BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a shielded flat
cable and, more particularly, to a shielded flat cable having
a shield formed in such a manner as to integrally cover a
plurality of electric wires, and to a method of manufacturing
thereof, and to a machining apparatus therefor.
2. Description of the Related Art
For example, a shielded flat cable of the aforementioned
type illustrated in FIG. 24 has been developed. This shielded
flat cable is constructed so that a plurality of coated wires
52, each of which is obtained by coating a conductor 54 with
an insulator 56, and a plurality of drain wires 58 constituted
only by conductors are arranged on the same plane in parallel
with one another, that these wires 52 and 58 (hereunder, these
wires 52 and 58 will be referred to generically as "core wires")
are covered with a shield 60, which is conducted only to the
drain wires 58, and that the shield 60 is covered with an
insulative external sheath 64.
In such a shielded flat cable 50, the shield 60 is formed
by usually bonding a pair of metallic foils 62a and 62b, which
sandwich the core wires 52 and 58 from both sides thereof, to
each other with an adhesive, as illustrated in this figure.
In the aforementioned shielded flat cable 50, the core
wires 52 and 58 are integrated with one another by using the
shield 60 and the external sheath 64. Thus, the distance D
between the adjacent core wires cannot be changed. Therefore,
in the case of some wiring manner, there is the need for forming
a slit 61 between the adjacent core wires 52 and 58 to thereby
enable the change of the distance therebetween.
FIG. 25 is a perspective diagram illustrating a state in
which the branching slits 61 are formed in the shielded flat
cable 50 shown in FIG. 24. The distance D between the adjacent
core wires 52 and 58 can be changed by forming the slits 61
as illustrated in FIG. 25. Thus, for instance, specific wires
can be inserted into cavities formed at certain intervals.
However, in the case of the aforementioned shield flat
cable 50, the distance between the adjacent core wires 52 and
58 is very narrow. Thus, when the slits 61 are formed, an area
of bonded portion of the metallic foils 62a and 62b is decreased.
This results in decrease in the adhesive strength of parts,
in each of which the slit 61 is provided, of the cable. Thus,
as illustrated in FIG. 25, an exfoliation is liable to occur
in each of the bonded portion of the metallic foils 62a and
62b. Consequently, this conventional shielded flat cable has
a problem that the shielding performance is degraded owing to
the exfoliation of the metallic foils 62a and 62b. Further,
the electrostatic capacity formed between the conductor 54 and
the shield 60, which has been maintained at a constant level,
varies owing to the exfoliation of the metallic foils 62a and
62b. This causes a problem that uniformity of impedance in
the longitudinal direction of a transmission path formed from
the conductor 54 and the shield 60 is degraded, and that what
is called a reflection phenomenon occurs, that is, a
precedently transmitted signal acts as a noise and affects a
subsequently transmitted signal.
The present invention is accomplished to solve the
problems of the conventional art. Accordingly, an object of
the present invention is to provide a shielded flat cable, which
can prevent a shield from peeling off conductors even in the
case of branching a terminal thereof and thus can suitably
maintain the shielding performance thereof, and to provide a
method of manufacturing such a shielded flat cable.
SUMMARY OF THE INVENTION
To solve the problems, according to an aspect of the
present invention, there is provided a shielded flat cable,
which includes a plurality of core wires arranged in parallel
with one another on the same plane, a shield having a pair of
metallic foils sandwiching each of the core wires in front and
rear directions perpendicular to the plane, and an external
sheath coating an outer circumference of the shield. This
cable comprises a slit selectively formed between the core
wires to branch a terminal of each of the core wires, and a
coupling portion formed at least at a part defining the slit
to maintain both the metallic foils of the shield in a coupled
state.
According to this aspect of the present invention, the
terminal of each of the core wires is branched by the slit.
Thus, the core wires can be suitably connected to cavities
provided at different intervals. In addition, the coupling
portion for maintaining both the metallic foils of the shield
in the coupled state is formed at least at a part, in which
the slit is formed, of the layered product having the shield
and the external sheath. Thus, this coupling portion
reinforces the coupling between the metallic foils of the
shield. Incidentally, the word "selectively" means that a
given number of slits may be formed at an arbitrary place. Thus,
the slit may be provided between each of all pairs of adjacent
ones of the core wires.
Especially, it is preferable that a plurality of the
coupling portions are formed along the longitudinal direction
of the slit.
Thus, the coupling force of the shield at the slit portion
is enhanced in proportion to the number of the formed coupling
portions.
The coupling portions may be constituted by welding the
metallic foils.
Thus, in the case of the cable of the present invention,
the shield itself is coupled to the metallic foils by a large
coupling force.
On the other hand, the coupling portion may be adapted
to connect the front and rear sides of the external sheath to
each other through a through hole formed in the shield.
Thus, the metallic foils are securely tightened together
by the external sheaths at the bonded portion thereof. That
is, the external sheaths provided at the front and rear sides
thereof are connected to each other by the external sheath
penetrating through the thorough hole. Thus, the bonded
portion is restrained by the external sheath from both sides.
Consequently, as compared with the conventional shield
structure in which the metallic foils are simply bonded with
an adhesive, a large coupling force acts between the metallic
foils. Moreover, the coupling portion can be constructed only
by forming the through hole in the shield without increasing
the number of components.
In this case, preferably, the external sheath is a resin
molded on an outer periphery of the shield in such a manner
as to fill the through hole.
Thus, when the external sheath is formed, the material
of the external sheath gets into the through hole, so that the
shield is, as it were, riveted.
It is preferable that especially, a peripheral edge
portion of the thorough hole is formed so that one of the
metallic foils is folded back in such a manner as to be supported
and surrounded by the other of the metallic foils.
