Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
The present invention relates to a process for
producing individually screened unitary elements or ele-
mentary circuits (pairs, quads, trefoils, coaxial cables
and the like), suitable for making communication cables,
as well as to apparatus intended to carry out said process
and the individually screened unitary elements or ele-
mentary circuits produced according to said process.
It is known that, in order to improve cross-talk
between the elements of a telecommunication cable, in
addition to adopting usual expedients, such as, for ex-
ample, the choice of appropriate quadding and doubling
pitches and the arrangement of said elements in convenient
relative positions, it may be necessary to provide each
element or elementary circuit constituting the cable with
an electromagnetic and/or electrostatic screen.
In particular, Italian Patent No. 983,995 of
the same applicant refers to an improved screen for the
unitary element or elementary circuit of a telephone cable.
Said improved screen has a tubular shape and is constituted
by a composite tape, namely, a tape consisting essentially
of a good-conducting metal sheet (for example, aluminum,
copper, etc.), plated on at least one face or surface with
thermoplastic synthetic resin material, for example,
polyethylene, turned towards the inside.
However, a preferred embodiment includes a triple
tape, namely, a tape in which both faces or surfaces are
plated with synthetic resin, but in which the surface
layer, which, in the individually screened unitary element
or elementary circuit is directed to the outside, is made
of polyester resin and preferably, but not necessarily,
of polyethyleneglycolterephthalate.
Among the various embodiments suggested in the
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cited Italian patent, the electrostatic and/or electromagnetic screen which
proved particularly effective is one in which the unitary screen is defined
as constituted by a first and a second composite tape adjacent to each other
and wound up on the unitary element or elementary circuit in such a way as
to result in their facing the one to the other and with each subtending a
center-angle of at least 180.
The corresponding edges of said tapes are two by two in mating
contact and are sealed along their inner surfaces coated with thermoplastic
material.
Practically, said electrostatic and/or electromagnetic screen is
therefore constituted by two strips of composite tape which enclose a unitary
element or elementary circuit, and the two strips are jointed along two
longitudinal ribs by casting the plating of thermoplastic material.
The present invention has, an object, the providing of a process
intended to carry out industrially a screened element enclosing a plurality
of unitary elements as indicated hereinbefore, arranged parallel to one
another and mutually screened, or with only one screened unitary element.
A further object of the invention is the provision of an apparatus
for carrying out the hereinbefore indicated process.
According to one aspect of the present invention, there is provided
a process for producing a plurality of individually screened unitary elements
or elementary circuits of electrical conductors, each element or circuit
being surrounded by a tubular screen, said tubular screen being constituted
by a pair of tapes sealed together, each tape comprising a sheet of good-
conductivity metal having its surface facing toward the element or circuit
plated with a thin layer of a thermoplastic synthetic resin, said process
comprising: continuously advancing a plurality of said elements or circuits
longitudinally toward a screen application zone with said elements or
circuits in spaced relation and substantially in the same plane; simultaneous-
ly advancing from opposite sides of said plane and toward said zone a first said
tape and a second said tape, said first tape and said second tape each
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having a width greater than the dimension between the outer sides of said
elements or circuits and being advanced at the same speed as said elements
or circuits with their plated surfaces facing toward said elements or
circuits; shaping said tapes into tubes around said elements or circuits in
said zone by bringing the tapes into contact at their plated surfaces both
intermediate said elements or circuits and at the outer sides of said ~:
elements or circuits to form longitudinal ribs both between and outside of
said elements or circuits while maintaining the thickness of the tapes sub-
stantially unaltered substantially throughout their widths except possibly
any thickness change at the ribs due to resin flow thereat when the plated
surfaces are brought together and heated as set forth hereinafter; and
applying heat to said tapes, at least along said ribs, to bond the resin
of one tape to the resin of the other tape.
