EP0236183A1 - Shape memory element for a joining braid on a connector - Google Patents

Abstract

The invention relates to a shape memory element for braid connection (1) on connector (2). The element consists of a winding (3), with two reversible stored shape states. A first state of memorized form ensures electrical contact and mechanical maintenance of the braid on the corresponding rear zone of the connector (2), and a second state of memorized form allows engagement or disengagement of the braid and the rear area of the connector. Application to connectors for electrical cables.

Description

The present invention relates to a shape memory element for braid connection or shielding conductor of a cable on a conductor.

Currently, the connection of the metallic braids, constituting the shielding conductor of an electric cable, is generally carried out by means of a copper or copper alloy ring subjected to a magnetostriction treatment. The metal braid having been previously suitably placed on the zone or rear part of the connector intended for this purpose, the aforementioned ring, surrounding the braid, is brought to this zone. The magnetostriction treatment has the effect of causing sufficient shrinkage or contraction of the ring on the braid and thus ensures the electrical contact and the mechanical retention of the braid on the rear region of the connector.

This procedure is costly insofar as it requires complex apparatus and expensive maintenance for the treatment by magnetostriction.

In addition, if the cable and connector are disassembled, which is necessary, the latter destroys the ring, which can no longer be carried out.

It has recently been proposed to replace these copper rings with rings of shape memory alloy capable, under the effect of heating, of occupying a state of shape memorized beforehand and then, by returning to ambient temperature, ensure electrical contact and mechanical support of the braid on the rear part or zone of the connector.

Satisfactory operation. However, this type of connector has the disadvantage of being unable to reuse the rings used, due to the absence of reversibility of the passage from the memorized state of shape allowing the mounting of the braid on the rear zone of the connector to the end state in which the electrical contact and the maintenance of the braid on the rear area of the connector are ensured. In addition, this type of ring in any case only allows an overall radial deformation of the order of 8%, which, in certain cases, can cause inconvenience in use during assembly of the braided.

The present invention relates to the implementation of a shape memory element for braid connection on a connector which does not have the aforementioned drawbacks.

Another object of the present invention is the implementation of a shape memory element for braid connection on a connector capable of being reused after dismantling the connector.

Another object of the present invention is the implementation of a shape memory element for braid connection on connector of a very great facility and a very great convenience of use.

The shape memory element for braid connection on connector, object of the invention is remarkable in that it is constituted by an element wound with two reversible shape memory states, the transition from one to the other state of shape being obtained by the only modification of the temperature of said element or of a part of it, below and / or beyond the transition temperature Ms of the constituent material of the element, a first state of memorized form making it possible to ensure electrical contact and the mechanical maintenance of the braid on the corresponding rear zone of the connector and a second state of memorized form allowing the engagement and / or disengagement of the braid and the aforementioned rear area.

The invention finds application in particular in the field of connectors, in particular for connectors of circular section or even of any section.

• . La figure 1a représente selon un mode de réalisation particulier, un élément pour raccord de tresse sur connecteur dans ses deux états de forme mémorisés,
• . La figure 1b représente, selon un mode de réalisation de la figure 1a, l'élément pour raccord de tresse sur connecteur au cours de l'opération de montage,
• . La figure 2 représente une variante de réalisation de l'élément pour raccord de tresse sur connecteur susceptible d'être utilisé.
• . Les figures 3a, 3b, 3c, 3d,3e représentent des variantes de réalisation avantageuses de l'élément pour raccord de tresse sur connecteur, conformément à l'invention.

It will be better understood on reading the description and on observing the drawings below in which:

• . FIG. 1a represents, according to a particular embodiment, an element for braid connection on connector in its two memorized shape states,
• . FIG. 1b represents, according to an embodiment of FIG. 1a, the element for braid connection on connector during the assembly operation,
• . FIG. 2 represents an alternative embodiment of the element for braid connection on a connector capable of being used.
• . Figures 3a, 3b, 3c, 3d, 3e show advantageous alternative embodiments of the element for braid connection on connector, according to the invention.

The invention will first be described in connection with Figure 1a.

