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Patent Searching and Data


Title:
A DISC FOR A DISC CHIPPER
Document Type and Number:
WIPO Patent Application WO/1997/048533
Kind Code:
A1
Abstract:
The invention relates to a disc (1) for a disc chipper, said disc (1) being adapted to rotate upon a chipper shaft (2) and provided with a number of tools for producing chips. The disc (1) is composed of two or more sector-shaped blocks (3).

Inventors:
KOKKO PEKKA (FI)
Application Number:
PCT/FI1997/000356
Publication Date:
December 24, 1997
Filing Date:
June 09, 1997
Export Citation:
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Assignee:
ANDRITZ PATENTVERWALTUNG (AT)
KOKKO PEKKA (FI)
International Classes:
B27L11/00; (IPC1-7): B27L11/00
Foreign References:
SE323872B1970-05-11
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Claims:
Claims
1. A disc (1) for a disc chipper, said disc (1) being adapted to rotate upon a discchipper shaft (2) and provided with a number of knives for producing chips, c h a r a c t e r i z e d in that the disc (1 ) is com¬ posed of two or more sectorshaped blocks (3).
2. A tool wheel as set forth in claim 1, c h a r a c t e r i z e d in that the sectorshaped blocks (3) are fixed to a flange (5) fixed to the discchipper shaft (2).
3. A disc as set forth in claim 1, c h a r a c t e r i ¬ z e d in that the sectorshaped blocks (3) are fixed between the flange (5) fixed to the discchipper shaft (2) and a flange (4) adapted to be axially movable relative to the discchipper shaft (2).
4. A disc as set forth in any of claims 13, c h a r a c t e r i z e d in that the sectorshaped blocks (3) are fixed to each other over the outer rim thereof by means of separate fastening elements.
5. A disc as set forth in claim 4, c h a r a c t e r i z e d in that the fastening element comprises a separate outer ring (6), included in the disc (1) and providing the outer rim for the disc (1).
6. A disc as set forth in claim 5, c h a r a c t e r i z e d in that the outer ring (6) is composed of one or more continuous annular elements (6', 6").
7. A disc as set forth in claim 5, c h a r a c t e r i ¬ z e d in that the outer ring (6) is composed of two or more elements joined together.
8. A disc as set forth in any of claims 17, c h a r a c t e r i z e d in that each sectorshaped block (3) is provided with one or more tool attachment points (7).
9. A disc as set forth in claim 8, c h a r a c t e r i z e d in that the tool attachment point (7) is machined directly on the sectorshaped block (3).
10. A disc as set forth in any of claims 19, c h a r a c t e r i z e d in that the disc (1) is provided with wedge elements (8) for tightening the sectorshaped blocks (3) between the chipper shaft (2) and the outer ring (6), serving as the outer rim of the disc.
Description:
A disc for a disc chipper

The present invention relates to a disc for a disc chip¬ per, said disc being adapted to rotate a disc-shipper shaft and provided with a number of knives for producing chips.

This type of chippers are used in the chipping of fibrous wood for pulping process. A typical diametric dimension for a disc in this type of a chipper is 2,5 - 3,8 m and the disc has a thickness of 150-250 mm. The discs are manufactured from a single quadratic piece of plate, the blank having a weight of about 10.000-30.000 kg. Manufac¬ turers of this caliber blank plates/castings are few and far between. It is also obvious that working on the blanks requires expensive special machines.

The possible breakdown of a large-mass rapidly rotating disc during the operation of a chipper would, even in the best of circumstances, cause at least an expensive invest¬ ment on spare parts, a long down-time and production halt. The disc and components associated therewith are subject to extremely strict requirements. The manufacturing costs for a qualitatively acceptable bulky blank are high and the risk of error is considerable. Therefore, it is always necessary to examine the blanks e.g. by means of ult¬ rasonic testing for discovering possible defective points.

An object of the invention is to provide a disc for a chipper, which fulfils the high standards set for such discs, yet is superior over the prior known solutions in terms of costs.

According to the invention, this object is achieved such and a disc of the invention for a chipper is characterized in that the disc is composed of two or more sector-shaped blocks or segments.

Assembling a disc from a plurality of sector-shaped blocks offers a number of benefits: losses of raw material remain low, number of available suppliers of raw material inc¬ reases, manufacturing is possible with small machine tools, the outer ring and flanges can be made from separa¬ te durable materials regardless of the material of the actual disc, the number of knives in a chipper can be altered by replacing the sector-shaped blocks (no need to replace the entire wheel), in a breakdown situation it is possible to replace only the damaged disc components, knives/knife cassettes can be provided with separate points of attachment directly in each sector-shaped block, all sector-shaped blocks can be provided with a caset- te/knife attachment surface beforehand at reasonable costs, the sector-shaped blocks and shaft of a disc chip¬ per can be transported separately to an installation site, which offers benefits both in terms of transportation and assembling, a disc composed of sector-shaped blocks has a good price value because of savings in raw material, machining is more economical, a possible machining error or raw material defect is limited to the defective sector- shaped component only, the entire disc blank need not be examined separately but just the blank components, sector- shaped blocks can be castings (standard size), different parts of a disc can be made of different raw materials.

Preferred embodiments for the invention are set forth in the sub-claims.

The invention will now described in more detail by way of an example with reference made to the accompanying dra¬ wings, in which:

Fig. 1 shows a disc of the invention.

Fig. 2 shows a disc of the invention mounted on the shaft of a chipper.

Fig. 3 shows a sector-shaped block for a disc of the invention in plan view.

Fig. 4 shows a sector-shaped block for a disc of the invention in side view.

Fig. 5 shows a guide element to be fitted between the sector-shaped block of a disc of the invention and the disc.

In figs. 1 and 2, a disc of the invention is generally designated by reference numeral 1. The disc 1 is adapted to rotate upon a chipper shaft 2 and provided with a number of knives (not shown in figs. 1 and 2) for produ- cing chips. The shaft 2 is fixed relative to a chipper frame by means of bearings 9, 10.

In a solution of the invention, the disc 1 is composed of two or more sector-shaped blocks 3. In the example shown in fig. 1, the disc 1 includes twelve sector-shaped blocks 3.

The sector-shaped blocks 3 can be secured to a flange which is fixed to the chipper shaft 2, in other words the flange can be made of the same material as and be integral with the shaft 2 or the flange can be a separate flange mounted on the shaft 2 in a per se known manner. In the preferred embodiment of the invention shown in fig. 2, the sector-shaped blocks 3 are secured between a flange 5 fixed to the chipper shaft 2 and a flange 4 adapted to be movable relative to the disc-chipper shaft 2. The flange which is stationary relative to the shaft 2 comprises, in the example of fig. 2, a flange designated by reference numeral 5, which is secured to the shaft e.g. by means of a crimp connection.

The flanges 4, 5 and the sector-shaped blocks 3 therebet¬ ween are clamped together by a number of screws 12, 13, for which the flange 4 and the sector-shaped blocks 3 are provided with through-holes and the flange 5 with threaded holes. The resulting assembly is further secured in axial direction to the end of the shaft 2 by means of screws 11 fastened through the flange 4.

In a preferred embodiment of the invention, the disc 1 includes a separate outer ring 6, providing an outer rim for the disc 1. The outer ring 6 can be composed of one or more - two, in the example of fig. 2 - continuous annular elements 6', 6". The outer ring 6 may also consist of peripherally extended elements (not shown). Instead of using the actual outer ring 6, the sector-shaped blocks 3 can be fixed to each other over the outer rim thereof by using various per se known separate fastening means.

Each sector-shaped block 3 is provided with one or more knife attachment points 7. The knife attachment point 7 is preferably machined directly on the sector-shaped block 3. A chip opening formed between two adjacent sector-shaped blocks 3 is designated with reference numeral 18.

In the preferred exemplary embodiment shown in fig. 2, the disc 1 is provided with wedge elements 8 for tigh¬ tening the sector-shaped blocks 3 between the disc-chipper shaft 2 and the outer ring 6, the latter providing the outer rim for the disc.

The sector-shaped blocks 3 can also be secured to the outer ring 6. In the example shown in fig. 2, the sector- shaped blocks 3 are clamped by means of screws 14 into a slot or groove formed between the joined elements 6', 6" of the outer ring 6.

In fig. 3, a sector-shaped block for a disc of the inven¬ tion is shown in plan view and in fig. 4 in side view. The block 3 includes an arched side surface, which faces the outer ring 6 and is designated by reference numeral 15. However, the radial guidance of the tool wheel 1 between the outer ring 6 and the block 3 is established in such a manner that the end of the block 3 is machined to include guide surfaces 16 for a guide element 17, best shown in figs. 5 and 2. The guide element 17 is provided with an arch section 18 matching the curvature of an internal groove included in the outer ring 6. Thus, as for the ends thereof facing the outer ring 6, two adjacent blocks 3 are adapted to be guided and secured to each other and to the outer ring 6 between two guide elements 18.