US3557811A

US3557811A - Dynamic flow sensor

Info

Publication number: US3557811A
Authority: US
Inventors: William L Livingston
Original assignee: Factory Mutual Research Corp
Current assignee: Factory Mutual Research Corp
Priority date: 1968-10-18
Filing date: 1968-10-18
Publication date: 1971-01-26
Anticipated expiration: 1988-01-26

Abstract

A flow sensing and control arrangement by which a jet of line fluid is continuously directed across a flow line against a biased pressure responsive device which moves to initiate a control function upon diffusion of the jet when line flow occurs. In a preferred embodiment, the pressure-responsive device controls a valve, normally closed by the jet but which opens upon the presence of line flow to introduce an additive to the flow line.

Description

United States Patent [72} lnventor William L. Livingston Sharon, Mass. [21] Appl. No. 768,862 [22 Filed Oct. 18, 1968 [45] Patented Jan. 26, 1971 [73] Assignee Factory Mutual Research Corporation Turnpike, Mass. a corporation of Massachusetts [54] DYNAMIC FLOW SENSOR 13 Claims, 1 Drawing Fig.

[52] U.S. Cl 137/7, 137/81.5: 169/15 [51] Int. Cl F15c 3/00, F15c 3/04 [50] Field of Search 137/7, 10, 13,815; 169/15, 14,8,2

[56] References Cited UNITED STATES PATENTS 1,619,130 3/1927 Jones 137/466 ADDITBI'VE CARRIER Primary Examiner-Samuel Scott Attorney-Lane, Aitken, Dunner and Ziems ABSTRACT: A flow sensing and control arrangement by which a jet of line fluid is continuously directed across a flow line against a biased pressure responsive device which moves to initiate a control function upon diffusion of the jet when line flow occurs. In a preferred embodiment, the pressureresponsive device controls a valve, normally closed by the jet but which opens upon the presence of line'flow to introduce an additive to the flow line.

BACK- UP POWER DYNAMIC FLOW SENSOR BACKGROUND OF THE INVENTION DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in the drawing, the dynamic flow sensor of this in- Thls mvermon felines to flow sensors" and more 5 vention is shown schematically as part of a fire extinguishing particularly, it concerns a novel arrangement for sensing fluid flow in a pipe line and actuating a control mechanism in response to the sensed flow. The arrangement has particular utility in certain types of fire extinguishing systems to be described but other applications are contemplated.

In a copending application entitled Method of Controlling Fire, Ser. No. 766,475, filed Oct. 10, 1968, by the inventors William L. Livingston and Russell W. Pierce and assigned to the assignee of the present invention, a fixed fire extinguishing system for enclosures is described and in which a water swellable polymer is mixed with water when the system is activated so that an ablative gel is dispensed from sprinkler heads located over the fire. The primary advantage of such a system is that the ablative gel is substantially more viscous than plain water and tends to cling to the surfaces on which it is sprayed. Consequently, a significantly lower quantity of extinguishant is required to put out a fire than is required with plain water, thereby enabling system designs with lower flow capacity than systems which have used plain water. Given such a system design, however, it becomes apparent that the introduction of gelling agent into the water line at the instant the system is activated is essential to proper operation.

Also it should be borne in mind that fire extinguishing systems in general, remain inactive for long periods of time often exceeding several years duration. Under such circumstances, conventional items of fluid handling hardware can and most likely will become deteriorated due to corrosion and the like, posing the possibility of a malfunction at the time when operation of them is called for. Malfunctioning of this type cannot be tolerated in fire extinguishing systems if their intended purpose is to be fulfilled.

SUMMARY OF THE INVENTION In accordance with the present invention, a dynamic or failsafe flow sensing arrangement is provided by which the velocity head of a fluid jet directed transversely of a pipe line is employed to retain a pressure-responsive diaphragm in an inactive position. This condition will be maintained until fluid flow develops in the pipe line and diffuses the jet to upset the balance of pressure across the diaphragm. When used in a fire extinguishing system of the type mentioned above, the diaphragm is used as an actuator for a valve which controls the introduction of the gelling agent additive. Accordingly the valve remains closed when the system is inactive, but opens immediately when flow occurs in the pipe line to provide the ablative gel extinguishant.

Among the objects of the present invention are therefore; the provision of a dynamic flow sensor for pipe lines in which the diffusion of a fluid jet by fluid flow is employed as a flow signal source; the provision of a flow sensing device particularly suitable for use in operating a valve for controlling the introduction of an additive to a flow line upon the development of fluid flow therein; the provision of a flow sensor of the type aforementioned which is capable of varying degrees of sensitivity; and a dynamic flow sensor of the type aforementioned which is particularly suitable for the introduction of a ablative gel additive to a water line in fire extinguishing systems. Other objects and further scope of applicability of the present invention will become apparent to those skilled in the art from the description to follow taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The single FIG. in the drawing is a schematic view illustrating in cross section the operative elements of the flow sensing and control device of the present invention in a fire extinguishing system.

system including a plurality of sprinkler heads 10 located in a water source 12 by a pipe line 14v In accordance with conventional practice, the system is provided with temperature detector (not shown) located in the vicinity of the sprinkler heads 10 so that upon the development of a fire in the space protected the system is activated automatically to supply the sprinklers with an extinguishant to put out the fire. In the particular system contemplated, the extinguishant is an ablative gel formed by a mixture of water from the source 12 and a gelling agent introduced into the pipe line as an additive and carrier mixture supplied from a reservoir 16.

The reservoir 16 is in fluid communication with the pipe line 14 by way of a line 18 and a valve 20 having an annular inlet chamber 22 positioned about a concentric outlet tube 24 in direct communication with a distributing head 26. Communication between the inlet chamber 22 and the outlet pipe 24 is controlled by a diaphragm valve 28 which, when closed, seats on the upper end of the outlet pipe 24 as shown in the drawing.

It will be understood that the additive and carrier mixture in the reservoir 16 is under a sufficient head so that when the valve 28 opens, the additive and carrier will flow through the valve and into the pipe 14 through the distributor head 26 to be mixed with the water in the pipe. To facilitate the introduction of the gelling agent, a plate 30 is positioned around the distributor head to create an area of turbulence upon flow in the pipe line 14 in a direction from the source 12 to the sprinkler heads 10. The turbulence will provide a zone of reduced pressure to facilitate an introduction and mixing of the additive and carrier with the water in the pipe line 14.

As pointed out above, it is imperative that the additive and carrier be introduced into the pipe line 14 when the fire extinguishing system is activated to effect water flow in the latter pipe line. At all other times, the valve 28 remains closed to prevent additive introduction into the water within the pipe line 14.T0 enable this mode of operation, the valve 28 is coupled by a connector rod 32 to a flexible diaphragm 34 establishing a pair of

chambers

36 and 38 in a closed vessel 40. It will be noted that the chamber 36 is in fluid communication with the pipe line 14 by way of a tube 42 having a flow restrictor 44 therein, whereas the chamber 38 is also in communication with the pipe line 14 through a tube 46. Further, it will be noted that the diaphragm 34 is urged upwardly by a helical compression spring 48, thereby biasing the valve 28 to its open position. In light of the static pressure balance across the diaphragm 34 through the

tubes

42 and 46, static pressure in the pipe line 14 does not have an effect on the positioning of the diaphragm 34 and thus of the valve 28.

To constrain the valve 28 in a closed position, a velocity head is imposed on the chamber 36 tending to overcome the bias of the spring 48 and retain the valve 28 in its closed position. This velocity head is developed by a continuously operating pump 50 which circulates water in the pipe line 14 through a nozzle 52 across the pipe line 14 and into the tube 54 communicating with the chamber 36. The pump 50 is driven continuously by an electric motor 56 connected witha power supply by lines 58. A source of backup power 60, such as a battery or the like, is connected to the lines 58 to keep the motor running in the event of a power failure.

