Title of Invention


Abstract This invention relates to an Improved energy efficient cooking process using a double walled cook-and -serve casserole. Water in the annular space is used to heat the cooking medium in the vessel. A steam bleeder screwed on the sidewall. acts innovative/y to maintain a higher than atmospheric pressure in the annular space and prevents mass transfer. thereby increasing the efficiency of cooking. After cooking the double wall acts as an insulator. making the utensil a casserole for warm storage. The water meniscus in the annular space does not touch the inner shell of the utensil. which innovatively reduces the convective heat transfer and retains heat for longer durations after cooking.
Full Text

1. Field of invention
The present invention relates to a process of increasing the themial efficiency of double walled cooking vessel particularly by maintaining a higher pressure than atmospheric pressure in the double-walled space.
2. Description of the related art
Double layered cooking vessels are in commercial use in the name of milk boiler, thermal cooker, etc. These make use of the principle of uniform heating of cooking medium ming the fluid in the double wall - water in the case of milk boiler and air in the case of thermal cookers. Fig-l and Fig.2 describe these prior arts. In both cases the outer and inner layers, namely 1 and 2 respectively are folded and joined into a double-walled vessel with a beading at the top ~ 3, thereby forming an annular space 13. The above joint 3 is not fully pressure tight and can allow the pressure to let out from the annular space (13) in very small measure, and reversely admit moisture into it while washing.
For the milk boiler in Fig. 1, the double wall annular space (13) is relieved completely of any build up of pressure by a whistle 6. As soon as the water in the wall 5 boils steam begins to ooze out through the whistle, after heating the milk 4 inside the vessel partially. The escaping steam is still caloritically valuable and represents a thermal loss. Item 9 is the handle.
In Fig.2, the second prior ar( is depicted, which is of similar construction as above and like numbers are used to represent the construction wherever applicable. The major difference in this construction is that the heating is through a conducting metal plate 7 and not through water as in milk boiler. The fluid in the annular space 13 is air in this case which provides an efficient convective heating. Prior art is available in commercial form without the valve 17. If the roll joint 3 were perfectly pressure tight and leak-proof, the valve 17 would be unnecessary as there is no build up of pressure. But in practice, moisture enters the annular space 13 through the roll joint 3 while washing and causes steam to be developed at high pressure inside the annular space. This causes danger of bursting or at least causes the vessel to loose shape. Therefore a relief valve 17 has been added with the specific purpose of venting out higher pressure and ensures safety of the vessel, in this case the handle has been modified 16 to contain the valve. The valve is made of an elastic materia! and acts in simple automatic way.
The present invention is with regard to a process of achieving higher thermal efficiency by trapping the steam inside the annular wall 13 and not letting it escape like in milk
boiler (Fig. 1).

The main object of the present invention is to allow steam of high calorific value to remain in the double wall and transfer its entire heat to the cooking medium 4 at slightly
higher pressure than atmospheric.
Another object of the present invention is to provide a relief for the higher build up of
pressure and thereby ensure safety of the device.
Another object of the present invention is to achieve further overall thermal efficiency by acting as an insulated casserole after cooking so that the food retains warmth even a few hours later.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be earned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these objectives, a spring loaded valve 8 is attached to the outer body of the vessel as in Fig. 3.
According to one aspect of the preferred embodiment, a steel ball valve is retained by spring pressure of a carefully assessed empirical value so as to open and close the annular space 13 as a trade-off between retention of heal and safety.
According to another aspect of the preferred embodiment, the heating of the vessel is to be controlled to be of low flame to allow gradual heating so that heat transferred to the water medium 5 is fully utilized without wastage.
According to another aspect of the preferred embodiment, the wall thickness of 13 in the radial direction is controlled to allow for maximum heat transfer while cooking and maximum insulation after cooking.
According to another aspect of the preferred embodiment, the annular space 13 serves as a space that transfers uniform heat to the cooking medium 4 while on fire, and insulates it while off the tire, thereby acting as a casserole retaining the heat of the food for long duration and obviating the need for reheating of food before consumption.
According to another aspect of the preferred embodiment, the roll joint 3 in fig.3 is sealed using commercial sealants to ensure that steam is not lost through it.
According to yet another aspect of the preferred embodiment, the cooking medium in the annular space of 13, namely 5 is not touching the inner shell 2 (Fig.3). This is intended to

