Patent Publication Number: US-2003221578-A1

Title: Detonator with onboard electronics mechanically connected to ignition element

Description:
BACKGROUND OF THE INVENTION  
       [0001] The present invention relates to pyrotechnic detonators, and more particularly, to a detonator having onboard electronics and an ignition element that are mechanically connected to each other.  
       [0002] The efficient use of explosives in mining operations and the demolition of structures often requires that many charges be placed in a predetermined pattern and detonated in a timed sequence. In general, timed detonation can be accomplished by detonators that use pyrotechnic delays, sequential-type blasting machines, and electronically programmable detonators. Some examples of detonators that have onboard electronics, i.e., electronics contained within the detonator itself, for processing an ignition signal from, e.g., a blasting machine, are described in U.S. Pat. Nos. 6,173,651, 6,085,659, 6,079,332, 5,602,360, 5,460,093, 4,869,170, 4,819,560, 4,730,558, and 4,712,477, the disclosures of which are hereby incorporated by reference herein.  
       [0003] Such detonators involve soldered connections between the ignition element of the detonator to the onboard electronics, which presents at least the risk of damaging or detonating the ignition element. It is believed that hitherto this problem has not been addressed through the provision of a means to mechanically connect the ignition element to the onboard electronics in a detonator.  
       SUMMARY OF THE INVENTION  
       [0004] It is an objective of the present invention to provide a means to mechanically connect the ignition element in a detonator to onboard electronics, thus eliminating the risk of making a soldered or similar connection in immediate proximity to the ignition element of the detonator. 
     
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
     [0005]FIG. 1 is a top sectional view of an embodiment of the present invention.  
     [0006]FIG. 2 is a partial top sectional view of the ignition element and connection portion of the embodiment shown in FIG. 1.  
     [0007]FIG. 3 is side view corresponding to FIG. 2.  
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 1    
     [0008] Referring to FIGS.  1 - 3 , a detonator utilizing an embodiment of the present invention is shown. Referring to FIG. 1, an ignition subassembly  8  is placed inside of a shell  40  that may contain a primary charge  36  and a base charge  38  loaded into its closed end. (A detonator shell is typically a metal cylinder 6 to 8 mm. in diameter and from 60-100 mm. in length). Subassembly  8  can then be secured in place in the shell  40 , such as by placing an elastomeric plug or the like (see elastomeric plug  46  and crimp  47  in FIGS. 5 and 6) in the open end of the shell and crimping the shell  40  to the plug, or other suitable method. Subassembly  8  may have a body portion formed of an encapsulation  31  and is preferably formed to snugly fit within the shell  40 , preferably with features such as ridges or other protuberances formed to dampen vibrations to which the detonator may be subjected, generally in accordance with the teachings of U.S. Pat. No. 6,079,332. Some relevant teachings regarding encapsulation are also set forth in U.S. Pat. Nos. 6,079,332 and 4,869,170.  
     [0009] A header-based, or automotive airbag initiator-style, ignition element  28  is shown in the embodiment depicted in the Figures, but a detonator according to the present invention may include any kind of suitable ignition element (e.g., matchhead-type). U.S. Pat. Nos. 6,274,252, 5,709,724, 5,639,986, 5,602,359, 5,596,163, 5,404,263, 5,140,906, and 3,971,320 are also hereby incorporated by reference herein for their disclosure concerning the construction of ignition elements based on a glass-to-metal sealed header feedthrough, including the types of pins commonly used.  
     [0010] As shown in FIG. 2, ignition element  28  includes a header assembly with a sealed electrical feedthrough, comprising an eyelet  10  (preferably stainless steel), insulator glass  14  (preferably a glass such as a sodasilicate, e.g., 9010, that is chosen to form a compression seal with the eyelet and center pin, or less preferably a matched seal), a center pin  18  (preferably iron/nickel alloy), a ground pin  20 , and an igniter wire  12  (preferably a low energy igniter wire with a diameter of 10 to 20 microns). The ignition element  28  further preferably includes a charge can  26  that is preferably metallic and hermetically sealed to the eyelet at circumferential through-weld  16 , with an ignition charge  30  contained between the can  26  and upper surface of the header, in tight contact with igniter wire  12 . An insulator cup  27  may preferably be attached around the can  26  so that, except for female connectors  52  that protrude from the input end of the subassembly, the entire outer surface of ignition subassembly  8  consists of insulating material, thus providing electrical isolation and vibration and environmental protection to the components within until such time as the subassembly is placed in the detonator shell.  
     [0011] Turning again to FIG. 1, it can be seen that a circuit board  24  and electronic components  25  are provided within ignition subassembly  8 , to provide a means of triggering ignition of the ignition element based on the processing of an electrical ignition signal from a blasting machine or the like that supplies power and commands to the detonator. Such electronic components are well-known and preferably include means for imparting a programmable period of delay to the ignition, means for ESD and RF protection, et cetera. (Another preferred alternative is the use of an application-specific integrated circuit). Circuit board  24  and electronic components  25  are preferably encapsulated together in encapsulation  31 , and connected to female connectors  52  and to plug and crimp connectors  50  at contacts  22  through soldering or other suitable connection.  
     [0012] Suitable plug and crimp connectors  50  that may be purchased off the shelf are suitable for use in an embodiment of the present invention like that depicted. Thus, after the plug and crimp connectors  50  are attached to the circuit board  24  (or other electronics), pins  18  and  20  of ignition subassembly  28  are inserted within the openings of connectors  50 , and a crimping tool is used to securely crimp the connectors  50  to pins  18  and  20 . Virtually any contact pin (of appropriate size) designed for use with a header is suitable for use with connectors  50 . After the plug and crimp connection has been made, ignition subassembly  8  can be completed by the provision of encapsulation  31  around the circuit board, electronics, plug and crimp connectors, pins, and bottom of the ignition subassemblies.  
     [0013] Alternately to a plug and crimp connection, a standard off-the-shelf “Insulation Displacement Connection” (IDC) can be made, with or without insulation sheathing on the pins. IDCs may be soldered during circuit board assembly in conventional fashion. The pins  18  and  20  of ignition subassembly  28  can then be inserted into an IDC and secured.  
     [0014] It should be noted that although the Figures depict embodiments including electronic components that receive, process, and deliver an ignition signal, such an ignition signal may alternately be received, processed, and delivered by a number of other well-known non-electronic or partly-electronic means, such as through the use of a shock tube to deliver an ignition signal to a piezoelectric device, column fuse delays, et cetera. It is noted that this detailed description of certain embodiments herein does not imply that such alternate embodiments are not within the scope of the invention.  
     [0015] A preferred embodiment of a detonator having an ignition element and onboard electronics that are mechanically connected together, and many of its attendant advantages, has thus been disclosed. It will be apparent, however, that various changes may be made in the form, construction, and arrangement of the parts without departing from the spirit and scope of the invention, the form hereinbefore described being merely a preferred or exemplary embodiment thereof. Therefore, the invention is not to be restricted or limited except in accordance with the following claims.