Stock material or miscellaneous articles – Hollow or container type article – Glass – ceramic – or sintered – fused – fired – or calcined metal...
Reexamination Certificate
2001-05-21
2004-02-03
Pyon, Harold (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Glass, ceramic, or sintered, fused, fired, or calcined metal...
C428S034600, C428S920000, C428S921000, C220S560010, C252S601000
Reexamination Certificate
active
06686003
ABSTRACT:
TECHNICAL FIELD
The present invention relates to fire-protection containers such as safes, storage boxes, filing cabinets, and the like, and to materials and methods of production thereof which optimize the desirable characteristics of such containers.
BACKGROUND ART
Fire protection containers generally comprise a double-walled box enclosure in which the space between the walls is filled with a heat dissipating material. This material is generally some type of cementitious product which has a high water content. By itself, this single water-bearing layer is usually sufficient for the protection of paper and similar items which can withstand temperatures between about 200 to 400 degrees F. However, electronic data storage media such as floppy disks and CD ROMS have a much lower heat tolerance and must be maintained at temperatures below 125 degrees F. Therefore, for such applications, one or more additional heat insulating and/or absorbing layers are added to the inside of the box. This usually comprises first a layer of high R-value foam such as polyurethane followed by a high heat capacity phase change material which has a melting point below 125 degrees F.
The prior art describes a number of structural designs for the box shell used to contain the outside insulation layer, typically made from steel or plastic. The steel shell has the obvious advantage of providing additional protection from the physical shock which could occur from a fall during the fire. However, the plastic shell provides a lighter, less expensive product which is much easier to manufacture. Numerous fire protective safe designs have emerged during the past several years. In particular, a number of designs employing a plastic shell have been introduced. These include the structures disclosed in U.S. Pat. Nos. 4,541,545, 4,048,926, Des.289,582, 4,683,732, and 5,377,514. Other general protective fire safe designs are disclosed in U.S. Pat. Nos. 4,574,454, 3,888,557, 4,893,397, and 4,685,402, for example.
The prior art also describes a number of methods of forming solid or gelled compositions from solutions of a soluble silicate such as sodium or potassium silicate. These materials generally possess the property of being able to absorb and dissipate large quantities of heat when exposed to fire and high temperatures due to their inherent high water content. When properly formulated to withstand temperatures exceeding 1700 degrees F., these materials also have utility in the area of fire-protection containers, in which they are sandwiched between walls of the container as a heat and fire protection layer. The prior art contains numerous references to gelled silicates for applications ranging from construction, insulation and fire protection materials to soil hardeners. Examples of the former categories are presented in U.S. Pat. Nos. 4,871,694, and 4,997,694. A less typical example for the use of gelled silicates is in the production of microwave absorbing materials (e.g., U.S. Pat. No. 4,806,718) for use in microwave cooking products, for example. The prior mentioned U.S. Pat. No. 4,997,694 also discloses a fire and heat protective gel material formed by polymerization reaction of sodium or potassium silicate and a salt of a monovalent alkali metal. This material exhibits intumescence upon application of heat, a property which may be desirable in certain applications, but undesirable in others.
Certain soil hardeners also employ the addition of a polyvalent metal salt (such as calcium chloride) to cause gelling of the soluble silicate (e.g., sodium silicate solution).
Examples of these soil hardening techniques are described in U.S. Pat. Nos. 4,056,937 and 4,466,831. The addition of polyvalent metal salts to sodium silicate in the production of soil hardeners is also mentioned to a lesser extent in U.S. Pat. Nos. 4,354,875 and 4,384,894. However, such materials have heretofore not been considered for use in connection with fire or heat protective enclosures.
Current methods used by the fire-protection industry for the production of fire/heat-proof containers such as fireproof filing cabinets and safes primarily utilize the principal of water liberation from a hydrated composition such as concrete or gypsum to absorb the external heat and liberate it via steam ablation from the material to maintain a safe temperature inside the container. Since these insulation materials generally weaken and crumble (like cement when the water is baked out) they have to be included between heavy gauge metal walls to provide and maintain structural integrity during and after a fire. This tends to make the product fairly heavy and expensive. As stated before, some commercial fire-protection containers using these types of cementitious insulation materials are provided only with plastic walls which burn away during a fire leaving the exposed insulation. Although the insulation will remain intact if undisturbed, even a slight impact or fall experienced by the fire-exposed container could cause the insulation layer to crumble or shatter, thus compromising its contents to the fire.
Objects of Invention
It is a principal object of the present invention to produce a low cost, easily manufacturable, light-weight fire protection container which is highly effective under realistic fire conditions.
An additional, important object is to provide a storage container which has superior fire protection qualities, as well as the ability to retain its basic structural integrity after prolonged exposure to high temperatures as experienced during a fire.
A further object is to provide a fire protection container which will effectively ensure the integrity of contents which cannot withstand temperatures higher than about 125 degrees F., including articles bearing magnetically recorded data.
Still further objects are concerned with novel and improved methods of fabricating fire protection containers and materials used in the fabrication of such containers.
Other objects will in part be obvious and will in part appear hereinafter.
Disclosure of Invention
The present invention discloses a specific set of gelled silicate materials which provide several advantages over the prior art insulations used for fire-protection containers, specifically cementitious materials such as concrete and gypsum. These advantages include a higher heat duration for a given wall thickness, and an increase in material strength after intense heating. The first of these is the result of numerous factors including a higher water density and the inherent high R-value of the porous silica layer that forms as the insulation is baked out. The second results from the fact that the silicate gel is actually an unfired ceramic which solidifies and toughens after being fired. By comparison, cementitious materials such as concrete and gypsum derive their physical strength from the chemically bound water which is integral to their crystalline structure. Once this water is driven off by heating, these materials weaken and crumble.
The silicate gel insulation layer of the present invention is generally formed by the combination of one or more polyvalent metal (preferably a Group II A metal, i.e., calcium, magnesium) salts (preferably halides), particularly calcium, magnesium, or aluminum chloride, and to a lesser extent, strantium, barium, zinc, or iron chloride, with a greater amount of an alkali metal silicate solution, particularly sodium silicate, having a silica to metal oxide ratio of two or higher. This combination forms a very dense, rigid material which contains over 50% water, has superior heat resistance and heat duration properties, and which retains or actually improves its structural integrity during fire exposure. It should also be noted that the gel material of the present invention remains essentially dimensionally stable upon application of heat, as opposed to the intumescing gel material of previously mentioned U.S. Pat. No. 4,997,694.
In one basic embodiment, the present invention includes the proposed new silicate gel insulation in combination with either a blow-molded
Bond Schoeneck & King , PLLC
Chevalier Alicia
Fireking International, Inc.
McGuire George R.
Pyon Harold
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