192 clutches and power-stop control – Stop mechanism – Overload release
Patent
1995-08-03
1997-05-06
Lorence, Richard M.
192 clutches and power-stop control
Stop mechanism
Overload release
192 5662, 464 36, 901 49, B25J 1906
Patent
active
056262167
DESCRIPTION:
BRIEF SUMMARY
This application claims the benefit of the filing date of International Application No. PCT/EP94/03053, filed Sep. 13, 1994.
Holders of that variety serve to hold a tool like a curing torch in the arm of a robot and let the tool swerve out of the way during a collision between the tool or the cutting torch and the work piece or a peripheral part during operations. This will avoid damaging the tool or the work piece. For such evasive movements of a tool, an emergency interrupt switch is activated, which either turns off the movement of the robot or resets the robot arm to home position.
A torch holder as initially described is familiar for instance from U.S. Pat. No. 4,998,606; it has a spring driven piston part within a housing, and the housing also contains a release lever for a stop plate in home position which is linked to a tool connection at the near housing wall. During excess pressure or deflection of the tool connection, the spring loaded piston part causes an axial deviation, which activates a switch for shutting off the robot or for resetting it to home position. Asymmetrically distributed in an arc on the stop plate are half spherical elements, which in home position are depressed into indentation in the adjacent housing lid. But the disadvantage is, that the spherical seats or indentations have to be tooled very precisely for the tool connection always to return to its home position. This is especially important on the robot arm for regaining the stated point of reference of the tool, as with welding or cutting torches. Tiffs point of reference is usually called Tool Center Point, TCP for short.
For this reason, the invention has the objective of developing a tool holder of the initially described variety in such a way, that it can achieve a uniform release force for all direction changes of the tool connection and can attain high precision in reversing to the home position, even in compact installations, with the greatest angle of radial excursion.
This is one of the objectives met by the characteristics identified in the paragraphs of claim 1.
The three point support of the stop plate linked to the tool connector assures a stable and especially tilt resistant support of the tool in its home position. The three point support also enables higher reset precision after a possible radial excursion of the tool because of a collision. Since a tilting movement makes more positioning elements available for support, the advantages of the multiple point support help in providing equal release forces for all tilt directions.
One design of the invention places the three positioning elements, located in the home position of the stop plate, in the comers of an isosceles triangle, which brings about a highly stable and tilt resistant positioning of the tool.
It is also recommended, that the active positioning elements between the stop plate and the housing am arranged symmetrically in an arc, which benefits the equalization of the relative forces of the various tilt directions.
One design of the invention requires the positioning elements to be spheres fixed in a mount with matching indentations in the stop plate, but the seats of the three positioning elements in the home position of the stop plate should be shallower than all the others. This simple construction and production method realizes a three point support in the home position and a six point or higher support during a tilting movement of the tool.
The piston part and the stop plate are prevented from rotating against each other, another advantage. The invention realizes this by including at least one alignment pin in the stop plate with a matching bored hole in the piston part. This assures that during an undesired tilting of the tool the movable piston part will also turn and the safety switch is activated.
A different arrangement of the invention proposes, that the piston part has a radial collar to the outside, which activates a switch element within a detector device during an axial displacement of the piston part. It is best, if this collar e
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Manche Jorg
Schwarz Jorg
Sperling Hermann
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