Abstract:
A linking tool links segments for a rehabilitating pipe for rehabilitating an existing pipeline. The segment is integrally formed at least from an internal surface plate that constitutes the inner circumferential surface of the rehabilitating pipe, and side plates that have an insertion hole formed thereon and are disposed on both sides of the internal surface plate so as to extend in the circumferential direction of the rehabilitating pipe. The linking tool includes a tubular linking pin that is separable into pin halves and can be inserted into the insertion hole in the side plate of a first segment with a part of the linking pin remaining outside the first segment. The linking tool further includes a separating pin that can be inserted into the linking pin to separate the linking pin into the pin halves and press them against the first segment for anchoring thereto. The pin halves remaining outside the first segment are snap-fitted into a second segment through the insertion hole of the side plate thereof, thereby linking the first and second segments in the longitudinal direction of the rehabilitating pipe. Such a linking tool allows the segments to be efficiently linked in a short period of time

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a method for linking segments and a linking tool, and more particularly to a method for linking segments that are used as an assembly unit of a pipe for rehabilitating existing pipes or pipelines, and to a linking tool used in this method. 
         [0003]    2. Description of the Related Art 
         [0004]    In cases where sewage pipes or other pipelines that are buried underground have aged, methods for constructing a pipe lining have already been proposed and are being employed in practical applications. 
         [0005]    With the aforementioned methods for constructing a pipe lining, a pipe-lining material, which is formed, e.g., by impregnating a tubular resin-adsorbent material with an uncured thermosetting resin, is inserted into a pipeline via fluid pressure while being everted, and the impregnated thermosetting resin is cured by heating the pipe-lining material in the state where the pipe-lining material is pressed against the inner circumferential wall of the pipeline by fluid pressure. This allows a plastic pipe to be installed within the pipeline to be repaired. 
         [0006]    In another well-known method for repairing a pipeline using a rehabilitating pipe (Japanese Laid-open Patent Application Nos. 2003-286742 and 2005-299711), a segment made of a plastic material is used which is integrally composed of an internal surface plate that constitutes the inner circumferential surface of the rehabilitating pipe and an outer-wall plate that is vertically disposed on the peripheral edges of the internal surface plate. Segments are linked in the circumferential direction to assemble pipe units, which are then linked in the longitudinal direction of the pipe via a linking member to assemble the rehabilitating pipe. This method is used for large-bore pipelines. 
         [0007]    When linked together in the longitudinal direction of the pipe as disclosed in Japanese Laid-open Patent Application Nos. 2003-286742 and 2005-299711, the segments are linked using a linking tool provided with a screw. A screw-fastening tool is therefore necessary, and time is required to tighten the screw. The screw may not be able to be turned when the operation is performed in confined spaces; moreover, the operation is troublesome and repetitive even when the screw can be turned. A significant burden is therefore placed on the worker, resulting in lengthened operational time. 
       SUMMARY OF THE INVENTION 
       [0008]    It is therefore an object of the present invention to provide a method for linking segments, and a linking tool, whereby segments can be efficiently linked in the longitudinal direction of the pipe in a short period of time using a simple method. 
         [0009]    The present invention provides a method for linking segments for a rehabilitating pipe for rehabilitating an existing pipeline. The segment is integrally formed at least from an internal surface plate that constitutes the inner circumferential surface of the rehabilitating pipe, and side plates that have an insertion hole formed thereon and are disposed on both sides of the internal surface plate so as to extend in the circumferential direction of the rehabilitating pipe. The method for linking the segments comprises the steps of preparing a linking pin that can be separated into pin halves by a separating pin; inserting the linking pin into the insertion hole in the side plate of a first segment with a part of the linking pin remaining outside the first segment; separating the linking pin into the pin halves by the separating pin, the separated pin halves being pressed against the first segment, thereby anchoring the pin halves to the first segment; and snap-fitting the pin halves remaining outside the first segment into a second segment through the insertion hole of the side plate thereof, thereby linking the first and second segments in the longitudinal direction of the rehabilitating pipe. 
