GB2173680A

GB2173680A - Microwave ovens

Info

Publication number: GB2173680A
Application number: GB08509466A
Authority: GB
Inventors: Stephen Geoffrey Thaine; Percy George Giles
Original assignee: Microwave Ovens Ltd
Current assignee: Microwave Ovens Ltd
Priority date: 1985-04-12
Filing date: 1985-04-12
Publication date: 1986-10-15
Also published as: GB8509466D0; GB2173680B

Abstract

A microwave oven has a food-receiving cavity (12) with a rear wall (24) behind which is a rear compartment (34) accommodating a fan (36) and an electrical resistance heating element. The rear wall (24) has inlet and outlet apertures (28, 30) by which a recirculating flow of hot air is forced by the fan through the cavity (12). The air entering the cavity (12) is directed towards the centre front of the cavity by a deflector plate (40) which extends vertically beside the inlet aperture (28) and which is attached to the rear wall (24) so as to project into the rear compartment (34). <IMAGE>

Description

SPECIFICATION Microwave Ovens Field of the invention This invention relates to microwave ovens.

Background to the invention The applicants European Patent Specification No.

0099705 discloses a microwave oven having a source of hot air which is forced by a fan through a food-receiving cavity of the oven. It has been found that the direction followed by the hot air as it enters the food-receiving cavity is important, and the present invention concerns the provision of a deflector plate which guides the hot air flow so that the hot air enters the cavity in the required direction.

Summary ofthe invention According to the invention a microwave oven has a food-receiving cavity with a rear wall, a source of microwave power for delivering microwave power to the cavity, a compartment located behind the rear wall and communicating with the cavity through inlet and outlet apertures in the rear wall, a hot air recirculation system comprising an electrical resistance heating element disposed in the compartment and a fan disposed in the compartment, the fan being operative to draw air from the cavity, through the outlet aperture and thence into the compartment, over the electrical resistance heating element and thence back into the cavity through the inlet aperture, and wherein a deflector plate is attached to the rear wall so as to project from the rear wall into the compartment, the deflector plate extending substantially vertically beside the inlet aperture on the side of the latter closer to the fan, the deflector plate extending beside the inlet aperture for the com'plete vertical height of the inlet aperture.

The inlet aperture is preferably constituted by a perforated region which has a height extending over the major part of the height of the cavity, the deflector having a vertical extend corresponding to that of the inlet aperture.

The deflector plate preferably has two angled flanges, one of which is attached to the rear wall and the other of which projects into the compartment, for example projecting about 12 mm into the compartment at an angle of between 50 and 60 , preferably about 55 , to the plane of the perforated region constituting the inlet aperture.

As a result of the presence of the deflector plate, the hot air is guided away from the rear wall before it is forced through the inlet aperture and into the cavity. In consequence, the hot air enters the cavity at an angle which directs the bulk of the air towards the centre/front of the cavity. This prevents the hot air entering the cavity in an oblique direction, which would mean that the hot air would either be reflected from the cavity side wall back toward the air outlet aperture, or would flow directly towards the air outlet aperture where it would be drawn from the cavity by the fan. In either case the hot air flow would not pass adequately to the front and middle of the cavity.

A microwave oven according to the invention will now be described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a front view of the oven with an oven door open to reveal the food-receiving cavity, Figure 2 is a perspective view of the rear of the oven with a back panel removed to show a hot air compartment behind the cavity, and Figure 3 is a fragmentary sectional view of a horizontal plane indicated at Ill-Ill in Figure 1.

The microwave oven shown in the drawings is similar to that disclosed in the applicants European Patent Application No. 0099705, in that the oven has not only a magnetron for delivering microwave power to the oven cavity, but also a hot air recirculation system for forcing hot air through the cavity simultaneously with the application of microwave power.

Referring to Figure 1, the oven has an outer casing 10 enclosing the food receiving cavity 12 which is closable by a hinged door partially shown at 14. The oven has a control panel 16 with touch pads (not shown) for governing operation of the oven. Behind the panel 16 is located a magnetron (not shown) for delivering microwave power to the cavity through a panel 18. A cooling fan (not shown) for the magnet- ron is able to vent the cavity by delivering to the cavity 12 air which enters at an inlet 20 in one of the side walls and leaves at an outlet 22 in the rear wall 24. The base of the cavity has rollers 26 for supporting a rotatable turntable (not shown) for supporting food which is cooked simultaneous exposure to the microwave power and a forced flow of hot air.

The rear wall 24 of the cavity 12 has, in addition to the outlet 22, a vertically elongated perforated region forming an air inlet aperture 28 and a circular perforated region forming an air outlet aperture 30.

Referring to Figure 2, a rear panel 32 is attached to the back of the casing 10, and the panel is shaped so that a compartment 34 is defined between the panel 32 and the rear wall 24. Within the compartment 34 are located a rotatably mounted fan 36 and an electrical resistance heating element 38. The fan 36 is driven by an electrical motor and draws air from the cavity 12 through the outlet aperture 30, delivers the air over the electrical resistance heating element 38 in order to heat the air which is then forced back into the cavity 12 through the inlet aperture 28. This recirculation of air through the cavity 12 and the compartment 34 is best illustrated in Figure 3.

A deflector plate 40 extends vertically beside the aperture 28 on the side of the latter closer to the fan 36. The deflector plate 40 has two angled flanges one of which is attached to the rear wall 24 and the other of which projects into the compartment 34 so as to make an angle of 55" with the perforated region forming the inlet aperture 28. The deflector plate 48 has a vertical extent corresponding precisely to the vertical extent of the inlet aperture 28, and the deflector plate 40 projects into the compartment 34 by about 12 mm.

The deflector plate 40 causes the air approaching the inlet aperture 28 to be guided away from the rear wall 24 so that the air is forced to enter the cavity 12 in a direction such that the bulk of the air is directed towards the centre/front of the cavity 12. Were the air to enter the cavity 12 in a direction more closely parallel with the rear wall 24 it would either be drawn directly out of the air outlet aperture 30, or would first be reflected from the side wall 42 and thence be drawn out of the outlet aperture 30. In either case, the air flow would "short-circuit" the desired flow path through the main space of the oven cavity 12.

The projecting edge of the deflector plate 40 is shown in Figure 2 with a notch 44 to provide clearance for one leg 46 of the electrical resistance heating element 38.

Claims

1. A microwave oven having a food-receiving cavity with a rear wall, a source of microwave power for delivering microwave power to the cavity, a compartment located behind the rear wall and communicating with the cavity through inlet and outlet apertures in the rear wall, a hot air recirculation system comprising an electrical resistance heating element disposed in the compartment and a fan disposed in the compartment, the fan being operative to draw air from the cavity, through the outlet aperture and thence into the compartment, over the electrical resistance heating element and thence back into the cavity through the inlet aperture, and wherein a deflector plate is attached to the rear wall so as to project from the rear wall into the compartment, the deflector plate extending substantially vertically beside the inlet aperture on the side of the latter closer to the fan, the deflector plate extending beside the inlet aperture for the complete vertical height of the inlet aperture.

2. A microwave oven according to claim 1, wherein the inlet aperture is constituted by a perforated region which has a height extending over the major part of the height of the cavity, the deflector having a vertical extent corresponding to that of the inlet aperture.

3. A microwave oven according to claim 1 or 2, wherein the deflector plate has two angled flanges, one of which is attached to the rear wall and the other ofwhich projects into the compartment.

4. A microwave oven according to claim 3, wherein said other flange projects substantially 12mm into the compartment at an angle of between 50 and 60 .

5. A microwave oven according to claim 4, wherein said other flange projects into the compartment at an angle of 55" to the plane of the rear wall.

6. A microwave oven constructed and arranged substantially as herein particularly described with reference to the accompanying drawings.