Electric resistance heating devices – Heating devices – Radiant heater
Reexamination Certificate
2002-06-28
2003-08-26
Jeffery, John A. (Department: 3742)
Electric resistance heating devices
Heating devices
Radiant heater
C219S213000, C244S129100
Reexamination Certificate
active
06611659
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to electrically heated aircraft floor panels made as composite material panels, particularly for use as a floor panel directly securable to a floor support grid structure of an aircraft. The panel comprises several layers and a lightweight core such as an open-cell or honeycomb core, and at least one step-on cover layer.
BACKGROUND INFORMATION
Conventional composite material panels including an electrical heater are known as sandwich panels and are referred to herein as composite panels which are multi-layer structures including a honeycomb, open-cell, or foam core bonded between upper and lower cover layers that are typically made of glass fiber and/or carbon fiber reinforced materials. The cover layers are bonded or laminated to the core in an autoclave under application of heat and pressure. The dimensions of the core and of the cover layers are selected according to the particular application or use and the strength required of the composite material panel. An example of a honeycomb sandwich structure without an electric heater is shown in the magazine “Flight International”, Apr. 17, 1982, pages 988 and 989. Panels with an electric heater are disclosed in U.S. Pat. No. 2,512,875 (Reynolds) and in U.S. Pat. No. 3,697,728 (Stirzenbecher). These conventional panels leave room for improvement especially with regard to strength, durability and particularly safety requirements that must take into account the electrical heating of such composite panels to avoid fire hazards.
U.S. Pat. No. 3,961,157 (Miller et al.) discloses a lightweight electrically heated panel that can be a portable heater or it may be installed as a so-called modesty panel in a desk. The temperature is controlled by a thermostat connected in series with a thermal fuse. The thermostat and fuse are inserted in a honeycomb core where both are thermally insulated from the electrical heater. Such a structure cannot meet the strength and safety requirement of an aircraft floor panel.
Composite panels, particularly those with a honeycomb or open-cell core have a low weight and high strength and, for this reason, are particularly suitable as construction material for aircraft. Honeycomb sandwich panels are used, for example, as floor panels in aircraft. In a passenger cabin of an aircraft, such floor panels are covered either with a synthetic covering NTF, so-called non-textile floor covering, or with carpeting. In both instances, the panel causes fire safety problems due to the electrical heating.
The floor area near the aircraft door in a passenger cabin has to be heated during flight because the temperature on the outer skin of an aircraft flying at high altitudes can be as low as −55° C. Therefore, the temperature in the floor area near the door can sink to as low as −15° C., particularly after prolonged flight durations of approximately 5 hours or more at these altitudes. Passive measures to protect the door area against the cold, such as providing an insulated floor covering, are generally not adequate at such low temperatures and heat energy must be provided to these areas. For this reason, conventional warm air heating systems are used to feed warm air to the floor area near the door. The use of warm air systems in aircraft, however, is inefficient for a number of reasons. Such systems require a substantial electrical power supply and an alternating airflow from the air conditioning system. These systems also increase the weight of the aircraft and may cause discomfort among passengers and/or flight personnel because of uneven surface temperatures or drafty dry air circulation. Contamination of the air vents and the danger of blocking air vents by baggage are further disadvantages of warm air heating systems.
An alternative solution to the problem of providing heat in the floor area near the door in an aircraft passenger cabin is to screw separately heatable metal floor panels onto the conventional floor panels. This solution also has the disadvantages of adding weight to the aircraft, as well as increasing the high energy consumption. Heatable metal floor panels add approximately 60 kg per panel to the weight of the aircraft which must be avoided.
German Patent Publication DE-02 39 22 465 A1 discloses a panel component in which an electric heating device is embedded. The known panel is preferably constructed as a plywood panel and is typically used in housing construction and particularly in household areas such as the kitchen. The heating device is constructed of a plurality of tape-shaped electrodes and a radiant heater formed as a layer of synthetic material. Carbon particle mixtures are used as the radiant heater layer. Because of the combustion properties of such carbon particle mixtures, carbon particle heaters cannot be used in the passenger areas of an aircraft unless extensive safety measures are taken which add to the weight and cost of the aircraft. Thus, for reasons of safety and economy, such conventional systems are generally unsuitable for use in commercial passenger aircraft. These considerations also apply to the disclosures of the following Japanese Patent Publications: JP 4-136630, JP 2-61435, and JP 63-161328. Each of these publications relates to building construction and does not meet aircraft safety requirements.
OBJECTS OF THE INVENTION
In view of the above it is the aim of the invention to achieve the following objects singly or in combination:
to provide a composite electrically heated aircraft floor panel that can be used instead of a conventional unheated floor panel in the area next to and alongside an aircraft door in a passenger cabin or in other cold spaces in the floor area of an aircraft, in order to achieve homogenous surface temperatures at the floor level, preferably in the range +20° C. to +35° C. under normal operating conditions;
to construct such a panel so that it achieves a reduction in weight and in energy consumption, compared to conventional aircraft floor heating solutions;
to construct such a panel that it simultaneously satisfies the mechanical strength of a step-on floor panel and the electrical safety requirements that must be met by aircraft floor panels particularly against fire hazards;
to achieve a uniform floor heat distribution by radiation that emanates in a controlled manner per surface area unit over the surface area of the panel so that for example panel areas directly next to the door radiate more heat than areas of the same panel further away from the door;
to avoid generating uncomfortable air drafts in the door areas of a passenger aircraft; and
to provide the present panels with surface area configurations that conform to the floor layout.
SUMMARY OF THE INVENTION
An aircraft floor heating panel according to the invention comprises a heat resistant fiber composite core structure for providing the structural strength of an aircraft floor panel, an outer first section including an electrical heater preferably a foil heater and a heat distributing metal plate forming a walk-on surface, a first adhesive bond between the electrical heater such as a foil heater and the heat distributing metal plate, a second adhesive bond between the foil heater and the fiber composite core structure, an outer second section including one or more heat insulating pads bonded to the fiber composite core structure opposite the outer first section so that the fiber composite core structure is sandwiched between the outer first and second sections. One or several cut-outs are provided in the composite core structure below the heat distributing metal plate. A PTC temperature sensor is embedded in at least one cut-out in heat sensing contact or proximity with the heat distributing metal plate. The positive temperature coefficient sensor is electrically connected to a control and power supply unit in the aircraft for switching a power supply on and off under normal operating temperatures. Redundant fire hazard protection components are electrically connected in series with the electrical foil heater for in
Airbus Deutschland GmbH
Fasse W. F.
Fasse W. G.
Jeffery John A.
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