GINNING

OBJECT OF GINNING

The primary object of the ginning consists in separating the fibres from the seed, and a Perfect ginning operation would be Performed if the separation of fibres from seed was effected without the slightest injury to either seeds or to the fiber.

DIFFERENT TYPES OF GIN

Previous to the introduction of Modern Machinery, ginning was performed by hand or by machines of a primitive character such as the "Foot Roller" and its improvement the "Churka".

As the cotton industry developed, greater production than these were capable of was necessary, and machines driven by power were introduced.

Numerous forms of gins have been tried, but at the present time only three are used to any large extent. They are

1. KNIFE ROLLER GIN

2. SAW GIN

3. THREE TYPES OF MACARTHY GIN

I. Single acting macarthy gin.

ii. Double acting macarthy gin

iii. Double roller macarthy gin.

KNIFE ROLLER GIN

Object: To separate the fibres from seed 

The constructional detail of the machine is clearly shown in fig. The seed cotton is placed in bulk on the table. By means of the reciprocating motion of the table by the crank arrangement, the seed cotton comes into contact with knife roller (formed of a number of knife discs).

Auxiliary roller breaks the large cluster of seed cotton and maintains a constant supply of cotton to knife roller.

Knife portion being arranged in such a manner that anything coming into contact with it is given a reciprocal or to and fro motion as well as being subject to a striking action due to its revolution. 

The seed cotton is carried forward in the direction of knife roller's    motion   until it is brought into touch with leather roller. This roller, which has a much roughened surface, due spirally-formed   saw    cuts. Has pressing against, it by   means    of spring and steel doctor Knife. 

The cotton fibres brought into contact with the leather adhere to it, and are carried round past .the knife. It is impossible for the seeds to follow. So, seeds will remain at the point of contact of the doctor knife and leather roller, with the fibres still connected with it. The essential feature of this gin now comes into play. 

The knife roller is so set as to act upon, these adhering seeds, and it gives to them a gentle to and fro motion, repeated very quickly 'and at the same time a slight striking action or pressure also repeated quickly. The combined action soon causes the seeds to separate from the fibres and to fall down through the grid to floor. The freed fibro passing forward is stripped from the roller by some arrangement of the stripping board. 

The seed cotton not taken up by one leather roller (on the right of the figure) is brought round into contact with another 1eather roller where same process as described above is gone through and to which the same parts equally apply.

SETTING

1. Seeds cannot get between dish rail and knife roller. Carelessness here produces large quantities of crushed seeds

2. Sharp edge of the doctor knife does not cut the fibres.

3. The degree of pressure of the doctor knife upon the leather roller can be varied by means of spring and thumb screw according to the tenacity with which the fibres adhere to the seeds.

4. The leather roller should be parallel to the     knife roller and the setting between leather roller and knife roller, should be 1/3 of the diameter of the largest seed.

If this setting is too near - the seeds would be broken. If this setting is too wider large seeds would not be acted   upon by   knives    and   m/c would block itself    by    an   accumulation   of un stripped seeds.

 Knife    roller gin is suitable to process coarser and   medium Types    of    Indian cotton. The Indian Cotton fibres    are   not    too easily   separated ' from   seeds, so heavier   beating    on   seed   is required to.Separate the fibres.    This is achieved in this gin by giving   heavier beating of the rapidly   revolving knives   of  the roller on the seed cotton.

SINGLE ACTING MACARTHY GIN

 Object:    To separate the fibres from seed

The   constructional details of the machine are clearly.

Shown

The seed cotton is placed on the table. By means of the reciprocating motion of the table by the crank arrangement, the seed cotton comes into contact with the revolving leather covered roller.

Some cotton fibres are carried in the direction of leather roller, but seed cottons are arrested by the doctor knife. 

A steel beater blade is connected by means of a connecting rod, with a crank on the driving shaft. 

