DESC:FIELD OF THE INVENTION
This invention involves use of a switch to turn off fuel supply to a flame burner automatically after a predetermined time of duration. The switch can be operative without using any electrical power or with electrical power.

BACKGROUND ART
There are many timer technology and related products in the art. Particularly, in oven-toaster-grill (OTG) or micro-wave ovens, use of electro-mechanical timer based switch off is known. However, use of such automation in LPG stove involves risk. Any physical implementation of sensors and actuation systems in a cooking gas stove can be risky as it involves highly inflammable LPG. All the kitchen timers, available in market (electronic or mechanical), are detached from the main system. They just provide an alarm once the preset duration is over. In such timers, it is expected that the oven-knob be operated manually afterwards.

For a complete timer-based cooking experience, it is expected that the timer not only gives an alarm but also switches off the knob automatically once the set-time is completed. Along with this, the timer should also allow the user to cook food at any flame position of his/her choice i.e. High-Flame, Medium-Flame or Low-Flame. Previously, some inventions (Patent No. - US 9,310,084 B2) tried automatic turn-off of knob in timer-based cooking but there was no option of flame control. The present invention solves the drawbacks in the prior art and provides a novel device or attachment to auto-switch off stove with flame control.

OBJECTS OF THE INVENTION
It is an object of the invention to disclose a turn-off switch with timer system useful for appliances using a flammable liquid or liquefied gas or compressed gas.

It is yet another object of the invention, a turn-off switch with timer system useful for appliances using a flammable liquid or liquefied gas or compressed gas, not only gives an alarm but also switches off the knob automatically once the set-time is completed.

SUMMARY OF THE INVENTION
To meet the objects of the invention and overcome the problems of the prior art, it is disclosed here, a device for switching off fuel supply to a flame burner of a stove comprising of an actuating assembly comprising of a spring loaded wheel with gears at some part of the outer edge of its circumference, one end of the spring fixed to the wheel and the other end to the stove, a projection on the wheel to rotate the wheel, the said wheel on a wheel sleeve mounted below a knob of the flame burner without in contact with it, the said knob through a shaft controls the amount of fuel sent the burner; and a timer assembly comprising of a rotatable timer shaft adapted to be rotatably coupled to the wheel through a timer shaft gear, characterised in that, each tooth on the wheel has a timing marked on it, and when engaged to the timer gear of the timer assembly, the wheel moves in the anti-clockwise direction to until the time set, and on completion of the time set the timer gear disengages the wheel to allow it to return to its position, wherein the projection on the wheel pushes the knob to switch-off the fuel supply.

It is disclosed here, a method of switching off fuel supply to a flame burner of a stove comprising the steps of: providing an actuating assembly comprising of a spring loaded wheel with gears at some part of the outer edge of its circumference, wherein each tooth on the wheel has a timing marked on it, one end of the spring fixed to the wheel and the other end to the stove, a projection on the wheel to rotate the wheel, the said wheel on a wheel sleeve mounted below a knob of the flame burner without in contact with it, the said knob through a shaft controls the amount of fuel sent the burner;
providing a timer assembly comprising of a rotatable timer shaft adapted to be rotatably coupled to the wheel through a timer shaft gear; and engaging the timer gear of the timer assembly to the wheel, wherein the wheel moves in the anti-clockwise direction to until the time set, and on completion of the time set the timer gear disengages the wheel to allow it to return to its position, wherein the projection on the wheel pushes the knob to switch-off the fuel supply.

BRIEF DESCRIPTION OF THE DRAWINGS
Fig.1 shows an embodiment of the invention mounted on the gas stove of a conventional design
Fig.2 shows the back side of an embodiment of the invention.
Fig.3 is a sectional view of an embodiment of the invention
Fig.4 is a sectional view of an embodiment of the invention
Fig.5 show a view of an embodiment of the invention.
Fig.6 shows a view of an embodiment of the invention.
Fig.7 shows a view of an embodiment of the invention in operation.
Fig.8 shows a view of an embodiment of the invention in operation.
Fig.9 shows a view of an embodiment of the invention in operation.
Fig.10 shows a view of an embodiment of the invention in operation.
Fig.11 shows a view of an embodiment of the invention in operation.
Fig.12 shows a view of an embodiment of the invention in operation.
Fig.13 shows a view of an embodiment of the invention in operation.

DETAILED DESCRIPTION OF THE INVENTION
The invention and its various embodiments is better understood by reading the description along with the accompanying drawings which appear herein for purpose of illustration only and does not limit the invention in any way.

Implementation of a turn-off switch with timer system useful for appliances using a flammable liquid or liquefied gas or compressed gas is disclosed. The disclosure uses an exemplary situation of using the invention in cooking related applications. But the applications are not limited to cooking appliances alone. The example described herein is not to be construed to limit the scope of the invention in any way.

Referring to FIG.1 and FIG.5, the system disclosed here may comprise atleast a mechanical timer, a temperature sensor and an actuator assembly. Fig.1 shows the mounting of the system on the gas stove (1) of a conventional design. The actuator assembly essentially consists of a spring loaded wheel (3) with gears (4) at some part of the outer edge of its circumference as shown in Fig.1.

Fig.2 shows the back side of the spring loaded wheel (3) (3). As can be seen in the figure, the wheel (3) is coupled to a sleeve which is called as wheel sleeve (8). The valve shaft (2) of the gas stove (100) passes through this wheel sleeve (8) but there is no coupling or drive transmission between the shaft and the sleeve. There is a bar projected on the front end of the spring loaded wheel (3) as can be seen in Fig.1 and Fig.2. With the help of this projected bar (5), user can turn the spring loaded wheel (3) in anti-clockwise direction. A torsion spring (7) is wound and coupled around the sleeve of the wheel (8). The spring can also be of other types such as spiral, conical, helical or coil spring. One end of the torsion spring (7) is attached to the wheel (3) while the other end is attached to the system mounting on the gas stove (1) as shown in Fig.2. The arrangement of the torsion spring (7) on the wheel (3) is such that it is in de-energized condition whenever the projected bar (5) is in the position as shown in Fig.1. This position of the spring loaded wheel (3) is called de-energized position. When the wheel (3) is rotated in anti-clockwise direction through projected bar (5), the coupled torsion spring (7) also gets twisted in anti-clockwise direction and gets energized. Under energized condition, the torsion spring (7) forces the wheel (3) to turn clockwise and go back to its de-energized position. As can be seen in Fig.3 and Fig.4, the stove knob (2) is mounted and coupled on the terminating end of the valve shaft (20). Whenever the knob (2) is turned ON in anti-clockwise direction, the valve shaft (20) also rotates in anti-clockwise direction to open the gas valve of the stove (100) for supply of gas to the burner. Similarly, when the knob is turned OFF in clockwise direction, the valve shaft (20) also rotates in clockwise direction thereby cutting off the gas supply to the burner.

The timer is of any conventional design which either can be of mechanical type or are made of dampers (hydraulic/pneumatic/linear/rotary). This timer contains a shaft called timer shaft (12). This timer shaft (12) rotates uniformly when the timer is counting. There is gear coupled to this timer shaft which is called as timer gear (13). The spring loaded wheel (3) gets engaged with the mechanical timer by inter-locking of teeth of gear of spring loaded wheel (3) and the teeth of timer gear (13)as shown in Fig.5.

Fig.5 also shows the arrangement of temperature sensor in the system. The temperature sensor can be an electronic type of any design available in the market. The temperature sensor can also be implemented by a mechanical/thermal element. This sensor is housed in a casing (9) just below the casing of mechanical timer as can be seen in Fig.5. There is a thermal rod (10) (made of high thermal conductivity metal) which transfers the heat of burner’s flame to temperature sensor. One end of the thermal rod (10) is connected at the input of the temperature sensor while the other end of the thermal rod (10) is arranged just over the burner so that this thermal rod (10) end comes under the flame when the LPG is lighted for flame creation. When the flame is ON, the thermal rod (10) gets heated up resulting into the increase in temperature of end which is connected to the temperature sensor. The temperature sensor senses the high temperature of the rod (10) and activates the electronic circuit to pull-in the timer shaft (12) so that the inter-locking of spring loaded wheel (3) and the timer gear (13) can happen as shown in Fig.6. The spring shaft with the gear can also be put in pull in state manually. When the flame is extinguished, the temperature of the thermal rod (10) comes down. Sensing the lowered temperature, the sensor de-activates the electronic circuit to push-out the timer shaft (12) so that the timer gear (13) cannot inter-lock with the gear of spring loaded wheel (3) as shown in Fig.7. The mechanical pull-in and push-out of timer shaft (12) can be done mechanically, electro-mechanically, magnetic or through piezoelectric principle.

