US3307445A

US3307445A - Borehole blasting device

Info

Publication number: US3307445A
Application number: US423784A
Authority: US
Inventors: Stadler Hans; Gawlick Heinz; Stahlmann Rudolf; Umbach Hans
Original assignee: Dynamit Nobel AG
Current assignee: Dynamit Nobel AG
Priority date: 1964-01-11
Filing date: 1965-01-06
Publication date: 1967-03-07
Anticipated expiration: 1984-03-07
Also published as: FR1420118A; SE309741B; DE1195696B; GB1084942A; BE658111A; NL6500191A

Description

March 7, 1967 H. STADLER ET AL BOREHOLE BLASTING DEVICE Filed Jan. 6, 1965 FIG. 2

FIG 3 INVENTORS HANS STADLER HEINZ GAWLICK RUDOLF STAHLMANN HANS UMBACH 0M ATTQR NEY United States Patent OfiFice 3,307,445 BQREHGLE BLASTING DEVICE Hans Stadler, Nurnberg, Heinz Gav/lick and Rudolf Stahlmann, Forth, Bavaria, and Hans Umbach, Staileln uber Nurnberg, Germany, assignors to Dynamit Nobel Alrtiengesellschaft, Troisdorf, Germany Fiied Jan. 6, 1965, S61. No. 423,784 Claims priority, application Germany, Jan. 11, 1964, D 43,329 20 Claims. (Cl. 86-20) The present invention relates to an installation for water-injection firing or blasting, and more particularly to improvements in the blast cartridge used with waterinjection blasting operations.

A blasting method utilized since a few years, above all for the mining of coal, is the so-called injection firing or blasting (as described in the Nobel-Heft 1960, page 128d and page 220d). This method is based on the fact that at first the charge is introduced into the borehole and thereupon water is pressed into the same with the aid of an injection hose. The firing or blasting takes place while maintaining the water pressure. The injection hose is expanded by the water pressure and abuts sealingly against the bore walls. The advantage of this method resides especially in the fact that with coal the proportion of lump coal is increased, the coal is not thrown so far which is important for the protection of the firing or blasting personnel, and the dust and cloud gas or smoke formation produced by the blast is reduced. Of course, this method may also be used with other types of rocks or stone formations other than coal.

The water-injection blasting is comprised of the following steps: Boring of a borehole, introduction of the hosed cartridge, insertion of the ignition cartridge, introduction of the water-injection hose, supply of water under pressure and blasting or firing. However, the blasting or firing should be carried out only when the firing foreman has determined at a manometer that the required water pressure is present.

The difficulties which had to be overcome in the realization of this method resided to a lesser extent in the construction of the water hose but rather in the blast cartridge. Completely satisfactory results could be achieved only when explosives had been developed that are insensitive to water pressure. However, also with these explosives, completely satisfactory ignitions could be achieved only When the cartridges were in natural contact. The cartridges could not be separated thereby from one another by washed-in or silted-up particles to assure proper operation.

The aim of the present invention is the creation of a blasting apparatus by means of which the injection blasting can be carried out in a considerably more simple and more safe manner. The present invention essentially consists in that the blast charge together with the ignition means thereof is constructed in the manner of a cartridge and is attached directly as head at a water-injection probe. A single, unitary apparatus now takes the place of the separate parts consisting of water hose, blast charge, ignition charge, and ignition device. It is only necessary for purposes of blasting to bore the blast bore, to introduce the probe together with its blast-head and to apply the water pressure to the injection probe. The difiiculties of the installation of the blast charge and the correct packing thereof in the blast-hole and the installation of the ignition charge are obviated by the present invention. The blast charge has in every case a shape and form by means of which, in contrast to the use of several individual cartridges, a safe ignition is assured. The size of the attached head containing the blast charge depends on the powder quantity necessitated for the blasting operation, and there- 3,37,445 Patented Mar. 7, 1967 fore can be chosen at will without having to change anything in the apparatus.

Experiments carried out with the novel probe of the present invention have demonstrated surprisingly that practically no damages occur at the probe and at the securing supporting parts for the cartridge but that instead these damages are limited to easily interchangeable parts appertaining to the cartridge so that the costs for each blasting operation are not increased by replacement parts for the probe.

