EP3057724A1

EP3057724A1 - A wire forming device

Info

Publication number: EP3057724A1
Application number: EP13895793.1A
Authority: EP
Inventors: Kurt VAN RYSSELBERGE; Lingjun Li
Original assignee: Bekaert NV SA
Current assignee: Bekaert Binjiang Steel Cord Co Ltd
Priority date: 2013-10-15
Filing date: 2013-10-15
Publication date: 2016-08-24
Also published as: CN105722620A; WO2015054820A1; EP3057724A4

Abstract

A wire forming device (300) comprises a first and second deforming wheel (302,304) turnable on shafts (322, 324) in a holder (310), a synchronizing coupling (410) for coupling the first and second wheel such that the first and second deforming wheels are rotatable with synchronized circumferential speed at the gap between the first and second wheel. A composite wire forming device comprises two or more wire forming devices. A sawing wire can be formed by the composite wire forming device or the wire forming device. The wire forming device can be used to crimp wires, more particularly steel wires for use, in steel cord or as a sawing wire or as a brush wire. In this way the phase difference between the deforming wheels can be adjusted at will.

Description

A wire forming device

Description

Technical Field

[1] The invention relates to wire forming device for inducing imprints or bends on a wire, more particularly steel wires for use in steel cord or as a sawing wire or as a brush wire.

Background Art

[2] In many steel wire applications it is beneficial to shape the steel wire in a specific shape. Mainly this is in the form of a wave in a single plane possibly combined with other deformations such as rotation or bending or a second crimping in a plane different from the first crimping plane.

[3] The reasons why crimps are introduced can be diverse. For example in the field of steel cord for reinforcement of rubber goods:

• filaments are crimped for influencing the elongation behaviour of the filament in the steel cord. A crimped wire has a higher elongation at break and a lower modulus than a straight wire. Moreover by adapting the amplitude and the wavelength of the crimp, these properties can be fairly well tuned.

• Filaments in tyre cord are also crimped in order to improve rubber penetration. The small induced bends form micro sized gaps between filaments where through rubber may ingress during extrusion or vulcanising.

In the field of sawing wire crimps are introduced for improved cutting performance:

• the crevices formed by the bends drag a slurry carrying abrasive powder better into the cut resulting in a better and more uniform sawing;

• as the wire is less contacting the sides of the cut, friction between wire and work piece is less

Crimped wire brushes are used on various industrial cleaning machines from handheld rotative brushes to big brush wheels for street cleaning. There crimping of the wire is mainly introduced to:

• make the wires stand apart from each other in the brush;

• crimping helps to absorb the flexing and vibration during use thereby improving the lifetime of the brush.

[4] In order to induce a crimp in a steel wire, at least part of the outer wire surface must be stretched plastically. It results that for fine wires - say thinner than 0.15 mm - already very small bending radii must be imposed on the wire before the strain at the outer wire surface (that is equal to the ratio of the wire diameter over twice the bending radius) brings the steel above its yield stress. The problem aggravates further when one wants to give a permanent crimp to a high tensile wire, as in high tensile wires (say wires with a tensile strength above 2000 N/mm²) the yield stress rises concomitantly. The 'yield stress¹ is that stress at which the steel will show a permanent deformation after removal of the load.

[5] Over and above - once one has succeeded in bringing part of the wire section into plasticity - the 'springback' of fine, high tensile wires is much higher than for thick, low tensile wires. 'Springback' can be defined as the difference between the imposed curvature during bending and the curvature that remains after removal of the bending moment. The 'springback' increases with increased yield stress and with decreasing diameter (other factors that influence the springback are the cross section of the wire and the modulus of the steel). Hence, it is more difficult to crimp high tensile, fine wires than thick, low tensile wires.

[6] Generally, the crimping of a steel wire is performed by guiding one or more parallel wires between a pair of intermeshing forming wheels that are slightly separated from one another to let the wire pass. Known devices are for example described in:

• WO 00/39385, Figures 2a and 2b wherein two forming wheels have pins in the plane of the wheel. The gap between the pins can be accurately set by a micrometer screw.

• CN101733846. The device comprises two intermeshing forming wheels of identical size that intermesh and are pushed against one another by means of springs.

• CN202239382U, describing a serial arrangement of two pairs of forming wheels wherein the gap between the forming wheels of a pair can be adjusted by means of a micrometer screw.

[7] The inventors observed that with the known crimping devices a particular problem can occur: as the forming wheels are independently rotating from one another and are separated by a gap, there is an angular 'play' between both forming wheels. During crimping one wheel can therefore have a slightly different angular phase compared to the other. See Figure 1 for an illustration describing a pair of intermeshing forming wheels in between of which a wire 130, 130' passes. In Figure la the upper wheel 102 lags slightly behind compared to the lower wheel 104 that is leading. Of course both wheels rotate at the same angular speed. As a result the crimp in the wire is not of the isosceles triangular form but shows a saw tooth (Figure lb) with a low slope leading edge 132 and a sharp slope trailing edge 134. Figure lc describes the opposite case wherein the upper forming wheel 102 leads in phase while the lower forming wheel 104 follows resulting in a sharp rise edge 132' and a low slope trailing edge 134' on the sawing wire 130'.

[8] The difference in phase can be due to a difference in friction on the axes of the wheels. Also the phase difference between the wheels need not be constant and therefore along the length of the wire once the upper wheel may lead while the lower wheel follows and on another length of wire just the opposite may occur. A length of wire like 130 is then followed by a length of wire like 130'. This leads to a non-uniform deformation of the wire along its length which may influence its properties. Moreover this shift in phase may lead to a variable tension on the wire that leads to a variable peak-to-peak (Figure lb, 2P¹) value for the deformation of the wire. For example in the case of a crimped sawing wire this may result in unequal cutting behaviour along the length of the wire. The varying phase difference may also result in a wire that gets locally pinched between the teeth of the deformation wheels leading to wire surface damage. For steel cord it is known that a damaged wire surface leads to a decreased fatigue life.

[9] The inventors have therefore come up with an inventive wire forming device that provides for a fixed phase angle difference in combination with an adjustable gap.

Disclosure of Invention

[10] The primary object of the invention is to do away with the problem of the prior art wire forming devices. It is a further object of the invention to provide a wire forming device wherein the phase angle difference between forming wheels can be adjusted at will. The use of the wire forming device leads under particular settings to other types of deformed wires which are another object of the invention.

[11] According a first aspect of the invention a wire forming device is claimed according the combination of features of claim 1. Additional features for preferred embodiments of the invention are defined in the claims depending from claim 1.

[12] The wire forming device comprises a first and second deforming wheel turnable on shafts in a holder wherein the shaft of the first wheel is held in position relative to said holder and the shaft of the second wheel is movable while remaining parallel to said first shaft for adjusting the gap between the first and second wheel. This first and second wheel have deforming teeth of equal circular pitch. What is special compared to the known wire forming devices is that the inventive wire forming device further comprises a synchronising coupling for coupling the rotation of the first and second wheel such that both first and second wheel are rotatable with synchronised circumferential speed at the gap.

[13] In what follows, and for the purpose of this application, and as further explained in Figure 2:

• the term 'deforming wheel' or 'wheel' for short (210, 212 in Figure 2) will be used for those parts of the wire forming device that come into contact with the wire.

• The term 'gears' will be reserved for intermeshing toothed wheels that transfer angular motion with virtually no angular play and that do not contact the wire.

• with 'circular pitch P' is meant that length of arc (expressed in mm) spanned between identical parts, for example at the pitch point, of subsequent teeth taking the axis of the wheel as centre of the arc. In practice the 'circular pitch P' corresponds to the wavelength of the crimp made in the wire (Figure lb).

• The 'pitch point' is that point where deforming teeth would touch one another provided no wire is present.

• With 'angular pitch τ ' is meant the angle subtended by subsequent teeth as measured from the centre of the deforming wheel. It is equal to 360°/N (in degrees) or 2π/Ν (in radians) wherein N is the number of teeth on the deforming wheel.

• 'circumferential speed' is the speed (in e.g. meters per second) of the pitch point at the gap. It is equal to the wire feeding speed.

• with 'synchronised circumferential speed at said gap' is meant that the phase angle difference between both wheels remains constant during use.

• The 'phase angle difference Δφ' between the wheels is the angle between the line connecting the axes of the deforming wheels and the angular position of a meshing tooth at the moment the opposing teeth passes the axes connecting line. It has a value between 0 and the angular pitch V. When Δφ is equal to Ό¹ or V the teeth of opposing wheels (203, 204) are facing one another. When Δφ is equal to 'τ/2' the meshing tooth (203) is positioned exactly in the middle of the opposing teeth (202, 204).

