Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
  • D21D1/00—Methods of beating or refining; Beaters of the Hollander type
  • D21D1/20—Methods of refining
  • D21D1/30—Disc mills
  • D21D1/306—Discs

Definitions

• the present invention relates to a grinding block for a re ⁇ finer, consisting of a sector or a part of a sector of a grinding disc or cone made of stainless steel.
• the most important phase in the process of pulp production is the grinding of the wood material, which is done by refi ⁇ ners specially designed for the purpose.
• the disc refiner which grinds the wood chips between two discs placed face to face, is the most commonly used type of refi ⁇ ner, although the conic refiner is also important. Since the grinding takes place under high pressure, with water used for fluidization and lubrication, and since plenty of orga ⁇ nic acids are produced from the disintegrating wood pulp, the material from which the grinding discs and cones are manufactured deserves .special attention.
• the grinding ele ⁇ ments must be hard and durable, but they must also have good resistance to corrosion. Moreover, they must be made of a material that is tough enough to withstand the various strains caused by pressure shocks and other disturbances.
• the steel material most commonly used in the grinding ele ⁇ ments is stainless martensite steel containing 14-18% of chrome, depending on the carbon content.
• Such steel is rela ⁇ tively inexpensive and hard and allows further heat treat ⁇ ment and hardening. In addition, it has good resistance to the chemical conditions present in the refiner.
• the worst drawback, especially with the hardest kinds of steel is the brittleness of the material, entailing a low resistance against impacts and tensile stress.
• these steels have provided the best compromise to meet the conflicting requirements, but when e.g.
• the entire grinding disc or cone used to be made of the same corrosion resistant, hard and durable ma ⁇ terial required by the pulp refining process.
• the discs and cones are composed of several so called grinding blocks, which in fact are sectors or parts of a sector of a disc or cone.
• US patent 4,423,845 proposes a grinding sector with a locally hardened grinding surface, thus allowing a better control of the refining process.
• the practice of incorporating various substances e.g.
• the object of the present invention is to eliminate the drawbacks mentioned and to provide a new type of grinding block for a disc or conic refiner in which the questions referred to above have been taken into consideration.
• the grinding block of the invention is cha ⁇ racterized in that at least part of the grinding surface of the block is constituted by one or more detachable segments made of a substantially harder and more durable material than the rest of the grinding block, and that the block is provided with means for securing this detachable segment.
• the advantages of the grinding block of the invention include ⁇ de an almost complete immunity to brittle fracture, the pos ⁇ sibility of partial replacement and renewal of the grinding elements and a high degree of hardness and durability of the detachable segments.
• the detachable parts will best serve their purpose if mounted near the periphery of the grindng block, where the radial velocity is highest and, therefore, the strain greatest.
• Fig. 1 is a front view of the grinding block of the invention as used in a disc refiner, with two detachable- grinding segments.
• Fig. 2 shows an embodiment of the grinding block of the invention in lateral view.
• Fig. 3 shows another embodiment of the grinding block of the invention in perspective.
• the grinding block 1 shown in fig. 1 is provided with two detachable parts or grinding segments 2, which are made of a substantially harder and more durable material than the rest of the block 1.
• the hardening may be effected on a forged bloom either before or after it is fitted in the grinding block.
• Ceramics suitable for use as a coating material.
• the embodiment in figure 2 is provided with means 3 for securing the detachable grinding segments.
• the grinding block 1 is provided with shoulders 3 which constitute a dovetail joint to secure the segments 2 in a form-locked manner.
• shoulders 3 which constitute a dovetail joint to secure the segments 2 in a form-locked manner.
• Figure 3 shows in perspective an embodiment employing bolts 4 to ensure that the cutter segments are firmly secured.
• Be ⁇ cause of the great centrifugal force generated by the fast rotation of the grinding block in practical use, it is al ⁇ ways preferable to provide the outer edge of the block 1 with a shoulder 3 to support the detachable segment 2, thus enabling the compressive strength of the segment 2 to be effectively utilized while at the same time firmly securing the segment in the grinding block 1.
• the detachable segments may be secured in the grin ⁇ ding block by means of a solid joint, e.g. a soldered or brazed one, either as a sole or an auxiliary means of secu- rement.
• a solid joint e.g. a soldered or brazed one
• this kind of oints are generally also disjoined, so that they will not present a notable obstruction to the replacement of the segments.
• the segments may also be fixed in place by means of an adhesive medium, such as glue.
• the detachable segments 2 are to be secured in the manner shown in fig. 2, it is also possible to make the segments from a durable cast iron, such as white martensite cast iron, by casting the segments in the space between the shoulders 3 in the grinding block. In this case it is natu ⁇ rally necessarry to use a casting mould, which is placed over the grinding block 1. The mould is not shown in the drawing. To facilitate the removal of the cast segments 2, a suitable loosening agent may be applied to the grinding block before the casting is performed.
• a durable cast iron such as white martensite cast iron

Landscapes

• Crushing And Grinding (AREA)
• Polishing Bodies And Polishing Tools (AREA)
• Disintegrating Or Milling (AREA)
• Paper (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8522605

Family Applications (1)

Country Status (6)

Cited By (2)

Citations (9)

Family Cites Families (5)

• 1986
  • 1986-05-13 FI FI861986A patent/FI80087C/sv not_active IP Right Cessation
• 1987
  • 1987-05-05 EP EP87902533A patent/EP0271502B1/en not_active Expired - Lifetime
  • 1987-05-05 JP JP62502967A patent/JPS63503469A/ja active Pending
  • 1987-05-05 WO PCT/FI1987/000060 patent/WO1987006963A1/en active IP Right Grant
  • 1987-05-05 AU AU73909/87A patent/AU596422B2/en not_active Ceased
  • 1987-05-12 NZ NZ220274A patent/NZ220274A/xx unknown

Patent Citations (9)

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