U.S. patent number 3,824,365 [Application Number 05/313,188] was granted by the patent office on 1974-07-16 for microwave oven control system.
This patent grant is currently assigned to Litton Systems, Inc.. Invention is credited to William R. Tapper.
United States Patent |
3,824,365 |
Tapper |
July 16, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
MICROWAVE OVEN CONTROL SYSTEM
Abstract
A control circuit for a microwave oven is disclosed which
functions to automatically control the running time of the
microwave generator to enable it to run continuously, during its
cooking cycle, or intermittently, during its defrosting cycle. The
control circuit includes a timer control switch operatively coupled
to a timer motor. The timer control switch functions to control the
current flow from the source of electrical power to the microwave
generator. The circuit also includes a defrost control switch which
functions to cyclically open and close a series current path to the
microwave generator. A bypass circuit is also provided across the
defrost control switch to short-circuit the defrost switch and
provide a bypass current path to the microwave generator. A
"cook-defrost" switch is provided to connect the circuit to the
bypass circuit for the cooking mode, or to disconnect the bypass
circuit to enable the current path to be governed by the defrost
control switch for the defrosting mode. In one embodiment, the
defrost control switch is coupled to a second timer motor which, in
turn, is adapted to be cut into and out of the circuit by the
"cook-defrost" switch. In a second embodiment, the defrost control
switch is coupled to the first timer motor and is continuously
operated thereby.
Inventors: |
Tapper; William R. (New
Brighton, MN) |
Assignee: |
Litton Systems, Inc. (Beverly
Hills, CA)
|
Family
ID: |
23214723 |
Appl.
No.: |
05/313,188 |
Filed: |
December 7, 1972 |
Current U.S.
Class: |
219/703; 219/718;
219/719; 968/815; 200/38FA |
Current CPC
Class: |
H05B
6/688 (20130101); G04F 3/06 (20130101); H05B
6/68 (20130101) |
Current International
Class: |
G04F
3/06 (20060101); H05B 6/68 (20060101); G04F
3/00 (20060101); H05b 009/06 () |
Field of
Search: |
;219/10.55
;200/38B,38BA,38C,38CA,38FA |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Goldberg; Elliot
Assistant Examiner: Jaeger; Hugh D.
Attorney, Agent or Firm: Vargo; Robert M.
Claims
What is claimed is:
1. A microwave oven defrosting and cooking cycle control system
comprising:
a microwave oven;
a microwave generating system for said microwave oven;
a current path coupling said microwave generating system to a
source of electrical energy;
timer control switch means for opening and closing said current
path;
defrost control switch means for opening and closing said current
path; and
bypass circuit means extending across said defrost switch means for
short-circuiting said defrost switch means to enable said current
path to be selectively controlled by said timer control switch
means in one mode and by both control switch means in a second
mode.
2. The invention of claim 1 further comprising means for cyclically
opening and closing said defrost control switch.
3. The invention of claim 1 further comprising a defrost-cook
switch means for cutting said bypass circuit into and out of said
current path.
4. The invention of claim 3 further comprising means for
automatically opening and closing said defrost-cook switch
means.
5. The invention of claim 1 wherein said timer control switch is
coupled to a first timer to be governed thereby.
6. The invention of claim 5 wherein said first timer comprises a
motor-cam assembly operatively coupled to said timer control switch
means.
7. The invention of claim 5 wherein said defrost control switch
means is coupled to a second timer to be governed thereby.
8. The invention of claim 7 wherein said second timer comprises a
second motor-cam assembly operatively coupled to said defrost
control switch means.
9. The invention of claim 5 wherein said defrost control switch
means is coupled to said first timer to be governed thereby.
10. The invention of claim 9 wherein said first timer comprises a
motor coupled to a pair of cam members, each cam member being
mechanically coupled to said respective switch control means.
11. The invention of claim 10 further comprising:
a defrost-cook switch means for cutting said bypass circuit into
and out of said current path; and
a third cam member coupled to said first timer motor, said third
cam being operatively coupled to said defrost-cook switch means for
automatically opening and closing said defrost-cook switch
means.
12. A control circuit for coupling a power supply to a microwave
generator comprising:
a pair of power lines interconnecting the power supply to a
microwave generator;
a first line connected in parallel to said pair of power lines,
said first line having a timer control switch and a relay coil
located thereon;
a holding contact switch serially connected to one of said power
lines, said contact switch being operatively coupled to said relay
coil;
a second line connected in parallel to said pair of parallel lines
beyond said holding contact switch with respect to the power
supply, said second line having a first timer motor coupled
thereto, said first timer motor being operatively coupled to said
timer control switch;
a defrost control switch serially connected to one of said power
lines beyond said second line with respect to the power supply;
and
a bypass circuit for selectively shortcircuiting said defrost
control switch.
13. The invention of claim 12 further including a defrost-cook
switch for opening and closing said bypass circuit.
14. The invention of claim 12 wherein said first timer motor is
mechanically coupled to said defrost control switch.
15. The invention of claim 12 wherein said first line further
includes a switch connected across said first line, said switch
being biased in the open position, and a bypass circuit having a
second holding contact switch coupled thereto, said second holding
contact switch being operatively coupled to said relay coil.
16. A control circuit for coupling a power supply to a microwave
generator comprising:
a pair of power lines interconnecting the power supply to a
microwave generator;
a first line connected in parallel to said pair of power lines,
said first line having a timer control switch and a relay coil
located thereon;
a holding contact switch serially connected to one of said power
lines, said contact switch being operatively coupled to said relay
coil;
a second line connected in parallel to said pair of parallel lines
beyond said holding contact switch with respect to the power
supply, said second line having a defrost timer motor coupled
thereto;
a defrost control switch serially connected to one of said power
lines beyond said second line with respect to the power supply,
said defrost timer motor being operatively coupled to said defrost
control switch; and
a third line connected in parallel to said pair of power lines
beyond said defrost control switch with respect to the power
supply, said third line having a timer motor coupled thereto, said
timer motor being operatively coupled to said timer control
switch.
17. The invention of claim 16 further including a defrost-cook
switch for opening and closing said bypass circuit.
18. The invention of claim 17 wherein said bypass circuit comprises
a lead interconnecting said second line to said third line.
19. The invention of claim 18 wherein said cook-defrost switch is
adapted to interconnect in one position, the second line with said
lead.
20. The invention of claim 19 wherein said cook-defrost switch is
adapted to interconnect, in a second position, the power line with
the defrost timer motor.
21. A microwave oven comprising:
a source of microwave energy,
a control circuit including a cyclically operated switch for
energizing the source of microwave energy in a mode of intermittent
energization of the source of microwave energy,
a bypass circuit path shunting the cyclically operated switch,
and
a mode selector switch in the bypass circuit path for closing the
bypass circuit path to initiate and maintain continuous operation
of the source of microwave energy in a mode of continuous
operation.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to microwave cooking ovens
and more particularly to systems for controlling the operating
cycle of the microwave generators.
2. Description of the Prior Art
It has been found that in defrosting frozen products within a
microwave cooking oven, the heating cannot be continuous but must
be intermittent in order to enable the heat absorbed in each frozen
product to be distributed throughout the body of the product. If
standing times were not permitted to allow for this heat
distribution, the exterior surfaces of the product would be
entirely cooked, while the center would still be frozen.
Heretofore, defrosting operations conducted in microwave ovens had
to be performed manually. In other words, the operator had to set
the timer on the oven to a very short time (approximately one
minute), then time the standing time with an independent timer, and
repeat this process as many times as necessary to accomplish
complete defrosting. This, of course, is very cumbersome, since it
requires the constant attention of the operator. As a result,
defrosting of frozen products, especially large frozen products,
was highly impractical.
SUMMARY OF THE INVENTION
The present invention obviates the above-mentioned short-comings by
providing a microwave oven having a control system which enables
both the cooking and defrosting cycles to be accomplished
automatically.
