The final machine used in the conversion of rove to the size of yarn
required is termed the spinning frame. The actual process of
spinning is performed in this machine, and, although the whole
routine of the conversion of fibre into yarn often goes under the
name of spinning, it is obvious that a considerable number of
processes are involved, and an immense amount of work has to be done
before the actual process of spinning is attempted. The nomenclature
is due to custom dating back to prehistoric times when the
conversion of fibre to yarn was conducted by much simpler apparatus
than it is at present; the established name to denote this
conversion of fibre to yarn now refers only to one of a large number
of important processes, each one of which is as important and
necessary as the actual operation of spinning.
A photographical reproduction of a large spinning flat in one of the
Indian jute mills appears in Fig. 20, showing particularly the wide
"pass" between two long rows of spinning frames, and the method
adopted of driving all the frames from a long line shaft. Spinning
frames are usually double-sided, and each side may contain any
practicable number of spindles; 64 to 80 spindles per side are
common numbers.
[Illustration: FIG 20. AN INDIAN SPINNING FLAT]
The rove bobbins, several of which are clearly seen in Fig. 20, are
brought from the roving frame and placed on the iron pegs of a creel
(often called a hake) near the top of the spinning frame-actually
above all moving parts of the machine. Each rove bobbin is free to
rotate on its own peg as the rove from it is drawn downwards by the
retaining rollers. The final drafting of the material takes place in
this frame, and a considerable amount of twist is imparted to the
drawn out material; the latter, now in the desired form and size of
yarn, is wound simultaneously on to a suitable size and form of
spinning bobbin.
When the rove emerges from the retaining rollers it is passed over a
"breast-plate," and then is entered into the wide part of the
conductor; it then leaves by the narrow part of the conductor by
means of which part the rove is guided to the nip of the drawing
rollers, The rove is, of course, drafted or drawn out between the
retaining and drawing rollers according to the draft required, and
the fibrous material, now in thread size is placed in a slot of the
"thread-plate," then round the top of the flyer, round one of the
arms of the flyer, through the eye or palm at the end of the flyer
arm and on to the spinning bobbin. The latter is raised and lowered
as in the roving frame by a builder motion, so that the yarn may be
distributed over the full range between the ends or flanges.
Each spindle is driven separately by means of a tape or band which
passes partially round the driving cylinder and the driven whorl of
the spindle, and a constant relation obtains between the delivery of
the yarn and the speed of the spindle during the operation of
spinning any fixed count or type of yarn. In this connection, the
parts resemble those in the roving frame, but from this point the
functions of the two frames differ. The yarn has certainly to be
wound upon the bobbin and at the same rate as it is delivered from
the drawing or delivery rollers, but in the spinning frame the bobbin,
which rotates on the spindle, is not driven positively, as in the
roving frame, by wheel gearing; each spinning bobbin is actually
driven by the yarn being pulled round by the arm of the flyer and
just sufficient resistance is offered by the pressure or tension of
the "temper band" and weight. The temper band is simply a piece of
leather or hemp twine to which is attached a weight, and the other
end of the leather or twine is attached to the builder rail.
[Illustration: FIG. 21 A LINE OF SPINNING FRAMES]
The front part of the builder rail is provided with grooves into one
of which the temper-band is placed so that the band itself is in
contact with a groove near the base of the bobbin flange. A varying
amount of resistance or tension on the bobbin is required in virtue
of the varying size of the partially-filled bobbin, and this is
obtained by placing the temper-band successively in different groves
in the builder so that it will embrace a gradually increasing arc of
the spinning bobbin, and thus impart a heavier drag or tension.
The spinning frames in Fig. 20 are arranged with the ends of the
frame parallel to the pass, whereas the end frames in Fig. 21 are at
right angles to the pass, and hence an excellent view of the chief
parts is presented. The full rove bobbins are seen distinctly on the
pegs of the creel in the upper part of the figure, and the rove
yarns from these bobbins pass downwards, as already described, until
they ultimately enter the eyes of the flyer arms to be directed to
and wound upon the spinning bobbins. The flyers--at one time termed
throstles--are clearly visible a little above the row of temper
weights. The chief parts for raising the builder--cam lever,
adjustable rod, chain and wheel--are illustrated at the end of the
frame nearest the observer.