FR2509903A1 - CABLE COMPRISING A HELICOIDAL WINDING - Google Patents

Abstract

THE INVENTION RELATES TO CABLE TECHNOLOGY. A CABLE INCLUDES IN PARTICULAR A CYLINDRICAL CORE ON WHICH IS COIL A LAYER OF HELICOIDAL ARMOR 209, 210. THE HELICOIDAL LAYER CAN BE PROVIDED FOR A REACTION IN THE FORM OF A TORQUE OF ZERO VALUE, WHEN THE CABLE IS SUBJECT TO AN AXIAL EFFORT , BY CHOOSING A PARTICULAR VALUE OF THE WINDING ANGLE TH. THIS TECHNIQUE CAN ADVANTAGEALLY BE USED FOR LIGHT GUIDED CABLES HAVING A METAL HELICOIDAL ARMOR LAYER, AND THUS TENDENCY OF THE CABLE TO FORM SHELLS IS AVAILABLE. APPLICATION TO OPTICAL TELECOMMUNICATIONS.

Description

The present invention relates to cables having a helical element,

  including coaxial cables, multi-pair cables and light guide cables for

  use in telecommunications.

  One or more cables are used

  helicoidal elements in various applications, among-

  which telecommunication cables such as coaxial targets, multipair cables or light guide cables A helically wound element can act as the armor of such a cable when it is near the outer part of the cable. Cable Other elements wrapped in

  propeller include bands, ribbons of

  tics, linking elements, etc. It is also possible to use

  a heicoidal winding of a conductive material for the transmission of electrical energy or information

in electrical form.

  If no measures are taken to prevent it, a helical element typically introduces into a cable a reaction in the form of a torque. Thus, when an axial force is applied to the target, which makes it lengthen,

  the cable tends to twist According to the structure of the c C-

  This twisting may occur either in the direction that led to a tightening of the helical winding or

  the meaning that tends to unfold it. Such a reaction under-

  torque can in some cases produce hulls in a cable, when unwinding the cable from a drum or manipulated in any other way, such as during the installation of the cable A reaction in form of

  may also lead to other difficulties in

  The tightening or unfolding of the heli element

  cordal may also have an adverse effect on

cable performance.

  It is possible to oppose the reaction as a couple of one or more helical layers by establishing a reaction in the form of a couple of senses

  opposite in another helical layer.

  to oppose the action of a helical layer wound in one direction, by a helical layer which covers it and

  which is wound in the opposite direction.

  to analyze the reaction as a couple of cables

  helically wound, which allow to predict the angle of

  For example, the document entitled: "Mechanical Charac- terization of Cables Containing Helically Wrapped Reinforcing Elements", by TCO Cannon and Mr. R. Santana, Proceedings of the 24th International Wire and Cable Symposium ( 1975),

Cherry Hill, New Jersey.

  According to the invention, a cable comprises a

  helicoidal element which surrounds a cylindrical gme, and the

  This winding element G of this helical element is chosen so that the helical element produces a reaction in the form of a torque of practically zero value when the cable

is subjected to an axial force.

  In a preferred embodiment according to

  According to the invention, this angle e is chosen according to the formula

  the: e = cotg EN -1/2 2 Ac / Rc where: N =, cc denoting by R the radius of _ soul, by 1 c the length of a segment of the soul, by A c the variation of the length of this segment that is produced

  by an axial force on the soul, and by AR the correct variation

correspondent of the ray of the soul.

  The invention will be better understood on reading the

  description that follows of an embodiment and in

  Referring to the accompanying drawings, in which: FIG. 1 represents an experimental setup which

  suitable for determining the parameters used for

  end of the helical winding angle.

  Figure 2 shows a fiber optic cable

  having a layer of helical armor conforming to the

vention.

