| CPC A61B 34/30 (2016.02) [A61B 34/70 (2016.02); A61B 34/25 (2016.02)] | 18 Claims |

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1. An end effector arm for use with a robotic surgical system comprising:
a base configured to attach to an end effector coupler of a surgical robot arm;
a mechanical linkage including a first end rotatably coupled to the base and a second end opposite the first end, the second end configured to be removably coupled to a handheld surgical tool; and
a spring mechanism configured to impart a variable rotational force on the mechanical linkage based on an angle of rotation of the mechanical linkage, the spring mechanism comprising:
a spring including a first end and a second end, the first end of the spring coupled to one of the base and the first end of the mechanical linkage;
a cable including a first end and a second end, the first end of the cable coupled to the first end of the spring; and
a cam coupled to the other of the base and the first end of the mechanical linkage, the second end of the cable coupled to the cam, the cam including a cam guide configured to receive and maintain the second end of the cable within the cam guide during rotation of the mechanical linkage with respect to the base.
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