The conduit includes a top wall (A) and a base (B). The top wall A has an apex area (10) which is connected with a first corrugated side wall (12) and a second corrugated side wall (32). The side walls having alternating peaks (22, 42) and valleys (24, 44). The peaks have apex ends (26, 46) which are disposed closely adjacent each other at the apex area to define a hinge region therebetween. Disposed along the apex area and on the side wall peaks are a plurality of outward projecting dimples (70, 72, 74) which are severable by a tangentially disposed knife blade to form a plurality of apertures (50, 52, 54). The base B is a flexible sheet of plastic mesh material.

This invention relates to the art of pipes, tubing, and conduits. The 
invention finds particular application in drainage tubing used to remove 
excess water from agricultural fields and will be described with 
particular reference thereto. It is to be appreciated, however, that the 
invention has other applications such as septic or leach bed tubing, 
culverts, tunnels, subterranean conduits, other types of drainage 
conduits, and the like. 
Conventionally, drainage tubing is used to remove excess surface and 
subsurface water from agricultural fields as well as from commercial and 
residential properties. Generally, a trench is dug in the soil by a 
trenching machine, the drainage tubing positioned on the floor of the 
trench, and the trench refilled. Water which enters the tubing at one end 
or at openings along its length are carried through the tubing for 
disposal. 
Most commonly, drainage tubing is corrugated plastic tubing which is 
circular in cross section. The tubing constructions consist of alternating 
outward projecting peaks and inward projecting valleys which increase the 
strength and rigidity of the tubing. The interior of the peaks are hollow 
and form troughs which collect sediment and cause turbulence in the flow 
of fluids. The tubing is normally constructed of a single layer of high 
density, thermoplastic material. For enhanced properties a filler is 
sometimes added to polyvinylchloride and polypropoglene. To prevent 
polyethylene from being weakened by ultraviolet light, carbon black is 
commonly added. To allow water or other fluids to enter or exit the 
tubing, the tubing is usually perforated in the valley areas at spaced 
intervals. 
An arched conduit construction is described and claimed in the present 
assignee's U.S. Pat. No. 4,245,924, issued January 20, 1981. In this 
patent, it is shown that perforating only a flat base portion of the 
arched conduit is at least as effective as perforating a circular conduit 
intermittently around its circumference. 
One of the problems with the prior art tubing has been the propensity of 
the carbon black filler to absorb energy. When exposed to sunlight during 
storage, handling, and installation, the carbon black readily absorbs 
solar radiation. This raises the temperature of the plastic which in turn 
lowers its elastic modulus i.e. softens it. The softened plastic tubing is 
easily deformed by the weight of other tubing in storage, by mechanical 
installation equipment, by rough handling, by the weight of backfill, and 
the like. 
Another problem with the prior art tubing is that perforating the 
corrugated top wall sometimes required interrupting the manufacturing 
process during the perforating. That is, the continuously moving tubing in 
the manufacturing line was intermittently stopped to allow the perforating 
process to take place. Other perforating apparatus included complex 
interrelated moving machinery parts, note for example U.S. Pat. No. 
4,180,357 issued Dec. 25, 1979.The above-referenced arched tubing patent 
of the present assignee overcame this problem by perforating only the 
flexible base. However, it has been found desirable for some applications 
to have the top wall perforated as well. 
Yet another problem with the prior art tubing occurs in shipping. Rigid 
non-foldable arched and circular tubing have a large volume due to the 
interior bore but relatively little weight due to the thin-walled 
construction. This tends to fill the volume capacity of transporting 
vehicles without meeting their weight capacity. To improve shipping 
efficiency, the arched conduit of the present assignee'above-referenced 
patent has a hinge at its apex area to enable the tubing to be flattened. 
When the hinge is defined by a sharp groove, there is a tendency for the 
plastic to fatigue or crack along the hinge. When the hinge is broadened, 
the actual fold line may vary altering the apex of the arch, hence 
changing the cross section of the arch and weakening it. 
The present invention contemplates a new and improved conduit product which 
overcomes the above problems and others. It provides a new and improved 
arched conduit construction which is economical to manufacture, high in 
both impact and structural strength, easy to ship and handle, and readily 
adaptable to use in a broad range of practical applications. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, there is provided a conduit 
product comprising a top wall and a generally flat base. The top wall 
includes a longitudinally elongated apex area having a plurality of 
apertures and first and second longitudinally elongated side walls having 
a longitudinally elongated apex edge area which is connected with the apex 
area. The generally flat base is operatively connectable with the first 
and second side walls adjacent base edge areas which are opposite from 
their apex edge areas. 
