Mechanical self-leveling lift arm structure for power machine

1. A mini-loader comprising:

a frame;

an operator station positioned toward the rear of the frame and configured to be used by an operator who is behind or on the rear of the frame;

a lift actuator movable between a retracted position and an extended position; and

a lift arm structure movable by the lift actuator relative to the frame, the lift arm structure including a multi-bar linkage configured to raise and lower an implement supported by the lift arm structure as the lift actuator moves between the retracted and extended positions, the multi-bar linkage including:

a follower link pivotally secured to the frame;

a lift arm pivotally secured to the follower link at a first pivotable joint and pivotally secured to the lift actuator; and

a driver link pivotally secured to the lift arm and to the frame;

a multi-joint member pivotally secured to the implement via an implement carrier actuator that is controllable to tilt the implement relative to the lift arm and pivotally secured to the lift arm; and

a leveling link pivotally secured to the follower link at a second pivotable joint that is spaced apart from the first pivotable joint, and pivotally secured to the multi-joint member, to transmit force from the follower link to the implement via the multi-joint member as the lift actuator moves between the retracted position and the extended position;

wherein the follower link is secured to the frame at a third pivotable joint; and

wherein the second pivotable joint is positioned at an opposite end of the follower link from the third pivotable joint and the first pivotable joint is positioned between the second and third pivotable joints along the follower link.

2. The mini-loader of claim 1 , wherein, as the lift actuator moves from the retracted position toward the extended position, the follower link is arranged to pivot in a first direction relative to the frame and subsequently to pivot in a second direction relative to the frame to move the leveling link toward the multi joint member.

3. The mini-loader of claim 1 , wherein the driver link is pivotally secured to frame separately from the follower link.

4. The mini-loader of claim 1 , wherein the multi joint member is configured to pivot forwards relative to the lift arm as the leveling link moves toward the multi joint member to limit backward tilting of the implement.

5. The mini-loader of claim 1 , wherein the second pivotable joint is positioned above the first pivotable joint.

6. The mini-loader of claim 1 , wherein the second pivotable joint is positioned below the first pivotable joint.

7. The mini-loader of claim 1 , wherein, as the lift actuator moves from the retracted position toward the extended position, the follower link is arranged to pivot in a first direction relative to the frame and subsequently to pivot in a second direction relative to the frame to move the leveling link away from the multi joint member.

8. The mini-loader of claim 1 , wherein the multi joint member is a single-piece multi joint member.

9. The mini-loader of claim 8 , wherein the single-piece multi joint member is a bell crank.

10. A lift arm structure for a power machine with a frame, for use with an implement and an implement actuator that is configured to tilt the implement, the lift arm structure comprising:

a vertical path lift arm structure that includes:

a first link and a second link, each of which is separately pivotally secured to the frame and to a lift arm;

a leveling link pivotally secured to the first link, wherein, along the first link, the pivotable joint that secures the first link to the lift arm is between a pivotable joint that secures the first link to the leveling link and a pivotable joint that secures the first link to the frame; and

a multi joint member pivotally secured to the leveling link, the lift arm, and the implement actuator, to mechanically transmit tilting force from the leveling link to the implement, via the implement actuator, as the lift arm structure is actuated to raise or lower the implement.

11. The lift arm structure of claim 10 , wherein, along the lift arm, a pivotable joint that secures the second link to the lift arm is between a pivotable joint that secures the first link to the lift arm and a pivotable joint that secures the multi joint member to the lift arm.

12. The lift arm structure of claim 11 , wherein the pivotable joint that secures the first link to the leveling link is above the pivotable joint that secures the first link to the frame, relative to the power machine.

13. The lift arm structure of claim 10 , wherein, with the lift arm in a fully lowered position relative to the power machine, the pivotable joint that secures the multi-joint member to the lift arm is forward of pivotable joints that secure the first link and the second link to the lift arm, from the perspective of the power machine.

14. The lift arm structure of claim 13 , wherein, with the lift arm in the fully lowered position relative to the power machine, the pivotable joint that secures the multi-joint member to the lift arm is configured to be forward of pivotable joints that secure the first and second links to the frame, from the perspective of the power machine.

15. A lift arm structure for a power machine with a frame, for use with an implement carrier, the lift arm structure comprising:

a multi-bar linkage pivotally secured to the frame, the multi-bar linkage including:

a lift arm,

a driver link pivotally secured to the lift arm and to the frame, and

a follower link with a leveling joint, the follower link being pivotally secured to the lift arm at a follower-lift-arm pivotable joint spaced apart from the leveling joint, and pivotally secured to the frame at a follower-frame pivotable joint opposite the follower-lift-arm pivotable joint, the leveling joint being positioned between the follower-frame and follower-lift-arm pivotable joints along the follower link; and

a leveling link pivotally secured to the follower link at the leveling joint, and pivotally secured to the implement carrier and to the lift arm via at least three pivotable joints on a multi-joint member, to mechanically transmit force from the follower link to the implement carrier and there by urge the implement carrier to pivot relative to the lift arm as the multi-bar linkage is actuated to raise or lower the implement carrier.

16. The lift arm structure of claim 15 , for use with an implement carrier actuator configured to tilt the implement carrier, wherein the leveling link is pivotally secured to the implement carrier via the implement carrier actuator; and

wherein the leveling link is pivotally secured to the implement carrier actuator via the multi joint member.

17. The lift arm structure of claim 15 , wherein the leveling link is configured to pivot in a direction away from the implement carrier before pivoting in a direction toward the implement carrier as the multi-bar linkage is actuated to raise the lift arm; and

wherein the leveling link is configured to rotate the multi-joint member relative to the lift arm, in the direction toward the implement carrier, as the leveling link pivots in the direction toward the implement carrier.