Indian Patents. 272556:A WET GRINDER TO IMPROVE PERFORMANCE AND EFFICIENCY

Title of Invention	A WET GRINDER TO IMPROVE PERFORMANCE AND EFFICIENCY
Abstract	This invention relates to an improved wet grinder to improve performance and efficiency comprising of inwardly tapered roller and base stone, which compensates the effect of centrifugal force forcing large particles to move outwards.

Full Text	FIELD OF INVENTION This invention relates to an improved wet grinder to improve performance and efficiency. PRIOR ART Wet grinders are tools used to make batter out of soaked grains and lentils. Wet grinder consisted of a large rock with a hole in it, where a cylindrical rock with a wooden handle fit in. The grain and lentil mixture was poured in, with water and the cylinder was rotated by the handle on the top to grind the food together. The batter is used for various food items like idli, dosa and vada. The earlier form of wet grinder used mechanical energy in which the user has to rotate the top stone to grind the medium. The invention of electricity has led to the development of electric-powered wet grinders. The powered wet grinders have both the top and base stone rotating. There are different types of wet grinders available such as conventional wet grinder, tilting wet grinder, table top wet grinder and commercial wet grinder. In conventional wet grinder, the base stone is rotated using the pulley and belt mechanism, while the smaller stone is held and rotated inside the pit though the arm set mechanism. The tilting wet grinder made it easy to remove the batter and clean the vessel more effectively. The base stone in the tilting wet grinder was replaced by a flat stone, whilst the grinding stone was substituted with roller stones, to make the grinding process easier. The table top wet grinder has been designed specially for ease of convenience and offers added features like a detachable drum that can be stored in the refrigerators. Commercial wet grinders are used in homes, hotel industry, and caterers. The existing form of wet grinder uses electrical energy which rotates the bottom stone fitted with the drum. A set of rollers are provided over bottom stone which rotates due to contact friction between base stone and rollers. In the existing designs, the rollers and the bottom stone have either flat surface or tapered surface wherein the base stone has a slope which allows the batter to flow towards the rim of the stone where grinding effect is negligible. Wet grinders are used to make batter out of soaked grain and lentils which consumes high power and takes more time for grinding. Reduced effective grinding area due to uneven distribution of contact pressure between roller and base stone and irregular flow of batter due to centrifuged effect are also observed. In the existing design the particles to be ground have the tendency to move towards the periphery due the centrifugal force. But effective grinding takes place only near the centre, where the contact pressure between the roller and the base stone is maximum. The contact pressure gradually reduces towards the periphery so that particles at the outer portion take more to be ground. OBJECTS OF THE INVENTION The primary object of the present invention is to propose an improved wet grinder to improve performance and efficiency so as to make the batter flow towards the effective grinding area. Another object of the present invention is to propose an improved wet grinder to improve performance and efficiency so as to increase the effective grinding area. Still another object of the present invention is to propose an improved wet grinder to improve performance and efficiency so as to reduce the time taken for grinding. Further object of the present invention is to propose an improved wet grinder to improve performance and efficiency so as to reduce the power consumption and power fluctuation. STATEMENT OF INVENTION According to this invention, there is provided an improved wet grinder to improve performance and efficiency comprising of inwardly tapered roller and base stone, which compensates the effect of centrifugal force forcing large particles to move outwards. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings and wherein: Fig. 1 shows: variation of viscosity with time. Fig. 1' shows: present invention. Fig. 2 shows: Variation of current with time. Fig. 3 (i) shows: Velocity plot for existing design. Fig. 3 (ii) shows: Velocity plot for existing design. Fig. 4 shows: Velocity plot for the present invention. Fig. 5 (i) shows: Displacement in existing design. Fig. 5 (ii) shows: Contact pressure in existing design. Fig. 5 (iii) shows: Contact pressure in 10° design. Fig. 5 (iv) shows: Contact pressure in 12° design. Fig. 5 (v) shows: Contact pressure in 15° finalized design. Fig. 6 (i) shows: Variation of viscosity with respect to time. Fig. 6 (ii) shows: Variation of current with respect to time. DETAIL DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS: Reference may be made to fig .1', wherein the improved wet grinder comprising of inwardly tapered roller and base stone. This provision compensates the effect of centrifugal force, which forces the large particles to move outwards. The taper angle for the bottom stone is 10-15° preferably 12°. A taper is provided in the base stone in such a way that the batter finds it uphill towards the rim and a corresponding taper is provided to the roller. The purpose of the taper angle is to compensate the centrifugal force on the particles during rotation, so that the particle remains in the effective grinding area. The inward tapper angle also provides uniform contact pressure throughout the roller-base stone interface. AVANATAGES Overall grinding time is reduced as compared with the existing wet grinders. As a result, the power consumption is reduced. The fluctuation of power and current is also reduced as there is uniform grinding action. Experiment for measuring viscosity and current: An experiment is conducted to measure the time taken for grinding process. A measured quantity of rice is soaked in water for a period of time. After soaking, the excess water is removed from the rice and the soaked rice is fed into the grinder gradually so that there is no overload to the grinder. Then water is added as per the requirement. After some period of time when the rice grains and water turn to colloidal form, the process of taking samples for measuring viscosity is started. Using a breaker the battery is taken from the grinder at specific intervals for measuring the viscosity. The viscosity is measured using Brookfield viscometer. After measuring the viscosity for each sample, the battery in the breaker is again added to the grinder. This process is continued until the grinder process is completed. The variation of viscosity and current with time is shown in fig. 1 and fig. 2 respectively. From the experiment, it is found that the viscosity decreases gradually as the grinding progresses. But if there is a lack of water, it starts increasing which in turn increases the motor load resulting in slowdown of motor and increased power consumption. The decrease in the speed of rotation indicated the need for addition of water. At a stage the viscosity remains constant for some period of time and this indicates that the grinding process is over. Study of process using high speed photography: The same experimental step is used for analyzing the flow of the batter. Before the grinding process, the high speed camera is focused on the grinder using the tripod covered. The camera is focused such that, the entire top view of the grinder is completely covered. From the experiment, it is found that the grinding process takes place effectively only on the inner portion of the roller. This indicates that, the remaining part is simply rotated consuming power without much contribution to grinding. While the grinding takes place, the heavier particles are forced towards the periphery due to centrifugal force and the smaller particles remain at the centre. These heavier particles at the periphery take more time to grind resulting in more power consumption. Analysis of flow behavior: The model is then analyzed in CFD-ACE+ software for finding the velocity distribution pattern of the batter. Modeling and meshing is done using the CFD-GEOM which is the pre-processor. The model is then imported to the CFD-ACE solver necessary boundary conditions such as wall type and angular velocity are given. Viscosity and density values are also given for the batter. After giving the necessary inputs, the problem is submitted to the solver. The results are viewed using the CFD-VIEW which is the postprocessor. Fig. 3(i) and Fig. 3 (ii) shows the velocity distribution for the existing design. The velocity distribution for the new design is shown in fig. 4. From the analysis, it is observed that the velocity of the batter is zero at the centre and increases towards the periphery. Therefore, velocity is maximum on the periphery where grinding does not take place and very less near the area of effective grinding. Analysis of pressure distribution: As effective grinding takes place only at the inner portion of the roller the model is analyzed for contact pressure distribution in ANSYS 10.0. Since the model is an ax symmetric one the problem is simplified to 2D form. The modeling is done in the preprocessor. The necessary boundary conditions are given in the solver where in the rollers are given its interia to account for its own weight. From the dimensions of the spring and its material, the spring pressure is calculated and entered as load. The problem is then submitted to the solver. The results are viewed using the post processor. From the analysis, it is verified that the contact pressure is effective only at the inner portion and gradually decreases towards the outer edge. The displacement and the pressure distribution for the existing design in shown in the fig. 5(1) and Fig, 5(ii) respectively. The contact pressure for the 10°, 12° and 15° inclination angles are shown in figures 5(iii), 5(iv) and 5(v) respectively. Fabrication and testing of present invention: The proposed new design is fabricated and the performance is compared with the existing design. During the course of fabrication, a problem is encountered in assembly. Since the bush seating is a standard component, it is unable to accommodate the tapered surface. So, a small step is provided at the centre which is haying flat surface. The variation of viscosity and current with time is shown in fig. 6(i) and fig, 6(ii) respectively. Finally, the new design is tested for its performance and it is found out that, the time required for grinding has reduced to 35%. From the graph obtained it can be interred that, the current variation is very less in the proposed design. The current value varies from 1.1 to 1 after 3 minutes and thereafter remains constant till the completion of grinding. This indicates that, the fluctuation of load on the motor is very less compared with the existing design. As a result, the power fluctuation is also minimized to a greater extent. The time taken for completion of the grinding is 13 minutes which is reasonable, less when compared with the existing design which takes 20 minutes for the same. Thus, the grinding time is reduced resulting in decreased power consumption. From the figures obtained from the high speed photograph, it is inferred that the particles constantly moves towards the centre and hence pass through the effective grinding area which results in quicker grinding. This indicates that, the effect of centrifugal force is compensated by the taper provided that makes the grinding process faster. Conclusion: In the existing design, the grinding is carried out effectively only at the inner portion of the roller. It is found out using high speed photography and verified in ANSYS 10.0. Hence, a new model which is having uniform contact pressure between the bottom stone and the rollers is proposed. Also due to the flat surface of the bottom stone, the heavier particles tend to move towards the periphery. This movement of particles due to centrifugal force is minimized by providing inward taper. The effect of the inward taper is analyzed in ANSYS 10.0 and CFD ACE+. It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims :- WE CLAIM: 1. An improved wet grinder to improve performance and efficiency comprising of inwardly tapered roller and base stone, which compensates the effect of centrifugal force forcing large particles to move outwards. 2. An improved wet grinder as claimed in claim 1 wherein the taper angle for the bottom stone is 10-15° preferably 12°. 3. An improved wet grinder as claimed in claim 1 or 2 wherein said taper is provided in the base stone in such a way that the batter finds it uphill towards the rim and a corresponding taper is provided to the roller. 4. An improved wet grinder to improve performance and efficiency substantially as herein described with reference to the accompanying drawings.

Full Text

FIELD OF INVENTION

This invention relates to an improved wet grinder to improve performance and efficiency.

PRIOR ART

Wet grinders are tools used to make batter out of soaked grains and lentils. Wet grinder consisted of a large rock with a hole in it, where a cylindrical rock with a wooden handle fit in. The grain and lentil mixture was poured in, with water and the cylinder was rotated by the handle on the top to grind the food together. The batter is used for various food items like idli, dosa and vada. The earlier form of wet grinder used mechanical energy in which the user has to rotate the top stone to grind the medium. The invention of electricity has led to the development of electric-powered wet grinders. The powered wet grinders have both the top and base stone rotating.

There are different types of wet grinders available such as conventional wet grinder, tilting wet grinder, table top wet grinder and commercial wet grinder. In conventional wet grinder, the base stone is rotated using the pulley and belt mechanism, while the smaller stone is held and rotated inside the pit though the arm set mechanism. The tilting wet grinder made it easy to remove the batter and clean the vessel more effectively. The base stone in the tilting wet grinder was replaced by a flat stone, whilst the grinding stone was substituted with roller stones, to make the grinding process easier. The table top wet grinder has been designed specially for ease of convenience and offers added features like a detachable drum that can be stored in the refrigerators. Commercial wet grinders are used in homes, hotel industry, and caterers.

The existing form of wet grinder uses electrical energy which rotates the bottom stone fitted with the drum. A set of rollers are provided over bottom stone which rotates due to contact friction between base stone and rollers. In the existing designs, the rollers and the bottom stone have either flat surface or tapered surface wherein the base stone has a slope which allows the batter to flow towards the rim of the stone where grinding effect is negligible. Wet grinders are used to make batter out of soaked grain and lentils which consumes high power and takes more time for grinding. Reduced effective grinding area due to uneven distribution of contact pressure between roller and base stone and irregular flow of batter due to centrifuged effect are also observed.

In the existing design the particles to be ground have the tendency to move towards the periphery due the centrifugal force. But effective grinding takes place only near the centre, where the contact pressure between the roller and the base stone is maximum. The contact pressure gradually reduces towards the periphery so that particles at the outer portion take more to be ground.

OBJECTS OF THE INVENTION

The primary object of the present invention is to propose an improved wet grinder to improve performance and efficiency so as to make the batter flow towards the effective grinding area.
Another object of the present invention is to propose an improved wet grinder to improve performance and efficiency so as to increase the effective grinding area.

Still another object of the present invention is to propose an improved wet grinder to improve performance and efficiency so as to reduce the time taken for grinding.

Further object of the present invention is to propose an improved wet grinder to improve performance and efficiency so as to reduce the power consumption and power fluctuation.

STATEMENT OF INVENTION

According to this invention, there is provided an improved wet grinder to improve performance and efficiency comprising of inwardly tapered roller and base stone, which compensates the effect of centrifugal force forcing large particles to move outwards.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings and wherein:

Fig. 1 shows: variation of viscosity with time.

Fig. 1' shows: present invention.

Fig. 2 shows: Variation of current with time.

Fig. 3 (i) shows: Velocity plot for existing design.

Fig. 3 (ii) shows: Velocity plot for existing design.

Fig. 4 shows: Velocity plot for the present invention.

Fig. 5 (i) shows: Displacement in existing design.

Fig. 5 (ii) shows: Contact pressure in existing design.

Fig. 5 (iii) shows: Contact pressure in 10° design.

Fig. 5 (iv) shows: Contact pressure in 12° design.

Fig. 5 (v) shows: Contact pressure in 15° finalized design.

Fig. 6 (i) shows: Variation of viscosity with respect to time.

Fig. 6 (ii) shows: Variation of current with respect to time.

DETAIL DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS:

Reference may be made to fig .1', wherein the improved wet grinder comprising of inwardly tapered roller and base stone. This provision compensates the effect of centrifugal force, which forces the large particles to move outwards. The taper angle for the bottom stone is 10-15° preferably 12°.

A taper is provided in the base stone in such a way that the batter finds it uphill towards the rim and a corresponding taper is provided to the roller. The purpose of the taper angle is to compensate the centrifugal force on the particles during rotation, so that the particle remains in the effective grinding area. The inward tapper angle also provides uniform contact pressure throughout the roller-base stone interface.

AVANATAGES

Overall grinding time is reduced as compared with the existing wet grinders. As a result, the power consumption is reduced. The fluctuation of power and current is also reduced as there is uniform grinding action.

Experiment for measuring viscosity and current:
An experiment is conducted to measure the time taken for grinding process. A measured quantity of rice is soaked in water for a period of time. After soaking, the excess water is removed from the rice and the soaked rice is fed into the grinder gradually so that there is no overload to the grinder. Then water is added as per the requirement. After some period of time when the rice grains and water turn to colloidal form, the process of taking samples for measuring viscosity is started. Using a breaker the battery is taken from the grinder at specific intervals for measuring the viscosity. The viscosity is measured using Brookfield viscometer. After measuring the viscosity for each sample, the battery in the breaker is again added to the grinder. This process is continued until the grinder process is completed. The variation of viscosity and current with time is shown in fig. 1 and fig. 2 respectively.
From the experiment, it is found that the viscosity decreases gradually as the grinding progresses. But if there is a lack of water, it starts increasing which in turn increases the motor load resulting in slowdown of motor and increased power consumption. The decrease in the speed of rotation indicated the need for addition of water. At a stage the viscosity remains constant for some period of time and this indicates that the grinding process is over.
Study of process using high speed photography:
The same experimental step is used for analyzing the flow of the batter. Before the grinding process, the high speed camera is focused on the grinder using the tripod covered. The camera is focused such that, the entire top view of the grinder is completely covered. From the experiment, it is found that the grinding process takes place effectively only on the inner portion of the roller. This indicates that, the remaining part is simply rotated consuming power without much contribution to grinding. While the grinding takes place, the heavier particles are forced towards the periphery due to centrifugal force and the smaller particles remain at the centre. These heavier particles at the periphery take more time to grind resulting in more power consumption.

Analysis of flow behavior:

The model is then analyzed in CFD-ACE+ software for finding the velocity distribution pattern of the batter. Modeling and meshing is done using the CFD-GEOM which is the pre-processor. The model is then imported to the CFD-ACE solver necessary boundary conditions such as wall type and angular velocity are given. Viscosity and density values are also given for the batter. After giving the necessary inputs, the problem is submitted to the solver. The results are viewed using the CFD-VIEW which is the postprocessor. Fig. 3(i) and Fig. 3 (ii) shows the velocity distribution for the existing design. The velocity distribution for the new design is shown in fig. 4.

From the analysis, it is observed that the velocity of the batter is zero at the centre and increases towards the periphery. Therefore, velocity is maximum on the periphery where grinding does not take place and very less near the area of effective grinding.

