Title of Invention

DRAFTING ASSEMBLY FOR DRAFTING A FIBRE WEB

Abstract A drafting assembly for drafting a fibre web, the drafting assembly comprising: upper and lower rear apron loops having first and second support surfaces respectively being ananged to grip the card web fibres between them and transport the card web fibres from a rear entrance to a rear nip point on displacement of the rear aprons; upper and lower front apron loops having third and fourth support surfaces respectively being arranged to grip the card web fibres between them and transport the card web fibres from a front nip point to an Exit on displacement of the front aprons; the front and rear mp points being adjacent and arranged such that the front mp point receives card web fibres which exit the rear nip point; characterised in that proximate to the nip point each loop is wedge shaped with the arms of the loop on each side of the nip point converging towards flip point and having an acute angle therebetween.
Full Text -2-
The present invention relates to a drafting assembly and method of drafting. More
particularly, but not exclusively, the present invention relates to a drafting apparatus
comprising two pairs of drafting aprons separated by a gap and arranged to generate a
drafting force on fibres in a web which span the gap; the drafting aprons each being
substantially wedge shaped proximate to the nip points.
It is known to draft slivers, rovings or strands by roller drafting. The drafting apparatus
comprises front and rear roller pairs. The front roller pair rotate more quickly than the rear
pair so creating a drafting force on the fibres in the sliver or strand.
Such an apparatus is suitable for drafting slivers, rovings or strands since the sliver, roving
or strand is thick enough or is immediately twisted so there is little problem of the fibres
lapping around the front rollers. It is also known to draft card webs. Fibres in a card web
are less consolidated and require larger rollers to prevent lapping. Fibres in a card web are
also not aligned. It has been found that drafting the fibres in the card web, by a relatively
small draft whilst in the web state or at least in an open state in comparison to the sliver,
followed by the normal process of producing the sliver package for the combing machine
has a beneficial effect of better preparing the sliver package as it results in a reduction in
the noil extracted by the combing machine. Furthermore, there is evidence that such
drafting of the card web results in overall higher quality of yarn. It appears that such a
process of web drafting partially or in some cases completely removes hooks but also re-
arranges the fibres so that the subsequent drafting is more efficient in removing hooks that
remaining the material.
In order for this drafting to be beneficial, it is essential that drafting occurs whilst the fibres .
including short fibres, remain under positive control as far as possible. For the avoidance
of doubt it should be stated that reference here to long and short fibres does not refer to the
intrinsic length of the fibres but the extension of the fibres along the length of the web. For
example an intrinsically long fibre may be looped or twisted upon itself or may be inclined

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to the length of the web. In such cases an intrinsically long fibre may be classed as a short
fibre.
Apparatus for the drafting of card webs are restricted to drafting of worsted type long
fibres, since it permits the use of relatively large rollers which prevent fibre lapping of
rollers whilst having sufficient control of the fibres in drafting. One cannot simply reduce
the diameter of the rollers to provide sufficient control in card web drafting of shorter
cotton type fibres because of this problem of fibre lapping.
Existing drafting assemblies are therefore unsuitable for drafting cotton type card webs.
The present invention seeks to alleviate this problem.
Accordingly, in the first aspect, the present invention provides;
a drafting assembly for drafting a fibre web, the drafting assembly comprising:
upper and lower rear apron loops having first and second support surfaces
respectively being arranged to grip card web fibres between them and transport the card
web fibres from a rear entrance to a rear nip point on displacement of the rear aprons;
upper and lower front apron loops having third and fourth support surfaces
respectively being arranged to grip the card web fibres between them and transport the card
web fibres from a front nip point to an exit on displacement of the front aprons;
the front and rear nip points being adjacent and arranged such that the front nip
point receives card web fibres which exit the rear nip point;
characterised in that
proximate to the nip point each loop is wedge shaped with the arms of the loop on.
each side of the nip point converging towards nip point and having an acute angle there
between.
The wedge shaped nature of the apron loops proximate to the nip point enables cotton type
card web to be drafted, so significantly improving the properties of the drafted web.

