Note: Descriptions are shown in the official language in which they were submitted.
37~3
This invention relates to cradles for twisting machines for
filamentary material.
High speed twisting machines are known for twisting together
two lengths of filamentary material, e.g. insulated telecommunications
conductors. In one form of twisting machine for twisting two insulated
conductors into a twisted pair with conductors of for instance, 22, 24 or
26 awg, the two lengths of insulated conductors are held upon reels which
are mounted upon reel shafts which in turn are rotatably mounted upon
opposite sides of a cradle to allow for rotation of the two reels. To
twist the lengths of conductor together, each length is fed from its reel,
around a rotatable pulley held with its axis stationary relative to the
axis of the reels shafts, and then around a tensioning pulley. The two
lengths are then brought to side-by-side positions in which they pass from
the cradle under a pulley and then upwardly along a curved flyer which
rotates about a vertical axis with its sweep encompassing a space
containing the two reels. By this means, the two lengths receive a double
twist e.g. at a flyer speed of 1,200 rpm, the conductors have 2,400 twists
per minute.
The tension pulley for each reel is mounted at one end of
the arm which is pivotally mounted concentrically with the reel spindle.
Conventionally, a disc brake arrangement is employed to maintain
predetermined tension in the conductor length being drawn from each reel
and around its tensioning pulley. When the conductor length is under
tension, the pulley and arm are pivoted downwards to release the brake and
reduce the resistance to rotation Or the reel and, when tension is
relaxed, the arm is pivoted upwards under spring pressure to apply the
brake. In the conventional arrangement, a torsion spring is
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concentrically arranged with the arm and the reel spindle and, in a
normal spring position, the disc brake is held engaged to prevent
rotation of the spindle. Concentrically within the spring is a ball
race with helical tracks for the balls. Upon the pulley and arm being
moved downwards, the spring is torsioned to rotate the outer housing of
the race which moves the outer housing axially by virtue of the
movement of the balls along their helical tracks. This axial movement
removes an axial end load upon the components of the disc brake,
whereby braking pressure is removed.
To overcome problems associated in use of this conventional
disc brake arrangement, a new brake design for a cradle has been
suggested. This is as described in U.S. Patent 4,375,875 entitled
"Cradle For A Twisting Machine" and granted ~arch 8, 1983 to W.L.
Richardson. In the brake arrangement described in this patent, two
brake discs are mounted at the ends of brake arms operated by a brake
operating means comprising a brake release linkage operable by movement
of the tensioning pulley. This structure avoids the use of the helical
ball tracks as used in the conven-tional disc brake arrangement.
In both of the above constructions, the braking force is
applied and removed by movement oF both brake discs simultaneously.
There is therefore a sudden application and release of braking
pressure, instead of a varying and small braking load, so that
substantially constant conductor tension is impossible to achieve at
fast feed speeds. While such variation in tension may be accommodated
without difficulty in a conventional twisting machine in which two
lengths of conductor after twisting are wound onto a further reel, in
some apparatus the avoidance of substantially constant tension may lead
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to problems in operation. One such apparatus is described in a
copending Canadian Application No~ 444,295, filed December 23, 1983,
and entitled "Forming Cable Core Units" in the names of J. Boufffard,
A. Dumoulin and M. Seguin. This apparatus is provided for making a
stranded core unit of twisted pairs of conductors in which a plurality
of twisting machines are provided. These machines twist pairs of
conductors which are then fed together to a downstrealn s-tranding
machine which strands together the twisted pairs of conductors.
Because of the high tensions produced in the twisting operation, the
apparatus described in the a-forementioned application also includes a
tension equalizing means and a tension reducing means which enable the
tensions in the twisted pairs to be reduced as they approach the
stranding machine, so that the stranding machine is able to deal
effectively with the stranding operation. In such an apparatus, any
undue tension in any of the twisted pairs should be avoided during or
after the twisting operation and any large variation in tension in any
twisted pair of conductors should also be avoided. Hence, in this
apparatus of the other application, it is advisable to avoid the use of
any twisting machine having a tensioning arrangement in which the
braking force is applied and removed by two brake discs simul-taneously.
