GB2329814A

GB2329814A - Microwave oven with tray and mode stirrer driven by a single motor

Info

Publication number: GB2329814A
Application number: GB9804038A
Authority: GB
Inventors: Sung-Ho Lee; Soon-Whan Myung; Jung-Eui Hoh
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 1997-09-29
Filing date: 1998-02-25
Publication date: 1999-03-31
Also published as: GB9804038D0; KR19990030202A; JPH11111447A; CN1213059A

Abstract

A microwave oven has a mode stirrer 90 and a turntable 87 arranged at the base of the oven and driven by the same motor 168. The output of the motor 168 is transmitted to coaxial drive shafts 182a and 186a by a first geartrain 154 and a second gear train 142 respectively, drive shaft 182a turning the mode stirrer, and shaft 186a controlling the turntable. The turntable and stirrer may be rotated at different speeds and in opposite directions.

Description

Microwave Oven Having A Stirrer And A Tray That Are Driven By A Single Motor Description The present invention relates to a microwave oven.

Referring to Figures 1 to 3, a known microwave oven comprises a cabinet 1 having a magnetron (not shown) therein, a cooking chamber 3 in the cabinet 1, a tray 37 in the cooking chamber 3 and on which the food is placed, and a door 5 for opening/closing the cooking chamber 3. Microwaves generated by the magnetron are directed into the cooking chamber 3, and food placed on the tray 37 is cooked by the microwaves.

The tray 37 is supported by a plurality of rollers 21 so that it can rotate. The rollers 21 are mounted by a supporting ring 22.

A motor is installed under the bottom 4 of the cooking chamber 3. The drive shaft 11 of the motor 10 passes through the bottom 4 of the cooking chamber 3, and a coupler 13 is coupled to an upper portion of the rotational shaft 11.

The coupler 13 is formed with a plurality of protrusions 36, protruding radially. The protrusions 36 engage protrusions 39 formed in the underside of the tray 37. The coupler 13 and the tray 37 are assembled to each other by the engagement of the coupler protrusions 36 and the tray protrusions 39 so that they are fixed relative each other.

The tray 37 is rotated by the motor while food is being cooked. Thus, the concentration of the microwaves on a specific portion of the food is prevented, and the food is uniformly cooked.

The microwave oven is equipped with a stirrer (not shown) for dispersing microwaves entering the cooking chamber 3. The stirrer is manufactured from a material that reflects microwaves and has a plurality of blades. Also, the stirrer is generally installed at the top of the cooking chamber 3 rotates during the operation of the microwave oven. The microwaves generated from the magnetron are guided into the cooking chamber 3 by a waveguide, and the microwaves are dispersed by the stirrer. Accordingly, the dispersed microwaves irradiate the food in a uniform manner, thus the food is cooked uniformly.

Since the stirrer is installed on the upper part of the cooking chamber 3, food in the lower part of the cooking chamber 3 may still be unevenly irradiated.

JP-A-92-12493 discloses a microwave oven that overcomes this problem by providing a stirrer under the food tray. However, its construction is undersirable complex. In particular, since the motor for driving the tray is installed at the upper side of the cooking chamber, a plurality of bars for supporting the tray are additionally required in order to connect the tray with the motor, and the area of the tray available for food is limited by the supporting bars.

According to the present invention, there is provided a microwave oven comprising a cooking chamber, a rotatable tray located at the bottom of the cooking chamber, a stirrer located under the tray, a motor and transmission means, wherein the transmission means is configured for transmitting drive from the motor to both the tray and the stirrer.

Preferably, the drive means includes a stirrer drive shaft and a tray drive shaft, and the tray drive shaft extends coaxially through the stirrer drive shaft.

Preferably, the stirrer is rotated at a higher speed than the tray.

A depression is preferably included in the floor of the cooking chamber and the stirrer is located in the depression. More preferably, the stirrer is covered by a microwave transparent cover extending across the depression.

Embodiments of the present invention will now be described, by way of example, with reference to Figures 4A to 7 of the accompanying drawings, in which: Figure 1 is a perspective view of a known microwave oven; Figure 2 is a partial sectional view of the oven of Figure 1; Figure 3 is a exploded perspective view of the elements of Figure 2; Figure 4A is a partial side sectional view of a microwave oven according to the present invention; Figure 4B is a partial enlarged view of Figure 4A; Figure 5 is a partial exploded perspective view of Figure 4A; Figure 6 is a perspective view of a stirrer driven by a the motor assembly shown in Figure 5; and Figure 7 is a perspective view of the motor assembly according to another embodiment of the present invention.

