Tool for cold drawing a metal wire

Abstract

A tool (10) for cold drawing a metal wire (4) is described. The tool comprises a succession of a sleeve (100) and a drawing die (200) in the advancement path of the metal wire; the sleeve comprises a hole (103) for the entry of the wire to be drawn and the drawing die comprises a conical hole (211 ). The tool comprises a first sleeve supporting casing (102), which comprises a seat (122) for the sleeve, and a second drawing die supporting casing (202); the first and second casings are coupled together so as to hold the sleeve and the drawing die in place to allow the advancement path of the metal wire from the sleeve to the drawing die. The first casing (102) comprises a hole (101 ) for the entry of the metal wire up to the seat (122) of the sleeve so as to precede the sleeve hole (103) in the advancement path of the metal wire; the entry hole (101 ) of the first casing is coaxial to the sleeve hole (103) and has a length (L) comprised between 20 and 100 mm.

Description

[0001] TOOL FOR COLD DRAWING A METAL WIRE

[0002] TECHNICAL FIELD

[0003] The present invention relates to a tool for cold drawing a metal wire, in particular the sleeve supporting casing; the present invention also relates to an apparatus for cold drawing a metal wire.

[0004] PRIOR ART

[0005] As is well known, drawing, i.e. the section reduction of a wire or other metal object through drawing dies, is obtained by pulling the material through the drawing die by means of drawing machines.

[0006] A commonly used technique, especially for round section metal wires, makes it possible to draw a metal wire by means of successive section reductions resulting from the wire passing through a number of drawing units through which the metal wire to be drawn is advanced and contained, together with a wire lubricant containment tank, in a single drawing apparatus. Lubrication is obtained by interposing the lubricant between the metal wire and the drawing units due to both the movement of the wire towards the drawing units and the spatial geometric profile of the drawing units.

[0007] Each drawing unit comprises a box and a die-holder unit inside which the tool for reducing the metal wire section is placed. Said tool comprises a succession of a sleeve and a drawing die in the advancement path of the metal wire; the sleeve comprises a hole for the entry of the wire to be drawn and the drawing die comprises a conical hole. First sleeve supporting means and second drawing die supporting means are provided, coupled to each other so as to hold the sleeve and the drawing die in position to allow the advancement path of the wire from the sleeve to the drawing die.

[0008] By assembling said tool in the die-holder unit, the wire drawing becomes a very simple operation.

[0009] However, the increasing use of lubricants without substances toxic to health and the environment, such as borax, makes it more difficult to lubricate the metal wire to be drawn. An object of the present invention is therefore to overcome the drawbacks described above.

[0010] A further object is to achieve such an objective in the context of a rational, effective and cost-effective solution.

[0011] These objects are achieved by the features of the invention set forth in the independent claim. The dependent claims outline preferred and / or particularly advantageous aspects of the invention.

[0012] DISCLOSURE OF THE INVENTION

[0013] In particular, the invention makes available a tool for cold-drawing a metal wire, said tool comprising a succession of a sleeve and a drawing die in the advancement path of the metal wire, said sleeve comprising a hole for inserting the wire to be drawn and said drawing die comprising a conical hole, a first sleeve supporting casing, comprising a seat for the sleeve, and a second drawing die supporting casing, said first and second casings being coupled together so as to hold said sleeve and said drawing die in place to allow the advancement path of the metal wire from the sleeve to the drawing die, said first casing comprising a hole for the entry of the metal wire up to the sleeve seat so as to precede the sleeve hole in the advancement path of the metal wire, said hole of the first casing being coaxial to the sleeve hole, characterised in that the length of the entry hole of the metal wire of the first casing in the advancement path of the metal wire is comprised between 20 and 100 mm.

[0014] Thanks to the present invention, it is possible to increase the amount of lubricant in the drawing tool due to the Venturi effect of the hole of the first casing.

[0015] Thanks to the present invention, it is possible to make a sleeve supporting casing of a tool for cold drawing a metal wire, said casing comprising a seat for the sleeve of the drawing tool and a hole for the entry of the wire to be drawn up to the sleeve seat, characterised in that the length of the entry hole of the metal wire in the advancement path of the metal wire is comprised between 20 and 100 mm.

