Patent Publication Number: US-2004055494-A1

Title: Detonator junction for blasting networks

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to blasting techniques. More specifically, the present invention relates to a detonator junction for use in a blast initiation system.  
       [0003] 2. Technical Background  
       [0004] The detonation of multiple explosives is common in both mining and construction applications. However, simultaneous detonation of a large quantity of explosives can result in excessive ground vibrations and can be counterproductive. Thus, initiating explosives in successive rows, layers, or groups can minimize these problems and more economically achieve the specific objectives of the explosions. In quarry blasting, for instance, sequential delays between explosions must be controlled within milliseconds to achieve desired objectives. Also, in construction, sequential blasts may be used to move or loosen large amounts of rock or earth.  
       [0005] Both pyrotechnic and electrical explosives may be used for sequential blasting. However, in many circumstances, electrical explosives are dangerous because a stray induced charge may accidentally set off an electrical explosive, injuring individuals near the explosive. Because of this danger, in mining and construction applications, pyrotechnic explosives are frequently used instead of electrical explosives.  
       [0006] Historically, the timing of the blasts was controlled by the length of the textile wrapped black powder fuses leading to each explosive. Typically, these fuses burned at a rate of about 120 seconds per yard. A longer fuse, of course, deferred detonation of an attached explosive for a longer period of time from lighting the fuse, while a shorter fuse produced an earlier explosion. Multiple fuses could be tied or otherwise joined together to form a network of explosives. The network of explosives could be initiated by lighting a single fuse connected to the network.  
       [0007] Later, textile wrapped fuses included a high energy explosive core such as PETN (Pentaerythritol Tetranitrate). These fuses can burn at about a rate of about 7000 meters per second. While the burn rate is much faster, these fuses suffered from a number of different problems. For instance, rain, snow, or other inclement weather could limit the effectiveness of the exposed fuses. Additionally, the high energy explosive core creates a loud noise during incineration. The noise posed a nuisance and perhaps a health risk to workers and adjacent populated areas.  
       [0008] To minimize these problems, the industry has adopted the use of shock wave transmission lines, also referred to as “shock tubes”. The shock tube is a hollow tube containing a combustible or reactive material, such as HMX (Cyclotetramethylenetetranitramine) and aluminum. Igniting the combustible material inside the tube initiates a shock wave within the transmission lines. The shock wave travels at about 2000 meters per second. The shock wave is similar to a dust explosion and will initiate explosives coupled to the transmission lines. These transmission lines may also be referred to as “shock tubes”, detonator cord, or percussion primer.  
       [0009] In contrast to conventional fuses, this type of transmission line may be virtually noiseless and produces no side blasts. Moreover, although combustion of the combustible material may be initiated at an open end of the tube with a percussion shock wave or source of heat, initiating combustion by using a shock wave provides greater flexibility and minimizes the risk of contamination of the combustible material.  
       [0010] As a consequence, a detonator or percussion primer that produces a small explosion or other source of a high pressure heat shock wave in response to receipt of a shock wave may be positioned proximate an outgoing transmission line or lines. The detonator may be coupled to an incoming transmission line. Thus, when a shock wave is received at the detonator via the incoming transmission line, a small detonation is produced by the detonator and the resulting shock wave passes through the wall of the transmission line and initiates a thermal shock wave within the outgoing transmission line or lines.  
       [0011] Detonator blocks have been developed for initiating a thermal shock waves in one or more outgoing transmission lines. These detonator blocks typically have a structure for receiving a detonator and a structure for receiving and retaining transmission lines. When positioned in the detonator block, a detonator output region of the detonator is situated proximate transmission lines retained in the detonator block. As explained above, upon receipt of a shock wave, the detonator generates a shock wave which is transmitted to the outgoing transmission lines, initiating a thermal shock wave within the lines.  
       [0012] These detonator blocks, however, may suffer from a number of drawbacks. Blasting networks can be extremely complex and timing is, obviously, of critical importance. As such, it is important that the detonator blocks securely retain inserted transmission lines. Otherwise, transmission lines can inadvertently be removed from the appropriate detonator blocks, potentially disrupting the entire blast sequence. Moreover, it may be difficult or time-consuming to locate the detonator blocks from which the transmission lines have been inadvertently removed. Worse still, such errors may go undetected.  
