Patent Publication Number: US-2018036901-A1

Title: Guide bar of chain saw

Description:
TECHNICAL FIELD 
     The present invention relates to a guide bar of a chain saw for use in, for example, felling and cutting of trees. 
     BACKGROUND ART 
     Chain saws are operated by workers and used for, for example, felling and cutting of trees. Conventionally, it has been sought to reduce the weight of the guide bar of chain saws for the purpose of improving the usability of the chain saws for the workers (see Patent Literatures 1 to 4, for example). 
     In order to realize weight reduction of the guide bar, the guide bar is manufactured, for example, in the following manner: form a large number of recesses by cutting in both surfaces of the guide bar body, which is made of a metal plate; fill the recesses with a resin; and after the resin is cured, grind the resin surfaces to make the resin surfaces flush with the guide bar body. 
     CITATION LIST 
     Patent Literature 
     PTL 1: Japanese Utility Model Registration No. 2502986 
     PTL 2: Japanese Utility Model Registration No. 2502991 
     PTL 3: U.S. Pat. No. 4,837,934 
     PTL 4: U.S. Pat. No. 5,025,561 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, in the above case, the cutting process for forming the large number of recesses takes a long time, and in addition, after the resin is cured, the resin surfaces need to be ground. For these reasons, the manufacturing time of the guide bar is long, and the manufacturing cost is high. 
     The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a guide bar of a chain saw with a reduced weight, the guide bar making it possible to reduce its manufacturing time and manufacturing cost. 
     Solution to Problem 
     In order to achieve the above-described object, a guide bar of a chain saw according to one embodiment of the present invention includes: an elongated plate-shaped guide bar body that supports a saw chain on its peripheral edge portion; a plurality of elongated holes formed through the guide bar body and positioned at both sides of a region that has a predetermined width and includes a central axis line extending in a longitudinal direction of the guide bar body, such that the region is positioned between the elongated holes, which are elongated in the longitudinal direction; and a plurality of attachment members, each of which is pre-formed in such a shape as to seal up a corresponding one of the elongated holes and attached to the corresponding elongated hole. 
     Advantageous Effects of Invention 
     The present invention is configured as described above, and has an advantage of being able to provide a guide bar of a chain saw with a reduced weight, the guide bar making it possible to reduce its manufacturing time and manufacturing cost. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a front view showing one example of a guide bar of a chain saw according to one embodiment of the present invention. 
         FIG. 2A  to  FIG. 2E  are each a sectional view showing one example of attachment members. 
         FIG. 3  is a sectional view showing one example of the attachment members. 
         FIG. 4  is a front view of an essential part of the guide bar, showing a first variation of a guide bar body. 
         FIG. 5A  to  FIG. 5E  are each a sectional view showing one example of the attachment members when the guide bar body shown in  FIG. 4  is used. 
         FIG. 6A  to  FIG. 6C  are each a sectional view showing one example of the attachment members when the guide bar body shown in  FIG. 4  is used. 
         FIG. 7  is a front view of an essential part of the guide bar, showing a second variation of the guide bar body. 
         FIG. 8  is a sectional view showing one example of the attachment members when the guide bar body shown in  FIG. 7  is used. 
         FIG. 9  is a front view of an essential part of the guide bar, showing a third variation of the guide bar body. 
         FIG. 10  is a sectional view showing one example of the attachment members when the guide bar body shown in  FIG. 9  is used. 
         FIG. 11  is a front view of an essential part of the guide bar, showing a fourth variation of the guide bar body. 
         FIG. 12  is a sectional view showing one example of the attachment members when the guide bar body shown in  FIG. 11  is used. 
         FIG. 13  is a front view of the guide bar, showing a fifth variation of the guide bar body. 
         FIG. 14  is a front view of the guide bar, showing a sixth variation of the guide bar body. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, one embodiment of the present disclosure is described with reference to the drawings. 
     The embodiment described below indicates specific examples of the present disclosure. Therefore, numerical values, shapes, materials, components, the arrangement and the manner of connection of the components, etc., indicated in the embodiment below are mere examples, and do not limit the scope of the present disclosure. 
     In the drawings, the same or corresponding components are denoted by the same reference signs, and repeating the same descriptions is avoided in some cases. The drawings show each component schematically in order to facilitate the understanding thereof. Therefore, in some cases, the drawings may not display precise shapes, dimensional ratios, etc. 
     Embodiment 
     A guide bar of a chain saw according the present embodiment includes: an elongated plate-shaped guide bar body that supports a saw chain on its peripheral edge portion; a plurality of elongated holes formed through the guide bar body and positioned at both sides of a region that has a predetermined width and includes a central axis line extending in a longitudinal direction of the guide bar body, such that the region is positioned between the elongated holes, which are elongated in the longitudinal direction; and a plurality of attachment members, each of which is pre-formed in such a shape as to seal up a corresponding one of the elongated holes and attached to the corresponding elongated hole (see  FIG. 1 ,  FIG. 13 , and  FIG. 14 , for example). 
