Inspection apparatus for circular knitting machines

Claim 1

A circular knitting machine having a series of knitting needles on a mount which rotates, a sensing arrangement positioned to respond to both broken and unbroken knitting needles as the mount rotates, a broken knitting needle giving a lower response than an unbroken knitting needle, means for deriving from the sensing arrangement a curved output current pulse for each knitting needle, the height of the pulse being less for a broken knitting needle than for an unbroken knitting needle, a timing circuit for comparing the instantaneous amplitude of the output current pulses with a preset level and issuing an initial timing signal when the instantaneous amplitude rises above the preset level and final timing signal when the instantaneous amplitude falls below the preset level; a pulse generator for generating reference pulses of predetermined duration, the initial timing signals being applied to the pulse generator to ensure that for each initial timing signal there is a reference pulse which starts in synchronism therewith; and a gate to which are applied as the gated input the reference pulses from the pulse generator or signals derived therefrom, the timing signal or signals derived therefrom being applied as the control input to the gate to close the gate during the period between an initial timing signal and a succeeding final timing signal; and output means responsive to reference pulse signals passing through the gate when it is open.