Thus, the metallic foils of the shield are coupled to each
other in a state in which the foils engage with each other.
Consequently, the coupling force of the shield is increased
still more.
Additionally, it is preferable that the shield is
constituted by metallic foils stuck to each other.
Thus, a sticking force acts on both the metallic foils
of the shield. Consequently, the coupling force of the shield
is increased still more.
Moreover, preferably, the through hole is formed by being
elongated in the longitudinal direction of the slit.
Thus, high sealing properties can be obtained at the slit
portion in a state in which the width thereof is limited to
a small value. Conversely, the proportion of the connected
portion increases. Thus, a more large coupling force can be
obtained. The elongated through holes are shaped like, for
example, an oval or ellipse, or an ovoid.
In the case of another embodiment of the present invention,
preferably, the coupling portion continuously extends along
the longitudinal direction of the slit.
Thus, the length of the coupling portion increases. The
coupling force is enhanced for that.
Further, preferably, the coupling portion is
continuously constituted at a part of the external sheath.
To form the slit continuously extending in the
longitudinal direction thereof in this way, it is sufficient
that a part of the external sheath is welded by, for instance,
thermal welding, and that the coupling portion is constituted
by coating the shield with such a welded portion. Thus, the
coupling portion can be constructed without adding special
components thereto. Consequently, desired adhesiveness can
be obtained.
According to another aspect of the present invention,
there is provided a shielded flat cable machining apparatus
for machining an intermediate product having a plurality of
core wires arranged in parallel with one another on the same
plane, a shield having a pair of metallic foils sandwiching
each of the core wires in front and rear directions
perpendicular to the plane and coating each of the core wires,
an external sheath coating an outer circumference of the shield,
and a slit formed in a layered product having the external
sheath and the shield, the slit branching a terminal of each
of the core wires, and the shielded flat cable machining
apparatus for forming a coupling portion maintaining the
metallic foils of the shield in a coupled state, at a part where
the slit is defined. This shield flat cable machining
apparatus comprises a pair of heating/pinching elements
enabled to pinch a branched terminal portion of the
intermediate product so as to melt slit portions of the
intermediate product, pinching surfaces each formed on the
heating/pinching elements and defining a plurality of grooves
corresponding to the core wires included in the branched
terminal portion, and partitioning elements each disposed
between adjacent ones of the plurality of grooves to be put
into the slit when the branched terminal portion is pinched.
In this apparatus, a face for enlarging the slit is formed in
each of the grooves so that a gap is formed between a
corresponding one of the core wires and a corresponding one
of the partitioning elements when the intermediate product is
pinched.
Further, according to another aspect of the present
invention, there is provided a shielded flat cable
manufacturing method having the steps of machining an
intermediate product having a plurality of core wires arranged
in parallel with one another on the same plane, a shield having
a pair of metallic foils sandwiching each of the core wires
in front and rear directions perpendicular to the plane and
coating each of the core wires, an external sheath coating an
outer circumference of the shield, and a slit formed in a
layered product having the external sheath and the shield, the
slit branching a terminal of each of the core wires, and forming
a coupling portion maintaining the metallic foils of the shield
in a coupled state, at a part where the slit is defined. In
this method, the step of forming a coupling portion comprises
the steps of disposing the intermediate product between the
pair of heating/pinching elements during enlarging the slit,
and coating the shield with a part of the external sheath, which
part corresponds to a slit portion melted by simultaneously
heating and pinching the intermediate product in a state in
which a partitioning element for heating is disposed in the
enlarged slit through a gap.
In the case of the machining apparatus and the
manufacturing method of the present invention, when the
coupling portion is formed, a face formed in the
heating/pinching element, for enlarging the slit enlarges the
slit in the intermediate product. Thus, a gap is formed between
the partitioning element put into the slit and this face.
Consequently, the intermediate product is pinched by the
pinching face of the heating/pinching element and also heated.
Thus, the external sheath melts and gets into the gaps formed
at both sides of the partitioning element. As a result, the
molten external sheath fill the gaps in a state in which the
shield exposed in the slit is coated with the molten external
sheath. Further, when the molten portion of the external
sheath, which has got into the gaps, are harden, the coupling
portion is formed. Practically, the heating/pinching element
may be either a platen formed like a plate, or a pair of heating
rollers. In either case, undulations formed on the coupling
surface can constitute the pinching surface including the
grooves that pinches the core wires and can constitute the face
for enlarging the slit. Moreover, a heat source for the
heating/pinching element may be an internal heater.
Alternatively, the intermediate product may be externally
heated.
Further, preferably, the pair of heating/pinching
element is configured in such a manner as to be able to open
and close between a semi-closed state, in which the branched
terminal portion of the intermediate product can be introduced,
and a pinched state in which the branched terminal portion can
be pinched.
This facilitates the introduction of the intermediate
product.
Moreover, preferably, the face for enlarging the slit is
adapted to enlarge the slit by pushing the core wires of the
branched terminal portion when the state of the pair of
heating/pinching elements are changed from the semi-closed
state to the pinched state.
This enables the enlargement of the slit without providing
a special step for enlarging the slit. Therefore, the
reliability of the slit enlarging operation is enhanced.
Moreover, the operability is improved. The face for enlarging
the slit is not limited to a flat one. A curved face may be
used as the face for enlarging the slit.
In the shielded flat cable manufacturing method,
preferably, the step of disposing the intermediate product
between the pair of heating/pinching elements during enlarging
the slit includes the steps of introducing a branched terminal
portion of the intermediate product between the pair of
heating/pinching elements that are preliminarily put in a
semi-closed state, and thereafter closing the pair of
heating/pinching elements.
