Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to the stranding of wires.
It is known that the twisting of wires together
during their assembly together offers physical and electrical
advantages when used in communications or other electrical
systems. For example, twisting of pairs of wires as used in
telephone systems improves electrical characteristics, such as
reducing crosstalk.
Conventionally, to continually twist wires
together in the same direction requires a heavy movable con-
struction as the wire spools for feeding wire into the apparatusmust also revolve about the machine axis. The heavy construc-
tion limits the operational speed. To avoid the rotation of the
spools, a periodically reversing twist is given to the wires and
as it is desirable to twist long lengths of wires, accumulators
become necessary.
In order to overcome problems with known twisting
apparatus, simplified apparatus has been devised to give a
periodic reverse twisting operation. This simplified apparatus,
as described in Canadian Patent No. 996,824 in the name of
Phillip John Reed, assignee Northern Electric Company Limited,
involves the use of a tubular member one end of whiah is held
stationary and the other twisted first in one direction and
then the other. Dividers positioned along the tube form separate
paths for wires pa~sing down the tube and a twisting means at a
tube outlet places the reverse twist in the wires.
The invention described in the above patent is
effective in creating reverse twist. It has certain disadvan-
tages, however, namely that because it is long, i.e. about 37
feet long (11.27 meters) with 0.5 inch (1.27 cms) inside
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diameter, it is difficult to thread or pass wires in their
correct positions down the tube and this procedure is a
tedious and time consuming operation. If the tube is formed
of transparent plastic to give visual aid to wire threading,
the transparency is lost after a short period of use due to
impurities deposited upon the tube surface and due to changes
in the plastic itself. Also, the friction between the wires
and the inside wall of the tube may be sufficiently high to
result in some stretch.
According to the present invention, apparatus for
stranding wirescomprises an elongate member having a longitudi-
nal axis and being rotationally flexible about said axis; a
plurality of wire guiding elements extending radially outwardly
from the member and defining a plurality of longitudinally
extending wire guiding holes, the holes being angularly spaced
around the axis, for passage therethrough of a plurality of
wires, and also being longitudinally spaced with each hole
corresponding with other longitudinally spaced holes to define
a single guide path for wire; wire twisting means at the
downstream end of the member, the twisting means extending
outwardly of the member and defining a plurality of longitudi-
nally extending holes, one for each of the paths and angularly
spaced around the axis; holding means for holding the member
stationary at a position upstream of the wire guiding elements
and of the downstream end; and means for rotating the downstream
end of the member and the twisting means for a predetermined
number of revolutions about the axis alternately in one direction -
and then the other.
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In a preferred arrangement, each of the guiding
elements is a disc through which the elongate member extends
with the disc secured to the member. Each disc is formed with
a plurality of angularly spaced holes, one for each guide path.
Alternatively, each guide element is a plate extending outwardly
from the elongate member and extending around predetermined
degrees of arc. The plates would each be provided with holes
for some, but not all, of the paths and plates would be angularly
as well as longitudinally spaced to provide holes for all of the
paths.
The elongate member may comprise a single tube,
rod or wire or may comprise a plurality of tubes, rods or wires
suitably joined end-to-end to transmit angular twisting motion
from the downstream end along the member. Alternatively, the
elongate member is of composite construction desi~ned to give
small inertial resistance to change in direction of rotational
movement. Composite constructions useful in this regard are
formed from plastic. One particular construction has a core of
plastic rope with a braided cover jacketed by a covering layer
which may be nylon. Low inertial resistance allows the
apparatus to be operated at higher speeds of oscillation than
is possible with apparatus described in Canadian patent 996,824
and with less driving power requirements.
