WO2017125740A1

WO2017125740A1 - Energy absorbing end terminal

Info

Publication number: WO2017125740A1
Application number: PCT/GB2017/050124
Authority: WO
Inventors: Steven Bowyer; Andrew Pardoe
Original assignee: Hill & Smith Holdings Plc
Priority date: 2016-01-21
Filing date: 2017-01-19
Publication date: 2017-07-27
Also published as: GB201601141D0; EP3405617B1; EP3405617A1

Abstract

An energy absorbing end terminal system (10) is connected to a crash barrier (12) by a connection piece (14). The energy absorbing end terminal system (10) has a length L indicated by an arrow. The system (10) comprises a rail (16), which is inclined such that it extends from the height of the crash barrier (12) down to the ground where it terminates at an end (18). The rail (16) is supported between the crash barrier (12) and its end 18 by a support post (19). The end (18) of the rail (16) is mounted on a base plate (20), which is anchored to the ground. An impact device (22) is mounted on the rail (16), close to the end (18) of the rail (16).

Description

Energy absorbing end terminal

The present invention relates to an energy absorbing end terminal system for a crash barrier. In particular, the invention relates to an energy absorbing end terminal system comprising a rail and an impact device.

Crash barriers are provided along the centre or side of vehicle carriageways for restraining impacting vehicles along their length, by absorbing energy from the collision. There remains the problem of designing barriers with end-on or obliquely/end-on collisions in mind. When a barrier terminates (into a ground anchorage or otherwise), the end of the crash barrier may itself present a danger to an oncoming vehicle in the event of an end-on collision. For example, if a vehicle impacts the end of a W-section crash barrier end-on, there is a risk that the end or edge of the barrier could penetrate the vehicle without providing an effective decelerating force on the vehicle itself.

There is therefore a need to provide a means for decelerating an impacting vehicle in the event of end-on barrier collisions. The present invention has been devised with the foregoing in mind.

According to a first aspect of the present invention, there is provided an energy absorbing end terminal system for a crash barrier, the system comprising an elongate rail, and an impact device, the impact device comprising:

a base member disposed on the rail so as to be slidable along the rail in a longitudinal direction;

an impact post extending generally upwardly from the base member; and

at least one shearing element extending from the base member.

In some embodiments, the rail comprises at least one cut out. In some embodiments, in an initial pre-impact position the at least one shearing element projects into the at least one first cut-out in the rail. In some embodiments, the shearing element is arranged to shear the rail on movement of the impact device relative to the rail, for example during an impact of a vehicle into the impact device. Upon an end-on collision of a vehicle into the impact post, load is transferred from the impact post to the shearing element(s), causing the shearing element(s) to shear through the rail in the longitudinal direction as the impact device travels along the rail. The impact device thus provides a shearing effect, which may be continuous, on the material of the rail which brings the vehicle to stop within the length of the rail. Thus, the rail itself provides a control mechanism for slowing an impacting vehicle. The invention provides an arrangement which is simple to manufacture and assemble, thus reducing costs.

According to a second aspect of the present invention, there is provided a barrier system comprising a crash barrier and an energy absorbing end terminal system in accordance with the first aspect of the invention. The rail may be connected to the crash barrier by a connection piece. The rail may be supported along its length by one or more support posts.

In accordance with a third aspect of the present invention, there is provided an impact device for an energy absorbing end terminal system, the impact device comprising:

a base member for slidably mounting on a rail;

an impact post extending generally upwardly from the base member; and

at least one shearing element extending from the base member. The shearing device may extend from an opposing side of the base member to the impact post. The following statements may be applicable to the first, second, third and/or fourth aspects of the invention, as appropriate.

The rail may be of any size and shape which is suitable for forming the end terminal of a crash barrier. In use, the rail may be inclined relative to the horizontal, extending from an end of a crash barrier to the ground. The "terminus" of the rail, as used herein, refers to the free end of the rail (i.e. the end not corrected to the crash barrier).

In some embodiments, the rail is rectangular in cross section. Alternatively, the rail may be square, circular or l-shaped in cross section, or any other convenient shape.

The rail may be solid, or it may be hollow, i.e. in the form of a tube. A hollow/tubular rail makes it easier for the shearing element(s) to shear the material of the rail. By controlling the thickness of the material forming the rail, the resistance of the rail to shearing, and thus rate at which a colliding vehicle is slowed, can be controlled. In some embodiments, the rail is in the form of a tube. The tube may be formed from a material such as metal (e.g. steel). The material forming the tube may have a thickness of from 2 mm to 8 mm, or from 3 mm to 6 mm (e.g. 4 or 5 mm). The first cut-out in the rail allows the shearing element to project into the rail in the pre-impact position, such that the shearing element cuts through the rail upon collision of a vehicle with the impact device. In some embodiments wherein the rail is in the form of a tube, the first cut-out is a hole or slot in a wall of the rail. In further embodiments, a portion of one or more side walls of the rail may cut-away at a terminus of the rail. For example, the rail may be in the form of a tube of rectangular cross-section wherein a top wall of the rail is cut away at the terminus of the rail, thereby creating an open channel. In some embodiments (for example wherein the rail is solid), the cut-out is a groove or notch in a surface of the rail. It will be appreciated that the first cut-out is be sized and shaped so as to receive the shearing element therein in the pre-impact position.

