Abstract:
An apparatus for manufacturing industrial slings which is especially adapted for making roundslings. The apparatus can make slings having one load-lifting core or multiple load-lifting cores. The apparatus has three primary sections, namely, a yarn feeder assembly, a control assembly and a tail section assembly. The sling-making apparatus may be left-handed or right-handed.

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to non-metal slings and, in particular, to an apparatus for manufacturing non-metal roundslings. 
   BACKGROUND OF THE INVENTION 
   The term “rigging” (sometimes referred to as industrial rigging or field rigging) is the branch of securing heavy loads in order to prepare the load to be lifted, moved or transported. Rigging usually refers to the ropes, wires, slings, and chains used to secure the load and not the cranes, boomlifts, air skates, forklifts, or other powered equipment that provides the actual force/energy to lift the object. 
   Wire rope slings made of a plurality of metal strands twisted together and secured by large metal sleeves or collars are common in the industry. Since wire rope slings are made of metal, they do not require any protection that may be afforded by a covering material. During the past thirty years, industrial metal slings have seen improvements in flexibility and strength. However, compared to non-metal or synthetic fiber slings, metal slings are relatively stiff and inflexible. 
   Synthetic fiber slings have gained popularity over the last approximately twenty years and are replacing metal slings in many circumstances. Thousands of synthetic slings are being used on a daily basis in a broad variety of heavy load lifting applications which range from ordinary construction (e.g., nuclear power plants, skyscrapers and bridges), plant and equipment operations, to ship building (e.g., oil rigs), and the like. 
   An advantage of synthetic slings over metal slings is that they have a very high load-lifting performance strength-to-weight ratio which provides for a lighter, more flexible and even stronger slings than their heavier and bulkier metal counterparts. An important disadvantage is that synthetic slings require extra steps (primarily encasing the lifting core inside a protective cover), in its manufacturing process. 
   Synthetic slings are usually comprised of a lifting core made of twisted strands of synthetic fiber and an outer cover that protects the core. The most popular design of synthetic slings is a roundsling in which the lifting core forms a continuous loop and the sling is generally ring-shaped in appearance. The lifting core fibers of such roundslings may be derived from natural materials (e.g., cotton, linen, hemp, etc.), but are preferably made of hemp, linen, etc. synthetic materials, such as polyester, polyethylene, nylon, and the like. The outer covers of synthetic slings are preferably made of synthetic materials and are designed to protect the core fibers from abrasion, cutting by sharp edges, or degradation from exposure to heat, cold, ultraviolet rays, corrosive chemicals or gaseous materials, or other environmental pollutants. 
   A popular method of manufacturing of prior art roundslings is to twist a plurality of yarns together to form a single strand; the strand was then rolled into an endless parallel loop that formed the core. In a separate step, the cover would be manufactured as a flat piece; then the lifting core would be laid on the flat material, and the flat piece of cover material would be bent around the endless core; finally, the edges of the cover are sewn together thereby encasing the core. This method of manufacturing roundslings is time consuming and labor intensive thus increasing the costs to manufacture the sling. 
   An important advancement in the rigging industry was the invention of multiple-path slings by Dennis St. Germain. (See U.S. Pat. No. 4,850,629, titled Multiple Path Sling Construction). The manufacturing process for a two-core roundsling is more difficult since it requires more time and labor than a single-core roundsling. 
   Machines used to manufacture round slings and multiple-path slings are still relatively labor intensive. Accordingly, there is a need in the industry to reduce the amount of labor needed in the manufacturing of synthetic slings. 
   SUMMARY OF THE INVENTION 
   It is a primary object of the present document to disclose an apparatus for manufacturing non-metal slings and, in particular, an apparatus for making multiple-path slings. 
   The subject sling-making apparatus may take on a number of embodiments. However, a preferred embodiment is the making of a two-path industrial sling, i.e., a roundsling having exactly two load-bearing cores. 
   The apparatus has three primary sections, namely, the yarn feeder assembly, the control assembly and the tail section assembly. 
   The yarn feeder assembly includes a yarn table consisting of a relatively flat table-top having a first end and a second end. The second end of the yarn table abuts the control assembly. 
