Metal deforming – Tool and/or tool holder – Tool comprising closed periphery deforming passageway
Reexamination Certificate
1999-04-13
2002-04-23
Crane, Daniel C. (Department: 3725)
Metal deforming
Tool and/or tool holder
Tool comprising closed periphery deforming passageway
C072S274000
Reexamination Certificate
active
06374659
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention consists of a tool perfected and particularly suited to the pressure wire drawing of wire rods and wires, with a separate and detachable pressure die and drawing die.
2. Description of the Related Art
The operation of wire drawing, well known in the technical literature, 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 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.
One well-known solution in the technical literature is that of wire drawing dies consisting of a single wire drawing 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 filled directly on machines designed for wire drawing operations.
A more recent tool has a case of steel, in two parts, that can be taken apart, where the upper part is shaped on the inside to house a die known as a pressure die made of tungsten carbide, while the lower part is designed to contain a wire drawing nib, again made of tungsten carbide, designed to perform the plastic deformation or the wire rod or wire. State of the art drawing nibs include a first section which has a truncated cone shaped surface (i.e. an entrance bell) which joins onto a subsequent truncated cone shape and finally onto a cylindrical section.
Although these devices meet the technical requirements described above, they nevertheless have the following disadvantages.
Once the tool consisting of a single piece 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.
The entrance bell portion of a state of the art drawing nib creates a chamber between the pressure die and the drawing die. In this chamber, due to the extremely high pressure and temperature caused by the deformation of the wire, the lubricant is retained having a kind of sintering effect, it becomes solid and hard. The sintered pieces of lubricant travelling through the drawing die cause abnormal die wear and damage to the wire surface as well as causing frequent breakages of the drawing nib.
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 speed of production is thereby lowered.
Tools consisting of more than one part that can be assembled and taken apart present the inconvenience of the possibility of leakage of the lubricant between the pressure die and the drawing nib as well as that of the 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 purpose of this invention is to resolve these inconveniences inherent in the prior technology.
SUMMARY OF THE INVENTION
The invention consists therefore of a very reliable and long lasting tool perfected and particularly suited to the pressure wire drawing of wire rods and wires, with the pressure die and drawing die separate and detachable, which by optimizing lubrication increases production speeds, lowers costs and thereby improves the entire wire drawing operation.
Briefly, a tool perfected and particularly suited to the pressure wire drawing of wire rods and wires, with the pressure die and drawing die separate and detachable, according to the invention, has been created which comprises a hole passing through the tool, containing a pressure die and a wire drawing nib on the inside that are separate from each other and aligned on the above mentioned hole, where there is at least one gasket between the wire drawing nib inserted at the bottom of the above mentioned case and the pressure die located at the top of the case. The gasket is designed to make the passage between the above mentioned pressure die and the above mentioned wire drawing nib leak-proof.
With the new tool suited to the pressure wire drawing of wire rods and wires, with pressure die and drawing die separate and detachable according to the invention, the following advantages are obtained.
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 functioning of wire drawing machines, consequently maintenance intervention is required less frequently.
A further advantage of the invention is its absolute 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.
The invention in one form comprises 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 tool, 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.
Other characteristics, advantages and particulars of the 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, are better shown by an examination of the following description with reference to the attached drawings that show the two preferred forms of the invention. The said drawings are given purely for the sake of illustration and not to set limits on the invention.
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Crane Daniel C.
Knuth Randall J.
Technovo S.r.L.
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