Device for maintaining a tool attachment in a knuckle boom crane on a constant level above the ground
US4828125A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 21, 1988 |
| Grant date | May 9, 1989 |
| Priority date | — |
| Expiry date | Apr 21, 2008 |
Classification
- Technology area (CPC E)Fixed Constructions
- CPC primaryE02F3/433
- WIPO fieldHandling
- WIPO sectorMechanical engineering
Abstract
The invention relates to a device for maintaining a tool attachment in a knuckle boom crane, preferably for forest machines, on a constant level above the ground. The knuckle boom comprises a main boom which can be raised and lowered by means of a double-acting hydraulic cylinder (4), and an outer boom pivotal relative to the main boom my means of a likewise double-acting hydraulic cylinder (6). To ensure the vertical adjustment of the tool attachment, the lift cylinder (4) is connectible to the outer boom cylinder (6) via a compensator (21) in such a manner that an amount of hydraulic fluid which is proportional to the amount of hydraulic fluid which upon activation of the outer boom is pressed out from the lifting or the lowering side, respectively, of one of the cylinders (4, 6), is pressed into the lowering or the lifting side, respectively, of the other cylinder. The compensator comprises at least one hydraulic cylinder (22) having two chamber (23, 26) which are separated by a piston (31) movable in the cylinder and having two different working areas or displacements (24, 25) in the two chambers (23, 26). The lift cylidner (4) is connectible to one chamber (26) and the outer b…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.