Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to the manufacture of
telecommunications cable core units.
A telecommunications cable is constructed with a core
comprising one or more core units, each having a multiplicity of
twisted units of conductors, each unit conventionally being a twisted
pair of conductors. A core may be formed as a sinllle core unit of
twisted pairs, e.g. 50 or 100 pairs, or larger cores, i.e. up to 3,600
twisted pairs, comprises a plurality of core units The twisted pairs
are stranded together to form a core unit with the conductors of each
pair twisted together with a predetermined lead to the twist, i.eu the
distance taken along the pair for each conductor to complete a single
revolution along its path. This distance will be referred to in this
specification as the "twist lay" of a pair. There are different twist
lays provided for the twisted pairs in a core unit with a pair having a
particular twist lay being adjacent to other pairs of different twist
lays. Care is taken, so far as is practicable, to ensure that pairs of
equal or similar twist lays are separated from each other. The reason
for this arrangement is to attempt to maximize the communications
performance of the cable, e.g. to lessen pair-to-pair capacitance
unbalance, to reduce crosstalk between pairs and to lower the
`~ ~ coefficient of deviation of mutual capacitance of pairs in the cable.
In a conventional core unit, the twisted conductor pairs
retain their positions relative to other pairs, within certain limits.
However, it is recognized that the pair-to-pair capacitance unbalance
and crosstalk between pairs is dependent to a large degree upon the
distance of the two pairs from one another. To reduce the pair~to-pair
capacltance unbalance and to improve crosstalk, suggestions have been
made to move the conductor pairs relative to one another as they
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progress towards a stranding machine for stranding them into a core
unit so that in the finished core unit, the conductor pairs change in
relative positions and distances apart. In a suggested method for
changing the relative positions of conductor pairs as they move towards
the stranding machine~ the conductor pairs enter a guide arrangement
which comprises a system of horizontal guides movable horizontally and
located in vertically tiered fashion. The pairs are distributed
throughout the tiers and relative horizontal movement of the guides
changes the relative positions of the pairs as they move downstream.
This method was first suggested by Sigurd Norblad of
Telefonaktiebolaget LM Ericsson, in a paper entitled "Multi-~aired
Cable of Non-Layer Design for Low Capacitance Unbalance
Telecommunications Networks" read before the International Wire ancl
Cable Symposium in 1971. In this method, the conductor pairs need to
be controllably arranged together in their changing relative positions
preparatory to their passage into a closing die, in ~hich they are
drawn together to form the core unit. Controllable arrangement of the
pairs should be possible by passing them from their various positions
partly around rollers. However, extreme height of the Ericsson
machine, even for changing positions of twenty-five pairs, is such that
severe change in angles of feedpaths of some of the conductor pairs is
required for them to pass around the rollers. Such a severe change can
cause damage to either the conductors or to their insulation,
particularly if the insulation is made from pulp, and will also induce
large tension variations between conductor pairs.
The present invention concerns a method and apparatus
for making core units involving changing the relative positions of
conductor units before they are brought together to form a core unit
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and in which the change in angle between conductor units is minimized
as -they move onto rollers to controllably arrange the conductor units.
Accordingly, the present invention provides an apparatus
for forminy a core unit from telecommunications conductor units, each
formed of twisted together insulated conductors and in which the
relative positions of the conductor units are changed along the core
unit, the apparatus comprising in order, downstream along a feedpath
for the unit: guide means to prevent conductor units from stranding
together as they move downstream from the guide means; a plurality of
position changing means for conductor units, each position changing
means for changing the position of a conductor unit across the
feedpath relative to other conductor units and each position changing
means comprising a guide and means to reciprocally move the guide along
a path across the feedpath, the position changing means disposecl in
series with one another along the feedpath with their paths of movement
substantially parallel to one another and with their reciprocating
means overlapping one another in a view taken along the feedpath and
with the arrangement of position changing means being such that each
guide is disposed for unobstructed passage of a conductor unit as it
moves along the feedpath; and a core unit forming and take up ~eans to
: draw the conductor units together to form the core unit.
In the above apparatus according to the invention, the
overlapping arrangement of the position changing means ensures that the
dlmensions of the apparatus are reduced to a minimum in the direction
of the separation of the conductor:units, these dimensions sufficient
to enable the unobstructed alignment of each guide For passage of its
respective conductor unit. This constructlon thereby allows for the
angle subtended between the furthest apart of the conductor units and
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arrangement rollers to be reduced to a minimum.