prevent heat loss by convection during the time when the tbod is kept inside the vessel after cooking. In that case, the superior insulating property of air helps in getting reduced heat transfer from food 4, thereby increasing length of time the higher temperature is retained in the food. This aspect of the embodiment increases the efficiency of the vessel as a casserole over the conventional art in Fig. I.
Therefore, the present invention is characterized in that it achieves high thermal efficiencies than the prior art form of Fig. 1 and Fig.2 while also acting as a thermally insulated double wall, helping the invention to function as a cook-and-serve casserole.
Moreover, the essential working of the invention is unique in that the cooking medium 5 is recycled completely without wastage, the valve 8 ideally not opening at all, which opens only in case of safety hazard of explosion. The cooking medium, namely water 5, receives heat from tire and gets converted into steam, rises in the annular space 13 ana transfers the complete heat to food 4, condenses m the walls I and 2, and returns to the bottom of annular space 13 to be heated again, and to repeat the above process. The wastage of cooking medium is minimal compared to prior art I (mile boiler).
It is to be understood that both the foregoing general description and the following detailed description of he present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
The accompanying drawings which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the principle of the invention.
Fig. 1 illustrates a cross-sectional view of a double-layered cooking vessel according to conventional art of milk boiler
Fig.2 illustrates a cross-sectional view of a double layered cooking vessel according to the conventional prior art of a thermal cooker where a thermally conducting metallic plate 7 and not a fluid medium 5 (Fig. I) transfers heat to the food 4. Here a valve of elastic material 17 contained m a handle 16 is used to control the pressure inside the annular space 13 to basically prevent hazards like explosion or distortion of vessel walls 1 and 2.
Fig. 3 illustrated a cross-sectional view of a double-layered cooking vessel according toe the preferred embodiment of the present invention, in which a valve located on the vertical walls 8 is opened in case of hither than anticipated pressure; and
Fig.4 illustrates a close-up view of the valve 8.

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.
Fig.3 illustrates ^ cross-sectional view of a double-layered cooking vessel made up of the outer vessel 1 and inner vessel 2, both made of staitifess steel. 3-is-a roll ioint'^ere the edges of the outer and inner shells 1 and 2 are secured together so as to provide the air pocket 13 between the outer and mner shells^Th? gap between the outer and inner shells 1 and 2 is such that the ideal heat transfer properties are obtained during direct heating by providing sufficient circulation of the steam without high build-up of dangerous pressure: if the wall thickness is too low, the pressure build-up is too fast, and if the thickness is too high, pressure doesn't develop and a lot of heat of the steam is lost in the lower wall;;, thereby causing uneven heating.
The roll joint 3 is sealed using sealing materials such as araldite so that steam generated out of 5 is trapped inside the space 13 and not allowed to escape, thereby preventing any mass transfer.
Refenring to Fig.4, it is a close-up view of the steam bleeder cum safety valve 8 of Fig.3,
which is attached to the outer shell 3. 15 is a sttd inserted into the shell iTwhich is
secured by a lock nut 18. 19 is the valve outer b-ody that is screwed onto the stud 15.15 has a steam pressure release duct 14, throu^ which the steam escapes in case the valve opens due to high pressure. 10 is a steel ball held in place using a helical spring 11 and a
retainer 12, The stiffness of the sprine 11 is so chosen that the valve opens at approximately 0.2-0.3 bar gauge pressure (above atmospheric). The retainer 12 is screwed into the valve outer body 19.
Accordingly, the present invention enables to retain some pressure inside the annular space of the double walled vessel, which prevents mass transfer and loss of latent heat, and thereby increases cooking efficiency.
The foregoing embodiments are merely exemplary and are not to be construed as limiting the present invention. The present teachings can be readily applied to other types of apparatuses- The description of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations Avill be apparent to those skilled in the art.

An improved energy efficient COOK-AND-SERVE double walled vessel;
made up of outer vessel [1], inner vessel [2 ] and a roll joint [3]where the edges of outer and inner shelves [1 &2 ] are secured together;
providing annular pocket [13] between the onto: and inner vessels, the gap between the outer and inner vessels [1 & 2] being such that it provides sufficient steam circulation without building up high or dangerous pressure and reduces the radiation heat transfer fix)m the inner vessel to the outer vessel;
and the Vessel is partially filled with water in annular space, fitted with a double walled lid and steam bleeder-cum-safety valve[8]which is attached to the outer shell [3];
and a stud [15] is inserted into the vessel [l]screwed by a lock nut [18 ];
and on to the stud [15]a valve is screwed to outer body;
and the stud [15] has a steam pressure release duct [14] through which steam escapes in case higher pressure than safe level is reached;
a steam ball [10] is held in its place by using as a helical spring [11] and a retainer [12 ] which enables to retain some pressure inside the aimular space of double walled vessel preventing loss of enthalpy and thereby increases the cooking efficiency as well as retaining heat for a long time even after cooking is over.


0609-che-2003 abstract-duplicate.pdf

0609-che-2003 claims-duplicate.pdf

0609-che-2003 description (complete)-duplicate.pdf

0609-che-2003 drawings-duplicate.pdf








609-che-2003-form 1.pdf

609-che-2003-form 13.pdf

609-che-2003-form 26.pdf

609-che-2003-form 5.pdf

Patent Number 221872
Indian Patent Application Number 609/CHE/2003
PG Journal Number 37/2008
Publication Date 12-Sep-2008
Grant Date 08-Jul-2008
Date of Filing 29-Jul-2003
Name of Patentee BOBY M. JACOB
# Inventor's Name Inventor's Address
PCT International Classification Number A47J 34/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA