Abstract: In the field of blasting, it is often desirable to ignite explosives at various relative times. Such delayed ignition can have advantages in better break up of rock and reduced ground vibration. A principle problem in using the time delay technique is the accuracy rate of a local oscillator which measures the delay time for each of the delay circuits. In the described system, a calibration interval, independent of any delay time, is transmitted from a control unit concurrently to each of the delay circuits wherein each delay circuit counts the output of its local oscillator during the calibration interval. This local oscillator output is then compared to a predetermined reference count, either at the delay circuit or at the control unit, and a correction factor is established. This correction factor is then applied to a delay count for the individual delay circuit.

Abstract: An electronic delay blasting circuit (100) receives an input signal through input lines (102, 104). The input signal is passed through a rectifier (106) to produce a DC signal for storing charge on capacitors (140, 152). The capacitor (152) serves as a power supply for a digital counting circuit. The capacitor (140) serves to store electrical energy for firing an electric match ignition element (174). A plurality of switches (200, 202, 244, 246, 248, 250 and 252) are set to a reference count to determine the delay period of the circuit (100). When the input signal is terminated, counter circuits (196, 198) are initiated to count the clock output of an oscillator (208). When the sequential count from the counters (196, 198) equals the stored reference count, an SCR (176) is triggered to apply the stored electrical charge from capacitor (140) to the electric match ignition element (174).

Abstract: An electronic delay blasting cap (10) receives an input signal over leg wires (12, 14). The input signal is passed through a rectifier (16) to produce a D.C. signal on output lines (26, 28). The D.C. signal charges a storage capacitor (32). When the input signal is removed or the wires (12, 14) are opened or shorted, the charge storage capacitor (32) discharges through a resistor (36) to produce a voltage which charges a timing capacitor (38). When the voltage on capacitor (38) reaches the threshold voltage of a zener diode (48) the diode is rendered conductive which in turn activates an SCR (46). A resistive ignition element (44) is connected in series with the SCR (46) and the charge storage capacitor (32) and is ignited when the SCR (46) is turned on. The charge stored in capacitor (32) causes ignition of the ignition element (44).

Abstract: An electronic delay blasting cap (10) receives an input signal over leg wires (12, 14). The input signal is passed through a rectifier (16) to produce a D.C. signal on output lines (26, 28). The D.C. signal charges a storage capacitor (32). When the input signal is removed or the wires (12, 14) are opened or shorted, the charge storage capacitor (32) discharges through a resistor (36) to produce a voltage which charges a timing capacitor (38). When the voltage on capacitor (38) reaches the threshold voltage of a zener diode (48) the diode is rendered conductive which in turn activates an SCR (46). A resistive ignition element (44) is connected in series with the SCR (46) and the charge storage capacitor (32) and is ignited when the SCR (46) is turned on. The charge stored in capacitor (32) causes ignition of the ignition element (44).

Abstract: An electronic blasting cap (10) includes a housing (12) which is closed at one end and has adjacent thereto it a base charge (14), a primer charge (16) and an ignition charge (18). The charges (14, 16, 18) are positioned within housing (12) by a metal capsule (20). An electric match assembly (26) is positioned within an insulated spacer (24) within housing (12). An electronic module (32) comprising an electronic delay circuit (90) fixed within a potting compound is positioned within housing (12). A sealing plug (38) closes housing (12) by means of crimps (40, 42). An input signal is received over leg wires (34, 36) for storing an electric charge within circuit 90 which fires the electric match assembly 26 following a preset time delay.

Abstract: A nonelectrically initiated delay booster assembly includes a booster shell containing an explosive material, a cap well extending through one end of the booster shell into the explosive material, a nonelectric delay cap in the well and a detonating cord tunnel surrounded by a shock absorbing material affixed to the side of the booster shell or enclosed inside the booster shell. A signal carrier extends from a point within the cap to a point adjacent a detonating cord extending through the detonating cord tunnel, and a sensor member is affixed to that end of the signal carrier that is external to the booster shell in such a manner that it is in initiating relationship with the detonating cord extending through the detonating cord tunnel. A plurality of these boosters can be affixed to a single detonating cord downline when conducting multi-deck blasting operations.