FIELD OF THE INVENTION
The invention disclosed herein relates to a system to detect gas leak from the gas-stove burner and a method to automatically arrest the gas leak. The system senses any gas leaking from the gas stove burner and automatically shuts-off the gas-stove knob thereby cutting off the gas supply to the burner to prevent any further leak.
BACKGROUND ART
Gas is one of the cleanest fuels available but is very dangerous if not handled properly. A significant number of domestic fire accidents have happened due to gas or LPG leakage and many of them have been due to sheer negligence of the residents. In some cases, the gas or LPG leak happens from the burner of the gas stove. This can happen in windy conditions when the sudden gush of wind can extinguish the flame, if the gas stove is too close to windows of the kitchen. Sometime liquid spillages over flame might extinguish the flame resulting into gas or LPG leakage through the gas or LPG stove burner.
Also, many users are busy while performing their daily household chores especially during morning hours. They tend to save time by multi-tasking while involved in cooking. Sometimes, they forget to ignite the gas/LPG, coming through the burner, after they put the gas-stove

knob to "ON" position. Incidents like this may lead to a dangerous situation of LPG leak resulting into a blast.
Devices to prevent gas leaks, and subsequent fire hazards are generally known in the art.
US5094259A discloses an automatic shut-off device for a gas stove, and more particularly, a safety valve control device that can be retrofitted between the gas inlet pipe and the catch base of the stove. The device includes a coupling such that operation of the knob of the gas stove at the time operates the circuit of a gas safety valve control device. This operation causes the forward movement of a function shaft of the gas safety valve device and opens the gas intake valve to supply the gas to the stove burner. The function shaft is also subject to the control by an electromagnetic control rod to maintain the open state of the gas intake valve. In case the fire goes out accidently, the circuit device energizes an electromagnetic coil to attract upwardly an electromagnetic control rod, thereby disconnecting the function shaft, which is spring loaded, and which in turn operates the gas intake valve. This action thus disconnects the gas supply to the stove. Also, if the cooking time is too long, and the fire does not go out (e.g., one forgets to turn off the gas) or the gas at the stove burner cannot be ignited within the given time, the device will also shut off automatically the gas intake valve.

CN2851893Y discloses a flameout gas stove with a dual gas leakage preventing and protecting function, which comprises a power supply (1), an air inlet pipe (2), a burner (3) and an igniter assembly, wherein the inner side of the burner (3) is provided with a thermocouple (4) and an igniting needle (5), and the thermocouple (4) is connected with an electromagnetic valve (6); the igniting needle is connected with the igniter assembly through a conducting wire. The igniter assembly, the power supply (1), the thermocouple (4) and the igniting needle (5) are separately connected with an electronic timing controller (7) through conducting wires. The utility model also comprises a self-absorption valve (8) which is installed on the air inlet pipe (2), and the self-absorption valve (8) is connected with the electronic timing controller (7) through a conducting wire. The utility model has the advantages that due to the adoption of the timing flameout technique, the gas stove can automatically cut off a gas circuit without need for users to watch aside at the same time of using the gas stove, and due to the adoption of a dual cutting off protective device, the utility model can safely cut off the gas circuit no matter after completing timing combustion or in the state of abnormal flameout when a main valve of a switch is not closed by hand, without occurring unsafe factors.
The devices known in the art either sense the gas, or work on gas supply by using complex electromechanical

devices. There is a need in the art to develop a non¬electronic, non-electrical, user operable device for arresting gas leaks in gas stoves and prevent fire hazards.
The disclosed invention will address one or more problems associated with use of gas or LPG through gas stove burners.
SUMMARY OF THE INVENTION
To meet the objects of the invention and overcome the problems of the prior art, it is disclosed herein a device for automatically switching off a stove having a fuel control knob (8) to control flow of fuel to the burner (1) of the stove, said device comprising of a temperature sensor (2) positioned close to the burner (1), a connecting rod (3) connecting the temperature sensor (2) to a latching rod (4), a spiral spring (12) loaded ratchet wheel (5) mounted below the knob (8), and adapted to be rotated anti-clockwise direction by a projection (7) on the top side of the wheel (5), characterised in that, when the wheel (5) is rotated anti-clockwise and the burner (1) switched on, the temperature increase causes the temperature sensor (2) to push the latching rod (4) to latch and lock one of the teeth of the ratchet wheel (5) , and upon reduction in temperature on the burner (1) consequent to extinguishing of the flame, the temperature sensor (2) retracts to release the wheel (5), wherein upon the

