Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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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
units of twisted conductors, each conductor unit conventionally being a
twisted pair of conductors. A core may be formed as a single 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.e.
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 Ullit with a pair
having a particular twist lay being adjacent to other pairs of
different twist lays. ~are 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 pair-to-pair
capacitance unbalance and to reduce the crosstalk, suggestions have
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been made to move the conductor pairs rela-tive to one another as they
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
chang;ng 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 suggested by Sigurd Norblad of Telefonaktiebolaget LM
Ericsson, in a paper entitled "Multi-Paired Cable of Non-Layer Design
for Low Capacitance Unbalance Telecommunications Networks" read before
the International Wire and Cable Syrnposium in 1971. The method
involves the use of sideways physical forces upon conductor pairs and
this could render it unsuitable for use on conductors insulated with
pulp which is sensitive to the degree of surface pressures which are
inherent with such forces.
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
and in which the high degree of surface pressures of previous apparatus
is avoided.
Accordingly, the present invention provides an apparatus
for forming a core unit from telecommunications conductor units, each
f~rmed of twisted togther 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
3 ~23~7~7
for the units:-
guide means to ensure that conductor units are notstranded together as they move downstream from the guide means,
position changing means for conductor units, including a
plurality of independent guides for the units, the guides movable
independently of and relative to each other in any direction within
confines laterally of the feedpath and under the influence of a fluid
force, and fluid force producing means to apply a fluid force across
the feedpath to cause the independent movement of the guides; and
a core unit forming and take-up means to draw the
conductor units together to form the core unit.
In the apparatus according to the invention, the fluid
force producing means may comprise a gas passage means which is
disposed at a gas flow station along the t`eedpath. The gas passage
means is for the purpose of directing a flow of gas upwardly towards
and across the feedpath and a means is provided to produce the gas flow
across the passage means. In this arrangement, each guide is buoyant
so as to be buoyed up by the gas flow whereby the independent guide
movement is provided. The gas passage means may be assisted in causing
movement of the guides by an electromagnetic means which is energizable
to create a magnetic field extending across the feedpath and to change
a characteristic of the field. In this case, at least some of the
guides include a magnetically permeable material to influence in
conjunction with the magnetic field created by the electromagnetic
means, the positions of the guides transversely of the feedpath~
In alternative constructions in which the gas passage
means and gas flow producing means are omitted, the fluid force
producing means comprises electromagnetic means which acts to cause
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movement of the guides. In preferred arrangements using
electromagnetic means without use of the gas passage means, each guide
comprises a permanent magnet having one pole extending along the outer
peripheral surface of the magnet and surrounding the other pole. These
5 magnets are preferably hollow cylinder magnets with radially spaced
poles and with the bore along each magnet forming a guide passage for a
conductor unit.
In practical arrangements, the electromagnetic means may
comprise a plurality of electromagnets which are in spaced apart
positions around the feedpath and each electromagnet is connected to a
source of electric power to be energizable independently of other
electromagnets to change a characteristic of the field across the
feedpath. The electromagnets may be movable relative to the feedpath
and to effect this movement they are preferably mounted upon an annular
carrier which is rotatable for at least a part of a revolution around
the feedpath.
