US3809843A - Microwave heating apparatus - Google Patents

Microwave heating apparatus Download PDF

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Publication number
US3809843A
US3809843A US00147974A US14797471A US3809843A US 3809843 A US3809843 A US 3809843A US 00147974 A US00147974 A US 00147974A US 14797471 A US14797471 A US 14797471A US 3809843 A US3809843 A US 3809843A
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US
United States
Prior art keywords
door
enclosure
cavity
microwave oven
oven
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
Application number
US00147974A
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English (en)
Inventor
T Takayama
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.)
Aerojet Rocketdyne Holdings Inc
Original Assignee
Gencorp Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Gencorp Inc filed Critical Gencorp Inc
Application granted granted Critical
Publication of US3809843A publication Critical patent/US3809843A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • 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
    • H05B6/76—Prevention of microwave leakage, e.g. door sealings
    • H05B6/763—Microwave radiation seals for doors

Definitions

  • a microwave oven having anelectromagv netic energy seal constituted by the oven enclosure [30]
  • Foreign Application Priority Data and its associated door each of which comprises a J l 1970 la n 45 53825 complementary stepped structure defining a pair of une pa i planes.
  • One of the stepped structure is formed with a cavity therein having a plurality of walls and a termi- (g1. mating wall and which has an p g pp to the 58] Fie'ld 219/10 55 step portion of the other stepped structure.
  • the terminating wall of the cavity is spaced substantially [56] References Cited wavelength from the middle point intermediate the step portion and the opening and is spaced an integral UNITED STATES PATENTS 1 multiple of, /z wavelength from the boundary of the 3,629,537 12/1971 Haagensen 219/1055 oven interior: 3,584,177 6/1971 Bucksbaum 219/1055 3,544,751 12/1970 Valles 219/1055 9 Claims, 4 Drawing Figures IIIIIIIJIIII [III/I177 PATENTED MAY 7 I974 saw 1mg FIG.
  • FIG. 1 A first figure.
  • the invention relates to a microwave oven, and more particularly to such an oven which is provided with a microwave energy seal operable to prevent leakage of electromagnetic energy to the exterior of the oven through a gap between an enclosure and a door associated therewith.
  • a microwave oven In order to avoid dangers resulting from leakage of an electromagnetic energy, a microwave oven is provided with a secure electromagnetic energy seal between the enclosure and its associated door. While it is unlikely that leakage of an electromagnetic energy occurs during the normal operation when the door is completely closed with this such a secure seal, the construction of such a seal is expensive. Usually a switching means is mechanically interlocked with the door to interrupt the supply of microwave energy to the oven chamber when the door is opened. A problem is encountered with this type of construction in that although the time required to interrupt the associated electrical circuit is almost a matter of moment, the electromagnetic energy supplied to the oven chamber in the interval is. free to leak through the small spacing provided by the door that is being opened.
  • modern microwave oven is provided with a mannual switching means that is separate from the first mention switching means associated with the door, a requirement being imposed upon a user of the oven that he operates the mannual switching means prior to opening the door.
  • the construction is such that the user may not operate the mannual switch in order to open the door, and hence the user may forget to operate the manual switch by inadvertence.
  • U. S. Pat. No. 3,182,164 issued to Richard lronfield on May 4, 1965 discloses an electromagnetic energy seal for use in a microwave oven which incorporates choke coupling or choke seal known in the waveguide technique.
  • This patent teaches formation of an arcpreventing gap between a metal enclosure and a metal in a manner to create a short circuit condition at the entrance of the gap without use of any metal bar so that an electromagnetic energy may not leak through the gap.
  • the gap as described in this patent is not one that is produced by opening the door, but refers to that one which is formed when the door is closed or in physical contact with the enclosure.
  • the short circuit condition cannot be maintained in the gap at the inlet of the enclosure which is formed below a sliding door shown in FIG. 1 of that patent when the door begins to be opened.
  • FIG. 1 is a fragmentary side elevation, partly in section, of an embodiment of a microwave oven according to the invention
  • FIG. 2 is an enlarged section taken along the line 2 2 shown in FIG. 1;
  • FIG. 3 is a section of another'embodiment of the invention which involves no metal contact between the enclosure and the first plane of the door;
  • FIG. 4 is a section of a further embodiment of the invention in which a cavity member is mounted on the side wall of oven shield.
  • the microwave oven illustrated comprises a metal enclosure 1 which includes an outer wall 2, an inner wall 3 and a frontwall 4, an interior being shown at 17 and having an entrance which is covered by a door 5.
  • the door 5 is hinged at 6 to the enclosure 1 and is adapted to be opened and closed in a pivotal movement by mannual operation of a handle 18 provided at the opposite or upper end of the door 5. While not shown, the enclosure 1 contains means for supplying microwave energy to the interior 17.
  • the interface between the enclosure 1 and the door comprises two planes which define a stepped construction.
  • a cavity is formed in one of the stepped spaces, for cooperation with the other step.
  • the cavity is located within the door structure 5, and such structure will be described more particularly below.
  • the front wall 4 of the oven is attached with an oven shield plate 7, which in turnis attached with an oven shield frame 8 which leaves a certain width of shield plate portion 7a.
  • an oven shield frame 8 which leaves a certain width of shield plate portion 7a.
  • a recess 10 in which is embedded a wave absorber 11.
  • a stepped structure which is defined by a first plane presented by the inner portion 7a of the oven shield plate 7, and a second plane presented by the front surface of the oven shield frame 8.
  • the sidewall 8b of the oven shield frame 8 which interconnects the first and second planes 7a, 8a is shown at right angles to the front surface 8a, but this need not be so restricted and a greater angle may be used to prevent deposition of dusts and other obstacles on that sidewall.
  • the oven shield frame 8 is rigidly secured together with the oven shield plate 7 to the front wall 4 with screws 9.
  • the door 5 is provided with a back-up plate 14 all cluding a base 12a, a short leg portion 12b and a long leg portion 120, these together constituting a cavity 13 which opens toward the sidewall 8b of the oven shield plate 7 and forms at its one end a gap 20 with the sidewall 8b of the oven shield frame when the door is closed.
  • the short leg portion 12b of the door shield frame terminates substantially at the same position with said one end of the door shield plate 15. Where the sidewall 8b is inclined as mentioned previously, the gap 20 may be substantially reduced to zero, the requirement on the gap 20 being to insure the capability of the door to be opened and closed.
  • the long leg portion of the door shield frame extends to the outer periphery of the door and lies opposite to and abuts against the front surface 8a defining the second plane. In this manner, a stepped structure comprising a first plane presented by the door shield plate and a second plane presented by the long leg portion 12c of the door shiel frame is formed around the door 5.
  • the opposing stepped structures formed around the enclosure 1 and the door 5 have a significance to the cavity 13 and enables a multiple electromagnetic energy seal to be provided in a simple manner.
  • the cavity 13 is formed by short and long leg portions 12b and 12c and a terminating wall or base 12a and has an opening which is opposite to and cooperates with the sidewall 8b of the oven shield frame.
  • An opening defining line can be considered as extending from the effective end of the short leg portion 12!), If the length of the gap defined between the above end and the sidewall 8b of the oven shield frame is assumed to be approximately zero, then the opening defining line for the cavity 13. can be regarded as extending along the sidewall 8b, and can be considered as representing a surface of the step of the door structure.
  • the terminating surface of the cavity 13 or base 12a which forms a sidewall thereof is located at a distance from the boundary 19 of the oven interior 17 which is substantially an integral multiple of a wavelength and is also located at a distance of substantially l4 wavelength from the center between the sidewall 8b and the opening defining line of the cavity 13, or from the middle point between the steps of the enclosure 1 and the door 5.
  • the term wavelength refers to that wavelength of an electromagnetic wave which is produced in theoven apparatus and propagates through the interspace between the oven walls and the door.
  • a practical microwave oven apparatus uses a radiation having a frequency of 2,450 MHZ, which will have a wavelength of approximately 5 inches in the atmosphere.
  • a propagation medium can be used which reduces the effective wavelength of a radiation energy, and therefore the wavelength as termed herein does not refer to a radiation of any fixed frequency, or only to those radiations capable of propagation through the atmosphere.
  • the base 12a of the cavity 13 presents a short circuit condition effectively to any electromagnetic energy propagating thereinto. This is reflected as an open circuit condition at the middle point between the opening defining line of the cavity 13 and the sidewall 8b of the oven shield frame which is spaced V4 wavelength from the terminating wall 12a, and also reflected as a short circuit condition at a point spaced therefrom by a further V4 wavelength. This means that a short circuit condition is eventually produced at the boundary 19 of the oven interior 17.
  • the wave absorber 11 comprises rubw ber material blended with ferite, which serves to absorb any adjacently existing wave without directly blocking the wave path.
  • the maximum length of the gap that may be formed between the enclosure and the door when opening the door by the time the switching means interlocked with door motion interrupts the electrical circuit of the microwave supply means is usually 3 mm or less. It will be understood that any gap length which may be left due to the presence of obstacles without being noticed by a user will be of a magnitude of the same order. A greater gap will be either noticeable or effective to operate an associated detector. Thus, the above figure can be taken as the magnitude of gap that may induce danger, and it is satisfactory to prevent leakage of electromagnetic energy through a gap of this magnitude.
  • FIG. 3 shows a door construction in which the door shield plate is opposite to, but does not abut against the oven shield plate 7.
  • the metal contact is not formed at the first planes as in FIG. 2, but the illustrated structure is effective to prevent leakage by virtue of the short circuit condition established at the boundary 19.
  • the opening of the cavity 13 is provided with a dressing member 21 in order to avoid ingress of dust or the like.
  • FIG. 4 shows such a modification.
  • the door shield frame is omitted, and instead the door shield plate 15 has a front portion 15a, defining a first plane, and a rear portion 150, defining a second plane and which is connected with the front portion 15a by a stepped sidewall 15b.
  • the cavity 13 is formed in the oven shield frame 8 at a position opposite to the sidewall 15b. It will be appreciated that a gap is formed between the opening of the cavity 13 and the sidewall 15b and that the bottom orterminating wall of the cavity 13 is spaced by M1 wavelength and by 7% wavelength, respectively, from the center of the space and from the boundary 19, respectively. It is noted that the opening of the cavity 13 is provided with a dressing member 21 as mentioned in connection with FIG. 3. This embodiment achieves the similar prevention of leakage of electromagnetic energy as other embodiments described before.
  • Amicrowave oven according to claim 1 wherein a gap is formed between said stepped structures.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Electric Ovens (AREA)
  • Constitution Of High-Frequency Heating (AREA)
US00147974A 1970-06-01 1971-05-28 Microwave heating apparatus Expired - Lifetime US3809843A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP1970053825U JPS5018181Y1 (fr) 1970-06-01 1970-06-01

