|Title of Invention||
'AN INDICATOR SYSTEM'
|Abstract||An indicator system for monitoring physical parameters such as temperature, pressure, velocity and other operating parameters to enable monitoring of such operating parameters and effecting corrective measures as and when required and in particular, a three level temperature indicator system for use with tea dryer and the like. The system basically utilises sensor means to constantly sense the relevant physical operating parameters ; comparator means comprising a first comparator having a preset reference value of said physical parameter indicative of the allowable lower limit of said operating parameter and a second comparator having a present reference value of said physical parameter indicative of allowable higher limit of said operating parameter ; and logic means and relay trigger circuitry adapted to continuously generate signals to actuate indicator means to indicate the status/conditions of operation of said operating parameter based on sensor value of the relevant physical operating parameter. The indicator system would enable constant monitoring of physical operating parameters such as tea dryer temperature for tea drying and also favour indication of drying conditions such as whether it is within normal limits or causing overdrying of fermented leaves or underdrying of fermented leaves. The system which would further enable continuous monitoring of the drying status and the feed status in the tea dryer to favour obtaining of product of desired quality and character and provide a method of drying tea in a controlled manner.|
|Full Text||The present invention relates to an indicator system for monitoring physical parameters such as temperature, pressure, velocity and other operating parameters to enable monitoring of such operating parameters and effecting corrective measures as and when required. In particular, the invention relates to a three level temperature indicator system for use with tea dryer and the like.
Tea is a high value crop throughout the world. Production of black tea (both CTC and Orthodox) involves certain well defined processing stages. Tea drying is also one of the most important process. During drying the moisture content(MC) of fermented leaf (FL) is reduced down to a level of about 3-5%. Drying is carried out on FL in drying machines. In the traditional dryers, FL is transported on perforated trays and hot air is blown through it. This is chain type dryer. When hot air passes through the FL loaded on the trays, the leaf temperature rises to such a level at which the fermentation stops. Then the FL is dried to remove the moisture until the MC remains at 3%. Nowadays, fluidised bed dryers (FBD) are more convenient compared to old traditional dryers.
Drying of FL may be performed in two steps. In single fire, the tea is dried to reduce the MC down to 3% in about 20 min. The inlet temperature of the dryer is generally of the order of 95-100°C. The outlet temperature of the drier is maintained at 50°C. The quality of the final made tea during drying usually depends on the following parameters.
a) temperature of the hot air
b) feed rate of the FL
c) run through time of the tea
d) volume of air
Keeping other parameters of above constant, if the feed rate is not proper, it may cause deterioration of the quality of the made tea. Hence the temperature of the hot air is a faithful representation of the quality of the made tea.. Therefore, measurement and monitoring of the temperature during drying (TDD) continuously becomes necessary. The TDD is a faithful representation of the feed rate which on the other hand determines the quality of the tea. This temperature goes down
with the feed rate of FL. Hence FL temperature increases and the tea is burnt whereas if the feed rate is increased FL is exposed to lower temperature which results tea of inferior quality due to under drying. If the above process is unattended for a long interval, the whole lot of tea inside the dryer gets spoiled. Moreover the supervisor is unaware about this phenomenon and comes to know it very lately from the burning smell of the tea. So, by the time the supervisor comes to know, the whole lot of tea gets already spoiled.
It is presently known to use pressure spring thermometers in the dryers to indicate the temperature of the dryer. But such thermometer can only indicate the temperature without any information about deviation from the normal drying conditions. It means that the thermometers are unable to generate any indication alone from which the supervisor can quickly ascertain if any detrimental effect has taken place in the drying process. Many devices are available for continuously monitoring the temperatures of the dryer at various locations. Assam Electronic Development Corporation (AMTRON) developed and commercialised an instrument specially for Tea dryer- the VERMIAC TCX Series 1000. But this instrument is not capable of directly indicating the over drying and under drying state. It can only monitor the temperatures at various locations. The operator will have to go on watching the display screen .hence it is not operators friendly. Moreover in use of such device the operator can get confused with the display of temperature of 16 locations inside the dryer. There is no direct relationship between the temperature and the over drying and under drying states.
It is thus the basic object of the present invention to provide an indicator system for monitoring and comparing various physical operating parameters such as temperature, pressure, velocity and the like with desired/permissible values and generate indicator signals to the operator for effective necessary corrective measures, if required, to thereby ensure proper processing involving such physical parameters.
Another object of the invention is to provide an indicator system for use with tea dryer and the like which would enable constant monitoring of dryer temperature
for tea drying and also favour indication of drying conditions such as whether it is within normal limits or causing overdrying of fermented leaves or underdrying of fermented leaves.
Yet further object is to provide a three level temperature indicating system for use with tea dryers which would favour constant monitoring of the drying process and favour effecting corrective measure if any to enable producing product of best and acceptable quality and character.
Yet another object of the present invention is to provide a three level indicator system which would enable continuous monitoring of the drying status and the feed status in the dryer to favour obtaining of product of desired quality and character.
Yet further object of the product invention is directed to provide a method of drying tea in a controlled manner using the above system of the invention.
Thus according to the present invention there is provided a three level temperature indicating system for use in tea drying comprising : at least one sensor means (S) adapted to sense the temperature of the dryer unit and means to generate output voltage corresponding to the temperature of the dryer;
at least two comparator means (Comp1 and Comp2) comprising a first comparator (Comp1) having a preset reference voltage (Vref1) applied thereto corresponding to the lower allowable operating temperature (t1) and a second comparator (Comp2) having a preset reference voltage (Vref2) applied thereto corresponding to the higher allowable operating temperature (th), wherein the comparator outputs (Vci and Vc2> are adapted to turn on provided transistor means (Ti and T2) through resistances (R4 and R5) and the said transistors being operatively connected to the logic and relay trigger circuitry to generate the indicator signal and each said comparator output being supplied to a respective relay such that a first relay means (RLY1) is operatively connected to the first comparator via a first transistor means and the second relay means (RLY2) is operatively connected to a second comparator via a second transistor means, the
said transistors being operatively connected to the relay means (RLY1 and RLY2) so as to generate the three level status of the relays based on the comparator outputs;
at least a switch means (SW1 or SW2) to variably change the said reference preset lower and higher comparator voltages corresponding to the said allowable lower and higher temperatures respectively, the said switch means being adapted to variably set the comparator means reference voltage to three levels of lower and higher reference voltages based upon the type of dryer and the moisture content of the fermented leaves for drying;
means for supplying the said sensor voltage to each said comparator means for individually comparing the said sensor voltage to the respective allowable reference voltages, wherein the sensor output (Vs) is applied to an operational amplifier and said amplifier output voltage (Vo) is adapted to drive said two comparators means, said first comparator adapted to go to high from low when the temperature of dryer crosses the lower allowable reference temperature (t1) while the other comparator is adapted to produce a high output when the dryer temperature crosses the higher allowable reference temperature (th); a logical and relay trigger circuitry operatively connected to said comparator outputs (Vc1 and VC2) and adapted to generate signals indicating the drying status as NORMAL DRYING when said drying temperature is within said allowable lower and higher temperature (t1 and th), OVER DRYING when said temperature of drying is beyond said allowable higher temperature (th) and UNDER DRYING when said temperature of drying is less than the allowed lower limit (t1);
characterised in that the said sensor means (S) is a linear thermal transducer.
Preferably, in order to facilitate effective monitoring and comparison of temperature, the output of said sensor means is amplified by means of an operating amplifier and the amplified sensor value is supplied to said comparator means.
In particular, the comparator means, logic means and relay trigger circuitry and the said indicator means are adapted to generate signals which could indicate a three level status of operation comprising NORMAL operation, UNDER operation and OVER operation. Also, in order to favour constant visual indication of the said states of operation, the indicator means is provided with visual indicator means to indicate NORMAL operation by GREEN light indicator, OVER operation by RED light indicator and UNDER operation by BLUE light indicator.
In the above disclosed three level temperature indicating system the logical and relay trigger circuitry is operatively connected to visual indicator means to indicate the status by visual indicator means to indicate the drying status and feeding status as per the logic table hereunder :
Dryer Temp Drying status Feeding status INDICATION
conditions Blue Green Red
|Indian Patent Application Number||501/CAL/2000|
|PG Journal Number||10/2007|
|Date of Filing||30-Aug-2000|
|Name of Patentee||BHUYAN DR. MANABENDRA|
|Applicant Address||DEPT. OF ELECTRONICS, TEZPUR UNIVERSITY , NAPAAM, TEZPUR, PIN - 784 028 ,|
|PCT International Classification Number||G 01R 19/00|
|PCT International Application Number||N/A|
|PCT International Filing date|