Link unit, arm module, and surgical apparatus including the same

An arm module comprising:

• a plurality of link units stacked upon one another, each of the link units having an upper portion and a lower portion, and each of the link units including,
• a head at the upper portion,
• a seat at the lower portion, the seat configured to have a shape corresponding to the head, and
• a sliding ball configured to protrude from a groove formed in a surface of the seat, and to translate between a first position and a second position in the groove,
• wherein the arm module is configured to operate in,
• a fixed mode, the fixed mode configured to enable the head of a first one of the plurality of link units and the seat of a second one of the plurality of link units to contact each other, the first link unit and the second like unit being adjacent to each other;
• and
• a steering mode, the steering mode configured to enable the head of the first link units and the sliding ball of the second link units adjacent to the first link unit to contact by sliding with respect to each other.

A link unit comprising:

• a head configured to have a hemispherical shape;
• a seat configured to have a shape corresponding to that of the head, the seat further configured to have an upwardly concave bottom surface;
• and
• a sliding ball configured to protrude from a groove formed in a surface of the seat, and to translate between a first position and a second position in the groove.

A surgical apparatus comprising:

• at least one arm module having at least one degree of freedom, the at least one arm module including,
• a plurality of link units stacked upon one another to form the at least one arm module, each of the link units having an upper portion and a lower portion, and each of the link units including,
• a head having a hemispherical shape, the head being at the upper portion,
• a seat on the lower portion, and
• a sliding ball configured to protrude from a groove formed in a surface of the seat, and to translate between a first position and a second position in the groove, wherein
• the head of one link unit is configured to sit on the seat of an adjacent link unite such that the one link unit and the adjacent link unit rotate with respect to each other.