The present invention relates to a structural link for permanently connecting two subassemblies of a rail vehicle assembly, such as two adjacent vehicle bodies or a vehicle body and a running gear.

A structural link for permanently connecting two subassemblies of a rail vehicle assembly is disclosed in US 2009/0008963 A1. This structural link comprises an energy absorption unit comprising a widened portion and a permanently deformable cylinder, which defines a reference axis. It further comprises a piston comprising an end portion provided with a non-deformable piston head, which is such as to effect a radial expansion of the permanently deformable cylinder while moving parallel to the reference axis within the permanently deformable cylinder in a stroke direction from an service position towards an end position. The piston is further provided with a guide for guiding a relative translation motion between the piston and the permanently deformable cylinder from the service position to the end position of the piston head. The guide protrudes from the piston head in the stroke direction and slides into the permanently deformable cylinder ahead of the piston head. The length of the permanently deformable cylinder is therefore greater than the stroke of the piston head from the service position to the end position to accommodate the guide in the end position. The piston is further provided with a bushing for receiving a pivot pin for articulating an end section of a coupling rod. The bushing defines a pivot axis perpendicular to the reference axis of the permanently deformable cylinder. The piston does not have a piston rod linking the bushing to the piston head. Hence, in the service position, the bushing protrudes outside the widened portion of the energy-absorption unit, but is very close to the widened portion. This may hinder the stroke motion of the piston head into the permanently deformable cylinder if the coupling rod is at angle with the reference axis of the permanently deformable cylinder during a collision.

The invention aims to provide an improved structural link for permanently connecting two subassemblies of a rail vehicle assembly.

According to a first aspect of the invention, there is provided a permanent structural link for permanently linking a first subassembly of a rail vehicle assembly with a second subassembly of the rail vehicle assembly, wherein the first subassembly and the second subassembly consist either of a first vehicle body and a second vehicle body or of a vehicle body and a running gear, wherein the structural link comprises:

• an energy absorption unit comprising a permanently deformable cylinder, which defines a reference axis and a widened portion, which has an inner cross-sectional area greater than the permanently deformable cylinder,
• a piston comprising an end portion provided with a non-deformable piston head, wherein the piston head in a service position is received in the widened portion of the energy absorption unit, wherein the piston head is such as to effect a radial expansion of the permanently deformable cylinder while moving within the permanently deformable cylinder in a stroke direction parallel to the reference axis, and
• an annular guide for guiding a relative translation motion between the piston and the permanently deformable cylinder in the stroke direction,

More specifically, the piston comprises a piston rod protruding from the end portion in a direction parallel to the reference axis and opposed to the stroke direction, the piston rod is provided with an outer cylindrical sliding surface, and the annular guide is fixed relative to the widened portion of the energy absorption unit and has an inner diameter such as to be in sliding contact with the outer cylindrical sliding surface of the piston rod at least when the piston head, after leaving the service position, moves towards the end position.

The permanently deformable cylinder does not need to have a length greater than the stroke of the piston head between the service position and the end position, since it does not have to accommodate the guide.

The piston rod and the annular guide cooperate to ensure that the piston head does not deviate from the stroke direction. During the stroke, the distance between the piston head and the annular guide increases while the distance between annular guide and the opposite end of the piston rod is reduced.

In practice, it is possible to define a predetermined collision threshold and a predetermined service limit lower than or equal to said collision threshold such that upon application of any collision load above said predetermined collision threshold in an axial direction parallel to the reference axis the piston head effects said radial expansion of the permanently deformable cylinder while moving parallel to the reference axis within the permanently deformable cylinder from the service position towards the end position, whereas upon application of any proof load or fatigue load below the predetermined service limit in the axial direction the piston head remains in the service position.

According to a preferred embodiment, the annular guide in the service position is press-fitted onto a cylindrical seat of the piston rod. The press-fitted connection defines a force threshold below which axial forces are transmitted between the piston and the annular guide without deformation of the energy absorption unit. Above said threshold, the piston rod separates from the annular guide and the piston starts moving in the stroke direction while the piston rod slides within the annular guide.

