Note: Descriptions are shown in the official language in which they were submitted.
STRANDING ~CHTNE PROVIDED WITH CENTRAL soBBINs
The present invention relates to a stranding machine
which comprises a plurality of bobbins assembled in idle relation
on the machine shaft, which bobbins are used both to strand and
to wind up new wire.
~ achines of this type are employed to strand several
wires together or to strand several wires about a central core,
as for instance a rope, the conductor of an electric cable, or a
similar element of considerable length progressively moved in
the direction of its axis.
In general, the machines comprise a plurality of hollow
shafts aligned with one another, each of which is-free to rotate
about a support and is driven into rotation by appropriate motor
means, at least one pair of bobbins assembled on the shaft in
idle relation but permanently fixed to it, a paying-off element
or arm for decoiling the wire from a bobbin, and appropriate
driving pulleys.
In these machines, during the stranding operation, the
wires of one of the bobbins of all the pairs assembled on each
shaft in idle relation thereto are progressively paid off from
the related adjacent decolling element which in said phase is
fast with the rotating shaft and, by means of a system of pulleys,
the wires are guided through the plurality of hollow shafts
towards the stranding station, the necessary tension being
exerted by appropriate tensioning means.
On their turn, the second bobbins of the various pairs,
adjacent on the same shaft to the stranding bobbins, are driven
into rotation to be loaded with coils of new wire which will be
subsequently used for the stranding phase when the first adjacent
bobbins are exhausted.
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In machines of this kind, it is necessary to impart to
the wire a correct paying-off tension and to provide convenient
tension regulation systems; also, i~ is important to carry out,
when the machine stops, a relevant braking action, stronger than
that exerted in the paying-off phase, so as to stop the bobbin
at the same moment at which the machine is stopped.
In fact, when the sense of rotation - in the paying-off
phase - is concordant with that of the arm, so that the latter
is always pulling the bobbin into rotation, the absolute speed
of the bobbin is equal to the arm speed, for instance of the ;~
order of 600-700 r.p.m., plus the paying-off speed, for instance
of the order of 50 r.p.m.
On the contrary, when the sense of rotation - in the
paying-off phase - is opposite to that of the arm, the absolute
speed of the bobbin is equal to the arm speed minus the paying-
off speed, but is still very high.
Therefore, in the above described machines it is necessary
to provide a system which - besides~putting the wire under `~
tension - must supply to the bobbin, when the machine stops, a
strong braking force, because the rotation of the bobbin in-
volves, besides the paying-off speed, also the speed caused by
pulling which is ten or more times higher than the paying-off
speed.
The provision of a satisfactory solution is complicated
by the need of further complying not only with the working con-
ditions of the machine to obtain a good stranding, but also with
those caused by a stopping due to any reason, this must be
ensured by means which are able to allow an automatic passage ~`
from the light tension action exerted on the wire to be payed-
off to the strong braking action necessary to stop the bobbin,
and a further feature must be the possibility of a quick release
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of the bobbin to enable it to pass from the stranding phase tothe reloading phase.
Further, the provided solution must be suitable for a
simple and economical application to a plurality of bobbins,
which sometimes is considerable, comprising, for instance, 18
pairs of bobbins or even more.
It is moreover to be noted that in the above indicated
machines, the involved speeds lead to the facing of the problems
originated by the high centrifuga~forces which could compromise
or handicap the means envisioned to put the wire under tension
and to brake the bobbins.
The Applicant considers that the improvements to be made
to the above indicated stranding machines must ensure the three
following characteristics: an immediate braking of the bobbins
when the machine stops, a tension of the wire being stranded
which can be automatically applied to all the bobbins mounted
on the shaft in a central position and a quick release of the
bobbins for their subsequent reloading.
The present invention aims at providing a stranding
machine provided with central bobbins which is able to solve all
of the above mentioned oroblems, ensuring, therefore, an im-
proved performance.
