JP7487915B2 - Energy Absorbing Lanyards - Google Patents

Description

The present invention relates to a lanyard that is used, for example, as a lifeline for workers working at height.

Lifelines are necessary to ensure the safety of workers working at height.
As a lifeline, it is required to function as an energy absorber (shock absorber) that gradually absorbs the energy of a fall so that the human body is not subjected to a sudden, large force (impact) when falling, and to function as a strong rope that ultimately provides the final strength to support the body.
Known examples of such lanyards are those that combine the above two functions by using multiple types of threads with different elongation and breaking strength as warp threads.
A separately manufactured shock absorber may also be attached to the lanyard to make it an energy absorbing lanyard.

Japanese Utility Model Publication No. 49-11428 Japanese Patent Application Laid-Open No. 50-4725 JP 2003-275333 A JP 2010-168687 A Japanese Patent Application Laid-Open No. 7-246909

However, new standards for lanyards (e.g. JIS) have increased the load capacity, requiring lanyards to support loads of 100 kg or more (100 kg or 130 kg). Also, the impact on the body is now expressed as an average impact load, rather than a maximum impact load.
However, it is becoming increasingly difficult to meet the above standards when a single belt is woven with both threads that provide final strength and threads that absorb energy (stretch threads or chopping threads).
Some energy absorbing lanyards are made by creating the part responsible for energy absorption and the part responsible for final strength as separate pieces and then combining the two to make an energy absorbing lanyard, but these have problems such as being too thick in diameter and being heavy, and they can also hinder the worker's work.
There is a demand for energy absorbing lanyards that meet the new standards in terms of safety performance while also offering improved ease of use and appearance.

The energy absorbing lanyard of the present invention comprises:
A tubular rope section woven into a cylindrical shape,
A core rope portion is woven separately from the tubular rope portion and is accommodated inside the tubular rope portion,
The tubular portion includes, as part of its warp yarns, high-elongation energy-absorbing warp yarns that stretch and absorb energy when a load is applied,
When an impact is applied to the tubular steel portion, the tubular steel portion gradually extends from a length LTs in an unloaded state while absorbing energy, to a length LTe after absorbing the impact,
The core steel portion is a steel having an ultimate breaking strength of 15 kN or more, and has a length LC that is at least longer than the length LTe of the tubular steel portion after shock absorption,
The starting end of the core rope portion and the starting end of the tubular rope portion are fixed, the end of the core rope portion and the end of the tubular rope portion are fixed, and the core rope portion is stored inside the tubular rope portion in a folded state.

In one embodiment of the present invention,
Further, an elastic string member having a natural length shorter than the length LTs of the tubular rope portion in an unloaded state is provided on the inside of the tubular rope portion,
It is preferable that the starting end of the tubular rope portion and the starting end of the elastic string member are fixed, and the end of the tubular rope portion and the end of the elastic string member are fixed, so that when in an unloaded state, the tubular rope portion becomes bellows-like and its length is shortened.

1A and 1B are diagrams showing a first embodiment of an energy absorbing lanyard according to the present invention. FIG. 4 is a cross-sectional view for explaining a steel portion. 1 is a schematic cross-sectional view of a tubular steel portion cut in a direction perpendicular to the longitudinal direction. FIG. 1 is a schematic cross-sectional view of a tubular steel portion cut in a direction along the length direction. FIG. FIG. 13 is a diagram showing an example of calculation of the strength of a rope. FIG. 1 is a diagram showing test results of Experimental Examples 1 and 2. FIG. 13 is a graph showing the time progression of impact load during a drop test in Experimental Example 1. For comparison, a figure showing the results of a drop load test on a conventional lanyard. FIG. 11 illustrates a second embodiment. This is a diagram illustrating an example of a modified energy absorbing lanyard having a separate energy absorbing section (shock absorber section).

First Embodiment
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be illustrated and described with reference to the reference numerals given to the various elements in the drawings.
FIG. 1 is a diagram showing a first embodiment of an energy absorbing lanyard 100 (hereinafter simply referred to as lanyard 100) according to the present invention.
The lanyard 100 comprises a fastener 110 at one end and a rope portion 120 .

One fixture 110 is fixed to the work site at height, and the other fixture 110 is fixed to the body of the worker at height.

The rope section 120 is a lifeline that gradually absorbs energy when a worker at height falls or the like so that the worker at height is not subjected to an impact of more than a predetermined value, and ultimately holds the worker at height in a suspended position.
FIG. 2 is a cross-sectional view for explaining the steel portion 120. As shown in FIG.
The steel section 120 includes a tubular steel section 200 and a core steel section 300 .

