Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02498227 2005-02-21
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FIRE HAZARD SAFETY DEVICE FOR HOUSEHOLD APPLIANCES
FIELD OF THE INVENTION
The present invention relates to a safety device that is installed between the
electrical cord of a household appliance, such as an oven and/or stove
elements,
and a 220V electrical outlet to which the appliance is usually plugged. The
safety
device prevents operation of the appliance when it is left unattended by a
user
past a preset time period, for example 15 minutes to avoid fire hazards that
might
occur when a user simply forgets to turn the appliance off.
BACKGROUND OF THE INVENTION
Heating appliances, such as electric cook-tops, electric ovens, or a
combination
thereof, use electro-mechanical or electronic controls to program the
operation of
the appliance. The controls are generally proprietary to individual OEM
manufacturers and are difficult to modify.
Known in the art, there is U.S. patent No. 6,140,620 (Aldridge et al.), which
discloses a device that can automatically disconnect an appliance from the
source
of electrical current after a preset period of time. The device is installed
between
the electrical cord of the appliance and a 220V electrical outlet to which the
cooking appliance is usually plugged. The device is designed to disconnect the
electric appliance such as a stove through a relay. The device automatically
disconnects the appliance from the power source after a preset period of time,
unless the user presses a switch, in which case a timer circuit is reset and a
new
countdown period is initiated, or alternately a specific time period is added
to the
remaining time period counted by the timer circuit each time the switch is
operated, until a maximum time period is reached. However, the drawbacks of
this
prior art device are that the activation period is permitted until a maximum
time is
reached and that lines L1 and L2 are completely disconnected from the 220VAC
source so that the entire appliance is shut down.
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SUMMARY OF THE INVENTION
The safety device according to a preferred embodiment of present invention
complements the electro-mechanical or electronic controls for home appliances
so
as to eliminate fire hazard situation when the heating elements are running
out of
control due to failure of the control elements or when a user is not present
and the
temperature reaches the fire condition. In particular, the safety device
according to
the present invention is designed so that the 120V-operated equipment of the
appliance is unaffected by it.
Preferably, the safety device for home electrical appliances can be used to
enable
a user to program the operation of the appliance through control switches or
electronic keyboard for selection of programs, i.e. time, temperature, the
display of
user selected functions, .etc.
The invention as well as its numerous advantages will be better understood by
reading of the following non-restrictive description of preferred embodiments
made in reference to the appending drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an electric block diagram of a fire hazard safety device,
according to a
preferred embodiment of the present invention.
Figure 2 is a top perspective view of a front part of a fire hazard safety
device,
according to a preferred embodiment of the present invention.
Figure 3 is a top perspective view of back part of a fire hazard safety device
that is
connectable to the front part shown in Figure 2.
Figure 4 is a perspective view of a remote command key transmitter that may be
used with a fire hazard safety device, according to a preferred embodiment of
the
present invention.
Figure 5 is a back perspective view of a control board of a fire hazard safety
device, according to a preferred embodiment of the present invention.
Figure 6 is a front perspective view of the control board shown in Figure 5.
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DETAILED DESCRIPTION OF THE INVENTION
Referring to Figures 2 and 3, the safety device according to a preferred
embodiment of the present invention is a self-contained unit having a male
plug
on the back side thereof for plugging it in an electrical power source of 220
Volts,
and a female receptacle on the front side for receiving the appliance's plug
(not
shown). Preferably, the safety device is designed to prevent operation of the
heating elements of a cooking appliance except when the user activates a
timing
function which enables their operation for a preset time period. The user must
reset the timing function before expiration of the time period to keep the
heating
elements operating. The safety device is also designed so that the 120V-
operated
equipment of the cooking appliance is unaffected by it.
Referring to Figure 1, the safety device according to a preferred embodiment
of
the present invention has a relay circuit connected between one of the power
prongs of the male plug 1 and a corresponding one of the contacts of the
female
receptacle 2. The 120V-operated equipment of the cooking appliance is powered
between the undisturbed power line in the safety device and the neutral line.
The
relay 6 is normally in open state and is responsive to a control signal
generated by
a micro-controller providing a timing function. The control signal triggers
the relay
into closed state as long as the time period measured by the timing function
of the
micro-controller has not elapsed. The relay gets back into open state whenever
the timing function stops. The micro-controller may be connected to a RF
module/decoder provided with an antenna for receiving a timer activating/reset
signal from a remote control as shown in Figure 4. The remote control has a
single push-button operable by the user of the cooking appliance for resetting
the
timing function and triggering a new count-down process for the preset time
period. The safety device has a power supply circuit connected to the
undisturbed
power line and the neutral line and providing the required power supply for
the
electronic and electrical components of the safety device.