Analysis of pressure distribution:

As effective grinding takes place only at the inner portion of the roller the model is analyzed for contact pressure distribution in ANSYS 10.0. Since the model is an ax symmetric one the problem is simplified to 2D form. The modeling is done in the preprocessor. The necessary boundary conditions are given in the solver where in the rollers are given its interia to account for its own weight. From the dimensions of the spring and its material, the spring pressure is calculated and entered as load. The problem is then submitted to the solver. The results are viewed using the post processor. From the analysis, it is verified that the contact pressure is effective only at the inner portion and gradually decreases towards the outer edge.

The displacement and the pressure distribution for the existing design in shown in the fig. 5(1) and Fig, 5(ii) respectively. The contact pressure for the 10°, 12° and 15° inclination angles are shown in figures 5(iii), 5(iv) and 5(v) respectively.

Fabrication and testing of present invention:
The proposed new design is fabricated and the performance is compared with the existing design. During the course of fabrication, a problem is encountered in assembly. Since the bush seating is a standard component, it is unable to accommodate the tapered surface. So, a small step is provided at the centre which is haying flat surface. The variation of viscosity and current with time is shown in fig. 6(i) and fig, 6(ii) respectively.

Finally, the new design is tested for its performance and it is found out that, the time required for grinding has reduced to 35%. From the graph obtained it can be interred that, the current variation is very less in the proposed design. The current value varies from 1.1 to 1 after 3 minutes and thereafter remains constant till the completion of grinding. This indicates that, the fluctuation of load on the motor is very less compared with the existing design. As a result, the power fluctuation is also minimized to a greater extent. The time taken for completion of the grinding is 13 minutes which is reasonable, less when compared with the existing design which takes 20 minutes for the same. Thus, the grinding time is reduced resulting in decreased power consumption.

From the figures obtained from the high speed photograph, it is inferred that the particles constantly moves towards the centre and hence pass through the effective grinding area which results in quicker grinding. This indicates that, the effect of centrifugal force is compensated by the taper provided that makes the grinding process faster.

Conclusion:

In the existing design, the grinding is carried out effectively only at the inner portion of the roller. It is found out using high speed photography and verified in ANSYS 10.0. Hence, a new model which is having uniform contact pressure between the bottom stone and the rollers is proposed. Also due to the flat surface of the bottom stone, the heavier particles tend to move towards the periphery. This movement of particles due to centrifugal force is minimized by providing inward taper.

The effect of the inward taper is analyzed in ANSYS 10.0 and CFD ACE+.

It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims :-

WE CLAIM:

1. An improved wet grinder to improve performance and efficiency comprising of inwardly tapered roller and base stone, which compensates the effect of centrifugal force forcing large particles to move outwards.

2. An improved wet grinder as claimed in claim 1 wherein the taper angle for the bottom stone is 10-15° preferably 12°.

3. An improved wet grinder as claimed in claim 1 or 2 wherein said taper is provided in the base stone in such a way that the batter finds it uphill towards the rim and a corresponding taper is provided to the roller.

4. An improved wet grinder to improve performance and efficiency substantially as herein described with reference to the
accompanying drawings.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=Y7PoKhsBzo1XnV1PpVcAnw==&loc=egcICQiyoj82NGgGrC5ChA==

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Patent Number

272556

Indian Patent Application Number

2076/CHE/2008

PG Journal Number

15/2016

Publication Date

08-Apr-2016

Grant Date

08-Apr-2016

Date of Filing

26-Aug-2008

Name of Patentee

PSG COLLEGE OF TECHNOLOGY

Applicant Address

PEELAMEDU COIMBATORE - 641 004.

Inventors:

#	Inventor's Name	Inventor's Address
1	K. PRAKASAN	PSG COLLEGE OF TECHNOLOGY, PEELAMEDU, COIMBATORE - 641 004.
2	C.S. RAMSHANKAR	PSG COLLEGE OF TECHNOLOGY, PEELAMEDU, COIMBATORE - 641 004.
3	K. RANGANATHAN	PSG COLLEGE OF TECHNOLOGY, PEELAMEDU, COIMBATORE - 641 004.
4	B. ARUN KARTHIK	PSG COLLEGE OF TECHNOLOGY, PEELAMEDU, COIMBATORE - 641 004.
5	P. DHAMODHARAN	PSG COLLEGE OF TECHNOLOGY, PEELAMEDU, COIMBATORE - 641 004.
6	S. KARTHIKEYAN	PSG COLLEGE OF TECHNOLOGY, PEELAMEDU, COIMBATORE - 641 004.

PCT International Classification Number

B24B

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA