Abstract:
A highly durable elastic crawler with a tensile cord having both ends thereof overlapped mutually in a crawler body thus being circumferentially wound around the crawler is provided. An elastic crawler includes; a crawler body including an endless belt-like elastic body; metal cores embedded in the crawler body, each of the metal cores including vanes and arranged at predetermined intervals circumferentially; and tensile cords transversely arranged, wound around the outer circumference side of the vanes, and embedded in the crawler body while vicinity portions of both ends of the tensile cords are overlapped mutually. An inner circumference side end is arranged at an outer circumference side of any one of the vanes. The distance between the vicinity portion of the inner circumference side end and the outer circumference side portion of the tensile cord overlapped there is increased from the vicinity portion toward the inner circumference side end.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an elastic crawler in a crawler traveling device used on a civil engineering machine, a construction machine, an agricultural machine, and the like. 
     2. Description of the Related Art 
     There is known, as a traveling device such as a civil engineering machine, a crawler traveling device traveling by providing a pair of drive sprockets (drive wheels) on respective sides in one of the forward and backward directions, providing a pair of idlers (rolling wheels) on respective sides in the other direction, and causing an endless belt-like elastic crawler wound around a plurality of rollers to circulate circumferentially. 
     The elastic crawler is composed of: an endless belt-like crawler body made of an elastic material such as rubber; and transversely extensive metal cores partly embedded in the body and circumferentially arranged at uniform intervals. In view of a high tension acting on the elastic crawler in the circumferential direction, a tensile body circumferentially surrounding the ground side of the metal cores is embedded in the elastic crawler. 
     The tensile body is configured, for example, so that both ends of each of tensile cords such as steel cords are overlapped (lap-jointed) with each other in the crawler body, the tensile cords are wound by one turn in the circumferential direction of the elastic crawler and arranged in the transverse direction of the crawler. 
     In such a tensile body, the inner-side end of the tensile cord, when traveling on the drive sprockets and the idlers, is less deformable than the other parts of the tensile cord. This causes a greater strain in the elastic body between the inner-side end of the tensile cord and a part of the tensile cord outside the inner-side end. Repeated strain develops fatigue on the strained part of the elastic body to cause damage such as cracking to the strained part, resulting in facilitated removal of the elastic body off the tensile body. 
     To address this problem, Japanese Unexamined Patent Publication JP-A 2006-315432 discloses a technique to eliminate cracking on the elastic body. Here, a portion of the tensile cord immediately beside the outer-side cord of the overlapping portion where the overlapping portion turns into a single cord is bent inwardly to render the outer-side cord of the overlapping portion an inwardly inclined portion, so that the inner-side end of the tensile cord is in immediate vicinity of the inwardly inclined portion. JP-A 2006-315432 also discloses a technique to improve durability of the elastic crawler by providing bent portions inclined in the same direction on the overlapping portion in the vicinity of both ends of the tensile cord. 
     The technique of inwardly bending a portion of the tensile cord immediately beside the outer-side cord of the overlapping portion where the overlapping portion turns into a single cord, as disclosed in the JP-A 2006-315432, has the following disadvantage. A great distortion is applied to the elastic body in the vicinity of the bent portions when the ends of the tensile cord travel on the drive sprockets and the idlers of the traveling device, thus failing to provide sufficient prevention of cracks on the elastic body. 
     The technique of providing the bent portions inclined in the same direction on the overlapping portions in the vicinity of both ends of the tensile cord, as disclosed in the JP-A 2006-315432, has the following disadvantage. Since the inner-side end of the tensile cord overlaps with the outer-side tensile cord in parallel as observed in the conventional art, the strain applied to the elastic body between the inner-side end of the tensile cord and the outer-side tensile cord in the vicinity of the inner-side end cannot be reduced. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the conventional disadvantages. It is an object of the present invention to provide a highly durable elastic crawler having a tensile body with a tensile cord having both ends thereof overlapped with one another in the crawler body thus being circumferentially wound around the crawler. 
     An elastic crawler according to one aspect of the present invention includes: a crawler body including an elastic body in the form of an endless belt; a plurality of metal cores embedded in the crawler body, each of the metal cores including vanes extending toward lateral ends of the crawler body and arranged at predetermined intervals in a circumferential direction of the crawler body; and a plurality of tensile cords arranged in a transverse direction of the crawler body, wound around the circumference side of the vanes, and embedded in the crawler body while vicinity portions of both ends of each of the tensile cords are overlapped with one another. An inner circumference side end of each of the tensile cords is arranged at a circumference side of any one of the vanes. A distance between a vicinity portion of the inner circumference side end of each of the tensile cords and an outer circumference side portion of the tensile cord overlapped with an inner circumference side portion of the tensile cord is increased from the vicinity portion toward the inner circumference side end or is larger than a distance between the rest of the overlapping portions of the tensile cord. 
