Patent Description:
Energy dissipation or energy absorption devices are frequently applied as shock dampers at coupling interfaces between interconnected railway cars and in front-end couplers of motorized cars and locomotives. It is a challenge to designers of shock dampers in train couplers or side buffers to manage the shock wave that propagates through the train set in parts of a second, from the first to the last unit of the train, in case of collision.

Although numerous older solutions can be found in literature and practise, there is still room for improvements both with respect to energy absorption structures and management strategy for dissolving the energy that is released in collision.

The energy dissipation device of the present invention can be referred to the category of passive, non-regenerative shock dampers designed to consume the energy, rather than storing energy in metal springs, elastomeric bodies, or hydraulic and gas-hydraulic arrangements, etc..

In the subject category of energy dissipating devices, numerous examples in the prior art relies on energy consumption by radial deformation and expansion of an outer tube having an inner diameter, the expansion being induced by a plunger or mandrel of greater diameter which is forced through the tube by the dynamics of an impact. It is also known the alternative design, wherein the deformation tube is deformed radially inwards by a compressive force applied from an outer member that is run down the exterior of the deformation tube.

If to mention one prior art example of radially deforming shock dampers, reference can be made to <CIT>. Said document is of interest also for disclosing a pivot bearing which can be sheared off from the car chassis to be retracted into a deformation tube which is arranged in the car chassis behind the pivot. A rear face of the pivot bearing is formed with an extended diameter that causes radial expansion of the deformation tube as the pivot bearing is sheared off and retracted into the deformation tube upon impact.

For an example of axially deforming shock absorbers, reference can be made to <CIT>. This design for a front-end coupler comprises a package of honeycomb-structured deformation elements which are installed between a pivot bearing in a front end of the honeycomb structure and a shear-off member in a rear end of the honeycomb structure. A couple of guide bars, in front ends fixed to the car chassis via a support element and in rear ends carrying the shear-off member, extend in parallel through the honeycomb structures which are positively guided on the guide bars during compression in order to avoid warping. A housing which is attached to the car chassis, or forming an integer part thereof, takes no active part in guidance of the honeycomb structures during compression.

It is further known, per se, that a steel tube of continuous, multi-cornered sectional profile can be controlled to fold progressively and buckle in a uniform manner when subjected to a compressive force applied in axial direction of the tube. As far as the applicant knows, this technology has hitherto not been applied nor adapted for implementation in shock dampers for train couplers.

A previous attempt to control the shock wave that is transferred via coupling interfaces between units in a train set is disclosed in <CIT>. The document suggests that the compression strength of collapsible structures in shock dampers is varied and adapted in order to achieve a stiffness curve in compression, which has a downward concavity and which increases in a monotonic manner throughout the train. In order to achieve that, the first two coupling interfaces in the front end of the train should be designed to provide a lower energy absorption capacity, whereas the third coupling interface etc. is designed to absorb an amount of energy which is decidedly greater.

Further energy dissipation devices for railway vehicle couplers are known from <CIT>, <CIT>, and <CIT>.

However, the development of crash forces through a train set in collision does not follow a monotonic and static scheme. On the contrary, halting the train to a stop is a dynamic process which involves a series of accelerations and retardations as each successive unit in the train crashes into the previous one. The series of internal impacts accumulate into a successively increasing load being transferred to train units and dampers that are closest to the point of collision. In respect of stroke length and energy absorption, the foremost dampers are typically fully exhausted in a crash. On the other hand, practise has also shown that the potential stroke lengths in dampers at intermediate interfaces of the train were only partially used as the train had come to a halt.

It is an overall object of the present invention to provide an energy dissipation device of alternative design.

One object of the present invention is to provide an energy dissipation device of lightweight design.

Another object of the present invention is to provide an energy dissipation device that requires few or less complicated machining operations during manufacture and assembly.

Still another object of the present invention is to provide an energy dissipation device which permits reuse of components that remain unaffected after dissipation of impact energy and which provides simplified exchange of exhausted deformation elements.

It is another object of the present invention to provide an energy dissipation device which can be integrated in front-end train couplers, in intermediate train couplers or in side buffers as well.

It is yet another object of the present invention to provide an energy dissipation device which is configured to be readily adapted for implementation at coupling interfaces between units of a train set in order to control the propagation of impact forces throughout a train of interconnected vehicles.

It is also an object of the present invention to provide an energy dissipation device that permits a higher degree of employment of the potential stroke length and resulting energy absorption by intermediate devices in a series of interconnected devices.

At least one of these or other objects/objectives will be satisfied in an energy dissipation device as defined in claim <NUM> and claim <NUM>. Other objects/objectives will be met through the different embodiments and implementations of the energy dissipation device as set forth in additional claims.

In a first aspect of the invention, an energy dissipation device for a train coupler adapted for absorbing kinetic energy from a collision comprises a cylindrical housing, in one end having coupling means for coupling the housing in fixed relation to a train coupler. At least one axially compressible, irreversibly deforming element of steel is installed in the housing, and extended in coaxial relation with the housing from said one end towards a second end of the housing. A compression means is retractable into the housing via said one or said second end of the housing. The at least one compressible element is pre-tensioned axially between said retractable compression means and a counter pressure means stationary secured in the housing in opposite relation to the retractable compression means. The compression means has a circular periphery shaped for guidance in non-destructive sliding contact with the inside wall of the housing upon retraction and compression of the compressible element(s), while preserving the integrity of the housing.

