Patent ID: 12224095

WAYS OF EMBODYING THE INVENTION

FIG.1shows in a schematic representation an electronic circuit10according to the invention for demagnetizing ferromagnetic material.

The circuit10comprises a demagnetizing coil41and a resonant circuit capacitor42, which are connected via a resonant circuit switch43to a demagnetizing resonant circuit40. At the beginning of the process, the resonant circuit switch43is open. The demagnetizing resonant circuit40is connected via a conductor loop30to a current source20, which can charge the resonant circuit capacitor42. The charging process can be interrupted via a resonant circuit charging switch31.

Once this charging process is completed with the resonant circuit voltage A, the resonant circuit charging switch31is opened and so the charging current is interrupted. After the resonant circuit switch43is closed, a resonance oscillation is set in motion: the resonant circuit capacitor42discharges via the demagnetizing coil41. The current prevailing in the resonant circuit corresponds to a free-running oscillation at the natural frequency with exponentially decaying amplitude.FIG.2shows the resonance oscillation in this demagnetizing resonant circuit40in the form of the curves of the resonant circuit voltage A and the demagnetizing current B against time t. After the amplitudes of the resonant circuit voltage A and demagnetizing current B have decayed, the resonant circuit switch43is opened again and the circuit10is available for the next demagnetizing cycle, which begins again by the closing of the resonant circuit charging switch31.

FIG.3shows an excerpt from the process of the decaying oscillation fromFIG.2with a resonant circuit voltage A and a demagnetizing current B, wherein with a recharging current shown above them, recharging pulses C are introduced at regular time intervals. The latter are bipolar current pulses that are each fed in at the time immediately after the zero crossing D of the resonant circuit voltage A. Due to the additional energy supplied, the decaying oscillation is delayed, and the amplitudes of the resonant circuit voltage A and demagnetizing current B thus decrease more slowly. This principle is well known, but it has been shown that its implementation in terms of circuit technology is cumbersome.

The embodiments according to the invention are shown in a general form inFIG.4and in a preferred version inFIG.5. InFIG.5, the components40,50and60are shown as examples in the form of electronic components. Optionally, only individual ones may be designed in this form.

FIG.4shows an electronic circuit10for demagnetizing ferromagnetic material by means of a resonance oscillation with a prolonged decay time. The circuit comprises a voltage source20and a conductor loop30connected thereto, in which a demagnetizing resonant circuit40is connected in order to form a decaying, alternating magnetic field in which ferromagnetic material can be demagnetized during a decay time t. This demagnetizing resonant circuit40can be constructed as described inFIG.1. Such a design was shown inFIG.5as an example. However, other arrangements of demagnetizing resonant circuits40are also known. Together with the resonant circuit charging switch31, which is arranged in series with the demagnetizing resonant circuit40in the conductor loop30, the demagnetizing process described inFIG.1can be carried out.

The electronic circuit10also comprises a recharging resonant circuit50in the conductor loop30, which is arranged in parallel with the demagnetizing resonant circuit40and the resonant circuit charging switch31. It is used to perform a pulsed recharging of a charging current into the demagnetizing resonant circuit40with the resonant circuit charging switch31closed momentarily in each case. As described above in relation toFIG.1, energy which is stored in the recharging resonant circuit50can be introduced into the demagnetizing resonant circuit40at regular intervals as short recharging pulses C. The term “short” refers to the much shorter duration t compared to an entire period of the resonance oscillation in the demagnetizing resonant circuit40, as shown inFIGS.2and3.

The natural frequency of the recharging resonant circuit50is preferably at least 10 times, preferably at least 100 times, greater than the natural frequency of the demagnetizing resonant circuit40.

Further, the conductor loop30of the electronic circuit10comprises a recharging store60, which is arranged in parallel with the voltage source20, the recharging resonant circuit50, and the demagnetizing resonant circuit40. The store is provided for supplying power to the recharging resonant circuit50during the decay time t. In addition, a recharging switch32is arranged in the conductor loop30which, when opened, interrupts the charging current from the voltage source20and from the recharging store60to the recharging resonant circuit50and to the demagnetizing resonant circuit40.

Finally, the electronic circuit10in the conductor loop30comprises a charging switch33, which when opened interrupts the connection from the charge source20to the recharging store60, to the recharging resonant circuit50and to the demagnetizing resonant circuit40. The charging switch33thus decouples the charge source20from the rest of the electronic circuit10.

In operation, a controller70controls all switches31,32,33,43,53, and by opening and closing the switches31,32,53can introduce recharging pulses C from the recharging resonant circuit50into the demagnetizing resonant circuit40, for prolonging the decay time until the energy from the recharging store60is exhausted.

Preferably, a rectifier diode34is arranged in the conductor loop30in series with the voltage source20and the charging switch33, in such a way that said diode can prevent feedback from the recharging store60, from the recharging resonant circuit50and the demagnetizing resonant circuit40into the voltage source20during use.

When the switches—charging switch33, recharging switch32and resonant circuit charging switch31—are closed, the demagnetizing resonant circuit40, the recharging resonant circuit50and the recharging store60are charged. The mentioned switches33,32and31are then opened again.

In this state, the demagnetizing process can begin. Until the end of this process, no more energy is supplied from the voltage source20. The charging switch33remains open during this time; the voltage source20therefore remains decoupled from the rest of the circuit10.

