Pressure wire drawing tool with detachable pressure and drawing dies

Abstract: A tool (1) suited to the pressure wire drawing of wire rods and wires having a hole (3) passing through it, includes a casing (2,17) detachably disposed within the casing (2,17), a wire drawing nib (10) separate from the pressure die (5) and detachably disposed within the casing (2,17) and aligned with the above mentioned hole (3), and at least one gasket (9) between the wire drawing nib (10) and the pressure die (5) designed to make the passage formed between the pressure die (5) and wire drawing nib (10) leak-proof.

Description: BACKGROUNG OF THE INVENTION 1. Field of the Invention The invention consists of an improved tool particularly suited to the pressure wire drawing of wire rods and wires, with a separate and detachable pressure die and drawing die. A tool according to the preamble of claim 1 is e.g. know from GB-A-2 077 646. 2. Description of the Related Art The operation of wire drawing, well known in the prior art, consists of reducing the diameter of wire rods or wires by means of plastic deformation effected by a tool of appropriate shape known as a wire drawing die. Wire is passed through the above mentioned tool by means of electrically driven bobbins so that the diameter of the wire is reduced during this forced passage. One critical aspect of the whole operation is that of lubrication of the wire, which must be optimum in order to prevent the tool from seizing. The length of the entrance cone of the wire drawing die, which acts as a pump for the lubricant due to the continuous movement caused by the sliding of the lubricant in the tool, improves the attachment of the lubricant to the wire, but there remain problems of sealing inside the wire drawing die itself. A well-known prior solution is that of wire drawing dies consisting of a single wire drawing core nib made of tungsten carbide encased by shrink-fitting in a case that is carefully shaped on the inside, altogether this constitutes one single piece which is fitted directly on machines designed for wire drawing operations. A more recent tool has a case of steel, made of two reversible mating parts, where the upper part is shaped on the inside to house a tungsten carbide die, while the lower part is designed to contain a wire drawing core nib, also made of tungsten carbide, designed to plastically deform the wire rod or wire. Although these devices meet the technical requirements described above, they nevertheless have the following disadvantages. As the single piece tool is worn it must be completely replaced with an increase in total costs since, because of its components, the worn tool becomes a special waste requiring adequate disposal. Furthermore, and again for reasons of cost, the dimensions of the tungsten carbide nib, which in this case cannot be recovered in any way, are reduced to the indispensable minimum with consequent negative results for lubrication. The quality of the finished product and the machining rate are thereby lowered. Tools consisting of more than one part that can be assembled and taken apart present the inconvenience of possible leakages of lubricant between the pressure die and the drawing nib as well as that of the steel case yielding due to the high working pressures. In this case too, costs are markedly increased because of both the mechanical breakages described above and the maintenance necessary to dismantle and replace damaged parts. Production speed in this case too, may not be such as to exploit the maximum potential speed of wire drawing machines due to problems connected with lubrication caused by the above described leakages. The object of this invention is to overcome the above drawbacks of the prior art. SUMMARY OF THE INVENTION The invention consists therefore of a very reliable and long lasting improved tool particularly suited to the pressure wire drawing of wire rods and wires, with disassemblable pressure die and drawing die, which by optimizing lubrication increases production speeds, lowers costs and thereby improves the entire wire drawing operation. Briefly, for achieving the above and other objects an improved tool particularly suited to the pressure wire drawing of wire rods and wires, with disassemblable pressure die and drawing die, according to the invention, comprises a disassemblable case having a throughgoing hole, containing a pressure die and a wire drawing core nib which are separate from each other and aligned with said hole, wherein at least one gasket is provided between the wire drawing core nib inserted at the bottom of said case and the pressure die located at the top of said case, said gasket being designed to make the passage between said pressure die and said wire drawing core nib leak-proof. The improved tool according to the invention is characterized by the features of Claim 1. The novel tool suited to the pressure wire drawing of wire rods and wire, with pressure die and drawing die separate and detachable according to the invention, provides the following advantages. Lubrication is optimum and without leaks, allowing constantly faster production speeds