       [0013] Another problem relating to conventional detonator blocks is properly positioning detonators within the detonator blocks. Generally, the detonator has a low output to minimize shrapnel on the surface of a blasting hole. For example, the output charge may be produced using lead azide. If such a detonator is not correctly positioned within a detonator block, the detonator may be too far from the transmission lines to impart a shock wave in the outgoing transmission lines. Also, if the detonator is not securely fastened within the detonator block, the detonator may become separated from the detonator block, again disrupting the blasting pattern. Furthermore, it is often difficult for a worker to determine when a detonator is properly positioned and securely fastened within a detonator block.  
       [0014] Thus, it would be an advancement in the art to provide a detonator block that limits inadvertent removal of transmission lines from the detonator block. It would be a further advancement in the art to provide a detonator block with a superior mechanism for retaining and correctly positioning a detonator within the detonator block.  
       [0015] Such a device is disclosed and claimed herein.  
       SUMMARY OF THE INVENTION  
       [0016] The apparatus and methods of the present invention have been developed in response to the present state-of-the-art, and, in particular, in response to problems and needs in the art that have not yet been fully resolved by currently available blasting networks. The present invention provides an apparatus for enhancing the effectiveness of blasting systems. To achieve the foregoing, and in accordance with the invention as embodied and broadly described in the preferred embodiment, a detonator junction for use in a network of explosives is disclosed.  
       [0017] The detonator junction may include a body having an interior surface defining a chamber for receiving a detonator. The body may be configured in various shapes. The shape of the body may be governed by the shape of the detonator to be received in the chamber. For example, if the detonator is an elongated cylinder, the body may also be elongated in shape. In certain embodiments, the body may be sized and shaped to facilitate handling by a worker wearing gloves during coupling of the detonator junction to a detonator and one or more transmission lines.  
       [0018] As will be understood by those skilled in the art, the body may be made from various types of materials, including plastics. Ideally, the body is resiliently deformable such that it can absorb any scattered shrapnel when the detonator disposed therein is activated. Also, the body should be made from a material that will retain its shape and resiliency in a wide variety of climates and temperature ranges.  
       [0019] Although detonators may be configured in various shapes, detonators may be and are usually embodied in a cylindrical shape. An explosive material may be disposed within an output region of the detonator. Low-energy detonators produce smaller explosions, less shrapnel, and are not as noisy as conventional detonators. The low energy detonators may be used to provide a pyrotechnic delay to accomplish a desired timing precision in an explosives network. Detonators are known to those skilled in the art.  
       [0020] The detonator junction may include a retaining member attached to the body. The retaining member extends away from the body and then runs along a side of the body. Thus, the retaining member and body define a slot for retaining one or more transmission lines within the detonator junction. More specifically, the slot may retain one or more transmission lines proximate the output region of a detonator disposed within the detonator junction. As stated above, application of heat to a transmission line initiates a thermal shock wave within the transmission line.  
       [0021] The body and the retaining member may each comprise a substantially planar surface that defines the slot. Of course, the “substantially planar surface” may include minor deviations from a perfectly planar surface. For instance, the body and retaining member may include opposing arcuate indentations for positioning the transmission lines at specific sites within the slot.  
       [0022] The detonator junction may also include a limiting member. The limiting member is attached to the retaining member. The limiting member may be attached to or integrally formed with the retaining member and/or body. The limiting member traverses an imaginary longitudinal extension of the slot. Thus, the limiting member covers a portion of the slot and limits insertion and removal of a transmission line from the slot. Additionally, the limiting member and the body may define a channel through which a transmission line passes before insertion into the slot.  
       [0023] The channel or the portion of the channel adjacent to the slot is more narrow than the diameter of a transmission line. Therefore, the limiting member serves to retain transmission lines within the slot.  
       [0024] The detonator junction may optionally include a protrusion. The protrusion may be attached to or be integrally formed with the body, retaining member, and/or limiting member. The protrusion is shaped and positioned to restrict movement of a transmission line from the slot into the channel. The protrusion may be embodied in a number of different configurations to serve this purpose, as will be understood by those skilled in the art. Also, the protrusion may define at least a portion of the channel. For instance, the protrusion may include an arcuate extension along the channel protruding up into the slot.  
       [0025] Transmission lines and detonator junctions may be assembled into a complex network to form a specific blasting pattern. If one of the transmission lines is inadvertently dislodged from a detonator junction, the error may go undetected, destroying at least one aspect of the blasting pattern. Alternatively, if the error is detected, it may require a great deal of time to determine which detonator junction the transmission line should be inserted into. The limiting member and/or protrusion securely retain transmission lines within the slot and make inadvertent dislodgment of the lines far less likely.  
       [0026] The detonator junction may also optionally include a clip. The clip is shaped to interlock with the detonator. A U-shaped opening of the clip may interlock with the detonator. For instance, the detonator may include a crimp for receiving the clip. The crimp serves to couple the detonator to a transmission line. The crimp includes a relatively wider portion of the detonator between two grooves which are relatively narrower portions of the detonator. The U-shaped opening of the clip may include ridges for mating with the grooves of the detonator and valleys for mating with the wider portion of the detonator. In one embodiment, the clip is sized and shaped such that the clip snaps around the crimp to engage the detonator. The clip may be biased to engage the detonator within an opening of the clip. Of course, those skilled in the art will understand that various structural configurations may be used to interlock the detonator and the clip.  
       [0027] The interior surface of the body may further define a mating interface within the chamber. The mating interface is shaped to receive and lock the clip and an interlocked detonator in the chamber. More specifically, the clip includes arms that are resiliently deformable. The mating interface includes an arm chamber for receiving the arms on the clip. Openings may be disposed in opposing sides of the arm chamber. A detent is disposed on each of the arms. A distance between the outer edges of the detents is slightly less than a distance between opposing sides of the arm chamber.  
       [0028] Thus, when the arms are inserted into the arm chamber, the outer edges of the detents contact the arm chamber, deforming the arms towards each other. When the detents reach the openings, the detents are pushed outwardly into the openings by the resilient force of the arms, locking the clip and an interlocked detonator in the chamber.  
       [0029] Use of a clip provides important advantages over prior techniques for positioning the detonator in the chamber. If the detonator is not correctly inserted and locked into the chamber, it may become dislodged or may not transmit a thermal shock wave to the associated transmission lines. The detonator junction makes such a scenario far less likely than conventional devices. The detonator junction enables a user to look at the openings and easily determine whether the detents are securely and properly positioned therein. Also, there is often a “snapping” sound or click when the detents are correctly positioned in the openings, as the arms strike the arm chamber. The “snapping” sound provides the user with an additional indication of proper placement of the detonator in the chamber.  
       [0030] A detonator junction may be used in the following manner. A thermal shock wave is initiated in a transmission line coupled to a detonator disposed within a detonator junction. Again, a thermal shock wave may be initiated by applying heat to either an end of a transmission line or a side of the transmission line. The thermal shock wave is a combustion or reaction front (where combustion or reaction is occurring) within the tubing of a transmission line.  
       [0031] When the combustion front reaches the detonator disposed within the detonator junction, the explosive output region within the detonator is activated. The resulting shock wave is then transferred through the walls of each transmission line disposed within the slot of the detonator junction, initiating a thermal shock wave within each such transmission line. Thus, thermal shock waves are propagated throughout a blasting network containing one or more detonator junctions.  
       [0032] When a thermal shock wave is received at an explosive such as ANFO (Ammonium Nitrate and Fuel Oil) or dynamite, the explosive is detonated. Again, the purpose of the blasting network is to detonate explosives in a timed sequence for various purposes, including both mining and construction.  
       [0033] In view of the foregoing, the detonator junction provides advantages over conventional devices. The limiting member assists in maintaining transmission lines within the slot to limit inadvertent dislodgment of transmission lines from a detonator junction. Furthermore, the clip helps to properly position and maintain the detonator within the channel so that the low energy detonator is correctly positioned with respect to the transmission lines.  
       [0034] These and other advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0035] In order that the manner in which the advantages and features of the invention are obtained, a more particular description of the invention summarized above will be rendered by reference to the appended drawings. Understanding that these drawings illustrate only selected embodiments of the invention and are not therefore to be considered limiting in scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:  
     [0036]FIG. 1 is a partially cut-away perspective view of a detonator junction that includes an exploded view of a detonator and a clip;  
     [0037]FIG. 2 a  is a top plan view of a detonator disposed within a clip;  
     [0038]FIG. 2 b  is a front plan view of a detonator disposed within a clip;  
     [0039]FIG. 3 a  is a bottom view of a body for a detonator junction, illustrating a chamber and mating interface for a clip;  
     [0040]FIG. 3 b  is a cross-sectional view of a body for a detonator junction taken across line  3   b,   3   c - 3   b,   3   c  of FIG. 3 a;    
     [0041]FIG. 3 c  is a cross-sectional view of a body for a detonator junction taken across line  3   b,   3   c - 3   b,   3   c  of FIG. 3 a,  including with a cross-sectional view of a clip and a perspective view of a detonator disposed therein;  
     [0042]FIG. 4 is a cross-sectional view of a detonator junction, including a cross-sectional view of a clip and a perspective view of a detonator;  
     [0043]FIG. 5 is a plan view of a blasting network using detonator junctions and transmission lines; and  
     [0044]FIG. 6 is a plan view of an alternative blasting network using detonator junctions and transmission lines. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0045] The preferred embodiments of the invention are now described with reference to FIGS.  1 - 5 . The members of the present invention, as generally described and illustrated in the Figures, may be implemented in a wide variety of configurations. Thus, the following more detailed description of the embodiments of the system and method of the present invention, as represented in the Figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of presently preferred embodiments of the invention.  
     [0046] Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to convey a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.  
     [0047]FIG. 1 is a cutaway perspective view of a detonator junction  12  including an exploded view of a detonator  14  and a clip  16  for use in a network of explosives. The detonator junction  12  may include a body  18 . As will be understood by those skilled in the art, the body  18  may be made from various types of materials, including plastics. Ideally, the body  18  is resiliently deformable such that it can absorb any scattered shrapnel when the detonator  14  disposed therein is activated. Also, the body  18  should be made from a material that will retain its shape and resiliency in a wide variety of climates and temperature ranges.  
     [0048] The body  18  may have an interior surface  20 . The interior surface  20  defines a chamber  22  shaped to receive a detonator  14 . The chamber  22  may be shaped to generally fit the detonator  14  that the chamber  22  is designed to receive.  
     [0049] The detonator  14  has an explosive output region  24 , which is activated upon receipt of a thermal shock wave from an incoming transmission line  26   a.  The explosive output region  24  may include an explosive and is understood by those skilled in the art. Although detonators  14  may be configured in various shapes, they may be and are usually embodied in a cylindrical shape, as illustrated. In alternative embodiments, the detonator  14  is manufactured with a built-in pyrotechnic delay.  
     [0050] As stated before, transmission lines  26  may include hollow tubing with a reactive or combustible material (e.g., HMX and aluminum) disposed therein. A thermal shock wave (a reaction or combustion front) within a transmission line  26  may be initiated by applying a shock wave to an open end or a side of a transmission line  26 . Also, low-energy detonators  14  and transmission lines  26 , which are known to those skilled in the art, may be used to reduce the noise accompanying propagation of a thermal shock wave through a network of explosives. Detonators  14  and transmission lines  26  are made by various companies, including Ensign-Bickford Company of Simsbury, CT, Orica of Melbourne, Australia, and Dyno Nobel of Oslo, Norway.  
     [0051] The detonator junction  12  may include a retaining member  28 . The retaining member  28  may be attached to or integrally formed with the body  18 . The retaining member  28  extends away from the body  18  and then runs along a side of the body  18  to form a slot  30 . The slot  30  retains one or more transmission lines  26   b  within the detonator junction  12 .  
     [0052] In one embodiment, up to four transmission lines  26  may be placed within the slot  30 . Of course, a detonator  14  with a larger or wider explosive output region  24  would enable construction of a detonator junction  12  in which more than four transmission lines  26  could be positioned and still allow proper initiation of a thermal shock wave within each of the lines  26 .  
     [0053] The body  18  and the retaining member  28  may each comprise a substantially planar surface  32   a - b  that defines the slot  30 . The “substantially planar surface”  32   a - b  may include minor deviations from a perfectly planar surface. Those deviations may include both manufacturing defects and predetermined deviations. For instance, the retaining member  28  and body  18  may include opposing arcuate indentations  34  for positioning the transmission lines  26  at specific sites within the slot  30 .  
     [0054] In addition, the substantially planar surface  32   a  of the body  18  and the substantially planar surface  32   b  of the retaining member  28  may be generally parallel to each other, as illustrated in FIGS. 1 and 4. This means that a plane that generally defines the substantially planar surface  32   b  of the retaining member  28  is parallel to a plane that generally defines the substantially planar surface  32   a  of the body  18 .  
     [0055] The detonator junction  12  may also include a limiting member  36 . The limiting member  36  may be attached to or integrally formed with the retaining member  28  and/or body  18 . The limiting member  36  traverses an imaginary longitudinal extension  38  of the slot  30  and limits insertion and removal of a transmission line  26  from the slot  30 . Additionally, the limiting member  36  and the body  18  may define a channel  40  through which a transmission line  26  passes before insertion into the slot  30 .  
     [0056] The portion  42  of the channel  40  adjacent to the slot  30  is more narrow than the diameter  44  of the transmission line  26 . Thus, the limiting member  36  serves the purpose of retaining a transmission line  26  within the slot  30 . Also, the limiting member  36  controls the force required to insert transmission lines  26  into the slot  30 .  
     [0057] Transmission lines  26  and junctions  12  may be assembled into a complex network to form a specific blasting pattern (see, e.g., FIG. 5). If one of the transmission lines  26  is inadvertently dislodged from a detonator junction  12 , the error may go undetected, destroying at least one aspect of the blasting pattern. Alternatively, if the error is detected, it may require a great deal of time, to determine which detonator junction  12  the transmission line  26  should be inserted into. The limiting member  36  securely retains transmission lines  26  within the slot  30  and makes inadvertent dislodgment of the lines  26  far less likely.  
     [0058] The detonator junction  12  may optionally include a protrusion  46 . The protrusion  46  may be attached to or be integrally formed with the body  18 , retaining member  28 , and/or limiting member  36 . The protrusion  46  is shaped and positioned to restrict movement of a transmission line  26  from the slot  30  into the channel  40 . As illustrated, the protrusion  46  is arcuate in shape. The protrusion  46  may be embodied in a number of different configurations to serve this purpose, as will be understood by those skilled in the art. Also, the protrusion  46  may define at least a portion of the channel  40 . The protrusion  46  provides a safeguard that, in addition to the limiting member  36 , serves to avoid inadvertent dislodgment of the transmission lines  26 .  
     [0059] As shown in FIG. 4, when the detonator  14  is disposed in the chamber  22 , the explosive output region  24  is positioned proximate outgoing transmission lines  26   b  to allow a shock wave to pass through the tubing of the outgoing transmission lines  26   b  and initiate a thermal shock wave within the outgoing transmission lines  26   b  upon activation of the explosive output region  24 . As used in this application, having the detonator  14  disposed in the chamber  22  does not mean that the detonator  14  is entirely disposed in the chamber  22 , but, instead, means that the detonator  14  is properly positioned in the chamber  22 .  
     [0060] Referring once again to FIG. 1, the detonator junction  12  may also optionally include a clip  16 . The clip  16  is shaped to interlock with the detonator  14 . A U-shaped opening  48  of the clip  16  may interlock with a crimp  50  disposed on the detonator  14  and retain a fixed position relative to the detonator  14 . The clip  16  may interlock with conventional detonators  14 . As such, the detonator  14  does not need to be specially manufactured to interlock with the clip  16 . One embodiment of the clip  16  will be discussed in further detail in connection with FIGS. 2 a - b.    
     [0061] The interior surface  20  of the body  18  may further define a mating interface  54  within the chamber  22 . The mating interface  54  is shaped to receive and lock the clip  16  and an interlocked detonator  14  in the chamber  22 . More specifically, the mating interface  54  includes a main chamber  56  for receiving the main portion  58  of the clip  16 , a lip chamber  60  for receiving a lip  62  of the clip  16 , and an arm chamber  64  for receiving arms  66  on the clip  16 . A detent  68  is disposed on each of the arms  66 . As will be explained in greater detail in connection with FIGS. 3 a - c,  the arms  66  are resiliently deformable such that the detents  68  may be disposed in openings  70  in the body  18  to lock the clip  16  and an interlocked detonator  14  in the chamber  22 .  
