AU754339B2 - Energy absorbing apparatus - Google Patents

Description

P/00/0 1 1 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention title: Energy absorbing apparatus The following statement is a full description of this invention, including the best method of performing it known to us: 22342780.do~hL! 2 ENERGY ABSORBING APPARATUS The present invention relates to an energy absorbing apparatus for absorbing impact energy in vehicles. The apparatus of the present invention is particularly suitable for use in railway vehicles and for convenience will hereinafter be described with reference to this application.

Recent accidents in the railway sector have led to the concept of railway vehicles requiring a crashworthiness aspect to their design. Traditionally railway vehicles have been designed to meet static strength loads, which have been empirically developed over the last few decades. A car that meets the static strength requirements are usually satisfactory in daily service. However, these requirements do not cater for accidents and actually may lead to a less safe vehicle during collisions. Crashworthiness is a term applied to the design process to ensure a vehicle is safe during accidents to specified limits. Safety is loosely defined as controlled and progressive deformation of the carriage to prevent catastrophic failure of the carriage. It does not imply absolute passenger safety.

Crashworthiness conditions are in addition to the static strength requirements.

Collisions involving railway vehicles are characterised by heavy vehicles, which are travelling at relatively high speed. This is stark difference to car collisions which have vehicles of relatively low mass.

20 The ability to handle crash loads is to be able to absorb energy in a controlled and progressive manner. As energy absorption is a product of the retarding force over the distance it implies that a very high static strength car body that buckles will not absorb much collision energy.

In order to improve the crashworthiness of railway vehicles, new railway 25 vehicle designs have incorporated one or more energy absorbing structures into the leading car. The energy absorbing structures must be designed such that they can absorb and dissipate the impact energy of a crash whilst ensuring that peak loads being transmitted from the energy absorbing structure to the rest of the car does not exceed the maximum strength of the rest of the car.

Previous energy absorbing structure designs have had difficulty meeting GWN:DMA:#33749. CAP 26 February 2001 004187550 3 these requirements. Furthermore, the performance of previous energy absorbing structures has been found to be very sensitive to slight changes in the degree of impact between railway vehicles. In this regard, it will be appreciated that the majority of railway crashes result from one train running into the rear of another train or two trains colliding head on. It has been thought that the cars that collide essentially hit with only horizontal components of motion. However, recent modelling has shown that these types of collisions between, trains results in vertical components of motion of up to several degrees from the horizontal, due to the dramatic decrease in speed when the trains collide and the concomitant settling of the trains on their suspensions as a result. Consequently, the impact forces act in a direction that is angled slightly to the S horizontal. Under these conditions, previously proposed designs for energy absorbing structures have been shown to catastrophically fail by buckling or bending, thereby resulting in a failure to 00 absorb the impact energy.

o *oIt is an object of the present invention to provide an improved energy absorbing structure O-o for vehicles, such as railway vehicles.

In a first aspect, the present invention provides an energy absorbing structure for a railway vehicle comprising: ooo S a first structure having an end wall, two lateral walls, a top wall and a bottom wall 0 a second structure having a first transverse wall, a second transverse wall and two lateral walls •oo@ 0 said second structure mounted with respect to said first structure such that the first and second structures move relatively towards each other under an impact load, and an energy absorbing material positioned at least partially within a volume defined by the end wall, two lateral walls, the top wall and the bottom wall of the first structure, said energy absorbing material comprising a honeycomb material positioned such that channels defined by the honeycomb extend in a direction generally parallel to the longitudinal axis of the vehicle, wherein said honeycomb material is deformed by relative movement between the first and second structures to thereby absorb and/or dissipate impact energy.

004187550 3a In one embodiment, the first structure includes a rearmost wall and two lateral walls and said energy absorbing material is positioned within a space defined by the rearmost wall and two lateral walls. The second structure may include at least two lateral walls, preferably positioned for engaging contact with inner portions of the two lateral walls of the first structure, and a transverse wall extending at least partly between the at least two lateral walls. The second structure, in this embodiment, is preferably positioned with respect to the first structure such that the at least two lateral walls of the second structure extend at least partly behind leading edges of the lateral walls of the first structure. In the event of a collision, the second structure is forced to move relatively backwards into the first structure, whereupon the transverse wall of the second structure contacts the energy absorbing material and deforms the energy absorbing material to thereby absorb impact energy.

