Writing implement mechanism

Claim 1

WRITING IMPLEMENT COMPRISING AN ELONGATED BARREL HAVING OPEN UPPER AND LOWER ENDS, AN ELONGATED CAP HAVING AN OPEN LOWER END AND RELEASABLY MOUNTED ON THE UPPER END OF SAID BARREL IN AXIAL ALIGNMENT THEREWITH, A BUSHING FIXED IN SAID CAP AND HAVING A BORE OFFSET FROM THE COMMON AXIS OF SAID BARREL AND CAP, A REPLACEABLE TUBE EXTENDING SLIDABLY THROUGH SAID BUSHING AND SAID BARREL AND HAVING LOWER END WRITING MEANS OF THE TYPE DESCRIBED, AN IMPELLER HAVING A SHANK EXTENDING AXIALLY IN SAID CAP ABOVE SAID TUBE AND TURNABLE ABOUT SAID AXIS, SAID SHANK HAVING MEANS ACCESSIBLE EXTERNALLY OF SAID CAP FOR MANIPULATION TO TURN SAID SHANK IN EITHER DIRECTION, SAID IMPELLER ALSO HAVING A HELIX DEPENDING FROM SAID SHANK COAXIALLY THEREWITH, SAID HELIX HAVING AN EDGE SURFACE ENGAGING THE UPPER END OF SAID TUBE, AND SPRING MEANS COUPLING SAID TUBE AND SAID BARREL AND URGING SAID TUBE UPWARDLY AGAINST SAID HELIX EDGE, SAID HELIX OPERATIVE UPON TURNING THEREOF IN ONE DIRECTION TO EXTEND THE LOWER END OF SAID TUBE OUT OF SAID BARREL AND IN THE OTHER DIRECTION TO RETRACT SAID LOWER TUBE END INTO SAID BARREL, SAID HELIX ALSO HAVING FIRST POSITIVE STOP MEANS THEREON ENGAGING THE SIDE OF SAID TUBE UPON EXTENSION OF SAID TUBE TO PREVENT FURTHER TURNING OF SAID HELIX IN TUBE EXTENDING DIRECTION SO THAT THE TUBE CAN BE RETRACTED ONLY WHEN THE BARREL IS ROTATED IN SAID OTHER DIRECTION AND SECOND STOP MEANS ON SAID HELIX ENGAGING THE SIDE OF SAID TUBE UPON RETRACTION OF SAID TUBE TO PREVENT FURTHER TURNING OF SAID HELIX IN TUBE RETRACTING DIRECTION.