US3753003A - Safety device against radiation leakage from microwave apparatus - Google Patents

Safety device against radiation leakage from microwave apparatus Download PDF

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Publication number
US3753003A
US3753003A US3753003DA US3753003A US 3753003 A US3753003 A US 3753003A US 3753003D A US3753003D A US 3753003DA US 3753003 A US3753003 A US 3753003A
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US
United States
Prior art keywords
transistor
circuit
potentiometer
microwave
bistable circuit
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Expired - Lifetime
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English (en)
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L Mazza
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Industrie Zanussi SpA
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Industrie Zanussi SpA
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/64—Heating using microwaves
    • H05B6/6414—Aspects relating to the door of the microwave heating apparatus
    • H05B6/6417—Door interlocks of the microwave heating apparatus and related circuits

Definitions

  • a safety device for microwave ovens which prevents radiation leakage from such an oven, the device being of the kind where a gas lamp is located in the area where radiation leakages may occur, said lamp being connected serially with a potentiometer which cooperates with a controlled diode which drives a relay which cuts the feed to the microwave generating circuit, the safety device being characterized by further comprising a bistable circuit and an amplifier which are connected to one another in cascade arrangement, the bistable circuit and the amplifier being inserted between the potentiometer voltage tap and the control electrode of the controlled diode.
  • this gas lamp is electrically and serially connected with a potentiometer from which the control voltage is drawn for a controlled diode which, in turn, is electrically and serially connected with a relay whose energization controls the opening ot the microwave generator feeding circuit.
  • An object of the present invention is to provide a device according to the main patent but having an enhanced sensitivity and improved promptness and reliability of actuation, and also to make the sensitivity adjustment of the device less critical, all this having in mind the final objective of improving the safety factor of the device.
  • Such a desirable improvement of sensitivity, promptness and reliability in entering action is obtained, according to this invention, by inserting between the voltage tap of the potentiometer and the control electrode of the controlled diode, a bistable circuit and an amplifier, mutually connected in cascade fashion, whereas the sensitivity adjustment is made less critical by providing an impedance match between the circuit connected to the potentiometer and the unblocking impedance of the controlled diode.
  • FIG. 1 shows the device in side elevational view, partly in section with the door set ajar
  • FIG. 2 shows the circuit diagram of the safety antiradiation device with which the oven is equipped.
  • the microwave oven shown in FIG. 1 comprises a substantially parallelepipedal body 1, having a cooking chamber 3 in its interior, into which projects the emitting antenna 3 ofa microwave generator 4.
  • the door 7, hinged and displaceable between a fully open and a fully closed position, has a handle 14 and a central transparent portion 15 consisting of a glass plate adapted to act as a shield against the microwaves as emitted by the generator 4 during the food cooking stage.
  • a gas lamp 16, located in a cavity 17 protected by a microwave-pervious wall 18, is an integral part of the device whose task is to block the operation of the microwave generator if radiation leakage occurs.
  • the gas lamp 16 is a part of an anti-radiation safety device whose circuitry diagram is shown in FIG. 2 and comprises a source of alternating current (not shown) which, via a pushbutton switch 20, feeds two circuit branches in parallel, the first of which comprises a diode 21 and the parallel connection of a capacitor 22 and a series connection composed by a relay 23 for controlling a normally open contact 24 inserted in the microwave generator (4) feeding circuit, a resistor 25, the gas lamp [6, a resistor'26 and a potentiometer 27, whereas the second branch comprises an SCR diode 30 and a relay 28 which respectively control a normally closed contact 29 inserted in the feeding circuit of the microwave generator and a normally open contact 46 connected in parallel with respect to the SCR diode 30.
  • the slider of the potentiometer 27 and the control electrode of the SCR, diode 30 are mutually connected by means of a circuit assembly comprising a snapping circuit of the bistable type and an amplifier.
  • the bistable circuit comprises two npn transistors 31 and 32 having their emitters connected to the ground through a common resistors 33 and their collectors connected to a positive feeding terminal 34 via the respective resistors 35 and 36.
  • the base of the transistor 31 is connected to the slider of the potentiometer 30 via a variable resistor 38, whereas the base of the transistor 32 connected to the ground via a resistor 39 via the parallel connection of a resistor 40 with a capacitor 41.
  • the amplifier comprises, in turn, an npn transistor 42 having its base directly connected to the collector of the transistor 31, its collector directly connected to the positive terminal 34 and its emitter connected to ground via a resistor 43 and to the control electrode of an SCR diode via a resistor 44. Between the control electrode of the SCR diode 30 and the ground there is arranged, in addition, a reverse bias diode 45.
  • the resistance of the lamp 16 remains high, so that the current flowing therethrough is low even if it is enough as to keep the relay 23 energized (thus the contact 24 is closed) and the transistor 31 conducting.
  • the transistor 42 is cut off and consequently so is the SCR diode 30.
  • the relay 28 is thus de-energized so that the contact 29 is closed and permits that the microwave generator 4 be fed.
  • the first incoming negative pulse switches it to a cutoff state (the reasoning should be reserved if the transistor 31 would be of the pnp type).
  • the relay 28 is energized and opens the contact 29, the result being the deactuation of the microwave generator and the closing of the contact 46 which keeps the relay 28 energized.
  • the device according to the present invention affords, in addition to a high sensitivity, an easy adjustment of sensitivity (through the potentiometer) in that, since the input impedance of the snapping circuit is high, an impedance match is obtained with the source of control pulses (drawn between the slider and the lower end of the potentiometer 27). Likewise, the impedance match is obtained also between the output of the snap circuit and the input of the current amplifier and also between the output of the latter and the impedance of the control circuit of the SCR diode.
  • a safety device for sensing and preventing radiation leakage from a microwave-producing apparatus having a microwave feeding circuit, said device comprising, in combination, a first circuit branch including a gas lamp which is sensitive to microwave radiation and which is disposed in a region of possible microwave radiation leakage from the microwave-producing apparatus, and a potentiometer electrically coupled with said gas lamp, said potentiometer having a voltage path providing a control voltage therefrom; a second circuit branch including a controllable diode having a control electrode, and a relay means serially connected to said controllable diode for energization thereby, said relay means upon energization opening the microwave feeding circuit; bistable circuit means receiving said control voltage from said potentiometer voltage tap for changing output states in response thereto; and amplifier means coupled between said bistable circuit means and said control electrode of said controllable diode for triggering saidcontrollable diode.
  • a device further including means effecting impedance matches between the output circuit of the control voltage and the input of the bistable circuit means, the output of said bistable circuit means and the input of said amplifier means and the amplifier output and said controlled diode input.
  • a device characterized in that in parallel with the controlled diode there is arranged a normally open movable contact which is driven to become closed by the energization of said relay.
  • a device characterized in that between the potentiometer voltage tap and the bistable circuit, there is inserted a capacitor for blocking the DC component of the control voltage taken from the potentiometer.
  • bistable circuit means comprises a transistor the conductivity of which is dependent on the voltage drawn from the potentiometer.
  • bistable circuit means further comprises a second transistor which is common-emitter connected with respect to the first transistor, the base of the second transistor being connected to the collector of the first transistor through a delay circuit.
  • a device characterized in that said amplifier means comprises a transistor, whose base is connected to the collector of the first transistor of said bistable circuit means and the collector-emitter circuit comprises a load resistor across which the control voltage for the controlled diode is drawn.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Constitution Of High-Frequency Heating (AREA)
  • Control Of High-Frequency Heating Circuits (AREA)
  • Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)
  • Rotary Switch, Piano Key Switch, And Lever Switch (AREA)
  • Lining Or Joining Of Plastics Or The Like (AREA)
US3753003D 1970-10-07 1971-10-05 Safety device against radiation leakage from microwave apparatus Expired - Lifetime US3753003A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
IT3070070 1970-10-07

