Traversing hoists – Adjustable to transport or nonuse position – Collapsible or foldable boom
Reexamination Certificate
2001-04-13
2003-04-22
Brahan, Thomas J. (Department: 3652)
Traversing hoists
Adjustable to transport or nonuse position
Collapsible or foldable boom
C212S238000, C212S261000
Reexamination Certificate
active
06550625
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a boom arrangement for moving a multi-function part of a work head, particularly a log loader harvester, which boom arrangement comprises a pillar mounted on a bearing around the vertical axis in a rotating manner, with mounting and rotational members; a lifting boom; a transfer boom; a lifting cylinder arranged between the pillar and the lifting boom; an intermediate lever mounted on the lifting boom; a tow bar, a transfer cylinder arranged between the lifting boom and the tow bar; an intermediate arm; and an arm.
Boom arrangements of the above-mentioned type are nowadays rather known apparatus. Log loaders for log loader harvesters used previously are most frequently what are called parallel loaders, the mechanism of which allows the work head to be moved horizontally by controlling only one actuator. The work head can be for example any wood handling apparatus, such as a cutting head, tree felling head, log collection grapple or some other apparatus.
Examples of the above solutions include the apparatus disclosed in SE patent publication 7411568-4 and Fl patent application 961846.
What the apparatus disclosed in the above publications have in common is that the lifting cylinder is not mounted directly between the pillar and the lifting boom but between the pillar and the lever pivoted in the zone between the root and middle of the lifting boom. The lever then transmits the force of the lifting cylinder further to the boom arrangement. A transfer cylinder is also mounted on said lever, the above-mentioned nearly horizontal parallel movement being achieved by means of this transfer cylinder.
In cranes L 170 V, L 200 V of the Loglift type, the lifting cylinder is positioned above and behind the pillar in an oblique position. The lever is preferably mounted on a bearing at the same pivot as the root of the lifting boom. A weakness of the structure is the relatively great height, which reduces the visual field of the driver. Also, it is difficult to make the lifting cylinder long enough, whereby either the working range of the crane at elevation is limited, or the transportation height of the crane is too great. Further, a weakness of the structural solution is that there is tension load in the lifting cylinder during the operation. The cylinder must therefore be designed in such a way that its volume becomes large and expensive. The oil on the side of the piston rod of the cylinder is continuously under high pressure, and the sealing solutions of both the piston and the piston rod must be of high quality. When the crane is in operation, the oil filling must be controlled all the time on the non-pressure side of the piston. The hydraulics of the structure is not the best possible.
In the crane according to Fl patent application 961846, part of the weaknesses of the above-mentioned solution have been successfully eliminated. Positioning the lifting cylinder upon the lifting boom in a nearly horizontal position reduces the height of the pillar and improves the visual field in the working range. Also, the solution allows the length of the lifting cylinder to be selected great enough as regards the correct working geometry and transportation height. Still, drawbacks of the solution include the tension load of the lifting cylinder and the problem points of the hydraulic system. Further, positioning the lifting cylinder behind the pillar makes it difficult to position the crane sufficiently close to the cabin of the work machine.
SUMMARY OF THE INVENTION
The lifting cylinder positioned above the lifting boom can also form a risk factor. The lifting cylinder is subjected to great fatigable tension load during the operation. Thus, some load-bearing structure in the cylinder can fail. Such failure points can include for example the loop of the cylinder liner, the loop of the piston rod and the wire-wraps between the parts. Not only do the work machine and the whole boom arrangement fall to the ground as a result of the fatigue failure, but the lifting cylinder may also move suddenly when it breaks down. If, for example, the loop of the piston rod fails for some reason, the cylinder may bounce backwards and turn, resting on the mounting of its one end, i.e. the end on the side of the pillar. The turning continues backwards until the cylinder hits an obstacle. There is often the cabin of the work machine behind the crane. It is easy to understand that when designed or manufactured defectively, the structure forms a safety risk.
An object of the invention is to provide a boom arrangement by means of which drawbacks of the prior art can be eliminated. This is achieved by means of the boom arrangement according to the invention. The boom arrangement according to the invention is characterized in that the lifting cylinder is positioned substantially below the lifting boom and between the pillar and the intermediate lever as a pushing cylinder, whereby the lifting of the work head is arranged to take place by increasing the length of the lifting cylinder, the tow bar is pivoted at the intermediate lever, at its end facing away from the lifting cylinder, and the transfer cylinder is mounted on the tow bar close to the tow bar end facing away from the intermediate lever, at a pivot positioned substantially apart from the straight line between the pivots a, b of the tow bar ends.
An advantage of the invention is that the boom arrangement can be made small in size and sufficient in length without problems with the transportation height, limited working range or safety. The performance of the hydraulic system is also better than in known solutions, because the volume of the non-pressure oil on the side of the piston rod of the cylinder is small. An advantage of the invention is further that the solution can utilize components of existing cranes manufactured for the loading use of timber. For example, the pillar and the lifting cylinder can be selected directly from a loading crane. This advantage is significant for a machine entrepreneur whose machine selection includes both harvester cranes according to the invention and above-mentioned loading cranes. The lifting cylinder is easy to protect against outside impact by means of a light and preferred structure. Positioning the lifting cylinder on the front side of the boom arrangement allows the crane to be positioned very close to the cabin and rear axle of the work machine, which improves the stability of the work machine. During the operation, the lifting boom must sometimes be lifted in a completely vertical position. In the invention this, too, can take place in a preferred manner. Not only is the stability improved but the rear axle weight and transportation length of the work machine are also reduced compared with the prior art. Hereby, the work machine can move in a more preferred manner than previously both on roads and off-road.
REFERENCES:
patent: 3690494 (1972-09-01), Shepherd
patent: 3708000 (1973-01-01), Duffty et al.
patent: 3774659 (1973-11-01), Bodine
patent: 4127152 (1978-11-01), Larson et al.
patent: 4583907 (1986-04-01), Wimberley
patent: 6079577 (2000-06-01), Heikkilä
patent: 6193087 (2001-02-01), Gunnarsson et al.
patent: 101785 (1990-05-01), None
patent: 961846 (1996-04-01), None
patent: 7411568 (1976-04-01), None
patent: 7411568-4 (1976-04-01), None
patent: 9201842 (1993-12-01), None
patent: 9701269 (1997-01-01), None
Inkinen Ismo
Sundberg Tom
Brahan Thomas J.
Loglift Oy AB
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