FR2536144A1 - Methods and devices for limiting traction forces of a suspended member, and especially of a cable, by longitudinal plastic deformation of an auxiliary member. - Google Patents

Abstract

The invention relates to a safe method for securing suspended members. According to its most advantageous variant, the auxiliary body 40 of the invention essentially consists of a bar 50 formed from a ductile metal 51 inserted into a wire-drawing die 64. One of the ends 70 of the bar 50 is subjected to one of the traction components t', the other traction component t being transmitted to the die 64 via a cylindrical hollow body 55. The rheological properties of the metal 51, as well as the cross-sections of the bar 50 of the die 64, are chosen in such a way that when the tension is normal, the bar 50 is subjected to forces in the range of deformations and because of this undergoes no degradation. On the other hand, when the traction forces are abnormal and exceed a critical value, the bar 50 is plastically drawn, undergoes large elongations and, as a result, strain relieves the suspended member. The most advantageous application of the invention consists in the securing of electrical lines to a vertical support such as a post by means of a metal stop-arming beam.

Description

 The present invention mainly relates to a means for limiting the tensile forces applied to a member stretched at its anchor point.

The problem it proposes to solve arises in all cases
- where a point of attachment of any organ must be
hanging as close as possible to an anchor point of a
fixed body,
where said member is subjected to tensile forces vis-à-vis
of said anchor point whose intensity decreases with distance
between the anchor point and the snap point
- and, finally, where it is necessary, in particular for reasons
of security, to limit below a certain value
criticizes the tensile forces experienced by the anchored organ.

 In particular, this situation is encountered in frequent cases where an elongate member, such as a cable, a chain, a bar, a tube. 1 is stretched between two points, above the ground and can be subjected under exceptional conditions to tensile forces greater than its resistance capabilities.

 The invention finds a particularly judicious application in mooring lines for the transport of electrical energy.

The cables constituting these lines are usually suspended by a series of intermediate anchoring points to raised reinforcement constituted by
- a vertical support, usually made of concrete, wood or
steel, planted in the ground,
- a metal beam, called "stop armament" or anchor
ge, arranged at the top of the support, perpendicular to this
latest,
- indeformable metal extensions, in number equal to
that of the cables suspended at the stop arming beam,
generally perpendicular to the latter and
vertical support,
- electrical insulators extending each of said ral
metal lanyards,
- and, finally, connection sleeves hanging on the end
mity of each of the insulators and in which are crimped
electrical conductors.

Depending on the type of cables used and the electrical power transported, the nominal tensile forces experienced by the cables are between 30 and 400 daN. On the other hand, the rigors of the climate and especially the deposits of snow and frost as well as the Depending on the region, wind action requires that these installations be sized so that their electrical cables can withstand service efforts of 150 to 2,000 daN. The resistance criteria, which are generally subject to legal specifications, are of course dictated by a concern to take into account at the same time
- security constraints,
- but also economic constraints.

 Nevertheless, it is not uncommon that under unusual circumstances, such as a particularly snowy winter, exceptional overload conditions occur.

It is understood that for reasons of security and continuity of the current distribution, it is useful to provide a means for these devices
- to suffer without deterioration the usual service efforts for
which they are sized,
- and, moreover, to resist the exceptional efforts
above (possibly with some irreverent deformations
sibles) in a range with a lower bound
This is to ensure the continuity of the cable suspension function while waiting for a repair of the installation.

It is conceivable, indeed, that it is
- less expensive to provide a sizing installation
and reduced cost capable of supporting, with
some minor damage requiring repair
further, the exceptional efforts to which it can be
subject in very limited cases,
- rather than oversize this installation.

Thus, it is currently accepted that it is sufficient for facilities to have a safety factor, compared to known service efforts,
- 3 for drivers and their insulation chains
- and 2.1 for the beams and their supports.

It has already been proposed in the prior art various solutions to achieve this result. They all involve interposing between the attachment point, located at the ends of the cable subjected to traction and its fixed anchoring point, a device
- designed to withstand normal scheduled service efforts
for this cable
- and able to ensure a distance from the point of attachment of the
cable, opposite the anchor point, in the direction of the
when the cable is subjected to
abnormal effort.

 It is understood, in fact, that any displacement of the attachment point in this direction has the effect of digging the cable chain development between its attachment points and limit the intensity of inclined traction forces to overcome the components of the vertical gravity efforts.

The method uniformly used to achieve this result is to take advantage of the rheological properties of ductile materials, such as metals, which have deformation characteristics as a function of applied stresses exhibiting
a phase called elastic, reversible, during which all
applied stress gives rise to proportional deformation
which vanishes at the same time as its cause, this elastic phase
ending when the effects exceed a limit, so-called limit
elastic,
- and a plastic phase, prolonging the elastic phase, during
from which the material irreversibly deforms before reaching
limit, which is the breaking point, which leads to the break-up of
material.

