Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Of varying cross-sectional area or with intermittent...
Reexamination Certificate
2002-03-27
2004-10-19
Mayes, Melvin C. (Department: 1734)
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Of varying cross-sectional area or with intermittent...
C264S103000, C264S209300, C264S209400, C264S563000, C264S566000
Reexamination Certificate
active
06805824
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for manufacturing an extruded drainage medium, more particularly to the manufacture of a multi-sectional subsoil porous drainage pipe for applications in the field of civil engineering.
2. Description of the Related Art
As shown in
FIG. 1
, a conventional porous drainage pipe is fabricated from thermoplastic resin by extruding molten resin material to form a plurality of strands
2
that travel downwardly after exiting the extruder
1
. The strands
2
are led to a forming apparatus
3
for making a tubular preform
201
. While passing through the forming apparatus
3
, the strands
2
are in a plasticised or softened condition and are blown by a fluid of high velocity, so that the strands
2
will be entangled to form a matrix with sufficient structural strength and possessing water permeability after setting. The tubular matrix exiting the forming apparatus
3
will travel through a roll unit
4
to smoothen the outer diameter thereof, and will subsequently enter into a cooling tank (not shown) located below the roll unit
4
.
Several disadvantages may be encountered in the above-described process for fabricating the porous drainage pipe. Particularly, when the preform
201
emerges from the tip rolls of the roll unit
4
and enters into the cooling tank, it becomes inflexible due to a sudden drop of temperature and forms a rigid pipe. Thus, the cooling tank must have a depth sufficient to receive a certain length of rigid pipe before cutting. Moreover, since the depth of the cooling tank is limited, the pipe has to be cut off after extending downward to a predetermined length.
SUMMARY OF THE INVENTION
An object of this invention is to provide a process for fabricating a subsoil porous drainage medium which is capable of being delivered easily from a cooling tank.
Another object of this invention is to provide a flexible, multi-sectional porous drainage medium consisting of a plurality of links connected by flexible necked-down sections which can be cut into pieces with a desired number of the links.
According to the present invention, there is provided a process for making a porous drainage medium. The process includes the steps of: extruding a molten thermoplastic resin material to form a plurality of strands; blowing the strands in a plasticised condition using a high-velocity fluid to entangle the strands while passing the strands through a forming device, so as to result in a preform consisting of entangled strands; pinching the preform to form necked-down sections at intervals along the length of the preform, thus providing a plurality of links interconnected by the necked-down sections; and cooling the preform having the necked-down sections to form the porous drainage medium.
REFERENCES:
patent: 4449910 (1984-05-01), Leloux
patent: 4553923 (1985-11-01), Lupke
patent: 4577998 (1986-03-01), Dorrn
patent: 4958770 (1990-09-01), Mitchell
patent: 5334336 (1994-08-01), Franz et al.
patent: 5366365 (1994-11-01), Sullivan, et al.
patent: 5417997 (1995-05-01), Creed
patent: 5462092 (1995-10-01), Franz et al.
patent: 5811038 (1998-09-01), Mitchell
Frommer & Lawrence & Haug LLP
Mayes Melvin C.
Santucci Ronald R.
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