Patent Publication Number: US-11638985-B2

Title: Cable tray hold-down

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure is related to a hold-down for a cable tray. 
     BACKGROUND OF THE DISCLOSURE 
     A cable tray is typically supported by a series of parallel supports (e.g., struts, C-Channel, I-beams, etc.) suspended at intervals and spaced lengthwise of the cable tray. The cable tray rests on these supports and is held in position on the supports by hold-downs which are affixed to the supports. These hold-downs are intended to retain the cable tray on the supports and to inhibit lateral shifting of the cable tray relative to the supports. Two types of hold-down members are common in the industry: one type acting as a clamp for rigidly clamping a cable tray against a corresponding support; and a second type acting as a guide which holds the cable tray loosely on the support to permit thermal expansion and contraction of the cable tray due to temperature variations. These hold-downs may not be suitable for high load applications, such as high wind applications. Instead, in such applications a penetrating fastener may be needed to secure the cable tray to the support. For example, a fastener may be driven through a lower flange of a rail of the cable tray and into the support. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a cable tray being retained on a cross support by a pair of hold-downs of the present disclosure. 
         FIG.  2    is an enlarged perspective of the hold-down. 
         FIG.  3    is an exploded perspective of the hold-down. 
         FIG.  4    is an enlarged, fragmentary view of  FIG.  1    showing one of the hold-downs in a clamp configuration. 
         FIG.  5    is a side view of the  FIG.  4   . 
         FIG.  6    is a front elevation of  FIG.  4   . 
         FIG.  7    is an enlarged, fragmentary view of  FIG.  1    showing the other the hold-down in a guide configuration. 
         FIG.  8    is a side view of the  FIG.  7   . 
         FIG.  9    is a front elevation of  FIG.  7   . 
         FIG.  10    is a perspective view of a cable tray being retained on a cross support by a pair of hold-downs of another embodiment of the present disclosure. 
         FIG.  11    is an enlarged perspective of the hold-down. 
         FIG.  12    is an exploded perspective of the hold-down. 
         FIG.  13    is a front elevation of one of the hold-downs in a clamp configuration. 
         FIG.  14    is a front elevation of one of the hold-downs in a guide configuration. 
         FIG.  15    is a first side view of the hold-down. 
         FIG.  16    is a second side view of the hold-down. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the drawings. 
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     The present disclosure is directed to a hold-down for a cable tray configured to retain the cable tray on a support. In one embodiment, the hold-down is non-penetrating (i.e., the hold-down does not extend through the cable tray or supports) and is configured for high-load applications, such as high wind applications. In this same embodiment, or another embodiment, the hold-down may be configured to retain the cable tray on an I-beam or other beam having a flange. The hold-down may be configured to clamp or otherwise attach to a flange of the I-beam. In this same embodiment, or another embodiment, the hold-down may be configurable between a clamp configuration, in which the hold-down engages or contacts a rail of the cable tray and functions as a clamp, and a guide configuration, in which the hold-down functions as a guide allowing some movement (e.g., expansion) of the cable tray relative to the support. 
     A hold-down having each of the above-features is indicated generally at reference numeral  10  throughout the drawings. Referring to  FIG.  1   , a pair of the hold-downs  10  are used to retain a cable tray, generally indicated at  12 , on a support, generally indicated at  14 . In the illustrated embodiment, the support  14  is an I-beam having an upper flange  18 . The illustrated cable tray  12  is of the type comprising a pair of generally parallel side rails, each generally indicated at  20 , interconnected by a series of parallel, spaced apart cross members  22 . The cross-sectional shape of the rails  20  may vary depending on the type of cable tray  12 . For example, the illustrated rails  20  are I-beams (e.g., aluminum I-beams), each having a vertical web  24  and upper and lower horizontal flanges, indicated at  25  and  26 , respectively, extending laterally outward from the web, such as on opposite sides of the web. The cable tray  12  may be adapted to carry various types of conduit. For purposes of illustration, one of the hold-downs  10  is shown in the clamp configuration, as also shown in  FIGS.  4 - 6   , and the other hold-down  10  is shown in the guide configuration, as also shown in  FIGS.  7 - 9   . It is understood that in use typically each of the hold-downs would be in the same configuration. 
