APPARATUS AND METHOD FOR PRODUCING TUBES

Abstract

The invention embodies an apparatus for producing resin tubes, the apparatus having a hollow supporting structure, wherein an endless carrier strip is windable around the outside of the supporting structure in a plurality of adjacent windings to form a mould.

Claims

1. An apparatus for producing resin tubes, the apparatus comprising: a hollow supporting structure around an outside of which an endless carrier strip is windable in a plurality of adjacent windings to form a mould; application means for applying a resin material on an outside of the mould; and a return head for supporting the carrier strip after leaving the supporting structure and for feeding the carrier strip into an interior of the supporting structure, the return head comprising variable-length elements for supporting the carrier strip.

2. The apparatus according to claim 1, wherein the variable-length elements comprise pressure elements for pressing the carrier strip radially outwards.

3. The apparatus according to claim 1, wherein the variable-length elements comprise length-adjustable support rods.

4. The apparatus according to claim 1, wherein the variable-length elements comprise carrier strip supports mounted at the radial outer ends of movable pistons.

5. The apparatus according to claim 1, wherein the variable-length elements are movable in radial directions, especially between inner and outer positions.

6. The apparatus according to claim 1, wherein the variable-length elements are movable in cylinders fixed on a return head disk extending perpendicular to a longitudinal axis of the supporting structure.

7. The apparatus according to claim 1, wherein the variable-length elements vary between preselected maximum and minimum distances depending on the radial distance between a carrier strip and a longitudinal axis of the supporting structure.

8. The apparatus according to claim 1, wherein the variable-length elements exert forces on the carrier strip against the resin material and maintain a tension and a position of the carrier strip.

9. The apparatus according to claim 1, wherein the variable-length elements comprise pneumatic, spring, hydraulic, magnetic and/or mechanical actuators.

10. A method for producing resin tubes comprising: winding an endless carrier strip around an outside of a hollow supporting structure in a plurality of adjacent windings to form a mould; applying a resin material on an outside of the mould; supporting the carrier strip via a return head after the carrier strip leaves the supporting structure, the return head having variable-length elements for supporting the carrier ship; and feeding the carrier strip, via the return head, into an interior of the supporting structure.

11. The apparatus according the claim 4, wherein the carrier strip supports are rollers.

Description

[0030] Further advantages, features and details of the invention will emerge from the following description of preferred examples of embodiment and with the aid of the drawings. In the figures:

[0031] FIG. 1 shows a diagrammatic representation of an embodiment of an apparatus according to the invention in a side view,

[0032] FIG. 2 shows a diagrammatic representation of a part of a return head the apparatus in a front view, and

[0033] FIG. 3 shows the return head of FIG. 1 in a side view.

[0034] The apparatus 20 according to the invention in FIG. 1 comprises a drive housing 1, a pusher guide cam plate 2, a steel band pusher 3, a set of several mandrel discs 4, spacer tubes 5, aluminium beams 6, a steel band tensioning apparatus 9, a steel band return tube 10 and a main shaft 11. The mandrel discs 4 are plates that are mounted on a central rotating shaft.

[0035] For a better representation FIG. 1 also shows a sectional view of the apparatus 20 in order to illustrate the mandrel discs 4, the spacer tubes 5, the aluminium beams 6 and the main shaft 11.

[0036] An endless steel band 8 (also called carrier strip) is wound around the mandrel discs 4 (also called supporting structure) to form the external surface of a mould for a resin, which is applied onto the steel band 8. After the resin is applied onto the mould, the resin is cured to form the resin tube.

[0037] The carrier strip 8 leaves the mould, enters the hollow rotating mould and returns to the start of the apparatus 20 to form the mould surface again.

[0038] The apparatus 20 further comprises a steel band return head 7. The return head 7 carries the carrier strip 8 when the carrier strip 8 leaves the mould and enters the hollow rotating mould to return to the start of the supporting structure 4.

[0039] The steel band 8 is pulled forward by a motor (not shown) inside the drive housing 1. Having passed the right extreme end of the apparatus 20, the band 8 is fed into the hollow interior of the apparatus 20. The endless steel band 8 runs through the inside of the supporting structure 4 and runs out of the apparatus 20 at its left end from which point it is redirected onto the outer surface of the mandrel discs 4. A spring-loaded rail ensures that the band 8 has the proper tension.

[0040] FIG. 2 shows a diagrammatic representation of a section of the return head 7 in a front view, and FIG. 2 shows the return head 7 of FIG. 1 in a side view.

[0041] The return head 7 comprises variable-length elements 12, 13 for supporting the carrier strip 8. In this embodiment the variable-length elements 12, 13 comprise pressure elements, wherein the pressure elements comprise movable pistons 12 and rollers 13. The rollers 13 are arranged at the radial outer ends of the pistons 12. The pistons 12 can move in radial direction between a radial inner position (the two pistons 12 on the left side) and a radial outer position (the two pistons 12 on the right side). Thus, the pistons 12 can be moved in radial directions with respect to the axis that extends through the inside of the apparatus 20.

[0042] The return head 7 further comprises a return head disk 14. The return head disk 14 extends perpendicular to the longitudinal axis of the supporting structure 4. The pistons 12 are movable in cylinders 15, which in turn are fixed to the disk 14 by brackets 16. The brackets 16 are fixed to the disk 14 by bolts 17 that are received and fixed in openings 18 in the disk 14.

[0043] In operation the return head 7 with its varying length support pistons 12 follows carrier strip 8, i.e. the mould. The lengths of the pistons 12 vary dependent on the mould passing and between preselected maximum and minimum distances to the centre point of the rotating shaft. The pistons 12 are so designed to return automatically to their longest length, wherein this length is equal to the greatest distance from the centre of the rotating shaft required for the mould geometry.

[0044] The pipe mould, with the manufactured pipe laminate, restrains the full extension of the pistons 12 so in turn, the pistons 12 exerts a force on the steel band against the GRP laminate and maintains the steel band tension and position. The minimum length of the pistons 12 is defined by the required minimum distance of the mould distance from the rotating shaft's central axis.

[0045] The pistons 12 can thereby follow the external geometry of the mould and support the steel band at all positions along the movement from minimum to maximum extension of the pistons 12.

[0046] The pistons' 12 position is controlled by suitable means and may include, but is not necessarily limited to, pneumatic, spring, hydraulic, magnetic or mechanical position control.

LIST OF REFERENCE NUMBERS

[0047] 1 drive housing [0048] 2 pusher guide cam plate [0049] 3 steel band pusher [0050] 4 mandrel disc [0051] 5 spacer tube [0052] 6 aluminium beams 6 [0053] 7 steel band return head [0054] 8 steel band [0055] 9 steel band tensioning apparatus [0056] 10 steel band return tube [0057] 11 main shaft [0058] 12 pistons [0059] 13 rollers [0060] 14 return head disk [0061] 15 cylinders [0062] 16 brackets [0063] 17 bolts [0064] 18 openings [0065] 20 apparatus for producing tubes