The tubular rope portion 200 is woven into a tubular shape. When an impact is applied to the tubular rope portion 200, the tubular rope portion 200 is a rope that gradually stretches while gradually absorbing energy, thereby absorbing the impact.
FIG. 3 is a schematic cross-sectional view of the tubular steel portion 200 cut in a direction perpendicular to the longitudinal direction.
FIG. 4 is a schematic cross-sectional view of the tubular steel portion 200 cut in the longitudinal direction.
The tubular rope portion 200 may be woven into a tubular shape using a plain weave (plain double weave), a twill weave (twill double weave), or the like.

In Figs. 3 and 4, the warp yarns are in two layers,
Weft threads 212, 232 are woven into warp threads 211, 231 of the upper layer 210 and lower layer 230, respectively. At this time, the weft threads 212, 232 are woven into the warp threads 211, 231 of the upper layer 210 and lower layer 230 in a hollow weave, forming a tube with openings at both ends consisting of the upper layer 210 and the lower layer 230.
The loops of the weft yarns 212 and 232 are secured together by a tangle thread 240 as a lock thread to reinforce the weft yarns so that they do not come apart.
The warp yarns 211, 231 constituting the tubular section 200 are undrawn yarns.
The weft yarns 212, 232 and the lock yarn 240 are made of undrawn yarns, but may be made of drawn yarns.
For example, the warp threads 211 and 231 are made of undrawn polyester yarns of 1100T to 6600T.
For example, six undrawn polyester threads of 560T are bundled and twisted to form a warp yarn.
If the number of warp threads is set to 145 to 200, the strength of the rope (belt) is theoretically calculated as shown in Figure 5.

The yarns used for the warp yarns 211 and 231 are not limited to undrawn yarns.
For example, the warp yarn may be a yarn (textured yarn) obtained by shrinking (polyester) drawn yarn (by heat processing or the like) to give it high elongation, or a yarn specially spun as a high elongation yarn.
Ordinary drawn yarns have a breaking elongation of 40% or less (usually about 30%), but this yarn may be (heat) processed or the like to have a breaking elongation of 50% or more, preferably 60% or more (high elongation yarn) as the warp yarn.

Furthermore, the weft yarns 212, 232 and the interlacing yarn 240 may also be yarns having a drawing power of 280T to 2200T, such as polyester yarn.
Since the tubular rope portion 200 constitutes the outside of the rope portion 120, it is preferable to make the weft thread pitch as fine as possible and to place the weft threads densely in order to ensure abrasion resistance.
For example, the weft pitch may be set to 30 pics/30 mm or more.
Since the tubular rope portion 200 constitutes the outer side of the rope portion 120, a weather-resistant material (especially a light-resistant material) (resin) or an abrasion-resistant material (resin) may be applied to the outer surface of the tubular rope portion 200, or the tubular rope portion 200 may be woven using thread coated with a weather-resistant material (especially a light-resistant material) (resin) or an abrasion-resistant material (resin).

The core rope portion 300 is a rope that will never break even to the very end, even if it is subjected to impact when a worker at high altitude falls.
The core steel portion 300 is, for example, a steel having an ultimate breaking strength of 15 kN or more, and desirably an ultimate breaking strength of 18 kN or more.
The ultimate breaking strength of 15 kN or more here complies with the criteria set forth in standards (e.g., ISO), and the ultimate breaking strength required for the core rope portion 300 is the value required for it to ultimately support the body as a lifeline.
The core rope portion 300 may have a common weave such as a plain weave, a plain double weave, or a twill weave.
Since the core rope portion 300 requires a final strength and must be contained within the tubular rope portion 200, it is preferable to use high-strength polyethylene or aramid fiber (which is thin and strong) as the thread used for the core rope portion 300.
For example, the warp threads of the core rope portion 300 are preferably twisted threads of 1100T or more, and the weft threads of the core rope portion 300 are preferably twisted threads of 560T or more.

Here, the core steel portion 300 needs to have a sufficient length to accommodate the elongation of the outer tubular steel portion 200 when the outer tubular steel portion 200 elongates during energy absorption.
The length of the tubular steel part 200 in an unloaded state is assumed to be the unloaded length LTs. The tubular steel part 200 gradually expands while absorbing energy, and the length after shock absorption becomes the post-shock absorption length LTe. At this time, the core steel part 300 is formed so that its length is longer than the post-shock absorption length LTe of the tubular steel part 200. As illustrated in FIG. 2, the core steel part 300 is stored inside the tubular steel part 200 in a folded state. The start end of the core steel part 300 and the start end of the tubular steel part 200 are fixed, and the end of the core steel part 300 and the end of the tubular steel part 200 are fixed.