The outlined solution ensures lightweight design through the use of steel in deforming elements which permit downsizing of wall thickness while maintaining compression strength and energy dissipation capacity.

The solution also permits reuse, on a case-to-case basis, of components such as the housing, the compression means and the counterpressure means.

In one embodiment of the energy dissipation device, said one end of the housing having coupling means arranged for coupling to a bracket for a pivot bearing which is retractable into the housing via said one end upon release from the bracket, and wherein a shear-off assembly, providing counter pressure in compression, is coupled to said second end of the housing.

This embodiment is adapted for integration in front-end couplers as well as intermediate couplers between cars, wherein coupler components are designed to be released to retract under the car chassis if subjected to an impact force above a specified shear-off magnitude.

It will be understood, that the stress acting on the housing in compression is restricted to axial tension, which provides the designer with freedom to maximize the length of the housing without adding undue mass weight to the housing.

More specifically, the shear-off assembly comprises a counter pressure disc of circular shape having a bevelled periphery bearing against the opposite faces of a number of yieldable tongues, the tongues depending individually at a slanting angle towards the centre from an inner circumference of a flanged ring that is connectable in surrounding relation with the counter pressure disc.

One advantage and technical effect of this embodiment is that the housing can be preserved and intact after shear-off, since the shear-off assembly includes a replaceable component, i.e., the ring, which can be connectable to the housing by means of a threaded engagement.

In one embodiment, the energy dissipation device comprises a first telescoping member in the form of a tube of a first diameter, said tube in one end carrying coupling means for coupling the tube to a drawbar of a train coupler in coaxial alignment with the centre axis of the drawbar. A second telescoping member has the form of a cylindrical housing of a second diameter which is larger than the first diameter, said housing in one end carrying coupling means for coupling the housing to a drawbar of a train coupler in coaxial alignment with the centre axis of the drawbar. A second end of the tube is inserted and arranged retractable into the housing via an opposite second end of the housing. At least one compressible steel element in the housing extends in coaxial relation with the housing from said one end of the housing towards the second end of the housing. The compressible element is pre-tensioned axially between the coupling means in said one end of the housing and a neck portion extended axially into the housing from a mounting flange, coupled to said second end of the housing. The retracting end of the tube carries a compression disc which has a circular periphery shaped for guidance in non-destructive, sliding contact with the inside wall of the housing upon retraction and compression of the compressible element(s), while preserving the integrity of the housing.

The embodiment with telescoping tubes makes possible an integration of the energy dissipation device in the drawbar of a train coupler or in side buffers. In the drawbar, all parts of the integrated device are aligned in concentric relation about the centre axis of the drawbar. The forces and kinetic energy that is transferred to the energy absorbing elements upon an impact is thus applied in the same direction as these elements are deforming while absorbing the energy. In other words, the nominal compression strength and resistance to deformation built into the design of the deforming elements can be fully utilized for energy absorption, without losses in efficiency and capacity caused by deflection of forces and counterforces.

The axial extension of the neck portion ends in a shoulder of radial extension providing support in axial direction for the compression disc which is carried in the retractable end of the tube.

The axial extension of the neck portion has an inner radius forming a circumferential control surface for the tube to move in sliding contact with the control surface upon retraction into the housing.

Embodiments of the invention may include an anti-rotation means in the form of a locking body shaped for form-fitting engagement in a correspondingly shaped seat which is formed in a flange of a member that is connectable to the housing. A heel on the locking body engages in locking position a recess that is formed circumferentially in the exterior of the housing.

In one embodiment, at least one intermediately positioned partition disc having a circular periphery is arranged in sliding contact with the inside wall of the housing, the partition disc axially clamped between a compressible element of a first compression strength and a compressible element of a second compression strength, and otherwise movable in the housing.

This embodiment provides a solution according to which energy dissipation units can be individually "tuned" for an adaptive and demand-driven (adjustable) force/stroke characteristics, which makes it possible to control the energy released (net contacting force) during longer impact time at each interface, such as for about <NUM> to <NUM>, by extending compression stroke minimum up to about <NUM>-<NUM> %, this way reducing forces and avoiding peak forces.

Another technical effect provided by this embodiment is that the energy dissipation device can be designed, by corresponding choice of length and/or stiffness in the compressible elements, for portional deformation in response to different magnitudes of impact.

An advantage provided by this embodiment is that after an impact of limited magnitude, only the softer and collapsed elements need to be replaced whereas the stiffer elements can be reused. In other words, to simplify overhaul and repair, the elements of lower compression strength which are first to collapse upon impact can be installed directly behind a shear-off assembly, which can be dismounted by unscrewing from the housing.

In one embodiment, the partition disc comprises a flange in its periphery that forms an inner cylinder or lining in the housing, the axial length of the lining adapted to ensure movement without tilting in the housing. The lining is preferably not longer than the remaining axial length of the deformed element(s) after maximum compression.

Although a tendency for tilting of partition discs moving in the housing is effectively prevented in effect of the supporting contact with the compressible elements, this embodiment avoids even further the risk of jamming.

