US2352378A - Fire extinguishing method and apparatus - Google Patents

Description

DGHE'CH HUGH FIRE EXTINGUISHING METHOD AND APPARATUS Fiied March 11, 1941 2 sheets-sheet 1 MWW www `'une 27, 1944. E. GEERTZ FIRE EXTINGUISHING METHOD AND ABPARATUS 2 Sheets-Sheet 2 Filed March 11, 1941 322' eerfz tllir. L/MmuumwLnU,

Patented June 27, 1944 UNITED Search Hom STATES PATENT OFFICE FIRE EXTIN GUISHIN G1 METHOD AND APPARATUS United States Application March 11, 1941, Serial No. 382,815

17, Claims.

This invention relates to new and useful improvements in methods and apparatus for extinguishing fires and preventing flame propagation as a result of fires or explosions. n coal mines, in storage bins/gr elevaiolgoal, rain, or the like, and; iwmcpnnectiorf'"withwallikiiids of apparatswf'handling any dusty carbonaceous material in enclosed spaces.

Carbonaceous materials which produce a considerable quantity of readily ignitable dust when disturbed by handling present an extremely troublesome re and explosion hazard if the handling takes place in enclosed, improperly ventilated spaces. Coal, while being mined and while being conveyed through relatively long passageways, will serve to illustrate the general problem and the application of the present invention to its solution.

Of course, it is impossible to mine coal without producing a substantial amount of dust which accumulates as a deposit on the floor of the mine and on all shelf-like surfaces of the mine walls, etc. The air in the various mine passages, breakthroughs, rooms, and the like,

particularly in the vicinities of operations, normally contains a considerable quantity of suspended dust. Coal dust will burn rapidly if properly ignited, and to rapidly propagate llame throughout an entire mine,it is only necessary to create a concussion or disturbanlce which is of suflicient intensity to dislodge the settled dust and mix it with the dust-laden air. Explosions resulting from the ignition of mine gases oifer the greatest possibilities of disaster. Such ex- -plosions usually result from the ignition of gas which has been permitted to accumulate in improperly ventilated pockets, or gas which is released into the working portion of a mine by accidentally drilling or blasting through to a natural cavity or void or an abandoned and closed-up portion of the mine which is lled with gas. When such an explosion occurs, the concussion creates an air wave which travels in all directions from the scene of the accident. This Wave dislodges the settled dust and mixes it with the dust laden air in the passages, etc., producing a highly combustible fuel mixture. The mixture is produced at a sufliciently rapid rate to propagate the ilame of the explosion almost directly in back of the air wave and in an extremely short length of time all portions of the mine which are not shut off by appropriate barriers will be involved.

If it were possible to economically operate a mine with all of its passages, etc.. divided up into relatively small sections or areas, which were continuously shut oli? from each other in a Way to prevent an explosion or a fire from spreading beyond its place of origin, a disaster would be successfully localized. Such a mode of operation of a mine, however, is not feasible for several obvious reasons.

Some work has been carried on with the idea of equipping mines with devices which will create temporary rock dust barriers in the passages leading away from the locality of an explosion or a re to lprevent spreading of the fire to portions which are not originally involved. Such rock dust barrier producing devices are located at suitable intervals along the passages of a mine and are intended to be automatically operated by the air Wave which precedes llame propagation. When a device is actuated, it releases a, quantity of non-combustible rock dust which mixes with the air to form a dense cloud across the passage. This cloud or screen of rock dust effects extinguishment of the propagating flame by cooling the air-coal dust fuel mixture, feeding the flame, to a temperature which is below the ignition temperature of the fuel.

One primary object of this invention is to provide methods and apparatus for establishing flame barriers across mine passages by employing either a mixture of carbon dioxide snow and vapor, resulting from the sudden expansion of liquid carbon dioxide, and rock dust, or just a mixture of carbon dioxide snow and vapor.

Of course, rock dust barriers are only effective in extinguishing propagating llame and are of no value as an extinguisher for a xed fire which may be started by the explosion or which may result from some other cause. In fact, the ordinary rock dust barrier producing device will not be actuated unless an air Wave is developed by an explosion, or some other violent disturbance. 'I'he carbon dioxide mixture released into the mine passage, as a result of practicing this invention, to form a flame barrier will remain in the lpassage after the propagating llame has been extinguished and the discharge of the carbon dioxide may be continued as long as is desired to create a fixed fire extinguishing atmosphere. Initiating the release of the .carbon dioxide either as a result of an explosion-created air wave or as a result of a rise in temperature will take care of lires regardles of how they are started.

A further important object of the invention is to provide methods and apparatus of the above noted type which will be automatically rendered operative either by the air Wave which precedes the propagating flame or by a rise in temperature caused by a re.

Coal mine fires which are not started by explosions and fires in storage bins or elevators and in the enclosures housing dusty material handling apparatus can be very effectively extinguished by ooding the involved spaces with carbon dioxide vapors. As carbon dioxoide is most usually stored as a liquid under considerable vapor pressure, its sudden release as a vapor-snow mixture must necessarily be at a..

considerable velocity. Such a discharge will naturally disturb the dust of the carbonaceous material which has settled in the involved space, and this disturbance will have very much the same eiect as an explosion with reference to producing flame propagation if proper precautions are not taken.

It has been determined that the propagation of flame will not take place in a dusty enclosed space, into which carbon dioxide is released, if a non-combustible substance, such as rock dust, is released simultaneously with the carbon dioxide and is mixed with the combustible dust of the involved carbonaceous material. The resultant mixture will not be sumciently combustible to support rapid name propagation.

Still another important object of the invention is to provide methods and apparatus for creating ame propagation barriers in coal mine passages, etc., and for extinguishing fixed res which may remain burning after the rapid spread of flame has been choked.

Another important object of the invention is to provide methods and apparatus for extinguishing lires in dusty enclosures by ilooding the latter with carbon dioxide vapors and for overcoming the tendency for such a high velocity discharge of vapors to act as a flame propagating energizing force.

Other objects and advantages of the invention will be apparent during the course of the following description.

In the accompanying drawings forming a part; of this specication and in which like numerals are employed to designate like parts throughout the same,

Figure 1 is a fragmentary vertical sectional view taken through a mine passage, or the like, and illustrates apparatus embodying this invention and operable to create a flame barrier across the passage,

Figure 2 presents a wiring diagram for the apparatus of Fig. 1,

Figure 3 is a front elevational view of a part of the apparatus disclosed in Fig. 1, A

Figure 4 is a detail side elevational view of a modied form of discharge device for carbon dioxide and rock dust which may be used either in place of the apparatus disclosed in Figs. 1 and 3 or in addition to such apparatus.

Figure 5 is a diagrammatic view of a conveyor system for handling dusty carbonaceous material with fire extinguishing apparatus embodying this invention properly applied thereto,

Figure 6 is a detail View illustrating the combined carbon dioxide and rock dust releasing mezhanism employed in the assembly of Fig. 5, an

Figure 7 is a' diagrammatic VView of a section of a coal mine withy nre extinguishing apparatus embodying this invention properly applied thereto, f 1- Y In the drawings, wherein for the purpose of illustration are shown the preferred embodiments of this invention, and particularly referring to Figs. 1 to 3, inclusive, the reference character 1 designates a section of a passage, breakthrough, or the like, of a coal mine. The roof of the passage, or the like, is shored up in the usual manner by a header 8 and props 9. These figures illustrate the apparatus employed for creating either a carbon dioxide vapor barrier or screen, or a combined carbon dioxide vapor and rock dust barrier or screen across the passage to prevent the propagation of flame resulting from a mine gas or coal dust explosion on either side of the prop structure.

To supply carbon dioxide for creating such a flame barrier or screen, the various portions of the mine are piped, as at Ill, and this piping system leads to a suitable source of supply which may be located either on the surface or at any suitable point in the mine at the Working level. It is preferred that carbon dioxide be maintained in the piping system I0 so that when liquid is discharged through appropriate nozzles, the sudden expansion of the liquid will produce a mixture of carbon dioxide snow and vapor.

The liquid carbon dioxide may be obtained from a bank of regular commercial cylinders, but there are many important reasons why the system can be more economically and eiiiciently operated if the piping system I0 is connected to a suiiiciently large heat insulated tank so that the liquid carbon dioxide in the entire system may be maintained at a constant, subatmospheric temperature. The term subatmospheric temperature is intended to mean any temperature below a normal atmospheric or room temperature of '70 F. In this insulated storage tank, the liquid carbon dioxide is maintained at the desired subatmospheric temperature by means of a mechanical refrigerating machine, of any suitable commercial design, and the cooling coil of the refrigerating machine is located in the vapor space of the storage tank. This refrigerating machine maintains the liquid in the tank at a constant temperature by condensing the carbon dioxide vapors which contact the cooling coil. The drops of condensation will be permitted to return to the body of liquid in thev lower portion of the storage tank. Patent No. 2,202,343, issued to Eric Geertz, on May 28, 1940, discloses and claims this type of storage apparatus for liquid carbon dioxide used in re extinguishing apparatus.

