Patent Publication Number: US-2013239377-A1

Title: Retractable energy absorbing webbing and method of manufacturing same

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of U.S. patent application Ser. No. 12/855,341 titled “Retractable Energy Absorbing Webbing and Method of Manufacturing Same” filed Aug. 12, 2010, the contents of which are incorporated herein by this reference. 
    
    
     BACKGROUND OF THE INVENTION 
     People at elevated positions above a floor or other relatively lower surface are at risk of falling and injury. For example, workers and other personnel who have occupations that require them to be at elevated positions, such as on scaffolding, are at risk of falling and injury. Safety harnesses are often worn to stop a person&#39;s fall and prevent or reduce injury. 
     Safety harnesses typically have a harness portion worn by the user and a tether or lanyard extending from the harness portion. The lanyard connects the harness portion to a secure structure. If a person falls from the elevated position the safety harness stops the person&#39;s fall when the lanyard is straightened. 
     A load limiter on a seat belt system can be worn to secure the occupant of a vehicle in the event of a sudden stop or collision to reduce the risk of injury. If a person is subjected to inertia due to a vehicle&#39;s sudden stop, the load limiter limits the person&#39;s forward movement when the load limiter is straightened. 
     Retractable lanyard devices are used in some fall protection applications, and retractable load limiter devices are used in some seat belt systems. Retractable lanyard devices are typically comprised of a flat webbing that is capable of being received within a retractor. Existing retractable lanyard devices have a mechanical device in the retractor to stop the fall (by preventing the webbing from advancing further out of the webbing) or to dissipate energy (by deforming metal). With typical retractable lanyards devices, however, the person&#39;s movement is stopped rather abruptly and the person is subjected to the shock force of the abrupt stop. Moreover, existing retractable lanyard devices are bulky, heavy, and costly. 
     Lanyards that attempt to absorb the shock of a person&#39;s fall are known. Such lanyards, however, have bunched, accordion-type sections that lengthen as energy is absorbed. These bunched sections prevent the use of an energy absorbing webbing in a retractor, since a retractor requires the use of a flat webbing. Thus, a need exists for a retractable lanyard that absorbs energy. 
     SUMMARY OF THE INVENTION 
     Certain embodiments of the invention generally pertain to energy absorbing webbings and lanyards, and methods of making them. More specifically, some embodiments of the invention pertain to an energy absorbing webbing that is generally flat and therefore capable of being received within a retractor. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a perspective view of a retractor in use with an energy absorbing webbing according to one embodiment of the invention. 
         FIG. 2  is a side cross-sectional view of the energy absorbing webbing shown in  FIG. 1 . 
         FIG. 3  is a top cut-away view of the energy absorbing webbing of  FIG. 1 . 
         FIG. 4  is an illustration of a heating process for manufacturing the energy absorbing webbing of  FIG. 1  according to one embodiment of the invention. 
         FIG. 5  is a pick diagram of a weaving pattern of the energy absorbing webbing of  FIG. 1  according to one embodiment of the invention. 
         FIG. 6  is a draw-in diagram of the energy absorbing webbing of  FIG. 1  according to one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Certain embodiments of the invention provide webbings  10  that are suitable for use in retractors, such as retractor  12  shown in  FIG. 1 . As illustrated in  FIG. 1 , because webbing  10  is generally flat, webbing  10  is capable of being received within retractor  12  and of being retracted in and out of retractor  12 . 
     As shown in  FIG. 2 , webbing  10  comprises elongation yarns  14  and ground yarns  16  that are interwoven together. In some embodiments, ground yarns  16  are nylon, polyester, Kevlar, or any other high modulus, high tenacity yarn or other suitable materials that are relatively higher strength and that do not shrink or shrink substantially less than the elongation yarns  14  during heat treatment. For example, in some embodiments, the ground yarns  16  have a strength of at least 5,000 pounds tensile strength. In other embodiments, the ground yarns have a nominal breaking strength of greater than 5,400 pounds and, in some embodiments, have a nominal breaking strength exceeding 6,000 pounds, in compliance with 29 C.F.R. 1926.104(d) (2008), American National Standards Institute (“ANSI”) Z335.1, Canadian standard Z259.1.1 Class 1A and 1B, European standard BS EN 355:2002, and Australian standard AN/NZS 1891.1.1995. 
     Elongation yarns  14  are highly extensible yarns and significantly stretch when placed under a tensile load. The elongation yarns  14  are one example of an energy absorbing member of the webbing  10 . In one embodiment, the elongation yarns  14  are partially oriented yarns (POY) made of polymer materials such as polyester, but the elongation yarns  14  can be made from one or more suitable materials having high elongation properties and the ability to shrink in length substantially more than the ground yarns, such as during heat treatment. In some embodiments, each of the elongation yarns has a linear density of between approximately 300 denier and approximately 5,580 denier. 
     The elongation yarns  14  have an elongation property that allows the elongation yarns  14  to stretch significantly under a predetermined tensile force. The elongation yarns  14  have this elongation property even after they are subjected to a heat treatment process. When the webbing  10  is placed under tensile load, the elongation yarns  14  stretch under tension and absorb some of the force or energy applied to the webbing  10 . Accordingly, the elongation yarns  14  are a shock and energy absorbing member that provides a shock and energy absorbing feature. 
     In some embodiments, lateral yarns  18  (also referred to as “weft” or “pick” yarns) are woven in a weft direction across the webbing  10  to secure the elongation yarns  14  and the ground yarns  16  laterally across the webbing  10 . In some embodiments, the lateral yarns  18  are approximately 1,000 denier polyester yarns. In other embodiments, the lateral yarns  18  are industrial filament polyester, nylon, Nomex, Kevlar, or any other suitable yarn. 
     Important properties of the elongation yarns  14 , which serve as the energy absorbing member, include some or all of high elongation, high shrinkage, and high shrink-force (the force produced during the shrinkage). The elongation yarns  14  should have sufficiently high elongation and load bearing properties under load to absorb the load energy so as to reduce shock to a person or other body in a sudden deceleration state such as that caused by a fall from a building, a parachute deploying, or an impact due to an automobile or aircraft accident. In some embodiments, the webbings are adapted for use where dissipation of kinetic energy is required. 
     Webbings of the present invention may be formed on any desired programmable loom, such as a needle loom. As described above, the webbing  10  includes elongation yarns  14 , ground yarns  16 , and lateral yarns  18 .  FIG. 5  is a pick diagram (also known as a chain diagram or cam draft) for the webbing  10 . The squares along the x-axis represent the weaving path/throw of the lateral yarns  18 , and the y-axis corresponds to groups of warp yarns (such as the elongation yarns  14  and the ground yarns  16 ). The pick diagram of  FIG. 5  shows an eight harness loom. When a square is shaded, it indicates that the harness corresponding to that square is lifted as the lateral yarn  18  is thrown across the loom. 
     The draw-in diagram of  FIG. 6  shows the placement of the elongation yarns  14  and the ground yarns  16  in harnesses to produce the webbing  10  of  FIGS. 2-3 , while the pick diagram of  FIG. 5  represents the action of the harnesses with respect to the lateral yarns  18  to create the webbing  10 . The y-axis of the draw-in diagram of  FIG. 6  represents the number of harnesses of a loom used to make the webbing  10 . In this embodiment, eight harnesses are used. In the embodiment shown in  FIG. 6 , the bottom four harnesses (harnesses  1 - 4 ) comprise the ground yarns  16  and the top four harnesses (harnesses  5 - 8 ) comprise the elongation yarns  14 . The x-axis of  FIG. 6  represents the yarns that are used to create the webbing  10 , with row  26  showing the number of times each segment of the diagram repeats. For example, in one embodiment, the first segment can repeat any number of times (n×), while the second segment repeats one time (1×). The first column of  FIG. 6  illustrates that the first yarn is in the first harness frame, and the second yarn is in the second harness frame. In one embodiment, the webbing may be formed on any narrow fabric loom, including shuttle looms. 
