Claims:We claim,
1) A downdraft kiln with the natural flow of gas, comprising; low-cost gas kiln made by angle iron, perforated MS sheet and other features having low-cost insulation system, fitted with a platform; having inlet doors for entry of hot air, wherein; an exhaust system is incorporated; having a LID specially designed.
2) The second claim is for low-cost wall of gas kiln as claimed in 1, is made by angle-iron (Fig. 1.9) and plain/perforated CRC sheet (Fig-1.8) or low-cost wall of gas kiln made by red clay country brick and mud mortar and plaster with the help of cow-dung and mud.
3) The third claim is for low cost insulation system as claimed in 1, is made by ceramic board (Fig-2.2) and ceramic fibre (Fig-2.3) which is pasted with the help of sodium-silicate and fixed with the help of stainless steel nut-bolts and washers (Fig-2.5).
4) The fourth claim is for the platform as claimed in 1, is 20 mm thick cordierite mullite refractory plates for loading of pottery wares which are suitable for firing upto 1200 degree centigrade temperate made above the level of gas inlet holes (Fig-3).
5) The fifth claim is for heat inlet door (Fig 4.4) as claimed in 1, which is made by 1.5 inches diameter porcelain pipe and the length of porcelain pipe is depended on overall thickness of kiln wall.
6) The sixth claim is for the position of heat entry holes made in the front wall (Fig. 4.4) and hits the heat diversion walls and after that the heat radiates inside the kiln and go over the ware then take a 180 o turn and come down to the flue gas exit.
7) The seventh claim is for the exhaust system as claimed in 1, is fitted below the platform (Fig. 4.7) and the diameter of galvanized iron pipe used as per the volume of kiln (Fig. 4.3).
8) The eighth claim is for the Lid/cover as claimed in 1, for top loaded kiln (Fig-2.1) made by angle iron frame (Fig. 2.6) and perforated sheet and insulated by ceramic fibre and board.
9) Having all components as per claim 1, 2, 3, 4, 5, 6, 7 & 8 is constituted the portable, energy efficient, low cost, down draft kiln with natural flow of gas.
Dated this 9th day of March, 2018,
(Dr. Ushoshi Guha)
Applicant’s Agent
To,
The Controller of Patents,
The Patent Office,
At Mumbai.
, Description:Title – “Portable, low cost, energy efficient, down draft, gas kiln for home scale pottery industry”
Field of Invention :
A portable, low cost, energy efficient, down draft, gas kiln has been developed to bake superior quality artistic terracotta products.

Prior Art :
In respect to firing & final product’s quality, the efforts by Research organizations like IITs, CGCRI etc have been carried out mostly with wood fired kilns, where the production cost of the kiln is always high due to high rejections through the breakages of pots etc. But the potters who are making traditional product are still working with traditional pit fired furnaces as the firing system is easy than those of improved kilns and potters who are making contemporary pottery product are using traditional up-draft kilns. Now the demand of contemporary pottery product is increasing day by day but accordingly the quality of pottery product is not enhanced. The basic reason is that the above mentioned Research Institutions could not do the fruitful research activities for smaller capacity wood fired kilns. A more complete treatise on the field of ceramics and the history, design and construction of kilns, may be found in suitable publications, such as for example, a book entitled “Kilns” by Daniel Rhodes, published by Chilton Book Company, Philadelphia 1968. Earlier a US Patent 4531910, 1985, is available on down draft gas kiln. This type of box kilns are used by several pottery industries but the efficiency of these kilns is very poor. So potters are not interested to use box type gas kilns because of high consumption of fuel. No other invention regarding portable, energy efficient, low cost, down-draft gas kiln is registered. Hence, there is urgent need to develop portable, energy efficient, low cost down draft gas kiln for micro pottery industry.

Summary:
If the present quality of terracotta product will not improved than slowly this market will decline and the pottery craft will be vanished. So in this juncture the most important factor was to develop a portable, low cost, energy efficient, down draft gas kiln. The aim of this invention is to develop energy efficient, low cost, down draft kiln for Indian rural pottery artisan. While doing so, the efforts were made by different R & D institutions have been carefully reviewed to incorporate meaningful aspects of design. The major benefits that the pottery artisans are getting from this invention as follows:
- the portable, energy efficient, low cost, down draft gas kiln for production of small terracotta products is affordable to majority of potters,
- eliminated on dependency of wood & reducing the environmental pollution,
- increased the productivity and reduced he cost of production,
- enhanced the quality and increased the demand of terracotta products,
-
- increased in income and improvement in standard of life is recorded.
The approximate manufacturing cost of portable, energy efficient, low cost, down draft kiln is depend upon the size which is in the range of Rs. 10,000 to 25,000/-. The gas kiln is very easy to manufacture at small fabrication workshop having facility of welding and drilling, also it is very easy to operate, requires low maintenance, portable and it can changes the overall life style of pottery artisans.