In this embodiment, the present invention may be described as a telescoping plunger and housing arrangement, with the first structure comprising the housing and the second structure comprising the plunger. In the event of a collision, the impact drives the plunger into the housing, during which the energy absorbing material is deformed and impact energy is thereby absorbed.

As the second structure moves into the first structure during an impact or collision, an increasing length of the lateral walls of the second structure moves inside the lateral walls of the first structure. As the lateral walls of the first and second structure are preferably positioned such that they are in engaging contact, movement of the lateral walls of the second structure into the first structure S°o effectively causes reinforcement of the lateral walls. As a result, the resistance of the energy absorbing apparatus to bending or buckling caused by impacts having 20 non-horizontal components of force is increased. This greatly reduces the chances of the energy absorbing structure buckling during an impact.

In this embodiment, it is preferred that the first structure also includes a top wall and a bottom wall. The top and bottom walls constrain the energy absorbing material during an impact and ensure that the energy absorbing material deforms essentially only in the longitudinal direction. This minimises or avoids buckling of the energy absorbing material which assists in ensuring that the energy absorbing :material absorbs impact energy in accordance with its design parameters.

The second structure in this embodiment preferably includes a front wall spanning the side walls of the second structure and the transverse wall is located rearwardly of the front wall and extends from one lateral wall to the other lateral GWN:DMA:#33749. CAP 26 February 2001 wall. This results in the second structure having a box or box-like configuration which increases the strength of the second structure and improves its resistance to bending or buckling. The second structure may be provided with further reinforcing means to increase its strength, if desired.

The energy absorbing material most preferably comprises a honeycomb material, especially an aluminium honeycomb. The honeycomb material is preferably positioned such that the channels defined by the honeycomb extend in a direction generally parallel to the longitudinal axis of the vehicle. Throughout this specification, the term "honeycomb material" refers to any material which includes a plurality of internal walls defining a number of channels, whether those channels be of hexagonal cross-section shape (as in conventional honeycomb) or of any other cross-sectional shape.

The honeycomb material may be in the form of a honeycomb cell or honeycomb block having two side walls, a top wall and a bottom wall enclosing the honeycomb cell or block.

Honeycomb material is especially suited to use in the present invention because its properties can be tailored to closely match the desired crush **characteristics required in the energy absorbing apparatus. In particular, the 00 honeycomb material, in comprising a plurality of relatively light weight elements, 20 exhibits crush or deformation characteristics that can absorb large amounts of impact energy at a relatively steady rate. In contrast, a graph of energy absorbed versus time for earlier energy absorbing devices for use in railway vehicles typically showed that the energy absorbed would exhibit distinct peaks and troughs. If one of the peaks exceeded the strength of the railway car, the car would break with 25 potentially deadly results for the occupants of the car.

0 The energy absorbing apparatus of the above-described embodiments of the present invention can briefly be described as a housing having the energy absorbing material mounted within its side walls and a plunger sized such that its side walls fit inside the side walls of the housing and positioned substantially in front of the housing. In the event of an impact, the plunger is driven into the housing.

GWN:DMA:#33749. CAP 26 February 2001 The present invention also encompasses a second embodiment in which the first structure has side walls and the second structure includes side walls that fit outside the side walls of the first structure. In this embodiment, the energy absorbing material is positioned within the second structure such that in the event of a collision the second structure moves rearwardly relative to the first structure and the energy absorbing material is deformed as the second structure moves relatively rearwardly.

In this embodiment, the first structure includes a forward wall that comes into contact with the energy absorbing material during a collision.

The apparatus of the present invention provides an energy absorbing apparatus that can greatly improve the crashworthiness of railway vehicles.

