Abstract:
A method is proposed for manufacturing a pipe-lining material comprising a tubular resin absorbent material covered with a tube comprised of an airtight plastic film. The tubular resin absorbent material is inserted into the tube, expanded in a columnar shape, and brought into close contact with the internal peripheral surface of the tube. A heater is wound in close contact with the external peripheral surface of the tube thus expanded. The tube and the tubular resin absorbent material are heated by energizing the heater, and the tube is thereby heat-fused to the tubular resin absorbent material. With such a method, a mechanism for moving the tube and the tubular resin absorbent material is not required. In addition, since heat non-uniformities are not generated, the tube can be uniformly heat-fused to the tubular resin absorbent material, thereby enabling a high-quality pipe-lining material to be manufactured.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a method for manufacturing a pipe-lining material for lining a deteriorated existing pipe. 
         [0003]    2. Description of the Related Art 
         [0004]    Pipe channel lining methods are used for repairing an existing pipe without unearthing the existing pipe in the case that the underground existing pipe such as a clean water pipe, sewage pipe, or the like has deteriorated. With this method, the pipe-lining material composed of a tubular resin absorbent material in which a thermosetting resin has been impregnated is inserted into an existing pipe by eversion or drawing, and is expanded by air pressure or the like and held in a state that the pipe-lining material is pressed against the internal peripheral surface of the existing pipe. In this state, the pipe-lining material is heated, and the thermosetting resin impregnated in the tubular resin absorbent material is cured to line the existing pipe (e.g., Japanese Laid-open Patent Application Nos. 2006-130899 and 2007-125703 and the like). 
         [0005]    The resin absorbent material of the pipe-lining material is composed of a soft felt or the like, and a soft tube composed of a highly airtight plastic film is heat-fused to the external peripheral surface of the resin absorbent material (the internal peripheral surface when the pipe-lining material is everted) to form a coating layer. The tube protects the curable resin impregnated in the tubular resin absorbent material and prevents the curable resin from being in contact with the exterior. In the case that the pipe-lining material is everted and inserted into a pipeline, the heat-fused tube becomes the internal peripheral surface, thereby preventing the resin impregnated in the tubular resin absorbent material from being in direct contact with compressed air when the pipe-lining material is expanded using the compressed air in the subsequent lining process, or preventing the resin from being in direct contact with heat medium in the case that the resin is heated by the heat medium, such as steam, hot water, or the like. 
         [0006]    In the case that the tube is heat-fused to the external peripheral surface of the resin absorbent material of the pipe-lining material, the tubular resin absorbent material is conventionally expanded inside the tube to be in close contact with the internal peripheral surface thereof. The tube is then conveyed into a columnar furnace provided with a heater that extends in the axial direction. The tube and the tubular resin absorbent material conveyed into the furnace are moved through the furnace toward the exit thereof, and heated from the exterior during movement, thereby the tube is heat-fused to the tubular resin absorbent material. 
         [0007]    With such a method, a mechanism is required for moving the tube and the tubular resin absorbent material through the furnace, and the tube and the tubular resin absorbent material must be moved while the center axis of the furnace is aligned with the center axis of the tubular resin absorbent material and the tube that are both expanded in a columnar shape. Without such movement, the distance from the heater to the tube and the tubular resin absorbent material differs in the upper part and the lower part of the furnace, so that non-uniformities are generated in heating and thereby the tube cannot be uniformly heat-fused to the tubular resin absorbent material. When heat-fusion is insufficient, there is a problem that the resin impregnated in the tubular resin absorbent material is not adequately cured and thereby reliable lining becomes unavailable. 
         [0008]    On the other hand, the entire heater extending over the entire length of the furnace must be energized when the distal end of the tube and the tubular resin absorbent material are conveyed into the furnace. In addition, electricity must be continuously fed to the heater until the rear end thereof pass out of the exit of the furnace. These cause another problem that wasteful heating and power consumption is inevitable. 
       SUMMARY OF THE INVENTION 
       [0009]    It is an object of the present invention to provide a method for manufacturing a pipe-lining material in which a tube is uniformly and efficiently heat-fused to the tubular resin absorbent material, and a high-quality pipe-lining material can be manufactured using a simple method. 
         [0010]    According to the present invention, a method is proposed for manufacturing a pipe-lining material comprising a tubular resin absorbent material covered with a tube comprised of an airtight plastic film, wherein the tube is heat-fused to an external peripheral surface of the tubular resin absorbent material. The method comprises inserting the tubular resin absorbent material into the tube, and expanding the tubular resin absorbent material and the tube in a columnar shape so as to bring the tubular resin absorbent material into close contact with the internal peripheral surface of the tube; winding a heater in close contact with the external peripheral surface of the tube thus expanded; and heating the tube and the tubular resin absorbent material by energizing the heater to heat-fuse the tube to the external peripheral surface of the tubular resin absorbent material. 
         [0011]    In the present invention, the heater is wound in close contact with the external peripheral surface of the tube that coves the tubular resin absorbent material. The tube and the tubular resin absorbent material are then heated by energizing the heater, so that the tube is heat-fused to the tubular resin absorbent material. Therefore, a mechanism for moving the tube and the tubular resin absorbent material is not required, and the tube can be uniformly heat-fused to the tubular resin absorbent material without generating heating non-uniformities, thereby manufacturing a high-quality pipe-lining material in a simple manner. 
         [0012]    In the present invention, the tube and the tubular resin absorbent material can be heated without waste, and the tube can be efficiently heat-fused to the tubular resin absorbent material using a small amount of power because the heater is wound in close contact with the external peripheral surface of the tube. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a perspective view showing the pipe-lining material when the tubular resin absorbent material has been inserted into a tube and expanded; 
           [0014]      FIG. 2A  is a perspective view showing the tubular resin absorbent material and the tube around which a heater has been wound, and  FIG. 2B  is a perspective view showing the tubular resin absorbent material and the tube around which a plurality of heaters has been wound; and 
           [0015]      FIG. 3  is an illustrative view showing the connections of the heating wires of the heater. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]    Now, referring to the drawings, description is made about embodiments of the present invention. The description is herein made as regards a method for manufacturing a pipe-lining material used to line a sewage pipe as an existing pipe. However, the present invention is not limited to this case, but can be applied to other cases in which the method for manufacturing a pipe-lining material is used to line a clean water pipe, an agricultural water pipe, or the like. 
         [0017]      FIG. 1  shows a process for manufacturing a pipe-lining material used to repair or rehabilitate an existing pipe. A pipe-lining material  1  comprises a soft tubular resin absorbent material  10  whose external peripheral surface  10   a  is covered with a soft tube  11  composed of polyethylene, polypropylene, nylon, vinyl chloride, or another highly airtight plastic film. 
         [0018]    The tubular resin absorbent material  10  is composed of a matte, a woven, or a nonwoven using polyamide, polyester, polypropylene, or another plastic fiber; a matte or a woven using glass fiber; or a matte, a woven, or a nonwoven that combines the use of the above-noted plastic fiber and fiber glass. The tubular resin absorbent material  10  is impregnated with unsaturated polyester resin, vinyl ester resin, epoxy resin, or another uncured liquid thermosetting resin. 
         [0019]    In order to manufacture such a pipe-lining material, the tubular resin absorbent material  10  is inserted into the tube  11 , and a tubular inner liner  12  that is closed at one end (the right side in  FIG. 1 ) is inserted into the tubular resin absorbent material  10  so that the tubular resin absorbent material  10  can be held between the tube  11  and the inner liner  12 . 
         [0020]    A hole is opened in the tubular resin absorbent material  10  and the tube  11 , and a vacuum hose  13  is attached to the hole to suck the tubular resin absorbent material  10  by vacuum. Compressed air is fed from the open end (left side of  FIG. 1 ) of the inner liner  12 . This causes the tube  11 , the tubular resin absorbent material  10  and the inner liner  12 , which are initially in a flat shape, to be all expanded in a columnar shape, as shown in  FIG. 1 . The tubular resin absorbent material  10  is brought into close contact with the internal peripheral surface of the tube  11 . The inside diameter of the tube  11  substantially coincides with the outside diameter of the tubular resin absorbent material  10  when both are expanded in a columnar shape, and the inside diameter of the tubular resin absorbent material  10  substantially coincides with the outside diameter of the inner liner  12  when both are expanded in a columnar shape. 
         [0021]    In  FIG. 1 , the vacuum hose  13  is provided in only a single location, but the vacuum hose is ordinarily attached in a plurality of locations in accordance with the length of the pipe-lining material in order to efficiently carry out the vacuum suction of the tubular resin absorbent material. 
         [0022]    As shown in  FIG. 2A , the tube  11 , the tubular resin absorbent material  10  and the inner liner  12  are kept in an expanded state, and a heater  20  is wound in close contact with the external peripheral surface of the tube  11  that covers the tubular resin absorbent material  10 . 
         [0023]    The heater  20  is such a heater in which Nichrome wires or other heating wires  20   b  are arranged in a periodic serpentine fashion at an equal pitch p (e.g., 7.5 mm) inside a rectangular or square insulating cloth (shown as an imaginary line in the drawing) that has one side Y and another side Y′, as shown in  FIG. 3 . Y′ is substantially equal to or greater than the outer circumference of the tube  11 , and has a length in which the both ends of the heater  20  are partially overlapping with each other ( FIG. 2A ) when the heater  20  is wound in close contact with the tube  11 . 
         [0024]    A heating wire  20   b  is turned back when the heating wire  20   b  has extended up to a predetermined distance in the Y′ direction, and is then turned back again when the heating wire  20   b  has extended up to the same distance in the opposite direction thereof, as shown in  FIG. 3 . This turning back is repeated so that the heating wire extends in a periodic serpentine fashion in the lengthwise direction of the pipe-lining material at a pitch p. The heating wire  20   b  is connected to a plug  20   c  at one end, and the heating wire  20   b  can be energized and heat can be generated in the heating wire  20   b  by plugging the plug  20   c  into a power source outlet  20   d  of the main line  21 . The quantity of heat generated by the heating wire is uniform over the entire heater  20  because the heating wire  20   b  is uniformly distributed over substantially the entire heater. 
         [0025]    When the pipe-lining material  1  has considerable length, a plurality of heaters  20  is disposed adjacent to each other and wound in close contact with the external peripheral surface of the tube  11 , as shown in  FIG. 2B . In this case, the smallest integer Z that satisfies the expression Y*Z&gt;X (where * is the reference symbol for multiplication) is calculated for the case in which X is greater than Y, wherein X is the length of the pipe-lining material in the axial direction (the length of the tube  11 ), and Y is the length over which one side of the heater  20  extends in the length direction of the pipe-lining material. The calculated number Z of heaters  20  is arranged adjacent to each other and wound in close contact with the external peripheral surface of the tube  11 . The Z number of heaters  20  is connected in parallel by plugging the plug  20   c  of each heater  20  into the power source outlet  20   d.    
         [0026]    In  FIGS. 2A and 2B , the first heater  20  (left end in the drawing) is wound slightly to the right from the distal end of the tube  11  in order to facilitate an understanding of the present invention. However, in actual practice, the left end of the heater  20  and the distal end of the tube  11  are disposed in substantially matching positions. 
         [0027]    In the case of the pipe-lining material  1  shown in  FIG. 2 , the length X in the pipe lengthwise direction is greater than the Y value of one side of the heater  20 . Therefore, Z number of heaters  20  is prepared using the formula described above, and the plugs  20   c  are plugged into the outlets  20   d  to connect the Z number of heaters  20  in parallel. In the example of  FIG. 2B , three heaters  20  are wound around the tube  11  and connected in parallel. However, the plugs of the heaters and the outlets are omitted in the drawing in order to avoid complexity. 
         [0028]    A predetermined number Z of heaters  20  is wound around the tube  11 , and the plugs  20   c  are plugged into the power source outlets  20   d  to energize the heaters  20 , respectively. The tube  11  and the tubular resin absorbent material  10  are uniformly heated, and the tube  11  is heat-fused to the tubular resin absorbent material  10 , thereby forming a coating layer thereon. 
         [0029]    Thus, the tubular resin absorbent material and the tube covering the tubular resin absorbent material can be entirely heated using a predetermined number of connected heaters even when the tubular resin absorbent material of the pipe-lining material is long. Therefore, heating can be uniformly and efficiently carried out, and the tube can be heat-fused to the tubular resin absorbent material with high quality. 
         [0030]    The portions in which the heaters  20  are adjacent to each other are less likely to be uniformly heated. Therefore, a thin metal sheet  30  (e.g., aluminum foil) having good thermal conductivity is wound around the tube  11  as shown by the imaginary line in  FIG. 2B . The heaters  20 ,  20  are then placed adjacent to each other and wound on the metal sheet, thereby rendering the quantity of heat to be uniform. The sheet  30  is shown in only one location in  FIG. 2B , but the sheet is also wound around other adjacent heaters. 
         [0031]    Thus, when the tube  11  has been heat-fused to the external peripheral surface of the tubular resin absorbent material  10 , vacuum suction via the vacuum hose  13  is stopped, and the supply of compressed air to the inner liner  12  is discontinued. This allows the tube  11 , the tubular resin absorbent material  10  and the inner liner  12  to contract. The inner liner  12  is then pulled out from the tube  11  and the tubular resin absorbent material  10 . 
         [0032]    A resin that cures by heating or by radiation of light, or a curable resin that cures at a normal temperature is impregnated in the tubular resin absorbent material  10  using a known method (described, e.g., in Japanese Laid-open Patent Application No. 2001-108555). In other words, the curable resin is injected into the tubular resin absorbent material  10 , and the tubular resin absorbent material  10  is then subjected to vacuum suction to produce negative pressure therein in order to impregnate the curable resin in the tubular resin absorbent material  10 . Accordingly, it is possible to manufacture a pipe-lining material in which a tube composed of an airtight plastic film is heat-fused to the external peripheral surface of the tubular resin absorbent material and a curable resin is impregnated therein. 
         [0033]    The pipe-lining material thus manufactured is inserted by eversion or by drawing into an existing pipe so that the tube becomes the internal peripheral surface. The pipe-lining material is then expanded by air pressure or the like so as to be pressed against the internal peripheral surface of the existing pipe. In this state, the pipe-lining material is heated or irradiated with light in order to cure the curable resin impregnated in the tubular resin absorbent material and line the existing pipe.