Woodworking – Bark rosser – Hollow head cutter
Reexamination Certificate
1997-12-22
2001-07-17
Bray, W Donald (Department: 3725)
Woodworking
Bark rosser
Hollow head cutter
C144S208100, C144S241000, C403S408100, C407S048000, C407S114000
Reexamination Certificate
active
06260592
ABSTRACT:
The present invention relates to a replaceable cutting piece for a debarking cutter for a debarking machine of a hollow-rotor type for debarking a log to be fed axially through a rotor, which cutting piece comprises a cutter forming a cutting edge and a projection protruding from the cutter, said cutter and projection forming supporting surfaces for receiving loads acting on the cutting piece during debarking, and means for securing the cutting piece to a cutting arm of the debarking cutter by the supporting surfaces of the cutting piece.
The main regulating units of a debarking machine comprise a rotor carrying out the debarking, debarking cutters supported by the rotor and feeding devices both in front of and at the rear of the rotor that guide the tree to be debarked to the centre of the rotor and feed it through the rotor.
The rotor of a debarking machine comprises a rotating drum through which the tree to be debarked is fed. The debarking cutters are secured to this rotating drum each on a shaft acting as a pivot, which cutters in a position of rest are directed towards the centre of the rotor in such a manner that when rotating, the cutting edges of the debarking cutters form a circle corresponding to the smallest diameter of a tree to be debarked with the machine. The cutting edges of the debarking cutters are pressed against the surface of the tree to be debarked by the action of a spring mechanism built inside the drum of the rotor. This spring mechanism keeps the debarking cutters closed towards their minimum opening when no tree is fed through the rotor.
The tree to be debarked is centralized by means of the feeding devices of the debarking machine to the centre of the rotor and is fed into the opening of the drum of the rotor. The end of the tree contacts the cutting arm of the debarking cutters which are in a closed position and rotate with the rotor in an area equal to the diameter of the tree.
Because of the rotating motion of the rotor and the effect of a lifting edge on the cutting arm in a closed position, the cutting piece secured to the cutting arm turns up on the surface of the tree to be debarked. The debarking takes places in such a manner that the lifting edge and the cutting edge of the cutting piece cut and remove the bark as a spiral-shaped cutting in accordance with the advancing movement of the tree.
Known rotor debarking machines primarily use two types of debarking cutters.
A basic debarking cutter comprises a cutting arm in which a lifting edge and a cutting edge are shaped. Today the use of these kinds of cutter solutions is being discontinued as when debarking different types of trees, for example, series of debarking cutters are needed for each kind of tree and for each debarking condition. Further, the maintenance of the debarking series is difficult because big, heavy objects must be handled.
For practical reasons, debarking cutter constructions for rotor debarking machines have increasingly been replaced by types that comprise a cutting arm and a replaceable cutting piece attached thereto. In that case, when the tree type or the conditions change, only the cutting pieces carrying out the debarking need be replaced. Also, the quality of debarking can be maintained in a considerably simpler way as maintenance procedures have to be made only on cutting pieces of a minimal weight, while the cutting arm used is the same in all conditions.
In known cutting piece solutions, e.g. Finnish Patents 72,457 and 84,703, the cutting piece is fastened by means of a screw on a planar abutment surface in the cutting arm, the cutting piece leaning onto the abutment surface on a corresponding supporting surface. In that case, some of the debarking forces produced during debarking will strain the retaining screws. In some solutions, attempts have been made to reduce the loads acting on the retaining screw by forming the abutment plane into a shallow conical shape or by using different kinds of recesses in the abutment plane, whereby the cutting piece has a protrusion that fits into a corresponding recess in the cutting arm, e.g. U.S. Pat. No. 4,709,737. In known solutions, the retaining screws of the cutting piece will always have to receive a significant portion of the debarking forces.
The object of the present invention is to achieve a replaceable cutting piece that will avoid the drawbacks mentioned above and will enable the loads acting on the cutting piece to be transmitted in full to the cutting arm instead of to the retaining screw.
This object is achieved with a cutting piece according to the invention, which is characterized in that the cutting piece comprises
at least one first supporting surface receiving a load acting on the cutting piece in an axial direction of the rotor,
at least one second supporting surface receiving a load acting on the cutting piece in a radial direction of the rotor, said second supporting surface being situated in a perpendicular plane with respect to the first supporting surface,
at least one third supporting surface receiving a load acting on the cutting piece in a tangential direction of the rotor, said third supporting surface being situated in a perpendicular plane with respect to the first and the second supporting surfaces, and
at least one fourth supporting surface receiving a torque acting on the cutting piece due to the load acting in the radial direction of the rotor and the load in the tangential direction of the rotor, said fourth supporting surface being situated in the projection of the cutting piece.
In accordance with the invention, the cutting piece can be positioned in the cutting arm so that the loads caused by debarking can be controlled by supporting surfaces formed in the cutting piece and by corresponding abutment surfaces formed in the cutting arm. When the loads caused by debarking can be controlled as shown above between the cutting arm and the cutting piece by means of surfaces in contact with one another, the only task remaining for the retaining screws is to position the cutting piece into the right position in the cutting arm. Thereby debarking forces acting on the screw can be avoided.
The object of this invention is also to obtain a cutting arm for a debarking cutter of a debarking machine of the hollow-rotor type with which the advantages mentioned in connection with the cutting piece are attained. This object is achieved by a cutting arm which is characterized by what is disclosed in the characterizing part of claim
5
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REFERENCES:
patent: 4209047 (1980-06-01), Weill
patent: 4384600 (1983-05-01), Kivimaa
patent: 4653559 (1987-03-01), Ackerman
patent: 4709737 (1987-12-01), Jonsson
patent: 5460212 (1995-10-01), Darden
patent: 811965 (1981-06-01), None
patent: 823822 (1982-11-01), None
patent: 72457 (1987-02-01), None
patent: 84703 (1991-09-01), None
patent: 430 391 (1983-11-01), None
patent: 463 660 (1991-01-01), None
patent: WO 97/04930 (1997-02-01), None
Bray W Donald
Burns Doane Swecker & Mathis L.L.P.
Valon Kone Oy
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