Safe and quick exit from a building during emergency conditions is critical. Passengers traveling in an elevator during a fire, for example, need to understand the conditions of the building before disembarking the elevator and entering a floor that may be experiencing intense heat, smoke, flames, or structural damage.

In the past, using elevators during a fire was not recommended. However, based on a study of the collapse of the World Trade Center, the Federal Emergency Management Agency is suggesting that elevators be used in the evacuation of tall buildings. One method for providing building safety is the use of paint to indicate points of egress. For example, the World Trade Center underwent building egress modifications following the 1993 bombing such that photo-luminescent paint was put on egress paths, primarily stair transfer corridors, to assist in way finding, much like track lights along the interior aisles of an airplane.

Despite these modifications, there remains a need for providing passengers on an elevator car with information about the condition of the building during emergencies.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a safety system for a passenger on an elevator car to enable him/her to view fire conditions during emergencies.

The foregoing object is attained by the safety system of the present invention.

In accordance with the present invention, a safety system for passengers on an elevator car broadly comprises means on at least one door associated with the elevator car for providing the passengers with information about fire conditions in the building at a particular floor. In a first embodiment, the information providing means comprises a liquid/lacquer applied to the at least one elevator door, which liquid/lacquer turns a normally opaque door transparent when subject to temperatures which exceed a threshold level, thus allowing a passenger inside to see what is happening outside without opening the door. In an alternative embodiment, the information providing means comprises a thermochromic paint or a label that changes color according to the ambient heat of the building on the floor where the elevator car has stopped.

Other details of the safety system of the present invention, as well as other objects and advantages attendant thereto, are set forth in the following detailed description and the following drawings wherein like reference numerals depict like elements.

BRIEF DESCRIPTION OF THE DRAWING (S) FIG. 1 is a sectional view of a safety system in accordance with the present invention ; and FIG. 2 is a sectional view of a safety system in accordance with an alternative embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT (S) Referring now to FIG. 1, a safety system 10 for elevators is illustrated. The safety system 10 includes an elevator car 12 in which one or more passengers travel in a known manner in a hoistway (not shown). As is customary in such elevator systems, the elevator car 12 has one or more interior doors 14 which open and close in concert with one or more landing doors 16 at the

floor where the elevator car 12 has stopped. Any suitable means known in the art may be used to open and close the interior doors 14 and the landing doors 16.

In accordance with the present invention, each of the elevator doors 14 and the landing doors 16 may be formed by a transparent material such as glass. Suitable glasses include those currently being sold by Sematic and Optima Architectural Glass. The glass used for the elevator doors 14 and the landing doors 16 may be framed or full glass.

In a preferred embodiment of the safety system of the present invention, a surface 20, preferably the back side, of each landing door 16 is provided with means 18 for providing passengers onboard the elevator car 12 with information about the temperature conditions on the floor where the elevator car 12 has stopped before the elevator doors 14 and the landing doors 16 open. The information providing means 18, in a first embodiment, comprises a thermochromatic paint which ordinarily is opaque in color at normal temperatures, but which turns transparent at temperatures above a particular threshold when exposed to heat such as if there is a fire on the floor where the elevator car 12 has stopped.

The information providing means 18 for example may be a layer of liquid or lacquer, such as OMEGALAQ Liquid LAQ Series, which changes from opaque to transparent when exposed to a threshold temperature such as about 200 degrees Fahrenheit. The liquid or lacquer is preferably applied to the glass landing doors 16, as opposed to the elevator doors 14, because it is the landing door surface that will bear the most heat during a fire in the building. The liquid or lacquer which is applied to the glass landing doors preferably changes from opaque to transparent in a matter of milliseconds. If desired, the liquid/lacquer may be applied to a surface of the elevator doors 14 in lieu of the landing doors 16.

Alternatively, the information providing means 18 may comprise a material which changes from an original color at normal temperatures to one or more other colors at a threshold temperature, such as 200 degrees Fahrenheit. In one embodiment, the material could be a colored label 30 affixed to the backside of one or more of the landing doors 16, which label 30 changes color when exposed to elevated temperatures. By using such a label, a passenger, such as a fireman, onboard the elevator car 12 can visually detect fire danger without opening the elevator doors 14. The label 30 may be a large stripe in the center of at least one landing door 16, several stripes on at least one landing door 16, e. g. one stripe at the top of the landing door, one stripe in the middle of the landing door, and one stripe at the bottom of the landing door, or may span the entire surface of the at least one landing door 16. The label 30 may be a reversible label or a non-reversible label. A reversible label is one that will return to its original color state after it has turned color from having been heated. A non-reversible label will not return to its original color state. Suitable labels which may be used in the safety system are manufactured and sold under the trade name OMEGALABEL as temperature monitors.

