Note: Descriptions are shown in the official language in which they were submitted.
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1 Background of the Invention
3 The present invention relates to continuously stranding
elongated stoc]i such as conductors, etc., particularly of the I '
variety having larger cross-section and/or complex profiles in cross-
6 section, to obtain a stranded cable, rope or the like.
8 Equipment ~or stranding elongated stock, particularly
9 ¦ of the heavy variety, uses storage drums or spools from which the
stock is continuously paid, and these drums or spools are r,lounted'
11 on a rotating device. The individual strands of stock are run
12 together at a stranding point and stranded. If the strands them-
13 selves are stranded filaments or the like, a higher order stranding
14 element is produced.'
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16 It is'inevitable that the known stranding machines require
17 movement of heavy components which l~mits the'production speed.
1~ Furthermore, the known equipment requires an inordinate amoullt o~
19 space while the storage capacity for the stock being stranded
together is quite limited. These ~eatures, in turn,'limit the
length of the p~oduct being made. A'typical stranding device is
22 shown, e.g. in US-Le,ters Patent No. 3,106,815.
23
2g The aforementioned drawbacks have been attempted to be
~leviated by means of stranding the stock with reversing pi~ch. -
26 Each strar~d is guided by particular means which reverse rotal:ion
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(see German Printed Patent Application No. 25 14 033 published October
7, 1976. The resulting equipment is indeed more economical and requires
less space, and less consideration can be gi~en to inertia forces result-
ing from rotation. Also, set-up and preparation times are considerably
reduced.
The known equipment as referred to in the preceding paragraph
are disad~antaged by torsion forces in strands of larger cross section.
If the strands are insulated the insulation may be damaged in the case
of cable, damage to the insulation cannot be tolerated.
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Description of the Invention
In accordance with the invention there is provided apparatus for
stranding elongated stock, comprising: a plurality of sta~.ionarily mounted,
reelable support spools storing individual strands to be unwound from the spools
upon rotation thereof; means for combining the strands as unwound in a bundle
and for providing a first stranding point through which the bundle passes;
means disposed for positively holding the strands of the b~mdle as a bundle
for a particular travel path as the bundle moves along the travel path together
and in engagement with the means for holding, said means for holding stranding
the strands together about an axis, but outside the travel path between the
means for positively holding and the first stranding point, while stranding
does not occur on and along the particular travel path due to said positive
holding; means defining a second stranding point through which the stranded
bundle passes by operation of rotation as between the means for positively
holding and the second stranding po:int; and means for moving the bundle through
the first and second stranding points, the means for holding engaging the
bundle as so moved through the travel path without stranding a portion of
the bundle while on the travel path due to the positive holding.
The means for gripping and holding will preferably include
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1 plural brackets which grip the bundle in paixs, hold it posi ively
2 for a certain length of commQn tra~el and release it thereafter,
3 but all the while revolviny about the stranding axis. The brackets
4 or bracket elements may be mounted on two endless belt-like carriers
constructed in caterpillar fashion and each carrying the spaced
6 bracketsO These brackets coopexate in pairs, one per carrier, to
7 hold and grip the bundle. Positive gripping of the bundle avoids
8 damage to the surface of the stxands. These carriers (such as end- ¦
9 less chains) and the brackets thereof constitute a capstan being
preferahly mounted in a frame and rotating about the stranding axis.
11 Depending upon the type of stranding xequired, the frame, i.e. the
12 means for gripping and holding, may rotate continuously resulting
13 in a continous mode of helically looping the strands abou-t each
1~ other anc~ tile colMto:n stranding axis. In other cases, it is desire-
able to more or less frequently reverse the rotation and ~o re~erse
16 the pitch, a~ter less than one twisting turn or several thereof.
i7 This way one obtains difEerent types of stranding patterns, suc~ as
18 a so-called ceander pattern or an S-Z pattern. The revolviny speed
19 may differ in the two direct~ons resultin~ in different pitch
~alues. Also, the number of unidirectional turns or, more generally,
21 t~e total angular displacement of the revol~ing capstan in between
22 reversals may be diferent ~n t~e two directions.
