Patent Publication Number: US-11021415-B2

Title: Conductive shock tube

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a conductive shock tube. 
     A conventional shock tube is capable of enabling communication in one direction only i.e. a fire signal that is transmitted from a blasting machine, via the shock tube, to an explosive charge. Communication from a detonator to the blasting machine is not possible. Thus, the status of the detonator prior to sending the fire signal cannot be confirmed, prior to detonation, using the shock tube. Additionally a shock tube cannot convey information, other than the fire signal, to a detonator. 
     An aim of the current invention is to address, at least partially, the aforementioned situation. 
     SUMMARY OF INVENTION 
     The invention provides a shock tube for propagating an initiating signal to an explosive charge, the shock tube including a body that is connectable to a blasting machine and at least first and second elongate flexible conductors on or in the body which enable two-way communication between the explosive charge and the blasting machine. 
     Each conductor may be in the form of a coating or a deposit made from a stretchable electrically conducting material. The material may be an organic/polymeric conductive material, a metal oxide-based material, or may be made from a mixture of an organic/polymeric conductive material and a metal oxide-based material. 
     Each conductor may be printed using a suitable technique on or in the body. Each conductor may be printed in a pattern which is suitable to flexing or stretching deformation of the shock tube, without breaking the conductor. 
     Each conductor may be printed on a respective layer of material that surrounds an energy propagating core of the shock tube. Preferably, a first conductor is printed on a first layer of material that surrounds the energy propagating core and a second conductor is printed on a second layer of material which surrounds the first layer of material. 
     The first and the second conductors may culminate in a suitable connecting member which is connectable to a connector located in or on a detonator. 
     The invention also provides a connector for connecting a shock tube of the aforementioned kind to the explosive charge which, preferably, is a detonator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is further described by way of example with reference to the accompanying drawings wherein; 
         FIG. 1  is a cross-sectional view of a conductive shock tube according to the invention; and 
         FIG. 2  is a schematic representation of a connecting member for connecting first and second conductors of the shock tube of  FIG. 1  to a detonator. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
       FIG. 1  of the accompanying drawings illustrates a shock tube  10  which includes an elongate tubular body  12  which defines a bore  18  housing a core  20  made from or containing an energy propagating material  20 A. 
     The energy propagating material  20 A is surrounded by a first protective layer  22  and a second protective layer  24 . Each layer  22 ,  24  consists of a suitable material having appropriate electrical insulating, waterproof and abrasion-resistant properties. 
     A first elongate flexible conductor  26  and a second elongate flexible conductor  28 , each in the form of a conductive coating, are printed on the first and the second layers respectively. Each of the conductors  26  and  28  completely surrounds the respective layer  22 ,  24 . This is by way of example only and is non-limiting. 
     The first and second conductors  26  and  28 , at an end  30  of the shock tube which, in use, is to be connected to a detonator  32 , culminate in a connecting member  34  which is connectable to a connector  36  of the detonator—see  FIG. 2 . The connecting member  34  includes a cap  38  which is fitted onto the end  30 , a support structure  40 , and contacts in the form of a first conductive pin  42  and a second conductive pin  44  which extend to one side of the support structure (to the left in  FIG. 2 ). Each pin  42 ,  44  is embedded in or penetrates the first conductor  26  and second conductor  28  respectively. 
     A first contact or conductive nub  46  and a second contact or conductive nub  48  are connected to the first and second pins  42  and  44  respectively which extend through the support structure  40 . The connector  36 , on the detonator, has annular conductive surfaces  50  and  52  which respectively oppose the conductive nubs  46  and  48 . 
     The cap  38  is attached to the end  30  in any suitable way e.g. by means of a crimping member  54 . The cap  38  includes an external thread  56 . 
     The connector  36  includes a formation  58  which is complementary to the cap  38  and has an internal thread  60  which is threadedly engageable with the thread  56 . In use, the formation  58  and the cap  38  are threadedly secured to each other to hold the nubs  46 ,  48  and the surfaces  50  and  52  respectively in electrical contact with one another. 
     Electrical leads  64  and  66  extend from the surfaces  50  and  52  to electronic components (not shown), in the detonator  32 . 
     As an alternative to the tubular conductors  26  and  28 , the first and second conductors may each be printed in a wavy or spiral pattern on respective tubular substrates or layers e.g. the layers  22 ,  24 . These patterns allow for flexing and stretching of the shock tube, without leading to breaking of the conductors. 
     The first and second layers  22 ,  24  could each be coated with the material which forms the first and second conductors, using techniques that do not require alteration of existing shock tube manufacturing techniques. 
     The conductors  26  and  28  are made from an organic/polymeric conductive material, or a metal oxide-based material, or a mixture of the organic/polymeric conductive material and a metal oxide-based material. This type of material can be “stretched” to a substantial degree without breaking. 
     In the drawings the conductors  26 ,  28  are shown enlarged. This is for illustrative purposes only. In practice the conductors are thin, particularly if formed by means of a printing technique, and the shock tube  10  would have a diametrical dimension substantially equal to that of a conventional shock tube.