Selective firing apparatus

Claim 1

In apparatus for selectively detonating from an operating location a plurality of electrically detonatable explosive charge means located at a remote location and having: a. first and second conductor means for conducting electrical signals extending from the operating location to the remote location, and defining a first correlative conductor and electrical common at the remote location; b. means at said operationg location connected to said first and second conductor means for applying electrical signals of the desired polarities to said first and second conductor means; the improvement comprising: c. a plurality of discrete and separable gun means for carrying and detonating a predetermined number of said charges, said gun means being disposed at the remote location, each said gun means carrying, in addition to the charges, a charge selector assembly comprising: i. a stepping switch means for connecting first and second main terminals sequentially with respective contacts spaced around respective first and second deck means of the stepping switch means, said stepping switch means having actuator means for advancing and effecting respective connections in response to an electrical signal; said stepping switch means having respective first and second main terminals of said first and second deck means connected with respective ultimate contacts before firing; said ultimate contacts being electrically isolated from contacts that are connected with respective charges; said first and second deck means having respective first and second penultimate contacts that are also electrically isolated from the contacts connected with said charges; said first penultimate contact of said first deck means being connected with a second conductor means, as recited in element (c), (ii), hereinafter, for advancing a next upper gun''s stepping switch means only after said first penultimate contact is connected with said first main terminal; a plurality of said contacts, exclusive of the ultimate and penultimate contacts, of the second deck means being electrically connected with respective charges such that said charges are fired upon the occurrence of firing current on their respective contact; a plurality of the same number of contacts, exclusive of the ultimate and penultimate contacts, of the first deck means being connected together, being electrically serially connected with the second main terminal of the second deck means and thence via respective said contacts of said second deck means and charges with said electrical common; the electrical connection with said second main terminal being via a first unidirectional conduction means that is connected for conduction in the forward direction for passing current of a first polarity through respective said charges to electrical common for firing said respective charges, said plurality of said connected together contacts of said first deck means also being connected with said actuator means via a second unidirectional conduction means that is connected for conduction in the forward direction for passing current of a second polarity for energizing said actuator means to advance said stepping switch means; ii. a first conductor means being serially connected with a first correlative conductor coming into said gun means and with said first main terminal of said first deck means; and a second conductor means being serially connected with said penultimate contact on said first deck and with a second correlative conductor on any higher guns means; iii. third and fourth conductor means defining first and second correlative conductors for electrical interconnection; said third conductor means being connected also with said ultimate contact on said first deck means; and said fourth conductor means being connected also with said actuator means via a third unidirectional conduction means that is connected for conduction in the forward direction for passing current of the secOnd polarity for energizing said actuator means; and d. an electrical interconnection electrically connecting the first and second correlative conductors on the bottom gun means so that a signal of the second polarity will energize said actuator means and consequently step said stepping switch means of the bottom gun only, and connect the respective first contacts on the respective first and second deck means with the respective first and second main terminals so that, thereafter, a signal of the first polarity will fire the charge connected with said first contact; whereby sequential signals of alternate polarity will effect advancing of said stepping switch means to and firing of all of said charges in a lower gun means and then advance the stepping switch means of the next higher gun after, and only after, the stepping switch means of the said lower gun means has been advanced beyond the last charge thereof and to its penultimate contact position.