CA1328234C - Spiral-wound tube - Google Patents

Abstract

Abstract of the Disclosure The present invention concerns a spiral-wound tube made of a hollow section (1) joined together by extruder welding or gluing. It is characteristic of the invention that the hollow section (1) is coextruded and comprises an outer layer (2) of a plastic with a homogeneous surface and with good weldability, as well as at least one inner layer (3) of modified polymer.

Description

~32~234 'i`', 1 "
Spiral-wound tube ,~
The present invention consern~ a spiral-wound tube made of a hollow section joined together by extruder welding or gluing.

In an attempt to manufacture tubes of ~aximum strength and permanence o~ shape with a certain co~sumption o~
material, spiral-wound tubes made o~ a hollow section have been achieved, ~aid section being ~oined together , preferably by extruder welding, but possibly also by means o~ gluing.
The object of the pre~ent invention i~ to lower the co~t of manufacture further a~ well as to pro~ide spiral-wound tubee wlth par~cular propçrti~s on the di~fer~nt faces of the tube.
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i Thi~ i9 achie~ed by mean~ of a splral-wound tube which ~s -¦ characterized in that the hollow s~ction i~ coextruded and compri~es an outer layer o~ a pla~tic with a homoge-! neou~ ~urfa~e and with good weldability, a~ well a5 at ;, 2S lea~t one inner layer of modified poly~er.
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l Further characteristic~ of the in~ention come out Prom .~l the accompanying patent claim~ 1 to 6.

~ 30 In the following, the invention will be described in more detail with reference to the accompanying drawing, wherein '`:1 '~ Fig. 1 ~s a partly sectional ~ide Yiew of an exemplifying :~ embodiment of a sp~ral-wound tube in accordance with the invention, and "~l ~- Fig. 2 shows an enlarged detail of a wel~ joint in the tube shown in Fig. 1.
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~.j . ~1 -., .' 2 ~32~34 The spiral-wound tube ln ac~ordance with the invention comprises a spiral-wound hollow ~ection 1, whose side ~:. walls in the adjoining layers in the spiral winding are joined together preferably by extruder welding, but S 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 coex~ruded hollow section 1 i used, which comprise~ an outer layer 2 of a pla~tic with a -. 10 ho~ogeneous surface and good ~eldability as well as at least one inner layer 3 of a modified polymer.

-, If the starting point is a hol~ow section 1 which, besidesthe homog neou outer layer 2, also comprises an inter-mediate layer 3 o~ modified polymer and an inner layer 4 of a plastic with a homogeneous surface, a tube with very ~ good properties i~ obtained.

.... ~ When the modi~ie~ polymer consi~t~ of a Poamed polyethyl-.~i 20 ene, polypropylene, or ~quivalent, a tube is obtained which has a con~iderably lower weight but substantially unchanged ring strength a~ compared with a conventlonal ~, ~piral-wound tube of ths same diameter and material thicknes~.
. 25 On the contra~y, if it i~ de.~irable to improve the ring trength o~ the tube remarkably, whereas the weight of ., the tube i5 of -~eco~dary 3ign~ficance, the modified polymer may appropriately con~i~t of a polymer filled with miner-al~. In thi~ way it i3 po~sible to improve the mechanical "~, propertie~ of the ~plral-wound tube considerably without ;;; i~creas~ material co t.

, As the outer layer, it ~ appropriately possible to use ;~,;`l 35 W-stabillzed polyethylene, polypropylene, polyvinyl-~ chloride, or polycarbonate.
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:~ The best result is obtained if the hollow section 1 has a substantially rectangular cross-section, whereby the ; extruder weld~ng c~n be carried out by means of two :~ extruder nozzl~is, one at the outer mantle of the tube and one at its inner mantle. The preheating of the side : faces of the hollow section that are to be welded together takes place appropriately by means of a, for example, electrically heated heating body or by means of blowing of warm air. The hollow profile 1 is spiral-wound around a relatively short mandrel, whose movement of rotation takes care o the forward fe~din~ of the hollow section.
The shifting of the ready-welded tube in the axial direc-~; tion is taken care of by rollers, which are freely rotat-able around statlonary shaft~ directed radially to the 15 main axis of the mandrel. A-Q a result of the fact that `~' the tube reaches its full strength as soon as the weld . ~oint S has cooled, just a very ahort mandrçl is required.

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By arranginq the extrusion o~ the hollow section 1 so that the outer layer 2 at one ~ide, i.e. the ~ide that ~` forms the in.~ide face in the }inished spiral-wound tub~, `:. consists of a polymer resistant to che~icals, a spiral-wound tub~ of very hlgh-class properties i-~ obtained at ~i reasonable cost of manufacture.
,~, 25 ~he manufacture o~ the Qpiral-~ound tube in accordance ~' wlth the ~nvention can be arranged either so that the coextruded hollow section 1 1~ passed ~ro~ th~ extruder nozzle through a cooling zone ~lrectly into the machine . 30 in which the spiral winding and the extruder welding take :~ place, or the hollow section 1 i~ gathered ln large rolls or intermedlate storage be~ore the hollow section 1 is ~ fed into the line or the manufacture of the spiral-wound `.:! tube.
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Claims (8)

1. Plastic tube formed by spiral winding of a co-extruded hollow section joined together by extruder welding or gluing, the hollow section comprising a first hollow section outer layer of a plastic material with a homogeneous surface and with good weldability, a second hollow section intermediate layer of modified polymer material, said inter-mediate layer being surrounded concentrically by said outer layer and a third hollow section inner layer of a plastic material with homogeneous surface, said inner layer being surrounded by and concentric with said intermediate layer.

2. Plastic tube as claimed in claim 1 wherein the outer layer consists of UV-stabilized polyethylene, poly-propylene, polyvinylchloride, or polycarbonate.

3. Plastic tube as claimed in claim 2, wherein the coextruded hollow section has a substantially rectangular cross-section.

4. Plastic tube as claimed in claim 3, wherein the outer layer at the side wall of the first hollow section that forms the inner face in the spiral-wound tube consists of a polymer resistant to chemicals.

5. Plastic tube as claimed in claim 1, wherein the modified polymer is foamed.

6. Plastic tube as claimed in claim 1, wherein the modified polymer consists of a polymer filled with minerals.

7. A plastic tube formed by spiral winding of a coextruded hollow tubular section joined together by extruder welding or gluing, the hollow tubular section comprising:
an inner tubular layer having an inner face surrounding a hollow space, said inner layer being formed of a plastic with a homogeneous surface;

an intermediate tubular layer of modified polymer, disposed around and concentric with said inner layer; and an outer tubular layer of plastic with a homogen-eous surface and with good weldability, said outer layer being provided around and concentric with said intermediate layer.

8. A spiral-wound tube formed of a hollow section joined together by extruder welding or gluing, the hollow section comprising:
a wall surrounding a hollow space providing three layers including an outer layer of plastic with a homogeneous surface and with good weldability;
an intermediate layer of modified polymer and an inner layer of plastic with a homogeneous surface, said inner layer having an inner surface facing and surrounding said hollow space.