Note: Descriptions are shown in the official language in which they were submitted.
1070510
This invention relates to electrical wiring ducts
for a building and more particularly to an improved method
and structure for forming electrical wiring ducts in a
concrete building floor.
Buildings formed from concrete are often partially
constructed before a final floor plan is selected. After the
basic building structure is erected, such buildings are
subdivided into spaces such as individual offices. Utility
ducts for wiring and comfort conditioning are sometimes formed
in poured concrete floors to facilitate supplying required
utilities to each space into which the building is
subsequently divided. One prior art method for forming
utility ducts in a poured concrete floor is shown in United
States Patent 3,093,933 which issued June 18, 1963 to
Slingluff and in United States Patent 2,975,559 which issued
March 21, 1961 to Hedgren. These patents disclose a building
floor structure having a metallic cellular subflooring which
forms parallel cells or conduits for carrying electrical
cables and for air handling. Electrical ducts also are
located immediately above and perpendicular to the cellular
subflooring, These ducts are spaced across the subflooring
to provide a desired 9pacing for electrical service
connections. Access fitting~ are attached to the ducts at
desired locations and the ducts are connected to the
appropriate subfloor cells. A concrete floor is then poured
over the cellular sub~ooring to embed the electrical ducts.
Wiring for power and ccmmunications is passed through the
subflooring cells and the desired ducts for serving the floor
area wherever such service is needed. ~y running electrical
power and communications wiring through different subfloor
~k
--1--
1070510
cells and through alternate ducts, the power wiring is shielded
in accordance with some building codes and the communications
wiring is isolated from the power wiring to minimize induced
electrical noise. However, a building floor structure of this
type is unnecessarily expensi~e because of the high cost for
the cellular metallic subflooring and of the need for using
separate metal channels for forming both power and communications
ducts in the floor.
According to the present invention, an improved method
is provided for forming wiring ducts or raceways in a concrete
building floor. The method provides separate raceways for
electrical power wiring and communications wiring with only the
power raceways being completely shielded by metal.
In accordance with the present method, a building
floor slab is poured from concrete or a similar hardenable
material to a depth leaving room for a concrete topping or
surface layer. At least one trench is formed in the upper
surface of the floor slab before the material hardens. After
the floor slab hardens sufficiently to maintain the shape of the
trench, a metal cover plate is placed over each trench. A metal
element is attached to the bottom of the cover plate to extend
the length of the trench for dividing the trench into at least
two and preferably three separate raceways. Adjustment means
can be provided to compensate for irregularities in the depth
of the trench. The metal element may be a U-sha~ed channel;
thus the center raceway, which is defined by the U-shaped metal
channel and the metal cover plate, is completely shielded for
carrying electrical power wiring while the remaining raceways
on each side of the U-shaped channel are unshielded. These
channels may carry communications wiring such as telephone wires,
computer input, output and control wires, process control wires,
intercom wires, etc. Access boxes are attached to the top of
-- 2 --
1070510
the trench cover plate for providing desired access to wires
located in the raceways. Metal channels may also be placed
perpendicular to and across all of the trenches for defining
main power distribution ducts interconnecting the various
parallel raceways. A topping Gr surface layer of concrete or
other hardenable material is then poured over the previously
poured concrete floor slab to extend flush with the top of the
access boxes and the channels forming the power distribution
ducts. Electrical wiring for servicing power and communication
needs on the floor area may be completed by passing wires through
the raceways between the main distribution channels and the
access boxes and finally attaching a cover plate over the main
distribution channels. Through this arrangement, power wiring
for the entire system is shielded from the communications wiring
to minimize electrical noise induced into the communications
wiring. Furthermore, the cost of placing a metallic cellular
subflooring in the building and separate metal ducts for
defining both power and communications raceways is eliminated.
In a modification of the method of the present
invention, a building is constructed with floors formed from
prefabricated concrete slabs. Parallel trenches are cast in
the slabs for forming wiring raceways or ducts. In some
slabs, one-half of a trench is formed along a slab edge.
Other trenches are spaced interior from the slab edges and
are provided with a cover plate having a U-shaped channel
attached thereto for dividing the trench into at least two
and preferably three separate wire raceways at the time the
slab is prefabricated. The cover plate and u-shaped channel
may be set in the trench while the concrete is partially
1070510 - -
hardened such that the U-shaped channel proiects into the
concrete to compensate for irregularities in the trench depth
and to completely isolate the wire raceways on either side of
the V-shaped channel. The trenches formed along edges of
the slabs are one-half the width of a finished trench in a
building floor. Two slabs, each having one-half of a trench
extending -along an edge are positioned with the trench h~lves
- abutting when a building is constructed from the slabs.
Grouting is then poured into a joint formed between the slabs
below the trench and a cover plate having an attached
U-shaped channel is then positioned on the trench. Preferably,
anchors spaced along the bottom of the U-shaped channel are
set within the grouted joint between the two slabs. The
wiring channels and the concrete floor in the building is
then completed as in the previously descr-ibed embodiments of
the invention.
Accordingly, it is a preferred object of the
invention to provide an improved method for forming wiring
ducts in a concrete building floor.
Another object of the invention is to provide a
method for constructing parallel communications and power
wiring ducts in a concrete floor with shielding for only the
power wiring.
Other objects and advantages of the invention will
become apparent from the following detailed description, with
- reference being made to the accompanying drawings.
Fig. 1 is a fragmentary, sectioned perspective view
of an improved concrete f~oor structure having wiring ducts
formed therein in accordance with the present invention;
Fig. 2 is an enlarged fragmentary, sectioned
perspective view of an inverted cover plate for dividing a
trench formed in a concrete floor slab into three separate
raceways,
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"- 1070510
Fig. 3 is an enlarged fragmentary, cross-sectional
view taken along line 3-3 of Fig. l; -
Fig. 4 is a fragmentary, sectioned perspective viewof an improved concrete floor structure having wiring ducts
formed therein in accordance with a modified embodiment of
the invention in whlch a portion of the floor is constructed
from prefabricated concrete slabs;
Fig. 5 is an enlarged fragmentary, cross-sectional
view taken along line 5-5 of Fig. 4; -
Fig. 6 is an enlarged fragmentary,-cross-sectional
view taken along line 6-6 sf Fig. 4; and
~ 8 ~`~
B Fig. 7 ~ *~ enlarged fragmentary cross-sectional
viewSthrough ~ further modified concrete floor and wiring
ducts formed in accordance with the present invention.
Turning now to the drawings and particularly to
Fig. 1, a ~uilding floor structure 10 is shown embodying the
structure and constructed by the method of the present
invention. ~he floor structure 10 basically comprises a
concrete floor slab 11 and a concrete surface or topping
layer 12. Ducts or raceways are formed in the slab 11 and
the surface layer 12 for supplying electrical power and
communications to predetermin,ed spaced locations in the
building in which the floor structure 10 is constructed.
Sufficient number of access points to the electrical ducts
are provided in the surface layer 12 for supplying power and
,, communications requirements o~er the floor area regardless
of the manner in which the floor area is subsequently
subdivided.
When the concrete floor sla~ 11 is poured, a
plurality of parallel trenches 13 are formed in an upper
surface 14 of the slab 11. The trenches 13 may be formed
by any suitable means, such as by placing wooden forms
--5--
- 1070510
.
~not shown) in the upper surface 14 for forminq the trenches 13
and, after the concrete in the floor-slab-ll has at least
partially hardened, removing such forms. After the sla~ 11 is
poured and hardened sufficiently to maintain the shape of the
trenches 13, at least some of-the trenches 13 are divided into
at least two separate wiring ducts or raceways, with three
raceways 15-17 shown in the drawinqs. The raceways 15-17 are
formed by placing a cover plate 18 over each trench 13 to
extend along the entire length of such trench. As best seen
in Fig. 2, a generally U-shaped channel 19 is attached to
the cover plate 18. The U-shaped channel 19 is attached to
the cover plate 18 by any suitable means, as by spot welds 20
or by rivets, screws, bolts, etc. The channel 19 has sides 21
of a height corresponding to the depth of the trench 13 for
d~viding the trench 13 into the separate ducts 15-17. It
will be noted that the center duct 16 is defined by the
U-shaped channels 19 and the cover plate 18, and, therefore,
is completely shielded with metal. The ducts 15 and 17 are
defined by the concrete walls of the trench 13 on two sides,
by the channel sides 21 and by the cover plate 18. Because
of the shielding, the duct 16 is particularly suitable for
carrying power wires while the ducts 15 and 17 preferably are
used for carrying communications wires such as telephone
wires, local intercom wires, process control wires, and the
~i~e. ~y shielding the power wires in the duct 16,
electrical noise induced into the communications wires
is minimized.
Groups of three knockouts 22, 23 and 24 are spaced
along each of the cover plates 18 for providiny access points
~0 through the cover plate 18 into the ducts 15-17,
respectively. If, for example, the trenches 13 are located
parallel to each other with a five foot center-to-center
070510- -
.
spacing and each group of knockouts 22-24 is placed at a five -
foot spacing in the cover plates 18, then~the floor
structure 10 will have access points into the ducts 15-17 in
a grid pattern across the floor struc~ure 10 with a five foot
- spacing. Such a spacing would normally be sufficient for
providing adquate power and communications outlets in a
building. The rectangular access boxes 25 may be attached
to the cover plate 18 at each group of-knoc~outs 22-24.
The access boxes are shown as having a width which permits
covering two adjacent ones of the knockouts, such as the
knockouts 22 and 23 for providing access to the communications
and power ducts 15 and 16 or the knockouts 23 and 24 for
providing access to the power and communications ducts 16 and
17. In a preferred embodiment, the access boxes 25 are
Ftaggered such that one box 25 on a cover plate 18 provides
access to the ducts 15 and 16 through the knockouts 22 and
23 a~d the next access box 25 on the cover plate 18 provides
access to the ducts 16 and 17 through the knockouts 23 and
24. However, it should be appreciated that the width of the
access boxes 25 may be such that a box 25 provides access
through only one knockout 22, 23 or 24 to one duct 15, 16
or 17, or that a box 25 provi~es access through all three
knockouts 22-24 to the three ducts 15-17.
- In addition to the access boxes 25, three
channels 26-28 are positioned to extend across and rest upon
the cover p7ates 18. The channels 26-28 are preferably
connected to each cover plate 18 to provide electrical
ground continuity. The channels 26 and 2~ are generally
C-shaped while the channel 27 spaced between the
channels 26 and 28 is generally U-shaped. In addition,
the channels 26-28 have the same height as the hei~ht of
the access ~oxes 25. After the channels 26-28 are
1070510 - -
positioned and attached eo the cover plates 18, the concrete
sur~ace or toppinq layer 12 is poured to form a top surface 12'
which extends flush with the tops of the access boxes 25 and
the channels 26-28.
After the surface layer 12 is poured and has
hardened, communications and power wires are run through the
raceways or ducts 15-17 and three main distribution
raceways 29-31 formed between the channels 26-28 and within
the channel 27. As previously indicated, the channels 26-28
extend across all of the cover plates 18 over the trenches 13.
Although not mandatory, it may be preferable to position the
channels 26-28 perpendicular to the trenches 13. The main
distribution raceway or duct 29 between the channels 26 and 27
communicates through an opening 32 in each cover plate 18 to
the raceway 17. An opening 33 passes through the bottom of
the U-shaped channel 27 and each cover plate 18 for
communicating within the duct 30 formed ~y the channel 27 to
each duct 16. Similarly, the duct or raceway 31 formed
. between the channels 27 and 28 is connected through an
opening 34 in each cover plate 18 to the duct or raceway 15.
Thus, communications wires are laid in the raceway or duct 29
and passed through the raceway 17 for communicating through
the knockouts 24 and access boxes 25 to predetermined
locations on the floor structure. Similarly, power wires
are passed through the duct 30 formed by the channel 27,
through the opening 33 and through the duct 16 for supplying
power through the knockouts 23 and access boxes 25 to
predetermined locations in the floor structure 10.
Communications wires may also be positioned in the duct or
raceway 31 and passed through the openings 34 and the ducts
or raceways 15. After the wires are positioned in the ducts
or raceways 29-31 and 15-17, a cover plate 35 is positioned
- - 10705~0
over the channels 26-28 and fastened to the channels 26 and
28 by means of suitable fasteners 36. The cover plates 35
and 18 and the channels 19 and 26-28 and the access boxes 25
~ are all grounded for safety. Since the power wires in the
duets 30 and 16 are completely surrounded by the channel 27
and its cover plate 35 and the channel 19 and its cover
plate 18, the power wires are all eompletely shielded. The
shielding protects~the communications wires from dama~e in
the event of a short,eireuit in the power wires and also
reduees electrieal noise which otherwise might be induced
into the eommunieations eircuits.
Turning now to Fig. 3, a cross section is shown
through the ducts 15-17 in one trench 13 and through an
aeeess box 25. Although it may not always be required, it
will ~e noted that fasteners 37 are shown attaching the
eover plate 18 to the poured eoncrete slab 11. The
fasteners 37 may be of a~y suitable desiqn, such as
explosively driven nails. ~he primary pur,pose for the
- , fasteners 37 is to maintain the eover plate 18 centered over
the treneh 13 while the surface layer 12 is poured. It
should be appreeiated that if the eover plate 18 is allowed
to move while pouring the su~faee layer 12, the conerete or
other hardenable material forming the surfaee layer 12 may
flow into the trench 13. After the cover plate 18 is
positioned over the treneh 13 to divide the treneh into the
- three separate raceways or ducts 15-17, the aeeess ~ox 25 is
attached to the eover plate 18 over either the knockouts 22
and 23 or the knoekouts 23 and 24. As shown in Fi~. 3,
the knockouts 22 and 23 are removed leaving openings 22' and
23', respectively, through the eover plate 18 and into the
duets 15 and 16. The aceess box 25 is then positioned over
these openings 22' and 23'. Wires are positioned in the
10705~0 . - -
- - ~ - - -
ducts 15-17 at any suitable time during construction of the
floor structure 10. For example, the wires may be run in the
ducts lS-17 at the time the cover plate 18 is positioned
- over the trench 13 and prior to pouring the surface layer 12. .
Or, wires may be pulled through the ducts 15-17 after the
floor structure 10 is completed. A telephone wire 38 is
shown exemplifying a typical wire located in the duct lS;
The telephone wire 38 passes through the cover plate
opening 22' and is terminated at a connector 39. When
telephone installation is completed, a serviceman connects
a mating connector 40 attached to a line 41 which connects
to a telephone (not shown) to the connector 39. The
connectors 39 and 40 are positioned within the access box 25
to eliminate any obstacles on the top floor surface 12'.
An exemplary p~wer wire 42 is shown in the power duct 16.
The power conductor 42 passes through the cover plate
opening 23' and is terminated at a standard power . -
receptacle 43. An electrical appliance line cord 44 having
a standard plug 45 may subsequently be passed through an
opening 46 in the access box 25 and plugged into the
receptacle 43. The opening 46 is sufficiently large as to
permit users of the building to remove the plug 4S or to
plug in other appliances.
As shown in Fig. 3, the access box 25 normally
provides access to the power duct 16 and to one of the two
communication ducts 15 or 17. It may be desirable, for
example, to place only telephone wires in one of the
communication ducts, duct lS shown, and to place other
communication t~ires in the duct 17. ~urthermore, it also
may be d2sirable to stagger the location o~ the access
boxes 25 such that every other access box on a cover plate 18
provides access to the duct 15 while the remaining alternate
1070510
- access boxes 25 provide access-to the duct 17. A-s represented -
by the dashed lines 47, if access is subsequentiy desired
into the duct 17 where such access is not provided by an
access box 25, an opening above the knockout 24 may be formed
-through the surface layer 12. Such an opening may be formed
by any suitable means, as by drilling through the surface
layer 12 or by providing a plug in the surface area 12 which
is readily removable at a later date. -Of course, where
access is desired into both of the communication ducts 15 and
17, the access box 25 may be constructed sufficiently large
as to cover each of the three knockouts 22, 23 and 2~.
