EP0313461A1 - Flexible shaft for use to join two openings, and particularly to canalize a luminous flux from a light catching opening to a light spreading opening, and building-room natural lighting system using said flexible shaft - Google Patents

Abstract

1. Flexible conduit (5) for the lighting of a room of a building and intended to connect two openings located in planes which are parallel or make an acute angle with one another and to channel a luminous flux from one of the openings acting as light pickup toward the other opening acting as light diffuser, characterised in that it is formed by a smooth-walled flexible sheath (6) of a material which is elastically deformable in both the longitudinal direction of the sheath and transversely such that the wall of said sheath remains smooth without the need to shape or cut the sheath when the straight sections at the ends of the taut conduit are in planes which are parallel or form an angle of up to about 45 degrees.

Description

The invention relates to a flexible conduit usable for connecting two openings and more particularly for channeling a light flux from an opening capturing light towards an opening diffusing the light thus channeled, said openings being located in parallel planes or forming between them an acute angle. It also relates to a system for natural lighting of a room in a building using said duct to channel the light.

To provide natural light to certain rooms in a building, including those that do not have windows on the outside, we sometimes use natural light captured on the roof of the building. This lighting obtained from a light sensor element, in particular glass tile, skylight or plastic dome, incorporated into the roof of the building, is most often channeled by a conduit, the shape of which takes that of the opening in the roof. , up to an opening arranged as a light diffusing element and arranged in the ceiling of the room to be lit. The realization of the conduit channeling the light is difficult because of the smallness of such a conduit and very often also of the inaccessibility of the roof space separating the ceiling from the room to be lit from the roof of the building. In addition, the walls of the conduit made of common materials have a low efficiency with regard to the reflection of light and therefore a non-negligible part of the light to be channeled is lost during the crossing of said conduit.

To overcome these difficulties, it has been proposed, as indicated in patent US-A-4 339 900, to use a flexible cylindrical or rectangular conduit produced by winding a reflectorized fabric on a spiral spring, said conduit each having its ends fixed, by cementing or using a clamp, on a sheath secured, as the case may be, to the light sensor element or the light diffusing element.

The use of such a conduit for conveying light from the sensor element to the diffuser element still has certain drawbacks. First of all, the flexibility of this conduit is constrained by its geometry. For a given section of spiral wire, the larger the interval between turns, the more flexible the conduit. Then, the deformations of the aforementioned conduit are reflected, at each angulation, by the appearance, on its inner face, of folds or wrinkles generally oriented along straight sections of said conduit, which is arranged in accordion. These folds constitute obstacles to the movement of the light flux inside the duct, with the result of a substantial reduction in the coefficient of transmission of the light flux through the duct as a result of light losses by reflection and diffraction at the folds. In addition, the securing of the conduit to the sheath associated with the sensor or light-diffusing element supposes that the wire of the spiral spring and the fabric wound on the spring are made integral with a frame, which is not easy to achieve. Finally, it is difficult to carry out such securing once the elements of the system are in place and since, moreover, this operation can only be carried out from the outside of the duct, that is to say in the attic of the building, it becomes practically impossible if the attic is inaccessible.

We have now found that these drawbacks could be overcome by using a flexible retractable and extensible conduit, the deformations of which do not alter the inner wall, which always remains taut and flexible, and the attachment of which to the sensor and diffuser elements. of light is carried out simply, including from inside the system once in place.

This flexible conduit allows in particular to connect two openings, which can be distant for example from 0.80 m to 3 m and be practiced in planes making one with respect to the other an angle which can range from 0 to about 45 ° . For small distances between these openings, provision is made according to the invention to store the non-useful part of the conduit so that the useful wall of said conduit remains in its entirety taut and smooth.

The flexible conduit according to the invention, which can be used to connect two openings located in parallel planes or forming an acute angle with each other and in particular for channeling a light flux from one of the openings acting as a sensor for light towards the other opening acting as a light diffuser, is characterized in that it is formed of a flexible sheath, with a smooth wall, of a material capable of deforming elastically both in the longitudinal direction of the sheath and transversely, so that the wall of said sheath remains smooth, without having to cut or cut the sheath, when the straight sections at the ends of the stretched duct are in parallel planes or at an angle of up to 45 ° about.

The material constituting the sheath of the flexible conduit advantageously has an elastic elongation of at least 10% in the longitudinal direction of the sheath and of at least 5% transversely. Said material can be chosen from the various known materials having the required elasticity characteristics indicated above as well as good resistance to aging. In particular, the material constituting the sheath of the flexible conduit may consist of a complex membrane formed of a fabric, for example of the jersey type, coated, in particular by coating, on one side at the by means of an elastomer, for example of the polyurethane type, the fabric of the membrane constituting the external wall of the sheath and preferably having its weft in the longitudinal direction of said sheath. When the material constituting the sheath of the flexible conduit consists of a complex membrane formed as indicated above, the fabric and the elastomer constituting said complex membrane preferably have comparable performances of elastic elongation.

Advantageously, the internal wall of the sheath of the flexible conduit can be surfaced with a reflective material having elongation performance comparable to that of the sheath.

Likewise, the internal wall of the sheath can carry, at least over part of its length, a system capable of preventing any loss of light, said system possibly consisting, for example, of a layer of glass beads forming a system reflector.

The sheath forming the flexible conduit can be associated with one or more rigid spacer rings having the desired shape, for example square or rectangular, and disposed between the two ends of the sheath, said ring or rings being either fixed, for example sewn, to the sheath outside of the latter is arranged inside the sheath so that said sheath is stretched over the inner ring or rings serving as a frame. In particular when external spacer rings are associated with the sheath, said rings are fixed to the latter so that there is a ring disposed at each end of the sheath and one or more rings arranged intermediate.

In one embodiment, at least one of the ends of the sheath forming the flexible conduit carries a collar of a flexible or rigid material, which is fixed to said end of the sheath on the outer wall of the latter and which has on its periphery a male clipping profile surrounding said sheath, said profile can be in one piece or, if necessary, to facilitate its insertion into the housing which it will be associated with it, consisting of a plurality of male profile elements which may or may not be joined.

In another embodiment, at least one of the ends of the sheath forming the flexible conduit has a frame-like frame that is both rigid and deformable so as to have the capacity to turn on itself, while retaining the shape of the sheath section, and make it possible to wind the sheath on this frame continuously. Such a winding of the sheath on the frame-shaped frame allows the storage of the excess lengths of sheath before fixing the flexible conduit brought by winding to the length required for its use. Advantageously, the aforementioned frame comprises a spiral spring, which has a length sufficient to go around the sheath and the ends of which are secured, said spiral spring being housed in a hem formed at the relevant end of the sheath and being traversed axially. by rectilinear stiffening elements, for example tubular rectilinear elements, arranged one after the other in said spring so as to give the desired section at the end of the conduit while providing a portion of spiral spring free of 'stiffening element between any two successive stiffening elements. For example, to obtain a square or rectangular reinforcement at the end of the flexible conduit, four straight non-contiguous straightening elements suitable for giving the spiral spring are inserted into the spiral spring, and therefore at the end of the flexible conduit carrying said spring, the desired rectangular or square configuration while providing at each corner of the rectangle or square thus formed a spiral spring part free of stiffening element, said part playing the role of universal joint.

As indicated above, the flexible conduit according to the invention can be used to connect two openings situated in parallel planes or forming an acute angle with each other, for example up to approximately 45 °, and in particular for channeling a luminous flux from one of the openings playing the role of light sensor towards the other opening playing the role of light diffuser.

In particular, said flexible duct can be used in a natural lighting system for a room in a building. Such a natural lighting system is of the type comprising a light sensor element incorporated into the roof of the building, a light diffusing element arranged in the ceiling of the room to be lit and a flexible duct connected by one of its ends to the light sensor element and by its other end to the diffuser element, and it is characterized in that the flexible duct is formed of a flexible sheath with a smooth wall according to the invention as defined above.

