Movable rack arm with counterbalance spring for contoured non-linear force transfer

1. A surgical console comprising:

a base;

a tray assembly;

a parallelogram arm comprising a first bar and a second bar; and

a movable rack arm assembly attached to at least one bar of the parallelogram arm, the movable rack arm assembly comprising:

a cam housing comprising an internal rack arm guide pin and an axle;

a circular gear comprising circular gear teeth and mounted on and rotatable about the axle;

a rack arm comprising:

a rack arm attachment attached to a bar of the parallelogram arm;

a rack gear comprising rack gear teeth; and

a rack arm track associated with the internal rack arm guide pin to hold the rack gear teeth engaged with the circular gear teeth as the rack arm is extended or retracted with respect to the cam housing such that the circular gear is rotated about the axle as the rack arm is extended or retracted;

a cam attached to the circular gear such that the cam rotates in a corresponding manner when the circular gear rotates about the axle as the rack arm is extended or retracted, the cam comprising a curved cam groove having an inner end and an outer end, wherein the inner end is located radially closer to the axle than the outer end; and

a spring assembly comprising:

a spring;

a spring arm attached to the spring at a first end and comprising a follower pin at a second end of the spring arm opposite the first end, the follower pin located in the cam groove such that the spring arm moves when the cam rotates, applying a force to the spring; and

a spring arm attachment attached to the parallelogram arm.

2. The surgical console of claim 1 , wherein the curved cam groove has a radial distance from the axle that consistently increases as curved cam groove distance from the inner end increases.

3. The surgical console of claim 1 , wherein the curved cam groove has a radial distance from the axle that increases and decreases as curved cam groove distance from the inner end increases.

4. The surgical console of claim 1 , wherein the spring is an extension spring.

5. The surgical console of claim 1 , wherein the spring is a compression spring.

6. A surgical microscope assembly comprising:

a parallelogram arm comprising a first bar and a second bar;

an arm body;

an arm head;

a surgical microscope; and

a movable rack arm assembly attached to at least one bar of the parallelogram arm, the movable rack arm assembly comprising:

a cam housing comprising an internal rack arm guide pin and an axle;

a circular gear comprising circular gear teeth and mounted on and rotatable about the axle;

a rack arm comprising:

a rack arm attachment attached to the arm head, the parallelogram arm;

a rack gear comprising rack gear teeth; and

a rack arm track associated with the internal rack arm guide pin to hold the rack gear teeth engaged with the circular gear teeth as the rack arm is extended or retracted with respect to the cam housing such that the circular gear is rotated about the axle as the rack arm is extended or retracted;

a cam attached to the circular gear such that the cam rotates in a corresponding manner when the circular gear rotates about the axle as the rack arm is extended or retracted, the cam comprising a curved cam groove having an inner end and an outer end, wherein the inner end is located radially closer to the axle than the outer end; and

a spring assembly comprising:

a spring;

a spring arm attached to the spring at a first end and comprising a follower pin at a second end of the spring arm opposite the first end, the follower pin located in the cam groove such that the spring arm moves when the cam rotates, applying a force to the spring; and

a spring arm attachment attached to the parallelogram arm.

7. The surgical microscope assembly of claim 6 , wherein the curved cam groove has a radial distance from the axle that consistently increases as curved cam groove distance from the inner end increases.

8. The surgical microscope assembly of claim 6 , wherein the curved cam groove has a radial distance from the axle that increases and decreases as curved cam groove distance from the inner end increases.

9. The surgical microscope assembly of claim 6 , wherein the spring is an extension spring.

10. The surgical microscope of claim 6 , wherein the spring is a compression spring.