Patent Publication Number: US-2018038064-A1

Title: Excavator arm having rotation device

Description:
TECHNICAL FIELD 
     The present invention relates to an excavator arm having a rotation device. More particularly, the present invention relates to an excavator arm having a rotation device, whereby the excavator arm is able to easily change an excavation direction not only into a forward excavation direction and a backward excavation direction, but also into excavation directions at predetermined angles from the forward and backward excavation directions even without separating and remounting a bucket because the rotation device is fixed between an upper arm and a lower arm and can rotate and fix a lower arm at 360° or more in both directions, and to remarkably improve efficiency of excavation, minimize fatigue of a worker, and improve work efficiency because there is no need to separate and remount a bucket. 
     BACKGROUND ART 
     In general, an excavator, which is construction equipment, includes a body mounted on a vehicle, a boom connected to the top of the body to be operated by a boom cylinder, an arm connected to the boom to be operated by an arm cylinder, and a bucket connected to an end of the arm to be operated by a bucket cylinder. 
     In an excavator having this configuration, the boom is moved up and down through a boom joint that is rotated by the boom cylinder and the arm makes crowding and dumping motions by being pulled forward and pushed backward by an arm joint that is rotated by the arm cylinder. 
     However, in an excavator having the configuration of the related art, the arm can be actuated forward and backward by the boom cylinder, but cannot rotate. Accordingly, in order to turn the bucket that has been operated in a forward excavation direction, in which the bucket excavates toward the excavator, into a backward excavation direction, in which the bucket excavates away from the excavator, it is required to stop excavation and then turn and mount the bucket at 180° into the backward excavation direction. Further, it is required to separate and remount the bucket in order to change the excavation direction, which makes the excavation inconvenient. 
     In other words, existing excavator arms cannot change the excavation direction of a bucket, so it is required separate and remount a bucket. Accordingly, it takes time to separate and remount a bucket in order to change the excavation direction of a bucket, which deteriorates efficiency of the excavation. 
     As described above, it is impossible to change the excavation direction of a bucket without separating and remounting the bucket once mounting the bucket on existing excavator arm. Further, since the excavation direction of a bucket is limited to the forward excavation direction and the backward excavation direction, it is required to turn the cab of an excavator or move the excavator, for example, in order to excavate in an arc shape. Accordingly, excavation work takes long time and efficiency of excavation is considerably deteriorated. 
     Accordingly, it is required to study and develop an excavator arm that can easily selectively change an excavation direction of a bucket not only into a forward excavation direction and a backward excavation direction, but into excavation angles at predetermined angles even without separating and remounting the bucket, thereby remarkably improving efficiency of excavation and work efficiency of a worker by minimizing fatigue of the worker. 
     PRIOR ART DOCUMENT 
     (Patent Document 1) Korean Patent Application Publication No. 2014-21084 (published on Feb. 20, 2014) 
     (Patent Document 2) Korean Patent Application Publication No. 2010-74428 (published on Jul. 2, 2010) 
     DISCLOSURE 
     Technical Problem 
     The present invention has been made in an effort to solve the problems and an object of the present invention is to provide an excavator arm having a rotation device disposed between an upper arm and a lower arm, the excavator arm being able to change an excavation direction into a forward excavation direction and a backward excavation direction, and excavation directions at predetermined angles from the forward and backward excavation directions. 
     Another object of the present invention is to remarkably improve efficiency of excavation, minimize fatigue of a worker, and improve work efficiency by easily changing an excavation direction not only into a forward excavation direction and a backward excavation direction, but into excavation directions at predetermined angles from the forward and backward excavation directions even without separating and remounting a bucket. 
     Another object of the present invention is to further stably maintain the lower arm that has been rotated at a predetermined angle during excavating and to further stably perform excavation with the lower arm rotated at a predetermined angle by further including an anti-rotation unit including a stopper gear that selectively engages with a worm wheel of the rotation device. 
     Another object of the present invention is to allow a lower arm to be rotated at 360° or more in both direction, and to be rotated again at a predetermined angle without twisting of the upper hydraulic lines or the lower hydraulic lines when it is required to rotate again the lower arm after rotating it at a predetermined angle, because there is provided a rotation device that is fixed between the upper arm and the lower arm, allows the lower arm to be rotated at 360° or more, and maintains the lower arm at a predetermined angle. Accordingly, the lower arm can be selectively rotated at a minimum rotation angle in a first direction or a second direction, so the lower arm can be more efficiently rotated. 
     Technical Solution 
     The present invention for accomplishing the objects is as follows. That is, an excavator arm having a rotation device according to the present invention is connected to a boom of an excavator to be operated by a cylinder, connected with a bucket for excavation at the lower end through a quick coupler, and connected with a bucket cylinder for operating the bucket over the arm. The arm is divided into an upper arm and a lower arm and a rotation device that selectively rotates the lower arm at predetermined angles over 360° in both directions is fixed between the upper arm and the lower arm. 
     The rotation device may include: an upper arm-fixing plate having a top to which a lower end of the upper arm is fixed; a fixed plate of which a top is fixed in close contact to a bottom of the upper arm-fixing plate; a fixed ring fixed to a bottom of the fixed plate with a lower end bent outward; a rotary ring rotatably fitted on the fixed ring with an upper end bent inward; a rotary plate fixed in close contact to a lower end of the rotary ring to be selectively rotated with the rotary ring; a lower arm-fixing plate fixed in close contact to a bottom of the rotary plate and fixing an upper end of the lower arm; a rotary shaft disposed through centers of the lower arm-fixing plate and the upper arm-fixing plate, with a lower end fixed to the rotary plate through a fixing plate and an upper outer side rotatably supported inside the fixed plate through a shaft bushing; a hydraulic connection cover having fixing brackets protruding outward from an outer side of the hydraulic connection cover with outer ends fixed to a lower inner side of the upper arm, having a coupling groove on a bottom, and having a hydraulic pressure supply guide line and a hydraulic pressure return guide line formed from both sides of a top to the coupling groove to be connected to upper hydraulic lines at both sides of the top; a hydraulic shaft disposed through a center of the rotary shaft, protruding a predetermined distance upward from a top of the rotary shaft having a flange protruding outward to be supported through the center of the rotary shaft by the flange, fixed such that the upper end protruding from the top of the rotary shaft can be rotated through the coupling groove of the hydraulic connection cover, having the hydraulic pressure supply guide line, a hydraulic pressure supply line that communicates with the hydraulic pressure return guide line, and a hydraulic pressure return line that are formed through two positions of an outer side, an inside, and two positions of a bottom thereof, and guiding hydraulic pressure, which is supplied and returned through the upper hydraulic lines connected to the hydraulic pressure supply guide line and the hydraulic pressure return guide line in the hydraulic connection cover, to the bucket cylinder through lower hydraulic lines connected to lower ends of the hydraulic pressure supply line and the hydraulic pressure return line; a driving unit disposed at aside on the top of the upper arm-fixing plate to transmit power for rotating the rotary shaft; an interlocking unit disposed perpendicular to the driving unit at a side on the top of the fixed plate to be operated by power from the driving unit; and an interlocking rotary unit engaged with the interlocking unit and fitted on the upper end of the rotary shaft to rotate the rotary shaft by transmitting power from the interlocking unit. 
     In order to guide hydraulic pressure from the hydraulic pressure supply guide line and the hydraulic pressure return guide line in the hydraulic connection cover to the hydraulic pressure supply line and the hydraulic pressure return line in the hydraulic shaft throughout a rotational direction of 360°, even through the rotary shaft is rotated by the interlocking rotary unit and the hydraulic shaft is rotated at a predetermined angle, a hydraulic pressure supply groove may be formed throughout 360° around the hydraulic shaft at a predetermined depth toward a center from an upper outer side of the hydraulic shaft at an upper end of the hydraulic pressure supply line; and a hydraulic pressure return groove may be formed throughout 360° around the hydraulic shaft at a predetermined depth toward the center from another predetermined position of the upper outer side of the hydraulic shaft at an upper end of the hydraulic pressure return line. 
     A sealing groove may be formed over and under the hydraulic pressure supply groove of the hydraulic shaft and sealing members may be inserted and fixed in the sealing grooves. Further, a sealing groove may be formed over and under the hydraulic pressure return groove of the hydraulic shaft and sealing members may be inserted and fixed in the sealing grooves. 
     The driving unit may include: a bracket fixed to a side on the top of the upper arm-fixing plate; a driving shaft rotatably disposed through the bracket; a driving motor connected with the driving shaft to operate the driving shaft; and a driving gear that is a conical gear disposed at an end of the driving shaft. 
     The interlocking unit may be disposed at a side on the top of the fixed plate to be operated by power from the driving unit, and may include: brackets disposed perpendicular to the driving unit and fixed at a side on the top of the fixed plate; a worm shaft rotatably supported at both ends on the brackets; a worm formed at a center of the worm shaft; an interlocking shaft extending from an end of the worm shaft and protruding a predetermined distance from the bracket; and an interlocking gear that is a conical gear disposed at an end of the interlocking shaft and is perpendicularly in mesh with the driving gear to transmit power from the driving unit to the interlocking shaft. 
     The interlocking rotary unit may be a worm wheel that is engaged with the interlocking unit to be rotated with the worm when the interlocking shaft is rotated. 
     The interlocking unit may be symmetrically fixed in pairs at both sides of the rotary shaft on the top of the fixed plate and the driving unit may also be symmetrically fixed in pairs at both sides of the rotary shaft on the top of the upper arm-fixing plate to correspond to the interlocking units. 
     An anti-rotation unit selectively preventing rotation of the worm wheel by selectively engaging with the worm wheel may be fixed at a side of the rotary shaft on the top of the upper arm-fixing plate in order to maintain the lower arm that has been rotated at a predetermined angle with the upper end fixed to the bottom of the lower arm-fixing plate by the rotary shaft rotating at a predetermined angle. 
     The anti-rotation unit may include: a bracket fixed at a side on the top of the upper arm-fixing plate; a stopper cylinder having a rod supported by the bracket to be able to horizontally reciprocate; and a stopper gear disposed at an end of the rod of the stopper cylinder to selectively engage with the worm wheel. 
     The lower arm may have a coupling bracket on a side of an upper portion to be linked to a lower end of the bucket cylinder so that the bucket can be operated for excavation by the bucket cylinder with the lower arm selectively rotated at a predetermined angle about the upper arm by the rotation device. 
     Advantageous Effects 
     Effects of the excavator arm having a rotation device according to the present invention are as follows. 
     First, since there is provided a rotation device fixed between an upper arm and a lower arm, it is possible to easily change an excavation direction not only into a forward excavation direction and a backward excavation direction, but into excavation directions at predetermined angles from the forward and backward excavation directions even without separating and remounting a bucket. 
     Second, since it is possible to easily change an excavation direction not only into a forward excavation direction and a backward excavation direction, but into excavation directions at predetermined angles from the forward and backward excavation directions even without separating and remounting the bucket, it is possible to remarkably improve efficiency of excavation, minimize fatigue of a worker, and improve work efficiency. 
     Third, it is possible to further stably maintain the lower arm that has been rotated at a predetermined angle during excavating and to further stably perform excavation with the lower arm rotated at a predetermined angle by further including an anti-rotation unit including a stopper gear that selectively engages with a worm wheel of the rotation device. 
     Fourth, since there is provided the rotation unit that is fixed between the upper arm and the lower arm, allows the lower arm to rotate at 360° or more, and maintains the lower arm at a predetermined angle, the lower arm can be rotated at 360° or more both directions, and when it is required to rotate again the lower arm after rotating it at a predetermined angle, the lower arm can be rotated again at a predetermined angle without twisting of the upper hydraulic lines or the lower hydraulic lines. Accordingly, the lower arm can be selectively rotated at a minimum rotation angle in a first direction or a second direction, so the lower arm can be more efficiently rotated. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a front view showing an excavator arm having a rotation device according to the present invention. 
         FIG. 2  is a perspective view showing a rotation device that is an important part of an excavator arm having a rotation device according to the present invention. 
         FIG. 3  is a cross-sectional view showing the rotation device that is an important part of an excavator arm having a rotation device according to the present invention. 
         FIG. 4  is a plan view showing the rotation device that is an important part of an excavator arm having a rotation device according to the present invention. 
         FIGS. 5 and 6  are views sequentially showing selective rotation of a lower arm of the excavator arm having a rotation device according to the present invention. 
         FIG. 7  is a plan view showing another embodiment of the rotation device that is an important part of an excavator arm having a rotation device according to the present invention. 
         FIG. 8  is a plan view showing another embodiment of the rotation device that is an important part of an excavator arm having a rotation device according to the present invention. 
     
    
    
       
     
       
         
           
               
             
               
                   
               
               
                 [Description of Reference Numerals] 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                   
                 100: Boom  
               
               
                   
                 200: Arm cylinder  
               
               
                   
                 300: Arm  
               
            
           
           
               
               
               
            
               
                   
                 310: Upper arm  
                 320: Lower arm  
               
            
           
           
               
               
            
               
                   
                 500: Rotation device  
               
            
           
           
               
               
               
            
               
                   
                 510: Upper arm-fixing plate 
                 511: Fixed plate  
               
               
                   
                 515: Fixed ring  
                 520: Lower arm-fixing plate  
               
               
                   
                 521: Rotary plate  
                 525: Rotary ring  
               
               
                   
                 529: Fixing plate  
                 530: Rotary shaft  
               
               
                   
                 535: Shaft bushing  
                 540: Hydraulic shaft  
               
            
           
           
               
               
            
               
                   
                 541: Flange  
               
               
                   
                 542: Hydraulic pressure supply line  
               
               
                   
                 542a: Hydraulic pressure supply groove  
               
               
                   
                 543: Sealing groove  
               
               
                   
                 543a: Sealing member  
               
               
                   
                 544: Hydraulic pressure return line  
               
               
                   
                 544a: Hydraulic pressure return groove  
               
               
                   
                 545: Sealing groove  
               
               
                   
                 545a: Sealing member  
               
               
                   
                 590: Hydraulic connection cover  
               
               
                   
                 592: Hydraulic pressure supply guide line  
               
               
                   
                 594: Hydraulic pressure return guide line  
               
            
           
           
               
               
               
            
               
                   
                 551: Worm  
                 552: Worm shaft  
               
               
                   
                 553: Interlocking shaft  
                 554: Interlocking gear  
               
               
                   
                 555: Bracket  
                 561: Worm wheel  
               
               
                   
                 570: Driving motor  
                 571: Driving shaft  
               
               
                   
                 573: Driving gear  
                 575: Bracket  
               
               
                   
                 580: Anti-rotation unit  
                 581: Stopper cylinder  
               
               
                   
                 583: Rod  
                 585: Stopper gear  
               
            
           
           
               
               
            
               
                   
                 587: Bracket  
               
            
           
           
               
               
               
            
               
                   
                 601: Upper hydraulic line  
                 605: Lower hydraulic line  
               
               
                   
                 700: Bucket  
                 750: Bucket cylinder 
               
               
                   
                   
               
            
           
         
       
