DE102021124386A1 - Damping element for impact loads - Google Patents

Abstract

Damping element for impact loads, comprising a hollow profile (1) with two end regions (2, 3), between which the hollow profile is designed with at least two circumferentially offset slot-shaped recesses (11) in radial expansion.

Description

The invention relates to a damping element for damping shock-like stresses, in particular when absorbing tensile stresses in a fall protection system according to the first patent claim.

Damping elements of the type mentioned are preferably combined with a fall protection for people or objects secured with a rope from exposed locations.

In a fall arrest system, one end of the rope used to secure the person or object is tied to an anchor point at the exposed location. If a fall occurs, the rope length between the person or object and the anchor point limits the fall depth. If the fall depth is reached during a fall, there is an abrupt deceleration, depending on the design of the rope; a force acts on the falling person or the falling object, the so-called impact force.

The impact force is the maximum force on the rope at the tie-in point, i.e. on the person or object in the event of a fall (see EN 892). According to EN 355, the maximum permissible impact force of a fall arrest system is limited to a maximum of 6kN.

Fall protection devices therefore preferably include facilities or devices such as the damping element mentioned at the beginning, which are intended to completely slow down and dampen falls of people or objects, in particular from great heights, e.g. from flat roofs, before they hit the ground or part of a building. During damping, kinetic energy is converted via the braking distance, whereby the maximum force acting on the falling person or the falling object (impact force) should be limited to a level that is harmless to health or technically tolerable.

So-called individual attachment points are common as rope-on points for fall protection, especially for flat roofs. They consist of a preferably vertically protruding rod, which is connected to the substructure via a tripod plate or is fastened with the help of an anchorage integrated into the roof structure. The single anchorage point has a distal attachment point for a safety line. In the event of a fall, the rod should be deflected sideways and bend over.

The individual anchor points currently used are designed in such a way that there is a sufficiently high load-bearing capacity to absorb the impact force forces during a fall. A reduction of the impact force forces through damping is also not planned for single anchorage points. To limit the impact forces to 6 kN, energy absorbers are currently being used, which are integrated into the personal protective equipment against falls.

In order to safely introduce the impact force in substructures with low load-bearing capacity, such as trapezoidal profiles, however, cost-intensive fastening with a high level of installation work may be necessary.

Proceeding from this, one object of the invention is to propose a damping element for damping shock-type stresses, in particular when absorbing tensile stresses in a fall protection system.

A further object of the invention is to propose a damping element, preferably for the aforementioned purpose, with a longer braking distance.

The object is achieved with a damping element according to claim 1. Subclaims referring back to this reflect advantageous embodiments.

To solve the problem, a damping element for shock-type loads is proposed, comprising a preferably tubular hollow profile with two end regions, between which the hollow profile is designed with at least two, preferably a large number of circumferentially and longitudinally offset slot-shaped recesses in radial expansion.

The slit-shaped recesses are intended to weaken the material in the hollow profile. On the one hand, they advantageously allow increased resilience of the hollow profile under load, both in the axial and in the radial direction. Due to the low resistance to bending loads (loads in the radial direction), the profile is aligned at a very early stage of the damping process in the lower section in such a way that it is subjected to significant axial loads. On the other hand, the weakening of the material ensures that the largest possible proportion of the cross section is plasticized under axial load and that as much energy as possible is dissipated. The spring constant is fundamentally lower; impact forces in particular can be absorbed over a fundamentally longer spring deflection.

The slot-shaped recesses preferably extend over the entire circumference of the hollow profile. This is further improved by that preferably in each case a predeterminable number of The slot-shaped recesses extend in a predeterminable number, lined up and separated from one another by slot-free wall regions, annularly along a ring plane (or alternatively helically) over the entire circumference of the hollow profile. A further improvement results if preferably several ring planes (or alternatively an axial section over several turning planes) each with the predeterminable number of slit-shaped recesses and slit-free wall areas between the two end areas of the hollow profile are provided one above the other and preferably parallel to one another, with the slit-shaped Recesses and slit-free wall areas to the immediately adjacent ring planes (or alternatively turning planes) are arranged offset to one another. This advantageously ensures a uniform axial extensibility, in particular over the length of the hollow profile, and on the other hand, in the event of a bending load, causes a load-deformation behavior that is approximately independent of the load direction.