As the barrier or screen to be formed with the carbon dioxide must operate to prevent the propagation of flame through and past the same, the barrier or screen must operate to extinguish the flame by cooling below the ignition temperature the air and coal dust mixture which acts as the fuel for the flame. It will be apparent, therefore, that the cooling effect of the carbon dioxide vapor is very important. Although a maximum constant temperature of slightly less than 70 F. would be a subatmospheric temperature for the stored liquid carbon dioxide, the released vapors will have a. much greater cooling effect and re extinguishing ability if the liquid carbon dioxide is stored at a much lower constant temperature. It is preferred that the liquid carbon dioxide be maintained at a substantially fixed temperature which will fall between 32 F. and 40 F. The temperature most frequently employed is 0 F. The ability of this lower temperatured carbon `dioxide to more quickly cool` and extinguish flame IDH.

593ml tim is readily understood when one notes that the latent heat of vaporization oi carbon dioxide varies directly in proportion with variations in temperature of the liquid. For example, at 87.8 F., the latent heat of vaporization is B. t. u. per pound of carbon dioxide; at -4.0 F., it is 122 B. t. u. per pound, and at 69.9 F., it is 149.6 B. t. u. per pound. An additional advantage obtained from employing lower temperatures is that the percentage of snow produced as a result of sudden expansion of liquid carbon dioxide depends on the temperature of the liquid. Theoretically, liquid carbon dioxide stored at a temperature of 70 F. produces a discharge mixture which contains 29% snow, while liquid carbon dioxide stored and released at 0 F. produces 60% snow.

The storage of liquid carbon dioxide in an insulated tank and at a relatively low subatmospheric temperature presents several economic advantages in maintaining the piping system sealed against leakage and in the cost of the storage tank. These economies are readily apparent when one considers that the vapor pressure of liquid carbon dioxide corresponds directly with the temperature of the liquid and drops as the temperature is reduced. For example, liquid carbon dioxide stored at 70 F. is under a vapor pressure of 853.4 pounds per square inch, abso' lute, while the liquid is under a vapor pressure of 305.5 pounds per square inch, absolute, at 0 F., and is at 145.8 pounds per square inch, absolute, at -40 F.

The piping system IIJ for the liquid carbon dioxide may be maintained in a dry condition if desired; that is, without liquid carbon dioxide being maintained in the piping system. However, if the piping system must extend for a considerable distance through the various passages, and the like, from the source of supply, it is preferred that the piping system be maintained filled with the liquid. If the piping system is maintained lled at all times, the liquid carbon dioxide will be available for instant release at the several points of discharge. The relatively constant year-round temperature maintained in the underground passages of mines will be helpful inv keeping the liquid carbon dioxide in the piping system at the desired constant low temperature. However, it will be necessary to resort to so-me other method to supplement the action of the constant underground temperature if the liquid carbon dioxide in the entire system is to be maintained at a temperature which is lower than the constant temperature in the mine.

For example, the storage tank for the liquid carbon dioxide may be maintained at a somewhat higher level than the piping .system I0. With this arrangement, the carbon dioxide vapors which form in the piping system as a result of absorption of heat will be permitted to work their way back through the system into the storage tank and will be condensed Whenthey reach the vapor space of the tank. Another way of accomplishing this desired result would be to assemble the piping system I0 as a. complete circuit with the inlet and outlet ends oi the circuit connected to the storage tank. The inherent thermosyphonic action of such a circuit inherently will cause the carbon dioxide to circulate through such a system so that the vapors will be returned .to the storage tank for being condensed. How- Aever, a circulating p ump may be employed to bring aboutV forced circulation of the carbon dioxide liquid through the system.

To produce the desired ame barrier or screen at the location shown in Fig. 1, the piping system I0 is provided with opposed discharge nozzles II which are connected to the piping by suitably shaped pipe sections I2. These pipe sections are attached to the outlets of the solenoid valves I3 which are coupled in the piping I I). By arranging these discharge nozzles Il so that thestreams or clouds of carbon dioxide vapor and snow discharged therefrom will directly impinge against each other, each discharge will check the other and the commingled discharges will spread out and entirely ll the cross-sectional area of the passage. As the temperature of this carbon dioxide vapor and snow mixture will be approximately F., it will be apparent that no name can survive in this vapor screen and the coal dust laden air which will be mixed with the carbon dioxide discharge will be so thoroughly cooled that its temperature cannot be raised to the ignition point by propagating ame.

Although the carbon dioxide may be used by itself to create the flame barrier or screen, it has been determined that a safer method involves the release of a non-combustible dust, such as rock dust formed of shale, simultaneously with the release of ythe carbon dioxide. The carbon dioxide necessarily must be released at a relatively high velocity, and these high velocity discharges will inherently disturb the coal dust which has settled on all possible supporting surfaces within the mine passage. This coal dust willvbe stirred up and mixed with the air, which is already laden with a lcertain amount of dust. As the full cross-sectional area of the mine passage will be very rapidly filled with the carbon dioxide vapors forming the flame barrier or screen, the carbon dioxide vapors must necessarily spread out or move along the passage in opposite directions, and this movement ofcarbon dioxide vapors will carry with it the air to which the disturbed coal dust has been added. The purpose of adding a non-combustible rock dust .d to the carbon dioxide vapor is to cause this rock dust to be mixed with the coal dust borne by the air and thereby produce a nal mixture which is relatively non--combustible and will not flash if it is exposed to a flame.

Figs. 1 and 3 disclose a supply of rock dust at the point where the carbon dioxide barrier or screen will be formed. The rock dust is maintained sealed against moisture, or the like, in the paper bags I4 which are suspended from the straps or brackets I5 by means of straps or bands I 6. The brackets I5 are clearly illustrated in Fig. 3 as being attached to the header 8 of the mine roof prop. The rock dust conned in the bags I5 is released by means of rip cords or wires I'I which extend lengthwise throughthe bags. The outer ends of these rip cords or wires I'I are attached at I8 to the header 8. The'inner ends of these cords are attached to weights I9.' It will be appreciated that if theseweights are permitted to drop, they will swing downwardly and will pull the rip cordsl or wires I'I through the bottoms of the bags I4 for splitting open the bags. The rock dust will be released through these openings formed in the bag and will drop downwardly into theI passageway.

To normally support the weightsY I9, anangular bar 20 is hooked over the flangedend of a lever 2| which is mounted in a notch 22 formed in the header 8 and is hinged at 24 tothe bottom'wa'll of this notch. The weights are supported on a shelf 25 carried by the bar 20. A vane 26 is attached to the lower end of the bar 20.

When a mine gas or coal dust explosion occurs in the passage 'I on either side of the vane 26, the concussion produced by the explosion will cause an air wave to travel along the passage. When this air wave strikes the vane 26, it will dislodge the bar 20 from the end of the lever 2| and the bar 20 with its vane 26 will fall to the oor of the passage. The shelf 25 will be withdrawn as a support for the weights I9 and these weights will then drop to accomplish the aforementioned ripping or opening of the rock dust bags |4.

Fig. 1 clearly discloses the lever 2| as being normally urged upwardly by the spring 2l. The lever has mounted on its upper side a switch contact 28 which is adapted to engage a second switch contact 29 when the weight of the bar 20, vane 26, and weights I9 is removed from the lever 2|. The closing of the circuit through the contacts 28 and 29 results in energizing the windings for the solenoids of the valves I3 with the result that carbon dioxide is discharged through both nozzles II substantially simultaneously with the release of the rock dust from its bags |4.

Fig. 2 discloses the wiring diagram for the solenoid valves I3. The two main, electrical supply lines are disclosed in this gure and are identified by the reference characters 30 and 3|. The solenoid coils |3a for the valves I3 are connected across these main supply lines 30 and 3| by the wire 32 which has the xed contacts 33 and the movable blade 34 of a relay 35 connected therein. This relay 35'Wil1 be energized to close the circuit through the solenoid valve windings |3a when the switch contact members 28 and 29 are engaged. The circuit for this relay 35 will be described as follows:

The main supply lines 39 and 3| have connected thereto the terminal wires of the primary coil of a transformer 36. One terminal of the secondary winding for this transformer is connected by the wire 31 to one terminal of the coil for the relay 35. The second terminal of this relay coil is connected by a wire 38 to a control circuit wire 39. The second terminal wire of the secondary coil of the transformer 36 is connected by a wire 40 with the second control circuit wire 4I. It will be seen that when the switch contacts 28 and 29 are engaged, the circuit will be completed through the winding of the relay 35, and energization of this relay will bring about closing of the circuit through both solenoid valve windings |3a.

It will be seen from the above description that the passage of an air wave along the mine passage 'I will bring about tripping of the vane 26 and bar 20 to actuate the switch represented by the contacts 28 and 29. The tripping and dropping of the vane 26 and bar 20 also will result in ripping open the rock dust bags I4. The air wave, therefore, is responsible for releasing the rock dust and the carbon dioxide.

It is also an object of this structure to produce either a carbon dioxide barrier or. screen or a combined carbon dioxide and rock dust barrier or screen across the mine passage in response to a re which does not produce an air wave. To accomplish this result, heat responsive devices 42 are spotted at proper intervals along the passage These heatresponsive devices are in the nature of thermostats which are connected in parallel across the `control wires 39 and 4|,

as is illustrated in Fig. 2. When one of these devices 42 responds to an increase in temperature resulting from a re, that device will close the circuit to the relay winding 35 and energize the coils |3a for the two solenoid valves I3. As a result of actuating the solenoid valves, carbon dioxide will be discharged through both of the nozzles I3. The turbulence or disturbance created by the released carbon dioxide will dislodge the bar 20 from the end of the switch lever 22 and the weights I9 will be dropped to bring about opening of the rock dust bags I4. It will be seen, therefore, that both the rock dust and the carbon dioxide will be released in response to actuation of one of the heat detecting devices 42.

Reference has been made above to the creation of a carbon dioxide barrier or screen without the use of rock dust. To accomplish this result, it is only necessary to dispense with the bags of rock dust and the rip cords or wires II with their weights I9.

The circuit of Fig. 2 clearly illustrates the fact that the two carbon dioxide discharge nozzles II and the rock dust equipment operates as a single unit. Each barrier or screen creating assembly scattered throughout the mine operates in this manner. It will be appreciated, therefore, that when a mine gas or coal dust explosion occurs at any location, one screen producing assembly will be actuated in each passage and the barriers or screens created by these several units or assemblies will isolate the location of the explosion from all other parts of the mine. By having the sets of heat responsive devices 42 for adjacent barrier or screen producing assemblies extend up to each other and meet, without being interconnected, at approximately the halfway point between these adjacent assemblies, a re at any given location in the mine will only bring about actuation of a single barrier producing assembly in each passage, or the like, so that portions of the mine which are not involved will not be disturbed.

Fig. 4 discloses a modied form of carbon dioxide and rock dust dispensing mechanism. This mechanism is susceptible of being used in two different ways in connection with the assembly disclosed and described while referring to Figs. 1 to 3, inclusive. For example, two of the mechanisms disclosed in Fig. 4 may be used in place of the carbon dioxide and rock dust releasing mechanism disclosed in Fig. 1. To accomplish this result, the two devices of Fig. 4 should be substituted for the discharge nozzles II of Fig. 1 and the rock dust bags I4 with their rip cords or wires I 'I and weights I9 should be dispensed with. The vane 26, its bar 20, and the switch lever 2| with its contacts 28 and 29 should be retained. The heat responsive devices 42, also, should be retained. With such an assembly, the two devices of Fig. 4 will operate either in response to the passage of an air wave through the mine or in response to a fire which does not cause an explosion, and a combined carbon dioxide and rock dust barrier or screen will be produced.

'I'his mechanism of Fig. 4 includes the piping system III in which is connected a branch line 43 having a valve 44 located therein and operated by the solenoid |3b. The pipe line 43 extends to and has connected thereon the discharge nozzle 45. A container 46 is suitably attached to the discharge end of the nozzle 45 and is supported, either from the piping system III or from some other suitable attaching surface, by means of the lUUi strap or bracket 41. The discharge end of the container 46 is closed by a door 48 which is normally held in place by a suitable latch mechanism 49. When the carbon dioxide is turned into the branch line 43 and is discharged from the nozzle 45, the force of the released carbon dioxide will be applied against the inner face of the door 48 and the door retaining latch 49 will readily operate to release the door. Outward swinging movement of the door around its hinge 50 will permit the rock dust 5I, confined within the casing 46, and the carbon dioxide vapor and snow discharged through the nozzle 45, to be dispersed into the mine passage. With two of these mechanisms of Fig. 4 located in spaced relation to each other and pointed toward each other, the two discharges will meet and impinge. As the commingled discharges spread out laterally, they will form an effective flame barrier or screen across the mine passage.

Fig. 7 shows a second way of utilizing the discharge mechanism of Fig. 4 is to locate a suitable number of the same in the portions of a mine which extend between barrier or screen producing assemblies of the character disclosed in Figs.

l to 3, inclusive. When used in this manner, two of the mechanisms will not be arranged in close proximity to each other and pointed toward each other to produce a flame barrier or screen. They will be utilized to discharge carbon dioxide and rock dust into the mine passage, or the like, for flooding the part of a passage located between actuated barrier or screen producing mechanisms of the type disclosed in Figs. 1 to 3, inclusive. The barriers or screens produced by the assemblies of these latter three figures will rather effectively act as barriers against the dissipation of the carbon dioxide and rock dust released between the several actuated barrier producing assemblies.

In other words, the barriers or screens produced by the assembly of Figs. 1 to 3, inclusive, in the several passages radiating from the scene of an explosion or a fire will function not only to prevent iiame propagation beyond the barriers or screens but will also operate to prevent too rapid a. dissipation of carbon dioxide and rock dust released between the various actuated barrier or screen producing assemblies.

When two mechanisms of the type disclosed in Fig. 4 are used in place of the assembly 'of Figs. 1 and 3, the solenoid windings I3b will be substituted for the solenoid windings 13a in the wire `32 of Figs. 2. When a suitable number of mechanisms of the type disclosed in Fig. 4 are used in the areas between barrier or screen producing assemblies, the solenoid windings I3b for these mechanisms will be connected in the circuit 32 and will be operated as a unit with the several unitary barrier or screen producing assemblies.

For example, let us assume that each varrier producing assembly is provided with four mechanisms of the type disclosed in Fig. 4. With such an arrangement, two of these Fig. 4 mechanisms will be located on each side of the barrier producing assembly and these several mechanisms will be pointed toward their particular assembly. When a barrier producing assembly is'actuated, either in response to an air wave or a rise in temperature, the four mechanisms of Fig. 4 will be placed in operation. Two of these mechanisms of Fig. 4 will then function to discharge carbon dioxide and rock dust von the fire side of Itheir barrier producing assembly andthe remaining two mechanisms of Fig. 4 will discharge carbon dioxide and rock dust on the side of their barrier producing assembly which is outside of the fire zone. However, these two mechanisms will be discharging their streams or clouds of carbon dioxide and rock dust toward their particular barrier producing assembly, land they will in that way function to retard spreading of the carbon dioxide and rock dust away from the scene of the re.

Figs. 5 and 6 are intended to illustrate the use of this invention to protect dusty, carbonaceous material handling equipment which operates in an enclosed space. It is to be understood, however, that the selection of this particular kind of material handling mechanism is not to be construed as limiting in any way this application of the invention.

We shall assume that the material handling mechanism of Fig. 5 operates to elevate a dusty, carbonaceous material from the ground level up to the top of a storage bin or elevator 52 in which the material 53 is deposited by gravity. The lower end of this material handling apparatus includes a transfer pit 54 in which is located a horizontal conveyor 55. This horizontal conveyor transfers material to the inclined belt conveyor 56 which extends the length of an enclosed tunnel or passageway 51 which is inclined and extends from the transfer pit 54 up to the top portion of the bin or elevator 52. The material is discharged over the outer side of the head pulley 58 of the apparatus.

To effectively protect this material handling mechanism against a fire resulting from ignition of the dust within the pit 54, the tunnel or passageway-51 and the storage bin or elevator 52, or against ignition of the carbonaceous material being handled in these various portions of the enclosure, a source of supply of carbon dioxide maintained at a constant, subatmospheric temperature and its corresponding low vapor pressure, is illustrated at 58. This source of supply will take the form of an insulated storage tank of any desired capacity. The liquid carbon dioxide in this tank will be maintained at the desired constant temperature by a refrigerating machine, in the manner described above. The liquid space of this storage tank 58 is connected by a pipe line 59, having a control valve 60 located therein, to a long header or piping system 6|. At suitable intervals along this header or piping system 6l there are located a number of carbon dioxide and rock dust dispensing mechanisms of the type disclosed in Fig. 6.

Each mechanism includes a branch line 62 connected in the piping system or header 6I by a suitable coupling 63 and a pair of cppositely pointing discharge nozzles 64 which are connected to the lower end of the branch 62 by means of a T coupling 65.

Suspended from the piping system 6|, or from any other -suitable supporting surface, by means of the straps or brackets 66 is a double rock dust holding box 61. This box has a compartment 68 for each carbon dioxide discharge nozzle 64. A supply of rock dus't 69 is located in each compartment. The outer side of each compartment is closed by a door 1|] which is hinged at 1| and is readily releasably retained in place by a latch 12. When carbon dioxide is turned into the piping system or header 6l, by the valve 60, carbon dioxide vapor and snow will be discharged from each one of the two discharge nozzles 64. 'I'he force of this carbon dioxide dischar'gewill unlatch the doors 1o and the 'rock'uu'si te will' bedispersed with the carbon dioxide. The carbon dioxide and rock dust discharged into the transfer pit 54, the relatively long tunnel or passageway 51, and the storage bin or elevator 52 will flood these enclosed spaces and will very effectively extinguish any form of fire, regardless of its intensity.

To bring about automatic actuation of this re extinguishing system, heat detecting devices 13 may be located at suitable intervals throughout the entire assembly, and these heat responsive devices may be suitably electrically connected with the solenoid winding of the valve 60 for releasing .the stored carbon dioxide into the piping system 6| in response to the starting of a lire anywhere in the protected enclosure.

To divide the material handling apparatus up into isolated hazards or sections, suitable fire barrier doors, or the like, 14 may be located at different points along the tunnel or passageway 51. These barriers or doors may be operated automatically in response to energization of any one of the heat responsive devices 13.

No attempt has been made to disclose a wiring circuit for the heat responsive Adevices 13, the solenoid actuated valve 60, and the releasing mechanisms for the lire barriers or doors 14 as many appropriate control systems can be found on the open market. As a matter of fact, the circuit of Fig. 2 might be used for this purpose by substituting the solenoid of the valve 60 and the releasing mechanisms of the fire doors 14 for the solenoid windings I3a of this Fig. 2! circuit.

It will be appreciated that the re extinguishing system disclosed in Figs. 5 and 6 operates to ood the enclosed, protected space with carbon dioxide vapor and snow and with rock dust being released to be mixed with dust laden air to prevent flashing of this potential fuel mixture.

It is to be understood that the forms of this invention herewith shown and described are to be taken as preferred examples of the same, and that various changes in the shape, size, and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the subjoined claims.

Having thus described the invention, I claim:

1. A method of extinguishing res in mines and other enclosed spaces where dust producing materials are handled, comprising creating re barriers of a mixture of inert gas and a non-combustible dust to prevent the propagation of flame from the place of origin of the fire, and creating a fire extinguishing atmosphere at the place of origin of the Iire by totally flooding with inert gas the portion of the enclosure located between said barriers.

2. A method of preventing the propagation of iiame along a mine passage, or the like, comprising discharging two streams of carbon dioxide vapors generally longitudinally of the passage and toward each other so that the streams will impinge and spread laterally and transversely of the passage to form a vapor screen or barrier across the passage through which flame will not pass.

3. A method of preventing the propagation of flame along a mine passage, or the like, comprising discharging two streams of carbon dioxide vapors toward each other so that the streams will impinge and spread laterally to form a vapor screen or barrier across the passage through which ame will not pass, and discharging into the vapor screen or barrier rock dust which will be mixed with the dust laden air in the passage to render the resultant mixture non-explosive and non-combustible.

4. A method of extinguishing fires in mines and other enclosed spaces where dust producing materials are handled, comprising creating re barriers of a mixture of carbon dioxide vapors and rock dust to prevent the propagation of flame from the place of origin of the re, and creating a re extinguishing atmosphere at the place of origin of the fire by discharging carbon dioxide vapors into the portion of the enclosure located between said barriers, the carbon dioxide vapors employed to create the fire barriers and the flre extinguishing atmosphere resulting from the sudden expansion of liquid carbon dioxide stored at a constant subatmospheric temperature and its corresponding vapor pressure.

5. A method of preventing the propagation of llame along a mine passage, or the like, comprising discharging two streams of carbon dioxide vapors, resulting from the sudden expansion of low temperature liquid carbon dioxide, generally longitudinally of the passage and toward each other so that the streams will impinge and spread laterally of their direction of flow and transversely of the passage to form a vapor screen or barrier across the passage through which flame will not pass.

6. A method of preventing the propagation of flame along a mine passage, or the like, comprising ldischarging two streams of carbon dioxide vapors toward each other so that the streams will impinge and spread laterally to form a flame barrier or screen of said vapor, the vapor of the barrier or screen being produced by the sudden expansion of liquid carbon dioxide stored at a.

constant subatmospheric temperature and its corresponding vapor pressure, and discharging into the barrier or screen rock dust which will be mixed with the dust laden air in the passage, by the turbulence created by the discharge of the carbon dioxide vapor, to render the resultant mixture non-explosive and non-combustible.

7. A method of preventing the propagation of flame along mine passages radiating from the scene of a fire or an explosion, comprising creating flame barriers across the several passages by discharging into the passages a. commingled mixture of carbon dioxide snow and vapors with rock dust, and discharging into the portions of the passages, adjacent the scene of the fire or explosion, and inwardly of said barriers, additional amounts of said carbon dioxide snow and vapors mixed with rock dust to create a re extinguishing atmosphere.

