Patent Publication Number: US-2021189684-A1

Title: Attachment for work machine

Description:
TECHNICAL FIELD 
     The present invention relates to an attachment of a work machine, the attachment being capable of being assembled with reduced effort. 
     BACKGROUND ART 
     There is conventionally known an attachment of work machine, including a first attachment body having a pair of sidewalls and a second attachment body that can be coupled to the pair of sidewalls. 
     For example,  FIGS. 7 and 8  of Patent Document 1 disclose a first insert boom and a second insert boom that are coupled to each other to constitute an attachment. The first insert boom has a pair of side walls and a fixing pin, which is fixed to rear ends of the pair of side walls. The second insert boom also has a pair of side walls, which are formed with a pair of notches, respectively. In a state where the opposite ends of the fixing pin and the pair of notches of the second insert boom are fitted with each other, the first insert boom and the second insert boom are coupled to each other (see  FIG. 10  of Patent Document 1). This reduces labor for a subsequent work such as removing and inserting a pin. 
     However, it is difficult to visually recognize the fitting state between the fixing pin and the notch from the side because, as shown in  FIG. 8  of Patent Document 1, the notches of the pair of side walls of the second insert boom are fitted with the fixing pin at respective positions on respective widthwise inner sides of the pair of side walls of the first insert boom. This hinders rapid engagement of the notch with the securing pin ( 24 ) and further quick connection of the first and second insert booms with each other. 
     CITATION LIST 
     Patent Document 
     Patent Document 1: Japanese Unexamined Patent Publication No. 2015-227611 
     SUMMARY OF INVENTION 
     It is an object of the present invention to provide an attachment for a work machine, the attachment including a first attachment body and a second attachment body that can be detachably coupled to each other and allowing the first and second attachment bodies to be quickly and easily coupled to each other. 
     Provided is an attachment for a work machine comprising a first attachment body having a first connection end and a second attachment body having a second connection end connectable to the first connection end. The first attachment body includes a first left side plate and a first right side plate arranged left and right, and a first connection plate interconnecting the first left side plate and the first right side plate in the first connection end. The first left side plate has a first left projecting portion that projects beyond the first connection plate toward the second connection end, and the first right side plate has a second right projecting portion that projects beyond the first connection plate toward the second connection end. The second attachment body includes a second left side plate and a second right side plate arranged left and right, a second connection plate interconnecting the second left side plate and the second right side plate in the second connection end, and a fitting pin extending in the left-right direction. The second left side plate includes a second left projecting portion that projects the second connection plate toward the first connection end, and the second right side plate includes a second right projecting portion that projects the second connection plate toward the first connection end. The second left projecting portion is formed with a left fitting pin insertion hole penetrating the second left projecting portion in the left-right direction, and the second right projecting portion is formed with a right fitting pin insertion hole penetrating the second right projecting portion in the left-right direction. The fitting pin is inserted through the left fitting pin insertion hole and the right insertion hole so as to have a left protruding portion protruding to the left outside of the first left projecting portion and a right protruding portion protruding to the right outside of the first right projecting portion. The first left projecting portion is formed with a left notch having a shape opened so as to be able to receive the left protruding portion of the fitting pin radially of the fitting pin, and the first right projecting portion is formed with a right notch having a shape opened so as to be able to receive the right protruding portion of the fitting pin radially of the fitting pin. The interval between the first left side plate and the first right side plate in the left-right direction is greater than the interval between the second left side plate and the second right side plate in the left-right direction. The first attachment body and the second attachment body are configured to be connected to each other in a state where the first left projecting portion and the second right projecting portion are disposed on both outer sides of the second left projecting portion and the second right projecting portion in the left-right direction, and the left projecting portion and the right protruding portion of the fitting pin are configured to be fitted with the left notch and the right notch, respectively, at respective positions on both outer sides of the second left projecting portion and the second right projecting portion in the left-right direction. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side view showing a main boom and an insert boom constituting an attachment of a work machine according to a first embodiment of the present invention. 
         FIG. 2  is a plan view of the main boom and the insert boom viewed in the direction of arrow II in  FIG. 1 . 
         FIG. 3  is a perspective view showing the main boom. 
         FIG. 4  is a perspective view showing a portion including a second connection end in the insert boom. 
         FIG. 5  is a side view showing the insert boom viewed in the direction of the arrow V in  FIG. 4 . 
         FIG. 6  is a diagram showing a cross section along VI-VI line of  FIG. 5 . 
         FIG. 7  is a side view showing the main boom and the insert boom connected to each other. 
         FIG. 8  is a plan view of the main boom and the insert boom viewed in the direction of the arrow VIII in  FIG. 7 . 
         FIG. 9  is a perspective view showing a part including a first connection end of the main boom constituting the attachment of the working machine according to a second embodiment of the present invention. 
         FIG. 10  is a plan view showing the main boom and the insert boom connected to each other in the second embodiment. 
         FIG. 11  is a perspective view showing a part of the insert boom constituting the attachment of the work machine according to a third embodiment of the present invention, the part including a pin holding unit. 
         FIG. 12  is a diagram showing a cross section along XII-XII line of  FIG. 11 . 
         FIG. 13  is a perspective view showing a part of the insert boom constituting the attachment of the working machine according to the first modification, the part including a pin holding unit. 
         FIG. 14  is a diagram showing a cross section along XIV-XIV line of  FIG. 13 . 
         FIG. 15  is a perspective view showing a part of the insert boom constituting the attachment of the working machine according to the second modification, the part including a pin holding unit. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     There will be described an attachment of a work machine according to a first embodiment of the present invention with reference to  FIGS. 1 to 8 . The attachment according to this embodiment includes a main boom  1  and an insert boom  2  shown in  FIG. 1 . The main boom  1  is an example of a first attachment body, and the insert boom  2  is an example of a second attachment body. In addition to the main boom  1  and the insert boom  2 , the attachment according to this embodiment can include other components such as a known arm and a bucket, but description of the other components is omitted. 
     The work of assembling the attachment includes a connection work of connecting the main boom  1  and the insert boom  2  to each other. As shown in  FIG. 1 , in the connection work, the main boom  1  is disposed on the side closer to the proximal end of the attachment than the insert boom  2  (the side close to the machine body of the working machine). In other words, the insert boom  2  is disposed on the side closer to the tip of the attachment than the main boom  1  (far side from the machine body of the working machine). The distal end of the main boom  1  is a first connection end connectable to the insert boom  2 , and the proximal end of the insert boom  2  is a second connection end connectable to the first connection end of the main boom  1 . 
     As shown in  FIG. 1  and  FIG. 2 , the main boom  1  includes a first upper plate  11  and a first lower plate  12  which are arranged up and down, and a first left side plate  13  and a first right side plate  14  which are arranged left and right. 
     The first upper plate  11  and the first lower plate  12  are disposed at positions spaced vertically. The first left side plate  13  interconnects the left end of the first upper plate  11  and the left end of the first lower plate  12  vertically. Specifically, the first left side plate  13  has an upper end joined to the left end of the first upper plate  11  and a lower end joined to the left end of the first lower plate  12 . The first right side plate  14  interconnects the right end of the first upper plate  11  and the right end of the first lower plate  12  vertically. Specifically, the first right side plate  14  has an upper end joined to the right end of the first upper plate  11  and a lower end joined to the right end of the first lower plate  12 . Hereinafter, the first left side plate  13  and the first right side plate  14  are collectively referred to as first left and right side plates  13  and  14 . The first left and right side plates  13 ,  14  are arranged so as to be substantially parallel to each other. 
     The main boom  1  further includes a first connection plate  15  shown in  FIG. 3 . The first connection plate  15  is included in a first connection end of the main boom  1 . The first connection end is a distal end to be connected to the insert boom  2 , the distal end being one of opposite ends of the main boom  1  in the longitudinal direction, i.e., a connection direction in which the main boom  1  and the insert boom  2  are connected to each other. In the first connection end, the first connection plate  15  interconnects the first left side plate  13  and the first right side plate  14  in the left-right direction (width direction). Preferably, the first connection plate  15  further interconnects the first upper plate  11  and the first lower plate  12  vertically. 
     The first left side plate  13  has a first left projecting portion  130 . The first left projecting portion  130  is a portion projecting toward the second connection end of the insert boom  2  beyond the first connection plate  15 , that is, projecting to the distal-end side. Similarly, the first right side plate  14  has a first right projecting portion  140 . The first right projecting portion  140  is a portion projecting toward the second connection end of the insert boom  2  beyond the first connection plate  15 , that is, projecting to the distal-end side. Hereinafter, the first left projecting portion  130  and the first right projecting portion  140  are collectively referred to as first left and right projecting portions  130  and  140 . 