This enables the supply of the intermediate product to
the pair of heating/pinching elements.
According to another aspect of the present invention,
there is provided a shielded flat cable manufacturing method
having the steps of machining an intermediate product having
a plurality of core wires arranged in parallel with one another
on the same plane, a shield having a pair of metallic foils
sandwiching each of the core wires in front and rear directions
perpendicular to the plane and coating each of the core wires,
an external sheath coating an outer circumference of the shield,
and a slit formed in a layered product having the external
sheath and the shield, the slit branching a terminal of each
of the core wires, and forming a coupling portion maintaining
the metallic foils of the shield in a coupled state, at a part
where the slit is defined. This method comprises the steps
of forming a through hole in the metallic foils sandwiching
the core wires in the front and rear directions, thereafter
forming the external sheath by molding, and subsequently
forming the slit at a position through which the through hole
passes.
According to this method of the present invention, only
the addition of a step of punching or boring enables the
external sheath to pass through the through hole formed in the
shield. Further, the coupling portion for coupling the shield
is formed without increasing the number of components.
Moreover, the slit is formed at the position through which the
through hole passes. Thus, the coupling portion is formed at
a cut end of the branching slit. In the case of forming the
slit by performing the branching step, the metallic foils are
reliably maintained in the coupled state at the part at which
the slit is formed.
In this manufacturing method, preferably, a plurality of
through holes are formed along the core wires.
Thus, when the slit is formed, the length of the slit can
be selected correspondingly to the plurality of through holes.
Furthermore, preferably, the through holes are formed in
the bonded portion of the metallic foils, and thereafter a burr
formed around each of the through holes is enlarged and deformed
with respect thereto.
Additionally, it is preferable that terminal processing
is performed on the core wires branched after the slit is
formed.
Thus, the forming and machining of the slit can be
performed simultaneously with the forming and machining of the
slit for machining the terminal. Consequently, the number of
the steps can be reduced.
Incidentally, in the description of the present
specification, the "plurality of core wires" may be a group
of electric wires including only coated wires (mainly, signal
lines) electrically insulated from the shield. Alternatively,
the "plurality of core wires" may be a group of electric wires
including coated wires and drain wires that are electrically
conducted to the shield. Furthermore, the "metallic foils"
are not limited to genuine metallic foils. The "metallic
foils" may include those, to which various kinds of coating
for, for example, reinforcement.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view illustrating an example of
a shielded flat cable according to the present invention.
FIG. 2 is a sectional view, which is taken on line A-A
of FIG. 1 and which illustrates the shielding structure of the
shielded flat cable.
FIG. 3 is a perspective view illustrating an example of
the use of the shielded flat cable shown in FIG. 1.
FIG. 4 is a schematic view illustrating a process of
manufacturing the shielded flat cable according to the present
invention.
FIG. 5 is a schematic sectional view taken on line C-C
of FIG. 4 illustrating the manufacturing process.
FIG. 6 is a schematic sectional view taken on line D-D
of FIG. 4 illustrating the manufacturing process.
FIG. 7 is a perspective view illustrating a layered
product manufactured by the manufacturing process illustrated
in FIG. 4.
FIG. 8 is a perspective view illustrating the layered
product manufactured by the manufacturing process illustrated
in FIG. 4.
FIG. 9 is a perspective view illustrating a process of
machining the layered product manufactured by the
manufacturing process illustrated in FIG. 4.
FIG. 10 is a schematic perspective view illustrating
another example of a coupling portion.
FIG. 11 is a schematic view illustrating another process
of manufacturing the external sheath.
FIG. 12 is a schematic side view illustrating a machining
apparatus that can be employed according to the present
invention.
FIG. 13 is a perspective view illustrating a layered
product machined by the manufacturing process illustrated in
FIG. 12.
FIG. 14 is a perspective view illustrating a layered
product machined by the manufacturing process illustrated in
FIG. 12.
FIG. 15 is a schematic perspective view illustrating a
machining apparatus according to another embodiment of the
present invention.
FIG. 16 is a perspective view illustrating a primary part
of the apparatus shown in FIG. 15.
FIG. 17 is a plan partial schematic view illustrating the
primary part of the apparatus shown in FIG. 15.
FIG. 18 is a perspective view illustrating an intermediate
manufacturing process of a shielded flat cable according to
another embodiment of the present invention.
FIG. 19 is an enlarged front view of the primary part of
the apparatus shown in FIG. 15.
FIG. 20 is an enlarged front view of the primary part shown
in FIG. 15, which illustrates a machining process corresponding
to FIG. 19.
FIG. 21 is a perspective view illustrating a shielding
flat cable in which a coupling portion is formed by being heated
and pinched.
FIG. 22 is a perspective view illustrating another
machining apparatus to which the present invention can be
applied.
FIG. 23 is an enlarged schematic plan view illustrating
a primary part of the apparatus shown in FIG. 22.
FIG. 24 is a sectional perspective view illustrating a
configuration of a conventional shielded flat cable.
FIG. 25 is a perspective view illustrating a state in which
branching slits are formed in the shielded flat cable shown
in FIG. 24.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Embodiments of the present invention are described
hereinafter by referring to the accompanying drawings.
FIG. 1 is a perspective sectional view illustrating a
shielded flat cable 10 according to the present invention. FIG.
2 is a sectional view taken on line A-A, which illustrates the
shield structure of the shielded flat cable. Further, FIG.