[0016] Preferably, the length is between the edge of the initial opening of the hole of the first casing and the initial edge of the sleeve seat in the advancement path of the metal wire. More preferably, the length of the entry hole of the metal wire of the first casing is between 25 and 100 mm.

[0017] Even more preferably, the length of the entry hole of the metal wire of the first casing is 27.5 mm.

[0018] Thus, the size of the sleeve supporting casing is not increased considerably, while at the same time obtaining a good Venturi effect on the lubricant.

[0019] Preferably, the first casing is fitted on said second casing by press-in fit.

[0020] Thus, both the first and second casings do not have threads as the sleeve and the drawing die, and the assembly of the first casing onto the second casing is easier.

[0021] Still according to the invention, it is possible to make an apparatus for cold drawing a metal wire, said apparatus comprising a wire lubrication tank and a drawing tool arranged at the outlet of said tank, said drawing tool being defined as above.

[0022] Preferably, the apparatus comprises an outer body provided therein with a tank containing a lubricant, said tank having, at a first end, an entry hole of the metal wire to be drawn and, at a second end, opposite to the first end, said drawing tool which is held in position on the outer body by a threaded cap attached to the outer body and crossed by a discharge hole for the exit of the drawn wire.

[0023] BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Further features and advantages of the invention will be more apparent after reading the following description provided by way of a non-limiting example, with the aid of the figures illustrated in the accompanying tables.

[0025] Figure 1 shows a cross-section of an apparatus for cold drawing a metal wire comprising the tool according to an embodiment of the present invention;

[0026] Figure 2 shows in more detail the tool of Figure 1 with the sleeve separated from the drawing die;

[0027] Figure 3 shows in more detail the tool of Figure 1 with the sleeve coupled with the drawing die;

[0028] Figure 4 shows in more detail the sleeve supporting means of Figure 2;

[0029] Figure 5 shows in more detail the sleeve supporting means of a tool for cold drawing a metal wire according to a variant of the embodiment of the present invention;

[0030] Figure 6 shows a cross-section of an apparatus for cold drawing a metal wire comprising the tool according to the variant of the embodiment of the present invention;

[0031] Figure 7 shows in more detail the tool of Figure 6 with the sleeve separated from the drawing die;

[0032] Figure 8 shows in more detail the tool of Figure 6 with the sleeve coupled with the drawing die.

[0033] BEST MODE TO IMPLEMENT THE INVENTION

[0034] Referring in particular to these figures, an apparatus for cold drawing a metal wire is globally referred to as 10. The apparatus comprises an outer body 1 provided therein with a tank 2 containing calcium or sodium stearates or other lubricating material 300. Said tank 2 has, at one side end, an entry hole 3 for the passage of a metal wire 4 (steel, copper, aluminium, etc.) to be drawn. The diameter of the hole 3 is larger than the section of the metal wire 4.

[0035] The tank 2 is provided, at its other side end opposite to the side end provided with the entry hole 3, with a drawing tool 10 according to the present invention which is adapted to draw the metal wire 4; the tool 10 is held in position on the body 1 by a threaded cap 18 attached to the outer body 1 and crossed by a discharge hole 17 for the exit of the wire 4.

[0036] Preferably, the tank 2, at its side end opposite to the side end provided with the entry hole 3, comprises a hole 31 communicating with a drawing die holder assembly 32 in which the tool 10 is housed. Preferably, the tool 10 is arranged entirely in the drawing die holder assembly 32 without coming out thereof, that is, without elements or extensions that are also partially internal to the tank 2. The drawing die holder assembly 32 is mounted so as to be adjacent to, and preferably in contact with, the hole 31 of the tank 2.

[0037] The tool 10, better shown in Figures 2 and 3, comprises, in the advancement path of the metal wire 4, a sleeve 100 comprising a body having a circular section, generally made of tungsten carbide commonly referred to as carbide or widia, provided with a hole 103 which in its central portion 104 has a cylindrical shape with a diameter slightly larger than that of the incoming wire 4 and in its initial portion 105 preferably has a truncated-cone shape with a decreasing diameter to ease the entry of the metal wire 4, as better visible in Figures 2 and 3. The opening or base with the smaller diameter of the initial truncated- cone-shaped portion 105 of the hole 103 coincides with the section of the cylindrical hole of the central portion 104. The sleeve 100 is supported and contained in a casing or supporting means 102, generally made of steel.

