US3683742A

US3683742A - Process and apparatus for the production of a fuse

Info

Publication number: US3683742A
Application number: US33684A
Authority: US
Inventors: Wilhelm Rohde; Werner Helfgen
Original assignee: Dynamit Nobel AG
Current assignee: Dynamit Nobel AG
Priority date: 1969-05-02
Filing date: 1970-05-01
Publication date: 1972-08-15
Anticipated expiration: 1989-08-15
Also published as: DE1922374A1; DE1922374C3; ZA702959B; FR2047205A5; DE1922374B2; NL7005118A; GB1267132A; CH544046A; AT296119B; BE749744A

Abstract

The present disclosure is directed to a method and apparatus for manufacturing a fuse containing a very fine, dust-like explosive wherein at least one thread is guided through the explosive to facilitate the introduction of said explosive into the fuse casing.

Description

United States Patent Rohde et al.

[ 1 Aug. 15, 1972 PROCESS AND APPARATUS FOR THE PRODUCTION OF A FUSE Inventors: Wilhelm Rohde; Werner Helfgen,

both of Troisdorf, Germany Dynamit Nobel AG, Troisdorf, Germany Filed: May 1, 1970 Appl. No.: 33,684

Assignee:

Foreign Application Priority Data May 2, 1969 Germany ..P 19 22 374.6

US. Cl. ..86/] R Int. Cl. ..F42b 33/10, C06c 5/08 Field of Search ..86/ 1; 102/27 [56] References Cited UNITED STATES PATENTS 1,705,360 3/ 1929 Fritzsche ..102/27 R 3,155,038 11/1964 Smith 102/27 R 3,435,764 4/ 1969 Kelly et al. ..102/27 R Primary Examiner-Benjmain A. Borchelt Assistant Examiner-J. J. Devitt Attorney-Craig, Antonelli and Hill [57] ABSTRACT The present disclosure is directed to a method and apparatus for manufacturing a fuse containing a very fine, dust-like explosive wherein at least one thread is guided through the explosive to facilitate the introduction of said explosive into the fuse casing.

25 Claims, 2 Drawing Figures PATENTEDAUB 15 I972 3.683, 742

FIGI

FIG. 2

INVENTORS WILHELM ROHDE WERNER HELFGEN ATTORNEYS PROCESS AND APPARATUS FOR THE PRODUCTION OF A FUSE BACKGROUND OF THE INVENTION The present invention relates to a process and apparatus for the manufacture of a fuse with a very finegranular or powdery explosive.

Fuses, as is well known, are used for the communication of detonations to far removed detonable systems. These fuses exhibit, in a sheath, or so-called casing, a continuous explosive core for propagating the initiating pulse. Depending on the type of the explosive employed and its compression (compacting), a corresponding propagation velocity of the initiating pulse can be obtained. The reliability with which the detonation is completed depends, among other things, on the grain diameter and the amount of the explosive employed, as well as on the diameter of the fuse. Furthermore, the type and construction of the casing of the explosive core are of importance for the advantageous utilization of the explosive properties of the charge.

It has been known for a long time to employ fuses containing explosive trinitrotoluene and a lead pipe as the casing. In the manufacture of said fuses, the explosive-filled lead pipe, which initially exhibits a relatively large diameter, is successively drawn through a number of drawing dies of respectively decreasing inside cross sections, until finally, with a corresponding elongation, the desired small diameter of the detonating fuse is obtained. However, this process is associated with various disadvantages, for example, the high weight of the lead pipe, and the brittleness of said pipe at low temperatures. This results in breakage, and a discontinuous production of fuses of limited length.

Also, another process for producing a fuse having a reduced explosive content, wherein the explosive is surrounded with a compact casing of a thermoplastic synthetic material, exhibits considerable disadvantages. In this conventional process, there are many moments of danger during the manufacture of the fuse, since the explosive is introduced directly behind an annular die into the still hot plastic hose extruded continuously from the die.