Modelling conducted by the present applicant has shown that the energy absorbing apparatus of the present invention can meet standards of crashworthiness equivalent to a 180 tonne train travelling at 50 km/hr crashing into a similar train moving in the opposite direction. In contrast, earlier designs had difficulty meeting similar tests conducted at 30 km/hr or 40 km/hr. As a further advantage, the energy absorbing apparatus of the present invention can function effectively in tests in which vertically offset impact forces of ±100 from horizontal are applied. Earlier energy 2 absorbing apparatus would fail such tests when vertically offset load angles of 20 from horizontal were applied. A further advantage of the present invention is that the apparatus can be of a relatively compact length and yet still meet crashworthiness requirements. This enables the apparatus of the present invention to be used in suburban and inter-urban trains which typically have short noses in the head cars and consequently minimal space in which to mount energy absorbing apparatus.

It is preferred that the first and second structures are mounted to each other such that there is a degree of overlap between the first and second structures in the longitudinal direction and that the first and second structures are mounted to each other by connecting means that, in ordinary travel of the vehicle, maintains the spatial relationship between the first and second structures but in the event of a GWN:DMA:#33749. CAP 26 February 2001 collision fractures or yields to allow the first and second structures to move relatively towards each other. The connecting means may suitably be shear bolts designed to shear at a predetermined impact load.

A further advantage of the present invention is that, in minor collisions, the first and second structures may be separated, the deformed energy absorbing material (eg honeycomb) replaced and the first and second structures re-mounted together. Earlier designs required replacement of the entire energy absorbing structure in the event of a minor collision.

In another aspect, the present invention provides an energy absorbing apparatus for absorbing impact energy in a vehicle comprising a first structure fixedly mounted to the vehicle, the first structure having at least two members extending in a longitudinal direction of the vehicle and a second structure having at least two members extending generally parallel to the at least two members of the first structure, said at least two members of the second structure being positioned such that side surfaces thereof are adjacent to respective side surfaces of associated side walls of the first structure and wherein in use, the second structure moves relatively towards the first structure when an impact load greater than a predetermined minimum load is applied to the apparatus, said apparatus further comprising energy absorbing material positioned such that it is deformed when the 20 second structure moves relatively towards the first structure to thereby absorb impact energy.

Preferably, the first structure has two members extending in the longitudinal direction and the second structure has two members extending in the longitudinal direction.

Preferably, the two members of the second structure are positioned such that outer side surfaces of those members are adjacent the inner side surfaces of the associated members of the first structure.

It is preferred that the side surfaces of the at least two members of the first structure are adjacent to and in contact with the side surfaces of the associated members of the structure. This assists in having the members reinforce each other GWN:DMA:#33749. CAP 26 February 2001 8 in the event of an impact which causes the first and second structures to move relatively towards each other. The members may be in direct contact or they may be in indirect contact in which the members of the first structure contact the members of the second structure via intermediate members or devices. Indeed, the present invention extends to situations where bearing surfaces, such as rollers or other bearings, are positioned between the respective members of the first and second structures, which bearing surfaces facilitate relative movement of the second structure towards the first structure in the event of an impact load being applied in excess of the predetermined minimum load.

In this aspect of the present invention, it is preferred that the energy absorbing material is positioned between the at least two members of the first structure. It is also preferred that the second structure has a transverse wall that contacts and deforms the energy absorbing material when relative movement of the second structure towards the first takes place.

In another embodiment, the first and/or second structures may be cylindrical or tubular in shape, or the shape of a flattened tube, and the first and second structures move telescopically with respect to each other in a collision to thereby deform the energy absorbing material.

~The present invention will now be described in greater detail with reference 20 to a preferred embodiment as shown in the accompanying Figures. In the Figures: Figure 1 shows a side view of a train with the position of the energy •absorbing apparatus shown in phantom; Figure 2 is a perspective view of an energy absorbing apparatus in accordance with the present invention; Figure 3 is a similar view to Figure 2 but with the top plates removed to more clearly show the internal detail of the energy absorbing structure; Figure 4 shows a plan view of the second structure or ram of the apparatus shown in Figures 2 and 3; Figure 5 shows a plan view of the first structure or housing of the energy absorbing structure shown in Figures 2 and 3; GWN:DMA:#33749. CAP 26 February 2001 Figure 6 is a front elevational view of the apparatus of Figure 5; and Figure 7 is a perspective view of a honeycomb cell used in the energy absorbing apparatus of the present invention.

