EP0248685B1 - Tubular joint formed by two rolling diaphragms under light over-pressure for a circular passage - Google Patents

Abstract

A tubular joint for connecting an intercommunication tunnel forming a passage compartment placed between two successive railroad on road vehicles or two successive members of access gangways to ships or to planes, said tubular joint being fitted on one hand to lateral, upper and lower walls of said vehicles or of said access gangways and on the other hand on said intercommunication tunnel, and being inflated with a gas under a relative pressure of 0.1 to 0.5 bar; said tubular joint having a symmetry plane and being composed of two rolling membranes (1a), (1b), that are U-Shaped, assembled by tightening of their ends (11a) and (11b) in said symmetry plane of said tubular joint (1) to provide a connection which can withstand all pulls exerted on the intercommunication tunnel.

Description

The invention relates to rail or road vehicles for travelers, where interconnection by a weatherproof and noise-tight gangway is provided between several successive vehicles. By extension, it is also applicable to gateways for access to an aircraft or a ship having similar kinematics.

A current orientation in railway construction, particularly for multiple-unit self-propelled trains or urban metros, is to provide passengers with free movement along the length of the train with as few physical or visual obstacles as possible. An improvement in the services offered on the train, a possible distribution of crowds and security against attacks and acts of vandalism are sought by means of open traffic as wide as possible over the entire width of the boxes and without making use of doors. separation even automatic.

To do this, we cannot be satisfied with the various types, which have become conventional bellows, such as those described in document FR-A-2 333 657, used in the construction of traditional cars or articulated buses, total weathertightness and especially soundproofing of the same level as that obtained in the walls of vehicles being requested from the deformable elements.

Tramway systems use a rigid gangway, which can have soundproofing the body walls, each half of which will pivot around a vertical axis secured to each body and will be fitted with appropriate seals.

Patent FR-A-2,357,409 to Alsthom Atlantique describes a means of connecting these two halves of the intercirculation compartment by a transverse horizontal axis close to the floor and supported by a median bogie between two boxes, thus linked in roll, but this system is unsuitable for linking a number of cases greater than two. Document EP 0134 202 from Fiat Ferroviara Savigliano describes a means of connecting two compartment halves by a single common point provided by a ball joint, conventional seals between the rigid walls which must allow roll movement between the vehicles thus connected .

Document FR-A-2.569.149 by S.I.G. describes an elastic connection allowing small deflections between the two halves of an intercirculation compartment, followed, beyond a certain stroke, by an offset by friction allowing compatibility with existing bellows, conforming to the standards of the International Union of Railways. Sealing membranes, U-shaped, fixed parallel to the walls of vehicles, known elsewhere, are described there to connect a body of a vehicle to a frame, movable relative to it in rotation and in small deflections.

Patent application FR-A-2,571,010 of the RATP describes an intercirculation device between railway vehicles positioned, at each of its ends on the ends of the bodies of vehicles by means of a deformable pneumatic seal.
However, it appears that a continuous pneumatic seal, of the necessary dimensions, which, according to the inventor, "constitutes, in the free state, a kind of large air chamber" is, in practice, impossible to achieve with the conventional means of the rubber processing industry.
In particular, the method of attachment shown diagrammatically in FIG. 10 of this document, forcing the O-ring to be pressed parallel to flat and cylindrical faces, would require before closing of said seal, the insertion of metal plywoods whose perimeter should necessarily vary during tightening intended to ensure sealing.
Despite the theoretical interest of the proposed system, the known means and simple enough to implement in the rubber processing industry do not allow an economic realization of such a seal.

Furthermore, the experience of soundproofing measures, described in patent application FR 85.16816 of the applicant, shows the need for a thickness of rubber of the order of 12 millimeters for such a membrane to have an efficiency. satisfactory acoustics, which makes the types of membranes described above lose the flexibility performance necessary to ensure their function.
The tests to which reference is made have shown that a double thickness of 6 millimeters would also be satisfactory, the multiplication of interfaces being always favorable to soundproofing.
A flexible rubber seal, having a U shape and subjected to internal pressure, is described in document FR-A-2 270 495. It is designed only to operate with an alternating rectilinear movement and presents great difficulties. clamping, positioning and mounting, due to the lack of possibility of access between the assembled elements. In addition, it requires the creation of grooves in the material to be sealed.