resultant clockwise rotation of the wheel (5), the projection on the wheel (7) pushes the knob (8) to switch off position to cut off fuel supply to the stove.
It is disclosed herein a method of automatically switching off a gas stove having a gas control knob (8) to control flow of gas to the burner (1) of the stove comprising the steps of: providing temperature sensor
(2) close to the burner (1); connecting the temperature sensor (2) to a latching rod (4); and providing a spring
(12) loaded wheel (5) below the knob (8) of the stove and adapted to be rotated anti-clockwise direction by a projection (7) on the top side of the wheel (5); characterised in that, when the wheel (5) is rotated anti-clockwise and the burner (1) switched on, the temperature increase causes the temperature sensor (2) to push the latching rod (4) to latch and lock one of the teeth of the ratchet wheel (5), and upon reduction in temperature on the burner (1) consequent to extinguishing of the flame, the temperature sensor (2) retracts to release the wheel (5) , wherein upon the resultant clockwise rotation of the wheel (5), the projection on the wheel (7) pushes the knob (8) to switch off position to cut off gas supply to the stove.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG.l shows a perspective view of an embodiment of the invention with a gas stove
FIG. 2 shows yet another perspective view of an embodiment of the invention with a gas stove

FIG. 3 is a schematic illustration of working the invention.
FIG. 4 is a schematic illustration of working the invention.
FIG. 5 is a schematic illustration of working the invention.
FIG. 6 is a schematic illustration of working the invention.
FIG. 7 is a schematic illustration of working the invention.
FIG. 8 is a schematic illustration of working the invention.
FIG. 9 is a schematic illustration of working the invention.
FIG. 10 is a schematic illustration of working the invention.
DETAILED DESCRIPTION OF THE INVENTION
The disclosed system detects the fuel leakage from the burner and automatically shuts-off the knob.
Though the disclosure for the purpose of describing and explaining the invention uses gas fuel, it can nevertheless be used in switching off any fuel, including fossil fuels, in the absence of flam eon the burner.

The system comprises of a temperature sensor and a stove knob mounted on a spring loaded wheel. Temperature sensor is placed touching the burner of the gas stove (or in proximity to the burner). It senses the variation of burner's temperature and whenever the temperature falls below a particular threshold, it activates the actuation mechanism to release the spring loaded wheel. Once released, the spring loaded wheel rotates back taking along the stove knob to "OFF" position resulting in the shut-off of the gas supply to the burner. Before starting cooking on a gas stove, the user has to rotate the wheel in order to load its spring. This loaded spring stores potential energy. After the wheel is rotated, the user can switch "ON" the stove knob at any flame position: "High", "Medium" or "Low" Flame. Whenever the spring loaded wheel gets released, the stored potential energy of the spring helps in turning back of the wheel thereby switching the knob to "OFF" position.
The invention is further described by way illustration by taking two exemplary cases, the example used here is merely for illustration alone and does not in any way to be construed to limit the scope of the invention, or the multiple possibilities and uses of the invention.
Case-1) If the knob is switched "ON" with the flame ignited and it gets extinguished (due to either sudden gush of wind or liquid spill-over from cooking vessel) with LPG supply still flowing to the burner.
Case-2) If the knob is switched "ON" to supply the gas to the burner and the flame is not ignited.

In both the cases, the burner's temperature becomes low (Case-1) or is already low (Case-2), even though the knob position is at "ON". This property is exploited by temperature sensor of the disclosed system for detecting LPG leak from the burner. Temperature sensor is to be realized by the use of bi-metallic strip. The bi-metallic strip touches the burner. Under variation in burner's temperature, there is differential expansion/contraction in the bimetallic strip. This mechanical expansion/contraction is sufficient to trigger the releasing of the spring loaded wheel to rotate back to bring the stove knob to "OFF" position thereby cutting off the gas supply to the burner.
Referring to Fig.l and Fig.2, the temperature sensor (2), preferably a bi-metallic strip is touching the burner (1) in a curved manner. One end of the curved bi-metal strip (2) is attached to the burner (1) while the other end is free to move. The free-end of the bi-metal strip (2) is connected to latching/de-latching rod (4) via a connecting rod (3) as depicted in Fig.2. There is a wheel (5) which is mounted on the gas stove structure. This wheel (5) is loaded with spiral spring (12). This wheel (5) incorporates two important designs in it. One is the incorporation of the ratchet (6) and other is the incorporation of the gear (9) as seen in Fig.l and Fig.2. The gear (9) part of the wheel is coupled with the rotary damper (10). The rotary damper (10) is an oil based delay element. It rotates freely in one direction and provides resistance for rotation in other direction. The gas stove knob (8) is arranged over the wheel (5) . The wheel (5)