[0038] As better visible in Figure 2, the sleeve 100 has a truncated-cone extension 109 at one end. Said casing 102 also has a lower annular portion 106 and an upper annular portion 107; the upper annular portion 107 has a larger diameter than the lower annular portion diameter so as to give the casing 102 a cap shape.

[0039] The tool 10 comprises, in the advancement path of the metal wire 4, after the sleeve 100, the drawing die 200 having a circular section body, generally made of widia, comprising a funnel-shaped entry cavity 210 and a conical hole which has, in its central portion 211 , a truncated-cone shape with a decreasing diameter and whose longitudinal axis of symmetry A coincides with the axis of symmetry of the hole of the sleeve 100. The drawing die 200 is supported and contained in a casing 202, generally made of steel, which has an upper annular protrusion 203 on the outer cylindrical shell 204.

[0040] The drawing die 200 is held in place or position, thereby similarly providing for the positioning of the sleeve 100, by coupling the upper annular protrusion 203 of the casing 202 of the drawing die 200 with the lower annular protrusion 106 of the casing 102 of the sleeve 100. This is implemented by manually press-in fitting the casing 102 onto the casing 202. In such a case, there is no threaded coupling between the casings 102 and 202 since both the upper annular protrusion 203 of the casing 202 of the drawing die 200 and the lower annular protrusion 106 of the casing 102 of the sleeve 100 have no threads. There is only one press-in fit of the casing 102 on the casing 202, preferably a manual press-in fit; as already stated above, the tool 10, and thus the assembly of the sleeve 100 and the drawing die 200, is held in position on the body 1 by a threaded cap 18 attached to the outer body 1 .

[0041] Preferably, the casing 102 of the sleeve 100 and the casing 202 of the drawing die 200 are coupled to each other so that the end part of the sleeve 100 is arranged partially inside the initial part of the drawing die 200.

[0042] Preferably, the casing 102 of the sleeve 100 and the casing 202 of the drawing die 200 are coupled to each other so that there are no elements arranged between the sleeve 100 and the drawing die 200 so that the metal wire 4 can pass from the sleeve 100 directly into the drawing die 200; that is, the metal wire 4 can pass from the sleeve 100 directly into the drawing die 200 without crossing elements interposed between the sleeve and the drawing die in the advancement path of the metal wire.

[0043] Preferably the casing 102 of the sleeve 100 and the casing 202 of the drawing die 200 are coupled to each other so that the sleeve 100, and also its casing 102, cannot rotate with respect to the drawing die 200 and to its casing 202; i.e. the sleeve 100, and its casing 102, and the drawing die 200, and its casing 202, are in fixed engagement after coupling by press-in fit. The assembly of the casings 102 and 202, once coupled by pressin fit, constitutes a single block without relative rotations of inner elements with respect to other inner elements.

[0044] There is also an annular gasket 108 on the portion 110 of the lower annular protrusion 106 which abuts against the annular protrusion 203 of the casing 202 of the drawing die 200 when the sleeve 100 is coupled with the drawing die 200.

[0045] During the drawing operation in the described structure, the metal wire 4 passing through the tank 2 draws the lubricant 300 contained therein. The metal wire 4 then passes through the sleeve 100 with no reduction in the diameter and through the drawing die 200 with a truncated-cone hole where drawing is performed. Together with the metal wire 4, the lubricant reaches the sleeve 100 where it has the pressure and retains the lubricating properties suitable for properly lubricating the wire 4 subject to drawing.

[0046] In the advancement path of the metal wire 4, the casing 102 comprises a wire entry hole 101 , preferably circular, which precedes the hole 103 of the sleeve in the advancement path of the metal wire 4, as better shown in Figure 4; the hole 101 of the support means 102 is coaxial to the hole 103 of the sleeve.

