IL167578A - Armor for protecting buildings from mortar shells or rockets - Google Patents

Description

18705/04 ARMOR FOR PROTECTING BUILDINGS FROM MORTAR SHELLS OR ROCKETS Armor for Protecting Buildings from Mortar Shells or Rockets Field of the Invention The present invention relates in general to energetic armors protecting structures from damage caused by explosive ammunition. More particularly, the invention relates to an armor that protects humans in buildings or structures or shipping containers from blasts caused mainly by rockets or mortar shells, etc.

Background of the Invention Terror groups or even military or semi-military organizations carry out operations by launching rockets or mortar shells toward civil and military locations in order to cause as many casualties and damage as possible. In many cases, civilians are exposed to danger even when situated inside buildings, as generally civil buildings are not designed for or adapted to absorbing the blast wave and the metal fragments that follow the blast.

Recently, some terror organizations have acquired knowledge and capability to produce or purchase rockets, which they launch toward civil locations. Civilians have found themselves exposed to a significant danger, even when situated inside buildings such as homes, schools, malls, stores, offices, etc.

For example, terror organizations from the Gaza strip occasionally launch Quassam rockets or mortar projectiles toward towns in southern Israel that are close to or within the Gaza Strip. The Quassam rocket typically has a range of between 3 to 8 Km, includes a conventional explosive warhead of 3 to 8 kg, and also contains about 2 to 4 kg of metal pieces, weighing several grams each. The Quassam blast causes a significant blast wave, which also accelerates the metal pieces to a velocity of 1000 to 15O0m/s. The blast wave and the metal pieces together can penetrate conventional external walls or roofs of civilian buildings, even when there is no direct hit. Such a penetration can cause injuries or death to the civilians within the building. The blast also transmits a blast wave passing through the concrete, which creates ruins at the inner side of the building roof.

The addition of concrete to existing civilian buildings in order- to provide protection from said danger is not practical in view of the complexity and weight involved in such a solution. On the other hand, there is a great necessity to provide armor to existing civilian buildings in potential danger which can be applied relatively easily, and within a short time period.

Several types of armors are known in the art and are conventionally used, steel. This is due to its chemical structure, as well as the way the polymer has been processed. d. Transparent protective armor: This type of armor is irrelevant to the present invention. e. Armor for buildings: This is the subject of the present invention. Prior art armors for buildings apply heavy concrete, steel, and even sacks filled with sand. However, such prior art armors are not practical or suitable for protecting existing civilian buildings from blast wave or metal pieces that follow blasts from exploding objects such as mortar shells or rockets.

It is therefore an object of the present invention to provide armor for protecting existing civilian buildings and shipping containers against the blast wave and flying fragments that follow the blast of a mortar shell or a rocket such as the Quassam rocket.

It is another object of the present invention to provide such an armor which is relatively thin and light in weight.

It is still another object of the present invention to provide ^ armor for buildings which can be adapted to the threat, and which can be modified to protect against variety of weapons.

It is still an object of the present invention to provide such a modular armor which can be easily assembled and disassembled.

It is still another object of the present invention to provide an armor which can be adapted to protect both sidewalls and roofs of buildings or shipping containers.

Other objects and advantages of the present invention will become apparent as the description proceeds.

Summary of the Invention The present invention relates to a multi-layer armor for protecting external walls or roofs of buildings or shipping containers from the blast wave and flying metal fragments that follow a blast, which comprises, in outward successive order: (a) a Kevlar or another reinforced composite layer having a thickness of 3 to 7mm or more; (b) a metal foam or Expanded Polystyrene layer having a thickness of 50 to 250mm or more; and (c) a steel layer having a thickness of 2 to 15mm or more.

Preferably, the multi-layer armor is produced in a form of pack tile-like elements Preferably, each tile-like element has a complementary shape which enables it to interlock to another adjacent tile-like element.

Preferably, the metal foam layer is an aluminum foam layer or Expanded Polystyrene, with a density of 0.1-0.15 gr./cc.

Brief Description of the Drawings In the drawings: - Fig. 1 discloses the general cross sectional structure of the multi-layer armor of the invention; Fig. 2 shows a cross sectional view of the armor of the invention, made in a tile -like form; and Fig. 3 shows a set-up of an experiment which was performed with armors of the invention.

Detailed Description of Preferred Embodiments As said, the present invention provides armor for both civil and military buildings to protect them from the blast wave and fragments that follow a blast of a mortar shell or a rocket such as Quassam rocket. The armor of the present invention prevents damage from the structure it protects and provides safety to the people within it.

As said, the Quassam rocket typically has a range of between 3 to 8 Km, includes a conventional explosive warhead of 3 to 5 kg, and also contains about 2 to 4 kg of metal pieces, weighing several grams each (typically lgr. to 4gr. each). The Quassam blast causes a significant blast wave, which also accelerates the metal pieces to a velocity of 1000 to 1500m/s. The blast wave and the metal pieces together can penetrate conventional external walls or roofs of both civilian and military buildings, even when there is no direct hit.

The present invention provides a multi-layer armor that can be applied to external walls or roofs of existing buildings. The general structure of the armor of the present invention is shown in Fig. 1. The armor comprises a Kevlar or another reinforced composite layer (2) of about 3 to 7mm being in contact with the building's external wall or roof. The Kevlar layer is followed by a metal foam or Expanded Polystyrene layer (3). The metal layer (3) may be, for example, an aluminum foam layer of 50 to 250mm with a density of 0.1-0.15 gr./cc. The armor front is completed by a steel layer of 2 to 15mm.

The object of the steel layer is to initiate the- charge of the shell or rocket warhead, to flatten the blast wave such that its pressure is divided over a larger surface area of the steel and thereafter over a larger surface area of the following aluminum foam and Kevlar layers, and also to decelerate the metal fragments. It is assumed, however, that the blast wave will penetrate the steel layer, in spite of the fact that the pressure of the blast wave will be spread over a larger area of the steel layer. In that case, the metal foam or Expanded Polystyrene layer absorbs about up to 50% of the blast wave energy, depending on the distance and explosive weight. It has been found that a thickness of 50 to 250mm is enough for the metal foam or Expanded Polystyrene to prevent damage by the blast wave to the following Kevlar layer and the building wall.

As said, the blast also involves flying of metal pieces at a velocity of 1000 to 1500m/s. The steel layer, in addition to flattening the blast wave, significantly decelerates the fragments energy.

The fragments (which have been decelerated by the steel layer) are stopped by the Kevlar layer. It should be noted that the foam layer essentially has no effect on the metal fragments.

It should be noted that the armor of the present invention could be produced in a form of tile-like elements. The larger each element is, the wider is the absorption and efficiency of the armor, as the blast wave pressure can be divided over a larger surface area.

An exemplary cross-section of an armor tile according to an embodiment of the invention is shown in Fig. 2. The tile comprises the same three layers; i.e., Kevlar layer (2), aluminum foam layer (3), and steel layer (4), having the same thicknesses as indicated. In addition, the sides of the tiles are associated with complementary steel sheets 6 that keep the tile pack, enable interlocking between adjacent tiles, and also keeps the Kevlar layer sealed from moisture. The sheets (6) may be glued, or attached to the steel and Kevlar layer in any conventional manner. It should be noted that the metal sheets 6 that provided have been given as an example only, and may vary in a manner well known to those skilled in the art.

The size of each tile may be, for example 100 X 100 cm.

EXAMPLE An experiment with the armor (10) of the invention was performed as shown in Fig. 3. A layer of wood (9) having a thickness of 50 mm was attached to a front surface of a concrete body (13) lying on the ground and having dimension of 1 X 1 X lm. The multi-layer armor was attached in front of said wood layer (9). A similar arrangement was made on the ground (21), wherein a wood layer (·9') was horizontally positioned on the ground. The armor (10') according to the invention was horizontally attached in contact with the horizontal wood plate (9') and above it. An explosion of a charge (20) of 5kg TNT + 4 Kg of 6 mm steel fragments + 3mm metal cover simulating the blast of a Quassam model 2 rocket was made on armor (10'), at a distance L of 180 cm from the front surface of armor (10). The warhead was set at 45° in order to simulate a roof hit of a Quassam rocket. After the blast, significant damage to the armors (10) and (10') of the invention was observed. However, no damage whatsoever to the wood layers (9) and (9') was observed following the blast and not a single penetration of metal fragment was found.

While some embodiments of the invention have been described by way of illustration, it will be apparent that the invention can be carried into practice with many modifications, variations and adaptations, and with the use of numerous equivalents or alternative solutions that are within the scope of persons skilled in the art, without departing from the spirit of the invention or exceeding the scope of the claims.

Claims (4)

18705/04 167578/2

1. A multi-layer armor for protecting external walls or roofs of buildings or shipping containers from the blast wave and flying metal fragments that follow a blast comprising, in outward successive order, a. a Kevlar or another reinforced composite layer having a thickness of 3 to 7mm or more; b. a metal foam or Expanded Polystyrene layer having a thickness of 50 to 250mm or more; and c. a steel layer having a thickness of 2 to 15mm or more.

2. A multi-layer armor according to claim 1, produced in a form of pack tile-like elements.

3. A multi-layer armor according to claim 1, wherein each tile-like element has a complementary shape which enables it to interlock to another adjacent tile-like element.

4. A multi-layer armor according to claim 1, wherein the metal foam layer is an aluminum foam or Expanded Polystyrene layer, with a density of 0.1 to 0.15 gr./cc. LUZZATTO ft LUZATTS By