Web stretching device disposed between a carding device and a cross-lapper

Abstract

Apparatus for forming a fibre mat, in particular a non-woven mat, comprising a fibre web-forming device, for example a card, a cross-tapper and a device for drafting the fibre web(s) disposed between the web forming device and the cross-lapper in order to draft the fibre web(s), in particular in a time-varying, specifically periodic manner, to thereby adjust a predetermined desired profile of the fibre mat leaving the cross-lapper, the web-forming device comprising at least one output belt (1, 2) for at least one web (5, 6), and preferably two output belts (1, 2) for two webs (5, 6), an upper and lower web respectively; wherein the cross-hipper has an input belt (7) for receiving the web(s) from the output belt(s) of the web forming device, characterised in that the arrangement is such that the path of the web, or of the at least one web, and preferably of the two, upper and lower, webs, between the output belt(s) of the web-forming device, in particular the card, and the input belt of the cross-lapper includes at least one inflection point (11, 12).

Claims

1. An apparatus for forming a fibre mat, comprising: a fibre web-forming device configured to form two fibre webs, a cross-lapper, and a drafting device disposed between the fibre web-forming device and the cross-lapper and being configured for drafting said two fibre webs to adjust a pre-determined profile of the fibre mat when leaving the cross-lapper, said drafting device comprising a drafting roller, the fibre web-forming device comprising two output belts, each of the two output belts being at a distance from said drafting roller and being configured to output a respective one of the two fibre webs at a respective output belt guide roller, the cross-lapper having one input belt configured for receiving the two fibre webs when leaving said two output belts of the fibre web-forming device, wherein each of the two fibre webs, between a respective one of the two output belts of the fibre web-forming device and the drafting roller, is configured to be convex on one side of a point where a respective one of the two fibre webs crosses an imaginary straight line extending between a centre point of the drafting roller and a centre point of the respective output belt guide roller, and is configured to be concave on another side of the point where said respective one of the two fibre webs crosses said imaginary straight line.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) As an example, preferred methods of realisation of the invention are described with reference to drawings in which:

(2) FIG. 1 is a diagram of an apparatus according to one method of realisation of the invention;

(3) FIG. 2 shows diagrammatically an apparatus according to another method of realisation of the invention;

(4) FIG. 3 shows diagrammatically the law of variation of the drafting roller speed as a function of the position of the cross-lapper carriage against the lapping width of the webs deposited;

(5) FIG. 4 shows diagrammatically an apparatus according to a third method of realisation of the invention; and

(6) FIG. 5 shows diagrammatically an apparatus according to a fourth method of realisation of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

(7) In FIG. 1, a card produces two non-woven webs 5 and 6 leaving the card on two card output belts 1 and 2, upper and lower respectively. The upper and lower card output belts 1 and 2 each comprise respective guide rollers 3 and 4 rotating at substantially identical and constant speed. The two webs 5 and 6 leaving the two card output belts 1 and 2 are directed towards the input belt 7 of a cross-tapper which itself has a guide roller 8.

(8) The web 9 formed by the meeting of the two webs 5 and 6 is then processed in the cross-lapper, and in particular unfolded in the form of sections transverse to each other to form a non-woven mat as it leaves the cross-lapper.

(9) Between the two card output belts 1 and 2 and the input belt 7 of the cross-lapper, the two webs are transported by a drafting roller 10 driven by a motor controlled by a control system to change the speed of rotation of the drafting roller 10 to stretch the card web more or less as required and, in particular, to adjust the transverse thickness profile of the mat formed at the output of the cross-lapper.

(10) The guide rollers 3 and 4 of the two card belts rotate substantially at the same, in particular constant speed, while the drafting roller 10 rotates at a time-varying peripheral speed, in particular periodic, greater than that of card leaves belts 1 and 2, thereby drafting the webs 5 and 6. The input belt 7 advances at a speed substantially equal to that of the drafting roller 10. However, slight drafting can also be applied (in particular from 1 to 10%) between the roller 10 and the input belt 7, the tension induced by this auxiliary drafting increasing the adhesion of the web to the roller 10.

