Apparel – Guard or protector – Penetration resistant
Patent
1996-08-29
2000-10-31
Neas, Michael A.
Apparel
Guard or protector
Penetration resistant
89 3605, F41H 102
Patent
active
061382752
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a protective shield suitable for use as ballistic-resistant or stab-resistant body armor.
Most body armor today makes use of ballistic cloth woven from aramid fiber such as that sold by Du Pont under their trade mark "KEVLAR" and by Akzo under their trade mark "TWARON". However, another form of ballistic cloth is now available woven from high density polyethylene fiber and sold by Allied Signal under their trade mark "SPECTRA" and by Dutch State Mines under their trade mark "DYNEEMA". The fibers of both of these cloths have a sufficiently high tensile strength to make them resistant to penetration by a bullet, the level of protection being dependent on the density of the fibers in the cloth and the number of layers of cloth employed in the armor. However, the weight and flexibility of the armor are also relevant factors if it is to be incorporated in protective clothing, and thus a balance is required between the level of protection required and the comfort of the user in selecting the materials to be used.
High density polyethylene fiber is also available in a non-woven film or sheet form in which the fibers are laid-up as two orthogonal sets of plies in an elastomeric matrix of low density polyethylene. This non-woven ballistic-resistant material is sold by Allied Signal under their trade mark "SPECTRASHIELD" and by Dutch State Mines under their trade mark "UD66". An advantage of this material is that the lack of a woven structure and the provision of a plastic matrix helps resist ply separation when struck by a bullet and thus it is more resistant to penetration. This in turn helps to improve the capability of "SPECTRASHIELD" to withstand penetration by bullets fired in a multi-shot sequence. Polyethylene fiber is also available as a non-woven mat and is sold by Dutch State Mines under their trademark "FRAGILITE".
It is also known from GB Patent No. 1556245 to produce body armor comprising layers of "KEVLAR" backed up by a layer of an impact-absorbing plastics material so as to absorb and limit transmission of the impact shock of a bullet to the body of a person being protected. The preferred impact-absorbing plastics material comprises a polycarbonate sheet which is backed up by a resiliently compressible sheet of a foamed plastics material that further spreads the impact and spaces the polycarbonate away from the body. This impact absorbing layer has become known as a "trauma pack" or "trauma shield", and the level of trauma protection it affords is measured in terms of the deformation of the backface of the layer.
The polycarbonate trauma shield in GB 1556245 consists of one or more polycarbonate sheets, each 0.75 mm thick. The polycarbonate sheet is flexible enough to conform, at least partially, to the body shape of a wearer when incorporated in a garment. Nevertheless, the polycarbonate sheet is still thick enough to be resistant to bending, especially bending in two or more directions simultaneously, and thus it limits the freedom of movement of the wearer. This problem has been alleviated by incorporating body armor in garments in the form of breast plates or backplates.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide body armor which is more flexible than hitherto without any reduction in the level of ballistic and trauma protection afforded by it.
This object is achieved according to the present invention by providing a protective shield comprising a flexible penetration-resistant layer backed up by a flexible impact-absorbing layer of plastics material, characterised in that the impact-absorbing layer consists of a plurality of layers of impact-absorbing plastics material each less than 0.75 mm thick.
The invention is based on an appreciation of the fact that even a relatively thin layer of an impact-absorbing plastics material, such as polycarbonate, manifests a high level of trauma protection. Further, it has been found that whilst the flexibility of such material increases substantially uniformly with reduction in t
REFERENCES:
patent: 4413357 (1983-11-01), Sacks
patent: 4683172 (1987-07-01), LeGrand et al.
patent: 4774724 (1988-10-01), Sacks
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