According to a preferred embodiment, the annular guide in the service position bears axially against a shoulder of a collar of the widened portion of the energy-absorption unit and the shoulder of the collar of the widened portion of the energy-absorption unit faces a direction that has an axial component opposite to the stroke direction. The shoulder of the widened portion of the energy-absorption unit ensures that the annular guide does not move in the stroke direction relative to the energy-absorption unit.

Preferably, the annular guide is secured to the collar of the widened portion of the energy-absorption unit by means of fixing elements such as screws, bolts or rivets. The fixing elements ensure that the annular guide does not move relative to the energy-absorption unit in the axial direction opposite to the stroke direction. Preferably, the permanent structural link further comprises a mounting plate, wherein the collar of the widened portion of the energy-absorption unit is sandwiched between the mounting plate and the annular guide and the fixing elements secure the annular guide to the mounting plate through holes provided in the collar of the widened portion of the energy-absorption unit.

According to one embodiment, the collar of the widened portion of the energy-absorption unit is welded, preferably butt welded with an end of the permanently deformable cylinder. Alternatively, the energy absorption unit can be formed in one piece.

According to a preferred embodiment, the annular guide in the service position bears axially against a shoulder of the end portion of the piston, wherein the shoulder of the end portion of the piston faces a direction that has an axial component opposite to the stroke direction. The shoulder of the end portion of the piston ensures that the structural link can withstand traction forces in the reference direction, i.e. forces that tend to pull the piston in the direction opposite to the stroke direction.

To avoid any undesired play and wear during the lifetime of the structural link, the annular guide preferably bears axially against the shoulder of the end portion of the piston with a predetermined axial preload and the piston head in the service position bears axially against a shoulder of the widened portion of the energy-absorption unit with a predetermined axial preload, equal in magnitude to the axial preload between the annular guide and the shoulder of the end portion of the piston.

According to one embodiment, the annular guide is made of a material having a Vickers hardness greater than 600 HV, preferably greater than 630 HV. The hardness of the annular guide contributes to the absence of deformation or play of the permanent structural link during its lifetime in the service position.

According to one embodiment, the piston head in the service position is press-fitted into the widened portion of the energy-absorption unit. Preferably, the piston head has a tapered end face and the shoulder of the widened portion of the energy-absorption unit is tapered.

The piston head is preferably annular.

According to one embodiment, the end portion of the piston is made in one piece. Alternatively, the end portion of the piston can be made of several parts including a piston head body and the non-deformable piston head. The piston head is preferably press-fitted or otherwise affixed to a body of the end portion. According to a preferred embodiment, the piston head is press-fitted to the body of the body of the end portion and the connection is secured by means of fixing elements such as screws, preferably locked with glue.

According to a preferred embodiment, the non-deformable piston head is preferably made of a material having a Vickers hardness greater than 650 HV, preferably greater than 700HV. The high hardness of the piston head ensures a controlled expansion of the permanently deformable cylinder.

According to one embodiment, the piston rod is tubular.

According to one embodiment, the end portion of the piston and the piston rod are made in a single piece, preferably a tubular piece.

Advantageously, the permanent structural link further comprises a coupling eye integral with an end of the piston opposed to the end portion. The coupling eye is part of a hinge connection or of a ball joint.

According to another aspect of the invention, the hinge connection or ball joint is part of the structural link.

According to another aspect of the invention, there is provided a a rail vehicle assembly comprising a first subassembly and a second subassembly of a rail vehicle assembly, wherein the first subassembly and the second subassembly consist either of a first vehicle body and a second vehicle body or of a vehicle body and a running gear, characterised in that the rail vehicle assembly further comprises a permanent structural link according to any one of the preceding claims for linking the first subassembly with the second subassembly. Preferably, the reference axis of the permanent structural link is parallel to a median vertical longitudinal plane of the rail vehicle assembly, and preferably parallel to a longitudinal axis of the rail vehicle assembly.

As stated above, it is possible to define a predetermined collision threshold and a predetermined service limit below said collision threshold such that upon application of any collision load above said predetermined collision threshold in an axial direction parallel to the reference axis the piston head effects said radial expansion of the permanently deformable cylinder while moving parallel to the reference axis within the permanently deformable cylinder from the service position towards the end position, whereas upon application of any proof load or fatigue load below the predetermined service limit in the axial direction the piston head remains in the service position.

The predetermined service limit is more than a standard proof load and a standard fatigue load of the rail vehicle according to the applicable standard load cases.

The predetermined service limit is more than a standard proof load and a standard fatigue load of the rail vehicle according to the applicable standard.

Other advantages and features of the invention will then become more clearly apparent from the following description of a specific embodiment of the invention given as non-restrictive examples only and represented in the accompanying drawings in which:

• figure 1 is a side view of a region of a train set comprising two adjacent car bodies and a running gear;
• figure 2 is a longitudinal cross-section of a detail of figure 1;
• figure 3 is an isometric view from below of some parts of the region of a the train set illustrated in figure 1;
• figure 4 is an isometric view of a structural link between the running gear and one of the adjacent car bodies shown in figure 1;
• figure 5 is an axial section of the structural link of figure 4, along section plane V-V of figure 8;
• figure 6 is an axial section of the structural link of figure 4, along section plane VI-VI of figure 8;
• figure 7 is an axial section of a detail of the structural link of figure 4, along section plane VII-VII of figure 8;
• figure 8 is a front view of the structural link of figure 4.

With reference to Figures 1 to 3, a train set 10 comprises a first car body 12, a second car body 14 and a running gear 16 located below adjacent ends of the first and second car bodies, 12, 14. A structural link 18 forms a permanent connection between the end of the first car body 12 and the second car body 18. The structural link comprises an energy absorption unit 20 fixed to the end of the first car body 12, a ball joint housing 22 fixed to the second car body 18 and a piston 24 for connecting the energy absorption unit 20 to the ball joint housing 22. The ball joint housing 22 has a vertical extension that protrudes though an aperture in a frame 26 of the running gear 16 and is linked to the frame 26 by longitudinal resilient members 27, which transfer longitudinal forces between the frame 26 of the running gear 16 and the ball joint housing 22.

The energy absorption unit 20 illustrated in figures 4 to 8 comprises a permanently deformable cylinder 28, which defines a reference axis 100, and an annular widened portion 30 at an open end of the permanently deformable cylinder 28. The opposite end of the permanently deformable cylinder 28 is closed with a cap 32. The axial direction 200 parallel to the reference axis 100 and directed from the open end towards the cap 32 is called stroke direction. The reference axis 100 is located in a median longitudinal vertical plane of the first car body 12. The reference axis 100 is preferably horizontal.

The widened portion 30 is coaxial with the permanently deformable cylinder 28 and has a slightly larger inner diameter than the permanently deformable cylinder 28. The widened portion 30 comprises a collar 34 that protrudes radially so as to form an annular planar shoulder 36 that faces in a direction opposite to the stroke direction 200. The collar 34 of the widened portion 30 is provided with a set of axial through holes 38. The collar 34 is welded, preferably butt welded with a widened extension 40 of the permanently deformable cylinder 30.

The piston 24 comprises a piston rod 42 and two opposite end portions, namely first end portion 44 which, in the service position depicted in the figures, is received in the widened portion 30 of the energy absorption unit 20, and a second end portion 46 opposed to the first end portion and provided with a coupling eye 48 for receiving the ball joint 49 fixed to the ball joint housing 22. The piston rod 42 protrudes from the first end portion 44 in a direction parallel to the reference axis 100 and opposed to the stroke direction 200. The piston rod 42 is tubular, as well as the first end portion 44.

The first end portion 44 of the piston 24 comprises a piston head body 50 integral with the piston rod 42 and a non-deformable tapered annular piston head 52 protruding at the free end of the first end portion 44 in the stroke direction 200. The piston head 52 is press-fitted onto the piston head body 50. The material of the piston head 52 has a greater hardness than the material of the permanently deformable cylinder 28. The hardness of the piston head body 50 is preferably greater than 650 HV, preferably greater than 700 HV. The piston head 52 in the service position bears axially against a tapered shoulder 54 of the widened portion of the energy-absorption unit 30, which marks the transition between the widened extension 40 of the widened portion 30 and the permanently deformable cylinder 28.

The first end portion 44 of the piston 24 is further provided with an annular planar shoulder 56, which faces the direction opposite to the stroke direction 200.

The energy absorption unit 20 further comprises an annular guide 58 for maintaining the piston 24 in the service position and guiding the piston 24 in translation parallel to the reference axis 100 in the stroke direction 200 relative to the permanently deformable cylinder.

The annular guide 58 bears axially against the shoulder 36 of the collar 34 of the widened portion 30 of the energy-absorption unit 20 and is provided with through holes 60 coaxial with the through holes 38 of the collar 34. The annular guide 58 has a hardness, which is preferably greater than 600 HV, preferably greater than 630 HV.

The structural link 18 further comprises a mounting plate 62 for securing the structural link 18 to the end of the first car body 12. The mounting plate 62 is provided with threaded holes 64 that are coaxial with the through holes 60 of the annular guide 58 and the through holes 38 of the collar 34. The collar 34 is sandwiched between the annular guide 58 and the mounting plate 62. Fixing elements such as screws 66 engaged in the through holes 60, 38 and threaded holes 66 are used to secure the annular guide 58 and the collar 34 to the mounting plate 62.

When the screws 66 are tightened with a predetermined torque, the annular guide 58 bears axially against the shoulder 56 of the end portion 44 of the piston 24 with a predetermined axial preload and the piston head 52 bears axially against the tapered shoulder 54 of the widened portion 40 of the energy-absorption unit 30 with a predetermined axial preload, equal in magnitude to the axial preload between the annular guide 58 and the shoulder 56 of the end portion 44 of the piston 24.

The mounting plate 62 is further provided with a set of though holes 68 for fixing the mounting plate 62 to the end of the first car body 12, by means of fixing elements 70.

The annular guide 58 in the service position is press-fitted onto a cylindrical seat 72 of the piston rod 42. The piston rod 42 is provided with a smooth outer cylindrical sliding surface 74, which has a diameter slightly smaller than the cylindrical seat 72.

The structural link 18 operates as follows.

The tight sandwiched connection between the end portion 44, the tapered shoulder 54 of the energy-absorption unit 20 and the annular guide 58 is such as to remain without play and without plastic deformation upon application of any proof load or fatigue load below a predetermined service limit in the axial direction the piston 24. To this end, the axial preload of the annular guide 36 against the shoulder 56 of the end portion 44 of the piston 24 in the absence of external force is preferably greater than the predetermined service limit.

However, whenever a collision load above a predetermined collision threshold in an axial direction parallel to the reference axis 100 is applied, the press fit connection between annular guide 58 and the seat 72 is overcome and the piston head 54 effects a radial expansion of the permanently deformable cylinder 28 while moving parallel to the reference axis 100 in the stroke direction 200 within the permanently deformable cylinder 28 from the service position towards an end position closer to the cap 100. The annular guide 58 has an inner diameter such as to be in sliding contact with the outer cylindrical sliding surface 74 of the piston rod 42 when the piston head 54, after leaving the service position, moves towards the end position.

The predetermined service limit is more than a standard proof load and a standard fatigue load of the rail vehicle according to the applicable standard load cases and less than the predetermined collision threshold.

In practice, the axial preload of the annular guide against the shoulder of the piston head in the absence of external force is greater than the predetermined service limit and smaller than the predetermined collision threshold.

The invention is not limited to this embodiment. As a variant, the end portion 44 of the piston is made in one piece, i.e. the piston head 54 and piston head body 50 are made in one piece. The energy absorption unit 20 can also be formed in one piece, i.e. the collar 64 can be made in one piece with the permanently deformable cylinder 28. The cap 32 is optional. The mounting plate 62 can be integral with the collar 64. The piston rod can 42 be a solid cylinder rather than a tubular cylinder.

The structural link 18 can be used in other train configurations, e.g. between two vehicle bodies 12, 14, or between a vehicle body 12 and a running gear 16 that is not a Jacob-type bogie.