Patent ID: 6896230

Claim:
An equipoise arm assembly for supporting an article in equipoise, the equipoise arm assembly comprising: a support arm with a body portion with a proximal end and a distal end; a proximal arm joint pivotally coupled to the proximal end of the support arm at a proximal pivot axis; a means for supporting an article relative to the distal end of the support arm; a spring arrangement with a distal end coupled to the body portion of the support arm and a proximal end pivotable about an effective pivot axis spaced a given distance from the proximal pivot axis to create a spring force moment arm of a given length whereby the spring arrangement will tend to provide a resistive torque in support of the support arm against rotation in a given direction wherein the spring arrangement includes a spring member with a proximal end and a distal end; and a means for altering the distance between the effective pivot axis of the spring arrangement and the proximal pivot axis of the support arm during a pivoting of the support arm to change the length of the spring force moment arm thereby to change the resistive torque per unit spring force provided by the spring arrangement in support of the support arm wherein the means for altering the distance between the effective pivot axis and the proximal pivot axis comprises a stop surface disposed adjacent to a portion of the spring arrangement in combination with an open area adjacent to the stop surface wherein the support arm can be pivoted through a given range of pivoting wherein the portion of the spring arrangement will pivot through at least part of the open area until the portion of the spring arrangement contacts the stop surface thereby to prevent further pivoting of at least part of the portion of the string arrangement whereby the effective pivot axis of the spring arrangement and the spring force moment arm will be altered.