Buffer assembly for a railway vehicle

Abstract

The present invention relates to a buffer assembly (100) comprising: a reversible energy absorption unit (10) comprising an inner housing (11) having an open end (111) and a closed end (112), and a plunger (12) received axially movable in the inner housing and movable between a neutral position and a compressed position, thereby reversibly absorbing energy up to an energy threshold, and further comprising an irreversible energy absorption unit (20) comprising an outer housing (21) and a deformation element (22) connected to the elongate outer housing, wherein further the reversible energy absorption unit (10) is received axially movable in the outer housing (21) with the plunger (12) protruding from the first end (211) of the outer housing (21), such that the inner housing (11) is configured to move towards the deformation element (22) when energised above the energy threshold such that a plastic deformation of the at least one deformation element (22) takes place.

Description

[0001] BUFFER ASSEMBLY FOR A RAILWAY VEHICLE

[0002] TECHNICAL FIELD

[0003] The present invention relates to a buffer assembly for a railway vehicle, wherein the buffer assembly is configured for energy absorption using both reversible and irreversible energy absorption.

[0004] BACKGROUND

[0005] In railway vehicles, buffer assemblies are used for reversible energy absorption, for instance when one railcar accelerates or decelerates in relation to another. The buffer assemblies then return to their neutral position and are used repeatedly during operation.

[0006] When larger forces occur, irreversible energy absorption takes place to protect the vehicles and prevent damage to other components or to passengers or cargo transported in the railway vehicle. For this purpose, deformation tubes and other components that undergo plastic deformation to irreversibly absorb energy are used.

[0007] There is a longstanding desire to provide energy absorption in a more space efficient manner. In particular, the combined strokes of a buffer assembly and a deformation tube arranged in series is very bulky and limiting to the design of the railway vehicles and in particular to the railway couplers provided to connect them. In many applications, the railway coupler must provide both reversible and irreversible energy absorption to protect the railcar on which it is arranged. The very limited space available on the coupler then restricts the stroke of the buffer assemblies and the deformation tubes, thereby severely limiting the total energy absorption available in the coupler.

[0008] One solution to this problem is provided by EP2845784A1, where the buffer assembly and deformation tube are combined in a single component. Although this is a significant step away from the traditional design of separate components, improvements are still needed to improve function of the buffer assembly. There is therefore a need for further improvements within this area.

[0009] SUMMARY

[0010] The object of the present invention is to eliminate or at least to minimize the problems discussed above. This is achieved by a buffer assembly according to the appended independent claims.

[0011] The buffer assembly according to the invention is suitable for reversible and non-reversible deformation and comprises a reversible energy absorption unit, in turn comprising an elongate inner housing having an open end and a closed end and also comprising a plunger that is received axially movable in the inner housing and movable between a neutral position and a compressed position, and wherein the plunger is arranged with at least one reversible energy absorber in the inner housing configured to reversibly absorb energy up to an energy threshold when the plunger is moved to the compressed position where it is pushed towards the at least one reversible energy absorber.

[0012] Furthermore, the buffer assembly according to the invention also comprises an irreversible energy absorption unit comprising an elongate outer housing with a first end and a second end, and at least one deformation element connected to the elongate outer housing. The reversible energy absorption unit is received axially movable in the outer housing with the closed end of the inner housing facing the at least one deformation element and with the plunger protruding from the first end of the outer housing, such that the inner housing is configured to move towards the at least one deformation element when energised above the energy threshold such that a plastic deformation of the at least one deformation element takes place.

[0013] The present invention has the significant advantage over the prior art that the reversible energy absorption unit is arranged with the plunger protruding from the buffer assembly. This serves to improve guiding of the inner housing towards the deformation element so that misalignment or buckling is avoided, and also to provide access to the plunger itself to enable monitoring of the buffer assembly and facilitate detection of faults or malfunction. It is particularly advantageous that it is the inner housing and not the plunger that acts to deform the deformation element, since the larger diameter of the inner housing compared with the plunger lowers the risk of misalignment during deformation of the deformation element.

[0014] Suitably, the inner housing is held in the outer housing with an overlap and the buffer assembly further comprises a guiding sleeve arranged between the inner housing and the outer housing for guiding the inner housing towards the at least one deformation element. Thereby, the inner housing is securely held in the outer housing and the guiding sleeve serves to guide the inner housing to ensure that movement towards the deformation element is in the axial direction without misalignment.