The slit-shaped recesses extend more preferably in a straight line or at least partially curved on the wall of the hollow profile, which particularly advantageously promotes a tight arrangement in the hollow profile in the aforementioned manner.

Slit-shaped recesses in the hollow profile also cause pronounced stress singularities, particularly in the area of no recess radii, i.e. in the case of slits at the slit ends. Stress singularities are usually the starting point for cracks that form in the material. With crack formation and crack propagation, more energy is absorbed, especially in ductile materials such as many metals or plastics or quasi-ductile materials such as fiber composites. The resistance resulting from the propagation of the crack generally increases with the speed of the crack, which in turn dampens impact loads in particular. The extent and height of the stress peaks of the stress singularities mentioned depend in particular on the radius of the recess. Correspondingly, it is preferably proposed to provide the slot-shaped recesses in their ends in a relief bore and to let them run out.

The hollow profile in a preferred embodiment is preferably made of a ductile material, preferably a ductile metal with a high elongation at break (e.g. over 20%), such as stainless austenitic or ferritic-austenitic steel, more preferably with an elongation at break of over 15%, more preferably over 20%. A material with a pronounced Lüder elongation, which further increases the breaking elongation, is also preferably proposed, for example an unalloyed and low-alloyed hypoeutectoid steel or alternatively a copper or aluminum alloy.

Alternatively, a quasi-ductile fiber composite material, more preferably with long fibers (fiber length preferably >50 mm, more preferably 100 to 500 mm), is proposed as the material for the hollow profile. In particular, GRP (gas fiber reinforced plastics) or CFRP (carbon fiber reinforced plastics) materials with ductile deformation behavior of the matrix material are proposed, which are advantageously characterized by higher E moduli and tensile strengths of the fibers compared to the respective fiber matrix.

The slot-shaped recesses are preferably arranged parallel to one another in the hollow profile.

Another embodiment provides for the interior of the tubular hollow profile to be additionally and at least partially (e.g. as a tube in the hollow profile) preferably completely filled with an elastically, preferably also plastically deformable material which, as a result of changes in shape (the hollow profile cross-section decreases with longitudinal expansion) with the energy conversion is involved. The material counteracts deformation of the interior volume occupied by the hollow profile. The material preferably comprises a plastic, more preferably a porous plastic or a pasty or viscous substance such as a bitumen. In the case of viscous substances, it is proposed to protect them as a component with a cover (rubber or plastic) against escaping, e.g. from the recesses. This sleeve preferably tears when the hollow profile is deformed and releases the substance, which can then exit the hollow profile via the recesses.

The damping element can be used in a fall protection device as a damper, which is part of the personal protective equipment against falls, or as a single anchor point.

For use as a single anchor point in a fall protection system for roped people (or objects) on a building roof, it is proposed to attach the damping element to the building with one end area and to tie the safety rope for the people to the second end area. In the event of a fall, tensioning the safety rope results in an exit steering of the damper element. Due to the material weakening caused by the slit-shaped recesses, the damping element aligns itself at an early stage in such a way that it is significantly axially stressed and can deform in an advantageous manner. Due to the associated flatter force-displacement curve of the damper element, the braking distance of the jerky deceleration is lengthened in an advantageous manner by additional stretching of the damper element. When used as a single anchorage point, the damper element is preferably aligned vertically upwards, with one end area fastened to a preferably horizontal building-side plate, so that in the event of a fall the cable force acts on the second end area radially to the hollow profile and loads it to bend.

When using the damping element as part of personal protective equipment against falls, the end areas are connected in an articulated manner to the safety rope and the safety harness. In the event of a fall, the damping element is then loaded in the axial direction.

• 1 eine schematische Darstellung eines Ausführungsbeispiels eines Dämpferelements aus einem Rundhohlprofil mit einer ersten Ausgestaltung der schlitzförmigen Ausnehmungen, die sich in Ringebenen über den Umfang des Hohlprofils erstrecken, als Einzelanschlagpunkt
• 2a, b und c jeweils Teilquerschnitte von Ausführungen einer Verbindung zwischen Hohlprofil und unterem Deckel,
• 3a und b weitere mögliche Ausgestaltungen der schlitzförmigen Ausnehmungen, schematisch dargestellt auf einer aufgeklappten Mantelfläche eines rohrförmigen Hohlprofils,
• 4 eine schematische Darstellung eines Versuchsaufbaus einer Absturzsicherung für eine Person oder einen Gegenstand mit einem Dämpferelement sowie
• 5 eine schematische Teilansicht eines verformten Dämpferelements aus einem Rundhohlprofil nach einem Absturz.