Referring to Figure 4A, a tray 87 is installed at the bottom 54 of a cooking chamber, and a stirrer 90 is installed under the tray 87. A depression 56 is formed in the floor 54 of the cooking chamber, and the stirrer 90 is accommodated in the depression 56.

The tray 87 is supported by a plurality of rollers 71 so that is can be rotated. The rollers 71 are mounted to a supporting ring 72. A pair of guide ribs 82 for guiding the rollers 71 are formed on the underside of the tray 87.

A motor assembly 100 for rotating the tray 87 and the stirrer 90 is installed under the floor 54 of the cooking chamber. The motor assembly 100 is comprises, as shown in Figure 5, a motor 168, a first gear part 144, a second gear part 154, a transmission gear part 142 for transmitting the drive from the motor 168 to the first and the second gear parts 144, 150, and a pair of rotational shafts 186a, 186b arranged to be rotated by the first and the second gear parts 144, 154.

The motor 168 has a motor casing 152, a conneaor 162 at a side of the motor casing 152, a stator 164 accommodated in the motor casing 152, and a rotor 166. The connector 162 is connected to an external power source, and conveys the electrical power required to drive the motor 168. When the motor 168 is supplied with the electrical power, the rotor 166 rotates. A driving gear 172 for driving the transmission gear part 142 is installed at the upper part of the rotational shaft 166a of the rotor 166.

A base plate 170 having a central hole is located above the motor 168. The transmission gear part 142, the first and the second gear part 142, 152, and the rotational shafts 182a, 186a are mounted to the base plate 170.

The transmission gear part 142 consists of a lower gear 142a having a large diameter, a middle gear 142b having a small diameter, and a upper gear 142c having a diameter of the diameters between those of the lower gear 142a and the middle gear 142b. The lower gear 142a is tooth-engaged with the driving gear 172 of the rotor 166, and the upper gear 142c and the middle gear 142b are tooth-engaged with the first gear part 144 and the second gear part 154 respectively.

The first gear part 144 consists of a large gear and a small gear, and the large gear thereof engages with the upper gear 142c of the transmission gear 142. The rotation of the transmission gear 142 is transmitted by the first gear part 144, thereby effecting a rotational speed reduction.

The second gear part 154 consists of first to fourth gears 146, 148, 150, 152. Each of the first to fourth gears 146, 148, 150, 152 comprises a large gear with a large diameter and a small gear with a small diameter. The first to fourth gears 146, 148, 150, 152 are connected to each other by the engagement between the large gear of one gear and the small gear of the next gear. The rotation of the transmission gear part 142 is transmitted through the first to fourth gears 146, 148, 150, 152 of the second gear part 154, thereby effecting a rotational speed reduction.

The rotational shafts 182a, 186a comprise a first rotational shaft 182a and a second rotational shaft 186a. The first rotational shaft 182a and the second rotational shaft 186a are coaxially disposed. The first rotational shaft 182a is formed with a first gear 182, and the second rotational shaft 186a is formed with a second gear 186. The first gear 182 is engaged with the small gear of the first gear part 144, and the second gear 186 is engaged with the small gear of the last gear 152 of the second gear part 154.

The first and the second rotational shafts 182a, 186a are rotated in the opposite direction to each other by the first gear part 142 and the second gear part 154.

The upper parts of the rotational shafts 182a, 186a are covered with an upper plate 150 which has an eccentric hole 150a. The rotational shafts 182a, 186a pass through the hole 150a and the floor 54 of the cooking chamber, wherein the first rotational shaft 182a is coupled to the stirrer 90 and the second rotational shaft 186a is coupled to the tray 87.

A coupler 63 is mounted to the upper end of the second rotational shaft 186a. The coupler 63 is formed with a plurality of hooking protrusions 86, and complementary protrusions 89 are formed in the tray 87. The coupler 63 and the tray 87 are assembled to each other so that they are fixed relative to each other.

A cover member 95, for preventing the spillage of food or dirt into the depression 56, is placed over the depression 56. A groove 96 for receiving the rim of the cover member 95 is formed around the top of the depression 56. The cover member 95 is preferably made of a transparent material.

The stirrer 90 comprises, as shown in Figure 6, a plate part 91, and a plurality of blades 94 extended radially from the plate part 91. The microwaves radiating into the cooking chamber are dispersed by the blades 94 when the stirrer 90 rotates. The dispersed microwaves are incident on the lower part of the tray 87, whereby the lower part of the food placed on the tray 87 is uniformly cooked.

The operation of the above-described microwave oven will now be described.

When a user loads food onto the tray 87 and operates the microwave oven, the magnetron generates microwaves and the food is cooked. During cooking, the tray 87 and the stirrer 90 are rotated by the motor 168.

