(under subclass 68) Implement including in the train of the advancing means a third member carrying an element in screw-feed engagement with one of the first said members so that it is axially displaceable with respect to each of said first members by actuation of said screw-feed means.
(1) Note. The drawing below illustrates one example of the subject matter of this subclass. The effect of the compound screw feed is additive, i.e., member B is screwed outwardly from member A, to the extent of their threaded engagement, and member C is simultaneously screwed outwardly from member B, to the extent of their threaded engagement, thus ultimately placing the axial lengths of the individual screw elements substantially in alignment end-to-end. Member A is rotatable, but not movable axially, in sleeve D. [figure]
SEE OR SEARCH THIS CLASS, SUBCLASS:
71, for an implement wherein the feed means includes a pin which is cammed by the cooperative action of oppositely oriented helical slots in concentric tubes, which tubes are not axially displaceable relative to each other.