Publications (1)

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US3809843A true US3809843A (en) 1974-05-07

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Family Applications (1)

Application Number Title Priority Date Filing Date
US00147974A Expired - Lifetime US3809843A (en) 1970-06-01 1971-05-28 Microwave heating apparatus

Country Status (6)

Country Link
US (1) US3809843A (fr)
JP (1) JPS5018181Y1 (fr)
CA (1) CA934828A (fr)
DE (1) DE2127113C3 (fr)
FR (1) FR2095763A5 (fr)
GB (1) GB1342672A (fr)

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3879595A (en) * 1973-01-08 1975-04-22 Tappan Co Microwave oven door seal
US3943319A (en) * 1974-02-26 1976-03-09 Matsushita Electric Industrial Co., Ltd. Microwave oven with hinged door and latch means
US3955060A (en) * 1974-08-14 1976-05-04 Philip Morris Incorporated Microwave oven construction
US3985993A (en) * 1974-08-29 1976-10-12 U.S. Philips Corporation Sealing arrangement in a microwave oven
US4000390A (en) * 1975-02-14 1976-12-28 Hobart Corporation Microwave oven door
US4013861A (en) * 1975-08-13 1977-03-22 The Frymaster Corporation Microwave oven door seal
US4046983A (en) * 1975-09-03 1977-09-06 Tdk Electronics Co., Ltd. Microwave heating oven having seal means for preventing the leakage of microwave energy
US4049939A (en) * 1976-04-29 1977-09-20 Mills Products, Inc. Microwave and radiant window for oven doors
US4053731A (en) * 1974-06-14 1977-10-11 Amana Refrigeration, Inc. Microwave energy oven seal
US4059742A (en) * 1975-07-09 1977-11-22 Litton Systems, Inc. Microwave seal for combination cooking apparatus
US4114013A (en) * 1977-07-28 1978-09-12 General Electric Company Choke for combined microwave and self-cleaning oven
US4146768A (en) * 1976-08-18 1979-03-27 U.S. Philips Corporation Door for a microwave oven
US4166207A (en) * 1977-05-31 1979-08-28 Whirlpool Corporation Microwave generating device--door seal
US4191877A (en) * 1977-07-11 1980-03-04 Matsushita Electric Industrial Co., Ltd. Microwave oven equipped with electric heating arrangement
US4347420A (en) * 1979-09-11 1982-08-31 Matsushita Electric Industrial Co., Ltd. Microwave seal structure in microwave oven
US4689460A (en) * 1985-01-04 1987-08-25 Tdk Corporation Absorber device for microwave leakage
FR2885004A1 (fr) * 2005-04-22 2006-10-27 Premark Feg Llc Four a micro-ondes avec un cache pour piege a ondes
US20150122805A1 (en) * 2013-11-01 2015-05-07 Richards Corporation Microwave oven door seals