In a preferred embodiment, the compressible element is a tube made of roll-formed steel sections, fused-together to form a multi-cornered cross-sectional profile wherein the tube wall, in circumferential direction, is a repeating pattern of angularly adjoining side planes connected in at least twelve outwardly protruding corners and at least eight inwardly protruding corners.

In one embodiment, at least one axially compressible non-biased element is arranged in the housing, the non-biased element(s) extended in parallel with at least one energy absorbing element that is axially pre-tensioned in the housing between a compression means and a counter pressure means arranged respectively in opposite first and second ends of the housing, wherein the non-biased element(s) are of shorter length(s) than the pre-tensioned element.

An advantage and technical effect provided from the auxiliary, non-biased element(s) is a gradual absorption of peak load from impact, similar to a concertina effect in compression.

Another advantage and technical effect is that a comparatively high and continuous and flat level of energy absorption can be maintained throughout the energy dissipation process. This is due to a phase shift and mutual displacement of the buckling behaviour during the compression sequence that is provided by compressible elements of stepwise decreasing lengths.

Energy dissipation devices according to the invention can be arranged in series and configured for integration at coupling interfaces between interconnected units of a train.

Advantageously, in a series of energy dissipation devices arranged for integration at coupling interfaces between interconnected cars and motor cars or locomotives of a train, wherein for individual devices of the series, stroke length and/or compression strength is predetermined with regard to the positions of the individual devices in the series, and with the object of minimizing peak loads absorbed in intermediate devices.

In coupling interfaces between train units, at least one energy dissipation device has a primary deformation zone of less compression strength than the compression strengths provided by successive deformation zones of the same device.

The distribution and relative absorption of kinetic energy among the devices in the series can be graphically represented by a levelling curve which has a slope in the range of <NUM> - <NUM> percent from the second to the fifth coupling interface of a six-unit train.

At least the foremost devices in the series may be configured to provide a higher peak compression strength than any intermediate device in the series. Devices in each fore and aft region of the series can be configured to provide a gradual increase of peak compression strength towards the foremost and rearmost devices in the series.

At least the foremost device in the series can be configured to provide a primary deformation zone of less peak compression strength than the peak compression strengths provided by a secondary and a third deformation zone of the same device.

In other words, the energy dissipation devices in the end regions of the series and train set can be made stiffer with respect to their dampening characteristics, than the successive or previous devices in the series, respectively.

Accordingly, while being designed or charged with a capacity to withstand high levels of energy, relatively speaking, the foremost and rearmost devices in the series may still preferably be configured to provide a stepwise increasing capacity. More precisely, the energy dissipation device which is first to be subjected to the energy released upon impact is advantageously designed with a first deformation zone of less compression strength than the compression strengths provided by a second, a third or a fourth deformation zone, e.g., of the same device.

It is contemplated that this gradual introduction of impact energy in the series of interacting devices, which can all be individually pre-tensioned in assembly, results in further biasing of the whole series of devices for an instant reaction, throughout the series, to the higher energy levels which are introduced as the second, third or fourth deformation zones of the first device become involved in the energy dissipation process. A technical effect is that the entire series of energy dissipation devices is triggered within milliseconds for dissipation of large amounts of energy when the shock wave reaches the last unit of the train. In result, kinetic energy is distributed throughout the train such that damage to car bodies and underframes can be reduced throughout the train set.

Further details, advantages and technical effects of the invention will appear from the detailed description provided with references to the accompanying, schematic drawings.

With reference to <FIG>, <FIG>, an energy dissipation device <NUM> of a first embodiment is adapted for mounting in the underframe <NUM> of a motor car or locomotive <NUM> (<FIG>) or in the underframe <NUM> of a trailing car <NUM> (<FIG>). The energy dissipation device <NUM> comprises a housing <NUM> wherein axially compressible steel elements <NUM>, <NUM> and <NUM> are installed and pre-tensioned axially between a compression means <NUM> and a counter pressure means <NUM>. One end of the housing <NUM> is stationary coupled to a structural component of the underframe, such as coupled in threaded engagement with a bracket <NUM> for a pivot bearing <NUM>. The engaging threads at <NUM> may be formed on an outer radius of the housing and on an inner radius of a locking ring <NUM>, respectively. The locking ring <NUM> is bolted to the bearing bracket <NUM> by means of bolts <NUM>.

The compression means <NUM> in said one end of the housing is realized in the form of the pivot bearing <NUM>. The pivot bearing <NUM> is operatively connected to the bearing bracket <NUM>, such as via radial shoulders <NUM>, for transfer of traction to a trailed unit in the draft direction D. Compressive forces in the buff direction B is transferred via the deforming elements <NUM>-<NUM> to a shear-off assembly <NUM> which is coupled to an opposite second end of the housing <NUM> via a threaded engagement <NUM>. The shear-off assembly <NUM> will be explained in more detail below.

The housing <NUM> is a cylinder, the inner diameter of which is adapted to the outer diameter and cylindrical exterior <NUM> of the pivot-bearing <NUM>. In case of an impact of sufficient magnitude being applied to the pivot bearing in the direction of B, the pivot bearing <NUM> and pivot pin <NUM> will relocate from the bearing bracket <NUM> and slide through the interior of the housing <NUM>, axially compressing at least one or some of the elements <NUM>-<NUM> which will be irreversible deformed in the process.

