Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Patent
1990-02-16
1991-12-24
Ball, Michael W.
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
138154, 156247, 156248, 156294, 156584, B29C 6332
Patent
active
050749439
DESCRIPTION:
BRIEF SUMMARY
This invention relates to slip control for helically wound pipes and in particular it relates to pipes formed of a plastics material which comprise a strip helically, sometimes referred to as spirally, wound with adjacent edges interconnected.
In U.S. Pat. No. 4,995,929 and Australian Patent Application No. PH 05111 dated Mar. 19, 1986 International Publication No. WO87/05677 by the same Inventor, a system was described in which a helically wound pipe was fed into a conduit such as a sewer line which was to be relined and the helically wound pipe was then progressively expanded to a larger diameter to engage the wall of the conduit being lined. Alternatively the helically wound pipe was formed over a conduit and the larger diameter of the pipe then reduced to cause the helically wound pipe to fit neatly to the conduit being over-wound. In that specification a number of ways for achieving the result were discussed, including a fracturable sealing tape over the join, and release means moved through the pipe.
One of the problems associated with this process is to initially lock the wound pipe at the winding diameter and then to positively unlock the pipe progressively to allow for a controlled diameter change. The adhesive or locking means applied to the helically joined edges was described to be of such a form as to allow the interengaging edges to slide one relative to the other when a diameter change was required but this invention relates to releasing means which during initial winding allow the join to be locked against slip but, when required, the lock is released to allow slip in a controlled sequential manner.
The invention thus relates to the provision of a lock means to maintain the helically formed pipe at the required diameter during the initial winding and to then positively control the unlocking of the convolutions of the strips forming the pipe to allow for the desired diameter change. The various forms of lock which are discussed herein relate among other things to the use of adhesive tape which can be mechanically withdrawn, the provision of an interference fit by including a releasing element at the join, the re-design of the profile to include a double lock (with the one lock becoming the releasing element), and the provision of friction-creating shape in the releasing element itself. Associated with the locking mechanism may be re-design of the profile to allow a steeper gradient between the wound and expanded diameters.
The invention thus relates to a method of providing a form of lock, which can subsequently be removed in a progressively controllable manner to allow slip to occur progressively along the pipe.
The invention can conveniently be brought into effect in a number of ways and according to one form, for instance, an adhesive tape can be applied internally or externally to the tube over the join at the edges of the convolutions as it is being formed in the winding apparatus, but when the helically wound tube has reached the required length, for instance between manholes, the adhesive tape is progressively removed to allow expansion of the tube to the required diameter in a progressively controlled manner. Removal of the tape can be achieved in a number of ways, and according to one form, the tape is applied at the pipe forming machine end, tape being subsequently removed at a rate selected to be proportional to the profile input rate so that a change of diameter occurs progressively along the pipe.
An adhesive tape may also form another function, for instance if the tape is applied externally to the tube it could also be used to transport a sealant or grout. Thus when the tube is expanded in say a relining application the sealant will be pressed against the conduit being repaired and spread to so form a method of interrupting the spiral path around the helically wound pipe, which is formed between the ribs of the strip.
Another form of mechanical locking device is to introduce a locking element between the interengaging edges of the helical tube. Such an element could consist of
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Ball Michael W.
Maki Steven D.
Rib Loc Australia Pty. Ltd.
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