Fall energy absorbing device

Abstract

Fall energy absorbing device (1) comprising a first pulling element (2) comprising a first anchoring portion (4) connected to a first base portion (6) through a first connecting portion (8); a second pulling element (3) comprising a second anchoring portion (5) connected to a second base portion (7) through a second connecting portion (9) and configured to move relative to the first pulling element (2) along a longitudinal direction (L); a honeycomb structure (10) comprising a plurality of interconnected open cells (11) configured to absorb energy through plastic deformation of said cells (11) in response to a compressive load applied in a longitudinal direction (L) to opposite bases (12,13) of the honeycomb structure (10); wherein the first and second base portions (6,7) are in contact with the opposite bases (12,13) of the honeycomb structure (10) such that, when the first and second anchoring portions (4,5) are moved away from each other along said longitudinal direction (L), the first and second base portions (6,7) press against the bases (12,13) of the honeycomb structure (10) thereby compressing the honeycomb structure (10) in the longitudinal direction (L); wherein the honeycomb structure (10) exhibits a crush strength, in the longitudinal direction (L), that is comprised between a first value that is inversely proportional to a pressed area of the base (12,13) of the honeycomb structure (10) for a given arresting force, and a second value that is inversely proportional to the pressed area of the base (12,13) of the honeycomb structure (10) and to a height (H) of the honeycomb structure (10) for a given fall energy.

Description

TITLEFALL ENERGY ABSORBING DEVICEDESCRIPTION TECHNICAL FIELD

[0001] The present invention relates to safety devices for fall protection, and more specifically to safety devices comprising energy absorbing devices operable for assisting in the arresting of downward movement of a person or object after a fall.BACKGROUND ART

[0002] In the state of the art energy absorbing devices for mitigating a fall from a height of a person are known. For example, the document US20090212474A1 describes a solution wherein a honeycomb is enclosed between two substantially u-shaped metal elements that are slidably engaged to each other. When these two elements are moved away, the honeycomb is compressed and the device absorbs the fall energy. This solution comprises a spring arranged between a base of the honeycomb and a base of one of the elements that are pulled. In general, the elastic deformation of this spring would be detrimental to the safe deceleration of the falling individual since during deformation the spring simply stores the energy of the fall, and then returns the energy in the form of rebound energy. This rebound can create forces as high as 90% of the initial fall, but in this solution, this rebound force is absorbed by the plastic deformation of the honeycomb. This solution is silent about the honeycomb characteristics and does not provide any indication on how the honeycomb has to be dimensioned for efficiently absorbing the energy of a falling man without under or over dimensioning the honeycomb.

[0003] Another solution is known from the document EP2095847A1 which describes an energy absorbing device for mitigating a fall from a height of a person. The energy absorbing device comprises a casing in which a honeycomb is arranged and the honeycomb has a longitudinal hole in which passes a rod of a pulling element. By pulling this element, the honeycomb is compressed against the base of the casing. Even in this case, the document does not provide any information about the honeycomb and how it has to be dimensioned in order to not make the energy absorbing device efficient and not too big. A similar solution is described in the document CN105620416A, which describes a safety belt energy absorption device including a honeycomb that is longitudinally compressed when the safety belt is pulled and the box containing the honeycomb squeezes.SUMMARY

[0004] Said and other drawbacks of the state of the art are now solved by a fall energy absorbing device comprising a first pulling element comprising a first anchoring portion connected to a first base portion through a first connecting portion, a second pulling element comprising a second anchoring portion connected to a second base portion through a second connecting portion and configured to move relative to the first pulling element along a longitudinal direction, and a honeycomb structure comprising a plurality of interconnected open cells configured to absorb energy by plastic deformation of said cells in response to a compressive load on the longitudinal direction applied to opposite bases of the honeycomb structure. The first and second base portions are in contact with the opposite bases of the honeycomb structure so that, when the first and second anchoring portions are moved away from each other along said longitudinal direction, said first and second base portions press said bases thus compressing said honeycomb structure in the longitudinal direction. The honeycomb structure has a crush strength that is comprised between a first value that, for a given arresting force, is inversely proportional to a pressed area of the base of the honeycomb structure and a second value that, for a given fall energy, is inversely proportional to a pressed area of the base of the honeycomb structure and to a height of the honeycomb structure. A honeycomb so structured is able to efficiently absorb the energy of a fall from a height of a person. The honeycomb so conceived is not over or under dimensioned and can mitigate a fall in terms of kinetic energy to be absorbed and peak force. The honeycomb so conceived is compact and lightweight.

[0005] In particular, the crush strength can be a function of the density of the honeycomb structure. By increasing the density, the crush strength increases. In particular, the crush strength is approximatively proportional to density raised to the second power. This allows to obtain great energy absorptions even with values of density quite low, thus leading to lightweight fall energy absorbing devices.