In this configuration, the operation of this embodiment is as follows.
In the event that a worker wearing the lanyard 100 of this embodiment falls, when the fixing brackets 110, 110 at both ends are pulled, both ends of the tubular rope portion 200 and the core rope portion 300 are pulled in the same manner.
At this time, the outer tubular rope part 200 first gradually expands while absorbing the energy, preventing a sudden large force from being applied to the worker's body. For example, the maximum impact on the worker's body can be prevented from exceeding 4 kN. After the tubular rope part 200 expands and absorbs all the energy, the core rope part 300 inside the tubular rope part 200 finally supports the weight of the worker and suspends him so as to prevent him from colliding with the ground.

In this embodiment, the tubular rope portion 200, which absorbs energy, and the core rope portion 300, which is responsible for the final strength, are constructed as separate entities. Therefore, the tubular rope portion 200 is specialized for absorbing energy, and the effect of gradually absorbing energy as the polyester thread stretches can be utilized. In addition, the core rope portion 300 is specialized for final strength, and may be strongly constructed from high-strength polyethylene or aramid fibers.

New standards for the lanyard 100 (e.g., JIS) have increased the specified load so that it must support a load of 100 kg or more (100 kg or 130 kg), and also stipulate that the instantaneous maximum impact load must not be less than a specified value (e.g., 4 kN) and that the average impact load during a fall must not be less than a specified value (e.g., 4 kN).
Many conventional lanyards were designed to combine final strength and energy absorption in a single belt, but it is now difficult to meet the above standards with a configuration in which a thread responsible for final strength and a thread responsible for energy absorption (stretch thread or shred thread) are woven together into a single belt.

In addition, there are conventional lanyards in which a belt responsible for final strength and a belt responsible for energy absorption are woven separately and then combined to meet the above standards. For example, there is a conventional lanyard in which the belt responsible for final strength is a tubular belt, a stretchable belt responsible for energy absorption is housed inside the strong tubular belt, and the outer strong tubular belt is folded in an accordion-like shape to make it shorter.
However, when the belt that provides the final strength is woven into a tubular shape, it becomes quite thick and heavy.
The tubular belt that provides the final strength is woven long to allow for the stretching of the energy absorbing belt inside, so it would take a lot of effort to manually fold it into a bellows shape. When folded into a bellows shape, its diameter becomes quite large.
In addition, if the tubular belt that provides the final strength is on the outside, it will deteriorate and become damaged more quickly due to light and wear, which raises concerns about whether the final strength that supports the worker's body will be maintained.

In this regard, in the lanyard 100 of this embodiment, the outer tubular rope portion 200 does not need to be bellows, and can look no different from a normal belt (string) with a narrow diameter (or width). The slim lanyard 100 does not get in the way of the worker and looks good. The outer tubular rope portion 200 is relatively soft and does not get in the way of the worker's work. The core rope portion 300, which is responsible for the final strength, is housed in the tubular rope portion 200, so it is protected from deterioration and damage, making the safety of the lanyard 100 more reliable.

(Experimental Example)
Experimental Examples 1 and 2 are shown.
In both experimental examples 1 and 2, the tubular steel portion 200 was configured as follows.
As the warp yarns, 201 yarns each consisting of six bundles of undrawn polyester yarns 560T are used.
The weft yarn is made of 1100T stretched polyester yarn.
The weft pitch was 30 pics/30 mm, and the fabric was flat double woven.
The intertwining yarn was made of 560T stretched polyester yarn.
In addition, 6 strands of undrawn polyester yarn of 560T is 3360T, which falls within the range of 1100T to 6600T.
The drawn polyester yarn 1100T falls in the range of 560T to 2200T.

The core steel portion 300 of the experimental example 1 was configured as follows.
As the warp yarns, 72 strands of 1670T polyethylene yarn (twist number 80 t/m) were used.
The weft yarn was polyester yarn 1100T.
The weft pitch was 25 pics/30 mm, and the fabric was flat double woven.
Polyester thread 470T was used as the entwining thread.
The length of the lanyard 100 when unloaded was 2320 mm.

The core steel portion 300 of the experimental example 2 was configured as follows.
As the warp yarns, 80 strands of 1670T polyethylene yarn (twist number 80 t/m) were used.
The weft yarn was polyester yarn 1100T.
The weft pitch was 18 pics/30 mm, and the fabric was twill woven.
Polyester thread 470T was used as the entwining thread.
The length of the lanyard 100 when unloaded was 2270 mm.

