FIELD OF THE INVENTION;
This invention relates to a process of withering the moisture Content of fresh tea leaves in a new circular rotating withering trough and the said trough.
BACKGROUND OF THE INVENTION:
Withering is the first processing step in tea making after plucked tea leaves reach the factory from gardens. The process of withering normally takes about 10 to 16 hours. The quality of made - tea is highly dependent on the perfection of the withering process.
The withering process involves both physical withering and chemical withering. In physical withering the moisture content of fresh leaf generally reduces from 74-83% to 65-68% for CTC tea and to 50-55% for orthodox tea.
In chemical withering complex biochemical compound changes to simpler form like conversion of protein to amino acid, carbohydrates to simpler sugar and change of caffeine to a desired value. Chemical withering starts immediately after plucking of leaf. The process is dependent on the rate of moisture loss and is a function of time and temperature. However, for quality made tea the temperature of the tea leaves during withering process should not exceed 35°C.
The conventional withering trough used in the tea industry is a horizontal bed static type having a wire-mesh bottom. The size of the bed may vary from industry to industry, but in general it is around 30m in length and around 2.5m in width accommodating 22-27kg/m2 of fresh leaf. The leaves are spread over the wire mesh with stacking height of around 150-250mm. The air blown by a fan through the bottom of the bed flows through the leaves to carry out the process of withering. By this process the leaves at the bottom layer are exposed to more air flow compared to those at the top. For this reason, the fan is rotated

in a reverse direction for some duration so that the leaves at the top layer also get air flow during the period of reverse operation of the fan. The leaves on the trough are manually reshuffled from time to time for uniform moisture removal from the leaves. A heater is sometimes provided for blowing hot air mostly in the rainy season when the leaves remain wet and humidity is high. The schematic view of the arrangement is shown in Fig.l.
Non-uniform air velocity along the length of the bed as well as across the bed is a major concern for non attainment of uniform withering in a conventional withering trough. For a given fan speed, a typical variation of air velocity, coming out from an empty trough along its length, is shown in Fig.2. It is observed that the air velocity is more towards the end of the trough, resulting in higher moisture removal from that position. Thus the variation of air velocity along the trough length leads to non-uniform withering of leaves as shown in Fig.2.
The limitation of this type of troughs is non-uniformity of moisture content in withered leaves, large space requirement and high energy consumption during withering process.
OBJECTS OF THE INVENTION:
Its is therefore an object of this invention to propose a rotating trough for withering tea leaves which lead to uniform moisture content in withered leaves.
It is a further of the present invention to propose a rotating trough for withering tea leaves, which requires less space for operation.
Another object of the present invention is to propose a rotating trough for withering tea leaves, which saves energy.

Yet another object of the present invention to propose a rotating trough for withering tea leaves, which is cost effective and can be adopted for industrial use.
These and other objects of the present invention will be apparent from the ensuing description when read in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING:
Fig 1 : Schematic view of a conventional horizontal bed static withering trough.
Fig 2 : Typical variation of moisture content of withered leaves and variation of air velocity along the length of horizontal bed withering trough.
Fig 3 : Schematic view of circular rotating type withering trough.
Fig 4 : Comparison of withering process performed on a conventional and a circular withering trough.
Fig 5 : Variation of moisture content of withered leaves in two different sections of circular withering trough.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION:
Thus, the proposed invention is a circular rotating withering trough for tea leaves.
In accordance to this invention, a new type of withering trough has been developed. In this design, the trough is circular and is of rotating type, as shown schematically in Fig.3.

The concept of circular withering trough (1) is that, as if the conventional horizontal bed withering trough is curved in the form of a circle and is rotated at a given speed. Therefore, the previous cubical space now becomes an annulus space. This annulus space is compartmentalized with partition where the tea leaves are stored. The trough (1) and the side cover (8) of the trough is made of wire mesh (10). The circular rotating trough (1) is connected to a motor (2) placed on the ground for getting the power to rotate continuously during the withering process. The trough rotates at a pre-determined particular speed of 40rpm. A construction (4) is fabricated to accommodate a shaft (5) of the trough (1). Two bearings (9) guide the rotation of the shaft (5) which is powered by the motor (2) and pulley (6). A series of blades (3), is placed in the inner annulus of the rotating trough (1) Fig.(3). Depending on the size of the trough, the blade angles may be altered. These blades act similar to a compressor blade for throwing air radially from inner eye to the periphery. As. the trough (1) is continuously rotating, there is a continuous flow of air cutting across the withering bed. Moreover, in this trough (1) the tea leaves undergo a natural shuffling during rotation. This ensures uniform air flow through the leaf bed and lesser chances of heat generation within the leaf mass. As for example a conventional withering trough of length 3.14m now in the new design occupies a space of one meter only. However, the width of the bed remains the same as conventional trough. Therefore the floor space requirement would be curtailed by more than 60% than a conventional trough. The requirement of additional fan is not required in the circular rotating trough. The need for manual reshuffling of the leaves is also not required for circular withering trough. Only, power is required to rotate the trough.
The circular trough according to the invention has been compared to the connectional trough. Experiments have been carried out with freshly plucked leaves from the garden. It is to be noted that the biological characteristic of

leaves do vary with seasons, clone type and plucking standards. Therefore, it is equally important to look into the qualitative trend of the results as the experimental findings may vary for the reasons stated above.
The representative comparisons of withering process in a circular withering trough and in a conventional horizontal bed withering trough for two different experimental conditions is shown in Fig.4 a and Fig.4 b.
It is observed from the above figures that for same duration of withering the moisture removal is more in the case of circular withering trough. From Fig.4 b it is observed that at the end of the withering process moisture removal is 5% more in the circular trough compared to that of the conventional trough.
The uniformity of moisture content in withered leaves in circular trough has also been studied. In this experiment two identical wire mesh sample boxes containing same amount of green leaf were kept in two opposite quadrant of the circular trough rotating at a given speed. Amount of moisture content was recorded at intervals during the withering process. The results are shown in Fig.5.
Fig.5 shows moisture content of tea leaves with time at two different locations of circular withering trough. It is observed that the moisture content of sample 1 and sample 2 at a given time are almost similar. Thus uniformity of withering in a circular trough compared to that in a conventional trough is one of the important outcome of the present invention.
The uniformity in withering of tea leaves in rotating trough is appreciable compared to that of a conventional trough. This will ensure increase in the quality of made tea.

Considerable amount of floor space of around 60% will be saved by the use of circular trough.
Apparently there will be energy saving as in steady state operation, energy is only required to support the frictional loss of the machine and air drag.
The circular rotating type withering trough has high potential for industrial use.

We Claim:
1. Process of withering the moisture content of fresh tea leaves in a circular
rotating withering trough comprising;
connecting the circular rotating trough (1) to a motor (2) and a pulley (6) to rotate the said trough at the required speed;
arranging a fabricated construction (4) to accommodate a shaft (5) receiving power from the motor (2) to rotate the said circular trough;
placing a plurality of blades (Vane) (3) in the inner annulus of the rotating wire mesh circular trough (1) to throw air radially from innereye to periphery of the said trough(l); wherein,
a continuous flow of air cutting across the withering bed of the said trough (1) when the said trough (1) rotates continuously causing a continuous flow of air cutting across the withering bed when the tea leaves undergo a natural shuffling during rotation ensuring uniform air flow through the leaf bed.
2. A process as claimed in claim 1, wherein implementing circular trough (1) saves 60% of floor space.
3. A process as claimed in claim 1, wherein implementing circular trough (1) after a given amount of time moisture removal is 5% more compared to conventional trough.
4. A process as claimed in claim 1, wherein implementing circular trough (1) moisture removal is uniform for all leaves placed in the circular trough compared to conventional trough.

5. A process as claimed in claim 1, wherein moisture removal is more for circular withering trough with side cover (8) compared to a circular trough (1) without side cover.
6. A process as claimed in claim 1, wherein implementing circular trough (1), need for manual shuffling of leaf is eliminated.
7. A process as claimed in claim 1, wherein implementing circular withering trough, surface moisture present in leaves, particularly in rainy season, is automatically removed by the action of centrifugal force caused due to the rotation of circular withering trough, eliminating the requirement of additional hot air to be blown to remove surface moisture of leaves as in the case of conventional trough.
8. A process as claimed in claim 1, wherein the circular trough (1) rotates at a particular speed during withering process.
9. A new circular rotating wire mesh withering trough (1) comprising; the said trough having a curved shape configuration forming an annular space;
a side cover (8) made of wire mesh;
a shaft (5) accommodated in fabricated support (4) and connected to a motor (2) through a pulley (6) for rotating the circular trough (1);
two bearings (9) disposed for guiding the shaft (5) and for smoothe rotation of the said shaft, wherein blades (3) are installed in the inner annulur of the said wire mesh trough (1) for blowing air to the tea leaves in the said trough; throwing air radially from inner eye to the periphery of the said trough
(1).