US3109371A - Blasting systems - Google Patents

Description

1963 R. v. WAKEFIELD ETAL 3,109,371

BLASTING SYSTEMS Filed Jan. 25, 1960 INVENTOR. RALPH VINCENT WAKEFIELD BHARRY CLARK FOSTER BY %::%W

United States Patent 351699571 BLASEENG SYSTEM-iii Ralph Vincent Wakefield, Godfrey, and Harry Clark Joster, East Alton, Ill, assignors to @lin Mat-hieson Qhemieal Corporation, East Alton, ill, a corporation ct Virginia Filed la 25, well, Ser. No. 49,348 2 Claims. Cl. mil-25) This invention relates to blasting systems and apparatus and particularly to such systems utilizing charges of compressed gas as the work performing medium.

A wide variety of compressed gas blasting cartridge-s have been employed, particularly in the mining industry to replace explosive charges. Generally, each cartridge is connected by a high pressure line to an air compressor or other source of compressed air and the cartridges fired individually when a predetermined discharge pressure is achieved within the cartridge. More recently, a system has been proposed for connecting a number of such compressed .gas blasting cartridges to one supply source and discharging the cartridges consecutively. Such a system represents a definite advance over the conventional manner of air shooting but possesses a number of inherent disadvantages. In accordance with such prior art systems, the control of the flow of high pressure gas is completely dependent upon means in the vicinity of the compressed gas source. Such means normally take the form of a manually controlled valve and vent in the immediate area of the compressor. Thus, the long extent of high pressure fluid lines between the manual valve and the compressed gas cartridges is not susceptible to any control. Such practice can be quite expensive and, in fact, hazardous. When a break in the line occurs beyond the manual valve and in the general area of the blasting cartridges, the pressure throughout the entire line is lost. Rebuilding the pressure in the line is quite time consuming and results in unnecessary and costly interruptions in the Work day. Also, in numerous cases in which the manually controlled valve fails to operate properly, the compressed gas will continue to flow to the blasting cartridges. When automatic shells are employed, this results in the repeated charging and discharging of the shells with the attendant hazards both to workmen and the equipment.

it is, therefore, an object of this invention to provide a novel and improved system and apparatus for the series shooting of compressed gas blasting cartridges overcoming the disadvantages of the prior art. Another object is to reduce operating cost and conservation of compressed gas, and to insure more reliable operation of compressed gas blasting cartridges as employed in series shooting. A further object is to provide a compressed gas blasting system in which the possibility of repetitive shooting is eliminated. A more specific object is to provide a safe, novel, economical method and apparatus for series shooting in which the cartridges are charged simultaneously.

The manner in which these and other objects are accomplished will be apparent from the following specification together with the drawing, in which:

FIGURE 1 is a schematic representation of a system illustrating the present invention; and

FIGURE 2 is a longitudinal sectional view of a valve illustrating another aspect of the invention.

As shown in FIGURE 1 of the drawing, work face 1 in ice chamber 2 of a coal mine is provided with bore holes 3, 4, and 5, containing automatic compressed gas blasting cartridges 6, 7 and h respectively. Compressed gas is delivered to the cartridges through main line 9 from a compressor or other suitable source (not shown). The main line is provided with a manually operated control valve It} and means ill for bleeding the line. Main line 9 terminates in manifold 12, and feed lines 13, 14 and 15 extend from the manifold to the cartridges in the system. in this preferred embodiment, cartridges 6, '7 and 8 are completely automatic and will discharge when the pressure therein reaches a predetermined level. Although any type of slu -type, semi-automatic or automatic shell can be employed, it has been found that an automatic shell of the type described and claimed in the copending application, Serial No. 842,082, of Harry Clark Foster, which is now abandoned, is particularly well suited for use in blasting systems and methods of the present type. The assembly is so designed that the shells will fire sequentially rather than simultaneously. This can be accomplished by adjusting each shell to discharge at a different pressure. Alternately, the shells can be adjusted to the same discharge pressure and the pressure diiierential can be obtained by varying the length of the feeder line, orifice size, or by any other equivalent means. Thus, all the cartridges in the system can discharrge at the same pressure, but the pressure within each shell is obtained after a time lag by restricting or varying the flow of gas into each shell.

As the compressed gas passes through the manifold,

it is divided into a number of substantially equal portions which are fed to the various cartridges in the system. Thus, prior to the discharge of any of the cartridges, the pressure throughout the entire system is substantially equal and the shells are filled simultaneously. In the present embodiment, cartridge 6 is adjusted to a discharge pressure of approximately 8,000 pounds, cartridge 7 to a discharge pressure of about 8,300 pounds, and cartidge 8 to a discharge pressure in the neighborhod of 8,600 pounds. As illustrated in FIGURE 1, feed line 13 is provided with valve 16 and feed line 14 is provided with valve 17.

In operation, compressed air or other suitable gas, is supplied to cartridges 6, 7 and 8 through main line 9 and feed lines 13, 1d and 15. The pressure in each of the cartridges increases at a substantially equal rate until the discharge pressure, namely 8,0 00 pounds, for cartridge 6 is attained. At this point, the compressed gas contained in cartridge 6 is discharged and the coal surrounding the cartridge is broken down. Immediately upon discharge of cartridge 6, cut-oil valve l6 stops the fiow of air through feed line 13. The air flow from main line 9 is then equally divided between teed lines 14 and 15. This condition continues until the pressure in the system reaches about 8,300 pounds, at which level cartridge 7 is discharged. Cu -o1i valve 17 then immediately closes feed line 34 and all of the air from the main line is then directed through feed line 15 into cartridge 8, which subsequently discharges at a pressure of about 8,606 pounds. It will be noted that feed line 15 in this embodiment is not provided with a cut-oil valve as shown in the remaining tfeed lines. Normally, it is not necessary to provide the feed line for the last firing cartridge with such a cut-off means. However, if desired, each of the feed lines can be provided =49 with a cut-off means to insure positive protection against loss of pressure throughout the system upon a failure of any part thereof. After cartridge 8 has been discharged, valve 16 is closed to stop the introduction of air into the system. The residual pressure in the lines can then be relieved through means 21.

Valves l6 and 17 can be of any appropriate design. It is necessary that they stop the flow of compressed gas through the feed line when the corresponding cartridge has been discharged, and reset automatically to permit charging for succeeding shots. in addition, such valves must not close prematurely as during charging.

A valve means particularly well suited for employment in accordance with the assembly of the present invention is illustrated in FIGURE 2. This valve assembly is provided with an inlet body 18 and an outlet cap 19 which are screw threadedly connected as indicated at 2G. The seal between the inlet body and the outlet cap is completed by resilient sealing means 21 positioned in groove 22 of the inlet body. A substantially cylindrical chamber 23 is contained within the inlet body and accommodates valve piston 24. A sliding seal between the wall of chamber 23 and valve piston 24 is provided by O-ring 25 positioned in groove 26 of the valve piston 24. Suitable means for connecting the valve body to the feeder line or between the feeder line and the cartridge are provided on the inlet body at 2'7 and on the outlet cap at 28. Also, the outlet cap is provided with opposed notched portions 29 or other suitable means to accommodate a wrench. Stem 39- of valve piston 24 forms a sliding fit with the inlet body at 31 so as to provide a relatively small annular passageway into obturated chamber 32. The assembly is so designed that the inlet port 33, bore 34 in the valve piston, and the outlet port 35 are in substantial alignment. The outlet port is spanned by valve seat 36 which is provided with diagonal ports 37 and central depression 38 in the face thereof. Central depression 38 must be larger in diameter than the outside diameter of stem 30 of the valve piston. The design of the valve can be modified by making the valve face planar and positioning a central depression in the base of the valve piston or in some instances, both the valve piston and the valve face can be dished to provide a larger air space between them. Likewise, annular space 39 can be formed by either member.

At the start of normal operation, valve piston 24 is in the position shown in FIGURE 2. The compressed gas enters inlet body 18 through inlet port 33, passes through bore 34 of valve piston 24, between the valve piston 24 and valve seat 36, and then through annular space 39. The air then continues through diagonal ports 37 in the valve seat and through the outlet port 35 to the cartridge being charged. Valve piston 24- Will remain in the position shown during the charging of the cartridge. Even if the valve piston is in contact with the valve seat when compressed gas is first introduced into the valve, the valve piston will necessarily assume the position as shown in the drawing. This will be apparent from the following explanation.

Air can enter obturated chamber 32. only through a very small clearance at sliding fit '31 around stem 30 of the valve piston. Thus, it passes through bore 34 and out let port 35 at a much greater rate than it enters obturated chamber 32 through sliding fit 31. Therefore, the first increment of air being charged is momentarily effective on that portion of the valve piston 34 which is opposite central depression 38 and on the external diameter of stem 30 of the valve piston. Since the diameter of depression 33 is slightly larger than the external diameter of stem 39, the differential effective areas of valve piston 24 when in contact with valve seat 35 will initiate movement of the valve piston to the left and away from the valve seat. This slight movement of the valve piston toward the left exposes the full area of the valve face at the right end of piston 24 to the air pressure. Although the charging pressure may drop somewhat as the air is permitted to flow through outlet port 35 into the shell, the relatively lower pressure in chamber 32 at this point permits the piston 24 to complete its shift to the left. During further charging of the shell with an increase of pressure, both in the line and in the valve, the pressure in obturated chamber 32 gradually increases and becomes substantially equal to the pressure throughout the remainder of the system. This increase in pressure in chamber 32 will have no immediate effect on the position of the piston since the pressures and areas 'on the right and loft ends of the piston are in substantial balance.

