Methods of forming a fiber reinforced pipe on an inflatable mandrel

Abstract

A method and apparatus is provided for continuously making fiber reinforced plastic pipe in which a conveyor tube is formed on an axially fixed hollow rotatable mandrel. A plurality of bands of resin impregnated fiber elements are wound on the conveyor tube as it advances to provide the pipe assembly. The terminal end of the generated pipe assembly is sealed with a plug. A fluid under pressure is fed through the hollow mandrel and out the forward end of the mandrel into a chamber formed by the generated pipe assembly, the plug, and a fluid sealing means within the pipe assembly being generated, thereby causing the pipe assembly to advance.

I claim: 
     
       1. A method for continuously making substantially rigid, fiber reinforced plastic pipe comprising providing an air impervious conveyor tube on an axially fixed, hollow mandrel, the mandrel being provided with means to furnish an air seal with the interior of the conveyor tube as the conveyor tube is continuously advanced over the mandrel, winding a plurality of bands of thermosetting resin composition impregnated continuous fiber elements onto the conveyor tube to provide a pipe assembly, rotating the pipe assembly with respect to the mandrel, curing the thermosetting resin composition, providing an air seal at the forward end of the pipe assembly being generated, linearly advancing the pipe assembly by directing air under pressure through the mandrel and out from the forward end thereof into the interior of the pipe assembly, .[.and.]. controlling the rate of linear advancement of the pipe assembly.[...]. .Iadd.and providing a temporary seal to prevent the loss of pressure within the advancing pipe assembly when a section thereof is cut and to allow providing an air seal at the forward end of the pipe assembling being generated. .Iaddend. 
     
     
       2. A method according to claim 1, wherein a resin tube is provided beneath the bands of thermosetting resin composition impregnated continuous fiber elements. 
     
     
       3. A method according to claim 1, wherein the air impervious conveyor tube is of a resin composition. 
     
     
       4. A method according to claim 1, wherein providing an air impervious conveyor tube on the mandrel comprises forming on the mandrel a tube of a thermosetting resin composition, and at least partially curing the resin composition prior to winding a band of thermosetting resin composition impregnated continuous fiber elements thereon, said tube being integrated into the pipe assembly to furnish a resin liner. 
     
     
       5. A method according to claim 1, wherein providing an air impervious conveyor tube on the mandrel comprises impregnating a continuous carrier strip with a thermosetting resin composition to provide the resin composition on both sides of the carrier strip, providing a portion of the length of the mandrel with a parting material, winding the resin impregnated carrier strip on said portion of the mandrel to form a tube, and at least partially curing the resin composition prior to winding a band of thermosetting resin composition impregnated continuous fiber elements thereon, said tube being integrated into the pipe assembly to furnish a resin liner. 
     
     
       6. A method according to claim 1 wherein providing an air impervious conveyor tube on the mandrel comprises impregnating a continuous carrier strip with a thermosetting resin composition, at least partially curing said resin composition prior to winding it on the mandrel, providing a portion of the length of the mandrel with a parting material, winding the at least partially cured resin impregnated carrier strip on said mandrel to form a tube; sealing the wall of said tube to make it air impervious prior to winding a band of thermosetting resin composition continuous fiber elements thereon, said tube being integrated into the pipe. 
     
     
       7. The method according to claim 6 wherein said thermosetting resin composition impregnated carrier strip is cured to a B-stage prior to being wound on said mandrel, said sealing comprising heating said resin composition impregnated strip material after it is wound on said mandrel to a temperature sufficient to cause said B-stage resin to soften and fuse with the resin composition on adjacent strips of said strip material, thereby forming said air impervious tube. 
     
     
       8. The method according to claim 6 wherein said sealing is provided by applying a continuous coating of a resin composition over the tube, and at least partially curing said coating prior to overwinding a band of thermosetting resin composition impregnated continuous fiber elements thereon. 
     
     
       9. A method according to claim 1, wherein the air impervious conveyor tube is formed to enable the removal thereof from within the completed pipe assembly. 
     
     
       10. A method according to claim 1, wherein providing an air impervious conveyor tube on the mandrel comprises forming the tube on the mandrel, the tube having a layer of parting material at the exterior thereof whereby the conveyor tube may be removed after the pipe assembly is completed. 
     
     
       11. A method according to claim 1, wherein providing an air impervious conveyor tube on the mandrel comprises forming the tube on the mandrel, the tube having a layer of parting material at the exterior thereof, the tube including a stripping wire adjacent the layer of parting material, and applying tension to the stripping wire to remove the conveyor tube after the pipe assembly has been completed. 
     
     
       12. A method according to claim 1 wherein the air impervious conveyor tube is formed with a resinous outer liner which becomes integral with the pipe and a removable inner liner. 
     
     
       13. The method according to claim 12 wherein the outer surface of said inner liner is coated with a layer of a solvent activated parting agent, whereby said inner liner is released by contacting the parting agent with the solvent for the parting agent. 
     
     
       14. A method according to claim 1 wherein producing an air impervious tube on the mandrel comprises providing a tape having an inner surface which is nonadhesive to said mandrel and a coating of a solvent activated parting agent on the outer surface thereof, helically winding a tape about said mandrel to provide a tube with the inner surface of said tape adjacent said mandrel, coating the outer surface of said tube with a thermosetting resin composition and at least partially curing said resin composition prior to winding a band of thermosetting resin composition impregnated continuous fiber elements thereon. 
     
     
       15. A method according to claim 14 wherein the parting agent is activated by water. 
     
     
       16. A method according to claim 14 wherein the tape is of paper coated on one side with a water-soluble adhesive. 
     
     
       17. A method according to claim 1, wherein winding a plurality of bands of thermosetting resin composition impregnated continuous fiber elements onto the conveyor tube comprises winding one set of bands having the fiber elements thereof at a high angle with respect to the longitudinal axis of the pipe assembly alternated with a second set of bands wound with the fiber elements at a lower angle and of opposite hand, rotating the pipe assembly by the winding of one of said sets of bands. 
     
     
       18. A method according to claim 1, wherein winding a plurality of bands of thermosetting resin composition impregnated continuous fiber elements onto the conveyor tube comprises winding one set of bands having the fiber elements thereof at a high angle with respect to the longitudinal axis of the pipe assembly alternated with a second set of bands wound with the fiber elements at a lower angle and of opposite hand, the fiber elements of adjacent pairs of hands being impregnated by a resin composition in the same bath. 
     
     
       19. A method according to claim 1 which includes providing an inflatable air seal .Iadd.as said temporary seal .Iaddend.within the pipe assembly rearward of the forward end of the pipe assembly, the air seal when inflated being movable with the advancing pipe assembly, inflating the air seal and cutting off a selected length of the advancing pipe assembly, thereby preventing the loss of pressure within the pipe assembly being generated, permitting uninterrupted advance of the pipe assembly and allowing positioning of the air seal on the forward end of the advancing pipe assembly. 
     
     
       20. A method according to claim 1, wherein the rate of linear advancement of the pipe assembly is synchronized with the rate of rotation of the pipe assembly, the rates of linear advancement and of rotation being responsive to power from a single source. 
     
     
       21. A method for making plastic pipe comprising forming a conveyor tube on a mandrel, the conveyor tube including at the exterior thereof a layer of parting material and a stripping wire adjacent said layer, winding a plurality of bands of resin impregnated fiber elements onto the conveyor tube to provide a pipe assembly, advancing the pipe assembly, and stripping the conveyor tube from within the pipe assembly by pulling on the stripping wire. 
     
     
       22. A method according to claim 21, wherein forming the conveyor tube on a mandrel comprises winding a plurality of strips on the mandrel and adhesively uniting the layers provided by the strips, winding a pair of strips including a strip of parting material in staggered relationship onto the assembly of layers and simultaneously winding a stripping wire between the staggered strips to secure the stripping wire between the strips, the strip of parting material being positioned on the exterior of the conveyor tube. 
     
     
       23. A method according to claim 21, wherein the fiber elements in each band are continuous and in parallel relationship wherein the resin impregnant for the fiber elements is a thermosetting resin composition; and wherein the resin impregnant is cured prior to pulling on the stripping wire to remove the conveyor tube from within the pipe assembly. 
     
     
       24. In a method for making fiber reinforced plastic pipe wherein a resin composition and fiber reinforcement are applied about a mandrel, the improvement which comprises providing a tube on the mandrel which is nonadhesive thereto on the side adjacent the mandrel, said tube having a separable adhesive coating on the opposite side effective to adhere the tub to the resin composition and to allow separation of the tube from the resin composition upon treatment with a separating agent, the resin composition in its polymerized state being unaffected by the separating agent, applying a resin composition and fiber reinforcement around the tube coated as aforesaid and polymerizing the resin composition to form the pipe, treating the separable adhesive coating with a separating agent, and removing the tube from within the pipe. 
     
     
       25. In a method according to claim 24 wherein the tube is of paper and the separable adhesive is a water soluble composition. 
     
     
       26. In a method according to claim 25 wherein prior to applying the resin composition and fiber reinforcement, water is applied to the water soluble adhesive coating to moisten the coating and dampen the paper, drying said coating, applying a heated resin composition coating to the water soluble adhesive coating, and at least partially polymerizing the resin composition. 
     
     
       27. In a method according to claim 25 including applying water to the tube within the pipe to cause separation of the paper tube from the pipe, and removing the paper tube from within the pipe. 
     
     
       28. In a method according to claim 26 including applying water to the tube within the pipe to cause separation of the paper tube from the pipe, and removing the paper tube from within the pipe. 
     
     
       29. In a method according to claim 25, wherein the tube comprises a pair of paper tapes coated with the water soluble composition helically wound upon the mandrel with their edges in overlapping relation. 
     
     
       30. In a method according to claim 29 including applying water to the tube within the pipe to cause separation of the paper tube from the pipe, and removing the paper tube from within the pipe. 
     
     
       31. A method of forming plastic pipe comprising applying strips of flexible release material longitudinally onto a mandrel in abutting relationship, applying adhesive strips beneath the side margins of the first-named abutting strips, whereby to form a release liner, winding strip material impregnated with a thermosetting resin onto the release liner, winding glass roving strands onto said strip material, heating to polymerize said resin, and supporting the release liner internally by inflating same with fluid under pressure during the heating of the superimposed materials. 
     
     
       32. A method of forming plastic pipe according to claim 31, wherein said fluid is allowed to escape at a restricted rate between the mandrel and the release liner, whereby to provide a supporting layer of fluid between the mandrel and the release liner. 
     
     
       33. A method of forming plastic pipe comprising applying strips of flexible material longitudinally onto a mandrel in abutting relationship, applying adhesive strips beneath the side margins of the first-named abutting strips, whereby to form a release liner, coating the release liner with a thermosetting resin, curing the thermosetting resin with suitable heat to provide a cured resin layer, winding a second strip material impregnated with a polymerizable resin over the cured resin layer at a point where said mandrel is reduced in diameter winding glass roving strands onto said second resin impregnated strip material, thus putting the cured resin layer in compression, heating the superimposed materials to polymerize the resin of said second resin impregnated strip, supporting the release liner internally by inflating same with fluid under pressure during the heating of said superimosed materials, and allowing fluid to escape at a restricted rate between the mandrel and the release liner, whereby to provide a supporting layer of fluid between the mandrel and the release liner.