Electricity: conductors and insulators – Conduits – cables or conductors – Combined
Reexamination Certificate
2000-06-14
2002-09-03
Nguyen, Chau N. (Department: 2831)
Electricity: conductors and insulators
Conduits, cables or conductors
Combined
C174S07100B, C174S0720TR, C174S1170FF
Reexamination Certificate
active
06444910
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a structure and method for connecting a flat electrical cable to bus bars. More particularly, the invention concerns a connection between relaying bus bars, and a flat cable used for steering equipment in automobiles. In automobiles, a flat cable is contained in a cable reel. The flat cable is then connected to lead cables joined to external circuits, through the relaying bus bars.
2. Description of Background Information
FIGS. 1 and 2
show a ring-shaped cable enclosure including a fixed element
1
joined to a steering shaft. The cable enclosure further includes a mobile element
2
connected to a steering wheel in a freely rotatable way around the fixed element
1
. A flat cable
3
is then stored in the cable enclosure in a helically wound condition. The flat cable
3
has a given length and each of its two ends is connected to an edge of a relay bus bar
5
attached to inner cases. The latter are respectively joined to the fixed element
1
and the mobile element
2
. The other edge of the relay bus bar
5
is connected to lead cables
6
leading to external circuits. The flat cable is wound or unwound in unison with the rotation of the mobile element
2
.
As shown in
FIG. 2
, when connecting the flat cable
3
to the relay bus bar
5
, a plurality of relay bus bars
5
having a narrow width are fitted into grooves aligned in the inner case
4
, and insert-molded with the latter. An end portion of the flat cable
3
is stripped of its resin coating, so that aligned conductor strips
3
a
are exposed. These conductor strips
3
a
are superposed on the plurality of relay buys bars
5
, and are bonded by ultrasonic welding. A lid
7
us then put on the inner case
4
, such that the joint section is protected.
As the number of circuits increases, the widths of the conductor strips
3
a
of flat cable
3
are reduced, as are the setting-up pitches of the conductor strips
3
a
. Consequently, the connection between the conductor strips
3
a
and the relay bus bars
5
are mechanically weakened, to the extent that the joint section can no longer be protected solely by the inner case
5
and the lid
7
. Further, the ribs formed by the neighboring grooves of inner case
4
, which isolate the conductor strip layers from each other, are also rendered smaller and narrower, so that the circuits can no longer be insulated sufficiently from one another.
As described above, when the relay bus bars
5
are insert-molded into the inner case
4
, the relay bus bars
5
are made smaller. Their mechanical strength is thus reduced. Accordingly, the relay bus bars
5
are easily broken during insert-molding. Moreover, their fixing positions in the inner case
4
become more prone to variations.
Further, manufacture of dies for insert-molding relay bus bars
5
with an inner case
4
, and for a protective lid
7
, incurs high costs.
SUMMARY OF THE INVENTION
In view of the above, a primary object of the present invention is to provide a joint section between a flat cable and bus bars which is securely protected and insulated, and to reduce production costs.
To this end, there is provided a structure for connecting a flat cable to bus bars, the flat cable exposing conductor strips. The structure includes bus bars and conductor strips adhered onto the bus bars, thereby forming a joint section including strip layers and strip gaps. The structure further includes a first and second insulator resin sheet placed respectively on a first and a second face of the joint section. In this structure, at least the first insulator resin sheet is configured such that it penetrates into the strip gaps and adheres onto the second insulator resin sheet, so as to form insulating grooves.
Preferably, at least the first insulator resin sheet is a thermoplastic insulator resin sheet. Further, the conductor strips may be adhered onto the bus bars by welding. Suitably, the strip layers includes at least one of the configurations chosen from the groups consisting of punched holes, embossed figures and rivet cramping.
The structure may further include a holder and a lid made of an insulator resin and enclosing the joint section including the first and the second insulator resin sheet.
There is further provided a method of connecting a flat cable to bus bars including preparing bus bars in the form of strips, stripping off a coating from an end portion of a flat cable, whereby conductor strips are exposed, and adhering the conductor strips onto the bus bars by welding, thereby forming a joint section having a first face and a second face, and including strip layers and strip gaps. The method also includes covering the first face with a thermoplastic insulator resin sheet, while covering the second face with an insulator resin sheet, respectively, providing a device including a pressing plane with alternating concave and convex configurations, and heating the device and pressing the pressing plane onto the thermoplastic insulator resin sheet, whereby the thermoplastic insulator resin sheet adheres to the strip layers by virtue of the concave configurations, while it adheres to the insulator resin sheet in the strip gaps by virtue of the convex configurations, thereby forming insulating grooves.
Alternatively, there is provided a method of connecting a flat cable to bus bars including preparing an insulator resin sheet, arranging bus bars in the form of strips on the insulator resin sheet, stripping off a coating from an end portion of a flat cable, whereby conductor strips are exposed, and adhering the conductive strips onto the bus bars by welding, thereby forming a joint section having a first face and a second face, and including strip layers and strip gaps. The method also includes covering the first face with a thermoplastic insulator resin sheet, while covering the second face with an insulator resin sheet, respectively, providing a device including a pressing plane with alternating concave and convex configurations, and heating the device and pressing the pressing plane onto the thermoplastic insulator resin sheet, whereby the thermoplastic insulator resin sheet adheres to the strip layers by virtue of the concave configurations, while it adheres to the insulator resin sheet in the strip gaps by virtue of the convex configuration, thereby forming insulating grooves.
Alternatively yet, there is provided a method of connecting a flat cable a bus bars including preparing bus bars in the form of strips, stripping off a coating from an end portion of a flat cable, whereby conductor strips are exposed, and adhering the conductor strips onto the bus bars by welding, thereby forming a joint section having a first face and a second face, and including strip layers and strip gaps. The method also includes covering the first face and the second face with a thermoplastic insulator resin sheet, respectively, providing a first device and a second device, respectively, including a pressing plane with alternating concave and convex configurations, and heating the first and second devices and pressing the pressing plane onto the first and second faces, respectively, whereby the thermoplastic insulator resin sheets adhere to the strip layers by virtue of the concave configurations, while they adhere to each other in the strip gaps by virtue of the convex configurations, thereby forming insulating grooves.
The above methods may further include enclosing the joint section covered with the thermoplastic insulator resin sheet and/or the insulator resin sheet, with a holder and a lid.
Suitably, the insulator resin sheet is made of polyethylene terephthalate, and has a thickness of about 70 &mgr;m.
As described above, a joint section (including welded strip layers), that includes bus bars and conductor strips aligned in parallel, is arranged on an insulator resin sheet (base plate). Another insulator resin sheet is then placed on the joint section and spread thereon. As the welded bus bars and conductor strips are covered with an insulator resin sheet f
Greenblum & Bernstein P.L.C.
Nguyen Chau N.
Sumitomo Wiring Systems Ltd.
Walkenhorst W. David
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