     According to the above configuration, weight reduction can be realized by using light-weight components made of, for example, a resin as the attachment members. Regarding the number of elongated holes to be formed, it will suffice if, for example, one elongated hole is formed at each side of the region that has the predetermined width and includes the central axis line. In this case, the pre-formed attachment members are required to be attached to only two positions (i.e., two elongated holes). This makes it possible to reduce the manufacturing time and manufacturing cost. 
     In the above guide bar, the attachment members may be fitted in the elongated holes, and each attachment member may be joined to opening edges of the corresponding elongated hole (see  FIGS. 2A to 2E  and  FIG. 3 , for example). 
     In the above guide bar, each attachment member may include two pieces of sheet metal that are disposed at both ends of the corresponding elongated hole in a thickness direction of the guide bar body. The two pieces of sheet metal and the opening edges of the elongated hole may be joined together by welding (see  FIGS. 2A to 2C , for example). 
     In the above guide bar, each attachment member may further include one or more components disposed between the two pieces of sheet metal, the one or more components each having a shape that is the same as a cross-sectional shape of the corresponding elongated hole (see  FIGS. 2A and 2B , for example). 
     In the above guide bar, chamfered portions may be: formed on portions of each attachment member, the portions contacting the opening edges of the corresponding elongated hole; and/or formed on the opening edges of the elongated hole. Each attachment member and the opening edges of the corresponding elongated hole may be joined together by filling the chamfered portions with an adhesive (see  FIGS. 2D and 2E , for example). 
     In the above guide bar, each attachment member may be formed by a single component having a shape that is the same as a cross-sectional shape of the corresponding elongated hole. The single component may be fitted in the elongated hole, and the single component and the opening edges of the elongated hole may be joined together by laser welding (see  FIG. 3 , for example). 
     In the above guide bar, the guide bar body may include sandwiched portions, each of which is formed by either a projecting portion or a beam portion, the projecting portion extending inward from a side wall of each elongated hole, the beam portion connecting between opposite parts of the side wall of the elongated hole. Each attachment member may include first and second components, between which a corresponding one of the sandwiched portions is sandwiched from both sides (see  FIGS. 4 to 12 , for example). 
     In the above guide bar, surfaces of the first and second components, the surfaces contacting the corresponding sandwiched portion, may be flat, and a gap between the first and second components may be filled with an adhesive (see  FIGS. 5A and 5B , for example). 
     In the above guide bar, a plurality of holes may be formed through each sandwiched portion in its thickness direction, and the holes may be filled with the adhesive (see  FIGS. 7 and 8 , for example). 
     In the above guide bar, each sandwiched portion may be formed by a plurality of the projecting portions arranged at intervals in a circumferential direction of the elongated hole (see  FIG. 9 , for example). 
     In the above guide bar, the first component may be provided with a plurality of holes formed therein, which are arranged at intervals in the longitudinal direction. The second component may be provided with a plurality of protrusions formed thereon, which are fitted in the respective holes of the first component (see  FIG. 5C , for example). 
     In the above guide bar, the first component may be provided with a plurality of holes formed therein, which are arranged at intervals in the longitudinal direction. The second component may be provided with a plurality of protrusions formed thereon, which are inserted through the respective holes of the first component such that portions of the protrusions stick out of the holes. The portions of the protrusions, which stick out of the holes, may be joined to the first component by friction stir welding (see  FIG. 5D , for example). 
     In the above guide bar, the first component may be provided with a plurality of holes formed therein, which are arranged at intervals in the longitudinal direction. The second component may be provided with holes formed therein, which are positioned corresponding to the respective holes of the first component. The first component and the second component may be joined together by press-fitting a single shaft into each hole of the first component and press-fitting the single shaft into the corresponding hole of the second component (see  FIG. 5E , for example). 
     In the above guide bar, the guide bar body may include projecting portions, each of which extends inward from a side wall of a corresponding one of the elongated holes. Each attachment member may include: first and second components, between which a corresponding one of the projecting portions is sandwiched from both sides; and two pieces of sheet metal disposed outside the first and second components, respectively. The two pieces of sheet metal and opening edges of the corresponding elongated hole may be joined together by welding (see  FIGS. 6A to 6C , for example). 
     In the above guide bar, surfaces of the first and second components, the surfaces contacting the corresponding sandwiched portion (projecting portion), may be flat, and a gap between the first and second components may be filled with an adhesive (see  FIG. 6B , for example). 
     In the above guide bar, the first component and the second component may contact each other. A surface of the first component, the surface contacting the second component, may be provided with a recess formed therein. A surface of the second component, the surface contacting the first component, may be provided with a protrusion formed thereon, the protrusion being press-fitted in the recess (see  FIG. 6C , for example). 