It is preferable that the means for rotating the
downstream end of the elongate member and the twisting means
is drivably connected directly to the twisting means which
in itself drives the elongate member. Advantageously,
the twisting means is drivably secured to the elongate member
by the downstream end of the member having a mechanically
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secure connection in the twisting means. To distribute
torsional stresses along the elongate member, the twisting
means is secured to an axially extending movement transmission
tube which is disposed within it and extends further along the
elongate member than the twisting means, the tube being securely
and non-rotationally held onto the elongate member, for instance
by epoxy resin poured into the tube and allowed to set.
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 showing the ,
basic concept of the invention;
Figure 2 is a cross-sectional view taken along
line II-II in Figure l;
Figure 3 is a side elevational view of
apparatus forming one embodiment;
Figure 4 is a detail of the first embodiment in .
longitudinal cross-section and on a larger scale;
Figure 5 is an end view in the direction of
arrow "V" in Figure 4.
Figure 6 is a side elevational view o~ apparatus
forming a second embodiment;
Figure 7 is a side elevational view of part of
an elongate member forming part of a third embodiment;
Figure 8 is a side elevational view of an
elongate member with ~uiding elements attached and forming a
part of a fourth embodiment.
As shown in Figure 1, the invention is basically
concerned with stranding wire by the use of apparatus which
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comprises an elongate member 10 having a longitudinal axis
and having a plurality of wire guiding elements 12 spaced
apart along the member 10. The guiding elements 12 are
secured to the elongate member and as shown may be discs
(see also Figure 2) with the member 10 passing through a
concentric hole in each disc.
To guide wires to be stranded as they are
passed longitudinally of the member 10, each guiding element
12 is formed with angularly spaced-apart wire guiding holes
14 (Figure 2), one hole in each guiding element for each wire.
In the example of Figures 1 and 2, four holes are provided but
the number may vary and is dependent upon the number of wires
to be stranded. Guide paths for the wire are provided by the
holes 14 with each wire passing between elements and through
corresponding holes in the elements. In Figure 1, one wire
16 only is shown passing between elements 12 for reasons of
clarity and so as not to be confused with the elongate member
10 .
The elongate member 10 is rotationally flexible
about its longitudinal axis. The member 10 is held stationary
in a frame (shown diagrammatically at 18) at an upstream end,
when considered in the ~ense of direction of wire movement,
by a holding means which may be a wire guide block 20 secured
to the frame. In end view, the block is similar to Figure 2
in having four holes 14 corresponding to those in the guiding
elements 12. An upstream end of the elongate member is secured
into the guide block to prevent their relative rotation.
At the downstream end of member 10 is provided a
twisting means which is conveniently à short so~id cylinder 22
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having holes 14 ~gain corresponding to the number of holes in
the guiding elements 12. The member 10 is non-rotatably secured
to the twisting means.
In use of the invention, the wires 16 are fed
along their paths through the discs and through the twisting
means 22. The twisting means and downstream end of member 10
are then rotated for a predetermined number of revolutions in
one direction and then the other alternately in each direction
from a normal untwisted position of member 10 in which all wire
paths through the holes 14 are substantially straight. The
number of revolutions on each side of the normal untwisted
position may be as desired and may, for instance, be 20 revolu-
tions. Rotation at the downstream end clearly twists the member
10 in each direction as the upstream end is fixed at 18 and the
wire paths take on helical configurations to guide the wires
through the xotating twisting means 22.
The wires are fed continuously through the holes
and along the member 10. The rotation of the twisting means
and its directional change causes the wires to be stranded to-
gether, as they issue from the twisting means, in oppositedirections of twists which alternate with one another. By
holding the twisted wires by some means (not shown), after they
emerge from the twisting means, any tendency for the wires to
become untwisted iB avoided.
In a first embodiment shown in Figure 3, in
which parts similar to those already described bear the same
reference numerals, apparatus is provided for stranding four
wires 16. The four wires are shown entering the guide block
20 and emerging from the cylinder 22 but are omitted in between
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for clarity.
