Metal fusion bonding – With control means responsive to sensed condition
Reexamination Certificate
2000-11-06
2001-12-18
Dunn, Tom (Department: 1725)
Metal fusion bonding
With control means responsive to sensed condition
C228S102000, C219S125100
Reexamination Certificate
active
06330966
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an automatic welding machine with a baseplate for placing the workpieces that are to be welded, and with a welding head that can move in the A-B-C direction and that is part of a welding apparatus, the welding head being coupled to an X-Y-Z motion mechanism for the automatic motion of the welding head along the workpieces according to the norm of a control routine that has been prescribed by a preceding teach-in-process and that has been stored in a control device.
Automatic welding machines are generally known and are used to perform welding processes on workpieces automatically in accordance with a prescribed program. By an automatic welding machine one generally understands the collection of all the equipment necessary for the mass production of welds on industrial products. Automatic welding machines in particular comprise clamping mechanisms and adjustment equipment for the workpieces or the welding tools, as well as equipment for guiding the welding electrodes or welding torches in the case of, gas flame welding, and the necessary supplementary materials. Automatic welding machines are frequently controlled by external equipment, which is designed as a separate unit. In the meantime, automatic welding machines are also known in which this machine itself contains an operating unit.
All automatic welding machines have in common that the welding electrodes or welding torches are guided automatically in accordance with a prescribed control routine. Due to the excellent welding results with automatic welding machines in comparison with manual welding, a trend has developed in the meantime to use automatic welding machines—as much as possible—not only for welding large parts, such as e.g. in automated linked lines in car body factories, but also for smaller workpieces.
Such automatic welding machines are especially needed where welds need to be very precise and the welding processes must be very reproducible. Consequently, automatic welding machines are especially necessary where slow precision welding is needed.
European Patent Application EP 0 701 884 A1 of the applicant already discloses an industrial robot with a movable working arm to handle workpieces and a mechanism to move the working arm. The mechanism controls three linear motion devices which can move the working arm in the X-Y-Z direction. The presence of three such linear motion devices makes it easily possible to move the working arm to a prescribed position. Depending on the point to be approached, the linear motion devices can be moved in their directions of motion completely independently of one another. Besides an X-Y-Z motion mechanism, the working arm itself has a motion device, so that it can be moved back and forth and/or turned independently of the X-Y-Z motion devices. A sensor device, in the form of a rotary encoder, is coupled to each of the motion or linear motion devices of the industrial robot. This sensor device is coupled to the control device, and it senses the motion of the respective motion or linear motion device, and thus also senses the position of the working arm. In their decoupled state, the motion devices and linear motion devices are in a state of equilibrium, and can be moved by hand without the exertion of a large force. In conjunction with the sensor devices, this is used to program the control device. A so-called “teach-in-process” is performed in this connection.
As regards the teach-in-process, express reference is made to the European Patent Application EP 0 701 884 A1 for the purpose of the disclosure. The industrial robot described there is indeed also suited in principle to perform welding processes on workpieces. However, the known industrial robot has the problem that very slow precision welding is not so readily possible, because, during the teach-in-process, the operator himself must work very exactly while simultaneously moving the X-Y-Z motion devices and the motion device coupled to the working head itself.
Consequently, it is the object of the invention to create an automatic welding machine which permits highly precise welding of workpieces in accordance with a previously executed teach-in-process.
SUMMARY OF THE INVENTION
An essential requirement of the invention is for the X-Y-Z motion mechanism to have three motors, one for each of the three X-Y-Z directions, and for each of these motors to be equipped with a self-locking gear mechanism. The X-Y-Z motion mechanism consequently cannot be moved manually. The X-Y-Z motion mechanism has a handle with integrated sensors and is intended as a sort of control stick for the operator.
The handle preferably is shaped in such a way that it gives the operator the impression that he himself holds the X-Y-Z motion mechanism in his hand, and thus forms a part of this motion mechanism. The handle is suitably placed at the front end of a holding tube which is seated on the Z axis. The sensors inside the handle are coupled to a control device such that the motors of the X-Y-Z motion mechanism move exclusively according to the measure specified by the output signals from the sensors.
In a further development of the invention, the X-Y-Z motion mechanism has a coupling device which, when decoupled, nevertheless permits manual displacement of the X-Y-Z motion mechanism. Such a further development makes sense if a defect of the X-Y-Z motion mechanism makes it impossible to drive it electrically any longer, and it nevertheless must be moved away from its instantaneous position. In this case, the coupling mechanism is decoupled, and the X-Y-Z motion mechanism is moved by hand. However, the X-Y-Z motion mechanism is coupled in during the teach-in-process, so that manual motion is excluded.
Moving the X-Y-Z motion mechanism exclusively through an electrical drive during the teach-in-process extraordinarily increases the accuracy of the motion of the welding head. This results in a vibration-free, uniform motion of the welding head.
The automatic welding machine suitably is designed in such a way that the control device adjusts the speed of the individual motors in dependence on the amplitude of the signals delivered by the sensors, This has the decisive advantage that, as the operator's s hand exerts more pressure on the handle, the X-Y-Z mechanism moves faster along the direction of the exerted pressure. This enhances the feeling of the operator that he himself moves the X-Y-Z motion mechanism by the pressure which he exerts, although this is not the case. Rather, it is only the output signal of the sensors that causes the control device to let one or another motor run faster or slower.
The inventive automatic welding machine therefore provides a kind of “servocontrol” for the X-Y-Z motion mechanism. Without this “servodrive,” the operator could move the very heavy and bulky X-Y-Z motion device only by exerting a very great force, which runs contrary to high-precision welding and the associated high-precision welds.
In a further development of the invention, the handle is shaped box-shaped at least approximately, and has a separate sensor on each of its walls. For example, these sensors can be pressure sensors.
In a suitable further development of the invention, the welding head of the automatic welding machine is a welding torch tip, so that the automatic welding machine can be used for gas flame welding. However, it would also be conceivable to provide an electrode welding head instead of a welding torch tip. However, in this case it is necessary for the melting metal electrode to be readjusted again and again in its guidance along the workpiece. Regardless of the design of the welding bead, it is seated on an A-B-C motion mechanism, which can be moved independently of the X-Y-Z motion mechanism, except for the fact that it is coupled to the latter.
In a further development of the invention, the X-Y-Z motion mechanism has two motion sleds, seated above the base plate, which preferably is a workbench standing on legs. Through these motion sleds, the welding head can be moved in the
Dunn Tom
Johnson Jonathan
Roman Eissfeller GmbH
Samuels , Gauthier & Stevens, LLP
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