     Referring to  FIGS.  2  and  3   , the illustrated hold-down  10  comprises a support clamp, generally indicated at  27 , and a hold-down arm, generally indicated at  28 , secured to the support clamp. The support clamp  27  includes a main body  30 , an insert  32  and one or more upper and lower threaded fasteners  34 ,  35 . In the illustrated arrangement, the main body  30 , the insert  32  and the threaded fasteners  34 ,  35  are all separate components from one another. However, other configurations also are possible. The insert  32  is a set screw bar that cooperates with the main body  30  to support one or more of the threaded fasteners  35 . In particular, the insert  32  receives two of the threaded fasteners  35  and transfers a load from the fasteners to the main body  30 . The fasteners  34 ,  35  secure the main body  30  to the beam or other support  14  thereby providing a multiple point (e.g., a three point) mechanical connection between the hold-down  10  and the beam. The upper fastener  34  also secures the hold-down arm  28  to the main body  30  of the support clamp  27 . The upper and lower fasteners  34 ,  35  can be aligned with one another in longitudinal and/or lateral directions of the hold-down  10 , or the fasteners  34 ,  35  can be offset from one another. 
     Referring still to  FIGS.  2  and  3   , the main body  30  generally comprises a bottom wall  40 . The main body  30  also comprises a first side wall  42  and a second side wall  44 . The first side wall  42  extends upward from the bottom wall  40  and the second side wall  44  extends upward from the bottom wall  40 . The first and second side walls  42 ,  44  can be mirror images of one another. A first top wall  46  extends inwardly from an upper portion of the first side wall  42 , and a second top wall  48  extends inwardly from an upper portion of the second side wall  44 . The illustrated main body  30  is hollow and generally rectangular in cross-sectional shape. Preferably, the first top wall  46  and second top wall  48  overlap one another along at least a majority portion, e.g., substantially entirety, thereof. 
     The terms “top,” “bottom,” “side” and the like are merely used to provide a frame of reference for this written description. The structures and component described herein can be mounted in any particular orientation and, therefore, the usage of these terms should not be considered limiting in any manner. Other relative or directional terms may be used herein. These terms are used in the context of the particular orientation(s) shown and should not be considered as limiting the structures to the illustrated orientation in actual use. 
     The main body  30  may be formed from a single plate or sheet of material. In other words, the main body  30  preferably is formed as a monolith or single structure and each of the walls  40 ,  42 ,  44 ,  46 ,  48  is integrally related. Stated yet another way, each of the adjoining walls (e.g., the top wall  40  and the first side wall  42 ) is connected at a bend. Other configurations are possible. 
     The first side wall  42  has an elongated first slot  52  extending through an edge  54  of the first side wall  42 . Similarly, the second side wall  44  has an elongated second slot  56  extending through an edge  58  of the second side wall  44 . The slots  52  and  56  preferably are aligned in a vertical direction and open in the same direction such that the main body  30  defines a jaw-like shape with a mouth configured to receive a flange  18  of the I-beam  14 , for example. The slots  52  and  56  may generally define an L-shape or J-shape when viewed from the side. A first, preferably rectangular, portion  60  of each of the slots  52  and  56  is configured to receive the flange of the beam or a portion of another support member  12 . A second, preferably rectangular, portion  62  of each respective slot  52  and  56  that is above, is sized and shaped to receive the insert  32 . The second portion  62  opens into the first portion  60  of each slot  52  and  56 . A support surface or shoulder  64  is defined at a juncture between the first portion  60  and second portion  62  of each slot  52  and  56  so that a portion of the insert  32  can rest on the shoulder when assembled. The first portion  60  and second portion  62  may each be formed by separate slots or openings. 
     The bottom wall  40  has a pair of holes  68 ,  70  sized to accommodate the fasteners  35  and, preferably, are somewhat, but not substantially, larger than the outer diameter of the shaft portion of the fasteners  35 . Thus, the holes  68 ,  70  limit radial movement of the fasteners  35 . Preferably, the holes  68 ,  70  are defined by relatively smooth walls. That is, preferably, the holes  68 ,  70  are not threaded. 
