Patent Publication Number: US-2021177126-A1

Title: Portable powered appliance support strap

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     The present continuation application claims priority under 35 USC § 120 from co-pending U.S. patent application Ser. No. 16/276,565 filed on Feb. 14, 2019 by Merten et al which was a non-provisional patent application claiming priority under 35 USC § 1169 from U.S. provisional patent application 62/630,582 filed Feb. 14, 2018, the full disclosures of which are hereby incorporated by reference. The present application is related to U.S. design Pats. D873649 and D841439, the full disclosures of which are incorporated by reference. 
    
    
     BACKGROUND 
     Portable powered appliances are used for a variety of tasks. Portable powered appliances are powered appliances that operate under the power supplied by a battery or an internal combustion engine and which or portable in that they are physically carried by a person using the appliance. Examples of portable powered appliances include, but are not limited to, edgers, trimmers, tillers and the like. Such portable powered appliances are often supported at least in part using a shoulder strap worn over a person&#39;s shoulders and coupled to the portable powered appliance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Response  FIG. 1  is a front perspective view of an example powered appliance support system having an example powered appliance support strap (schematically illustrated) and worn by a person to assist in carrying an example powered appliance. 
         FIG. 2  is a schematic diagram of an example powered appliance support strap of the system of  FIG. 1 . 
         FIG. 3  is a schematic diagram of an example powered appliance support strap of the system of  FIG. 1 . 
         FIG. 4  is a schematic diagram of an example powered appliance support strap of the system of  FIG. 1 . 
         FIG. 5  is a schematic diagram of an example powered appliance support strap of the system of  FIG. 1 . 
         FIG. 6  is a perspective view one example of the powered appliance support system of  FIG. 1 . 
         FIG. 7  is a front perspective view of an example powered appliance support strap of the system of Figure numeral six. 
         FIG. 8  is a bottom perspective view of the example powered appliance support strap of  FIG. 7 . 
         FIG. 9  is a front view of the powered appliance support strap of  FIG. 7 , the rear view of the powered appliance support strap being a mirror image of the front view. 
         FIG. 10  is a left side view of the powered appliance support strap of  FIG. 7 . 
         FIG. 11  is a right side view of the powered appliance support strap of  FIG. 7 . 
         FIG. 12  is a top view of the powered appliance support strap of  FIG. 7 . 
         FIG. 13  is a bottom view of the powered appliance support strap of  FIG. 7 . 
         FIG. 14  is a front perspective view of the example powered appliance support system of  FIG. 6  illustrating stretching of the example powered appliance support strap while being worn by a person to assist in carrying an example powered appliance. 
         FIG. 15  is a graph illustrating an example stretch profile for the powered appliance support strap of  FIGS. 6-14 . 
     
    
    
     Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements. The figures are not necessarily to scale, and the size of some parts may be exaggerated to more clearly illustrate the example shown. Moreover, the drawings provide examples and/or implementations consistent with the description; however, the description is not limited to the examples and/or implementations provided in the drawings. 
     DETAILED DESCRIPTION OF EXAMPLES 
     Disclosed is an example powered appliance support strap (PASS) configured to be operably coupled between the shoulder strap and the portable powered appliance, wherein the PASS is stretchable. The stretchability of the PASS facilitates repositioning of the PASS by the user during use of the PASS. The stretchability of the PASS absorbs weight of the portable powered appliance and relieves body tension. At the same time, the PASS stabilizes the powered appliance to facilitate enhanced control over the powered appliance. 
     In one implementation, the PASS is configured so as to not undergo stretching until experiencing a stretch triggering load of at least 4.5 kg (approximately 10 pounds) and no greater than 7 Kg (approximately 15.4 pounds). In another implementation, the PASS is configured so as to not undergo stretching until experiencing a stretch triggering load of at least 4.5 kg (approximately 10 pounds) and no greater than 5 kg (approximately 11 pounds). As a result, the PASS may better transfer the weight of the powered appliance to the shoulders of the person carrying the portable powered appliance in the absence of intentional stretching of the PASS. Moreover, the PASS is less likely to undergo inadvertent and/or excessive bouncing during use. 
     Disclosed herein is an example powered appliance support strap that may include a first portion to extend from a continuous loop of a shoulder strap, a second portion to extend from a powered appliance to be manually carried by a person wearing the shoulder strap and a stretcher extending between the first portion and the second portion. The stretcher does not undergo stretching until experiencing a stretch triggering load at least 1 kg and no greater than 7 kg, and in one implementation, no greater than 7 kg. 