For starting the timer/temperature based actuator assembly, the user first has to ensure that the timer shaft (12) along with timer gear (13) is in pull-in state as shown in Fig.6. Now, in-order to give a time-duration for cooking, the spring loaded wheel (3) is to be energized by turning it anti-clockwise with the help of a projected bar (5) on the wheel. The spring loaded wheel (3) is rotated till the teeth of gear (4) of spring loaded wheel inter-locks with the teeth of timer gear (13) as shown in Fig.8. Once interlocked, the further anti-clockwise rotation of the spring loaded wheel (3) translates into the clockwise rotation of the timer gear (13) as shown in Fig.9. The clockwise rotation of the timer gear (13) charges the mechanical timer. Once user stops the anti-clockwise rotation, the wheel starts moving in clockwise direction to its de-energized state under the influence of the coupled torsion spring (7). But this clockwise rotation of the wheel is timed because the wheel is coupled by a charged timer. This gives a time-duration for the spring loaded wheel (3) to come back to its dis-charged position.

As can be seen in Fig.10, the teeth of gear (4) of spring loaded wheel (3) is labelled with preset time in minutes (15). Therefore, the total amount of time-duration for the spring loaded wheel (3) to come back to its dis-charged position is determined by the number of teeth of gear of the wheel (4) which got engaged with timer gear (13) during the anti-clockwise rotation of the wheel. In the present design, every teeth of gear of the wheel (4) that engages with the timer gear (13) gives an additional time-duration of 2 minutes. Therefore, with 15 number of teeth of gear of the wheel (4), a maximum time- of 30 minutes and a minimum delay of 2 minutes can be achieved. This time can be varied by increasing or decreasing the number of teeth of either gear of wheel (4) or timer gear (13).

Once the spring loaded wheel (3) is charged and the time-duration is fixed, the user can switch ON the gas supply by turning the knob (2) anti-clockwise. The user can cook food in any position of flame: High, Medium or Low without disturbing the movement of the spring loaded wheel (3) (flame control). This is possible because there is no coupling between sleeve of wheel (8) and the shaft of gas stove (100). Once the spring loaded wheel (3)gets dis-engaged with the timer after the time-duration is completed, the spring loaded wheel (3) charges back to its de-energized position as depicted in Fig.11. During this charging back rotation, the projected bar (5) hits the knob projection and takes it along in clockwise direction to switch-off the gas supply as depicted in Fig.12. Hence, after the set-time is completed, the knob (2) is switched-off automatically.

The spring loaded wheel (3)can also be de-coupled with the charged timer at any time, if the flame is extinguished, through the temperature sensor as shown in Fig.7. Once de-coupled, the spring loaded wheel (3) charges back to its de-energized state thereby closing the knob (2) to OFF with the help of projected bar (5) as shown in Fig.13. Therefore, whenever the flame is extinguished, the knob (2) switches-off even if the user had set the time-duration for his/her cooking.

The disclosed invention can be designed in "Plug & Play" mode. The assembly may be independent of shaft or knob and therefore, can be mounted on any knob of gas stove of any manufacturer. Mounting of this assembly over gas stove knob is very safe and reliable as it does not interfere with any parts of the gas stove. So essentially this is more flexible system compatible to any existing knob of an oven and does not need to replace any knob altogether.

This system preset a time-duration for cooking a particular item and ensures that the supply of gas to the burner is closed automatically after the duration by switching-off the knob irrespective of the current knob position of High, Medium or Low flame. This system need not use any electronic equipment therein. It can be completely mechanical system; although one can use electronic parts as well. The system does not interfere with the LPG flow, hence, is very safe in its use. Like the available kitchen timers in the market, this system additionally produces a sound once the job is done. Unlike the conventional kitchen timers, this system also turns-off the oven knob or switch once the preset duration is over. This system enables the user to change the flame position as per his/her cooking recipe without disturbing the preset duration of the timer.