In more detail, when electric power is supplied into the motor 168, the rotor 166 rotates, and thereby the driving gear 172 is rotated. According to the rotation of the driving gear 172, the transmission gear 142 rotates, and the rotation of the transmission gear 142 is transmitted to the first and the second rotational shafts 182a, 186a through the first gear part 144 and the second gear part 154. Consequently, the rotational shafts 182a, 186a are rotated. The rotational shafts 182a and 186a rotate in opposite directions. In other words, if the transmission gear 142 is rotated in a clockwise direction by the rotor 172, the first rotational shaft 182a is rotated in the clockwise direction by the first gear part 144 which is a single gear, and the second rotational shaft 186a is rotated in an anticlockwise direction by the second gear part 154 which consists of an even number of gears.

As the rotational shafts 182a, 186a rotate, the stirrer 90 and the tray 87 rotate. The stirrer 90 and the tray 87 are rotated in the directions opposite to each other.

Therefore, microwaves are uniformly incident on the food loaded on the tray 87 both by the rotation of the tray 87 and by the stirrer 90 rotating under the tray 87. Also, since the stirrer 90 and the tray 87 are driven by a single motor 168, the construction is simplified and the manufacturing costs are reduced.

The cover member 95 prevents the spillage of food or dirt into the stirrer 90 during the cooking operation of the food. Also, if the cover member 95 is made of a transparent material, the user can perceive whether the stirrer 90 is operating normally or not.

A second embodiment of the present invention will now be described.

Referring to Figure 7, the second gear part 154a is comprised of an odd number of gears 146a, 148a, 150a, whereby the rotational directions of the second rotational shaft 186b and the first rotational shaft 182b are the same. However, the rotational velocities of the rotational shafts 182b, 186b are different. The rotational velocities of respective rotational shafts 182b, 186b can be controlled by changing the number of the gears consisting of the first and the second gear parts 144a and 154a and the number of the teeth in respective gears.

It is preferable that, as shown in Figure 7, the first rotational shaft 182b is faster than the second rotational shaft 186b, and thereby the stirrer 90 is faster than the tray 87.

Since the tray 87 is loaded with the food, it is preferred that the tray 87 is rotated slowly, and the stirrer 90 is rotated quickly to enhance the effect of dispersing the microwaves.

As described above, according to the present invention, a microwave oven is provided which can apply microwaves uniformly at the upper part and the lower part of food placed on the tray, and especially, the construction of the microwave oven is simplified and thereby manufacturing costs are lowered since the tray and the stirrer are driven by a single motor.

Claims

Claims 1. A microwave oven comprising a cooking chamber, a rotatable tray located at the bottom of the cooking chamber, a stirrer located under the tray, a motor and transmission means, wherein the transmission means is configured for transmitting drive from the motor to both the tray and the stirrer.
2. An oven according to claim 1, wherein the drive means includes a stirrer drive shaft and a tray drive shaft, the tray drive shaft extending coaxially through the stirrer drive shaft.
3. An oven according to claim 1 or 2, wherein the stirrer is rotated at a higher speed than the tray.
4. An oven according to claim 1, 2 or 3, including a depression in the floor of the cooking chamber, wherein the stirrer is located in the depression.
5. An oven according to claim 4, wherein the stirrer is covered by a microwave transparent cover extending across the depression.
6. A microwave oven comprising: a tray being installed on a bottom of a cooking chamber, said tray on which food to be cooked is placed; a stirrer being installed under said tray, said stirrer for dispersing microwaves being irradiated into said cooking chamber; a motor for rotating said tray and said stirrer simultaneously; a first gear means for transmitting a torque of said motor to said stirrer; a second gear means for transmitting the torque of said motor to said tray; and a pair of rotational shafts being rotated respectively by said first and second gear means, said rotational shafts for rotating said stirrer and said tray respectively.
7. The microwave oven as claimed in claim 1, wherein said rotational shafts are rotated by said first and second gear means at different speeds from each other.
8. The microwave oven as claimed in claim 2, wherein said stirrer is rotated at a higher speed than said tray.
9. The microwave oven as claimed in claim 1, wherein said rotational shafts are rotated by said first and said second gearing means in directions opposite to each other.
10. The microwave oven as claimed in claim 1, wherein said rotational shafts are coaxially disposed.
11. The microwave oven as claimed in claim 1, wherein a depression for accommodating said stirrer is formed on a bottom of said cooking chamber, and a cover member for preventing a spillage of food and dirt into said depression is installed on an upper side of the depression.
12. A microwave oven substantially as hereinbefore described with reference to Figures 4A to 6 of the accompanying drawings.
13. A microwave oven substantially as hereinbefore described with reference to Figures 4A, 4B, 6 and 7 of the accompanying drawings.