In the housing <NUM>, the compressible elements <NUM>, <NUM> or <NUM> are maintained under axial pre-tension and bias. This pre-tension is provided from the compression means <NUM>/pivot bearing <NUM> on one hand, and on the other hand from a counter pressure disc <NUM> being an operative component of the shear-off assembly <NUM>. More precisely, pre-tension is created in assembly by applying the force from a jack to the package of compressible elements upon securing them in the housing. The pre-tension is maintained by means of a release structure in the form of a flanged ring <NUM> with yielding elements <NUM>, wherein a thread on the inner radius of the ring (see at <NUM>) engages a thread on the outer radius of the housing <NUM>.

The yielding elements <NUM> are realized as fingers or tongues <NUM>, which are distributed circumferentially about an inner circumference of the ring <NUM>. The tongues <NUM> extend rearwards from said inner circumference, at a slanting angle towards an axial centre of the ring. A circular, outwardly bevelled periphery <NUM> on the counter pressure disc <NUM> forms a conical rear face <NUM> which bears against the opposite faces of the tongues <NUM>. Upon release, the tongues will yield from the pressure by bending or breaking to let the counter pressure disc <NUM> pass through the ring <NUM>.

In this connection reference can be made to <FIG> which illustrates the shear-off assembly <NUM> in alternative mounting behind the pivot bearing, bolted directly to a bearing bracket <NUM> by means of bolts <NUM> and a locking ring <NUM>, onto which the flanged ring <NUM> can be secured in threaded engagement.

<FIG> illustrates a cut-out portion of the flanged ring <NUM> in the shear-off assembly <NUM>. Via a thinned-out portion <NUM>, the yieldable tongue <NUM> adjoins an inwardly bevelled and conical face <NUM> that runs circumferentially on the inner periphery of the flanged ring <NUM>. The conical face <NUM> adjoins the threaded cylindrical inner face <NUM> at an angle α of about <NUM>°. The transition from the conical face <NUM> to the threaded face <NUM> is made with a radius at <NUM> in order to avoid fracture indications at the transition region. For a similar reason, the gaps <NUM> between adjacent tongues <NUM> are formed with a radius <NUM> at the tongue base and connection to the conical face <NUM>.

In the embodiment of <FIG>, the housing <NUM> accommodates a pair of partition discs <NUM> and <NUM>. The partition discs <NUM>, <NUM> divide the housing <NUM> in three separate deformation zones, in <FIG> named <NUM>st, <NUM>nd and <NUM>rd deformation zones, each of which contains at least one compressible element <NUM>, <NUM> or <NUM> under axial pre-tension.

The first, second and third deformation zones may be equipped and "charged" with compressible elements of different compression strengths and deformation resistance. It will be realized, that regardless of the internal order among the elements of different compression strengths, the deformation zone which contains the least resistant element/elements will be first to collapse in case of a crash. For this reason, advantageously, the rearmost zone of the housing can be equipped with the less resistant elements in order this way to reduce time and labour for repair and replacement of compressible elements in case of a minor impact.

The significance of a progressively increasing deformation resistance will be more discussed below.

In this context, reference is made to <FIG> of the drawings. <FIG> illustrates the damping characteristics of a three-zoned energy dissipating device wherein the first deformation zone <NUM>st is equipped to yield under an impact force of <NUM> kN, a second zone <NUM>nd is yielding under a force of <NUM> kN, and a third zone <NUM>rd resists up to <NUM> kN before yielding. Finally, the shear-off assembly releases at an impact force of <NUM> kN. In the example illustrated in <FIG>, the total length of compression is <NUM> before shear-off.

It must be realized that <FIG> illustrates a non-limiting example only.

Of course, the invention can be realized in other embodiments comprising one or more deformation zones separated by partition discs and equipped with deforming elements of different peak compression strengths. The design with freely moving or "floating" partition discs as separators between deformation zones provides unlimited freedom to equip and "tune" each device with regard to its position in a train set. In other words, the number and lengths of deformation zones, as well as length, sectional profile, wall thickness and steel grade of deforming elements, are adjustable parameters which can be used by an engineer to customize each device with respect to its position in the train, while paying attention to the total number of cars, individual car weights, accumulated weight of the train set, stability in underframes or car bodies, train's running speed etc. These parameters can be defined mathematically and used in software simulators when computing specifications for each device in a series of interacting energy dissipation devices, upon implementation of the impact management strategy as taught by the present invention.

The compression means <NUM> at least, and also the partition discs of multi-zoned embodiments, are dimensioned and configured to move under non-destructive sliding contact with the inside surface of the housing <NUM>. In this context, the axial length of the continuous radius section <NUM> of the pivot bearing <NUM> is deemed enough to ensure non-tilting and a jam-free movement in the housing.

In order to ensure a jam-free motion in the housing for partition discs, the circular peripheries <NUM> of the partition discs <NUM>, <NUM> may be shaped with an axial extension or flange <NUM> which counteracts tilting and supports the partition disc so as to maintain a transverse orientation throughout its movement in the housing. The axial length of this flange should not, preferably, exceed the remaining axial length of the corresponding compressible element after its full compression.

In this connection it can be mentioned, that "full compression" will usually leave the deformed element with a remaining rest length in the order of about <NUM> %.

In addition to constructive matters, a lubricant may be applied to the inner surface of the housing, if appropriate.

In the embodiment of <FIG>, a stroke length indicator rod <NUM> extends through the energy dissipation device <NUM> from its attachment in the rear face of the pivot bearing <NUM>. The indicator rod <NUM> reaches through a hole in the centre of the counter pressure disc <NUM> in the opposite second end of the housing, and extends likewise through all partition discs of multi-zone embodiments. The indicator rod <NUM> provides an indication of the axial length of compression and the amount of deformation of the compressible elements. Registration may involve optical or electrical registering means, which can be read from a driver's cabin or by computer on car or by remote computer outside the train.

Next, an alternative embodiment <NUM> of the energy dissipation device will be described with reference to <FIG>, <FIG>. To the extent that the embodiments <NUM> and <NUM> share the same components or components of equal function with respect to the operation of the component, these components will be equally numbered in the descriptions of the two embodiments.

The energy dissipation device <NUM> is adapted for integration in a drawbar of a front-end train coupler <NUM> (<FIG>) or in the drawbar of an intermediate train coupler <NUM> (<FIG>). The energy dissipation device <NUM> is a telescopic structure comprising a first or inner tube <NUM> of a smaller diameter which is retractable into a second and outer tube <NUM> of larger diameter. Each tube carries in one of its ends a coupling flange <NUM> and a coupling flange <NUM> respectively. The coupling flange <NUM> in said one end of the inner tube <NUM> is adapted for connecting the device <NUM> in coaxial alignment with a pivot pin bearing <NUM>, whereas the coupling flange <NUM> in said one end of the outer tube <NUM> is adapted for connecting the device <NUM> in coaxial alignment with a drawbar section <NUM>.

The outer tube <NUM> constitutes a housing <NUM> in which compressible steel elements <NUM>, <NUM> or <NUM> are pre-tensioned axially between, on one hand, a compression means <NUM> here realized in the form of a compression disc <NUM>, having a circular periphery <NUM> and supported in the retractable end of the inner tube <NUM>, and on the other hand a counterpressure means <NUM> here realized in the form of a wall member <NUM> integrated in the coupling flange <NUM>. Partition discs <NUM>, <NUM> may be installed for separation of deformation zones in the housing <NUM>, as previously explained with reference to the embodiment <NUM>.

Pre-tension of the energy dissipation device <NUM> is accomplished on assembly. More precisely, an axial load can be applied from a jack that is acting on the compression means <NUM> to press the compressible elements in the housing <NUM> towards the counter pressure means <NUM> and coupling flange <NUM>, the latter fixedly attached to said one end of the housing in a threaded engagement at <NUM>. While under pressure from the jack, a mounting flange <NUM> is coupled to the housing <NUM> by means of engagement at <NUM> between a thread formed on an inner radius of the housing and a thread formed on an outer radius of a neck portion <NUM>, the neck portion <NUM> forming an integral part of the mounting flange <NUM>. The neck portion <NUM> on the flange <NUM> projects axially into the housing and presents a shoulder <NUM> of radial extension which abuts the compression disc <NUM> so as to maintain the device under pre-tension also when the jack is removed.

Next, reference is made also to <FIG> of the drawings. Recesses <NUM> formed in the region of the peripheral edge of the mounting flange <NUM> provide seats <NUM> for locking bodies <NUM> which can be bolted to the mounting flange in a form-fitting engagement. Each locking body <NUM> has a heel <NUM> that engages a recess <NUM> which runs circumferentially about the exterior of the housing <NUM>. The locking bodies <NUM> fixate the mounting flange <NUM> and housing <NUM> in relative position and prevent rotation between them. In similar way, locking bodies <NUM> may be applied to prevent relative rotation between the housing <NUM> and the coupling flange <NUM>. The same anti-rotation arrangement can be applied to the coupling flange <NUM> in said one and first end of the housing <NUM>.

Although not being shown in <FIG> for clarity reasons, it should be pointed out that the anti-rotation arrangement of reference numbers <NUM> to <NUM> can be applied also to the embodiment <NUM> of <FIG> (see, e.g., the recess <NUM> formed in the exterior of the housing <NUM> and the seats <NUM> formed in the peripheral edge of the flanged ring <NUM>).

In compression of the energy dissipation device <NUM> upon impact, the inner tube <NUM> operates like a plunger that moves in sliding contact with a cylindrical control surface <NUM>, formed on the axial extension and inner radius of the neck portion <NUM>. In compression, the inner tube <NUM> pushes the compression disc <NUM> through the housing in non-destructive sliding contact with the inner wall of the housing. The same applies to the partition discs <NUM>, <NUM> etc., in sectioned or multi-zoned embodiments. The same measures as previously described can be applied to prevent movable discs from tilting and jamming in the housing <NUM>.

A stroke length indicator-wire <NUM> extends through the energy dissipation device <NUM> from its attachment at an inner face of the coupling flange <NUM>. The indicator-wire <NUM> reaches through a hole in the centre of all movable compression discs in the housing <NUM> to a counter means <NUM> supported on the coupling flange <NUM>. In a way known per se, the counter means <NUM> can comprise a spring-biased wheel (not shown in the drawing) onto which the wire is wound up when the energy dissipation device is compressed. A reader <NUM> counts the revolutions of the wheel which is related to the wound-up length of the wire. The counts can be visually observed at the reader, or reported by wire to an on-board computer for display in a driver's cabin, e.g..