The connection of the ends of the sheath forming the flexible conduit respectively to the light-sensing element and to the light-diffusing element can be carried out simply by stapling each of said ends to a wooden frame of suitable shape forming part, according to the case, the light sensor element or the light diffusing element.

It is also possible to make the connection of the ends of the sheath forming the flexible conduit respectively to the light sensor element and to the light diffusing element by means of an attachment means provided at the end of the sheath and cooperating with an additional attachment member associated, as the case may be, with the light sensor element or with the light diffuser element. When the sheath forming the flexible conduit carries a spacer ring at its ends and possibly one or more intermediate spacer rings or else is fitted with a spiral spring frame at its ends, said duct is fixed on the one hand to the light sensor element by one of its rings or by the spiral spring frame cooperating with a first attachment member associated with the light sensor element, and on the other hand with the light diffusing element by the other of its extreme rings or by a ring intermediate or by the spiral spring frame cooperating with a second attachment member associated with said light-diffusing element, so that the wall of the sheath of said conduit located between said first and second attachment members is kept in tension sufficient to be smooth and ensure the subjection to the attachment members, of the rings or coils with spiral spring cooperating with said members. The attachment member associated with the light sensor element and cooperating with the end ring or the corresponding spiral spring frame of the flexible conduit to ensure the connection of said conduit to said light sensor element, may consist of an integral frame. of the light sensor element and having directed upwards a housing having a shape complementary to that of said ring or of the spiral spring frame and such that this ring or this frame is applied in this housing as a result of the setting in tension of the sheath forming the flexible conduit. Likewise, the attachment member associated with the light-diffusing element and cooperating with the extreme or intermediate ring or with the corresponding spiral-spring frame of the flexible conduit to ensure the connection of said conduit to said light-diffusing element, may consist of a frame integral with the light diffusing element and having a housing directed downwards shape complementary to that of said ring or said frame and such that this ring or this frame is applied in this housing as a result of the tensioning of the sheath of the conduit. When the sheath forming the flexible conduit carries a spacer ring at each of its ends and one or more intermediate spacer rings, it is possible, between the light-diffusing element and the attachment member associated with it, to provide an annular space around the light-diffusing element, said space forming a reservoir for the part of the flexible duct, if it exists, situated below the ring maintained by the attachment member secured to the light-diffusing element.

When the sheath forming the flexible conduit carries at at least one of its ends a collar externally having a protruding male profile of clipping surrounding said sheath, said profile being in one piece or being formed of a plurality of elements of non-contiguous male profiles, the connection of the end of the sheath to, as the case may be, the light-sensing element or the light-diffusing element is produced by clipping or embedding said male profile in an elastic slot formed in the inner lateral surface of a frame associated, as the case may be, with the light-sensing element or the light-diffusing element and having a shape complementary to the section of the sheath at the relevant end of the latter, the insertion of said male profile into the slot leading to an assembly of the profile to the frame by locking.

• la figure 1 représente schématiquement un conduit souple selon l'invention comportant une gaine associée à des anneaux entretoises extérieurs à la gaine ;
• - la figure 2 donne, en coupe, un schéma d'un système d'éclairement naturel d'une pièce d'un bâtiment utilisant le conduit souple de la figure 1 ;
• -les figures 3a et 3b montrent respectivement une gaine équipée, à l'une de ses extrémités, d'une armature à ressort spiralé et un chassis utilisable pour l'accrochage de ladite gaine ;
• - la figure 4 représente schématiquement une gaine sans anneau entretoise et pourvue à chacune de ses extrémités d'un collier présentant un profilé male de clipsage ; et
• -la figure 5 représente schématiquement un système d'éclairement naturel d'une pièce d'un bâtiment utilisant le conduit souple selon la figure 4.

The invention will be better understood on reading the following description of several of its embodiments illustrated by the figures of the appended drawing, in which:

• Figure 1 schematically shows a flexible conduit according to the invention comprising a sheath associated with spacer rings external to the sheath;
• - Figure 2 gives, in section, a diagram of a natural lighting system of a room in a building using the flexible duct of Figure 1;
• FIGS. 3a and 3b respectively show a sheath fitted, at one of its ends, with a spiral spring frame and a frame usable for hooking said sheath;
• - Figure 4 shows schematically a sheath without spacer ring and provided at each of its ends with a collar having a male profile of clipping; and
• FIG. 5 schematically represents a natural lighting system for a room in a building using the flexible duct according to FIG. 4.

