CA1081549A - Blanking and forming tapered wall articles - Google Patents
Blanking and forming tapered wall articlesInfo
- Publication number
- CA1081549A CA1081549A CA316,023A CA316023A CA1081549A CA 1081549 A CA1081549 A CA 1081549A CA 316023 A CA316023 A CA 316023A CA 1081549 A CA1081549 A CA 1081549A
- Authority
- CA
- Canada
- Prior art keywords
- blank
- die
- aperture
- exit aperture
- entrance aperture
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D51/00—Making hollow objects
- B21D51/16—Making hollow objects characterised by the use of the objects
- B21D51/54—Making hollow objects characterised by the use of the objects cartridge cases, e.g. for ammunition, for letter carriers in pneumatic-tube plants
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
- B21D22/20—Deep-drawing
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
- B21D22/20—Deep-drawing
- B21D22/21—Deep-drawing without fixing the border of the blank
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D35/00—Combined processes according to or processes combined with methods covered by groups B21D1/00 - B21D31/00
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Shaping Metal By Deep-Drawing, Or The Like (AREA)
- Perforating, Stamping-Out Or Severing By Means Other Than Cutting (AREA)
- Wire Processing (AREA)
- Metal Extraction Processes (AREA)
- Press Drives And Press Lines (AREA)
Abstract
Abstract of the Disclosure Elongated, thin wall shells are formed from substan-tially circular blanks cut from sheet material by steps including providing a blank in a blank holder on a die having an effective entrance and exit aperture, the entrance aperture having an extent substantially commensurate in size with the size of the blank to be drawn, the die having a cavity, the wall of which converges inwardly from the entrance aperture to the effective exit aperture. The wall connecting the entrance and exit aper-tures is defined by an arc of a sector of a circle, the sector having an angle in the range of 12 to 34°. The thin wall shell is formed by displacing the blank through the die by action of a punch.
Description
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This invention relates to the production of blanks and shaped articles such as elongated, thin wall shells and, more par~icularly, to a method and apparatus for forming elongated, tapered wall shells useful in the fabrication of cartridge cases and the like.
In the prior art, generally the fabrication of tapered wall shells, such as those used for forming into cartridge cases, has required a series of steps or h~s required complicated machines which permit the fabrication of the shell in a single operation. United States Patent 3,g84,259 and United States Patent 3,498,221 illustrate a typical series of steps used to form the tapered wall shell and a cartridge case there-from. United States Patent 3,088,225 discloses a method for forming a tapered wall shell in a single continuous operation. However, this patent requires triaxial forces, e.g. use of a cushion, to ensure ductility and to control flow of metal in the blank.
The present invention includes a method and apparatus for producing blanks and forming shaped articles such as elongated, thin walled shells having relatively thick integral ends thereon. A simple, double action draw press may be used, for example.
According to one aspect o the inven~ion there is provided a method of forming an elongated, unitary shell having a thin side wall and relatively thick end integral therewith, the shell formed from a substantially circular blank cut from sheet material, the method comprising the steps of: ~a~ providing a blank in a blank holder on a die having an effective entrance aperture and an effective exit aperture, the entrance aperture having an extent substantially commensurate in size with the size of the blank to be drawn, said die having a cavity, the walls of which converge inwardly from said entrance aperture to said e~ective exit aperture, said wall defined by an arc of a sector of a circle, said arc passing from the entrance aperture to the exit aperture, said sector having an angle in the range of 12 to 34, said circle having its center located in substantially the same plane as said effective exit aperture; and tb~
displacing said blank through said die by action of a punch to form said .. , . - 1 - ~ :
~L~8~5~ .
shell.
According to another aspect of the inv~ntion there is provided a method of forming elongated, unitary shell having a thin wall and a relatively thick end, the shell formed from sheet material, the method comprising the steps of: ta) supporting the sheet material on a blanking die having a substantially circular entrance aperture, an exit aperture and an inwardly converging transition zone extending from thc entrance aperture to the exit aperture; (b) punching a blank from the sheet material using a cylindrical blanking punch axially alignqd with said blanking die and having a cross-sectional area less than the cross-sectional area of the entrance aperture, the punching being effected by displacing the blnnking punch into the entrance aperture, the transition zone controlling the motion of the blank on shearing from the sheet material and permitting the blanking punch to maintain engagement with the blank as it is moved through the blanking die to the exit aperture; (c) providing a combination ;~draw and ironing die in axial alignment with the exit aperture of the blanking die to receive the blank ~herefrom, the draw and ironing die having an effective entrance aperture and an effective exit aperture, the draw and ironing die entrance aperture having an extent substantially commensurate ~:in size with the size of the blank to be drawn and having a cavity, the walls of which converge inwardly from draw and ironing die entrance aperture to the effective exit aperture, said wall defined by an arc of a sector of a circle, said arc passing from the entrance aperture to the exit aper~ure, said sector having an angle in the range of 12 to 34, said circle having i~s center located in substantially the same plane as said effective exit aperture; and (d) displacing said blank through the combination draw and forming die by action of a punch to form said thin walled shell.
According to a further aspect of the invention there is provided in the method of forming a cartridge case from an elongated, unitary shell having a thin side wall and a relatively thick end integral there~ith, the shell formed from a substantially circular blank, the steps comprising:
(a) providing a blank in a blank holder on a die having an effective a ~
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entrance aperture and an effective exit apeTture, the entrance aperture having an extent substantially commensurate in size with the size of the blank to be drawn, said die having a cavity, the walls of which converge inwardly from said entrance aperture to said effective exit aperture, said wall defined by an arc of a sector of a circle, said arc passing from the entrance aperture to the exit aperture, said sector having an angle in the range o 12 to 34, said circle having its center located in substantially the same plane as said effective exit aperture; and tb) displacing said blank through said die by action of a punch to form said shell.
According to yet another aspect of the invention there is provided in the method of forming a cartridge case from an elongated, tapered wall shell having a relatively thick end integral therewith, the shell formed from a substantially circular blank cut from sheet material, the steps comprising: (a) supporting the sheet material on a blanking die having a substantially circular entrance aperture, an exit aperture and an inwardly converging transition zone extending from the entrance aperture to the exit aperture; (b) punching a blank from the sheet material using a cylindrical blanking punch axially aligned with said blanking die and having a cross-sectional area less than the cross-sectional area of the entrance aperture, the punching being effected by displacing the blanking punch into the entrance aperture, the transition zone controlling the motion of the blank on shearing from the sheet material and permitting the blanking punch to maintain engagement with the blank as it is moved through the blanking die to the exit aperture; (c) providing a combination dra~ and ironing die in axial alignment with the exit aperture of the -blanking die to receive the blank therefrom, the draw and ironing die having an effective entrance aperture and an effective exit aperture, the draw and ironing die entrance aperture having an extent substantially commensurate in size with the size of the blank to be drawn and having a cavity, the walls of which converge inwardly from draw and ironing die entrance aperture to the effective exit aperture, said wall de~ined by an arc of a sector of a circle, said arc passing from the entrance aperture to lb -L54~
.
the exit aperture, said sector having an angle in the ra~ge o 12 to 34J said circle having its center located in substantially the Same plane as said effective exit aperture; and (d) displacing said blank through the combination draw and forming die by action of a punch to form said thin walled shell.
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In the accompanying drawings:
Figure 1 is a simplified diagrammatic view, partially in cross section, including a cylindrical blanking punch and die assembly with sheet material therebetween in accordance with one embodiment of the invention.
Figure 2 is a view similar to that shown in Figure 1 showing a blank cut from the sheet material in accordance with the invention.
Figure 3 is a view similar to that shown in Figure 2 showing a partially formed shell.
Figure 4 shows a tapered wall shell formed by a punch and die in accordance with the present invention.
Referring now more specifically to Figure 1, there is shown a novel combination of blanking punch and die assembly generally referred to as 10 and 20, respectively. ~ workpiece 30, e.g. sheet material, is shown between blanking punch 10 and ;;
die 20. For purposes of illustration, blanking punch 10 and die 20 are shown as substantially circular in cross section. Blanking die 20 has an entrance aperture 21 and an exit aperture 22 and an inwardly converging transition zone 23 extending from entrance aperture 21 to exit aperture 22. Preferably, transition zone 23 is substantially conical in shape as depicted in Figure 1.
Blanking punch 10 can be substantially cylindrical and can accolNmodate a punch 50 which in cooperation with a die (not shown in Figure 1) can form a blank into a cup shaped article in one continuous operation.
Blanking die 20 has aperture 21 axially aligned with blanking punch 10 substantially as shown in Figure 1. Entrance aperture 21 has an effective extent larger than the cross-sectional area of blanking punch 10. When the blanking punch and die are circular, preferably, aperture 21 has a radius 15 to 25% of the sheet material 30 greater than the radius of blanking punch 10.
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In addition, typically exit aperture 22 o die 20 has an extent greater than the cross-sectional area of the blanking punch, depending largely on the thickness of workpiece 30. For an entrance aperture having a diameter of 3.235 inches (82.169 mm) and a sheet thickness of 0.625 inch (15.875 mm), typically exit aperture 22 would have a diameter of about 3.231 inches (82.067 mm).
By effective extent it is meant that entrance aperture 21 is such that upon displacing blanking punch 10 lineally towards blanking die 20l blank 32 is cut or sheared from work-piece 30, Figure 2. The blank has a slightly curved configura-tion. It will be understood that the curved configuration is obtained by providing the clearance between blanking punch and blanking die, as noted hereinabove. Further, it will be under-stood that in conventional blanking punch and die assemblies, the clearance is less than those set forth above and typically have a difference of about 8~ of the sheet material.
If blank 32 is cut from the workpiece by a conventional blanking punch and die assembly, the sheared edge often exhibits what is referred to as secondary fractures. Secondary fractures often result in laps in the wall of the formed article, e.g.
utensils, cartridge cases and the like, during the draw and ironing operation and, of course, must be avoided since they provide weak areas in the wall. ~owever, when the blank is cut from the workpiece in accordance with the present invention, the sheared edge is substantially free of secondary fractures.
