Ball roller spindle

An apparatus for converting a rotational movement into a back and forth movement, comprising:

• a spindle having an outer surface having at least one guiding groove;
• a bearing body having a wall section surrounding said outer surface concentrically, said spindle and said bearing body being rotatable and axially shiftable relative to one another, said wall section including bearing bores;
• a plurality of ball mechanisms each mounted in one of said bearing bores, said ball mechanisms protruding into one of said at least one guiding groove and beyond an outer surface of said wall section, each of said ball mechanisms including at least one driving ball;
• a ball race biasing said ball mechanisms in a direction toward said at least one guiding groove, said ball race being arranged around said bearing body and over said ball mechanisms, said ball race having a driving ball bearing surface with first and second axial ends, said driving ball bearing surface applying said bias to said ball mechanisms, and is substantially concentric with respect to said wall section;
• and
• said ball race having arresting surfaces at said first and second axial ends of said driving ball bearing surface and protruding radially inward thereof which are engageable with said ball mechanisms such that said ball race is fixed in position with respect to an axial movement relative to said ball mechanisms.