It would be advisable, therefore, to devise a cradle for a twisting
machine in which braking pressure is apPlied and reduced in smaller
increments than is possible with presently known machines.
In Canadian Patent 1,189,000 entitled "Braking Device" and
granted on June 18, 1985, in the name of W.L. Richardson, there is
described a braking device which is used in cable production. However,
this particular braking device is used for the control of tension in a
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taping apparatus for applying tape as a wrapping around a core for a
cable. This particular braking device has a mechanism which applies
and removes the braking pressure of two brake shoes at different times
from a brake drum. Unfortunately, this mechanism occupies a large area
of the taping machine and would be completely unsuitable for use in a
restricted region, such as is required upon a cradle of a twisting
machine where non ro-tatable parts need to be disposed within the sweep
of the flyer bar.
The presen-t invention provides a cradle for a twisting
machine for filamentary material comprising a reel spinclle for a reel
of filamentary material rotatably mounted upon a support, and a
tensioning device for the material as it is drawn from the reel, the
tensioning device comprising a brake drum rotatable with the spindle
and having an inner and outer cylindrical brake surface; first and
second brake shoes disposed for braking engagement, the first shoe with
the inner and the second shoe with the outer brake surface, the shoes
mounted upon first and second brake arms respectively to move the shoes
towards and away from their braking surfaces; a rotatable tensioning
pulley; biasing means to urge the pulley and its axis in one direction
of movement and to urge pivotal movement of the first and second brake
arms to hold the shoes normally in brake engaged positions with the
brake surfaces, the pulley being movable in the opposite direction
against the biasing means; and a brake release actuator operably
disposed between the pulley and the arms and comprising a brake release
link pivotally movable about either of two relatively o-ffset axes, and
a brake operating link, the actuator operable when the pulley moves in
said opposite direction and with the links connected and relatively
A
inclined to subject the release link to a component of load causing it
to pivot primarily about a first of the of-fset axes to move the first
brake arm and its brake shoe from its brake engaged position and then
to pivot primarily about the second axis to move the second brake arm
and its brake shoe from its brake engaged position.
With one of the brake shoes located within the confines of
the brake drum, the tensioning device is as compact as possible. Also
the arms are placed closely together in a preferred arrangement where
the brake shoes lie in opposed positions, one on the inside and the
other on the outside of the brake drum. Further to this, the fact that
the links are relatively inclined so that the brake operating link
places a component of load on the release link to cause it to move
primarily about one of the axes before the other, avoids the necessity
of using any form of additional biasing means to enable such a pivotal
movement to take place. Hence the total structure is simplified as far
as possible, thereby enabling the design to be located within the sweep
encompassed by a flyer bar of the twisting machine.
One embodimen-t of the invention will now be described by way
of example wi-th reference to the accompanying drawings in which:
Figure~1 is a side elevational view of a twisting machinei
Figure 2 is a view taken in the direction of arrow II in
Figure 1 showing part of the cradle of the machine and on a larger
scale than Figure 1;
Figure 3 is a view similar to Figure 2 with parts of the
cradle removed;
Figure 4 is a diagrammatic view, on a larger scale than
Figure 2, of the operating parts of a tensioning device of the twisting
3~
machine and showing one position of -the parts as in Figures 2 and 3,
and a second chain-dotted position showing a first stage of movement;
Figure 5 is a view similar to Figure 4 showing the first and
second stages of movement; and
Figure 6 is a cross-sectional view through the operating
parts taken along line VI-VI in Figure 3.
In -the embodiment as shown by Figure 1, a twisting machine 10
is one of a plurality of similar machines which are arranged in banks
of machines and forms part of an apparatus as described in a copending
Canadian Application No. 444,295, entitled "Forming Cable Core Units"
and filed December 23, 1983 in the names of J. Bouffard, A. Dumoulin
and M. Seguin. As described in that application, apparatus is provided
for making a stranded core unit of twisted pairs of conductors in which
twisting machines twist individually insulated conductors together into
their pairs. These twisted pairs are fed to a stranding machine to
provide a stranded core or core unit for a cable. In -the apparatus
described in the aforementioned application, main inventive features
concern the inclusion of a tension equalizing means and a tension
reducing means for both reducing the tension in the twisted pairs of
conductors and for minimizing the differences between -the tensions in
the pairs before these pairs are passed to the stranding machine. By
the reduction of tension and the minimizing of the tension differences,
the apparatus enables the stranding and twisting operations to be
performed in tandem. As will be described in this embodiment each of
the -twisting machines, as exemplified by the twisting machine 10,
provides a tensioning device which prevents the sudden application and
removal of substantial tensile loads upon the twisted pairs.
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As shown by Figure 1, the twis-ting machine 10 comprises a
rigid sub-frame 12 having upper and lower horizontal frame members 14
and 16, which are secured to a main ver-tical member 180 This sub-frame
is detachably secured to a rigid main frame 20 by four bolts 22, -two o-f
which secure the frame member t4 to a box beam 24 and the other two
secure the frame member 16 to a box beam 26. The method of attachment
of the sub-assembly of the twisting machine and its sub-frame to the
main frame is described in greater de-tail 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.
The twisting machine 10 also comprises a twisting assembly
28. Each twisting assembly comprises a reel cradle 30 for rotatably
holding two reels 32 of insulated telecommunications conductor and a
-tensioning device 34 (shown in greater detail in -the other figures),
which is operable to control the rotdtional speeds of the reels
dependent upon tension in the conductors as they are drawn from the
reels, around two guide rolls 35 and around dancing rolls or tensioning
pulleys 36, one of which forms part of the tensioning device for each
reel. The conductors 37 pass from their reels, around the two
tensioning pulleys, downwardly through a central aperture 38 in the
cradle and then around either of the lower pulleys 40 to pass upwardly
along one of two diametrically opposed flyers 42 and 44. The
conductors continue dround an upper guide pulley 46 to pass upwardly
and outwardly from the machine through a central aperture 48 before
progressing around a final guide pulley 50 and away -from the machine.
The construction of the twisting assembly including the two flyers is
A
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described in greater detail in copending Canadian Application No.
444,294, entitled "Twisting Machine", filed concurrently herewith in
the names of J. Bouffard, A. Dumoulin and 0. Axiuk. This particular
application deals with the use of a twisting machine having two
diametrically opposed flyers and associated guide pulleys for the
purpose of twisting conductors insulated with different materials, and
also for providing rotational balance and stability to the twisting
assembly. The two flyers and their guide pulleys 40 and 46 are mounted
as a rotatable assembly in bearings in the frame members 14 and 16.
Each twisting machine is also provided with its own individual electric
drive motor 52 secured above the frame member.
As shown in greater detail in Figures 2 and 3, at each side
of the cradle there is a horizon-tal reel spindle 64 provided for
supporting a reel 32. The tensioning device also comprises a brake
drum 66 which is secured concentrically to a flange 68 of the spindle
(Figure 3) by screws 70 (Figure 2). The brake drum carries a friction
engaging means such as is described in copending Canadian Application
No. 444,293, entitled "Cradle For A Twis-ting Machine" filed December
23, 1983, in the names of J. Bouffard, A. Dumoulin and E.K. Lederhose.
This friction engaging means is for frictional engagement with a reel
32 when mounted upon the spindle so as to retain the reel in driving
engagement with the drum and the spindle. The friction engaging means
comprises an annular friction pad 7~ which is moun-ted upon the brake so
as to face along the spindle. Springs be-tween the pad and the drum
urge the pad axially along the spindle and cause the
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pad to frictionally engage the reel 32 for driving it with drum rotation
as described in the application entitled "Cradle For A Twisting Machine".
The tensioning device for each spindle 64 is further
constructed as follows. With reference to Figures 2 and 3, the tensioning
pulley 36 is mounted upon the end of an arm 76 which is secured to a
radial extension 78 formed integrally with an annulus 80, which surrounds
and is concentric with the spindle 64. This annulus is rotatably received
upon a mounting 82, which rotatably carries the spindle 64 within it and
the annulus is retained in place by a spring clip 84 which engages within
a peripheral groove of the support 82. At a position angularly spaced
around the annulus from the extension 78 there is a further extension 86.