3 is a perspective view illustrating an example of the use of
the shielded flat cable 10 of FIG. 1. The shielded flat cable
10 illustrated in these figures has a plurality of coated wires
12, each of which is constituted by conductors 14 coated with
an insulator 16, and drain wires 18 constituted only by
conductors. These core wires (the coated wires 12 and the drain
wires 18 in this embodiment) are arranged on the same plane
in such a manner as to be in parallel with one another. The
shield 20 and the external sheath 24 are formed therearound
in such a manner as to be integrated therewith. In the case
of the illustrated embodiment, peeling is performed on a
terminal portion so that the shielded flat cable 10 is connected
to a pressure terminal 72 accommodated in a pole 71 of a pressure
connector 70 (see FIG. 3). Thus, the external sheath 24 and
the shield 20 are cut off. Consequently, the insulator 16 is
exposed from the terminal portion of the coated wire 12.
The shield 20 is formed by bonding a pair of electrically
conductive metallic foils 22a and 22b together in such a way
as to sandwich the core wires 12 and 18, as illustrated in FIG.
2. Incidentally, genuine metallic foils, such as copper foils,
or metallic foils on each of which a reinforcement layer made
of a resin is formed, are used as the metallic foils 22a and
22b.
A slit S is formed in a portion between the core lines
12 and 18, that is, a bonded portion at which the metallic foils
22a and 22b are bonded to each other. The slit S branches the
terminal portion of each of the core wires 12 and 18. When
the shielded flat cable 10 is connected to the pressure
connector 70, and formed along the longitudinal direction of
each of the core wires 12 and 18 so as to connect the individual
wires 12 and 18 to the poles 71 provided at different intervals
(see FIG. 3).
Several coupling portions 26 are formed at a part (that
is, the cut end portion of the slit S) in which the slit S is
defined. In the illustrated embodiment, the coupling portions
26 are configured so that through holes 28 are linearly formed
in the bonded portion of the shield 20 at regular intervals,
and that the peripheral edge portion of each of the through
holes 28 is folded back to a rear side (a bottom surface side,
as viewed in this figure) of the shield 20, more particularly,
the peripheral edge portion 22c of the metallic foil 22a is
folded back so that a corresponding part of the rear-side
metallic foil 22b is supported and surrounded by a
corresponding part of the front-side metallic foil 22a, and
that the external sheath 24 penetrates through this through
hole 28. That is, in the coupling portion 26, the metallic
foils 22a and 22b are made by folding back the peripheral edge
portion 22c to engage with each other. Furthermore, the
metallic foils 22a and 22b are, as it were, rivet-fastened
(riveted) to each other by the external sheath 24.
In the case of the aforementioned shielded flat cable 10,
the coupling portion 26 is provided in the portion in which
the slit S of the shield 20 is formed. Thus, as compared with
the conventional shield structure in which the metallic foils
are simply bonded with an adhesive, an extremely large coupling
force acts between the metallic foils 22a and 22b. Thus, even
in the case that the slit S is formed in the portion between
the core wires 12 and 18, the metallic foils 22a and 22b do
not easily peel off from each other. The shielding performance
is effectively prevented from being degraded owing to the
exfoliation of the metallic foils 22a and 22b.
Further, a plurality of coupling portions 26 are provided
in the part in which the slit S is formed. Thus, the coupling
force of the metallic foils 22a and 22b can be enhanced still
more.
Moreover, in a state in which the metallic foils 22a and
22b are, as it were, riveted by the external sheath 24 as
illustrated in FIG. 2, high strength can be obtained, in
comparison with the structure in which the front side and the
rear side of the external sheath 24 are stuck to each other
in the through hole 28.
Next, a method of manufacturing the shielded flat cable
10 is described hereafter by referring to FIGS. 4 to 9. FIG.
4 is a schematic view illustrating an outline of a process of
manufacturing the shielded flat cable 10. Further, FIG. 5 is
a schematic sectional view taken on line C-C of FIG. 4. FIG.
6 is a schematic sectional view taken on line D-D of FIG. 4.
Moreover, FIGS. 7 and 8 are perspective views of a layered
product manufactured by the manufacturing process illustrated
in FIG. 4. FIG. 9 is a perspective view illustrating a process
of machining the layered product manufactured by the
manufacturing process illustrated in FIG. 4.
Referring first to FIG. 4, the process of manufacturing
the shielded flat cable 10 fundamentally comprises three steps,
that is, a shield forming step 30, a punching step 34, and an
external sheath forming step 36.
At the shield forming step 30, during the core wires 12
and 18 are drawn from reel members (not shown), around which
the core wires 12 and 18 are wound, and a pair of metallic foils
22a and 22b are bonded to each other by an adhesive in such
a manner as to sandwich these core wires 12 and 18. This
operation is performed by letting the core wires 12 and 18 and
the metallic foils 22a and 22b pass through between a pair of
pressure rollers 32a and 32b and by integrally pressing such
wires and foils. Thus, as illustrated in (a) of FIG. 7, the
core wires 12 and 18 are introduced in between the pair of
pressure rollers 32a and 32b in a state in which the core wires
12 and 18 are arranged in parallel with one another on the same
plane (in a direction perpendicular to paper along a lateral
direction as viewed in FIG. 4). Then, the core wires 12 and
18 are sandwiched between and coated with the metallic foils
22a and 22b in the front and rear directions (namely, upward
and downward directions, as viewed in FIG. 4) perpendicular
to the plane. Consequently, as illustrated in (b) of FIG. 7,
the shield 20 is formed, and a flat layered product Sl is formed
in such a way as to be integrated with the core wires 12 and
18.
