ANCHOR POINT FOR A PERSONNEL FALL ARREST SYSTEM

Abstract

 The invention relates to an anchor point (1) for a personnel fall arrest system comprising a mount (2) to be fixed on a roof, in particular a flat roof or a roof with a slight inclination, at least one energy absorbing element (3), a fastener, such as an eye (8) or guide intended for attaching a safety line, such as a system cable delimiting a safe perimeter or a life line, and a stiffener (7) located between the mount (2) on the one hand and energy absorbing element (3) and the fastener (8) on the other. The stiffener (7) comprises two parts (9, 10) that are connected by at least one break element (11) .

Description

[0001] The invention relates to an anchor point for a personnel fall arrest system comprising a mount, e.g. a base plate, to be fixed on a roof, in particular a flat roof or a roof with a slight inclination, e.g. less than 10 degrees, at least one energy absorbing element, e.g. to prevent, in case of a fall, subjecting personnel to arresting loads greater than maximum safe values, a fastener, such as an eye or guide intended for attaching, e.g. hooking or guiding, a safety line, such as a system cable delimiting a safe perimeter or a life line, and a stiffener located between the mount on the one hand and energy absorbing element and the fastener on the other. The invention further relates to a method of configuring an anchor point.

[0002] WO 01/87420 relates to an energy absorber which comprises a helically coiled store of at least partially yielding material that is drawn over a roller, or two rollers on perpendicular rotational axes, and securely fixed to a base that is attached to fragile structure such as a roof so that when an external force of sufficient size is applied to the roller or rollers through a connecting attachment eye the coil together with roller or rollers moves away from the attachment to the base whilst the coiled material is deployed over the roller or rollers. The absorber may be housed in a casing that is fixed to the base such that the strength of the fixing to the base is sufficient to withstand a pre-determined load after which the fixing fails and the housing moves with the coiled store providing protection for both the coiled store and fragile structure.

[0003] Figure 3 of WO 01/87420 shows an absorber housed in a casing (indicated by numeral 15) which is attached to the base (11) by fastenings (16) and (17). "In order to prevent bending of the material 3 under low loads the casing 15 supports the absorber, holding the eye 9 in a fixed position relative to the base 11. The casing 15 is designed to resist becoming detached from base 11 until the load on eye 9 has reached a pre-determined size. At this point the fastenings 16 and 17 fail and allow casing 15 to part from base 11. This pre-determined detachment load is designed to be sufficiently low to avoid significantly damaging the roof and is lower than the load required to deploy the material 3 from helical store 1 over the roller 4."

[0004] It is an object of the present invention to provide an improved anchor point for use on roofs, in particular an anchor point that is to be installed permanently on a flat roof.

[0005] To this end, the anchor point according to the invention is characterized in that the stiffener comprises two parts that are connected by a break element. In an embodiment, the two parts are connected by a shear pin, such as the shank of a bolt.

[0006] In another embodiment, the break element has been provided with a weakened portion or is made from a metal having a yield strength that is less than the yield strength of the metal from which the stiffener is made.

[0007] In a refinement, the break element has a portion having a reduced diameter. E.g. the break element comprises a pin having a first diameter over most of its length and at least one portion having a second diameter, which is smaller than the first diameter.

[0008] The energy absorbing element reduces, in case of a fall, the risk of serious injury, whereas the stiffener reduces the risk of or prevents inadvertent deformation of the energy absorbing element, which would imply that the anchor point must be replaced in its entirety. On the other hand, if the stiffener would not yield in case of a fall, the anchor point could be ripped from the roof to which it is attached, resulting in a serious or even lethal event. With the break element according to the present invention, the force at which the stiffener yields can be controlled precisely and reliably, e.g. by i) selecting, e.g. based on regulation, the force at which the energy absorbing element, reinforced by the stiffener, should yield, i.e. plastically deform, ii) establishing the strength of the roof where the anchor point is or is to be attached, and iii) selecting or modifying the break element to set the force at which the stiffener yields.

