US3892376A

US3892376A - Metal wire felt

Info

Publication number: US3892376A
Application number: US480388A
Authority: US
Inventors: Glyn Beresford Redmond; Ernest John Harold Hill; Maurice James Evans
Original assignee: Dunlop Ltd
Current assignee: Dunlop Ltd
Priority date: 1973-06-26
Filing date: 1974-06-18
Publication date: 1975-07-01
Anticipated expiration: 1992-07-01
Also published as: DE2430764A1; GB1472065A; FR2234938B1; CA1004113A; BR7405221D0; JPS5068952A; FR2234938A1; AU7028374A

Abstract

A method of making a felt from continous metal wires or bunches of wires which each have a torsional rigidity of greater than 2 X 10 7 Nm2. The method comprises crimping the wires by passing each wire or bunch of wires under tension over a curved surface, at least some of the wires or bunches of wires passed over the surface in a manner such that the predominating resultant helix is in the opposite direction to that of the remaining wires or bunches of wires, continuously assembling the wires in aligned relationship under tension and allowing the assembly to relax to interpenetrate to form a mat, of which the following is a Specification.

Description

United States Patent Redmond et al. July 1, 1975 [54] METAL WIRE FELT 1,976,491 10 1934 Gottschalk 140 71 2J2], 27 6 l938 M 4 71 [751 Inventors: 39mm"! 2 I65 i711 71939 i48i71 Birmingham; Ernest John Harold Hill, Wolverhampton; Maurice James Evans, Sutton Coldfield, all Pnmary Exammer lfoweu Larson Attorney, Agent, or firm-Stevens, Davis, Miller & of England Mosher [73] Assignee: Dunlop Limited, England [22] Filed: June 18, i974 [57] ABSTRACT [21] Appl. No.: 480,388 A method of making a felt from continous metal wires or bunches of wires which each have a torsional rigid- -7 2 [30] Foreign Application Priority Data of f f than 2 10 Nm T method. Com- I pnses crimping the wires by passing each wire or June U'med Kmgdom 30254/73 bunch of wires under tension over a curved surface, at least some of the wires or bunches of wires passed [52} U.S. Cl. 245/6; 140/7l C Over the Surface in a manner Such that the pred0mi III". nating resultant helix i in the pp direcion to [58] Fleld of Search 140/31 that of the remaining wires or bunches of wires, conl40/92.6; 245/1. 2. 6; 28/723; 161/169 tinuously assembling the wires in aligned relationship under tension and allowing the assembly to relax to [56] References cued inter-penetrate to form a mat, of which the following is UNITED STATES PATENTS a Specification, 149,823 4/l874 Baker et all 245/6 1,959,104 5 1934 Mahan 140/71 33 Clfllms, 6 Drflwmg Figures SHEET 2 FIGS FIG.4

METAL WIRE FELT This invention relates to metal wire felts.

It has previously been proposed in, for example, British Pat. No. 1,016,551 to make a felt of continuous manmade fibres such as textile fibres or metal wires. The Patent No. 1,016,551 disclosed a felt comprising a needled mat of interpenetrated substantially aligned crimped continuous man-made fibres and a method of making the felt by assembling extended fibres in aligned relationship, relaxing the fibres into a crimped condition and needling the resultant mat of fibres with a barbed needle.

The crimp in the man-made fibres in both textile fibres and metal wires can be achieved in a number of ways. For example, by false twisting, i.e. twist the fibres or bunch of fibres, stabilize the twist by, e.g. passing through a series of rollers and remove the twist; by stuffer box treatment, i.e. feeding the fibre(s) into a chamber having a smaller exit than inlet thereby crushing the fibre (s); by gear crimping in which the fibre(s) is passed between fluted rollers, and by edge crimping in which the fibre(s) is drawn over an edge.

In making a metal wire felt in accordance with the previous proposals, for example, as taught by British Pat. No. 1,016,551 it has been found that it is preferable to crimp the wires by the edge crimping process. This process can produce a preferred helical crimp, the amplitude of which can be varied considerably accord ing to the applied crimping conditions e.g. the radius of the crimping edge, line tension. Due to the form of, and the large amplitudes possible with, helical coils produced by edge crimping, the tendency for an array of relaxed edge-crimped wires to interpenetrate is high. Additionally, the ease with which the edge-crimped structure can be varied allows a wide range of felt textures to be obtainable.

