Drainage device

The drainage device includes a stiff plastic core having rigid raised portions and valleys therebetween is oriented vertically and tangentially to a drain pipe which has axially spaced raised annular portions contacting the core and annular recesses with slots to provide passageways for ground water into the pipe. A permeable plastic membrane is warpped around the core and the pipe to prevent fill from filling the passageways so defined.

This invention relates generally to drainage devices of the type for 
carrying away subsurface water either on a hillside, in the vicinity of 
foundations or the like, or in filtration systems. More specifically, this 
invention deals with an improvement over drainage devices of the type 
which include a drainage pipe provided below a core surrounded by a ground 
water pervious material to provide a pathway for the water through the 
core into the drainage pipe. 
The primary aim of the present invention is to provide an improved core and 
pipe assembled with an improved non-woven filter material around both of 
them such that water is carried downward to the drainage pipe in a very 
efficient manner.

Referring to the drawings in greater detail, FIG. 1 shows an elongated 
drain pipe 10 having axially spaced annular segments 10a defining valleys 
10b therebetween, and with slots 10c provided in the sidewall of the pipe, 
said slots being formed in staggered relationship approximately 90 degrees 
apart and in diametrically opposed paired relationship to one another so 
as to preserve the structural integrity of the plastic drain pipe 10 
without adversely effecting the drainage characteristics of the pipe 
itself. 
The pipe 10 extends through a non-woven thermoplastic envelope material 
indicated generally at 12 which material has opposed faces 12a and 12b 
stitched to one another at the top 12c and bottom 12d to provide an 
envelope for receiving the pipe 10 as best shown in FIG. 2. The said 
envelope 12 may be open at its opposite ends, or may instead be folded at 
one end, as shown for example at 12e in FIG. 1, but must of necessity be 
slit or open at least along a bottom portion thereof as shown at 12f, to 
be capable, conveniently, of receiving the elongated drain pipe 10. 
Inside the envelope 12 a core or armature 14 is provided alongside the pipe 
10, and is generally tangentially arranged with respect to the pipe 10. 
This core 14 serves several purposes, namely to provide a separation 
between the opposed front and back layers 12a, 12b of the non-woven filter 
material making up the envelope 12, and to provide a convenient assembly 
of the filter material 12 with the pipe 10 in order to provide a plurality 
of passageways for the downwardly flowing ground water to direct this 
water into the corrugations or valleys defined by the pipe 10 and thence 
into the slots defined in the pipe so that water can be carried away 
inside the pipe in a conventional fashion to a catch basin or the like. 
The size of the core or armature 14 is preferably equivalent to that of the 
rectangular space defined between the front and back layers 12a and 12b of 
the non-woven filter material 12, but the core may be slightly smaller 
than the vertical dimension of the envelope and also slightly smaller than 
the horizontal dimension thereof as suggested in FIG. 1. It will be 
apparent that several such envelopes and core sheets 12 and 14 
respectively can be provided on a single section of pipe 10 in order to 
fabricate a complete system using drainage devices of the present 
invention. While it is possible to provide for the overlapping of the 
envelope 12 in this situation such overlapping is not necessary, and forms 
no part of the present invention. 
The core 14 comprises a plastic sheet which has been formed by passing it 
between appropriately configured mandrels in a suitable machine (not 
shown) while the plastic is in a heated condition so that alternate 
valleys and raised portions are defined in the sheet as suggested in the 
drawings. The depth of these valleys and raised portions preferably 
corresponds closely to the depth of the valleys in the drain pipe 10, 
which dimension is preferably less than 3/8 of an inch for best results. 
The valleys and raised lands are spaced from one another in the sheet by a 
distance of approximately 3/4 of an inch and the sheet is preferably 
formed from a stiff plastic material such as polystyrene having a 
thickness of between 15 and 45 mils, preferably on the order of 1/32 of an 
inch in thickness. 
As so constructed the drainage device of the present invention is well 
adapted to handle the downward flow of water beneath the surface of a 
ground in a drainage system or a septic system filter such that normal 
hydrostatic pressure will force this water inwardly through the water 
permeable filter material 12 and into the valleys defined in the core 14 
where gravity carries the water downwardly to the drainage pipe and more 
particularly to the slotted openings in the drainage pipe 10 as described 
above.