WO2013159124A1

WO2013159124A1 - Impact energy management system

Info

Publication number: WO2013159124A1
Application number: PCT/ZA2012/000023
Authority: WO
Inventors: Festus Maina MWANGI; Krishnan Kanny
Original assignee: Mwangi Festus Maina; Krishnan Kanny
Priority date: 2012-04-17
Filing date: 2012-04-17
Publication date: 2013-10-24
Also published as: ZA201500390B

Abstract

The invention provides an impact energy management system for managing impacts in collisions, explosions, and the like. The system includes: granular elements (12), e.g. spheres; at least one resiliently, deformable inner container (14) within which the granular elements are held in a loosely packed arrangement; and an outer casing (16) housing the inner container (14) and having at least one resiliently impact incident wall (16.1) and biasing formations (20) projecting inwardly therefrom. Peripheral regions of the outer casing and/or inner container may be disconnected from each other so that the system forms an open-sided "sandwich" structure. Multiple inner containers (14) may be present and each container may include capsules (22) holding the granular elements (12). Interface layers, also with biasing formations (20), may be provided between the inner containers (14). Also provided are articles of manufacture which include the system, for example a bumper for a motor vehicle, a traffic light assembly and a tollgate crash barrier.

Description

IMPACT ENERGY MANAGEMENT SYSTEM

Technical Field

THIS INVENTION relates to an impact energy management system.

Background Art

In numerous applications across a broad spectrum of human endeavour there exists a need to mitigate, attenuate or otherwise manage the destructive effects of impacts. Systems are known for absorbing or dissipating the energy incident upon an article of manufacture when an impact, crash or explosion affects said system.

United States Patents Documents US 3,529,306 A and US 3,629,882 A in the name of Thorne, EP disclose a helmet and other articles of manufacture which comprise a number of plunger-shaped units displaceably arranged in direct contact with a plurality of solid round pellets.

German Patent Document DE 36 42 979 Al in the name of BMW AG relates to a motor vehicle bumper comprising an outer body which defines a single, inner elongate ridge. The ridge abuts an internal compartment which can be filled with granulate material.

PCT Patent Document WO 2006 081942 in the name of Audi AG & Jansen, J discloses a deformation element for the front area of a motor vehicle, which includes cylindrical bodies or balls disposed behind a flexible shell. Inner surfaces defined by the flexible shell are substantially flat (before deformation) and the bodies or balls are in direct contact with these flat surfaces.

Japanese Patent Document JP 2008 147417A in the name of Canon Electronics Inc. discloses a buffer structure for a portable electronic device. Granules are contained within an outer shell, or within sub-compartments of the shell. The shell (or sub-compartments) define ribs which are in direct contact with the granules. The granules are magnetised and are, accordingly, not loosely associated with one another.

There are on-going demands for improvements in the efficiency, versatility and cost- effectiveness of impact energy management systems, and for alternatives to existing such systems. In addition, many existing systems operate sacrificially, that is they can be used only once to protect against an impact, are damaged by that impact and cannot be restored to their pre-impact condition. A need exists for impact energy management systems which have different and efficient modes of operation, and which, in defined circumstances, can recover, to some extent, their pre-impact condition.

Definitions

For purposes of the present specification, the term "energy management" includes reference to absorption, dissipation, displacement, attenuation and/or redirection (and combinations thereof) of kinetic energy involved in an impact.

In addition, the reader of the present specification should interpret the word "impact" in a broad manner, to take in any type of impact by any type of material, body, fluid or wave. The meaning of the word shall include, but not be limited to, reference to an impact by a solid body against an impacted object (such as an impact associated with a collision) but shall also include reference to impacts by shock waves or blast waves, for example shock waves associated with explosions.

As used herein, the term "transverse" is intended to be interpreted broadly, to mean lying across or crosswise, and does not necessarily imply lying perpendicularly crosswise.

As used herein, the term "outer casing" is intended to be interpreted broadly, and does not necessarily require that the casing define a cavity, or that it enclose a space. Thus, while the term can refer to a container or enclosure, it can also refer to a flat, rounded or curved skin, plate or partition, such as a bumper fascia, or to an article of manufacture comprising two such skins, plates or partitions disposed in a mutually spaced relationship to each other and configured as the outer layers of a "sandwich". Such a sandwich may be of open or closed configuration, that is, the skins, plates or partitions of the outer casing may be separate from one another or may be partially or fully connected to each other about their outer peripheries.

For purposes of this specification the terms "dispersive angle" and "dispersion angle" refers to a dispersion angle Θ as used in granular mechanics, and include reference to the deviation of an impact force vector away from its incident direction. For present purposes the dispersive or dispersion angle Θ lies in a range from 0° > Θ > 90°, in which 0° may be perceived to represent a system with a flat surface (back layer) with no biasing formations, while 90° represents a dynamic transitional phase just before cratering-like phenomena and induction of secondary inter-granular collisions within the capsules. Disclosure of Invention

According to a first aspect of the invention there is provided an impact energy management system which includes:

a plurality of impact managing granular elements, at least one of which is of a predetermined, regular geometric shape;

at least one resiliently deformable inner container within which the granular elements are held in a loosely packed arrangement; and

an outer casing housing the inner container and having at least one resiliently deformable impact incident wall and a plurality of biasing formations projecting inwardly therefrom, which are operable to act on the inner container in response to an impact force acting on the impact incident wall, causing inward deformation thereof, thereby to cause displacement of the granular elements within the inner container in directions transverse to the direction of application of the impact force.

Portions of at least one component selected from the outer casing and inner container may define peripheral regions that are disconnected from each other, thereby to expose the interior of such component so that the system forms an open-sided "sandwich" configuration.

For example, the outer casing may include a face formation and a rear formation mutually spaced from each other and disconnected from each other.

