FR2588889A1 - Canvas or network with a shape memory, and material shape thus constituted - Google Patents

Abstract

The present invention relates to a canvas or network with a shape memory and to the material shapes constituted by such a canvas. The canvas with shape memory comprises a meshed network formed by at least one thread made from a material with a shape memory. The threads may be arranged in warp O, j, N and in weft O, i, M. The shapes obtained from the aforementioned canvas comprise two reversible memorised-shape states. Application to connections, robotics, tooling, packaging, plastic arts or clothing.

Description

 The present invention relates to a canvas or network with shape memory, to a material form constituted by the latter and to their applications.

 Shape memory materials have already been the subject of numerous works because of the potential they represent in the most varied fields of application, such as robotics, connectors and tools.

 To date, however, the production of objects capable of occupying two shape states memorized as a function of their temperature relative to the transition temperature of the shape memory material constituting them has not been able to give satisfactory results, these materials being most often delivered in the form of stems or sheets, which lend themselves poorly to the conformation to a determined form and, in the case of complex forms, a process called education necessary for the memorization of the states of stable form depending on the temperature.

 The object of the present invention is to remedy the aforementioned drawbacks by using a material of the canvas or fabric type with memory.

 Another object of the present invention is the implementation of a canvas or network with shape memory, capable of being shaped or shaped with great ease, and capable moreover of being subjected to a process known as education , capable of giving the shape thus produced at least one distinct memorized shape state.

 Another object of the present invention is furthermore the implementation, from the aforementioned canvas or memory network, of material forms provided with the aforementioned stored states of shape, each shape state being functionalized with a view to 'technical applications.

 Another object of the present invention also relates to the various applications of the aforementioned functionalized material forms.

 The shape memory fabric object of the present invention is remarkable in that it consists of a mesh network formed by at least one wire of shape memory material.

 The material form which is the subject of the present invention is remarkable in that it is made up of a canvas as mentioned above, and that it comprises at least one memorized state of reversible form, the passage from one to the other state of form memorized being obtained by global or local modification of the temperature of the form below and beyond the transition temperature of the material of the fabric constituting the material form.

 The invention finds application in the technical fields of robotics, connector technology, tools and mechanical construction, in the techniques of packaging valuable or highly technical objects, as well as in the fields of plastic arts and clothing.

It will be better understood on reading the description and on observing the drawings in which the relative dimensions and proportions of the various elements have not been respected so as not to harm the clarity of the assembly and where
FIG. 1 represents a fabric or array with shape memory in accordance with the present invention,
FIG. 2 represents an advantageous alternative embodiment of the fabric or network represented in FIG. 1,
FIGS. 3a and 3b respectively represent sections of wire which can be used and a section along a line AA in FIG. 2 of an advantageous variant embodiment of the fabric or shape memory array object of the invention,
FIG. 4 represents an embodiment of material form in accordance with the present invention,
FIGS. Sa and 5b represent another embodiment of material form functionalized in accordance with the present invention,
FIG. 6 represents another variant embodiment of material form in another application in accordance with the present invention,
FIG. 7a represents a particularly advantageous application of the object of invention to an electric cable,
FIG. 7b represents another particularly advantageous application of the subject of the invention to an electric cable,
- Figure 7c shows, by way of non-limiting example, adaptation variants made
on the back of an electrical connector, to ensure perfect use of the app
cation represented in FIG. 7a and / or 7b of the object
of the invention.

The invention will first be described
in conjunction with Figure 1.

According to this figure, the web or network to
shape memory object of the invention is constituted
by a mesh network formed by at least one wire in
a shape memory material. By mesh network,
we actually hear a regular nesting or not
at least one wire of a shape memory material.

In Figure 1, the canvas is shown
formed by a single wire arranged to form
a regular mesh network, and can form a fabric.