In accordance with another aspect of the present invention, there is 
provided a conduit product comprising a top wall and a generally flat 
base. The top wall includes a longitudinally elongated apex area and first 
and second longitudinally elongated side walls which are operatively 
connected with the apex area. At least one of the apex area and the first 
and second side walls has a plurality of dimples thereon such that the top 
wall is conveyable past a sharp blade in such a manner that the blade 
severs the dimples creating apertures through the top wall. The generally 
flat base is operatively connectable with the first and second side wall 
base edge areas. 
One advantage of the present invention is that it provides a conduit 
construction which is easier to manufacture and perforate. 
Another advantage of the present invention is that it yet is stronger, it 
requires less plastic material to manufacture. 
Yet other advantages of the present invention include that it inhibits heat 
build up, it is foldable to reduce its bulk, it protects filter materials 
from damage during storage and shipping, it has improved fluid flow 
characteristics, and it reduces the amount of collected sediment. 
Still other advantages and benefits of the present invention will become 
apparent to those skilled in the art upon reading and understanding the 
following detailed description of the preferred embodiments and the 
accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
With primary reference to FIG. 1, the conduit construction includes a top 
wall A which is strong relative to top compressive loading forces and a 
base B which is relatively strong in tension. The top wall A includes a 
longitudinally elongated apex or hinge area 10 which extends along the 
length of the conduit construction. A first longitudinally elongated side 
wall 12 has a longitudinally elongated apex edge area 14 and a 
longitudinally elongated base edge area 16. The first side wall apex edge 
area is connected longitudinally with the apex area 10. Adjacent the first 
side wall base edge area 16, the first side wall has an outward extending 
foot or flange portion 18 and a downward extending claw portion 20. When 
installed, the claw portion 20 digs into the soil to anchor the base edge 
areas against moving toward each other folding or collapsing the conduit. 
Extending generally between the first side wall apex and base edge areas 
are a plurality of alternating peaks 22 and valleys 24. The first side 
wall peaks have apex ends 26 which taper from a corrugation height of 
about 0.190-0.250 inches to the valley level along a generally semiround 
interface area. The alternating first side wall peaks and valleys provide 
a transverse corrugation along the first side wall such that the first 
side wall is corrugated. p A second longitudinally elongated side wall 32 
has a longitudinally elongated apex edge area 34 and a longitudinally 
elongated base edge area 36. The second side wall apex edge area 34 is 
connected with the apex area 10. Adjacent the second side wall base edge 
area 36, is an outward extending second side wall foot or flange portion 
38 and a downward extending claw portion 40. Disposed transversely 
generally between the second side wall apex and base edge areas are a 
plurality of alternating second side wall peak portions 42 and valley 
portions 44. The second side wall peaks have apex ends 46 which taper from 
a corrugation height of about 0.190-0.250 inches down to the valley level 
along a generally semiround interface area. 
The apex area 10 and the first and second side wall valleys 24 and 44 
define a continuous arch cross section. The apex area is sufficiently 
flexible that it functions as a hinge about which the first and second 
side walls are foldable. The first and second side wall peak apex ends 26 
and 46 which are disposed closely adjacent each other to define a 
longitudinal fold line or hinge region along the apex ends, are displaced 
by about twice the thickness of the apex area, i.e. about 0.125 to 0.160 
inches. Optionally, the apex area 10 and the first and second side wall 
peaks may define a continuous arch with the valleys recessed therebelow. 
As yet another option, the peaks may extend across the apex area removing 
the ready apex folding property of the conduit. To facilitate the ingress 
or egress of fluids into the conduit product, a plurality of apex 
apertures 50 are disposed in the apex area 10. The apex apertures are 
centered along the apex hinge region at its intersection with corrugation 
valleys. The apex apertures define weakened spots along the hinge region 
to assist in centering the fold. Preferably, the apex apertures are about 
0.1-0.250 inches in diameter. A plurality of first side wall apertures 52 
are disposed in the peak portions 22 of the first side wall and second 
side wall aperture portions 54 are diposed in second peak portions 42 of 
the second side wall. 
In the preferred embodiment, the base portion B is a flexible sheet which 
is connectable adjacent the first and second side wall base end edges 16 
and 36. More specifically, the base B is attached to the flange portions 
18 and 38. Further to the preferred embodiment, the base B is a sheet of 
extruded porous hydrophilic plastic material. The porous material, such as 
netting or mesh, is sufficiently fine that it blocks soil and sand 
particles from entering the conduit while allowing fluids to enter and 
leave. A mesh having apertures with a nominal size on the order of 100 to 
300 microns is preferred. Optionally, other apertured sheets may be 
utilized, such as spun bonded materials, slit or slotted fluid impermeable 
sheets, and the like. Preferred porous plastic materials include DELNET 
plastic netting from the Hercules Corporation or CONWED plastic netting 
from the Conwed Company. 
With particular reference to FIGS. 2 and 3, the top wall A is a layered 
plastic construction. The top wall has an inner layer 60 of a first 
plastic material and an outer layer 62 of a second plastic material. In 
the preferred embodiment, the inner plastic material is polyethylene with 
carbon black filler and the outer layer 62 is polyethylene with a titanium 
dioxide filler. This provides the exterior of the top wall with a white, 
light reflective surface which inhibits the conduit from becoming warm 
when stored in sunlight. This retards the top wall from becoming softer or 
decreasing its elastic modulus from an increase in heat and from becoming 
deformed or damaged. Optionally, other combinations of layers of material 
may be used, such as expanded polymeric material which is expanded with a 
CELLOGEN additive in amounts to cause a 20 to 40% reduction in the 
specific gravity. Other top wall materials include virgin and reprocessed 
polymers, polyethylene, polyurethane, nylon, polyvinyle chloride, styrene 
polymers, and the like. 
With reference to FIGS. 2, 3, and 4, the top wall A of the conduit product 
is initially formed with a dimple where each of the apertures is to be 
located. Specifically, the apex area 10 is molded with a plurality of 
dimples 70 projecting outward therefrom. The first side wall peak portions 
22 have dimples 72 projecting outward therefrom and the second side wall 
peak portions 42 have dimples 74 projecting outwardly therefrom. In the 
preferred embodiment, dimples are disposed on alternate peaks of the side 
walls. Optionally, on conduit in which the top wall is open along one edge 
rather than closed as in circular conduit, the dimple may project inward 
from the apex area and the valleys. 
With reference to FIG. 5, the apex and side wall apertures are formed by 
passing the conduit along knife blades such that the dimples are severed. 
To emphasize that the formation of apertures from dimples is also 
applicable to circular and other shaped conduit, circular conduit is 
illustrated in FIG. 5. The circular conduit has a circular corrugated side 
wall 12' having alternating peak portions 22' and valley portions 24'. 
Projecting outward from the peak portions are a plurality of dimples 72' 
and 74' which are severed to form apertures 52' and 54'. A dimple severing 
means 80' includes a horizontally disposed guide surface 82 along which 
the dimples slide. A knife blade 84 is disposed adjacent a downstream end 
of the horizontal surface 82. The guide surface has a guide portion 86 
which extends below the knife blade 84 to inhibit the dimples from 
flipping out of contact with the blade and being only partially severed. A 
like severing means 80' severs the other longitudinally disposed row of 
dimples 72'. If the top wall is open on one side or able to be opened 
outward, the dimples may project inward and the severing means may be 
disposed along the interior of the top wall. 
The present invention is applicable to corrugated and non-corrugated 
conduits of various stages in addition to the parabolicly arched conduit 
of FIGS. 1-4 and the circular conduit of FIG. 5. For example, as 
illustrated in FIG. 6, the conduit may have a generally triangularly 
arched cross section. In the embodiment of FIG. 6, like elements with the 
embodiment of FIGS. 1-4 are denoted with the same reference numeral 
followed by a double prime ("). The top wall A includes an apex area 10", 
a first side wall 12", and a second side wall 32". The first side wall has 
alternate peaks 22" and valleys 24" and projecting dimples 72" which are 
severable to form side wall apertures. The second side wall 32" has 
alternating peaks 42" and valleys 44". Side wall apertures 54" are formed 
in the valleys or peaks by severing projecting dimples. 
The invention has been described with reference to the preferred 
embodiment. Obviously, modifications and alterations will occur to others 
upon reading and understanding the preceeding detailed description. It is 
our intention that the invention be construed as including all such 
modifications and alterations insofar as they come within the scope of the 
appended claims or the equivalents thereof.