GB2027086A

GB2027086A - Wall Structure for Security Enclosures

Info

Publication number: GB2027086A
Application number: GB7926283A
Authority: GB
Original assignee: ABERCOM AFRICA Ltd
Current assignee: ABERCOM AFRICA Ltd
Priority date: 1978-07-27
Filing date: 1979-07-27
Publication date: 1980-02-13
Also published as: ZA784277B

Abstract

A wall structure for use in the construction of safes, vaults, strong rooms and like security enclosures comprises a body (14) located between a pair of metal plates (10, 12), the body (14) comprising a high alumina cement matrix, the cement having an alumina content in the range 38 to 42 percent by weight, containing 25 to 50 percent by weight abrasive particles of particle size less than 30 mm and less than 5 percent by weight steel fibres randomly distributed therein. <IMAGE>

Description

SPECIFICATION Security Enclosures This invention relates to security enclosures such as safes, vaults, strongrooms and the like.

Safe doors and walls, particularly doors, usually consist of spaced metal plates having an aluminium casting provided between the plates. The aluminium casting has embedded therein an abrasive material such as aluminium oxide particles.

Other structures for security enclosures have been proposed. For example, Trowbridge U.S.

Patent No. 1,474,389 provides a security wall structure having pieces of hard steel distributed in a concrete matrix, while Landingham Patent 3,794,551 describes a light armor material comprising a beryllium boride ceramic matrix having metal wires embedded therein.

It is an object of the present invention to provide a structure for use in the construction of safes, vaults, strongrooms and like security enclosures which has a high resistance to cutting, for example by means of an oxyacetylene torch, and drilling.

According to the invention, there is provided a structure for use in the construction of safes, vaults, strongrooms and like security enclosures comprising a body located between a pair of plates, the body comprising a high alumina cement matrix containing a mass of abrasive particles and a mass of metal fibres randomly distributed therein. The essential feature of the structure is the body located between the plates. It is this body which provides the structure with its resistance to cutting and drilling.

The body may be anchored or bonded to the plates in any conventional manner. Firm anchoring may be achieved by providing one or both of the plates with protruberances which extend into the body. These protruberances may be formed integrally with the plate or plates or be secured, e.g. by welding in the case of metal, to the plate or plates.

There may also be provided a metal mesh or baffle located in the body and parallel to the plates.

The plates will generally be metal plates, particularly steel plates.

The cement matrix of the body is a high alumina cement matrix. High alumina cements have a high alumina content, generally greater than 35 percent by weight typically 38 to 42 percent by weight. They are typically made by grinding ciinker of monocalcium aluminate and dicalcium silicate formed by calcining or fusing bauxite and lime.

For added strength and hardness, the body may also contain Alag. Alag is a high alumina cement as defined above, but having a particle size distribution which stretches over a range. Fine Alag has a particle size distribution ranging from dust to 2,5 mm while coarse Alag has a particle size distribution ranging from 2,5 mm to 1 3 mm. The preferred Alag is fine Alag. The Alag, of course, reacts with and firmly bonds to the cement matrix.

The abrasive particles will generally be alumina particles, but other abrasive particles may also be used. The abrasive particles will usually be provided in a range of 25 to 50 percent by weight of the body. The particles are preferably fine and have an average size of less than 30 mm, preferably in the range 8 to 10 mm.

The mass of randomly distributed metal fibres are also important for the strength arid hardness of the body and structure. The metal for the fibres is preferably a hard metal such as steel. The fibres will generally be provided in an amount of less than 5, typically 1 to 3, percent by weight of the body. The fibres have a length typically in the range 10 to 40 mm. The fibres will generally be circular in crosssection having a diameter of less than 0,5 mm.

The structures of the invention may be made by the following method which forms another aspect of the invention. The method includes the steps of providing a pair of spaced plates, making a mixture of high alumina cement, the abrasive particles, the metal fibres-and water, pouring the mixture into the space between the plate and allow the cement to set.

The cement will generally be provided in an amount of 1 5 to 25 percent by weight of the mixture while the ratio of cement to water on a mass/mass basis is preferably greater than 2,7. The mixture will also preferably contain Alag, as defined above. The Alag will usually be provided in an amount of 15 to 35 percent by weight of the mixture. The structure of the invention may be used in the construction of safes, vaults, strongrooms and like security enclosures. In particular, the structure may be used to construct doors for such enclosures.

An embodiment of the invention is illustrated by the attached drawing which is a fragmentary perspective view of a structure of the invention.

Referring to the drawing, there is shown a laminated structure comprising a pair of metal plates 10, 12 having a body 14 located therebetween. The body is of the type described above. The plate 10 has a number of longitudinal lugs or protruberances 1 6 welded to its inside surface 11. The lugs serve to anchor the body firmly in position.

Located in the body is a metal mesh or baffle 18 which lies parallel to the two plates. This baffle will generally be made of a hard steel such as stainless steel.

The structure is completed by providing top, bottom and side plates (not shown) which are welded to the two plates 10, 12.

The invention is further illustrated by the following examples.

Example 1 A mixture was made of aluminium oxide particles (8-10 mm in size), high alumina cement and fine Alag. The mixture occupied one cubic metre and consisted of 1080 kg of aluminium oxide particles, 660 kg of the high alumina cement and 840 kg of the Alag. To this mixture was added stainless steel fibre in an amount of 74 kg/cubic metre. This was thoroughly mixed to produce a random orientation of steel fibre in the mixture.

The high alumina cement consisted of the following essential ingredients (on a weight basis): Awl203 39% CaO 38,5% SiO2 4,5% Fe203 12% FeO 4% The density of the material was 1150 kg/m2 and the fineness was 3000 cm2/gm.

The steel fibres each had a length of about 25 mm and a diameter of about 0,33 mm.

The Alag had the same essential ingredients as the high alumina cement mentioned above and a particle size distribution in the range dust to 2,5 mm.

To the dry mixture, was added water in an amount sufficient to produce a ratio of cement to water on a mass/mass basis of greater than 2,7. The watered mixture was poured and vibrated into the space provided between a pair of spaced steel plates. The mixture was allowed to set. The resulting product was a body having uniformly dispersed therethrough aluminium oxide particles, Alag and steel fibres, sandwiched between a pair of steel plates. The product was ideally suited for use as a door for a safe.

Examples 2 to 4 Using the same method as in Example 1, but the mixtures set out in the Table below, three further structures were produced. All three structures had excellent strength and hardness, although the structure produced in Example 4 was the best with the body so produced having a hardness of 0,9 on the Moh scale.

Table Example 2 3 4 Awl203 25-30 12-15 8-10 Kg Kg Kg Cement 665 690 670 Al203 930 1210 1140 Fine Alag 615 805 760 Stainless Steel Fibre 80 40 85 Coarse Alag 465 - Water 246 246 246

Claims

1. A structure for use in the construction of safes, vaults, strongrooms and like security enclosures comprising a body located between a pair of plates, the body comprising a high alumina cement matrix containing a mass of abrasive particles and a mass of metal fibres randomly distributed therein.

2. A structure according to claim 1, wherein the body also contains fine Alag, as hereinbefore defined.

3. A structure according to claim 1 or claim 2, wherein the high alumina cement has an alumina content in the range 38 to 42 percent by weight.

4. A structure according to any one of the preceding claims, wherein the abrasive particles are present in an amount of 25 to 50 percent by weight of the body.

5. A structure according to any one of the preceding claims, wherein the abrasive particles are alumina particles.

6. A structure according to any one of the preceding claims, wherein the abrasive particles have an average size of less than 30 mm.

7. A structure according to any one of claims 1 to 5, wherein the abrasive particles have an average size of 8 to 10 mm.

8. A structure according to any one of the preceding claims, wherein the fibres are present in an amount of less than 5 percent by weight of the body.

9. A structure according to any of claims 1 to 7, wherein the fibres are present in an amount of from 1 to 3 percent by weight of the body.

10. A structure according to any one of the preceding claims, wherein the fibres are steel fibres.

11. A structure according to any one of the preceding claims, wherein the fibres have a length in the range 10 to 40 mm.

12. A structure according to any one of the preceding claims, wherein fibres are substantially circular in cross-section and having a diameter of less than 0,5 mm.

13. A structure according to any one of the preceding claims, wherein the plates are metal plates.

14. A structure according to claim 13, wherein the metal is steel.

1 5. A structure according to any one of the preceding claims, wherein at least one of the plates has a plurality of protruberances extending into the body.

1 6. A structure according to any one of the preceding claims which also contains a metal mesh located in the body and parallel to the plates.

1 7. A method of making a structure according to any one of the preceding claims including the steps of providing a pair of spaced plates, making a mixture of high alumina cement, the abrasive particles, the metal fibres and water, pouring the mixture into the space between plates and allowing the cement to set.

18. A method according to claim 17, wherein the cement is provided in an amount of 1 5 to 25 percent by weight of the mixture.

1 9. A method according to claim 1 7 or claim 18, wherein the mixture also contains Alag, as hereinbefore defined.

20. A method according to claim 19, wherein the Alag is provided in an amount of 1 5 to 30 percent by weight of the mixture.

21. A method according to claim 15 substantially as herein described with reference to any one of the Examples.

22. A structure according to claim 1 made by the method claimed in any one of claims 1 7 to 21.

23. A safe, vault, strongroom or like security enclosure having at least one wall or door comprising a structure as claimed in any one of claims 1 to 1 6.