 This plastic phase is also often accompanied by a hardening of the metal, that is to say a structural hardening raising before rupture the level of its elastic limit and allowing him to somehow better withstand the efforts to which he is submitted.

The technique currently most commonly used is to use a stop arming beam, at the ends of which are anchored the cables and having a mechanical strength such that it can flex and arch under the action of traction forces cables acting perpendicular to its axis, in such a way
- elastic and reversible when the traction forces are
in the field of usual service,
- plastic and permanent, when overloads exception
(but nevertheless lower than the breaking limits of the
cables) are applied to it.

The bending of the beam thus causes
a displacement of the hooking point of the cable,
- an increase in his arrow
- And correlatively a decrease in the tensile force.

 According to the most basic variant of this technique, the beam is made by folding a sheet so as to form a profile fixed perpendicularly to the vertical support, whose longitudinal geometric characteristics, and in particular the variation of its moment of inertia, allow to ensure the plastic bending of the beam only from a critical level of tensile stresses considered as exceptional when it is defined.

This variant requires
- on the one hand, the realization of a profile and a structure
beam geometry appropriate for each critical level
imposed,
- and, on the other hand, the complete replacement of the beam and
including the stowage method at the post, after each
exceptional overload of one of the cables.

This is the reason why a more judicious variant, described in the French patent application No. 2,466,888 in the name of the applicant, is to realize the stop arming beam by combination
- a cross-piece having, at each of its ends,
means for attaching cables
- and a horizontal piece, secured to the vertical support and
Sleeve for the sleeper.

 Furthermore, the crosspiece has a length greater than that of its sheath from which it exceeds, so that the crosspiece biased in bending by the perpendicularly stretched cables has the right of the ends of the sheath, that is to say at its embedded in this sheath, points of least resistance.

 It is understood that it is in these places of least resistance that initiates the plastic deflection of the cross, when the critical level of traction is reached.

 It is also understood that, even if the cross section of the cross is constant, the longitudinal dimensions of the sleeve make it possible to impose to a large extent the arm of the deflection lever of the crossbar and therefore its level of plastic deformation.

 Finally, it is understood that, in case of exceptional overloads, this device requires only the replacement of the cross member, the sleeve remaining undistorted.

 This arrangement is therefore a very advantageous improvement.

 Nevertheless, it is conceivable that in the systems described above the cable is subjected, under the action of its weight, to an inclined traction relative to the horizontal, causing in this case the arrow of the cable.

As a result, the stop beam intended to flex undergoes a force perpendicular to its decomposing axis.
- in a horizontal pull
- and in a vertical traction.

It is the horizontal pull that is used to give the beam its character "fuse" ensuring safety. On the contrary, vertical traction is a parasitic
- to rotate the arm
- and reduce its tensile strength by disorienting its
maximum moment of inertia.

 The French patent application 2,379,927 in the name of DERVAUX proposes to join the beam and the post by a horizontal joint whose dimensions are calculated to enable it to resist accidental surges.

 In this way, the beam is always well oriented vis-à-vis the cables.

 Previous Liart has therefore managed to solve the problem of anchoring cables under exceptional overload conditions mentioned above.

 On the other hand, it will be noted that, whatever the system of the prior art used in a simple manner or in combination with others, any exceptional overvoltage of one of the cables requires the complete replacement of the stop beam or any case of the cross which materializes it.

 Likewise, all the cables anchored on the support considered must be unstacked during the replacement operation. This is both painful and induces equipment constraints and staff downtime resulting in an operating budget of extremely expensive electrical installations, especially in regions with severe winter.

 On the other hand, assuming that one of the cables undergoes a particularly intense increase in overvoltage and exceeds the breaking coefficient of the safety system, it appears that this leads to the destruction of the stop beam and generally to the reduction of the entirety. cables anchored to it, even though some of these cables operate under quite normal voltage conditions.

Moreover, it can be seen, with reference to the general properties of the ductile materials mentioned above, that the entry into the safety phase of a conventional fastening system causes,
- in parallel with the irreversible plastic deformations
the bending lever arm,
- hardening of the beam which generally lowers its
breaking limit.

So that, assuming that one of these systems supports several cycles of overload of one or the other of these cables, the critical level of security will evolve each time and in an unfavorable sense.
Moreover, it is easily realized that the existing systems mentioned above are incapable of ensuring any secure anchoring of cables, one end of which is located in the central part of the stop beam, that is to say ie, opposite the end of the vertical support.

 Indeed, the mode of plastic deformation by bending requires a certain lever arm vis-à-vis the support to be provoked. However, precisely, this lever arm is canceled for cables anchored near the center of the beam.

