GB2135048A

GB2135048A - Microwave ovens

Info

Publication number: GB2135048A
Application number: GB08327037A
Authority: GB
Inventors: Takamichi Sujaku; Shuki Aoyama; Takaaki Fukasawa
Original assignee: Tokyo Shibaura Electric Co Ltd
Current assignee: Toshiba Corp
Priority date: 1982-10-18
Filing date: 1983-10-10
Publication date: 1984-08-22
Also published as: DE3337679C2; NL188779B; GB2135048B; AU2023183A; AU541068B2; KR840006400A; KR880001087B1; NL188779C; NL8303588A; DE3337679A1; GB8327037D0

Abstract

A microwave oven having an oven cabinet 10 is provided with a heating chamber 11 formed in the cabinet such that microwave heating and ordinary electrically resistive heating can be carried out. An oven door 19 is pivotably mounted on the front side of the heating chamber and an inclined control panel 20 is disposed below the oven door such that the panel inclines downwardly and projects forwardly from the front side of the cabinet to define an encasing portion for at least a part of electric components 25 of the microwave oven underside of the heating chamber. The microwave oven further comprises an improved base plate 35 vertically located between the lower end of the front wall and the bottom wall 28 of the cabinet behind the inclined control panel board. Ventilation holes 27 in the bottom wall 28 allow cooling air into the chamber 12 and also permit drainage of liquid leaking through the turntable drive shaft hole 15. <IMAGE>

Description

SPECIFICATION Microwave ovens BACKGROUND OF THE INVENTION This invention relates to a high-frequency electronic cooking device and more particularly to a microwave oven wherein the arrangement of a control panel and electric parts or elements connected with the control panel is substantially improved.

A conventional microwave oven generally comprises a box-shaped cabinet, a heating chamber provided in the box-shaped cabinet, an oven door provided on the front side of the heating chamber, and a control panel including a number of control switches and the like, provided on one lateral side of the heating chamber. The microwave oven has such a drawback that it occupies a relatively wide horizontal space in a kitchen or the like in which effective utilization of a horizontal space is desired rather than that of a vertical space.

To eliminate such a drawback of the conventional microwave oven, there has been proposed a microwave oven wherein the control panel is provided below the oven door.

This type of microwave oven has a heating chamber provided in the box-shaped cabinet, an oven door pivotably provided on the front side of the heating chamber, a turntable for supporting foodstuff provided in heat chamber, which is rotated by an electric motor disposed below the heating chamber, and a control panel, as described above, now ar- ranged below the oven door. The control panel extends vertically, and electric components including a printed circuit board connected with the switches and the like on the control panel are located at a portion of the cabinet below the heating chamber and on the rear side of the control panel.

With the construction of the newly developed microwave oven, the lateral space occupied by the oven can be reduced in comparison with the afore-mentioned laterally elongated construction, without affecting the performances.

However, the electric components are inevitably provided within the cabinet of the microwave oven below the electric motor driving the turntable. Since most of the foodstuff placed on the turntable to be cooked contains a liquid substance, such substance tends to be spilled out of the turntable onto the bottom plate of the heat chamber, and then through a penetrating hole of a rotating shaft for the turntable to the electric motor while the foodstuf is heated in the heating chamber. Accordingly, the above described arrangement having the printed circuit board and the like below the electric motor is not desirous because of the tendency of spoiling the electrical insulation of the circuit board and the like by the liquid substance spilled out of the turntable.Furthermore, the temperature of the cabinet portion underside of the heating chamber ordinarily rises up to 70"C or more due to heat transmitted from the heating chamber. Exposure to such a temperature tends to deteriorate the circuit board and other electric parts or elements.

According to the invention there is provided a microwave oven as set out in Claim 1 of the claims of this specification.

Examples of the prior art and of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a vertical sectional view of a conventional microwave oven having a control panel below the oven door; Figure 2 is a perspective view of a microwave oven according to the present invention wherein a control panel provided below the oven door is inclined to project forwardly downwardly; Figure 3 is a vertical sectional view of the microwave oven shown in Fig. 2; Figure 4 is a vertical sectional view showing one part of the microwave oven shown in Fig.

