U.S. patent number 3,770,930 [Application Number 05/215,050] was granted by the patent office on 1973-11-06 for microwave oven apparatus.
Invention is credited to Arthur Y. C. Tang.
United States Patent |
3,770,930 |
Tang |
November 6, 1973 |
MICROWAVE OVEN APPARATUS
Abstract
Disclosed is a safety switch apparatus for microwave ovens that
insures that the microwave generator is enabled only when the oven
door is closed. The switch is responsive only to an irregularly
shaped actuator that is operable only when the oven door is closed
so that protection is afforded against exposure to microwaves
generated while one is tampering with the oven as well as against
accidental irradiation resulting from an open door.
Inventors: |
Tang; Arthur Y. C. (Framingham,
MA) |
Family
ID: |
22801433 |
Appl.
No.: |
05/215,050 |
Filed: |
January 3, 1972 |
Current U.S.
Class: |
219/724; 70/134;
200/61.67; 292/147; 292/341.17; 70/104; 200/61.64; 292/DIG.69;
292/340 |
Current CPC
Class: |
H05B
6/6417 (20130101); Y10T 70/5212 (20150401); Y10T
292/1024 (20150401); Y10T 292/702 (20150401); Y10S
292/69 (20130101); Y10T 70/5341 (20150401); Y10T
292/68 (20150401) |
Current International
Class: |
H05B
6/76 (20060101); H05b 009/06 () |
Field of
Search: |
;219/10.55 ;200/44 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Truhe; J. V.
Assistant Examiner: Jaeger; Hugh D.
Claims
What is claimed is:
1. A microwave oven comprising:
a. a housing defining a cooking chamber with one wall thereof
comprising a movable door means;
b. energy source means operatively coupled to said chamber for
generating microwave energy and supplying said energy to said
chamber;
c. first and second switching means connected to said energy source
means so as to selectively enable said energy source means;
d. operator means comprising an actuator having an irregularly
shaped portion for causing actuation of said first and second
switching means and operatively coupled to said door means such
that said operator means is functional only with said door means in
a closed position but functions independently of door movement;
and
e. actuator responsive means responsive to said actuator for
actuating said first and second switching means and comprising
blocking means to prevent actuation of said switching means by
objects not having said irregularly shaped portion.
2. A microwave oven according to claim 1 wherein said operator
means comprises latch means for latching said door in a closed
position when said switching means is actuated.
3. A microwave oven according to claim 1 wherein said actuator is
mounted in said door and said actuator responsive means is mounted
in said housing.
4. A microwave oven according to claim 2 wherein said blocking
means comprises a blocking spring disposed transversely in the path
followed by said actuator during actuation and said actuator
comprises a cam portion adapted to displace said spring during
actuation of said switching means.
5. A microwave oven according to claim 4 wherein said actuator is
slidably mounted in said door and said latch means comprises a
latching block with a hole therethrough for receiving said
actuator.
6. A microwave oven according to claim 3 wherein said actuator
comprises a key, said actuator responsive means comprises a lock,
and said blocking means comprise lock tumblers.
7. A microwave oven according to claim 1 wherein said operator
means comprises latch means for latching said door in a closed
position when said switching means is actuated.
8. A microwave oven according to claim 7 wherein said actuator is
mounted in said door and said actuator responsive means is mounted
in said housing.
9. A microwave oven comprising:
a. a housing defining a cooking chamber with one wall thereof
comprising a movable door means;
b. energy source means operatively coupled to said chamber for
generating microwave energy and supplying said energy to said
chamber;
c. switching means connected to said energy source means so as to
selectively enable said energy source means;
d. operator means comprising an actuator having an irregularly
shaped portion for causing actuation of said switching means and
operatively coupled to said door means such that said operator
means is functional only with said door means in a closed position
but functions independently of door movement; and
e. actuator responsive means responsive to said actuator for
actuating said switching means and comprising movable blocking
means to prevent actuation of said switching means by objects not
having said irregularly shaped portion, said blocking means being
moved out of a blocking position by said irregularly shaped portion
to allow actuation of said switching means.
10. A microwave oven according to claim 9 wherein said actuator is
rectilinearly reciprocable.