Instead, the outer casing and/or inner container or containers may be closed. For example, the inner container can be substantially entirely encased within the outer casing.

The inner container may have a plurality of capsules holding the granular elements. The system may include a plurality of inner containers, and at least one interface layer may be mounted between said inner containers. The interface layer or layers may have a plurality of biasing formations projecting inwardly from at least one side thereof, typically both sides. The biasing formations may be operable to act on at least one of the inner containers in response to an impact force acting on the impact incident wall of the outer casing.

The inner container(s), capsules and other components of the system may define interchange means for exchange of fluid between inside and outside regions thereof. Additionally, the outer casing may include pressure regulating means for regulating pressure inside the outer casing. The interchange means and/or pressure regulating means may be provided, at least in part, by valves, apertures, passages and/or vents defined through the component(s) concerned. The granular elements may be spherical in shape. In selected embodiments at least some of the granular elements may have a density which varies across their cross-section. For example, the granular elements may be hollow.

The biasing formations projecting from the outer casing or the interface layers may be part-spherical in shape, of generally the same diameter as the granular elements, and may be arranged on the outer casing and interface layers in a predetermined manner to form, in combination with at least some of the granular elements, a configuration approximating a Bravais lattice structure, due tolerance being allowed for separation of the biasing elements and granular elements from one another by the material of the, or each, inner container. The, or each, inner container may be located within the outer container in an arrangement wherein, in unstressed configurations of the outer casing and the inner container, a space is defined between the, or each, inner container and the outer casing into which the inner container or containers can expand when the outer casing deforms inwardly as an impact force is applied to the outer casing, in use. At least some of the inner containers and capsules may each have a membranous wall with elastic properties.

At least a portion of the outer casing, or of each inner container, may be laminated, comprising a plurality of sub-layers. The sub-layers may be arranged in displaceable abutment with one another, that is they may abut one another without being bonded to one another. Instead, or in addition, some of the sub-layers may be bonded to one another.

The impact energy management system may define a regular array of inner containers or capsules. The inner containers or capsules making up the array may be spatially separated from one another.

Each inner container and/or capsule may define a uniform cross-sectional footprint as it extends inwardly from the impact incident wall of the outer casing. Instead, each inner container and/or capsule may vary in cross-sectional footprint. Thus, each inner container and/or capsule may taper in one or more directions, becoming thinner or thicker or having a complex shape.

Each inner container or capsule may define a long, major axis and a shorter, minor axis, and the relative ratio of the lengths of the two axes and their alignment relative to the impact incident wall of the outer casing may be predetermined with reference to a design load anticipated to be experienced by the system and a space available for occupation by the system. Thus, the major and minor axis can interchangeably be dimensioned and/or oriented depending on the particular design load and space. For the same volumetric dimensions, namely (i) the surface area of impact incidence interface between an impactor and the system and (ii) the total through thickness of the layers of granular elements, it may be necessary to have only a single inner container or several smaller capsules. The total through thickness of the granular elements is dependent on the magnitude of the design impact load.

The impact energy management system may be characterised by a dispersive (or dispersion) angle exhibited by the granular elements following impact on the impact incident wall of the outer casing, in use, which falls in a range from 0° > Θ > 90°, preferably in a range between 40° to 80°. Most preferably, the dispersion angle Θ is 63.43°.

Any cavities defined by the outer casing or by the inner containers or capsules may be at least partially filled with at least one substance selected from the group consisting of the following, or a mixture thereof: compressible fluids; sparingly compressible fluids; aerosols; suspensions; non-Newtonian fluids; semi-solids; and solids; provided that said substance shall have lubricating properties.

Thus, the inner containers, the capsules, and the outer casing may be partially or completely filled with the above substance(s), and/or the granular elements may be partially or fully engulfed in said substance(s).

In other embodiments of the system, a lubricant composition may be applied to surfaces of the granular elements and the inner containers and/or capsules.

In those embodiments where there are a number of inner containers or capsules present, these need not be identical to one another (although in certain embodiments they are identical). Accordingly, the inner containers or capsules may differ in shape, dimension and/or configuration from one another. They may also be arranged in a regular array or in a wide variety of different positions relatively to one another. Such differences may be designed into the system having regard to different applications of the system and different purposes and expected impact forces for a given part of the system.

According to a further aspect of the invention there is provided a post assembly which includes:

a post;

an impact energy management system as described herein, said system configured to surround at least a portion of said post; a functional formation connected to tne post, tor periormmg a design function of the post assembly; and

spring means mounted intermediate the functional formation and the system, for absorbing forces transmitted to the functional formation by collision of a vehicle with the post assembly.

The post assembly may further include damping means for damping oscillations of the spring means. The functional formation may, without limitation, be selected from the group consisting of a traffic light cluster, a street light, a sign, and an advertisement. In other words, the post assembly may be traffic light assembly, a street light, a signpost, or an advertisement assembly. Many other functional formations may form part of the post assembly, as will be appreciated by one skilled in the art. Any type of functional formation required to be elevated above a substrate by a post can be selected for inclusion in the assembly.

According to a further aspect of the invention there is provided a crash barrier which includes:

an impact energy management system as described herein;

guide means for guiding displacement of at least one interface layer of said system in the event of an impact; and

engagement means mounted on the interface layer, for displaceable engagement with the guide means.

In a further aspect, the invention provides a component for a motor vehicle, which includes an impact energy management system as described herein. The component is typically a bumper, door or other impact-prone component of the motor vehicle.

