« PreviousContinue »
LADDER-TYPE CABLE TRAY SYSTEM
BACKGROUND OF THE INVENTION
This invention relates generally to cable tray systems and, 5 more particularly, to ladder-type cable tray systems.
Conventional ladder-type cable trays are typically suspended from a building support structure in non-residential buildings to carry electrical cables, such as power, telephone, and computer cables. The cable trays are generally 10 shipped to construction sites in sections, with a typical section being twenty feet long. To install the cable tray system, two sections are suspended from the building support structure. The sections are then positioned end-to-end and securely fastened together by threaded fasteners, such as 15 screws or bolts. After the two sections are securely fastened together, another section is suspended from the support structure and securely fastened to one of the first two sections. This procedure is repeated for every additional section of the cable tray system. 20
A difficulty associated with such cable tray systems is that adjacent sections must be securely fastened together to maintain alignment of the adjacent sections. The sections must be secured together before an additional section may be added. The installer must hold the two sections in 25 alignment with one hand while using the other hand to operate an appropriate tool, such as a screw driver, to secure the sections together. This can be difficult since the sections are typically quite bulky and cumbersome to manipulate. Also, since installation of the cable tray requires alternating 30 back and forth between the suspending procedure and the securement procedure, installation of the cable tray system is time consuming. Further, the installer must constantly carry the tools necessary to perform both procedures. Moreover, since the fasteners function to hold adjacent rail 35 sections together, the fasteners must bear the load placed on the rail sections. Failure of the fasteners of even one rail section will cause the section to separate from an adjacent section.
SUMMARY OF THE INVENTION
Among the several objects of this invention may be noted the provision of an improved ladder-type cable tray system; the provision of such a cable tray system which may be 45 quickly and easily assembled and installed; the provision of such a cable tray system in which all sections may be suspended and connected end to end before any of the sections are securely fastened together; the provision of such a cable tray system having a plurality of splices for con- 50 necting cable tray sections end to end; the provision of such a cable tray system which is of a durable and lightweight construction; and the provision of such a cable tray system which is economical to manufacture.
Generally a ladder-type cable tray system of the present 55 invention includes a first cable tray section and a second cable tray section. Each cable tray section comprises first and second rails extending lengthwise of the section at opposite sides of the section and a plurality of rungs adapted to extend between the rails at intervals spaced lengthwise of 60 the section. Each of the first and second rails have a tubular portion forming a hollow beam extending the length of the rail. The tubular portion has open ends at opposite ends of the rail, and a rung-supporting portion integrally formed as one piece with the tubular portion and depending therefrom. 65 The system further comprises means for securing the rungs to the rung-supporting portions of the first and second rails
in a position wherein the rungs span the rung-supporting portions, and a plurality of splices for connecting the first and second cable tray sections end to end. The splices include a first splice sized and shaped for a snug telescoping fit within adjacent open ends of the tubular portions of the first rails of the two cable tray sections, and a second splice sized and shaped for a snug telescoping fit within adjacent open ends of the tubular portions of the second rails of the two cable tray sections.
Other objects and features will be in part apparent and in part pointed out hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded perspective view of two sections of a cable tray of the present invention;
FIG. 2 is an end elevational view of a cable tray section of FIG. 1 with portions broken away to show connection of a rung to first and second rails;
FIG. 3 is an enlarged partial sectional view showing the rung of FIG. 2 connected to a rail of the cable tray section by an adhesive fastener;
FIG. 4 is an enlarged partial sectional view similar to FIG. 3 with adhesive material filling gaps between the rung and rail;
FIG. 5 is a side elevational view of one of the adhesive fasteners;
FIG. 6 is a sectional view taken along the plane of line
6— 6 of FIG. 5;
FIG. 7 is a sectional view taken along the plane of line
7— 7 of FIG. .1 showing the connection between a splice and a rail of one of the cable tray sections;
FIG. 8 is a side elevational view of one of the splices;
FIG. 9 is a sectional view taken along the plane of line 9—9 of FIG. 8;
FIG. 10 is a perspective view of a cable tray configuration in which the cable tray sections are configured to form a vertical bend;
FIG. 11 is a top plan view of a cable tray configuration in which the cable tray sections are configured to form a horizontal bend; and
FIG. 12 is a top plan view of a cable tray configuration in which the cable tray sections are arranged to form a horizontal tee.
Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.
DESCRIPTION OF THE PREFERRED
Referring now to the drawings, and first more particularly to FIG. 1, a ladder-type cable tray of the present invention is indicated in its entirety by the reference numeral 20. The cable tray 20 comprises a first cable tray section, generally designated 22, and a second cable tray section, generally designated 24. Each cable tray section 22, 24 has first and second rails 26, 28 extending lengthwise of the section at opposite sides of the section and a plurality of rungs, each designated 30, extending between the rails 26,28 at intervals spaced lengthwise of the section. Each of the two rails has a tubular portion 32 forming a hollow box beam extending the length of the rail and a rung-supporting portion 34 integrally formed as one piece with the tubular portion 32 and depending therefrom. Preferably, the rails 26, 28 and rungs 30 are pultruded members of fiber reinforced resin.
Opposite ends of the rungs 30 are secured to the rungsupporting portions 34 of the rails 26, 28 in a position wherein the rungs 30 span the rung-supporting portions 34. Rungs 30 may be secured to rung-supporting portions 34 by fasteners, such as screws or clamps, or by a fluent bonding 5 agent, or by any other suitable securing means. Preferably, rungs 30 are secured to the rung-supporting portions 34 by adhesive fasteners 36 (see FIGS. 2-5), described in greater detail below.
The two cable tray sections 22, 24 are connected end to 10 end by first and second splices, indicated at 38, 40. The first splice 38 is sized and shaped for a snug telescoping fit within adjacent open ends 42 of the tubular portions 32 of rails 26 of the two cable tray sections 22, 24. The second splice 38 is sized and shaped for a snug telescoping fit within adjacent open ends 44 of the tubular portions 32 of rails 28 of the two cable tray sections 22, 24.
Referring to FIGS. 2 and 3, the tubular portion 32 of each rail is generally rectangular in transverse cross-section and has an upper wall 46, a lower wall 48, and opposite side 2Q walls 50 and 52. The height of the tubular rail portion 32 is preferably at least twice as great as its width. In an exemplary rail, the tubular rail portion 32 has a height H of approximately 47/s", a width W of approximately VA" and a wall thickness t of approximately V&". The rung-supporting 25 portion 34 of each rail is generally L-shaped in transverse cross-section and has a first (generally vertical) leg 54 extending down from the lower wall 48 of the tubular portion 32 and a second (generally horizontal) leg 56 extending generally laterally inwardly from the vertical leg 3Q 45 at a location spaced below and generally parallel to the lower wall 48 of the tubular portion 32. Preferably, the wall thickness of the rung-supporting portion 34 is equal to the wall thickness t of the tubular rail portion 32. However, it is to be understood that the wall thickness of the rung-sup- 35 porting portion could be greater than or less than the wall thickness of the tubular rail portion without departing from the scope of this invention. The box shape of the tubular portion provides the highest structural integrity by weight and the L shape of the rung-supporting portion provides an 4Q efficient connection layout to the tray. Because of the combination of these shapes, the rails resist lateral movement and twisting, thereby resulting in a uniform distribution of load on the cable tray. Thus, the rails have greater stability than cable tray rails with conventional cross-sec- 45 tional shapes.
The L-shaped rung-supporting portion 34 of each rail combines with the lower wall 48 of the tubular portion 32 of each rail to define a laterally inwardly opening channel 58 for receiving respective ends of the rungs 30 spanning the 50 two rails 26, 28 of each cable tray section. As shown in FIGS. 2 and 3, each rail has a plurality of first holes 60 in its horizontal leg 56 and a plurality of second holes 62 in its lower wall 48, each of the first holes 60 being aligned with a corresponding one of the second holes 62. Each rung 30 is 55 tubular and generally square in transverse cross-section and has aligned holes 64 and 66 through opposite walls of the rung 30 adjacent an end thereof. The holes 64 and 66 of the rung are alignable with and positionable between an aligned pair of the first and second holes 60 and 62 when an end of 50 the rung 30 is inserted into the rung-receiving channel 58.
As mentioned previously, each rung 30 is connected to the rails 26, 28 by fasteners 36. As shown in FIGS. 2-5, each fastener 36 has a head 68, a shank 70 extending up from the head 68 and terminating in a tapered upper end 72, a 65 longitudinal bore 74 extending axially through the head 68 and into the shank 70, and first and second axially spaced
lateral bores 76 and 78 extending laterally through the shank 70 and communicating with the longitudinal bore 74. The shank 70 of each fastener 36 is insertable through a hole 60 in leg 56, holes 64 and 66 in rung 30, and a hole 62 in lower wall 48, all of which holes are aligned when an end of the rung is positioned in the rung-receiving channel 58. Preferably, the horizontal leg 56 of the rung-supporting portion 34 has a raised bead 80, constituting a first spacer, running the entire length of the horizontal leg 56. This bead 80 projects upward and is adapted to contact the lower wall of a rung 30 for maintaining a first space or gap 82 between the horizontal leg 56 and lower wall of the rung. Similarly, the lower wall 48 of the tubular rail portion 32 has a raised bead 84, constituting a second spacer, raiining the entire length of the lower wall. This bead 84 projects downward and is adapted to contact the upper wall of the rung 30 for maintaining a second space 86 or gap between the lower wall 48 of the tubular portion 32 and the upper wall of the rung 30. The distance between the beads 80 and 84 is approximately the same as the distance between opposite faces of a rung 30 to provide a close fit of the rung 30 in the rung-receiving channel 58. The fastener 36 is configured such that when its head 68 contacts horizontal leg 56 and its shank 70 extends up through aligned holes 60, 62, 64 and 66, the first lateral bore 76 is aligned with and in fluid communication with the lower gap 82 and the second lateral bore 78 is aligned with and in fluid communication with the upper gap 86. When the fastener 36 is so positioned, a fluent adhesive 87 (see FIG. 4) introduced into the longitudinal bore 74 through the head 68 will flow through the lateral bores 76 and 78 and into the upper and lower gap or spaces 82 and 86 to fill the bores 74, 76, and 78 and the gaps 82 and 86. When the adhesive 87 hardens, the fastener 36 is permanently bonded to the rung and rail, the horizontal leg 56 of the rung-supporting portion 34 is permanently bonded to the lower wall of the rung 30, and the lower wall 48 of the tubular rail portion 32 is permanently bonded to the upper wall of the rung 30.
Splice 40 is shown in detail in FIGS. 7-9. It is to be understood that splice 38 is preferably identical in construction and that the description of splice 40 and its connection to rails 28 is equally applicable to splice 38 and its connection to rails 27. Splice 40 has a tubular body 88 and a flange 90 extending laterally outwardly from the periphery of the body 88, generally midway between opposite ends of the body 88. The body 88 has an upper wall 92, a lower wall 94, and opposite side walls 96 and 98. The body also has opposite end portions 100, 102, defined as portions of the body 88 from the flange 90 to respective ends of the body 88. These end portions are adapted for insertion in the open ends of the tubular portions 32 of the rails. The flange 90 constitutes a stop adapted to be positioned between and to contact adjacent open ends 44 of the tubular rail portions 32 to ensure that a proper amount (i.e., approximately half) of the splice is inserted into each rail for proper strength. The transverse cross-sectional shape of the body 88 is substantially the same as but slightly smaller than the crosssectional shape of the open ends 44 of the tubular portions 32 of the rails 28, so that the end portions 100,102 fit snugly within the open ends of the tubular portions 32. Preferably, the body 88 of the splice and the open ends 44 of the rails are generally rectangular in transverse cross-section. It is to be understood, however, that the splices may alternately have a "C" cross-sectional shape or any other suitable cross=sectional shape.
Referring to FIGS. 1 and 8, the side wall 96 of splice 40 has eight through apertures therein, each designated 104. Four of these apertures 104 are in end portion 100 and the