According to this figure, the shape memory element for braid connection on connector is constituted, according to the invention, by a wound element denoted 3 with two reversible shape memory states. The transition from one to the other state of shape, denoted I and II in FIG. 1a, is obtained by the only modification of the temperature of the element 3 or of a part of it, below and / or beyond the transition temperature Ms of the material constituting the element 3. The so-called transition temperature Ms is in fact the temperature at the start of transformation of the material in the crystallographic state of martensitic type. The material can also be brought, preferably, to a temperature situated below its end of martensitic state temperature Mf.

The first memorized form state noted

I, ensures electrical contact and mechanical maintenance of the braid on the corresponding rear area of the connector. The second memorized shape state II allows engagement and / or disengagement of the braid and the rear area of the aforementioned connector.

In Figure 1a, the wound element 3 is shown as formed, without limitation, so as to constitute a substantially cylindrical winding. Preferably, the winding can consist of turns of the same diameter.

The transition from one to the other memorized form state of element 3 can be obtained by means of any cold source available in industrial environment, such as for example liquid nitrogen.

In Figure 1b, there is shown the element 3, during its assembly phase, on the connector 2, the element 3 surrounding the braid 1, as shown in this figure. In order to allow the introduction of the element 3 around the braid 1 to be connected, the latter, by means of the abovementioned cold source, has been brought into its second state of memorized form, denoted II, state in which the the element is in the so-called expanded position, a position which of course allows the introduction of the rear portion or zone denoted 20 of the connector into the open end of the braid 1, and the placing of the element 3 in the suitable position at this rear zone 20. The return to ambient temperature of the element 3, brings it back to the memory position of shape denoted I, so-called retracted position, in which the electrical contact and the mechanical holding of the braid 1 on the rear part 20 of the connector are provided.

It will of course be noted that during the transition from one to the other state of memorized form of the element 3, it undergoes substantially no elongation, the only transformations undergone by the corresponding element 3 in a variation of the diameter of the turns and their number in both the memorized form state.

The transformations undergone by the element 3 are such that, in the first state of memorized form, which makes it possible to ensure the electrical contact stick e ^A mechanical retainer clips 1 of the corresponding rear region 20 of the connector, the material of which the element 3 is in the crystal state of the austenitic type, while in the second state memorized shape, which allows the engagement and / or disengagement of the braid 1 and the aforementioned rear zone 20, it is on the contrary in the crystallographic state of martensitic type.

Preferably, but not limited to, the rear region or part of the connector 20 can be provided with protruding parts intended to ensure good electrical contact and good mechanical support of the braid 1 thereon. In Figure 1b, there is shown by way of example, the projecting parts of the area or rear part 20 of the connector 2, in the form of a sharp edge thread, in which the metal wires constituting the braid 1 can be engaged by jamming, under the effect of the pressure exerted by the element when the latter has returned to its state of memorized form I.

It will of course be understood that the transformations previously described undergone by the element 3, have for main character, an essentially radial modification of the turns of the winding. This particularly advantageous effect, in the application to the connection of a metal braid 1 to the rear part 20 of a connector, can be obtained by the implementation of a so-called education process, making it possible to obtain the aforementioned effect.

By way of nonlimiting example, the element 3 can be made of a shape memory material, included in the group nickel-titanium, nickel-titanium-iron, copper-zinc-aluminum, and copper-aluminum-nickel, nickel-aluminum, in the form of an intermetallic compound or in an alloyed form.

The winding 3 may preferably be formed from a wire or the like, the constituent material of which belongs to the aforementioned group. By way of example, tests were carried out using a wire 3 mm in diameter, made of an alloy comprising about 4% by atomic mass of aluminum, 25% of zinc and the remainder in percentage of copper and for which the transition temperature Ms is close to 75 ° C. The embodiment presently described makes it possible to satisfy the requirements of the specifications relating to the conditions of use of the connectors, in an industrial environment. The so-called element 3 education process will now be described.