   The control assembly includes an electric motor that provides the motive force for the sling-making apparatus, a power button used to turn the sling-making apparatus on and off, and a control circuit used to track the length of yarn used in the manufacturing of the load-bearing core. 
   The tail section assembly includes a pair of diametrically opposed rails on which an idler roller assembly rides. The pair of rails abut the side of the control assembly opposite to the side on which the yarn feeder assembly is located. The idler roller assembly is comprised primarily of an idler roller and the mating section for sliding on the rails. The length of the pair of rails depends on the maximum length of sling to which the sling-making apparatus is designed to make. In a preferred embodiment, the length of the rails is forty feet and the idler roller assembly can slide along the rails to make a roundsling up to eighty feet in circumference. 
   Once the length of the sling to be manufactured is determined, the idler roller assembly is slid, in a straight line, along the rails to the determined position—this is away from the controller assembly for long slings and towards the controller assembly for short slings. The idler roller may be allowed to spin or it may be locked into place. 
   As will be evident to one skilled in the art, and to provide maximum adaptability for its location, the sling-making apparatus may be left-handed or right-handed. When the yarn table is positioned to the left of the control assembly and the tail section assembly is positioned to the right of the control assembly, the sling-making apparatus is considered left-handed; when the yarn table is positioned to the right of the control assembly and the tail section assembly is positioned to the left of the control assembly, the sling-making apparatus is considered right-handed. However, the side on which each assembly is located with respect to the center control assembly does not affect the operation or process of making a sling. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and form a part of the specification, illustrate the embodiments of the present invention and, together with the following description, serve to explain the principles of the invention. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred, it being understood, however, that the invention is not limited to the specific instrumentality or the precise arrangement of elements or process steps disclosed. 
     In the drawings: 
       FIG. 1A  is a top plan view of an apparatus for making slings in accordance with the present invention; 
       FIG. 1B  is a side view of the apparatus illustrated in  FIG. 1A ; 
       FIG. 2A  is a top plan view of the fiber guide/separator that forms a part of the yarn table assembly; 
       FIG. 2B  is a side view of the fiber guide/separator shown in  FIG. 2A ; 
       FIG. 3A  is a top plan view of the control assembly and tail section assembly of the subject apparatus; 
       FIG. 3B  is a side view of the control assembly and tail section assembly of  FIG. 3A ; 
       FIG. 4A  is a side view of the encoder wheel which forms a part of the control; and 
       FIG. 4B  is a top view of the encoder wheel shown in  FIG. 4A . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   In describing a preferred embodiment of the invention, specific terminology will be selected for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents that operate in a similar manner to accomplish a similar purpose. 
   Before the invention is disclosed, it is important to remember some terminology used in the rigging industry and to understand the parts of a sling is made. The term “roundsling” is used to refer to a sling having a ring-like or circular shape. A roundsling has two primary sections; namely, a load-bearing core and a tubular cover which protects the load-bearing core. In a single core roundsling, there is one endless load-bearing core. In a roundsling having exactly two load-bearing cores (e.g., TWIN-PATH® brand dual-core slings), the cover has two separate and distinct channels parallel to each other, and two endless load-bearing cores situated within its own respective channel in the cover. 
   DEFINITIONS 
   Abrasion: The mechanical wearing of a surface resulting from frictional contact with materials or objects. 
   Breaking Strength: The total force (lb. or kg.) at which the sling fails. The total weight strain which can be applied before failure, which is usually at least five times the rated capacity. 
   Core: The load-bearing multiple fibers of synthetic material which when wound into the seamless tubes becomes the load-bearing yarns of the sling. 
   Cover: The seamless tubes that contains the cores. Covers may be of polyester, covermax, Aramid, or other suitable material depending on the desired finished characteristics of the product. Preferably, the cover is made of an inner material hearing a high visibility color, and an outer material made of a contrasting color; when the outer cover material is damaged or worn through, the inner cover material becomes visible allowing for a quick inspection means. 
   Elongation: The measurement of stretch, expressed as a percentage of the finished length. 