• The 'mesh depth δ' is the depth the top of a meshing tooth (204) enters the circle of the tops of the opposing teeth (203, 205). The mesh depth is negative when the deforming wheels do not mesh. The mesh depth is zero when at zero phase difference the top of teeth of the forming gears touch one another.

[14] The deforming wheels can be in the form of 'gears' wherein the teeth have a certain shape and roundness adapted to the purpose and are milled out circumferentially from a cylindrical roll. The materials used are usually hardened steels, ceramics or cermets as the wire tends to wear the teeth greatly. Alternatively the deforming wheels can be in the form of discs whereon pins are mounted perpendicular to the disc at the rim. Deforming wheels can then be mounted with the sides with pins facing one another. Pin deforming wheels have the advantage that they allow a larger mesh depth.

[15] The deforming wheels are turnable on shafts that are held in a holder. Bearings can be mounted between the wheel and the shaft, the shaft being fixed to the holder or the wheel can be fixedly connected to the shaft while the shaft is rotating in bearings fixed in the holder. The holder keeps the axis of the deforming wheels parallel to one another while the gap between the deforming wheels can be adapted. The holder can be in the form of a plate whereon the forming wheels are mounted (single side bearing) or may take the form of a block with a wide slot in it for receiving the pair of deformation wheels in it (two sided bearing). The shaft of one deforming wheel can be held by the block while the shaft of the other deforming wheel can move in a slit in the block. This shaft can for example be held in a U -piece outside or inside to the holder with a set screw or micrometer mounted between the U-piece and the holder.

[16] In a further preferred embodiment the phase angle difference between the first and second deforming wheel can be adjusted through said synchronising coupling. The phase angle difference Δφ can be varied between zero and the angular pitch Y of either the first or the second deforming wheel.

[17] As long as the circular pitch of both the deforming wheels is identical the wheels will stay in sync during rotation whatever the diameters of the wheels are. Hence the deforming wheels may have a different diameter and a different number of teeth: let ΤΓ be the number of teeth on the first deforming wheel and 2¹ the number of teeth on the second deforming wheel. Then in a first preferred embodiment ΤΓ is different from 2\ Even more preferred is if Τ and 2^f are co-prime numbers i.e. the only integer that divides both ΤΓ and 2¹ is 1. Wheels with a co -prime number of teeth have an additional advantage in that each tooth meshes with the largest possible periodicity (being equal to the product of Tl xT2) to the opposing pair of teeth. In a second preferred embodiment, the numbers Γ and 2¹ may be equal to one another. This has the advantage that only one type of wheel must be available.

[18] The synchronising coupling can be electrical e.g. when both deforming wheels are driven individually by synchronised motors. Although such solution is rather expensive it is therefore not a priori excluded.

[19] By preference the synchronising coupling is mechanically implemented. A first preferred embodiment to synchronously couple the deforming wheels is by means of a gear train. A gear train is an assembly of gears wherein gears are rotatably coupled either by intermeshing gear pairs (having the same circumferential speed) or by gear pairs that share the same axis (having the same angular speed).

[20] The simplest gear train is a pair of intermeshing gears. If for example the first deforming wheel is attached to a first gear with Zl teeth and the second deforming wheel is attached to a second gear with Z2 teeth, as long as the ratio T2/T1 is equal to Z2/Z1, the deforming wheels will run at equal circumferential speed.

[21] The above synchronous coupling can be extended by the use of four intermeshing wheels having teeth numbers Zl, Z2, Z3 and Z4 wherein the first gear is attached to the first deforming wheel and meshes with the second gear, the second gear meshes with the third gear, the third gear meshes with the fourth gear that is attached to the second deforming wheel. As long as

(T2/Tl)=(Z2/Zl)x(Z3/Z2)x(Z4/Z3)=(Z4/Zl) the deforming wheels will run synchronously. An embodiment with four gears has the additional advantage that the gap between the deforming wheels can be adapted over a larger range than when only two gears are present.

[22] The gear train can be extended to comprise any number of gear pairs that are either intermeshing or share the same axis. As long as the combined gear ratio is equal to the deforming teeth ratio, the wheels will run synchronously:

(T2/Tl)=(Z2/Zl)x(Z3/Z2)x(Z4/Z3)x ...x(Z_2n/Z_2n-1) wherein the first gear with Zl teeth is attached to the first deforming wheel and the last gear (2n) is attached said second deforming wheel.