     The first left and right projecting portions  130  and  140  are formed with a left notch  131  and a right notch  141  at respective edges of the first left and right projecting portions  130  and  140 , respectively. The first left and right projecting portions  130  and  140  are further formed with respective connection pin insertion holes  133  and  143  that penetrate the first left and right projecting portions  130  and  140  in the left-right directions, respectively. Through each of the connection pin insertion holes  133  and  143  can be inserted in the left-right direction a not-graphically-shown connection pin for interconnecting the main boom  1  and the insert boom  2 . 
     As shown in  FIG. 1  and  FIG. 2 , the insert boom  2  includes a second upper plate  21  and a second lower plate  22  which are arranged up and down, and a second left side plate  23  and a second right side plate  24  which are arranged left and right. 
     The second upper plate  21  and the second lower plate  22  are arranged at positions spaced vertically. The second left side plate  23  interconnects the left end of the second upper plate  21  and the left end of the second lower plate  22  vertically. Specifically, the second left side plate  23  has an upper end joined to the left end of the second upper plate  21  and a lower end joined to the left end of the second lower plate  22 . The second right side plate  24  interconnects the right end of the second upper plate  21  and the right end of the second lower plate  22  vertically. Specifically, the second right side plate  24  has an upper end joined to the right end of the second upper plate  21  and a lower end joined to the right end of the second lower plate  22 . Hereinafter, the second left side platf the second right side plate  24  are also referred to as second left and right side plates  23  and  24 . The second left and right side plates  23  and  24  are arranged substantially parallel to each other. 
     The interval W 2  between the second left and right side plates  23  and  24  in the left-right direction as shown in  FIG. 4  is smaller than the interval W 1  between the first left and right side plates  13  and  14  in the left-right direction as shown in  FIG. 3 . Thus, the main boom  1  has a larger width than the width of the insert boom  2 . 
     The insert boom  2  further includes a second connection plate  25  shown in  FIG. 4 . The second connection plate  25  is included in the second connection end of the insert boom  2 . The second connection end is, as described above, a proximal end connected to the first connection end of the main boom  1 , the proximal end being one of opposite ends of the insert boom  2  in the longitudinal direction, i.e., the connection direction. In the second connection end, the second connection plate  25  interconnects the second left side plate  23  and the second right side plate  24  in the left-right direction (width direction). Preferably, the second connection plate  25  further interconnects the second upper plate  21  and the second lower plate  22  vertically. 
     The second left side plate  23  has a second left projecting portion  230 . The second left projecting portion  230  is a portion projecting toward the first connection end of the main boom  1  beyond the second connection plate  25 , that is, the portion projecting to the proximal side. The second right side plate  24  has a second right projecting portion  240 . The second right projecting portion  240  is a portion projecting toward the first connection end of the main boom I beyond the second connection plate  25 , that is, the portion projecting to the proximal side. Hereinafter, the second left projecting portion  230  and the second right projecting portion  240  are collectively referred to as second left and right projecting portions  230  and  240 . 
     The insert boom  2  further includes a fitting pin  5  extending in the left-right direction. The second left and right projecting portions  230  and  240  have respective upper portions, which are formed with respective fitting pin insertion holes  231  and  241  penetrating the second left and right projecting portions  230  and  240  in the left-right directions, respectively. The fitting pin  5  is inserted through the fitting pin insertion holes  231  and  241  in the left-right direction, thereby being supported by the second left and right projecting portions  230  and  240 . Besides, the second left and right projecting portions  230  and  240  have respective lower portions, which arc formed with respective connection pin insertion holes  233  and  243  penetrating the second left and right projecting portions  230  and  240  in the left-right directions, respectively. The connection pin insertion holes  233  and  243  allow the connection pin for interconnecting the main boom  1  and the insert boom  2  to be inserted through the connection pin insertion holes  233  and  243  in the left-right direction. 
