Abstract:
In one aspect, an apparatus for measuring a tension force on a net cord of a sports net is disclosed. The apparatus may include a housing configured to connect to a static post. The apparatus may also include a slidable member and attachment members. The attachment members may be configured to engage a portion of the net cord. A resilient member inside the housing may be connected to the slidable member, and an indicator member may be connected to the slidable member within the housing. The slidable member may be configured to move within the housing in response to and by a distance proportional to an amount of tension force on the net cord. The indicator member may be connected to the slidable member such that a portion of the indicator member may be exposed through a slotted opening defined in the housing.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This application claims the benefit, pursuant to 35 U.S.C. §119(e), of U.S. Provisional Patent Application Ser. No. 61/507,854, filed Jul. 14, 2011, entitled “Device and Method for Indicating Tension of Support Cables in Sports Nets” by David E. Glass, which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     Several games and sports that involve game-specific balls or projectiles use nets or netting to divide one participant or team from the other. Popular examples include tennis in its various forms, volleyball, and table tennis. Each of the courts or playing surfaces for these games includes a net terminated by standards or posts at each end, with a support cable or cord inside a headband atop a mesh or fabric netting, for the purpose of establishing the topmost boundary of the dividing net. Typically, this cable or cord has a fixed loop at one end, to attach to the support post by means of a hook, bolt, or other protruding anchor point. 
     The tension applied to this cable or cord (commonly referred to as the “net cord”) has a significant effect on the playability of the net, in the way the ball is deflected when it strikes the net cord during play. As examples, in tennis and table tennis, a ball that strikes the net cord when “served” may stay within the field of play and be re-served. A net cord with too little tension may absorb the kinetic energy of the ball, resulting in a soft falling of the ball to the playing surface, while a net cord that is too tight can deflect the ball higher from the playing surface, causing it to fly past the playing surface boundary or targeted area or to bounce high into the air making an easy shot for the opposite player. 
     If the net tension on courts at a common facility vary unpredictably from court to court, players may be uncertain how a ball may react if it strikes the net cord. Furthermore, if the net cable is pulled too tightly, the net, net posts and footings may be damaged. For instance, over-tension on the net cable may result in cracks in the courts and damage to net post foundations, necessitating repairs that can cost thousands of dollars and result in down court time. Regulatory bodies of the above-mentioned and other games have indicated the desire to have all playing courts play equally, whether the playing surface friction and dimension, and response of ball strikes on net cords. 
     It is with respect to these and other considerations that the various aspects and exemplary embodiments are presented below. 
     SUMMARY 
     In one aspect, the present disclosure relates to an apparatus for accurately indicating the tension on a sports net cable, also referred to herein as a net cord. According to one or more embodiments, by using a compressible, resilient member such as a compression spring housed within a largely square or cylindrical housing, the tensile force of a net cable is transmitted by mechanical interface through a measurement section of the apparatus to the opposite end of the resilient member, which compresses in an amount proportional to the tensile force applied to the net cable. The housing is largely adjacent to and parallel to a static support post for the sports net and retained to the support post by a lower loop that connects the device to a hook affixed to the support post, or by fasteners that directly attach the housing to the support post. The housing is configured with a slotted opening, upon which a flat indicator member may be viewed for referencing the compression of the resilient member against a scale of marks placed on the housing such as to indicate, by comparison to the flat indicator, the tension force on the net cable. 
     These and other features will be apparent from a reading of the following detailed description and a review of the associated drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings illustrate one or more embodiments of the disclosure and, together with the written description, serve to explain aspects of the disclosure. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like elements of an embodiment, and wherein: 
         FIG. 1A  provides a partial, plan view of a sports net system which includes an apparatus according to an example embodiment of the present disclosure, a sports net, and a support post; 
         FIG. 1B  schematically shows a view of the sports net system of  FIG. 1A . 
         FIG. 2  schematically shows an apparatus according to an example embodiment of the present disclosure, included in a sports net system. 