- Although Figs. 1-3 of the drawings specifically
show a floor structure 10 hàving three parallel ducts formed
in each trench 13, it will be appreciated that any other
desired number of ducts may be formed in a floor trench.
For example, if only a single communication duct and a single
power duct are desired, the trench 13 may be formed of a
width sufficient to form only a single communication duct,
duct 15 for example, and a single power duct 16. In such
event, the U-shaped channel 19 would be located near one
side of the cover plate 18 rather than centered as shown in
the drawings. Where additional ducts are desired, it will
also be appreciated that more than one U-shaped channel 19
may be attached to the bottom of the trench cover plate 18
for forming the desired number of ducts in the concrete
floor slab 11.
Turning now to Fig. 4, a floor structure 50 is
shown constructed in accordance with a modified embodiment
of the method of the present invention. The floor
structure 50 is constructed from a plurality of prefabricated
floor slabs, of which two exemplary slabs 51 and 52 are
shown in transverse section. The slabs 51 and 52 are Precast
at a factory in standard widths such as eight feet or twelve -
feet, and in various lengths for various size structures.
To reduce the weight of the slabs 51 and 52, voids 53 are
formed to extend longitudinally through the slabs 51 and 52.
The strength of the slabs 51 and 52 is maintained through
the use of reinforcement rods or bàrs 54. If desired, the
bars 54 may prestress the slabs in a known manner. Wiring
ducts 55 are formed in a trench between the abutting slabs 51
and 52 with one half 56 of the trench formed in the slab 51
and a second half 57 of the trench formed in the slab 52. A
grouted joint 58 extends between the slabs 51 and 52 and
below the trench halves 56 and 57. A grouted joint 59 is
also provided between the slab 51 and a next adjacent slab 60
and a grouted joint 61 is provided between the slab 52 and a
next adjacent slab 62. Tr~nches for use in forming wiring
ducts are formed above the grouted joints only when a desired
location for wiring ducts or raceways is above such joints.
In addition to the trench defined by the trench halves 56
and 57 in the abutting portions of the slabs 51-and 52,
wiring ducts or raceways 63 are formed in a trench 64 located
interior from the edges of the slab Sl and wiring ducts 65
are located in a trench 66 l~cated interior from the edges
of the slab 52. An exemplary access box 67 is shown for
providing access to the wiring ducts SS which are located
between the slabs 51 and 52 and an exemplary access box 68
is shown for providing access to the ducts 63 within the
slab 51. The access boxes 67 and 68 are shown embedded
within a topping layer 69 formed from concrete or any other
suitable hardenable floor material.
Turning now to Fig. S, details are shown for the
wiring ducts or raceways 63 spaced from the edges of and
extending the longitudinal length of the floor slab Sl. A
1070S10
generally U-shaped channel 70 divides th~ trench 64 into at
least two and pref'erably three separate.wiring ducts or
raceways.71, 72 and 73. The V-shaped channel 70 has upper
flanges-74 which are welded,-bolted or otherwise attached
to a cover plate iS which completely covers the trench 64.
Three sides of the duct 71 are defined by the U-shaped
channel 70 and the fourth side is defined by the metal
cover plate 63. As a consequence, the duct 71 is completely
' shielded to prevent passage of electromagnetic radiation
from wires within the duct 71. ~he ducts 72 and 73 are
located on opposite sides of the U-shaped channel 70 and are
, defined on two sides'by the slab 51, on a third side by the
U-shaped channel 70 and on a fourth side by the cover
plate 75. Thus, the ducts 72 and 73 are not shielded.
Electrical power wiring about which substantial
electromagnetic fields may be established is preferably
located within the duct 71 while control and communications
wiring is located within the ducts 72 and,73. In the event
that only two ducts are required, one of the two ducts 72
and 73 may be eliminated either by shortening the size of
the trench 64 or by moving the channel 70 to one side of
the trench 64. On the other hand, if additional ducts are
required, more than one U-shaped channel 70 may be attached
to the cover plate 75.
The U-shaped channel 70 is provided with two
~ spaced paral~el sides 76 and 77 and a flat bottom 78'. The
sides 76 and 77 extend below the bottom 78 to define lower
fins or projections 79 on each side of the channel 70. The
projections extend below the cover plate 75 and below the
bottom a distance greater than the depth of the trench 64.
The cover plate 75 and attached U-shaped channel 70 are
positioned over the trench 64 after the slab 51 is formed and
10705~0
the concrete has solidified only sufficiently to maintain ~ts
shape. When the cover plate 75 is positioned over the
trench 64, sufficient downward force is applied to force the
projections 79 into the concrete at the bottom of t-he
trench 64. By deforming the concrete with the projection 79, ~'
the two ducts 72 and 73 are completely isolated, despite minor
variations in the depth of the trench 64 along the length of
the slab 51. If desired, the cover plate 75 can be anchored
to the slab 51 with fasteners similar to the fasteners 37 in
~ig. 3 to retain the cover plate 75 in place-during shipment
and installation of the slab 51. Thus, the slab 51 with the
attached cover plate 75 and the U-shaped channel 70 dividing
the trench 64 into the three separate ducts 71-73 are
prefabricated in a factory.
Durin~ construction of a building from the slab 51,
the slab 51 is positioned on suita~le supports which may be
concrete walls or columns or steel beams. One or more of the
access covers 68 are positioned over the trench 64 and-
attached to the cover plate 75 to provide access into the
ducts 71-73, as required. In the embodiment shown in Fig. 5,
the access box 68 is positioned over the ducts 71 and 73.
The access box 68 has an inte~ior opening 80 which
communicates through a hole 81 in the cover plate 75 leading
into the duct 71 and through a hole 82 in the cover plate 75
leading into the duct 73. The holes 81 and 82 may be formed,
for example, ~y removing knoc~outs or by a~y other
conventional method. The final step in constructing the
f~oor structure 50 is to pour the topping layer 6g over
the slab 51 and flush with a removable cover 83 attached to
the top of the access box 68.
Turning now to Fig. 6, a cross sectional view is shown
through the wirinq ducts 55 and the access box 67 from Fig. 4.
--14-- r
070510 , . . .
The ducts 55 are defined by a U-shaped channel 86 and an
attached cover plate 87 which enclose and separate the trench
halves 56 and 57. The ducts 55 include a completely shielded
duct 88 formed by the~U-shaped channel 86 and the cover
plate 87, and unshielded duct 89 formed by the trench half 56
in the slab 51, one side of the U-shaped channel 86 and the
cover plate 87 and an unshielded duct 90 formed by the trench
half 57 in the slab 52, the duct 86 and the cover plate 87.
The ducts 88-90 are formed during the construction of a
building including the floor structure 50. Initially, the
slabs 51 and 52 are positioned on a suitable support
structure (not shown). The grouted joint 58 is then formed
by filling a groove 91 extending between the slabs 51 and
52 and below the trench halves 56 and 57 with a suitable
ccncretious grouting material. Before such grouting material
within the joint 58 has hardened, the cover plate 87 is
positioned over the trench halves 56 and 57 with the
U-shaped channel 86 abutting the grouted joint 58.
Preferably, a plurality of studs 92 having ir~egular surfaces
or a plurality of other suitable anchors are attached to the
bottom of the U-shaped channel 86 at predetermined spacings
along its length. The studs or other suitable anchors 92
are pressed into the grouted joint 58 to securely anchor in
place the cover plate 87 and attached U-shaped channel 86.
The grouted joint 58 is also deformed sufficiently by the
- U-shaped channel 86 to assure that the ducts 89 and 90 are
completely isolated from each other. After the U-shaped
channel 86 and cover plate 87 are positioned over the trench
halves 56 and 57 and the grouted joint 58, the floor
structure 50 is completed in a manner similar to that
described for Figs. 1-3. The access box 67 and other access
boxes, as needed, are attached to the cover plate 87 either
- - ~o705~
- over the channels 88 and 90 or over ~he channels B8 and 89 or
- over all three channels 88-90, as required and at any
desired location. The topping layer 69 is then applied to
complete the floor. The topping layer 69 is of a thickness
~ufficient to extend flush with a removable cover 93 for the
access box 67. After the floor structure 50 is completed,
the space above the floor structure 50 may be divided into
- rooms, as desired. A typical partition 95 is shown in
dashed lines in Fig. 6 located adjacent the access box
cover 93. At the same time the building is partitioned into
rooms, or if necessary at a subsequent date, suitable
electrical power wiring, control wiring, communications
wirin~ and the like is run through the ducts 8B-90 to supply
the needs of the space above the floor structure 50.
In the embodiment shown in Fig. 5, projections 79
at the bottom of the U-shaped channel 70 were forced into
the slab 51 before the concretious material forming the
slab 51 had completely hardened. The function of the
projections 79 was to assure that the ducts 72 and 73 were
completely isolated by the U-shaped channel 70.
Turning now to Fig. 7, a different method is shown
for assuring that two ducts 97 and 98 spaced on either side
of a U-shaped channel 99 are completely isolated, despite
variations in the depth along the length of a trench 100 in
which the U-shaped channel 99 is located. The U-shaped
- channel 99 includes two upper side flanges 101 and 102 which
are welded or otherwise attached to a cover plate 103. A
lower U-shaped channel member 104 is positioned between the
flan~es 101 and 102. The U-shaped member 1~4 includes
sides 105 and 106 which are firmly held between the
flanges 101 and 102, respectively, by spring tension. When
the U-shaped chanr,el 99 and cover plate 103 are positioned
-16-
'1070510- - -
.
~ within the trench 100, the U-shaped channel 104 is forced
upwardly between the flanges 101 and-102 as a bottom 107
of the channel 104 contacts the trench 100. Through this
method, the lower U-shaped member 104-contacts the trench 100
to completely isolate the ducts 97 and 98, despite
variations in the depth of the trench 100 along its length.
Turning to Fig. 8, still another structure and
method are shown for compensating for variations in the
-depth of a trench llO when a floor structure is constructed
in accordance with the present invention. In this emobdiment,
a U-shaped channel 111 is not attached to a cover plate 112,
as in the previously described embodiments. The trench 110
is formed within a concrete slab 113 having an upper
surface 114. The U-shaped channel 111 includes a lower
~U-shaped member 115 having spaced sides 116 and 117. 8O1ts
118 pass through vertical slots within a flange 119 and
attach such flange 119 to the side 116. Similarly, others
of the bolts 118 pass through vertical slots in a flange 120
and attach such flange 120 to the side 117. ~he bolts 118
are threaded lnto the sides 116 and 117 and are sufficiently
short as not to project appreciably into the duct 122.
During construction of ducts 121-123 in the trench 110, the
U-shaped channel 111 is positioned in the center of the
trench 110. A workman then positions a straightedge on the
upper surfaces ?14 of the slab 113 to span the trench 110
- and to extend over the flanges 119 and 120 of the U--shaped
channe} ~11. The flanges 119 and 120 are then moved into
contact with such straightedge so they are flush with the
upper surfaces 114. ~he cover plate 112 is then positioned
over the trench 110 and the U-shaped channel 11, access
boxes are installed as necessary, and a topping layer 124
is applied to complete the floor structure. Seals 125 are
- 1~705~
located between the flanges 119 and 120 and the. cover -
plate 112. The seals 125 may consist of resilient members
formed from a suitable synthetic resinous material or they
may consist of a suitable adhesive which bonds the flanges 119
and 120 to the cover plate 112.
Although several different methods have been
described for adjusting or compensating for variations in the
depth of a trench when such trench is divided into a
plurality of ducts, it will be appreciated that other methods
may also be used without departing from the invention. For
example, the U-shaped channel member may fit within a recess
in the bottom of the trench formed in the concrete ~loor
slab. Before positioning the U-shaped channel member within
the recess, a suitable hardenable material such as a synthetic
resinous material or a concretious material may be positioned
within the recess to bond the U-shaped channel member to the
floor slab and also to isolate ducts formed on either side
of the V-shaped member.
It will be appreciated that various other
modifications and changes may be made in the above-described
preferred embodiments of the invention without departing
from the spirit and the scope of the following claims.
