U.S. patent number 3,759,331 [Application Number 05/248,090] was granted by the patent office on 1973-09-18 for fire protection system utilizing dry pipes normally maintained in a vacuum.
This patent grant is currently assigned to Factory Mutual Research Corporation. Invention is credited to William L. Livingston.
United States Patent |
3,759,331 |
Livingston |
September 18, 1973 |
FIRE PROTECTION SYSTEM UTILIZING DRY PIPES NORMALLY MAINTAINED IN A
VACUUM
Abstract
A fire protection system in which a plurality of extinguishant
discharge heads are disposed in elevated position in a space to be
protected from fire and are connected by a piping system for
supplying extinguishant to the heads. Flow of extinguishant to the
heads is normally prevented until a predetermined increase in fluid
pressure is affected in the piping system in response to a fire
condition in the space.
Inventors: |
Livingston; William L. (Sharon,
MA) |
Assignee: |
Factory Mutual Research
Corporation (Norwood, MA)
|
Family
ID: |
22937638 |
Appl.
No.: |
05/248,090 |
Filed: |
April 27, 1972 |
Current U.S.
Class: |
169/17; 169/20;
169/39 |
Current CPC
Class: |
A62C
35/605 (20130101) |
Current International
Class: |
A62C
35/60 (20060101); A62C 35/58 (20060101); A62c
035/00 () |
Field of
Search: |
;169/1,3,5,16,18,19,20,37,39,17 ;251/5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wood, Jr.; M. Henson
Assistant Examiner: Mar; Michael
Claims
I claim:
1. A fire protection system comprising a plurality of discharge
heads disposed in an elevated position in a space to be protected
from fire, a piping system connecting said heads, a source of
extinguishant connected to said piping system, means for normally
maintaining the fluid pressure in said piping system below a
predetermined maximum value, control means normally preventing the
flow of extinguishant from said source to said heads, said control
means being responsive to an increase in said fluid pressure above
said maximum value for permitting the flow of extinguishant to said
heads, and means responsive to a predetermined fire condition in
said space for causing said increase in said fluid pressure.
2. The system of claim 1 wherein said predetermined maximum value
of said fluid pressure is atmospheric pressure.
3. The system of claim 1 wherein said means for causing said
increase in said pressure comprises means for venting said piping
system to atmosphere.
4. The system of claim 3 wherein said venting means comprises a
venting assembly associated with each of said heads.
5. The system of claim 4 wherein each venting assembly comprises a
spring loaded cap extending over the outlet of its respective head,
a thermal link normally maintaining its respective cap in an
extinguishant discharge preventing position relative to said
outlet, each of said links adapted to release its respective cap in
response to said predetermined fire condition, whereby said cap
moves from said extinguishant discharge preventing position to a
venting position by virtue of its spring force.
6. The system of claim 1 wherein said means for normally
maintaining the fluid pressure in said piping system below a
predetermined maximum value comprises a vacuum pump connected to
said piping system.
7. The system of claim 1 wherein said control means comprises a
pinch valve disposed in said piping system, and an actuator
responsive to the pressure in said piping system being below said
predetermined maximum value for closing said valve, and responsive
to said increase in pressure for opening said valve.
8. The system of claim 7 wherein said means for causing said
increase in said pressure comprises means for venting said piping
system to atmosphere.
9. The system of claim 7 wherein said actuator comprises a housing,
a diaphragm defining a chamber in said housing and movable in said
housing in response to fluid pressure variations in said chamber,
means connecting said diaphragm to said pinch valve, and means
communicating said chamber with said piping system.
Description
BACKGROUND OF THE INVENTION
This invention relates to a fire protection system and, more
particularly, to such a system utilizing dry pipes normally
maintained at a vacuum.
Dry pipe fire protection systems are generally well known and
usually consist of a plurality of sprinkler heads disposed in an
elevated position with respect to the space to be protected from
fire. A piping system connects the various heads to a source of
extinguishant, usually in the form of a municipal water supply, and
a cutoff valve or the like is usually disposed between the source
of extinguishant and the piping system to maintain the latter in a
dry state to prevent possible damage to the piping system as a
result of the water freezing. Upon the occurrence of a fire, the
valve is opened and the water flows through the piping system for
discharge through the heads.
Several disadvantages are inherent in the use of these type
systems. For example, the response time for the water to actually
discharge from a head after the occurrence of a fire is relatively
high due to the fact that the water must flow a relatively large
distance from the valve to the heads before discharge. Also, air
which accumulates in the dry portion of the piping system must
first be purged out of the system before the water can discharge
from the heads. A related problem is that a relatively high water
pressure must be available in order to purge the air out, since the
air can provide a relatively high resistance to water flow through
the piping system.
As a result, delays as great as two minutes can occur between
actuation of the system in response to a fire and the actual
discharge of the extinguishant from the heads. This delay can often
be disastrous, especially in connection with protection involving
high challenges, such as in the use of warehouses, or the like.
Attempts have been made to offset this disadvantage by utilizing
larger pipes, heads and/or water supplies in order to compensate
for the above-mentioned delay. However, it is apparent that the
economic consequences of this are often prohibitive.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a dry
pipe system which eliminates the above-mentioned delay in discharge
of the extinguishant after actuation of one or more heads.
It is a further object of the present invention to provide a fire
protection system of the above type in which water is continuously
discharged from the piping system during inaction of same.
Toward the fulfillment of these and other objects, the present
invention comprises a plurality of discharge heads disposed in an
elevated position in a space to be protected from fire, a piping
system connecting said heads, a source of extinguishant connected
to said piping system, control means normally preventing the flow
of extinguishant from said source to said heads, said control means
being responsive to a predetermined increase in fluid pressure in
said piping system for permitting the flow of extinguishant to said
heads, and means responsive to a predetermined fire condition in
said space for causing said predetermined increase in said pressure
in said piping system.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic perspective view of a building having the
system of the present invention installed therein;
FIG. 2 is an enlarged sectional view showing a portion of the
system of FIG. 1;
FIGS. 3 and 4 are enlarged sectional views taken on the lines 3--3
and 4--4, respectively;
FIG. 5 is a perspective view of a discharge head utilized in the
system of the present invention; and
FIG. 6 is an enlarged sectional view taken along the line 6--6 of
FIG. 5.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1 of the drawings, a building 10 is shown in
phantom lines which is equipped with an automatic fixed fire
protection system 12 embodying features of the present invention.
The system comprises a buried feed main 14 connected to a municipal
water supply line 16 for delivering the extinguishant, in this case
water, to a piping system including a riser 18 connected to a
crossmain 20 which, in turn, is connected to a plurality of branch
lines 22. Each branch line has a plurality of discharge heads 24
mounted thereon which are operated automatically in response to a
fire, as will be described, to deliver a spray of water to the
fire. The buried feed main 14 extends beyond the riser 18 and can
be connected to risers of other buildings or, in the case of a
large building, to other risers in the same building. The crossmain
20 and the branch lines 22 are suspended near the ceiling of the
building in a conventional manner.
As shown in FIG. 2, the riser 18 is divided into two portions 18a
and 18b which are connected together by means of a pinch valve 26
which will be described in detail later.
A vacuum pump 28 is connected to the riser portion 18a, and a
manually operated gate valve 30 is connected to the riser portion
18b. Since the vacuum pump 28 and the gate valve 30 are of a
conventional design, they are not shown, nor will be described, in
any further detail.
The pinch valve 26 consists of a tubular boot 32 of an elastomeric
material which is bolted at each end to flanges formed on the
facing end portions of the riser portions 18a and 18b, as shown.
One half portion of the boot 32 is maintained in a permanent
pre-pinched condition by means of a fixed pinch bar 34 which is
affixed in a permanent position with respect to the riser 18 by
means of a pair of support brackets 36 and 38 which are also bolted
to the flange of the riser portion 18b, as shown in connection with
the support bracket 36 in FIG. 2.