Referring to Figure 1, the flexible conduit 5 according to the invention is formed of an extensible and retractable sheath 6, of a material capable of deforming elastically both in the longitudinal direction of the sheath and in the transverse direction, associated to a plurality of rigid spacer rings (7a to 7g) made of a sufficiently resistant material such as steel. The spacer rings are independent of each other and surround the sheath by being fixed to the latter so that there is a ring (7a, 7b) disposed at each end of the sheath and one or more rings (7c to 7g ) arranged intermediately, said rings having in the present case a square shape but being able to have any other desired shape, for example rectangular, circular or even polygonal. The attachment of the rings to the sheath is for example carried out by sewing said rings to the sheath. The material constituting said sheath consists, in the present embodiment, of a complex or composite membrane having an elastic elongation of approximately 15% in the longitudinal direction of the sheath and concomitantly an elastic elongation of approximately 8% in the transverse direction sheath. This complex membrane is made of a fabric, for example of the jersey type, coated by coating on one of its faces by means of an elastomer of polyurethane type, the fabric and the elastomer having comparable performances of elastic elongation corresponding substantially to those given above for the complex membrane. The fabric of said membrane constitutes the outer wall of the sheath and has its weft in the longitudinal direction of said sheath.

When such a duct or a portion of such a duct is tensioned between its two end rings (7a, 7b) in the case of the duct or between an end ring (7a) and an intermediate ring (7f) in the case of a portion of said duct, the deformations to which the duct is then subjected do not alter its wall, which remains smooth and taut. Each of the faces of the conduit subjected to deformation can deform due to the elasticity of the sheath, remaining a wrinkle-free surface.

In the natural lighting system of a room in a building, which is shown diagrammatically in FIG. 2, a light sensor element 1 incorporated into the roof 2 of the building is connected, by means of a flexible conduit 5 as described with reference to FIG. 1, to a light diffusing element 3 arranged in the ceiling 4 of the room to be lit, the roof 2 making with the ceiling 4 an acute angle equal to approximately 30 °. The light sensor element 1 consists for example of a glass tile 14 mounted in a square frame 15 fixed in known manner to the rafters 16 of the roof. On the lower part of the frame 15 is mounted a first attachment member 8 consisting of a rigid metal frame whose internal edge carries a portion 17 bent upward so as to define a housing 10 turned upward and of complementary shape to that of the duct rings 5.

The light diffusing element 3, which can be of any known type, consists for example of a square porthole comprising a frame 18 incorporated in the ceiling 4 of the room to be lit and associated with a double window 19, which is mounted so watertight at the bottom of said chassis. At the upper end of the chassis is mounted a second fastening member 9 consisting of a rigid metal frame, the internal edge of which carries a part 20 bent downwards so as to define a housing 11 turned downwards and of complementary shape. that of the rings of the conduit 5. In addition, between the fastening member 9 and the double window 19, the frame 18 is arranged to define an annular space 12 forming a reservoir for the flexible conduit, the internal diameter of said space 12 being slightly lower than that of the flexible duct rings.

The flexible conduit 5 is connected on the one hand to the light sensor element 1 by its end ring 7a which is applied in the complementary housing 10 of the first attachment member 8 and on the other hand to the light diffusing element 3 by that of the rings other than the ring 7a, which makes it possible to put the sheath in sufficient tension so that its wall remains smooth, said ring, in this case intermediate ring 7f, being applied in the complementary housing 11 of the second member d 'hooking 9. The tension of the sheath of the flexible conduit ensures the securing of the rings 7a and 7f to the fastening members 8 and 9 with which they cooperate respectively. The non-stretched excess part 13 of the flexible conduit, which is between the rings 7f and 7b is received in the reservoir 12 provided for this purpose.

