EP0435755B1 - Link coupling between railway cars of an articulated train - Google Patents

Abstract

Coupling joint between rail vehicles resting on a middle bogey, which comprises an element made of elastic composite material (5) formed from seven layers of elastomeric composition (7) sandwiched by six metal hoops (6) of constant thickness, the contact surfaces being in the form of truncated cones preferably of an apex angle of 25 degrees, the inner reinforcement (8), forming an assembly surface (9), and the outer reinforcement (4), supporting the element made of elastic composite material (5), being adhesively bonded to the adjacent layers of elastomeric composition (7a) and (7g). <??>The invention is used for the coupling of railway trains.

Description

The invention relates to a coupling articulation between railway vehicles resting on a common, middle bogie, articulation produced by means of laminated elastic elements.

The articulations between railway vehicles in so-called articulated trainsets, where two body ends rest on a single median bogie, can use a ball joint with spherical bearing, linked to a vehicle resting on the other, itself suspended and recalled in roll by a suspension on said median bogie. These articulations carrying a high load, by means of elements in laminated elastomer and hooped by several intermediate reinforcements, which are possibly prestressed, require a large number of machining operations and are, for this reason, of a high cost price. , for a fairly reduced anti-vibration filtering, due to their notable rigidity.

Document FR-A-2,357,409 from Alsthom provides for several separate articulations around two vertical axes and a third, horizontal axis, all integral with an intercirculation compartment; this arrangement is used in the case where two consecutive vehicle bodies remain linked in roll by a gimbal system. The elastomeric member carrying the permanent load is then forced to rotate around the single vertical axis connecting a body and a half-circulation compartment. Its angular performance therefore requires only half the angle between the boxes, the compartment placed on the median bogie by its horizontal axis remaining bisector of this angle. The part therefore has only limited performance to be satisfied in this case, which is not applicable to a train of more than two successive boxes, because no flexibility in roll or left track separates them. As a result, the application remains limited to trams or multiple units with two inseparable bodies.

The document FR-A-2,631,917, also from Alsthom, meets, on the contrary, the needs of a long train, by providing an O-shaped part with a frustoconical surface in its lower zone and a support part which envelops it. , connected to the other vehicle on which it is fixed. An O-ring element of elastic composite material, formed of metal plates "sandwiched between layers of elastic material" is provided, "surrounding and in contact" with the frustoconical external surface. A variant is described there, in which the metal plates and the layers of the material are in the form of a spherical sector.
Document US-A-3,667,820 describes an articulation interposed between support plates of the chassis of a conventional railway vehicle, composed of two layers of elastomer sandwiching a metal frame whose contact surfaces are frustoconical, the number of layers of elastomer and metal being capable of being increased as required. Such a device, the shapes and dimensions of which are not optimized cannot meet the contradictory requirements of the specifications of a joint intended for a high-speed train.

The present invention relates to the optimization of an articulation device to meet the specific needs arising from the use on articulated vehicles having median bogies in common, the optimization having related to the number and the angular arrangement of the layers. of elastic material as well as on the law of evolution of their dimensions.
The invention therefore relates to a coupling articulation between railway vehicles resting on a median bogie, connected by means of elastic elements, interposed between a support piece, integral with one of the vehicles, and an internal frame, constituting the assembly surface in support of the other vehicle on the first, the element in elastic composite material comprising metallic hoops of constant thickness sandwiching layers of elastomeric composition and the contact surfaces being in the form of trunks of cone.
The present invention is characterized in that said element of elastic composite material is formed from seven layers in elastomeric composition sandwiched by six metal hoops, in that the internal reinforcement, which constitutes the bearing surface in support of the toric piece is intimately linked, by adhesion during the crosslinking, to the layer of elastomeric composition la more internal by a contact surface in the form of a truncated cone of the same angle as the bearing surface in support, in that said internal reinforcement has a constant thickness, at most equal to the thickness of the layers of elastomeric composition, in that the external reinforcement, of triangular cross section, which supports the element of elastic composite material, is intimately linked, by adhesion during the crosslinking, to the layer of outermost elastomeric composition by its shaped contact surface truncated cone, and in that the variation in the height of the metal frets and, therefore, that of the width of the layers in elastomeric composition is done inversely proportional to the square of their average radius, with a view to favoring the most homogeneous shear rate possible in torsional stresses around the axis of the cones.
Furthermore, the angle of said truncated cones, forming a contact surface, is close to twenty-five degrees relative to the axis of the joint.

