Electric heating – Metal heating – For bonding with pressure
Reexamination Certificate
1999-04-28
2001-05-29
Shaw, Clifford C. (Department: 1725)
Electric heating
Metal heating
For bonding with pressure
C219S098000
Reexamination Certificate
active
06239401
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to stud welding, and more particularly to a chuck electrode for automatically capturing studs fed to a stud welding tool.
BACKGROUND OF THE INVENTION
The art of stud welding, is well known. The present invention is directed to that part of the stud welding art employing a manual stud welding tool. Prior art workers have devised a number of different types of stud welding tools, all of which operate in substantially the same manner. The tool operator manually mounts an individual stud on the electrode of the tool, which is typically in the form of a cylindrical collet for holding a stud. The operator then causes the tool to press the free end of the stud against the workpiece surface at the position to which the stud is to be mounted. Electrical current is imparted to the stud which is slightly raised from the workpiece to initiate an arc. The free end surface of the stud and the adjacent surface area of the workpiece are rendered molten by the arc. The molten end of the stud is pressed against the molten surface of the workpiece to weld the stud to the workpiece, and the electrical current is turned off. The tool is then manually pulled off of the stud and is ready to receive a new stud.
The prior art tools are characterized by the fact that each stud to be welded to the workpiece must be individually and manually engaged with the tool electrode. This requires a considerable amount of manipulation and inconvenience, and increases the time required to weld each stud. Furthermore, a given tool may be used with studs of multiple different diameters, but in a typical tool, to use a different diameter stud the electrode of the tool must be removed and replaced with an appropriately sized electrode to hold the new stud diameter.
SUMMARY OF THE INVENTION
In accordance with the present invention, the operation of a conventional stud welding tool is substantially improved by providing the tool with an electrode with an adjustable aperture capable of grasping studs with a variety of sizes.
In the disclosed particular embodiment, the adjustable aperture is in the form of a chuck having a plurality of sliding fingers movable along intersecting axes and positionable along these axes to form an aperture of a desired diameter. In this embodiment, the fingers have a threaded exterior surface, and the chuck includes a wheel having a threaded interior surface for engaging the threaded exterior surfaces of the fingers for moving the fingers along their axes in response to rotation of the wheel.
In the particular embodiment, the chuck wheel has a circular threaded surface to permit driven rotation of the chuck wheel. This threaded surface may be located at an outer periphery of the chuck wheel or along an interior surface of the chuck wheel. A chuck drive motor having an output shaft and a pinion that rotates with the output shaft, is coupled to the threaded surface of the chuck wheel for driving the chuck to an open or closed position. The drive motor pinion may be coupled directly to the threaded surface of the chuck wheel, or coupled indirectly to the threaded surface of the chuck wheel via a transmission of one or more idler gears. Also, the axis of the output shaft of the drive motor may be parallel to the axis of the chuck, or orthogonal to it (in which case bevel gears are used to couple the drive motor pinion to the chuck wheel), or at another relative angular position.
In this particular embodiment, the chuck is automatically driven to open or closed positions by a control circuit. The control circuit is response to a sensor detecting positioning of a stud at a proper location inside of the chuck, to close the chuck. The control circuit is further responsive to detection of a completed weld process, to open the chuck. A manual override to open the chuck may also be provided.
In the disclosed particular embodiment, the tool includes a vertical drive motor for lifting the adjustable aperture electrode of the tool and a stud held therein as part of the welding operation. A solenoid is used as the vertical drive motor. The control circuit controls the solenoid to perform a lifting operation as part of stud welding. The control circuit is responsive to a trigger on the tool, and the existence of an electrical connection between the stud and a workpiece, to initiate and control the vertical drive motor during a welding operation.
In the disclosed specific embodiment the tool is provided with a stud supporting and collating strip assembly made of two identical pieces of a collating strip, to feed studs to the electrode of the tool for engagement by the adjustable chuck. A unique drive assembly is utilized for shifting each stud, in sequence, to its proper position with respect to the tool to be welded to the workpiece. That part of the support and collating-strip assembly from which studs have been welded and removed will simply part and bend out of the way during subsequent welding operations. When all of the studs of the strip assembly have been welded, the rearwardmost position of the strip assembly may be removed from the tool and the strip assembly may be discarded.
The above and other objects and advantages of the present invention shall be made apparent from the accompanying drawings and the description thereof.
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McCardle Thomas A.
Miser, Jr. James W.
Wottreng, Jr. Mathias
Senco Products Inc.
Shaw Clifford C.
Wood Herron & Evans L.L.P.
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