Abstract:
A reinforced flexible pipe having a tubular core member and a plurality of reinforcing tape members wrapped on the core member; the innermost tape member includes a plurality of openings that communicate with the external surface of the core member; and a polymer material embedded in the openings in the tape such that the polymer material contacts the core member and the tape to improve the hoop strength and the collapse resistance of the pipe. The polymer layer may also be bonded to the outer reinforcing tape to provide abrasion resistance to the reinforced flexible pipe.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   Not applicable. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable. 
   REFERENCE TO MICROFICHE APPENDIX 
   Not applicable. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The field of the invention is reinforced tapes used with tubing or flexible pipe for conducting petroleum or other fluids subsea or on land and the method of manufacture. 
   2. Description of the Related Art 
   This is an improvement on the invention disclosed in U.S. Pat. No. 6,491,779. When the pipe disclosed therein is used to transport compressed gas, some gas can permeate through the inner core or the pipe over time and gather between the inner core and extrusions causing a steady rising inward pressure on the core. Although not in itself a problem under normal circumstances, this can cause a problem if the pressure in the bore of the pipe is released more quickly than the pressure between the layers. When that happens, the inner core can collapse due to the adverse pressure differential and its poor hoop strength. Some degree of protection can be provided to pipes by relieving the pressure between the two extrusions through a valve or valves in the end fittings but this is insufficient for all circumstances and collapse of the inner core may still occur. 
   Pipe collapse has happened in the past with prior art pipes that have steel based flexible pipes and therefore prior art pipes used for gas transmission are normally constructed using a central interlocking metallic carcass under the inner core. The metallic carcass provides sufficient radial strength to withstand any collapse forces generated by the scenario described above but the overall diameter of the pipe necessarily requires an increase of twice the thickness of the carcass. Furthermore, the inclusion of a carcass increases each reinforcement layer for the same performance because the reinforcement layers have to be wound on larger diameters. 
   BRIEF SUMMARY OF THE INVENTION 
   The method and device made according to this inventive method, are described below based on the inventive method of securing the inner core or pipe to the first layer of reinforcement thus preventing the inner core from collapsing when pressure on its outside surface is greater than in its bore. By securing the inner core or pipe to the first layer of reinforcement, its collapse pressure then becomes the sum of the inner core collapse pressure and that of the first reinforcement which can be wound either as pressure reinforcement or as a hoop layer. 
   The present inventive method improves upon a polymeric tubular core that is subject to internal fluid pressure, and which has a plurality of reinforcing tapes wrapped thereon for resisting the internal fluid pressure, such as is shown in U.S. Pat. No. 6,491,779. Each tape which is in contact with the core has an inner surface in contact with the external surface of the core. 
   The improvement comprises forming a plurality of laterally spaced openings in the tape, each of which is in communication with the external surface of the core; embedding a polymer in the laterally spaced openings; and bonding the embedded polymer in the tape to the polymer of the core, whereby a collapse of the core is prevented when a reduction in internal fluid pressure in the core occurs. 
   The bonding may be accomplished by welding the embedded polymer in the tape to the polymer of the core by applying heat, or by applying an adhesive between the embedded polymer in the tape and the polymer of the core, or by other bonding methods. 
   By using this method, the bore of the pipe remains smooth as opposed to being corrugated which improves the fluid or gas flow and prevention of liner collapse then becomes a matter of choosing suitable reinforcement strength while ensuring that the lower tape with its integral polymer layer does not part from the core or pull apart under the expected forces. 
   From a practical standpoint, most polymer cores are usually difficult if not impossible to bond to, and where this is the case, a preferred method is to make the first tape in each reinforcement tape stack wound onto the core with the same or compatible polymer attached to its lower surface so that the reinforcement stack can be welded or bonded to the outside diameter of the core. Sometimes it is possible to bond similar polymers together but it is preferable that localized heat will be applied to the interface between the tape and the outer surface of the core and the pressure generated during the wrapping process will be used to bond the assemblies together. 
   Polymer tapes locked to reinforcing tapes can also be used on the outside of a reinforcement layer to provide an outer jacket that provides a wear coating or a corrosion barrier to protect the inner layers of the pipe. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  is a view of an embodiment of the invention showing the inner layer. 
       FIG. 1B  is a view of an embodiment of the invention showing the inner layer and the outer jacket. 
       FIG. 2  is an isometric view of a typical fiber arrangement for the tape of an embodiment of this invention. 
       FIG. 2A  is an isometric view of a method of constructing an embodiment of the invention with an extrusion device. 
       FIG. 3  is a view of an embodiment of the invention showing the inner layer and rivet shaped openings in the perforated laminate. 
       FIG. 4  is an isometric, schematic illustration of a method of construction of the invention showing the plenum and wrapped core. 
       FIG. 5  is an isometric view of a pipe made in accordance with this invention, showing the arrangement of the tapes wound on the fluid conducting tube or core. 
       FIG. 6A  is a view of an embodiment of the invention showing a flap extending beyond the width of the laminate. 
       FIG. 6B  is a view of an embodiment of the invention showing flaps extending over adjacent tapes. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to  FIG. 1A , the letter A- 1  generally refers to a plurality of superimposed tapes  15 , with an inner tape  18  which initially has a plurality of perforations  17  which are spaced apart laterally and may be formed by punching or by otherwise forming them longitudinally in the tape  18 . The tape  18  has a polymer or other extrudeable material filling in the perforations  17  and preferably also has a substantially continuous polymer layer  16  bonded thereto. The tape  18  in this invention may be a reinforcing tape, a bondable tape, a low volume fraction tape, or a zero volume fraction tape. The volume fraction of fiber in a tape, as is known in the art, is equal to the volume of fiber divided by the sum of the volume of fiber plus the volume of matrix, where the matrix is usually resin. In other words, low volume fraction tape is generally a tape with a relatively small amount of fibers while a zero volume tape is generally a tape with no fibers at all. 
