EP1432854B1 - Device for detecting and eliminating foreign bodies on a nonwoven fabric, produced by means of a card - Google Patents

Abstract

The invention relates to an elimination device (6), which is controlled by a detecting device (5) and arranged in the area of the doffer roller (3) or doffer device (4) of a card. Said elimination device comprises at least one guide wall (19) for the nonwoven fabric (2), in which at least a series of suction orifices (20) is arranged over the total width of said wall. Each suction orifice adjoins to a flow channel, provided with a Venturi nozzle for producing a suction effect.

Description

The invention relates to a device for detecting and eliminating foreign substances on a nonwoven fabric formed by a carding according to the preamble of claim 1. With the excretion of foreign substances from the nonwoven fabric on the card should be prevented that they remain in the card sliver, where they later only are difficult to remove and lead to loss of quality and production interruptions in the spinning mill. At the non-woven fabric of the carding machine, the foreign substances are easily controllable from the motion guide and embedded in a relatively thin fiber layer.

By EP-B 606 626 a generic comparable device has become known, in which disturbing particles such. Nissen, shell parts, etc. are torn at the pickup device by a directed transversely to the fiber web airflow. For this purpose, a series of air nozzles is distributed over the entire width, which can be acted upon by individual valves with compressed air.

A similar device is also described in CH-A 689 600. As an alternative, it is also proposed to suck the foreign substances already on the surface of the doffer roll via a series of nozzles. The detection of foreign substances is also carried out already at the doffer roller.

A disadvantage of the known devices is that the tearing of the foreign matter from the nonwoven fabric is associated with a considerable design effort and that while the nonwoven fabric with respect to uniformity, flatness, etc. is adversely affected. Also the anisotropic behavior of the fiber fleece because of the partial rectification of the fibers in the transport direction causes problems by the web on a line parallel to the transport direction breaks faster than transverse to the transport direction. It is therefore an object of the invention to provide a device of the type mentioned, in which an efficient control of the air flow can be achieved with simpler means, in particular, the tight spatial conditions on the card should be considered.

According to the invention, the object can be achieved with a device which contains the features in claim 1. An essential element here is the baffle in which over the entire width of at least one row of several Ausscheidequerschnitte defining suction openings is arranged. Each suction opening is adjacent to a flow channel with a Venturi nozzle for generating a suction effect. In this way, the suction effect can be generated with a blast of compressed air, this compressed air blast also serves the further transport of foreign substances. The Ausscheidequerschnitte could be defined using the flow restrictors described below. In certain cases, it would also be conceivable to completely omit the flow restrictors so that the openings on the guide wall are permanently exposed.

In order to prevent the foreign substances from being returned, at least one chicane may be arranged in the flow channel downstream of the Venturi nozzle and downstream of the suction opening. The baffle may define the fibrous web at a suitable location on the doffer roll or on the doffer device. Particularly advantageously, the baffle is formed by a non-woven bridge on the pickup device. However, the baffle can also be formed by a curved concentric to the doffer roll portion above the doffer roll.

For reasons of space and to provide a locally finely graded as possible Ausscheidemöglichkeit multiple rows of suction ports can be arranged one behind the other, wherein the suction openings of the individual rows are offset relative to each other based on the width of the baffle. In the feed direction, the suction openings of the individual rows can easily overlap laterally.

Further advantages can be achieved with a device having the features in claim 6. The at least two relative to each other movable flow apertures, each with an opening make it possible to expose a Auslegeideguerschnitt directly on the nonwoven fabric. Depending on the number and arrangement of the openings and depending on the motion guide, it is possible to rapidly disperse separation areas across the entire width of the nonwoven fabric. For this purpose, the two openings in at least one first relative position form a first Ausscheidequerschnitt, wherein in at least a second relative position, a second Ausscheidequerschnitt is exposed, which is arranged transversely to the feed direction offset from the first Ausscheidequerschnitt. The baffle, which contains one of the two flow restrictors, causes a support and guidance of the fiber fleece, whereby the targeted tearing of the foreign matter is greatly facilitated.

The openings may be intersecting slots, the relative displacement of which leads to a displacement of the Ausscheidequerschnitts transverse to the feed direction. The Ausscheidequerschnitt is formed by the crossing area. Alternatively, it can also be individual openings, which are covered or exposed depending on the relative position.

The flow diaphragms can be arranged above the doffer roll and optionally be adapted to the roll curvature. However, it is also conceivable to arrange the flow diaphragms on the doffer device, in particular on a nonwoven bridge. At least one of the flow panels is displaceable in the feed direction and / or transversely to the feed direction. But it is also conceivable to store both flow screens movable and if necessary to move simultaneously.

It is conceivable to combine several Ausscheidequernitte to a group, each group is connected to a common flow channel. Although several flow channels must be performed, but they serve several Ausscheidequerschnitte within a group.

The sensor device can act on the surface of the fiber web directly. These can be sensors that react to different physical parameters. Preferably, however, these will be photosensitive sensors which react to certain wavelengths of light. In order to develop hard-to-access locations for detection, it is particularly advantageous if the signal transmission from a detection field extending across the width of the fiber fleece to the actual sensor takes place via a plurality of optical waveguides. This allows the use of a non-imaging sensor system, which manages without complex lens systems. The ends of the optical fibers can be made very close to the nonwoven fabric and are relatively impervious to contamination.

The lighting of the fleece can be done in incident or transmitted light. It is conceivable that the nonwoven or the detection field is also illuminated via optical fibers.

The detection field could easily be arranged in the region of the pickup roller.

Figur 1:

eine schematische Seitenansicht einer Karde,

Figur 2:

die Abnehmerwalze einer Karde mit Sensoreinrichtung und Ausscheidevorrichtung mit Strömungsblenden,

Figur 3:

eine Draufsicht auf ein Ausführungsbeispiel von Strömungsblenden,

Figur 4:

eine schematische Seitendarstellung einer Abnehmervorrichtung mit Vliesbrücke,

Figur 5:

eine Draufsicht auf die Vliesbrücke gemäss Figur 4,

Figur 6 :

eine perspektivische Darstellung einer Sensoreinrichtung mit Lichtwellenleitern an einem frei gespannten Faservlies,

Figur 7 :

eine perspektivische Darstellung einer Sensoreinrichtung mit Lichtwellenleitern auf einer Abnehmerwalze,

Figur 8 :

die Abnehmerwalze einer Karde mit Sensoreinrichtung und Ausscheidevorrichtung mit Venturi-Düsen, und

Figur 9:

eine Draufsicht auf eine Leitwand mit versetzt angeordneten Saugöffnungen.

Further individual features and advantages of the invention will become apparent from the following description of exemplary embodiments and from the drawings. Show it:

FIG. 1:

a schematic side view of a card,

FIG. 2:

the doffer roller of a card with sensor device and separation device with flow diaphragms,

FIG. 3:

a top view of an embodiment of flow panels,

FIG. 4:

a schematic side view of a pickup device with fleece bridge,

FIG. 5:

a top view of the nonwoven bridge according to Figure 4,

FIG. 6:

a perspective view of a sensor device with optical waveguides on a freely tensioned fiber fleece,

FIG. 7:

a perspective view of a sensor device with optical waveguides on a doffer roll,

FIG. 8:

the doffer roller of a card with sensor device and separation device with Venturi nozzles, and

FIG. 9:

a plan view of a baffle with staggered suction openings.

FIG. 1 shows a part of a carding machine 1, in which cotton fibers of a feed device 12 are fed in a manner known per se in the feed direction a). The fibers pass from there to the spool 13, where they are rectified to fixed Kardierelementen, as well as to the revolving lids 14. At the opposite of the spool slower moving doffer roller 3, the nonwoven fabric 2 is removed and released at the pickup device 4 of the doffer roller. For this purpose, a skimming roller 15 is provided in the exemplary embodiment, which guides the nonwoven fabric onto a nonwoven bridge 17. For removal a pull roller pair 16 is provided.

