GB2259270A

GB2259270A - Extruding foam sleeve around tube bundle

Info

Publication number: GB2259270A
Application number: GB9216137A
Authority: GB
Inventors: John Stafford Rowland
Original assignee: Extrudit Ltd
Current assignee: Extrudit Ltd
Priority date: 1991-09-07
Filing date: 1992-07-29
Publication date: 1993-03-10
Anticipated expiration: 2012-07-29
Also published as: GB9216137D0; GB2259270B

Abstract

A method of manufacturing thermally insulated, synthetic plastics piping, comprises assembling a cluster of synthetic plastics tubes (3) and extruding a flexible external sleeve (11) of a plastics foamable material around the cluster, the latent heat in the material of the sleeve (11) from the extrusion process activating the foamable agent of the sleeve (11) to effect foaming. The invention also includes apparatus for carrying out the above defined method comprising an extrusion machine (10), means (7, 15) to pass at least one synthetic plastics tube (3) through the extrusion machine (10) to provide a coating of plastics foamable material (11) externally to the tube(s) (3) as an annular sleeve, of desired wall thickness. <IMAGE>

Description

PLASTICS PIPING This invention relates to a method of manufacturing plastics piping being a so-called insulated python loom, to apparatus for carrying out the method, and to piping made by the method and/or apparatus.

Certain applications of plastics piping, such as for the conveyance of cooled or heated beverages, e.g. in the dispending of beer, soft drinks etc, require the piping to be thermally insulated - being a composite of inner plastics tubing, and an outer sleeve of insulation - and in the brewing industry, this composite is produced by either of three methods. In a first method a sleeve of foam insulation, of suitable internal diameter, is slit longitudinally, fitted over usually a cluster of tubes and its slit ends secured together with adhesive. In a second method, vacuum is applied to the foam insulation sleeve so that the inner diameter of the sleeve is enlarged to enable ready insertion of the cluster of tubes, with vacuum release causing the sleeve to shrink back elastically to its original dimension so that the sleeve lightly grips the cluster of tubes.In a third method air pressure is applied to the foam insulation sleeve to cause temporary inflation for insertion of the cluster of tubes, with pressure release allowing the sleeve to shrink onto the cluster of tubes.

All three methods involve the manufacture of thermally insulated piping as a two stage operation - usually by brewery personnel - as the piping is usually extruded by a first manufacturer and the foam insulation sleeves are produced by a second manufacturer.

According to a first aspect of the present invention, there is provided a method of manufacturing thermally insulated, synthetic plastics piping, comprising assembling a cluster of synthetic plastics tubes and extruding a flexible external sleeve of a plastics foamable material around at least one extruded synthetic plastics tube, with the latent heat in the material of the sleeve from the extrusion process activating the foamable agent of the sleeve to effect foaming.

According to a second aspect of the present invention, there is provided apparatus for carrying out the above defined method comprising an extrusion machine for plastics foamable material and means to pass at least one synthetic plastics tube axially through the extrusion machine to provide coating of plastics foamable material externally to the tube(s) as an annular sleeve, of desired wall thickness.

According to a third aspect of the invention, there is provided thermally insulated plastics piping manufactured by the method and/or apparatus of the first or second aspects.

Thus, the invention in its various aspects, operates on the principle of direct application of the foamable material around the exterior of a core of say 1 to 100 tubes, avoiding the need for any secondary heat source, at least in the majority of circumstances, and making use of the latent heat inherent in the extrusion process to activate the foamable agent dispersed within the plastics of the insulating sleeve, and provides composite, thermally insulated piping, in whatever lengths are convenient for the manufacturer and/or user, which lengths may be cropped off for coiling and consequent ease of storage and/or transportation.

Although the plastics foamable material may be polyethylene or EVA, it is preferably PVC.

As indicated previously, multiple synthetic plastics tubes may be assembled into a cluster. In order to maintain the coherence of the cluster and maintain the tubes in a required and predetermined formation, the cluster is preferably bound, as soon as conveniently possible after assembly, with a strip of foil or cling film, before passage of the bound cluster through a cross-head of the extrusion machine for application of the thermally insulating sleeve.

Assembly of the cluster may be by passing whatever number of tubes, stored on drums or reels, of whatever diameter(s) are required by a customer through a template ahead of a binding station. Conveniently the cluster is drawn from the individual drums, or reels by upper and lower endless belts of a haul-off unit, which unit draws the tubes through the template and through the binding station, with the bound cluster emerging from the haul-off unit and entering the cross head. Downstream of the extrusion machine is a cooling device, conveniently in the form of a water cooling tank with a vacuum capacity which may be desirable if a smooth external finish and/or calibration were required.Preferably, after emerging from the cooling device, the composite piping is wrapped externally with a tape e.g., to meet fire regulations, at a wrapping station with a further haul-off unit downstream of the wrapping station and with the finished composite piping coiled onto a take up drum.

