Technology for blast containers

Abstract

Improved blast resistant container assemblies and processes for their formation using a special band-winding technique around the corner areas of each band. High performance fibrous materials are continuously wound around a mandrel having edges that meet at indented corner areas, to create a multilayered rectangular band. These indented corner areas have a small radius of curvature to reduce the stress concentration and avoid excessive bending of the band material during winding. This winding procedure gives a slack for the internal band layers at the corners that is not provided using the conventional straight winding technique, achieving a uniform tension of the inner and outer band layers upon an explosion and minimizing blast related damage.

1 . A process for forming a blast resistant band comprising: 
 a) providing a first mandrel having edges, which edges meet at indented corner areas;    b) wrapping at least one sheet comprising a fibrous material around the mandrel edges and indented corner areas in a plurality of layers;    c) securing the plurality of layers of fibrous material together to form a band; and then    d) removing the band from the mandrel.    
   
   
       2 . The process of  claim 1  wherein the wrapping is conducted to provide each layer of fibrous material with an amount of slack at the indented corner areas, wherein outwardly successive layers of fibrous material have an amount of slack less than or equal to the amount of slack at the indented corner areas of underlying layers.  
   
   
       3 . The process of  claim 1  comprising attaching the at least one sheet comprising a fibrous material to the mandrel.  
   
   
       4 . The process of  claim 1  further comprising repeating steps b) through d) at least once to form at least one additional larger band; each additional band being formed around a mandrel having a successively larger perimeter than the other mandrel or mandrels; and uniting the band and the additional bands to form a container.  
   
   
       5 . The process of  claim 4  wherein steps b) through d) are repeated twice to form three bands which are united to form a container.  
   
   
       6 . The process of  claim 5  wherein each of said three bands has a central longitudinal axis and said bands are united such that the central longitudinal axis of each band is substantially perpendicular to the central longitudinal axis of the other bands.  
   
   
       7 . The process of  claim 5  further comprising attaching said bands to one another.  
   
   
       8 . The process of  claim 4  further comprising attaching said bands to one another.  
   
   
       9 . The process of  claim 1  wherein said securing step comprises bonding the plurality of layers of fibrous material together with an adhesive.  
   
   
       10 . The process of  claim 1  wherein said fibrous material comprises high strength fibers having a tenacity of at least about 10 g/d and a tensile modulus of at least about 200 g/d.  
   
   
       11 . The process of  claim 1  wherein said fibrous material is selected from the group consisting of extended chain polyolefin fibers including polyethylene fibers, aramid fibers, polybenzazole fibers, polybenzothiazole fibers, polyvinyl alcohol fibers, polyamide fibers, polyethylene terephthalate fibers, polyethylene naphthalate fibers, polyacrylonitrile fibers, liquid crystal copolyester fibers, glass fibers, carbon fibers, fibers comprising pyridobisimidazole-2,6-diyl(2,5-dihydroxy-p-phenylene) moieties, and combinations thereof.  
   
   
       12 . The process of  claim 1  wherein said fibers comprise polyethylene fibers.  
   
   
       13 . The process of  claim 1  wherein said band is polygonal in cross-section.  
   
   
       14 . The process of  claim 1  comprising repeating steps b) through d) twice to form three rectangular bands which are united to form a container; wherein said fibers comprise polyethylene fibers; wherein each additional band is formed around a mandrel having a successively larger perimeter than the other mandrel or mandrels; wherein each of said three bands has a central longitudinal axis and said bands are united such that the central longitudinal axis of each band is substantially perpendicular to the central longitudinal axis of the other bands; and wherein the wrapping is conducted to provide each layer of fibrous material with an amount of slack at the indented corner areas, wherein outwardly successive layers of fibrous material have an amount of slack less than or equal to the amount of slack at the indented corner areas of underlying layers.  
   
   
       15 . The process of  claim 1  further comprising impressing a cogwheel into said at least one sheet at each of said indented corner areas, producing an impression in said sheet at said indented corner areas.  
   
   
       16 . A process for forming a blast resistant band comprising: 
 a) providing a first mandrel having edges, which edges meet at indented corner areas;    b) positioning at least one spacer at each of the indented corner areas;    c) wrapping at least one sheet comprising a fibrous material around the mandrel edges and spacers in a plurality of layers;    d) securing the plurality of layers of fibrous material together to form a band; and then    e) removing the band from the mandrel.    
   
   
       17 . The process of  claim 16  wherein the wrapping is conducted to provide each layer of fibrous material with an amount of slack at the indented corner areas, wherein outwardly successive layers of fibrous material have an amount of slack less than or equal to the amount of slack at the indented corner areas of underlying layers.  
   
   
       18 . The process of  claim 16  comprising attaching the at least one sheet comprising a fibrous material to the mandrel.  
   
   
       19 . The process of  claim 16  further comprising repeating steps b) through e) at least once to form at least one additional larger band; each additional band being formed around a mandrel having a successively larger perimeter than the other mandrel or mandrels; and uniting the bands to form a container.  
   
   
       20 . The process of  claim 16  wherein steps b) through e) are repeated twice to form three bands which are united to form a container.  
   
   
       21 . The process of  claim 16  further comprising repeating steps b) through d) to form at least one additional band around a completed band, wherein at least one additional spacer is positioned on the exterior corner areas of the outermost completed band; then removing the bands from the mandrel; and uniting the bands to form a container.  
   
   
       22 . The process of  claim 16  wherein said spacers comprise flexible tubes.  
   
   
       23 . The process of  claim 16  wherein said spacers comprise inflatable tubes.  
   
   
       24 . The process of  claim 23  wherein said inflatable tubes are inflated at the beginning of said wrapping step and deflated at the end of said wrapping step.  
   
   
       25 . The process of  claim 16  comprising repeating steps b) through d) twice to form three rectangular bands which are united to form a container; wherein said fibers comprise polyethylene fibers; wherein each additional band is formed around a mandrel having a successively larger perimeter than the other mandrel or mandrels; wherein each of said three bands has a central longitudinal axis and said bands are united such that the central longitudinal axis of each band is substantially perpendicular to the central longitudinal axis of the other bands; and wherein the wrapping is conducted to provide each layer of fibrous material with an amount of slack at the indented corner areas, wherein outwardly successive layers of fibrous material have an amount of slack less than or equal to the amount of slack at the indented corner areas of underlying layers.  
   
   
       26 . A blast resistant container formed by the process of  claim 1 .  
   
   
       27 . A blast resistant container formed by the process of  claim 2 .  
   
   
       28 . A blast resistant container formed by the process of  claim 3 .  
   
   
       29 . A blast resistant container formed by the process of  claim 16 .  
   
   
       30 . A blast resistant container comprising at least one band, each band comprising at least one sheet, said sheet comprising a plurality of layers of a fibrous material, each band having edges that meet at corner areas, each layer of fibrous material having an amount of slack at the corner areas, wherein outwardly successive layers of fibrous material have an amount of slack less than or equal to the amount of slack at the corner areas of underlying layers.  
   
   
       31 . The blast resistant container of  claim 30  comprising at least one band and at least one additional larger band; each band having edges that meet at corner areas, each layer of fibrous material having an amount of slack at the corner areas, wherein outwardly successive layers of fibrous material have an amount of slack less than or equal to the amount of slack at the corner areas of underlying layers; each additional band being having a successively larger perimeter than the other bands; the at least one band and the at least one additional larger band being united to form a container.  
   
   
       32 . The blast resistant container of  claim 30  comprising three bands.  
   
   
       33 . The blast resistant container of  claim 32  wherein the bands are united in a nested manner to form a container.  
   
   
       34 . The blast resistant container of  claim 32  wherein said fibrous material comprises high strength fibers having a tenacity of at least about 10 g/d and a tensile modulus of at least about 200 g/d.