[0015] The guiding sleeve suitably extends at least half, preferably at least 75 % and more preferably at least 90 % of the overlap. The large overlap further improves guiding of the inner housing towards the deformation element.

[0016] Suitably, the outer housing comprises an internal stop and the inner housing comprises an external stop, and the internal stop and the external stop are configured to engage to prevent removal of the inner housing from the outer housing. Thereby, the inner housing is securely held in the outer housing in a desired position, preferably held against the deformation element so that deformation starts immediately when the energy threshold is exceeded.

[0017] The at least one deformation element may in some embodiments be connected to the outer housing by being fixed to or integrated with the outer housing. Thereby, the at least one deformation element is securely held and cannot inadvertently come loose from the outer housing. This also ensures that the at least one deformation element is held in a desired position in relation to the inner housing so that deformation can take place as intended.

[0018] In other embodiments, the at least one deformation element is connected to the outer housing by the outer housing comprising a deformation element stop and the at least one deformation element being arranged inside the outer housing so that the deformation element stop prevents the at least one deformation element from escaping through the second end. Thereby, the at least one deformation element may comprise one or a plurality of deformation elements that are placed inside the outer housing and that can be irreversibly deformed between the inner housing and the deformation element stop.

[0019] Suitably, the inner housing comprises a tapered portion at the closed end and the at least one deformation element comprises a deformation tube having a diameter smaller than a diameter of the inner housing so that the deformation tube is deformable by the tapered portion of the inner housing to forcibly increase the diameter of the deformation tube. Thereby, energy is absorbed in a reliable and efficient way by the inner housing being able to act as a plunger in the deformation tube to increase its diameter.

[0020] In embodiments including a deformation tube, the outer housing suitably has an inner diameter that fits around the deformation tube in a deformed state when energised by the inner housing such that plastic deformation of the deformation tube causes the deformation tube to fit between the inner housing and the outer housing in a radial direction. Thereby, the outer housing is provided to securely hold the deformation tube in its deformed state and to further ensure that the deformation takes place as intended.

[0021] Suitably, the buffer assembly also comprises a sensor for monitoring at least one parameter of the buffer assembly, said sensor being arranged in connection with a portion of the plunger that protrudes from the inner housing in the neutral position. Thereby, one or more parameters that relate to the performance or state of the buffer assembly can be detected or measured. This is advantageous both in monitoring the performance of the buffer assembly and in detecting a possible fault in the buffer assembly so that repair or replacement can take place.

[0022] Also, the reversible energy absorption unit and the irreversible energy absorption unit in the neutral position of the buffer assembly are arranged such that a first plunger overlap of the inner housing with the plunger is larger than a second plunger overlap of the outer housing with the plunger. Thereby, the plunger is securely guided when moving and the risk of buckling or bending is significantly reduced or even eliminated. In some embodiments, the reversible energy absorption unit is a damper so that the inner housing is a damper housing and the plunger is a piston that is received axially movable in the damper housing with a piston head of the piston facing the closed end of the damper housing. Also, the at least one reversible energy absorber then comprises a working chamber housing a working fluid, said working chamber being formed between the piston head of the piston and the closed end of the damper housing, wherein the piston is movable between the neutral position and the compressed position. Also, the piston in such embodiments further comprises an overflow chamber that is connected to the working chamber by a flow passage in the piston head with a flow restriction so that the working fluid is able to flow from the working chamber to the overflow chamber through the piston head when the piston is moved towards the compressed position, thereby reversibly absorbing energy up to the energy threshold. Thereby, a damper such as a hydraulic damper, a gas-hydraulic damper, or any suitable kind of damper can be used as the reversible energy absorption unit. This is highly advantageous in ensuring a reliable absorption of energy up to the energy threshold and enables absorbing a large amount of energy so that the energy threshold can be set as desired. Also, the damper may be configured to absorb energy also when subjected to draft forces, thereby enabling reversibly absorbing draft forces during operation in a railway coupler or a railway vehicle.

[0023] In other embodiments, the at least one reversible energy absorber is a spring, preferably a ring spring, or at least one but preferably a plurality of elastomeric elements. Thereby, a reliable and convenient reversible energy absorption is provided, using components that seldom require maintenance and that have a long lifetime. Also, since no working fluid is used, the risk of leakage of fluid from the buffer assembly is eliminated.

[0024] Many additional benefits and advantages of the present invention will be readily understood by the skilled person in view of the detailed description below.

