Fire door core assembly

Abstract

A laminated fire door including a core, containing panels or boards made from an organic material including flax, and a fibrous binder constituting a sodium silicate adhesive, is used to make a door exhibits at least a 45 minute fire rating. In accordance with a preferred form of the invention, the fire door core is formed by using a silicate adhesive, preferably sodium silicate, in the order of 25 mils (0.6 mm) to laminate together two flax boards, each having a thickness in the range of 0.625-0.875 inches (approximately 16-22 mm), with each of the laminated flax boards having a density of between 20 and 45 pounds per cubic foot (320-700 kgs/m³).

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention pertains to the art of doors and, more particularly, to the construction of a door having a fire resistant core. [0003] 2. Discussion of the Prior Art [0004] Doors for commercial, and even domestic, applications are often rated for fire resistance. More specifically, fire doors are rated based on their ability to resist burning in the case of a fire, with standard ratings being defined as 20, 45, 60 and 90 minutes depending on the length of time a door can withstand a rating temperature, typically in the range of 1700+° F. The higher the minute rating, the better the fire rating. For instance, low rated fire doors are typically made from an organic material, while high rated fire doors are generally made from mineral or metal materials. More specifically, a 20 minute door typically includes a particle or stave board core. For 45, 60 and 90 minute ratings, a wood door generally has a mineral cor...

AI Technical Summary

Benefits of technology

[0009] The present invention is directed to producing a laminated fire door including a core containing panels or boards made from an organic material and a fibrous binder or adhesive, wherein the door exhibits at least a 45 minute fire rating. More specifically, a fire door constructed in accordance with the invention includes a core having multiple panels made from an organic material containing flax, having sandwiched therebetween a relatively thick layer of a fibrous binder, preferably a sodium silicate adhesive. In accordance with a preferred form of the invention, the fire door core is formed by using a silicate adhesive, preferably sodium silicate, in the order of 25 mils (0.6 mm) to laminate together two flax boards, each having a thickness in the range of 0.625-0.875 inches (approximately 16-22 mm). In accordance with the most preferred form of the invention, each of the laminated flax boards has a density of between 20 and 45 pounds per cubic foot (320-700 kgs / m3). The laminated flax board panels can then be trimmed to be used as a core in making a specified sized door. With the exposed organic surfaces, outer door skins can be readily and effectively laminated to the core.

Problems solved by technology

In general, the higher rated fire doors have more costly constructions.

It is known in the door industry that a particle board or wood fiber board can achieved a 20 minutes fire rating, but cannot withstand the hose stream test in a 45 minutes fire test.

It is also more difficult or impossible when two layers of fiberboard are laminated together with PVA adhesive.

These panels have disadvantages of not being able to provide good mechanical strength specially for screws or nails and they are very dusty for any cutting or boring.

They are also very fragile and do not provide always good lamination for the door skins.

Of course, these materials are more expensive than wood or wood-based products.

It has also been more difficult to obtain such results with lamination of two layers of particle board or wood fiber board because of delamination of one layer during the fire test.

Also, a high level of distortion or cupping is occurring on a large door, specially when the density of the core is exceeding 40 lbs.

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