   The perforations or initial voids  17  in the tape  18 , when filled with polymer, act as “rivets” or wedges to more securely bond the polymer of the tape  18  to the core C, and to thereby serve to prevent the collapse of the core C. Preferably, the shape of the perforations  17  for the polymer therein are formed with tapered surfaces  17   a  that extend upwardly and outwardly as shown in  FIG. 1A  so that the cured polymer in the perforations  17  locks and holds the core C to the tape  18  when they are bonded together to prevent collapse of the core C when the fluid pressure in the core C is sufficiently low enough to cause a collapse to occur. The polymer layer  16  is located on the lowermost side of the tape A. One or more laminates or layers  15  are then applied to the top of the tape  18  to provide hoop strength or other reinforcement. 
   An alternative embodiment of the tape A- 2  of the invention is shown in  FIG. 1B  wherein a polymer layer  16  is located below laminate  18  and below a laminate  15 . In addition, a polymer layer  16   b  is located above the upper tape  18   b , which is above laminate  15 . Multiple layers or laminates  15  may also be used. Instead of polymer layers  16  or  16   b , alternative materials may also be used that are compatible with the material composition of the tube or core C. The embodiment in  FIG. 1B  may also be constructed without any resin or adhesive or other material between the upper perforated laminate  18   b , the laminate  15  and the lower perforated laminate  18  so that the layers can slide relative to each other to reduce the stiffness of the laminates  15  relative to the perforated laminates  18  and  18   b  interface and therefore improve the flexibility of the entire assembly of tapes A on pipe C. 
   In  FIG. 2  a stitched or woven fiber tape T referred to in the inventor&#39;s U.S. Pat. Nos. 6,491,779 and 6,804,942 is shown. U.S. Pat. Nos. 6,491,779 and 6,804,942, which more fully describe tape T, are hereby incorporated by reference. Tape T includes warp fibers  11  and weft fibers  12 , which are joined together with stitching  14 . The resulting tape T provides an open lattice structure that can then be impregnated with epoxy, vinyl ester or other resin leaving a matrix of holes between the resin loaded fibers. 
   As shown in  FIG. 2A , the tape T can then be passed through a polymer extruder  42  in which a molten polymer can be introduced under pressure through an inlet  44  and into the matrix of holes in the tape T. 
   In  FIG. 3  the tape A- 3 , is constructed by extruding a profile or preferred shape that has longitudinal grooves  17   b  along its length. The profile of the grooved polymer layer  16  can be formed from the shape of the opening or cross section of a die. The grooves  17   b  may be filled with composite material, resin, adhesive or paste made from short fibers and resin or other filler materials  17   c , either during or prior to the application of the tapes to the core C. The resultant tape A- 3  can be welded on its bottom surface  16  to a compatible tube C of a compatible material and bonded to the layer or laminate  15  above the polymer layer  16 . 
     FIG. 4  shows a preferred method of producing the tape A- 1 . The perforated laminate  18  is shown outside of the resin plenum, and parallel to the tapes  15 , which are passed through a resin plenum  32  while resin is injected into the inlet  35 . The resin is generally injected under pressure. The resin will fill the grooves in the tape and lock the stack of laminates  15  together when the resin cures. The perforated laminate  18  may also be passed through the resin plenum  32  together with the tapes  15 , wherein the perforated laminate  18  is bonded together with the tapes  15  with the resin or other bonding material. It is to be understood that the alternative embodiments of the tapes A- 2  or A- 3  may also be applied to the core C as seen in  FIG. 5 . A holdback wire  22  is shown attached to the top of the resin plenum  32 . The holdback wire  22  is used to secure the position of the plenum  32  during the fabrication process. Additional holdback wires  22  may be positioned on the bottom of the plenum  32  or the plenum  32  may be supported with an alternative, or well known structure. 
   The polymer layer  16  can be bonded to the surface of the pipe or core C by heating the surfaces being joined with a suitable heater  40 . The heating and pressure from winding the tape A to the surface of the core C results in a welded bond between the polymer layer  16  and the surface of the core C. The polymer layer  16  can also be bonded with an adhesive or other bonding agent. 
     FIG. 5  shows the inventive pipe after the tape has been applied to the core C. The polymer layer  16  is shown bonded to the core C and also bonded to the perforated layer  18 . The resulting configuration provides reinforced hoop strength for the above described structure to prevent the collapse of the pipe in the event of a reduced pressure in the pipe or core C as explained above. Additional layers of laminate  15  are shown wrapped outside of the perforated layer  18 . An outer jacket B is shown in  FIG. 5 , which provides abrasion and chemical resistance is shown outside of the layers of laminate  15 . 
   The embodiment shown in  FIG. 1B , which may include only a polymer layer  16   b  with depending polymer  17   b  in upper layer  18   b , on the outside upper layer may be wrapped around the core C to provide a modified construction of  FIG. 1B  which provides wear resistance, corrosion protection and a surface that is suitable for identification purposes. 
   In  FIG. 6A , an alternative embodiment is shown that includes a polymer flap  16   a  that extends the polymer beyond the width of the layers of laminate  15  and perforated laminate  18 . As shown in  FIG. 6B , the attached polymer flap  16   a  extends up and over the adjacent layers of laminate  15  and can be used to separate spiral stacks of reinforcing layers as shown. 
   The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the details of the illustrated apparatus and construction and method of operation may be made without departing from the spirit of the invention.