At the punching step 34, the through hole 28 is formed
in the bonded portion, in which the metallic foils 22a and 22b
of the shield 20 are bonded to each other. This operation is
performed by letting the layered product S1 pass through
between a male roller 38a having projections 40 provided at
uniform intervals on a circumferential surface thereof and a
female roller 38b having recess portions 42 corresponding to
the projections 40 provided on a circumferential surface
thereof, and then causing each of the projections 40 to
penetrate through the bonded portion, in which the metallic
foils 22a and 22b are bonded to each other, as illustrated in
FIGG. 5. Thus, as illustrated in (c) of FIG. 7, the through
holes 28 are formed in the bonded portion of each of the metallic
foils 22a and 22b of the shield 20 in such a manner as to be
arranged in the longitudinal direction of the layered product
S1. At that time, burrs (a peripheral edge portion 22c shown
in FIG. 2) are formed on a peripheral edge portion of the through
hole 28 in such a manner as to be directed in a direction from
the front surface to the rear surface of the shield 20 (namely,
in a downward direction, as viewed in FIG. 5).
In the case of the illustrated embodiment, the through
hole 28 is shaped like an ellipse extending along the
longitudinal direction of the core wires 12 and 18. Further,
other shapes of the through hole may be, for instance, an oval
and an ovoid. In either case, preferably, the through hole
28 is established in such a manner as to be as narrow as possible,
so long as width of the through hole 28 is larger than that
of the slit S, so as to maintain favorable electrical
characteristics of the shield 20. Furthermore, it is
preferable for enhancing sticking strength against the
exfoliation at the part P, in which the slit S is formed, that
the through hole 28 is as long as possible along the core wires
12 and 18.
Preferably, these through holes 28 are formed in a central
portion between the adjacent core wires 12 and 18 in such a
manner as to extend along the longitudinal direction of the
core wires 12 and 18.
The layered product Sl having undergone the punching step
34 is caused to pass through between two rollers 39a and 39b
provided for pressing down the burrs, as illustrated in FIG.
4. Thus, as illustrated in FIG. 6, the burrs are destructed
by forcibly pressing down a part, whose thickness is increased
due to the burrs, of the shield 20. At that time, a part of
the burr formed around the through hole 28 is outwardly bent
owing to the deformation of the burrs. Consequently, an
engaging structure illustrated in FIG. 2 is formed.
At the external sheath forming step 36, the external
sheath 24 is formed around the layered product S1 by letting
the layered product S1 pass through an extruding machine 37.
To put it concretely, the layered product is caused to
pass through a cavity (that is, a mold path for forming the
external sheath) formed in the extruding machine 37. Moreover,
a sheath material, such as a thermoplastic material, is
supplied to the cavity. Thus, the external sheath 24 is formed
around the layered product by drawing the layered product
therefrom while the sheath material is stuck to the periphery
of the layered product. Then, when the sheath material is
supplied to the cavity, the sheath material penetrates through
the through hole 28. Thus, the shield 20 is rivet-fastened.
Moreover, the coupling portion 26, which is operative to, as
it were, rivet the shield 20 is formed. Furthermore, as
illustrated in (a) of FIG. 8, another layered product S2 is
formed in such a way as to coat the layered product Sl
illustrated in FIG. 7(a) with the external sheath 24.
Subsequently, the peeling operation is performed so as
to connect this layered product S2 to the pressure connector
70 (see FIG. 3) . The peeling operation is conducted by forming
a slit 29 in a portion between the core wires 12 and 18 along
the longitudinal direction thereof, as illustrated in (b) of
FIG. 8, and cutting off the external sheath 24 and the shield
20, which cover the terminal portions of the coated wires 12,
from the end of this slit 29 along a direction perpendicular
to the core wires 12 and 18.
Subsequently, the slit S for branching the terminal end
portion of the shielded flat cable 10 are suitably selectively
formed at a position, through which the through holes 28 pass,
as illustrated in (a) and (b) of FIG. 9, so as to connect the
core wires 12 and 18 correspondingly to the poles 71 of the
crimping connector 70. The position and length of this slit
S are changed depending on an object to which the shielded flat
cable 10 is connected. However, in the illustrated embodiment,
the coupling portions 26 are arranged at equal intervals along
the longitudinal direction of the core wires 12 and 18.
Consequently, the length and position of the slit S can be
suitably changed. Moreover, the terminal portion can be
branched for general purpose use.
Further, each of the core wires 12 and 18 can be connected
to a corresponding one of the pressure terminals 72
accommodated in the poles 71 provided at different intervals,
by providing the slits S.
According to the aforementioned method of manufacturing
the shielded flat cable 10, the burrs formed in association
with the formation of the through holes 28 are enlarged and
deformed during the formation of the through holes 28 in the
shield 20, so that the coupling portions 26 are formed.
Therefore, the coupling portions 26 can easily be formed.
Especially, the coupling portions 26 are formed at a stretch
by undergoing a sequence of the steps, namely, the shield
forming step 30, the punching step 34, the burr pressing-down
step 39, and the external sheath forming step 36. Consequently,
the shielded flat cables can be efficiently manufactured.
Incidentally, the aforementioned shielded flat cable 10
and the manufacturing method therefor are examples of the
shielded flat cable, the manufacturing method, and the
machining apparatus according to the present invention. The
practical configuration of the shielded flat cable, and the
practical manufacturing method therefor can be suitably
changed without departing the scope of the invention.
For example, in the shielded flat cable 10, circular
through holes 28 are formed in the bonded portion, in which
the metallic foils 22a and 22b of the shield 22 are formed.
Then, the coupling portions 26 are formed by enlarging and
deforming the burrs formed at that time. However, holes each
having an elliptic or rectangular section may be formed and
used. Further, for instance, as illustrated in (a) of FIG.
