Machine element or mechanism – Control lever and linkage systems – Multiple controlling elements for single controlled element
Patent
1992-06-22
1993-11-30
Herrmann, Allan D.
Machine element or mechanism
Control lever and linkage systems
Multiple controlling elements for single controlled element
414917, 901 21, B25J 906, B25J 1700
Patent
active
052654893
DESCRIPTION:
BRIEF SUMMARY
FIELD OF ART
The present invention relates to an arm-driving device for an industrial robot having a plurality of articulations.
BACKGROUND OF THE INVENTION
There is a conventional method of pivoting an arm of an industrial robot by directly driving pivot axes of the arm with driving motors through speed reducers. However, this method is not suitable for those robot having a heavy arm or load because an unbalanced moment at the arm increases the load to the pivot axes. Therefore, in an industrial robot having relatively heavy arms and loads, parallel links are normally constituted by an arm A which corresponds to a driven bar, an arm B, driving bar C. and a connecting bar D as shown in FIG. 5.
However, when the arms are configurated using parallel links, there is interference between the arm B and connecting bar D and the operating range is thus narrowed. As a solution to this problem, the description of U.S. Pat. No. 4,329,111 and unexamined Japanese published patent application No. 59-110578 disclose a type wherein the swinging plane of driving bars and driven bars are shifted.
in the above-described conventional configuration, however, when an articulated arm is driven, a driving motor of a second parallel link constituting an arm at the end portion must be secured to the end of a first link supporting a second parallel link to constitute an arm. This increases the weight of the first link and, consequently, the load applied to the driving motor of the first link. Thus, a problem arises in that the rigidity of the first link must be high and the capacity of the driving motor must be large.
It is an object of the present invention to provide an arm-driving device wherein the arms are lightweight so that the operation of the arms can be quick, and wherein the interference of a parallel link driving a second arm is eliminated to enable expansion of the operating range.
DISCLOSURE OF THE INVENTION
The present invention is an arm-driving device for an industrial robot having a first pivot axis pivotally support by a base, a first arm secured to said first pivot axis on one end thereof, a second pivot axis pivotally supported by the other end of said first arm, a second arm secured to said second pivot axis on one end thereof, and parallel links connecting a parallel link pivot axis pivotally provided in a concentric relationship with said first pivot axis, to said second pivot axis, wherein the driven bars of said two parallel links are secured to both ends of said second pivot axis with said first arm sandwiched therebetween; and two connecting bars connecting the driving bars secured to said parallel link pivot axis and said driven bars are offset outside said driving bars and driven bars, respectively.
The driving bars and driven bars of said two parallel links are secured to the parallel link pivot axis and second pivot axis so that a phase difference at a predetermined angle is provided between them.
Two parallel links, each having two connecting bars which are outwardly offset, are connected to both sides of the pivot axis driving the second arm so that said pivot axis can be driven up by a driving motor. This eliminates the possibility of interference from the parallel links.
Further, when the driving bar, connecting bar, driven bar and first arm that constitute a parallel link straightly extend, this single parallel link cannot cause a rotation. However, there is provided another parallel link having another driving bar secured to the pivot axis at a predetermined phase angle with respect to said driving bar. As a result, when one of the parallel links straightly extends, the other parallel link does not straightly extend, and, therefore, it can swing the second arm by the other parallel link.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a sectional elevation showing an embodiment of the present invention.
FIG. 2 is a side view taken along the line II--II in FIG. 1.
FIG. 3 is a side view showing another embodiment.
FIG. 4 is a sectional elevation showing another embodiment.
FIG. 5 is a side view
REFERENCES:
patent: 4329111 (1982-05-01), Schmid
patent: 5187996 (1993-02-01), Torii et al.
Iwanaga Toshiaki
Tohnai Shuichi
Herrmann Allan D.
Kabushiki Kaisha Yaskawa Denki
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