     In one embodiment, the webbing  10  is a 4 foot by 1 and ⅜ inch nylon structure formed from approximately 248 Kevlar ground yarns (the ground yarns having a linear density of approximately 1,500 denier) and 90 elongation yarns (the elongation yarns being partially oriented yarns with a linear density of approximately 5580 denier). 
     In some embodiments, one end of the webbing  10  is attached to a hardware component, such as a clip  11 , metal clasp, harness, or seatbelt component, while the other end of the webbing  10  is situated within a retractor  12  (shown in  FIG. 1 ) that is then secured to a stable structure. In some embodiments, one end of the webbing  10  is attached to a harness and/or a clip for attachment to a child seat for use, for example, in an automobile or other vehicle. 
     In some embodiments, the webbing  10  is used as a deceleration device, to secure the occupant of a vehicle against harmful movement that may result from a sudden stop, or in any other application where rapid human or other body deceleration may occur. When using the webbing as a fall protection device, one end of the webbing  10  is securely attached to a safety harness worn by a user. The opposite end of the webbing  10  is securely attached to a fixed structure. If the user falls, the webbing  10  stops the person&#39;s fall and reduces the shock felt by the person as the user is brought to a controlled deceleration. As the person falls, the webbing  10  straightens and the load of the user is applied to the webbing  10 . The elongation yarns  14  stretch and absorb the force of the load applied to the webbing  10 . As the elongation yarns  14  stretch, the webbing  10  elongates. In the embodiments where the webbing is used with a retractor, once the webbing  10  has retracted from the retractor  12 , the webbing  10  stops the person from falling any farther. The shock of stopping the fall that would otherwise be felt by the falling person is reduced or cushioned by the energy-absorbing elongation yarns  14 . 
     Also provided is a process of manufacturing a generally flat energy absorbing woven webbing, such as webbing  10 . In one embodiment, webbing  10  is subjected to heat treatment to shrink the length of the elongation yarns  14 . When the webbing  10  is subjected to heat treatment, the elongation yarns  14  shrink in length while the ground yarns  16  do not, resulting in a greater weave-in of the elongation yarns  14  than the weave-in of the ground yarns  16 , where weave-in refers to the percentage difference in the length of the yarn before weaving and the length of the webbing after weaving. In some embodiments, the ground yarns  16  and the elongation yarns  14  both start with an about 6% weave-in, such that the length of the elongation yarns  14  and the ground yarns  16  are approximately 6% greater than the length of the webbing  10 . In one embodiment, after the webbing  10  is subjected to heat treatment, the length of the elongation yarns  14  and the length of the webbing  10  shrink by approximately 20%, while the length of the ground yarns  16  does not shrink. Thus, in this embodiment, the elongation yarns  14  will remain at around 6% weave-in while the ground yarns will have around 26% weave-in. In this way, the relative lengths of the elongation yarns  14  and the ground yarns  16  are automatically adjusted upon heat treatment. In one embodiment, the webbing  10  is heat treated in a manner so that shrinkage of the elongation yarns  14  is controlled. 
     For example, as illustrated in  FIG. 4 , the webbing  10  may be subjected to a heat treating process to adjust the length of the yarns of the webbing  10 . The heat treatment apparatus of  FIG. 4  includes a first set of rollers  22 , a second set of rollers  20 , and a heat source  24  located between the first and second set of rollers. Optionally, the apparatus may also include controls and/or monitors to control and/or monitor the feed ratio between the two sets of rollers and/or the temperature of the heat source. 
     In one embodiment, the webbing  10  is fed through the first set of rollers  22  to the heat source  24 , and out through the second set of rollers  20 . As shown in  FIG. 4 , the thickness of the webbing  10  changes as the webbing  10  is drawn from the first set of rollers  22  toward the second set of rollers  20 . This is because the weave-in of the ground yarns  16  increases as the webbing  10  is subjected to heat treatment. In certain embodiments, the amount of shrinkage of the elongation yarns  14  is controlled by varying the difference in speed of the first set of rollers  22  and the speed of the second set of rollers  20 . This difference in speed is referred to herein as the feed ratio of the rollers. 
     In one embodiment, the speed at which the webbing  10  is fed through the first set of rollers  22  is greater than the speed at which the webbing  10  is fed through the second set of rollers  20 . For example, in one embodiment, the feed speed associated with the first set of rollers  22  is approximately 10 yards per minute, while the feed speed associated with the second set of rollers  20  is approximately 8 yards per minute, for a feed ratio of 20%. Since the webbing  10  is exiting the heat source  24  at a speed that is 20% slower than the speed at which it entered the heat source  24 , the webbing  10  is subjected to an over feed ratio of 20% during heat treatment by the heat source  24 . In this way, the elongation yarns  14  will remain in tension between the first set of rollers and the second set of rollers and will be allowed to shrink approximately 20%, while the other materials (such as the ground yarns  16 ) are gathered by the forces of the elongation yarn shrinkage, which results in a greater than 20% weave-in and a length reduction of 20%. Because the elongation yarns  14  shrink when subjected to heat, while the ground yarns  16  do not have more than minimal shrinkage, the heat treatment process adjusts the relative length of the elongation yarns and the ground yarns. In some embodiments, the webbing  10  is subjected to approximately less than 5 minutes of heat treatment at a temperature of about 220° F. 
     The amount of elongation yarns  14  in the webbing  10  may be varied to adjust the forces required to elongate the webbing  10 . Similarly the shrinkage of the elongation yarns  14  in the webbing  10  may be varied to adjust the elongated distance, or the relative difference in length between the elongation yarns  14  and the ground yarns  16  of the webbing  10 . As described above, the difference in length between the two sets of yarns is caused by the difference in weave-in of the yarns. Similarly, the feed ratios between the first set of rollers  20  and the second set of rollers  22  may be varied to adjust the forces required to elongate the webbing  10  and the elongation distance of the webbing  10 . Finally, the duration and amount of heat applied to the webbing  10  also may be varied to adjust the forces required to elongate the webbing  10  and the elongation distance of the webbing  10 . This allows the properties of the webbing  10  to be tailored to the needs of the user and/or the application. 
     Various heat treating processes can be used to shrink the elongation yarns  14 . For example, a continuous oven may be used in an in-line, continuous heating process. The webbing  10  may be continuously woven and fed into the continuous oven for heat treatment. Another example of heat treatment is a batch process in which individual webbings are heat treated. 
     In one embodiment, a webbing  10  is designed to stop a falling person within 3.5 feet, which is in compliance with 29 C.F.R. 1926.104(d) (2008). In this embodiment, the webbing  10  has a finished, ready-for-use length of about 6 feet. Prior to the heat treatment, the elongation yarns  14  and the ground yarns have a length of approximately 9.5 feet. After heat treatment, the elongation yarns  14  have a reduced length of about 6 feet and the ground yarns  16  essentially retains their length of 9.5 feet. During use of the webbing  10 , the elongation yarns  14  will stretch from about 6 feet to about 9.5 feet. When the webbing  10  reaches the maximum 9.5 feet length, the webbing  10  stops the person&#39;s fall. The elongation yarns  14  absorb the energy of the fall and reduce the abrupt shock to the person when the webbing  10  stops the fall. In other embodiments, the webbing has a finished, ready-to-use length of about 4 feet. In one embodiment having a ready-to-use length of about 4 feet, the percentage of elongation yarns to ground yarns is approximately the same, however, the ratio of ground yarns to elongation yarns may vary depending on the application. For example, more ground yarns to elongation yarns may be required for higher strength applications, and more elongation yarns to ground yarns may be required when a greater deployment force is required. 
     In another embodiment of the present invention, a webbing has lengths of the elongation yarns and the ground yarns to stop a falling person within about 11.75 feet. The webbings, however, can be made in any desired length according to the present invention. 
     The webbings of the present invention can be made of any suitable materials including, but not limited to, synthetic material yarns woven to form the fabric structure. 
     Various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the invention and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.