         [0010]    A linking tool according to the present invention comprises a tubular linking pin that is separable into pin halves and can be inserted into the insertion hole in the side plate of a first segment with a part of the linking pin remaining outside the first segment; and a separating pin that can be inserted into the tubular linking pin to separate the linking pin into the pin halves and press them against the first segment for anchoring thereto. The pin halves remaining outside the first segment are snap-fitted into a second segment through the insertion hole of the side plate thereof, thereby linking the first and second segments in the longitudinal direction of the rehabilitating pipe. 
         [0011]    According to the present invention, a linking pin, which is inserted into the insertion hole of the side plate of a segment, is separated into pin halves by a separating pin. The pin halves are pressed against the segment, thereby anchoring the linking pin to the segment. The other end of the linking pin outside the segment is snap-fitted into another segment, allowing the two segments to be linked in the longitudinal direction of the rehabilitating pipe. Screw-fastening is therefore unnecessary, and the segments can be assembled in confined spaces where a manual screwing motion is difficult to perform. The assembly operation can be simplified and shortened even during assembly in open spaces. Excellent effects are obtained in that construction time is shortened, the burden on workers is lightened, and the number of workers required is reduced even during a construction work for assembling a rehabilitating pipe using the segments to repair an existing pipeline. 
         [0012]    Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and following detailed description of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a perspective view of a segment shown partially broken and partially in cross-section; 
           [0014]      FIG. 2  is a perpendicular cross-sectional view of two segments, as seen when both segments are linked in the circumferential direction; 
           [0015]      FIG. 3  is a perspective view of a pipe unit wherein the segments are linked in the circumferential direction to provide the pipe unit; 
           [0016]      FIG. 4   a  is a perspective view of a linking tool; 
           [0017]      FIG. 4   b  is a perspective view of the linking tool, as viewed when it is disassembled; 
           [0018]      FIG. 4   c  is a vertical cross-sectional view of the linking tool; 
           [0019]      FIG. 5   a  is a lateral view of the linking tool in which linking pin halves have been spread apart horizontally; 
           [0020]      FIG. 5   b  is a lateral view of the linking tool showing a state in which the linking pin halves are folded together and overlaid; 
           [0021]      FIG. 6  is a cross-sectional view showing the dimensions of the linking pin, the separating pin, the side plate of the segment, and the internal plate thereof; 
           [0022]      FIG. 7   a  is a plan view showing a state in which the linking tool is ready for insertion into a segment; 
           [0023]      FIG. 7   b  is a plan view in which the linking tool is inserted and anchored to the segment; 
           [0024]      FIG. 8   a  is a cross-sectional view in which the linking pin is inserted to the forward part of the internal plate of the segment; 
           [0025]      FIG. 8   b  is a cross-sectional view in which the linking pin is inserted to the insertion hole of the internal plate of the segment; 
           [0026]      FIG. 8   c  is a cross-sectional view showing a state in which the separating pin is pressed in, and the linking pin is separated into the linking pin halves; 
           [0027]      FIG. 8   d  is a cross-sectional view in which the separating pin has been pushed further in; 
           [0028]      FIG. 8   e  is a cross-sectional view in which the linking pin is pushed into the insertion hole of the side plate of another segment; 
           [0029]      FIG. 8   f  is a cross-sectional view in which two segments have been linked by the linking pin; 
           [0030]      FIG. 9   a  is a plan view in which two segments are being linked by the linking pin; 
           [0031]      FIG. 9   b  is a plan view in which both segments have been linked; 
           [0032]      FIG. 10  is a cross-sectional view along a segment arc, in which segments are linked in the longitudinal direction of the pipe via the linking tool and the linking rod; 
           [0033]      FIG. 11  is an illustrative view showing a state in which a rehabilitating pipe composed of the segments is laid in an existing pipeline; and 
           [0034]      FIG. 12  is a perspective view showing the exterior of the rehabilitating pipe laid within the existing pipeline. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0035]    The present invention will be described in detail hereinafter on the basis of the embodiments shown in the accompanying drawings. 
         [0036]      FIG. 1  shows a segment  1  that serves as an assembly unit for a pipe for rehabilitating an existing pipe such as a sewerage pipe, a waterworks pipe, an agricultural water pipe and the like. The segment  1  is a block-shaped member that is integrally formed of plastic from an internal surface plate  101  that constitutes an inner circumferential surface of the rehabilitating pipe; side plates  102 ,  103  that are vertically disposed at both sides of the internal surface plate  101  so as to extend in the circumferential direction of the rehabilitating pipe; and end plates  104 ,  105  that are vertically disposed at both ends of the internal surface plate  101  so as to extend in the longitudinal direction of the pipe. The side plates  102 ,  103  and the end plates  104 ,  105  of the segment  1  have the same height and form an outer-wall plate that surrounds the rim of the internal surface plate  101  on all four sides. The widths (thicknesses) of the side plates  102 ,  103  of the segment  1  in the longitudinal direction of the pipe have the same value. The segment  1  has a shape bent into an arc shape of a predetermined angle that divides the circumference of a circle into a plurality of equal parts, e.g., five equal parts of 72 degrees each. The segment is not limited to arc or fan shapes, however, and may also be another shape, such as a bent shape obtained by rounding off a cuboid or right angle, in accordance with the shape of the cross-section of the existing pipe, the size thereof, and the location of the existing pipe to be repaired. 
         [0037]    A plurality of internal plates (reinforcement plates)  106 ,  107  that are similar to the side plates are provided vertically on the upper surface of the internal surface plate  101  inside the side plates  102 ,  103  in order to reinforce the mechanical strength of the segment  1 . Convex plates  103   b,    106   b,    107   b  that project laterally are formed at a plurality of locations on both lateral surfaces of the internal plates  106 ,  107  and the inner lateral surfaces of the side plates  102 ,  103  in order to prevent deformations thereof, resulting in a ribbed structure and increasing the strength of the segment  1 . 
         [0038]    A plurality of circular or substantially circular insertion holes  102   a,    103   a  are formed in the circumferential direction at equal intervals on the side plates  102 ,  103  so that a linking tool can be inserted. The linking tool links the segments in the longitudinal direction of the pipe, as described hereinafter. A plurality of circular or substantially circular insertion holes  106 a for inserting the linking tool are also formed in the internal plates  106  in positions corresponding to the insertion holes  102   a,    103   a  of the side plates  102 ,  103  when viewed in the longitudinal direction of the pipe. The diameter of the insertion holes  106   a  is smaller than the diameter of the insertion holes  102   a,    103   a,  as described hereinafter. A plurality of notches  107   a  are formed on the internal plates  107  in positions that correspond to the respective insertion holes  102   a,    103   a  of the side plates  102 ,  103 . 
         [0039]    The internal surface plate  101 , the side plates  102 ,  103 , the end plates  104 ,  105 , as well as the internal plates  106 ,  107  and the convex plates that function as reinforcement plates for these parts, are all made of the same clear, translucent, or opaque plastic and are formed integrally using well-known molding techniques. 
         [0040]    A plurality of rectangular opening parts  101   a  are formed on the ends of the internal surface plate  101  on the sides having the end plates  104 ,  105  so that the operation for linking the segments  1  in the circumferential direction can be performed from the inside. 
         [0041]    The segments  1  are linked in the circumferential direction by bringing the outer surfaces of the end plates  104  and  105  of each of the segments  1  in close contact with one another, inserting bolts  6  into insertion holes  104   a,    105   a  from the opening parts  101   a  of the internal surface plate  101 , threading on nuts  7 , and fastening together both of the end plates  104 ,  105 , as shown in  FIG. 2 . Concave parts  104   b,    104   c  and convex parts  105   b,    105   c  for fitting to the respective concave parts  104   b,    104   c  are formed across the entire length of the end plates  104  and  105  in the longitudinal direction of the pipe. Both segments can therefore be readily held in position and brought into close contact during the linking operation. A sealant (not shown) is applied to the parts to be fit, whereby the water-tightness of the linking parts can be increased. 
         [0042]    Once the linkage of the segments  1  in the circumferential direction is completed, the opening parts  101   a  are sealed shut using a lid (not shown) or the like. The bottom surface of the lid in such instances is continuous with the bottom surface of the internal surface plates  101 , and the inner surfaces (the surfaces facing the center of the pipe) of the internal surface plates  101  form a uniform surface. 
         [0043]    The segments  1  are linked in the circumferential direction so that the inner surfaces of the internal surface plates  101  form a uniform surface, and so that the outer surfaces of the respective side plates  102 ,  103  all form a single surface. A closed, ring-shaped pipe body  10  (referred to as a pipe unit hereinafter) having a short, predetermined length can therefore be assembled when the segments  1  are sequentially linked in the circumferential direction, as shown in  FIG. 3 . The pipe unit  10  has a shape obtained by cutting a round pipe perpendicularly with respect to the longitudinal direction X thereof with a predetermined width D. The outside diameter of the pipe unit is smaller than the inside diameter of the existing pipeline to be repaired. The segments  1  correspond to the members that are obtained when the pipe unit  10  is cut along a radial direction R and divided into a plurality of pieces (five in the embodiment in the drawings). 
         [0044]    The internal surface plates  101 , the side plates  102 ,  103 , and the end plates  104 ,  105 , which are the primary structural members of the segment, are shown in  FIG. 3 . The internal plates  106 ,  107 , the convex plates, other reinforcing structures, the insertion holes  102   a,    103   a,  and the like are omitted from  FIG. 3  in order to avoid complexity. 
         [0045]    A linking tool  20  for linking the segments  1  or the pipe units  10  in the longitudinal direction of the pipe is shown in  FIGS. 4   a  through  4   c  and  5   a,    5   b.  The linking tool  20  comprises a tubular hollow linking pin  21  and a separating pin  24 . The linking pin has a hollow part constructed from overlaying linking pin halves  22 ,  23 , and the separating pin separates the linking pin  21  into the linking pin halves  22 ,  23 . The linking pin  21  has a shape formed integrally of plastic, in which the linking pin halves  22 ,  23  are linked by thin parts  22   a,    23   a,  as shown in  FIG. 5   a . As shown in  FIG. 5   b , the linking pin  21  can be bent at the thin parts  22   a,    23   a  and folded. The linking pin thereby becomes a tubular pin having a structure in which the linking pin halves  22 ,  23  are overlaid as shown in  FIG. 4   a.    
         [0046]    As shown in  FIGS. 4   b ,  4   c , the linking pin half  22  has the thin part  22   a  that links to the linking pin half  23 ; a half-pipe part  22   c  having a shape obtained when the portion of a circular tube above a pipe axis x 1  is cut off in the horizontal direction; a projecting part  22   b  that has a half-pipe shape having a small diameter and that projects farther toward the distal end than the half-pipe part  22   c;  a first protruding part  22   d  and a second protruding part  22   e  that extend in the circumferential direction over the outer circumferential surface of the half-pipe part  22   c;  and a slanted part  22   f.  The mutually facing surfaces of the first and second protruding parts  22   d  and  22   e  are vertical, while the opposite portions thereof are slanted and are continuous with the half-pipe part  22   c.    
         [0047]    The linking pin half  23  is shaped to be laterally symmetric with the linking pin half  22  when viewed as in  FIG. 5   a . The linking pin half  23  has the thin part  23   a,  a projecting part  23   b,  a half-pipe part  23   c,  a first protruding part  23   d,  a second protruding part  23   e,  and a slanted part  23   f  that correspond respectively to the thin part  22   a,  the projecting part  22   b,  the half-pipe part  22   c,  the first protruding part  22   d,  the second protruding part  22   e,  and the slanted part  22   f  of the linking pin half  22 . 
         [0048]    The linking pin halves  22 ,  23  have shapes that would result from horizontally cutting off a circular tube a predetermined small distance above (or below) a horizontal plane that passes through the central axis of the circular tube. The moderately flat, tubular linking pin  21 , which has an ellipsoid cross section, is therefore obtained when the linking pin halves  22 ,  23  are overlaid as shown in  FIG. 4   a.    
         [0049]    As shown in  FIG. 4   c , when the linking pin halves  22 ,  23  are overlaid, a hollow part  21   a  having a small diameter and a hollow part  21   b  having a larger diameter are formed on the inside of the linking pin. The thickness of the linking pin halves  22 ,  23  decreases beyond the first protruding parts  22   d,    23   d  toward the end (the right side) of the linking pin. A hollow part  21   c  having a larger diameter than the hollow part  21   b  is therefore formed. 
         [0050]    The separating pin  24  is a cylindrical pin of plastic or metal and has a conical distal part  24   a,  a cylindrical distal part  24   b,  a cylindrical center part  24   c,  and a cylindrical proximal part  24   d.    
         [0051]    The dimensions of the segment  1 , the separating pin  24 , and the linking pin  21  obtained when the linking pin halves  22 ,  23  are overlaid are shown in  FIG. 6 . 
         [0052]    A diameter D 2  of the circular insertion hole  103   a  formed in the side plate  103  of the segment  1  is larger than a diameter D 1  of the circular insertion hole  106   a  of the internal plate  106  adjoining the side plate  103 . The size of the linking pin  21  allows the projecting parts  22   b,    23   b  of the linking pin to pass through the insertion hole  106   a  of the internal plate  106  with a predetermined spacing, and allows the half-pipe parts  22   c,    23   c  to pass through the insertion hole  103   a  of the side plate  103  with a substantially identical spacing. The first protruding parts  22   d,    23   d  of the linking pin  21  are slanted on the inserting side (the left side) and protrude outwardly so high as to be able to pass through the insertion hole  103   a  due to its elasticity if forcefully pressed. The second protruding parts  22   e,    23   e  of the linking pin  21  are also of an identical size and have lateral symmetry with the first protruding parts  22   d,    23   d.    
         [0053]    A distance t 1  from a boundary surface S 1  between the projecting parts  22   b,    23   b  and the half-pipe parts  22   c,    23   c  of the linking pin  21  to a vertical surface S 2  of the first protruding parts  22   d,    23   d  is approximately equal to the distance between the opposing surfaces of the side plate  103  and the internal plate  106  of the segment  1 . A distance t 3  between opposing vertical surfaces S 2 , S 3  of the first protruding parts  22   d,    23   d  and the second protruding parts  22   e,    23   e  is approximately double a thickness t 2  of the side plate  103  (or the side plate  102 ) of the segment  1  in the longitudinal direction of the pipe. 
         [0054]    The outside diameters of the distal part  24   b,  the center part  24   c,  and the proximal part  24   d  of the separating pin  24  are p 1 , p 3 , and p 2 , respectively, where p 3 &gt;p 2 &gt;p 1 . 
         [0055]    When the linking pin halves  22 ,  23  are in an overlaid state, the size of the center part  24   c  of the separating pin  24  allows the center part to be housed in the hollow part  21   c  of the linking pin  21  but does not allow insertion into the hollow part  21   b.  The size of the distal part  24   b  of the separating pin  24  also prevents insertion into the hollow part  21   a  of the linking pin  21 . However, when pressure is applied and the separating pin  24  is pushed in, the center part  24   c  of the separating pin  24  is pressed into the hollow part  21   b  of the linking pin  21 , and the size of the distal part  24   b  of the separating pin  24  now allows the separating pin to be pressed into the hollow part  21   a  of the linking pin  21 . When the center part  24   c  of the separating pin  24  is pressed into the hollow part  21   b  of the linking pin  21 , and the distal part  24   b  of the separating pin  24  is pressed into the hollow part  21   a  of the linking pin  21 , the linking pin  21  is pushed apart, and the joining parts  22   a,    23   a  of the linking pin  21  are split. This causes the linking pin  21  to be separated into the linking pin halves  22 ,  23 . The separated linking pin halves  22 ,  23  are pressed against the insertion holes  103   a,    106   a  of the side plate  103  and the internal plate  106  of the segment  1  by the separating pin  24 . 
         [0056]    A method for linking segments in the longitudinal direction of the pipe using a linking tool configured in this manner will be described next. 
         [0057]    With the linking pin halves  22 ,  23  overlaid and the separating pin  24  housed inside the linking pin  21 , as shown in  FIGS. 4   a ,  4   c , the linking pin  21  is inserted into an insertion hole  103   a  in the side plate  103  of the segment  1 , as shown in  FIG. 7   a.    
         [0058]    The half-pipe parts  22   c,    23   c  of the linking pin  21  can pass through the insertion hole  103   a  of the side plate  103  of the segment  1 , and the projecting parts  22   b,    23   b  can pass through the insertion hole  106   a  of the internal plate  106 . The linking pin  21  is therefore inserted into the insertion holes  103   a,    106   a  with a predetermined spacing, as shown in  FIG. 8   a . The insertion sides (the left side) of the first protruding parts  22   d,    23   d  of the linking pin  21  are slanted, and therefore, if the separating pin  24  is forcefully pushed, the first protruding parts  22   d,    23   d  will pass through the insertion hole  103   a  due to the elasticity of the linking pin  21 , as shown in  FIG. 8   b . The distance t 1  from the boundary surface S 1  between the projecting parts  22   b,    23   b  and the half-pipe parts  22   c,    23   c  to the vertical surface S 2  of the first protruding parts  22   d,    23   d  is equal to the distance between the opposing surfaces of the side plate  103  and the internal plate  106 . The boundary surface S 1  therefore contacts the inside surface of the internal plate  106 , and the vertical surface S 2  contacts the inside surface of the side plate  103 . 
         [0059]    As shown in  FIGS. 8   c ,  8   d , when the proximal part  24   d  of the separating pin  24  is pushed in, the center part  24   c  of the separating pin  24  is pressed into the hollow part  21   b  of the linking pin  21 , and the distal part  24   b  of the separating pin  24  is pressed into the hollow part  21   a  of the linking pin  21 . The linking parts  22   a,    23   a  are then split, and the linking pin  21  is separated into the linking pin halves  22 ,  23 . The separated linking pin halves  22 ,  23  are thus pushed apart by the separating pin  24 , the projecting parts  22   b,    23   b  of the linking pin  21  are pressed against the insertion hole  106   a  of the internal plate  106 , and the half-pipe parts  22   c,    23   c  thereof are pressed against the insertion hole  103   a  of the side plate  103 . The linking pin is thereby anchored to the segment  1 . The boundary surface S 1  of the half-pipe parts  22   c,    23   c  is pressed against the inside surface of the internal plate  106  at this point, and the vertical surface S 2  of the first protruding parts  22   d,    23   d  is pressed against the inside surface of the side plate  103 . The linking pin  21  is therefore reliably anchored to the segment  1 , and the linking pin  21  can be prevented from passing back through the insertion hole  103   a  of the side plate  103  of the segment  1  and detaching therefrom. This state is also shown in  FIG. 7   b.    
         [0060]    Next, as shown in  FIGS. 8   e  and  8   f , the end opposite the inserted end of the linking pin  21 , which has been separated into the linking pin halves  22 ,  23 , is inserted into the insertion hole  102   a  of the side plate  102  of another segment  1 ′. The linking pin halves  22 ,  23  are separated and flex to the inside, and are therefore readily inserted. The side plate  102  slides over the slanted surfaces of the second protruding parts  22   e,    23   e,  and the side plate  102  of the segment  1 ′ and the linking pin  21  are snapped together and anchored. The distance between the opposing vertical surfaces S 2 , S 3  of the first protruding parts and the second protruding parts is approximately twice the thickness of the side plate  103  ( 102 ), and therefore the side plate  102  of the segment  1 ′ is anchored in a state of being pressed between the vertical surface S 3  of the second protruding parts  22   e,    23   e  and the side plate  103  of the segment  1 . The segment  1 ′ is prevented from detaching from the linking pin  21  by the second protruding parts  22   e,    23   e.  The segment  1 ′ is thus anchored to the segment  1  by the linking pin  21 , and therefore the segments  1  and  1 ′ can be firmly linked in the longitudinal direction of the pipe. 
         [0061]      FIGS. 9   a ,  9   b  show the linkage of the segments  1 ,  1 ′ via the linking tool  20  as viewed from above. 
         [0062]    The cross-section of the linking pin can be made into a hexagonal or other polygonal shape instead of a tubular shape. The shapes of the insertion holes of the internal plates and the side plates of the segments are formed accordingly in such instances. The first and second protruding parts of the linking pin may also be formed around the entirety of the linking pin in the circumferential direction or may be formed intermittently in the circumferential direction. 
