Electricity: conductors and insulators – Conduits – cables or conductors – Insulated
Reexamination Certificate
1999-11-18
2001-10-30
Nguyen, Chau N. (Department: 2831)
Electricity: conductors and insulators
Conduits, cables or conductors
Insulated
C174S078000
Reexamination Certificate
active
06310296
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a cable used in a device such as a computer, and more particularly to a method of manufacturing a multicore cable which needs accurate of electrical characteristics.
The multicore cable means a cable which has a plurality of signaling core wires in parallel. In most cases, the individual signaling core wire is covered with an inner insulating layer, and is formed together with a grounding core wire in such a manner that a shield is wound around them.
FIG. 2
shows a cross sectional view of a flat-type multicore cable as an example of the multicore cable used in a device such as a computer. The flat-type multicore cable is constituted by locating a plurality of cables in parallel. The individual cable is formed by paring a signaling core wire, which is covered with an inner insulating layer, with a grounding core wire, and then by winding a shield around the pair thus created. Since the flat-type multicore cable comprises a plurality of signaling core wires, grounding core wires and shields, it is one type of the above-described multicore cable. At the same time, the flat-type multicore cable, in which the plurality of cables are placed transversely in a line, has a flat configuration. In
FIG. 2
, a signaling core wire
6
, which is covered with an inner insulating layer
5
, is paired with a grounding core wire
4
provided along a side portion of the inner insulating layer, and a shield
3
of aluminum is wound around the pair, thus forming a shield layer. Moreover, a plurality of the cables, in any of which this shield layer is formed, are arranged in parallel and, with insulation between any two cables being maintained, the cables are fusion-welded using a jacket
2
made of a thermosetting resin.
In many cases, a component such as a connector is connected with one end of this flat-type multicore cable. This allows the flat-type multicore cable to be used in a state of being easily connected with or disconnected from an electronic appliance. JP-A-3-102783 discloses this flat-type multicore cable and a technique for connecting the component such as the connector with the flat-type multicore cable. The connecting steps, as shown in
FIG. 4
, are as follows: First, the jacket
2
and the shields
3
are cut and stripped, thereby exposing the inner insulating layers
5
and the grounding core wires
4
. Second, being careful not to cut the signaling core wires
6
, the inner insulating layers
5
, which cover the signaling core wires
6
, are cut. Third, being careful not to develop a short-circuit between an inner insulating layer
5
and a grounding core wire
4
, the inner insulating layers
5
are stripped so as to expose the signaling core wires
6
. Fourth, the grounding core wires
4
and the signaling core wires
6
are formed in such a manner as to fit a configuration of terminals
9
of a connector
8
. Finally, the grounding core wires
4
and the signaling core wires
6
are connected with the terminals
9
, thereby connecting the connector
8
with the flat-type multicore cable.
In the above-mentioned flat-type multicore cable
1
, however, improvement has been made concerning the structure thereof and an insulator material of the inner insulating layer
5
so that the flat-type multicore cable
1
can respond to speeding-up of a signal transmission speed accompanied by an enhancement of machine cycle of a computer. In particular, the material of the inner insulating layer
5
is made closer to air so as to lower the permittivity thereof, thereby speeding up a transmission speed of a signal which transmits in the signaling core wire
6
. As a result, the inner insulating layer
5
shown in
FIG. 2
has become soft and has been found to be easily modified by the winding of the shield
3
. This modification makes unstable a contact between the grounding core wire
4
and the shield
3
, and especially when a subtle vibration is exerted on the cable, the effect of the poor contact becomes more apparent. This poor contact between the grounding core wire
4
and the shield
3
gives rise to a variation in characteristic impedance of the signaling core wire
6
, and this variation in the characteristic impedance causes a failure to occur in the computer.
FIGS. 5A and 5B
show variations in the characteristic impedance of the multicore cable.
FIG. 5A
is a graph representing the characteristic impedance when the cable itself is at rest.
FIG. 5B
is a graph representing the characteristic impedance when a vibration is exerted on the cable. It can be recognized that, as compared with the characteristic impedance shown in
FIG. 5A
, the characteristic impedance shown in
FIG. 5B
is varied more extensively under the influence of the vibration.
As a countermeasure to be taken against this, what can be considered, for example, is that gold with high conductivity is plated on a surface of the grounding core wire
4
, thereby maintaining the electrical contact between them. However, this method is an expensive one because of the use of gold plating, and also was not successful in avoiding a problem in that the vibration makes imperfect the contact between the grounding core wire
4
and the shield
3
. This poor contact between the grounding core wire
4
and the shield
3
has resulted in a drawback that the multicore cable lacks a reliability in a device such as a computer in which even a subtle variation in the characteristic impedance is not permitted.
SUMMARY OF THE INVENTION
It is an object of the present invention to obtain a multicore cable which, by securely connecting the grounding core wire
4
with the shield
3
, makes it possible to maintain, even in a state of vibration, a stable characteristic impedance as is shown in FIG.
5
A.
In order to accomplish the above-described purpose, in the present invention, as is shown in
FIG. 1
, incisions are cut into the jacket
2
and the shields
3
of the multicore cable
1
in such a manner that a stair difference is formed between the upper and the lower parts thereof, and then the stripping of the jacket
2
is performed. Moreover, an electrically conductive adhesive
7
is coated between an exposed shield
3
and an exposed grounding core wire
4
, thereby bonding the shield
3
and the grounding core wire
4
. At this time, if an ultrasonic wave vibration is exerted on the grounding core wire
4
, even if oxide films are formed on a surface of the shield
3
and on a surface of the grounding core wire
4
, it becomes possible to eliminate the oxide films. Also, the ultrasonic wave vibration allows the electrically conductive adhesive
7
to penetrate between the grounding core wire
4
and the shield
3
in a right degree. This increases a connection area between them, thus making it possible to securely perform the connection therebetween. As a result, even in a state in which a vibration is exerted on the multicore cable
1
, it is possible to obtain a stable characteristic impedance.
REFERENCES:
patent: 4152226 (1979-05-01), Mueller
patent: 4588852 (1986-05-01), Fetterolf et al.
patent: 4943688 (1990-07-01), VanDeusen et al.
patent: 5038001 (1991-08-01), Koegel et al.
patent: 5399808 (1995-03-01), Carter et al.
patent: 5455383 (1995-10-01), Tanaka
patent: 5554825 (1996-09-01), Parker et al.
patent: 5872334 (1999-02-01), Trazyik
patent: 2-037621 (1990-02-01), None
patent: 2641302 (1997-05-01), None
Nishi Yasushi
Suzuki Morio
Tanaka Kiyofumi
Hitachi , Ltd.
Mattingly Stanger & Malur, P.C.
Nguyen Chau N.
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