engages the knob (8) through the projection on the wheel (5) . The wheel (5) is independent to rotate. Before switching "ON" the gas stove knob (8) for cooking, the wheel (5) is to be rotated in anti-clockwise direction. Also whenever the wheel (5) moves in anti-clockwise direction, it gets energized because of the stored potential energy of the attached spiral spring (12) . The spiral spring (12) is arranged in such a way that it stores potential energy whenever it gets twisted in anti¬clockwise direction.
Now, consider Case-1. The user rotates the wheel (5) in anti-clockwise direction as shown in Fig.3. After the rotation of the wheel (5), the stove knob (8) is switched "ON" as can be seen in Fig.4. The stove knob (8) can be kept at any position of "High", "Medium" or "Low" flame for the supply of the gas to the burner (1). There is a rise in burner's (1) temperature when the flame is ignited. The increase in burner's (1) temperature leads to differential expansion in the bi-metal strip (2) resulting in the free end of the bi-metal strip (2) to move away from the burner (1) as shown in Fig. 5. This movement of the bi-metal strip (2) pushes the latching/de-latching rod (4) forward (towards the wheel). After a slight forward movement, the latching/de-latching rod (4) latches in one of the teeth of the ratchet (6) of the wheel (5) thereby holding the wheel (5) as depicted in Fig.5. As the wheel (5) and the knob (8) are de-coupled to each other, the user can cook the food at any position of the knob (8) (i.e. "High",

"Medium" or "Low") without disturbing the latching of the rod (4) to the ratchet (6).
The burner's (1) temperature starts decreasing, whenever the flame goes off and the stove knob (8) is still "ON". This leads to contraction in the bi-metal strip (2) resulting in its movement towards the burner (1). When the burner's (1) temperature goes below a particular threshold, the bi-metal (2) contraction is sufficient for the latching/de-latching rod (4) to de-latch from the ratchet (6) and release the spring loaded wheel (5) as shown in Fig.6. Once released, the spring loaded wheel
(5) turns clockwise. During this clockwise rotation of
the wheel (5), the projection in the wheel (5) hits the
knob (8) and turns the knob (8) clock-wise to "OFF"
position thereby cutting off the gas supply to the burner
(1) as can be seen in Fig.7.
When the stove knob (8) is switched "ON" and the flame is ignited, it takes some time for the burner's (1) temperature to reach a particular threshold so that the latching/de-latching rod (4) gets latched to the ratchet
(6) of the wheel (5). This time can be termed as latching
time. During this latching time, the energized spring
loaded wheel (5) (which is turned anti-clockwise prior
to switching "ON" of stove knob) will always turn back
along with the knob (8) to "OFF" position under the
influence of the spring (12) force. This happens because
the latching/de-latching rod (4) is not in a latching
position to hold the ratchet (6) of the energized wheel

(5) . In order to avoid this spurious turn-off of the knob (8), the wheel (5) is provided with a delay after it is turned anti-clockwise by the user. This delay should be more than the latching time. The delay to the wheel is provided by the rotary damper (10). The rotary damper (10) is free to move in clock-wise direction and provides a resistive rotation in anti-clockwise direction. As shown in Fig.8, the rotation of the wheel
(5) in anti-clockwise direction also rotates the damper
(10) freely in clockwise direction through the
interlocking of its gear (9) with the gear of the damper
(11) . As seen in Fig. 9, once user leaves the wheel (5)
after rotating it anti-clockwise, the wheel (5) starts
rotating back in clockwise direction under the influence
of the energized spring (12). But this clockwise rotation
of the wheel (5) is slow because the wheel's (5) rotation
is inter locked with resistive anti-clockwise rotation
of the damper (10) . This slow motion of the wheel (5)
provides sufficient delay for the latching/de-latching
rod (4) to get latched to the ratchet (6) of the wheel
(5) .
Now, consider Case-2. The user rotates the wheel (5) in anti-clockwise direction and turns "ON" the knob (8) as shown in Fig. 3 and Fig. 4. Now, if the user forgets to ignite the flame, the burner's (1) temperature does not increase. Due to this, the bimetal (2) does not expand and hence the latching/de-latching rod (4) does not engage the ratchet (6) of the wheel (5). The wheel (5) does not get latched during its slow clockwise rotation and once the gear (9) of the wheel (5) and the damper