This forces
- not to ensure safety for one of the cables anchored to the
center of the beam,
- or to pile cable anchors in the vicinity of
ends of the beam what
causes risks of contact between these days
windy
or impose to increase the length of the beam.

 This limitation is, moreover, particularly disadvantageous because the practice and the use want that, in most cases, the electrical energy is currently delivered in three-phase and thus requires the suspension of three electric cables. It is understandable that the division of these three cables into two groups is very inadequate.

 Finally, when, according to what is said above, several cables are anchored on the same side of a stop arming beam, it is imposed by the construction that the critical safety level is decreasing with the distance between the attachment point of the cables and the vertical support. It is also conceivable that this constraint is very disadvantageous when one has to deal with cables of the same nature and in particular of the same section and of the same resistance to breaking.

 The present invention aims to solve all of the problems mentioned above.

 Thus, a first object of the invention is to provide a method and a particularly simple and inexpensive device for securely anchoring a suspended body.

 A second object of the invention is to propose an application of these devices and methods to the anchoring of a plurality of electric cables vis-à-vis the same vertical support.

A third object of the invention is to describe such methods and devices which make it possible to ensure, independently of one another,
- safe operation
and, possibly, the replacement of the anchors of a plurality of members to the same support.

A fourth object of the invention is to provide an auxiliary body anchoring safe suspended organ
- who undergoes without irreversible deformation the efforts transmitted
by the organ he supports when they are less than
a critical value
- and which lengthens plastically when this value is exceeded
to reduce the tensile forces of the organ
suspended.

A fifth object of the invention is to propose a particular design of this auxiliary body, such as
- in the safe phase of plastic defortnation this one
lengthens with constant effort
- and after several cycles of safe operation
has the same critical level of safe release.

A sixth object of the invention is to propose a new design of the anchor reinforcement, using a plurality of auxiliary bodies such as above, which allow
each auxiliary body to function, in the safety phase
re, independently of the others,
- to be replaced independently of others
- and finally to own, also independently of the others,
any critical level of safe operation.

 A seventh object of the invention is to provide such a frame design that allows anchoring, under the same safety conditions as the others, cables (or organs) whose end is opposite the vertical support.

 An eighth object of the invention is to provide such a frame design which in case of overload of a single cable (or organs) it supports, beyond the limit of rupture of its security system, ensures ultimate retention and possibly only allows the fall of this particular organ.

 Finally, a ninth object of the invention is to provide a method of repairing such frames, particularly simple and fast.

For this purpose, to limit below a certain critical value, the tensile forces experienced by a member, secured to a fixed anchoring body such as a pole at an anchorage point of this body, via of a point of attachment of the organ, the invention consists first of all, in a manner known in itself,
- to connect the fixed anchor point of the anchor body and the
point of attachment of the suspended organ via
an auxiliary liaison body consisting at least in part
of a ductile material,
- to transmit the tensile forces between said point of addiction
chage and anchor via said body
intermediate
- and to choose the position, the geometric characteristics
as well as the mechanical and rheological characteristics of
material constituting the auxiliary connecting body, in such a way that
when the suspended member undergoes tensile stresses in
less than the critical value, the auxiliary body
transmits undergoing internal mechanical stresses
only located in the field of elastic deformation
c
- and moreover, as soon as said suspended organ undergoes
tensile forces of intensity greater than said value
critical, the auxiliary body transmits them by undergoing
internal mechanical stresses located, at least in certain
of its parts, in the field of plastic deformation
ticks of its constituent material.

 However, the method of the invention is remarkable in that the anchoring point, the axis of the connecting body and the point of attachment with the vectors resulting from the torsor of the traction forces transmitted to the auxiliary body are aligned. by the suspended organ and the anchoring body.

In this way, it is conceivable that one makes work the auxiliary body
not in flexion, as is the case in the prior art
laughing,
- but on the contrary in traction, causing an elongation
longitudinal axis of the latter, along its axis, elastic when the
tensile forces of said organ are below the value
critical and plastic beyond.

 This improvement makes it possible in particular to define with more theoretical accuracy the critical value of plastic deformation of the material.

It is also conceivable that this method is particularly suitable for relieving an anchoring body, such as a cable, a chain,
- suspended between two points,
- for which the tensile forces which it undergoes are connected, of
decreasing way, at the distance between the anchor point
fixed and its point of attachment
- which, for reasons of security, of impregnable continuity
of operation, ... or other, must be located the most
possible near the anchor point (as is the case for
an electric cable which must imperatively remain suspended).

 According to a first variant of the method of the invention, the traction forces are transmitted between the attachment point and the anchoring point by simply stretching the auxiliary body on at least one of its portions, when the transmitted traction forces exceed their critical value.