A preferred embodiment of the invention is a process as described,
in which, before the final shaping phase, a phase for pre-forming said first
and second tapes is employed, which pre-forming is intended to give to each
tape a form approximate to the final one destined to be subjected to the
heat sealing.
Another preferred embodiment of the invention is a process as
described in which, after the heat sealing phase, there is a phase of shear-
ing longitudinally the sealed ribs of said first and second tapes, so as to
separate each individually screened unitary element or elementary circuit
of said plurality from the adjacent one or ones.
According to another aspect of the invention, there is provided
apparatus for performing the process, the apparatus comprising shaping and
sealing means for shaping and sealing said tapes into tubes with adjacent
ribs without significantly altering the thickness of the tapes throughout
their widths except possibly any thickness change at the ribs due to resin
flow thereat when the plated surfaces are brought together and sealed,
feeding means in advance of said shaping and sealing means for feeding a
plurality of electrical conductors in spaced relation and substantially in -
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a plane to said shaping and sealing means, a pair of tape feeding means in
advance of said shaping and sealing means, one tape feeding means on one
side of said plane and the other tape feeding means on the other side of
said plane, for feeding said tapes to said forming and sealing means at the
same speed as said conductors are fed to said shaping and seallng means
and with one tape at one side of said conductors and the other tape at the
other side of said conductors.
A further embodiment of the above apparatus contemplates, down-
stream of the forming and/or heat sealing equipment, a device provided with
circular knives.
Other objects and advantages of the invention will be apparent
; to those skilled in the art from the following detailed description of the
presently preferred embodiments thereof, which description should be con-
sidered in conjunction with the accompanying drawings in which:
Fig. 1 shows schematically an embodiment of the apparatus intended
to carry out the process of the invention;
Fig. 2 shows in perspective elementary circuits or unitary
screened elements obtained with the process of the invention and the
apparatus shown in
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Fig. l;
Fig. 3 shows in perspective a single elementary
circuit or unitary screened element obtainable
according to the invention; and
Fig. 4 represents schematically and in perspect-
ive a detail of the apparatus shown in Fig. 1. -
The apparatus schematically shown in Fig. 1 re-
presents a practical line of production for individually
screened unitary elements or elementary circuits.
The apparatus illustrated in Fig. 1 includes a
unit 41 for feeding a plurality of unitary elements or
elementary circuits 10 (pair, quad, trefoil, etc.). The
elements or circuits lO are formed by insulated electrical
conductors, such as the conductors 23 and 24 in Fig. 2 or
the conductors 35 in Fig. 3. Such feeding unit 41 for
the unitary elements or elementary circuits 10 may con-
sist either of doubling or quadding machines, etc., feeding
the elements 10 directly, or may consist of appropriate
storing coils arranged in such a way as to allow the feed-
ing of a plurality of unitary elements or elementary cir-
cuits 10 all lying substantially in the same plane, spaced
the one from the other and fed at constant speed in the
direction of the arrow F.
At the opposite sides of the plane of said
plurality of unitary elements or elementary circuits 10,
there are a first and a second feeding coil 11 and 12,
respectively, of a first and a second composite tape 13
and 14. The feeding coils 11 and 12 rotate in opposite
directions.
Downstream of the feeding coils 11 and 12, there
are two pairs 15 and 16 of transversal guide rollers,
respectively for the tapes 13 and 14, followed by equip-
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ment for forming and simultaneously heat sealing said
composite tape along longitudinal ribs. In the example,
this equipment consists of at least one pair of rollers,
that is to say, a first roller 17 and a second roller 18
cooperating with each other.
The faces of these rollers 17 and 18 (see Fig.
4) are provided with reliefs 29a, 29_ and 29c alternating
with grooves 30. In the working position, the reliefs
29 of the first roller 17 engage the reliefs 29 of the
second roller 18, the roller 17 being pushed against the
roller 18 by means of elastic elements (not shown), which
may, for example, be springs.
