US2274771A - Apparatus for charging compressed gas material breaking cartridges - Google Patents

Description

March 3, 1942, F. H. ARMSTRONG APPARATUS FOR CHARGING GOMPRESSD GAS MATERIAL BREAKING CARTRIDGES Filed May 9, 1941 3 Sheets-Sheet 1 March 3, 1942. F, H, ARMSTRONG 2,274,771

APPARATUS FOR CHARGING COMPRESSED GAS MATERIAL BREAKING CARTRIDGES Filed May 9, 1941 5 Sheets-Sheet 2.

March 3, 1942. F. H. ARMsTRoNG 2,274,771

APPARATUS FOR CHARGING COMPRESSED GAS MATERIAL BREAKING CARTRIDGES Filed May 9, 1941 3 Sheets-Sheet 3 Uyuivi UNITED STATES PATENT OFFICE APPARATUS FOR CHARGING COMPRESSED GAS MATERIAL BREAKING CARTRIDGES Frank H. Armstrong, Chicago, Ill., assignor to Cardox Corporation, Chicago, Ill., a corporation of Illinois Application May 9, 1941, Serial No. 392,815

11 Claims.

This invention relates to new and useful improvements in apparatus for charging reusable cartridges with compressed gases for use in breaking down coal, or similar materials, in mines.

The possibility of employing highly compressed gases, such as air, as a medium for breaking down coal, or the like, in mines definitely was established quite some time ago as a resultl of perfection of such equipment items as:

1. A compressor unit which would develop the high pressures required to break down the coal; which could be operated at a satisfactorily low maintenance cost, and which would have a sufliciently long working life to permit its initial cost to be written oi at an economical rate.

2. A compressed gas receiver of proper strength and capacity to receive a suiicient volume of gas compressed to a proper value to permit cartridges to be charged therefrom in relatively rapid succession without causing the receiver pressure to drop below the desired maximum operating pressure of the cartridges.

3. A cartridge of practical dimensions which would withstand the rough usage to which it was subjected under normal working conditions and the repeated recharging with the highly compressed gases.

4. A diierential pressure operated valve mechanism for releasing the cartridge charges which was capable of being operated a large number of times without having to be serviced, and which could be controlled at a. remote point with respect to the working face of the coal vein being broken down.

Even with the above items satisfactorily developed, coal mine owners were slow in approving this compressed gas material breaking method because of the amount of special cartridge charging equipment required and the troublesome trame problem created by the need for moving the equipment into several locations during each working shift.

Up to the time of the development of this invention, it was considered to be necessary to employ one of the following types of mechanisms for charging cartridges after they were placed in drill holes formed in the coal to be broken down:

1. A transportable charging plant, including a compressor and a receiver mounted on a wheel or traveling-tread supDOfted Chassis Which h ad to be moved into proper operating relation w1th respect to each location in which it was to be used in breaking down coal. The cartridge or cartridges to be charged by the plant were connected to the receiver by tubing which had to be strong enough to withstand internal pressures ranging as high as approximately 12,000 pounds per square inch and yet be flexible enough to allow for easy manipulation. Copper tubing having an outside diameter of of an inch and a wall thickness of s of an inch was used for this purpose.

2. Av transportable receiver unit consisting of a single tank, or a series of tanks, mounted 0n a wheeled chassis and charged with the compressed gases at a stationary, central charging plant and moved into proper operating relation with respect to each location in which it was to be used in breaking down coal. The cartridge or cartridges used in connection with such a unit had to be connected to the tank or tanks in the same way as when a transportable charging plant was employed.