Figure 1 shows a schematic diagram of a railway car having an energy absorbing apparatus in accordance with the present invention fitted thereto. In Figure 1, the railway car 1, which comprises the lead car of a train, has a driver's cabin 2 located at the front part thereof and a passenger compartment 3 located rearwardly of the driver's compartment 2. As can be seen from Figure 1, railway car 1 has a relatively short nose 4. The energy absorbing apparatus 10 in accordance with the present invention is located just rearwardly of the nose 4 of the railway car 1 such that energy absorbing apparatus 10 is fitting underneath the floor of driver's compartment 2.

The energy absorbing apparatus 10 is shown in greater detail in Figures 2 to 7. In particular, energy absorbing apparatus 10 comprises a first structure or housing 11 that is fixedly mounted to the railway car. Throughout the remainder of this specification, the first structure 11 will be referred to as the housing. The energy absorbing apparatus 10 further includes a second structure or ram 12.

Throughout the remainder of this specification, the second structure 12 will be referred to as the ram.

20 As best seen in Figures 2, 3, 5 and 6, the housing 11 has a rear wall 13 and two lateral walls 14, 15. Lateral walls 14, 15 extend forwardly from rear wall 13 in 5oS5o5 S• a direction that is generally parallel to the longitudinal axis of the railway car 1.

The housing 11 also includes top plate 16 and bottom plate 17. The housing 11 also includes side wall 18 that, in combination with lateral wall 15, rearmost wall 13, top plate 16 and bottom plate 17, defines compartment 19. Side wall 18 and compartment 19 provide one way of distributing load to the structure of the car.

The lateral walls 14, 15, top plate 16, bottom plate 17 and rearmost wall 13 of housing 11 define an open mouthed volume 20. This volume receives the energy absorbing material, which will be discussed in more detail hereunder.

For reinforcement and spacing purposes, rearmost wall 13 is also provided GWN:DMA:#33749. CAP 26 February 2001 004187550 with reinforcing spacers 21, 22, 23 that have transverse wall member 24 joined to the leading edges thereof.

As ca best be seen from Figure 6, laterals walls 14, 15 of housing 11 have a generally C shape cross-section.

The energy absorbing apparatus 10 further comprises ram 12. Ram 12 is most clearly shown in Figures 2, 3 and 4. Ram 12 includes lateral walls 25, 26. Lateral wall 25 has spacer 27 connected thereto and lateral wall 26 has spacer 28 connected thereto. Ram 12 further includes a transverse wall 29 that extends between lateral walls 25 and 26. The ram 12 also includes a front wall 30. As best seen in Figures 2 and 3, front wall 30 includes a plurality of projecting ribs 31 S that provide a safety interlocking device to react to vertical components of motion. A reinforcing wall 32 extends between transverse wall 29 and front wall 30. A top plate 33 encloses the top of ram 12 and a bottom plate 34 closes the bottom of ram 12.

SAs best shown in Figure 4, lateral walls 25, 26 of ram 12 include portions that extend S rearwardly from transverse wall 29. As best shown in Figures 2 and 3, ram 12 is dimensioned and positioned such that the lateral walls 25, 26 and their associated spacers 27, 28 fit snuggly within the lateral walls 14, 15 of housing 11. It is preferred that the lateral walls 25, 26 and associated spacers 27, 28 of ram 12 come into contact with the inner surfaces of lateral walls 14, 15 of housing 11 when the ram 12 is put into position in relation to housing 11.