[23] The phase angle difference can be changed by changing the mounting angle between first deforming wheel and first gear, between second deforming wheel and last gear or by changing the mounting angle of any gear pair that shares the same axis or by any combination thereof.

[24] An alternative mechanical embodiment of the synchronising coupling can be implemented by means of a toothed belt. There a first toothed pulley with Z 1 teeth is fixedly connected to the first deforming wheel, and a second toothed pulley with Z2 teeth is fixedly connected to the second deforming wheel. Rotation of both toothed pulleys is coupled by a double sided toothed belt. The toothed belt may run on a pair of separate toothed pulleys, different from the first or second one. Alternative one of the pulleys of the pair on which the belt is running may by the first or the second toothed pulley. In any case one of the first and second toothed pulley is inside the belt, while the other is outside the toothed belt.

[25] If for example the outer side of the belt has 'N' teeth that mesh with the first toothed pulley (i.e. they have the same tooth pitch) and the inner side of the belt has 'n' teeth that mesh with the second toothed pulley, one can show that whenever:

(T2/Tl)=(Z2/Zl)x(N/n) both deforming wheels will run synchronously. In most practical cases, the number of inner belt teeth will be equal to the number of outer belt teeth or ^fn=N\ Furthermore, the embodiment is easiest to implement if both toothed pulleys are equal i.e. 'Ζ2=Ζ . If follow that then both deforming wheels must have equal number of teeth and as both must have equal circular pitch their pitch diameters must be identical too.

[26] The use of a toothed belt has an additional advantage in that the phase angle difference between the forming wheels cannot only be adapted by changing the mounting angle between first deforming wheel and first toothed pulley or second deforming wheel and second toothed pulley but also by changing the distance along the toothed belt between engagement of first and second toothed pulley to the toothed belt.

[27] Instead of double sided toothed belt, a double sided gear having 'n' teeth on the internal circumference and 'N' teeth on the outer circumference could also be used.

[28] Alternatively, the double sided toothed belt can be replaced by a closed roller chain and the first and second toothed pulley can be replaced by a first and second sprocket. When using a roller chain the pitch of both first and second sprocket must be equal to the pitch of the roller chain. In a roller chain the inner and outer pitch is of course identical which corresponds to the case 'η=Ν' of a double sided toothed belt. Similarly, the roller chain may run on a pair of sprockets not corresponding to the first and second sprocket mentioned. Alternatively one of the sprockets in the pair carrying the roller chain may correspond to either the first or second sprocket. In any case when the first sprocket is within the roller chain loop the second must be placed outside the roller chain loop or vice versa.

[29] Use of a roller chain loop also has the advantage that the phase angle difference between first and second deforming wheel can be adapted not only by changing the mounting angle of first deforming wheel on the first sprocket and/or the second deforming wheel on the second sprocket, but also be adjusting the distance between the engagement of first and second sprocket.

[30] In a further preferred embodiment the synchronising coupling is so precise in that the backlash is less than 50% of the circular pitch of the deforming wheels, or lower than 30% or lower than 10%. The inventors are confident that for example with a synchronising coupling based on gears, a backlash of less than 5% of the circular pitch of the deforming wheel can be reached. With 'backlash' is meant the length of arc movement of the pitch point of a tooth of the second deforming wheel when it is pushed back and forward while the first deforming wheel is kept blocked.

[31] The wire forming device as described so far can be 'passive' or 'active'. With 'passive' is meant that the deforming wheels are driven by the wire being pulled through. As the bends of the wire induces some elasticity into it, care must be taken that the exit tension remains sufficiently constant. Alternatively the wire forming device can be made 'active¹. In that case the system is driven by a motor at the synchronising coupling or on one of the deforming wheels. In this way the forming device can be used as a 'pull-through' device. More preferred is if the speed of the driving motor is controlled by the entrance or exit tension of the wire. In this way a more constant deformation of the wire is obtained.

[32] According a second aspect of the invention, a number of wire forming devices as described above can be put in series thus forming a composite wire forming device. During operation a wire is then fed from one wire forming device to the next. The wire forming devices can induce crimps or indentations in different planes of the wire.

[33] According a third aspect of the invention a sawing wire is claimed. The sawing wire has a substantially round cross section of diameter 'd'. By passing the wire through a wire forming device or composite wire forming device as described above wherein the angular phase difference has been set to as close as possible to zero and the gap between the top of teeth has been set to between 0.70 to 0.95 time the diameter 'd' of the wire, the wire is pinched at the teeth. Alternatively the gap can be defined as having a 'negative mesh depth' of -0.70 to -0.95 x d. The wire shows regular 'pairs of flats', diametrically opposite to one another at regular distances equal to the circular pitch of the forming wheels.

[34] Alternatively - according a fourth aspect of the invention - a sawing wire is described that has a substantially round cross section of diameter 'd'. The wire is processed through a wire forming device or composite wire forming device as described above. The phase angle difference is between the forming wheels is set between a quarter and three quarters of the angular pitch of said forming wheels. The mesh depth is set positive to between 0.5 to 2.0 times the diameter 'd' of the wire and more preferably 1.05 and 1.5 x d times the diameter of the wire. The wire thus obtains a zigzag crimp with a substantially isosceles triangular crimp.

Brief Description of Figures in the Drawings

[35] Figures la, lb, lc and Id explain the problem with prior-art wire forming devices.

[36] Figure 2 describes the geometry of wire forming wheels.

[37] Figure 3 is a schematic presentation of a first embodiment of the invention.

[38] Figure 4a and 4b describe a first mode to operate the wire forming device and the wire resulting therefrom.

[39] Figure 5a and 5b describe a second mode to operate the wire forming device and the wire resulting therefrom.

[40] Figure 6 describes a second embodiment of the wire forming device.

[41] Figure 7 describes a third embodiment of the wire forming device.

[42] In the following terms such as 'lower' or 'upper' or 'left' or 'right' should not be taken absolutely. The skilled person will readily understand that they can be interchanged by changing the orientation of the forming device or mirroring it. Even more: in all orientations, the device will work equally well.

Mode(s) for Carrying Out the Invention

[43] Figure 3 shows a first preferred embodiment of the inventive wire forming device 300. It consists of a holder 310 in which deforming wheels 302 and 304 are mounted. Deforming wheels 302 and 304 are mounted on shafts 322 and 324 respectively. The bearings of the deforming wheels (not shown) are mounted between the shafts 322, 324 and the holder 310 in the bearing housings 332, 332' and 334, 334' respectively. The top shaft 322 can

.2

SUBSTITUT JHEETfRyLFj261„ . be lowered or raised by means of set screws 318, 318' thereby adjusting the gap between the deforming wheels. The crimped wire 330' exists from between the deforming wheels. Two slots 320, 320' are provided in the holder 310 to allow the top deforming wheel shaft to move parallel to the lower deforming wheel shaft.

[44] The difference with prior-art crimpers lays in the presence of a synchronising coupling that couples the rotative motion of the first and second deforming wheel. In this particular embodiment this synchronising coupling takes the form of two gears 306 and 308 that are fixedly connected to their respective deforming wheels 302 and 304. The gears precisely mesh and have minimal backlash. Backlash can be minimised by reducing the pressure angle which is the acute angle between the line of action and the normal to the line connecting the gear centres. The line of action is the line formed by the contact point between meshing gear teeth during rotation. When the gear is an involute type gear, this line of action is a straight line.

[45] The phase between both deforming wheels can be adjusted by changing the mounting angle between gear and deforming wheel attached to it. This is illustrated in Figure 4. In Figure 4a, the phase angle difference Δφ is set to half of the angular pitch τ: Δφ= τ/2 in the synchronising coupling represented by 410. The mesh depth δ is set between 1.0 and 1.5 times the wire diameter. The resulting crimped wire 430' shown in Figure 4b shows a regular deformation throughout the length of the wire with equally sloped leading 432 and trailing 434 segments.

[46] When setting the phase angle difference Δφ in the synchronising coupling 510 to zero and opening the forming wheels such that a gap of about 0.70 to 0.95 times the wire diameter forms a wire with regular flats can be made like shown in Figure 5b. For example a 140 μηι high tensile steel wire (tensile strength 3725 N/mm², breaking load 57 N) was led through the device with forming wheels with a circular pitch of 2.59 mm. The resulting wire 530' (Figure 5b) showed regular, diametrically opposed flats 532 separated by straight segments 534 with a periodicity of the circular pitch. The mesh depth δ was set to -120 μηι or -0.86 x d. The wire showed a somewhat lower breaking load (52 N) but this was not prohibiting the use of the wire for sawing. When used as a sawing wire, the wire showed a lower bow than the corresponding wire without flats during sawing i.e. has an improved cutting performance. The inventors conjecture that this is due to an improved slurry drag in the hollows.

