Abstract:
A robot arm assembly with tubes or pipes carrying fluids or electrical cables which do not get bent and are relatively straight, and are not disrupted by, the moving parts of the robot arm includes a first robot arm, a second robot arm, a third robot arm, and a flexible carrying tube. The second robot arm includes a first axle base, a first input shaft, a first bevel gear, and a second bevel gear. The flexible tube is inserted into the first bevel gear and the second bevel gear along a first axis, and fixed to the output shaft.

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to robot arm assemblies, particularly to a robot arm assembly including several robot arms rotatably connected. 
     2. Description of Related Art 
     Robots are applied to perform tasks in environments hazardous or difficult for human operators, such as to spray or clean a workpiece, for example. Tubes or cables are provided to transfer liquid for spraying or cleaning in robots, in spraying or cleaning process. In order to maintain an orderly appearance, the cables are received in a tube which is placed inside the robot and pass through a plurality of arms of the robot. However, because the arms of the robot rotate along different axes, the tubes for receiving the cables are bent following an operation of the robot. The flow of liquid in the cable may be disrupted, which results in a lower spraying efficiency or cleaning efficiency. In addition, action of the arms may abrade or even sever the tube. 
     Therefore, there is room for improvement in the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout several views. 
         FIG. 1  is an isometric view of an embodiment of a robot arm assembly. 
         FIG. 2  is a cross-sectional view of the robot arm assembly taken along line II-II shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 and 2  show one embodiment of a robot arm assembly  100 . The robot arm assembly  100  includes a first robot arm  10 , a second robot arm  30 , a third robot arm  50 , and a flexible cable receiving tube  70 . The first robot arm  10  is sleeved on the second robot arm  30 , and is rotatably connected to the second robot arm  30 . The second robot arm  30  is sleeved on the third robot arm  50 , and is rotatably connected to the third robot arm  50 . The flexible cable receiving tube  70  is inserted into the second robot arm  30  and the third robot arm  50 , and an end of the flexible cable receiving tube  70  is connected to an end of the third robot arm  50  away from the first robot arm  10 . In the illustrated embodiment, the robot arm assembly  100  is configured for a six-axis robot. The first robot arm  10 , the second robot arm  30 , and the third robot arm  50  are a fourth robot arm (not shown), a fifth robot arm (not shown), and a sixth robot arm (not shown) of a six-axis robot, respectively. 
     The first robot arm  10  is substantially cylindrical, and rotates around a first axis A (shown in  FIG. 2 ). The second robot arm  30  includes a first input shaft  31 , a first axle base  33 , a first bevel gear  35 , a first bearing  36 , a second bevel gear  37 , and a second bearing  38 . The first input shaft  31  is substantially cylindrical, and a diameter of the first input shaft  31  is smaller than a diameter of the first robot arm  10 . The first input shaft  31  is coaxially received in the first robot arm  10 , and the first input shaft  31  rotates around the first axis A. An end  311  of the first input shaft  31  is substantially coplanar with an end  11  of the first robot arm  10 . 
     A shape of the first axle base  33  is substantially configured to be a shape of a cylinder cut along a line intersecting with an axis of the cylinder, and thus a longitudinal sectional view of the first axle base  33  is substantially triangular. The first axle base  33  includes a first opening end  331 , and a second opening end  333  opposite to the first opening end  331 . A diameter of the first opening end  331  is substantially equal to a diameter of the end  11  of the first robot arm  10  that is substantially coplanar with the first input shaft  31 . A diameter of the second opening end  333  is substantially greater than the diameter of the first opening end  331 . An axis of the second opening end  333  is defined as a second axis B. The second axis B is inclined relative to an axis of the first opening end  331 . The first opening end  331  is fastened to the end  11  of the first robot arm  10 , and thus the axis of the first opening end  331  overlaps with the first axis A. The first axis A is inclined relative to the second axis B. 
     A diameter of the first bevel gear  35  is substantially equal to a diameter of the first input shaft  31 . The first bevel gear  35  is mounted on the first opening end  331  of the first axle base  33 , and is fixed to the first input shaft  31  by fasteners, which enables the first input shaft  31  to rotate the first bevel gear  35 . The first bearing  36  is sleeved on a connecting portion of the first input shaft  31  and the first bevel gear  35 , to avoid a rotation of the first axle base  33  following a rotation of the first bevel gear  35  or a rotation of the first input shaft  31 . 
     The second bevel gear  37  is mounted on the second opening end  333  of the first axle base  33 , and is connected to the third robot arm  50 , thus the second bevel gear  37  rotates around the second axis B. An end of the second bevel gear  37  adjacent to the first bevel gear  35  meshes with the first bevel gear  35 , and thus the first bevel gear  35  rotates the second bevel gear  37 . The second bearing  38  is sleeved on the second bevel gear  37 , to avoid a rotation of the first axle base  33  following a rotation of the second bevel gear  37 . 
     The third robot arm  50  includes a second input shaft  51 , a second axle base  52 , a third bevel gear  53 , a third bearing  54 , a fourth bevel gear  55 , a fifth bevel gear  56 , a fourth bearing  57 , an output shaft  58 , and a fifth bearing  59 . 
     The second input shaft  51  is substantially cylindrical, and a diameter of the second input shaft  51  is substantially smaller than that of the first input shaft  31 . The second input shaft  51  is coaxially received in the first input shaft  31 , thus the second input shaft  51  rotates around the first axis A. An end  511  of the second input shaft  51  is substantially coplanar with the end  311  of the first input shaft  31 . 
     A shape of the second axle base  52  is substantially configured in a shape of a frustum cut along a line intersecting with an axis of the frustum. The second axle base  52  is located at a side of the second input shaft  51  adjacent to the second bevel gear  37 , and includes a third opening end  521  and a fourth opening end  523  opposite to the third opening end  521 . The third opening end  521  is substantially ring-like, and a diameter of the third opening end  521  is substantially smaller that that of the second opening end  333  of the first axle base  33 . The fourth opening end  523  is substantially a ring, and a diameter of the fourth opening end  523  is substantially smaller than that of the third opening end  521 . An axis of the third opening end  521  is inclined relative to an axis of the fourth opening end  523 . An inclined angle between the axis of the third opening end  521  and the axis of the fourth opening end  523  is substantially equal to an inclined angle between the axis of the first opening end  331  and the axis of the second opening end  333 . The third opening end  521  is located opposite to the second opening end  333 , and is fastened to the second bevel gear  37 . Thus, the axis of the third opening end  521  substantially overlaps the second axis B, and the axis of the fourth opening end  523  substantially overlaps the first axis A. 
     A diameter of the third bevel gear  53  is substantially equal to a diameter of the second input shaft  51 . The third bevel gear  53  is mounted in the first opening end  331  of the first axle base  33 , and is fastened to the second input shaft  51 , which enables the second input shaft  53  to rotate the third bevel gear  53 . The third bearing  54  is sleeved on a connecting portion of the third bevel gear  53  and the second input shaft  51 , thus the third bevel gear  53  and the first bevel gear  35  can rotate freely. 
     The fourth bevel gear  55  is coaxially received in the second bevel gear  37 , and an end of the fourth bevel gear  55  located adjacent to the third bevel gear  53  meshes with the third bevel gear  53 . The fifth bevel gear  56  is coaxially received in the third opening end  521 , and meshes with the fourth bevel gear  55 . The fourth bevel gear  55  rotates around the second axis B. The fifth bevel gear  56  rotates around the second axis B. The fourth bearing  57  is sleeved on a connecting portion of the fifth bevel gear  56  and the fourth bevel gear  55 , to avoid a rotation of the second axle base  52  and the second bevel gear  37  following a rotation of the fifth bevel gear  56  or a rotation of the fourth bevel gear  55 . 
     The output shaft  58  is substantially cylindrical, mounted in the fourth opening end  523 , and is fastened to the fifth bevel gear  56 , thus the fifth bevel gear  56  rotates the output shaft  58  around the second axis B. The fifth bearing  59  is mounted between the second axle base  52  and the output shaft  58 , to avoid a rotation of the second axle base  52  following a rotation of the output shaft  58 . 
     The flexible cable receiving tube  70  is substantially cylindrical, and is inserted into the third bevel gear  53 , the fourth bevel gear  55 , the fifth bevel gear  56 , and the output shaft  58 . An end of the flexible cable receiving tube  70  communicates with the second input shaft  51 , and the other end of the flexible cable receiving tube  70  is fixed on the output shaft  58 , to receive cables carrying electrical power or liquids. The flexible cable receiving tube  70  is positioned along the first axis A, and rotates around the first axis A. 
     In assembly, the third bevel gear  53  is fixed on the second input shaft  51 , and the third bearing  54  is sleeved on a connecting portion of the third bevel gear  53  and the second input shaft  51 . The first input shaft  31  is sleeved on the second input shaft  51 . The first bevel gear  35  is sleeved on the third bearing  54 , and is fixed to the first input shaft  31 . The first bearing  36  is sleeved on the first bevel gear  35 . The first robot arm  10  is sleeved on the first input shaft  31 . The first axle base  33  is sleeved on the first bearing  36 , and is fixed to the first opening end  331 . The fourth bevel gear  55  is mounted on the second opening end  333 , and meshes with the third bevel gear  53 . The fifth bevel gear  56  is mounted on the second opening end  333 , and meshes with the fourth bevel gear  55 . The output shaft  58  is fixed to the fifth bevel gear  56 . The fifth bearing  59  is sleeved on the output shaft  58 . The fourth bearing  57  is sleeved on a meshing portion of the fifth bevel gear  56  and the fourth bevel gear  55 . The second bevel gear  37  is sleeved on the fourth bearing  57 . The second axle base  52  is sleeved on the fifth bearing  59 , and the second bevel gear  37  is fixed to the third opening end  521 . The second bearing  38  is mounted between the second bevel gear  37  and the first axle base  33 . The flexible cable receiving tube  70  is inserted into the third bevel gear  53 , the fourth bevel gear  55 , the fifth bevel gear  56 , and the output shaft  58 , and is fixed to the output shaft  58 . 
     In use, cables carrying liquids, for example, are inserted into the flexible cable receiving tube  70 , and extend to the output shaft  58 . The first robot arm  10  rotates around the first axis A, and then drives the first axle base  33  to rotate around the first axis A. The first input shaft  31  rotates around the first axis A, and then the second axle base  52  rotates around the second axis B when driven by the first bevel gear  35  and the second bevel gear  37 . The second input shaft  51  rotates around the first axis A, and then the output shaft  58  rotates around the first axis A when driven by the third bevel gear  53 , the fourth bevel gear  55 , and the fifth bevel gear  56 , and thus rotates the flexible cable receiving tube  70  around the first axis A. 
     In an alternative embodiment, the first robot arm  10 , the first input shaft  31 , and the second input shaft  51  do not rotate along a same axis, and may rotate along different parallel axes. An axis of the first opening end  331  may be parallel to the first axis A. An axis of the second opening end  333  may be parallel to the second axis B. 
     It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the embodiments or sacrificing all of its material advantages.