   Fitting: A load-bearing metal component which is fitted to the sling. A fitting can be made from steel, aluminum or other material that will sustain the rated capacity of the sling. The fitting must be smooth and large enough to allow the sling to perform without bunching. 
   Length: The distance between bearing points of the sling when laid flat and closed. Measurements are taken from the inside points of contact. 
   Proof Test: A term designating a tensile test applied to the item for the sole purpose of detecting injurious defects in the material or manufacture. 
   Synthetic Fiber: Any of a multiple of man-made materials used to manufacture the cover, the core, and the thread of the non-metal slings. 
   Tell-Tails: Core yarns which extend past the tag area of each sling. When the sling is stretched beyond its elastic limit, they shrink and eventually disappear under the tag. If either tell-tail is showing less than ½″, the sling must be removed from service. If the tell-tails show evidence of chemical degradation, the sling must be removed from service. These may be a fiber-optic cable which will help identify core deterioration. 
   Thread: The synthetic yarn which is used to sew the slings, covers, tag and also to provide the stitch which separates the individual load covers. 
   Multiple-path non-metal slings were unknown approximately twenty-five years ago. Dennis St. Germain, the inventor herein, invented multiple-path slings in the mid-1980&#39;s. The multiple-path sling and, in particular, a sling having exactly two load-bearing cores, has been a commercial success. Slings having two load-bearing cores are sold under the TWIN-PATH® brand. The multiple-path sling is described in U.S. Pat. No. 4,850,629, titled MULTIPLE PATH SLING CONSTRUCTION. U.S. Pat. No. 4,850,629, is hereby incorporated by reference as if fully set forth herein. 
   Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings in which an apparatus for making slings in accordance with the present invention is generally indicated at  10 . 
   Referring now to  FIGS. 1A and 1B , a yarn feeder assembly  20 , a control assembly  30  and a tail section assembly  40  are shown. The yarn feeder assembly  20  includes a yarn feeder table  22  having a flat table top  11  with a first end  12  and a second end  13 ; the second end is abutted up against and, is preferably attached to, the control assembly  30 . As illustrated in  FIG. 1B , the yarn feeder table  22  has one or more legs  14  to support the table top  11 . 
   Spaced at regular intervals, the yarn feeder table  22  has a plurality of openings  23  for allowing an individual strand  25  of yarn to pass therethrough. The individual strands of yarn will be twisted together, as will be described herein, to make the load-bearing inner core of the sling.  FIG. 1A  illustrates an apparatus  10  having exactly eight yarns used to make the inner core; therefore, this particular yarn table has openings  23 A through  23 H. If the machine is set up to manufacture a multiple-path (e.g., a TWIN-PATH® brand dual-core sling), the yarns are twisted together to make each core of the multiple-path sling. 
   The individual strands are made in a separate manufacturing step. As an individual strand of yarn is manufactured, it is rolled onto a heavy-weight cardboard tube. Once the desired length of yarn is rolled onto the heavy-weight cardboard tube, the yarns are delivered to customers in a spool or roll  99 . The denier, weight and materials used to manufacture the yarn are chosen depending on the type and size of sling to be manufactured. However, in order to reduce inventory, to keep storage space at a minimum, and to streamline the manufacturing process, it is preferable to choose one medium-weight synthetic yarn. 
   Beneath the yarn feeder table  22  lies a spool table  24  for holding a plurality of spools  99  of yarn. In a preferred embodiment, as illustrated in  FIG. 1B , yarn table  22  can hold two rows of four rolls of yarn (for a total of eight rolls), wherein yarn  25 A is unrolled from spool  99 A, yarn  25 B is unrolled from spool  99 B, etc. However, not every sling that will be manufactured will use the maximum number of yarns. For example, slings designed and rated to lift relatively small loads may use less than eight yarns. 
   The spool table  24  has a plurality of elongated extensions  26 A,  26 B,  26 C through  26 H (preferably rod-shaped) that extend from the top surface of the spool table towards the underside of the yarn table  22 . (Although extensions  26 E through  26 H cannot be seen from the drawings, each half of the spool table is identical.) A spool of yarn  99  is slid vertically over each of the extensions  26  on the spool table  24  and the spool&#39;s weight keeps it on the spool table. 