[47] When using only two meshing gears the possible gap adjustment between the forming wheels is limited: increasing the gap may lead to more backlash. However, the advantage is that it is easy to implement. By using four or more gears one can increase the adjustable range of the gap. As the total backlash of a gear train is simply the sum of all backlashes of each intermeshing pair, backlash will increase with the number of intermeshing gears. Using four intermeshing gears is a good compromise between gap adjustability and backlash. This is described in the second embodiment of Figure 6.

[48] Figure 6 shows a wire forming device 600 wherein the synchronous coupling is implemented through five gears 606, 608, 612, 614 and 616. The deforming wheels 602 and 604 are provided with round pins 603, 605 protruding from the plane of the wheels 602, 604. The wheels are arranged such that the sides with pins face one another. In between the pins wire 630 is guided, leaving as a crimped wire 630'. The shaft 624 of the lower forming wheel 604 is mounted to holder 610. The bearing (not shown) is between forming wheel 604 and shaft 624. The gap between pins 603 and 605 can be adjusted by sliding shaft 622 of the upper forming wheel 602 through slits 620 in an arc centred at the axis 626 of gear 612. Again the bearing (not shown) is situated between shaft 622 and forming wheel 602.

[49] Gears 606 (33 T 'teeth') and 608 (39 T) are fixedly connected to deforming wheels 602 and 604 respectively at the side opposite of the protruding pins. The gear train is formed by meshing gear pairs 608 and 614 (29T), 614 and 616 (26T), the gears 612 (22 T) and 616 share the same axis 626 and gears 612 and 606 are meshing. The axes 628 and 626 have a fixed position relative to the holder 610. The combined gear ratio of the gear train is such that it is equal to the teeth ratio of the deforming wheels (which in this embodiment is set to 1):

By using precision ground gears with a high number of teeth, the total backlash of the gear train can be held below 5% of the circular pitch of the deforming teeth. Again the phase angle difference Δφ can be adjusted by changing the mounting angle between one deforming wheel and the attached gear. However, in this case the phase angle difference can also be adjusted by changing the mounting angle between gears 612 and 616. So the phase angle can be adjusted on any gear pair that share the same axis in the gear train.

[50] In a third preferred embodiment 700 (Figure 7) the synchronous coupling is implemented by means of a toothed belt 722 coupling the first 702 and second 704 deforming wheel through first 706 and second 708 toothed pulleys that are fixedly connected to the respective deforming wheels. One of the toothed pulleys - in this embodiment 706 - must be running inside the toothed belt 722 while the other 708 is situated outside the belt. This in order to invert the turning directions of the pulleys. This is of course makes necessary the presence of a third pulley 720 to tension the toothed belt 722.

[51] The number of teeth internal 'n' and external 'N' to the toothed belt, the number of deforming teeth of first and second wheel T₇₀2, T₇₀₄ and the gear teeth numbers Z₇₀6 and Z₇₀s must obey the relation:

...to ensure that both deforming wheels are running at synchronised circumferential speed. The number of teeth on the tension pulley 720 is immaterial.

[52] The use of a toothed belt offers the additional advantage that the phase angle difference between the deforming wheels can be set by changing the distance between where the toothed pulleys contact the toothed belt.

[53] In this third preferred embodiment the tensioning pulley 720 is driven by an electrical motor. The rotational speed of the motor can be controlled proportional to either a feedback signal of the tension of the wire 730' exiting the deforming device, or by means of a feed forward signal of the tension of the wire 730 entering the wire forming device.

[54] In a further preferred embodiment different forming devices can be set in series wherein the one device feeds the other. So for example to produce a wire that is crimped in two planes differing from one other (such as generally described in WO 99/28547 or specifically for use as a sawing wire in WO 2006/067062) two devices according the first embodiment can be put in series. Preferably, when a crimp has been induced in one plane between the deforming wheels of the first wire forming device, in the next forming device the wire is first received on a deforming wheel with the plane of the crimp parallel to the deforming teeth, then held for about 180° on that wheel before entering the gap in between the second pair of deforming wheels. And after having received there a second crimp in a plane perpendicular to that of the first crimp the wire is guided for 180° on the second deforming wheel thus describing an 'S' shape through the second forming device. The advantage of this threading path is that the wire cannot turn when guided from first to second forming device as it is prevented from rotation by the 'S' shape path.

