Safe with refractory laminate walls

A safe, vault or container 10 has a laminate wall that is resistant to the cutting effects of a high-temperature torch. The wall of the safe, vault or container 10 comprises a hardened steel outer panel 21 and a hardened steel inner panel 22. A refractory abrasive layer 23, as of Carborundum, is disposed adjacent the outer panel 21 to break any drill that might penetrate through the outer panel 21. A thermally conductive layer 24 is disposed adjacent the abrasive layer 23 to conduct heat rapidly away from any localized hot spots that might develop within the abrasive layer 23 when heat from a high-temperature torch is applied to a region of the outer panel 21. A thermally insulating layer 25 is disposed between the thermally conductive layer 24 and the inner panel 22 to inhibit heat transfer from the thermally conductive layer 24 to the inner panel 22. The thermally insulating layer 25 comprises a porous ceramic material consisting of vitreously fused ceramic fibers.

TECHNICAL FIELD 
This invention pertains generally to safes, vaults and the like for storing 
valuable items, and more particularly to a safe, vault or container with a 
laminate wall comprising a thermally insulating layer made of a porous 
ceramic refractory material that retards the cutting effects of a 
high-temperature torch. 
BACKGROUND ART 
A new generation of easily portable high-temperature cutting torches has 
recently been developed for use in emergency rescue operations. However, 
such torches have also been implicated in a number of burglaries in which 
safes and vaults have been cut open. A need has been perceived for an 
upgraded type of safe or vault that is more resistant than storage 
containers of the prior art to the cutting effects of high-temperature 
torches. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a safe, vault or 
container for valuable items that is more resistant than storage 
containers of the prior art to the cutting effects of high-temperature 
torches. 
It is a particular object of the present invention to provided a container 
having a laminate wall that comprises a thermally insulating layer made of 
a porous ceramic material, which retards the cutting effects of a 
high-temperature torch. The wall has an outer panel made of metal (as of 
hardened steel), and an inner panel made of metal (as likewise of hardened 
steel). The thermally insulating layer is disposed between the outer and 
inner panels. As intense heat is applied by a cutting torch to an exterior 
surface portion of the outer panel, the contents of the safe are shielded 
from the intense heat of the torch by the thermally insulating layer. 
The thermally insulating layer preferably comprises ceramic fibers that are 
fused to form a rigid structure. The thermally insulating layer can be 
made of HTP fibrous ceramic insulation developed by Lockheed Missiles & 
Space Company, Inc. of Sunnyvale, Calif., or of FRCI-12 fibrous ceramic 
insulation developed by NASA, for use in fabricating thermal insulation 
tiles for NASA's space shuttles. The HTP and FRCI-12 materials are very 
porous and can absorb many times their own weight of water. It is 
preferable that the thermally insulating layer be saturated with water to 
provide additional thermal protection. 
In a preferred embodiment of the invention, a layer of refractory abrasive 
material is also provided within the wall of the safe, preferably in 
contact with the interior surface of the outer panel, in order to dull or 
otherwise ruin drills used to cut into the wall. The abrasive layer, which 
can also function as thermal insulation, comprises a composite containing 
carbide granules, which are preferably of different (i.e., coarse and 
fine) grain sizes. The carbide granules preferably consist of silicon 
carbide. 
Also in the preferred embodiment, a thermally conductive layer (as of 
copper) is provided within the wall of the safe, preferably between the 
layer of refractory abrasive material and the thermally insulating layer. 
The thermally conductive layer has a sufficient thermal mass to conduct 
heat rapidly away from any localized area in the vicinity of where intense 
heat might be applied to the outer panel of the safe by a cutting torch.

BEST MODE OF CARRYING OUT THE INVENTION 
In FIG. 1, a safe 10 is illustrated as a walled structure of generally 
conventional external configuration, which defines a volume within which 
valuable items can be securely stored. The safe 10 comprises: 
a) a cavity-defining member of integral construction, which has a top 
portion, a bottom portion, two opposite side portions and a back portion; 
and 
b) a door member, which is hingedly attached in a conventional manner to 
the cavity-defining member. 
The top, bottom, side and back portions of the cavity-defining member, 
together with the door member that is hingedly attached to the 
cavity-defining member, collectively comprise a wall enclosing the 
interior volume of the safe 10. 
It is a feature of the present invention that every portion of the wall of 
the safe 10, or at least those portions of the wall that are accessible to 
a person who might attempt to cut therethrough with a high-temperature 
torch, are of laminate construction as described hereinafter. 
FIG. 2 illustrates the laminate construction of a portion of the wall of 
the safe 10 in enlarged detail. The wall portion as illustrated could have 
an exterior metal plating 20, which would be polished (and perhaps also 
painted) on its outwardly facing surface in accordance with aesthetic 
criteria. A burglar attempting to cut open the safe 10 with a 
high-temperature cutting torch would apply a flame produced by the torch 
to a region of the plating 20 as illustrated in FIG. 2. Structural 
strength of the wall of the safe 10 is provided by an outer panel 21 and 
an inner panel 22, which are both made of a strong hard metal (typically, 
steel). In a less elaborately appointed embodiment, the exterior metal 
plating 20 would be omitted--in which case a burglar attempting to cut 
open the safe 10 would apply the flame of the cutting torch directly to a 
region of the outer panel 21. 
An abrasive layer 23, which comprises a refractory matrix containing a 
mixture of abrasive granules, is disposed adjacent the outer panel 21. The 
abrasive granules could be, e.g., silicon carbide or silicon boride 
granules. In particular embodiments, the abrasive layer 23 could be formed 
of commercially marketed Carborundum material. The function of the 
abrasive layer 23 is to hinder or defeat the use of a drill that might be 
used to breach the outer panel 21. Preferably, the mixture of abrasive 
granules comprising the abrasive layer 23 includes granules in a range of 
coarse and fine sizes so as to hinder or defeat drills of various sizes. 
Other strategies known to the art could also be utilized to hinder or 
defeat the use of a drill. For example, a gap (not illustrated in FIG. 2) 
could be provided between the outer panel 21 and the abrasive layer 23, 
which would be filled with steel ball bearings that would continually fill 
the grooves of any drill passing therethrough--thereby greatly reducing or 
eliminating the cutting effect of the drill. 
As also shown in FIG. 2, a thermally conductive layer 24 (as of copper) is 
provided adjacent the abrasive layer 23. The refractory abrasive layer 23 
serves a thermally insulative function, whereby heat that is conducted 
through a localized region of the outer panel 21 tends to dissipate 
throughout the mass of the abrasive layer 23. However, if any "hot spots" 
develop within the abrasive layer 23, the thermally conductive layer 24 
conducts heat rapidly away from such "hot spots" so as to achieve a 
substantially uniform heat distribution within the wall of the safe 10. 
In accordance with the present invention, a thermally insulating layer 25 
made of a porous ceramic material is provided between the thermally 
conductive layer 24 and the inner panel 22. The thermally insulating layer 
25 functions to prevent or inhibit heat transfer to the inner panel 22, 
thereby protecting the contents of the safe 10. In the preferred 
embodiment, the ceramic material comprising the thermally insulating layer 
25 consists of vitreously bonded ceramic fibers--e.g., silica, alumina or 
zirconia fibers, or a mixture of such fibers. Fluxes that promote vitreous 
bonding of such ceramic fibers include oxides of boron, silicon, and 
alkali and alkaline earth elements. 
A particular commercially available porous ceramic material contemplated 
for the thermally insulating layer 25 is HTP ceramic insulation developed 
by Lockheed Missiles & Space Company, Inc. of Sunnyvale, Calif. for the 
thermal insulation tiles used on NASA's space shuttle orbiters. HTP 
ceramic insulation consists of a mixture of silica and alumina fibers 
obtainable from commercial vendors and "Nextel 312" fibers obtainable from 
3M Company. "Nextel 312" material contains a small amount of boron, which 
welds the silica and alumina fibers into a rigid structure during 
high-temperature sintering in a furnace. Alternatively, the thermally 
insulating layer 25 can be made of conventional refractory brick. However, 
fibrous ceramic material has the advantage of providing optimal thermal 
protection. The thermally insulating layer 25 can be enclosed in a 
water-tight receptacle (e.g., a plastic sack) 30; and the fibrous ceramic 
material comprising the thermally insulating layer 25 contained within the 
receptacle 30 can be saturated with water to provide additional thermal 
protection. 
FIG. 3 illustrates a particular application for the present 
invention--viz., as the vault of an automated teller machine (ATM), which 
is apt to be located in an area accessible to the public but distant from 
immediate attention by security personnel. FIG. 4 illustrates the laminate 
construction of the wall of such a vault in detail. The reference numbers 
shown in FIG. 4 correspond to the reference numbers shown in FIG. 2. 
The present invention has been described above in terms of certain 
exemplary embodiments. However, other embodiments that would become 
apparent upon perusal of the foregoing description and the accompanying 
drawing are also within the scope of the present invention. Therefore, the 
legal definition of the present invention is broadly provided by the 
following claims and their equivalents.