Abstract:
A spliced fiber tow ( 40 ) having a uniform density along its entire length is provided. The spliced fiber tow is manufactured by rarefying the ends ( 22, 32 ) of the two fiber tow segments to be joined, aligning the rarefied regions ( 26, 36 ) and then applying pressurized gas to entangle the filaments in the rarefied regions. An apparatus ( 50 ) for forming the spliced fiber tow includes a pair of rarefying blades ( 86, 92 ) and an entanglement element ( 58 ).

Description:
This application is a national phase of International Application No. PCT/US2011/026069 filed Feb. 24, 2011 and published in the English language, which claims priority to Application No. U.S. 61/308,516 filed Feb. 26, 2010. 
    
    
     TECHNICAL FIELD 
     The present invention relates to splicing of fiber tows and more specifically, to spliced lengths of carbon fiber tow and to a method and apparatus for manufacturing the same. 
     BACKGROUND 
     Carbon fibers are long, thin filaments of material about 0.005 to 0.010 mm in diameter and composed mostly of carbon atoms. Carbon fibers are typically produced as tows or yarns consisting of several thousands of carbon fibers. The carbon fiber tow may be used by itself or woven into a fabric. The tow or fabric is combined with epoxy or other polymer and wound or molded into shape to form various composite materials. Carbon fiber reinforced composite materials are used in many applications where light weight and high strength are needed. 
     In order to provide continuous lengths of carbon fiber tow, it is necessary to splice the ends. Conventional methods of splicing fiber ends include applying a coating composition onto the fiber ends, placing the coated ends in contact and drying or curing the coating to form a bonded splice. However, during subsequent manufacturing operations, the bonded area may not be compatible with the resin used to impregnate the fibers, which could also cause a local potential failure or premature failure. 
     Joining the ends of fibers from lengths of tow or yarn by air entanglement methods is known. In this method, the ends of the tow or yarn are overlapped with each other and an air stream is applied to the overlapped portions to cause the fibers therein to become entangled with each other. However, the fiber density at the joined portion becomes much greater than the fiber density in the main portions of the tow. In other words, the fiber density is double in the splice area. This increased bulk can damage part of the tow and may cause problems in subsequent operations. For example, in pultrusion processes, the increased bulk may have difficulty passing through the die and/or cause the resin impregnated therein not to fully penetrate the tow or not to cure completely. 
     SUMMARY 
     In accordance with a first aspect of the present invention, there is provided a spliced fiber tow that includes (a) a first fiber tow having a terminal end, a starting end, and a rarefied portion, the rarefied portion extending from the terminal end to a first joint end; (b) a second fiber tow having, a terminal end, a starting end, and a rarefied portion, the rarefied portion extending from the starting end to a second joint end; and (c) a splice joint comprising joined rarified portions of the first fiber tow and the second fiber tow; wherein the density of the spliced fiber tow is substantially uniform from the starting end of the first fiber tow to the terminal end of the second fiber tow. 
     In one embodiment, the first and second fiber tows are each made up of 3,000 or more carbon filament fibers. The first and second fiber tows may each be made up of about 50,000 or more carbon filament fibers. 
     In one embodiment, the splice joint comprises entangled fibers of the rarefied portions of the first and second fiber tows. 
     The dry splice joint, in one embodiment, is able to withstand a tension force of at least 40 kg, or at least 60 kg. The splice joint of the carbon fiber tows, in one embodiment, when impregnated with uncured epoxy resin, is able to withstand a tension force of at least 28 kg, or at least 50 kg. 
     In accordance with a second aspect of the present invention, there is provided a method for forming a spliced fiber tow, which includes the steps of (a) providing a first fiber tow having a terminal end and a starting end, and a second fiber tow having a terminal end and a starting end, the first and second fiber tows each made up of a plurality of fiber filaments; (b) cutting and removing a portion of the fiber filaments of the first fiber tow to form a rarefied region that extends from the terminal end of the first fiber tow to a first joint end; (c) cutting and removing a portion of the fiber filaments of the second fiber tow to form a rarefied region that extends from the starting end of the second fiber tow to a second end joint; (d) aligning the rarefied region of the first fiber tow with the rarefied region of the second fiber tow so that the starting end of the second fiber tow substantially meets the joint end of the first fiber tow, and the terminal end of the first fiber tow substantially meets joint end of the second fiber tow; and (e) subjecting the aligned rarefied regions of the first fiber tow and the second fiber tow to gas turbulences to effect entanglement of the fiber filaments of the first and second fiber tows with each other so as to form a splice. The density of the spliced fiber tow produced is substantially uniform from the starting end of the first fiber tow to the terminal end of the second fiber tow. 
