Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to twisting machines for indefini-te
lengths of filamentary material.
In the twisting of filamentary material, frictional contact
between the material being twisted and machine parts performing the
twisting operation and creating a drag upon movement of the material along
its feed path, cause a build up in tension applied to the material. In at
least some twisting procedures, this tension build up is disadvantageous
and should be minimized as much as possibleO
In one particular process, reduction in tension during
twisting would be beneficial. In this process, insulated conductors are
twisted together in twisted units or pairs durins the manufacture of
telecommunications cable. Cable core includes many pairs, e.g. up to
3600, of insulated conductors. In the manufacture of cable core, the
summation of tension applied to the conductors of all of the twisted pairs
(e.g. with a tensile load in the region of 4 lbs. per conductor), makes
the total load unmanageable whereby stranding of the twisted pairs into
the core and in tandem with the twisting operation is highly impractical.
Any manner of reducing tension in the insulated conductors during twisting
of them into pairs would assist in rendering a practical realization for
the pair twisting and core stranding operation to be perforrned in tandem
(sometimes referred to as "in-line").
This invention relates to a twisting machine having features
designed to reduce the tension in filamentary material during twisting.
According to the present invention~ a twisting machine for
filamentary material has a guide pulley freely rotatably mounted about a
first axis upon a support which is rotatable about a second axis, the
pulley having a rim portion defining a peripheral guide channel for the
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material and a plurality of impeller surfaces extending inwardly of the
rim portion and faciny from one side of the pulley at an angle to the
first axis whereby flow of air impinging upon the impeller surfaces and at
said one side of the pulley applies a rotational force upon the pulley
around said first axis, and the pulley lies in a plane extending in a
direction having a radial component to the second axis to cause air
to impinge upon said surfaces during rotation of the support and pulley
about the second axis.
Ir, a preferred construction, the pulley has arms which
define the irnpeller surfaces, the arms being spaced apart around the
pulley by gaps extending through the pulley. To produce the impeller
surfaces in a manner convenient to manufacture, the arms are of
substantially constant cross-sectional shape along their lengths~ with
each impeller surface substantially planar and each arm is inclined to the
axis of the pulleyO
One embodiment 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 part of a twisting
head of a twistiny machine for forming twisted insulated conductor pairs;
Figure 2 is a view of part of the head of Figure 1~ on
larger scale and showing yreater detail; and
Figure 3 is a cross-sectional view taken along line III-III
in Figure 2.
As shown by Figure 1~ d twisting machine 10 is carried in a
'c' shaped rigid frame 12 comprising a vertical member 14 and spaced upper
and lower horizontal frame members 16 and 18~ The frame is detachably
bolted to a vertical main frame 200 The main frame carries a plurality of
iden-tical frames l4 and twisting mdchines lO and the whole arrangemen-t
is described in greater detail in a copending Canadian Application No.
444,292 entitled "Apparatus For Twisting Insulated Conductors" filed
December 23, 1983 in the names of J. Bouffard, A. Dumoulin and 0.
Axiuk.
Each twisting machine comprises d verticdl reel cradle 24
held in fixed position between -the cross members 16 and 18. The
structure 24 rotatably carries two spools 26 of insulated electrical
conductor on shaf-ts 28. In conventional manner, each insulated
conductor 30 is drawn from its spool, around a guide roll 31, around a
dancing roller 32 carried upon pivotal arm 34, through a lower aperture
36 of cradle 24, then together around one of two guide pulleys 38,
through one of two upwardly extending flyers 40, around a guide pulley
41 and through upper aperture 42 before passing around a single pulley
46 and away from the twisting machine. The flyers 40 are rotated in
diametrically opposed positions around a vertical axis 48 as is more
fully described in copending Canadian Application No. 444,294, entitled
"Twisting Machine" filed December 23, 19~33 in the names of J. 5Ouffard,
A. Dumoulin and 0. Axiuk. As described in that application, the two
flyer bars and associated pulleys provide a balanced rotational
structure while avoiding conventional balancing masses. During
rotation of the flyers, the cradle 24 together with spools 26, guide
rolls 31 and dancing roller 32 is held stationary, in known manner for
twisting machines, by sun and planet gears 4g and 51. The ro-tational
movement of the flyers imposes a twist upon each conductor 30 such that
the conductors twist together to form a twisted pair 50 and it is in
this condition that they move around pulley 46.
