Electric heating – Metal heating – For bonding with pressure
Reexamination Certificate
1999-02-02
2001-08-14
Shaw, Clifford C. (Department: 1725)
Electric heating
Metal heating
For bonding with pressure
C219S091200
Reexamination Certificate
active
06274840
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electrode position detecting system and method for spot welders. In particular, the invention relates to an electrode position detecting system and method for spot welders in which a welding robot is responsible for carrying, handling and/or manipulation (hereafter collectively “manipulation”) of a welding gun that has a pair of relatively movable welding electrodes for pinching, and conducting a welding current through, a spot of work to be thereby welded, wherein a position of a mobile welding electrode (hereafter called “mobile electrode”) is detected by a position detector for measurement, analysis and/or control purposes, such as for measurement or analysis of inter-electrode distance or electrode deformation or abrasion, analysis on electrical or mechanical characteristics or performances, correction of electrode feed or inter-electrode distance, compensation such as for an orientation or bend of a manipulated welding gun, or control of welding quality.
A conventional spot welder has an electrode position detecting system in which: a mobile electrode is moved by a servo motor; a sensing element senses the electrode in a position after movement; and a position detector is responsible for servo control data associated with the movement to detect the position of the electrode.
The sensing element is fixed to a measuring installation placed on a foundation on which a welding robot is installed for manipulation of a welding gun.
SUMMARY OF THE INVENTION
In view of the inventor, the foundation has a conforming level defined in an absolute coordinate system, as the robot is operative in a mobile coordinate system bound to the absolute coordinate system, and the measuring installation is furnished on the foundation with a severe check for the sensing element to have a precise fixed position to the absolute coordinate system, permitting a position of the electrode to be accurately measured in the absolute coordinate system.
In spot welders in which a welding spot has a defined absolute position, a measured absolute position of an electrode is directly employable for position control relative to the welding spot. For the concerned purposes, however, the measured position is precisely analyzed for conversion to determine an electrode position relative to the gun which is manipulated by the robot.
It appeared to the inventor that severe requirements have been provided for such checks and analyses. However, should such requirements have to be provided?
Moreover, manipulation of the gun in the reference coordinate system is frequently interrupted by a significant interval of time for sensing the electrode in the absolute coordinate system.
The invention has been achieved with such points in view.
It therefore is an object of the invention to eliminate redundant conventional requirements in the field of endeavor described. It also is an object of the invention to eliminate conventional frequent interruption of gun manipulation.
To achieve the object, an aspect of the invention provides an electrode position detecting system for spot welders in which a welding robot manipulates a welding gun having a pair of relatively movable welding electrodes, the electrode position detecting system comprising a coordinate system fixed to a welding gun, a sensor fixed to the coordinate system, the sensor sensing a mobile electrode moved in a position, and a position detector cooperative with the sensor to detect the position of the mobile electrode relative to the welding gun.
According to the aspect of the invention, a mobile electrode in a moved position is sensed by a sensor fixed to a coordinate system, and a position detector detects the moved position of the electrode relative to a welding gun. The position detector may calculate servo control data on movement of the electrode for detection of the electrode position.
As the coordinate system is fixed to the gun, the position of the sensed electrode is directly detected in terms of a relative position to the gun, without the need of conventional severe requirements for furnishing a measuring installation nor conventional frequent interruption of gun manipulation for a sensing in an absolute coordinate system.
Further, to achieve the object described, another aspect of the invention provides an electrode position detecting method for spot welders in which a welding robot manipulates a welding gun having a pair of relatively movable welding electrodes, the electrode position detecting method comprising having a coordinate system fixed to a welding gun, fixing a sensor to the coordinate system, sensing by the sensor a mobile electrode moved in a position, and having a position detector cooperating with the sensor to detect the position of the mobile electrode relative to the welding gun.
REFERENCES:
patent: 4151451 (1979-04-01), Maertins
patent: 4567347 (1986-01-01), Ito
patent: 4973814 (1990-11-01), Kojma
patent: 5192845 (1993-03-01), Kirmsse
patent: 5405075 (1995-04-01), Narita
McDermott & Will & Emery
Nissan Motor Co,. Ltd.
Shaw Clifford C.
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