Hot-air circulation unit and a shaking blade of a baking apparatus

The baking apparatus includes a surrounding wall that defines a heating chamber, and a kneading case provided centrally in the chamber. The surrounding wall has an upper opening and a lower opening which are formed through the surrounding wall. A guide fin unit is installed on the surrounding wall near the lower opening so as to guide air to enter into the chamber via the lower opening to flow upward along a passage defined between the surrounding wall and the kneading case. The kneading case is provided with a shaking blade that has a vertical rotating shaft adapted to be fastened to the motor shaft of a driving motor, a horizontal plate projecting radially from the rotating shaft, and a trapezoidal sheet fixed on and inclined relative to the plate. The trapezoidal sheet has an inclined side adjacent to but spaced apart from the rotating shaft of the plate in such a manner that, during a kneading operation, the sheet permits sliding movement of dough between the rotating shaft and the inclined side of the trapezoidal sheet.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to an automatic baking apparatus, more particularly 
to a hot-air circulation unit and a shaking blade of the baking apparatus. 
2. Description of the Related Art 
According to U.S. Pat. No. 4,903,587, an automatic baking apparatus 
includes a surrounding wall that defines a heating chamber therein, a 
kneading case mounted centrally in the heating chamber, a hot-air 
circulation unit for supplying hot air into the heating chamber, a shaking 
blade mounted rotatably within the kneading case and rotatable about a 
vertical axis, a motor for driving the shaking blade, and a microcomputer 
having means for controlling operation time of the motor and the hot-air 
circulation unit to vary duration of kneading, fermentation, baking and 
cooling steps. The microcomputer is effective to complete baking process 
with uniform product quality within a constant length of time. 
Some of the drawbacks resulting from the use of the aforementioned baking 
apparatus are as follows: 
(I) The hot-air circulation unit includes a lower heater installed below 
the kneading case at one side of the heating chamber. During circulation 
of hot air within the heating chamber, the flow speed of hot air decreases 
upon reaching a corner of the heating chamber located under the kneading 
case opposite the lower heater. This slowdown retards the succeeding hot 
air so as to lower the baking ability of dough in the kneading case. 
(II) In the aforementioned baking apparatus, the shaking blade is shaped as 
an elongated vertical plate with uniform width so that the blade has a 
large kneading face to strike the dough. A high-power motor is thus 
required to drive the blade in order to knead the dough. 
SUMMARY OF THE INVENTION 
The main object of the present invention is to provide an automatic baking 
apparatus which has a highly efficient flow rate of hot air within the 
heating chamber and which is formed with a blade that can be driven by a 
small-power motor. 
According to the present invention, an upper opening and a lower opening 
are formed through a surrounding wall which defines a heating chamber. A 
guide fin unit is installed on the surrounding wall near the lower opening 
so as to guide air to enter into the heating chamber via the lower opening 
to flow upward along a passage defined between the surrounding wall and a 
kneading case which is disposed centrally within the heating chamber and 
in which dough is kneaded, fermented and baked into bread. The kneading 
case is provided with a shaking blade having a vertical rotating shaft 
that is adapted to be fastened to the motor shaft of a driving motor, a 
horizontal plate that projects radially from the rotating shaft, and a 
trapezoidal sheet that is fixed on and that is inclined relative to the 
plate. The trapezoidal sheet has an inclined side adjacent to but spaced 
apart from the rotating shaft in such a manner that, during a kneading 
operation, the sheet permits sliding movement of dough between the 
rotating shaft and the inclined side of the trapezoidal sheet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIGS. 1 and 2, an automatic baking apparatus of the present 
invention includes a casing 9 constituted by a lower half 91 and an upper 
half 90, a surrounding wall 34 that defines a heating chamber 3 therein, a 
kneading case 4 mounted centrally in the heating chamber 3, a hot-air 
circulation unit for supplying hot air into the heating chamber 3, a 
shaking blade 43 mounted to a rotatable shaft 42 of the kneading case 4, a 
motor 60 for driving the shaking blade 43, and a microcomputer 8 having 
means for controlling operation time of the motor 60 and the hot-air 
circulation unit to vary duration of kneading, fermentation, baking and 
cooling steps. The microcomputer 8 is effective to complete baking process 
with uniform product quality within a constant length of time similar to 
that of the prior art. 