There were several principal objections to the use of transportable charging plants for charging the cartridges after they were placed in the drill holes in the material to be broken down. The first of these objections involved the added cost required to render such a compressor-receiver assembly light enough and compact enough to permit it to be easily moved through entries of conventional dimensions so that the plant could be operated in several different locations during each working shift. As such a transportable charging plant possessed a capacity which was only suiiicient to charge enough cartridges to break down from 700 to '750 tons per working shift, it was necessary for even a reasonably large mine to employ several of these plants to break down the tonnage required for a normal days operation. Additionally, each charging plant in operation required a horse power electric motor to operate the same with the result that the simultaneous use of several charging plants would add very materially to the power load of a mine. This power load problem was found to be very serious because very few mines have any surplus power during a working shift. It, therefore, was found to be necessary for a mine to either enlarge its power developing equipment or limit its use of cartridge charging plants to oi shifts. ASuch a restriction on the use of compressed air for material breaking purposes destroyed an important advantage this method possessed over the use of explosives because practically all State mining laws permit material to be broken down with compressed air during working shifts.

These same State laws prohibit the use of explosives during working shifts.

A second serious objection to the use of transportable charging plants involved interference with normal traflic. As it was necessary to move each one of these plants from one location to another several times during a single shift, the use of several plants added a material burden to the trackage systems which, as laid out, were only capable of satisfactorily handling the normal underground equipment.

A third serious objection had to do with the problem of obtaining from each transportable charging plant the tonnage per shift it was capable of breaking down. To be able to operate such a plant at its maximum capacity of '700 to r750 tons per shift, the coal to be broken down must be fairly well concentrated. This operating condition is not a desirable one because of the corresponding concentration of other equipment on the trackage system. The traiiic burden placed on any trackage system can be best taken care of if operations are being carried on in several, fairly well separated locations.

The use of transportable receiver units provides the same traffic problems as the use of transportable charging plants. In fact, a receiver unit has to be moved more frequently than a charging plant because of its limited capacity. For example, if a greater number shots are to be fired at a given location than can be charged from a receiver unit, it becomes necessary to either move two units into that location or interrupt the material breaking operation while an emptied receiver unit is returned to the central charging plant for recharging and then moved back to the said location for completion of the operation.

These transportable receiver units, however, do eliminate the need for employing more than one charging plant and this plant can be of a heavy duty type because it is not necessary to transport the same.

The daily capacity of even the most efficient type of transportable receiver unit so far developed is only about one-half to one-third that of a transportable charging plant. It will be appreciated therefore, that even under the most favorable operating conditions, the equipment of a mine must 'be increased by a considerable number of units if transportable receivers are employed for charging the compressed air cartridges.

The primary object of this invention is the provision of apparatus for charging with compressed gas the reusable cartridges employed for breaking down coal, or the like, in mines which, as compared with either transportable charging plants or receiver units, greatly reduces the amount of special equipment required for and the initial, power consumption, and maintenance costs of an installation; which practically eliminates the need for reserve or idle equipment; which increases to a substantial extent the daily tonnage yield per dollar of initial cost and the flexibility of this type of material breaking apparatus; and which entirely removes all obstructions to normal underground traiic without requiring any modification of the original or conventional trackage system.

Another important object of this invention is to provide a cartridge charging system that employs a fixed, central charging plant as the original source of compressed gas; that provides all mine rooms or locations being worked with gas obtainable from a closely positioned receiver which is of ample capacity and is constantly maintained charged to a sufficiently high pressure to permit cartridges to be quickly charged therefrom in relatively rapid succession without causing the receiver pressure to drop below the desired maximum operating pressure of the cartridges; and that eliminates all need for moving heavy or bulky equipment over the trackage system of a mine.

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 specification and in which like numerals are employed to designate like parts throughout the same,

Figure 1 is a vertical sectional view, partly broken away, of a coal mine in which has been installed one form of apparatus embodying this invention,

Figure 2 is a fragmentary, horizontal sectional View of a portion of the mine and apparatus illustrated in Fig. 1 and discloses specifically the approved practice of locating the cartridge shooting or control valves in a cross-cut or a break-through between two entries, rooms, or the like,

Figure 3 is a fragmentary horizontal sectional view, partly broken away, of a coal mine in which a slightly different apparatus arrangement, embodying this invention, has been installed,

Figure 4 is a fragmentary, horizontal sectional view of a. coal mine with a further embodiment of the invention installed therein, and

Figure 5 is a fragmentary, vertical sectional view taken on line 5-5 of Fig. 4.

In the drawings, wherein for the purpose of illustration are shown the preferred embodiments of this invention, and first particularly referring to Figs. 1 and 2, there is disclosed a fragmentary portion of a coal mine, or the like, which includes the main shaft 5 connected at its lower end to the parallel entries 6 that follow the vein of coal 1. At a distant point from the shaft 5 is located the face 8 of the coal vein which is being worked upon; i. e., is being broken down by means of charges of compressed gas, such as air, at a pressure which is usually around 9000 or 10,000 pounds per square inch, but which may under certain operating conditions reach as high as 12,000 pounds per square inch. These material breaking charges are released from one or more reusable cartridges 9 which are placed in suitable drill holes formed in the working face. These compressed air cartridges may be of the construction covered by my Patent No. 2,083,548, issued June 15, 1937. This prior patent discloses a cartridge structure from which a compressed air charge is released, at any desired pressure, by means of a valve, which is actuated to effect release of the charge by means of a diierential fluid pressure operated mechanism. This mechanism is actuated by venting the compressed air from a relatively small control chamber through the tubing employed to deliver the charge to the cartridge when positioned within a drill hole.

Fig. 1 discloses a building I0 which is located on the mine property at the surface and adjacent the upper end of the shaft 5. This building may either be the engine house of the mine or any other existing or specially built enclosure. This building l0 is intended to house a stationary gas 'by appropriate couplings.

compressor, not shown, which is capable of compressing gas a suitable amount in excess of the maximum material breaking pressure to be used in the cartridges to be charged by this compressor. It is preferred that the compressor be capable of building up a pressure which will exceed the normal cartridge charging pressure by from 250 to 500 pounds per square inch.

A main line of steel tubing II is connected to the compressor at its upper end and extends over to and down the shaft 5. Thissteel tubing II, also, extends through the appropriate mine entries 6 to all of the sections or locations of the mine in which the coal is being broken down. This tubing II, of course, is made up of sections of convenient length which are interconnected No attempt has been made to illustrate this sectional construction of the tubing and the couplings with the exception of the points at which the tubing branches or changes its direction. This tubing, of course, is permanently attached to a side of the mine shaft and either a side wall or the roof of the entries by means of suitable pipe hangers or straps.

`This steel tubing II is intended to function as a receiver and is fully charged with compressed air at the desired pressure. By extending this tubing type of receiver to all sections or locations of the mine where material is being broken down, these various sections or locations are provided with an adequate supply or volume of compressed air for rapidly charging cartridges at a desired rate and without causing the receiver pressure to drop to any material extent. To permit the receiver II to accomplish this desired result, it should have a volumetric capacity for each section or location of the mine of at least 10,000 cubic inches. That is to say1 if the receiver II extends to and serves three different mine sections or locations, the total volumetric capacity of the receiver should at least equal 30,000 cubic inches. It has been determined that the volume of compressed air used at any one location or section of a mine will not exceed from 200 to 300 cubic inches per minute. If the receiver I I has a volumetric capacity, for each mine section or location to be served, of approximately 11,000 cubic inches, and the inside diameter or bore of the steel receiver tubing is not less than 5A, of an inch in diameter, the drop in pressure at all of the mine sections or locations will be nil. With the inside diameter of the receiver being at the minimum value of of an inch, the receiver must have a length equal to 3000 feet times the number of mine locations or sections being served. Of course. as the inside diameter of the receiver is increased from the 5/8 inch minimum, the desired volumetric capacity may be obtained with a total length Which is less than 3000 feet for each section or location.

In the specic illustration of Figs. 1 and 2, the receiver II extends to a point which is located a suitable distance from the face 8 of the coal vein being broken down. As the entries 6 are being extended in this illustration, the receiver is illustrated as stopping at this section or location of operation. The receiver II terminates at the elbow coupling I2 which is located at one end of the cross-cut I3 which extends between and connects the parallel entries 6. From this elbow I2, copper tubing Il extends into the cross-cut and is connected at its outer end to the diagrammatically illustrated mechanism I5 which consists of a suitable shooting or control valve and a pressure gauge. This shooting or control valve may be considered as being of the type disclosed and claimed in my previously issued Patent No. 2,146,879, dated February 14, 1939, although numerous refinements have been incorporated in the shooting or control valve mechanism now being commercially used which are not disclosed in this last mentioned patent. Any suitable pressure gauge which will record or'register the high pressures-used in this type of system can be em` ployed in connection with the shooting or control valve. From this control mechanism I5, copper tubing I5 extends to the working face 8 and is properly attached to the cartridge 9.

This copper tubing must be strong enough to withstand the high internal pressures to which itis subjected and, additionally, it must be sufliciently flexible to permit it to be properly manipulated without rupturing. A copper tubing which will respond to these requirements possesses an outside diameter of of an inch `and a wall thickness of 116 of an inch. It will be appreciated, therefore, that the aforementioned minimum inside diameter for the receiver II provides a cross sectional area which is approximately 25 times the cross sectional area provided by the inside diameter of the copper tubing I4 and I6. With the point of connection to the receiver located within or'150 feet of the working face 8 of the coal vein, and with the receiver charged to a pressure which will exceed the desired material breaking pressure charged into the cartridge 9 by approximately 250 pounds per square inch, it will require less than ten seconds to charge the cartridge. The principal reason for requiring a cartridge to be charged at as rapid a rate as possible is the time it saves for the shot firing crew.

In the use of the apparatus, or system, disclosed in Figs. 1 and 2, the cartridge 9 is placed in a drill hole formed in the working face 8 and the shot firing crew then retires to the cross-cut I3 so that the control mechanism I5 may be manipulated. The valve of this mechanism is then operated to cause the compressed air to ow from the receiver II to the cartridge 9 through the copper tubing I 4 and I6. When the pressure gauge of the mechanism I5 registers the desired pressure, the valve of the control mechanism is again actuated to shut oi the ilow of compressed air from the receiver I I and to vent the air from the control chamber of the cartridge 9 and the copper tubing I6. This venting results in manipulation of the valve operating mechanism of the cartridge to cause the valve to be opened to release the compressed air charge into the drill hole to break down the coal. The cartridge 9 is then recovered from the broken down coal and is inserted in the next drill hole to be red.

The location of the compressor at the surface like in Fig. 1, or at least close to the foot of the shaft 5, is very desirable because it makes the use of an A. C. electric motor for driving the compressor economically practical. Alternating current motors are more satisfactory for this type of service because they provide a more dependable, steady source of power and are less expensive to operate. Mines usually are Wired for direct current because of the variable speed motors required for driving the mine locomotives, etc. Therefore, any need for alternating current at a point in a mine which is remote from the source of electricity makes it necessary to wire the mine for both types of current. Running the receiver II from the surface to the remote locations is not the equivalent of wiring for alternator more additional sections or locations of the mine where, it is to be presumed, additional material breaking operations are being performed.

This installation is operated on the principle of having the compressor I8 located in one of the cross-cuts I9 which extends between the parallel entries 6. The location of the compressor in this cross-cut removes the same from the entries and the several rooms so that the compressor will not interfere in any way with traffic on the conventional trackage system, not shown. Although this compressor I8 is illustrated as being positioned in a cross-cut, it is to be understood that the compressor might just as well be located in the underground repair shop, which is generally located fairly close to the foot of the main shaft, and in which coal loaders, locomotives, and the like are serviced.

The receiver II, which corresponds in every respect with the receiver of Figs. 1 and 2, extends from the compressor I8 along one of the entries 6 to all of the various sections or locations in which material breaking operations are being performed. This receiver, therefore, extends past the location or section of the mine which includes the rooms Il. T couplings 20 are connected in the receiver II to permit the copper tubing 2I to be connected to the receiver for supplying the rooms I1 with compressed air for breaking down the coal. These two lengths of tubing 2| extend to the respective cartridge shooting or control valves and gauges which are again designated by the reference character I5. From these control mechanisms I5, copper tubing 22 extends to the four cartridges 9. Each one of these cartridges is being employed in a room I'I to break down the coal from a working face 8. As shown, these cartridges are being fired in pairs; i. e., two cartridges are simultaneously controlled by a single mechanism I5. The tubing 2I and 22 is the same as the tubing I4 and I6 of Figs. l and 2. The control mechanisms I5 in this layout are located in the break-throughs 23, instead of being located in a cross-cut like the illustration of Figs. 1 and 2. In all such operations, the control mechanism mustbe located at some point which is around at least one corner from the working face being broken down. To comply with the various State mining laws, the members of the shot firing crews are required to be out of alignment with the cartridges being operated so that they will not be injured in case a cartridge fiies out of its drill hole when its compressed air charge is released.

Figs. 4 and 5 may be considered as illustrating a layout in which an entirely new part of the mine is being opened up. That is to say, the previous operations have been served by the entries 6 which extend from the shaft, not shown, to the various sections or locations which have been worked out. This portion of the mine has been closed oil. and the receiver I I that served the same has been removed. The new entries 6a have been formed in this new portion of the mine to a suiiicient extent to accommodate the various rooms 24. As operations in this new portion of the mine will be carried on for a tridges 9 attached to their outer ends.

considerable iengtn of time. tne underground compressor unit I8 has been installed in one of the cross-cuts, 25. This location for the compressor is relatively close to the rooms 24. For that reason, a receiver of proper volumetric capacity to serve the rooms 2l will not be provided by merely running the receiver out to one of the entries 6a and then once along the length of this entry. To provide the proper capacity, the receiver II is doubled back and forth several times in the short length of the entry 6a. Suitable return bends 26 may be employed for interconnecting the adjacent ends of the several lengths of steel tubing which forms this type of receiver assembly. It will be appreciated that as the entries 6a are extended farther into this newly opened portion of the mine, the receiver lII may be straightened out so that it finally will extend along the entry in the manner illustrated in Figs. l to 3 inclusive. However, the compressor I8 may remain in this initial location during the entire time this portion of the mine is being worked.

From suitable T couplings 2l, connected in the outer length of the receiver, copper tubing 28 extends into the rooms 24 for serving the control mechanisms I5. These control devices are connected to copper tubes 29 which have the car- These cartridges are being employed for breaking down coal from the working faces 8.

From the above descriptions of the installations in three diiferent mine arrangements, it will be appreciated that the material breaking apparatus embodying this invention can be installed so as to take care of any situation which might be encountered in different mines. Therefore, the invention should in no way be limited to the specific arrangements illustrated by the several figures.

It will be noted that the compressors are shown as being positioned either on the surface, entirely outside of a mine, or at any suitable location within a mine which will not obstruct normal underground transportation. As the compressors are seldom moved, they can be made large enough to possess the desired capacity and to be a dependable machine. The cost, per rated horsepower, will be less for this type of a stationary unit than for a charging plant which is designed so that it may be moved from place to place through the mine entries. 'I'he location of the compressor outside of the mine has the eiect of materially lengthening its working life because it is not subjected to the dust laden air of the mine. When the compressor is located in the engine house, on the surface, it may be kept under constant supervision by the mine engineers. Also, it can be worked on when the mine is idle. This is not the case with a compressor located at some out of the way spot in the mine.

By forming the receiver II of interconnected lengths of steel tubing, the receiver can be extended into all portions of a mine so that every location or section being worked is provided with adequate receiver service. As one section or location of a mine is lcompletely worked out and abandoned, the portion of the receiver that served that section or location can be dismantled without interrupting operations in any other portion of the mine and the sections of tubing which constituted the dismantled portion of the receiver can be used again in extending the receiver into newly opened sections or locations.

With this type of installation, there is no rolllng stock which must be maintained, like with the two types of transportable cartridge charging methods described above, and the compressor constitutes the only piece of equipment which possesses movable parts that are subject to wear. The sections of steel tubing employed to form the receiver are subject to practically no wear and tear and will last indefinitely. It has been determined that this type of receiver system may be extended through several miles of mine entries and all sections or locations of the mine will be properly served with compressed air at the desired pressure and volume. This is due to the fact that uniform pressure is maintained in the receiver right up to the extreme outer end of the same.

It was noted above that the capacity of a transportable charging plant was limited to a considerable extent by, or was dependent upon, the extent to which the coal being broken down was concentrated. It, additionally, was pointed out that mine operators prefer to have the sections or locations of the mine being worked fairly well separated or scattered so that traiiic jams would not occur. With this type of charging apparatus, it makes no difference whether the locations or sections being worked are concentrated or widely scattered. The capacity of the system is the same in either case.

It was further explained above that when transportable charging plants or receiver units are used, it usually is necessary to have reserve plants or units which are idle at least a part of each shift. No such idle equipmentis needed for the type of system embodying this invention.

As only one compressor need be employed with the present system, there will be a considerable saving in horse-power consumption as compared to a system employing transportable compressor plants which must be provided in proper number to supply all sections or locations of a mine being worked.

Fig. 1 discloses the receiver Il as extending from the surface into the mine through the main shaft of the mine. It is to be understood, however, that a special, small diametered hole may be drilled from the surface to the mine level at any other point on the mine property and the receiver may be placed in this special hole. A compressor then may be located on the surface adjacent the upper end of the receiver hole and enclosed in a suitable building or housing provided especially for that purpose. Such an arrangement may be found to be desirable for a large mine where all of the operations are being carried on several miles from the main shaft. In such a situation, it would be impractical to have the receiver extend from the surface down the main shaft and along these several miles of entries to the active portion of the mine. All of this long stretch of receiver equipment is not needed to provide the required receiver capacity. Of course, the same situation can be taken care of by a compressor located in the mine. Some mine operators, however, strongly favor locating the compressors on the surface.

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.

through the entries, or the like, to a mine section in which coal is being broken down, said relceiver having a volumetric capacity and being charged with gas at a pressure which will permit cartridge charges to be quickly withdrawn therefrom in relatively rapid succession without causing the receiver pressure to drop below the desired maximum operating pressure of a cartridge, a discharge line extending from the working face of the coal to the receiver and connected to the latter, a cartridge, having differential gas pressure operated discharge mechanism, connected to the discharge line, and means in said discharge line for controlling ow of gas to the cartridge and for controlling operation of the discharge mechanism of the cartridge to eiect release of a material breaking charge.

2. A material breaking system for coal mines, or the like, comprising a compressor stationed on the mine property, a compressed gas receiver connected to the compressor and extending through entries, or the like, in the desired directions to the several sections f a mine in which coal is being broken down, said receiver having a volumetric capacity for each of said mine sections and being charged with gas at a pressure which will permit cartridge charges to be quickly withdrawn therefrom at any desired number of said sections in relatively rapid succession without causing the receiver pressure to drop below the desired maximum operating pressure of any of the cartridges being employed at the several sections, a discharge line extending from the working face, of the coal at each section to an adjacent portion of the receiver and connected to the latter, a cartridge having differential gas pressure operated discharge mechanism connected to each of the discharge lines, and means in each discharge line for controlling ow of gas to its cartridge and for controlling operation of the discharge mechanism of its cartridge to elect release of a material breaking charge.

3. A material breaking system for coal mines, or the like, comprising a compressor stationed on the mine property, a compressed gas receiver connected to the compressor and extending through entries, or the like, to a mine section in which coal is1 being broken down, said receiver having a volumetric capacity of at least 10,000 cubic inches and being charged with gas at a pressure suiilciently in excess of the required material breaking pressure to permit cartrige charges to be quickly withdrawn therefrom in relatively rapid succession without causing the receiver pressure to drop below the said required material breaking pressure, a discharge line extending from the working face of the coal to the receiver and connected to the latter, a cartridge, having differential gas pressure operated discharge mechanism, connected to the discharge line, and means in said discharge line for controlling flow of gas to the cartridge and for controlling operation of the discharge mechanism of the cartridge to eilect release of the material breaking charge.

4. A material breaking system for coal mines, or the like, comprising a compressor stationed on the mine property, a compressed gas receiver connectedV to the compressor and extending through entries, or the like, in the desired directions to the several sections of the mine in which coal is being broken down, said receiver having a volumetric capacity for each of said mine sections of at least 10,000 cubic inches and being charged with gas at a pressure which will be sufiiciently in excess of the required material breaking pressure to permit cartridge charges to -be quickly withdrawn therefrom at any desired number of said sections in relatively rapid succession without causing the receiver pressure to drop below the said required material breaking pressure, a discharge line extending from the working face of the coal at each section to an adjacent portion of the receiver and connected to the latter, a cartridge, having differential gas pressure operated discharge mechanism, connected to each one of the discharge lines, and means in each discharge line for controlling flow of gas to its cartridge and for controlling operation of the discharge mechanism of its cartridge to effect release of a material breaking charge.

5. In a material breaking system for coal mines, or the like, a compressor stationed in a building on the surface of the mine, a compressed gas receiver connected to the compressor and extending down the mine shaft and through entries, or the like, to a mine section in which coal is being broken down, said receiver having a volumetric capacity and being charged with gas at a pressure which will permit cartridge charges to be quickly withdrawn therefrom in relatively rapid succession without causing the receiver pressure to drop below the desired maximum operating pressure of a cartridge, a discharge line extending from the working face of the coal to the receiver and connected to the latter, a cartridge, having differential gas pressure operated discharged mechanism, connected to the discharge line, and means in said discharge line for controlling iiow of gas to the cartridge and for controlling operation of the discharge mechanism of the cartridge to effect release of a material breaking charge.

6. A material breaking system for coal mines, or the like, comprising a compressor stationed in a building on the surface of the mine. a compressed gas receiver connected to the compressor and extending down the mine shaft and through entries, or the like, in the desired directions to the several sections of the mine in which coal is being broken down, said receiver having a volumetric capacity for each oi' said mine sections and being charged with gas at a pressure which will permit cartridge charges to be quickly withdrawn therefrom at any desired number of said stations in relatively rapid succession without causing the receiver pressure to drop below the desired maximum operating pressure of a cartridge, a discharge line extending from the working face of the coal at each section to an adjacent portion ofthe receiver and connected to the latter, a cartridge, having differential gas pressure operated discharge mechanism, connected to each discharge line, and means in each discharge line for controlling flow of gas to its cartridge and for controlling operation of the discharge mechanism of the cartridge to effect release of a material breaking charge.

'7. A material breaking system for coal mines, or the like, comprising a compressor stationed in the mine at a point where it will offer no obstruction to normal underground trailic, a compressed gas receiver connected to the compressor and extending through entries, or the like, to a mine section in which coal is being broken down, said receiver having a volumetric 75 capacity and being charged with gas at a pressure which will permit cartridge charges to be quickly withdrawn therefrom in relatively rapid succession without causing the receiver pressure to drop below the desired maximum operating pressure of a cartridge, a discharge line extending from the working face of the coal to the receiver and connected to the latter, a cartridge, having diierential gas pressure operated discharge mechanism, connected to the discharge line, and means in said discharge line for controlling fiow of gas to the cartridge and for controlling operation of the discharge mechanism of the cartridge to eiect release of a material breaking charge.

