US3728512A - High frequency heating apparatus - Google Patents

High frequency heating apparatus Download PDF

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Publication number
US3728512A
US3728512A US00122631A US3728512DA US3728512A US 3728512 A US3728512 A US 3728512A US 00122631 A US00122631 A US 00122631A US 3728512D A US3728512D A US 3728512DA US 3728512 A US3728512 A US 3728512A
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United States
Prior art keywords
door
cavity
high frequency
enclosure
opening
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US00122631A
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English (en)
Inventor
Y Shirakami
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sanyo Electric Co Ltd
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Sanyo Electric Co Ltd
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Filing date
Publication date
Application filed by Sanyo Electric Co Ltd filed Critical Sanyo Electric Co Ltd
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Publication of US3728512A publication Critical patent/US3728512A/en
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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 high frequency heating apparatus including a eubiform cavity or oven of conductive material having an opening, a supply source for supplying high frequency energy into the cavity and a door for providing access to the cavity mounted so as to close the opening; a periphery of the door has a sash with a groove thereon extending along the periphery and a periphery surrounding the opening of the cavity has a sensing member with a protrusion for fitting in the groove when the door is closed.
  • the sensing member is urged away from the peripherel surface of the cavity by virtue of a spring and when the door is closed the protrusion of the member is fitted in the groove.
  • the obstacle depresses the protrusion and the sensing member is forced toward the peripheral surface of the cavity.
  • a safety switch is provided in engagement with the sensing member for turning off the supply source in response to the depression of the member caused by the obstacle. Therefore, leakage of the high frequency energy caused by the sandwiched obstacle is prevented.
  • This invention relates to a high frequency heating apparatus and more specifically to such an apparatus as to effectively prevent leakage of high frequency electromagnetic energy through a gap with respect to such energy caused by an obstacle undesirably sandwiched between a periphery of a closed door and a periphery of an oven enclosure of such apparatus.
  • the heating apparatus of this type includes a cubiform cavity or oven of conductive, typically metallic, material, and a supply source for supplying high frequency energy into the cavity.
  • a cubiform cavity or oven of conductive, typically metallic, material and a supply source for supplying high frequency energy into the cavity.
  • One of the walls of the oven defining the cubic cavity is constructed as a door providing access to the cavity and which, when shut, effects a suitable seal of the cavity.
  • Typical conventional seal means for preventing leakage of radiation are metallic spring contact means, conductive rubber, magnetic rubber, etc. provided either on the door of the heating apparatus or on the front of the oven enclosure.
  • Another one of the greatest problems in high frequency heating apparatus is leakage of the high frequency electromagnetic energy through a gap with respect to such energy caused by an obstacle un desirably sandwiched between a periphery of the door and a periphery of an oven enclosure of such heating apparatus when the door is closed and the apparatus is put into operation. More specifically, when the door is inadvertently closed with pieces of food attached to or a dishcloth hanged over the periphery of the door, sealing between the door and the oven enclosure is not perfect due to the presence of dielectric material or a gap with respect to the high frequency electromagnetic energy arises therebetween, resulting in leakage of such energy therethrough. Such leakage of the energy should be avoided absolutely.
  • either the periphery of the door or the periphery of the opening of the oven enclosure or cavity of the high frequency heating apparatus has a sensing strip provided extending along the periphery thereof and movably toward the surface of the periphery thereof in response to an obstacle undesirably sandwiched between both peripheries of the door and the opening of the oven enclosure and a safety switch is provided in engagement with said sensing strip for turning off the power source for high frequency energy source.
  • the safety switch is turned off to deenergize the high frequency energy source.
  • an object of the present invention is to provide an apparatus for preventing the leakage of the high frequency energy through a gap with respect to the high frequency energy caused by an obstacle undesirably sandwiched between both peripheries of the door and the opening of the oven enclosure of the high frequency heating apparatus when the door is closed.
  • Another object of the present invention is to turn off the safety switch of the high frequency heating apparatus in response to an obstacle sandwiched between both peripheries of the door and the opening of the cavity when the door is closed.
  • object of the present invention is to turn off the safety switch of the high frequency heating apparatus in response to an obstacle sandwitched between both peripheries of the closed door and the opening of the cavity, wherever along the peripheries of the obstacle may be located.
  • FIG. 1 is a side view of the high frequency heating apparatus with the door closed in accordance with the present invention
  • FIG. 2 is a front view of the apparatus of FIG. 1. with the door removed,
  • FIG. 3 is a perspective view from the backside of the door in an opened state
  • FIG. 4 is an enlarged sectional view of a portion shown in a dotted line circle in FIG. 1,
  • FIG. 5 is an enlarged sectional view along line V-V in FIG. 2 but in a state of the door being closed
  • FIG. 6 is an enlarged sectional view similar to FIG. 4 but in case of the door being closed with an obstacle sandwiched between the door and the cavity,
  • FIG. 7 is an enlarged sectional view similar to' FIG. 4 but of another embodiment in accordance with the present invention.
  • FIG. 8 is an enlarged sectional view similar to FIG. 5 but of the same embodiment as FIG. 7,
  • FIG. 9 is an enlarged sectional view similar to FIG. 6 but of the same embodiment as FIG. 7, and
  • FIG. 10 is a schematic diagram of a control circuit for the embodiment of a control circuit for the embodiment shown in FIGS. 7 through 9.
  • FIGS. 1 and 2 there are shown a side view of the high frequency heating apparatus with the door closed in accordance with the present invention and a front view of the apparatus of FIG. I with the door removed, respectively.
  • the high frequency heating apparatus as shown comprises an oven enclosure or cavity 1 which is housed in a housing 2 and defined by a conductive, typically metallic, wall and a high frequency supply source 4, typically a magnetron, which supplys high frequency energy into the cavity 1.
  • a high frequency supply source 4 typically a magnetron
  • One side (bottom side in an illustrated embodiment) of the periphery encompassing the opening is rotatably provided with a conductive door 10 by means ofa hinge 31 and when the door 10 is closed, the said opening 3 is shut, providing a closed heating chamber.
  • high frequency energy is supplied from the high frequency energy supply source 4 through a waveguide 5 into the cavity 1.
  • stirring blades are provided in order to make even the distribution mode of high frequency energy in the cavity 1, thereby heating evenly materials being heated.
  • a time period for energizing the source 4 is controlled e.g. by a timer 8 provided on the control panel 6.
  • the time set by the timer 8, is indicated by means of a scale 9 provided on the panel 6.
  • a main switch 7 is also provided on the panel 6 for energizing the high frequency heating apparatus.
  • FIG. 3 there is shown a perspective view from the backside of the door 10 in an opened state.
  • the door 10 comprises in a given central area thereof a plurality of small apertures 11 so that materials being heated placed inside the cavity 1 may be observed from the outside.
  • Sashes 14, preferably of metal, with grooves 13 thereon are secured by means of screws 15 along the periphery of the door 10 opposite the periphery l2 encompassing the opening 3 of the cavity 1.
  • FIGS. 4 and 5 there are shown an enlarged sectional view of a portion shown in a dotted line circle in FIG. 1 and an enlarged sectional view along line V V in FIG. 2 but in a state of the door being closed.
  • a metal flat spring strip 16 of an inverted V in section is provided extending along the whole periphery l2 encompassing the opening 3 by securing one side of the strip 16 by means of screws l7'on the periphery 12, whereby the other side of the strip 16 is urged away from the peripheral surface 12 due to the elasticity of the strip 16. Therefore, when the door 10 is closed, as shown in FIGS.
  • the protruded portion of the strip 16 comes in contact with the periphery of the door 10 under a certain value of pressure as determined by the elasticity of the strip 16.
  • the metal strip 16 effects the sealing between both peripheries of the door 10 and the cavity 1 to prevent leakage of high frequency energy through therebetween.
  • Extending along the periphery l2 encompassing the opening 3 in parallel with the metal strip 16 is also provided metal flat spring strip 18 by securing one side of the strip 18 on the periphery 12 of the cavity 1 with the screws 17, whereby the other side of the strip 18 is urged away from the peripheral surface of the cavity 1.
  • a protrusion 19 formed at the other side of the strip 18 is so adapted that it may be fitted in the groove 13 of the sash 14, when the door 10 is closed.
  • a plurality of microswitches 20 are provided spaced apart from each other and arranged along with the periphery 12 surrounding the opening 3 of the cavity 1, as shown as at P in FIG.
  • each switch 20 is mounted in a space between a housing wall and a cavity wall and an actuator 22 of the switch 20 is protruded from the peripheral surface 12 through an aperture thereof to be opposite to the rear side depressing portion 22 of the metal strip 18. All these switches 20 are connected in series with each other and with a power source for the high frequency energy source 4, so that actuation of any one of the switches 20 deenergizes the high frequency source 4.
  • such obstacle 23 is also sandwiched between the sash 14 and the strip 18, in view of the fact that the sash l4 and the strip 18 are positioned adjacent the strip 16.
  • the obstacle 23 interrupts the protrusion 19 fitting in the groove 14.
  • the protrusion side of the strip 18 is depressed by the obstacle 23 toward the peripheral surface 12 of the cavity 1. Accordingly, the
  • rear side depressing portion 22 depresses the actuator 21 to turn off the switch 20.
  • the high frequency source 4 is deenergized and the high frequency energy is not supplied into the cavity 1.
  • FIGS. 7 through 10 shows another embodiment of the present invention, which merely comprises a modified switching means responsive to the obstacle.
  • FIGS. 7, 8 and 9 correspond to FIGS. 4, 5 and 6, respectively, referred to in connection with the first embodiment. Therefore, in these figures, like numerals designate like part.
  • the strip 18 is, as to be more fully described later, connected to the ground or held in the same potential as the cavity 1.
  • a contact layer 20' is provided on an insulation plate 21' extending along the periphery 12 surrounding the opening 3 of the cavity 1.
  • the contact portion 22' of the strip 18 and the contact layer 20' are so adapted that in a normal state both are spaced apart from or are out of contact with each other, because the strip 18 urged away from the peripheral surface 12, but when the strip 18 is depressed by an obstacle, both come in contact with each other.
  • the strip 18 or the contact portion 22 and the contact layer 20' constitute a switch, which corresponds to the microswitch 20 in the first embodiment.
  • a drive circuit D for driving the magnetron 4 includes a relay contact 27 as well as the main switch 7 and the timer 8 connected in series with each other.
  • a relay coil 24 for the relay contact 27 is connected in series with a thyristor 25, a gate of which is connected to a transistor 26, a base of which is connected to the switch formed by the contacts 22 and 20'.
  • the protrusion 19 of the strip 18 is fitted in the groove 13 of the sash 14 of the door 10, assuming that no obstacle has been sandwiched between the peripheries of the door and the cavity opening 3. Since the contact and 22 are out of contact, the transistor 26 and, accordingly, the thyristor 25 remain off, which keeps the contact 27 closed. By setting the switch 7 and timer 8, the magnetron 4 is energized for heating the material placed inside the cavity 1.
  • High frequency heating apparatus comprising:
  • conductive enclosure means including a peripheral portion of electrically conductive material defining an opening into a cavity formed by said enclosure means, I means for supplying high frequency electromagnetic wave energy into the cavity of said enclosure means,
  • door means having a portion of electrically conductive material for closing the opening of said enclosure means by having said portion of electrically conductive material brought into opposed relationship with the peripheral portion of said enclosure means defining said opening, means for mounting said door means along a side thereof to said enclosure means to permit said door to be moved to open and close said opening of said cavity means, switch means mounted on said apparatus and connected in circuit with said means for supplying energy, an elongated stationary element having a groove therein substantially along its length mounted on said door means and extending for a substantial portion of the length of a side of said door means, an elongated actuating means mounted on said enclosure means, said'actuating means including a spring strip and having a free end for actuating said switch means, said free end extending toward said door and having a.
  • said actuating means being responsive to the presence of an object substantially at any location along the length of said sensing means between the groove of said stationary element and the projection of the actuating means when the door means is closed to be moved to a position to actuate said switch means to disable said means for supplying energy.
  • said spring strip of the actuating means includes a portion of resilient electrically conductive material mounted to contact the electrically conductive portion of the opposed surface of the door when the door means is closed for sealing the cavity with respect to leakage of the high frequency electromagnetic energy.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Electric Ovens (AREA)
  • Constitution Of High-Frequency Heating (AREA)
US00122631A 1970-10-23 1971-03-01 High frequency heating apparatus Expired - Lifetime US3728512A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP45093735A JPS4939574B1 (enrdf_load_stackoverflow) 1970-10-23 1970-10-23