A
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As is shown more clear1y by Fiyure 2, each of the guide
pulleys 38 is freely rotatab'ly moun~ed upon a horizontal axis in a bearing
carrier 52 secured ~o a frame member 54 which extends obliquely between
'lower and upper platforms ~6, 58~ Lower ends of the flyers 40 are secured
to the upper platform which, together with the lower platform and the
guide pulleys 38, is rotated around ver~ical axis 48 with the Flyers. As
shown, the yuide pulleys 38 also lie in planes extending substantially in
a radial direction to the axis 48. Hence, each guide pulley is rotatable
around axis 48 with one side of the pulley facing in the direction of
rotation about that axis.
Although the guide pulleys 38 are freely rotatable about
their horizontal axes, frictional contact between bearing parts and
between a 'V'-shaped guide channel provided in a rim portion 60 of each
pulley and insulated conductor 30 passing around it, places a drag upon
the movement of each conductor along its pa~h and is one of the reasons
for a build up in tension ir the conductor~ Each of the guide pulleys is
provided with a means to counteract the effects of the fric~ional contact
and hence reduces the drag and tension build up. This means is in the
form of impeller surfaces which face in the direction of rotation of each
pulley about axis 48, these surfaces lying at an angle to the horizontal
axis of the pulley whereby flow of air impinging upon the impeller
surfaces during pulley rotation about axis 48, applies a rotational force
upon the pulley. More particularly, as shown by Figures 2 and 3, each
pulley 38 is formed with six radial arms or spokes 62 which extend
inwardly from the guide channel 60 to a central boss 64, the arms defining
gaps 66 between them. As shown by Figure 3, each arm 62 is generally of
planar strip form. One side of each arm has two flat surfaces 68 and 70
which are slightly inclined relative to each other from a central plane of
the arm, these surfaces 68 and 70 forming impeller surfaces For one
direction of travel of the pulley around axis 48. Each arm is inclined at
approximately 30 to the axis 76 of its pulley (see Figure 3).
In use of the machine, the flyers and pulleys 38 and 41 are
rotated in the appropriate direction around axis 48 to produce the
direction of twist required in the conductors 30. As rotation takes place
around axis 48, one of the two pulleys 38 is rotated about its horizontal
axes by passage of the conductors 30 around it and then up the
corresponding flyer. In effect, therefore, pulley 38 in the position
shown to the right of Figure 2 rotates anticlockwise about axis 76.
Hence, the direction of rotation about axis 48 is such that the pulley 38
on the right hand side is moving upwardly from ~igure 2 while the other
pulley is moving downwardly.
Rotation of the pulleys 38 about axis 48 in the appropriate
direction, assists in pulley rotation as desired about axis 76. Rotation
about axis 48 presents the impeller surfaces 68 and 70 at the inclined
angle of 30 to the flow of air through the gaps 66 whereby the air flow
creates a component of force upon each impeller surface which is a
rotational force upon each pulley. The rotational movement caused by the
air flow is sufficient to overcome frictional force in the bearings of the
pulleys and which normally offers a resistance to pulley rotation. It
follows that the frictional resistance in these bearings is significantly
reduced and does not add to tension build up in the insulated conductors
as they are drawn along their paths. Hence, the tension build up in the
twisted pair of conductors drawn through the machine of the embodiment is
below that in use of dn identical machine in which no impeller surfaces
are provided upon the pulleys~
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