In addition to providing a blank which is curved, the blanking punch and die of the present invention cooperate to cut or shear blank 32 from sheet 30 in a way which results in blank top 6~ having a dimension commensurate in size with the size of blanking punch 10 and blank bottom 66 having a dimension comrnen-surate in size with the extent of entrance aperture 21. It is ~8~5~
believed that shearing the blank -from the workpiece in this way aids in ensuring the absence of secondary fractures and the ;~
resulting formation of laps in the subsequent forming operations.
It should be understood that in a conventional blanking die, the blank tends to shoot ahead of the blanking punch on being sheared or cut from the workpiece. When the blank is ;
permitted to move ahead of the blanking punch, it can become misali~ned in the die for the next step, e.g. draw and ironing die, resulting in the formation of a nonsymmetrical cup shaped article. However, by providing transition zone 23 ln the blank-ing die in accordance with the principles of the present invention, the motion of the blank, upon being sheared from the workpiece, is restricted thereby ensuring that the blank remains in contact -~
with the blanking punch and that it does not become misaligned with respect to positioning thereof for the next forming opera- `~
tion.
Another aspect of the present invention includes the formation of elongated, thin walled shells such as tapered wall ~-shells 80, Figure 4. That is, the present invention includes a blanking operation substantially as described above and the ~ !
formation of the elongated, tapered wall shell in one continuous operation. The shells can have a -tapered wall or a substantially uniformly thick wall depending on the shape of the punch used.
If the shells have a tapered wall for forming into cartridge cases, a typical thickness at the mouth of the shell for a 30 mm cartridge would be about 0.03 inch (0.762 mm~. Similarly for a 20 mm cartridge, the shell would have a thickness of about 0~02 inch (0.508 mm~ at its mouth. It will be appreciated that formation of the shell in one continuous operation eliminates ~
many steps including preforming and cupping operations thereby ~ `
permitting the formation of cartridge cases, for example, in a highly economical manner. Figures 2, 3 and 4 depict combination 5~L~
draw and ironing die 100 and tapered punch 50 used in forming the elongated, tapered wall shell. It will be seen from an inspec-tion of Figures 2, 3 and 4 that the blanking die exit aperture 22 can be used as a blank holder for draw and ironing die 100.
Draw and ironing is used herein in its ordinary sense.
That is, ~he term draw refers to an operation where a ~lat blank is turned upwardly at its peripheral margin and simultaneously smoothed by use of a punch and die to form a cup shaped article.
The term ironing refers to an operation wherein the wall of the cup shaped article is elongated by reducing the thic~ness of the wall and without appreciable reduction in the diameter of the cup ;
shaped article. It will be noted that in drawing, the wall of the cup shaped article is also elongated but the diameter of the cup is reduced. By reference to "combination draw and ironing", it is meant that a large part of the drawing operation and the ironing operation take place substantially simultaneously in die 100.
Combination draw and ironing die 100 also has an entrance aperture 102, an exit aperture 104 and a die cavity 106 defined by wall 108. From Figure 2 it will be noted that entrance aperture 102 has an effective extent substantially commensurate in size with the size of blank 32. Also, it will be noted that wall 108 defining die cavity 106 converges inwardly and connects entrance aperture 102 and exit aperture 104. Wall 108 of die caVity 106 has a contoured shape which, along with tapered punch 50 permits the formation of elongated tapered wall shell 80 from blank 32 in one continuous operation. Wall 108 is defined by an arc of a sector of a circle, the arc passing from entrance aperture 102 to exit aperture 104. The sector has an an~le A
(Figure 4) in the range of 12 to 34 and preferably the center of the circle of which the sector is a part has a center located in substantially the same plane as effective exit aperture 104, ~Bl~
as shown in Figure 4. It should be noted that exit aperture 10 also has an effective extent ~hich controls the outside dimen-sions of the elongated tapered wall shell. The cross-sectional configuration of tapered punch 50 controls the inside dimensions of the shell. In addition, the amount of taper in the wall of the shell is controlled by the taper of the punch.
In the present invention, the diameter of blank 32 and therefore the extent of entrance aperture 102 of die 100 is determined largely by the height of the tapered wall shell. That ::
is, because the amount or volume of material in head 82 of the shell 80 is constant for a particular size of exit aperture 104, -additional material in the blank is utilized in producing longer or higher walls on the shells. Thus, the extent or size of entrance aperture 102 is fixed in this way. ~lso, the size of the exit aperture is fixed by the outside diameter of the tapered -wall shell which in the instance of cartridge cases would depend on the caliber desired. ~hus, entrance aperture 102 and exit aperture 104 are determined and can be connected by the arc of a sector of a circle whose center should be in substantially the same plane as exit aperture 104 (Figure 4). The sector has a preferred angle in the range of 18 to 26. ~ith respect to the thickness of the blank, it is determined largely by thickness desired in head 82 of the tapered wall shell. Head 82 has a thickness substantially the sarne as the starting blank in most cases. However, in some instances, the thickness of head 82 can be slightly thicker than the blank.
I~hen it is desired to fabricate cartridge cases, the tapered wall shell formed as above may be subject to additional operations including trimming, providing a head, pocket, vent and extractor grooye.
The present invention is highly advantageous in that by use of the novel blanking punch and die assembly blanks can be .. . .:. ~. .; . ~ ~
.~ 5~:~
cut or sheared from sheet material which blanks, by ~irtue of the blanking die, are positioned symmetrically in a highly consistent basis for forming into shaped articles in subsequent steps. In addition, the present invention is advantageous in that blanking and forming of elongated tapered wall shells can be performed in one continuous operation in a double action press.
By use of the apparatus described, tapered wall, elongated cylindrical shells were produced from aluminum alloys 7475 and 5454 and from brass and mild steel. The brass had a composition of 70 wt.% copper and 30 wt.% zinc. The metal blanks and the tapered wall shell were produced in a single continuous action. The blanks, which were cut from sheet and used for aluminum and brass shells, had a diameter of 0.900 inch (22.860 mm) and a thickness of 0.200 inch (5.080 mm). The elongated, tapered wall shells made from aluminum and brass had a wall thickness at the mouth of the shell oE 0.022 inch (0.5588 mm).
The shells had a length of about 1.40 inch (35.560 mm) and an outside diameter of 0.550 inch (13.970 mm), providing a length to diameter ratio of 2.55:1. The angle of the arc sector for the combination draw-ironing die was 22. It was found that the mild steel was much more difficult to form into tapered wall shells because of the reIatively high yieId strength. However, using steel sheet having a thickness of 0.115 inch (2.921 mm), a tapered wall shell having a length of about 0.85 inch (21.590 mm) was produced. It will be understood that a steel blank having a greater thickness as well as a larger blank diameter can be used in order to form a deeper shell. However, in the case of higher yield stren~th steel, higher press tonnage is required.
Various modifications may be made in the invention without departing from the spirit thereof, or the scope of the claims, and therefore, the exact form shown is to be taken as illustrative only and not in a limiting sense, and it is desired -- . .. . , : .
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that only such limitations shall be placed thereon as are imposed by the prior art, or are specifically set forth in the appended claims.
This invention relates to the production of blanks and shaped articles such as elongated, thin wall shells and, more par~icularly, to a method and apparatus for forming elongated, tapered wall shells useful in the fabrication of cartridge cases and the like.
In the prior art, generally the fabrication of tapered wall shells, such as those used for forming into cartridge cases, has required a series of steps or h~s required complicated machines which permit the fabrication of the shell in a single operation. United States Patent 3,g84,259 and United States Patent 3,498,221 illustrate a typical series of steps used to form the tapered wall shell and a cartridge case there-from. United States Patent 3,088,225 discloses a method for forming a tapered wall shell in a single continuous operation. However, this patent requires triaxial forces, e.g. use of a cushion, to ensure ductility and to control flow of metal in the blank.
The present invention includes a method and apparatus for producing blanks and forming shaped articles such as elongated, thin walled shells having relatively thick integral ends thereon. A simple, double action draw press may be used, for example.
According to one aspect o the inven~ion there is provided a method of forming an elongated, unitary shell having a thin side wall and relatively thick end integral therewith, the shell formed from a substantially circular blank cut from sheet material, the method comprising the steps of: ~a~ providing a blank in a blank holder on a die having an effective entrance aperture and an effective exit aperture, the entrance aperture having an extent substantially commensurate in size with the size of the blank to be drawn, said die having a cavity, the walls of which converge inwardly from said entrance aperture to said e~ective exit aperture, said wall defined by an arc of a sector of a circle, said arc passing from the entrance aperture to the exit aperture, said sector having an angle in the range of 12 to 34, said circle having its center located in substantially the same plane as said effective exit aperture; and tb~
displacing said blank through said die by action of a punch to form said .. , . - 1 - ~ :
~L~8~5~ .
shell.
According to another aspect of the inv~ntion there is provided a method of forming elongated, unitary shell having a thin wall and a relatively thick end, the shell formed from sheet material, the method comprising the steps of: ta) supporting the sheet material on a blanking die having a substantially circular entrance aperture, an exit aperture and an inwardly converging transition zone extending from thc entrance aperture to the exit aperture; (b) punching a blank from the sheet material using a cylindrical blanking punch axially alignqd with said blanking die and having a cross-sectional area less than the cross-sectional area of the entrance aperture, the punching being effected by displacing the blnnking punch into the entrance aperture, the transition zone controlling the motion of the blank on shearing from the sheet material and permitting the blanking punch to maintain engagement with the blank as it is moved through the blanking die to the exit aperture; (c) providing a combination ;~draw and ironing die in axial alignment with the exit aperture of the blanking die to receive the blank ~herefrom, the draw and ironing die having an effective entrance aperture and an effective exit aperture, the draw and ironing die entrance aperture having an extent substantially commensurate ~:in size with the size of the blank to be drawn and having a cavity, the walls of which converge inwardly from draw and ironing die entrance aperture to the effective exit aperture, said wall defined by an arc of a sector of a circle, said arc passing from the entrance aperture to the exit aper~ure, said sector having an angle in the range of 12 to 34, said circle having i~s center located in substantially the same plane as said effective exit aperture; and (d) displacing said blank through the combination draw and forming die by action of a punch to form said thin walled shell.
According to a further aspect of the invention there is provided in the method of forming a cartridge case from an elongated, unitary shell having a thin side wall and a relatively thick end integral there~ith, the shell formed from a substantially circular blank, the steps comprising:
(a) providing a blank in a blank holder on a die having an effective a ~
~ - la -8~54~
entrance aperture and an effective exit apeTture, the entrance aperture having an extent substantially commensurate in size with the size of the blank to be drawn, said die having a cavity, the walls of which converge inwardly from said entrance aperture to said effective exit aperture, said wall defined by an arc of a sector of a circle, said arc passing from the entrance aperture to the exit aperture, said sector having an angle in the range o 12 to 34, said circle having its center located in substantially the same plane as said effective exit aperture; and tb) displacing said blank through said die by action of a punch to form said shell.
According to yet another aspect of the invention there is provided in the method of forming a cartridge case from an elongated, tapered wall shell having a relatively thick end integral therewith, the shell formed from a substantially circular blank cut from sheet material, the steps comprising: (a) supporting the sheet material on a blanking die having a substantially circular entrance aperture, an exit aperture and an inwardly converging transition zone extending from the entrance aperture to the exit aperture; (b) punching a blank from the sheet material using a cylindrical blanking punch axially aligned with said blanking die and having a cross-sectional area less than the cross-sectional area of the entrance aperture, the punching being effected by displacing the blanking punch into the entrance aperture, the transition zone controlling the motion of the blank on shearing from the sheet material and permitting the blanking punch to maintain engagement with the blank as it is moved through the blanking die to the exit aperture; (c) providing a combination dra~ and ironing die in axial alignment with the exit aperture of the -blanking die to receive the blank therefrom, the draw and ironing die having an effective entrance aperture and an effective exit aperture, the draw and ironing die entrance aperture having an extent substantially commensurate in size with the size of the blank to be drawn and having a cavity, the walls of which converge inwardly from draw and ironing die entrance aperture to the effective exit aperture, said wall de~ined by an arc of a sector of a circle, said arc passing from the entrance aperture to lb -L54~
.
the exit aperture, said sector having an angle in the ra~ge o 12 to 34J said circle having its center located in substantially the Same plane as said effective exit aperture; and (d) displacing said blank through the combination draw and forming die by action of a punch to form said thin walled shell.
l c -`:
In the accompanying drawings:
Figure 1 is a simplified diagrammatic view, partially in cross section, including a cylindrical blanking punch and die assembly with sheet material therebetween in accordance with one embodiment of the invention.
Figure 2 is a view similar to that shown in Figure 1 showing a blank cut from the sheet material in accordance with the invention.
Figure 3 is a view similar to that shown in Figure 2 showing a partially formed shell.
Figure 4 shows a tapered wall shell formed by a punch and die in accordance with the present invention.
Referring now more specifically to Figure 1, there is shown a novel combination of blanking punch and die assembly generally referred to as 10 and 20, respectively. ~ workpiece 30, e.g. sheet material, is shown between blanking punch 10 and ;;
die 20. For purposes of illustration, blanking punch 10 and die 20 are shown as substantially circular in cross section. Blanking die 20 has an entrance aperture 21 and an exit aperture 22 and an inwardly converging transition zone 23 extending from entrance aperture 21 to exit aperture 22. Preferably, transition zone 23 is substantially conical in shape as depicted in Figure 1.
Blanking punch 10 can be substantially cylindrical and can accolNmodate a punch 50 which in cooperation with a die (not shown in Figure 1) can form a blank into a cup shaped article in one continuous operation.
Blanking die 20 has aperture 21 axially aligned with blanking punch 10 substantially as shown in Figure 1. Entrance aperture 21 has an effective extent larger than the cross-sectional area of blanking punch 10. When the blanking punch and die are circular, preferably, aperture 21 has a radius 15 to 25% of the sheet material 30 greater than the radius of blanking punch 10.
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In addition, typically exit aperture 22 o die 20 has an extent greater than the cross-sectional area of the blanking punch, depending largely on the thickness of workpiece 30. For an entrance aperture having a diameter of 3.235 inches (82.169 mm) and a sheet thickness of 0.625 inch (15.875 mm), typically exit aperture 22 would have a diameter of about 3.231 inches (82.067 mm).
By effective extent it is meant that entrance aperture 21 is such that upon displacing blanking punch 10 lineally towards blanking die 20l blank 32 is cut or sheared from work-piece 30, Figure 2. The blank has a slightly curved configura-tion. It will be understood that the curved configuration is obtained by providing the clearance between blanking punch and blanking die, as noted hereinabove. Further, it will be under-stood that in conventional blanking punch and die assemblies, the clearance is less than those set forth above and typically have a difference of about 8~ of the sheet material.
If blank 32 is cut from the workpiece by a conventional blanking punch and die assembly, the sheared edge often exhibits what is referred to as secondary fractures. Secondary fractures often result in laps in the wall of the formed article, e.g.
utensils, cartridge cases and the like, during the draw and ironing operation and, of course, must be avoided since they provide weak areas in the wall. ~owever, when the blank is cut from the workpiece in accordance with the present invention, the sheared edge is substantially free of secondary fractures.
In addition to providing a blank which is curved, the blanking punch and die of the present invention cooperate to cut or shear blank 32 from sheet 30 in a way which results in blank top 6~ having a dimension commensurate in size with the size of blanking punch 10 and blank bottom 66 having a dimension comrnen-surate in size with the extent of entrance aperture 21. It is ~8~5~
believed that shearing the blank -from the workpiece in this way aids in ensuring the absence of secondary fractures and the ;~
resulting formation of laps in the subsequent forming operations.
