APPARATUS AND METHODS USING THE APPARATUS FOR TREATING METAL WIRE

Abstract

An apparatus for treating metal wire by multiple reverse bending and associated methods for using the apparatus are disclosed. The first roller has a first roller diameter, is followed by N−1 intermediate rollers with intermediate roller diameters and ends with an exit roller with an exit roller diameter. The exit roller is larger than the first roller and any one roller in the sequence of rollers has a roller diameter that is not smaller than the preceding roller in the sequence. The progressively larger diameters impose a well-controlled, gradually decreasing curvature to the wire resulting in a cast controlled wire. By folding the wire path together, a compact arrangement is obtained accommodating the increasingly larger rollers. A method to operate the apparatus is also described that allows for an easy adjustment of the apparatus in function of wire thickness.

Claims

1. An apparatus for treating metal wire by multiple reverse bending comprising a first roller having a first roller diameter, a number of intermediate rollers having intermediate roller diameters and one exit roller having an exit roller diameter, said first roller, intermediate rollers and exit roller forming a sequence of rollers, said rollers comprising a circumferential groove for receiving said metal wire, the groove of said rollers being organised in one groove plane, wherein the exit roller diameter is larger than the first roller diameter and any one roller in the sequence of rollers has a roller diameter that is not smaller than the preceding roller in the sequence.

2. The apparatus according to claim 1, wherein any one roller in the sequence of rollers has a roller diameter that is larger than the preceding roller in the sequence.

3. The apparatus according to claim 1, wherein the ratio of the diameter of any one intermediated roller or exit roller to the diameter of the preceding roller in the sequence of rollers is between 1.00 and 2.00.

4. The apparatus according to claim 3, wherein the ratio of the diameter of the intermediate roller following the first roller to the diameter of the first roller is between 1.05 and 1.20.

5. The apparatus according to claim 3, wherein the ratio of the diameter of the exit roller to the diameter of the roller preceding the exit roller in the sequence of rollers is between 1.2 and 2.0.

6. The apparatus according to claim 1, wherein the axes of the rollers are oriented perpendicular to said groove plane, said rollers being positioned in said groove plane such that an imaginary wire guided over the rollers forms a meandering multiple reverse bending path comprising curved sections and straight sections, where in the meandering multiple reverse bending path after each one roller of the first roller and intermediate rollers in the sequence of rollers a straight section follows, the length of said straight section being shorter than the diameter of that one roller.

7. The apparatus according to claim 1, wherein the apparatus has an apparatus axis corresponding to the tangent line to the circumferential groove of the first roller and the circumferential groove of the exit roller, and wherein the distance along the apparatus axis from the tangent point of said first roller to the tangent point of said exit roller is smaller than the sum of the diameters of said intermediate rollers plus the radii of said first roller and exit roller.

8. The apparatus according to claim 1, wherein the apparatus has an apparatus axis that corresponds to the tangent line to the circumferential groove of the first roller and the circumferential groove of the exit roller, and wherein the second roller and optionally even numbered rollers following in the sequence of rollers can be moved from a position at the one side of the apparatus axis to a position at the opposite side of the apparatus axis and vice versa.

9. A combination of two, three or more apparatuses according to claim 1, each of said apparatuses having a groove plane, each one of said apparatuses having an apparatus axis corresponding to the tangent line to the circumferential groove of the first roller and the circumferential groove of the exit roller, all of the apparatus axes of the two, three or more apparatuses coinciding to one another, wherein the groove planes of the two, three or more apparatuses are pairwise different from one another.

10. The combination according to claim 9 of two apparatuses, wherein the groove plane of the first apparatus is perpendicular to the groove plane of the second apparatus.

11. A method to treat a metal wire by multiple reverse bending using the apparatus according to claim 1 comprising the following steps: continuously providing a metal wire having a wire thickness; running said metal wire through the complete or part of said sequence of rollers in a multiple reverse bending path from an entry roller to the exit roller, said entry roller being the roller of the apparatus that that first bends said wire wherein the ratio of the diameter of the entry roller to the metal wire thickness is between 15 and 90.

12. The method according to claim 11, wherein the metal wire contacts the intermediate rollers over a contact angle centred at the axis of said intermediate roller, the sum of the absolute contact angles being larger than 360°.

13. The method according to claim 12, wherein the metal wire contacts any one of the intermediate rollers over a contact angle centred at the axis of said one roller, said contact angle being between 90° and 270°.

