FORM 2
THE PATENT ACT, 1970
(39 of 1970)
and
THE PATENTS RULES , 2003
COMPLETE SPECIFICATION
[See Section 10 and rule 13]
1. Title: High efficiency solid biofuel pellet stove
2. Applicant: Abellon Clean Energy
Sangeeta Complex,
Near Parimal Railway Crossing,
Ellisbridge, Ahmedabad - 380006,
INDIA
The following specification particularly describes the invention and the manner in which it is to be performed.

Field of invention
The invention relates a healthy and sustainable way to use pellets as renewable energy for a stove apparatus customized for community cooking for rural and semi-urban area.
Background of invention
People have been using biomass for cooking since before recorded history. Nowadays, this method is still widely spread for various reasons: thermal efficiency, low cost fuel, scarce availability of the other fuels, ambiance and comfort and simplicity of the combustion device. However, in rural and semi-urban areas the renewable and non-renewable raw biomass is being used without control on environment pollutants, having lesser efficiency, high risk to cook and no ease of operations.
Out of four types of energy sources for cooking (Gas, Electricity, Petrol and Biomass), biomass becomes more interesting. Firstly, agro-waste based pellets are considered as renewable fuel. Secondly, biomass is much cheaper, compared to other non-renewable sources of energy. In case of converting of renewable biomass into pellets, the use of renewable fuels would be promoted in efficient and safe manner while having control on environmental impact. The pellets are easy to transport, handle and feed into the cooking device.
The present invention adds a new and novel member to this class of combustion device. By this, the efficient fuel would be used by the grass root community and will replace the prevailed non-sustainable practices. However, it is necessary to master the cooking stove design fairly well and finely regulated where the pellets would be combusted for various types of cooking to provide reasonable efficiency in such combustion.
Prior art
Lots of technologies have been developed to use pellets as solid fuel for their greater efficiency while combustion and for their huge scopes especially for agriculture based economy countries.

The technologies developed up to now for similar uses mainly concentrate on the following parameters:
• Fuel efficiency depending on fuel and air feeding regulation, shape of combustion chamber, resulting in environmental improvement (less emission, complete combustion...)
• Automatized temperature regulation
• Air circulation efficiency
• Transportability, cleanable and ash removable possibility
• Heat insulation
The prior art pellet combustion devices tend to be adapted to solve one particular problem often at the expense of other problems. They generally do not simultaneously optimize all the parameters enlisted above.
The Patent WO 2010/029567 A2 describes the design of an innovative stove presenting some specific features to obtain a complete combustion and a very good energy efficiency in any range of temperature required for cooking. Therefore, they elaborate a technology with a fire pot with variable volume while having a grate with adjustable height. Moreover the combustion is done along two stages. The primary and the secondary benefit two independent fresh air flow input in order to get an accurately complete combustion. However there is no automatic feeding systems. This missing element induce a lack of flexibility in the required temperature as well as in the firing and switching off duration.
Whereas in the design described in the US Patent 5,429,110, the innovation is mainly concentrating on heat insulation issues. While establishing a cold and a hot compartment separated by a double layer wall where air flow is circulating, they ensure stability at the required temperature in the pellet storage and electrical components. However the heat transfer between the cooked stuff and the superheated air is not optimized, and the exhaust goes through the cooking dish before spreading in the kitchen.

According to the patent US 5,123,360, the innovation consists in an optimization of air circulation by splitting the supply stream for different uses: combustion air feeding, depressurization of the combustion chamber, heat exchange (heat the inlet air and cool the exterior of the devices), preventing back flue gas in auger feed. However the main function of this innovation is air heating. As a result, cooking efficiency and diversity in types of cooking are reduced.
In the US Patent 2009/0036803, the S shaped stove provides a heating oven area between upper and lower stove sections. The pellet feeding can not be regulated and insulation being nil, the stove surfaces are extremely hot and so dangerous for the user. Even if innovative the design of that stove is not providing an adapted technical solution for cooking purpose.
The integration of the ergonomic, safety, and health aspect up to now has not
been taken in account in pellets cooking stove design. The exhaust from the
stove can contain toxic gases like carbon monoxide, blacken the cooking area and
sometimes have high flying ash content. Most of the above mentioned patents do
not include any exhaust management enhancing pollution of the cooking area,
discomfort, health threatening and spoiled food with flying ashes. In our
invention, the diverted smoke is not contacting with food neither released in the
cooking room.
Highly efficient combustion are claimed in above mentioned stoves of prior-art, but the heat transfer efficiency to the end applications is mostly neglected. Though the combustion efficiency is high in these stoves, there are limitations in transferring the heat in efficient manner to the vessels. These stoves are also not designed for various types of cooking. Our invention includes the specific design of fire pot for efficient heat exchange with the cooking dish. This strategy of integrated optimized technology enhance global high efficiency, healthy cooking conditions and cost effectiveness.

Summary of the present invention
The present invention relates to a stove incorporating a hopper, a combustion chamber (integrated fire pot), a blower, a feeding screw conveyor and a chimney. The fire pot achieves a complete combustion. The fire bed received a double air supply from the blower and pellets from the screw conveyor system. The flames heat the cooking vessel which is being held by the top of the fire pot while the exhaust are conveyed to the chimney. Therefore, the fire pot has a double-layered wall forming a multipurpose cavity in-between, which is further fragmented in three portions horizontally. The lower portion is used for air supply circulation and the upper portion for outlet exhaust circulation. The inner surface of the fire pot is perforated on the bottom and the top for air supply and venting out respectively. Out of three sections, the middle portion of the cavity is completely filled with the ceramic insulator. Pellet feeding is being regulated automatically to achieve the required temperature and the air supply is being regulated manually from the control panel. The fuel is burned efficiently with a little or no smoke except at starting and ending phases.
According to the first aspect of the invention, the cooking stove provides some features that make it unique for its safety. The invention consists in a large and circle top cross-sectioned fire pot directly holding the cooking vessel. While cooking, the vessels covers the mouth of the stove and there is no possibility of exhaust leakage into the room and the operator cannot have any contact with the flames. The insulated chimney carry away the flue gases of about 300°C safely outside the cooking room.
The heat insulation by the double-layered wall of the fire pot filled with ceramic avoid the hopper to reach the auto ignition temperature, protects electronic components from damage and users from burn. To avoid flow of back flue gases to get into the pellets feeding system, an air inlet pipe is connected to the screw conveyor outlet.

According to the second aspect of the invention, the stove is able to reach high efficiency and to compete with the conventional fuel stoves in terms of heating efficiency and heating duration. Therefore, the stove efficiency is improved by two ways:
- Pellet combustion optimization: lateral and top double air supply is provided with a continuous and regulated pellet feeding. These features preserve the good proportion of products for the combustion, allowing a complete combustion releasing maximum of heat and a minimum of ashes.
- Heat transfer to the cooking vessel optimization: the conical shape of the fire pot provides a large area for heat exchange between exhaust / flames and cooking dish.
According to the third aspect of the invention, the stove is designed for ergonomic cooking and can be used for several cooking purposes i.e. steam cooking, boiling, roasting, frying, grilling etc... The design and system of the stoves provides maximum and optimum safety to the user. The ash collection tray is easily removable and the screw conveyor system is manually removable for cleaning and maintenance. The storage hopper, the fire pot and the other components are easily cleanable. Maintenance is an important factor of lifespan for devices working in corrosive atmosphere.
As a result, our invention embodying a simple and low-cost design is user friendly, highly thermal-efficient, safe and chain for the user as much as for the environment.
A brief description of the drawing
In the accompanying drawings which form a part hereof and wherein like

numerals of reference refer to similar parts throughout.


FIG. 1 a schematic global external view is of present stove, indicated by the arrows, to show various internal structure.
FIG. 2 is a cross-section view through the stove of FIG. 1, showing various of its parts, their configuration and relationship
FIG. 3 is a top view of the stove of FIG. 1 according to the present invention.
Detailed description of the invention
In accordance with a preferred embodiment of the invention as shown in the front perspective view in FIG. 1, a pellet cook stove includes a mild steel angle framed canopy having front cover made of Mild steel sheet, and rear, right and left walls made of mild steel grill 2 to ensure the consistent air flow inside the system. A top cover 6 made up of Stainless Steel is provided with two openings. First is for the fire pot 12 which is called mouth of the stove 7 and second is the fuel storage hopper 1 opening. A thin circular air layer separates the mouth of the stove 7 from the top surface 6 to avoid conduction of heat to external surface, the Some of the portion of hopper I is projected from top surface 6, outside the stove walls. Hence, the top of the hopper 1 is half covered by the top surface 6 and rest open space of hopper 1 is used to feed the fuel. A range of cooking plates viz. full plate for roasting, meshed-wire plate for grilling, flat and broad rings of various inner diameters in order to accommodate the shape of any cooking vessel, are provided to be placed on the mouth of the stove 7 .
On the right hand top corner of the front wall 8 , a control panel box 29 provides different control switches including Mains supply ON/OFF switch 32; Blower ON/OFF switch 36; Screw feeder speed controller 35 regulating the pellet feeding speed from 1 to 7 kg/hour and Temperature Display, composed of two buttons (+/-) for setting the required temperature 33. The Fig 1 shows an opening at the left hand bottom corner of the left side grill wall 8 intended to allow accessibility

to the ash tray 23. For easier mobility and maneuverability of the pellet cook stove, rollers 10 and handles 30 are provided.
The left side grill wall 3 has an opening connecting the exhaust outlet 4 to the removable chimney 5 by a flange 22. The insulated chimney 5 conveys the exhausts of about 300°C out of the cooking area. The chimney 5 is attached to the stove on the opposite face of the feeding system and it can be easily removed while transportation of stove. An optional arrangement provides heat recovering from the exhausts to boil water for per-cooking use. After heat-exchange, the exhausts is released to the atmosphere.
In the cutaway parallel to the front wall 8 view showed Fig 2, the internal system is visible with each components. The square cross-sectioned hopper 1, with 45° sloped side walls, has a storage capacity of 5kg of pellets. The general structure provides a flexibility of fuel storage volume and stove mouth size either in single or series of mouths. The hopper 1 has a hole at the end of the inclined edge feeding the screw conveyor-Pellet feeding
The pellets advanced forwardly to the fire pot 12 through a ascendant motor-driven screw-conveyor 13. The mechanism of the screw conveyor uses a low capacity motor 14 which is provided with gear box of 1.5 inch . The shaft less spiral type screw-conveyor is supported by the motor 14 at one end and the screw bearing 11 at the other end. The screw conveyor motor is provided with a 7 speed mechanism, which can be controlled either automatically or manually by the speed controller 35. The Fig. 2 shows the screw-conveyor 13 leading to the feeding tube 15. This feeding tube 15 goes through the double-layered fire pot wall 16 to ensure distribution of pellets across the bed of the fire pot 17. The slope of the feeding pipe 15 increases the traveling speed of pellets significantly on gravitational basis. As a result, pellets are not ignited inside the feeding pipe