The sensor device 5 and the separating device 6 can optionally be arranged in the peripheral region of the doffer roller 3 or in the region of the doffer device 4. A multiple arrangement of sensor device and separation device at different sections of the feed path would be conceivable.

According to FIG. 2, the separating device 6 consists of two flow diaphragms 8 and 9 which can be displaced relative to one another. The diaphragms are curved concentrically with the doffer roll 3 and they each have an opening which exposes a separating cross section 7 in a relative position. The first panel 8 is fixed, while the lying on her second aperture 9 in the circumferential direction b) is displaceable. The first panel 8 also forms a guide wall for the nonwoven fabric, or is part of such.

As will be explained in more detail below, different Ausscheidquerschnitte can be exposed by relative displacement of the two panels to each other over the width of the nonwoven fabric distributed, of which at least individual groups open into a common flow channel 18. About this flow channel, the foreign substances are torn out of the fiber fleece and transported away.

According to FIG. 3, two rows of three first openings 10a, 10b, 10c and 10d, 10e, 10f are arranged offset to one another in the first flow aperture 8 at an angle of approximately 45 ° to the feed direction. In the second flow aperture 9, two parallel rows of second openings 11a, 11b, 11c and 11d, 11e, 11f are also arranged at an angle of about 90 ° to the feed direction. In the illustrated relative position to each other, all openings 10a to 10f are hidden, so that no cutting cross-section is exposed.

If the second flow restrictor 9 is displaced in the direction of the arrow c by the distance e, the opening 11a corresponds to the underlying opening 10a, the corresponding Ausscheidequerschnitt is exposed. All other openings in the first flow aperture 8 remain hidden. At a Movement in the direction of the arrow c about the distance f corresponds to the opening 11b with the underlying opening 10b, while also all other openings remain hidden. In a shift in the opposite direction d to the corresponding distances can be exposed in the same way, the openings 10d, 10e or 10f.

The displacement of the flow orifices to each other for selectively exposing the desired Ausscheidequerschnitts via a drive device not shown here, e.g. via an electric motor. The control of this drive device via a control device in dependence on the position and the feed rate of the detected by the sensor device foreign matter.

The shift does not necessarily have to be in the feed direction. Also movements transverse to the feed direction are conceivable.

In the embodiment according to FIG. 4, the nonwoven fabric 2 is removed from the stripping roller 3 by a stripping roller 15 and transferred to a nonwoven bridge, which is formed by a guide wall 19. As can be seen from FIG. 5, a plurality of suction openings 20 are arranged in the guide wall, each opening into an underlying flow channel 18. Through this flow channel can be passed in the direction of flow h a compressed air shock. Based on the flow direction immediately before each opening 20, a Venturi tube or a Venturi nozzle 21 is arranged. This, apparently, causes an increase in the flow velocity and a pressure drop at the narrowest cross-section, which can be determined by means of the Bernoulli equation. By this suction, the detected point of the carded web is sucked into the flow channel 18 and fed to a collecting container 27. Baffles 22 prevent recirculation of the foreign matter. The compressed air surges are controlled by a sensor device, not shown here, which can be arranged in the region of the doffer roll or in the region of the nonwoven bridge.

FIGS. 6 and 7 show possibilities of optical detection on the fiber fleece 2 in the stretched state or else on the take-off roller 3 with the aid of optical waveguides 25. The individual conductors are brought very close to the surface of the nonwoven to be detected. This makes it possible for the sensor 23 or the individual sensors to be relatively far away from the detection field 24 to arrange. As illustrated in FIG. 7, the illumination can also be effected via the individual optical fibers or via optical fibers routed in parallel. An illumination of the detection field is also possible in transmitted light, as shown in Figure 6. The use of optical waveguides in devices comparable in terms of genre has already become known through Uhlmann Jürg, "Foreign Substance Identification in Raw Rockwool", Diss. ETH Zurich, 1996.

Figure 8 shows an embodiment of an invention with a similar function as that according to Figure 4. The baffle 19 is formed here as a concentric to the center of the doffer roller 3 curved portion. Of course, the baffle could also extend over a larger sector of the doffer roll and the suction openings 20 could also be located elsewhere, e.g. Again, the venturi nozzles 21 are arranged in the flow channel 18 immediately in front of the suction openings 20, wherein the baffles 22 prevent a return of the foreign substances.

As shown in FIG. 9, a plurality of rows of suction openings 20a, 20b and 20c could be arranged one after the other, wherein the suction openings of the individual rows are each offset relative to one another based on the width of the guide wall 19. Depending on the given pressure conditions, it would certainly be possible for a group of suction openings to be arranged in the area of influence of a common Venturi nozzle, that is to say that a single flow channel 18 serves a group of suction openings.

Claims (13)

1. Apparatus for detecting and separating foreign materials in and from a fibre nonwoven (2) formed by a carding machine (1), having a doffing roll (3) and having a doffing apparatus (4), a sensor device (5) for detecting the foreign materials and a separating apparatus (6) which is arranged after the sensor device in the direction of forward movement of the fibre nonwoven and which has means for selectively pulling the foreign materials out of the fibre nonwoven by means of an air stream limited to a separation cross section (7), characterized in that the separating apparatus has at least one guide wall (19) for the fibre nonwoven (2), in which at least one row of suction openings (20) defining a plurality of separation cross sections is arranged over the entire width, and in that each suction opening adjoins a flow duct having a Venturi nozzle (21) for producing a suction effect.
2. Apparatus according to Claim 1, characterized in that at least one chicane (22) is arranged in the flow duct, after the Venturi nozzle and after the suction opening, in order to prevent the foreign materials from being fed back.
3. Apparatus according to Claim 1 or 2, characterized in that the guide wall is formed by a nonwoven bridge on the doffing apparatus.
4. Apparatus according to Claim 1 or 2, characterized in that the guide wall is formed by a curved section over the doffing roll which is concentric with the doffing roll.
5. Apparatus according to one of Claims 1 to 4, characterized in that a plurality of rows of suction openings is arranged one after another, and in that the suction openings of the individual rows are arranged offset from one another in relation to the width of the guide wall.
6. Apparatus according to one of Claims 1 to 5, characterized in that the separation cross sections are defined by at least two flow shutters (8, 9) which can be displaced relative to one another, each of which contains at least one opening (10, 11) in each case, the two openings forming a separation cross section (7) in at least one relative position, and in that one flow shutter is arranged in the guide wall for the fibre nonwoven.
7. Apparatus according to Claim 6, characterized in that the two openings (10, 11) form a first separation cross section in at least a first relative position, and in that, in at least a second relative position, a second separation cross section can be opened which is arranged offset in relation to the first separation cross section in the direction transverse to the direction of forward movement.
8. Apparatus according to Claim 6 or 7, characterized in that the flow shutters (8, 9) are arranged above the doffing roll (3).
9. Apparatus according to one of Claims 6 to 8, characterized in that at least one of the flow shutters can be displaced in the direction of forward movement and/or transversely with respect to the direction of forward movement.
10. Apparatus according to one of Claims 6 to 9, characterized in that a plurality of separation cross sections over the entire width of the fibre nonwoven are combined into groups, and in that each group is connected to a common flow duct.
11. Apparatus according to one of Claims 1 to 10, characterized in that the sensor device contains at least one light-sensitive sensor for detecting the foreign materials in the fibre nonwoven, and in that the signal transmission from a detection area (24) extending over the width of the fibre nonwoven to the sensor (23) is carried out via a plurality of optical fibres (25).
12. Apparatus according to Claim 11, characterized in that the detection area (24) is illuminated via optical fibres.
13. Apparatus according to either of Claims 11 and 12, characterized in that the detection area (24) is arranged on the doffing roll (3).

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