This variant has the advantage of being excessively simple but, as it appears below,
- on the one hand, poses certain problems of complication
design
- and, on the other hand, causes a shift in value
critical during prolonged or cyclic operation of
overload, due to a tendency to the narrowing of the body
auxiliary in its stretched area.

 This is the reason why, according to a second preferred variant of the invention, it is recommended, when the tensile forces subjected to the suspended member exceed their critical value, to lengthen the auxiliary connecting body with a constant force whose resultant is pa parallel to the axis of the auxiliary body.

 This feature, which ensures even after prolonged or repeated operation safe operation at the same critical value, has never been achieved because it is not possible according to the usual techniques because during operation in plastic phase the deformation arm of the beam decreases.

On the contrary, according to the invention, this result is obtained by drawing, along its axis, at least a portion of said auxiliary connecting body.
But the invention also relates to an auxiliary anchoring body suitable for the application of one of the methods as described above.

 Such an auxiliary body, of substantially oblong shape along its axis, is intended to be linked, on the one hand, to said fixed anchor point and, secondly, to the point of attachment of the organ. It has, along its axis, at least one portion made of a ductile material, subjected to longitudinal plastic deformation when the tensile forces of said member exceed their critical value. Once in place between said anchor point and the point of attachment of the member, the particularity of this body is to be almost aligned with the vector resulting from the torsor tensile forces submitted by said member. In general, this amounts to saying that the auxiliary body is in the near extension of the end of the suspended member.

According to a particularly advantageous variant, such an auxiliary anchoring body is constituted in combination by
a hollow body of oblong shape,
first means of joining one of the two points
anchoring or hooking, secured to an end of said
hollow body,
a die with a mouth, in particular a cone, directed according to
the axis of said hollow body and partially obstructing the other said
end of this hollow body,
a bar disposed on either side of the die,
and second securing means to the other of the two
anchoring points or hooking, secured to the end
free from the bar.

 A first end portion of the bar has a section greater than that of the mouth of the die and is introduced into the hollow body. The other second end portion of the bar protrudes from the hollow body, outside the die and has a section almost equal to that of the mouth of the die.

 This bar is made of a ductile material whose elastic limit is such that the product of this elastic limit by the section of the second end portion of the bar is almost equal to the critical value of the tensile forces on the suspended member.

It appears that a plurality of auxiliary bodies of the above type can be interposed between a plurality of members to hang and the same support. In particular, if the members are electrical cables suspended from a stop arming beam, it is advisable to have the auxiliary bodies in place of the "extensions",
This will result in line extension and safe cable-to-cable operation, independently of each other, when these are subject to exceptional mechanical overvoltages exceeding the critical value.

 The technological background proposes various voltage compensating devices or shock absorbers with a deformation effect of constitutive material.

French Patent No. 1,197,417, in the name of the company known as FELTEN & GUILLEAUME CARLSWERK AKTIENGESELLSCHAFT, describes a waterproof anchoring device, more specifically for submarine cables, constituted
- a self-erecting conical part, on the periphery of which are
arranged a plurality of recesses within which are
introduced the armor wires of the cable
- and a counter-cone fitted on the part in such a way that the
mounting resists tensile forces.

 This device is representative of a technique widely used to effect a joining consisting of deforming a body around an organ anchored on this body.

In any case, we will notice
- that the constraints applied are mainly circular
or radial and not longitudinal
- and that the systems are intended not to provide a
moving an attachment point of an organ vis-à-vis
a fixed point of anchoring a body when the organ is
overvoltage, but on the contrary that their preoccupation
pation is to ensure a perfectly rigid and independant
formable.

French Patent No. 1,375,206, in the name of the so-called LIN
CRUSTA, relates to a device for absorbing energy by creeping a cylindrical piece moving inside a tube. Similarly, French Patent No. 1,511,502, in the name of Mr. Oskar Eric PETER, relates to a shock absorbing device whose operating principle is based on creep and is designed to equip seat belts.

 One could, at first glance, consider that these devices have a structure similar to that of the auxiliary bodies of the invention.

But, if one analyzes the stresses undergone by the deformable bodies which they comprise, one notices that these are essentially radial and not longitudinal. In addition, the materials used are not ductile; it is rubber and so-called plastic materials that do not actually have a plastic phase.

 The bumper device described in French Patent No. 2,181,044, in the name of the so-called S.A. NISSAN MOTOR COMPANY, is based on creep by means of two telescopic elements of different sections nested one inside the other. One of the elements consists of a malleable material, plastically deformed when the two elements are forced to move longitudinally relative to each other following a shock applied to the device with a force greater than the elastic limit of the malleable material.

 It will be seen that the object of this device is totally different from that of the invention. This is to amortize an impact (that is to say to undergo a sudden compression). Furthermore, the deformation forces experienced by the malleable body are radial with respect to the axis of application of the forces and not longitudinal.

 It will therefore be found that neither the means nor the result of the invention are described or suggested in the prior art.

 Other features and advantages of the invention will become apparent from the description which follows with reference to the drawings, which description and drawings are given by way of non-limiting example.

On these drawings
FIG. 1 is a perspective view of a weapon beam
climb to the top of a pole and equipped with
auxiliaries according to the invention to support a series of cables
suspended electric,
FIG. 2 is a longitudinal sectional view of the variant
preferred embodiment of an auxiliary anchoring body according to
the invention operates by drawing.

FIG. 3 is a view, also in section, of another
variant embodiment of an auxiliary anchoring body according to
the invention operates by stretching.

- Figure 4 shows a detail of the body functioning
auxiliary shown in FIG.

- Finally Figure 5 schematizes the behavior of a material
ductile subjected to longitudinal tensile forces within
an auxiliary body as shown in Figures 3 and 4.

 In Figure 1, there is a vertical concrete post 1, the upper part 2 which is perpendicularly fixed a metal beam 4 which constitutes the "Arresting Arm" or "anchoring" of a conventional power line.

 This beam 4 consists of an L-shaped trade section or any other laminated profile adapted to service efforts.

The beam 4 is secured by welding 6 to a plate 7 and by bolting to a longitudinally deformed plate 10 which encloses the post 1.

Note that the metal armature 12 formed of the beam 3 and the plate 10 is a set very resistant to bending.

The attachment of this armature 12 to the top of the post 1 is provided by two bolts 14 and 15 successively passing through the beam 4, the post 1 and the plate 10.

 At both ends of the beam 4 as well as in the center thereof, anchoring brackets 16, 17, 18 defining three fixed anchoring points 20, 21, 22 are respectively adapted.

 Each of these anchoring brackets is fixed firmly to the beam 4 with nuts located at the rear of the beam 4 and appearing in 24 in disassembled position.

 The system described above is intended to serve as a fixed anchoring body for a three-phase electrical line 30 consisting of three cables of which only one has been shown at 31, accompanied by its connection chain 33.

The latter comprises successively between the end 35 of the cable and the corresponding anchoring point 21,
a connection sleeve 36 crimped onto the cable 31,
an insulator 37 possibly equipped with an anti-oi device
buckets 38,
and a safe anchoring auxiliary body 40 which is the object
of this application.

This auxiliary body 40 as well as the other elements of the chain 33 is articulated in a horizontal direction parallel to the axis xx 'of the beam 3
- at the same time vis-à-vis the beam 3
- and the insulator 37, this using the ring of the stirrup 8 and a removable shaft 46.

 It is found that each of the cables 31 is inclined downwards relative to the horizontal yy 'of an angle i. This inclination is caused by the resultant tensile forces on the cable 31 induced by its weight P thereon.

 The structure of the auxiliary body 40 will now be described with reference to Figures 2 and 3.

 In general, it essentially comprises a bar 50 made of a ductile material 51, such as hardened copper or aluminum, elastic limit Re. This bar 50 is stretched at least in a zone Z by action tensile forces transmitted by the axis yly'1 the cable 31 and the beam 3.

 According to the preferred variant represented in FIG. 2, the auxiliary body 40 further comprises a hollow cylindrical body 55 cut from a very strong inner diameter metal tube D, provided at one left end 56 with an annular inner rim 57.

 At the right free end 70 of the bar 50 is screwed an eyelet 71 constituting a second means of securing the annular body 40 connected to the bar 50.

 Finally, at the left end 73 of the bar 50 is a bulge 74 of diameter greater than sîb.

 The operation of the auxiliary body 40 appears clearly with reference to FIG.

The cable anchoring device 31 has been the subject of a safety study, depending on the climatic conditions of the region where it is to be installed, which has made it possible to determine the critical safety value.
S to impose the tensile forces for each cable 31. The rheological characteristic of the metal 51, and in particular its elastic limit
RE, as well as the extreme section s of the die, are fixed in such a way that Re xs = S.

 Because of its articulation both with respect to the beam 4 by the eyelet 58 and the stirrup 17 and the attachment point 46 of the cable 31 which they support via the eyelet 71 , each of the auxiliary bodies 40 has an axis yly'1 aligned with the end portion of the cable 31 according to the angle i and follows the variations of inclination of the cable 31 as a function of changes in its tension ten remaining aligned therewith.

Under the effect of the tension t of the cable 31, aligned with the axis y1y'1, the bar 50 is both subject
- on the one hand to the traction t ', (/ t' / = / t /) of the beam 3 on
its eyelet 71, directed according to y'1.

- and, on the other hand, to the constraints of hardening,
aunt t, oriented y1 applied to the conical portion E
located between the left and right portions 66 66, in support
against the industry 64.

Thereby
when the intensity of the traction forces t is less than
the critical value S, the part 67 of the bar is subject to
a reversible elastic elongation, that is to say that the bar
50 does not suffer any damage and low elongations,
- on the other hand, when the intensity of the traction forces t
exceeds the critical value S, the left portion 66 of the
bar 50 is plastically deformed and drawn through
the die 64; the length of this portion 66 decreases and that
of the right portion 67 increases significantly.

 It therefore appears that, when exceptional overloads are borne by the cable 31, its attachment point 46 moves away from the anchoring point 21, the angle of deflection i of the cable 31 increases and the voltage ta tends to decrease for relieve the cable 31.

 Incidentally, it will be noted that to allow the drawing of the bar, it is preferable that the metal of the bar 51 is workable.

So that the straight portion 67 having undergone a plastic deformation and also having a section s2b smaller than the left section slb, nevertheless has a modulus of elasticity R'E after higher deformation (FIG. 5) so as to undergo without excessive deformation the traction t leading to the plasticization of the left portion 66.

 It will also be noted that during the evolution of an overload, as well as following an overload cycle, the plastification conditions of the zone E are the same. The extension of the bar 50 in the safe phase therefore takes place at constant effort regardless of the number or duration of safe operating cycles.

 Finally, if these same numbers or durations of safe cycles of a body 40 persist, it is realized that, when the entire left portion 66 has been consumed by drawing, the bulge 74 of the left end 73 of the bar 50 comes resting on the die 64 to ensure a last retention of the cable 31. In this way, it is the possible breakage of a cable 31 which causes its affalement and not a separation between the bar 50 and the hollow body 55.

 According to the variant of Figure 3, the auxiliary body 40 consists essentially of the bar 50 on which is welded to the left the fastening eyelet 58 and screwed to the right part the eyelet 71. Accessorily, the bar 50 comprises in its central part, a circular bulge 74 '. Furthermore, it is surrounded by a cylindrical oblong hollow body 55 supported by its left edge 57 on the metal pellet 59 of the eyelet 58 and partially obstructed by the guide 80 screwed to the right part. This guide 80 is further pierced by a central recess 81 along the yly'1 axis.

 The bar 50 made of hardened copper (whose characteristic pulling curve appears in FIG. 5) has a portion 85 on the left of the bulge 74 ', of smaller diameter than the straight portion 86 sliding inside the recess 81.

 The operation of the auxiliary body 40 of FIG. 3 is described in FIG. 4. The section α 0 of the left portion 85 and the initial elastic limit RE of the material characterizing the strip have been chosen in such a way that RE x is = S.

 The body 40 is (like that of FIG. 2) hinged by way of the eyelet 58 and the stirrup 17 to the beam 4 and, thanks to the eyelet 71 as well as the hinged pin 46 to the point of attachment 46 of the cable 31.

 When the tension t of the cable 31 is lower than the critical value S, the portion 85 of the bar 50 undergoes plastic extensions of small amplitudes, proportional to the tensile force t. These appear on the common OA portion of the tensile curves (a) and (b) (Figure 5). The bar 50 is not damaged.

 On the other hand, as soon as the cable 31 undergoes an overload greater than the critical value S, the part 85 undergoes traction forces exceeding its elastic limit RE, the characteristic point M of the state of the constraints relating to the initial section is , representing the quantity t / s'o = fo, goes through the part AC of the curve (a). That is, portion 85 undergoes large elongations by stretching. These elongations make it possible to move the attachment point 46 away from the anchoring point 21, thus to relieve the cable 31.

 If the overvoltage stops at a point M 'of the curve (a), there remains a residual elongation OO' permanent.

 If again an overvoltage reappears, we notice that the bar behaves similar to the initial one but with yield strength R'E 7d RE.

 If the overvoltage persists, it happens that the section s' at a point 90 of the portion 85 of the bar decreases more than elsewhere (Figure 4). As a result, the stress f increases in this section and this tends to increase again the elongation of this point, hence increasing the necking of the local section (s') and the phenomenon accelerates.

 However, as it appears on the curve (b) representing the variations of the stress f = t / s' at the point 00, the consolidation of the metal 51 by plastic deformation tends to oppose this phenomenon.

 The person skilled in the art knows the rheological characteristics to give to the constituent metal of the portion 85 so that the resistance to deformation is sufficiently increased by the plasticization, in order to compensate for the decrease in section and the increase in necking.

 They are given by the formula d12> 0 (second derivative of the stress with respect to the positive elongation at any point).

 This condition makes it possible for one skilled in the art to define and carry out, by any known metallurgical process, a bar 50 making it possible to ensure large plastic elongations without undergoing local necking.

 Nevertheless, when the rupture limit C is reached, it is understood that the portion 85 breaks. Under the action of the tension of the cable 31, the bulge 74 'bears against the guide 80 to ensure ultimate retention of the cable 31.

 It can be seen that the auxiliary bodies 40, previously described, arranged on the electric lines in place of the usual extension pieces make it possible to lengthen each cable 31 as soon as it is subjected to an overvoltage t thus avoiding the destruction of the beam 4 and the support 1.

 It is also noted that this security function is performed independently on each of the cables 31.

 It is further noted that an anchoring body as described in FIG. 1, comprising a very strong stop arming beam 4 surmounting a pole 1 and on which is adapted by anchoring points 20, 21, 22 a plurality of auxiliary bodies 40 arranged perpendicularly to the beam 3, can independently support a large number of cables 31.

 Moreover, the arrangement of the end of the cables 31 with respect to the beam 3 has no consequence on the critical limit S of safe behavior of the corresponding body 40. In particular it appears that it is possible according to the invention to anchor cables at the anchoring point 22, facing the post 2, under the same safety conditions as those anchored at any point of the beam 4 .

 It also appears that it is possible to choose, for each cable 31, any particular critical limit S, regardless of its position or the relative position of the other cables. It suffices for this to play on the geometric characteristics of the auxiliary body 40 and the rheological of the metal 51.

 Finally we realize that an anchor body as described in Figure 1 and a cable 31 has been overloaded can be very simply and quickly repaired. To do this we extract the hinge pins of the corresponding auxiliary body 40 and replace it with a new one; the other cables and the beam 4 remaining in place during all this operation. It is noted that it is also possible, because of the removable nature of the die 64 and the guide 80, to simply interchange the bar 50 having undergone plastic deformation.

The invention now having been described and its interest justified on
an example the applicant reserves the exclusivity for the duration of the patent without limitation other than that of the terms of the claims below.

Claims (13)

1. Method for limiting below a certain critical value  that the tensile forces t experienced by an organ, in particular a  cable 31, to be secured to a fixed anchoring body (14) at a point  determined anchorage (20,21,22), via a point  hooking 46 of the organ 31  said tensile forces t of the member 31 being connected,  decreasing way, at the distance between the anchor point  fixed 20,21,22 and the attachment point 46 of said member 31  and said attachment point 46 of said member 31 in front by  elsewhere be located as close as possible to the anchor  20,21,22  this process consisting of a known manner  - to connect said anchor fixed point 20,21,22 and said point  latching 46 by an auxiliary body 40 of consti  killed of a ductile material 51,  - to submit said auxiliary body 40 to said efforts of  traction t of the organ 31,  - and choose  the position,  geometric features  and the mechanical characteristics of the material 51 of said  auxiliary body 40  as such manner that  when said member 31 undergoes tensile forces t  of intensity less than said critical value S, the body  auxiliary 40 transmits them undergoing constraints f  located in the field of elastic deformation of its  constituent material 51  and that, on the contrary, as soon as said organ 31 undergoes  tensile forces t greater than said critical value  S, the auxiliary body 40 transmits them while undergoing  situated at least in certain  the field of plastic deformations of its material  constituent,  said method being characterized in that  - I'on allign  said anchor point 20, 21 or 22,  the axis y1y'1 of said auxiliary connecting body 40  the point of attachment 46  and the resulting vectors t and t 'of the torsor of the efforts  traction transmitted to said auxiliary body 40 by said  member 31 and said anchor body 14,  and it is subjected to said auxiliary body 40 an elongation  longitudinal along its axis yly'1  elastic, when the tensile forces of said organ  are below said critical value S,  and plastic beyond. 2. Method according to the preceding claim 1, for limiting the  tensile forces t of an anchored member 31, characterized in that  when the tensile forces t submitted to said member 31 exceed  their critical value S, said auxiliary link body is extended  40 according to a constant effort whose resultant t is parallel to  the axis y1y'1 of said auxiliary body 40. 3. Method according to one of the preceding claims 1 and 2,  limitation of the tensile forces t of an anchored member 31, characterized  rised in that when the tensile forces are submitted to that  organ exceed their critical value S, it is stretched along its axis  there is at least one portion 85 of said auxiliary connecting body 40. 4. Method according to one of the preceding claims 1 to 3,  limitation of the tensile forces t of an anchored member 31, characterized  risé in that one draws, according to its axis yly'1, a portion  minus 67 of said auxiliary linkage 40. 5. Auxiliary body 40 for anchoring, according to the method of one of the claims  cations 1 to 4, of an organ, such as in particular a cable 31, one of which  snap point 46 is suspended at an anchor point 20,21 or  22 of a fixed body. This auxiliary body 40, of substantially  oblong along its axis y1y'1  - being linked  on the one hand, at said anchor point 20, 21 or 22  and secondly, at the point of attachment 46 of said organ  and having along its axis yly'l at least one con  stitué of a ductile material 51, subjected to deformations  longitudinal plastics when tensile forces t  said member 31 exceed said critical value S,  said auxiliary body 40 being characterized in that its axis y1y'1  is almost aligned with the resulting vector t of the Torsor of  tensile forces transmitted to said auxiliary body 40 by said  organ 31. Anchoring auxiliary body 40, according to claim 5, for  implement a method according to one of claims 1 to 4  previous and characterized in that it comprises a bar 50  stretched, along the axis y1y'1 of said auxiliary body 40, parallel  the resultant vector of the Torseur  traction of said member 31,  - whose end is secured to said anchor point 20, 21  or 22 and the other end secured to said anchor point 20,  21 or 22  - and made of a ductile material 51 whose elastic limit  RE is such that the product of the yield stress  traction force (RE) by the smallest section of the bar s is  equal to the critical value S of the traction forces on the said  organ. 7. Auxiliary anchoring body 40, according to one of claims 5 and  6, characterized in that said auxiliary body 40 is  articulated vis-à-vis  - said fixed anchor body (14)  and said organ 31  in order to constantly align its axis y1y'1 with the vector  resulting from the Torsor tensile forces of the member 31 8. Anchor auxiliary body 40, according to one of claims 6 and  7 preceding, intended to implement the method according to the  claim 4 and characterized in that it comprises a die 64,  inside which is drawn longitudinally said bar  50 made of a ductile material 51, under the action of the vector  resulting T torsor tensile forces of the member 31. 9. Auxiliary anchoring body 40, characterized in that it comprises in  combination  a hollow body 55 of oblong shape  first means 58 for securing to one of the two  anchoring points 20, 21, 22 or the catch 46, linked by a  end of said hollow body 55  a die with a mouth 65, in particular conical, directed along the axis  said hollow body 55,  obstructing the other end of said hollow body 55,  - a bar 50  disposed on either side of said die 64  whose first extreme portion 66 has a  section sib greater than that of the mouth 65 of  said die 66 and is introduced into said interior  hollow body 55,  whose other second portion 67 extreme exceeds said  hollow body 55 outside said die 66 and  has a section s2b almost equal to that of  the mouth 65 of said die 66  and made of a ductile material 55 whose limit  elastic RE is such that the product of the elastic limit  that (RE) multiplied by the section of said second  portion 67 extreme of the bar 50 (s2b) is equal to the  critical value of tensile forces on said member (C)  and second means 71 for securing to the other of the two  anchoring points 20, 21 or 22 or hooking 46, secured  of the free end of said second extreme portion 67 of  the bar 50. Anchor support body 40 according to one of claims 6 to  10 previous, characterized in that its said bar 50 is consti  killed of a ductile material 51 such as hardened copper or alumina  minium. 12. Device for anchoring at least one power line cable on  a vertical support 1, in particular made of concrete and comprising in  characteristic combination  a stop arming beam 4,  whose longitudinal moment of inertia gives it a  significant flexural strength,  arranged horizontally and transversely on the  else of the upper end 2 of the vertical support  1  at least one auxiliary body 40 for anchoring according to one of the  vendications 5 to 11 solidarisé  at one end 58 at an intermediate point of said  arming beam 4, perpendicular to yin'1 to  the axis xx 'of the latter  and by the other end 71 at one end 46 of the  electric line cable 30, in the extension of this  latest. 13. Device, according to the preceding revendicaiton 12, anchor for  electric line cables characterized in that at least one  of said auxiliary anchoring bodies 40 is secured to the  stop arm 4, opposite the upper end  of said vertical support 1 14. Device according to one of the preceding claims 12 and 13,  anchor for power line cables characterized in that  its said transverse arming beam 4 has at least one  articulation member (16, 17, 18) of one of said auxiliary bodies  anchor 40  - vis-à-vis her  - around an axis xx 'of rotation parallel to that of said  beam 4. 15. A method of repairing an anchoring device 40, according to one  previous claims 13 and 14, following a  mechanical load of one of his cables 31 above their value  S, the process of simply replacing, on  said arming beam 4, said auxiliary body 40 anchoring  having undergone plastic deformation as a result of the overload  mechanical cable 31 he supported and / or more simply his  bar 50. 16. Auxiliary body 40 of anchor according to claim 7 for  facilitate the implementation of the process of repair of the revenge  15 and characterized in that it is provided at both ends.  mited a hinge axis 46 removable at a time vis-à-vis  of said arming beam 4  and said cable 31 which it supports