US3594882A - Warhead and method of making same - Google Patents

Abstract

A warhead and the method of making same by cutting a tube blank from a length of metal tubing at a position on the length of tubing which will result in the blank containing the amount of material required in the finished warhead, cold extruding the blank to elongate the blank and to form an enlarged annular section about a first end, cold extruding the blank to taper the blank toward the second end, cold extruding the blank to move the enlarged section radially inward so that the blank has a substantially constant diameter form the first end to the taper, and cold extruding the blank to taper the first end. During or before the first or an early extrusion step groove may be formed in the surface of the blank so that during a subsequent extruding step metal adjacent the grooves if forced and moved together to smooth the surface and establish fault lines so as to control the fragmentation pattern of the warhead.

Description

United States Patent [72] inventor Robert Lovell Bloomfield Hills, Mich. [2]] Appl. No. 778.249 [22] Filed Nov. 22, I968 [45] Patented July 27, 1971 I73] Assignee Lawrence B. Boenscli Birmingham, Mkli.

a part interest {54] WARHEAD AND METHOD OF MAKING SAME 26 Claims, 7 Drawing Figs.

[52] US. Cl. 2911.2, l02l92.5 [S1] Int.Cl ..B2lk21l06 [$0] Fleld ofSenrch ..29/l.2, L2]

[56] References Cited UNITED STATES PATENTS l,l3l,973 3/l9l5 While 29/].2 2,325,079 7/1943 Soderholm 20H .2 X 2,663,068 l2/l953 Towner....................,... 29/12 3,0l9,733 2/[962 Braid 29/l.2X

Primary Examiner-Harrison L. Hinson AnorneyBarnard, McGlynn & Reising ABSTRACT: A warhead and the method of making same by cutting a tube blank from a length of metal tubing at a position on the length of tubing which will result in the blank containing the amount of material required in the finished warhead, cold extruding the blank to elongate the blank and to form an enlarged annular section about a first end, cold extruding the blank to taper the blank toward the second end, cold extruding the blank to move the enlarged section radially inward so that the blank has a substantially constant diameter form the first end to the taper, and cold extruding the blank to taper the first end. During or before the first or an early extrusion step groove may be formed in the surface of the blank so that during a subsequent extruding step metal adjacent the grooves if forced and moved together to smooth the surface and establish fault lines so as to control the fragmentation pattern of the warhead.

maminm sum 1 BF 2 WAIIIIEAD AND METHOD OF MAKING SAME This invention relates to a warhead and the method of making the same. The invention has been found very satisfactory for warheads of the type utilircd in mortars. This type of warhead is sent through the air in a trajectory to the target. The weight of the warheads must, therefore, be maintained within very close tolerances otherwise the trajectory and the closeness of the hit to the target can be seriously affected. Additionally, the warhead must have an outer surface which is aerodynamically and ballistically stable. Furthermore, such a warhead is an antipersonnel explosive device and should fragment into many small pieces upon detonation.

An example of a warhead of this type is one approximately l inches long and a little over 3 inches in diameter at the largest portion and having a wall thickness of approximately onequarter inch.

warheads of this type have heretofore and are now being made by casting or hot extrusion.

A warhead made by casting inherently has a high degree of porosity and must be machined on all surfaces including both the complete inner and outer diameters of the warhead. The warhead must be machined to the proper weight and in the case of castings the reduction in weight due to this machining approximates 50 percent. The warhead is also machined to in sure against porosity and to smooth the outer surface for aerodynamic stability. All warheads must pass hydrostatic and air pressure tests, as for example, hydrostatically being subjected to 6,000 p/.s.i. for 6 seconds. Because of the high porosity in castings, even after machining, the scrap rate of warheads made by casting is extremely high, i.e., a very high percentage of such warheads fail the hydrostatic test. Warheads made by casting are, relative to the instant invention, very expensive due to the precise machining necessary and the attendant loss of material thereby and because of the high scrap rate for failure to pass the air and hydrostatic test.

In making the warheads by hot extrusion, a heated oversized billet is pressed into a cup-shape and then extruded. This process also requires extreme metal removal by machining.

In warheads made by either casting or hot extrusion it is very difficult, and frequently impossible to provide a fragmentation pattern which is consistent.

Accordingly, it is an object and feature of this invention to provide an improved warhead and the method for making same which results in a higher quality warhead at a significantly reduces cost.

Another object and feature of this invention is to provide a method of making a warhead wherein; the material loss is insignificant, which requires negligible machining, and wherein the tolerances from warhead to warhead are very consistent.

Another object and feature of this invention is to provide a warhead and the method of making same wherein the fragmentation pattern is substantially consistent.

Another object and feature of this invention is to provide a method of making a warhead by cold extruding a metal tubular blank so as to elongate the blank and form a precise enlarged annular section about one end thereof and thereafter extruding the blank to move the enlarged annular section radially inwardly to develop the precise amount of material and dimensions in the ogive section of the warhead and thereafter tapering and/or nosing the ends of the blank.

In correlation with the foregoing objects and features, another object and feature of this invention is to provide a warhead having the desired fragmentation pattern by forming grooves in the warhead prior to one of the cold extruding steps so that during a subsequent cold extruding step metal adjacent the grooves is forced together to smooth the surface and form fault lines.

Other objects and attendant advantages of the present in vention will be readily appreciated as the same becomes better understood by reference to be following detailed description when considered in connection with the accompanying drawings wherein:

FIG. I is a view of a length of pipe from which tubular blanks are cut',

FIG. 2 discloses the extruded tubular blank as extruded to be elongated and to have an enlarged annular section about one end;

FIG. 3 shows the tubular blank with the second end thereof being tapered;

FIG. 4 discloses the tubular blank with the enlarged annular section at the first end thereof having been moved radially inwardly;

FIG. 5 discloses the blank with the first end thereof having been tapered;

FIG. 6 is a cross-sectional view taken substantially along line 6-6 of FIG. 2; and

FIG. 7 is an enlarged view of the tubular blank with grooves in the outer surface thereof prior to the first extruding step.

FIG. I discloses a length of tube I0. Initially, a tubular blank 12 is cut from the length of tube at a position 14 on the length of tube which will result in the blank 12 containing the amount of material required in the finished warhead. The length of tube It] utilized in the instant method is preferably of a high quality in that it has a consistent density along its entire length. After the first blank 12 has been cut from the length of tubing I0, it is weighed to make sure that it is of the proper weight. If the first blank is not at the proper weight, the position I4 is adjusted accordingly so that the next blank does have the exact weight and amount of material required for the final or finished warhead. Instead of weighing the blank, the length of the blank may be changed if after one or more extruding steps, the volume in the blank is found to be out of tolerance. It has been found satisfactory to use medium or low-carbon steels as well as alloy steels such as SAE I0l 8 or SAE I340 steel.

As will be understood to those skilled in the art, the steps described and illustrated hereinafter may be performed simultaneously with other steps and in varying sequences.

As illustrated in FIG. 2, an initial step is to cold extrude the metal tubular blank to elongate it and to simultaneously form an enlarged annular section 16 about a first end thereof. In this step the blank is cold worked to reduce the wall thickness or the cross-sectional area of the material. This is accomplished by forcing the blank through a first female die 18 with the punch 20 and the sleeve 22, the sleeve 22 engaging the upper end of the blank I2. The female die 18 has a land 24 through which the blank is forced so as to be elongated as the wall thickness thereof is reduced. As shown at 25, there is a relief below the land 24, i.e., the die 18 has a larger diameter below the land 24 than the diameter of the land itself. A radius of between 0.40 and 0.70 inches leading into the land 24 has been satisfactory, although this may vary with changes in other parameters. In an example, the blank I2 is approximately 6-3/4 inches long and is elongated to approximately 9 inches long during the step illustrated in FIG. 2. In FIG. 2, as in the remaining FIGS. the large metal member shown in cross section and surrounding the extruding members are support and retaining members of the type well known in the art.

The next step illustrated is that of FIG. 3 wherein the blank is extruded to taper the second end thereof as indicated at 26. This is accomplished by forcing the blank into the tapered female die 28 with a tapered punch 30 and sleeve 32. It will be noted that the tapered female die 28 has a shoulder 34 for engaging the enlarged angular section at the first end of the blank.

The fourth step is illustrated in FIG. 4, wherein the blank is extruded to move the enlarged section 16 radially inwardly so that the outer diameter of the blank is substantially constant from the first end thereof to the taper 26. This is accomplished by forcing the blank downwardly through the die member 36 which has the land 38 for forcing the enlarged angular section l6 radially inwardly. Again, there is a relief 39 below the land 38. The upper end of the blank is engaged by the punch 40.

The last step is illustrated in FIG. 5 wherein the first end of the blank is nosed by the female die 42 as the blank is held in position by the tapered member 44.

Each of the steps subsequent to the step illustrated in FIG. 2 is also a cold extruding step in that the blank changes shape and size or dimension and in one example is actually elongated approximately one hundred and fifty to three hundred thousandths of an inch in each step. Also, as will be specified hereinafter, the physical characteristics and the mechanical properties of the blank are altered during each step.

Preferably grooves are formed in the surface of the blank prior to one of the extruding steps so that a subsequent extruding step forces the metal adjacent the grooves together to smooth the surface and mechanically establish fault lines. Such grooves are preferably formed in the blank 12 before the first cold extruding step, as illustrated in FIG. 7 but at least some of the grooves may be formed either on the inner or outer diameter during the first cold extruding step, forming the grooves on the inner diameter by extruding is illustrated in FIG. 2.

A blank 12 is illustrated in FIG. 7 with longitudinal grooves 52 and circumferential grooves 54. These grooves are formed prior to the first cold extrusion step illustrated in FIG. 2 The grooves 54 are formed in the surface of the blank transversely to the first mentioned longitudinal grooves 52. The grooves 54 are disposed circumferentially about the blank and are defined by a single-helical groove. The grooves 52 and 54 are preferably formed by moving metal as by cold rolling although may be formed by cutting the blank to remove material therefrom. Cutting, however, must be done very accurately to control the final weight of the warhead. Once the grooves 52 and 54 are formed in the warhead blank the metal adjacent the groove: is forced together during the first extruding step thereby smoothing the surface and establishing the mechanical fault lines. A fault line is the interface where the metal adjacent the grooves is forced together so as to be contiguous and nonhomogeneous at the interface yet whereby the outer surface is smooth and such lines are substantially invisible to the naked eye. These fault lines may be on the inner or outer surface of the warhead but are preferably on the outer surface of the warhead because upon detonation die warhead balloons which tends to separate the metal along the fault lines so that the warhead will fragmentize along the fault lines into numerous identical fragments.

As alluded to'above, the grooves may also be formed on the outside or inside of the blank by cold extruding. An example of extruding the grooves on the inner diameter is shown in FIG. 2 wherein the punch is splined so as to have spaced ridges 50 which form grooves on the inner surface of the blank during the first extruding step. The circumferential curves may be then formed on either the inner or outer surface after the first extruding step by cold rolling or threading. The subsequent extruding steps smooth the surface to establish the fault lines.

The finished warhead, therefore, has a very smooth outer surface and is within strict tolerances as to its weight. One last step is performed on the warhead in the configuration illustrated in FIG. 5 and that is to form threads along the surface for receiving a detonation device. The forming of these threads can be accurately controlled so as to provide a warhead having a weight within specified tolerances.

When using a steel having a tensile of approximately 96,000 p.s.i., a hardness of approximately 92 as measured on the Rockwell B Scale, a yield strength of approximately 75,000 p.s.i., and the elongation being approximately 23 percent, the mechanical properties of the blank are altered during the extrusion steps described so that the finished warhead has a hardness of approximately 31 on the Rockwell C Scale, a tensile of approximately 145,000 p.s.i., a yield strength of approximately 140,000 p.s.i., and the elongation being approximately 10 percent which, of course, perfects the fragmentation of the warhead upon detonation. It is also to be noted that low-car bon steel could not be satisfactorily utilized in the prior methods for making warheads because the finished warhead would fragmentize into large pieces. However, low-carbon steel can be utilized with the instant method including the grooving thereof because such establishes a fragmentation pattern such that the warhead of low-carbon steel fragmentizes into a large number of small pieces.

In forming a warhead by casting or hot forging as described hereinabove, the wall thickness can be maintained within a tolerance of plus or minus thirty thousandths whereas the wall thickness of the warhead made in accordance with the instant method may be maintained between 5 and i0 thousandths. Furthermore, the dies utilized to cold extrude the warhead in accordance with the instant invention may be revised in size very easily to change the desired weight of the finished warhead. Additionally, a warhead may be made in accordance with the instant invention at a cost which is approximately one-third less than the cost of a warhead made by casting or hot forging. Although the step of reducing the diameter of the first end of the warhead has been referred to as nosing because, as illustrated. it does not have a straight taper whereas the second does, it will be understood that in the general sense these terms are interchangeable.

The invention has been described in an illustrative manner and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

I. A method of making a warhead comprising the steps of: cold extruding a metal tubular blank to form an enlarged annular section about a first end thereof, and cold extruding the blank to move the enlarged section radially inward.

2. A method as set forth in claim 1 further defined as cold extruding the blank to elongate the blank while forming said enlarged section.

3. A method as set forth in claim 2 further defined as cold extruding the blank to nose the first end and to taper the second end thereof.

4. A method as set forth in claim 3 further defined as first cold extruding the blank to taper the second end thereof and then cold extruding the blank to move the enlarged section radially inward so that the blank has a substantially constant diameter from the first end thereof to the taper end then cold extruding the blank to nose the first end thereof.

5. A method as set forth in claim 4 including initially cutting the tubular blank from a length of tubing at a position on the length of tubing which will result in the blank containing the amount of material required in the finished warhead.

6. A method as set forth in claim 4 wherein said blank comprises steel having a tensile of approximately 96,000 p.s.i., a hardness of approximately 92 I IS measured on the Rockwell B Scale, I yleld strength of approxlmately 75,000 p.s.i. and the elongation being approximately 23 percent.

7. A method as set forth in claim 4 wherein said blank comprises one of SAE 1018 and SAE 1340 steel.

8. A method as set forth in claim 5 including forming grooves in the surface of said blank prior to one of said extruding steps so that a subsequent extruding step forces the metal together to smooth the surface and establish fault lines.

9. A method as set forth in claim 8 further defined as forming said grooves in said blank prior to the first cold extruding step.

10. A method as set forth in claim 8 further defined as forming the grooves in one of the inner and outer surfaces of said blank and including the step of forming other grooves in one of said surfaces transverse to said first mentioned grooves.

II. A method as set forth in claim 10 further defined as forming said other grooves prior to one of said extruding steps so that a subsequent extruding step forces the metal together and smooths the surface to establish fault lines.

[2. A method as set forth in claim further defined as forming said first mentioned grooves longitudinally along said blank.

13. A method as set forth in claim 12 further defined as forming said other grooves circumfcrentially about said blank.

14. A method as set forth in claim 13 further defined as forming said first mentioned grooves by extruding said blank with a member having ridges.

15. A method as set forth in claim 14 further defined as forming said other grooves by forming a helical groove.

[6. A method as set forth in claim 15 further defined as moving metal to form said helical groove.

l7. A method as set forth in claim l6 further defined as forming all of said grooves in the outer surface of said blank.

18. A method of making a warhead which will fragmentize in a predetermined pattern comprising the steps of; forming grooves in a surface ofa warhead blank, and forcing the metal adjacent the grooves together to smooth said surface and establish fault lines.

19. A method as set forth in claim l8 further defined as cold extruding said blank to smooth said surface and establish fault fill lines.

20. A method as set forth in claim 18 further defined as forming said grooves by cold extruding.

21. A method as set forth in claim 20 wherein said blank is a generally tubular member and further defined as forming said grooves longitudinally along the surface of said blank.

22. A method as set forth in claim 2] further defined as forming said grooves by extruding said blank with a member having ridges thereabout.

23. A method as set forth in claim 20 including the step of forming other grooves in a surface of said blank transverse to said first mentioned grooves.

24. A method as set forth in claim 23 further defined as extruding said blank to force the metal adjacent said other grooves together to smooth said surface and establish fault lines.

25. A method as set forth in claim 24 wherein said other grooves are formed by a helical groove.

26. A method as set forth in claim 25 further defined as moving metal to form said helical groove.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3,594,88 Dated July 227 1971 Inventor(s) Robert Lovell It is certified that error appears in the above-identified patent t and that said Letters Patent are hereby corrected as shown below:

Abstract, line 9 "form" should be --from--; abstract, line 12 "groove" should be --grooves--. Column 1, line #7 "reduces" should be --reduoed--; column 1, line 73 "he" should be --the--. Column 4, line 3 of Claim 6 after 92 delete "l".

Signed and sealed this 26th day of March 1 972.

(SEAL) Attest:

EDWARD M.FLETCHER, JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents FORM PO-1050 (10-69) USCOMM-DC 60376-P69 9 U S, GOVERNMENY PRINTING OFFICE I569 O365-334

Claims (26)

1. A method of making a warhead comprising the steps of: cold extruding a metal tubular blank to form an enlarged annular section about a first end thereof, and cold extRuding the blank to move the enlarged section radially inward.

2. A method as set forth in claim 1 further defined as cold extruding the blank to elongate the blank while forming said enlarged section.

3. A method as set forth in claim 2 further defined as cold extruding the blank to nose the first end and to taper the second end thereof.

4. A method as set forth in claim 3 further defined as first cold extruding the blank to taper the second end thereof and then cold extruding the blank to move the enlarged section radially inward so that the blank has a substantially constant diameter from the first end thereof to the taper end then cold extruding the blank to nose the first end thereof.

5. A method as set forth in claim 4 including initially cutting the tubular blank from a length of tubing at a position on the length of tubing which will result in the blank containing the amount of material required in the finished warhead.

6. A method as set forth in claim 4 wherein said blank comprises steel having a tensile of approximately 96,000 p.s.i., a hardness of approximately 92 l as measured on the Rockwell B Scale, a yield strength of approximately 75,000 p.s.i. and the elongation being approximately 23 percent.

7. A method as set forth in claim 4 wherein said blank comprises one of SAE 1018 and SAE 1340 steel.

8. A method as set forth in claim 5 including forming grooves in the surface of said blank prior to one of said extruding steps so that a subsequent extruding step forces the metal together to smooth the surface and establish fault lines.

9. A method as set forth in claim 8 further defined as forming said grooves in said blank prior to the first cold extruding step.

10. A method as set forth in claim 8 further defined as forming the grooves in one of the inner and outer surfaces of said blank and including the step of forming other grooves in one of said surfaces transverse to said first mentioned grooves.

11. A method as set forth in claim 10 further defined as forming said other grooves prior to one of said extruding steps so that a subsequent extruding step forces the metal together and smooths the surface to establish fault lines.

12. A method as set forth in claim 10 further defined as forming said first mentioned grooves longitudinally along said blank.

13. A method as set forth in claim 12 further defined as forming said other grooves circumferentially about said blank.

14. A method as set forth in claim 13 further defined as forming said first mentioned grooves by extruding said blank with a member having ridges.

15. A method as set forth in claim 14 further defined as forming said other grooves by forming a helical groove.

16. A method as set forth in claim 15 further defined as moving metal to form said helical groove.

17. A method as set forth in claim 16 further defined as forming all of said grooves in the outer surface of said blank.

18. A method of making a warhead which will fragmentize in a predetermined pattern comprising the steps of; forming grooves in a surface of a warhead blank, and forcing the metal adjacent the grooves together to smooth said surface and establish fault lines.

19. A method as set forth in claim 18 further defined as cold extruding said blank to smooth said surface and establish fault lines.

20. A method as set forth in claim 18 further defined as forming said grooves by cold extruding.

21. A method as set forth in claim 20 wherein said blank is a generally tubular member and further defined as forming said grooves longitudinally along the surface of said blank.

22. A method as set forth in claim 21 further defined as forming said grooves by extruding said blank with a member having ridges thereabout.

23. A method as set forth in claim 20 including the step of forming other grooves in a surface of said blank transverse to said first mentioned grooves.

24. A method as set forth in claim 23 further defined as extruding said blank to force the metal adjacent said other grooves together to smooth said surface and establish fault lines.

25. A method as set forth in claim 24 wherein said other grooves are formed by a helical groove.

26. A method as set forth in claim 25 further defined as moving metal to form said helical groove.

Images