  The following detailed description refers to a C-

  helically wound wound, in which a single winding

  Helicoidal produces a reaction in the form of

  In the cable structure of the invention, a single helicoidal winding exerts a zero torque on the core of the cable on which it is wound. Thus, if the core of the cable has a torque reaction which is virtually zero before the helical element is wound on it, the resulting C cable, with the helical element,

  also presents a reaction in the form of a practical torque

  zero, in the presence of axial deformation

  cated. As indicated in the document by Cannon and Santana supra, the deformation in a helical element (Es) is related to the axial deformation in the cable by equation (1): Es = (cos 2 ON sin 20) -0 (1 Rs sin 29) (1) where E is the axial deformation in the cable, e is the winding angle of the helical element (angle formed by the longitudinal axis of the core of the cable and by the axis of the helical element), O is the torsion of the cable, in revolutions per unit length, which results from the axial deformation, Rs is the radial position of the helical element, and N is the radial deformation by axial deformation unit to which the core of the ceble is subjected at the level of the helicoidal element, under the effect of axial deformation, and is given by equation (2):

to R / R

  N = c c (2) A Lc / c where R is the radius of the core on which the helical element is wound, and Lc is the length of a segment

of soul.

  It has been determined that it is possible to obtain a zero-valued torque reaction by solving

  equation (1) in the following way: by imposing a

  final edition corresponding to a null twist (O = 0), we obtain equation (3): s = E (cos 2 e-N sin 2 e) (3)

  In the condition of zero torque, Es, that is to say the defor-

  in the helical element, becomes equal to zero

  occurs when the winding angle O is chosen

  Thus, by evaluating the values of Rc / Rc and Ic / Lc, it is possible to determine the winding angle which can be determined by the following equation:

gives a zero torque.

  FIG. 1 represents a test assembly that is suitable for determining these values. The force can be produced by a traction hoist 11, equipped with a ratchet wheel, connected to the target core by a stranded steel wire of 6.35 mm, with the reference 12 A hook 13 is fixed to the rope by a pivoting coupling and is fixed by a clamp 14 to the core of the cable under test, 16 The soul of the target under test is fixed to a device of Charge Measurement 18 by Clamp 17 The Load Measuring Cell Tyco JP-2000 from Data Instruments Inc. can be used as a load measuring device, and this cell is in turn attached to a fixed object. starting from a condition of zero effort, or given, one determines the variation of the

  length of the cable under test, over a length of

  This data is measured under the effect of an applied force. The length of the test piece is measured to determine the length of the core of the cable as it is suspended, including the possible arrow of the soul of the target. specimen gives the value of c 'while the length variation is the value of AI c The diameter of the core of the

  c 6 ble under test, for example by using a sensor de-

  G-57-11 type cross-training from Instron.

  The diameter is first determined under stress conditions identical to those in which the length of the test piece was measured, then again determined with the same applied force as that with which AL 6 c Ia was measured. value of R is then half of the initial diameter, and AR is half of the diameter variation in the presence

  of the applied effort mentioned above.

  To improve the accuracy and homogeneity of N determination, the above data are preferably measured over a series of stress increments, and the resulting values of N are averaged. even more desirable is to find a regression formula consistent with the data that results from successive effort increments.

  to identify an identification process in the sense of the least

  res If we assume that we have a zero strain for a certain low value precharge, we can use the formula (5), in which is the radial deformation of the core, EL is the axial deformation of the core and K is a constant: E r = L + (5) In this formula, each set of At c / Rc data points, A Lc 1 c is plotted or otherwise recorded on a graph whose coordinate axes correspond to E r and E 1 Then choose the values

  N and K so as to obtain a line with a minimum deviation of

  (least squares) compared to the data According to a

  In order to obtain N and K from the data points, numerical computation can be used according to known methods. This technique has been successfully applied to a

  cable with light guides In the cable-guided cebles

  first, it is important to reduce the target's tendency to

  to form hulls during handling This is easily

  when a layer of armor formed on the cable has a reaction in the form of a pair of zero value

  example of the technique of the invention, a C c is measured.

  light guide cable comprising optical fibers, de-

  also written in US Pat. No. 4,241,979, for determining

  undermine the proper winding angle of a helical armor layer.

EXAMPLE

  A light guide cable, as practically shown in Figure 2, is constructed in accordance with the

  following description The soul of the cable encompasses all

  parts of the cable that lie inside the helical armor layer (209, 210) In the center of the soul is a space for light guides, which can be assembled in the form of ribbons Each ribbon ( 201) typically comprises 12 optical fibers, of which

  a smaller number is represented, for the sake of clarity.

  the ribbons can be twisted, with a twist for 46 cm of the cable shown.

  polytetrafluoroethylene (PTFE) (not shown)

  It is heat-treated, and this strip is intended to function as a thermal barrier. The PTFE strip is approximately 21 mm wide by 0.08 mm thick, and

  it is applied longitudinally, with a gasket

  cover A polyethylene tube 202, extruded on the

  of PTF acts as a protection chamber for the tape structure The tube material is polyethylene

  high density formed by continuous extrusion, having a di-

  inner meter 6.35 mm and a thickness of 0.71 mm

  polyester strip 203 in the form of a monofil sheet

  tinus is applied on the polyethylene tube The tape measures 2.54 cm wide by 0.2 mm thick It is

  applied longitudinally with a lap joint.