[0006] Preferably, when the cells have cylindrical shape, the density can be a function of the ratio between thickness of cells' sidewall and the cells' diameter. In particular, the density is equal to the density of the material multiplied Stricter cylinders for a given thicknessmake the honeycomb denser, as well as thicker cell's sidewalls for a given cylinder's diameter make the honeycomb denser. Therefore, by correctly balancing the sidewall's thickness to cell's diameterratio, it's possible to achieve a significative density and thus great values of crush strength and in turn an efficient energy absorption.

[0007] Advantageously, said honeycomb structure can be made of a polymer, preferably is made at least in part of polycarbonate, and has a density comprised between 20 and 150 kg / m3. These values of density in combination with the use of cells made of a polymeric material, preferably made at least in part of polycarbonate, lead to honeycombs very lean and consequently to compact and efficient fall energy absorbing devices.

[0008] Preferably, for said given arresting force and said given fall energy, the height of the honeycomb structure can be greater than the fall energy multiplied by a coefficient of friction and divided by the arresting force multiplied by a crushing strain percentage. The crushing strain percentage is comprised between 65% to 85% of the height of the honeycomb structure. Preferably, crushing strain percentage is comprised between 70% to 80% of the height of the honeycomb structure. Independently from the pressed area, the height of the honeycomb is proportional to the fall parameters and to a factor typical of honeycombs. Moreover, the height of the honeycomb is proportional to a coefficient of friction, thus to a factor that considers the friction between first and second pulling elements and, sometimes, with the honeycomb. The coefficient of friction also considers any internal friction, thus any elongation of the materials of first and second pulling elements and any other dissipation mechanism involved in the fall energy absorbing device. This coefficient of friction is comprised between 35% and 95%, preferably between 40% and 70%, and considers that a part of the fall energy is dissipated by friction of the sliding elements forming the fall energy absorbing device or their elongation / deformation, and not only by the compression of the honeycomb. In this way, it's easier to size the honeycomb and thus the fall energy absorbing device. Preferably the honeycomb when ends to absorb fall energy through cell's crumpling has a height that is comprised between 65% and 85%, preferably between 70% and 80%, of its original height before compression.

[0009] In particular, for an arresting force of 6.000 N and a pressed area of 0,0025 m2, the crush strength can be smaller than 2,4 MPa. When the pressed area is a square and its side is 5 cm, the crush strength is smaller than 2,4 MPa for passing certain standard rules.

[0010] Advantageously, the crush strength of the honeycomb structure can be greater than the ratio between 5 times the fall energy and 7 times the volume of the honeycomb structure.

[0011] In particular, along the longitudinal direction, the second base portion can be arranged between the first anchoring portion and the first base portion, and the first base portion can bearranged between the second anchoring portion and the second base portion. The honeycomb is sandwiched between the first and second base portions and the honeycomb is compressed when the first and second anchoring portions are moved away from each other.

[0012] Preferably, the honeycomb structure can comprise a plurality of interconnected open cells having longitudinal axes parallel to said longitudinal direction. The honeycomb so structured absorbs more efficiently the energy during crumpling, in particular when the open cells are discrete open cells interconnected to each other via their sidewalls.

[0013] Advantageously, one or both the first and second coupling portions can laterally support the honeycomb structure during its compression on at least a side of the honeycomb structure. The honeycomb structure can bend during crumpling of its cells and the longitudinal portions can be shaped to support the honeycomb during its deformation. In this manner, the energy is efficiently absorbed, moreover if the honeycomb tends to bend, the friction between the honeycomb's sides and the longitudinal portion / s also contribute to improve the energy absorption.

[0014] At least one among the first and second pulling elements can comprise a fabric band that wraps at least in part the honeycomb structure.

[0015] Preferably, both the first and second pulling elements can comprise fabric bands that wrap different sides of the honeycomb structure and cross each other. This fall energy absorbing device is economic, lightweight and compact. Preferably, a transversal fabric band transversally surrounds the other fabric bands, in this manner, the honeycomb does not bend during its longitudinal compression.

[0016] In particular, the height of the honeycomb structure can be less than two or three times the size of shortest base's side. A parallelepiped shape that is taller than wider allows to keep the honeycomb lean and consequently to obtain fall energy absorbing devices that are compact and easy to be transported. For a given base area of the honeycomb, great heights of the honeycomb lead to a longer crushing path, but by exaggerating with the height, the honeycomb is not able to completely or almost completely crush during a fall absorption. Moreover, if the honeycomb's height is more than two or three times the shortest side of its base, the honeycomb becomes instable during compression.