In some embodiments, the first cut-out is formed in an (in-use) upper surface or top wall, or in a lower surface or bottom wall, of the rail. In some embodiments, the first cut-out is formed in one or both side walls of the rail. In further embodiments, first cut-outs are formed in the upper surface/top wall, the lower surface/bottom wall and/or in one or both sides of the rail. For example, the first cut-out may extend completely through the rail from the upper surface or top wall to the lower surface or bottom wall, or from one side of the rail to the other.

In some embodiments the first cut-out is a slot for receiving a shearing element, such as a blade, therethrough. The slot may be sized and shaped to receive the shearing element with a snug fit. In some embodiments the slot extends in a direction parallel to the longitudinal axis of the rail. Alternatively, the slot may be angled relative to the longitudinal axis of the rail. This provides greater frictional resistance to shearing.

In some embodiments, the or each first cut-out in the rail is positioned such that, when the impact device is mounted on the rail (prior to vehicle impact), the or each first-cut out is aligned with a corresponding second cut-out in the base member, so that or each shearing element(s) can pass through the cut-outs in both the base member and the rail. This arrangement facilitates in situ assembly of the system. For example, where the first cut-out is a notch, and the end of the rail is open at its in-use upper side, the impact device may be slid onto the rail, thus facilitating easy assembly.

The base member is configured to secure the impact device on the rail while being moveable relative thereto. A vehicle colliding end-on with the impact post thus causes the impact device to slide along the rail in the direction of impact. The base member may extend entirely around the rail or only partially around the rail. The base member may have a cross section having a shape which substantially matches the cross section of the rail. In embodiments, the base member may have a C shaped cross-section, which is open at the lower edge of the rail, and wraps only partially around the lower edge to hold itself onto the rail, while otherwise generally confirming to the outer cross-sectional contour of the rail. This allows the impact device to pass over a support post holding the rail in position on above the ground its incline. The support post assists in keeping the rail straight and avoiding buckling during impact as the base member of the impact device moves along the rail.

In some embodiments, the base member is a sleeve which is configured to receive the rail therethough. In such embodiments it will be appreciated that the area of the cross section of the base member will be greater than that of the rail so as to allow the base member to slide along the rail. Alternatively, the base member may be C-shaped or U-shaped, or any other suitable shape in cross-section.

In some embodiments, the base member is elongate, having a first end and a second end. When the base member is mounted on the rail, the first end is proximal to the terminus of the rail and a second end is distal to the terminus of the rail.

In some embodiments the base member comprises one or more second cut-outs for receiving a shearing element therethrough. The second cut-out may be formed in an (in-use) upper surface of the base member, and/or in one or both sides of the base member. The second cut-outs may be sized and shaped to receive the shearing elements with a snug fit. The second cut-out may be a hole or a slot. The shearing elements may be held in the second cut-outs by any suitable means, for example bolts, screws or welding. In an initial pre-impact position the first and second cut-outs of the rail and base member may be aligned and the shearing element is positioned in said first and second cut-outs so as to prevent relative movement of the rail and the impact device in the absence of an impact force. In some embodiments, the second cut-out is a slot. The slot may extend in a direction corresponding to the longitudinal axis of the base member and the rail. Alternatively, the slot may be angled relative to the longitudinal axis of the base member and the rail. Angled slots provide greater frictional resistance to the shearing effect. The impact post extends generally upwardly from the base member. In some embodiments, the angle (Θ) measured along the longitudinal axis between the impact post and the base member is 90°. In other embodiments the angle may be more or less, for example from 45° to 120°, from 50° to 1 10°, from 60° to 100° or from 70° to 80°. The common plane in which the impact post and the longitudinal axis of the rail lie may be vertical or inclined to the vertical.

In some embodiments, the impact post extends from or adjacent a first end of the base member.

The post and the base member may be integrally formed. Alternatively, the impact post and the base member may be separate components welded, screwed, bolted or otherwise secured to each other. The post may be of any suitable size and shape. In some embodiments, the post is substantially rectangular in cross section. Alternatively, the post may be square or circular, or any other suitable shape, in cross section. The post may be solid, or it may be hollow, i.e. in the form of a tube. Hollow components are advantageous in that they are lighter, facilitating transport and assembly, as well as more cost- effective.

In some embodiments, the impact device comprises a single shearing element. In some embodiments, the impact device comprises two, three, four or more shearing elements.

The shearing element may be any element which is capable of shearing or cutting through the rail material due to the force applied by a colliding vehicle on the impact device. For example, the shearing element may be a blade or a bolt. In some embodiments, the shearing element is a blade. The blade may have a cutting edge which faces generally away from the impact post and which, when the impact device is mounted on the rail, is aligned with the longitudinal axis of the rail. In other words, the blade faces the direction of travel of an impacting vehicle such that upon impact, the blade(s) shears the rail enabling the impact device to travel along the rail. In some embodiments in which the slot is angled relative to the longitudinal axis of the base member and/or the rail, the blade is also angled by the same degree.

The cutting edge of the blade can be shaped as required so as to control the shearing effect of the blade. As viewed from above, the cutting edge of the blade may be shaped to have a flat or square edge, a sharp or flat point, a rounded tip, or be provided with one or more teeth. In some embodiments, the cutting edge is asymmetrical. Asymmetrical blades may conveniently help to direct the sheared material more controllably.

It will be appreciated that the thickness of the blade will be selected according to the thickness of the rail material to be sheared. Generally, the thicker the rail material, the thicker the blade must be, although it will also be understood that the thickness of the blade will also depend on the materials of both the rail and the blade. In some embodiments, the blade is from 5 mm to 30 mm thick, or from 10 mm to 20 mm thick, e.g. about 15 mm thick. The shearing element is secured to the base element of the impact device. In some embodiments, the shearing element is attached to an inner or rail-facing surface of the base member. In these embodiments, second cut-outs in the base member for receiving the shearing elements are not required. Alternatively, the shearing element is secured in a second cut-out in the base member. The shearing element may be attached to the base element by any suitable means, for example by screw, bolts or by welding.

In some embodiments, the impact post extends from a first face of and generally away from the base member, while the or each shearing element extends from an opposite face and generally away from the base member. In other words, the impact post and the or each shearing element extend away from the base member in opposite directions.

The shearing element is formed from a material which is capable of shearing the rail. The hardness of the shearing element, relative to that of the rail, determines the level of resistance of the rail to shearing by the shearing elements and the energy required for the shearing element to cut through the rail and, in turn, the rate at which an impacting vehicle is slowed and eventually brought to a stop. Thus, the material of the shearing element and the rail, the relative thicknesses of the shearing element and the rail, and the number of shearing elements, can all be selected according to the desired rate of deceleration of the impacting vehicle. The invention thus enables greater control over the arresting of an impacting vehicle.

In some embodiments, the shearing element is formed from a hardened material (e.g. hardened steel). It will be appreciated by those skilled in the art that hardened materials are those which have undergone e.g. a heat-treatment process that increases their hardness as compared to the untreated material. In some embodiments wherein the impact device comprises two or more shearing elements, the shearing elements may all be formed from the same material, or they may be formed from different materials. In some embodiments, one or more of the shearing elements are formed from a hardened material while the other shearing element(s) are formed from a non-hardened material. Alternatively, all of the shearing elements may be formed from a hardened or a non-hardened material.

In some embodiments, the energy absorbing end terminal system for a crash barrier comprises a rail having at least one first slot, which may be elongated in the direction of the longitudinal axis of the rail, and an impact device, the impact device comprising:

a base member slidably disposed on the rail, said base member being provided with at least one second elongate slot;

an impact post extending generally upwardly from the base member; and

at least one blade extending from the base member,

wherein in an initial pre-impact position the first and second elongate slots are aligned and the blade is secured in said first and second elongate slots so as to prevent relative movement of the rail and the impact device in the absence of an impact force.

In some embodiments the impact device further comprises a bracing strut. The bracing strut may be arranged so as to provide additional support to the post and prevent the post from bending upon vehicle impact.

In some embodiments, the bracing strut extends at an angle between the impact post and a second end, or adjacent the second end, of the base member. It will be appreciated that the angle of the bracing strut will be selected in accordance with the height of the impact post and the length of the base member.

In some embodiments the impact post and/or the strut is selected or modified so as to absorb some of the energy on initial contact of a colliding vehicle with the impact post. For example, the stiffness of the post and/or strut may be selected to allow the post and/or strut to deform in a controlled manner during impact. Alternatively, the post and/or strut may have holes therein to enable localized collapse during impact. In some embodiments wherein the base member comprises one or more second cut-outs for receiving one or more shearing elements, an end of the bracing strut may attach to the base member at a position which is adjacent to, or overlapping with, the second cut-outs. This arrangement helps to stiffen the impact device at the point where the shearing elements are positioned, which in turn helps to prevent unwanted movement of the shearing element(s) in the cut-out(s). In some embodiments, the shearing element(s) is (are) positioned in the region of the strut, and may be connected to the strut to provide a stronger connection between the shearing element and the base member. In this way, by having the force required to shear the base member, or move the shearing element relative to the base member, significantly higher than the force required to shear the rail, the shearing member can be maintained on the base member when shearing of the rail occurs. In some embodiments, the shearing element is placed below or in the region of the post, rather than below or in the region of the strut. In this way, the base element is guided by the rail, and the shearing element trails a large part of the base member, and is thus more stable. If desired, the shearing element can be placed under the strut, which may encourage some rotation of the shearling element relative to the rail, thus increasing the energy absorbed. If more than one shearing element is provided, they may be arrange in any combination under or in the region of the strut and/or post, or elsewhere in relation to the base member. The shearing member may be arranged to trail the base member partially or entirely, or to lead it partially or entirely, in a direction away from the terminus of the rail.

In some embodiments the energy absorbing end terminal system further comprises a base plate for fixing the terminus of the rail to the ground. In some embodiments the base plate is substantially rectangular, although other suitable shapes may be used. The base plate may be bent to provide a ground portion which can be fixed flat against the ground, and an angled portion for connecting to the rail and which enables the rail to extend upwardly from the ground. The rail may be attached to the base plate by any suitable means, for example by welding. The base plate may be fixed to the ground by any suitable ground restraint means. For example, the base plate may comprise one or more holes for receiving bolts by which the plate can be secured to the ground.

In some embodiments, the rail comprises one or more discontinuities in the material, i.e. points or regions where the force required to shear the plate is reduced relative to the rest of the rail. For example the discontinuities may be holes or cuts in the material of the rail, or may be portions where the thickness of the rail is reduced. These discontinuities may be placed in the (in-use) upper surface of the rail. In embodiments, they can be modified and configured on manufacture of the rail to control and adapt the force required to shear the rail along the length of the rail. Providing more or larger discontinuities in the rail reduces the force required to shear the rail, and increases the length of travel of the impact device along the rail for a given impact energy. The positioning of the discontinuities can be tailored to modulate the shear force at different parts of the rail. For example, the initial shearing force required as the impact device begins to shear the rail may be relatively low, by providing a relatively high number of and/or size of discontinuity. In this way small vehicles are not halted too abruptly. Further along the rail away from the pre-impact position of the impact device, the number and/or size of the discontinuities can be decreased. If an impact causes the impact device to travel so far along the rail, then the vehicle or at least the total energy contained in the impacting vehicle is larger. Then greater shearing force is required in this further region to halt the vehicle, without requiring a higher length of rail. In some embodiments, one or more elongate plates may be provided underneath the upper surface of the rail, which may be inside the rail where it is of tubular construction. The plate(s) may be bolted to the inside of the upper (in-use) side of the rail. The length of the bolts may be chosen so that the end of the bolt distal its head. The thickness and/or hardness of the plate may be different from that of the rail. It may also vary along the length of the rail, for example, by placing different plates in different positions along the rail. The plate(s) may also include discontinuities (egg holes) along its (their) length. This (these) may also be varied along the length of the plate for similar reasons as discussed above in relation to discontinuities placed in the rail. The discontinuities may be placed only in part of the plate. In addition to, or instead of the discontinuities, rods or bolts or short horizontal plates across the inside of the rail which are sheared by the shearing element in addition to the rail, and plate, if provided, and thus contribute to the energy absorption and allow for greater absorption per unit of length along the rail. In these ways, the absorption can be configured easily as required.

Preferred embodiment is square lead on blade - gives double shear, as each corner is separate shear into rail, rather than a point which only provides a single shear point.

The base can be raised (egg by around 120mm or another amount), using a packer, between the base plate and the base member. This allows for redirection of a vehicle during initial impact, and avoids a wheel of the vehicle riding up onto the rail.

In some embodiments, the rail comprises one or more energy-absorbing elements along its length. Two or more energy-absorbing elements may be spaced along the length of the rail. The energy-absorbing elements are positioned such that, upon vehicle impact, the shearing element(s) shears through one or more of the energy absorbing elements in addition to the rail. The energy-absorbing elements may be in the form of a pin, bolt, plate or any other suitable structure which increases the thickness of the material through which the shearing element passes or provides additional resistance. The energy-absorbing elements may include a sleeve or collar of similar construction to the base member and at least one further shearing element. It may include one or more pins, bolts, blades, plates or other shearing structure. The energy- absorbing element(s) may comprise one or more blades, arranged in a similar manner to the arrangement of the base member, and/or in any of the configurations discussed above. Such an arrangement allows multiple stage impact energy absorption. Small vehicles involved in an impact may not require such additional absorption, and having too much absorption initially may cause severe deceleration of an impacting vehicle, which may not be desirable. However, when a larger vehicle impacts the terminal, then additional energy absorption is required and the further energy-absorbing element provides the additional energy absorption if required. In this way, impacts from different sizes and masses of vehicle can be accommodated.

The components of the energy absorbing end terminal system can be formed of any suitable material, such as metal (e.g. steel). The base member, the post, the bracing strut, the shearing element and/or the rail may be formed of the same material, or different materials. In some embodiments, all components of the system are formed from a metal, such as steel. In addition, the strut may be partially or fully covered by a cowling extending at least partially, and in embodiments fully between the strut, post and base member. The cowling may be partially or fully structural, holding and retaining the post relative to the base member. The cowling may cover the hole between the post and strut, avoiding the potential for objects to be caught in the gap between post and strut. In a reverse collision, extending the end of the cowling distal from the post generally upwards and/or away from the post, may reduce tendency for vehicles impacting from the cowling side of the impact device to rise up over the impact device, which could cause the vehicle to be deflected excessively upwardly, which is undesirable. The base member, the post, the bracing strut and/or the shearing element(s), which together form the impact device, may be connected together by any suitable means, for example by bolts, screws or welding. In some embodiments, one or more parts of the impact device are integrally formed. In some embodiments, the impact device, or even the energy absorbing end terminal system, can be assembled prior to installation, enabling quick installation on site. Alternatively, the system may be assembled in situ. In some embodiments, the impact device itself (or parts thereof) is assembled on the rail. For example, in embodiments wherein the shearing element is received in respective first and second cut-outs in the rail and base member in the pre-impact position, it may be necessary to position the base member on the rail, and align the first and second cut-outs, before inserting the shearing element into the cutouts and securing the shearing element to the base member.