     [0062]FIG. 2 a  is a top plan view and FIG. 2 b  is a front plan view of a clip  16  interlocked with a detonator  14 . As stated before, the clip  16  includes a U-shaped opening  48  that is configured to interlock with a crimp  50  on the detonator  14 . Again, the clip  16  includes arms  66  with detents  68  disposed thereon for mating with the openings  70  in the mating interface  54  of the body  18 . As illustrated, the clip  16  includes ridges  72  to mate with grooves of the crimp  50  of the detonator  14  and valleys  74  to mate with a relatively wider portion of the detonator  14 . The ridges  72  and valleys  74  of the clip  16  tightly conform to the crimp  50  of the detonator  14  providing a secure fit between the clip  16  and detonator  14 . Preferably, when properly engaged the detonator  14  “snaps” into the clip  16 . Of course, as will be understood by those skilled in the art, both the clip  16  and detonator  14  may be configured in various shapes to interlock.  
     [0063] As also will be understood by those skilled in the art, the clip  16  may be made from various types of materials, including plastics. As with the body  18 , the material should be resiliently deformable in a wide variety of temperature ranges and conditions.  
     [0064]FIGS. 3 a - c  provide further illustration of the interaction between the clip  16  and the mating interface  54 . Specifically, FIG. 3 a  is a bottom plan view of the body  18  that illustrates the mating interface  54  and chamber  22 . FIG. 3 b  is a cross-sectional view on line  3   b,   3   c - 3   b,   3   c  of the mating interface  54  and body  18 , while FIG. 3 c  is a cross-sectional view on line  3   b,   3   c - 3   b,   3   c  of the mating interface  54  and body  18 , including a cross-sectional view of the clip  16  and a perspective view of an interlocked detonator  14  disposed in the chamber  22 .  
     [0065] As stated above, an interior surface  20  defines a chamber  22  and a mating interface  54  within the body  18 . The mating interface  54  is configured to receive and lock into place a clip  16  and an interlocked detonator  14 . More specifically, the mating interface  54  includes a main chamber  56  for receiving the main portion  58  of the clip  16 , a lip chamber  60  for receiving the lip  62  of the clip  16 , and the arm chamber  64  for receiving the arms  66  of the clip  16 .  
     [0066] The openings  70  are disposed just above the arm chamber  64 . The distance  76  between the outer edges of the detents  68  of the clip  16  is slightly greater than the distance  78  between opposing sides of the arm chamber  64  just below the openings  70 . Again, the arms  66  are resiliently deformable. Thus, as explained more broadly above, when the clip  16  is inserted into the mating interface  54 , the arms  66  of the clip  16  are positioned within the arm chamber  64 , the detents  68  contact opposing sides of the arm chamber  64 , and the arms  66  deform towards each other. When the detents  68  reach the openings  70 , the arms  66  move apart, pushing the detents  68  in the openings  70  and locking the clip  16  and an interlocked detonator  14  in the chamber  22 . Of course, those skilled in the art will recognize that the clip  16  and mating interface  54  may be configured in various ways to secure the detonator  14  in the chamber  22 . The illustrated embodiment is merely exemplary.  
     [0067] Use of a clip  16  provides important advantages over prior techniques for positioning the detonator  14  in the chamber  22 . If the detonator  14  is not correctly inserted and locked into the chamber  22 , it may become dislodged or may not transmit a thermal shock wave to the associated transmission lines  26 . The detonator junction  12  makes such a scenario far less likely than conventional devices. The detonator junction  12  enables a user to look at the openings  70  and easily determine whether the detents  68  are securely and properly positioned therein. In addition, there is often a “snapping” sound or click when the detents  68  are correctly positioned in the openings  70 , as the arms  66  strike the arm chamber  64 . The “snapping” sound provides the user with an additional indication of proper placement of the detonator  14  within the chamber  22 .  