For the purpose of confining the guides within a defined
area, a housing is preferably provided which extends along and
surrounds the feedpath. The housing is preferably in the form of a
hollow cylinder having radially spaced poles. The relationship of the
poles of the guides and housing may be such that the housing either
attracts or repels the guides from its inner surface. In a case where
there is attraction of the guides to the housing~ then the energized
electromagnets should repel guides from the housing surface so as to
force them to a new position upon the housing whereby the relative
positions of the guides are changed. Where the guides are to be
repelled from the housing, then an energized electromagnet should
attract the guides so as to partly overcome the repelling force of the
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housirlg and thereby cause the relat;ve movement and repositioning of
the guidesO
The invention also includes a method of forming a core
unit from telecommunications conductor units, each comprising twisted
together insulated conductors and in which the relative positions of
the conductor units are changed along the core unit, the method
; comprising:-
passing conductor units separately and side-by-side
along a feedpath and through a plurality of independent guides which
are laterally movable independently of each other in any direction
within certain confines and laterally of the feedpath under influence
of a fluid force;
applying a fluid force across the feedpath to cause
independent movement of the guides and thus cause relative sideways
movement of the conductor units and constant change in their positions
in a plane normal to the feedpath; and
passing the conductor units in their constantly changing
positions into a core unit forming and take-up means to draw the
conductor units together into the core unit, the relative positions of
the conductor units in the core unit at any position along the length
thereoF influenced by the relative positions of the conductor units as
they are drawn into the forming and take-up means.
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 a general in-line
apparatus for twisting conductor units and stranding them together in a
: tandem operation;
Figure 2 is a cross-sectional view along lines II-II in
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Figure 1 and on d larger scale;
Figure 3 is an isometric view on a larger scale of a
position changing means of an apparatus according to a first embodiment
and as shown generally in Figure 1;
Figure 4 is a cross-sectional view through part of the
position changing means of the first embodiment;
Figure 5 is a cross-sectional view through part of the
position changing means of the first embodiment;
Figure 6 is a view similar to Figure 1 of an alternative
general apparatus;
Figure 7 is an isometric view on a larger scale of a
position changing means of apparatus according to a second embodiment;
Figure 8 is a cross-sectional view throuyh the position
changing means of the second embodiment taken along line VIII-VIII in
Figure 7;
Figure 9 is an isometric view of a position changing
means according to a modification of the second embodiment;
Figure 10 is an isometric view of a position changing
means according to a third embodiment;
Figure 11 is an end view of the position changing means
in the direction of arrow XI in Figure 10;
! Figure 12 is a plan view of a position changing means of
apparatus according to a fourth embodiment; and
Figure 13 is an end view in the direction of arrow XIII
upon the position changing means of Figure 12.
As shown by Figure 1, apparatus for forming a core unit
10 from conductor pairs 12 of twisted together conductors generally
comprises twenty-five twisting machines 14 which are disposed in a
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single straight bank 16 of machines. Each twisting machine 14 is of
conventional construction (not shown) and comprises, in conventional
manner, a reel cradle for holding in rotatable Fashion two reels of
individually insulated conductors to enable the conductors to be clrawn
from the reels under the drawing influence of a stranding machine 18.
Each machine 14 comprises either a single flyer in conventional manner,
or it may comprise two flyers and associated pulleys to provide a
balanced rotational structure such as is described in a copending
Canadian Patent Application No. 444,294 entitled "Twisting Machine",
filed December 23, 1983 and in the names of J. Bouffard, A. Dumoulin
and E~D. Lederhose. The conductors as they are drawn through the flyer
of each machine are drawn together towards the top of the machine, to
become twisted together, and are then fed outwardly as a twisted
conductor pair 12 from and along the bank 16 of machines as shown in
Figure 1.
The stranding machine 18 forms part of a core u~it
forming and take-up means 20 which also comprises a flying strander 22
and includes a helper capstan 24. The helper capstan is to assist in
the drawing cf the core unit 10 into the machine 18, the main force for
which is taken by a motor 26 which drives a core unit take-up reel 28.
Upstream of the flying strander 22 is a drawing means in the form of a
closing die 28 for drawing the conductor pairs together, and a binding
head 30. As the structure is conventional, no further description is
required.
Because the twisting and core unit operation is
performed in tandem, then a tension reducing means is necessary in the
apparatus shown in Figure 1. The tension reducing means is of the
constru~tion described in a Canadian Patent Application No. 444,295
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filed December 23, 1983, entitled "Forming Cable Core Units" and in the
names of 0. Bouffard, A. Dumoulin and M. Seguin. As described therein,
the tension reducing means 32 comprises two drivably rotatable
cylinders 34 and 36 around each of which the conductor pairs pass after
leaving the bank 16 of twisting ~achines and moving towards the
stranding machine. The two cylinders are of substantially equal
diameter and have a common drive in the form of a drive motor 38, which
is connected to -the cylinder 34 by drive belt 40, as shown in Figure 2.
