DESCRIPTION OF THE INVENTION
[0001] The present invention relates to a drafting device for a fine spinning frame of a
sliver-to-yarn type. More particularly, the present invention relates to a three line
type drafting device which is suitable for spinning at a high drafting ratio.
[0002] Known in the prior art is a drafting device of a sliver-to-yarn type fine spinning
frame, in which a spun yarn is obtained directly from a sliver. In such a sliver-to-yarn
type fine spinning frame, a large value of a drafting ratio, which is a ratio, to
a rotating speed of a roller at a inlet side (back roller), of a rotating speed of
a roller at an outlet side (front roller) is used. In order to execute such a high
draft operation, a drafting device of a four line type or a five line type has been
proposed. In such a type of drafting device, a multiplicity of drafting zones are
provided, which is advantageous in that a large value of a total drafting ratio is
obtained. However, this type of the drafting device is disadvantageous in an increased
number of sets drafting rollers and drive elements for the rollers, which makes the
construction complicated and increases the cost. Furthermore, complicated setting
is required for various factors, such as spacing (roller gauges) and an allocation
of draft ratios between the roller pairs, which makes maintenance of the system complicated.
[0003] In view of the above difficulties when using the four line type or five line type
drafting device, it has been, usual to use, in place of such a device, a three line
type drafting device of double an apron type for a drafting device in the sliver-to-yarn
fine spinning frame. Namely, in such a three line type drafting device, second or
middle top and bottom rollers are constructed by apron rollers. The employment of
the aproned, second rollers allows floating fibers to be controlled at the front drafting
zone, so that a large drafting ratio can be obtained at the main drafting zone over
the back drafting zone, even though the drafting ratio at the back drafting zone is
relatively small, thereby obtaining a high total drafting ratio. However, such a "one
sided" increase in a drafting ratio at the front drafting zone causes an allocation
of the drafting ratios to be improper between the main and back drafting zones, thereby
reducing yarn quality.
[0004] In the aproned three line type drafting device an improvement can be conceived, wherein
the back roller pair is, also, constructed by apron rollers. However, an employment
of apron rollers also at the back rollers causes the speed of the sliver, as fed thereby,
to vary due to an inevitable variation in the thickness of the aprons. Such a variation
of the speed of the sliver fed by the back rollers causes the total drafting ratio
between the back and front rollers to vary. Such a variation in the total drafting
ratio causes the yarn thickness to largely vary, thereby causing the yarn quality
to be worsened.
[0005] An object of the present invention is to provide a three line drafting device capable
of increasing a drafting ratio at a back drafting zone, while preventing a variation
in the total drafting ratio from being increased, thereby realizing a high drafting
operation while preventing the yarn quality from being worsened.
[0006] According to the present invention, a three line type drafting device is provided
which comprises first and second pairs of top and bottom rollers, between which a
main drafting zone is created, the top and bottom rollers in said second pair being
constructed as apron rollers, and a third pair of top and bottom rollers, a back drafting
zone being created between said second and third pairs, an allocation of drafting
amounts being adjustable between said main and back drafting zones, characterized
in that said third, top roller is constructed as an apron roller, that the said third,
bottom roller is constructed as a fluted roller, and that, between said third, bottom
fluted roller and said second, bottom roller, a guide plate is arranged so that the
latter is under a contacted condition with a lower surface of said apron of the third,
top roller via the sliver.
[0007] In an operation of the present invention, the sliver is fed forwardly while being
nipped between an outer peripheral surface of the fluted roller as a back, bottom
roller and the apron of the back, top roller. The rotating movement of the fluted
roller causes the apron of the top roller to be directly moved, so that the speed
of the movement of the apron is always equalized to the peripheral speed of the fluted
roller. As a result, the sliver nipped between the fluted roller and the apron is
moved at the speed which is equal to the peripheral speed of the fluted roller. The
fluted roller is directly driven by a rotating movement source, so that the rotating
speed of the fluted roller is maintained unchanged irrespective of an inevitable variation
in thickness of the apron. Thus, the speed of the movement of the sliver, which is
in direct contact with the sliver to be fed, is also maintained unchanged, thereby
preventing the total drafting ratio from being varied. Furthermore, the sliver fed
from the fluted roller is moved in the back drafting zone, while being nipped between
the guide plate and the apron of the top, back roller, thereby controlling floating
fibers in the back drafting zone, which also serves to obtain an increased value of
the drafting ratio at the back drafting zone over that in the prior art. The sliver,
which is subjected to the drafting operation of a higher drafting ratio at the back
drafting zone, is introduced into the main drafting zone, and is subjected to a drafting
operation of a higher drafting ratio, thereby obtaining a highly increased drafting
ratio.
