Shielding tape and shielding wire using the same

Details Shielding tape and shielding wire using the same Shielding tape and shielding wire using the same

1999-06-25

2001-07-17

Zirker, Daniel (Department: 1771)

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

Adhesive outermost layer

C428S354000, C428S377000, C428S379000, C174S1170AS, C174S107000, C174S1170FF

Reexamination Certificate

active

06261683

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to a shielding wire for electronic equipment such as copiers, facsimile machines, audio devices, such as tape recorders, and the like, and further for automobiles. The present invention also relates to a shielding tape to be used with a shielding wire, wherein the shielding wire is a flat cable type wire that can improve productivity, without adversely affecting processing terminals of the shielding wire, and can provide excellent shielding of electromagnetic noise. The present invention is also directed to shielding wires using such a shielding tape. Further, this invention also relates to a shielding wire composed of an environmentally-friendly, non-halogen-containing material that does not pollute the environment and does not adversely affect the shielding or production of the wire.
2. Description of Related Art
Flat cable type shielding wires, as shown in
FIG. 1
, have been used as a shielding wires for electronic equipment including, but not limited to, copiers, facsimile machines and audio equipment.
In flat cable type shielding wires, core wires
3
,
3
are formed integrally by wrapping lead wires
1
with insulation sheathing materials
2
(generally polyvinyl chloride) and drain wire
4
, arranged in parallel with fixed distances. Also, a shielding tape
5
is adhered closely on the outer peripheries of the core wires
3
,
3
and the drain wire
4
, while shielding tape
5
is adhered to form bridging parts
7
,
7
′ for maintaining fixed distances. The shielding tape
5
is further protected with sheaths
6
(generally polyvinyl chloride). In the above-described shielding wire, the insulation shielding material
2
and the sheath
6
generally exhibit excellent thermal resistance, insulation and flexibility. In addition, because the shielding material
2
and the sheath
6
are made of polyvinyl chloride, the shielding material
2
and the sheath
6
are relatively inexpensive.
The shielding tape, shown in
FIG. 2A
, comprises a shielding layer
11
, a reinforcing seat layer
12
, laminated on the side of a sheath
6
of the shielding layer
11
, a sheath adhesive agent layer
13
, for adhering the reinforcing seat layer
12
and the sheath, and a core adhesive agent layer
14
, for adhering the shielding layer
11
and the core wire
3
. The shielding layer
11
is generally composed of a combination of a metal foil
11
a
of high electric conductivity, such as copper or aluminum, and a metal foil
11
b
of high permeability, such as iron or tin. Since the reinforcing seat layer
12
exhibits insufficient strength when combined only with the shielding layer
11
composed of the metal foil, the reinforcing seat layer is ordinarily laminated with a polyester in order to increase strength without substantially increasing cost. Although, laminated shielding tapes are preferred, the present invention may also be directed to shielding tapes that are not laminated with a polyester reinforcing seat layer. Generally, the sheath adhesive agent layer
13
, includes adhesive agents of the polyethylene terephthalate group (hereafter referred to as “PET”). In addition, the core adhesive agent layer
14
, generally includes adhesive agents of a copolymer of vinyl chloride and vinyl acetate (hereafter briefly called a “vinyl chloride-vinyl acetate copolymer”).
The core adhesive agent layer
14
is, as shown in
FIG. 2B
, formed by coating the core adhesive agent in oblique stripes on one side of the shielding layer
11
. That is, pails
14
a
, to be coated with the core adhesive agent, and parts
14
b
, not to be coated, are alternately arranged in a lengthwise direction of the tape, and in the non coating parts
14
b
, the metal foils composing the shielding layer
11
are exposed. Thus, via the non-coating parts
14
b
, the drain wire
4
and the metal foil composing the shielding layer
11
are directly contacted to provide electric conductivity. The shielding tape
5
is thereby grounded to shield electromagnetic waves inside and outside of the cable that can cause strains of signals or noises. On the other hand, by adhesion of the coating part
14
a
of the core adhesive agent layer
14
, the shielding tape
5
closely adheres to the core wire
3
to prevent the core wire
3
from slipping out, and to form bridges
7
,
7
′ between the core wires
3
and
3
as well as between the core wire
3
and the drain wire
4
to prevent misregistration of the core wire
3
.
With respect to processing at a terminal of a flat cable type shielding wire having the above-structure, an outermost diameter of the portion of the drain wire
4
(outer diameter shielded with the shielding tape
5
and the sheath
6
) is made equal to the outer diameter of the core wire
3
, and the terminal is processed using a pressure connection system. The pressure connection system is, as shown in
FIG. 3
, operates so that the sheath
6
and the shielding tape
5
, shielding the core wires
3
, are scaled off to expose the core wires
3
and so that a portion of the drain wire
4
is covered with the shielding tape
5
and the sheath
6
. Then, under these conditions, contact pins
20
are inserted.
The insertion of the contact pin
20
is performed so that connecting terminals (not shown) having a number of connecting contact pins
20
, as shown in
FIG. 4A
, corresponding to a total number of the core wires
3
and the drain wires
4
, are inserted with the exposed core wires
3
(FIG.
4
B). In addition, the core wires
3
are pushed so that the contact pins
20
contact the conductors
1
(FIG.
4
C), and are further forced into the conductors
1
(FIG.
4
D), so that the conductors
1
break through the insulation shielding materials
2
and contact the contact pins
20
. In a case of the drain wire
4
, the contact pin
20
breaks through the shielding tape
5
and sheath
6
, and contacts the drain wire
4
.
In such a connection system, by maintaining a fixed pitch between the contact pins
20
,
20
, a pitch between the core wires
3
,
3
and a pitch between the core
3
and the drain wire
4
, it is possible to automatically cut the shielding wires, exfoliate the shielding tape
5
and the sheath
6
, and automatically attach the connecting terminals by pressure.
Therefore, to accurately connect the conductors
1
of the plurality of core wires
3
in the shielding wires and the contact pins
20
in a bundle, it is necessary to fix the pitch between the core wires
3
,
3
and the pitch between the core wires
3
and the drain wire
4
in response to the pitch between the pins
20
,
20
. For this, the shielding tape
5
should be close to the core wire
3
and the drain wire
4
so as to prevent the core wire from misregistration even after scaling off the shielding tape
5
and the sheath
6
.
On the other hand, if the adherence between the shielding tape
5
and the core wire
3
is too great, when exfoliating the sheath
6
and the shielding tape
5
from the terminal of cut face, only the sheath
6
is removed, and the shielding tape
5
remains adhered to the core wire
3
. If the shielding tape
5
adheres to the core wire
3
, the contact pin
20
and the shielding layer
11
of the shielding tape
5
will likely come in contact, and will result in undesirable contact shorts to the drain wire
4
via the shielding layer
11
.
In order to solve these problems, manufacturers have developed shielding wires, wherein the exfoliation of shielding tape is made easier to prevent contact shorts that can occur during processing at the terminals. For example, JP-A-4-133319U gazette discloses a shielding wire wherein a core wire is shielded on its outer periphery with a tape coiled layer coated with a mold releasing agent. Thus, the shielding wire of JP '319 is covered with a shielding tape via a tape coiled layer. By shielding the wire using a tape coiled layer, the shielding tape is easily released from the core wire, between core wires, and between a core wire and a drain wire. Accordingly, the core wire ca

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