US3058195A

US3058195A - Method for the manufacture from sheet metal of hollow objects having a wall thickness in the closed end exceeding the wall thickness of the starting material

Info

Publication number: US3058195A
Application number: US853383A
Authority: US
Inventors: Ericsson Karl Folke
Original assignee: Svenska Metallverken AB
Current assignee: Svenska Metallverken AB
Priority date: 1958-11-17
Filing date: 1959-11-16
Publication date: 1962-10-16
Anticipated expiration: 1979-10-16

Description

, 3,058,195 OF HOLLOW OBJECTS END E NG MATER XCEEDING THE IAL Oct. 16, 1962 K. F. ERICSSON METHOD FOR THE MANUFACTURE FROM SHEET METAL HAVING A A L THICKNESS IN THE CLO L TH NESS OF THE STA iled Nov. 16, 1959 Ill/fill!!! ICA/EL fQJLAQF EKUCSSCVV United States Patent METI-IOD FOR THE MANUFACTURE FRUM SHEE METAL 0F HGLLOW OBJECTS HAVING A WALL THICKNESS IV THE CLOSED END EXCEEDDJG THE WALL THICKNESS OF THE STARTING MA- TERIAL Karl Folke Ericsson, Vast-eras, Sweden, assignor to Aktiebolaget Svenska Metailverken, Vasteras, Sweden, a joint-stock company limited of Sweden Filed Nov. 16, 1959, Ser. No. 853,383 Claims priority, application Sweden Nov. 17, 1958 Claims. (Ci. 291.21)

The present invention relates to a method for the manufacture from sheet metal of hollow objects closed in one end and having a wall thickness in the closed end exceeding the wall thickness of the starting material by forming a disk of the material into a cup which by repeated procedure is reduced to its final diameter while simultaneously being increasing to its final length.

In the manufacture of such hollow objects it is a desire to start from a sheet or plate having the smallest possible wall thickness, since such plates. are economically more convenient than thicker plates and the mechanical stress upon the working tools on the other hand will be less the more flexible, thinner and more ductile is the starting material.

One of the most important fields of application of the present invention is the manufacture of projectile shells of the kind which is adapted to be filled with lead for obtaining correct ballistic values. Hitherto such projectile shells were manufactured substantimly with an essentially equal wall thickness along the entire wall, but with increasing characteristics of resistance of the steel plates used for defensive purposes and particularly the plates used in steel helmets, such a projectile shell lacks sufficient structural strength. This has per se led to a desire to render possible the manufacture of such projectile shells having a considerable wall thickness in the closed parabolic or ogival end portions of said projectile shells. For the solution of this problem it was earlier suggested to produce according to various methods blanks with concentrated wall thickness in the top of the projectile shell. These earlier suggestions, however, will make considerable requirements upon the construction and resistance of the tools and furthermore the production of such blanks in mass production, which is obviously required, involves so esesntial economical drawbacks that the manufacture will entail considerable economical problems.

The invention which has for its object to remove the above inconveniences is substantially characterized in that the material in the closed end of the cup is upset along a predetermined outline and that the material at the same time is allowed to move or flow out in increasing directions of the wall thickness.

The invention also relates to a tool for carrying the method according to the invention into practice, particularly for the production of projectile shells or the like from cup-shaped blanks and is characterized by a punch die having a parabolic or ogival section and a shouldered punch cooperating therewith and provided with indications for the anchoring of the blank onto it.

The invention will now be more clearly explained with reference to an embodiment diagrammatically shown in the attached drawing and in connection therewith further characterizing features of the invention will be brought out.

FIGURE 1 diagrammatically shows a drawing or pressing tool which is adapted to produce a cup-shaped blank from a sheet or disk-like starting material.

FIGURE 2 shows a successive tool adapted to preform 3,058,195 Patented Get. 16, 1962 in a successive step the cup-shaped blank according to FIGURE 1 for continued drawing.

FIGURE 3 shows a further drawing tool for continued treating of the cup-shaped blank.

FIGURE 4 diagrammatically illustrates a procedure of cutting off projecting irregularities in the open end of the cup-shaped blank resulting from the drawing operations.

FIGURE 5 illustrates a tool for the preforming of projectile shells from preformed cup-like blanks.

FIGURE 6 shows substantially a tool according to the invention adapted for use in final pressing operations on the projectile shell blank manufactured in the tool of FIGURE 5.

In FIGURE 1 of the drawing reference numeral 1 designates a punch and 2 a die, which die is provided with a preferably annular fitting recess 3 for a circular plate blank designated by 4. The die presents a so-called draweye 5 which has two coaxial circular holes 6 and 7 of different diameters so that an annular shoulder 8 is formed between them. The preferably circular blank designated by 4 is drawn or pressed by the punch 1 through the draw-eye 5 to form a cup-shaped starting blank designated by 9 and located below the draw-eye. It may be mentioned as an information that with projectile shells for hand weapon ammunition preferably punched disks 4- are employed, having a wall thickness amounting to approximately 1 mm, which wall thickness will not considerably strain the tools which have to work with accuracy and high speed for obtaining an economic capacity of production.