A drive belt (not shown) also drivably connects the two cylinders
to9ether. The drive motor 38 is electrically influenced by the line
speed to provide a peripheral speed to each of the cylinders 34 and 36
which is slightly in excess of the drawing speed of the conductor pairs
into the stranding machine~ The degree of excess in speed is subject
to choice, dependent upon design, but in this particular mdchine lies
between one and f1ve per cent and is preferably in the region of three
per cent. It is of importance to realize that the two cylinders 34 and
36 are not a capstan drive and do not operate in the accepted sense for
drawing twisted pairs of conductors through apparatus in cable
manufacture. As described in application serial number 565,634~ the
cylinders 34 and 36 do not engage each of the conductor pairs along a
sufficiently long arc of contact to provide enough frictional grip to
draw the pairs from the twisting machines 14 without the assistance of
tension upon the pairs downstream of the cylinders and as provided by
the rotation of the reel 18. Hence, if the stranding machine were
omitted, the cylinders 34 and 36 would be incapable of drawing
conductor pairs 12 from the twisting machines. Additional frictional
grip between the cylinders and the conductor pairs is created by
tension downstream of the cylinders pulling the pairs down onto the
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g
cylinder surfaces. ~hile this tension is maintained, the cylinders
will draw the conductor pairs from the twisting machines with some
slippage because of the excess peripheral speed of the cylinders.
If the grip of the cylinders tend to increase the speed
of any pair as it passes around them, towards its draw speed into the
stranding machine, then the downstream tension from the cylinders
decreases and the frictional grip of the pair around the cylinders is
lessened. Thus, the cylinders slip to a greater extent upon the
conductor pair and there is a decrease in the tendency for further
increase in speed of the pair, as caused by the drive of the cylinders.
In any event, i-f the downstream tension from the cylinders drops
towards zero in any conductor pair, the cylinders could not drive that
conductor pair around -the cylinders at a speed equal to the draw speed
of the twisting machine because increase in slippage would prevent
this.
Between the tension reducing means 32 and the closing
die 28 is disposed a position changing means 38, which is the main
feature of the present invention. This position changing means may
take various forms, as shown by the following embodiments of the
apparatus now to be described. In all of these embodiments and
according to the invention, the apparatus for forming a core unit
includes a guide means to ensure that conductor units are not stranded
together as they approach the position changing means 38. The guide
means may be any suitable device for holding conductor pairs separate
from one another as they are fed side-by-side through the apparatus.
Conveniently, however, in the apparatus described in this
specification, the guide means comprises a freely rotatable guide
roller 40 which is carried upon a stand 42 of the machine which also
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carries -the cylinders 3~ and 36. As shown by Figure 2, the guide
roller 40 is formed with annular peripheral grooves 44 which space the
conductor pairs apart and arrange them in a planar array for them to
continue through the position changing means 380
Apparatus according to a first embodiment for forming a
core unit comprises a position changing means of the construction shown
in Figures 3, 4 and 5. In the first embodiment, the position changing
means comprises a gas passage means disposed at a gas flow station
along the feedpath for the conductor pairs. As shown by Figure 3, this
gas passage means comprises a plurality of housings ~6 positioned in
series along the feedpath. Figure 3 merely shows two of these
housingsS but in this embodiment four are actually provided to assist
in providing independent movement of conductor pairs, as will be
described. The four housings ~6 are identical in construction. Each
housing extends across the feedpath for the conductor pairs and
defines a gas duct 48 below the feedpath and a gas duct 50 above the
feedpath, both gas ducts being of rectangular configuration, as shown
by Figure 3, and in vertical alignment so that gas issuing upwardly
from the lower duct passes across the feedpath into the duct 50. Gas
pressurizing means (not shown) is provided for forcing the flow of gas~
i.e. air, upwardly through the duct 48 and an exhaust 51 is associated
with the duct 50 for withdrawing the air.