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Preferably the aims of at least one of the loops on each side of the nip point are
substantially planar.
Preferably, the drafting assembly further comprises a drive assembly for displacing the
aprons, the drive assembly being adapted to displace the front aprons more rapidly than the
rear aprons so generating a drafting force on the fibres in the web gripped by the front and
rear nip points.
At least one of the aprons can comprise a planar portion defining a support surface. The
loop can be nylon, PVC or rubber, preferably reinforced rubber. The loop can be a
composite material. The loop can be polyurethane.
Preferably, the drafting assembly comprises upper and lower rear nip rollers arranged to nip
the upper and lower rear aprons between them to create the rear nip point. Alternatively
the drafting assembly could comprise upper and lower rear nip bars arranged to nip the
upper and lower rear aprons between them to create the rear nip point. The drafting
assembly could also comprise upper and lower front nip rollers arranged to nip the upper
and lower front aprons between them to create the front nip point. Alternatively, the
drafting assembly could comprise upper and lower front nip bars arranged to nip the upper
or lower front spans between them to create the front nip point.
The drive assembly can comprise at least one drive roller which abuts an apron and is
adapted to displace the apron on rotation of the drive roller. The drive roller can be
positioned within the loop.
In a further aspect of the invention there is provided a carding assembly comprising
at least one carding roller for creating a fibre web; and
a drafting assembly for drafting the fibre web
the drafting assembly comprising
upper and lower rear apron loops having first and second support surfaces
respectively being arranged to grip the fibre web between them and transport the web from
a rear entrance to a rear nip point on displacement of the rear aprons;

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upper and lower front apron loops having third and fourth support surfaces
respectively being arranged to grip the fibre web between them and transport the web from
a front nip point to an exit on displacement of the front aprons;
the front and rear nip points being adjacent and arranged such that the front nip
point receives fibre web which exits the rear nip point;
characterised in that
proximate to the nip point each loop is wedge shaped with the arms of the loop on
each side of the nip point converging towards nip point and having an acute angle
therebetween.
The carding assembly can lurther comprise consolidating means for partially reducing the
width of the web before it is received by the drafting assembly. The carding assembly
could also comprise a further consolidating means for receiving the drafted web from the
drafting assembly and iurther reducing its width to a sliver.
In a further aspect of the invention there is provided a method of drafting a fibre web
comprising the steps of
(a) providing a drafting apparatus, the drafting apparatus comprising
upper and lower rear apron loops having first and second support surfaces
respectively being arranged to grip the fibre web between them and transport the web from
a rear entrance to a rear nip point on displacement of the rear aprons;
upper and lower front apron loops having third and fourth support surfaces
respectively being arranged to grip the fibre web between them and transport the web from
a front nip point to an exit on displacement of the front aprons;
the front and rear nip points being adjacent and arranged such that the front nip
point receives fibre web which exits the rear nip point;
characterised in that
proximate to the nip point each loop is wedge shaped with the arms of the loop on
each side of the nip point converging towards nip point and having an acute angle
therebetween.
(b) providing a fibre web to the drafting apparatus for drafting.

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The present invention will now be described by way of example only, and not in any
limitative sense with reference to the accompanying drawings in which
figures 1 and 2 show, in schematic form, drafting assemblies for drafting slivers, rovings
or strands;
figure 3 and 4 show further known drafting assemblies in cross section;
figure 5 shows a further known drafting assembly in cross section;
figure 6 shows a drafting assembly according the invention in cross section; and
figure 7 shows a carding assembly according to the invention.
A number of different types of machine are known for processing cotton type and worsted
type fibres into yarn. In general these machines provide the steps of: .
(1) The opening, cleaning and reducing fibres to small tufts;
(2) "carding" the fibres to open or individualise fibres. This process forms a web of
fibres which is consolidated at the output end into a rope like form called a sliver; and,
(3) aligning the disordered carded fibres and progressively reducing the sliver
thickness or linear density by a series of machines until in the final "spinning" machine a
strand of fibres is formed which is consolidated by twisting to form a yarn.
Short fibres are not conducive to the production of high quality yarns. The yarns are
therefore combed to remove these. Combing takes place after carding but before spinning.
The fibres need to be aligned before they can be subjected to the combing process. This is
done by drafting.

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Shown in figures 1 and 2 in schematic form are known as roller drafting assemblies (1).
The drafting assembly (1) of figure 1 comprises a pair of front rollers (2) and a pair of rear
rollers (3). The front rollers (2) are arranged to rotate more rapidly than the rear rollers (3]
so producing a drafting force on the fibres (4) as they move between the two sets of rollers
(2, 3). The assembly (1) shown in figure 2 includes a pair of rear aprons (5, 6) for better
control of fibres.
Roller drafting is typically performed on slivers and rovings or occasionally on card webs.
It is known that a large proportion of the fibres in the card sliver or web are hooked as a
result of the carding process. Hook free material can lead to better quality of yarn and/or
lower the amount of comber waste. The assemblies of figures 1 and 2 are however only
suitable for drafting of slivers and rovings. The consolidated nature of slivers and rovings
reduces the tendency of the fibres to lap around the rollers. The apparatus of figures 1 and
2 are not suitable for drafting card web fibres. This is because fibres in the web are less
consolidated and can lap more easily. If the apparatus of figure 2 were to be used to draft
card webs the diameter of the rollers would have to be large to reduce fibre lapping. This
would however increase the distance between the nip points to an unacceptable degree.
Shown in figures 3 and 4 are further known drafting assemblies. These assemblies are
attempts to overcome this problem. Each of the assemblies comprises upper and lower rear
aprons (7, 8). The upper and lower rear aprons (7, 8) each comprise a flexible loop of
material (9,10), typically pvc, nylon, rubber, polyurethane or a composite material.
Positioned within each loop (9,10) is a drive assembly (11, 12) comprising a drive roller
(13,14) which abuts the loop (9,10). Turning the drive roller (13, 14) turns the loop (9,
10), Each of the aprons (7, 8) includes a planar support portion (15, 16). Thetwoplanar .
support portions (15,16) are arranged to grip the fibres of a sliver received at an entrance
(17) between them. As the drive rollers (13, 14) turn the fibres of the input fibre sliver are
drawn from the entrance (17) to a rear nip point (18). The rear nip point (18) is created by
upper and lower rear nip rollers (19, 20) which nip the upper and lower aprons (7, 8)
between them.

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The embodiment of figure 3 does not include a front apron and is generally used for
drafting worsted card slivers. The drafting assembly of figure 4 further comprises a front
apron (21) in the form of a loop (22) having a shape defined by tensioning means (23). In
the drafting assembly of figure 4 a lower front nip roller (24) is positioned within and abuts
against the front apron loop (22). An upper nip roller (25) nips the apron (21) between it
and the lower nip roller (24) creating a front nip point (26). The front and rear nip points
(26, 18) are arranged such that the fibres which exit the rear nip point (18) are received by
the front nip point (26).
Such drafting assemblies can be used for sliver drafting or worsted type web drafting.
However, again they are not suitable for drafting cotton type card webs as the distance
between the nip point is unacceptably large.
The reduction in size of one of the front nip point rollers partially reduces the distance
between front and rear nip points and is suitable for worsted type card web drafting. The
relatively large upper nip rollers (25) in figures 3 and 4, necessary to avoid fibre lapping,
places a limit on how close together the front and rear nip point (26, 18) can be. This in
turn places a relatively large lower limit on the length of fibre which can be controlled in
the drafting process. Fibres below this limit either because of their length or because of
their relative orientation or configuration will tend to be uncontrolled. However, reducing
of the size of the upper front drafting roller would result in the fibres from the web lapping
around the roller. Because of this such apparatus is not suitable for drafting cotton type
card web.
Shown in figure 5 is an assembly similar to that of figure 2. Like reference numerals are
used for like parts. Further aprons are arranged around the front rollers. Such a system is
disclosed in DE 4141237. The use of further aprons in such systems is to carry the fibres
forward to further rollers in some arrangement that improves yarn quality. Such assemblies
are also not suitable for drafting cotton type card webs. One cannot simply reduce the front
rollers to reduce the distance between the nip points. As the roller diameters are reduced to
the levels required for effective drafting of cotton type cad webs the rollers become
difficult to drive.

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Shown in figure 6 is a drafting assembly according to the invention. The drafting assembly
comprises upper and lower rear aprons (27,28). The drafting assembly further comprises
upper and lower front aprons (29, 30) in the form of loops. Associated with each apron
(27-30) is a drive assembly (31) within the loop. Each drive assembly (31) comprises a
drive roller (32) which abuts against the inside of each respective loop and which drives
rotation of the loop. The upper and lower front aprons (29,30) have third and fourth
support surfaces (33, 34) respectively. These are arranged to grip the fibre web received at
a front nip point (35) and transport it to an exit point (36).
The front nip point (35) is created by upper and lower front nip rollers (37,38). These nip
the upper and lower front aprons (29,30) between them. The rear nip point is created by
upper and lower rear nip rollers.
In use the above drive assembly (31) rotates the upper and lower rear aprons (27, 28)
transporting the web from the entrance (39) to the rear nip point (40). The web exits the
rear nip point (40) and is received by the front nip point (35). From here it is transported to
the exit point (36). The drive rollers (32) rotate the front aprons (29, 30) more rapidly than
the rear (27,28) so producing a drafting action on fibres as they span the gap between the
front and rear nip points (35, 40). The aprons close to the nip points are arranged to be
wedge shaped with the arms of the apron on each side of a nip roller converging toward the
nip roller and having an acute angle between them. The wedge shaped aprons on opposite
sides of the nip points face each other. In this embodiment the arms are planar. This
wedge shaped arrangement allows the front and rear nip points to be positioned close
together. The apparatus according to the invention can use small front rollers. The aprons
avoid the problem of fibre lapping. The arrangement of the aprons results in a short
distance between the nip points and rollers which are relatively easy to drive. The
apparatus can therefore be used to draft shorter fibres under control in webs than known
drafting apparatus. This results in a commercially significant improvement in the web with
a significant reduction in noil in the subsequent combing process.

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Shown in figure 7 is a carding assembly (41) according to the invention. The carding
assembly (41) comprises a carding roller (42) for producing a web which is received by the
drafting assembly of figure 6. Arranged between the carding roller (42) and drafting
assembly is a consolidating means (not shown). The consolidating means reduces the
width of the web. The web is however still maintained wider and more open than a sliver.
In a further embodiment of the invention (not shown) the carding assembly comprises a
further consolidating means which further consolidates the drafted web as it leaves the
drafting assembly.
In a further embodiment of the invention (not shown) the carding assembly does not
include a consolidating means for reducing the width of the web.
In a further embodiment of the invention (not shown), the nose rollers are replaced by nose
bars. This however reduces the drafting speed.

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We Claim :
1. A drafting assembly for drafting a fibre web, the drafting assembly comprising:
upper and lower rear apron loops having first and second support surfaces
respectively being arranged to grip the card web fibres between them and transport the card
web fibres from a rear entrance to a rear nip point on displacement of the rear aprons;
upper arid lower front apron loops having third and fourth support surfaces
respectively being arranged to grip the card web fibres between them and transport the card
web fibres from a front nip point to an exit on displacement of the front aprons;
the front and rear nip points being adjacent and arranged such that the front nip
point receives card web fibres which exit the rear nip point;
characterised in that
proximate to the nip point each loop is wedge shaped with the arms of the loop on
each side of the nip point converging towards nip point and having an acute angle
therebetween.
2. A drafting assembly as claimed in claim 1, when the arms of at least one of the
ioops on each side of the nip point is substantially planar,
3. A drafting assembly as claimed in either of claims 1 or 2 further comprising a
drive assembly for displacing the aprons, the drive assembly being adapted to displace the
front aprons more rapidly than the rear aprons so generating a drafting force in fibres in the
web gripped between the front and rear nip points.
4. A drafting assembly as claimed in any one of claims 1 to 3, at least one of the
aprons comprising a planar portion defining the support surface.
5. A drafting assembly as claimed in claim 4 wherein the loop is nylon, PVC,
polyurethane or rubber, preferably reinforced rubber.

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6. A drafting assembly as claimed in any one of claims 1 to 5 further comprising
upper and lower rear nip rollers arranged to nip the upper and lower rear aprons between
them to create the rear nip point.
7. A drafting assembly as claimed in any one of claims 1 to 5, further comprising
upper and lower rear nip bars arranged to nip the upper and lower rear aprons between
them to create the rear nip point.
8. A drafting assembly as claimed in any one of claims 1 to 7 further comprising
upper and lower front nip rollers arranged to nip the upper and lower front aprons between
them to create the front nip point.
9. A drafting assembly as claimed in any one of claims 1 to 7 further comprising
upper and lower front nip bars arranged to nip the upper and lower front aprons between
them to create the front nip point.
10. A drafting assembly as claimed in claim 2 wherein the drive assembly comprises ,
at least one drive roller which abuts the apron and is adapted to displace the apron on
rotation of the drive roller.
11. A drafting assembly as claimed in claim 10 wherein the drive roller is positioned
within the loop.
12. A carding assembly comprising
at least one carding roller for creating a fibre web; and
a drafting assembly for drafting the fibre web
the drafting assembly comprising
upper and lower rear apron loops having first and second support surfaces
respectively being arranged to grip the fibre web between them and transport the web from
a rear entrance to a rear nip point on displacement of the rear aprons;

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upper and lower front apron loops having third and fourth support surfaces
respectively being arranged to grip the fibre web between them and transport the web from
a front nip point to an exit on displacement of the front aprons;
the front and rear nip points being adjacent and arranged such that the front nip
point receives fibre web which exits the rear nip point;
characterised in that
proximate to the nip point each loop is wedge shaped with the arms of the loop on
each side of the nip point converging towards nip point and having an acute angle
therebetween.
13. A carding assembly as claimed in claim 12 comprising consolidating means for;
partially reducing the width of the web before it is received by the drafting assembly.
14. A carding assembly as claimed in claim 13 comprising a further consolidating
means for receiving the drafted web from the drafting assembly and further reducing its
width to a sliver.
15. A method ofdrafting a fibre web comprising, the steps of
providing a drafting apparatus, the drafting apparatus comprising
upper and lower rear apron loops having first and second support surfaces
respectively being arranged to grip the fibre web between them and transport the web from
a rear entrance to a rear nip point on displacement of the rear aprons;
upper and lower front apron loops having third and fourth support surfaces .
respectively being arranged to grip the fibre web between them and transport the web from
a front nip point to an exit on displacement of the front aprons;
the front and rear nip points being adjacent and arranged such that the front nip
point receives fibre web which exits the rear nip point;
characterised in that
proximate to the nip point each loop is wedge shaped with the arms of the loop on
each side of the nip point converging towards nip point and having a acute angle
therebetween; and
(b) providing a fibre web to the drafting apparatus for drafting.

A drafting assembly for drafting a fibre web, the drafting assembly comprising:
upper and lower rear apron loops having first and second support surfaces
respectively being ananged to grip the card web fibres between them and transport the card
web fibres from a rear entrance to a rear nip point on displacement of the rear aprons;
upper and lower front apron loops having third and fourth support surfaces
respectively being arranged to grip the card web fibres between them and transport the card
web fibres from a front nip point to an Exit on displacement of the front aprons;
the front and rear mp points being adjacent and arranged such that the front mp
point receives card web fibres which exit the rear nip point;
characterised in that
proximate to the nip point each loop is wedge shaped with the arms of the loop on
each side of the nip point converging towards flip point and having an acute angle
therebetween.

Documents:


Patent Number 247728
Indian Patent Application Number 1029/KOL/2005
PG Journal Number 19/2011
Publication Date 13-May-2011
Grant Date 09-May-2011
Date of Filing 11-Nov-2005
Name of Patentee SUPER SPINNING MILLS LIMITED,
Applicant Address SUPER SPINNING MILLS LIMITED, of Eigi Towers, 7370 Puliakulam Road, Green Fields, Coimbatore 6410045, India An Indian Company
Inventors:
# Inventor's Name Inventor's Address
1 IYPE CHERIAN 11 SUNNINGDALE GREEN, ALWOODLEY LEEDS LS17 7SQ
PCT International Classification Number D01H 5/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 0424896.9 2004-11-11 U.K.