8. A material breaking system for coal mines, or the like, comprising a compressor stationed in the mine at a point where it will oiTer no obstruction to normal underground traic, a compressed gas receiver connected to the compressor and extending through entries, or the like, in the desired directions to the several sections of the mine in which coal is being broken down, said receiver having a volumetric capacity for each of said mine sections and being charged with gas at a pressure which will permit cartridge charges to be quickly withdrawn therefrom at any desired number of said sections in relatively rapid succession without causing the receiver pressure to drop below the desired maximum operating pressure of a cartridge, a discharge line extending from the working face of the coal at each section to an adjacent portion of the -receiver and connected to the latter, a cartridge, having differential gas pressure operated discharge mechanism, connected to each discharge line, and means in each discharge line for controlling flow of gas to its cartridge and for controlling operation of the discharge mechanism of its cartridge to effect release of a material breaking charge.

9. A material breaking system for coal mines, or the like, comprising a compressor stationed on the mine property, a compressed gas receiver formed of connected sections of tubing having an inside diameter 0f at least 5A; of an inch and a total length which will provide a volumetric capacity of not less than 10,000 cubic inches connected to the compressor and extending through entries, or the like, to a mine section in which coal is being broken down, said receiver being charged at a pressure sufficiently in excess of the required material breaking pressure to permit cartridge charges to be quickly withdrawn therefrom in relatively rapid succession without causing the receiver pressure to drop below the desired maximum operating pressure of a cartridge, a discharge line extending from the working face of the coal to the receiver and connected to the latter, a cartridge, having differential gas pressure operated discharge mechansm, connected to the discharge line, and means in said discharge line for controlling flow oi' gas to the cartridge and for controlling operation of the discharge mechanism of the cartridge to effect release of a material breaking charge.

l0. A material breaking system for coal mines, or the like, comprising a compressor stationed on the mine property, a compressed gas receiver formed of connected sections of tubing having an inside diameter of at least of an inch and a total length which will provide a volumetric capacity of not less than 10,000 cubic inches for each section or location of the mine being worked, said receiver being connected to the compressor and extending through entries, or the like, in the desired directions to the several sec'v tions of the mine in which coal is being broken down and being charged at a pressure sufliciently in excess of the required material breaking pressure to permit cartridge charges to be quickly withdrawn therefrom at any desired number of said sections in relatively rapid successionwithout causing the receiver pressure to. drop below the desired maximum operating pressure of a cartridge, a discharge line extending from the working face of the coal at each section to an adjacent portion of the receiver and connected to the latter, a cartridge, having differential gas pressure operated discharge mechanism, connected to each discharge line, and means in each of said discharge lines for controlling flow of gas to its cartridge and for controlling operation of the discharge mechanism' of the cartridge to effect release of a material breaking charge.

11. A material breaking system for coal mines, or the like, comprising a compressor stationed on the mine property, a. compressed gas receiver connected to the compressor at one end and formed o! connected sections of tubing doubled back and forth along an entry from the compressor to a mine section in which coal is being broken down, said receiver having a volumetric capacity and being charged with gas at a pressure which will permit cartridge charges to be quickly withdrawn therefrom in relatively rapid succession without causing the receiver pressure to drop below the desired maximum operating pressure of a cartridge, a discharge line extending from the working face of the coal to the receiver and connected to the latter, a cartridge, having differential gas pressure operated discharge mechanism, connected to the discharge line, and means in said discharge line for controlling flow of gas to the cartridge and for controlling operation of the discharge mechanism of the cartridge to eiect release of a material breaking charge.

vFRANK H. ARMSTRONG.

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