10, the coupling portions 26 may be formed by making a cruciform
cut and folding back each of triangular portions 48a to 48d,
whose oblique sides are the cut portions 46, to the rear side,
as illustrated in (a) of FIG. 10, by using the corresponding
base thereof as a fulcrum. In short, it is sufficient that
the coupling portion 26 has a structure obtained by folding
back a part of the bonded portion, in which the metallic foils
22a and 22b are bonded, so that one 22a or 22b of the metallic
foils supports and surrounds the other metallic foil 22b or
22a. It is sufficient that the practical shape of the coupling
portion 26 is suitably selected in such a manner as to
effectively prevent the metallic foils 22a and 22b from peeling
off from each other.
Incidentally, regarding the coupling portions 26, it is
not always necessary to fold back the peripheral edge portion
22c of the through hole 28. Thus, the folding back of the
portion 22c may be omitted. Further, regarding the
construction of the shield 20, it is not always necessary to
bond the metallic foils 22a and 22b by an adhesive. Thus, the
bonding thereof using the adhesive may be omitted. In short,
only in the case that the peeling of the metallic foils 22a
and 22b cannot be sufficiently prevented by forming the
external sheath according to the use and usage conditions of
the shielded flat cable 10 in such a manner as to penetrate
the bonded portion, in which the metallic foils 22a and 22b
are bonded to each other, the coupling force of the metallic
foils 22a and 22b may be enhanced by employing the configuration
obtained by folding back the peripheral edge portion of the
through hole 28.
Furthermore, at the step of forming the external sheath
24, a laminating method may be employed in addition to the
aforementioned molding method.
FIG. 11 is a schematic view illustrating another process
of manufacturing the external sheath 24.
In the case of the method illustrated in this figure, the
external sheath 24 is formed from a pair of insulative tapes
81 and 82 by using a laminator 80.
The laminator illustrated in FIG. 11 comprises supply
reels 83 and 84 for supplying insulative tapes 81 and 82 stuck
onto both sides of the punched layered product S1, release tape
reels 87 and 88 for supplying release tapes 85 and 86 to the
rear sides of the supplied insulative tapes 81 and 82, three
pairs of heating rollers 88 for putting the insulative tapes
81 and 82 and the release tapes 85 and 86 onto both the top
and rear sides of the layered product S1 in this order and for
heating the tapes, a take-up device 89 for taking up the release
tapes 85 and 86 after heated, a slitter 90 for uniformly cutting
both sides of the layered product S2 formed by the pairs of
heating rollers 88, and a take-up device 91 for taking up the
layered product S2, on which the external sheath 24 is formed
by being cut by the slitter 90. Incidentally, a pair of guide
rollers 92 is disposed at an appropriate place on a conveying
path for conveying the layered product S1 and the layered
products S2. Furthermore, a take-up portion 93 for taking up
cut chips is provided at the downstream side of the slitter
90. A take-off capstan 94 is disposed between the take-up
device 91 and the slitter 90. Furthermore, reference numeral
95 designates a starting chip pinch roller, and reference
numeral 96 denotes a traverse roller, and reference numeral
97 designates a pinch roller.
According to this apparatus, the insulative tapes 81 and
82 are stacked on both sides of the layered product S1 in which
the wires 12 and 18 are coated with the shield 20. Then, these
tapes and the product are laminated by the pair of heating
rollers 88. Thereafter, the product is cut by the slitter 90
to a predetermined constant width. Thus, the layered product
S2 is formed, and taken up by the take-up device 91.
Next, a slit forming step and a peeling step performed
by another embodiment of the present invention are described
hereafter by referring to FIG. 12 and the following figures.
FIG. 12 is a schematic side view illustrating a machining
apparatus that can be employed according to the present
invention. Furthermore, FIGS. 13 and 14 are perspective views
illustrating the layered product machined in the manufacturing
process illustrated in FIG. 12.
An apparatus 100 illustrated in FIG. 12 has a cable feeding
reel 101, an accumulator 102, a straightener 103, a slitter
104, and a sizing cutter 105, which are arranged on a
predetermined conveying path ph in this order from the upstream
side thereof. Further, a shielded flat cable 10 wound around
the cable feeding reel 101 is supplied through the accumulator
102 to the straightener 103. Then, in a state in which the
curl of the cable is eliminated, the slits S are formed in the
terminal portion of the cable by the slitter 104 (see (b) of
FIG. 13). Furthermore, the total length of the cable is
adjusted by the sizing cutter 105. The terminal portion of
the external sheath 24 is cut in a state, in which the coated
wires 12 are partly removed, to the desired length. Thus, the
shielded flat cable 10 illustrated in (a) of FIG. 14 is
completed.
A collector 106 is disposed at the downstream side of the
sizing cutter 105. The sized and cut shield flat cable 10 is
conveyed and collected by a conveyer (not shown) of this
collector 106.
Referring next to FIG. 14, the terminal portion of the
shielded flat cable 10 manufactured as described above is moved
according to the postprocessing step, that is, for example,
is subjected directly to a pressure welding step, as
illustrated in (a) of FIG. 14, alternatively, subjected to a
crimping step through a peeling step of peeling the coated wires
12 and the terminal portion of the external sheath 24 of the
drain line 18, as illustrated in (b) of FIG. 14.
Meanwhile, although the punching of the shield 20 is
indispensable for the aforementioned embodiment, the present
invention is not limited to such an embodiment. The coupling
portion can be formed by using a machining apparatus 120
illustrated in FIG. 15 without punching.
FIG. 15 is a schematic perspective view of the machining
apparatus 120 according to the another embodiment of the
present invention. FIG. 16 is a perspective view illustrating
a primary part of the apparatus shown in FIG. 15. FIG. 17 is
a schematic partial plan view of the primary part of FIG. 15.
Further, FIG. 18 is a perspective view illustrating an
intermediate manufacturing process of a shielded flat cable
10 according to this embodiment.
Referring first to FIG. 15, the machining apparatus 120
illustrated in this figure has a base 121, a mounting plate
122 erected on a middle portion of the base 121, a lower platen
124 carried by the mounting plate 122, and an upper platen 125
disposed on the lower platen 124. This apparatus is adapted
to melt a part of the external sheath 24 and to form the coupling
portion 26 by pinching an intermediate product S4 (see (b) of
FIG. 18) by using both the platens 124 and 125 (an example of
the heating/pinching element) in a heated state (about at 130°C
to 160°C) . Blowers 130 for industrial use may be used as means
for heating the platens 124 and 125.
The lower platen 124 is fixed to the mounting plate 122
through a platen base 126. The upper platen 125 is a movable
member connected to a block 128, which is guided by an LM guide
127 in such a manner as to be moved upwardly and downwardly
by a drive member (for example, an air cylinder) 129 adapted
to lift and lower this block 128. Lifting and lowering
operations of this upper platen 125 can be controlled in such
a manner as to be put in an opened state illustrated in FIG.
16, and brought by an operating means (for instance, a foot
switch) connected to a control unit (not shown) in a partly
fitted state, which is illustrated in FIG. 19, and a fitted
state, which is illustrated in FIG. 20.
Referring now to FIGS. 16 and 17, the opposed surfaces
of the platens 124 and 125 compose pinching surfaces 124a and
125a, (to be described later) for pinching the intermediate
product S4 (see (b) of FIG. 18). Introducing grooves 131 for
introducing the core wires 12 and 18 of the intermediate product
S4, on which the slits are formed, are formed in the pinching
surfaces 124a and 125a. In the illustrated embodiment, the
introducing grooves 131 correspond to two coated wires 12, 12
and one drain line 18. The introducing groove 131
corresponding to the drain wire 18 (in FIG. 19, the rightmost
one) is set so that the diameter thereof is smaller than the
diameters of the other introducing grooves. Incidentally, in
the case of the illustrated embodiment, a shielded flat cable
10 having three core wires 12 and 18 is manufactured. However,
as exaggeratingly illustrated in FIG. 16, both the side
introducing grooves 131 have inclined portions 131a (namely,
examples of a face for enlarging the slit S) formed so that
the downstream-side parts thereof are inclined in directions
in such a way as to be increasingly away from each other. These
inclined portions 131a act with the central introducing groove
131 in such a way as to enlarge each of the slits S formed in
the intermediate product S4 introduced to the apparatus.
A Blade 132 serving as a partitioning element is provided
between each pair of adjacent ones of the introducing
grooves131, 131. In the lower platen 124, a slit 133 facing
this blade 132 is provided.
When the machining apparatus 120 is employed, the coupling
portions 26 canbe formed by performing the following procedure
without punching.
That is, the layered product S1, on which punching is not
performed, is supplied to the apparatus disclosed in FIG. 11.
Then, the layered product S3 having the external sheath is
manufactured on the product S1 (see (a) of FIG. 18).
Subsequently, the intermediate product S4, in which the slits
are formed, are manufactured (see (b) of FIG. 18).
FIG. 19 is an enlarged schematic front view of a primary
part of FIG. 15. FIG. 20 is an enlarged schematic front view
of the primary part, which illustrates the machining process
corresponding to FIG. 19.
After the intermediate product S4 is manufactured, the
platens 124 and 125 of the machining apparatus 120 are brought
into a partly fitted state, as illustrated in FIG. 19. Then,
the branch terminals of the intermediate product S4 are
introduced into the introducing grooves 131, respectively. In
this partly fitted state, during the blade 132 is put into the
slit 133, the upper platen 125 faces and is slightly floated
above the lower platen 124 (by, for example, 0.5 mm). When
the branch terminals, that is, the core wires 12 and 18 of the
intermediate product S4 are introduced to the introducing
grooves 31 in the partly fitted state, the core wires 12 and
18 are pushed into the grooves 131 by the inclined portions
formed in the side introducing grooves 131 so that the distance
between the ends of the adjacent core wires 12 and 18 is broaden
toward the inner end of the slits S. Therefore, at this stage,
a gap, into which the molten part of the external sheath 24
flows, is formed between the wall surface of the slit S and
the blade 132 (see FIG. 20).
In this state, the upper platen 125 is caused to descend,
so that a mold is clamped. Then, the intermediate product S4
is heated while pinched. Thus, as illustrated in FIG. 20, the
molten part of the external sheath 24 flows into both side
portions of the blade 132. Then, the shield 20 exposed in the
slit S at the time of forming the slit S is coated with the
molten part. Thereafter, the upper platen 125 is lifted, so
that both the platens 124 and 125 are opened, and a work is
taken out thereof and cooled. Thus, the shielded flat cable,
in which the slit S is continuously sealed with the external
sheath 24 along the longitudinal direction thereof, can be
obtained (see (a) of FIG. 21).
FIG. 21 is a perspective view of the shielded flat cable
10 in which the coupling portion is formed by heating and
pinching. As illustrated in (a) of FIG. 21, the coupling
portion 26 is formed along the longitudinal direction of the
slit S by performing the aforementioned process. The shield
20 exposed in the slit S in the intermediate manufacturing
process is almost completely covered with this coupling portion
26. Further, after this coupling portion 26 is formed, the
peeling is performed thereon, similarly as in the case
illustrated in FIG. 14. This enables the formation of the
branch portion that can be connected to a pressure terminal
(see (b) of FIG. 21). Needless to say, when this cable is
applied to the pressure contact terminal, this peeling can be
omitted.
