Abstract:
Multiple independent penetrating electrode non-electric tips in which the electrodes are separated in a non-coaxial arrangement so as to generate a spark gap internal to the non-electric shock tube, with the electrodes being brought together inside of the shock tube at a very precise distance, improving longevity by eliminating ablation of the insulating material between the inner and outer electrodes, reducing electrical shorting of the electrodes, and providing more consistent and reliable ignition of shock tubes.

Description:
STATEMENT OF RELATED APPLICATIONS  
       [0001]    This patent application claims priority on U.S. Provisional Patent Application No. 60/368,812, having a filing date of Mar. 29, 2002. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of Invention  
           [0003]    The invention generally relates to the blasting industry and the explosive ordnance disposal (EOD) industry as a reliable initiation device for non-electric shock tube, which is achieved by electronic means, and more specifically relates to the field of initiator tip devices for igniting a shock tube.  
           [0004]    2. Prior Art  
           [0005]    FIGS.  1 - 3  illustrate a standard a standard coaxial initiator tip device assembly showing an outer electrode tube  1  with insulator material  2  such as Teflon® and a center electrode  3 , thus comprising a coaxial electrode assembly. The precise gap is achieved by regulating the distance between the center electrode  3  and the outer electrode tube  1 . High voltage with a potential difference of between 1500˜3000 volts is applied to the two electrodes  1 ,  3 , which will produce a hot plasma arc and ignite the non-electric shock tube  4 .  
           [0006]    Standard coaxial initiator tip devices shown such as that shown in FIGS.  1 - 3  are known in the art and are in common usage. However, the existing method of a coaxial spark gap suffers from disadvantages such as excess ablation of the insulating material between the inner and outer electrodes, thus leading to electrical shorting of the electrodes and hence a failure to provide enough energy to ignite the shock tube. As a result, the standard coaxial initiator tip devices are suitable only for a limited number of uses, with each successive use generally being less effective that the prior use.  
           [0007]    While the prior art proceeds to disclose an array of initiator tip devices for igniting shock tubes, the prior art devices generally do not provide a consistent and reliable spark throughout the life of the device. What is needed but not found in the prior art is a device for the initiation or ignition of shock tubes that significantly improves the consistency and reliability of spark generation throughout a longer lifetime.  
           [0008]    It is to these needs and others that the present invention is directed. By utilizing a non-coaxial design contained in a compact casing, and utilizing simple mechanical means for inserting the electrodes into the shock tube for ignition, the present invention has distinct advantages over the known prior art.  
         BRIEF SUMMARY OF THE INVENTION  
         [0009]    The function of the multiple independent penetrating electrode non-electric initiator tip of the present invention is for the purpose of igniting the small quantity of explosives contained inside the plastic tubing, such as RDX or PETN, of a shock tube. The combination of the explosive material combined with the plastic tubing forms a low velocity shock tube, as known by those practiced in the art as a non-electric shock tube. A non-electric shock tube is used to initiate a blasting cap&#39;s primary explosive charge, which in turn ignites the base charge. Non-electric blasting caps rely on the ignition of the shock tubing attached to them as a means of ignition.  
           [0010]    Briefly, the multiple independent penetrating electrode non-electric tip of the present invention comprises at least two electrodes that are separated from each other in a non-coaxial arrangement. The separation generates a spark gap internal to the non-electric shock tube, with the electrodes being brought together inside of the shock tube at a very precise distance. Two non-coaxial electrodes are inserted into a shock tube at different locations so as to create the spark gap between the electrodes such that when the electric charge is delivered a spark is created within the spark gap thus igniting the shock tube. This construction improves the longevity of the device when compared to other devices by eliminating ablation of the insulating material between the inner and outer electrodes of other devices, reduces electrical shorting of the electrodes, and provides more consistent and reliable ignition of shock tubes.  
           [0011]    The present invention further comprises a structure containing the electrodes and allowing for a shock tube to be inserted and ignited. At a minimum, the structure containing the electrodes should have a place where the shock tube can be inserted into the structure, a means for inserting a first electrode into the shock tube, a means for inserting a second electrode into the shock tube, and a means for providing an electric current across the electrodes to create the ignition spark.  