     The insert boom  2  further includes a pin holding unit  7 . The pin holding unit  7  holds the fitting pin  5  so as to fix the axial position of the fitting pin  5  that is being inserted through the fitting pin insertion holes  231  and  241  (i.e., the position in the left-right direction of the insert boom  2 ). Specifically, the pin holding unit  7  holds the fitting pin  5  at a position where the left end of the fitting pin  5  forms a left protruding portion  53  protruding to the outside (left side) of the second left projecting portion  230 , and the right end of the fitting pin  5  forms a right protruding portion  54  protruding to the outside (right side) of the second right projecting portion  240 . 
     The pin holding unit  7  includes a left holding portion  7   a  and a right holding portion  7   b.  The left holding portion  7   a  includes a left bracket  71   a  attached to the second left side plate  23 , and a left plate  73   a  fixed to the left bracket  71   a.  Similarly, the right holding portion  7   b  includes a right bracket  71   b  attached to the second right side plate  24  and a right plate  73   b  fixed to the right bracket  71   b.    
     The left bracket  71   a  is fixed to the outer surface of the second left projecting portion  230 , i.e., the surface facing outward (leftward) in the left-right direction. Similarly, the right bracket  71   b  is fixed to the outer surface of the second right projecting portion  240 , i.e., the surface facing outward (rightward) in the left-right direction. 
     The left plate  73   a  has a proximal end and a distal end opposite thereto. The proximal end of the left plate  73   a  is fastened to the left bracket  71   a  through a plurality (e.g., four) of bolts  72   a  as shown in  FIG. 4 , thereby being attached to the second left projecting portion  230  through the left bracket  71   a.  The distal end of the left plate  73   a  is fastened to the fitting pin  5  by a bolt  74   a  while making contact with the left end of the fitting pin  5 . The bolt  74   a  is screwed into the fitting pin  5  axially of the fitting pin  5 . 
     The right plate  73   b  has a proximal end and a distal end opposite thereto. The proximal end of the right plate  73   b  is fastened to the right bracket  71   b  through a plurality of (e.g., four) bolts  72   b,  thereby being attached to the second right projecting portion  240  through the right bracket  71   b.  The distal end of the right plate  73   b  is fastened to the fitting pin  5  by a bolt  74   b  while making contact with the right end of the fitting pin  5 . The bolt  74   b  is screwed into the fitting pin  5  axially of the fitting pill  5 . 
     As shown in  FIGS. 7 and 8 , the main boom  1  and the insert boom  2  are configured to be connected to each other in the connection direction in a state where the first left and right projecting portions  130  and  140  of the main boom  1  are disposed on both outer sides of the second left and right projecting portions  230  and  240  of the insert boom  2 . 
     The fitting pin  5  can be fitted with the left notch  131  and the right notch  141 . Specifically, in the fitting pin  5 , the left protruding portion  53  protruding outward (leftward) beyond the second left projecting portion  230  is fitted with the left notch  131 , and the right protruding portion  54  protruding outward (rightward) beyond the second right projecting portion  240  is fitted with the right notch  141 . The left notch  131  has a shape opened so as to receive the left protruding portion  53  radially of the fitting pin  5 , that is, so as to allow the left protruding portion  53  to be fitted with the left notch  131  radially. The right notch  141  has a shape opened so as to receive the right protruding portion  54  radially of the fitting pin  5 , that is, so as to allow the right protruding portion  54  to be fitted into the right notch  141  radially. 
     In a state where the left and right protruding portions  53  and  54  of the fitting pin  5  are fitted with the left and right notches  131  and  141 , respectively, the connection pin insertion holes  133  and  143  of the main boom  1  (see  FIG. 3 ) and the connection pin insertion hole  233 , 243  of the insert boom  2  (see  FIG. 4 ) can be aligned and a not-graphically-shown connection pin can be inserted through the connection pin insertion holes. The main boom  1  and the insert boom  2  are thereby connected to each other. 
     As described above, the fitting of the left and right protruding portions  53  and  54  of the fitting pin  5  with the left and right notches  131  and  141  enables the main boom  1  and the insert boom  2  to be roughly aligned for connecting. The rough alignment facilitates the alignment of the connection pin insertion holes  133  and  143  of the main boom  1  and the connection pin insertion holes  233  and  243  of the insert boom  2  for insertion of the not-graphically-shown connection pin. 
     Furthermore, the structure according to the first embodiment allows the fitting pin  5  and the notches  131  and  141  to be quickly fitted with each other, thereby allowing the main boom  1  and the insert boom  2  to be quickly connected to each other. Specifically, in a state where the first left and right projecting portions  130  and  140  of the main boom  1  are disposed on both outer sides of the second left and right projecting portions  230  and  240  of the insert boom  2 , the left protruding portion  53  protruding outward (leftward) from the second left projecting portion  230  and the right protruding portion  54  protruding outward (rightward) from the second right projecting portion  240  of the fitting pin  5  are fitted with the left notch  131  and the right notch  141 , respectively, which fitting allows an operator to perform work while visually recognizing the fitting state of the fitting pin  5  and the left and right notches  131  and  141  from the side. This makes it possible to fit the fitting pin  45  with the left and right notches  131 ,  141  easily, thus making it possible to interconnect the main boom  1  and the insert boom  2 , the components of the attachment, quickly and easily. 
     Besides, the interval W 1  between the first left and right side plates  13  and  14  of the main boom  1  in the left-right direction (see  FIG. 3 ), which is greater than the interval W 2  between the second left and right side plates  23  and  24  of the insert boom  2  in the left-right direction (see  FIG. 4 ), allows the insert boom  2  disposed on the distal end side to be relatively lighter and allows the main boom  1  disposed on the proximal end side to be relatively heavy. This allows the attachment to be lifted more safely with the center of gravity of the entire attachment close to the machine body. 
     The pin holding unit  7  can fix the axial position of the fitting pin  5  with a simple configuration including left and right holding portions  7   a  and  7   b  disposed left and right sides, the left and right holding portions  7   a  and  7   b  including the left and right plates  73   a  and  73   b  and the left and right brackets  71   a  and  71   b,  respectively. 
     Next will be described an attachment of the work machine according to the second embodiment of the present invention with reference to  FIGS. 9 and 10 . 
     The attachment according to the second embodiment includes the main boom  1  and the insert boom  2  in the same manner as the first embodiment, but the insert boom  2  includes a left auxiliary projecting plate  330  and a right auxiliary projecting plate  340  in addition to the components of the insert boom  2  according to the first embodiment. The left and right auxiliary projecting plates  330  and  340  are formed with left and right auxiliary notches  331  and  341  similar to the left and right notches  131  and  141 , respectively, and the four notches  131 ,  141 ,  331  and  341  in total are fitted with the common fitting pin  5  similarly to the first embodiment. 
     As shown in  FIG. 9 , the left and right auxiliary projecting plates  330  and  340  are fixed to the first connection plate  15  of the main boom  1  so as to project from the first connection plate  15  toward the second connection end of the insert boom  2 . The left and right auxiliary projecting plates  330  and  340  are disposed on the inner side of the first left and right projecting portions  130  and  140  in a posture substantially parallel to the first left and right projecting portions  130  and  140 . 
     The left and right auxiliary notches  331  and  341  are formed in the left and right auxiliary projecting plates  330  and  340 , respectively, so as to have respective shapes capable of being fitted to the body portion of the fitting pin  5 . 
     As shown in  FIG. 10 , for connection of the main boom  1  and the insert boom  2  to each other, the first left and right projecting portions  130  and  140  of the main boom  1  are disposed on respective outer sides of the second left and right projecting portions  230  and  240  of the insert boom  2 , respectively, similarly to the first embodiment, and the left and right auxiliary projecting plates  330  and  340  are disposed on respective inner sides of the second left and right projecting portions  230  and  240  of the insert boom  2 . In other words, the main boom  1  and the insert boom  2  are connected to each other in a state where the first left and right projecting portions  130  and  140  are disposed on the outer sides of the second left and right projecting portions  230  and  240 , and the left and right auxiliary projecting plates  330  and  340  are disposed on the inner sides of the second left and right projecting portions  230  and  240 . 
     Similarly to the first embodiment, in the fitting pin  5 , the left protruding portion  53  protruding outward (leftward) beyond the second left projecting portion  230  is fitted with the left notch  131  of the first left projecting portion  130 , and the right protruding portion  54  protruding outward (rightward) beyond the second right projecting portion  240  is fitted with the right notch  141  of the first right projecting portion  140 . In addition, the left and right parts of the fitting pin  5  that are located on respective inner sides of the second left and right projecting portions  230  and  240  are fitted with the left and right auxiliary notches  331  and  341  formed in the left and right auxiliary projecting plates  330  and  340 , respectively. This enables the body portion of the fitting pin  5  to be supported not only by the first left and right projecting portions  130 ,  140  but also by the left and right auxiliary projecting plates  330 ,  340 , as shown in  FIG. 10 . This allows the bending moment acting on the fitting pin  5  to be reduced as compared with the first embodiment in which the body portion of the fitting pin  5  is fitted only in the left and right notches  131  and  141  to be supported only by the first left and right projecting portions  130  and  140 . As a result, the strength required for the fitting pin  5  can be low. This allows the fitting pin  5  to he given a small diameter and reduced in weight, and allows the fitting pin  5  to be made of inexpensive material. 
     The attachment of a work machine according to the present invention is not limited to the above-described embodiment, being allowed to be variously modified and improved within the scope of the claims. 
       FIGS. 11 and 12  show a second connection end of an insert boom  2  according to a first modification. The second connection end includes a pin holding unit  8  shown in  FIGS. 11 and 12 , instead of the pin holding unit  7  shown in  FIGS. 4 to 6 . 
     The pin holding unit  8  includes a bracket  81  which is fixed to a second connection plate  25  of the insert boom  2 , and a left locking member  83   a  and a right locking member  83   b  which are supported by the bracket  81 . 
     The bracket  81  includes a left vertical plate  81   a  and a right vertical plate  81   b.  Each of the left and right vertical plates  81   a  and  81   b  has a shape extending obliquely upward from the second connection plate  25  and bending to the side opposite to the main boom  1  in the middle portion thereof. 
     The left and right locking members  83   a  and  83   b  are attached to the left and right vertical plates  81   a  and  81   b  while engaging with the fitting pin  5 , thereby restraining the fitting pin  5 . The body portion of the fitting pin  5  has an outer peripheral surface formed with left and right grooves extending circumferentially thereof. Each of the left and right locking members  83   a  and  83   b  is substantially U-shaped. Specifically, each of the left and right locking members  83   a  and  83   b  has an intermediate portion curved with a radius of curvature equivalent to the radius of curvature of the left and right groove portions, and opposite ends on both sides of the intermediate portion. The left and right locking members  83   a  and  83   h,  in which the opposite ends are fixed to the left and right vertical plates  81   a  and  81   b,  respectively, while the intermediate portions are fitted to the left and right groove portions, prevent the fitting pin  5  from axial movement. 
       FIGS. 13 and 14  show a second connection end of an insert boom  2  according to a second modification. The second connection end includes a pair of left and right pin holding units  9  shown in  FIGS. 13 and 14  instead of the pin holding unit  7  shown in  FIGS. 4 to 6 . 
     Each of the pair of pin holding units  9  includes a bracket  91 , a holding member  93  and a retaining pin  95 , which are shown in  FIG. 14 . 
     The bracket  91  is erected on the second connection plate  25  of the insert boom  2 , having a shape projecting from the second connection plate  25  toward the fitting pin  5  and bending upward in the middle. 
     The holding member  93  has a shape for holding the fitting pin  5  while being fixed to the distal end of the bracket  91 . Specifically, the holding member  93  has a base portion  93   a  fixed to and supported by the bracket  91 , and a pair of holding portions  93   b  protruding from opposite ends of the base portion  93   a  to the side opposite to the bracket  91 . The pair of holding portions  93   h  have respective inner surfaces opposed to each other, and hold the fitting pin  5  between the inner surfaces. Each of the pair of holding portions  93   b  is formed with a retaining pin insertion hole penetrating therethrough. 
     The retaining pin  95  is held by the pair of holding portions  93   b  while penetrating the fitting pin  5  in the diameter direction, thereby preventing the fitting pin  5  from axial movement. There are formed through holes that penetrate the fitting pin  5  in the diameter direction in respective parts of the fitting pin  5 , the parts being to be held by the pair of pin holding units, respectively. The retaining pin  95  can be fixed to the pair of holding portions  93   b  through a bolt or the like while being inserted through the through hole and the retaining pin insertion hole. 
     The number of the pin holding units  9  is not limited. For example, the insert boom  2  may have a single pin holding unit  9 , or may include three or more pin holding units  9  arranged in the left-right direction. 
