Hammer protection device for high-speed line printers

Claim 1

In a high-speed impact printer in which a plurality of hammers can fire simultaneously, apparatus for protecting said hammers from excessive current flow comprising, in combination: a comparator having a signal input means, said comparator producing a characteristic output signal if the signal at said input means exceeds a predetermined level, means for generating a signal level proportional to the current flow respectively in each of said hammers, means for coupling said comparator input means to each of said generating means, a power supply, means for coupling said power supply to said print hammers to energize said print hammers, said power supply coupling means including means For decoupling said power supply from said print hammers in response to said characteristic output signal, said predetermined signal level being substantially less than the signal level generated by said generating means when a print hammer is energized, and means preventing said uncoupling of said power supply from said print hammers during that portion of a print cycle during which said print hammers are firing.