           [0012]    These features, and other features and advantages of the present invention will become more apparent to those of ordinary skill in the art when the following detailed description of the preferred embodiments is read in conjunction with the appended figures. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a sectional side view of a prior art coaxial initiator tip assembly.  
         [0014]    [0014]FIG. 2 is an end view of the prior art coaxial initiator tip assembly shown in FIG. 1.  
         [0015]    [0015]FIG. 3 is a sectional side view of a prior art coaxial initiator tip assembly tip shown with a power supply and inserted into a shock tube.  
         [0016]    [0016]FIG. 4 is a schematic sectional side view of a first embodiment of a multiple independent penetrating electrode non-electric initiator tip according to the present invention in a perpendicular electrode arrangement.  
         [0017]    [0017]FIG. 5 is a schematic sectional side view of a second embodiment of a multiple independent penetrating electrode non-electric initiator tip according to the present invention in an opposing electrode arrangement.  
         [0018]    [0018]FIG. 6 is a schematic sectional top view of a third embodiment of a multiple independent penetrating electrode non-electric initiator tip according to the present invention in an opposing cutting wheel arrangement.  
         [0019]    [0019]FIG. 7 is a schematic sectional top view of a fourth embodiment of a multiple independent penetrating electrode non-electric initiator tip according to the present invention in an opposing cutting wheel with a tertiary electrode arrangement.  
         [0020]    [0020]FIG. 8 is a schematic sectional side view of a fifth embodiment of a multiple independent penetrating electrode non-electric initiator tip according to the present invention in an arrangement having two independent penetrating electrodes mounted in an insulating block.  
         [0021]    [0021]FIG. 9 is a schematic sectional side view of a sixth embodiment of a multiple independent penetrating electrode non-electric initiator tip according to the present invention in an arrangement having two independent penetrating electrodes mounted by plasma deposition on a ceramic rod.  
         [0022]    [0022]FIG. 10 is an isometric view of a preferred embodiment of the present invention.  
         [0023]    [0023]FIG. 11 is a side view of the embodiment of the present invention shown in FIG. 10.  
         [0024]    [0024]FIG. 12 is a top view of the embodiment of the present invention shown in FIG. 10 in the load position.  
         [0025]    [0025]FIG. 13 is a top view of the embodiment of the present invention shown in FIG. 10 in the fire position.  
         [0026]    [0026]FIG. 14 is an exploded view of the embodiment of the present invention shown in FIG. 10 showing the various parts of the invention.  
         [0027]    [0027]FIG. 15 is a side detail view of the adjustable electrode, spring, current path connecting link, and banana plug assembly of the embodiment of the present invention shown in FIG. 10.  
         [0028]    [0028]FIG. 16 is a bottom view of the embodiment of the present invention shown in FIG. 10.  
         [0029]    [0029]FIG. 17 is a top view of the pinion gear and rack piercing assembly of the embodiment of the present invention shown in FIG. 10.  
         [0030]    [0030]FIG. 18 is a schematic sectional side view of the rack piercing assembly, adjustable electrode, and shock tube of the embodiment of the present invention shown in FIG. 10. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    The design of the multiple independent electrode non-electric initiator of the present invention separates the electrodes from each other in a non-coaxial arrangement so as to generate a spark gap between the electrodes and also internal to the non-electric shock tube. The electrodes are brought together inside of the shock tube at a very precise distance apart from each other. This provides improved longevity compared to the prior art devices as the prior art method of using a coaxial spark gap suffers from ablation of the insulating material between the inner and outer electrodes and thus leads to electrical shorting of the electrodes and hence a failure to provide enough energy to ignite the shock tube.  
         [0032]    The ignition of the shock tube is greatly enhanced by introducing the electrodes independently, internal to the shock tube, as opposed to placing the electrodes external to the shock tube. While it is possible to provide ignition with external electrodes, relative to the shock tube, the energy available to ignite the explosive within the shock tube is diminished. Therefore, it is a preferred method of this embodiment to generate the electric spark, or plasma arc, internal to the shock tube with multiple independent penetrating electrodes.  
         [0033]    The present invention can be configured in many equivalent manners having the same end result. Illustrative embodiments of several preferred configurations are shown in FIGS.  4 - 9 . However, the invention is not limited to these illustrative embodiments, which are presented to provide a basic understanding of the invention.  
         [0034]    A first preferred embodiment of the invention is shown schematically in FIG. 4. The embodiment shown in FIG. 4 employs two internal electrodes  4 ,  5  that are inserted into shock tube  6  perpendicular to each other. Spark gap G formed between electrodes  4 ,  5  internal to shock tube  6  is an example of a multiple independent penetrating electrode non-electric shock tube initiator in a perpendicular electrode arrangement.  
         [0035]    A second preferred embodiment of the invention is shown schematically in FIG. 5. The embodiment shown in FIG. 5 employs two internal electrodes  7 ,  8  that are inserted into shock tube  6  from opposing sides. Spark gap G formed between electrodes  7 ,  8  internal to shock tube  6  is an example of a multiple independent penetrating electrode non-electric shock tube initiator in an opposing electrode arrangement.  
         [0036]    A third preferred embodiment of the invention is shown schematically in FIG. 6. The embodiment shown in FIG. 6 employs two opposing razor wheels  9 ,  10 . As shock tube  6  is pushed into the razor wheels  9 ,  10 , shock tube  6  is displaced by the cutting or slicing action of razor wheels  9 ,  10  such that razor wheels  9 ,  10  form a fixed distance spark gap G between razor wheels  9 ,  10 . FIG. 6 is a second example of a multiple independent penetrating electrode non-electric shock tube initiator in an opposing electrode arrangement.  
         [0037]    A fourth preferred embodiment of the invention is shown schematically in FIG. 7. The embodiment shown in FIG. 7 combines the two opposing razor wheel  12 ,  13  arrangement shown in FIG. 6 with a tertiary electrode  11 . The embodiment shown in FIG. 7 is both an insulation displacement technique using razor wheels  12  and  13  to displace the shock tube  6  and a tertiary electrode  11  that forms a fixed gap G with the razor wheels  12 ,  13  thus forming a third example of a multiple independent penetrating electrode non-electric shock tube initiator in an opposing electrode arrangement.  
         [0038]    A fifth preferred embodiment of the invention is shown schematically in FIG. 8. The embodiment shown in FIG. 8 comprises two independent electrodes  14 ,  15  that are maintained at a fixed gap G by an insulating block  16 . Insulating block  16  can be made of a material such as, but not limited to, polymer, glass, ceramic, or composite materials, as illustrative examples. The electrodes  14 ,  15  and the insulating block  16  are slid inside shock tube  6 , forming a multiple independent penetrating electrode non-electric shock tube initiator assembly.  
         [0039]    A sixth preferred embodiment of the invention is shown schematically in FIG. 9. The embodiment shown in FIG. 9 also comprises two independent electrodes  18 ,  19  that are plasma coated to a ceramic or other insulative rod  17 . The ceramic rod  17  creates spark gap G between electrodes  18 ,  19 . The electrodes  18 ,  19  and the ceramic rod  17  are slid inside shock tube  6 , forming a multiple independent penetrating electrode non-electric shock tube initiator assembly.  
         [0040]    Each of the embodiments shown in FIGS.  4 - 9  can be contained in an independent electrode holder structure  50 , such as that shown in FIG. 10. For illustrative purposes, the embodiment of FIG. 4 will be used as the example embodiment in the following disclosure of a preferred structure  50 . However, those practiced in the art will be able to modify the structure  50  to contain any of the preferred embodiments, and their equivalents, without undue experimentation.  
         [0041]    [0041]FIG. 10 is an isometric view of a preferred embodiment of the multiple independent penetrating electrode non-electric shock tube initiator assembly of the present invention in a usable casing. Generally speaking, structure  50  comprises upper housing  23  and lower housing  28  that together form the casing containing electrodes  4 ,  5 ,  7 ,  8 ,  9 ,  10 ,  11 ,  12 ,  14 ,  15 ,  18 ,  19 . For ease of disclosure, the invention will be explained using two electrodes, namely moving electrode  38  and adjustable electrode  32 , as shown in more detail in FIG. 14. Shock tube  6  is inserted into structure  50  through insertion hole  36  and contacted to or impaled upon adjustable electrode  32 . This can be seen through viewing/exhaust port  37 . As discussed in more detail in connection with FIG. 18, adjustable electrode  32  is inserted into the end of shock tube  6 .  