       FIG. 1  schematically illustrates an example powered appliance support system  10  supporting an example powered appliance  12  from the shoulders of a user  14 . System  10  comprises shoulder strap  16  and powered appliance support strap (PASS)  20  (schematically illustrated). As shown by  FIG. 1 , strap  16  is in the form of a continuous loop that wraps over one shoulder and beneath an opposite shoulder of user  14 . In one implementation, strap  16  may have two ends which are releasably connected to one another. In one implementation, strap may have two ends which are releasably connected to one another via a buckle arrangement to provide strap  16  with an adjustable length. In one implementation, shoulder strap  16  may additionally comprise padding  18 . 
     PASS  20  is operably coupled between shoulder strap  16  and appliance  12 . For purposes of this disclosure, the term “coupled” shall mean the joining of two members directly or indirectly to one another. Such joining may be stationary in nature or movable in nature. Such joining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate member being attached to one another. Such joining may be permanent in nature or alternatively may be removable or releasable in nature. The term “operably coupled” shall mean that two members are directly or indirectly joined such that motion may be transmitted from one member to the other member directly or via intermediate members. 
     PASS  20  comprise a first portion  22  that extends from the continuous loop of shoulder straps  16 , a second portion  24  that extend from the powered appliance  12  and a stretcher  26  extending between the first portion  22  and the second portion  24 . In one implementation, the first portion  22  comprises a ring through which shoulder straps  16  extends, allowing portion  22  and PASS  22  slide along portions of the length of shoulder straps  16  to further facilitate repositioning of appliance  12 . Second portion  24  connects PASS  26  directly or indirectly to a portion of portable powered appliance  12 . In one implementation, the second portion  24  comprises a ring for connection to a quick disconnect to facilitate easy coupling and decoupling of PASS  20  from appliance  12 . In other implementations, the second portion  24  may be connected to powered appliance  12  in other fashions. In the example illustrated, second portion  24  is connected to powered appliance  12  between an engine/motor  27  of appliance  12  and a projecting bar or looped handle  28  of appliance  12 . In other implementations, second portion  24  may be connected to other portions of appliance  12 . 
     Stretcher  26  comprises that portion of PASS  20  that stretches. In one implementation, stretcher  26  is configured so as to not undergo stretching until experiencing a stretch triggering load at least 4.5 kg and no greater than 7 kg (approximately 15.4 pounds). In one implementation, the PASS is configured so as to not undergo stretching until experiencing a stretch triggering load of at least 4.5 kg (approximately 10 pounds) and no greater than 5 Kg (approximately 10 pounds). In another implementation, the PASS is configured so as to not undergo stretching until experiencing a stretch triggering load of at least 4.5 kg (approximately 10 pounds) and no greater than 5 kg (approximately 11 pounds). As a result, the PASS  20  may better transfer the weight of the powered appliance to the shoulders of the person carrying the portable powered appliance in the absence of intentional stretching of the PASS  20 . Moreover, the PASS  20  is less likely to undergo inadvertent and/or excessive bouncing during use. 
     In one implementation, structure  26  consists of a homogeneous, non-fibrous material. For example, in one implementation, stretcher  20  consists of a rubber or rubber-like material. In one implementation, stretcher  20  comprises a single homogeneous unitary body of a rubber or rubber-like material. In one implementation, the stretcher may comprise multiple beams interconnected by a web of elastic material or elastic segments expand between the beams. In one implementation, the multiple beams and the web of elastic material may be a single unitary homogeneous body of material, such as a rubber or rubber-like material. The multiple beams and web facilitate enhanced stretching performance while reducing the size and weight of PASS  20 . 
       FIG. 2  schematically illustrates PASS  120 , an example of PASS  20  that may be utilized as part of system  10 . PATH  120  comprises shoulder strap connector portion  122 , portable appliance connector portion  124  and stretcher portion  126 . Shoulder strap connector portion  122  connects to shoulder strap  16 . In one implementation, shoulder strap connector (SSC) portion  122  comprises a ring, loop or other structure that is slidable along portions of the length of shoulder straps  16  to facilitate repositioning of PASS  120 . In one implementation, show strap connector portion  122  is slidable along a length of at least 6 inches and nominally of at least 12 inches along an axial length of shoulder straps  16 . 
