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CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/892,567, filed on Oct. 18, 2013, which is incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates a supporting structure of excavator. 
         [0004]    2. Background Art 
         [0005]    Conventionally, a tractor with an excavator to the rear portion is known. Such a tractor has a support structure of the backhoe. A general structure of a supporting structure is designed to have an attachment mount on the frame and to fix the excavator on the attachment mount (for example, see JP 2010-71054 A). 
         [0006]    By the way, the tractors have different ground clearances (the distance between the lowest portion of the vehicle body from the ground surface on tires) in accordance with their spec. By adopting the same supporting structure regardless of the spec of the tractor, there may need to change the design of the excavator in each spec. On the contrary, by adopting the same excavator there may need to change the design of the supporting structure in each spec. Accordingly, those tractors have problem which increases numbers of process and the cost. Therefore, the supporting structure which changes the fitting height for the excavator is required. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    Embodiments described herein aim at providing a supporting structure for the excavator changes the fitting height of the backhoe. 
         [0008]    In one embodiment, a supporting structure of excavator for attaching the backhoe with variable height is disclosed comprising: an attachment mount fixed to a frame, andan adjuster plate fixed to the attachment mount, wherein the backhoe is mounted to an appropriate position of the adjuster plate. 
         [0009]    In one embodiment, a through hole is formed in the joint plate of the backhoe, a plurality of through holes corresponding to the through hole of the joint plate is formed in the adjuster plate, and the backhoe is mounted to an appropriate position of the adjuster plate by inserting a bolt through the through hole of the joint plate and one of the through holes of the adjuster plate overlapping one another. 
         [0010]    In one embodiment, a pin is disposed on a side surface of the attachment mount, a hook is formed in a lower edge portions of the adjuster plate, and the adjuster plate is fixed to the attachment mount with the hook of the adjuster plate hooked on the pins of the attachment mount. 
       Advantageous Effects 
       [0011]    In one embodiment, the attachment mount fixed to the frame is equipped. The adjuster plate fixed to the attachment mount is also equipped. And the backhoe is mounted to an appropriate position of the adjuster plate. Therefore, even when the specs of the tractors are different, it is possible to common supporting structure of the excavator and the excavator and to solve the problems increasing process steps and the cost. 
         [0012]    In one embodiment, the through hole is formed in the joint plate  68  of the backhoe. A plurality of through holes corresponding to the through hole of the joint plate is formed in the adjuster plate. And the backhoe is mounted to an appropriate position of the adjuster plate by inserting a bolt through the through hole of the joint plate and one of the through holes of the adjuster plate overlapping one another. Therefore, it makes change the fitting height for the excavator is required. Setting the through holes for each spec of tractors, assembling process becomes easier and the productivity is increased. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES 
         [0013]      FIG. 1  is a diagram showing a tractor. 
           [0014]      FIG. 2  is a diagram showing a supporting structure for a backhoe. 
           [0015]      FIG. 3  is a diagram showing an attachment mount and an adjuster plate. 
           [0016]      FIGS. 4A and 4B  are diagrams showing a step for fixing the adjuster plate to the attachment mount. 
           [0017]      FIGS. 5A and 5B  are diagrams showing a step of mounting the backhoe to an appropriate position of the adjuster plate. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    First, a tractor  100  is briefly described. A supporting structure  7  according to the present invention can be applied to vehicles other than tractors. 
         [0019]      FIG. 1  shows the tractor  100 . In the figure, the front and rear direction and the upper and lower direction of the tractor  100  are indicated. 
         [0020]    The tractor  100  mainly includes a frame  1 , an engine  2 , a transmission  3 , a front axle  4 , and a rear axle  5 . The tractor  100  further includes a backhoe  6 . 
         [0021]    The frame  1  serves as the main structure for the tractor  100 . The engine  2  and the like described below are attached to the frame  1 . 