The elongate member in this embodiment is steel
rod which is high strength music wire but some alternative
may be used such as steel wire. The diameter of the rod is
small (around .06") and is capable of transmitting sufficient
torque to rotate the discs 12 with it. As shown in Figure 4,
the twisting means or cylinder 22 is about .625" diameter and is
securely attached to a concentric stainless steel transmission
tube 24 of greater axial length than the cylinder. This tube
has the downstream end of the elongate member lO extended
through it and secured within it by epoxy resin 26 which
fills the tube and completely embeds the part of the member 10
within the tube. Because of the extra axial length of the tube
24 over member lO, torsional stresses are more evenly distributed
over its downstream end than would be the case if the member 10
was directly connected to the cylinder 22.
The end of member 10 is also non-rotatably
attached directly to the cylinder 22 by providing the end with
a radially extending element in the form of a closed eye 28
which is received within a diametral slot 30 in the cylinder
(see Figure 5). The slot is filled with solder.
Means 32, shown generally in Figure 3, is
provided for rotating the downstream end of the elongate
member 10 and the cylinder 22. This means comprises two
clutches 34, 36 mounted in axial alignment upon a hollow
shaft 38 which is secured around the upstream end of the
cylinder 22 as is clearly shown in Figure 4. Each clutch
has a stub shaft 40 freely carried upon shaft 38 and a pulley
wheel 42 on each stub shaft is drivable by a belt 44. The
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pulley wheels are driven in opposite directions by
separate motors. Alternatively, the two belts 44 are
replaced by a single pulley belt which passes around one
pulley wheel in the opposite direction to the other pulley
wheel. A single motor is then used to drive the belt which
passes around conveniently positioned idler gears. The
clutches are electromagnetically operated through leads 46.
Each clutch has a driving portion drivably connected to its
pulley wheel and a driven portion connected to the shaft 38.
The clutches are actuated sequentially to
drive the cylinder 22 in opposite directions. It is important
that at the high speeds of operation possible with this
apparatus, that the clutches are actuated precisely as required
to prevent build-up of cummulative errors. An error of a
fraction of a rotation in one direction if left uncorrected
in the other direction could result in wire damage.
In this embodiment, the clutches are controlled
by microswitches 48, 50 actuated by a finger 52 held by a nut
54. The nut is non-rotatably and axially slidably held in the
frame in a manner not shown and is axially moveable along a
screw thread 56 provided upon the shaft 38 between the clutches.
Upon the finger 52 reaching a microswitch during rotation of
the shaft 38 and cylinder 22 in one direction, the switch is
actuated to de-energize one clutch and energize the other so
that rotation is immediately reversed. With this arrangement,
an accumulation of errors cannot occur. Leads 58 connect from
the microswitches to a switch box (not shown) to which leads
46 of the clutches also connect.
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In use, the wires 16 are fed from spools 60
through the block 20, guiding elements 12 and cylinder 22.
Because of the exterior positioning of the holes 14, it is
a simple matter to thread the wires through the holes and
involves a small amount of time. This is especially important
when a wire breakage occurs during manufacture. As the wires
are visible during the whole of their passage, they are easily
checked to see whether they are threaded correctly and their
colour sequence around the elongate member is easily controlled.
The structure has a smaller mass than is pro-
vided by apparatus described in the aforementioned patent and
smaller inertia forces are involved as less mass acts at
rotational distances away from the longitudinal axis of the
member 10. As a result, the rotatable structure is rotatable
at much higher speeds than the structure described in the
earlier patent and the power required to rotate it and reverse
its rotation is thus reduced. With the apparatus of this
embodiment, speeds of the order of 3800 r.p.m. should be
attainable.
The twist in the wires exiting from the cylinder
22 may be provided by physical holding means which has to
operate against ten~ion in the wires. Alternatively, the
wires may be relieved of their tension immediately after
twisting. One way of relieving tension and locking in the
twist is to heat the wires rapidly as they emerge from
cylinder 22. If there is any insulation on the wires, as
with electrical or telecommunications wires, it is he~ted
for a very short period, e.g. 10-15 milliseconds and slight
fusing occurs between the insulating coatings on adjacent
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wires. The heating and cooling is so quick that no damage
occurs to the conductors nor any detrimental change to the
insulating layer.
