Patent Application
20080173063
The present invention relates to a die assembly for the cold drawing of wire both for wet and dry applications.
In wire drawing processes, the drawing of wire stock through a drawing-die assembly generates heat during the reduction of the diameter of the wire stock. Lubricants are generally applied to help reduce this heat of drawing.
Additional methods directed towards reducing this heat of drawing include use of a pressure die prior to a drawing die to increase the amount of lubricant separating the drawing die from the wire during drawing, improving the lubricant properties such as melting point, fat content and viscosity, improving the lubricant carrier by adding polomerized materials in lieu of borax or changing the drawing machine after drawing.
Examples of equipment applied after the drawing die include using a larger drawing block, improvement of cooling in the drawing block by means such as reducing the drawing block thickness, blowing air over the wire on the drawing block, and changing the method of water application to the inside of drawing blocks from spray jets to narrow gap cooling.
Increasing the outside drawing die holder surface area of a pressure-die drawing die assembly, e.g. the wire drawing assembly of U.S. Pat. No. 5,402,664, by cutting grooves is an example of another approach to improve heat transfer. However this approach, exacerbated by ineffective interference fit between the drawing nib and case, has created marketplace issues with circumferentially and axially cracked nibs for this particular wire drawing assembly.
Related art that addresses these and other problems includes the following patents.
U.S. Pat. No. 1,896,674, issued to Longwell on Feb. 7, 1933, discloses a wire drawing apparatus having means for forcing lubricant between a die and the material being drawn during the drawing process, under sufficient pressure to urge the lubricant between the die and the work and includes a lubricant-expelling system for pressure developed therebetween.
U.S. Pat. No. 2,028,652, issued to Mulatier on Jan. 21, 1936, discloses an apparatus having several dies disposed in succession with each other co-axially in the same die-holder with a liquid coolant passed between.
U.S. Pat. No. 2,539,716, issued to Bairstow et al. on Jan. 30, 1951, discloses a lubricating tungsten carbide die holder for wire coated with a dry lubricant.
U.S. Pat. No. 3,740,990, issued to Prajanar et al. on Jun. 26, 1973, discloses a pressure drawing die designed for drawing wires, rods and tubes made of materials having varied mechanical properties, whereby use is made of the effect of hydrodynamic friction. The drawing die incorporates a system of dies with a pressure sleeve with hydrodynamic action. A cooling system is built into the drawing-die body or housing. The inlet portion of the pressure sleeve extends outside the body through the orifice in a pressure nut. Between dies a seal in a form of labyrinths and metal powders is provided. The working dies are provided with metal jackets which separate the die core from the pressure mounting.
European Patent Application No. EP0175497, inventor New, published on Mar. 26, 1986, discloses a die for tube drawings comprising a housing, a die member in a bore in the housing and a screw-threaded collar engaging a screw-threaded portion of the bore. The die member and bore are tapered. Rotation of the collar exerts axial pressure on the die member to give fine adjustment of the die internal dimension..
U.S. Pat. No. 5,189,897, issued to Lionetti et al. on Mar. 2, 1993, discloses a method and apparatus for drawing steel wire to produce high tensile strength, steel wire with increased torsional ductility. The wire is drawn through a plurality of standard dies in a wire drawing machine. The cross section of the wire is reduced by a constant reduction of about 15% to about 18% at each of the standard dies with the exception of the final two dies. The wire is then reduced by about 10% to about 90% of the typical reduction at the next to last die and the remainder of the reduction at the final die.
U.S. Pat. No. 5,402,664, issued to Sarver et al. on Apr. 4, 1995, discloses a wire drawing die assembly which has removable pressure and draw nibs held in screw-together holders. The pressure nib projects somewhat from its holder and presses the draw nib into a converging passageway in the draw nib holder. A lubricant pressure chamber is formed between the nibs for lubricant which is introduced through the front end of the pressure nib. When the draw nib becomes worn, the holders can be separated and the worn nib can be readily replaced.
U.S. Pat. No. 5,916,323, issued to Bellina on Jun. 29, 1999, discloses a tool suited to the pressure wire drawing of wire rods and wires having a hole passing through it, includes a casing detachably disposed within the casing, a wire drawing nib separate from the pressure die and detachably disposed within the casing and aligned with the above mentioned hole, and at least one gasket between the wire drawing nib and the pressure die designed to make the passage formed between the pressure die and wire drawing nib leak-proof.
U.S. Pat. No. 6,026,672, issued to Miller on Feb. 22, 2000, discloses a inventive pressure die holder comprised of an elongate hollow steel cylinder which receives a series of dies in an interior cavity. The dies are maintained within the cavity by means of a cap which is attached to one end of the pressure die holder. The inventive pressure die holder is provided with two sets of vents which relieve lubricant pressure within the pressure die holder. The first set of vents is located in mid portion of the body of the pressure die holder in alignment with the dies. The first set of vents reduces pressure between the die pair, allowing the lubricant to flow through the die at a cooler temperature. The second set of vents are located in the body of the pressure die holder adjacent the cap, and allow the cap to be removed from the pressure die holder at the end of the drawing operation.
U.S. Pat. No. 6,374,659, issued to Bellins on Apr. 23, 2002, discloses a tool suited to the pressure wire drawing of wire rods and wires having a hole passing through it, includes a casing detachably disposed within the casing, a wire drawing nib separate from the pressure die and detachably disposed within the casing and aligned with the above mentioned hole, and at least one gasket between the wire drawing nib and the pressure die designed to make the passage formed between the pressure die and wire drawing nib leak-proof.
While these patents and other previous methods have attempted to solve the problems that they addressed, none have utilized or disclosed a torsional wire treatment drawing system that improves wire torsional properties, allows for increased drawing speeds and die life by distributing the heat of drawing over two or more drawing dies, thus increasing the ability to remove heat from the system, as does embodiments of the present invention.
Therefore, a need exists for a torsional wire treatment drawing system with these attributes and functionalities. The torsional wire treatment drawing system according to embodiments of the invention substantially departs from the conventional concepts and designs of the prior art. It can be appreciated that there exists a continuing need for a new and improved torsional wire treatment drawing system which can be used commercially. In this regard, the present invention substantially fulfills these objectives.
The foregoing patent and other information reflect the state of the art of which the inventor is aware and are tendered with a view toward discharging the inventor's acknowledged duty of candor in disclosing information that may be pertinent to the patentability of the present invention. It is respectfully stipulated, however, that the foregoing patent and other information do not teach or render obvious, singly or when considered in combination, the inventor's claimed invention.
The general purpose of the present invention, which will be described subsequently in greater detail, is to provide a torsional wire treatment drawing system. In particular, the present invention relates to an assembly that allows for increased drawing speeds and die life by forcing lubricant into the system by means of a pressure die chamber and distributing the heat of drawing over two or more working or drawing dies, thus increasing the ability to remove heat from the system. To help ensure that sufficient lubricant in available subsequent to the initial drawing die one or more lubricant pressure chambers can be included in the system between subsequent drawing dies.
Embodiments of the present invention improve dry or wet wire drawing performance by applying a three or more die system including a pressure die and at least two drawing dies to wire drawing. A pressure-die forces lubricant into a multiple-die drawing system. This lubricant may be a dry lubricant, a liquid lubricant or a lubricant of intermediate viscosity like a paste depending upon the application. When two or double drawing dies are incorporated less work per die and better drawing heat distribution is obtained by splitting or sharing a “normal” reduction between two double drawing dies. The double drawing dies are adjacent to each other so there is substantially no possibility of light reductions resulting in central bursting (commonly about 0.004 seconds between the first and second double drawing dies in the first die holder and less time between subsequent double dies). The wire produced shows significantly lower strain aging which allows for higher drawing speeds and longer die life and results in markedly improved torsional properties.
One embodiment of the present invention splits a “normal” reduction into two smaller reductions in very close proximity and includes a pressure die and a pressure zone between the double drawing dies. To ensure that a sufficient amount of lubricant is introduced into the system the pressure die is designed to force lubricant into the double die system used prior to the drawing dies. All three dies (the pressure die and two drawing dies) and two high pressure lubricant zones (one in the pressure die and one between the double dies) are contained inside one drawing die holder. As an example, a 20% reduction of cross sectional area (e.g. 4.5 mm reduced to 4.02 mm) may be split into a 12% reduction of cross sectional area immediately followed by a 9% reduction of cross sectional area (4.5 mm reduced to 4.21 mm reduced to 4.02 mm). By splitting the reduction the amount of heat generated remains roughly the same but the surface available to remove the heat is doubled.
Although the torsional wire treatment system may include a pressure die and at least two drawing dies, for ease of understanding the invention description contained herein will rely on a three die system for illustration.
In an exemplary embodiment, the torsional wire treatment drawing system may be comprised of a suitable die holder, a pressure die, at least a first drawing die insert and a second drawing die insert, means to prevent lubricant from escaping between the pressure die and first drawing die, and means to prevent lubricant from escaping between the first drawing die and second drawing die as well as a means to prevent lubricant from escaping between subsequent dies.
For the torsional wire treatment drawing system to function optimally in the simplest example the three dies will be in an interference fit preventing the escape of drawing lubricant. One way to accomplish this is for the bottom of the pressure die, the top and bottom of the first drawing die and the top of the second drawing die to be ground to be substantially parallel when assembled or coated with a soft material like dipped or electroplated copper and ground or ground and coated with a soft material like dipped or electroplated copper or simply coated with a soft material like copper.
A second method to accomplish this is for the bottom of the pressure die and the top of the first drawing die to be ground to be substantially parallel when assembled, or to be coated with a soft material, e.g. dipped or electroplated copper, and ground, or ground and coated with a soft material, e.g. dipped or electroplated copper, or simply coated with a soft material like copper and the outside tapered diameter of all drawing dies and the mating surface of the drawing die holder be ground to create an appropriate interference fit. On the first drawing die, it is important for optimal results that the reduction angle and bearing (points where the wire contacts the nib) are below the junction of the working or drawing die holder and the pressure die holder.
The pressure die may be a manufactured from a carbide pressure die, a hardened steel pressure die, a diamond pressure die, a diamond pressure die mounted in a suitable mount, or another suitable pressure die material.
The drawing dies may be a carbide drawing die, a diamond drawing die, a diamond drawing die mounted in a suitable mount, or another material suitable for a drawing die.
The torsional wire treatment drawing system may be further comprised of a void area in the exit end of the first drawing die in order to create a second lubricant pressure area.
The torsional wire treatment drawing system may be further comprised of a void area in the entrance end of subsequent drawing dies to create additional lubricant pressure areas.
The torsional wire treatment drawing system may be further comprised of a void area in the exit end of previous drawing die and a void area in the entrance end of the subsequent drawing dies to create an additional lubricant pressure areas.
The torsional wire treatment drawing system may be further comprised of a void area consisting of a space between the drawing dies to create additional lubricant pressure areas.
In some embodiments of the torsional wire treatment drawing system the mating surfaces of the pressure die and first drawing die may have grinding applied.
In some embodiments of the torsional wire treatment drawing system the mating surfaces of a prior drawing die and a subsequent drawing die may have grinding applied.
In some embodiments of the torsional wire treatment drawing system the mating surfaces of the pressure die and first drawing die may be covered with a soft material, e.g. copper.
In some embodiments of the torsional wire treatment drawing system the mating surfaces of drawing dies may be covered with a soft material, e.g. copper.
