Roller screw device for converting rotary to linear motion

In a roller screw apparatus for converting rotary motion to linear motion comprising an elongated screw, a nut positioned circumferentially about said screw and separated from said screw by an annular region, and a plurality of elongated roller elements positioned in said annular region in general simultaneous contact with said screw and nut, in axial parallel alignment with said screw, the improvement comprising:

• said screw being externally helically threaded including a lead screw portion having a start thread of given pitch, a start thread form and a lead screw axis;
• said nut being internally grooved with at least one set of generally annular grooves, each of the grooves lying in a respective one of a plurality of parallel planes thereby forming a set of non-helical grooves having a form matching said start thread form;
• said roller elements each being externally grooved with annular non-helical grooves having a form matching said forms of said nut grooves and said start thread;
• and
• said nut having at least one radially inner lobed region so as to allow said roller elements to radially and rollingly cycle from regressive lead disengagement through progressive re-engagement without allowing axial displacement with respect to the nut body.