US2373606A - Metal drawing - Google Patents

Description

Patented Apr. 10, 1945 (UNITE STATES PATE T OFFICE METAL DRAWING l taymond E. Slater, New Rochelle, N. Y.,.assignor #toRemington Arms Company, Inc., Bridgeport, "Conn, a corporation of Delaware 4 Application May 20, 1944, .Serial No. 536,478

" 9. Claims. (01. 205-8)- The present invention relates to adrawing die, particularly for the drawing of tubular or shell shaped articles, such for instance as bullet jacket components produced by one or moredrawing operations from a cup shaped blank or apreviously drawn shell.

In the drawing of a tubular article the tubular wall is usually drawn to a greater height at one side than the other, this unevenness in the tube sides being due in part to the fact that the wall of the cup from which the shell is drawn is usually slightly uneven in height, and this unevenness increases with each successive drawing operation. The usual type of drawing die is provided with a relatively short land, this being necessitated in practice in order to prevent excessive frictional drag such'as might occur in the case of a relatively high land. Where the height of the land is less than the maximum disparity between the high and low sides of an unevenly drawn tube the long side of the tube which is still to be drawn is worked to a greater thickness than the other portions of the tube. This thicker portion or lip will be deformed by bending and this bending is usually great enough to induce further bending in subsequent drawing operations. Also, as the last portions of the metal on the short side of the tube are being pulled out of the 'di land the pressure difierential builds up from zero to its maximum amount, and this variation in pressure on the last few particles on the short side works height between the long and short sides of ,the .drawn article, the short side will be supported by the die land while the long side is being sized between the punch and the 'die land. This is impractical, however, because of the increased frictional drag due to the increased land height and because the total compressive force developed increases with an increase in land height,

' with the result that the forces exerted on the die of the drawn article is supported by the die landwhile the end portion of the long side is being sized between the punch and a die land, to the end that the tube wall remains straight and is of uniform thickness throughout. It is particularly proposed to provide a multiple land die, wherein adjacent die lands are of identical diameter and are separated by a clearance groove,

the metal. so that the wall is bent inwardly toward the axis of the tube in a curvilinear manner, Consequently the metal which forms the inward radius is decreased in thickness by the squeezing action oi the die and the deflected punch. Thus, a drawn tube having uneven sides may be considerably bent at its end, the high side may be substantially thicker than the normal wall thickness of the tube, and the short side may be substantially thinner. The current practice, to obvi- 7 die land before any portion of its end edge leaves the lower die land.

ate diiilculty in succeeding drawing operations,

is to cut off the end of the drawn tube' below the thickened and bent end.

the height of each die land being insufilcient to create excessive frictional drag, and the height of the groove between the die lands being such that the short side of the tube will be in contact with and supported by a lower die land while the long side of the tube is being formed between an upper die land and the punch. In practice, it is proposed to provide a set of die lands separated by one or more grooves, each die land having a height less than the maximum height disparity between the tube sides, the total axial length of said lands and grooves having a combined or total height at least equal to the maximum disparity. Hence, the article is completely formed to uniform wall thickness by the upper With the above and other objects in view, an

embodiment of the invention isshown in the its cooperating punch, according to the illustrated exemplary embodiment of the invention,-

a cup to be drawn being shown in relation thereto.

Fig. 215 a-simiiar view, showing the tube partially drawn.

Fig. 3 is a similar view, showing the tube completely drawn and with its upper end portion enthe drawing.

' Referring to the drawing, the tube drawing apparatus, of the punch and die type illustrated by way oi example in the present disclosure, comprises a die holder. Ill provided with a down:- wardly extending cylindrical pocket ll having a central opening H in its bottom. In the lower portion of the pocket there is engaged a die block it, superimposed by a top die and bushing member I having an annular shouldered recess I 5 at its upper side engaged by a retaining rin l6 secured upon the upper side of the holder l0.

The top die and bushing member I4 is of conventional form and is provided with a passage therethrough including an upper cylindrical entrance portion H, a downwardly converging tapered portion l8 and a lower cylindrical land portion M. This member is for the purpose of positioning and guiding the cup 20 to the die block l3 which incorporates the improved structure of the invention. the cup being engaged within the passage of the upper die member and pressed downwardly therethrough through the downstroke of the punch 2?. As illustrated, this upper die member in addition to positioning and centering the cup is adapted to ,impart a slight preliminary draw to it.

The die block it is provided with-a vertical passage in axial alignment with the passage of the upper die member i6, and comprising a downwardly converging tapered portion 22 extending to the upper cylindrical die land 23. 'In spaced relation below the die land 23 there is provided a second die land 24 of identical diameter-therewith, an annular clearance groove 25, semi-circular in cross section, being provided between the upper and lower die lands 23 and 25. Below the die land 25 there is provided a short downwardly divergent outlet portion 25.

It is pointed out that the upper die land, which is adapted to cooperate with the punch to draw and form the tube, is relatively narrow in order to eliminate excessive frictional drag and excessive total compressive force, and in practice its axial width dimension is less than the maximum or'average disparity in height between the high and low sides of an unevenly drawn tube. While the height of the lower die land 24 is preferably the same as that of the upper die land it may in greater than the maximum or average disparity between the high and low sides of an unevenly drawn tube, so that as the tube is drawn no part of its upper end portion will leave the lower die land before the entire tube is drawn and formed between the upper die land and the punch.

The operation is as follows:

As shown in Fig. 1 the cup 20 is slightly uneven at its upper edge, this being an average condition. As this cup is drawn by the cooperating punch and die this unevenness increases, so that the drawn tube is of substantially greater height at one side than at the other. As seen in Fig. 2, the tube is partially drawn, the lower side of its upper edgejust starting to be formed between the upper die land 23 and the punch. As seen in Fig. 3, the high side of the tube has been drawn into the position 01 minimum clearance between the upper die land and the punch and at the same time the low side of the tube has left the upper die land and is being supported by the lower die land 24. As seen in Fig. 4, the drawn tube is disengaged at its low side from'the lower die land 24, and from this position the punch carries it below the die where it is stripped from the punch as the latter is moved upwardly. It will be seen that at all times during the'forming of the tube the punch is supported in concentric relation within the die through the support of the drawn tube interposed between the punch and the lower die land 24, so that there is no possibility of the punch being forced out of concentricity. Consequently, the tubular wall of the drawn article is of straight form and uniform thickness therethrough, and the drawing operation is carried out without creating an undue stress in the die or in the drawn article. The proper positioning of the punch with the die eliminates any possibility oi inward bending of the end portion of the short side of the tube or of the thickening of the end portion'of its long side. The drawn tube, may therefore be subjected to further drawing operations without the necessity for cutting off the end, and straightness and uniformity'oi thickness will be maintained through the successive drawing operations.

In Fig. 5 is shown an alternative type of die holder such as disclosed in detail in copending application Serial No. 535,011, filed May ii, 3.9%. The die holder 35 has a tapered aperture 35 which engages the tapered exterior surface iii of the die 38. The die 33 has lands and it and clearance groove M similar to that just de scribed for die block it of Figs. 1 to a, inclusive. As set forth in said copending application, the die is preferably hard and the holder relatively elastic, such as a spring steel. The taper and elasticity of the holder, hardness of the die, downwardly converging mouth portion, area of lands, etc., are chosen so that increase of drawing pressure and impact as the work piece first hits the die will not affect the size of the piece being drawn, the die being movable downwardly in the holder with increase of drawing pressure and thus expanding the holder, and returnable to its free position upon completion of the drawing, thereby removing the stress on the die due to the holder. By the use of the tapered die and holder, the lands are kept at a constant diameter regardless of drawing pressure so as to produce work of'a constant diameter. v

The form of the invention illustrated in the drawing and described herein is typical and illustrative only, and it is evident that the invention is capable of embodiments in other forms, all falling within the scope of the appended claims, which are to be broadly construed.

What is claimed is:

1. The method of drawing tubular article's wherein the tube wall is drawn to a greater height at one side than the other, comprising passing the tube through a drawing die having a drawing passage including a plurality of axially spaced annular die lands, the total height of said lands,

and spacing being at least equal to a predetermined disparity in height between the sides of annular die lands, the first of said die lands being of less axial height than ,a predetermined disparity in height between the sides of said drawn article, and said plurality of die lands and spacing having a total axial height at least equal to said predetermined disparity.

3; The method of drawing tubular articles wherein the tube wall ,is drawn to a greater height at one side than the other, comprising passing the tube through a drawing die having 'a converging drawing passage terminating in a plurality of axially spaced annular die lands, the first of said die lands being of less axial height than a predetermined disparity in height between the sides of said drawn article, said plurality of die lands and spacing having a total axial height at least equal to said predetermined disparity.

4. The method of drawing cup-shaped tubular articles wherein the tube wall is drawn to a greater height at one side than the other, comprising passing the article through a drawing die having a drawing passage including annular die lands having a height at least equal to a predeof die lands and spaces therebetween having a total axial height at least equal to said predetermined disparity.

6. The method of drawing cup-shaped tubular ammunition components wherein the tube wall is drawn to a greater height at one side than the other, comprising passing the component through a drawing die having a drawing passage including a plurality of axially spaced annular die lands and spaces having a total height at least equal to a predetermined disparity in height between the' sides of said drawn component.

'7. The method of drawing cup-shaped tubular articles wherein the tube wall is drawn to a greater height at one side than the other, comprising passing the article through a relatively nonelastic drawing die having a tapered exterior surface, said die having a plurality of axially spaced annular dielands, said die lands and spaces hav- 'a total height at least equal to a predetermined disparity in height between the sides of said drawn article, and an elastic die holder having a tapered aperture freely supporting the exterior tapered surface of said die, said holder being adapted to expand to enable said die to move relative thereto during the processing of a workpiece to substantially prevent expansion. of said die.

8. A drawing die for drawing cup-shaped tubular articles wherein the tube wall is drawn to a greater height at one side than the other, having a drawing passage including a plurality of axially spaced die lands, said lands being of the same diameter, the total axial height of said lands and spaces being at' least equal to a predetermined disparity in height between the two sides of said drawn article. a

9. A drawing die for drawing cup-shaped tubular ammunition components. wherein the tube wall is drawn to a greater-height at one side than the other, having a converging drawing passage terminating in a plurality of axially spaced annular die lands, said lands being of the same diameter, the first ofsaid die lands being of less axial height than a predetermined disparity in height between the sides of said drawn article, and said plurality of die lands and spacings having a total axial height at. least equal to said predetermined disparity.

v RAYMOND E. SLATER.

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