Preferably, one of the two rollers, for example,
the roller 18, has the support for its own shaft held in
a fixed position. The roller 17 has the support for
its own shaft movable, so that the axes of the two rollers
may be moved away from or toward each other, the axes
remaining always parallel. Said elastic elements, e.g.,
springs, are also adjustable and hold the rollers 17 and
18 in mutual contact, with the pressures in the contact
zones adjustable according to the requirements of the
tape hea~ sealing.
Each roller 17 or 18, or at least one, either
totally or at least along the reliefs, is heated, for ex-
ample, by means of a heating device consisting of a re-
sistance heating unit (not shown), preferably internal to
each roller and inside a recess 40 provided in one or
both of the lateral faces of the roller itself.
The number of the grooves 30 of each roller 17
and 18 corresponds to the number of the unitary elements
or elementary circuits 10.
In the particular case illustrated, the equip-
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ment for forming and the equipment for heat sealing are
the same, but it is possible to have embodiments in which
the forming equipment and the heating equipment are
separate
The drawing element 42 for the plurality of
unitary elements or elementary circuits 10, as well as
of said first and second tapes 13 and 14, may be located
downstream of the heat sealing device. However, in an
embodiment of the invention, said drawing element may be
the forming and heat sealing rollers 17 and 18. In this
case, the rollers 17 and 18 are motor driven so as to act
as the drawing element.
In a further embodiment, the drawing element 42
may be the collection device for the individually screened
unitary Plements or elementary circuits 10.
Downstream of said first and second rollers 17
and 18, there is a device provided with knives, e.g.,
peripheral knife edges. Said device, in the illustrated
case, consists of a second pair of cooperating rollers
which are shown as a third roller 19 and a fourth roller
20.
Preferably, only one of the rollers of the se-
cond pair, for example, the roller 19, is provided with
knives. In this case, the other roller 20 is provided
with abutments corresponding to each knife of the roller
19. The knives of the third and/or fourth roller 19 and
20 are lined up with the center-line 28 (Fig. 2) of the
corresponding reliefs 29b of said first and second rollers
17 and 18. In an embodiment of the invention, said
knives may be lined up only with the intermediate reliefs
29_ and not with the end reliefs 29a and 29c of the
rollers 17 and 18. In this case, the number of knives
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would be equal to the number of the plurality of unitary
elements 10 less one, that is, n - 1.
In a further embodiment, said device provided
with knives may be omitted and, instead, there may be the
collection device of the group of n individually screened
unitary elements or elementary circuits 10, which exit
from the forming and heat sealing pair of rollers 17 and
18.
During the working of the apparatus schemati-
cally illustrated in Fig. 1, the plurality of unitary ele-
ments or elementary circuits 10 spaced from each other
advances in the direction of the arrow F in a plane inter-
mediate the two feeding coils 11 and 12. The first compo-
site tape 13 and the second composite tape 14, unwinding
respectively from coils 11 and 12, are respectively driven
transversely to the direction of feed by the two pairs of
rollers 15 and 16, have transverse dimensions larger than
the transverse dimensions of said plurality of elements
10. The image produced by projection of the periphery
of the unitary elements 10 on said first and second tapes
13 and 14 is within the edges of the tapes 13 and 14.
Said tapes 13 and 14 consist of at least a good-
conducting metal sheet, such as aluminum, plated at least
on one face with thermoplastic material, e.g., polyethylene,
but preferably, also plated on the other face with a syn-
thetic resin of the polyester type, e.g., polyethylenegly-
colterephthalate.
Said first composite tape 13 and said second
composite tape 14 unwind specularly with respect to each
and with their faces or surfaces 33 and 34, respectively,
plated with thermoplastic material, facing toward the
plurality of elements 10, on which they converge, from
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opposite sides, in the leading zone 21 of said first
roller 17 and second roller 18 which cooperate with each
other. From the zone 21, the tapes 13 and 14 with said
plurality of elements 10 pass at constant speed between
the roller 17 and 18, pulled by the drawing element 42 or
by the rollers 17 and 18, in case these latter are motor
driven. The grooves 30 of the rollers 17 and 18 allow
the passage of the unitary element or elementary circuit
with the tape strips enclosing it, whereas the reliefs 29,
besides forming ~he tapes around the unitary elements or
elementary circuits 10, heat them at a temperature which
will bring their thermoplastic plating to a plastic state,
so as to allow the heat sealing along longitudinal ribs
28 (Fig. 2) intermediate one unitary element and the adja-
cent one, namely, between two contiguous unitary elements,
and along peripherals ribs 25 and 26 (Fig. 2), on the out-
side with respect to the unitary elements 10.
In Fig. 2, the plurality of unitary elements or
elementary circuits 10 is represented by only two units
23 and 24 (n=2), but it will be understood that the num-
ber of unitary elements or elementary circuits 10 can be
greater than 2.
The tape-shaped product 27 of the heat sealing
could be sent, either directly or after a passage through
a cooling apparatus or another apparatus, to the collection
device or to an appropriate processing line, because it
represents an assembly of individually screened unitary
elements or elementary circuits which are enclosed by a
first and a second composite tape, which are spaced from
one another, and which are screened with respect to one
another and to the external ambient by means of heat-
sealed longitudinal ribs 22, 25 and 26.
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When it is wished to obtain single screened
unitary elements or elementary circuits (see Fig. 3), in
which only one unitary element 35 is enclosed between two
strips of composite tape 36, 37, sealed or heat-sealed
along two peripheral ribs 38 and 39, the tape-shaped pro-
duct 27 is caused to advance through the second pair of
rollers 19 and 20. These rollers 19 and 20, by means of
their knives (not illustrated), but being of conventional
shape, shear the longitudinal ribs 22 (Fig. 2) along the
center-line 28 (shown in dotted lines in Fig. 2).
A further and preferred embodiment of the
apparatus or production line according to the invention
provides, upstream of the rollers 17 and 18, at least a
device, preferably a pre-shaping mold (not shown) for the
tapes 13 and 14, which allows the latter to reach
gradually the final shape without suffering rapid, one-
stage deformations which might produce cracks in the
tapes.
As already indicated hereinbefore, a further
and preferred embodiment provides a cooling system (not
shown) downstream of the rollers 17 and 18. This serves
in particular, but not exclusively, to bring the ribs to
be cut to a non-plastic state in a short time. Among
the cooling systems, the use of a ventilation device em-
ploying air jets is preferred.
The same result can be obtained by providingelements (not shown) able to adjust the temperature of
the heat-sealing device, or of the rollers 17 and 18.
To this purpose, for example, use could be made of a
thermocouple in contact with the rollers 17 and 18, or an
optical thermometer able to measure the temperature of
the tape-shaped product 27 exiting from the rollers 17
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and 18. When said temperature exceeds the pre-established
value, the resistance heating unit for heating the rollers
17 and 18 is automatically cut off.
A further embodiment provides, downstream of
the feeding unit 41, elements able to space or to line up
the unitary elements or elementary circuits 10.
A further and preferred embodiment also provides
means for marking the unitary elements or elementary cir-
cuits contained in the tape-shaped product 27 exiting from
the forming and/or heat sealing station. For said differ-
entiation by marking, resort can be had to identification
marks both outside and inside the screening envelope. Use
could be made of marking techniques employing dyes, to be
carried out on the production line, downstream of the
rollers 17 and 18.
In a further embodiment, screening tapes could
be adopted which are numbered or colored on their surfaces
directed towards the outside.
The identification mark could also be inside the
screening envelope. As is already known, it could be
based on appropriate colors of the unitary elements or ele-
mentary circuits, or could be made by joining to these an
identification thread of colored cotton.
Although preferred embodiments of the present
invention have been illustrated and described, it will be
apparent to those skilled in the art that various modifi-
cations may be made without departing from the principles
of the invention.
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