Analysis of the prior art therefore shows that a sealed connection device between rail or road vehicles which is simultaneously capable of withstanding all stresses in service, ensuring soundproofing of the same level as that of vehicle walls and have good fire resistance while being economical to manufacture and easy to install is not known.

To overcome the drawbacks presented by existing solutions, the invention aims to propose a device, usable for the tight connection of rail or road vehicles but also of access gangways to ships or planes which is simple and economical to manufacture and which has all the mechanical properties, sound insulation and fire resistance necessary for the application.

The object of the present invention is to propose an industrial solution to the problem to which the device described in document FR-A-2 571 010 provided only a theoretical solution.

The invention consists in having, in order to form a flexible tubular joint having the general shape of a closed ring overlapping with the ends of rail or road vehicles or access gangways to ships or aircraft, two rolling membranes, in U-shaped, made of elastomeric composition and to introduce, into the closed deformable enclosure, thus formed, a moderate pressure relative to atmospheric pressure, for example an overpressure of the order of 0.2 bars.

The invention is characterized in that said rolling membranes are assembled as they come from molding, according to the plane which is then common at their ends and which serves as a plane of symmetry for said tubular joint and that they are gas tight ensuring said overpressure and continuous over the entire periphery of the intercirculation ring, owing to the fact that said ends are each clamped between two rigid walls contained in parallel planes transverse to the axis of the vehicle or of the gangway.
The plane of symmetry of the tubular joint consists of either a rigid external fixing frame and a rigid, independent internal fixing frame, on which the ends of the rolling membranes are enclosed by studs, straddling both sides. another of said external and internal fixing frames, that is to say the walls themselves of the rolling membranes, the ends of which are placed on profiles or extensions, inside or outside.

On a sheet of rubber 6 millimeters thick, with the usual modules, in particular synthetic rubbers well protected against fire, U-shaped, for example of width 60 millimeters, a tension of the order of six Newton per centimeter of section will cause an entirely minimal elongation, not compromising the resistance to rolling fatigue between two flat walls, arranged opposite, to maintain parallel the branches of the U between the rigid wall of the vehicle and the compartment of 'intercirculation.
In addition, the examination of the stresses exerted on the rectilinear part of the wall connecting the two U-shaped membranes shows that all the loads and stresses liable to be exerted on said intercirculation compartment are easily supported by the moderate pressure exerted on the inside the volume formed by the two membranes.
Loads - permanent and variable - of a few hundred kilograms are balanced, with the same radius of curvature of the free part, by a support difference of a few centimeters made between the top seal, located on the ceiling, and the bottom seal , located under the floor, said difference being measured in the longitudinal direction of the vehicles.

The variation of these forces, which are exerted at constant pressure due to the practically constant volume of the enclosure, is easily balanced by the flattening of one side which then lengthens the bearing surface of the seal thereon.

Likewise, the spacing of the opposite rigid faces quickly shortens this bearing surface.
This results in a return rigidity not exceeding one centimeter of deviation for the highest possible stresses.

During a rotation, due to the course of a curve by the vehicles, the lateral parts of the tubular joint, thus formed by the U-shaped membranes, roll effortlessly on their support plane, while presenting a notable rigidity to the forces side. The calculation proves that no mechanical connection is necessary to support and resiliently return to an equilibrium position the traffic compartment.

Such a low pressure - of the order of 0.2 times atmospheric pressure - is very low to keep entire months, permanently, with periodic control or automatic detection, which constitutes an excellent means of warning before failure, at the slightest crack, long before the joint's rolling possibilities are compromised.

• la figure 1 est une vue générale du joint dans un plan perpendiculaire à l'axe des véhicules ;
• la figure 2 est une coupe horizontale des parois latérales des véhicules et de l'anneau d'intercirculation, reliés par un joint roulant, conforme à l'invention, à chacune des extrémités dudit anneau d'intercirculation ;
• la figure 3 est un agrandissement de la précédente, dans la zone d'un joint ;
• la figure 4 représente les éléments de la figure 2 soumis à une déformation de rotation ;
• la figure 5 est un agrandissement de la précédente; elle sert d'épure au calcul des déformations du joint tubulaire;
• la figure 6 est une variante de configuration où le centre de déformation se trouve hors du joint tubulaire ;
• la figure 7 est un agrandissement de la précédente montrant une variante de montage du joint tubulaire.

The invention and its variants will be better understood on reading the following description and the drawings, in which:

• Figure 1 is a general view of the seal in a plane perpendicular to the axis of the vehicles;
• Figure 2 is a horizontal section of the side walls of the vehicles and the intercirculation ring, connected by a rolling joint, according to the invention, at each end of said intercirculation ring;
• Figure 3 is an enlargement of the previous one, in the area of a joint;
• Figure 4 shows the elements of Figure 2 subjected to rotational deformation;
• Figure 5 is an enlargement of the previous one; it serves as a sketch to calculate the deformations of the tubular joint;
• Figure 6 is an alternative configuration where the deformation center is outside the tubular joint;
• Figure 7 is an enlargement of the previous showing an alternative mounting of the tubular joint.

Figure 1 is a view along the axis of the vehicle, cut by the fixing plane of the tubular joint according to the invention. The tubular joint (1) is secured to the vehicle body (5) by a rigid frame (2) for external fixing. It is another rigid frame (3) for internal fixing which provides the connection with the intercirculation ring (7).

The tightening of the tubular joint (1), by bolts (or by rivets), is done in a direction parallel to the axis of the vehicles.

The internal pressure is introduced and controlled by known means such as a valve (4) which can be placed anywhere in the tubular joint (1).

The outline of the exterior profile of the vehicle body (5) and of the vehicle axle (6) give the relative positions of the intercirculation ring (7) and of the walls of the vehicle bodies (5), the purpose essential being to provide as much free passage as possible from one vehicle to another, for psychological and visual reasons. Figure 2 is a horizontal section along AAʹ of Figure 1, the side walls of the vehicle bodies (5a) and (5b) and the intercirculation ring (7), all floors removed. The side wall, thinned in this region, represented by the section (5a) or (5b) as well as the floor and the ceiling of the two ends of the vehicles surround, on the whole periphery, the complete ring of intercirculation (7).

The housing with parallel faces of the two tubular seals (1) is extended by an external profile (8), for the vehicle bodies (5a) and (5b) and by an internal profile (9) for the intercirculation ring ( 7), these two profiles (8) and (9) being here shown bevelled at their end.

The rotational deformations by village of the tubular joints (1) are around the vertical axes shown in (B) and (Bʹ).

The generally planar bearing face of the tubular seals (1) can optionally receive a cylindrical curvature around the axes (B) and (Bʹ).

Figure 3 is an enlargement of Figure 2 which details the U-shaped section of the two membranes (1a) and (1b) forming the tubular joint.

Said membranes (1a) and (1b) are not subjected, in service, to significant stresses and deformations which would require a formulation of the rubber-based mixture giving it great resistance to dynamic weariness. The designer of mixtures is therefore free to seek a composition of the rubber-based mixture allowing him to achieve fire resistance and / or improved sound insulation characteristics.

With regard to fire resistance, the possibilities for formulating rubber-based mixtures are manifold, but the two most effective routes lie in the choice of the elastomer and in that of the fillers incorporated therein.

It is thus advantageous to choose the elastomer from polymers having, in their molecular structure, halogen atoms such as chlorine or bromine. Among the common elastomers of this type, the mixture formulator can select, by way of nonlimiting examples, polychloroprene, chlorinated polyethylene, chlorobutyl or bromobutyl. Elastomers containing fluorine atoms in their molecule could also be used, but this solution does not go in the direction of the desired economy.