According to an alternative embodiment of the object
of the invention, the memory canvas or network
shape can consist of a plurality of wires
arranged so as to form a regulated mesh network
bind. The wire (s) can be arranged according to
chain lines and weft lines. On the
figure 2, the chain lines are noted from 0 to j, N
and the raster lines are noted from 0 to i, M. The
chain lines are preferably superimposed on
weft lines or vice versa and the wire (s) are
thus knitted, as shown in Figure i, or woven, as shown in Figure 2.

 According to another advantageous alternative embodiment of the subject of the invention, the warp lines and / or the weft lines comprise, according to a determined pitch multiple of the weft pitch or of the warp pitch, at least one metallic wire of classic type intended to form a frame.

In Figure 2, the conventional type son are shown in gray, arranged in a pitch p taken arbitrarily without limitation equal to three times the warp pitch or the weft pitch. The frame thus constitutes a mesh sub-network integrated into the network of wires made of shape memory material.

 Of course, in the case where a single wire of shape memory material is used, one or more metal wires of conventional type can be used to constitute the reinforcement, the latter can be knitted together with the shape memory wire or arranged in any suitable manner.

 The shape memory wires or the conventional type wires can, as shown in FIG. 3a, be constituted by wires of circular, rectangular, laminated or triangular section. In addition, the threads may preferably be combined into bundles of woven threads, the bundles being constituted by threads of very small diameter and configured so as to present, for example, a flattened rectangular section. They can have any section.

 According to a particularly advantageous embodiment of the subject of the invention, the shape memory wire or wires can be made of a material such as nickel-titanium, nickelaluminium, nickel-titanium-zirconium nickel-titanium -iron. copper-zinc-aluminum, copper-aluminum-nickel, these materials being used in the form of intermetallic compounds or in alloyed form. These wires can be constituted by single-strand wires or of course by multi-strand wires such as twisted or braided wires.

 The conventional type of son can on the contrary consist of steel wires, wires of the piano wire type or the like metallic or not.

 On the other hand, as regards the wires made of shape memory material, the relative composition in percentage of atomic mass of the constituents of the above-mentioned intermetallic compounds or alloys is determined according to the choice of the value of the transition temperature of the material constituting the son. Examples of embodiment of wires with regard to the composition of these will be given later in the description.

 According to an advantageous embodiment of the fabric or shape memory array object of the invention, as shown in FIG. 3b, according to a section AA of FIG. 2, the mesh network is coated in a layer of plastic or synthetic material . According to the aforementioned embodiment, the canvas or fabric with shape memory object of the invention has the advantage of sealing against liquids or gases, this property opening to the canvas or fabric with shape memory object of the invention. invention, a very important field of application.

 The layer of conventional or synthetic material may consist of a silicone material, polyethylene, elastomer of the neoprene type, EPDM rubber, polyvinyl chloride PVC, phenylene polysulfide or any thermoplastic material, in particular biocompatible, such as polytetrafluoroethylene for biomedical applications such as for example catheters or connection of veins or the like.

 The mesh network constituting the fabric or shape memory network object of the invention having been knitted or woven, as already described, the coating thereof in a layer of conventional material or synthetic material, can be carried out , for example, by a hot coating or by overmolding.

 The canvas or formal memory network shown in FIG. 3b can be advantageously used in techniques for packaging valuables or highly technical items. Preferably, the canvas is subjected to an education process, which will be described later in the description, making it possible to provide the canvas with two stored shape memory states, a first state allowing the introduction of the object to be packed into the enclosure constituted by the fabric shaped for this purpose and the second state, stable at room temperature, corresponding to a withdrawal of the fabric immobilizing the object definitively in its transport or storage position, the tightness of the assembly, the packaging that can be produced under vacuum, which can also be produced by local melting of the plastic or synthetic material coating the mesh network.

 Different embodiments of material shapes obtained in accordance with the invention by means of a shape memory canvas, as previously described, will now be described in conjunction with FIGS. 4 to 6.

 In accordance with the object of the invention, and according to FIGS. 4 to 6 above, the material form comprises at least one state of memorized reversible form. The transition from one to the other memorized shape state is obtained by global or local modification of the temperature of the shape below and beyond the transition temperature of the material making up the threads with memory of shape of the fabric constituting material form.