     Each of the tensile cords includes, for example: a first step provided in the vicinity of the inner circumference side end of the tensile cord so that the inner circumference side end is arranged further on an inner circumference side than an opposite side; and a second step provided in vicinity of a starting point so that a portion of overlapping of the outer circumference side portion of the tensile cord ranging from the starting point of overlapping or from a portion in immediate vicinity of the starting point to an outer circumference side end of the tensile cord is arranged further on an outer circumference side than a portion beside the starting point. 
     An elastic crawler according to another aspect of the present invention includes: a crawler body including an elastic body in the form of an endless belt; a plurality of lugs arranged at predetermined intervals in a circumferential direction of the crawler body and protruding outwardly from an outer surface of the crawler body; and a plurality of tensile cords arranged in a transverse direction of the crawler body and embedded in the crawler body while vicinity portions of both ends of each of the tensile cords are overlapped with one another. An inner circumference side end of each of the tensile cords is arranged at the inner circumference side of one of the lugs. A vicinity portion of the inner circumference side end of each of the tensile cords is bent so that a distance between the vicinity portion and an outer circumference side portion of the tensile cord overlapped with an inner circumference side portion of the tensile cord is increased from the vicinity portion toward the inner circumference side end. 
     An elastic crawler according to another aspect of the present invention includes: a crawler body including an elastic body in the form of an endless belt; a plurality of metal cores embedded in the crawler body, each of the metal cores including vanes extending toward lateral ends of the crawler body and arranged at predetermined intervals in a circumferential direction of the crawler body; and a plurality of tensile cords arranged in a transverse direction of the crawler body, wound around the circumference side of the vanes, and embedded in the crawler body while vicinity portions of both ends of each of the tensile cords are overlapped with one another. An inner circumference side end of each of the tensile cords is arranged at a circumference side of any one of the vanes. A distance between a vicinity portion of the inner circumference side end of each of the tensile cords and an outer circumference side portion of the tensile cord overlapped with an inner circumference side portion of the tensile cord is increased from the vicinity portion toward the inner circumference side end or is larger than a distance between the rest of the overlapping portions of the tensile cord. A distance between the inner circumference side end of each of the tensile cords and the inner circumference side end of the one of the vanes is larger than a distance between the inner circumference side portion of the tensile cord and the other vanes at the rest of the overlapping portions of the tensile cord. 
     The elastic crawler includes a plurality of lugs arranged in the circumferential direction of the crawler body and protruding outwardly at predetermined intervals from an outer surface of the crawler body. The inner circumference side end of each of the tensile cords is arranged at the inner circumference side of one of the lugs. 
     Preferably, at least one group of the plurality of tensile cords is arranged at substantially uniform intervals in the transverse direction of the crawler body, and all the inner circumference side ends of the group of the tensile cords are arranged at the inner circumference side of the one of the lugs. 
     A method of manufacturing an elastic crawler according to another aspect of the present invention includes the steps of: wrapping the inner circumference side end of each of the tensile cords along a crease of an unvulcanized sheet rubber folded into a U shape; and after the wrapping step, overlapping the outer circumference side portion of each of the tensile cords over the inner circumference side portion thereof and vulcanizing the unvulcanized sheet rubber. 
     As used herein, the “vicinity portion of the end” of each of the tensile cords refers to an extremely short portion measured from the end relative to the entire length of the tensile cord. According to the present invention, the portion is within the range of, as measured from the end, the distance between (centers of) the metal cores in the circumferential direction (moving direction of the elastic crawler mounted on the crawler traveling device), the circumferential distance between (centers of) the lugs, or larger one of the foregoing circumferential distances. 
     Thus, the present invention provides a highly durable elastic crawler having a tensile body with a tensile cord having both ends thereof overlapped with one another in the crawler body thus being circumferentially wound around the crawler. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a crawler traveling device to which an elastic crawler according to the present invention is attached. 
         FIG. 2  is a partial schematic cross-sectional side view of the elastic crawler. 
         FIG. 3  is a cross-sectional view taken along a line A-A of  FIG. 2 . 
         FIG. 4  is a cross-sectional view taken along a line B-B of  FIG. 2 . 
         FIG. 5  is a cross-sectional view taken along a line C-C of  FIG. 3 . 
         FIG. 6  is a schematic cross-sectional side view of the elastic crawler when the inner circumference side end of the tensile cord travels on the drive sprocket. 
         FIG. 7  is a partial schematic cross-sectional side view of an elastic crawler according to another embodiment of the present invention. 
         FIG. 8  is a partial schematic cross-sectional side view of an elastic crawler according to yet another embodiment of the present invention. 
         FIG. 9  is a partial schematic cross-sectional side view of an elastic crawler so that a curvature of a bent portion is set low. 
