Boom assembly with translatable counterbalance mass

1. A boom assembly comprising:

a base;

a support member connected to the base;

a lower boom structure connected to the base so that the lower boom structure is pivotable with respect to the base between a lowered position of the lower boom structure and a raised position of the lower boom structure;

an upper boom structure having a first end connected to the lower boom structure, and an opposite second end, wherein the upper boom structure is pivotable with respect to the lower boom structure between a lowered position of the upper boom structure and a raised position of the upper boom structure in which the second end is positioned above the lower boom structure;

a counterweight movably mounted on the lower boom structure and movable along the lower boom structure when at least a portion of the lower boom structure is moved relative to the base; and

a link having a first end pivotably connected to the counterweight and a second end pivotally connected directly to the support member.

2. The boom assembly of claim 1 wherein the counterweight is slidably mounted on the lower boom structure.

3. The boom assembly of claim 1 wherein the link is configured to move the counterweight downwardly along the lower boom structure when the lower boom structure is moved from the lowered position of the lower boom structure to the raised position of the lower boom structure.

4. The boom assembly of claim 1 wherein the link comprises a cylinder connected to the counterweight for translating the counterweight along the lower boom structure.

5. The boom assembly of claim 1 wherein the lower boom structure includes an elongated guide member, and the counterweight includes one or more guide elements that are engageable with the elongated guide member.

6. The boom assembly of claim 1 further comprising a connecting element for connecting the link to the counterweight, and a first bearing element and a second bearing element positioned at opposite ends of the connecting element for slidably engaging the lower boom structure.

7. The boom assembly of claim 6 wherein the lower boom structure comprises two elongated guide members disposed on opposite sides of the counterweight, and the counterweight includes a first bearing element and a second bearing element that are each engageable with a first side of a respective elongated guide member, wherein the first and second bearing elements positioned at opposite ends of the connecting element are each located adjacent to a second side of a respective elongated guide member that is opposite the first side of the elongated guide member.

8. The boom assembly of claim 1 wherein the counterweight is translatable along the lower boom structure when the lower boom structure is pivoted with respect to the base.

9. The boom assembly of claim 1 wherein the counterweight is translatable along the lower boom structure when a section of the lower boom structure is moved between a retracted position and an extended position.

10. The boom assembly of claim 1 wherein the support member is rotatably mounted on the base, the lower boom structure has a first end pivotally connected to the support member, and a second end pivotally connected to the first end of the upper boom structure, and wherein the counterweight is movable along the lower boom structure between the first and second ends of the lower boom structure.

11. The boom assembly of claim 1 wherein the link is configured to move the counterweight downwardly along the lower boom structure when the lower boom structure is moved from the lowered position of the lower boom structure to the raised position of the lower boom structure.

12. A vehicle comprising:

a chassis;

a support member rotatably mounted on the chassis;

a lower boom structure mounted on the chassis so that the lower boom structure is pivotable between a lowered position of the lower boom structure and a raised position of the lower boom structure;

an upper boom structure having a first end attached to the lower boom structure, and an opposite second end, and wherein the upper boom structure is pivotable relative to the lower boom structure between a lowered position and a raised position in which the second end is positioned above the lower boom structure;

a counterweight movably mounted on the lower boom structure and translatable along the lower boom structure when at least a portion of the lower boom structure is moved relative to the upper boom structure; and

a drive member having a first end connected to the counterweight and a second end connected directly to the support member;

wherein the lower boom structure has a first end pivotally connected to the support member, and a second end pivotally connected to the first end of the upper boom structure, and wherein the counterweight is movable along the lower boom structure between the first and second ends of the lower boom structure.

13. The vehicle of claim 12 wherein the drive member comprises a link for moving the counterweight along the lower boom structure when the upper boom structure is pivoted between the lowered and raised positions.

14. The vehicle of claim 12 wherein the drive member is configured to translate the counterweight along the lower boom structure.

15. The vehicle of claim 12 wherein the drive member comprises a cylinder.

16. The vehicle of claim 12 further comprising a control unit associated with the drive member and configured to control operation of the drive member, based on position of one or both of the boom structures, in order to control position of the counterweight with respect to the lower boom structure.

17. The vehicle of claim 12 wherein the counterweight is translatable along the lower boom structure when the upper boom structure is pivoted with respect to the lower boom structure or when the lower boom structure is pivoted with respect to the upper boom structure.

18. The vehicle of claim 12 wherein the counterweight is translatable along the lower boom structure when a portion of the upper boom structure is moved between a retracted position and an extended position or when a portion of the lower boom structure is moved between a retracted position and an extended position.

19. A boom assembly comprising:

a base;

a support member rotatably mounted on the base;

a lower boom structure pivotally connected to the support member so that the lower boom structure is pivotable with respect to the support member and the base between a lowered position of the lower boom structure and a raised position of the lower boom structure;

an upper boom structure connected to the lower boom structure and movable between a lowered position of the upper boom structure and a raised position of the upper boom structure;

a counterweight movably mounted on the lower boom structure; and

a link having a first end pivotably connected to the counterweight and a second end pivotally connected directly to the support member, wherein the link is configured to move the counterweight downwardly along the lower boom structure when the lower boom structure is moved from the lowered position of the lower boom structure to the raised position of the lower boom structure.