Thus it will be appreciated that so long as the pump 50 remains in operation the velocity head or dynamic pressure of the fluid or water jet issuing from the nozzle 52 will be transmitted to the chamber 56 to maintain the diaphragm 34 against the bias of the spring 48. The restrictor 44 in the tube chamber 36 to avoid minor fluctuations or noise" that may be present in the system. Also, the size of the restrictor 44 can be selected to vary the velocity head imposed on the diaphragm 34 and thus control the sensitivity of the diaphragm.

When the fire extinguishing system is activated so that water from the source 12 flows through the pipe line 14 to the sprinkler heads 10, the fluid jet passing from the nozzle 52 will be diffused. As a result, the velocity head thereof imposed upon the diaphragm 34 in the chamber 36 will be removed. The spring 48 then will move the diaphragm 34 upwardly to open the valve 28 and permit the additive and carrier to pass from the reservoir 16 through the valve 20 and distributor head 26 into the pipe line M.

Thus it will be appreciated that an extremely effective fluid flow sensor and control apparatus is provided by which the above-mentioned objectives are completely fulfilled. Though the system described has particular utility in fire extinguishing systems where an additive is introduced upon activation of the system, it will be appreciated that the flow sensing and control features of this invention can be used in any application where it is required to introduce an agent into a flow line upon the existence of fluid flow therein. Also the sensing feature of this invention could be used solely to provide indication of fluid flow .by coupling the diaphragm 34 to an appropriate switch mechanism or the like in a circuit with an indicating device.

It is intended that the foregoing description is illustrative of a preferred embodiment only, not limiting, and that the true spirit and scope of the present invention be determined by reference to the appended claims.

lclaim:

l. Apparatus for sensing fluid flow, said apparatus comprising: a conduit normally containing fluid under static conditions and through which conduit said fluid flows during passage thereof from a source to a point remote from said source; means to develop a continuous jet of fluid across at least a portion of the conduit; and pressure sensitive means movable between first and second positions, said pressure sensitive means normally being retained in said first position by said jet and movable to said second position upon diffusion of said jet due tofluid flow in said conduit.

2. The apparatus recited in claim 1 wherein said means to develop a continuous jet comprises a pump having an intake in communication with the conduit and a nozzle outlet directed transversely of the conduit. 1

3. The apparatus recited in claim 1 including a valve for controlling the admission of an additive to thefluid in said conduit, said pressure sensitive means being coupled to said valve, said valve being closed when said pressure sensitive means is in said first position and opened when said pressure sensitive means is in said second position.

4. The apparatus recited in claim 1 when said pressure sensitive means is a diaphragm and including means to bias said diaphragm to said second position.

5. The apparatus recited in claim 2 wherein said biasing means includes a compression spring.

6. The apparatus recited in claim 2 including means defining a chamber on each side of said diaphragm, one of said chambers including said biasing means and the other of said chambers being exposed tosaid jet.

7. The apparatus recited in claim 6 including a flow line having one end opening to the-conduit at a'location so that the said flow line receives said jet, the opposite end of said flow line opening to the other of said chambers.

8. The apparatus recited in claim 7including a vent line ex tending between each of said chambers and the conduit, the vent line connected to the other of said chambers having a flow restrictor therein to develop a back pressure in the other of said chambers acting on said diaphragm as a result of said jet.

9. In a fire extinguishing system of the type in which an ablative gel formed of a mixture of water and a gelling agent is sup plied as an extinguishant to sprinkler heads upon the existence of a fire in the vicinity of the sprinkler heads, apparatus for introducmg the gelling agent into a water supply line upon the existence of water flow in the line, said apparatus comprising valve-means for controlling admission of said gelling agent tothe pipe line and means for retaining of said valve means in a closed position in the absence of water flow in said pipe line and to open said valve upon the existence of water flow in said pipe line, said last mentioned means including means for directing a jet of water transversely of said pipe line, and means responsive to said jet to retain said valve in said closed position, whereby diffusion of said jet due. to flow in said pipe line results in said valve moving to its open position.

10. The method of controlling the introduction of an additive to a fluid in a conduit, said method comprising the steps of: directing a continuous jet of fluid across at least a portion of sajdconduit; developing a continuous output to block the introduction of additive in response to the presence of said jet at a point spaced in said conduit from the origin of said jet; and initiating the introduction of said additive upon the interruption of said output due to diffusion of said jet by fluid flow in said conduit.

11. The method recited in claim 10 wherein said fluid is water and wherein said additive is a gelling agent.

12. The method recited in claim 11 wherein said conduit supplies an ablative gel formed by the mixture of said gelling agent and said water to the sprinkler heads of a fixed fire extinguishing system.

13. The method of sensing flow of fluid in a conduit said method comprising the steps of: continuously directing ajet of fluid across at least a portion of said conduit; developing a continuous output in response to the presence of said jet at a point spaced in said conduit from the origin of said jet; and providing a flow signal upon the interruption of said output due to diffusion of said jet by fluid flow in said conduit.

Claims

2. The apparatus recited in claim 1 wherein said means to develop a continuous jet comprises a pump having an intake in communication with the conduit and a nozzle outlet directed transversely of the conduit.
3. The apparatus recited in claim 1 including a valve for controlling the admission of an additive to the fluid in said conduit, said pressure sensitive means being coupled to said valve, said valve being closed when said pressure sensitive Means is in said first position and opened when said pressure sensitive means is in said second position.
4. The apparatus recited in claim 1 when said pressure sensitive means is a diaphragm and including means to bias said diaphragm to said second position.
5. The apparatus recited in claim 2 wherein said biasing means includes a compression spring.
6. The apparatus recited in claim 2 including means defining a chamber on each side of said diaphragm, one of said chambers including said biasing means and the other of said chambers being exposed to said jet.
7. The apparatus recited in claim 6 including a flow line having one end opening to the conduit at a location so that the said flow line receives said jet, the opposite end of said flow line opening to the other of said chambers.
8. The apparatus recited in claim 7 including a vent line extending between each of said chambers and the conduit, the vent line connected to the other of said chambers having a flow restrictor therein to develop a back pressure in the other of said chambers acting on said diaphragm as a result of said jet.
9. In a fire extinguishing system of the type in which an ablative gel formed of a mixture of water and a gelling agent is supplied as an extinguishant to sprinkler heads upon the existence of a fire in the vicinity of the sprinkler heads, apparatus for introducing the gelling agent into a water supply line upon the existence of water flow in the line, said apparatus comprising valve means for controlling admission of said gelling agent to the pipe line and means for retaining of said valve means in a closed position in the absence of water flow in said pipe line and to open said valve upon the existence of water flow in said pipe line, said last mentioned means including means for directing a jet of water transversely of said pipe line, and means responsive to said jet to retain said valve in said closed position, whereby diffusion of said jet due to flow in said pipe line results in said valve moving to its open position.
10. The method of controlling the introduction of an additive to a fluid in a conduit, said method comprising the steps of: directing a continuous jet of fluid across at least a portion of said conduit; developing a continuous output to block the introduction of additive in response to the presence of said jet at a point spaced in said conduit from the origin of said jet; and initiating the introduction of said additive upon the interruption of said output due to diffusion of said jet by fluid flow in said conduit.
11. The method recited in claim 10 wherein said fluid is water and wherein said additive is a gelling agent.
12. The method recited in claim 11 wherein said conduit supplies an ablative gel formed by the mixture of said gelling agent and said water to the sprinkler heads of a fixed fire extinguishing system.
13. The method of sensing flow of fluid in a conduit said method comprising the steps of: continuously directing a jet of fluid across at least a portion of said conduit; developing a continuous output in response to the presence of said jet at a point spaced in said conduit from the origin of said jet; and providing a flow signal upon the interruption of said output due to diffusion of said jet by fluid flow in said conduit.