Hammer driving circuit for a dot system line printer

Claim 1

A hammer driving circuit for a dot system line printer, said printer having a plurality of hammers which are controlled by an electromagnet means including hammer driving coils and which are arranged in a row on a carriage, printing being effected while simultaneously shifting said hammers, wherein said hammers are divided into (n+1) interspersed groups which are arranged such that two hammers from one group are separated by one hammer from each of said other groups, wherein n is a positive integer, and the hammers of all but one of said groups are arranged so as to be displaced from a position in said row that they would be in if all of said hammers were arranged such that adjacent hammers in said row were spaced apart by equal distances, and wherein one end of the hammer driving coils of the same group are respectively connected to a negative terminal of a DC driving power source through an anti-inhibit diode and group operated electrical switches, and wherein the other end of each of said hammer driving coils is connected to a positive terminal of said DC driving power source through a data operated electrical switch, and wherein fly-wheel diodes are respectively connected to parallel with each series circuit comprising said hammer driving coils, said anti-inhibit diode and said group operated electrical switches; and wherein each of said group operated electrical switches are driven once in a pulse repetition period of each of said hammer driving circuits by a first pulse driving signal having a pulse width which is less than or equal to 1/(n+1) times its pulse repetition period and said data operated electrical switches are selectively driven as necessary by a second pulse driving signal having a pulse width which is less than that of said first pulse driving signal and having a pulse repetition period which is equal thereto so as to thereby print said desired characters.