8. A method of preventing the propagation of flame along mine passages radiating from the scene of a re or an explosion, comprising creating flame barriers across the several passages by discharging into the passages a commingled mixture of carbon dioxide snow and vapors with rock dust, discharging into the portions of the passages, adjacent the scene of the re or explosion, and inwardly of said barriers, additional amounts of said carbon dioxide snow and vapors mixed with rock dust to create a re extinguishing atmosphere, and discharging into the several passages outwardly of said barriers streams of carbon dioxide snow and vapors mixed with rock dust, which streams are directed lengthwise of the passages toward the said barriers to retard the dissipation of carbon dioxide vapors from the scene of the fire.

9. In a device for protecting a. mine passage, a pipe line for liquid carbon dioxide extending H39. URE EXllNGUlSH-tli,

Search toon along the passage, a pair of carbon dioxide vapor discharge nozzles connected to the pipe line and pointed toward each other so that their streams will impinge and spread laterally to form a vapor barrier across the passage, and means for releasing rock dust into the said vapor barrier.

10. A method of extinguishing res in mines and other enclosed spaces where dust producing materials are handled, comprising isolating the place of origin of a re to prevent the propagation of flame by creating re barriers of inert gas across all passageways leading away from said lire in response to the movement of a re created air Wave through said passageways, and creating a re extinguishing atmosphere in the fire space isolated by said barriers by discharging inert gas into said space in response to the rise in temperature caused by the re.

11. A method of extinguishing fires in mines and other enclosed spaces where dust producing. materials lare handled, comprising creating lire barriers of a mixture of inert gas and a non-combustible dust to prevent the propagation of llame from the place of origin of the re, and creating a re extinguishing atmosphere at the place of origin of the re by discharging a mixture of inert gas and a non-combustible dust into the portion of the enclosure located between said barriers.

12. Fire extinguishing apparatus for protecting passages in which dusty carbonaceous materials are handled, comprising a bag for holding in readiness for use a body of non-combustible dust, means including a weighted rip cord for releasing the body of dust from said bag, a supply line for carbon dioxide, a discharge nozzle connected to the supply line, a valve for initiating discharge of carbon dioxide through the nozzle, means for actuating said valve, heat responsive means for rendering active said valve actuating means, and means operated by the discharge of carbon dioxide from said nozzle, following the actuation of said heat responsive means, for rendering operative said Weighted rip cord.

13. Fire extinguishing apparatus for protecting Dassageways in which dusty carbonaceous materials are handled, comprising means for holding in readiness for use a body of non-combustible dust, means for releasing the body of dust, a supply line for carbon dioxide, a discharge nozzle connected to the supply line, a valve for initiating discharge of carbon dioxide through the nozzle, means for actuating said Valve, heat responsive means for rendering active said valve actuating means, and means operating in response to the movement of an air Wave through the passage for rendering operative said dust releasing, means and said valve actuating means and also operating in response to the discharge of carbon dioxide from said nozzle, following the action of the heat responsive means, for rendering operative said dust releasing means.

14. Fire extinguishing apparatus for protecting passages in which dusty carbonaceous materials are handled, comprising means for holding in readiness for use a body of non-combustible dust, means for releasing the body of dust, a vane operating in response to impingement thereagainst of a owing i'luid for rendering operative said dust releasing means, means for discharging carbon dioxide vapors into the passage so that they will impinge against and operate said vane, a valve for controlling the carbon dioxide discharge means, and heat responsive means for actuating said valve to effect discharge of the carbon dioxide.

15. Fire extinguishing apparatus for protecting passages in which ldusty carbonaceous materials are handled, comprising means for holding in readiness for use a body of non-combustible dust, means for releasing the body of dust, means for discharging into said passage suicient carbon dioxide to create a barrier thereacross in the immediate vicinity of the body of dust, and means operated by the discharge of carbon dioxide for actuating the dust releasing means to cause the dust to mix with the carbon dioxide forming said barrier.

16. Apparatus for extinguishing lires in mines and other enclosed spaces where dust producing materials are handled, comprising means for discharging sufcient inert gas to create barriers to prevent the propagation of flame from the place of origin of the re, means for releasing noncombustible dust to mix with the inert gas of said barriers, and means for releasing sufficient additional inert gas between said barriers to create a iire extinguishing atmosphere at the place of origin of said nre.

17. Apparatus for extinguishing res in mines and other enclosed spaces where dust producing materials are handled, comprising means for discharging sulicient inert gas to create barriers to prevent the propagation of flame from the place of origin of the re, means for releasing noncombustible dust to mix with the inert gas of said barriers, and means for releasing sufficient additional quantities of inert gas and non-combustible dust, in a manner to cause them to mix, between said .barriers to create a fire extinguishing atmosphere at the place of origin of the re.

ERIC GEERTZ.

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