and therefore a lower overall cost for the finished product. Perfect lubrication also allows greater durability of the drawing nib which is the part most subject to wear because of the high operating pressures during the operation of wire drawing machines, consequently maintenance intervention is required less frequently. A further advantage of the invention is that its great simplicity of manufacture allows the manufacturing costs of its various parts to remain almost unchanged in relation to those already existing for the parts available on the market. BRIEF DESCRIPTION OF THE DRAWINGS Other characteristics, advantages and details of the improved tool particularly suited to the pressure wire drawing of wire rods and wires, with a separate and detachable pressure die and drawing die according to the invention, will become more apparent from an examination of the following description with reference to the attached drawings showing by way of a not limitative example two preferred embodiments of the invention, where: Fig. 1 is an exploded perspective view of a first embodiment of the improved tool suited to the pressure wire drawing of wire rods and wires, according to the invention; Fig. 2 is a cross section view of the first embodiment of the tool according to the invention illustrated in Figure 1; Fig. 3 is an exploded perspective view of a second embodiment of the tool suited to the pressure wire drawing of wire rods and wires, according to the invention; and Fig. 4 is a cross section view of the second embodiment of the tool according to the invention illustrated in Figure 3. DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the numbers in Figures 1 and 2, a first embodiment of the tool 1, particularly suited to the wire drawing of wire rods and wires according to the invention, comprises a case with a hole through the center, preferably made of steel, which has an upper part 2, and a lower part 17. Said upper part 2, has a central hole 3 passing through it, forming a first inlet for the wire or wire rod to be drawn and an outer thread 4, for removably engaging the lower part 17. Into said upper part 2, a pressure die 5, advantageously made of tungsten carbide,is inserted. This pressure die has a central throughgoing hole 6, the upper section of which has a truncated cone shaped surface 7, which joins a subsequent cylindrical portion 8. Below the above mentioned pressure die 5, a wire drawing core nib 10 is located, which is suitably engaged in the lower part 17 of the case of the device 1, according to this embodiment of the invention. Said core nib is also advantageously made of tungsten carbide and is provided with a top tapering portion 11, joining a seating 13 provided to house a gasket 9. The seating 13 defined moreover a central throughgoing hole 12, which has an inner frustum of cone shaped surface section 14, meeting with a subsequent cylindrical section 15 ending with a tapering section 16. The gasket 9, advantageously made of copper, has the function of sealing the joint between the pressure die 5 and the wire drawing nib 10 under all operating conditions. The lower part 17 has a cylindrical outer surface and a hole 19 passing through the center of it, with a thread 18 at the top to allow it, as described previously, to be connected to and detached from the upper part 2 and a truncated cone shaped section 20, at the bottom, designed to house the wire drawing nib 10. Finally, it should be noted that once the tool according to the invention is assembled, the holes 3, 6, 12 and 19 are all perfectly aligned, each with the others. With reference to the numbers in Figures 3 and 4, a second embodiment of the tool 21, particularly suited to the wire drawing of wire rods and wires according to the invention, comprises a case with a hole through the center, preferably made of steel, which has an upper part 22 and a lower part 34, which can be connected together and detached from each other. The upper part 22 has a central hole passing through it, 23, this being the initial entrance for the wire or wire rod to be drawn and a thread 24 on the outside. The hole 23 is designed to house a pressure die 25, this too being advantageously made of tungsten carbide. This pressure die has a hole 26 passing through the center of it, the upper section of which has a truncated cone shaped surface 27, which joins a subsequent cylindrical shaped surface 28. A gasket 29, again made of copper, separates the pressure die 25 from a wire drawing nib 30, made of tungsten carbide and also having a hole 31 passing through the center of it. The above mentioned wire drawing nib 30 is inserted into the lower part 34, of the case of the tool 21 according to this embodiment of the invention and the above mentioned hole 31 has a truncated cone shaped inner surface 32 followed by a cylindrical shaped section 33. The lower part of the case 34 also has a central hole 35 passing through it with a thread on the inside allowing it to be joined to and detached from the above mentioned upper part 22 of the case. Finally, below the threaded section 36, the lower part of the case 34 has a truncated cone shaped section 37 designed to house the wire drawing nib 30. In this case too, once the tool according to this embodiment of the invention has been assembled, the holes 23, 26, 31 and 35 passing through the component parts of the invention are all perfectly aligned each with the others. Naturally the shape and dimensions of the various components of which the improved tool particularly suited to the pressure wire drawing of wire rods and wires, with the separate and detachable pressure die and drawing die, may differ according to differing requirements, but remain, however, within the scope of the invention as defined by the appended claims. Once assembled the tool 1 or 21, according to the embodiment of the invention, can be connected without any modifications on any existing wire drawing machine. The wire rod or wire to be drawn is inserted into the entrance hole 3, 23 of the upper part of the case and is passed through the tool 1, 21 according to the embodiment of the invention by means of electric motor driven coils. The lubricants mainly used such as oils, soaps and calcium or sodium stearates are also introduced through the entrance hole 3, 23, and are fed along the wire by means of the pump action generated by the continuous movement of the wire and the truncated cone section 7, 27 at the entrance of the pressure die 5, 25, immediately after the entrance hole 3, 23. The copper gasket 9, 29 located between the pressure die 5, 25 and the drawing nib 10, 30, then prevents the above mentioned lubricant from escaping to the outside, keeping it as firmly attached as possible to the wire that is being drawn, thereby guaranteeing optimum lubrication. In fact the temperatures and pressures created inside the drawing nib 10, 30 during the operation are considerably different from those found inside the pressure die 5, 25, and consequently the deformation to which these two parts are subject is also different. The presence between them of a gasket 9, 29, made of a material with considerably different mechanical properties functions to seal the join between them by exploiting the difference in susceptibility to deformation of the material of which the above mentioned gasket 9, 29 is made and this perfectly compensates for the difference in deformation of the pressure die 5, 25 and the nib 10, 30. This also has the advantage of preventing the possible breakage, by bursting, of the outer steel case 1, 21 of the tool according to the embodiment of the invention. The speed of current wire drawing machines can therefore be exploited to the maximum with all the consequent advantages previously described, because the inconveniences due to imperfect lubrication have been eliminated.

Claims: A tool (1, 21) for pressure drawing rods and wires by separate and detachable pressure and drawing dies, said tool comprising a disassemblable casing (2, 22, 17, 34) comprising a casing upper part (2, 22) and a casing lower part (17, 34), that can be threadedly connected to one another, said casing upper part (2, 22) having a throughgoing central hole (3, 33) and said casing lower part (17, 34) having a corresponding throughgoing hole (19, 35) to be aligned with said throughgoing hole of said upper part, said tool further comprising a pressure die (5, 25), a wire drawing core nib (10, 30) and at least one gashet (9, 29) arranged between said pressure die (5, 25) and said wire drawing core nib (10, 30) for tightly sealing the passage between them, characterized in that said pressure die (5, 25) is removably contact-engaged in said throughgoing hole (3, 33) of said upper part (2, 22) of said casing and said wire drawing core nib (10, 30) is removably contact-engaged in said throughgoing hole (19, 35) of said lower part (17, 34) of said casing. A tool, according to Claim 1, characterized in that said throughgoing hole (19, 35) of said casing lower part (17, 34) has a truncated cone shaped section below a threaded surface (18, 36 of said casing lower part. A tool, according to Claims 1 and 2, characterized in that said pressure die (5, 25) has a throughgoing central hole (6, 26), comprising a first section having a truncated cone shape, followed by a second cylindrical shape section. A tool, according to one of the preceding claims, characterized in that said wire drawing nib (10, 30) has a first section with a truncated cone shape followed by a second cylindrical shaped section. A tool, according to one of the preceding claims, characterized in that said wire drawing nib (10, 30) is countersunk (11) at its top followed by a seat (13) to house said gasket (9), said wire drawing nib beibg countersunk at its bottom. A tool, according to one of the preceding claims, characterized in that said upper (2, 22) and lower parts (17, 34) of said casing (2, 22) are made of steel. A tool, according to Claim 1, characterized in that said pressure die ( 5, 25) and said wire drawing core nib (10, 30) are made of tungsten carbide and said gasket (9, 29) is made of copper.

Inventors: BELLINA FERRUCCIO, BELLINA, FERRUCCIO
Applicants: TECNOVO SRL, TECNOVO S.R.L.
Application year: 1998
Main classification: B21C3
IPC codes: B21C3