Referring back to Figures 2 and 3, the safety device may be especially used
for
insurance-related purposes. In such a case, the safety device would be
installed
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by an authorized technician who would place a seal lock on one of the screws
securing the safety device to the wall when plugged in the usual power outlet
for
the cooking appliance. The seal lock would provide evidence of any tampering
to
by-pass the safety device, in a similar way to seal locks put on electrical
company
meters.
Referring back to Figure 1, the male plug's 1 pin Line1 is connected to relay
contact NO and the output of the relay is connected to female receptacle 2.
Relay
coil is driven by timer with approved time as set by a Safety Regulation
Specification Standard.
The time ON is announced by two (2) beeps. Before the safety time expires
multiple beeps are sounded and a user can in this remaining time extend the
Run
Time Program by the same Approved ON Time by sending the signal from remote
control (single key) one-touch. This cycle could be repeated all the time set-
up by
the user by original home appliance settings, therefore the user sets up the
cooking process by entering time, temperature and other features as convection
bake, broil, tender cook, etc.
The purpose of this device is to automatically cut-off one (1) line of the
power after
determined number of minutes specified by the safety specification standard.
The safety device according to the present invention prevents a home cooking
appliance to continue the cooking process with out user supervision.
The fire hazard safety device according to the present invention complements
the
electromechanical or electronic controls for home appliances to eliminate fire
hazard conditions such as: when running out of control due to incorrect
program
setting; when a user is not present in the surrounding of the controlled
appliance;
when the condition of the appliance causes a fire condition; or by misused
domestic appliance, i.e. heating a home by electric oven or cook-top. The
safety
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device periodically checks the user's intention to continue the set-up
functions for
cooking.
The safety device is a self-contained unit comprising of a male plug 40A-
125/250V
5 on the back side of the safety device with 50A-125/250V female receptacle on
the
front side of the safety device.
Line 2 (or 1 ) from the male plug is connected directly to contact 2 (or 1 )
of the
female receptacle. The connecting wire is branched directly to the power
supply
terminal. The neutral wire is connected the same way from male plug to neutral
connector of female receptacle with branch connected to the power supply
terminal.
Installed inside the self-contained box is a Control Board containing
reprogrammable micro-controller, micro-encoder, RF module, antenna and main
relays 1/30A, 240VAC or 2I30A, 240VAC.
Line 1 (or 2) of male plug is connected to NO terminal of Relay RL-1 and the
solid
contact of RL-1 is connected to Line 1 (or 2) contact terminal of female
receptacle.
During the time when there is no activity with the home appliance the power
circuit
is open. Only Line 2 (or 1) and neutral line are solidly connected between
male
plug and female receptacle. Neutral connection is branched to Control Board
neutral terminal of power supply.
Relay RL-1 is controlled by preprogrammed micro-controller. Program of the
micro-controller is activating the time relay. The ON/OFF time varies
according to
the safety regulations standards as specified by states (CA, USA) and
municipal
fire departments.
The timer is wirelessly controlled by the remote command key transmitter shown
in Figure 4. The remote command key transmitter is used for remote control of
the
safety device. Selectable addressing provides security and allows distinct
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transmitter-receiver relationships (CA or USA). The receiver/decoder is paired
with a decoder micro-controller. The key transmitter may be configured to meet
specific requirements. Remote control/command and keyless entry combines an
RF receiver with an on-board decoder and antenna.
After the safety device is installed permanently by an authorized or certified
company. The electric oven, range, cook-top or combination electric oven c/w
cook-top could be plugged into 120/240V receptacle.
The person using the heating appliance can now set-up functions for cooking
process using complete instructions from the owner's manual. Time of day,
minute
minder and oven/range light could be set-up at anytime without activating
safety
device. Now the cooking/baking process could be started by activating remote
command key transmitter. The Receiver/Decoder announced by several beeps
that the Safety Time ON is activated and set-up cooking process started. The
safety time expires after a predetermined setting, this is indicated by a
number of
beeps to get the attention of the user to confirm that the appliance should
continue
the cooking process. The user will confirm this by pressing the remote command
key transmitter. Confirmation of acceptance is also announced by predetermined
number of beeps. This process will continue after the setting program in the
home
appliance is complete or when the person using the heating appliance decides
not
to continue the cooking/baking process using the appliance control device or
by
not confirming the process by pressing key of RF transmitter. The power will
be
cut-off by electronic safety device after the safety time expires and is not
extended
by the user. The safety time cycle could be repeated during the cooking
process
entered by the user.
Although preferred embodiments of the present invention have been described in
detail herein and illustrated in the accompanying drawings, it is to be
understood
that the invention is not limited to these precise embodiments and that
various
changes and modifications may be effected therein without departing from the
scope or spirit of the present invention.