2~
241 The vundling of the ~tr~nds can be separated from the
;25 fixst ~tranding po;nt by nleans of anQthex capstan which grips
and ~olds the bundle ~or a cert~n len~th but does not xotate.
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1 ¦ Upon adjusting and synchronizing the capstans, particularly as
2 ¦ far as opening and closing of brackets is concerned, the length
of the bundle between the capstans in any instant can be made
4 constant. Analogously, the second stranding point downstream
from the revolving capstan can be established by another capstan~
6 The spacings between the capstans may be varied to change the lay and
7 pit`ch of twisting.
~ If three such capstans are disposed in series, only the
middle one revolving, the propagation speed of the stock from
11 capstan to capstan reduces in downstream direction. All three
12 capstans should be driven at -the same constant speed for reasons
13 of ensuring the requisite synchronization. The brackets should
1~ be mounted ~n the carriers to pexmit additional lon~itudinal
movement during the time of en~agement with the stock to compen-
16 sate the above-mentloned speed differential of the stock.
17
-18 Downstream from the second stranding point, one may wrap
a ribbon or the like around the cable for preventing untwisting.
However, upon holding and stranding the twisted stock, e.g. by
21 a downstream~ non-revolving capstan, such wrapping may not be
22 I needed~ Additionally ox alternatively, a secGnA lay may be
23 stranded on top of the stock after leaving the device described above¦
2~
~5 Strandiny may be carried out in steps in that a second
26 revolving capstan is provided downstream from the first re~olving
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l one but rotating in opposite direction. This way, the lay (pitch)
2 is doubled. If the two capsians revolve uniformly, the path bet-
3 ween the~ serves as temporary storage.
In special cases, it may be desirable to open and reclose
6 tne brackets; during the open period they change their azimu*hal
7 position relative to the bundle. The brackets, therefore, will
8 exert torsion upon the bundle for twisting it intermittently only
:; ~il whiFh r ults in a non unii~rm speed oF strandi~g
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1 Descrlption of the ~_awings
3 While the specification concludes with claims particularly
4 pointing out and distinctly claiming the subject matter which is
regarded as the invention, it is believed that the invention, the
6 objects and features of the invention and further objects, features
and advantages thereof will be better understood from the following
8 description taken in connection with the accompanying drawings
in which:
11 Figure 1 is a schematic view of an apparatus for stranding
1~ stock in accordance with the preferred embodiment of the invention;
13
14 Figu.re 2 is a schematic view of a modified and improved
device for that pu~pose;
16 .
17 Figure 3 is a schematic view of a different modification; and
18
19 Figure 4 is a perspective view of clamping elements used
20 ~ in either of the aforementioned examples, preferabl~ in the one
~1 shown in Figure 2
Z2
23 Proceeding now to the detailed description of the drawings,
24 Figure 1 illustrates several drums or spools 2, journalled for
rotation about their own axis, but bèing otherwise stationarily
26 mounted in a plant or the like. Individual strands 1 are taken
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l ¦ from these drum~ ~r spools and pass through sets of straightening
2 ¦ rollers 3. The straightened and, possibly, oriented strands 1
3 ¦ are fed to a stranding head or nipple 4 which, in the ssence,
~ombines the strands in a bundle la. The number of slrands to
be bundled and stranded is, of course, not limited to three.
7 The bund~e la is received by the stranding device 5 arranged
8 downstre~m from nipple or head 4. The device 5 is essentially
constructed as a capstan being comprised of two endless chains 6
carrying clamping jaws or brackets 7, which cooperate in pairs,
11 one jaw or bracket per chain of each pair. The brackets grip the
12 bundle positively in form closed engagement. The chains are driven
13 by drives 8 and synchronized as to speed and phase by a linking
14 bel~t sprocket belt 1~ or the like. Refer~nc~ numexal 9 refers
to reversing pulleys or sprockets ~or each chain.
16
l~ The capstan chains with bracke~s, drives and reversing
18 rolls 9 are mounted in a frame lO having hollow shafts which are
l9 journalled in bearings 11 and 12, to permit rotation of the frame
so that the capstan S revolves about the stranding axis. The
21 frame is driven by a motor 14 such as a d.c. four quadrant motor,
22 in that the motor drives a transmission gear 15 which, in turn,
~3 drives a belt, sprocket chain or the like, 13.
24
The motor i5 is a reversible one (or the transmission is
26 ~ constr~ated for reveraing th~ dire~tion of rotation), so that
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1 the frame and stranding device 5 can rotate in one or the opposite
2 direction as indicated by the two arrows. If stranding is carried
~ out without reversing pitch,, a reversibility of the drive is not
4 required. The distance between the capstan and the head 4 may
be adjustable to vary the lay, i.e. the number of twists per unit
6 length. The drives 8 could be disposed outside of the frame so
that they do not revolve with the capstan proper. A transmission
8 is needed in this case to drive the chains whereby the chain speed
9 is the composite of drive speed and revolving speed.
10 . .
11 A second stranding head or nipple 17 is disposed downstream
12 from device 5, behind which a ribbon 19 is helically wrapped
13 around the stranded conductors. A spool 18 fr~m which the ribbon
1~ 19 is paid, revolves about the stranding axis thereby rotating
about its own axis as the ribbon is paid and wrapped.
16
17 The device operates as follows. The strands 1 may be
~ 18 regular solid conductors or stranded conductors to obtain a higher
1 19 order of stxanding. The invention is of particular interest for
stranding particularly profiled conductors'having, e.g. pie-shaped
21 cross sections. The conductors may be insulated so that gentle
22 handling of the insulation envelop2 is required. In either case,
23 the conductors 1 are reeled'off the drums or spools 2 and pass
24 through straightening rollers 3. The rollers in each set are
staggeredIy arranged and they are oriented to straighten the
26 conductors and to orient, for example, each sector in accordance
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l with the position it is to have in the bundle. Straightening
2 is particularly important if the strands have solid and rather
3 large cross-sections. Sector or pie-shaped conductors are notably
4 stiff and require straightening.
6 The bundle la results from the combining action by nipple
7 or head 4. The two chains 6 run continuously so that each bracket
8 is moved in a position vis-a-vis another one and together they
9 grip the incominy bundle la,hold it for a certain distance, where-
lO ¦ after the brackets open. The brackets grip the bundle positively
11 ¦ without permitting relative movement between the strands and the
12 ¦ bracket elements. The surface area of contact must be chosen to
13¦ be surficiently large so that the per unit surface area clamping
l~ force is not too high. This aspect is also important for ensuring
l~ that only very low torsion forces act on the insulation. It must
16 ¦ not be forgotten that stranding does require the exertion of
17 twisting torsion upon the conductors,underneath the insulation.
18
19 During the period of time in ~,7hich the stock is held by
20 ¦ brackets, the ~rame lO rotates about the stranding axis so that
21 each hracket pair closes about the bundle in a disposition which
22 is angularly offset b~ a particular amount with regard to the dis-
23 position the frame had when the preceding bracket pair closed
24 about the bandle. The number of twists as so imparted depends
2~ on the dimensions of the apparatus, on the relative speed of
26¦ stock and the revolving c~pstan, and on the distance between
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l¦ capstan 5 and head 4. As stated, one may strand the conductors in
2 the so-called ceander pattern, in which each twisting turn covers
3 at the most 360 in between reversals. Reversals after 180 are
4 quite common in other cases. Less frequent reversals result in the
so-called S-Z pattern, wherein the conductors are stranded about
6 each other in several helical turns, before the sense of winding and
7 direction of stranding is changed for plural turns in the opposite
8 direction, etc. The pattern actually results by chosing the instants
9 and phases of reversing the capstan revolution.
101 The brackets hold the conductor bundle immobile in the
ll capstan, except for the movement forced upon the bundle at the
12 point of engagement with the brackets on account of the trans-
13 latory and revolving movement of the brackets. Therefore, upon
1~ being released, ~ut while traveling from the point of release
to nipple 17, an additional twist is provided because the bundle
16 upstream is hel`d by a still closed pair of brackets which continues
17 t~ revolve. One obtains, therefore, a couble twist stranding.
18
19 The wrapping device 18 provides the stranded stock with a
20 ` helical winding for preventing the stranded conductors from un-
21 twisting. The stranded and wrapped stock can be processed further
22 downstream, for example, by extruding insulation on and around
23 the assembly or by jacketing the assembly otherwise. Particularly,
24 the stranded stock can be used as a core, about which are twisted
further strands.
261
271 It should be noted that the effective stranding length
2B ¦ is a continuously variable one. A certain length of the bundle la
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1 i5 twisted in any instant by coopexation of head 4 and a pair of
2 brackets 7. When the two bxackets of a pair close about the bundle,
3 they have a particular distance from the nipple 4 and begin to twist
4 the portion of the bundle between brackets and head as a whole,
while receding from the nipple on account of the chain movement.
The effective stranding lengt~ is, therefore, continously lenghtened
7 until the next pair grips the bundle etc. In cases, this variation
8 in effective length may be deemed undesirable.
¦ Figure 2 illustrates an example in which the effective
stranding length remains (or can be made to remain) constant
11 throughout. The equipment includes storage spools 23 for strands
12 24, sets 25 of straightening rollers and a nipple 26 which, how-
13 ever, does not part.icipate in the stranding action but merely
14 forms a bundle 27. The bundle is gripped by the brackets of a
first capstan 21 constructed as the capstan 5 in Figure 1 but
16 without rotating about the bundle axis. The individual brackets
17 serve as stranding nipples, pa.rticularly the downstream most
18 pair of brackets of capstan 21 which is still closed (the one next
downstream has already opened) will serve as stranding nipple, .
20 holding the bundle azimuthally immobile but feeding a free bundle
21 portion beyond to the stranding capstan.
22
23 Reference numeral 20 refers to the stranding capstan assembly
24 being similar to the one identifie~d by numeral 5 in Figure 1,
2b and including a frame and revolving dr-ve means as described.
26 ¦ rrhe two arrows indicate the fact that this capstan 20 revolves
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1 about the bundle and strandin~ axis. The chain drives for the
21 capstans 20 and 21 are synchronized in speed and phase; more
3 about that aspect below. Particularly, a bracket pair of capstan .
4 20 closes on the bundle exactly when a bracket pair of capstan
21 releases the bundle. This way, the length of stock between
6 the last one of brackets on non-revolving capstan 21, being the
7 str`anding nipple and holding the stock, and the first pair of
8 brackets of revolving capstan 20 holding the stock, remains
9 exactly the same even though the brackets participating change.
11 Another non-revolving capstan 22 is provided downstream
12 from capstan 20, and is synchronized thereto in exactly the same
13 fashion, so that the brackets of capstan 22 serve as downstream
14 stranding nipples. A stationary downstre~m nipple is not used -
here; rather the device 28 wraps the stranded stock right after
16 being released from brackets of capstan 22. The capstan 22
17 operates, in fact/ also as a straightening device preventing the
18 stranded stock from untwisting,-so that wrapping may not be needed.
19
The device 22 functions additionally as capstan proper,
21 pullinq the stock through the equipment and the individual strands
22 off the storage spools 23, though load relief may be provided
23 for the latter. The capstans 20 and 21 may, in fact, be dragged
2~ along by the stock in engagement therewith, though load relief
may also be provided here. As long as the brackets close positively
26 around the stock, slippage w~ll not occux,and the brackets open and
27 close n s~nchronism from capstan to capstan.
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1 It may, however, be more advantageous to drive additionally
all of the capstans. In tha-t particular case the following aspect
has to be observed.