     In one embodiment, the first and second fiber tows each contain 3,000 or more carbon fiber filaments. The first and second fiber tows may each contain 50,000 or more carbon fiber filaments. 
     In the method of forming a spliced fiber tow, cutting the first carbon fiber tow and cutting the second fiber tow may be carried out simultaneously. 
     In accordance with a third aspect of the invention, there is provided an apparatus for forming a spliced fiber tow. The fiber splicing apparatus includes: a pair of rarefying blades spaced apart from each other for rarefying end portions of flat fiber tows; a pair of support bases spaced apart from each other for supporting the end portions of the flat fiber tows, each support base having a top surface opposed to one of the pair of the rarefying blades, the top surface having an insection aligned with the rarefying blade; and an entanglement element that includes a first comb-shaped blowing head, a second comb-shaped blowing head, and a passage therebetween, each blowing head having a plurality of nozzles facing the passage for directing gas at fiber tows within the passage, the entanglement element positioned between the pair of support bases. 
     The fiber splicing apparatus may further include at least one moveable member disposed between the entanglement element and one of the support bases for aligning the flat fibers within the passage. 
     In one embodiment, the fiber splicing apparatus further includes at least one terminating blade, the terminating blade spaced apart from one of the rarefying blades, the distance between the terminating blade and the rarefying blade defining the length of the rarefied end portion of the fiber tow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1C  are schematic views illustrating steps of a method of joining fiber tows according to an embodiment of the present invention. 
         FIG. 2  is a schematic view illustrating a spliced fiber tow in accordance with the present invention. 
         FIG. 3  is a schematic perspective view of an embodiment of the splicing assembly of the present invention. 
         FIG. 4  is an enlarged partial view of the splicing assembly of  FIG. 3  illustrating placement of the fiber tows in a first assembly portion. 
         FIG. 5  is an enlarged partial view of the splicing assembly of  FIG. 3  illustrating placement of the fiber tows in a second assembly portion. 
         FIG. 6  is a front view of the splicing apparatus shown in  FIG. 3   
         FIG. 7  is a view along the dashed line of  FIG. 4 . 
         FIG. 8  is a side view of the splicing apparatus shown in  FIG. 3 . 
         FIG. 9  is a top view of the splicing apparatus shown in  FIG. 3 . 
         FIGS. 10A and 10B  are schematic perspective views of the upper and lower blowing heads, respectively, of the splicing apparatus shown in  FIG. 3 . 
         FIG. 10C  is a schematic perspective view showing the upper and lower blowing heads of  FIGS. 10A and 10B  positioned for the joining operation. 
         FIG. 11  is a photograph of a carbon fiber tow splice in accordance with the present invention. 
         FIG. 12  is a histogram showing the splice strength of a dry, spliced carbon tow according to the present invention. 
         FIG. 13  is a histogram showing the splice strength of a spliced carbon tow according to the present invention after being impregnated with uncured epoxy resin. 
         FIG. 14  is a graph of the force vs. elongation characteristic of an impregnated spliced carbon tow according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     A spliced fiber tow having a substantially uniform density along its length and a method for manufacturing the spliced fiber tow is provided in accordance with the present invention. In one embodiment, the spliced fiber tow is made by joining two lengths of carbon fiber tow, each carbon fiber tow having 3,000 or more carbon fiber filaments. In one embodiment, each carbon fiber tow has about 50,000 carbon fiber filaments. Although described herein with reference to carbon fiber tows, the material of the fiber tows is not limited to carbon fiber, but includes aramid fiber, polyethylene fiber, glass fiber, and other fibers. 
     Referring to  FIG. 1A , a first carbon fiber tow  20  and a second carbon fiber tow  30  are spliced to form a continuous length of carbon fiber tow. The first carbon fiber tow  20  has a starting end  22  and a terminal end  24 . The second carbon fiber tow  30  has a starting end  32  and a terminal end  34 . As illustrated in  FIG. 1B , at the starting end  22  of the first carbon fiber tow  20 , some of the filaments of the tow are removed to create a rarefied portion  26  that begins at the starting end  22  and extends to a joint end  28 . Similarly, at the starting end  32  of the second carbon fiber tow  30 , some of the filaments of the tow are removed to create a rarefied portion  36  that begins at the starting end  32  and extends to a joint end  38 . The length of the rarefied portion  26  of the first carbon tow  20  is substantially the same as the length of the rarefied portion  36  of the second carbon fiber tow. 
     In one embodiment, approximately half of the filaments are removed in each of the rarefied portions  26  and  36 . The step of cutting the filaments to rarefy the ends of the first and second carbon fiber tows may be performed sequentially or simultaneously. In one embodiment, the second carbon fiber tow  30  at the starting end  32  region is positioned over the first carbon fiber tow  20  in the starting end  22  region, and both carbon fiber tows are rarefied at the same time. 