   The number of elongated extensions  26  are ultimately determined by the maximum size of sling to be manufactured on the apparatus  10 . The number of spools of yarn  99  used to manufacture a specific sling depends on the size of the sling to be manufactured at that time. The number of spools of yarn  99  should not exceed the number of elongated extensions on the spool table. Although the disclosure and the drawings illustrate that there are eight spools of yarn that are slid over eight elongated extensions  26 , the spool table can be enlarged to accommodate more elongated extensions  26  and more spools  99  in order to make larger slings. Similarly, apparatus  10  that are designed to make lower-strength slings may not require a yarn table that can accommodate eight yarns. 
   The number of spools that can be held by the spool table  24  corresponds to the number of openings  23 A, through  23 H in the yarn table. Once the size of the sling to be manufactured is determined, the number of yarns to be used to form the load-bearing core can be calculated based on the known weight an individual yarn can hold. Although the first time a sling is made, the number of yarns and other factors may be calculated, some of this information may be obtained through trial and error by manufacturing slings made of varying diameters of yarn, destructively testing the sling, and recording the results. Over time, the number of yarns needed to manufacture a specific load-bearing core will become well-known since all of the other measurements are known (e.g., the thickness of the yarn used, etc.) For example, by doing an initial calculation, then through years of experience in making slings, it is known that eight yarns of relatively medium weight synthetic (e.g., Kevlar® of Kevlar® blend) yarn are required to manufacture the load-bearing core of a 20,000 pound sling. This information can be collected and quantified in a chart which can be consulted by the operator immediately before the manufacturing process. 
   Referring again to  FIGS. 1A and 1B , proximate each yarn opening  23 A through  23 H, is a spring-tensioning device  27 A through  27 H, respectively. The spring-tensioning devices  27 A through  27 H applies proper resistance to its respective yarn to prevent any slack in the yarn during the cover-making step. The spring-tensioning devices each have their own adjustment to increase or decrease the amount of tension applied to its respective yarn. The spring-tensioning devices are well-known in the industry. 
   The sling-making apparatus  10  includes an encoder  29 . The location of encoder  29  can be seen in  FIGS. 1A ,  1 B,  3 A and  3 B. The encoder  29  includes an encoder wheel  98  and its related circuitry that counts the number of revolutions of the encoder wheel. 
   Referring now to  FIGS. 4A and 4B , an enlarged view of the encoder wheel  98  is shown. The encoder wheel  98  has a central groove  65  of known circumference. The circuitry is preferably stored in control box  34 . One of the yarns (preferably one farthest away from the control assembly) is wrapped at least partially around the encoder wheel  98 . Since the wheel&#39;s circumference is known, the length of the yarn used to manufacture the load-bearing core will be easy to compute. As one skilled in the art can appreciate, after reading the present disclosure, the encoder circuitry may be modified to provide a reading in any length measurement (e.g., feet, yards, meters, etc.) 
   A counter circuit that is connected to the wheel actually determines how many feet are used. Since the circumference of the wheel is known (2*pi*r—where “r” is the radius of the wheel  98  in feet), the number of rotations of the wheel will convey the number of feet of yarn that has been pulled from a roll  99  to make the inner core(s). The encoder and its associated circuitry are well-known off-the-shelf products. 
   Referring again to  FIGS. 1A and 1B , the location of a comb or fiber guide  92  proximate the second end  13  of the yarn table  11  is shown. Preferably the fiber guide  92  is positioned at the junction between the yarn table assembly  20  and the control assembly  30 . The fiber guide  92  ensures that the yarns do not prematurely begin twisting and/or become tangled. The fiber guide  92  includes a base section  93  and a plurality of elongated projections  94  (sometimes referred to as “teeth” or “tines”). The base section  93  has a plurality of projection-holding receptacles  95  into which the elongated projections  94  may be inserted. The elongated projections  94  are preferably rod-shaped and are removable and can be re-inserted into different holding recesses to adjust the separation between each individual yarn with respect to adjacent yarns. 
   An enlarged view of the base section  93  of the fiber guide  92  is illustrated in  FIGS. 2A and 2B . The base  93  may be made of wood or metal and is secured to the yarn table by using bolts  91 . The base  93  preferably has more projection-holding receptacles  95  than there are the elongated projections  94 . (commonly referred to as “teeth”). Each projection  94  is inserted into a desired receptacle  95  and secured preferably by a friction fit. 
   The receptacles  95  do not have to be spaced in a regular pattern but it may be easier to manufacture the base  93  if they are spaced apart in a regular or repeating manner. The operator of the machine  10  may insert one or more teeth  94  into the receptacles. The primary factor for determining the number of teeth  94  to be inserted into receptacles  95  is the size of the sling to be made which will determine the number of yarns that will be used to make the core. 
   The fiber guide  92  is designed to keep the yarns separated until the last possible second to ensure a tight twisting of the yarns as it forms the load-bearing core of the sling. In one embodiment, the teeth  94  are shaped like rods and are frictionally-fitted into the receptacles  95 . In another embodiment, one end of each projection  94  can be manufactured with threads, and the receptacles  95  can be manufactured with mating threads so that the projection  94  may be screwed into its respective receptacle. By moving the projection  94  into different receptacles 95 , the separation of the yarns can be controlled and managed, and ultimately the “tightness” of the wrap of yarns that form the load-bearing core can be controlled. 
   Referring again to  FIGS. 1A and 1B , the control assembly  30 , including a control box  34  housing control circuitry, and control panel  31  are illustrated. As stated previously, the counter circuit for the encoder  29  may also be stored in the control box  34 . A display  35  that is electrically connected to the counter circuit may be mounted on the control panel  31  for conveying to the machine&#39;s operator the length of yarn pulled from the spool  99  of yarn and used to manufacture the load-bearing core. 
   The control assembly  30  also includes an electric motor  32  that provides the motive force for the apparatus  10 . The electric motor  32  turns a drive roller  38  and is connected by a chain (using sprockets), belt or preferably a worm gear reducer  33 . An on/off switch  39  controls power to the apparatus  10  and, more specifically to the control circuit. 
   The encoder  29  along with the encoder wheel  98  are illustrated as being mounted on the yarn table  11 , but may be placed anywhere so that at least one yarn can engage the wheel  98  to turn it, thereby allowing the encoder circuit to determine the length of yarn used to manufacture the load-bearing core. The encoder display  35  conveys to the operator how many feet of yarn was used in manufacturing the load-bearing core. 
   Referring now to  FIGS. 3A and 3B , the control assembly is mounted on a table  61  supported by one or more legs  62 . The tail section assembly  40  may be mounted on a table or an open frame  47  so that the working area of the yarn table assembly  20 , control assembly  30  and tail section assembly  40  are all relatively in the same working plane. One or more legs  63  support the frame  47  of the tail assembly  40 . The apparatus  10  is designed to be somewhat modular to allow for easy assembly and disassembly. 
   The tail-back assembly  40  is positioned after the control assembly  30 . The tail-back assembly  40  includes a pair of rails  41 ,  42  on which an idler roller section  44  slides. The rails ensure that the idler roller assembly  44 , and in particular the idler roller  45 , is parallel to the drive roller. This, in turn, ensures that the yarns that form the load-bearing core are properly twisted and slide with the least amount of friction into the cover of the sling. 
   The idler roller section  44  is slidably attached to the pair of rails  41 ,  42  for moving the idler roller section in a straight line (i.e., horizontal motion) away from or towards the motor-driven roller  38 . The straight-line distance between the idler roller  45  and the driven roller  38  is approximately one-half the size of the sling that is being made. In other words, if it is desired to make a roundsling having a twenty-foot perimeter, the idler roller section is positioned ten feet away from the driven roller. 
   The idler roller section  44  includes means for locking down the idler roller section to one or both rails  41 ,  42  thereby preventing the idler roller section  44  from sliding along the rails during the manufacture of the sling. The locking means may be one or more bolts that are secured to the idler roller section  44  and which can be tightened so the bolts frictionally engage one or both rails. As the drive roller  38  pulls the yarn into the cover of the roundsling, a certain amount of tension is created on the idler roller section  44 . By locking the idler roller section  44  into place, the load-bearing cores can be manufactured in substantially one continuous step. 
   In one embodiment, the operator keeps track of the number of feet as indicated on the encoder display  35  and stops the apparatus  10  using the on/off switch when the requisite length of yarn to form the load-bearing core is drawn from the spools  99  of yarn. The actual length of yarn pulled from the spools  99  and used to form the load-bearing cores is not precise as long as the minimum length that was calculated at the beginning of the process is used. A few extra feet will only strengthen the load-bearing cores. 
   In the preferred embodiment, an electronic decoder control circuit may be employed to automatically turn off the apparatus when the minimum length of yarn is pulled from the spool. As in the manual process, the encoder wheel  29  is used to determine the length of yarn pulled from the spool during the manufacturing of the load-bearing core. The counter circuit can be integrated into the control circuitry via the electronic decoder control circuit for turning off the power to the electric motor when a pre-determined number of feet is pulled from the spool. The operator will program the number of feet of yarn to be used to manufacture the load-bearing cores into the control circuitry at the beginning of the manufacturing process. After the operator turns on the machine  10 , the motor will continue to run until the number of feet programmed into the control circuitry is reached as determined by the encoder wheel  29  and signaled to the control circuitry. In this manner, the control circuitry will automatically turn the machine off thereby stopping the motor and the drive roller. Automating this step in the manufacturing process frees the operator to monitor other steps. 
   As indicated previously, the encoder and its associated circuitry are off-the-shelf items that can be easily incorporated in the power circuit of the present machine  10 . 
   During the manufacturing process, the cover of the sling is placed around the idler roller  45 . As indicated previously, a leader yarn has been threaded through the channel of the sling cover. In a sling having two load-bearing cores, the cover has two channels in parallel relationship; in this embodiment, a leader yarn is threaded through both channels in the cover. Similarly, for slings having more than two load-bearing cores, a leader yarn is thread through each channel of the cover. 
   The cover of the sling is cut to allow access to the interior of the cover. The exposed leader yarn has its ends tied together to form an endless loop. The leader yarn is then placed around the drive roller  38 . The idler roller section  44  is then slid away from the control assembly thereby placing tension on the leader yarn. The number of yarns (e.g., eight) that were determined to be needed to form each load-bearing core are then tied to each leader yarn. 
   When the machine  10  is turned on, the leader yarns, being in frictional contact with the driver roller  38 , begins to rotate within their respective cover channels. As the leader yarns rotate, they pull a plurality of yarns off of the spools. As the yarns are pulled from their spools, then through comb  92 , and they are drawn eventually through their respective channels in the cover in a circular motion. The plurality of individual yarns begin to twist in a regular manner as they are drawn within the channel of the cover thereby forming the endless-loop load-bearing cores. 
   A preferred embodiment is the making of a two-path industrial sling. The process of making a two-path sling using the apparatus that is the subject of this patent application is straight forward once the apparatus has been disclosed. 
   In order to streamline the manufacturing process, the covers are manufactured in an independent step. In this manner, hundreds or thousands of covers can be manufactured at a time. Moreover, the covers can be manufactured off-site using conventional manufacturing techniques. The covers are then shipped to the location where the subject sling-making apparatus is located to manufacture the load-bearing core and for final assembly of the sling. The covers are manufactured with a leader line in each channel. Therefore, if a two-core roundsling is to be made, the cover is manufactured having two channels and there are two leader lines placed in the cover-one for each channel. 
   The first step in the manufacturing of a sling is to determine the size of sling to be made (including diameter of load-bearing core which depends on the weight to be lifted and the overall length of the sling) and to determine the type of sling to be made. Based on the size (in particular the length), the idler roller assembly  44  is slid along the rails  41 ,  42  to the proper position and secured by the lock-down means. 