[0047] Preferably the sleeve 100 is arranged in the casing 102 so that the wire 4 can pass from the hole 101 directly into the hole 103 of the sleeve 100; i.e. the metal wire 4 can pass from the hole 101 directly into the hole 103 of the sleeve 100 without passing through interposed elements in the advancement path of the metal wire. Preferably the hole 101 of the casing 102 ends where the seat of the sleeve 100 begins, in particular where the hole 103 of the sleeve 100 begins.

[0048] According to the invention and as best visible in Figure 4, the length L of the entry hole of the metal wire 101 of the first casing 102 in the advancement path of the metal wire is comprised between 20 and 100 mm; in particular, the length L is comprised between the edge 120 of the initial opening 111 of the hole 101 of the casing 102 and the initial edge 121 of the seat 122 of the sleeve 100 in the advancement path of the metal wire and varies in a range between 20 and 100 mm. More specifically, the length L of the hole 101 coincides with the distance between the edge 120 of the initial opening 111 of the hole 101 of the casing 102 and the edge 155 of the initial opening 105 of the hole 103 of the sleeve 100, with the sleeve inserted into the seat 122, and is comprised between 20 and 100 mm. Preferably, the edge 120 of the initial opening 111 of the hole 101 of the support means 102 coincides with the upper face 130 of the casing 102.

[0049] Preferably the hole 101 is a cylindrical hole, i.e. it has a constant circular section, for most of its length L, i.e. for more than half of its length L while the initial part is of the countersink type. Even more preferably the hole 101 is cylindrical for at least three quarters of its total length L. In particular the hole 101 has a cylindrical shape for almost its entire length L, except for the initial part which is of the countersink type. Preferably the cylindrical shape of the hole 101 allows to obtain a good Venturi effect on the lubricant 300.

[0050] In other words, the hole 101 has a length L greater than the holes of the sleeve supporting means in the known wire drawing tools.

[0051] The greater length of the hole 101 allows for a greater Venturi effect and thus a greater lubrication of the metal wire to be drawn. This makes it possible to obtain a good lubrication of the metal wire even when using lubricants that do not contain substances that are toxic to health and the environment, such as borax.

[0052] More preferably, the length L of the hole 101 is between 25 and 100 mm.

[0053] In order not to considerably increase the size of the casing 102 while obtaining a good Venturi effect on the lubricant 300, and thus good lubrication of the metal wire 4 passing through the tool 10, the hole 101 preferably has a length L of 27.5 mm.

[0054] However, the holes 101 can be made longer as required; for example, according to a variant of the embodiment of the present invention shown in Figures 5-8, a hole 101 with a length L of 57.5 mm allows for a very good Venturi effect to increase the amount of lubricant 300 on the metal wire passing through the tool 10. Figures 5-8 show a tool for cold drawing the metal wire that is at all similar to the tool of Figures 1 -4 but with the only difference being a longer hole 101 and consequently a longer casing 102 supporting the sleeve 100.

[0055] Preferably, the entry hole 101 for the metal wire 4 has a diameter smaller than the initial opening 11 1 for most of its length; for example, a hole 101 with a length L of 27 mm has a diameter of 6.5 mm for a length of 20.5 mm. Preferably the edge 120 of the initial opening 11 has a diameter of 20.5 mm.

[0056] Preferably, the hole 101 has a diameter smaller than the initial opening 105 of the sleeve hole in the advancement path of the metal wire; the initial opening 111 coincides with the largest base of the truncated cone-shaped initial portion 105 of the hole 103. Thus, the lubricant 300 drawn from the metal wire 4 does not return to the tank 2 but remains within the space between the truncated-cone portion 105 of the hole 103 and the metal wire 4. Thus, the efficiency of cold-drawing a metal wire is improved even at low drawing speeds. The presence of said space allows for an efficient cold drawing of the metal wire 4 at both high speeds, typically 40 m / s, and low speeds, typically 1 m / s. In fact, the lubrication of the metal wire 4 obtained at a drawing speed of 1 m / s is considerably greater than that obtained at the same drawing speed with a known tool.

[0057] Furthermore, the tool according to the present invention allows to use a lubricant 300 at high pressure, e.g. at 200 atm; this improves the wire drawing efficiency.

[0058] Improved lubrication of the metal wire 4 results in a longer service life of the tool 10 than known tools.