The assembly of the natural lighting system shown diagrammatically in FIG. 2 can be carried out as follows. First of all, the installation of the light sensor element 1, equipped with the fastening member 8, is carried out in the roof of the building as well as the mounting of the frame 18 of the light diffuser element 3, equipped with the organ hanging 9, in the ceiling 4 of the room to be lit. These operations being carried out, the flexible conduit 5 is then put in place. To do this, the extreme ring 7a of said conduit is first inserted in the complementary housing 10 of the first attachment member 8 associated with the sensor element. from light. By operating through the chassis and from inside the flexible conduit, one then pulls on said conduit to tension it, without however going to the limit of its elongation capacities, so as to bring one of the rings other than 7a , in the present case ring 7f, at the level of the second attachment member 9 associated with the light-diffusing element 3, then the part of said ring 7f is inserted, on the side where the development of the duct is the weakest, in the corresponding part of the complementary housing 11 of said second attachment member and finally the ring 7f is pivoted around its already fixed side to secure the flexible conduit 5 to the second attachment member, the extensibility of the sheath of the flexible conduit allowing this operation. The flexible conduit being in place, the double window 19 is then mounted to the lower part of the frame 18.

The flexible conduit thus laid has a stretched wall without wrinkles and therefore makes it possible to ensure optimal transmission of the light flux from the light sensor element to the light diffusing element, which the known systems did not allow. natural lighting with flexible duct. In addition, as for said known flexible pipe systems, the flexible pipe according to the invention prevents the entry of dust and insects into the lighting system.

The flexible conduit 5 shown in FIG. 3a in cutaway view is formed of an extensible and retractable sheath 6 with a smooth wall, made of a material identical to that constituting the sheath of the flexible conduit of FIG. 1, said sheath 6 having a cross section rectangular. At one of its ends, namely the end 30, the sheath carries a hem 31 into which is inserted a spiral spring 32 having a length sufficient to surround the sheath and the ends of which are secured. The spiral spring 32 is traversed axially by four straight stiffening elements such as 33a and 33b, for example four rigid tube segments, which are arranged one after the other in said spring so as to give the spring the shape of a rectangle while providing a part 34 of a spiral spring free of stiffening element between any two successive stiffening elements such as 33a and 33b, said part 34 playing the role of universal joint. The assembly formed by the hem 31 in which is inserted the spiral spring 32 held in shape by the stiffeners such as 33a and 33b constitutes a frame having the shape of a rectangular frame which can rotate on itself, the four angles 34 of said frame, free of stiffening element, playing the role of universal joints. Said frame can be used as a mandrel for winding the sheath, the rolled sheath can be deployed to the length required for use by rotating the frame in opposite directions.

To produce a natural lighting system for a room in a building of a type similar to that shown diagrammatically in FIG. 2, using the flexible duct shown in FIG. 3a, the first hooking member 8 associated is eliminated. to the wooden frame 15 of the light sensor element 1 and the chassis 18 comprising the annular space 12 of the light diffusing element 3 is replaced by a chassis similar to the chassis 35 shown in FIG. 3b, the upper edges, respectively 36a to 36d, are equipped with semi-cylindrical housings, respectively 37a to 37d, having a shape complementary to that of the section of the frame comprising the hem 31 of the flexible conduit and turning their concavity downwards. The flexible conduit 5, wound on its frame 31, is firstly connected to the light sensor element 1 by stapling of the upper end 38 of the sheath 6 constituting the conduit 5 to the frame 15 of said light sensor, then the necessary length of the sheath is deployed by rotation of the frame and then the cylindrical edges of the rectangular frame, on which the excess sheath part remains wound, in the semi-cylindrical housings 37a to 37d corresponding to the frame 35, operating in such a way that the sheath is put under sufficient tension so that its wall remains smooth.