Invention:
A portable, low cost, energy efficient, down draft, gas kiln has been developed to bake superior quality artistic terracotta products.

Description of invention:
A kiln may be described as an enclosure to contain heat, to heat up the potter’s pots. So far the Potters have developed a countless number of different types of kilns depending upon the demand, tradition, skills and materials available. The traditional kilns are primarily based on wood as fuel and can be of different types: bonfire kilns, up-draught kilns or downdraught kilns. Bonfire kilns, dating back to 10000 years, involve open firing in a shallow pit. Despite flexibility of fuel that can be used, these kilns suffer from low temperatures of firing, poor ware strength and extensive breakage.
The energy efficient, low cost, down draft kiln with natural flow of gas is made by mild steel angle iron, perforated iron sheet, ceramic fibre and ceramic board. The down draft kiln avoids much of the temperature variation problems found in other types of kilns and is generally considered to be the ultimate development in fuel burning kilns. As burning of natural and compressed gas is safe, non hazardous for health, easily burned, relatively cheaper than wood, also it is readily available to both commercial & non-commercial users and burners for this type of fuel is simple, cheaper and easily available in local markets. For development of low cost, energy efficient, down draft gas kiln the detail process is as follows -

Description of the preferred embodiments
Referring now to the drawing and more particularly to Fig. 1, there is shown a gas fired top loaded, down draft kiln for transferring heat by radiation and convection to objects placed in its chamber, defined by four vertical side walls, the top cover Fig. 2.1 is fixed with the help of four clamps Fig. 2.7. Natural gas flow is used to operate the kiln. Experimentations are conducted for one to eight cubic feet volumes of kilns and it is found that the natural flow of gas with these volumes gives best energy efficiency. Two types of kilns are made first one is movable and second one is permanent structure.

A. Body of kiln
The movable type kiln (Fig. 1) is constructed as one complete unit with welded steel frames (Fig 1.9). The wall of the kiln is made with the help of perforated iron sheet (Fig. 1.8). The base of the body is fabricated on suitable height of angle iron frame (Fig. 1.6).

B. Inner insulation of kiln
Two layers of insulations are used inside the kiln. For the first layer 1.5 inches thick ceramic fiber (Fig. 2.3) is used. Also two inches thick ceramic board (Fig. 2.2) is fixed as a second layer for better insulation and stability. The ceramic board is pasted on the ceramic fiber with the help of diluted sodium silicate with water. The ceramic fiber & ceramic board is pasted on the wall with the help of Sodium-silicate.

C. Heat inlet door
The heat inlet door (Fig 4.4) is made by 1.5 inches diameter porcelain pipe and the length of porcelain pipe is depended on overall thickness of kiln wall.

D. LPG heating torch with burner
In manufacturing industries, heating torches and flame heaters have a wide range of uses such as high capacity staking, curing, drying, heat-shrinking, air-heating, sterilization, adhesive activation, air-scrubbing, and air-knives. The heating torch/ burner is used to heat the kiln are natural draft, simple, inexpensive and easily available in the local market. The number and size of burners is directly related with volume of kiln and the rate of flow of hot air inside the kiln. As it is very clear that when the volume of kiln increases, then accordingly the size and number of burners are also increasing. For one cubic feet (1x1x1 foot) size kiln one heating torch with 22 mm diameter is sufficient. If the size increases upto 3.38 cubic feet (1.5 x 1.5 x 1.5 feet) then there is requirement of two heating burner of same size. Two burners of 25 mm diameter are found suitable for 8 cubic feet kiln. Each burner is connected by individual gas cylinder. Two burners should not be connected with the help of T–coupling (Fig. 1.4) because any time some accidents may occur. The gas heating torches / burner (Fig. 1.7) are fixed just in front of heat inlet door with the help of MS stand (Fig 1.5).

E. Hose
The gas hose (Fig. 1.3) transports gases from the regulators to the heating torch. Popper care and maintenance of the hose assists the operator in maintaining a safe, efficient shop or work area. Gas hoses are often exposed to severe abuse. They can provide efficient service with proper care. Hose splices (Fig. 1.4) and excessive hose length can restrict and reduce the amount of gas flow within the hose. Operator should frequently inspect the hose and when necessary, replace them. For 2, & 3 size burners use of M-68 nipple and M-6 LPG industrial rubber hose and for 4, 5 & 6 size burners use of M-88 nipple and M-8 LPG industrial rubber hose gives better results.

F. Regulator
Commercially available pressure regulator (Fig. 1.2) attached with pressure gauge is used for this kiln. During firing the pressure gauge is essential component because during smoking or slow firing or fast firing certain range of pressure of gas is to be maintained for achieving constant increase in firing temperature.

G. Chimney
The chimney (Fig -1.8) is made of GI bend and GI pipes. If proper diameter of chimney is selected for the kiln then only it will generate appropriate draft inside the kiln. Two centimeter diameter and 1.5 meter height chimney is sufficient for the kiln of volume upto 0.1 cubic meters. But if the volume of kiln is in between 0.1 to 0.5 cubic meters then for better draft the diameter of chimney is in between 3 to 4 centimeter and height of the chimney must be more than 2 meter.

H. Lid
The top loaded gas kiln is closed by rectangle lid (Fig. 2.1). The lid is fabricated by angle iron (Fig. 2.6) and perforated sheet. A layer of ceramic fiber is fixed in the inner side of perforated metal sheet and ceramic sheet is pasted on the ceramic fiber for better insulation and durability. Four numbers of steeliness steel nut-bolts with washer (Fig. 2.5) are used to keep intact the insulating materials with perforated sheet. The lid panel is fixed with kiln body with the help of 4 nos of clamps, butterfly nut-bolts (Fig. 2.4 & 2.7).

I. Platform
Inside the kiln a platform (Fig. 3) is fixed to channelize the flame and to protect the pottery articles from direct heating. The pottery wares are loaded on the platform (Fig – 3.1) and the level of platform is fixed above the level of gas inlet pipe. Care should be taken that the wares should be above the level of flame and flame should not touch the wares. The platform is made by 20 mm thick cordierite mullite refractory plates which are suitable for firing upto 1200 degree centigrade temperate. The thickness of cordierite mullite refractory plate is as per loading mass of wares. A tunnel (Fig -3.2) is made inside the middle portion of platform to move out the flue gases from kiln (Fig-3.3). Some slots (Fig. 3.4) are made on the platform to move flue gases and for uniform distribution of heat specially above the platform.

J. Movement of hot air through diversion wall
Two numbers of diversion walls (Fig. 4.2) are constructed by high alumina insulating brick. It is positioned just in front of both the hot air inlet passages (Fig. 4.4) and in the middle of side walls (Fig. 4.9). The hot gases (Fig. 5.5) enter the kiln from both burners (Fig. 1.7) and through the hot air inlet door / burner openings (Fig. 4.4) and strikes on the bottom of diversion walls (Fig. 5.4). Than a portion of hot air travels in the direction of pottery wares kept on the platform of kiln and major portion of hot air travels on upper free passage (Fig. 5.3). Again hot air strikes on the upper wall (Fig. 4.6) and travels in different directions (Fig. 5.6). So in this case maximum heat transferred to the pottery masses and flue gases moves towards the downward side (Fig.5.7 & 5.8) and enter inside the exhaust tunnel of the platform (Fig. 5.9). After moving the 360 degree rotation the flue gases enters in the chimney (Fig. 5.2) and exit at the top of the kiln (Fig. 5.1). The natural draft of a chimney is used to expel the flue gases.

H. Easy to fabrication
The kiln’s design is so simple that it can be fabricated at very small workshop of any small town. Manufacturing of kiln in large quantity will reduced the cost of production but if anyone wants of fabricate a single piece at their own place; it can be fabricated very easily.

I. Precautions
It is not recommended to fir the kiln during rainy session when humidity is very high. Even if firing is required then it is better to partial open the LID of kiln upto 450 degree centigrade. Then the moisture will not damage the kiln or pottery articles.

Surprising features of the gas kiln
1. This type of downdraft kiln consumes very less gas as compare to existing old model down draft gas kilns because the hot air enters from front wall and hits the heat diversion wall and radiates maximum heat to the pottery articles.
2. Breakage of pottery wares during baking is almost nil.

Comparative chart
S No Existing kiln Newly developed kiln
1 The hot air enters through inlet door which is made in the bottom of kiln. The hot air inlet door is made in front wall.
2 The hot air hits the on the top arch shaped wall and pass the kiln without much obstacles and maximum heat goes out without transferring much energy to the pottery articles. The hot air enters from front wall and hits the heat diversion wall then again it hits the upper LID and radiate maximum heat to the pottery articles.

Novelty of kiln
For the village pottery production introduction of portable, cost effective, energy efficient very simple designed, down-draft gas kiln reduces the cost of pottery products and enhance the quality of pottery products. In this down draft gas kiln upto 1100 degree centigrade temperature is easily achieved. The natural flow of gas makes the kiln cost effective and easy to operate. Even in rural area after three days training, the illiterate women’s are operating this kiln without any difficulties. The design of kiln is very simple so that it can be made at any small workshop because the body of kiln is made by angle iron and perforated sheet. The red clay brick and clay mortar is easily available in rural area and this can be used as second alternative for making of kiln’s body. The ceramic fiber, ceramic board, cordierite mullite refractory plates, heating torch/ burner, gas regulator and GI pipe for chimney are standard product which is easily available in small town of reputed suppliers. The hot gases from one/both burners enter the kiln from the side wall, hits the heat diversion wall and go over the ware then take a 180 o turn and come down to the flue gas exit. The natural draft of a chimney is used to expel the flue gases. The flue gases come out of the openings at the top of the kiln. The kiln is energy efficient because 2 to 3 kg gas is used to bake 50 kg wet pottery products.

Attachments:
Following compulsory and optional attachments are listed for the energy efficient small down-draft gas kiln -
Compulsory – For minimum loss of energy two inches thick ceramic board must be used. For better efficiency of kiln appropriate diameter and size of burner and chimney must be selected.
Optional – For reduction of cost the outer wall of kiln can be made by red clay bricks and clay mortar instead of angle iron and perforated metal sheet. The outer surface of the wall will be polished with the mixture of cow-dung and clay. The mixture of clay and cow-dung is good binder and it protects the wall of kiln from cracks. After every alternate firing the surface of wall is maintained with the help of above said mixture.

Field Trial:
For field trial the small portable gas kiln, is issued to the artisans of Jai Durga Self Help Group, Waigaon, Wardha, (Maharashtra). The newly developed kiln has resulted in multiple benefits to the beneficiary’s like-
1) The firing cost of products reduced drastically.
2) The newly designed kiln enables to increases the productivity, as the beneficiary no longer has to depend upon the wood fired kilns.
3) Human drudgery and environment pollution completely eradicated.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1. Isometric-view of energy efficient down-draft gas kiln with other attachments
1.1. Gas cylinder
1.2. Gas regulator
1.3. Gas hose pipe
1.4. T–coupling for gas pipe
1.5. Bracket holder for gas torch
1.6. Base of the body made by angle iron
1.7. Gas heating torch with other accessories
1.8. Walls made by perforated mild iron sheet
1.9. Angle iron frame with wall of perforated sheet

Figure 2. Isometric-view of down draft gas kiln
2.1. Lid made by perforated mild iron sheet
2.2. Inner portion of wall made by ceramic board
2.3. Intermediate insulation made by ceramic fiber
2.4. Clamp hole to lock lid with kiln
2.5. Stainless steel nuts-bolts and washers
2.6. Angle iron frame of lid / cover
2.7. Clamp to lock lid with kiln

Figure 3. Loading platform of down draft gas kiln
3.1. Platform of kiln
3.2. Below the platform passage to travel flue gases
3.3. End of passage made inside the platform and connected to exhaust pipe
3.4. Slots to travel flue gases

Figure 4. Cut-section of down draft gas kiln
4.1 Outlet of chimney
4.2 Front face of diversion wall
4.3 Chimney
4.4 Heat inlet door made by porcelain pipe fixed in the front wall of kiln
4.5 GI bend fixed on chimney
4.6 Top wall made by LID
4.7 Supports below the loading platform.
4.8 Loading platform
4.9 Middle of side walls

Figure 5. Cut-section with flow of gases inside the down draft gas kiln
5.1 Exit of flue gases
5.2 Flue gases are travelling inside the chimney
5.3 Hot air going upward
5.4 Hot air hits the heat diversion wall
5.5 Hot air enters though burner openings
5.6 Hot airs are hitting the top wall
5.7 After hitting the top wall hot airs are travelling from top to bottom
5.8 Hot airs are travelling from side to bottom
5.9 Hot airs are travelling from tunnel of platform and enters in the chimney

Sheet 1 of 5

Name of inventors – S P Mishra, Mr Anil Kumar Gupta, and Mr Vivek Masne
Patent Attorney – Dr Ushashi Guha

Sheet 2 of 5

Name of inventors – S P Mishra, Mr Anil Kumar Gupta, and Mr Vivek Masne
Patent Attorney – Dr Ushashi Guha

Sheet 3 of 5

Name of inventors – S P Mishra, Mr Anil Kumar Gupta, and Mr Vivek Masne
Patent Attorney – Dr Ushashi Guha

Sheet 4 of 5

Name of inventors – S P Mishra, Mr Anil Kumar Gupta, and Mr Vivek Masne
Patent Attorney – Dr Ushashi Guha

Sheet 5 of 5

Name of inventors – S P Mishra, Mr Anil Kumar Gupta, and Mr Vivek Masne
Patent Attorney – Dr Ushashi Guha

We claim,
1) A downdraft kiln with the natural flow of gas, comprising; low-cost gas kiln made by angle iron, perforated MS sheet and other features having low-cost insulation system, fitted with a platform; having inlet doors for entry of hot air, wherein; an exhaust system is incorporated; having a LID specially designed.
2) The second claim is for low-cost wall of gas kiln as claimed in 1, is made by angle-iron (Fig. 1.9) and plain/perforated CRC sheet (Fig-1.8) or low-cost wall of gas kiln made by red clay country brick and mud mortar and plaster with the help of cow-dung and mud.
3) The third claim is for low cost insulation system as claimed in 1, is made by ceramic board (Fig-2.2) and ceramic fibre (Fig-2.3) which is pasted with the help of sodium-silicate and fixed with the help of stainless steel nut-bolts and washers (Fig-2.5).
4) The fourth claim is for the platform as claimed in 1, is 20 mm thick cordierite mullite refractory plates for loading of pottery wares which are suitable for firing upto 1200 degree centigrade temperate made above the level of gas inlet holes (Fig-3).
5) The fifth claim is for heat inlet door (Fig 4.4) as claimed in 1, which is made by 1.5 inches diameter porcelain pipe and the length of porcelain pipe is depended on overall thickness of kiln wall.
6) The sixth claim is for the position of heat entry holes made in the front wall (Fig. 4.4) and hits the heat diversion walls and after that the heat radiates inside the kiln and go over the ware then take a 180 o turn and come down to the flue gas exit.
7) The seventh claim is for the exhaust system as claimed in 1, is fitted below the platform (Fig. 4.7) and the diameter of galvanized iron pipe used as per the volume of kiln (Fig. 4.3).
8) The eighth claim is for the Lid/cover as claimed in 1, for top loaded kiln (Fig-2.1) made by angle iron frame (Fig. 2.6) and perforated sheet and insulated by ceramic fibre and board.
9) Having all components as per claim 1, 2, 3, 4, 5, 6, 7 & 8 is constituted the portable, energy efficient, low cost, down draft kiln with natural flow of gas.
Dated this 9th day of March, 2018,
(Dr. Ushoshi Guha)
Applicant’s Agent
To,
The Controller of Patents,
The Patent Office,
At Mumbai.
ABSTRACT
Portable, low cost, energy efficient, down draft, gas kiln
for home scale pottery industry

The energy efficient, portable, low cost, down draft kiln with natural flow of gas (Fig. 1) is made by mild steel angle iron (Fig. 1.9), perforated iron sheet (Fig. 1.8), ceramic fibre (Fig. 2.3) and ceramic board (Fig. 2.2). The platform of 20 mm thick cordierite mullite refractory plates (Fig-3) for loading of pottery wares which are suitable for firing upto 1200 degree centigrade temperate made above the level of gas inlet holes. The hot gases from one/both burners enter the kiln from the front wall (Fig. 4.4), hits the heat diversion wall (Fig-4.2) and go over the ware then take a 180 o turn and come down to the flue gas exit. The down draft kiln avoids much of the temperature variation problems found in other types of kilns and is generally considered to be the ultimate development in fuel burning kilns. As burning of natural and compressed gas is safe, non hazardous for health, easily burned, relatively cheap, also it is readily available to both commercial & non-commercial users and burners for this type of fuel is simple and easily available.