This invention relates to carding apparatus, particularly but not exclusively for woollen carding.

In woollen carding one often finds variations in the weight of slubbings produced across the card. These variations which can be substantial, are in part caused by uneven splitting of the web or by other factors associated with the tapes. Variations are also present across the web before the web is split. Cross card variations can also be caused by imperfect setting of the feeding arrangement of the carder in a woollen card. In a card these variations exhibit a characteristic profile which may persist over a long period. Slubbings or ends at either or both sides of the card are also usually lighter than those from the centre of the card. Other common trends include a general increase in weight from one side of the card to the other. The presence of light ends limits the fineness of the slubbings which can be produced and may lead to slubbing breakages in carding or breakages in subsequent spinning, warping and weaving. Irregularity in cloth structure may be also observed.

In conventional woollen carding apparatus the sliver of material is laid across the feed lattice of the carder part by a mechanism such as a Scotch feed which has a carriage driven at constant speed.

According to a first aspect of the present invention the carding apparatus includes a laying device which includes a carriage adapted to traverse a feeding device, the laying device including means for laying a sliver of material across said feeding device, signal means arranged to provide a signal characteristic of variation in the weight of output web or slubbings across the card, control means responsive to said signal and adapted to control said laying device to produce slubbings having reduced weight variation across the card.

According to a second aspect of the present invention a method of laying a sliver across a feeding device of a carding apparatus comprises the steps of: providing a signal characteristic of the variation in weight of output web or slubbings across the card, modifying

said signal to provide a control signal arranged to control the laying of said sliver across the feeding device to alter the cross card density between sections across the web supplied to the feed and controlling the layering or attenuation or both layering and attenuation of said sliver using said control signal to produce slubbing having reduced weight variation across the card.

Preferred methods include the step of detecting variations in weight of the slubbings or undivided output web to provide said signal characteristic of the variation in weight.

The laying device may include elements of the sliver transport system adapted to provide the required amount of material to other elements of the laying device.

The apparatus may be adapted for the Scotch feed but can also be adapted for other types of feed, including other types of intermediate feed such as the Broad-band feed. The apparatus may be adapted for woollen carding of wool, although cotton or other fibres including blends may be employed.

In a first preferred embodiment of the invention the control means is arranged to control the traverse of the carriage. The traverse of the carriage allows the density of fibres laid across the lattice to be controlled to compensate for the variations in slubbing weight which may otherwise occur. Constant thickness or density of cross-card feed is not sought because carding with prior art feeding arrangement generally results in uneven cross-card densities at the output. The compensation may take the form of increasing or decreasing the cross-card density between sections across the web supplied to the feed to produce variations, the degree of which is determined by the control arrangement so as to provide reduced weight variation across the card at the output.

The control means may be adapted to control the rate of traverse of the carriage and, if necessary incorporating arrangements to prevent sliver breakage.

Alternatively or in addition the control means may be adapted to control the direction of traverse so that it can

make a plurality of passes over a particular region of the lattice to increase the thickness of the web.

The control means may also be adapted to control the amount of material deposited at any section of the feed lattice whilst the carriage is driven at a fixed speed.

The signal means may include a memory having a record of previously determined weights of slubbings which may be determined off line and updated periodically for increased accuracy of control. In alternative embodiments of the invention automatic compensation may be provided for thinning at the ends of cards. The control means may incorporate a switch or programmed memory to provide different degrees of compensation for different materials. In preferred embodiments of the invention the signal means includes a detector responsive to variation in weight or other parameter characteristic of the weight of the slubbings or web. An array of photocells may be arranged to measure the reflectance, and hence density of the web. The detector may be also arranged to determine the diameter or some other parameter characteristic of slubbing weight. Alternatively a weighing station may measure the weight of slubbings off line. The characteristics of all or representative specimens of the slubbings or sections of web may be determined either individually or in groups as convenient.

On line measurement of the weight or some characteristic of the weight of the slubbings or web and direct control of the traverse of the carriage or other elements of the laying device is preferred, to provide a flexible and accurate control of slubbing weight across the card.

The carriage is preferably driven independently of the carding apparatus. The position of the carriage relative to the card may be determined by a sensor which provides a signal to the control means. The latter signal in combination with the signal derived from the slubbing or web weight across the card or some characteristic of the slubbing or web weight is used to determine the speed of the elements of the laying device.

The invention is further described by means of example but not in any limitative sense, with reference to the accompanying drawings of which:

Figure 1 is a diagrammatic view across the lattice of a first embodiment of the invention;

Figure 2 is a diagrammatic view of a second embodiment of the invention;

Figure 3 is a diagrammatic view of the third embodiment of the invention;

Figure 4 is a graph of the weight of slubbings across a card; and

Figure 5 is a graph of the motor speed and corresponding feed web density across the card.

The examples show the adaptation of the apparatus for the Scotch feed but can also be adapted for other types of feed, including other types of intermediate feed such as the Broad-band feed.

The apparatus shown in Figure 1 comprises a traverse bar 1 extending across the lattice (not shown) of the carding apparatus. The carriage 3 is arranged to reciprocate along the traverse bar 1. A sliver or consolidated web of material 2 passes through a nip of two rollers 9 driven by a motor 10. The sliver 2 is then drawn between rollers 7 and is deposited on the feed lattice. The rollers 7 may be coupled to the carriage drive so that they rotate at a speed dependent of the velocity of the carriage. The thickness of the deposited sliver or web is dependent on the rate and position of traverse of the carriage 3 along the bar 1. A position sensing device 4 is arranged to provide a signal indicative of the position of the carriage, the signal being received by a control apparatus 6. The control apparatus also receives input signal 12 related to the cross card variation in slubbing or web weight or some characteristic of slubbing or web weight. The control apparatus 6 provides a signal to a regulating member 5 which may comprise a regulatable direct control motor arranged to drive the carriage 3 by means of a screw drive or other coupling. The rollers 9 and the motor 10 are mounted on the

carriage. The speed of the rollers 9 is fixed and is determine by the tension in the sliver 2. A third pair of rollers (no shown) below the rollers 9 and adjacent the feed lattice may b employed to assist in laying the material on to the fee lattice of the carder.

Figure 2 illustrates an alternative embodiment of th invention. The arrangement is generally similar to that show in Figure 1 and like components are given the same referenc numbers as in Figure 1. A single pair of rollers 7' is drive at a fixed speed determined by the tension in the sliver 2. second pair of rollers (not shown) may be located within the carriage or other laying device close to the surface of the lattice or apron to facilitate accurate laying of the web ont the feed lattice or apron.

The regulating member 5 may be arranged to reduce th variation across the web or slubbings by controlling the effective thickness of the web deposited at any point by regulating the speed of traverse of the carriage or other laying device.

In both embodiments of the invention control can also be exercised by controlling the direction and speed of traverse, so that a plurality of passes of the carriage or other laying device over particular regions can control the thickness of the deposited sliver or web.

Figure 3 illustrated a further embodiment of the invention. The arrangement is again generally similar to that shown in Figure 1 and like components are given the same reference numbers as Figure 1. The control apparatus provides a signal to the regulating member 5, which may comprise a regulatable direct current motor to regulate the speed of the roller 7". The carriage is driven to reciprocate at a constant speed. The control apparatus provides a second signal to a second regulating member 13. This can regulate the position of roller 15 by regulating the movement of member 14, thereby controlling the store of sliver and providing the amount of sliver which is required dependent on the speed of the rollers 7".

-6-

Apparatus in accordance with this invention may be fitted to existing carding equipment.

Figure 4 is a graph illustrating the weight of slubbings of a 48 end card. Without control the slubbings at each side of the web are generally lighter and there is a general trend for the slubbings to become lighter from ends 13 to 48. With control in accordance with the apparatus described with reference to Figure 1 irregularities across the card are significantly reduced.

Figure 5 is a graph illustrating feed web density and corresponding motor speed variations. The feed web density and motor speed values for the prior art arrangement, with no control of the laying of the sliver, are shown by the dotted line. When the motor speed and consequently the rate of traverse of the carriage increases or decreases there is a corresponding decrease or increase respectively in the feed web density. The profile of densities across the card compensates for variations in density produced during carding so that a constant cross-card density carded product is obtained.