Among the fillers, the formulator of mixtures also has a large palette in which it will advantageously choose from the class of borates - such as sodium borate - or also from chlorinated paraffins which will have to be associated with antimony oxide or still hydrated alumina.

With regard to the improvement of sound insulation, while retaining the fire-fighting properties, the designer of mixtures can combine with the above-mentioned elastomers fillers based on lead salts or oxides such as litharge.

The establishment of the tubular joint formed by the two membranes (1a) and (1b) will be facilitated by the preparation on the rigid frame, for example metallic, exterior (2) and on the analogous frame, interior (3), said frames being completely independent of each other but their solidity allowing the manipulation of the tubular joint (1), very flexible by itself since constituted by the rubber membranes (1a) and (1b), shaped by vulcanization a simple rubber blank.

A convenient implementation of said tubular joint (1) consists of a prior fixing, by fitting or by screwing the studs (10), straddling the frames (2) and (3), where the membranes (1a) and (1b ) - preferably pre-drilled - are threaded, before this assembly is placed, on one side on the vehicle body (5) and the interior profile (9), on the other side on the exterior profile ( 8) and the intercirculation ring (7) itself.

The ends (11a) and (11b) of the membranes (1a) and (1b) will be tightened, to ensure sealing, by nuts on each thread of the studs (10) as shown or, possibly, by screws (not shown) fixing in a thread made in the profiles (8) and (9).

The inflation and control valve (represented in (4) in FIG. 1) will advantageously consist of a tube secured to the rigid outer frame (2) and located at a low point thus allowing the evacuation of any condensation.

FIG. 4 represents a deformed position of the assembly which is illustrated in the aligned position in FIG. 2.

If the vehicle (5a) makes an angle (G) with respect to the intercirculation ring (7), symmetry with respect to the plane DDʹ of the latter provides a representation of the course of a curve by two consecutive vehicles whose axes form an angle between them (2G).

On the contrary, if the other vehicle (5b) also makes an angle (G) in the opposite direction with respect to the intercirculation ring (7), that is to say that the axes of the two vehicles are parallel, this figure represents the most unfavorable case for intercirculation, los of a crossing of a switch for example, where the vehicles are laterally offset by an offset (2e) which corresponds, moreover, to the product of the distance between the axes (B) and (Bʹ) by the tangent of the angle (G).

Figure 5 is a schematic enlargement of the areas of particular interest to the tubular joint (1), according to the invention. Only the diagram of the maximum deformations that said tubular joint (1) has to undergo in the entire vertical part along the side walls (5) and the intercirculation ring (7), according to the cutting plane AAʹ of the figure. 1.

In view 5a, the deformations due to the angle (G) are accumulated with a bearing which brings the intercirculation ring (7) as close as possible towards the interior of the vehicle.

In view 5b, the deformations due to the angle (G) are, on the contrary, accumulated with a maximum spacing tending to cause the tubular joint (1) to come out of its length, beveled, for this reason, at its ends.

This sketch was used to calculate the balance of forces exerted by the pressure - internal to the volume enclosed by the tubular joint (1) - on the walls of the housing of said joint. These forces are equal, per unit of height, to the product of the internal pressure by the length (C) of the support line (visible in Figure 3), in the absence of angular deviation.

The variation of these forces, when a transverse acceleration force is exerted, is due to the increase in length of this support line (c) on the overloaded side and to the simultaneous reduction of this length of the unloaded side.

The order of magnitude of the rigidity provided by this link will be close to 1 centimeter for values at the limit of lateral comfort such as 0.15 times the gravity.

The calculation of this rigidity for the section shown in FIG. 3, when it applies to the horizontal parts of the tubular joint corresponding to the floor and the ceiling, makes it possible to support the vertical, permanent and variable loads of the intercirculation ring (7) without requiring any other elastic member.

Vertical variations of less than one centimeter can be ensured by this balance between the minimum unladen situation and the maximum admissible load.

It will easily be understood that the balancing of a permanent load can be obtained without variation of the spacing of the walls, that is to say at the same radius of curvature of the free wall of the tubular joint on the sole condition that the length total (1) of Figure 3 and, therefore, the length of the support line (c), differ between ceiling and floor by the amount necessary for balance, which requires barely a few centimeters for usual loads .

The same internal pressure, for example 0.2 bar exerted over the entire periphery of the tubular joint (1), the diagram shown in views 5a and 5b shows that all the deformations take place at practically constant volume, without variation of this pressure. The tension of the wall of the rubber sheet constituting the membranes (1a) and (1b), for example 0.6 daN per centimeter of section, causes an elastic elongation - therefore reversible - of the elastomer, very moderate, in relative value, from 2 to 3% of the development of the U-shaped section. This very low elongation is not likely to disturb the resistance to fatigue in bending during the rolling of the membranes and is intended only to facilitate twisting, without wrinkling of the tubular joint during bending (shown in Figure 4).

In the event of a pressure failure, the natural stiffness of the rubber sheet constituting the membranes (1a) and (1b) is sufficient for roughly normal operation of the tubular seal (1) before it is replaced.

The tubular joint (1) must pass, very repetitively, from the position as close as possible as shown in view 5a to the position stretched as far as possible shown in view 5b. This torsional deformation of the tubular joint (1) is distributed over the approximate width of the vehicle, only by shearing of the material in a longitudinal plane of the vehicle, shearing of the order of 10% in relative value; such a low deformation rate guarantees a very long fatigue life and allows the choice of rubber-based mixtures optimized more particularly for their fire resistance.

The restoring force towards the aligned position in the arrangement deviated to the maximum from the angle (G) described above is practically due only to the effect of this twisting of the tubular joint, intervening by the shearing of the rubber sheet. constituting the membranes (1a) and (1b) and is therefore also very moderate.

A rolling of the tubular joint (1) parallel to the axis of the vehicles due to the small elastic variations in length of the coupling between the consecutive vehicles (5a) and (5b) will be, by definition, without any effort, at constant length (1) of the wave formed by the membranes (1a) and (1b) (see Figures 2 and 3).

The two support faces of length (c) shift on the rigid walls with unwinding by bending of the tubular joint, this constituting the only constraint, minute, which is opposed to displacement.

In the deformations shown in views 5a and 5b, a very small righting torque is exerted due to the different bending radii in the free part. The diagram shows that the rotation occurs - roughly - around one of the vertical axes (B) or (Bʹ) visible in fig. 4.

At most centimetric elastic recall occurs in the event of lateral forces.

The strongest stresses opposing the rotation would, rather, be due to the twisting shearing the wall of the tubular joint (1); they are extremely moderate, negligible with respect to the forces exerted by the lateral suspensions of the vehicles.

It is not at all the same for roll connections around a longitudinal axis for the bodies of vehicles (5) connected by the intercirculation ring (7) through the two successive tubular seals (1), therefore located in series on the differential twist angle.

Again, due to the shearing of the entire thin wall of the membranes (1a) and (1b) but in a plane transverse to the vehicles, without wrinkling - thanks to the tension due to the internal pressure -, this elastic torque of roll back will be very absorbed by the sliding of the membranes on the walls. However, this return torque has such a large lever arm around the roll center that the order of magnitude of the elastic connection between two vehicles will be equal to or greater than the roll return effect of the primary suspensions and secondary.

At the usual speeds of movement of trains fitted over the entire length of this type of intercirculation, this connection between vehicles will have as much importance for the successive entry of vehicles on a slope as a differential elastic return of the suspensions, each vehicle being requested, mainly, by its predecessor. The same is true for deferred recovery at the end of the slope.

FIG. 6 represents a possible variant, advantageous for the kinematics of the floors, when the instantaneous vertical axes of rotation (B) or (B sont) are distant from the plane of installation of the tubular joints (1).