The energy absorbing material that is placed into open mouthed volume 20 of housing 11, comprises a cell 35 of aluminium honeycomb material. The cell 35 has side walls 36, 37, top wall 38 and bottom wall 39. The space defined between side walls 36, 37 is filled with a plurality of hexagonal channels 38 to define the honeycomb structure of the cell In use of the energy absorbing apparatus 10 of the present invention, housing 11 is first installed and fixed into the railway car. The cell 35 of aluminium honeycomb is then positioned within open mouthed volume 30 in housing 11 such that the rearmost part of cell 35 abuts transverse wall 24 of housing 11. The ram 12 is then inserted into position in which lateral walls 26 and associated spacers 27, 28 are positioned within respective lateral walls 14, 15 of housing 11. The forward most part of cell 35 of aluminium honeycomb material may extend beyond the forward edges of lateral walls 14, 15 of housing 11 and into abutment with transverse wall 29 of ram 12.

As can be seen from Figures 2 and 3, when ram 12 is positioned in place, a portion of the longitudinal length of lateral walls 25, 26 is positioned within lateral walls 14, 15 of housing 11. This constitutes the normal in-use arrangement of the energy absorbing apparatus 10. As can be seen from Figures 2 and 3, a plurality of shear bolts 40 are used to hold the housing 11 and ram 12 in position with respect to each other. Shear bolts 40 are designed to shear if a predetermined minimum impact energy is placed upon the energy absorbing apparatus 10. In the event of an impact that does not exceed the minimum predetermined breaking energy of shear bolts 40, as may be experienced in very low speed collisions or during a shunting, shear bolts 40 do not break and energy absorbing apparatus 10 remains as shown in Figures 2 and 3.

If an impact or collision is experienced which exceeds the breaking point of shear bolts 40, shear bolts 40 will fracture and ram 12 will be forced to move towards the rearmost wall 13 of housing 11. As ram 12 moves rearwardly (relative to housing 11), the cell 35 of aluminium honeycomb positioned within open 20 mouthed volume 20 in housing 11 is deformed. Deformation of the cell 35 results in the absorption of energy in a controlled manner. Indeed, the correct selection of aluminium honeycomb material in cell 35 will allow significant impact energy to be absorbed and dissipated by the energy absorbing apparatus 10. The top plate 16 and bottom plate 17 of housing 11 act to assist in preventing the aluminium honeycomb deforming by buckling upwardly or downwardly. This ensures that the aluminium honeycomb material in cell 35 deforms in a controlled and predictable manner.

*Furthermore, as ram 12 is pushed rearwardly into housing 11, a larger portion of the longitudinal length of lateral walls 25, 26 and associated spacers 27, 28 of ram 12 enters into lateral walls 14, 15 of housing 11. This acts to reinforce the lateral walls of the housing 11 to thereby increase the resistance of housing 11 to GWN:DMA:#33749. CAP 26 February 2001 buckling or bending in a vertical direction. Therefore, the buckling resistance of the energy absorbing apparatus 10 is increased by this mechanism and the risks associated with uncontrolled energy dissipation caused by buckling of the energy absorbing apparatus are minimised.

The energy absorbing apparatus of the present invention provides an effective and reliable apparatus for dissipating quite large impact energies. Indeed, the present applicants have conducted modelling that has shown that the apparatus in accordance with the present invention can pass crashworthiness test conducted at speeds of up to 50 km per hour. Moreover, the energy absorbing apparatus of the present invention is particularly resistant to impact loads that are applied in a direction that includes non-horizontal components. In particular, the energy absorbing apparatus of the present invention has successfully past modelling test in which impact loads were placed on the apparatus at an angle of 5 degrees to horizontal. Indeed, preliminary testing has suggested that the apparatus will pass tests in which impact loads are placed upon the apparatus at up to 10 degrees to the horizontal. This compares most favourably with prior art energy absorbing structures which had difficulty coping with impact loads applied at angles of only

O

plus or minus two degrees to the horizontal.

oo The various components of the housing 11 and ram 12 shown herein are 20 preferably made from mild steel. The housing 11 is preferably manufactured by joining the relevant components by welding. Similarly, the ram 12 is preferably manufactured by joining the relevant components by welding.

Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described.

