Material or article handling – Vertically swinging load support – Grab
Patent
1984-12-31
1987-01-20
Siemens, Terrance L.
Material or article handling
Vertically swinging load support
Grab
414736, 414 7, 901 21, 901 29, 74 892, B25J 900
Patent
active
046377735
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
Technical Field
The present invention relates to an industrial robot, more particularly to an industrial robot of the articulated arm type.
BACKGROUND
Known industrial robots of the articulated arm type generally are provided with a movable robot body arranged on a base. A first arm or upper arm having root and tip portions is rotatably pivoted to the robot body at the root portion. A second arm or forearm having rear and front ends is rotatably pivoted to the top portion of the upper arm at a portion between the rear and front ends. Generally, a wrist assembly arranged at the front end of the forearm includes two or three moving elements which are rotatable about different axes. The moving element forming the output end of the robot is adapted to support, a robot hand, welding gun, painting gun, or other working attachment. The moving elements of the wrist assembly are driven by independent wrist drive units about the corresponding axes. Conventional wrist drive units generally comprise a first sprocket arranged in the upper arm, a drive motor arranged on the upper arm and coupled with the first sprocket to rotate the first sprocket, a second sprocket arranged where the forearm is pivoted to the upper arm, a third sprocket arranged in the tip portion of the forearm and operatively coupled with the corresponding moving element of the wrist assembly, an endless chain for transmitting rotational movement of the first sprocket to the second sprocket, and another endless chain for transmitting rotational movement of the second sprocket to the third sprocket.
In the conventional articulated robots with the wrist drive units as mentioned above, many power-transmission components are used between the drive motors and the moving elements of the wrist assembly. Since a chain generally has low rigidity, known robots in which chains account for a large part of the wrist drive unit have a disadvantage of low rigidity against loads acting on the wrist assembly. Furthermore, conventional robots in which chains account for a large part of the wrist drive unit have a disadvantage of a lower accuracy in positioning of the output end of the wrist assembly due to chain elongation due to wear.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide an industrial robot of an articulated arm type with a wrist drive unit made of few parts.
Another object of the present invention is to provide an industrial robot of the articulated arm type which has high rigidity against loads acting on the wrist assembly.
According to the present invention, there is provided an industrial robot of the articulated arm type comprising: a movable robot body arranged on a base; an upper arm having root and tip portions and rotatably pivoted to said robot body at said root portion; a forearm having rear and front ends and rotatably pivoted to said tip portion of said upper arm at a position between said rear and front ends; a wrist assembly arranged on said front end of said forearm and rotatable in relation to said front end about at least one axis; and at least one wrist drive unit for driving said wrist assembly and rotating it about said axis, said wrist drive unit including a first sprocket which is rotatably arranged in said rear end of said forearm, a drive motor arranged on said rear end of said forearm and coupled with said first sprocket to rotate it, a second sprocket arranged in said front end of said forearm and operatively coupled with said wrist assembly, and a wrapping connector for transmitting rotational movement of said first sprocket to said second sprocket.
Preferably, said wrapping connector includes a first chain meshing with said first sprocket, a second chain meshing with said second sprocket, and a pair of rods for connecting the two ends of said first chain to the two ends of said second chain, respectively. This construction increases the rigidity of the wrapping connector.
Preferably, said wrapping connector further includes means for absorbing any elongation of said first and s
REFERENCES:
patent: 4299533 (1981-11-01), Ohnaka
patent: 4503722 (1985-03-01), Suzuki et al.
Nakashima Seiichiro
Nihei Ryo
Torii Nobutoshi
Toyoda Kenichi
Fanuc Ltd.
Siemens Terrance L.
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