2 constituting one embodiment according to the present invention; Figure 5 is an exploded perspective view showing a portion surrounded by a dotted line in Fig. 4; Figure 6 is a cross-sectional view showing the portion of Fig. 5 after assembly; Figure 7 is a cross-sectional view showing a duct provided on a base plate of the control panel; Figures 8-13 are diagrams showing various modifications of the duct shown in Fig. 7; and Figure 14 is a perspective view, in a disassembled state, of one side sash to be attached to the cabinet of the microwave oven.

DESCRIPTION OF THE PREFERRED EMBODI MENT For better understanding of the present invention, a conventional example of the microwave oven and difficulties accompanying therewith will be firstly described with reference to Fig. 1.

In the conventional microwave oven shown in Fig. 1, which has been recently developed and now in practical use, a heating chamber 2 and a control panel 3 are vertically arranged in a cabinet 1 of the microwave oven so that a vertically elongated construction is obtained.

A waveguide 4 has a radiation opening at one end through an upper wall of the heating chamber 2 and the other end coupled with a microwave oscillator 5 such as a magnetron also provided in the cabinet 1. Electric heaters 6 and 7 of an ordinary type are provided at upper and lower portions in the heating chamber 2. A turntable 9 for supporting a foodstuff A is further disposed in the heating chamber 2 at a position slightly upward from the lower electric heater 7 and is rotated by an electric motor 8 located below the heating chamber 2. The heating chamber 2 has an access opening, and a door 2a is secured pivotably to one side of the opening. Downwardly from the door 2a, is provided a control panel 3 which extends in a vertical plane substantially aligning with the surface of the door 2a.

Various switches and indicators are provided on the control panel 3. Electric components, such as, a printed circuit board P and electric parts 3a, connected to switches and indicators on the control panel board 3 are arranged below the heating chamber 2 of the cabinet 1.

In the above described conventional microwave oven, the printed circuit board P and the electric parts 3a are inevitably arranged in an area directly below the electric motor 8 having a driving shaft extending to the turntable 9 through a hole 2b formed through the bottom plate of the heating chamber 2. Since the foodstuff placed and cooked on the turntable 9 mostly contains a large quantity of liquid substance, a part of the liquid substance spilled onto the bottom plate tends to leak through the hole 2b of the bottom plate downwardly to the electric motor 8, and then to the printed circuit board P and the electric parts to deteriorate the same.Furthermore, since the electric components are placed substantially below the electric motor 8, they tend to be exposed to heat transmitted from the heating chamber, and microwave energy leaked out of the same, thus entailing problems on the electrical insulation and the durability and else of the microwave oven.

According to the present invention the above described difficulties of the conventional microwave ovens can be substantially eliminated. A preferred embodiment of the present invention will now be described with reference to Figs. 2 and 3.

In a cabinet 10 of a microwave oven of this invention, is provided a heating chamber 11 having an access opening on the front side.

One end of a waveguide 1 3a opens to the heating chamber 11 through the upper wall of the heating chamber 11 and the other end of the waveguide 1 3a is coupled with a microwave oscillator such as a magnetron 1 3. A pair of electric heaters 1 4a and 1 4b are disposed in upper and lower portions of the heating chamber 11, respectively. In the bottom wall of the heating chamber 11 is provided a through hole 15, through which a driving shaft 1 7 of an electric motor 1 6 located in a chamber 1 2 defined underside of the bottom wall extends upwardly into the heating chamber 11. In the heating chamber 11, the driving shaft 1 7 is detachably coupled with the lower side of a turntable 18, on which a foodstuff A to be cooked is placed.

An oven door 1 9 is pivotably mounted on the front wall of the cabinet 10 so as to horizontally open or close the opening of the heating chamber 2. On the front side of the cabinet 10 and below the oven door 19, is provided a control panel 20. The control panel 20 has an upper edge projecting forwardly from the cabinet by a distance equal to the thickness of the oven door 1 9 and a lower edge further projecting forwardly in excess of the upper edge so that the control panel is tapered forwardly downwardly. An indicator 21 and control switches 22 inclusive of a power switch, a cooking start switch and a timer switch are provided on the control panel 20.On the rear side of the control panel 20, is provided electric components such as a printed circuit board 23 and the like which are secured to the bottom plate of the chamber 1 2 by means of fixing members 24 in such a manner that most part of the circuit board is received in tapered space defined by the control panel 20 and the lower portion of the cabinet 10. As a result, a comparatively large distance can be provided between the circuit board 23 and the position immediately below the electric motor 1 6. On the upper surface of the printed circuit board 23 are mounted various electric parts of elements 25 connected to the indicator 21 and the control switches 22 on the control panel 20.Although in Fig. 3, some part of the printed circuit board 23 and electric parts or elements 25 are arranged within the chamber 12, it may otherwise be so arranged that the printed circuit board 23 and the electrical parts or elements 25 are completely encased in the tapered space on the rear side of the control panel 20.