According to a further aspect of the invention there is provided an article of manufacture comprising an impact energy management system, as described herein, combined with a device designed for use in an application selected from the group consisting of: automotive (e.g. bumpers, doors), aerospace (e.g. crash landing mechanisms), personal safety (e.g. body armour, helmets), packaging, shipping and freight, armour, military, domestic appliances (e.g. outer shells or housings), construction (e.g. earthquake management), roads infrastructure (e.g. roadside guards), entertainment, sports and recreation (e.g. punching bags, playground paving), communication (e.g. cellphone housings) and banking (e.g. security of automated teller machines). According to yet a further aspect of the invention there is provided a method of assembling an article of manufacture which includes the steps of: manufacturing at least one impact energy manufacturing system as described herein, selling it, separating it into smaller functional units after sale, and introducing at least one of the smaller units into the assembly of said article of manufacture. The type of system which is suitable for use in such a method is an open-sided "sandwich" configuration in which the inner container is compartmentalized or has a number of capsules.

In addition to the applications described above, the system of the invention lends itself to numerous other applications where an article of manufacture may be susceptible of, or prone to, impacts, or where management and/or mitigation of the effects of an explosion are required. The invention described and illustrated herein therefore has industrial applicability, as will appear more clearly from the following sections.

Brief Description of Drawings

The invention will now be described with reference to the accompanying diagrammatic drawings, in which like reference numerals are used correspondingly throughout to indicate like or similar features. In the drawings:

Figure 1 shows, schematically, a cross-sectional side view of an impact energy management system according to the invention, being of open-sided "sandwich" construction and having a compartmentalized inner container;

Figure 2 shows, schematically, a perspective cut-away view of the system shown in Figure 1;

Figure 3 shows, schematically, a cross-sectional side view of a closed or encased impact energy management system according to the invention;

Figure 4 shows, schematically, a cross-sectional side view of a system according to the invention, the system in this case having dual inner containers stacked one above the other and separated by an interface layer;

Figure 5 shows, schematically, a cross-sectional side view of a system according to the invention, for explaining the operational dynamics of such a system when it is subjected to an impact, in use; Figure 6 shows, schematically, an exploded view of a rear bumper for a motor vehicle, the bumper including an impact energy management system according to the invention;

Figure 7 shows, schematically, a side elevation of a traffic light assembly according to the invention;

Figure 8 shows, schematically, a side elevation and plan view of a cylindrical interface layer of the traffic light assembly shown in Figure 7; and

Figure 9 shows, schematically, an exploded view of a tollgate crash barrier according to the invention.

Modes for Carrying out the Invention

With reference to the drawings, an impact energy management system, in accordance with the invention, is indicated generally by the reference numeral 10. The system includes a plurality of impact managing granular elements 12, of a predetermined, regular geometric shape. Typically the granular elements 12 are spherical and of constant diameter. The granular elements 12 may have numerous other predetermined geometries (not shown). However, use of spheres for the granular elements 12 is preferred since spheres are considered to enhance buildup of regular transient virtual reinforcement structures, to allow more degrees-of-freedom of movement, and to limit granular interlocking phenomena.

Dimensions of the granular elements 12 can vary widely. Typically, however, the constant diameter of a spherical granular element lies in a range from 1mm to 100mm, depending upon the application. In one sample embodiment, the elements 12 have a diameter of approximately 16mm and are manufactured from glass, a material typically known to exhibit very low impact strength.

The granular elements 12 may be manufactured from a wide variety of materials, for example glass, polymers, metals, ceramics, and/or composite material(s) thereof.

The granular elements 12 can have density that varies across their cross-section. For example, they may be hollow. In other embodiments (not shown) they may have a core material which differs in density from the material of their outer shell. Thus, they may have a less dense core manufactured from, for example, rubber, polystyrene, etc. If r and R are, respectively, the internal and external radii of a typical hollow, spherical granular element (or one having a less dense core), there is a ratio a = r/R for which the energy absorption and/or dissipation per unit weight of the granular element is optimal. This value may be determined experimentally or by way of simulation.

Important material properties for the granular elements 12 include relatively low density (to achieve lightness), impact and compression strength, resilience, coefficients of restitution, energy absorption and hardness, heat- and electrical resistance (or conductivity) depending on design specifications and the contextual working environment.

The system 10 has at least one resiliently deformable inner container 14 within which the granular elements 12 are held in a loosely packed arrangement. In the container 14 the granular elements 12 are not fixed, bound or fastened to one another.

Typically the inner container 14 has a membranous wall which should be resiliently deformable and preferably should have elastic properties. It may be manufactured from an elastomeric material. Important material properties for the inner container 14 include, but are not limited to, tensile strength, compression set, allowable working temperature and elongation to rupture. Other properties, including resistance to chemical degradation, may be important depending on the application. The thickness of the membranous wall of the inner container 14 is typically uniform throughout its profile with the optimal thickness depending on a number of factors, including the size of the granular elements 12 and the design impact energy, and the chosen lattice structure of biasing elements 20 (discussed further below).

Unless the context indicates otherwise, the term "core" is used herein for convenience to refer to an inner container 14 in combination with the granular elements 12 which it contains. In some embodiments the inner container 14 is compartmentalized and/or contains separate substructures, e.g. capsules (discussed further below). These sub-structures also fall within the ambit of the term "core". The reference sign C is used in Figure 1 to indicate the core.

The system 10 also has an outer casing 16 which houses the core(s) C. In some embodiments the outer casing 16 is injection moulded from a mouldable material and has a resiliently deformable impact incident front wall or face formation 16.1. Depending upon the particular embodiment concerned, the following may also be present: an opposed rear formation or wall 16.2, side walls 16.3 and end walls 16.4. The rear formation 16.2, when present, is relatively more rigid than the face formation 16.1 and is generally thicker than it.

The wall thickness of the outer casing 16 may be constant throughout or may vary according to requirements. Of prime importance is that the face formation 16.1 should be able to undergo and withstand large deflections elastically, yet retain its profile before and after the impact loading cycle. It is designed in such a way that its ability to absorb impact energy does not compromise its ability to conform to the changing profile of the impacting object and of the core C. Hence it is designed to have good flexural yield strength and elasticity, and to be capable of accommodating very large localised deflections without failure by way of cracking or fracture, and without forming permanent dents. Thus, it must be capable of recovering from physical deformation after the load is removed. Its wall thickness needs to be limited as far as practically feasible.