14. The method according to claim 11, wherein the apparatus is a combination of two, three or more apparatuses, each of said apparatuses having a groove plane, each one of said apparatuses having an apparatus axis corresponding to the tangent line to the circumferential groove of the first roller and the circumferential groove of the exit roller, all of the apparatus axes of the two, three or more apparatuses coinciding to one another, wherein the groove planes of the two, three or more apparatuses are pairwise different from one another, wherein the metal wire is treated in a the combination of apparatuses, wherein the metal wire is first multiple times and reversibly bent in a first plane, followed by one or more multiple and reverse bends in one or more subsequent planes, said subsequent planes differing from said first plane, said subsequent planes mutually differing form one another.

15. The method according to claim 11, wherein said thickness ‘d’ is larger than or equal to 0.25 mm and smaller than or equal to 3.0 mm.

16. The method according to claim 11, wherein said metal wire is a steel wire.

Description

BRIEF DESCRIPTION OF FIGURES IN THE DRAWINGS

[0053] FIG. 1 shows an implementation of a prior art straightener threaded with a small diameter wire;

[0054] FIG. 2 shows an implementation of a prior art straightener threaded with a larger diameter wire;

[0055] FIG. 3 shows a first embodiment of the inventive apparatus, threaded in a first way;

[0056] FIG. 4 shows the same embodiment of the inventive apparatus according FIG. 3, but threaded in second way;

[0057] FIG. 5 shows an embodiment of the apparatus with a displaceable second roller in a first position with a threading for a fine diameter wire;

[0058] FIG. 6 shows an embodiment of the apparatus as in FIG. 5 wherein the second roller is moved into a second position to allow threading of a larger wire diameter;

[0059] FIG. 7 shows a combination of the apparatus for multiple reverse bending in two directions.

[0060] FIG. 8 shows an embodiment wherein many of the inventive features are combined.

[0061] The hundred digit in the references of the figures refer to the figure number, while the ten and unit digit refer to corresponding items over the different figures. Throughout the figures the wire is depicted at its lowest possible position at the bottom of the groove of the rollers.

MODE(S) FOR CARRYING OUT THE INVENTION

[0062] In FIGS. 1 and 2 the problems with the prior art straighteners is illustrated. In FIG. 1 a straightener 100 with five rollers 110, 112, 114, 116, 118 is depicted that is wired with a small diameter wire 102. All rollers are provided with a groove through which the wire runs. All rollers have the same diameter. The wire is pulled through the device with a pull-through force ‘F.sub.out’ at speed V. The power needed to pull the wire through the straightener is ‘F.sub.out v’. At the entry a pull-back force ‘F.sub.in’ is applied to keep the metal wire in the straightener.

[0063] The radius R.sub.0 shown is the radius of curvature taken by the metal wire as it passes the roller 110. In this case—as the wire diameter is small hence the bending stiffness is low—the wire accurately follows the curvature of all the rollers. The bending stiffness ‘(EI)’ (in Nmm.sup.2) of a wire is proportional to its material modulus ‘E’ (in N/mm.sup.2) and the second axial moment of area ‘I’ (in mm.sup.4) that for a round wire with diameter ‘d’ is equal to (πd.sup.4/64). The bending of the wire to a radius of curvature R.sub.0 takes energy hence each roller will add some pull-back force ‘ΔF.sub.i’ to the entry pull-back force ‘F.sub.in’ making the pull-through force ‘F.sub.out’ bigger than the entry pull-back force ‘F.sub.in’. Further, by increasing the indentation of the rollers ‘Δ.sub.i’ (i=2, 3, 4) it is generally believed that more curvature is given to the wire. However, for a small wire diameter, with low bending stiffness, that touches the roller with diameter D over its contact angle the curvature applied will be 2/(D+d), irrespective of the indentation given to the roller.

[0064] When the metal wire is larger in diameter the situation changes to what is shown in FIG. 2. Again, the metal wire 202—with a larger diameter than metal wire 102—is guided in between opposed placed rollers 212, 216 against 210, 214 and 218. However, due to the increased bending stiffness ‘(EI)’ of the wire (‘I’ scales with ‘d.sup.4’ !) the metal wire will not adopt the rounding of the radius of the rollers 210, 212, 214, 216 and 218 but rather its own radius of curvature indicated with R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 with a respective centre—not corresponding to the axis of the roller —C.sub.1, C.sub.2, C.sub.3, C.sub.4 and C.sub.5.

[0065] Only when the tension on the wire is sufficiently large, a non-zero contact angle will form between the roller and the metal wire, hence the radius of curvature imposed on the metal wire will—over the contact angle touch path—be equal to the radius of the roller. Following classical Euler-Bernoulli elastic bending theory one can demonstrate that the minimum tension ‘T.sub.min’ (in N) required to have a non-zero contact angle is T.sub.min≥EI/D.sup.2 with ‘D’ (in mm) being the diameter of the roller.

[0066] An obvious measure is then to increase the diameter of the rollers and to increase indentation in order to ensure the contact angle is non-zero. However, this has then also consequences on the pull-through force that on its turn influences the contact angle. The conclusion is that in a prior-art straightener, the amount of curvature given to the metal wire depends primarily on the local tension applied on the wire and the indentation given to the wire, variables that have mutual influence on one another and depends less on the diameter of the rollers. This at least for relatively thick wires. This makes the control of properties of wire exiting prior-art straighteners difficult.

[0067] In order to overcome this control problem the apparatus of the inventors starts from a different approach. Rather than controlling the applied curvature to the wire through tension, diameter of rollers and indentation, their idea is to keep the indentation constant and adapt the diameter of the rollers as the metal wire travels through the apparatus.

[0068] A first embodiment of this principle is depicted in FIG. 3. There the metal wire 302 is guided through a first roller 310, five intermediate rollers 312,314,316,318, 320 and an exit roller 322. Each of the rollers has a circumferential groove that is a rectangular groove in case of flattened wires or a V-groove of which the bottom radius of curvature is much smaller than half of the wire diameter in case of a round wire. The rollers have a diameter D.sub.1 at the bottom of the groove, the entry roller 310 having diameter D.sub.0 the exit roller 322 having diameter D6. The grooves are all in one groove plane. The purpose of the groove is that it should prevent the wire from rotation when travelling from one roller to the next.

[0069] In the inventive apparatus the exit roller 322 is larger than the entry roller 310, and any one roller in the sequence of rollers has a roller diameter that is not smaller than the preceding roller in the sequence. Even more: any one roller in the sequence of rollers has a roller diameter that is larger than the preceding roller.

[0070] When wiring the apparatus, the roller of which the diameter D.sub.i is between 15 and 90 times the thickness of the metal wire ‘d’ is selected as the entry roller. Note that the entry roller need not be the same as the first roller. The ratio must be chosen so as to bring the outer fibres of the entering wire immediately into plasticity. For example a ratio of 40 brings an elongation to the outer fibres of the wire of 2.44% (100/41) and is for example for steel wires sufficient to bring the outer fibre into plasticity i.e. to impart a permanent bending to the wire.

[0071] The idea of the invention is that by putting the smallest roller at the beginning, the metal wire is plastically bent and given a predetermined amount of cast. This cast is in the subsequent rollers gradually increased by counter bending the metal wire over increasingly larger rollers. In this way the curvature given to the wire is stepwise driven near zero i.e. to an almost straight wire.

[0072] The ratio between the diameter of the roller 312 to the first roller 310 is between 1.05 and 1.20 for example 1.10. The ratio of the diameter of the exit roller 322 to the diameter of roller 320 is between 1.20 and 2.00 for example 1.90. The intermediate rollers have increasing diameters: the ratios of the intermediate rollers are D.sub.i/D.sub.i−1=1.20 (‘i’ now running from 2 to N−1).

[0073] The indentations Δ′.sub.i, i=2, 3, 4, 5 and 6 given to the wire are always the same and—for the purpose of the invention—is not a controllable parameter i.e. may be held fixed. Of course there must be some indentation to at least hold the wire in the grooves of the sequence of roller. The axes of the rollers (indicated with crosses ‘+’ in the Figures) are oriented perpendicular to the groove plane. They are positioned such that a multiple reverse bending path forms with curved sections and straight sections as followed by the wire 302 in FIG. 3. The contact angles in this multiple reverse bending path are between 15° and 90°. Furthermore an axis 330 can be defined that corresponds to the tangent line to the circumferential groove of the first roller 310 and the circumferential groove of the exit roller 322.

[0074] In order to ensure a further increased contact angle between rollers and metal wire, the same apparatus as depicted in FIG. 3 can be threaded in a different way by selecting a meandering multiple reverse bending path, between the rollers ensuring that the contact angles to the intermediate rollers 412, 414, 416, 418 and 420 remain between 90° and 270° as is shown in FIG. 4. This path is a meandering multiple reverse bending path because the average absolute contact angle subtended over the intermediate rollers is larger than 180°. It remains important to reduce the straight sections S.sub.i, i=1, 2, 3, 4, 5 and 6 as much as possible and to keep them in any case shorter than the diameter of the roller preceding the straight section. The reason for keeping the straight sections short is to prevent that the reverse bending of the following roller would make the metal wire rotate around its own axes.

[0075] Note that the axis of the apparatus is now 430 in FIG. 4. As the number of rollers is odd (seven) the exit roller 422 is situated at the same side of the apparatus axis 430 as the first roller 410.

[0076] FIG. 5 illustrates the advantageous use of the second roller 512 that can be moved from one side of the apparatus axis 530 to the other side 512′. When processing small diameter wire, the wire must enter at a roller with a smaller size than when processing a thicker wire. By moving the roller 512 to the position at the same side of the first roller relative to the apparatus axis, the roller that first bends the wire 502 i.e. the entry roller becomes the first roller 510. So the entry roller is set to correspond to the first roller.

[0077] When the apparatus is now to be used for a thicker wire 602—switching to FIG. 6—for which an entry roller with higher diameter is needed, the wire roller 612 is moved to the position opposite of the first roller indicated with 612′ i.e. the second roller 612 is taken out of the wire path. Consequently, the roller 614—the third roller in the sequence of rollers—becomes the entry roller. As this roller 614 has a larger diameter it imposes the right elongation to the wire 602.

[0078] This feature makes the changeover from one diameter range to another diameter range particularly simple: [0079] When a changeover from a thin to a thick wire is to be made, the wire end of the thin wire is welded to the start of the thick wire. Before the weld passes the apparatus, the apparatus is set from the situation of FIG. 5 to the situation in FIG. 6. The weld will pass without problem as it is not severely bent. [0080] Mutatis mutandis when a changeover form a thick to a thin wire is to be made, the weld is first allowed to pass the apparatus before the situation is set from FIG. 6 to FIG. 5.

[0081] It will be clear to the skilled person how the feature of having a movable roller can be extended not only to the second roller 612 but also to the fourth roller 616 and so on.

[0082] FIG. 7 shows how a combination 700 of two apparatuses 704, 704′ can be made. Two mounting plates 734, 734′—that are parallel to the groove planes of their respective apparatuses 704, 704′ are mounted on a carrying beam 732. Both apparatuses 704, 704′ share the same single axis 730 as the apparatus axis. Each of the apparatuses 704, 704′ are provided with a sequence of rollers 710, 712, 714, 716, 718 and 710′, 712′, 714′, 716′, 718′ that are pairwise equal. The wire 702 first enters the first apparatus 704 wherein it is multiple times reverse bent in the groove plane of 704. The wire 702 subsequently enters the second apparatus 704′, wherein the wire is multiple times and reversibly bent in the direction orthogonal to the first direction.

[0083] It will clear to the skilled person that further multiple reverse bends can be induced in other directions by subsequent apparatuses in sequence.

[0084] FIG. 8 illustrates how the total length of the apparatus can be reduced. Positioning the axis of the rollers such that a highly meandering wire path is formed greatly reduces the overall length of the apparatus. The length of the apparatus is dimensioned based on the distance between the tangent points of the first roller 810 and the exit roller 824. Each of the intermediate rollers 812 to 822 have a diameter D.sub.i, 1=1, 2, . . . to 6. When adding half the diameter i.e. the radius of 810 plus half the diameter of the exit roller 824 to all diameters of the intermediate rollers, the sum is larger than the length ‘L’.

[0085] Further in FIG. 8 the total sum of the absolute contact angles to the intermediate rollers is about 1140°. Note that the roller 812 can be moved from a position at one side of the apparatus axis 830 to a position 812′ at the opposite side of the apparatus axis;

[0086] The metal wire 302, 402, 502, 602, 702 or 802 can be any metal wire such as a flat or round copper, aluminium or steel wire with a thickness that is larger than or equal to 0.25 mm and smaller than 3.0 mm. A particular advantageous use of the apparatus and method is in the production of bead wire as used for making beads of tires. Also in the production of flat wires such as flat wires for use in wind shield wiper arms or flat wires that form the backbone of a wiper blade the apparatus is of use.