Patent Publication Number: US-3878785-A

Title: Propagation device and initiation system for low energy fuses

Description:
0 United States Patent 11 1 1,111 3,878,785 Lundborg Apr. 22, 1975 15 1 PROPAGATION DEVICE AND lNlTlATlON 3.349.706 10/1967 Schaumann 102/27 R L w ER Y F SES 3.570.402 3/1971 Anderson et 31.... 102/27 R; SYSTEM FOR 0 EN G U 3.614.928 10/1971 Partridge et a1. 102/27 X [75] Inventor; Hans Krlster Lundborg, g v 3.713.384 1/1973 Turnbull 102/27 R swede FOREIGN PATENTS OR APPLICATIONS 1 Assigneel Nit&#34;! Nfibel Akfiebolaga Gytmrpa 599.612 6/1960 Canada 102/27 Sweden 22 Filed; No 5 7 Primary E.\&#39;aminer-Ver1in R. Pendegrass Anurnev. Agent. or Firm-Hana, Baxley &amp; Spiecens [21] Appl. No.: 306,923  
  ABSTRACT [30] Foreign Application Priority Data An explosive assemblage including a first length of Dec. 1. 1971 Sweden 15380/71 fuse having one end which receives an iniiialing pulse and a second end in contact with a detonator in 52 us. (:1. 102/27 R; 102/22 a connecting block which 8189 engages an intermedi- 51 1111. c1. C06c 5/06 ate region of a second length 9f fuse against the [58] Field of Search 102/22. 27 R, 28 R- nawr- One end of the Second length of fuse is nected to a detonator explosive assemblage while the [5 Rgferences Cited other end is connected to a detonator in another con- UNn-ED STATES PATENTS necting block which also engages a mid-point in an- 3.175.491 3/1965 Robertson 102/27 R other length of fuse 3.212.439 10/1965 Rcync 102/28 7 Claims, 15 Drawing Figures PATENTEE APR 2 2 I975 SHKU 2 [IF 3 PROPAGATION DEVICE AND INITIATION SYSTEM FOR LOW ENERGY FUSES The present invention relates to a development when using low energy fuses for propagating or generating a detonation consisting of an elongate casing in the form of a tubular, rigid or flexible conductor which contains a quantity of explosive and/or other reactive substance distributed along the conductor, which fills up only part of the cross section of the conductor which, for the remainder, is filed with gas (Swedish Pat. No. 333,321). The invention can also be applied to other embodiments of low energy fuses, e.g.. with completely filled explosive cores or other embodiments of the gas channel of the conductor. In the present application, low en ergy fuses denotes fuses with such a low self explosive effect they are not capable of propagating a detonation from one fuse connected to another or to an explosive of the conventional type used for blasting work without the aid of an exploding or initiating device.  
  In order to initiate e.g., a blasting charge set in a drill hole, a low energy fuse is fitted with a detonator; the explosive or initiating charge of which is initiated by the gas shock wave from the fuse. The explosive charge of the detonator in turn initiates the blasting charge. The gas shock wave is generated in the fuse by means of an appropriately adapted shock wave, spark discharge or the like.  
  A known and commonly used method of simultaneously initiating several low energy fuses in a blasting salvo is, with the aid of appropriately designed fastening devices and possibly initiating detonators, to connect the respective low energy fuses along a detonating fuse (detonating cord) which has such a great self explosive effect that this is capable of initiating the detonation process in the low energy fuses in the respective connection points. The detonating fuse is usually initiated with a detonator.  
  Initiation with detonating fuse involves a number of drawbacks, in the form of great self explosive effect, which can cause damage to the environment or cause the disengaging of connected, but not yet initiated low energy fuses which, in turn, results in the blasting salvo being. Another major drawback consists of the noise made by the detonating fuse, which in many cases makes it impossible to use in densely populated areas.  
  An object of the present invention is to reduce to a considerable extent and in certain cases to eliminate these drawbacks. This is achieved in that the length of detonating fuse required for each igniter in a blasting salvo of the kind described is replaced entirely by an extension of the low energy fuse, an initiating detonator or an explosive charge with its explosive effect having been given a maximum reduction for its purpose and an appropriately designed connection block.  
  The connection to form an initiation system according to the invention of several such igniters, each consisting of a detonator, a low energy fuse of a certain length and a propagation device requires that a gas shock wave generated at one point in an igniter is propagated to the fuses of the other igniters for initiation of the respective detonators. The transmission of the gas shock wave takes place without any reduction of its propagation velocity, even if the gas shock wave has an intermittent propagation process.  
  It has proved that fuses according to the Swedish Pat. No. 333,321 are sensitive to high air humidity, fog,  
 water (even in the form of a single, very small drop) and to foreign matter in the gas channel.  
  in order to ensure functioning of the igniters and the connected initiation system, the gas channel or channels along which the gas shock wave is to be propagated must be protected internally. The protection is arranged in such a way that when connecting several individually closed igniters together a coherent fuse system is obtained, which must not be exposed to water or dirt during the connection procedure.  
  Each individual igniter, i.e., the ignition function required for each charge or drill. hole, consists of a fuse with detonator and propagation device according to the invention and thus constitutes a moisture-proof closed unit, which can have varying lengths of fuse and delay intervals. The connecting together of igniters to form a continuous initiation system is carried out with the aid of propagation devices (connection blocks with initiating detonators or pressed-in explosive charges) which can be connected to another low energy fuse anywhere along its length. The connection block conmeets the igniters together mechanically. and with the aid of the shock wave from its initiating detonator or explosive charge transmits the gas shock wave from one fuse to the other, in two opposite directions, one leading down to the igniter in the drill hole, and one leading to the next propagation device, which, in turn, ignites the next fuse in two directions, etc. The connection block also constitutes a protection from and dampens the explosive effect of the initiating detonator and, finally, constitutes a protectionfor the initiating detonator from external mechanical damage.  
 The connection between blasting salvos with different charges, or between charges where the length of the fuse is insufficient, can be made with specially manufactured splicing fuses with a propagation device in one end and a moisture-proof closure in the other end.  
  A connection block (or propagation device) according to the invention for connecting together individual igniters to form an initiation system consists of a body, particularly of plastic, with a recess for the insertion of a fuse with a crimped-on initiating detonator and one or several fuse channels for the insertion of one or several fuses to be initiated. The fuses can appropriately be folded double when they are inserted in the fuse channels. The block can also have a configuration as above, but with a recess in which an explosive charge has been pressed in, either directly or via a casing (propagation device). The fuse is inserted in the recess, and the block is crimped onto the fuse. The fuse channels can be parallel, at right angles or at a certain angle to the inserted detonator, or the pressed-in explosive charge. The fuse channel can also be arranged axially with the initiating detonator. At one end of the fuse channel or channels the connection block can be provided with mechanical locking; members, e.g., protruding parts, for securing the folded fuse.  
  The embodiment in which the fuse which it is desired is to be initiated is folded double when inserted in the block and is parallel in direct connection with the initiating detonator permits the energy of the fuse to be reduced by approx. 50 percent, which is of great importance when it is desired to dampen the self explosive effect of the propagation device. This reduction is obtained due to the fact that when folding the fuse double, the directed component of the shock wave from the initiating detonator is efficiently utilized for initiatcedure according to the invention, compared with using detonating fuse according to earlier known techniques, the following example can be given:  
 Detonating fuse Low energy fuse 10 g/m according to Swedish patent application No. 333 321 and propagation device Total-quantity of 180 grammes 2.4 grammes explosive. in grammes of PETN,&#39;which detonates outside drill holes in conjunction with -l-hole salvo with 2 metres distance between holes Several embodiments according to the invention will now be described in more detail in conjunction with the accompanying drawings, in which FIGS. 1-4 show four alter-native embodiments of connection blocks, FIGS. -7 and 8-13 show two embodiments of connection blocks consisting of two parts which can be fastened together, FIG. 14 shows an igniter according to the invention, and FIG. shows schematically an initiation system according to the invention. The reference figures are common for all of the figures.  
  The connection blocks comprise of a body 1, particularly made of plastic, with a recess 2 for the insertion of an initiating detonator, which is connected with a fuse, and one or several fuse channels 3 for the insertion of one or several fuses 4 which have been folded double. The channels are to be arranged in such a way that .some part of the fuse 4 comes into direct contact with the detonator or in close proximity thereto. According to FIG. 1 the fuse channel is parallel with the detonator recess 2, according to FIG. 2 at right angles and according to FIG. 3 at an oblique angle to the detoznator=recess 2. According to FIG. 4 the fuse channel is arranged axially with the detonator recess 2.  
