Elevator Cab Fire Extinguishing System

The present invention relates generally to fire safety, and pertains, more specifically, to the protection of passengers and property in elevator cabs from the ravages of fire.

While much attention has been given to fire prevention in buildings of all kinds, and to the provision of fire escape devices and procedures, and fire fighting systems designed to protect property as well as occupants in buildings, very little effort has been expended in providing for the safety of passengers and property in elevator cabs. As a result, over the years, fires in elevator cabs have been the cause of grievous injury, and even death, as well as a great deal of property damage. Experience has shown that most elevator fires occur within the elevator cab itself, and are the result of flammable items in the elevator cab which either ignite accidentally or are ignited by vandalic acts. When such fires do occur, passengers usually are present in the cab and are subjected to devastating injury, and even death. It would be advantageous to have available a simple, yet reliable system for extinguishing a fire in an elevator cab, with safety, in order to prevent injury to passengers unfortunate enough to be present in the elevator cab at the outbreak of the fire.

The present invention provides a simple and effective system for extinguishing a fire in an elevator cab quickly and with safety to passengers in the cab, and attains several objects and advantages, some of which may be summarized as follows: Immediate and effective response to the presence of a fire in an elevator cab, to extinguish the fire quickly; rapid extinguishing of a fire in an elevator cab with safety to passengers in the cab and minimal damage to property; automatic operation for almost instantaneous response without the necessity for the actuation of any control by a passenger; versatility of installation so as to meet the requirements of almost any elevator system; and simple and low-cost operation and maintenance for encouraging widespread use with economy.

The above objects, as well as further objects and advantages, are attained by the present invention, which may be described briefly as an elevator cab fire extinguishing system for use in extinguishing a fire within the interior of the cab of an elevator in response to the presence of the fire itself, the elevator cab fire extinguishing system comprising: a source of non-toxic fire extinguishing agent maintained under superatmospheric pressure; a conduit communicating with the source and the interior of the elevator cab; and a valve in the conduit, the valve including combustion-responsive means associated with the interior of the elevator cab for maintaining the conduit closed in the presence of normal operating conditions in the interior of the elevator cab and for opening the conduit in response to a condition associated with a fire within the interior of the elevator cab to discharge the fire extinguishing agent from the source into the interior of the elevator cab.

The invention will be understood more fully, while still further objects and advantages will become apparent, in the following detailed description of preferred embodiments of the invention illustrated in the accompanying drawing, in which:

FIG. 1 is a pictorial illustration, partially broken away, of a fire extinguishing system constructed in accordance with the invention and installed in a conventional elevator cab;

FIG. 2 is a partially diagrammatic perspective view of the fire extinguishing system;

FIG. 3 is an elevational, cross-sectional fragmentary view of an alternate installation; and

FIG. 4 is a pictorial illustration similar to FIG. 1, but showing another embodiment of the invention.

Turning now to the drawing, and especially to FIGS. 1 and 2 thereof, an elevator cab 10 of an elevator 11 of the type employed in connection with the transport of passengers has a pair of elevator cab doors 12 placed behind hoistway doors 13 and leading to the interior 14 of the elevator cab 10, the interior 14 being bounded by side walls 16, a floor 18 and a ceiling 20. Elevator cab 10 traverses several stories, or levels, within an elevator shaft 21 of a building 22 within which the elevator 11 is installed, under the control of an elevator controller 24 placed in a remote location in the building 22, usually in a motor room (not shown) provided for the purpose. A ventilation fan 28 is located adjacent the ceiling 20 and normally operates to maintain adequate ventilation within the elevator cab 10 for the comfort and safety of passengers using the elevator. The present invention provides a fire extinguishing system 30 for use in connection with the elevator cab 10 for the safety and protection of the passengers.

Fire extinguishing system 30 includes an enclosure 32 mounted upon and secured to the elevator cab 10, preferably outside the elevator cab 10 at the ceiling 20, the enclosure 32 having a base 34, side walls 36 and an access cover 38. It is best that the enclosure 32 be constructed of a sturdy, fire-resistant material, a suitable material being stainless steel. An aperture 40 in the base 34 is juxtaposed with a passage 42 through the ceiling 20 so that the interior 14 of the elevator cab 10 is accessible to the fire extinguishing system 30, as will be explained in detail below.

A source of fire extinguishing agent is located in the enclosure 32 and is seen to include a container in the form of a cylinder 44 of fire extinguishing fluid held under superatmospheric pressure within the cylinder 44. Cylinder 44 is secured in place within the enclosure 32 by hold-down brackets 45 and includes a fitting 46 which provides a conduit juxtaposed with the aperture 40 and the passage 42 in the ceiling 20 of the elevator cab 10. Discharge means is shown in the form of a discharge head 48 affixed to the fitting 46 and located at the passage 42, the fitting 46 including a discharge orifice at 50 aimed so as to enable the discharge of fire extinguishing agent from the cylinder 44 into the interior 14 of the elevator cab 10. A valve 52 maintains the discharge orifice 50 normally closed so that the fire extinguishing fluid is confined within cylinder 44 awaiting use. Valve 52 is of the type which is actuated in response to a change in temperature, and includes temperature-responsive means in the form of a fusible link 54 juxtaposed with the passage 42 so as to be in direct communication with the interior 14 of the elevator cab 10. A deflector plate 56 is a part of the discharge head 48.

Should there be a fire in the elevator cab 10, the temperature in the interior 14 of the elevator cab 10 will rise. Very shortly, the temperature at the ceiling 20 will reach that which will cause the fusible link 54 to melt, thereby opening valve 52 and discharging fire extinguishing fluid from the cylinder 44 into the interior 14 of the elevator cab 10. The temperature at which the fusible link 54 will melt is about 165.degree. F., and that temperature is reached very quickly, so that the fire extinguishing system 30 reacts very quickly to flood the interior 14 of the elevator cab 10 with fire extinguishing agent and extinguish the fire. Distribution of the fire extinguishing fluid will be aided by the deflector plate 56 and in a very short time the fire will be extinguished. The fire extinguishing agent is chosen from available non-toxic fire extinguishing agents. The preferred agent is a bromotrifluoromethane, available commercially under the trademark HALON, and more particularly HALON 1301, which exhibits the necessary fire extinguishing characteristics and has no toxic effects upon the passengers in the elevator cab 10.

As soon as the fire extinguishing fluid is discharged from the cylinder 44, a sensor in the form of a pressure-sensitive switch 60 in fitting 46 is actuated in response to the drop in pressure in the fitting 46. As best seen in FIG. 2, switch 60 is connected to a control circuit 62 which performs several functions in response to the actuation of switch 60. First, the control circuit 62 shuts down the ventilation fan 28 so that the fire extinguishing fluid is not exhausted from the elevator cab 10 before the fire can be extinguished. In addition, the ventilation fan 28 is precluded from introducing more oxygen to the fire in the elevator cab 10. Control circuit 62 also activates an audible alarm in the form of a siren 64 to apprise others in the building 22 of the fire. Further, control circuit 62 is connected to the elevator controller 24 and automatically activates the elevator controller 24 to shift the elevator controller to the mode known as "Phase I" fire operation, a standardized operating mode in which the elevator cab 10 is delivered to the level in the building 22 designated as the egress floor, or level, which ordinarily is the lowest terminal landing and, upon arrival of the elevator cab 10 at the designated egress level, the elevator doors 12 are opened automatically to enable safe egress of the passengers. When the elevator mode of operation is shifted to Phase I fire operation, the emergency stop switch (not shown) of the elevator is disabled automatically, thereby preventing manual actuation of the emergency stop switch by a passenger and assuring that the elevator cab 10 will be delivered to the designated egress level without delay. Once the emergency is passed, the system 30 is deactivated, the exhausted cylinder 44 is removed and is replaced with a fully-charged cylinder so that the system once again is fully functional, with minimal interruption in elevator operation and in the protection afforded by the system 30.