         [0063]    A plurality of the insertion holes ( 102   a,    103   a,    106   a ) for the linking tool of the segments is formed along the circumferential direction of the side plates and the internal plates, as shown in  FIG. 1 . The linking tool  20  is therefore inserted into a predetermined number of the plurality of the insertion holes, and the segments are linked in the longitudinal direction of the pipe by the linking tools. However, the linking tools  20  that link the segments are short, and therefore the linkage is weak. A linking rod that extends along the width of the segment in the longitudinal direction of the pipe is therefore inserted into the insertion hole of the segment, and one end of the linking rod is joined to the other end of a linking rod that has already been anchored to another segment, as disclosed in Japanese Laid-open Patent Application No. 2005-299711. The linking rod is thereby affixed to the segment, and the segment is thereby linked to another segment in the longitudinal direction of the pipe via the linking rod. This state is shown in  FIG. 10 . 
         [0064]    Segments  1 ,  1 ′,  1 ″ are partially linked via the linking tools  20  in  FIG. 10 . A metal anchoring nut  32  is inserted into the side plate  103  of the segment  1  and the side plate  102  of the segment  1 ′. A metal bolt  33  is screwed through the internal plates  106  of the segment  1  into the anchoring nut  32 , whereby the anchoring nut  32  is anchored to the segment  1 . 
         [0065]    An axle part  31   b  of a metal linking rod  31  that extends across both of the side plates  102 ,  103  of the segment has a screw part  31   a  on one end and a nut part  31   c,  which has a screw  31   d  on the inside, on the other end. 
         [0066]    The linking rod  31  is passed through the insertion holes of the side plates and the internal plates of the segment  1 ′, and the portion of the nut part  31   c  that juts out from the side plate  103  of the segment  1 ′ is rotated, whereby the screw part  31   a  of the linking rod  31  is screwed into the anchoring nut  32 . The linking rod  31  is screwed in until the end of the nut part  31   c  on the insertion side presses against the internal plate  106 . This causes the linking rod  31  to be anchored to the segment  1 ′, and the segment  1 ′ is linked and fastened to the segment  1  by the linking rod  31 . The nut part  31   c  of the linking rod  31  of the segment  1 ′ performs the function of the anchoring nut  32  affixed to the segment  1 , and therefore the segment  1 ″ can be linked to the segment  1 ′ using another linking rod  31  in the same manner. A plurality of the segments can be sequentially linked in the longitudinal direction of the pipe via the linking rods by repetition of the same procedure. 
         [0067]    A method for rehabilitating an existing pipeline using the segments will be described below. 
         [0068]    The segments  1  are first transported into an existing pipeline  41  via a manhole  40 , as shown in  FIG. 11 . The segments  1  are then sequentially linked in the circumferential direction to assemble the pipe units  10 , as shown in  FIG. 3 . 
         [0069]    The pipe units  10  are assembled in the same manner and then linked to previously assembled pipe units  10  in the longitudinal direction of the pipe. The pipe units  10  are linked by linking the segments  1  of the pipe units  10  using the above-mentioned linking tools  20  and/or linking rods  31 . 
         [0070]    The pipe units  10  are sequentially linked in the longitudinal direction of the pipe inside the existing pipeline  41  as described above, whereby a rehabilitating pipe  42  can be laid inside the existing pipeline  41 . This state is shown in  FIG. 12 . As in  FIG. 3 , only the essential components are shown in  FIG. 12 . The linking tools, linking rods, and other means for linking in the longitudinal direction of the pipe or in the circumferential direction have been omitted in order to avoid complexity. 
         [0071]    A gap  43  is present between the outer circumferential surface of the rehabilitating pipe  42  and the inner-wall surface of the existing pipeline  41 . A grouting material or other filler is therefore poured into the gap  43  to make the rehabilitating pipe  42  and the existing pipeline  41  integrated. The assembly of the pipe unit  10  in the present embodiment is such that the end plates of the segments thereof are offset from the end plates of the segments in other pipe units, but the assembly may also be such that the respective end plates are aligned.  FIG. 9  shows an example of an assembly in which the end plates of the segments are aligned.