Bottomless trench duct

An underfloor electrical distribution system is comprised of a bottomless trench duct transversely overlying a cellular subfloor deck assembly. The bottomless trench duct has spaced-apart, parallel L-shaped side rails, the vertical legs of which terminate in an inverted U-shaped channel and form the sidewalls of the trench. Preshaped void closure plates, which are attached to the side rails, transversely extend into the troughs of the cellular subfloor deck assembly to prevent the ingress of concrete into the trench duct while the concrete floor is being constructed. The preshaped void closure plates may be held in place within the inverted U-shaped channel by means of rivets fastened to the vertical leg of the side rail. Alternatively, horizontal slots in the inverted U-shaped channel may be cut to receive the void closure plates, which are frictionally held within the U-shaped channel.

BACKGROUND OF THE INVENTION 
This invention relates to void closures used in a bottomless trench duct in 
an underfloor wire distribution system. 
The underfloor wiring system is comprised of a cellular subfloor deck 
assembly through which electrical and communication wires are channeled. 
Generally, the cellular subfloor deck consists of a base wall and a 
corrugated upper wall having a plurality of crests and troughs. The base 
wall need not be continuous, but may be discontinuous to define 
predetermined raceway cells with the corrugated upper wall. Overlying the 
cellular subfloor at right angles to the raceway cells are one or more 
bottomless trench ducts, the top walls of which are provided with 
removable access cover plates. The electrical and communication wires are 
strung through the trench duct and access openings are provided in 
predetermined raceway cells so that the wires may be branched into the 
raceways for communication with electrical and communication terminals and 
connectors. 
Underfloor trench ducts for wiring systems are frequently used in buildings 
where many electrical and communication outlets are required. Some typical 
examples of trench ducts are disclosed in the following U.S. Pat. Nos.: 
3,435,568; 3,453,791; 3,721,051; and 3,593,472. 
In forming a bottomless trench duct, the problem encountered is to keep the 
concrete from flowing into the trough in the cellular subfloor below the 
side rails of the trench duct. In the past, the troughs have been blocked 
off by means of plugs disposed under the sidewall of the trench duct or 
the inner sidewall of the trench duct has been formed with vertically 
downwardly extending portions to block off the trough, as is disclosed in 
U.S. Pat. No. 3,721,051. 
The plugging method of blocking the trough is unsatisfactory because the 
plug may become dislodged and move out of position while the concrete is 
being poured. The alternative method of cutting downwardly extending 
projections on the inner sidewalls of the trench duct is unsatisfactory 
because the troughs are not of uniform shape and spacing, and in order to 
accommodate the various irregular spacings and configurations of the 
trough, the projections on the sidewalls must be precut or stamped in 
small sections. This operation requires the use of many different dies, 
and results in the need for many end welds on the short side rail 
sections. 
SUMMARY OF THE INVENTION 
The present invention overcomes many of the prior art problems in blocking 
concrete from the duct by providing void closures which are provided in a 
variety of shapes to accommodate different trough shapes and which may be 
attached to the side rails of the trench duct at locations which will 
accommodate different trough spacings of the cellular subfloor. 
In the present invention, therefore, the void closures are not an integral 
part of the side rail and so the side rail may be cut to longer lengths, 
e.g., 10 feet, thereby spanning the width of several cross sections of the 
cellular subfloor duct assemblies, and thus eliminating the need for 
several end welds on the supporting side rails. 
The trench ducts have parallel L-shaped supporting side rails. The 
horizontal leg of the side rail is fastened to the top walls of the cells 
of the subfloor assembly by, for example, tack welding. Individual void 
closures are precut to conform to the configuration of the trough and they 
may be attached to the vertical leg of the side rails by means of rivets, 
or they may be inserted through slots spaced along the inverted U-shaped 
channel on the side rail. The void closures may be attached to the side 
rails by the manufacturer before shipment or by the workers at the job 
site. When the bottomless trench duct is assembled and the void closures 
are in place, the concrete floor is poured around the trench covering the 
side rails to a level flush with the top wall of the trench. The vertical 
leg of each side rail is straddled by an extruded rail, which supports the 
removable access cover to define the trench. The extruded rail is 
vertically adjustable relative to its side rail so that it may be adjusted 
to the level of the concrete to be poured. From the trench duct, access 
may be had to the cellular raceways by periodic openings in those 
raceways.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to the drawings, and particularly to FIGS. 1 through 7, there 
is illustrated an underfloor electrical distribution system which includes 
a cellular subfloor duct assembly 10 and a bottomless trench duct 11. The 
cellular floor unit 10 is embedded in and covered by the concrete 12 of 
the floor. The cellular floor unit includes a top plate 13 formed with 
alternate crests 14 and troughs 15. The floor unit also includes a bottom 
plate which may extend beneath a predetermined number of crests 14 and 
troughs 15, as illustrated in FIG. 1, or may extend beneath all of the 
crests and troughs. The top plates 13 and the base plate 16 cooperate to 
define a plurality of raceway cells 17 which extend along the floor 
parallel to each other to receive wire and cable of an electrical 
distribution system. 
