SLUBBING AND ROVING MACHINES.
(225) The sliver as left by the drawing frame consists of a number
of fibres arranged in a parallel order, and contains a little
twist introduced by the coiler. It is not practicable to carry the
parallelising process much further, as the drawn slivers are so
attenuated that very little more draught would pull the fibres asunder.
As, however, it is essential, in order to produce a yarn of the
requisite fineness, that a further reduction shall be effected, it is
the practice to gradually introduce into the sliver a small amount of
twist. This is done by stages, and at each stage the partially twisted
fibre is subjected to the action of drawing rollers. The machines about
to be described, therefore, have a dual action, and, in most cases,
are three in number, known respectively as slubbing—second slubbing
or intermediate—and roving frames. While this is the rule, it is not
the universal practice. In spinning coarse counts, for instance, only
the first and third of the series are sometimes employed, while the
production of very fine yarns is aided by the use of a fourth machine,
known as a “jack” frame. Whatever may be the number of steps by which
the process is completed the object is the same—to reduce the sliver to
an even round thread of such proportions that it can be readily twisted
into yarn of the requisite diameter. The introduction of a slight twist
binds the fibres together, and enables them to be drawn as required
without breakage. The thread finally produced is technically known as
a “roving.” The various machines being practically identical in their
details, varying only in correspondence with the increasing fineness of
the thread, it is only necessary to give a description of one of the
series.
(226) In Fig. 128 a front view of a slubbing frame, and in Fig. 134
a back view of a roving frame, as made by Mr. John Mason, are shown.
The sliver is brought from the drawing frame in the cans in which it
is coiled, these being placed at the back of the slubbing machine. It
is drawn from the cams over a guide roller, and is then conducted to
the drawing rollers. After being treated in the slubbing frame the
bobbins produced are placed upon wooden pegs, pointed at both ends,
which are sustained in bearings in the light frame =S= shown in Fig.
134, this being known as a “creel.” The bobbins are borne in an almost
vertical position, and revolve easily as the slubbing is being drawn
off. There may be two or three rows placed in the creel, which is
described as a one, two, or three height creel accordingly. In either
case the material is conducted as in the slubbing frame to the drawing
rollers. Of these there are usually three, but sometimes four lines,
their construction being generally similar to those used in the drawing
frame, the back set of top rollers being ordinarily heavier than the
front ones. The rollers are carried in brass bearings, fixed to the
roller beam, and are weighted as in the drawing frame. Top clearers
are fitted above the rollers, which are quite covered by polished
cast-iron covers. The bottom rollers are kept clean by the aid of a
revolving clearer kept closely pressed against them by a two-armed
spring, the ends of the arms being grooved to form bearings for the
axes of the clearer roller. The “under clearer” spring is attached to
the roller beam, and is usually made of flat steel, stamped out of a
sheet. A better form, made from round bright wire, has been recently
introduced by Mr. C. H. Pugh, of Birmingham, which has the great
merits of catching less fly and being more easily cleaned. As was said
in the previous chapter, the absolute cleanliness of the rollers is
essential, as otherwise the sliver will adhere to them—this being known
as “licking”—and will be wrapped round them, thus producing “roller
laps.” The drawing action having been fully described in the preceding
chapter, it is not necessary to go over the same ground. The diameter
of the front rollers in the slubbing frame are about 1-1/4 inch, and in
the roving frame 1-1/8 inch. The weights are heavier in the slubbing
frame, and in all the series the back rollers are more lightly weighted
than the front. Thus the weights used for the front, middle, and back
lines in the slubbing frame are respectively 18, 14, and 10lbs; in
the intermediate frame 14, 10, and 8lbs.; and in the roving frame
(with single bossed rollers) 10, 8, and 6lbs; and (with double bossed
rollers) 18, 14, and 12lbs.
(227) The mode of constructing the spindles A, is illustrated in
sectional elevation in Fig. 129. The spindles are made from round
steel from 9/16 inch to 7/8 inch diameter, and are arranged in two
rows, one behind the other, with their centres alternating thus _
-_ - _. This arrangement permits of more spindles being fitted into
the space at liberty. Usually the distance from centre to centre
of adjoining spindles denotes the “gauge” of a machine, but in the
series of machines now being dealt with, the peculiar setting of the
spindles prevents this. The “gauge” in this case is denoted by the
number of spindles in a defined number of lineal inches. Thus, to
take an illustration from actual practice, a slubbing frame may have
4 spindles in 17-1/2 inches, that being its gauge; an intermediate, 6
in 19-1/2 inches; or a roving frame 8 in 20-1/2 inches. The spindles
are accurately ground so as to be quite round, and vary in length from
28 to 42 inches. At the “foot” the diameter of the spindle is reduced,
and the extreme lower end or “toe” is conical, being borne by a brass
footstep fixed in a longitudinal rail. Immediately below the bobbin is
an upper bearing or bolster, fixed in a similar rail. On the top of
the spindle a flyer =B= is placed, this being of the shape shown, and
constructed of steel. The legs are oval in section, and may be either
tubular or solid, being made as light as possible. At the centre of
the bridge connecting the legs is a circular double boss =C=, which
is bored throughout, the hole so formed being carefully rounded and
polished at its upper orifice. At a point near the top a hole is bored
penetrating to that in =C=, and being also well rounded and polished.
The lower portion of =C= constitutes a socket, into which the upper end
of the spindle fits, the latter passing above the point at which the
bridge is attached to the boss. A slot is cut across the upper end of
the spindle, and a round pin, engaging with the slot, is fixed in the
socket of the flyer, which is thus positively driven.
[Illustration: FIG. 128. WATKINSON ENG.]
[Illustration: FIG. 129. J.N.]
(228) Attached to one or both legs of the flyer are two snugs or
projections =D D^{1}= acting as bearings for pressure fingers or
“pressers” =E=. The latter are round rods, hooked at their upper ends
and bent at right angles at their lower ends. The hooked portion can
be dropped into a socket in the upper snug =D=, and the presser thus
oscillates freely on the centre of the bearings =D D^{1}=. The inner
end of the finger =E= is flattened and curved so as to correspond with
the surface of the bobbin =F=, being formed with a guide-eye, as shown.
It is made of such a length as always to press upon the surface of the
bobbin during the rotation of the flyer, which it is caused to do by
the centripetal action set up by the latter. The amount of pressure
exerted depends entirely on the rate of the revolution of the flyer,
and the practical effect is that the roving is more tightly wound on
the body than it would otherwise be. It was at one time customary to
use two pressers with each flyer, but it is more generally the practice
now to employ one only. Great care is taken to balance the flyer, and,
when single pressers are used, one leg is made solid and the other
tubular, the presser being fitted to the latter. The sliver, after
leaving the rollers, is passed through the upper part of the boss =C=,
emerging by the small hole referred to, being then wrapped round the
presser two or three times, and finally conducted through the guide-eye
in the finger to the bobbin =F=. Both the inner and outer surface of
the flyer must be absolutely smooth, as otherwise it catches the fibre
and forms “fly.” For this reason, steel, as a constructive material,
has entirely superseded the fine iron formerly used.
