Field of Invention:
The present invention relates to a 'Table top continuous wet cum dry grinder' for variety of food materials, for grinding of wet and dry food materials like cereals, pulses, spices. The 'Table top continuous wet cum dry grinder' henceforth can be referred as a device. The device of the present invention is particularly useful for grinding of cereals, pulses, spices and other food items. The product processed by using this device has uniform particle size and processed under hygienic conditions in a continuous manner.
In case a table top device is made available for grinding of cereals, pulses and spices in wet and dry form, it would result in reduction in human drudgery, clean and hygienic end product and will have uniform particle size continuously.
Background and Description of prior Art:
Presently the wet and dry grinding machines available in the market are of batch type and are used for dry and wet grinding of cereals, pulses and spices. The major problem in these grinding machines is non-uniform particle size resulting in variation in particle size and manual handling of raw materials which leads to poor and unhygienic end product. These units are tedious and labour intensive and time consuming in their operations. In case a suitable table top continuous device is made available for both wet cum dry grinding of cereals, pulses and spices which would result in reduction in hardship, clean and hygienic end product and will have uniform particle sized flour and wet cum dry grinding machine would benefit the society at large and food industry in particular. Realizing the importance and necessity. Central Food Technological Research Institute, Mysore, India has successfully designed and developed a Table top continuous wet cum dry grinder of cereals (rice, ragi etc), pulses (Black gram etc.) and spices (turmeric, chilly etc.).
:BLWT 11>03-20I5- 17':

Hitherto the process of wet and dry grinding of cereals, pulses and spices is done in big dry grinders and small-scale batch type wet grinding machines. The dry grinders are of different concepts ranging from hammer mill (both vertical and horizontal), pin mill, friction/disc grinder, ball mill, domestic mixer grinder are a few to mention. Whereas for grinding of wet material, different batch type models are available in the market and would range from single oscillating stone wet grinder, twin stone grinder, mixer grinder Etc.
Hammer mill (Vertical and horizontal models): Hammer mill is based on the concept of hammering action to the food materials and is as shown in figure - 1. The powdered material is forced through the sieve kept below the hammer which forces the ground . material away from the grinding zone. In its construction the hammer mill consists of hammers either fixed or swivel (1) are fixed to the rotating shaft (2), which is supported at the housing (3) ends by a set of bearings (4). Hammers are rotated by an electric motor of suitable power (5) mounted on a frame (6). A suitable sieve (7) having a known hole size/aperture is mounted inside the housing (3) and a swivel door (8) to cover the grinder housing. The housing has an outlet for discharging the ground material. A feed tray (9) is kept above the housing (3) for feeding of the raw material. All the contact parts of the hammer mill are made of stainless steel or alloy steel. The major drawbacks of hammer mill are
> The machines are large in size.
> Cost of the machine is too expensive.
> The particle size can be varied only by changing of the sieve, that too giving a size range.
> Sieves have a limited life time as they are prone for ruptures.
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> Machine has to rotate at high speeds, in the range of 6000-8000 RPM, resulting in vibration needing grouting.
> A slight imbalance could lead to violent vibrations.
> Due to pressure creation inside the grinding zone, the feed material and powder will escape from the feeding point.
> Dust is created in the grinding room, leading to environmental problems, due to high speed operations.
> Machine is not suitable for wet grinding of food and other wet/dry non-food materials.
Pin mill: Pin mill is based on the concept shearing the food material between stationery and fixed pins as shown in figure-2. The powdered material is forced through the sieve kept below the rotating pins which forces the ground material away from the grinding zone. In its construction the pin mill consists of fixed pins (10) mounted on the body (11) and an end cover (Ha) of the dry grinding mill and rotating pins (12) are fixed to the rotafing disc (13) which is connected to a shaft (14). A driven pulley (15) is mounted on to the shaft (14) and the shaft rotates inside the bearings (16). The driven pulley mounted on the shaft is connected to the drive pulley (17) by a set of bells (18) and Ihe driven pulley is mounted on the extended shaft of the electric motor (19) and is mounted on a main frame (19a). A feeding tray is mounted above the body (11) for storing and feeding of the raw materials. An outlet chute (20) will discharge the ground material away from the grinding zone.
All the contact parts of the pin mill are made of stainless steel or alloy steel. The drawbacks of pin mill are
> The machines are too big in size.
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> The particle size can be varied only by changing of the sieve.
> Sieves have a limited life time as they are prone for ruptures.
> Machines rotate at high speeds and in the range of 10000-12000 RPM, resulting in vibration needing grouting.
> A slight imbalance makes the machine to vibrate violently.
> Machine vibration is very high and needs, to be grouted.
> When the pressure is generated inside the grinding zone, the feed material and powder will escape from the feeding point.
. > Dust is created in the grinding room, leading to environmental problems, due to high speed operations.
> Machine is not suitable for wet grinding of food and other wet/dry non-food
materials.
Disc/Friction mill: Disc/Friction mill is based on the concept shearing the food material between stationery and rotating disc and as shown in figure-3. The powdered material is forced through an out let mounted below the grinding zone. In its construction the disc/friction mill consists of fixed disc (21) mounted on the body (22) of the dry disc/friction grinding mill and rotating disc (23) is cormected to a shaft (24). Gap between the fixed disc and the rotating disc is varied by a hand wheel (26). A driven pulley (25) is mounted on to the shaft (24) and the shaft rotates inside the bearings (27). The driven pulley mounted on the shaft is connected to the drive pulley (28) by a set of belts (29) and the driven pulley is mounted on the extended shaft of the electric motor (30). A feeding tray is mounted above the body (31) for storing and feeding of the raw materials. An outlet chute (32) will discharge the ground material away from the grinding zone. All the contact parts of the disc/friction mill are made of stainless steel or alloy steel.
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The drawbacks of using disc/friction mill are
> The machines large in size.
> Machine rotates at high speeds and in the range of 3000 RPM.
> Machine vibration is very high and need to be grouted.
> Dust is created in the grinding room, leading to environmental problems..
> Machine is not suitable for wet grinding of food and other wet/dry non-food materials.
Wet grinders (oscillating/twin stone): Stone grinder is a batch type grinder, and is extensively used in households as well as in commercial applications for grinding of spices, batter and other snack food such as Dosa and Idli and other adjuncts. They work on the principle of compression and shear and the grinder is shown in figure-4. Food material (soaked in water) is fed in to the container (33) of the wet grinder along with a known amount of water. The food material is carried along with the rotating stone (34) of the grinder and fed into the rotating stone (35). Due to its own weight as well as due to momentum of the stone, the soaked grain crushed between the stationery and mobile stones. With continuous grinding of the food material, as it is pushed to grinding zone several times, the particle size is reduced to a desired size and consistency by adding water at regular intervals. After attaining the desired level of grinding, material/batter is discharged manually into a container. The drawbacks of using stone grinder are
> The machine grinds the material in batch mode.
> Machine speed is in the range of 400-600 RPM.
> Machine vibrates due to non uniform load.
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> Each batch of dry/wet grinding takes at least 20-25 minutes and water need to added at regular intervals.
> They are not suitable for fine grinding.
> Particle size in the ground batter is not uniform.
Domestic Mixer/Grinder: This domestic appliance as shown in figure-5 works on the principle of shear at high speed. The motor (36) of the grinder rotates at around 11000-14000 RPM and works on a batch mode. Different blade profiles (37) are available for different applications such as juice extraction, wet and dry grinding. They are very popular and extensively used in households. In its construction it has an electric motor (36) and a constant volume vessel (38). The vessel is fit with cutting blades at the center and the food material is ground due to high shear force of the blades (37). The drawbacks of domestic mixer grinder are,
> The machine grinds the material in batch mode.
> Machine rotates at high speeds and in the range of 11000-13000 RPM.
> Machine carmot be operated continuously as there is a tendency for generation of heat inside the motor and would trip.
> Each batch of dry/wet grinding takes a minimum of 10-15 minutes.
> They are not suitable for fine grinding.
> The particle size is not uniform.
Reference may also be made to the wet grinding machine developed at Central Food Technological Research Institute at Mysore (India). The machine is used for grinding of food materials and has a pair of grinding wheels. Gap between the stationer and rotary wheels is adjusted by axial movement of the stationery wheel and relative motion between the pair of grinding wheels which induces sheaf. Soaked materials is fed into the grinding
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zone along with water and food material experiences shear when it comes in between the
wheels, thereby reduction in particle size. Subsequent reduction in particle size is achieved
by reducing the gap between the wheels. The machine is not intended for domestic
application.
The drawbacks of wet grinding machine are,
• It is difficult to vary gap between the stationer and rotary wheels.
• Device uses a cylindrical disc where in there is tendency for the wheel to crack.
• The wheels touch one another during application of axial thrust.
• There is no stopper/arrester for the final gap.
• Gap will vary during grinding as the stationer wheel is held in position by a spring.
• Device requires higher torque for the given grinding rate.
• Machine is heavy and cannot be used for domestic applications. Object of the invention:
The main object of the present invention is to design a table top continuous wet cum dry
grinder machine having silicon carbide wheels for grinding of cereals, pulses and spices.
Still another object is to provide table top continuous wet cum dry grinder machine is to
conserve energy.
Yet another object is to provide table top continuous wet cum dry grinder machine having
truncated conical wheels.
Still yet another object is to provide table top continuous wet cum dry grinder machine
which transmits maximum torque form the motor to the rotating grinding wheel.
-Still another object is to provide table top continuous wet cum dry grinder machine
having silicon carbide wheels for grinding of food materials.
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Yet another object is to provide table top continuous wet cum dry grinder machine which grinds the food material continuously.
Still yet another object is to provide table top continuous wet cum dry grinder machine to grind the food material to the required particle size. Still another object of the present invention is to reduce manual drudgery. Yet another object is to increase productivity.
Still another object is to provide a table top continuous wet cum dry grinder machine capable of working with a wide range of material for grinding.
The device of the present invention overcomes most of the drawbacks of the existing grinding equipments. Brief Description of Drawings:
In the drawing accompanying this specification, figure-6 (also figure -7) represents the entire assembly of the grinder and has the following sub-assemblies; a) The conical base sub-assembly, b). Electric drive sub - assembly, c). Rotary grinder , d). Cutting blade sub-assembly, e). Discharge chute sub-assembly, f). Stationery grinder sub-assembly, g). A feed hopper sub-assembly. Machine has the provision for varying the particle size of the ground material. The following are the brief specifications of the machine.
• Capacity of Grinder 15-20 kg/h (wet batter)
• Grinding Wheel SiC (Black wheel with grit size 24-36)
• Motor Horsepower 1.0 HP
• Supply voltage 230 VAC/1 Ph/50 Hz
• Material of Housing Stainless Steel
• Weight of the machine 20-25 kg (Aprox.)
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• Floor space needed 0.2 * 0.2 m^
• Height of the machine 0.5 m (Aprox.)
In the drawing accompanying this specification, figure-6 represents an embodiment of the
table top continuous wet cum dry grinder machine for cereals, pulses and spices.
In the drawing accompanying this specification, figure-5 represents The Domestic
Mixer/Grinder.
In the drawing accompanying this specification, figure-4 represents The Wet grinders
(oscillating/twin stone).
In the drawing accompanying this specification, figure-3 represents The Disc/Friction
mill.
In the drawing accompanying this specification,, figure-2 represents The Pin mill.
In the drawing accompanying this specification, figure-1 represents Hammer mill (Vertical
and horizontal models.
Summary of the Invention:
Accordingly, the present invention provides table top continuous wet cum dry grinder
machine, comprises of a main frame (1) which houses all the parts of the machine. An
electric motor (2) having one half of coupling (3) at the end of the shaft, is fit inside the
main frame (1) through a set of fasteners (4) and the electric supply to the motor is by a set
of switches (5). One end of the drive shaft (6) is fit with another half of the coupling (3)
and mounted inside the bearings (7) which in turn is mounted inside a bearing housing (8)
and is welded to the collector (9). Other end of the shaft carries a truncated conical (male)
silicon carbide wheel (10a) and a primary grinding blade (11) is mounted on the silicon
carbide wheel (10a) and is firmly held to the drive shaft (6) by a nut (12). A top cover (13)
is screwed to the collector (9) wherein the particle size of the ground material can be
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varied by rotation of the top cover (13) and inside of the top cover (13) has a matching
silicon carbide (female) wheel (10b). A feed hopper (14) is mounted on top cover (13).
In another embodiment of the present invention, the device has main frame (1).
Yet another embodiment of the present invention, the device has an electric motor (2) of
power rating from 750-1000 W, which acts as a prime mover.
Yet another embodiment of the present invention, the device has one half of the coupling
(3).
Still another embodiment of the present invention, the electric motor is fastened to the
main frame by a set of fasteners (4).
Yet another embodiment of the present invention, the device has a set of switches (5) to
switch ON/OFF the electric motor.
Still another embodiment of the present invention, the device has a shaft (6).
Still yet another embodiment of the present invention, the device has a set of bearings (7).
Yet another embodiment of the present invention, the device has a bearing housing (8).
Another embodiment of the present invention, the device has a collector (9).
Yet another embodiment of the present invention, the device has a truncated conical
(male) silicon carbide wheel (10a).
Still yet another embodiment of the present invention, the device has a primary grinding
blade (11).
Yet another embodiment of the present invention, the device has a nut (12). ,
Still another embodiment of the present invention, the device has a top cover (13).
Still yet another embodiment of the present invention, the device has a matching silicon
carbide (female) wheel (10b).
Yet another embodiment of the present invention, the device has a feed hopper (14).
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Still another embodiment is to develop a negative pressure is generated along the axis of
rotation and thereby the feed material is sucked in to the grinding zone continuously.
Yet another embodiment of the present invention, in which, the food material is ground in
single pass which saves the time.
Still yet another embodiment of the present invention, table top continuous wet cum dry
grinder machine is useful for grinding of different varieties of grains like Ragi, Wheat and
Spices.
Still another embodiment of the present invention, grinding operation can be started or
stopped with short notice.
Still yet another embodiment of the present invention, the dry/wet grinding process is
continuous.
All food /non food contact parts of the machine are made of either stainless steel or silicon
carbide wheels and the use of any other material such as Coated steel. Brass, Bronze,
plastics, granite, stone, silicon carbide of different grades and bonding materials etc. will
not restrict the inventive steps of the invention.
The following example is given by way of illustration of the present invention and
therefore should not be construed to limit the scope of the present invention. The working .
of the table top continuous wet cum dry grinder machine is explained below with
particular reference to rice/ragi and urdhal.
Novelty
The novelty of the table top continuous wet cum dry grinder machine design lies in its
continuous wet cum dry grinding of food /non-food material to the required particle size.
The design uses a set of truncated conical silicon carbide wheels (one wheel is stationer
and the other movable) a having a grit size of 24-36 Taylor mesh and the grits are bound
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together (to hollow truncated conical prism) by vitrified bonding. The design is free from cracking of SiC stationery and rotary wheels. Advantage of using the conical wheels is the usage of available torque of the electric motor efficiently. Angle of the cone is in the range of 30-35 degrees with linier flow length of 25-30 mm which change the flow of the ground material vertically.
Exiample 1
The working of the top continuous wet cum dry grinder machine is explained below with particular reference to grinding of Rice and Urdhal. The Rice and Urdhal soaked in water for 4 hours. Rice and dhal are in the ratio of 1:0.2 and the mixture is soaked in water with a mixture to water ratio of 1:1.1. It is observed that the increased in volume of Rice was 1.45 times the initial volume and that of Urdhal is around 2.18. The silicon carbide rotor of the table top continuous wet cum dry grinder machine rotates at a speed of 1440-2880 RPM. The soaked mixture of Rice and Urdhal is fed in to the feed hopper and a little amount of water is added for smooth flow of the grain mixture. The primary cutter reduces the particle size of the rice mixture and the final particle size of 60 micron is obtained by grinding between the silicon carbide wheels. The ground batter is collected in a container for further processing.
Example 2 The working of the table top continuous wet cum dry grinder machine is explained below with particular reference to grinding of Ragi and Urdhal. The Ragi and urdhal soaked in water for 4 hours. A Ragi and Urdhal are in the ratio of 1:0.2 and the mixture of Ragi and Urdhal is soaked in water with mixture to water ratio of 1:1.1. It is observed that the
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increased in volume of Ragi was 1.2 times the initial volume and that of Urdhal is around 2.18. The table top continuous wet cum dry grinder machine's silicon carbide rotor rotates at a speed of 1440-2880 RPM. The soaked mixture of Ragi and Urdhal is fed into the feed hopper and little amount of water is added for smooth flow of the grain mixture. The primary cutter reduces the particle size of the Ragi mixture and the final particle size of 60 micron is. obtained by grinding between the silicon carbide wheels. The ground batter is collected in container for further processing.
Different types of grinding machines are needed for different raw materials and each has its drawbacks.
The main advantages of the present invention are:
> Varying the gap between the stationary and rotary silicon carbide wheel will result in different particle sizes, but a uniform size for a given gap.
> The primary cutter develops a negative pressure along the axis of rotation and thereby the feed material is sucked in to the grinding zone continuously.
> Single pass grinding saves the time of grinding.
> The table top continuous wet cum dry grinder machine is useful for grinding of different varieties of grains like Ragi, Rice, Wheat, Urdhal and Spices.
> The grinding operation can be started or stopped with a short notice.
> The dry/wet grinding process is continuous.
> Grinding process has been divided in two parts, primary size reduction by primary cutter then secondary size reduction by silicon carbide wheels.

We Claim
1. The table top continuous wet cum dry grinder machine, comprises of a main frame (1) which houses all the parts of the machine. An electric motor (2) having one half of coupling (3) at the end of the shaft, is fitted inside the main frame (1) through a set of fasteners (4) and the electric supply to the motor is by a set of switches (5). One end of the drive shaft (6) is Fit with another half of the coupling (3) and mounted inside the bearings (7) which in turn is mounted inside a bearing housing (8) and is welded to the collector (9). Other end of the shaft carries a truncated conical (male) silicon carbide wheel (10a) and a primary grinding blade (11) is mounted on the silicon carbide wheel (10) and is firmly held to the drive shaft (6) by a nut (12). A top cover (13) is screwed to the collector (9) wherein the particle size of the ground material can be varied by rotation of the top cover (13) and inside of the top cover (13) has a matching silicon carbide (female) wheel (10b). A feed hopper (14) is mounted on top of the top cover (13).
2. A table top continuous wet cum dry grinder as claimed in claim 1, has main frame (l)is made of stainless steel or any other material such as Coated steel. Brass, Bronze, plastics, granite, stone etc.
3. A table top continuous wet cum dry grinder as claimed in claim 1 - 2 has an electric motor (2) of power rating from 750-1000 W which acts as a prime mover.
4. A table top continuous wet cum dry grinder machine as claimed in claim 1 , has a truncated conical (male) silicon carbide wheel (10a), and has a matching silicon carbide (female) wheel (10b), having grit size of 24-36 Taylor mesh.

5. A table top continuous wet cum dry grinder as claimed in claim 1, has a top cover (13). Top cover (13) is screwed to the collector (9) wherein the particle size of the ground material can be varied by rotation of the top cover.
6. A table top continuous wet cum dry grinder as claimed in claim 1, where in a negative pressure is generated along the axis of rotation and thereby the feed material is sucked in to the grinding zone continuously.
7. A table top continuous wet cum dry grinder as claimed in claim 1, wherein, the food material is ground in single pass thereby saving of time.
8. A table top continuous wet cum dry grinder as claimed in claim 1, is useful for grinding of different varieties of grains like Ragi, Wheat, and Cereals, Pulses, Spices.
9. A table top continuous wet cum dry grinder as claimed in claim 1, wherein the dry/wet grinding process is continuous.
10. A table top continuous wet cum dry grinder as claimed in claim 1, wherein, all food/non food contact parts of the device are made of either of stainless steel and silicon carbide wheels and the use of any other material such as Coated steel, Brass, Bronze, plastics, granite, stone, silicon carbide of different grades and bonding materials etc.