US2891625A - Fire sprinkler alarm system - Google Patents

Description

June 23, 195Q HUBE 2,891,625 FIRE SPRINKLER ALARM SYSTEM 4 Filed July 5, 1957 s Shets-Sheet 1 June 23, 1959 Filed July 3, 1957 B. HUBE FIRE SPRINKLER ALARM SYSTEM 5 She ets-Shee t 2 TO su ERV asosw STATION "A? LOOP I LOOP To SUPERVISORY 1 55 N STATION Q 54 I T T '3' 5 '52 65 i '65 I\,. J L\NE 5WITCH N HOV A I June' 23, 1959 3 Sheets-Sheet 3 Filed July 3, 1957 '3 'I'S'd zunssalld United States Patent FIRE SPRINKLER ALARM SYSTEM Arthur B. Hube, Huntington Station, N.Y., assignor to American District Telegraph Company, Jersey City, NJ., a corporation of New Jersey Application July 3, 1957, Serial No. 669,815

3 Claims. (Cl. 169-23) This invention relates in general to fire extinguishing systems wherein water is supplied to a distributing system of pipes and discharged therefrom through suitable sprinkler heads and more particularly to a fire sprinkler system wherein pressure within the distributing system is maintained at a pressure higher than that existing in the city main.

In fire sprinkler systems in which a decrease in pressure due to water flow results in the transmission of an alarm it is important that the system be able to discriminate between pressure reductions caused by emergency operation in the event of a fire and variations due to other effects which do not require emergency fire fighting apparatus such as the pressure variation normally occurring in the city main. One arrangement hitherto utilized to prevent transmission of false alarms from this cause includes an excess pressure pump provided to maintain the system at a sufficiently higher pressure than the city main pressure so that the valve is not affected by pressure fluctuations in the main. One common arrangement is to provide for the pump to operate in response to a drop in pressure in the sprinkler system to restore the system to a predetermined pressure. This has been effective in eliminating false alarms due to city main pressure fluctuations as well as providing compensation for incidental leakage which may occur.

It is also important in systems of the excess pressure type that the recycling time of the system be as short as possible since the system cannot transmit an alarm as a result of a new emergency until the excess pressure pump has re-established the predetermined pressure level above the pressure in the city main. In order to provide a short and therefore efficient recycling period, an excess pressure pump of high capacity is highly advantageous. However, because an alarm is initiated only when the pressure drop in the system is at a rate in excess of the capacity of the pump such a pump tends to delay the initiation of an alarm signal and in certain circumstances, as when only a single or a few sprinklers have been actuated, an alarm signal if initiated at all may be unduly delayed.

In order to provide a system with a high degree of sensitivity and thereby minimize the delay in initiating alarms, an excess pressure pump of low capacity is needed. A low capacity pump however in addition to causing a long recycling period and thus inefficient operation of the system may also have a tendency to cause the transmission of false alarms as a result of leakage or transient conditions not due to a fire.

It is therefore a principal object of this invention to provide a fire sprinkler system in which the pressure is independent of variations in the city main pressure and which has a high degree of sensitivity together with a r, 2,891,625 Patented June 23, 1959 short recycling period which results in efficient operation and a minimum tendency to transmit false alarms.

Another object of this invention is to provide a fire sprinkler system in which the pressure variation is normally maintained within a smal range below the desired excess pressure and in the event that the pressure drops below this small range for any reason a supervisory warning signal is transmitted and upon a further drop in pressure an alarm signal is transmitted.

A further object of this invention is to provide a simplified control system for use at a local installation for transmitting a warning signal to a central supervisory station in advance of the transmission of an alarm signal.

In accordance with this invention there is provided a pump of the type in which the discharge varies inversely as the pressure at the discharge side of the pump. When the system is close to the desired excess pressure, this pump has a low capacity and thus provides a high degree of sensitivity. However, when the system has only a low pressure such as results after the emergency operation of the system, the pump has a high capacity and thus the system is quickly restored to the desired excess pressure. The pump is actuated by control means including pressure responsive means, which, in response to a predetermined pressure drop in the sprinkler system, closes a microswitch and closes the pump operating circuit.

In accordance with a further feature of this invention, a continuing pressure drop, if unchecked by the operation of the pump, sequentially gives rise to a supervisory warning signal and then to a fire alarm signal. The arrangement is such that the operating range may be shifted widely without disturbing the absolute pressure differential between actuation of the pump, initiation of the supervisory signal and initiation of the fire alarm signal.

Furthermore, the arrangement is such that the pressure differential between the actuation of the pump and the initiation of the supervisory warning signal and the pressure differential between the initiation of the supervisory warning signal and the initiation of the fire alarm signal may be varied independently of each other and of the operating range of the system.

Further objects and advantages of this invention will be apparent from the following description thereof and the accompanying drawings, in which:

Figure 1 is a diagrammatic representation of a fire sprinkler system in accordance with this invention;

Figure 2 is a front view partly in section of the pressure responsive control means;

Figure 3 is a sectional view taken through line 3-3 of Figure 2 and partially broken away;

Figure 4 is a graph indicating in diagrammatic fashion the operation of the system under varying conditions; and

Figure 5 is a schematic circuit diagram for the apparatus showing the positions of the switches and relay when the desired excess pressure has been attained and the pump is not in operation.

Referring now to the drawings in detail, water from the city main 10 enters the system through valve 11 and then is directed through the distributing system riser 12 to various conduits 13, 14, which have mounted thereon sprinkler heads (not shown). The valve 11 may be of any suitable construction and as shown includes a clapper 11a. Pump 15 driven by an electric motor 16 is connected across the valve 11 by conduits 17 and 18. As will be more fully pointed out, pump has a discharge capacity which varies inversely as the back pressure at its discharge outlet and normally serves to maintain the pressure in the sprinkler system at a predetermined level well above that in the city main. A check valve 19 is located in the pump discharge conduit 18 to prevent a reverse flow from the distributing system back through the pump and into the city main. Pump 15 is preferably a turbine type pump and in the present in stance has a rated capacity of about six gallons per minute at zero pumping head and a cut-off or zero flow at about 200 p.s.i. discharge pressure. This pump may be operated for extended periods of time when dry or with no discharge and may be either integrally connected or closely connected with the motor 16. Bellows chamber 20 containing a pressure sensitive bellows element 42:: is, attached to the pressure control switch box 21 and communicates, with the distributing system riser 12 through the conduit 22.

H The pressure control switch mechanism is located within the pressure control switch box 21 and includes a C-shaped lever 37 pivotally mounted by means of pin 38 in box 21. A compression spring 39 is mounted within the pressure control switch box 21 with one end bearing against the lower horizontal leg 37!) of the C-shaped lever 37 and the other end bearing against a nut 40 mounted on the range adjusting screw 41. The compression spring 39 tends to urge the C-shaped lever 37 in a clockwise direction when viewed as in Figure 3. .The force exerted by the spring may be varied by .rotat ing the range adjusting screw 41 which changes the vertical location of the nut 40 with respect to the range adjusting screw 41. The lower horizontal leg 37b of the C-shaped lever 37 bears against the tip of a vertically slidable .pin 42, the opposite end of which is attached to the movable bellows 42a located in the bellows chamber 20. Pin 42 is urged upwardly by the fluid pressure existing. in the bellows chamber 20 below the movable bellows 42a and thus the fluid pressure tends to urge the .ceshaped lever 37 in a counterclockwise direction when viewed as in Figure 3.

U Three screws 43, 44 and 45, adjusted by lock nuts 46, 47 and 48, respectively, are located in the upper horiz ontal leg 37a of the C-shaped lever 37 so as to strike the respective operating contacts of microswitches 24, 31 and 34. The microswitches are firmly attached to the pressure control switch box 21 by means of screws 49 and 50. The microswitches are preferably insulated from each other and the switch box by strips of insulating material 51.

The pump motor 16 is controlled by a circuit including a relay 23 and microswitch 24. The pump motor ciredit in the present instance is a series circuit and comprises a conductor 28 connected to line conductor 26, the pump motor 16, conductor 29 connected between the pump motor and one of the contacts of relay 23, and conductor 30 connected between the other contact of relay 23 and line conductor 27. The pump control circuit includes the coil of relay 23 connected in series with microswitch 24 by conductor 25 across the line conductors 26 and 27.

The supervisory warning circuit includes microswitch 31 and conductors 32 and 33 which are connected to a transmitter 65 and remote warning signal device (not shown). In the present instance, the transmitter 65 in cludes a normally closed circuit in which conductor 33 is connected in series with microswitch 31, conductor 32 and alarm relay 66. Operation of the alarm relay 66 is initiated by the opening of microswitch 31 and which in turn initiates the operation of a remote warning signal device. The alarm relay 66 may be part of a transmitter 65 provided for transmitting a warning signal over a supervisory network 67 to a supervisory station. Various types of such transmitters and remote signal devices are 4 well known and consequently it is unnecessary to describe the transmitter in detail here.

The alarm circuit includes microswitch 34 and con ductors 35 and 36, which are connected to loop circuits A and B respectviely. In the present instance, network loops A and B are connected in series through an alarm relay 69 and also on impedance element 70 so that a limited amount of power fiows through loops A" and B from a power supply (not shown). The circuit constants are so chosen that relay 69 is de-energized under these conditions; the resistance of the impedance element 70 being such that when it is shunted out on the closing of the normally open microswitch 34 the current flowing in the circuit increases to a value suflicient to energize the alarm relay 69 and thereby transmit an alarm signal over a supervisory network 7 1 to aremote alarm signal device (not shown) located at a supervisory station. Various types of such transmitters and remote signal devices are well known and consequently it is unnecessary to describe the transmitter 68 in detail here.

When the sprinkler system is in its normal condition, i.e., the desired excess pressure exists and the pump is not operating, the C-shaped lever 37 is positioned in its extreme counterclockwise position when viewed as in Figure 3. In this position the C-shaped lever holds the operating contacts of microswitches 24 and 34 in the open position and the operating contact of microswitch 31 in the normally closed position. If the pressure in the sprinkler switch drops as a result, for instance, of the actuation of one or more sprinkler heads, the C-shaped lever 37 moves in a clockwise direction when viewed as in Figure 3 away from the operating contacts of the microswitches, thus closing microswitch 31 and thereby actuating sequentially the pump, the supervisory warning signal device and the alarm signal device in the order stated.

The screws 43, 44 and 45 are adjusted so that, when the C-shaped lever 37 moves in a clockwise direction from its extreme counterclockwise position, microswitches 24, 31 and 34 are actuated sequentially in the order stated. Screws 43, 44 and 45 are adjustable so that the differential pressure which occurs between the actuation of microswitches 24 and 31 may be varied within wide limits and likewise the differential pressure which occurs between the actuation of microswitches 31 and 34 may be varied within wide limits. This adjustment is independent of the range adjustment provided by the range adjustment screw 41 previously described.

In the present instance the screws 43, 44 and 45 are adjusted so that microswitch 24 closes at about 2 p.s.i. below the desired excess pressure. Microswitch 31 opens when the pressure drops an additional 1 p.s.i. while microswitch 34 closes when the pressure drops a further additional 3 p.s.i. Thus all three microswitches are actuated when the pressure drop equals 6 p.s.i. from the desired excess pressure. These settings of course may be varied as desired for particular installations as hereinbefore stated.

The range adjusting screw 41 may be adjusted so that the excess pressure varies from about 20 to about .200 p.s.i. over the pressure in the city main. In the present instance the range adjusting screw 41 is adjusted so that the desired excess pressure is approximately 25 p.s.i. abovethe city main pressure. It will be appreciated that the excesspressure required in any given system will be dependent upon the volume of water involved in the particular system. As will be apparent to those skilled in the art, the Water flow required to cause a pressure loss sulficient to actuate the three microswitches and associated warning and alarm signals may be decreased by increasing the excess pressure at which the system is operated.

The operation of the system will now be described withreferenceto the graph shown in Figure 4. .Under normal conditions the system has an excess pressure 01 approximately 25 p.s.i. and thus microswitches 24 and 34 will be heldin the open position by the G-shaped lever 37 and microswitch 31 will be held in the closed position. As incidental leakage occurs the pressure in the system will gradually drop until the point 52 is reached. At point 52 the pressure in the system is about 2 p.s.i. below the desired excess pressure of 25 p.s.i., i.e., 68 p.s.i., where the maximum surge pressure in the city main is 45 p.s.i. and 25 p.s.i. excess pressure has been determined to be adequate. At point 52 therefore microswitch 24 closes and actuates relay 23 which causes motor 16 and pump to operate. The pressure rises until the desired excess pressure is attained at point 53. At point 53 microswitch 24 again opens and the pump 15 ceases to operate. The drop in pressure between points 53 and 54 reflects leakage in the system and the pump will commence operation again at point 54 to restore this loss and cease operation at point 55. Thus between 52 and 55 the system is operating under the usual conditions. Leakage occurs between points 55 and 56. At point 56, however, it is assumed that one or more sprinkler heads are actuated due to fire. The pressure therefore quickly drops to point 57 which causes the pump to operate. Even though the pressure drop thenceaforth may be relatively slow, as when only a few or even one sprinkler head is actuated, the pressure drops further because of the low capacity of the pump at this pressure to point 58, at which point microswitch 31 opens and actuates the supervisory warning signal device. Since there is an emergency, the pressure continues to drop to point 59 at which point microswitch 34 closes and the alarm signal device is actuated. Even though the pump is operating the pressure will continue to fall until it becomes approximately equal to the city main pressure at point 60. After an interval of time during which the fire is extinguished, the fused sprinkler heads are replaced and as indicated at point 61 the pressure in the system begins to rise. The pump 15 will restore pressure to the system as shown by the curve 61, 62, 63, 64.

The use of a variable capacity pump results in a rapid pressure rise initially but the rate of the pressure rise decreases as the pressure in the system approaches the desired excess pressure. Thus the requirements of a high degree of sensitivity and a short recycling period are attained by the apparatus of this invention. At point 62 microswitch 34 opens, thus opening the alarm circuit while at point 63 microswitch 31 closes, thus opening the supervisory warning circuit. The two alarm signal devices may then be rewound or otherwise reset for subsequent use. At point 64 microswitch 24 opens and the pump ceases to operate. The system having been recycled, normal operation may again proceed.

If the rate at which the pressure in the system drops is relatively slow as compared to that between points 56 and 59 as would be the case when the pressure loss was due to a power failure or other similar cause, then the time interval occurring between the points 56 and 59 would be increased since the leakage rate is much lower than the flow rate due to the opening of one or more sprinkler heads. It is apparent that in such a case the extended time interval between the actuation of the supervisory warning signal device and the actuation of the alarm signal device would be suflicient to allow corrective action to be taken which would eliminate the transmission of a false alarm.

The use of a turbine type pump, together with sequentially operating pump, warning and alarm circuits, pro vides a fire sprinkler system in which the desired excess pressure may be maintained within a small range of pressure variation in an eflicient manner without loss of sensitivity and at the same time the possibility of transmitting false alarms is minimized by providing opportunity for correction of failures in the system which result in a pressure loss.

As shown in the drawings, the sprinkler system incorporating the present invention includes one valve 11, pump 15 and control means 21. It is to be understood, however, that a plurality of risers 12 may be employed as where the system is installed in a large building or in a group of buildings. In that event, each riser 12 is equipped with a valve 11 together with the associated pump means 15 and control means 21. The additional switch 34 is connected across the existing loop circuits A and B as shown by the dotted lines in Figure 5. Additional warning signal switches 31 may be connected in circuit with transmitter 65.

The terms and expressions which have been employed are used as terms of description and not of limitation and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.

What is claimed is:

1. In a fire sprinkler system, a normally closed valve through which water passes from a source of water supply into the sprinkler system when the pressure on the supply side of the valve is greater than that on its sprinkler system side, pressure responsive means free for limited displacement proportionate to pressure variations in said system, resilient means biasing said pressure responsive means in a direction to oppose displacement of said pressure responsive means in response to an increase in pressure in said system, a pump having an inlet communicating with the source side of said valve and an outlet communicating with the sprinkler system side of said valve, said pump having a discharge capacity which varies inversely with. the pressure in said system, and means responsive to the displacement of said pressure responsive means for controlling operation of said pump and thereby normally maintaining said system at a predetermined pressure in excess of that on the source side of said valve.

2. In a fire sprinkler system having fire alarm signal transmitting means and supervisory trouble Warning signal transmitting means, a normally closed valve through which water passes from a source of Water supply into the sprinkler system when the pressure on the supply side of the valve is greater than that on its sprinkler system side, pressure responsive means free for limited displacement proportionate to pressure variations in said system, resilient means biasing said pressure responsive means in a direction to oppose displacement of said pressure responsive means in response to an increase in pressure in said system, a pump having an inlet communicating with the source side of said valve and an outlet communicating with the sprinkler system side of said valve, said pump having a discharge capacity which varies inversely with the pressure in said system, electric circuit means including switch means for controlling the operation of said fire alarm signal transmitting means, said supervisory trouble warning signal transmitting means and said pump, a movable lever connected to said pressure responsive means and displaceable therewith, and means on said lever for actuting said switch means in a predetermined sequence.

3. In a fire sprinkler system having fire alarm signal transmitting means and supervisory trouble warning signal transmitting means, a normally closed valve through which water passes from a source of water supply into the sprinkler system when the pressure on the supply side of the valve is greater than that on its sprinkler system side, pressure responsive means free for limited displacement proportionate to pressure variations in said system, resilient means biasing said pressure responsive means in a direction to oppose displacement of said pressure responsive means in response to an increase in pressure in said sprinkler system, a pump having an inlet communicating with the source side of said valve and an outlet communicating with the sprinkler system side of lever fpr actugting said switch means in a pr e dgt j d sequence. z

Befereqces Cited in the file of pgte ljt lqceLt'ed m the upper'hdrizoiital leg offsgid'C-shaped 10 2,573,340

UNITED STATES PATENTS Hamilton Feb. 7, 1922 A11zin' 1 Aug. 20, .1935 Queen 11, 19 39 Schaefer' Qct. 17', 1944 De Lapcey Dec. 11, 1951

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