     The insert  32 , which can be referred to as a locking bar, is generally elongated and rectangular with a first end positioned in the second portion  62  of the slot  52 , and a second end positioned in the second portion  62  of the slot  56 . The insert  32  is in a generally perpendicular relation to the side walls  42 ,  44  and partially rests on the shoulder  64 . The insert  32  has one or more threaded holes to accommodate the threaded fasteners  35 . Preferably, the insert  32  has a pair of threaded holes  76  and  78  adjacent to the side walls  42  and  44 , respectively, and are aligned with the holes  68  and  70 , respectively, when the insert  32  is positioned in the main body  30 . Thus, the threaded fasteners  35  preferably pass through a respective one of the holes  68 ,  70  and threadably engage a respective one of the threaded holes  76 ,  78 . With the insert  32  partially resting on the shoulder  64 , the threaded fasteners  35  engaging the insert  32  and the holes  68 ,  70  of the main body  30  inhibiting substantial movement of the threaded fasteners  35 , the insert  32  preferably is held in place within the second portions  62  of the slots  52 ,  56 . That is, the interaction between the threaded fasteners  34  and the holes  68 ,  70  restricts a forward end of the insert  32  from rotating in a downward direction, thereby inhibiting removal of the insert  32  from the second portions  62  of the slots  52 ,  56 . Conveniently, the insert  32  is held in place even with the threaded fasteners  35  backed off to ease assembly of the sway brace attachment  10  to the support, as described further herein. 
     The first top wall  46  has a first opening  80  and the second top wall  48  has a second opening  82  that are aligned with one another ( FIGS.  6  and  9   ). In the illustrated arrangement, the first opening  80  and the second opening  82  are also aligned in a forward-rearward direction with the openings  68 ,  70  of the top wall  40 . Preferably, the openings  80 ,  82  are centered or substantially centered in a width direction of the main body  30 . The first opening  80  and the second opening  82  are configured to accommodate the threaded fastener  34 . One of the first opening  80  and the second opening  82  may be threaded and the other of the first opening  80  and the second opening  82  may be unthreaded. In the illustrated arrangement, the first opening  80  of the first top wall  46  (i.e., the relative upper one of the top walls  46 ,  48 ) is threaded and the second opening  82  of the second top wall  48  (i.e., the relative lower one of the top walls  46 ,  48 ) is not threaded or is unthreaded. However, in other arrangements, this order could be reversed or both openings  80 ,  82  could be threaded. The presence of the threaded fastener  34  within the openings  80 ,  82  inhibits or prevents significant relative movement between the first top wall  46  and the second top wall  48 . In particular, lateral movement of the top walls  46 ,  48  is inhibited or substantially prevented to inhibit or substantially prevent spreading of the top walls  46 ,  48  and side walls  42 ,  44  of the main body  30 , thereby maintaining the strength of the hold-down  10 . Thus, the unthreaded opening  80  or  82  (if any) is sized relatively closely to the outside diameter of the shaft portion of the fastener  34 . Although the fastener  34  may be provided as a means of coupling the top walls  46 ,  48  to inhibit or at least substantially prevent spreading of the bottom walls  46 ,  48 , other suitable mechanisms can also be used for this purpose, including fasteners (e.g., rivets, screws) that do not contact the flange, clamps, welding, interference structures and other suitable arrangements for fixing the top walls  46 ,  48  relative to one another. 
     In the illustrated arrangement, the upper threaded fastener  34  (i.e., the threaded fastener passing through the upper walls  46 ,  48 ) includes a nut/washer combination  90  threadably engaging a threaded shaft portion of the fastener  34 . The upper threaded fastener  34  can alternatively comprise a nut without a washer or separate nut and washer. 
     The hold-down arm  28  of hold-down  10  includes a base  92  having first and second longitudinal ends. The base  92  can be generally rectangular in shape. Opposite first and second wings  94 ,  96  extend generally transverse to a longitudinal axis of base  92  beginning at the respective first and second ends of the base  92 . Together, interior faces of the base  92  and wings  94 ,  96  define a general U-shape and are sized and shapes to nest on top of support clamp  27 , in particular, to nest on top of top wall  46  of support clamp  27 . A fastener opening  98  extends through base  92  and is generally aligned with openings  80 ,  82  of top walls  46 ,  48 , respectively. 
     The first wing  94  extends further downward than the second wing  96  to define a clamping portion. The clamping portion is configured to engage and clamp the lower flange  26  of rail  20 . In the illustrated embodiment, the clamping portion extends downward at an angle of about 90 degrees relative to the base  92 , although it will be understood that the clamping portion could extend downward at a variety of angles. As illustrated in  FIGS.  4 - 6   , the hold-down  10  is shown as mounted in the clamping configuration in which a portion of the base  92  overlies the lower flange  26  of the cable tray  12  and the first wing  94  is in clamping engagement with the flange  26  of the cable tray  12 , thereby holding the rail  20  of the cable tray  12  in a fixed position relative to support  14 . 
     Referring to  FIGS.  7 - 9   , the second wing  96  comprises the guide. In this configuration, the second wing  96  is not in clamping engagement with the rail  20  to permit free lengthwise thermal expansion and contraction of the rails relative to the support. The length of the second wing  96  is preferably sufficient to enable the second wing  96  to clear (but only slightly), the bead adjacent the outer edge of the lower flange  26 . In this way, the second wing  96  is generally shorter in length than the first wing  94 . 
     As can be understood and seen by  FIGS.  4 - 9   , the hold-down arm  28  can be orientated in either the clamp configuration ( FIG.  6   ) or the guide configuration ( FIG.  9   ) by merely rotating the hold-down arm  28  about a transverse axis extending transverse to the length of the hold-down  10  and through the opposite faces of the hold-down  10  so that either the clamp (first wing  94 ) engages the rail  26  or the guide (second wing  96 ) extends over the rail  26 . There is no need to invert or flip over the hold-down arm  28 . This makes orientating the hold-down easier and faster for the installer. To further enhance ease of use for the installer, the base  92  of the hold-down arm  98  can contain indicia  104  to indicate which side (i.e., which of the first and second wings  94 ,  96 ) functions as the clamp configuration and which functions as the guide configuration. This indicia  104  can also be contained on any other part of the hold-down  10  to indicate to the installer the proper orientation, for example, on first and second wings  94 ,  96 . 
     The main body  30 , the insert, or locking bar,  32 , and the hold-down arm  28  can be fabricated from hot-rolled, low-carbon steel to meet the standards set by the Underwriters Laboratories (U.L.), Factory Mutual Engineering (F.M.), or other such quality control groups, though other suitable materials may also be used. Additionally, the main body  30  and the insert  32  may have a plain or electro-galvanized finish. 
     The threaded fasteners  34 ,  35  may also be referred to herein as set screws. Preferably, each threaded fastener  34 ,  35  has a head portion and a threaded portion. As described, the threaded fasteners  35  extends through holes  68 ,  70 , respectively, and are threaded into the holes  76  and  78  of the insert  32 , thereby capturing the insert  32  within the slots  52 ,  56 . The set screws  35  are long enough to be threaded through the insert  32  to engage a flange, or other structure, positioned in the slots  52 ,  56 . Another set screw  34  preferably extends through the holes  80  and  82  of the upper walls  46  and  48 , respectively, and hole  98  of hold-down arm  28 . This set screw  34  is long enough to engage the flange, or other structure, positioned in the slots  52 ,  56 . Each of the set screws  34  has an end, which preferably is in the form of a relatively sharp cone point for engaging the flange, or other structure. The cone point facilitates the set screws  34  in creating a deformation in the flange, or other structure, to increase the bite of the set screw  34  in the flange, or other structure, to inhibit or prevent sliding movement of the set screw  34 . The cone point does not necessarily need to possess a sharp point. A small flat surface at the end can be permissible. Preferably, any flat surface at the end  96  is less than about 0.05 inches, less than about 0.04 inches or less than about 0.031 inches. In other arrangements, the end can be a cup point or other type of end structure, if needed or desired. 
     The screw head may be adapted to break off at a particular torque level or particular torque range, which may be a threshold or predetermined torque level or range. This feature is a convenient method for ensuring that the set screw  34  has been properly torqued or tightened. A portion of the shaft of the set screw  34  can include a reduced cross-section portion. The reduced cross-section portion can have a particular minimum diameter (or cross-sectional dimension for non-circular shapes) selected in view of the material properties, heat treatment and/or other relevant factors such that the screw head will break off at a particular torque level, which may be a particular minimum value or a range of values. In one or more embodiments, the screw head may not be configured to break off. 
     In the illustrated embodiment, the main body  30  is about 0.25 inches thick. The overall peak dimensions of the main body  30  are about 3.5 inches high, 2.375 inches wide, and 3 inches long. The lower wall  40  is preferably about 2.375 inches wide and spaces the inner surfaces of the side walls  42  and  44  by about 1.875 inches. The side walls  42  and  44  preferably have a peak height of about 3.5 inches. The first portions  60  of the slots  52  and  56  have dimensions of about 1.5 inches by about 0.9 inches (length by height). With such dimensions, the hold-down  10  is capable of use with flanges between about ⅜ inch and ⅞ inch thickness. The second portions  62  of the slots  52  and  56  have dimensions of about 1.031 inches by about 0.39 inches (length by height). The rearward ends of the first portions  60  and second portions  62  are offset from one another such that the shoulder  64  has a length of about 0.156 inches. The bottom wall  40  and lower portions of the side walls  42 ,  44  below the slots  52 ,  56  have a length (in a forward-rearward direction) of about 2.75 inches. The top walls  46 ,  48  and upper portions of the side walls  42 ,  44  above the slots  52 ,  56  have lengths of about 3 inches. Thus, the lower portions of the edges  54 ,  58  of the side walls  42 ,  44  below the slots  52 ,  56  are offset in a rearward direction from the lower upper of the edges  54 ,  58  of the side walls  42 ,  44  above the slots  52 ,  56  by a distance of about 0.25 inches in a forward-rearward direction. The lengths of the first portions  60  of the slots  52 ,  56  are measured from the upper portions of the edges  54 ,  58 . The upper top wall  46  has a width of about 1.841 inches and a length of about 3 inches. The lower top wall  48  has a width of about 1.966 inches and a length of about 3 inches. A vertical gap between the upper top wall  46  and the lower top wall  48  is about 0.063 inches. The holes  68 ,  70  have diameters of about 0.531 inches. The centers of the holes  68 ,  70  are spaced about 0.891 inches rearward of the forward edge of the bottom wall  40 , about 1.313 inches from one another and about 0.531 inches from the side edges of the top wall  40 . The centers of the holes  80  and  82  are spaced about 1.141 inches from the front edges of the top walls  46 ,  48  and substantially centered in the lateral direction of the walls  46 ,  48  and/or along the center line of the main body  30 . The threaded hole  80  has a diameter of about 0.5 inches and the unthreaded hole  82  has a diameter of about 0.563 inches. 
     The insert  32  may be about 0.375 inches thick, about 1 inch wide (forward-rearward or length direction of the assembled sway brace attachment  10 ) and about 2.5 inches in length (lateral or width direction of the hold-down  10 ), which permits it to fit comfortably in the second portions  62  of the slots  52 ,  56  and slightly extend outwardly side walls  42 ,  44  when the insert  32  is placed in the main body  30 . The spacing between the threaded holes  76  and  78  may be about 1.313 inches, which disposes them in substantial alignment with the holes  68  and  70 , respectively. The threaded holes  76 ,  78  comprise standard ½-inch female threads. 
     The threaded portion of each set screw  34  comprises standard ½-inch threads. The shaft portion of the set screw  34 , including the threaded portion, end and reduced cross-section portion can be about 2.5 inches in length, so that the cone point can extend into the area defined between the slots  52  and  56 . The reduced cross-sectional portion can have a length of about 0.188 inches. The set screws  34  can be fabricated from a hardened carbon steel, though other suitable materials may be used. Of course, those skilled in the art will recognize that these and other dimensions presented herein are illustrative of one preferred embodiment, and that the present disclosure may be alternatively dimensioned with efficacy, as required or desired. 
     The hold-down  10  is capable of withstanding a large force in multiple directions. For example, the hold-down  10  is capable of withstanding a large force applied transverse to the longitudinal axis of the cable tray  12  away from the support and transverse to the axis of support  14  away from the support (“tray pull-off” load). The hold-down  10  is also capable of withstanding a large force applied transverse to the longitudinal axis of the cable tray  12  and along the longitudinal axis of support  14  (“across the tray” load). Either or each of the tray pull-off load and the across the tray load may be over 2,000 lbf. (8,896 N), over 2,250 lbf. (10,008 N), over 2,500 lbf. (11,121 N), over 2,750 lbf. (12,233 N), over 3,000 lbf. (13,345 N), over 3,250 lbf. (14,457 N), or over 3,500 lbf. (15,569 N), for example, from 2,000 lbf. to 5,500 lbf. (8,896 N to 24,688 N), from 2,250 lbf. to 5,500 lbf. (10,008 N to 24,688 N), from 2,500 lbf. to 5,500 lbf. (11,121 N to 24,688 N), from 2,750 lbf. to 5,500 lbf. (12,233 N to 24,688 N), from 3,000 lbf. to 5,500 lbf. (13,345 N to 24,688 N), from 3,250 lbf. to 5,500 lbf. (14,457 N to 24,688 N), or from 3,500 lbf. to 5,500 lbf. (15,569 N to 24,688 N) in either or both the clamp and guide configurations. 
