DESC:
FIELD OF INVENTION

[0001] The present invention is directed to safety knob for gas cooktops, and more particularly to an improved safety knob having better reliability, enhanced operational life and quick assembly on the gas cooktops.

BACKGROUND OF INVENTION

[0002] Hydrocarbon gases such as Natural Gas or Liquefied Petroleum Gas (LPG) have been a popular fuel for domestic cooking in majority countries of the world. Safety in appliances such as gas cooktops are of paramount importance since the hydrocarbon gases are highly flammable. In many countries especially in South Asia, South-East Asia, Africa etc., the gas cooktops used in domestic cooking is highly unsafe. Many incidents have been reported in countries like India where fire accidents involving domestic cooking happen because of the unsafe cooking practices.
[0003] Many times, it happens that the user switches the knob to “On” position of the Gas Cooktop and forgets to ignite the gas coming through the burner of the Gas Cooktop. This becomes a source of gas leaking through the burner. This is a hazardous situation where gas starts filling up the surroundings and becomes a potential source for explosion.
[0004] It might also happen that the flame over the burner gets extinguished by the sudden gush of wind or by food spill-over while the knob is still in “On” position. This again becomes a potential source of gas leak through the burner and can lead to explosion. In the background of foregoing limitations, and to avoid such hazardous situations, it becomes important that gas cooktops should be enabled with safety technology to detect the gas leak through the burner and immediately cut-off the gas supply to the burner.
OBJECT OF THE INVENTION

[0005] The primary object of the present disclosure is to provide a safety knob for gas cooktop that has better reliability, increased operational life and quick assembly on gas cooktop, capable of automatically cutting-off the gas supply to the burner in any hazardous situation.
[0006] Another object of this disclosure is to provide a safety knob for gas cooktop that is capable of sensing the absence of flame on the burner so that it can be switched off in case of any unsafe event.
[0007] Yet another object of the disclosure is to provide a safety knob that can be retrofitted to any gas cooktop.
[0008] Yet other object of the present disclosure is to provide a safety knob that can control existing gas supply valve to the burner, which renders the entire apparatus inherently safe in its operation.
[0009] In yet another embodiment, the disclosure provides a simple, albeit a sophisticated safety knob that does not require any electric power in form of battery or from any external source for its operation.
[0010] In yet another embodiment of present system, a cost effective and scalable safety knob is provided that can be produced in bulk.
[0011] These and other objects will become apparent from the ensuing description of the present invention.

SUMMARY OF THE INVENTION

[0012] In accordance with one significant aspect of resent disclosure, a gas cooktop with a safety knob is provided. The safety knob comprises of a first unit and a second unit. The first unit provided at front side of the gas cooktop, consisting of: a first support structure, a wheel comprising of a latching projection, a hitting bar and spring holding bar. Further, the safety knob comprising a knob having knob projection configured to engage with the hitting bar of the wheel and cause the wheel to rotate along therewith when rotated in a first anticlockwise direction to ignite a flame in on position.

[0013] The first unit further includes a circular spring placed between the support structure and the wheel, wherein the circular spring has a stationary first end connected to the support structure, and a second end mounted on the wheel configured to rotate along with the wheel and store potential energy in the first anticlockwise direction. Next, a lever assembly is hinged to the support structure and tunneled through a cut section of the support structure and a cut section of the gas cooktop.

[0014] Now, a second unit is provided at back side of the gas cooktop, which consists of a second support structure; a solenoid comprising a solenoid coil and a spring-loaded metallic cylinder; and a thermocouple wire electrically connected with the solenoid, and having a thermocouple sensing tip configured to sense the flame when ignited and generate electric potential such that an electric current flows through the solenoid coil and attracts the metallic cylinder.
BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figs. 1(a) and 1(b) illustrate assembly of first unit and a second unit on gas cooktop, in accordance with one preferred embodiment of present disclosure.
[0016] Figs. 2(a) and 2(b) show arrangement of first unit components of gas cooktop, in accordance with one preferred embodiment of present disclosure.
[0017] Fig. 3 shows arrangement of second unit components of gas cooktop, in accordance with one preferred embodiment of present disclosure.
[0018] Fig. 4 shows the support structure of first unit, in accordance with one preferred embodiment of present disclosure.
[0019] Figs. 5(a) and 5(b) show structure of wheel, in accordance with one preferred embodiment of present disclosure.
[0020] Fig. 6 shows exploded view of circular spring, in accordance with one preferred embodiment of present disclosure.
[0021] Fig. 7, Fig. 7(a) and Fig. 7(b) shows circular spring as connected to support structure, in accordance with one preferred embodiment of present disclosure.
[0022] Figs. 8(a) 8(b) and 8(c) show lever and spring loaded claw; lever hinged to support structure; and lever connected with spring loaded claw respectively in accordance with one preferred embodiment of present disclosure.
[0023] Figs. 9(a), 9(b) and Fig. 9(c) show circular spring placed on support structure; circular spring mounted on spring holding bar of wheel; circlip to hold wheel, respectively, in accordance with one preferred embodiment of present disclosure.
[0024] Figs. 10(a)-10(g) show lever coupled with support structure and spring loaded claw and positioned on gas cooktop; and Figs. 10(h) - 10(j) show stem of gas supply valve along with knob positioned over the valve, respectively, in accordance with one preferred embodiment of present disclosure.
[0025] Figs. 11(a)-11(g) show second unit provided on gas cooktop, in accordance with one preferred embodiment of present disclosure.
[0026] Figs. 12(a) and 12(b) show first unit and second unit positioned on front and back side of the gas cooktop, in accordance with one preferred embodiment of present disclosure.
[0027] Fig. 13 shows claw engaging with the latching projection with wheel rotation, in accordance with one preferred embodiment of present disclosure.
[0028] Figs. 14(a) and 14(b) show energizing and de-energizing of linear spring, respectively, as claw engages with the latching projection, in accordance with one preferred embodiment of present disclosure.
[0029] Fig. 15 shows knob direction for flame ignition, in accordance with one preferred embodiment of present disclosure.
[0030] Figs. 16(a) -16(c) show anticlockwise rotation of knob and engagement of knob with wheel to energize circular spring, in accordance with one preferred embodiment of present disclosure.
[0031] Figs. 17(a)-17(c) show thermocouple sensing with generation of electric potential and attracted position of metallic cylinder, in accordance with one preferred embodiment of present disclosure.
[0032] Fig. 18 shows knob position in anticlockwise direction, in accordance with one preferred embodiment of present disclosure.
[0033] Fig. 19 shows knob position at low-flame position, in accordance with one preferred embodiment of present disclosure.
[0034] Figs. 20(a) and 20(b) show free rotation of knob as wheel is held by claw at low flame position, in accordance with one preferred embodiment of present disclosure.
[0035] Figs. 21(a)-21(e) and Fig. 22 show functioning of safety knob, when the flame is extinguished, in accordance with one preferred embodiment of present disclosure.
[0036] Figs. 23(a) and 23(b) show example scenario where closing force of circular spring is increased, in accordance with one preferred embodiment of present disclosure.
[0037] Fig. 24 shows example scenario where proximity is seen for spring holding bar and ratchet teeth with respect to each other, in accordance with one preferred embodiment of present disclosure.
[0038] Fig. 25 shows preferable distance between center of wheel to latching projection and spring holding bar, in accordance with one preferred embodiment of present disclosure.
[0039] Fig. 26 shows design of present safety knob and other components in an event of the increased circular spring force, in accordance with one preferred embodiment of present disclosure.
DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] It has to be understood and acknowledged for this specification and claims, that the term “safety knob” refers, though not limiting, only to depicted full assembly of safety knob for gas cooktops or gas stoves that is provided with a whole host of other components and support structure, but can be extended to accommodate other obvious alterations to the disclosed apparatus/system.
[0041] Before the present design and configuration of safety knob for gas cooktop is described, it is to be understood that this disclosure is not limited to the particular system, as described, since it may vary within the specification indicated. It is also to be understood that the terminology used in the description is for describing the particular versions or embodiments only and is not intended to limit the scope of the present invention, which will be limited only by the appended claims. The words "comprising," "having," "containing," and "including," and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. The disclosed embodiments are merely exemplary methods of the invention, which may be embodied in various forms.
[0042] Broadly, in accordance with one general embodiment of present disclosure, full assembly of safety knob attached to the gas cooktop 55 is described. The “Safety Knob” 30 is designed in a modular way and comprises of unit-1 and unit-2. The modular design enables quick assembly of “Safety Knob” 30 on the gas cooktop 55 as explained: Unit-1 and Unit-2 are manufactured and assembled separately and brought at the gas-cooktop-factory-assembly-line where both units (Unit-1 and Unit-2) are quickly assembled on the gas cooktop 55 by the assembly operators. This method of modular manufacturing and assembly saves lot of assembly time which helps in bulk production.
[0043] As already described, “Safety Knob” 30 is divided into two units: Unit-1 and Unit-2. Fig. 1(a) and Fig. 1(b) show the assembly of Unit-1 and Unit-2 on the gas cooktop 55. Precisely, Unit-1 comprises of “Support Structure -10”, “Wheel” 20, “Knob” 31, “Circular Spring” 40 and “Lever Assembly” 60 (will be shown in subsequent Figs.). Now, Fig. 2(a) and Fig. 2(b) shows the arrangement of “Support Structure-1” 10, “Wheel” 20, and “Lever Assembly” 60 of Unit-1. Unit-2 comprises of “Support Structure” 50, “Solenoid” 70 and “Thermocouple” 75 as shown in Fig.3.
[0044] Unit-1 consists of five components: “Support Structure” 10, “Wheel” 20, “Circular Spring” 40, “Knob” 31 and “Lever Assembly” 60. Fig.4 shows the “Support Structure” 10 which is fixed on the front side of the Gas Cooktop frame 55 through screw and bolts. There is a cut-section in the “Support Structure” 10 which is aligned with the cut-section of gas cooktop frame 55 (the “Lever Assembly” 60 tunnels through these cut-sections). There is also a hole in the “Support Structure” 10. The stem of the gas supply valve 25 of the Gas Cooktops 55 passes through this hole.
[0045] The structure of the “Wheel” 20 is shown in Fig.5 (a) & (b). There are two “Latching-Projections” 45(a) and 45(b), (collectively referred by numeral 45) on the outer circumference of the “Wheel” 20. Also, there is a “Hitting Bar” 46 on the “Wheel” 20 as shown in Fig. 5(a). The “Wheel” 20 also has a hole at its center through which the stem of the gas supply valve 25 of the gas cooktop 55 passes. Further, there is a “Spring-Holding-Bar” 47 on the other side of the “Wheel” 20 for holding one end of the “Circular Spring” 40 as shown in Fig. 5(b).There is also a back projection 21 of the “Wheel” 20 with the groove 22 in it. Furthermore, the circular spring 40 is placed between “Wheel” 20 and the “Support Structure” 10.
[0046] Fig.6 shows the exploded view of the “Circular Spring” 40 between the “Wheel” 20 and the “Support Structure” 10. “Circular Spring” 40 rests inside the groove of the “Support Structure” 10 as shown in Fig.7 (a). One end 40(a) of the “Circular Spring” 40 is connected to the “Support Structure” 10 as depicted in Fig. 7(a). The other end 40(b) of the “Circular Spring” 40 is mounted on the “Spring-Holding-Bar” 47 of the “Wheel” 20 as can be seen in Fig. 7(b). This end 40(b) of the “Circular Spring” 40, which is mounted on the “Spring-Holding-Bar” 47 of the “Wheel” 20, rotates along with the rotation of the “Wheel” 20.
[0047] The end 40(a) of the “Circular Spring” 40 which is connected to the “Support Structure” 10 remains stationary and does not move with the rotation of the “Wheel” 20. This arrangement of the “Circular Spring” 40 on the “Wheel” 20 and the “Support Structure” 10 ensures that whenever the “Wheel” 20 is rotated (in anti-clockwise direction) as shown in Fig.7(c), the “Circular Spring” 40 is twisted and stores potential energy. In this energized state of the “Circular Spring” 40, the “Wheel” 20 has the tendency to turn clockwise (rotational direction reference: seeing the front side of the gas cooktop frame) as the “Circular Spring” 40 tries to un-wind.
[0048] The “Lever Assembly” 60 incorporates Lever 60a and spring-loaded Claw 64 as shown in Fig. 8(a). Lever 60a is hinged at one point 61 (a) of the “Support Structure” 10 through dowel-pin 60b as shown in Fig. 8(b). Instead of dowel-pin, a screw/bolt can also be used. One end of the Lever 60a incorporates spring-loaded Claw 64, shown in Fig. 8(c). The spring-loaded claw 64 is hinged at one point 64(a) on the Lever 60a.
[0049] In next working embodiment, method of assembly of unit 1 on frame of gas cooktop 55, is disclosed. “Circular Spring” 40 is first placed on the “Support Structure” 10 with one end 40(a) of the “Circular Spring” 40 connected to the “Support Structure” 10 as shown in Fig.9(a). A rubber stopper 10a is also installed on “Support Structure” 10. The stopper 10a can also be of other material such as plastic etc. The use of rubber stopper will be explained later. After this, the “Wheel” 20 is placed by inserting the back projection 21 of wheel 20 inside the hole of the “Support Structure” 10 and in the same process the other end 40(b) of the “Circular Spring” 40 mounts on the “Spring-Holding-Bar” 47 as shown in Fig. 9(b).
[0050] After this placement, a circlip 48 is inserted on the groove of the back projection 21 of wheel 20 as shown in Fig.9(c). The circlip 48 purpose is to hold the “Wheel” 20 on the “Support Structure” 10 and to provide stability to the “Wheel” 20 during “Wheel” rotation. After the “wheel” 20 is assembled, the “Lever Assembly” 60 is to be hinged on the “Support Structure” 10.
[0051] The lever 60a has got three holes: hole-1, hole-2 and hole-3 and claw 64 has two holes: hole-1 and hole-2 as can be seen in Fig. 10(a). Claw 64 is hinged to lever 60a by a pin, snap-fitted to hole-1 of claw 64 and hole-1 of lever 60a. This hinge position is referred as point 64 (a). A linear spring 65 is snap fitted to hole-2 of claw 64 at one of its end. The other end of the linear spring 65 is snap fitted to hole-3 of the lever 60a by a pin as shown in Fig. 10(b). After assembling the spring loaded claw 64 to lever 60a, the lever 60a is hinged to “Support Structure” 10. The “Support Structure” 10 has a hole (referred to as point 61(a)). Lever 60a is placed inside the cut-section of “Support Structure” 10 in such a way that the hole-2 of Lever 60a is aligned to hole at point 61(a) of “Support Structure” 10 as can be seen in Fig.10(c). After this, dowel-pin 60b is inserted through hole-2 and point 61(a) to hinge lever 60a to “Support Structure” 10 as seen in Fig. 10(d).
[0052] After the “Lever Assembly” 60 is hinged to “Support Structure” 10, the “Support Structure” 10 is mounted on the gas cooktop frame 55 through screw and bolts. It is to be noted that the mounting/fixing of the “Support Structure” 10 on the gas cooktop frame 55 can be done differently from screw and bolt. There is a cut-section in frame 55. The mounting is done in such a way that the cut-section of “Support Structure” 10 and frame 55 are aligned and the lever assembly is tunneled through the cut-sections of “Support Structure” 10 and gas cooktop frame 55 as shown in Fig. 10(e).
[0053] The stem of the gas supply valve 25 of the Gas Cooktop 55 passes through the holes of the “Support Structure” 10 and the “Wheel” 20 as shown in Fig. 10(f) and 10(g). Fig.10 (h), (i) and (j) shows the “Knob” 31 placed over the stem of the gas supply valve 25 of the gas cooktop 55. There is a projection below the “Knob” 31 known as “Knob Projection” 32, shown in Fig. 10(j).
[0054] In next embodiment, component details of unit 2 are discussed. There are three components in Unit-2: “Support Structure” 50, “Solenoid” 70 and “Thermocouple” 75. All the components of the Unit-2 are present at the back side of the gas cooktop frame 55. “Solenoid” 70 further comprises of Solenoid coil 74 and spring-loaded metallic-cylinder 62. “Solenoid” 70 along with “Thermocouple” 75 is connected to the “Support Structure” 50 as shown in Fig. 11(a). After connecting “Solenoid” 70 and “Thermocouple” 75 to “Support Structure” 50, the “Support Structure” 50 is screwed to the back side of the gas cooktop frame 55 as shown in Fig. 11(b). There is a cut-section in the “Support Structure” 50 (ref. Fig. 11(a)) which is aligned with the cut-section of gas cooktop frame 55 as seen in Fig. 11(b).
[0055] As seen in Fig. 11(c) and 11(d), one side of the “Solenoid” 70 is having the solenoid coil 74 and the other side is electrically connected to the thermocouple wire 75. The sensing tip 75(a) of the thermocouple 75 is placed just above the burner 15 as can be seen in Fig. 11(e). Metallic-cylinder 62 is placed above the solenoid-coil 74. The metallic-cylinder 62 is loaded by a linear spring 62(a). The spring loaded metallic-cylinder 62 is placed inside a cap 62(b). Cap 62(b) is snap-fitted to “Solenoid” 70. Cap 62(b) can be of any material hard or soft like plastic/metal or flexible-rubber. The purpose of cap 62(b) is to physically support the spring loaded metallic-cylinder 62. The full assembly of the spring loaded metallic-cylinder 62 inside the cap 62(b) is shown in Fig. 11(f) (It is to be noted that Cap 62(b) is shown in Fig. 11(f) as translucent cover to make spring loaded metallic-cylinder 62 visible which is placed inside Cap 62(b)).
[0056] After both Unit-1 and Unit-2 are screwed to the gas cooktop frame 55, one end of the lever 60a is connected to the spring loaded metallic-cylinder 62 as shown in Fig. 12(a). As the lever 60a tunnels through the cut-sections of the “Support Structure” 10, “Support Structure” 20 and gas cooktop frame 55, one end of the “Lever Assembly” 60 (which is having the claw 64) accesses the front side of the gas cooktop frame 55 and the other end of the “Lever Assembly” 60 (which is connected to spring loaded metallic cylinder 62) accesses the back side of the frame 55 as can be seen in Fig. 12(a) &(b).
[0057] The claw 64 engages with the “Latching-Projection” 45 of the “Wheel” 20. Now, whenever the “Wheel” 20 is rotated in anticlockwise direction as shown in Fig.13, the “Latching-Projection” 45 of the “Wheel” 20 comes in contact with the spring-loaded Claw 64. The spring-loaded claw 64 functions in such a way that it allows the “Latching-Projection” 45 of the “Wheel” 20 to pass through it when the direction of rotation of the wheel 20 is as shown in Fig.13 (i.e. anti-clockwise, direction reference: as seen at the front side of frame 55). This is because the “Latching-Projection” 45 of the “Wheel” 20 presses the Claw 64 (during rotation of the Wheel) and the Claw 64 moves about the hinge point 64(a) of the claw 64 on the Lever 60a as shown in Fig. 14(a).
[0058] During this pressing of the Claw 64 the linear spring 65 (at the Claw end) elongates and gets energized. Once the “Latching-Projection” 45 passes the Claw 64 (as the Wheel continues to rotate), the linear spring 65 de-energizes to pull back the Claw 64 to its original position as shown in Fig.14(b).
[0059] Next working embodiment discusses operation of the safety knob 31. To ignite flame, the user turns the “Knob” 31 in anti-clockwise direction (rotational direction reference: seeing the front side of the gas cooktop frame) from “Off” position to “On” position as shown in Fig.15. During this anti-clockwise rotation of the knob 31, the “Knob Projection” 32 engages with “Hitting Bar” 46 of the “Wheel” 20 and therefore the “Wheel” 20 also gets rotated along with the “Knob” 31 in anti-clockwise direction (rotational direction reference: seeing the front side of the gas cooktop frame) as seen in Fig.16(a). In this rotation of the “Wheel” 20, first “Latching-Projection” (45(a)) passes the Claw 64. During this rotation of the “Wheel” 20, the “Circular Spring” 40 gets twisted and stores potential energy as shown in Fig. 16(b).
[0060] Once energized, the “Circular Spring” 40 tries to un-wind and applies force on the Spring-Holding-Bar 47 of the “Wheel” 20, thus trying to rotate the “Wheel” 20 in clockwise direction (rotational direction reference: seeing the first/front side of the gas cooktop frame). Thus, the “Latching-Projection” 45 of the “Wheel” 20, under the influence of energized “Circular Spring” 40, gives a force to Claw 64 in the direction as shown in Fig.16(c). Once the “Knob” 31 is at “On” position, the user holds the “Knob” 31 in that position and tries to ignite the flame. If the user leaves the “Knob” 31 before flame is ignited, the “Circular Spring” 40 will un-wind and the “Wheel” 20 will rotate clockwise(rotational direction reference: seeing the front side of the gas cooktop frame) and push the “Knob” 31 to “Off” position. The mechanism of pushing the “Knob” 31 to “off” position by the “Wheel” 20 (while “Wheel” 20 is rotating clockwise) is explained later.
[0061] Once the flame is ignited, thermocouple sensing tip 75(a) senses high temperature and thus small electric potential is generated at the terminal of “Solenoid” 70 where the thermocouple wire 75 is connected. This electric potential is generated due to the law of thermocouple principle. Due to the generated potential, a small electric current flow through the solenoid coil 74 making the solenoid coil as an electromagnet. This solenoid coil 74 attracts the Metallic-Cylinder 62 (which is connected to one end of the Lever 60a) due to the magnetic effect of the electromagnet coil of the solenoid 70. Once attracted, the position of the “Lever Assembly” 60 is as shown in Fig. 17(a).
[0062] In this attracted position of the “Lever Assembly” 60, the Lever 60a does not move and the Claw 64 of the Lever 60a latches the first “Latching-Projection” 45(a) of the “Wheel” 20 and thus holds the “Wheel” 20 as can be seen in Fig.17(b). The “Wheel” 20, which has a tendency to rotate clockwise (rotational direction reference: seeing the front side of the gas cooktop frame 55) under the influence of the energized “Circular Spring” 40 gets held by the Claw 64 because of the following reason: When the “Wheel” 20 is under the influence of energized “Circular Spring” 40, the Lever 60a is under a clockwise-torque about its hinged point 61(a), due to the force exerted by the first “Latching-Projection” 45(a) of the “Wheel” 20 on to the Claw 64 of the Lever 60a as can be seen in Fig.17(c).
[0063] This torque is counter-balanced by another anti-clockwise-torque on the Lever 60a about its hinged point 61(a) produced by the magnetic force of the solenoid coil 74 on the Metallic-Cylinder 62. Hence, the resultant torque on the lever (60) is nil and the lever remains stationary. Thus, the claw 64 of the stationary lever 60 latches the first “Latching-Projection” 45(a) and holds the “Wheel” 20.
[0064] Once the first “Latching-Projection” 45(a) of the “Wheel” 20 gets latched, the user can leave the “Knob” 31 and can cook the food at High-Flame position. It is to be noted that the latching of the “Latching-Projection” 45 of the wheel 20 happens very quickly (within few seconds) after the flame is ignited because the response time of the thermocouple 75 and the solenoid 70 is very quick. Therefore, the user does not have to wait for long for the latching of the “Latching-Projection” 45 of the “Wheel” 20 and can leave the “Knob” 31 within few seconds after the flame is ignited.
[0065] During cooking, user can rotate the “Knob” 31 in anti-clockwise direction (rotational direction reference: seeing the front side of the gas cooktop frame 55) from high-flame position to low-flame position as shown in Fig.18. During this anti-clockwise rotation of the knob 31, the “Knob Projection” 32 engages with “Hitting Bar” 46 of the “Wheel” 20 and therefore the “Wheel” 20 also gets rotated along with the “Knob” 31 in anti-clockwise direction (rotational direction reference: seeing the front side of the gas cooktop frame 55) as seen in Fig.16(a).
[0066] At low-flame position of the “Knob” 31, second “Latching-Projection” 45(b) of the “Wheel” 20 passes the Claw 64 of the Lever 60a. Once, the Claw 64 of the Lever 60a passes second “Latching-Projection” 45(b) of the “Wheel” 20, it latches the second “Latching-Projection” 45(b) of the “Wheel” 20 and thus holds the “Wheel” 20 due to the attracted position of the lever 60a as shown in Fig. 19.
[0067] The reason for the second “Latching-Projection” 45(b) to get held by Claw 64 is already explained in Fig.17 (a),(b),(c). Once the “Wheel” 20 is held at the low-flame position of the “Knob” 31, the user can freely rotate the “Knob” 31 from Low-Flame to High-Flame or from High-Flame to Low-Flame. This free rotation of the “Knob” 31 is ensured because the “Knob Projection” 32 of the “Knob” 31 does not engage the “Hitting Bar” 46 of the “Wheel” 20 once the “Wheel” 20 is held by the Claw 64 at the low-flame position of the “Knob” 31 as shown in Fig. 20(a)&(b).
[0068] In next working embodiment, the mechanism of closing of knob 31 when the flame of the burner is extinguished, is discussed. During the course of cooking, when the flame on the burner gets extinguished due to wind or food spill over, the “Knob” 31 immediately rotates to “Off” position. This is explained as follows:
[0069] When the flame gets extinguished, the thermocouple sensing tip 75(a) senses a low temperature and thus there is no electric potential at the terminal of “Solenoid” 70. Due to lack of electric potential, no electric current flows through the solenoid coil 74 and therefore the electromagnetic effect of the solenoid ceases. Hence, there is no magnetic force on the metallic cylinder 62. Therefore, the claw 64 of lever 60a is experiencing just one force which is exerted by the “Latching-Projection” 45 of the “Wheel” 20 as the “Wheel” 20 is under influence of energized “Circular Spring” 40. This force produces a clockwise torque on the lever 60a about its hinged point 61(a) as shown in Fig. 21(a). Under this clockwise torque, the lever 60a rotates about its hinged point 61(a) and the claw 64 moves away to de-latch the “Latching-Projection” 45 of the “Wheel” 20 and hence releases the “Wheel” 20 as shown in Fig.21 (b).
[0070] This movement of the lever 60a also moves the spring(62(a))-loaded Metallic-Cylinder 62 within the Cap 62(b) thereby compressing the spring 62(a) as shown in Fig.21(c). Due to this compression, the linear spring 62(a) energizes and stores potential energy. As can be seen in Fig. 21(d), once the “Wheel” 20 is fully released, the energized linear spring 62(a) releases its stored potential energy and de-compresses, thereby pushing the Metallic-Cylinder 62 towards the solenoid coil 74. This in turn pulls back the lever 60a to its original position. After the “Wheel” 20 is fully released, it rotates clockwise (rotational direction reference: seeing the front side of the gas cooktop frame 55) as the “Circular Spring” 40 un-winds. During this clockwise rotation of the “Wheel” 20, the “Hitting Bar” 46 of the “Wheel” 20 engages the “Knob Projection” 32 and turns the “Knob” 31 clockwise towards “Off” position as shown in Fig. 21(d). During this clockwise rotation of the wheel, the “wheel” 20 gets stopped by the rubber stopper 10a and thus the “knob” 31 stops at off position as shown in Fig.21(e) and Fig.22.
[0071] Now, in other working embodiment of present disclosure, closing of the knob 31 when the flame on the burner is not ignited, is discussed. Consider the case when the user rotates the “Knob” 31 to “On” position and forgets to ignite the flame. In the absence of flame, there is no electromagnetic force at the solenoid coil 74 and thus the Claw 64 cannot hold the “Wheel” 20 at the “Latching-Projections” 45. If the user leaves the “Knob” 31 at this position (without flame ignition), the “Wheel” 20 will turn clockwise (rotational direction reference: seeing the front side of the gas cooktop frame) and will push the lever 60a away (as shown in Fig. 21(b)) due to the un-winding of the “Circular Spring” 40. During this clockwise rotation of the “Wheel” 20, the “Hitting Bar” 46 of the “Wheel” 20 engages the “Knob Projection” 32 and turns the “Knob” 31 clockwise to “Off” position as shown in Fig. 21(d), Fig. 21(e) and Fig. 22.
[0072] In one advantageous embodiment of present disclosure, the safety knob 30 has a better reliability and more operational life if it keeps on performing its desired operation (i.e. to cut-off the gas supply to the burner whenever burner experiences flame-failure) without fail for as long as possible. Generally, the gas supply valve of the gas cooktops 55 will become tighter to rotate because of increase in friction as it ages. For better reliability and operational life, the safety knob 30 should be able to close the gas supply valve even if the tightness is increased during its operational lifetime. Hence, if the closing force of the “Circular Spring” 40 is increased, the reliability and the operational life of Safety Knob 30 will also be higher since the higher closing force of the “Circular Spring” 40 can overcome the increased friction of the gas supply valve due to age related tightness. Therefore, it is better if the “Circular Spring” 40 has higher closing force.
[0073] However, in contemporary art (refer Fig. 23(a)), there are issues if the closing force of “Circular Spring” 40 is increased (for better reliability and operational life). With increased closing force of “Circular Spring” 40, the claw 64 of the lever 60 will not be able to hold the “Wheel” 20 even in the presence of the electromagnetic force at the metallic-cylinder 62 of the Lever 60. Thus, even if the flame is present on the burner, the “Wheel” 20 will always turn the “Knob” 31 clockwise (rotational direction reference: seeing the front side of the gas cooktop frame) to “Off” position and the user will not be able to cook the food. Following is the reason for this.
[0074] The “Spring-Holding-Bar” 47 (“Spring-Holding-Bar” 47 is the point on the “Wheel” 20 where moving end of “Circular Spring” 40 is mounted and hence 47 experiences all the force of “Circular Spring” 40) and the “Ratchet Teeth” 80 (“Ratchet Teeth” 80 is the point on the “Wheel” 20 where Claw 64 of the Lever latches the “Wheel” 20) are located very close to each other. Due to the close proximity of “Spring-Holding-Bar” 47 and “Ratchet Teeth” 80, both locations experience the same amount of force when the “Wheel” 20 is under the influence of energized “Circular Spring” 40. Therefore, un-winding of energized “Circular Spring” 40 of higher force will result into higher force on the “Spring-Holding-bar” 47 as well as the “Ratchet Teeth” 80 of the “Wheel” 20. Hence, the Claw 64 of the Lever 60 experiences higher force from the “Ratchet Teeth” 80 when the Claw 64 tries to hold (through latching) the “Wheel” 20, where the “Wheel” 20 is trying to rotate under the influence of higher force “Circular Spring” 40, as shown in Fig.23 (b).
[0075] This increased force on the Claw 64 of the Lever 60 results into an increased clockwise torque experienced by the Lever 60 (about its hinged point) as shown in Fig.24. When the flame is ignited, solenoid coil 74 generates a magnetic force which is exerted on the Metallic-Cylinder 62 of the Lever 60. This magnetic force produces an anti-clockwise torque on the Lever (about its hinged point) as can be seen in Fig.24. This anti-clockwise torque tries to balance the clockwise torque but is unable to balance as the clockwise torque is much higher because of the increased force seen by the Claw 64 from the “Wheel” 20. Thus, due to this increased clockwise torque, the Claw 64 of the Lever 60 moves away to de-latch the “Ratchet Teeth” 80 as shown in Fig.24. Due to this Lever movement, the “Wheel” 20 gets released and closes the “Knob” 31 to “Off” position despite the presence of electromagnetic force at the solenoid coil 74.
[0076] In the present design, the Claw 64 holds the “Wheel” 20 by latching at the “Latching-Projection” 45 which is present at the outer circumference of the “Wheel” 20. Thus, even with the increased force of “Circular Spring” 40 applied at the “Spring-Holding-Bar” 47, the force experienced by the Claw 64 at “Latching-Projection” 45 of the “Wheel” 20 is much less. This is because of the following reason: Refer Fig.25, the distance of “Latching-Projection” 45 from the center of the “Wheel” (d1) is greater than the distance of “Spring-Holding-Bar” 47 from the center of the “Wheel” (d2). Therefore as every point in the “Wheel” 20 experiences the same torque (under the influence of energized “Circular Spring” 40), the force at the “Latching-Projection”(f1) is less than the force at the “Spring-Holding-Bar” (f2) since, f1=(f2×d2)÷d1.
[0077] Therefore, even with increased “Circular Spring” 40 force, the clockwise torque on the Lever 60a (produced by force on the Claw 64 by the “Latching-Projection” 45) is much less and is easily counter-balanced by the anti-clockwise torque on the Lever 60a (produced by the magnetic force on the Metallic-Cylinder 62) as shown in Fig.26. Hence, once the flame is ignited, the user can freely rotate the “Knob” 31 for cooking since the Claw 64 can hold the “Wheel” 20 even if higher force “Circular Spring” 40 is used. Thus, in this new design, scope of using higher force “Circular Spring” 40 increases the reliability and operational life of the technology.
[0078] In the present design, the assembly of the safety knob 30 on the gas cooktop frame 55 is done in a modular way (Unit-1 and Unit-2 are manufactured and assembled separately and then both units are screwed to gas cooktop 55 in the gas cooktop assembly line). This modular way of assembly reduces the assembly time and ensures increased bulk production which further reduces per-unit -production-cost. The details of assembly of “Safety Knob” 30 is already explained.
[0079] Also in the present design, majority of the components (such as “Support Structure” 50, “Solenoid” 70, “thermocouple” 75 etc.) are behind the frame of the gas cooktops 55. This makes the front side of the safety knob 30 (which is visible to the user) smaller and hence the user-friendly experience to operate the safety knob 30 as well as the aesthetics of the safety knob increases.
[0080] The foregoing description is a specific embodiment of the present disclosure. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.
,CLAIMS:We Claim:

1) A safety knob (30), comprising:
a first unit provided at front side of the gas cooktop (55), consisting of:
a first support structure (10),
a wheel (20) comprising of a latching projection (45), a hitting bar (46) and spring holding bar (47);
a knob (31) comprising a knob projection (32) configured to engage with the hitting bar (46) of the wheel (20) and cause the wheel (20) to rotate along therewith when rotated in a first anticlockwise direction to ignite a flame in on position;
a circular spring (40) placed between the support structure (10) and the wheel (20), wherein the circular spring (40) has a stationary first end (40(a)) connected to the support structure (10), and a second end (40(b)) mounted on the wheel (20) configured to rotate along with the wheel (20) and store potential energy in the first anticlockwise direction;
a lever assembly (60) hinged to the support structure (10) and tunneled through a cut section of the support structure (10) and a cut section of the gas cooktop (55).
a second unit provided at back side of the gas cooktop (55), consisting of:
a second support structure (50);
a solenoid (70) comprising a solenoid coil (74) and a spring-loaded metallic cylinder (62); and
a thermocouple wire (75) electrically connected with the solenoid (70), and having a thermocouple sensing tip (75a) configured to sense the flame when ignited and generate electric potential such that an electric current flows through the solenoid coil (74) and attracts the metallic cylinder (62).

2) The safety knob (30), as claimed in claim 1, wherein the wheel (20) further comprises of:
the hitting bar (46) configured to engage with the knob projection (32) in the event of wheel rotation in the first anticlockwise direction;
the spring holding bar (47) configured to hold the second end of the circular spring (40).
3) The safety knob (30), as claimed in claim 2, wherein the circular spring (40) upon storing the potential energy gets energized, and unwind to apply force on the spring holding bar (47) to rotate the wheel (20) in a second clockwise direction.

4) The safety knob (30), as claimed in claim 1, wherein the wheel (20) is held onto the support structure (10) via a circlip (48) that facilitates in providing stability to the wheel (20) during rotation.

5) The safety knob (30), as claimed in claim 1, wherein the lever assembly (60) comprises of:
a lever (60a) having hole-1, hole-2 and hole-3;
a spring-loaded claw (64) comprising hole-1 and hole -2, wherein claw (64) is hinged to the lever (60a) via snap fitting of the hole-1 of the lever (60a) with the hole-1 of the claw (64), and hole-3 of the lever (60a) is connected with the hole-2 of the claw (64) via a linear spring (65).
6) The safety knob (30), as claimed in claim 5, wherein one end of the lever (60a) is connected to the spring loaded metallic cylinder (62) to access the back side of the gas cooktop (55) and other end of the lever (60a) is connected to the spring loaded claw (64) to access the front side of the gas cooktop (55).