The flexible conduit 5 shown in FIG. 4, in half-section through a longitudinal plane, is formed of an extensible and retractable sheath 6 with a smooth wall, made of a material identical to that constituting the sheath of the flexible conduit of FIG. 1 , said sheath having a square cross section and carrying at each of its ends, respectively 40a and 40b, a collar, respectively 41a and 41b, of a flexible material such as flexible PVC, which is sewn, by seams such as 42a and 42b respectively, to the extreme outer wall of the sheath 6. Each of said collars 41a and 41b carries on its periphery, in the vicinity of the free end, respectively 40a and 40b, of the sheath 6, a male clipping profile, respectively 43a and 43b, surrounding said sheath, said profile being in one piece or else being incised at each of its angles to form four male profile elements contiguous or not.

To produce the natural lighting system for a room in a building shown diagrammatically in FIG. 5, in which a light sensor element 1 produced as described in connection with FIG. 2 is connected to a light diffusing element similar to that shown schematically in Figure 2, using a flexible conduit 5 as shown in Figure 4, we replace the first attachment member 8 associated with the light sensor element 1 and the frame 18 of the light-diffusing element 3 carrying the annular space 12 and the second attachment member 9, by a frame, respectively 50a and 50b, of square shape in the surface inner side of which is provided an elastic slot having a configuration such that the male profile located at the corresponding end of the sheath can be embedded therein so as to assemble the profile to the frame carrying the slot, the said frame being made of a material rigid such as rigid PVC or aluminum. The flexible conduit 5 is firstly connected to the light sensor element 1 by fitting the male section 43a, present at the end 40a of the sheath 6, in the complementary slot of the attachment frame 50a associated with said sensor. light 1. The flexible conduit 5 is then connected to the light diffusing element by fitting the male section 43b, present at the end 40b of the sheath 6, into the complementary slot of the hanging frame 50b associated with said diffusing element. lumen 3, operating in such a way that the sheath is tensioned enough so that its wall remains smooth.

In this embodiment, one could also operate by using a flexible conduit 5 having a single collar 41a at the upper end 40a of the sheath and replacing the slot frame 50b with a wooden frame, the connection of the end 40b without collar of the sheath to the light-diffusing element 3 then being produced by stapling while still operating so that the wall of the sheath remains smooth.

Of course, the invention is not limited to the embodiments described and shown, but on the contrary encompasses the various variants thereof, which are accessible to those skilled in the art while remaining within the scope of the invention.

Claims (27)

