US2846056A - Drawing dies - Google Patents

Description

Aug. 5, 1958 Filed April 16, 1954 2 Shets-Sheet 1 FIG. 2-

a Is i \I 5 Inventor A ttorneys R. HAMPTON 2,846,056

DRAWING DIES United States Patent 1. DRAWING DIES Ronald Hampton, Wightwick, near Wolverhampton, England, assignor to Patents and Investments Limited, Wolverhampton, England Application April 16, 1954, Serial No. 423,732

Claims priority, application Great Britain May 26, 1953 1 Claim. (Cl. 205-26) This invention relates to drawing dies, that is to say, dies having apertures through which work-pieces are forced, either by pulling or pushing upon the work-pieces, such a die operating upon the work-piece to form the latter to a cross section corresponding to the shape of the aperture in the die. In this connection a die may be merely reducing the dimensions of the cross sectional form of a work piece, or it may be altering the cross sectional form with or without reducing the cross sectional area of the work-piece.

The object of the present invention is to provide an improved construction of die, particularly for use in cold drawing bar stock, which will be more efiicient in use than dies as hitherto constructed.

In drawing dies as hitherto constructed, a central aperture in the die block, of contour corresponding to the finished section to be produced, is defined by the socalled bearing surfaces of the die, and leading up to said bearing surfaces are curved surfaces known as the leads or leading surfaces, which surfaces are curved longitudinally but are transversely parallel with the bearing surfaces.

According to the present invention, a die is provided with leading surfaces which are not only curved longitudinally but also have a convex curvature in transverse direction.

An embodiment of the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a front elevation of a drawing die.

Figure 2 is a sectional side elevation on the line 2-2 of Figure 1.

Figure 3 is a sectional plan view on the line 3-3 of Figure 1.

Figure 4 is a sectional elevation on the line 4-4 of Figure 3.

Figure 5 is a further sectional elevation on the line 55 of Figure 3.

Referring to the drawings, the die block has a central hexagonal aperture or throat 11 defined by the six bearing surfaces 12.

The leads of leading surfaces 13 of the die are curved longitudinally, i. e., from the front face or mouth 14 of the die said leading surfaces 13 are of convex curvature in rearward direction so as together to afford a converging lead toward the die throat 11. In addition to this longitudinal curvature, the leading surfaces 13 are all formed with an arcuate convex curvature which extends in transverse direction across the entire width of the leading surface with the convexity diminishing uniformly from the mouth to the throat where it merges with the sides thereof, as is most clearly illustrated in Figures 1, 4 and 5.

The embodiment above described is an example of a die suitable for use in the production of hexagonal bar sections from raw material which is merely closely related in section to the finished section produced by the die.

2,846,656 Patented Aug. s, 1958 Hitherto, in the production of bar sections, metal bars have been cold bright drawn from raw material which has-been hot rolled to a corresponding section within reasonable limits of the finished bar section to be pro duced, the said hot rolled bars being then drawn through a die, constructed in the known manner previously referred to, to produce the finished section, the leading and bearing surfaces of the die working the material from the hot rolled section to a corresponding finished section of smaller dimensions.

Taking into consideration the flow of metal of the bars being worked, when the material being worked is of suitable corresponding section and of appropriate dimension relative to the finished work, it has been found satisfactory to employ the said known dies having the leading surfaces parallel with the bearing surfaces.

The present invention however, provides a die by means of which, for example, a bar of hexagonal, septagonal,

octagonal or like polygonal section can be produced by cold drawing from round section bar stock, or bar stock of any other closely related section to the finished section which is practicable as regards the displacement of metal which can be effected by cold work.

This is achieved by the transverse curvature of the leading surfaces 13 in accordance with the invention, the arrangement being such that little work shall be performed upon the extreme points or corner portions of the section being drawn until said points or corner portions actually make contact with the bearing surfaces 12 of the die.

In a die as hitherto constructed such extreme points or corner portions of the section under work, through restriction in the flow of metal, tend to fail ultimately to come into contact with the bearing surfaces of the die, so that a true and clean section is not obtained.

In a die constructed according to this invention the initial heavy work on the section being drawn is effected by the leading surfaces 13 along the centerlines of the surfaces of the finished section, which not only causes the metal to elongate and flow into its correct proportions at the points of contact, but also causes the metal to flow laterally outwards to the extreme points or corner portions of the section, since the construction of the leading surfaces 13 alfords clearance which allows 1 this lateral outward flow, so that when the said extreme points or corner portions reach the bearing surfaces 12 of the die, there is a sufiiciency of metal to fill completely the die aperture 11, this ensuring a true and clean finished section. The clearance here referred to is provided in part by relating the size of the die mouth to the throat so that a circle circumscribing the former is much greater than a circle circumscribing the latter, as will be apparent from an inspection of the drawings.

The invention thus provides a die by means of which it is possible to manufacture a finished section from a size of bar which is of minimum dimensions relative to the maximum dimensions of the finished section.

It will also be found expedient to use the improved die in the manufacture of bars which are to be cold bright drawn from raw material which has been hot rolled to a section similar to the finished section to be produce-d. In the event of the hot rolled bars not being rolled fully to the extreme points or corner portions of the section, the action of the improved die in spreading the metal toward said extreme points or corner portions gives a satisfactory finished section.

It will be appreciated that whereas the foregoing description mentions cold bright drawing, and sections of regular polygonal form, the present invention is equally applicable to all sections, and also to dies for other specific uses, e. g., metal extrusion.

Having now fully described my invention, what I claim and desire to secure by Letters Patent is:

In a die for drawing polygonal bars from metal stock, a one-piece die block,,a polygonal die throat in said block having sides corresponding infnumber and size to the finished bar, a bell-shaped mouth .i'n said, die block defined by a plurality of integrally joined leading faces, one for each side of said throat, said mouth being so related in size to said throat that avcircle circumscribing said mouth is much greater than a circle circumscribing said throat, each of said faces having a longi- References Cited in the file of this patent .UNITED STATES PATENTS 2,012,022 Richardson Aug. 20; 1935

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