Fire-blocking insulation blanket

Details Fire-blocking insulation blanket Fire-blocking insulation blanket

1999-06-04

2002-03-19

Morris, Terrel (Department: 1771)

Stock material or miscellaneous articles

Sheet including cover or casing

Noninterengaged fibered material encased

C428S068000, C428S121000, C428S192000, C428S920000, C428S921000, C442S054000, C442S058000, C442S136000, C442S178000, C442S180000

Reexamination Certificate

active

06358591

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to insulation blankets for providing thermal and acoustic insulation for aircraft. More particularly, this invention relates to insulation blankets that contain fire-blocking materials for preventing rapid penetration of fire into an aircraft fuselage in case of a fire outside the aircraft.
2. Description of the Related Art
The passenger cabins of commercial passenger airplanes are insulated from temperature extremes and noise by the use of thermal/acoustic insulation blankets. Examples of such insulation blankets are described in U.S. Pat. No. 5,108,821 (Dooley, et. al.) and in U.S. Pat. No. 5,624,726 (Sanocki et. al.). Such insulation blankets are typically placed adjacent to the interior skin of the aircraft fuselage, between fuselage frame members that are typically parallel and spaced at regular intervals along the length of the fuselage. The insulation blankets are typically constructed to a uniform width to fit snugly between the fuselage frame members, and are attached to the frame members by means of connectors inserted through the selvedge of the insulation blanket. Other portions of the interior of the fuselage, such as the interior edges of the frame members, bulkheads, and ducts, are also insulated by means of blankets that are constructed to fit the particular portion to be insulated. The blankets have other features and qualities as described in U.S. Pat. Nos. 5,624,726 and 5,108,821, which are incorporated herein by reference.
Thermal/acoustic insulation blankets for aircraft are typically comprised of a fibrous lofted insulation such as fiberglass batting encased within a protective covering. The protective covering is typically made from primarily two pieces of lightweight, tear-resistant reinforced polymer films. The primary purpose of the protective covering is to prevent moisture from being absorbed by the fiberglass batting during the service life of the insulation blanket, to facilitate installation, and to protect the insulation batting from damage during installation. Other means for making the insulation blanket more rugged and impervious to moisture are available, but presently protective coverings made from lightweight reinforced polymer films are preferred. Typically a blanket is constructed by cutting two separate pieces of protective covering film to a shape slightly larger than the piece of batting to be contained. The two pieces of film are then joined together along the edges of the insulation batting to form a selvedge. The selvedge is typically a thin, ribbon-like structure between one-half inch and three inches wide, attached at its interior edge along a line roughly midway between the two major surfaces of the insulation batting and around the circumference of the insulation blanket. One function of the selvedge is to join and seal the two pieces of covering film together. The selvedge is also useful for attaching the insulation blanket to the aircraft frame as described below.
Insulation blankets are typically attached to the aircraft frame members using attachment posts, known in the industry as “Christmas trees,” fixed to the frame members at intervals along the length of the frame members. The selvedge of the insulation blanket is put over the attachment post. The selvedge is held in place on the attachment post by a washer. The washer is held in place by annular serrations on the attachment post which are oriented to permit the washer to be slid onto the post more easily than it may be removed. Another typical attachment method uses u-shaped spring clips to clip the selvedge of the insulation blanket to the aircraft frame.
Fire-blocking materials for incorporation into insulation blankets are known in the art. For example, heat-treated partially carbonized polyacrylonitrile fibers known by the trade name CURLON® may be formed into fire-blocking high-loft batts with a density of 0.2 to 1.0 pounds per cubic foot (pcf), typically 0.2 to 0.5 pcf. CURLON fibers are available from ORCON Corporation of Union City, Calif. , and are described in U.S. Pat. No. 4,837,076 (McCulloch et. al.). U.S. Pat. No. 4,897,303 (McCulloch et. al.) describes an insulation material made from CURLON fibers and suitable for use in aircraft. CURLON fibers may also be formed into felts and papers having densities of greater than about 1.0 pcf, typically 3 to 5 pcf. Other fire-blocking materials include ceramic materials such as refractory aluminoborosilicate and aluminosilica fibers known by the trade name 3M™ NEXTEL™, available from 3M Ceramic Fiber Products of St. Paul, Minn. U.S. Pat. No. 5,624,726 describes an insulation blanket incorporating a layer of NEXTEL fibers as a component. Other refractory materials, such as other ceramic fibers, basalt fibers, leached glass fibers, and rock wool, may also be used as fire-blocking materials if processed into a suitable form for use in aircraft insulation blankets.
The purpose for incorporating fire-blocking materials such as CURLON into insulation blankets is to protect the occupants of the aircraft in case of a ground fuel fire. A ground fuel fire, often called a “post-crash” fuel fire, occurs when fuel spilled on the ground outside the fuselage of a grounded aircraft ignites. Survivable post-crash fuel fires have occurred in the past after crash landings that were not severe enough to cause the fuselage to be destroyed upon impact, but were severe enough to cause fuel to spill from the aircraft and ignite. Survival rates from such crashes may be improved if the occupants are protected from the fire long enough to evacuate the aircraft. If the fuel fire penetrates the fuselage interior too quickly, the occupants will be overcome by smoke and heat before they can evacuate the aircraft, and will perish in the fire.
Tests conducted by the Federal Aviation Administration have shown that a typical aircraft fuselage insulated with fiberglass will provide about 1.5 to 2 minutes of protection from an intense fuel fire, before flame penetration occurs. Insulation blankets made with fire-blocking materials such as CURLON and NEXTEL can provide over five minutes of protection. However, in order to provide this extended period of protection, the insulation blankets must remain in position after the aluminum skin of the aircraft is consumed or melted away (typically in 20 to 60 seconds). In addition, the fire-blocking insulation must be firmly secured to the aircraft frame members so that no gap forms between the edge of the blanket and the aircraft frame. Such a gap would provide a pathway for the penetration of flames into the aircraft's interior, even if the insulation blanket remains generally in place.
Current methods commonly in use for securing insulation blankets to aircraft frame members will reduce the effectiveness of fire-blocking insulation blankets. The selvedge currently used to secure the insulation blanket will rapidly melt or bum when exposed to the heat of a fuel fire. When its selvedge is destroyed, the insulation blanket can fall away from the attachment post or spring clip holding it in place on the frame, allowing flames to penetrate into the interior of the aircraft. It is desirable for a fire-blocking insulation blanket to remain secured in place for at least two minutes, and preferably for more than five minutes, when subjected to a fuel fire. It is further desirable to secure fire-blocking insulation blankets to the aircraft frame members so that no gap permitting flame penetration forms between the aircraft frame members and insulation blanket when subjected to a fuel fire. Current insulation blankets and methods of attachment will not provide the desired duration and quality of attachment when exposed to a fuel fire.
SUMMARY OF THE PRESENT INVENTION
The invention provides an insulation blanket for aircraft that includes thermal/acoustic insulation, such as lofted fibrous insulation, foam insulation, or a combination thereof, and one or more fire-blocking layers of material adjacent to the insulation and extending past

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