An apparatus for application of surgical clips to body tissue, the apparatus comprising:a handle assembly including: a housing； a drive assembly including: a drive block axially and slidably supported in the housing, wherein the drive block defines a threaded lumen therethrough； and a drive screw rotatably supported within the housing, the drive screw including a threaded surface configured for mating with the threaded lumen of the drive block； a trigger operatively connected to the drive assembly such that actuation of the trigger acts on the drive block； a ratchet mechanism supported in the housing, the ratchet mechanism including: a pawl pivotably supported on the drive block； a toothed-rack defined in the housing, the toothed-rack having a distal reversing recess and a proximal reversing recess configured for housing the pawl； and a pawl spring supported on the drive block and configured to bias the pawl into operative engagement with at least one tooth of the toothed-rack to restrict longitudinal movement of the drive block in a first direction when the pawl is translated in the first direction； wherein as the trigger is actuated, the drive block is moved in the first direction causing the drive screw to rotate and the pawl to move from the distal reversing recess to the toothed-rack such that the trigger is restricted from returning to an un-actuated position until a complete stroke is achieved.
