Patent Publication Number: US-2021162245-A1

Title: Energy absorbing apparatus

Description:
BACKGROUND 
     Technical Field 
     Described herein is an energy absorbing apparatus and methods of use. More specifically, apparatus and methods of use are described that utilize varying energy absorbing relationships between the apparatus members to absorb an energy input. 
     Description of the Related Art 
     Energy absorbing apparatus may take a variety of forms, the aim being in a broadest sense, to absorb and/or transfer an energy input by converting the energy in some different manner. One non-limiting example may be to disperse a torque force imposed on a shaft or coupling by transferring the torque force to heat energy, movement of another member, causing a change in gravitational energy, causing a mechanical deformation and so on. 
     For the purposes of the description below and for brevity, reference will be made to safety apparatus and in particular self-retracting lifelines (SRLs) however this should not be seen as limiting. Note that SRLs may also be termed fall limiters, personal fall limiters, yo-yos, road side barrier, road side barrier terminal end, and seatbelts. 
     SRLs are used in industrial safety applications to prevent falls from height. An SRL typically comprises an extendable and retractable line wound on a spool. The user connects one end of the line to their body, typically via a harness with a connection point. In the event of normal movement, the SRL allows the line to extend and retract. Should a line extension force occur beyond a predetermined rate, the SRL acts to slow and/or stop further line extension. The rapid line extension may be the result of a fall and the slow/stop property of the SRL acts to prevent injury to the user. 
     For an SRL to be effective, a sudden force generated by a line extension must be rapidly detected and the force absorbed/transferred quickly, and potentially reduced to full energy transfer (e.g. to a halt motion). Many art devices already exist, often utilizing latches or other mechanical interactions between the members to absorb the energy and slow/stop a fall. Potential problems with art SRL devices may be reliability, the art mechanisms utilized in the absorption of energy being susceptible to contamination, environmental decay, deformation, and wear that might be generated from the manufacturing process or use in the field. Such reliability issues demand onerous checking and servicing requirements, and the potential for further harm to users of such art devices. The apparatus described herein may address some of these potential problems or at least provides the public with a choice. 
     Further aspects and advantages of the energy absorbing apparatus and methods of use should become apparent from the ensuing description that is given by way of example only. 
     BRIEF SUMMARY 
     Described herein are apparatus and methods of use that utilize varying energy absorbing relationships between the apparatus members to absorb an energy input particularly via various metal forming processes. 
     In a first aspect, there is provided an energy absorbing apparatus comprising: 
     a first energy producing member; 
     a second energy absorbing member; and 
     when an energy input is produced by the first energy producing member that exceeds a predetermined threshold, the second energy absorbing member absorbs at least part of the first member energy via a material forming process. 
     In a second aspect, there is provided a method of absorbing energy by the steps of: 
     (a) selecting an energy absorbing apparatus substantially as described above; 
     (b) applying an energy input on the first energy producing member that exceeds the predetermined threshold thereby triggering the second energy absorbing member to absorb at least part of the first member energy via a material forming process. 
     The inventors have established that material forming processes may provide useful ways of absorbing energy. The absorbing noted above may act as an arrest force, slowing or stopping movement of the first energy producing member. 
     Advantages of the above material forming processes may be varied depending on the final configuration but may include:
         Rapid deployment of an absorbing force beyond a predetermined threshold;   Rapid absorbing/transfer from part to full energy transfer.   The apparatus described have an inherent reliability since they are mechanically simple and rely on known and predictable properties of the materials;   The sudden stop that might be generated from an art latch device can be avoided through material selection and design;   High density forces may be absorbed;   The energy absorbing member or parts thereof may be replaced post activation allowing the apparatus to be re-set post activation; and   The energy absorbing member or parts thereof have a long deformable length (high strain capacity).       

    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Further aspects of the energy absorbing apparatus and methods of use will become apparent from the following description that is given by way of example only and with reference to the accompanying drawings in which: 
         FIG. 1  illustrates an example of a wire drawing embodiment; 
         FIG. 2  illustrates a potential SRL embodiment utilizing wire drawing; 
         FIG. 3  illustrates an alternative potential SRL embodiment utilizing wire drawing; 
         FIG. 4  illustrates a linear motion extrusion embodiment; 
         FIG. 5  illustrates a rotational motion extrusion embodiment; and 
         FIG. 6  illustrates a friction welding embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     As noted above, described herein are apparatus and methods of use that utilize varying energy absorbing relationships between the apparatus members to absorb an energy input particularly via various metal forming processes. 