(229) The spindle is borne, as was shown, by a bolster and footstep.
In order to give steadiness and reduce friction it is the practice to
fit in the former a collar or tubular bearing. This is either “short”
or “long.” Formerly short collars were the rule, these merely acting
as a somewhat longer bearing, the bobbin in its vertical movement
sliding upon the spindle. Mr. John Mason then introduced the “long”
collar which is shown in Fig. 128. The collar =I= is of sufficient
length to extend from the bolster, bearing upwards through the bobbin
to a point within the flyer. It is recessed internally, so as not to
bear the entire length, but simply to be in contact with the spindle at
two points. The latter is thus sustained high up, in addition to being
borne, as usual, at the two lower points. The effect is that a much
less amount of vibration is set up, and the flyer revolves with greater
steadiness. This has an important bearing upon the operation, as it
diminishes considerably the risk of breakage.
(230) Another method which, in many respects, is superior to any other,
is that shown in Figs. 130 and 131 in vertical section and elevation.
This is the plan previously adopted by Messrs. William Higgins and
Sons, and now made by Messrs. Crighton and Sons, and Shepherd and
Ayrton. In this case the spindle =A= is carried in a long tube =I=,
which extends downwards until it is formed, as shown, into a footstep
for the spindle toe. In short, the spindle is sustained in a kind of
tubular cradle, being to a certain extent entirely free of the fixed
bearing rails =J K=. To these the tube =I= is attached by swivel
joints, so arranged that they are universal, thus allowing the spindle
=A= and flyer =B= to adjust themselves as required to compensate for
any unevenness of balance which may exist in the bobbins or flyers.
The tube =I= is recessed for a certain part of its length, so as to
form an oil chamber and reduce the friction set up during work. The
advantages arising from this arrangement are that, even when the
spindle is running at high velocities, any untrueness in the balance
of the spindle merely causes it to find its true centre of gravity,
and thus avoid vibration or wear. Spindles constructed in this manner
can be worked for many years without showing any wear which is at all
detrimental, and on this account higher velocities are attainable with
ease than can be reached with the ordinary methods of construction.
(231) The spindles are positively driven as shown in Fig. 130, by means
of bevel wheels fastened near the foot. In the arrangement shown in
these drawings the spindle pinions =F= are formed with square holes,
into which the spindles, similarly shaped, are fitted. This allows the
spindle to be easily lifted out when required for examination. Usually
the pinions =F= are fastened to the spindle by means of a set screw. In
either case they engage with a bevel wheel =G= fastened on a shaft =H=,
carried in brackets fixed to the framing, and extending longitudinally
along the frame. The spindles being set zig-zag, as described, there
are two lines of them, and consequently there must be two shafts =H=
to drive them, and in order to distinguish between the two, they are
supposed to be shown in position in Fig. 131, and the back wheels are
marked =F^{1} G^{1}=. The shafts =H= are geared so as to revolve at the
same velocity, but in opposite directions, and, as it is imperative
that the spindles shall revolve in the same direction, this is attained
by gearing the pinions =F F^{1}= on different sides of the centres of
the wheels =G G^{1}=, as clearly shown. To enable this to be done, the
teeth of the wheels are cut at a special angle or “skew” to suit.
[Illustration: FIGS. 130 AND 131. J. N.]
(232) The bobbin =L= rests upon a flange of the bevel pinion =M= placed
on the collar, and driven by the wheel =N=. The pinions are, as shown
in Fig. 129, fixed in the “bobbin rail,” or, as in Fig. 130, carried on
the top of a bearing sustained by the swivel joint. The upper flange
of each pinion has formed on it oblong “snugs” or projections, which
take into corresponding slots made in the bottom of the bobbins. The
wheels =N= are keyed on the shafts =O=, which also extend the whole
length of the machine, and are suitably borne by brackets fastened
to the underside of the bobbin rail. Thus the latter sustains both
the driving shafts and the bevel pinions which, as in the case of the
spindles, are driven by wheels gearing at different sides of the centre.
(233) This mode of construction lends itself very easily to the
formation of the bobbin or spool of roving, which, at its completion,
is of the shape shown in Fig. 128, cylindrical with conical ends. In
order to wrap the yarn upon the bobbin =L= it is necessary to give the
latter not only a rotary but a vertical movement. It is, of course,
possible to give this motion to the spindle and flyer and not to the
bobbin, but this is not a convenient method in the case of machines
like those under notice, for many reasons. The rail, therefore, which
carries the bobbin pinions and bobbin, known as the “bobbin rail,”
receives a vertical traverse to an extent which is determined by the
class of material to be dealt with. This traverse is a reciprocal one,
and is technically known as the “lift,” a machine being said to have a
lift of so many inches according to the extent of the vertical movement
of the bobbin rail. This varies from 10 or 12 inches in the case of the
slubbing frame to 5 or 6 inches in the roving frame, and is obtained in
a manner which will be presently described. While it is taking place
the bobbins are slid upon the spindle, the presser eye continuing
to revolve in the same horizontal plane. From this it follows that
any yarn drawn through the eye by the rotation of the bobbin is of
necessity wound upon a fresh portion of the surface of the latter.
It only remains now to point out, before proceeding to deal with the
machine in detail, that it has been shown the spindles and bobbins
are driven independently, and may, if desired, rotate at various and
different speeds; and that provision is also made for the maintenance
of the vertical position of the spindles and flyers while permitting
that of the bobbin to be altered. These, added to the regular delivery
of sliver by means of the rollers, constitute the essential features of
these machines, but the effective manipulation of them gives rise to a
number of interesting mechanical problems.
(234) It has been pointed out that the action of the rollers in
attenuating the sliver is identical with that of those in the drawing
frame, so that no special description need be given of them. But these
machines are the first in which the process of twisting is carried
out, and the rollers form an important part of the mechanism for this
purpose. In introducing twist into any strand or sliver it is necessary
that one end of it should be held, while the other is also held and
turned at a higher or lower speed. If this is done the strand will be
twisted, and the amount of twist is strictly defined by the number of
times it is turned. In actual working it is not practicable to continue
so to twist the strand without at the same time submitting it to the
action of the spindles continuously. Unless it was so delivered it
would be broken because of the shortening which takes place during
twisting, and it is therefore necessary to furnish a fresh portion of
the sliver to the action of the twisting mechanism. For this reason
the sliver, while being firmly held by the nip of the front rollers,
is also delivered by them at a definite rate, which depends on their
size and rate of revolution. Now, assuming that no such delivery takes
place, and that a length of sliver of 10 inches is turned 100 times,
there would be in each inch of it 10 turns or twists. Suppose, now,
that another 10 inches was delivered and the same number of turns
made, a similar result would be obtained. It does not matter whether
the delivery is constant or intermittent, provided only that the ratio
of the length delivered and the number of revolutions of the twisting
mechanism remain the same. Intermittent delivery would, however, be
very inconvenient in practice in producing rovings, and thus it is
requisite to provide for a steady and regular delivery of yarn, as well
as a uniform speed of the spindle and flyer. Granting the attainment of
these conditions, it is easy to define the amount of twist put into any
thread, it being in the same ratio as the number of revolutions made
by the twisting mechanism during the delivery of one inch of sliver or
roving. Twists are always defined as being so many “turns” per inch,
and are arrived at in the way just indicated. As a matter of fact
there is a little slip in the rollers, which does not, however, to any
large extent modify the rule enunciated. The constants in a machine
of this kind are therefore the rate of revolution of the spindles and
front rollers; and, generally speaking, the amount of twist increases
as the roving becomes finer. This can be attained by an increase of
spindle speed or a decrease of that of the rollers, as will be readily
understood, but considerations of a mechanical nature generally lead
to the latter course being pursued. The spindle speeds in a slubbing
intermediate, and roving frame, dealing with the same class of roving,
would be approximately 700, 800, and 1,100 revolutions per minute. A
table of productions, speeds, etc., is given on page 174, which will
throw some light on this point.