     In the above guide bar, the plurality of elongated holes may be formed such that, at each side of the region having the predetermined width and including the central axis line, one elongated hole is formed along the region having the predetermined width, and a length of the one elongated hole in the longitudinal direction may be not less than ⅓ of an overall length of the guide bar body (see  FIG. 1 , for example). Alternatively, the plurality of elongated holes may be formed such that, at each side of the region having the predetermined width, multiple elongated holes are formed along the region having the predetermined width, and a total length of the multiple elongated holes in the longitudinal direction may be not less than ⅓ of the overall length of the guide bar body (see  FIG. 13  and  FIG. 14 , for example). 
     Specific Configuration Examples 
       FIG. 1  is a front view showing one example of a guide bar of a chain saw according to the present embodiment. It should be noted that an arrow-x direction indicates the longitudinal direction of the guide bar, and an arrow-y direction indicates the width direction of the guide bar. Also, the direction perpendicular to both the arrow-x direction and the arrow-y direction (i.e., the direction perpendicular to the plane of  FIG. 1 ) is the thickness direction of the guide bar. 
     The guide bar includes: an elongated plate-shaped guide bar body  1 ; a plurality of elongated holes  2   a  and  2   b , which are formed through the guide bar body  1  and elongated in the longitudinal direction of the guide bar body  1 ; a plurality of attachment members  3 , each of which is pre-formed in such a shape as to seal up a corresponding one of the elongated holes  2   a  and  2   b  and attached to the corresponding one of the elongated holes  2   a  and  2   b.    
     A proximal end portion  1 R of the guide bar body  1  is provided with, for example, round holes  6  and an elongated hole  7  for enabling engagement with a chain saw body (not shown) so that the proximal end portion  1 R can be attached to the chain saw body. A guide groove  4  (see  FIG. 2A , for example) for guiding a saw chain (not shown) is formed along the outer periphery of the guide bar body  1 . That is, the saw chain is supported by the peripheral edge portion of the guide bar body  1 . 
     In the example of  FIG. 1 , the guide bar body  1  is configured such that, for example, a distal end portion  1   b  is fixed to a body portion  1   a  made of a steel plate. A sprocket  5  is mounted to the distal end of the distal end portion  1   b , and the distal end portion  1   b  is replaceable together with the sprocket  5 . It should be noted that the distal end portion  1   b , which includes the sprocket  5 , and the body portion  1   a  may be integrated together. Alternatively, the distal end portion  1   b  and the body portion  1   a  may be integrated together without including the sprocket  5 . 
     The two elongated holes  2   a  and  2   b  are formed through the guide bar body  1 , and are positioned at both sides of a central axial portion  1   c , which is a region having a predetermined width L 3  and including a central axis line CL extending in the longitudinal direction of the guide bar body  1 , such that the central axial portion  1   c  is positioned between the two elongated holes  2   a  and  2   b . Thus, the elongated holes  2   a  and  2   b  are formed at both sides of the central axis line CL in such a manner that a predetermined distance (L 3 ) is present between the elongated holes  2   a  and  2   b , and thereby the central axial portion  1   c  of the guide bar body  1  is formed. 
     The thickness of the guide bar body  1  excluding the elongated holes  2   a  and  2   b  is uniform in a region that is indicated by a length L 2  in the longitudinal direction. Thus, the thickness of the region that includes at least the central axial portion  1   c  and the entire peripheral portions of the respective elongated holes  2   a  and  2   b , the entire peripheral portions serving as the side walls of the respective elongated holes  2   a  and  2   b , is uniform. Each of the elongated holes  2   a  and  2   b  is formed such that, except their both end portions in the longitudinal direction, the distance between the outer edge of each of the elongated holes  2   a  and  2   b  and the outer peripheral edge of the guide bar body  1  is constant as indicated by distances L 4  in the drawing. As a result, the section modulus of the guide bar body  1  in its elongated hole formation region, except both the end portions of each of the elongated holes  2   a  and  2   b  in the longitudinal direction, is substantially constant, which makes it possible to prevent the bending strength from varying. 
     Next, examples of the attachment members  3  attached to the elongated holes  2   a  and  2   b  are described. Each of  FIG. 2A  to  FIG. 2E  and  FIG. 3  shows an example of the attachment members  3 , and shows a sectional view taken along a line A-A of  FIG. 1 . 
     Each attachment member  3  of  FIG. 2A  is formed by two thin metal plates (two pieces of sheet metal)  11  and a light-weight component  12  sandwiched between the thin metal plates  11 . The light-weight component  12  is made of, for example, a synthetic resin, and is formed in a shape that matches the shape of each of the elongated holes  2   a  and  2   b . The light-weight component  12  is fitted in each of the elongated holes  2   a  and  2   b . The metal plates  11  are each formed in a shape that matches the shape of each of the elongated holes  2   a  and  2   b , and the metal plates  11  are fitted to each of the elongated holes  2   a  and  2   b  in such a manner that the metal plates  11  are in contact with respective opening edges on both sides of the hole. The peripheral portion of each metal plate  11  is fixed to the guide bar body  1  by laser welding or the like. For example, aluminum plates or steel plates are used as the metal plates  11 . Also, as the light-weight component  12 , for example, a resin member with a honeycomb structure may be used, and thereby the weight can be further reduced. Alternatively, a light metal member with a honeycomb structure may be used as the light-weight component  12 . 
     Each attachment member  3  of  FIG. 2B  is formed by two thin metal plates  11  and three light-weight components  13  and  14  (two light-weight components  13  and one light-weight component  14 ) sandwiched between the thin metal plates  11 . These light-weight components  13  and  14  are formed by light-weight members made of, for example, a resin or aluminum, and are each formed in a shape that matches the shape of each of the elongated holes  2   a  and  2   b . The metal plates  11  are fixed to the guide bar body  1  in a manner similar to the case of  FIG. 2A . 
     Each attachment member  3  of  FIG. 2C  is formed only by two thin metal plates  11 , between which a void  15  is formed. The metal plates  11  are fixed in a manner similar to the case of  FIG. 2A . 
     In the case of  FIG. 2D , chamfered portions  18  are formed around the opening edges on both sides of each of the elongated holes  2   a  and  2   b . Each attachment member  3  is formed by a light-weight component  16 , which is made of, for example, a synthetic resin and formed in a shape that matches the shape of each of the elongated holes  2   a  and  2   b . The light-weight component  16  is inserted in each of the elongated holes  2   a  and  2   b , and these light-weight components  16  are fixed to the guide bar body  1  by an adhesive  19  applied to the chamfered portions  18 . 
     The configuration shown in  FIG. 2E  is such that, in the configuration of  FIG. 2D , a light-weight component  17 , which is obtained by forming chamfered portions  20  on the edges of the light-weight component  16 , is used as each attachment member  3 . As a result, the area of the adhesion by the adhesive  19  is increased, and thereby the adhesion strength can be increased. 
     The left side of  FIG. 3  shows the attachment members  3  and the guide bar body  1  before the attachment members  3  are attached to the guide bar body  1 . The right side of  FIG. 3  shows the guide bar body  1  with the attachment members  3  attached thereto. In the case of  FIG. 3 , each attachment member  3  is formed by the light-weight component  16 , which is made of, for example, a synthetic resin and formed in a shape that matches the shape of each of the elongated holes  2   a  and  2   b . After the light-weight components  16  are fitted in the elongated holes  2   a  and  2   b , respectively, the light-weight components  16  and the opening edges of the elongated holes  2   a  and  2   b  are welded together by laser (i.e., laser welding), and thereby welds  37  are formed. In this manner, the attachment members  3  are fixed to the guide bar body  1 . 
     According to the above-described configuration, regarding the number of elongated holes to be formed, it will suffice if two elongated holes  2   a  and  2   b  are formed in the guide bar body  1 , and the elongated holes  2   a  and  2   b  can be formed within a short time by laser machining or press working. In this configuration, the pre-formed attachment members  3  are required to be attached to only the two elongated holes  2   a  and  2   b . This makes it possible to reduce the manufacturing time and manufacturing cost. 
     Furthermore, weight reduction can be realized by using the light-weight components  12 , the light-weight components  13  and  14 , the light-weight components  16 , or the light-weight components  17  as the attachment members  3  attached to the elongated holes  2   a  and  2   b.    
     In order to realize the weight reduction, preferably, the length L 2  of each of the elongated holes  2   a  and  2   b  in the longitudinal direction is not less than ⅓ of the overall length L 1  of the guide bar body  1 . 
     Each of the light-weight components  12 ,  13 ,  14 , and  16  can be readily fabricated, for example, from a sheet-shaped material by performing laser cutting or punching thereon. 
     By using the metal plates  11  as components disposed on the outside of each attachment member  3  as shown in  FIG. 2A  and  FIG. 2B , problems resulting from long-term use, such as breakage, detachment, abrasion, etc., of the light-weight components  12 ,  13 , and  14 , can be prevented. 
     Next,  FIG. 4  is a front view of an essential part of the guide bar, showing a first variation of the guide bar body  1 . 
     The guide bar body  1  shown in  FIG. 4  is different from the guide bar body  1  shown in  FIG. 1  in the following point: a projecting portion f 1  is formed on the side wall (inner wall) of each of the elongated holes  2   a  and  2   b  along the entire periphery of the hole, the projecting portion f 1  projecting inward from the side wall of the hole at its central portion in the thickness direction. 
     The guide bar body  1  shown in  FIG. 4  is fabricated, for example, in the following manner: form through-holes by laser machining or press working through respective regions positioned inward of regions that are to be the projecting portions f 1 ; and then form the projecting portions f 1  by cutting. In this manner, the guide bar body  1  can be fabricated within a short time at low cost. 
     Examples of the attachment members  3  when the guide bar body  1  shown in  FIG. 4  is used are described. Each of  FIG. 5A  to  FIG. 5E  and  FIG. 6A  to  FIG. 6C  shows an example of the attachment members  3 , and shows a sectional view taken along a line B-B of  FIG. 4 . 
     Each attachment member  3  of  FIG. 5A  is formed by two light-weight components  21 . The light-weight components  21  are made of, for example, a synthetic resin, and are each formed in a shape that matches the shape of each of the elongated holes  2   a  and  2   b . An adhesive layer  22  is formed between the two light-weight components  21 . The adhesive layer  22  is made of an adhesive, by which the two light-weight components  21  are adhered together. The two light-weight components  21  are brought into contact with the projecting portion f 1 , such that the adhesive serving as the adhesive layer  22  and the projecting portion f 1  are sandwiched between the two light-weight components  21 . In this manner, the two light-weight components  21  are fitted in each of the elongated holes  2   a  and  2   b . In this case, the thickness of the adhesive layer  22  is the same as the thickness of the projecting portion f 1 . By setting the thickness of the projecting portion f 1  to a desirable thickness of the adhesive layer  22 , the thickness of the adhesive layer  22  can be made the desirable thickness. 
     Each attachment member  3  of  FIG. 5B  is formed by two light-weight components  23 . The light-weight components  23  are made of, for example, a synthetic resin, and are each formed in a shape that matches the shape of each of the elongated holes  2   a  and  2   b . An adhesive layer  24  is formed between the two light-weight components  23 . The two light-weight components  23  are adhered together by the adhesive layer  24 , and the adhesive layer  24  becomes elastic after being cured. The adhesive used as the adhesive layer  24  may be, for example, a rubber-based adhesive whose major component is nitrile rubber or some other synthetic rubber. In the case of  FIG. 5B , the thickness of the projecting portion f 1 , i.e., the thickness of the adhesive layer  24 , is greater than in the case of  FIG. 5A . Since the adhesive layer  24  is elastic, it absorbs vibrations occurring during the use of the chain saw. 
     The light-weight components  21  and  23  in  FIGS. 5A and 5B  can be readily fabricated, for example, from a sheet-shaped material by performing laser cutting or punching thereon. 
     Each attachment member  3  of  FIG. 5C  is formed by two light-weight components  25  and  26 . The light-weight components  25  and  26  are made of, for example, a synthetic resin, and are each formed in a shape that matches the shape of each of the elongated holes  2   a  and  2   b . One light-weight component  26  is provided with a plurality of protrusions  26   a , which are, for example, round protrusions and which are formed at intervals in the longitudinal direction of the guide bar body  1 , such that the plurality of protrusions  26   a  are, for example, arranged in a plurality of regions P 1  shown in  FIG. 4 . The other light-weight component  25  is provided with a plurality of holes  25   a , in which the respective protrusions  26   a  are inserted. The light-weight component  25  is also provided with a recess  25   f , in which the projecting portion f 1  is fitted. An adhesive is applied to opposite surfaces of the two respective light-weight components  25  and  26 , and the two light-weight components  25  and  26  are adhered together by the adhesive. 
     Each attachment member  3  of  FIG. 5D  is formed by two light-weight components  25  and  26 . The light-weight components  25  and  26  are made of, for example, a synthetic resin, and are each formed in a shape that matches the shape of each of the elongated holes  2   a  and  2   b . Similar to the holes  25   a  and the protrusions  26   a  of  FIG. 5C , a plurality of holes  25   b  of one light-weight component  25  and a plurality of protrusions  26   b  of the other light-weight component  26  are formed at intervals in the longitudinal direction of the guide bar body  1 , such that the plurality of holes  25   b  and the plurality of protrusions  26   b  are, for example, arranged in the plurality of regions P 1  of  FIG. 4 . The protrusions  26   b  of the light-weight component  26  in a pre-attachment state shown in  FIG. 5D  protrude to a greater degree than the protrusions  26   a  of the light-weight component  26  shown in  FIG. 5C . The holes  25   b  of the light-weight component  25 , in which the protrusions  26   b  are inserted, are provided with chamfered portions  25   c . In this case, when the two light-weight components  25  and  26  are placed in each of the elongated holes  2   a  and  2   b  and brought into contact with each other, the heads of the protrusions  26   b  stick out of the holes  25   b . The sticking-out portions are subjected to friction stir welding and thereby deformed. As a result, the chamfered portions  25   c  are filled with the deformed portions. Consequently, the light-weight components  25  and  26  are fixed to the guide bar body  1  in such a manner that the projecting portion f 1  is sandwiched between the light-weight components  25  and  26 . Therefore, no adhesive is necessary. 
     Each attachment member  3  of  FIG. 5E  is formed by two light-weight components  27  and  28  and a shaft  29 . The light-weight components  27  and  28  are made of, for example, a synthetic resin, and are each formed in a shape that matches the shape of each of the elongated holes  2   a  and  2   b . The shaft  29  is made of a synthetic resin. The light-weight components  27  and  28  are provided with a plurality of holes  27   a  and  28   a , which are, for example, round holes and which are formed at intervals in the longitudinal direction of the guide bar body  1 , such that the holes  27   a  and  28   a  are, for example, arranged in the regions P 1  of  FIG. 4 . The light-weight components  27  and  28  are also provided with recesses  27   f  and  28   f . One half of the projecting portion f 1  is fitted in the recess  27   f , and the other half of the projecting portion f 1  is fitted in the recess  28   f . An adhesive is applied to opposite surfaces of the two respective light-weight components  27  and  28 , and the two light-weight components  27  and  28  are adhered together by the adhesive. In addition, the shaft  29  is joined to the holes  27   a  and  28   a  by being press-fitted therein. 
     Each attachment member  3  of  FIG. 6A  is formed by two light-weight components  31  and  32  and two thin metal plates  11 . The two light-weight components  31  and  32  are made of, for example, a synthetic resin, and are each formed in a shape that matches the shape of each of the elongated holes  2   a  and  2   b . The light-weight components  31  and  32  are provided with recesses  31   f  and  32   f . One half of the projecting portion f 1  is fitted in the recess  31   f , and the other half of the projecting portion f 1  is fitted in the recess  32   f  The light-weight components  31  and  32  are fitted in each of the elongated holes  2   a  and  2   b . The metal plates  11  are fixed to the guide bar body  1  in a manner similar to the case of  FIG. 2A . 
     Each attachment member  3  of  FIG. 6B  is formed by two light-weight components  33  and two thin metal plates  11 . The two light-weight components  33  are made of, for example, a synthetic resin, and are each formed in a shape that matches the shape of each of the elongated holes  2   a  and  2   b . An adhesive layer  34  is formed between the two light-weight components  33 . The adhesive layer  34  is made of an adhesive, by which the two light-weight components  33  are adhered together. This configuration is a result of placing the metal plates  11  on both sides in  FIG. 5A . The metal plates  11  are fixed to the guide bar body  1  in a manner similar to the case of  FIG. 2A . 
     Each attachment member  3  of  FIG. 6C  is formed by two light-weight components  35  and  36  and two thin metal plates  11 . The two light-weight components  35  and  36  are made of, for example, a synthetic resin, and are each formed in a shape that matches the shape of each of the elongated holes  2   a  and  2   b . One light-weight component  36  is provided with a linear protrusion  36   a , which extends in the longitudinal direction of the guide bar body  1  and which is, for example, disposed in a region P 2  shown in  FIG. 4 . The other light-weight component  35  is provided with a groove (recess)  35   a , in which the protrusion  36   a  is press-fitted. The light-weight component  35  is also provided with a recess  35   f , in which the projecting portion f 1  is fitted. The two light-weight components  35  and  36  are fitted in each of the elongated holes  2   a  and  2   b . The metal plates  11  are fixed to the guide bar body  1  in a manner similar to the case of  FIG. 2A . 
     It should be noted that the one light-weight component  36  may be provided with not the linear protrusion  36   a  but, for example, a plurality of protrusions arranged in the plurality of regions P 1  of  FIG. 4 , and the other light-weight component  35  may be provided with not the groove  35   a  but bottomed holes in which the plurality of respective protrusions are press-fitted. 
     By using the metal plates  11  as components disposed on the outside of each attachment member  3  as shown in  FIG. 6A  to  FIG. 6C , problems resulting from long-term use, such as breakage, detachment, abrasion, etc., of the light-weight components  31 ,  32 ,  33 ,  35 , and  36 , can be prevented. 
     Next,  FIG. 7  is a front view of an essential part of the guide bar, showing a second variation of the guide bar body  1 . 
     The guide bar body  1  shown in  FIG. 7  is different from the guide bar body  1  shown in  FIG. 1  in the following points: the projecting portion f 1  is formed on the side wall (inner wall) of each of the elongated holes  2   a  and  2   b  along the entire periphery of the hole, the projecting portion f 1  projecting inward from the side wall of the hole at its central portion in the thickness direction; and a plurality of holes f 1   a  are formed in the projecting portion f 1 , such that the holes f 1   a  are arranged at intervals. 
     The guide bar body  1  shown in  FIG. 7  is fabricated, for example, in the following manner: form through-holes by laser machining or press working through respective regions positioned inward of regions that are to be the projecting portions f 1 ; and then form the projecting portions f 1  and the holes f 1   a  by cutting. In this manner, the guide bar body  1  can be fabricated within a short time at low cost. 
       FIG. 8  shows one example of the attachment members  3  when the guide bar body  1  shown in  FIG. 7  is used, and shows a sectional view taken along a line C-C of  FIG. 7 . 
     Each attachment member  3  of  FIG. 8  is formed by two light-weight components  41 . The light-weight components  41  are made of, for example, a synthetic resin, and are each formed in a shape that matches the shape of each of the elongated holes  2   a  and  2   b . In this case, each light-weight component  41  and a surface of the projecting portion f 1 , the surface contacting the light-weight component  41 , are adhered together by an adhesive. Also, the holes f 1   a  in the projecting portion f 1  are filled with the adhesive. In this manner, the adhesion strength can be increased. A gap  42  between the two light-weight components  41  may be an empty space, or may be filled with the adhesive. By filling the gap  42  with the adhesive, the adhesion strength can be further increased. 
     Next,  FIG. 9  is a front view of an essential part of the guide bar, showing a third variation of the guide bar body  1 . 
     The guide bar body  1  shown in  FIG. 9  is different from the guide bar body  1  shown in  FIG. 1  in the following point: projecting portions f 2  are formed on the side wall (inner wall) of each of the elongated holes  2   a  and  2   b , the projecting portions f 2  projecting inward from the side wall of the hole at its central portion in the thickness direction. Unlike the above-described projecting portion f 1 , which is formed continuously along the entire periphery of each of the elongated holes  2   a  and  2   b , the projecting portions f 2  are formed as a plurality of divided portions. 
     The guide bar body  1  shown in  FIG. 9  is fabricated, for example, in the following manner: form through-holes by laser machining or press working through respective regions positioned inward of regions that are to be the projecting portions f 2 ; and then form the projecting portions f 2  by cutting. In this manner, the guide bar body  1  can be fabricated within a short time at low cost. 
       FIG. 10  shows one example of the attachment members  3  when the guide bar body  1  shown in  FIG. 9  is used, and shows a sectional view taken along a line D-D of  FIG. 9 . 
     Each attachment member  3  of  FIG. 10  is formed by two light-weight components  51 . The light-weight components  51  are made of, for example, a synthetic resin, and are each formed in a shape that matches the shape of each of the elongated holes  2   a  and  2   b . In this case, each light-weight component  51  and surfaces of the projecting portions f 2 , the surfaces contacting the light-weight component  51 , are adhered together by an adhesive. A gap  52  between the two light-weight components  51  may be an empty space, or may be filled with the adhesive. By filling the gap  52  with the adhesive, the adhesion strength can be increased. 
     Next,  FIG. 11  is a front view of an essential part of the guide bar, showing a fourth variation of the guide bar body  1 . 
     The guide bar body  1  shown in  FIG. 11  is configured such that each of the elongated holes  2   a  and  2   b  is provided with not the projecting portions f 2  of  FIG. 9  but a beam portion f 3  extending in the longitudinal direction of the guide bar body  1  and a beam portion f 4  extending in the width direction of the guide bar body  1 . Each of the beam portions f 3  and f 4  extends from a part of the side wall (inner wall) of each of the elongated holes  2   a  and  2   b  at its central portion in the thickness direction, and connects to the opposite part of the side wall. 
     The guide bar body  1  shown in  FIG. 11  is fabricated, for example, in the following manner: form through-holes through regions that are to be the elongated holes  2   a  and  2   b  by laser machining or press working while leaving regions that are to be the beam portions f 3  and f 4 ; and then form the beam portions f 3  and f 4  by cutting. In this manner, the guide bar body  1  can be fabricated within a short time at low cost. 
       FIG. 12  shows one example of the attachment members  3  when the guide bar body  1  shown in  FIG. 11  is used, and shows a sectional view taken along a line E-E of  FIG. 11 . 
     The attachment members  3  of  FIG. 12  are the same as the attachment members  3  of  FIG. 10 . A gap  52  between the two light-weight components  51  may be an empty space, or may be filled with an adhesive. By filling the gap  52  with the adhesive, the adhesion strength can be increased. 
     It should be noted that holes similar to the holes f 1   a  of  FIG. 7  may be formed in the projecting portions f 2  of  FIG. 9  and also in the beam portions f 3  and f 4  of  FIG. 11 . These holes may be filled with an adhesive, and thereby the adhesion strength may be increased. 
     Next,  FIG. 13  and  FIG. 14  are front views of the guide bar, showing a fifth variation and a sixth variation of the guide bar body  1 , respectively. 
     The guide bar body  1  shown in  FIG. 1  is configured such that one elongated hole  2   a  is formed at one side, and one elongated hole  2   b  is formed at the other side, of the central axial portion (the region having the predetermined width L 3 )  1   c . On the other hand, the guide bar bodies  1  shown in  FIG. 13  and  FIG. 14  are examples, in which a plurality of elongated holes are formed at each side of the central axial portion  1   c , such that the plurality of elongated holes are arranged in the longitudinal direction of the guide bar body  1  along the central axial portion  1   c.    