[0009] In an embodiment, the energy absorbing element comprises two legs defining an apex, where the fastener is located, and diverging downwards.

[0010] In another embodiment, the energy absorbing element is rotatably fastened to the mount to enable it to rotate to the direction of a force exerted on it, e.g. by a perimeter cable or during an incident, such as a fall.

[0011] It is preferred that the anchor point has an open structure, i.e. with the energy absorbing element exposed to the environment and not enclosed by a casing or the like.

[0012] In an embodiment, at least one of the energy absorbing element, the stiffener, and the break element is removable from the anchor point. In an example, at least one of these elements is bolted to one or more of the other elements. The advantages of this are that, in case of damage or wear of one or more elements or in case of modifications to the trajectory of a perimeter cable or changes in the load requirements, these elements can be replaced or adapted quickly as needed.

[0013] In an embodiment, the anchor point is fixed to a roof by means of the mount and the break element is designed, selected and/or modified to break at a load on the anchor point, in particular on the fastener, sufficiently low to avoid damaging the roof during normal use, i.e. during work on the roof without incidents such as a fall, and higher than the load at which the energy absorbing element plastically deforms.

[0014] The invention further relates to a method of configuring an anchor point as described above, comprising the steps, in no particular order, of
selecting the force at which the energy absorbing element, reinforced by the stiffener, should yield,
establishing the strength of the roof where the anchor point is or is to be fixed, and, after these steps,
selecting or modifying the break element to set the force at which the stiffener yields.

[0015] In an embodiment, material is removed from the break element to set the force at which the stiffener yields.

[0016] For the sake of completeness, attention is drawn to the following prior art systems.

[0017] EP 2 216 466 relates to a fall protection for installation on the roof of a building. This fall protection has a thin-walled, hollow deformation part bearing on the roof; an anchor point mounted on top of the deformation part; a fastener that is fixed to the bearing substructure; a tensile member that substantially centrally inside the deformation part extends downward and is mounted so that the external force exerted to the anchor point is transferred to the fastener through the tensile member.

[0018] The REZ-3 cable fall protection system is a system consisting of a continuous stainless steel safety line and anchor points which are attached to the roof construction of the building. With a cable fall protection system, the entire route can be followed without the user having to disconnect. As a result, the number of actions to be performed is minimal.

[0019] US 5,287,944 relates to a fall arrest system comprising permanently installed anchors. A catenary, i.e. horizontal, cable (26) is secured to roof mounted anchors (10) .

[0020] The invention will now be explained in more detail with reference to the Figures, which show an embodiment of the anchor point according to the present invention.

Figure 1 is a perspective view of an anchor point and base plate according to the present invention.

Figure 2 is an exploded view of the anchor point shown in Figure 1.

Figures 3A to 3C are perspective view, a side view, and a cross-section of the stiffener used in the anchor point shown in Figures 1 and 2.

[0021] Figures 1 and 2 show an anchor point 1 comprising a base plate 2 to be mounted on, e.g. bolted to, a flat roof or a roof with a slight inclination, and an energy absorbing element 3. In this example, the latter is made from bended metal sheet and comprises two legs 4, which legs define an apex 5 and diverge downwards towards a bottom plate 6. The ends of the legs are fastened to the bottom plate.

[0022] A stiffener 7 is fastened to the bottom plate 6 and extends through and is fastened to the apex 5 of the energy absorbing element 7. An eye, e.g. a ring 8, intended for attaching, a safety line (not shown), such as a system cable delimiting a safe perimeter or a life line, is fastened to the top end of the stiffener 7. The bottom plate 6 is rotatably mounted on the base plate 6 to enable the ring 8 and the energy absorbing element to rotate to the direction of a force exerted on it.

[0023] The stiffener 7 comprises an upper part 9 and a lower part 10 that are interconnected by a break element, in this example a shear pin 11, such as the shank of a bolt. As can be seen in Figures 3A to 3C, a pulling force on the upper part 9 will result in a shear force on the pin 11. The required shear strength of the pin has been calculated and then set by locally reducing the diameter of the pin, e.g. by cutting an annular notch by means of a lathe. The deeper the notch, the lower the shear strength of the pin and the lower the force at which the upper part of the stiffener will break away from the lower part and plastic deformation of the energy absorbing element is initiated.

[0024] More specifically, in this example, the anchor point 1 is fixed to a thin metal roof by means of the base plate 2. The strength of the roof where the anchor point is fixed is calculated or measured and the force at which the energy absorbing element, reinforced by the stiffener, should yield is selected. Based on these data, the pin 3 is modified in a manner as discussed above to set the force at which the stiffener yields sufficiently low to avoid damaging the thin roof during normal use, i.e. during work on the roof without incidents such as a fall, and higher than the load at which the energy absorbing element plastically deforms.

[0025] The invention is not restricted to the above-described embodiments which can be varied in a number of ways within the scope of the claims. For instance, in this example, the various elements, such as the legs, the bottom plate, the stiffener, and the ring have been bolted together, to facilitate replacement of these elements, but in other embodiments, one or more of these elements could be welded together.

Claims

1. Anchor point (1) for a personnel fall arrest system comprising a mount (2) to be fixed on a roof, in particular a flat roof or a roof with a slight inclination, at least one energy absorbing element (3), a fastener, such as an eye (8) or guide, intended for attaching a safety line, such as a system cable delimiting a safe perimeter or a life line, and a stiffener (7) located between the mount (2) on the one hand and energy absorbing element (3) and the fastener (8) on the other, characterized in that the stiffener (7) comprises two parts (9, 10) that are connected by at least one break element (11).

2. Anchor point (1) according to claim 1, wherein the two parts (9, 10) are connected by at least one shear pin (11) .

3. Anchor point (1) according claim 1 or 2, wherein the at least one break element (11) has been provided with a weakened portion or is made from a metal having a yield strength that is less than the yield strength of the metal from which the stiffener (11) is made.

4. Anchor point (1) according to claim 3, wherein the at least one break element (11) has a portion with a reduced diameter.

5. Anchor point (1) according to claim 4, wherein the at least one break element comprises a pin (11) having a first diameter over most of its length and at least one portion having a second diameter, which is smaller than the first diameter.

6. Anchor point (1) according to any one of the preceding claims, wherein the energy absorbing element (3) comprises two legs (4) defining an apex (5), where the fastener (8) is located, and diverging downwards.

7. Anchor point (1) according to any one of the preceding claims, wherein the energy absorbing element (3) is rotatably fastened to the mount (2) to enable it to rotate to the direction of a force exerted on it.

8. Anchor point (1) according to any one of the preceding claims, having an open structure.

9. Anchor point (1) according to any one of the preceding claims, wherein at least one of the energy absorbing element (3), the stiffener (7), and the break element (11) is removable from the anchor point (1).

10. Anchor point (1) according to any one of the preceding claims that is fixed to a roof by means of the mount (2) and wherein the break element (11) is designed, selected and/or modified to break at a load on the anchor point (1) sufficiently low to avoid damaging the roof during normal use and higher than the load at which the energy absorbing element (3) plastically deforms.

11. Method of configuring an anchor point (1) according to any one of the preceding claims, comprising the steps of
selecting the force at which the energy absorbing element (3), reinforced by the stiffener (7), should yield,
establishing the strength of the roof where the anchor point (1) is or is to be fixed, and
selecting or modifying the break element (11) to set the force at which the stiffener (7) yields.

12. Method according to claim 11, wherein the break element (3) is designed, selected and/or modified to break at a load on the anchor point (1), in particular on the fastener (8), sufficiently low to avoid damaging the roof during normal use and higher than the load at which the energy absorbing element (3) plastically deforms.

13. Method according to claim 11 or 12, wherein material is removed from the break element (11) to set the force at which the stiffener yields.

Drawing