(11) The path of the upper web 5 between the upper exit belt 1 and the cross-lapper input belt 7 is such that it passes over a part of the outer surface of roller 10. In addition, it is arranged so that an inflection point is formed between the output roller 3 of belt 1 and the cross-lapper input roller 8 of belt 7.

(12) In the same way, an inflection point is formed for the lower web 6 leaving the lower output belt 2, between the output roller 4 of the output belt 2 and the input roller 8 of the cross-lapper input belt. However, according to another method of realization, only a single inflection point may be provided for the upper web 5, but not for the lower web 6.

(13) According to another possible method of realisation, the system can also be improved by arranging that roller 10 employs suction to assist guidance of the two webs 5 and 6 between rollers 3 and 4 and the input belt 7.

(14) As can be seen in FIG. 1, each of the output belts 1 and 2 is inclined with respect to the cross-lapper input belt 7. The output end point of each of the belts 4 and 5 is offset in height with respect to, in particular above, the end input point of the cross-lapper input belt 8. The end, or guide, rollers 3 and 4 of each output belt, in particular their respective shafts 13 and 14, are offset in height with respect to, in particular above, the end, or guide roller 8 of the cross-lapper, in particular with respect to its shaft 15.

(15) On leaving roller 3, the upper web 5 comes into contact with the outer surface of roller 10 and is moved along this outer surface up to the cross-lapper input belt 8.

(16) On leaving roller 4, the web 6 comes into contact with the upper web 5, itself in contact with the outer surface of roller 10 and is moved with web 5 along this outer surface up to the cross-lapper input belt 8.

(17) The space between roller 10 and roller 3 is greater than the sum of the thicknesses of the belt 1 and the web 5, so that no pinching force is applied to web 5 in this space. In particular, this space may be between 5 and 20 mm, for example between 7 and 15 mm, for a web area density of between 10 and 50 g/m.sup.2, and preferably between 20 and 40 g/m.sup.2.

(18) The space between roller 10 and roller 4 is greater than the sum of the thicknesses of the belt 2, web 5 and web 6, so that no pinching force is applied to the two webs 5 and 6 in this space. In particular, this space may be between 10 and 30 mm, for example between 15 and 25 mm, to give a web area density of between 10 and 50 g/m.sup.2, and preferably between 20 and 40 g/m.sup.2.

(19) The space between roller 10 and roller 8 is greater than the sum of the thicknesses of belt 7 and the web 9, so that no pinching force is applied to the web 9 in this space.

(20) According to the method of realisation shown in FIGS. 1, 2 and 4, a drafting device in the form of a cylindrical roller has been provided. However, a component of any other shape could be provided, it being important that a driving surface in contact with the web 5 is formed to route it between roller 3 and roller 8 while drafting the web 5. For example, an endless belt could be provided as shown in FIG. 5, having a straight portion extending between the two rollers 3 and 8.

(21) The portion of belt 1 before the guide roller 3 is inclined downwards in the direction of roller 3, while the portion of belt 7 is inclined in the other direction, that is to say upwards from the guide roller 8.

(22) The portion of belt 2 before the guide roller 4 is substantially horizontal.

(23) FIG. 2 shows another method of realisation of an apparatus according to the invention. Components having the same function as in FIG. 1 are designated by the same numerical reference with the sign.

(24) A card produces a non-woven fibre web 5 leaving the card on a card output belt 1. The card output belt 1 includes a guide roller 3 rotating at a substantially constant speed. The web 5 leaving the card is routed towards a cross-lapper input belt 7 which itself has a guide roller 8.

(25) The web 5 is then processed in the cross-lapper, and in particular laid out in the form of sections transverse to each other to form a non-woven mat at the output of the cross-lapper.

(26) Between the card output belt 1 and the cross-lapper input belt 7, the web is transported by a drafting roller 10 driven by a motor controlled by a control system to change the speed of rotation of the drafting roller 10 to stretch the card web more or less as required, and in particular to adjust the transverse thickness profile of the fibre web formed at the output of the cross-lapper.

(27) The card belt guide roller 3 rotates at a substantially constant speed, while the drafting roller 10 has a peripheral speed that is time-varying, in particular periodic, and higher than that of card output belt 1, thereby drafting the web 5, the stretched web entering the cross-lapper reference 9 in FIG. 2. The input belt 7 advances at a speed substantially equal to that of the drafting roller 10. However, a slight drafting can also be applied (in particular from 1 to 10%) between roller 10 and the input belt 7, the tension induced by this auxiliary drafting improving control of the web during transfer from roller 10 to belt 7.

(28) The path of the web 5 between the upper output belt 1 and the cross-lapper input belt 7 is such that it passes over a part of the lower surface of roller 10, in particular over a sector with an angle of between 60 and 100.

(29) Roller 10 employs suction to assist guidance of the web 5 between roller 4 and the input belt 7 and hold it against the surface of roller 10 during drafting. To do this, a suction sector 17 connected to a fan (not shown) creates a negative pressure inside roller 10 to produce the negative pressure necessary to hold the web 5 against the lower surface of the roller 10. The suction sector 17 and its associated fan are arranged so that the thickness of the web 5 passing over the surface of roller 10 is not less than 50% of the thickness of web 5 directly upstream of the roller and preferably not less than 75% of its thickness directly upstream of the roller, and preferably not less than 90%, and even more preferably substantially equal to the thickness directly upstream of the roller and still more preferably, equal to its thickness directly upstream of roller 10. In particular the suction sector 17 and its associated fan are dimensioned to create, for a web area density of between 20 and 100 g/m.sup.2, in particular between 40 and 80 g/m.sup.2, a negative pressure of between 10 millibars and 100 millibars, and in particular between 40 and 70 millibars.

(30) On leaving roller 4, the web 5 comes into contact with the lower surface of roller 10 and is moved along this surface towards the cross-lapper input belt 7.

(31) The space between roller 10 and the belt 1 is greater than the thickness of the web 5, so that no pinching force is applied to the web 5 in this space. In particular, this space may be between 5 and 20 mm, for example between 7 and 15 mm giving a web area density of between 10 and 50 g/m.sup.2, and preferably between 20 and 40 g/m.sup.2.

(32) The space between roller 10 and roller 8 is greater than the thickness of the web 9, so that no pinching force is applied to the web 9 in this space.

(33) FIG. 4 shows a third method of realisation of an apparatus according to the invention. Components with the same function as in FIG. 1 are designated here by the same numerical reference with the sign.

(34) A card produces a non-woven fibre web 5 leaving the card on a card output belt 1. The card output belt 1 includes a guide roller 3 rotating at a substantially constant speed. The web 5 leaving the card is routed towards input belt 7 of a cross-lapper which itself has a guide roller 8.

(35) The web 5 is then processed in the cross-lapper, and in particular laid out in the form of sections transverse to each other to form a non-woven mat at the output of the cross-tapper.

(36) Between the card output belt 1 and the input belt 7 of the cross-lapper, the web is transported by a drafting roller 10 driven round by a motor controlled by a control system that varies the speed of rotation of the drafting roller 10 to stretch the web more or less as required, and in particular to adjust the transverse thickness profile of the mat formed at the output of the cross-lapper.

(37) The guide roller 3 of the card belt rotates at a substantially constant speed, while the drafting roller 10 rotates at a peripheral speed that is time-varying, in particular periodic, and greater than that of the card output belt 1 thereby drafting the web 5, the stretched web entering the cross-tapper reference 9 in FIG. 4. The input belt 7 advances at a speed substantially equal to that of the drafting roller 10. However, slight drafting can also be applied (in particular from 1 to 10%) between the roller 10 and the input belt 7, the tension induced by this auxiliary drafting improving control of the web during its transfer from roller 10 to the belt 7.

(38) The path of the web 5 between the upper output belt 1 and the cross-tapper input belt 7 is such that it passes over a part of the lower surface of roller 10, in particular over a sector with an angle of between 60 and 100.

