Electrical transmission or interconnection systems – Switching systems – Condition responsive
Patent
1996-08-05
1998-09-22
Gaffin, Jeffrey A.
Electrical transmission or interconnection systems
Switching systems
Condition responsive
307 91, 32420712, 32420715, H01H 3500
Patent
active
058118934
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a magnetic field-actuated approximation or proximity switch, as it is used in many technical fields for the contactless initiation and execution of electrical switching, controlling and regulating processes.
THE PRIOR ART
The design and function of such an approximation switch are described, for example in DE 40 03 426 A1. According to the latter, the HF oscillating circuit serving as the sensor, such circuit being predamped by means of an amorphous metal body with high permeability due to eddy current losses, is deattenuated by the magnetic field of an approximating tripping device, and said process is used for controlling a switching device downstream.
In this connection, the sensor of the approximation switch, which is to be actuated in a defined way by a variable magnetic field, is susceptible to interference to a particularly high degree by any foreign magnetic field within its closer environment. Such interference fields occur, for example due to high current intensities particularly in connection with electric welding installations, where the sensors present there for controlling the equipment of the installation may be put out of operation by such interference fields.
Therefore, the invention is based on the problem of securing an approximation switch of the generic type specified above against being influenced by magnetic interference fields, which occur in the process of an operation in varied ways and at intervals.
BACKGROUND OF THE INVENTION
For solving said problem in connection with a magnetic field-actuated approximation switch provision is made according to the invention for a second sensor, which reacts to intermittently occurring magnetic interference fields, and which, in its activated state, returns the instantaneously present output signal of the switching stage to the input of the amplifier stage for maintaining the lead signal transmitted by the magnetic field sensor determining the function.
Accordingly, the interference field to be neutralized is not always present, but acting on an approximation switch only intermittently, such switch being actuated or not actuated at the given time. In this connection, by returning the corresponding output signal of the switching stage to the input of the amplifier stage according to the invention, a superposition of said output signal with the lead signal from the side of the magnetic field sensor takes place in the sense of a "preservation" of the latter signal, and at the same time a stabilization of the overall function of the approximation switch. Furthermore, an approximation switch so secured, when used in electric welding installations, is independent of the type and control of welding current used.
Useful embodiments and advantageous further developments of the invention are contained in the dependent claims and their features can be understood by the expert in the field without additional explanations.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring to the drawings, wherein similar reference characters denote similar elements in the two views;
FIG. 1 is a simplified schematic diagram representing an embodiment of the invention; and,
FIG. 2 is a detailed electrical block diagram of the circuit of the invention.
DESCRIPTION OF PREFERRED EMBODIMENT
As shown by the block diagram according to FIG. 1, the lead signal transmitted by the magnetic field sensor 1 in dependence of a tripping magnetic field provided for such transmission, is supplied via an amplifier stage 2 to a transistorized switching stage 3, and converted by the latter into a defined output signal. In the event of interference, the output potential of the switching stage 3 is subsequently returned to the input of the amplifier stage 2 by means of a second sensor 4, the latter reacting to an intermittently occurring foreign magnetic field as it occurs, for example in electric welding installations, in order to preserve by superpositioning the lead signal fed in by the magnetic field sensor 1, and to make the approximation switch in its given swi
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Gaffin Jeffrey A.
Kaplan Jonathan
Soyck GmbH
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