To this extension is attached one end of a tension spring 88, the other
end of which has a pin 90 attached to it. This pin is locatable within
any of a plurality of vertically spaced apart pin receiving holes 92,
which are provided within a member 94 extending downwardly from the
extension 86. Thus the spring 88 is a biassing means which tends to
rotate the annulus and thus the pulley 36 in an anticlockwise direction
as viewed in the figures, and therefore urges the pulley against insulated
conductor being fed around it as the conductor is passed from a reel
during a twisting operation. The resistance of the spring is adjustable
by moving the pin into any of the holes 92 as indicated and this varies
the amount of force required to move the pulley 36 in a clockwise
direction. Hence, the tension in the conductor passing around the pulley
36 must vary to move the pulley by a certain amount if the position of the
pin 90 is changed. The brake drum has inner and outer brake engaging
surfaces 96 and 98. Two brake shoes, 100 and 102 are provided for
engagement with the surfaces, the shoes having curved surfaces
~Z~IL37~3
complimentary to the surface of the brake drum against which they are to
be applied. The two shoes are mounted upon two brake arms which lie
substantially vertically and in substantially parallel relationship as
shown in Figures 2 and 3. These arms 106 and 108 are pivoted at upper
ends 110, 112, to a horizontal support 114 extending from the central
support 116 of the cradle. Because of the location of the brake shoes 100
and 102 extending lengthwise of the arms 106 and 108, then the arms extend
behind the flange of the brake drum having the surfaces 96 and 98.
A brake release actuator is provided for moving the brake
shoes out of their normal position in which they engage the surfaces 96
and 98 of the drum. This brake release actuator comprises a brake release
link 118. This link, as shown in Figures 2, 3 and 6, extends
substantially horizontally in the vicinity of the lower ends of the arms
106 and 108. The actuator also comprises a brake operating link 120,
which is pivotally mounted at one end 122 to the extension 86 and at the
other end 124 to one end of the link 118. As shown in Figures 2 and 3,
the angle subtended between the two links 118 and 120 is an acute angle.
This is to provide a relative inclination of the links so as to subject
the release link 118 to a component of load causing it to pivot in a
particular fashion as will be described below. Also, as shown, the
connection between the links at the lower end 124 of link 120 is at the
radially outer position of the links relative to the axis of the spindle
64. With this arrangement, the mechanism forming the actuator lies in
close proximity to the brake drum itself, so as to ensure that there is
sufficient space to enable rotation of the flyers around the non-rotatable
parts of the cradle. The other end of the release link 118 has secured
thereto an eccentric pivot pin 126 (see particularly Figure 6). The pivot
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pin has a pivot part 128 which is rotatably mounted within the lower end
of the arm 108. The pin also has a part 130, which is eccentrically and
integrally formed with the part 128 and is of smaller diameter. This part
130 extends through the release link 118 and is secured thereto. The
positions apart of the axes of the pin parts 128 and 130 is in the order
of approximately .25 inches. Thus the release link 118 is pivotally
connected to the arm 108 and relative movement between these two elements
may take place either around the axis of the part 128 or around the axis
of the part 130.
An arm control link is provided for the arm 106. This link
132 has an enlarged end 134 which surrounds and is pivotally mounted upon
the part 130 of the pin 126. The other or narrower end 136 extends
through a support 138 which is rotatably mounted at the lower end 140 of
the arm 106. A compression spring 142 surrounding the part 136 of the
link is provided normally to hold the arm 106 away from the arm 108, a
distance which is controlled by a head 14~ on the link 132, the spring
acting between shoulders provided on the support 138 and upon the enlarged
end 134.