After desensitized mercury fulminate, penthrite, Hexogen (Cyclonite), and similar explosives became popular for fuse manufacture, the practice was altered to surrounding a granular explosive core with spun textile and/or natural and/or synthetic fibers. In this process, the explosive is introduced from a feeding funnel into a thin strip of paper, synthetic material, or other suitable substances which is continuously wound in a helically overlapping fashion at the lower end of the feeding funnel. This explosive-filled strip is then helically surrounded by various layers of wound or spun textile threads twined from fibers, or like materials. Depending on what is desired or required, particularly with respect to moisture protection, the thus-obtained fuse can then additionally be provided with a coating of varnish, thermoplastic synthetic material, or the like. For protection against mechanical damage, the fuse may optionally also be provided with a widemesh spun envelope of metallic wires.

However, in addition to the quality of the casing, the type and shape of the explosive employed plays an essential part in connection with the quality of the fuse from the viewpoint of explosive technique, and the reliability of complete detonation of the fuse.

In the manufacture of the fuses with continuously woven sheaths, the central problem of a unifonn introduction of the explosive into the sheaths presents itself. In these woven (knitted, cloth-type) fuses, pentaerythritol tetranitrate (penthrite) is usually employed as the explosive, but other high explosives are also usable, such as Hexogen (trimethylene trinitramine), mannitol hexanitrate, and similar substances. In case the explosive is present in a granular shape, a satisfactory fluidity and thus a uniform introduction of the explosive into the sheath are ensured. However, in case of an extremely small granular size of the explosive, i.e., in dust form, for example, when about percent of the powder exhibits a grain diameter of smaller than about 0.1 mm., the uniform flow of the explosive, which is so important for ensuring a reliable complete detonation is no longer achieved, since the fluidity of the explosive is insufficient. An irregularly filled fuse results in fluctuating detonating velocities and also in an interruption of the detonation itself.

On the other hand, it is known that a fuse having a core of an explosive in an extremely fine, dust-like phase, for example extremely fine penthrite, is superior, with respect to explosive (detonating) quality and with respect to reliable and complete detonation when compared to an explosive core composed of a granular, fluid explosive, since the former exhibits more satisfactory detonating propagation properties.

Various methods are known, wherein dust-like explosive, for example, penthrite, are introduced into a preformed sheath. One method resides in introducing dust-like penthrite in the form of a slurry, or by flushing, and another method consists in trickling (flowing) granular penthrite dust into the sheath. However, these methods require additional complicated operating steps during the manufacturing process. In the slurry method, the explosive dust is moistened and flushed into the sheath of the fuse in a wet condition. After the crude fuse has been produced, it is dried. Thus, two time-consuming, complicated operating steps are involved. When using extremely fine penthrite, in granular form, a granulating process with all secondary operating steps must first be conducted for the dustlike explosive. In this manner, a fluid, granular penthrite dust is obtained. This method is likewise expensive and complicated.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved process and apparatus for producing a fuse containing a very fine powdery explosive.

Another object of the present invention is to provide a process and apparatus for forming an explosive core for a fuse, made of a very fine-grained or dust'like, dry explosive, for example pentaerythritol tetranitrate (extremely fine penthrite) or extremely fine hexogen. The explosive is enclosed is a spun or braided sheath.

A further object of the present invention is to provide an improved process and apparatus for producing a fuse which substantially eliminates the uncertainties inherent in the use of fuses containing granular explosives.

Still another object of the present invention is to provide an improved process and apparatus for the manufacture of a detonating fuse which uses an explosive which does not exhibit any fluidity in its solid phase.

Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

The present invention is directed to a process and apparatus for the manufacture of a fuse having a very fine-grained or dust-like explosive, wherein the explosive is introduced from a filling funnel into a sheath continuously manufactured at the lower end of the funnel. According to the present invention, at least one thread, deflected from the vertical axis of the feeding funnel (feed hopper) is guided through the feeding funnel preferably in a circular direction and continuously introduced into the sheath at the end of the feeding funnel, together with the explosive. Because of the constant motion of the thread running through the feeding funnel, eccentric with respect to the vertical axis, the cone of explosive is continuously cut, and the explosive dust can be uniformly fed through the funnel due to its inherent weight. In this manner, it is possible for the first time to employ very fine-grained and dust-like explosive, such as penthrite, which is extremely fine, in its natural, dry form, without any preliminary and/or post treatment, for the formation of a uniform explosive core. By means of the process and apparatus of the present invention, any desired amount of charge, i.e., explosive weight per 1 meter of fuse, as required by the blasting operation, can be provided. The process and apparatus of the present invention is suitable for the manufacture of low-energy fuses, used, for example, as detonating fuses for base detonation or in areas endangered by firedamp, with charge amounts of 3 g./m. and, in special cases, of less than 1 g./m. In these cases, a dust-like explosive, such as extremely fine penthrite, is the only substance which ensures a reliable complete detonation of very weak explosive cores, which are required, for example, for the prevention of lateral detonation propagations.