(10) gets dis-engaged (as shown in Fig.10), the wheel (5) immediately hits the knob (8) to take it to "OFF" position and cut-off the gas supply to the burner (1).
Different form of design and techniques are possible in which the bi-metallic strip and the spring loaded knob can be engineered to carry out the intended operation of an embodiment of the invention as disclosed in this document.
The disclosed invention is used to detect gas leak from the burner of gas stoves and shuts-off the gas supply to the burner by closing the stove knob thus preventing any further leak. It is a safety device which may also be used in domestic LPG stoves for household cooking application.
Disclosure of the invention using LPG as an example is for the purpose representation only. It is not to be construed to be limited to LPG. The invention can be used in stoves, burners or similar devices using multiple fuels.
The principle of automatic switch-off after sensing gas leak from the stove burner may have larger applications than the specific application described in this invention.

1. A device for automatically switching off a stove
having a fuel control knob (8) to control flow of
fuel to the burner (1) of the stove, said device
comprising of a temperature sensor (2) positioned
close to the burner (1), a connecting rod (3)
connecting the temperature sensor (2) to a latching
rod (4), a spiral spring (12) loaded ratchet wheel
(5) mounted below the knob (8), and adapted to be rotated anti-clockwise direction by a projection
(7) on the top side of the wheel (5), characterised in that, when the wheel (5) is rotated anti-clockwise and the burner (1) switched on, the temperature increase causes the temperature sensor
(2) to push the latching rod (4) to latch and lock
one of the teeth of the ratchet wheel (5) , and upon reduction in temperature on the burner (1) consequent to extinguishing of the flame, the temperature sensor (2) retracts to release the wheel (5), wherein upon the resultant clockwise rotation of the wheel (5), the projection on the wheel (7) pushes the knob (8) to switch off position to cut off fuel supply to the stove.
2. The device as claimed in claim 1 wherein the said temperature sensor (2) is a bi-metallic strip.
3. The device as claimed in any of the preceding claims wherein the said fuel is a fossil fuel.

4. The device as claimed in any of the preceding claims further comprises of a damper (10) with a gear (11) to engage with a gear (9) on the ratchet wheel (5) and slow its clockwise rotation before the engagement of the latching rod (4) with the ratchet wheel (5) .
5. A method of automatically switching off a gas stove having a gas control knob (8) to control flow of gas to the burner (1) of the stove comprising the steps of:
providing temperature sensor (2) close to the burner (1);
connecting the temperature sensor (2) to a latching rod (4); and
providing a spring (12) loaded wheel (5) below the knob (8) of the stove and adapted to be rotated anti-clockwise direction by a projection (7) on the top side of the wheel (5); characterised in that, when the wheel (5) is rotated anti-clockwise and the burner (1) switched on, the temperature increase causes the temperature sensor (2) to push the latching rod (4) to latch and lock one of the teeth of the ratchet wheel (5), and upon reduction in temperature on the burner (1) consequent to extinguishing of the flame, the temperature sensor (2) retracts to release the wheel (5), wherein upon the resultant clockwise rotation of the wheel (5), the projection on the wheel (7) pushes the knob

(8) to switch off position to cut off gas supply to the stove.
6. The method as claimed in claim 5 wherein the said temperature sensor (2) is a bi-metallic strip.
7. The method as claimed in claims 5 or 6 wherein the said fuel is a fossil fuel.
8. The method as claimed in claims 5,6 or 7 further comprises the step of damping the clockwise rotation of the ratchet wheel (5) by a damper (10) with a gear (11) to engage with a gear (9) on the ratchet wheel (5) and slow its clockwise rotation before the engagement of the latching rod (4) with the ratchet wheel (5).