Publications (1)

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US3728512A true US3728512A (en) 1973-04-17

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Application Number Title Priority Date Filing Date
US00122631A Expired - Lifetime US3728512A (en) 1970-10-23 1971-03-01 High frequency heating apparatus

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US (1) US3728512A (enrdf_load_stackoverflow)
JP (1) JPS4939574B1 (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3944767A (en) * 1973-05-25 1976-03-16 U.S. Philips Corporation Dishwashing machine closure safety switch device
US4101750A (en) * 1977-05-31 1978-07-18 Whirlpool Corporation Door interlock system for microwave oven
US4321445A (en) * 1980-01-28 1982-03-23 Whirlpool Corporation Door latch interlock system for microwave oven

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3544751A (en) * 1969-02-04 1970-12-01 Litton Precision Prod Inc Microwave oven having meshing microwave door seal

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3544751A (en) * 1969-02-04 1970-12-01 Litton Precision Prod Inc Microwave oven having meshing microwave door seal

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3944767A (en) * 1973-05-25 1976-03-16 U.S. Philips Corporation Dishwashing machine closure safety switch device
US4101750A (en) * 1977-05-31 1978-07-18 Whirlpool Corporation Door interlock system for microwave oven
US4321445A (en) * 1980-01-28 1982-03-23 Whirlpool Corporation Door latch interlock system for microwave oven

Also Published As

Publication number Publication date
JPS4939574B1 (enrdf_load_stackoverflow) 1974-10-26

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