In the case of forming the coupling portion 26 by using
the machining apparatus of FIG. 15, the need for punching is
eliminated. Moreover, in such a case, the coupling portion
26, which continuously covers the shield 20 in the longitudinal
direction of the slit S, can be formed. Thus, the necessity
for pressing down the burrs can be eliminated. This is
advantageous in machining the flat cable.
Amachining apparatus (or method) 140 illustrated in FIGS.
22 and 23 may be employed as the apparatus (or method) for
forming the coupling portion by heating and melting the
external sheath 24 without punching.
FIG. 22 is a perspective view illustrating another
machining apparatus 140 to which the present invention can be
applied. FIG. 23 is a schematic front view of the primary part
shown in FIG. 22. Incidentally, in FIG. 22, like or
corresponding parts are designated by the same reference
characters denoting like or corresponding parts illustrated
in FIG. 15. Thus, the description of such parts is omitted
herein.
As illustrated in FIG. 22, the machining apparatus 140
has a pair of heating rollers 141 and 142 (each of which is
another example of the heating/pinching element) . The heating
rollers 141 and 142 are provided in such a manner as to face
each other in the upward or downward directions, and constitute
nip rollers (see FIG. 23). The lower heating rollers 141 are
rotated and driven by being connected to the drive unit 143.
The upper heating roller 142 is a driven roller rotatably
attached to a block 128 and upwardly and downwardly movably
held by a drive member 129 for lifting and lowering the block
128.
Referring to FIG. 23, the circumferential surfaces of the
heating rollers 141 and 142 constitute pinching surfaces 141a
and 142a for pinching the intermediate product S4.
Three introducing grooves 143a to 143c for introducing
the terminal portion of the intermediate product S4 are formed
in the lower heating roller 141 correspondingly to the core
wires 12 and 18 of the intermediate product S4 to be machined.
Each of the introducing grooves 143a to 143c is implemented
by circumferential grooves formed in the pinching surface 141a
of the heating roller 141. On the other hand, a circumferential
groove 144a, which faces the central introducing groove 143a,
and nearly tapered pinching curved surfaces (namely, inclined
surfaces) 144b and 144c, which face both the side introducing
grooves 143b and 143c) are formed in the upper heating roller
142. Further, in the illustrated embodiment, when the
intermediate product S4 is pinched, both the side core wires
12 and 18 are taken away from the central core wire 12 by the
arcuate shapes of the pinching curved surfaces 144b and 144c
(each of which is another example of the face for enlarging
the slit S) formed on both sides thereof, so that each of the
slits S can be enlarged. Further, a pair of ring-like blades
145 are fixed at a part, which faces the slit S of the
intermediate product S4, of the upper heating roller 142.
Moreover, the ring-like groove 146 for setting the
corresponding ring-like blade therein is formed in the lower
heating roller 141.
With the aforementioned configuration, the branch
terminal of the intermediate product S4 is introduced into
between the nip rollers put in the partly fitted state
illustrated in FIG. 23, after the intermediate product S4 (see
(b) of FIG. 18) is preliminarily manufactured. Then, the upper
heating roller 142 is lowered. Thus, the intermediate product
S4 is pinched during heated, so that the slit S formed in the
bonded portion between the core wires 12 and 18 is enlarged.
Then, the upper heating roller 142 is lowered, and the mold
is clamped. The intermediate product S4 is heated by being
simultaneously pinched. Consequently, a shielded flat cable
10, in which the slit portion S is continuously sealed with
the external sheath 24 along the longitudinal direction of the
slit portion S, can be obtained (see (a) of FIG. 21) , similarly
as in the case of the embodiment illustrated in FIG. 15.
Furthermore, if possible, the burr pressing-down step 39
(see FIG. 4) may be omitted from the process of manufacturing
the shielded flat cable 10. That is, when the external sheath
is formed, burrs formed on the peripheral portion of each of
the through holes 28 can be pressed down by the material of
the sheath and enlarged and deformed by the pressure of this
material in the case of some shape of the cavity in the extruding
machine 37 and some position at which the material of the sheath
is introduced. Thus, the coupling portion 26 can be formed.
Therefore, in such a case, when the external sheath 24 is formed,
the coupling portion 26 is formed together with the sheath by
omitting the burr pressing-down step 39. Consequently, the
coupling portion 26 can be efficiently formed.
Meanwhile, in the shielded flat cable 10, the metallic
foils 22a and 22b are first bonded to each other. Then, the
coupling portion 26 is formed in the bonded portion in which
these foils are bonded. However, the coupling portion may be
configured by performing spot welding on the bonded portion,
instead of forming the through hole 28. In such a structure
of the shield 20, the coupling force of the metallic foils 22a
and 22b having the slit S can be effectively enhanced, similarly
as in the case of the shielded flat cable 10. Even in the case
that the slit is formed between the core wires, the metallic
foils can be effectively prevented from peeling off from each
other. Incidentally, in the case of this structure, it is not
always necessary to bond the metallic foils 22a and 22b by an
adhesive. Therefore, the bonding of the metallic foils by the
adhesive may be omitted.
Further, the shielded flat cable 10 can be applied not
only to the pressure connector but also to the pressure
connector having a pressure contact terminal.
As described above, according to the present invention,
there is provided a shielded flat cable, which can prevent the
metallic foils from peeling from each other even when the slit
is formed between the core wires, and which also can effectively
prevent the shielding performance thereof from being degraded
owing to the exfoliation of the metallic foils.