         FIG. 10  is a schematic cross-sectional side view of an elastic crawler according to yet another embodiment of the present invention. 
         FIG. 11  is a schematic diagram showing a process of manufacturing the elastic crawler. 
         FIG. 12  is a cross-sectional view taken along a line C-C of  FIG. 3  according to yet another embodiment of the present invention. 
         FIG. 13  is a partial schematic cross-sectional side view of an elastic crawler according to yet another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a side view of a crawler traveling device  2  to which an elastic crawler  1  according to the present invention is attached.  FIG. 2  is a partial schematic cross-sectional side view of the elastic crawler  1 .  FIG. 3  is a cross-sectional view taken along a line A-A of  FIG. 2 ,  FIG. 4  is a cross-sectional view taken along a line B-B of  FIG. 2 , and  FIG. 5  is a cross-sectional view taken along a line C-C of  FIG. 3 . 
     In  FIGS. 2 to 4 , a crawler body  3  is not hatched. 
     Referring to  FIG. 1 , the crawler traveling device  2  is configured to include drive sprockets (drive wheels)  4  provided on respective both sides in one of front and rear portions in a traveling direction, idlers (rolling wheels)  5  provided on respective both sides in the other portion, a plurality of rollers  6  provided on the both sides, and the elastic crawler  1  wound around the drive sprockets  4  and the like on the both sides. 
     An inner circumference side of the elastic crawler  1  when being wound around the drive sprockets  4 , the idlers  5 , and the like will be referred to as an “inner circumference side”, and an outer side (a ground surface side) thereof will be referred to as an “outer circumference side”, hereinafter. Further, a moving direction of the elastic crawler  1  when the crawler traveling device  2  travels will be referred to as “circumferential direction”, and a direction orthogonal and horizontal to the circumferential direction will be referred to as “transverse direction”, hereinafter. 
     Each of the drive sprockets  4  includes a plurality of teeth  7  on its outer circumference and makes a rotational movement by a power unit arranged in the crawler traveling device  2 . Each of the drive sprockets  4  is designed to engage the teeth  7  with engagement holes  8 , to be described later, of the elastic crawler  1  to circularly move the elastic crawler  1  in the circumferential direction of the crawler  1 , thereby traveling the crawler traveling device  2 . 
     Each of the idlers  5  freely rotates without being coupled to the power unit or the like, and folds back the elastic crawler  1  wound around the idlers  5 , thereby enabling the elastic crawler  1  to circularly move in the circumferential direction. 
     A plurality of rollers  6  is arranged side by side in a lower portion of the crawler traveling device  2  in a longitudinal direction of the device  2 . Each of the rollers  6  freely rotates and a height of the roller  6  from a traveling surface of the crawler traveling device  2  is defined by the elastic crawler  1  supported below the rollers  6 . 
     Referring to  FIGS. 2 to 5 , the elastic crawler  1  is configured to include a crawler body  3 , metal cores  9 , lugs  10 , and tensile bodies  11 . 
     The crawler body  3  serves as a base of the elastic crawler  1  formed endlessly. The crawler body  3  includes a plurality of engagement holes  8  penetrating from an inner surface  12  of the crawler body  3  to an outer surface (a ground side surface)  13  thereof and arranged equidistantly at a center of the crawler body  13  in the transverse direction over an entire circumference of the crawler body  3 . 
     The metal cores  9  are made of a hard material such as metal. Each of the metal cores  9  is arranged between the two adjacent engagement holes  8  so that a longitudinal direction of the metal core  9  is orthogonal to the circumferential direction of the crawler body  3 , and a part of the metal core  9  is embedded in the crawler body  3 . Each of the metal cores  9  is configured to include a central portion  14  that occupies the center of the crawler body  3  in the transverse direction of the crawler body  3  (hereinafter, often simply “transverse direction”), vanes  15  extending from the both sides of the central portion  14  in the transverse direction toward lateral ends of the crawler body  3 , respectively, a pair of core protrusions  16  protruding outwardly from the central portion  14  of the inner surface  12  of the crawler body  3  and arranged side by side in the transverse direction. 
     The core protrusions  16  are engaged with the drive sprockets  4 , the idlers  5 , and the rollers  6 , thereby preventing the elastic crawler  1  from being released from the drive sprockets  4 , the idlers  5 , and the rollers  6  during traveling. 
     The lugs  10  protruding outwardly from positions overlapped with the metal cores  9  in the circumferential direction are provided equidistantly over the entire circumference of the outer surface  13  of the crawler body  3 . The lugs  10  are provided in pairs in the transverse direction and each of each pair of lugs  10  extends from a position in the vicinity of an end of the engagement hole  8  to a position in the vicinity of the lateral end of the engagement hole  8  on one of the sides in the transverse direction. Each of the lugs  10  is formed so that a longitudinal direction of a ground surface (top surface)  17  of the lug  10  is not at right angle with respect to the circumferential direction but inclined therefrom at a predetermined angle. The lugs  10  are formed symmetric about arrangement of the engagement holes  8  on the both sides in the transverse direction. 
     Each of the tensile bodies  11  is configured to include a plurality of tensile cords  18  such as steel cords. The tensile bodies  11  are formed by arranging the tensile cords  18  at substantially uniform intervals in the transverse direction. Each group of tensile bodies  11  is arranged between the engagement hole  8  and both ends of the crawler body  3  in the transverse direction so as to be wound on outer circumference side of the vanes  15  of the metal core  9  and so that vicinity portions of ends  19  and  20  are overlapped with each other, and embedded in the crawler body  3  ( FIG. 2 ). Further, the vicinity portions both ends  19  and  20  of the respective tensile cords  18  of each tensile body  11  are overlapped over a distance of three to four metal cores  9  arranged in the circumferential direction. The tensile cords  18  are arranged altogether so that inner circumference side ends  19  and outer circumference side ends  20  are inclined with respect to the circumferential direction almost similarly to inclination of ground surfaces  17  of the lugs  10 . Moreover, the tensile cords  18  are arranged so that ranges of the ends  19  and  20  arranged altogether are present between the metal cores  9  and the lugs  10  ( FIG. 3 ). 
     Each of the tensile cords  18  includes, on the outer circumference side portion thereof overlapped with the vicinity portion of the inner circumference side end  19 , a bent portion  21  outwardly curved to secure a larger distance between the overlapping portions of the tensile cord  18  than that between the rest of the overlapping portions ( FIG. 2 ). The bent portions  21  are arranged side by side so that each bent portion  21  is arranged between the metal core  9  and the lug  10 . The bent portions  21  are arranged side by side so as to be inclined with respect to the circumferential direction almost similarly to the inclination of the ground surfaces  17  of the lugs  10  ( FIG. 4 ). 
     By providing the bent portions  21  on the outer circumference side portions overlapped with the vicinity portions of the inner circumference side ends  19  of the respective tensile cords  18 , a distance between the vicinity portion of the inner circumference side end  19  and the outer circumference side portion of each tensile cord  18  overlapped with the vicinity portion of the inner circumference side end  19  is increased from the vicinity portion of the inner circumference side end  19  to the inner circumference side end  19 . Preferably, the range over which the increasing distance of the vicinity portion of the inner circumference side end  19  relative to the outer circumference side portion is provided is within, as measured from the inner circumference side end  19 , a larger one of the distance between the centers of two adjacent metal cores  9  in the circumferential direction and the distance between the centers of the lugs  10 . 
     Moreover, the inner circumference side end  19  of each tensile cord  18  is arranged between the bent portion  21  and the metal core  9 . 
     Preferably, the distance between the bent portion  21  and the inner circumference side portion of the tensile cord  18  satisfies b 1 ≧1.5×a 1  and c 1 ≦3.5×a 1 , where a 1  denotes the distance between the rest of the overlapping portions, b 1  denotes the distance between the bent portion  21  and the inner circumference side portion at the portion where the inner circumference side portion starts overlapping with the metal core  9 , and c 1  denotes the largest distance between the bent portion  21  and the inner circumference side portion. 
     In the case where the tensile bodies  11  are formed so that the overlap distance is gradually increased from the portions at which the overlap starts toward the end, the difference in strain between the outer circumference side portion and the inner circumference side portion of the tensile body  11  during bending and a strain between the both ends generated due to the difference in bending curvature therebetween can be alleviated. 
       FIG. 6  is a schematic cross-sectional side view of the elastic crawler  1  when the inner circumference side end  19  of the tensile cord  18  travels on the drive sprocket  4 . 
     The elastic crawler  1  is wound around the drive sprockets  4 , the idlers  5 , and a plurality of rollers  6 , and circularly moves around the drive sprockets  4 , the idlers  5 , and the rollers  6  by rotation of the drive sprockets  4 , thereby moving the crawler traveling device  2  forward or backward. The tensile bodies  11  are bent into a generally semicircular shape when the elastic crawler  1  travels on the drive sprockets  4  and the idlers  5 . When the elastic crawler  1  travels on the drive sprockets  4  and the idlers  5 , the continuous portion excluding the vicinity portions of the ends  19  and  20  of each tensile cord  18  equally receive the same bending moment and are curved at almost the same curvature. On the other hand, when the inner circumference side end  19  of the tensile cord  18  travels on the drive sprockets  4  or the idlers  5 , a bending moment applied to the vicinity portion of the inner circumference side end  19  is lower than that applied to the continuous portions. A bending degree of the vicinity portion of the inner circumference side end  19  is smaller than that of the portion continuous from the vicinity portion (see a broken line shown in  FIG. 6 ). 
     One cause for the conventional problems, i.e., the cracking due to the fatigue of the elastic body in the elastic crawler, the release of the elastic body from the tensile bodies  11 , and the like is excessive compression of the elastic body due to less flexibility of the vicinity portion of the inner circumference side end  19  of the tensile cord  18 . 
     In the elastic crawler  1 , the bent portion  21  is provided on the outer circumference side portion of the tensile cord  18  in the vicinity of the inner circumference side end  19  of the tensile cord  18  to secure a larger distance between the tensile cord  18  and the vicinity portion of the inner circumference side end  19  of the tensile cord  18 . 
     Due to this, as shown in  FIG. 6 , the thickness of an elastic body E 1  filled up between the vicinity of the inner circumference side end  19  and the outer circumference side portion of the tensile cord  18  is large as compared with the thickness in the case where the bent portion  21  is not provided. A compressive strain (thickness change/thickness) generated in the elastic body E 1  when the inner circumference side end  19  of the tensile cord  18  travels on the drive sprocket  4  or the idler  5  is smaller if the thickness is larger. Therefore, the elastic crawler  1  can reduce a degree of the compressive strain repeatedly generated in the elastic body E. Further, the elastic body E 1  is thicker around the inner circumference side end  19  of the tensile cord  18 , so that it is possible to avoid concentration of a compressive stress on a specific region of the elastic body E. 
     In this manner, by reducing the compressive strain, the elastic crawler  1  can reduce the stress generated in the elastic body E 1 , and relax the adverse effect of the concentration of the generation of the compressive stress on a specific narrow range. Since the fatigue of the elastic body E 1  can be reduced, the elastic crawler  1  can ensure high fatigue resistance. 
     Moreover, the elastic crawler  1  is formed so that all the inner circumference side ends  19  of the tensile cords  18  are arranged at the inner circumference side of (on the inner circumference side relative to) the lugs  10 . The portion where each lug  10  is provided has high rigidity because of the thickness of the lug  10 , and is subjected to a smaller compressive strain when each tensile cord  18  travels on the drive sprocket  4  or the idler  5  or is grounded on a surface having many irregularities. The elastic crawler  1  in which the inner circumference side ends  19  of the tensile cords  18  are arranged in the portions where the lugs  10  are provided can suppress the compressive strain of the elastic body in the vicinity of the tensile cords  18 , reduce the fatigue of the elastic body, and ensure high durability. 
     The elastic crawler  1  is configured so that the inner circumference side ends  19  and the bent portions  21  of the tensile cords  18  are arranged between the lugs  10  and the vanes  15 . Even in the case where the inner circumference side ends  19  and the bent portions  21  of the tensile cords  18  are arranged to satisfy the requirement of arranging the inner circumference side ends  19  and the bent portions  21  at the inner circumference side of the lugs  10  or at the outer circumference side of the vanes  15  or arranged not to satisfy either requirements, the inner circumference side ends  19  and the bent portions  21  are overlapped with one another to increase the thickness of the elastic body E 1  therebetween. It is thereby possible to obtain a certain effect of improvement in durability. 
       FIG. 7  is a partial schematic cross-sectional side view of an elastic crawler  1 B according to another embodiment of the present invention. 
     The elastic crawler  1 B is configured to include a crawler body  3 , metal cores  9 , lugs  10 , and tensile bodies  11 B. The crawler body  3 , the metal cores  9 , and the lugs  10  are similar to those of the elastic crawler  1  according to the previous embodiment. In  FIG. 7 , the crawler body, the metal cores, and the lugs are denoted by the same reference symbols as those according to the elastic crawler  1  of the previous embodiment and will not be described. 
     Each of the tensile bodies  11 B is configured to include a plurality of tensile cords  18 B such as steel cords aligned in the transverse direction. Each of the tensile bodies  11 B is arranged so that both ends  19 B and  20 B are inclined with respect to the circumferential direction almost similarly to the inclination of the ground surface  17  of each of the lugs  10  and so that each of the ends  19 B and  20 B is arranged between the lug  10  and the metal core  9 . Further, the tensile cords  18 B of each tensile body  11 B are arranged side by side so that the both ends  19 B and  20 B are inclined with respect to the circumferential direction almost similarly to the inclination of the ground surface  17  of each lug  10  and so that each of the both ends  19 B and  20 B is arranged between the metal core  9  and the lug  10 . Arrangement of the ends  19 B and  20 B is similar to that of the ends  19  and  20  in the elastic crawler  1 . 
     Portions continuous to the ends  19 B and  20 B of the tensile cords  18 B are overlapped over a distance of three to four metal cores  9  arranged in the circumferential direction. The inner circumference side end  19 B of the tensile cord  18 B is inclined toward the metal core  9  (the inner circumference side) in a range from the inner circumference side end  19 B to a length generally corresponding to or smaller than a width of the metal core  9  in the circumferential direction so as to be closer to the metal core  9  side between the metal core  9  and the lug  10 . An inclination angle θ 1  in the vicinity of the inner circumference side end  19 B is preferably 2 to 15 degrees with respect to a portion of the tensile cord  18 B before inclination in a state (in which the inner circumference side end  19 B does not travel on the drive sprocket  4  or the like) shown in  FIG. 7 . 
     In this manner, by inclining the vicinity portion of the inner circumference side end  19 B of each tensile cord  18 B relative to the outer circumference side portion of the tensile cord  18 B, the distance between the vicinity portion and the outer circumference side portion of the tensile cord  18 B overlapped with the vicinity portion is increased from the vicinity portion toward the inner circumference side end  19 B. Furthermore, by increasing the distance between the vicinity portion of the inner circumference side end  19 B and the outer circumference side portion of the tensile cord  18 B to increase the thickness of an elastic body E 2  therebetween, the elastic crawler  1 B can reduce a compressive strain of the elastic body E 2  in the vicinity of the inner circumference side end  19 B, which is difficult to bend when traveling on the drive sprocket  4  or the like, and realize improvement in fatigue resistance. 
     Constituent elements of the tensile cord  18 B other than those described above are almost similar to those of the tensile cord  18  of the elastic crawler  1 . 
     Preferably, the range over which the increasing distance between the vicinity portion of the inner circumference side end  19 B and the outer circumference side portion of the tensile cord  18 B toward the inner circumference side end  19 B is provided as measured from the inner circumference side end  19 B is within a maximum distance, which is a larger one of the distance between the centers of two adjacent metal cores  9  in the circumferential direction and the distance between the centers of the lugs  10 . 
       FIG. 8  is a partial schematic cross-sectional side view of an elastic crawler  1 C according to yet another embodiment of the present invention. 
     In the elastic crawler  1 C, configurations of a crawler body  3  except for tensile bodies  11 C, metal cores  9 , and lugs  10  are almost similar to those of the elastic crawler  1 . In  FIG. 8 , the same constituent elements of the elastic crawler  1 C as those of the elastic crawler  1  are denoted by the same reference symbols and will not be described herein. 
     Each of the tensile cords  18 C constituting each tensile body  11 C includes a bent portion  21 C outwardly bent on the outer circumference side portion of the tensile cord  18 C overlapped with a vicinity portion of an inner circumference side end  19 C, similarly to the tensile cords  18 . The bent portions  21 C are arranged side by side so that each bent portion  21 C is arranged between the metal core  9  and the lug  10 . A range of the bent portions  21 C in the transverse direction is inclined with respect to the circumferential direction almost similarly to the inclination of the ground surface  17  of the lug  10 . The inner circumference side end  19 C of the tensile cord  18 C is arranged between the bent portion  21 C and the metal core  9 . The vicinity portion of the inner circumference side end  19 C is inclined toward the bent portion  21 C (outer circumference side). 
     As a result of inclination of the vicinity portion of the inner circumference side end  19 C toward the outer circumference side so as to be closer to the bent portion  21 C, a distance between the inner circumference side end  19 C of each tensile cord  18 C and the vane  15  arranged at the inner circumference side of the inner circumference side end  19 C is larger than the distance between the inner circumference side portion of the tensile cord  18 C and the other vanes  15  at the rest of the overlapping portions of the tensile cord  18 C. 
     An inclination angle θ 2  of the vicinity portion of the inner circumference side end  19 C is preferably 2 to 10 degrees with respect to a portion of the tensile cord  18 C before inclination. For a largest distance c 2  of the bent portion  21 C relative to a distance a 2  in the rest of the overlapping portions, the preferable range specified for c 1  relative to a 1  for the elastic crawler  1  applies here. 
     Each of the tensile cords  18 C of the elastic crawler  1 C includes the bent portion  21 C on the outer circumference side portion of the tensile cord  18 C, and the vicinity portion of the inner circumference side end  19 C of the tensile cord  18 C is inclined toward the outer circumference side. By doing so, the distance between the vicinity portion of the inner circumference side end  19 C and the outer circumference side portion of the tensile cord  18 C (bent portion  21 C) is larger to increase the thickness of an elastic body E 3  therebetween. Furthermore, the distance between the vicinity portion of the inner circumference side end  19 C and the vane  15  (metal core  9 ) is larger to increase the thickness of an elastic body E 4  therebetween. As a result, the elastic crawler  1 C can reduce a compressive strain of the elastic bodies in the vicinity of the inner circumference side end  19 C, which is difficult to bend when traveling on the drive sprocket  4  or the like, and realize improvement in fatigue resistance. Moreover, since the elastic bodies around the inner circumference side end  19 C are thick, it is possible to relax a movement of the inner circumference side end  19 C and thereby relax an influence of a protrusion (compression) of the inner circumference side end  19 C. 
     Furthermore, similarly to the elastic crawlers  1  and  1 B, the elastic crawler  1 C is configured so that the distance between the vicinity portion of the inner circumference side end  19 C of each tensile cord  18 C and the outer circumference side portion of the tensile cord  18 C overlapped with the vicinity portion is increased from the vicinity portion toward the inner circumference side end  19 C. Preferably, the range over which the increasing distance of the vicinity portion of the inner circumference side end  19 C relative to the outer circumference side portion is provided is within, as measured from the inner circumference side end  19 C, a larger one of the distance between the centers of two adjacent metal cores  9  in the circumferential direction and the distance between the centers of the lugs  10 . A combination of a curvature and a length of each bent portion  21 C and a degree of the inclination of the vicinity portion of the inner circumference side end  19 C is selected to satisfy these requirements. 
     Constituent elements of the tensile cord  18 C other than those described above are almost similar to those of the tensile cord  18  of the elastic crawler  1 . 
       FIG. 9  is a partial schematic cross-sectional side view of an elastic crawler  1 D configured, as compared with the elastic crawler  1 C, so that the curvature of the bent portion  21 C is set low. 
     In the elastic crawler  1 D, similarly to the elastic crawler  1 C, the thickness of an elastic body E 3 ′ between a vicinity portion of an inner circumference side end  19 D of each tensile cord  18 D and a bent portion  21 D thereof and the thickness of an elastic body E 4 ′ between the vicinity portion of the inner circumference side end  19 D of each tensile cord  18 D and the metal core  9  are larger than those of the rest of the overlapping portions. Therefore, similarly to the elastic crawler  1 C, it is possible to reduce compressive strains of the elastic bodies E 3 ′ and E 4 ′ and to improve fatigue resistance of the elastic crawler  1 D. 
     In  FIG. 9 , the same constituent elements of the elastic crawler  1 D as those of the elastic crawler  1 C are denoted by the same reference symbols shown in  FIG. 8 . 
       FIG. 10  is a schematic cross-sectional side view of an elastic crawler  1 E according to yet another embodiment of the present invention. 
     In the elastic crawler  1 E, configurations of a crawler body  3  except for tensile bodies  11 E, metal cores  9 , and lugs  10  are almost similar to those of the elastic crawler  1 . In  FIG. 10 , the same constituent elements of the elastic crawler  1 E as those of the elastic crawler  1  are denoted by the same reference symbols and will not be described herein. 
     Each of tensile cords  18 E constituting each of the tensile bodies  11 E has a step (outer step)  22 E formed on the outer circumference side portion of the tensile cord  18 E overlapped with a vicinity portion of an inner circumference side end  19 E of the tensile cord  18 E. The tensile cord  18 E is deviated toward the outer circumference side over the outer step  22 E and closer to the outer surface  13  of the crawler body  3 , and the deviated state continues to an outer circumference side end  20 E of the tensile cord  18 E. Namely, a portion starting being overlapped with the vicinity portion of the inner circumference side end  19 E up to the outer circumference side end  20 E of the outer circumference side portion of the tensile cord  18 E is farther away from the inner surface  12  of the crawler body  3  than the portion behind the overlap-starting portion. 
     A step (an inner step)  23 E is formed in the vicinity of the inner circumference side end  19 E of each tensile cord  18 E for making the inner circumference side portion of the tensile cord  18 E closer to the outer circumference side portion of the tensile cord  18 E over an area in the vicinity of the outer circumference side end  20 E. Further, a step (end step)  24 E is formed in the vicinity of the inner circumference side end  19 E of each tensile cord  18 E for returning to the original position of the tensile cord  18 E behind the inner step  23 E. A predetermined distance c 3  is formed between the inner circumference side end  19 E of each tensile cord  18 E and the outer circumference side portion of the tensile cord  18 E overlapped with the inner circumference side end  19 E. 
     Similarly to the elastic crawlers  1  and  1 B to  1 D, the elastic crawler  1 E is configured so that the distance between the vicinity portion of the inner circumference side end  19 E of each tensile cord  18 E and the outer circumference side portion of the tensile cord  18 E overlapped with the inner circumference side end  19 E is increased from the vicinity portion of the inner circumference side end  19 E toward the inner circumference side end  19 E. The range over which the increasing distance between the vicinity portion of the inner circumference side end  19 E and the outer circumference side portion of the tensile cord  18 E toward the inner circumference side end  19 E is provided as measured from the inner circumference side end  19 E is within a maximum distance, which is a larger one of the distance between the centers of two adjacent metal cores  9  in the circumferential direction and the distance between the centers of the lugs  10 . 