     Also provided herein is a method of securing a cable tray to a support, such that the cable tray is able to withstand a large force. The method generally comprises positioning the hold-down  10  in the correct configuration (i.e., clamp configuration or guide configuration) relative to the lower flange  26  of the rail  20  of cable tray  12  and sliding slots  52  and  56  of the support clamp  27  over the flange  18  of support  14 , as shown in  FIG.  1   . The lower set screws  35  (i.e., the set screws that engage the insert  32 ) are inserted through respective holes  68  and  70  in the main body  30  and threaded into holes  76  and  78  in the insert  32  until the cone points of set screws  35  make contact with the flange. The set screws  35  can be tightened until their heads break off, whereby the set screws  35  securely contact the flange. Before or after inserting set screws  35 , the hold-down arm  28  is aligned with support clamp  28  and the upper set screw  34  is inserted through fastener openings  80 ,  82 , and  98 . The upper set screw  34  (e.g., the set screw that engages the main body  30 ) is tightened until its head breaks off. This results in the hold-down  10  being securely fastened to the flange  18  of the support  14 . As described, the provision of upper and lower set screws  34 ,  35  increases the bite of the hold-down  10  on the flange  18  of support  14  to increase resistance to overturning (rotation) of the hold-down  10 . This method allows the cable tray to securely withstand large forces as described herein. 
     Referring to  FIGS.  10 - 16   , another embodiment of a hold-down capable of withstanding a large force in multiple directions, as described above, is generally indicated at reference numeral  110 . The hold-down generally includes a support clamp, generally indicated at  120 , and a hold-down arm, generally indicated at  125 , coupled to the support clamp. The support clamp includes a clamp body  121 , a set screw bar  122  coupled to the body, and at least one set screw  124  (e.g., two set screws or more than two set screws) coupled to the set screw bar. The illustrated body  120  is generally C- or channel-shaped, although it may be of other shapes. The illustrated body  121  includes a back wall  128  and opposing left and right side walls, generally indicated at  130   a ,  130   b , respectively, extending forward from the back wall. Together, the back wall  128  and the side walls  130   a ,  130   b  define an open channel  129  having open upper and lower ends and an open front side. In the illustrated embodiment, the body  120  is integrally formed as a one-piece, monolithic component. For example, the body  120  may be fabricated from sheet metal, such as steel or other metal, as would be readily apparent by one of ordinary skill in the art. 
     The left and right side walls  130   a ,  130   b  define slots  138   a ,  138   b , respectively, extending through a front of the respective side walls toward the back wall  128 . The slots  138   a ,  138   b  are generally aligned with and oppose one another and are sized and shaped to receive a flange (or other portion) of the structural support (e.g., a flange of a beam, such as an I-beam). Accordingly, the left and right side walls  130   a ,  130   b  may be generally C-shaped. The left and right side walls  130   a ,  130   b  include upper arms  140   a ,  140   b  and lower arms  142   a ,  142   b  on opposite sides of the respective slots  138   a ,  138   b . As indicated in  FIG.  12   , upper surfaces  144   a ,  144   b  of the left and right side walls  130   a ,  130   b  (e.g., upper surface of the upper arms  140   a ,  140   b ) are chamfered or beveled toward the front side of the sway brace  110 . The hold-down arm  125  sits on these upper surfaces  144   a ,  144   b , as explained in more detail below, such that the hold-down arm is tilted or sloped downward toward the front side of the attachment  110 . 
     As shown in  FIG.  12   , the side walls  130   a ,  130   b  (e.g., the upper arms  140   a ,  140   b ) define aligned and opposing openings  148   a ,  148   b , respectively, disposed above the slots  138   a ,  138   b . The openings  148   a ,  148   b  are sized and shaped to receive and capture the set screw bar  122  therein. In the illustrated embodiment, the openings  148   a ,  148   b  are generally rectangular, similar to the set screw bar  122 , having a slightly larger area than the cross section of the bar so that the set screw bar is slidably receivable therein and captured. The openings  148   a ,  148   b  are configured such that when the bar  122  is received therein, the bar is tilted or sloped downward toward the front side of the attachment  10 . In this way, as shown best in  FIG.  15   , a plane P 2  of the bar  122  is angled relative to the axes A 3  of the slots  138   a ,  138   b . For example, the bar  122  may be angled between about 10 degrees and about 60 degrees, or about 15 degrees to about 30 degrees, or in one example about 15 degrees. As coupled to the side walls  130   a ,  130   b , opposite end portions of the set screw bar  122  extend outward from the corresponding side walls  130   a ,  130   b  (e.g., upper arms of the corresponding side walls). The opposite ends of the bar  122  define openings  150  configured to receive set screws  152 . The illustrated openings  150  are threaded to threadably receive the set screws  152 . The axes A 4  of the openings  150  (and axes of the fasteners, indicated by the same reference numeral) extend at an acute angle (i.e., less than 90 degrees) from the longitudinal axis of the bar  122  and the axis A 3  defined by the slots  138   a ,  138   b  to enhance the strength of the connection to the beam or other structural support. In this way, the set screws  124  engage the flange of the structural support outside the body  120  and the channel  129  and at an angle less than 90 degrees (i.e., an acute angle) when threaded through the openings  150 . For example, the set screws  124  may engage the flange at an angle from about 85 degrees to about 60 degrees, or from about 80 degrees to about 75 degrees. The set screws  124  may have torque off head that are sheared off the screws after a predetermined or threshold amount of torque is applied to the head. 
     Like the first embodiment of the hold-down arm  28 , the present embodiment of the hold-down arm  128  includes a base  192  having first and second longitudinal ends. The base  192  can be generally rectangular in shape. Opposite first and second wings  194 ,  196  extend generally transverse to a longitudinal axis of base  192  at the respective first and second ends of the base  192 . Together, interior faces of the base  192  and wings  194 ,  196  define a general U-shape and are sized and shapes to nest on top of the body  120 , in particular, to sit or rest on the upper surfaces  144   a ,  144   b . A fastener opening  198  (e.g., non-threaded opening) extends through the base  192  and is generally aligned with a threaded central opening  180  in the set screw bar  122  so that the threaded fastener  126  extends through the fastener opening  198  and threads into the opening  180  in the set screw bar to couple the hold-down arm  128  to the set screw bar  122  and position the hold-down arm relative to the lower flange  26 . In addition, the set screws  124  extend through openings  182  (e.g., non-threaded openings) in the base  192  and thread into the threaded openings  150  in the set screw bar  122  to secure the support clamp  120  to the support  18 . The axes A 4  of the openings  150  (and axes of the fasteners, indicated by the same reference numeral) extend at an acute angle (i.e., less than 90 degrees) from the longitudinal axis of the base  192  of the hold-down arm  122  (and the bar plane P 2 ) to enhance the strength of the connection to the beam or other structural support. 
     As secured to the body  120 , the hold-down base  192  is tilted or sloped downward toward the front side of the hold-down  110 . In this way, a plane P 3  of the base  192  is angled relative to the axes A 3  of the slots  138   a ,  138   b . For example, the base  192  may be angled between about 10 degrees and about 60 degrees, or about 15 degrees to about 30 degrees, or in one example about 15 degrees. The first and second wings  194 ,  196  extend at an acute angle (i.e., less than 90 degrees), as indicated by axis A 4 , from the longitudinal axis (and plane P 3 ) of the base  192  of the hold-down arm  122 . Ends of the wings  194 ,  196  are also tapered to a point, although the ends of the wings may be blunt, such that portions of the ends are parallel to the axis A 3 . 
     The first wing  194  extends further downward than the second wing  196  to define a clamping portion. The clamping portion is configured to engage and clamp the lower flange  26  of rail  20 . In the illustrated embodiment, the clamping portion extends downward at an acute angle (i.e., less than 90 degrees) from the longitudinal axis (and plane P 3 ) of the base  192  of the hold-down arm  122  (and the bar plane P 2 ) to enhance the strength of the connection to the beam or other structural support, although it will be understood that the clamping portion could extend downward at a variety of angles. As illustrated in  FIG.  13   , the hold-down  110  is shown as mounted in the clamping configuration in which a portion of the base  192  overlies the lower flange  26  of the cable tray  12  and the first wing  194  is in clamping engagement with the flange  26  of the cable tray  12 , thereby holding the rail  20  of the cable tray  12  in a fixed position relative to support  14 . 
     Referring to  FIG.  14   , the second wing  196  comprises the guide. In this configuration, the second wing  196  is not in clamping engagement with the rail  120  to permit free lengthwise thermal expansion and contraction of the rails relative to the support. The length of the second wing  196  is preferably sufficient to enable the second wing  196  to clear (but only slightly), the bead adjacent the outer edge of the lower flange  126 . In this way, the second wing  196  is generally shorter in length than the first wing  194 . 
     As can be understood and seen by  FIGS.  13  and  14   , the hold-down arm  128  can be orientated in either the clamp configuration ( FIG.  13   ) or the guide configuration ( FIG.  14   ) by merely rotating the hold-down arm  128  about a transverse axis extending transverse to the length of the hold-down  110  and through the opposite faces of the hold-down  110  so that either the clamp (first wing  194 ) engages the rail  126  or the guide (second wing  196 ) extends over the rail  126 . There is no need to invert or flip over the hold-down arm  128 . This makes orientating the hold-down easier and faster for the installer. To further enhance ease of use for the installer, the base  192  of the hold-down arm  198  can contain indicia  204  to indicate which side (i.e., which of the first and second wings  194 ,  196 ) functions as the clamp configuration and which functions as the guide configuration. This indicia  104  can also be contained on any other part of the hold-down  110  to indicate to the installer the proper orientation, for example, on first and second wings  194 ,  196 . 
     The hold-down  110  is capable of withstanding a large force in multiple directions. For example, the hold-down  110  is capable of withstanding a large force applied transverse to the longitudinal axis of the cable tray  12  away from the support and transverse to the axis of support  14  away from the support (“tray pull-off” load). The hold-down  110  is also capable of withstanding a large force applied transverse to the longitudinal axis of the cable tray  12  and along the longitudinal axis of support  14  (“across the tray” load). Either or each of the tray pull-off load and the across the tray load may be over 2,000 lbf. (8,896 N), over 2,250 lbf. (10,008 N), over 2,500 lbf. (11,121 N), over 2,750 lbf. (12,233 N), over 3,000 lbf. (13,345 N), over 3,250 lbf. (14,457 N), or over 3,500 lbf. (15,569 N), for example, from 2,000 lbf. to 5,500 lbf. (8,896 N to 24,688 N), from 2,250 lbf. to 5,500 lbf. (10,008 N to 24,688 N), from 2,500 lbf. to 5,500 lbf. (11,121 N to 24,688 N), from 2,750 lbf. to 5,500 lbf. (12,233 N to 24,688 N), from 3,000 lbf. to 5,500 lbf. (13,345 N to 24,688 N), from 3,250 lbf. to 5,500 lbf. (14,457 N to 24,688 N), or from 3,500 lbf. to 5,500 lbf. (15,569 N to 24,688 N) in either or both the clamp and guide configurations. 
     Also provided herein is a method of securing a cable tray to a support, such that the cable tray is able to withstand a large force. The method generally comprises positioning the hold-down  110  in the correct configuration (i.e., clamp configuration or guide configuration) relative to the lower flange  26  of the rail  20  of cable tray  12  and sliding slots  130   a ,  130   b  of the support clamp  120  over the flange  18  of support  14 . The fasteners  124  are tightened to secure the support clamp  120  to the flange  18 . The fastener  126  is tightened to position the corresponding wing  194 ,  196  of the hold-down arm relative to the lower flange  26  of the rail  20 . 
     In view of the above, it will be seen that several features of the disclosure are achieved and other advantageous results obtained. 
     Having described the disclosure in detail, it will be apparent that modifications and variations are possible without departing from the scope of the disclosure defined in the appended claims. For example, where specific dimensions are given, it will be understood that they are exemplary only and other dimensions are possible. 
     When introducing elements of the present disclosure or the preferred embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
     As various changes could be made in the above constructions, products, and methods without departing from the scope of the disclosure, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.