   The next step in manufacturing a sling involves selecting the appropriate cover material as determined by the sling type and/or customer specifications. Generally, the required length of tubing to form the cover is twice the desired length plus five feet. 
   In a preferred embodiment, the inner-side of the cover material will be a contrasting color than the outer-side of the cover material to expedite the inspection process. 
   All multiple-core slings are fabricated using the same basic instructions. The required tube widths and requirements are determined by trial-and-error or through experience, and may be quantified and placed in a chart for future look-up. 
   Next, the operator moves the (non-rotating) tail stock to the appropriate position as determined by the sling length (2×sling length+about five feet) and secures the tail stock using securing clamps or other means provided to secure the tail stock. 
   Using a vise grip pliers or other suitable tool, the operator clamps the end of the cover with the long rolled back cuff to the cross bar  83 . The operator then pulls the cover towards the tail stock assembly  40  and loops the cover material around the idler roller  45 . 
   The next step in the manufacturing process is to tie the required number of yarns to the leader yarn in the cover. Any excess polyester leader yarn is cut off after tying it to the cover yarns  99 . The core yarn is inserted into this original loop, and secured (e.g., by taping) in place allowing a sufficient tail. This tail will be used to tie the beginning yarn to the end yarn after load-bearing core is made. 
   Once the yarns  99  are tied to the leader yarn, the operator hits the on/off switch  39  to start the electric motor  32  thereby turning the drive roller. The sling-making machine  10  is run until the requisite number of loops, or more accurately the requisite length of yarn  99  has been pulled from the spools. The minimum number of feet of yarn that was calculated at the beginning of the manufacturing process must be pulled from the spools for the size and load-bearing capacity of the sling to be made. (The number of loops of the load-bearing core that are formed depends on the distance between the idler roller and the drive roller.) The motor is pulsed on and off until the original loops and tails are positioned at the drive roller and are accessible to the operator. Since the cover does not rotate during the manufacturing process, the opening of the cover remains proximate to the driver roller. 
   The operator feeds each of the filler strands through its respective hole in yarn table and through the tension wheels. The operator adjusts the tension wheels to ensure that there is sufficient tension as the drive roller pulls the yarn from its respective spool. 
   Although any of the yarns may be used to wrap around the encoder wheel  98 , the yarn from the spool furthest from the drive roller is preferred. 
   The operator loops the filler yarns through the bowline knot of each leader string allowing a sufficiently long tail and then tapes them into an interlocking loop. 
   The operator then places pins in the fiber guide  92  to separate the strands entering the cover paths. 
   In order to ensure that an appropriate amount of tension is applied to the leader strings, the idler roller  45  may have to be readjusted. The leader strings must be snug against the drive roller  38  so that when the drive roller rotates, the leader string is pulled through its respective channel in the cover. For a multiple-path sling, each leader strings requires substantially equal tension. 
   The operator ties a (bowline) knot on each leader string at the end of the cuff. While holding the top knotted end of the leader string, the operator loops the bottom end around the drive roller. The operator pulls out any excess slack from each leader string. The operator then pulls the unknotted end until the desired tension is achieved and secures the unknotted end with two half hitches. The operator then cuts off any excess leader string. These steps are repeated for each of the remaining leader strings if all paths are to be run at the same time. 
   The operator then turns on the machine  10  by switching the switch  39  from off to on, and carefully feeds the yarn into the channels of the covers. 
   When the counter indicates that the appropriate amount of core material has been used to form the load-bearing cores, the control circuitry from the encoder  29  will automatically stop the machine. As a check, the operator may count the number of strands needed to form each of the load-bearing cores. 
   The ends of the load-bearing core are tied together. The sling can then be removed from the drive roller  38  and idler roller  44 . It should be noted that some slings are best manufactured locking the idler roller  44  to prevent rotation. 
   The cover is sewn over the opening and closed up allowing only the tell-tails to be seen outside the cover, thereby completing the sling. 
   Although this invention has been described and illustrated by reference to specific embodiments, it will be apparent to those skilled in the art that various changes, modifications and equivalents may be made which clearly fall within the scope of this invention. The present invention is intended to be protected broadly within the spirit and scope of the appended claims.