Linear screw and/or circulating ball actuator

A linear circulating ball actuator, comprising:

• a nut made of sintered material and having an axial hole therethrough, said nut having an internal thread on an inner surface of said hole, said nut having opposite faces and a through passage extending through the nut between said opposite faces and at a location spaced from said hole;
• a head wall fixed to each of said opposite faces of said nut, each head wall having an opening aligned with said hole and means for fixing said head wall to an opposite face of said nut, each head wall having an outer surface facing away from said nut and a thrust bearing race in the outer surface of each head wall for use in forming part of a thrust bearing for supporting opposite ends of the nut, each head wall including an end passage communicating with a face of said nut and communicating with an end of said through passage for supplying ball bearings to and receiving ball bearings from said through passage, each of said head walls being made of sintered material;
• a screw mounted for rotation in said hole and through said openings of said head walls, said screw having an external thread alignable with said internal thread of said nut to form a groove, opposite ends of said groove communicating with said end passages;
• and
• a plurality of ball bearings in said groove, said end passages and said through passage, for circulation therealong with relative rotation and linear movement between said screw and said nut.