  .FIG. .5 shows another connection block I, viewed frorn the side, FIG. 6 a cross-section view, and FIG. 7 the two parts in cross section. The block consists of the twosparts 5 and 6, which can be fastened together, as ;shown in FIG. -7. One of the parts 5 is made with a central recess 2, for insertion of an initiating detonator, and two fuse channels 3, parallel therewith, for insertion of two fuses 4, folded double. For holding theidetonator in place there is an upper part 6, made with a corresponding cavity 2 for securing the detonator. There is also a channel 8 for letting through the fuse provided -with the initiating detonator. Further, the part 6 is made with two protrusions 7, over which the folded ends of the fuse 4 can be snapped and secured. See FIGS. 5 and 6.  
  FIGS. 8-13 show another embodiment of a connection blockl, consisting of two parts 5 and 6, which can be fastened together. One of the parts 5 is made with one large central recess 2 and two smaller recesses 3 in the bottom, which constitute part of the fuse channels. The part 6 is made in the form of a plastic body with a central hole 8, into which the explosive charge 10 is pressed down, either directly or via a casing 9. The part 6 is also made with two parallel recesses 11, which together with part 5 constitute the fuse channels 3. The  
 protrusions 7 constitute members for securing the folded fuses 4. Parts 5 and 6 arefastened together and secured through snap locking. i  
  -As the blocks according to FIGS. 5l3 have two channels, for the insertion of two fuses, i&#39;gniters can be connected together, as well as the initiation of two salvos connected in parallel.  
  An example of an embodiment of an igniter which has previously been described is shown schematically in FIG. 14, in which 9 designates a detonator for initiation of the blasting charge in e.g., a drill hole, 4 designates the low energy fuse and a propagation device consisting of the connection block 1 and the initiating detonator or pressed-in explosive charge 10. The designation propagation device is a common term meaning a connection block enclosing an inserted detonator crimped directly on the fuse, or a connection block with a fixed explosive charge pressed into the block, either directly or via a casing: In the latter case, the block is connected directly to the fuse.  
  FIG. 15 shows schematically an initiation system in which propagation devices according to the invention are used. An initiating detonator is initiated in an appropriate way according to an earlier description. A gas shock wave follows the initiating fuse and initiates the detonator in the propagation device No. 1. Igniter No. l is thereby punctured and initiated in two directions, one direction down to an interval detonator in the drill hole No. 1 and the other direction to the initiating detonator in propagation device No. 2, after which the process and the initiation is repeated to an unlimited number of blasting charges in a series of drill holes.  
  The connection blocks, the propagation devices and the initiation system have been developed for low energy fusesaccording to the Swedish&#39;Pat. No. 333,321. The same connection blocks, propagation devices and initiation system can also be used for other fuses of low energy type.  
 I claim:  
  1. An explosive assemblage comprising in combination a first length of impulse propagating means having first and second ends, a first connecting block engaging said first length of impulse propagating means intermediate its first and second ends, said connecting block having an impulse intensifier means operatively adjacent the engaged region of said first length of impulse propagating means, a second length of impulse propagating means having one end for receiving an initiation impulse and a second end engaged by said first connecting block operatively adjacent said impulse intensifier means, a detonator for an explosive charge connected to the first end of said first length of impulse propagating means, and a second connecting block including another impulse intensifier means connected to the second end of said first length of impulse propagating means so that when said one end of said second impulse propagating means receives an initiation impulse it propagates to the impulse intensifier means in said first connecting block which generates an intensified impulse which propagates simultaneously to the first and second ends of said first impulse propagating means.  
  2. The explosive assemblage of claim 1 wherein said connecting blocks are made of non-explosive material.  
  3. The explosive assemblage of claim 1 wherein at least said first connecting block is provided with a plurality of parallel channels,&#39;two of said&#39;channels housing 6. The explosive assemblage of claim 3 further comprising locking means at one end of said channels for mechanically securing the lengths of impulse propagating means.  
  7. The explosive assemblage of claim 1 wherein said first impulse intensifier means and the engaged region of said first length of impulse propagating means form a unit sealed against the elements.