(235) It has been already noticed that the bobbin receives a vertical
traverse, while the spindle is vertically stationary, and that, in
consequence, the yarn is wrapped upon the bobbin in spiral coils. The
speed of this traverse is carefully regulated so that each layer is
quite free from any overlap, while, at the same time, no space should
be left between the coils. When the bobbin has wrapped round it for
the whole of its length one layer of roving, its diameter is increased
by an amount equal to double the thickness of the roving. Thus its
circumference is enlarged, and every revolution it makes requires a
longer length of material to cover the surface than it did when it was
bare. This extra amount must either be fed to the bobbin, or its speed
must be reduced, and as the rollers deliver at a constant rate, the
latter is the course pursued. Further, the length of roving wrapped
upon the bare bobbin during the whole lift is, of necessity, less than
that which would be wrapped upon it after a layer has been wound on
if the lift were constant. It is essential that the length of each
complete layer should be as nearly as possible equal, and for this
reason the traverse of the bobbin is shortened slightly after each of
its reciprocal movements. The amount of the diminution in lift is in
exact correspondence with the excess of length which would be taken up
if it remained constant. The increase in the diameter of the spool has
thus an important bearing on the lift, and it is of equal moment in
relation to another function of the machine.
(236) A reference to Fig. 129 will show that the flyer and bobbin
rotate round the same centre, and the roving delivered by the rollers
is passed on to the bobbin through the presser eye, as pointed out. If
it be assumed that the yarn passes on to the bobbin at some imaginary
point in the circumference of the latter, and that this occupies during
its rotation a definitely relative position to that of the flyer eye
during its revolution in a concentric circle, it follows that no
roving can pass from the flyer to the bobbin. A little thought will
make this clear, but Fig. 132 will serve to illustrate it. In this
figure, =A= is the spindle, =B= the circumference of the bobbin,
and =C= the path of the flyer eye. Now, as =A= and =C= are attached
in the manner previously described, they must of necessity revolve
at the same speed. On the other hand, the rate of rotation of =B= is
capable of variation by reason of its independent driving. Let =D=
and =E= represent respectively the points at which the yarn leaves
the flyer =C= find passes on to the bobbin =B=. It is obvious that
if the relative position of =D= and =E= remain unchanged—that is, if
they travel at equal speeds, so that the line between them is always
alike—there can be no passage of roving from =D= to =E=; or, in other
words, there can be no winding. But if the point =E= makes a complete
revolution in less time than =D= does, or _vice versâ_, winding will
take place. In the first case the quicker motion of =E= would result in
the bobbin =B= taking up roving from =D=; and in the second the greater
velocity of =D= would cause it to wrap the roving round the bobbin. To
make this clear, suppose the lines =A D= and =A E= to represent radial
lines drawn through the points =D E= at the commencement of winding,
and that at the termination of say three revolutions, the position of
these lines relatively is the same. It is perfectly clear that the line
=D E= will have remained unaltered, and no passage of the roving will
have occurred. But now assume that the flyer =C= had moved so much
faster than the bobbin =B=, that the radial lines through =D= and =E=
were in the position shown in Fig. 133. It will at once be seen that
=C= will have drawn forward a certain length of roving corresponding to
its gain, and that the portion of its circumference between the point
where the material from =D= passes on to it and the point =E= will be
covered by the roving. In the event of =B= moving faster than =C=, the
effect is identical with that described, although it is obtained in an
entirely different way.
[Illustration: FIGS. 132 AND 133. J.N.]
(237) This statement of the general principle is sufficient to show
the conditions under which winding is successfully effected. The gain
either of the bobbin or flyer upon the other is technically called
the “lead,” and thus a frame is said to be constructed with a bobbin
or flyer “lead.” The determination of the amount of lead is very
simple, and is fixed by the speed of the rollers, it being manifestly
impossible to take up more yarn than is delivered. It follows,
therefore, that the excess of the surface speed of the bobbin or spool
at any stage of its development must accurately correspond with that
of the front rollers. If this condition be departed from, either by
the lead given being too great or too little, the result will be
broken yarn; in the first case by stretching, and in the second by
the production of slack places which become entangled and broken. It
may here be stated that it is now almost universally the practice to
let the bobbin lead, as, with the flyer leading, a certain amount of
stretch is put into the yarn, which is very injurious. This defect
is especially noticeable in starting the frame, and it is entirely
remedied by giving the lead to the bobbin.
(238) Assuming, then, that the bobbin leads, it is necessary to
consider the effect of the gradual increase in the size of the bobbin,
caused by the winding on of the yarn. This difficulty is rendered acute
by reason of the positive driving of the bobbin. In flyer frames, used
for spinning or doubling, the bobbin has a little slip which can be
easily adjusted, but which is not obtainable in this case. The slip of
the bobbin is caused by the drag of the yarn, a procedure which at this
stage is practically impossible. Every traverse of the bobbin rail is,
as has been seen, accompanied by an increase of the circumference of
the bobbin corresponding to the diameter of the roving. Thus, to take
an extreme case, assuming the diameter of the empty tube to be 1-1/2
inch, it would take up at each revolution 4·7 inches of yarn. If the
yarn was 1/8 inch thick, the diameter of the bobbin would be 1-3/4
inch after one layer, and each revolution would take up 5·5 inches
of yarn. This is, of course, assuming that the flyer is absent, and
that the bobbin was winding. As the surface velocity of the bobbin
and front roller must correspond, and no more sliver is delivered at
one time than at another, it follows that the rate of revolution of
the bobbin must diminish in exact proportion to the increase of its
circumferential speed. It is, therefore, easy to calculate the exact
amount of retardation at each traverse by a knowledge of the diameter
of the yarn, or the number of layers to be wound on any spool.
(239) It is thus easy to see that with the bobbin leading it should
gradually diminish in speed, and it is consequently the practice to
run it at a much higher speed at the beginning than at the termination
of winding. For instance, an empty spool 1 inch diameter takes up per
revolution 3·1416 inches of roving, while one 3 inches diameter would
take up 9·42 inches. It thus becomes imperative to reduce the speed of
the bobbin wheels, and these being constantly geared with their driving
wheels, it is necessary to reduce the velocity of the bobbin shafts.
These are driven, as described hereafter, by a train of gearing from
the main shaft, and special means are adopted to compass the reduction.
The spindles are running at a constant speed, and it follows, in
consequence, that the bobbin must run at the same rate, plus the number
of revolutions necessary to take up the length of yarn delivered in any
given time. If, for instance, the spindles made 100 revolutions while
10 inches of yarn was being delivered, the bobbin must revolve 100
times plus the number necessary to take up the 10 inches of yarn.
(240) When the flyer leads, the application of this principle is not
quite so clearly seen at first sight, but a little reflection will
make it understood. In this case the winding is effected by the excess
of the speed of the flyer over that of the bobbin. This is exactly
the reverse of the practice when the bobbin leads, but the essential
condition is, as before, the preservation of the relative surface
speeds of the bobbin and roller. Suppose that, in starting, the
diameter of these two are the same, then the bobbin must lag behind
the flyer to the extent of one revolution for each revolution of the
roller. But as the bobbin increases in diameter, it requires more
yarn to cover its surface, and a less difference in speed is needed,
as, if the bobbin continues to lag one revolution, the difference
between the speed of delivery and that of winding become so great as
to stretch and break the roving. Instead of wrapping it round, for
instance, a circumference of three inches it has eventually to be
wound on one of six inches, and it is obvious that if the speed of the
bobbin remains constant the roving will be drawn and broken. It is,
therefore, necessary to gradually increase the speed of the bobbin so
that for every inch of yarn delivered, an inch of the circumference
will be covered by it. The difference between this and the former
case consists in the fact that the roving is wrapped on a concentric
surface, revolving in the same direction at a slower speed, while,
with the bobbin leading, the surface on which the roving is wound,
moving in excess of the speed of the flyer, draws the roving through
the flyer eye at a rate equal to that of its delivery. In other words,
it is in one case _wrapped_ on by the excess of the flyer speed or the
drag of the bobbin, while, in the other, it is _drawn_ on by the excess
of speed of the bobbin. The conclusion is thus arrived at that when
the flyer leads, the bobbins must start at their slowest speed, and
gradually increase; while, when the bobbin leads, it must begin at its
highest speed and gradually diminish.
(241) Having thus explained the principle of the machine, it now
remains to describe the mechanism by which it is carried into effect,
referring for this purpose to Fig. 134. The driving, or “jack,” shaft
A has a fast and loose pulley on its outer end, and has fastened on it
two spur wheels. One of these drives, by means of a carrier wheel, a
wheel fixed on one of the spindle shafts, and motion is given to the
spindles in the way previously described. The speed of the spindles,
being independently obtained, can be changed without reference to
the other motions. The pinion =C= is known as the “twist wheel,” and
is made as large as convenient. It drives, by the intervention of a
carrier wheel, a pinion =D= fixed on the shaft on which the cone =E= is
also keyed. The shaft carrying =D= has also fastened on it, within the
framing, a pinion which directly gears into a wheel fixed on the roller
axis. Thus the twist wheel =C= drives the cone =E= and the rollers, so
that if it is replaced by a smaller wheel, both of these revolve at a
lower speed, or _vice versâ_. This is important, because as the speed
of the rollers and that of the bobbins are both regulated from the
twist wheel, the alteration of their velocities is made simultaneously.
[Illustration: FIG. 134. J.N.]
(242) This part of the mechanism is easily understood and involves no
difficulty, but the driving of the bobbins gives rise to a complex
problem which necessitates the employment of some ingenious mechanism.
The upper cone =E= drives, by means of a strap or band, the lower cone
=E^{1}=. The circumferences of each of these cones are accurately
turned to corresponding, but converse, parabolic curves, one cone
being convex and the other concave. They must be exactly the same in
their largest and smallest diameters, and are turned in lathes fitted
with “former” plates, by which the slide rest is guided in its correct
path. The lower cone is carried in bearings =B=, formed in two arms
connected by a tubular stay, oscillating on a shaft (=M=, Fig. 134),
on which is the pinion =H=. This arrangement is shown separately in
plan and elevation in Figs. 135 and 136. A pinion =G= is fixed on the
spindle of the lower cone, and gears with a spur wheel =F= fastened on
the shaft named. Thus, when the cone =E^{1}= is raised or lowered, the
pinion =G= rolls round its engaging wheel =F=, being always fully in
gear. This arrangement is utilised to keep the strap tight, the lower
cone being coupled by an adjustable connecting rod or chain =I= to
a disc fixed on the cross shaft shown, the former being preferable. By
revolving the shaft =J=, the cone =E^{1}= can be raised or lowered,
and the tension on the strap can be regulated by means of a right and
left-handed nut which couples the two parts of the connecting rod
=I=, Fig. 134. Motion is given to the pinion =H=, as will be easily
understood, from the cone =E^{1}=, and from it to the shaft =K= by the
carrier pinion which gears with =H^{1}= on =K=. On =K= also is fixed
a spur pinion =L^{1}= driving the plate wheel =L=, and the worm which
engages with the worm-wheel on the upright shaft =M=. The latter is
thus revolved, its precise function being explained hereafter.
[Illustration: FIGS. 135 AND 136. J.N.]
(243) The wheel =L= forms a part of the ingenious winding, or, as it
is sometimes called, “the differential motion,” invented by Mr. Henry
Holdsworth. This is one of the class of epicyclic wheel trains, of
which many instances are known and which are very interesting. Fig.
137 is a drawing on an enlarged scale of this motion, the reference
letters, with the exception of =L= and =N=, being used for this figure
specially. Upon the shaft =A= a fixed cast-iron tube is placed, upon
which the wheel =L= and the compound wheel =D N= revolve. The jack
shaft =A= revolves in the tube, and on the shaft is fastened a bevel
wheel =B= which gears with similar pinions =C= and =E=. These are
carried in bearings formed in the wheel =L= at equal distances from
its centre, and have perfect freedom of revolution. They also engage
with the bevel wheel =D=, cast in one piece with the spur wheel =N=,
which is known as the “bobbin wheel.” The latter gears with a spur
pinion carried in a double swing frame =O O^{1}= (Fig. 134), centred
on the jack shaft and attached at its other end to the bobbin rail. In
this way, as the latter rises and falls, the swing frame or “swing”—as
it is shortly called—oscillates on its centre, and the spur pinion
rolls round the bobbin wheel =N=, being always in full gear. By means
of a carrier wheel—also borne by the swing—the motion of the bobbin
wheel is communicated to a spur wheel on one of the bobbin shafts, and
by equal sized pinions on each shaft to the other. Thus, the bobbins
are driven by a train of wheels, which are always in gear, no matter
what the vertical position of the bobbin may be. The bobbin wheel and
its compound bevel run loose upon the cast-iron tube, as previously
stated.
(244) The foregoing description of the winding motion will serve to
show the principle of its construction, and its mode of action can now
be explained. Suppose first, that the bearings of the pinions =C= and
=E= are fixed instead of revolving with the wheel =L=, and that the
shaft =A= is revolved, it is obvious that the revolution of the wheel
=B= would be communicated to =C= and =E=. These would rotate on their
axes, and would consequently drive the wheel =D N= at the same speed
as =B=, but in the opposite direction. This may be called one pole of
the operation of this motion. The other is reached when the plate wheel
=L= is rotated in the same direction as =B= at an equal velocity, the
wheel =D N= being then carried round in the same direction, and at the
same speed as =B=. But if the relative velocity of =L= is reduced,
there will be a lessened speed communicated to the wheel =D N= in
the proportion of two revolutions less than that of =B= for every
revolution of =L=. That is to say, if =B= was running at 20 revolutions
per minute and =L= in the same time made one revolution, =D N= would
make 18 revolutions. This gives rise to a curious result in working.
When the number of revolutions made by =L= is half of those made by
=B=, the motion of =D N= entirely ceases, but as the proportion is
varied so as to be slower than =B=, the velocity of =D N= is reduced as
described, but its direction of rotation will be different. That is,
if =L= makes more than half as many revolutions as =B=, the wheel =D
N= will move in the same direction as =B=; but if it makes less than
half, =D N= will rotate in the opposite direction to =B=. This motion
is admirably treated in Professor Goodeve’s “Elements of Mechanism,”
where its rationale is fully described, and where the student will find
ample explanations of the operation of this class of mechanism. It is
sufficient for the present purpose, however, to reiterate that the
loss of motion in the bobbin wheel =D N=, is equal to two revolutions
of =B= for each one of =L=; and that the direction of motion of =D N=
depends on the speed of =L=. It may be said, in amplification, that
when =L= revolves at less than half the speed of =B=, the velocity of
=D N= increases as that of =L= decreases; while if the plate wheel =L=
makes more than one-half the number of turns of =B= the speed of =D N=
increases with that of =L=. The middle point thus becomes a sort of
zero, a fact which it is desirable to remember. Treated algebraically,
the formula may be stated as follows, where _b_ = the velocity of the
driving pinion =B=, _l_ = that of the plate wheel =L=, and _n_ that of
the bobbin =D N=, if =L= revolves in the same direction as the shaft,
_n_ = _b_ - 2_l_; but if in the contrary direction, then _n_ = -_b_ -
2_l_.
(245) The effect of the application of this formula in the latter case
is different entirely to the results already described. If the wheel
=L= revolves at the same speed as =B=, but in the contrary direction,
then _n_ = - 3_b_, if the value of _b_ be substituted for that of
_l_. If =L= makes half the number of revolutions that =B= does, then
_n_ = -2_b_. The relations of =B= and =D N= can thus be accurately
ascertained, and by the aid of this formula the speed of the bobbin
wheel can be easily calculated. It is only necessary to know the value
of the entire train of gearing from the fixed wheel =B= to the plate
wheel =N= to be able to apply the formula given above. Thus, if it is
found that the ratio of the velocity of =L= and the fixed wheel =B= be,
say, as 1: 40, and that =B= makes 250 revolutions per minute, the speed
of =D N= could be arrived at easily. Substituting the arithmetical
value of _l_ and _b_ for those signs, the result would be _n_ = 250 -
2(250÷40) = -262·5. As the changing position of the cone strap is the
only variable factor in the problem, it is only necessary to know the
diameters at various points to ascertain accurately the reduction or
acceleration of speed which will occur during the time it is making the
necessary traverse. It should be explained, before passing on to deal
at greater length with the practice of the subject, that the minus sign
merely indicates that the bobbin wheel revolves in a contrary direction
to the wheel =B= and the shaft =A=.
[Illustration: FIG. 137. J.N.]
(246) The application of this mechanism to the purposes of winding
depends, therefore, upon the regulation of the speed of =L=. It has
been seen that the motion of the latter is derived from the bottom cone
=E^{1}=. Assuming the plate wheel to run in the same direction as the
wheel =B=, it follows that when the bobbin leads, the wheel =L= must
start at its slowest relative speed, and increase as the bobbin fills.
It is for many reasons desirable that the speed of the plate wheel
should be as low as possible, which is the course generally adopted.
If the flyer leads, the opposite plan is pursued. When, as is the
case in the machine made by Mr. John Mason, the plate wheel revolves
in the reverse direction to that of the wheel =B=, it commences
at its quickest and finishes at its lowest relative speed, with a
bobbin lead. Under these circumstances the full value of the special
arrangement, illustrated in Fig. 137, is seen. The highest velocity of
the cone is obtained when the bobbins are empty and have in consequence
the lightest weight. Where spindles are revolving at 800 to 1,000
revolutions per minute, this is undoubtedly a great consideration,
because the strain upon the strap is lessened by reason of the
decreased velocity at a time when the strap is on the smallest diameter
of the driving cone. It is sometimes the practice to run =L= and =D=
on the bare jack shaft in the contrary direction, this creating a good
deal of friction and necessitating extra driving power. For this reason
the introduction of a tubular bush, such as is shown in Fig. 137, is
attended with considerable advantage. The friction existing when the
wheels run upon the bare shaft, but in the contrary direction, is very
great, as will be understood when the speed of the wheels—about 400
revolutions per minute—is remembered. Any rotation of one or more of
the wheels in the opposite direction to the shaft is therefore equal to
an increase of the friction on the latter by the rate of the movement
of the former.
[Illustration: FIG. 138. J.N.]
(247) To overcome this defect, therefore, the motion has been
re-arranged in one or two cases, so that all the parts revolve in the
same direction. Messrs. Curtis, Sons, and Co. employ Curtis and Rhodes’
motion, which is illustrated in section in Fig. 138. The bobbin wheel
=A= is cast in one piece with, or fixed to, an internal wheel =C=,
which is loose upon the shaft =B=. The disc =D= is fastened on the
shaft, revolving with it, and carrying a pin or spindle, on each end of
which are fastened the pinions =E= and =F=. =E= gears with the internal
wheel, and =F= with a compound pinion =G=, which in turn engages with
the pinion =H=. The latter is cast on the collar =L=, which is driven
from the lower cone and is loose upon the shaft =B=, revolving in the
same direction. If the collar =L= is fastened to the shaft, the whole
of the wheels become locked together, and the bobbin wheel =A= and the
driving pinion =H= will revolve together at the same speed and in the
same way. This arises from the fact that the disc =D= is fixed on the
shaft, and as it carries the train of wheels the fastening of =L= keeps
the teeth of =E= and =F= locked, so causing the rotation of the latter
and its attached wheel =A=. The carrier wheels would be standing under
these conditions, while the Holdsworth motion in the same circumstances
would have the whole of the wheels in rapid motion. Thus, if in actual
work, when the collar =L= is loose, it is revolved at the same speed as
the disc =D= or at one nearly approaching it, there would be no motion
in the carrier wheels, or very little, and the speed of =A= would equal
that of =H=. As the velocity of the latter is reducing, more motion is
given to the wheels, which thus retard the wheel =A= while allowing
it to rotate in the same direction as the shaft. In this way the wear
and tear of the parts, and the power required to drive them, are alike
materially reduced.
[Illustration: FIG. 139. J.N.]
(248) Messrs. Howard and Bullough use Tweedale’s motion, which is
illustrated in Fig. 139. The shaft =A= has a boss fastened on it,
which is constructed with a second boss =G= at right angles to, but on
one side of it. The latter is bored to receive a short shaft, on each
end of which the two wheels =F H= are fixed. The wheel =B= is driven
from the lower cone, and is compounded with the bevel wheel =E=, both
being free to revolve on the shaft. The bobbin wheel =C= is cast in
one piece with the wheel =D=, and also runs loosely upon the shaft.
It will be noticed that only the wheels =F= and =H= are positively
rotated on the shaft =A=, being carried round with the boss. The motion
is communicated from =E= to =D= as follows: =E= drives the wheel =F=,
thus rotating the short cross shaft and the pinion =H=. The latter
gears with and drives the wheel =D=, the pinion =F= acting merely as a
carrier. The action of this mechanism can be readily understood from
the preceding explanation, and it need only be pointed out that the
regulation comes from the wheel =B=. There is introduced into this
mechanism the element of a double set of driving and driven wheels.
Thus =G= drives the wheel =F=, and =H D=, so that there is a difference
between this and the Holdsworth motion, in which the intermediate
pinions act as carriers only. In order, therefore, to get the speed
communicated to the wheel =D=, it is necessary to multiply the number
of teeth in the driving wheels and divide by those of the driven, by
which means the proportions of the two are arrived at. By the use of
the following formula the speed of =D= can easily be arrived at. Let
_m_ = revolutions of the shaft, _n_ = revolutions of the pinion =B=,
which is variable, _a_ = the constant arrived at as above, and _v_ =
the speed of bobbin wheel =D=, then _v_ = _m_ - _a_(_m_ + _n_). Having
obtained the speed _v_ it is of course easy to calculate the necessary
wheels to give the speed of the bobbins.
(249) The operation of the differential motion is controlled, as has
been seen, by the lower cone, the speed of which is carefully regulated
by altering the position of the driving strap laterally. It has been
pointed out that the cones are correspondingly but conversely curved,
the reason for this being that the actual increase which takes place
in the diameter of the bobbin is not in the same proportion to the
actual diameter at the end as at the beginning of winding. There is a
slight decrease occurring as the bobbin fills, and in the early stages
of spinning it was the practice to use a rack with uneven teeth cut
to a parabola, which was a costly process, and is entirely avoided by
the use of cones of that shape. Further, it is found that the bite of
the strap is better during a change of position. It will be readily
understood that the position of the strap on the two cones determines
the speed of the plate wheel =L=. It is therefore essential to provide
means by which the traverse of the strap can be effected, and, as the
addition of one layer of roving implies the necessity for a change in
the bobbin speed, the movement of the strap is given at the termination
of each lift, at the moment of the change of traverse. It follows,
therefore, that the mechanism by which the strap is moved, and that by
which the reversal of the lift is effected, must be connected. Before
proceeding to describe how this is done it may be stated that the strap
passes between two guides fastened to the toothed rack or slide =P=
(Fig. 134), sustained by bearings fixed to the frame of the machine.
The operation of traversing the rack is performed by an interesting
piece of mechanism which has several functions.
(250) The “building motion,” or “box of tricks” as it is sometimes
called, is placed in the position shown in Fig. 133 by the letter
=Q=. In order that its details may be better understood, a front and
back elevation and plan of it is given in Figs. 140, 141, and 142,
to which special reference will be made. The objects of the building
motion are three-fold: 1st, to give the requisite traverse to the cone
strap; 2nd, to give the reciprocal traverse to the bobbin; and 3rd,
to shorten that traverse or lift at the termination of the winding of
each layer. It has been already explained why the two first objects
have to be attained, and it will be profitable to explain the reason
for the third. Suppose that in commencing winding the tube is 1-1/4
inches diameter, the lift say 10 inches, and the diameter of the roving
1/8 inch, there would be wrapped upon that surface during one lift 80
coils or 314 inches of roving. Now, assuming that four layers have
been wound, the diameter of the bobbin would be 2-1/4 inches, which,
if the lift remained constant, would cause 563 inches to be wound on
the surface. But as the rate of delivery by the rollers is definite
during the time occupied by the lift, it follows that such a length of
roving could not be wound. It, therefore, becomes necessary to reduce
the lift after each layer of yarn is wound, so as to compensate for the
increased area of the cylindrical surface, and provide that the whole
of the length delivered by the rollers is taken up, but no more.
[Illustration: FIG. 140. J.N.]
(251) Referring now to Figs. 140 and 141 it will be noticed that there
are two cradles =A= and =B=, centred respectively on the pins =A^{1}=
and =B^{1}=. Fixed in the upper cradle =A= are hooks, one at each side,
which are connected, as shown, with double hooks =C D=, passing through
ears on the lower cradle =B=, having weights attached to their lower
ends. The lower cradle =B= has fixed in it a pin =E^{1}=, engaging with
a slot in the lever =E=. =E= is centred on the pin =F=, and is coupled
at its lower end to the rod =R=, which is connected with the double
bevel wheel =T T=, this connection being shown in Fig. 134. Two catches
=G G^{1}=, centred at their lower ends to the frame carrying the
cradles, are coupled by the helical spring =H=. It will be noticed that
the pawls of the catch levers are differently shaped, so as to engage
with the teeth of the rack or ratchet wheel =I= on the upper and lower
side of the centre respectively. The rack wheel is fixed on the same
centre as the cradle =A=, as is also a bevel pinion =J=, gearing with
a similar one =J^{1}= fixed on the upright shaft =K=, Fig. 141. At a
higher point on =K= a spur pinion =P^{1}= is fastened, which gears with
the teeth on the rack =P=, controlling the strap guides. Two levers
=L L^{1}= are pivoted to the frame as shown, and are coupled at their
inner ends by a helical spring =M=, which is carried round the centre
=B^{1}=. The inner ends of =L L^{1}= engage with shoulders or corners
=N N^{1}=, formed in the lower cradle =B=. Fixed to the bobbin rail
is the double slide =Q=, which has a pin =O= sliding in it, on which
the end of the connecting rod =S= is centred. This rod passes through
bearings placed in the cradle =A= (see Fig. 140), and is formed with
a toothed rack at its lower side with which a wheel =T= fixed on the
pin =A^{1}= gears. These are the whole of the parts of this particular
mechanism, but a reference to Fig. 134 will show that the rack =P= has
a weight attached to it by a chain, which is always tending to draw it
inwards, and move the strap. In addition to this it causes a torsional
strain to be exercised on the shaft =K=, and consequently on the rack
wheel, which causes the latter, when released by the catches, to rotate.
(252) The action of this mechanism is as follows: The slide =Q= in its
reciprocal vertical movement causes by means of the “diminishing rod”
or “hanger bar” =S=, the upper cradle =A= to oscillate in its centre.
When the bobbins are midway in their lift, the centre of the slide =Q=
should be in a line drawn horizontally through the centre of the pin
=A^{1}=, and the rod =S= should be capable of being moved horizontally
without producing any oscillating movement in the cradle =A=. When
this is the case, the two levers =L L^{1}= engage respectively with
the shoulders =N N^{1}=. Assuming that the bobbins are descending, the
cradle =A= is turned from left to right when looked at from the back of
the frame as in Fig. 141. In this way the hook =D= is raised with its
pendant weight, while =C= is simultaneously lowered. As the shoulder on
the upper part of the hook =C= prevents it passing through the hole in
the ear on the cradle =B=, it follows that a pressure is exercised on
the latter, which causes it to turn in the same direction as =A=. The
weight attached to =D= is finally completely taken off the cradle =B=,
and the continuance of the movement causes the point of contact of =L=
and =N= to become the fulcrum by which the rotary movement of =A= is
arrested for the time. This movement closely resembles the action of
an anchor, the cradle =B= being practically fixed as a ship is by its
anchor. In some modifications of the mechanism this resemblance is more
pronounced than in the one immediately under notice. Thus the point
through which =D= passes continues to be free, while the whole weight
is thrown upon the hook =C=, which thus exercises a proportionate
strain on =B=. The continued oscillation of =A= in the direction
indicated causes the screw =X=, fixed in the left hand arm of =A=,
as shown in Fig. 140, to come into contact with the outer end of the
lever =L=. The increasing pressure so applied causes =L= to turn upon
its centre, destroying the contact of its inner end with the shoulder
=N=, and allowing the cradle =B= to make a sudden movement, which is
partially rotary, but is also vertical in character. The movement being
reversed, the parts assume the position shown in Fig. 140, shortly
after the reversal. The screws fixed in the arms of the cradle =A= can
be readily adjusted and locked so as to make the release of the lower
cradle =B= simultaneous with the termination of the bobbin traverse.
[Illustration: FIG. 141. J.N.]
[Illustration: FIG. 142.]
(253) In consequence of the sudden release so effected, the lever
=L^{1}= assumes the position shown in Fig. 140, and at the same time
the pin =E^{1}= strikes one side of the hole in the lever =E= (see Fig.
141), and causes the latter to turn rapidly on the pin =F=. This is
followed by three things. The head of the lever =E= strikes the catch
=G^{1}= and throws it out of gear with the ratchet wheel. The latter
at once makes a rotary movement to the extent of half a tooth, but is
then arrested and retained by the catch =G=. As the catch levers =G
G^{1}= are coupled by the spring =H= it will be easily understood how
the movement of one of them to the right or left is accompanied by a
corresponding movement of the other. By this release of the ratchet
wheel and its partial revolution, the upright shaft =K= also moves
and causes the rack =P= to travel inwards and so move the strap on the
cones. This is the first effect of the movement of the lever =E=.
(254) As shown in Fig. 134, and also in Fig. 141, the lower end of the
lever =E= is attached to the rod =R=, which is connected at its other
extremity by a forked lever to the double bevel or “striking” wheel
=T T^{1}=. The latter engage alternately with the small bevel pinion
fixed on the lower end of the upright or “change” shaft =M= and slide
upon a short shaft =U=, which they drive by means of a feather key. On
=U= is also fixed a spur pinion =V= which drives, by the intervention
of suitable gearing, a shaft running longitudinally and placed just
behind the spindles. This shaft has a number of spur pinions fixed on
it, which engage with vertical racks or “pokers” fastened to the bobbin
frame. In this way the rotation of the pinion =V= in either direction
is followed by the traverse of the bobbins either upwards or downwards.
When, therefore, the rod =R= is traversed by the oscillation of the
lever =E= and the bevel wheels =T T^{1}= are respectively thrown into
gear with the pinion on =M=, the bobbin traverse in a corresponding
direction is obtained.
(255) A further effect which arises from the rotation of the ratchet
wheel is found in the fact that the wheel =T= (Fig. 140) also moves,
and as it engages with the rack on the underside of the rod =S= draws
the latter inward. As will be readily understood, the position of the
pin =O= plays an important part in the oscillation of the cradle =A=.
If, for instance, the pin were at the extreme point of =Q= furthest
from =A=, the motion of the latter would be made much more slowly than
if =O= were at the other end of the slide, when, owing to the shorter
radius, =A= would make its oscillatory movement more quickly, and, if
=Q= made the same vertical traverse, =A= would move through a greater
arc. Thus, if =O= is drawn inwards, it is followed by a more rapid
movement of the cradle =A=, and, as a consequence, the change of the
position of the lever =E= occurs at an earlier moment. This causes the
reversal of the traverse of the bobbin rail to take place sooner, and,
in this way, each succeeding layer of roving occupies a shorter portion
of the bobbin surface longitudinally than its predecessor. Thus the
bobbin is built accurately in the double conical shape required, and
the shortening of the lift, the necessity for which has been previously
demonstrated, is properly effected.
(256) A reference to Fig. 134 will show that the weight attached to
the rack =P= is fastened to the latter by a chain, which passes over
a pulley at the lower end of the lever =W=, which is sustained in
position by a catch placed at =X=. When the rack =P= has made its
extreme inward traverse the catch is released, and the lever =W= is
caused to strike the collar on the rod =Y=, so as to cause the latter
to move longitudinally. As the rod is connected with the driving strap
fork, the strap is thrown over on to the loose pulley, and the frame
is stopped. Attached to the bobbin frame are chains, to the other end
of which balance weights are fastened so as to relieve the work of the
lifting pinions. These chains are passed over pulleys fixed to the
framing as shown in Fig. 134.
(257) Recurring now to the action of the building and winding motions,
it is necessary to note that the number of the releases of the ratchet
wheel =I= correspond to those of the reversals of the bobbin rail,
and consequently to the number of the layers of roving. It therefore
becomes necessary to alter the wheel =I= whenever a change in the
roving which is being produced is made. As the ratchet wheel is the
governing factor in the regulation alike of the speed of the strap
traverse and of that of the inward movement of the rod =S=, the reason
for changing it is easily seen. Thus the increase in the diameter of a
bobbin on which a roving 1/16th inch diameter is being spun would be
less than that which occurs when a roving 3/32nd inch diameter is made.
It follows, therefore, that the rate at which the strap is moved along
the cones would in the first case be only two-thirds of that at which
it moves in the last case. Again, the lessened increase in diameter
involves, as was shown, the winding on of a shorter length of roving
during the “lift” of the bobbin, and consequently the latter does not
require to be diminished in the same ratio. Therefore, it is desirable
to substitute for the ratchet wheel one with more teeth, the number of
which must be in direct ratio to the number of coils it is intended to
wind on the full bobbin.
(258) Let it be assumed that the pitch of the teeth of the rack =P=
and of that in =S= is one-quarter inch; that the ratchet wheel =I= has
30 teeth, the pinion engaging with =P= 31 teeth, and the pinion =T=
19 teeth. As was shown, the wheel =I= moves to the extent of half the
pitch of the tooth every time the traverse of the bobbin rail takes
place. In this case 60 such reversions would take place during the time
that the ratchet wheel made a complete revolution. During that time the
wheel engaging with =P= would also have made a complete revolution,
and =P= would have moved in 7-3/4 inches, giving a corresponding
traverse to the strap. In the same time the pinion =T= would have made
a revolution, and the “diminishing rod” =S= would move in 4-3/4 inches.
Assuming—a purely hypothetical assumption—that the distance from the
centre =A^{1}= of the cradle =A= to the outermost point of the slide
=Q= to which the pin =O= can be pushed is 15 inches, and that the lift
of the bobbin be 7 inches, it will follow that the above reduction of
the distance of =O= from =A^{1}= will cause a more rapid oscillation
of the cradle =A=. A simple calculation will show that this would
cause the change of the direction of the lift to take place when 4-3/4
inches was covered. This example will serve to illustrate the principle
involved, but does not necessarily represent any actually existing
case. It is only intended to show that the reduction of the lift takes
place in exact accordance with the period occupied by the ratchet wheel
=I= in its rotation. During the time the traverse has been shortened
the speed of the bobbin, owing to the traverse of the strap along the
cones, has also been diminished in the exact proportion required to
compensate for the increased diameter.
(259) Now, if it be assumed that a coarser roving requires producing,
and that the ratchet wheel =I= is changed for one containing only 20
teeth, it will be seen that while the same necessity exists for the
full traverse of the strap guide and diminishing rod, a smaller number
of layers of roving will be wound in the same time. In this case 40
layers only will be laid, although the strap makes the same movement.
That is, the same reduction of the speed of the bobbin is made while 40
layers are wound that was previously made while 60 were wound. Now, as
the diminution of the speed of the bobbin must be exactly proportionate
to the increase of its diameter, it follows that the roving in the
former case must be correspondingly thicker. It should also be observed
that the inward traverse of the diminishing rod =S= is quickened as
well as that of the racks =P=, because the time occupied by the ratchet
wheel in making a complete revolution is, of course, less than when one
with 30 teeth is employed. Thus the speed of the bobbin and the length
of its traverse are both decreased at a more rapid rate when a ratchet
wheel is employed, which is exactly what is wanted when coarser roving
is being produced.
(260) A locking motion is fitted to the machine by which, when the rack
=P= is released in the manner described, the stop rod is locked in
such a way that until the rack has been wound back by hand into proper
position the frame cannot be started. There are two advantages in this
motion, viz., that the size of the bobbins is accurately regulated, and
damage to the frame is prevented.
[Illustration: FIGS. 143, 144, 145, AND 146.]
(261) In order to avoid the uneven wear of the top rollers, caused by
the slubbing or roving passing through them at one point constantly,
it has become the practice to give a slight lateral traverse to the
guide bar. One of the latest developments of this special treatment
is illustrated in Figs. 143 to 147, this being the invention of Mr.
George Paley, a spinner, of Preston. It consists of a worm =I= fixed
upon the end of the roller spindle, which gears into two wheels =G
H=, carried on a pin fixed in a bracket. The number of teeth in the
wheels are different, =H= having one more tooth than =G=. In this
way =G= is revolved once for every 24 revolutions of the worm, while
=H= requires 25 revolutions of the latter before making a complete
rotation. The wheel =H= has a boss =J=, the upper part of which =K= is
formed eccentrically, and on this portion the eccentric =L= is placed.
To the clip of =L= the traverse rod =P= is coupled. =L= is driven from
the wheel =G= by means of a pin fastened in =L=, and engaging with a
slot in =G=. Thus the rotation of the eccentric =L= is followed by the
traverse of the guide bar.
(262) It will be noticed that the outer eccentric =L= is not only out
of centre with the pin =S=, but also with the inner eccentric =K=. Thus
the rotation of the latter perpetually establishes a new condition of
eccentricity. At one point the throw of the combined eccentrics is
smaller than at another, and there are fixed limits within which many
positions are assumed. If the throw of =K= is 3/8 inch, and of =L= 5/8
inch, it is obvious that if they are both at the front centre their
combined throw will be 1 inch. But if =K= is at its back centre and
=L= at its front one the combined throw is only 1\4 inch. Now owing to
the fact that the wheels =G= and =H= are made with one tooth more or
less, it happens that 25 complete revolutions of the eccentrics are
needed before they are brought with their centres coinciding after
that position had been abandoned. The result is, that during every one
of the 25 traverses a different throw occurs, and the length of the
traverse is varied, as shown diagramatically in Fig. 147. By altering
the size of the wheels =G H= any number of variations desired can be
obtained.
[Illustration: DIAGRAM SHOWING VARIATIONS OF TRAVERSE
FIG. 147.]
(263) Messrs. Howard and Bullough fit to their intermediate frame an
electric stop motion. It should be explained that it is customary to
pass two slubbings through the rollers at once, twisting them together
to form one thread. If from any cause one of these ends breaks, the
other may go on twisting, and a thin defective place would result. To
obviate this, the arrangement named is applied. The slubbing bobbins
are placed in a creel, and are passed between the surface of a metallic
spring, and a roller placed at the back part of the machine. The
drawing rollers are fixed in their usual position, and the spring
is held by a bracket attached to one pole of an electro magnet and
battery, the back roller being connected to the other pole. When the
thread of slubbing breaks, contact between the spring and the roller
occurs, and the circuit is closed. Thereupon a current is passed
through the magnet, and one end of a lever is attracted so as to bring
its other end in the path of a constantly rotating ratchet wheel. This
arrests the motion of the latter, and so releases a catch on the stop
rod, allowing it to be drawn along by the action of a helical spring.
In this way the machine is rapidly stopped.
PRODUCTION OF SLUBBING AND ROVING FRAMES IN LBS. PER WORKING WEEK OF 56
HOURS.
+-------+------------------+-------+-----------+--------------------+
| |Speed of Spindles.|Twist | | |
|Hank | Revolutions |per |Production.| Maker’s Name. |
|Roving.| Per Minute. |Inch. | | |
+-------+------------------+-------+-----------+--------------------+
| ·50 | 600 | ·85 | 114 |John Mason. |
| ·50 | 600 | ·85 | 116 |Crighton and Sons. |
| ·50 | 700 | ·84 | 115 |Howard and Bullough.|
| 1·00 | 700 | 1·20 | 56 |John Mason. |
| 1·00 | 700 | 1·20 | 56 |Crighton and Sons. |
| 1·00 | 700 | 1·20 | 59 |Howard and Bullough.|
| 3·00 | 1000 | 2·08 | 17 |John Mason. |
| 3·00 | 1000 | 2·08 | 16 |Crighton and Sons. |
| 3·00 | 1100 | 2·07 | 16·53 |Howard and Bullough.|
| 6·00 | 1400 | 2·94 | 7·25 |John Mason. |
| 6·00 | 1300 | 2·94 | 7·20 |Crighton and Sons. |
| 6·00 | 1100 | 2·92 | 6·25 |Howard and Bullough.|
+-------+------------------+-------+-----------+--------------------+
NOTE.—The velocity of the spindles and amount of twist introduced
will largely influence the productions as given above, which are only
illustrative of the capacity of these machines.