Non-electric double delay borehole downline unit for blasting operations

Claim 1

A preassembled non-electric double delay borehole downline unit for sequential firing blasting operations for delaying both initiation of a charge within a first borehole after the signal has been received therein and passage of signal transmission down a second borehole and toward succesive boreholes comprising a length of flexible impulse propagating tubing having first and second ends and an impulse propagating hollow channel extending along the length thereof, a non-electric high strength blasting cap containing a first delay element connected to said first end for initiation by an impulse traveling along said channel and for initiating the borehole explosive charge within said first borehole, an impulse amplifying and transmitting cap containing a second delay element connected to said second end for initiation by an impulse traveling along said channel and for delaying signal transmission beyond said transmitting cap, said delay elements being comprised of pyrotechnic material having different time delay periods with said first delay element having a substantially longer time delay period than said second delay element and a protective block having a plurality of elongated apertures with one of said apertures fully and snugly receiving said amplifying cap therein.