Electric heating – Metal heating – For bonding with pressure
Reexamination Certificate
2000-01-05
2001-10-16
Dunn, Tom (Department: 1725)
Electric heating
Metal heating
For bonding with pressure
C219S091100, C219S108000
Reexamination Certificate
active
06303894
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to resistance welding apparatus and more particularly to a lightweight, portable spot resistance welding device.
In resistance spot welding, electrode pressure is used to force the two pieces together. Heat, generated by the resistance of the workpieces to the flow of electricity, either melts the material at the interface, or at least makes it plastically adhesive. When the flow of current stops, the electrode force is further maintained for a fraction of second, while the weld rapidly cools and solidifies.
There are two types of welding equipment: Direct energy machines and stored energy machines. The stored energy mode is usually preferred because it is a more efficient and a more controlled process than the direct energy mode, and causes less extra heating, oxidation and deformation of the workpieces.
In principle, the stored energy welding machine extracts energy from the power line over a period of time and stores it in a high voltage capacitor's bank. The stored energy is discharged through a pulse transformer which converts the high voltage pulse into the required high current pulse (at low voltage) which is delivered by highly conductive cables to the welding head and passes through the workpiece. A third cable runs from the supply to the welding head and ensures that the firing switch of the discharge will close only after the two electrode are pressed together against the workpiece.
Commercial stored energy power supplies have a peak output voltage of 6 to 10 Volts and deliver up to several hundred Joules during a pulse (or two pulses) which can have a duration of several milliseconds. Typical weight of supplies range in 15 to 30 kg. Even portable battery powered light duty welding power supplies have a typical weight of about 10 kg.
Thus, no truly portable resistance welding system exists in a sense that the complete welding system can be conveniently carried and operated by the operator; or without being connected to the supply by heavy duty welding cables in the direct energy mode.
SUMMARY AND OBJECTS OF THE INVENTION
The present invention solves the deficiencies of the prior art power supplies by the application of an electrochemical capacitor as the source for the high current pulses that are required in the resistance welding process. It is based on the properties of electrochemical capacitors, especially their large electrical capacitance which enables them to store energy at low voltages and their ability to deliver this energy fast enough so it can produce sufficient heat to spot weld two metal sheets.
The invention is based on the properties of an electrochemical capacitor which is characterized by its large capacitance and energy density to serve as a power source for resistance welding. The capacitor was based on the “quasi capacitance” phenomena of the RuO
2
electrode in a solution of 4M H
2
SO
4
, which is described by Conway et al, “The Role and Utilization of Pseudocapacitance for Energy Storage by Supercapacitors”, Journal of Power Sources, Vol. 66, 1997, 1-14, incorporated herein by reference.
Thus, the energy needed for the welding process is stored in a very compact electrical storage device which is tightly attached to the welding head where its energy can be extracted directly in the appropriate form of high current and low voltage to perform the welding job.
It is therefore an object of the present invention to provide a lightweight, compact low voltage, high-current pulse to electrodes employing an electrochemical capacitor.
REFERENCES:
patent: 4332098 (1982-06-01), Estenevy
patent: 4446513 (1984-05-01), Clenet
patent: 4458132 (1984-07-01), Reynolds et al
patent: 4716267 (1987-12-01), Reynolds
patent: 5272306 (1993-12-01), Hirane
patent: 5384685 (1995-01-01), Tong et al
patent: 5464453 (1995-11-01), Tong et al
patent: 5469325 (1995-11-01), Evans
patent: 5683598 (1997-11-01), Moro
patent: 5714733 (1998-02-01), Moro
patent: 5737181 (1998-04-01), Evans
patent: 5867363 (1999-02-01), Tsai et al
patent: 5875092 (1999-02-01), Jow et al
patent: 744 809 A3 (1993-03-01), None
patent: 744 809 A2 (1993-03-01), None
patent: 685 859 A1 (1995-05-01), None
Klein Naftali
Laser Daniel
Yarnitzky Chaim
Dunn Tom
Friedman Mark M.
Pittman Zidia
Rafael-Armament Development Authority Ltd.
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