Abstract This is an electrical circuit for time limiting the application of current to an external load. A charging network is fed by alternating current having a capacitor charged through resistance means and a diode when a switching element is positioned conductive between the capacitor and resistance means. A pulsing network is fed by the alternating current which network has a transformer, resistance means, diode and Zener diode providing a pulse to a first silicon controlled rectifier on the half-cycle when the switching element is positioned nonconductive between the capacitor and the resistance means and is positioned conductive between the capacitor and the first rectifier. A second silicon controlled rectifier receives the potential of the capacitor through the first rectifier in its conducting state which in turn allows the second rectifier to conduct and thus permit the capacitor to discharge through said second rectifier to the external load to be controlled. This circuit is particularly adapted to the firing of electrically activated delay blasting caps without arcing when using high voltage.
An electrical circuit for controlling the time duration of current application to an external load comprising in combination: a. a charginG network fed by a source of alternating current said charging network comprising input terminals, a capacitor, resistance means, a diode and a switching element, said capacitor being charged through the resistance means and diode when the switching element is positioned conductive between the capacitor and resistance means; b. a pulsating network fed by the alternating current, said pulsating network comprising a transformer, resistance means, diode, Zener diode and a first silicon controlled rectifier, said pulsing network providing a pulse to the first silicon controlled rectifier on the half-cycle when the switching element is positioned nonconductive between the capacitor and resistance means of the charging network and is positioned conductive between the capacitor and the first silicon controlled rectifier in the pulsing network; and c. a second silicon controlled rectifier receiving the potential of the capacitor through the first silicon controlled rectifier in its conducting state which in turn allows the second silicon controlled rectifier to conduct and thus permit the capacitor to discharge through said second silicon controlled rectifier to the external load to be controlled.
Claim 2
Dependent Claim
197 words
An electrical circuit for controlling the time duration of current application to an external load comprising in combination: a. a charginG network fed by a source of alternating current said charging network comprising input terminals, a capacitor, resistance means, a diode and a switching element, said capacitor being charged through the resistance means and diode when the switching element is positioned conductive between the capacitor and resistance means; b. a pulsating network fed by the alternating current, said pulsating network comprising a transformer, resistance means, diode, Zener diode and a first silicon controlled rectifier, said pulsing network providing a pulse to the first silicon controlled rectifier on the half-cycle when the switching element is positioned nonconductive between the capacitor and resistance means of the charging network and is positioned conductive between the capacitor and the first silicon controlled rectifier in the pulsing network; and c. a second silicon controlled rectifier receiving the potential of the capacitor through the first silicon controlled rectifier in its conducting state which in turn allows the second silicon controlled rectifier to conduct and thus permit the capacitor to discharge through said second silicon controlled rectifier to the external load to be controlled.
Claim 3
Dependent Claim
17 words
The circuit of claim 1 in which the external load comprises at least one delay blasting cap.
Claim 4
Dependent Claim
33 words
The combination of claim 2 in which the time constants of the circuit provide a time-duration application of current to the delay blasting cap which is from about 5 to about 7 milliseconds.
Claim 5
Dependent Claim
16 words
The circuit of claim 1 in which a timer means is connected across the input terminals.
Claim 6
Dependent Claim
44 words
The circuit of claim 4 in which the external load comprises at least one delay blasting cap and the time constants of the circuit provide a time-duration application of current to the delay blasting cap which is from about 5 to about 7 milliseconds.