Patent Abstract:
A rope and method of making the same. The rope comprises a plurality of yarns. At least one of the yarns comprises first and second sets of fibers. The first fibers are formed of a first material, and the second set of second fibers at least partly surrounds the first fibers. The second fibers are formed of a second material. The first material defines a set of operating characteristics adapted to bear tension loads on the rope. The second material defines a set of operating characteristics adapted to affect at least one surface characteristic of the rope.

Full Description:
RELATED APPLICATIONS 
   This application claims priority of U.S. Provisional Application Ser. No. 60/530,132, which was filed on Dec. 16, 2003. 

   TECHNICAL FIELD 
   The present invention relates to rope systems and methods and, in particular, to wrapped yarns that are combined to form strands for making ropes having predetermined surface characteristics. 
   BACKGROUND OF THE INVENTION 
   The characteristics of a given type of rope determine whether that type of rope is suitable for a specific intended use. Rope characteristics include breaking strength, elongation, flexibility, weight, and surface characteristics such as abrasion resistance and coefficient of friction. The intended use of a rope will determine the acceptable range for each characteristic of the rope. The term “failure” as applied to rope will be used herein to refer to a rope being subjected to conditions beyond the acceptable range associated with at least one rope characteristic. 
   The present invention relates to ropes with improved surface characteristics, such as the ability to withstand abrasion or to provide a predetermined coefficient of friction. Typically, a length of rope is connected at first and second end locations to first and second structural members. Often, the rope is supported at one or more intermediate locations by intermediate structural surfaces between the first and second structural members. In the context of a ship, the intermediate surface may be formed by deck equipment such as a closed chock, roller chock, bollard or bit, staple, bullnose, or cleat. 
   When loads are applied to the rope, the rope is subjected to abrasion where connected to the first and second structural members and at any intermediate location in contact with an intermediate structural member. Abrasion and heat generated by the abrasion can create wear on the rope that can affect the performance of the rope and possibly lead to failure of the rope. In other situations, a rope designed primarily for strength may have a coefficient of friction that is too high or low for a given use. 
   The need thus exists for improved ropes having improved surface characteristics, such as abrasion resistance or coefficient of friction; the need also exists for systems and methods for producing such ropes. 
   RELATED ART 
   U.S. Pat. No. 3,367,095 to Field, Jr, discloses a process and apparatus for making wrapped yarns. The wrapped yarn of the &#39;095 patent comprises a core formed of continuous fibers and a wrapping formed of discontinuous fibers. The &#39;095 patent generally teaches that all synthetic and natural fibers including metal, glass, and asbestos may be used to form the core and wrapping but does not specify particular combinations of such materials for particular purposes. 
   SUMMARY OF THE INVENTION 
   The present invention is a rope having improved surface characteristics and method of making the same. The rope comprises a plurality of yarns. At least one of the yarns comprises first and second sets of fibers. The first fibers are formed of a first material, and the second set of second fibers at least partly surrounds the first fibers. The second fibers are formed of a second material. The first material defines a set of operating characteristics adapted to bear tension loads on the rope. The second material defines a set of operating characteristics adapted to affect at least one surface characteristic of the rope. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  is a side elevation view of a wrapped yarn that may be used to construct a rope of the present invention; 
       FIG. 1B  is an end elevation cutaway view depicting the yarn of  FIG. 1A ; 
       FIG. 2  is a side elevation view of a first example of a rope of the present invention; 
       FIG. 3  is a radial cross-section of the rope depicted in  FIG. 2 ; 
       FIG. 4  is a close-up view of a portion of  FIG. 3 ; 
       FIG. 5  is a side elevation view of a second example of a rope of the present invention; 
       FIG. 6  is a radial cross-section of the rope depicted in  FIG. 5 ; 
       FIG. 7  is a close-up view of a portion of  FIG. 6 ; 
       FIG. 8  is a side elevation view of a first example of a rope of the present invention; 
       FIG. 9  is a radial cross-section of the rope depicted in  FIG. 8 ; 
       FIG. 10  is a close-up view of a portion of  FIG. 9 ; and 
       FIG. 11  is a side elevation view of a first example of a rope of the present invention; 
       FIG. 12  is a radial cross-section of the rope depicted in  FIG. 8 ; 
       FIG. 13  is a close-up view of a portion of  FIG. 9 ; and 
       FIG. 14  is a schematic diagram representing an example process of fabricating the yarn depicted in  FIGS. 1A and 1B . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring initially to  FIGS. 1A and 1B  of the drawing, depicted therein is a blended yarn  20  constructed in accordance with, and embodying, the principles of the present invention. The blended yarn  20  comprises at least a first set  22  of fibers  24  and a second set  26  of fibers  28 . 
   The first and second fibers  24  and  28  are formed of first and second materials having first and second sets of operating characteristics, respectively. The first material is selected primarily to provide desirable tension load bearing characteristics, while the second material is selected primarily to provide desirable abrasion resistance characteristics. 