 As also appears in FIG. 4, the material form, shown, constitutes a cylindrical sleeve forming a metallic braid.

 In order to ensure the existence of two reversible shape memory states for the shape, the material shape after configuration with the corresponding desired shape of a fabric element or shape memory array previously described, is subjected to a process called capable of endowing the material form with two different memorized form states, the reversible transition from one to the other form memory state or memorized form state being obtained, after education, by global or local modification of the temperature of the material form, below and / od beyond the transition temperature of the material constituting the son with shape memory.

 The shape memory fabric is firstly configured or shaped so as to constitute the material shape in its first memorized shape state or in a shape state close to it. The aforementioned shape is then subjected to a heat treatment capable of bringing it or at least the wires of shape memory material constituting it, in a crystallographic phase state of the austenitic type. The material form is then subjected to cooling to a temperature close to ambient temperature, for example without limitation by means of a treatment of the soaking type, so as to avoid the appearance of parasitic crystallographic phase.

 Of course, according to alternative embodiments of the above-mentioned operating mode, the thread or threads in the raw state may be subjected to the preceding heat treatment and soaking or even the canvas after weaving.

 The process of actual education of the material form, which has been configured in a state of form corresponding substantially to its first state of shape memory, consists in repetitively imposing on the material form a mechanical stress such that this one is deformed so as to bring the material shape into a shape position ~ close to the second state of memorized shape and to subject the assembly, the mechanical stress being maintained, to a lowering of temperature capable of bringing the material shape, or at least zones or parts of the material form subjected to mechanical stress, in the martensitic phase state. The lowering of temperature can be carried out by means of any cold source applied either to the whole of the material form, or at the level of the only zone of deformation thereof. Mechanical stress can be applied by any means such than a press or the like, until the desired shape memory position or stored shape state is obtained. After removal of the mechanical stress, the material form is subjected to a gradual warming up to ambient temperature.

The material form then resumes its stable form state, or first memorized form state.

The repetition of the cycle imposed for education as defined above, must be sufficient to obtain a good degree of reproducibility of transition between the first state and the second state of form memorized later, by the only lowering of the temperature of the material form at a temperature below the end temperature, the martensitic transition Mf takes place, then by a successive rise in the temperature of the material form, at a temperature above the temperature Af, the end temperature of crystallographic transformation into an austenitic state. The temperature control of the material form which is the subject of the invention can be obtained from any cold source normally available in an industrial environment and in particular by means of liquid nitrogen.

 Of course, the above-mentioned education process and the operation of the material form which is the subject of the invention may be modified. Thus, it is possible to produce material forms for which the transition from one to the other state of memorized form is established by cooling or by heating of the material form or of the particular zones having undergone the deformations during the process of These material forms capable of passing from one state of form to the other state of memorized form use the change of form caused by the variations of temperature in the domains of deformation such as superelastic domain, for T> - Ms, or in the so-called rubber domain for T <Mf (Mf being the temperature at which all of the constituent alloy of the shape memory wires is in martensitic phase) or in the intermediate domain by composition of the preceding effects, c ' that is to say in fact for T lying between Ms and Mf.

 In the case where the canvas or the shape memory array used for the production of the aforementioned material shape comprises a frame constituted by metallic wires of conventional type, the education process can be modified in the following manner. Advantageously, the material form is first of all configured no longer in its first memorized form state but preferably in a non-memorized form state intermediate between the first memorized form state and the second memorized form state. It will be understood that for this purpose, the metal frame allows a conformation of the fabric to the desired shape due to the particular mechanical properties of the frame constituted by wires of conventional type. The state of form called intermediate between the first state of memorized shape and the second memorized state of shape is preferably chosen so that, during the application of mechanical stresses capable of bringing the material form to its first state of shape memory then to its second state of memory in shape and vice versa, these do not cause deformation of the conventional type of son beyond their normal elasticity zone. Thus, the whole of the structure in the first or in the second memorized form state, corresponds to a structure in which tensions are induced in the wires of conventional type, conferring on the whole of the structure an increased rigidity.

It will also be understood that, due to the particular texture of the shape memory canvas object of the invention, the relative free play of the set of wires at their crossing, in fact allows an easy conformation of the canvas. with shape memory, to any material form of given type. In addition, and in a nonlimiting manner, adjacent or non-adjacent wires, constituted by the same material or by a different material each endowed with shape memorizing properties, these materials being able advantageously to have different transition temperatures, can be used. In this case one of the wires, used in its super-elastic Ms-Md temperature zone or its temperature zone below pseudo-elastic Mf, makes it possible to obtain an amplification of the effect of the elasticity obtained. with a conventional type wire.

 An example of the functionalization of the material form of the island constituting a sleeve forming a metal braid as shown in FIG. 4 will now be given.

In accordance with this figure, and in order to provide shielding for electrical conductors, the metal braid can be formed by bundles of contiguous warp and weft son. The sleeve considered in fi gure 4 can thus be adapted to occupy a first state of shape, called expanded, for a temperature higher than the transition temperature Mf, state in which the sleeve previously connected to a shielding braid of the usual type, can normally be engaged on the rear area of a connector. The heating of the sleeve 4 beyond the transition temperature, that is to say in particular at room temperature in the above example, allows the withdrawal of the sleeve in position or memorized form state II, the connection to the rear part of the connector and the mechanical maintenance being ensured by the withdrawal of the sleeve in the aforementioned form state. This type of sleeve is particularly advantageous for the connection of the metallic braids for shielding conductors or cables conducting electricity, the fastenings by ring or the like to the rear part of the conductor being thus able to be eliminated.

 Another embodiment of a material form according to the invention will be described in connection with Figures Sa and 5b.

 According to the above figures, the material form constitutes a sleeve closed at one of its ends. A functionalization of this second embodiment can be obtained in the following manner. The closed sleeve is capable in its first state of shape memory, denoted I and represented in FIG. Sa, of constituting a plug-in contact card, the contact being ensured in this state of form, as represented in FIG. Sa. On the contrary, in the memorized state of shape shown in FIG. 5b, the electrical contact with the contact plug is broken and the contact plug can be released from its corresponding female contact part. The closed sleeve is thus likely to constitute a plug-in contact plug with zero insertion or withdrawal force.

 Another embodiment of a material form in accordance with the invention will be described in connection with FIG. 6.

 According to this figure, the material form is constituted by a shape memory canvas in which the mesh network is coated in a layer of plastic material, as described above.

 A functionalization of the aforementioned material form can be obtained in order to form a seal. In this case, the material form constitutes for example a sleeve or possibly a crown, the layer of plastic material coating the mesh network having a thickness of two to three times the average thickness of the mesh network. In Figure 6, there is shown at 6, the form constituted by a sleeve, the layer of plastic material being represented at 1 and the corresponding wires being represented in the thickness of the layer of plastic material. In a similar manner to the case of the figure 4, the sleeve 6 can be adapted so as to occupy two distinct stored shape states, a first state in which the sleeve can be engaged at the connection of two pipes or two conductors, for which it is desired to ensure a junction seal , and a second state corresponding to a withdrawal of the sleeve, in which the seal between the two conductors or pipes is ensured.

 A new variant of application of a material form as shown in FIG. 6, the material form constituting a sleeve, will now be described in connection with this figure.

In accordance with the aforementioned figure, and in order to ensure the shielding and sealing of the connection of two electrical conductors for example, the metal braid constituting a sleeve is coated in a layer of insulating material. The electrical connection of the metal braid to the rear part of the connector, for example, can then be carried out by a connection of the insulation displacement type.

Thus, the sleeve as shown in FIG. 6 can be attached to the shielding conductor of an electric cable and the connection and fixing of the sleeve 6 to the rear part of the connector can be carried out by a connection of the displacement type d 'insulator, on rough edges of the rear part of the connector.

 A particularly interesting application of the subject of the invention will now be given in conjunction with the description of FIGS. 7a, 7b, 7c.

