Hot air circulating cooker

A hot air circulating cooker includes a box-like casing defining a heating chamber. A rear plate of the casing has suction holes at its center portion and upper and lower discharge holes located above and below the suction holes. A cover is fixed to the outer surface of the rear plate to define a storing chamber. A fan is arranged in the storing chamber to face the suction holes. When being rotated in a predetermined direction, the fan draws air in the heating chamber into the storing chamber through the suction holes, flows the drawn air in the predetermined direction, and discharges the air to the heating chamber through the discharge holes. An upper airflow-directing mechanism is provided in the storing chamber so as to guide part of the air flow to those of the upper discharge hole which are located at an upstream side of the air flow in the storing chamber. A lower airflow-directing mechanism is provided in the storing chamber so as to guide part of the air flow to those of the lower discharge holes which are located at an upstream side of the air flow in the storing chamber.

BACKGROUND OF THE INVENTION 
The present invention relates to a hot air circulating cooker for heating 
and cooking food in a heating chamber by supplying hot air to the heating 
chamber using a fan. 
Generally, a hot air circulating cooker has an inner casing defining a 
heating chamber and a disk-like cover attached on the outer surface of the 
rear wall of the inner casing. The cover and the rear wall define a fan 
chamber. A hot air circulating fan and a heater are provided in the fan 
chamber. A plurality of suction holes are cut by punching in the central 
portion of the rear wall. Upper discharge holes are cut by punching in a 
rectangular area of the upper portion of the rear wall, and lower 
discharge holes are cut in a rectangular area of the lower portion of the 
rear wall. Bath rectangular area extend in the horizontal direction. The 
fan opposes the suction holes and is driven by a motor provided outside 
the cover. The heater has an annular shape and is provided around the fan. 
When the fan and heater are operated, the air in the heating chamber is 
drawn into the fan chamber through the suction holes and is heated by the 
heater. The hot air is blown into the heating chamber through the 
discharge holes. As a result, the hot air is circulated in the heating 
chamber to heat and cook food in the heating chamber. 
In the cooker having the above arrangement, the fan is rotated in a one 
predetermined direction. The hot air in the fan chamber also flows in the 
same direction. Thus, the hot air discharged from the discharge holes is 
unpreferably biased in the rotating direction of the fan. For example, 
where the upper discharge holes are concerned, the amount of hot air 
discharged from the holes located at the downstream side of the hot air 
flow is larger than that discharged from the holes located at the 
upstream-side. This imbalance in the hot air discharge amount at different 
portions of the discharge holes causes the food in the heating chamber to 
be nonuniformly cooked. 
In another type of known cooker, a rotating tray is provided in a heating 
chamber and food is cooked while being rotated by the rotating tray. 
According to this cooker, nonuniform cooking of food can be decreased to a 
certain degree. However, in a cooker having a stationary cooking tray, 
e.g., a cooker having two cooking trays in its heating chamber so as to 
cook a large amount of food at once, nonuniform cooking can easily occur 
due to the imbalance in hot air discharge amount. 
SUMMARY OF THE INVENTION 
The present invention has been made in view of the above situation and has 
as its object to provide a hot air circulating cooker which can uniformly 
discharge hot air from its discharge holes, thereby decreasing nonuniform 
heating of food. 
In order to achieve the above object, a cooker according to the present 
invention comprises: a box-like casing having top and bottom plates and a 
plurality of side plates and defining a heating chamber for storing food 
therein, one of the side plates having a plurality of suction holes formed 
in a central portion thereof, a plurality of upper discharge holes formed 
in an area which is located above the suction holes and extends along a 
horizontal direction, and a plurality of lower discharge holes formed in 
an area which is located under the suction holes and extends in the 
horizontal direction; a cover fixed to an outer surface of said one side 
plate, for defining, associated with said one side plate, a storing 
chamber communicating with the suction holes and the upper and lower 
discharge holes; a fan arranged in the storing chamber to oppose the 
suction holes and rotated in a predetermined direction, for drawing air in 
the heating chamber to the storing chamber through the suction holes, 
flowing the air in the predetermined direction in the storing chamber, and 
discharging the air to the heating chamber through the discharge holes; a 
heater arranged in the storing chamber and located to surround the fan, 
for heating air drawn into the heating chamber; drive means for rotating 
the fan; upper airflow-directing means provided in the storing chamber, 
for guiding part of an airflow formed by the fan to those of the upper 
discharge holes which are located at an upstream side of the air flow in 
the storing chamber; and lower airflow-directing means provided in the 
storing chamber, for guiding part of the airflow formed by the fan to 
those of the lower discharge holes which is located at an upstream side of 
the air flow in the storing chamber.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The embodiments of the present invention will be described in detail with 
reference to the accompanying drawings. 
As shown in FIGS. 1 to 3, a cooker has outer casing 10 and inner casing 12 
which is provided in casing 10 and defines heating chamber 14. Casing 12 
is a box having top and bottom plates 12a and 12b and three side plates 
12c to 12e. The front portion of casing 12 is opened to constitute 
inlet/outlet port 16 for allowing food to be placed in and removed from 
heating chamber 14 therethrough. Port 16 is opened/closed by door 18 
attached to casing 10. 
A pair of horizontal support rails 20 are formed on the inner surface of 
each of side walls 12d and 12e. Upper and lower cooking trays 22a and 22b 
are arranged in heating chamber 14 while their side edges are put on rails 
20. Rails 20 are positioned such that the distances between top plate 12a 
of casing 12 and tray 22a, between trays 22a and 22b, and between tray 22b 
and bottom plate 12b are substantially the same. 
A plurality of suction holes 24 are cut by punching in the central portion 
of side plate 12c constituting the rear plate of casing 12 and are 
distributed in a rectangular form. Holes 24 are located between cooking 
trays 22a and 22b. A plurality of upper and lower discharge holes 26 and 
28 are formed in rear plate 12c and located above and below suction holes 
24, respectively. Upper discharge holes 26 are arranged in a rectangular 
area which extends throughout substantially the entire width of plate 12c 
and are located between top plate 12a and upper cooking tray 22a. Lower 
discharge holes 28 are arranged in a rectangular area which extends 
throughout substantially the entire width of plate 12c and are located 
between bottom plate 12b and lower cooking tray 22b. 
Rectangular disk-like cover 30 is fixed to the outer surface of rear plate 
12c. Cover 30 and plate 12c define storing chamber 32. Chamber 32 
communicates with heating chamber 14 through suction holes 24 and 
discharge holes 26 and 28. As is apparent from FIGS. 1 and 3, cover 30 has 
bottom plate 30a opposing rear plate 12c, upper and lower inclined plates 
30b and 30c extending in the horizontal direction, and a pair of side 
plates 30d extending in the vertical direction. Plates 30b and 30c oppose 
upper and lower discharge holes 26 and 28, respectively. In chamber 32, 
fan 34 is arranged so as to face suction holes 24, and substantially 
annular electric heater 36 is provided to surround fan 34. Fan 34 is 
rotated by motor 38, provided outside cover 30, in a predetermined 
direction, i.e., counterclockwise in FIG. 3. 
As indicated by arrows in FIG. 1, when fan 34 is rotated, air in heating 
chamber 14 is drawn from suction holes 24 into storing chamber 32. After 
being heated by heater 36, the air is guided by upper and lower plates 30b 
and 30c and discharged from upper and lower discharge holes 26 and 28 into 
heating chamber 14. 
With the above arrangement, the hot air in storing chamber 32 flows 
counterclockwise to make a whirl. Thus, the hot air to be blown from holes 
26 and 28 is biased to the upstream side of the hot air flow. More 
specifically, as shown in FIG. 2, the amount of hot air discharged from 
some holes 26 in region B located at the downstream side of the hot air 
flow in storing chamber 32 is larger than that discharged from some other 
holes 26 in region A at the upstream side of the hot air flow. Similarly, 
the amount of hot air discharged from some holes 28 in region D located at 
the downstream side of the hot air flow in storing chamber 32 is larger 
than that discharged from some other holes 28 in region C at the upstream 
side. Therefore, in order to prevent the unbalance of the amount in 
discharged hot air, according to this embodiment, upper and lower 
airflow-directing mechanisms 40 and 42 are provided in chamber 32 so as to 
face regions A and C, respectively. 