   In addition to abrasion resistance, the first and second sets of operating characteristics can be designed to improve other characteristics of the resulting rope structure. As another example, certain materials, such as HMPE, are very slick (low coefficient of friction). In a yarn consisting primarily of HMPE as the first set  22  for strength, adding polyester as the second set  26  provides the resulting yarn  20  with enhanced gripping ability (increased coefficient of friction) without significantly adversely affecting the strength of the yarn  20 . 
   The first and second sets  22  and  26  of fibers  24  and  28  are physically combined such the first set  22  of fibers  24  is at least partly surrounded by the second set  26  of fibers  28 . The first fibers  24  thus form a central portion or core that is primarily responsible for bearing tension loads. The second fibers  28  form a wrapping that at least partly surrounds the first fibers  24  to provide the rope yarn  20  with improved abrasion resistance. 
   The example first fibers  24  are continuous fibers that form what may be referred to as a yarn core. The example second fibers  28  are discontinuous fibers that may be referred to as slivers. The term “continuous” indicates that individual fibers extend along substantially the entire length of the rope, while the term “discontinuous” indicates that individual fibers do not extend along the entire length of the rope. 
   As will be described below, the first and second fibers  24  and  28  may be combined to form the example yarn using a wrapping process. The example yarn  20  may, however, be produced using process for combining fibers into yarns other than the wrapping process described below. 
   With the foregoing understanding of the basic construction and characteristics of the blended yarn  20  of the present invention in mind, the details of construction and composition of the blended yarn  20  will now be described. 
   The first material used to form the first fibers  24  may be any one or more materials selected from the following group of materials: HMPE, LCP, or PBO fibers. The second material used to form the second fibers  28  may be any one or more materials selected from the following group of materials: polyester, nylon, Aramid, LCP, and HMPE fibers. 
   The first and second fibers  24  and  28  may be the same size or either of the fibers  24  and  28  may be larger than the other. The first fibers  24  are depicted with a round cross-section and the second fibers  28  are depicted with a flattened cross-section in  FIG. 1B  for clarity. However, the cross-sectional shapes of the fibers  24  and  28  can take forms other than those depicted in  FIG. 1B . The first fibers  24  are preferably generally circular. The second fibers  28  are preferably also generally circular. 
   The following discussion will describe several particular example ropes constructed in accordance with the principles of the present invention as generally discussed above. 
   First Rope Example 
   Referring now to  FIGS. 2 ,  3 , and  4 , those figures depict a first example of a rope  30  constructed in accordance with the principles of the present invention. As shown in  FIG. 2 , the rope  30  comprises a rope core  32  and a rope jacket  34 .  FIG. 2  also shows that the rope core  32  and rope jacket  34  comprise a plurality of strands  36  and  38 , respectively.  FIG. 4  shows that the strands  36  and  38  comprise a plurality of yarns  40  and  42  and that the yarns  40  and  42  in turn each comprise a plurality of fibers  44  and  46 , respectively. 
   One or both of the example yarns  40  and  42  may be formed by a yarn such as the abrasion resistant yarn  20  described above. However, because the rope jacket  34  will be exposed to abrasion more than the rope core  32 , at least the yarn  42  used to form the strands  38  should be fabricated at least partly from the abrasion resistant yarn  20  described above. 
   The exemplary rope core  32  and rope jacket  34  are formed from the strands  36  and  38  using a braiding process. The example rope  30  is thus the type of rope referred to in the industry as a double-braided rope. 
   The strands  36  and  38  may be substantially identical in size and composition. Similarly, the yarns  40  and  42  may also be substantially identical in size and composition. However, strands and yarns of different sizes and compositions may be combined to form the rope core  32  and rope jacket  34 . 
   As described above, fibers  44  and  46  forming at least one of the yarns  40  and  42  are of two different types. In the yarn  40  of the example rope  30 , the fibers  44  are of a first type corresponding to the first fibers  24  and a second type corresponding to the second fibers  28 . Similarly, in the yarn  42  of the example rope  30 , the fibers  46  are of a first type corresponding to the first fibers  24  and a second type corresponding to the second fibers  28 . 
   Second Rope Example 
   Referring now to  FIGS. 5 ,  6 , and  7 , those figures depict a second example of a rope  50  constructed in accordance with the principles of the present invention. As perhaps best shown in  FIG. 6 , the rope  50  comprises a plurality of strands  52 .  FIG. 7  further illustrates that each of the strands  52  comprises a plurality of yarns  54  and that the yarns  54  in turn comprise a plurality of fibers  56 . 
   The example yarn  54  may be formed by a yarn such as the abrasion resistant yarn  20  described above. In the yarn  54  of the example rope  50 , the fibers  56  are of a first type corresponding to the first fibers  24  and a second type corresponding to the second fibers  28 . 
   The strands  52  are formed by combining the yarns  54  using any one of a number of processes. The exemplary rope  50  is formed from the strands  52  using a braiding process. The example rope  50  is thus the type of rope referred to in the industry as a braided rope. 
   The strands  52  and yarns  54  forming the rope  50  may be substantially identical in size and composition. However, strands and yarns of different sizes and compositions may be combined to form the rope  50 . The first and second types of fibers combined to form the yarns  54  are different as described above with reference to the fibers  24  and  28 . 