The wire and cable are fed into a raceway cell 17 by the trench duct 11 
which runs generally perpendicular to the cells 17, and to provide access 
to the cells a predetermined number of holes are cut through the crests 
14. The trench duct 11 comprises a pair of spaced supporting side rails 18 
and 19, which run generally perpendicular to the crests and troughs 14 and 
15. Each side rail is generally L-shaped, and has a horizontal leg portion 
20 and a vertical leg portion 21 terminating in an inverted, U-shaped 
channel 22. The horizontal leg 20 is tack welded to the crests 14. Each 
side rail 18 and 19 is provided with individually replaceable void 
closures 23-28, which have configurations which are adapted to conform to 
the particular configuration of the trough into which they enter. For 
example, the void closure 26, as shown in FIG. 4, is intended to close a 
trough having a flat bottom and flat sloping sidewalls. A void closure 29 
(FIG. 5) and the void closure 24 (FIG. 6) are intended to conform to a 
seam 30 between adjacent sections of the duct assembly by having a 
U-shaped portion 31 cut therefrom. Stiffening ribs 32 may be provided in 
some of the troughs 15 and FIG. 7 illustrates that the void closure 28 is 
adapted to conform to that stiffening rib by having a cut-out portion 33 
in its bottom edge. 
As may best be seen in FIG. 3, each void closure 23-28 is affixed to the 
side rails 18 and 19 by rivets 34 and in-plane twisting of the void 
closures is prevented, since the top of the closure projects into the 
U-shaped channel 22. This operation may be done at the job site or by the 
manufacturer after determining the spacing between the troughs and the 
particular configuration of the troughs. 
A removable cover assembly is provided to close the trench duct. This 
assembly includes extruded rails 35 having bifurcated lower portions which 
loosely fit over the U-shaped channel 22. Such side rails are shown more 
clearly in U.S. Pat. No. 3,593,472, the subject matter of which is 
incorporated herein by reference. The extruded side rails 35 may be 
adjusted relative to the side rails 18 and 19 by adjusting screws 36 
attached to the side rails 35, but which are axially movable relative to 
the side rails 35 by being unthreaded from a block 37. The head of the 
adjusting screws 36 is received under one of a series of clips 38 spot 
welded to the horizontal leg portion of the side rails 18 and 19. A 
removable hatch cover 39 closes the trench duct. 
Referring now to FIGS. 8 and 9, a side rail assembly according to another 
aspect of this invention is illustrated. The side rail assembly includes a 
generally L-shaped supporting side rail 50 having a horizontal leg portion 
51 and an upwardly extending vertical leg portion 52 terminating in an 
inverted U-shaped channel 53. Notches 54 are cut into the U-shaped channel 
to receive individually replaceable void closures 55 and 56. The void 
closures 55 and 56 may be driven through the notches 54 by a hammer after 
the side rails are spot welded to the cellular subfloor so that the void 
closures 55 and 56 seek their proper seated positions within the troughs. 
The closures 55 and 56 form a tight frictional fit relative to the side 
rails 50, since they are provided with dimples 57, which are wedged in the 
U-shaped channel 53. 
Referring to FIGS. 10 and 11, there is illustrated a side rail assembly 
according to a still further aspect of this invention. The side rail 
assembly includes a generally L-shaped supporting side rail 60 having a 
horizontal leg portion 61 and an upwardly extending vertical leg portion 
62 terminating in an inverted U-shaped channel 63. Notches 64 are cut into 
the U-shaped channel to receive individually replaceable void closures 65. 
The void closures 65 may be driven through the notches 64 by a hammer 
after the side rails are tack welded to the cellular subfloor so that the 
void closures 65 seek their proper seated positions within the troughs. 
The closures 65 form a tight frictional fit relative to the side rails 60, 
since metal forming the U-shaped channel 63 is bent inwardly, as may be 
seen in FIG. 11. The edge of the horizontal leg portion 61 is turned up to 
form a channel 66 for receiving the adjusting screws of the extruded side 
rails, such as the adjusting screws 36 of the side rails 35. Slots 67 are 
cut into the channel 66 to facilitate tack welding and the insertion of 
the adjusting screws. 
The invention is not restricted to the slavish imitation of each and every 
detail set forth above. Obviously, devices may be provided which change, 
eliminate, or add certain specific details without departing from the 
scope of the invention.