Feller-bunchers are used to fell, or cut down, a number of trees and then to bunch the trees together for transport. The bunched trees are then transported to a storage site for further processing. Typical feller-bunchers are articulated machines that include a front frame and a rear frame that are pivotally coupled by a hitch. The hitch allows the front frame to pivot relative to the rear frame so as to steer the fell-buncher. The front frame includes a front axle having a pair of wheels mounted thereon, and the rear frame includes a rear axle also having a pair of wheels mounted thereon.
The feller-buncher further includes a work tool that cuts down trees and secures the cut trees to the feller-buncher. The work tool is mounted on a yoke that is pivotally attached to the front frame of the fell-buncher. The yoke can be raised or lowered relative to front frame in order to position the work tool during operation. The work tool includes a rotating saw which is used to cut down trees. In addition, the work tool has a number of hydraulically powered work arms which are used to secure the trees within the work tool after the trees have been cut down.
The feller-buncher further includes a tilt cylinder which is operable to pivot the work tool relative to the yoke. To unload the trees from the work tool, the work tool is tilted forward relative to the yoke and the work arms release the trees from the work tool. A disadvantage of feller-bunchers that have heretofore been designed is that as the work tool is tilted forward, a leading edge of the rotating saw is moved significantly closer to the ground. If the rotating saw contacts a hard object, such as a rock, the rotating saw can become damaged. Such damage may require expensive and time consuming repairs to the rotating saw. To compensate for moving the rotating saw closer to the ground, the operator must raise the work tool to provide additional clearance between the rotating saw and the ground as the work tool is tilted forward. However, raising the work tool has two disadvantages. First, raising the work tool raises the center of gravity of the entire feller-buncher thereby decreasing the stability of the feller-buncher. Second, raising the work tool adds an extra step to the unloading process, which can potentially slow down the unloading process and lead to reduced productivity from the feller-buncher.
What is needed therefore is an apparatus and method for felling and bunching trees which overcome one or more of the above-mentioned drawbacks.