[001] Various embodiments relate generally to fall-protection safety equipment, especially energy absorbing devices.

BACKGROUND

[002] Fall-protection safety equipment is widely used in activities that are conducted at dangerous heights. Fall-protection safety equipment is used both in employment activities and in recreational activities. New technologies may introduce new employment needs for people requiring fall-protection. For example, high- voltage power line construction and maintenance may require workers to operate high above ground level. Wind turbine towers present many employment opportunities as well. Wind turbine towers may have complex electricity generators in the turbines as well as sophisticated mechanical elements. Such turbines may require frequent maintenance. Workers who ascend these towers may be required to wear fall-protection equipment. Insurance costs may be reduced if an employer would require strong safety measures for its employees.

SUMMARY

[003] Apparatus and associated methods relate to an energy-absorbing device having a coiled shearing strip that is circumierentiaily pulled past a shearing device creating multiple parallel sheared strips. A take-up spool may coil the multiple parallel sheared strips accumulating the sheared strips during an energy absorbing event. When the diameter of the sheared strips accumulated on the take-up spool exceeds a radial distance from the center of the take-up spool to the shearing device, frictional resistance to rotation may substantially increase. The shearing strip may be scored in the pre-coiled longitudinal direction to promote the position where shearing will occur. The shearing device may be a pin. The pin may have independent rollers having a. one-to-one correspondence with the sheared strips. The rollers may reduce the resistance of the sheared strips as they are pulled past the shearing device. By coiling the shearing strip, multiple circumferences of shearing travel may be packaged in a small volume. [004] Various embodiments may achieve one or more advantages. For example, some embodiments may provide a safe force profile to the user while a fall is arrested. In some embodiments, a fall arrest may permit a long but gentle force profile. In some embodiments, a predetermined force profile may result. An exemplary embodiment may permit energy absorption be wearing a small device. A replaceable shearing member may be a low-cost consumable. A custom shearing member may be selected for each worker based upon the weight of the worker. In some embodiments, the small size of the energy absorbing device may permit its use in applications where space is limited. An easily replaceable shearing member may permit companies and individuals to perform their own maintenance.

[0051 The details of various embodiments are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims,

BRIEF DESCRIPTION OF THE DRAWINGS

[006] FIG. 1 depicts a scenario in which an exemplary Self-Retracting Lifeline (SRL) energy absorption system is used to provide safety to a workman.

[007] FIG. 2 depicts a perspective view of an exemplary energy-absorbing device with coiled shearing.

[008] FIG. 3 depicts a plan view of an exemplary energy-absorbing device with coiled shearing.

[009] FIG. 4 depicts a perspective view of a cutaway of an exemplar}' energy- absorbing device with coiled shearing.

[0010] FIG. 5 depicts a cross-sectional view of an exemplary energy-absorbing device with coiled shearing.

[001 1] FIG. 6 depicts a perspective view of an exemplary shearing member in isolation.

[0012] FIG. 7 depicts a schematic drawing of an exemplary shearing member.

[0013] FIG. 8 depicts a plan view of an exemplary shearing member.

[0014] FIG. 9 depicts an exploded perspective view of an exemplary energy- absorbing device with coiled shearing member.

[0015] FIG. 10 depicts a plan view of an exemplary energy-absorbing device with coiled shearing member. [0016] FIG. 11 depicts a plan view of an exemplary rotating member of an exemplary energy-absorbing device.

[00171 FIG. 12 depicts a plan view of an exemplar}' shearing strip of an exemplar}' energy-absorbing device.

[0018] FIG. 13 depicts a plan view of an exemplary rotating member of an exemplary energy-absorbing device.

[0019] FIG. 14 depicts a schematic drawing of an exemplary shearing strip.

[0020] FIG. 15 depicts a graph showing exemplary relationships between arresting force and felling for falls that use energy absorbing devices and for falls that do not use energy absorbing devices.

[0021] Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0022] To aid understanding, this document is organized as follows. First, an exemplary scenario in which a fall-protection safety harness may be used is briefly introduced with reference to FIG. 1. Second, with reference to FIGs, 2-8, an exemplar}' energy absorbing device is described. The discussion turns to another exemplary embodiment that illustrates other aspects of exemplary coiled element energy absorbing devices, with reference to FIGs. 9-14. Finally, with reference to FIG. 15, further explanatory discussion is presented to explain exemplar}' fall force profiles. Comparisons between fall force profiles falls using energy absorbing devices and falls without such devices will be presented,