[0008] Now, an embodiment of the present invention will be explained with reference to attached
drawings in which:
Fig. 1 is a side cross-sectional view of a drafting device of a fine spinning frame
according to the present invention.
Fig. 2 is a cross sectional view of a back roller pair in Fig. 1.
Fig. 3 is a front view of the back roller pair in Fig. 2.
Fig. 4 is a cross sectional view of a back roller pair in a modification.
Fig. 5 is a front view of the back roller pair in the modification in Fig. 4.
Fig. 6 shows graphs illustrating yarn quality as obtained by the present invention
in comparison with that as obtained by a prior art.
Fig. 7 is a side cross-sectional view of a drafting device in a prior art.
[0009] Now, an embodiment of a three line type drafting device for a fine spinning frame
according to the present invention will be explained with reference to the attached
drawings. In Fig. 1, reference numeral 1 denotes, generally, a spinning frame. The
spinning frame 1 includes a three line type drafting device 2, which is constructed
by three pairs of drafting rollers. Namely, the first pair at a front side of the
frame is constructed by a front top roller 4 and a front bottom roller 5. The top
roller 4 is formed at a rubber coated roller having an outer layer formed by a rubber
material, while the bottom roller 5 is constructed as a fluted roller made of a steel
material. The second pair at the middle of the frame is constructed by a top apron
roller 6, which includes a top roller member 8a, a tensor 8b and an apron 8 looped
between the top roller member 8a and the tensor 8b and by a bottom apron roller 7,
which includes a bottom roller member 9a, tensors 9b and 9C urged downwardly moved
by means of a lever 9d, an apron 9 looped between the bottom roller member 9a and
the tensors 9b and 9C. Finally, the third pair at a back side of the frame is constructed
by a back top apron roller 13, which includes a top roller member 14-1, a tensor member
(cradle) 28 and a top apron 14 of the similar structure as that of the apron 8 of
the middle top roller 6 and looped between the top roller member 14A and the tensor
member 28, and by a back bottom roller 16 constructed as a fluted roller made of a
steel material.
[0010] In this three line type drafting device, two drafting zones are created, the zones
being a main drafting zone 10 between the front pair including the top and bottom
rollers 4 and 5 and the middle roller pair including the top and bottom apron rollers
6 and 7, and a back drafting zone 20 between this middle pair and the rear pair including
the top apron roller 13 and the bottom fluted roller 16. In Fig. 1, the fine spinning
frame includes a roller stand 3 for rotatably supporting the front bottom roller 5.
Mounted horizontally slidably on the roller stand 3 is a middle bottom rotor supporting
member 18, on which the bottom apron roller 7 is rotatably supported. Mounted, also,
horizontally slidably on the roller stand 3 is a back bottom roller supporting member
19, on which the bottom back fluted roller 16 is rotatably supported. These front,
middle and back bottom rollers 5, 7 and 16 are in connection with a drive train (not
shown), which has gear wheels in meshed condition. A change in a gear ratio between
the meshed gears wheels causes a ratio of rotational speeds between the gear wheels
to be changed, which allows values of draft ratio to be changed between the main drafting
zone 10 and the back drafting zone 20. The second slide member 18 and the back slide
member 19 are mounted slidably adjustably on the roller stand 3, so that a spacing
(gauge) of the pair of the middle rollers 6 and 7 from the pair of the front rollers
4 and 5 and a spacing (gauge) of the pair of the pair of the back rollers 13 and 16
from pair of the middle rollers 6 and 7 can be desirably adjusted. After the completion
of the adjustment of the gages (spacing between the adjacent rollers), bolts 21 and
22 are tightened by means of nuts 21a and 22a, respectively, which allows the middle
and back roller pairs to be located on fixed positions on the stand 3.
[0011] In a well known manner, a top arm 25 is rotatable with respect to the roller stand
3 about an axis 25-1, and, in the top side of the drafting roller assembly, the front
roller 4, the middle, apron roller 6 and the back, apron roller 13 are rotatably connected
to the top arm 25. Also in a known manner, a lever 26 is provided for allowing the
top arm 25 to be rocked between an operating position as shown in Fig. 1, where the
front roller 4, the middle roller 6 and the back roller 13 on the top side are in
contact with the front roller 5, the middle, apron roller 7 and the back, fluted roller
on the bottom side, respectively, and a rest position, where the paired rollers are
detached from each other.
[0012] In Fig. 1, the apron 14 of the top, back roller 13 has a portion 14a looped around
the tensor member 28 at an acute angle, so that the portion 14a is located at a location
adjacent the second or middle pair of the rollers 6 and 7 as near as possible, which
allows a supporting length of a sliver S to be increased to as long as possible between
the apron 14 and a guide plate 41, which is located below the apron 14 and the construction
of which will be in detail explained later, while the distance is reduced to as short
as possible between a nipping point between the apron (back) roller 13 and the guide
plate 41 and a nipping point between the middle (second) top and bottom apron rollers
6 and 7.
[0013] In Fig. 1, at a location upstream from the pair of the back (first) top rollers 13
and the bottom (fluted) roller 16, a trumpet 29 is arranged for collecting a silver
S supplied from a can. The trumpet 29 is mounted to a traverse bar 32 at its side
wall, which is mounted slidably to a back slide 19 along the length of the machine
frame.
[0014] As explained above, between the fluted, bottom roller 16 of the back (first) roller
pair and the apron roller 7 of the middle (second) roller pair, the guide plate 41
is located below a lower side of the apron 14 of the top roller 13 of the middle roller
pair. The guide plate 41 extends along the length of the machine frame and has a pair
of ends tightened to the corresponding back slide members 19 at their upper walls
by means of bolts (not shown). The guide plate 41 has, at its upper side, guide portions
41a opposite the aprons 14 of the top rollers 13 of the corresponding back (first)
roller pairs. Each of the guide portion 41a forms an upwardly curved guide surface,
to which the lower surface of the apron 14 of the back, top roller 13 is in a press
contacted condition. The guide plate 41 is, at both sides of the each of the guide
portions 41a, formed with flat surface portions 41b which are lower than the guide
portions 41a. Guide member 42, which are vertically displaceable, are arranged on
both sides of each of the apron rollers 13 as shown in Figs. 2 and 3. Each of the
guiding members 42 has a U-shaped end which is engaged with a shaft 13-1 of the roller
13. The tensor member 28 is connected to the guiding members 42 on both side of the
roller 13. A spring (not shown) is provided for generating a spring force which causes
the apron 14 to be in a press contacted condition with the faced curved guide surface
41a of the guide plate 41 flat surface portions 41b are guide plate 42. The guide
member 42 has a downwardly directed projected portion 42a, which is press contacted
with the flat lowered portion 41b of the guide plate 41, so that a predetermined relative
vertical position of the top, apron roller 13 at the back roller pair is obtained,
which allows the sliver S to be positively held under a desired force between the
apron 14 and the guiding surface 41a. The guide plate 41 can be suitably made from
a material with low friction including a metal or a synthetic resin. The projections
42a may be detachably connected to the guide plate.
[0015] Figs. 4 and 5 show a modification of the cradle supporting means, wherein a pair
of tensors 28 are supported by a guide member 42, which is arranged between the rollers
13 which are adjacent with each other. Namely, the guide member has a portion 42-1
extending forwardly, from which portion the tensors 28 extend transversely into the
corresponding aprons 14. The portion 42-1 has an integral pin 42-2, to which a distance
piece 44 is detachably snapped, so that a desired distance is obtained between the
lower surface of the apron 14 and the upper surface 41a of the guide plate 41, when
the guide member 42 is urged downwardly by means of a spring (not shown). It should
be noted that the upper surface of the guide plate 41 facing the aprons is at the
same vertical level with respect to the remaining parts.
[0016] A collector 50 is arranged between the back (first) set of the rollers (13 and 16)
and a middle (second) set of rollers (6 and 7).
[0017] Now, an operation of the drafting device 1 according to the present invention will
be explained. Prior to the spinning operation, an allocation of values of drafting
ratio at the main drafting zone 10 between the middle roller pair (6 and 7) and the
front roller pair (4 and 5) and at the back drafting zone 20 between the back roller
pair (13 and 16) and the middle roller pair (6 and 7) is done while maintaining a
predetermined total drafting ratio between the back roller pair (13 and 16) and the
front roller pair (4 and 5).
[0018] An operation of the driving motor (not shown) of the drafting device 1 causes the
fluted roller 16 (back, bottom roller) at the back drafting zone 20 to be rotated,
while the rotating movement of the fluted roller 16 is, under a frictional force,
transmitted to the apron 14 of the back, top roller 13, so that the sliver S nipped
between the fluted roller 16 and the apron 14 is moved and introduced into the back
drafting zone 20 at a speed which is identical with the surface speed of the fluted
roller 16. The sliver S introduced into the back drafting zone 20 is moved while being
nipped between the apron 14 and the guide surface 41a of the guide plate 41. Due to
such a movement while being nipped between the apron 14 and the guide plate 41, a
positive control of a movement of floating fibers in the sliver S at the back drafting
zone 20, which are not nipped by both of the back roller pair (14-1 and 16) and the
front roller pair (50 and 9a), is realized. Such a positive control of the movement
of the floating fibers in the sliver allows the drafting ratio to be increased at
the back drafting zone 20 when compared with that obtained in the prior art. As a
result, a desired allocation of drafting ratios between the back drafting zone 20
and the main drafting zone 10 is obtained.
[0019] The sliver thus passed through the back drafting zone 20 is, then, introduced into
the main drafting zone 10, whereat the sliver S is subjected to a further drafting
operation, thereby obtaining a predetermined thickness of a yarn Y.
[0020] According to the present invention, as explained above, the feeding speed of the
sliver S to the back drafting zone 20 is purely dependent on the rotating movement
of the fluted roller 16. Furthermore, the front top and bottom rollers 4 and 5 in
the front roller pair (4 and 5) for taking out the sliver are, also, not apron rollers.
As a result, the existence of the aprons 8, 9 and 14 does not cause the speed of the
sliver S to be changed at the inlet or the outlet sides of the drafting system.
[0021] In short, the three line type drafting device 2 according to the present invention
can obtain a constant value of a total drafting ratio irrespective of a fact that
the apron roller 13 is used as a top roller of the back roller pair. In other words,
a constant value of the total drafting ratio between the back roller pair and the
front roller pair is obtained regardless a variation of a thickness of the apron of
the apron roller 13, which otherwise would cause the quality of the yarns Y to be
worsened.
[0022] Fig. 7 shows a three line type drafting device 2A in a prior art, which includes
a front set of top and bottom rollers 3 and 4, a middle set of top and bottom rollers
6 and 7 as apron rollers, and a back set of top and bottom rollers 13 and 16. In this
prior art three line type drafting device, the back top roller 13 is a metal roller
and not an apron roller unlike the present invention.
[0023] In the construction of the prior art in Fig. 7, employment of the apron roller type
middle rollers 6 and 7 allows movement of floating fibers in a sliver S to be positively
controlled at a main drafting zone 10 between a middle pair of rollers (6 and 7) and
the front pair of rollers 4 and 5, so that an increased drafting ratio as high as
200 can be obtained at the main drafting zone 10 over a back drafting zone 20 between
the back pair of rollers 13 and 16 and the middle pair of rollers 6 and 7. However,
at the back roller pair, both of the top and bottom rollers 13 and 16 are metal rollers,
so that a drafting ratio at the back drafting zone 20A cannot be so high. As a result,
an allocation of drafting ratios between the main and back drafting zones cannot be
optimized, which may cause the yarn quality to be worsened.
[0024] In the prior art three line drafting device in Fig. 7, in order to obviate this problem,
both of the back rollers 13 and 16 may be constructed as apron rollers, which allows
the drafting ratio at the back drafting zone 20A to be increased. However, the influence
on a total drafting ratio when constructing the middle rollers 6 and 7 by apron rollers
is different from the influence on a total drafting ratio when constructing, additionally,
the back rollers 13 and 16 by apron rollers. Namely, a total drafting ratio is a ratio
of the rotating speed of the front rollers 4 and 5, which corresponds to the speed
of the yarn being spun to the rotating speed of the back rollers 13 and 16, which
corresponds to the speed of a sliver fed to the back rollers. On the other hand, the
apron of the bottom roller is looped around an outer periphery of the bottom roller
member subjected to a rotating movement of a driving source, so that the rotating
movement of the roller induces the movement of the apron. As a result, a variation
in the surface speed of the apron occurs when there is a change in the thickness of
the apron. In case where the aprons are employed only at the middle rollers as shown
in Fig. 7, a variation in the thickness of the aprons causes the values of the drafting
ratios to be changed at the back drafting zone 20A and the front drafting zone 10,
respectively. The variation in the thickness of the aprons, however, does not cause
the total drafting ratio to be changed, because the rotating speed ratio between the
back rollers and front rollers is unchanged due to the fact that both of the back
rollers 13 and 16 and the front rollers 4 and 5 are under a direct contact with the
sliver S, i.e., without any intervention of apron means. As a result, the variation
in the thickness of the aprons would not cause the yarn quality to be affected. Contrary
to this, if the top and bottom back rollers 13 and 16 are modified so as to be provided
with the aprons in the prior art drafting system as shown in Fig. 7, a variation of
a surface speed of the apron looped around the back, bottom roller 16 and driven thereby
would cause the speed change to be generated in the sliver S fed between the apron
on the back, bottom roller 16 and the apron on the back, top roller 13 in a press
contacted with the apron on the bottom roller 16 and entrained thereby, so that an
amount of sliver being fed is correspondingly changed. Such a change in the sliver
fed amount causes the total drafting ratio between the back rollers (13 and 16) and
the front rollers (4 and 5) to be changed, thereby reducing the yarn quality as obtained.
The present invention, wherein the back, top roller 13 is constructed by an apron
roller, and the back, bottom roller 16 is a fluted roller as shown in Fig. 1, can
overcome these problems since the speed of the sliver is only influenced by the bottom
roller 16, as fully explained with reference to Fig. 1.
[0025] Fig. 6 shows a result of a test by the inventors in view of relationships between
a back drafting ratio and an average deviation in thickness of spun yarns Y, so called
U-%, as obtained by the device according to the present invention in Fig. 1 and the
prior art device as shown in Fig. 7, respectively. The test was done under a condition
that the sliver S being fed is a 100% combed sliver, the thickness of the sliver is
350 grain per 6 yards, the total drafting ratio is 280 and a thickness of the yarn
Y as produced is 25 grain per 120 yards, which is designated to obtain a yarn count
of 40. In Fig. 6, a solid curve is the yarn thickness variation of the yarn obtained
by the device 2 according to the present invention in Fig. 1, while a dotted curve
is a yarn thickness variation of the yarn obtained by the device 2A in the prior art
in Fig. 7. As will be easily understood from the curves in Fig. 6, according to the
present invention, for the same value of the U-%, an increased value of the drafting
ratio at the back drafting ratio at the back drafting zone is obtained over the prior
art.
[0026] In other words, the present invention makes it possible that a difference of the
value of the drafting ratio at the back drafting zone 20 from that at the main drafting
zone 10 can be reduced when compared with the prior art construction. It will be also
understood from a comparison of the curves in Fig. 6 that the present invention makes
it possible that, along a wide range of the values of the drafting ratio, a reduced
value of the U-% of the produced yarn is obtained, i.e., an increased yarn quality
is obtained when compared with the yarn as produced by the prior art device 2A in
Fig. 7. In short, due to an employment of a direct feed construction of the sliver
S by the fluted back, bottom roller 16 as well as of the nipping of the sliver S between
the back apron 14 of the back roller and the guide plate 41 according to the present
invention, an increased yarn quality is obtained.
1. A three line type drafting device comprising first and second pairs of top and bottom
rollers, between which a main drafting zone is created, the top and bottom rollers
in said second pair being constructed as apron rollers, and a third pair of top and
bottom rollers, a back drafting zone being created between said second and third pairs,
an allocation of drafting amounts being capable of being adjusted between said main
and back drafting zones, characterized in that said third, top roller is constructed
as an apron roller, that the said third, bottom roller is constructed as a fluted
roller, and that, between said third, bottom fluted roller and said second, bottom
roller, a guide plate is arranged so that the latter is under a contacted condition
with a lower surface of said apron of the third, top roller via the sliver.
2. A drafting device according to claim 1, wherein said third top roller comprises a
roller member, an apron, and a cradle for obtaining a press contact of the apron with
said guide plate, said cradle include guide members arranged on both sides of the
roller member and a tensor extending between guide members, the guide members having
portions which are in contact with the guide plate.
3. A drafting device according to claim 1, wherein each of said third top rollers comprises
a roller member, an apron, and a cradle for obtaining a press contact of the apron
with said guide plate, said cradle includes a guide member arranged between roller
members which are adjacent with each other, tensor members extend integrally from
the guide member toward respective aprons, and a spacer is arranged between the guide
member and the guide plate.
4. A drafting device according to claim 1, wherein a spacer is detachably connected to
the guide plate, thereby adjusting the force for making the apron and the guide plate
to be contacted via the sliver.