         [0022]    The engine  2  converts energy obtained by burning a fuel into rotational movement. When an operator operates an acceleration lever, the engine  2  changes the driving state in accordance with the operation. The engine  2  maintains the rotational speed at a constant level even when the load changes. 
         [0023]    The transmission  3  switches between forward and backward movement of the tractor  100  and shifts the speed of the tractor  100 . When the operator operates a shift lever, the operation state of the transmission  3  changes in accordance with the operation. The transmission  3  includes a hydromechanical continuously variable transmission (HMT or I-HMT) as a transmission device. 
         [0024]    The front axle  4  transmits the rotational energy from the engine  2  to front tires  41 . The rotational energy from the engine  2  is input to the front axle  4  through the transmission  3 . The front axle  4  is disposed next to a steering device. When the operator operates a handle, the steering device changes a steering angle of the front tires  41  in accordance with the operation. 
         [0025]    The rear axle  5  transmits the rotational energy from the engine  2  to rear tires  51 . The rotational energy from the engine  2  is input to the rear axle  5  through the transmission  3 . The rear axle  5  is provided with a PTO output mechanism. If a rotary tiller or the like is mounted instead of the backhoe  6 , the PTO output mechanism inputs the rotational energy to the rotary tiller and the like. 
         [0026]    The backhoe  6  is used for excavating the soil and the like. A hydraulic oil is supplied to the backhoe  6  through a hydraulic circuit not shown. The backhoe  6  is coupled to the frame  1  through the supporting structure  7 . The backhoe  6  and the supporting structure  7  for the backhoe  6  are described in detail below. 
         [0027]    First, the supporting structure  7  for the backhoe  6  will be described. 
         [0028]      FIG. 2  shows the supporting structure  7  for the backhoe  6 .  FIG. 3  shows an attachment mount  71  and an adjuster plate  72 , as well as a joint plate  68  of the backhoe  6 . In the figure, the front and rear direction, the left and right direction, and the upper and lower direction of the tractor  100  are indicated. 
         [0029]    The attachment mount  71  mainly includes two plate members  71 P. One plate member  71 P is arranged in parallel with the other plate member  71 P and the plate members  71 P each have a front end portion attached to the frame  1 . Thus, the attachment mount  71  is fixed to the frame  1 . The attachment mount  71  includes a link shaft  71 S having both end portions supported by the two plate members  71 P. 
         [0030]    When the attachment mount  71  is fixed to the frame  1 , the plate members  71 P of the attachment mount  71  are in parallel with the front and rear direction and the upper and lower direction, and thus are perpendicular to the left and right direction. 
         [0031]    A lack portion  71 Pa where the plate member  71 P lacks a front portion is formed in an upper portion of the plate member  71 P. The lack portion  71 Pa is disposed so as not to interfere with a ROPS  11  (see  FIGS. 4 and 5 ). An upper plate  73  to come into contact with the ROPS  11  is attached to a bracket portion  71 Pb described later. The plate member  71 P is also fixed to the ROPS  11  via the upper plate  73  (see  FIGS. 4 and 5 ). 
         [0032]    The bracket portion  71 Pb extending backward is formed in the upper portion of the plate member  71 P. A shaft hole  71   h  is formed in the bracket portion  71 Pb. An upper guide  74  in parallel with the bracket portion  71 Pb is attached to the bracket portion  71 Pb. The upper guide  74  is also provided with a shaft hole  74   h.  The shaft holes  71   h  and  74   h  are formed in such a manner as to be capable of receiving a lock pin  81  (see  FIGS. 4 and 5 ). An end portion of the upper guide portion  74  is bent outward so that a bracket portion  72 Pa described later is able to be received. 
         [0033]    A bracket portion  71 Pc extending forward is formed it a lower portion of the plate member  71 P. The bracket portion  71 Pc is formed to have a lower end positioned lower than the rear axle  5  (see  FIG. 1 ). A lower plate  75  extending below the rear axle  5  is attached to the bracket portion  71 Pc. The plate member  71 P is coupled to the other plate member  71 P through the lower plate  75 . 
