Bullet trapping medium, system for employing said medium and method of use of said medium

• US 7,571,912 B2
• Filed: 11/03/2004
• Issued: 08/11/2009
• Est. Priority Date: 12/02/2002
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Secretary Of The Army (Government of the United States of America)
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Weiss, Charles A., Fransen, Edward J., Tom, Joe G., Malone, Philip G., Larson, Steven L.
• Primary Examiner(s): Graham; Mark S
• Application Number:
  US10/979,834
• Publication Number:
  US 20050093243A1
• Time in Patent Office: 1,742 Days
• Field of Search: 273403-410, 89/360.2, 528/484, 442/409, 106/672, 428/306.6
• US Class Current: 273/410
• CPC Class Codes: F41J 13/00 Bullet catchers

Abstract

A stable fire retardant mixture for use in a backstop for decelerating and trapping projectiles. The backstop generally includes a support structure having an inclined surface and the stable fire retardant mixture serving as a projectile trapping medium disposed on the inclined surface. The projectile trapping medium is a resilient granular material intimately mixed with a hydrated super absorbent polymer (SAP) gel and additives. Preferably, the support structure is made of a shock absorbing, foamed, fiber-reinforced concrete, such as SACON®. In embodiments, the support structure also includes an enclosure. The additives control alkalinity, chemically stabilize the mixture, prolong life of the mixture, retard mold formation and bacterial growth and prevent leaching of heavy metals.

Claims

1. A stable fire retardant mixture for decelerating and trapping projectiles comprising at least in part heavy metals, said mixture at least reducing leaching of said heavy metals, said mixture at least comprising:

a resilient granular material;

a hydrated super absorbent polymer (SAP) gel,

wherein said hydrated SAP gel is intimately mixed with said resilient granular material to yield a first interim mixture, and

wherein said hydrated SAP gel adheres to said resilient granular material, resisting removal by either aqueous solutions or abrasion from said projectiles;

at least one first additive,

wherein said first additive chemically stabilizes at least said hydrated SAP gel, and

wherein said first additive facilitates maintaining the pH of at least said hydrated SAP gel at above about 4.5, and

wherein said first additive forms a passive coating on metallic particles introduced to said stable fire retardant mixture;

at least one second additive,

wherein said second additive at least reduces said leaching of heavy metals, and

wherein said first and second additives remain as powdery solids in said stable fire retardant mixture, and

wherein at least one of said first and second additives at least prevent the leaching of phosphate, and

wherein at least one of said first and second additives retards the growth of mold and bacteria, and

wherein said first and second additives are intimately mixed with said first interim mixture to yield said stable fire retardant mixture.

2. The stable fire resistant mixture according to claim 1, in which said resilient granular material is selected from the group consisting of rubber chunks, wood chips, plastic scrap, and any combination thereof.

3. The stable fire resistant mixture according to claim 1, in which said hydrated SAP gel is selected from the group consisting of sodium acrylate, potassium acrylate, sodium acrylamide, potassium acrylamide, sodium carboxylate, potassium carboxylate, and any combination thereof,

wherein each said additive is added to said hydrated SAP gel in the ratio of about 5 to about 10 parts by weight per 100 parts by weight of said hydrated SAP gel, and

wherein addition of each said additive results in at least a saturated solution of each additive in said mixture, and

wherein the concentration of each said additive is such that said concentration does not adversely affect the water absorbance of said hydrated SAP gel.

4. The stable fire resistant mixture according to claim 1, in which said first additive is selected from the group consisting of phosphates, carbonates, hydroxides, silicates, bicarbonates, and any combination thereof.

5. The stable fire resistant mixture according to claim 1, said first additive employed in sufficient quantity to adjust the pH of said hydrated SAP gel in a range of about 8 to about 12.

6. The stable fire resistant mixture according to claim 1, in which said second additive is selected from the group consisting of calcium carbonate, calcium phosphate, aluminum hydroxide and combinations thereof.

7. A backstop for decelerating and trapping projectiles traveling along a line of fire, said backstop at least comprising:

a support structure having an upper surface, said upper surface having at least one segment inclined with respect to the line of fire; and

a stable fire retardant mixture for decelerating and trapping projectiles comprising at least in part heavy metals, said mixture at least reducing leaching of said heavy metals, said mixture comprising;

resilient granular material selected from the group consisting of rubber chunks, wood chips, plastic scrap, and combinations thereof;

hydrated super absorbent polymer (SAP) gel,

wherein said hydrated SAP gel is intimately mixed with said resilient granular material to yield a first interim mixture, and

wherein said hydrated SAP gel adheres to said resilient granular material, resisting removal by either aqueous solutions or abrasion from said projectiles;

at least one first additive selected from the group consisting of phosphates, carbonates, hydroxides, silicates, bicarbonates, and combinations thereof,

wherein said first additive chemically stabilizes at least said hydrated SAP gel, and

wherein said first additive facilitates maintaining the pH of said hydrated SAP gel at above about 4.5; and

at least one second additive,

wherein said second additive at least reduces said leaching of heavy metals, and

wherein said first and second additives are intimately mixed with said first interim mixture to yield said stable fire retardant mixture, and

wherein said stable fire retardant mixture is disposed on at least a portion of said upper surface, and

wherein said backstop reduces ricochets and requires reduced maintenance compared to conventional backstops.

8. The backstop according to claim 7, in which said first additive is selected from the group consisting of phosphates, carbonates, hydroxides, silicates, bicarbonates, and any combination thereof,

wherein said first additive is employed to adjust the pH of at least said hydrated SAP gel in a range of about 8 to about 12.

9. The backstop according to claim 7, wherein said support structure further comprises at least one sidewall.

10. The backstop according to claim 9, wherein said support structure further comprises opposing first and second sidewalls.

11. The backstop according to claim 7, wherein said support structure further comprises a back wall.

12. The backstop according to claim 7, wherein said support structure further comprises a toe block.

13. The backstop according to claim 7, wherein said support structure further comprises a shock-absorbing, foamed, fiber-reinforced concrete enclosure surrounding at least a portion of said stable fire resistant mixture.

14. The backstop according to claim 7, in which said second additive is selected from the group consisting of calcium carbonate, calcium phosphate, aluminum hydroxide and combinations thereof.

15. The backstop according to claim 7, in which said resilient granular material is selected from the group consisting of rubber chunks, wood chips, plastic scrap, and any combination thereof.

16. The backstop according to claim 7, wherein said hydrated SAP gel is selected from the group consisting of sodium acrylate, potassium acrylate, sodium carboxylate, potassium acrylamide, sodium carboxylate, potassium carboxylate, and any combination thereof.

17. The backstop according to claim 7, wherein said inclined segment is inclined by an angle less than or equal to an angle of repose of said stable fire retardant mixture.

18. A method of forming a stable fire retardant mixture for decelerating and trapping projectiles, said mixture further reducing leaching of said heavy metals, comprising:

providing resilient granular material;

providing hydrated super absorbent polymer (SAP);

intimately mixing said hydrated SAP gel with said resilient granular material to establish a first interim mixture,

wherein said hydrated SAP gel adheres to said resilient granular material;

providing at least one first additive,

wherein said first additive chemically stabilizes at least said hydrated SAP gel, and

wherein said first additive facilitates maintaining the pH of said hydrated SAP gel at above about 4.5;

providing at least one second additive,

wherein said second additive reacts with said projectiles to at least reduce said leaching of said heavy metals; and

intimately mixing said first and said second additives into said first interim mixture to establish said stable fire retardant mixture.

19. The method according to claim 18, selecting resilient granular material from the group consisting of rubber chunks, wood chips, plastic scrap, and any combination thereof.

20. The method according to claim 18, selecting said hydrated SAP gel from the group consisting of sodium acrylate, potassium acrylate, sodium acrylamide, potassium acrylamide, sodium carboxylate, potassium carboxylate, and any combination thereof.

21. The method according to claim 18, said first additive from the group consisting of phosphates, carbonates, hydroxides, silicates, bicarbonates, and any combination thereof,

wherein said first additive is employed to at least adjust the pH of said hydrated SAP gel in a range of about 8 to about 12.

22. The method according to claim 18, said second additive from the group consisting of calcium carbonate, calcium phosphate, aluminum hydroxide and combinations thereof.

23. A method of fabricating a backstop for decelerating and trapping projectiles traveling along a line of fire, comprising:

providing a support structure having an upper surface, at least one segment of the upper surface being inclined with respect to the line of fire;

providing a stable fire retardant mixture for decelerating and trapping projectiles comprising at least in part heavy metals, said stable fire retardant mixture at least reducing leaching of said heavy metals, said stable fire retardant mixture comprising;

resilient granular material;

hydrated super absorbent polymer (SAP) gel,

wherein said hydrated SAP gel is intimately mixed with said resilient granular material to yield a first interim mixture;

at least one first additive,

wherein said first additive chemically stabilizes at least said hydrated SAP gel, and

wherein said first additive facilitates maintaining the pH of said hydrated SAP gel at above about 4.5; and

at least one second additive,

wherein said second additive at least reduces said leaching of heavy metals;

intimately mixing said first and second additives with said first interim mixture to yield said stable fire retardant mixture; and

disposing the stable fire retardant mixture on at least a portion of the upper surface of the support structure,

wherein said backstop reduces ricochets and requires reduced maintenance compared to conventional backstops.

24. The method according to claim 23, further comprising enclosing at least a portion of the stable fire retardant mixture.

25. The method according to claim 23, further comprising enclosing at least a portion of the stable fire retardant mixture within a shock-absorbing, foamed, fiber-reinforced concrete enclosure.

26. The method according to claim 23, further comprising selecting said first additive from the group consisting of phosphates, carbonates, hydroxides, silicates, bicarbonates, and any combination thereof,

wherein said first additive is employed to at least adjust the pH of said hydrated SAP gel in a range of about 8 to about 12.

27. The method according to claim 23, selecting said second additive from the group consisting of calcium carbonate, calcium phosphate, aluminum hydroxide and combinations thereof.

28. The method according to claim 23, selecting said hydrated SAP gel from the group consisting of sodium acrylate, potassium acrylate, sodium acrylamide, potassium acrylamide, sodium carboxylate, potassium carboxylate, and any combination thereof.

29. The method according to claim 23, selecting said resilient granular material from the group consisting of rubber chunks, wood chips, plastic scrap, and any combination thereof.