Ball screw assemblies

A ball screw comprising:

• a screw shaft, a ball nut, and alpha and beta load circuits in which
• the alpha and beta load circuits each comprise first and second parts,
• the screw shaft is longitudinally extending with a longitudinal central axis and at least part of a longitudinally extending surface of the screw shaft comprises an external thread, and at least one of the first parts of the alpha and beta load circuits comprise a part of the external thread,
• the ball nut comprises a body, a bore, the second parts of the alpha and beta load circuits, and an alpha and a beta lubricant channel, in which
• the bore is defined by the body, is longitudinally extending with a longitudinal central axis, has a first and second end, and has at least one longitudinally extending surface extending between the first and second ends,
• the first and second ends of the bore each comprise a mouth, and each mouth opens through an outside surface of the body,
• the longitudinally extending surface of the bore comprises at least one internal thread, and the second parts of the alpha and beta load circuits comprise at least a part of an internal thread,
• the screw shaft extends through the bore of the ball nut and the screw shaft and bore are so configured that they are co-axial, the external thread and each internal tread are so configured that the external thread and at least one of the internal threads together define at least one of a portion of the alpha load circuit and a portion of the beta load circuit,
• the alpha load circuit is spaced from the first end of the bore and extends an axial distance along the bore,
• the beta load circuit is spaced from the second end of the bore and extends an axial distance along the bore,
• the alpha and beta load circuits are spaced from each other,
• the alpha lubricant channel comprises a first and a second channel end and a flow path between the first and second channel ends, in which the first channel end is located between the first end of the bore and the second part of the alpha load circuit, and the second channel end is located between the second part of the alpha load circuit and the second part of the beta load circuit,
• the beta lubricant channel comprises a first and a second channel end and a flow path between the first and second channel ends in which the first channel end is located between the second end of the bore and the second part of the beta load circuit, and the second channel end is located between the second part of the alpha load circuit and the second part of the beta load circuit,
• rotation of one of the screw shaft and the ball nut relative to the other around the longitudinal axis causes axial movement of the ball nut relative to the screw shaft, the ball screw further comprises a shuttle, in which the shuttle is engaged with the longitudinally extending surface of the screw shaft, the shuttle is located between the first parts of the alpha and beta load circuits, and the shuttle is in sliding contact with the ball nut, and
• rotation of one of the screw shaft and the ball nut relative to the other around the longitudinal axis drives lubricant through one of the alpha and beta lubricant channels.