The fire extinguishing system 30 is entirely self-contained and the above-described control functions are powered by a rechargeable battery 66. Preferably, battery 66 is a standard twelve-volt battery and a battery charger 68, powered by an external source 70 of electrical power, is controlled by control circuit 62 to maintain battery 66 at full charge, in readiness for activation of the control functions of the system 30 upon demand. It is noted, however, that no electrical power is needed to activate the system 30 to extinguish a fire in the elevator cab 10 since valve 52 is opened solely in response to the presence of the fire and requires no electrical power to discharge the fire extinguishing agent into the interior 14 of the elevator cab 10.

Turning now to FIG. 3, an alternate installation is illustrated. In the installation of FIG. 3, the elevator cab 10 is of the type provided with a dropped ceiling 80 below the outer ceiling 20 of the elevator cab 10. The fire extinguishing system 30 is installed above the ceiling 20, as described above; however, a flexible extension 82 is connected between the fitting 46 and the discharge head 48 to extend the conduit between the cylinder 44 and the interior 14 of the elevator cab 10 so that the discharge head 48 is located at a passage 84 through the dropped ceiling 80. In this manner, the temperature-responsive means is located for quick response to the conditions in the interior 14 of the elevator cab 10 and the discharge head 48 will deliver discharged fire extinguishing fluid effectively to the interior 14 of the elevator cab 10, should a fire occur. Thus, it will be seen that the fire extinguishing system 30 is adapted readily to a variety of site requirements.

In the embodiment illustrated in FIG. 4, fire extinguishing system 30 has been modified in that the valve 52 is actuated in response to combustion conditions within the interior 14 of the elevator cab 10, other than merely the presence of a temperature high enough to melt link 54. Thus, a smoke detector 90 is located within the interior 14 of the elevator cab 10 and is connected to the control circuit 62. Preferably, smoke detector 90 is of the type which includes temperature rise detection capabilities as well as smoke detection capabilities so that upon the occurrence of a fire within the elevator cab 10, smoke detector 90 will react in response to either the presence of smoke in the interior 14 of the elevator cab 10 or to a predetermined rise in temperature to provide a signal to the control circuit 62. The control circuit 62, in turn, activates an actuator in the form of a protractor 92 mounted immediately adjacent link 54 such that upon activation of the protractor 92, the plunger 94 of the protractor 92 will be extended to engage the link 54 and displace the link 54 by pushing the link 54 aside, enabling valve 52 to open and discharge fire extinguishing fluid from the cylinder 44 into the interior 14 of the elevator cab 10. Should the smoke detector 90 fail to provide the necessary activating signal to control circuit 62, the fusible link 54 still is available to operate the fire extinguishing system 30 by fusing in response to the presence of a melting temperature, in the manner described in connection with the embodiment of FIG. 1. In either event, once valve 52 is actuated to discharge fire extinguishing fluid into the interior 14 of the elevator cab 10, control circuit 62 operates to perform the subsequent functions set forth above.

Smoke detectors of the type suitable for use as smoke detector 90 are available commercially, one such smoke detector being of the ionization type, such as that sold by Electro Signal Lab, Inc. of Rockland, Mass. under model number 445CRT, which smoke detector includes a temperature-sensitive device for detecting temperature rise, as well as a smoke-sensitive device, for providing the desired activating signal. Protractors of the type suitable for use as protractor 92 are available commercially, one such protractor being of the explosive type, such as a piston protractor sold by Nobel's Explosives Company Limited under the trademark METRON, which responds very quickly to the signal provided by control circuit 62.

It will be apparent that the fire extinguishing system 30, in any of the illustrated embodiments, provides a safe and effective means for protecting passengers as well as property in an elevator cab from the ravages of a fire in the elevator cab itself. The system responds quickly and effectively to extinguish any such fire before extensive harm can occur. The system is simple and is easily installed and readily maintained with economy, so that widespread use is encouraged, resulting in increased safety and confidence on the part of elevator passengers.

It is to be understood that the above detailed description of preferred embodiments of the invention are presented by way of example only. Various details of design and construction may be modified without departing from the true spirit and scope of the invention as set forth in the appended claims.