       FIG. 15  shows a second connection end of an insert boom  2  according to a third modification. The second connection end includes a pin holding unit  6  shown in  FIG. 15  instead of the pin holding unit  7  shown in  FIGS. 4 to 6 . The pin holding unit  6  holds the fitting pin  5  so as to restrain the left and right ends of the fitting pin  5  by the second left and right projecting portions  230  and  240  of the insert boom  2 , respectively. 
     Specifically, the pin holding unit  6  includes a left restraining plate  60   a  and a right restraining plate  60   b  shown in  FIG. 15 . The left restraining plate  60   a  has a U shape straddling a left protruding portion  53  of the fitting pin  5  and a second left projecting portion  230 , and the right restraining plate  60   b  has a U shape straddling a right protruding portion  54  of the fitting pin  5  and a second right projecting portion  240 . More specifically, the left restraining plate  60   a  includes a left outer plate portion  61   a  located on the outer side of the left end surface of the fitting pin  5  and a left inner plate portion  63   a  located on the inner side of the second left projecting portion  230 , and the right restraining plate  60   b  includes a right outer plate portion  61   b  located on the outer side of the right end surface of the fitting pin  5  and an outer plate portion  63   b  located on the inner side of the second right projecting portion  240 . The left and right outer plate portions  61   a  and  61   b  are fastened to the fitting pin  5  through bolts  65  while making respective contacts with the left and right end faces of the fitting pin  5 . On the other hand, the left and right inner plate portions  63   a  and  63   b  are disposed at respective positions close to the inner surfaces of the second left and right projecting portions  230  and  240 , respectively. The left and right restraining plates  60   a  and  60   b  can prevent the fitting pin  5  from axial movement with respective contacts of the inner plate portions  63   a  and  63   b  thereof with respective inner surfaces of the left and right projecting portions  230  and  240 . Thus using the left and right holding sections  6 A and  6 B eliminates the need for securing special brackets or the like to the insert boom  2 , allowing the total number of components to be reduced. 
     The first attachment body and the second attachment body according to the present invention are not limited to the main boom  1  and the insert boom  2  according to the above-described embodiment, respectively. For example, the first attachment body and the second attachment body may be two arms connected to each other, or may be a boom and an arm connected to each other. 
     As described above, there is provided an attachment for a work machine, the attachment including a first attachment body and a second attachment body that can be detachably coupled to each other and allowing the first and second attachment bodies to be coupled to each other quickly and easily. 
     Provided is an attachment for a work machine, comprising a first attachment body having a first connection end and a second attachment body having a second connection end connectable to the first connection end. The first attachment body includes a first left side plate and a first right side plate arranged left and right, and a first connection plate interconnecting the first left side plate and the first right side plate in the first connection end. The first left side plate has a first left projecting portion that projects beyond the first connection plate toward the second connection end, and the first right side plate has a second right projecting portion that projects beyond the first connection plate toward the second connection end. The second attachment body includes a pair of a second right side plate and a second right side plate, a second connection plate interconnecting the second left side plate and the second right side plate in the second connection end, and a fitting pin extending in a left-right direction. The second left side plate has a second left projecting portion that projects beyond the second connection plate toward the first connection end, and the second right side plate has a second right projecting portion that projects beyond the second connection plate toward the first connection end. The second left projecting portion is formed with a left fitting pin insertion hole penetrating the second left projecting portion in the left-right direction, and the second right projecting portion is formed with a right fitting pin insertion hole penetrating the second right projecting portion in the left-right direction. The fitting pin is inserted through the left insertion hole and the right insertion hole so as to have a left protruding portion protruding to the left outside of the first left projecting portion and a right protruding portion protruding to the right outside of the first right projecting portion. The first left projecting portion is formed with a left notch having a shape opened so as to be able to receive the left protruding portion of the fitting pin radially of the fitting pin, and the first right projecting portion is formed with a right notch having a shape opened so as to be able to receive the right protruding portion of the fitting pin radially of the fitting pin. The interval between the first right side plate and the first left side plate in the left-right direction is greater than the interval between the second right side plate and the second left side plate in the left-right direction. The first attachment body and the second attachment body are configured to he connected to each other in a state where the first left projecting portion and the second right projecting portion are disposed on both outer sides of the second left projecting portion and the second right projecting portion in the left-right direction, and the left projecting portion and the right protruding portion of the fitting pin are configured to be fitted with the left notch and the right notch, respectively, in respective positions on both outer sides of the second left projecting portion and the second right projecting portion in the left-right direction. 