[0025] DRAWINGS The invention will now be described in more detail with reference to the appended drawing, wherein

[0026] Fig. 1 discloses a cross-sectional view from the side of a first embodiment of the buffer assembly according to the invention.

[0027] The figure is schematic, not necessarily to scale, and generally only shows parts which are necessary in order to elucidate the respective embodiments, whereas other parts may be omitted or merely suggested.

[0028] DETAILED DESCRIPTION

[0029] Fig. 1 discloses a first embodiment of a buffer assembly 100 according to the invention. The buffer assembly 100 is suitable for use in railway vehicles in general and more particularly in railway couplers. Since railway vehicles and couplers are already well known, they will not be described in detail herein. Suffice it to say that the buffer assembly 100 when in use is mounted between two structures that are movable in relation to each other, such as a front part and a rear part of a coupler. When one part moves towards or away from the other, a buff force or draft force is applied to the buffer assembly 100 and is absorbed as will be explained in more detail below.

[0030] The term “buffer assembly” is used herein to denote an assembly that serves to absorb energy when subjected to a buff force (and optionally also a draft force) . The buffer assembly may comprise a damper, a buffer with springs such as ring spring or elastomeric elements, a deformation tube, and / or other energy absorption devices and elements as set forth herein.

[0031] When it is stated herein that a component contacts another or that a component is attached to or mounted on another, this is to be understood as encompassing both that the components are in direct contact or mounted / attached in direct contact and that the components are arranged with at least one intermediary object between them. Thus, when it is stated that two components engage each other, this also includes arrangements where an intermediary component is attached to one or both or is movably arranged between them as long as the engagement of the two components mean that a force or movement can be transferred from one to the other. Also, when it is stated that two components are connected to each other, this is to be understood as encompassing arrangements where the components are connected to each other directly as well as arrangements where at least one intermediary component is provided between them and to also include arrangements where they are integrated. A connection or a contact is thus to be understood as an arrangement where a force or a movement is transferred from one component to the other, possibly through at least one intermediary object or component.

[0032] The buffer assembly 100 comprises a reversible energy absorption unit 10 that is mounted in an irreversible energy absorption unit 20. When subjected to smaller forces, energy is reversibly absorbed in the reversible energy absorption unit 10 that is then returned to its neutral position and able to continue operation. The maximum energy that can be reversibly absorbed is an energy threshold that is predetermined and decided during manufacture so that dimensions of the reversible energy absorption unit 10 are selected accordingly. When subjected to forces above the energy threshold, the reversible energy absorption unit 10 absorbs the maximum energy possible and the remaining energy is instead applied to the irreversible energy absorption unit 20. By the arrangement of the reversible energy absorption unit 10 inside the irreversible energy absorption unit 20, an elongate inner housing 11 of the reversible energy absorption unit 10 acts as a plunger and causes plastic deformation of at least one deformation element 22. When the irreversible energy absorption unit 20 has been activated in this way so that a plastic deformation takes place, the buffer assembly 100 can no longer return to its neutral position and instead needs to be repaired or replaced.

[0033] The components of the buffer assembly 100 will now be disclosed in more detail and their operation explained. Fig. 1 discloses the first embodiment where a damper is provided as the reversible energy absorption unit 10. In a second embodiment described further below, the reversible energy absorption unit 10 instead comprises a spring or at least one elastomeric element for reversibly absorbing energy. It is in particular to be noted that the invention has the same function and technical advantages regardless of which type of unit is used for the reversible energy absorption unit 10 and that what is said of the first embodiment also applies to the second embodiment, except where the description concerns internal operation of the damper as such. It is also to be noted that features from one embodiment may freely be combined with features from another within the scope of the appended claims, as long as such a combination is not explicitly stated as unsuitable or undesirable.

[0034] In Fig. 1, the buffer assembly 100 is shown with the reversible energy absorption unit 10 comprising the inner housing 11 and a plunger 12 that is received axially movable in the inner housing and able to move from a neutral position shown in the figure to a compressed position where the plunger 12 is moved as far into the inner housing 11 as allowed by at least one reversible energy absorber 101 in the reversible energy absorption unit 10 to absorb the energy of the energy threshold. The inner housing has an open end 111 where the plunger 12 is received and a closed end 112 against which the plunger 12 moves to compress the reversible energy absorption unit 10. The plunger 12 in turn has an outer end 121 that is connected to a structure of the coupler or railway vehicle so that a movement of the structure causes the plunger 12 to move in relation to the inner housing 11.

[0035] In the first embodiment, the inner housing 11 is a damper housing and the plunger 12 is a piston 12 that moves axially in the damper housing 11 in order to compress a working chamber 101 holding a working fluid. In the following when describing the first embodiment, the terms “inner housing” and “damper housing” will be used interchangeably, as will the terms “plunger” and “piston”.

[0036] When the piston 12 is pushed in a first direction D towards the damper housing 11, the working chamber 101 arranged between the closed end 112 of the inner housing 11 and a piston head 122 of the piston 12 is compressed. The piston head 122 is arranged at the end of the piston 12 facing the closed end 112 of the inner housing 11. The working chamber 101 in the first embodiment holds the working fluid that may be a hydraulic fluid, a gas, a liquid elastomer, or any other suitable substance in liquid or gas form that is suitable for use in a buffer. When the working chamber 101 is compressed, the working fluid is pushed through a flow passage 104 in the piston head 122 with a flow restriction 103 to reach an overflow chamber 102 inside the piston 12. The flow restriction is in this embodiment in the form of a metering pin 103, but may in other embodiments be other types of flow restrictions such as e.g. a throttle arranged in the flow passage 104.

[0037] These components are schematically shown in Fig. 1 but the operating principles of a buffer or damper are well known within the art. We refer in particular to EP3187748 that discloses a damper where hydraulic fluid is transported through a piston head in response to a compression of a working chamber.

[0038] By the flow passage comprising a flow restriction to prevent a free flow of working fluid into the overflow chamber 102, energy is absorbed by the reversible energy absorption unit 10. Inside the piston 12, there may also be other chambers such as for instance a gas chamber 105 of variable volume that acts to bias the reversible energy absorption unit 10 towards the neutral state where the working chamber 101 is not compressed. Alternatively or additionally, springs or other biasing means may be provided in the piston 12 or connected to the piston for this purpose. Other components may also be provided inside the piston 12.

[0039] When the working chamber 101 is compressed, the reversible energy absorption unit 10 eventually reaches a compressed position where energy up to the energy threshold has been absorbed. This is a position where a volume of the working chamber 101 is at a minimum and where the piston 12 is pushed to an end position with the piston head 12 close to the closed end 112 of the inner housing 11.

[0040] As soon as the force pushing the piston 12 towards the inner housing 11 is released, the reversible energy absorption unit 10 is returned to the neutral position by the working fluid returning to the working chamber 101, suitably through a return passage in the piston head 122. In some embodiments, the piston 12 is preloaded towards the neutral position so that the preload acts on the piston 12 as soon as the force acting on the piston 12 from the structure to which the piston 12 is connected is no longer applied. Also, in some embodiments the reversible energy absorption unit 10 is double acting so that forces are absorbed both in a buff direction (i.e. where the piston 12 is pushed into the inner housing 11) and in a draw direction (i.e. where the piston 12 is pulled out of the inner housing 11). In other embodiments, only energy applied in the buff direction is absorbed.

[0041] To summarize, the reversible energy absorption unit 10 operates by the piston 12 compressing the working chamber 101 so that working fluid is forced into the overflow chamber 102. During this compression, the inner housing 11 is held immobile in an elongate outer housing 21 that forms part of the irreversible energy absorption unit 20. The closed end 112 of the inner housing 11 faces at least one deformation element 22 and is suitably held against the deformation element 22 so that movement of the inner housing 11 in the first direction D takes place only when deformation of the deformation element 22 commences. Thereby, there is no delay in response time of the reversible energy absorption unit 10, i.e. compression of the working chamber 101 takes place as soon as the piston 12 moves in the first direction D.