Each embodiment <NUM> and <NUM> of the energy dissipation device relies on tube lengths of steel to absorb and consume the energy in case of collision. As used herein, the expression steel shall be understood to include, but is not limited to, steel grades which are commonly referred to in the trade as steel, high-strength steel (HSS), advanced high-strength steel (AHSS), ultra-high-strength steel (UHSS), as well as stainless steel.

The steel tubes, forming the compressible elements <NUM>-<NUM>, are preferably realized as continuous profiles of multi-cornered cross section. Beside four-sided rectangular profiles, the wall of the compressible element may consist of a repeating pattern of angularly adjoining side planes, providing corners some of which are outwardly protruding and some of which are inwardly protruding.

As a rule of thumb, more corners and side planes included in the profile will result in higher compression strength and resistance to axial compression and buckling. On the other hand, the more complicated a profile is the more complex it will be to ensure a uniform buckling and deformation when the profile is compressed axially. Therefore, it serves no purpose to provide general rules in this respect, and it remains a task for the skilled person or engineer to combine steel grade, sectional profile, tube diameter and length as well as wall thickness in order to achieve a desired compression strength and resistance to buckling.

It is also known in the art that folding triggers such as indentations, holes or recesses can be formed in the tube wall in order to achieve a desired buckling pattern and behaviour. By proper application of folding triggers, the designer can avoid a chanceful dependency on material properties and instead control the buckling behaviour. It is possible this way to limit a variation in compression resistance during axial compression to stay within a range of about +/- <NUM> % (see <FIG>).

For illustration, <FIG> show a couple of non-limiting examples of profiles <NUM> and <NUM> suitable for implementation as energy absorbing elements in the energy dissipation device. Each embodiment is composed of roll-formed sections which are welded together at longitudinal welding seams. In particular, a compressible element may comprise one singular section which is folded such that longitudinal edges meet to be fused together in one longitudinal welding seam W. Other embodiments may include two or more sections which are combined in a symmetrical arrangement about a tube centre Tc and fused together at welding seems W. The profile <NUM> contains twelve outwardly projecting corners <NUM> and eight inwardly projecting corners <NUM> interconnected by side planes <NUM>, whereas the profile <NUM> contains twelve outwardly projecting corners <NUM> and twelve inwardly projecting corners <NUM> interconnected by side planes <NUM>.

On assembly, steel tubes such as the profiles <NUM> or <NUM> are typically individually installed with the tube centre Tc coinciding with the longitudinal centre axis of device housing <NUM> or <NUM>. If appropriate, several tubes may be jointly installed and concentrically arranged with coinciding tube centres Tc (not shown). Several tubes may alternatively be arranged in symmetric distribution about the centre axis of the housing, in such case equally angularly spaced and with their tube centres Tc on equal radial distance from the housing's centre axis (also not shown).

An alternative embodiment <NUM> of the energy dissipation device is illustrated in <FIG>. In this embodiment of an energy dissipation device <NUM>, a set of axially compressible, elements <NUM> and <NUM> are arranged in a housing <NUM>. The housing <NUM> is in a first or one end coupled to a pivot bearing bracket <NUM>, such as by means of a coupling ring <NUM>. At least one compressible element <NUM> is axially pretensioned between a pivot bearing <NUM>, forming a compression means <NUM> with a circular outer periphery that is axially movable in the housing <NUM> upon impact and release, and a counter pressure disc <NUM> forming part of a shear-off device <NUM> that is connected to the housing <NUM> in a second end of the housing <NUM>, in axially opposite relation to the pivot bearing <NUM> received in the first end of the housing.

The compressible elements <NUM> extend substantially in parallel with the at least one pre-tensioned compressible element <NUM>. The compressible elements <NUM> are in one end respectively secured to either one of the pivot bearing <NUM> or the counter pressure disc <NUM>. The compressible elements <NUM> may be secured to the pivot bearing <NUM> or to the counter pressure disc <NUM> by welding. The compressible elements <NUM> may extend cantilevered from their anchored ends. However, mounting studs <NUM> may advantageously be arranged on the pivot bearing <NUM> and/or on the counter pressure disc <NUM> for positioning of the compressible elements <NUM> without the need for fixation. Spacers <NUM> may alternatively be arranged for holding the compressible elements <NUM> in fixed parallel positions. In <FIG>, three compressible elements <NUM> are visible whereas a fourth element is hidden on the far side of the pre-tensioned element <NUM>.

In a set of compressible elements, individual elements <NUM> may be equally angularly spaced about a central, pre-tensioned element <NUM>. In other embodiments, compressible elements <NUM> may be arranged inside the wall of a surrounding pre-tensioned compressible element (not shown in the drawings).

The compressible elements <NUM> are not pre-tensioned in assembly. More precisely, the compressible elements <NUM> are cut to shorter lengths than the pre-tensioned element(s) <NUM>. In order to avoid confusion, the compressible elements <NUM> of shorter lengths will hereinafter be referred to as non-biased elements <NUM> this way reflecting the fact that they are not set in pre-tension upon assembly of the energy dissipation device <NUM>.

In one embodiment, a first non-biased element <NUM> is shorter in length by a few mm as compared to a pre-tensioned element <NUM>. Each additional non-biased element <NUM> is a few mm shorter in length than the previous one, such that upon impact and compression of the energy dissipation device, an additional energy absorbing element will be employed for each travel of a few mm in length of compression.

