Material or article handling – Vertically swinging load support – Grab
Patent
1980-12-10
1984-01-10
Paperner, Leslie J.
Material or article handling
Vertically swinging load support
Grab
219 8624, 219 8641, 294103R, B25J 304, B23K 1136
Patent
active
044250738
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a gripping mechanism and, more particularly, to a gripping mechanism which is pivotal about an axis having a horizontal component, has gripping members which can be moved toward and away from one another, a clamping mechanism for producing relative movement between the gripping members, and a source which supplies energy to the clamping mechanism.
BACKGROUND OF THE INVENTION
Gripping mechanisms are generally designated to grip a workpiece at a first place, to move it to a second place and to set it down there. The gripping mechanisms have for this purpose gripping means which clamp the workpiece between themselves. Among the movements which are to be carried out in practice are also pivoting movements about a horizontal axis, or about inclined axes with a limited horizontal projection. Such movements change the orientation of the gripping means with respect to the direction of the acceleration due to gravity, and this results in the weight of the gripping means contributing in a position-dependent manner to the clamping force and/or in changing the distance of the gripping means from the pivot axis. A change in the clamping force is undesired during transport of breakable articles or also during transport of easily deformable articles. The latter case exists for example in spot-welding tongs which are used at the same time for transport purposes, in which the part of the workpiece lying between the electrodes, which at the same time act as the gripping means, is plasticized by the welding operation. In order to prevent an uncontrolled deformation of the plasticized material volume during the pivoting of the welding tongs, due to the changing relatively large weight component of the gripping means (and the parts of the drives rigidly moved along with the gripping means), with conventional welding tongs pivoting of the workpiece must be delayed until the welding site has substantially cooled off. This means a considerable reduction in the productive capability of the welding mechanism.
The present invention is intended to further develop a pivotal gripping mechanism of the above-mentioned type so as to compensate for the change of the weight component of the moved parts of the gripping mechanism, which change occurs during the pivoting.
SUMMARY OF THE INVENTION
Starting out from a gripping mechanism of the abovementioned type, this purpose is attained inventively by providing an angle indicator which determines the angular position of the gripping mechanism and a modulator which is responsive to an output signal of the angle indicator and is connected between the energy source and the clamping mechanism, the modulator varying the force exerted by the clamping mechanism on the gripping members in dependence on the angular position of the gripping mechanism.
It is understood that one can adjust a gripping mechanism having these structural characteristics also so that the clamping force is not maintained constant, but is changed in a preselected manner dependent on the angle of traverse of the gripping mechanism. Thus, it is possible for the angle indicator of the gripping mechanism to simultaneously act as a limit switch and through a modulator to control the clamping drive so that the workpiece after a preselected pah of swing is set free by the gripping means. It is also possible, in particular during transport of heavy workpieces, to set at a large value the clamping force needed to produce a sure frictional gripping of a workpiece hanging between the gripping means and then to progressively reduce the gripping force as the workpiece pivots further away from the hanging position and the workpiece is increasingly supported by the gripping means.
However for pivotable welding tongs, it is preferred to maintain constant the closing force of the gripping means. In this way, the welding and cooling of the workpiece can occur under constant conditions simultaneously with the transport of the workpiece from a first place to a second place, and in this manner v
REFERENCES:
patent: 3422965 (1969-01-01), Lloyd
patent: 3759092 (1973-09-01), Fishel
patent: 3865424 (1975-02-01), Jabkowski
patent: 4201510 (1980-05-01), Montjanoff
patent: 4229136 (1980-10-01), Panissidi
Article-"Master-Slave-Manipulator EMSM I" by Koehler and Salaske, Kerntechnik, May 1976, pp. 212-218.
Article-"For Versatile, Heavy Handling Put a Man in the Loop" by Brust, Automation, Dec. 1973, pp. 78-83.
Article-"Force-Reflecting Electrohydraulic Servomanipulator" by Mosher and Wendel, Electro-Technology, Dec. 1960, pp. 138-141.
Festo-Maschinenfabrik Gottlieb Stoll
Paperner Leslie J.
Siemens Terrance L.
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