[0017] In particular, the fall energy absorbing device can be entirely made of plastic for being disposed in the same recycling stream once crushed. Being the entire fall energy absorbing device made of plastic, after a fall absorption, thus when the fall energy absorbing device cannot be reused and needs to be trashed, it can respect the environment and be entirely recycled.

[0018] Advantageously, the honeycomb structure can have a first pass-through hole and the second connecting portion has a second pass-through hole and the first connecting portion is a rod arranged in said first and second holes. In this manner the honeycomb compression is more stable during a fall and the honeycomb bending is less probable.

[0019] These and other advantages will be better understood thanks to the following description of different embodiments of said invention given as non-limitative examples thereof, making reference to the annexed drawings.DRAWINGS DESCRIPTIONIn the drawings:Fig. 1 shows an isometric exploded view of a fall energy absorbing device according to a first embodiment;Fig. 2 shows a schematic cross-sectional view of a fall energy absorbing device according to the first embodiment;Fig. 3 shows an isometric view of a fall energy absorbing device according to a second embodiment; Fig. 4 shows a schematic cross-sectional view of a fall energy absorbing device according to the second embodiment;Fig. 5 shows an isometric view of a fall energy absorbing device according to a third embodiment; Fig. 6 shows a schematic cross-sectional view of a fall energy absorbing device according to the third embodiment;Fig. 7 shows an isometric view of a fall energy absorbing device according to a fourth embodiment; Fig. 8 shows a schematic cross-sectional view of a fall energy absorbing device according to the fourth embodiment;Fig. 9 shows an isometric view of a fall energy absorbing device according to a fifth embodiment; Fig. 10 shows a schematic cross-sectional view of a fall energy absorbing device according to the fifth embodiment;Fig. 11 shows an isometric view of a fall energy absorbing device according to a sixth embodiment; Fig. 12 shows a schematic cross-sectional view of a fall energy absorbing device according to the sixth embodiment;Fig. 13 shows an isometric view of a fall energy absorbing device according to a seventh embodiment;P133Fig. 14 shows a schematic cross-sectional view of a fall energy absorbing device according to the seventh embodimentFig. 15 shows a schematic isometric view of a honeycomb employed in a fall energy absorbing device according to the present invention.DETAILED DESCRIPTION

[0020] The following description of one or more embodiments of the invention is referred to the annexed drawings. The same reference numbers indicate equal or similar parts. The object of the protection is defined by the annexed claims. Technical details, structures or characteristics of the solutions here-below described can be combined with each other in any suitable way.

[0021] In Fig. 1,3,5,7,9,11,13 are represented different embodiments of a fall energy absorbing device 1 according to the present invention.

[0022] Substantially, the fall energy absorbing device 1 is configured to receive and accommodate a honeycomb 10 inside it. The fall energy absorbing device 1 is structured to longitudinally compress the honeycomb 10 when the fall energy absorbing device's anchoring portions 4,5 are strayed each other according to a longitudinal direction L. Practically, when the fall energy absorbing device 1 elongates, the honeycomb 10 is longitudinally compressed and the energy of the fall is absorbed by the honeycomb's cells crumpling.

[0023] In the following the term "fall energy absorbing device" is abbreviated with "absorbing device" for the sake of conciseness. Also the term "honeycomb structure" is abbreviated with "honeycomb" for the same reason.

[0024] The absorbing device 1 comprises a first pulling element 2, a second pulling element 3 and the honeycomb 10. The first and second pulling elements 2,3 are shaped and arranged so as to move relative to each other along the longitudinal direction L. Each pulling element 2,3 comprises a respective base portion 6,7 that is connected to a connecting portion 8,9 which in turn is connected to an anchoring portion 4,5.

[0025] In particular, the first pulling element 2 comprises a first base portion 6 connected to a first connecting portion 8 which, in turn, is connected to a first anchoring portion 4. Similarly, the second pulling element 3 comprises a second base portion 7 connected to a second connecting portion 9 which, in turn, is connected to a second anchoring portion 5.

[0026] The honeycomb 10 has opposite bases 12,13 according to the longitudinal direction L. The bases 12,13 of the honeycomb 10 respectively lie on the first and second base portions 6,7. In thisP133manner, when the first and second anchoring portions 4,5 are moved away from each other along the longitudinal direction L, the honeycomb 10 is compressed along the longitudinal direction L.

[0027] In order to compress the honeycomb 10, the first and second base portions 6,7 are opposed with respect to the first and second anchoring portions 4,5. Substantially, base portions 6,7 and anchoring portion 4,5 are arranged on opposite side of the honeycomb 10 along the longitudinal direction L.