15. The fuel inlet 18 end point is situated at some height above the fire bed. The secondary air supply 24 flows from the blower 19 to the fuel feeding pipe 15 and travels along with pellets to fire bed 17. Hence, the flow supplies the oxygen over the top of the fire bed 17 and moreover,reinforces the feeding system security while blowing air in the opposite direction of back flue gas and nullify the firing possibility of the fuel storage. The air flow also preserves a temperature lesser than the pellets auto-ignition temperature until the fuel reaches the fire pot bed 17. The blower is supported by a drive mounting 38 and driven by a low capacity motor. Fresh air is propelled by the blower 19 to the fire pot bed 17 by two channels. The primary air supply is introduced at the bottom of the fire bed 17 through a series of 12 perforations 25 situated in circular manner on the inner layer of the fire pot 12 wall. And the secondary air supply, as mentioned above, is introduced from the top on the fire bed 17 from the feeding pipe 18. A damper 21 is provided with the blower 19 for air supply manual regulation from the Blower Switch 36 of the control panel 29.
Air supply
The conical shape fire pot 12 double-layer wall 16, composed of two circular metal sheets, is a multipurpose cavity fragmented in three portions horizontally. The lower portion 28 is used for air supply circulation and the conical shaped upper portion 35 is for exhaust circulation. The inner layer of the fire pot 12 is perforated on the bottom 25 and the top 26 for air supply and venting out respectively. Out of three sections, the middle portion 37 of the cavity is completely filled with the ceramic insulator 37. The fire pot insulation 37 keeps the temperature down to an average of 60°C inside the structure of the stove, which is below the auto-ignition temperature of pellets and low enough not to damage the electronic devices. The combustion takes place in the fire bed of the fire pot 17, supported by a meshed-wire-plate. Once pellets are reduced to ash by combustion, it it falls through the meshed-wire plate in the ash tray 23, positioned beneath of the fire pot 12. The ash tray 23 with handle 9 is screwed to the bottom

of the fire pot 12 with the help of wing nuts 39 and allows manual removal of ash tray 23. The said ash tray 23 is made up of Mild steel and 3mm thick. The ash tray 23 is tightened by wing nuts 39 to the bottom of the fire pot 12, prevents hot air or fly ash leakages and avoids heat losses and increases safety of the operator. The wing nuts 39 can be easily removed manually for the ash removal.
The flames and exhaust come up to the top of the fire pot 12 where the vessel is lying on the mouth of the stove 7. The conical shape of the upper part of the fire pot 12 improves convectional heat exchange rate due to increased heat exchange area. A partial amount of heat is transferred to the cooking vessel by convection. The unused energy is evacuated by the exhaust through a series of 12 perforations 26 in circular manner at the top of the inner layer of the fire pot 12. The exhaust is conveyed through the the fire pot double layer cavity 35 to the single opening on the external layer of the fire pot wall through the perforations 26, which is directly connected to the air outlet 4 and eventually to the chimney 5. Exhausts generated by the pellets combustion is discharged via chimney 5 of 50mm diameter outside the cooking area.
Operation of the present invention
The pellets are placed in the hopper 1. Any type and quality of commercialized pellets can be used. The storage capacity allows an average of one hour autonomy and enhances the ease of cook by avoiding repetitive pellet feeding. An initial layer of 250g of pellets is introduced by the motorized screw-conveyor 13 in the fire pot 12 before initial ignition. Two options are available for the initial ignition of fuel. One, is to spread kerosene over the initial layer of pellets. In these conditions a single spark is sufficient for pellets ignition. The second solution is provided by a electrical heating coil 28 in the bed of the fire pot 17, above the me shed-wire-plate 17, covered by the initial layer of pellets. The heat rendered by the coil causes auto-ignition of the pellets. Once the fuel is fired, the heating coil 28 is switched off. The entire process takes about 3 minutes. It is recommended to

put the cooking vessel on the mouth of the stove 7 before the initial ignition to prevent smokes inside the cooking area.
The automatized program regulates the temperature of the fire pot 12 from atmospheric temperature to 750 °C. First, the required temperature for cooking is set with the Temperature Controller 33. The temperature sensor 31 depicts the temperature on the top of the fire pot 12 and induces the automatic regulation of pellets feeding motor 14: The screw conveyor 13 continues to feed the pellets until the pre-set temperature is achieved in the fire pot. When the temperature sensor detects the pre-set temperature condition inside, it automatically stops the fuel feeding motor 14 and as the temperature goes below the set threshold, it automatically starts feeding fuel again.
Air flow regulated by the operator himself with the Blower Regulator 36 of the panel 29, which is directly connected to the Blower 19 ( two-gears are available: Speed 1- Speed 2).
When the cooking operation is over, the pellets feeding mechanism 14 must be stopped from the panel 29 with the feeding regulation 35 switch whereas the blower 19 reduces progressively the air flow under the damper 21 action. The decreasing air input maintains combustion until the fuel left inside the fire pot 12 is fully consumed. A progressive decrease in air flow allows the full combustion of fuel left in the fire pot 12 at the end of the operation, and prevent black smokes emissions generally due to lack of oxygen and so incomplete combustion. To reach the ambient temperature, the inner part of the stove takes minimum three hours and the external surface barely takes half an hour. The ash collection tray 23 is then safely manually taken out and the ashes are disposed-off suitably. The stove is ready for use again for the next batch of operations.

Electronic part
An electrical cord 20 is provided to connect the stove to the mains 220 V. single phase supply. The 220V supply is stepped down to 24V through a 24V step down transformer which is provided in the control panel box 29. The output of the transformer is given to Screw-feeder speed control switch 35 and temperature display 33 which are connected to screw feeder drive 13 and temperature sensor 31 respectively.
The temperature sensor 31 is installed on the top of the fire pot 12 and calibrated' to a variable and adjustable cut-off temperature thereby controlling fuel feed and hence controlling combustion in the fire pot 12,
The sensor 31 is regulated through the control panel 29 and is operated depending on the nature of food to be prepared to adjust the temperature and flame requirements and commands the feeder motor accordingly.

We claim:
1. A high efficiency solid biofuel pellet stove comprising,
a. a conical shaped double-layered fire pot;
b. an integrated air circulation system;
c. a global design integrating occupational safety with leakage proof
exhaust evacuation.
2. The multipurpose insulated fire pot as claimed in claim 1, consists of
combustion system, cooking vessel holder and air circulation system.
3. The fire pot as claimed in claim 1, consists of large and circle top cross-section to hold the cooking vessel, used for various type of cooking including roasting, steam cooking, boiling and grilling.
4. The fire pot as claimed in claim 1, consists of double layered wall with the lower portion used as air supply circulation, upper portion as outlet exhaust circulation.
5. The fire pot as claimed in claim 3 consists of circle top cross-section mouth of stove completed with flat broad rings of various inner diameters in order to accommodate the cooking vessel's shape of any volumetric capacity.
6. The double layer fire pot as claimed in claim 4, consists in series of perforation of the inner surface on the top for exhaust venting to chimney.
7. The fire pot as claimed in claim 2, consists of conical upper part leading to a larger top cross-section area enhancing efficient convectional heat transfer.

8. The fire pot as claimed in claim 1, insulated with refractory material including clay or ceramic in-between the double layered walls of the fire pot and thin air layer separating the mouth of the stove from the top surface metal sheet to prevent heat conduction to any outer surface accessible to operator, protecting electrical components from damages and avoiding auto-ignition of the stored pellets.
9. The fire pot as claimed in claim 1, solid biofuel pellets fed by a pellet feeding mechanism consists of an automated horizontal shaft less screw conveyor connected to a sloped feeding pipe with a secondary air supply flowing along with the pellets going through the double layered fire pot. The mechanism nullify back flue gas in the hopper and ignition of pellets in the feeding mechanism.

10. The high efficiency solid biofuel pellet stove as claimed in claim 1, consists of screwed ash tray to bottom of the fire pot by wing nuts, manually operable and enhancing no exhaust neither heat leakages.
11. The high efficiency solid biofuel pellet stove as claimed in claim 1, includes a square cross-sectioned hopper for pellets storage with 45° slope sides.
12. The high efficiency solid biofuel pellet stove as claimed in claim 1, includes a hopper for storage is external to the stove main structure for a better mechanical balance of the whole on-rollers structure as much as for a better heat insulation of the fuel storage.
13. The high efficiency solid biofuel pellet stove as claimed in claim 1, easily transportable with four rollers and handles on each sides and a removable chimney with adaptive shape from flange to room exhaust outlet.
14. A high efficiency solid biofuel pellet stove as herein described with reference to foregoing drawings.