However, the applicants have found that when the size of the metal wires used is of a magnitude sufficient for the wires to be approximately one hundred or more times stiffer than polymeric fibres, e.g. nylon or polyester filaments, problems arise in making felts from edgecrimped wires or bunches of wires. The applicants found that the edge-crimped structure was not torsion free.

This was considered to be surprising since it was well known in the art that edge-crimping processes produce a torque-free yarn of filament comprising continuous helices of randomly alternating S or 2 direction of twist; reference, for example, "Modern Yarn Production from Man-Made Fibres, edited by G. R. Wray, published by Columbine Press, Manchester 1960.

The problems arising with the edge-crimped stiff wires are that the wires tend to reinforce each other and form a rope-like structure instead of an interpenetrated fibre mat; or if a mat can be formed, the felt tends to curl in one direction of twist or the other.

It is an object of the present invention to provide a method of making a felt and a felt of such previously mentioned stiff wires.

According to the present invention, a method of making a felt comprises crimping continuous metal wires or bunches of wires, each individual wire having a torsional rigidity greater than 2 X l Nm, by passing each wire or bunch of wires under tension over a curved surface, at least some of the wires or bunches of wires being passed over the surface in a manner such that the predominating resultant helix is in the opposite direction to that of the remaining wires or bunches of wires, continuously assembling the crimped wires or bunches of wires in substantially aligned relationship under tension, continuously relaxing the assembly of wires so formed to allow interpenetration thereof to form a mat.

According to a further aspect of the invention, a felt comprises a mat of interpenetrated substantially aligned edge-crimped continuous metal wires or bunches of wires, each individual wire having a torsional rigidity of greater than 2 X 10 Nm", the interpenetration of the wires being in the nature of an intermingling in three dimensions produced by laying crimped wires or bunches of wires of mixed residual torsional direction under tension and releasing the tension.

The interpenetrated mat of wires may be needled using a barbed needle.

According to a further aspect of the method, the wires or bunches of wires are each batched-up after crimping, a plurality of the wires or bunches of wires, some of which have the opposite residual torsional direction to the remainder, then being assembled together to form the mat.

The curved surface referred to preferably has a radius equal to or less than 13 mm.

The metal wires preferably comprise steel wires having individual diameters greater than 0.08 (substantially equivalent to a torsional rigidity of 2 X 10" Nm but no greater than 0.56 mm. The upper limit of 0.56 mm diameter has been found to be the highest diameter wire in which crimp can be induced at the present time, due to practical difficulties in handling the wire during the crimping process, but the invention will not necessarily always to limited to this diameter of wire.

The torsional rigidity of the wire may be calculated as described below.

Consider a wire of any cross-section twisted by couples M applied at the ends thereof. At a distance Z from the origin the cross-section rotates through an angle OZ, where 0 is the angle of twist per unit length. The factor by which the torque M must be divided to obtain the twist per unit length, 6, is called the torsional rigidity C. Therefore:

C MM (1) It is well known that for a wire of circular crosssection having a diameter d, C may be calculated from:

C dn/32 (2) where n is the shear modulus of the material of the wire. Also for a wire of elliptical crosssection having semi-major axes a and b.-

C (rm b la b) n (3) or alternatively:

C= (n/41r2) (Allp) (4) where A is the cross-sectional area, and

[p is the polar moment of inertia of the cross-section.

For a wire having a uniform cross-section of general shape, the torsional rigidity thereof may be approximately calculated from equation 4 by substituting for the wire, a wire with an elliptical cross-section having the same cross-sectional area and the same polar moment of inertia as said wire.

The bunch of wires may be twisted into a strand or, alternatively, into several strands which, in turn, may also be twisted into a cord.

In one form of the method each wire or bunch of wires may he passed round a guide member prior to passing over a curved surface, the distance between the member and the surface being adjustable whereby the angle at which each wire is fed to a surface is easily adjusted to vary the degree oferimp obtained. Preferably each wire is passed round a second guide member after passing over a curved surface, the surface being offset from a straight line connecting the guide members. The surface may be situated either on one side of such lines or on the opposite side of the lines such that some of the wires can pass over a surface curved in a direction opposite to the direction of curvature of the surface over which the remainder of the wires pass. The distance between a second guide member and a surface may also be adjustable to vary the angle at which each wire is taken off the surface. It has also been found that the use of a second guide member produces a more open helix structure on relaxation of a crimped wire.

The passing of wires over surfaces curved in opposite directions has been found to give control of the type, i.e. S or Z configuration, of helix configuration obtained thereby allowing cancellation of the torsional forces in felts by using both configurations therein. The use of guide members enables this control to be increased. In one form of the invention the guide members. and the curved surfaces, may comprise cylindrical rods. In a preferred form of the invention, however, the guide members may be freely rotatable, e.g. of pulley wheel construction, and the rotatable members are preferably displaced one from another in a direction substantially perpendicular to both the line drawn therebetween and the direction in which a curved surface is offset therefrom whereby each wire is passed over a surface at an angle. The displacement of the rotatable members one from the other is preferably at least mm.

In this preferred form of the invention it is thought that passing a wire over a surface at an angle creates roll in the direction in which the crimp and therefore the helix configuration is required thus the rotatable guide members create higher control the helix configuration obtained by the method. Some reversal of helix direction is found to occur in a crimped length of wire, but the reversal occurs only over a short length of the wire before reversing again (i.e. S reversing to Z reversing to S configuration) to the primary configuration of the wire.

In an alternative form of the invention, the curved surface and/or the guide means may each comprise at least one bore, formed with flared ends, in a plate, any of which plates are capable of oscillating and/or reciprocating.

It is preferred that the felts are balanced by inducing one of the helix configurations in 50% of the wires, but there may be as little as 30% of one of the helix configurations present in a felt.

In addition, it has been found that the balancing of the torsional forces may be assisted by differential crimping of each wire, i.e. varying the amplitude and/or frequency ofthe helix induced in the wires by crimping.

The wires are formed into an array by passing the wires through an adjustable width comb whereby varying widths of felt can be obtained. The assembled array of crimped wires is tensioned by passing it through an undriven three roll nip and then through a driven three roll nip, the assembly so formed relaxing immediately on leaving the driven nip and passing into a needle punch machine.

Preferably the metal wire felt is incorporated into an article ofeg. rubber or plastics material. The incorporation of the felt into the article in the manufacture of the article may be carried out by either hot or cold calendering of the material on to the felt or by injection moulding of the material on to the felt.

Such processes as calendering further consolidate the felt to provide the felt in the form of a substantially fiat sheet.

The felt may be consolidated by stitching in a needle punch either in a single mat of wires or in two or more mats of wires superimposed on each other. Additionally or alternatively, the mat or mats may be assembled with and needled on to a base sheet of knitted or woven fabric.

The degree of hardness of the felts produced may be increased by increasing the number of needled punches stitching the mat of wires. Soft felts may be produced by limiting the depth of penetration of the needles into the mat of wires during at least part of the needling operation.

The invention will now be described, by way of example only, with reference to the accompanying formal drawings, of which:

FIGS. IA and [8 show arrangements of guide members crimping wire in accordance with the invention and in which Z and S configurations are formed respectively;

FIGS. 2A and 2B show modified arrangements of guide members similar to FIGS. IA and H3, in which 2 and S configurations are formed respectively;

FIG. 3 shows a schematic diagram of an apparatus on which a part ofthe method of the invention may be carried out; and

FIG. 4 shows an alternative curved surface and/or guide member.

Referring to FIGS. 1A and [B a method of crimping using guide members. The wires 1 and 2 are passed over curved surfaces of cylindrical rods 3 and 4 respectively. Two guide members in the form of

cylindrical rods

5, 6 and 7, 8 for each of wires 1 and 2 respectively are provided.

The

rods

5, 6 and 7, 8 are preferably located in the line of travel of the wires 1 and 2 respectively, as the lines A-A and 8-H joining their bases indicate, these lines being substantially parallel to the line of travel of wires 1 and 2 as indicated by the arrows C and D respectively.

The rods 3 and 4 are offset perpendicularly in opposite directions, to the lines AA and 8-8 respectively; the resultant arrangement shown in FIG. IA inducing Z configuration helixes in the relaxed wire, and the resultant arrangement shown in FIG. 1B inducing S configuration helixes in the relaxed wire.

In FIGS. 2A and 2B arrangements similar to those shown in FIGS. 1A and 1B are shown.

However, the

rods

5, 6, 7 and 8 each act as axles for freely rotatably pulley wheels 9, 10, I1 and I2 respcctively. The wheels 9 and I0 and 11 and 12 are preferably displaced one from another in a direction substantially perpendicular to the lines AA and B-B respectively, and to the direction of offset of rods 3 and 4, respectively. This may be achieved by the use of spacers 13 and [4 located on the rods 5 and 7 respectively. This arrangement causes the wires 1 and 2 to pass over the rods 3 and 4, respectively, at an angle thus enabling high control of the Z and 8 configuration helixes formed by the wires 1 and 2 in the relaxed state thereof.

Wires so crimped under tension can either be stored in a creel to accumulate the number of wires available, or fed straight into the apparatus for forming the felt.

Referring to FIG. 3, bunches of wires l5, 16 are fed from a creel, under tension, through an adjustable width comb I7 and through undriven three roll nip [8 and driven three roll nip [9. The rollers of the nips are preferably rubber covered to prevent slippage of the wires. On leaving the nip 19 the assembly of wires relaxes and intermingles to form the relaxed felt 20 which is passed through a needle punch 21 to consolidate the felt 20.

FIG. 4 shows diagrammatically a cross-section plate 33 having a bore 34, provided with flared ends 35, which may act as the curved surface and/or the guide members. Obviously, a plurality of such bores may be provided in the or each plate. Additionally, means can be provided for oscillating and/or reciprocating the or each plate.

The invention is further described with reference to the following examples.

EXAMPLE I A metal wire felt was made by passing steel wires over a crimping peg 3, 4 of 3.85 mm diameter and wheels 9, ll, 12 as described in connection with FIGS. 2A and 2B. The displacement of the wheel 9, 11 from the wheel l0, I2 is 10 mm and the wires each have an individual diameter of 0.08 mm.

The wires so crimped were then formed, under tension, into balanced bunches i.e. the wires were present in the bunches in equal amounts of S and Z configuration helices. The bunches were then laid down on a rotating frame whilst being traversed across the frame thereby producing a sheetlike structure of parallel laid wires. The tension in the wires was then released and the wires intermingled to form the felt.

The felt so formed was then rubberised by being pressed between a layer of 100% crepe rubber and a layer of another rubber compound (both layers having a thickness of 0.7 mm) for 1 minute at 80-90C. under a pressure of 11.5 lbs/in. Crepe rubber was used for one layer to enable the configuration of the wires to be seen in the rubberised felt.

For comparison purposes a second rubberised felt was made in a similar manner except that the wires all were in Z configuration helices.

The balanced felt was substantially flat whilst the unbalanced felt curled.

EXAMPLE II Two felts, one balanced and substantially flat, one unbalanced which curled were made as described in Example I using steel wires having an individual diameter of 0.10 mm.

EXAMPLES IIl Two felts. one balanced and substantially flat, one unbalanced which curled were made as described in Example l using steel wires having an individual diameter of 0.15 mm.

EXAMPLE IV Two felts, one balanced and substantially flat, one

unbalanced forming a rope-like structure were made as described in Example I using steel wires having an individual diameter of0.30 mm. with the exception that the felts were not rubberised.

EXAMPLE V Two felts, one balanced and substantially flat, one unbalanced forming a rope-like structure were made as described in Example I using steel wires having an individual diameter of 0.56 mm. with the exception that the felts were not rubberised.

The felts made in accordance with the invention are balanced and flat whereas the unbalanced felts were twisted and at the higher diameters, i.e. high torsional rigidities, the wires tend to reinforce each other and form rope-like structures.

EXAMPLE VI Two felts, one balanced, one unbalanced, were made as described in Example I with the exception that the felts were not rubberised. The felts were made from strands of four wires each of 0.25 mm. diameter twisted together with a lay of 8.5s. The balanced felt was a satisfactory, substantially torsion free felt whereas the unbalanced felt formed a rope-like structure.

EXAMPLE VII Two felts, one balanced, one unbalanced, were made as described in Example I with the exception that the felts were not rubberised. The felts were made from cords of seven strands twisted together with a lay of 14.7s, each strand comprising four wires each of 0.2 mm. diameter twisted together with a lay of 9.5s. The balanced felt was a satisfactory, substantially torsion free felt whereas the unbalanced felt formed a rope-like structure.

Some problems arise in forming cords into felts e.g. the strand or cord twists direction influences the helical configuration induced into the strand or cord by crimping i.e. the influence can be such as to tend to cause the resultant helical configuration to be the same as the twists direction even though the induction was for the opposite helical direction. This can be overcome by using larger diameter crimping pegs and varying the guide member offset and spacing. However, this solution is not very satisfactory and therefore it is preferred to overcome this problem by inducing the helical configuration to be the same as the twist direction of the strand or cord. Therefore, using the latter solution, to make a balanced felt it is necessary to use strands or cords of opposite twist direction.

In one form of the invention, the formation of the predominating resultant helical configuration in the wire or bunches of wires may be assisted by preforming by, for example, false twisting prior to the step of crimping.

Having now described our invention, what we claim I. A method of making a felt comprises crimping continuous metal wires or bunches of wires, each individual wire having a torsional rigidity greater than 2 X l0 Nm. by passing each wire or bunch of wires under tension over a curved surface, at least some of the wires or bunches of wires being passed over the surface in a manner such that the predominating resultant helix is in the opposite direction to that of the remaining wires or bunches of wires, continuously assembling the crimped wires or bunches of wires in substantially aligned relationship under tension, continuously relax ing the assembly of wires so formed to allow interpene tration thereof to form a mat.

2. A method according to claim 1 including the step of batching-up each of the wires or bunches of wires after crimping, a plurality of the wires or bunches of wires. some of which have the opposite residual torsional direction to the remainder. then being assembled together to form the mat.

3. A method according to claim 2 wherein the wires or bunches of wires are assembled by passing through an adjustable width comb followed by tensioning between an undriven three-roll nip and a driven three-roll nip. the assembly so formed relaxing on leaving the driven nip to interpenetrate and form the mat.

4. A method according to claim 1 comprising using a curved surface having a radius not greater than 13 5. A method according to claim 1 comprising form ing the felt from metal wires which are steel wires.

6. A method according to claim 5 comprising forming the felt from metal wires which are steel wires each having an individual diameter of more than 0.08 mm.

7. A method according to claim 5 comprising forming the felt from metal wires which are steel wires each having an individual diameter not greater than 0.56

8. A method according to claim 1 wherein the interpenetrated mat is needled in a needle punch.

9. A method according to claim 8 wherein at least two mats are superimposed prior to needling.

10. A method according to claim 8 wherein at least one mat is assembled with and needled onto a base sheet of knitted or woven fabric.

H. A method according to claim 1 wherein the felt is calendered.

12. A method according to claim 1 which includes the step of incorporating the felt into an article.

13. A method according to claim I wherein each wire or bunch of wires is passed around a first guide member prior to passing over a curved surface, the distance between the curved surface and the guide member being variable.

14. A method according to claim 13 wherein each wire or bunch of wires is passed around a second guide member after having passed over a curved surface, the curved surface being offset from a straight line connecting the two guide members, the distance between the curved surface and the second guide member being variable.

15. A method according to claim 14 wherein one surface is situated on one side of the line connecting a first set of two guide members and a second surface is situated on the side of the line connecting a second set of two guide members opposite to the side the first surface is situated such that some of the wires can pass over a surface curved in a direction opposiste to the direction of curvature of the surface over which the remainder of the wires pass.

16. A method according to claim 14 comprising using first and second guide members in the form of cylindrical rods.

17. A method according to claim l4 comprising using first and second guide members which are each freely rotatable pulleys mounted on an axis.

18. A method according to claim 17 comprising displacing the pulleys one from the other along their axes in a direction substantially perpendicular to both the straight line connecting the axes of the members and the direction in which a curved surface is offset therefrom.

19. A method according to claim 1 comprising passing the wires or bunches of wires over a curved surface in the form of a substantially cylindrical rod.

20. A method according to claim 14 comprising passing the wires or bunches ofwires over a curved surface and/or guide member each of which comprises at least one bore, formed with flared ends, in a plate.

21. A method according to claim 20 wherein the plate can be oscillated and/or reciprocated.

22. A method according to claim 1 wherein the bunches of wires are each twisted to form at least one strand prior to crimping.

23. A method according to claim 22 wherein the bunches of wires are each twisted to form at least two strands prior to crimping, the strands being twisted to form a cord.

24. A method according to claim 22 wherein the predominating resultant helix is induced in the same direction as the direction of twist in the strand.

25. A method according to claim 23 wherein the predominating resultant helix is induced in the same direction as the direction of twist in the cord.

26. A method according to claim 1 comprising mixing the wires such that between 30 and 50% of the wires have one predominating resultant helix and the remainder of the wires have the other predominating resultant helix.

27. A felt comprising a mat of interpenetrated substantially aligned edge-crimped continuous metal wires or bunches of wires, each individual wire having a torsional rigidity of greater than 2 X 10 Nm*, the interpenetration of the wires being in the nature of an intermingling in three dimensions produced by laying crimped wires or bunches of wires of mixed residual torsional direction under tension and releasing the tension.

28. A felt according to claim 27 wherein the felt is a needled felt.

29. A felt according to claim 28 wherein at least two mats have been needled together.

30. A felt according to claim 28 wherein at least one mat has been needled to a base sheet of knitted or woven fabric.

31. A felt according to claim 27 wherein the metal wires comprise steel wires.

32. A felt according to claim 31 wherein the steel wires have individual diameters of greater than 0.08

33. A felt according to claim 31 wherein the steel wires have individual diameters of not greater than 0.56 mm.

34. A felt according to claim 27 by having been calendered.

35. A felt according to claim 27 wherein the felt is incorporated into an articlev 36. A felt according to claim 27 wherein the bunches of wires are in the form of at least one twisted strand.

37. A felt according to claim 36 wherein the bunches of wires are in the form of at least two twisted strands which have been twisted to form a cord.

38. A felt according to claim 27 wherein between 30 to 50% of the wires or bunches of wires have one residual torsional direction and the remainder of the wires have the other residual torsional direction.

t i l

Claims

1. A method of making a felt comprises crimping continuous metal wires or bunches of wires, each individual wire having a torsional rigidity greater than 2 X 10 7 Nm2, by passing each wire or bunch of wires under tension over a curved surface, at least some of the wires or bunches of wires being passed over the surface in a manner such that the predominating resultant helix is in the opposite direction to that of the remaining wires or bunches of wires, continuously assembling the crimped wires or bunches of wires in substantially aligned relationship under tension, continuously relaxing the assembly of wires so formed to allow interpenetration thereof to form a mat.

2. A method according to claim 1 including the step of batching-up each of the wires or bunches of wires after crimping, a plurality of the wires or bunches of wires, some of which have the opposite residual torsional direction to the remainder, then being assembled together to form the mat.

3. A method according to claim 2 wherein the wires or bunches of wires are assembled by passing through an adjustable width comb followed by tensioning between an undriven three-roll nip and a driven three-roll nip, the assembly so formed relaxing on leaving the driven nip to interpenetrate and form the mat.

4. A method according to claim 1 comprising using a curved surface having a radius not greater than 13 mm.

5. A method according to claim 1 comprising forming the felt from metal wires which are steel wires.

7. A method according to claim 5 comprising forming the felt from metal wires which are steel wires each having an individual diameter not greater than 0.56 mm.

11. A method according to claim 1 wherein the felt is calendered.

13. A method according to claim 1 wherein each wire or bunch of wires is passed around a first guide member prior to passing over a curved surface, the distance between the curved surface and the guide member being variable.

17. A method according to claim 14 comprising using first and second guide members which are each freely rotatable pulleys mounted on an axis.

20. A method according to claim 14 comprising passing the wires or bunches of wires over a curved surface and/or guide member each of which comprises at least one bore, formed with flared ends, in a plate.

27. A felt comprising a mat of interpenetrated substantially aligned edge-crimped continuous metal wires or bunches of wires, each individual wire having a torsional rigidity of greater than 2 X 10 7 Nm2, the interpenetration of the wires being in the nature of an intermingling in three dimensions produced by laying crimped wires or bunches of wires of mixed residual torsional direction under tension and releasing the tension.

28. A felt according to claim 27 wherein the felt is a needled felt.

31. A felt according to claim 27 wherein the metal wires comprise steel wires.

32. A felt according to claim 31 wherein the steel wires have individual diameters of greater than 0.08 mm.

34. A felt according to claim 27 by having been calendered.

35. A felt according to claim 27 wherein the felt is incorporated into an article.

36. A felt according to claim 27 wherein the bunches of wires are in the form of at least one twisted strand.