In FIGURE 2 reference numerals 1t) and 11 denote sections of a further punch in a successive tool. This punch is modified in such respect in comparison with the punch 1 according to FIGURE 1 that it presents an end r 11 having a less diameter than the remainder of the punch and a suitably downwardly tapering shoulder 12 located between the dilferent sections 10 and 11 of the punch. The die designated by 13 in FIGURE 2 also presents a so-called draw-eye 14 which also has two

hole sections

15 and 16 of different diameters. In comparison with the section 6 of the tool according to FIGURE 1 it is presumed that the diameter of the hole 15 in the embodiment shown is somewhat less. Likewise the diameter of the hole 16 is somewhat less than the diameter of the corresponding hole 7 of FIGURE 1. By this the blank 9 being placed in the tool according to FIGURE 2 will obtain a less diameter after it has been drawn through the draweye 14 to form the preformed blank 17. As will be evident from considering this blank the shoulder 12 of the punch has caused a reduction of the wall thickness of the open end of the cup-shaped blank so as to form a thinner shell or jacket 18 at this end at the same time as the remainder of the cup has been extended in an axial direction. I

The cup-shaped blank 17 manufactured in the tool according to FIGURE 2 is thereafter placed in the tool shown in FIGURE 3 and somewhat modified as compared with the tool according to FIGURE 2. The punch section 19 has here obtained a somewhat less diameter than the diameter of the section 10 of the punch according to FIGURE 2. The same is applicable to the relation between the section 20 and the section 11. Between the

sections

19 and 20 there is a suitably conical shoulder. The corresponding draweye 22 of the punch die 23 is also divided into two

holes

24 and 25, the diameter of the hole 24 being somewhat less than the diameter of the hole 15 of FIGURE 2 and the diameter of the hole 25 being less than the diameter of the hole 16. This means that the cup-shaped blank 17 after being drawn through the die to form a blank 26 obtains a further reduced diameter and an increased length. Furthermore, it should be noted that the thin wall has been extended to form a jacket 27 of a considerable length at the same time as certain irregularities of the edge 28 have been caused in the open end of the cup. It may be mentioned that such irregularities also may occur in earlier operations and as far as such irregularities are troublesome in the production they should preferably be cut off at desired times, for instance such as diagrammatically shown in FIGURE 4, by means of for instance lathe tools or the like 29.

The blank 26 is subjected to complete operations by first being placed in the tool shown in FIGURE 5. This tool presents a punch section 30 preferably having a less diameter than the punch section 19 of FIGURE 3. Furthermore, there is a shoulder 31 and a parabolic or ogival top 32 thereon. Correspondingly the die 33 presents a parabolic or ogival outline of the hole 34. Cut in the bottom of the hole 34 in this die 33 is a fine hole 35 serving to provide communication with the atmosphere.

The blank 26 is now pressed down to the bottom of this tool whereupon the cup-shape is transferred into the outline of a parabolic hollow object, the closed end of which is considerably extended forwardly. This hollow object 36 is shown in a position just before the top of the punch has reached the bottom of the die of the tool. Difficulties would, however, arise in connection with the withdrawal of the completed blank 36 from the die 33, if not particular measures were taken in order that the blank after the forming procedure will again be carried with the punch out of said die. In accordance with the invention for instance the section 30 of the punch is provided with indications in the form of sharp-edged holes 37 or other suitable anchoring means. By the drawing procedure thus the material of the jacket wall of the blank 26 preferably from the thin section 38 will be pressed into said anchoring means which in other respect may be small and inconsiderable. The result will be that the friction thereby obtained will be sufficient for the blank to be lifted clear of said die. Thereafter the blank may be removed from said punch in a known Way by stripper means.

i It is to be noted that particularly the closed end of the blank 36 is considerably extended in this drawing operation as compared with the blank 26 of FIGURE 3. The completed blank 36 is finally brought to the tool shown in FIGURE 6 and comprising a die 39 and a punch t stroke in which, as will be evident from the figure, the

distance between the walls of point and the Wall of the die is considerably increased in order to be able to receive excess material during the upsetting operation which is carried out in this tool on the considerably extended closed end of the blank shown in FIGURE 5. In accordance with the invention this end will be upset to follow the outline 42 of the die 39 and the material being there by displaced is allowed to move and be forged or headed into an end product which has an ogival end thickness surrounding the point 41 of the punch substantially everywhere in excess of the corresponding thickness of the initial blank 36. Although the materialin the figure has been shown as completely filling the entire space between the point of the punch and the die, it is obviously possible that the material, for instance stops at the dotted line 43, but since it maybe frequently suitable to obtain a certain defined guiding and distribution of the material, especially in connection with such projectile objects, it may be suitable to calculate the material which has been transferred in earlier operations to the projectile point so that it will suffice also for accommodating the outline of the point of the punch. It will also be seen that part of the space designated by 44 between the punch and the die remains unfilled and the size of this hollow may'obviously be calculated according to requirement. By the procedure according to the invention starting from a plate having a relatively small thickness a hollow object has now been provided which presents at its end a Wall thickness which considerably exceeds the thickness of the starting material, while obtaining the advantages referred to in the opening statement of the description.