The invention will be better understood on reading the description accompanying the single figure.
The figure is a section through a vertical plane passing through the hinge axis, which serves as an axis of revolution for the hinge according to the invention.
The support piece (1) which is an integral part of the first vehicle comprises a vertical cylindrical flange (2) in which is fixed, by bolts such as (3), an external frame (4), of triangular cross section, supporting the element in elastic composite material (5). This comprises six metallic frets (6), of constant thickness, in the form of trunks of cones. Said metal hoops (6), preferably made of welded rolled steel sheet, sandwich seven layers of elastomeric composition (7), preferably made of natural rubber or synthetic polyisoprene, of great resilience and resistance to alternative fatigue improved by the choice of appropriate fillers for reinforcing the elastomeric composition.
In the same way as the external reinforcement (4), of triangular cross section, serves as a support on the support part (1), an internal reinforcement (8) constitutes the support assembly surface (9), coming in contact on the lower part of an O-ring (10), secured to the adjacent vehicle.
The external reinforcement (4) and the internal reinforcement (8), as well as each face of the metal frets (6), all in the form of truncated cones, are intimately linked, by the physico-chemical phenomenon known as in situ adhesion, layers of elastomeric composition (7). By convention, a good quality of said adhesion is obtained when the rupture occurs in full rubber in destructive tensile test. A so-called "bond-test" allows, without destruction, under a tensile stress opposite to the normal load for which the part is designed, to verify the absence of degradation.
Preferably, the internal reinforcement (8), constituting the bearing assembly surface (9), in front of, for reasons of space, occupy the least possible thickness between said bearing assembly surface (9) and the element of elastic composite material (5) is of constant thickness and at most equal to the thickness of each of the layers of elastomeric composition (7).
The main function of the articulation object of the invention being the alternating rotation around the axis of the trunks of cones, under a permanent compressive load, the optimization aims at geometric shear rates as equal as possible in the material, during this rotation between the different solids connected by the layers of elastomeric composition (7). It follows, for each of the seven layers of elastomeric composition (7), the need for torsional rigidity inversely proportional to their thicknesses, said thickness being constant in one layer, but different from one layer to another.
Strictly speaking, the angular rotation being the same at each end of a layer of elastomeric composition (7), the shearing of the elastomeric material, which remains the same thickness, done at a rate which is proportional, more precisely, to the radius considered at each point. However, the mean value of this geometric shear rate, - for mean radii of the layers which are different - can only be maintained if the stress is substantially the same in the material of constant modulus. This implies that the cross-section of the layer of elastomeric composition varies in inverse function to the lever arm (or average radius), which subjects each layer to the same torque, the elastic connections being, in series, subjected to it.

This condition is in contradiction with an identical stress rate under the effect of the vertical load, as well as under horizontal forces. Indeed, this condition would require a constant cross-section of the layers of elastomeric composition (7) between each metal hoop (6), which would lead to choosing a width of the layers of elastomeric composition (7) inversely proportional to the mean radius. This condition, little penalizing, does not need to be satisfied with the same rigor as that dictated by the optimization in alternating rotation.

To satisfy identical torque and identical shear rate, substantially, in each rotating layer, the law favors a thickness of the layers inversely proportional to the mean radius and a width inversely proportional to the square of said mean radius. The same law governs the height of the metal frets (6), also inversely proportional to the square of said mean radius.

It should be noted that better homogeneity within each layer would require, for the same geometric shear, a thickness proportional to the radius, that is to say different cone angles all having the same vertex. The choice of a cone of identical angle, for each metallic hoop (6), is therefore an approximation, making it possible to limit the costs of such reinforcements to realistic values, while also maintaining constant thicknesses at their sheets.

These provisions have the consequence, but also as a second objective, of assigning to each layer of elastomeric composition (7) a constant form factor, communicating to each a ratio of rigidities, between pure compression and pure, constant shear. The form factor results, in fact, from the ratio between the bonding surface between the metal of the metallic ferrule (6) and the elastomer of the layer of elastomeric composition (7) on the one hand and the free surface at the ends of the thickness of each layer, on the other hand. The axial rigidity, vertically, which is predominantly due to the projection on the axis of a normal compression of the elastic material, is therefore distributed, from one layer to the other, in the same way as the shear. The elastic deformation strokes are therefore distributed inversely proportional to the square of the mean radius for each layer, under the same axial load, obviously in series.

To satisfy the optimization, the number of layers required by the needs of the application cannot be arbitrary, since a cumulative thickness of the layers of notable elastomeric composition is necessary but limited by the geometry.

In an example of application where the large diameter of the joint measures 400 millimeters, the total height in the free state not exceeding 200 millimeters, the cumulative thickness of the seven layers of elastomeric composition (7) reaches 61 millimeters, each metallic hoop (6) having a thickness of 2.5 millimeters, ie a thickness of the elastic part of the joint of 76 millimeters measured normally between faces opposite the external frame (4) and the internal frame (8).
Furthermore, it results from the same optimization that the angle of the truncated cones is about 25 degrees relative to the axis, that is to say an angle at the top of the cone of about 50 degrees.
In the same application example, the thicknesses of the different layers of elastomeric composition are decreasing from the innermost layer (7a) to the outermost layer (7g), taking the values below:
The layer 7a has a thickness of 11.2 millimeters.
The layer 7b has a thickness of 10.1 millimeters.
The layer 7c has a thickness of 9.1 millimeters.
The layer 7d has a thickness of 8.3 millimeters.
The layer 7e has a thickness of 7.8 millimeters.
The layer 7f has a thickness of 7.4 millimeters.
The layer 7g has a thickness of 7.1 millimeters.

A number of layers higher than seven would obstruct the torsional rigidity, by aggravating the heterogeneity of the stresses within each layer and, procuring a higher conical rigidity, would limit excessively the possible left between two boxes.
A lower number would insufficiently participate normal compression in the various rigidities, by reduction of the form factor. A higher modulus of the material, which would make it possible to compensate for this effect, would result in insufficient resistance to alternating fatigue.

For the same reason, it was not considered advisable to envisage a module different from one layer to another of the elastomeric composition. This variant would have been made possible by an embodiment of the part in compression molding of blanks, themselves inconvenient to produce due to the conical shape, but, however, of constant thickness in each layer, all thicknesses then being different from one layer to another.

The most advantageous manufacturing method for producing the joint according to the invention is therefore transfer molding, in a preheated mold, containing the metal frames previously treated and coated with the adhesives necessary for adhesion in situ, each hoop metallic (6) being glued on its two faces, the internal reinforcement (8) and the external reinforcement (4) being glued only on their face intended to come into contact with the layer of elastomeric composition (7a) or ( 7g), adjacent.

All the physico-chemical connections are thus made, during vulcanization, under controlled temperature and pressure. The joint, rid of its burrs and pins, is directly ready for use after demolding and cooling.

The articulation according to the invention allows all the elastic deformations of a coupling, between rail vehicles of a train articulated on bogies common to the two ends of bodies opposite. It is optimized for the best lifetime under dynamic stresses and good filtering of parasitic vibrations between said boxes. It provides a rational and optimized solution to the design of joints required in this type of integrated railway trains, called articulated trains, while simplifying coupling and decoupling operations.

Claims (3)

1. A coupling joint between rail vehicles resting on a common bogie, said vehicles being linked through the intermediary of a resilient element interposed between a support part (1) firmly attached to one of the vehicles and an inner reinforcement (8) constituting the bearing surface (9) for mounting the other vehicle on the first, comprising an element made of resilient composite material (5) in which metal hoops (6) of constant thickness form a sandwich with layers of elastomeric composition (7), the contact surfaces being in the form of truncated cones, characterised

   - in that said element made of a resilient composite material (5) if formed of seven layers of elastomeric composition (7) forming a sandwich with six metal hoops (6),

   - in that the inner reinforcement (8) which constitutes the bearing surface (9) for mounting the toric part (10) is intimately linked, by bonding during reticulation, to the innermost layer of elastomeric composition (7a) by a contact surface in the form of a truncated cone with the same angle as the bearing surface (9) for mounting,

   - in that said inner reinforcement (8) is of constant thickness, equal to or less than the thickness of the layers of elastomeric composition (7),

   - in that the outer reinforcement (4), of triangular cross section, which supports the element made of resilient composite material (5), is intimately linked, by bonding during reticulation, to the outermost layer of elastomeric composition (7g) by its contact surface in the form of a truncated cone,

   - and in that the variation in height of the metal hoops (6) and, therefore, the width of the elastomeric composition layer (7) is inversely proportional to the square of their mean radius, with a view to favouring the most homogeneous possible shear rate in terms of torsional stresses around the axis of the cones.
2. A coupling joint between rail vehicles according to Claim 1, characterised in that the variation in thickness of the layers of elastomeric composition (7) is inversely proportional to their mean radius, with a view to balancing the torsional moment around the axis of the cones to a value which is as constant as possible between each couple of intermediate, adjacent metal hoops (6).
3. A coupling joint between rail vehicles according to one of Claims 1 or 2, characterised in that the angle of the truncated cones is close to twenty-five degrees relative to the axis of the joint.

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