A movable pinch bar 40 engages a portion of the boot 32
diametrically opposite from that portion engaged by the fixed pinch
bar 34, and is supported for movement by means of a pair of support
rods 42 and 44 extending through openings formed in the pinch bar
34 and connected by an arcuate shaped bracket 46.
As shown in FIG. 2, an actuator, shown in general by the reference
numeral 50, is provided for actuating the pinch valve 26. The
actuator 50 comprises a housing 52 in which a diaphragm 54 is
disposed for movement in response to pressure variations in a
chamber 56 defined by a portion of the housing 52 and the
diaphragm. A connecting rod 57 connects the bracket 46 to the
diaphragm 54 so that movement of the diaphragm causes a resultant
movement of the bracket and therefore the pinch bar 40. A conduit
58 communicates the interior of the riser portion 18a with the
chamber 56 for reasons that will be explained in detail later.
A valve 60 is associated with the actuator and is shown in detail
in FIG. 4. The valve 60 comprises a tubular insert 62 disposed in
the wall of the housing 52 of the actuator 50, and having an
arcuate flange portion formed on its inner wall to define a valve
seat 64. A valve plunger is provided in the tubular insert 62 and
consists of a disc-like valve head 66 adapted to seat on the valve
seat 64, and a valve stem 68 connected at one end to the valve head
66 and supported for slidable movement within the tubular insert 62
by means of a support strut 70. A compression spring 72 extends
between the valve head 66 and the support strut 70 to urge the
valve head in a direction to the right as viewed in FIG. 4.
The details of each discharge head 24 are shown in FIGS. 5 and 6.
Each head consists of a base member 72 having a relatively large
central opening 74 and several relatively small vent openings 75
extending therethrough, for reasons to be explained in detail
later. A tubular fixture 76 projects from the upper surface of the
base member 72 and registers with the central opening 74. The
fixture 76 is externally threaded for connection to a branch line
22 of the fire protection system. A pair of spaced circular flanges
78 and 80 are formed on the bottom surface of the base member 72,
with the flange 78 being slightly greater in height than the flange
80. It is understood that the head 24 can be provided with a
device, such as a swirl vane (not shown), or the like, for
imparting a swirling action to the water as it discharges through
the outlet defined by the central opening 74 of the base member 72,
in a conventional manner.
A circular snap disc 82 extends over the outlet of the discharge
head 24 defined by the central opening 74 and seats on the flanges
78 and 80 in order to seal off the vent openings 75. The snap disc
82 is not flat but is normally biased by its own internal spring
force to a position shown by the dashed lines in FIG. 6, while
being adapted to attain an inverted position against this internal
spring force as shown by the solid lines.
A yoke 83 is supported by, and extends downwardly from, the base
member 72 and supports a pair of substantially T-shaped lever arms
84 and 86. One projecting portion of the lever arm 84 engages the
disc 82 to force it into the position shown by the solid lines in
FIG. 6, while one projecting portion of the lever arm 86 is
supported by the apex of the yoke 83. The other projecting portions
of the lever arms 84 and 86 engage each other, while the ends of
the lever arms are engaged by a fusible link 90 extending thereover
in a manner to apply a force to the lever arms of a sufficient
amount to maintain them in the position shown. The fusible link 90
may be of any standard material which is adapted to fuse, or melt,
at a predetermined elevated temperature, such as 286.degree.F. and
release its engagement with the lever arms 84 and 86.
In operation of the system of the present invention, the valve 30
is manually closed and the system drained so that the riser portion
18a, along with the remainder of the piping system including the
crossmain 20 and the branch lines 22, are placed in a dry state,
with the heads 24 being connected to the branch lines 22 in their
position shown in FIGS. 5 and 6.
The vacuum pump 28 is then actuated in order to maintain the
pressure in this dry portion of the system between a predetermined
range such as between -11 pounds per square inch (hereinafter
referred to as psi) and -12 psi. This negative pressure is imparted
to the chamber 56 via the conduit 58, and the design of the pinch
valve 26 and the actuator 50 are such that the latter pressure
causes the diaphragm 54 and therefore the movable pinch bar 40 to
move in the direction indicated by the arrows in FIGS. 2 and 3,
with the pinch bar 40 thus compressing the tubular boot 32 to the
position shown by the dashed lines in FIGS. 2 and 3. As a result,
the pinch valve 26 operates to prevent water flow from the riser
portion 18b to the riser portion 18a. The valve 30 is then opened
to permit the water to flow to the immediate vicinity of the closed
pinch valve 26. The system is then left in this condition in the
space to be protected.
Upon a fire condition occurring in the space of a magnitude that
causes a fusion of the fusible link 90 of one or more discharge
heads 24, the link will release the lever arms 84 and 86 from their
engagement between the yoke 83 and the snap disc 82. As a result,
the snap disc 82 will snap to the position shown by the dashed
lines in FIG. 6 by virtue of its internal spring force, with the
vacuum occurring in the system initially maintaining the disc
against the flange 78. As a result, atmospheric pressure will be
admitted into the system through the vent openings 75 in the base
member 72. This atmospheric pressure, which for the purpose of
example will be assumed to be approximately 14.7 psi, will increase
the pressure in the system to an extent that the vacuum pump 28
will not be able to maintain a sufficient negative pressure in the
chamber 56 to maintain the valve 26 in its flow preventing
position. As a result of this increase in pressure in the chamber
56, the force exerted by the water pressure acting on the closed
boot 32 will be sufficient to move the boot in a direction opposite
to that shown by the arrows in FIGS. 2 and 3. As a result, water
will immediately flow into the riser portion 18a and into the
crossmain 20 and the branch lines 22 for discharge through the head
or heads 24 that were previously opened.
It can be appreciated that the pinch valve 26 opens at a relatively
fast rate due to the force of the water pressure acting on the boot
32 as well as the rapid deterioration of the negative pressure in
the chamber 56. Also, once the water passes the pinch valve 26, it
incurs very little resistance to flow due to the absence of any
appreciable air pressure or the like in the dry portion of the
system due to the existence of the negative pressure.
In order to provide an even more rapid opening of the pinch valve
26, the valve 60 comes into operation. In particular, the force
exerted on the valve head 66 by the compression spring 72 can be
designed so that the valve head will move to the opened position
shown by the dashed lines in FIG. 4 in response to a slight rise in
the pressure in the dry portion of the system as a result of the
opening of one or more heads 24. As an example of the latter,
assuming that the vacuum pump maintains the pressure in the dry
portion of the system at an upper limit of -11 psi, and that the
atmospheric pressure acting on the exposed surface of the valve
head 66 is 14.7 psi, the compression spring 72 can be designed to
exert an effective pressure of 25 psi on the valve head 66 which,
during inaction of the system, is insufficient to open the valve
head. However, when the pressure in the dry portion of the system
rises to a predetermined value above -11 psi, such as to -10 psi,
in response to the actuation of one or more heads 24, the 25 psi
pressure exerted by the spring 72 will be sufficient to open the
valve head 66. As a result, atmospheric pressure will rush directly
into the chamber 56 and accelerate the deterioration of the
negative pressure therein and thus increase the rate of movement of
the pinch valve 26 to the open position as discussed above.
It can be appreciated that the system of the present invention
eliminates any appreciable delay in discharge of extinguishant
after actuation of one or more heads and therefore provides a
substantial improvement over prior art dry pipe systems.
Also, the system of the present invention insures that the dry
portion of the system is in fact maintained in a substantially
completely dry state during inaction of the system due to the
presence of the vacuum pump.
Of course, variations of the specific construction and arrangement
of the system disclosed above can be made by those skilled in the
art without departing from the invention as defined in the appended
claims.
* * * * *