     As illustrated in  FIG. 1C , the rarefied region  36  of the second carbon fiber tow  30  is positioned over the rarefied region  26  of the first carbon fiber tow  20 , so that the starting end  32  of the second carbon fiber tow  30  is substantially aligned with the joint end  28  of the first carbon fiber tow  20 , and the starting end  22  of the first carbon fiber tow  20  is substantially aligned with the joint end  38  of the second carbon fiber tow  30 . It does not matter which of the two carbon fiber tows is positioned on top, so long as the rarefied portions ( 26 ,  36 ) are aligned. The cut filaments are removed and a splice is formed in the overlapping rarefied regions by air entanglement. 
     Using an air entanglement apparatus or pneumatic splicing apparatus, high pressure gas, e.g., air, generally causes the fibers of the yarn or tows therein to loosen and mingle with each other thereby to effect a splice. A preferred embodiment of a splicing apparatus is described below. 
     As illustrated in  FIG. 2 , the filaments in the rarefied regions  26  and  36  are entangled to create a splice  42 . The density of the spliced carbon fiber tow  40  along its length is substantially uniform from the terminal end  24  of the first carbon fiber tow  20  to the terminal end  34  of the second carbon fiber tow  30 . 
     The spliced carbon fiber tow includes (a) a first carbon fiber tow having a terminal end, a starting end, and a rarefied portion, the rarefied portion extending from the starting end to a first joint end; (b) a second carbon fiber tow having, a terminal end, a starting end, and a rarefied portion, the rarefied portion extending from the starting end to a second joint end; and (c) a splice joint comprising joined rarified portions of the first carbon fiber tow and the second carbon fiber tow. The density of the spliced carbon fiber tow is substantially uniform from the starting end of the first carbon fiber tow to the terminal end of the second carbon fiber tow. 
     With the method described herein, not only can longer lengths of carbon fiber tow be produced, but precisely metered spools of product can be provided to customer specifications. 
     Referring now to  FIGS. 3 to 10 , an exemplary splicing apparatus  50  is shown schematically. The splicing apparatus  50  includes a baseboard  52 , onto which are mounted a first rarefier assembly  54 , a second rarefier assembly  56  and a tow joining assembly  58 . First rarefier assembly  54  includes a first tow holder  60  having a first guide channel  62  on the upper surface that extends laterally from an inner edge to an outer edge of the first tow holder  60 . The guide channel  62  facilitates placement of the first tow  20  within the first rarefier assembly  54  for rarefying the starting end  22  of the first tow. The width of guide channel  62  is generally equal to the width of the fiber tow prior to rarefying. 
     Second rarefier assembly  56  located on the opposite side of the tow joining assembly  58  includes a second tow holder  64 , which includes a second guide channel  66  for facilitating placement of the extending length of the first fiber tow  20 . Second rarefier assembly  56  also includes third tow holder  68  having a third guide channel  70  on the upper surface that extends laterally from an inner edge to an outer edge of the third tow holder  68 . The guide channel  70  facilitates placement of the second tow  30  within the second rarefier assembly  56  for rarefying the starting end  32  of the second tow. The width of the guide channel  70  is generally equal to the width of the fiber tow prior to rarefying. The first rarefier assembly  54  further includes a fourth tow holder  72  having a guide channel  74  on its upper surface for facilitating placement of the extending length of the second tow  30 . 
     Referring to  FIGS. 4 and 5 , placement of the first and second tows  20 ,  30  within the splicing apparatus  50  is illustrated. Prior to the splicing operation, first tow  20  is positioned in the splicing apparatus  50  with its starting end  22  extending beyond of the outer edge of first tow holder  60  of first rarefier assembly  54 . The length of the first tow  20  extends through first guide channel  62 , across the joining assembly  58  between guide plates  76  and through second guide channel  66  of the second tow holder  64  so that the terminal end  24  of the first tow extends beyond the outer edge of the second tow holder  64 . Tabs  78 ,  80  secured to the first tow holder and second tow holder, respectively, may be included to hold the first tow within the guide channels  62 ,  66 . 
     Second tow  30  is positioned in the splicing apparatus  50  above the first tow  20 , with its starting end  32  extending beyond the outer edge of the third tow holder  68  of the second rarefier assembly. The length of the second tow  30  extends through third guide channel  70 , across joining assembly  58  and through fourth guide channel  74  of the fourth tow holder  72  so that the terminal end  34  of the second tow extends beyond the outer edge of the fourth tow holder  72 . Tabs  82 ,  84  secured to the third tow holder and fourth tow holder, respectively, may be included to hold the second tow within the guide channels  70 ,  74 . 
     Before entangling the fibers of the first tow  20  with the fibers of the second tow  30 , a rarefied portion  26  is formed in the first tow  20  and a rarefied portion  36  is formed in the second tow  30 . Referring to  FIGS. 6 and 7 , rarefied portion  26  having a width R is formed by removing the outer fibers on each side edge of the first tow  20  having an initial width W, the rarefied portion being proximate to the starting end  22 . First blade holder  85  holds a first rarefying blade  86  and a first terminating blade  88 . When the first blade holder  85  is lowered, first terminating blade  88  severs a portion of the first tow  20  to form a “clean” starting end  22 . First rarefying blade  86  severs only the fibers at the side edges of first tow  20 , as the first tow holder has a first insection  100  below blade  86  at the inner edge of guide channel  62  of the first tow holder so that first rarefying blade  86  cannot sever the center fibers at joint end  28 . 
     Similarly, rarefied portion  36  having a width R is formed by removing the outer fibers on each side edge of the second tow  30  having an initial width W, the rarefied portion being proximate to the starting end  32 . Second blade holder  90  holds a second rarefying blade  92  and a second terminating blade  94 . When the second blade holder  90  is lowered, second terminating blade  94  severs a portion of the second tow  30  to form a “clean” starting end  32 . Second rarefying blade  92  severs only the fibers at the side edges of second tow  30 , as the third tow holder  68  has a second insection  102  below blade  92  at the inner edge of guide channel  70  of the third tow holder  68  so that second rarefying blade  92  cannot sever the center fibers at joint end  38 . Rarefying of first tow  20  and second tow  30  may occur sequentially or simultaneously. 
     To bring rarefied second tow  30  down into position over rarefied first tow  20 , U-shaped first and second tow pullers  98  and  96 , respectively, are lowered from a retreated position to a first position that is vertically aligned with the first tow  20  which is supported by first tow holder  60  and second tow holder  64 . Tow pullers  96  and  98  may be moved by an actuator. In one embodiment, the tow pullers are moveable by the action of a pneumatic cylinder. 
     Referring to  FIGS. 8 and 9 , upper blowing head  104  and lower blowing head  106  are moved forward (perpendicular to the lengthwise direction of the fiber tows) via a first slider  108  and a second slider (shown in  FIG. 3 ), so that the first and second tows  20  and  30  are positioned between the upper blowing head  104  and the lower blowing head  106 . Upper and lower blowing heads  104  and  106  may be moved by an actuator. In one embodiment, the blowing heads are moveable by the action of a pneumatic cylinder. 
     To position rarefied second tow  30  so that the rarefied portion  36  is between the upper and lower blowing heads  104  and  106 , second tow puller  96  is lowered to a second position that is proximate to baseplate  52 , so that it contacts the second tow  30  and pulls it to the right. To position rarefied first tow  20  so that the rarefied portion  26  is in overlapped alignment with the rarefied portion  36  of second tow  30  between the upper and lower blowing heads  104  and  106 , first tow puller  98  is lowered to a second position that is proximate to baseplate  52 , so that it contacts first tow  20  and pulls it to the left. Vertical movement of first tow puller  98  is guided by the movement of first linear bearing  120  within first rail  122 . Vertical movement of second tow puller  96  is guided by the movement of second linear bearing  124  within second rail  126 . 
     With the rarefied portions  26  and  36  of first and second tows  20  and  30 , respectively, aligned between the upper blowing head  104  and the lower blowing head  106 , the fibers of the tows can be entangled to form the splice  42 . Referring to  FIGS. 10A-10C , upper blowing head  104  includes multiple arms  112 , each arm having a plurality of gas nozzles  116 . Lower blowing head  106  includes multiple arms  114 , each arm having a plurality of gas nozzles  118 . Upper blowing head  104  is positioned over lower blowing head  106 , creating a passage  130  between the upper and lower blowing heads. The gas nozzles  116  of the upper blowing head face the gas nozzles  118  of the lower blowing head  106 . High pressure gas injected from the gas nozzles  116  and  118  is directed at the fibers of overlapped rarefied portions  26  and  36  positioned within passage  130 . The turbulent gas flow causes the fibers to become entangled, forming splice  42 . 
     The splicing apparatus may be provided with a controller (not shown) operatively coupled to the actuator for automatically controlling the operating sequence of the individual components and procedures. 
     EXAMPLE 
     Two lengths of Panex® 35 carbon fiber tow, having 50,000 fibers each were spliced by rarefying an end of each tow, overlapping the rarefied ends and subjecting the rarefied portion to air entanglement. The tensile strength of the Panex® 35 carbon fiber tow used was about 4137 Mpa, the tensile modulus was about 242 GPa, and the density was about 1.81 g/cc. The fiber diameter of the fibers of the tow was about 7.2 microns.  FIG. 9  is a photograph of the carbon fiber tow splice of two joined lengths of Panex® 35 carbon fiber tow. The density of the spliced carbon fiber tow is substantially uniform along the length of the tow. 
     The strength of the splice of the resulting spliced carbon fiber tow as tested by measuring the force required to split the splice. Table 1 below lists the splice strength for a number of tested splices.  FIG. 10  is a histogram of the splice strength (in Newtons) vs. the frequency for the tested splices. 
     
       
         
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Standard PX-35, 2x25K splice split 
               
             
          
           
               
                   
                 N 
                 lbs 
                 kg 
               
               
                   
                   
               
             
          
           
               
                   
                 1 
                 540.5 
                 121.5 
                 55.1 
               
               
                   
                 2 
                 800.9 
                 180.1 
                 81.7 
               
               
                   
                 3 
                 523.7 
                 117.7 
                 53.4 
               
               
                   
                 4 
                 665.5 
                 149.6 
                 67.9 
               
               
                   
                 5 
                 662.5 
                 148.9 
                 67.6 
               
               
                   
                 6 
                 625.4 
                 140.6 
                 63.8 
               
               
                   
                 7 
                 573.3 
                 128.9 
                 58.5 
               
               
                   
                 8 
                 777.2 
                 174.7 
                 79.3 
               
               
                   
                 9 
                 536.9 
                 120.7 
                 54.7 
               
               
                   
                 10 
                 548.3 
                 123.3 
                 55.9 
               
               
                   
                 11 
                 877.8 
                 197.3 
                 89.5 
               
               
                   
                 12 
                 539.1 
                 121.2 
                 55.0 
               
               
                   
                 13 
                 658.4 
                 148.0 
                 67.1 
               
               
                   
                 14 
                 915.0 
                 205.7 
                 93.3 
               
               
                   
                 15 
                 798.5 
                 179.5 
                 81.4 
               
               
                   
                 16 
                 710.5 
                 159.7 
                 72.5 
               
               
                   
                 17 
                 562.4 
                 126.4 
                 57.3 
               
               
                   
                 18 
                 779.8 
                 175.3 
                 79.5 
               
               
                   
                 19 
                 613.6 
                 137.9 
                 62.6 
               
               
                   
                 20 
                 663.1 
                 149.1 
                 67.6 
               
               
                   
                 21 
                 527.5 
                 118.6 
                 53.8 
               
               
                   
                 22 
                 431.4 
                 97.0 
                 44.0 
               
               
                   
                 23 
                 676.9 
                 152.2 
                 69.0 
               
               
                   
                 24 
                 686.3 
                 154.3 
                 70.0 
               
               
                   
                 25 
                 700.9 
                 157.6 
                 71.5 
               
               
                   
                 26 
                 536.9 
                 120.7 
                 54.7 
               
               
                   
                 27 
                 658.6 
                 148.0 
                 67.2 
               
               
                   
                 28 
                 583.4 
                 131.1 
                 59.5 
               
               
                   
                 29 
                 693.7 
                 155.9 
                 70.7 
               
               
                   
                 30 
                 464.5 
                 104.4 
                 47.4 
               
               
                   
                 31 
                 451.2 
                 101.4 
                 46.0 
               
               
                   
                 32 
                 426.2 
                 95.8 
                 43.5 
               
               
                   
                 Min 
                 426.2 
                 95.8 
                 43.5 
               
               
                   
                 Max 
                 915.0 
                 205.7 
                 93.3 
               
               
                   
                 Avg 
                 631.6 
                 142.0 
                 64.4 
               
               
                   
                   
               
             
          
         
       
     
     The strength of the splice was also tested by submerging the spliced carbon fiber tow in epoxy resin and then measuring the force required to split the splice wetted by the epoxy resin. Table 2 below lists the splice strength for a number of tested splices.  FIG. 11  is a histogram of the splice strength (in Newtons) vs. the frequency for the tested splices. 
     
       
         
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Standard PX-35, 2x25K splice split strength, impregnated 
               
             
          
           
               
                   
                 N 
                 lbs 
                 kg 
               
               
                   
                   
               
             
          
           
               
                   
                 1 
                 701.3 
                 157.7 
                 71.5 
               
               
                   
                 2 
                 468.3 
                 105.3 
                 47.7 
               
               
                   
                 3 
                 612.6 
                 137.7 
                 62.5 
               
               
                   
                 4 
                 453.1 
                 101.8 
                 46.2 
               
               
                   
                 5 
                 320.1 
                 72.0 
                 32.6 
               
               
                   
                 6 
                 480.2 
                 107.9 
                 49.0 
               
               
                   
                 7 
                 350.2 
                 78.7 
                 35.7 
               
               
                   
                 8 
                 774.6 
                 174.1 
                 79.0 
               
               
                   
                 9 
                 563.4 
                 126.7 
                 57.5 
               
               
                   
                 10 
                 278.1 
                 62.5 
                 28.4 
               
               
                   
                 11 
                 444.1 
                 99.8 
                 45.3 
               
               
                   
                 12 
                 511.8 
                 115.1 
                 52.2 
               
               
                   
                 13 
                 348.4 
                 78.3 
                 35.5 
               
               
                   
                 14 
                 655.1 
                 147.3 
                 66.8 
               
               
                   
                 Min 
                 278.1 
                 62.5 
                 28.4 
               
               
                   
                 Max 
                 774.6 
                 174.1 
                 79.0 
               
               
                   
                 Avg 
                 497.2 
                 111.8 
                 50.7 
               
               
                   
                 Dev 
                 149.5 
                 33.6 
                 15.2 
               
               
                   
                   
               
             
          
         
       
     
     The dry splice joint, in one embodiment, is able to withstand a tension force of at least 40 kg, or at least 60 kg. The splice joint, in one embodiment, when impregnated with uncured epoxy resin, is able to withstand a tension force of at least 28 kg, or at least 50 kg. 
       FIG. 12  is a graph of the force vs. elongation characteristic of an impregnated spliced carbon tow produced by the method described herein. 
     While the invention has been explained in relation to various embodiments, it is to be understood that various modifications thereof will be apparent to those skilled in the art upon reading the specification. The features of the various embodiments of the articles described herein may be combined within an article. Therefore, it is to be understood that the invention described herein is intended to cover such modifications as fall within the scope of the appended claims.