Heavy-weight charges of the explosive core can also be advantageously produced by the process of the present invention. By the use of the threads, a uniform introduction and a uniform distribution of the explosive in the explosive core are ensured. Thus, in addition to using minor amounts of charge of 1 g. per meter of fuse, large amounts of charge, up to above about 100 g. per meter of fuse can be realized. Of course, the process of the present invention, developed specifically for the introduction of very fine-grained explosive material into a fuse can also be employed in connection with more granular explosives, since the present process also promotes the uniform flow of the explosive particles into the fuse in these explosives, particularly in case of high loading (charge) weights of the fuse.

According to the present invention, it is possible, by the use of dust-like explosive, to produce fuses having a substantially reduced explosive content as compared to fuses utilizing granular, fluid explosive contents, whereby substantial savings in explosive can be achieved. It is thus possible to reduce the weight of the explosive in the explosive core up to about 25 or 30 percent, as compared with the previously conventional fuses utilizing granular, fluid explosive. This is because the dust-like explosive, in connection with such cross sections of the explosive core, will still reliably propagate the detonation completely in those cases where a granular explosive is not able to provide such a complete propagation. Thus, with a reduction in the amount of explosive employed, a more favorable manufacturing expense can be obtained in the production of the explosive fuse.

One example of the thread guidance according to the present invention is that at least one thread is circularly guided within the feeding funnel at a short distance from the wall of the feeding funnel, so that the cone of explosive present in the feeding funnel continually is being cut close to its periphery.

The principle developed by the present invention is based on the use of one or several threads playing the part of a conveying means. This is effected, according to a further feature of the invention, by roughening the thread surface, so that the thread, during its passage through the dry, dust-like explosive, entrains a certain amount of the explosive. In this manner, the explosive is conducted into the sheath. One property of the thread which facilitates the entrainment of the explosive dust is to provide the thread with a suitable surface characteristic, i.e., a surface which is more or less roughened, and possesses a concomitant sufficient tensile strength, so that the dust particles adhere to the thread.

According to another feature of the present invention, the thread can be drawn off from the storage reel under tension. Also, the thread can be made to vibrate. This is possible, for example, by the selection of a suitable tension for the thread. The vibration of the thread, during passage through the funnel filled with explosive dust, sets a certain amount of explosive in motion, depending on the thickness of the thread, the surface characteristics thereof, and the intensity of the vibration, such that the formation of an explosive core about the thread in a uniform fashion is promoted.

The motion of the thread in the funnel filled with explosive can be effected in various ways. One possibility resides in guiding the thread on the circumference of a disk provided between the storage reel and the upper opening of the feeding funnel. One embodiment of the present invention provides that the thread is clamped to the circumference of the disk, or is guided in an eyelet or a similar means, and is set into motion by the rotation of the disk. However, it is just as effective to have the thread rotate about a stationary disk disposed between the storage reel and the upper opening of the feeding funnel. However, it is likewise possible to set the thread into circular motion by means of a cam gear. Also, a reciprocatory motion of the disk arranged between the storage reel and the upper opening of the feeding funnel in the vertical direction promotes the uniform feeding of the explosive. This motion can be superimposed, for example, by a circular motion of the thread.

Another embodiment of the process of the present invention suggests setting the thread into circular motion by pulling the thread off from a vertically arranged yarn reel (spool) and superimposing on this motion a second motion, preferably circular, by moving the yarn reel holder of the yarn reel.

The threads which can be employed are generally twisted from short fibers, such as for example synthetic fibers, natural fibers, or mixtures of natural and synthetic fibers. Thus, the synthetic fibers can be mixed with cell wool, wool, flax, and the like.

DESCRIPTION OF THE DRAWINGS The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only and thus are not limitative of the present invention and wherein,

FIG. 1 shows a schematic structure illustrating a process for producing a detonating fuse; and

FIG. 2 shows a modification of the process of the present invention with a superimposed motion of the thread.

DESCRIPTION OF THE PREFERRED EMBODIMENT The manufacture of a fuse with an explosive core of a dust-like explosive, for example pentrhite, wherein 80 percent of the explosive exhibits a grain diameter of smaller than about 0.l mm. and thus no longer possess fluidity, is conducted on the schematically shown spinning apparatus. The hose 9 of said apparatus is made of natural and/or synthetic fibers which is continuously woven and envelopes the explosive core 8.

The dust-like penthrite 1 is contained in a funnel 2 disposed above the spinning plane 7 of the device. Above the funnel 2, the rotating circular disk 5 is provided, the thread 4 being guided over the rim thereof in such a manner that it passes a short distance, for example, only about a few millimeters, from the inner wall of the funnel and extends out of the lower end of the funnel. The storage reel of the thread 4 is attached, in the illustrated example, on the rotating disk 5 by means of the reel holder 6. In this manner, it is ensured that the thread 4 executes a circular motion, and cuts the cone of explosive l in the funnel 2 continuously at its periphery so that the explosive dust can be continuously uniformly replenished, due to its inherent weight. The thread 4 is guided, between the reel holder 6 and the explosive core 8 surrounded by the hose 9, over the circumference of the disk 5 in such a manner that it is under such tension that it is set into slight vibration during the circular guiding procedure. By using this system, it is ensured that the thread 4 entrains a constantly uniform amount of penthrite dust from the funnel 2. Upon exiting from the lower end of the funnel 2, the explosive core (thread 4 plus penthrite) is surrounded by a film strip 3 of paper, a synthetic material, or another suitable material. This can be achieved by winding at least one of said materials around the core.

Depending on the requirements to be met by the detonating fuse, complete freedom can be used in surrounding the fuse core, produced according to the present process, with an explosive core of a very finegrained or dust-like explosive, and with additional external casings of all types.

In the process of the present invention, other devices, for example, cam gears or similar means, can also be used, by means of which the thread 4 can be guided within the funnel 2 in the desired manner.

FIG. 2 shows a variation of the process of the present invention for the production of a fuse with an explosive core of a dry, very fine-granular or dust-like explosive, operating with refined methods. Two or more arms 11 utilized for receiving the yarn reels 10 are provided in substantially vertical alignment at the reel holder 6, said reel holder being mounted so that it rotates about its longitudinal axis. By drawing the thread 4 ofi the yarn reels l0, movably disposed on the arms 11 of the reel holder 6, the thread 4 executes a circular motion about the disk 5 which is connected in a fixed manner with the reel holder 6 and is disposed between the lower end of the yarn reel 10 and the feeding funnel 2. In addition to this motion of the thread 4, another circular motion is superimposed by a slow rotation of the reel holder 6 about its longitudinal axis. In this manner, the continuous, uniform cutting of the cone of explosive l by the threads 4 is ensured, and detonating fuses of any desired amount of charge, i.e., weight of explosive per meter of fuse, can be manufactured.

Any desired other ways of guidance of the thread, including pendulating ones, are possible within the scope of the present invention, in order to convey the nonfluid substance out of the feeding funnel 2 in any desired, but always uniform and constant, amount.

The yarns from which the hose 9 is woven comprise cellulose fibers, cell wool (synthetic wool), nylon, Perlon, rayon, Dralon (polyacrylic fiber), wires of ductile metals, polycarbonates, polyesters, polytetrafluorethylene, and the like.

Suitable threads 4 which can be used in the present invention include threads of wool, cell wool, flax hemp, and the like. Synthetic fibers are generally unsuitable due to their character, since they exhibit too smooth a surface. However, if the surfaces of synthetic fibers can be appropriately roughened, said fibers are also useable.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention and all such modifications as would be apparant to one skilled in the art are intended to be included.

It is claimed:

1. A method for manufacturirig a fuse containing a very fine, dust-like explosive which comprises introducing the explosive from a feeding means into a casing disposed at the discharge end of said feeding means, wherein at least one thread having a roughened surface is deflected from the vertical axis of the feeding means, is guided under tension through the feeding means containing the explosive and is continuously introduced into the casing, together with the explosive, at said discharge end of the feeding means, and wherein amounts of the explosive are entrained in the surface of the thread during the passage of the thread through the feeding means into the casing.

2. The method of claim 1 wherein about percent of the explosive possesses a grain diameter less than about 0. 1 mm.

3. The method of claim 1, wherein the casing is being continuously manufactured at the lower end of the feeding means.

4. The method of claim 1 wherein the thread is introduced into the feeding means and is guided in a circular manner through said feeding means.

5. The method of claim 1 wherein the feeding means is a feeding funnel and the thread is guided in a circular manner through the explosive contained in the feeding funnel and in close proximity to the wall of said funnel so that the cone of explosive present in the feeding funnel is continually cut in the proximity of its periphery.

6. The method of claim 1 wherein the thread is made to vibrate.

7. The method of claim 1 wherein the thread is guided on the circumference of a disk disposed above the upper opening of the feeding means.

8. The method of claim 1 wherein the thread is attached to the circumference of a disk and is set into motion by the rotation of the disk.

9. The method of claim 7 wherein the disk reciprocates in the vertical direction.

10. The method of claim 1 wherein the thread is set into circular motion by means of a cam gear.

1 l. The method of claim 1 wherein the thread is set into a first circular motion by being drawn from a vertically disposed yarn reel, and a second circular motion is superimposed on said first motion by the movement of the holder of the yarn reel.

12. The method of claim 1 wherein the thread is twisted from short fibers of synthetic or natural fibers or mixtures thereof.

13. The method of claim 11 wherein two threads are introduced into different portions of the feeding means containing the explosive material.

14. The method of claim 1 wherein the explosive is selected from the group consisting of pentaerythritol tetranitrate, trimethylene trinatramine, and mannitol hexanitrate.

15. The method of claim 1 wherein the explosive in an amount of about 1 to 100 grams per meter of fuse is introduced into the sheath of said fuse.

16. The method of claim 1, wherein the thread has a smooth surface and including the step of roughening the surface of the thread to enable the entrainment of amounts of the explosive in the surface of the thread.

17. An apparatus for manufacturing a fuse which comprises a feeding means adapted to contain an explosive material, deflecting means for introducing at least one thread, which is deflected from the vertical axis of the feeding means into said feeding means, and means for guiding the thread through the feeding means and continuously introducing the explosive plus the thread into the casing at the discharge end of the feeding means, the thread being provided with a roughened surface for entraining amounts of the explosive during its movement through the feeding means and into the casing.

18. The apparatus of claim 17 wherein spinning means are provided for continuously manufacturing the casing.

19. The apparatus of claim 17 wherein the deflecting means is a circular disk disposed above the feeding means and storage reel means are provided for conveying the thread over the periphery of said disk and introducing it into the feeding means.

20. The apparatus of claim 19 wherein means are provided for rotating the disk.

21. The apparatus of claim 19 wherein the storage reel means containing the thread is attached to the top i f e apparatus of claim 17 wherein the deflecting means is a cam gear.

23. The apparatus of claim 17 wherein the deflecting means are two circular disks, each of which communicate with rotatable storage reels.

24. The apparatus of claim 20 wherein the rotatable storage reels communicate with a rotatable reel holder, and means are provided for rotating the rotatable storage reels and the rotatable reel holder.

25. The apparatus of claim 17 including means for vibrating the thread during its passage through the feeding means and into the casing.

Claims

1. A omethod for manufacturing a fuse containing a very fine, dust-like explosive which comprises introducing the explosive from a feeding means into a casing disposed at the discharge end of said feeding means, wherein at least one thread having a roughened surface is deflected from the vertical axis of the feeding means, is guided under tension through the feeding means containing the explosive and is continuously introduced into the casing, together with the explosive, at said discharge end of the feeding means, and wherein amounts of the explosive are entrained in the surface of the thread during the passage of the thread through the feeding means into the casing.

2. The method of claim 1 wherein about 80 percent of the explosive possesses a grain diameter less than about 0.1 mm.

6. The method of claim 1 wherein the thread is made to vibrate.

11. The method of claim 1 wherein the thread is set into a first circular motion by being drawn from a vertically disposed yarn reel, and a second circular motion is superimposed on said first motion by the movement of the holder of the yarn reel.

20. The apparatus of claim 19 wherein means are provided for rotatiNg the disk.

21. The apparatus of claim 19 wherein the storage reel means containing the thread is attached to the top of the disk.

22. The apparatus of claim 17 wherein the deflecting means is a cam gear.