Spinning Mule - Operation of A Mule

Operation of A Mule

• Watch video demonstration #1

Mule spindles rest on a carriage that travels on a track a distance of 60 inches (1.5 m), while drawing out and spinning the yarn. On the return trip, known as putting up, as the carriage moves back to its original position, the newly spun yarn is wound onto the spindle in the form of a cone-shaped cop. As the mule spindle travels on its carriage, the roving which it spins is fed to it through rollers geared to revolve at different speeds to draw out the yarn.

Marsden in 1885 described the processes of setting up and operating a mule. Here is his description, edited slightly.

The creel holds bobbins containing rovings. The rovings are passed through small guide-wires, and between the three pairs of drawing-rollers.

• The first pair takes hold of the roving, to draw the roving or sliver from the bobbin, and deliver it to the next pair.
• The motion of the middle pair is slightly quicker than the first, but only sufficiently so to keep the roving

uniformly tense

• The front pair, running much more quickly, draws out (attenuates) the roving so it is equal throughout.

Connection is then established between the attenuated rovings and the spindles. When the latter are bare, as in a new mule, the spindle-driving motion is put into gear, and the attendants wind upon each spindle a short length of yarn from a cop held in the hand. The drawing-roller motion is placed in gear, and the rollers soon present lengths of attenuated roving. These are attached to the threads on the spindles, by simply placing the threads in contact with the un-twisted roving. The different parts of the machine are next simultaneously started, when the whole works in harmony together.

The back rollers pull the sliver from the bobbins, and passing it to the succeeding pairs, whose differential speeds attenuate it to the required degree of fineness. As it is delivered in front, the spindles, revolving at a rate of 6,000–9,000 rpm twist the hitherto loose fibres together, thus forming a thread.

Whilst this is going on, the spindle carriage is being drawn away from the rollers, at a pace very slightly exceeding the rate at which the roving is coming forth. This is called the gain of the carriage, its purpose being to eliminate all irregularities in the fineness of the thread. Should a thick place in the roving come through the rollers, it would resist the efforts of the spindle to twist it; and, if passed in this condition, it would seriously deteriorate the quality of the yarn, and impede subsequent operations. As, however, the twist, spreading itself over the level thread, gives firmness to this portion, the thick and untwisted part yields to the draught of the spindle, and, as it approaches the tenuity of the remainder, it receives the twist it had hitherto refused to take. The carriage, which is borne upon wheels, continues its outward progress, until it reaches the extremity of its traverse, which is 63 inches (160 cm) from the roller beam. The revolution of the spindles cease, the drawing rollers stop.

Backing-off commences. This process is the unwinding of the several turns of the yarn, extending from the top of the cop in process of formation to the summit of the spindle. As this proceeds, the faller- wire, which is placed over and guides the threads upon the cop, is depressed ; the counter-faller at the same time rising, the slack unwound from the spindles is taken up, and the threads are prevented from running into snarls. Backing-off is completed.

The carriage commences to run inwards; that is, towards the rollerbeam. This is called putting up. The spindles wind on the yarn at a uniform rate. The speed of revolution of the spindle must vary, as the faller is guiding the thread upon the larger or smaller diameter of the cone of the cop. Immediately the winding is finished, the depressed faller rises, the counter-faller is put down.

These movements are repeated until the cops on each spindle are perfectly formed: the ' set is completed. A stop-motion paralyzes every action of the machine, rendering it necessary to doff or strip the spindles, and to commence anew.

Doffing is performed by the piercers thrutching, that is raising, the cops partially up the spindles, whilst the carriage is out. The minder then depressing the faller, so far as to guide the threads upon the bare spindle below. A few turns are wound onto the spindle, to fix the threads to the bare spindles for a new set. The cops are removed and collected into cans or baskets, and subsequently delivered to the warehouse. The remainder of the "draw" or "stretch," as the length of spun yarn is called when the carriage is out, is then wound upon the spindles as the carriage is run up to the roller beam. Work then commences anew. The doffing took only a few minutes, the piecers would run the length of the mule gate thrutching five spindles a time, and the doffing involved lifting four cops from the spindles with the right hand and piling them on the left forearm and hand. To get a firm cop bottom, the minder would whip the first few layers of yarn. After the first few draws the minder would stop the mule at the start of an inward run and take it in slowly depressing and releasing the faller wire several times. Alternatively, a starch paste could be skillfully applied to the first few layers of yarn by the piecers – and later a small paper tube was dropped over spindle – this slowed down the doffing operation and extra payment was negotiated by the minders.