Description
BACKGROUND OF THE INVENTION
In recent years quick cooking characteristics have increased the
popularity of microwave ovens. However, a disadvantage of microwave
cooking is that exposure to microwave radiation can produce serious
injury. Such radiation exposure can occur if the microwave
generator is operated while the oven chamber is open. Although
safety interlock switches of various forms have been used to
prevent generation of microwave power when the oven door is open,
accidents may still occur because conventional switches can be
bypassed, as for example, by the prodding fingers of a curious
child thereby exposing him to dangereous radiation. Likewise, a
homeowner with a defective oven may wish to attempt the repairs
himself and purposely defeat the safety switch. Such tampering is
most difficult to prevent and can result in irradiation of the
human body.
Accordingly, the object of this invention is to provide a safety
switch system for microwave ovens that prevents accidental exposure
to microwave radiation and cannot be subverted by tampering of
unauthorized personnel.
SUMMARY OF THE INVENTION
This invention is characterized by a microwave oven with a housing
that defines a cooking chamber, one side thereof being defined by a
movable oven door. Microwave energy is supplied to the cooking
chamber by an energy source that is selectively enabled by a
switching system including a switch operator that is functional
only when the oven door is in a closed position. An irregularly
shaped key in the switch operator is inserted into a key responsive
switching device only when the oven door is in the closed position.
Coat hangers, screw drivers and other items commonly found around
the home cannot successfully be used to defeat the safety switch
since actuation occurs only in response to the irregularly shaped
key.
Another feature of the invention is the inclusion of two switches
in the switching system that are connected in series so that both
switches must be activated before the microwave energy source is
enabled. The dual switch arrangement renders the switching circuit
less susceptible to tampering in that an object such as a
screwdriver or piece of wire may possibly actuate one of the
switches if the key responsive device is prodded thereby, but
successfully closing both switches simultaneously with any object
other than the key is highly improbable. In addition, should one
switch become defective or stick in the actuated position, the
second switch still provides interlock protection to the user of
the oven.
Yet another feature of the invention is the inclusion of a latch in
the switch operator so that the oven door must be closed and
latched before actuation of the switches is possible. Sufficient
coupling for a radiation shield between the door and the housing is
thereby insured.
DESCRIPTION OF THE DRAWINGS
These and other features and objects of the present invention will
become more apparent upon a perusal of the following description
taken in conjunction with the accompanying drawings wherein:
FIG. 1 shows a perspective view of a microwave oven utilizing the
subject switch;
FIG. 2 shows a sectional elevation view of a switch actuator used
in the embodiment of FIG. 1 with the door in a closed position and
the switch inactivated;
FIG. 3 shows a sectional elevation view of the switch actuator
shown in FIG. 2 with the switch actuated;
FIG. 4 shows a sectional view of the switch shown in FIG. 3 taken
along the line 4-4,
FIG. 5 shows a perspective view of a microwave oven utilizing
another preferred embodiment of the subject switch; and
FIG. 6 shows a detailed elevation view of the switching apparatus
used in the embodiment shown in FIG. 5.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring first to FIGS. 1, 2 and 3 there is shown a microwave oven
21 including a housing 22 with a movable door 23 that defines one
side of a cooking chamber 24. Retained within another portion of
the housing 22, but not shown in FIG. 1 in order to preserve
clarity, is a conventional microwave energy source that is
operatively coupled to the cooking chamber 24 to supply microwave
energy thereto in response to selective enabling signals from a
safety switching apparatus 25. Included in the switching apparatus
25 is a lower switch 26 and an upper switch 27 in series that
supply the enabling signals when both are actuated. Also included
in the switching apparatus is an operator 28 including a handle 31
and an actuator 29 that rides in a shaft 32 within the door 23. If
the door 23 is in a closed position as shown in both FIGS. 2 and 3,
an opening 33 within a latching block 34 is directly above the
shaft 32 and, as shown in FIG. 2, the opening is blocked on an
upper end by a blocking spring 35 transverse thereto. When the
actuator 29 is in an upper position passing through the opening 33,
as shown in FIG. 3, the door 23 is locked. An irregularly shaped
wedge 36 at the top of the actuator 29 forces the blocking spring
35 from the path of the actuator 29 as it is moved upward. As shown
in FIG. 3, blocking spring 35 is pushed to the left by the wedge
36, and upon further upward motion of the actuator 29 eventually
comes to rest in a groove 37 within the actuator 29. Only when the
blocking spring 35 is within the groove 37 is the actuator rod 29
in contact with a button 38 on the upper switch 27, causing
actuation thereof.
Referring now to FIG. 4 there is shown the blocking spring 35
mounted on a shaft 41. Normally the blocking spring 35 is disposed
over the center of the opening 33 in the block 34. However, when
the actuator 29 is in the upper position and the spring is in the
groove 37, it is displaced as shown in FIG. 4. This displacement,
which is in the downward direction when seen as in FIG. 4, and
towards the front or left as shown in FIGS. 2 and 3, depresses a
button 42, thereby actuating the switch 26.
During operation of the oven 21 as shown in FIGS. 1-4, the actuator
29 must be in the lowered position as shown in FIG. 2 in order to
open the door 23. When the door 23 is opened, as shown in FIG. 1,
the actuator 29 may be moved to the upper position as shown in FIG.
1 with no effect on the energy source, which is not enabled.
However, when the door 23 is closed and the handle 31 is moved to
the upper position as shown in FIG. 3, the wedge 36 displaces the
blocking spring 35 against the button 42 actuating the switch 26 as
shown in FIGS. 3 and 4. In addition, the actuator 29 presses upward
against the button 38, actuating the switch 27 and consequently the
microwave energy source is enabled for cooking. However, the
actuator 29 passing through the block 34 securely latches the door
23 closed. The actuator responsive buttons 38 and 42 respond only
to the predetermined shape of the actuator 29 because only a wedge
shaped object can displace the spring 35 and travel upward
sufficiently to actuate the switch 27. In addition, the wedge must
be of the proper size and length and must be sloped toward the left
as shown in FIGS. 2 and 3. If an attempt is made to energize the
switches 26 and 27 with a wedge sloped to the right the point of
the wedge will not strike the button 38, therefore the switch 27
will remain inactivated. Only a remote possibility remains that
tampering with an object such as a screw driver or coat hanger will
simultaneously displace the spring 35 properly and simultaneously
actuate the switch 27.
Referring next to FIG. 5 there is shown an alternate microwave oven
51 including a housing 52 and a movable door 53 that define a
cooking chamber 54. A conventional microwave energy source in the
upper portion of the housing 52 in not shown in order to preserve
clarity. A safety switch device 55 as shown in FIG. 6 includes a
first switch 56 and a second switch 57 that are wired in series and
selectively enable the microwave energy source. Both switches 56
and 57 must be activated for energization to occur. Shown in FIG. 6
is a portion of the housing 52 and a portion of the door 53.
Protruding from the door 53 through an opening 58 in the housing 52
is a latching bar 59 that is firmly affixed to the door 53 and
defines an opening 61 near an end 62 thereof. A shaft 63 defined by
the door 53 encloses a cylindrical extension 64 that couples a
handle 65 and an irregularly shaped key 66. The shaft 63 is larger
than the extension 64 to permit relative movement between the key
66 and the door 53. At the back of a cavity 67 defined by the
housing 52 is a lock 68 with a locking pin 69 protruding from the
top thereof. The switches 56 and 57 are affixed to a rear section
of the lock 68. Protruding from the rear of the lock 68 is a shaft
71 with two wings 72 and 73 thereon. As the shaft 71 rotates
reciprocally the wings 72 and 73 translates to selectively activate
the switches 56 and 57 respectively. The locking pin 69 is normally
in the position shown in FIG. 6, but in response to actuation of
the lock 68 by the key 67, it moves upward to the position shown by
the dotted line in FIG. 6. Simultaneously, the wings 72 and 73
respond to the key 66 by actuation of the switches 56 and 57
respectively.
During operation of the embodiment 51, as shown in FIGS. 5 and 6,
when the door 53 is open the key cannot possibly be inserted into
the lock 68, therefore the switches 56 and 57 cannot be activated.
When the door is closed as shown in FIG. 6, the key 66 rests in the
cavity 67 so that proper manipulation of the handle 65 causes the
key 66 to enter the lock 68. Turning the key 66 then actuates the
lock 68 to displace the pin 69 to the position shown by the dotted
line in FIG. 6, thereby securely locking the door. Simultaneously,
the shaft 71 rotates causing activation of the switches 56 and 57,
thereby enabling the microwave energy source.
It will be noted that in both embodiments 21 and 51 an operator
must be actuated to both deenergize the energy source and unlatch
the door before any opening movement thereof is possible. This is
made possible by the arrangement wherein deenergization of the
source is independent of oven door movement. Because of this
feature, a complete termination of energy transmission is insured
before any door opening movement can be initiated.
Obviously, many modifications and variations of the present
invention are possible in light of the above teachings. For
example, some of the important features of both embodiments can be
included in other embodiments. It is to be understood, therefore,
that the invention can be practiced otherwise than as specifically
described.
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