     Portable appliance connector (PAC) portion  124  connects a lower end of PASS  20  to a portable powered appliance, such as appliance  12  shown in  FIG. 1 . In one implementation, PAC portion  124  comprise a quick release connector. In other implementations, PAC may be fixedly connected or primly formed as part of the powered appliance. 
     Stretcher  126  extend between portions  122  and  124 . Stretcher  126  is similar to stretcher  26  described above. Stretcher  26  is configured so as to not undergo stretching until experiencing a stretch triggering load at least 10 pounds and no greater than 15 pounds. As a result, the PASS  120  may better transfer the weight of the powered appliance to the shoulders of the person carrying the portable powered appliance in the absence of intentional stretching of the PASS  120 . Moreover, the PASS  120  is less likely to undergo inadvertent and/or excessive bouncing during use. 
       FIG. 3  schematically illustrates PASS  220 , an example of PASS  20  that may be utilized as part of system  10  described above. PASS  220  is similar to PASS  120  except that PASS  220  comprises stretcher  226  in place of stretcher  126 . The remaining components of PASS  220  which correspond to components of PASS  120  are numbered similarly. 
     PASS  226  comprises beams  230 A,  230 B (collectively referred to as beams  230 ) and webbing  240  (schematically shown). Beams  230  extend between SSC portion  122  and PAC  124  on opposite sides of stretcher  226 . Beams  230  are each formed from a resiliently stretchable material, such as a rubber or rubber-like material. 
     Webbing  240  comprises a web of material that spans between beams  230 . Webbing  240  is resiliently stretchable. Webbing  240  cooperates with beams  230  to provide stretcher  226  with a resilient stretchability. In one implementation, webbing  240  and beams  230  provide stretcher  226  with a stretchability, wherein stretcher  226  does not undergo stretching until experiencing a stretch triggering load of at least 4.5 kg and no greater than 7 kg, anyone up limitation, no greater than 5 kg. For purposes of disclosure, “resilient” or “resiliently” or the rotors there from show mean that in the absence of an applied load, stretcher  226  or the individual component of stretcher  226  returns to its original unstretched size, shape and length. 
     In one implementation, webbing  240  and beams  230  are collectively resiliently stretchable so as to stretch, once the initial stretch threshold has been exceeded, by at least 0.6 and no greater than 0.9 cm in response to an applied load of 5 kg. In such an implementation, webbing  240  and beams  230  are collectively resiliently stretchable so as to stretch by at least 1.2 cm and no greater than 1.7 cm in response to an applied load of 7 kg. Further in such an implementation, webbing  240  and beams  230  are collectively resiliently stretchable for us to stretch by at least 2.7 cm and no greater than 2.11 cm in response to an applied load of 10 kg, once the initial stretch threshold has been exceeded. It has been found that such a resiliently stretchability for stretcher  226  provides enhanced support and shock absorption while avoiding excessive bouncing. In other implementations, stretcher  226  may have other elasticities. 
     In one implementation, webbing  240  comprises a series of crisscrossing elastic segments. In another implementation, webbing  240  comprises a weave of elastic segments. In another implementation, webbing  240  may comprise both parallel and oblique elastic segments. In one implementation, webbing  240  is integrally formed as a single unitary body with beams  230  from an elastomeric material, such as an elastomeric polymer, a rubber or rubber-like material. In another implementation, webbing  240  may comprise resilient elastic segments or strands that are separate from beams  230  but which are connected to beams  230 . For example, webbing  240  may comprise resilient elastic segments or strands having ends captured and embedded within beams  230 . In another implementation, webbing  240  may comprise resilient elastic segments or strands, bonded or welded to beams  230 . In another implementation, webbing  240  may comprise resilient elastic segments or strands repeatedly or continuously wrapping about each of beams  230 , wherein beams  230  form supporting sides of the overall webbing  240 . 
     In one implementation, webbing  240  and beams  230  a form from the same elastomeric material. In another implementation, webbing  240  may have a different material structure as compared to beams  230 . For example, in one implementation, beams  230  may be formed from a resiliently stretchable rubber or rubber-like material while webbing  240  comprises a resiliently stretchable webbing of elastomeric strands covered or encapsulated by a fabric or a resiliently stretchable fabric. 