In other words, the energy dissipation device of the embodiment <NUM> provides absorption of impact load in what can be referred to as a concertina effect: instead of an instant rise to the peak load, the maximum effect is reached incrementally through a number of compressible elements <NUM>, <NUM> which are successively activated in the energy absorption process. <FIG> is a series of snapshots that illustrate, schematically, the mutually displaced buckling of compressible elements during the process, from impact in <FIG> to shear-off in <FIG>.

The operational characteristics of the embodiment of <FIG> is illustrated in the force vs displacement/time diagram of <FIG> is a graphic plot generated in load tests performed on a laboratory setup including <NUM> pcs of four-sided tubes of high-strength steel as the compressible elements, one of which is pre-tensioned in assembly. In <FIG>, the vertical axis indicates force absorbed by the set of tubes whereas the horizontal axis illustrates the displacement (length of compression), or lapse of time from point of impact. The axes are dimensionless, the diagram nevertheless illustrating the true operational characteristics of this embodiment.

The tubes employed in the test are quadrangular in cross section, all sides of the cross section equal at <NUM> in length (tube width) and having a wall thickness of about <NUM>. The tube lengths are ranging from <NUM> to <NUM>, the tube lengths gradually reducing by <NUM> (each tube <NUM> shorter in length than the previous one). Triggers for a controlled deformation were applied as indentations <NUM> on two mutually opposite sides of the tubes. The indentations were <NUM> in depth, <NUM> in length and oriented transversely to the tube length at about <NUM> distance from the end of the tube. The indentations were produced using a punch and a punch pad.

The longest tube was set in pre-tension by a hydraulic press, whereas the rest four tubes were provided as non-pretensioned non-biased elements arranged in parallel with the pre-tensioned element. Impacts were simulated by an instant release of <NUM> kN and <NUM> kN respectively to the sets of tubes.

In <FIG> it can readily be observed that the maximum load is reached through a number of overlapping peaks as the separate tubes are successively employed in absorption of the impact force. The displacement to maximum load is <NUM> in this test, as determined by the gradual tube length reduction of <NUM> in a set of five tubes. Maximum load was reached within approximately <NUM> sec.

To be further noted in <FIG> is the constant level and continuity or flatness of the curve that illustrates the load absorbed after reaching the load maximum. By incrementally displacing the compression of non-biased elements as provided for in this embodiment, the buckling of the compressible elements <NUM>, <NUM> is shifted in phase and synchronized, such that one or some of the compressible elements provide their maximum resistance to buckling when one or some of the other compressible elements provide less resistance to buckling. By this phase-shift, a comparatively high and above all continuous level of energy absorption can be maintained throughout the energy absorption process.

The length reduction may be the same and equal among all compressible elements <NUM>, <NUM>, however, this is not an absolute requisite since the compressible elements need not all be of equal dimension and material properties.

For example, the length reduction between compressible elements may be in the order of about <NUM>-<NUM>, or in the order of about <NUM>-<NUM> if appropriate, depending on overall size of the energy dissipation device. In one embodiment as illustrated, a preferred length reduction is in the order of about <NUM>-<NUM>. If appropriate, the lengths of the compressible elements may be determined with tolerances down to tenths of millimetres as one of available measures for fine-tuning of the phase shift in the energy absorption sequence. Other available measures are, e.g., choice of material and cross-sectional dimensions or shape of the compressible elements <NUM>, <NUM>.

However, since buckling of the compressible elements is also governed by tube dimension and choice of material, it is not possible to provide detailed specifications for any arbitrary implementation of the invention. As a rule of thumb, the difference in length between two successively employed compressible elements may be determined such that the shorter element begins compressing at substantially the same time that the longer element completes its first buckling sequence. Although the embodiment <NUM> of <FIG> is illustrated and explained in connection with a pivot coupling, the same teachings can be applied, mutatis mutandis, in a drawbar and intermediate train coupling, or in other words, in automatic couplers or in semi-permanent couplers as well.

<FIG> illustrates a train <NUM> of interconnected railroad units wherein each coupling interface between motorcars and trailing cars comprises energy dissipation devices <NUM>, <NUM> or <NUM>. In the train <NUM>, the underframes of motorcars <NUM> and trailing cars <NUM> form axially rigid connecting members in a series of interconnected and interacting energy dissipation devices <NUM>, <NUM>, <NUM>. At both ends of the series, front-end couplers <NUM> and rear-end couplers <NUM> may use one, two or all embodiments of the energy dissipation device <NUM>, <NUM> or <NUM> as illustrated in <FIG>. At intermediate connections, also the couplers at interfaces <NUM>-<NUM> may use one, two or all embodiments of the energy dissipation device <NUM>, <NUM> or <NUM> as illustrated in <FIG>.

In a case of collision and impact of sufficient magnitude being applied in the direction of F, a shock wave will translate from the front-end coupler <NUM> to the last intermediate coupler <NUM>, involving the energy dissipation devices in the front-end coupler and in all intermediate couplers. Since the energy dissipation devices <NUM>, <NUM> and <NUM> are pre-tensioned in assembly, and interconnected through the underframes of cars and motorcars, the entire series of energy dissipation devices will act unanimously, on impact performing substantially as one singular damper.

In order to remove any accidental slack in the connecting structures before peak loads are introduced in the intermediate devices, devices in the front-end coupler <NUM> and in the rear-end coupler <NUM> can be equipped and tuned for a gradually or stepwise increasing reaction to the impact force, as illustrated and explained with reference to <FIG>. In result, the whole series of devices will react instantly and simultaneously to the peak load which is transferred to the first coupling interface as the first "triggering" stage is consumed in the energy dissipating device of the front-end coupler <NUM>.

This strategy contributes to minimizing the impact damages at intermediate interfaces <NUM> to <NUM>. If fully implemented throughout the train set as provisioned for in <FIG> and in <FIG>, the potential total length of axial compression or stroke length of all energy dissipation devices involved amounts to <NUM> in the train set of <FIG> (six units). It is here assumed that the maximum compression length of the energy dissipation devices <NUM> or <NUM> is <NUM> before shear-off, and the maximum compression length of the energy dissipation devices <NUM> is <NUM>.

Thus, the accumulated stroke length and energy absorption capacity of devices <NUM>, <NUM> and <NUM> operating in series provide the ability of distribution and absorption of a comparatively large amount of kinetic energy throughout the train set.

According to the invention, a higher amount of the potential stroke length in dampers is made available throughout the train. The solution involves the provision of at least one energy dissipation device, at each coupling interface in a train, which has a primary deformation zone of less compression strength than the compression strengths provided by a secondary or a third, or more if appropriate, deformation zones of the same device.

A technical result from this is that absorption of kinetic energy from a collision occurs for an extended time sequence and under a more completely utilized stroke length at each coupling interface.

The operational characteristics of the series of devices <NUM>, <NUM>, <NUM> is illustrated by the gradually levelling curve in the diagram of <FIG>, which results from computations assuming train units <NUM>, <NUM> of equal length.

The horizontal axis represents the distance L from the point of impact, whereas the vertical axis KEabs represents the amount of kinetic energy absorbed in percentage of the potential capacity of devices at interfaces <NUM> to <NUM>. That is, the curve represents the relation between devices at the second, third, fourth etc. interfaces of the train, in terms of employed amount of potential stroke length and potential energy absorption. The curve is thus not related to the nominal kinetic energy that is translated through the series of devices, but is valid for all levels of energy within the operative limits of the devices at interfaces <NUM>-<NUM>. Hence, the vertical axis is dimensionless. Also, the diagram starts at the first interface <NUM>, while it is also assumed that the energy absorption capacity of devices in the front-end coupler, in most cases, will be exhausted upon impact (front collision).

From the diagram of <FIG> it will be noted, that onwards from the second interface <NUM>, connecting cars number two and three, the curve levels out to assume an almost horizontal projection. Modelling shows that a slope S of about <NUM> - <NUM> percent between the second and fifth interfaces <NUM> and <NUM> can be achieved by equipping the energy dissipation devices accordingly. Expressed in other way, a chord length between the second and fifth interfaces on the levelling portion of the curve has a slope angle of about <NUM>° to about <NUM>° with respect to the horizon. Further optimization of the devices may result in an even flatter curve over the subject series of devices. On the other hand, in train sets of random composition, the slope of the curve over the second to fifth coupling interfaces may be somewhat steeper while still utilizing the benefits of a high degree of employment of available stroke length and distribution of kinetic energy throughout the series of devices, as provided for by the impact management strategy of the present invention. In this connection it will be realized that a slope S in the region of about <NUM> % to about <NUM> % between the second and fifth interfaces is clearly achievable and, within this region, is an improvement above the prior art.

Among the advantages achieved, for example, is that the crash protection system as disclosed provides the possibility of designing the first two interfaces after point of collision for absorption of less energy whereas the third to sixth interfaces, e.g., being designed for absorption of comparatively more energy. It enables "softening" of the energy absorption performance for the interfaces near the collision and transferring part of the energy absorption to the interfaces that are further away from the collision, without compromising the position of the complete energy absorption, and keeping the crash peak/wave/acceleration to a minimum.

Claim 1:
An energy dissipation device (<NUM>; <NUM>; <NUM>) for a train coupler adapted for absorbing kinetic energy from a collision, the energy dissipation device comprising:
- a cylindrical housing (<NUM>; <NUM>; <NUM>), in one end having coupling means (<NUM>; <NUM>; <NUM>) for coupling the housing in fixed relation to a train coupler,
- at least one axially compressible, irreversibly deforming element (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>) of steel in the housing, the compressible element(s) extended in coaxial relation with the housing from said one end towards a second end of the housing,
- a compression means (<NUM>; <NUM>) retractable into the housing via said one end or said second end of the housing,
- wherein at least one compressible element (<NUM>; <NUM>; <NUM>; <NUM>) is pre-tensioned axially between said retractable compression means (<NUM>; <NUM>) and a counter pressure means (<NUM>; <NUM>) stationary secured in the housing in axially opposite relation to the retractable compression means in said one end or said second end of the housing,
and wherein the retractable compression means has a circular periphery (<NUM>; <NUM>) shaped for guidance in non-destructive sliding contact with the inside wall of the housing (<NUM>; <NUM>; <NUM>) upon retraction and compression of the compressible element(s) (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>), while preserving the integrity of the housing.