     For the purposes of this specification, the term ‘about’ or ‘approximately’ and grammatical variations thereof mean a quantity, level, degree, value, number, frequency, percentage, dimension, size, amount, weight or length that varies by as much as 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1% to a reference quantity, level, degree, value, number, frequency, percentage, dimension, size, amount, weight or length. 
     The term ‘substantially’ or grammatical variations thereof refers to at least about 50%, for example 75%, 85%, 95% or 98%. 
     The term ‘comprise’ and grammatical variations thereof shall have an inclusive meaning—i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. 
     The terms ‘rod’, ‘wire’ and ‘bar’ may be used interchangeably. For brevity, the description below may refer to generally round or circular cross section rods, wires or bars however this should not be seen as limiting since other cross sections may be used and still achieve the same or similar function such as square, oblong or elliptical cross sections. Further, a rod, wire, bar, or similar may be referred to in the singular context, however it will be appreciated that the invention is possible with multiples of such elements in parallel to achieve the desired function and are therefore within the scope of the invention. These multiples may each be of different form, area, and material, to the others, selected to achieve the desired function and performance characteristic. 
     The term ‘member’ may refer to one part or element or multiple parts or elements that together achieve the function noted. 
     In a first aspect, there is provided a device comprising: 
     at least one moving mass; 
     at least one energy absorbing member; and 
     when the at least one moving mass reaches a predefined threshold, the at least one energy absorbing member engages and applies a retarding force on movement of the at least one moving mass, transferring kinetic energy from the at least one moving mass into work energy by plastic deformation of a material associated with the at least one energy absorbing member. 
     The inventors have established that material forming processes may provide useful ways of absorbing energy. The absorbing noted above may act as an arrest force, slowing or stopping movement of the first energy producing member. 
     The predefined threshold noted above may be a distance of movement of the moving mass and/or speed/rate of movement of the moving mass. 
     Engagement noted above may be by coupling of the at least one moving mass and the at least one energy absorbing member. 
     The retarding force may result in a halt in movement of the at least one moving mass although retarding may also refer to a slowing in speed or rate of movement and not a complete halt in movement. 
     Prior to engagement, the at least one moving mass may be free to move relative to the at least one energy absorbing member. For example the moving mass may be a spool of line that is free to rotate until the predetermined threshold, for example rapid deployment of line from the spool, at which point coupling and absorption occurs. 
     An external force may impose motion to the at least one moving mass. 
     The at least one moving mass may move in a linear direction and the retarding force applied to the at least one moving mass may be a linear force. Alternatively, the at least one moving mass rotates and the retarding force applied to the moving mass may be a torque force. 
     The retarding force may be applied in a direction substantially opposite that of the moving mass direction of travel. 
     The rate at which kinetic energy may be absorbed by the at least one energy absorbing member may be related to:
         (a) the force or torque applied to the at least one energy absorbing member from the at least one moving mass; and/or   (b) the distance travelled or rotated by the at least one moving mass.       

     Plastic deformation as noted above may be achieved by methods selected from: wire drawing, deep drawing, tube inversion, and combinations thereof. 
     Wire drawing is an industrial process where a wire or bar may be reduced in diameter by pulling the bar through a reduced diameter member such as a die with a narrowing waist or shoulder. 
     Deep drawing or tube inversion are processes are similar in style to wire drawing, that is metal being drawn through a die however, deep drawing refers to drawing a plate and tube inversion is drawing a tube. These processes may be adapted in a similar style as noted above for energy absorbing apparatus as described above. 
     The wire, sheet or tube used in the methods above may have substantially uniform material characteristics resulting in a substantially linear retarding force being applied to the at least one moving mass. 
     The term ‘uniform characteristics’ used above refers to reaching a substantially constant retarding force but optionally including at least one limited duration variation in retarding force e.g. at the time of engagement allowing for an initial increase in retarding force imposition. 
     Alternatively, the wire, sheet or tube used may have non-uniform material characteristics resulting in a non-linear retarding force being applied to the at least one moving mass. 
     The material characteristics may be varied along part or all of the wire length, the characteristics being selected from alterations to the: wire/sheet/tube diameter or width, wire/sheet/tube composition, wire/sheet/tube material treatments prior to forming; and combinations thereof. 
     The force required to pull the wire/sheet/tube through the die may be predictable and is related to the strain energy required to deform the material within the die. Through choice of material, the force required to pull the wire through the die may be tuned. This process may also be capable of absorbing high energy density forces. This may be because:
         The entire volume of the material is strained as it passes through the die;   The material being worked is confined within the die and is subject to hydrostatic compression forces so high stresses can be sustained;   The material being deformed may be of high strength, so that a significant amount of strain energy can be generated from a small volume of material.       

     As noted above, the arrest force profile, being the rate of line speed extension slowing or stopping, may be modulated by pre-forming the wire. For example, the section of wire that initially enters the die may be tapered from a fully formed diameter to an un-formed diameter over a finite length. In addition, the force required to draw the wire through the die may be modulated through for example use of varying materials, use of varying diameters, material treatments prior to forming and the like. As a result of the above variations, the torque exerted on the first energy causing member (e.g. a spool) can be controlled in either a linear or non-linear manner depending on various pre-determined aspects. 
     In an alternative embodiment, plastic deformation may be by methods selected from: bar bending or controlled buckling where a wire, rod, bar or plate bends or buckles in a predetermined manner to absorb kinetic energy and impose the retarding force. In a rotational embodiment, bending or buckling may be torsional deformation through the act of twisting a wire, rod or bar. 
     The wire, rod, bar or plate may have substantially uniform material characteristics resulting in a substantially uniform retarding force being applied to the moving mass. 
     Alternatively, the wire, rod, bar or plate may have non-uniform material characteristics resulting in a non-linear retarding force or forces being applied to the moving mass. 
     The non-uniform characteristics may comprise multiple layers of material, the layers having differing deformation moduli therefore providing varying energy absorbing characteristics. 
     Alternatively, the material forming process may be bar bending or controlled buckling. In these embodiments, a wire, rod, bar or plate may bend or buckle in a predetermined manner when a first member force is applied over a predetermined level. In a further form, this may be bending in the rotational sense, commonly referred to as torsional deformation through the act of twisting a wire, rod or bar. The degree of material strain may govern the rate of energy absorbing. In this embodiment, the amount of strain may vary through the thickness of the material and as a result, the degree of energy absorbing may be tuned. For example, multiple layers of material may be used, the materials having differing moduli of elasticity therefore providing varying energy absorbing characteristics. 
     In a further alternative embodiment, plastic deformation may be by slitting or shearing where a wire or bar is slit or sheared through to absorb kinetic energy and impose the retarding force. In this embodiment a wire, rod or bar may be slit or sheared through in the event of a predetermined force being imposed on the second energy absorbing member. 
     In a further embodiment, plastic deformation may be by extrusion using a material that re-crystallizes at room temperature. Further, plastic deformation may be by extrusion using a material that becomes deformable under energy loading. In both of these embodiments, the methods alone or together absorb kinetic energy and impose the retarding force. The material used for deformation may depend on whether the embodied item is a single use device or multiple use device. Single use devices may use materials that permanently deform, examples including metals or metal alloys and/or plastics. If the intention is to design a multi-use device, then having a material that has properties that remain unchanged or return to an original position post deformation (via a material memory for example) may be useful. Examples of multi-use materials may include rubber, gels or metals that re-crystalize. In one embodiment, the material may be lead or lead alloy. 
     The material may be formed as a wire with a bulged element that passes through a confined volume relative to the extrudable material shape and size. In a linear motion embodiment, the bulged portion may be a rod enclosed within a housing and when relative movement occurs between rod and housing, the bulged portion is forced into a more confined region of the housing. Alternatively, in a rotational motion embodiment, the bulged portion is formed inside a housing, the housing being formed from co-rotating, different speed elements or counter rotating elements and a circular opening between the rotating elements in which the extrudable material is housed; and wherein when relative rotation occurs between the elements, the extrudable material is forced into a more confined spacing causing material forming to occur and retarding relative motion between the elements. 
