EP0708849B1

EP0708849B1 - Carding/drafting leveller system

Info

Publication number: EP0708849B1
Application number: EP94920560A
Authority: EP
Inventors: John Crosrol Limited Varga
Original assignee: Carding Specialists Canada Ltd
Current assignee: Carding Specialists Canada Ltd
Priority date: 1993-07-14
Filing date: 1994-07-13
Publication date: 1999-03-10
Anticipated expiration: 2014-07-13
Also published as: DE69417036D1; IN181817B; WO1995002720A1; EP0708849A1; JPH09502770A; GB9314538D0

Description

This invention relates to a carding / drafting leveller system for controlling the production of sliver.

It is known to provide so-called "closed loop levelling" in a card, in which a lap is fed to the card via a feed system (usually a feed roller and cooperating feed plate), and after treatment by the card and passage through a funnel or trumpet, a sliver is fed to measuring rollers, usually referred to as TG rollers (tongue and groove). On of the measuring rollers is usually mounted in such a way as to allow its axis of rotation to move radially relative to the other roller in response to variation in sliver thickness of the sliver passing between the rollers, and this movement is monitored and provides, where necessary, feedback to vary the speed of the feed roller.

In this way, long term levelling of the sliver is obtained, in that any measured reduction, or increase, in sliver thickness calls for automatic increase, or reduction respectively in feed roller speed. However, in practice the movements of the movable measuring roller are monitored on a regular basis and integrated, and the integrated signal is applied to the feed roller to provide a smooth response to monitored sliver variation.

The sliver issuing from the measuring rollers then usually passes to a coiler. Other times it passes to a drafting system, comprising drafting rollers whose relative speed of rotation is set to provide a required "drafting ratio", which might typically be of the order of 1.3:1.

It is known from EP-A-0354653 to provide an apparatus for controlling the formation of a sliver and which comprises:

a card;

a feeding device upstream of the card for feeding a lap or bat to the card;

a condenser downstream of the card to form a sliver;

a set of measuring rollers arranged to receive the sliver and to monitor the parameters of the sliver, said rollers being arranged to respond to deviations from a desired value;

drafting rollers arranged downstream of the measuring rollers;

drive means for driving the drafting rollers at a predetermined speed relative to the speed of the measuring rollers; and

a feed-forward control arranged to respond to deviation monitoring by the measuring rollers and coupled with the drive means so as to provide corresponding variation in speed of the drafting rollers.

A generally similar construction of apparatus is also disclosed in US-A-5152033.

It is an object of the invention to provide an automatic adjustment of an apparatus for controlling the formation of a sliver in improved manner, and which is substantially "driftless".

The invention seeks to achieve this object by the features of the sliver formation apparatus defined below.

Accordingly, the present invention provides apparatus for controlling the formation of a sliver and comprising:

a card;

a feeding device upstream of the card for feeding a lap or bat to the card;

a condenser downstream of the card to form a sliver;

a feedback control arranged to respond to deviation monitoring (APD) by the measuring rollers and to make compensating adjustment in the speed of operation of the feeding device;

a drafting system including drafting rollers arranged downstream of the measuring rollers;

drive means for driving the drafting rollers to provide a required drafting ratio; and

a feed-forward control also arranged to respond to deviation monitoring by the measuring rollers and coupled with said drive means so as to provide corresponding variation in speed of the drafting rollers;

characterised by:

a) a device for monitoring the ratio between the peripheral distance D1 travelled by consecutive rollers of the drafting system, said device comparing the average ratio over a period of time with a desired value and where necessary issuing a deviation signal; and
b) means for applying the deviation signal as a further control to said drive means to vary the speed of the drafting rollers.

Therefore, the invention provides sliver formation apparatus in which there is automatic control over the feeding supply to the card as a result of downstream monitoring of the sliver by the measuring rollers (so-called closed loop levelling), and in addition the transmission of drive to the drafting rollers at a predetermined drafting ratio is subject to two-part feed-forward control, one part of which is responsive to sliver deviation monitoring by the measuring rollers and the other part of which is responsive to relative peripheral distance monitoring by said monitoring device.