(39) Roller 10 employs suction to assist in guidance of the web 5 between input belts 1 and belt 7 and hold it against the surface of roller 10 during drafting. To do this, a suction sector 18 together with a fan (not shown) produces a negative pressure inside the roller 10 to obtain the negative pressure necessary to hold the web 5 against the lower surface of roller 10. The suction sector 18 and its associated fan are dimensioned so that the thickness of the web 5 passing over the surface of roller 10 is not less than 50% of the thickness of the web 5 directly upstream of the roller, and preferably not less than 75% of its thickness directly upstream of the roller, and preferably not less than 90%, and even more preferably substantially equal to the thickness directly upstream of the roller and still more preferably equal to its thickness directly upstream of roller 10, in particular the suction sector 18 and its associated fan are dimensioned to create, for a web area density of between 20 and 100 g/m.sup.2, and in particular between 30 and 80 g/m.sup.2, a negative pressure of between 10 millibars and 100 millibars, and in particular between 40 and 70 millibars.

(40) As it leaves belt 1, the web 5 comes into contact with the lower surface of roller 10 and is moved along this surface towards the cross-lapper input belt 7.

(41) The space between roller 10 and the belt 1 is greater than the thickness of the web 5, so that no pinching force is applied to the web 5 in this space. In particular, this space may be between 5 and 20 mm, for example between 7 and 15 mm giving a web area density of between 10 and 50 g/m.sup.2, and preferably between 20 and 40 g/m.sup.2.

(42) The space between roller 10 and roller 8 is greater than the thickness of the web 9, so that no pinching force is applied to the web 9 in this space.

(43) A suction chamber 16 together with a fan (not shown) is also disposed near belt 1 to provide auxiliary holding of the web 5 by suction against a part of the upper surface of the belt 1. The suction chamber 16 is arranged so that the thickness of the web 5 downstream of the fan is not less than 50% of the thickness of the web 5 directly upstream of the chamber 16, and preferably not less than 75% of its thickness directly upstream of the chamber 16, and preferably not less than 90%, and more preferably substantially equal to the thickness directly upstream of the chamber 16 and still more preferably equal to its thickness directly upstream of the chamber 16. In particular the suction chamber 16 and its associated fan are dimensioned to create, for an area density of the web 5 of between 20 and 100 g/m.sup.2, in particular between 30 and 80 g/m.sup.2, a negative pressure of between 10 millibars and 100 millibars, and in particular between 40 and 70 millibars.

(44) FIG. 5 shows a fourth method of realisation of an apparatus according to the invention.

(45) A card produces a non-woven fibre web 50 leaving the card on a card output belt 100. The card output belt 100 comprises a guide roller 30 rotating at a substantially constant speed. The web 50 leaving the card is routed towards a cross-lapper input belt 70 which itself has a guide roller 80.

(46) The web 50 is then processed in the cross-lapper, and in particular laid out in the form of sections transverse to each other to form a non-woven mat at the output of the cross-lapper.

(47) Between the card output belt 100 and the cross-lapper input belt 70, the web is transported by an endless belt 110 driven by a motor controlled by a control system that varies the speed of the endless belt 110 to stretch the card web more or less as required, and in particular to adjust the transverse thickness profile of the mat formed at the output of the cross-lapper.

(48) The card belt guide roller 30 rotates at a substantially constant speed, while the endless belt 110 has a speed that is time-varying, in particular periodic, and higher than that of the card output belt 100, thereby drafting the web 50, the stretched web entering the cross-lapper bearing reference 90 in FIG. 5. The input belt 70 advances at a speed substantially equal to that of the endless belt 110. However, slight drafting can also be applied (in particular from 1 to 10%) between the endless belt 110 and the input belt 70, the tension induced by this auxiliary drafting improving control of the web during its transfer from the endless belt 110 to belt 70.

(49) The path of the web between the upper output belt 100 and the cross-lapper input belt 70 is such that it passes over a part of the lower surface of the endless belt 110.

(50) The endless belt 110 employs suction to assist in guidance of the web between the belt 100 and the input belt 70 and hold it against the surface of belt 110 during drafting. To do this, a suction chamber 111 together with a fan (not shown) produces a negative pressure inside the endless belt 110 to obtain the negative pressure necessary to hold the web against the lower surface of the endless belt 110. The suction chamber 111 and its associated fan are dimensioned so that the thickness of the web 50 passing over the surface of the endless belt 110 is not less than 50% of the thickness of the web 50 directly upstream of the endless belt, and preferably not less than 75% of its thickness directly upstream of endless the belt, and more preferably not less than 90%, and even more preferably substantially equal to the thickness directly upstream of the endless belt and still more preferably equal to its thickness directly upstream of the endless belt 110. In particular the suction chamber 111 is arranged to create, for a web area density of between 20 and 100 g/m.sup.2, in particular between 30 and 80 g/m.sup.2, a negative pressure of between 10 millibars and 100 millibars, and in particular between 40 and 70 millibars.

(51) On leaving belt 100, the web 50 comes into contact with the lower surface of the endless belt 110 and is moved along this surface towards the cross-lapper input belt 70.

(52) The space between the endless belt 110 and belt 100 or roller 30 is greater than the thickness of the web 50, so that no pinching force is applied to the web 50 in this space. In particular, this space may between 5 and 20 mm, for example between 7 and 15 mm for a web area density of between 10 and 50 g/m.sup.2, and preferably between 20 and 40 g/m.sup.2.

(53) The space between the endless belt 110 and belt 70 or the roller 80 is greater than the thickness of the web 90, so that no pinching force is applied to the web 90 in this space.

(54) FIG. 3 shows a curve giving the speed variation of the rollers 10, 10, 10 respectively of the endless belt 110, with respect to the speed of the output belts 1 and 2, and belts 1, 1 respectively, 100 as a percentage, the minimum speed corresponding to 100% of the speed of belts 1 and 2 respectively, belts 1, 1, 100 and the maximum speed being preferably between 140% and 160% of the speed of belts 1 and 2, belts compared with 1,1, 100 as a function of the expected transverse position in the final mat of the stretched section at time t, the speed variation thus being cyclical with a period corresponding to passage from one edge to the other (forwards and backwards) of the cross-lapper lapping carriage. This periodic speed profile (FIG. 3 shows a single cycle) produces a fibre web with a uniform, or substantially uniform transverse thickness profile, that is to say a profile whose relative thickness variation from one edge to the other is not greater than 20%, and preferably not greater than 15%, and even more preferably not greater than 10%, and highly preferably not greater than 5%, and in particular not greater than 3%, or even 1%.

(55) If on the other hand it is desired to obtain a non-uniform profile, a speed variation cycle suited to the desired profile can be produced by varying the drafting, always keeping it between the extremes of 100% and 160%, but according to a different curve than that shown in FIG. 3.

(56) According to the second aspect of the present invention, the use of suction at the drafting component avoids pinching the web to hold it during drafting and thereby eliminates the harmful effects of pinching on the final mat. However, it goes without saying that the present invention also envisages methods of realisation in which one or more pinch points are provided, combined with suction. The quality of the mat obtained in this way will obviously be diminished, but will still be higher than if no suction were provided. In particular, a method of realisation can be envisaged in which, in addition to suction, one or more pinch points could be provided, as in the prior art, but which would, because suction is provided, exert less force and thus have less marking effect on the web. One or more auxiliary suction points could also be provided in the path.

(57) In addition, it is obvious that the different methods of realisation described in the figures may be combined, and in particular one characteristic provided among others may be incorporated in each of the other methods of realisation described without having to incorporate it in this new method of realisation, consisting in the combination of one of the said other methods of realisation and the characteristic thus incorporated, would only be one out of all the other characteristics of the method of realisation from where the said characteristic was drawn.

(58) Thus, for example, the auxiliary suction described in FIG. 4 could be added to the methods of realisation in FIGS. 1, 2 and 5. According to another example, two card output belts as provided and shown in FIG. 1 could be added to the methods of realisation of FIGS. 2, 4 and 5.