         [0042]    [0042]FIG. 11 is an isometric side view of structure  50  showing in particular viewing/exhaust port  37 , adjustable electrode  32 , and electrical connections  29 ,  30 . High voltage shroud  40 , which is recessed, also indicated. Structure  50  is connected to a source of electricity (not shown) via connections  29 ,  30 , which provide the necessary electricity to electrodes  32 ,  38  to cause the spark.  
         [0043]    [0043]FIG. 12 is a top view of structure  50  with piercing assembly control arm  20  in the load position. FIG. 13 is a top view of structure  50  with piercing assembly control arm  20  in the fire position, exposing fire position warning indicator  39 . As discussed in more detail in connection with FIGS. 17 and 18, the rotation of piercing assembly control arm  20  from the load position to the fire position moves movable electrode  38  from a position outside of shock tube  6 , as shown in FIG. 17, and causes movable electrode  38  to pierce the side of shock tube  6  so as to penetrate shock tube  6  to a position proximal to adjustable electrode  32 , forming spark gap G, as shown in FIG. 18.  
         [0044]    [0044]FIG. 14 is an exploded side schematic view of the component parts of a preferred embodiment of the invention showing the structural and proximal relationship of the various components to each other. FIG. 15 is a side detail schematic view of adjustable electrode  32 , post adjustment retention spring  31 , high current connecting link  33 , and second banana post/retention screw connection  30 . FIG. 16 is a bottom detail schematic view of the invention showing second banana plug/retention screw connection  30 , adjustable electrode  32 , rear retention screw  35 , first banana plug/screw assembly  29 , and high voltage shroud  40 .  
         [0045]    [0045]FIG. 17 is a top detail schematic view of piercing assembly  25  with movable electrode  38 , and pinion drive gear  22  that is attached to control arm  20 . A cross-section of shock tube  6 , loaded onto adjustable electrode  32  also is shown. FIG. 18 is a side detail schematic view of piercing assembly  25  with movable electrode  38  penetrating a shock tube  6  segment with adjustable electrode  32  inserted into shock tube  6  through an end.  
         [0046]    The preferred embodiment of the invention uses independent electrodes  32 ,  38  that enter non-electric shock tube  6  at a non-coaxial and preferably perpendicular angle to achieve a spark gap G inside of non-electric shock tube  6  and that are encased in a polymeric housing structure  50 . The overall design is optimized for vertical integration; that is, shock tube  6  is inserted vertically into structure  50 . As electrodes  32 ,  38  do not use a coaxial design, the invention does not require an insulator in the vicinity of the plasma electrodes arc (the spark) to provide a separation between electrodes  32 ,  38 . The typical wear out mechanism of the coaxial initiator is removed from the design, thus insuring an improved longevity of the initiator tip.  
         [0047]    [0047]FIG. 14 shows the main components of the invention. Shaft  22  extends through upper housing  23  and connects control arm  20  to pinion drive gear  26 . Roll pin  21  secures control arm  20  to shaft  22  and setscrew  24  secures pinion drive gear to shaft  22 . First banana plug connection  29  is secured to lower housing  28  by lock nut  27  and provides electric current to pinion drive gear  26  by spring interface conductor  34 . These components act as a perpendicular piercing conductor assembly, as shown in FIGS. 17 and 18. The shaft  22  motion is facilitated by control arm  20 .  
         [0048]    Adjustable electrode  32 , which enters the hollow interior of shock tube  6  and forms spark gap G in conjunction with the rack piercing assembly  25 , has a post adjustment tensioning spring  31  that doubles as a current path for conductor interface link  33 . Conductor interface link  33  is held in place by the second banana plug screw assembly connection  30 , which serves both as a retention fastener for holding upper housing  23  and lower housing  28  together and as a current path for adjustable electrode  32 . Adjustable electrode  32  can have a screw-type structure allowing adjustable electrode  32  to be raised or lowered within structure  50 , thus allowing an adjustable insertion depth within shock tube  6 . Screw  35  serves as a secondary retention fastener for holding upper housing  23  and lower housing  28  together.  
         [0049]    Movable electrode  38  is attached to or a part of rack piercing assembly  25 . Rack piercing assembly  25  has a gear component that cooperates with pinion drive gear  26 . When control arm  20  is rotated from the load position to the fire position, shaft  22  is rotated, rotating pinion drive gear  26 . Pinion drive gear  26  then interacts and cooperates with the gear component of rack piercing assembly  25 , causing rack piercing assembly to move sideways, urging movable electrode  38  towards and piercing into shock tube  6 . When control arm  20  is rotated from the fire position to the load position, this process is reversed, withdrawing movable electrode  38  from shock tube  6 .  
         [0050]    [0050]FIG. 16 illustrates high voltage shroud  38  that protects the operator from high voltage, adjustable electrode  32 , rear retention screw  35 , and front retention banana plug connection  30 .  
         [0051]    Referring now to FIGS.  10 - 18 , an exemplary description of how the use of the device will be given. The device is attached to an electric source (not shown) with the control arm  20  in the retracted or disarmed or safety position. As shown more specifically in FIG. 10, shock tube  6  is inserted into insertion port  36  in upper housing  23  of structure  50  and pressed down on an electrode, typically second or adjustable electrode  32 . Adjustable electrode  32  enters shock tube  6  from the end of shock tube  6 , that is adjustable electrode  32  and shock tube  6  preferably are coaxial to each other.  
         [0052]    Control arm  20 , which is connected to rack piercing assembly  25 , which in turn comprises first or movable electrode  38 , is moved from the retracted or disarmed or safety position as shown more specifically in FIG. 12 to the inserted or armed or firing position as shown more specifically in FIG. 13. This movement, as illustrated in FIG. 17, causes movable electrode  38  to pierce the side of shock tube  6 , as illustrated in FIG. 18. Movable electrode  38  in this example enters shock tube  6  perpendicular to both the axis of shock tube  6  and adjustable electrode  32 , creating a spark gap G between electrodes  32 ,  38 .  
         [0053]    Once control arm  20  has been moved to the inserted or armed or firing position, electric current is sent through the electrodes  32 ,  38 , causing a spark in spark gap G between electrodes  32 ,  38 . This spark causes the ignition of shock tube  6 . After shock tube  6  has been ignited and used, it can be removed from insertion port  36  and another shock tube  6  substituted, and the device used again. It is contemplated that the device can be used many times with less wear that associated with the prior art, making the present invention more economical and more efficient, as well as easier and more convenient to use.  
         [0054]    As shown in the other figures, such as FIGS.  5 - 9 , the above description is illustrative only, and it is contemplated that other configurations of electrodes can be used. All such structures, and their equivalents, are covered by the present invention, which is the use of non-coaxial electrodes penetrating into a shock tube.  
         [0055]    In the second preferred embodiment shown in FIG. 5, opposing electrodes  7 ,  8  can be inserted in a piercing manner into shock tube  6 . Either or both electrodes  7 ,  8  can be connected to rack piercing assemblies  25 . In the third preferred embodiment shown in FIG. 6, shock tube  6  is urged against razor wheel electrodes  9 ,  10 . For example, razor wheel electrodes  9 ,  10  can be located on either side of insertion port  36  such that when shock tube  6  is inserted into insertion port, the sides of shock tube  6  contact and are penetrated (by cutting) by razor wheel electrodes  9 ,  10 . Similarly, in the fourth preferred embodiment shown in FIG. 7, tertiary electrode  11  can substitute for adjustable electrode  32 , and razor wheel electrodes  11 ,  12  act in the same manner of razor wheel electrodes  9 ,  10 . In this embodiment, the use of tertiary electrode  11  helps ensure a suitable spark.  
         [0056]    In the fifth preferred embodiment shown in FIG. 8, parallel or slightly converging electrodes  14 ,  15  are contained in an insulating block  16 . The combination of electrodes  14 ,  15  and insulating block  16  can substitute for adjustable electrode  32 . Similarly, in the sixth preferred embodiment shown in FIG. 9, electrodes  18 ,  19  are attached to ceramic rod  17 . The combination of electrodes  18 ,  19  and ceramic rod  17  can substitute for adjustable electrode  32 .  
         [0057]    The above description and examples set forth the best mode of the invention as known to the inventor at this time, and is for illustrative purposes only, as one skilled in the art will be able to make modifications to this process without departing from the spirit and scope of the invention and its equivalents as set forth in the appended provisional claims.