     [0068]FIG. 4 is a cross-sectional view of a detonator junction  12 . A cross-sectional view of a clip  16  and a perspective view of an interlocked detonator  14  disposed within the chamber  22  are illustrated in this Figure. The explosive output region  24  of the detonator  14  is disposed proximate transmission lines  26   b  positioned within the slot  30 . As such, when the explosive output region  24  is activated, a shock wave is transmitted through the tubes into the combustible material within the transmission lines  26 . In response thereto, a thermal shock wave is initiated in each of the transmission lines  26   b  disposed within the slot  30 .  
     [0069] As illustrated in FIG. 4, the chamber  22  opens up into the slot  30 , allowing for unimpeded transmission of explosive output from the explosive output region  24  of the detonator  14  to the transmission lines  26   b.  Of course, in alternative embodiments, although a barrier (not illustrated) may separate the chamber  22  and the slot  30 , the shock wave may still be transferred from the explosive output region  24  to transmission lines  26   b  disposed within the slot  30  sufficient to initiate a thermal shock wave within the transmission lines  26   b.    
     [0070] The channel  40  created by the limiting member  36  is more narrow than the transmission lines  26   b,  restricting exit of the transmission lines  26   b  from the slot  30  into the channel  40 . Moreover, the channel  40  is disposed at an angle with respect to the slot  30 , again making it more difficult for transmission lines  26   b  to inadvertently be removed from the slot  30 . Stated more precisely, a longitudinal axis  80  of the slot  30  is disposed at an angle with respect to (is not parallel to) a longitudinal axis  82  of the channel  40 .  
     [0071] A combination of the retaining and limiting members  28 ,  36  may be referred to as a restraint mechanism  84 . A distance between the protrusion  46  and restraint mechanism  84  is more narrow than the diameter  44  of the transmission line  26   b  such that passage of transmission lines  26   b  through this area  86  into the channel  40  is limited. In embodiments with or without protrusions  46 , the channel  40  may be more narrow than a diameter  44  of the transmission line  26   b,  again limiting movement of transmission lines  26   b  through the channel  40 . Thus, the restraint mechanism  84  limits removal of transmission lines  26   b  from the slot  30  through the channel  40 .  
     [0072] Transmission lines  26   b  may be inserted into the slot  30  through the channel  40 . To this end, the restraint mechanism  84  and/or transmission lines  26   b  may be resiliently deformable. Thus, the restraint mechanism  84  and/or the transmission lines  26   b  may deform slightly when transmission lines  26  pass from the channel  40 , through the area  86  between the protrusion  46  and the restraint mechanism  84 , and into the slot  30 . Thus, the restraint mechanism  84  limits insertion of transmission lines  26   b  through the channel  40  into the slot  30 .  
     [0073]FIG. 5 is a plan view of a blasting network  88  using detonator junctions  12   a - c  and transmission lines  26   a - i  for timed initiation of explosive charges  90   a - f.  Of course, the illustrated network  88  is only one example of sequential blasting. Those skilled in the art will recognize that blasting networks  88  may be used in a wide variety of configurations and circumstances, such as mining and construction. One advantage of the detonator junction  12   a - c  is its flexibility and the ease with which a blasting network  88  may be assembled. The explosives  90   a - f  used in connection with the detonator junction  12   a - c  are initiated by a high strength detonator (not shown), as opposed to surface connections which use low output detonators  14 .  
     [0074] As illustrated in FIG. 5, explosives  90   a - f,  coupled to the network  88 , are disposed within boreholes  92   a - b  in the earth. Typically, to most efficiently break up rock, the explosives  90  are positioned at different at different levels within a bore hole  92 . This process may be referred to as “decking.” For example in bore hole  92   a,  three explosives  90   a - c  are positioned to cover about a third of the bore hole  92   a.  Such positioning allows for use of less explosive  90   a - c  and control of the timing of the explosives  90   a - f.  Timing the detonation of such explosives  90   a - f  is critical to prevent one explosive  90   a - f  from influencing, or detonating, an adjacent explosive  90   a - f  Although only one explosive  90   a - f  is illustrated at each level, or deck, in alternative embodiments, multiple explosives  90   a - f  may be placed on each deck. Additionally, each explosive may be separated by a timing delay. For example, explosive  90   a  may detonate before explosive  90   b  and explosive  90   b  may detonate before explosive  90   c.    
