| 主权项 |
1. A torque-free robot arm comprising: a base unit;
a first link rotatably connected at a first end thereof to the base unit to form a first joint as a rotary axis horizontal to a ground surface, center of gravity being separated from the first joint, wherein the first link comprises a first counter balancer that is disposed at the first end thereof at the first joint and is disposed at a second end thereof opposite to the first end in a longitudinal direction of the first link so that the first counter balancer compensates for weight of the first link when the first link is rotated about the first joint; a second link rotatably connected at a first end thereof to the first link to form a second joint as a rotary axis horizontal to the ground surface, a center of gravity being separated from the second joint; a first pressing flange disposed at the base unit and configured to transfer a rotational force applied thereto to the first link; and a unit including a link pulley and a wire, wherein the link pulley is rotatably disposed at one end of the second link where the second joint is formed, wherein the wire is arranged in pairs such that a pair of wires are fixed to the first pressing flange at a first end of each of the pair of the wires so as to be surroundingly wound around an outer circumference of the link pulley, and then is retained by a link pulley retaining part disposed on an outer circumferential surface of the link pulley, wherein references of rotation angles of the first pressing flange and the link pulley respectively forming the first joint and the second joint relative to the ground surface are formed identically, wherein a parallel wrist pulley is disposed at a second end of the second link opposite the first end of the second link to form a third joint that is in parallel with the second joint, and wherein in order for the unit to match reference of rotation angle of the parallel wrist pulley relative to the ground surface with that of rotation angle of the link pulley and the first pressing flange relative to the ground surface when the first link rotates about the first joint or the second link rotates about the second joint the pair of wires extend along the longitudinal direction of the second link after being retained by the link pulley retaining part of the link pulley, are wound at a second end of each of the pair of the wires around an outer circumferential surface of the parallel wrist pulley, and are fixedly retained by a parallel wrist pulley retaining part formed on an outer surface of the parallel wrist pulley. |