1 - Flexible duct (5), usable for connecting two openings located in parallel planes or forming an acute angle with each other and in particular for channeling a luminous flux from one of the openings acting as a sensor for light towards the other opening acting as a light diffuser, characterized in that it is formed of a flexible sheath (6), with smooth wall, in a material capable of deforming elastically both in the longitudinal direction of the sheath only transversely so that the wall of said sheath remains smooth, without having to cut or cut the sheath, when the straight sections at the ends of the stretched duct are in parallel planes or at an angle up to 45 ° approximately. 2 - flexible conduit according to claim 1, characterized in that the material constituting the sheath of said conduit concomitantly has an elastic elongation of at least 10% in the longitudinal direction of the sheath and at least 5% transversely. 3 - flexible conduit according to claim 1 or 2, characterized in that the material constituting the sheath of said conduit is a complex membrane formed of a fabric coated on one side by means of an elastomer, the fabric of the membrane constituting the wall external of the sheath and preferably having its frame in the longitudinal direction of said sheath. 4 - Flexible conduit according to claim 3, characterized in that the fabric and the elastomer, which constitute the complex membrane forming the sheath of said conduit, have comparable performances of elastic elongation. 5- flexible conduit according to one of claims 1 to 4, characterized in that the inner wall of the sheath of said conduit is surfaced with a reflective material having elongation performance comparable to that of the sheath. 6 - flexible duct according to one of claims 1 to 5, characterized in that the internal wall of the sheath carries, at least over part of its length, a system capable of preventing any loss of light, said system being constituted , for example, a layer of glass beads forming a reflector system. 7 - flexible conduit according to one of claims 1 to 6, characterized in that the sheath (6) is associated with one or more rigid spacer rings (7c to 7g) independent of each other and arranged between the two ends of the sheath, the said ring or rings being either fixed to the sheath outside of the latter (7c to 7g) or arranged inside the sheath so as to underpin said sheath without being integral with it. 8 - flexible conduit according to claim 7, characterized in that the sheath is associated with spacer elements fixed to the sheath (6) outside of the latter so that there is a ring (7a, 7b) arranged at at least one of the ends of the sheath and one or more rings (7c to 7g) arranged intermediately. 9 - Flexible duct according to one of claims 1 to 8, characterized in that at least one of the ends of the sheath (6) forming said duct carries a collar (41a, 41b) made of a flexible or rigid material, which is fixed to said end of the sheath on the external wall of the latter and which has at its periphery a male clipping profile (43a, 43b) surrounding said sheath, said profile being in one piece or else consisting of a plurality of male profile elements of clipping whether joined or not. 10 - flexible conduit according to one of claims 1 to 9, characterized in that at least one of the ends of the sheath (6) forming said conduit comprises a frame-shaped frame (31) both rigid and deformable to have the ability to turn on itself, while retaining the shape of the sheath section. 11 - Flexible conduit according to claim 10, characterized in that said frame comprises a spiral spring (32), which has a sufficient length to go around the sheath and whose ends are secured, said spring being housed in a hem ( 31) produced at the end concerned (30) of the sheath (6) and being traversed axially by rectilinear stiffening elements (33a, 33b) arranged one after the other in said spring so as to give the desired section, for example square or rectangular, at the end (30) of the duct, while providing a portion (34) of spiral spring free of stiffening element between any two successive stiffening elements (33a, 33b). 12 - Natural lighting system of a room in a building, comprising an element (1) light sensor incorporated into the roof (2) of the building, an element (3) light diffuser arranged in the ceiling (4) of the room to be lit and a flexible conduit (5) connected by one of its ends to the light sensor element and by its other end to the diffuser element, characterized in that the flexible conduit (5) consists of a flexible sheath (6), with smooth wall, made of a material capable of deforming elastically both in the longitudinal direction of the sheath and transversely so that the wall of said sheath remains smooth, without having to cut or cut the sheath, when the straight sections at the ends of the stretched conduit are in parallel planes or at an angle of up to approximately 45 °, said conduit being in tension between said light sensor (1) and light diffuser (3) elements. 13 - Lighting system according to claim 12, characterized in that the material constituting the sheath of the flexible conduit has an elastic elongation of at least 10% in the longitudinal direction of the sheath and of at least 5% transversely. 14 - Lighting system according to claim 12 or 13, characterized in that the material constituting the sheath of the flexible conduit is a complex membrane formed of a fabric coated on one side with an elastomer, the fabric of the membrane constituting the outer wall of the sheath and preferably having its frame in the longitudinal direction of said sheath. 15 - Illumination system according to claim 14, characterized in that the fabric and the elastomer, which constitute the complex membrane forming the sheath of the flexible conduit, have comparable performances of elastic elongation. 16 - Lighting system according to one of claims 12 to 15 characterized in that the internal wall of the sheath of the flexible conduit is surfaced with a reflective material having elongation performance comparable to that of the sheath. 