In operation of the twisting machine, and with a reel 32
mounted on each spindle 64, the insulated conductor 37 is fed from each
reel around the pulley wheel 36 downwardly through the aperture 38,
(during which the conductors converge), around one of the pulleys 40,
through one of the Flyers and upwardly around one of the pulleys 46 to
pass through the aperture 48 and around pulley 50. The normal position of
the tensioning device which includes the pulley 36 and the brake release
actuator is as shown in Figures 2 and 3, i.e. with the brake shoes 102 and
104 held in engagement with the brake drum surfaces by the tension spring
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88. This position is also shown in full outline in Figure 4. As tension
in the conductor passing from either reel 32 builds up, it causes the
corresponding tensioning pulley 36 to pivot downwards as viewed in Figures
2, 3 and 4. This movement, which acts against the tension spring 88,
cause the extension 86 and the brake operating link 120 to move upwardly
to raise the end 124 of the link 118. Because of the acute angle formed
between the two links 118 and 120, the lifting movement upon the link 120
places a component of load upon the link 118 directed upwardly, but
towards the axis of spindle 64 as viewed in the figures. As a result of
this component of load, the link 118 pivots primarily around the axis of
part 130 of pin 126. When viewing the tensioning device structure 34 as
represented in Figure 4, this causes the pivot pin part 128 to move
towards the right. This effects pivoting movement of the arm 108 about
its top end 112 in an anticlockwise direction, thereby causing the brake
shoe 102 to reduce its frictional grip upon the brake drum surface 98.
The degree to which this grip is reduced depends upon the tension being
applied to the conductor, i.e. it corresponds to the downwards movernent of
the tensioning pulley 36. If the pull upon the conductor moves the pulley
36 down sufficiently far, then the brake shoe 102 is moved completely away
from engagement with the brake drum. Hence the braking effect of the
brake shoe 102 is reduced as the demand for the conductor from the reel
increases. Upon the brake shoe being completely removed, the arm 108
engages a stop 148 provided upon the cradle support and this prevents the
arm 108 moving any further in the anticlockwise direction. The position
of arm 108 and corresponding positions of other parts upon engagement with
the stop are shown as chain-dotted in Figure 4. Upon any continued upward
movement of the operating link 120, after the arm 108 has reached its
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limit of movement, then any further rotational movement of the link 118
must occur around the axis of the pin part 128 which can no longer move
towards the right as viewed in the figures. Hence the pivot pin part 130
then commences to move towards the left or in a clockwise direction around
the part 128 as viewed in Figure 5. This movement is translated to a
clockwise movement of the arm 106 about its upper end 110 by pressure of
the compression spring 142 upon the arm~ This movement causes a reduction
in braking pressure of brake shoe 100 upon the surface 96 of the drum
until the pressure is completely removed. The full outline positions of
Figure 5 corresponds to the chain-dotted outline positions of Figure 4.
The chain-dotted outline positions of Figure 5 are the Final positions
upon removal of brake shoe 100 from surface 96.
Upon the demand for the conductor becoming lessened, the
link 120 moves downwardly together with the link 118 under the force of
the spring 88. This results in the movement of the arm 106 towards the
brake engaged position with the shoe 100 engaging the drum. After this,
the arm 108 moves back to place the shoe 102 in braking engagement with
the drum. This reverse movement is exactly opposite to that for removing
the shoes from the drum as described above.
As shown by the above embodiment, the cradle according to
the invention is provided with a brake release actuator, which is
cons~ructed so as to enable the braking pressure by one brake shoe to be
reduced and then to be completely removed before pressure of the other
brake shoe so that there is a substantial control of braking pressure
dependent upon the demand for the conductor being fed from the reel 32.
Thus any sudden increase or decrease in braking conditions is avoided so
that the tension in the conduc-tor as it is being fed from the reel at
3l2gl 37~
different demand speeds does not vary abruptly. Because of this, the
tension in the conductor is maintained more constant than would be
possible using a conventional braking arrangement in which all the
friction surfaces are removed simultaneously. The tension in the twisted
pair of conductors is thus maintained more constant along its length,
thereby reducing the tendency for the conductors to twist more tightly
together in some places than in others. Hence with the use of a cradle
according to this invention, the electrical characteristics of the twisted
pair, and thus of a cable formed with a core of such twisted pairs, are
maintained more constant than would be possible with a cradle of
conventional construction. In particular, the mutual capacitance between
conductors in a cable core, is maintained more constant which is desirable
because mutual capacitance is a primary design requirement.
Further to this, the braking arrangement is constructed in
such a way as to enable the flyers to sweep around the cradle structure
without hindrance. This is partly because of the location of the arms 106
and 108 with one of the shoes 102 located within the confines of the brake
drum. Also, the disposition of the links 118 ancl 120 with their pivotal
position at the outermost location from the spindle axis, enables a
compact design of the total mechanism.
14
