Woodworking – Slicer – Rotary disk
Patent
1995-12-21
1997-08-26
Bray, W. Donald
Woodworking
Slicer
Rotary disk
1441621, 144241, 241 92, 241294, B27C 700, B02C 1818
Patent
active
056602189
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a knife system, a knife, a guide component and a filler part for a machine used in wood chipping and a method of exchanging knives in accordance with the preambles of claims 1, 2, 3, 4, 7 and 8.
Disc chippers are commonly used in the forest industry for chipping wood before further processing. Knives chipping out chip pieces from a log against fixed counter knife are attached to a rotating disc of the chipper evenly divided and at a certain displacement from the radius. The chipper knife and its mounting form a very important part of the operation of the machine used for chipping pulpwood.
The problem with disc chippers is their knife maintenance which is expensive and time-consuming. Logs of a big diameter require a long cutting length and thus also a long knife. Traditional one-piece knives which must be sharpened by grinding are heavy to handle and they constitute a hazard in terms of labour safety.
The market has nowadays seen an introduction of reversible knife systems formed of section knives. The reversible knives have two cutting edges on their long sides, both of which can be used by reversing the knife. The knife length is only a part of the total cutting length of the disc, and several such section hives are fitted into the disc in a line one after the other. Section hives are exchanged when required, but they are not usually sharpened. When mounting, it is important to place the cutting edges of the section knives exactly on the correct line. Also during operation, the cutting edges must be kept absolutely in the correct position. The main advantage of section knives is that only the poor part of the cutting length may be exchanged. (In this context the cutting length means either the total length of one one-piece knife or the total length of a knife consisting of several section knives.)
One such reversible system is described in SE publication 453 373. The sections are guided along the same line with the aid of the cross-sectional profile of the knife. Disadvantages of the knife according to SE publication 453 373 are high manufacturing costs due to the complexity of the knife and the complexity of the knife mounting system. The knife mounting system which consists of several weak parts will usually break when a stone or a steel object gets into the chipper.
A reversible knife system is also described in US patent publications U.S. Pat. Nos. 4,423,758 and 4,503,893. According to these publications, a knife block as long as the total cutting le is used for guiding the short section knives. The knife block has longitudinal ridges fitting into corresponding longitudinal grooves in the knives and thus they guide the section knives along the correct line. US patent publication U.S. Pat No. 4,351,487 again describes an arrangement wherein the section knives are guided directly in line by a rod of a circular cross-section and of a length equal to the total cutting length and fitting into a longitudinal groove in the knife and in the knife holder. Alternatively, a protrusion which is one piece with the knife holder may be used instead of a separate guiding rod. The knives according to these inventions suffer from the disadvantage that the deep groove in the knife adds to the manufacturing costs and weakens the strength of the knife. The protrusion of the same size as the knife also gives rise to much increased costs of manufacture.
The object of the present invention is to bring about an exchangeable knife allowing minimized knife maintenance costs. The characteristic features of the invention are stated in claims 1, 2, 3, 4, 7 and 8.
According to the invention, the cutting length of a disc chipper knife is divided preferably into two or three pieces. Guiding of knife pieces On the same line and keeping in place of the pieces is ensured by a guide, the position of which is changed after sharpening. In a disc chipper, chipping and thus also knife wear are greatest in the central part of the disc. Use of the knives can hereby be continued by changing the position of section kn
REFERENCES:
patent: 4351487 (1982-09-01), Haller et al.
patent: 4405092 (1983-09-01), Sybertz et al.
patent: 4423758 (1984-01-01), Haller et al.
patent: 4503893 (1985-03-01), Demopoulos
Bray W. Donald
Sunds Defibrator Woodhandling Oy
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