Due to the seeds being acted upon by the rapid reciprocating motion given to the beater blade by the crank, the seeds are separated from fibres.

Ginned cotton fibres are carried onward in the direction of leather roller, stripping board strip the fibres from the leather roller and empty seeds are thrown into grid, through which they pass into suitable receptacle. 

SETTING:

1. The supporting rod which is connected with beater blade and centered as shown in fig. is used to adjust the distance between blade and leather roller. 

2. The vertical movement of the beater blade should be 3/8 inch above the doctor knife. 

3. Sharp edge of the doctor knife-does not cut—the-fibres. 

4. The degree of pressure of the doctor knife upon the leather roller. Can be varied according to the tenacity with which the fibres adhere to the seeds. This is done by adjusting the spring and thumb screws. 

5. The   pressure of the doctor knife.. and   distance   between leather roller and doctor knife should be in such a way that no seed will be allowed to pass in the direct ion of leather roller. 

SUITABILITY:

 All type of macarthy gins are suitable to process long stapled cotton such as sea island cotton, Egyptian cotton and long stapled Indian cottons. Long stapled cottons are of a type in which the fibres are easily separated from seeds, so light beating on seed is enough to separate the fibres, this is achieved in this gin by light beating action of the beater blade on seed, fibre damage & broken seeds are the results if processed through other gins of heavier beating points such as knife roller gin and saw gin.

 DOUBLE ROLLER MACARTHY GIN 

Object: To separate the fibres from seed.

CONSTRUCTION:

As shown in the figure, there are two leather roller and a" doctor knives is pressed against each leather roller. The beater knives act from above, and are given a reciprocating motion from a crank. Crank pin slide in a slot of arm carried by a vibrating shaft. Beater blades are fixed on arms projecting from vibrating shaft. Also grid and fingers are fixed on vibrating shaft.

WORKING:    Seed    cotton    is    fed into    hopper   -spaces.    The    ^c movement    lowers this cotton into contact with leather roller in one side and raises it away from the roller on other side.

When the cotton comes into contact with leather roller, some cotton fibres are carried in the direction of leather roller but seed cottons are arrested by the doctor knife due to the seeds being acted upon by-the rapid reciprocating motion given to the beater blade by crank,_{ the seeds are separated from fibres. Ginned cotton fibres are carried forward in the direction of leather roller. 

Empty seeds are thrown   into grid.

As the grid lowers, the space in it permit the fixed finger to pass between them, and so shake the seed to cause them to fall out readily.

SAW GIN

Object:

To separate the cotton fibres from the seed.

WORKING:
The seed cotton is fed upon the lattice and carried forward to the spiked roller, which loosens the cotton and throw; it into the hopper.


In hopper, the seed cotton comes into contact with rapidly revolving saw roller. App.70 saws are threaded on a shaft.
As the saws revolve, the teeth carry the fibres forward, but it is impossible for the seeds to follow and also, due to the heavier beating of the rapidly revolving saws on the seed cotton, the fibres are separated from seed and taken round until the brush strips the fibre from the teeth.
Empty seeds husks and other broken seeds are thrown into grid, through which they pass into suitable receptacle. An air current from the cage draw the fibres along the trunk passage, and on reaching the revolving cage are brought under the pressure roller and delivered as a sheet, from which it is taken to the baling press.
SETTINGS:
The bars (I) are adjusted at K. The plate, adjustable at H, can be regulated to prevent the seeds falling away until thoroughly cleaned. An air current from cage should be optimum to 'suck only fibres. If air current is high - it will "suck seed also with fibres. If air current is low - fibre accumulation under brush roller causes to block the machine.
Saw gin is suitable to process American cotton and wherever American cotton is grown, such as west Africa- India, Ceylon etc.
These cottons are '.oil a "type in which-' the fibres are not too easily separated from the seeds, so heavier beating on seed is required to separate the fibres. This is achieved in this gin by giving heavier beating of the rapidly revolving saws on the seed cotton.