1. Field of the Invention
This invention relates to a articulated robot, which has a robot arm of double arm structure composed of one arm piece formed as an endoskeletal arm to transmit a drive force and the other arm piece formed as an arm to house cables and pipes or the like and is available for an arc welding robot, a trimming robot, a handling robot or the like.
2. Description of the Prior Art
A articulated robot having a robot arm of double arm structure composed of one arm piece formed as an endoskeletal arm to transmit a drive force and the other arm piece formed as an arm to house cables and pipes or the like has been already known. A description will now be given of the well-known articulated robot having the robot arm of double arm structure with reference to FIGS. 3 and 4.
A base 1 is mounted with a turn portion 2 which turns about the center of axis perpendicular to a mounting surface (not shown) of the base 1. One end of a first arm piece 3a and that of a second arm piece 3b are fitted to the turn portion 2 so that these arm pieces 3a and 3b can rotate about the common axis perpendicular to the turning axis of the turn portion 2. The first arm piece 3a and the second arm piece 3b constitute a first robot arm 3 in double arm structure.
The first arm piece 3a, serving as one of the arms constituting the first robot arm 3, is of endoskeletal structure to transmit a drive force, and one end of the first arm piece 3a is rotatably fitted to the turn portion 2. On the other hand, the second arm piece 3b, serving as the other of the arms constituting the first robot arm 3, is of structure to house cables and pipes or the like, and one end of the second arm piece is rotatably supported by the turn portion 2.
A housing 4c is mounted to the other end of the first arm piece 3a and that of the second arm piece 3b so that the housing 4c can rotate about the common axis perpendicular to the center of turning axis of the turn portion 2. The housing 4c constitutes a second robot arm 4. A motor and a speed reducer (not shown) or the like for causing the second robot arm 4 to rotate relatively to the first robot arm 3, a motor and a speed reducer for causing a wrist 5, which will be later described, to rotate and air pipes and valves or the like for an end effector (not shown) are housed in the housing 4c.
The housing 4c is open at its top, and a cover 4d for covering an open portion of the housing is mounted to the housing 4c with a fixing tool such as bolts. Further, the wrist 5 adapted to mount the end effector thereto is connected to the housing 4c (the second robot arm 4).
When a drive source (not shown) to drive the turn portion 2 is operated to drive the turn portion 2, the turn portion 2 makes a pivotal motion about the axis perpendicular to the mounting surface of the base 1, and the first robot arm 3, the second robot arm 4 and the wrist 5 are also turned together with the turn portion 2. Further, when a drive source (not shown) to drive the first robot arm 3 is operated to drive the first arm piece 3a, the first arm piece 3a makes a pivotal motion relatively to the turn portion 2 to move the second robot arm 4. The second arm piece 3b is also rotatably moved whenever the first arm piece 3a is rotatably moved. The reason is that one end of the second arm piece 3b is rotatably supported by the turn portion 2, while the other end thereof is rotatably supported by the housing 4c (the second robot arm 4).
Further, when a drive source (not shown) to drive the second robot arm 4 is operated to drive the second robot arm 4, the second robot arm 4 makes a pivotal motion relatively to the first robot arm 3 (the first arm piece 3a and the second arm piece 3b).
In the articulated robot having the robot arm of double arm structure as described above, when maintenance of equipment such as the motors, the speed reducers and the valves housed in the housing 4c is carried out, there is a need for access to the equipment and parts inside the housing 4c as shown in FIG. 4 in the manner of removing the cover 4d and also a cover of the second arm piece 3b containing the cable and pipes. However, since only the upper surface of the housing 4c is opened, and cables and pipes are installed in the housing 4c, it is necessary to carry out maintenance of the equipment and parts contained in the housing 4c while operating cables and pipes in the uncovered second arm piece 3b, so that operability of the robot is degraded, making maintenance of the robot difficult.
Further, it may also be necessary to insert cables and pipes into the housing 4c when assembling the robot, and installation of the cover to the second arm piece 3b of the first robot arm 3, in which cables and pipes are arranged and installation of cables and pipes in the housing 4c can not be carried out concurrently with each other and in respective processes, resulting in the degradation in efficiency of production.