Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
This invention relates generally to fire protection systems
and, more particularly, to fire protection systems in which a
plurality of individual fire suppressor units are simultaneously
activated to extinguish a fire.
Certain fire protection systems employ a plurality of
strategically located suppressor units, each including an ex-
tinguishant filled vessel and an electrically operated release
mechanism for inducing discharge of the extinguishant in response
to detection of a fire. When simultaneous operation of all suppressor
units is desired, the system is provided typically with a
control circuit that produces coincident activation of all release
mechanisms. In such systems, it is common technique to electri-
cally supervise the electric integrity of the release mechanisms
by providing and monitoring a trickle current through a series
connection thereof. Although this series supervision establishes
a constant knowledge of release mechanism ihtegrity, there remains
the possibility that a single release member failure will cause
~ failure of the entire serles system. In addition, even a
detected failure of a release mechanism can prevent system opera-
tion if the detected failure occurs coincidentally with a demand
for system actuation.
The object of this invention, therefore, is to provide a
more reliable fire protection system of the type employing a plur-
ality of individual suppressant units all having electrically
operated release mechanisms adapted for coincident activation.
SUMMARY OF THE INVENTION
The present invention provides a fire protection system
including a plurality of suppressor units activatable to s~ppress a
detected fire; a plurality of electrical current responsive acti-
vators, one associated with each of said suppressor units and adapt-
ed to induce activation thereof; a control circuit connecting the
- 1 , - ~
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activators in series and including an actuator for initiating acti-
vating current flow to the activators; and an auxiliary circuit com-
prising switch means for connecting the activators in parallel in
response to the initiation of activating current ~low by the actuator.
Because of the switching provided by the auxiliary circuit, all func-
tional activators will operate even in the event that a single ac-
tivator fails in such a way as to prevent normal series operation of
the system.
In a preferred embodiment of the invention, the individual
suppressor units comprise vessels filled with a fire suppressing
agent that is released by activation of an explosive squib. The
actuator is a device that initiates current flow to the series con-
nected activator squibs and can be either a manually operated switch
or a condition responsive device such as a thermal switch, or a
products-of-combustion detector.
Another feature of the invention is the provision of a
delay for the auxiliary circuit that ensures normal series opera-
tion of the individual activators in the absence of any individual
failure thereof that would prohibit such operation.
DESCRIPTION OF THE DRAWING
-
These and other objects and eatures of the present in-
vention will become more apparent upon a perusal of the following
description taken in conjunction with the accompanying drawing, which
is a schematic circuit diagram illustrating a preferred embodiment
of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawing, there are shown a plurality
of vessels filled with a suitable fire extinguishing agent and dis-
tributed strategically throughout a fire protected zone. Each of
the vessels 11 is provided with an explosive squib 12 that is
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detonated by electrical current flow to induce release of the agent
contained in the associated vessel 11. The vessels 11 and activators
12 are conventional and of a type, for example, disclosed in United
States Patents Nos. 2,693,240 and 3,523,583. Connecting the acti-
vators 12 in series with a power source 13 is a control circuit
that includes an actuator switch 14. Although the actuator 14 can
be a simple manual switch, it preferably comprises a condition res-
ponsive sensor that closes the circuit between the power source 13
and the activators 12 in response to detection of a given abnormal
condition such as fire. Suitable condition responsive sensors in-
clude, for example, thermal switches such as disclosed in United
States Patents Nos. 2,537,028 and 3,423,585. ~onnected in series
between activators 12 an~ the power source 13 is a supervisory net-
work including a relay coil 16 that provides a limited supervisory
current flow through the activators 12. Operated by the coil 16
are normally-closed contacts 17 connecting a power supply 18 and an
indicator light 19.
An auxiliary control circuit 21 includes a plurality of
normally open contacts Kl and K2 that, when closed, connect the
activators 12 in parallel: across the power source 13. Controlling
the contacts Kl and K2 is a relay coll K connected in series with
a delay circuit 22 across the actuator 12 and the power source 13.
During normal operation, a suprevisory current of, for
example, 5 - 10 milliamps flows through the activators 12 and the
relay 16 maintaining the contacts 17 open and the indicator light
19 de-energized. However, any failure such as an individual acti-
vator with an abnormally high resistance that would prevent activat-
ing current flow through the series-connected activators 12 also
will reduce supervisory current flow to less than the hold-in level
for the winding 16, allowing the contacts 17 to close and thereby
energize the indicator lamp 19. Having observed the energized light
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19, maintenance personnel can examine the control circuit and correct
the fault to regain system inte~rity.
In response to an abnormal environmental condition such
as fire, the closing of the switch, either manually or by a suitable
sensor, will initiate activating current flow and thus coincidentally
activate all of the activator devices 12. Also, when the switch 1~
is closed, the Delay 22 is activated. Upon expiration of the speci-
fied delay, the relay coil K will activate, resulting in the closing
of the relay contacts Kl and K2. These contact closures transfer
the activators 12 from their initial series connection into a par-
allel connection with the result that they are now independentlyplaced in parallel across the power source 13. If there were a
partial or total system failure during the initial series initia-
tion due to an open or high resistance activator, then all but the
affected activator would be activated with the transfer to parallel
mode. Thus, a series activator failure will result in no more than
a single failure rather than potentially a total system failure.
Obviously, many modifications and variations of the
present invention are possible in light of the above teachings.
For example, it will be obvious that the invention can be used with
systems having more than three suppressor units by merely increasing
the number of switches in the auxiliary circuit 21. It is therefore
to be understood that within the scope of the appended claims the
invention can be practised otherwise than as specifically described.