[0023] FIG. 1 depicts a scenario in which an exemplary Sel -Retracting Lifeline

(SRL) energy absorption system is used to provide safety to a workman. In FIG. 1, a construction site 100 shows a fallen workman 105 dangling beneath a. beam 110. The workman 105 has fallen a fair distance from the beam 1 10. The workman's fall was arrested by a lanyard 1 15 connecting the beam 1 10 to a fall-protection harness 120 that the workman 105 is wearing. The workman's fall was arrested in a controlled manner to prevent injury to the workman 105. The fall-protection safety harness 120 has an exemplary energy- absorbing device 130. The energy-absorbing device 130 has a coiled sharing member (not depicted in FIG. 1) within a circular housing 135. Without such an energy absorbing device 130 a workman's fall may be abraptly arrested imparting a large force to the workman 105. The energy-absorbing device may soften the fail by distributing the impacts force profile over a duration of time. The distribution of the force profile over time may permit the reduction in the maximum force imparted to the workman 105, for example. An increased distance of the fall during an arrest portion may be traded for a decreased maximum force, for example.

[0024] FIG. 2 depicts a perspective view of an exemplary energy-absorbing device with coiled shearing. In FIG. 2, an energy-absorbing device 200 includes a rotating cable reel 205 coupled to a fixed member 210. The energy-absorbing device 200 may be attached to a fail -protection safety harness for example. In some embodiments the energy-absorbing device 200 may be deployed on a boom. The rotating cable reel 205 may rotate on a bearing, for example. In some embodiments, the rotating cable reel 205 may rotate on a bushing. The rotating cable reel 205 may have a spring return for automatic recoiling of cable, for example. In some embodiments, the energy -absorbing device 200 may uncoil the cable from the rotating cable reel 205 in response to the user demanding more cable at a slow rate. In various embodiments, should the user demand cable rapidly, such as for example during a fall event, a brake may engage which may couple the rotating cable reel 205 to a take-up spool 215. In various embodiments, the cable may be unspooled only as a user actuates a cable release mechanism. In some embodiments, for example, a cable release mechanism may temporarily uncouple the rotating cable reel 205 from the take-up spool 215 as cable is permitted to unspool. In some embodiments, while a cable release mechanism is not actuated, the rotating cable reel 205 may be coupled to the take-up spool 215. When a rotating cable reel is coupled to the take-up spool, rotation of the rotating cable reel may cause the take-up spool to rotate. In various embodiments, the rotating cable reel 205 may be permanently coupled to the take-up spool 215.

[00251 FIG. 3 depicts a plan view of an exemplar}' energy-absorbing device with coifed shearing. In the FIG. 3 embodiment, an energy-absorbing device 300 includes a rotating cable reel 305 and a take-up spool 310. A shearing strip 315 is attached to the take- up spool 310 via a connecting tab 320. A shearing pin 325 is interposed within a pre-sheared portion of the shearing strip 315. The shearing strip 315 is coiled within a shearing cavity 330 within the rotating cable reel 305. In the depicted embodiment, there is a coiling space 335 between an outside 340 of the shearing pin 325 and an inside 345 of the shearing cavity 330. Various embodiments may have larger or smaller coiling space 335. The coiling space 335 may permit a shearing strip 315 to be coiled three rotations for example. In the depicted embodiment, the coiling member 315 is coiled two full rotations within the shearing cavity 330. Thus, the shearing strip 315 is attached to the take-up spool 310. From there it becomes pre-sheared and passes both above and below the shearing pin 325. From there it coils around the inside of the shearing cavity 330 two full rotations.

[0026] FIG. 4 depicts a perspective view of a cutaway of an exemplary energy- absorbing device with coiled shearing. In FIG. 4, a shearing strip 400 is shown without a rotating cable reel. The shearing strip 400 is attached to a take-up spool (not depicted) via an angled tab 405. The shearing strip 400 has a pre-sheared region 410 where a width 415 of the shearing strip 400 has been pre-sheared into three strips 420, 425, 430. The two outside pre-sheared strips 420, 430 travel above a shearing pin 435. The inside pre-sheared strip 425 travels below the shearing pin 435. The shearing strip 400 resumes its unsheared character on either side of the pre-sheared region and is coifed for two full rotations. Should the take- up spool rotate in a counter-clockwise direction, the unsheared coils would offer resistance to rotation. If the rotational torque becomes greater than the resistance to rotation, the unsheared coils would begin to shear so as to permit strip travel past the shearing pin 435. As rotation of the take-up spool continues, the sheared portion of the shearing strip 400 may lengthen and the sheared portion of the shearing strip 400 may be coiled upon the take-up spool.

[0027] The shearing pin 435 is positioned within the pre-sheared region 410 of a shearing strip 400. In this embodiment, the shearing pin 435 has three rollers 440 445 450. Each roller 440, 445, 450 corresponds to a sheared strip 430, 425, 420, respectively. The rollers may freely rotate on a shaft of the shearing pin. The rollers 440, 445, 450 may provide a. low-friction path for the sheared strips 430, 425, 420as they are pulled past the shearing pin 435. In some embodiments the rollers 440, 445, 450 may have bushings to faciliiate their rotation. In some embodiments the rollers 440, 445, 450 may have bearings to facilitate their rotation. In some embodiments the rollers may be made of an oil impregnated brass, for example. In some embodiments, the rollers may be made of bronze. In various embodiments the rollers may be made of a polymer material.

[0028] FIG. 5 depicts a cross-sectional view of an exemplary energy-absorbing device with coiled shearing. In this cross-sectional view, a rotating cable reel 500 may include an attached shearing pin 505. A take-up spool may be attached to a fixed member 515. In such an arrangement, rotating the rotating cable reel 500 may pull the shearing pin 505 through a coiled shearing strip 520. In some embodiments, rotating the rotating cable reel 500 may pull the coiled shearing strip 520 past the shearing pin 505. [0029] FIG. 6 depicts a perspective view of an exemplary shearing strip in isolation.

In FIG. 6, an exemplary shearing strip 600 includes a take-up spool tab 605, a pre-sheared region 610, and two coiled rotations 615. In some embodiments, the shearing strip may be made of steel. In some embodiments, the shearing strip may be made of aluminum. The exemplary shearing strip 600 has three pre-sheared regions 620, 625, 630, Various embodiments may have more or fewer pre-sheared regions. Some embodiments may have an odd number of pre-sheared regions. Some embodiments may have an even number of pre-sheared regions. Various embodiments may have a pin roller corresponding to each pre- sheared region, for example. In some embodiments pin rollers may not be used.

[00301 FIG. 7 depicts a schematic drawing of an exemplary shearing strip. In FIG. 8, a plan view of a shearing strip 700 shows a pre-sheared region 705 and a shearing prepared region 710. Also depicted is a transition region 715, between the pre-sheared region 705 and the shearing prepared region 710. In the pre-sheared region 705, the shearing strip 700 has channels 720 cut in the longitudinal direction. In the shearing prepared region 710, grooves 725 are scored into the surface of the shearing strip 700. The grooves 725 may perhaps better be seen in an end elevation view of the shearing strip 700. A side perspecti ve view of the shearing strip 700 details the transition region 715. The groove 725 transitions to the channel 720 at a slope 730. This slope 730 may direct the shearing from the channels 720 to along the grooves 725 during a fall event,

[0031] FIG. 8 depicts a plan view of an exemplary shearing strip. In the FIG. 8 embodiment, an exemplary shearing strip 800 is depicted with exemplary dimensions. The dimensions of a take-up spool 805 are given. As the diameter of the take-up spool is made larger, a longer length of material may be pulled through a shearing pin and sheared, for a fixed arrest distance. In this way, the diameter of the take-up spool can be a design parameter which can either decrease or increase the arrest distance. In some embodiments, the take-up spool diameter can be a design parameter that permits greater or lesser arrest force.

A shearing pin 810 is shown in relation to a shearing strip 815, and a take-up spool 805. A take-up dimension 820 is the distance between an outside 825 of the take-up spool 805 and an outside surface 830 of a sheared portion of the shearing strip 810. As the take-up spool 805 coils sheared material, the take-up dimension 820 becomes consumed by the sheared material being so coiled. When the take-up dimension 820 is completely consumed, the sheared material may begin to contact the outside surface 835 of the sheared portion of the shearing strip 815 that is adjacent to the shearing pin 810. When this condition arises, the rotation of the take-up spool 805 may be inhibited by the friction of the contact. This fric tion may become very large, which may provide a stop for further rotation of the take-up spool 805.

[0032] FIG. 9 depicts an exploded perspective view of an exemplar}? energy- absorbing device with coiled shearing strip. In FIG. 9, an exemplary energ -absorbing device 900 includes a rotating member 905, a shearing strip 910, and a fixed member 915. In some embodiments, the shearing strip 910 may be attached to the fixed member 910. In some embodiments the shearing strip 910 may be attached to the rotating member 905. The exemplar)' shearing strip 910 depicted in this figure has a longitudinal score 920 in the center on both faces of the shearing strip 910. The fixed member 915 has an attachment slot 925 to attach the shearing strip 910.

[0033] in some embodiments, the rotating member 905 has a shearing blade 930 which may slice the shearing strip 910 in a fall event. An end tab 935 may attach the shearing strip 910 to the attachment slot 925 of the fixed member 15,

[0034] In some embodiments, the shearing strip 910 may have a pre-sheared region

940. The pre-sheared reion 940 of the coiled shearing s trip 910 is depic ted as having been sheared into two strips 945, 950. An end tab 935 is on the end of one of the strips 945.

[0035] FIG. 10 depicts a plan view of an exemplary energy -absorbing device with coiled shearing strip. In the FIG. 10 embodiment, a coiled shearing strip 1000 is depicted within a fixed member 1020. In some embodiments, the coiled shearing strip 1000 may include two pre-sheared strips 1005, 1025. One of the pre-sheared strips 1005 has an attachment tab 1010. A shearing point 1015 at which shearing may proceed and at which a shearing blade of a rotating member shows the location where the coiled shearing strip 1000 is being sheared. The shearing point 1015 may rotate in the clockwise direction as the rotating member continues to rotate.

[0036] FIG. 11 depicts a ian view of an exemplary fixed member of an exemplary energy-absorbing device. In FIG. 1 1, an exemplary fixed member 1 100 includes a locking notch 1105 in which a corresponding locking tab of a shearing strip may attach, FIG. 12 depicts a plan vie of an exemplary shearing strip of an exemplary energy-absorbing device. In FIG. 12, an exemplary shearing strip 1200 includes a locking tab 1205, a pre-sheared region 1210 and a shear point 1215. FIG. 13 depicts a plan view of an exemplary rotating member of an exemplary energy-absorbing device. In FIG. 13, an exemplary rotating member 1300 includes a shearing blade.

[00371 FIG. 14 depicts a schematic drawing of an exemplar}' shearing strip. In FIG.

14, an exemplary shearing strip 1400 is shown in various perspective views. A pre-sheared region 1405 is shown. In this embodiment, the pre-sheared region 1405 has two strips 1410, 1415. One of the pre-sheared strips 1410 has a locking tab 1415. A shear-prepared region 1420 has two tear channels 1425, one on either an inside face 1430 or an outside face 1435. The tear channels 1425 are longitudinal scores in the center of the inside face 1430 and the outside face 1435. The tear channels 1425 may provide a preferential shearing path for shearing to take place.

[0038] FIG. 15 depicts a graph showing exemplary relationships between arresting force and falling for falls that use energy absorbing devices and for falls that do not use energy absorbing devices. In FIG. 15, a graph 1500 has a horizontal axis 1505 representing fall distance and a vertical axis 1510 representing the force that is exerted upon a worker as the fall is arrested, A dangerous force level 1515 is drawn as a horizontal line on the graph 1500. If a harmful force is applied to the worker, the worker may be injured. For example, a worker may suffer whiplash if the fall is arrested in a very abrupt fashion. An exemplar)' force profile 1520 corresponds to a force profile for a fall in which a worker is tethered to a beam but has not energy absorbing device. A peak force 1 25 greatly exceeds the harmful force level 1515 below which safe fall arrest may be performed. Also depicted on this graph 1500 is a force profile 1530 of a fall in which a worker is tethered to a beam and the worker is wearing an exemplary energy absorbing device. A peak force 1535, in this force profile 1530 if below the harmful force threshold 1515. An even lower peak force 1540 may be achieved by using a different take-up spool radius, for example.

[0039] Although various embodiments have been described with reference to the

Figures, other embodiments are possible. For example, some embodiments may use different shearing element materials. Some embodiments may use steel shearing strips. Some embodiments may use aluminum shearing strips, for example. Some embodiments may use synthetic shearing strips. For example, some embodiments may use polymeric materials in which preferential fiber directions may encourage longitudinal shearing. In various embodiments, different lengths of shearing strips may be used. For example, in some embodiments, a shearing strip may be coiled numerous times within shearing cavity. Some embodiments may have a single coiled rotation. [0040] Various embodiments may pull the shearing strip past the shearing element.

Some embodiments may pull the shearing element past the shearing strip. Various embodiments may use various geometries of shearing elements. Some shearing elements, for example may present a sharp edge to the shearing strip. Other shearing elements may facilitate shearing by directing the sheared strips along divergent paths. Some shearing elements may facilitate a tearing of the shearing strip. Some shearing elements may facilitate a slicing of the shearing strip.

[0041] Various shearing strips may be pre- scored to assist the preferential location of shearing. Some shearing strips may be worked in such a way as to provide a preferred shearing path. In an exemplar}' embodiment, a shearing strip may be machined to provide a narrowing on the preferred shearing path. The shearing path may be non-uniform is some embodiments. For example, the preferred shearing path may be easily sheared for the first half-rotation, and then the preferred path may be strengthened so that more arresting force may be applied for the next half-rotation of shearing. The shearing profile may be customized to provide a predetermined force profile for a fall event.

[0042] A number of implementations have been described. Nevertheless, it will be understood that various modification may be made. For example, advantageous results may be achieved if the steps of the disclosed techniques were performed in a different sequence, or if components of the disclosed systems were combined in a different manner, or if the components were supplemented with other components. Accordingly, other

implementations are within the scope of the following claims.