4 ~
Due to the stranding operation, the effective ~ranslatory
6 speed of the stock downstream is reduced from capstan to capstan.
This is apparent if one realizes that the twistlng amounts to a
8 helical coiling of each individual strand which reduces its
9 effective length in the direction of propagation. Thus, the
linear speed of capstan 21 is larger than the linear speed of
11 capstan 20, and the linear speed of the latter is still larger
12 than the linear speed of capstan 22, assuming, of course, that
13 the clamping brackets always positively engage the stock without
14 relative movemen~. The speed relation is established automatically ! `
if the devices 20 and 21 are passive, do not actively drive the
16 stock, but are being driven by it.
17
18 It is of advantage, however, to drive all capstans, and
19 for reasons of achieving synchronism, constant uniform speed
20 ¦ should be imparted on all of t~em. Accordingly, compensation of
21 the difference in speed of the stock along the line must be pro-
22 vided for. In particular, one must provide for relative move-
23 ment bet~een the chain drives of the capstans 2Q, 21, and their
2-~ cla~ping ~rackets.
26 ~iguxe 4 illustrates a cla~ping bxacke~ of the type used
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1 on the capstans 20, 21. Each clamping bracket 40 is slidably
2 mounted on a earriage 41. The earriage 41 is secured to an
~ endless chain of the respective eapstan, the bracket 40 as posi- ¦
4 tively engaging the bundle or stranded stock, is shifted gradually
on the carriage 41. The bracket 40 is spring biased, and the
6 said shifting occurs against the force of the spring 42. The .
7 spring returns the bracket on the carriage to the other position
8 upon disengagement from the s*ock. -.
The displacement a bracket undergoes is directly proportional
11 to the length of the path a bracket translates in enyagement with
12 the stock (and the opposite bracket on the companion chain).
13 The displacement is further proportional to (f-1) wherein f is
14 the stranding factor. Actually, the displacement is the direct
product of these two factors. Please note that stranding occurs
16 upstream and downstream from capstan 20.
17
18 .- The displacement of the several brackets, i.e. the force
19 needed to e~ect the displaeement, must be produeed by the down
stream most capstan~ But all capstans are driven so that they
21 all partieipate in dragging and pulling the stock through the
22 deviee; the capstan 22 merely provides additionally the displace-
23 ¦ ment forces needed to move all engaging brackets 40 of capstans 20
24 and 21 aga~nst the respective spr~ngs.
~igure 3 illustrate~ ho~ the temporary storage capactiy
26 of the stranding equipment itself ean be increased without inter-
27 .
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1 fering with the ~eatures outllned above. The elements 30, 31,
2 32 and 33, respectively, correspond to parts 1, 2, 3 and 4 in
3 Figure 1, producing a bundle 34 to be stranded downstream from
4 nipple 33. The bundle is gripped by a first revolving capstan
5 35 constructed and operated like capstan 5 above. Downstream
6 from capstan 35 is provided another revolving capstan 36. Another
7 strand nipple 37 is provided downstream from capstan 36. Stranding
8 is provided between the nipples and the capstans which run in
9 synchronism. Of course, they should also reverse simoultaneously.
Reference numeral 38 refers again to a device for wrapping the
11 siranded stock.
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13 This machine, employing two revolving capstans, establishes
14 a variable storage capacity for the stock. The capacity can be
varied by varying the distance between the two capstans 35, 36. This
16 feature, in turn, permits the selection of the lays number of the
17 stranding in one direction.
18
19 T~e capstan 36 does not have to revolve at the same speed
as capstan 35. Moreover, the two capstans 35, 36 may actually
21 revolve in opposite directions. Additional stranding, however,
22 is obtained in that fashion only when the downstream nipple is
23 more closely spaced to capstan 36 than the capstans are spaced
24 from each other.
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1 The invention is not limited to the embodiments described
2 above but all changes and modifications thereof not constitutj.ng
3 departures from the spirit and scope of the invention are intended .
A to e il luded.
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