   Third Rope Example 
   Referring now to  FIGS. 8 ,  9 , and  10 , those figures depict a third example of a rope  60  constructed in accordance with the principles of the present invention. As perhaps best shown in  FIG. 6 , the rope  60  comprises a plurality of strands  62 .  FIG. 7  further illustrates that each of the strands  62  in turn comprises a plurality of yarns  64 , respectively. The yarns  64  are in turn comprised of a plurality of fibers  66 . 
   The example yarn  64  may be formed by a yarn such as the abrasion resistant yarn  20  described above. The fibers  66  of at least some of the yarns  64  are of a first type and a second type, where the first and second types and correspond to the first and second fibers  24  and  28 , respectively. 
   The strands  62  are formed by combining the yarns  64  using any one of a number of processes. The exemplary rope  60  is formed from the strands  62  using a twisting process. The example rope  60  is thus the type of rope referred to in the industry as a twisted rope. 
   The strands  62  and yarns  64  forming the rope  60  may be substantially identical in size and composition. However, strands and yarns of different sizes and compositions may be combined to form the rope  60 . The first and second types of fibers are combined to form at least some of the yarns  64  are different as described above with reference to the fibers  24  and  28 . 
   Fourth Rope Example 
   Referring now to  FIGS. 11 ,  12 , and  13 , those figures depict a fourth example of a rope  70  constructed in accordance with the principles of the present invention. As perhaps best shown in  FIG. 12 , the rope  70  comprises a plurality of strands  72 .  FIG. 13  further illustrates that each of the strands  72  comprise a plurality of yarns  74  and that the yarns  74  in turn comprise a plurality of fibers  76 , respectively. 
   One or both of the example yarns  74  may be formed by a yarn such as the abrasion resistant yarn  20  described above. In particular, in the example yarns  74  of the example rope  70 , the fibers  76  are each of a first type corresponding to the first fibers  24  and a second type corresponding to the second fibers  28 . 
   The strands  72  are formed by combining the yarns  74  using any one of a number of processes. The exemplary rope  70  is formed from the strands  72  using a braiding process. The example rope  70  is thus the type of rope commonly referred to in the industry as a braided rope. 
   The strands  72  and yarns  74  forming the rope  70  may be substantially identical in size and composition. However, strands and yarns of different sizes and compositions may be combined to form the rope  70 . The first and second types of fibers are combined to form at least some of the yarns  74  are different as described above with reference to the fibers  24  and  28 . 
   Yarn Fabrication 
   Turning now to  FIG. 14  of the drawing, depicted at  120  therein is an example system  120  for combining the first and second materials  24  and  28  to form the example yarn  20 . The system  120  basically comprises a transfer duct  122 , a convergence duct  124 , a suction duct  126 , and a false-twisting device  128 . The first material  24  is passed between a pair of feed rolls  130  and into the convergence duct  124 . The second material  28  is initially passed through a pair of back rolls  142 , a pair of drafting aprons  144 , a pair of drafting rolls  146 , and into the transfer duct  122 . 
   The example first fibers  24  are continuous fibers that extend substantially the entire length of the example yarn  20  formed by the system  120 . The example second fibers  26  are slivers, or discontinuous fibers that do not extend the entire length of the example yarn  20 . 
   The second fibers  28  become airborne and are drawn into convergence duct  124  by the low pressure region within the suction duct  126 . The first fibers  24  converge with each other and the airborne second fibers  28  within the convergence duct  124 . The first fibers  24  thus pick up the second fibers  28 . The first and second fibers  24  and  28  are then subsequently twisted by the false-twisting device  128  to form the yarn  20 . The twist is removed from the first fibers  24  of the yarn  20  as the yarn travels away from the false-twisting device  128 . 
   After the yarn  20  exits the false-twisting device  128  and the twist is removed, the yarn passes through let down rolls  150  and is taken up by a windup spool  152 . A windup roll  154  maintains tension of the yarn  20  on the windup spool  152 . 
   First Yarn Example 
   A first example of yarn  20   a  that may be fabricated using the system  120  as described above comprises the following materials. The first fibers  24  are formed of HMPE fibers and the second fibers are formed of polyester fibers. The yarn  20   a  of the first example comprises between about sixty to eighty percent by weight of the first fibers  24  and between about twenty to forty percent by weight of the second fibers  28 . 
   Second Yarn Example 
   A second example of yarn  20   b  that may be fabricated using the system  120  as described above comprises the following materials. The first fibers  24  are formed of LCP fibers and the second fibers are formed of a combination of LCP fibers and Aramid fibers. The yarn  20   a  of the first example comprises between about fifteen and thirty-five percent by weight of the first fibers  24  and between about sixty-five and eighty-five percent by weight of the second fibers  28 . More specifically, the second fibers  28  comprise between about forty and sixty percent by weight of LCP and between about forty and sixty percent by weight of Aramid. 
   Given the foregoing, it should be clear to one of ordinary skill in the art that the present invention may be embodied in other forms that fall within the scope of the present invention.

Technology Classification (CPC): 3