The Applicant has identified critical material properties for the outer casing 16 as being lateral, impact and tensile strength, with other material properties including, but not being limited to, heat resistance or conductivity, resistance to environmental degradation, and predetermined electrical properties in certain applications.

The shape and configuration of the outer casing 16 may vary depending upon the intended application of the system 10. It can be open-sided as shown in Figures 1 and 2, giving rise to an open-sided "sandwich" configuration of the system 10, or it may take the form of a closed container as shown in Figure 3. In the system 310 of Figure 3 the core C is completely encased within the outer casing 16.

In embodiments where the outer casing 16 is open-sided, it can have face- and rear formations 16.1, 16.2 which are mutually spaced from each other and which are either only partially connected to each other or are entirely separate from one another. Thus, a separate face laminate layer 16.1 and a separate back laminate layer 16.2 may be provided. Furthermore, the outer casing 16 may consist only of the face formation 16.1 (without a rear formation 16.2).

A plurality of biasing formations 20 project inwardly from the face formation 16.1 and other parts of the outer casing 16 and are operable to act on the inner container 14 in response to an incident dynamic impact force F acting on the face formation 16.1. In certain modes of the invention the biasing formations 20 bear upon and act directly on the inner container 14. The invention also encompasses a configuration (not shown) whereby layers, membranes, films or other structures may be interposed between the biasing formations 20 and the inner container(s) 14, so that the biasing formations 20 act on the inner container(s) 14 through the interposing medium.

For improvement of the shear strength of the biasing formations 20, a filleted plateau may be provided between adjacent biasing formations 20. This is best seen in Figure 3.

In preferred embodiments, the biasing formations 20 are hemispherical in shape, are of generally the same diameter as the granular elements 12, and are positioned on the outer casing

16 in a predetermined manner to form, in combination with at least some of the granular elements 12, a configuration approximating a Bravais lattice structure. It can be difficult to achieve a precise Bravais lattice structure because the membranous material of the inner container 14 (and in some cases the capsule 22) intervenes between the granular elements 12 and the biasing formations 20, and due allowance is made for this. Accordingly, for purposes of this specification, all references to Bravais lattice structures do not imply precise Bravais structures, but general or approximate such structures.

In selected embodiments the biasing formations 20 are mounted such that slightly more than half of their respective volumes are exposed. This mounting arrangement applies, for example, where the biasing formations 20 are formed from spheres set into a component. Exposing more than half of the spheres takes account of a fundamental correlation between radius and length of all sides of the cube in Bravais cubic lattice structures.

The Bravais lattice structure may be selected from a Body-Centred-Cubic (BCC) structure, a Face-Centred-Cubic (FCC) structure and/or a Simple-Cubic structure. Numerous other arrangements of the biasing formations 20 (including random arrangements) may be used depending on the application. The arrangement of the biasing formations 20 on the front wall 16.1 and the rear wall 16.2 of the outer casing 16 may be a mirror representation of each other, or in an alternative embodiment, may be different. Biasing formations 20 may also be provided on the side walls 16.3 and/or end walls 16.4, if present.

The inner container 14 can be sub-divided or compartmentalized into a plurality of capsules 22, each of which holds a number of the granular elements 12 in a loosely packed arrangement. The capsules 22 typically have membranous walls with elastic properties. These walls may be manufactured from an elastomeric material, for example, silicon rubber, and their deformation behavior can be modeled using the neo-Hookean model. Use of an elastic or resiliently deformable membrane can improve flexibility or degrees-of-freedom of the encapsulated granular elements 12 and enhance dimensional recovery of the system 10 after loading cycles.

In the embodiments shown in Figures 1 and 2 the capsules 22 are mutually spaced from one another, so that spaces or cavities 24.1 are defined inside the inner container 14, into which side walls 26 of the capsules 22 can deform when the impact force F is applied. It should be noted here that other spaces or cavities can be defined in different embodiments. The outer casing 16 may define an internal space or cavity 24.2 between itself and the inner container 14. The core C is located within this cavity 24.2 in an arrangement wherein, in unstressed configurations of the outer casing 16 and the core C, sufficient space is defined between the core C and the outer casing 16, into which the core C can expand or deform when an impact force F is applied to the front wall 16.1 of the outer casing 16, in use. As shown in Figure 1, voids 24.3 can also be defined by and between the granular elements 12 inside the capsules 22. These can, for example, occur as a natural consequence of the packing of the granular elements 12. In preferred embodiments these voids 24.3 are kept to a minimum. Thus, the extent of filling of the capsules 22 is such that all the capsules are full with minimal stretching of the membranous walling.

The capsules 22 do not necessarily have to be spaced from one another and can be arranged in abutment with one another.

The illustrated embodiments show capsules 22 which are regularly shaped, dimensioned and configured (having a circular cross-sectional profile), and which are arranged in a regular array. However, in other embodiments (not shown) the capsules can be differently shaped, dimensioned and configured from one another and can be arranged in a wide variety of regular, irregular or random positions within the inner container 14. These differences can be implemented by predetermined design based on intended function and placement of the capsules 22 for a particular application.

Packing density in the cores C or in the array of compartments or capsules 22 may vary according to design specifications. Preferably any pre-stretch should be evenly distributed throughout the cores C.

Each core C can take the form of a "sub-sandwich", comprising two spaced elastomeric sheets or membranes 14.1, 14.2, and a "filling" of perpendicularly oriented cylindrical compartments serving as the capsules 22 encapsulating the granular elements 12. Cores C can be open-sided if compartmentalized in this way, i.e. the sheets or membranes 14.1, 14.2 do not have to be connected to each other along their peripheral edges or regions. (These peripheral regions or edges are best seen in Figure 2, indicated by reference numeral 27.) The sheets or membranes 14.1, 14.2 may, accordingly, be connected to each other only by the compartments or capsules 22 that are mounted between them. Such a core C would typically be found in the open-sided "sandwich" structures of the system 10 shown in Figures 1 and 2.