Another way of physically locking in the twist
is to arrange for the twisted wires to be fed directly into
a coating extruder. It can be arranged that the exit from
the cylinder 22 is very close to the extruder inlet.
Alternatively, a short length of flexible tube can be
positioned between the cylinder and the inlet of the extruder.
The wires are contacted by the extruding material, for example
PVC, as soon as the wires enter the extruder and are then -
locked in their twisted state.
The wires can be relieved of the tension by
passing over a capstan. The twisted wires pass a number of
times round the capstan and the capstan can be overdriven
slightly so that tension is applied to the wires passing
through the apparatus but the wires pass from the capstan,
for example to a take-up spool, under little or no tension.
Alternatively a caterpillar capstan can be used.
Another alternative is to bring several groups
of twisted wires together and twisting or forming into a cable.
Physical contact between the wires would then prevent un-
twisting even if tension were applied.
The music wire of the elongate member has a
useful life at least as good as, and possibly better than
that provided by the tubular member of the aforementioned
patent.
In a second embodiment shown in Figure 6,
apparatus for stranding wire comprises an elongate member
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62 has a plurality of wire guiding elements 12 as described
for member 10 in the first embodiment. Means 32 is provided
for rotating the downstream end of the member. Only an out-
line of means 32 is shown in Figure 6 but it is of the same
construction and operates in a similar manner to the means
32 described in the first embodiment. Four wires to be
stranded are fed from wire give-up devices 64 (only one
being shown), the wires passing over driven pulley wheels 66
to the guiding elements 12.
The apparatus of the second embodiment differs
from that of the first embodiment in the holding means for
holding the upstream end of the member 62 stationary. In
Figure 6 the holding means comprises a counterweight 68
attached to the upstream end of the member 62, the end portion
of the member extending around at least one pulley wheel 70
to be held downwardly by the counterweight. The use of the
counterweight reduces residual tension.
In a third embodiment shown by Figure 7,
apparatus for stranding wire is substantially as described
for the first embodiment. It is different however in that
an elongate member 72 is of composite construction and is
made from plastic. The member 72 has a core 74 of rope
formed from plastic monafilaments (KEVLAR or some oth0r
suitable high strength type) which is covered with a braided
layer 76 of plastic wires such as Nylon. This composite
is then coated with a layer of high strength plastic 78.
This design is particularly light in weight and offers low
inertia forces while being rotationally flexible to allow
for high rotating speeds. The member 72 is held within the
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cylinder 22 in the manner described for member 10 in the
first embodiment. The plastic material of member 62 may even
be formed at its end into a radially extending element mounted
within a slot of the cylinder in a manner similar to that in
the first embodiment so as to assist in transmitting the
driving force to the member.
In a fourth embodiment (Figure 8) which is also
basically similar to the first embodiment, the apparatus
includes an elongate member 80 made from a plurality of rods
82 joined end-to-end. Each rod is joined to an adjacent rod
or rods by a means which allows for a twisting movement along
the member without each rod being individually rotatably
flexible. In fact each rod may be substantially rigid
rotationally. The rods are joined together by interconnected
eyes 84 formed at their ends. The eyes allow for a predetermined
angular movement between rods. This angle may be anything
desirable and could for instance be around 40 of movement.
Hence, with a sufficient number the rods joined end-to-end,
a large number of revolutions of the downstream end of the
member and of cylinder 22 is possible while the up6tream end
is held stationary. It follows that where each rod carries
one disc 12 as shown in Figure 7, the end di~c has a limited
angular movement relative to other discs to enable the wires
to follow helical paths and out through the cylinder 22. The
interconnected eye couplings used in this embodiment will
either eliminate or reduce residual stresses caused by
oscillation.
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