17 - Lighting system according to one of claims 12 to 16, characterized in that the internal wall of the sheath of the flexible conduit carries, at least over part of its length, a system capable of avoiding any loss of light , said system being, for example, constituted by a layer of glass beads forming a reflector system. 18 - Lighting system according to one of claims 12 to 17, characterized in that the connection of at least one of the ends of the sheath (6) of the flexible conduit (5) to the light sensor element (1) or to the light diffusing element (3) is produced by stapling said end to a suitable frame forming part of the light sensing element (1) or of the light diffusing element (3). 19 - Lighting system according to one of claims 12 to 18, characterized in that the connection of at least one of the ends of the sheath (6) of the flexible conduit (5) to the light sensor element (1) or to the light-diffusing element (3) is produced by means of an attachment means provided at the end of the sheath (6) and cooperating with an associated additional attachment member, depending on the case, the light sensor element (1) or the light diffuser element (3). 20 - Lighting system according to one of claims 12 to 19, characterized in that the sheath (6) is associated with one or more rigid spacer rings (7c to 7g) independent of each other and arranged between the two ends of the sheath, the said ring or rings being either fixed to the sheath on the outside of the latter (7c to 7g) or arranged inside the sheath so as to underpin said sheath without being integral with it . 21 - Lighting system according to claim 19, characterized in that the sheath (6) carries a spacer ring (7a, 7b) at at least one of its ends and possibly one or more intermediate spacer rings (7c to 7g ), said end ring (7a, 7b) or one of the intermediate rings (7f) constituting the attachment means provided at the end of the sheath (6) and cooperating with the attachment member associated with the light sensor (1) or the light diffuser (3) to connect the conduit (5) to said light sensor elements (1) and light diffuser (3). 22 - Lighting system according to claim 21, characterized in that the fastening member (8) associated with the light sensor element (1) and cooperating with the corresponding end ring (7a) of the flexible conduit ( 5) to ensure the connection of said conduit to said light sensor element, consists of a frame integral with the light sensor element and having directed upwards a housing (10) having a shape complementary to that of said ring and such that this ring applies in this housing as a result of the tensioning of the sheath of the flexible conduit. 23 - Lighting system according to claim 21 or 22, characterized in that the fastening member (9) associated with the element (3) light diffuser and cooperating with the extreme ring (7b) or intermediate ( 7f) corresponding to the flexible conduit (5) for ensuring the connection of said conduit to said light diffusing element, consists of a frame integral with the light diffusing element and having directed downwards a housing (11) having a shape complementary to that of said ring and such that this ring is applied in this housing as a result of the tensioning of the sheath of the flexible conduit. 24 - Lighting system according to one of claims 21 to 23, characterized in that between the light diffusing element (3) and the attachment member (9) which is associated with it, a space is provided annular (12) around the light-diffusing element, said space forming a reservoir for the part (13) of the flexible conduit (5), if it exists, situated below the ring (7f) held by the fastening member (9) integral with the light diffusing element (3). 25 - Lighting system according to claim 19 or 20, characterized in that at least one of the ends of the sheath (6) carries a collar (41a, 41b) of a flexible or rigid material, which is fixed to said end of the sheath on the external wall of the latter and which has at its periphery a male clipping profile (43a, 43b) surrounding said sheath, said profile being in one piece or consisting of a plurality of male profile elements of clipping whether joined or not, this profile forming the attachment means which is provided with said end of the sheath and in that the attachment member associated with the light sensor (1) or with the light diffuser ( 3) and cooperating with said attachment means for making the connection of the conduit (5) to said light sensor and light diffuser elements consists of a frame (50a, 50b) which has a shape complementary to the section of the sheath (6 ) at the relevant end of the latter and in the lateral surface e internal of which an elastic slot is formed in which the male section is inserted in order to assemble the section (43a, 43b) to the frame (50a, 50b). 26 - Lighting system according to claim 19 or 20, characterized in that at least one of the ends of the sheath (6) has a frame-shaped frame (31) that is both rigid and deformable to have the ability to turn on itself while maintaining the shape of the section of the sheath, said armature forming the attachment means which is provided with the relevant end of the sheath and in that the attachment member associated with the light sensor (1) or the light diffuser ( 3) and cooperating with said attachment means for making the connection of the conduit (5) to said sensor and light diffuser consists of a frame (35) whose edges (36a to 36d) include a housing (37a to 37d). having a shape complementary to that of the frame and such that this frame is applied in this housing as a result of the tensioning of the sheath (6) of the conduit (5) when the connection is made. 27 - Lighting system according to claim 26, characterized in that said frame comprises a spiral spring (32), which has a length sufficient to go around the sheath and whose ends are secured, said spring being housed in a hem (31) produced at the relevant end (30) of the sheath and being traversed axially by rectilinear stiffening elements (33a, 33b) arranged one after the other in said spring so as to give the configuration desired, for example square or rectangular, at the end (30) of the duct while providing a part (34) of spiral spring free of stiffening element between any two successive stiffening elements (33a, 33b).

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