It is well known problem with variable open loop drafting systems that, taken over the long term, there is "drift" in roller speed for a variety of reasons, and the invention provides automatic adjustment in operation of the drafting rollers to compensate for this, bearing in mind that the long term weight of the sliver being fed to the drafting zone is correct and driftless.

The feedback control (to the feeding device) may take any suitable mechanical or electromechanical form, of a type known per se in "autolevellers".

The drive means to the drafting rollers may take any suitable mechanical, electromechanical or electronic form. In one preferred arrangement, a differential gear drive acts between the measuring rollers and the drafting rollers e.g. providing direct transmission between one roller of each set, and this provides the normal required drafting ratio.

A further differential gear may be provided, which adds to, or subtracts from the output of the first mentioned differential gear, and which receives two separate control inputs, one of which is supplied by a sliver deviation monitoring signal rom the measuring rollers, an the other of which is derived from a deviation signal from the comparator which receives from the monitoring device a signal representative of the ratio between peripheral distance travelled by one of the measuring rollers relative to the peripheral distance travelled by one of the drafting rollers.

However, while a mechanical gear train (the first and second differential gears) is one preferred form of drive means, plus two part control applied thereto, evidently other forms of mechanical and electronic drive and control means may be provided within the scope of this invention.

In one embodiment, the drafting system comprises a single pair of drafting rollers arranged downstream of the measuring rollers, in which case the monitoring device monitors the ratio between the peripheral distance travelled by the measuring rollers relative to the peripheral distance travelled by the drafting rollers.

In a further embodiment, the drafting system comprises consecutive pairs of drafting rollers.

Preferred embodiments of the invention will now be described in detail, by way of example only, with reference to the accompanying schematic drawings, in which:

Figure 1 is a schematic illustration of a first embodiment of carding / drafting leveller system according to the invention for controlling the production of sliver;

Figure 2 is a schematic illustration of a control system for controlling the operation of the drafting rollers as a consequence of variation in operating parameters of the system; and,

Figures 3 to 6 are schematic illustrations of further embodiments of the invention

Referring first to Figure 1 of the drawings, there is shown schematically a combined carding and drafting system, in which the carding zone and measuring rollers is shown by zone A, and the drafting zone is shown by reference B. A carding machine is shown schematically by reference 10, and a feeding device in the form of feed plate 11 and feeding roller 12 provide input of lap to the card in well known manner, and a funnel or trumpet 13 forms part of a condenser downstream of the card 10 to form a sliver. A set of

measuring rollers

14 and 15 is arranged to receive the sliver, and rotate at a generally pre-set speed, but are provided with monitoring devices which are able to monitor the sliver parameters, and to provide command signals in response to deviation of these parameters from a desired value. Usually, sliver thickness is monitored, and one of the measuring rollers is able to move radially relative to the other roller as a consequence of fluctuation in sliver thickness, and thereby provide an appropriate position detection signal (PDS - see Figure 2).

A feedback control (not shown in detail) is provided which responds to deviation monitoring by the

measuring rollers

14, 15, and to make compensating adjustment in the speed of operation of the feeding device, which may comprise adjustment in the speed of rotation of feeding roller 12. This type of control over the rate of input to the card 10 is well known, and may take any convenient mechanical or electromechanical form.

The component parts of the zone A which have been described comprise a standard "closed loop levelling card".

The drafting zone B comprises a set of drafting rollers 16 arranged downstream of the

measuring rollers

14, 15, and operable to rotate at a predetermined peripheral speed relative to the speed of the

measuring rollers

14, 15, to provide a required drafting ratio.

The zone B comprises an open loop draft leveller, in which sensing is carried out in the

measuring rollers

14, 15, and the drafting rollers 16 are capable of being driven at variable speed.

On average, the zone A produces a precise long term levelled sliver, namely long lengths of sliver having the same weight per yard.

The average draft carried out in zone B is shown by reference d, and therefore if the sliver weight measured at the measuring rollers (TG rollers) 14, 15 doubles, the draft immediately doubles.

Because the long term average weight of the sliver is constant, the periphery of drafting rollers 16 in the long run (long term) must travel d times the periphery travelled by the

measuring rollers

14, 15. The peripheral distances run by the

measuring rollers

14, 15, and the drafting rollers 16 are constantly measured, as will be described in more detail below with reference to Figure 2. If the ratio of the distances run differs from d, then a small increment of base speed is added to, or subtracted from the original speeds of the drafting rollers 16, as commanded by deviations from correct sliver weight as signalled by the

measuring rollers

14, 15.

Therefore, while for zone A there is provided a feedback control which responds to deviation monitoring by the measuring rollers when deviation in sliver parameter is measured, and which thereby makes compensating adjustment (after integration) in the speed of operation of the feeding device, in respect of the zone B, there is a two-part feed-forward control which is coupled with the drafting rollers 16 and which detects long term deviation or "drift" from the pre-set speed, and thereby make compensating adjustment in the speed of the drafting rollers 16.

Referring now to Figure 2, this shows schematically a mechanical coupling between the measuring rollers and the drafting rollers, and this is one preferred way of achieving the necessary control. However, other mechanical, electromechanical, or electronic control systems may be provided if desired.

As shown schematically in Figure 2, measuring roll 14 is movable up and down as shown by the arrows, in response to sliver variation, and an axial position detector APD responds to this movement, and issues a position detector signal PDS to motor M. This signal will also be utilised to control the speed of operation of the feeding device 12, after integration as shown schematically. A peripheral distance detector shown by reference D1 (e.g. a rotational speed monitor) monitors the peripheral distance travelled by measuring roller 15, and a peripheral distance detector D2 monitors the distance travelled by one of the drafting rollers 16. These provide respective electrical peripheral distance signals which are supplied to a comparator 17 which compares these values with a desired value and where appropriate, issues a deviation signal DS to an input of control motor m, which operates at a slow but variable speed, dependent on the signals from the two roller assemblies.

A differential gear I provides primary drive between the measuring rollers and the drafting rollers and is shown schematically between roller 15 of the set of measuring rollers, and to one of the drafting rollers 16. This drives the drafting rollers at a predetermined speed to provide a required drafting ratio (say 1.3:1). However, there is superimposed on this drive transmission two separate controls via a second differential gear II which is operated by motor M and control motor m. This provides input to the differential gear I, to control the output speed transmitted to the drafting rollers 16.

Sliver parameter monitoring by the measuring

rollers

14 and 15 issues position detector signal PDS to the motor M, which drives the differential gear II accordingly, and thereby provides a first part of a feed-forward control to the drive means (first differential gear I) in order to vary the speed of the drafting rollers accordingly.

Deviation signal DS to motor m applies an input to second differential gear II, which provides a further and separate control input to the differential gear I.

The carding and drafting operations which can be carried out by the apparatus described herein, and shown schematically in the drawings, provides a novel and technically advantageous way of controlling the production of sliver, and provides automatic compensation for any long term "drift" in the operation of the measuring rollers.

As an alternative embodiment of the apparatus according to the invention (improving or modifying the embodiment described with reference to Figures 1 and 2) a further set of measuring rollers (not shown) may be added downstream of the drafting system, and preferably with a trumpet or funnel upstream of the further set of rollers. These additional rollers (preferably tongue and groove rollers) may, for example, form part of existing equipment e.g. the calender rollers in a coiler, and measure instantaneous sliver thickness, and integrate the expression keds, in which k is a constant converting the roller radial displacement e to sliver weight per unit length and s is the distance travelled by the sliver through the roller. This way an average sliver weight for longer lengths of sliver is calculated. The deviation of this from the desired or set sliver weight is fed to comparator 17 (and replaces the input derived from D1 and D2 in the arrangement of Figure 2), and in a similar way as deviation of peripheral distances run differ from d (as described with reference to Figure 2), it controls motor m. Therefore, the differences of average sliver weight as measured by this additional set of measuring (T6) rollers from the set value also controls motor m, thereby restoring the sliver issuing from the drafting system to the set value.

There is now no need for upstream levelling using the feed roller and therefore according to a further aspect of the invention feedback to the feeding system may be excluded. However, for practical purposes, in order to have constant material loading onto the carding cylinder, feed roller levelling will generally still be used.