Apart from providing a time-duration, this system also provides safety to LPG based cooking by detecting LPG leak from the burner. LPG leak occurs from the stove burner when the burner’s flame goes off because of wind or liquid spill-over from the vessel while the knob is still in ON position (High, Medium or Low flame). An additional temperature sensor is attached in the system to monitor if there is a flame in the burner. In case the flame goes-off, the temperature sensor immediately actuates the assembly for turning-off of the knob regardless of the time-duration set in the timer of the system. The temperature sensor along with its associated assembly for turning-off of knob can be electromechanical in nature where the electronic energy is used for temperature sensing and mechanical energy will be used for turn-off assembly. This configuration ensures minimum electrical energy use and therefore can be powered by a battery which will last long. The sensor can also be implemented through some thermal element which ensures that the sensor along with its turn-off assembly does not require any electrical energy.

It will be obvious to a person skilled in the art that with the advance of technology, the basic idea of the invention can be implemented in a plurality of ways. The invention and its embodiments are thus not restricted to the above examples but may vary within the scope of the claims.

Further the above-described embodiments of the present invention are intended to be examples only. Alterations, modifications and variations may be effected to the particular embodiments by those of skill in the art without departing from the scope of the invention, which is defined solely by the claims appended hereto. ,CLAIMS:We Claim:

1. A device (1) for switching off fuel supply to a flame burner of a stove comprising of an actuating assembly comprising of a spring loaded wheel (3) with gears (4) at some part of the outer edge of its circumference, one end of the spring (7) fixed to the wheel (3) and the other end to the stove (100), a projection on the wheel (5) to rotate the wheel (3), the said wheel (3) on a wheel sleeve (8) mounted below a knob (2) of the flame burner without in contact with it, the said knob (2) through a shaft controls the amount of fuel sent the burner; and a timer assembly comprising of a rotatable timer shaft (12) adapted to be rotatably coupled to the wheel (3) through a timer shaft gear (13), characterised in that,
each tooth on the wheel (3) has a timing marked on it (15), and when engaged to the timer gear (13)of the timer assembly, the wheel (3) moves in the anti-clockwise direction to until the time set, and on completion of the time set the timer gear (13) disengages the wheel (3) to allow it to return to its position, wherein the projection (5) on the wheel (3) pushes the knob (2) to switch-off the fuel supply.

2. The device as claimed in claim 1 wherein the said timer shaft (12) may be further be coupled with a temperature actuator, the actuator comprising of a thermal rod (10), one end of it touching the flame, the other end to a temperature sensor, and on reaching an undesirable temperature the actuator disengages the timer shaft (12) from the wheel (3) to allow it to return to its position, wherein the projection (5) on the wheel pushes the knob (2) to switch-off the fuel supply.

3. The device as claimed in claim 1 or 2, wherein the said fuel may be flammable liquid or liquefied gas or compressed gas, or their combinations thereof.

4. The device as claimed in claim 1, 2 or 3 wherein the said timer may be mechanical or made of dampers.

5. A method of switching off fuel supply to a flame burner of a stove comprising the steps of:
providing an actuating assembly comprising of a spring loaded wheel (3) with gears (4) at some part of the outer edge of its circumference, wherein each tooth on the wheel (3) has a timing marked on it (15), one end of the spring (7) fixed to the wheel (3) and the other end to the stove (100), a projection (5) on the wheel (3) to rotate the wheel (3), the said wheel (3) on a wheel sleeve (8) mounted below a knob (2) of the flame burner without in contact with it, the said knob (2) through a shaft (20) controls the amount of fuel sent the burner;
providing a timer assembly comprising of a rotatable timer shaft (12) adapted to be rotatably coupled to the wheel through a timer shaft gear (13); and
engaging the timer gear (13) of the timer assembly to the wheel (3), wherein the wheel (3) moves in the anti-clockwise direction to until the time set, and on completion of the time set the timer gear (13) disengages the wheel (3) to allow it to return to its position, wherein the projection (5) on the wheel (3) pushes the knob (2) to switch-off the fuel supply.

6. The method as claimed in claim 5, wherein the said fuel may be flammable liquid or liquefied gas or compressed gas, or their combinations thereof.

7. The method as claimed in claim 5 or 6 wherein the said timer may be mechanical or made of dampers.