Elevator cab fire extinguishing system

An elevator cab fire extinguishing system is carried by an elevator cab and is arranged to discharge a non-toxic fire extinguishing agent into the interior of the elevator cab in response to a fire in the elevator cab to extinguish the fire quickly and without harm to passengers and property present in the elevator cab, and includes controls responsive to the discharge of the fire extinguishing agent for automatically shutting down the ventilation fan of the elevator cab, sounding an audible alarm, and delivering the elevator cab to a designated egress level in the building within which the elevator cab travels.

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 
temperature-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 high temperature 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.

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, fireresistant 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-sensitive 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 t 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-sensitive 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. 
It will be apparent that the fire extinguishing system 30 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.