When the cartridge attached to outlet cap 19 discharges, the pressure on the right end face of valve piston 24 is substantially reduced. Due to the large bore in the piston, it is quite likely that there may also be a lowering of pressure on the left end of piston stem 30. However, the pressure in chamber 32 will decrease at a much slower rate. Thus, the high pressure air trapped in chamber 32 expands and forces valve piston 24 against valve seat 36. The residual back pressure from the cartridge is then effective only upon the reduced annular area of piston 24 in annular space 39 While the line pressure is effective on the entire left side of the piston and on the right hand portion of the piston opposite central depression '58. Therefore, the effect of these clifierential areas is to hold the valve piston 24 closed against seat 36 and to prevent further flow of compressed gas into the discharged shell while charging of the other shells in the system continues. After the last shell in the system has been fired, control valve is is manually closed and the pressure in the line reduced by bleeding at 11. As the line pressure falls sufficiently below the residual pressure in each shell, the valve pistons are urged to the left. This permits bleeding of residual pressure from the cartridges and concomitantly resets the valve for the next charging cycle.

Valves of the type shown or any cut-oil valve with equal capabilities can be utilized to advantage in accordance with the present invention for the firing of a plurality of compressed gas blasting cartridges from a common supply line. Valve piston 24 can be replaced by a cup shaped valve member slidable within bore 23 while utilizing the principles of the valve shown. In addition, it will be appreciated that valves of this type can be used in single firing operations to prevent air from leaking into the shell after discharge. Thus, the possibility of the cartridge discharging repeatedly is reduced to an absolute minimum. The present invention also positively insures that the air supply is shut off immediately upon discharge of the shell. This not only conserves air when slug type shells are employed but also facilitates the utilization of completely automatic shells by eliminating double shooting.

In the assembly described herein, each of the feed lines, with the exception of the one connected to the last discharging cartridge is provided with a cut-off valve. While such a valve is not necessary to the last feed line, it can be used to advantage and will prevent loss of pressure in the system, should a break occur beyond the valve. Also, cut-off valves of the type described can be placed at intervals in the main line for the same purpose.

The connection between the main line and the feed lines is most conveniently made through a manifold as indicated in FIGURE 1 of the drawing. Any type of manifold adaptable to high pressure usage can be employed. Alternately, the connection between the main line and feed line can be through a series of junctures or in any other conventional manner.

Although the invention has been described in considerable detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that many modifications can be made without departing from the spirit and scope of the invention.

What is claimed is:

l. A system for discharging a plurality of compressed gas blasting cartridges in a predetermined order comprising a main high pressure fluid line extending from a source of compressed gas to a point proximate the work face to be broken down, amanually controlled valve in the main line, a plurality of blasting cartridges positioned in the work face and being provided with mechanisms to release a charge of compressed gas at predetermined discharge pressures, each of said cartridges having a dilferent discharge pressure, a manifold connected to said main line proximate the work face, a feed line extending from each cartridge and connected to the main line through said manifold, a pressure actuated cut-off valve in each feed line except one, each cut-off valve being positioned between the release mechanism of a cartridge and said manifold, means in each pressure responsive cutoff valve being adapted to allow the simultaneous charging of the cylinders and to stop the flow of air through lines after the cartridges have been discharged.

References Cited in the file of this patent UNITED STATES PATENTS 2,146,879 Armstrong Feb. 14, 1939 2,403,689 Sprague July 9, 1946 2,633,147 Badami Mar. 31, 1953 2,710,626 Burdick et al June 14, 1955 2,858,764 Hesson et al Nov. 4, 1958 2,867,426 Dowie Jan. 6, 1959 3,041,969 Filstrup July 3, 1962

Claims (1)

1. A SYSTEM FOR DISCHARGING A PLURALITY OF COMPRESSED GAS BLASTING CARTRIDGES IN A PREDETERMINED ORDER COMPRISING A MAIN HIGH PRESSURE FLUID LINE EXTENDING FROM A SOURCE OF COMPRESSED GAS TO A POINT PROXIMATE THE WORK FACE TO BE BROKEN DOWN, A MANUALLY CONTROLLED VALVE IN THE MAIN LINE, A PLURALITY OF BLASTING CARTRIDGES POSITIONED IN THE WORK FACE AND BEING PROVIDED WITH MECHANISMS TO RELEASE A CHARGE OF COMPRESSED GAS AT PREDETERMINED DISCHARGE PRESSURES, EACH OF SAID CARTRIDGES HAVING A DIFFERENT DISCHARGE PRESSURE, A MANIFOLD CONNECTED TO SAID MAIN LINE PROXIMATE THE WORK FACE, A FEED LINE EXTENDING FROM EACH CARTRIDGE AND CONNECTED TO THE MAIN LINE THROUGH SAID MANIFOLD, A PRESSURE ACTUATED CUT-OFF VALVE IN EACH FEED LINE EXCEPT ONE, EACH CUT-OFF VALVE BEING POSITIONED BETWEEN THE RELEASE MECHANISM OF A CARTRIDGE AND SAID MANIFOLD, MEANS IN EACH PRESSURE RESPONSIVE CUTOFF VALVE BEING ADAPTED TO ALLOW THE SIMULTANEOUS CHARGING OF THE CYLINDERS AND TO STOP THE FLOW OF AIR THROUGH THE CORRESPONDING FEED LINE WHEN THE CARTRIDGE ATTACHED THERETO IS DISCHARGED.

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