Spindle drive assembly with recirculating balls

Claim 1

A spindle drive assembly comprising: a spindle including means defining an external circumferential surface; a spindle nut completely surrounding said spindle and including means defining a helical internal ball guide completely surrounding said spindle; said spindle and said spindle nut being operably arranged with said external circumferential surface and said internal ball guide cooperating to form a helical duct adapted to have recirculating balls of said spindle assembly pass therethrough; a plurality of recirculating balls within said helical duct for transmitting an axial load between said spindle and said spindle nut upon relative rotation therebetween; ball return means outside said spindle for passing said recirculating balls to and from said helical duct; clamping means engaging said spindle nut to apply a circumferential tension thereto to maintain said balls in operative load-bearing engagement within said helical duct between said spindle and said spindle nut such as to engage said ball guide in both axial directions; and means defining at least one substantially axially extending compensating gap in said spindle nut to effect circumferential division of said spindle nut to enable said spindle nut to circumferentially adapt to the circumferential forces applied by said clamping means, said gap having a radially innermost side contiguous with said internal ball guide, said balls running across said radially inner side of said gap and being in said load-bearing engagement also in the area of said radially inner side of said gap, said compensating gap being defined to have a gap width taken circumferentially of said spindle nut at said radially inner side of said gap which is not greater than 15% of the diameter of said recirculating balls.