In this variant, the intercirculation ring (7) surrounds the end of the vehicle bodies (5), unlike the previous configurations where it was inside.

Independent of the position of the articulation centers of the couplings, a permanent traction reaction of these, less than 10% of the usual traction force, must balance the oblique reaction on the support surfaces of the tubular joints (1 ), whose component (T) of pressure reactions normal to the support plane (R) and (Rʹ), purely axial, tends to separate the two vehicles linked by such an intercirculation ring (7).

All the explanations relating to FIG. 4, for the curvature of the angle trajectory (2G) or during a transverse offset of value (2e) between the bodies of the vehicles remain valid, with the exception of the longitudinal movements of the couplings which are made at variable volume for the tubular joint (1), the play of which must be arranged compatible with the usual movements.

In the event of maximum accidental compression causing the vehicle bodies (5) to contact the intercirculation ring (7), where anti-overlap devices must be fitted, the membranes will come into material contact over a very large area, causing an increase in internal pressure capable of creating swelling of the internal and external free rays of the tubular joint (1). The burst limit of said tubular joint (1) must therefore be provided accordingly, so that the tubular joint can resist in such extreme accidental cases.

Figure 7 is an enlargement of Figure 6, in the area of the tubular joint (1).

In this configuration, the mounting of said tubular joint (1) on the extension (9a), now inside, must be done with a slight tension. It is then possible to simplify this mounting by eliminating the frame (2a), now inside because the tubular joint (1), pre-assembled, can be manipulated simply placed on the extension (9a).

A similar simplification is possible by removing the frame (3a), now external, if the tubular joint (1) is manipulated fixed in advance on the extension (8a), now external, of the intercirculation ring (7) .

The extensions (8a) and (9a) are conical in the curved parts; they are rectilinear and oblique in the lateral and horizontal walls.

In the event of the removal of one or other of the rigid frames (2a) or (3a), one of the essential characteristics of the invention remains: it is the fixing of the tubular joint (1), by its plane assembly, perpendicular to the axis of the vehicles.

The U-shaped membrane (1a) and (1b) manufacturing method does not require any modification, for this configuration, compared to that described in FIG. 3 due to the very great deformability of the part.

One of the most economical manufacturing methods is the production by molding, in one piece, from a continuous rubber blank, placed in a compression mold having the size of the part and which can be heated. by any means used in the rubber processing industry, such as an autoclave, elastic stirrups ensuring the sealed closure of the mold during the operation. The holes in the membranes can be obtained in this way, upon molding.

The prior mounting on the extension proposed in one of the variants (see Figure 7) possibly involves an intermediate bonding of the U-shaped membranes by their planar facing faces, with or without the interposition of rigid interior and exterior fixing frames.

Another possible embodiment, even more favorable to sound insulation, is the replacement of the area, in the internal volume defined by the U-shaped membranes, by a heavy gas whose speed of propagation of sounds is lower than that of air, such as carbon dioxide, which improves the fatigue life of rubber compounds and is safe for passengers in the event of a leak or fire.

The use of this gas also has the advantage, in the event of a fire, of increasing the fire resistance of the tubular joint by limiting the presence of oxygen in contact with it and therefore by reducing combustion.

• il est capable de supporter toutes les sollicitations mécaniques qui s'exercent sur un anneau d'intercirculation assurant la liaison entre deux véhicules ferroviaires ou routiers ou des passerelles d'accès, permettant un passage dégagé sur toute la largeur,
• il offre une très longue durabilité,
• il assure une bonne isolation acoustique dans les parties d'formables, de même niveau que celle des parois normales des caisses de véhicules,
• il peut être réalisé dans un mélange à base de caoutchouc auquel sa formulation confère des propriétés anti-feu,
• il est économique à fabriquer puisqu'il ne comporte aucun élément de renfort,
• il est simple à mettre en place, grâce à un pré-assemblage permettant une manipulation aisée,
• il "prévient" de l'imminence d'une défaillance, grâce au contrôle périodique ou permanent de la pression du gaz contenu dans le volume clos formé par les deux membranes en forme de U.