[0028] As shown in Fig. 15, the honeycomb 10 is realized by a plurality of cells 11 that are open at their longitudinal ends so that each open cell 11 realizes a tube through which the air can flow. Each cell 11 is connected to neighbour cells 11, via their sidewalls 15, and together they form an array of interconnected cells 11. Each cell 11 has a longitudinal axes X that is parallel to the longitudinal direction L.

[0029] Preferably, the cells 11 are discrete tubes connected via their sidewalls each other in order to form an array of energy-absorbing open cells.

[0030] The tubular shape of the cell 11 can be defined by a single-piece sidewall 15 or by a multipieces sidewall 15. The open cell 11 can have a circular cross-section as represented in Fig. 15. Alternatively, the open cell 11 can be a cylinder having a base shaped like an arrowhead, or squared, hexagonal, triangular, or having another shape like a re-entrant hexagon or a chiral truss.

[0031] As shown the various embodiments of Fig. 1-14, when the anchoring portions 4,5 are moved away from each other, the honeycomb 10 is compressed. In particular, the opposite bases 12,13 of the honeycomb 10, that at rest are in contact with the base portions 6,7, are pressed by the base portions 6,7 along the longitudinal direction L. During this compression of the cells 11, they tend to buckle, but each cell 11 is supported by the neighbour cells 11 and don't globally buckle. The cells 11 thus longitudinally crumple absorbing the energy by plastic deformation. In this way the energy absorbed is maximized.

[0032] During honeycomb 10 crumpling, the honeycomb 10 sometimes tends to laterally buckle. As shown in Fig. 1,2,5-14, certain absorbing devices 1 can comprise connecting portions 8,9 shaped to laterally support, at least in part, the honeycomb 10 during its compression. In this manner a global buckling of the honeycomb 10 is avoided because the side 14 of the honeycomb 10 leans on the connecting portion 8,9. Moreover, the friction of the honeycomb side 14 with the first and / or second connecting portion / s 8,9 improves the energy absorbed by the absorbing device 1.P133

[0033] When the anchoring portions 4,5 are moved away from each other, the opposite bases 12,13 of the honeycomb 10 are pressed by the respective base portion 6,7. It's pressed the entire base 12,13 of the honeycomb, therefore the entire area of the base 12,13 is involved in the compression.

[0034] Generally, the honeycomb 10 has a parallelepiped or cylindrical shape.

[0035] When the anchoring portions 4,5 are moved away from each other, the honeycomb 10 is compressed and it longitudinally crumples. The honeycomb 10 is dimensioned so that it entirely crumples for a specific amount of energy to be absorbed. In this way, it's not over dimensioned and the absorbing device 1 remains more compact.

[0036] In order to correctly dimension the honeycomb, the Applicant has performed various studies, tests and calculations and it has been founded that the optimal honeycomb 10 has a crush strength CS with a value that lies between a first value and a second value. The first value, for a given arresting force AF, is inversely proportional to the pressed area A of the base 12,13 of the honeycomb structure 10. The second value, for a given fall energy FE, is inversely proportional to a pressed area A of the base 12,13 of the honeycomb structure 10 and to a height H of the honeycomb structure 10.

[0037] In particular, for a given arresting force AF, the crush strength CS is smaller than the ratio between the arresting force and the pressed area, thus CS < AF / A.

[0038] Crush strength CS refers to the maximum compressive stress the honeycomb structure 10 can withstand before its cells' sidewalls 15 densify.

[0039] For example, if the arresting force is 6.000 N and the pressed area is 25 cm2, the crush strength CS is smaller than 2,4 MPa.

[0040] In particular, for a given kinetic fall energy FE to be absorbed, the crush strength is greater than the ratio between the fall energy FE multiplied by a coefficient of friction CF and the product of the pressed area A of the honeycomb 10, the height H of the honeycomb 10 and a crushing strain percentage CSP that is typical of the specific honeycomb. Normally, the crushing strain percentage CSP is comprised between 65% and 85%, preferably between 70% and 80%. Normally, the coefficient of friction CF is comprised between 35% and 95%, preferably between 40% and 70%.

[0041] The crushing strain percentage CSP is a measure that is typical of the honeycomb 10 and is measured as the percentage of the height H of the honeycomb 10 that is involved in the crumpling before densification of the honeycomb 10. In a typical stress-strain diagram of an out-of-plane compression of the honeycomb 10, the crushing strain percentage CSP is associated to the plateau of stress in the stress-strain diagram and represents the deformation of the honeycomb 10 that isP133related to this almost constant (plateau) value of stress. When an out-of-plane compression of a honeycomb 10 occurs, the stress plateau is an almost constant value of stress that the honeycomb 10 so conceived shows between an initial stress peak associated to the end of elastic deformation and a bottoming out phenomena that occurs when the honeycomb 10 densifies. Normally, the stress plateau is almost horizontal in the stress-strain diagram, while the elastic behaviour and the densification of honeycomb 10 are peaks / increases in the diagram. The area below the stress curve in the stress-strain diagram is the quantity of energy absorbed by the honeycomb 10 that is out-of-plane compressed. The stroke of initial height H of the honeycomb associated to the stress plateau is the crushing strain percentage CSP. The crushing strain percentage CSP is thus the percentage of the height H of the honeycomb that is involved in the out-of-plane compression up to honeycomb 10 bottoms out. The crushing strain percentage CSP measures the efficiency of energy absorption.