It should be understood that in a conventional blanking die, the blank tends to shoot ahead of the blanking punch on being sheared or cut from the workpiece. When the blank is ;
permitted to move ahead of the blanking punch, it can become misali~ned in the die for the next step, e.g. draw and ironing die, resulting in the formation of a nonsymmetrical cup shaped article. However, by providing transition zone 23 ln the blank-ing die in accordance with the principles of the present invention, the motion of the blank, upon being sheared from the workpiece, is restricted thereby ensuring that the blank remains in contact -~
with the blanking punch and that it does not become misaligned with respect to positioning thereof for the next forming opera- `~
tion.
Another aspect of the present invention includes the formation of elongated, thin walled shells such as tapered wall ~-shells 80, Figure 4. That is, the present invention includes a blanking operation substantially as described above and the ~ !
formation of the elongated, tapered wall shell in one continuous operation. The shells can have a -tapered wall or a substantially uniformly thick wall depending on the shape of the punch used.
If the shells have a tapered wall for forming into cartridge cases, a typical thickness at the mouth of the shell for a 30 mm cartridge would be about 0.03 inch (0.762 mm~. Similarly for a 20 mm cartridge, the shell would have a thickness of about 0~02 inch (0.508 mm~ at its mouth. It will be appreciated that formation of the shell in one continuous operation eliminates ~
many steps including preforming and cupping operations thereby ~ `
permitting the formation of cartridge cases, for example, in a highly economical manner. Figures 2, 3 and 4 depict combination 5~L~
draw and ironing die 100 and tapered punch 50 used in forming the elongated, tapered wall shell. It will be seen from an inspec-tion of Figures 2, 3 and 4 that the blanking die exit aperture 22 can be used as a blank holder for draw and ironing die 100.
Draw and ironing is used herein in its ordinary sense.
That is, ~he term draw refers to an operation where a ~lat blank is turned upwardly at its peripheral margin and simultaneously smoothed by use of a punch and die to form a cup shaped article.
The term ironing refers to an operation wherein the wall of the cup shaped article is elongated by reducing the thic~ness of the wall and without appreciable reduction in the diameter of the cup ;
shaped article. It will be noted that in drawing, the wall of the cup shaped article is also elongated but the diameter of the cup is reduced. By reference to "combination draw and ironing", it is meant that a large part of the drawing operation and the ironing operation take place substantially simultaneously in die 100.
Combination draw and ironing die 100 also has an entrance aperture 102, an exit aperture 104 and a die cavity 106 defined by wall 108. From Figure 2 it will be noted that entrance aperture 102 has an effective extent substantially commensurate in size with the size of blank 32. Also, it will be noted that wall 108 defining die cavity 106 converges inwardly and connects entrance aperture 102 and exit aperture 104. Wall 108 of die caVity 106 has a contoured shape which, along with tapered punch 50 permits the formation of elongated tapered wall shell 80 from blank 32 in one continuous operation. Wall 108 is defined by an arc of a sector of a circle, the arc passing from entrance aperture 102 to exit aperture 104. The sector has an an~le A
(Figure 4) in the range of 12 to 34 and preferably the center of the circle of which the sector is a part has a center located in substantially the same plane as effective exit aperture 104, ~Bl~
as shown in Figure 4. It should be noted that exit aperture 10 also has an effective extent ~hich controls the outside dimen-sions of the elongated tapered wall shell. The cross-sectional configuration of tapered punch 50 controls the inside dimensions of the shell. In addition, the amount of taper in the wall of the shell is controlled by the taper of the punch.
In the present invention, the diameter of blank 32 and therefore the extent of entrance aperture 102 of die 100 is determined largely by the height of the tapered wall shell. That ::
is, because the amount or volume of material in head 82 of the shell 80 is constant for a particular size of exit aperture 104, -additional material in the blank is utilized in producing longer or higher walls on the shells. Thus, the extent or size of entrance aperture 102 is fixed in this way. ~lso, the size of the exit aperture is fixed by the outside diameter of the tapered -wall shell which in the instance of cartridge cases would depend on the caliber desired. ~hus, entrance aperture 102 and exit aperture 104 are determined and can be connected by the arc of a sector of a circle whose center should be in substantially the same plane as exit aperture 104 (Figure 4). The sector has a preferred angle in the range of 18 to 26. ~ith respect to the thickness of the blank, it is determined largely by thickness desired in head 82 of the tapered wall shell. Head 82 has a thickness substantially the sarne as the starting blank in most cases. However, in some instances, the thickness of head 82 can be slightly thicker than the blank.
I~hen it is desired to fabricate cartridge cases, the tapered wall shell formed as above may be subject to additional operations including trimming, providing a head, pocket, vent and extractor grooye.
The present invention is highly advantageous in that by use of the novel blanking punch and die assembly blanks can be .. . .:. ~. .; . ~ ~
.~ 5~:~
cut or sheared from sheet material which blanks, by ~irtue of the blanking die, are positioned symmetrically in a highly consistent basis for forming into shaped articles in subsequent steps. In addition, the present invention is advantageous in that blanking and forming of elongated tapered wall shells can be performed in one continuous operation in a double action press.
By use of the apparatus described, tapered wall, elongated cylindrical shells were produced from aluminum alloys 7475 and 5454 and from brass and mild steel. The brass had a composition of 70 wt.% copper and 30 wt.% zinc. The metal blanks and the tapered wall shell were produced in a single continuous action. The blanks, which were cut from sheet and used for aluminum and brass shells, had a diameter of 0.900 inch (22.860 mm) and a thickness of 0.200 inch (5.080 mm). The elongated, tapered wall shells made from aluminum and brass had a wall thickness at the mouth of the shell oE 0.022 inch (0.5588 mm).
The shells had a length of about 1.40 inch (35.560 mm) and an outside diameter of 0.550 inch (13.970 mm), providing a length to diameter ratio of 2.55:1. The angle of the arc sector for the combination draw-ironing die was 22. It was found that the mild steel was much more difficult to form into tapered wall shells because of the reIatively high yieId strength. However, using steel sheet having a thickness of 0.115 inch (2.921 mm), a tapered wall shell having a length of about 0.85 inch (21.590 mm) was produced. It will be understood that a steel blank having a greater thickness as well as a larger blank diameter can be used in order to form a deeper shell. However, in the case of higher yield stren~th steel, higher press tonnage is required.
Various modifications may be made in the invention without departing from the spirit thereof, or the scope of the claims, and therefore, the exact form shown is to be taken as illustrative only and not in a limiting sense, and it is desired -- . .. . , : .
~8~54~
that only such limitations shall be placed thereon as are imposed by the prior art, or are specifically set forth in the appended claims.
Claims (12)
1. A method of forming an elongated, unitary shell having a thin side wall and relatively thick end integral there-with, the shell formed from a substantially circular blank cut from sheet material, the method comprising the steps of: (a) providing a blank in a blank holder on a die having an effective entrance aperture and an effective exit aperture, the entrance aperture having an extent substantially commensurate in size with the size of the blank to be drawn, said die having a cavity, the walls of which converge inwardly from said entrance aperture to said effective exit aperture, said wall defined by an arc of a sector of a circle, said arc passing from the entrance aperture to the exit aperture, said sector having an angle in the range of 12 to 34°, said circle having its center located in substantially the same plane as said effective exit aperture; and (b) displacing said blank through said die by action of a punch to form said shell.
2. The method according to claim 1 wherein the sheet material employed is metal.
3. The method according to claim 1 wherein the sector of the circle has an angle in the range of 18 to 26°.
4. The method according to claim 1 wherein the elon-gated shell has a tapered wall.
5. The method according to claim 1 wherein the end of the shell has a thickness substantially the same as the thickness of the blank.
6. A method of forming elongated, unitary shell having a thin wall and a relatively thick end, the shell formed from sheet material, the method comprising the steps of: (a) supporting the sheet material on a blanking die having a substan-tially circular entrance aperture, an exit aperture and an in-wardly converging transition zone extending from the entrance aperture to the exit aperture (b) punching a blank from the sheet material using a cylindrical blanking punch axially aligned with said blanking die and having a cross-sectional area less than the cross-sectional area of the entrance aperture, the punching being effected by displacing the blanking punch into the entrance aperture, the transition zone controlling the motion of the blank on shearing from the sheet material and permitting the blanking punch to maintain engagement with the blank as it is moved through the blanking die to the exit aperture; (c) providing a combination draw and ironing die in axial alignment with the exit aperture of the blanking die to receive the blank therefrom, the draw and ironing die having an effective entrance aperture and an effective exit aperture, the draw and ironing die entrance aperture having an extent substantially commensurate in size with the size of the blank to be drawn and having a cavity, the walls of which converge inwardly from draw and ironing die entrance aperture to the effective exit aperture, said wall defined by an arc of a sector of a circle, said arc passing from the entrance aperture to the exit aperture, said sector having an angle in the range of 12 to 34°, said circle having its center located in substantially the same plane as said effective exit aperture; and (d) displacing said blank through the combination draw and forming die by action of a punch to form said thin walled shell.
7. The method according to claim 6 wherein the sector of the circle has an angle in the range of 18 to 26°.
8. The method according to claim 6 wherein the shell has a tapered wall and an end which has a thickness substantially the same as the thickness of the blank.
9. The method according to claim 6 wherein the blank-ing die aperture has a radius 15 to 25% of the sheet material greater than the radius of the blanking punch.
10. The method according to claim 6 wherein the blank cut from the sheet material by the blanking punch and die is substantially free of secondary fractures.
11. In the method of forming a cartridge case from an elongated, unitary shell having a thin side wall and a relatively thick end integral therewith, the shell formed from a substan-tially circular blank, the steps comprising: (a) providing a blank in a blank holder on a die having an effective entrance aperture and an effective exit aperture, the entrance aperture having an extent substantially commensurate in size with the size of the blank to be drawn, said die having a cavity, the walls of which converge inwardly from said entrance aperture to said effective exit aperture, said wall defined by an arc of a sector of a circle, said arc passing from the entrance aperture to the exit aperture, said sector having an angle in the range of 12 to 34°, said circle having its center located in substantially the same plane as said effective exit aperture; and (b) displacing said blank through said die by action of a punch to form said shell.
12. In the method of forming a cartridge case from an elongated, tapered wall shell having a relatively thick end integral therewith, the shell formed from a substantially cir-cular blank cut from sheet material, the steps comprising: (a) supporting the sheet material on a blanking die having a substan-tially circular entrance aperture, an exit aperture and an in-wardly converging transition zone extending from the entrance aperture to the exit aperture; (b) punching a blank from the sheet material using a cylindrical blanking punch axially aligned with said blanking die and having a cross-sectional area less than the cross-sectional area of the entrance aperture, the punching being effected by displacing the blanking punch into the entrance aperture, the transition zone controlling the motion of the blank on shearing from the sheet material and permitting the blanking punch to maintain engagement with the blank as it is moved through the blanking die to the exit aperture; (c) provid-ing a combination draw and ironing die in axial alignment with the exit aperture of the blanking die to receive the blank therefrom, the draw and ironing die having an effective entrance aperture and an effective exit aperture, the draw and ironing die entrance aperture having an extent substantially commensurate in size with the size of the blank to be drawn and having a cavity, the walls of which converge inwardly from draw and ironing die entrance aperture to the effective exit aperture, said wall defined by an arc of a sector of a circle, said arc passing from the entrance aperture to the exit aperture, said sector having an angle in the range of 12 to 34°, said circle having its center located in substantially the same plane as said effective exit aperture; and (d) displacing said blank through the combination draw and forming die by action of a punch to form said thin walled shell.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/849,996 US4129024A (en) | 1977-11-09 | 1977-11-09 | Method and apparatus for forming elongated, tapered wall shells |
| US849,996 | 1977-11-09 | ||
| US852,319 | 1977-11-17 | ||
| US05/852,319 US4142396A (en) | 1977-11-17 | 1977-11-17 | Blanking and forming tapered wall articles |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1081549A true CA1081549A (en) | 1980-07-15 |
Family
ID=27126889
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA316,023A Expired CA1081549A (en) | 1977-11-09 | 1978-11-09 | Blanking and forming tapered wall articles |
Country Status (11)
| Country | Link |
|---|---|
| JP (1) | JPS5499070A (en) |
| CA (1) | CA1081549A (en) |
| CH (1) | CH632427A5 (en) |
| DE (1) | DE2847812A1 (en) |
| FR (1) | FR2408406A1 (en) |
| GB (1) | GB2007570B (en) |
| IL (1) | IL55784A (en) |
| IT (1) | IT1106787B (en) |
| NL (1) | NL7810626A (en) |
| NO (1) | NO783613L (en) |
| SE (1) | SE7810891L (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2508504B2 (en) * | 1986-03-28 | 1996-06-19 | 三菱マテリアル株式会社 | Method for manufacturing thick cylindrical hollow body made of copper-based memory alloy |
| CN113102532B (en) * | 2021-04-14 | 2022-03-25 | 中北大学 | Labor-saving forming method suitable for large-size thin-wall conical shell |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2345863A (en) * | 1939-03-04 | 1944-04-04 | Remington Arms Co Inc | Projectile |
| US2379450A (en) * | 1942-06-16 | 1945-07-03 | Musser Clarence Walton | Primer manufacture |
| US2415940A (en) * | 1944-10-05 | 1947-02-18 | Remington Arms Co Inc | Metal cupping process |
| US2490926A (en) * | 1945-06-01 | 1949-12-13 | Remington Arms Co Inc | Blanking and cupping die unit |
| US3977225A (en) * | 1975-03-27 | 1976-08-31 | Aluminum Company Of America | Forging method |
-
1978
- 1978-10-19 SE SE7810891A patent/SE7810891L/en unknown
- 1978-10-20 GB GB7841430A patent/GB2007570B/en not_active Expired
- 1978-10-24 IL IL55784A patent/IL55784A/en unknown
- 1978-10-25 NL NL7810626A patent/NL7810626A/en not_active Application Discontinuation
- 1978-10-25 NO NO783613A patent/NO783613L/en unknown
- 1978-11-02 DE DE19782847812 patent/DE2847812A1/en not_active Withdrawn
- 1978-11-07 IT IT51794/78A patent/IT1106787B/en active
- 1978-11-08 JP JP13776578A patent/JPS5499070A/en active Pending
- 1978-11-08 CH CH1150878A patent/CH632427A5/en not_active IP Right Cessation
- 1978-11-09 FR FR7831694A patent/FR2408406A1/en not_active Withdrawn
- 1978-11-09 CA CA316,023A patent/CA1081549A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| FR2408406A1 (en) | 1979-06-08 |
| GB2007570B (en) | 1982-06-30 |
| NL7810626A (en) | 1979-05-11 |
| IL55784A (en) | 1981-07-31 |
| IT7851794A0 (en) | 1978-11-07 |
| GB2007570A (en) | 1979-05-23 |
| SE7810891L (en) | 1979-05-10 |
| CH632427A5 (en) | 1982-10-15 |
| JPS5499070A (en) | 1979-08-04 |
| DE2847812A1 (en) | 1979-05-10 |
| IT1106787B (en) | 1985-11-18 |
| NO783613L (en) | 1979-05-10 |
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