Method of lining channels

Details Method of lining channels Method of lining channels

1999-05-27

2001-06-05

Vargot, Mathieu D. (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

Forming structural installations in situ

Uniting preform member with molding material

C156S287000, C156S294000, C264S036160, C264S269000

Reexamination Certificate

active

06241925

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a method of lining channels, and more particularly to a method of lining a channel with a rigid or semirigid plastic pipe as a lining material.
BACKGROUND ART
For example, JP-A No. 42220/1989 discloses a conventional method of lining channels. With this conventional method, a rigid or semirigid plastic pipe shaped initially in the form of a round tube is flattened, then folded in two and wound up in a folded U shape on a roll when produced in a plant. At a work site, the pipe is inserted into a channel while being paid off from the roll in a state softened by heating. The inserted pipe is inflated by applying heat and pressure thereto from inside for restoration to the round tubular form as shaped initially, forming a lining along the inner surface of the channel with the rigid or semirigid plastic pipe.
According to the lining method described, the pipe is diminished in effective outside diameter by being deformed to the folded U shape and can therefore be inserted into the channel if not fully satisfactorily, whereas since the pipe memorizes the initial shape, the U-shaped folded portion tends to become unfolded as indicated in broken lines in
FIG. 6
to correspondingly increase the effective outside diameter when the pipe is so softened by heating as to be paid off from the roll, with the result that the pipe encounters increased resistance when inserted into the channel, hence a reduced work efficiency. Especially if made of polyethylene, the pipe remains somewhat elastic even when softened by heating, consequently exhibiting a marked tendency to restore its shape before deformation when released from the restraint of the deforming step.
Further if the pipe is held wound on a roll in the folded U shape before use, a folding tendency is afforded in the U-shaped folded portion of the pipe during the preservation period. The folding tendency partly becomes a permanent deformation when the pipe is inflated for restoration, preventing restoration to the form as shaped initially.
Since the bottom part X inside the U-shaped portion of the pipe (see
FIG. 6
) is rounded in a direction opposite to the restoration direction Y, the rounded part needs to be reversed by inflation for restoration, so that the inflation entails a considerable adverse effect. If the bottom part X has such a folding tendency and when the rounded part is reversed by inflation for restoration, numerous minute cracks are likely develop to impair the quality of the lining undesirably.
DISCLOSURE OF THE INVENTION
The main object of the present invention is to provide a method of lining a channel with a rigid or semirigid plastic pipe serving as a lining material, wherein the pipe can be inserted into the channel with reduced resistance so as to achieve an improved work efficiency.
Another object of the invention is to diminish a folding tendency in the pipe to the greatest possible extent for use in the lining method to preclude the adverse effect of the folding tendency on the quality of the lining.
Other features of the invention will become apparent from the following description.
The present invention provides a method of lining a channel including the steps of:
installing at a work site a roll having wound thereon a rigid or semirigid plastic pipe shaped initially in the form of an approximately round tube and deformed from the initial form to a flat tubular form,
paying off the pipe as softened by heating from the roll installed at the work site toward an inlet of the channel to be lined, and
folding the paid-off flat pipe in two to a U shape at a position between the roll and the channel inlet,
the lining method being characterized in that the U-shaped pipe is hardened by forced cooling from outside immediately after the folding step while being restricted in shape, then inserted into the channel while being thus hardened and thereafter restored to the initial form by being inflated with heat and pressure applied from inside.
According to the lining method of the present invention, the pipe as U-shaped by folding is hardened by forced cooling while being restricted in shape, so that the pipe can be inserted into the channel with the U-shaped pipe portion closed, accordingly with reduced resistance, hence an improved work efficiency. Since the pipe is U-shaped by folding immediately before insertion into the channel, the U-shaped folded portion exhibits substantially no folding tendency. This eliminates the cause of minute cracking that would otherwise occur when the pipe is inflated for restoration, consequently providing a lining of high quality.


REFERENCES:
patent: 4883557 (1989-11-01), Morinaga et al.
patent: 5354586 (1994-10-01), Yokoshima et al.
patent: 64-55225 (1989-03-01), None
patent: 3-104625 (1991-05-01), None
patent: 3-151225 (1991-06-01), None
patent: 4-314525 (1992-11-01), None

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