       FIG. 4  schematically illustrates PASS  320  an example of PASS  20  that may be utilized as part of system  10  described above. PASS  320  is similar to PASS  220  except that PASS  220  comprises stretcher  326  in place of stretcher  226 . Stretcher  326  is similar to stretcher  226  except that stretcher  326  comprises an additional beam  230 C and comprises webbing  340  in place of webbing  240 . The remaining components of PASS  320  which correspond to components of PASS  120  and  220  are numbered similarly. 
     Beam  230 C is similar to beams  230 A and  230 B. With respect to those implementations having greater than two beams, each of the beams may be collectively referred to as beams  230 . Beam  230 C extends between and spans between SSC portion  122  and PAC  124 , between beams  230 A and  230 B. Beam  230 C is transversely spaced from each of beams  230 A,  230 B. In the example illustrated, beam  230 C is thicker and/or wider than corresponding portions of beams  230 A,  230 B. Beam  230 C provides enhanced strength and durability to stretcher  326 . 
     In one implementation, beam  230 C is formed from the same material as that of beams  230 A and  230 B. In one implementation, beam  230 C integrally formed as a single unitary body with beams  230 A,  230 B from a resiliently stretchable material, such as a rubber or rubber-like material. In one implementation, beam  230 C. In one implementation, beam  230 C is integrally formed as a single unitary body from a single homogeneous resiliently stretchable material with beams  230 A,  230 B and webbing  340 . 
     Webbing  340  is similar to webbing  240  described above except that webbing  340  comprises two separate spaced webbing portions or webs  342 A,  342 B (collectively referred to as webs  342 ). Webs  342  are each resiliently stretchable. Each of webs  342  may have a composition or structure similar to the individual webbing  340  described above. Web  342 A spans between and interconnects beams  230 A and  230 C. Web  342 B spans between and interconnects beams  230 B and  230 C. 
     Webbing  340  cooperates with beams  230  to provide stretcher  326  with a resilient stretchability. In one implementation, webbing  340  and beams  230  provide stretcher  326  with a stretchability, wherein stretcher  226  does not undergo stretching until experiencing a stretch triggering load of at least 1 kg and no greater than 7 kg and, in one implementation, no greater than 5 kg. In one implementation, webbing  340  and beams  230  are collectively resiliently stretchable so as to stretch by at least 0.6 and no greater than 0.9 cm in response to an applied load of 5 kg after the stretch threshold has been satisfied. In such an implementation, webbing  340  and beams  230  are collectively resiliently stretchable so as to stretch by at least 1.2 cm and no greater than 1.7 cm in response to an applied load of 7 kg. Further, in such an implementation, webbing  340  and beams  230  are collectively resiliently stretchable for us to stretch by at least 2.7 cm and no greater than 2.11 cm in response to an applied load of 10 kg. It has been found that such a resiliently stretchability for stretcher  226  provides enhanced support and shock absorption while avoiding excessive bouncing. In other implementations, stretcher  326  may have other elasticities. 
       FIG. 5  schematically illustrates PASS  420  an example of PASS  20  that may be utilized as part of system  10  described above. PASS  420  is similar to PASS  320  except that PASS  420  comprises stretcher  426  in place of stretcher  326 . Stretcher  426  is similar to stretcher  326  except that stretcher  426  comprises beams  430 A and  430 B (collectively referred to as beams  430 ) in place of beams  230 A and  230 B, respectively. The remaining components of PASS  420  which correspond to components of PASS  220 ,  120  and  220  are numbered similarly. 
     Beams  430 A,  430 B are each similar to beams  230 A,  230 B as described above except that beams  430  outwardly bow or curve away from beam  230 C. beams  430  are connected to beam  230 C by webs  342 A,  342 B (described above). In the example in  FIG. 5 , webbing  342  each have a slightly different to accommodate the outward bowing of beams  430 . The outward bowing of beams  430  enhances the control stretching performance of stretcher  426 . During such stretching, beams  430  moved towards a straightened state, a state in which beams  430  are parallel with beam  230 C. the bowed nature of beams  430  results in beam  430  initially straightening in response to an applied load. During such time, the linear shape of being  230 C (perpendicular between or with respect to portions  122  and  124 ) results in the material of beam  230 C resiliently stretching in response to an applied load straightening beam  230 C prior to the resilient stretching of beams  430 . 
     Webbing  340  cooperates with beams  430 ,  230  to provide stretcher  426  with a resilient stretchability. In one implementation, webbing  340  and beams  430 ,  230  provide stretcher  426  with a stretchability, wherein stretcher  426  does not undergo stretching until experiencing a stretch triggering load of at least 1 kg and no greater than 7 kg and, in one implementation, no greater than 5 kg. In one implementation, webbing  440  and beams  430 ,  230  are collectively resiliently stretchable so as to stretch by at least 0.6 and no greater than 0.9 cm in response to an applied load of 5 kg. In such an implementation, webbing  340  and beams  430 ,  230  are collectively resiliently stretchable so as to stretch by at least 1.2 cm and no greater than 1.7 cm in response to an applied load of 7 kg. Further in such an implementation, webbing  340  and beams  430 ,  230  are collectively resiliently stretchable for us to stretch by at least 2.7 cm and no greater than 2.11 cm in response to an applied load of 10 kg. It has been found that such a resiliently stretchability for stretcher  426  provides enhanced support and shock absorption while avoiding excessive bouncing. In other implementations, stretcher  426  may have other elasticities. 
       FIGS. 6-13  illustrate portions of an example portable appliance system  510 . Similar to system  10 , system  510  is configured to support an example powered appliance  12  (shown in  FIG. 1 ) from the shoulders of a user  14  (shown in  1 ). System  510  comprises shoulder strap  516 , powered appliance coupler  517 , quick disconnect  518  and powered appliance support strap (PASS)  520  (schematically illustrated). Strap  516  is in the form of a continuous loop that wraps over one shoulder and beneath an opposite shoulder of user  14 . In the example illustrated, strap  516  has two ends which are releasably connected to one another. In one implementation, strap  516  has two ends which are releasably connected to one another via a buckle arrangement  519  to provide strap  516  with an adjustable length. In one implementation, shoulder strap  516  may additionally comprise padding  521 . 
     Powered appliance coupler  517  comprises a connector that releasably connects to a shaft or other portion of the portable powered appliance, such as appliance  12  shown in  FIG. 1 . Powered appliance coupler  517  facilitates use of system  510  on pre-existing portable powered appliances. Powered appliance coupler  517  facilitates connection of PASS  520  to the powered appliance using quick disconnect  518 . Quick disconnect  518  comprises a quick disconnect device, such as a carabiner, hook or other similar connection mechanism connected to PASS  520  and releasably connected to or passing through a ring, loop, hook or other connection portion of coupler  517 . 
     PASS  520  is shown in more detail in  FIGS. 7-13 . PASS  520  comprises shoulder strap connector portion  522 , powered appliance connector portion  524  and stretcher  526 . Portions  522  and  524  each comprise rings through which or by which PASS  520  may be connected to shoulder strap  516  and the powered appliance  12  (shown in  FIG. 1 ). Portion  52  comprises a flat bar or ring forming a rectangular opening  523  through which a generally flat strap of shoulder strap  516  may extend and slide. Portion  124  comprises a more circular or curved ring having an opening  5254  being connected to quick disconnect  518 . In the example illustrated, each of portions  522  and  524  are partially embedded into the single continuous integral unitary body forming stretcher  526 . In one implementation, the metallic rings forming portions  522  and  524  are molded into the material forming stretcher  526 . In yet other implementations, the rings forming portions  522  and  524  are passed through the body of material forming stretcher  526 . 
     Stretcher  526  extends between portions  522  and  524 . Stretcher  526  comprises end caps  528 ,  529 , beams  530 A,  530 B,  530 C (collectively referred to as beams  530 ) and webs  542 A,  542 B (collectively referred to as webs  542 ). End caps  528 ,  529  extend along opposite ends of stretcher  526 . End cap  528  spans across and connects each of beams  530 . End cap  529  also stands across and connects each of beams  530 . As noted above, in the example illustrated, end caps  528 ,  529  are molded about portions of the rings that form connector portion  522  and  524 , respectively. End caps  528 ,  529  are part of a single integral unitary body with each of beams  530  and each of webs  542 . The example illustrated, due to the embedded metallic rings within and  52 A,  529 , and  52 A,  529  and a greater rigidity and stiffness and are generally not resiliently stretchable as compared to beams  530  and webs  542  which do not encapsulate or include internally embedded stiffening structures. 
     In other implementations, end caps  528 ,  529  may be formed from material different than the materials forming beams  530  and webs  542 . For example, in other implementations, end caps  528 ,  529  may be formed from a more rigid or stiffer polymer which is co-molded with the resiliently stretchable rubber or rubber-like material forming beams  530  and webs  542 . In still other implementations, end caps  528 ,  529  may be formed from a first rigid metal or polymer material that encapsulates or surrounds the rings forming portions  522 ,  524 , wherein the resiliently stretchable rubber or rubber-like material forming the integral and unitary structure providing beams  530  and webs  542  is over molded about end caps  528 ,  529  and/or through apertures passing through the rigid metal or polymer material forming end caps  528 ,  529 . 