Instead a core C may be closed. A closed core C may be tapered as shown in Figure 3, having a substantially "lozenge"-shaped cross-section.

The system may include a plurality of inner containers 14 (and hence of cores C). For example, the embodiment of the system 410 shown in Figure 4 includes two cores C which are stacked one above the other. As a second example, the system 710 shown in Figure 7 has two concentrically arranged layers of cores (not shown) arranged one inside the other. As a third example, the system 910 shown in Figure 9 has a series of cores C arranged linearly, one in front of the other.

One or more interface layers 28 can be provided when there are multiple inner containers 14. The interface layer or layers 28 have biasing formations 20 projecting inwardly from one or both sides (typically from both sides of each interface layer). The biasing formations 20 of the interface layers 28 are similar to those projecting inwardly from the impact incident wall 16.1 of the outer casing 16.

The surface texture of the granular elements 12 can be optimised either by coating them with suitable lubricant or by customising them to a predetermined optimal coefficient of friction. Also, a layer of lubricant composition can be applied to internal surfaces of the inner containers 14 and/or capsules 22. Lubrication can enhance reflex-action-like responsiveness of the system 10 while in use, and also provide for dimensional recovery of the system after loading cycles.

At least one type of fluid (not shown) can be present in the impact energy management system 10. The fluid can completely engulf the inner containers 14, capsules 22 and/or granular elements 12 or it may only partially bathe them. In one embodiment the fluid (not shown) is a sparingly compressible- or incompressible fluid. As the particular application may demand, a- suspension (e.g. a non-Newtonian fluid), a semi-solid (e.g. grease) or even a solid lubricant (e.g. graphite powder) may serve as the fluid. Components and spaces of the system 10 may also be more simply designed to contain compressible fluids, e.g. air, aerosol, or a particular gas. There may be a number of different fluids present inside different components and spaces of the impact energy management system 10, each fluid having different properties. The fluid or fluids may either be compressed or may be present at atmospheric pressure, or any combination thereof.

In certain embodiments the fluid has lubricating properties. In other design applications, friction as an energy dissipating mechanism may be harnessed by omitting all or part of the fluids or other lubrication means.

In preferred embodiments (not shown), fluid interchange means are provided for exchange of fluid between components of the system 10. For example, one or more apertures may be defined through a wall 26 of each capsule 22 and/or a wall of the inner container 14, so that fluid interchange may take place between interior spaces 24.3 of each capsule, interior spaces 24.1 of the inner container 14, and interior spaces of the outer casing 16. The fluid interchange means are provided so that fluid can move within the system 10 and pressure can equalise between its regions. Similarly, in preferred embodiments the outer casing 16 defines pressure regulation means, for example a vent passage (not shown), for equalising pressure inside and outside the outer casing 16.

Portions of the outer casing 16, inner containers 14, capsules 22 and interface layers 28 may be laminated, that is they may comprise several sub-layers, sheets or membranes (not shown). These sub-layers may be bonded to one another. Instead, they may be unbonded, that is, they may abut one another in a loose or displaceable fashion so that, for example, they can slide over one another in use of the system 10. It is believed that displaceable (non-bonded) sublayers like this can assist to instigate discontinuity in an impulsive impact energy wave.

Additionally, boundaries or interfaces between the cores C and any laminating layers, sheets, interface layers 28, or components of the outer casing 16 may be completely non- bonded, partially bonded, or completely bonded.

In use, the impact incident front wall 16.1 is deflected inwardly when an impact force F is applied to it, causing the biasing formations 20 to be displaced inwardly. The biasing formations 20 of the front wall 16.1 and the opposed rear wall 16.2 (and, where applicable, those of the interface layer 28) act on the inner container 14 and the spheres 12 contained therein, causing elastic deformation of the core C and displacement of the spheres 12 in a direction T which can be transverse to or, in some cases, substantially perpendicular to, the direction of application of the impact force F. The anticipated altered shape of the inner container 14 when it is acted upon by the front wall 16.1 when deflected inwardly, is shown by the broken lines in Figure 3. It will be appreciated that the side walls 16.3 and the end walls 16.4 of the outer casing 16 may be displaced outwards in response to the front wall 16.1 being deflected inwardly.

In Figure 5, reference numeral 510 indicates a simplified scheme for illustrating the perceived operational dynamics of a system provided by the invention. In other words, the drawing illustrates the various granular- and other dynamics which are understood by the Applicant to take place during operation of the system. Note, however, that the Applicant does not wish to be bound by any particular theory in this regard.

When the force F acts on the impact incident wall 16.1, it is thought that the hemispherical biasing formations 20 provide an induced boundary condition effective to rearrange the packing of the encapsulated spherical granular elements 12 from their generally random packing to an approximation of a particular lattice arrangement. The biasing formations 20 are thought to produce a reactive impulse wave in response to the one incident on the front wall 16.1. It is thought that a series of instantaneous virtual reinforcement lattice structures 34 are set up. The granular elements 12 interact with each other in a variety of modes of mechanical granular dynamics, for example by spinning, rotating, sliding, by elastic and/or inelastic collisions, and/or by the shearing of granular layers. These modes are indicated generally by reference numeral 36. In this way the granular elements 12 act individually and en masse to transfer, absorb, redirect and/or dissipate the force F. A pseudo-plastic, bulk granular fluid flow can be set up in directions T which are angled relatively to the direction of the force F, i.e. transverse to it. Further absorption and/or dissipation of the impact force F typically takes place by elastic or resilient deformation of the outer casing 16, the inner container 14, the capsules 22 and the granular elements 12. The Inventors have established by experiment that force acting on the rear formation or back laminate layer 16.2 is reduced relative to the incident dynamic load F. For instance, in an experiment involving an impact velocity of 13.88 m/s (50 km/h), a maximum residual force in the region of 188N was recorded at the rear formation (a "back plate"), compared to an incident force of 14,715N. This represents a significant "shielding" against the impact force. The modes of absorption and dissipation described above (as well as other modes of granular mechanics) may be selectively targeted during design of systems according to the invention, with certain modes being favoured over others depending on the space available for implementation of a given design, and other factors such as cost.

In preferred embodiments of the invention (not shown), the dispersive or dispersion angle exhibited by the granular elements 12, after an impact on the impact incident wall 16.1, has a value, ideally, of 63.43 degrees as measured from the axis of impact vector incidence. The dispersive angle can be adjusted by varying the signature spacing δ (reference symbol not shown) between adjacent biasing formations 20 and between adjacent granular elements 12.

Also, the system 10 can be designed with the aim of achieving a displacement quotient of approximately 0.5. The displacement quotient is a measurement of the "squashing" of an inner container 14 or capsule 22 for a given impact, and is arrived at by dividing the compressive displacement along the axis of impact vector incidence (the Z-axis in Figure 5) by the displacement associated with outward expansion (along the Y-axis in Figure 5). These preferred ranges and measurements were arrived at based on insights of the Inventors into the biomechanics associated with a human arm engaged in catching a free-falling object (pivoting at the shoulder and elbow).

In Figure 6 a rear bumper for a motor vehicle is shown in exploded form and is indicated generally by reference numeral 40. The bumper 40 integrates an impact energy management system according to the invention. An outer casing 16 having an open-sided "sandwich" configuration consists of a face formation or fascia 16.1 and a rear formation or back laminate layer 16.2. The fascia 16.1 and the back laminate layer 16.2 each include multiple rows of inwardly projecting biasing formations 20.

A core C is provided, containing spherical granular elements (not shown) or, in some embodiments, capsules (not shown), within which the granular elements are held. The core C is shaped, dimensioned and configured to conform to the inner aspects of the fascia 16.1 and back laminate layer 16.2, and to fit snugly between them.

For feeding the granular elements into the core C, or emptying them out as the case may be, an aperture (not shown) is defined through the inner container 14 and closed off with a screw cap 41.

In this embodiment the biasing formations 20 are only distributed over those areas of the fascia 16.1 and the layer 16.2 which are designed to be in contact with the core C. The biasing formations 20 are hemispherical and are so arranged so that, within practical limits, a Bravais Body-Centred-Cubic (BCC) lattice structure is formed in combination with the granular elements contained within the core C.

Ancillary components of the bumper 40 are shown. A bracket 42 serves to reinforce the bumper and to interface between the bumper 40 and the motor vehicle (not shown) onto which is it mounted. Reference numerals 44 indicate representative fasteners for facilitating this mounting.

The features and configuration of the bumper 40 can be extended to the front bumper of a motor vehicle and to other components and panels of a vehicle, for example the doors. Profiling, finishing, specification of dimensions, and materials selection are subject to alignment with particular vehicle models and makes and to applicable statutory and regulatory requirements.

Systems provided by this invention allow manufacturing in a wide variety of different ways. Firstly, a variety of shapes, sizes and configurations of inner containers 14, cores C and capsules 22 can be designed according to need. Secondly, variation can be achieved by subdividing or cutting to size a compartmentalized core (that is, one which has separate internal capsules 22 or other compartments). In this manner, a single, monolithic core can be cut up into separate pieces as required at a point of assembly, or a core which does not meet specification can be trimmed and adjusted to fit correctly. Thus, compartmentalized cores (and/or systems incorporating such cores) can be manufactured in slabs, tablets, boards, tiles, panels, sheets or rolls, transported elsewhere and only cut into separate pieces as needed at the point of assembly. Thus, the primary functional difference between the open-ended and encased sandwich structures relates to limitations and scope for extending or partitioning them along the three conventional primary co-ordinates (x-, y-, and z-axes). The open-ended sandwich configuration allows extension and partitioning; the sandwiched product can be manufactured as one big unit and then partitioned into smaller sections as needed, or vice versa. By contrast, the enclosed or encased sandwich configuration is limited to the original size as manufactured.

Compartmentalization of the core is expected to be important in the automotive industry, for example in the manufacture of bumpers, owing to critical dimensional tolerances typical of that industry.

With appropriate adjustments to dimensions and shape, safety helmets can be made following the same broad configuration used for the bumper 40.

Figures 7 and 8 illustrate integration of the invention's system into a traffic light assembly 46. The traffic light assembly 46 is one variation of a general post assembly provided by the invention. The assembly 46 includes a post 48; an impact energy management system 710 which surrounds a lower portion of said post 48; a functional formation 50 (in this case a cluster of traffic lights) connected to the post 48; and spring means 52 mounted intermediate the traffic light cluster 50 and the system 710.

The spring means 52 are provided for absorbing forces transmitted to the light cluster 50 upon collision of a vehicle with the assembly 46. The spring means 52 can, for example, include a coil spring comprised of spring steel or otherwise a resiliently deformable, elongate member comprised of polymeric material, or other appropriate spring means. Additionally, damping means (not shown) can be provided for damping oscillations of the spring means 52 and the lights cluster 50 after an impact. Such damping means may, for example, involve fluid- or friction- based dampers of conventional type. In certain embodiments the spring means 52 are completely engulfed in a damping fluid. A corrugated tube or boot 54, configured concertina- fashion, surrounds the spring means 52 and may have elastic properties. It is clamped at upper and lower end portions to the post 48.