According to FIG. 7a, an electrical conductor cable is shown comprising two conductors constituting in fact the central core of the
cable, the conductors being represented by 71 and
72 and surrounded by their respective insulators 710 and
720. The two central conductors and their insulators
are encased in a plastic core or
rubber 73. In accordance with the subject of the invention
tion, the outermost conductor of the cable by
relation to the central core is constituted by a braid
metallic 74 constituted by a memory cloth of
shape as described above. The driver
74 is in fact the shield conductor of
the entire cable. Of course, the metal braid
lique 74 prior to its implementation for
constitute the cable has been subjected to a process said
education, as previously described, so
that it is likely to occupy two states
shape as a function of temperature. As shown in Figure 7a, the metal braid 74
is in its first state of shape memorized at room temperature. When using the cable and mounting it in a connector as shown in FIG. 7c for example, the conducting cables 71 and 72 being introduced in the appropriate places, the braid metal subjected to a lowering of temperature below the transition temperature of the material constituting it is engaged at the rear part of the connector 80 and in particular at the roughness 801 specially provided on this rear part. The subsequent heating of the metal braid 74 makes it possible to ensure the electrical connection of the metal braid 74 to the rear part of the connector 801 and the mechanical cohesion of the latter with the rear part of the connector 80.

Of course the cable shown in Figure 7a can advantageously be provided with a protective sheath 75 as shown in this figure.

 According to an advantageous variant of the application represented in FIG. 7a, the electric conductive cable represents in FIG. 7b, can on the contrary, include as conductor outermost with respect to the central core, also constituted by the conductors 71 and 72, a metallic braid 76 constituted by a shape memory fabric, in which the mesh network is coated in a layer of plastic material, as previously described. In FIG. 7b, the metallic braid is referenced 76, the layer of plastic material also being referenced 1. Prior to its use on the cable, the metallic layer 76 was subjected to a process known as education, so as to that it is likely to occupy two distinct stored shape states. In FIG. 7b, the metal braid 76 occupies a first shape shape stored at room temperature, in which the position occupied is that of withdrawal.

By lowering the temperature during assembly of the end of the cable in the connector shown in FIG. 7c, the conductors 71 and 72 are engaged in the corresponding parts of the connector 80 and, the metal braid 76 is engaged on the rear part of the connector. 80 and in particular at the level of the asperities 801. The rear part of the connector can, moreover, be provided with a sealing ring 802 constituted by a ring in polytetrafluoroethylene or the like. When returning to ambient temperature, that is to say during reheating, the braid 76 regains its first state of shape memory and is applied to the roughness and to the sealing ring 802.

The electrical connection is made at the rear part of the connector with the metallic braid 76 by displacement of the insulator coating the metallic braid constituting the mesh network. On the contrary, perfect sealing is ensured by pressing the metal braid 76 on the sealing ring 802. In this case, it is not necessary to provide an additional protective sheath at the level of the cable.

 In the described embodiment of network fabric with shape and material memory as shown in the aforementioned drawings, the functionalization of all of the aforementioned material forms was provided in the case of an application to connectors. For this purpose, and in order to satisfy the specifications of the corresponding materials, and by way of nonlimiting example, the wires used may have circular sections of the order of 5 / 10ths of a millimeter and the composition for wires in a copper-zinc-aluminum alloy can be as follows: 4% aluminum, 28% zinc and the rest of the percentage in copper, so as to have a transition temperature close to -800C. For a temperature close to ambient temperature, that is to say 250C, all of the aforementioned modes correspond to the representations given in all of the figures, the metal braids according to the various embodiments occupying the first state of shape memorized.

For a lowering of temperature below -806C, by means of a source of liquid nitrogen for example, the transition to the state of memorized form called expanded is obtained, making it possible in fact to ensure insertion or release of the corresponding connector or plug, the return to the initial shape being obtained for the return to a temperature above - 800C.

 A new type of shape memory material has thus been described which is particularly advantageous in that it allows the production of very varied material shapes and of very easy implementation.