Accordingly, the object of the present application is a
stranding machine for several wires, which comprises a plurality
of pairs of bobbins, used both to strand and to wind up new wire
and assembled in idle relation on at least a hollow shaft free
to rotate about a support, a pair of discs idle Oll said shaft
and h~ving an axially inner position with-respect to a pair of
bobbins, each of said discs being made fast with the shaft when
the adjacent bobbin is in the stranding phase and.which com-
prises a paying-off element or decoiling arm with a respective
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.
pulley intended to guide - in combination with a group of
pulleys - the wire payed-off from the bobbin towards the inside
of the hollow shaft where it is subjected to tension and is
dragged inside said shaft towards the stranding station, the
machine being characterized in that it comprises connection
means between the bobbin and the disc which originate in the
stranding phase a controlled relative movement between the
bobbin and the disc and secure the -former to the latter when
the machine stops, and means to disengage the bobbin from the
disc to prepare it for the subsequent phase of reloading with
new wire and during said phase. In a preferred embodiment, said
connection means comprises a band brake wrapped at a pre-
established angle around the periphery of a suitable brake drum
for the bobbin, the band ends being respectively connected to a
point on the disc and to a first spring having pre-established
characteristics and applied to the disc in such a way as to
transmit to the band a braking orce able to stop the bobbin
loaded with the wire, rotating at its rated speed, at the same
time at which the machine stops, a unit for adjusting the
tension of the wire to be payed-off formed by a system of levers
swinging about a pin on the disc in accordance with the wire ~;
tension and acting on a pulley associated with a first side of
the lever and with the contrasting action of a second spring of
pre-established characteristics, applied to the disc with one
end on the second side of the lever, and hy an element able to
transmit a tension of the wire, which is higher than the con-
trast force of said second s~ring from the lever system to the
band brake, to vary the braking action of the band on the ~
bobbin drum and to maintain at a constant value the tension of ~ .
the wire being payed-off. According to a particular solution,
the means for releasing the bobbin from the disc when the
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machine is stopped comprises a device permanently associated
with the disc and provided with an element exerting a tension
action on one of the two ends of the first sprin~ during the
stranding phase and ahle to nullify the camber o~ said first
spring when the machine is stopped.
From the above, it can be noted that according to the
~referred solutions, the main features of the invention consist
in a band connection between the bobbin and the disc, a device
for adjusting the tension action in the stranding operation,
and a releasing device for the immediate passage of the bobbin
from the stranding phase to its-reloading with new wire.
The band connection, associated with the tension
adjusting system, produces a wire tension of constant value in
the relative movement between the bobbin and the disc; in par~
ticular, owing to the above described characteristics, during
the transitory step preceding the machine stopping, the action
exerted by the element transmitting the wire tension on the
band brake is progressively reduced, thus giving rise to a
progressively increased braking action of the first spring,
until the elimination of the relative movement between the disc
and the bobbin.
The releasing device completes the above cited band
connection since in the stranding phase it has the task of
loading the first spring; when the machine stops, the relative
approach of the ends of said first spring permits the disengage-
ment between the disc and the bobbin. ~;~
According to a preferred embodiment, particularlyintended to reduce the effect of the centrifugal force on the
wire tension adiusting system, the machine is characterized
in that in the lever system, the lever pin and the axis of
rotation of the pulleys on the lever are in a position radial
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to the axis of rotation of the machine.According to a further embodiment, the st~anding machine
is characterized in that the wire to be payed-off, before
passing on the swinging pulley of said lever system, travels on
a return roller arranged parallel to the bobbin axis and im-
mediately outside the bobbin flange.
The present invention will now be better understood from
the following detailed description, given by way of non-limiting
example and made with reference to the figures of the attached
sheets of drawings, in which:
Fig. 1 is a longitudinal view of the machine which,
for simplicity's sake, comprises only two pairs of
bobbins;
Fig. 2 is a front view of the disc adjacent to a
central bobbin and shows the wire tension adjusting
means, the bobbin braking means and the bobbin release
device;
Fig. 3 illustrates a detail of the wire tension
adjusting system in a longitudinal partial view of the
machine, but not showing the band brake;
Fig. 4 is a partial perspective view of the machine
showing the travel of the wire through the pulleys as
far as the inside of the machine shaft; and
Fig. 5 illustrates a detail of the bobbin releasing
device.
