NON-ELECTRIC DOUBLE DELAY BOREHOLE DOWNLINE UNIT FOR BLASTING OPERATIONS

摘要

ABSTRACT OF THE DISCLOSUREA non-electric double delay borehole downlineunit is provided for delaying transmission of an explo-sive signal down a borehole and also delaying initiationof the charge within the borehole after the signal hasbeen received therein. The double delay unit comprisesa length of flexible impulse propagating tubing havingfirst and second ends and an impulse propagating hollowchannel extending along the length thereof, a non-electrichigh strength blasting cap containing a first delayelement connected to the first end for initiating aborehole explosive charge, an impulse amplifying andtransmitting cap containing a second delay element con-nected to the second end and a protective block having aplurality of elongated apertures with one of said aper-tures fully and snugly receiving the amplifying captherein.The present invention relates generally toexplosive signal transmission assemblies for boreholeblasting operations. More particularly it is concernedwith a new and improved non-electric delay blasting unitfor use in boreholes to provide a delay in both the ini-tiation of the borehole charge and the transmission ofthe signal to succeeding boreholes.In borehole blasting operations certain advan-tages have been achieved by providing dual delays forexplosive signal transmission to each borehole charge. Afirst delay is provided at the detonator cap positionedwithin the borehole while a second delay controls signaltravel into the borehole. Heretofore, in order to-1-accomplish this, it has been necessary to splice a delayconnector into the surface trunkline of the system andto use a blasting cap having a different delay intervalwithin the borehole. Conventionally, the delay providedwithin the cap is of substantially longer duration thanthe delay provided by the surface connector. This assuresthat the signal is transmitted along the trunkline to asufficient number of borehole downlines prior to theinitiation of the explosive charge within the first bore-hole. Such sequential or rotational firing minimizes thepossibility of cut-offs at the trunkline due to groundmovement while at the same time reduces vibration andimproves fragmentation in the blasting operation. Aswill be appreciated, dual delay blasting systems usedheretofore have required warehousing of a number ofdifferent types of delay devices having different timedelay intervals. From a practical standpoint, suchblasting operations also have been limited to about 7 to8 delays within the system in order to maintain therequisite control over the time delay period. Additional-ly, not only have two separate delay products beenrequired but these products have also been extremely noisyin operation, and their use has been limited to thoseareas where their inherent noise character would not pre-sent a problem, thus limiting their use.The present invention provides for a substantiallymore simplified delay hook-up for borehole blasting oper-ations by the utilization of a single non-electric doubledelay borehole downline unit that will provide the re-quisite delay in sending the signal down the borehole as-2-well as the appropriate delay in initiating the charge with-in the borehole after the signal has been received therein.Another feature of the present invention is toprovide a new and improved non-electric double delay bore-hole downline unit that effects millisecond delay blastingcoupled with the efficiency of purchasing and warehousingonly a single product while at the same time achievingthese advantages at a substantially reduced noise level.Still another object of the present inventionis to provide a new and improved double delay unit of thetype described wherein the explosive content of theassembly is significantly lower than presently availablenon-electric delay systems yet provides improved reli-ability and safety coupled with ease of hook-up and useof the same unit to initiate a larger number of sequen-tially fired holes.A further object of the present invention isto provide a double delay unit of the type described thatis capable of functioning as a replacement for a portionof the trunkline at substantially reduced noise levelsand permits rapid, easy interconnection within theblasting system while exhibiting advantages of manufacture,distribution and use.Other objects will be in part obvious and inpart pointed out more in detail hereinafter.These and related objects are accomplished inaccordance with the present invention by providing a newand improved non-electric double delay borehole downlineunit for both delaying transmission of an explosivesignal down a borehole and also delaying initiation of-3-the charge within the borehole after the signal has beenreceived therein. This single double delay unit is com-prised of a length of flexible explosive impulse pro-pagating fuse or tubing having first and second ends andan impulse propagating channel extending along the lengththereof. A non-electric high strength detonator orblasting cap containing a first delay element is connectedto the first end of the signal propagating tubing forinitiating the borehole explosive charge. Connected tothe second end of the tubing is an impulse or signalamplifying and transmitting cap containing a second delayelement. A protective connecting block having a pluralityof elongated apertures protectively houses the amplifyingand transmitting cap within one of the apertures andfully and snugly retains the cap while facilitatinginterconnection with adjacent signal transmitting lines.A better understanding of the invention will beobtained from the following detailed description and theaccompanying drawing of an illustrative application ofthe invention.