[55] In a further preferred embodiment, different forming devices can be coupled synchronously so that the phase difference between different forming devices can be controlled.

Claims

1. A wire forming device comprising a first and second deforming wheel turnable on shafts in a holder wherein the shaft of said first wheel is held in position relative to said holder and the shaft of said second wheel is movable while remaining parallel to said first shaft for adjusting the gap between said first and second wheel, said first and second wheel having deforming teeth of equal circular pitch, characterised in that

said wire forming device further comprises a synchronising coupling for coupling said first and second wheel such that said first and second wheel are rotatable with synchronised circumferential speed at said gap.

2. The wire forming device according to claim 1 wherein the phase angle difference between first and second deforming wheel can be adjusted through said synchronising coupling.

3. The wire forming device according to any one of claim 1 or 2 wherein the number of teeth of said first deforming wheel is different from the number of teeth of said second deforming wheel.

4. The wire deforming device according to any one of claims 1 to 3 wherein said synchronising coupling comprises a gear train of which the first gear is fixedly connected to said first wheel, the last gear is fixedly connected to said second wheel wherein the combined gear ratio of said gear train is equal to the deforming teeth ratio of said deforming wheels.

5. The wire forming device according to claim 4 wherein the number of gears in said gear train is between two to five.

6. The wire forming device according to any one of claims 4 to 5 wherein the phase angle difference between first and second deforming wheel can be adjusted by changing the mounting angle between first gear and first wheel and/or last gear and second wheel and/or by changing the mounting angle between any gear pair sharing the same axis in the gear train.

7. The wire forming device according to any one of claims 1 to 3 wherein said synchronising coupling comprises a first toothed pulley fixedly connected to said first deforming wheel, and a second toothed pulley fixedly connected to said second deforming wheel said first and second toothed pulley being coupled by a double sided toothed belt, one of said toothed pulleys being inside to the toothed belt, the other toothed pulley being outside to the toothed belt, the combined transmission ratio being equal to the deforming teeth ratio of said deforming wheels.

8. The wire forming device according to claim 7 wherein the phase angle difference between first and second deforming wheel can be adjusted by changing the mounting angle between first toothed pulley and first wheel and/or second toothed pulley and second wheel and/or changing the distance along the toothed belt between engagement of first and second pulley to the toothed belt.

9. The wire forming device according to any one of claims 1 to 3 wherein said synchronising coupling comprises a first sprocket fixedly connected to said first deforming wheel, and a second sprocket fixedly connected to said second deforming wheel said first and second sprocket being coupled by a roller chain, one of said sprockets being inside of said roller chain, the other sprocket being outside to the roller chain, the sprocket ratio being equal to the deforming teeth ratio of said deforming wheels.

10. The wire forming device according to claim 9 wherein the phase angle difference between first and second deforming wheel can be adjusted by changing the mounting angle between first sprocket and first wheel and/or second sprocket and second wheel and/or changing the distance along the roller chain between engagement of first and second sprocket to the roller chain.

11. The wire forming device according any one of claims 1 to 10 wherein the backlash in said synchronising coupling is smaller than 50% of the said circular pitch.

12. The wire forming device according to any one of claims 1 to 11 wherein said wire forming device is driven.

13. A composite wire forming device comprising two or more wire forming devices according to any one of claims 1 to 12 mounted in series wherein, during operation, a wire is fed from one wire forming device to the next.

14. A sawing wire of substantially round cross section with diameter 'd' formed by passage through any one of the wire forming devices according to any one of claims 1 to 12 or through a composite wire forming device according claim 13 wherein the phase angle difference between said forming wheels is substantially zero and the gap between the tops of the teeth of opposite forming wheels is between 0.70 to 0.95 times 'd' for pinching the wire during passage at distances equal to said circular pitch.

15. A sawing wire of substantially round cross section with diameter 'd' formed by passage through any one of the wire forming devices according to any one of claims 1 to 12 or through a composite wire forming device according claim 13 wherein the phase angle difference between said forming wheels is between a quarter and three quarters of the angular pitch of said forming wheels for imparting a zigzag crimp into said wire.