The invention is applicable to machines for manufacturing
one-layer strands or several layer strands having alternate
senses and/or different pitches.
The following description concerns one of the possible
embodiments of the invention; for instance, it concerns a
machine 1 (Fig. 1) used to strand several wires 2 about a
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t~
central core or, still by way of example, to form a screening
about the central part 3, formed by the conductor and relative
insulation, of a power cable.
The machine comprises several units 4, equal in number
to the number of wires to be stranded. Each unit comprises a
hollow shaft 5 (Figs. 1;3) free to rotate about a central
support 6, a pair of bobbins 7,8 assembled in idle relation on
the shaft 5 at the sides of the support 6 and used simultaneously
both to strand and to wind up the wire, their function being
inverted in successive steps, a pair of discs 9,10 mounted to
idle on the shaft 5 at the sides of the support 6 in an axially
inner position with respect to the bobbin, a paying-off element
or decoiling arm 11 carried by each disc with a related pulley
12 and intended to pay-off wire from the bobbin and to guide it
- by means of a further pulley 13 mounted on the revolving
shaft 5 - inside the latter, a single dispenser 14 (Fig. 1) of
the wire to be alternatively wound up on either bobbin of the
pair of bobbins 7,8, and a system for transmitting motion to
the bobbins in the winding-up phase.
The units 4 of machine 1 - iIlustrated in number of two
for simplicity's sake - have their respective shafts 5 aligned
and separated so as to allow an advantageous connection between
the end of the wire payed-off from bobbin 8 in the stranding
phase and the end of the adjacent bobbin 7' of other units 4,
loaded by dispenser 14 during the stranding phase of bobbin 8.
An appropriate auxiliary shaft 15, by means OL gears or
other equivalent driving means provided on supports 6, rotates
the shafts 5 and the discs associated with them ~ith suitable
means in the stranding phase of the respective adjacent bobbins.
All the units 4 (Fig. 1) are situated between a core
paying-off stand 16 and a final station 17 which comprises a
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P~l~
perforated plate 18, for the passage of the wires 2 through
suitable holes, which plate 18 rotates integrally with the
shaft of the last unit, a die 19 secured to a base 20 and con-
ventional tensioning and collection means (not illustrated).
Therefore, the wires 2 and the core 3 are guided
inside the plurality of shafts 5 and are subjected to the
tension imparted by the tensioning means.
Of course, when the machine is used to manufacture
multi-layer strands, for instance, two-layer strands, the
machine units are divided into two successive groups, one for
each layer, each group having units whose rotation senses and
speeds are egual to or different from, those of the units of
the other group, depending on whether the layers have alternate
laying senses or not, each group being moreover provided with
the relative plate 18 for the passage of the wires and with the
thereto associated die 19.
The dispenser 14 of the wire to be alternatively wound
up on either bobbin of one same pair and the system for im-
parting motion to the bobbins in the winding up phase can be
identical to those described in the Canadian Application No.
363,576 of the same applicant filed on October 30, 1980.
In particular, mention is made of the fact that dis-
penser 14 comprises an arm 21 which is rotatable through an
angle of 180 from one bobbin to the other and which can be
moved in a direction parallel to the machine axis with a stroke
corresponding to the distance between the flanges of the bobbin
and an end pulley 22, able to guide the wire coming from a i`
feeding drum on the machine bobbin, which moves together with
arm 21.
The actuation system of the bobbins in the winding-up
phase can comprise a central shaft, positioned between the
discs and driven by a motor independent of the main shaft 15,and two
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lateral shafts, assembled on the discs in idle position and
connected to gears of the bobbins. This embodiment foresees
specific claw clutches between the lateral shafts and the
central shaft, which are ex~lained in detail in the above cited
application of the applicant and are not described herein for
brevity in the present specification.
Some main characteristics of the invention illustrated
in detail in Fig. 2 will now be explained more particularly.
