Process for preparing composite tube

Claim 2

A process as claimed in claim 1, wherein said tube is rigid.

Claim 3

A process as claimed in claim 1, wherein said tube is a self-supporting flexible tube.

Claim 4

A process as claimed in claim 1 wherein the ribbon of flexible material is crepe paper.

Claim 5

A process as claimed in claim 1, wherein the ribbon of flexible material is a plastics film.

Claim 6

A process as claimed in claim 1, wherein the nascent foam is a polyurethane foam.

Claim 7

A process as claimed in claim 1, in which the coated ribbon is fed tangentially on to the rotating tube with its coated face adjacent the tube, so that the foam is contained In the annulus between the tube and the spirally wound ribbon.

Claim 8

A process as claimed in claim 8, wherein the ribbon is fed on to the rotating tube at an angle such that successive convolutions of the ribbon do not overlap but abut each other or are closely adjacent to each other.

Claim 9

A process as claimed in claim 8 wherein the ribbon is fed on to the rotating tube at an angle such that successive convolutions of the ribbon overlap partly at their edges.

Claim 10

A process as claimed in claim 10, wherein said layer of nascent foam is deposited over substantially the whole width of said face of the said ribbon except that edge thereof which overlaps the preceding convolution of the ribbon, so that substantially no foam is present between the overlapping edges of successive convolutions of the ribbon.

Claim 11

A process as claimed in claim 11, which comprises the steps of (a) rotating a tube having a wall thickness small in relation to its overall diameter around its longitudinal axis and moving the said tube along its longitudinal axis, (b) dispensing continuously a ribbon of flexible material, (c) forming an edge strip along one side of the ribbon by folding its edge back on to itself through at least 90* so that the edge strip comes to lie below the remaining width of the ribbon, (d) moving the ribbon past foam-dispensing means and depositing a layer of nascent foam on the remaining width of the ribbon leaving the folded-back edge strip uncoated, (e) feeding the ribbon tangentially on to the rotating tube at an angle Alpha such that Psin Alpha is substantially equal to W-w where P is the distance the tube moves forward in one complete revolution, W is the total width of the ribbon, and w is the width of the folded-back edge strip, (f) unfolding the uncoated folded-back edge strip during its transit from the foam-dispensing means on to the rotating tube so that the ribbon reassumes its full width and so that the edge strip, free from foam, partly overlaps the internally coated preceding convolution of the ribbon, thereby forming a neatly jointed spirally wound envelope free from exuded foam around the tube, and (g) causing or allowing the foam to expand and cure.

Claim 12

A process as claimed in claim 1, in which said coated ribbon is fed on to the rotating tube with the uncoated face of the ribbon adjacent the tube and the foam-coated face of the ribbon facing outwardly.

Claim 13

A process as claimed in claim 13, wherein a second ribbon of flexible material is fed tangentially to the foam-coated rotating tube to form a spirally wound envelope around the foam, so that the foam is contained in the annulus between the two spirally wound ribbons.

Claim 14

A process as claimed in claim 14, wherein said second ribbon is fed tangentially to the foam-covered rotating tube at an angle such that successive convolutions of the ribbon do not overlap but abut each other or are closely adjacent to each other.

Claim 15

A process as claimed in claim 14, wherein said second ribbon is fed tangentially to the foam-covered rotating tube at an angle such that successive convolutions of the ribbon overlap partly at their edges.

Claim 16

A process as claimed in claim 1, wherein the tube which is rotated is made up of individual units preassembled and held together to form a tubelike structure. 18 A process as claimed in claim 1 in which it is arranged that the expansion of the foam is incomplete at the point at which the coated ribbon contacts the rotating tube.

Claim 17

A process as claimed in claim 1 in which the nascent foam is based on cross-linkable polymeric material and it is arranged that completion of cross linking is delayed until after one full convolution of the coated ribbon has been formed round the rotating tube.

Claim 18

A process according to claim 1 wherein said layer of nascent foam begins to expand when deposited on the face of said ribbon in step (b) and wherein expansion and curing of said foam are completed in step (d).