Textiles: fiber preparation – Working – Drafting
Reexamination Certificate
1999-10-15
2001-03-27
Gravini, Stephen (Department: 3749)
Textiles: fiber preparation
Working
Drafting
Reexamination Certificate
active
06205621
ABSTRACT:
The present invention relates to machines for carding of textile fibers, in which the flock fibers are worked in order to produce a web of fibers. In this operation, the short fibers and tangles are removed from the fibers, which are stretched and placed in parallel in a web of fibers, which is disposed on the covering of the drum of the carder, from which the web of fibers is collected by a rotary detachment cylinder with a suitable covering, which is commonly known as a doffer, and is then transferred by another doffer to a compactor unit and to a drawing unit, in order to produce a strip of fibers.
More particularly, the present invention relates to the method and the device in which the web which is detached from the carder is transformed into a strip, and is subjected to controlled drawing, in order to obtain a constant, pre-determined yarn count.
In order to make more apparent the technical aspects involved in the carding, reference is made to a diagram of a collection and drawing unit according to the known art, which is described in European patent application no. 775,768 in the name of the same applicant, illustrated in
FIGS. 1 and 2
, which show respectively a schematic lateral view and a plan view of the collection and drawing unit.
The detachment cylinder, or doffer, of the carder, is indicated as
1
, and on the latter the web
2
of fibers is carried to the unloading cylinder
3
, and is conveyed to the compactor unit
4
, which consists of a pair of smooth rotary cylinders
5
,
6
, with a substantially horizontal axis, which compact the web
2
, which still has a transverse dimension which corresponds to that of the carder, and transfer the web to the subsequent belt conveyor. The compactor unit
4
works at a speed which is compatible with that of the web
2
which is obtained from the unloader
3
.
The belt conveyor
10
is in a position which is integral with the collection unit of the web
2
, and consists of a pair of belts
11
in a loop, which are opposite, and are guided by means of rollers
12
which have a substantially vertical axis, rotate on pins
13
, and are provided with rotary drive
14
, by means of their own motor, or by motion derived from other units, in a known manner. The said belts
11
extend along the entire front of the collection unit, as far as lateral return rollers which are not shown in the figure for the sake of simplicity, and leave a central gap
15
. The belts are actuated such as to be moved, in the area which is provided for the web of fibers obtained from the compactor unit
4
, from the sides towards the center, in order to concentrate and convey the web
2
of fibers into a strip
16
, which has a width which corresponds to the gap
15
between the two belts
11
. The stretched web
2
, which has been condensed into the form of a strip
16
, is then yielded to the drawing unit
20
, and the linear speed of transfer of the fibrous body is substantially maintained from the compactor unit
4
to the drawing unit
20
.
The equipment of the drawing unit
20
is mounted on a mobile carriage, which can move longitudinally, towards and away from the preceding collection unit. This movement is obtained, for example, by placing the equipment of the drawing unit on a transverse frame
21
, which slides forwards and rearwards according to the arrow
22
on guides, and is piloted by a double-effect hydraulic cylinder, which is not shown in the figure for the sake of simplicity.
The drawing unit comprises a body in the shape of a funnel
30
, which receives the fibers conveyed by the belts
11
in order to form the strip
16
, and admits and guides them to the two pairs of cylinders downstream, which carry out the drawing of the strip
16
. Of these pairs of cylinders, a first pair of cylinders or rollers
31
and
32
with a horizontal axis comprises the upper roller
31
, which is smooth and idle, and is pressed against the roller
32
beneath by means of an adjustable thruster
33
on its shaft
34
. The roller
32
is embossed in a transverse direction, and is rotated with a specific drive ratio in a known manner, for example with a pulley and belt drive system, by means of the motor
35
. According to the known art, and in general, the first pair of rollers
31
,
32
works at a linear speed which is slightly greater than that of the strip which is released by the belt conveyor
10
, via the funnel
30
.
The second pair of cylinders or drawing rollers comprises the roller
38
, which is also smooth and idle, and is pressed against the roller
39
beneath, similarly to the first pair of cylinders. The roller
39
is also worked on its surface, and is actuated such that it is driven at a linear speed which is substantially greater than that of the roller
32
, according to a ratio which is adjustable, and greater than
1
, which gives rise to the drawing, i.e. to the elongation of the strip, which is conveyed between the two pairs of rollers. In other words, the second pair of cylinders
38
,
39
is actuated such as to be driven at a specific linear speed, which is greater than that of the first pair of cylinders
31
,
32
. Owing to the effect of the linear speed difference between the rollers upstream which release the body of fibers, and the rollers downstream which draw this body towards them, the fibers which are drawn downstream slide relative to the fibers which are retained upstream, and give rise to elongation and drafting of the said body of fibers. The drawing values express ratios between the linear speeds of the fibrous body input, and the fibrous body output.
For this purpose, the two pairs of drawing rollers
31
,
32
and
38
,
39
are actuated in a known manner, for example by means of the same motor
35
, which is provided with a drive with belts and pulleys of a different diameter, and maintain a pre-determined, constant ratio between the linear speeds at which the strip which is gripped between the two pairs of rollers is yielded by the first pair
31
,
32
, and drawn by the second pair
38
,
39
. In general, the drawing values which are established between the two pairs of rollers are between 1.0 and 2.0, whereas the values which are currently used are within the narrower interval between 1.1 and 1.5.
The strip which is thus produced and drawn is then sent to be collected in a container, for further processing. The distance between the drawing unit and the collection unit is regulated in accordance with the speed at which the carder is actuated, and with the linear speed of collection of the web, as well as in accordance with the characteristics of the fibers worked.
The structural system described hitherto is complex, and requires careful co-ordination of the various members of the collection and drawing units. During the step of collection of the web and drawing of the strip of fibers according to the known art, some problems also arise as a result of the ever-increasing trend towards increasing the speeds, in order to obtain high production volumes. The web must be collected and drawn at a rate of 250-400 m of strip per minute, and this value is destined to increase further, according to the expectations of the textile industry. High speeds of work create problems, in particular in the steps of re-starting, or in general in a transitional stage, in which the sections of web and strip between one point of collection and control and the other can be loose or slack, and can also be disposed in a highly accentuated catenary position. This occurrence is problematic because the consistency of the web and the strip is substantially reduced, since they consist of fibers in parallel. In these loose sections the web and the strip can lose continuity, owing to their own weight, and because of lack of continuity of the drawing to which they are subjected, and this can cause stoppage of production. The technical problem which is derived from these requirements of high carding productivity consists of control and recovery in good time of the loose sections of the web and strip, such that the latter are kept satisfactorily t
Pasini Giovanni Battista
Patelli Silvano
Gravini Stephen
Marzoli S.p.A.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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