Lithographic fragmentation technology

Patent metadata

Field	Value
Publication number	US-9946159-B2
Application number	US-201615281250-A
Country	US
Kind code	B2
Filing date	Sep 30, 2016
Priority date	Mar 29, 2016
Publication date	Apr 17, 2018
Grant date	Apr 17, 2018

Abstract

A fragmentation pattern is formed on a surface of a warhead using a lithographic process. A photoresistant material is coated on an interior surface of the warhead casing. A portion of the photoresistant material is selectively cured by projecting an image of the fragmentation pattern onto the photoresistant material. The uncured portion of the photoresistant material is removed and an etchant is applied to the exposed portion of the warhead casing surface thereby etching the fragmentation pattern. Alternatively, a protective coating is applied over the entire surface thereby creating the fragmentation pattern.

First claim

We claim:

1. A method for etching a fragmentation pattern into a warhead comprising the steps of:
applying a photosensitive material coating to an interior surface of a warhead casing;
according to a desired fragmentation pattern, selectively curing a portion of the photosensitive material with light radiation;
removing the uncured portion of the photosensitive material; and
applying an etchant material to the interior surface of the warhead casing thereby etching the desired warhead pattern into the interior surface of the warhead to create a sufficient differential natural stress riser in the presence of an explosive blast.

2. The method of claim 1 wherein the step of selectively curing a portion of the photosensitive material with light radiation further comprises exposing a portion of the photosensitive material coating to light radiation thereby curing the exposed portion of the photosensitive material coating.

3. The method of claim 2 wherein the portion of the photosensitive material exposed to light radiation corresponds to positive image of the fragmentation pattern and the uncured portion of the photosensitive material corresponds to the negative image of the fragmentation pattern.

4. The method of claim 2 wherein the portion of the photosensitive material exposed to light radiation corresponds to negative image of the fragmentation pattern and the uncured portion of the photosensitive material corresponds to the positive image of the fragmentation pattern.

5. The method of claim 1 wherein the photosensitive material is selected from one of the following: a photoresist material and a light cure resin based polymer material.

6. The method of claim 1 wherein the step of applying the photosensitive material coating to the interior surface of the warhead casing further comprises the step of inserting a photosensitive material applicator into an opening of the warhead casing.

7. The method of claim 1 wherein the step of exposing a portion of the photosensitive material coating corresponding to the fragmentation pattern to light radiation further comprises the step of inserting a light source into an opening of the warhead casing.

8. The method of claim 4 wherein the light source further comprises a mask for blocking the transmission of light through the portions of the mask.

9. The method of claim 8 wherein the mask overlaid on the light source is sized and dimensioned to produce a light pattern on the interior surface of the warhead corresponding to the desired positive image of the fragmentation pattern.

10. The method of claim 1 wherein the light radiation is ultraviolet light radiation.

11. The method of claim 1 wherein the photosensitive material removal process is a chemical wash.

12. The method of claim 1 wherein the exposed interior surface of the warhead casing is exposed the etchant material until the fragmentation pattern is etched to a depth sufficient to create a differential natural stress riser in the presence of an explosive blast wave.

13. The method of claim 1 wherein the warhead casing is composed of HF-1 Steel.

14. The method of claim 1 further comprising the steps of:
cleaning the interior surface of the warhead;
dehydrating the interior surface of the warhead; and
applying an adhesive promoter to the interior surface of the warhead.

15. A method for creating a fragmentation pattern on a warhead casing comprising the steps of:
applying a photosensitive material coating to an interior surface of a warhead casing;
according to a desired fragmentation pattern, selectively curing a portion of the photosensitive material with light radiation;
removing the uncured portion of the photosensitive material; and
depositing a stress protection coating to the interior surface of the warhead casing to create a sufficient differential natural stress riser in the presence of an explosive blast.

16. The method of claim 15 wherein the step of selectively curing a portion of the photosensitive material with light radiation further comprises exposing a portion of the photosensitive material coating to light radiation thereby curing the exposed portion of the photosensitive material coating.

17. The method of claim 16 wherein the portion of the photosensitive material exposed to light radiation corresponds to positive image of the fragmentation pattern and the uncured portion of the photosensitive material corresponds to the negative image of the fragmentation pattern.

18. The method of claim 16 wherein the portion of the photosensitive material exposed to light radiation corresponds to negative image of the fragmentation pattern and the uncured portion of the photosensitive material corresponds to the positive image of the fragmentation pattern.

19. The method of claim 15 wherein the photosensitive material is selected from one of the following: a photoresist material and a light cure resin based polymer material.

20. The method of claim 15 wherein the step of applying the photosensitive material coating to the interior surface of the warhead casing further comprises the step of inserting a photosensitive material applicator into an opening of the warhead casing.

21. The method of claim 15 wherein the step of exposing a portion of the photosensitive material coating corresponding to the fragmentation pattern to light radiation further comprises the step of inserting a light source into an opening of the warhead casing.

22. The method of claim 18 wherein the light source further comprises a mask for blocking the transmission of light through the portions of the mask.

23. The method of claim 8 wherein the mask overlaid on the light source is sized and dimensioned to produce a light pattern on the interior surface of the warhead corresponding to the desired positive image of the fragmentation pattern.

24. The method of claim 15 wherein the light radiation is ultraviolet light radiation.

25. The method of claim 15 wherein the warhead casing is composed of HF-1 Steel.

26. The method of claim 15 further comprising the steps of:
cleaning the interior surface of the warhead;
dehydrating the interior surface of the warhead; and
applying an adhesive promoter to the interior surface of the warhead.

Assignees

• Us Army

Inventors

• Manz Paul C
• Magnotti Philip J
• Nguyen Ductri H

Classifications

• F42B33/00

  Manufacture of ammunition; Dismantling of ammunition; Apparatus therefor (F42B5/188 takes precedence; manufacturing processes for hollow charges F42B1/036; manufacture of blasting cartridge initiators F42B3/195) · CPC title

• F42B12/24 Primary

  with grooves, recesses or other wall weakenings {(F42B12/26, F42B12/28 take precedence)} · CPC title

• F42B12/32 Primary

  the hull or case comprising a plurality of discrete bodies, e.g. steel balls, embedded therein {or disposed around the explosive charge} · CPC title

• G03F7/30 Primary

  Imagewise removal using liquid means · CPC title

• B22F10/20

  Direct sintering or melting · CPC title