     The elastic crawler  1 E is similar to the elastic crawlers  1  and  1 B to  1 D in that the inner circumference side ends  19 E of the respective tensile cords  18 E are arranged side by side so as to be arranged between the metal cores  9  and the lugs  10 . 
     In the elastic crawler  11 E, by providing the outer step  22 E, the inner step  23 E, and the end step  24 E in each tensile cord  18 E, the thickness of an elastic body E 5  between the vicinity portion of the inner circumference side end  19 E of each tensile cord  18 E and the outer circumference side portion of the tensile cord  18 E can be made larger than that of the rest of the overlapping portions. Therefore, for the same reason as those for the elastic crawlers  1  and  1 B to  1 D, it is possible to improve fatigue resistance of the elastic crawler  1 E. 
     For a distance c 3  between the inner circumference side end  19 E and the outer circumference side portion of the tensile cord  18 E relative to a distance a 3  in the overlapping portions of the tensile cord  18 E, the preferable range specified for c 1  relative to a 1  for the elastic crawler  1  applies here. 
       FIG. 11  is a schematic diagram showing a process of manufacturing the elastic crawler  1 . 
     Referring to  FIG. 11 , to manufacture the tensile body  11 , vicinity portions of the inner circumference side ends  19  of the tensile cords  18  arranged in line are put between both sides of an unvulcanized sheet rubber  25  folded into a U shape. The vicinity portions of the inner circumference side ends  19  of the tensile cords  18  put between both sides of the unvulcanized sheet rubber  25  are arranged at an outer circumference side of any one of the metal cores  9  so as to put one side of the U-shaped bent rubber  25  between the vicinity portions and the metal core  9 . The outer circumference side portion of each of the tensile cords  18  is overlapped over the inner circumference side portion of the tensile cord  18  so that the bent portion  21  is arranged at an outer circumference side of the inner circumference side end  19  of the tensile cord  18  via the rubber  25 . 
     The elastic crawler  1  is manufactured by subsequently vulcanizing the rubber  25  to make the rubber  25  elastic. 
     Each of the ends of all the tensile cords  18  constituting the tensile body  11  is put between the two sides of the unvulcanized U-shaped bent rubber  25 , thereby making it advantageously possible to relax the compressive stresses applied to the ends of all the tensile cords  18  as a whole. Furthermore, since it suffices to use only one component, it is efficient to enable high operatively. 
     On the other hand, in the case where, for example, the ends of some of the tensile cords  18  are put between the two sides of the unvulcanized sheet rubber  25  folded into a U shape, portions on which the stress concentrates during bending are disadvantageously generated due to differences in expansion, compression, strain, and the like among different types of rubber having different vulcanization histories. 
     The manufacturing of the elastic crawler  1  using the unvulcanized sheet rubber bent into the U-shape is applicable to manufacturing of the other elastic crawlers  1 B to  1 E and that of similar elastic crawlers. 
     In the embodiments, the present invention can be applied to elastic crawlers  1 F and  1 G different in arrangement, shapes, and the like of the metal cores  9 , the lugs  10 , and the like. 
     For example, as shown in  FIG. 12 , lugs  10 F may be arranged circumferentially and alternately only on one side of the engagement holes  8  in the transverse direction, and all of ends  19 F of the inner circumference side portions of the tensile cords  18 F constituting the tensile bodies  11 F and all of bent portions  21 F on the outer circumference side portions of the tensile cords  18 F may be arranged at the inner circumference side of a single lug  10 F. All of outer circumference side ends  20 F of the tensile cords  18 F are also arranged at the inner circumference side of a single lug  10 F. In FIG.  12 , the same constituent elements of the elastic crawler  1 F as those of the elastic crawler  1  are denoted by the same reference symbols as those denoting the respective constituent elements. 
     Moreover, as shown in  FIG. 13 , in an elastic crawler  1 G in which the lugs  10 F are provided alternately in the transverse direction as shown in  FIG. 12 , a vicinity portion of an end  19 G of the inner circumference side portion of the tensile cord  18 G may be inclined inwardly. In this case, an inclination angle θ 1  is preferably 2 to 15 degrees with respect to a portion of the tensile cord  18 G before inclination, similarly to the inclination angle of the elastic crawler  1 B. In  FIG. 13 , the same constituent elements of the elastic crawler  1 G as those of the elastic crawler  1  or  1 F are denoted by the same reference symbols as those denoting the respective constituent elements. 
     Furthermore, it is possible to appropriately change the crawler traveling device  2  and the elastic crawlers  1  and  1 B to  1 G and the respective configurations or overall structure, shapes, dimensions, numbers, materials and the like of the crawler traveling device  2  and the elastic crawlers  1  and  1 B to  1 G, within the scope of the present invention. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be used for an elastic crawler in a crawler traveling device used as a civil engineering machine, a construction machine, an agricultural machine or the like.