         FIG. 3A  schematically shows an apparatus according to an example embodiment of the present disclosure, with a flexible attachment member at an anchoring end and slidable, flexible attachment member on a measurement end; 
         FIG. 3B  schematically shows an apparatus according to an example embodiment of the present disclosure, with rigid attachment members upon each end; 
         FIG. 3C  schematically shows an apparatus according to an example embodiment of the present disclosure, with a slidable, flexible attachment member upon a measurement end and fasteners affixing the apparatus to a sports net support post; 
         FIG. 4A  schematically shows subassemblies of an apparatus according to an example embodiment of the present disclosure, including some components of the example embodiment shown in  FIG. 3A ; 
         FIG. 4B  schematically shows subassemblies of an apparatus according to an example embodiment of the present disclosure, including some components of the example embodiment shown in  FIG. 3B ; 
         FIG. 4C  schematically shows subassemblies of an apparatus according to an example embodiment of the present disclosure, including some components of the example embodiment shown in  FIG. 3C ; 
         FIG. 5A  schematically shows components of an apparatus according to an example embodiment of the present disclosure, including some components of the example embodiments shown in  FIGS. 3A and 4A ; 
         FIG. 5B  schematically shows components of an apparatus according to an example embodiment of the present disclosure, including some components of the example embodiments shown in  FIGS. 3B and 4B ; 
         FIG. 5C  schematically shows components of including some components of the example embodiments shown in  FIGS. 3C and 4C ; and 
         FIG. 5D  schematically shows components of an apparatus according to an example embodiment of the present disclosure, including some components of the example embodiments shown in  FIGS. 3B ,  4 B, and  5 B, and wherein an attachment member of a measurement end corresponds to a rigid attachment member. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, references are made to the accompanying drawings that form a part hereof, which illustrate specific embodiments or examples. Referring now to the drawings, aspects of the various implementations provided herein and an exemplary operating environment will be described. The terms used in this specification generally have their ordinary meanings in the art, within the context of the disclosure, and in the specific context where each term is used. The first digit of each element numeral represents the first reference to the element in correspondence to the figure number of the several figures. 
     In various aspects, the present disclosure relates to apparatuses for indicating a tension force on a support cable for a sports net.  FIG. 1A  and  FIG. 1B  illustrates a sports net system  110  including an apparatus  120  according to one example embodiment of the present disclosure. The net system  110  may be used in sports such as tennis, table tennis, volleyball, or badminton. A sports net assembly  117  incorporates a mesh section and a flattened, tubular headband portion affixed to the top of the mesh section. A net support cable  118  may pass through the headband, and net cord loop terminations  112  on each end serve as force-bearing anchor members for the cable to a support post  119  having a net support post cap  116  which functions to guide the cable and to re-direct the applied tension force to be approximately parallel to the net post so that the cable may be anchored to the post or attached to the apparatus. Also shown is a post attachment point  115 , which may also be referred to herein as a second force-bearing member, which can be configured as a mount for termination of the system  110 . 
     Example embodiments of apparatuses of the present disclosure are configured to, when attached in-line to a net support cable, indicate the tensile force on a net support cable, which force may be applied by a cable reeling or levered take-up mechanism that is part of an opposite support post in the net system. 
       FIG. 1B  illustrates an apparatus  120  according to an example embodiment of the present disclosure. The apparatus  120  is configured to attach in-line to the net system  110  on one end to a post attachment point at member  115  fixed to the net post  119  by an interface connector (e.g., interface connector  134  through the opening of the attachment loop formed by the flexible material of slidable member  334  in example embodiments of  FIG. 3A  and  FIG. 3C , or eyebolt opening  332  of  FIG. 3B ). Member  115  can be a hook, bolt, rod, or other means of interfacing an anchoring section (e.g., anchoring section  340  in example embodiment of  FIGS. 3A and 341  in example embodiment of  FIG. 3B  and anchoring sections  340  and  341  in example embodiments of  FIGS. 5A and 5B  respectively). Sports net assembly  117  typically includes a mesh section, a flattened, tubular headband portion affixed to the top of such mesh, and a net support cable  118  passing through the headband. A net cord loop termination  112  serves as an anchor member for the net support cable  118  to a force-bearing post  119  having a top portion  116  also referred to herein as a net support post cap. The apparatus  120  is configured to, when attached in-line to the net support cable  118  either directly or by an interface connector  134  installed through the opening of the attachment loop formed by the flexible material of slidable member  334  and net cord loop  112 , indicate the tensile force on the cable  118 . 
       FIG. 2  illustrates an apparatus  222  according to another example embodiment of the present disclosure, implemented in a sports net system  110 . A sports net assembly  117  includes a mesh section, a flattened, tubular headband portion affixed to the top of the mesh section, and a net support cable  118  passing through the headband portion. A net cord loop termination  112  serves as an anchor member for the net support cable  118  to a post  119  having a top portion  116 , also referred to herein as a net support post cap. The apparatus  222  is configured to be affixed to the post  119  by means of fasteners  224  and to a net cord loop  112  either directly or by an interface connector  134  installed through the opening formed by the flexible material of slidable member  334  and net cord loop  112 . The apparatus  222  is configured to, when attached in-line to the net support cable  118 , indicate the tensile force on the net support cable  118 . In all examples, the tensile force may be applied by a cable reeling or levered take-up mechanism located on one of either net post  119 . 
       FIG. 3A  illustrates an apparatus  120  according to an example embodiment of the present disclosure, with a flexible attachment member upon each of an anchoring end  340  and measurement end  330 , according to an example embodiment of the present disclosure. The anchoring end  340  of apparatus  120  is configured with an attachment means and, in particular, a static wire rope loop  345  or rigid element with an integrated loop or hook  348  to interface with support posts (e.g., support post  119  in example embodiment of  FIG. 2  that includes a post attachment point  115 ). The post attachment point may be a welded hook, bolt, cleat, or other attachment fixture having various distance from the outside surface of the post. An end block  365  of the measurement end  330  is configured with a slidable member  334  formed with flexible material such as wire rope or cable to have the dual functionality of bearing the tension force applied to the net support cable and maintaining the application of the force along the longitudinal, central axis of the apparatus (see centerline A in  FIG. 5A ). Guide holes (see, e.g.,  FIGS. 5A and 5C ) in the measurement section end block  365 , through which the slidable member  334  is threaded, are sized to accommodate slip fit of the slidable member  334 , and drilled upon locations parallel to and equidistant from the longitudinal center A of the apparatus  120  in order to re-direct any off-parallel tension forces to the longitudinal axis. 
       FIG. 3B  illustrates an apparatus  321  according to an example embodiment of the present disclosure, with an anchoring section  341  configured with rigid attachment means and, in particular, an eyebolt configured to interface with a support post (e.g., support post  119  in example embodiment of  FIG. 2 ) when configured with post attachment point (e.g., post attachment point  115  in example embodiment of  FIG. 2 ). The post attachment point may be a welded hook, bolt, rod, cleat, or other attachment fixture having various distance from the outside surface of the post. Apparatus  321  can have the measurement section  331  alternately configured with a slidable member formed as a rigid means (see, e.g., similar components  546  in exploded view of example embodiment shown in  FIG. 5B ), which may use one or more of eye bolts, hook bolts, swaged sleeves, and/or unswaged terminations, for example. 
       FIG. 3C  shows an apparatus  222  according to an example embodiment of the present disclosure, configured to be anchored to a support post (see, e.g., support post  119  in example embodiment of  FIG. 2 ) by direct attachment to the exterior surface of the post using fasteners  224 . The fasteners  224  may include shear and tensile strength fasteners such as bolts, screws, and/or rivets. It should be appreciated that a method of attaching the device  222  does not preclude an alternate configuration of measurement section  330  using, for example, a slidable member  334  formed with flexible material or rigid means  546 . Although shown in the example embodiments in  FIG. 1B ,  FIG. 2 , and  FIGS. 3A-3C  as a loop fastener with threaded closure barrel, interface connector  134  may alternatively take the form of a hook, loop, shackle, carabiner, spring clip, and/or chain link, depending upon specific interface needs. 
       FIGS. 4A-4C  provide exploded subassembly views of three example embodiments of apparatuses according to the present disclosure. In  FIG. 4A  and  FIG. 4B , the measurement end subassembly  330  or  331 , including flat centering indicator  350 , is inserted into dual-loop housing  424  which is configured to also have anchoring end subassembly  340  or  341  inserted into the opposing end of the dual-loop housing  424 , or into direct-mount housing  426  ( FIG. 4C  and  FIG. 2 ), which is configured to incorporate only measurement end  330  or  331 . With the indicating element  351  of flat centering indicator  350  visible through the opening created by slot  363 , fasteners  368  such as screws, bolts with nuts, rivets, roll pins, and/or dowel pins are inserted through openings of the housing  424  or housing  426  into holes for that purpose upon measurement section end block  365 .  FIG. 4A  and  FIG. 4B  also show the anchoring end subassembly  340  or  341  as secured into the housing  224  by fasteners  368  to form the configurations shown in  FIG. 3A  and  FIG. 3B , respectively. 
       FIGS. 5A-5C  illustrate components which can comprise measurement sections  330  or  331 , housings  224  and  226 , and the anchoring section  340  or  341  according to example embodiments. In  FIG. 5A  and  FIG. 5C , and as shown in subassembly in  FIG. 4A  and  FIG. 4C , respectively, measurement end  330  is configured with slidable member  334  is fabricated from a length of flexible material such as wire rope, rod, cord, or similar. The flexible material of slidable member  334  is folded so as to be formed into generally parallel lengths, each end of which is threaded through holes defined on measurement section end block  365  (see, e.g.,  568   FIGS. 5A and 5C ) and then passing through the inside diameter of rigid cylindrical sleeve  535 , resilient member  432 , a hole defined on the center of flat centering indicator  350 , and thrust washer  564 . The ends of the slidable member  334  are then inserted fully through openings upon clamping means  438 , which has the purpose for connecting the ends of the flexible material formed into slidable member  334  and acting as force-bearing component to resilient member  432 , acting through flat centering indicator  350  and thrust washer  564 . In  FIG. 5A , and shown in subassembly in  FIG. 4A , flexible material, which is fabricated from a length of material such as wire rope, rod, cord, or similar, is formed into generally parallel lengths, each end of which is threaded through holes drilled upon end block  466 , then cross-inserted fully through openings upon clamping means  447 , which has the purpose for connecting the ends of the flexible material which has been formed into loop  345  and acting as force-bearing component for end block  466  of the anchoring end  340  when installed into dual-loop housing  224 . 
     Measurement section end block  365  and anchoring section end block  466 , when utilized with slidable member  334  for measurement end  330  or flexible material formed into loop  345  in anchoring end  340 , have the dual functionality of bearing the tension force applied to the net support cable  118  and maintaining the longitudinally centered application of the force upon the apparatus, in a direction aligned with a central, longitudinal axis of device  120  or device  222  (see, e.g, longitudinal centerline A in  FIG. 5A ). Guide holes  568  drilled upon measurement section end block  365  through which the flexible material lengths are threaded are specifically located equal radial distance from the radial center of the end block  365  (see, e.g., intersection of longitudinal centerline A with end block  365 ), spaced apart so that slidable member  334  passes unencumbered through the rigid cylindrical sleeve  535  and resilient member  432 , and specifically sized to accommodate slip fit of the flexible material of slidable member  334 , to be a guide for the flexible material so that the force applied to the measurement end  330 , when configured with the flexible material, if applied in a vector that is not parallel to the longitudinal centerline A will be re-aligned, by the guiding function of the guide holes, to be parallel to the longitudinal central axis. 
     In  FIG. 5B , and shown in subassembly in  FIG. 4B , measurement end  331  is configured to include the rigid slidable member  546 , which is configured on one end with a loop or hook  332  for the purpose of interfacing with the net loop  112 , either directly or through the interface connector  134  installed between attachment loop  332  and net cord loop  112 . The shank length of the rigid slidable member  546  is inserted through a single slip-fit hole drilled upon the radial center of end block  367 , and passes through the inside diameter of rigid cylindrical sleeve  535 , resilient member  432 , a hole drilled upon flat centering indicator  350 , and thrust washer  564 . In the example embodiment shown, threads formed upon the distal end of the rigid slidable member  546  are inserted into a self-locking fastener  451   a , which may be selected from a group comprising nylon insert lock nuts, upset-thread lock nuts, jam nuts, or similar. 
     The self-locking fastener  451   a  may be positioned on the rigid slidable member  546  to remove end-play by the rigid slidable member  546  without initiating compression of the resilient member  432 .  FIG. 5B  also shows in component view the anchoring end  341  subassembly shown at the left side of  FIG. 4B . In this example embodiment, static anchoring loop  348  is shown as one end of a rigid anchoring means  548  which may be selected from a group comprised of eye bolts, hook bolts, swaged sleeves, unswaged terminations, and similar, for the function of interfacing with support post  119  when configured with installed anchoring means  115  that is a bolt or rod protruding from support post  119  such that the interface distance from anchoring end block  468  to static attachment means  348  is not a fixed measurement. The shank length of the rigid anchoring means  548  is inserted through a single slip-fit hole drilled upon end block  468 . In the example embodiment shown, threads formed upon the distal end of the rigid anchoring means  548  are inserted into a self-locking fastener  451   b , which may be selected from a group comprising nylon insert lock nuts, upset-thread lock nuts, jam nuts, or similar. It should be noted that the end blocks  365 ,  466 ,  367 , and  468  are each radially sized for slip fit within the open ends of housings  424  and  466 , to provide dimensional positioning coaxial with the central longitudinal axis (along centerline A). 
     In an example operation, each example embodiment is anchored to support post  119  by any configuration of anchoring end  340  of device  120  or anchoring section  341  of device  321  or by the fasteners  224  that attach housing  226  of device  222  to the support post  119 . The tension force applied to the net system support cable  118  is transmitted through optional interface connector  134  to the measurement end  330  of device  120  or device  222  or measurement end  331  of device  321 . The flexible material of the slidable member  334  or the rigid slidable member  546 , passing through the inside diameter of rigid cylindrical sleeve  535 , resilient member  432 , flat indicator  450 , and thrust washer  564 , to clamping device  438  or locking device  451   a , compress the resilient member a distance proportional to the applied force. Referring to  FIGS. 3A-3C , as the resilient member  432  is compressed, flat centering indicator  350 , interfaced to the end of the resilient member  432 , moves within housing slot  363 , and indicates the magnitude of the tension force by the position of indicating element  351  adjacent to the several marks  352  labeled upon housing  224  or housing  226 , so positioned to quantify the force. 
     Rigid cylindrical sleeve  535 , additional to the radial centering function provided by its position inside the resilient member  432 , is fabricated to a length that provides a fixed limit to the compression of the resilient member, at a compression that preserves the mechanical integrity of the resilient member. That is, the rigid sleeve is configured to have a length that is less than the length of the resilient member when the resilient member is in an uncompressed or partially compressed state, such that the rigid sleeve restricts the resilient member from compressing by an amount greater than a corresponding yield compression of the resilient member in response to an applied force. Those skilled in the art will recognize that the yield compression of a resilient member such as a compression spring refers to the effect on the relaxed length and therefore the spring rate of the compression spring due to forces applied that cause one or more of the spring coils to make contact one with the other; that is, a spring that has been forced beyond a compression length where individual coils make contact has been stressed such that the indicator member would not return to a zero-force indication when relaxed and would indicate incorrect forces when compared to the pre-stress indicator markings. 
     The foregoing description of the exemplary embodiments has been presented in order to explain aspects of the disclosure and their practical application so as to enable others to utilize aspects of the disclosure according to various embodiments, and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present disclosure pertains without departing from its spirit and scope. Accordingly, the scope of the present disclosure is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein.