WO1999046066A1

WO1999046066A1 - Process and device for straightening wire

Info

Publication number: WO1999046066A1
Application number: PCT/EP1999/001380
Authority: WO
Inventors: Martin Müller; Gerd Peytsch; Norbert Giegeler
Original assignee: Ethicon Gmbh
Priority date: 1998-03-10
Filing date: 1999-03-05
Publication date: 1999-09-16
Also published as: DE19811209A1; DE19811209C2; EP1062062B1; EP1062062A1

Abstract

In a process for straightening wire, a wire (1) coming from a first reel (2) is drawn through a straightening unit (3) with straightening rolls. The straightening unit (3) rotates about a first axis (A-A) which is defined by the longitudinal direction of the path of the wire in the region of the straightening unit (3). After emerging from the straightening unit (3), the wire (1) is wound onto a second reel (4), the diameter of which is greater than that of the first reel (2). The second reel (4) is rotated in accordance with the direction of rotation of the straightening unit (3) about a second axis (C) which is defined by the path of the wire leading tangentially onto the second reel (4).

Description

Process .and device for stra σhteirinσ wire

The invention relates to a process for straightening wire according to the preamble of claim 1 and to a device for carrying out such a process .

By way of example, in the manufacture of surgical needles, wire is used which is delivered on reels having a relatively small diameter. Before such wire can be further processed to produce straight surgical needles, for example, it must be straightened (i.e. bent straight). This happens with the help of a straightening unit through which the wire coming from the reel (in the following: first reel) is drawn. The straightening unit contains a number of straightening rolls, e.g. eight pieces, which force the wire alternately upwards and downwards, so that it passes through the straightening unit in a roughly wave- shaped form, the wave amplitude decreasing in the direction of the end at which the wire emerges. The straightening rolls can be of different sizes and their arrangement inside the straightening unit is variable, so that the straightening unit can be adjusted to wires of different thicknesses and different material properties . A straightening of the wire is achieved by virtue of the fact that the wire is deflected in alternating directions inside the straightening unit. To achieve the most isotropic conditions possible perpendicular to the wire axis, the straightening unit is rotated about an axis (in the following: first axis) which is defined by the longitudinal direction of the path of the wire in the region of the straightening unit, - 2 -

i.e. the first axis essentially coincides with the "zero line" of the wave-shaped path of the wire.

The wire is elastically and also plastically deformed by the rotation movement of the straightening unit about the first axis, i.e. it is subject to torsion in the wire axis ("twist"). This effect is unwanted, and various processes have therefore been employed to reduce or compensate the twist effect .

One possibility is to place a second, similarly structured straightening unit behind the straightening unit. The setting of the straightening rolls in the first and in the second straightening unit is matched in such a way that the wire is straightened only after emerging from the second straightening unit. While the wire is being pulled through, the second straightening unit rotates about the same axis as the first straightening unit, but in the opposite direction. In this way, the twist produced in the first straightening unit is at least partly removed from the wire by deformation about the wire axis in the reverse direction. With this process the setting of the straightening rolls, which must be matched for both straightening units, is very difficult. Another disadvantage is the marked plastic deformation of the wire which occurs as a result of the interaction of the two straightening units . This results in a high strain hardening and thus an unwanted embrittlement of the wire. The reject ratio, i.e. the proportion of wire which does - 3 -

not meet the desired quality requirements, is correspondingly high.

It is also known to dispense with the second straightening unit and, instead, not to wind the wire onto a reel after it emerges from the straightening unit, as can be the case when using two straightening units , but cut it into pieces of predetermined length. These pieces can be several metres long, or shorter. The wire can relax within the individual pieces , so that there is no excessive strain hardening on the one hand and no unwanted twist on the other. However, the disadvantage is that the wire which is to be further processed is much more awkward to handle in the form of pieces than if it were available on a reel.

The object of the invention is to improve the process mentioned at the outset for straightening wire, in which a straightening unit is used, in such a way that the wire is available for further processing in a low-stress and readily manageable state.

This object is achieved by a process for straightening wire which has the features of claim 1. Advantageous versions emerge from the dependent claims. The subject-matter of claim 8 is a device for carrying out such a process .

With the process according to the invention for straightening wire, a wire coming from a first reel is drawn through a straightening unit with straightening rolls . The straightening _ 4 _

unit rotates about a first axis which is defined by the longi_¬ tudinal direction of the path of the wire in the region of the straightening unit. After emerging from the straightening unit, the wire is wound onto a second reel, the diameter of which is greater than that of the first reel. The second reel rotates in accordance with the direction of rotation of the straightening unit about a second axis which is defined by the path of the wire leading tangentially onto the second reel.

With the process according to the invention, only one straightening unit is thus used, which can be adjusted much more easily to the properties of the wire to be straightened than would be the case when using two straightening units . After emerging from the straightening unit, the wire is wound up so that it is available in continuous form for further processing in subsequent processes which are the not the subject of the invention. Handling is thereby made much easier compared with wire pieces of predetermined length. The di.ameter of the second reel should be so great that the curvature of the wire wound onto it is so small that the wire automatically assumes a straight shape when removed from the second reel in subsequent processes, i.e. the wire is deformed merely in the elastic range and not plastically on the second reel. Because, when the wire is wound on, the second reel rotates about a second axis which lies essentially where the wire runs tangentially onto the second reel, i.e. along the axis of the wire, the wire can be wound on in a low-stress and twist-free state. The twist produced in - 5 -

the wire by the straightening unit is thus compensated when the wire is wound onto the second reel, by means of guiding the second reel accordingly.

The process according to the invention can be carried out cheaply, as the device needed to carry out the process is relatively simple and there is no difficult matched setting of two straightening units .• The straightened wire experiences only slight strain hardening and is therefore not embrittled. The reject ratio is correspondingly small.

The angular velocity of the rotation movement of the second reel about the second axis is preferably less than the angular velocity of the rotation movement of the straightening unit about the first axis . The optimum angular velocities depend on various parameters , in particular on the properties of the wire and on the speed at which the wire is drawn through the straightening unit. The angular velocities should be matched to each other in such a way that the wire is wound onto the second reel in a largely twist-free state, something which can be ascertained by means of tests .

In a preferred version, the first and second axes coincide, and the directions of rotation of the straightening unit about the first axis and of the second reel about the second axis are the same. This is the simplest geometry for carrying out the process. However, it is also conceivable that the wire is deflected - 6 -

after emerging from the straightening unit and ahead of the second reel (e.g. with the help of one or more deflecting rolls) and the first and second axes do not coincide. Such a configuration can make possible a space-saving device for carrying out the process; however, when setting the device it must be ensured that an additional twist possibly occurring when the wire is deflected is compensated in the correct manner by the rotation movement of the second reel.

While the wire is being wound up on the second reel, the distance between the winding axis of the second reel and the tangent along which the wire runs onto the second reel shifts, depending on the amount of wire already wound on. If the second axis is fixed, it accordingly does not coincide exactly, during the whole winding-on process, with the path of the wire leading tangentially onto the second reel. As long as the shift between the winding axis of the second reel and the tangent does not become too great, this deviation from the optimum geometry does not lead to inconvenient tensions in the wire wound up on the second reel. However, in a preferred version the shift, dependent on the amount of wire already wound on, of the path of the wire leading tangentially onto the second reel relative to thό winding axis of the second reel is compensated by displacing the second reel transversely relative to the second axis during the winding-on of the wire. The path of the wire leading tangentially onto the second reel can thereby be maintained on the second - 7 -

axis , so that optimum geometry conditions are constantly present in order to remove the twist from the wire.

The speed of drawing of the wire is preferably set by the wind_¬ ing speed of the second reel. The wire can be unwound from the first reel and drawn through the straightening unit with the help of the second reel.

In a preferred version of the process, the wire is moved through a cleaning bath after emerging from the straightening unit and ahead of the second reel. Oil which reached the wire in the straightening unit can be washed off in the cleaning bath.

A -device for carrying out the process according to the invention has a straightening unit with straightening rolls through which a wire coming from a first reel can be drawn and which is rotatable about a first axis which is defined by the longitudinal direction of the path of the wire in the region of the straightening unit, as well as a mounting and drive apparatus for a second reel, onto which the wire can be wound after emerging from the straightening unit, and the diameter of which is greater than that of the first reel and which is rotatable in accordance with the direction of rotation of the straightening unit about a second axis which is defined by the path of the wire leading tangentially onto the second reel. Depending on the configuration of the process carried out, components such as deflecting rolls or an apparatus for displacing the second reel transversely relative to the second axis are added to the device .

The invention is explained in more detail below with reference to an embodiment. The drawings show in

Figure 1 a schematic lateral overall view of a device for carrying out the process according to the invention,

Figure 2 an enlarged schematic view of the straightening unit according to Figure 1 and

Figure 3 a front view of the second reel, looking in the direction of the arrows from Figure 1.

In Figures 1 to 3 a device is represented with the help of which the process according to the invention for straightening wire can be carried out. In the embod.iment, wire 1 which is used for the manufacture of surgical needles is straightened. The wire 1 is delivered on a first reel 2 which preferably consists of plastic material. The wire 1 is already hardened in the embodiment, for which reason the surgical needles which are later manufactured from it do not require secondary hardening. As the first reel has a relatively small diameter, the wire 1 wound up on it is so markedly curved that it has to be straightened first before it is suitable for the production of surgical needles . A straightening unit 3 of conventional design, through which the - 9 -

wire 1 is drawn with the help of a second reel 4, serves to straighten the wire 1. The second reel 4 has a greater diameter than the first reel 2. The wire 1 wound onto the second reel 4 is elastically deformed, so that it automatically assumes a straight shape when it is unwound in subsequent processes. In the embodiment, the second reel 4 consists of wood.

The device shown in Figures 1 to 3 and the process carried out with its help are considered in more detail in the following.

The first reel 2 is rotatably attached to a holder 10 which is secured to a base 12. The holder 10 is fitted with a brake in order that, when the wire 1 is drawn through the straightening unit 3, a tensile stress can be built up. The rotation axis of the first reel 2 lies parallel to the paper plane of Figure 1. The wire 1 is unwound tangentially in a vertical direction from the first reel 2 and deflected over a deflector roll 14 into the horizontal direction.

Situated above the base 12 is the straightening unit 3, which is represented in enlarged view in Figure 2. The straightening unit 3 has a housing 20 in which straightening rolls 22 are rotatably fitted on adjustable mountings 24. The wire 1 enters the housing 20 via the entry end 26 and leaves it via the exit end 28. When the wire 1 is drawn through the straightening unit 3 under the drive action of the second reel 4, it moves in the direction of the arrow drawn in in Figure 2. - 10 -

The mountings 24 of the straightening rolls 22 are set in such a way that the curvature of the wire 1, which stems from the fact that it was wound up relatively narrowly on the first reel 2, is gradually reduced. To achieve this, the wire 1 is repeatedly deflected with the help of the straightening rolls 22, with the result that the path of the wire inside the housing 20 is wave-shaped. The wave amplitude decreases from the entry end 26 to the exit end 28,. i.e. the wire 1 increasingly assumes the desired straight shape. The setting of the straightening rolls 22 at the mountings 24 must be individually matched to the type of wire used and the diameter of the wire. The optimum setting must be established empirically.

The straightening unit 3 rotates about a first axis A-A, which is defined by the longitudinal direction of the path of the wire in the region of the straightening unit 3. In the embodiment, the first axis A-A coincides with the path of the wire outside the housing 20, as can be seen from Figure 2. The rotation movement of the straightening unit 3 about the first axis A-A results in largely isotropic properties of the wire 1 in a plane perpendicular to the first axis A-A. However, the wire 1 is also plastically deformed and given a twist. The drive unit needed to rotate the straightening unit 3 is located in the base 12.

After emerging from the straightening unit 3, the wire 1 is moved through a cleaning bath 30 which is arranged on a supporting arm 32 secured to the base 12. Oil which is necessary to - 11 -

operate the straightening unit 3 and can reach the wire 1 via the straightening rolls 22 is washed off from the wire 1 in the cleaning bath 30.

The wire 1 is wound up by the second reel 4. The second reel 4 has two guide disks 40 and a winding core 42 having a large diameter, see Figure 3. The second reel 4 is mounted rotatable about a winding axis B at a fitting arm 44 (see Figure 1). The winding axis B stands perpendicular to the paper plane of Figure 1 and lies parallel to the paper plane of Figure 3. The fitting arm 44 is secured to a support 46, the extension of which towards the straightening unit 3 is designed as a guide aid 48 for the wire 1, see Figure 1. The support 46 is located at the housing of a drive apparatus 50. The drive apparatus 50 contains a motor for rotating the second reel 4 about the winding axis B. The wire 1 is drawn through the straightening unit 3 and the cleaning bath 30 with the help of the second reel 4. The speed of drawing of the wire 1 can be set by the winding speed of the second reel 4, i.e. by its angular velocity during the rotary movement about the winding axis B . An even drawing speed is preferably applied.

The second reel 4 performs a further rotary movement. For this, the support 46 rotates with the fitting arm 44 and the second reel 4 about a second axis C (see Figure 1) which is defined by the path of the wire leading tangentially onto the second reel 4. In the embodiment, the second axis C stands perpendicular to - 12 -

the drawing plane of Figure 3 and lies in the drawing plane of Figure 1; it coincides with the first axis A-A. The motor which effects this rotation movement is also located in the drive apparatus 50.

The rotation movement of the second reel 4 about the second axis C takes place in the direction of the^" arrow drawn in in Figure 3. During the rotation movement about the second axis C, the direction of rotation of the second reel 4 is the same as the direction of rotation of the straightening unit 3 during its rotation movement about the first axis A-A. The angular velocity of the rotation movement of the second reel 4 about the second axis C is however less than the angular velocity of the rotation movement of the straightening unit 3 about the first axis A-A. The angular velocities are matched to each other in such a way that the wire 1 is wound onto the second reel 4 with the smallest possible twist or twist-free. The effect is based on the fact that the second reel 4, because of the rotation movement about the second axis C, is readjusted to the twisting of the wire 1 effected by the rotation movement of the straightening unit 3 about the first axis A-A.

As the amount of wire 1 already wound onto the second reel 4 increases, the path of the wire leading tangentially onto the second reel 4 moves in a direction away from the winding axis B and then no longer coincides exactly with the second axis C. However, in the embodiment this has only a small influence on - 13 -

the freedom from stress of the wire 1 wound onto the second reel 4 since, because of the large diameter of the second reel 4, the geometric conditions are still favourable even under these conditions .

Claims

- 14 -Claims

Process for straightening wire, in which a wire (1) coming from a first reel (2) is drawn through a straightening unit (3) with straightening rolls (22), the straightening unit (3) rotating about a first axis (A-A) which is defined by the longitudinal direction of the path of the wire in the region of the straightening unit (3), characterized in that, after emerging from the straightening unit (3), the wire ( 1 ) is wound onto a second reel ( 4 ) , the diameter of which is greater than that of the first reel (2) and which rotates in accordance with the direction of rotation of the straightening unit (3) about a second axis (C) which is defined by the path of the wire leading tangentially onto the second reel (4).

Process according to Claim 1, characterized in that the angular velocity of the rotation movement of the second reel (4) about the second axis (C) is less than the angular velocity of the rotation movement of the straightening unit (3) about the first axis (A-A).

Process according to Claim 1 or 2, characterized in that the first axis (A-A) and the second axis (C) coincide, and the directions of rotation of the straightening unit (3) about the first axis (A-A) and of the second reel (4) about the second axis (C) are the same. - 15 -

4. Process according to Cla.im 1 or 2, characterized in that the wire (1) is deflected after emerging from the straightening unit (3) and ahead of the second reel (4) and in that the first axis (A-A) and the second axis (C) do not coincide.

5. Process according to one of the previous claims, characterized in that, during the winding-on of the wire (1), the second reel (4) is displaced transversely relative to the second axis (C) in order to keep the path of the wire leading tangentially onto the second reel (4) on the second axis (C) and compensate the shift, dependent on the amount of wire (1) already wound on, of the path of the wire leading tangentially onto the second reel (4) relative to the winding axis (B) of the second reel (4).

6. Process according to one of the previous claims, characterized in that the wire (1) is moved through a cleaning bath (30) after emerging from the straightening unit (3) and ahead of the second reel (4).

7. Process according to one of the previous claims, characterized in that the speed of drawing of the wire (1) is set by the speed of winding of the second reel (4).

8. Device for carrying out a process according to one of Claims 1 to 7, - 16 -

- with a straightening unit (3) which has straightening rolls (22) and through which a wire (1) coming from a first reel (2) can be drawn and which is rotatable about a first axis (A-A) which is defined by the longitudinal direction of the path of the wire in the region of the straightening unit ( 3 ) , and

- with a mounting and drive apparatus (44, 46, 50) for a second reel ( 4 ) , onto which the wire ( 1 ) can be wound after emerging from the straightening unit ( 3 ) , and the diameter of which is greater than that of the first reel ( 2 ) and which is rotatable in accordance with the direction of rotation of the straightening unit (3) about a second axis (C) which is defined by the path of the wire leading tangentially onto the second reel (4).