Publications (1)

Publication Number Publication Date
US3753003A true US3753003A (en) 1973-08-14

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ID=11231139

Family Applications (1)

Application Number Title Priority Date Filing Date
US3753003D Expired - Lifetime US3753003A (en) 1970-10-07 1971-10-05 Safety device against radiation leakage from microwave apparatus

Country Status (3)

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US (1) US3753003A (es)
JP (1) JPS5734634B1 (es)
ES (1) ES208792Y (es)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4529855A (en) * 1982-04-12 1985-07-16 Henry Fleck Microwave radiation detector
US4628439A (en) * 1983-12-12 1986-12-09 Robertshaw Controls Company Supervised start system for microprocessor based appliance controls
FR2612034A1 (fr) * 1987-03-04 1988-09-09 Brun Alain Detecteur d'ondes electromagnetiques
WO1990003092A1 (fr) * 1988-09-09 1990-03-22 Castillon, Alain Detecteur d'ondes electromagnetiques
US6346692B1 (en) * 1999-09-20 2002-02-12 Agere Systems Guardian Corp. Adaptive microwave oven
US20020089017A1 (en) * 2001-01-05 2002-07-11 Lai Chun Hsiang Electostatic discharge protection circuit coupled on I/O pad
EP2152047A1 (de) * 2008-08-04 2010-02-10 Topinox Sarl Sicherheitseinrichtung zur Detektierung von Leckagestrahlung
US10009965B2 (en) 2015-01-28 2018-06-26 Samsung Electronics Co., Ltd. Gas detection apparatus, cooking apparatus, and method of controlling the apparatuses

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3063010A (en) * 1960-04-25 1962-11-06 Alfred W Richardson Microwave dosimeter
US3350702A (en) * 1965-01-26 1967-10-31 Ruth A Herman Infrared detection system for fault isolation and failure prediction

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3063010A (en) * 1960-04-25 1962-11-06 Alfred W Richardson Microwave dosimeter
US3350702A (en) * 1965-01-26 1967-10-31 Ruth A Herman Infrared detection system for fault isolation and failure prediction

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4529855A (en) * 1982-04-12 1985-07-16 Henry Fleck Microwave radiation detector
US4628439A (en) * 1983-12-12 1986-12-09 Robertshaw Controls Company Supervised start system for microprocessor based appliance controls
FR2612034A1 (fr) * 1987-03-04 1988-09-09 Brun Alain Detecteur d'ondes electromagnetiques
WO1990003092A1 (fr) * 1988-09-09 1990-03-22 Castillon, Alain Detecteur d'ondes electromagnetiques
US6346692B1 (en) * 1999-09-20 2002-02-12 Agere Systems Guardian Corp. Adaptive microwave oven
US20020089017A1 (en) * 2001-01-05 2002-07-11 Lai Chun Hsiang Electostatic discharge protection circuit coupled on I/O pad
US8164112B2 (en) * 2001-01-05 2012-04-24 Macronix International Co., Ltd. Electostatic discharge protection circuit coupled on I/O pad
EP2152047A1 (de) * 2008-08-04 2010-02-10 Topinox Sarl Sicherheitseinrichtung zur Detektierung von Leckagestrahlung
US10009965B2 (en) 2015-01-28 2018-06-26 Samsung Electronics Co., Ltd. Gas detection apparatus, cooking apparatus, and method of controlling the apparatuses

Also Published As

Publication number Publication date
ES208792Y (es) 1976-07-16
JPS5734634B1 (es) 1982-07-23
ES208792U (es) 1976-04-01

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