[0059] The invention thus conceived is susceptible to several modifications and variations, all falling within the scope of the inventive concept.

[0060] Moreover, all details can be replaced by other technically equivalent elements.

[0061] In practice, the materials used, as well as the contingent shapes and sizes, can be what- ever according to the requirements without for this reason departing from the scope of protection of the following claims.

Claims

CLAIMS1. Tool (10) for cold-drawing a metal wire (4), said tool comprising a succession of a sleeve (100) and a drawing die (200) in the advancement path of the metal wire, said sleeve comprising a hole (103) for inserting the wire to be drawn, and said drawing die comprising a conical hole (211 ), a first sleeve supporting casing (102), comprising a seat (122) for the sleeve, and a second drawing die supporting casing (202), the first and second casings being coupled to each other so as to hold said sleeve and said drawing die in place to allow the advancement path of the metal wire from the sleeve to the drawing die, said first casing (102) comprising a hole (101 ) for inserting the metal wire up to the seat (122) of the sleeve so as to precede the sleeve hole (103) in the advancement path of the metal wire, said hole (101 ) of the first casing being coaxial to the sleeve hole (103), characterised in that the length (L) of the entry hole (101 ) of the metal wire of the first casing in the advancement path of the metal wire is comprised between 20 and 100 mm.

2. Tool (10) according to claim 1 , characterised in that the length (L) is between the edge (120) of the initial opening (111 ) of the hole (101 ) of the first casing (102) and the initial edge (121 ) of the seat (122) of the sleeve (100) in the advancement path of the metal wire3. Tool (10) according to claim 1 or 2, characterised in that the length (L) of the entry hole of the metal wire of the first casing is comprised between 25 and 100 mm.

4. Tool (10) according to any of the preceding claims, characterised in that the length (L) of the entry hole of the metal wire of the first casing is 27.5 mm.

5. Tool (10) according to any one of the preceding claims, characterised in that said first casing (102) is mounted on said second casing (202) by press-in fit.

6. Tool (10) according to any one of the preceding claims, characterized in that the hole (101 ) for the entry of the metal wire of the first casing (102) in the advancement path of the metal wire has a cylindrical shape for most of its length.

7. Tool (10) according to claim 6, characterized in that the hole (101 ) for the entry of the metal wire of the first casing (102) in the advancement path of the metal wire has a cylindrical shape for at least three quarters of its length.

8. Tool (10) according to any one of the preceding claims, characterized in that said first casing (102) once mounted on said second casing (202) cannot rotate withrespect thereto.

9. Tool (10) according to any one of the preceding claims, characterized in that the first and second casing are coupled to each other without interposed elements in the advancement path of the metal wire so that the metal wire (4) can pass from the sleeve directly into the drawing die.

10. Apparatus for cold drawing a metal wire (4), said apparatus comprising a wire lubrication tank (2) and a drawing tool (10) arranged at the outlet of said tank (2), said drawing tool (10) being defined as in any one of claims 1 to 5.

11. Apparatus according to claim 10, characterised in that it comprises an outer body (1 ) provided therein with a tank (2) containing a lubricant (300), said tank (2) having, at a first end, a hole (3) for the entry of the metal wire (4) to be drawn and, at a second end opposite to the first end, said drawing tool (10) which is held in position on the outer body (1 ) by a threaded cap (18) attached to the outer body (1 ) and crossed by a discharge hole (17) for the exit of the drawn wire.12.Apparatus according to claim 10, characterized in that said drawing tool (10) does not extend inside the tank (2).

13. Apparatus according to claim 10, characterized in that the hole (101 ) for the entry of the metal wire of the first casing (102) in the advancement path of the metal wire has a cylindrical shape for most of its length.

14. Apparatus according to claim 13, characterized in that the hole (101 ) for the entry of the metal wire of the first casing (102) in the advancement path of the metal wire has a cylindrical shape for at least three quarters of its length.15.Apparatus according to claim 10, characterized in that said first casing (102) once mounted on said second casing (202) cannot rotate with respect thereto and in that the first and second casing are coupled to each other without interposed elements in the advancement path of the metal wire so that the metal wire (4) can pass from the sleeve directly into the drawing die.

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