The surrounding wall 34 is fixed on an upper surface of an inverted 
U-shaped base 2 which, in turn, is secured to a bottom of the lower half 
91 and which defines a space 20 therein. The surrounding wall 34 has a 
circular opening unit formed through the lower end portion thereof and 
defined by an inner wall 31, three spaced axially extending engaging keys 
310 formed on the inner wall 31, and a rotatable shaft 32 extending 
axially into the heating chamber 3. An actuator 33 is provided with two 
engaging tabs 330 and is fastened to the upper end of the rotatable shaft 
32. The kneading case 4 has a tubular insert 41 integrally formed with a 
bottom portion thereof, the rotatable shaft 42 mounted rotatably on the 
bottom portion thereof in such a manner that a top end 420 of the shaft 42 
extends into the kneading case 4 while a lower end of the shaft 42 extends 
into the insert 41. The tubular insert 41 is inserted into the opening 
unit of the surrounding wall 34 so that the keys 310 engage the engaging 
notches 410 of the kneading case 4, while the engaging tabs 330 of the 
actuator 33 abut against the flat surfaces 421 of the central shaft 42. A 
heating element 5 is provided in the chamber 30. An opposed pair of 
positioning units 50 abut against the kneading case 4 so as to prevent 
shaking of the latter during a kneading operation. 
The surrounding wall 34 further has an upper opening 35 and a lower opening 
36 which are formed through the surrounding wall 34, and a fin unit 37 
installed on the surrounding wall 34 near the lower opening 36 so as to 
guide air to enter into the chamber 3 via the lower opening 36 to flow 
upward along a passage defined between the surrounding wall 34 and the 
kneading case 4. The upper opening 35 is constituted by a plurality of 
vertical slots, while the lower opening 36 is constituted by a plurality 
of horizontal slots. The guide fin unit 37 includes a plurality of 
L-shaped plates. 
The hot-air circulation unit 7 includes an elongated tubular fan casing 71 
(see FIG. 2) mounted on an external surface of the surrounding wall 34 of 
the chamber 3 in communication with the upper and lower openings 35, 36 
thereof, an air inlet 701 formed under the base 2 and in communication 
with the fan casing 71, an electrically operated fan unit 70 disposed at a 
position lower than the lower opening 36 and in communication with the fan 
casing 71. 
Referring to FIGS. 3 and 4, a driven wheel 62 is disposed below the base 2 
and has an axle extending into the lower end portion of the heating 
chamber 3 to connect with the rotatable shaft 32. The motor 60 is mounted 
on the upper surface of the base 2 outside of the heating chamber 3 and 
has a driving axle 601 which extends into the space 20 of the base 2 to 
connect the driven wheel 62 by means of an endless chain 61. Thus, when 
the motor 60 is actuated, rotation of the motor 60 is transmitted to the 
rotatable shaft 42 of the kneading case 4 via the driven wheel 62. 
Referring to FIG. 5, the shaking blade 43 has a vertical rotating shaft 431 
which is shaped in the form of a tube that defines a pivot hole 430 and 
which is sleeved securely on the top end 420 (see FIG. 2) of the rotatable 
shaft 42, a horizontal plate 432 projecting radially from the rotating 
shaft 431, and a trapezoidal sheet 433 that is fixed on and that is 
inclined relative to the plate 432. The sheet 433 has an inclined side 436 
adjacent to but spaced apart from the rotating shaft 431 in such a manner 
that, during a kneading operation, dough can slide between the rotating 
shaft 431 and the inclined side 436 of the trapezoidal sheet 433. 
From the above explanation, it can be appreciated that the baking apparatus 
of this invention has better hot air circulation so as to provide more 
effective kneading, fermentation and baking operations. Due to the unique 
structure of the shaking blade 43, it is not necessary for the motor 60 to 
generate so much torque, thus prolonging the life service of the motor 60. 
With the present invention thus explained, it is obvious to those skilled 
in the art that various modifications and variations can be made without 
departing from the scope and spirit thereof. It is therefore intended that 
the invention be limited only as in the appended claims.