It is conceivable that in certain circumstances - such as a requirement for thin walled tubing and/or for thick walled insulation and/or an inability to apply the foamable material in close proximity to the emerging tubing - complete activation of the foaming agent cannot be guaranteed, and if such circumstances are encountered or envisaged, completion of activation may be effected by a downstream heating means, such as a microwave heater.

The invention will now be described in greater detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic side elevation of apparatus in accordance with the second aspect for carrying out the method of the first aspect; and Figure 2 is a sectional view of piping in accordance with the third aspect manufactured by the apparatus of Figure 1.

In Figure 1, a frame 1 carries a plurality of drums 2 on each of which is coiled synthetics plastics piping 3 of the same or different diameters or wall thicknesses, and in numbers to suit the requirements of a customer. Downstream of the frame 1, all the piping 3 is brought together into a cluster at a template 4, and the coherence of the cluster is maintained by binding with cling film 5 at a binding station 6 downstream of the template 4.The cluster of piping, and its binding, is displaced by a haul-off unit 7 located downstream of the binding station 6 and comprising a pair of opposed upper and lower, driven endless belts 8, adapted to grip the wrapped cluster of piping externally and to feed this into a crosshead 9 of an extrusion machine 10 for applying, continuously, a coherent external sleeve 11 of plastics foamable material to the wrapped cluster, with, in accordance with the method of the invention, the latent heat of the foamable material resulting from the extrusion process employed to activate the foaming agent. Downstream of the extrusion machine 10 is cooling means 12 comprising a water cooling tank and a source of vacuum. After emerging from the cooling means 12, the wrapped cluster of piping, now with its foamed external thermal insulating sleeve 11, is advanced to a downstream wrapping station 13 where a fire regulation tape 14 is applied. Downstream of the wrapping station 13, advance of the wrapped cluster of piping with its external sleeve 11 is maintained by a further haul-off unit 15 comprising a pair of opposed, driven, endless belts 16, which mechanism 15 feeds the finished piping to a drum 17, which is freely rotatable on an A-frame 18, and on which drum the piping is coiled.

Figure 2 illustrates the finished piping, i.e. the socalled insulated python loom.

Claims

1. A method of manufacturing thermally insulated, synthetic plastics piping, comprising assembling a cluster of synthetic plastics tubes and extruding a flexible external sleeve of a plastics foamable material around at least one extruded synthetic plastics tube, with the latent heat in the material of the sleeve from the extrusion process activating the foamable agent of the sleeve to effect foaming.

2. A method as claimed in Claim 1, wherein the plastics foamable material may be polyethylene or EVA or preferably PVC.

3. A method as claimed in Claim 1 or Claim 2, wherein multiple synthetic plastics tubes are assembled into a cluster.

4. A method as claimed in Claim 3, wherein the cluster is bound, as soon as conveniently possible after assembly, with a strip of foil or cling film.

5. A method as claimed in any preceding claim, wherein, after extrusion of the plastics foamable material around the tube(s), cooling is effected.

6. A method as claimed in Claim 5, wherein, after cooling, an external tape is applied around the sleeve.

7. A method as claimed in any preceding claim, wherein the finished piping is collected as a coil.

8. A method as claimed in any preceding claim, wherein, downstream of the extruding machine, a heating means is provided.

9. A method of manufacturing thermally insulated, synthetic platics piping, substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.

10. Apparatus for carrying out the above defined method comprising an extrusion machine for plastics foamable material and means to pass at least one synthetic plastics tube axially through the extrusion machine to provide coating of plastics foamable material externally to the tube(s) as an annular sleeve, of desired wall thickness.

11. Apparatus as claimed in Claim 10, comprising, upstream of the extrusion machine, a haul-off unit.

12. Appartus as claimed in Claim 11, wherein the haul-off unit comprises upper and lower opposed endless belts.

13. Apparatus as claimed in Claim 10 and 11, comprising, upstream of the haul-off unit, a binding station.

14. Apparatus as claimed in Claim 13, comprising, upstream of the binding station, a template.

15. Apparatus as claimed in Claim 14, comprising, upstream of the template, a plurality of drums on each of which is coiled plastics piping.

16. Apparatus as claimed in any one of Claims 10 to 15, comprising, downstream of the extrusion machine, a cooling means.

17. Apparatus as claimed in Claim 16, comprising downstream of the cooling means, a wrapping station.

18. Apparatus as claimed in Claim 17, comprising, downstream of the wrapping station, a haul-off unit.

19. Apparatus as claimed in Claim 18, comprising, downstream of the haul-off unit, a drum onto which the finished piping is adapted to be coiled.

20. Apparatus as claimed in any one of Claims 10 to 19, comprising, downstream of the extruding machine a heating means, such as a microwave heater.

21. Apparatus for manufacturing thermally insulated, synthetic plastics piping substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.

22. Thermally insulated plastics piping manufactured by the method of any one of Claims 1 to 9.

23. Thermally insulated plastics piping manufactured by the apparatus of any one of Claims 10 to 21.