 Of course, in a nonlimiting manner, the material forms analogous to those represented in FIGS. 4, Sa or 5b can be produced by means of a three-dimensional network constituted by at least one wire made of a shape memory material, the network constituting the canvas is not limited to a two-dimensional network. The shapes themselves can be formed by a braided or other three-dimensional network.

 Finally, the shape memory network or fabric can particularly advantageously constitute a fabric or even be integrated into a fabric, by weaving fine threads, so as to constitute a shape memory fabric capable of being used in decoration or in clothing.

By fabric is understood of course any work of interlaced threads comprising threads of shape memory material and threads of vegetable, animal origin, natural or synthetic fibers, and capable of constituting a fabric, a sheet or textile with memory of form.

Claims (20)

 1. Canvas, or network, with shape memory, characterized in that it is constituted by a mesh network formed by at least one wire made of a shape memory material.  2. Canvas according to claim 1, characterized in that it is constituted by a single wire arranged so as to form a regular mesh network.  3. Canvas according to claim 1, characterized in that it is constituted by a plurality of wires arranged so as to form a regular mesh network.  4. Canvas according to one of the preceding claims, characterized in that the son or son are arranged in warp lines and weft lines, the warp lines being superimposed on the weft lines or vice versa.  5. Canvas according to claim 4, characterized in that the warp lines and / or the weft lines comprise, according to a predetermined multiple of the weft or the warp, at least one metallic wire of conventional type or a memory wire of different transition temperature shape capable of working in its superelastic or pseudoelastic domain, intended to form an armature, said armature constituting a mesh sub-network integrated into the wire network made of shape memory material.  6. Canvas according to one of the preceding claims, characterized in that the said thread or threads are knitted or woven.  7. Canvas according to one of the preceding claims, characterized in that the said wire or wires are of circular, rectangular or triangular section.  8. Canvas according to one of the preceding claims, characterized in that the one or more shape memory wires are made of a material such as: nickel-titanium, nickel-aluminum, nickel-titanium-iron, riicke l-titanium- z irconium, copper-aluminum, copper-aluminum-nickel, in the form of intermetallic compounds or in alloyed form.  9. Canvas according to one of claims 1 to 8, characterized in that said mesh network is coated in a layer of plastic material such as silicone material, polytetrafluoroethylene, polyethylene, elastomer of the neoprene type or EPDM rubber, PVC, phenylene polysulphide , thermoplastic material.  10. Material form, characterized by  what it consists of a shape memory fabric according to one of the preceding claims 1 to 8.  11. Form according to claim 10,  characterized in that it comprises two reversible stored form states, the passage of  one to the other memorized form state being obtained  by global or local modification of the temperature  ture of said form below and beyond tem  transition temperature of the constituent material  wires of the metallic fabric constituting the  form.  12. Form according to claim 11,  characterized in that it constitutes a sleeve  forming a metallic braid.  13. Form according to claim 12, characterized in that, in order to ensure a shielding of electrical conductors, said metal braid is formed by bundles of son in contiguous warp and weft.  14. Shape according to claims 10 to 12, characterized in that it constitutes a sleeve, closed at one of its ends, said closed sleeve being capable in its two states of shape memory of constituting a plug contact plug force d 'zero insertion or withdrawal.  15. Material form, characterized in that it consists of a fabric according to claim 9.  16. Material form according to claim 15, characterized in that in order to form a seal, said form constitutes a sleeve, the layer of plastic material coating the mesh network having a thickness of two to three times the thickness average of the mesh network.  17. Material form according to Claims 12 to 16, characterized in that, in order to provide shielding and sealing, the metal braid constituting a sleeve is coated in a layer of insulating material, the electrical connection of the metal braid to the rear part of the connector being a connection of the insulation displacement type.  18. Electrically conductive cable, characterized in that it comprises, as the outermost conductor with respect to the central core, a metal braid constituted by a fabric according to one of claims 1 to 8 or 9.  19. Network according to claim 1, characterized in that it is three-dimensional.  20. Fabric, characterized in that it comprises a network according to one of claims 1 to 6 or 19, the network being integrated into said fabric.