[0042] In the first embodiment, the inner housing 11 is also prevented from moving out of the outer housing 21, i.e. in a direction opposite to the first direction D. This is achieved by an internal stop 213 that is provided on an inside of the outer housing 21 or on a component that is mounted in the outer housing 21. The inner housing 11 comprises or is connected to an external stop 113 that is configured to engage with the internal stop 213 so that movement of the inner housing 11 in the direction opposite to the first direction D is prevented, i.e. so that removal of the inner housing 11 through a first end 211 of the outer housing 21 is not possible. In embodiments where the internal stop 213 and / or the external stop 113 are comprised in the outer housing 21 and the inner housing 11, respectively, they can be in the form of protrusions or flanges that form meeting surfaces so that they contact each other in the neutral position or if the inner housing 11 is moved a small distance in the direction opposite to the first direction D. In embodiments where the internal stop 213 and / or the external stop 113 are connected to the outer housing 21 and the inner housing 11, respectively, they may be provided as protrusions or flanges on a component attached to or mounted in / on the outer housing 21 and the inner housing 11. Such a component may e.g. be a guide sleeve 31 (see below). The internal stop 213 and / or external stop 113 may be provided on only one side of the inner housing 11 and outer housing 21 but is advantageously provided around an entire outer circumference of the inner housing 11 and inner circumference of the outer housing 21 to improve stability of the buffer assembly 100.

[0043] The at least one deformation element 22 is in the first embodiment of Fig. 1 a deformation tube 22 that is mounted in the outer housing 21 and connected to the outer housing 21 by being held against a deformation element stop 214 so that movement of the at least one deformation element 22 in the first direction D is securely prevented. The deformation element stop 214 may be a closed second end 212 of the outer housing 21 or may alternatively be an edge or an area of smaller diameter inside the outer housing 21 or an internal bottom surface or similar as long as it is able to prevent the at least one deformation element 22 from moving. Providing the at least one deformation element 22 as a deformation tube is also highly suitable in the second embodiment described below.

[0044] When the reversible energy absorption unit 10 is at its compressed position it is not able to reversibly absorb energy. If the buffer assembly 10 is energised by energy above the energy threshold, this therefore causes the inner housing 11 to act as a plunger on the at least one deformation element 22 and move in the first direction D to cause a plastic and irreversible deformation of the at least one deformation element 22. In the first embodiment, this takes place by a forced diameter increase in the deformation tube 22 that is caused by a tapered portion 114 of the closed end 112 of the inner housing 11 pushing into the deformation tube 22 to cause walls of the deformation tube 22 to expand in a radial direction that is perpendicular to the first direction D. In the neutral position, the inner housing 11 has a diameter that is larger than a diameter of the deformation tube 22 so that insertion of the inner housing 11 into the deformation tube 22 forces its diameter to increase, thereby absorbing energy required to force the deformation tube to expand.

[0045] Suitably, the deformation tube 22 comprises or is connected to a widening portion 221 that serves as a gradual increase in diameter to enable the forced diameter increase to take place in a controlled manner. The widening portion 221 may thus be integrated with the deformation tube 22 or may be a separate component connected to the deformation tube 22, and the tapered portion 114 may also be integrated with the closed end 112 of the inner housing 11 or may be a separate component that is mounted on or inserted into the closed end 112.

[0046] The at least one deformation element 22 is suitably adapted to the energy threshold so that it is not energised by energy below the energy threshold. Thus, when lower energy levels are applied to the buffer assembly 100, only the reversible energy absorption unit 10 operates and absorbs energy in the manner explained above. When the energy threshold is crossed, however, the at least one deformation element 22 deforms in response to the force with which the inner housing 11 presses against the at least one deformation element 22.

[0047] Preferably, the outer housing 21 has an inner diameter that fits around the deformation tube 22 in a deformed state when it is energised by the inner housing 11 so that the plastic deformation causes the deformation tube 22 to expand so that the inner housing 11 fits inside and contacts the outer housing 21. The outer housing 21 thus has an inner diameter that is suitably close to an outer diameter of the deformation tube 22 in the deformed state and this serves to support the deformation tube 22 and ensure that the movement of the inner housing 11 along the length of the deformation tube 22 during deformation takes place in the first direction D without buckling or bending. In other embodiments, the deformation tube 22 is connected to the outer housing 21 by being fixed to or integrated with the outer housing 21. Thus, rather than being held against the deformation element stop 214, the deformation tube 22 is attached to or integrated with the outer housing 21 as such. When the deformation tube 22 is integrated with the outer housing 21 this may in some embodiments mean that the outer housing 21 in at least a portion of its length has a diameter that is smaller than the inner housing 11 so that the outer housing 21 itself acts as a deformation tube.

[0048] Also, in some embodiments other deformation elements 22 than a deformation tube may be provided inside the outer housing 21. This may include any kind of axially compressible, irreversibly deforming elements such as e.g. steel elements that are held inside the outer housing and are deformed between the closed end 112 of the inner housing 11 and a meeting surface. Such axially compressible, irreversibly deforming element may be in the form of a honeycomb structure. Alternatively the closed end of the buffer housing may comprise a cutting edge suitable to plastically deform a deformation element through cutting or peeling.