In its broadest aspect, the present invention comprises a microwave
oven control circuit having a defrost control switch for opening
and closing a current path between the power supply and the
microwave generator, and a bypass circuit to short-circuit the
defrost control switch and provide a bypass current path to the
microwave generator. A "cook-defrost" switch is provided to
selectively connect the circuit to the bypass circuit for the
continuous cooking mode, or to disconnect the bypass circuit to
enable the current path to be operated intermittently by the
defrost control switch for the defrosting mode.
The features of the present invention which are believed to be
novel are set forth with particularity in the appended Claims. The
present invention, both as to its organization and manner of
operation, together with the further advantages thereof, may best
be understood by reference to the following description, taken in
connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of the control circuit for a microwave
oven of the present invention; and
FIG. 2 is a schematic view of a second embodiment of the control
circuit for a microwave oven of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, FIG. 1 illustrates a control circuit
generally indicated by arrow 10 for controlling the on-time of a
microwave generating system 11. Shown schematically, the microwave
generating system 11 is conventional in construction and typically
includes a magnetron for emitting microwaves into an oven
cavity.
The control circuit 10 includes a two-part power line 13 and 15,
the two parts being connected at their one ends to a source of
electric power 17. Three lines 19, 21, and 23 are connected in
parallel across the lines 13 and 15. The first line 19 includes a
manual "cook" switch 25 which is normally biased in an open
position, a timer control switch 27, and a relay coil 33. The cook
switch 25 is preferably positioned to physically extend through the
control panel of the oven. A bypass line 29 is connected across the
cook switch 25 and includes a normally open relay switch 31.
A second normally open relay switch 35 is located on the power line
13 between the parallel lines 19 and 21. Both of the relay switches
31 and 35 are operatively coupled to the relay coil 33 to be closed
thereby when energized.
The timer control switch 27 is mechanically coupled to a timer
motor 37 which is located across the line 23. This coupling is
accomplished by means of a cam 38 mounted on the output shaft of
the timer motor 37. The angular position of the timer motor 37 and
its cam 38 are adapted to be manually set by an interconnected dial
which is preferably adapted to extend through the control panel of
the oven. The cam 38 is adapted to be circular in shape with a
single projection or cut-out located on the periphery thereof. The
projection is adapted to trigger the timer control switch 27 at the
end of the cam travel.
The line 21 includes a defrost timer motor 39 which is mechanically
coupled to a defrost control switch 41 to open and close the
current path through that portion of the power line 13 extending
between the parallel lines 21 and 23. As in the prior instance,
this mechanical coupling is accomplished by a cam 40 mounted on the
output shaft of the defrost timer motor 39. The cam 40 is
irregularly shaped to have a lower and upper cam surface, each
representing half of the total cam travel. The cam 40 then
functions to open and close the switch once for each cam
revolution. For convenience, a conventional minute-timer motor
rotating a one RPM is provided to enable the defrost control switch
41 to operate in 30-second equal cycles.
A cook-defrost switch 43 is provided to operate in a first
position, which closes the line 21 to energize the defrost timer
motor 39, and a second position to interconnect the portion of the
line 21 connected to the power line 13 with a lead 45 which, in
turn, is connected to the line 23. For convenience, this current
path shall be called the bypass circuit which functions to
short-circuit the defrost control switch 41 and enable current to
be bypassed to the timer motor 37 and the microwave generating
system 11. It is preferable to have the cook-defrost switch 43 also
extend through the control panel of the oven.
In operation when it is desired to operate the microwave oven in
its cooking cycle, the timer dial on the control panel is first set
to a setting corresponding to the duration of oven on-time desired.
This action sets the cam 38 of the timer motor 37 to a
predetermined position which in turn closes the timer control
switch 27. The cook switch 25 is then depressed to close the line
19 and activate the relay coil 33. Upon actuation the relay coil 33
closes the relay switches 31 and 35. The first relay switch 31
functions to keep the line 19 closed after the cook switch 25 is
released. The line 19 will remain closed until the timer control
switch 27 is again opened by the timer motor 37. The second relay
switch 35 functions to close the power line 13 to enable current to
pass therethrough.
In the cooking cycle, the cook-defrost switch 43 is in its second
position to enable current to pass through the bypass circuit to
energize the timer motor 37 and the microwave generating system 11.
Current continues to be fed to the microwave generating system 11
until the cam 38 on the timer motor 37 reaches its zero-time
position to open the timer control switch 27. This action functions
to open the line 19 and de-energize the relay coil 33, thereby
releasing the first and second relay switches 31 and 35. As a
result, the line 19 is maintained in an open position and the power
line 13 is opened. The opening of the line 13 stops the current
flow to the timer motor 37 and the microwave generating system 11,
thereby shutting off the magnetron located therein. As can be seen,
the microwave generating system 11 is dependent only upon the
operation of the timer control switch 27 during the cook cycle, and
the operation of the oven is continuous.
In the defrost mode, the timer dial is again set as before to close
the timer control switch 27. The manual cook switch 25 is then
depressed to energize the relay coil 33 and close the relay
switches 31 and 35. The cook-defrost switch 43 is then manually
depressed to move to its first position as shown on FIG. 1. In this
position, current is fed to the line 19 to energize the defrost
timer motor 39. The defrost timer 39 then functions to open and
close the defrost control switch 41. In the open position of the
defrost control switch 41, current cannot pass to the microwave
generating system 11 or to the timer motor 37, since the bypass
path circuit 45 is also opened by the cook-defrost switch 43.
In the closed position of the defrost control switch 41, current
passes through the line 13 to the timer motor 37 and the microwave
generating system 11. As stated previously, the cam 40 and the
speed of the defrost timer motor 39 cooperate to cause the timer
motor 37 and the microwave generating system to operate
intermittently; i.e., 30 seconds on and 30 seconds off. After the
timer motor 37 has been on the duration predetermined by the dial
setting, the cam 38 reaches its zero-time position to open the
timer control switch 27, which in turn releases the relay switches
31 and 35 through the relay coil 33.
The second embodiment of the present invention is shown in FIG. 2.
In this embodiment, the second timer motor 39 is eliminated and the
defrost control switch 41 is mechanically coupled to the first
timer motor 37. Since the timer motor 37 is continuously running
during the operation of the oven, the defrost control switch 41 is
continuously opening and closing. This is different than the
operation of the first embodiment in which the defrost timer motor
39 was inactivated during the cooking cycle and the defrost control
switch 41 did not operate. In the second embodiment, the bypass
circuit 45 is provided to again extend across the defrost control
switch 41 to short-circuit the defrost cycler switch 41. As a
result, during the cooking cycle, the cook-defrost switch 43 is
closed to provide a current path to the microwave generating system
11 independent of the defrost control switch 41. During the defrost
cycle, the cook-defrost switch 43 is opened to enable the current
path to be controlled by the defrost control switch 41. The
operation of the manual cook switch 25, the timer control switch
27, and the relay switches 31 and 35 all function in the same
manner as described in the first embodiment.
In the second embodiment, the cams 38 and 40 can be coupled to the
timer motor 37 through gear train in order to slow down their
rotational speed with respect to the speed of the timer motor 37.
In this embodiment, the speed of the defrost cam 40 is sufficiently
slowed down to enable the cam 40 to be profiled with a plurality of
cam projections spaced about the periphery thereof. As in the first
embodiment, the defrost cam 40 is profiled to enable the defrost
control switch 41 to be sequentially opened and closed at 30 second
intervals.
As shown in FIG. 2, the oven control system 10 further includes a
third cam 47 connected to the output shaft of the timer motor 37.
The third cam 47 is operatively coupled to the defrost-cook switch
43 to automatically open and close the switch 43. In its preferable
mode of operation, the defrost-cook switch 43 is manually opened to
initiate the defrost cycle. The angular position of the cam 47 is
then set to a predetermined setting, deemed sufficient to allow the
frozen product within the oven to be completely defrosted. As with
the timer control cam 38, the cam 47 has a single projection at its
zero time position to close the defrost-cook switch 43 and enable
the oven to automatically switch to the cooking mode.
As can be seen, the present invention provides a microwave oven
that functions automatically in both the cooking and defrosting
modes.
It should be noted that various modifications can be made to the
apparatus while still remaining within the purview of the following
claims.
* * * * *