A high volage transformer 26 and other electric devices such as condensers and a blower motor (not shown) are disposed in a rear part of the chamber 1 2 and electrically connected with the printed circuit board 23, magnetron 12, and the electric heaters 1 4a and 14b. A plurality of ventilation holes 27 are perforated through the bottom wall of the cabinet 10.

In the operation of the microwave oven of the present invention, a foodstuff A to be cooked is placed on the turntable 18, the oven door 1 9 is closed, and the control switches 22 are manipulated as desired for instructing the type of heating, heating time, heat intensity and the like. Thus, the turntable 1 8 is rotated, and either or both of the magnetron 1 2 and the electric heaters 1 4a and 1 4b are operated as instructed to cook the foodstuff A.

At this time, if liquid substance of the foodstuff (water or else) is spilled in the heating chamber 11, it tends to leak out of the heating chamber 11 through the hole 1 5 along the driving shaft 1 7 of the electric motor 16, into the chamber 1 2 underside of the heating chamber 11. In this case, however, since the printed circuit board 23 together with the electric parts and elements, and also the transformer 26 and like devices are all arranged at positions spaced apart from the position directly below the electric motor 16, the water leaked into the chamber 1 2 underside of the heating chamber 11 is delivered outside through the ventilation holes 27 provided on the bottom wall of the cabinet 10 without deteriorating the electric components.

Furthermore, in case where energy leaks into the microwave chamber 1 2 through the hole 15, it does not cause any harmful effect on the electric components.

When the temperature of the heating chamber 11 rises up under operation of the magnetron 1 3 and/or the electric heaters 1 4a and 14b, it is difficult for hot air in the heating chamber 11 to come down to the chamber 1 2 because cool air is always supplied through the ventilation holes 27 of the bottom wall.

Further, the control panel 20 in addition to the cabinet 10 functions as means for dissipating heat transmitted from the heating chamber 11. Therefore, the printed circuit board 23 and other electric parts or elements 25 are not suffered from the high temperature and no harmful effects are thereby presented.

According to the present invention, since a control panel 20 provided below the pivotable door 1 9 of the heating chamber 11 is inclined such that the lower edge thereof projects forwardly in excess of the upper edge, and at least a part of electrical components such as the printed circuit board 23 and the like are arranged in space formed on the rear side of the inclined control panel 20, electrical components can be protected from harmful effects of liquid substance of the foodstuff A and microwave energy leaked out of the heating chamber, and the durability and reliability of the microwave oven can be substantially improved. Furthermore, by the provision of the inclined control panel 20, the operability of the microwave oven can be much improved, and the space in the kitchen required for the microwave oven can be thereby effectively utilized.

Fig. 4 illustrtes a detailed construction of the tapered control panel 20 and a base plate 35 which is disposed between the lower end of the front wall and the bottom wall of the cabinet behind the control panel 20. An angular frame member 34 having a horizontally extending web 34a is provided integrally with the oven cabinet 10 for supporting the bottom plate of the heating chamber 11. Furthermore, the bottom wall 28 of the chamber 1 2 below the heating chamber 11 has a forward portion 28a rising upwardly. The base plate 35 having an opening 35d at an intermediate portion thereof has a lower portion 35a and an upper portion 35b provided on the lower side and the upper side of the opening 35d, respectively.The upper portion 35b is bent at its upper end horizontally rearwardly, and is secured to the horizontally extending lower side 34a of the frame member 34, for instance, by welding. Members 36 and 37 such as angle irons are further provided such that the member 37 is secured directly to the upper portion 35b of the base plate 35 by screws 38, while the member 36 is secured to the lower portion 35a of the base plate 35 by screws 38 (see Fig. 5) with the rising-up portion 28a of the bottom wall 28 interposed there-between.

The tapered control panel 20 comprises a frame member 40 having a wide window 40a opening forwardly, and a panel plate 45 bentformed into a box-shape and secured to the rear side of the frame member 40 by screws 46. The hereinbefore described indicator 21 and control switches or key board 22 are mounted on the panel plate 45 together with filters 42, fluorescent lamps 47 and a printed circuit board 48 by means of screws 49. A flat member 50 secured to a lower portion of the panel plate 45 by screws extends horizontally rearwardly, and supports another printed circuit board P in a spaced apart relation from the flat member 50.

Figs. 5 and 6 illustrate the construction of a part A surrounded by a dotted line in Fig. 4 in more detail.

As best illustrated in Fig. 5, the bottom wall 28 of the cabinet 10 has the afore-mentioned rising-up portion 28a. Although it is not restricted to such an arrangement, a pair of horizontally elongated holes 52 are provided in the rising-up portion 28a of the bottom plate 28 at positions equally spaced apart from its centre. Laterally inwardly from the elongated holes 52, two pairs of through holes 53 are further provided in the rising-up portion 28a at positions equally spaced apart from the center.

Corresponding to these holes 52 and 53, a pair of through holes 55, a pair of vertically elongated holes 54, and a pair of screw threaded holes 56 are formed in the lower portions 35a of the base plate 35, while the angular member 36 is provided with two pairs of projection 36c and one pair of through holes 36d in the vertically disposed web 36b.

Thus when the angle members 36 and 37 are secured to the lower portions 35a and the upper portion 35b of the base plate 35, respectively, the angle member 36 is firstly brought into abutment with the rising-up portion 28a of the bottom wall 28 of the cabinet 10 such that a pair within the two pairs of the projections 36c are inserted through the horizontally elongated holes 52 provided in the rising-up portion 28a, while another pair within the two pairs of the projections 36c are passed through the corresponding pair of the through holes 53 of the rising-up portion 28a.

Then the rearward ends of the two pairs of the projections 36c are passed through the one pair of through holes 55 and the pair of vertically elongated holes 54 formed in the lower portion 35a of the base plate 35, so that the angle member 36, the rising-up portion 28a of the bottom plate 28 and the lower portion 35a of the base plate 35 are brought into a state substantially aligning with each other with respect to horizontal and vertical directions. In this state, the screws 38 are driven through the through holes 36d of the angle member 36, through holes 53 of the rising-up portion 28a, into the screw-threaded holes 56 provided in the lower portion 35a of the base plate 35, comparatively easily without requiring jigs and the like. The frame member 40 of the tapered control panel 20 is then secured to the angle members 36 and 37 by means of the screws 41 as shown partly in Fig. 6.

Since the horizontally elongated holes 52 and the vertically elongated holes 54 are provided in the rising-up portion 28a and the lower portion 35a for receiving the projections 36c projecting from the angle member 36, the assembling work in this emboidment is much simplified.

Figs. 7 through 1 3 illustrate still another embodiment of the present invention wherein the upper edge of the opening 35d provided through the base plate 35 is utilized for protecting the electric members such as the printed circuit board P and the like from a liquid substance or else tending to be spilled out of the heating chamber 11 forwardly through a gap betwen the oven door 1 9 and the cabinet 10 and a joint portion between the angle member 37, the upper portion of the frame member 40 and the upper portion 35b of the base plate 35 joined together through screws 38 and 41 onto the electric members.

The opening 35d of the base plate 35 is defined by a circumferential edge 60, the upper part of which is formed into a crosssectional configuration of a triangular duct shape as best illustrated in Fig. 7.

The opening 35d and hence the circumferential edge 60 may be formed into a rectangular configuration as shown in Fig. 8. Otherwise, an upper portion 60a of the circumferential edge 60 may be tapered downwardly from an intermediate part thereof as shown in Fig. 9 or from one end toward other end as shown in Fig. 10. Alternatively, the upper portion 60a of the circumferential edge 60 may be tapered downwardly from an end thereof as shown in Fig. 10 and the angle member 37 may be formed into a tapered construction as shown in Fig. 11, such that the lower edge of the angle member 37 extends in parallel with the upper edge 60 of the opening 35d. Furthermore, as shown in Figs. 1 2 and 13, the angle member 37 may be formed with a lower edge 37c which extends obliquely into the inclined upper edge 60 of the opening so as to form a closed duct 60.

With these constructions, any liquid substance tending to be spilled out of the heating chamber 11 through the gap between the front door 1 9 and the mating part of the cabinet 10, and then through the joint portion of the frame member 40 of the control panel 20 and the cabinet 10 can be guided out of the electric members, so that any accidental fault of the electric members caused by the liquid substance can be prevented.

