(272) It is now possible to define the various stages in the whole process of mule spinning. These are as follows:—
First. The period during which roving is being delivered and twisted. During it, the rollers are revolving at a defined speed; the carriage is being drawn outwards at a constant rate; the spindles are revolving rapidly at a velocity definitely relative to that of the front roller. During this period the faller and counter faller are held in the position shown in Fig. 148, being quite clear of the yarn.
Second. The period during which the movements just named are stopped. The roller driving gear is detached; the mechanism by which the carriage is drawn out is stopped; the spindles are stopped because of the transfer of the driving strap to the loose pulley and the consequent cessation of the motion of the driving band; and preparation for the engagement of the faller and counter-faller with the yarn takes place.
Third. This is the period of “backing-off.” During it the driving band is driven in the contrary direction to its normal one, and the spindles are reversed. The faller wire is drawn down, depressing the yarn; the yarn between the nose of the cop and spindle point is uncoiled; the counter faller rises and takes up the slack yarn; and the faller is “locked.”
Fourth. During this period “winding” takes place. The rollers are stationary; the carriage is “running in” at a variable speed; the spindles are revolving in the same direction as when twisting; and the winding faller is operated so as to guide the yarn on the cop.
Fifth. The carriage comes to rest; the faller and counter faller are released; the roller driving gear is re-engaged; the strap is moved on to the fast pulley and the driving band put in motion; and the drawing out gear is again engaged.
With this the cycle of movements is completed, and the whole of the operations begin anew.
(273) There are thus five periods, viz., 1st, twisting; 2nd, arrestation; 3rd, backing-off; 4th, winding; and 5th, re-engagement. In addition to these, when fine yarns are spun, there is sometimes a sixth period, which takes place immediately after the termination of the first as at present defined. This is a period of supplementary twisting after the rollers have stopped. This operation is sometimes known as “twisting at the head,” and will be dealt with at a later stage.