In lieu of the label 30, temperature sensitive polymer based pigments may be applied to a surface of one or more of the landing doors 16. Temperature sensitive polymer based pigments can visually and reversibly change colors at temperatures in the region of-31 degrees Fahrenheit to 257 degrees Fahrenheit. The color is changed by the structure of the polymer based pigment and can be tailored by chemical modification. The thermochromic polymers can be incorporated into commercially available paints and via injection molding into plastics and rubbers. Articles containing 0.1 to 1.0 wt% thermochromic pigments in a host polymer have a visually retrievable, reversible thermochromic transition.

In still another embodiment of the present invention, the transparent glass elevator doors 14 may have a layer of lacquer or liquid which changes from opaque to transparent applied to one of its surfaces and at least one of the transparent glass landing doors 16 may have a thermochromic paint applied to its backside. In such a system, the elevator doors 14 change from opaque to transparent when they reach the heat threshold to allow the a passenger, such as a fireman to see any thermochromic color change on the backside of the landing door (s) 16.

In yet another embodiment of the present invention, the safety system 10 may have a plurality of different temperature sensitive paints applied to one or more of the landing doors 16.

Each paint would preferably have a different color and a different thermosensitive range. Each paint would change color when it reached its specific heat or cold threshold.

In yet another embodiment of the present invention, as shown in FIG. 2 a peephole 40 may be inserted into at least one of the elevator doors 14. A passenger on the elevator car 12, such as a fireman, could then look through the peephole 40 and see a temperature sensitive paint or label adhered to the backside of at least one of the landing doors 16. In this way, the passenger can see whether the paint had changed color during a fire. If desired, the peephole 40 could be accessible only through a fireman's box in the elevator car 12, thus preventing the general public from tampering with it. The peephole 40 could be a fisheye lens and there could be a light (not shown) between the elevator door (s) 14 and the landing door (s) 16 to allow greater visibility of the conditions on the backside of the landing door (s) 16. In such a system, the thermochromic area would be sandwiched between the front surface of the elevator door 14 and the backside of the landing door 16.

In still another embodiment of the present invention,

electrochromatic glass may be used for the elevator doors 14 and/or the landing doors 16. Electrochromatic glass alters its light transmission properties when a voltage is applied to it.

For example, applying voltage makes the glass dark, while not applying voltage makes the glass transparent. By dimming or brightening the glass elevator doors 14 and the glass landing doors 16, floor conditions can be shown or hidden. The electrochromatic glass elevator doors 14 may be used in combination with thermochromic paint on the backside of the landing doors 16. A voltage change on the elevator doors 14 would make the elevator doors transparent and allow a passenger, such as a fireman, to see any thermochromic color changes on the backside of the landing door (s) 16. The electrochromatic glass elevator doors 14 may also be used in combination with the application of the lacquer/liquid on the landing door (s) 16. A voltage change on the elevator doors 14 would make those doors transparent. A heat threshold would then change the landing door (s) 16 from opaque to transparent. A passenger, such as a fireman, could then see through both sets of doors.

In still another alternative embodiment, a video camera 42 aimed at the landing door (s) 16 on each floor tapes the scene near the doors. A portable display carried by a passenger, such as a fireman, in conjunction with the video camera 42, would portray information about the scene before the passenger opened the doors. The video camera 42 may be mounted in any suitable location, for example, on the outside of the elevator car 12.

If desired, the landing doors 16 may have a thermochromic paint on their backside which could be viewed by a video camera inside the elevator.

In accordance with the present invention, a safety system is provided which utilizes an information providing means as an indicator of the level of severity of building conditions during a fire. The information providing means may also be used to

color the landing doors 16 so that passengers on the elevator car 12 can not see the elevator shaft, the cables, and other hardware associated with the elevator car 12.

The safety system 10 of the present invention enables passengers, such as firemen, onboard the elevator car 12 to visually comprehend the situation and elect to travel elsewhere in the building in order to egress safely. As part of the safety system 10, the elevator doors 14 and the landing doors 16 will be able to open if there is a fire and the condition is such that it remains possible to egress safely from that floor of the building, i. e. continue by walking down the stairs or leave from that end of a main floor. In severe situations, the elevator doors 14 and the landing doors 16 will not be capable of being opened because the landing doors 16 will be locked in a fire. Because people (general public) in the elevator car 12 will be able to see the situation, some of the panic associated with not being able to witness the reason for the door lockage will be avoided.

It is apparent that there has been provided in accordance with the present invention a safety system for elevator cars which fully satisfies the objects, means and advantages set forth hereinbefore. While the present invention has been described in the context of specific embodiments thereof, other alternatives, modifications, and variations will become apparent to those skilled in the art having read the foregoing description. Accordingly, it is intended to embrace those alternatives, modifications, and variations as fall within the broad scope of the appended claims.