Note: Descriptions are shown in the official language in which they were submitted.
il78859
This invention relates to apparatus for stranding wires.
It is known that the twisting of wires together during
their assembly 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 construction as the wire
spools for feeding wire into the apparatus must also revolve about the
machine axis. The heavy construction 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 appdratus has been devised to give a periodic
reverse twisting operation. This simplified apparatus, as described in
United States Patent No. 3,910,022 granted October 7, 1975 in the name
of Phillip John Reed and entitled "Apparatus For Stranding Wires",
involves the use of a tubular member one end of which 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 passing 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 has a certain
disadvantage in that it is difficult to thread or pass wires in their
correct positions down the tubular member and this procedure is a
tedious and time consuming operation. If the tube is formed of
`` 1~78859
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.
The above disadvantages of wire threading has been
overcome by apparatus described in United States patent No. 4,325,214
granted April 20, 1982, in the name of Bretislav Pavel Zuber and
entitled "Apparatus For Stranding Wire". In this patent, the cubular
member is replaced by an elongate member which is held stationary at an
upstream end and is rotatable at its downstream end for twisting it. A
plurality of wire guiding elements extend radially outwards from the
elongate member and have wire guiding holes whereby the wires are
threaded through the holes from guiding element to guiding element
while being located outwards from the elongate member. Thus the wires
are completely accessible and are visible during the threading
procedure.
According to the present invention there is provided a
practical apparatus for stranding wires with a recovering twist and for
covering them with an insulation material.
The present invention is concerned in one aspec~ with
apparatus for stranding and coverinq wires comprising an elongate
member having a longitudinal axis, being rotationally flexible about
said axis to enable it to be torsionally twisted in alternating
directions, and defining a plurality of feedpaths for wires along the
member; holding means for holding the elongate member stationary at a
position upstream of the wire guiding elements; wire twisting means
secured to the elongate member and defining a plurality of angularly
11~ .
spaced and longitudinally extending holes, one for each of the
feedpaths; rotating means for rotatiny the twisting means together
with a downstream portion of the elongate member for a predetermined
number of revolutions about the axis alternately in one direction and
then the other; reversible driving means drivably connected to the
rotating means of the elongate member, an extension of the elongate
member extending downstream from the rotating means to ensure that
stranding together of wires is avoided until wires pass from a
downstream end of the extension; and an extruder for plastic
insulation for stranded wires, the extruder having an annular barrel
extending along and surrounding the extension, and extending radially
inwards at an outlet end to define an extrusion orifice adjacent to and
immediately downstream from the downstream end of the extension.
It is preferable that the extension is a tube. The
twisting means is conveniently close to the position of the rotating
means along the guide paths of the wires. However, the twisting means
may be at a downstream end of the extension and thus in this case~ the
twisting means prevents the torsionally twisted wires from stranding
together until they have passed through the twisting means. When the
twisting means are close to the rotating means, the extension is
provided with means separate from the twisting means to ensure that the
torsionally twisted wires are not stranded together between the
twisting means and the downstream end of the extension.
According to another aspect of the invention, apparatus
for stranding and covering wires comprises a plurality of elongate
members, each having:
a) a longitudinal axis being rotationally flexible about
said axis to enable it to be torsionally twisted in alternating
.,
1~788S9
.
directions, and defining d plurality of feedpdths for wires along the
member;
b) holding means for holding the elongate member
stationary at a position upstream of the wire guiding elements,
c) wire twisting means rotatable with a downstream end of
the elongate member and defining a plurality of angularly spaced and
longitudinally extending holes, one for each of the feedpaths,
d) rotating means fo. rotating the twisting means
together with the downstream end of the elongate member for a
predetermined number of revolutions about the axis alternating in one
direction and then the other; and
e) an extension extending downstream from the rotating
means to ensure stranding together of the wires is avoided until wires
pass from the downstream end of the extension;
the apparatus also comprising:-
(i) a frame means holding the wire twisting means and
the rotating means and with the elongate members being disposed to
locate the guide paths for the wires through openings defined in the
frame;
(ii) reversible driving means mounted upon the frame and
drivably connected to the rotating means of the elongate members; and
(iii) an extruder for plastic insulation for stranded
wires, the extruder having an annular barrel extending along and
surrounding the extensions and extending radially inwards at an outlet
end to define an annular extrusion orifice around a feed path for
stranded wires and adjacent to and immediately downstream from the
downstream end of the extensions.
'
. ~ .
i~ 78BSg
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 firstembodiment, partly in section;
Figure 2 is a sectional view along the axis of part of
the apparatus of Figure 1 and on a larger scale;
Figure 3 is a cross-sectional view of the apparatus taken
along line 'III-III' in Figure 1;
Figure 4 is a cross-sectional view taken along line
' IV-IV' in Figure 2;
1178859
Figure 5 is a side elevational view of a second
embodiment, partly in section;
Figure 6 is a cross-sectional view of the second
embodiment taken along line 'VI-VI' in Figure 5 and on a larger scale;
and
Figure 7 is a cross-sectional view of the second
embodiment taken along line 'VII-VII' in Figure 5 and on a larger
scale.
In a first embodiment shown in Figure 1, apparatus for
stranding and covering wire comprises an elongate member 10 having a
longitudinal axis and a plurality of wire guiding elements 12 in the
form of discs secured to the member lO in longitudinally spaced-apart
positions. The member 10 passes through a concentric hole in each disc
and each disc is formed with guide holes 14 angularly spaced apart
around the longitudinal axis, one hole 14 for each of a plurality of
wires 16 which are to be stranded together. As there are two wires to
be stranded, there are two holes 14 in each disc, diametrically opposed
across the member 10. Guide or feedpaths are thus provided for the
wires from spools 17 and through corresponding holes from one element
12 to another.
The elongate member 10, which may be constructed as a
steel rod or a cable of composite plastic construction, for instance as
described in above-mentioned United States Patent No. 4,325,214 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 sense of direction of wire
movement, by a holding means which may be a wire clamping block 20
.:
` ` 1~78~359
secured to the frame. Alternatively to reduce residual tension or to
take up any slack in the member 10 caused by stretch during use, the
holding means may either comprise a counterweight such as is described
in the above-mentioned Patent No. 4,325,214, or the clamping block
itself is spring-loaded in the frame. The apparatus of the first
embodiment also includes means for changing the direction of rotation
of the downstream end of member 10 after a predetermined number of
rotations in one direction or the other. This direction changing means
22 is disposed towards the upstream end of the member 10 and is
constructed in accordance with the direction changing means described
in copending Canadian patent application Serial No. 409,974, filed
concurrently with this present application in the names of John
Nicholas Garner, Jean Marc Roberge and Norbert Meilenner, and entitled
"Apparatus For Stranding Wire".
At the downstream end of the member 10, it is secured to
a downstream extension in the form of a tube 24 (Figure 2). A thick
collar 26 is brazed or otherwise attached to the upper end of the tube.
As shown in Figure 4, the thick collar provides a wire twisting means
for the member 10, and to this end is formed for part of its length
with a plurality of radial slits 28 (namely four) from its outer
surface to a central aperture 30. The upstream end of the collar is
thus formed into segments by the slits. These segments are collapsed
radially inwards sufficient to grip the downstream end of member lO
passing through the aperture 30, by a narrowing of the slits, caused by
a tapered screw-threaded means between the outside of the collar and a
nut 31 received thereon. Conveniently, the screw thread in the nut is
- slightly tapered to cause a greater gripping action as the nut is
tightened upon the collar.
-` 1178859
As may be seen from Figures 2 and 3, the collar 26 has
two opposed holes 32 through which the wires 16 pass and then into the
tube 24.
The upstream end region of the tube is located through a
clearance hole 34 in a vertical frame 36. The tube is supported
downstream from frame 36 by axially spaced bearings 3~ carried in a
hollow elongate support 40 held as a cantilever at an upstream end by
frame member 42.
Rotating means is provided for rotating the tube 24 and
the twisting means or collar 26 for a predetermined number of
revolutions about the longitudinal axis alternately in one direction
and then the other. As shown by Figures 1 and 2, this rotating means
comprises a peripherally toothed wheel 44 which is secured to the tube
in a position between the frame 36 and frame member 42.
Driving means drivably connected to the rotating means
comprises a low inerta DC motor 46 mounted upon an upstream face of the
frame 36. The motor is reversible and is of a type known as "pancake"
motor such as sold by Mavilor Motors, Hartford, Connecticutt under
model no. MOA-600. It is imperative that the reversing time of the
motor is as short as possible to restrict the lengths of stranded wire
which extend between changeover positions from one direction of twist
to the other. In this particular motor, it is estimated that reversal
time is about 40 to 60 milliseconds. The driving means also includes a
peripherally toothed pulley wheel 48 on the drive shaft of the motor
and a toothed pulley belt 50 extending around and in mesh with the
pulley wheels 44 and 48.
'
1~78859
The tube 24 and its elongate support 40 are disposed
radially within an annular barrel 52 of a plastics extruder 54. The
tube 24 protrudes beyond the support 40 to terminate adjacent to an
annular extrusion orifice 56 of the extruder, the word "adjacent" in
this sense meaning a distance insufficient to allow for any significant
unstranding of wires after they have emerged from the tube and before
they are covered with a layer of plastic insulation by the extruder.
This distance may be of the order of up to 5 or more inches.
The extruder is provided for forming a tube around the
wires with sufficient interference between the tube and wires to
prevent them from becoming unstranded. To this end, the extruder has a
tubing sleeve 58 defining the inner surface of the orifice 56 and
through which the stranded wires pass. Alternatively, in a
construction not shown, the tubing sleeve is not used and plastic is
extruded from the orifice so as to embed the stranded wires firmly
within it so that no distinct tube of insulation is formed.
The tube 24 has as its primary purpose to avoid the wires
16 from stranding together until they have passed through the
downstream end of the tube whereby the distance from the stranding
position to the extrusion orifice is maintained as small as possible as
referred to above. Prevention of stranding within the tube is provided
by a passage defining means in the form of a diametral rod 60 to form
two passages, one on each side of the rod for each of the wires.
In use of the apparatus of the first embodiment, the
wires 16 are passed, as shown, througl~ the holes 14 from one guiding
element 12 to another, through the holes 32 in collar 26, along the
tube and one on each side of the rod 60.
"` 1178859
Under the control of the direction changing means 22, the
motor 46 rotates alternately in its two directions to torsionally twist
the elongate member 10 alternately in each direction. This effects
a twist in periodically reversing manner in the two wires which are
held apart diametrically on each side of the elongate member. Actual
twist upon the wires is caused by the collar 26. The wires after
passing through the holes 32 in the collar are held apart, so as to
remain unstranded, along the length of tube 24 by the rod 60.
The torsional twist in the wires then causes them to
strand together with alternating direction of lay when their paths are
less restrained downstream of the rod 60. The stranded wires are fed
through the sleeve 58 of the extruder to become enclosed within a tube
layer 62 of plastic insulation. This grips the wires sufficiently to
prevent their untwisting.
The insulated and stranded wires then pass onto a reeling
drum or through some other process stage which provides the pulling
action to unreel the wires.
The above described embodiment is an extremely practical
method of stranding and insulating wires in cable manufacture. In this
embodiment, two wires are stranded together and are useful as cable
pairs in telecommunications cables. Because of the use of the
extension to the elongate member, the wires are located as close as is
physically possible to the extruder orifice before they are permitted
to strand together whereby they are held securely by the extruded
insulation before having any opportunity for becoming unstranded
particularly at their lay direction changeover positions. Also, the
apparatus is of simple construction to perform its task of stranding
`` 1~78859
and insulating as compared to conventional apparatus which involves use
of heavy and cumbersome machinery parts.
The apparatus according to the invention is not limited
for stranding and covering of two wires. For instance, as shown by the
second embodiment, three pairs of wires are stranded together in their
pairs and the pairs are brought together for the insulation stage.
In the second embodiment now to be described, parts
bearing the same reference numerals as in the first embodiment are of
identical or similar construction.
In the second embodiment, shown in Figures 5 and 6, three
elongate members 10, each carrying wire guiding elements 12, extend
substantially side-by-side from their fixed upper ends 18, each member
10 having direction changing means 22 as described in the first
embodiment. For simplicity one only of the upper ends of the members
10 is shown together with its associated equipment. The members 10 are
secured at their downstream ends to tubes 24 in exactly the manner
described in the first embodiment. Upper ends of the tubes are located
within a clearance hole 64 of a vertical frame 66. Figure 5 shows only
two members 10 and tubes 24 because as is clear from Figures 6 and 7,
the lower members and tubes are superimposed in Figure 5. The tubes
are held in side-by-side relationship by being carried separately in
axially spaced bearings in parallel passages formed in an elongate
support 70. Figure 7 shows the relationship of the tubes at their
downstream ends with one bearing 72 for each tube. As may be seen from
Figure 5, with the tubes sufficiently close together, the support 70
and the tubes are locatable radially within the annular extruder 54
with their downstream ends adjacent the extrusion orifice for
insulation purposes.
1~788S9
Driving means for drivincl the rotating means of each
elongate member 10 comprises a low inertia ~C motor 46. As ~ay be seen
from Figure 6, a separate motor and pulley belt 50 is provided for each
member 1n, the motors being positioned substantially equally spaced
apart around the clearance hole 64. The use of three separate motors
enables the individual direction changing means 22 to change the
direction of rotation of its individual motor when it has torsionally
twisted its elongate member the desired number of times in each
direction to impart the appropriate twist to its wires. Thus the
elongate members 10 have their twist controlled individually.
Alternatively, the three members 10 are twisted together by one driving
means. A difficulty here in a practical sense, is that if the twist of
one of the elongate members is out of phase with the others, then this
member will be twisted more in one direction than the other whereby the
eventual twist of the wires passing along that member will be more in
one direction than the other. The use of separate driving means and
direction changing means 22 does not permit this to occur as each motor
changes direction independently of the directional change of the other
motors.
In use of the second embodiment, two wires are fed
through the holes 14 along each elongate member and pass through the
twisting means of that member and along tube 24 as described in the
first embodiment. The motors 46 operate to place torsional twist ln
the wires and upon leaving the tubes 24, the wires from each member
become stranded together and the three pairs of stranded wires are
passed through the extruder orifice for covering with an extruded layer
74 of plastics insulation.
" ~859 `
The second embodiment illustrates the compact nature of a
design having separate drive motors placed around a centralized
grouping of tubes for twisting wires and then for brinqing the twisted
wires together at an extrusion orifice.
