Change-over mechanism for operating screwdriver in automatic or latched state

A screwdriver operable in an automatic or latched state, said screwdriver comprising:

• a screwdriver shank, said shank having a front and rear portion, a first helical groove extending along a portion of said shank, and an annular groove in the periphery of a segment of said rear portion;
• a cylindrical main body surrounding a portion of said shank for supporting said shank and allowing axial and rotational movement relative thereto;
• a closure member fixedly positioned inside the rear portion of said main body;
• a first spring having one end abutting said closure member and the other end abutting said shank for spring biasing said shank forward relative to said main body;
• a ratchet means for engaging said helical groove and preventing said relative rotational movement of said shank in one direction;
• a locking means for locking said shank when it is in its most rearward position;
• said locking means including:
• a latch pawl for engaging said annular groove and thereby locking said shank;
• a rotatable change-over ring in engagement with said latch pawl for, when said ring is rotated in one direction, causing said latch pawl to engage said annular groove and, when said ring is rotated in the other direction, causing said latch pawl to disengage said annular groove;
• and
• an engaging rod for engaging said ring when said shank is in other than its most rearward position and locking said locking means in a position whereby it is not engaging said annular groove.