Prior to the actual education process, the winding must first of all be brought to the desired shape at room temperature, that is to say to the shape corresponding substantially to the first memorized shape state noted I, of the Figure 1a.

A rod of shape memory material, or a wire, the composition of which is that indicated above, is firstly brought to a temperature allowing the entire rod or wire to be brought into a crystallographic state comprising two α phases and little equilibrium. By way of example, the above-mentioned rod can be brought to a temperature of 500 ° C. This rise in temperature has the effect of making the raw material more pliable. The rod is then brought to room temperature, with or without quenching, so as to allow the actual shaping.

The actual shaping, that is to say the shaping in the final state constituting the final state, beyond the transition temperature Ms of the material, is then carried out by plastic deformation of the rod at room temperature. The rod is wound on a support or mandrel, by means of a winder or any other means, so as to form the winding 3. Preferably, this is made so as to have contiguous turns.

The winding 3-thus constituted, is then, in the absence of any mechanical constraint, brought to high temperature, so as to bring the material with shape memory constituting the winding, in crystallographic phase of the austenitic type. Typically, the winding 3 can be brought to a temperature between 700 ° C and 850 ° C, then it is then subjected to quenching, in order to cause, the winding being maintained above the transition temperature Ms of the material, elimination of quenching gaps. Then the winding 3 is then subjected to the education stage proper.

The education consists in applying to the winding 3, a mechanical stress capable to impose on it, a deformation constituting, for the winding, a path by which the winding will pass from its final state of form to its various successive states of form, which in fact constitute the aforementioned path.

For this purpose, a mechanical stress is applied to the winding 3, the stress being directed in the direction of deformation of the winding. In the example described above, where the deformation consists of a rotation and a radial deformation of the turns, the force or stress can be applied to the winding 3, which is in a state of shape corresponding to the state of shape memorized I of FIG. 1a, by means of a tool of the helical die type, the path of which corresponds for example to the aforementioned path, so as to bring the element 3 into its state of memorized form II, the die having advantageously, substantially , the form denoted II corresponding to the second stored form. The element 3 can of course be introduced into the die, by traction. The amplitude of the stress applied to the winding 3 is chosen such that it does not substantially exceed the elastic deformation limit of the winding at the temperature above the transition temperature Ms. Then, the stress being maintained, the winding is cooled and brought to a temperature below its transition temperature Ms, and preferably below its end of martensitic state temperature Mf. The winding 3, under the effect of the stress, deforms by plasticity of deformation, in the direction imposed by the stress. It deforms by a number of turns per rotation of the turns which depends of the constraint imposed, of the characteristics of the winding including the initial number of turns, and the modification of the diameter of the turns results in a change in the number of turns or turns, without appreciable change in the length of the winding 3.

The winding 3 is then brought back to a temperature higher than the Ms temperature, the stress being maintained.

The temperature transitions below and beyond the transition temperature Ms of the material, the stress being maintained, are repeated cyclically. It has been observed that a repetition of the aforementioned transitions greater than five times, in fact allows a quasi-indefinite subsequent use of the winding 3, by only modifying its temperature.

Of course, the aforementioned education process does not prejudge the deformation applied to the winding 3. In fact, the tool allowing the implementation of the education process, previously designated by a sector, can be replaced by a cylindrical element mounted for rotation and translation on a threaded axis, and on which a motor torque is applied. The setting in motion in rotation and in translation of the cylinder, at least one end of the winding 3 being integral with the cylinder, has the effect of causing the corresponding education of the winding 3, along a path resulting from the composition of the movements of rotation and translation mentioned above.

An alternative embodiment of the shape memory element for braid connection on connector, according to the invention, will now be described in conjunction with FIG. 2.

According to this figure, the winding 3 is arranged so as to form a torus. The mean plane of the turns of the winding 3 is oriented along a diametral plane P of the torus, substantially. Of course, it will be understood that the winding 3 is previously formed, as has been described in connection with Figures 1a and 1b, it is then shaped so as to produce a torus. In FIG. 2, the state of form noted I also corresponds to the first state of shape memorized making it possible to ensure electrical contact and the mechanical maintenance of the braid on the corresponding rear region of the connector, and the state of form noted II , corresponds on the contrary to the second state of memorized form, allowing the engagement and / or the release of the rear zone and the braid, this state corresponding to a state called expanded.

Preferably, as shown in FIG. 2, the element 3 in the first state of memorized shape, in which the electrical contact and the mechanical maintenance of the braid on the rear region of the connector are ensured, is such that the turns forming the windings are contiguous, at least in the vicinity of the contact zone denoted Z between the turns and the braid. Of course, it will be understood that in the case of Figure 1a or the element is formed so as to cons titrate a substantially cylindrical element, the turns are contiguous over their entire circumference, when the element is in its first state of memorized shape.

In the case of the alternative embodiment of FIG. 2, the education process can be modified as follows: the winding 3 having been shaped and treated in a substantially identical manner, until the phase allowing the elimination of the gaps in hardening, the actual education is carried out according to steps similar to those described above, the tool allowing the application of mechanical stress, being of course only modified.

In order to obtain a particularly simple and easily achievable education process in an industrial environment, the tool can, in the case of an education process applied to element 3 represented in FIG. 2, consist of, without limitation, in a rigid cone, on the top of which, the element 3 is engaged, the latter in its initial state of shape corresponding substantially to the memorized state of shape noted I, being brought into contact with the wall of the cone along a line director of it. The deformation constraint allowing the element 3 to be brought into its memorized form state, corresponding to the second form state denoted II, can then be applied by a female conical element with an opening angle identical to that of the previously mentioned rigid cone. , allowing to exert a uniform force on the element 3, which causes the displacement thereof, in translation along the longitudinal axis of symmetry of the cone rigid. This operating mode appears particularly advantageous, in that the element 3 can thus be subjected, in a precise manner, to a deformation, due to the sole adjustment of the stroke of the female conical element relative to the rigid cone.

Of course, the application of the mechanical stress and of the temperature transitions below and beyond the transition temperature Ms of the material constituting the winding 3 are repeated as described above.

Another alternative embodiment of the shape memory element for braid connection, object of the invention will now be described in conjunction with Figures 3a, 3b, 3c, 3d and 3e.

In accordance with FIG. 3a, the wound element can consist of a substantially cylindrical sleeve, split or not.

The sleeve is for example split along one of its generating lines, the first state of memorized shape, noted I in FIG. 3a, and in which the electrical contact and the mechanical maintenance of the braid is ensured allows the edges of the slot to be overlapped. of the sleeve.

The sleeve may advantageously, as shown in FIG. 3a and in FIG. 3b, be constituted by a sheet of shape memory material of the above-mentioned composition cut out then rolled or by a canvas or network of shape memory material. The network or fabric can in this case be constituted by an arrangement of wires of memory material of intertwined form. All or only part of the wires can be made of the aforementioned shape memory material, the other wires can be made of a conventional material, piano wire or the like capable of providing a basic infrastructure for the sleeve. When it consists of a fabric or network, the sleeve ensures better shielding capacity and greater flexibility of use.

According to another alternative embodiment as shown in FIG. 3c, the edges of the slot may have indentations, these being nested in the first shape memory state, noted I, in which the electrical contact and the mechanical maintenance of the braid is assured.

Another variant embodiment which is also very advantageous can be implemented as shown in FIG. 3d. In this figure, the sleeve body is constituted by nested flexible blades. The flexible blades are directed substantially in a direction parallel to the generating lines of the sleeve.

The sleeve, as it appears in the aforementioned 3d figure, can be produced from a sheet of metallic material with shape memory by stamping and then by rolling. This embodiment appears particularly well suited to the connection of metallic braids of cables due to the large degree of freedom of swelling, in the central part, of the sleeve due to the flexibility of the blades at their free end. Preferably, the blades, in their longitudinal direction, can be contiguous or almost contiguous.

Another alternative embodiment of the sleeve will be described in connection with FIG. 3e. In this figure, the sleeve appears split along a continuous line oblique to the directions of the generating lines of the body of the sleeve. In this embodiment, the sleeve can advantageously consist of a wound ribbon, the edges of the ribbon in the first shape memory state, denoted I, in which the electrical contact and the mechanical maintenance of the braid is ensured being substantially contiguous. .

Of course, for all of the embodiments represented in FIGS. 3a to 3e, the corresponding wound elements are also subjected to an education process analogous to the education process previously described, this consisting essentially, in a cycle of passages from the state, noted I, to the state, noted II, by application of a mechanical stress exerted by means of an appropriate suitable tool, the whole of the sleeve, or a zone of deformation at less of it, being correspondingly brought to a temperature below or above the transition temperature previously defined.

A particularly advantageous shape memory element for braid connection on connector has thus been described, in which the percentage of overall radial deformation can without disadvantage reach 20%, which makes it possible to improve the ease and convenience of implementation. elements according to the invention, during their use.

Claims (16)

1. Shape memory element for braid connection on connector, characterized in that it is constituted by a wound element with two reversible shape memory states, the transition from one to the other shape state being obtained by the sole modification of the temperature of said element or of a part thereof, below and / or beyond the transition temperature Ms of the material of which the element is made, a first state of memorized shape making it possible to ensure the electrical contact and the mechanical holding of the braid on the corresponding rear zone of the connector and a second state of memorized shape allowing the engagement and / or disengagement of the braid and the aforementioned rear zone. 2. Element according to claim 1, characterized in that the wound element is constituted by a winding. 3.Element according to claim 1, characterized in that said winding is formed so as to constitute a substantially cylindrical element. 4. Element according to one of claims 2 or 3, characterized in that said winding is constituted by turns of the same diameter. 5. Element according to one of the preceding claims, characterized in that it is arranged so as to form a torus, the mean plane of the turns of the winding being oriented along a diametral plane of the torus substantially. 6. Element according to one of the preceding claims, characterized in that it is made of a shape memory material included in the group nickel-titanium, nickel-aluminum, nickel-titanium-iron, copper-zinc-aluminum and copper-aluminum-nickel in alloyed form or in the form of an intermetallic compound, 7. _E lement according to one of the preceding claims, characterized in that said first memorized shape state to ensure electrical contact and mechanical support of the braid on the corresponding rear region of the connector corresponds to the crystallographic state of the austenitic type of the material constituting said element, said second state of memorized shape allowing the engagement and / or the release of the braid and of the aforementioned rear zone corresponding to the crystallographic state of martensitic type. 8. Element according to one of the preceding claims, characterized in that in the first state of memorized shape, in which the electrical contact and the mechanical maintenance of the braid on the rear region of the connector are ensured, the turns forming said winding are contiguous , at least in the vicinity of the contact zone between said turns and the braid. 9. Element according to claim 7, characterized in that in the case where said element is formed so as to constitute a substantially cylindrical element, said turns are substantially contiguous over their entire circumference. 10. Element according to claims 1 and 6, characterized in that said wound element is constituted by a substantially cylindrical split sleeve. 11. Element according to claim 10, characterized in that said sleeve is split along one of its generating lines, the first state of memorized shape in which the electrical contact and the mechanical maintenance of the braid is ensured allowing recovery of the edges of the sleeve slot. 12. Element according to claim 10 or 11, characterized in that said sleeve is constituted by a sheet or by a canvas or network of shape memory material. 13. Element according to one of claims 10 or 12, characterized in that the edges of the slot have indentations, said indentations being nested in the first shape memory state in which the electrical contact and the mechanical maintenance of the braid is assured. 14. Element according to one of claims 10 or 11, characterized in that the sleeve body is constituted by nested flexible blades, said flexible blades being directed substantially in a direction parallel to the generating lines of the sleeve. 15. Element according to claim 10, characterized in that said sleeve is split along a continuous line oblique to the directions of the generating lines of the body of the sleeve. 16. Element according to claim 15, characterized in that it is constituted by a wound ribbon, the edges of the ribbon in the first shape memory state in which the electrical contact and the mechanical maintenance of the braid is ensured being substantially contiguous .

Images