Figure 1 of the drawings shown an embodiment in which the drafting zone B is defined between a pair of measuring rollers, 14, 15 and a downstream pair of drafting rollers 16. However, other embodiments of the invention may have different types of drafting system, in which consecutive pairs of drafting rollers form the drafting system. The relative speeds of the consecutive pairs of rollers is controlled by drive means to provide the required drafting ratio. Thus, as shown in Figure 3, sliver passing through measuring

rollers

14, 15 is then received by a drafting zone comprising consecutive pairs of drafting

rollers

31 and 32, whose relative speeds can be varied to provide a required drafting ratio by suitable drive means. This provides a constant speed tension draft in the zone between upstream drafting rollers 31 and the tongue and

groove measuring rollers

14, 15.

An alternative arrangement is shown in Figure 4, in which the drafting zone comprises tongue and groove rollers 33, a trumpet 34 downstream of rollers 33, and a second set of tongue and groove rollers 35. Variable speed between pairs of

rollers

33 and 35 provides the required drafting ratio.

In the arrangement of Figure 3, feedback to the feed roller 12 is utilised, whereas in the arrangement of Figure 4 feedback to the feed roller 12 is optional.

Figure 5 shows another embodiment, in which drafting zone B is an "open loop" system. Sliver first passes between tongue and groove rollers 36, and then onwardly to further rollers 37, and a variable speed is set between

rollers

36 and 37, and downstream of rollers 37 is a further pair of tongue and groove rollers 38, from which can be derived a signal feeding to control motor m.

A still further embodiment is shown in Figure 6, in which the drafting zone B include tongue and groove rollers 36, and downstream thereof two consecutive pairs of vari-

speed rollers

39 and 40, followed by trumpet 41 and final tongue and groove rollers 42, also supplying signal to control motor m.

Claims

Apparatus for controlling the formation of a sliver and comprising:

a card (10);

a feeding device (11, 12) upstream of the card for feeding a lap or bat to the card;

a condenser (13) downstream of the card (10) to form a sliver;

a set of measuring rollers (14, 15) arranged to receive the sliver and to monitor the parameters of the sliver, said rollers being arranged to respond to deviations from a desired value;

a feedback control arranged to respond to deviation monitoring (APD) by the measuring rollers (14, 15) and to make compensating adjustment in the speed of operation of the feeding device (11, 12);

a drafting system including drafting rollers (16) arranged downstream of the measuring rollers (14, 15);

drive means for driving the drafting rollers to provide a required drafting ratio; and

a feed-forward control also arranged to respond to deviation monitoring by the measuring rollers (14, 15) and coupled with said drive means so as to provide corresponding variation in speed of the drafting rollers (16);

characterised by:

a) a device for monitoring the ratio between the peripheral distance D1 travelled by consecutive rollers (16) of the drafting system, said device comparing the average ratio over a period of time with a desired value and where necessary issuing a deviation signal; and

b) means for applying the deviation signal as a further control to said drive means to vary the speed of the drafting rollers (16).
Apparatus according to Claim 1, in which the feedback control to said feeding device (11, 12) comprises a mechanical or electro-mechanical control of a type used in auto-levellers.
Apparatus according to Claim 1 or 2, in which the drive means to the drafting rollers comprises a mechanical, electromechanical or electronic drive means.
Apparatus according to Claim 3, in which the drive means is a mechanical drive including a differential gear drive (I), acting directly between the measuring rollers (14, 15) and the drafting rollers (16).
Apparatus according to Claim 4, including a further differential gear (II) arranged to add to, or subtract from the output of the first mentioned differential gear, and arranged to receive two separate control inputs, one of which is supplied by a sliver deviation monitoring signal from the measuring rollers (14, 15) and the other of which is derived from a deviation signal from a comparator (17) which receives the deviation signal from the monitoring device.
Apparatus according to any one of Claims 1 to 5, in which the drafting system comprise a single pair of drafting rollers (16) arranged downstream of the measuring rollers, and in which the monitoring device monitors the ratio between the peripheral distance travelled by the measuring rollers relative to the peripheral distance travelled by the drafting rollers.
Apparatus according to any one of Claims 1 to 5, in which the drafting system comprises consecutive pairs of drafting rollers (31, 32; 33, 35).