It is to be understood that the present invention encompasses all stich variations and modifications that fall within its spirit and scope.

oo GWN:DMA:#33749. CAP 26 February 2001

Claims (8)

1. An energy absorbing structure for a railway vehicle comprising: a first structure having an end wall, two lateral walls, a top wall and a bottom wall a second structure having a first transverse wall, a second transverse wall and two lateral walls said second structure mounted with respect to said first structure such that the first and second structures move relatively towards each other under an impact load, and 10 an energy absorbing material positioned at least partially within a volume defined by the end wall, two lateral walls, the top wall and the bottom wall of the first structure, said energy absorbing material comprising a honeycomb material positioned such that channels defined by the honeycomb extend in a direction generally parallel to the longitudinal axis of the vehicle, 15 wherein said honeycomb material is deformed by relative movement between the first and second structures to thereby absorb and/or dissipate impact oo ~energy.

2. An energy absorbing structure as claimed in claim 1 wherein the two lateral walls of the second structure are positioned for engaging contact with inner portions of the two lateral walls of the first structure.

3. An energy absorbing structure as claimed in claim 1 or claim 2 wherein the second structure is positioned with respect to the first structure such that the at least two lateral walls of the second structure extend at least partly behind leading edges of the lateral walls of the first structure.

4. An energy absorbing structure as claimed in any one of the preceding claims wherein the second structure further includes reinforcing means. An energy absorbing structure as claimed in any one of the preceding laims wherein the first and second structures are mounted to each other such that there is 004187550 14 a degree of overlap between the first and second structures in the longitudinal direction and that the first and second structures are mounted to each other by connecting means that, in ordinary travel of the vehicle, maintains the spatial relationship between the first and second structures but in the event of a collision fractures or yields to allow the first and second structures to move relatively towards each other.

6. An energy absorbing apparatus as claimed in claim 5 wherein the connecting means comprise shear bolts designed to shear at a predetermined impact load.

7. An energy absorbing structure as claimed in any one of the preceding claims wherein the first structure is mounted to the vehicle. 10 8. An energy absorbing structure as claimed in any one of claims 1 to 7 wherein the second structure is mounted to the vehicle.

9. An energy absorbing structure as claimed in any one of the preceding claims wherein.

110. An energy absorbing apparatus as claimed in any one of the preceding 15 claims wherein said at least two lateral walls of the second structure are positioned such that side surfaces thereof are adjacent to respective side surfaces of associated lateral walls of the first structure. 11. An energy absorbing apparatus as claimed in claim 10 wherein the two lateral S"walls of the second structure are positioned such that outer side surfaces of those walls are adjacent inner side surfaces of associated lateral walls of the first structure. 12. An energy absorbing structure as claimed in claim 11 wherein the side surfaces of the at least two lateral walls of the first structure are adjacent to and in contact with the side surfaces of the associated lateral walls of the second structure. 13. An energy absorbing apparatus as claimed in claim 12 wherein lateral walls of the second structure are in indirect contact with the associated lateral walls of the first structure in that the lateral walls of the first structure contact the lateral walls of the second structure via intermediate members or devices. 004187550 14. An energy absorbing apparatus as claimed in claim 13 wherein bearing surfaces are positioned between the respective lateral walls of the first and second structures, which bearing surfaces facilitate relative movement of the second structure towards the first structure in the event of an impact load being applied in excess of the predetermined minimum load. An energy absorbing apparatus as claimed in any one of the preceding claims wherein the honeycomb material comprises two side walls, a top wall and a bottom wall enclosing a honeycomb cell or honeycomb block., 16. An energy absorbing material as claimed in any one of the preceding 10 claims wherein the honeycomb material comprises an aluminium honeycomb. S17. An energy absorbing apparatus substantially as hereinbefore described with reference to the accompanying drawing. 18. A rail vehicle having an energy absorbing structure as claimed in any one of the preceding claims mounted to a forward position thereof. 15 Dated this 3rd day of July 2002 Evans Deakin Pty Ltd by its attorneys Freehills Carter Smith Beadle oo Evans Deakin Pty Ltd by its attorneys Freehills Carter Smith Beadle