7) The safety knob (30), as claimed in claim 5, wherein the spring loaded claw (64) is configured to engage with the latching projection (45) of the wheel (20) in an event the wheel (20) is rotated in the first anticlockwise direction, and wherein the spring loaded claw (64) gets pressed when engaged with the wheel (20) and the linear spring (65) is energized.

8) The safety knob (30), as claimed in claim 1, wherein in an event the knob (31) is in “on” position with no ignition, the circular spring (40) unwinds and applies force on the spring holding bar (47) of the wheel (20) to enable the wheel (20) rotate in clockwise direction and turn “off the knob (31).

9) The safety knob (30), as claimed in claim 5, wherein in an event of metallic cylinder being in an attracted position, the spring loaded claw (64) of the lever (60a) latches the latching projection (45) of the wheel (20) making the wheel (20) immobile.

10) The safety knob (30), as claimed in claim 1, wherein in an event of absence of the flame and the knob (31) remains rotated in the first anticlockwise direction, the circular spring (40) unwinds causing the wheel (20) to rotate in a second clockwise direction to push the safety knob (31) to off position.

11) The safety knob (30), as claimed in claim 5, wherein in the attracted position, the lever (60a) remains stationary as influence of the circular spring (40) with stored potential energy on the lever (60a) due to a clockwise torque from the latching projection (45) of the wheel (20) on the spring loaded claw (64) is counterbalanced by an anticlockwise torque on the lever (60) produced by the solenoid coil (74) on the metallic cylinder (62).

12) The safety knob (30), as claimed in claim 5, wherein in an event of no electric current flows through the solenoid coil (74), the lever (60a) experiences force exerted by the latching projection (45) of the wheel (20) under influence of energized circular spring (40) causing the lever (60a) to rotate about its hinged point thereof and the spring loaded claw (64) to de-latch the latching projection (45) of wheel (20) and causing the wheel (20) to rotate in clockwise direction.

13) The safety knob (30), as claimed in claim 1, wherein the wheel (20) rotates in the clockwise direction, the hitting bar (46) of the wheel (20) engages the knob projection (32) and turns the knob (31) to off position automatically.

14) The safety knob (30), as claimed in claim 1, wherein distance of the latching projection (45) from center of the wheel (20) is greater than distance of the spring holding bar (47) from the center of the wheel (20).