Electrical connector for flexible plane-type conductor cable

An electrical connector comprises crimping pieces of tongue-like sheet integrally provided on the side edges of a web in such a manner as to erect therefrom and arc contact portions each comprising an arc substantially normal to the sheet body of the crimping piece, and the crimping piece is formed as a curled portion so as to be superimposed over the contact portion, whereby a flexible plane-type conductor cable is securely held between the superimposed portions for establishing electrical connection therebetween. The arc contact portion is formed as a recessed arc contact portion, and the external arc of the curled portion and this recessed arc are brought into concentric arc relationship.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an electrical connector connected to a 
flexible plane-type conductor cable formed as a flexible thin sheet body 
which comprises belt-like conductor portions arranged in parallel to each 
other and a film-like insulation sheath applied thereover. This flexible 
plane-type conductor cable is hereinafter referred to as an "FPC". 
2. Statement of the Prior Art 
A conventional electrical connector for an FPC is known in the official 
gazette of Japanese Patent Publication No. 48833/1982 (examined) or the 
like. The construction and problems of this known electrical connector 
will be described with reference to FIGS. 5 to 7 for convenience. FIG. 5 
is a perspective view of the known electrical connector, FIG. 6 a 
cross-sectional view taken along the line VI--VI of FIG. 5, and FIG. 7 a 
partially enlarged cross sectional view showing a state in which the 
electrical connector shown in FIG. 5 is in use. 
As shown in FIG. 5, the known electrical connector 1 is basically 
constructed such that crimping pieces 3 of tongue-like sheet are provided 
on the side edges of a web 2 in such a manner as to erect therefrom and 
that an arc contact portion 5 comprising an expanded arc 4 substantially 
normal to the sheet body of the crimping piece 3 is provided on the web 4 
at a position adjacent to the joint between the crimping piece 3 and the 
web 2 in a raised fashion for each crimping piece 3. 
As shown in FIGS. 6 and 7, an FPC 6 to which this electrical connector 1 is 
attached is formed into a flexible sheet body comprising belt-like 
conductor portions 7 arranged in parallel to each other and securely 
sealed with a film-like insulation sheath 8. The crimping pieces 3 are 
caused to penetrate through this FPC 6 at predetermined positions, and the 
upper half portion of each crimping piece 3 that has penetrated through 
the FPC 6 is then crimped in a direction indicated by an arrow 31 in FIG. 
6, i.e. toward over the arc contact portion 5 so as to form a curled 
portion 10, which is then brought into press contact with the arc contact 
portion 5 to thereby securely hold the FPC 6 therebetween. When securely 
held by means of the curled portion, the insulation sheath 8 of the FPC 6 
is partially stripped off by means of the leading-end edge of the crimping 
piece 3, which allows to the conductor portion 7 and the curled portion 10 
of the crimping piece 3 to electrically contact each other. Thus, the 
electrical connector 1 is securely attached to the FPC 6 for electrical 
connection. 
In the conventional electrical connector 1 constructed as described above, 
since the arc contact poerion 5 that is laid over the curled portion 10 
comprises the expanded arc 4, the external arc 11 of the curled portion 10 
and the expanded arc 4 are brought into circumscribed arc relationship via 
the FPC 6 from a geometrical point of view. 
As a result of this, since a dot contact or an approximate dot contact is 
established between the conductor portion 7 and the circumscribed arcs 4 
and 11, it is not possible to have a contact allowing good electricity 
conducting therebetween at all times. Moreover, if there is even a slight 
error in the accuracy with which the crimping piece 3 is curl processed, 
the dot contact between the leading-end edge of the crimping piece 3 which 
is on the moving side and the FPC 6 which is on the fixed side becomes too 
much or too little, causing a case in which the FPC 6 is damaged or the 
insulation sheath 8 is not sufficiently stripped off. However, the control 
of accuracy with which curl processing is carried out is extremely 
difficult from a mass-production technology point of view, and there is a 
drawback that articles having unstable electrical connection with the FPC 
6 are produced. 
SUMMARY OF THE INVENTION 
An object of the present invention is to obtain an electrical connector 
having a stable electricity conducting performance. 
Another object of the present invention is to obtain an electrical 
connector which is easily processed for electrical connection with an FPC. 
In order to accomplish the above objects, the present invention provides an 
electrical connector for an FPC comprising crimping pieces of tongue-like 
sheet integrally provided on the side edges of a web in such a manner as 
to erect therefrom and arc contact portions each comprising an arc 
substantially normal to the sheet body of the crimping piece, wherein the 
crimping piece is formed as a curled portion so as to be superimposed over 
the contact portion, the conductor portion of the FPC being thereby 
securely held between the superimposed portions for establishing 
electrical connection therebetween, the electrical connector being 
characterized in that the contact portions are each formed as a recessed 
arc, and that external arcs of the curled portions and the recessed arcs 
are brought into concentric arc relationship, respectively. 
The electrical connector of the present invention has on the web an arc 
contact portion comprising a recessed arc. When the crimping piece is bent 
so as to form a curled portion, which is then superimposed on the arc 
contact portion, the external edge of the curled portion and the recessed 
arc are brought into concentric circle relationship, and the leading-end 
edge of the crimping piece is guided along the recessed arc on the fixed 
side when it is moved to be curled, and is smoothly superimposed 
thereover, and this serves to reduce as low as possible a risk of the FPC 
securely held between the recessed arc and the crimping piece being 
damaged or of the insulation sheath applied on the FPC being 
insufficiently stripped off, whereby a surface contact is established 
between the conductor portion of the FPC and the crimping piece of the 
electrical connector, stable electricity conduction being thereby 
accomplished.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIGS. 1 to 4, an embodiment of an electrical connector 
according to the present invention will be described. 
Referring first to FIG. 1 showing one embodiment of an electrical connector 
1a for an FPC according to the present invention, crimping pieces 3a of 
tongue-like sheet are provided on the side edges of a web 2 in such a 
manner as to erect therefrom. Arc contact portions 5 are provided on the 
upper side of the web 2 in such a manner as to become substantially normal 
to the crimping pieces 3a, respectively. The electrical connector is 
attached to the FPC 6 by causing the upper half portions of the crimping 
pieces 3a to penetrate through the FPC 6 at predetermined positions, and 
the crimping pieces 3a so penetrating the FPC 6 are then inwardly bent so 
as to form a curled portion 10. This curled portion 10 is then 
superimposed over each arc contact portion 5 to securely hold the FPC 6 
therebetween. Thus, the crimping pieces 3a are electrically attached to 
the conductor portion 7 of the FPC 6, and an electrical connection is 
established therebetween. 
In the electrical connector 1a for an FPC, the arc contact portion 5 
comprises a recessed arc 12, and this recessed arc 12 and an external arc 
11 of the curled portion 10 that is superimposed over the recessed arc 12 
are brought into concentric arc relationship and constitute a recessed arc 
contact portion. 
When deciding on the configuration of the recessed arc 12, the 
configuration of the curled portion 10 formed by the crimping piece 3a is 
taken into consideration in advance and is formed such that when the 
curled portion 10 formed by bending the crimping piece 3a is superimposed 
over the recessed arc 12, the external arc 11 of the curled portion 10 and 
the recessed arc 12 are brought into concentric arc relationship. 
The electrical connector 1a so constructed is, as in the case of the 
conventional counterparts shown in FIGS. 6 and 7, attached to the FPC at 
the predetermined positions thereof by causing the crimping pieces 3a to 
penetrate through the FPC. Afterwards, the upper half portions of the 
crimping pieces 3a are formed as the curled portion 10 using a crimping 
tool (not shown) and are then pressed downwardly, during which the moving 
lower end edge of the curled portion 10 strips off the part of the 
insulation sheath 8 of the FPC 6 securely held between the recessed arc 12 
and the curled portion 10, and the exposed conductor portion 7 and the 
curled portion 10 are brought into press contact with each other for 
electrical connection. 
In the electrical connector according to the above embodiment functioning 
as described above, it is possible to establish stable electricity 
conduction via surface contact. Furthermore, since it is possible to 
control the degree of contact between the curled portion 10 and the arc 
contact portion 5 using, for instance, the crimp height as an alternative 
characteristic, the control during the production processes can easily be 
achieved, a risk of FPC damage or electricity conduction failure caused by 
excessive or insufficient contact being thereby reduced as low as 
possible. 
Furthermore, the radius of the recessed arc 12 of the present invention is 
not limited to a single radius, but a composite arc comprising a series of 
arcs having different radii may be used, and the recessed arc 12 and the 
external arc 11 of the curled portion 10 may not necessarily be brought 
into geometrically concentric arc relationship, but may be brought into 
any approximate/similar concentric arc relationship. 
As is described above, the electrical connector of the present invention 
has the following advantages: since it provides surface electrical contact 
between the conductor portion of the FPC and itself, the electricity 
conducting performance can be improved; processing for electrical 
connection with the FPC can smoothly be carried out to thereby prevent the 
production of defective articles having electricity conduction failures; 
and the operational control of processing for electrical connection can 
easily be achieved.