The gas passage means and associated equipment fcr
causing the airflow form part of a fluid force producing means to apply
the fluid force across the feedpath. The fluid force producing means
also includes an electromagnetic means which is energizable to create a
magnetic field e~tending across the feedpath at the gas flow station
and also to change a characteristic of the field for reasons to be
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discussed. With respect of each of the housings 46, the
electromagnetic means comprises an electrical coil 52 disposed at each
side of the housing and in a position between the ducts 48 and 50. In
practice as shown, each of the coils 52 is attached to a side member 54
of the housing, the side member extending between the ducts 48 and 50
so as to define with the ducts a rectangular passageway 56 which
defines the feedpath for the conductor pairs. Each of the coils 52 is
connected to a source of electrical energy for intermi-ttent and
independent operation for the purpose of changing not only the flux
intensity of the magnetic field produced either by each coil singly or
the two coils together, but also to change directions of the flux lines
dependent upon the strength of the current passing through the coils at
any particular time.
The position changing means also includes a plurality of
independent guides, one for each conductor pair. Six guides are
associated with each of the first three housings 46 (two only being
shown) and the remaining seven guides with the downstream housin~ (not
shown)O
As shown by Figures 3, 4 and 5, each of the guides 58 is
substantially spherical. In the detail shown in Figure 4, each guide
58 is formed with a closed cell foam plastics body 60 having a central
diametrical passage 62 for carrying a conductor pair. Each guide 58
also includes a magnetically permeable member which is a conventional
permanent bar magnet 64 having its poles at the ends.
In use of the apparatus, the pairs 12 of conductors are
fed from their respective twisting machines 14 and through the tension
reducing means 32 towards the in-series housings 46. In the tension
reducing means 32, each conductor pair passes around the two cylinders
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34 ancl 367 as shown~ and then around the guide roller 40 with a
conductor pair in each of the grooves 44 so that the pairs are
maintained separately from one another. As the conductor pairs pass
around the cylinders 34 and 36, the pull of the stranding machine 20
increases the frictional contac-t of the pairs against the surface of
the cylindersO Although the cylinders are rotating at a peripheral
speed which is greater than the throughput speed of the conductor pairs
into the strandiny machine, their degree of grip upon the pairs is
insufficient to draw the pairs from the twisting machine at the
peripheral speeds of the cylinders. This is as explained above and in
greater detail in the aforementioned Canadian Patent Application No.
444,295. Rather, the degree of drive by the cylinders is
dependent upon the frictional grip upon them by the conductor pairs
which increases and decreases in proportion to the downstream tension
created by the draw of the stranding machine. Hence, the pull by the
cylinders upon each pair increases its speed until it approaches that
of the draw speed of that pair into the stranding machine sufficiently
to reduce the frictional grip of the conductor pair upon the cylinders
to remove the driving force. Any slight increase in the downstream
~o tension from the cylinders will improve their driving engagement with
the pair, thereby reducing the tension again. It follows that the
tension which has built up during twisting of each conductor pair from
its machine 14 and during its movement into the tension reducing means
(e.g. up to 3 lbs.) is reduced on the downstream side to an acceptable
level (e.g. about 0.5 lbs~) for drawing into the stranding machine.
This reduction in tension assists, but is not essential to, the
; operation of the position changing means for independently moving the
guides 58 which will now be described.
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As shown by Figure 3, the twenty-five conductor pairs 12
pass in the planar array (left hand side of Figure 3) towards the first
housing 46. The conductors pass through the passageways 56 of all the
housings and each conductor pair passes also through one oF the guide
holes 62 of a guide 58 so that each guide is associated with a
particular conductor pair. The guides are associated with particular
housings as discussed above. Each guide is located upon its conductor
pair and disposed within the particular passageway 56 formed by its
associated housing. The passage of the airflow through each passageway
56 lifts the guides 58 in that space because of the buoyancy of the
guides themselves, thereby causing them to move vertically and slightly
horizontally relative to the other guides in that passageway and also
relative to the conductors passing through that passageway but devoid
of guides at that position. Hence, the vertical movement of the guides
58 at any particular housing eFfects some independent movement of the
guides and thus of the conductor pairs at that position. The movement
of the conductor pairs along the feedpath imposes a drag upon the
guides which tends to move them in the downstream direction. However,
the upward passage of the airstream prevents each guide from completely
leaving its particular passageway 56 by virtue of the Bernoulli effect.
This action is shown by Figure 5. The two ducts 48 and 50 are formed
with downstream planar ends which have the effect of forming a curtain
of air through the passageway 56. This air curtain tends to drag air
upwardly along the downstream edge of the duct 48 and upwardly into the
duct 50. This is shown by the arrow 66 in Figure 5. With no conductor
pair passing through each guide 58, then the guide would tend to lie
towards the centre, i.e. between ups-tream and downstream ends, of the
associated passageway 560 However, the drag of the conductor pair upon
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the guide urges the guide towards the downstream end of its passageway.
As the guide approaches the downstream end and commences to move out of
the passageway 56, as shown in Figure 5, then there is a higher
pressure on the downstream side of the guide than at the upstream side
because of the airflow upwardly through the passageway 56 which is
assisted by the airflow at 66, as previously indicated. Thus, a
Bernoulli efFect is provided which tends to draw the guide back into
the passageway 56. However, the drag effect of the conductor pair will
not allow this to happen and each guide 58 assumes a position at the
downstream end of the passageway 56, as shown by Figure 5, in which the
drag load upon the guide caused by the conductor pair balances the
inward force created by the Bernoulli eFfect attempting to draw the
guide upstream. Hence, each of the guides 58 assumes a position of
balance, as shown by Figure 5, in which it is buoyed upwardly by the
airflow.
During operation of the airflow, the coils 52 at each
side of each passageway 56 are energized intermittently and
independently of one another to create the magnetic field across the
passageway 56. This field is constantly changing in flux strength and
in direction of the lines of force and thus changes its influence upon
: the magnets 6~ in each of the guides 58. As the field strength at
difFerent positions across the space is different, then the guides 58
are caused to move laterally in different ways at different times. In
consequence of the combined effects of the airflow and the changing
magnetic field, the guides are moved independently of each other, both
laterally and vertically, thereby changing the relative positions oF
the conductor pairs passing through them and also relative to other
conductors passing through that particular passageway 56 and without
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guides in that passageway.
It follows that at each of the hous1ngs 46~ some of tile
conductor pairs are changed in their positions relative to the other
conductor pairs~ Movement of the guides, both laterally and vertically
in each of the passageways 56~ is constant and thus the relative
positioning of t'ne conductor pairs is constantly changing.
After passing through the position changing means 38,
the conductor pairs then proceed through the closing die 28 and into
the stranding machine. The relative positions of the pairs at any
I0 instant, as they pass through the closing die, are influenced by the
relative positions of the pairs as they mo-ve from the position changing
means 38. This affects the relative positions and change in positions
of the pairs in the core unit 10. Hence, in the completed stranded
core unit, the pairs change their relative positions to each other in a
lS completely randomized fashion.
As may be seen, little pressure is required to move the
conductor pairs during their passage through the guides 58. The
buoyancy of the guides ensures the movement of the pairs easily and
effectively without imposing a significant positive sideways force
which would be experienced with the mcvement of a mechanical device.
