Patent ID: 7252277

Claim:
A support arm, comprising: a first strut having a proximal portion; a proximal link pivotally coupled to the proximal portion of the first strut at a first proximal joint, the proximal link comprising a cam, wherein the first strut is rotatable relative to the cam about the first proximal joint; a distal link pivotally coupled to a distal portion of the first strut at a first distal joint, wherein the first strut is rotatable relative to the distal link about the first distal joint; and a cam follower coupled to the first strut, the cam follower contacting a cam surface of the cam at a first contact point; the cam and the cam follower cooperating to apply a cam moment to the first strut; and the cam moment being sufficient to balance a load supported by the distal link, further comprising a means for urging the cam follower against the cam surface of the cam wherein the means for urging the cam follower against the cam surface of the cam comprises a spring, and further comprising an adjustment mechanism for varying a characteristic of the spring, wherein the adjustment mechanism comprises a spring plate coupled to the spring.