An essential characteristic of the injection blasting method according to the present invention is the fact that it does not release a blast effect, properly speaking, but instead a pushing or sliding effect. Consequently, the blast charge which is more properly designated as propellant charge, is a slowly burning explosive, for example, nitrocellulose powder that is assembled in the cartridge in loose packing. It is only necessary that the propellant charge does not burn little by little but instead completely simultaneously as much as possible. This can be achieved in accordance with the present invention by the application of a guide-duct-ignition. A tubular pipe member, for example of cardboard, is extended longitudinally of the propellant charge which is operatively connected to the rear of a booster charge which, in turn, is ignited by an ignition device or fuse. The ignition jet of the booster charge guided through the guide duct or pipe ignites the propellant charge instantaneously over the entire length thereof.

Appropriately the bottom piece of the cartridge and/or the support part thereof are so constructed that the fuse or ignition device can be installed only shortly prior to the firing or blasting operation so that cartridge and fuse can be stored separately. The cartridge case is made appropriately of conventional plastic material, especially of polyethylene. It has been found that the case is not burned out or consumed.

According to a further development of the present invention, the bottom piece of the cartridge, into which the ignition device or fuse is inserted, is also made of plastic material. Since the booster charge is assembled or installed into a channel of the bottom piece, it might happen that the bottom piece is deformed by the pressure produced during the ignition. This may be prevented if according to a special construction of the present invention, a metallic cylinder is inserted into the bottom piece which absorbs the pressure and keeps the same away from the parts of plastic material.

With longer cartridges for the propellant charge, it may be appropriate to subdivide the propellant charge cartridge case. The parts are clamped together by a frictionforrn-locking connection. In order to facilitate with subdivide-d cases the introduction of the guide duct for the ignition jet of the booster charge, the case parts may be separated from one another by intermediate bottoms with cylindrical projection for the emplacement of the pipe sections of the guide duct ignition.

As already pointed out above, the firing or blasting foreman should release the ignition of the propellant charge only when a sufiiciently high water pressure is present. The correct carrying out of the blasting operation is therefore subjected to his attentiveness. This may under certain circumstances lead to human errors. In order to exclude possibilities of this type, according to a further feature of the present invention, a switch-manometer is connected into the ignition current circuit of the electric ignition which permits a transmission of a firing or blasting command signal only when the prescribed or intended water pressure is present. For the realization of such types of switching manometers, numerous possibilities exist in the prior art so that a detailed description thereof is dispensed with herein. In its simplest form such a switching manometer has the form of a membrane or diaphragm capsule expandable by pressure which closes a contact in the ignition circuit only in the presence of a predetermined pressure.

Accordingly, it is an object of the present invention to provide an apparatus for water-injection blasting which eliminates by simple means the aforementioned shortcomings encountered with the prior art constructions.

Another object of the present invention resides in the provision of a unitary water-injection blasting apparatus that not only facilitates the firing operation but also increases the safety and reliability of operation thereof.

Another object of the present invention resides, for blasting equipment with water injection, in the provision of a unitary probe containing one propellant charge, ignition device, and water supply means which obviates the need for numerous separate parts, facilitates greatly the installation of the necessary element in the borehole and enhances the firing safety.

Still another object of the present invention resides in the provision of a blasting equipment of the type described above which obviates the need for separately installing the blast charge in the borehole and eliminates the necessity for high degree of correct packing thereof.

A further object of the present invention resides in the provision of a water-injection blasting apparatus that permits the selection, at will, of the proper quantity of eX- plosives as needed for the particular blasting operation without having to change in any way the apparatus, properly speaking.

A still further object of the present invention resides in the provision of a blasting apparatus of the type described above which etfectively minimizes the costs by the absence of replacement of costly parts for the probe.

Still another object of the present invention resides in the provision of a probe assembly containing the blast charges which is so constructed and arranged as to assure a substantially simultaneous burning of the entire propellant charge.

A further object of the present invention resides in the provision of a blasting apparatus of the type described above which automatically controls the blasting in de pendence on the presence of a predetermined water pressure thereby eliminating human errors.

These and further objects, features, and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing which shows, for purposes of iilustration only, two embodiments in accordance with the present invention, and wherein:

FIGURE 1 is an elevational view, partly in cross section, of a water-injection probe with attached cartridge of a blast equipment in accordance with the present invention.

FIGURE 2 is a partial cross sectional view through a sub-divided cartridge case in accordance with the present invention, and

FIGURE 3 is a partial cross-sectional view, on an enlarged scale, through a modified embodiment of a bottom piece of the cartridge in accordance with the present invention.

Referring now to the drawing wherein like reference numerals are used throughout the various views to designate like parts, reference numeral 1 generally designates in FIGURE 1 the water-injection probe which essentially consists of the connecting piece generally designated by reference 2 for the pressurized water, of the expanding hose 3, of the connecting sleeves 4, of the pressurized water discharge-head 5, and of the propellant charge cartridge generally designated by reference numeral 6. The supply line for the water under pressure is connected to the nipple 7. As a result of the supply of water under pressure the hose 3 is expanded so that it abuts sealingly against the walls of the blast bore. Additionally, water under pressure is discharged through the head 5 and fills 4- the borehole about the cartridge 6 as well as possibly present gaps and crevices in the stone or rock formation within the vicinity of the cartridge. The propellant pressure of the cartridge 6 is thus transmitted by way of the pressurized water to the rock formation, especially to the coal.

The cartridge 6 consists of a case 7, which is made appropriately of polyethylene, and of a unitary bottom piece 8 connected therewith, through which extends a channel 9. The case 7 is filled with a powder charge 10 serving as propellant charge. A tubular member or pip 11 extends through the powder charge 10. The tubular pipe member 11 is supported at 12 on a projection of the bottom piece 8. The channel 9 is filled with a booster charge 30. The bottom piece 8 is further provided with claw-like projections 14 for forming a bayonet-type closure device. The cartridge 6 is connected with the probe 1 by threadably connected intermediate piece 15, and more particularly by way of a case or sleeve 16 which is provided with apertures or recesses corresponding to the claws 14 so that it can be placed over the claws 14 and then rotated until it extends with the surfaces 17 over the bottom piece 8. The case 16 has a thread 13 to which is coordinated a counter-thread at the intermediate piece 15. By tightening the threaded connection the bottom piece 8 is securely clamped against the surface 19. A ring 20 of any suitable material is inserted as a precautionary measure to provide a proper seal. An electric ignition means 21 of conventional construction is inserted additionally into the intermediate piece 15.

The case 7 is assumed to be of two-partite construction in the illustrated embodiment. The two parts thereof are connected with one another at 22 by a form-lockingforce-locking connection.

If the cartridge is ignited after the blast foreman has determined the presence of the required water pressure, or after the manometer switch closes the ignition circuit, then at first the booster charge 30 is ignited whose ignition jet ignites with the least time delay the propellant charge It) over the entire length of the tubular member 11.

A special measure is illustrated in FIGURE 2 in con junction with the subdivision of the case at 22. The lower case part 7a is initially filled with propellant charge. Then a disc 23 is inserted which is provided on both sides thereof with a tubular extension 24. The pipe or tubular member 11 is subdivided into the two parts 11a and 11b. The disc 23 initially holds the pipe section 11a. Thereupon the second case part 7b is emplaced and the pipe section 11b is introduced into the extension 24.

In the illustrated embodiment of FIGURE 1, the case 7 and the bottom piece 8 are made in one piece. FIG- URE 3 illustrates a modified embodiment in which the bottom piece and case are separate parts.

The bottom piece generally designated by reference numeral 25 in FIGURE 3 and provided with the claws 14 is made of plastic material and passes over into a collar portion 26 into which is inserted the case 7 with form-locking and force-locking connection, as illustrated in FIGURES l and 2 at 22. Additionally, a conically tapered annular groove 27 is formed into the bottom piece 25 into which is clampingly or wedgingly introduced the end of the case 7. Reference numeral 28 designates a recess serving for the accommodation of conventional ignition means. It may be readily recognized from both FIGURES 1 and 3 that the ignition means is not a fixed component part of the cartridge but instead that the bottom piece and the connection with the probe are so constructed that the ignition means can be inserted only shortly prior to the blasting operation. A bottom piece 25 made of plastic material might be deformed under certain circumstances by the pressure stemming from the ignited booster charge. In order to avoid such deformation, a metallic pipe 29 is inserted into the bottom piece 25 in accordance with the present invention, which is filled with booster charge 30 corresponding to the channel 9 of FIGURE 1.

. Otherwise the construction of the cartridge of FIGURE 3 is in principle the same as in FIGURE 1.

While we have shown and described several embodiments in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to a person skilled in the art and we therefore do not wish to be limited to the details shown and described herein but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.

We claim: 1. A blasting apparatus, comprising: probe means operable to be inserted into a borehole and including means radially expandable against the side walls of the borehole for closing the rearward portion of the borehole to form a forward sealed chamber, said probe means being operable to inject a liquid under pressure into the forward sealed chamber of the borehole, a cartridge containing propellant charge means and ignition means, connection means operatively connecting said cartridge to the forward end of said probe means to constitute a head portion for said probe means.

2. A blasting apparatus, comprising:

probe means operable to be inserted into a borehole for closing the rearward portion of the borehole to form a forward sealed chamber, said probe means being operable to inject a liquid under pressure into the forward sealed chamber of the borehole, a cartridge containing propellant charge means and ignition means, connection means operatively connecting said cartridge to the forward end of said probe means to constitute a head portion for said probe means, said propellant charge means being a slowly burning explosive assembled into said cartridge case in loose packing, said probe means including a radially expandable hose means operable to expand into sealing engagement with the sides of the borehole when conducting the liquid under pressure.

3. A blasting apparatus according to claim 2, wherein said slowly burning explosive essentially consists of nitrocellulose powder.

4. A blasting apparatus, according to claim 1, wherein said ignition means includes open flame conducting ignition duct means extending longitudinally through the propellant charge means, booster charge means outside of and aligned with said duct means operable to fire into said duct means for igniting said propellant charge, and independent means for igniting said booster charge means.

5. A blasting apparatus, according to claim 1, wherein said cartridge case consists essentially of plastic material.

6. A blasting apparatus, comprising:

probe means operable to be inserted into a borehole for closing the rearward portion of the borehole to form a forward sealed chamber, said probe means being operable to inject a liquid under pressure into the forward sealed chamber of the borehole, a cartridge containing propellant charge means and ignition means, connection means operatively connecting said cartridge to the forward end of said probe means to constitute a head portion for said probe means, said cartridge case consisting essentially of polyethylene plastic material, said probe means including a radially expanding hose means operable to expand into sealing engagement with the sides of the borehole when conducting the liquid under pressure.

7. A blasting apparatus, according to claim 1, wherein said cartridge has a bottom piece and said ignition means includes an electric ignition device adapted to be inserted into said bottom piece prior to the firing.

8. A blasting apparatus, according to claim 2, wherein said ignition means includes open flame conducting ignition duct means extending longitudinally through the pro- 6. pellant charge means, booster charge means at the side of and aligned with said duct means operable to fire into said duct means for igniting said propellant charge, and independent means for igniting said booster charge means, the cartridge case consisting essentially of plastic material.

9. A blasting apparatus, according to claim 1, wherein said cartridge has a multi-partite construction including a plurality of case container parts, each filled with said propellant charge means, and form-locking and forcelocking connecting means operatively connecting together said plurality of parts.

10. A blasting apparatus, comprising: probe means adapted to be inserted into a borehole for injecting liquid under pressure into the borehole,

and means in the form of a cartridge structure including case means, propellant charge means, booster charge means and ignition means, said cartridge structure being attached to said probe means as head portion thereof,

said ignition means including rnuiti-partite ignition guide duct means so arranged that the ignition jet duct extends substantially through the propellant charge means from the booster charge means,

said cartridge case means being of multi-partite construction, and form-locking and force-locking connecting means operatively connecting together the several parts of said casing means, and intermediate disc means at the separating place of two adjoining case parts having pipe-like extensions for the emplacement of the tubular sections of said multipartite tubular guide duct means.

11. A blasting apparatus, according to claim 1, wherein:

said cartridge includes bottom means essentially consisting of plastic material, an ignition channel containing a booster charge means, and metallic bushing means inserted into said channel.

12. A blasting apparatus, according to claim 1, wherein:

said connection means includes bayonet-type connecting means and threaded clamping means for clamping said bayonet-type connecting means.

13. A blasting apparatus, according to claim 1, wherein:

said ignition means includes an electric ignition circuit,

and switching manometer means in said circuit includes means for closing said circuit only in the presence of a predetermined pressure of said liquid.

14. A blasting apparatus, according to claim 11, wherein:

said cartridge case essentially consists of plastic material,

said connection means including bayonet-type connecting means and threaded clamping means for clamping said bayonet-type connecting means.

15. A blasting apparatus, according to claim 13, wherein said cartridge has a bottom piece and said ignition means includes an electric ignition device adapted to be inserted into said bottom piece prior to the firing.

16. A blasting apparatus, according to claim 15, wherein:

said cartridge essentially consists of plastic material,

said cartridge including bottom means essential-1y consisting of plastic material, an ignition channel containing a booster charge means, and metallic bushing means inserted into said channel for reinforcing the structure.

17. A blasting apparatus, comprising:

probe means adapted to be inserted into a borehole for injecting liquid under pressure into the borehole, and means in the form of a cartridge structure including case means, propellant charge means, booster charge means and ignition means, said cartridge structure being attached to said probe means as head portion thereof,

said propellant charge means slowly burning explosive,

said ignition means including multi-partite ignition guide duct means so arranged that the ignition jet duct extends substantially through the propellant charge means from the booster charge means,

and means threadably mounting the cartridge structure With the parts thereof onto the probe structure,

said ignition means being an electric ignition device adapted to be inserted into the bottom means of the cartridge prior to the firing,

said cartridge case means being of multi-partite construction, and form-locking and force-locking connection means operatively connecting together the several parts of said casing means, and intermediate disc means at the separating place of two adjoining case parts having pipe-like'extensions for the emplacement of the tubular sections of said multi-partite tubular guide duct means, i

said ignition means including an electric ignition circuit, and switching manometer means in said circuit including means for closing said circuit only in the presence of a predetermined pressure of said liquid.

18. A blasting apparatus, comprising:

probe means adapted to be inserted into a borehole for injecting liquid under pressure into the borehole,

and means in the form of a cartridge structure including case means, bottom means, propellant charge means, booster charge means and ignition means, said cartridge structure being attached to said probe means as head portion thereof,

said ignition means including multi-partite ignition guide duct means so arranged that the iginition jet duct extends substantially through the propellant charge means from the booster charge means,

the cartridge case means essentially consisting of plastic material, 7

said cartridge case means being of multi-partite construction, and form-locking and force-locking connecting means operatively connecting together the several parts of said casing means, and intermediate disc means at the separating place of two adjoining case parts having pipe-like extensions for the emplacement of the tubular sections of said multi-partite tubular guide duct means,

said bottom means essentially consisting of plastic material and being provided with an ignition channel, and metallic bushing means inserted into said channel for reinforcing the structure.

19, A blasting apparatus, comprising: probe means adapted to be inserted into a borehole for injecting liquid under pressure into the borehole, and means in the form of a cartridge structure including case means, bottom means, propellant charge means, booster charge means and ignition means, said cartridge structure being attached to said probe means as head portion thereof,

being constituted by a said propellant charge means being constituted by a slowly burning explosive,

thecartridge case means essentially consisting of plastic material,

said cartridge case means being of multi-partite construction, and form-locking and force-locking connecting means operatively connecting together the several parts of said casing means, and intermediate disc means at the separating place of two adjoining case parts having pipe-like extensions for the emplacement of the tubular sections of said multipartite tubular guide duct means,

said bottom means essentially consisting of plastic material and being provided with an ignition channel, and metallic bushing means inserted into said channel for reinforcing the structure,

20. A blasting apparatus, according to claim 1, wherein said connection means includes sealing gasket means forming a fluid tight connection between said cartridge and said probe means, and said probe means injecting the liquid into the bore hole rearwardly of said cartridge.

References Cited by the Examiner OTHER REFERENCES Military Explosives, Department of the Army Technical Manual, 1955, pp. 132-3. BENJAMIN A. BORCHELT, Primal Examiner.

55 R. v. LOTTMANN,P. A. SHANLEY,

Assistant Examiners.

Claims

1. A BLASTING APPARATUS, COMPRISING: PROBE MEANS OPERABLE TO BE INSERTED INTO A BOREHOLE AND INCLUDING MEANS RADIALLY EXPANDABLE AGAINST THE SIDE WALLS OF THE BOREHOLE FOR CLOSING THE REARWARD PORTION OF THE BOREHOLE TO FORM A FORWARD SEALED CHAMBER, SAID PROBE MEANS BEING OPERABLE TO INJECT A LIQUID UNDER PRESSURE INTO THE FORWARD SEALED CHAMBER OF THE BOREHOLE, A CARTRIDGE CONTAINING PROPELLANT CHARGE MEANS AND IGNITION MEANS, CONNECTION MEANS OPERATIVELY CONNECTING SAID CARTRIDGE TO THE FORWARD END OF SAID PROBE MEANS TO CONSTITUTE A HEAD PORTION FOR SAID PROBE MEANS.