The angle is further decreased when the position
changing means are arranged in groups. For instance, in one
construction, each reciprocating means comprises an endless moving
means having its associated guide secured to one flight of the moving
means and all of the guide carrying flights of the moving means are
non-aligned to provide the unobstructed passage of the conductor
unitsO In a case where the guide carrying flights are disposed
substantially horizontally, then the two groups of endless means are
disposed vertically one above the other, and the guide carrying flights
in each group are vertically displaced progressively in one direction
from one endless moving means to the next. In this two group
arrangement, if the lower group has the guide carrying flights at the
: tops of the moving means, and the guide carrying flights in the upper
group are disposed at the bottoms of the moving means, then the flights
are preferably disposed so as to approach each other progressively
downstream from moving means to moving means. Thus, the guides of the
two groups which are furthest apart lie at the upstream ends of the
groups and are furthest removed from the arrangment rollers. Thus, the
angle subtended between conductor units passing through these guides
and the rollers is reduced to a minimum.
Embodiments of the invention will now be described, by
way of example, with reference to the accompanying drawings, in which:-
Figure 1 is a side elevational view of an apparatus
according to a first embodiment for forming a core unit from conductor
~: pairs;
Figure 2 is a side elevation of a position changingmeans for conductor pairs of the apparatus and on a larger scale than
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shown in Figure 1;
Figure 3 is a view of the apparatus in the direction of
arrow 3 in Figure 2;
Figure 4 is a cross-sectional view of the apparatus
along line IV-IV in Figure 2 and on a larger scale;
Figure 5 is an end view of a detail in the same
direction as Figure 3 and on larger scale;
Figure 6 is a cross-sectional view taken along line VI-~I
in Figure ~ and on a larger scale than Figure 4;
Figure 7 is a cross-sectional view along line VII-VII in
Figure 6 and on a larger scale;
Figure 8 is a cross-sectional view along line VIII-VIII
in Figure 7;
Figure 9 is a view in the direction of arrow IX in
Figure 1; and
Figure 10 is a view of features of a second embodiment.
In the first embodiment as shown in Figure 1,
twenty-five conductor pairs 10, each formed from two twisted together
individually insulated conductors, are drawn from twenty-five reels 12
2D of the conductor pairs, in conventional fashion, for forming into a
core unit 14. The core unit 14 is formed at the downstream end of the
apparatus by passing the conductor pairs through a closing die 16 which
draws the conductor pairs together, and a binding head 18 at which
position a binding material is closed around the drawn together
conductor pairs to hold them together in conventional manner.
A stranding machine 20 forms part of a core unit forming
and take-up means which also includes the closing die 16 and binding
head 18. The stranding machine is of conventional construction and
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comprises a motor driven core unit take-up reel 22. As the stranding
machine structure is conventional, no further description is required.
Upstream from the closing die 16 is a position changing
means 24 for conductor pairs. Further upstream from the position
changlng means is a guide means to ensure that concluctor units are not
stranded together as they move downstream from the guide means. This
guide means comprises a roller 26 which is freely rotatably mounted
upon a machine frame 28 (see Figure 9) and the roller is provided with
a plurality of annular grooves 30, one for each conductor pair. As may
be seen from Fi9ures 1 and 9, the conductor pairs are passed From the
reels '2 towards the position changing means 24 by disposing each
conductor pair in its own individual groove 30 so as to maintain the
conductor pairs separate from one another as they approach the position
changing means 24.
As shown by Figures 2 and 3, a plurality of position
changing means 32 are provided for the conductor pairs, one position
changing means for each pair. The position changing means are all
housed within the straight sided frame 33. As shown by Figures 2 and
3, the position changing means are disposed in two groups, one
vertically above the other, with the position changing means in each
group lying in series with one another along the feedpath for the
conductor pairs.
Each position changing means comprises a guide 34 for a
conductor pair (see Figure 4). Each guide has a guide passage 36 and
is formed with two side wings 38 by which it is attached, for instance,
with rivets 40 to an endless moving means of a reciprocating means for
the guide, the endless moving means comprising a flat plastics belt 42
through which the rivets 40 pass. The endless moving means also
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comprises a chain ~ which extends between ends of the belt 42, as
shown by Figure 6. Each endless moving means has a horizontal flight
~5 formed by the belt 42 and carrying the associated guide 3~, the belt
mounted around two pulleys ~6 at the sides of the machine frame to
proceed as two flights ~8 towards a sprocket 50 around which the chain
44 passes for reasons to be described. As shown by Figures 2 and 3,
the two groups of position changing means are mounted with their
reciprocating means overlapping one another in a view taken along the
feedpath (see Figure 3 particularly) and the arrangement is such that
each guide is aligned with an unobstructed passage for its conductor
pair as the pair moves along the feedpath. This clear passage for
movement of a conductor pair through each guide is achieved by
disposing the horizontal flights ~5 of the belts ~2 of each group of
position changing means at different vertical levels, as shown by
Figure 3. In practice, with the lower group, the horizontal flights
are displacecl progressively vertically upwards from one position
changing means to the next in a downstream direction of the feedpath by
locating the pulleys upwardly from each position changing means to the
next on supports 55. This is shown in the larger scale detail of
Figure 5. In contrast, the horizontal flights of the upper group are
displaced progressively vertically downwards in a downstream direction
of the feedpath. In fact, the arrangement is such that, as shown by
Figure 2, the horizontal flights of the two groups oppose each other
across the feedpaths and approach each other progressively in a
downstream direction along the feedpath. The advantage of this will be
discussed below. Hence, as can be seen from above, the distance apart
of the uppermost and lowermost guides is minimized by the fact that the
guides are displaced vertically by a minimal amount, which merely
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ensures that each of the guides is unobstructed for passage of its
conductor pair. As the reciprocating means of the position changing
means in each group overlap from one end of the group to the other,
then the height is not increased unduly by the position changing
means. This minimal displacement for unobstructed view of the guides
is shown in Figure 3, in which the guides are clearly unobstructed by
horizontal flights of the belts.
As will now be described, each reciprocating means is
operable to move its guide independently of the movement of other
guidesO To allow for this independent movement, each position changing
means is provided with its own individual drive means in the form of a
reversible stepper motor 52 (Figures 2 and 3). All of the stepper
motors 52 are mounted remotely from the hori20ntal flights by being
attached to upper and lower panels 54 of the machine stand. Each motor
is directly drivably connected to a sprocket 5~. As the succeeding
changing means are closely adjacent to one another, then it is
necessary for the motors 52 to be displaced from one another laterally
of the feedpath, as shown in Figure 6, to provide space for them to be
mounted. ~s a result of this and the vertical displacement of pulleys
46, the path fiollowed by each of the endless moving means in each group
is different from the others, as shown by Figure 3. The motors 52 may
be drivable at the same speed as each other, whereby the guides 34 move
along their horizontal flights at the same speed but out of phase with
each other. However, in this embodiment, the drive motors are driven
at speeds which are slightly different from each other, so that the
positional relationship of all of the guides is continuously changing
while reducing the possibility of a set pattern of movement of the
guides 34.
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Each drive motor 52 is provided with a reversing means
so as to cause the be1ts ~2 to reciprocate, thereby moving the guides
from side to side of the machine stand. As shown by Figures 7 and 8,
the reversing means for each direction of movement of the belts 42
comprises a magnetic field producing means in the form of a magnet (not
shown) carried in one leg of a U-shaped head 58, the other leg carrying
a magnetic field receiving means in the form of a coil (not shown)
affected by inductance of the magnetic field created by the magnet.
Each coil sends signals into an electrical circuit (not shown), the
strength of the signals dependent upon the strength of the magnetic
field induced in the coil and produced by the magnet. The reversing
means also comprises a magnetic field inter-Ference means for each
direction of movement of the belt 42. This interference means
comprises a trigger device in the form oF an arm 60 which is secured to
and projects sideways from the chain 44 so as to be aligned with the
gap in the head 58, as shown by Figure 8. The position of the arm 60
on the chain on each flight 48 of the endless moving means is dictated
by the position required to influence the magnetic field, i.e. by
location within the gap, when the guide is at the end of its movement
on the horizontal flight of its belt in the appropriate direction.
In use of the apparatus described above, the conductor
pairs 10 are fed to the position changing means in the manner described
with reference to Figure 1c Each conductor pair, upon reaching the
machine frame 24, is passed through a respective guide 34 and proceeds
from there around two in-series arrangement rollers 62 prior to passing
through the closing die 16. As the conductor pairs move along their
feedpaths in spaced positions through the position changing means, the
independent motors 52 rotate at their own fixed speed, possibly
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controlled by computer, so as to move the belts 42 to reciporcate the
guides horizontally. During this movementl each of the conductor pairs
passes both over and under horizontal flights of the belts 42 of
pos1tion changing means in its own group, as shown by Figure 2. In
this figure, the paths of three conductor pairs 10 only are shown for
clarity. ~lovement of the guides independently of other guides
continuously changes the relative positions of all of the conductor
pairs as they pass through the position changing means. Thus, as -the
conductor pairs pass around the arrangement rollers 62, their positions
in the plane of contact with the rollers are dependent upon the
positions of the pairs at any particular time moving through the guides
34. Hence, the relative positions o-F the conductor pairs on the roller
also continuously change, thereby changing the relative positions in a
continuous fashion in the pairs as they enter the closing die 16.
Hence, the position changing means described above is effective in
providing constant change in rela-tive positions oF the conductor pairs
in the finished core unit, which is wound onto the drum in the
stranding machine.
A main advantage with the apparatus according to the
invention and as described in the embodiment is that because the
reciprocating means of the position changing means overlap each other,
then the total height of the position changing means is minimized. In
the particular construction which has been described, the height of the
machine stand for changing position of the twenty-five conductor pairs
is approximately 48 inches and the width is approximately 20 inches,
with the depth alony the feedpath being of the order of approximately
30 inches. Also, as the horizontal flights of the belts 42 are
displaced only sufficiently to enable each of the guides to be
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unobstructed for the passage of its conductor pair, then the height
between uppermost and lowermost guides is minimized. This distance,
i.e. at the upstream end of the two groups of position changing means,
is approximately 7 inches, Because of this and as -the guide means of
-the two groups approach each other in a downstream direction of the
feedpath, then the uppermost and lowermost guides are furthes-t from the
two arrangement rollers 62 so that the angle subtended between the
conductor pairs from the guides to the rollers is minimized. On the
other hand, if the positions of the guides were reversed in the
downstream direction so that the guides of the two groups which were
furthest apart were at the downstream end of the machine frame, then a
greater angle would be produced between the conductor pairs passing
through those guides and the rollers 62.
It Follows that the apparatus according to the invention
and as described in the embodiment produces an arrangement for changing
positions of conductor pairs in which the vertical height across the
pairs in the position changing means is minimized, thereby reducing any
tendency for insulation to be damaged by the arrangement rollers.
Also, the minimized angle subtended between the conductor pairs and the
arrangement rollers serves to minimize tension variation between the
pairs.
In a second embodiment (Figure 10) in which the two
flights 48 of each of the belts 42 is avoided, thereby decreasing the
height of the position changing means from that discussed above, each
reciprocating means comprises a rigid member or bar 64 which extends
across the feedpath for the conductor pairs and carries a guide 32 of
similar construction to that described in the first embodiment. The
guide 64 depends from two upwardly extending ends 66, one of the ends
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having an aperture to slidably receive a mounting sp;ndle 68 secured to
the machine frarne~ The other end 66 is provided with a nut 70 which is
in screw--threaded engagement with a screw-threaded shaft 72, which is
rotatable in the machine Frame and is dri~/able, possibly through
gearing, by an electric stepping motor 74. The connection between the
motor and the spindle 72 is shown diagrammatically~ The motor 74 is
reversible and rotation in either direction moves the bar 64 in the
appropriate direction through the screw-threaded shaft and nut.
Reversing means is provided for moving the bar 64 in the opposite
direction upon limit of movement in either direction. This reversing
means comprises at each end of the bar, a magnetic field interrupter
arm 76 (one only being shown) which moves with the bar to interfere
with the magnetic field procluced by a magnet provided in one leg of a
head 78. The heads 78 are mounted upon the frame a-t each end of the
bar. These heads are of the same construction as described in the
first embodiment and include, in addition to the magnet, a coil in the
other leg of the head for sensing when the magnetic field is
interrupted by the presence of the arm 76 in the gap of the head. As
discussed with regard to the first embodiment, upon the coil sensing
the presence of the arm, a signal produced results in the drive of the
motor 74 being reversed to move the bar 64 in the opposite direction.