This is of importance in a case where a pulp insulated conductor is
being formed into a core unit as this could be damaged by the use of
conventional mechanical moving devices e"gaging the surface of the
pulp, i.e. with a crushing effect. Lack of crushing ensures that there
is no variation in electrical properties in the finished cable, e.g. in
mutual capacitance between conductors.
The reduction in tension in the conductor pairs as
described with the use of the tension reducing means 32 does, of
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course, reduce any resistance to sideways movement of the conductor
pairs and assists in minimizing any damage which may be caused to the
insulation, However~ with this invention, exemplified by the first and
Further embodiments to be described, the reduction in tension in the
conductor pairs is unnecessary.
The apparatus according to the invention does not, of
course, need to be for use in the tandemization of twisting conductor
pairs and of forming a core unit as described with reference to Figure
1. For instance, apparatus according to the invention and including a
postion changing means may be of more conventional construction in that
the core unit 10 formed by the core unit forming and take-up means 20
may have the structure shown in Figure 6. In that Figure, the position
changing means 38 and part of the apparatus downstream therefrom are as
described above. The conductor pairs 12 have been previously twisted
in conventional manner and are carried upon reels 70, from which they
are fed, towards the position changing means 38. Little tension is
required to pull the conductor pairs from each of the reels and to pass
them directly around guide pulleys and also around a guide means to
ensure that the conductor pairs are not stranded together before
entering the position changing means 38. In this particular case, the
guide roller 40j as described in a first embodiment, is again employed
as the guide means.
In other embodiments, now to be described, the apparatus
is basically as described above with regard to Figure 1 or Figure 5,
but the position changing means, indicated generally as item 38, is
changed in each case from that described in the first embodiment.
In a second embodiment, the position changing means has
a fluid Force producing means which comprises electromagnetic means
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which are not assisted by gas flow means. In this embodiment, the
apparatus comprises a cylindrical housing in two coaxial housing
portions 80 and ~2 and which extend along and surround the feedpath for
the conductor pairs. These housings are cylindrical magnets having
radially spaced poles.
The electromagnetic means further comprises a plurality
of electromagnets 8~ which are radially disposed relative to the
cylindrical housing in spaced apart positions around the feedpath, as
shown in Figure 7. Each electromagnet is energizable independently of
the other electromagnets to change a characteristic of a magnetic field
which is to be produced, as will be described, and the electromagnets
are mounted upon an annular carrier 86 which is disposed between the
housing portions 80 and 82. The carrier 86 is rotatable for at least
part of a revolution around the feedpath. In practice, as in this
embodiment, because of the convenience of connecting each of the
electromagnets to a source of electricity by wires 88, then the carrier
86 is rotatable for only part of a revolution to enable the wire
connections to be made. In fact, the carrier is reciprocally rotatable
around an angle possibly between 60 and 90 degrees around the
feedpath. The carrier may be rotated, for instance, by a stepping
motor 90 and a drive shaft and gear 92 which is in mesh with an annular
gear 9~, located at one axial end of the carrier 86.
Located within the housing and the carrier 86 are a
plurality of guides, one guide for each of the conductor pairs~ As
shown in Figures 7 and 8, some of the guides for the twenty-five pairs
are omitted for clarity. Each of these guides is formed from a
magnetically permeable material and, in fact, comprises a tubular
permanent magnet 96 of substantial length so as to extend for
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substantially the whole axial length of the housing portions or
cylindrical magnets 80 and 82. The permanent magnets 96 have their
poles displaced radially of one another, each magnet having its outer
pole with the same polarity as the pole at the inner surface of the
cylindrical magnet portions 80 and ~2.