In conclusion, the flexible tubular joint, consisting of two rolling membranes, U-shaped, associated according to the plane of symmetry of said joint and containing a gas - usually air - with a low overpressure compared to atmospheric pressure , object of the invention, has the following advantages:

• it is capable of withstanding all the mechanical stresses exerted on an intercirculation ring ensuring the connection between two rail or road vehicles or access walkways, allowing a clear passage over the entire width,
• it offers very long durability,
• it provides good sound insulation in the formable parts, at the same level as that of the normal walls of vehicle bodies,
• it can be produced in a rubber-based mixture to which its formulation confers fire-fighting properties,
• it is economical to manufacture since it has no reinforcing element,
• it is simple to set up, thanks to a pre-assembly allowing easy handling,
• it "warns" of the impending failure, thanks to the periodic or permanent control of the pressure of the gas contained in the closed volume formed by the two U-shaped membranes.

Claims (8)

1. Tubular joint for intercommunication ring between railway or road vehicles or for access gangways or steps to ships or to aeroplanes, having the general form of a closed ring over lapping the ends of said vehicles or gangways or steps, containing a gas at excess pressure of 0.1 to 0.5 bars with respect to atmospheric pressure, consisting of two U-shaped moving membranes (1a) and (1b), made of an elastomeric composition, said tubular joint being characterised in that said moving membranes (1a) and (1b), assembled as moulded, in the plane which is then common to their ends (11a) and (11b) and serves as the plane of symmetry for said tubular joint (1), are sealed off from the gas providing said excess pressure and continuous over the whole periphery of the intercommunication ring, due to the fact that said ends (11a) and (11b) are each held tightly between two rigid walls contained in parallel planes transverse to the axis of the vehicle or of the gangway or steps.
2. Tubular joint according to claim 1, characterised in that its plane of symmetry consists of a rigid outer fixing frame (2) or (3a) and a separate rigid inner fixing frame (3) or (2a), the ends (11a) and (11b) of the moving membranes (1a) and (1b) being held tightly by nuts fixed to each of the screw threads of bolts (10), straddling said rigid outer fixing frame (2) or (3a) or rigid inner fixing frame (3) or (2a).
3. Tubular joint according to claim 1, characterised in that its plane of symmetry consists of the walls of said moving membranes (1a) and (1b), the ends of which are fixed on the one hand to an extension (8a) and on the other hand, under slight tension, to an extension (9a).
4. Tubular joint according to any of claims 1 to 3, characterized in that the length of the bearing lines (C) of the arms of the U differs between the ceiling and floor of the vehicle in order to ensure balancing of permanent loads.
5. Tubular joint according to any of claims 1 to 4, characterised in that the valve for inflation and control of the internal pressure (4), known in the art, is integral with the rigid outer fixing frame (2) or (3a), which allows emphasis of the slightest deficiency of the joint, by detection of a decrease in said internal pressure.
6. Tubular joint according to any of claims 1 to 5, characterised in that the gas contained in the closed space formed by the moving membranes (1a) and (1b) is a heavy gas with a low speed of sound transmission such as carbon dioxide.
7. Tubular joint according to any of claims 1 to 6, characterised in that the moving membranes (1a) and (1b), in order to ensure soundproofing equivalent to that of the walls of the vehicle bodies (5), have a thickness at least equal to six millimetres.
8. Tubular joint according to any of claims 1 to 7, characterised in that the elastomeric composition of the moving membranes (1a) and (1b), which must simultaneously satisfy properties of resistance to alternating flexions and to the permanent tension due to excess pressure, sealing, soundproofing and incombustibility, is a compact, homogeneous elastomeric composition comprising on the one hand an elastomer having halogen atoms in its molecular structure and on the other hand reinforcing fillers based on lead salts or oxides.

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