At this time, the entire energy, which can be recharged until the end of the resonance oscillation of the demagnetizing resonant circuit40, is contained in the recharging store60. This comprises, for example, a storage capacitor62, as shown inFIG.5. This means that only a single voltage source20is needed. The capacitance of the storage capacitor62is preferably at least twice as large, preferably at least three times as large, as that of the resonant circuit capacitor42.

All switches31,32,33are controlled by the controller70, which preferably also controls the voltage source20. In addition, other switches can be controlled by this controller70. The controller70can be separate from the circuit10or be part of it.

As already described in relation toFIG.3, the resonant circuit charging switch31is briefly opened after the resonance oscillation in the demagnetizing resonant circuit40has begun and the resonant circuit voltage A has passed through the zero point D. The recharging resonant circuit50then delivers its recharging pulse C to the demagnetizing resonant circuit40. The resonant circuit charging switch31is closed again.

By opening the recharging switch32, the recharging resonant circuit50is now charged by a current flowing from the recharging store60. When the recharging resonant circuit50is fully charged again, the recharging switch32is closed again. Now, the recharging resonant circuit50is ready again to deliver a further recharging pulse C to the demagnetizing resonant circuit40after the next zero crossing of the resonant circuit voltage A in this circuit. By means of the controller70, the resonant circuit charging switch31is opened again briefly at the correct time, for a time much shorter than a quarter period of the resonance oscillation.

This process is repeated until the energy in the recharging store60is exhausted.

It must be ensured that the recharging pulses C have the correct signs in each case. These must alternate. The recharging resonant circuit50preferably comprises, as shown inFIG.5, a recharging coil51and a recharging capacitor52arranged in series therewith. When charging and discharging the recharging capacitor52, a half-oscillation of the recharging resonant circuit50is executed in each case. In order to change the polarity, a polarity reversing switch53can preferably be arranged in parallel with the recharging coil51and the recharging capacitor52, for reversing the polarity of the charge in the recharging capacitor52during a half-oscillation. After every second charge of the recharging capacitor52the polarity reversing switch53is opened for a half-oscillation, so that the polarity in the recharging capacitor52changes.

Alternatively, an changeover switch may be provided between the recharging store60and the recharging resonant circuit to charge the recharging capacitor52in the reverse direction at every second charge.

In the method according to the invention for generating a decaying electromagnetic field, an electronic circuit10described here is used to demagnetize ferromagnetic material during a decay time. Firstly, the demagnetizing resonant circuit40, the recharging resonant circuit50and the recharging store60are charged by means of the voltage source20, while the charging switch33, the recharging switch32and the resonant circuit charging switch31are closed.

The mentioned switches31,32and33are then opened again. The resonance oscillation is started at its natural frequency and with a decaying amplitude, for example by closing the resonant circuit switch43. An alternating magnetic, periodic demagnetizing field is produced.

Next, by briefly closing and opening the resonant circuit charging switch31, a short, first recharging pulse C in the form of a recharging current is introduced into the demagnetizing resonant circuit40from the recharging resonant circuit50.

The recharging resonant circuit50is then charged by the recharging store60by briefly closing and opening the recharging switch32. The last two steps are repeated until the energy supply in the recharging store60is exhausted.

In a preferred method, each first recharging pulse C is followed by one or more further short recharging pulses C with the same sign and these are transferred to the demagnetizing resonant circuit40. The total duration of the series of recharging pulses C is no more than one quarter, preferably no more than one eighth of an oscillation period of the demagnetizing resonant circuit40. Each first recharging pulse C is preferably fed directly into the resonance oscillation of the demagnetizing resonant circuit after a zero crossing of the resonant circuit voltage A. Since the resonant circuit voltage A changes sign as a result, the sign of each subsequent first recharging pulse C must also be changed accordingly.

To achieve this, the polarity of the charge in the recharging capacitor52is reversed. This can be achieved by providing the recharging resonant circuit50with a polarity reversing switch53. The polarity reversing switch53is closed with the recharging switch32open and the resonant circuit charging switch31open, causing a resonance oscillation of the capacitor52and the recharging coil51to appear in the recharging resonant circuit50, which is interrupted again after a half-oscillation by opening the polarity reversing switch53. Each first recharging pulse C therefore preferably begins exactly half a period of the resonance oscillation of the demagnetizing resonant circuit40later than the previous first recharging pulse C.

At or before the start of the method, a ferromagnetic workpiece is brought into the effective range of the demagnetizing resonant circuit40in order to demagnetize said workpiece. If necessary, the procedure described here can be repeated multiple times.

The circuit10described here and the method carried out therewith permit a simple and safe demagnetization of ferromagnetic bodies. The circuit is composed of simple components that enable a safe, trouble-free process.

LIST OF REFERENCE SIGNS

10electronic circuit; circuit20voltage source30conductor loop31resonant circuit charging switch32recharging switch33charging switch34rectifier diode40demagnetizing resonant circuit41demagnetization coil42resonant circuit capacitor43resonant circuit switch50recharging resonant circuit51recharging coil52recharging capacitor53polarity reversal switch60recharging store62storage capacitor70controllerA resonant circuit voltageB demagnetizing currentC recharging pulseD zero crossing, zero pointt time