     Specifically, the guide bar body  1  shown in  FIG. 13  is configured such that two elongated holes  2   a A and  2   a B are formed at one side, and two elongated holes  2   b A and  2   b B are formed at the other side, of the central axial portion  1   c . Attachment members  3 A and  3 B are attached to these elongated holes. Those similar to the attachment members  3  of the guide bar body  1  shown in  FIG. 1  can be used as the attachment members  3 A and  3 B. 
     In order to reduce the weight of the guide bar of the guide bar body  1  shown in  FIG. 13 , preferably, the total length of the elongated holes ( 2   a A and  2   a B; or  2   b A and  2   b B) in the longitudinal direction (i.e., L 2 A+L 2 B) is not less than ⅓ of the overall length L 1  of the guide bar body  1 . 
     The guide bar body  1  shown in  FIG. 14  is configured such that three elongated holes  2   a C,  2   a D, and  2   a E are formed at one side, and three elongated holes  2   b C,  2   b D, and  2   b E are formed at the other side, of the central axial portion  1   c . Attachment members  3 C,  3 D, and  3 E are attached to these elongated holes. Those similar to the attachment members  3  of the guide bar body  1  shown in  FIG. 1  can be used as the attachment members  3 C,  3 D, and  3 E. 
     In order to reduce the weight of the guide bar of the guide bar body  1  shown in  FIG. 14 , preferably, the total length of the elongated holes ( 2   a C,  2   a D, and  2   a E; or  2   b C,  2   b D, and  2   b E) in the longitudinal direction (i.e., L 2 C+L 2 D+L 2 E) is not less than ⅓ of the overall length L 1  of the guide bar body  1 . 
     It should be noted that each of the elongated holes ( 2   a A,  2   a B,  2   b A, and  2   b B) shown in  FIG. 13  and each of the elongated holes ( 2   a C,  2   a D,  2   a E,  2   b C,  2   b D, and  2   b E) shown in  FIG. 14  may be provided with a projecting portion (f 1 ), projecting portions (f 2 ), or beam portions (f 3  and f 4 ) as previously described in the first to fourth variations, and an attachment member suited thereto may be attached to each elongated hole. 
     As described above with reference to  FIG. 1 ,  FIG. 4 ,  FIG. 7 ,  FIG. 9 ,  FIG. 11 ,  FIG. 13 , and  FIG. 14 , by forming the elongated holes ( 2   a  and  2   b ;  2   a A,  2   a B,  2   b A and  2   b B; or  2   a C,  2   a D,  2   a E,  2   b C,  2   b D, and  2   b E) in the guide bar body  1  while leaving the central axial portion  1   c  including the central axis line CL, reduction in the strength of the guide bar, such as reduction in the bending strength, can be suppressed. 
     The guide bar bodies  1  shown in  FIG. 1 ,  FIG. 4 ,  FIG. 7 ,  FIG. 9 ,  FIG. 11 ,  FIG. 13 , and  FIG. 14  may be suitably combined with the above-described various attachment members  3 . For example, also in the case of using any of the guide bar bodies  1  shown in  FIG. 7 ,  FIG. 9 , and  FIG. 11 , the metal plates  11  may be used as components disposed on the outside, at both sides, of each attachment member  3 . 
     From the foregoing description, numerous modifications and other embodiments of the present invention are obvious to a person skilled in the art. Therefore, the foregoing description should be interpreted only as an example and is provided for the purpose of teaching the best mode for carrying out the present invention to a person skilled in the art. The structural and/or functional details may be substantially altered without departing from the spirit of the present invention. 
     INDUSTRIAL APPLICABILITY 
     The present invention is useful as, for example, a guide bar of a chain saw with a reduced weight, the guide bar making it possible to reduce its manufacturing time and manufacturing cost. 
     REFERENCE CHARACTER LIST 
     
         
         
           
             CL central axis line 
               1  guide bar body 
               1   c  central axial portion (region having a predetermined width) 
               2   a ,  2   b  elongated hole 
               2   a A,  2   a B,  2   b A,  2   b B elongated hole 
               2   a C,  2   a D,  2   a E,  2   b C,  2   b D,  2   b E elongated hole 
               3 ,  3 A,  3 B,  3 C,  3 D,  3 E attachment member 
               4  guide groove 
               11  metal plate (sheet metal) 
               12 ,  13 ,  14 ,  16 ,  17  light-weight component 
               18 ,  20  chamfered portion 
               19  adhesive 
               21 ,  23 ,  25 ,  26 ,  27 ,  28  light-weight component 
               22 ,  24  adhesive layer 
               25   a ,  25   b ,  27   a ,  28   a  hole 
               26   a ,  26   b  protrusion 
               29  shaft 
               31 ,  32 ,  33 ,  35 ,  36 ,  41 ,  51  light-weight component 
               34  adhesive layer 
               35   a  groove (recess) 
               36   a  protrusion 
             f 1 , f 2  projecting portion 
             f 1   a  hole in the projecting portion 
             f 3 , f 4  beam portion