Machine element or mechanism – Control lever and linkage systems – Multiple controlling elements for single controlled element
Patent
1991-10-15
1993-02-23
Herrmann, Allan D.
Machine element or mechanism
Control lever and linkage systems
Multiple controlling elements for single controlled element
414917, 901 26, G05G 1100, B25J 906, B25J 1700
Patent
active
051879964
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to an industrial robot, and more particularly, to an industrial articulated robot using a linkage for transmitting a torque of a drive source means to thereby drive a robot arm for a swing motion in a vertical plane.
2. Background Art
As is generally known, conventional industrial articulated robots, particularly an industrial articulated robot having robot arms capable of swinging, respectively, on a joint in vertical planes, are classified into those having two robot arms directly coupled together by a joint, and those of a parallel linkage type having two robot arms joined together by a joint in such a manner that a torque for driving the front arm among the two robot arms is transmitted thereto from a drive motor through a parallel linkage.
FIG. 7 illustrates a mechanism of a conventional vertical articulated robot of a directly coupled arm type. In this vertical articulated robot, a robot body 3 is mounted on a robot base 1 for rotation on a joint 2 about an axis .theta., a first robot arm 4 is supported pivotally for forward and backward swing motions ( W-axis motion) on the extremity of the robot body 3 at a pivotal supporting point 3a, a second robot arm 5 is pivotally supported on a joint for upward and downward swing motions (U-axis motion) on the extremity of the first robot arm 4 at a pivotal supporting point 4a, and a robot wrist 6 is supported for turning and swing motions on the extremity of the second robot arm 5. An end-effector and a workpiece inclusively indicated at " Wk" are held on the robot wrist 6. In this robot having the first robot arm 4 and the second robot arm 5 directly coupled together by the joint, drive motors, not shown, are provided at the pivotal supporting points 3a and 4a for directly driving the robot arms 4 and 5, respectively, and the operation space of the robot covered by the robot arms 4 and 5 extends to a large space designated by "A". If, however, a vertical articulated robot of such a type is of a large size and capacity, the vertical articulated robot must be provided with a heavy first robot arm 4, and a heavy second robot arm 5 for handling heavy work, and thus the first robot arm 4 nearer to the robot base 1 is loaded with the very heavy second robot arm 5, and the work and end-effector Wk is supported on the extremity of the second robot arm 5. To reduce such a large load on the first robot arm 4, a parallel linkage 7 including the first robot arm 4 as one of the links, and provided with a balance weight " Wb" as shown in FIG. 8, is employed for driving the second robot arm 5 extending from the extremity of the first robot arm 4.
When such a parallel linkage is employed, the drive motors, not shown, for driving the robot arms 4 and 5 are disposed opposite each other at the pivotal supporting point 3a.
In the operation of the robot of a parallel linkage type shown in FIG. 8, however, a robot operating space "B" covered by the robot actions of the first robot arm 4 and the second robot arm 5 with the robot body 3 held at an angular position is a limited region excluding a large space extending over a position where the robot is installed, as shown in FIG. 8, because it is possible that the parallel linkage 7 will become flat, (such a position of the parallel linkage 7 will be referred to as "dead center" and such a state of the same will be referred to as "dead center state" hereinafter) and accordingly, its torque transmitting function will become almost null and the parallel linkage 7 will be unable to transmit a large enough torque of the drive motor to swing the second robot arm 5 extending from the extremity of the parallel linkage 7. Accordingly, the robot is unable to meet conditions required of industrial robots, i.e., that the industrial robot must require a narrow area for installation and that the industrial robot must be capable of carrying out its functions in a wide operating region.
DISCLOSURE OF THE INVENTION
Accordingly, an object of the present invention is to provide a drivi
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Kinoshita Satoshi
Naito Yasuo
Torii Nobutoshi
Fanuc Ltd.
Herrmann Allan D.
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