[0049] It is to be noted that the various embodiments mentioned herein can freely be combined within the scope of the appended claims. Thus, for any embodiments mentioned herein any element or component may be combined with any other embodiment as long as such a combination is not explicitly stated as unsuitable or undesirable. Also, apart from the first embodiment the embodiments herein are described mainly in the features that differ from other embodiments. Any features not specifically stated to be different in any one embodiment are to be understood as similar or identical to any other embodiment. For instance, where embodiments of the buffer assembly 100 having different types of deformation elements are disclosed, any other features of said buffer assembly 100 is to be understood as similar or identical to the first embodiment described above.

[0050] In the second embodiment, the at least one reversible energy absorber 101 is a spring, preferably a ring spring, or at least one but preferably a plurality of elastomeric elements. Thus, instead of using a damper as the reversible energy absorption unit 10 as disclosed above, the plunger 12 is configured to push against at least one element that acts to absorb the energy up to the energy threshold and that are then able to then expand and resume their original position and shape. In the second embodiment, the plunger 12 may comprise or be connected to a disc that is slidable inside the inner housing and that contacts the reversible energy absorber to be able to act with a buff force. The reversible energy absorber is then compressed between the plunger 12 or the disc connected to the plunger 12, and the closed end of the inner housing 1 1 (or optionally another surface or stop provided in the inner housing 11). When elastomeric elements are used, they are suitably provided in a stack and the plunger 12 may comprise or be connected to a central shaft that extends through the stack to ensure that they are aligned properly inside the inner housing 11. Other configurations are also possible within the scope of the present invention, as long as the plunger 12 is able to push against at least one elastically deformable element that is then able to resume its original shape and / or position afterwards.

[0051] The buffer assembly 10 according to any embodiment preferably also comprises the guiding sleeve 31 that is arranged between the outer circumference of the inner housing 11 and the inner circumference of the outer housing 21. The guiding sleeve 31 is preferably attached to the inner housing 11 and is slidable in relation to the outer housing 21, at least in the first direction D. The guiding sleeve 31 is a separate component that is mounted on the inner housing 11 before it is inserted in the outer housing 11, but in other embodiments the guiding sleeve 31 can instead be attached to the outer housing 21 or be a component placed between the inner housing 11 and the outer housing 21 but not fixedly attached to either. In such embodiments, a stop is preferably provided to prevent the guiding sleeve 31 from sliding out of the outer housing 21. Where the guiding sleeve 31 is attached to the inner housing 11 or the outer housing 21, it may be glued or shrink fitted into place, or alternatively it may be provided with a thread that mates with a matching thread of the outer housing 21 or the inner housing 11. Other fastenings are also possible, as will be readily understood by the skilled person. In the first embodiment, a sealing ring 32 is provided to prevent a leakage from the buffer assembly 100, but in other embodiments this may be omitted.

[0052] The purpose of the guiding sleeve 31 is to guide the inner housing 11 in relation to the outer housing 21 to ensure that a movement of the inner housing 11 towards the at least one deformation element 22 takes place in the first direction D and that the deformation takes place in a controlled manner as intended. The guiding sleeve 31 may in some embodiments also serve to lower friction between the inner housing 11 and the outer housing 21. The guiding sleeve 31 may be made from the same material as any part of the buffer assembly 100 or may alternatively be made from a different material.

[0053] It is advantageous to provide the guiding sleeve 31 over a large part, preferably at least half, of an overlap O between the inner housing 11 and the outer housing 21 in the neutral position shown in Fig. 1. This overlap O extends to but does not include the tapered portion 114, since the tapered portion 114 if present should advantageously be held against the widening portion 221 of the deformation tube 22. However, in embodiments where the tapered portion 114 is not provided on the inner housing 11, the overlap O may extend all the way to the closed end 112.

[0054] Thus, the guiding sleeve 31 advantageously extends at least half of the overlap O, i.e. 50 % of a distance from the first end 211 of the outer housing 21 to the tapered portion 114 (or to the closed end 112 if no tapered portion 114 is provided). More preferably, the guiding sleeve 31 extends at least 75 % and even more preferably at least 90 % of the overlap O. To provide a longer guiding sleeve 31 increases the advantage of guiding the inner housing 11 securely towards the at least one deformation element 22.

[0055] In the neutral position shown in Fig. 1, the arrangement of the reversible energy absorption unit 10 and the irreversible energy absorption unit 20 in the neutral position is such that a first plunger overlap Pl of the inner housing 11 with the plunger 12 is larger than a second plunger overlap P2 of the outer housing 21 with the plunger 12. Thereby, guiding of the plunger 12 in the buffer assembly 10 is improved so that the risk of bending or buckling is minimized or even eliminated. It is particularly advantageous that the second plunger overlap P2 is present even in the neutral position, since this decreases the risk of buckling of the plunger 12 even as the plunger 12 starts moving. During movement to the compressed position, the second plunger overlap P2 increases to ensure a stable guiding of the piston 12.

[0056] Preferably, the buffer assembly 100 also comprises at least one sensor 33 that is arranged on or in connection with the plunger 12. The sensor 33 is configured to measure or detect at least one parameter of the buffer assembly 100 to enable or facilitate monitoring of the buffer assembly 100.

[0057] Such parameter can be a stroke of the reversible energy absorption unit 10, i. e. a position of the plunger 12 in relation to the inner housing 11, or a stroke of the irreversible energy absorption unit 20, i.e. a position of the plunger 12 in relation to the outer housing 21. A combined stroke of the reversible energy absorption unit 10 and the irreversible energy absorption unit 20 can also be measured or detected in this way. This gives information of whether the plunger 12 is in the neutral or the compressed position in relation to the inner housing 11 and / or whether irreversible deformation is taking place so that the plunger 12 is further in the first direction D in relation to the outer housing 21 than in the compressed position. If the reversible energy absorption unit 10 is configured to absorb energy from draft forces as well, the sensor 33 can detect or measure a position of the plunger 12 in the direction opposite to the first direction D in relation to the inner housing 11.

[0058] Also or alternatively, the at least one sensor 33 can be configured to detect possible faults of the reversible energy absorption unit 10 by e.g. detecting a leakage of working fluid. This may be done by determining a position of the plunger 12 in relation to the inner housing 11 when the reversible energy absorption unit 10 is not compressed, i.e. in a neutral state. If a leakage takes place, an actual neutral position will differ from an intended neutral position to show that a total volume of working fluid in the neutral state is less than intended. It is a particular advantage of the invention that the at least one sensor 33 can be provided on or in connection with a portion of the plunger 12 that protrudes from the inner housing 11 so that it is available from outside the buffer assembly 100. This significantly facilitates monitoring of the buffer assembly 100 to verify that operation takes place as intended or to determine if a fault has occurred. It is particularly advantageous to be able to detect faults in a robust and convenient manner without having to place the at least one sensor 33 inside any of the reversible or irreversible energy absorption units 10, 20 since this is a more efficient and reliable design and enables both detection by the sensor 33 and maintenance or replacement of the sensor 33 in a highly convenient way.

[0059] The at least one sensor 33 may be arranged or mounted directly on the plunger 12 or may alternatively be mounted on another part of the buffer assembly 100 or an auxiliary part and be arranged to measure or detect the parameter of the plunger 12 or of the buffer assembly 100.

[0060] When the buffer assembly 100 is mounted, the at least one deformation element 22 is placed inside the outer housing 21 or attached to the outer housing 21. The reversible energy absorption unit 10 is then inserted into the outer housing 21 and arranged in a desired position in relation to the at least one deformation element 22. It is particularly advantageous that the reversible energy absorption unit 10 is placed with the closed end 112 of the inner housing 11 facing the at least one deformation element 22, since this enables pre-loading the at least one deformation element 22 in a convenient and reliable manner. By pre-loading the at least one deformation element 22, it is ensured that the response time of the irreversible energy absorption unit 20 is minimized, since deformation of the at least one deformation element 22 starts immediately when the inner housing 11 starts to move towards the at least one deformation element 22.

[0061] It is to be noted that features from the various embodiments described herein may freely be combined, unless it is explicitly stated that such a combination would be unsuitable.

Claims

CLAIMS1. Buffer assembly (100) for reversible and non-reversible deformation, the buffer assembly comprising:- a reversible energy absorption unit (10) comprising- an elongate inner housing (11) having an open end (111) and a closed end (112),- a plunger (12) that is received axially movable in the inner housing and movable between a neutral position and a compressed position, wherein the plunger (12) is arranged in the inner housing (11) with at least one reversible energy absorber (101) configured to reversibly absorb energy up to an energy threshold when the plunger (12) is moved to the compressed position, and wherein the buffer assembly (100) further comprises- an irreversible energy absorption unit (20) comprising- an elongate outer housing (21) with a first end (211) and a second end (212),- at least one deformation element (22) connected to the elongate outer housing, wherein further the reversible energy absorption unit (10) is received axially movable in the outer housing (21) with the closed end (112) of the inner housing (11) facing the at least one deformation element (22) and with the plunger (12) protruding from the first end (211) of the outer housing (21), such that the inner housing (11) is configured to move towards the at least one deformation element (22) when energised above the energy threshold such that a plastic deformation of the at least one deformation element (22) takes place.

2. Buffer assembly according to claim 1, wherein the inner housing (11) is held in the outer housing (21) with an overlap (O) and wherein the buffer assembly (100) further comprises a guiding sleeve (31) arranged between the inner housing (11) and the outer housing (21) for guiding the inner housing (11) towards the at least one deformation element (22).

3. Buffer assembly according to claim 2, wherein said guiding sleeve (31) extends at least half, preferably at least 75 % and more preferably at least 90 % of the overlap (O) .

4. Buffer assembly according to any of claims 1-3, wherein the outer housing (21) comprises or is connected to an internal stop (213) and the inner housing (11) comprises or is connected to an external stop (113), and wherein the internal stop (213) and the external stop (113) are configured to engage to prevent removal of the inner housing (11) from the outer housing (21).

5. Buffer assembly according to any of claims 1-4, wherein the at least one deformation element (22) is connected to the outer housing (21) by being fixed to or integrated with the outer housing (21).

6. Buffer assembly according to any of claims 1-4, wherein the at least one deformation element (22) is connected to the outer housing (21) by the outer housing (22) comprising a deformation element stop (214) and the deformation element (22) being arranged inside the outer housing (21) so that the deformation element stop (214) prevents the at least one deformation element (22) from escaping through the second end (212).

7. Buffer assembly according to any of claims 1-5, wherein the inner housing (11) comprises a tapered portion (114) at the closed end (112) and wherein the at least one deformation element (22) comprises adeformation tube having a diameter smaller than a diameter of the inner housing (11) so that the deformation tube (22) is deformable by the tapered portion (114) of the inner housing (11) to forcibly increase the diameter of the deformation tube.

8. Buffer assembly according to claim 7, wherein the outer housing (21) has an inner diameter that fits around the deformation tube (22) in a deformed state when energised by the inner housing (11) such that plastic deformation of the deformation tube (22) causes the deformation tube to fit between the inner housing (11) and the outer housing (21) in a radial direction.

9. Buffer assembly according to any previous claim, further comprising a sensor (33) for monitoring at least one parameter of the buffer assembly (100), said sensor (33) being arranged in connection with a portion of the plunger (12) that protrudes from the inner housing (11) in the neutral position.

10. Buffer assembly according to any previous claim, wherein the reversible energy absorption unit (10) and the irreversible energy absorption unit (20) in the neutral position of the buffer assembly (100) are arranged such that there is a first plunger overlap (Pl) of the inner housing (11) with the plunger (12) and a second plunger overlap (P2) of the outer housing (21) with the plunger (12), said first plunger overlap (Pl) being larger than said second plunger overlap (P2).

11. Buffer assembly according to any previous claim, wherein the reversible energy absorption unit (10) is a damper so that the inner housing (11) is a damper housing and the plunger (12) is a piston that is received axially movable in the damper housing with a piston head (122) of the piston (12) facing the closed end (112) of the damper housing (11) and wherein the at least one reversible energy absorber comprises a working chamber (101) housing a working fluid, saidworking chamber (101) being formed between the piston head (122) of the piston (12) and the closed end (112) of the damper housing (11), wherein the piston (12) is movable between the neutral position and the compressed position, and wherein the piston (12) further comprises an overflow chamber (102) that is connected to the working chamber (101) by a flow passage in the piston head (122) with a flow restriction so that the working fluid is able to flow from the working chamber (101) to the overflow chamber (102) through the piston head (122) when the piston (12) is moved towards the compressed position, thereby reversibly absorbing energy up to the energy threshold.

12. Buffer assembly according to any of claims 1- 10, wherein the at least one reversible energy absorber (101) is a spring, preferably a ring spring, or at least one but preferably a plurality of elastomeric elements.

Images