A composite protective body and its use

Abstract: A composite protective body (2) of the kind comprising a pliable flat case with at least one panel of soft ballistic material and an insert within the case comprising a plurality of constituent bodies (5) of glass or ceramic material. The constituent bodies (5) of the insert are of axisymmetrical or centrosymmetrical shape and of a size commensurate with that of a threatening object against which protection is to be afforded, and they are arranged in at least two superimposed, mutually staggered layers. Each constituent body (5) of the insert is glued to all surrounding constituent bodies by thermoplastic or thermosetting material. There are further provided garments embodying such constituent bodies.

Description: The present invention is in the field of protection against threats such as kinetic missiles, e.g. in form of firearm bullets, against knife-thrusts and the like, and by one of its aspects aims at providing pliable composite protective bodies suitable for incorporation in protective garments such as bullet-proof vests. By another aspect the invention aims at providing an outer armour on enclosures such as, for example land vehicles, marine vessels and aircraft. The invention further concerns improved protective garments. Known protective garments such as bullet-proof vests, comprise as a rule a plurality of so-called ceramic ballistic plates in combination with a so-called ballistic material, e.g. soft panels made of Kevlar™, Spectra™, Aramid™ and the like. In the ceramic plate insert which, depending on the intended use, may be flat or curved, the individual plates are densely laid out with neighbouring plates tightly bearing on each other. EP-A-208 499 discloses an armour component having a pair of layers of flexible high impact resistant material with at least two juxtaposed layers of hard beads between the flexible layers. The insert forming plates in known composite protective bodies of the kind specified are usually large relative to the diameter of the threatening object such as a kinetic energy missile, against which it is to afford protection, e.g. of the order of 5 cm². Where the composite body has only one single layer of ceramic plates it affords a relatively low multi-hit capability since every hit destroys one of the plates leaving a relatively large unprotected area. In some known bullet-proof vests the multi-hit capability is improved by provision of inserts with two or more mutually staggered overlapping layers of ceramic ballistic plates. However, this renders the vest relatively heavy and gives rise to significant discomfort of the wearer. It is the object of the present invention to provide an improved, relatively light-weight composite protective body of the kind specified. It is a further object of the present invention to provide an improved insert for a protective garment. It is yet another object of the invention to provide improved protective garments. In the following description and claims, the expression "ballistic material" means a pliable woven or non-woven material capable of absorbing the kinetic energy of a missile such as a firearm bullet and thereby damping a missile to a large extent; and the term "size" when used in relation to kinetic energy missiles or ceramic bodies means width or diameter. The above objects are solved with the features of the claims. The axisymmetric or centrosymmetric constituent glass or ceramic bodies of the insert employed in accordance with the invention, may be of any suitable shape such as spherical, ellipsoidal, cylindrical, prismatic, pyramidal and the like, spherical bodies being preferred. Due to the fact that in accordance with the invention the individual constituent bodies are spaced from each other with the gaps between constituent bodies in one layer being bridged by a constituent body of another layer, the composite protective bodies according to the invention combine a relative light weight with a good multi-hit capability. The multi-hit capability is enhanced by the fact that the size of the ballistic bodies is commensurate with that of the threatening objects against which protection is to be afforded. Typically, the size of a body may be between 1/3 and twice the size of a threatening object such as a bullet. For example, spherical ballistic glass or ceramic bodies having a diameter from 4 - 18 mm may afford adequate protection against all conventional small calibre firearms. In the following the invention will be described with reference to kinetic energy missiles such as firearm bullets as the threatening objects, it being understood that it is also effective against other threatening objects, e.g. thrusts of various cold weapons such as knives, daggers and the like. In use a composite protective body according to the invention is placed with the insert turned towards the environment. In operation, an impinging kinetic missile such as a firearm bullet, is effectively deflected from its original trajectory and damped by the insert body or bodies which it hits to such an extent that it is subsequently captured by the soft ballistic material panel of the case. For incorporation of a composite protective body according to the invention in a protective garment such as a bullet-proof vest, it may be fabricated in a shape most suitable for that purpose. For better understanding the invention will now be described, by way of example only and without limitation, with reference to the annexed drawings in which: Fig. 1 is a front view, partly broken open of a bullet-proof vest comprising a composite protective body according to the invention; Fig. 2 is a section along line II-II of Fig. 1: and Fig. 3 is a diagrammatic perspective illustration of a phase in the manufacturing process; and Fig. 4 is a section along lines IV-IV of Fig. 3. Referring first to Figs. 1 and 2, there is shown a bullet-proof vest having front and back composite protective bodies made each in accordance with the invention and only one of which is shown. As shown, the vest 1 has a front composite protective body 2 comprising a case with a back panel 3 of a soft ballistic material such as Kevlar™ and a front sheet 4, holding an insert comprising a plurality of spherical ceramic constituent bodies 5. As seen in Fig. 2, the constituent ceramic bodies 5 are arranged in two rows with the constituent bodies 5 in each row being spaced from each other by a distance smaller than the diameter of a ceramic body 5 and the gaps between them being bridged by constituent bodies of the other row. Each of the constituent bodies 5 is glued to all surrounding constituent bodies. A composite protective body of the kind shown in Figs. 1 and 2 was subjected to a shooting test. In the tested body the soft ballistic material panel 3 was 12 mm thick and made of Kevlar™ while the front sheet 4 was of ordinary cloth. The ceramic spherical protective bodies 5 measured 10 mm in diameter and were made of alumina. All spherical constituent bodies were glued together in the manner specified by means of the thermoplastic-polyester Hytrel™. Armour piercing bullets fired from an automatic assault rifle AK-47 (known as Kalashnikov) from a distance of 10 metres were stopped and did not penetrate across the composite protective body. Attention is now directed to Figs. 3 and 4 which show a sintering fixture for the preparation of a ceramic body insert according to the invention. The fixture 7 has a plurality of depressions 8 each capable of holding a ceramic or glass sphere 9. As shown in Fig. 4, the first, bottom layer of ceramic spheres 9 is covered with a second, top layer of identical bodies such that each body 9 of the top layer bridges the gap between two bodies 9 of the bottom layer and likewise each body 9 of the lower layer bridges the gap between two bodies 9 of the upper one. Fig. 3 shows an intermediary phase in the arrangement of spheres 9 in sintering fixture 7. In the course of production, spheres 9 are first subjected to a treatment by which they are coated with suitable thermoplastic or thermosetting material, as will be described in Examples 1 and 2 below, and once placed in fixture 7 they are subjected to sintering in a suitable oven. After cooling, a cohesive two-layer insert structure of ceramic spherical bodies is withdrawn from the form and is ready for insertion in a case for forming a composite protective body according to the invention. The preparation of cohesive inserts of ceramic spheres of the kind referred to above is further described in the following non-limiting Examples. Example 1 Alumina spheres having a uniform diameter of 9.5 mm were heated to 160°C for 30 minutes and then immersed in a powder bed of the thermoplastic copolyester Hytrel™, whereby the alumina spheres were coated by a 0.5 mm thick uniform layer of the thermoplastic material. Following cooling, the coated spheres were placed in a sintering fixture of the kind illustrated in Figs. 3 and 4 and placed for 10 minutes in an oven for sintering at 160°C. After cooling a cohesive two-layer insert body of coated ceramic spheres was withdrawn from the sintering fixture. The insert was pliable and could be bent without damage at radius of curvature of 30° and more. The total thickness of the body was 16 mm. It was attached to a 12 mm thick Aramid™ panel and a shooting test was performed as described hereinbefore. Cohesive insert bodies produced in this manner are ready for further use and processing in accordance with the teachings of this invention. Example 2 Alumina spheres having a uniform diameter of 9.5 mm were placed into a sintering fixture of the kind illustrated in Figs. 3 and 4. Liquid room temperature vulcanising (RTV) silane was poured at room temperature onto the spheres. Following degassing in a manner known per se to remove trapped air, the sintering fixture was placed in an oven and heated for 30 minutes at 100°C. The resulting cohesive insert body was ready for further processing in accordance with the present invention.

Claims: A composite protective body (2) comprising a pliable flat case with at least one back panel (3) of a pliable woven or non-woven material capable of absorbing the kinetic energy of a missile and a front sheet (4) and an insert within said pliable flat case comprising a plurality of constituent bodies (5) of glass or ceramic material, wherein the constituent bodies (5) of the insert are of axisymmetrical or centrosymmetrical shape and of a size commensurate with that of the threatening object against which protection is to be afforded and are arranged in at least two superimposed layers characterized in that the front sheet (4) is of ordinary cloth material, in each of the layers the constituent bodies (5) are spaced from each other by a distance smaller than the size of a constituent body (5) with each constituent body (5) in one layer bridging a gap between two constituent bodies (5) of another layer, and in that each constituent body (5) of the insert is glued to all surrounding constituent bodies (5) by thermoplastic or thermosetting material. A composite protective body according to Claim 1, characterised in that said constituent bodies (5) are spherical. A cohesive pliable insert for incorporation in a protective garment, comprising a plurality of axisymmetrical or centrosymmetrical constituent bodies (5) of glass or ceramic material arranged in at least two layers characterized in that in each of the layers the constituent bodies are spaced from each other by a distance smaller than the size of a constituent body with each constituent body (5) in one layer bridging the gap between two constituent bodies (5) in another layer, and in that each constituent body (5) is glued to all surrounding constituent bodies (5) by thermoplastic or thermosetting material. An insert according to Claim 3, characterised in that said constituent bodies (5) are spherical. A protective garment (1) having a pliable flat case with a back panel (3) of a pliable woven or non-woven material capable of absorbing the kinetic energy of a missile and a front sheet (4), holding a cohesive pliable insert comprising a plurality of axisymmetrical or centrosymmetrical constituent bodies (5) of glass or ceramic material arranged in at least two layers characterized in that the front sheet (4) is of ordinary cloth material, in each of the layers the constituent bodies (5) are spaced from each other by a distance smaller than the size of a constituent body (5) with each constituent body (5) in one layer bridging the gap between two constituent bodies (5) in another layer, and in that each constituent body (5) is glued to all surrounding constituent bodies (5) by thermoplastic or thermosetting material.

Inventors: YESHURUN YEHOSHUA, ZIV DAN, YESHURUN, YEHOSHUA, ZIV, DAN
Applicants: ISRAEL STATE, PLASAN SASA ISRAEL LIMITED PAR, PLASAN-SASA ISRAEL LIMITED PARTNERSHIP OF KIBBUTZ SASA, THE STATE OF ISRAEL MINISTRY OF DEFENCE RAFAEL ARMAMENT DEVELOPMENT AUTHORITY
Application year: 1992
Main classification: F41H1
IPC codes: F41H5