This application claims the benefit of priority of Italian Patent Application No. 102022000007115 filed Apr. 11, 2022, which is incorporated by reference in its entirety.
The present invention refers to a bulletproof protective structure, composed of a flexible base constituted by a ballistic fabric and of a panel made of rigid elements of ballistic material adhering to a second layer of ballistic fabric.
More in detail the invention concerns a protective structure suitable for making bulletproof vests or panels capable of guaranteeing high levels of protection, in particular higher than level Ma according to US NIJ regulations.
Effective bulletproof protections are known to be obtained by means of structures made by combining intertwined or unidirectional fibers capable of absorbing and dispersing the force of impact and penetration of the bullets through plastic deformation (elongation) of the fibers themselves; the fibres most commonly used for this purpose are the aramid fibres generally known by the name “Kevlar®” (registered trademark of E. I. du Pont de Nemours and Company), or the ultra-high molecular weight polyethylene fibers (also known as UHMWPE), in particular the Dyneema® fibers (registered trademark of Royal DSM N.V.).
The number of overlapping layers determines the protection capacity of the structure.
Typically, fiber-only structures can provide effective protection against firearm bullets up to gauge 7.65 9 Parabellum 357 and 44 Magnum. This corresponds to a protection level Ina according to the regulations defined by the US National Institute of Justice (NIJ). These structures are particularly light, usually have an areal density that can vary between 4.5 and 7 kg/m2, are comfortable to wear and with a degree of flexibility that allows large zones of the body to be covered.
However, these structures made of polymer fiber alone are not sufficient for protecting against bullets with gauge greater than those indicated above, for example those fired by long weapons such as 7.62×51 NATO BALL, 7.62×39, AK47 and SS109 NATO. To achieve superior protection, it is necessary to add a series of rigid elements, capable of fragmenting the bullets fired by long weapons into smaller parts that can be more easily stopped by the underlying fiber structure, also thanks to the decrease in their energy. These rigid elements can be adjacent or spaced from each other, and are made of metallic materials or more often with the so-called ballistic ceramics, in particular alumina (aluminum oxide), silicon carbide or boron carbide, able to fragment the bullets and divide them into chips.
These structures, if made with monolithic ceramic elements of relatively large dimensions are, due to their rigidity, limited to the protection of vital organs only. An extension to the entire torso (chest, back and hips) would make them uncomfortable and not wearable. These solutions use rigid supports made of fiber combined with monolithic ceramic plates (approximately 250 mm×300 mm).
To improve the comfort of these structures, one possibility is to adopt flexible configurations, which comprise a non-monolithic ceramic layer, but based on mosaics of small-sized tiles (about 30 mm×30 mm), associated with a support that is also flexible.
A structure of this type is disclosed in patent EP 3098560 B1. In the structure of this document the rigid elements are in the form of short prisms (square-based parallelepipeds or hexagonal prisms are exemplified), adjacent to each other along their lateral surfaces and glued to a ballistic fabric via one of their basal surfaces. This structure has the disadvantage of still presenting a limited flexibility, due to the fact that the elements are glued on the entire surface of contact with the fabric, so that the bending zone is limited only to lines at their edges.
To overcome the problem, patent application EP 3805691 A1 describes a structure consisting of rigid elements glued on a base in ballistic fibers, wherein the rigid elements have a complex shape, with a central raised zone on the basal face destined for gluing with the fibers. Two embodiments of rigid elements of this document are shown schematically in
Another problem encountered with the known structures made of rigid ballistic ceramic elements is a decay in the performance on the edge: a bullet impacting the edge of the element, thus also hitting the adjacent element, is more likely to penetrate the structure; currently, to overcome the problem, the thickness of the ceramic elements is sized so as to ensure sufficient mechanical performance at the edges; this results in the thickness used at the center of the element being oversized compared to what is necessary, with a consequent increase in the weight of the final structure.
Aim of the present invention is to realize a bulletproof structure with a degree of flexibility sufficient to ensure full-body coverage with a protection level higher than level Ina of the US NIJ standard, but without the problems of the prior art. In particular, aim of the invention is to provide a bulletproof protective structure with improved performance at the edges of the rigid elements without having to increase their thickness uniformly and therefore the overall weight of the final structure.
These aims are achieved according to the present invention, which in a first aspect thereof concerns a bulletproof protective structure comprising a flexible base including intertwined or unidirectional ballistic fibers on which rigid metallic or ceramic elements are adhered adjacent to each other, characterized in that the face of said elements adhering to the fibers is convex, the rigid elements adhere to the flexible base only for a fraction of said convex surface, and in a plan view they have a polygonal or pseudo-polygonal shape, such that there are no voids between the sides of two abutting elements.
In a preferred embodiment of the invention, the main faces of said rigid elements are two curved surfaces, one concave and one convex, said rigid elements adhere to the flexible base for a fraction of their convex surface, and the thickness at the edge of the element is between 0.5 and 2 mm greater than the thickness at the center of the element itself.
The invention will be described in the following with reference to the figures, wherein:
The bulletproof structure of the invention comprises a flexible base, made of ballistic fibers on which rigid elements are adhered which, unlike those of the known structures, have the surface adhering to the flexible base which has a convex shape and therefore is neither flat nor comprises flat portions.
These rigid elements have two main surfaces, with greater extension, destined the former to stop the bullets and the latter to adhere to the flexible base of polymer fibers, and lateral surfaces with smaller extension that in the overall structure are adjacent to each other.
In the following, the surface destined to stop the bullets will also be defined as the front surface, while the convex one, destined to adhere to the flexible base of polymer fibers, in the following will also be defined as the rear surface.
In an even more preferred embodiment, the two main faces, 12 and 21, of a rigid element of type 20 are two portions of spherical caps; in this case, the condition that the thickness at the edge of the element is between 0.5 and 2 mm greater than the thickness at the center of the element itself entails that the radius of curvature of the concave surface 21 is less than that of the convex surface 12. Depending on the lateral dimensions of a rigid element of type 20, the radius of curvature of the concave surface can vary between 30 and 300 mm; the radius of curvature of the convex surface will vary accordingly, to ensure the condition of greater thickness at the edge with respect to the center of the element.
The rigid elements, both of type 10 and of type 20, are produced with the materials that are typically used for this application, i.e. metals or, preferably, ballistic ceramics such as aluminium oxide (alumina), silicon carbide or boron carbide. The production methods for these rigid elements are well known to those skilled in the art, and generally consist in sintering powders of the aforementioned materials, typically at temperatures between 1500 and 2200° C. The advantage of the rigid elements of the invention with respect to those known (for example, those of EP 3805691 A1) is that since the two main surfaces are spherical, during their production the pressure is exerted uniformly in all their points, which ensures the maximum homogeneity of structural and mechanical characteristics of the rigid elements obtained.
In a plan view, the rigid elements of the structures of the invention may have any shape suitable for tessellating a flat surface, i.e. typically triangular, rectangular, preferably square or even more preferably hexagonal shape.
The lateral dimensions of the rigid elements useful for the invention, in any of the possible shapes illustrated above, may vary within wide margins; for the preferred hexagonal shape, the lateral dimensions may vary indicatively between 10 and 50 mm, while the thicknesses typically vary between 2 and 10 mm.
The flexible base is the same as the one of known bulletproof structures. This base is made with the aramid (for example Kevlar®) or ultra-high molecular weight polyethylene (UHMWPE, for example Dyneema®) fibers mentioned above; the fibers can be arranged unidirectionally, variously intertwined or woven, according to methods known to those skilled in the art. The number of layers of fibers can be varied, depending on the degree of protection to be obtained; typically the flexible base has a thickness between about 1 to 5 mm.
The rigid elements are adhered to the base in polymer fibers by gluing, typically with thermoplastic elastomeric resins, for example polyurethane elastomers.
Since the gluing surface is convex, while normally the flexible base is kept in planar arrangement during the production of the structures, virtually the adhesion area would be a single point; however, to favour gluing, during the same and until the glue has solidified, a pressure is exerted on the rigid elements, so that these are partially “pushed” inside the base of polymer fibers, so that the gluing zone extends to a spherical cap. This condition is schematically represented in
The bulletproof structure is then completed with an additional layer of textile material, not necessarily of ballistic type, arranged on the front part of the rigid elements, for aesthetic reasons and to favour the maintenance of the correct positioning of said elements.
Number | Date | Country | Kind |
---|---|---|---|
102022000007115 | Apr 2022 | IT | national |
Number | Name | Date | Kind |
---|---|---|---|
5996115 | Mazelsky | Dec 1999 | A |
6170378 | Neal | Jan 2001 | B1 |
8434396 | Wiley | May 2013 | B1 |
11884047 | Adelson | Jan 2024 | B1 |
20030167910 | Strait | Sep 2003 | A1 |
20060243127 | Cohen | Nov 2006 | A1 |
20080307553 | Jbeili | Dec 2008 | A1 |
20100005955 | Ohnstad | Jan 2010 | A1 |
20130160639 | Lee | Jun 2013 | A1 |
20200033097 | Speyer | Jan 2020 | A1 |
20230228535 | Shackelford | Jul 2023 | A1 |
Number | Date | Country |
---|---|---|
1980813 | Oct 2008 | EP |
3098560 | Nov 2016 | EP |
3805691 | Apr 2021 | EP |
1980813 | Mar 2008 | IL |
9424894 | Nov 1994 | WO |
WO-0229351 | Apr 2002 | WO |
2012083395 | Jun 2012 | WO |
Entry |
---|
Italian Search Report and Written Opinion in corresponding Italian Patent Application No. 102022000007115 mailed Nov. 23, 2022. 7 pages. |
Number | Date | Country | |
---|---|---|---|
20230384061 A1 | Nov 2023 | US |