[0042] The coefficient of friction CF is a dimensionless number showing how much force resists sliding between two surfaces and measures the energy dissipated by friction between the elements of the fall energy absorbing device that slide relative to each other. Optionally, it can also measure the internal friction, thus the energy dissipated during elongation / deformation of absorbing device's elements. Coefficient of friction CF is the ratio of the sliding (kinetic) friction force to the normal force pressing the relative sliding elements together. When the first pulling element 2 slides with respect to the second pulling element 3, in their points of contact a friction is realized which dissipates part of the fall energy. Moreover, in certain embodiments, the honeycomb 10 scrabs on the first and / or second pulling elements 2,3, by increasing the energy dissipated by friction. It has been verified by the Applicant that the coefficient of friction CF can vary between 35% and 95% depending on the construction of the fall energy absorbing device 1. For example, for the first embodiment of Fig 1 and 2, the coefficient of friction CF is about 50%.

[0043] When the honeycomb 10 is a squared-based parallelepiped, the area A of the bases 12,13 is S2, wherein S is length the side of the base 12,13. Vice versa, when the honeycomb 10 has a cylindrical shape, the area A of the bases 12,13 is nR2, wherein R is the radius of the bases 12,13. Other shapes of the bases 12,13 of the honeycomb 10 are possible without departing from the present inventive concept.

[0044] The height H of the honeycomb 10 is the height, at rest, of the honeycomb 10 measured along the longitudinal direction L.

[0045] The crush strength CS is a function of the density of the honeycomb 10. The density is not the density of the material of which the cells 11 of the honeycomb 10 are made, but it takes inP133consideration also the void portions of the honeycomb 10. It's thus an average density between solid and void portions of the honeycomb 10.

[0046] In particular, the crush strength CS is directly proportional to the density of the honeycomb 10. Approximatively, the crush strength CS is proportional to the square of the density.

[0047] When the cells 11 have a cylindrical shape with circular base, the density of the honeycomb 10 is proportional to the ratio between the thickness T of cell's sidewall and the cells' diameter D. In particular, the density is equal to the average density of the material of which the honeycomb's cells 11 is made multiplied wherein D is diameter of the cells 11 and T thethickness of cells' sidewall.

[0048] In particular, the Applicant has observed that when the honeycomb 10 is made at least in part of polycarbonate and has a density comprised between 20 and 150 kg / m3, the absorbing device is particularly lightweight. Similar values of density can be obtained with a honeycomb 10 like that of Fig.15 having a diameter of cells comprised between 2 mm and 8 mm, and a thickness T of cell's sidewall that is comprised between 0,05 mm and 0,2 mm.

[0049] For having an optimal honeycomb 10 in terms of energy absorption efficiency, it's preferable FE-CFto employ a honeycomb 10 having a height H greater thanaf csp, wherein FE is the fall energy that the honeycomb 10 has to absorb, AF is the arresting force that the honeycomb 10 has to bear, CSP is the crushing strain percentage as described above and CF is the coefficient of friction as described above.

[0050] For example, when the arresting force AF is 6.000 N and the fall energy FE is 588 J, the height H of the honeycomb 10 is at least 7 cm, if the crushing strain percentage CSP is 70% and the coefficient of friction CF is 50%. In this case, the fall energy FE corresponds to a mass of 100 kg dropping from a height of 60 cm.

[0051] If a honeycomb 10 having a volume V and a crushing strain percentage CSP is compressed in an absorbing device 1, the crush strength CS of the honeycomb 10 is greater than the ratio between the product of the fall energy FE and the coefficient of friction CF and the product of the volume V and the crushing strain percentage CSP. This means that, if the crushing strain percentage CSP is 70% and the coefficient of friction CF is 50%, the crush strength CS is greater than the ratio of 5 times the fall anergy FE and 7 times the volume V of the honeycomb 10.

[0052] During tests, the Applicant has noted that is preferable to use honeycombs 10 that are not excessively lean, otherwise the honeycomb 10 becomes instable and can globally buckle duringP133compression. In particular, the height H of honeycomb 10 is preferably less than two or three times the shortest side of the honeycomb's base 12,13. If the base 12,13 is a square, the height H is less than 2S or less than 3S, wherein S is the size of the base's side of the honeycomb 10.

[0053] All the above characteristics are valid for all the following embodiments.

[0054] In the first embodiment of Fig. 1-2, the first and second pulling elements 2,3 are shaped like a sort of question mark and they fit each other with the honeycomb 10 in between them. Each pulling element 2,3 has a respective base portion 6,7 that is in contact with the honeycomb 10, a respective anchoring portion 4,5 and a respective connecting portion 8,9, that connects the base portion 6,7 with the respective anchoring portion 4,5. The anchoring portions 4,5 are substantially aligned along a common longitudinal direction L. A retainer 23 is in part integral with one of the pulling elements 2,3 and in part connected to it to circumferentially close the absorbing device 1 and avoid a disjunction between the pulling elements 2,3 and a lateral buckling of the honeycomb 10. Lanyards 22 are connected to respective anchoring portions 4,5. When, due to a fall, the lanyards 22 are tensed, the anchoring portions 4,5 are moved away in the longitudinal direction L and the base portions 6,7 press the opposite bases 12,13 of the honeycomb 10. By compressing the honeycomb 10, the cells 11 crumple as described above and absorb the fall energy.

[0055] In the second embodiment of Fig. 3-4, the first pulling element 2 comprises a plate constituting the first base portion 6 that is connected to an end of a rod 8', which represents the first connecting portion 8. At the opposite end of the rod 8' is connected an eyebolt that represents the first anchoring portion 4. The second pulling element 3 comprises a plate constituting the second base portion 7 that is connected to the ends of a U-shaped element. The straight parts of the U-shaped elements represent the second connecting portion 9. The curved part of the U-shaped element is the second anchoring portion 5. The U-shaped element passes through holes or recesses of the plate constituting the first base portion 6 for providing more stability to the absorbing device 1 when the tensed lanyards 22 pull away from each other the anchoring portions 4,5. The rod 8' passes through a first pass-through hole 20 of the honeycomb 10 and through a second pass-through hole 21 of the second connecting portion 9. In this solution, some cells 11 of the honeycomb 10 are sacrificed for realizing said first pass-through hole 20, vice versa the honeycomb 10 is more supported and less prone to lateral buckling. As the previous embodiment, when the anchoring portions 4,5 are moved away from each other along the longitudinal direction L by the lanyards 22 tensed by a fall, the pulling elements 2,3 compress the honeycomb 10 and its cells 11 absorb through a plastic deformation the fall energy.P133

[0056] The third embodiment of Fig. 5,6 comprising first and second pulling elements 2,3 that are made of a fabric band 17,18 closed to form a fabric ring. The fabric band 17,18 can form a single or double loop. These fabric bands 17,18 wrap different sides 14 of the honeycomb 10 and cross each other, as shown in Fig. 5. The fabric bands 17,18 are linked each other like links in a chain. Between these fabric bands 17,18 is arranged the honeycomb 10, as shown in Fig. 6. A first fabric band 17 wraps the base 12 and two opposite sides 14 of the honeycomb 10, while a second fabric band 18 wraps the other base 13 and the other two opposite sides 14 of the honeycomb 10. A third transversal fabric band 19 transversally surrounds the first and second fabric bands 17,18, in this way, the honeycomb 10 cannot escape from the absorbing device 1 when the fabric bands 17,18 are pulled by the lanyards 22 tensioned by the fall. All the fabric bands 17,18,19 are preferably made of a polymeric fabric, e.g. with polyamide thread, and also the honeycomb 10 is made of polycarbonate and / or polyester. In this manner, the absorbing device 1 is entirely made of plastic materials and, after the honeycomb 10 is crushed due to a fall, the entire absorbing device 1 can be trashed in the garbage of plastics, by reducing the environment footprint of the absorbing device 1. In this version of the absorbing device 1 the honeycomb 10 is preferably lean, thus tall and strict as shown in Fig. 5, thus with a height that is larger than two or three times the size of the base's side.

[0057] The absorbing device 1 of fourth embodiment of Fig. 7,8 is a hybrid version between the absorbing device of second and third embodiments. Indeed, it works like the absorbing device 1 of the second embodiment but it has the second pulling element 3 made of fabric band 17. This fabric band 17 is connected to a plate that represents the second base portion 7. A rod 8' is connected to the first base portion 6 and slides into a second pass-through hole 21 of the second base portion 7. In between the base portions 6,7 is arranged a honeycomb 10 having a first pass-through hole 20 wherein the rod 8' is arranged. The end of the rod 8' is connected an eyebolt that represents the first anchoring portion 4. The distal portion of the fabric band 17 of the second pulling element 3 represents the second anchoring portion 5. When the lanyards 22 are tensed by a fall and pull away from each other the anchoring portions 4,5, the base portions 6,7 approach and the honeycomb 10 is compressed.

[0058] The fifth embodiment of Fig. 9,10, is similar to the second embodiment but the second pulling element 3 comprises sidewalls defining an empty space in which the honeycomb 10 is arranged. The sidewalls represent the second connection portion 9 and they are joined with the second anchoring portion 5. To the sidewalls, a cap is connected which represents the second base portion 7. The first pulling element 2 is substantially equal to that of second embodiment. In thismanner, during cells' crumpling, the honeycomb 10 is sustained by the rod 8' and by the sidewalls of the second pulling element 3. Moreover, the honeycomb 10 is protected from potential external impacts. Indeed, the honeycomb 10 of all embodiments has an out-of-plane stiffness that is greater than the in-plane stiffness. Moreover, a lateral impact on the honeycomb 10 can create a geometric perturbation on sidewalls 15 of cells 11 which can widely reduce the energy-absorption of the honeycomb 10. This problem is solved, at least in part, by all embodiments that protect one or more side 14 of the honeycomb 10.

[0059] The sixth embodiment of Fig. 11,12 has a second pulling element 3 comprising a U-shaped frame to which a bolt is connected. The bolt with one or more bushing forms the second anchoring portion 5, while the sidewalls of the frame represent the second connecting portion 9 that are joined with a base of the frame that represents the second base portion 7. The first pulling element 2 is substantially equal to that of second embodiment with the only difference that one or two pins 24 laterally protrude from the plate constituting the first base portion 6. The one or two pins 24 slide into straight longitudinal slit / s 25 realized in the frame of second connecting portion 9. The cooperation of pin / s 24 and slit / s 25 allows to compress the honeycomb 10 along the longitudinal direction L. The honeycomb 10 is arranged within the frame of second pulling element 3 and the first base portion 6. Moreover, the honeycomb 10 comprises a first pass-through hole 20 and the second base portion 7 comprises a second pass-through hole 21 in which the rod 8' of the first pulling element 2 slides. When the anchoring portions 4,5 are moved away from each other by the lanyards 22 tensioned by a fall, the honeycomb's cells 11 crumple absorbing the fall's energy.

[0060] The seventh embodiment of Fig. 13,14 has a second pulling element 3 that is similar to that of sixth embodiment. The first pulling element 2 is made of a fabric band 17, like the fourth embodiment, the fabric band 17 is connected to a plate that constitutes the first base portion 6. The longitudinal portions of the fabric band 17 represent the first connecting portion 8, while the central part of the fabric band 17 represents the first anchoring portion 4. The fabric band 17 pass into apertures realized in the base portion 7 of the second pulling element 3, in this way the longitudinal portions of the fabric band 17 slide longitudinally when the absorbing device 1 is in action. The plate constituting the first base portion 6 has pins 24 that slide into respective slits 25 realized in the sidewalls of the frame of second connecting portion 9 like in the sixth embodiment. In this manner, when the lanyards 22 are tensed and the anchoring portions 4,5 are moved away from each other, the plate constituting the first base portion 6 remains perpendicular to the longitudinal direction L and the honeycomb 10 is regularly compressed along the longitudinaldirection L. The honeycomb 10 is arranged within the fabric band 17 of first pulling element 2 and the frame of second pulling element 3.

[0061] Even if it is not described in detail, the ends that are not show in the figures of the lanyards 22 are respectively connected to a secure point and to a user. In this way, when the user accidentally fall from a height, the lanyards 22 are tensioned and the fall energy absorbing device 1 is stretched and it elongates by compressing the honeycomb 10.

[0062] Concluding, the invention so conceived is susceptible to many modifications and variations all of which fall within the scope of the invention which is defined in the appended claims. Practically, the quantities can be varied depending on the specific technical requirements. All features of previously described embodiments can be combined in any way, so to obtain other embodiments that are not herein described for reasons of practicality and clarity.

[0063] Legend of reference signs:1 fall energy absorbing device2 first pulling element3 second pulling element4 first anchoring portion (of the first pulling element)5 second anchoring portion (of the second pulling element)6 first base portion (of the first pulling element)7 second base portion (of the second pulling element)8 first connecting portion (of the first pulling element)8' rod9 second connecting portion (of the second pulling element)10 honeycomb structure11 cell (of the honeycomb structure)12 first base (of the honeycomb structure)13 second base (of the honeycomb structure)14 side (of the honeycomb structure)15 sidewall (of cell)17,18 fabric band19 transversal band20 first pass-through hole (of the honeycomb structure)21 second pass-through hole (of the second connecting portion structure)22 lanyard23 retainer24 pin25 slitL longitudinal directionX longitudinal axis (of cell)T thickness (of cell's sidewall)H height (of the honeycomb structure)S side (of the base of the honeycomb structure) D diameter (of cell)