More precisely, such characteristics relate to the c~nnection
means between the bobbin and the disc which are able to produce,
in the stranding phase, a controlled relative movement to obtain
a correct tension of the wire, and to secure the bobbin to the
disc when the machine stops, as well as to the means able to
disengage the bobbin from the disc to prepare it for reloading
with new wire and during the latter step.
These means, the same for each unit of the machine, are
described with reference to bobbin 8 and to disc 10 of Fig. 1.
The connection means comprises (Fig. 2) a band brake 23
acting on bobbin 8, a lever system 24 sensitive to the variations
of tension of t~e wire payed-off from bobbin 8, an element 25
arranged between the lever system 24 and the band 23 for trans-
mitting a change in the tension of the wire being payed-of
which is higher than a pre-established value, saia element being
able to vary the braking of the band on the bobbin, adjusting,
therefore, to a practically constant value the tension of said
wire payed-off.
The band 23 is wrapped - at a pre-established angle -
around the periphery of an appropriate brake drum 26 secured to
the bobbin, one end 27 of the band being connected to a fixed
point on disc 10 and the other end 28 being subjected to the
action of a first spring 29 having such characteristics and
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ap~lled to the disc in such a manner as to transit to the band
a braking force able to stop the bobbin, loaded with the wire
and rotating at the rated speed, at the same moment at which
the machine is stopped.
Preferably, the band brake 23 comprises a plate 30
rotatable about a pin 31 parallel to the disc 10 axis and
mounted on the disc. The plate 30 is attached to, respectively
applied on opposite parts with respect to the pin 31, a first
end 32 of the first spring 29, the second end 33 of which is
secured and stretched on a part 34 fast with the disc 10, and
an end 35 of the element 25 which transmits the variation of
the wire tension between the lever system 24 and the band 23.
The plate 30 carries moreover the end 28 of band 23,
the connection being made at the same side - with respect to the
pin 31 - on which is applied the first spring 29.
By means of the above indicated arrangement, the first
spring 29, subjected to tension by the action exerted on end 33
secured to the disc, originates with respect to pin 31 a rota~ -
tion of plate 30, the sense of rotation - as shown in Fig. 2 -
being such as to wrap closely the band 23 around the brake drum
and to impart to it the maximum braking force.
The release of this braking action depends on the action
exerted on plate 30 by element 25 in accordance with the oscil-
lations of system 24 providing the wire tension adjustment,
which will now be explained in detail.
Substantially, said lever system 24 is based on the use
of a lever, having a rotation pin on an appropriate support fast
with the disc, and with sides respectively subjected to the action
of the wire and to that of an opposing spring 43.
The spring 43 has pre-established characteristics, in
the sense that it ensures an unvaried position of the lever as
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lor.g as the wire does not exceed a pre-established tension; in
the contrary case, the oscillation of the lever act~ on the
transmission element 25 and the bobbin is released to bring again
the wire tension to a practically constant value.
Several typical solutions in respect of the wire tension
adjusting system can be provided iII accordance with the above
indicated principle. The preferred one will be described here-
below.
Said solution comprises a lever 36 whose mounting pin
37 is associated with a support 38 (see Figs. 3,4) extending in
a direction substantially parallel to the bobbin axis. The side
39 of the lever bears a pulley 41 having an axis of rotation 42,
whilst the side 40 is, instead, subjected to the action of a
second spring 43 having the already cited function and shown in
Fig. 2. The pin 37 of the lever is directed radially to the
bobbin axis (see Figs. 3,4) so that the lever can swing along
planes orthogonal to said direction, with the advantageous
result not to be subjected to the influence of the centrifugal
forces involved, which might otherwise compromise the whole
adjusting system.
The second spring 43 has one end 44 applied to a fixed
point on the disc 10 and the other end ~5 fixed to a further
lever 46 (Figs. 2,3) which has a pin 47 in orthogonal position
to the disc and associated thereto and a side 48 associated at
48' to lever 36 by means of connections (not shown) comprising
a pin slidable in accordance with the oscillations of the system
provided at the fork end of side 40 of lever 36.
The end ~14 of the spring can be situated on the disc in
different positions in order to vary the load of the same springs.
Regulation means of conventional type (not illustrated) are pro-
vided for this purpose.~
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~Ztit71~
The second lever 46 is attached moreover (Fig. 2),
and associated with it, to the end 49 of the transmission
element 25 between the lever system 24 and the band brake 23.
In one embodiment, said element 25 is flexible and
transmits only tension forces. For instance, it is a metallic
rope or a nylon string whose end 49 is connected to the lever
46, at the opposite side of spring 43 with respect to the
position of pin 47.
The use of a metallic rope instead of a rigid element
represents a further advantage of the invention. In fact,
being flexible, the rope can be curved by passing, for instance,
over a pulley 25' associated to the disc (Figs. 2,5), permitting
an easy arrangement of both springs inside the space defined by
the rope itself. Effectively, in this case, the two springs can
be situated very near to the centre of rotation of the disc 10,
reducing therefore the influence of the centrifugal force and,
ultimately, affording the advantage of a correct braking of the
bobbin.
Still with reference to the preferred embodiment con-
cerning the lever system 24, description will now be made ofthe travel of the wire payed-off from the bobbin, before and~
after its passage about the pulley 41 swinging about pin 37.
The wire 2 outcoming from the bobbin 8 is at first
directad on the return roller 50 (Fig. 4), which is mounted to
idle on shaEt 11 :in a direction parallel to the bobbin axis
and immeaiately outside flange 51. Then, it passes around
pulley 41 of lever 36, and then it is directed around pulley 52
which idles on shaft 11, in a way independent from roller 50.
Subse~uently, it is deviated towards pulley 13 mounted on the
shaft 5 and then passes inside the shaft 5 towards the stranding
station.
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According to the above cited preferred solution, the
wire 2, instead of passing at first on a pulley integral with a
paying-off arm and then on a pulley secured to the shaft 5,
namely instead of following a practically rectilinear travel,
the wire 2 travels along a multi-directional line, namely is
substantially deviated several times, hence, with a reduction
of the maximum radius of the rotating parts of the machine owing
to the presence of the return roller 50, on which the wire
passes directed to pulley 41, and with the consequent possi-
bility of increasing the machine speed because - the radial
dimensions being reduced - the problems regarding balance and
structure are less, so that a lesser power absorption due to
aerodynamic resistance is achieved.
The further main characteristic of the machine, regarding
the means for releasing the bobbin from the disc to prepare it
to be reloaded with new wire and during said phase, will now be
explained.
Said means (Figs. 2,5) comprise a device 53 permanently
secured to disc 10 and moved into rotation with the latter even
during the stranding phase.
The device 53 acts on one of the two ends of the first
spring of the band brake 23 and is based on the principle of
stretching said spring during the stranding phase and of allowing
an approach of the spring ends and therefore a reduction of the
relative camber, with release of the bra~e when the machine
stops.
As indicated in the figures, the device 53 acts on the
second end 33 of spring 29 and comprises a peg 54 and a seat 55
on the disc 10, intended to receive the end of the peg pushed
by a small spring 56.
On its turn, said peg 54 can be situated at the end of a -
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lever 57 having a rotation pin 58 on the disc lO, an end 33 of
spring 29 being applied to said lever 57 in a position opposite
to the peg 54. The device further comprises a handle 58' to
rotate the lever 57 in the clockwise direction with reference to
Fig. 2, thus releasing spring 29 and opening the band brake 23.
After the description of the main features of the in-
vention, it will be easy to understand the relative working
operations herebelow indicated, starting from the arrangement of
Fig. 1, in which the bobbin 7,7' and 8,8' of the units of
machine 1 work in the winding phase and in the stranding phase,
respectively.
During the reloading with new wire, the disc 9 of bobbin
7 is secured, for instance, by a pin, to the central support 6
with an appropriate orientation which is just selected to move
the paying-off arm ll downward and to avoid any interference with
the wire guiding system 14.
The bobbin 7 is rotated by the motor purposely included
for re-winding the wire coming from a feeding drum and/or reel,
an adjusting action on the coils to be formed being exerted by
dispenser 14 which moves in one sense or in the opposite sense
the moving arm 21 and the pulley 22 at a speed correlated, by a
pre-established rate, to the revolutions of bobbin 7.
The winding up of new wire on bobbin 7' is carried out
in an analogous manner.
During the stranding phase, disc lO of bobbin 8 is
connected, for instance, by a pin, to an appropriate flange, not
shown, of shaft 5, which is rotated by the~auxiliary shaft 15,
and the transmission motion for reloading the bobbln with new
wire is interrupted.
The bobbin 8 is rotated about shaft 5 in consequence -
of the tension exerted on the wire 2 by the tensioning means,
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and said wire ~ is guided in its passage from the outside to
the inside of shaft 5 at first through its contact with the
periphery of the return roller 50 (Fig. 4), then on pulley 41
of the adjusting lever 36, then on pulley 52 at the end of
roller 50 and finally on pulley 13, the mounting of which
rotates with shaft 5.
Simultaneously with wire 2, the cable core 3 passes
inside shaft 5. Also, said core 3 is subjected to the tension
exerted by the tensioning means and is directed from the
paying-off stand 16, through the hollow shafts of all units 4
of the machine, towards the stranding station 18-19.
Still in this phase~the tension of wire 2 passing over
pulley 41 on the swinging lever 36 is balanced by the reaction
force of the spring 43 (Fig. 2). The tension resulting from
; said balance, through the metallic rope 25, exerts a reducing
action on the braking of band 23 exerted by spring 29, the band
23 being around the brake drum of the bobbin.
When the machine stops for any reason, disc 10 is braked
separately by a suitable brake, for instance pneumatically
actuated~ and bobbin 8 tends still to rotate relative to the
disc.
Consequently, a slackening of the wire takes place, so
that the action exerted by the wire on the band brake 23 through
the pulley 41 and the swinging lever 36 and intended to reduce
the braking action is eliminated. Therefore, the brake, no
longer subjected to the tension exerted on the metallic rope 25,
may apply its maximum braking force, giving rise to a closer
coupling between disc 10 and bobbin 8 until their relative
movement is stopped.
The operation of bobbin 8' in the stranding phase takes
place analogously to what is indicated for bobbin 8.
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In the intermediate steps, the inversion in the function
of the bobbins of a same unit occurs as follows:
- when the machine is stopped, the bobbin 7 is disengaged
from the motor intended to reload new wire and disc 9
is coupled to a suitable flange of shaft 5;
- then the end of the wire on bobbin 7 is connected to
the end of the wire on the bobbin which is already
empty and which is carried by the adjacent unit
nearest the stranding station 19.
An analogous system is used to prepare for the stranding
phase the bobbins reloaded with wire in the preceding phase in
all the units of the machine.
Then the bobbin 8, already empty, is prepared to its
subsequent reloading with new wire.
This is carried out by acting on handle 58l (Figs. 2,5)
of device 53, thus causing the disconnection of peg 54 from its
seat 55 on disc 10 (Fig. 5) and the consequent release of
spring 29, which results in the release of the bobbin.
Then - with bobbin 8 free to rotate - the following
operations are carried out:
- at first disc 10 is angularly moved in such a way that
the paying-off arm 11 does not interfere with the
position to be taken by dispenser 14 with its wire~
guiding arm 21; ~;~
- th~e moving arm 21 is then rotated through 180 until
pulley X2 is aligned with bobbin 8;
- the disc 10 is secured to the support and the wire
reloading motor is mechanically connected to bobbin 8;
- at last the wire coming from the feeding drum or resl
is guided around pulley 22 and hence around bobbin 8
and the reloading of bobbin 8 is started.
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In particular, the invention has the advantage that the
bobbin braking elements, namely the two springs and the brake
band, are arranged in a position extremely near to the disc, ::
without an excessive deviation in axial direction, so that they,
together with the other parts of the machine, contribute to the
arrangement of many pairs of bobbins in a relatively reduced
area.
Although the present invention ha~ been described and
illustrated with reference to a preferred embodiment, it is : -
understood that its.scope includes any other possible embodiment
deriving from the above indicated inventive principle.
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.A.