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5127004B1 (fr) * 1971-04-19 1976-08-10
SE375599B (fr) * 1973-08-17 1975-04-21 Philips Svenska Ab
JPS5743599U (fr) * 1980-08-26 1982-03-10

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3525841A (en) * 1968-11-04 1970-08-25 Litton Precision Prod Inc Door seal for microwave ovens
US3544751A (en) * 1969-02-04 1970-12-01 Litton Precision Prod Inc Microwave oven having meshing microwave door seal
US3584177A (en) * 1969-10-24 1971-06-08 Amana Refrigeration Inc Energy seal for microwave oven apparatus
US3629537A (en) * 1970-09-09 1971-12-21 Matsushita Electric Ind Co Ltd Microwave oven door seal having dual cavities fed by a biplanar transmission line
US3678238A (en) * 1970-04-23 1972-07-18 Sanyo Electric Co High frequency heating apparatus

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3525841A (en) * 1968-11-04 1970-08-25 Litton Precision Prod Inc Door seal for microwave ovens
US3544751A (en) * 1969-02-04 1970-12-01 Litton Precision Prod Inc Microwave oven having meshing microwave door seal
US3584177A (en) * 1969-10-24 1971-06-08 Amana Refrigeration Inc Energy seal for microwave oven apparatus
US3678238A (en) * 1970-04-23 1972-07-18 Sanyo Electric Co High frequency heating apparatus
US3629537A (en) * 1970-09-09 1971-12-21 Matsushita Electric Ind Co Ltd Microwave oven door seal having dual cavities fed by a biplanar transmission line

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3879595A (en) * 1973-01-08 1975-04-22 Tappan Co Microwave oven door seal
US3943319A (en) * 1974-02-26 1976-03-09 Matsushita Electric Industrial Co., Ltd. Microwave oven with hinged door and latch means
US4053731A (en) * 1974-06-14 1977-10-11 Amana Refrigeration, Inc. Microwave energy oven seal
US3955060A (en) * 1974-08-14 1976-05-04 Philip Morris Incorporated Microwave oven construction
US3985993A (en) * 1974-08-29 1976-10-12 U.S. Philips Corporation Sealing arrangement in a microwave oven
US4000390A (en) * 1975-02-14 1976-12-28 Hobart Corporation Microwave oven door
US4059742A (en) * 1975-07-09 1977-11-22 Litton Systems, Inc. Microwave seal for combination cooking apparatus
US4013861A (en) * 1975-08-13 1977-03-22 The Frymaster Corporation Microwave oven door seal
US4046983A (en) * 1975-09-03 1977-09-06 Tdk Electronics Co., Ltd. Microwave heating oven having seal means for preventing the leakage of microwave energy
US4049939A (en) * 1976-04-29 1977-09-20 Mills Products, Inc. Microwave and radiant window for oven doors
US4146768A (en) * 1976-08-18 1979-03-27 U.S. Philips Corporation Door for a microwave oven
US4166207A (en) * 1977-05-31 1979-08-28 Whirlpool Corporation Microwave generating device--door seal
US4191877A (en) * 1977-07-11 1980-03-04 Matsushita Electric Industrial Co., Ltd. Microwave oven equipped with electric heating arrangement
US4114013A (en) * 1977-07-28 1978-09-12 General Electric Company Choke for combined microwave and self-cleaning oven
US4347420A (en) * 1979-09-11 1982-08-31 Matsushita Electric Industrial Co., Ltd. Microwave seal structure in microwave oven
US4689460A (en) * 1985-01-04 1987-08-25 Tdk Corporation Absorber device for microwave leakage
FR2885004A1 (fr) * 2005-04-22 2006-10-27 Premark Feg Llc Four a micro-ondes avec un cache pour piege a ondes
US20080149629A1 (en) * 2005-04-22 2008-06-26 Premark Feg L.L.C. Microwave Oven With a Mask For Wave Trap
US20150122805A1 (en) * 2013-11-01 2015-05-07 Richards Corporation Microwave oven door seals

Also Published As

Publication number Publication date
FR2095763A5 (fr) 1972-02-11
JPS5018181Y1 (fr) 1975-06-04
DE2127113A1 (de) 1971-12-09
CA934828A (en) 1973-10-02
DE2127113B2 (de) 1974-11-28
GB1342672A (en) 1974-01-03
DE2127113C3 (de) 1975-07-10

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