     This attachment, in which the fitting state of the left and right projecting portions of the fitting pin and the left and right notches can be visually recognized from the side, allows the fitting pin and the left and right notches to be easily fitted to each other. This makes it possible to connect the first and second attachment bodies to each other quickly and easily. 
     Preferably, the first attachment body and the second attachment body are configured to be connected to each other in a state where the first attachment body is disposed on a proximal end side and the second attachment body is disposed on a distal end side. 
     This attachment, where the first attachment body disposed on the proximal end side can have a width larger than that of the second attachment body disposed on the distal end side, allows the center of gravity of the entire attachment to be close to the machine body, thereby enabling the attachment to be lifted more safely. 
     It is preferable that: the first attachment body further includes a left auxiliary projecting plate and a right auxiliary projecting plate that project from the first connection plate toward the second connection end of the second attachment body substantially parallel to the first left and right projecting portions on respective inner sides of the first left projecting portion and the first right projecting portion in the left-right directions; the left auxiliary projecting plate and the right auxiliary projecting plate are formed with a left auxiliary notch and a right auxiliary notch, respectively, each having a shape capable of receiving the fitting pin radially of the fitting pin; the first attachment body and the second attachment body are configured to be connected to each other in a state where the first left projecting portion and the first right projecting portion are disposed on both outer sides of the second left projecting portion and the right projecting portion in the left-right directions and the left auxiliary projecting plate and the right auxiliary projecting plate are disposed on respective inner sides of the second left projecting portion and the right projecting portions in the left-right directions, and configured such that the left projecting portion and the right protruding portion of the fitting pin are fitted to the left notch and the right notch and respective inner portions of the fitting pin on respective inner sides of the second left projecting portion and the second right projecting portion in the left-right direction are fitted to the left auxiliary notch and the right auxiliary notch, respectively. 
     According to this attachment, the fitting pin can be supported not only by the first left and right projecting portions formed with the left and right notches but also by the left and right auxiliary projecting plates formed with the left and right auxiliary notches. This allows the bending moment generated in the fitting pin to be reduced as compared with the case where the fitting pin is supported only by the first left and right projecting portions. As a result, the strength required for the fitting pin is reduced. This allows the fitting pin to be given a small diameter to be lighter and allows the fitting pin to be made of an inexpensive material. 
     Preferably, the second attachment body further includes a pin holding unit that holds the fitting pin so as to fix the position of the fitting pin in the left-right direction, the fitting pin being inserted through the fitting pin insertion hole. 
     The pin holding unit according to this embodiment can fix the position, in the left-right direction, of the pin hold unit inserted through the fitting pin insertion hole to be thereby supported with sufficient strength by the second left and right projecting portions. 
     The pin holding unit preferably includes left and right plates fastened to the fitting pin axially of the fitting pin while making contact with the left and right ends of the fitting pin, respectively, and left and right brackets fixed to respective outer surfaces of the second left and right projecting portions to support the left and right plates, respectively. 
     The pin holding unit can fix the position of the fitting pin in the left-right direction with a simple configuration including the left and right plates and the left and right brackets. 
     Alternatively, the pin holding unit preferably holds the fitting pin so as to restrain the left end and the right end of the fitting pin to the second left projecting portion and the second right projecting portion, respectively. 
     Specifically, it is preferable that the pin holding unit has a left restraining plate having a shape straddling the left protruding portion and the second left projecting portion, and a right restraining plate having a shape straddling the right protruding portion and the second right projecting portion; the left restraining plate has a left outer plate portion that is fastened to the left end surface of the fitting pin in a state of being located on an outer side of the left end surface and making contact with the left end surface, and a left inner plate portion that is in proximity to the inner surface of the second left projecting portion; and the right restraining plate has a right outer plate portion that is fastened to the right end surface in a state of being located on an outer side of the right end surface of the fitting pin and making contact with the right end surface, and a right inner plate portion that is in proximity to the inner surface of the second right projecting portion. 
     The use of the left holding portion and the right holding portion eliminates the need for a bracket or the like to be fixed to the second attachment body to allow the number of parts to be reduced.