     [0075] Each deck, or level of explosives  90   a - f,  may be separated by a layer of stemming  96 . Generally, stemming  96  is sized, crushed stone, such as drill cuttings. Layers of air may also serve as stemming  96 . Stemming  96  is strategically placed to produce the desired blasting effects from the explosives  90   a - f.    
     [0076] The network  88  illustrated in FIG. 5 may be used in the following manner. A thermal shock wave is transmitted to a first detonator junction  12   a  via a first transmission line  26   a.  Within the first detonator junction  12   a,  the thermal shock wave is received at a detonator  14 . The detonator  14  includes an explosive output region  24 , which is activated upon receipt of a thermal shock wave.  
     [0077] Within the detonator junction  12   a,  the explosive output region  24  is disposed proximate a second and a third transmission line  26   b - c.  The shock wave generated by the detonator  14  simultaneously initiates a thermal shock wave within the second and third transmission lines  26   b - c.  Each of the outgoing transmission lines  26   b - i  may be sealed at one end to prevent contamination.  
     [0078] The thermal shock wave in the second transmission line  26   b  is received at a second detonator junction  12   b.  Thereafter, the explosive output region  24  in the second detonator junction  12   b  is activated initiating a thermal shock wave within the fourth, fifth, and sixth transmission lines  26   d - f.  Here, the explosives  90   a - c  will be detonated in a sequence according to the length of the transmission line  26   d - f  between the second detonator junction  12   b  and each of the explosives  90   a - c.  The explosives  90   a - c  coupled to shorter transmission lines  26   d - f  will be detonated first.  
     [0079] The thermal shock wave transmitted along the third transmission line  26   c  will initiate a thermal shock wave within the seventh, eighth, and ninth transmission lines  26   g - i  at the third detonator junction  12   c.  Accordingly, the fourth, fifth and sixth explosives  90   d - f  will be activated in that sequence.  
     [0080] The blasting network  88  of FIG. 5 is one of many different configurations which may be used with detonator junctions  12 . In FIG. 5, the detonator junctions  12  are connected in parallel. The first detonator junction  12   a  is connected by transmission lines  26  directly to the second detonator junction  12   b  and the third detonator junction  12   c.  When the detonator  14  in the first detonator junction  12   a  detonates, a shock wave is initiated in both transmission line  26   b  and transmission line  26   c  almost simultaneously. The shock wave then continues to propagate and pass as described above in relation to FIG. 5. The configuration of detonator junctions  12   a - c  in FIG. 5 may be referred to as a parallel blasting network  88 .  
     [0081] Referring now to FIG. 6, alternatively, detonator junctions  12  may be used to configure a serial blasting network  98 , one in which the shock wave passes in series from one detonator junction  12  to the next. FIG. 6 includes the same elements as in FIG. 5, except that the network connection between detonator junctions  12  is different.  
     [0082] Once a shock wave is initiated in the first detonator transmission line  26   a,  the shock wave is communicated, in the manner described above, from the detonator  14  in the first detonator junction  12   a  to the transmission lines  26   d - f  coupled to the explosives  90   a - c  and to the transmission line  26   b  of the second detonator junction  12   b.  This process of communicating the shock wave from the first detonator junction  12   a  to the second detonator junction  12   b  may continue for as many detonator junctions  12   c - e  connected in series in the serial blasting network  98 . Of course detonator junctions  12  may be used to create a mixed blasting network (not shown) in which some detonator junctions  12  are connected in series and some detonator junctions  12  are connected in parallel.  
     [0083] In view of the foregoing, the detonator junction  12  provides advantages over conventional devices. The limiting member  36  assists in maintaining transmission lines  26  within the slot  30  to limit inadvertent removal of transmission lines  26  from a detonator junction  12 . Furthermore, the clip  16  helps to maintain and properly position a detonator  14  within the channel  40  to insure proper positioning of the detonator  14  relative to transmission lines  26  within the slot  30 .  
     [0084] Furthermore, the present invention may be embodied in other specific forms without departing from its scope or essential characteristics. The described embodiments are to be considered in all respects only illustrative, not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.