|Title of Invention||
A COOKING APPLIANCE
|Abstract||An invention that is a device for cooking food wherein the size and power of the fuel source is reduced and optimally related to the diameter and charge of the cooking vessel above; wherein the food is placed in vertically stacked compartments; wherein the cooking vessel is shielded by insulation during the cooking process to minimise heat losses; wherein the fuel supply is cut off before cooking is complete to allow the food to continue cooking in its own heat; and where, as a result of using the device as instructed, the total fuel required for cooking is significantly reduced and the food cooks more slowly resulting in improved flavour and taste for many foods.|
|Full Text|| Form 2
THE PATENTS ACT 1970 (39 of 1970)
A COOKING APPLIANCE
SHIRISH BHAILAL PATEL, an Indian National residing at "Nanda Deep", 2-A M L Dahanukar Marg, Mumbai 400-026, Maharashtra, India
The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed.
Field of the Invention
The present invention relates to a fuel-efficient (poking appliance/that saves fuel to the extent of 70% or more as compared to normal cooking in addition to being safe and easy to operate. The cooking appliance operates primarily on steam and calls for slow cooking, and hence good flavor is imparted to the food cooked in the appliance.
Objects of the Invention
The main object of the invention is to provide a novel fuel-efficient cooking appliance which may be easily manufactured at dispersed location in developing countries, thus minimizing transportation and distribution costs.
Another object of the invention is to provide a iooking appliance wherein several food items can be cooked simultaneously, instead of sequentially.
Yet another object of the invention is to provide a cooking appliance
which is safe and has none of the hazards of explosion associated with
Still another object of the invention is to provide a cooking appliance wherein cooking is effected by circulation of steam.
Another object is to provide a cooking appliance wherein the cooking of
the food items is effected slowly so that it produces more flavourful and
Another object is to provide a cooking appliance in which there is no danger of the food burning, or of the food attaining elevated temperatures which would affect the flavour and quality of the cooked food.
Still another object is to provide a cooking appliance that can be operated employing any conventional or unknown fuel as a source of heat, such as gas, kerosene, coal, wood or cow-dung, electricity, etc.
Another object is to provide a cooking appliance which saves fuel to the extent of 70% or more.
One more object is, to provide an efficient cooking system susceptible to low cost manufacture with simple technology and with low costs in regard to materials and labour and consequently, a cooking system that can be sold at a low price to the consuming public, thereby making such an efficient cooking system which saves fuel economically available to the buying public.
Detailed description of the Invention
Accordingly, the present invention provides a novel and fuel-efficient cooking appliance embodying the principles and concept of the present invention as shown in Figures 1 to 5 the accompanying drawings. The focus of the invention is to provide a cooking system wherein the process of cooking is effected slowly and the fuel consumed for cooking is saved to the extent of more than 70%. The efficiency of the cooking appliance of the invention is attributed to the following principles used in the construction thereof:
(i) The cooking flame is small in diameter in relation to the diameter of the base of the cooking system in contact with the flame. The rate of heat supply is also diminished, being of the order of 0.5KW as against conventional cooking that uses 1KW or 2KW or more. These two measures ensure that all the heat supplied is concentrated towards the center of the base of the cooking system, and as much of the heat as possible is absorbed by the cooking system. It also ensures that heat in excess of that required for cooking of the food items is not supplied to the system and therefore no heat is wasted up the sides of the cooking system, and a substantial portion of the heat provided by the flame is absorbed by the cooking system, (ii) Insulation of the cooking pot around its perimeter: This ensures that a layer of air as insulator is contained between the cover over the cooking utensils and a second, exterior cover thereof. Trapped air acts as an insulator and helps retain the heat which is supplied to the cooking system. Retention of heat in this manner speeds up the rise of temperature and helps maintain the elevated temperature in the cooking system with a minimal supply of additional heat, (iii) Terminating heat supply before cooking is complete: On account of the insulator provided in the cooking system, once a temperature of 100°C has been reached, it is possible to maintain
elevated temperatures sufficient for continuing slow cooking of the
food items with no further supply of heat. Therefore, if the supply
of heat is terminated after a brief period, the food kept in the system
continues to cook with the heat retained in the system by the
insulator. During this period, the system is slowly cooling but still
cooking as the vessels containing the food items are insulated from
(iv) Stacking of food items in containers: This system of stacking food
in a series of containers saves fuel to a great extent compared to the
process of cooking the same quantity of food in a single large
container. The principle behind this system is known in chemical
engineering technology as "multi-stage evaporation". This says that
once steam is generated in the lower-most portion of the stack, the
steam travels upwards and condenses at the bottom of the
immediate next portion. The heat absorbed by the said immediate
portion then generates steam in turn and by condensation the heat
is passed on to the next portion and so on.
The cooking appliance of the invention is illustrated by the accompanying drawings wherein:
Figure 1(a) is an exploded frontal view of an embodiment of the cooking
appliance of the invention.
Figure 1(b) is a view of the final assembly of the cooker of the invention.
Figure 2(a) is the frontal view of the basal receptacle of the cooker of the
Figure 2(b) is the top view of the basal receptacle of the cooker of the
Figure 2(c) is the cross-sectional view of the basal receptacle of the cooker
of the invention.
Figure 3(a) is the cross-sectional view of the stack of cooking utensils of the
cooker of the invention.
Figure 3(b) is the top view of the stack of cooking utensils of the cooker of
Figure. 4 is a view of the first cover of the cooking appliance of the
Figure 5 is the view of the second cover of the cooking appliance of the
As shown in Figures 1(a) and 1(b), the cooking appliance of the invention consists of the following parts:
(i) basal receptacle (1) of heat conductive metal or material, fitted with lifting handles (5)
(ii) a series of cooking utensils (2) stacked one on top of the other and having constant or variable diameter, wherein the diameter of the cooking vessels is in general less than the diameter of the basal receptacle.
(iii) the first cover (3) capable of being engaged with the basal receptacle and covering the stack of cooking utensils, said first cover having a diameter greater than that of the widest cooking utensil and less than the basal receptacle.
(iv) the second cover, (4) capable of engaging firmly to the basal
receptacle, and covering the entire assembly, wherein the
diameter of the such second cover is greater than the cooking
utensils as well as the first cover, but less than or equal to the
diameter of the basal receptacle.
The basal receptacle of the cooking appliance (1) may be made of any metal or material capable of excellent heat conductivity. The receptable is concave. This basal receptacle has two separate means for firm engagement of the first and the second covers that fit over the basal receptacle. The means may be such as grooves (not shown in the diagrams). In a preferred embodiment, ribs may be provided for engagement of the first and the second covers with the basal receptacle. The first and the second covers may optionally be threadably engaged to the basal receptacle. This basal receptacle may optionally be fitted with means for easy transportation of the assembled system. One example of such means are horizontally projecting handles. Figure 2(a) shows the frontal view of the basal receptacle. Figure 2(b) shows the view of the receptacle from the top. Figure 2(c) that shows the cross sectional view of the basal receptacle of the cooking appliance. This figure also shows the steam vents in the basal receptacle. In one embodiment, the basal receptacle must be provided with a plurality of steam vents (6) as shown in Figure 2(c). They allow steam to escape from below the lowest cooking vessel into the steaming chamber. Too few vents, or too small a venting area results in a build-up of steam below the lowest cookings vessel. This expels the water out of the basal recepfacle^ As a result the water in the basal receptacle dries up, steam can no longer be generated, and the food does not get fully cooked. In another embodiment, the basal receptacle may not have the stepped
bottom that provides a seating for the cooking vessels above; this dispenses with the need for steam vents altogether, since the entire annular space between cooking vessel wall and basal receptacle inner wall is available for steam escape: the cooking vessels in this case would sit on a separate stand placed on the basal receptacle bottom. In yet another preferred embodiment, the cooking appliance of the invention may be provided with an indicator means such as a lamp that is capable of glowing and indicating whether the food items are being cooked or not. A green light might indicate that the temperature attained within is 100°C and that the heat can now be switched off. In yet another embodiment, the heat could be switched off automatically when the temperature attained within reaches 100°C, and the green light would come on about half and hour later, when cooking is complete.
Each of the cooking vessels placed as a stack in the basal receptacle, is
generally of a constant diameter, although the height of each of the vessels
may be varied depending upon the quantity of the food items to be
cooked. The cooking vessels could also be of varying diameter, such that
when placed in order of diminishing diameter they nest one within the
other, and when placed in reverse order they stack above each other. A
tight fit between one vessel and the next is not essential. Again, the
cooking utensils are made of metal or material capable of excellent heat
conductivity. As shown in Figure 3(a) the stack of utensils is such that they
each fit into the other, and as an assembly fit into the basal cooking
receptacle. The upper-most vessel of the stack may be provided with a lid ,
in order to trap and retain the flavour of the food in that vessel. The top I
view of the assembly is shown in Figure 3(b). The stack of utensils may j
optionally be provided with a frame or cradle for easy handling of the j
The first cover that covers the cooking utensils is in the form a cylinder with one end open. It may acquire different shapes or heights depending on the basal receptacle, its height and the height of the stack of cooking vessels. If this first cover is in the form of a cylinder, and if the basal receptacle is low in height, then the first cover is designed such that it covers the assembly and engages firmly within the basal receptacle. Steam condensing inside this first cover must drip back into the basal receptacle. This cover must essentially be made of material that provides rigidity, is unbreakable, easy to clean, and cheap to produce. Ideally, it should have very low heat conductivity. Figure 4 shows an example of the first cover
envisaged according to the invention. The material proposed is metal, which satisfies all the requirements set out above except the one in respect of low heat conductivity.
The second cover that covers the entire assembly is fitted such that it covers the entire assembly including the upper part of the basal receptacle. This second cover is only required if the first cover is made of metal or other material of high conductivity. In such a case, the second cover provides an air gap between the two covers, and it is this air gap that provides the insulation needed by the cooking system. The second cover is also designed such that its height is adjusted depending on the height of the basal receptacle, and the height of the first cover. Care is taken to ensure that there is a sufficient but not excessive gap between the first cover and the second cover such that air is trapped in this gap and acts as an insulator. The requirements for the second cover are the same as for the first: it must be rigid, unbreakable, easy to clean, cheap to produce, and preferably of low heat conductivity. In order to achieve an economical cooking system, this second cover may be made of metal. If the first cover is made of an insulating or other material of low heat conductivity, the second cover may be dispensed with altogether. Figure 5 shows an example of the second cover made of metal for the cooking appliance of the invention.
As mentioned earlier, it is important in the device of the invention to provide a means for trapping and retaining the_heat generated by the supply of heat to the system Such a means may be an insulator. While any kind of insulation may be used around the cooking pot cover, the cheapest insulator is air. It is the air gap between the cooking pot cover and the outer cover that provides the desired insulation. For best results, this gap is required to be 5mm or less. With such a narrow gap air does not circulate, there are no convection currents, and heat losses by convection across the air gap are prevented. Various other insulators can be used such as ceramics, fiberglass, glass wool, or any other insulating material, or a vacuum, in which case, the first and second covers around the basal receptacle may have to be merged or the second cover eliminated.
Heat is supplied through an external source. The supply of heat to the system may be through any fuel system such as coal, kerosene, , electricity, gas, wood, biomass or cow-dung. Where electricity is the desired fuel system, a heating element may be provided in the basal receptacle along
with appropriate means to enable absorption of heat and transmission of electric supply to the cooking system. It is essential that the size of the flame or stove below should be small in relation to the diameter of the basal receptacle of the cooking appliance. This minimizes heat losses from the edges of the stove and up the sides of the cooking system. This ensures that most of the heat produced by the flame or stove is absorbed by the cooking appliance. If the heat source is electricity, it is important to ensure that the diameter of the source be significantly smaller than the diameter of the basal receptacle of the cooking appliance. Similarly, for firewood or charcoal stoves, the source of supply of heat must have a much smaller diameter than the basal receptacle of the cooking appliance.
The division between basal receptacle and the covers of the cooking appliance may be at any height For example, the Basal receptade could be gerrerally cancave and supplied with a flat lid on top. In an embodiment, the stack of cooking vessels may be placed inside a lifting frame, with the help of which the assembly of cooking vessels would be lowered into the cooking pot, and after cooking is complete lifted out again. However, lifting a full load in and out is inconvenient. The present design has the split between basal receptacle and cover at a low level. This eliminates the lifting frame, thus saving cost, and has the added advantage that the cooking vessels can be removed one by one, including the lowest vessel, without the need to lower one's hands inside the basal receptacle. The level at which the split between basal receptacle and cooking pot cover is made makes no difference to the performance of the cooker.
Method of cooking: According to a preferred method of the practice of the invention, various food items are first prepared, and each item is placed in one of the cooking vessels that make up the stack. The food that is kept in the vessels is prepared in the usual way, as one would do for normal cooking. All spices are added, including salt. If cooking calls for spices spluttered in oil to be added to the food, these too could be added at this stage.
It is important that the water in the basal receptacle is in contact with the lowest cooking vessel when cooking begins. This is to allow rapid heat transfer from the water in the basal receptacle to the food in the lowest container.
The cooking vessels are assembled in a stack, with the hardest-to-cook item placed at the bottom, other items in between, and the second-hardest-to-cook item on top. It is not necessary that the largest cooking utensil should be at the bottom, or the smallest at the top. The cooking utensils can be placed in any order. The number of utensils will depend on the number of items to be cooked. It is not necessary to use all the cooking vessels supplied. If there are fewer items to cook, fewer vessels may be used. But when there are fewer items, and these include a large quantity of one particular item, it is better to divide this larger quantity into two vessels containing the same item. For the same volume of cooking, the larger the count of vessels in the stack the more economical the cooking in terms of fuel consumption.
The basal receptacle is preferably in the form of a basin allowing space for utensils to be stacked, water to be placed therein, etc. The basal receptacle is placed on the stove, and filled with water until the water touches and embraces the lowest cooking vessel.
The stack of cooking vessels, with food inside, is placed in the center of the cooking pot. The vessels should be firmly engaged to the basal receptacle. The bottom of the lowest vessel must be in contact with the water in the base.
The assembly of cooking vessels is covered with the first and second covers.
If the fuel being used is gas, the burner must be kept on 'low flame' or 'simmer' position from the start. The flame should be the lowesPpossible from the smallest burner available. This will normally provide a gas flow rate of about 5 cc/second.
At the end of about one hour, the flame is switched off. During the hour that it is burning, the cooker needs no attention, and the cook can go about doing other work. It is important to ensure that the stove is not in a windy place, where the flame can get blown out and the gas will then continue to leak. The one-hour period is for a almost fully charged cooker, with each of the cooking containers more or less full to capacity. For reduced volumes of cooking one can shorten the time the flame is left on. The exact duration for different volumes of food can be determined by trial and error, but a good thumb rule is 20 minutes + 10 minutes per kilogram of charge. It is also important that when the flame is switched off,
after an hour or so, the water is no longer in contact with the lowest vessel. The period of "cooling", when the flame is switched off but the cooker is not opened, is important to finish cooking. During this cooling period the cooking vessels must be maintained at as high a temperature as possible, as food continues to cook during this time. If water were to remain in contact with the lowest vessel, this vessel would cool too rapidly, and the food within might remain only partially cooked.
In a preferred embodiment, where electricity is the desired source of heat supply, means for manually or automatically regulating or controlling temperature can be provided. for example the basal receptacle may be fitted with a heating element, thermostatic control means and timer means so as to control the application of power to the heating element in the basal receptacle. The thermostatic control unit includes a temperature sensor element which is placed in contact with the cooking appliance such that the thermostatic control means is able to determine the temperature of the cooking medium in the cooking appliance. A power cord is also provided extending from the device for supplying power to the thermostatic control means and timer means as well as to the heating element in the cooking appliance via connections. In one embodiment, the basal receptacle is provided with a temperature indicator means. The temperature indicator indicates when the temperature within reaches 100°C, at which time the heat supply may be manually or automatically switched off. After switching off, a timer device could indicate when the half-hour period for continued cooking while cooling takes place is complete, and the system can then be opened. It is also possible to provide, as a preferred embodiment, a microcomputer that is capable of accepting "time to hold at 100°C " and "time to cook while cooling ". Depending upon the food items to be cooked, these two timings may be set. Once the supply of heat is commenced, the cooking of the food items in the system commences once each item of food reaches its minimum cooking temperature. The process of cooking continues for each food item as long as its temperature is above its minimum cooking temperature. The thermostatic control means regulates the fuel/heat supply, and terminates the supply of heat to the system at a suitable point. With the termination of fuel supply, the cooking in the system continues until the temperature of each item in the system falls below its minimum cooking temperature. The termination of fuel supply is effected when the food items are partially-cooked.
After switching off the flame, the cooker must not be opened for at least another half an hour. This is because cooking is only partly complete when the flame is switched off: the food continues to cook in its own heat for a half-hour or more. The user may take the assembly off the stove and put it to one side if so desired, thus freeing the stove for other cooking. Care needs to be exercised when lifting the assembly to make sure that it does not overbalance or topple. If desired, the the handles can be made taller so that the danger of toppling is minimized.
Ideally, the cooker should be opened just prior to serving the food. This ensures that no re-heating is required. The outer and inner covers are removed using appropriate conventional means and methods. Ridges may be provided on the covers to improve the grip. The cooking vessels are similarly removed.
There is no damage to the food if the gas is left on for too long. It only results in some waste of fuel. If left on for far too long, say for several hours, the basal receptabld may dFy out totally, and metal-to-metal heat conduction may then result in some of the food in the lowest container being partially burnt.
Ideally, when the cooker is opened, there should be a small amount of water left in the basal receptacle of the cooking appliance. This indicates that the desired fuel economy is being achieved.
If the fuel being used is other than gas or kerosene, the user may have to experiment as to how best to maintain low heat in the cooker for one hour without the fire needing repeated attention.
The foregoing description of the cooking device is considered illustrative of some of the preferred embodiments of the invention. Various modifications and changes that can be readily made by a person skilled in the art, are considered to be encompassed within the scope of the present invention. Accordingly, the embodiments illustrated above are not desired to limit the scope of the invention to the exact constructional and operational features as herein described. Suitable modifications and equivalents may be resorted to, within the scope of the invention.
Details of distinguishing features as compared with Prior Art
The traditional method of cooking is by boiling the food or simmering in a vessel with an open top. In some cases, the top is covered by a lid. Food is placed inside the vessel with adequate quantity of water and the bottom of the vessel is placed directly on the flame. This is shown in FIG. A. Cooking in the device of FIG. A takes place as the temperature in the cooking vessel rises to 100°C., and is maintained at that temperature until cooking is complete.
U.S. patent No. 2,097,478 discloses a cooking utensil comprising an outer vessel that supports an inner vessel in lowered and raised positions. The outer vessel includes a cylindrical flange that is permanently fitted within a circumferential trough in the wall of outer vessel. The outer vessel is adapted to support the inner vessel thereby requiring the vessel to be purchased as a combination. Also, the support flanges in the cooking utensil may prove a hindrance when trying to clean the utensil.
Similarly, the prior art has yet another cooking utensil called Rukmini cooker as shown in FIG. B. comprising a stack of cylindrical cooking vessels that fit one on top of the other, with a lid over the upper- most cooking vessel. Each cooking vessel may contain a different food item. The entire assembly is held together by a lifting or cradle, so that it can be lifted as a single unit. This assembly is then lowered into a deep container of slightly larger diameter, which has water at the bottom. This deep outer container has a tight-fitting lid. It is placed on a stove usually of the same diameter as the outer container. The water in the deep outer container gets converted into steam when heated and this steam helps in cooking the food within the cooking vessels. This steam condenses, returns to the base as water, and is once again converted to steam. The temperature of the food in the cooking vessels is gradually raised to 100°C., and maintained at that temperature as long as steaming continues. The advantage of this cooker is that several food items are cooked simultaneously, and that the food requires no stirring since it cannot be charred by overheating. The disadvantage is that the heat energy dissipates from inside to outside and hence, significant fuel is burnt to cook the food using this, cooker. In addition, as the outer container is hot, it is not safe.
A somewhat similar steam cooker, without the outer vessel of the Rumini Cooker, is shown in FIG. C. This cooker consists of a stack of cylindrical cooking vessel placed directly on the flame. The lowest vessel contains water only. The steam produced is passed into the upper vessel in various ways. Some vessels have a perforated bottom. Other vessels are fitted with a central pipe which serves to carry steam, into the vessels above the basal vessel.
