Patent Publication Number: US-2010116078-A1

Title: Electrical connecting device of joint unit and robot having the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority benefit of Korean Patent Application No. 10-2008-0111945, filed on Nov. 12, 2008, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     Embodiments relate to a robot joint. More particularly, embodiments relate to a robot joint having an electricity connecting device. 
     2. Description of the Related Art 
     A robot has joints to perform a mechanical motion. For example, a robot arm includes an upper arm part, a forearm part, and an elbow joint. The upper arm and forearm parts are folded or unfolded by the elbow joint. 
     The robot includes an electric system to operate a required function. The electric system includes numerous harnesses to operate the robot. Here, the harnesses may include an electric power line, a communication line, a sensor line, etc. These harnesses are installed in the robot. In general, most harnesses are installed in the robot while passing through the robot joint. 
     Particularly, in the case of the harnesses passing through the robot joint, the harnesses must have a length margin to ensure a mobile angle of the robot joint when the robot joint moves. For example, in the case of a robot arm, an upper arm part and a forearm part are folded or unfolded according to the operation of an elbow joint. At this time, the harness, which passes through the elbow joint, must have the length margin in order to facilitate the motion of the elbow joint. 
     However, if the harness is provided in the robot joint with the length margin, the harnesses may be entangled when the robot joint operates so that the harnesses may be broken down. If the harnesses are broken down, the electric system may not normally operate. 
     SUMMARY 
     Accordingly, it is an aspect of exemplary embodiments to provide an electrical connecting device of a joint unit, capable of ensuring a mobile angle of a robot joint. 
     It is another aspect of exemplary embodiments to provide an electrical connecting device of a joint unit, capable of enabling a robot to normally perform functions thereof. 
     In accordance with an aspect of exemplary embodiments, there is provided an electrical connecting device of a joint unit including a first link, a second link rotatably coupled to the first link, a first conductor provided at the first link, and a second conductor provided at the second link to make contact with the first conductor. 
     At least one of the first conductor and the second conductor may have an arc shape having a constant radius about a rotational center of the second link. 
     The first and second conductors may have arc shapes having a constant radius about the rotational center of the second link. 
     The second conductor may slide on the first conductor as the second link rotates. 
     The first and second conductors may be press-fitted to each other. 
     The first conductor may include a receptacle and the second conductor may include a protrusion so that the protrusion is inserted into the receptacle. 
     The electrical connecting device may include a first electric cable provided at the first link and connected to the first conductor, and a second electric cable provided at the second link and connected to the second conductor. 
     According to another as aspect of exemplary embodiments, there is provided a robot including a first link, a second link, and a joint unit connecting the first link to the second link and including a first joint part fixed at one side of the first link, and a second joint part fixed at one side of the second link and rotatably coupled to the first joint part, wherein first and second conductors are provided between the first and second joint parts to make contact with each other such that the first and second conductors are electrically connected to each other. 
     The second conductor may slide on the first conductor as the second joint part rotates. 
     The first conductor may be provided at the first joint part, the second conductor may be provided at the second joint part, the first conductor may be connected to a first electric cable provided at the fist link, and the second conductor may be connected to a second electric cable provided at the second link. 
     As described above, according to the electrical connecting device of the joint unit of exemplary embodiments, the mobile angle of the joint unit can be increased by allowing two conductors to be electrically connected to the joint unit. 
     In addition, by removing the electric cables from the joint unit, problems caused by the electric cables, such as breakage of the electric cables, can be prevented so that the robot can normally perform all functions thereof, thereby improving reliability of the electric system. 
     In addition, the joint unit may be configured to be electrically connected at all time, so that the joint unit can be used in the form of a module. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects of exemplary embodiments will become apparent and more readily appreciated from the following description of exemplary embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a perspective view showing a robot leg according to an exemplary embodiment; 
         FIG. 2  is a sectional view showing a knee joint unit of the robot leg according to an exemplary embodiment; 
         FIG. 3  is an exploded perspective view showing a knee joint unit according to an exemplary embodiment; 
         FIGS. 4 and 5  are schematic views showing the operation of a knee joint unit according to an exemplary embodiment; and 
         FIG. 6  is a perspective view showing first and second conductors of an electrical connecting device according to another exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. 
       FIG. 1  is a perspective view showing a robot leg according to an exemplary embodiment, and  FIG. 2  is a sectional view showing a knee joint unit of the robot leg according to an exemplary embodiment. 