The invention is explained in more detail using the following exemplary embodiments, the following figures and descriptions. All of the features shown and their combinations are not just limited to these exemplary embodiments and their configurations. Rather, these should be viewed as representative of other possible configurations that are not explicitly shown as exemplary embodiments and can be combined. Show it

• 1 a schematic representation of an embodiment of a damping element made of a round hollow profile with a first embodiment of the slot-shaped recesses, which extend in ring planes over the circumference of the hollow profile, as a single stop point
• 2a, b and c each partial cross-section of versions of a connection between the hollow profile and the lower cover,
• 3a and b further possible configurations of the slot-shaped recesses, shown schematically on an opened lateral surface of a tubular hollow profile,
• 4 a schematic representation of a test setup for fall protection for a person or an object with a damping element, and
• 5 a schematic partial view of a deformed damping element from a round hollow profile after a crash.

The aforementioned damper element includes - as in 1 shown - a hollow profile 1 with an upper and a lower end region 2 and 3, each with a schematically illustrated upper and lower cover 4 and 5. The upper end region 2 has an eyelet 6 or another component for the connection of a power transmission means such as Example of a safety rope on the upper cover 4 for receiving a safety rope, with which one example, a force in the axial and or radial direction 7 or 8 in the upper end portion 2 of the hollow profile can be introduced. In contrast, the lower end region 3 is fastened in or on a base 9 via the lower cover 5 .

In the example, the hollow profile has a preferably round cross section. Pipes with round cross-sections have the same axial area moment of inertia in all radial directions.

Essential are the slot-shaped recesses 11 provided in the hollow profile 1 between the covers, which are offset in the circumferential direction and extend radially, which are preferably made by means of a laser, plasma or water jet cutting process.

• - Eine erste Ausgestaltung gemäß 2a sieht hierzu bevorzugt eine Löt- oder Schweißverbindung, alternativ grundsätzlich auch eine Klebe- oder Klemmverbindung vor, wobei das Hohlprofil vorzugsweise zumindest am unteren Deckel 5 auf einen in das Hohlprofil einschiebbaren deckelseitigen Kernansatz 12 (wie auf einen Dorn) aufgeschoben wird und umlaufend mit dem Deckel verschweißt oder verlötet wird (vgl. 1 und 2a, Schweißnaht 10). Der Kernansatz weist vorzugsweise einen Außendurchmesser entsprechend dem Innendurchmesser des Hohlprofils 1 auf und bildet mit diesem eine Spiel- oder leichte Presspassung. Vorzugsweise bewirkt der Kernansatz im Hohlprofil insbesondere am unteren Ende in vorteilhafter Weise wie ein eingeschobener Dorn eine Entlastung des Hohlprofils unmittelbar an der Schweißnaht, d.h. an der Stelle, an dem ein Biegemoment, hervorgerufen durch eine an der Öse 6 angreifenden Kraft in radialer Richtung 8, am größten ist und die Festigkeit durch den thermischen Fügeprozess womöglich reduziert ist. Der Kernansatz verhindert insbesondere eine Abknickung mit Querschnittsänderung des Hohlprofils, indem sie den rohrförmigen Querschnitt von innen stützt. Vorzugsweise ist der im Hohlprofil endende Kernansatz am Ende zur Vermeidung von lokalen Spannungsspitzen abgerundet.
• - Eine alternative, jedoch bevorzugte Ausgestaltung sieht lösbare Verbindungen vor, beispielsweise Schraubdeckel 13, der entweder mit einem Außengewinde (2b) oder einem Innengewinde (2c) in oder auf ein entsprechendes Innen- bzw. Außengewinde 14 bzw. 15 des Hohlprofils 1 schraubbar ausgestaltbar sind. Vorzugsweise ist nur das Hohlprofil 1 ein Austauschteil, das nach einem Abfangen eines Stoßes verformt wird und zwischen den beiden Deckel einfach austauschbar ist. Diese Ausgestaltung ermöglicht in vorteilhafter Weise eine Mehrfachnutzung der Deckel. Ein unterer Deckel muss damit nur einmal im Boden oder Untergrund verankert werden, um für eine Absturzsicherung mehrfach nutzbar zu sein. Ebenso ist ein oberer Deckel mit z.B. einer Öse mehrfach nutzbar. Dies spart Transport- und Montageaufwand, insbesondere für einen Transport von Absturzsicherungen zu schwer zugänglichen Einzelanschlagpunkten (Gebirge, Industriekaminen, historischen Bauwerken, Gefahrenbereiche bei Kernkraftwerken oder in der verfahrenstechnischen Industrie etc.). Im Rahmen einer Absturzsicherung bei Hochbauten oder Industrieanlagen ändern sich die Einzelanschlagspunkte für eine Absturzsicherung in der Regel nur wenig (z.B. bei Inspektions- oder Wartungsintervallen). Die Überlappungsbereiche des Gewindes bewirken in vorteilhafter Weise eine Erhöhung des Widerstandes gegen Beulen im Bereich der Verbindungsbereiche zwischen Hohlprofil und Deckel.

The covers 4 and 5 are rigidly connected to the hollow section 1 as follows:

• - A first embodiment according to 2a preferably provides a soldered or welded connection for this purpose, alternatively basically also an adhesive or clamped connection, with the hollow profile preferably being pushed at least on the lower cover 5 onto a core attachment 12 on the cover side that can be pushed into the hollow profile (like on a mandrel) and circumferentially connected to the cover is welded or soldered (cf. 1 and 2a , weld 10). The core attachment preferably has an outer diameter corresponding to the inner diameter of the hollow profile 1 and forms a loose or slight press fit with it. Preferably, the core attachment in the hollow profile, especially at the lower end, advantageously brings about a relief of the hollow profile directly at the weld seam, ie at the point at which a bending moment, caused by a force acting on the eyelet 6 in the radial direction 8, is greatest and the strength is possibly reduced by the thermal joining process. In particular, the core attachment prevents the hollow profile from buckling with a change in cross section by supporting the tubular cross section from the inside. Preferably, the end of the core attachment ending in the hollow profile is rounded to avoid local stress peaks.
• - An alternative, but preferred embodiment provides for detachable connections, for example wise screw cap 13, which either has an external thread ( 2 B) or an internal thread ( 2c ) can be screwed into or onto a corresponding internal or external thread 14 or 15 of the hollow profile 1 . Preferably, only the hollow profile 1 is a replacement part, which is deformed after a shock has been absorbed and can be easily replaced between the two covers. This configuration advantageously allows multiple use of the cover. A lower cover only has to be anchored once in the floor or substructure in order to be used multiple times for fall protection. An upper cover with an eyelet, for example, can also be used several times. This saves transport and assembly costs, especially when transporting fall protection systems to individual attachment points that are difficult to access (mountains, industrial chimneys, historic buildings, hazardous areas in nuclear power plants or in the process engineering industry, etc.). In the context of fall protection in high-rise buildings or industrial plants, the individual attachment points for fall protection usually change only slightly (e.g. with inspection or maintenance intervals). The overlapping areas of the thread advantageously increase the resistance to buckling in the area of the connecting areas between the hollow profile and the cover.

The circumferentially offset slot-shaped recesses 11 in radial expansion are in 1 illustrated embodiment each executed offset arcuate, the recesses of each second axial plane (ring plane) have a kink. Compared to an offset rectilinear configuration in planes, such as those shown, for example, in 3a is shown, a pronounced plasticization of the webs and an advantageous course of the load-time curve in the event of a fall. In principle, the extensibility also increases with the length of the recesses and the webs arranged between them. Another embodiment provides V-shaped offset recesses ( 3b) before, which can be optimized due to the longer webs between the recesses in particular to a further increased resilience under axial tensile loads as well as radial bending loads. The higher the slope of these V-shaped recess flanks of a recess in relation to the axial plane (annular plane), the higher the extensibility of the hollow profile.

4 shows a schematic representation of the structure of a fall test on a fall protection for one person with a damping element as a single anchor point. The test setup represents a model for fall protection for people on buildings, in which the damping element 17 is set up vertically via the lower cover and fastened to a rigid substructure 16 representing the roof of the building (single attachment point). There is an eyelet 6 on the upper cover of the damping element, to which a load cell 22 is connected. A steel cable 23 is fastened to the other end of the load cell, which in turn is connected to a mountain cable 18 with a defined length. The steel cable is first deflected downwards via a deflection roller 19 simulating the roof edge of the building. A lifting weight 20 (eg 100 kg) is fastened to the climbing rope 18 oriented vertically downwards. Furthermore, the vertically deflected mountain rope serves as a guide for a drop weight 21, which is raised in the test by a drop height h defined in accordance with the specifications in EN 795 above the attachment weight (preferably 1 to 2 m) and then released. The resulting impact forces are introduced into the damping element and recorded using the load cell 22 connected in between. The connection of the steel cable (in the example 12 mm diameter, 6x19, with thimbles and cable clamps) to the sensors and the eyelet is preferably done with shackles with a minimum breaking load of 5 tons.

The impact force is initially entered as a bending load in the damping element. This is followed by a kinking of the tubular hollow profile above the lower cover 5 and then a widening of the slit-shaped recesses 11 (cf. 5 ) under the predominant tensile load in the hollow profile in the bent state.

reference list

1

tubular hollow profile

2

upper end area

3

lower end area

4

top lid

5

lower lid

6

eyelet

7

axial direction

8th

radial direction

9

underground

10

Weld

11

slotted recess

12

core approach

13

screw cap

14

Internal thread of the hollow profile

15

External thread of the hollow profile

16

substructure

17

damper element

18

mountain rope

19

pulley

20

stop weight

21

drop weight

22

load cell

23

steel cable

Claims (16)

Damping element for impact loads, comprising a hollow profile (1) with two end regions (2, 3), between which the hollow profile is designed with at least two slot-shaped recesses (11) offset in the circumference and extending radially. damper element claim 1 , characterized in that the hollow profile (1) consists of a ductile material. damper element claim 1 or 2 , characterized in that the slot-shaped recesses (11) are arranged parallel to one another. Damping element according to one of the preceding claims, characterized in that a large number of slot-shaped recesses (11) are provided. damper element claim 4 , characterized in that the slot-shaped recesses (11) extend over the entire circumference of the hollow profile (1). damper element claim 4 or 5 , characterized in that a predeterminable number of slit-shaped recesses (11) lined up and separated from one another by slit-free wall regions extends either annularly along a plane or along a helical line over the entire circumference of the hollow profile (1). damper element claim 6 , characterized in that several levels, each with the predeterminable number of slit-shaped recesses (11) and slit-free wall areas between the two end areas (2, 3) of the hollow profile (1) are provided one above the other and preferably parallel to one another, the slit-shaped recesses and slit-free wall areas are arranged offset to each other to the immediately adjacent ring planes. Damping element according to one of the preceding claims, characterized in that the slot-shaped recesses extend in a straight line, at least partially curved and/or kinked on the wall of the hollow profile (1). Damping element according to one of the preceding claims, characterized in that the slot-shaped recesses (11) each terminate in a relief bore at their ends. Damping element according to one of the preceding claims, characterized in that at least one of the end regions (2, 3) is closed off by a cover (4, 5), a non-detachable or detachable connection being provided between the cover and the hollow profile (1). damper element claim 10 , characterized in that the covers (4, 5) are equipped with a means (6) for connecting a force transmission means and/or fixing means in or on a base (9) or substructure or on personal protective equipment against falls. damper element claim 10 or 11 , characterized in that the non-detachable or detachable connection comprises a form-fitting and/or friction-locking screw connection (14, 15) or a material-locking bonded, soldered or welded connection (10) between the cover (4, 5) and the hollow profile (1). Damper element according to one of Claims 10 until 12 , characterized in that the covers (4, 5) each have a core attachment (12) that can be pushed into the hollow profile and has an outer diameter corresponding to the inner diameter of the hollow profile (1) and forms a loose or slight press fit with it. damper element Claim 13 , characterized in that the core approach is rounded at the end in the hollow profile. Damping element according to one of the preceding claims, characterized in that the hollow profile is additionally and at least partially filled with a resiliently deformable material or component. Use of a damping element according to one of the preceding claims as a single unit impact point or as part of personal protective equipment against falls.

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