Claims

SET OF CLAIMS1. Fall energy absorbing device (1) comprising:a first pulling element (2) comprising a first anchoring portion (4) connected to a first base portion (6) through a first connecting portion (8);a second pulling element (3) comprising a second anchoring portion (5) connected to a second base portion (7) through a second connecting portion (9); the second pulling element (3) being movable relative to the first pulling element (2) along a longitudinal direction (L);a honeycomb structure (10) comprising a plurality of interconnected open cells (11) configured to absorb energy through plastic deformation of said cells (11) in response to a compressive load applied in a longitudinal direction (L) to opposite bases (12,13) of the honeycomb structure (10);wherein the first and second base portions (6,7) are in contact with the opposite bases (12,13) of the honeycomb structure (10) such that, when the first and second anchoring portions (4,5) are moved away from each other along said longitudinal direction (L), the firstand second base portions (6,7) press against the bases (12,13) of the honeycomb structure (10) thereby compressing the honeycomb structure (10) in the longitudinal direction (L);wherein the honeycomb structure (10) exhibits a crush strength, in the longitudinal direction (L), that is comprised between a first value that is inversely proportional to a pressed area of the base (12,13) of the honeycomb structure (10) for a given arresting force, and a second value that is inversely proportional to the pressed area of the base (12,13) of the honeycomb structure (10) and to a height (H) of the honeycomb structure (10) for a given fall energy.

2. Fall energy absorbing device (1) according to claim 1, wherein the crush strength is a function of the density of the honeycomb structure (10).

3. Fall energy absorbing device (1) according to claim 2, wherein, when the cells (11) have cylindrical shape, the density is a function of the ratio between thickness (T) of cells' sidewall (15) and the cells' diameter (D).

4. Fall energy absorbing device (1) according to any one of preceding claims, wherein said honeycomb structure (10) is made of a polymer, preferably is made at least in part of polycarbonate, and has a density comprised between 20 and 150 kg / m3.

5. Fall energy absorbing device (1) according to any one of preceding claims, wherein for said given arresting force and said given fall energy, the height (H) of the honeycomb structure (10) is greater than the fall energy multiplied by a coefficient of friction and divided by the arresting force multiplied by a crushing strain percentage, being the crushing strain percentage comprised between 60% to 85%, preferably comprised between 65% to 80%, and the coefficient of friction being comprised between 35% and 95%, preferably between 40% and 70%.

6. Fall energy absorbing device (1) according to any one of preceding claims, wherein for an arresting force of 6.000 N and a pressed area of 0,0025 m2, the crush strength is smaller than 2,4 MPa.

7. Fall energy absorbing device (1) according to any one of preceding claims, wherein the crush strength of the honeycomb structure (10) is greater than the ratio between 5 times the fall energy and 7 times the volume of the honeycomb structure (10).

8. Fall energy absorbing device (1) according to claim 1, wherein, along the longitudinal direction (L), the second base portion (7) is arranged between the first anchoring portion (4) and the first base portion (6), and the first base portion (6) is arranged between the second anchoring portion (5) and the second base portion (7).

9. Fall energy absorbing device (1) according to claim 1 or 2, wherein the honeycomb structure (10) comprises a plurality of interconnected open cells (11) having longitudinal axes (X) parallel to said longitudinal direction (L), preferably said interconnected open cells (11) are discrete open cells.

10. Fall energy absorbing device (1) according to any one of preceding claims, wherein one or both the first and second connecting portions (8,9) laterally support the honeycomb structure (10) during its compression on at least a side (14) of the honeycomb structure (10).

11. Fall energy absorbing device (1) according to any one of preceding claims, wherein at least one among the first and second pulling elements (2,3) comprises a fabric band (17) that wraps at least in part the honeycomb structure (10).

12. Fall energy absorbing device (1) according to claim 12, wherein both the first and second pulling elements (2,3) comprise fabric bands (17,18) that wrap different sides 14 of the honeycomb structure (10) and cross each other; preferably a transversal fabric band (19) transversally surrounds the other fabric bands (17,18).

13. Fall energy absorbing device (1) according to any one of preceding claims, wherein the height (H) of the honeycomb structure (10) is less than two or three times the size of shortest base's side.

14. Fall energy absorbing device (1) according to any one of preceding claims, that is entirely made of plastic for being disposed in the recycling stream once crushed.

15. Fall energy absorbing device (1) according to any one of preceding claims, wherein the honeycomb structure (10) has a first pass-through hole (20) and the second connecting portion (9) has a second pass-through hole (21) and the first connecting portion (8) is a rod (8') arranged in said first and second holes (20,21).

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