     As shown in  FIGS. 1 and 2 , a robot leg  10  according to an exemplary embodiment includes a femoral part  11 , a lower leg part  12 , and a knee joint unit  13 . As the knee joint unit  13  is driven, the femoral part  11  and the lower leg part  12  are folded or unfolded. 
     The robot leg  10  includes a motor  17 , which provides power to the knee joint unit  13 . The motor  17  is installed in the femoral part  11  to provide power to the knee joint unit  13  through a power transmission device  14 . 
     The power transmission device  14  connects the motor  17  to the knee joint unit  13 . In detail, the power transmission device  14  connects a driving shaft  18  of the motor  17  to a rotation shaft  23  of the knee joint unit  13 . Therefore, as the driving shaft  18  of the motor  17  rotates, the rotation shaft  23  of the knee joint unit  13  also rotates by the power transmission device  14 .  FIG. 1  shows the power transmission device  14  including a belt  15  and a pulley  16 . The power transmission device  14  may also include a gear. 
     The knee joint unit  13  includes a rotation shaft  23 . The rotation shaft  23  can be integrally formed with the lower leg part  12  or can be fixed to the lower leg part  12  as a separate member. 
     Driving force of the motor  17  is transferred to the rotation shaft  23  of the knee joint unit  13  by the power transmission device  14 , so that the rotation shaft  23  can rotate. As the rotation shaft  23  rotates, the lower leg part  12  can rotate together with the rotation shaft  23 . Therefore, the lower leg part  12  rotates relative to the femoral part  11 , so that the lower leg part  12  and the femoral part  11  can be folded or unfolded. 
     The robot leg  10  includes an electric system to perform a required function. The electric system includes electric cables  35  and  36  capable of transmitting electric power, electric signal, etc. These electric cables  35  and  36  are installed in the robot leg  10 . For example, as shown in  FIGS. 1 and 2 , the first electric cable  35  is installed in the femoral part  11  and the second electric cable  36  is installed in the lower leg part  12 . The first and second electric cables  35  and  36  are connected with each other by an electric connecting device  30 , which is provided in the knee joint unit  13 . 
     If the first and second electric cables  35  and  36  are connected with each other at the knee joint unit  13  by the electric connecting device  30 , the mobile angle of the joint unit can be sufficiently ensured. Hereinafter, this will be described in detail. 
       FIG. 3  is an exploded perspective view showing a knee joint unit according to an exemplary embodiment. 
     As shown in  FIGS. 2 and 3 , the knee joint unit  13  according to an exemplary embodiment includes a first joint part  21  provided at one side of the femoral part  11  and a second joint part  22  provided at one side of the lower leg part  12 . The first and second joint parts  21  and  22  are coupled to each other by a shaft. That is, a rotation shaft  23  of the second joint part  22  is rotatably inserted into a groove  24  of the first joint part  21 . The rotation shaft  23  rotates together with the second joint part  22 . As described above, the rotation shaft  23  can be integrally formed with the second joint part  22  or can be fixed to the second joint part  22  as a separate member. 
     The knee joint unit  13  includes an electric connecting device  30  for electrically connecting the first joint part  21  and the second joint part  22 , which are relatively rotating. The electric connecting device  30  includes a first conductor  31  provided at the first joint part  21  and a second conductor  32  provided at the second joint part  22 . As shown in  FIG. 2 , the first and second conductors  31  and  32  are in contact with each other in such a manner that they can be electrically connected at all time. 
     In addition, the knee joint unit  13  may include an absolute encoder or a torque sensor in order to transmit a detecting signal corresponding to rotation angle thereof. The knee joint unit  13  may also include a sensor, such as a mechanical stopper or a photo limit switch, to prevent the knee joint unit  13  from excessively moving beyond the mobile angle. 
     The first conductor  31  has an arc shape having the constant radius about the rotation shaft  23  and the second conductor  32  has an arc shape having the constant radius about the rotation shaft  23 . The first and second conductors  31  and  32  are press-fitted to each other such that a protrusion  34  of the second conductor  32  can be inserted into a receptacle  33  of the first conductor  31 . According to these shape and structure, if the second joint part  22  rotates, the second conductor  32  slides on the first conductor  31  and the first and second conductors  31  and  32  are in contact with each other in such a manner that they can be electrically connected at all time. In contrast, although not shown in drawings, the first conductor  31  can be provided with a protrusion and the second conductor  32  can be provided with a receptacle in such a manner that the protrusion of the first conductor  31  can be inserted into the receptacle of the second conductor  32 . 