In some embodiments of the torsional wire treatment drawing system the outside surface of some or all of the drawing dies may have grinding applied.
In some embodiments of the torsional wire treatment drawing system the outside surface of the drawing dies may be covered with a thermally conductive material, e.g., aluminum.
In some embodiments of the torsional wire treatment drawing system the outside surface of the drawing dies may be covered with a soft material, e.g., copper.
An exemplary embodiment of the present invention in a three die dry application may be made as follows:
One aspect of the present invention is that it improves dry and wet wire drawing performance by applying, at a minimum, a three die system including a pressure die and two drawing dies to wire drawing.
Another aspect of the present invention is that it improves wire cooling compared to standard single die or single die pressure systems like the Paramount Paroloc pressure die system.
Another aspect of the present invention is that due to the drawing dies being in such close proximity to each other, there is substantially no possibility of light reductions resulting in central bursting (commonly about 0.004 seconds between passes in the first die, less time duration in subsequent dies).
Another aspect of the present invention is that the resulting wire shows significantly lower strain aging, allowing for higher drawing speeds and longer die life resulting in improved torsional properties.
Another aspect of the present invention is that it may be made from readily available components.
Another aspect of the present invention is that it may be economically manufactured.
Another aspect of the present invention is that it may be made utilizing existing manufacturing techniques.
These and other features and advantages of the present invention will be presented in more detail in the following specification of the invention and the accompanying figures, which illustrate by way of example the principles of the invention.
There are additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto. In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways for example in wet drawing applications. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.
The invention, together with further advantages thereof, may best be understood by reference to the following description of the simplest form of the invention, a three die system comprised of one pressure die and two drawing dies (double drawing dies) taken in conjunction with the accompanying drawings in which:
The present invention will now be described in detail the simplest form of the invention, a three die system comprised of one pressure die and two drawing dies (double drawing dies) with reference to a few preferred embodiments thereof as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without some or all of these specific details. In other instances, well known operations have not been described in detail so not to unnecessarily obscure the present invention.
Referring now to
Wire stock 900 enters the top of male top 110 and exits the bottom of female bottom 120, forcing by hydraulic pressure lubricant 800 through the pressure die 200 and into the first lubricant pressure zone 710 under extreme pressure during the process. This same hydraulic pressure forces lubricant between the first drawing die 300 and the wire stock 900 helping to prevent wear in the first drawing die 300. After exiting the first drawing die 300 the wire is exposed to the second pressure zone 720 further increasing the hydraulic lubricant pressure. Hydraulic pressure from the second lubricant pressure zone forces lubricant between the second drawing die 400 and the wire stock 900 further helping to prevent wear in the second drawing die 400. The wire stock 900 is reduced in diameter by a combination of a first reduction zone 730, and a second reduction zone 740. Wear of the first drawing die 300 is reduced by hydraulic pressure developed in the first pressure zone 710 and wear of the second drawing die 400 is reduced by hydraulic pressure developed in the second pressure zone 720.
About a 60 percent of the total reduction in diameter of the wire stock is achieved by the first drawing die insert 300. About 40 percent of the total reduction in diameter of the wire stock is achieved by the second drawing die inset 400.
The two drawing dies in embodiments of the present invention generate approximately the same percent reduction in wire stock as the commercially available single pressure die, single pressure zone and single drawing die Paraloc system with substantially the same amount of heat generated. However this substantially equivalent heat is dissipated over substantially twice the surface area of drawing zones 730 and 740, thus resulting in an improvement in heat dissipation and wire cooling, e.g. a two fold increase in wire cooling resulting in improved wire torsional properties. Adding additional drawing dies to an assembly yields additional heat dissipation.
From the foregoing, it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. For example, many of the features and components described above in the context of a particular torsional wire treatment drawing system configuration can be incorporated into other configurations in accordance with other embodiments of the invention.
Accordingly, the invention is not limited except by the appended claims.