During the manufacturing procedure which may be carried out using a desired number of tools the cupshaped blank during the entire drawing process can be manufactured with a wall thickness which is below, above or essentially equal to that of the starting material. According to the invention the closed end of the cup is extended through the treatment and the upsetting operation is carried out to such an extent that the material in the closed end after the upsetting operation will be sufficient in order to accommodate carefully to the defined outline or to obtain at least the desired wall thickness.

Particularly in the case of manufacturing projectile shells and the like it is frequently started from plated iron sheet, for instance copper plated iron sheet. In such connection the cup is only drawn to such an extent that the plating is not broken or so that it after the upsetting operation will again be continuous without presenting indications for possible onset of corrosion on the protected sheet material.

During the manufacture the hollow object may obtain a Wall thickness in its open end which is below the wall thickness of the starting material.

It should also be noted that shouldered punches are used for arresting the material in the closed end of the cup from being considerably urged rearwardly towards the open end during the extending and upsetting operations respectively of the closed end of the cup. It should also be mentioned that cutting operations are preferably carried out on the thin walled projectible jacket of the cup at such places where the drawing of the material has contributed to deteriorate or remove the plating which is often the case with the outermost end.

The invention is not limited to the embodiment of it described and shown but may be varied in different ways within the scope of the basic inventive idea. Although the invention is preferred in connection with the production of projectile shells, it may also be applied to other hollow objects or vessels, Where it is preferred to obtain products from a material having a relatively small thickness, the bottom thickness of which is larger than that of the starting material.

Having now described the invention, what I claim as new and desire to secure by Letters Patent, is:

1. A method of making a cup like article having a thickened closed end from a relatively thin disc comprising forming said disc into a cup shaped element of uniform thickness, elongating said cup like element while forming a shoulder in the interior thereof, deforming said element between the shoulder and the closed end into desired shape by exerting pressure on said shoulder while permitting the free movement of the material of said element between the shoulder and the open end, and displacing the inner layers of material of the element towards the closed end of the element by exerting pressure on said shoulder to obtain a thickness at the closed end which exceeds that of the original disc.

2. A method of making a cup like article having a thickened closed end from a relatively thin disc comprising forming said disc into a cup shaped element of uniform thickness, elongating said cup shaped element while forming the same into two portions each having a respective uniform thickness and joined by a shoulder, the portion between the shoulder and the open end being of less thickness than the other portion, deforming said element by engaging a punch on the shoulder of the element and forcing said punch and element into a die while freely. permitting the material of the element to move away from the closed end of the element through an annular space between the punch and the die, and displacing inner layers of material of the element towards said closed end by engaging a further punch on said shoulder and moving said further punch towards said closed end of the element until the thickness of the closed end exceeds a predetermined value which is greater than the thickness of the disc.

3. A method of making a cup like article having a thickened closed end from a relatively thin disc comprising forming said disc into a cup shaped element of uniform thickness, elongating said element and reducing its external diameter while forming a jacket portion of reduced thickness at the open end of the element, forming said element into ogive shape by deforming said element below the jacket portion While permitting free movement of the jacket portion away from the closed end of the element, and displacing the inner layers of material of the element towards the closed end while maintaining the ogive shape of the element to form a closed end of increased thickness relative to that of the original disc.

4. A method of making a cup like article having a thickened closed end from a relatively thin disc comprising forming said disc into a cup shaped element of uniform thickness, the element defining a cavity, positioning a punch with a shoulder thereon into the cavity of the element, passing said punch and element through a die to form a shoulder in said element corresponding to that of the punch, passing said element through a further die by engaging the shoulder of a further punch with that of the element to elongate said element While forming a jacket portion of reduced thickness between the shoulder and the open end, upsetting said element to desired external shape by engaging the shoulder of another punch with that of the element and deforming the element in a further die while permitting free movement of the jacket portion away from the closed end of the element through an annular space between the other punch and said further die, and displacing the inner layers of material of the element towards the closed end thereof by exerting downward pressure on the shoulder of the element while maintaining the element in said further die.

5. A method as claimed in claim 2 comprising trimming the edge of said element at said open end before said deforming step.

References Cited in the file of this patent UNITED STATES PATENTS 407,536 Kynoch et a1 July 23, 1889 726,800 Langbein Apr. 28, 1903 1,054,669 Bowen Mar. 4, 1913 1,323,532 Hoar Dec. 2, 1919 2,150,708 Andrews et al Mar. 14, 1939 2,301,565 Moore Nov. 10, 1942 2,350,491 Butler et a1. June 6, 1944 2,350,535 Sarulla June 6, 1944 2,979,188 Dufiield Apr. 11, 1961