Note: Descriptions are shown in the official language in which they were submitted.
CA 02455665 2011-10-17
SAFETY SHUT-OFF SYSTEM
FIELD OF THE INVENTION
The present invention relates to a safety shut-off system for controlling
power supply to an appliance, for example a cooking range to discontinue power
being supplied in the event of a prescribed fire condition.
BACKGROUND
A known occurrence when using a cooking appliance is for fires to
develop when the appliance is left unattended. If forgotten for an elapsed
period of
time, the appliance being left on can cause the fire to continue for a greater
duration
or to worsen causing greater damage then had the appliance been turned off.
United States patents 6,130,412, 5,945,017 and 5,742,464 disclose
devices which address similar problems. United States patent 4,659,909 to
Knutson
in particular discloses a kitchen range safety shutoff in which an appliance
is
arranged to be turned off in response to detection by a smoke detector of a
possible
fire. Reliance upon a smoke detector can be misleading however and can cause
many false alarms. Furthermore arrangement of the shutoff disclosed in Knutson
would permit the appliance to continue to operate in the event of a power loss
or
failure of some form to the detector.
SUMMARY
According to one aspect of the present invention there is provided a
safety shut-off system, for controlling power supply to an appliance, the shut-
off
system comprising:
a shut-off switch for connection in series with the power supply of the
appliance;
a detector for detecting a prescribed fire condition; and
a controller for opening the switch in response to detection by the
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detector of the prescribed fire condition;
the controller including failsafe means for opening the shut-off switch in
response to a malfunction of the detector.
The use of a safety shutoff system including failsafe means ensures
that the appliance is only permitted to operate under safe conditions when the
detector is properly operating. In order to avoid false alarms the detector
may take
various forms including the detection of sound or other conditions which may
be
indicative of a potential fire.
The prescribed fire condition may include elevated temperatures,
ionization of air, smoke which blocks the light transmission through air,
sounds
indicative of a fire about to start or any combination thereof.
The prescribed fire condition preferably comprises noises which are
recorded by the detector which are indicative of the noises made by a cooking
fire
just before ignition thereof.
Loss of power to the detector is preferably interpreted as a malfunction
for opening the switch.
There may be provided a relay to prevent opening of the switch until
the prescribed fire condition is detected over an elapsed period of time.
The detector preferably activates a first indicator immediately in
response to detecting a prescribed fire condition and the controller
preferably
activates a second indicator in response to the shutoff switch being opened.
The controller may include a reset switch located remotely therefrom.
Working components of the system may be integrally located within a
common housing in a first embodiment of the system. Alternatively, working
components of the system may be located remotely from one another within
respective housings for hardwiring within a building structure.
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There may be provided a receptacle receiving power from the power
supply which is interrupted by the shutoff switch.
There may be provided a main control station monitoring a plurality of
controllers in association with respective appliances.
The main control station preferably includes a memory for recording
detections of prescribed fire conditions and resetting means for remotely
closing the.
shut-off switch.
According to another aspect of the present invention there is provided
a safety shut-off system, for controlling power supply to an appliance, the
shut-off
system comprising:
a shut-off switch arranged for connection in series with the power
supply of the appliance;
a detector arranged to detect a prescribed fire condition;
a first indicator arranged to immediately indicate the prescribed fire
condition in response to the detector detecting the prescribed fire condition;
a controller arranged for opening the switch in response to detection by
the detector of the prescribed fire condition;
a timer relay arranged to prevent opening of the switch until the
prescribed fire condition is detected over an elapsed period of time; and
a second indicator arranged to be activated in response to the shutoff
switch being opened after the elapsed period of time has expired.
According to another aspect of the present invention there is provided
a safety shut-off system, for controlling power supply to a plurality of
appliances, the
= shul-off system comprising:
a shut-off switch arranged for connection in series with the power
supply of each appliance;
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a detector associated with each shut-off switch and arranged to detect
a prescribed fire condition which is indicative of a potential fire before the
potential
fire ignites;
a controller associated with each shut-off switch and arranged for
opening the switch in response to detection by the detector of the prescribed
fire
condition;
the controller including a failsafe mechanism arranged for opening the
shut-off switch in response to a malfunction of the detector; and
a main control station arranged for monitoring the controllers in
association with the respective appliances.
According to another aspect of the present invention there is provided
a safety shut-off system, for controlling power supply to an appliance, the
shut-off
system comprising:
a shut-off switch arranged for connection in series with the power
supply of the appliance;
a detector arranged to detect a prescribed fire condition; and
a controller arranged for opening the switch in response to detection by
the detector of the prescribed fire condition;
wherein the prescribed fire condition comprises noises which are
recorded by the detector which are indicative of the noises made by a cooking
fire
just before ignition thereof.
According to another aspect of the present invention there is provided
a safety shut-off system arranged for controlling power supply to a plurality
of
appliances, the shut-off system comprising:
a shut-off switch arranged for connection in series with the power
supply of each appliance;
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a detector arranged to detect a prescribed fire condition;
a controller associated with each switch arranged for opening the
switch in response to detection by the detector of the prescribed fire
condition; and
a main control station arranged for monitoring the controllers in
association with the plurality of appliances respectively;
the main control station including a memory arranged for recording
detections of prescribed fire conditions.
According to another aspect of the present invention there is provided
a safety shut-off system arranged for controlling power supply to a plurality
of
appliances, the shut-off system comprising:
a shut-off switch arranged for connection in series with the power
supply of each appliance;
a detector arranged to detect a prescribed fire condition;
a controller associated with each switch arranged for opening the
switch in response to detection by the detector of the prescribed fire
condition; and
a main control station arranged for monitoring the controllers in
association with the plurality of appliances respectively;
the main control station including a resetting mechanism arranged for
remotely closing the shut-off switches.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings, which illustrate exemplary
embodiments of the present invention:
Figure 1 is a schematic view of the components of the safety shutoff
system.
Figure 2 is a flow chart illustrating the steps of operation of the system.
Figures 3 and 4 are perspective views of two different embodiments of
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the safety shutoff system.
DETAILED DESCRIPTION
Referring to the accompanying drawings, there is illustrated a safety
shutoff system generally indicated by reference numeral 10. The system 10 is
particularly useful for shutting off appliances, for example an electrical
cooking range
12, in the event of a prescribed fire condition.
While various embodiments are possible and illustrated herein, the
common features of each as schematically illustrated in Figure 1 will first be
described herein. The system includes a controller 14 which interrupts the
normal
power supply 16 to which the cooking range 12 plugs into. The controller 14
branches the power supply 16 into a steady power branch 18 which remains
unaffected by the shutoff of the system and a regulated power branch 20 which
is
shutoff and interrupted in response to the prescribed fire condition. The
regulated
power branch is interrupted by a shutoff switch 22 formed integrally within
the
controller 14 to interrupt power when the switch is open. The regulated power
branch includes a socket 24 at a line voltage of 220 volts, or other suitable
voltage
where available, for plugging in a conventional electric cooking range
therein. An
electrical outlet is also provided having a receptacle 26 formed therein which
is
associated with each one of the regulated and steady power branches 18 and 22
at
a lesser line voltage of 110 volts.
The controller also provides power to a relay 28 which relays an alarm
signal from a detector 30 of the system. The detector 30 may comprise a
conventional smoke detector for producing an alarm signal in response to heat,
ionisation, smoke or any combination thereof. The detector 30 may also
comprise a
sound detector which is able to record sounds and compare them to known sounds
indicative of a prescribed fire condition. An example of a sound which may be
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indicative of a fire is the sound produced by grease cooking just prior to
ignition
thereof to produce a grease fire on a cooking range.
The detector 30 typically receives power from the relay 28, however in
alternative embodiments the detector may be provided with a battery 32 for
wireless
and remote operation thereof. In this instance a transformer 34 is provided on
the
detector for communication with a receiver 36 on the relay 28.
The relay 28 receives the alarm signal from the detector in the event
that a prescribed fire condition is detected and the normal indicators of the
detector
itself are immediately activated in the form of lights or noise to alert an
operator.
The relay includes an integral time delay to record the alarm signal and in
turn relay
a shutoff signal to the controller only if the alarm signal is detected from
the detector
for an elapsed period of time.
The relay is arranged to receive a steady power signal from the
detector under normal conditions and accordingly the alarm signal from the
detector
to the relay takes the form of an interrupted signal or absence of signal for
an
elapsed period of time. Accordingly if the detector either detects a
prescribed fire
condition or loses power or occurs any other failure, the absence of a signal
from the
detector to the relay in the form of the alarm signal will cause the relay to
send a
shutoff signal to the controller upon expiration of the elapsed period of time
prescribed by the relay. Once the shutoff signal has been sent, the relay 28
is reset
by a reset signal activated from the controller. Resetting typically takes
place by
means of a manual reset switch 38.
Receipt of the shut-off signal from the relay by the controller cause the
indicator 39 of the controller to be activated. This indicator may also be any
conventional type of indicator including lights or noises and the like similar
to the
integral indicators of the detector.
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Once the controller has been notified by a shutoff signal from the relay
the shutoff switch 22 is opened to interrupt the regulated power branch 20 of
the
power supply which effectively cuts off power to the appliance. Activation by
the
manual reset switch 38 or other reset means causes power to be resumed and
causes the relay and detector to be reset to start over the cycle of checking
for
prescribed fire conditions by the detector.
A main control station 40 may be provided which is particularly useful
when a plurality of controllers are provided, each associate with a respective
appliance, for example in an apartment complex where each apartment is
provided
with its own appliance regulated by power from a respective controller. The
controller and the relay are suitably arranged for reporting alarm signals
from the
detector and shutoff signals from the relay so that these reported incidents
can be
kept in a memory log of the control station in which each incident is
associated with
an identification of the appliance in question affected by the detection of a
prescribed
fire condition. Resetting in this instance can be accomplished by a reset
signal sent
remotely from the main controller 40 directly to the controller 14 of a
respective one
of the appliances of the system.
In the embodiment of Figure 3, the components of the system are
shown supported integrally within a single housing 50 in which a male
connector 52
and a female power connector 54 are provided for connection in series with the
conventional plug in of an appliance to a receptacle in the wall. The
indicator 39 of
the system is provided in a visible location on the housing 50 as is the
manual reset
switch 38. The detector 30 remains positioned remotely from the housing 50 in
an
optimum location for detecting the prescribed fire condition in the cooking
area over
the appliance. In the embodiment of Figure 3, antennas relating to the
transmitter
34 and receiver 36 are illustrated in solid line while a direct wired
communication is
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shown in dotted line.
Turning now to Figure 4 a further embodiment of the system is
illustrated in which the components are hardwired into a building. In this
instance
the reset switch 38, the indicator 39, the receptacles 26, the socket 24, the
detector
30 and the controller 14 each include their own respective housing with wiring
being
mainly hidden from view within the walls of the building.
As illustrated in Figure 2, operation begins with the detector first
checking if a prescribed fire condition exists. This includes ensuring that
the
detector receives suitable power, that all connections are properly made and
that
any sensors of the detector have not detected any alarming conditions
including
heat, fire or smoke, and more particularly including sounds which may be
indicative
of a fire about to start, especially cooking fires for example grease fires.
If a problem
is detected and power is interrupted to the relay, an alarm signal is
interpreted by the
relay and this alarm signal is then reported to the main control station 40.
If the
alarm signal persists for the prescribed elapsed period of time, a prescribed
fire
condition is determined and a shutoff signal is sent to the controller to open
the
shutoff switch and accordingly interrupt power in the regulated power branch
which
interrupts the power supply to the appliance. Though any indicators of the
detector
itself are already actuated at this point, further indication that the
appliance is being
shut off then takes place and the shutoff signal is further reported to the
main control
station 40. The system remains in the shutoff condition until the circuit is
reset by
manual activation using the reset switch or by a remote reset signal from the
main
control station 40. Once this reset signal is received, the shutoff switch is
closed to
resume normal power to the regulated power branch and the relay and detector
are
reset to their starting positions. The detector then resumes checking for
prescribed
fire conditions. In the event that the elapsed period of time is not met by
the relay,
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the shutoff signal is not generated but instead the detector is reset and then
is
permitted to continue checking for prescribed fire conditions.
The system according to the present invention relates to a cooking
appliance and method of controlling its safe operation, while cooking.
A hazard control unit is added to an existing kitchen range or other
appliance (electric, gas or other power source) with a fail safe detection
circuit to
allow intervention. The hazard control unit includes a switch for controlling
all
heating stove and oven elements, of the cooking appliance, wherein the entire
appliance power supply can be switched off in the case of a predetermined
unsafe
condition, which is before stove fires can develop. The hazard control unit
itself has
a feature which indicates its on position. When the device is in off position
the stove
power supply is also off. The safety system is for electric stoves and ovens
and
uses a sensor to determine when the stove is heating beyond a certain rate
which
could constitute a safety hazard and for detecting the excessive presence of
heat,
smoke and/or flame, or other types of hazard indicators as in specific types
of
sounds. When a predetermined tolerance is exceeded, the power supply of the
electric stove is shut down. Other sources of power supply such as natural
gas,
propane, heating fuel or others can also be controlled and shut down. Based
upon
the principle that when there is heat, smoke, and accumulations of various
types of
sounds, a fire will follow, the system intervenes upon certain accumulations
of such
harmful environmental factors. The user of the appliance is notified by means
of
audible sound, flashing warning lights, vibrating mechanisms or other means.
When
the user does not respond within a predetermined time, the system takes over
and
shuts down all cooking operations.
Typical fire detectors note abnormal environmental conditions such as
the presence of smoke or an increase in temperature, light intensity ,or total
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radiation. Detectors for this purpose operate on principles involving thermal
expansion, thermoelectric sensitivity, thermo conductivity, or
photosensitivity. Of
special interest in the present invention is that a specific sound is
associated with
cooking grease fires, therefore, a sound detector is incorporated into the
system.
The sound detection assists in eliminating false alarms as a result of non-
threatening
and minor occurrences (from a toaster for example) to the environment as
mentioned.
While various embodiments of the present invention have been
described in the foregoing, it is to be understood that other embodiments are
possible within the scope of the invention. The invention is to be considered
limited
solely by the scope of the appended Claims.