  The next layer consists of fourteen stainless steel wires

  204, each having a diameter of 0.43 mm, and

  both type 302 stainless steel wires are applied

  in order to make a complete turn on a longitudinal distance

  25.4 cm, the next layer is a polyethylene sheath

  thylene 205 which is applied to the steel wires The sheath is obtained by continuous extrusion of high density polyethylene having a wall thickness of 0.69 mm, with an outside diameter of 9.78 mm. Then a polyester strip is applied 206, in the form of a continuous monofil sheet,

  and this band is 2.54 cm wide by 0.2 mm thick.

  The strip is applied longitudinally, giving a gap of about 5.6 mm. Fourteen stainless steel wires 207 form the next layer and are wound by turning in the opposite direction to the previous wires.

  and making a complete turn in 38.4 cm The son ccnsis-

  Stainless steel type 302 and they have a diameter of 0.43 mm A polyethylene sheath 208 forms the layer

  following, and the steel wires are incorporated into the thick-

  polyethylene wall thickness The thickness of this sheath is 1.02 mm, with an outer diameter of 12.2 mm.

  reaction in the form of a couple of this cable core is practiced

only equal to zero.

  This cable core has been tested with the ex-

  which is shown in Figure 1, to determine

  The value of N was suspended between rollers 15, as shown, a length of cable core sufficient to give a test piece length of about 297 cm. The diameter of the cable was measured, approximately in the middle, with a transverse deformation sensor of the firm

  Instron An effort was then made to cable using

  the winch, to produce a 0.79 mm elongation of the cable (AL). The transverse deformation sensor was used again to measure the diameter in order to determine the value of 4 Rc. The axial force applied by the winch, to produce an additional elongation of 0.79 mm and repeated measurements This procedure was performed for 24 increments of the value of the effort, producing a

  length of 1.91 cm For each increment, we determined

  minus the firing values / l and & R 0 / R When the complete set of data points was obtained, the values of N and K were determined by a "least squares identification" method for equation (5) Three separate sets of elongations were performed, starting each time with an effort of approximately zero. An average value of N equal to 0.42 was then determined. Equation (4) was then calculated. the value of the winding angle e, and it was determined that it was approximately 570. For the above core, this leads to 40 turns per meter for the layer

  helical armor on the soul A layer of armor suitable for

  required comprises two helical windings made of steel,

  folded with a winding angle of 570 Each winding

  The following characteristics are available: 16.3 mm wide, 0.127 mm thick and a 5.59 mm overlap on each side These windings can be applied in two parts

  209, 210, overlapping partially, in the manner

  shown in Figure 2, to ensure that no space

  does not appear in case of bending of the cable.

  while these parts still constitute a single helical element with respect to the invention, because they have the same winding angle, the same "sense" of winding (i.e. both have a step to the right or

  one step to the left), and practically the same distance

  Instead of alternating overlapping edges, as shown in Figure 2, one of the windings can be applied so that it covers the other winding on the two edges. similarly use additional windings, while

  considering that it is a single helical element.

  Finally, a high density polyethylene sheath 211 can be extruded onto the helicoidal weave layer. The resulting torque response of the resulting cable is substantially zero. To determine the torque response of a cable, a simple approximation is to measure the free twist that the cable takes when it is

  charged We can suspend a cable vertically and the char-

  With respect to the invention, it is considered that a cable has a torque response which is substantially zero when the twist of the cable is

  less than 3 turns for a vertical hanging length-

  100 m, when axial strain of 1% is applied. This criterion can be proportionally

  for other lengths and other tendencies, such as

  a twist of less than 0.3 turns for a length of 10 m, when applying axial strain of -1% A

  another measurement method which gives practical information

  similar is to measure the torque of a C Able

  when energized in an international condition

  saying the torsion, and to divide the torque by the torsional rigidity of the cable. For example, the experimental setup of FIG.

  torque mounted in place of the load cell.

  the TQ 1600 static transducer manufactured by the firm Vibrac

  Corporation is a suitable torque transducer.

