Abstract:
An alarm which emits an audible alarm upon the detection of a hazardous condition and which discontinues or changes a characteristic of the audible alarm upon detection that it is unsafe to use the exit with which the alarm is associated. Methods are also disclosed.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to an alarm system and method and more particularly to an alarm system on which persons may home to exits which are safe to use.  
           [0002]    While applicable to hazardous conditions of various types, the present invention may perhaps be most readily understood in the context of a fire. Fire alarms are in common use in enclosed areas of all types of structures, e.g. homes, office buildings, ships, etc. Exits from such enclosed areas are generally marked with elevated “EXIT” signs attached to the wall over the exit or suspended from the ceiling so that they may be seen from a distance to direct the occupant to the exit. Such signs may be provided with strobe or high intensity lights to increase the likelihood that they can be seen once smoke begins to accumulate in the space.  
           [0003]    However, and as is well known, the human eye reacts to smoke by involuntary closure and visual directions to exits are often ineffective. Audible alarms are also conventional, but often are ineffective as direction indicators because they compete with the alarms associated with other exits within the space, particularly in emergencies when the persons in need of guidance may panic and/or become disoriented from the smoke and/or the alarms.  
           [0004]    Even where persons blinded by smoke and in need of directional guidance can distinguish the direction to an exit from an audible alarm, known alarms to not indicate whether or not it is safe to use the exit and attempts to use the exit may have disastrous consequences not only to the persons attempting to use the exit but to the area and others therein.  
           [0005]    It is accordingly an object of this invention to provide a novel alarm system and method which obviates many of the deficiencies in known alarm systems and which has the capability of audibly guiding persons within an enclosed space to a exit which is safe to use.  
           [0006]    These and many other objects and advantages of the present invention will be readily apparent to one skilled in the art to which the invention pertains from a review of claims, the appended drawings and the following detailed description of preferred embodiments. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a pictorial representation of one embodiment of the present invention.  
         [0008]    [0008]FIG. 2 is a schematic diagram of the embodiment of FIG. 1. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0009]    [0009]FIG. 1 illustrates one embodiment of an alarm in the environment of a hallway or corridor, it being understood that the alarm has utility in any enclosed space having exits through which persons must leave to avoid a potentially unsafe condition in the space.  
         [0010]    With reference to FIG. 1, the exits  10  to a space are generally marked with elevated “EXIT” signs  12  so that they may be seen from a distance. Such signs  12  may be provided with strobe or high intensity lights to increase the likelihood that they can be seen once smoke begins to accumulate in the space, and often include audible alarms.  
         [0011]    As shown in FIG. 1, the alarm  14  is desirably located low on the wall adjacent an exit and may include any suitable visual indicators. The alarm my be mounted into or on the wall with any necessary electrical wiring internal or external to the wall.  
         [0012]    As schematically illustrated in FIG. 2, the alarm  14  may be connected by any suitable conventional means to a source of alternating current power and be provided with a conventional auxiliary power supply such as the illustrated battery  18  so that the alarm is operable in the event of failure of the a.c. power supply.  
         [0013]    One or more conventional sensors  20  may be provided in the immediate vicinity of the exit  10  or located at some distance therefrom to sense an alarm condition, e.g. temperature, radiant energy or smoke. Once an alarm condition is sensed, the alarm  14  may provide an appropriate audible alarm. It is desirable that the audible alarm be distinctive, e.g. a warble or pulsed, to indicate not only the existence of the alarm condition but also the direction to the exit  10 . Obviously, it is desirable that the particular sound be internationally accepted so that individuals will be able to appropriately respond thereto anywhere in the world.  
         [0014]    In one embodiment, the sensor  20  or the communication from the sensor  20  to the alarm may be disabled by the opening of a suitable conventional normally closed switch  22  responsive, e.g., to a sensor  24  located proximate to the exit  10 . In this manner, the audible alarm may be effectively interrupted by the sensor  24  when, e.g., the temperature adjacent the exit reaches an unsafe threshold. The sensor  24  and contacts  22  may be integrated and form a conventional thermostat controlled switch, and it may be convenient to locate the thermostat  24  inside the alarm  14 .  
         [0015]    In an alternative embodiment also illustrated in FIG. 2, the sensor  24  may be any suitable conventional sensor located on the near or far side of the wall through which the exit  10  provides passage.  
         [0016]    As an alternative, the alarm may be provided with two noise generators having distinctive audible alarms. The sensor  24  may be operatively connected to the second of the noise makers so that concurrent alarms may be used as an indication that it is not safe to use the exit 10 . The two noise makers may be independent, or connected by any suitable conventional circuit so that the first noise maker is disabled by or at the same time as the second noise maker is enabled.  
         [0017]    In a typical operation, the alarm of the present invention may be initiated by a smoke detector to provide an indication to a hotel guest or office worker that there is a fire somewhere in the building, and that evacuation should proceed through the available exits. Where, for example, the stairway on the other side of the exit is filled with smoke or flames, the second alarm will be triggered to disable the first alarm and/or to provide an alternative audible indication that the exit is not safe to use.  
         [0018]    While preferred embodiments of the present invention have been described, it is the be understand that the embodiments described are illustrative only, and that the scope of the invention is to be defined solely by the appended claims when accorded a full range of equivalents, many variations and modifications naturally occurring to the skilled in the art from a perusal of this application.