The system 710 is similar to the system 10 except that the components of the system 710 are arranged concentrically around the post 48. The face formation 16.1 is cylindrical in this instance. The rear formation (not shown) is also cylindrical and is positioned inwardly of the face formation 16.1, closer to the post 48. In preferred embodiments the rear formation is mounted flushly around a cylindrical collar or spacer (not shown) that serves to increase the functional diameter of the post 48, thereby increasing the active surface area of the reaction-force-vector during accidental impact of a vehicle into the traffic light assembly 46. To reduce material usage, elongate cylindriform rebated portions or cavities can be defined within the cylindrical wall of the collar, running its entire length.

Between the cylindrical face formation 16.1 and the cylindrical rear formation (not shown), two layers of cores (not shown) are arranged. An inner cylindrical core layer is surrounded by an outer cylindrical core layer. Each core layer consists of two semi-cylindrical half-shells, which, when married to each other, form a cylindrical core. The half shells of the core can be of the type shown in Figures 1 and 2, being open-sided i.e. compartmentalized (associated with an open-sided "sandwich" structure), or of the type shown in Figure 3, being closed (associated with an encased "sandwich" construction).

An interface layer 828 (not shown in Figure 7) separates the aforementioned two layers of cores.

Both sides of the interface layer 828 as well as the interior (or core-facing) sides of the cylindrical face formation 16.1 and the cylindrical rear formation are provided with arrays of hemispherical biasing formations facing towards the cores and arranged to emulate, as far as practically feasible, a Bravais Body-Centred-Cubic (BCC) lattice structure layout when interacting with the spherical granular elements in the cores (not shown).

Reference numeral 56 indicates a pedestrian-operable control box as found in existing traffic light installations.

The features of the traffic light assembly 46 can be adapted for application in other structures involving poles or posts, for example: street-lighting posts, road signposts, advertising posts, protective poles (e.g. for protecting pumps at service stations), structures along a roads infrastructural network, highway barrier posts, general safety posts and guards, etc.

The functional formation 50 accordingly need not be a traffic light cluster and in other embodiments of the invention it may be a light (for example a street light), a sign, an advertisement or any other formation typically mounted on a post and performing a function by design.

Turning to Figure 9, reference numeral 58 indicates generally a crash barrier, specifically a crash barrier for use in the management of impacts occurring near tollgate booths. The features of the barrier 58 can be transferred to crash barriers for other applications. The barrier 58 includes an impact energy management system 910 as described herein. At least two separate interface layers 928 are provided, although only two of these are shown in Figure 9. The barrier 58 further includes guide means in the form of spaced mounting rails 60 which define inside grooves or channels 62 adapted to guide backward and forward translational movement of the interface layers 928 (and other parts of the system 910) during an impact, that is, to guide the active deformation of the system 910, in use. The rails 60 can be fixed to a road either by means of fasteners (not shown) or by being embedded in the paving material. The interface layers 928 have pins 64 or other means for connecting to roller blocks 66. Each roller block 66 includes roller bearings on three sides. In use, the roller blocks 66 fit into the channels 62 defined by the rails 60, so that the interface layers 928 engage with the rails 60 for horizontal displacement along the rails 60. The roller blocks 66 are held captive within the channels 62 but remain free to roll backwards and forwards to facilitate movement of the interface layers 928 and other parts of the system 910, during an impact event.

The crash barrier 58 includes multiple cores C, although only one is shown. The number and configuration of cores C may be varied according to the application. The cores C fit between the face laminate layer 16.1 and the back laminate layer 16.2 and are separated from one another by the interface layers 928. The back laminate layer 16.2 is fixed, in use, to an appropriate backstop, e.g. a concrete wall (not shown), or is positioned in abutment with it.

The face- and back, laminate layers 16.1, 16.2, as well as the interface layers 928 have arrays of hemispherical biasing formations 20 projecting from their core-facing surfaces. These are so arranged as to emulate, as far as practically feasible, a Bravais Body-Centred-Cubic (BCC) lattice structure layout when interacting with the spherical granular elements (not shown) in the cores C.

A base-plate 68 is provided. It is upon this base plate 68 that the cores C sit when the crash barrier 58 is at rest, and slide when the crash barrier 58 is active during an impact. During assembly of the crash barrier 58, the base plate 68 is slid into position between the rails 60. Spacing between any pair of roller blocks 66 engaged with opposed rails 60 must therefore be sufficient for the base plate 68 to slide through horizontally and along the length of the rails 60.

The gap defined at the front of the rails 60, extending between them, is closed up using a front cover plate 70 while the top of the entire assembly is covered with an appropriate flexible or foldable, weather-resistant cover 72. Those skilled in the art will appreciate that the specific embodiments of the invention described herein are representative samples only, and that the invention can be extended to a large number of other articles of manufacture, all of which fall within the scope of the invention. Selected examples of such fields have been listed elsewhere in this specification.

The Inventors believe that the embodiments of the impact energy management system described herein have certain advantages as compared with existing systems for handling impact. Firstly, many existing systems generally exploit material properties, whereas the invention as described herein places reliance on impact energy dissipation, redirection and absorption mechanisms based on granular mechanics. This can provide advantages. For example, systems can be made non-destructive (within limits) and can exhibit dimensional recovery in certain circumstances; hence the possibility of re-use over several impact-loading cycles. Flexibility and versatility can also result: with appropriate modifications the system described herein can be integrated into numerous articles of manufacture in contexts of impact energy management and some contexts of explosion management.

Another expected advantage can be found in the compartmentalized, open-sided

"sandwich" configuration of the outer casing 16 and cores C, as shown in Figures 1 and 2. Being open-sided, these embodiments can be manufactured in the form of monolithic boards, rolls, or the like, transported to a site of assembly and cut-to-size at the point of assembly. This may facilitate lowered cost, ease of transport and versatility by comparison with existing impact management systems.

The provision of the biasing formations in the system is also advantageous. The formations instigate particular instantaneous build-up and collapse of virtual-grid reinforcement structures, as opposed to the typical random behaviour of encapsulated granular media.

Lower maintenance costs are a further possible advantage, and are provided, in part, by the fact that components of the system are modular, and that the materials of manufacture are low-cost.

Finally, it is expected that the system as described herein may offer safety benefits, especially in respect of low-medium velocity impacts, as compared with many currently existing and mostly rigid impact energy management systems.

Claims

CLAIMS:

1. An impact energy management system which includes:

2. A system as claimed in Claim 1 , in which portions of at least one component selected from the outer casing and inner container define peripheral regions that are disconnected from each other, thereby to expose, the interior of such component so that the system forms an open- sided "sandwich" configuration.

3. A system as claimed in Claim 1 or Claim 2, in which the inner container includes a plurality of capsules holding the granular elements.

4. A system as claimed in Claim 2 or Claim 3, which includes a plurality of inner containers.

5. A system as claimed in Claim 4, which includes at least one interface layer mounted between the inner containers, and wherein the, or each, interface layer has a plurality of biasing formations projecting from at least one side thereof, which are operable to act on at least one of the inner containers in response to an impact force acting on the impact incident wall of the outer casing.

6. A system as claimed in Claim 1 or Claim 2, which defines interchange means for exchange of fluid between components of the system.

7. A system as claimed in Claim 1 or Claim 2, in which the outer casing includes pressure regulating means for regulating pressure inside the outer casing.

8. A system as claimed in Claim 1 or Claim 2, in which the granular elements are spherical in shape.

9. A system as claimed in Claim 1 or Claim 2, wherein at least some of the granular elements have a density which varies across their cross-section.

10. A system as claimed in Claim 1 or Claim 2, in which the biasing formations are part- spherical in shape, are of generally the same diameter as the granular elements, and are arranged on the outer casing in a predetermined manner to form, in combination with at least some of the granular elements, a configuration approximating a Bravais lattice structure, due tolerance being allowed for separation of the biasing elements and granular elements from one another by the material of the, or each, inner container.

11. A system as claimed in Claim 2 or Claim 5, wherein the, or each, inner container is located within the outer container in an arrangement wherein, in unstressed configurations of the outer casing and the inner container, a space is defined between the inner container and the outer casing into which the inner container can expand when the outer casing deforms inwardly as an impact force is applied to the outer casing, in use.

12. A system as claimed in Claim 5, wherein at least two components are bonded to one another, the components being selected from the group consisting of outer casing, inner containers, capsules and interface layers.

13. A system as claimed in Claim 1 or Claim 2, wherein at least a portion of one component selected from the group consisting of the outer casing and the inner container is laminated, comprising a plurality of sub-layers displaceably abutting one another.

14. A system as claimed in Claim 1 wherein at least a portion of a component selected from the group consisting of the outer casing and the inner container is laminated, comprising a plurality of sub-layers bonded to one another.

15. A system as claimed in Claim 3, which includes a regular array of capsules spatially separated from one another.

16. A system as claimed in Claim 15, wherein each capsule defines a uniform cross-sectional footprint as it extends inwardly from the impact incident wall of the outer casing.

17. A system as claimed in Claim 15, wherein each capsule varies in cross-sectional footprint as it extends inwardly from the impact incident wall of the outer casing.

18. A system as claimed in Claim 3, wherein at least one capsule defines a long, major axis and a shorter, minor axis, and wherein the relative ratio of the lengths of the two axes and their alignment relative to the impact incident wall of the outer casing are predetermined with reference to a design load anticipated to be experienced by the system and a space available for occupation by the system.

19. A system as claimed in Claim 1 or Claim 2, characterised by a dispersion angle exhibited by the granular elements, following impact on the impact incident wall of the outer casing, in use, which falls in a range between 40° and 80° as measured from the axis of the incident impact vector.

20. A system as claimed in Claim 1 or Claim 2, in which cavities defined by the outer casing and by the at least one inner container are at least partially filled with at least one substance selected from the group consisting of the following, or a mixture thereof: compressible fluids; sparingly compressible fluids; aerosols; suspensions; non-Newtonian fluids; semi-solids; and solids; provided that said substance shall have lubricating properties.

21. A system as claimed in Claim 3, in which at least two of the capsules differ from each other in respect of at least one property selected from the group consisting of: shape, dimensions, and configuration.

22. A system as claimed in Claim 4, in which at least two of the inner containers differ from each other in respect of at least one property selected from the group consisting of: shape, dimensions, and configuration.

23. A post assembly which includes:

a post;

an impact energy management system as claimed in Claim 5, said system being configured to surround at least a portion of said post;

a functional formation connected to the post, for performing a design function of the post assembly; and

24. A post assembly as claimed in Claim 23, which further includes damping means for damping oscillations of the spring means.

25. A post assembly as claimed in Claim 23, wherein the functional formation is selected from the group consisting of: a traffic light cluster, a street light, a sign, and an advertisement.

26. A crash barrier which includes:

an impact energy management system as claimed in Claim 5;

27. A component for a motor vehicle, which includes a system as claimed in Claim 1 or Claim 2.

28. An article of manufacture comprising a system as claimed in Claim 5 integrated into a device designed for use in an application selected from the group consisting of: automotive, aerospace, personal safety, packaging, shipping and freight, armour, military, domestic appliances, construction, roads infrastructure, entertainment, sports and recreation, communication and banking.

29. A method of assembling an article of manufacture, the method including the steps of: manufacturing at least one impact energy manufacturing system as claimed in Claim 2, selling it, separating it into smaller functional units after sale, and introducing at least one of the smaller units into the assembly of said article of manufacture.

30. A system as claimed in Claim 1 or Claim 2, substantially as described in the specification, with reference to and as illustrated in any of the accompanying drawings.