  For a given deformation, the torque in newton-

  Then, the torsional stiffness of the same

  cable length, by known techniques By dividing the torque due to deformation by torsional stiffness, a merit factor is obtained expressed in revolutions per meter and per unit of deformation. With this measurement procedure, it is considered that a cable having a merit factor of less than three turns per meter and per deformation unit has a torque response that is virtually zero,

  In some cases, the use of

  tion of the technique of the invention makes it possible to obtain a

  less than 1 turn per meter and per unit deforma-

in industrial practice.

  In modern manufacturing operations of c-

  it is possible to obtain an angle of

  impeller bearing in a range + 1 compared to the nominal value In the cable of the example above, this corresponds to a difference of + 1.7 turns per meter,

  compared to the nominal value of 40 turns per meter.

  Having thus determined that a single, substantially torque-free, helical layer can be applied, it can be seen that other techniques can be used to find the appropriate winding angle. The most straightforward technique is simply to vary the winding angle, giving more or less turns per meter to the helical element placed on a core, and to test the reaction in the form of torque that manifests the cable can be obtained in this way a helical layer having

  a response in the form of practically zero torque Normal-

  the soul on which the helical layer is free of

  torque is applied also has an answer under-

  practically zero torque so the resulting cable

  has a torque response that is virtually zero

  It is however possible to apply a layer of

  coalescent reaction in the form of zero-value torque, according to the technique of the invention, on souls

  who do not have a torque reaction

  If the torsion of the resulting cable is prevented,

  a reaction in the form of a couple that is practically

  the same as that of the core before the helical element is applied. The value of N in equation (4) can also be determined by techniques other than

  For example, if the soul is a material

  virtually isotropic and incompressible, we can calculate

  by the theory that the value of N is 0.5 With a material

  anisotropic soul, the method is advantageously used

  above to evaluate N, especially when

  that N differs by more than 10% o from the theoretical value

  above, that is to say when N is less than 0.45 or higher

  at 0.55 It is also possible to apply advantageously

  Helicoidal layers other than layers of weave For example, strip layers or braided layers may be applied. It goes without saying that many other modifications can be made to the device described and shown,

  without departing from the scope of the invention.

1 1

Claims (1)

1 comprising a helical element which surrounds a cylindrical core, characterized in that the winding angle e of the helical element is chosen such that this helical element produces a reaction in the form of a torque of practically no value. zero, when the cable is subjected to an axial force. 2 Cable according to claim 1, characterized in that the angle O is chosen according to the formula: O o = cotg N -1/23 -R / R wherein N = c, denoting by R the radius of c 'Vs, by Lc the length of a segment of the soul, by 4c the variation of the length of this segment which is produced by an axial force on the soul, and by AR the corresponding variation of the radius of soul. 3. The cord as claimed in claim 2, wherein Sc, A Lcs Rc and A Rc are determined by the following operations: a segment of the core is suspended, the length of this segment or a portion of the latter, the diameter of the core is measured, a force is applied to the segment to obtain a deformation in the segment, the resulting variation of the length is measured, and the resulting variation of the diameter is measured. 4 C Oble according to claim 3, characterized in that the core is not substantially incompressible, so that the value of N differs from 0.5 with a difference greater than 10% and is less than 0, 45 or greater than 0.55. Cable according to claim 3, characterized in that the measurements are performed several times for several deformations produced by several increments of effort, and then a least squares identification is applied to the resulting values to obtain the value. of N by the equation: r = N úL + K in which Er is the radial deformation of the soul, EL is the axial deformation of the soul, and K is a constant. 6 Cable according to any one of claims 1 to 5, characterized in that the cylindrical core also produces a reaction in the form of a torque of practically zero value when it is subjected to an axial force, which makes that the cable comprising the helical element and the core produces a reaction in the form of a torque of practically zero value when it is subjected to an axial force. C Oble according to any one of claims 1 to 6, characterized in that the cylindrical me comprises one or more light guides. C Cable according to any one of the claims   1 to 7, characterized in that the helical element is a metallic armor element.