered to the outer periphery of the 
insulating layer 5. At the same time, the low-melting film can be melted 
to form an insulating membrane on the meshed metal 7. 
Alternatively, the opposite sides of the signal conductors 3 arranged in 
parallel on the same plane can be adhered to two insulating films like a 
sandwich. The meshed metal 7 can be adhered via the low-melting film onto 
the insulating films. 
The flat cable 1 has the meshed metal 7 on its outer periphery, but the 
linear diameter of the meshed metal 7 is 0.02 mm to 0.2 mm. The meshed 
metal 7 is so thin that the flat cable 1 is flexible. Like the flat cable 
without the meshed metal 7, the flat cable 1 is compact and light-weight. 
Moreover, the flat cable 1 contributes to the decrease of wrongly placed 
wirings, and has high reliability. The flat cable 1 is connected via 
connectors or solders on both ends to the electronic equipment to be 
wired. 
Since the flat cable 1 comprises the meshed metal 7 of copper which 
conducts electricity on its outer periphery, the signal conductors 3 are 
electromagnetically shielded from the outside. Consequently, 
electromagnetic noise is not transmitted to the signal conductors 3, and 
the flat cable 1 does not function as an antenna. By using the flat cable 
1 of the present embodiment, the electronic equipment does not have to be 
shielded, and the distance between the electronic equipment and the flat 
cable does not have to be considered. Electromagnetic noise can be easily 
and inexpensively avoided. Furthermore, the electronic equipment such as 
an electronic typewriter can be designed without limitation. 
As shown in FIG. 2, in a second embodiment, a flexible printed wiring board 
100 comprises an insulating panel 101 composed of a flexible film such as 
a polyester film or a polyimide film, and eight electrical wires 103 of 
copper foil formed in parallel on the surface of the insulating panel 101. 
The flexible printed wiring board 100 further comprises an insulating 
layer 105 coated on the electrical wires 103, and a meshed metal 107 of 
copper wire with the linear diameter of 0.02 mm to 0.2 mm adhered over all 
the surfaces of the insulating layer 105 and the insulating panel 101. The 
flexible printed wiring board 100 is manufactured as follows. 
After a copper foil is placed on the insulating panel 101, the electrical 
wires 103 are formed on the insulating panel 101 through the known 
processes for manufacturing printed wiring boards, such as the 
transcription of the wiring pattern, etching, etc. Subsequently, the 
insulating layer 105 composed of an insulating resin such as polyvinyl 
chloride resin is applied onto the insulating panel 101 to coat the 
electrical wires 103. The meshed metal 107 is then formed all over the 
surfaces of the insulating layer 105 and the insulating panel 101, and is 
soaked in silicone resin. After the silicon resin is cured by heating and 
drying, the meshed metal 107 is adhered to the surfaces of the insulating 
layer 105 and the insulating panel 101. The meshed metal 107 can be 
adhered by using hot-melt adhesive such as polyvinyl acetate or 
ethylene-vinyl acetate copolymer. 
Like the flat cable 1 of the first embodiment, the printed wiring board 100 
comprising the meshed metal 107 on its outer periphery is flexible. The 
printed wiring board 100 is so flexible that it may be used for wiring 
between a thermal printing head and a printing-head controller of a 
thermal-head type electronic typewriter. This wiring does not interfere 
with the lateral movement of the thermal printing head. 
In the same way as the flat cable 1 of the first embodiment, since the 
flexible printed wiring board 100 is covered by the meshed metal 107 of 
conductive copper, the electrical wires 103 are electromagnetically 
shielded from the outside. The electrical wires 103 fail to receive or 
transmit electromagnetic noise. The flexible printed wiring board 100 is 
prevented from functioning as an antenna. By using the flexible printed 
wiring board 100, the electronic equipment that generates electromagnetic 
noise does not require shielding. Moreover, the distance between the 
electronic equipment and the flexible printed wiring board 100 does not 
have to be considered. Consequently, electromagnetic noise can be easily 
and inexpensively eliminated from the flexible printed wiring board 100. 
In addition, a variety of designs can be allowed for the electronic 
equipment such as an electronic typewriter. 
When the mesh size of the meshed metals 7 and 107 is altered according to 
the frequency of electromagnetic noise, electromagnetic noise can be 
shielded more precisely. 
Although specific embodiments of the invention have been shown and 
described for the purpose of illustration, the invention is not limited to 
the embodiments illustrated and described. This invention includes all 
embodiments and modifications that come within the scope of the claims. 
For example, instead of the meshed metal, woven or nonwoven fabric composed 
of conductive fiber or synthetic resin coated with metal can be used. The 
conductive fiber can be made by coating fiber with conductive metal 
through electroless plating or evaporation.