Another instance of cooking vessel in the prior art is the Haybox or Insulation Cooker, which is shown in the FIG. D. It consists of a thermally insulating chamber with a thermally insulating lid. Food is brought to boiling point in a vessel, but is not yet fully cooked. It is covered with a lid, and is then placed in the Haybox. The insulating lid of the Haybox is put into place, and the whole assembly is left undisturbed for a while. The food inside the cooking vessel continues to cook in its own heat. Fuel economy results because part of the cooking takes place in the insulating chamber, with no explicit supply heat.
As mentioned in the foregoing section, several cooking utensils are known in the prior art. One typical utensil is depicted in FIG. A, wherein the utensil consists of a simple vessel (1) provided with a lid (2). A modification of this cooking utensil i.e. Rukmini cooker is shown in FIG. B which has an outer vessel (3) into which are placed a series of cooking vessels (4). This cooker is provided with a lid (5). It may optionally be provided with a stand (6) and the cooking vessels may be provided with a cradle or lifting frame (7). Another steam cooker is shown in FIG. C wherein a stack of cooking vessels (8) is provided with lid (9) and pipes (10) to carry steam to each cooking vessel. Some of the vessels of this cooker have a perforated bottom.
The Haybox cooker shown in FIG. 4 is yet another cooking system having a thermally insulating chamber (11) with a thermally insulating lid (12). A vessel (10A) is kept in this chamber. For cooking, the food in the vessel is brought to boiling point and when the food is still uncooked, the vessel is placed in the Haybox. The Haybox is covered with a lid and the entire assembly is left: undisturbed for completion of cooking.
1. A cooking appliance comprising:
a) basal receptacle (1) of heat conductive metal or material for holding water;
b) one or more cooking utensils (2) stacked one on top of the other such that each of the utensils in the stack fit into each other and the diameter of the largest cooking vessel is in general less than the diameter of the basal receptacle and the water in the basal receptacle touches the lower cooking utensil;
c) an inner cover (3) capable of being engaged with the basal receptacle and covering the stack of cooking utensils, said inner cover having a diameter greater than that the widest cooking utensil and the diameter at the base of the inner cover being less than basal receptacle;
d) an outer cover, (4) capable of engaging with the basal receptacle, and covering the entire assembly, wherein the diameter of the outer is greater than the cooking utensils as well as the inner cover and the diameter at the base of the outer cover being less than or equal to the diameter of the basal receptacle.
2. An appliance as claimed in claim 1 wherein the basal receptacle is provided with means for engagement of the first cover and second cover.
3. An appliance as claimed in claim 1 wherein the appliance comprises an insulator between the first cover and the second cover, or an insulator that replaces either one or both covers.
4. An appliance as claimed in claim 1 wherein the insulation is selected from ceramic, fiberglass, glass wool, or any other insulating material, vacuum and air.
5. An appliance as claimed in claim 1 wherein the source of supply of heat is selected from gas, electricity, wood, kerosene, biomass, cowdung and charcoal.
6. An appliance as claimed in claim 1 wherein the basal receptacle is optionally provided with a heating element.
7. An appliance as claimed in claim 1 wherein the basal receptacle is provided with a plurality of steam vents.
8. An appliance as claimed in claim 1, wherein the basal receptacle provides no direct seating for the cooking vessels, which are instead seated on a stand placed on the floor of the basal receptacle.
9. An appliance as claimed in claim 1 wherein a gap of about 5 mm is left between the first cover and the second cover to trap air which remains stagnant and free of convection currents and provides insulation.
10. An appliance as claimed in claim 1 further comprising indicator means to indicate whether cooking is complete or not.
11. An appliance as claimed in claim 1 further comprising a frame for lowering and raising of the stack of cooking utensils in and out of the basal receptacle.
12. An appliance as claimed in claim 1 wherein the diameter of the basal receptacle is significantly larger than the source of supply of heat such as burner.
|Indian Patent Application Number||882/MUM/2003|
|PG Journal Number||43/2008|
|Date of Filing||02-Sep-2003|
|Name of Patentee||SHIRISH BHAILAL PATEL|
|Applicant Address||"NANDA DEEP", 2-A M L DAHANUKAR MARG, MUMBAI 400 026, MAHARASHTRA, INDIA.|
|PCT International Classification Number||A23L 1/00|
|PCT International Application Number||N/A|
|PCT International Filing date|