     Beams  530 A and  530 B (collectively referred to as side beams  530 ) are transversely spaced from one another in extend along opposite sides of stretcher  526  of PASS  520 . Side beams  530  extends between and  528 ,  529 . Each of side beams  530  outwardly bows away from beam  530 C, providing stretcher  526  and PASS  520  with a substantially flat oval shape. 
     Beam  530 C forms a center beam or spine for stretcher  526  and PASS  520 . Beam  530 C generally extends perpendicular to the transverse axes of end caps  528 ,  529  from end cap  528  to end cap  529 . Beam  530 C has a width greater than the width of side the individual beams  530 . In the example illustrated, beam  530 C has an elongated oval shape, being wider at a midpoint and narrower in those regions proximate to end caps  528 ,  529 . 
     The shape of beams  530  accommodates the elongation or stretching of stretcher  526 . During initial stretching, the oval or bowed shape of side beams  530  allow side beams  530  straighten while undergoing a lesser degree of resilience stretching as compared to beam  530 C. the oval shape of beam  530 C, being wider at the center narrower at the end portions, accommodates the resilience stretching of beam  530 C, where the center portion of beam  530 C undergoes greater stretch and thinning in response to tensile forces as compared to the end portions of beam  530 C. The non-uniform width W (shown in  FIG. 9 ) facilitates resilience stretching of being  530 C and prolonging such stretchability prior to failure of beam  530 C. 
     Webs  542  span between beams  530 . Web  542 A spans between beams  530 A and  530 C. Web  542 B spans between beams  530 B and  530 C. Each of webs  542  may have a configuration similar to that described above with respect to webbing  240  or webs  342 . As noted above, webs  542  facilitates resilience stretching by connecting beams  530  or reducing the mass and weight of stretcher  526  and that of PASS  520 . As explained above, webs  520  may have a variety of different sizes, shapes and configurations as well as a variety of different patterns or arrangements. 
       FIGS. 14 and 15  illustrate stretching of PASS  520  during use. As shown by  FIG. 14 , stretcher  526  absorbs a weight and release body tension while stabilizing the powered appliance for enhanced control. As shown by  FIG. 14 , during such elongation, sidewalls  530  move inward towards spine  530 C. At the same time, PASS  520  is permitted to slide along shoulder strap  16  to center the load upon the user shoulders. 
       FIG. 15  illustrates an example stretch profile for the example PASS  520 . In the graph illustrated in  FIG. 5 , the center curve represents the average or nominal stretch profile while the uppermost and lowermost curves represent variations or tolerances for the average or nominal stretch profile. In the example illustrated, PASS  520  does not start to stretch until a weight or load of 1.13 kg (roughly 2.5 pounds) is exerted upon  520 . One stretching has begun, stretching occurs at a midpoint of PASS  520  pursuant to the depicted mathematical expression y=0.0276x 2 +0.0149x, where y is the length (in cm) of PASS  520  and where x is the applied weight or load (in kilograms). In the example illustrated, the stretching of PASS  520  has a variability of +/−13% of the applied weight. In other implementations, PASS  520  may delay stretching and begin to stretch at other triggering weight thresholds. In other implementations, once the stretch threshold has been exceeded, PASS  520  may stretch in accordance with other mathematical expressions or formulas. 
     Although the present disclosure has been described with reference to example implementations, workers skilled in the art will recognize that changes may be made in form and detail without departing from the scope of the claimed subject matter. For example, although different example implementations may have been described as including features providing benefits, it is contemplated that the described features may be interchanged with one another or alternatively be combined with one another in the described example implementations or in other alternative implementations. Because the technology of the present disclosure is relatively complex, not all changes in the technology are foreseeable. The present disclosure described with reference to the example implementations and set forth in the following claims is manifestly intended to be as broad as possible. For example, unless specifically otherwise noted, the claims reciting a single particular element also encompass a plurality of such particular elements. The terms “first”, “second”, “third” and so on in the claims merely distinguish different elements and, unless otherwise stated, are not to be specifically associated with a particular order or particular numbering of elements in the disclosure.