     
     BEST MODE 
     Hereinafter, preferred embodiments of an excavator arm having a rotation device according to the present invention will be described with reference to accompanying drawings. 
       FIG. 1  is a front view showing an excavator arm having a rotation device according to the present invention,  FIG. 2  is a perspective view showing a rotation device that is an important part of an excavator arm having a rotation device according to the present invention,  FIG. 3  is a cross-sectional view showing the rotation device that is an important part of an excavator arm having a rotation device according to the present invention, and  FIG. 4  is a plan view showing the rotation device that is an important part of an excavator arm having a rotation device according to the present invention. 
       FIGS. 5 and 6  are views sequentially showing selective rotation of a lower arm of the excavator arm having a rotation device according to the present invention. 
     As shown in  FIGS. 1 to 6 , an excavator arm  300  having a rotation device according to an embodiment of the present invention is connected to a boom  100  of an excavator to be operated by a cylinder  200 , connected with a bucket  700  for excavation at the lower end through a quick coupler (not indicated by reference numeral), and connected with a bucket cylinder  750  for operating the bucket  700  over the arm  300 . The arm  300  is divided into an upper arm  310  and a lower arm  320  and a rotation device  500  that selectively rotates the lower arm  320  at predetermined angles over 360° in both directions is fixed between the upper arm  310  and the lower arm  320 . 
     In the excavator arm  300  having a rotation device according to the present invention, the lower arm  320  may have a coupling bracket (not indicated by reference numeral) on a side of the upper portion to be linked to the lower end of the bucket cylinder  750  so that the bucket  700  can be operated for excavation by the bucket cylinder  750  with the lower arm  320  selectively rotated at a predetermined angle about the upper arm  310  by the rotation device  500 . 
     In the excavator arm having a rotation device according to the present invention, particularly, the rotation device  500  includes an upper arm-fixing plate  510 , a fixed plate  511 , a fixed ring  515 , a rotary ring  525 , rotary plate  521 , a lower arm-fixing plate  520 , a rotary shaft  530 , a hydraulic connection cover  590 , a hydraulic shaft  540 , a driving unit, an interlocking unit, and an interlocking rotary unit. 
     In detail, the lower end of the upper arm  310  is fixed to the top of the upper arm-fixing plate  510 , and in this case, the lower end of the upper arm  310  may be fixed to the upper arm-fixing plate  510  by welding. 
     The fixed plate  511  is fixed to the upper arm-fixing plate  510  with the top in close contact with the bottom of the upper arm-fixing plate and the upper end of the lower arm  320  may be fixed to the upper arm-fixing plate  520  by welding. 
     Further, the fixed ring  515  is fixed to the bottom of the fixed plate  511  with the lower end bent outward and the rotary ring  525  is rotatably fitted on the fixed ring  515  with the upper end bent inward. 
     The rotary plate  521  is fixed in close contact to the lower end of the rotary ring  525  to be selectively rotated with the rotary ring  535  and the lower arm-fixing plate  520  is fixed in close contact to the bottom of the rotary plate  521  with the upper end of the lower arm  320  fixed thereto. Further, the rotary shaft  530  is disposed through the centers of the lower arm-fixing plate  520  and the upper arm-fixing plate  510 , with the lower end fixed to the rotary plate  521  through a fixing plate  529  and the upper outer side rotatably supported inside the fixed plate  511  through a shaft bushing  535 . 
     Meanwhile, the hydraulic connection cover  590  has fixing brackets  590 ′ protruding outward from the outer side of the hydraulic connection cover with the outer ends fixed to the lower inner side of the upper arm  310 , has a coupling groove  591  on the bottom, and has a hydraulic pressure supply guide line  592  and a hydraulic pressure return guide line  594  formed from both sides of the top to the coupling groove  591  to be connected to upper hydraulic lines  601  at both sides of the top. 
     The hydraulic shaft  540  is disposed through the center of the rotary shaft  530 , protrudes a predetermined distance upward from the top of the rotary shaft  530 , and has a flange  541  protruding outward, so it is supported through the center of the rotary shaft  530  by the flange  541 . 
     The hydraulic shaft  540  fixed such that the upper end protruding from the top of the rotary shaft  530  can be rotated through the coupling groove  591  of the hydraulic connection cover  590 , and the hydraulic pressure supply guide line  592 , a hydraulic pressure supply line  542  that communicates with the hydraulic pressure return guide line  594 , and a hydraulic pressure return line  544  are formed through two positions of the outer side, the inside, and two positions of the bottom. 
     The hydraulic shaft  540  guides the hydraulic pressure, which is supplied and returned through the upper hydraulic lines  601  connected to the hydraulic pressure supply guide line  592  and the hydraulic pressure return guide line  594  in the hydraulic connection cover  590 , to the bucket cylinder  750  through lower hydraulic lines  605  connected to the lower ends of the hydraulic pressure supply line  542  and the hydraulic pressure return line  544 . 
     The driving unit is disposed at a side on the top of the upper arm-fixing plate  510  to supply power for rotating the rotary shaft  530 . 
     The driving unit may include a bracket  575  fixed to a side on the top of the upper arm-fixing plate  510 , a driving shaft  571  rotatably disposed through the bracket  575 , a driving motor  570  connected with the driving shaft  571  to operate the driving shaft  571 , and a driving gear  573  that is a conical gear disposed at an end of the driving shaft  571 . 
     The interlocking unit is disposed perpendicular to the driving unit at a side on the top of the fixed plate  511  to be operated by power from the driving unit. 
     The interlocking unit is disposed at a side on the top of the fixed plate  511  to be operated by the power from the driving unit and includes brackets  555 , a worm shaft  552 , a worm  551 , an interlocking shaft  553 , and an interlocking gear  554 . 
     The brackets  555  may be disposed perpendicular to the driving unit and fixed at a side on the top of the fixed plate  511 . 
     Further, the worm shaft  552  is rotatably supported at both ends on the brackets  555  and the worm  551  is formed at the center of the worm shaft  552 . 
     The interlocking shaft  553  extends from an end of the worm shaft  551  and protrudes a predetermined distance from a bracket  555  and the interlocking gear  554  is a conical gear disposed at an end of the interlocking shaft  553  and is perpendicularly in mesh with the driving gear  573  to transmit the power from the driving unit to the interlocking shaft  553 . 
     The interlocking rotary unit is engaged with the interlocking unit and is fitted on the upper end of the rotary shaft  530  to rotate the rotary shaft  530  by transmitting the power from the interlocking unit. 
     The interlocking rotary unit may be a worm wheel  561  that is engaged with the interlocking unit to be rotated with the worm  551  when the interlocking shaft  553  is rotated. 
     That is, when the worm wheel  561  is rotated in mesh with the worm  551 , the rotary shaft  530  is rotated, and accordingly, the rotary plate  521  fixed to the lower end of the rotary shaft  530  by the fixing plate  529  can be rotated. 
     In other words, as the rotary plate  521  is rotated, the lower arm-fixing plate  520  fixed in close contact to the bottom of the rotary plate  521  is rotated, and the lower arm  320  of which the upper end is fixed to the bottom of the lower arm-fixing plate  520  is rotated. 
     In the excavator arm  300  having a rotation device according to the present invention, it is important to guide hydraulic pressure from the hydraulic pressure supply guide line  592  and the hydraulic pressure return guide line  594  in the hydraulic connection cover  590  to the hydraulic pressure supply line  542  and the hydraulic pressure return line  544  in the hydraulic shaft  540  throughout the rotational direction of 360° or more in both directions, even through the rotary shaft is rotated by the interlocking rotary unit and the hydraulic shaft  540  is rotated at a predetermined angle. 
     Accordingly, a hydraulic pressure supply groove  542   a  is formed throughout 360° around the hydraulic shaft  540  at a predetermined depth toward the center from a predetermined position of the upper outer side of the hydraulic shaft  540  at the upper end of the hydraulic pressure supply line  542 . 
     A sealing groove  543  may be formed over and under the hydraulic pressure supply groove  542   a  of the hydraulic shaft  540  and sealing members  543   a  may be inserted and fixed in the sealing grooves  543 . 
     Accordingly, a hydraulic pressure return groove  544   a  is formed throughout 360° around the hydraulic shaft  540  at a predetermined depth toward the center from another predetermined position of the upper outer side of the hydraulic shaft  540  at the upper end of the hydraulic pressure return line  544 . 
     A sealing groove  545  may be formed over and under the hydraulic pressure return groove  544   a  of the hydraulic shaft  540  and sealing members  545   a  may be inserted and fixed in the sealing grooves  545 . 
     Use of the excavator arm having a rotation device according to the present invention is described with reference to  FIGS. 1 to 4 , for rotation angle of 180° of the bucket  700  that is rotated by the lower arm  320 , as shown in  FIGS. 5 and 6 . 
     MODE FOR INVENTION 
     Use of the excavator arm having a rotation device according to the present invention is described hereafter. First, when it is required to rotate the bucket  700  at a predetermined angle, a work in the cab operates the driving motor  570  so that the worm  551  is rotated by power transmitted through the interlocking unit. 
     When the worm  551  is rotated, the worm wheel  561  engaged with the worm  551  is rotated, and the rotary shaft  530 , the rotary plate  521 , and the lower arm-fixing plate  520  are correspondingly rotated. Accordingly, the lower arm  320  of which the upper end is fixed to the bottom of the lower arm-fixing plate  520  is rotated. 
     When the rotary shaft  530  is rotated, the hydraulic shaft  540  is rotated with the rotary shaft  530 , but the upper end of the hydraulic shaft  540  is fixed to the coupling groove  591  of the hydraulic connection cover  590 . 
     After the lower arm  320  is rotated at a predetermined angle through this process, the worker stops the driving motor  570  and then he/she can start excavating. 
     Since the worm wheel  561  and the worm  551  are in mesh with each other, once the lower arm  320  is rotated at a predetermined angle, excavation can be stably performed with the lower arm  320  rotated at the angle. 
     The use of the excavator arm having a rotation device according to the present invention is described for the rotation angle of 180° that is rotated by the lower arm  320 , but the bucket  700  that is rotated by the lower arm  320  can be rotated at 360° in a predetermined direction and a worker can variously change the angle in the cab into 30°, 45°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 310°, 330°, etc. 
     Obviously, the rotation angle of the bucket  700  that is rotated by the lower arm  320  can be changed in the same way in the other direction. 
     In other words, in order to variously change the rotation angle of the bucket  700  that is rotated by the lower arm  320  in first and second directions, the driving motor  570  may be a forward-reverse motor that is selectively rotated forward and backward, so a worker can variously change the rotation angle of the bucket  700  by rotating the lower arm  320  through the motor in the cab. 
     Further, in the excavator arm having a rotation device according to the present invention, first ends of the lower hydraulic lines  602  may be connected to the hydraulic shaft  540  and second ends may be connected to the bucket cylinder  750  through the lower arm  320 . 
       FIG. 7  is a plan view showing another embodiment of the rotation device that is an important part of an excavator arm having a rotation device according to the present invention. 
     As shown in  FIG. 7 , this embodiment is different from the embodiment described with reference to  FIGS. 1 to 6  only in that there is further provided an anti-rotation unit  580 , so the same components are not described herein. 
     Referring to  FIG. 7  with  FIGS. 1 to 6 , in this embodiment of the rotation device that is an important part of an excavator arm having a rotation device according to the present invention, an anti-rotation unit  580  that selectively prevents rotation of the worm wheel  561  at a side of the rotary shaft  530  on the top of the upper arm-fixing plate  510  by selectively engaging with the worm wheel  561  so that the lower arm  320  of which the upper end is fixed to the bottom of the lower arm-fixing plate  520  is maintained at a predetermined angle after rotated at the angle by the rotary shaft  530 . 
     The anti-rotation unit  580  may include a bracket  587  fixed at a side on the top of the upper arm-fixing plate  510 , a stopper cylinder  581  having a rod  583  supported by the bracket  587  to be able to horizontally reciprocate, and a stopper gear  585  disposed at an end of the rod  583  of the stopper cylinder  581  to selectively engage with the worm wheel  561 . 
       FIG. 8  is a plan view showing another embodiment of the rotation device that is an important part of an excavator arm having a rotation device according to the present invention. 
     As shown in  FIG. 8 , this embodiment is different from the embodiment described with reference to  FIGS. 1 to 6  only in that there is provided pairs of driving units and interlocking rotary units, so the same components are not described herein. 
     Referring to  FIG. 8  with  FIGS. 1 to 6 , pairs of driving units and interlocking rotary units may be provided in this embodiment of the rotation device that is an important part of an excavator arm having a rotation device according to the present invention. 
     In other words, the interlocking units may be symmetrically fixed in pairs at both sides of the rotary shaft  530  on the top of the fixed plate  511  and the driving units may also be symmetrically fixed in pairs at both sides of the rotary shaft  530  on the top of the upper arm-fixing plate  510  to correspond to the interlocking units. 
     Since the driving units and the interlocking rotary units are provided each in pairs, the lower arm can be more stably rotated. Further, when the worm wheel  561  that is being rotated is stopped, the worms  551  restrict the worm wheel  561  in pairs by engaging with the worm wheel  561 . Accordingly, the bucket  700  can be stably fixed without moving, for example, rotating with respect to the lower arm  320  that is rotated by the worm wheel  561  when excavating after rotated. 
     According to the embodiments of an excavator arm having a rotation device according to the present invention, since the rotation device  500  is disposed and fixed between the upper arm  310  and the lower arm  320 , it is possible to easily change an excavation direction not only into a forward excavation direction and a backward excavation direction, but into excavation directions at predetermined angles from the forward and backward excavation directions even without separating and remounting the bucket  700 . 
     Further, since it is possible to easily change an excavation direction not only into a forward excavation direction and a backward excavation direction, but into excavation directions at predetermined angles from the forward and backward excavation directions even without separating and remounting the bucket  700 , it is possible to remarkably improve efficiency of excavation, minimize fatigue of a worker, and improve work efficiency. 
     Further, since there is further provided the anti-rotation unit  580  including the stopper gear  585  that selectively engages with the worm wheel  561  of the rotation device  500 , it is possible to further stably maintain the lower arm  320  that has been rotated at a predetermined angle during excavating, so it is possible to further stably perform excavation with the lower arm  320  rotated at a predetermined angle. 
     Further, since there is provided the rotation device  500  that is fixed between the upper arm  310  and the lower arm  320 , allows the lower arm  320  to rotate at 360° or more, and maintains the lower arm at a predetermined angle, the lower arm can be rotated at 360° or more both direction, and when it is required to rotate again the lower arm after rotating it at a predetermined angle, the lower arm can be rotated again at a predetermined angle without twisting of the upper hydraulic lines  601  or the lower hydraulic lines  605 . Accordingly, the lower arm  320  can be selectively rotated at a minimum rotation angle in a first direction or a second direction, so the lower arm  320  can be more efficiently rotated. 
     Although embodiments of the present invention were described above, the present invention is not limited thereto, the present invention may be modified in various ways by those skilled in the art, and the modifications are included in the scope of the present invention.