In uxe of the apparatus of the second embodiment, the
conductor pairs are fed through the apparatus towards the position
changing means. After the conductor pairs have passed around the guide
roller 40, as shown in Figures 1 or 6, the pairs then pass axially
through the cylindrical magnets 80 and 82 while also passing each
through one of the tubular magnets 96. The conductor pairs then
proceed towards the closing die and the stranding machine. As may be
expected, the tubular magnets 96 are attracted to the inner surface of
the cylindrical magnets 80 and 82, in which position they will remain
unless acted upon by some external force. To cause the tubular magnets
to move independently of one another and within the cylindrical magnet,
the electromagnets 84 are energized intermittently and independently of
each other while being rotated reciprocally around the feedpath in the
manner described. Whenever an electromagnet, or electromagnets, is
energi~ed, a magnetic field which has been created between the
cylindrical magnet and the tubular magnets has its characteristics
changed, i.e. the flux strength or direction of the flux lines is
altered. More importantly, the electromagnets are polar orientated in
such a way that, upon being energized, each electromagnet repels any
ZS tubular magnet which is adjacent to it through the thickness of the
cylindrical magnet. Any tubular magnet so displaced is immediately
drawn by the cylindrical magnet to a new position upon the wall of the
cylindrical magnet so that the positions of the tubular magnets, and
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thus of the conductor pairs, constantly change as the pairs are fed
through the apparatus. Figure 8 shows positions of tubular magnets in
the cylindrical magnet during operation of the apparatus, and also
illustrates the movement of certain tubular magne-ts 96 across the
feedpath to assume new positions when repelled from the cylindrical
magnet by energization of the appropriate electromagnets.
Thus, the conductor pairs in the use of the second
embodiment are constantly changed in position as they are fed towards
the stranding machine so that the effect achieved in the first
embodiment again results. It follows from this that the relative
positions of the conductor units in the Finished core unit at any
position along the length of the core unit are influenced by the
relative positions of the conductor units as they are dra~n into the
forming and take-up means. The relative positions of the conductor
pairs in the finished core unit therefore change in a random fashion.
In a modification of the second embodiment (Figure 9),
the apparatus is visually exactly as described above. However, in the
modification, the polarity around the outer surface of the tubular
magnets and around the inner surface of the cylindrical magnets 80 and
82 is the same, so that the cylindrical magnets repels the tubular
magnets from it. In this case, the electrolnagnets 84 when energized
serve to attract the tubular magnets towards them. Thus, in use, the
cylindrical magnet tends to move the tubular magnets towards the axis
of the feedpath and the tubular magnets move around each other because
of their mutual repelling forces. Energization of any electromagnet 84
attracts the closest tubular magnets toward the inner surface of the
cylindrical magnet, thereby causing relative movement of the tubular
magnets. When any electromagnet 84 is de-energized, then the tubular
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magnets which 'nave been at-tracted tnwards it immediately move back
towards the axis of the feedpath and assume new positions within the
tubular magnet group.
The modification of the second embodiment differs from
the second embodiment in that it is provided with d limiting means for
the tubular magnets to prevent the tubular magnets moving downstream,
both under the pull of the conductor pairs and under the repelling
force of the cylindrical magnets 80 and 82~ This limiting means is
shown in Figure 9. The limiting means is in the form of a housing 98
which surrounds the feedpath, as shown. The housing may be of any
suitable shape, but in this case is cylindrica1. The housing is
substantially coaxial with the cylindrical magnet and is placed
sufficiently close to the ends of the tubular magnets to provide
positive limiting action to their downstream movement. The housing 98
is itself a magnet having axially displaced poles with its upstream end
having the same polarity as the outer surfaces of each of the tubular
magnets. Thus, if there is any tendency for the tubular magnets to
move downstream, then this is prevented by the repelling magnetic force
created between the like poles of the tubular magnets and the housing
98.
A third embodiment is illustrated in Figures 10 and 11.
In this embodiment, the repelling action of a housing is used to
levitate the guides for the conductor pairs and is similar in its
action in some ways to the modification of the second embodiment.