         [0034]    A bracket portion  71 Pd extending backward is formed in a lower portion of the plate member  71 P. The bracket portion  71 Pd is provided with a shaft hole  71   i.  A lower guide  76  in parallel with the bracket portion  71 Pd is attached to the bracket portion  71 Pd. The lower guide  76  is also provided with a shaft hole  76   i.  A pin  77  is inserted in the shaft holes  71   i  and  76   i  to have both ends supported. An end portion of the lower guide  76  is bent outward so that a bracket portion  72 Pc described later is able to be received. 
         [0035]    The adjuster plate  72  includes a pair of two plate members  72 P. One plate member  72 P is arranged in parallel with the other plate member  72 P and the plate members  72 P each have a front end portion attached to the plate member  71 P. Thus, the adjuster plate  72  is fixed to the attachment mount  71 . The shapes of the plate members  72 P are symmetrical with one another. 
         [0036]    When the adjuster plate  72  is fixed to the attachment mount  71 , the plate members  72 P of the adjuster plate  72  are parallel with the front and rear direction and the upper and lower direction, and thus are perpendicular to the left and right direction. 
         [0037]    A bracket portion  72 Pa extending forward is formed in an upper portion of the plate member  72 P. The bracket portion  72 Pa has such a thickness to be capable of being inserted between the plate member  71 P (bracket portion  71 Pb) and the upper guide  74  without largely rattling. The bracket portion  72 Pa is provided with a shaft hole  72   h  formed in such a manner that the lock pin  81  can be inserted therethrough (see  FIGS. 4 and 5 ). 
         [0038]    A bracket portion  72 Pc extending forward is formed in a lower portion of the plate member  72 P. The bracket portion  72 Pc has such a thickness to be capable of being inserted between the plate member  71 P (bracket portion  71 Pd) and the lower guide  76  without largely rattling. The bracket portion  72 Pc is provided with a hook  72   f  formed to be capable of being hooked on the pin  77  (see  FIGS. 2 ,  4 , and  5 ). 
         [0039]    The plate member  72 P is provided with a total of eight shaft holes in two rows and four stages. Here, a total of four shaft holes in the first and the third stages from the upper side are defined as “through hole  72   ta ”, whereas a total of four shaft holes in the second and the fourth stages from the upper side are defined as “through hole  72   tb ”. The through holes  72   ta  and  72   tb  are formed in such a manner that a bolt  82  can be inserted therethrough (see  FIGS. 2 and 5 ). In the supporting structure  7 , a total of eight through holes  72   ta  and  72   tb  in two rows and four stages are formed. Alternatively, for example, a total of twelve through holes in two rows and six stages may be formed. 
         [0040]    Next, the backhoe  6  will be described. 
         [0041]    The backhoe  6  mainly includes a boom  61 , an arm  62 , and a bucket  63  (see  FIG. 1 ). The boom  61  has one end supported by a boom bracket  64 , and is rotated by a boom cylinder  65  movable to extend and contract. The arm  62  has one end supported by the boom  61 , and is rotated by an arm cylinder  66  movable to extend and contract. The bucket  63  has one end supported by the arm  62 , and is rotated by a bucket cylinder  67  movable to extend and contract. The boom bracket  64  is supported by a joint plate  68 . 
         [0042]    The joint plate  68  includes a pair of two plate members  68 P. One plate member  68 P is arranged in parallel with the other plate member  68 P and the plate members  68 P each have a front end portion attached to the plate member  72 P. Thus, the joint plate  68  is fixed to the adjuster plate  72 . The shapes of the plate members  68 P are symmetrical with one another. 
         [0043]    When the joint plate  68  is fixed to the adjuster plate  72 , the plate members  68 P of the joint plate  68  are parallel with the front and rear direction and the upper and lower direction, and thus are perpendicular to the left and right direction. 
         [0044]    The plate member  68 P is provided with a total of four shaft holes in two rows and two stages. All the shaft holes are defined as “through hole  68   t ”. The through hole  68   t  is formed in such a manner that the bolt  82  is able to be inserted therethrough (see  FIGS. 2 and 5 ). 
         [0045]    A step for fixing the adjuster plate  72  to the attachment mount  71  is described below. 
         [0046]      FIG. 4  shows the step for fixing the adjuster plate  72  to the attachment mount  71 , and more specifically shows a step for attaching the plate member  72 P to the plate member  71 P. 
         [0047]    First, the operator uses a crane and the like to lift the adjuster plate  72 . Then, the operator inserts the bracket portion  72 Pc between the plate member  71 P (bracket portion  71 Pd) and the lower guide  76 , and hooks the hook  72   f  on the pin  77  (see  FIG. 4A ). Then, the operator rotates the plate member  72 P so that the bracket portion  72 Pa is inserted between the plate member  71 P (bracket portion  71 Pb) and the upper guide  74 . The operator overlaps the shaft hole  72   h  on the shaft holes  71   h  and  74   h.  Finally, the operator inserts the lock pin  81  into the shaft holes  71   h,    72   h,  and  74   h  (see  FIG. 4B ). Thus, the plate member  72 P is attached on the plate member  71 P. Thus, the adjuster plate  72  is fixed to the attachment mount  71 . 
         [0048]    Technical features of the present invention described above are summarized as follows. 
         [0049]    As a first feature, the supporting structure  7  includes the attachment mount  71  to be fixed to the frame  1 . The supporting structure  7  further includes the adjuster plate  72  to be fixed to the attachment mount  71 . The backhoe  6  is mounted to an appropriate position of the adjuster plate  72 . 
         [0050]    Thus, the attachment height of the backhoe  6  can be appropriately changed. Therefore, the backhoe  6  and the supporting structure  7  for the backhoe  6  can be shared between the tractors  100  of different types. Thus, a problem of increase in designing steps and cost can be solved. 
         [0051]    As a second feature, for the supporting structure  7 , the through hole  68   t  is formed in the joint plate  68  of the backhoe  6 . The supporting structure  7  has, in the adjuster plate  72 , a plurality of through holes  72   ta  and  72   tb  corresponding to the through hole  68   t  of the joint plate  68 . The bolt  82  is inserted through the through hole  68   t  of the joint plate  68  and one of the through holes  72   ta  and  72   tb  of the adjuster plate  72  overlapping one another. Thus, the backhoe  6  is mounted to an appropriate position of the adjuster plate  72 . 
         [0052]    Thus, the attachment height of the backhoe  6  can be changed in stages (in two stages in the supporting structure  7 ). Thus, by determining the through hole  72   ta  or  72   tb  through which the bolt  82  is inserted in accordance with the type of the tractor  100 , the assembly process is facilitated, whereby the productivity is improved. 
         [0053]    As a third feature, in the supporting structure  7 , the pins  77  are disposed on the side surfaces of the attachment mount  71 . In the supporting structure  7 , the hooks  72   f  are formed in the lower edge portions of the adjuster plate  72 . The adjuster plate  72  is fixed to the attachment mount  71 , with the hooks  72   f  of the adjuster plate  72  hooked on the pins  77  of the attachment mount  71 . 
         [0054]    Thus, a simple structure with a small number of parts is achieved, whereby reduction of the designing steps and the cost is able to be achieved.

Summary:
For providing a supporting structure for the excavator changes the fitting height of the backhoe, This invention provides a supporting structure of excavator for attaching the backhoe with variable height which comprising: an attachment mount fixed to a frame, and an adjuster plate fixed to the attachment mount, wherein the backhoe is mounted to an appropriate position of the adjuster plate.