According to a fourth aspect of the invention, there is provided a kit of parts for an impact device, the kit comprising:

at least one shearing element for shearing a rail;

a base member for slidably mounting on the rail; and

an impact post for mounting on the base member. The kit for an impact device may further comprise a bracing strut.

According to a fifth aspect of the invention, there is provided a kit of parts for an energy absorbing end terminal system, the kit comprising:

a rail; at least one shearing element for shearing a rail;

a base member for slidably mounting on the rail; and

an impact post for mounting on the base member. The kit for an energy absorbing end terminal system may further comprise one or more of the following components: a bracing strut, a base plate, a connection piece for connecting the rail to a crash barrier, one or more support posts and one or more energy-absorbing elements.

In addition to the post, additional impact members in the form of absorption and/or guiding means may be provided mounted on the post extending in a direction away from the rail and safety barrier. These may be any convenient shape, for example hollow with a round cross- section, which may vary or may be the same over the height of the absorption means. The hollow cross section allows deformation and thus energy absorption. These may be mounted to each other and/or the post so that, during an off centre impact, as well as or instead of collapsing and absorbing energy, they pivot about each other and/or the post as desired to guide the , vehicle during a collision. The impact members may be one or more hollow 'cans', mounted directly to one another, and to the post by any suitable fixing, for example bolting.

Embodiments of the invention will now be described with reference to the accompanying figures in which:

Figure 1 shows a crash barrier connected to an energy absorbing end terminal system in accordance with an embodiment of the present invention;

Figure 2a is a perspective view of an energy absorbing end terminal system in accordance with an embodiment of the present invention;

Figure 2b is an elevation view of the energy absorbing end terminal system of Figure 2a;

Figure 2c is a plan view of the energy absorbing end terminal system of Figures 2a and 2b;

Figure 3 is a perspective view of a sleeve for an energy absorbing end terminal system in accordance with an embodiment of the present invention;

Figure 4 is a perspective view of a section of a rail for an energy absorbing end terminal system in accordance with an embodiment of the present invention;

Figure 5 is a perspective view of an energy absorbing end terminal system in accordance with an alternative embodiment of the present invention; Figure 6 shows plan views of different embodiments of a blade for an energy absorbing end terminal system in accordance with an embodiment of the present invention;

Figure 7 shows a perspective view of an energy absorbing end terminal system in accordance with an embodiment of the present invention;

Figure 8 shows a perspective view of an energy absorbing end terminal system in accordance with an embodiment of the present invention;

Figure 9 shows a plate for use with an energy absorbing end terminal system in accordance with an embodiment of the present invention;

Figure 10a shows an end portion of a rail for use with an energy absorbing end terminal system in accordance with an embodiment of the present invention;

Figure 10b shows an energy-absorbing element for use with an energy absorbing end terminal system in accordance with an embodiment of the present invention;

Figure 1 1 shows a spacer element for use with an energy absorbing end terminal system in accordance with an embodiment of the present invention; and

Figure 12 shows a crash barrier connected to an energy absorbing end terminal system in accordance with an embodiment of the present invention.

With reference to Figure 1 , an energy absorbing end terminal system 10 is connected to a crash barrier 12 by a connection piece 14. The energy absorbing end terminal system 10 has a length L indicated by an arrow. The system 10 comprises a rail 16, which is inclined such that it extends from the height of the crash barrier 12 down to the ground where it terminates at an end 18. The rail 16 is supported between the crash barrier 12 and its end 18 by a support post 19. The end 18 of the rail 16 is mounted on a base plate 20, which is anchored to the ground. An impact device 22 is mounted on the rail 16, close to the end 18 of the rail 16.

As shown in more detail in Figures 2a-2c, the impact device 22 comprises a base member in the form of an elongate sleeve 24 of substantially rectangular cross section which receives the rail 16 therethrough. The sleeve 24 has a first end 26, which is proximal to the end 18 of the rail, and a second end 28. The sleeve 24 has a lower, ground-facing surface 30 and an opposite upper surface 32. An impact post 34 is mounted on the upper surface 32 of the sleeve 24, towards the first end 26 thereof, and extends upwardly from the sleeve 24 at a substantially perpendicular angle (Θ) thereto. The impact post 34 is constituted by a hollow tube of substantially rectangular cross section, the long sides of the rectangle being parallel with the length of the sleeve 24. In the arrangement shown the post is inclined to the vertical as measured along the longitudinal axis of the rail. In other embodiments the post may be vertical (θ<90°) or inclined at a different angle. The post may be configured to both transfer load to the base member and absorb energy by buckling, for example. The impact post 34 is supported on the sleeve by a strut 36. A first end 38 of the strut 36 is connected to the post 34, close to its top end 42. A second end 44 of the strut 36 abuts the upper surface 32 of the sleeve 24 towards the second end 28 of the sleeve 24, and angle (a) being subtended of about 45°. The base plate 20 has three holes 21 therein, arranged in a triangular pattern, for receiving bolts (not shown) for attaching the base plate 20 to the ground. As shown in Figure 2b, the base plate 20 has a slight bend in the middle, thus allowing the rail 16 to extend upwardly from the ground. The impact device 22 further comprises a shearing element in the form of a blade 46, which extends through the upper surface 32 of the sleeve 24. The blade 46 protrudes above the upper surface 32 of the sleeve 24 and projects into the rail 16. As shown in Figure 2b, a portion of the blade 46 which shears through the rail passes underneath the strut 36. As can be seen more clearly in Figure 3, the upper surface 32 of the sleeve 24 has an elongate first slot 48 therein. The slot 48 extends in the direction of the longitudinal axis of the sleeve 24, towards the second end 28 of the sleeve, and is positioned centrally.

As shown in Figure 4, the rail 16 has a corresponding second elongate slot 50 in an in-use upper surface 52. The second slot 50 in the rail 16 is the same size and shape as the first slot 48 in the sleeve 24, both slots 48, 50 being sized and shaped so as to have a snug fit with the blade 46. The second slot 50 is positioned a short distance from the end 18 of the rail 16, such that when the impact device 22 is mounted on the rail 16, the first slot 48 of the sleeve 24 is precisely aligned with the second slot 50 of the rail 16 so that the blade 46 passes through both slots 48, 50.

Figure 5 shows an alternative embodiment of an energy absorbing end terminal system 100 in accordance with the present invention. The system is substantially the same as that shown in Figure 3, having an impact device 122 comprising an elongate sleeve 124 having a first end 126 and a second end 128, the sleeve 124 being slidably mounted on a rail 1 16. The impact device 122 further comprises an impact post 134 and a supporting strut 136, having substantially the same arrangement as the embodiment shown in Figure 2a. In this case, however, three blades 146 are provided, the blades 146 passing through respective slots in an upper surface 132 of the sleeve 124 and the rail 1 16. The blades 146 are arranged in a parallel fashion, aligned with the longitudinal axis of the rail 1 16 and sleeve 124. A middle one of the blades 146 is positioned slightly closer to the second end 128 of the sleeve 124 than the outer blades. The middle blade passes beneath the strut 136, while the two outer blades are flush with side faces 160 of the strut 136. The outer blades may be supported during shearing by welding them to the side faces 160 of the strut 136. The three-blade arrangement shown in Figure 5 will shear through the rail material at three points, thereby increase the resistance.

Figure 6 shows various embodiments of blades for use in the present invention, each embodiment differing in the shape of the leading or cutting edge. The blade may have a cutting edge which, as viewed from above, is square (Figure 6a), pointed (Figure 6b), rounded (figure 6c), has a flattened point (Figure 6d), is asymmetrical (Figures 6e-6g) or has a number of teeth (Figure 6h).

Figure 7 shows an alternative embodiment of an energy absorbing end terminal system in accordance with the present invention. The system is substantially the same as that shown in Figures 2a-2c and 3 having an impact device 222 comprising an elongate sleeve 224 having a first end 126 and a second end 128, the sleeve being slidably mounted on a rail (not shown). Elements not described are the same as described above. A post 234 is provided extending away from the sleeve 224 in the region of a first end 226 of the sleeve 224, proximal to the end of the rail, and a strut 236 extends from a region of a top end 242 of the post 234 at a first end of the strut 238 to a region of a second end 226 of the sleeve 224, distal to the end of the rail at the second end of the strut 244. In this embodiment, the shearing element, which again is in the form of a blade 246, is positioned beneath the post 234, rather than below the strut 236. As in the embodiment of Figure 5, multiple blades may alternatively be provided.

An additional difference between this embodiment and that shown in Figures 2a-2c is that the sleeve 224 is not closed in cross section, but rather has a generally 'C shaped cross section, with the opening 250 in the lower ground facing surface of the sleeve 224. The sleeve 224 extends around the rail (not shown) at two in-turns 255, which engage with the lower surface of the rail and ensure that the sleeve 224 is retained thereon.

Figure 8 shows a further alternative embodiment of an energy absorbing end terminal system in accordance with the present invention. The system is similar to that described above with reference to figure 7, although this embodiment could be applied to any of the embodiments described herein. Therefore, only differences will be described. In this embodiment a cowling 360 extends over the strut (not shown) from the post 334 to the sleeve 324, so enclosing the space between the strut, post 334 and sleeve 324. This prevents objects from being caught in the generally triangular hole between the post 334, strut and sleeve 324 during an impact. In this embodiment, the in-turns 265 are formed by welding separate flanges to the open ends of a 'LT shaped sleeve 324. Therefore, while the sleeve 324 does not engage itself directly with the rail, the flanges engage with the lower surface of the rail and hold the sleeve 324 onto the rail. Alternatively, the flanges may be omitted, and the sleeve may be 'C shaped in cross-section as shown in Figure 7, while still including the cowl.

Figure 9 shows an elongate metal plate 400 which can be placed into the rail (not shown) in the other embodiments described herein. The plate is mounted to the rail with bolts (not shown) through bolt holes in the rail and bolt holes 410 in the plate 400. The plate 400 includes discontinuities in the form of holes 420. The holes 4210 lie on the path of the blade of the impact device (not shown). The plate increases the energy required to shear the rail/plate assembly, compared to the rail alone. The holes 420 reduce the energy required to shear the plate 400, compared with if it was solid and the holes 420 were not provided. In this way, the energy absorption of the system by unit length can be modified and configured easily by altering the gauge of the metal of the plate and/or by changing the size and/or number off holes 420 per unit length.

Figure 10a shows an alternate end portion 520 of a rail 516 according to an embodiment of the invention. In this embodiment, the rail 516 has an open in-use upper side 525 in the end portion 520, forming a cut-out in the form of a hole therein. Elements not described are the same as described above. Where the rail 516 transitions to a closed cross-section, another cut-out, in the form of a notch 530, is formed. The notch 530 is substantially V shaped, with the apex pointing away from the end portion along the elongate length of the rail 516. During assembly of the system, an impact device (not shown), as described above, is arranged with the blade positioned in the open end portion 520 of the rail 516. The blade can be positioned to abut with and lie partially within the notch 530, or may be positioned within hole formed by the open upper side of the rail 516 in the end portion. In this way, a fully constructed impact device can slide onto the rail during assembly of the system.

Figure 10b shows an energy-absorbing element 550 for use in a system according to an embodiment of the invention. The energy-absorbing element 550 is mounted on a rail 516 and comprises a sleeve 574, which is closed in cross-section, and which conforms to the outer shape of the rail 516 so that it can slide along the rail 516 during an impact. The energy- absorbing element 550 comprises, in the present embodiment, two shearing elements in the form of blades 546. The blades 546 are welded to the sleeve 574 and extend through the sleeve 574 and through the rail 516, through slots (not shown). The slots may each include a notch (not shown) at the leading end, to aid the blade 546 as it starts to shear the rail 516. The relative strengths of the sleeve 574 and the rail 516 are chosen so that the blades 546 shear the rail 516 and do not shear through the sleeve 574 as the sleeve 574 travels along the rail 516 during impact.

Figure 1 1 shows a spacer element 600, which can be positioned between the base plate 20 described specifically in Figure 2a and the impact device according to any of the embodiments described. The spacer element 600 raises the end portion of the rail, and the impact device positioned thereon, up from the ground. Raising the impact device from the ground reduces the possibility that a vehicle will ride up over the impact element and onto the rail.

Finally, Figure 12 shows a crash barrier connected to an energy absorbing end terminal system in accordance with an embodiment of the present invention. Figure 12 incorporates the energy absorbing end terminal system of Figure 7, the rail 516 of figure 10a, the energy-absorbing element of Figure 10b and the spacing element 600 of Figure 11. The barrier could alternatively or additionally incorporate the features of any of the other embodiments, as appropriate. The barrier also comprises additional impact members 650. One of the impact members 650 is mounted to the post 234 of the impact device 222. The next impact member 650 is then mounted to the first impact member 650, a further impact member 650 mounted to that impact member 650, and so on.

The energy-absorbing element 550 is positioned on the rail 516 at a point part way along the rail 516 between the impact device 222 and the barrier 12. A support post 19 is mounted below the rail 516 part way along its length to maintain the rail straight so that the impact device 222 can slide along the rail 516. During a vehicle collision from the, as shown, left hand side, a vehicle first impacts with the impact members 650. These are in the form of hollow cylinders or 'cans' and deform upon impact so providing initial energy absorption. During a glancing or off centre collision, the impact members 650 may also act as guides to maintain the vehicle within the carriageway, rather than the vehicle potentially leaving the carriageway at the side of which the crash barrier is mounted. The force of the impact is also transferred through the impact members 650 to the impact device 222. The post 234 receives the force from the collision and may be designed to allow some degree of buckling. The post is maintained generally in position by the strut 236 mounted between the top of the post 234 and the sleeve 224 of the impact device. The impact device 222 is then pushed up the rail 516, causing the blade 246 to begin shearing the rail 516 (and the internal plate, if provided). The shearing slows the movement of the impact device consistently, so that, after the initial impact with the barrier, the rate of energy absorption flattens out. If the vehicle in the collision is a relatively light vehicle, then the impact device 222 may come to a stop on the rail 516 before the impact device 222 reaches the energy-absorbing element 550, having brought the colliding vehicle to a stop over a length of the rail 516 less than the distance to the energy-absorbing element. However, if the colliding vehicle is a heavy vehicle, then the impact may push the impact device 222 along the rail 516 to the energy- absorbing element 550. When the sleeve 224 of the impact device 222 reaches the energy- absorbing element 550, it abuts the sleeve 574 thereof and the impact device 222 begins to push the energy-absorbing element 550 along the rail 516. The blades 546 of the energy- absorbing element 550 thus also begin to shear the rail 516 as well as the blade 246 of the impact device 222. As the blades 546 of the energy-absorbing element 550 are off-set laterally relative to the blade 246 of the impact device 222, all three blades 246, 546 then act to shear the rail 516, and the energy absorption rate is increased. Thus a heavier vehicle, in which more energy absorption is required during the collision, can be brought to a stop before reaching the end of the rail 516, while a lighter vehicle is not brought to a stop too quickly on the initial portion of the rail 516. If desired, more than one energy-absorbing element 550 can be provided, to provide stepped rates of energy absorption as a vehicle, and the impact device 222 travel further along the rail during an impact.

Claims

1. An energy absorbing end terminal system for a crash barrier, the system comprising a rail having at least one first cut-out therein, and an impact device, the impact device comprising: a base member disposed on the rail so as to be slidable along the rail in a longitudinal direction;

an impact post extending generally upwardly from the base member; and

at least one shearing element extending from the base member,

wherein in an initial pre-impact position the at least one shearing element projects into the at least one first cut-out in the rail.

2. The energy absorbing end terminal system of claim 1 , wherein the or each first cut-out is a hole, a slot, a groove or a notch in a wall or a surface of the rail.

3. The energy absorbing end terminal system of claim 1 or claim 2, wherein the or each first cutout is a slot for receiving the shearing element therethrough.

4. The energy absorbing end terminal system of claim 3, wherein the slot extends in a direction parallel to the longitudinal axis of the rail.

5. The energy absorbing end terminal system of any one of claims 1 to 4, wherein the base member is a sleeve which is configured to receive the rail therethough.

6. The energy absorbing end terminal system of any one of the preceding claims, wherein the or each shearing element is attached to an inner or rail-facing surface of the base member.

7. The energy absorbing end terminal system of any one of claims 1 to 5, wherein the base member comprises at least one second cut-out, wherein the or each second cut-out receives a shearing element therethrough, and wherein in an initial pre-impact position the first and second cut-outs are aligned and the or each shearing element is positioned in said first and second cutouts so as to prevent relative movement of the rail and the impact device in the absence of an impact force.

8. The energy absorbing end terminal system of claim 7, wherein the or each second cut-out is an elongate slot which extends in a direction parallel to the longitudinal axis of the rail.

9. The energy absorbing end terminal system of any one of the preceding claims, wherein the or each shearing element is a blade.

10. The energy absorbing end terminal system of claim 1 1 , wherein the blade has a thickness of from 10 to 20 mm.

1 1. The energy absorbing end terminal system of any one of the preceding claims, wherein the shearing element is formed from a hardened material.

12. The energy absorbing end terminal system of any one of the preceding claims, wherein the impact device further comprises a bracing strut which extends at an angle between the impact post and the base member.

13. The energy absorbing end terminal system of claim 12 when dependent on claim 7, wherein an end of the bracing strut attaches to the base member at a position which is adjacent to, or overlapping with, the or each second cut-out.

14. The energy absorbing end terminal system of any one of the preceding claims, further comprising a base plate for fixing a terminus of the rail to the ground.

15. The energy absorbing end terminal system of any one of the preceding claims, wherein the rail comprises one or more energy-absorbing elements positioned along its length such that, upon vehicle impact, the or each shearing element shears through the energy absorbing elements in addition to the rail.

16. An impact device for an energy absorbing end terminal system, the impact device comprising:

a base member for slidably mounting on a rail;

an impact post extending generally upwardly from the base member; and

at least one shearing element extending from the base member.

17. A barrier system comprising a crash barrier and an energy absorbing end terminal system in accordance with any one of claims 1 to 15.

18. A kit of parts for an impact device, the kit comprising:

at least one shearing element for shearing a rail;

a base member for slidably mounting on the rail; and

an impact post for mounting on the base member.

19. The kit of claim 18, further comprising a bracing strut.

20. A kit of parts for an energy absorbing end terminal system, the kit comprising:

a rail;

at least one shearing element for shearing a rail;

a base member for slidably mounting on the rail; and

an impact post for mounting on the base member.

21. The kit of claim 20, further comprising one or more of the following components: a bracing strut, a base plate, a connection piece for connecting the rail to a crash barrier, one or more support posts and one or more energy-absorbing elements.

22. An energy absorbing end terminal system substantially as described herein, with reference to the accompanying figures.

23. An impact device system substantially as described herein, with reference to the accompanying figures.

24. A crash barrier substantially as described herein, with reference to Figure 1.