       FIGS. 4 and 5  are schematic views showing the operation of the knee joint unit according to an exemplary embodiment. 
     As shown in  FIGS. 4 and 5 , according to the knee joint unit  13  of exemplary embodiments, the femoral part  11  and the lower leg part  12  of the robot leg  10  are unfolded at the initial state as shown in  FIG. 4 . Meanwhile, the femoral part  11  and the lower leg part  12  of the robot leg  10  are folded at the operation state as shown in  FIG. 5 . Here, the operation state refers to a state that the knee joint unit  13  is operated by a motor  17  to rotate the second joint part  22  (or lower leg part  12 ) by a certain degree. 
     In the initial state of the knee joint unit  13 , a right part of the first conductor  31  overlaps a left part of the second conductor  32 . However, in an operation state of the knee joint unit  13 , the first conductor  31  completely overlaps the second conductor  32  as the second conductor  32  slides on the first conductor  31 . As described above, the first and second conductors  31  and  32  are in contact with each other in such a manner that they can be electrically connected at all time. Thus, if the arc shapes of the first and second conductors  31  and  32  are larger, the mobile angle of the knee joint unit  13  can be sufficiently increased. That is, the rotation angle of the second joint part  22  can be increased. 
     In addition, since the first and second conductors  31  and  32  are not easily broken down, they can perform all functions of the robot. Referring to  FIG. 3 , the first electric cable  35  is connected to one end  31   a  of the first conductor  31  and the second electric cable  36  is connected to one end  32   a  of the second conductor  32 . Since the first and second conductors  31  and  32  are in contact with each other at all time, the first electric cable  35 , the first conductor  31 , the second conductor  32 , and the second electric cable  36  can be electrically connected with each other. Since the first electric cable  35  rotates together with the first joint part  21 , the margin of the first electric cable  35  is not required. Since the second electric cable  36  also rotates together with the second joint part  22 , the margin of the second electric cable  36  is not required. Thus, the problem occurring in the prior art, in which the margin of the electric cable installed between the first joint part  21  and the second joint part  22  is broken down, can be prevented. 
     Meanwhile, the knee joint unit  13  can be used in the form of a module. That is, in order to connect the femoral part  11  to the lower leg part  12 , the first joint part  21  of the knee joint unit  13  is coupled with the femoral part  11  and the second joint part  22  of the knee joint unit  13  is coupled with the lower leg part  12 . Thereafter, when the first electric cable  35  is connected to the first conductor  31  and the second electric cable  36  is connected to the second conductor  32 , the electric system can perform all functions thereof. 
     The above-mentioned joint unit can be formed into a module and then applied to the numerous joints of the robot. For example, if an upper arm part of the robot is a first link and a lower leg part of the robot is a second link, the first link and the second link can be connected using the modulized joint unit. 
       FIG. 6  is a perspective view showing first and second conductors of an electrical connecting device according to another exemplary embodiment. 
     As shown in  FIG. 6 , according to another exemplary embodiment, the first conductor  31  has an arc shape having the constant radius about a rotation shaft  23  and the second conductor  32  has a protrusion shape adapted to make contact with the first conductor  31 . 
     The first and second conductors  31  and  32  are press-fitted to each other in such a manner that a protrusion  34  of the second conductor  32  can be inserted into a receptacle  33  of the first conductor  31 . Accordingly, if the second joint part  22  rotates, the second conductor  32  not only slides on the first conductor  31 , but also keeps the electric contact with the first conductor  31 , continuously. 
     Therefore, if the arc shape of the first conductor  31  becomes larger, the sliding distance of the second conductor  32  can be increased. This means that the rotation angle of the second joint part  22  or the mobile angle of the knee joint unit  13  can be increased. 
     The first and second conductors  31  and  32  may have various shapes in addition to the shapes shown in  FIGS. 3 and 6 . That is, the first and second conductors  31  and  32  may have various shapes if the first and second conductors  31  and  32  can make contact with each other during the rotation of the second joint part  22  (or lower leg part  12 ). 
     Although a few exemplary embodiments have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these exemplary embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents.