Adjustable linkage for variable displacement

1. An apparatus comprising:

a crank-slider linkage, wherein the crank is coupled to the slider by a jointed connecting rod, the jointed connecting rod having a first link and a second link, the first link coupled to the second link by a first revolute joint, the first link coupled to the crank and having a longitudinal axis;

a rocker link having a rocker end and a ground end, the rocker end coupled to the jointed connecting rod and the ground end coupled to ground by a second revolute joint, the rocker link and the second link disposed on a common side of the longitudinal axis;

wherein the slider is configured for linear movement along a center axis, one end of the linear movement includes a first position; and

wherein the second revolute joint is adjustable along an arc and wherein the location of the first position remains fixed with a change in the position of the second revolute joint along the arc.

2. The apparatus of claim 1 wherein the rocker end is coupled to the connecting rod at the first revolute joint.

3. The apparatus of claim 1 wherein the second link is coupled to the slider and further wherein the second link and the rocker link are of equal length.

4. The apparatus of claim 1 wherein displacement of the slider decreases as a relative distance between the second revolute joint and the center axis of the slider decreases.

5. The apparatus of claim 1 wherein the slider remains in a fixed position with crank rotation and with the second revolute joint aligned with a center axis of the slider.

6. The apparatus of claim 1 wherein displacement of the slider increases as a relative distance between the second revolute joint and the crank decreases.

7. An assembly comprising:

a variable displacement chamber having a piston in a cylinder;

a linkage coupled to the variable displacement chamber;

a rotary shaft coupled to the linkage, the linkage including a coupler link coupled to the rotary shaft, the coupler link having a longitudinal axis and the coupler link coupled to a connecting rod by a first revolute joint, the connecting rod coupled to the chamber, and the linkage including a rocker link coupled to ground at a second revolute joint and the rocker link coupled to the first revolute joint and further wherein the second revolute joint and the chamber are disposed on a common side of the longitudinal axis and further wherein the chamber has a displacement determined by a position of the second revolute joint relative to a center axis of the piston in the cylinder;

wherein the relative movement as to the piston and the cylinder is configured for linear movement along the center axis, one end of the linear movement includes a first position; and

wherein the second revolute joint is adjustable along an arc and wherein the location of the first position remains fixed with a change in the position of the second revolute joint along the arc.

8. The assembly of claim 7 wherein the variable displacement amber is configured to carry a fluid.

9. The assembly of claim 7 wherein the rotary shaft is configured to be driven.

10. The assembly of claim 7 wherein the rocker link and the connecting rod are of equal length.

11. The assembly of claim 7 wherein the position is user selectable.

12. The assembly of claim 7 wherein at least one of the coupler link, the connecting rod, and the rocker link have an adjustable length.

13. The assembly of claim 7 wherein displacement decreases as a relative distance between the second revolute joint and the center axis decreases.

14. The assembly of claim 7 wherein the chamber maintains a fixed displacement with rotation of the rotary shaft and with the second revolute joint aligned with the center axis.

15. The assembly of claim 7 wherein displacement increases as a relative distance between the second revolute joint and the rotary shaft decreases.

16. A system comprising:

a four-bar crank-rocker assembly having a first revolute joint configured to travel in a planar arc with rotation of the crank, the first revolute joint coupled to the crank by a coupler link, the coupler link having a longitudinal axis, the first revolute joint coupled to a rocker link, the rocker link coupled to ground at a second revolute joint;

a slider joint having a center axis and having a connecting rod coupled to the four-bar crank-rocker assembly, wherein the second revolute joint and the slider joint are disposed on a common side of the longitudinal axis and further wherein displacement of the slider joint is determined by a position of the second revolute joint relative to the center axis; and

wherein the slider joint is configured for linear movement along the center axis, one end of the linear movement includes a first position; and

wherein the second revolute joint is adjustable along an arc and wherein the location of the first position remains fixed with a change in the position of the second revolute joint along the arc.

17. The system of claim 16 wherein the connecting rod is coupled to the four-bar crank-rocker assembly at the first revolute joint.

18. The system of claim 16 wherein displacement decreases as a relative distance between the second revolute joint and the center axis decreases.

19. The system of claim 16 wherein the slider joint remains stationary with rotation of the rotary shaft and with the second revolute joint aligned with the center axis.

20. The system of claim 16 wherein displacement increases as a relative distance between the second revolute joint and the crank decreases.