FIG. 6 shows the results of a drop load test of Experimental Examples 1 and 2 using a weight of 100 kg.
It can be seen that the maximum impact load and the average impact load are kept below 4 kN.

FIG. 7 shows a graph of the impact load versus time during the drop test of Experimental Example 1.
Not only are the maximum and average impact loads below 4 kN, but the rise in load is smooth and the material gradually begins to absorb energy, reaching a nearly constant value just before the maximum impact load reaches 4 kN, demonstrating a consistent, stable and smooth energy absorption performance until the very end.

FIG. 8 shows, for comparison, the results of a drop load test on a conventional lanyard.
The comparative example is a product sold commercially under the name G-Cut Lanyard.
With conventional products, the impact load is suddenly large from the initial rise, and then there are multiple large impacts.
Also, as energy absorption begins to stabilize, the energy is gradually absorbed and the impact smoothly decreases, but there is still a tendency for a large impact to occur at the end.
If this were to actually apply to the human body, it would result in the body being subjected to relatively large shocks multiple times, which is not desirable.

There are also energy absorbing lanyards in which the lanyard itself is a belt or rope that does not absorb energy, and a separate absorber with a breakable thread woven into it is attached, but with energy absorbing lanyards of this configuration, the impact tends to be more wavy.

In contrast, in the present invention, the rise in energy absorption is smooth and the energy absorption starts gradually, becoming almost constant just before the maximum impact load reaches 4 kN, and constant stable and smooth energy absorption performance is exhibited until the end.
By improving the energy absorption as much as possible, it is possible to absorb energy of 3kN or less within the standard elongation, making it possible to make a lanyard that is even gentler on the body.

Second Embodiment
Furthermore, it is preferable to insert an elastic string member 400 whose natural length is shorter than the length LTs of the tubular rope part 200 in an unloaded state into the tubular rope part 200, and to fix the ends of the tubular rope part 200, the core rope part 300, and the elastic string member 400 together. The elastic string member 400 may be a rubber belt woven with elastic thread, or a single synthetic resin (rubber) string.
9, this configuration allows the tubular rope portion 200 to be folded into an accordion shape to shorten the entire length, resulting in a lanyard 100 with bellows-like elasticity. In addition, since the tubular rope portion 200 of the present invention is relatively soft, it naturally folds into an accordion shape due to the contraction of the elastic string member (rubber belt).

The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit and scope of the present invention.
All of the warp threads in the tubular rope section 200 may be high-elongation threads, or the tubular rope section 200 may contain multiple other types of threads (warp threads, weft threads), and may include shredded threads with low elongation and low breaking strength, for example.

The energy absorbing lanyard of the present invention has strength and energy absorbing properties in itself and may be used alone, or may be further provided with an energy absorbing section (shock absorber section) 500, as illustrated in Figure 10, for example.
For example, the energy absorbing section (shock absorber section) 500 is normally sewn in a folded state, and when a sudden tensile force equal to or greater than a predetermined value is applied, the sewing thread breaks and the section stretches, absorbing the impact (energy) when the thread breaks.

100 Lanyard 110 Fixing device 120 Rope portion 200 Tubular rope portion 300 Core rope portion 400 Elastic rope member

Claims (2)

A tubular rope section woven into a cylindrical shape,
A core rope portion is woven separately from the tubular rope portion and is provided in a state of being housed inside the tubular rope portion,
The tubular portion includes, as part of its warp yarns, high-elongation energy-absorbing warp yarns that stretch when a load is applied to absorb energy,
When an impact is applied to the tubular steel portion, the tubular steel portion gradually extends from a length LTs in an unloaded state while absorbing energy, to a length LTe after absorbing the impact,
The core steel portion is a steel having an ultimate breaking strength of 15 kN or more, and has a length LC that is at least longer than the length LTe of the tubular steel portion after shock absorption,
An energy absorbing lanyard characterized in that the starting end of the core rope portion and the starting end of the tubular rope portion are fixed, the end of the core rope portion and the end of the tubular rope portion are fixed, and the core rope portion is stored inside the tubular rope portion in a folded state. 2. The energy absorbing lanyard of claim 1,
Further, an elastic string member having a natural length shorter than the length LTs of the tubular rope portion in an unloaded state is provided on the inside of the tubular rope portion,
An energy absorbing lanyard characterized in that an initial end of the tubular rope portion and an initial end of the elastic cord member are fixed, an end of the tubular rope portion and an end of the elastic cord member are fixed, and when in an unloaded state, the tubular rope portion becomes bellows-like and its length is shortened.

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