As shown in FIGS. 3 and 4, upper airflow-directing mechanism 40 has a pair 
of first airflow-directing plates 44 and a pair of second 
airflow-directing plates 46a and 46b. First plates 44 have a triangular 
shape, are fixed to upper plate 30b of cover 30, and extend in the 
vertical direction. Second plates 46a and 46b are perpendicularly fixed to 
bottom plate 30a of cover 30 and located between the outer periphery of 
fan 34 and heater 36. Plates 46a and 46b have a rectangular shape. Plate 
46a is shorter than plate 46b. Plates 46a and 46b are arranged parallel to 
each other and extend from the regions close to the lower ends of first 
airflow-directing plates 44 toward the rotational center of fan 34. 
Similarly, lower airflow-directing mechanism 42 has a pair of first 
airflow-directing plates 48 and a pair of second airflow-directing plates 
50and 50b. First plates 48 and second plates 50a and 50b are 
point-symmetrical to first plates 44 and second plates 46a and 46b, 
respectively, with respect to the rotational center of fan 34. In other 
words, first plates 48 are fixed to lower plate 30c of cover 30 and extend 
in the vertical direction, and second plate 50a and 50b are fixed to 
bottom plate 30a of cover 30 and located between the outer periphery of 
fan 34 and heater 36. 
The sizes of the respective portions of first and second airflow-directing 
mechanisms 40 and 42 are set as follows so as to provide a good 
airflow-directing effect. 
As shown in FIGS. 2 to 4, diameter a of fan 34 is set in a range of about 
1/2 to 1/3 width b of heating chamber 14. In other words, assuming that 
width b is 300 mm, diameter a of fan 34 is 130 mm. In upper 
airflow-directing mechanism 40, distance c between second 
airflow-directing plate 46b and the outer periphery of fan 34 is set to be 
about 1/10 to 1/20 diameter a of fan 34 and is, in this embodiment, 9 mm. 
Distance e between second airflow-directing plate 46a and the outer 
periphery of fan 34 is set to be about 1/5 to 1/10 diameter a of fan 34 
and is, in this embodiment, 19 mm. Distance d between plates 46a and 46b 
is set in a range of about 1/3 to 1/6 diameter a of fan 34 and is, in this 
embodiment, 33 mm. Distance between first airflow-directing plates 44 
corresponds to distance d. 
Distance f between second airflow-directing plates 46a and 46b, and heater 
36 is set in a range of about 1/2 to 1/10 diameter g of heater 36. A 
general heater has diameter g of about 7 mm and hence distance f is set to 
1 mm. Width h of the regions, wherein upper and lower discharge holes 26 
and 28 are formed, is set to 2/3 or more of width b of heating chamber 14 
(h &gt; 200 mm). Holes 26 and 28 are uniformly distributed in the right and 
left portions of heating chamber 14 so that the hot air uniformly reaches 
the entire area of heating chamber 14. 
The airflow-directing plates of lower airflow-directing mechanism 42 have 
sizes similar to those of upper airflow-directing mechanism 40 and a 
description thereof is omitted. 
In FIG. 1, reference numeral 54 denotes a motor. Rotation shaft 54a of 
motor 54 extends into heating chamber 14 through bottom plate 12b of 
casing 12. With cooking trays 22a and 22b not in use, a turntable (not 
shown) is placed in engagement with rotation shaft 54a within heating 
chamber 14 such that it may be rotated by motor 54. The cooker is also 
further provided with a magnetron (not shown) and can be used as a 
microwave oven. 
The operation of the cooker having the above arrangement will be described. 
When a large amount of food is heated and cooked simultaneously, upper and 
lower cooking trays 22a and 22b placing food 52 thereon are set in heating 
chamber 14 through inlet/outlet port 16. After door 18 is closed, an 
operating section (not shown) is operated to energize motor 38 and heater 
36. When fan 34 is rotated counterclockwise by motor 38, the air between 
trays 22a and 22b in chamber 14 is drawn into storing chamber 32 through 
suction holes 24. The sucked air flows to the periphery of fan 34, and 
makes a counter-clockwise whirl around fan 34. At the same time, the air 
is heated by heater 36. 
The hot air abuts against upper and lower plates 30b and 30c of cover 30 
and directed toward rear plate 12c of inner casing 12. Thus, the hot air 
is discharged from discharge holes 26 and 28 into heating chamber 14. The 
hot air from holes 26 is blown into a space between top plate 12a of 
casing 12 and upper cooking tray 22a, and the hot air from holes 28 is 
blown into a space between bottom plate 12b of casing 12 and lower cooking 
tray 22b. 
In the upper region of storing chamber 32, part of the hot air is prevented 
by airflow-directing plates 44, 46a and 46b of upper airflow-directing 
mechanism 40 from flowing along the rotating direction of fan 34 and 
guided to a region opposing upstream-side region A of discharge holes 26. 
The hot air is then directed toward rear plate 12c by upper plate 30b of 
cover 30 and discharged to heating chamber 14 through discharge holes 26 
at upstream-side region A. The remaining hot air is discharged from holes 
26 located at downstream-side region B. 
Similarly, in the lower region of storing chamber 32, part of the hot air 
is prevented by lower airflow-directing mechanism 42 from flowing along 
the rotating direction of fan 34 and discharged to heating chamber 14 
through discharge holes 28 located at upstream-side region C. The 
remaining hot air is discharged from holes 28 located at downstream-side 
region D. As a result, the hot air is not biased in a single direction but 
is uniformly discharged from holes 26 and 28 of the respective regions. 
As described above, according to the hot air circulating cooker having the 
above arrangement, the amount of hot air discharged from discharge holes 
26 and 28 located at upstream-side regions A and C is increased because of 
the straightening function of upper and lower airflow-directing mechanisms 
40 and 42, and becomes equal to that discharged from holes 26 and 28 
located at downstream-side regions B and D. As a result, imbalance in 
amount of discharged hot air between the holes in the upstream- and 
downstream-side regions is eliminated, and hot air can be uniformly 
supplied to the entire portion in the heating chamber. Thus, a hot air 
does not locally blow against part of food in the heating chamber, and 
nonuniform heating and cooking caused by the nonuniform hot air amount can 
be prevented. According to this embodiment, in addition to the first 
airflow-directing plates, each airflow-directing mechanism has the second 
airflow-directing plates that extend to the regions close to the outer 
periphery of fan 34. Therefor, the hot air can be guided to the discharge 
holes located in the upstream-side region immediately after fan rotation 
is started. 
The sizes of the respective portions were examined in an experiment, and 
most effective, uniform supply of hot air was obtained when sizes a to g 
were set in the ranges described above. When the sizes of the respective 
portions are out of the above described ranges, the following problems 
arose. 
For example, when diameter a of fan 34 exceeded 1/2 width b of heating 
chamber 14, the distance between the outer periphery of fan 34 and heater 
36 was decreased, and the straightening effect by upper and lower 
airflow-directing mechanisms 40 and 42 was excessive, resulting in 
nonuniform heating. In accordance with increase of diameter a, the 
discharge amount of hot air was decreased. Conversely, when diameter a was 
set to be less than 1/3 width b, the blow amount by fan 34 was decreased, 
and the supply of hot air to heating chamber 14 was delayed. 
When distance c between the second airflow-directing plate and the outer 
periphery of fan 34 exceeded 1/10 diameter a of fan 34, the straightening 
effect by the airflow-directing mechanism was degraded, and the cooked 
color of the food placed on the left portion of upper cooking tray 22a in 
FIG. 2 was darker. Conversely, when distance c was less than 1/20 diameter 
a, the cooked color of the food placed on the left front portion of tray 
22a was extremely pale. A change in distance e caused effects similar to 
that in distance c described above. 
When distance d between the second airflow-directing plates exceeded 1/3 
diameter a of fan 34, the straightening effect by the airflow-directing 
mechanism was excessive, and nonuniform heating occurred. When distance d 
was less than 1/6 diameter a, the hot air blowing state was the same as in 
the case wherein no airflow-directing mechanism was provided. 
When distance f between the second airflow-directing plate and heater 36 
exceeds 1/2 diameter g of heater 36, hot air leaks from a gap between the 
airflow-directing plates and heater 36, and the blow amount of air 
straightened by the airflow-directing mechanism is decreased. As a result, 
nonuniform heating occurs. When distance f is less than 1/10 diameter g, 
the second airflow-directing plates may unpreferably contact heater 36 by 
vibration during operation of the cooker or impact when the cooker is 
being moved. 
When the sizes of the respective portions are set properly as in the above 
embodiment, the above-mentioned problem can be solved, and hot air can be 
blown into the heating chamber with good balance. 
The present invention is not limited to the above embodiment but various 
changes and modifications may be made within the spirit and scope of the 
invention. 
For example, in the embodiment, each airflow-directing mechanism has a pair 
of second airflow-directing plates. However, the inner one, i.e., the 
smaller one of the second airflow-directing plates can be omitted. Second 
airflow-directing plates 46a and 46b, or 50a and 50b can be arranged in 
the vertical direction as shown in FIG. 5. In this case, the dimensional 
relationship among the width of heating chamber 14, the diameter of fan 
34, the distance between fan 34 and the airflow-directing plates, and the 
distance between the second airflow-directing plates and heater 36; and 
the sizes and mounting positions of the first and second airflow-directing 
plates are set so as to obtain hot air blowing characteristics to 
effectively decrease nonuniform heating. 
As shown in FIGS. 6 and 7, each airflow-directing mechanism can be 
constructed by only first airflow-directing plates. The number of the 
first airflow-directing plates is increased/decreased as needed, and the 
sizes and mounting positions thereof are properly set. However, first 
airflow-directing plate 44 of upper airflow-directing mechanism 40 and 
airflow-directing plate 48 of lower airflow-directing mechanism 42 are 
point-symmetrically arranged with respect to the rotational center of fan 
34, irrespective of the number of the first airflow-directing plates. When 
the number of the airflow-directing plates is increased, the hot air blow 
amount can be finely adjusted. 
In the modification shown in FIG. 8, upper airflow-directing mechanism 40 
has a plurality of first airflow-directing plates fixed to upper plate 30b 
of cover 30. These plates 44 are separated from each other at the same 
intervals along the horizontal direction and extend in the vertical 
direction. The lengths of respective airflow-directing plates 44 are set 
such that a line connecting the lower ends of plates 44 coincides with 
diagonal line a of plate 30b. This increases straightening effect in a 
region at the upstream-side of the hot air flow. Airflow-directing 
mechanism 40 has second airflow-directing plate 46 located in the upper 
region of storing chamber 32. Plate 46 extends substantially horizontally 
from side plate 30d of cover 30, located at the downstream side of the hot 
air flow, to the substantially central portion of storing chamber 32. 
Plate 46 is positioned between fan 34 and heater 36. Similarly, lower 
airflow-directing mechanism 42 has a plurality of first airflow-directing 
plates 48 and second airflow-directing plate 50 and is point-symmetrical 
with mechanism 40 with respect to the rotational center of fan 34. 
In the modification shown in FIGS. 9 and 10, airflow-directing mechanisms 
40 and 42 have a plurality of airflow-directing plates 44 and 48 fixed to 
the inclined plates of cover 30, i.e., upper and lower plates 30b and 30c 
and extending in the vertical direction, respectively. Straightening plate 
44a (48a) horizontally extends from each airflow-directing plate. Each 
plate 44a or 48a is formed by cutting part of the corresponding 
wind-directing plate and bending the cut portion upright, or fixing a 
separate plate on the corresponding airflow-directing plate by spot 
welding or the like. Assuming that the inclined angle of upper plate 30b 
with respect to the horizontal plane is .theta.1, plate 44a is inclined at 
angle .theta.2 (the same as or smaller than angle .theta.1) with respect 
to the horizontal plane. Plate 48a is also inclined at a predetermined 
angle with respect to the horizontal plane. 
In the above modification, the air supplied from fan 34 is straightened by 
airflow-directing plates 44 and 48 and partially directed by straightening 
plates 44a and 48a in a direction different from that of the air directed 
by inclined plates 30b and 30c of cover 30. As a result, the hot air is 
sufficiently dispersed and uniformly discharged in heating chamber 14. 
In FIGS. 5 to 10, the same portions as in the above embodiment are 
indicated by the same reference numerals and a detailed description 
thereof is omitted. 
A plate for fixing the cover defining the storing chamber is not limited to 
the rear plate of the inner casing, but can be another side plate.