Electric heating – Metal heating – By arc
Reexamination Certificate
2000-02-04
2001-02-27
Paschall, Mark (Department: 3742)
Electric heating
Metal heating
By arc
C219S121570, C219S130320, C219S130400, C219S121390
Reexamination Certificate
active
06194681
ABSTRACT:
This invention relates to a power supply apparatus for a machine, e.g. a non-consumable electrode arc welder or a non-consumable electrode arc cutter, in which an arc is generated between a non-consumable electrode and a workpiece for processing the workpiece with the arc.
BACKGROUND OF THE INVENTION
A non-consumable electrode arc welder or cutter has a gap between its non-consumable electrode and a workpiece to be processed. A high-frequency voltage is applied between the electrode and the workpiece to cause breakdown of the insulation between them so that an arc is generated. Some such machines are arranged to maintain the arcing by applying a DC voltage between the electrode and the workpiece, which form a load.
An example of such non-consumable electrode welders is disclosed in Japanese Unexamined Patent Publication (KOKAI) No. SHO 63-212071 A published on Sep. 5, 1988. The non-consumable electrode arc welder disclosed in this publication converts a commercial AC voltage into a DC voltage, which, in turn, is converted to a high-frequency voltage in an inverter. The high-frequency voltage is applied to a primary winding of a transformer so that a voltage-transformed high-frequency voltage is induced in a secondary winding. The high-frequency voltage induced in the secondary winding is converted back into a DC voltage, which is applied between a non-consumable electrode of the welder and a workpiece. A high-frequency ignition voltage generator applies a high-frequency ignition voltage between the electrode and the workpiece to initiate an arc between them. The arc is to be sustained by the DC voltage.
A current detector detects load current flowing through the electrode and the workpiece, and an inverter control unit controls the inverter in such a manner as to make the detected load current have a predetermined magnitude. The high-frequency ignition voltage generator is driven with the high-frequency voltage induced in the secondary winding of the transformer. The high-frequency ignition voltage generator is disabled when the current detector detects the load-current.
In some cases where the gap between a non-consumable electrode and a workpiece is large, a high-frequency voltage from a high-frequency ignition voltage generator may not be able to cause breakdown between the electrode and the workpiece. Then, no arcing occurs, and, therefore, the high-voltage generator keeps on generating the high-frequency voltage. The high-frequency voltage generates undesirable electromagnetic waves, which could interfere with the operation of other apparatuses around the arc welder.
An object of the present invention is to provide a power supply apparatus for arc-utilizing machines, having a high-frequency ignition voltage generator which can be immediately disabled when arcing cannot be established between a non-consumable electrode and a workpiece.
This and other objects of the present invention will be understood from the following detailed description of this invention.
SUMMARY OF THE INVENTION
A power supply apparatus for arc-utilizing machines according to the present invention includes high-frequency switching means for switching a DC signal from a DC signal source to develop a first high-frequency signal. The DC signal source may be, for example, an AC-to-DC converter which converts a commercial AC signal into a DC signal. The high-frequency switching means may be, for example, an inverter or a chopper. The first high-frequency signal from the high-frequency switching means is applied to a primary winding of a transformer, which also includes a secondary winding. A second high-frequency signal is induced in the secondary winding of the transformer and is converted into a DC signal in a converter. The DC signal from the converter is applied between two output terminals, which are to be connected to a non-consumable electrode of an arc-utilizing machine and a workpiece to be processed by the arc-utilizing machine. A high-frequency ignition voltage generator generates and applies a third high-frequency signal between the two output terminals. A current detector detects load current supplied to the non-consumable electrode and workpiece and generates a load-current-representative signal representing the detected load current. The load-current-representative signal is applied to high-frequency switching means control means, which controls, when an enabling signal is provided from an enabling signal generator, the high-frequency switching means so as to make the load-current-representative signal have a predetermined value. The enabling signal is also applied to high-frequency ignition voltage generator control means for controlling the high-frequency ignition voltage generator. When the enabling signal is applied to the high-frequency ignition voltage generator control means, it causes the high-frequency ignition voltage generator to start operating and keeps it operating until the load-current-representative signal is generated. If no load-current-representative signal is generated during a predetermined time period following the generation of the enabling signal by the enabling signal generator, disabling means stops the operation of the high-frequency ignition voltage generator.
The disabling means may include a timer which is enabled by the enabling signal from the enabling signal generator to generate an expiration signal when the predetermined time period has lapsed. This timer is reset when the load-current-representative signal is generated during the predetermined time-measuring period. In this case, the high-frequency ignition voltage generator may be arranged to receive the second high-frequency signal induced in the secondary winding of the transformer, and the disabling means is provided with stopping means for stopping the operation of the high-frequency switching means control means when the timer develops the expiration signal.
The disabling means may be arranged to disable the high-frequency ignition voltage generator control means.
REFERENCES:
patent: 5630952 (1997-05-01), Karino et al.
patent: 5864110 (1999-01-01), Moriguchi et al.
patent: 63-212071 (1988-10-01), None
Danjou Kenzo
Ikeda Tetsuro
Kinoshita Atsushi
Moriguchi Haruo
Duane Morris & Heckscher LLP
Paschall Mark
Sansha Electric Manufacturing Company Limited
LandOfFree
Power supply apparatus for arc-utilizing machine does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Power supply apparatus for arc-utilizing machine, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Power supply apparatus for arc-utilizing machine will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2565257