Pipes and tubular conduits – Spirally seamed
Patent
1991-02-07
1992-07-07
Bryant, III, James E.
Pipes and tubular conduits
Spirally seamed
138129, 138111, 138115, 138148, F16L 916
Patent
active
051274426
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention concerns a spiral-wound tube made of a hollow section joined together by extruder welding or gluing.
BACKGROUND OF THE INVENTION
In an attempt to manufacture tubes of maximum strength and permanence of shape with a certain consumption of material, spiral-wound tubes made of a hollow section have been achieved, said section being joined together preferably by extruder welding, but possibly also by means of gluing.
SUMMARY AND OBJECTS OF THE INVENTION
The object of the present invention is to lower the cost of manufacture further as well as to provide spiral-wound tubes with particular properties on the different faces of the tube.
This is achieved by means of a spiral-wound tube which is characterized in that the hollow section is coextruded and comprises an outer layer of a plastic with a homogeneous surface and with good weldability, as well as at least one inner layer of modified polymer.
According to the invention, the tube which is to be spirally wound, is formed with a layered tubular structure having an outer tubular layer of plastic with a homogenous surface and an inner tubular layer of plastic with a homogenous surface and an intermediate layer, between the outer layer and the inner layer wherein the intermediate layer is also tubular and is preferably formed of a modified polymer. The outer layer preferably consists of a UV-stabilized polyethylene, polypropylene, polyvinylchloride, or polycarbonate. The tubular portions define a hollow interior section which is preferably substantially rectangular in cross-section. The tubular outer layer has a sidewall which forms an inner face of the spiral-wound tube and preferably consists of a polymer resistant to chemicals. The modified polymer which forms the intermediate layer is preferably foamed. This modified polymer may also be formed as polymer filled with minerals.
In the following, the invention will be described in more detail with reference to the accompanying drawing, wherein
FIG. 1 is a partly sectional side view of an exemplifying embodiment of a spiral-wound tube in accordance with the invention, and
FIG. 2 shows an enlarged detail of a weld joint in the tube shown in FIG. 1.
The spiral-wound tube in accordance with the invention comprises a spiral-wound hollow section 1, whose side walls in the adjoining layers in the spiral winding are joined together preferably by extruder welding, but alternatively possibly by gluing. In view of minimizing the material cost while, at the same time, retaining or improving the properties of the finished tube, according to the invention, a coextruded hollow section 1, is used, which comprises an outer layer 2 of a plastic with a homogeneous surface and good weldability as well as at least one inner layer 3 of a modified polymer.
If the starting point is a hollow section 1 which, besides the homogeneous outer layer 2, also comprises an intermediate layer 3 of modified polymer and an inner layer 4 of a plastic with a homogeneous surface, a tube with very good properties is obtained.
When the modified polymer consists of a foamed polyethylene, polypropylene, or equivalent, a tube is obtained which has a considerably lower weight but substantially unchanged ring strength as compared with a conventional spiral-wound tube of the same diameter and material thickness.
On the contrary, if it is desirable to improve the ring strength of the tube remarkably, whereas the weight of the tube is of secondary significance, the modified polymer may appropriately consist of a polymer filled with minerals. In this way it is possible to improve the mechanical properties of the spiral-wound tube considerably without increased material cost.
As the outer layer, it is appropriately possible to use UV-stabilized polyethylene, polypropylene, polyvinylchloride, or polycarbonate.
The best result is obtained if the hollow section 1 has a substantially rectangular cross-section, whereby the extruder welding can be carried out by means of two extruder nozzles, one at the outer mantle of
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Bryant III James E.
OY Kwh Pipe AB
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