In the third embodiment, the position changing means
comprises a plurality of -tubular magnets 100 to act as guides, one for
each of the conductor pairs. The polarity of the guides is as
described in the second embodiment. The feedpath for the conductor
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pairs is bordered heneath it and at its two sides by a three-sided
housing 102, which is itself a magnet. The polarity of the magnet 102
is such that its poles are displaced through its thickness with the
polarity at its inner surface the same as the polarity at the outer
surface of the tubular guides 100. Thus, the repelling force of the
housing 102 holds the guides 100 levitated away from its base and away
From the sides. To prevent the guides 100 from moving downstream, a
limiting means is provided which is a surrounding housing 104 spaced
slightly away from the housing 102 in the downs-tream direction. The
housing I04 is itself a magnet having axially displaced poles and the
upstream polarity repels that at the outside surface of the tubular
magnets 100. Thus, as discussed with regard to the modification of the
second embodiment, the tubular magnets are retained in position along
the feedpath by the repelling force of the housing 10~ against any
tendency for the tubular magnets to be forced away from the housing 102
by the magnetic field at that position, and also by the drag imposed by
the conductor pairs~ Thus, the housing 102 is a fluid force producing
means which also includes an electromagnetic means comprising a
plurality of electromagnets 106 positioned at and carried by the sides
and base of the housing, as shown in Figures 10 and 11~
In use of the apparatus of the third embodiment, the
conductor pairs are fed in unstranded fashion, as described above,
through the tubular magnets 100, one through each magnet. The pairs
then proceed towards the closing die and the stranding machine to form
the core unit. The tubular magnets are held in levitated position
within the housiny 102 by the mutual repelling force of housing and
magnet and the conductor pairs tilemselves prevent the tubular magnets
from being repelled upwardly and completely from within the housing.
To effect independent and relative movement of the tubular magnets, the
electromagnets 106 are energized intermittently so as to change the
flux pattern and strength of the magnetic field within the housing in a
randomized fashion. This change in the field affects each of the
tubular magnets differently because of their different positions, and
hence relative movement~ either vertically or hori~ontally, of the
magnets takes place. Thus, the positions of the conductor pairs
constantly change as they move through the housing 102 and this
constantly changing position is reflected in the constantly changed
positions along the length of the finished core unitO
In a fourth embodiment as illustrated in Figures 12 and
137 in a position changing means, guides 108 for the conductor pairs
are again tubular magnets of the same structure as described in the
second embodiment. A fluid force producing means in this construction
comprises an inner bar magnet 110 which, as can be seen, is disposed
centrally of the feedpath which is defined outwardly by a cylindrical
housing 112. As shown by Figure 12, the bar magnet 110 extends
substantially the whole length of the tubular magnets 108, whereas the
cylindrical housing is axially shorter and is of sufficient axial
length for the purpose of supporting electromagnetic means in the form
of a plurality of electromagnets 114 in spaced apart positions around
the feedpath. The cylindrical housing is carried by a base plate 116
and the bar magnet 110 is itself carried upon a support by a
non-permeable plate 118~ The bar magnet has radially displaced poles,
wi~h the outer pole being of the same polarity as the outer pole of
each of the tubular magnets 108.
In use of the apparatus of the fourth embodiment, the
tubular magnets and their conductor pairs are supported in normal
~9 .
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- 23 -
supported positions in their passage through cylinder 112 by guide
rollers (not shown) upstream and downstream of the cylinder. The
magnets are repelled From the bar magnet so that they move outwardly
within the space defined by the cylindrical housing 112 and from their
normal supported positions. Upon any of the electromagnets 114 being
energized independently and intermittently, this energization changes
the pattern of the magnetic field within -the housing, thereby
displacing a tubular magnet or magnets relative to others and this
displacement is enhanced by the fact that the tubular magnet needs to
avoid the bar magnet 110. Thus, a randomized movement of the tubular
magnets result.
In a modification of the fourth embodiment (not shown),
the electromagnets 114 are rotatable around the feedpath. This may be
effected by rotatably mounting the cylindrical housing 112, possibly in
the manner described with regard to the carrier 86 described in the
second embodiment.