In Fig. 14, there is illustrated still another embodiment of this invention, wherein a pair of side sashes 80 provided on both sides of a forward part of the cabinet 10 are formed into a construction secured to the mating parts of the cabinet 10 firmly without utilizing screws, so the outside appearance of the microwave oven is further improved, and the assembling and the inspection of the oven are more facilitated.

According to this embodiment a pair of bent-formed projections 66 each having a vertically disposed forward edge are provided on both sides of the frame member 40 of the control panel 20. On the other hand, each of the side sashes 80 has a portion 80a tapered forwardly downwardly and a cut-out portion 68 engageable with the projection 66 is formed on the internal side of the tapered portion 80a of the side sash 80 facing the frame member 40 of the control panel 20. On an upper part of each side sash 80 is provided another cut-out portion 69 which is engageable with a projection 70 projecting outwardly from an upper sash 1 Ob integral with the cabinet 10.

At the time of assembling the microwave oven, the side sashes 80 are combined with the frame member 40 of the control panel 20 and also with the upper sash 1 Ob with the projections 66 and 70 of the frame member 40 and the upper sash 1 0b engaging the cutout portions 68 and 69, respectively, so that the side sashes 80 are secured firmly to both sides of the microwave oven without utilizing any screws.

Claims

1. A microwave oven of the type comprising an oven cabinet having a front wall, a rear wall, side walls, a top wall, and a bottom wall, the front wall including an access opening for a foodstuff to be cooked while the bottom wall including a plurality of ventilation holes, a heating chamber formed in said oven cabinet and supplied with microwave energy, an oven door pivotably mounted on the front wall of said oven cabinet, electric components disposed in said cabinet for electrically controlling operation of the microwave oven, and a control panel board disposed between the lower end of the front wall of said cabinet and the bottom wall thereof and for arranging an indicator and control switches connected to said electric components, characterized in that said microwave oven further comprises a base plate vertically arranged between the lower end of said front wall and said bottom wall of said cabinet behind said control panel board, said base plate being provided with an opening, and that said control panel board inclines downwardly outwardly from the lower end of the front wall of the cabinet to the bottom wall thereof so that said control panel and said cabinet define space below said heating chamber for arranging and for protecting at least a part of said electric components from liquid substance of the foodstuff and dissipate heat transmitted from said heating chamber.

2. A microwave oven as set forth in claim 1 wherein said base plate is secured, at its upper portion, to said cabinet and also to a first angle member, while it is secured, at its lower portion, to a forward rising-up edge portion of said bottom wall through a second angle member, said control panel being detachably secured to said first and second angle members, a pair of horizontally elongated holes are provided through said rising-up edge portion, while a pair of vertically elongated holes are provided through said lower portion of said base plate, projections insertable into said horizontally elongated holes and said vertically elongated holes are further provided to project from said second angle member for facilitating positioning of said lower portion of said base plate relative to said second angle member and said rising-up edge portion of said bottom wall when these are secured together.

3. A microwave oven as set forth in claim 1 wherein a duct-like portion is further formed along an upper part of peripheral edge of said opening provided through said base plate.

4. A microwave oven as set forth in claim 3 wherein said duct-like portion formed along the upper part of said peripheral edge tapers from an intermediate portion thereof downwardly towards lateral ends of the upper part of the peripheral edge of said opening.

5. A microwave oven as set forth in claim 3 wherein said duct-like portion tapers downwardly from an end to the other end of upper part of the peripheral edge of said opening.

6. A microwave oven as set forth in any one of claims 3-5 wherein a lower end of said first angle member secured to an upper portion of said base plate is extended into said duct-like portion formed along the upper edge of said opening to cover the same.

7. A microwave oven as set forth in any one of claims 3-6 wherein the lower end of said first angle member is extended substantially in parallel with an inclined surface of said duct-like portion.

8. A microwave oven as set forth in claim 1 wherein said side walls of said oven cabinet include side sashes detachably secured to remaining parts of said side walls, each of said side sashes being provided with upper and lower cut-out portions, said upper cut-out portion being engaged with a projection of an upper sash formed integrally with said upper wall of the cabinet and said lower cut-out portion being engaged with an engaging piece provided at a side of a frame of said control panel board.

9. A microwave oven substantially as herein described with reference to and as illustrated in Figs. 2 to 7 alone or as modified by any one of Figs. 8 to 14 of the accompanying drawings.