     In a further embodiment, plastic deformation may be by friction welding. Friction welding may be achieved for example whereby the at least one moving mass is a rotating bar that may engage a stationary reaction bar acting as the energy absorbing member via axial loading and, when the mass and member meet, friction between the two surfaces caused by axial loading results in sufficient heat to weld the two components together and the retarding force is achieved by adhesion of the absorbing member during the welding process. The rate of retarding force applied to the moving mass may be substantially uniform. Alternatively, the rate of retarding force applied to the at least one moving mass may be non-uniform achieved by varying the materials used and the rate of the at least one moving mass movement or the applied level of axial load. In an SRL embodiment for example, the fall detection mechanism may activate axial loading of the welded components by triggering the application of a spring force. This embodiment may be useful in order to allow easy resetting of the SRL—for example by removing and replacing the welded components after the fall event. 
     In a second aspect, there is provided a method of absorbing energy by the steps of: 
     (a) selecting a device substantially as described above; 
     (b) applying a motion causing energy input on the at least one moving mass that exceeds the predefined threshold thereby triggering the at least one energy absorbing member to absorb at least part of the at least one moving mass kinetic energy via a material forming process. 
     Final embodiments for the device described herein may be varied. For example, an autobelay or self-retracting lifeline (SRL) embodiment may use the energy absorbing mechanisms. In an SRL embodiment, a line may extend and retract from the SRL device and when the line extends from the SRL device at a rate beyond a predefined threshold, the energy absorbing member engages and applies a retarding force on the rate of line extension, transferring kinetic energy from the line into work energy by plastic deformation of a material associated with the energy absorbing member. SRL and autobelay applications should not be seen as limiting since the devices described may be used for a wide variety of other applications, non-limiting examples including speed control or load control of:
         a rotor in a rotary turbine;   exercise equipment e.g. rowing machines, epicyclic trainers, weight training equipment;   roller-coasters and other amusement rides;   Elevator and escalator systems;   evacuation descenders and fire escape devices;   conveyer systems:   rotary drives in factory production facilities;   materials handling devices such as conveyer belts or a braking device in a chute;   roadside safety systems e.g. the energy absorber may be connected in a system to provide crash attenuation though the dissipation of energy via the energy absorber e.g. a roadside barrier or roadside barrier terminal end;   seat belts in vehicles;   zip lines;   braking mechanisms for trolleys and carriages;   Bumpstops in transport applications;   Bumpstops in crane applications;   Torque or force limiting devices in mechanical drive train;   Structural overload protection in wind turbines;   Load limiting and energy dissipation in structures, buildings and bridges.       

     Advantages of the above material forming processes may be varied depending on the final configuration but may include:
         Rapid deployment of an absorbing force beyond a predetermined threshold;   Rapid absorbing/transfer from part to full transfer.   The apparatus described have an inherent reliability since they are mechanically simple and rely on known and predictable properties of the materials;   The sudden stop that might be generated from an art latch device can be avoided through material selection and design;   High density forces may be absorbed; and   The energy absorbing member or parts thereof may be replaced post activation allowing the apparatus to be re-set post activation.       

     The embodiments described above may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more said parts, elements or features. 
     Further, where specific integers are mentioned herein which have known equivalents in the art to which the embodiments relate, such known equivalents are deemed to be incorporated herein as of individually set forth. 
     WORKING EXAMPLES 
     The above described energy absorbing apparatus and methods of use are now described by reference to specific examples. 
     Example 1 
       FIG. 1  shows the principle of wire drawing. The energy absorbing member generally indicated by arrow  1  may be a wire or rod  2  of a varying diameter  2 A,  2 B. The wire  2  passes through a waisted die  3  in direction X when an energy input is imposed on the wire  2 , and in doing so, wire  2  drawing occurs through the waisted die  3  causing the wire  2  to deform by a reduction in diameter through the die  3 . This reduction in area through the deformation of the wire absorbs energy. 
     Example 2 
       FIG. 2  shows an SRL embodiment with the wire or bar  2  noted in Example 1 attached to the rim  10  of a disc  11  that is normally stationary during the extension/retraction operation of a spool (not shown) on which a line (not shown) is attached. If a fall occurs, the rapid rate of increase in line extension (the first energy producing member) causes movement of the spool. An activation mechanism connects the spool to the disc  11  (the second energy absorbing member), causing the disc  11  to spin and in turn drawing the wire  2  through the die  12 . The resulting material forming process absorbs the fall energy and thereby slows (or stops) pay out of the line. 
     Example 3 
     Alternatively, as shown in  FIG. 3 , the SRL may have a rotating disc  20  and the die  21  forms part of/is integrated into the rotating disc  20 . The unformed wire  2  is coiled around the disc  20  and a free end is anchored to an SRL housing  22 . When an energy input is applied to the rotating disc  20  beyond the predetermined level, the wire  2  is forced through the die  21  thereby causing material forming to occur. 
     Example 4 
     Metal forming may instead be completed via extrusion.  FIG. 4  illustrates an extrusion embodiment using a first energy producing member  30 , supported in a housing  30   a . The housing  30   a  and first energy producing member  30  encloses a second energy absorbing member  31 , in  FIG. 4  shown as an elongated rod with a bulge  32  region. The first energy absorbing member  30  may be manufactured from a malleable material such as lead. 
     An energy input may be produced by the housing  30   a  moving when subject to an applied force. When this input is below a predetermined threshold, the energy absorbing member  30  does not deform and hence prevents movement of the housing  30   a  about the bulge  32  region. Should the energy input exceed a predetermined threshold, the first energy absorbing member  30 —the lead—deforms about the bulge  32 . This forces the bulge  32  material into a more confined space within the housing  30   a  and in doing so, absorbs at least part of the first member  30  and housing  30   a  energy via a material forming process. 
     Example 5 
       FIG. 5  shows an alternative extrusion embodiment to Example 4. Example 4 and  FIG. 4  above illustrate a linear or generally linear movement direction of the housing  30 . A rotational approach may instead be used as shown in  FIG. 5  using a first energy producing member  41  supported within a housing  40 . The housing  40  and first energy producing member  41  enclose a second energy absorbing member  42 , in  FIG. 5  shown as an annulus with two bulge portions  43  about the circumference. The energy absorbing member  42  may be made from a malleable material such as lead. An energy input may be produced by the housing  40  rotating when subject to an applied force. When this input is below a predetermined threshold, the first energy absorbing member  42  does not deform and hence prevents movement of the housing  40 . If the energy input exceeds a predetermined threshold, the first energy absorbing member  42  deforms about the bulges  43 . This forces the bulge  43  material into a more confined space within the housing  40  and in doing so, absorbs at least part of the first member  41  and housing  40  energy via a material forming process. 
     Example 6 
     Alternatively, the material forming process may be via friction welding.  FIG. 6  illustrates one means for achieving metal forming. As shown in  FIG. 6 , a spool  50  (the first energy producing member) with extendable line  51  on it, is linked to a rotating bar  52  axially aligned with a stationary bar  53 , the rotating bar  52  and stationary bar  53  being the energy absorbing member. 
     In normal operation the rotating bar  52  and stationary bar  53  are not connected. In the event of a predetermined threshold being reached, the rotating bar  52  is axially loaded against the stationary bar  53  by axial movement of the stationary bar  53  or rotating bar  52 . When the rotating bar  52  and stationary bar  53  surfaces meet, the friction between the two surfaces may, through material selection, rate of member  52 ,  53  movement and so on, result in sufficient heat to weld the two components  52 ,  53  together. As welding occurs, the rotating component  52  will experience a braking force caused by adhesion to the stationary component  53 , energy therefore being absorbed during the welding process. In an SRL embodiment, the fall detection mechanism may activate axial loading of the components  52 ,  53 , for example, by triggering the axial movement via a spring force. Post welding, the components  52 ,  53  may be removed and replaced with new separate parts  52 ,  53 . 
     Aspects of the energy absorbing apparatus and methods of use have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope of the claims herein. 
     These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.