Surgical tool and assembly

A surgical tool assembly, comprising:

• a handle assembly establishing a handle axis;
• a frame assembly, said frame assembly having a shaft, said shaft establishing a shaft axis;
• a first intermediate rigid body extending from said handle assembly;
• a second intermediate rigid body extending from said frame assembly;
• a third intermediate rigid body;
• a first joint residing between said first intermediate rigid body and said third intermediate rigid body, said first joint providing a pitch rotational degree of freedom or a yaw rotational degree of freedom of said first intermediate rigid body with respect to said third intermediate rigid body;
• and
• a second joint residing between said second intermediate rigid body and said third intermediate rigid body, said second joint providing a pitch rotational degree of freedom or a yaw rotational degree of freedom of said third intermediate rigid body with respect to said second intermediate rigid body, the pitch or yaw rotational degree of freedom provided by said second joint being opposite the pitch or yaw rotational degree of freedom provided by said first joint;
• wherein a virtual center of rotation established by said first joint and by said second joint resides at a location that is occupied by said handle assembly, by a user's hand when manipulating said handle assembly amid use of the surgical tool assembly, or by both said handle assembly and the user's hand when manipulating said handle assembly amid use of the surgical tool assembly;
• wherein said handle assembly is translationally constrained along a z-axis relative to said frame assembly via said first intermediate rigid body, said second intermediate rigid body, and said third intermediate rigid body, said handle axis generally intersects said virtual center of rotation and said shaft axis generally intersects said virtual center of rotation.

A surgical tool assembly, comprising:

• a handle assembly establishing a handle axis, a first intermediate rigid body rigidly fixed to said handle assembly;
• a frame assembly having a shaft, said shaft establishing a shaft axis, a second intermediate rigid body rigidly fixed to said frame assembly;
• and
• a deviation ring joined to said first intermediate rigid body via a first joint and joined to said second intermediate rigid body via a second joint, said first joint providing a pitch rotational degree of freedom or a yaw rotational degree of freedom and said second joint providing the other of the pitch rotational degree of freedom or the yaw rotational degree of freedom, a first pulley situated at said first joint and a second pulley situated at said second joint;
• wherein, when said handle assembly lacks rotation about said first joint and lacks rotation about said second joint, said handle axis and said shaft axis are arranged generally coincident with respect to each other.